Patent ID: 6135149
Filing Date: 2000-10-24
Classification: F15B,Y10T

Abstract:
A pressure compensating valve disposed at an inlet side of a metering throttle of a directional control valve for controlling a differential pressure between inlet and outlet pressures of the metering throttle so that the differential pressure corresponds to a differential pressure between a delivery pressure of a hydraulic pump and a signal pressure in a signal line comprising:a step-shaped spool having a larger diameter portion and smaller diameter portions positioned at opposed sides of the larger diameter portion, the larger diameter portion being formed with flow control notches;first and second pressure receiving chambers disposed to sandwich the larger diameter portion of the spool for respectively applying a delivery pressure of the hydraulic pump in a direction opening the flow control notches and the inlet pressure of the metering throttle of the directional control valve in a direction closing the flow control notches;a third pressure receiving chamber disposed at an end of the smaller diameter portion of the spool on the same side as the first pressure receiving chamber;a fourth pressure receiving chamber disposed at an end of the smaller diameter portion on the same side as the second pressure receiving chamber;a fifth pressure receiving chamber disposed on the same side as the third pressure receiving chamber with respect to the larger diameter portion and to which the outlet pressure of the metering throttle is introduced; anda sleeve slidably fitted on an outer periphery of the smaller diameter portion of the spool on the same side as the first pressure receiving chamber and having opposed ends respectively positioned in the first pressure receiving chamber and the fifth pressure receiving chamber whereby the sleeve is moved so as to introduce the outlet pressure of the metering throttle to the third pressure receiving chamber when the delivery pressure of the hydraulic pump in the first pressure receiving chamber becomes higher than outlet pressure of the metering throttle in the fifth pressure receiving chamber.