Experimental Investigation of Tripod Constant Velocity (CV) Joint Friction
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abstract
Constant Velocity (CV) joints are an integral part of modern vehicles, significantly affecting steering, suspension, and vehicle vibration comfort levels. Each driveshaft comprises of two types of CV joints, namely fixed and plunging types connected via a shaft. The main friction challenges in such CV joints are concerned with plunging CV joints as their function is to compensate for the length changes due to steering motion, wheel bouncing and engine movement. Although CV joints are common in vehicles, there are aspects of their internal friction and contact dynamics that are not fully understood or modeled. Current research works on modeling CV joint effects on vehicle performance assume constant empirical friction coefficient values. Such models, however are not always accurate, especially under dynamic conditions which is the case for CV tripod joints. In this research, an instrumented advanced CV joint friction tester was developed to measure the internal friction behavior of CV joints using actual tripod-type joint assemblies. The setup is capable of measuring key performance parameters, such as friction and wear, under different realistic operating conditions of oscillatory speeds and CV joint installation angles. The tester incorporates a custom-installed tri-axial force transducer inside the CV joint to measure in-situ internal CV joint forces (including friction). Using the designed test setup, we investigated the interfacial parameters of CV joints in order to understand their friction mechanism. Specifically the slip-to-roll ratio of the roller inside the CV joint was measured to better understand the sliding and rolling friction between the tripod's roller and housing. Intrinsic interfacial parameters, such as torque, articulation angle, plunging velocity and rotational phase angle of CV joints were also varied in order to examine their effects on the friction. Based on these experiments, one can establish a better understanding of CV joint friction and develop a model that can be used in designing improved CV joints. Copyright 2006 SAE International.
