Abstract:
A fuel injector for an engine includes a continuous endoskeletal injector tube enclosing an imperforate continuous passage for fuel flow from an inlet end to an outlet end of the tube. A valve seat, injection valve, tubular magnetic pole, biasing spring and adjusting sleeve are mounted within the tube, optionally with other elements, all being exposed to fuel in the passage defined by the tube. A solenoid coil and a magnetic body together with mounting components and seals are mounted on the exterior of the tube where they are protected from exposure to the fuel, which is restricted to passage within the continuous tube. The body, pole and armature form a magnetic flux concentrating path operative to attract the armature to the pole and open the valve when the coil is energized. The solenoid coil may be preassembled with its connector in a body forming a separate coil assembly for subsequent installation on the injector tube. During assembly, the tubular pole may be adjusted to set the desired stroke of the injection valve prior to fixing the pole in the tube. Various other features are also disclosed.

Description:
TECHNICAL FIELD 
     This invention relates to engine fuel injectors. A particular embodiment involves a solenoid actuated fuel injector including an endoskeletal continuous tube within which fuel flow is contained and which supports the various components making up the injector. 
     BACKGROUND OF THE INVENTION 
     It is well known in the automotive engine art to provide solenoid actuated fuel injectors for controlling the injection of fuel into the cylinders of spark ignition engines, generally through intake manifold runners or intake ports of the cylinders. Generally, such injectors include a body having added internal and external components which are assembled and welded, brazed or otherwise sealed together to provide internal fuel passages for conducting fuel flow. In some designs, the actuating solenoid coil is exposed to fuel passing through the injector. Such injectors may also involve assembly of many small components housed within a body having an internal coil joined with a connector and enclosed by an overmolded protective material. 
     It is desirable to provide an injector having reduced complexity and assembly costs as well as improved protection against fuel leakage and coil failures. 
     SUMMARY OF THE INVENTION 
     The present invention provides a novel injector having a number of improved features combined in a preferred embodiment. Some of the features are optionally combinable with other forms of injectors and components to provide various combinations of components and features. 
     A primary feature of the invention is that it includes a continuous endoskeletal tube enclosing a continuous passage for fuel flow through the injector from an inlet end to an outlet end of the tube. In general, the tube provides a skeleton or support within or on which all the other components of the injector are mounted. 
     A valve seat is fixed at the outlet end of the tube which may have a straight or expanded outlet end for supporting the valve seat. 
     An injection valve is slidable within the tube and is biased against the valve seat to close off fuel flow therethrough. The valve has an armature which is attracted to a tubular pole mounted within the tube by energizing of a coil surrounding the tube. Optionally, the tubular pole may be adjusted during assembly to establish the operating stroke of the valve prior to fixing the tubular pole in the adjusted position. 
     The electrical coil may be formed as a coil assembly including an attached connector with enclosed terminals. The complete coil assembly has a central opening through the coil that allows the coil assembly to be slipped over the tube during assembly of the injector. The continuous tube prevents fuel in the internal passage from contacting the coil and other elements that are mounted on the exterior of the tube. 
     A magnetic body or strap at least partially surrounds the coil and has upper and lower ends connected with the exterior of the tube to form a magnetic flux concentrating path through the body, coil and armature so as to attract the armature to the pole when the coil is energized. 
     A separate tubular or hollow component or support element may be provided which is assembled over the tube to engage and possibly surround the coil body. The support element may include a clip groove for connecting the support element and the injector to an associated fuel rail by means of a retaining clip or other suitable retaining means. The support element may also provide a backup surface for an inlet end seal ring which may be retained in place by a push-on rail seal retainer forced over the inlet end of the injector tube and retained by friction or other suitable means. 
     Various embodiments of valve seats and/or associated components are possible. 
     In one embodiment having a straight line tube, a valve seat is secured to the outlet end of the tube and includes an integral multi-hole director for directing fuel spray from one or more openings in the valve seat which are controlled by the associated valve. 
