Patent ID: 8612102

Claim:
A hydraulic excavator comprising: a travel unit configured to drive a vehicle; a revolving unit mounted upon the travel unit and swingably provided to the travel unit; an engine; a hydraulic pump driven by the engine; a work machine driven by hydraulic fluid discharged by the hydraulic pump; an electric accumulator; an electric power generating motor driven by driving force from the engine, whereby a power-generating action is performed, the electric power generating motor being configured to store electrical energy in the electric accumulator; an electric swing motor configured to swing the revolving unit using the electrical energy from the electric accumulator; a first operating device configured to operate the swinging of the revolving unit; a second operating device configured to operate the work machine; and a control unit configured to control output of the engine on the basis of a first engine output torque line that defines an upper limit of engine output torque relative to engine rotation rate, the control unit being configured to determine which of a high hydraulic load operation in which the work machine is subjected to a high hydraulic load and a low hydraulic load operation in which the work machine is subjected to a low hydraulic load is being performed, and the control unit being configured to control the output of the engine on the basis of a second engine output torque line having lower engine output torque than the first engine output torque line when the operation for swinging the revolving unit and the low hydraulic load operation are performed as a combined operation.