Abstract:
A fuel injector having a fuel inlet, a fuel outlet, and a fuel passageway extending along an axis between the fuel inlet and the fuel outlet. The fuel injector includes a body having an inlet portion, an outlet portion, and a neck portion disposed between the inlet portion and the outlet portion. An adjusting tube is disposed within the neck portion of the body. A fuel filter is mounted inside the adjusting tube prior to the insertion of the adjusting tube into the fuel injector inlet tube. A spring is disposed within the neck portion of the body, the spring having an upstream end proximate to the adjusting tube and a downstream end opposite the upstream end. An armature having a lower portion is disposed within the neck portion of the body and displace able along the axis relative to the body. The downstream end of the spring is disposed proximate to the armature, the spring applying a biasing force to the armature. A valve seal is substantially rigidly connected to the lower portion of the armature. The fuel injector includes a modular valve group subassembly that is connected to a coil group subassembly.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    It is believed that examples of known fuel injection systems use an injector to dispense a quantity of fuel that is to be combusted in an internal combustion engine. It is also believed that the quantity of fuel that is dispensed is varied in accordance with a number of engine parameters such as engine speed, engine load, engine emissions, etc.  
           [0002]    It is believed that examples of known electronic fuel injection systems monitor at least one of the engine parameters and electrically operate the injector to dispense the fuel. It is believed that examples of known injectors use electromagnetic coils, piezoelectric elements, or magnetostrictive materials to actuate a valve.  
           [0003]    It is believed that examples of known valves for injectors include a closure member that is movable with respect to a seat. Fuel flow through the injector is believed to be prohibited when the closure member sealingly contacts the seat, and fuel flow through the injector is believed to be permitted when the closure member is separated from the seat.  
           [0004]    It is believed that examples of known injectors include a spring providing a force biasing the closure member toward the seat. It is also believed that this biasing force is adjustable in order to set the dynamic properties of the closure member movement with respect to the seat.  
           [0005]    It is further believed that examples of known injectors include a filter for separating particles from the fuel flow, and include a seal at a connection of the injector to a fuel source.  
           [0006]    It is believed that such examples of the known injectors have a number of disadvantages. It is believed that examples of known injectors must be assembled entirely in an environment that is substantially free of contaminants. It is also believed that examples of known injectors can only be tested after final assembly has been completed.  
         SUMMARY OF THE INVENTION  
         [0007]    According to the present invention, a fuel injector can comprise a plurality of modules, each of which can be independently assembled and tested. According to one embodiment of the present invention, the modules can comprise a fluid handling subassembly and an electrical subassembly. These subassemblies can be subsequently assembled to provide a fuel injector according to the present invention.  
           [0008]    The present invention provides a fuel injector for use with an internal combustion engine. The fuel injector comprises a valve group subassembly and a coil group subassembly. The valve group subassembly includes a tube assembly having a longitudinal axis extending between a first end and a second end; 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 includes a first armature assembly end having a magnetic portion and a second armature assembly end having a sealing portion; 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 disposed at least within the tube assembly; and a first attaching portion. The coil group subassembly includes at least one electrical terminal; a solenoid coil operable to displace the armature assembly with respect to the seat, the solenoid coil being axially spaced from the at least one electrical terminal; a terminal connector axially connected to the at least one electrical terminal, the terminal connector electrically connecting the at least one electrical terminal and the solenoid coil; and a second attaching portion fixedly connected to the first attaching portion.  
           [0009]    The present invention further provides a fuel injector for use with an internal combustion engine. The fuel injector comprises a valve group subassembly and a coil group subassembly. The valve group subassembly includes a tube assembly having a longitudinal axis extending between a first end and a second end; 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 includes a first armature assembly end having a magnetic portion; a second armature assembly end having a sealing portion; and an armature tube interposed between and connecting the magnetic portion and the sealing portion; 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 disposed at least within the tube assembly; and a first attaching portion. The coil group subassembly includes at least one electrical terminal; a solenoid coil operable to displace the armature assembly with respect to the seat, the solenoid coil being axially spaced from the at least one electrical terminal; a terminal connector axially connected to the at least one electrical terminal, the terminal connector electrically connecting the at least one electrical terminal and the solenoid coil; and a second attaching portion fixedly connected to the first attaching portion.  
