Circuit pressure control system for hydrostatic power transmission.

摘要

A circuit pressure control system for a hydrostatic power transmission having a variable-displacement hydraulic pump driven by a prime mover, a hydraulic actuator for actuating a load and a displacement adjusting mechanism for the pump. The pump and actuator are connected in closed or semi-closed circuit, and the adjusting mechanism is actuated by a signal indicating the operating level manipulated variable and a signal indicating the actual displacement of the hydraulic pump to control the speed of the hydraulic actuator. The system comprises a sensor (17) for sensing the circuit pressure of the transmission and generating a signal indicating the sensed circuit pressure, a device (19-23) for calculating based on the manipulated variable and circuit pressure signals a hydraulic pump displacement command causing displacement of the pump to be changed at a maximum rate when the circuit pressure is below a predetermined value and causing the changing rate of the displacement to be reduced when the predetermined value is exceeded thereby, and a device (14) for comparing the displacement command with the actual displacement of the hydraulic pump and producing a signal for decreasing the difference between them and supplying such signal to the displacement adjusting mechanism (2a).