Influence of Contamination between Clutch Release Bearing and Sliding Tube on the Clutch Pedal Hysteresis

In recent years vehicle ergonomists have begun dedicating effort towards the study of human motion in the vehicle regarding moving comfort when using commands such as the steering wheel, gear shift and pedals. Correlation between subjective responses of human comfort and the maximum force achieved during the end-of-travel impact and the average slope of the force-displacement curve during the initial disengagement phase is difficult [1]. When end customers complain about clutch pedal actuation comfort, car salesmen and automakers change the entire clutch system, including pressure plate, clutch disc and clutch release bearing (CRB) to solve the problem and the suspicious root cause lies on the CRB. In most cases, previous analyses showed bearing still functional but strong contamination inside the bell housing, on the clutch and between the CRB with plastic housing and the sliding tube. Experiments to study the effects of contamination under high temperature, speed and the use of grease on the plastic housing made of PA66 on the friction and wear have been performed. Clutch release bearings mounted with PA66 housing rubbing against steel tubes were tested. The advantages and disadvantages of using grease on the sliding tubes were also analyzed under dirty and clean environments.