SYSTEM / Control System Relief Flow Rate Reducing Control (Relief Cut Off) Purpose: Reduces hydraulic energy loss and prevents hydraulic oil temperature from rising. (Flow Rate Reducing Control (Relief Cut Off)) Operation: 1. When an actuator is operated, the pump delivery pressure varies due to changing load applied to each actuator. 2. The pump delivery pressure sensor detects de- livery pressure and sends the signals to MC. 3. When pump delivery pressure reaches 30.9 MPa (315 kgf/cm 2 , 4490 psi), MC compares pump de- livery pressure with the actual pump displacement angle detected by the pump regulator pressure sensor, and activates the pump control solenoid valve.
Therefore, pump delivery flow rate de- creases and becomes the minimum flow rate. 4. If the pressure sensor (travel right or left) detects travel pilot pressure or the pressure sensor (swing) detects swing pilot pressure, MC cancels the relief flow rate reducing control to the main pump (relief cut off override). Q Qm Flow Rate Relief Cut Off Override Relief Cut Off Relief Flow Rate Reducing Qo Pressure P Pc Pr Travel (Right) Travel (Left) Pump 2 Delivery Pressure Sensor Swing Pump 1 Delivery Pressure Sensor Engine Con- trol Dial Pump 1 Regulator Pressure Sensor Pump 2 Regulator Pressure Sensor T1J1-02-02-005 Pump 1 Control Solenoid Valve Pump 2 Control Solenoid Valve T2-2-29