Fuel injector having differential piston for pressurizing fuel

A fuel injector for periodically flowing fuel to a combustion chamber, comprising:

• an injector housing having a fuel passage therethrough, a fuel inlet, an inlet valve movable between open and closed positions for supplying fuel to said fuel passage when said inlet valve is in said open position and a fuel control valve for periodically supplying fuel from the injector to the combustion chamber;
• a differential piston movable axially within said housing between first and second positions, said differential piston having a passageway extending between opposite ends thereof and forming part of said fuel passage;
• an air chamber within said housing for communication with an air intake manifold at substantially ambient pressure, a first face of said differential piston in part defining said air chamber and a second face of said differential piston exposed to pressure extant in the combustion chamber whereby differential pressure on said faces enables said differential piston to move from said first position to said second position to pressurize the fuel in said passage and from said second position to said first position enabling fuel flow into said fuel passage upon movement of said fuel inlet valve to said open position thereof;
• an armature carried by and within said differential piston for movement therewith and movement relative to said differential piston;
• said fuel flow control valve including a valve seat carried by said differential piston and a valve element carried by said armature, said valve element being carried for movement with said armature and said differential piston;
• a coil carried by said housing about said differential piston for displacing said armature and said valve element relative to said differential piston upon energization of said coil, from a fuel control valve-closed position to a fuel flow control valve-open position for flowing fuel under pressure in said passage to the combustion chamber.