Cushion Spring Sensitivity to the Temperature Rise in Automotive Dry Clutch and Effects on the Frictional Torque Characteristic

In automotive dry clutch systems the cushion spring plays an important role in terms of gradually torque transmitted during the engagement phase. In fact, it strongly influences the clutch torque transmission from engine to driveline through its non-linear loaddeflection curve. Therefore, to improve the gearshift performance in automated manual transmission is fundamental the knowledge of the cushion spring compression behaviour. Furthermore, the cushion spring compression behaviour is influenced by the temperature due to the frictional heat generation of clutch facings with the flywheel and the pressure plate surfaces during the engagement phase. In this paper an analysis on the load-deflection curve, taking into account the thermal load to which it is subjected, of a typical passenger car cushion spring is proposed. Four temperature load values, in addition to the room one, have been analysed to investigate how the cushion spring load-deflection curve depends from temperature.