| 摘要 |
PROBLEM TO BE SOLVED: To provide an oil pressure control circuit for a hydraulic grab bucket continuously operable for a long time, by suppressing temperature up caused by heating working oil due to relief actuation, etc., in setting pressure in a pressure control valve for setting conventional hydraulic cylinder working pressure when closing the bucket to grip cargoes and the like. SOLUTION: In an oil pressure control circuit for a hydraulic grab bucket equipped with a hydraulic cylinder 15 for opening/closing a bucket, a hydraulic pump for driving the cylinder 15, and an electromagnetic switch valve 11 linked to the discharge pipe of the hydraulic pump to switchingly supply pressure oil to the head and rod side chambers 15a and 15b of the cylinder 15; the hydraulic pump is adopted as a variable discharge type hydraulic pump 19 equipped with a discharge amount control mechanism for making the discharge amount Q of the hydraulic pump minimum when hydraulic pump discharge pressure is increased to set pressure PS, that is, the discharge Q is restricted to the minimum discharge amount needed to pressurize the cylinder 15.
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