let. - vol. A~7 C2D01] št. - no. 1 1 JOURNAL OF MECHANICAL ENGINEERING strani - pages 6-41 - BBB ISSN 0039-24B0 . Stroj V . STJVAX cena BOO SIT delava in optimizacija nove tehnologije varjenja pedala za avtomobilsko zavoro Development nad Optimisation of a New Technology for Welding the Brake Pedal of a Motor Vehicle Elasto-plastična analiza deformiranja naprave za zaščito pred podletom za motorna vozila Elasto-Plastic Deformation Analysis of a Rear-Underrun Protection Device for Load-Carrying Vehicles Določitev imenske moči motorja s poskusom pospeševanja vozila Determining an Engine's WOT Performance from a Vehicle Speed-Up Test Priprava motorja za tekmovalni razred How to Prepare an Engine for Motorcycling's Supersport Class 5. konferenca IAT'01 Razstava Inovativna avtomobilska tehnologija 5. - 6. april 2001 Ljubljana, Slovenija 5. Conference IAT01 Exhibition Innovative Automotive Technology April 5th - 6th 2001 Ljubljana, Slovenia 9770039248001 © Strojni{ki vestnik 47(2001)11,641 Mese~nik ISSN 0039-2480 © Journal of Mechanical Engineering 47(2001)11,641 Published monthly ISSN 0039-2480 Vsebina Contents Strojni{ki vestnik - Journal of Mechanical Engineering letnik - volume 47, (2001), {tevilka - number 11 Razprave Tušek, J., Uran, M., Jonke, M.: Izdelava in optimizacija nove tehnologije varjenja pedala za avtomobilsko zavoro 642 Glavač, M., Ren, Z, Prašnički, M.: Elasto-plastična analiza deformiranja naprave za zaščito pred podletom za motorna vozila 654 Medica, V., Imper, B., Imper, Z.: Določitev imenske moči motorja s poskusom pospeševanja vozila 662 Bizjan, F., Rodman, S., Trenc, F.: Priprava motorja za tekmovalni razred 672 Osebne vesti Navodila avtorjem 682 685 Papers Tušek, J., Uran, M., Jonke, M.: Development nad Optimisation of a New Technology for Welding the Brake Pedal of a Motor Vehicle Glavač, M., Ren, Z, Prašnički, M.: Elasto-Plastic Deformation Analysis of a Rear-Underrun Protection Device for Load-Carrying Vehicles Medica, V, Imper, B., Imper, Z: Determining an Engine’s WOT Performance from a Vehicle Speed-Up Test Bizjan, F, Rodman, S., Trenc, F: How to Prepare an Engine for Motorcycling’s Supersport Class Personal Events Instructions for Authors stran 641 I^HSflTTMlDC © Strojni{ki vestnik 47(2001)11,642-653 © Journal of Mechanical Engineering 47(2001)11,642-653 ISSN 0039-2480 ISSN 0039-2480 UDK 621.791:629.3.017.5 UDC 621.791:629.3.017.5 Izvirni znanstveni ~lanek (1.01) Original scientific paper (1.01) Izdelava in optimizacija nove tehnologije varjenja pedala za avtomobilsko zavoro Development nad Optimisation of a New Technology for Welding the Brake Pedal of a Motor Vehicle Janez Tu{ek - Miro Uran - Miran Jonke V prispevku sta predstavljeni izdelava in optimizacija nove tehnologije varjenja pedala za avtomobilsko zavoro, ki temelji na elektrouporovnem bradavičnem in točkovnem varjenju. Opisani so problemi do sedaj uporabljenega obločnega varjenja in razlogi za zamenjavo tehnologije. Za novo tehnologijo je bila izdelana vpenjalna priprava za hkratno vpetje telesa pedala, stopalke in naslona stikala. Optimizirani so bili parametri za bradavično varjenje stopalke na telo pedala, bradavično varjenje dela naslona na telo pedala in točkovno uporovno varjenje drugega dela naslona na telo pedala. Izveden je bil ekonomski izračun, ki je pokazal, da je bila zamenjava tehnologije ekonomsko potrebna, saj se z novo tehnologijo poenostavi proizvodnja zavornega pedala za osebni avtomobil. © 2001 Strojniški vestnik. Vse pravice pridržane. (Ključne besede: varjenje točkovno, varjenje bradavično, zavore avtomobilske, pedali, varjenje obločno) We have developed and optimised a new technology for welding the brake pedal of a motor vehicle that is based on resistance-projection and spot-welding processes. We describe the problems encountered when using arc welding and the reasons for substituting the technology. To apply the new technology we constructed a fixture for the simultaneous clamping of a pedal body, a foot treadle and a stop-switch rest. We then optimised the parameters for the projection welding of the foot treadle to the pedal body and the stop-switch rest to the pedal body; we also optimised the resistance spot welding of the other part of the rest to the pedal body. Our costing of the process showed that the substitution of the technology was economically justified since the new technology simplified the manufacture of the motor-vehicle brake pedal. © 2001 Journal of Mechanical Engineering. All rights reserved. (Keywords: resistance spot welding, resistance projection welding, vehicle brakes, brake pedals, arc welding) 0 UVOD Izdelava, uvajanje in optimatizacija novih izdelovalnih tehnologij so najintenzivnejše in tudi najzahtevnejše prav v avtomobilski industriji. Med vsemi izdelovalnimi tehnologijami v celotni avtomobilski proizvodnji je varilska tehnologija prav gotovo tista, ki je najpomembnejša. Izboljšave njenih uporab in optimatizacija potekajo v več smereh. Pomembni sta dve. Prva je uvajanje avtomatiziranih in robotiziranih trakov za izbran varilni postopek oziroma tehnologijo, ki sta integrirana v celotnem sistemu in vodena ter nadzirana iz enega mesta. Druga, prav tako zelo pomembna pa je optimalna izbira varilnega postopka in v okviru tega optimatizacija samega varilnega procesa. V našem primeru bomo prikazali zamenjavo obločne tehnike varjenja s tanko žico (varjenje MAG) zavornega pedala z elektrouporovno tehniko brez dodajnega materiala. Predstavljena bo izdelava tehnologije za elektrouporovno bradavično varjenje stopalke na telo zavornega pedala in uporovno 0 INTRODUCTION Introducing, developing and then optimising new production technologies are some of the main challenges in the automotive industry. Among the production technologies used in the automotive industry, welding technology is certainly one of the most important. Its applications are spreading and its optimisation is proceeding in several directions. Two of these directions are important. The first direction is the introduction of automated and robotised lines for a selected welding process, which is then integrated into the system and controlled from a single location. The second direction is choosing the best welding process and then optimising it. In our case we have substituted resistance welding without a filler material for arc welding with a thin wire, i.e. MAG welding. We will describe the development of the technology of projection welding the foot treadle to the brake-pedal body and re- 01-11 grin^(afcflM]SCLD I ^BSfiTTMlliC | stran 642 J. Tu{ek - M. Uran - M. Jonke: Izdelava in optimizacija - Developemnt and Optimisation točkovna ter uporno bradavično varjenje naslona stikala prav tako na telo zavornega pedala. Zavorni pedal oziroma pedalni sklop je z varnostnega vidika eden najpomembnejših delov vsakega motornega vozila. Glede na to morajo biti tudi izbrani materiali za pedal, tehnologija izdelave, vključno z varjenjem in nadzorom po varjenju, zelo kakovostni in izvedeni v skladu z najstrožjimi varnostnimi predpisi. To pomeni, da morajo biti zvari, ki bi s porušitvijo povzročili nevarnost za poškodbe potnikov v avtomobilu ali drugačno gmotno škodo, označeni kot varnostni zvari. Za te vare morajo biti varilni parametri med varjenjem nadzorovani, zapisovani pri vsakem varu in pri vsakem kosu ter po varjenju shranjeni še 15 let po izdelavi oziroma po prodaji avtomobila naročniku. Po varjenju mora biti na zvarih in zvarnih spojih izvedeno preverjanje kakovosti spoja po zahtevah veljavnih standardov ali pa po navodilih naročnika. 1 OPIS PROBLEMA Že v uvodu smo zapisali, da je pedalni sklop iz varnostnih in upravljalskih vidikov eden pomembnejših delov vsakega avtomobila. V pedalni sklop, ki je z notranje strani privit na sprednjo steno avtomobila, spadata pedal sklopke in zavorni pedal. Pedal za plin je poseben sklop, ki ne spada v pedalni sklop. V tem prispevku bo predstavljena nova tehnologija zvarjanja stopalke in naslona stikala na telo zavornega pedala. Zavorni pedal je z vsemi deli in z dolžino obločno zvarjenih zvarov prikazan na sliki 1. 2 x 6 mm zvara 2 x 6 mm welds sistance spot welding and resistance projection welding of the stop-switch rest to the brake pedal. In terms of safety, the brake pedal, i.e. the pedal assembly, is one of the most important elements in any motor vehicle. Consequently, the materials selected for the pedal and the production technology including the welding and control after welding should be of high quality and in accordance with the most stringent safety regulations. Furthermore, welds that could fail and produce serious injuries to car passengers or any other material damage should be marked as safety welds. The welding parameters of such welds should be controlled and registered, with each weld and workpiece stored for a period of 15 years after production, i.e. after the sale of the car. After welding, the welds and welded joints should be subjected to quality control in accordance with the relevant standards or the manufacturer’s instructions. 1 THE PROBLEM TO BE ADDRESSED The pedal assembly is one of the most important elements of every motor vehicle. It is mounted to the front car wall from the inside and consists of a clutch pedal and a brake pedal. The gas pedal is a separate assembly that is not part of the pedal assembly. This paper describes a new technology for welding the foot treadle and the stop-switch rest to the brake body. The brake pedal with its elements and the arc welds are shown in Fig. 1. Pesto Hub Telo pedala zavore Brake-pedal body Naslon stikala Stop-swich rest Stopalka 2 x 30 mm zvara Foot treadle 2 x 30 mm welds 2 x 10 mm zvara 2 x 10 mm welds Sl. 1. Zavorni pedal sestavljajo telo pedala, stopalka, naslon stikala zavorne luči in pesto Fig. 1. Brake pedal consisting of a pedal body, a foot treadle, a stop-switch rest, and a hub stran 643 01-11 ilTMDDC J. Tu{ek - M. Uran - M. Jonke: Izdelava in optimizacija - Developemnt and Optimisation Telo zavornega pedala je izdelano iz 6 mm debele jeklene pločevine. Na telo se po sedanji tehnologiji privarita po postopku MAG stopalka in naslon stikala. Kljub temu da je obločno varjenje robotizirano, je celoten postopek zamuden, negospodaren in kakovost zvara pogosto vprašljiva ali celo nezanesljiva. Vse to so bili razlogi, da smo se odločili za zamenjavo sedanje tehnologije z novo, ki bo odpravila pomanjkljivosti obločnega varjenja s taljivo elektrodo. 2 OPIS SEDANJE TEHNOLOGIJE Pri sedanji tehnologiji najprej z orodji za preoblikovanje (štancanje) in s stiskalnicami izdelamo telo pedala, stopalko in naslon stikala ter na obdelovalnem avtomatu pesto iz cevi (sl. 1). Nato v telo pedala vtisnemo pesto, za tem pa je na vrsti najpomembnejša operacija, to je varjenje naslona stikala stop in stopalke na telo pedala. Varjenje izvajamo na robotski celici, ki sestoji iz šestosnega členkastega robota Motoman K 10S, pozicionirne naprave, komandnega pulta, električne omare, vira varilnega toka Fronius Transarc 450, pnevmatskega čistilnika varilne pištole, zaščitne ograje in svetlobne zavese. Varilne priprave za vpetje varjencev so pritrjene na dveh varilnih paletah (vsaka na eni strani mize H). Na vsaki paleti sta po dve gnezdi za varjenje naslona stikala zavorne luči in dve gnezdi za varjenje stopalke na telo pedala. Silo vpenjanja dobimo prek pnevmatskega sistema. Delavec najprej vloži v prvo gnezdo telo zavornega pedala in nato še naslon stikala. V drugo gnezdo pa vloži stopalko in nanjo namesti telo pedala z že zavarjenim naslonom. Pozicioniranje telesa pedala se izvede prek nakrčenega pesta. Nato delavec vklopi vpenjanje varjencev in pritisne gumb za obračanje mize. Po obračanju mize se prične robotsko varjenje. Ko robot konča varjenje, se pozicionirnik obrne, robot prične variti na drugi paleti, na prvi pa se varjenci avtomatično izpnejo, delavec vzame pedal z zvarjeno stopalko iz drugega gnezda in ga odloži v zaboj, tako se postopek ponavlja. Iz povedanega lahko ponovno ugotovimo, da je celoten postopek izdelave zavornega pedala z obločnim varjenjem drag, da je v proces vključena draga oprema, da se med varjenjem porabljata [1] zaščitni plin in dodajni material, da so zaradi sevanja obloka in brizganja taline obremenjeni delavci in okolica. Odločilno vlogo pri odločitvi o zamenjavi tehnologije pa je imela kakovost zvarnih spojev. Zaradi razmeroma velikih toleranc izmer polizdelkov (telo pedala, stopalke, naslon stikala) je namreč lega vara zelo različna, ker zvarni stik med stopalko in telesom pedala ter naslonom in telesom zaradi odstopanja ^BSfirTMlliC | stran 644 The brake-pedal body is made of a 6-mm-thick steel plate. The current technology involves MAG welding the foot treadle and the stop-switch rest to the pedal body. Although the arc-welding process used is robotised, the whole procedure is time consuming and uneconomic, and the weld quality is often questionable or unreliable. For these reasons we decided to substitute a new technology for the old one and, consequently, eliminate the weak points of arc welding by using a consumable electrode. 2 DESCRIPTION OF THE CURRENT TECHNOLOGY With the current technology, first the pedal body, the foot treadle, and the stop-switch rest are made by forming, i.e. stamping and pressing, whereas the hub is made from a tube by automatic machining (Fig. 1). The hub is then inserted into the pedal body. Finally, the most important operation, i.e. welding of the stop-switch rest and the foot treadle to the pedal body, takes place. The weld is made in a robotic cell consisting of a Motoman K 10S six-axis articulated-arm robot, a positioner, a control panel, an electric cabinet, a Fronius Transarc 450 welding current supply, a pneumatic cleaning device for the welding gun, a protective fence, and a light curtain. Welding jigs for the workpieces are mounted on two welding pallets, one at each side of an H table. At each pallet there are two clusters for welding the stop-switch rest and two for welding the foot treadle to the pedal body. The clamping force is supplied through a pneumatic system. A worker first places the brake-pedal body and then the stop-switch rest in the first cluster. In the second cluster, he then places the foot treadle and the pedal body with the rest already welded to it. The pedal-body positioning is accomplished with a shrink hub. Then the worker switches on the clamping of the workpieces and the table-turning. After the table is turned the robotic welding starts. When the robot stops welding, the positioner turns, and the robot starts welding at the other pallet. At the first pallet the workpieces are automatically removed. The worker takes the pedal with the foot-treadle welded to it from the second cluster and puts it to one side in a case. The whole procedure is then repeated. The above description suggests that the manufacturing of the brake pedal by arc welding is quite expensive; it requires costly equipment as well as a shielding gas and a filler material that are consumed during welding [1]. In addition, the workers and the environment are at risk from arc radiation and molten-pool spatter. A key role in the technology substitution is played by the weld quality. Because of the comparatively high tolerances and the size of the semi-products, i.e. the pedal body, the foot treadle, and the stop-switch rest, the position of the weld varies considerably, which means that the weld J. Tu{ek - M. Uran - M. Jonke: Izdelava in optimizacija - Developemnt and Optimisation izmer ni vedno na natančno istem mestu. To pa je razlog, da je en varjenec slabo prevarjen drugi pa premočno ali nasprotno. 