Electromagnetic unit fuel injector with pivotable armature

An electromagnetic unit fuel injector of the type including a pump means to pressurize fuel;

• a supply/spill passage means in flow communication with said pump means and having a valve operatively associated therewith for movement between an open position and a closed position to control flow therethrough, a spring means operatively associated with said valve to normally bias said valve to said open position and, a solenoid means including a fixed pole piece means and a movable armature operatively associated with said valve to effect movement thereof to said closed position:
• the improvement wherein said pole piece means includes a U-shaped core having spaced apart legs the free ends of which define working surface of equal areas and wherein said armature is in the form of a rocker arm and includes a first lever arm portion operatively associated with said valve, an intermediate fulcrum portion pivotally positioned in abutment against a fixed element of said pole piece means and a second lever arm portion, of a length greater than said first arm portion, said first and second lever arm portions defining spaced apart working surfaces opposed predetermined distances from said working surfaces of said core of said pole piece means whereby upon energization of said pole piece means, said second lever arm is attracted to said core to effect movement of said valve to said closed position via said first lever arm, by a force greater than the attractive force applied by the said solenoid pole piece means upon said second lever arm portion as multiplied by the effective respective lengths of said second lever arm portion relative to said first lever arm portion.

An electromagnetic unit fuel injector of the type including a pump means to pressurize fuel;

• a supply/spill passage means in flow communication with said pump means and having a valve operatively associated therewith for movement between an open position and a closed position to control flow therethrough, a spring means operatively associated with said valve to normally bias said valve to said open position and, a solenoid means including a fixed pole piece means and a movable armature operatively associated with said valve to effect movement thereof to said closed position:
• the improvement wherein said armature is in the form of a rocker arm and includes a first lever arm portion operatively associated with said valve, an intermediate fulcrum portion pivotally positioned in abutment against a fixed element of said pole piece means and a second lever arm portion, of a length greater than said first arm portion, and wherein said pole piece means includes a U-shaped core having one leg thereof associated with said first lever arm portion and having its other leg associated with said second lever arm portion so as to define a pair of working air gaps of substantially equal areas whereby upon energization of said pole piece means, said second lever arm can be attracted to said pole piece means to effect movement of said valve to said closed position via said first lever arm, by a force greater than the attractive force applied by the said solenoid pole piece means upon said second lever arm portion as multiplied by the effective respective lengths of said second lever arm portion relative to said first lever arm portion.