Deep pocket seat assembly in modular fuel injector having a lift setting assembly for a working gap and methods

A fuel injector and various methods relating to the assembly of the fuel injector. The fuel injector includes a power group subassembly and a valve group subassembly having a respectively connected first and second connector portions. The power group subassembly includes an electromagnetic coil, a housing, at least one terminal, and at least one overmold formed over the coil and housing. The valve group subassembly insertable within the overmold includes a tube assembly having an inlet tube and a filter assembly. A pole piece couples the inlet tube to one end of a non-magnetic shell having a valve body coupled to the opposite end. An axially displaceable armature assembly confronts the pole piece and is adjustably biased by a member and adjusting tube toward engagement with a seat assembly. A lift setting device sets the axial displacement of the armature assembly. The seat assembly includes a flow portion and a securement portion having respective first and second axial lengths at least equal to one another.

BACKGROUND OF THE INVENTION

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.

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.

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.

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.

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.

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

The present invention provides for; in one aspect, a fuel injector for use with an internal combustion engine. In a first preferred embodiment, the fuel injector includes an independently testable power group subassembly connected with an independently testable valve group subassembly so as to form a single unit. The power group subassembly has a first connector portion and includes an electromagnetic coil, a housing surrounding at least a portion of the coil, at least one terminal electrically coupled to the coil to supply electrical power to the coil, and at least one overmold formed over at least a portion of the coil and housing. The overmold has a first overmold end and a second overmold end opposite the first overmold end. The overmold also defines an interior surface. The valve group subassembly has a second connector portion and includes a tube assembly having at least a portion engaged with the interior surface of the overmold. The tube assembly has an outer surface and a longitudinal axis extending between a first tube end and a second tube end. The tube assembly includes an inlet tube having a first inlet tube end and a second inlet tube end. The fuel injector and valve group subassembly further includes a filter assembly having a filter element, and at least a portion of the filter assembly can be disposed inside the inlet tube. A non-magnetic shell extends axially along the longitudinal axis and has a first shell end and a second shell end. A pole piece having at least a first portion connected to the inlet tube and a second portion connected to the first shell end couples the first shell end to the inlet tube. A valve body is coupled to the second shell end, and an armature assembly is disposed within the tube assembly. The armature assembly is displaceable along the longitudinal axis upon supplying energy to the electromagnetic coil and the armature assembly has a first armature end confronting the pole piece and a second armature end. The first armature end has a ferromagnetic portion and the second armature end has a sealing portion. The armature assembly further defines a through bore and at least one aperture in fluid communication with the through bore. The first connector portion is preferably fixedly connected to the second connector portion such that the at least a portion of the armature assembly is surrounded by the electromagnetic coil. Also included is a member disposed and configured to apply a biasing force against the armature assembly toward the second tube end. The filter assembly can be disposed within the inlet tube so as to engage an adjusting tube disposed within the tube assembly proximate the second tube end thereby adjusting the biasing force. The adjusting tube being disposed within the tube assembly proximate the second tube end. A lift setting device is preferably disposed within the valve body to set the axial displacement of the armature assembly. The valve group further includes a seat assembly disposed in the tube assembly proximate the second tube end such that at least a portion of the seat assembly is disposed within the valve body. The seat assembly includes a flow portion extending along the longitudinal axis between a first surface and a second surface at a first length. The flow portion has at least one orifice defining a central axis and through which fuel flows into the internal combustion engine. The seat assembly further includes a securement portion having an outer surface, the securement portion extends distally along the longitudinal axis from the second surface at a second length at least as long as the first length.

In yet another aspect, the present invention provides for a method of assembling a fuel injector for use with an internal combustion engine. The fuel injector has an independently testable power group subassembly connected to an independently testable valve group subassembly so as to form a single unit. The method of assembly includes providing a power group subassembly, providing a valve group subassembly including a tube assembly having a longitudinal axis extending between a first tube end and a second tube end, and an armature assembly substantially disposed within the tube assembly and displaceable along the longitudinal axis. In addition, the method includes providing a lift setting device to set the axial displacement of the armature assembly and coupling the valve group and the power group subassemblies including welding at least a portion of the power group subassembly to at least a portion of the valve group subassembly to assemble the fuel injector. The method further includes inserting a seat assembly into the tube assembly. The seat assembly includes a flow portion having a first surface and a second surface defining a seat orifice, an orifice disk fixed to the second surface in a fixed spatial orientation with respect to the flow portion, and a securement portion extending distally from the second surface. The method also includes welding a portion of the securement portion to the tube assembly such that the flow portion and the fixed spatial orientation with respect to the orifice disk are maintained within a tolerance of 0.5%. The method can further include coupling the valve group and the power group subassemblies including welding at least a portion of the power group subassembly to at least a portion of the valve group subassembly to assemble the fuel injector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Shown inFIGS. 1,1A and1B are preferred embodiments of a solenoid actuated fuel injector100for dispensing a quantity of fuel that is to be combusted in an internal combustion engine (not shown). The fuel injector100extends along a longitudinal axis A-A between a first injector end110and a second injector end120, and includes a valve group subassembly200, shown inFIG. 2, and a power group subassembly400, shown inFIG. 5. The valve group subassembly200performs fluid handling functions, e.g., defining a fuel flow path and prohibiting fuel flow through the injector100. The power group subassembly400performs electrical functions, e.g., converting electrical signals to a driving force for permitting fuel flow through the injector100.

