| 摘要 |
PROBLEM TO BE SOLVED: To keep high torque when an operating lever is quickly operated or the hardness of an object of excavation changes abruptly. SOLUTION: The pump-control circuit of a construction machine includes a variable-displacement hydraulic pump 1, a discharge-quantity controlling means 3, and a torque controlling means 8. In the pump-control circuit, a pressure detection means 11 for detecting discharge pressure of the hydraulic pump, and a control part 8a of the torque controlling means are connected individually to a controller 9. When the discharge pressure is lower than a specified pressure Pα, and the rate of increase in the discharge pressure is higher than a specified rateα, or when the discharge pressure is higher than the specified pressure Pαand the rate of increase in the discharge pressure is at least at a specified rateβsmaller than the specified rateα, a signal (current value) is derived from the controller to the control part of the torque controlling means so as to reduce the output torque of the hydraulic pump to a specified value, and the moving speed of the discharge-quantity controlling means is assisted to increase the tilting speed of the hydraulic pump to prevent torque-over, and maintain a high-output torque by controlling the signal. COPYRIGHT: (C)2009,JPO&INPIT
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