3 ELEKTROUPOROVNO VARJENJE ZAVORNEGA PEDALA Pri iskanju rešitev za večjo produktivnost varjenja in doseganje boljše kakovosti zvarnih spojev smo proučili več različnih možnosti. Za povečanje produktivnosti smo raziskali uporabo več različnih obločnih zelo produktivnih postopkov, ki omogočajo varjenje z razmeroma velikimi hitrostmi. Slaba stran vseh teh postopkov je v velikem vnosu energije v varjenec in zato nastanek deformacij varjencev, stroški zaradi zaščitnega plina in dodajnega materiala ter slab izkoristek obločne energije in dodajnega materiala zaradi brizganja Večjih hitrosti varjenja pa zaradi zapletenih oblik spojev in zahtevnih trajektorij robotskega varilnega gorilnika ni bilo mogoče uporabiti. Za doseganje boljše kakovosti zvarnega spoja smo raziskali možnosti za uporabo zaznaval za sledenje varilnega gorilnika po zvarnem stiku in ob morebitni napaki popravek njihovega obnašanja. Tudi za to izvedbo je poznana cela vrsta bolj ali manj natančnih naprav. Vsem pa je skupno to, da jim z zanesljivostjo delovanja cena močno naraste, pri čemer se pojavi vprašanje gospodarnosti. Analiza rezultatov zgoraj omenjenih raziskav je pokazala, da je daleč najboljša rešitev zamenjava celotne tehnologije varjenja in uvedba elektrouporovnega namesto obločnega varjenja MAG (sl. 2). joint is not always found at the same location due to the inaccurate dimensions of the parts. This results in too strong or too poor penetration. 3 RESISTANCE WELDING OF THE BRAKE PEDAL Several alternatives were studied in order to achieve higher productivity and a better weld quality. To increase the productivity, several high-productivity arc-welding processes that permit comparatively high welding speeds were considered. A disadvantage of these processes is the high energy input into the workpiece resulting in workpiece strains, increased costs due to gas and filler-material consumption and the low efficiency of the arc energy and the filler material due to spatter. Higher welding speeds, however, could not be used because of the complex joint shapes and the exacting trajectories of the welding torch of the robot. With regard to weld quality, we looked at using sensors to track (and possibly correct) the welding blowpipe along the joint. A number of sensors with a range of accuracies are available, however, the necessary reliability comes at a high price, which reduces the cost-effectiveness. An analysis of the results obtained in our studies indicates that the best solution is the substitution of the new technology for the old one and the introduction of resistance welding (Fig. 2). narebričena stopalka ribbed foot treadle telo zavornega pedala brake-pedal body bradavični zvari projection welds MAG varjenje MAG welding uporovno bradavično varjenje projection welding Sl. 2. Shematski prikaz zvarnega stika med stopalko in telesom zavornega pedala z oznakami za obločno (kotni zvar) in bradavično varjen spoj Fig. 2. Schematic representation of a weld joint between the foot treadle and the brake-pedal body with markings for the arc fillet) welded and projection welded joints ^vmskmsmm 01-11 stran 645 I^BSSIPTMIGC J. Tu{ek - M. Uran - M. Jonke: Izdelava in optimizacija - Developemnt and Optimisation 3.1 Elektrouporno bradavično varjenje stopalke na telo zavornega pedala Na sliki 2 sta shematsko prikazana način spajanja zavornega pedala in stopalke. Stopalka ni popolnoma ravna, ampak je valovito deformirana in na ta način mehansko ojačena oziroma se tako poveča njena togost. Prav valovitost stopalke v veliki meri onemogoča izdelavo kakovostnega kotnega zvara po talilnem obločnem postopku. Na desni strani iste slike lahko vidimo, da rebra na valoviti stopalki pomenijo bradavice, ki omogočajo uvedbo uporovnega bradavičnega varjenja brez dodatnih operacij in stroškov. Uporovno bradavično varjenje je mogoče izvesti na stroju s posebno izdelano vpenjalno pripravo, ki je shematsko prikazana na sliki 3. 1 3.1 Resistance projection welding of the foot treadle to the brake-pedal body Figure 2 schematically shows the joining of the brake-pedal body and the foot treadle. The foot treadle is wavy rather than completely flat, which makes it stiffer. And it is this waviness of the foot treadle that makes the production of a quality fillet weld by arc welding almost impossible. The right sketch in Figure 2 shows ribs in the wavy foot treadle which may be considered as projections permitting the introduction of projection welding without any additional operations and costs. Resistance projection welding is possible with a machine having a special fixture as shown schematically in Fig. 3. 5 2 3 4 6 7 8 Sl. 3. Shematski prikaz priprave za uporno bradavično varjenje telesa zavornega pedala s stopalko 1 - zgornji del varilne priprave; 2 - zgornja elektroda za dovod toka; 3 - spodnja elektroda z ležiščem za stopalko; 4 - spodnji del varilne priprave; 5 - izolacija; 6 - stopalka; 7 - telo pedala; 8 - pozicioniranje in vpetje na pesto Fig. 3. Schematic representation of a fixture for resistance projection welding of the brake-pedal body and the foot treadle 1 - upper part of the welding fixture; 2 - upper electrode for current supply; 3 - lower electrode with a bed for the foot treadle; 4 - lower part of the welding fixture; 5 - insulation; 6 - foot treadle; 7 - pedal body; 8 - positioning and fixing to the hub Glede na velikost stičnih ploskev ali bradavic potrebujemo varilni stroj z minimalno močjo 300kVA ([2] in [3]). Ena večjih težav, ki se pri tem pojavi, je, kako po čim krajši poti s čim manjšo upornostjo dovesti zelo visoko jakost toka na telo pedala. Dovod toka na stopalko je dokaj preprost, saj ga izvedemo prek vpenjalne priprave in ležišča. Na sliki 3 je shematsko prikazana optimalna rešitev za dovod toka na stranski ploskvi telesa pedala. Glede na to, da je površina oziroma prerez zvara 108 mm2, mora biti površina stika med With regard to the size of the contact surfaces, i.e. projections, a welding machine with a minimum power of 300 k VA is required ([2] and [3]). One of major difficulties is how to supply a very high current to the pedal body, while keeping the distance and the resistance as small as possible. The current supply to the foot treadle is comparatively simple since it is accomplished through the fixture and the bed. Figure 3 schematically shows the best solution for current supply to the side faces of the pedal body. As the cross-sectional area of the weld equals 108 mm2, the contact area between the workpieces 01-11 grin^(afcflM]SCLD I ^BSfiTTMlliC | stran 646 J. Tu{ek - M. Uran - M. Jonke: Izdelava in optimizacija - Developemnt and Optimisation varjencema in elektrodami petkrat večja, to je 540 mm2. Drugi pomembnejši podatek je, da mora varilni stroj zagotoviti zadosti veliko silo stiskanja med varjencema in zadosti veliko hitrost stiskanja bradavic med varjenjem [1]. Pri premajhni hitrosti stiskanja se namreč lahko zgodi, da se bradavica segreje do tališča in da se pojavi brizganje taline zaradi prevelike gostote toka v bradavici ali zaradi prepočasnega stiskanja varjencev. Telo pedala je pozicionirano vodoravno s pozicionirnim trnom za pesto. Stopalka prosto leži na ležišču spodnje elektrode. S tem je omogočeno razmeroma veliko odstopanje lege stika med telesom pedala in stopalko, kar pa še vedno zagotavlja izvedbo kakovostnega zvarnega spoja v dopustnih mejah odstopanja. Prav v tem, v možnosti manj natančnih toleranc polizdelkov, pa je ena večjih prednosti uporabe bradavičnega varjenja v primerjavi s talilnim obločnim varjenjem MAG. Poleg tega pa so tu še druge prednosti, ki smo jih že navedli v točki 2. 3.2 Elektrouporovno točkovno varjenje naslona stikala zavorne luči Naloga naslona stikala zavorne luči je, da vklaplja in izklaplja luč na zadnjem delu avtomobila, ki opozarja udeležence v prometu, da voznik avtomobila pred njim zavira. Naslon stikala mora biti izdelan iz kakovostnega jekla in dobro privarjen na telo zavornega pedala ([4] in [5]). Na sliki 4 je shematsko prikazan naslon stikala. Kakor je razvidno s slik 1 in 4, je treba po “stari” tehnologiji izdelati dva 6 mm dolga zvara in dva 10 mm dolga zvara v različnih legah. Pri varjenju kratkih varov pomenijo velik strošek vmesni časi med varjenjem posameznih varkov, še posebej, če se varjenje izvaja z varilnim robotom. and the electrodes should be five times that of the cross-sectional area, i.e. 540 mm2. It is also important that the welding machine should provide a sufficiently high contact force between the workpieces and a sufficiently high rate of projection pressing during welding [1]. If the rate of pressing is too low projection can heat up to the melting point and spatter occurs due to the current density being too high in the projection or due to the rate of pressing the workpieces together being too slow. The pedal body is horizontally positioned by means of a hub mandrel. The foot treadle lies freely in the bed of the lower electrode. This permits a comparatively large mismatch between the pedal body and the foot treadle, but still ensures a good quality welded joint within the allowable limits. This possibility of using semi-products that have less accurate tolerances is one of the greatest advantages of projection welding in comparison to MAG welding. Other advantages were mentioned in section 3. 3.2 Resistance spot welding of the stop-switch rest The purpose of the stop-switch rest is to switch the light at the rear of the car on and off to warn other road users that a driver is applying the brake. The stop-switch rest should be made of a high-quality steel and correctly welded to the brake-pedal body ([4] and [5]), see Fig. 4. From Figures 1 and 4 we can see that the old technology requires two welds that are 6 mm long and two welds that are 10 mm long in different positions. For the shorter welds the cost is increased because of the intervals between the welding of the individual weld beads, particularly if the welding is robotised. Sl. 4. Shematski prikaz naslonjala stikala zavorne luči z eno bradavico Fig. 4. Schematic representation of the stop-switch rest with a single projection ^uTsKsUIMliilKD stran 647 I^IMlfiHMlEC |VB§TO J. Tu{ek - M. Uran - M. Jonke: Izdelava in optimizacija - Developemnt and Optimisation Z novo tehnologijo bomo naslon stikala privarili na telo pedala z dvema zvarnima točkama. Eno bomo zvarili uporovno bradavično z vnaprej izdelano bradavico in eno točkovno uporovno s primerno oblikovanima elektrodama. Obeh zvarnih spojev ni mogoče izdelati bradavično, čeprav bi bilo to iz več vidikov zelo ugodno. Izdelava bradavic v celotnem izdelovalnem postopku ne pomeni praktično nobenega stroška. Prednosti bradavičnega varjenja v primerjavi z uporovnim točkovnim pa je splošno znana in je večkratna (lažje pozicioniranje, manjša obraba elektrod, lepši videz vara, vnaprej določeno mesto vara, ni brušenja elektrod). Po izbiri tehnologije varjenja naslona na telo pedala je treba izdelati vpenjalno pripravo, ki bi omogočila vpetje obeh varjencev in bradavično ter točkovno zvarjanje. Na sliki 5 je shematsko prikazana naprava, ki omogoča izvedbo zgoraj opisane tehnologije. 3.3 Hkratno varjenje stopalke in naslona stikala zavorne luči na telo pedala S celovito analizo vseh treh uporovno zvarjenih spojev stopalke in naslona stikala na telo zavornega pedala ter s študijem obeh priprav za vpetje varjencev smo prišli do sklepov, da je mogoče privariti oba elementa na zavorni pedal pri enem samem vpetju v eno samo vpenjalno napravo na enem stroju s tremi ločenimi viri toka za tri vare. Na sliki 6 je prikazana varilna naprava s sklopom za pozicioniranje in vpetje pedala na nakrčeno pesto. Slika prikazuje tudi osnovno ploščo 1 2 3 The new technology requires only two spot welds between the stop-switch rest and the pedal body. One spot weld will be made by projection welding with a projection provided in advance and the other one by spot welding using suitably shaped electrodes. It is not possible to make both welded joints by projection welding although this would be very favourable from several viewpoints. Making the projections costs almost nothing in terms of the entire production process. The advantages of projection welding are multiple and well known, i.e. positioning is easier to accomplish, the electrodes are subjected to less wear, the weld has a nicer appearance, the weld position is determined in advance, and there is no grinding of the electrodes required. After the technology for welding the stop-switch rest to the pedal body was selected, it was necessary to construct a fixture for the two workpieces and the projection as well as the spot welding. Figure 5 schematically shows such a fixture. 3.3 Simultaneous welding of the foot treadle and the stop-switch rest to the pedal body A thorough analysis of the three resistance welded joints of the foot treadle and the stop-switch rest to the pedal body shows that it is possible to weld the two components to the brake-pedal body by fixing them only once in a single fixture at a single machine using three separate current sources for the three welds. Figure 6 shows the welding device with the assembly for positioning and fixing of the pedal to the shrink hub. It also shows the base plate with the 4 5 6 7 Sl. 5. Shematski prikaz vpenjalne priprave za vpetje telesa pedala in naslona stikala zavorne luči ter lega obeh parov elektrod za bradavično in točkovno varjenje 1 - zgornja elektroda za bradavično varjenje naslona; 2 - pozicioniranje in vpetje pedala; 3 - izolacija; 4 -zgornji del priprave; 5 - varilne klešče za točkovno varjenje naslona; 6 - spodnji del priprave; 7 - spodnja elektroda za bradavično varjenje naslona Fig. 5. Schematic representation of the fixture for fixing the pedal body and the stop-switch rest and position of both pairs of electrodes, that is for projection and spot welding 1 - upper electrode for projection welding of the rest; 2 - positioning and fixing of the pedal; 3 - insulation; 4 - upper part of the fixture; 5 - welding pliers for spot welding of the rest; 6 - lower part of the fixture; 7 - lower electrode for projection welding of the rest 1 BnnBjfokJ][p)l]Olf|i[gO | | ^SSfiflMlGC | stran 648 J. Tu{ek - M. Uran - M. Jonke: Izdelava in optimizacija - Developemnt and Optimisation 1 2 3 4 5 6 7 8 9 Sl. 6. Prostorski prikaz naprave za privarjanje stopalke in naslona stikala zavorne luči na telo pedala 1 - pozicioniranje naslona; 2 - vodilo naslona; 3 - pozicionirni del; 4 - vodilo; 5 - spodnja miza; 6 - pritrditev klešč; 7 - klešče za varjenje naslona; 8 - naslon; 9 - telo zavornega pedala Fig. 6. 3D representation of the device for welding of the foot treadle and the stop-switch rest to the pedal body 1 - positioning of the rest; 2 - guidance for the rest; 3 - positioning part; 4 - guidance; 5 - lower table; 6 - fixing of pliers; 7 - pliers for welding the rest; 8 - rest; 9 - brake-pedal body z vsemi elementi za vpetje vseh treh varjencev in zvarjenje vseh treh zvarov. Dobro so vidni lega zgornje elektrode s pritrdilno mizo za varjenje stopalke, klešče za dovod toka na telo pedala skupaj s horizontalno premičnimi sanmi in horizontalne klešče za varjenje točkovnega zvara na naslonu. 4 ANALIZA UPOROVNO ZVARJENIH SPOJEV Po izčrpnem študiju in iskanju optimalnih rešitev enotne izvedbe celotnega sistema (sl. 6) za skoraj hkratno zvarjanje vseh treh zvarov smo morali za vsak zvar ugotoviti optimalne parametre. Za vse načine elektrouporovnega varjenja so najpomembnejši parametri sila stiskanja obeh varjencev med varjenjem, jakost toka in čas varjenja. Vse tri parametre lahko prikažemo v varilnem ciklusu. 