           [0010]    The present invention also provides for a method of assembling a fuel injector. The method comprises providing a valve group subassembly, providing a coil group subassembly, and inserting the valve group subassembly into the coil group subassembly. The valve group subassembly includes a tube assembly having a longitudinal axis extending between a first end and a second end; 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 includes a first armature assembly end having a magnetic portion and a second armature assembly end having a sealing portion; 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 disposed at least within 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. The coil group subassembly includes a solenoid coil operable to displace the armature assembly with respect to the seat; and a second attaching portion. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate an embodiment of the invention, and, together with the general description given above and the detailed description given below, serve to explain features of the invention.  
         [0012]    [0012]FIG. 1 is a cross-sectional view of a fuel injector according to the claimed invention.  
         [0013]    FIGS.  1 A- 1 C are cross-sectional views of interchangeable armature assemblies usable in the fluid handling subassembly of the fuel injector shown in FIG. 1.  
         [0014]    FIGS.  1 D- 1 F are cross-sectional views of various closure members usable in the fluid handling subassembly of the fuel injectors shown in FIG. 1. FIG. 2 is a cross-sectional view of a fluid handling subassembly of the fuel injector shown in FIG. 1.  
         [0015]    [0015]FIG. 2A is a cross-sectional view of a variation of the fluid handling subassembly of the modular fuel injector according to the claimed invention.  
         [0016]    [0016]FIG. 3 is a cross-sectional view of an electrical subassembly of the fuel injector shown in FIG. 1.  
         [0017]    [0017]FIG. 3A is a cross-sectional view of the two overmolds for the electrical subassembly of FIG. 1.  
         [0018]    [0018]FIG. 3B is an exploded view of the electrical subassembly of FIG. 3.  
         [0019]    [0019]FIG. 4 is an isometric view that illustrates assembling the fluid handling and electrical subassemblies that are shown in FIGS. 2 and 3, respectively.  
         [0020]    [0020]FIG. 5 is a flowchart of the method of assembling the modular fuel injector of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    Referring to FIGS.  1 - 4 , a solenoid actuated fuel injector  100  dispenses a quantity of fuel that is to be combusted in an internal combustion engine (not shown). The fuel injector  100  extends along a longitudinal axis A-A between a first injector end  238  and a second injector end  239 , and includes a valve group subassembly  200  and a power group subassembly  300 . The valve group subassembly  200  performs fluid handling functions, e.g., defining a fuel flow path and prohibiting fuel flow through the injector  100 . The power group subassembly  300  performs electrical functions, e.g., converting electrical signals to a driving force for permitting fuel flow through the injector  100 .  
         [0022]    Referring to FIGS. 1 and 2, the valve group subassembly  200  comprises a tube assembly extending along the longitudinal axis A-A between a first tube assembly end  200 A and a second tube assembly end  200 B. The tube assembly includes at least an inlet tube, a non-magnetic shell  230 , and a valve body  240 . The inlet tube  210  has a first inlet tube end proximate to the first tube assembly end  200 A. A second end of the inlet tube  210  is connected to a first shell end of the non-magnetic shell  230 . A second shell end of the non-magnetic shell  230  is connected to a first valve body end of the valve body  240 . And a second valve body end of the valve body  240  is proximate to the second tube assembly end  200 B. The inlet tube  210  can be formed by a deep drawing process or by a rolling operation. A pole piece can be integrally formed at the second inlet tube end of the inlet tube  210  or, as shown, a separate pole piece  220  can be connected to a partial inlet tube  210  and connected to the first shell end of the non-magnetic shell  230 . The non-magnetic shell  230  can comprise non-magnetic stainless steel, e.g., 300 series stainless steels, or any other material that has similar structural and magnetic properties.  
