Quantification of Friction Component Engagement Controllability 2001-01-1156

Conventional automatic transmissions (AT) use wet friction components, such as plate clutches and band brakes to engage gears or change speed ratios during vehicle operation. The quality of engagements and ratio changes depends greatly on the frictional characteristics of the friction components, which are typically evaluated with industry standard SAE #2 test machines. These inertia absorption-type dynamometer test stands energize a friction component with prescribed level of apply force and load of inertia flywheels rotating at a specified speed until the friction elements are brought to a stop. During the slip, apply force, engagement torque, and rotating speed are digitally recorded for visual evaluation of dynamic engagement behavior. The shape of the dynamic torque curve during the engagement is known to affect AT shift quality. When many curves are generated, it becomes intractable to quantify torque curve shape differences. A new digital rating method is developed that allows these torque curves to be efficiently compared and differences effectively quantified. Single number ratings can be generated representing deviation of the individual curve from a pre-determined ideal shape.