Piezoelectric hydraulic control valve

Abstract

A hydraulic control valve having a piezoelectric actuator comprises an expansible sleeve loosely received within a bore of the valve housing, with one end thereof being fixedly or stationarily mounted relative to the housing and the other end thereof being expansibly mounted within the bore. A slidable first piston is mounted within the bore of the valve housing and is urged against the other end of the expansible sleeve. This first piston floatingly supports one end of the piezoelectric actuator, the other end of which is supported by a second piston which is slidably mounted within the sleeve and is coupled to a valve member operable to cooperate with a valve seat to open and close an inside fuel passage communicating an inlet port with an outlet port. The linear expansion of the sleeve due to a change in the ambient temperature causes the first piston to displace in one direction together with the piezoelectric actuator supported thereby so that the linear expansion of the piezoelectric actuator occurring in the opposite direction due to a similar ambient temperature change is counterbalanced whereby the second piston, serving as an output member of the piezoelectric actuator, is maintained at a constant distance with respect to the valve member regardless of change in the ambient temperature. Such a temperature compensation structure enabling precise positioning of the second piston ensures improved injection timing and injection quantity control of a fuel injection system for an internal combustion engine.