Referring toFIGS. 1,1A and1B and shown specifically inFIGS. 2,2A and2B are various preferred embodiments of the valve group subassembly200, which includes at least a tube assembly202extending along the longitudinal axis A-A between a first tube assembly end204and a second tube assembly end206. The tube assembly202includes at least an inlet tube210, a non-magnetic shell230, and a valve body250. The inlet tube210has a first inlet tube end212and a second inlet tube end214connected to a first shell end232of the non-magnetic shell230. A second shell end234of the non-magnetic shell230is connected to a first valve body end252of the valve body250opposite the second valve body end254. The inlet tube210can be formed preferably by a deep drawing process or by a rolling operation. The inlet tube210can also include a projection213, shown inFIGS. 2A and 2B, for facilitating an interference fit with the power group subassembly400, preferably with an overmold430as is specifically shown inFIGS. 1 and 1A. A pole piece270can be integrally formed at the second inlet tube end214of the inlet tube210, as shown inFIGS. 1B and 2, or as shown inFIGS. 1,1A,2A and2B, a pole piece270can be preferably formed separately and connected to second inlet tube end214at a first portion272of pole piece270. A second portion274of the pole piece270, integral or separate from the inlet tube210, can be connected to the first shell end232of the non-magnetic shell230. More specifically, the second portion274of the pole piece can engage an interior surface231of the non-magnetic shell230. The non-magnetic shell230can include non-magnetic stainless steel, e.g., 300 series stainless steels, or other materials that have similar structural and magnetic properties. The inlet tube210, pole piece270, non-magnetic shell230, and valve body250can be dimensioned and configured so as to have a generally constant outer diameter extending between the first tube assembly end204and second tube assembly end206. As used herein, the term “generally,” “approximately,” or “about” indicates an acceptable level of tolerance that would still permit the preferred embodiments of the assembled fuel injector to meter fuel. Preferably the inlet tube210and non-magnetic shell230are non-magnetic 305 stainless steel, and the pole piece is ferromagnetic 430 stainless steel.

As shown inFIGS. 2A and 2B, inlet tube210can be attached to pole piece270by suitable attachment techniques such as, for example, welds. Preferably the weld is formed by laser welding through the two members210,270. Formed into the outer surface of pole piece270are shoulder portions276. Inlet tube end214can engage shoulder portions276for connection of the pole piece270with inlet tube210. Moreover, a shoulder277can be formed on the interior surface of the power group subassembly400to act as a positive mounting stop when the fuel injector100is assembled. Specifically shown, for example, inFIG. 1is the interaction of shoulder277with an interior portion of the power group subassembly400, specifically a bobbin405forming an electromagnetic coil402, as shown inFIG. 5. As shown inFIGS. 2C and 2D, the length of pole piece270can be fixed whereas the length of inlet tube210,210′ can be variable according to operating requirements. By forming inlet tube210separately from pole piece270, different length injectors can be manufactured by using different inlet tube lengths during the assembly process. As shown inFIGS. 1 and 1A, inlet tube210can be flared at the inlet end212to retain a sealing or O-ring290circumscribed about the first tube end110, as seen inFIG. 1. Alternatively to the configurations shown inFIGS. 1,1A,2,2A and2B, the inlet tube210can be attached to the separate pole piece270at an inner circumferential surface of the pole piece270.

Shown inFIGS. 1,1A and2is an armature assembly300disposed in the tube assembly distally of the pole piece270. Seen in greater detail in FIGS.3and3C-3E, the armature assembly300includes an armature core301having a first armature core end302including an armature or ferromagnetic portion304and a second armature core end306having a sealing portion308. The armature assembly300is disposed in the tube assembly210such that the ferromagnetic portion304, or “armature,” confronts the pole piece270at the second portion of the pole piece274. The sealing portion308can include a preferably ferromagnetic closure member310, e.g., a spherical valve element, that is moveable for regulating the flow of fluid through the fuel injector100. Preferably, the closure member310is 440 C stainless steel and the armature core301is 430 FR stainless steel.

