RATIO CONTROL TECHNIQUE FOR CONTINUOUSLY VARIABLE TRANSMISSION

摘要

A ratio control system for use in a continuously variable transmission is disclosed in conjunction with an improved technique for operation thereof. Individual gain schedules provide proportional gain in response to a selected one of a number of modes dependent upon clutch input speed, transmission belt ratio, or engine set point. Engine speed set point is determined as a function of a set point schedule (114) in conjunction with a limiter (116) and a filter (120) to provide a gradual response to rapid changes in a throttle input or driver demand signal and vehicle speed. The error signal generated as an output of any of the proportional gain loops is integrated (154) and combined (in 104) with a null signal (N0) to provide a signal (e4) to generate a duty cycle for a pulse width modulation controlled electrohydraulic control valve to control the pressure to the primary sheave in a continuously variable transmission system for modifying the belt ratio. The integration function (154) may be used or bypassed at appropriate times to account for physical limitations in the possible range for the belt ratio. Full low and full overdrive conditions are provided through an open loop gain corresponding to maximum and minimum duty cycle signals.