| 摘要 |
<p>A hydraulic driving unit that, in order to effectively utilize the pressure oil in the rod chamber (6a) of a boom cylinder (6) when the bottom pressure in an arm cylinder (7) becomes high during a composite operation in which pressure oil is fed to the bottom chambers (6a, 7a) of the boom cylinder (6) and the arm cylinder (7) in a hydraulic shovel, comprises a boom-associated direction control valve (23) and an arm-associated direction control valve (24) for controlling the boom cylinder (6) and the arm cylinder (7), respectively, that are driven by the pressure oil delivered from a main hydraulic pump (21), a boom-associated operating device (25) for controlling the switching of the boom-associated direction control valve (23), an arm-associated operating device (26) for controlling the switching of the arm-associated direction control valve (24), wherein a communication control means is provided for establishing communication between the rod chamber (6b) of the boom cylinder (6) and the bottom chamber (7a) of the arm cylinder (7) when the bottom pressure in the arm cylinder (7) becomes a predetermined pressure or above.</p> |