Shown inFIGS. 3 and 3A, the second portion274of pole piece270and the ferromagnetic portion304of the armature core301can define impact surfaces275and305respectively. Surface treatments can be applied to at least one of the impact surfaces275,305and second portion274and ferromagnetic portion304to improve the armature's response, reduce wear on the impact surfaces or variations in the working air gap between the respective portions274and304. The surface treatments can include coating, plating or case-hardening. Coatings or platings can include, but are not limited to, hard chromium plating, nickel plating or keronite coating. Case hardening on the other hand, can include, but are not limited to, nitriding, carburizing, carbonitriding, cyaniding, heat, flame, spark or induction hardening. Preferably, the coating is a chromium plating.

The surface treatments will typically form at least one layer of wear-resistant material273on the respective portions274,304of the pole piece270and armature core301. These layers, however, tend to be inherently thicker wherever there is a sharp edge or junction between the circumference and the radial end face of either portions274,304. Moreover, this thickening effect results in uneven contact surfaces at the radially outer edge of the end portions. However as seen in the detail ofFIGS. 3A and 3B, by forming the wear-resistant layers on at least one of the portions274and304, where the at least one portion274or304has a surface generally oblique to longitudinal axis A-A, both impact surfaces275,305are now substantially in mating contact with respect to each other due to the thickening of the layers on the oblique surface. As shown inFIG. 3, the portions274,304are generally centrally and coaxially disposed about the longitudinal axis A-A. The outer surface of at least one of the end portions274,304, for example, outer surface278of second portion274of pole piece270, can be of a general conic, frustoconical, spheroidal or a surface generally oblique with respect to the axis A-A. Preferably, at least one of the oblique surfaces of portions274,304defines an oblique angle of about 2Nwith respect to an axis orthogonal to longitudinal axis A-A. Alternatively and preferably, at least one of the oblique surfaces of portions274,304defines an arcuate surface relative to longitudinal axis A-A.

Since the surface treatments can affect the physical and magnetic properties of the ferromagnetic portion304of the armature core301or the pole piece270, a suitable material, e.g., a mask, a coating or a protective cover, can surround areas other than the respective end portions304and274during the surface treatments. Upon completion of the surface treatments, the material can be removed, thereby leaving the previously masked areas unaffected by the surface treatments.

FIGS. 3,3C and3D show a three-piece armature assembly300including the armature core301, an intermediate portion or armature tube312, and the closure member310. The three-piece armature assembly300preferably includes the separately formed armature tube312for connecting the ferromagnetic portion304to the closure member310. The armature tube312can 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. The armature tube312is preferable due to its ability to reduce magnetic flux leakage from the magnetic circuit of the fuel injector100. This ability arises from the armature tube312being formed from non-magnetic material, thereby magnetically decoupling the magnetic portion or ferromagnetic portion304from the ferromagnetic closure member310. Because the ferromagnetic closure member310is decoupled from the ferromagnetic portion304, flux leakage is reduced, thereby improving the efficiency of the magnetic circuit. An additional variation of the three-piece armature assembly300is shown inFIG. 3Din the form of an extended tip three-piece armature assembly300′ in which the armature tube312can be substantially elongated. Alternatively, a two-piece armature assembly300″, shown here inFIG. 3E, includes the armature core301and the second armature core end306configured for direct connection to the closure member310. Although the three-piece and the two-piece armature assemblies300,300′,300″ are interchangeable, the three-piece armature assembly300or300′ is preferable due to magnetic decoupling feature of the armature tube312.

Fuel flow through the armature assembly300can be provided by at least one axially extending through-bore314and at least one aperture316through a wall of the armature assembly300. Any number of apertures can be provided as needed for a given application. The aperture316, which can be of any shape, can preferably be noncircular, e.g., axially elongated, as shown inFIG. 3Cto facilitate the passage of gas bubbles. For example, in the three-piece armature assembly300having an armature tube312that is formed by rolling a sheet substantially into a tube, the aperture316can be an axially extending slit defined between non-abutting edges of the rolled sheet. However, armature tube312, in addition to the aperture316, would preferably include additional openings extending through the sheet as is required for a given application. The aperture316provides fluid communication between the at least one through-bore314and the interior of the valve body250. Thus, in the open configuration, fuel can be communicated from the through-bore314, through the aperture316and the interior of the valve body250, around the closure member310, and through the opening into the engine (not shown). The elongated apertures316serve two related purposes. First, the elongated apertures316allow fuel to flow out of the armature tube312. Second, the elongated apertures316allow hot fuel vapor in the armature tube312to vent into the valve body250instead of being trapped in the armature tube312, and also allows pressurized liquid fuel to displace any remaining fuel vapor trapped therein during a hot start condition. In the case of the two-piece armature assembly300″, the aperture316can be formed directly in the armature core301proximate the second armature core end306as is shown inFIG. 3D.