         [0023]    A seat  250  is secured at the second end of the tube assembly. The seat  250  defines an opening centered on the fuel injector&#39;s longitudinal axis A-A and through which fuel can flow into the internal combustion engine (not shown). The seat  250  includes a sealing surface surrounding the opening. The sealing surface, which faces the interior of the valve body  240 , can be frustoconical or concave in shape, and can have a finished surface. An orifice plate  254  can be used in connection with the seat  250  to provide at least one precisely sized and oriented orifice in order to obtain a particular fuel spray pattern.  
         [0024]    An armature assembly  260  is disposed in the tube assembly. The armature assembly  260  includes a first armature assembly end having a ferro-magnetic or armature portion  262  and a second armature assembly end having a sealing portion. The armature assembly  260  is disposed in the tube assembly such that the magnetic portion, or “armature,”  262  confronts the pole piece  220 . The sealing portion can include a closure member  264 , e.g., a spherical valve element, that is moveable with respect to the seat  250  and its sealing surface  252 . The closure member  264  is movable between a closed configuration, as shown in FIGS. 1 and 2, and an open configuration (not shown). In the closed configuration, the closure member  264  contiguously engages the sealing surface  252  to prevent fluid flow through the opening. In the open configuration, the closure member  264  is spaced from the seat  250  to permit fluid flow through the opening. The armature assembly  260  may also include a separate armature tube  266  connecting the ferro-magnetic or armature portion  262  to the closure member  264 .  
         [0025]    Fuel flow through the armature assembly  260  can be provided by at least one axially extending through-bore  267  and at least one apertures  268  through a wall of the armature assembly  260 . The apertures  268 , which can be of any shape, are preferably non-circular, e.g., axially elongated, to facilitate the passage of gas bubbles. For example, in the case of a separate armature tube  266  that is formed by rolling a sheet substantially into a tube, the apertures  268  can be an axially extending slit defined between non-abutting edges of the rolled sheet. However, the apertures  268 , in addition to the slit, would preferably include openings extending through the sheet. The apertures  268  provide fluid communication between the at least one through-bore  267  and the interior of the valve body. Thus, in the open configuration, fuel can be communicated from the through-bore  267 , through the apertures  268  and the interior of the valve body, around the closure member, and through the opening into the engine (not shown).  
         [0026]    To permit the use of extended tip injectors, FIG. 1A shows a three-piece armature  260  comprising the armature tube  266 , elongated openings  268  and the closure member  264 . One example of an extended tip three-piece armature is shown as armature assembly  260 A in FIG. 1B. The extended tip armature assembly  260 A includes elongated apertures  269  to facilitate the passage of trapped fuel vapor. As a further alternative, a two-piece armature  260 B, shown here in FIG. 1C, can be utilized with the present invention. Although both the three-piece and the two-piece armature assemblies are interchangeable, the three-piece armature assembly  266  or  266 A is preferable due to its ability to reduce magnetic flux leakage from the magnetic circuit of the fuel injector  100  according to the present invention. This ability arises from the fact that the armature tube  266  or  266 A can be non-magnetic, thereby magnetically decoupling the magnetic portion or armature  262  from the ferro-magnetic closure member  264 . Because the ferro-magnetic closure member is decoupled from the ferro-magnetic or armature portion  262 , flux leakage is reduced, thereby improving the efficiency of the magnetic circuit. Furthermore, the three-piece armature assembly can be fabricated with fewer machining processes as compared to the two-piece armature assembly. It should be noted that the armature tube  266  or  266 A of the three-piece armature assembly can be fabricated by various techniques, for example, a plate can be rolled and its seams welded or a blank can be deep-drawn to form a seamless tube.  
