Patent ID: 7155907
Filing Date: 2007-01-02
Classification: F16D

Abstract:
1. An electro-hydraulic system for operating a hydraulic motor for a vehicle cooling fan and providing pressurized hydraulic fluid to a power steering system of the vehicle, said system comprising: a hydraulic pump unit including at least first and second fixed displacement pumps and a common drive shaft to drive each of said pumps; a hydraulic fluid reservoir fluidly connected to at least one inlet of said pumps and capable of providing sufficient hydraulic fluid for operation of said pump unit; an electro-hydraulic drive circuit adapted for hydraulic fluid connection to said hydraulic motor for operating said cooling fan, said drive circuit including an electro-hydraulic proportional control valve operatively connectible to said pump unit for controlling and limiting the operational speed of said hydraulic motor and further including a priority valve for providing a constant flow of hydraulic fluid to said power steering system, the operation of said priority valve being controlled by hydraulic pressure in said fan drive circuit during use of the electro-hydraulic system, wherein said proportional control valve is adapted for electrical connection to an electronic control device capable of electrically operating and controlling said proportional control valve from predetermined input variable readable by said control device, said variables including at least one temperature variable, said control device being capable of calculating an appropriate cooling fan speed, generating electrical control signals based on said calculation, and transmitting these control signals to said proportional control valve in order to direct said cooling fan towards a more appropriate speed for cooling, and wherein said priority valve is arranged to direct excess flow of hydraulic fluid, if any, from the pump unit so that said excess flow is combined with hydraulic fluid flow from said second pump in order to drive said hydraulic motor and operate said fan.