| 摘要 |
PURPOSE:To prevent lowering of the engine speed in a HST hydraulic driving device for controlling a discharge capacity of a variable capacity hydraulic pump with a differential pressure, of which pressure loss against a passing flow quantity is primarily proportioned in outline, even in the case, for example, a load except for a HST circuit is input to an engine. CONSTITUTION:The pushing force corresponding to the operation quantity of an accelerator pedal 21 is given to a switching valve 20. A differential pressure generating unit 8 generates the differential pressure to be primarily proportioned to the engine speed in outline. The pressure receiving force corresponding to this differential pressure is given to the switching valve 20 so as to resist the described pushing force. In the case that the pushing force is smaller than the pressure receiving force, the switching valve 20 increases a discharge capacity of a hydraulic pump 2, and in the case that the pushing force is larger than the pressure receiving force, the switching valve 20 reduces the discharge capacity. When a load of a hydraulic pump 14 driven by the same engine is applied, an engine load is increased, but discharge capacity of the hydraulic pump 2 is reduced by the increased quantity of the torque absorbed by the pump 14 by working of the switching valve 20 to prevent lowering of the engine speed. |
