SWING CIRCUIT OPERATION SWING CIRCUIT OPERATION SWING MOTOR DEVICE PG AU FROM SWING PARKING SOLENOID VALVE DR PORT BLOCK ASSY MAKE UP VALVE MB MOTOR BRAKE VALVE VA(CCW) VB(CW) ANTI-INVERSION VALVE TO/FROM MAIN CONTROL VALVE 480A3HC17 1) 1) MOTOR BRAKE VALVE MOTOR BRAKE VALVE Motor brake valve for the swing motor limits to cushion the starting and stopping pressure of swing operation and controls the swing motor operating pressure to 285 kgf/cm 2 (4054 psi ). 2) 2) MAKE UP VALVE MAKE UP VALVE The make up valves prevent cavitation by supplying return oil to the vacuum side of the motor.
3) 3) PARKING BRAKE PARKING BRAKE This is function as a parking brake only when the swing control lever is not operated. PARKING BRAKE "OFF" OPERATION PARKING BRAKE "OFF" OPERATION When the swing control lever is tilted, the swing parking solenoid valve is energized by the MCU that senses the pilot oil pressure of the swing control lever. The discharged oil from pilot pump flows to swing motor PG port through the swing parking solenoid valve. This pressure is applied to swing parking brake piston, thus the brake is released.
PARKING BRAKE "ON" OPERATION PARKING BRAKE "ON" OPERATION When the swing control lever is set in the neutral position, the swing parking solenoid valve is de-energized, oil in the swing parking brake chamber is drained through the the swing parking solenoid valve, thus the brake is applied by spring force. 4) 4) ANTI-INVERSION ANTI-INVERSION VALVE VALVE This anti-inversion valve absorbs shocks produced as swing motion stops and reduced oscillation cause by swing motion. 3-21 3-21