Electrically operated trigger valve for fuel injection pump

Abstract

An electrically operated trigger valve for a fuel injection pump includes a valve member secured to an armature to form an armature and valve member assembly. The valve member is slidably mounted in a bore and controls communication between the fuel inlet and a fuel outlet. In use, the valve is maintained in its closed position by energizing a stator coil to attract the armature. When the stator is de-energized the armature and valve member assemblies moved in the valve opening direction by a valve opening spring. The length of the valve opening spring is such that when the valve is in the fully open position a gap exists between one end of the opening spring and its adjacent seat. Accordingly, initial movement of the armature and valve member assembly in the closing position, upon subsequent energization of the state of coil, is not opposed by the spring until the gap has been eliminated by initial movement of the armature. This arrangement reduces the initial stator current necessary to produce movement of the armature and valve member assembly. It also permits a relatively stiff opening spring to be used, thereby reducing the impact with which the valve member engages the seat upon closing, and producing a rapid initial movement in the opening direction after de-energization of the stator coil.