Shown inFIGS. 1,1A and2is a seat assembly330engaged with the closure member310. The seat assembly330is secured at the second end of the tube assembly202, and more specifically, the seat assembly330is secured at the second valve body end254. Shown in greater detail inFIG. 4is seat assembly330, which can include a flow portion335and a securement portion340. The flow portion335extends generally along the longitudinal axis A-A over a first length L1between a first surface331and a second surface or disk retention surface333. The securement portion340extends distally from the second surface333generally along the longitudinal axis over a second length L2. Length L2can preferably be dimensioned such that the second length is at least equal to the first length L1and more preferably greater than L1. Both portions extend generally along the longitudinal axis over a third length L3greater than either one of L1or L2.

The flow portion335and more of the seat assembly330defines a first or sealing surface336and an orifice337preferably centered on the axis A-A and through which fuel can flow into the internal combustion engine (not shown). The sealing surface336surrounds the orifice337and can preferably be configured for contiguous engagement in one position of the closure member310. The orifice337is preferably coterminous with the second or disk retention surface333. The sealing surface336, which faces the interior of the valve body350, can be frustoconical or concave in shape, and can have a finished surface, e.g. polished or coated. An orifice disk360can be used in connection with the seat assembly to provide oriented orifice337to provide a particular fuel spray pattern and targeting. The precisely sized and oriented orifice337can be disposed on the center axis of the orifice disk360or, preferably disposed off-axis, and oriented in any desirable angular configuration relative to the longitudinal axis A-A or any one or more reference points on the fuel injector100. It should be noted that both the seat assembly330and orifice disk360can be fixedly attached to the valve body250by known conventional attachment techniques, including, for example, laser welding, crimping, and friction welding or gas welding. The orifice disk360is preferably tack welded with welds361to the orifice disk retention surface333in a fixed spatial (radial and/or axial) orientation to provide the particular fuel spray pattern and targeting of the fuel spray.

The securement portion340of the seat assembly330preserves the spatial orientation between first surface331, disk retention surface333and preferably includes orifice disk360. Specifically, the securement portion340can be dimensioned and configured so as to prevent substantial deformation to the surfaces331,333and orifice disk360upon applying heat from, for example, a weld. The seat assembly330can be attached to the valve body250by any suitable technique, such as, for example, laser welding or tack welding. Preferably, the securement portion340is secured to the inner surface of the valve body250with a continuous laser seam weld342extending from the outer surface of the valve body250through the inner surface of the valve body250and into a portion of the securement portion340in a pattern that can circumscribe the longitudinal axis A-A such that the seam weld342forms a hermetic lap seal between the inner surface of the valve body250and the outer surface of the securement portion340. Also preferably, the seam weld342can be located at a distance L4distally at about 50% of the second length L2from the disk retention surface333. By locating the seam weld342at such a position from the flow portion335so as to be sufficiently far from the sealing surface336, the orifice337and orifice disk360are fixed in a desired orientation. Preferably, the fixed configuration of the orifice disk360relative to the seat assembly330prior to its installation in the valve body250is maintained within a tolerance of ±0.5% with respect to a predetermined configuration. In addition, the dimensional symmetry (i.e., circularity roundness, perpendicularity or a quantifiable measurement of distortion) of the flow portion335or the orifice disk360about the longitudinal axis A-A is approximately less than 1% as compared to such measurements prior to the seat assembly330being secured in the valve body. An O-ring338can be located between seat assembly and the interior of valve body250for ensuring a tight seal between the seat assembly and the interior of the valve body250. Preferably, the seat350is 416 H stainless steel, guide318is 316 stainless steel and valve body250is 430 Li stainless steel.

In addition to welding the orifice disk360, a retainer365, as seen inFIGS. 4A-4C, can be located at the second valve body end254for retaining a sealing or O-ring290. Shown inFIGS. 4A-4Cis a partial cross-sectional view of a preferred embodiment of the second injector end120with an O-ring290supported or retained by retainer365so as to properly seal the second injector end120. The retainer365includes finger-like locking portions366allowing the retainer365to be snap-fitted on a complementarily grooved portion255of the valve body250. Additionally, retainer365can include a dimple or recess367for engaging a portion of the seat assembly330. Preferably, retainer365is configured to engage the orifice-disk360and securement portion340. To ensure that the retainer365is imbued with sufficient resiliency, the thickness of the retainer365should be at most one-half the thickness of the valve body250. In order to support the O-ring290, the retainer365can preferably include a flange368.

