Abstract:
A valve that is well-suited for controlling the injection of fuel into an engine. The valve may include an inner housing that includes a movable valve stem and that is removably attachable to an engine. An electrically-actuatable coil assembly is removably attached to the inner housing of the valve for selectively moving the valve stem within the inner housing to permit fuel to pass through the valve into the engine upon an application of an electrical current to the electrically actuatable coil.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to valves. More particularly, the present invention is directed to electronically-actuatable valves adapted for controlling the injection of a fuel into an engine. 
     2. Description of the Background 
     Many conventional engines of all fuel types including gasoline and diesel typically employ a fuel injector for supplying known quantities of fuel to each combustion chamber at precise times during the engine cycle. Typically, a fuel injector assembly is mounted on the engine cylinder head of a combustion chamber. The fuel injector functions to open and close the fuel pump supply line to each engine cylinder head when commanded to do so by an electrical signal from the engine control computer. 
     One type of conventional fuel injector is a one-piece electromechanical assembly having a housing, a spring-loaded armature of magnetically permeable material and an electromagnetic coil adjacent the armature that is axially positioned within a fuel supply passage. The housing surrounds both the armature and coil. The electrical wires must pass through this housing without leakage and must be electrically isolated from the housing. When this fuel injector is unenergized, the valve is closed and the armature is held against a valve seat by spring and hydraulic forces to prevent fuel from entering the engine cylinder head. As an electrical current is passed through the electromagnetic coil, a magnetic field is created. When the force from the magnetic field becomes sufficient to overcome the hydraulic and spring forces, the armature will be urged away from the valve seat and fuel will pass through the engine cylinder head to the combustion chamber. When the electrical energy is no longer supplied to the electromagnetic coil, the magnetic force starts to decay and the spring and hydraulic forces then become dominant and move the armature against the valve seat to the closed position. 
     One disadvantage of this type of conventional fuel injector is that it is difficult to accommodate all of the components of the fuel injector within the limited amount of space available in a reciprocating, opposed cylinder aircraft engine. In many aircraft engine arrangements, for example, the minimum diameter of space for a fuel injector is less than 0.75 inches. Fuel injectors used in automotive applications occupy a space with a diameter of about 1.25 inches. Thus, sufficient room is not available within the aircraft engine envelope to accommodate the available automotive-type fuel injector components and also to provide for installation and removal of the fuel injector components from the engine cylinder head port. 
     Existing fuel injector assembly internal designs are also complicated by the need to connect electrical signals across internal fuel to air barriers, together with requiring the means to operate the internal electromagnetic components in a fuel wetted environment. The sealing arrangements needed to address this problem, besides impacting size and weight, also preclude separate replacement of electrical and fluid handling elements within the assembly. Therefore, the entire assembly must be discarded in the event of a single failure in either element. Such one-piece construction also prevents the desirable use of a threaded port for installation to the engine cylinder head or inlet manifold, because it would not be practical to rotate the complete assembly. 
     Yet another disadvantage with conventional fuel injectors is that the electromagnetic coil and electrical supply cable are located within the same unit as the fuel passageway. Thus, the electromagnetic coil and the electrical supply cable are susceptible to decay caused by fuel and fuel vapor. As such, coil wire insulation material has to be carefully selected so as to not break down in the presence of fuel or fuel vapors should internal seepage occur despite such sealing arrangements. Such requirements place restrictions on the overall assembly design which result in injector assemblies that are difficult to accommodate within the engine envelope due to their physical size. It also requires that the electrical coil and connection structure be an integral, non-removable part of the injector assembly housing. Such condition also necessitates injector installation to the engine as a complete assembly, not permitting the use of a threaded installation port. 
     Accordingly, there is a need for a fuel injector that is compact and that can be easily installed and removed from an engine. 
     The need also exists for a fuel injector that has an electromagnetic coil and an electrical supply cable that can be readily separated from the mechanical valve components of the fuel injector, such that the mechanical portion of the valve can be replaced without also replacing the valve&#39;s electrical component or the electrical components can be replaced without also replacing the mechanical portion of the valve. 
