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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.

The clutch actuation system has the function of convert force made by the user on the pedal to a force acting on the clutch fingers. This system is compound with many components and one of than is the clutch release bearing. The clutch release bearing has direct contact with the finger of the clutch and materials in contact suffer a relative motion. In some case this relative motion is desired and other undesired. Thus this contact surface and the relative motion are important parameters to correct operation and to avoid wear. This paper will study the contact mechanic of this system and for this a large bibliographical review will be made and rise. Basic models and simulations will be developed to visualize the behavior of this system and also some experimental test will be done with different contact surface. This work will help to better understand the contact behavior and design contact geometry for minimum wear.

The clutch actuating systems evaluated from mechanic to semi-hydraulic and finally to hydraulic. Over this time, it was necessary to improve the projects reducing vibrations and discomfort during clutch actuation. In search of the design improvement, polytetrafluoroethylene (PTFE) polymer, which is an important engineering material and also very popular due to its resistance to chemical attack in a wide variety of solvents and solutions, high melting point and low coefficient of friction when it slides against a hard surface. However, the weakness of PTFE is its poor wear resistance. This present work aims to evaluate the wear between the sliding tube and the PTFE after tests performed in rigs under predefined and controlled conditions, such as, temperature, sliding velocity, amount of actuations, application of dirty solution outside and samples with minimal and maximum clearance.