4.1 Uporovno bradavično zvarjene stopalke na telo zavornega pedala Pri ugotavljanju optimalnih varilnih parametrov smo izvedli številne praktične poskuse v razumno širokem naboru parametrov. Merilo za optimalne parametre so bili mehanska trdnost spoja, način porušitve, analiza makro obrusa in vizualna ocena poteka postopka med varjenjem. Raziskave so pokazale, da je optimalna jakost toka med 20 kA in 25 kA, optimalni čas varjenja elements for fixing the three workpieces and welding the three welds. The position of the upper electrode with a fixing table for welding the foot treadle, pliers for current supply to the pedal body with a horizontally moving sleigh and horizontal pliers for making a spot weld at the rest are clearly shown. 4 ANALYSIS OF RESISTANCE WELDED JOINTS After a thorough study and investigating the best solutions for a uniform execution of the system (see Fig. 6) for almost simultaneous welding of the three welds, the optimum parameters for each weld had to be found too. With all resistance welding processes the most important parameters are the force of pressing the two workpieces together during welding, the welding current, and the welding time. These three parameters can be shown in a welding cycle. 4.1 Stop-switch rest projection welded to the pedal body In order to find the optimum welding parameters, numerous practical experiments were made with a reasonably large number of parameters. In terms of optimum parameters, the mechanical strength of the welded joint, an analysis of a macro specimen, and a visual assessment of the welding process were considered. The study showed that the optimum current intensity (I) ranged between 20 kA and 25 kA, gfin^OtJJlMISCSD 01-11 stran 649 I^BSSIfTMlGC J. Tu{ek - M. Uran - M. Jonke: Izdelava in optimizacija - Developemnt and Optimisation L 1 Sl. 7. Porušitev bradavično zvarjenega spoja stopalke in telesa zavornega pedala 1 - porušitev v osnovnem materialu Fig. 7. Failure of projection welded joint between the foot treadle and the brake-pedal body 1 - failure in parent metal med 9 in 11 periodami omrežnega toka ter optimalna sila stiskanja varjencev 19 kN. Na sliki 7 je prikazan posnetek porušitve spoja med stopalko in telesom pedala. Že iz samega načina porušitve lahko vidimo, da je trdnost spoja dobra, saj je do porušitve prišlo zunaj spoja v osnovnem materialu, in da je pred porušitvijo prišlo do močne deformacije stopalke. Za natančno ugotovitev velikosti prevaritve bradavic in toplotno vplivane cone okoli njih smo napravili makro obruse. Shematski prikaz makro obrusa je prikazan na sliki 8. 4.2 Bradavično in točkovno zvarjeni naslon stikala zavorne luči na telo pedala Podobno kakor zgoraj smo tudi tu z eksperimentalnimi rezultati ugotovili optimalne varilne parametre. Za bradavično zvarjanje znašajo: I = 5 do 8 the optimum welding time (t) between 9 and 11 periods of the mains current, and the optimum force of pressing (F) was 19 kN. Figure 7 shows a failure of the welded joint between the foot treadle and the pedal body. The mode of failure indicates that the strength of the joint was good since the failure occurred outside the joint, i.e. in the parent metal, and that prior to the failure, a strong deformation of the foot treadle occurred. In order to establish the penetration size of the projections and the heat-affected zone next to them we made macro specimens. An example is shown in Fig. 8. 4.2 Stop-switch rest projection and spot welded to the pedal body As with the previous example we again looked for the optimum welding parameters. For projection welding the optimum parameters were: I = 5 to Pločevina 6 mm 6 mm plate Zvarne leče Weld nuggets Stopalka - narebričena pločevina 2 mm Ribbed foot treadle 2 mm sheet Sl. 8. Shematski prikaz makro obrusa bradavično zvarjenega spoja stopalke in telesa zavornega pedala (I = 24,9 kA, t = 11 P = 0,22 s, F = 19,0 kN) Fig. 8. Schematic representation of a macro specimen of the projection welded joint between the foot treadle and the brake-pedal body (I = 24.9 kA, t = 11 P = 0.22 s, F = 19.0 kN) 1 BnnBjfokJ][p)l]Olf|i[gO | | ^SsFvWEIK | stran 650 J. Tu{ek - M. Uran - M. Jonke: Izdelava in optimizacija - Developemnt and Optimisation kA, t = 6 do 9 P, F = 5 kN. Optimalni vrednosti smo dobili s trdnostno analizo spoja po varjenju in z oceno poteka varjenja (brizganje). Za točkovno varjenje naslona pa optimalni parametri znašajo: I = 6,5 do 8 kA, t = 17 do 19 P in F = 5 kN. Shematsko prikazan makro obrus točkovno uporovno zvarjenega spoja naslona na telo pedala pa lahko vidimo na sliki 9. S slike so razvidni velikost zvarne leče, velikost toplotno vplivane cone in vtis v naslonu zaradi pritiska elektrode med varjenjem. Na debelejši pločevini, na telesu pedala, pa vtiska ne opazimo, ker je premer elektrode večji in je s tem specifični pritisk na pločevini manjši, kar vodi do manj prizadete in manjše toplotno vplivane cone. Pločevina 2 mm 2 mm sheet Zvarna leča Weld nugget 8 kA, t = 6 to 9 P, F = 5 kN. The optimum values were obtained by analysing the joint strength after welding and by assessing the welding process (spatter). With spot welding,the optimum parameters were: I = 6.5 to 8 kA, t = 17 to 19 P, and F = 5 kN. A macro specimen of the spot-welded joint between the stop-switch rest and the pedal body is schematically shown in Fig. 9. The figure shows the sizes of the weld nugget and the heat-affected zone as well as an indentation in the rest due to electrode pressure during welding. With the thicker plate, i.e. at the pedal body, no indentation is observable because the electrode diameter is larger and the specific pressure on the plate is smaller, which produces a smaller and less heat-affected zone. Odtis elektrode Electrode indentation Pločevina 6 mm Toplotno vplivane cone Toplotno vplivana cona 6 mm plate na 6 mm pločevini na 2 mm pločevini Heat-affected zones Heat-affected zone at 6 mm plate at 2 mm sheet Sl. 9. Shematski prikaz makro obrusa točkovno zvarjenega spoja med naslonom in telesom pedala Fig. 9. Schematic representation of a macro specimen of the spot welded joint between the rest and the pedal body 5 EKONOMSKA UPRAVIČENOST ZAMENJAVE TEHNOLOGIJE Z doslej napisanimi dejstvi v tem prispevku smo pokazali, da je zamenjava varilskih tehnologij s tehnološkega vidika mogoča in primerna. S preprostim ekonomskim izračunom želimo pokazati, da je bila zamenjava tudi potrebna in ekonomsko upravičena. Pri izračunu stroškov obločnega varjenja smo izračunali čase robotskega varjenja stopalke in dvakrat dveh zvarov naslona stikala. Pri tem smo poleg čistih časov varjenja upoštevali tudi druge čase: to so časi obračanja, vrtenja mize, prehodov robota, čiščenja gorilnika in časi, potrebni za pripravo varjenja. V izračunu stroškov porabljene električne energije smo upoštevali energijo za varjenje vseh varov, obračanje in pogon robota ter pogon vpenjalne mize z gnezdi. Izračunali smo stroške za porabljen zaščitni plin in varilno žico kot dodajni material in vse stoške dela, delovne sile in opreme. V stroške dela smo všteli ceno strojne ure, amortizacijo stoja, stroške prostora, vzdrževanja, potrošni material, stoske delovne sile z dejanskimi in pripravljalnimi 5 ECONOMIC JUSTIFICATION OF THE TECHNOLOGY SUBSTITUTION We have shown that the substitution of the welding technology is feasible and reasonable from the viewpoint of technology. A simple economic calculation should also show that the substitution was necessary and economically justified. When costing the arc welding we took into account the times required for robotic welding of the foot treadle and the two times for the two welds of the stop-switch rest. In addition to the welding times, we also considered the times for table rotation, the robot passages, the gun cleaning and the preparation for welding. The costs of electricity included the energy required for all the welds, turning and operating the robot and operating the fixing table with the clusters. The costs of the shielding gas and the wire filler material were calculated too. We also included into the calculations all the costs relating to workforce and machines. A similar calculation of the costs gfin^OtJJIMISCSD 01-11 stran 651 I^BSSIfTMlGC J. Tu{ek - M. Uran - M. Jonke: Izdelava in optimizacija - Developemnt and Optimisation ter režijskimičasi. Podobno smo ravnali pri izračunu stroŠkov pri uporabi nove varilske tehnologije. Tudi tu smo najprej izračunali čase varjenja vseh treh zvarnih spojev, nato stroške energije, stroške delovne sile, stroške stroja (amortizacija) ter stroške porabljenih elektrod. Povzetek vseh stroškov in časov za obe tehnologiji je podan v preglednici 1. Z izračuni smo ugotovili, da so stroški izdelave enega kosa z obločnim varjenjem 67,79 SIT in po uporovnem le 29,10 SIT, kar pomeni, da je z novo tehnologijo pri vsakem zvarjenem pedalu prihranek 38,69 SIT. S preprostim izračunom lahko ugotovimo, da bo investicija, če ta stane 12 mio SIT in če je letni obseg proizvodnje 220.000 kosov, povrnjena v osemnajstih mesecih. was made for the new technology. In this case the welding times for all the three welds were calculated first, then the costs of energy, the workforce, the machine (depreciation), and the electrodes. A summary of all the costs and the times for both technologies can be found in Table 1. The calculations made show that the cost of manufacture of one piece using arc welding amounts to 67.79 SIT and with resistance welding to 29.10 SIT, which means that 38.69 SIT can be saved by using the new technology. A simple calculation also shows that an investment of 12 million SIT would be paid off in eighteen months if the size of production is 220000 pieces per year. Preglednica 1. Primerjalna razpredelnica porabljenega časa, energije, pomožnega materiala, stroškov delovne sile in stroškov proizvodnih sredstev Table 1. A comparative table of the time, energy, auxiliary material consumed and of the costs of workforce and production means Obločno varjenje Arc welding Uporovno varjenje Resistance welding Čas varjenja / kos (min) Welding time/piece (min) 0,636 0,350 Strošek energije / kos (SIT) Cost of energy/piece (SIT) 1,262 0,210 Zaščitni plin / kos (SIT) Shielding gas/piece (SIT) 3,441 / Žica / kos (SIT) Welding wire/piece (SIT) 1,38 / Delavec / ura (SIT) Man-hour (SIT) 3070 2800 Stroj / ura (SIT) Machine hour (SIT) 2445 1900 Strošek elektrod / kos (SIT) Cost of electrodes/piece (SIT) 1592 6 MNENJE Za pravilno in verodostojno oceno kakovosti ter zahtevnosti opisanih raziskav in dobljenih rezultatov je treba dodati, da predstavljeni postopki, ki temeljijo na elektrouporovnem varjenju, niso standardne strojniške ali mehansko-preoblikovalne operacije, pri katerih sta potrebna orodje in mehanska sila, ampak so zapleteni metalurško-mehanski in elektromagnetno-fizikalni pojavi ki jih je bilo treba med raziskavo upoštevati. V prvi vrsti je izmenično magnetno polje, ki ga povzroči izmenični varilni tok z jakostjo več desettisoč amperov. Prav razmerje med ohmsko in induktivno upornostjo, ki je odvisno od številnih dejavnikov, lahko odigra pomembno vlogo. Velik 6 OPINION In order to assess the investigations made and the results obtained, it must be pointed out that the processes involved in resistance welding are not the conventional operations of mechanical engineering or mechanical forming using just tools and a mechanical force but very intricate metallurgical-mechanical and electromagnetic-physical processes. First we have an alternating magnetic field generated by an alternating current of more than several times 10000 A. The relationship between the ohmic and inductive resistances, which depends on a number of factors, can play a very important role. An impor- 1 SšnnatafcflM]! ma stran 652 J. Tu{ek - M. Uran - M. Jonke: Izdelava in optimizacija - Developemnt and Optimisation vpliv na to imajo oblika, velikost in vrsta materiala, ki je v “oknu” med dvema elektrodama. Pri velikem »oknu« med obema elektrodama, ali če so v oknu varjenec, del kovinske priprave ali drugi elementi, se jakost toka lahko »porazgubi« in se spremeni v jalovo energijo. Vse te dejavnike je bilo treba pri raziskovalnem, teoretičnem in eksperimentalnem delu upoštevati. To nam je po napornem delu tudi uspelo. Drugi problem pa so toplotne napetosti, ki se pojavijo v varjencu med varjenjem in po njem. Tudi tega smo s pravilno oblikovano vpenjalno napravo in s pravilnim vrstnim redom varjenja uspešno rešili. 7 SKLEP Z izdelavo nove tehnologije zvarjanja zavornega pedala za osebni avtomobil in z zamenjavo s staro obločno tehniko smo povečali produktivnost, izboljšali kakovost zvarov, zmanjšali izmet, izboljšali delovne razmere zaposlenih, zmanjšali potrebe po nabavi materiala (varilna žica, zaščitni plin). Najboljši sklep na koncu študije poda ugotovitev, da z novo tehnologijo varjenja pri vsakem pedalnem sklopu prihranimo 38,69 SIT in da bodo pri sedanjem obsegu proizvodnje investicijska sredstva povrnjena v enem letu in pol. tant influence is exerted by the shape, the size and the type of material in the space between the two electrodes. If this space is large or the workpiece, a part of the metal device or other elements are located in this space, current may get “lost” and transform into waste energy. All these factors had to be considered in the theoretical and experimental investigation. Eventually this was done successfully. Another problem are the thermal stresses occurring in the workpiece during and after welding. The problem was successfully solved by a correctly shaped fixture and a correct welding sequence. 7 CONCLUSION The substitution of the new technology of welding the brake pedal for a motor vehicle for the arc welding technology resulted in increased productivity, an improved weld quality, less scrap, improved working conditions for workers, lower consumption of the welding wire and the shielding gas. The most encouraging conclusion is that the new welding technology permits a saving of 38.69 SIT for each pedal assembly and the investment in the equipment can be paid off in a year and a half. 8 LITERATURA 8 REFERENCES [1] Rihar, G. (1988) Gradivo za seminar “Evropski inženir varilstva”; Ljubljana. [2] Kralj, V., Z. Kodrič, A. Koveš (1991) Točkovno uporovno varjenje; Institut za varilstvo; Ljubljana, 34-36. [3] Kordič (1987) Elektrootporno zavarivanje. Društvo za tehniku zavarivanja Hrvatske; Zagreb, 56-61. [4] PSA (1999) But de la procedure; Support pedale debrayage et de frein. [5] PSA (2000) Norma R 17 1103 - Mehanski sklopi za upravljanje vozila: Pedalni sklop, Nosilec pedalov kpl. iz pločevine. Naslova avtorjev: prof.dr. Janez Tušek Miro Uran Institut za varilstvo,d.o.o. Ptujska 19 1000 Ljubljana Miran Jonke Cimos commerce, do.o. Cesta Marežganskega upora 2 6000 Koper Authors’ Addresses: Prof.Dr. Janez Tušek Miro Uran Institute of welding Ltd. Ptujska 19 1000 Ljubljana, Slovenia Miran Jonke Cimos Commerce, do.o. Cesta Marežganskega upora 2 6000 Koper, Slovenia Prejeto: Received: 28.8.2001 Sprejeto: Accepted: 7.12.2001 stran 653 01-11 firTNEK © Strojni{ki vestnik 47(2001)11,654-661 © Journal of Mechanical Engineering 47(2001)11,654-661 ISSN 0039-2480 ISSN 0039-2480 UDK 629.3.018.4:629.351:004.94 UDC 629.3.018.4:629.351:004.94 Izvirni znanstveni ~lanek (1.01) Original scientific paper (1.01) Elasto-plasti~na analiza deformiranja naprave za za{~ito pred podletom za motorna vozila Elasto-Plastic Deformation Analysis of a Rear-Underrun Protection Device for Load-Carrying Vehicles Matej Glava~ - Zoran Ren - Martin Pra{ni~ki V prispevku je prikazan postopek računalniško podprtega simuliranja elasto-plastičnega deformiranja naprave za zaščito pred podletom od zadaj, ki omogoča oceno konstrukcijske rešitve pred homologacijo. Homologacijski pravilnik ECE R 58 namreč predpisuje način preskušanja zaščitne naprave, dopušča pa tudi, da zaščitno napravo poleg praktičnega preskušanja preverimo tudi z računalnikom. Prispevek prikazuje nadaljnji razvoj postopka elasto-plastičnega računalniškega simuliranja z metodo končnih elementov, ki smo ga predstavili na IAT 99 [5]. Rezultati elasto-plastične analize obetajo možnost optimiranja zaščitne naprave v fazi konstruiranja brez izvedbe praktičnih preskusov. Računalniško simuliranje tudi precej poceni postopek homologacije novih naprav. © 2001 Strojniški vestnik. Vse pravice pridržane. (Ključne besede: naprave zaščitne, zaščita pred podletom, preskušanje, simuliranje računalniško) The paper describes a procedure for simulating the elasto-plastic behaviour of a rear-underrun protection device (RUPD), which can be used to estimate whether the design fulfils the ECE R 58 regulation. This regulation prescribes practical device testing, but also allows a computational safety inspection of the protection device. The paper also includes the development of the elasto-plastic computational simulation using the finite-element method that was presented at IAT 99 [5]. The results of the elasto-plastic analysis simulations lead to the conclusion that this method can be used to optimize the RUPD in the design process without the need for practical testing. Computational simulation also reduces the cost of the approval procedure. © 2001 Journal of Mechanical Engineering. All rights reserved. (Keywords: protection devices, rear underrun protection, experimental testing, computational simulations) 0 UVOD Motorna tovorna vozila morajo imeti na zadnji površini vgrajeno zaščitno napravo, ki jo imenujemo tudi podletna zaščitna naprava. Njena naloga je, da prepreči zagozditve osebnega ali podobnega nizkega vozila pod tovornim vozilom pri naletu od zadaj (sl. 1). S tem je zagotavljena večja varnost potnikov. 