     Yet another need exists for a fuel injector assembly that can be readily attached to the cylinder head of an engine by a threaded port arrangement. 
     Still another need exists for injecting a fuel into the combustion chamber of an engine that does not require the use of prior bulky fuel injectors which lead to increased engine weight and engine size. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a valve having an inner housing with an outlet port, a stopper member movably supported within the inner housing, a central housing member received within the inner housing and a magnetic flux that travels in a loop though the inner housing and the stopper member such that the magnetic flux urges the stopper member from a closed position, wherein the stopper member blocks the outlet port to an opened position. 
     The present invention further provides a valve having an inner housing of magnetically permeable material, a stopper member of magnetically permeable material, a central housing member of non-magnetically permeable material and an electrically-energizeable coil adjacent the inner housing, wherein the central housing member acts as a shunt such that the magnetic flux created by the coil bypasses the central housing member and travels through the stopper member. 
     The present invention further provides a fuel injector having an inner housing of magnetically permeable material with a valve passage and an outlet port, a valve stem movably received with the valve passage between a closed position, wherein the valve stem blocks the outlet port and an opened position, a biaser in contact with the valve stem, and an electrically-energizeable coil extending around at least a portion of the central housing member and adjacent the inner housing such that upon an application of current to the electrically energizeable coil, a magnetic flux is established within the magnetically permeable materials of the inner housing and the valve stem to cause the valve stem to move to the opened position. The inner housing of the fuel injector may be releasably connected to a cylinder head of an engine such as an aircraft engine. 
     The present invention further provides a two-part electromechanical valve having an electrical assembly and a fluid handling assembly, wherein these two separate assemblies provide a sealing arrangement that isolates the electrical components from the fluid that is passing through the valve. The electrical assembly includes a magnetically permeable cover with an opening for receiving an electrical supply cable, a bobbin inserted inside the cover, potting material contained within the cover and an electrically-energizeable coil wound around the bobbin and able to be electrically connected to the electrical supply cable. The fluid handling assembly includes a housing having a fluid passage that receives a stopper member and the fluid handling assembly is releasably connected to the electrical assembly using a connector. 
     The present invention further provides a method of injecting fuel into an engine comprising attaching an inner housing of a fuel injector to an engine, wherein the inner housing is made of magnetically permeable material with an outlet port and a passage, and the fuel injector further comprises a stopper member of magnetically permeable material and a central housing member of nonmagnetically permeable material, and wherein the stopper member is received within the inner housing, and the central housing member is received within the inner housing and adjacent the stopper member; transporting fuel into the passage; supplying fuel to the passage; and creating a magnetic flux through the inner housing and the stopper member such that the magnetic flux urges the stopper member from a closed position, wherein it blocks the outlet port, to an opened position. 
     Other details, objects and advantages of the present invention will become more apparent with the following description of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     For the present invention to be understood and readily practiced, the present invention will be described in conjunction with the following Figures wherein: 
     FIG. 1 a  is a cross-sectional view of a fuel injector of the present invention, wherein the valve stem is in the closed position; 
     FIG. 1 b  is a cross-sectional view of the fuel injector shown in FIG. 1 a,  wherein the valve stem is in the opened position; 
     FIG. 2 is an enlarged cross-sectional view of the inner housing and the central housing member of the fuel injector shown in FIG. 1 a;    
     FIG. 3 is an enlarged cross-sectional view of the valve stem, the fluid conduit supporter structure and the spring of the fuel injector shown in FIG. 1 a;    
     FIG. 4 is an enlarged cross-sectional view of the electrical supply assembly of the fuel injector shown in FIG. 1 a;    
     FIG. 5 is an enlarged cross-sectional view of the spherical union and connector of the fuel injector shown in FIG. 1 a;  and 
     FIG. 6 is a schematic of an internal combustion engine assembly employing the fuel injector of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will be described below in terms of a fuel injector. It should be noted that describing the present invention in terms of a fuel injector is for illustrative purposes and the advantages of the present invention may be realized using other structures and technologies that have a need for a valve configuration, wherein the valve configuration is compact, provides for easy installation, removal and servicing as well as provides a high integrity mechanical separation of the electrical components from the fluid passing through the valve. 
