Multi-plate wet clutches used in motorbikes transmit the torque by friction under pressure between driving and driven Plates. The life & performance of the clutch for the friction material used, depends on amount of energy generated during clutch slip, amount & uniformity of heat dissipation amongst the plates and surface texture of mating surfaces.
Above parameters if not properly considered during design stage may lead to higher temperature of rubbing surfaces. Higher temperature further reduces the friction coefficient and increases the wear rate of friction material leading ultimately to lower torque capacity of clutch. The temperature rise in a wet clutch is the balance between amount of heat generated and the amount of heat dissipated by oil flowing through clutch. The maximum amount of oil is limited by the requirement of clutch drag torque, Which decides the quality of neutral finding and gear shift feel on vehicle.
Further, if roughness of rubbing surfaces is not controlled in mass production, it leads to fast wear of friction material during initial operating cycles. The rate of wear is faster if the heights of surface asperities are of high magnitude.
This paper explains the design features of clutch developed by Endurance Technologies Ltd., optimized to achieve above aspects, for the engines having clutch cooling oil supply through the gear box input shaft.
An innovative oil management concept is incorporated which distributes the oil as per requirement amongst the plates. Adequate distribution of oil facilitates to have optimum oil flow with minimum desired drag torque. It also ensures effective heat dissipation throughout the clutch assembly. A part of oil is directed to cool the clutch clamping springs which reduces the clamping load loss.
The validation procedure to confirm the adequacy of oil flow through the plurality of plates is developed.
The defined controlled surface texture of steel plates provides consistent and controlled wear rate in mass production. Further, it ensures the dynamic torque capacity within a narrow band over the longer life span. The above two features of multi-plate wet clutch design achieved reduction in wear by 56 % and improved dynamic torque capacity by 16 % at the end of durability tests.