0 INTRODUCTION A load-carrying vehicle must be equipped at the rear with a safety device called a rear-underrun protection device (RUPD). It is intendent to prevent vehicles being wedged under the chassis during accidental crashes from behind (Fig. 1). This device significantly increases the safety of road users. Sl. 1. Naprava za zaščito pred podletom Fig. 1. The rear underrun protection device (RUPD) 1 BnnBjfokJ][p)l]Olf|i[gO | | ^SSfiFlMlGC | stran 654 M. Glava~ - Z. Ren - M. Pra{ni~ki: Elasto-plasti~na analiza - Elasto-Plastic Analysis Pravilnik ECE R 58 [1] predpisuje pogoje, ki jih mora zaščitna naprava izpolnjevati, da proizvajalec zanjo pridobi ustrezno homologacijsko dovoljenje v Sloveniji. Ena najpomembnejših zahtev pravilnika določa največjo dovoljeno deformacijo zaščitne naprave pod vplivom sil, ki delujejo v smeri vzdolžne osi vozila. Pravilnik predpisuje praktični preskus naprave na preskuševališču z obremenjevanjem na določenih mestih. Kadar gre za zaščitno napravo samo, ki je namenjena za vgradnjo v neznano vozilo, je praktični preskus obvezen. Če je zaščitna naprava integrirana v nadgradnjo tovornega vozila, praktični preskus ni obvezen, če lahko z računom dokažemo, da zaščitna naprava zadostuje predpisu ECE R 58. Ker preskusna sila v večini primerov povzroči plastično preoblikovanje zaščitne naprave, je treba izvesti elasto-plastični preračun naprave. V fazi konstruiranja zadovoljevanje izmer zaščitne naprave praviloma ne pomeni problema. Problem pa se pojavi pri optimiranju mase in trdnosti. Zaščitna naprava večji del svoje dobe trajanja ne rabi praktičnemu namenu, zato je z vidika gospodarnosti mase vozila zgolj nepotreben balast. Vendar pa mora naprava v primeru trka od zadaj učinkovito preprečiti zagozditev vozila pod karoserijo in s tem zmanjšati možnost kritičnih poškodb potnikov v nesreči udeleženega vozila. Možnost računskega preverjanja zadostitve zahtevam predpisov za pridobitev homologacije je vspodbudila raziskavo uporabe računalniškega simuliranja deformiranja zaščitne naprave. V ta namen je bila uporabljena metoda končnih elementov, ki omogoča zelo dobro ponazoritev elasto-plastičnega deformiranja zaščitne naprave pod obremenitvijo. Metoda je uporabna tudi že v zgodnji fazi razvoja, še preden je izdelan prvi prototip zaščitne naprave. 1 PRAKTIČNI PRESKUS PO PRAVILNIKU ECE R 58 Pravilnik ECE R 58 natančno predpisuje izmere zaščitne naprave, odvisne tudi od izmer vozila, na katerega je vgrajena. Predpisana preskusna sila deluje na zaščitno napravo prek hidravličnega bata, katerega naležna površina meri največ 250 mm v višino in 200 mm v širino ter mora biti na robovih zaobljena. Bat mora biti povezan z batnico preskusnega stroja s krogelnim zgibom, ki omogoča prosto prilagajanje naležne površine deformacijam zaščitne naprave. Pravilnik ECE R 58 predpisuje tri različne obremenitvene primere glede na velikost preskusne sile in točko delovanja (sl. 2), in sicer: P1 - vodoravna sila velikosti 25 kN ali 12,5 % mase vozila, karkoli je manjše, ki deluje zaporedoma v The ECE R 58 [1] regulation prescribes the conditions that must be fully met by the RUPD or the load-carrying vehicle, if such a vehicle is to be registered in Slovenia. The most important condition is the RUPD’s resistance to loading forces acting along or parallel to the vehicle’s longitudinal axis. The regulation also calls for practical RUPD testing on a testing machine, where the RUPD is subject to prescribed loads at some particular loading points. Practical testing is required for all standard mounted RUPDs. However, for a standard RUPD, which is already mounted on serial production vehicles or RUPD, and which is an integral part of the vehicle chassis, the practical testing is not necessary, if it can be proven with a calculation that the RUPD fully complies with the ECE R 58 regulations. Since the RUPD usually undergoes plastic deformation when subjected to the test forces, it is therefore necessary to perform an elasto-plastic analysis. Usually it is not difficult to fulfil the design demands during the design phase of the RUPD. But a problem occurs as soon as the RUPD’s mass and stiffness need to be optimized. During most of its lifetime the RUPD does not have a function and represents, from the economic viewpoint, only ballast. However, in the event of a crash, the RUPD prevents other vehicles from being wedged under the chassis and so reduces the level of critical injuries to road users involved in a crash. The possibility of a computational RUPD safety inspection prompted research into the possibilities of a computational simulation of RUPD behaviour under loading. A computational simulation based on a finite-element method allows for a better estimation of the device’s elasto-plastic deformation behaviour under a variety of loadings. The described method can also be used in the early development stage of the RUPD. 1 PRACTICAL DEVICE TESTING ACCORDING TO ECE R 58 The ECE R 58 regulation provides strict requirements in terms of device design depending on the dimensions of the vehicle that the protection device is mounted on. The prescribed testing forces should be applied to the device via a loading surface not more than 250-mm high and 200-mm wide, with a radius at the vertical edges. The loading surface (piston) must be connected to the piston rod of the testing machine with a ball joint, which enables free adaptation of the loading surface to the deforming protection device. The ECE R 58 regulation prescribes the following three different load cases in terms of the testing-force size and its loading position (Fig. 2): P1 – a horizontal force of 25 kN or 12,5% of the force generated by the maximum mass of the vehicle, whichever is smaller, should be applied | lgfinHi(š)bJ][M]lfi[j;?n 0111 stran 655 I^BSSIfTMlGC M. Glava~ - Z. Ren - M. Pra{ni~ki: Elasto-plasti~na analiza - Elasto-Plastic Analysis Sl. 2. Točke delovanja preskusnih sil Fig. 2. The points of testing-force application dveh točkah, ki sta oddaljeni 300±25 mm od največje širine zadnje osi vozila proti sredini zaščitne naprave, P - vodoravna sila velikosti 100 kN ali 50 % mase vozila, karkoli je manjše, ki deluje v dveh točkah, ki sta simetrični glede na srednjo navpično ravnino naprave oziroma vozila in sta med seboj oddaljeni za 700 do 1000 mm, P3 - vodoravna sila velikosti 25 kN ali 12,5 % mase vozila, karkoli je manjše, ki deluje na srednji navpični ravnini zaščitne naprave. Zaščitna naprava zadosti predpisu, če skupna oddaljenost točke, v kateri deluje preskusna sila, od zadnjega skrajnega roba vozila v vzdolžni osi vozila ne preseže vrednosti 400 mm med delovanjem preskusne sile. 2 RAČUNALNIŠKA ANALIZA ZAŠČITNE NAPRAVE Za računalniško preverjanje zaščitne naprave je uporabljena metoda končnih elementov, ki da ob pravilni določitvi robnih pogojev zelo dobre rezultate tako v elastičnem kakor tudi v plastičnem področju deformiranja. consecutively to two points located 300+25 mm from the outer edges of the wheels on the rear axle towards the centre of the protection device, P - a horizontal force of 100 kN or 50% of the force generated by the maximum mass of the vehicle, whichever is smaller, should be applied consecutively to two points situated symmetrically about the vertical cente line of the device or the vehicle at a minimum distance apart of 700 mm and a maximum of 1000 mm, P3 - a horizontal force of 25 kN or 12,5% of the force generated by the maximum mass of the vehicle, whichever is smaller, should be applied at the median vertical plane of the protection device. The protection device can be approved if during and after testing with the prescribed forces the horizontal distance between the RUPD and the outermost rear end of the vehicle does not exceed 400 mm. 2 COMPUTATIONAL ANALYSIS OF THE PROTECTION DEVICE The finite-element method was used for the computational analyses of the protection device. If the boundary conditions are well defined, this method gives very good results in the elastic and elasto-plastic regions of deformation. Sl. 3. Zamrežen model zaščitne naprave Fig. 3. Discretised model of the protection device 1 BnnBjfokJ][p)l]Olf|i[gO | | ^SSfiflMlGC | stran 656 M. Glava~ - Z. Ren - M. Pra{ni~ki: Elasto-plasti~na analiza - Elasto-Plastic Analysis Analizirana zaščitna naprava je sestavljena iz dveh pokončnih stebrov in prečnega profiliranega nosila (branik). Prečno nosilo je privijačeno na pokončna stebra s štirimi vijaki. Pokončna stebra sta izdelana iz jekla z naslednjimi podatki: modul elastičnosti Eel = 2,068x105 MPa, modul plastičnosti E l = 2,068x104 MPa, Poissonovo število v = 0,29, p meja plastičnosti a > 260 MPa ter porušitvena trdnosta>420 MPa. Prečni profiliran branik je izdelan iz aluminijaste zlitine s podatki: E l = 7,5x104 MPa, E l = 7,5x103 MPa, v = 0,33,c= 195 MPa tercM = 216 MPa. trdno The subject of our computational analysis is a real protection device that consists of two vertical pillars and a transversal cantilever. The transversal profile is fastened onto vertical pillars with four bolts. The vertical pillars are made of steel profiles with the following properties: Young’s modulus El = 2,068x 105 MPa, Poisson’s ratio v = 0,29, yield stress a > 260 MPa and ultimate stress aM > 420 MPa. The transversal profile is made of aluminium alloy with the following properties: Ee = 7,5x104 MPa, v = 0,33, a= 195 MPa andaM = 216 MPa. fixed vrzelni element (stik) gap dements (contact) spojni vozli (čepi) ititTwd nodes [bolls I Sl. 4. Stranski pogled zaščitne naprave in robni pogoji Fig. 4. Side view of the protection device and boundary conditions Sl. 5. Obremenitev zaščitne naprave Fig. 5. The loading of the protection device Zaščitna naprava je modelirana enako, kakor je to razloženo v [5] (sl. 3). Model sestoji iz 11480 štirikotnih tankostenskih lupinskih končnih elementov. V področju vijačnih zvez med stebroma in branikom so vozlišča končnih elementov spojena. Na mestih naleganja prečnega branika in navpičnega stebra je med oba vstavljenih 384 posebnih vrzelnih elementov, ki med numeričnim reševanjem problema zagotavljajo stik (sl. 4). Glede na glavne podatke vozila in zaščitne naprave ter pogoje praktičnega preskusa [5], so The protection device is modelled as described in [5] (Fig. 3). The model is fully discretised with 11480 thin-shell linear four-noded finite elements. The bolt connections of the transversal and vertical profiles are modelled by merging the nodes on the flanges, which resemble 4 bolt connections. At points where the transversal and vertical profiles contact, 384 special gap elements are used, which ensure contact between the profiles during the computational analysis (Fig. 4). Following from the basic vehicle and protection-device data and the requirements of gfin^OtJJlMISCSD 01-11 stran 657 I^BSSIfTMlGC M. Glava~ - Z. Ren - M. Pra{ni~ki: Elasto-plasti~na analiza - Elasto-Plastic Analysis določene velikosti preskusnih sil P, P in P in lega točk obremenjevanja na naletni površini prečnega branika (sl. 3, 5): v vodoravni smeri: P1 = 25 kN levo ali desno v razdalji 950 mm od srednje navpične ravnine naprave, P = 100 kN levo ali desno v razdalji 500 mm od srednje navpične ravnine naprave, P = 25 kN na srednji navpični ravnini naprave, v navpični smeri: P1, P2 in P : 100 mm od spodnjega roba prečnega profila. Preskusna sila je predpisana kot normalni tlak na končne elemente v območju naleganja površine preskusnega bata na zaščitno napravo. Za analizo po metodi končnih elementov sta bila uporabljena programska paketa I-DEAS Master Series 8.0 [4] ter MSC.Nastran 70. 5 [6]. I-DEAS Master Series je rabil za pripravo mreže končnih elementov ter predstavitev rezultatov analize, MSC.Nastran pa za dejanski preračun po metodi končnih elementov. Ker program I-DEAS ne podpira celotnega zapisa v formatu MSC.Nastran za nelinearno analizo, je bila v vmesno datoteko zapisana zgolj geometrijska oblika končnih elementov. Fizikalne in materialne lastnosti ter nadzorni parametri preračuna pa so bili v vhodno datoteko programa MSC.Nastran vneseni ročno. Za preveritev modela je bila v prvi fazi izvedena elastična analiza z modulom MSC.Nastran 101. Za elasto-plastično analizo zaščitne naprave je bil uporabljen modul MSC.Nastran 106, ki omogoča statično nelinearno elasto-plastično analizo. Pri tem je bila lupinskim končnim elementom samodejno omejena 6. prostostna stopnja (rotacija okoli normalne osi lupinastega končnega elementa), ki v formulaciji elementa matematično ni definirana. S tem je bila zagotovljena stabilnost numeričnega preračuna. Za vsako lego delovanja preskusne sile sta bila predpisana po dva obremenitvena primera. Prvi je obsegal obremenitev zaščitne naprave z imensko vrednostjo preskusne sile, drugi pa popolno razbremenitev. Slednji obremenitveni primer je rabil za določitev preostale trajne deformacije. Zaradi nelinearnosti numeričnega preračuna je bila obremenitev po korakih večana v dvajsetih enakih prirastkih (od 0 do P), medtem ko je razbremenitev potekala v desetih enakih korakih (od P do 0). Togostna matrika sistema je bila obnovljena pri vsakem prirastku obremenitve. 