HYDRAULIC DRIVING DEVICE FOR CONSTRUCTION MACHINE

PROBLEM TO BE SOLVED: To shorten time of warming-up for operation oil by setting first pump pushing capacity according to sensed oil temperature, setting second pump pushing capacity according to a pilot sensed value, and controlling a target pump pushing capacity unit according to the larger set value. SOLUTION: A flow amount control valve 7 is switched by pilot pressure from a pilot pump 17, which pressure is applied to a pilot pressure application part 7a. A pressure reduction valve 15 reduces the pilot pressure according to an operation rate of an operation lever 16. In controlling a pressure oil pump 2, pressure difference across a neutral circuit 6 is sensed by pressure sensors 19a, 19b, and a pump pushing capacity unit 3. In controlling pump pushing capacity at a low temperature, first, temperature of operation oil is sensed by an oil temperature sensor 18. A value in a map according to the oil temperature is compared to pump pushing capacity which is set according to the pressure difference sensed by the pressure sensors 19a, 19b. The larger value is selected for discharging the larger amount of pressure oil. It is thus possible to perform warming-up of the operation oil for a short time, with a simple structure.