The actuation force of a clutch is essentially proportional to the contact force and/or clutch torque to be transferred. Higher torques values necessitate a correspondingly higher actuation force. With conventional passenger car clutches, the maximum actuation force and force in friction contact is usually a factor of 4, whereby the actuation force increases by approx. 40% over the clutch's lifespan.
With the self-adjusting clutch , the “force equilibrium” principle and a self-actuating mechanical wear correction mechanism significantly alter the relationship between transferable torque and maximum actuation. The SAC uses the two existing spring forces to utilise the principle of force equilibrium.Once such force is the lining resilience between clutch linings on the friction disc and the other is the plate resilience, whose performance curve is modified such that a high max./min. ratio force prevails.
A solution for further reducing the actuation forces and/or optimising the actuation force curve is developing the modified SAC IIconcept. With this clutch type, the performance curve of the force sensor has altered to such a degree that the clutch is less sensitive to large actuation strokes. This situation is achieved through diaphragm springs with degressive performance curves and a sensor diaphragm spring with linear performance curve, which engages with the main diaphragm spring above the centre of motion. In many cases, this sensor diaphragm spring can also be formed directly from the diaphragm spring in the shape of sensor reeds. This eliminates the need for the entire sensor diaphragm spring. The SAC II can reduce actuation force by up to 15%, sustaining the same transferable torque. Alternatively, the maximum actuation force can be left at the original level and the potential derived for optimising the performance curve can be utilized.