     It is to be further understood that the Figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the present invention, while eliminating, for purposes of clarity, other elements and/or descriptions thereof found in a typical fuel injector. Those of ordinary skill in the art will recognize that other elements may be desirable in order to implement the present invention. However, because such elements are well known in the art, and because they do not facilitate a better understanding of the present invention, a discussion of such elements is not provided herein. 
     FIGS. 1 a  and  1   b  illustrate cross-sectional views of a fuel injector  10  which employs the present invention, wherein the valve stem  18  or stop member of the fuel injector  10  is shown in its closed position and open position, respectively. The fuel injector  10  substantially comprises a fluid handling assembly  12  and an electrical supply assembly  13 . The fluid handling assembly  12  includes an inner housing  14  valve housing, a central housing member  16 , a valve stem  18 , a spring  20  and a fluid supply conduit supporter  22 . The electrical supply assembly  13  includes a cover  24  with a cap member  26 , a bobbin  28 , an electromagnetic coil  30 ′, potting material  32  and an electrical supply cable  34 . The fluid handling assembly  12  is releasably connected to the electrical supply assembly  13  by a nut  36 . 
     FIG. 2 is an enlarged cross-sectional view of the inner housing  14  and the central housing member  16  of the fuel injector  10  of the present invention shown in FIG. 1 a.  The inner housing  14  has a first end portion  38  and a second end portion  40 . The first end portion  38  has a first passage  41  therein and the second end portion  40  has a second passage  41 ′ therein. The first end portion  38  has a nozzle portion  44  with an outlet port  46  and a seat portion  48  that communicates with the first passage  41  therein. The seat portion  48  is substantially conical shaped; however, alternative configurations can be used. The outer surface of the nozzle portion  44  has threads  50  which are adapted to engage a threaded cylinder head  52  of an engine, shown in FIGS. 1 a  and  1   b.  In addition, the first end portion  38  is provided with a hexagonal shoulder  54  to permit wrenching of the inner housing  14  into the engine cylinder head  52 . 
     The outer surface of the second end portion  40  has threads  56  for threadably receiving the nut  36  thereon, as shown in FIGS. 1 a  and  1   b.  The inner housing  14  is made of stainless steel C40 alloy which is a magnetically permeable material. As used herein, the term “magnetically permeable material” means any material that the magnetic flux preferentially conducts within rather than the surrounding air. Specifically, Carpenter Technology high permeability 49 alloy can be used. Other magnetically permeable materials can be used to manufacture the inner housing  14  such as Carpenter Technology stainless steel 430F or other ferritic steels. 
     The central housing member  16  is a substantially tubular member having two end surfaces  39  and a passage  17  extending therethrough. The central housing member  16  is received between the first end portion  38  and the second end portion  40  of the inner housing  14  such that passage  17  is coaxially aligned on axis A—A with the first passage  41  and the second passage  41 ′ to form a continuous passageway  42 . See FIG.  2 . The central housing member  16  is fixedly connected to the first and second end portions  38  and  40  at its end surfaces  39  by conventional inertial welds  43 . The inertial welds  43  are produced by holding one of the two parts being joined stationary and rotating the other part with a machine spindle. Thus, utilizing this method, to attach the first end portion  38  to the central housing member  16 , one end  39  of the central housing member  16  is abutted against a corresponding end of the first end portion  38  such that the passage  17  is coaxially aligned with the passage  41 . Thereafter, a rotational force is applied to either the first end portion  38  or the central housing member  16  while retaining the adjacent member stationary. Those of ordinary skill in the art will appreciate that, as the rotating member abuts the stationary member heat is generated therebetween which results in the welding together of the member. That is, energy for the weld  43  is supplied by the kinetic energy stored in the rotating part. The central housing member  16  is manufactured from 304 stainless steel which is a readily and widely available and is a non-magnetically permeable material. As used herein, the term “non-magnetically permeable material” means material that magnetic flux has no preference for conducting within rather than air. Other non-magnetically permeable materials can be used for the central housing member  16  such as 303 stainless steel or 304L stainless steel or martensitic steels or non-ferrous materials. 