Other seat assemblies can be utilized to control spray trajectory, such as, for example, the seat assembly shown and described in the following copending applications which are incorporated herein by reference thereto: U.S. patent application Ser. No. 09/568,464, entitled, “Injection Valve With Single Disc Turbulence Generation;” U.S. Patent Publication No. 2003-0057300-A1, U.S. patent application Ser. No. 10/247,351, entitled, “Injection Valve With Single Disc Turbulence Generation;” U.S. Patent Publication No. 2003.0015595-A1, U.S. patent application Ser. No. 10/162,759, entitled, “Spray Pattern Control With Non-Angled Orifices in Fuel Injection Metering Disc;” U.S. Patent Publication No. 2004-0000603-A1, U.S. patent application Ser. No. 10/183,406, entitled, “Spray Pattern and Spray Distribution Control With Non-Angled Orifices In Fuel Injection Metering Disc and Methods;” U.S. Patent Publication No. 2004-0000602-A1, U.S. patent application Ser. No. 10/183,392, entitled, “Spray Control With Non-Angled Orifices In Fuel Injection Metering Disc and Methods;” U.S. Patent Publication No. 2004-0056113, U.S. patent application Ser. No. 10/253,467, entitled, “Spray Targeting To An Arcuate Sector With Non-Angled Orifices In Fuel Injection Metering Disc and Methods;” U.S. Patent Publication No. 2004-0056115-A1, U.S. patent application Ser. No. 10/253,499, entitled, “Generally Circular Spray Pattern Control With Non-Angled Orifices In Fuel Injection Metering Disc and Methods;” U.S. patent application Ser. No. 10/753,378, entitled, “Spray Pattern Control With Non-Angled Orifices Formed On A Dimpled Fuel Injection Metering Disc Having A SAC Volume Reducer;” U.S. patent application Ser. No. 10/753,481, entitled, “Spray Pattern Control With Non-Angled Orifices Formed On A Generally Planar Metering Disc and Subsequently Dimpled With A SAC Volume Reducer;” U.S. patent application Ser. No. 10/753,377, entitled, “Spray Pattern Control With Non-Angled Orifices Formed A Generally Planar Metering Disc and Reoriented On Subsequently Dimpled Fuel Injection Metering Disc.”

Referring toFIGS. 1,1A,1B,2,2A,2B and4, the closure member310can be movable between a first position, so as to be in a closed configuration, and a second position so as to be in an open configuration (not shown). In the closed configuration, the closure member310contiguously engages the sealing surface336to prevent fluid flow through the orifice337. In the open configuration, the closure member310is spaced from the sealing surface336so as to permit fluid flow through the orifice337via a gap between the closure member310and the sealing surface336. In order to ensure a positive seal at the closure member310and sealing surface336interface when in the closed configuration, closure member310can be attached to armature tube312by welds313and biased by a resilient member370so as to sealingly engage the sealing surface336. Welds313can be internally formed between the junction of the armature tube312and the closure member310. To achieve different spray patterns or to ensure a large volume of fuel injected relative to a low injector lift height, it is preferred that the spherical closure member310can be in the form of a flat-faced ball, shown enlarged in detail inFIG. 4B.

In the case of where the closure member is in the form of a spherical valve element, for example closure member310, the spherical valve element can be connected to the second armature portion306or armature tube312at 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 sealing surface336. Again referencingFIG. 4, lower armature guide318can be preferably disposed in the tube assembly, proximate the seat assembly330, so as to slidingly engage the diameter of the closure member310. The lower armature guide318can additionally facilitate alignment of the armature assembly300along the axis A-A.

Referring back toFIGS. 1,1A and1B, the resilient member370, preferably in the form of a helical spring, can be disposed in the tube assembly so as to bias the armature assembly300toward the seat assembly330. The resilient member370can be further preferably dimensioned and configured so as to engage the interior face307of the first armature assembly end302. The resilient member370can also be engaged by an adjusting tube375. The adjusting tube375can preferably be disposed generally proximate the resilient member375. The adjusting tube375engages the resilient member370and adjusts the biasing force of the member370with respect to the tube assembly. In particular, the adjusting tube375provides a reaction member against which the resilient member370reacts in order to bring the armature assembly300and closure member310to the closed position upon de-energization of the solenoid or the electromagnetic coil402. The position of the adjusting tube375can be retained with respect to the inlet tube210by an interference fit between the adjusting tube375and a portion of the interior of the inlet tube210or separate pole piece270. The adjusting tube375can be configured in any manner so as to facilitate a preferred engagement with the filter assembly380and resilient member370, insertion into the inlet tube210and interference with at least a portion of the interior of the inlet tube210or separate pole piece270. Thus, the position of the adjusting tube375with respect to the inlet tube210can be used to set a predetermined dynamic characteristic of the armature assembly300.

