| 摘要 |
PURPOSE:To reduce a severe dynamic load during operation, by connecting pilot oil chambers of flow control valves and pilot oil chambers of relief valves in variable displacement hydraulic pumps with a tank and a pilot pump through a selector valve. CONSTITUTION:Flow control valves 24, 25, equipped with pilot oil chambers D having a function decreasing the maximum delivery oil amount by a pressure signal from the outside, are provided in variable displacement hydraulic pumps 2, 3, and relief valves 22, 23, having pilot chambers E increasing the pressure of preset value, are provided in delivery side oil paths 5, 6 of said hydraulic pumps 2, 3, while the pilot chambers D, E are connected with a tank 29 and a pilot pump 4 through an electromagnetic selector valve 30. In this way, a severe dynamic load can be reduced during operation because the delivery oil amount of the variable displacement hydraulic pumps 2, 3 decreases if the preset pressure of the relief valves 22, 23 increases.
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