Modular fuel injector having a low mass, high efficiency electromagnetic actuator and having an integral filter and O-ring retainer assembly

1. A method of assembling a fuel injector, comprising:

providing a valve group subassembly including:

a tube assembly having a longitudinal axis extending between a first end and a second end, the tube assembly including a magnetic pole piece having a first face having a first surface area;

a seat secured at the second end of the tube assembly, the seat defining an opening;

an armature assembly disposed within the tube assembly, the armature assembly having a second face disposed from the first face by a gap, the second face having a second surface area smaller than the first surface area;

a member biasing the armature assembly toward the seat;

an adjusting tube located in the tube assembly, the adjusting tube engaging the member and adjusting a biasing force of the member;

a filter located at the first end of the tube assembly, the filter having retaining portion;

an O-ring circumscribing the first end of the tube assembly, the retaining portion of the filter maintaining the O-ring proximate the first end of the tube assembly; and

a first attaching portion;

providing a coil group subassembly including:

a solenoid coil operable to displace the armature assembly with respect to the seat;

a coil housing that surrounds the solenoid coil; and

a second attaching portion;

an overmold that encloses a portion of the coil housing within the overmold; and

inserting the valve group subassembly into the coil group subassembly.

2. The method according to claim 1 , further comprising: connecting the first and second attaching portion together.

3. The method according to claim 2 , wherein the connecting comprises welding.

4. The method according to claim 1 , further comprising: welding the coil group subassembly to the valve group subassembly.

5. A method of assembling a modular fuel injector comprising:

inserting a valve group subassembly into a coil group subassembly, the coil group subassembly having an overmold that defines first end, second end, and a coil housing including a portion disposed within the overmold, the coil housing having a first attaching portion, the valve group subassembly having a tube assembly extending between an inlet end and an outlet end along a longitudinal axis, the tube assembly having a second attaching portion; and

securing the first attaching portion to the second attaching portion proximate the outlet end.

6. The method of claim 5 , wherein the securing further comprises welding the first attaching portion to the second attaching portion.

7. The method of claim 6 , wherein the welding comprises forming a weld extending through the first attaching portion to the second attaching portion.

8. A method of assembling a modular fuel injector comprising:

inserting a valve group subassembly into a coil group subassembly, the coil group subassembly having a first end, second end, and a coil housing disposed therebetween, the coil housing having a first attachment portion, the valve group subassembly having a tube assembly extending between an inlet end and an outlet end along a longitudinal axis, the tube assembly having a second attaching portion, the inserting includes:

locating an electromagnetic coil formed on a bobbin in a coil housing having a

first coil housing end and a second coil housing end, the second coil housing end forming a flange;

disposing a flux washer proximate the first coil housing end;

connecting wire ends of the electromagnetic coil to respective terminal connectors;

molding the electromagnetic coil, bobbin, flux washer, terminal connectors and the coil housing into a one-piece coil group subassembly; and

performing a high potential electrical test of the coil group subassembly independent of the valve group subassembly; and

securing the first attaching portion to the second attaching portion proximate the outlet end.

9. The method of claim 8 , wherein the inserting comprises:

connecting a body to one end of a non-magnetic shell;

welding a seat to a preset position in the body;

locating an armature assembly in the body;

welding a pole piece to the other end of the non-magnetic shell;

locating a biasing spring and filter/adjusting tube in the body;

welding an inlet tube to the pole piece; and

leak testing the valve group subassembly independently of the coil group subassembly.

10. The method of claim 9 , wherein the welding of the seat comprises forming a weld with a laser through outer and inner surfaces of the body to a circumferential outer surface of the seat so that a hermetic lap seal is formed between the inner surface of the body and the circumferential surface of the seat.

11. The method of claim 10 , wherein the welding comprises welding a lift sleeve in the body and welding a guide plate to a first surface of the seat facing the inlet end and an orifice plate to a second surface facing the outlet end.

12. The method of claim 8 , wherein the inserting comprises forming a tube assembly having an outer surface of a generally constant cross-sectional area about the longitudinal axis.

13. The method of claim 12 , wherein the inserting comprises forming a coil group subassembly having internal surfaces of a generally constant cross-sectional area about the longitudinal axis to permit insertion of the valve group subassembly into the coil group subassembly.