FLOW RATE/PRESSURE CONTROLLING CIRCUIT

摘要

PURPOSE:To keep a differential pressure between front and rear points of a variable throttle to a constant value by disposing a constant flow rate control valve between an inflow-side oil passage of a constant difference reduction valve and a secondary side pilot chamber, and a sequence valve between the secondary side pilot chamber and the outlet of the variable throttle. CONSTITUTION:A constant flow rate control valve 14 is disposed in an oil passage 13 which connects a main oil passage 11 to the secondary side pilot chamber of a constant difference reduction valve 2. A sequence valve 18 is disposed in an oil passage 17 which connects the secondary side pilot chamber to the outflow side main oil passage 11 of a variable throttle 1. A check valve 22 is connected to the sequence valve 18 in parallel with it. And a relief valve 24 is disposed in an oil passage which extends from the outflow side of the constant flow rate control valve 14 to a tank. Without the need of enlarging both the sizes of the pressure compensating spool of the constant pressure reduction valve 2 and a differential pressure setting spring, a differential pressure between front and rear points of the variable throttle 1 can be always kept constant within a range of rated flow rate and the rated flow rate can be also determined appropriately.