     In other embodiments, the outlet end of the tube is expanded to form a short cylindrical portion in which a valve seat is received and retained by crimping over the outlet end of the tube. A lower guide disc may be seated in the cylindrical portion between the valve seat and a flange formed by the outwardly expanded portion of the tube. A discharge opening in the valve seat may connect with a circular recess in which a director having multiple spray directing holes is retained. The director may be a disc element retained by a press fitted cup-shaped member. Alternatively, the director may be formed as a cup-shaped member retained by press fitting. Either of these versions could be supplementally retained by tack welding or other means for positively holding the retainer in place. 
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a transverse cross-sectional view along the axis of a preferred embodiment of fuel injector according to the invention; 
     FIG. 2 is a view similar to FIG. 1 but showing an alternative embodiment of fuel injector together with a cup of an associated fuel rail; 
     FIG. 3 is a cross-sectional view of a separately formed coil assembly for use with the injectors of FIGS. 1 and 2; 
     FIG. 4 is an enlarged view of the outlet end of the injector of FIG. 1 including an expanded tube portion in which a valve seat and lower guide are retained and including a disc director held in a circular outlet recess of the valve seat by a cup-shaped director retainer; 
     FIG. 5 is a view similar to FIG. 4 wherein the director is formed in a cup-shape and pressed into the circular recess; 
     FIG. 6 is a view similar to FIG. 5 wherein the director is supplementally retained by the combination of a retention lip and a spot weld; 
     FIG. 7 is an inlet end view of a push-on rail seal retainer similar to that shown in FIG. 1; 
     FIG. 8 is a cross-sectional view of the retainer of FIG. 7; 
     FIG. 9 is an inlet end view of an alternative push-on rail seal retainer including spring fingers; and 
     FIG. 10 is a cross-sectional view of the retainer of FIG.  9 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1 of the drawings in detail, numeral  10  generally indicates a solenoid actuated fuel injector having many of the  10  features of the present invention. Injector  10  includes a continuous endoskeletal injector tube  12  which is centered on a central axis  14  and encloses a continuous passage  15  through the injector from an inlet end  16  of the tube to an outlet end  18 . Preferably, the tube  12  has no openings except at the inlet and outlet ends and defines a continuous imperforate passage in which fuel is conducted and kept separate from all the components of the injector that are mounted externally of the tube. These include a separately formed coil assembly  20  including a solenoid coil  22  extending around and closely adjacent to the tube but isolated thereby from the fuel in the tube. A magnetic coil body or strap  24  surrounds the coil  22  and has upper and lower ends  26 ,  28  fixed to the outer surface of the tube. 
     A support element  30  is formed as a tubular member that slides over the tube and engages the body  24  surrounding an upper portion thereof. The support element includes a slot  32  for receiving a retainer clip, not shown, that holds the injector inlet end within a cup, not shown, of an associated fuel rail. The support element also provides a backup surface  34  at one end for constraining a seal ring  36  of the conventional O-ring type. A push-on seal retainer  38  is frictionally or otherwise retained on the inlet end  16  of the injector tube  12  to form with the other parts an annular groove in which the seal ring  36  is retained. A split spacer ring  46  extends around the lower end of the body  24  and engages an annular O-ring seal  48  which is retained, in part, by an expanded diameter portion  50  at the lower end of the injector tube  12 . 
     Within the injector tube  12 , an inlet fuel filter  52  is provided at the inlet end of the tube. A tubular magnetic pole is fixed within the tube in engagement with its interior surface. The pole extends from adjacent the upper end  26  of the body  24  to a position within the axial extent of the coil  22 . An injection valve  56  is reciprocable within the tube  12  and includes a ball end  58  connected with a hollow armature  60  that slides within the tube. A biasing spring  62  engages the armature and an adjusting sleeve  64  fixed within the magnetic pole  54  to urge the injection valve downward toward a closed position. 
