HYDRAULIC DRIVING UNIT FOR WORKING MACHINE, AND METHOD OF HYDRAULIC DRIVE

摘要

A fuel injection control device (an electronic governor (12) and a controller (13)) for an engine (1) is capable of controlling the governor region to an isochronus characteristic. A working machine controller (18) receives a delivery pressure signal (P) and controls a regulator (16) in such a manner that when the delivery pressure of a hydraulic pump exceeds a predetermined pressure (P1), the displacement volume of the hydraulic pump does not exceed a value determined by a preset pump absorption torque curve (20) and when the delivery pressure of the hydraulic pump (2) is not more than a predetermined pressure (P1), the displacement volume of the hydraulic pump increases as the delivery pressure of the hydraulic pump lowers from the predetermined pressure (p1). This makes it possible, even if the governor region is controlled to an isochronus characteristic, to increase the delivery rate of the hydraulic pump as the engine load becomes lighter.