Pressure compensation valve unit and pressure oil supply system utilizing same

A pressure compensation valve unit comprising:

• a check valve provided with a check valve bore to which an inlet port and an outlet port are opened and a spool inserted into said check valve bore, adapted to communicate said inlet port with said outlet port and to block the communication therebetween, pushed in the communication direction by a pressure at said inlet port and pushed in the blocking up direction by a pressure at said outlet port;
• and
• a pressure reducing valve provided with a pressure reducing valve bore to which a first port and a second port are opened, a spool inserted into said pressure reducing valve port, adapted to communicate said first port with said second port and to block the communication therebetween and having a small diameter rod opposing to said check valve, a third pressure receiving chamber receiving a pressure for pushing said spool in the blocking up direction through the communication with said second port, and first and second pressure receiving chambers formed on both end sides of a free piston slidably fitted to said small diameter rod and adapted to receive a pressure for pushing said spool in the communication direction thereof,
• wherein load pressures of different actuators are introduced into said first and second pressure receiving chambers.

A pressure oil supply system wherein a pressure compensation valve unit is disposed in a discharge passage of a hydraulic pump, said pressure compensation valve unit comprising:

• a check valve which is pushed in an opening direction thereof by an inlet side pressure and in a closing direction thereof by an outlet side pressure and a pressure reducing valve cooperating with said check valve and actuating to establish communication between the inlet side and the outlet side of said check valve and block the communication therebetween, said pressure reducing valve having a pressure reducing valve member pushed in the blocking direction by a pressure in a pressure receiving chamber to push the check valve in the closing direction thereof, said pressure reducing valve member being pushed in the communication direction with a highest pressure in a plurality of pressures selected by a selection pressure receiving means, and communicating said outlet side with said pressure chamber;
• a plurality of actuators connected to the output side of said pressure compensation valve unit through a plurality of directional control valves;
• the discharge passage of said hydraulic pump connected to the inlet side of the pressure reducing valve of said pressure compensation valve unit;
• and
• load pressure of the respective actuators are introduced into said pressure selective receiving means so as to push said pressure reducing valve by the highest load pressure.

A pressure oil supply system provided with a pressure compensation valve unit comprising:

• a check valve provided with a check valve bore to which an inlet port and an outlet port are opened and a spool inserted into said check valve bore, adapted to communicate said inlet port with said outlet port and to block the communication therebetween, pushed in the communication direction by a pressure at said inlet port and pushed in the blocking up direction by a pressure at said outlet port;
• and
• a pressure reducing valve provided with a pressure reducing valve bore to which a first port and a second port are opened, a spool inserted into said pressure reducing valve port, adapted to communicate said first port with said second port and to block the communication therebetween and having a small diameter rod opposing to said check valve, a third pressure receiving chamber receiving a pressure for pushing said spool in the blocking up direction through the communication with said second port, and first and second pressure receiving chambers formed on both end sides of a free piston slidably fitted to said small diameter rod and adapted to receive a pressure for pushing said spool in the communication direction thereof;
• and
• wherein a plurality of actuators are connected to the output side of said pressure compensation valve unit through a plurality of directional control valves;
• the discharge passage of said hydraulic pump is connected to the inlet side of the pressure reducing valve of said pressure compensation valve unit;
• and
• load pressures of different actuators are introduced into the first and second pressure receiving chambers of said pressure reducing valve to thereby push said pressure reducing valve in the communication direction with the highest load pressure.

A pressure compensation valve unit, comprising:

• a check valve which is pushed in an opening direction thereof by an inlet side pressure and in a closing direction thereof by an outlet side pressure;
• and
• a pressure reducing valve, cooperating with said check valve, actuating to establish communication between the inlet side and the outlet side of the check valve and block communication therebetween, said pressure reducing valve provided with a pressure reducing valve bore to which a first port and a second port are opened, a spool inserted into said pressure reducing valve port, adapted to communicate said first port with said second port and to block the communication therebetween and having a small diameter rod opposing to said check valve, a third pressure receiving chamber receiving a pressure for pushing said spool in the blocking direction through the communication with said second port, and first and second pressure receiving chambers formed on both end sides of a free piston slidably fitted to said small diameter rod and adapted to receive a pressure for pushing said spool in the communication direction thereof;
• and
• a pressure selective receiving means for selectively receiving a highest pressure in a plurality of pressures in said first and second pressure receiving chambers to push said spool in the communication thereof.