3 PRIMERJAVA REZULTATOV Deformacije zaščitne naprave pod preskusnimi silami so prikazane na slikah 6, 7 in 8. Primerjava rezultatov praktičnega preskusa in računalniškega simuliranja je podana v preglednici 1. Kot pomik pod silo je v primeru ^BSfirTMlliC | stran 658 practical testing (see [5]), the magnitude and application positions of the testing forces P1, P2 and P3 on the surface of the transversal profile are (Fig. 3, 5): in the horizontal direction: P1 = 25 kN left and right at a distance of 950 mm from the median vertical plane of the device, P2 = 100 kN left and right at a distance of 500 mm from the median vertical plane of the device, P3 = 25 kN in the median vertical plane of the device, in the vertical direction: P1, P2 and P3: 100 mm from the bottom edge of the transversal profile. The test forces are applied as a constant normal pressure on the shell finite elements in the contact area between the loading surface and the transversal profile. The engineering computer systems SDRC/ I-Deas 8.0 [4] and MSC.Nastran 70.5 [6] were used for this study. I-Deas 8.0 was used for mesh generation and visualization of the results, while MSC.Nastran was used as a solver. Since the I-Deas does not support the complete Nastran format for the nonlinear analysis, only the geometry of the finite elements was written into the intermediate file. Physical and material properties and the control parameters of the calculation were entered into the MSC.Nastran input file manually. For the purpose of model validation an elastic analysis with the Nastran module 101 was conducted first. Only then was the Nastran module 106 used for the elasto-plastic analysis of the protection device. This module is dedicated for a static elasto-plastic analysis. Since the 6th degree of freedom (rotation around the normal axis) of the thin shell elements used is mathematically not defined, it was automatically bounded. This ensured the stability of the computational analysis. Two load sets were defined for every position of the test force. The first was used to simulate the deformation under test forces. The second simulated the unloading of the testing force and was used to estimate the permanent (plastic) deformation of the RUPD. For the purpose of nonlinear computational analysis the load was incrementally increased (from 0 to Px) in twenty equal steps, while the load was decreased (from Px to 0) in ten equal increments in the unloading phase. The stiffness matrix of the system was updated at every increment. 3 COMPARISON OF RESULTS Deformation of the protection device under the testing force is shown in Figures 6, 7 and 8. The comparison of the practical testing and the computer simulation results is given in Table 1. For the case of the practical testing the displacement M. Glava~ - Z. Ren - M. Pra{ni~ki: Elasto-plasti~na analiza - Elasto-Plastic Analysis Sl. 6. Pomiki (mm) strukture zaščitne naprave pod preskusno silo P Fig. 6. Displacements (mm) of the protection device under test force P1 preskusa upoštevan pomik preskusnega bata (središča obremenjevane površine), merjen med obremenjevanjem zaščitne naprave, v primeru računalniškega simuliranja pa povprečni pomik srednje linije zgornje in spodnje naletne površine v območju obremenitve. Trajni pomik je pomik zaščitne naprave na mestu delovanja sile, ki pri praktičnem preskusu ostane po razbremenitvi. Primerjava rezultatov kaže na dobro ujemanje simuliranih pomikov s pomiki, izmerjenimi pri preskusu. Preskušana naprava vsekakor zadovoljuje homologacijske zahteve, saj je skupna največja vodoravna razdalja med deformirano zaščito in skrajnim zadnjim robom vozila enaka 150 + 21 = 171 mm in tako ni večja od dovoljene največje razdalje 400 mm under force is the displacement of the loading piston (the centre of the loading surface) measured during the force application to the protection device, while in the case of the computational simulation this is the average displacement on the median vertical line of the lower and upper contact loading surface. The permanent displacement is the displacement of the protection device still present at the point of force application after the unloading during practical testing. The comparison of results indicates good agreement between simulated and actually measured displacements during testing. The tested device fully complies with the requirements, since the total largest horizontal distance between the RUPD and the outermost rear end of the vehicle is equal to 150 + 21 = 171 mm, which is well below the allowable distance of 400 mm. Sl. 7. Pomiki (mm) strukture zaščitne naprave pod preskusno silo P Fig. 7. Displacements (mm) of the protection device under test force P2 ^vmskmsmm 01-11 stran 659 I^BSSIfTMlGC M. Glava~ - Z. Ren - M. Pra{ni~ki: Elasto-plasti~na analiza - Elasto-Plastic Analysis Sl. 8. Pomiki (mm) strukture zaščitne naprave pod preskusno silo P Fig. 8. Displacements (mm) of the protection device under test force P3 Preglednica 1. Primerjalne vrednosti rezultatov preskusa in računalniškega simuliranja Table 1. Comparison of test and computational simulation results Obremenitveni primer Loading case P1 P2 P3 Preskusna sila Testing force [kN] Pomik pod silo Trajni pomik Displacement under force Permanent displacement [mm] [mm] Preskus Test Simulacija Simulation Preskus Test 25 21 20 4 5 100 12,4 10,8 3 2,3 25 7,6 6,3 0,5 0,5 Simulacija Simulation 4 SKLEP Prispevek prikazuje možnost uporabe računalniško podprtega simuliranja homologiranja naprave za preprečevanje podleta od zadaj. Rezultati elasto-plastične analize se dobro ujemajo s praktičnim preskusom. To vodi k ugotovitvi, da se predstavljena metoda lahko uporabi za homologacijo zaščitnih naprav. Ker je potrebno zgolj virtualno testiranje, in ne drago praktično testiranje, so prihranki pri postopkih homologacije zaščitnih naprav precejšnji. MSC. Nastran se je izkazal kot primerno in učinkovito orodje za izvajanje takšnih analiz. Metoda je uporabna tudi za konstruiranje in optimiranje novih podletnih naprav in se s tem namenom trenutno uporablja v podjetju RTI d.o.o. 4 CONCLUSION The paper illustrates the possibilities of applying computational simulation for the purpose of RUPD approval. The results of elasto-plastic computational analysis show a good agreement with the experimental results. This leads to the conclusion that the presented computational procedure can be safely used for approval of the RUPD. The potential savings are substantial, since only virtual testing is required, which is far cheaper than regulated experimental testing. The MSC.Nastran system is clearly an appropriate and extremely efficient tool for such simulations. The procedure is also suitable for design and optimisation of new RUPDs and is currently being used in RTI for this purpose. 5 REFERENCE 5 REFERENCES [1] Odredba o homologiranju naprav za preprečevanje podleta od zadaj, vozil glede na montažo naprav za preprečevanje podleta in vozil glede na zaščito pred podletom (št. 58.01), Uradni list Republike Slovenije, št. 3, 20.1.1995, 182-183. 1 BnnBjfokJ][p)l]Olf|i[gO | | ^SSfiFlMlGC | stran 660 M. Glava~ - Z. Ren - M. Pra{ni~ki: Elasto-plasti~na analiza - Elasto-Plastic Analysis [2] [3] [4] [5] [6] Zienkiewicz, O.C, and R.L. Taylor (1989) The finite element method, IVth Ed., Volume 1 - Basic formulation and linear problems, McGraw-Hill Book Company. Zienkiewicz, O.C, and R.L. Taylor (1991) The finite element method, IVth Ed., Volume 2 - Solid and fluid mechanics dynamics and non-linearity, McGraw-Hill Book Company. I-DEAS-Master series, User’s Guides, 1997 Ren, Z., M. Prašnički, M. Glavač(1999) Računalniško preverjanje ustreznosti zaščitne naprave pred podletom motornih tovornih vozil, Strojniški vestnik 11. MSC.Nastran-Handbook for nonlinear analysis, 1992. Naslova avtorjev: Matej Glavač mag. Martin Prašnički RTI do.o. Ptujska 184 2000 Maribor profdr. Zoran Ren Univerza v Mariboru Fakulteta za strojništvo Smetanova 17 2000 Maribor Authors’ Addresses: Matej Glavač M.Sc. Martin Prašnički RTI Ltd. Ptujska 184 2000 Maribor, Slovenia Prof.Dr. Zoran Ren University of Maribor Faculty of Mechanical Eng. Smetanova 17 2000 Maribor, Slovenia Prejeto: Received: 21.8.2001 Sprejeto: Accepted: 7.12.2001 stran 661 01-11 ilTMDDC © Strojni{ki vestnik 47(2001)11,662-671 © Journal of Mechanical Engineering 47(2001)11,662-671 ISSN 0039-2480 ISSN 0039-2480 UDK 629.33:629.3.018 UDC 629.33:629.3.018 Pregledni znanstveni ~lanek (1.02) Review scientific paper (1.02) Dolo~itev imenske mo~i motorja s poskusom pospe{evanja vozila Determining an Engine’s WOT Performance from a Vehicle Speed-Up Test Vladimir Medica - Branko Imper - Zoran Imper V prispevku so prikazani rezultati novo razvite metode, potrebnih naprav in postopka za določitev imenske moči motorja s preskušanjem pospeševanja vozila. Preverjanje karakteristike motorja navadno zahteva demontiranje pogonskega motorja iz vozila pred meritvijo na preskusni zavori, ali pa je treba med motor in preostali del pogonskega sistema vozila vgraditi ustrezen dajalnik vrtilnega momenta. V prispevku predstavljena metoda je preprosta in zanesljiva. Vgraditev merilnih naprav je zelo preprosta, za uspešno meritev pa ni treba odstraniti nobenega sestavnega dela vozila. Metoda omogoča, da izmerimo imensko moč motorja s tremi preskusi: ene meritve pri zaviranju in dveh meritev pospeševanja vozila. Pri tem potrebujemo za izračun moči motorja le omejeno število vhodnih - izmerjenih podatkov. © 2001 Strojniški vestnik. Vse pravice pridržane. (Ključne besede: motorji avtomobilski, karakteristike motorjev, modeli matematični, meritve) We present a newly developed method, devices and a procedure for determining an engine’s wide-open throttle (WOT) performance from a vehicle speed-up test. The control of an engine’s performance often requires that the engine is dismantled from the vehicle in order to be able to conduct engine braking test on a bench, or it is necessary to build a torque meter into the drive train of the vehicle. The presented method is very simple and reliable. The mounting of the devices is also very simple, with no need to dismantle any part from the vehicle. The method enables us to derive the WOT performance from three probes, one vehicle deceleration test and two vehicle acceleration tests. The collected test data are processed together with only limited vehicle input data to derive accurate engine-performance figures. © 2001 Journal of Mechanical Engineering. All rights reserved. (Keywords: automotive engines, engine performance, mathematical models, measurements) 0 UVOD Meritev moči motorja navadno opravimo z meritvami na preskuševališču z uporabo ustreznih preskusnih zavor. Motor je treba pred meritvijo odstraniti iz vozila in ga šele potem pritrditi na merilno zavoro. Omenjeni postopek nas omejuje pri izvajanju meritev na motorju v pogostejših oziroma zaradi vzdrževanja zaželenih in predpisanih časovnih korakih. Poznavanje trenutne moči motorja lahko izdatno pomaga pri ugotavljanju stanja motorja. Poleg meritev moči motorja na zavori je mogoče moment motorja ugotoviti tudi z uporabo merilnika momenta v pogonskem sklopu vozila. Ne nazadnje določamo moč motorja tudi na preskuševališču - zavori za vozila z valji Tam seveda lahko izmerimo moč na kolesih vozila. Pri tem postopku se vozilo ne premika, kolesa pa poganjajo valje merilne naprave. Z izmerjenim navorom pri zaviranju in hitrosti vozila lahko izračunamo pogonsko moč vozila. Preskuševališče z valji je po izmerah zelo veliko in zelo drago. 0 INTRODUCTION The performance of an engine can be measured on an engine test bed using an appropriate engine-braking device. To carry out these measurements it is necessary to dismantle the engine from the vehicle. This puts some limits on the practicality of performing these measurements at regular intervals or during regular servicing periods. A knowledge of the engine’s performance could be very useful in evaluating the health of the engine. Instead of measuring an engine’s performance on an engine test bed it is also possible to use a torque meter to determine the engine’s torque in the vehicle drive train, however, this procedure necessitates dismantling the drivetrain parts. There is also the possibility of using a vehicle-brake-test stand with rollers, which is adapted for measuring the driving power on the vehicle’s wheels. The vehicle is fixed to the building’s structure and vehicle’s wheels drive braking rollers. The drive 1 BnnBjfokJ][p)l]Olf|i[gO | | ^SSfiFlMlGC | stran 662 V. Medica - B. Imper - Z. Imper: Dolo~itev imenske mo~i - Determining a WOT Performance Omenjenih merilnih naprav ne srečujemo pogosto v manjših ali celo večjih servisnih delavnicah. V prispevku je opisana nova merilna naprava, ki omogoča določitev imenske moči motorja pri polnem plinu (v nadaljevanju PPP - WOT) s testom pospeševanja vozila. Naprava je zelo preprosta tako po zgradbi kakor tudi pri uporabi. Pri meritvah ni treba izgraditi iz vozila niti motorja, niti katerega koli drugega sestavnega dela vozila. S tem ohranimo tudi jamstvo izdelovalca vozila in izključimo možnosti za okvare delov zaradi nestrokovnega posega. Predstavljena naprava sestoji iz prenosnega osebnega računalnika (laptop, notebook ipd.), naprave z zaznavalom za merejenje vrtilne frekvence koles, električnih kablov in ustreznih računalniških programov V računalnik je treba poprej vnesti osnovne tehnične podatke o vozilu in prenosu. Poleg tega potrebujemo še vodoraven, vsaj 1 km dolg odsek preskusnega cestišča, ki ni obremenjen s prometom. Preskuse lahko opravimo v lepem, suhem vremenu brez vetra. Preskus sestavljajo tri faze: en del s prostim zaustavljanjem vozila in dveh meritev s prostim pospeševanjem vozila (v drugi in tretji prestavi). Programska oprema omogoča pobiranje in obdelavo zbranih podatkov do končnega poročila. Zbrani podatki ostanejo spravljeni v računalniku za kasnejše primerjave oziroma ponovljene preskuse. Pri zasnovi metode je bilo predpostavljeno, da doseže pogonski motor med testom pospeševanja vozila navidezno ustaljeno stanje hitreje kakor se spremeni njegova vrtilna frekvenca. Ta predpostavka je upravičena le pri uporabi sesalnih motorjev. Merilna metoda je le delno uporabna za tlačno polnjene motorje zaradi značilnega “časovnega zaostajanja” teh motorjev Uporabimo jo lahko pogojno tudi za težja gospodarska vozila s tlačno polnjenimi motorji (s turbopolnilnikom na izpušne pline), vendar mora biti preskus pospeševanja znatno daljši, vozilo pa moramo voziti v višjih prestavah. 1 OPIS MATEMATIČNEGA MODELA Povezavo med hitrostjo vozila in vrtilno frekvenco vozila podaja enačba: Do vrtilne frekvence motorja lahko pridemo prek prestavnega razmerja prenosnika moči in vrtilne frekvence koles: Kadar se motor pospešuje pri določeni vrtilni frekvenci koles vozila, potrebujemo za pospeševanje vozila in za premagovanje uporov (aerodinamičnega, hidrodinamičnega kotalnega in drsnega) ustrezno moč: power is calculated from the braking torque and the vehicle’s speed. This type of test stand is usually large and expensive, and these devices are not usually found in small servicing facilities. This paper presents a new device that can determine the wide-open throttle (WOT) performance of an engine from a vehicle speed-up test. This device is very simple and easy to use and the procedure does not involve the dismantling of the engine or the vehicle’s parts. The vehicle’s warranty is preserved and there is no intervening in any vital part of the vehicle’s engine. The device consists of a portable computer (laptop, notebook or similar), a sensing device for the wheel’s rotation, wiring and software. It is necessary to input basic vehicle data and drive train parameters. It is also necessary to find an approximately horizontal and straight section of road with a length of 1 km or more. These tests should be made when the traffic is light and when the weather is dry and without wind. The measurement procedure consists of three parts: a single vehicle free-decelerating test and two vehicle accelerating tests (in 2nd and 3rd gears). The software collects and processes the sampled data and then produces a final report. Sampled data are saved for later use or further processing. During the development of the device it was assumed that the engine driving the vehicle during the speed-up test reached the quasi-steady state faster than the engine speed changes. This assumption holds for naturally aspirated engines but is of limited use for turbocharged engines due to turbo-charger lag. Nevertheless, the device could be used even for turbocharged engines in long-term vehicle speed-up tests in higher gears and on long straight tracks. 