     FIG. 3 is an enlarged cross-sectional view of the valve stem  18 , the fluid supply conduit supporter  22  and the spring  20  of the fuel injector  10  of the present invention, as shown in FIG. 1 a.  The valve stem  18  is a substantially tubular member having a conical nose portion  57 , an inlet port  58  and two outlet ports  60  which communicate with a duct  62  that extends generally along the centerline of the valve stem  18 . The duct  62  has a large-diameter section  63 , a small-diameter section  65  and a ledge  64  formed between the large-diameter and small-diameter sections  63  and  65 . The ledge  64  is substantially perpendicular to the centerline of the duct  62 . The spring  20  extends within the large-diameter section  63  of the duct  62  and contacts the ledge  64 . The spring  20  is made from 303 stainless steel and exhibits approximately one pound (1 lb.) to one and one-quarter pounds (1.25 lbs.) force. It has been discovered that such spring biasing force serves to overcome external forces, such as engine vibration forces, to thereby prevent the inadvertent opening of the fuel injector  10 . However, other suitable biasing forces may be employed. Although not illustrated, any number of biasers can be used in place of the spring  20  which meet the size constraints of the present invention. The valve stem  18  is movably received within the passage  42  of the inner housing  14  and central housing member  16 , as shown in FIGS. 1 a  and  1   b.  The valve stem  18  is manufactured from Carpenter Technology high permeability 49 alloy, which is a magnetically permeable material. Other magnetically permeable materials can be used to manufacture the valve stem  18  such as ferritic steels. 
     The fluid supply conduit supporter  22  is substantially tubular-shaped and defines an inlet port  66  and an outlet port  68 , wherein the shape of the inlet port  66  is frustro-conical. A duct  70  extends along the centerline of the fluid supply conduit supporter  22  and has a small-diameter section  72  and a large-diameter section  74 . The duct  70  is in fluid communication with the inlet port  66  and the outlet port  68 . A ledge  76  is formed at the junction of the small-diameter section  72  and the large-diameter section  74 . When the fluid supply conduit supporter  22  is coaxially aligned with the valve stem  18 , as shown in FIG. 3, and an end of the spring  20  is received within the large-diameter section  74  of the supporter  22 , the spring  20  extends between and engages the valve stem ledge  64  and the supporter ledge  76 . The end of the supporter  22  adjacent the inlet port  66  has a flange  78  formed thereon. As can be seen in FIGS. 1 a  and  1   b,  the supporter  22  is received within passage  42  and is fixedly connected relative to the inner housing  14  and the central member housing  16  such that the flange  78  abuts the second end portion  40  of the inner housing  14 . The supporter  22  is formed of Carpenter Technology 49 alloy, which is a magnetically permeable material. However, the supporter  22  can be formed of a variety of magnetically permeable materials such as ferritic steels. The materials selected for the invention were chosen for their magnetic permeability and corrosion resistant properties. Many magnetically permeable materials are not corrosion resistant. Although not illustrated, the supporter  22  and the second end portion  40  of the inner housing  14  can be a unitary member. 
     FIG. 4 is an enlarged cross-sectional view of the electrical supply assembly  13  of the fuel injector  10  of the present invention, shown in FIG. 1 a.  The electrical supply assembly  13  includes a cover  24 , a cap member  26 , a bobbin  28 , potting material  32 , an electromagnetic coil  30 ′ and an electrical supply cable  34 . The bobbin  28 , the cover  24  and the cap member  26  form an electrical housing, designated generally as  96 . The cover  24  may be configured, as shown in FIG. 4, with a cup-shaped cross-section. In this embodiment, the cover  24  is fabricated from  430  stainless steel. However, other materials such as ferritic steels may be employed. As can be seen in FIG. 4, the cover  24  has a side portion  82  and a bottom portion  80  that has an aperture  90  extending therethrough. The cap member  26  includes a wall member  93  that is attached to the side portion  82  of the cover  24  by a weld and a cable-receiving portion  95 . The cap member  26  is made from the same materials as the cover  24 . An opening  87  is provided through the cap member  26 . Cap member  26  may also receive the electrical supply cable  34 . 
