| 摘要 |
PROBLEM TO BE SOLVED: To prevent cavitation from occurring when a suction side is at negative pressure when a revolving motor or a traveling motor is suddenly stopped. SOLUTION: A makeup circuit 59 is formed between circuits 53, 54 for driving. The circuits 53, 54 are connected to each other through a communication circuit 20. An opening/closing valve 30 is interposed in the communication circuit 20. A pilot port 31 is formed. A circuit 33 communicating with a tank 60 is formed and a spring 32 for returning the opening/closing valve in the closing direction is installed. The secondary port 41 of a selector valve 40 is connected to the pilot port 31, and a throttle value 34 is interposed in the circuit 33 communicating with the tank 60. A hydraulic pressure source 68 and the tank 60 are connected to the primary side 42 of the selector valve 40. The selector valve 40 is set at the hydraulic pressure source position when revolving or traveling operation is not performed, and sets the opening/closing valve 30 at the opening position. When the revolving or traveling operation is performed, the selector valve 40 is changed to the tank position, and the pilot pressure is released to the tank 60 to set the opening/closing valve 30 at the closing position. COPYRIGHT: (C)2008,JPO&INPIT
|