1 MATHEMATICAL MODEL The relation between the vehicle’s speed and the wheel’s rotation frequency is: v = aR = 2%Rn (1). The drive train transmission ratio relates the engine’s rotation frequency to the wheel’s rotation frequency: (2). When the engine accelerates the vehicle at a given wheel-rotation frequency, the engine’s power is needed to accelerate the vehicle and to overcome all friction losses due to the aerodynamic, hydrodynamic, rolling and sliding frictions. Pen (nw )hdt = Pacc (nw )+Pfr (nw (3). stran 663 01-11 firTNEK V. Medica - B. Imper - Z. Imper: Dolo~itev imenske mo~i - Determining a WOT Performance Moč za pospeševanje vozila se porablja za The power for the vehicle’s acceleration premagovanje vozila s potniki oziroma tovorom, za consists of the parts required to increase the povečanje kinetične energije pri premočrtnem gibanju translational kinetic energy of the vehicle (with vozila in tistega dela, ki povečuje kinetično energijo passengers and payload) and the rotational kinetic vrtečih se delov prenosnika moči. energy of the drive train. Pacc (nw mvvv d Jw2 ef w dt mvvv d 2 dt Jw2 dt mvRw2nw dt dt 4J 2 dnw ef w dt Pacc ( nw )=^2nw(mvRw2+Jef) dnw dt (4), (5), (6), (7). Celotni dejanski masni vztrajnostni moment vrtenja prenosnika moči sestavljajo posamezni vztrajnostni momenti pogonskih koles vozila, vrtečih se delov prenosnika in vrtečih se delov pogonskega motorja z vztrajnikom: The drivetrain’s effective moment of inertia is the sum of the vehicle’s wheels’ moments, the drive train’s parts’ moments and the engine with flywheel and coupling, which are all related to the vehicle’s wheels: J ef 2-1 w,i + 2-1 dt,j + J encidt j (8). V večini primerov zgoraj omenjenih treh posameznih masnih vztrajnostnih momentov vnaprej ne poznamo. Ta nepoznani podatek lahko dobimo s pomočjo dveh preskusov pospeševanja vozila v različnih prestavah (v tem primeru v drugi in tretji prestavi). V prikazanem merilnem postopku ni treba analizirati posameznih uporov oziroma izgub in njihovih deležev, ampak le skupno vsoto izgub. Potrebna moč za premagovanje tornih izgub je določena s preskusi ustavljanja (zaviranja) vozila. Vozilo poženemo - v določeni prestavi - do hitrosti, pri kateri dosežemo imensko vrtilno frekvenco motorja. Nato ob sproščeni sklopki pustimo, da se vozilu zaradi tornih izgub zmanjša hitrost. Moč trenja lahko izračunamo z enačbo (3): In most of cases, the moment of inertia of the drivetrain’s components, the wheels and the engine are not known. These unknown values are determined by using two acceleration tests in different gears (in this case 2nd and 3rd). In the presented measurement procedure it is not necessary to analyze various parts of friction losses while only the summary losses are accounted for. The power needed to overcome the friction losses was determined from the vehicle’s deceleration test. The vehicle is driven to a speed that corresponds to the maximum engine rotation frequency, with regard to the transmission ratio. The coupling is then disengaged and the vehicle decelerates only as a result of frictional forces. The friction power is determined from equation (3) to be: Pfr ( nw ) = -Pacc ( nw ) = -4^2nw (mvRw2 + Jef ) dnw dt (9). Iz dosedaj omenjenih enačb lahko povzamemo, da je mogoče določiti moč motorja z uporabo osnovnih podatkov o vozilu in z uporabo časovne spremembe izmerjene vrtilne frekvence koles. Tako izračunano moč motorja, ki temelji na poznavanju vrtilne frekvence koles vozila, lahko preračunamo na vrtilno frekvenco motorja. Iz te vrednosti moči pa lahko določimo tudi moment motorja. Opisani preračun je tudi jedro opisane metode. Iz treh prej omenjenih preskusov lahko določimo naslednje neznanke: - celotno moč trenja vozila, Using this equation we have the possibility to determine the engine’s power from given vehicle parameters and by measuring the rate of the wheel’s rotation frequency with time. The derived engine power, which is related to the rotation frequency of the vehicle’s wheel, is recalculated to the engine’s rotation frequency. From the derived engine power, the engine torque is determined. This is the basis of the device’s operation. From three tests the following unknowns were determined: - vehicle friction power, 1 BnnBjfokJ][p)l]Olf|i[gO | | ^SsFvWEIK | stran 664 d V. Medica - B. Imper - Z. Imper: Dolo~itev imenske mo~i - Determining a WOT Performance - dejansko moč motorja, - skupni masni vztrajnostni moment vrtenja pogonskega dela vozila. Pri tem so bili predpostavljeni, oziroma poznani: - podatki o motorju in vozilu (skupaj z nosilnostjo - tovorom oziroma težo potnikov), prehodni režim delovanja motorja se izvede v zelo kratkem času, izkoristek prenosa je poznan, med cesto in pogonskimi kolesi ni zdrsa, prav tako tudi ni zdrsa na sklopki motorja, preskusna steza - cestišče je vodoravno, v okolici ni vetra. Meritev časovnega poteka vrtilne frekvence koles vozila je opravljena z meritvami časa, ki je potreben, da se kolo enkrat zavrti. Od časa odvisne podatke shranimo v ustrezno datoteko. Po meritvah so podatki obdelani glede izračuna neznank in za pripravo končnega poročila. V začetni fazi so izmerjeni podatki pregledani, napačni podatki pa izločeni iz nadaljnje obdelave. Izbrani podatki so potem ustrezno zglajeni (da se izognemo kasnejšim posledicam numeričnega šuma pri določanju sprememb vrtilne frekvence) in nato še računalniško obdelani. Iz časovne vrste podatkov za pretečeni čas enega vrtjaja na merjenem kolesu vozila lahko izračunamo časovni potek prevožene poti vozila v posamezni (od treh) meritvi. Opravljeno pot vozila izračunamo iz enačbe: - engine power, - sum of the engaged moment of inertia. The following assumptions were made: - the engine and vehicle data are known (also the mass of passengers and payload), - the engine transient is very fast, - the drive train efficiency is known, - there is no slip in the engine coupling or between the wheels and the road, - the road is horizontal and there is no strong influence from the wind. The wheel’s rotation frequency was taken from measurements of the time elapsed for one revolution of the wheel. During the tests, these time-related data were sampled to a data file. After the tests the data were processed to determine the unknowns and the final report was prepared. Data processing of the first sequence data was used to detect and to eliminate false data. The supervised data set is then processed, together with data smoothing to avoid numerical noise amplified by determining the change rate of the rotation frequency. From the sampled data for the elapsed times for each revolution of the wheel, the time history of the vehicle’s travel is determined for one of the vehicle tests. The traveled distance is calculated from the equation: Lv=^RwNt (10). Vrtilna frekvenca kolesa v poljubnem/-tem vrtljaju je določna z izrazom: Časovno spremembo vrtilne frekvence lahko izračunamo iz enačbe: The wheel’s rotation frequency for the i-th turn is derived from: 1 Dti (11). The rate of rotation frequency change is calculated from the equation: i ) dt Dti+1 + Dti (12). 2 OPIS MERILNE NAPRAVE 2 MEASURING DEVICES Merilni sistem z vsemi sestavnimi deli je shematično prikazan na sliki 1. Zaznavalo za merjenje vrtilne frekvence kolesa sestavlja majhen magnet (pritrjen je na notranji rob platišča kolesa). Za merjeneje vrtilne frekvence pogonskega dizelskega motorja je uporabljen elektromagnetni rele, ta ga pred mehanskimi poškodbami, ki bi lahko nastale zaradi neustrezne medsebojne lege z vzbujevalnim magnetom, varuje okrov iz plastične mase. Medsebojno lego releja in magneta lahko nastavimo z vmesnikom za prilagoditev, s katerim pritrdimo rele na nosilec blažilnika udarcev (sl. 1). The complete measuring set-up is presented in Fig. 1. The revolution sensor consists of a small magnet (cemented to the inner part of the wheel hub) and a small reed-relay (Fig. 2). The reed-relay is from a setup for measuring the revolution frequency of an automotive Diesel engine. A plastic housing protects the reed-relay from any damage caused by a misalignment of the magnet. To keep the reed-relay in the same postion with respect to the magnet an adapter for mounting the reed-relay to the shock-absorber leg was used (Fig. 1). stran 665 01-11 ilTMDDC V. Medica - B. Imper - Z. Imper: Dolo~itev imenske mo~i - Determining a WOT Performance platišče kolesa wheel hub \ magnet Zaznavalo z ensor D25 vzporedni podatkovni vhod D25 parallel data port vmestnik za prilagoditev lege adaptor blažilnik udarcev shock absorber nosilnik holder pritrdilne^objemke fixators električni kabli wiring računalnik computer Sl. 1. Shema merilne verige in zbiranja podatkov Fig. 1 Measuring set-up for data sampling Sl. 2. Magnet in rele za merjenje vrtilne frekvence kolesa Fig. 2 Magnet and the reed-relay used for sensing the rotation of the wheel Signal, ki prihaja iz releja, se odvaja prek vodnika do vzporednega vhoda osebnega računalnika. Krmilni del vzporednega vhoda vsebuje povezavo prekinitvene zveze (PZ - IRQ) (sl.3) in omogoča samodejno zaznavanje sprememb vhodnih podatkov. Ta signal sporoča informacijo mikroprocesorju o začasni zaustavitvi delovanja in sproži želeno funkcijo. Ko je ta funkcija opravljena, procesor nadaljuje svojo prejšnjo dejavnost. Kadar je signal PZ v vklopljeni legi, je prekinitev dokazana vsakič, ko je potrditveni (POT - ACK) vhodni signal na položajnem vhodu preklopljen iz lege “pravilen“ v lego “napačen“ (ali izklop napetosti). Nastanek in prenos signala k POT vhodu je prikazan na sliki 4. The signal from the reed-relay switches is fed by wiring to the parallel port of the laptop computer. The control part of the parallel port contains an IRQ Enable connection (Fig. 3) to allow the automatic registration of any change in the input data. This signal is a hardware event giving the information to the microprocessor to interrupt the operation temporary and activate the desired function. When this function is performed, the processor continues with its normal operation. When the IRQ signal is set to the logical “True” (or voltage “ON”), the interrupt is seen each time the ACK input on the status port is switched from logical “True” to logical “False” (or voltage “OFF”). The generation of the signal to the ACK input is shown in Fig. 4. 1 BnnBjfokJ][p)l]Olf|i[gO | | ^SsFvWEIK | stran 666 V. Medica - B. Imper - Z. Imper: Dolo~itev imenske mo~i - Determining a WOT Performance Podatkovni vhod Date Port Stanjski vhod Status Port Krmilni vhod Control Port D7 D6 D5 D4 D3 D2 Dl DO Data 7 Data 6 Data 5 Data 4 Data 3 Data 2 Datal DataO D7 D6 D5 D4 D3 D2 Dl DO ^ ~m Busy ATX PE Select Error mo Reserved Reserved D7 D6 D5 D4 D3 D2 Dl DO Reserved Reserved Direction IRQ Enable Select_In INIT Autofeed Strooe Sl. 3. Posnetek vzporednih podatkovnih in krmilnih vhodov na merilni napravi Fig. 3 Parallel ports and port’s controls F N POT /. /ACK 10 IS OZ / CND +5V K Sl. 4. Povezava zaznavala z vzporednim vhodom Fig. 4 Connection of the sensing device to the parallel port Razvita je bila tudi posebna programska oprema, ki omogoča pobiranje podatkov med meritvijo. Čas med dvema zaporednima zaustavitvama, ki ustreza času enega vrtljaja kolesa vozila se tudi vnaša v podatkovno bazo. Raven natančnosti merjenja tega časa ustreza eni mikrosekundi. Del programa za zbiranje podatkov je bil uporabljen za kalibracijo merilnika hitrosti vozila. Ustrezni program je omogočil tudi prikaz natančne hitrosti vozila in vrtilne frekvence motorja v vrt/min na zaslonu računalnika. Omenjena podatka sta namenjena za vodenje poteka meritve in preprečevanje morebitne prekoračitve vrtilne frekvence motorja med meritvijo. Računalniški program za obdelavo izmerjenih podatkov je razdeljen na prvi del, ki preverja in izloča prave in napačne podatke. Napačni podatki nastanejo zaradi neželenega nihanja stikala releja, ali pa merilni podatek včasih tudi izostane. Če je pri meritvi veliko napak, se vsi podatki zavrnejo in meritev je treba ponoviti. Primer vrste popačenih podatkov lahko vidimo na sliki 5. Preverjeni podatki so potem urejeni, zglajeni in ob koncu prirejeni za končno poročilo o izračunani moči motorja. Program omogoča tudi prikaz vseh podatkov, njihovo obdelavo in prikaz končne oblike To enable the data sampling during the measurement we developed software. The time elapsed between two successive interrupts, which corresponds to the time of one full revolution of the wheel is written to the data file. The precision of the measurement was at the microsecond level. One part of the data-sampling software was used to calibrate the vehicle’s speed indicator. The software indicates the accurate vehicle speed and engine revolution frequency in rpm on the laptop screen. These data are used to control the test procedure and to avoid engine overspeed during the tests. The software for sampled-data processing contains the first part for data supervision to detect and to eliminate false data. False data are the result of erroneous reed-relay switch vibrations or due to missing data. If there are a lot of errors, the sampled data are discarded and a new measurement has to be performed. Examples of erroneous data are presented in Fig. 5. The supervised data set is then processed and smoothed to give a final report on the engine’s performance. The software enables sampled-data visualization, processing and presentation of the final stran 667 01-11 ilTMDDC V. Medica - B. Imper - Z. Imper: Dolo~itev imenske mo~i - Determining a WOT Performance 140,203294 140,743865 141,441164 4,010286 138,052741 142,701352 143,513778 73,840134 73,852941 73,863457 148,088236 74,081291 74,175382 74,317489 Sl. 5. Primer vrste napačnih podatkov; levi stolpec - vzrok je v nihanju stikala, desni stolpec - vzrok je v nesklenjenem stikalu Fig. 5. Examples of erroneous data. Left - due to the switch vibrations, Right - due to missing the switch closure končnega poročila. Matematični model, ki je bil prikazan v drugem poglavju je uporabljen v opisanem računalniškem programu skupaj z nadzorom in obdelavo podatkov. Celoten merilni sistem je bil pred uporabo skrbno preverjen. Preverjen in določen je bil pravilen razmik med magnetom in zaznavalom. Ugotovljeni razmik naj ne bi presegel 10 mm. Signal zaznavala, ki je bil priključen na vzporedni vhod, in program za zbiranje podatkov sta bila preverjena z generatorjem, ki je dajal pravokotne signale z nastavljivimi frekvencami signala. Signal je bil nato ojačen in posredovan tuljavi, ki je vklopila rele (sl.6). To preverjanje je bilo namenjeno določitvi uporabnega področja delovnih frekvenc uporabljenega releja. Odzivnost releja se je izkazala za ustrezno; delovne frekvence so močno presegle pričakovane vrtilne frekvence koles vozila. report. The mathematical model presented in section 2 is implemented into the software, together with the data supervision and the data smoothing procedures. The complete measuring system was carefully tested before use. This testing was performed to determine the allowable distance between the magnet and the sensing device, which was found to be up to 10 mm. The sensing device, connected to the parallel port and the software for data sampling, was tested using a rectangular signal generator with