Hydraulic circuit system

摘要

PCT No. PCT/JP91/01284 Sec. 371 Date Jun. 3, 1992 Sec. 102(e) Date Jun. 3, 1992 PCT Filed Sep. 26, 1991 PCT Pub. No. WO92/06304 PCT Pub. Date Apr. 16, 1992.This invention has for its aim to provide a hydraulic circuit system arranged such that, even at the time of commencement of drive of a hydraulic actuator with a large inertia, a slow rise in the drive pressure can be achieved, thereby preventing the occurrence of hunting phenomenon. The hydraulic circuit system according to the present invention comprises a plurality of operating valves (15) provided in a discharge conduit (10a) of a hydraulic pump (10), and pressure compensating valves (18) provided in connection conduits between these operating valves (15) and respective hydraulic actuators (16), wherein each of the pressure compensating valves (18) is set at a highest value of load pressures of each of the hydraulic actuators (16), and the displacement of the pump is controlled by a change-over valve (14) adapted to be actuated by the difference between the pump discharge pressure and the load pressure. The hydraulic circuit comprises a bypass conduit (31) connected with a load pressure introduction conduit (30) for introducing the load pressure into a pressure receiving portion of the change-over valve (14). This bypass conduit is connected through a bypass valve (32) adapted to conduct throttling of fluid in inverse proportion to the change in the area of opening of each of the operating valves (15).