Wyniki wyszukiwania - BazTech

1

Metal transfer, film formation and surface temperatures on a cam in an automotiye engine

Furey M., Reinholtz Ch., Vick B.

Tribologia

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2007

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nr 6

87-117

EN

In an attempt to better understand the mechanisms of valve train wear and lubrication, a study was made to connect two earlier observations with a recent theoretical treatment of tribological processes occurring in the highly-loaded cam/valve lifter assembly of an automotive engine. In previous valve train wear studies conducted by one of the authors (MJF), neutron-activated valve lifters were installed in a V-8 engine connected to a dynamometer for basic research and continuous wear measurements. One important discovery was that metal transfer occurred from the radioactive valve lifters to the cam in a narrow strip at the cam nose. This is where calculations of oil film thickness would predict the thinnest film. In a follow-up study using the identical engine but with non-radioactive valve lifters, tests were carried out with P-32-tagged zinc di(C6)alkyl dithiophosphate (ZDDP) under conditions in which this additive reduced valve lifter wear by 90%. After disassembly of the engine, autoradiographs were made of the cams and valve lifter faces. The results were striking, showing significant film formation localized in the region of the cam nose and encompassing the previously-found narrow strip of metal transfer. Zn, Fe, and Ni di(C6)alkyl dithiophosphates-all thermally decomposing completely at around 205-210°C-were equally effective in reducing valve lifter wear in engine tests while more thermally stable Zn dithiophosphates (C13 and aryl derivatives) had no effect whatsoever on valve lifter wear. Since the cam nose represents not only the region of highest load but also of highest sliding velocity, this would correspond to that of highest expected surface temperature in the absence of an EHL or oil film. But the duration of contact at the peak temperature at the cam nose is short. Is there enough time for a protective film-forming reaction to occur? To examine this and other questions, a general theoretical model developed by Vick was applied to a model cam/valve lifter system with varying load, speed, contact geometry, deformation, and presence of an oil film. Specific conditions were selected to correspond to previous engine studies and to illustrate the theoretical distribution of surface temperatures over the entire rotating cam, including time and decay effects. This information was then compared to the two experimental observations. It is suggested that these studies may add to our understanding not only of the wear mechanisms involved but also of tribochemical reactions, including tribopolymerization as an antiwear mechanism, e.g., the "in situ" surface polymerization of condensation-type monomers.

PL

W obszarze wierzchołka krzywki rozrządu silnika samochodowego występują nie tylko najwyższe obciążenia, ale także największe prędkości poślizgu, co prowadzi do najwyższych spodziewanych temperatur powierzchni w przypadku braku elastohydrodynamicznej warstwy smarowej. Jednak czas występowania szczytowej temperatury w okolicy wierzchołka krzywki jest bardzo krótki. Powstaje więc pytanie czy wystarczy czasu dla wystąpienia reakcji tworzącej warstwę ochronną. W celu rozstrzygnięcia tej i innych kwestii ogólny model teoretyczny opracowany przez Vicka został zastosowany do modelowania systemu krzywka-popychacz ze zmiennym obciążeniem, prędkością, geometrią styku, odkształceniem i występującą warstwą smarową. Wybrano dane wyjściowe odpowiadające zrealizowanym wcześniej przez Fureya badaniom eksperymentalnym silników. Określono rozkłady temperatury na całej powierzchni krzywki. Uwzględniając efekty czasowe i zanikania. Porównano wyniki teoretyczne z rezultatami dwu serii badań eksperymentalnych. Zrealizowane studium może uzupełnić naszą wiedzę nie tylko o mechanizmach zużywania, lecz także o reakcjach tribochemicznych - z uwzględnieniem tribopolimeryzacji jako mechanizmu przeciwzużyciowego np. polimeryzacji monomerów typu kondensacyjnego "in situ" na powierzchni tarcia.

2

Using the manufactured part enclosed transducers to control the automotive engine's way of working

Chereches T., Copae I.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2004

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z. 62 [209]

43--48

EN

The paper underlines the necessity of implementing specialized transducers as components of the manufactured parts that could provide real-time information concerning the working process of the technical processes, especially for the automobiles. It is also underlined that modern technique and technologies provide normal working conditions, satisfying all the inquired demands, even under the conditions of manufacturing lack of accuracy, mounting, tuning and maintenance, due to the electronic control of the incorporated transducers. Some examples of functional interactions are presented, using the experimental data got during testing a car. It is also underlined the necessity of a minimal set of transducers and executive devices that should allow a working regime within the imposed conditions taking into account the normal wear of the system.

3

Theoretical and experimental study of the automotive fuel saving

Copae I., Chereches T.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2004

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z. 62 [209]

49--54

EN

The paper presents some theoretical considerations concerning the energetic efficiency and fuel saving of the machines, as a general issue, and of the automotive as a specific issue. The paper also presents experimental aspects with respect to the vehicle's fuel consumption. The main assessment indices of the vehicle's and engine's fuel saving are stressed. Theoretical and experimental results, according to some test data are provided. The work also makes some connections to the fuel usage efficiency and the components of the energetic balance are presented. The work makes a comparison between the fuel consumplion and the degree of the energy usage for different working conditions of the vehicles that have electronically controlled engines and mechanical transmissions.

4

Analiza pola magnetycznego w rozruszniku samochodowym z magnesami trwałymi i przekładnią planetarną

Sęk A., Polakowski K.

Przegląd Elektrotechniczny

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2004

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R. 80, nr 7-8

702-705

PL

W artykule omówiono podstawowe cechy rozruszników z magnesami trwałymi i przekładnią planetarną. Przedstawiono wyniki obliczeń przy użyciu programu PC Opera rozkładu pola magnetycznego w przekroju poprzecznym rozrusznika. W pracy wyznaczono moment rozrusznika w funkcji prądu obciążenia.

EN

The article describes the basic features of the electric engine starters based on permanent magnets and the planetar gear design. It also presents the calculation results obtained by using the PC Opera software, showing the transverse cross-sectional electromagnetic field distribution inside the starter. The torsional moment on the starter shaft nas been evaluated as the function of the load current.