         [0027]    To ensure a positive seal, closure member  264  is attached to intermediate portion or armature tube  266  by welds as shown in FIG. 1D. To achieve different spray patterns or to ensure a large volume of fuel injected relative to a low injector lift, it is contemplated that the spherical closure member  264  be in the form of a flat-faced ball, shown enlarged in detail in FIGS. 1E and 1F. Welds  261  can be internally formed between the junction of the armature tube  266  and the closure member  264  to the armature tube  266 , respectively. Valve seat  250  can be attached to valve body  240  in two different ways. As shown in FIG. 1E, valve seat may simply be floatingly mounted between valve body  240  and orifice plate  254  with an O-ring  251  to prevent fuel leakage around valve seat. Here, the orifice plate  254  can be retained by crimps  240 A that can be formed on the valve body  240 . Alternatively, valve seat  250  may simply be affixed by at least a weld  251 A to valve body  240  as shown in FIG. 1F while the orifice plate  254  can be welded to the seat  250 .  
         [0028]    The elongated openings  269  and apertures  268  in the three-piece extended tip armature  260 A serve two related purposes. First, the elongated openings  269  and apertures  268  allow fuel to flow out of the armature tube  266 A. Second, elongated openings  269  allows hot fuel vapor in the armature tube  266 A to vent into the valve body  240  instead of being trapped in the armature tube  266 A, and also allows pressurized liquid fuel to displace any remaining fuel vapor trapped therein during a hot start condition.  
         [0029]    In the case of a spherical valve element providing the closure member  264 , the spherical valve element can be connected to the armature assembly  260  at a diameter that is less than the diameter of the spherical valve element. Such a connection would be on side of the spherical valve element that is opposite contiguous contact with the seat. A lower armature guide can be disposed in the tube assembly, proximate the seat, and would slidingly engage the diameter of the spherical valve element. The lower armature guide can facilitate alignment of the armature assembly  260  along the axis A-A, while the intermediate portion or armature tube  266  can magnetically decouple the closure member  264  from the ferro-magnetic or armature portion  262  of the armature assembly  260 .  
         [0030]    A resilient member  270  is disposed in the tube assembly and biases the armature assembly  260  toward the seat. A filter assembly  282  comprising a filter  284 A and an adjusting tube  280  is also disposed in the tube assembly. The filter assembly  282  includes a first end and a second end. The filter  284 A is disposed at one end of the filter assembly  282  and also located proximate to the first end of the tube assembly and apart from the resilient member  270  while the adjusting tube  280  is disposed generally proximate to the second end of the tube assembly. The adjusting tube  280  engages the resilient member  270  and adjusts the biasing force of the member with respect to the tube assembly. In particular, the adjusting tube  280  provides a reaction member against which the resilient member  270  reacts in order to close the injector valve  100  when the power group subassembly  300  is de-energized. The position of the adjusting tube  280  can be retained with respect to the inlet tube  210  by an interference fit between an outer surface of the adjusting tube  280  and an inner surface of the tube assembly. Thus, the position of the adjusting tube  280  with respect to the inlet tube  210  can be used to set a predetermined dynamic characteristic of the armature assembly  260 . Alternatively, as shown in FIG. 2A, a filter assembly  282 ′ comprising adjusting tube  280 A and inverted cup-shaped filtering element  284 B can be utilized in place of the cone type filter assembly  282 .  
         [0031]    The valve group subassembly  200  can be assembled as follows. The non-magnetic shell  230  is connected to the inlet tube  210  and to the valve body  240 . The filter assembly  282  or  282 ′ is inserted along the axis A-A from the first inlet tube end of the inlet tube  210 . Next, the resilient member  270  and the armature assembly  260  (which was previously assembled) are inserted along the axis A-A from the second valve body end of the valve body  240 . The filter assembly  282  or  282 ′ can be inserted into the inlet tube  210  to a predetermined distance so as to abut the resilient member. The position of the filter assembly  282  or  282 ′ with respect to the inlet tube  210  can be used to adjust the dynamic properties of the resilient member, e.g., so as to ensure that the armature assembly  260  does not float or bounce during injection pulses. The seat  250  and orifice plate  254  are then inserted along the axis A-A from the second valve body end of the valve body  240 . The seat  250  and orifice plate  254  can be fixedly attached to one another or to the valve body  240  by known attachment techniques such as laser welding, crimping, friction welding, conventional welding, etc.  
