Patent ID: 6082106
Filing Date: 2000-07-04
Classification: E02F,F15B

Abstract:
A hydraulic device comprising:a variable displacement pump;first and second hydraulic actuators driven by delivery oil from the pump, each hydraulic actuator having a loaded pressure;first and second directional valves for controlling the delivery oil flowing into the first and second actuators, respectively;first and second pressure compensation valves coupled to and for compensating pressures of the first and second directional valves, respectively, the first pressure compensation valve receives an oil pressure on a downstream side of a throttle of the first directional valve coupled to the first pressure compensation valve, a maximum loaded pressure of the loaded pressures of the hydraulic actuators of the hydraulic device, and an oil pressure communicated with the loaded pressure of the first actuator communicating with the first pressure compensation valve,such that the oil pressure on the downstream side of the throttle of the first directional valve to act in a first control pressure chamber of the first pressure compensation valve to open the first pressure compensation valve, and the maximum loaded pressure to act in a second control pressure chamber of the first pressure compensation valve to close the first pressure compensation valve, and the oil pressure communicated with a loaded pressure of the first actuator to act in a third control pressure chamber of the first pressure compensation valve to close the first pressure compensation valve,each pressure receiving area of the first and second control pressure chambers is made the same, while a pressure receiving area of the third control pressure chamber is made far smaller than that of the first control pressure chamber,thereby the first pressure compensation valve decreasing output flow of the delivery oil to the first actuator communicating with the first pressure compensation valve when the loaded pressure of the first actuator is increased;a constant power control means coupled to the variable displacement pump; anda delivery oil varying means associated with the constant power control means.