Continuously variable transmission clutch control system including

Abstract

The system provides an improved clutch control system for use in a continuously variable transmission system. The system provides for generation of a clutch pressure setpoint to re-engage the clutch during special conditions in which the torque created by the vehicle inertia would tend to drive the engine to an undesirable operating point. Clutch slip speed is monitored as a difference value and integrated to provide a gradually decreasing error signal to return the clutch input speed to the clutch output speed, at which time clutch lockup will occur. Additionally, throttle position is monitored and a maximum torque schedule used to provide a maximum torque signal to prevent driver demand from undesirably racing the engine in similar conditions. A filtered output of the maximum torque schedule provides a pressure setpoint signal representative of actual driver demand which may be added to the clutch slip speed error signal to generate the clutch pressure setpoint. In this fashion, an engine may be loaded by an increase in the clutch pressure at the same time that the clutch input speed is returned to the clutch output speed to restore clutch lock up. Addition of a constant value to the clutch slip speed error signal ensures positive clutch lockup.