     As also can be seen in FIG. 4, the electrical supply assembly  13  includes a bobbin  28  that is fabricated from nylon or other plastic insulator materials. The bobbin  28  has a cylindrical center portion  86  and a flange  88  extending substantially perpendicularly from each end of the cylindrical center portion  86 . The cylindrical center portion  86  defines a passage  84  that extends therethrough. In this embodiment, a conductor  30  such as high temperature insulated copper magnetic wire is wound around the cylindrical center portion  86  of the bobbin  28  between the flanges  88  thereof to form the electromagnetic coil  30 ′. The conductor  30  is a standard, maximum rated, high temperature wire that is capable of withstanding 200° F. continuously. Conductors, which meet NEMA STD MW-1000, MW-73-C/A, MW 35-C/A and Federal Spec. J-W-1177/14B(K), such as model GP/MR-200 manufactured by Essex Group, Inc.; model Armored Poly Thermaleze, APTZ manufactured by Phelps Dodge Magnetic Wire Co.; model Therm Amid, TAI manufactured by Rea Magnet Wire Co.; model Omega Klad II, OKII, manufactured by Westinghouse Electric Co.; and model Daitherm-3, DT-3 manufactured by Optec D.D. USA, Inc. may be successfully employed. In one embodiment, wherein the outer diameter of the cylindrical center portion  86  is approximately 0.369 and the outer diameter of each of the flanges  88  is approximately 0.640 and the distance between the flanges  88  is approximately 0.560, a total of approximately 51.94 feet of the conductor  30  is wrapped around the cylindrical center portion  86 . Those of ordinary skill in the art will appreciate that when a current of 3.54 amps is passed through the conductor  30 , a magnetic flux of approximately 1368 ampere-turns is established by the electromagnetic coil  30 ′. 
     Referring further to FIG. 4, an electrical supply cable  34  is attached to the electromagnetic coil  30 ′. In this embodiment, the electrical supply cable  34  has a metal braided exterior layer  101 , a shield  103 , a metal conduit  105  and a conductor portion  109 . The conductor portion  109  is made from stranded copper wire. The bobbin  28  and the coil  30 ′ are installed in the cover  24 , such that the passage  84  extending through the center portion  86  of the bobbin  28  is coaxially aligned with the opening  90  in the cover  24  along axis B—B. The insulating conduit  105  and the conductor  109  extends through the cable-receiving portion  95  in the wall portion  93  of the cap member  26 , as shown in FIG.  4 . The conductor  109  is soldered, welded, or otherwise electrically attached to the two leads of the coil  30 ′ and a commercially available retainer ring  99  is used to affix the cable to the cap member  26  by placing the ring  99  around the cable-receiving portion  95  and crimping it in a known manner. The conductor  109  and the coil  30 ′ are sealed, as shown in FIG. 4, in a potting material  32 . The potting material  32  is a high dielectric, insulating potting material such as epoxy resin that eliminates arcing and sparking between the coil  30 ′ and the conductor  109 . For example, Thermoset 300 Resin and APC Lab Project WO82198-6 can be used. 
     The bobbin  28 , the electromagnetic coil  30 ′, the conductor  109  and potting material  32  are received within the cover  24 , such that the passage  84  is coaxially aligned with opening  90  in the cover  24 . Thereafter, the cap member  26  is affixed to the walls  82  of the cover  24  by laser welding or other method of controlled penetration. As noted above, the electrical supply cable  34  is connected to the electrical housing  96  by positioning the braided exterior layer  101  between the metal ring  99  and the tube portion  95  and crimping the metal ring  99  around the braided exterior layer  101 . An alternate method of shield termination can also be employed by inserting the shield  103  into tube  83  and securing the shield  103  with a silver filled epoxy to achieve electrical conductivity. It will be appreciated that the potting material  32  fills the space remaining in the electrical housing  96  such that the potting material  32  surrounds the electromagnetic coil  30 ′ and the electrical supply cable  34  within the electrical housing  96 . 
