The Effect of ZDDP Additive in CVT Fluid on Increasing Friction Coefficient between Belt Elements and Pulleys of Belt-Drive Continuously Variable Transmissions

Abstract

This paper discusses the effect of the zinc-dialkyldithiophosphate (ZDDP) additive on increasing the friction obtained at the sliding interfaces between the elements and the pulleys of a belt-drive continuously variable transmission (B-CVT).

Rig tests were performed with different types of CVT fluid to verify the effect of the ZDDP additive. The effect of surface roughness on film formation was also examined. The ZDDP additive increases the friction coefficient at the interfaces due to a film adsorbed on the sliding surface. A quantitative correlation was seen between the amount of Zn contained in the film and the friction coefficient as a measure of the B-CVT torque capacity.

Under boundary conditions, the friction coefficient between the belt elements and the pulleys decreased as the amount of Zn was reduced due to oil degradation. Among the elements of the ZDDP additive and Ca phenate detergent, only the Zn concentration showed a correlation with the friction coefficient, which is attributed to the fact that the film contained Zn generated from the ZDDP additive.

Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference In Toronto, Ontario, Canada, October 26–28, 1998

KEY WORDS:

• Zinc-Dialkyldithiophosphate
• Surface Analytical Techniques
• Belt-Drives

Notes

Presented as a Society of Tribologists and Lubrication Engineers paper at the ASME/STLE Tribology Conference In Toronto, Ontario, Canada, October 26–28, 1998