| 摘要 |
PURPOSE:To enhance controllability by exactly switching set values by a method in which during the operation of motor, an overload relief valve on the suction side of the motor is switched to high pressure controllably, and during the braking operation, the pressure is controlled to a low-pressure set condition. CONSTITUTION:A main oil-pressure pump 1, a slewing switch valve 2, a slewing oil-pressure motor 3, and overload relief valves 4a and 4b are provided. Pilot switch valves 5a, 5b are provided as detecting means for rotation direction of the motor 3. During the slewing operation, the set values of the valves 4a and 4b on the suction side of the motor 3 are controlled to higher one than the main relief valve 12 through set value controllers 41a and 41b. During braking operation, the set values of the valves 4a and 4b are kept at a lower pressure set condition than that of the valve 12 to control the pressure on the discharge side of the motor. The durability of the whole of machine on the braking side can thus be raised. |