         [0032]    Referring to FIGS. 1 and 3, the power group subassembly  300  comprises an electromagnetic coil  310 , at least one terminal  320  (there are two according to a preferred embodiment), a housing  330 , and an overmold  340 . The electromagnetic coil  310  comprises a wire that that can be wound on a bobbin  314  and electrically connected to electrical contact  322  supported on the bobbin  314 . When energized, the coil generates magnetic flux that moves the armature assembly  260  toward the open configuration, thereby allowing the fuel to flow through the opening. De-energizing the electromagnetic coil  310  allows the resilient member  270  to return the armature assembly  260  to the closed configuration, thereby shutting off the fuel flow. Each electrical terminal  320  is in electrical communication via an axially extending contact portion  324  with a respective electrical contact  322  of the coil  310 . The housing  330 , which provides a return path for the magnetic flux, generally comprises a ferro-magnetic cylinder  332  surrounding the electromagnetic coil  310  and a flux washer  334  extending from the cylinder toward the axis A-A. The washer  334  can be integrally formed with or separately attached to the cylinder. The housing  330  can include holes and slots  330 A, or other features to break-up eddy currents that can occur when the coil is de-energized. Additionally, the housing  330  is provided with scalloped circumferential edge  331  to provide a mounting relief for the bobbin  314 . The overmold  340  maintains the relative orientation and position of the electromagnetic coil  310 , the at least one electrical terminal  320 , and the housing  330 . The overmold  340  can also form an electrical harness connector portion  321  in which a portion of the terminals  320  are exposed. The terminals  320  and the electrical harness connector portion  321  can engage a mating connector, e.g., part of a vehicle wiring harness (not shown), to facilitate connecting the injector  100  to a supply of electrical power (not shown) for energizing the electromagnetic coil  310 .  
         [0033]    According to a preferred embodiment, the magnetic flux generated by the electromagnetic coil  310  flows in a circuit that comprises the pole piece  220 , a working air gap between the pole piece  220  and the magnetic armature portion  262 , a parasitic air gap between the magnetic armature portion  262  and the valve body  240 , the housing  330 , and the flux washer  334 .  
         [0034]    The coil group subassembly  300  can be constructed as follows. As shown in FIG. 3B, a plastic bobbin  314  can be molded with the electrical contact  322 . The wire  312  for the electromagnetic coil  310  is wound around the plastic bobbin  314  and connected to the electrical contact  322 . The housing  330  is then placed over the electromagnetic coil  310  and bobbin  314  unit. The bobbin  314  can be formed with at least one retaining prong  314 A which, in combination with an overmold  340 , are utilized to fix the bobbin  314  to the housing once the overmold is formed. The terminals  320  are pre-bent to a proper configuration such that the pre-aligned terminals  320  are in alignment with the harness connector  321  when a polymer is poured or injected into a mold (not shown) for the electrical subassembly. The terminals  320  are then electrically connected via the axially extending portion  324  to respective electrical contacts  322 . The completed bobbin  314  is then placed into the housing  330  at a proper orientation by virtue of the scalloped-edge  331 . An overmold  340  is then formed to maintain the relative assembly of the coil/bobbin unit, housing  330 , and terminals  320 . The overmold  340  also provides a structural case for the injector and provides predetermined electrical and thermal insulating properties. A separate collar (not shown) can be connected, e.g., by bonding, and can provide an application specific characteristic such as an orientation feature or an identification feature for the injector  100 . Thus, the overmold  340  provides a universal arrangement that can be modified with the addition of a suitable collar. To reduce manufacturing and inventory costs, the coil/bobbin unit can be the same for different applications. As such, the terminals  320  and overmold  340  (or collar, if used) can be varied in size and shape to suit particular tube assembly lengths, mounting configurations, electrical connectors, etc.  