     Within the expanded diameter portion  50  of the tube  12 , a valve seat  66  and a lower valve guide  68  are retained by crimped over portions of the tube outlet end  18 . The lower valve guide  68  is a disc positioned between the valve seat and a flange-like surface formed by the expanded diameter tube portion  50  to guide the ball end  58  of the injection valve. The disc includes openings  70  to allow fuel flow through the guide  68  to a conical surface  72  of the valve seat against which the ball end  58  seats in the valve closed position. A central discharge opening  74  of the valve seat  66  connects the conical surface  72  with a circular recess  76  in which a multi-hole spray director  78  is press fitted or otherwise retained. An outer seal ring  80  is captured in a groove of the valve seat and prevents fuel from leaking around the valve seat and bypassing the discharge opening  74 . 
     To properly control the speed and efficiency of valve action in a solenoid actuated injector, it is important that the valve stroke be established at a desired predetermined value. Typically, this has been accomplished by making the position of the valve seat adjustable relative to the body of the injector. The present invention avoids the complexity of providing an adjustable seat position by making the magnetic pole  54  adjustable within the tube  12  in order to establish the desired clearance between the pole and the valve armature in the valve closed position. This is done by sliding the pole inside the tube prior to its being fixed to the tube in order to retain the valve stroke at the adjusted position. In a similar manner, adjusting sleeve  64  is slidable within the tubular pole  54  in order to provide the proper compression of spring  62  which biases the valve against the valve seat in the closed position. 
     In operation, energizing of the coil  22  draws the armature  60  upward into engagement with the end of the magnetic pole  54 , moving the ball end  58  of valve  56  upward away from the conical surface  72  of the valve seat  66 . Fuel is then allowed to flow through the tube  12  and valve seat  66  and out through the director  78  into an associated intake manifold or inlet port of an associated engine, not shown. Upon de-energization of the coil  22 , the magnetic field collapses and spring  62  seats the valve  56  on conical surface  72 , cutting off further fuel injection flow. 
     Referring now to FIG. 2 of the drawings, numeral  82  generally indicates an alternative embodiment of an injector formed according to the invention. Except for the outlet end, injector  82  is essentially similar in construction to injector  10  previously described so that like numerals are used to indicate like parts, as to which further description is not believed required. 
     Injector  82  differs in that its continuous endoskeletal tube  84  does not have an expanded diameter portion at the lower end but instead is a straight tube with a constant diameter between its opposite ends  16 ,  18 . If desired the tube could have varying diameters, for example as in FIG. 1. A valve seat  86  is fixed in the lower end  18  by welding or in any suitable manner. The valve seat includes a flat seat surface  88  that is engaged by a valve element  90  having a flat surface that seats against the valve seat surface  88  to close the valve. The valve element  90  forms part of an injection valve  92  that includes an armature  60  reciprocable in the tube  84  as in the previous embodiment. Within the flat surface  88 , the valve seat  86  provides an integral spray director comprising a plurality of openings  94  for directing fuel spray discharged from the injector when the valve is open. A conventional O-ring seal  48  seals the lower end of the tube as in the embodiment of FIG.  1 . 
     The inlet end of the injector, adjacent tube end  16 , is illustrated as being inserted within a fuel rail cup  98  of an associated fuel rail, not shown. The cup includes a lip  100  which may be gripped by a clip, not shown, that also engages the slot  32  in the support element  30  to retain the injector within the cup  98 . Operation of injector  82  is identical to that of injector  10  so that further description is not required. 
     FIG. 3 illustrates in cross section the coil assembly  20  which is usable with both of the previously described injectors. Assembly  20  includes the wire solenoid coil  22  which is wrapped around a bobbin  102  in a conventional manner. The coil  22  is electrically connected by means, not shown, to a pair of terminals  104 , only one being shown, which extend outwardly into a connector end  106  of the coil assembly  20  for connection of the coil to an external electrical power source. The bobbin, coil and terminals are completely encased within a body  108  which is molded of suitable plastic material about the coil and terminals after they are positioned in their proper relationship. A through-opening  110  is provided extending axially through the coil to allow the coil assembly to be installed by sliding it over the tube  12  or  84  during the injector assembly process. Formation of the coil assembly with the terminal connector as a separate preassembled component, greatly simplifies the assembly process for the injector itself as will be subsequently further described. 
