Patent ID: 8919115
Filing Date: 2014-12-30
Classification: E02F,F15B

Abstract:
1. A hydraulic drive device for a hydraulic excavator, which is provided in the hydraulic excavator including a front attachment, the front attachment being connected to a swing body in a vertically rotatable manner and including an arm, a bucket, an arm cylinder, and a bucket cylinder, comprising: an engine; a first hydraulic pump, a second hydraulic pump, and a pilot pump that are driven by the engine; a bucket directional control valve and a second arm directional control valve that are each connected in parallel tandem with the first hydraulic pump, the bucket directional control valve controlling a flow of pressurized oil supplied to the bucket cylinder, the second arm directional control valve controlling a flow of pressurized oil supplied to the arm cylinder; a swing directional control valve and a first arm directional control valve that are each connected in parallel tandem with the second hydraulic pump, the swing directional control valve controlling a flow of pressurized oil supplied to a swing motor for rotating the swing body, and the first arm directional control valve controlling a flow of pressurized oil supplied to the arm cylinder; a flow rate restriction device that restricts a flow rate of pressurized oil supplied to the second arm directional control valve; and a disable control device that performs a control to disable the restriction of the flow rate by the flow rate restriction device when a pressure of pressurized oil discharged from the first hydraulic pump becomes a high pressure equal to or higher than a predetermined pressure regardless of each operation status of the crowd operation of the bucket and the crowd operation of the arm and swing operation of the swing body, wherein