Fan revolution speed control method
The invention is a fan revolution control method for controlling a pump-motor system, by controlling the fan revolution speed of a cooling fan adapted to be rotated by a fan motor to cool cooling target fluids. The pump-motor system drives the fan motor by a hydraulic fluid fed from a fan pump driven by an engine. The pump-motor system is controlled so the fan revolution speed starts from the minimum fan revolution speed when the engine is started up; the minimum fan revolution speed is maintained for at least several seconds; after the elapse of several seconds, the fan revolution speed is gradually increased from the minimum fan revolution speed. The fan revolution speed reaches a target fan revolution speed over a period of at least several seconds. The method prevents generation of peak pressure or pressure hunting.
1. A fan revolution speed control method for controlling a pump-motor system so as to control the fan revolution speed of a cooling fan that is adapted to be rotated by a fan motor so as to cool a cooling target fluid, said pump-motor system adapted to drive said fan motor by means of hydraulic fluid supplied from an engine-driven fan pump, wherein said fan revolution speed control method comprises steps of:
detecting a temperature of a cooling target fluid,
determining a target fan revolution speed of said cooling fan based on the detected temperature of said cooling target fluid,
controlling said pump-motor system so that the fan revolution speed starts from a minimum fan revolution speed at the-start-up of the engine, wherein said minimum fan revolution speed is a predetermined speed not dependent upon the detected temperature of said cooling target fluid, and
further controlling said pump-motor system so that the fan revolution speed gradually increases to said target fan revolution speed.
2. A fan revolution speed control method as claimed in claim 1 , wherein: said minimum fan revolution speed is maintained for a given period of time at the start-up of the engine.