Patent ID: 8613420

Claim:
A solenoid valve for controlling flow of hydraulic fluid in a hydraulic system, comprising: a coil of electrically conductive material wound on a coil support, the coil support having an inner surface defining an internal chamber; a cup-shaped tubular sleeve disposed in the internal chamber and having an outer surface located in close spatial proximity to the inner surface of the coil support; a valve element seat disposed in the internal chamber of the coil support and secured in a fluid-tight manner to an open end of the tubular sleeve so as to define a valve chamber therebetween, the valve chamber communicating with hydraulic fluid from the hydraulic system; an armature supported for sliding movement within the valve chamber and defining an annular chamber between its outer surface and the inner surface of the tubular sleeve such that the armature floats in the hydraulic fluid within the annular chamber; a valve element extending through a bore in the valve element seat into the valve chamber and engaging a first end of the armature for movement in response to movement of the armature, wherein the valve element is spaced from a valve seat when the solenoid valve is not activated and is received in the valve seat when the solenoid valve is activated, and a control unit for activating the solenoid valve by supplying a current to the coil that is greater than a minimum current required to move the armature against hydraulic pressure in the valve chamber and push the valve element into the valve seat and to heat the hydraulic fluid within the annular chamber, and wherein the control unit supplies a current to the coil that is lower than a minimum current required to move the armature against the hydraulic pressure in the valve chamber to keep the valve element spaced from the valve seat and heat the hydraulic fluid within the annular chamber whenever the solenoid valve is not activated.