Patent ID: 8532855

Claim:
A hybrid construction machine, comprising: an engine; a hydraulic pump configured to be driven by the engine; a hydraulic actuator configured to be driven with a hydraulic pressure from the hydraulic pump; an electric motor configured to assist driving of the engine; and a generator configured to be driven by the engine to generate a power, wherein a number of revolutions of the engine is caused to vary in accordance with a size of a load on the engine, the engine is decelerated by causing the generator to generate the power, in response to a decrease in the load requested of the engine, and the engine is accelerated by assisting the engine by driving the electric motor, in response to an increase in the load requested of the engine, wherein: one of the generator and the electric motor is driven until the number of revolutions of the engine reaches one of a predetermined low number of revolutions and a predetermined high number of revolutions, and an output of the one of the generator and the electric motor for the deceleration or the acceleration is stopped after the number of revolutions of the engine reaches the one of the predetermined low number of revolutions and the predetermined high number of revolutions.