     FIG. 5 is an enlarged cross-sectional view of the spherical union  100  and the connector  102  of the fuel injector  10  of the present invention, as shown in FIG. 1 a.  The spherical union  100  and the connector  102  join a fuel supply conduit  104  to the support inlet port  66  and also fixedly connect the supporter  22  to the inner s housing  14  and the central housing member  16 , as shown in FIGS. 1 a  and  1   b.  The spherical union  100  has a spherical head portion  106 , a shoulder  107 , a tubular body  108  and a channel  110  which receives the fuel supply conduit  104 . The fuel supply conduit  104  is fixedly connected to the spherical union  100  by brazing. The connector  102  is a hex nut with internal threads  112  which mate with the threads  56  of the inner housing  14 , as shown in FIG. 1 a.  The head portion  106  is received within the supporter inlet port  66 . The connector  102  is then slid over the tubular body  108  of the spherical union  100  and threaded onto threads  56  until the spherical union shoulder  107  engages the connector shoulder  114 . The head portion  106  is spherical such that when the supporter inlet port  66  receives the spherical head portion  106  and the connector  102  fully engages the threads  56 , a fluid tight connection is made between the fuel supply conduit  104  and the fluid supply conduit supporter  22 . By threading the connector  102  onto the threads  56  of the inner housing  14 , the flange  78  of the supporter  22  is fixedly held in place relative to the inner housing  14  between the inner housing  14  and the connector  102 . Specifically, the flange  78  is wedged between the spherical union  100  and the inner housing  14 . The fuel supply conduit  104 , the connector  102  and the spherical union  100  are metal. In general, metals are used for most of the components of the fuel injector  10  to minimize static that may cause electronic instrumentation to malfunction. 
     FIG. 6 is a schematic view of an internal combustion engine system  120  employing the fuel injector  10  of the present invention. The internal combustion engine system  120  depicted in that Figure includes a fuel supply conduit  104 , a pump  124  and a plurality of individual cylinder heads  52  connected to combustion chambers  127 . A fuel injector  10  is connected to and between each of the plurality of engine cylinder heads  52  and the fuel supply conduit  104 . 
     Referring to FIGS. 1 a,    1   b  and  6 , the fuel injector  10  is assembled in the following manner. The threaded nozzle portion  44  is threaded onto mating threads in the engine cylinder head  52 . The electrical supply assembly  13  is slid over the fluid handing assembly  12  such that the inner housing  14  and central housing member  16  extend through the cover aperture  90 , the bobbin passage  84  and the cap member opening  87 . The electrical supply assembly  13  is releasably retained on the fluid handling assembly  12  by nut  36 . The nut  36  is threaded onto the threads  56  of the inner housing first end portion  40  until the nut  36  contacts the cap member  26 . 
     The fuel supply conduit  104  is attached to the fluid handling assembly  12  by inserting the head portion  106  into the supporter inlet port  66 . The connector  102  is then slid over the tubular body  108  of the spherical union  100  and threaded onto threads  56  until the spherical union shoulder  107  engages the connector shoulder  114 . Because the fuel injector  10  of the present invention can be installed onto the engine cylinder head  52  by rotating the fluid handling assembly  12  into the engine cylinder head  52  and subsequently installing the electrical supply assembly  13  onto the fluid handling assembly  12  without rotation of the fuel injector  10 , the present invention is especially well suited for use in engine applications wherein fuel injector space is limited. 