         [0035]    Alternatively, as shown in FIG. 3A, a two-piece overmold can be used instead of the one-piece overmold  340 . The two-piece overmold allow for a first overmold  341  that is application specific while the second overmold  342  can be for all applications. The first overmold is bonded to a second overmold, allowing both to act as electrical and thermal insulators for the injector. Additionally, a portion of the housing  330  can extend axially beyond an end of the overmold  340  and can be formed with a flange to retain an O-ring.  
         [0036]    As is particularly shown in FIGS. 1 and 4, the valve group subassembly  200  can be inserted into the coil group subassembly  300 . To ensure that the two subassemblies are fixed in a proper axial orientation, shoulders  222 A of the pole piece  220  engages corresponding shoulders  222 B of the coil subassembly. Next, the resilient member  270  is inserted from the inlet end of the inlet tube  210 . Thus, the injector  100  is made of two modular subassemblies that can be assembled and tested separately, and then connected together to form the injector  100 . The valve group subassembly  200  and the coil group subassembly  300  can be fixedly attached by adhesive, welding, or another equivalent attachment process. According to a preferred embodiment, a hole  360  through the overmold exposes the housing  330  and provides access for laser welding the housing  330  to the valve body  240 .  
         [0037]    The first injector end  238  can be coupled to the fuel supply of an internal combustion engine (not shown). The O-ring can be used to seal the first injector end  238  to the fuel supply so that fuel from a fuel rail (not shown) is supplied to the tube assembly, with the O-ring making a fluid tight seal, at the connection between the injector  100  and the fuel rail (not shown).  
         [0038]    In operation, the electromagnetic coil  310  is energized, thereby generating magnetic flux is the magnetic circuit. The magnetic flux moves armature assembly  260  (along the axis A-A, according to a preferred embodiment) towards the integral pole piece  220   50 , i.e., closing the working air gap. This movement of the armature assembly  260  separates the closure member  264  from the seat  250  and allows fuel to flow from the fuel rail (not shown), through the inlet tube, the through-bore  267 , the elongated openings and the valve body  240 , between the seat  250  and the closure member  264 , through the opening, and finally through the orifice plate  254  into the internal combustion engine (not shown). When the electromagnetic coil  310  is de-energized, the armature assembly  260  is moved by the bias of the resilient member  270  to contiguously engage the closure member  264  with the seat, and thereby prevent fuel flow through the injector  100 .  
         [0039]    Referring to FIG. 5, a preferred assembly process can be as follows:  
         [0040]    1. A pre-assembled valve body and non-magnetic sleeve is located with the valve body oriented up.  
         [0041]    2. A screen retainer, e.g., a lift sleeve, is loaded into the valve body/non-magnetic sleeve assembly.  
         [0042]    3. A lower screen can be loaded into the valve body/non-magnetic sleeve assembly.  
         [0043]    4. A pre-assembled seat and guide assembly is loaded into the valve body/non-magnetic sleeve assembly.  
         [0044]    5. The seat/guide assembly is pressed to a desired position within the valve body/non-magnetic sleeve assembly.  
         [0045]    6. The valve body is welded, e.g., by a continuous wave laser forming a hermetic lap seal, to the seat.  
         [0046]    7. A first leak test is performed on the valve body/non-magnetic sleeve assembly. This test can be performed pneumatically.  
         [0047]    8. The valve body/non-magnetic sleeve assembly is inverted so that the non-magnetic sleeve is oriented up.  
         [0048]    9. An armature assembly is loaded into the valve body/non-magnetic sleeve assembly.  
         [0049]    10. A pole piece is loaded into the valve body/non-magnetic sleeve assembly and pressed to a pre-lift position.  
