| 摘要 |
A primary object is to provide a hydraulic drive device for a work machine that is capable of optimum control of pump absorption horsepower according to a change of working condition, thereby reducing fuel consumption, and a secondary object is to provide a hydraulic drive device for a work machine that is based on this primary object and capable of restraining variations in the pump absorption horsepower. When working condition identifying unit ( 41 ) determines that, for example, a working condition has changed from working condition (a) to (b), engine control system ( 40 a) changes engine output torque characteristic line from engine output torque characteristic line (ELa) to (ELb), and hydraulic pump control system ( 40 b) changes hydraulic pump absorption torque characteristic line from hydraulic pump absorption torque characteristic line (PLa) to (PLb). At output torque points (Ma), (Mb) at which output of engine ( 17 ) reaches a maximum, output torque of engine ( 17 ) is matched with absorption torque of hydraulic pump ( 18 ).
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