| 摘要 |
PURPOSE:To control a surge pressure to be generated in a return circuit to a minimum without damaging the response of an actuator by joining the return circuit of the switch valve of an oil hydraulic circuit with an integrated filter case. CONSTITUTION:In an oil hydraulic shovel 1, for example, the capacity of a filter case 26 with two filter elements 20 is increased to two times that of a case 18, and the return circuits of switch valves 11 and 23 are joined with the case 26. In excavation work by turning a boom 2, an arm 4, and a bucket 6, particularly in excavating soft ground, soil and sand adhered to the bucket 6 are removed by the abrupt operation of the bucket switch valve 23. Since the capacity of the case 26 is large, muffler effect becomes greater and the variation of pressure becomes smaller, and also no damage occurs to the respense of the actuator. The surge pressure can thus be controlled. |
