HYDRAULIC UNIT, AND CONSTRUCTION MACHINE HAVING THE UNIT

摘要

A hydraulic unit is switched among a first region (A), in which the capacity of a variable capacity type pump is kept the maximum so that the flow rate is adjusted by the speed control of an electric motor, a second region (B), in which the speed of the electric motor is held at the minimum speed lower than that of the first region (A) so that the capacity of the variable capacity type pump is changed to adjust the flow rate, and a region (C), in which, while the allowable maximum capacity of the variable capacity type pump introduced from the discharge output and the maximum axial torque of the electric motor is being kept within the range having the higher discharge pressure of the variable capacity type pump than that of the first region (A), the speed of the electric motor is varied within a range larger than that of the minimum speed, thereby to adjust the flow rate.