Apparatus for controlling pressure and flow rate

Abstract

A differential pressure regulator is arranged in series on the inflow side of a variable throttle for adjustment of a flow rate. An inlet pressure of the variable throttle is led into a primary pilot chamber of the differential pressure regulator. A constant flow control valve is provided in an oil passage connecting an oil passage on the inflow side of the differential pressure regulator with a secondary pilot chamber in order to allow a fluid of a constant flow rate to flow. The inflow side of a sequence valve is connected to the side of the secondary pilot chamber of the differential pressure regulator. The outflow side of the sequence valve is connected to the outlet side of the variable throttle or a tank. The inlet passage of the variable throttle is led into the primary pilot chamber of the sequence valve. An outlet pressure of the variable throttle is led into the secondary pilot chamber of the sequence valve. Further a check valve or a throttle is connected in parallel to the sequence valve. A relief valve is provided in an oil passage starting from the outflow side of the constant flow control valve and reaching the tank in order to prevent an increase in peak pressure when a load stops and thereby to control the pressure.