ELECTRO-HYDRAULIC FAN DRIVE COOLING AND STEERING SYSTEM FOR VEHICLE

摘要

An electro-hydraulic system for operating a cooling fan and providing hydraulic fluid to a power steering system of the vehicle includes a hydraul ic pump unit including first and second fixed displacement pumps and a common drive shaft for these pumps. A hydraulic fluid reservoir is connected to the inlet of each of the pumps. A priority valve is operatively connected to the outle t of the first pump and has an outlet connectible to the power steering system. This valve also has a second outlet connectible to a hydraulic motor for the cooling fan. This valve is arranged to provide a constant flow of hydraulic fluid to the power steering system. A hydraulic line connects an outlet of the second pum p to the hydraulic motor. Hydraulic fluid flow through this line is combined with hydraulic fluid flow from the first pump to drive the motor. An electro- hydraulic proportional control valve has an inlet connected to the aforementioned line and an outlet connectible to the reservoir inlet and this control valve controls and limits the rotational speed of the motor. An electronic control device electrically operates and controls the control valve during use of the system.