Flow area armature for fuel injector

An armature for an electrically operated fuel injector for injecting fuel into an internal combustion engine the fuel injector having a fuel inlet, a nozzle having a valve seat via which fuel is injected into the engine from the injector, an internal passage within the injector for conveying fuel that has entered the fuel inlet to the nozzle, and a solenoid-operated valve mechanism for selectively opening and closing the valve seat, the mechanism having an armature and a valve element joined together for axial reciprocal movement within the internal passage, and an electromagnetic coil operative to open and close the valve seat in accordance with selective energizing of the electromagnetic coil, and a spring biasing the valve element closing the valve seat, the armature comprising:

• an elongated member having a first axially extending section with a first outside diameter at one end, a second axially extending section with a second outside diameter at the opposite end and a third axially extending frustoconical section connecting said first and second sections;
• a stepped passageway extending from the internal passage and extending the length of said elongated member, said stepped through-hole having a first counterbore axially extending a distance less than the axial length of said first section, a second counterbore extending from said opposite end of said tubular member a distance into said frustoconical section and a third counterbore interconnecting said first and second counterbores;
• said second counterbore having an internal diameter that is smaller than said third counterbore which has an internal diameter that is smaller than said first counterbore;
• a shoulder formed at the junction of said first and third counterbores for seating the spring, and
• a single additional through-hole having an axis normal to an element of a surface of said frustoconical section extending into said third counterbore, said through-hole having its circumferential periphery on the surface of said frustoconical section with a portion of said periphery axially below the junction between said second and third counterbores;
• whereby fuel flows from the fuel inlet through said internal passage and through said first counterbore into said second counterbore and said additional through-hole of said armature to the nozzle.