a controllable signal frequency. The signal was amplified and applied to the wire coil activating the reed-relay (Fig. 6). This control was performed to determine the applicable reed-relay frequency domain, which was found to be much higher than the expected wheel rotation frequency. generator signala signal generator _TL elektromagnet V coil JftW/lrele R R OZ / GND Sl. 6. Shema preverjanja merilne opreme Fig. 6 Test setup for the measuring device 3 PRIMERI MERITEV MOČI MOTORJA Vzorčno preskušanje metode je bilo v praksi preverjeno na različnih osebnih avtomobilih in opravljeno na vzletni letalski stezi z dolžino 1800 m. Meritve so bile opravljene s tridelnim preskusnim postopkom. V prvem delu se je vozilo ob izklopu pogonskega agregata prosto zaustavljalo; ta del je bil uporabljen za določitev voznih uporov vozila. V drugem 3 MEASUREMENT EXAMPLES Sample measurements on various passenger cars were performed at a local airport runway with a length of 1800 m. Measurements were performed in three succesive tests. The first test was performed using free vehicle deceleration to determine the vehicle’s driving resistance. The second and third tests were performed using the vehicle’s 1 BnnBjfokJ][p)l]Olf|i[gO | | ^SSfiFlMlGC | stran 668 V. Medica - B. Imper - Z. Imper: Dolo~itev imenske mo~i - Determining a WOT Performance in tretjem delu je bilo vozilo pospešeno v drugi oziroma tretji prestavi. Na slikah 7, 8, in 9 so prikazani rezultati meritev na treh različnih osebnih avtomobilih. acceleration with an engaged engine in 2nd and 3rd gears. Three examples of the results are presented in Fig. 7, 8 and 9. ^ moment motor engine torque a ^ ------ «V moč motorja ~ ™«inpnnwpr ¦< - *1fW vehicle acceleration power Lmr^trmiisi vrwilsi H vehicle friction — i 0 500 1000 1500 2000 2500 3000 3500 4 000 4500 5000 5500 5000 6SO0 7000 Vrtilna frekvenca, min-1 Engine speed, rpm Sl. 7. Rezultati meritev karakteristik motorja PPP na osebnem vozilu Citroen BX 1.6 Fig. 7. WOT performance for a Citroen BX 1.6 100-1 85^ 9fr 85^ 8fr 75^ 7CH 65^ 60-55-i 50^ 45-40: 3& 30 ¦: 25-20^ 15^ 5: oo moment moto engine torq! >rja ue ^ k, \ moč motorja engine power m oč med pospeševanjem hicle acceleration power V " m ottrenja vozila vel vehicle friction power —i—t- i I ) 500 1000 1500 2000 2500 3000 3500 4000 4,500 5000 5500 6000 6500 7C Vrtilna frekvenca motorja, min-1 Engine speed, rpm Sl. 8 Rezultati določanja PPP karakteristike motorja na osebnem avtomobilu Renault Clio 1.2 Fig. 8 WOT performance for a Renault Clio 1.2 4 SKLEP V prispevku je prikazana cenena in praktična naprava za merjenje karakteristike pogonskega motorja vozila PPP. Naprava omogoča hitro določanje moči motorja brez odstranitve katerega koli sestavnega dela v pogonskem sklopu vozila. Takšen postopek določanja moči je cenen in primeren tudi za manjše servisne delavnice; pri tem ni prizadeta nedotakljivost pogonskega sklopa ali njegovih delov in s tem ogrožena veljavnost jamstva izdelovalca vozila. Za izvedbo meritev moči je, v nasprotju z obširno in zelo zahtevno in drago merilno opremo, potrebna le skromna in cenena merilna oprema. 4 CONCLUSIONS An inexpensive and easy-to-use device for determining a vehicle’s engine’s WOT performance is presented. The device enables fast measurements of engine performance without any dismantling or disconnecting of the engine or any of the drive train parts. This enables cheap and easy tests for small servicing enterprises without breaking any vehicle warranty conditions and without investing in expensive measuring equipment. stran 669 01-11 firTNEK V. Medica - B. Imper - Z. Imper: Dolo~itev imenske mo~i - Determining a WOT Performance 1Mh mom engine torque ------ \ ™nZ „.„<—:- • ower _ "^ ----- \ \_ moč med pospeševanjem """"moč trenja vozila vehicle accelerate ™ ¦ ^" vehicle friction power, O^ TrrFr^". .T.. j 0 500 1000 1500 2000 2 500 3000 3500 4000 4500 5000 5500 6000 6500 7000 Vrtilna frekvenca motorja, min-1 Engine speed, rpm Sl. 9. Rezultati določanja PPP karakteristike motorja na osebnem avtomobilu Opel Kadett 1.6D Fig. 9 WOT performance for a Opel Kadett 1.6D Predstavljena metoda in postopek zahtevata osebni prenosni računalnik z ustrezno programsko opremo, zaznavalo za določanje vrtilne frekvence koles in ožičenje. Z opisanim sistemom je mogoče zelo natančno določiti karakteristiko moči sesalnega motorja, ki “opravi” prehod na nov režim delovanja v sorazmerno kratkem času. The presented device consists of a laptop computer, software, a sensor for wheel rotation and wiring. This measurement setup determines very accurate performance figures for naturally aspirated engines due to the very fast transient response of the vehicle’s transient. This method is, under certain conditions, also applicable to turbocharged engines. 5 SIMBOLI 5 SYMBOLS prestavno razmerje prenosnika moči i transmission ratio masni vztrajnostni moment J kg-m2 moment of inertia L m travelled distance masa m kg mass vrtilna frekvenca n s-1 rotation frequency število vrtljajev kolesa N number of wheel revolutions moč P W power polmer R m radius čas t s time hitrost vožnje po ravnem v m/s linear velocity časovni korak Dt s elapsed time step izkoristek h efficiency kotna hitrost w s-1 angular velocity Indeksi Indices pospeševanje acc acceleration prenosnik moči dt drivetrain upor pri trenju fr friction, resistance dejanski ef effective motor en engine motor z vztrajnikom in sklopko enc engine with flywheel and coupling indeks i index indeks j index celoten t total vozilo v vehicle kolo w wheel 1 SšnnsOJiM]! ma stran 670 V. Medica - B. Imper - Z. Imper: Dolo~itev imenske mo~i - Determining a WOT Performance [1] [2] [3] [4] [5] 6 LITERATURA 6 REFERENCES Imper, B. (2000) Project of the device for determination of the engine WOT performance (in Croatian), BSc degree thesis, Faculty of Engineering, University of Rijeka. Imper, Z. (2000) Project of the changes in the intake system of the spark ignition engine (in Croatian), BSc degree thesis, Faculty of Engineering, University of Rijeka. Heywood, J. B. (1988) Internal combustion engine fundamentals, McGraw Hill Book Co., ISBN 0-07-028637-X. Anderson, P. H. (1996) Use of a PC printer port for control and data acquisition. Malmstadt, H. V. , C.G. Enke (1969) Digital electronics for scientists, W. A. Benjamin, Inc. Naslov avtorjev: prof. dr. Vladimir Medica Branko Imper Zoran Imper Tehnički fakultet Sveučilište u Rijeci Vukovarska 58 HR-51000 RIJEKA Authors’ Address: Prof. Dr. Vladimir Medica Branko Imper Zoran Imper Faculty of Engineering University of Rijeka Vukovarska 58 HR-51000 RIJEKA, Croatia Prejeto: Received: 19.10.2001 Sprejeto: Accepted: 7.12.2001 stran 671 01-11 firTNEK © Strojni{ki vestnik 47(2001)11,672-681 © Journal of Mechanical Engineering 47(2001)11,672-681 ISSN 0039-2480 ISSN 0039-2480 UDK 629.326.5:621.43 UDC 629.326.5:621.43 Pregledni znanstveni ~lanek (1.02) Review scientific paper (1.02) Priprava motorja za tekmovalni razred How to Prepare an Engine for Motorcycling’s Supersport Class Fran~i{ek Bizjan - Samuel Rodman - Ferdinand Trenc Motorji za motorna kolesa v razredu Supersport so zanimivi za razvojne inženirje, ki razvijajo nove izdelke zaradi omejitev, določenih s predpisi. Ti praktično onemogočajo večje posege v motor, niti ne dopuščajo svobodne izbire delov za zamenjavo. Kljub temu, da se motorji pripravijo skoraj brez zamenjave delov, pa po drugi strani dosegajo velike moči. Ker se s tem spreminja velikoserijski izdelek, so lahko doseženi rezultati uporabni tudi pri razvoju motorjev. Predelani motorji ne dosegajo izrazito višjih vrtilnih frekvenc, imajo pa sorazmerno zelo visoke srednje dejanske tlake, med najvišjimi pri sesalnih motorjih. Prispevek prikazuje delni potek dogajanja pri predelavi motorja vključno s spoznanji o pomenu in zmožnostih računalniških simuliranj, ki se običajno uporabljajo pri močnejših tekmovalnih razredih. © 2001 Strojniški vestnik. Vse pravice pridržane. (Ključne besede: kolesa motorna, motorji ZNZ, karakteristike motorjev, programiranje računalniško) Motorcycle engines used in the Supersport Class are interesting for engineers who develop new products because of the restrictions imposed by the regulations. These regulations do not allow major changes to the engine and restrict the choice of replacement parts that can be used. Nevertheless, the prepared engines achieve great power and the lessons learned during such an exercise can be put to good use in the development of mass-produced engines. These modified engines are not capable of significantly higher engine speeds, however, they can have a very high mean effective pressure, amongst the highest found in naturally aspirated engines. This article describes the steps involved in modifying an engine as well as our impressions of the importance and the possibilities of computer simulations in such types of racing. © 2001 Journal of Mechanical Engineering. All rights reserved. (Keywords: motorcycles, internal combustion engines, engine preformance, computer programming) 0 UVOD Že pri prvih korakih motorizacije je bila opazna tekmovalna strast med ljudmi, ki so upravljali stroje. Pravzaprav gre samo za tekmovalnost med ljudmi; med vozniki in skupinami tehnikov, ki pripravljajo vozilo. Vse do današnjih dni ta takmovalna strast ni popustila, ampak se - nasprotno - povečuje. To je pripeljalo postopoma do vrste tekmovalnih razredov, ki so nastali predvsem zaradi tehničnih različnosti. Prav določeni okviri - predpisi pa omogočajo do neke mere enakovredne možnosti za vozila oziroma tekmovalce, ki tekmujejo v posameznih razredih ali kategorijah. Tekmovalni razred Supersport je mlad in predstavlja motorje s prostornino 600 cm3, ki so malo predelani glede na vzeto osnovo oziroma velikoserijski izdelek. Prav zaradi tega so stroški predelave majhni, kar nadalje omogoča udeležbo na tekmovanjih širšemu krogu ljubiteljev. Pravzaprav tehnična izhodišča omogočajo razmeroma dostopno ceno za predelavo, če pa imajo posamezniki več znanja, se lahko dokažejo potem tudi z rezultati na progi. 0 INTRODUCTION From the earliest days of motorised transport there has been a spirit of competition amongst people who work with engines. There has always been rivalry between drivers, technicians and all the people involved in preparing a vehicle. Over the years this rivalry has not decreased, on the contrary, it has increased. The result is a wide range of competitions that are organised for different classes of vehicle. These classes impose regulations in order to try and equalise the chances of the different vehicles that compete in the same class or category. Motorcycling’s Supersport Class is relatively new and consists largely of motorbikes with 600 cm3 engines that are only slightly modified versions of the mass-produced originals. Because the costs involved in rebuilding the engines are relatively low, large numbers of amateurs can take part in the races. This combination of low costs and limited modifications means that the better riders are able to demonstrate their skills through results on the racetrack. 1 BnnBjfokJ][p)l]Olf|i[gO | | ^SsFvWEIK | stran 672 F. Bizjan - S. Rodman - F. Trenc: Priprava motorja - How to Prepare an Engine Motor (Kawasaki Ninja ZX-R6 - slika 1) [1] je primer velikoserijskega izdelka, ki ima sodobno zasnovo in pomeni za tehnike izziv glede na dovoljene spremembe. Te sicer onemogočajo bistveno povečanje moči, s tem pa je zagotovljena sorazmerna izenačenost motorjev na stezi. Prav to pomeni zadovoljstvo gledalcev, tehnike pa spodbuja k novim rešitvam, ki omogočajo dosegati zmagovite lastnosti motorja. 1 SPLOŠNA PRAVILA ZA RAZRED SUPERSPORT Pri hitrostnih tekmovanjih veljajo določena pravila, ki jih postavlja mednarodna organizacija za avto-moto šport. Tehnični del teh pravil dejansko vpliva na končne lastnosti motorja oziroma vozila. Glede na to so v razredu Supersport dovoljene naslednje splošne spremembe: - Prostornina motorja je od 401 do 750 cm3 glede na število valjev; v praksi so se uveljavili štirivaljni motorji s prostornino 600 cm3. - Vsi deli motorja morajo biti serijski, izjema so deli in nastavitev, ki so poprej potrjeni od mednarodne organizacije na podlagi dokumentacije izdelovalca motorja. - Obdelava delov motorja je mogoča le z odvzemanjem in še to do določene tolerančne meje - površinska obdelava. - Dodatna toplotna obdelava ali površinska mehanska utrditev delov ni dovoljena. - Ročični mehanizem mora ostati nedotaknjen, dovoljeno je le uravnoteženje delov. The Kawasaki Ninja ZX-R6 [1] motorcycle in Figure 1 is an example of a mass-produced motorcycle of modern design that represents a challenge when it comes to making improvements and staying within the regulations. Significant changes to the engine’s capacity are not allowed and, as a result, the bikes have roughly equal chances on the racetrack. This provides the spectators with exciting racing and spurs the motorcycle technicians to look for new ways to enhance the performance of the engine. 1 GENERAL REGULATIONS FOR THE CLASS SUPERSPORT In motorcycle racing there are certain rules to be observed, these rules are imposed by the international organisation for auto-motor sports. The technical part of the rules places certain limitations on the engine. The Supersport Class allows the following general changes: - The engine’s capacity should be between 401 and 750 cm3, depending on the number of cylinders. The most usual engine configuration is four cylinders with a total capacity of 600 cm3. - All the engine parts must be mass produced, with the exception of the parts and settings that are formerly approved by the international organisation after reviewing the documentation of the producer. - Modifications to the engine parts are possible, but only by removing material, and then only to a limited extent. Some surface treatment is permitted. - Additional thermal treatment or mechanical strengthening of the surfaces of parts is not allowed. - The crank mechanism should remain unaltered although balancing of the parts is permitted. Sl. 1. Motor Kawasaki Ninja ZX-R6 Fig. 1. Engine of the Kawasaki Ninja ZX-R6 stran 673 Im^fmiccI F. Bizjan - S. Rodman - F. Trenc: Priprava motorja - How to Prepare an Engine - Okrov motorja in oljna posoda morata ostati nedotaknjena. - Sesalni sistem je omejen z določenim premerom uplinjača, okrov filtra in prostornina pred njim ostaneta nespremenjena, odstrani se lahko vložek. - Vžigalni sistem je določen, omogočena je le prestavitev najvišje vrtilne frekvence do meje, ki velja za vse enako. - Oblika izpušnega sistema, vključno z dušilnikom, mora ostati nespremenjena. - Glavo motorja je mogoče deloma obdelati (glajenje), materiali morajo ostati enaki, v primeru zamenjave pa morajo biti homologirani, kar velja predvsem za ventile, sedeže in vodila ventilov. - Dele krmilnega sistema je mogoče zamenjati za homologirane (odmični gredi, pogonska veriga, napenjalnik itn.). Iz predstavljenih predpisov se vidi, da je mogoče zamenjati le malo delov motorja. Največ dela je zato v teh primerih namenjenega urejanju tokovnih razmer v glavi motorja. 2 PRIPRAVA MOTORJA Izhodiščno stanje, kakor so: lastnosti motorja, pretočne karakteristike kanalov in delov, smo preverili na zavori, napravi za določanje tokov skozi kanale glave in z mehanskimi meritvami. Namen tega je bilo preverjanje znanih podatkov (pregl. 