         [0050]    11. Dynamically, e.g., pneumatically, purge valve body/non-magnetic sleeve assembly.  
         [0051]    12. Set lift.  
         [0052]    13. The non-magnetic sleeve is welded, e.g., with a tack weld, to the pole piece.  
         [0053]    14. The non-magnetic sleeve is welded, e.g., by a continuous wave laser forming a hermetic lap seal, to the pole piece.  
         [0054]    15. Verify lift  
         [0055]    16. A spring is loaded into the valve body/non-magnetic sleeve assembly.  
         [0056]    17. A filter/adjusting tube is loaded into the valve body/non-magnetic sleeve assembly and pressed to a pre-cal position.  
         [0057]    18. An inlet tube is connected to the valve body/non-magnetic sleeve assembly to generally establish the fuel group subassembly.  
         [0058]    19. Axially press the fuel group subassembly to the desired over-all length.  
         [0059]    20. The inlet tube is welded, e.g., by a continuous wave laser forming a hermetic lap seal, to the pole piece.  
         [0060]    21. A second leak test is performed on the fuel group subassembly. This test can be performed pneumatically.  
         [0061]    22. The fuel group subassembly is inverted so that the seat is oriented up.  
         [0062]    23. An orifice is punched and loaded on the seat.  
         [0063]    24. The orifice is welded, e.g., by a continuous wave laser forming a hermetic lap seal, to the seat.  
         [0064]    25. The rotational orientation of the fuel group subassembly/orifice can be established with a “look/orient/look” procedure.  
         [0065]    26. The fuel group subassembly is inserted into the (pre-assembled) power group subassembly.  
         [0066]    27. The power group subassembly is pressed to a desired axial position with respect to the fuel group subassembly.  
         [0067]    28. The rotational orientation of the fuel group subassembly/orifice/power group subassembly can be verified.  
         [0068]    29. The power group subassembly can be laser marked with information such as part number, serial number, performance data, a logo, etc.  
         [0069]    30. Perform a high-potential electrical test.  
         [0070]    31. The housing of the power group subassembly is tack welded to the valve body.  
         [0071]    32. A lower O-ring can be installed. Alternatively, this lower O-ring can be installed as a post test operation.  
         [0072]    33. An upper O-ring is installed.  
         [0073]    34. Invert the fully assembled fuel injector.  
         [0074]    35. Transfer the injector to a test rig.  
         [0075]    To set the lift, i.e., ensure the proper injector lift distance, there are at least four different techniques that can be utilized. According to a first technique, a crush ring or a washer that is inserted into the valve body  240  between the lower guide  257  and the valve body  240  can be deformed. According to a second technique, the relative axial position of the valve body  240  and the non-magnetic shell  230  can be adjusted before the two parts are affixed together. According to a third technique, the relative axial position of the non-magnetic shell  230  and the pole piece  220  can be adjusted before the two parts are affixed together. And according to a fourth technique, a lift sleeve  255  can be displaced axially within the valve body  240 . If the lift sleeve technique is used, the position of the lift sleeve can be adjusted by moving the lift sleeve axially. The lift distance can be measured with a test probe. Once the lift is correct, the sleeve is welded to the valve body  240 , e.g., by laser welding. Next, the valve body  240  is attached to the inlet tube  210  assembly by a weld, preferably a laser weld. The assembled fuel group subassembly  200  is then tested, e.g., for leakage.  
         [0076]    As is shown in FIG. 5, the lift set procedure may not be able to progress at the same rate as the other procedures. Thus, a single production line can be split into a plurality (two are shown) of parallel lift setting stations, which can thereafter be recombined back into a single production line.  
         [0077]    The preparation of the power group sub-assembly, which can include (a) the housing  330 , (b) the bobbin assembly including the terminals  320 , (c) the flux washer  334 , and (d) the overmold  340 , can be performed separately from the fuel group subassembly.  
