Electromagnetic unit fuel injector

Claim 1

An electromagnetic unit fuel injector comprising a housing means (1,2) having a fuel passage means (30) connectable to a source of fuel for the ingress or egress of fuel at a suitable supply pressure, a supply/drain chamber (35) in flow communication with said fuel passage means, a valve stem guide bore (46) in said housing means with a conical valve seat (50) encircling said guide bore at the supply/drain chamber end thereof; a pump cylinder means (3) in said housing means; an externally actuated plunger (4) reciprocable in said cylinder means to define therewith a pump chamber (14) open at one end for the discharge of fuel during a pump stroke and for fuel intake during a suction stroke of said plunger; a valve (91) controlled injection nozzle means (15) operatively positioned in one end of said housing means; a discharge passage means (40,76) connecting said pump chamber to said injection nozzle means; a solenoid (60) actuated, poppet valve (38) controlled passage means (5l,etc.) for effecting flow communication between said pump chamber and said supply/drain chamber and including a solenoid actuated poppet valve (38) having a head (52) with a stem (53) extending therefrom journalled in said valve guide bore (46) for reciprocable movement whereby said head is movable between an open position and a closed position relative to said valve seat (50), said stem having a reduced diameter stem portion (53a) next adjacent to said head which defines with said valve stem guide bore an annulus portion (54) of said valve controlled passage means; a solenoid means (60) operatively positioned in said housing means, said solenoid means including an armature (61) operatively connected to said poppet valve; and a spring means (55) operatively positioned to normally bias said poppet valve to said open position; characterised by a piston (101) slidably journalled in said housing means (1,2) concentric to said poppet valve (38) with one end of said piston positioned to abut against said head (52) of said poppet valve, the opposite end of said piston being in flow communication with said discharge passage means (76,80) whereby said piston is operative to assist in holding said poppet valve in said closed position.