Engagement Model of Dry Friction Clutch with Diaphragm Spring

The duration of engagement of automotive clutch plays an important role in the driving comfort and smooth launching of the vehicle. It is a transient phenomenon controlled by many variables like dynamics of release bearing and linkage, relation between release bearing travel and pressure plate lift, the clamp load developed with respect to cushion deflection and inertia of driver and driven shafts. Modern automobiles employ diaphragm spring clutch, which is advantageous in terms of less overall height and weight, number of components, low release load and increased service life. The non-linear characteristics of the diaphragm spring can be exploited favorably in achieving smooth engagement process. In this paper a mathematical model of transient engagement dynamics is developed correlating the parameters like spring characteristics, clamp load characteristics, pressure plate lift and release bearing travel characteristics, clutch pedal kinematics during engagement, vehicle driveline dynamics during startup, etc. The engagement duration of the clutch can be simulated along with the clamp load build up and torque transmission to the driveline using this model. Results of simulation are also included here which were verified through actual tests. This analysis should be useful in design of release mechanism for achieving smooth clutch engagement and to compare various clutches on the duration of slippage.