     In operation, the fuel is pumped through the fuel supply conduit  104  to the fuel injector  10  where the fuel is injected in a measured amount and at desired times through the engine cylinder heads  52  to the combustion chamber  127 . When the fuel injector  10  is in the closed position, as shown in FIG. 1 a,  the conical nose portion  57  is received within the seat portion  48 , fuel is prevented from passing through the outlet port  46  into the combustion chamber  127 . Those of ordinary skill in the art will appreciate that, when the coil  30 ′ of the fuel injector  10  is unenergized, the spring  20  and the fluid pressure of the fuel within the valve stem  18  biases the valve stem  18  in the direction represented by arrow “C” such that a substantially fluid-tight seal is established between the nose portion  57  of the valve stem  18  and the seat portion  48 . When the valve stem  18  is in its opened position, as shown in FIG. 1 b,  the fuel can flow out of the outlet ports  60  of the valve stem  18  and through the outlet port  46  of the inner housing  14  into the combustion chamber  127 . 
     To open the fuel injector  10 , an electrical current is supplied to the electromagnetic coil  30 ′ to create a magnetic flux A, shown in FIGS. 1 a  and  1   b.  The electrical current is regulated by a controller  135 , shown in FIG. 6, wherein the controller  135  can be the controller described in U.S. patent application Ser. Nos. 09/268,181 and 09/268,173, entitled Automatic Aircraft Engine Fuel Mixture Optimization and System and Method for Ignition Spark Energy Optimization, respectively, and being filed concurrently with this application, the entire disclosures of which are heareby incorporated by reference herein. The magnetic flux A travels through the cover  24 , the cap member  26 , the nut  36 , along the supporter  22  and the valve stem  18 , through the first end portion  38  of the inner housing  14  and back to the cover  24  to create a closed loop, as shown in FIGS. 1 a  and  1   b.  The cover  24 , the cap member  26 , the nut  36 , the supporter  22 , the valve stem  18  and the inner housing  14  are all made of magnetically permeable material to support the establishment of the flux therein. However, the magnetic flux A does not travel through the central housing member  16  because it consists of non-magnetically permeable material. Thus, the central housing member  16  acts as a magnetic break to force the flux to pass through the supporter  22  and valve stem  18 . When the forces created by the magnetic flux A become sufficient to overcome the hydraulic and spring forces in the “C” direction, the magnetic flux force will urge the valve stem  18  towards the supporter  22  (i.e., in the “D” direction, as shown in FIG. 1 b.  ) in order to permit fuel to flow through the outlet port  46  and into the combustion chamber  127 . Once the electrical current is no longer supplied to the electromagnetic coil  30 ′, the magnetic flux force starts to decay and the spring and hydraulic forces become the dominant forces and move the valve stem  18  in the “C” direction into sealing contact with the seat portion  48 . 
     The flux path defined by the inner housing  14 , the valve stem  18 , the supporter  22 , the cover  24 , the nut  36 , and the cap member  26 , exhibits enhanced efficiency which enables the necessary magnetic flux force to be achieved using a small overall fuel injector  10  with an outer diameter of, for example, approximately 0.75 inches. Therefore, the fuel injector  10  of the present invention can be used in an engine design having space limitations, such as aircraft engines. In addition, because the electrical supply assembly  13  can be quickly detached from the fluid handling assembly  12 , the fluid handing assembly  12  can be conveniently attached to the engine cylinder head  52  by a threaded connection. That is, the fluid handling assembly  12  can be screwed into the cylinder head  52  before the fuel supply conduit  104  and the electrical supply assembly  13  are attached. After the fluid handling assembly  12  is connected securely and without leakage to the engine cylinder head  52 , the electrical supply assembly  13  and the fluid supply conduit  104  can be attached thereto in the above-described manners. Thus, this arrangement permits the fuel injector  10  to be quickly attached and detached from engine cylinder head  52 . In addition, should the fluid handling assembly  12  needs to be replaced, it can be quickly replaced without requiring replacement of the electrical supply assembly  13 . Similarly, should the electrical supply assembly  13  need to be replaced, it can be quickly replaced without replacing the fluid handling assembly  12 . 
     Those of ordinary skill in the art will recognize, however, that many modifications and variations of the present invention may be implemented without departing from the spirit and scope of the present invention. The foregoing description and the following claims are intended to cover such modifications and variations.