| 摘要 |
PURPOSE:To restrain working fluid from overheat in failures of a change-over valve system by providing a change-over valve obtaining stepwise variable volume by the selection of discharge flow paths on the way of the discharge flow paths of a plurality of respective pumps, while providing a temperature sensitive valve in at least one of the discharge flow paths. CONSTITUTION:A fixed cylinder type radial piston pump PRP consisting of a large and small volume pumps PL, PS is provided, and check valves 3, 4 are respectively in discharge flow paths 1, 2 of the respective pumps PL, PS. Both discharge flow paths 1, 2 join at the downstream side of the check valves 3, 4 to provide a variable volume discharge flow path 6 connected to a hydraulic actuator 5. A branch flow paths 8, 9 leading to a pump intake flow path 7 are provided at the upstream side of the check valves 3, 4 in the respective discharge flow paths 1, 2, and a three-position change-over valve 11 giving three-stage discharge amounts by selectively opening and closing the branch flow paths 8, 9 and a communicating flow path 10 on the way of these branch flow paths 8, 9. Further, a temperature sensitive valve 12 is provided in the discharge flow path 1, which returns discharge oil to an intake flow path 7 in a predetermined high oil temperature. |
