Release bearing characteristic of diaphragm spring under dynamical condition

Abstract

Diaphragm spring design has a critical importance on engagement and disengagement mechanism for a clutch system. The release bearing load characteristic of diaphragm springs determines the quality of disengagement. Release bearing load may change significantly especially under dynamic conditions compared to static conditions. For instance, a significant drop in release bearing load may be experienced under high engine velocities. This is an undesirable situation in terms of clutch performance. Drop in release bearing load may cause not to be transmitting reliably torque from engine to gearbox since minimum release bearing load is not ensured. Drop in release bearing load increases incrementally in proportion to the engine speed increase. This problem has not been addressed in technical literature. Therefore, new design of diaphragm spring becomes necessary to avoid weakening of clutch performance as the engine speed increases which leads to highly dynamic conditions. In this study, the effect of some design parameters for diaphragm springs such as outer radius and embossing are investigated using nonlinear finite element modeling. Three different outer radius with and without embossing were analyzed under boundary conditions representing actual diaphragm tests. Based on the results of FEA, it is concluded that unwanted load drops increases as the outer radius increases while embossing also leads to higher load drop. On the other hand, embossing increases the stiffness of diaphragm fingers and therefore a smaller deformation and a more long-lasting clutch load performance. As a result, an optimum design is required as the diaphragm outer radius increases for a robust disengagement behavior. © 2019 SAE International. All Rights Reserved.