| 摘要 |
PURPOSE: To perform an ordinary excavation work in a given range, to reduce only a maximum speed when no load is applied and to reduce a load to an engine by reducing the maximum delivery pressure of a variable displacement pump when the engine of a construction vehicle is brought into an overheat state and a cooling water temperature exceeds a given value. CONSTITUTION: When an engine is brought into an overheat state and a load pressure to a pump 3 is low during operation of a construction vehicle, a control device 20 outputs a command to an electromagnetic pilot control valve 9 based on a signal from a water temperature sensor 2, attached to an engine 1, for a fact that the temperature of an engine 1 exceeds a threshold, and a signal from a pressure sensor 23, detecting the delivery pressure of the pump 3, for a fact that the pressure of the pump 3 is below a given threshold. The pilot control valve 9 is switched to a position 9b and a servo control valve 8 is switched to a position 8b. This constitution feeds the delivery pressure of the pump 3 to a servo piston 5 and reduces the delivery capacity of the pump 3 from maximum delivery capacity to low delivery capacity. |
