Hydraulic drive, in particular hydraulic fan drive for the cooling system of an internal combustion engine

摘要

A known drive of this type has a variable displacement pump and a valve arrangement containing an electromagnet and controlling a servo piston of the variable displacement pump. The servo piston assumes various positions as a function of the magnitude of the electric current flowing through the electromagnet, the variable displacement pump being adjustable in the direction of greater delivery volume when the electric current through the electromagnet is reduced, and vice versa. Such a hydraulic drive is to be of simple and inexpensive design. This is achieved in that the valve arrangement has a pressure-relief valve, the setting of which can be varied by an electromagnet, and a 3/2-way directional valve with a control piston which can be acted upon by the pump pressure for moving in the direction of smaller delivery volume and can be acted upon by a control pressure, tapped between a choke and the pressure-relief valve, and by a first spring element for moving in the direction of a larger delivery volume, and that the pressure-relief valve has a closing body which can be acted upon in the opening direction by the control pressure and the electromagnet and in the closing direction by a second spring element.