Further affecting the ability of the closure member310to seal and the overall performance of the fuel injector100is the setting of the lift of the armature assembly. Lift is the amount of axial displacement of the armature assembly300defined by the working air gap413between the pole piece270and the armature core301, shown inFIG. 3A, and as determined by the relative axial spatial relation between either the non-magnetic shell230and valve body250; non magnetic shell230and inlet tube210; or seat assembly330and valve body250. 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 and as detailed in the exploded view ofFIG. 4F, a crush ring321or a washer can be inserted into the valve body250between the lower guide318and the valve body250. The crushing ring is axially deformable by a known amount. Upon engaging the armature assembly300with the seat assembly330, the intermediate crush ring321is deformed by a known amount that corresponds to the desired amount of lift between the armature assembly300and seat assembly330. According to a second technique, the relative axial position of the valve body250and the non-magnetic shell230can be adjusted and measured before the two parts are affixed together. According to a third technique, the relative axial position of the nonmagnetic shell230and the pole piece270can be adjusted before the two parts are affixed together. And according to a preferred fourth technique, as shown in the exploded view ofFIG. 4E, a lift sleeve319can be displaced axially within the valve body250. If the lift sleeve technique is used, the position of the lift sleeve319can be adjusted by moving the lift sleeve319axially. The lift distance can be measured with a test probe. Once the lift is correct, the sleeve319can be fixed or other wise welded to the valve body250, e.g., by laser welding. The assembled valve group subassembly200can then be tested, e.g., for leakage. Shown inFIG. 4is a cross-sectional view of lift sleeve319.

Referring again toFIGS. 1,1A and1B fuel injector100can additionally include a filter assembly380having a filter element382. The filter element382includes an intake surface384and discharge surface386defining a fluid flow path. The filter element382can be of any shape that can be accommodated within inlet tube210, for example, cylindrical shaped or more preferably frustoconical or conical. As seen inFIGS. 1,1A and2B, the filter assembly380can be engaged with the adjusting tube375. Alternatively, as shown inFIG. 1B, the filter assembly380can be disposed proximate the first inlet tube end212. To facilitate positioning of the filter assembly380proximate the first tube inlet end212, the filter assembly can further include an integral-retaining portion387for supporting the filter assembly380at the first inlet tube end212. The integral-retaining portion387can be dimensioned and configured so as to further support an O-ring290circumscribed about the first tube assembly end204so as to provides a seal at a connection of the injector100to a fuel source (not shown). Preferably, the filter assembly380can be substantially enclosed within the inlet tube210. InFIG. 1, the filter assembly380and filter element382can be configured such that such that at least a portion of the fluid flow path is substantially normal to the longitudinal axis, for example, wherein the intake surface384of the filter element382is substantially parallel to the longitudinal axis such that the fluid flows therethrough is substantially normal to the longitudinal axis. Alternatively the intake surface384and discharge surface386can define a fluid flow path that is substantially parallel or coaxial with the axis A-A.

The valve group subassembly200can be assembled as follows. The non-magnetic shell230is connected to the inlet tube210and to the valve body250so as to form the tube assembly202. The armature assembly300, preferably including the armature tube312and closure member310is inserted into the tube assembly202at the second tube assembly end206. In addition, the resilient member370can be inserted with the armature assembly300at the second tube assembly end206. Wherein any of the previously described lift setting techniques are utilized, the seat assembly330can be inserted into the tube assembly at the second tube assembly end206. Preferably, where a lift sleeve, or alternatively, a crush ring has been used, the seat assembly300with preferred orifice disk360and armature guide224affixed, is preassembled prior to insertion into the tube assembly202. With the lift properly set, the seat assembly can be accordingly affixed to the valve body in a manner as previously described. The resilient member370and adjusting tube375can be loaded into the tube assembly202at the first tube assembly end204. The adjusting tube375can be located within the tube assembly so as to preload the resilient member375thereby adjusting the dynamic properties of the resilient member375, e.g., so as to ensure that the armature assembly300does not float or bounce during injection pulses. Preferably the adjusting tube375is fixed with respect to the inlet tube210by an interference fit in a manner as previously described. Preferably, the filter assembly380can be preassembled and engaged with the adjusting tube375so as to be disposed within tube assembly202upon insertion of the adjusting tube375into the tube assembly202. Alternatively, the filter assembly380having an integral-retaining portion386for insertion can be fixedly positioned at the first inlet tube end212of the inlet tube210. The retainer365can be affixed at the second valve body end254of valve body250.