1) in pridobitev takih, ki običajno niso dostopni ([2] do [4]). Glede na znano izhodišče in predelave, določene s predpisi, smo se odločili za naslednje spremembe na motorju: - Glava motorja: obdelani so bili kanali in zgorevalni prostori, posebna pozornost je bila namenjena obdelavi površin, razširitvam kanalov in sedežev ventilov. Skrbno je bila nastavljena špranja med batom in glavo - izstiskovalna površina, ki opazno vpliva na lastnosti motorja. - Okrov motorja z oljno posodo: dovoljena je načeloma le dodelava, ki ni bila dokončana s strojem, to je raziglanje delov. - Ročični mehanizem: tu je dovoljeno le uravnoteženje delov ali pa izbira izvirnih delov z enako maso. - Krmilni mehanizem: mogoča je menjava odmičnih gredi z drugimi, ki pa se malo razlikujejo od serijskih, obdelava ventilov je bila simbolična zaradi omejene teže, zamenjane pa so bile vzmeti zaradi doseganja višjih vrtilnih frekvenc. - Sesalni sistem: prilagojeni so bili prehodi na stikih delov, zamenjane šobe in preoblikovan vstop zraka v sesalno cev. - Izpušni sistem: za primerjavo sta bila preskušena dva sistema, pri katerih sta bila spremenjena le zbiralnika. - Hladilni sistem: potrebne spremembe so bile določene z najvišjo dovoljeno temperaturo vode; kar pomeni samo zamenjavo hladilnika. ^BSfirTMlliC | stran 674 - The engine block and oil pan should remain unaltered. - The intake system is defined by the diameter of the carburettor, the filter frame and the air box in front of it. These parts should remain unchanged, only the filter element can be removed. - The ignition system is defined, the maximum engine speed can be increased. - The form of the exhaust system, including the silencer, should remain unchanged. - The cylinder head can be partly remodelled by polishing, the materials should remain the same, in the case of changes they should be homologies, this applies to the valves, the valve seats and the valve guides - Parts of the timing system can be exchanged for homologated parts, i.e. camshaft and timing chain. The above conditions allow only a few changes to the engine parts. The studies are devoted mainly to flow conditions in the cylinder head. 2 PREPARATION OF THE ENGINE The initial conditions of the engine, i.e. performance, flow characteristics of the port and parts were checked on a dynamometer, a device for determining the flow through the cylinder ports as well as by mechanical measuring. The aim was to check the known data (Table 1) as well as get some other information, which is normally not available ([2] to [4]). With regards to the known facts and the modification conditions imposed by the regulations we decided on the following changes: - Cylinder head – ports and combustion chamber were polished, special attention was given to surface preparation, widening of the ports and the valve seats. The piston clearance was carefully set, as was the extrusion surface, which significantly influences the engine performance. - Engine block and oil pan - only final works are allowed, which were not done with the engine i.e. burring of the parts, - Crank mechanism - only balancing of these parts is allowed, or the use of original parts with the same mass. - Timing mechanism – it is possible to change the camshafts, but these are only slightly different from the mass-produced versions, changes to the valves are not significant due to the weight limit, the springs were replaced because of the higher engine speeds. - Intake system - gangways on the connections of the parts were adapted, nozzles were replaced and the air inflow into the intake tube was changed. - Exhaust system - two systems with different collector boxes were examined. - Cooling system - changes were limited by the maximum allowed water temperature, which means the radiator was replaced. F. Bizjan - S. Rodman - F. Trenc: Priprava motorja - How to Prepare an Engine Preglednica 1. Osnovne lastnosti motorja - tovarniški podatki Table 1. Basic engine performance - factory data Lastnosti Properties Vrednosti Values Tip motorja Engine type 4-valjni, 4-taktni Otto motor, 4 ventili na valj, 2 odmični gredi 4-cylinder, 4-stroke Petrol Engine, 4-valves per cylinder, 2 camshaft Hlajenje Cooling tekočinsko liquid Premer x gib Bore x stroke 66,0 x 43,5 [mm] Prostornina Capacity 599 [cm3] Kompresijsko razmerje Compression ratio 11,8 : 1 Moč Power 79,4 [kW] / 12000 [min-1] Moment Torque 65,7 [Nm] / 10000 [min-1] Napajanje z gorivom Fuel feeding 4 x uplinj- (Mikuni BDSR 36R) 4 x carburators Programska oprema Po primerjavah med različnimi programskimi paketi ([5] do [7]), namenjenimi predelovalcem motorjev, smo izbrali paket, katerega teoretična podlaga je metoda karakteristik. Ker ta program izračunava predvsem nihajne pojave v ceveh, je nujno pri njegovi uporabi poznati izhodiščno stanje motorja, na katerem želimo opraviti spremembe. Vstopni podatki, potrebni za izračun, so [2]: - Zahteve pri računanju, geometrijska oblika motorja, koti odmične gredi, geometrijska oblika sesalne cevi, geometrijska oblika izpušne cevi, pretočne razmere v kanalih in način dovoda goriva. Računalniški programi, ki smo jih preverjali, zahtevajo v večini primerov izmerjene podatke motorja pri nekem začetnem stanju. Za začetno stanje se običajno vzame še nepredelan oziroma izviren motor. Nadaljnje zahteve so še oblika in mere sesalnih in izpušnih poti ter tokovne razmere v kanalih. To pomeni, da posredno določimo tudi dogajanja v valju, hkrati pa tudi predpostavimo, da se dogajanje v valju bistveno ne spreminja. 3 PRIMERJAVA LASTNOSTI MOTORJA PRED PREDELAVO Osnovne lastnosti motorja so bile izmerjene na zavori (metoda pospeševanja mase). Na tak način se dejansko izmerijo dinamične lastnosti motorja pri pospeševanju. Zanimivo je, da tak način merjenja lahko prikaže večje vrednosti moči, kakor bi jih dobili pri standardnih (zavora na vrtinčne tokove) meritvah. Tokovne razmere v sesalnem, izpušnem kanalu in uplinjaču so bile izmerjene na posebni | lgfinHi(š)bJ][M]lfi[j;?n 0111 stran 675 I^BSSIfTMlGC Software equipment After comparing different software designed for engine rebuilders ([5] to [7]), we decided on a programme that is based on the method of characteristics. Since the programme first of all calculates oscillating procedures in the pipes, it is necessary to know the initial properties of the engine that is to be modified. The input data required for the calculation were: the geometry of the engine, the angles of the camshaft, the geometry of the intake pipe, the geometry of the exhaust pipe, the flow characteristics in the ports and the method of fuel intake [2]: - The programme provides us with the calculated engine properties such as power, torque, mean effective pressure, volume effectiveness, graphical indication of the pressure flow, and velocity of the media. The computer programmes that we examined in most cases required measured data taken from the engine at a particular starting point. The original engine is usually taken as the starting point. Further requirements include the form and the dimensions of the intake and the exhaust pipes as well as the flow conditions in the ports. This means that we indirectly determine the conditions in the cylinder and assume, at the same time, that the conditions in the cylinder are not essentially changing. 3 INITIAL COMPARISON OF THE ENGINE PERFORMANCE Basic engine performances were measured on the dynamometer (mass accelerating method). This method measures the dynamic properties of the engine during acceleration. It is interesting that this method can give higher power values than those obtained by the classical (eddy-current dynamometer) measurements. The flow conditions in the intake, the exhaust pipe and the carburettor were measured on a special F. Bizjan - S. Rodman - F. Trenc: Priprava motorja - How to Prepare an Engine napravi. S tem so bili določeni pretočni koeficienti, device. The flow coefficients were defined for the total določeni za celotno pot toka v kanalu (upoštevane way of flow in the channel (all narrowings and widenings so bile vse zožitve in razširitve ter ožina pri sedežu were taken into consideration as well as the narrowing oziroma vodilu ventila), pri različni odmikih ventila. at the valve seat, or guide) at different valve positions. P kW 80 70 60 50 40 30 ----------P merjen/measured -----------P izračun/calculated ------------M merjen/measured -----------M izračun/calculated -- 94 /- 84 74 ¦j- 64 -f- 54 44 r 34 24 14 4 M Nm 6500 7500 8500 9500 10500 11500 12500 n 1/min Sl. 2. Primerjava lastnosti motorja med izmerjenimi in izračunanimi rezultati (izvirno stanje) Fig. 2. Comparison of the engine performance between the measured and calculated results (original) Iz tako pridobljenih podatkov smo potem izračunali lastnosti motorja in jih primerjali z izmerjenimi vrednostmi na zavori, kar je prikazano na sliki 2. Bolj kakor sam potek krivulje moči in mo-menta je zanimivo pogledati razlike med izračunanimi in izmerjenimi vrednostmi. Opazimo razmeroma dobro skladnost krivulj, kar velja splošno, prav tako pa vidimo tudi odstopke med izračunanimi in izmerjenimi vrednostmi, posebno na začetku in koncu krivulje. Večja odstopanja pri nižjih frekvencah so odvisna od računskega modela oziroma širine področja (vrtilne frekvence) računanja. Pri višjih vrtilnih frekvencah pa je vzrok za odstopanje deloma prevelika občutljivost ali pa nenatančnost matematičnega modela. Nenatančnost računanja je mogoče odpraviti z natančnejšim računanjem, kar program sicer omogoča, toda čas računanja se opazno podaljša. Po drugi strani je treba omeniti, da je uporabno področje vrtilne frekvence obravnavanega motorja približno v mejah med 8 in 12 000 min-1. V tem področju je povprečna razlika med meritvami in izračuni približno 3 %, kar je povsem zadovoljivo. Dolžina sesalnih cevi Primerna dolžina sesalne cevi je dosežena takrat, ko prispe kompresijski val do ventila v trenutku navečje hitrosti bata, to je približno pri 73o do 83o zavrtitve ročične gredi (RG) po zgornji mrtvi legi (ZML). Poleg tega pa si želimo, da se poviša tlak v sesalni cevi tik po odpiranju in tik pred zapiranjem sesalnega ventila. S tem namreč Using the above information we have calculated the engine’s characteristics and compared them with the values measured with the dynamometer (Figure 2). As well as the shape of the power and torque curves it is interesting to see the difference between the measured and the calculated values. The curves correspond comparatively well, but at the beginning and at the end we can see deviations between the measured and the calculated values. The larger deviation at low speeds is due to the calculation model, or the lack of accuracy in the area engine-speed calculation. At higher speeds the reason for the deviation is partly the great sensitivity, or inaccuracy of the mathematical model. The inaccuracy of the calculation can be improved, the programme allows for this possibility, but the calculation time is longer. On the other hand, it should be mentioned that the relevant engine speeds are between 8000 and 12000 rev/min. In this range the average difference between the measurements and the calculations is approximately 3 %, which is satisfactory. Length of the intake pipes The intake pipe is long enough if the compression wave reaches the valve at the moment when the piston speed is at its highest, this moment occurs when the crankshaft has rotated 73° to 83° past top dead centre. Our second aim was to increase the pressure in the intake pipe immediately after the opening and immediately after the closing of the intake valve. By doing this the possibility of media irruption in the intake channel 1 BnnBjfokJ][p)l]Olf|i[gO | | ^SsFvWEIK | stran 676 F. Bizjan - S. Rodman - F. Trenc: Priprava motorja - How to Prepare an Engine 15 10 %+100 ----------krajša cev/shorter pipe ----------daljša cev/longer pipe 6500 7500 8500 9500 10500 11500 12500 n 1/min Sl. 3. Vpliv dolžine sesalne cevi na izkoristek polnjenja valja Fig. 3. Influence of the intake-pipe length on the cylinder’s volumetric efficiency zmanjšamo možnost vdora sredstva v sesalni kanal oziroma preprečimo povratni tok, ki je pogosto vzrok za slabe lastnosti motorja pri nizkih in srednjih vrtilnih frekvencah. Polnitev valja ali izkoristek polnjenja ni odvisen samo od dolžine, ampak še bolj od prereza cevi, hitrosti sredstva, spremembe prereza in pretočnih koeficientov. V prikazanem primeru je bilo mogoče vplivati na polnitev valja le z dolžino cevi in pa z obdelavo sten kanalov. Na sliki 3 je prikazan vpliv dolžine sesalnega kanala na izkoristek polnjenja valja. Ker želimo motor z večjo močjo pri višjih vrtilnih frekvencah, lahko ugotovimo, da je krajša sesalna cev ugodnejša rešitev. Pomanjkljivost take rešitve je ožje področje uporabne moči, kar lahko vpliva na vozne lastnosti. Dobra polnitev valja je kompromis med nastavitvami sesalne in izpušne strani in še drugih dejavnikov, ki jih v našem primeru ne moremo v celoti izkoristiti. Vpliv krmilnih kotov odmične gredi Kljub razmeroma majhnim spremembam kotov odmičnih gredi kažejo izračuni in preskusi, da se največja moč premakne v območje višjih vrtilnih frekvenc (sl. 4). Zanimivo je, da se moč pri tem bistveno ne spremeni, še več, se celo zelo malo spreminja. Delni vzrok za zamenjavo odmičnih gredi je tudi v spreminjanju kompresijskega razmerja oziroma zmanjševanju razdalje med batom in ventilom. S spremembami kotov posežemo v nihajne pojave v sesalni in izpušni cevi. Njihov namen je zagotoviti, da pri odpiranju in zapiranju ventilov dosežemo čim manjše motnje toka v sesalnem in izpušnem kanalu. To pomeni, da se pri odpiranju in zapiranju sesalnega ventila pojavi čim manjši povratni tok v sesalni cevi. Med odprtjem izpušnega ventila pa naj bi zagotovili čim nižji tlak v izpušni cevi. S tem bi si zagotovili visok is diminished and reverse flow is prevented, something which is often the cause of poor engine performance at low and medium engine speeds. The induction of the cylinder and the induction efficiency do not depend only on the length, they are also very dependent on the section of the pipe, the speed of the media, the change of the intersection and the flow coefficients. In our case it was only possible to influence the cylinder induction by changing the pipe length and treating the channel walls. Figure 3 shows the influence of the intake-pipe length on the cylinder induction efficiency. Since it was our aim to have an engine with greater power at higher engine speeds we can prove that a short intake pipe is an advantage. The disadvantage of this solution is that the power band is narrower, which can have a negative influence the motorbike’s performance in real situations. The efficient induction of the cylinder is a compromise between the setting of the intake and the exhaust pipe as well as other factors, which in our case cannot be fully used. Influence of the timing angles of the camshaft In spite of relatively small changes in the angles of the camshafts, the calculations as well as the tests show that the highest power is shifted to the range of higher engine speeds (Figure 4). It is interesting, however, that the power has changed very little. Other reasons for changing the camshafts are to alter the compression ratio, or shorten the distance between the piston and the valve. By changing the angles we influence the oscillation phenomena in the intake and exhaust pipe. The aim is to ensure that by opening and closing the valves we achieve the smallest possible flow disturbances in the intake and exhaust ports. This means that while opening or closing the valve the arising counterblow in the intake pipe is as weak as possible. During the opening of the exhaust valve there should be the lowest possible pressure in the exhaust pipe. In this way we can reach gfin^OtJJIMISCSD 01-11 stran 677 I^BSSIfTMlGC V 5 0 F. Bizjan - S. Rodman - F. Trenc: Priprava motorja - How to Prepare an Engine pe 15 14 13 bar 12 11 /V ^