Patent ID: 8214110

Claim:
A construction machine comprising: an engine and a generator motor coupled to each other; a storage device for storing electric power generated by the generator motor and supplying electric power to the generator motor; a hydraulic pump driven by the engine and the generator motor; a hydraulic actuator to which pressure oil discharged from the hydraulic pump is supplied; an operating unit for operating the hydraulic actuator; a pump target discharge flow rate calculating unit for calculating a pump target discharge flow rate of the hydraulic pump based on an operated amount of the operating unit; a temperature detecting unit for detecting temperature of an electric device mounted on the construction machine; a storage unit for storing an engine minimum speed, which is a minimum possible speed of the engine in carrying out low-speed matching for matching output of the engine and pump absorbing horsepower of the hydraulic pump to each other in a low-speed region where a speed of the engine is lower than a set speed, as a function of the temperature of the electric device where the engine minimum speed increases or is a constant value as the temperature increases; an engine minimum speed calculating unit for calculating the engine minimum speed corresponding to the temperature of the electric device detected by the temperature detecting unit based on the temperature of the electric device and the function stored in the storage unit; and an engine target speed candidate generating unit for generating a maximum value out of a corresponding speed of the pump target discharge flow rate calculated by the pump target discharge flow rate calculating unit and the engine minimum speed calculated by the engine minimum speed calculating unit as a candidate for an engine target speed.