This content is not included in your SAE MOBILUS subscription, or you are not logged in.
Wet Clutch Degradation Monitored by Lubricant Analysis
ISSN: 0148-7191, e-ISSN: 2688-3627
Published October 25, 2010 by SAE International in United States
Annotation ability available
In the competitive market of the car industry today, companies need to continuously strive to optimize the performance, price and environmental properties of their products in order to survive. Wet clutches, as parts of transmission components of passenger cars are no exception. An understanding of how the wet clutch system functions and fails is necessary to optimize price and service life. The friction characteristics of the wet clutch system are determined by lubricant-surface interactions in the contact between the friction discs. Wet clutch failure can often be associated with the deterioration of friction characteristics which eventually leads to stick-slip or shudder. Consequently, knowledge of why and of how friction characteristics change over time is of the outermost significance to enable the understanding and prediction of wet clutch performance. As the lubricant is an essential component of the wet clutch system, lubricant ageing is a factor of importance. Oxidation, thermal degradation, shearing, additive degradation and water contamination could all be considered to influence lubricant ageing. The aim of this work was therefore to find suitable ways of measuring the remaining useful life of wet clutch lubricants and to correlate changes in friction characteristics with changes in lubricant properties. Both field trials and measurements in a wet clutch test rig were performed. Viscosity, acid number, additive degradation, water contamination, particle content and metal content were measured for the lubricant as it degraded. Particle content results showed a rapid increase early in the ageing process. However, as ageing progressed particle levels actually decreased and this was probably a result of particles slowly grinded between contacting surfaces. On the other hand, metal content increased as ageing progressed, which could indicate slowly progressing wear. Water levels were found to be higher in field trials than in lubricants used in wet clutch test rigs. It is concluded that this was due to the severe and accelerated operating conditions of the wet clutch test rig.
CitationBerglund, K., Marklund, P., Larsson, R., Pach, M. et al., "Wet Clutch Degradation Monitored by Lubricant Analysis," SAE Technical Paper 2010-01-2232, 2010, https://doi.org/10.4271/2010-01-2232.
- Van De Velde, F. De Baets, P. “The relation between friction force and relative speed during the slip-phase of a stick-slip cycle,” Wear 219 2 220 226 1998
- Kato, Y. Akasaka, R. Shibayama, T. “Experimental study on the lock-up shudder mechnism of an automatic transmission,” Japanese journal of tribology 39 12 1529 1538 1994
- Nakada, T. Nomura, T. Yoshioka, T. Nonoyama, M. “A Study of Additive Effects on ATF Frictional Properties Using New Test Methods,” SAE Technical Paper 902150 1990 10.4271/902150
- Scott, W. Suntiwattana, P. “Effect of oil additives on the performance of a wet friction clutch material,” Wear 181-183 850 855 1995
- Shirahama, S. “Adsorption of additives on wet friction pairs and their frictional characteristics,” Japanese journal of tribology 39 12 1479 1486 1994
- Tohyama, M Ohmori, T. Ueda, F. “Anti-Shudder Mechanism of ATF Additives at Slip-Controlled Lock-up Clutch,” SAE Technical Paper 1999-01-3616 1999 10.4271/1999-01-3616
- Zhao, H. Neville, A. Morina, A. Durham, J. Vickerman, R. “A new method to evaluate the overall anti-shudder property of automatic transmission fluids - multiple parameters spider chart evaluation,” Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 222 3 459 69 2008
- Devlin, M.T. Li, S. Tersigni, S.H. Turner, T.L. et al. “Fundamentals of Anti-Shudder Durability: Part II - Fluid Effects,” SAE Technical Paper 2003-01-3254 2003 10.4271/2003-01-3254
- Slough, C.G. Ohtani, H. Everson, M.P. Melotik, D.J. “The Effect of Friction Modifiers on the Low-Speed Friction Characteristics of Automatic Transmission Fluids Observed with Scanning Force Microscopy,” SAE Technical Paper 981099 1998 10.4271/981099
- Igari, S. Ichihasi, T. Takigawa, Y. Shimada, K. “Degradation mechanism of friction modifier containing amide groups,” Japanese journal of tribology 44 5 505 516 1999
- Wright, B. du Parquet, J. P. R. “Degradation of polymers in multigrade lubricants by mechanical shear,” Polymer Degradation and Stability 5 425 447 1983
- Covitch, M. J. “How polymer architecture affects permanent viscosity loss of multigrade lubricants,” SAE Technical Papers, no. 982638 1998
- Marklund, P. Larsson, R. “Wet clutch friction characteristics obtained from simplified pin on disc test,” Tribology International 41 9-10 824 830 2008
- Berglund, K. Marklund, P. Larsson, R. “Lubricant ageing effects on the friction characteristics of wet clutches,” Proceedings of the Institution of Mechanical Engineers, Part J:Journal of Engineering Tribology 224 7 639 647 2010
- Marklund, P. Berglund, K. Larsson, R. “The influence on boundary friction of the permeability of sintered bronze,” Tribology Letters 31 1 1 8 2008
- Coverdell, A. “A comprehensive look at the acid number test,” Practicing Oil Analysis 9 7-8 2007