Patent ID: 7631495
Filing Date: 2009-12-15
Classification: B60W,E02F,F02D

Abstract:
1. A hydraulic drive device for a hydraulic excavator, the hydraulic excavator including a travel device, travel operating levers for operating the travel device, a swing device, a work implement and implement operating levers for operating the swing device and the implement, the hydraulic drive device comprising: an engine; a hydraulic pump driven by the engine; a hydraulic actuator operated by pressure oil discharged from the hydraulic pump, the hydraulic actuator driving the travel device, the swing device and the implement; operating condition identifying means for identifying operating conditions of the hydraulic excavator; and hydraulic pump controlling means for controlling absorption torque of the hydraulic pump; wherein when the operating condition identifying means identifies a specific operating condition wherein the implement operating levers and the travel operating levers are in neutral positions, the hydraulic pump controlling means controls the absorption torque of the hydraulic pump to match an output torque of the engine at a specified engine output torque point at which a fuel consumption rate of the engine is at a minimum.