Referring toFIG. 5, the power group subassembly400includes a solenoid or electromagnetic coil402for generating a magnetic flux, at least one terminal406, a housing420, and at least one overmold430. The electromagnetic coil402can include a wire403that that can be wound on a bobbin405and electrically connected to a planar surface at least one electrical contact407on the bobbin405. The terminal406can have a generally planar surface contiguous with a generally planar surface of a terminal connector409to allow for electrical communication. The housing420generally includes a ferromagnetic cylinder422surrounding at least a portion of the electromagnetic coil402and a flux washer424extending from the cylinder422toward the axis A-A. The washer424can be integrally formed with or separately attached to the cylinder422. The housing420can include holes, slots, or other structures to break-up eddy currents that can occur when the coil is energized. The overmold430maintains the relative orientation and position of the electromagnetic coil402, the at least one terminal406(two are used in the illustrated example), and the housing420. The overmold430can include an electrical harness connector portion432in which a portion of the terminal406is exposed. The terminal406and the electrical harness connector portion432can engage a mating connector, e.g., part of a vehicle wiring harness (not shown), to facilitate connecting the fuel injector100to an electrical power supply (not shown) for energizing the electromagnetic coil402. The overmold430when formed includes a proximal or first overmold end433proximate the harness connector and a distal or opposite second overmold end435. An exploded view of the power group subassembly is shown inFIG. 5B. Preferably, the overmold430and bobbin405are nylon616, flux washer is 1008 steel, the coil housing420is 430 Li stainless steel.

According to a preferred embodiment shown here inFIG. 6A, the magnetic flux401generated by the electromagnetic coil402flows in a circuit that includes, the pole piece270, the armature assembly300, the valve body250, the housing420, and the flux washer424. As seen inFIGS. 6A and 6B, the magnetic flux401moves across a parasitic airgap411between the homogeneous material of the ferromagnetic portion304and the valve body250into the armature core301and across the working air gap413towards the pole piece270, thereby lifting the closure member310off the seat assembly330. Referring back toFIGS. 3A and 3B, the width “a” of the impact surface275of pole piece270is preferably greater than the width “b” of the cross-section of the impact surface305of ferromagnetic portion304. The smaller cross-sectional area “b” allows the armature core301of the armature assembly300to be lighter, and at the same time, causes the magnetic flux saturation point to be formed near the working air gap413between the pole piece270and the ferromagnetic portion304, rather than within the pole piece270. The ratio of “b” to “a” can be

Furthermore, since the armature core301is partly within the interior of the electromagnetic coil402, the magnetic flux401is denser, leading to a more efficient electromagnetic coil. Finally, as previously noted, because the ferromagnetic closure member310is magnetically decoupled from the ferromagnetic portion304via the armature tube312, flux leakage of the magnetic circuit to the closure member310and the seat assembly330is reduced, thereby improving the efficiency of the electromagnetic coil402.

The power group subassembly400can be constructed as follows. A plastic bobbin405can be molded with at least one electrical contact407. The wire403for the electromagnetic coil402is wound around the plastic bobbin405and connected to the electrical contacts407. The housing420is then placed over the electromagnetic coil402and bobbin405. The terminal406, which is pre-bent to a proper shape, is then electrically connected to each electrical contact407by known methods for example, brazing, soldered welding or, preferably, resistance welding between respective tips so that the tips abut each other on their circumference. Preferably, the generally planar surface of the terminal406is contiguous to the generally planar surface of the terminal connector406. The partially assembled power group subassembly can be placed into a mold (not shown) for forming the overmold430. The overmold430maintains the relative assembly of the coil/bobbin unit402,405, housing420, and terminal406. The overmold430also provides a structural case for the fuel injector100and provides predetermined electrical and thermal insulating properties. A separate collar440can be connected, e.g., by bonding, and can provide an application specific characteristic such as an orientation feature or an identification feature for the injector100. Thus, the overmold430provides a universal arrangement that can be modified with the addition of a suitable collar440. By virtue of its pre-bent shape, the terminal406can be positioned in the proper orientation for the harness connector432when a polymer is poured or injected into the mold. The assembled power group subassembly400can be mounted on a test stand to determine the solenoid's pull force, coil resistance and the drop in voltage as the solenoid is saturated. To reduce manufacturing and inventory costs, the coil/bobbin unit402,405can be the same for different applications. As such, the terminal406and overmold430and/or collar440can be varied in size and shape to suit particular tube assembly lengths, mounting configurations, electrical connectors, etc. The preparation of the power group subassembly400can be performed separately from the fuel group subassembly200.

