Automatic speed ratio control system for stepless transmission of automotive vehicles

摘要

An automatic speed ratio control system of integration servo mechanism type for a stepless transmission of an automotive vehicle. Speed ratio is controlled by a hydraulic pump motor of variable displacement type, which in turn is controlled by an actuator having a piston and a cylinder to which hydraulic oil is supplied. The system comprises a desired value signal generator which produces a desired value signal for an engine speed corresponding to a throttle opening or an output torque of an engine or which produces a desired value signal for an engine output torque corresponding to a throttle opening or an engine speed, a detector for producing a signal indicative of an engine speed or an output torque of an engine, a control signal generator for comparing the signal from the detector against the signal from the target desired value signal generator to produce a control signal in accordance with a deviation therebetween, and a controller responsive to the control signal to drive the actuator to change a speed ratio of the stepless transmission. The system is characterized by further comprising means for producing a signal indicative of the differential or pseudo-differential of a throttle opening during the time the throttle opening increases, a signal from said means being added algebraically in opposing relationship with the signal from the desired value signal generator in the control signal generator or in opposing relationship with the signal from the control signal generator in the controller to prevent an abnormal rise in rotational speed of an engine of the vehicle during a rapid starting.