| 摘要 |
PURPOSE:To perform switching of a hydraulic motor speed in good condition by providing auxiliary pipe lines with orifices on feed/discharge pipe lines led to a hydraulic motor, and a directional control valve in the feed/discharge pipe lines, and also relief valves operated by the differential pressure between the upper/lower stream sides of the orifices, in the auxiliary pipe lines. CONSTITUTION:A directional control valve 4 which switches the supplying direction of pressure oil led to a pump 2 is provided in pipe lines 3, 3' and auxiliary pipe lines 6, 6' with orifices 7, 7' branched from the pipe line 3, 3' are provided. The pilot ports of relief valves 10, 10' are connected to pilot tubes 11, 11' branched from the lower stream side and the upper stream side of the orifice 7, 7' respectively and they are operated by the differential pressure between the orifices 7, 7'. And the switching of the directional control valve 4 can switch the speed of hydraulic motor 1 without the change of the power of the hydraulic pump 2.
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