         [0078]    According to a preferred embodiment, wire  312  is wound onto a pre-formed bobbin  314  with at least one electrical contact  322  molded thereon. The bobbin assembly is inserted into a pre-formed housing  330 . To provide a return path for the magnetic flux between the pole piece  220  and the housing  330 , flux washer  334  is mounted on the bobbin assembly. A pre-bent terminal  320  having axially extending connector portions  324  are coupled to the electrical contact portions  322  and brazed, soldered welded, or preferably resistance welded. The partially assembled power group assembly is now placed into a mold (not shown). By virtue of its pre-bent shape, the terminals  320  will be positioned in the proper orientation with the harness connector  321  when a polymer is poured or injected into the mold. Alternatively, two separate molds (not shown) can be used to form a two-piece overmold as described with respect to FIG. 3A. The assembled power group subassembly  300  can be mounted on a test stand to determine the solenoid&#39;s pull force, coil resistance and the drop in voltage as the solenoid is saturated.  
         [0079]    The inserting of the fuel group subassembly  200  into the power group subassembly  300  operation can involve setting the relative rotational orientation of fuel group subassembly  200  with respect to the power group subassembly  300 . The inserting operation can be accomplished by one of two methods: “top-down” or “bottom-up.” According to the former, the power group subassembly  300  is slid downward from the top of the fuel group subassembly  200 , and according to the latter, the power group subassembly  300  is slid upward from the bottom of the fuel group subassembly  200 . In situations where the inlet tube  210  assembly includes a flared first end, bottom-up method is required. Also in these situations, the O-ring  290  that is retained by the flared first end can be positioned around the power group subassembly  300  prior to sliding the fuel group subassembly  200  into the power group subassembly  300 . After inserting the fuel group subassembly  200  into the power group subassembly  300 , these two subassemblies are affixed together, e.g., by welding, such as laser welding. According to a preferred embodiment, the overmold  340  includes an opening  360  that exposes a portion of the housing  330 . This opening  360  provides access for a welding implement to weld the housing  330  with respect to the valve body  240 . Of course, other methods or affixing the subassemblies with respect to one another can be used. Finally, the O-ring  290  at either end of the fuel injector can be installed.  
         [0080]    The method of assembling the preferred embodiments, and the preferred embodiments themselves, are believed to provide manufacturing advantages and benefits. For example, because of the modular arrangement only the valve group subassembly is required to be assembled in a “clean” room environment. The power group subassembly  300  can be separately assembled outside such an environment, thereby reducing manufacturing costs. Also, the modularity of the subassemblies permits separate pre-assembly testing of the valve and the coil assemblies. Since only those individual subassemblies that test unacceptable are discarded, as opposed to discarding filly assembled injectors, manufacturing costs are reduced. Further, the use of universal components (e.g., the coil/bobbin unit, non-magnetic shell  230 , seat  250 , closure member  264 , filter/retainer assembly  282 , etc.) enables inventory costs to be reduced and permits a “just-in-time” assembly of application specific injectors. Only those components that need to vary for a particular application, e.g., the terminals  320  and inlet tube  210  need to be separately stocked. Another advantage is that by locating the working air gap, i.e., between the armature assembly  260  and the pole piece  220 , within the electromagnetic coil  310 , the number of windings can be reduced. In addition to cost savings in the amount of wire  312  that is used, less energy is required to produce the required magnetic flux and less heat builds-up in the coil (this heat must be dissipated to ensure consistent operation of the injector). Yet another advantage is that the modular construction enables the orifice disk  254  to be attached at a later stage in the assembly process, even as the final step of the assembly process. This just-in-time assembly of the orifice disk  254  allows the selection of extended valve bodies depending on the operating requirement. Further advantages of the modular assembly include out-sourcing construction of the power group subassembly  300 , which does not need to occur in a clean room environment. And even if the power group subassembly  300  is not out-sourced, the cost of providing additional clean room space is reduced.  
         [0081]    While the preferred embodiments have been disclosed with reference to certain embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims, and equivalents thereof.