Alternatively to the single overmold430, a two-piece overmold430′ as shown inFIG. 5B, can be formed allowing for a first overmold430A that is application specific while a second overmold430B can be for all applications. Two separate molds (not shown) can be used to form the two-piece overmold430′. The first overmold430A can be bonded to the second overmold430B, allowing both to act as electrical and thermal insulators for the injector. Additionally, as shown inFIG. 5Aand in the cross-sectional views ofFIGS. 1,1A and1B, a portion of the housing420can extend axially beyond an end of the overmold430,430′ to allow the injector to accommodate different length injector tips. The overmold430,430′ can be formed such that a portion of housing420can extend beyond the second overmold end435. In addition, housing420can also be formed with a flange421to retain the O-ring290. Flange421offers an alternate configuration to the flared portion368of retainer365for supporting the O-ring290as was previously described.

The individual assembly and testing of the valve group subassembly200and the power group subassembly400is independent of one another and therefore the assembly and testing of each can be performed without concern as to sequence of assembly and test operation of the other. ReferencingFIG. 7, to assemble the fuel injector100, the valve group subassembly200can be inserted into the power group subassembly400. Thus, the injector100can be made of two modular subassemblies200,400that can be assembled and tested separately, and then connected together to form the injector100. The valve group subassembly200and the power group subassembly400can be fixedly connected by adhesive, welding, or any other equivalent attachment process. Preferably, the overmold430includes a hole434that runs through the overmold430into and through the internally disposed housing420so as to expose a portion of the valve body250. A laser weld can be formed in the hole434thereby joining the housing420to the valve body250and thus connecting the valve group subassembly200to the power group subassembly400. In order to further facilitating the connection between the valve group subassembly200and the power group subassembly400, the inlet tube210preferably includes the projection213, as previously described, for an interference fit with the overmold430. More preferably, the valve body250is dimensioned and configured so as to have a generally constant outer diameter such that upon assembly with the inlet tube210and non-magnetic shell230the tube assembly200defines a generally constant outer diameter substantially along the axial length of the tube assembly200. In addition, the power group subassembly400, more specifically, the overmold430defines a generally constant inner diameter to hold the tube assembly200. The inserting of the valve group subassembly200into the power group subassembly400can involve setting the relative rotational orientation of the valve group subassembly200with respect to the power group subassembly400. According to the preferred embodiments, the fuel group and the power group subassemblies200,400can be rotated such that the included angle between reference point(s), for example, a first reference point on the orifice disk360(including opening(s) thereon) and a second reference point on the injector harness connector434can be set within a predetermined angle. The relative orientation can be set using robotic cameras or computerized imaging devices to look at respective predetermined reference points on the subassemblies, calculate the angular rotation necessary for alignment, orientating the subassemblies and then checking with another look and so on until the subassemblies are properly orientated. Once the desired orientation is achieved, the subassemblies200,400can be inserted together. The insertion operation can be accomplished by one of at least two methods: “top-down” or “bottom-up.” According to the former, the power group subassembly400is slid downward from the top of the valve group subassembly200, and according to the latter, the power group subassembly400is slid upward from the bottom of the valve group subassembly200. In situations where the inlet tube210includes a flared first end, the bottom-up method is required. Also in these situations, the O-ring290that is retained by the preferred flared first inlet tube end212can be positioned around the power group subassembly400prior to sliding the valve group subassembly200into the power group subassembly400. After inserting the valve group subassembly400into the power group subassembly200, these two subassemblies are affixed together in a manner as previously described. Finally, the O-ring290at either end of the fuel injector can be finally installed.

The use of O-rings290at the proximate and distal of the first and second overmold ends433,435respectively ensure a tight seal connection between the fuel injector300and other engine components. For example, the first injector end110can be coupled to a fuel supply line of an internal combustion engine (not shown). The O-ring290can be used to seal the first injector end110to the fuel supply so that fuel from a fuel rail (not shown) is supplied to the tube assembly202with the O-ring290making a fluid tight seal, at the connection between the injector100and the fuel rail (not shown).

In operation of the fuel injector100, the electromagnetic coil402can be energized, thereby generating magnetic flux401in the magnetic circuit. The magnetic flux401moves armature assembly300preferably along the axis A-A towards the pole piece270thereby closing the working air gap. This movement of the armature assembly300separates the closure member31from the seat assembly330, places the closure member310in the open configuration and allows fuel to flow from the fuel rail (not shown), through the inlet tube210, the through-bore314, the apertures316and the valve body250, between the seat assembly330and the closure member310, through the orifice337, and finally through the orifice disk360into the internal combustion engine (not shown). When the electromagnetic coil402is de-energized, the armature assembly300is moved by the bias of the resilient member370to contiguously engage the closure member310with the seat assembly330, placing the closure member in the closed configuration, and thereby prevent fuel flow, through the injector100.