| 摘要 |
PROBLEM TO BE SOLVED: To provide a hydraulic driving device capable of preventing cavitation and the reduction of brake capability. SOLUTION: In the hydraulic driving device constituted such that a hydraulic source and a hydraulic motor M are connected in discharge side and return side main circuits 1, 2, a counterbalance valve 3 is provided in each main circuit to switch freely, the counterbalance valve has discharge passages 10, 11 opened and closed in the discharge side main circuit and a check valve in a discharge passage, springs 15, 16 are provided on one side of the counterbalance valve, and pilot circuits 17, 18 are connected with the other side thereof, branch passages 21, 22 are connected with the upstream side of the check valve in the counterbalance valve, return circuits 23, 24 are connected with the return side main circuit, a high pressure selection valve 4 allowing a flow from the return side main circuit is provided, a bypass circuit 27 is connected with the return circuit on the downstream side of the high pressure selection valve so as to open and close freely, and the other end of the bypass circuit is selectively opened and closed in the branch passage.
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