     Referring now to FIGS. 4-6, three alternative embodiments for spray directors are illustrated assembled in the recess  76  formed on the discharge side of valve seat  66  of the injector of FIG.  1 . In FIG. 4, a spray director  114  is formed as a disc that is retained in the recess  76  by a cup-shaped retainer member  116  which may be press fitted or otherwise retained in the recess  76 . A plurality of spray openings  118  are provided through the spray director disc  114  to direct the flow of fuel spray from the injector into the associated inlet runner or port, not shown. 
     FIG. 5 illustrates an alternative embodiment of identical construction with FIG. 4, except that the spray director  120  is now a cup-shaped element received in recess  76  and including spray openings  118  for directing fuel spray as before. Spray director  120  is again press fitted into the recess  76  for retention therein. 
     FIG. 6 illustrates another embodiment with a spray director  120  like that of FIG.  5 . In this case, however, the spray director is provided with a combination of a retention lip  122  on one side and one or more spot welds  124  on the other side to more positively retain the director  120  in the recess  76 . Alternatively, either a plurality of retention lips  122  or multiple spot welds could provide supplemental retention of the spray director. Obviously, these manners of retention could alternatively be applied to the embodiment of FIG.  4 . The other components of FIGS. 5 and 6 are identical to those of FIG. 4 so that the reference numerals to these parts have been omitted for clarity. 
     FIGS. 7-10 illustrate some alternative inlet seal retainer rings for use in place of retainer  38  shown in FIGS. 1 and 2. FIGS. 7 and 8 show a retainer  126  somewhat similar to retainer  38  and including a generally axially extending hub or gripping portion  128  which is connected with a generally radially extending flange portion  130 . The hub  128  is resiliently expandable for sliding over the tube  12  or  84  and has a relatively sharp or narrow edge  131  so as to grip the tube and provide resistance against removal. The flange  130  is, of course, provided to engage and retain the O-ring  36  in position on the inlet end of the injector. 
     The alternative embodiment of FIGS. 9 and 10 features a spring fastener  132  having a curved outer stiffening flange  134  connecting inwardly with spring fingers  136  separated by slots  138  and having inner edges  140  which engage and grip the tube  12  or  84  when the fastener  132  is pressed thereon to act as a seal retainer. Alternatively, other forms of seal retainers and manners of retention of these retainers could be used, if desired. 
     An exemplary manner of assembly of a fuel injector according to the invention will now be described by reference to the embodiment of FIG.  1 . The various components are first manufactured and partially preassembled where needed for final assembly of the entire injector. The coil assembly is preassembled in the manner previously indicated to provide a single unit ready for installation. The continuous endoskeletal injector tube  12  is preformed of suitable stainless steel material, or other suitable alternative material, having a constant diameter from its inner end  16  to adjacent the outer end  18  where the expanded diameter portion  50  is formed. If desired, the diameter of upper portions of the tube could also be varied but that might affect the exemplary manner of assembly being here described. The lower valve guide  68  and valve seat  66  containing the seal ring  80  are then inserted into the expanded diameter portion  50  and aligned, and the tube outer end is then crimped over to retain these elements in position. 
     One of the alternative spray director embodiments may be press fitted into the circular recess  76  either before or after installation of the valve seat in the expanded diameter portion  50  of the injector tube  12 . The injection valve  56  and magnetic pole  54  may then be slid into the tube from the inlet end  16 , the pole  54  being adjusted at some point thereafter to provide the proper gap for setting the stroke of the valve  56 . The magnetic pole  54  is preferably fixed to the tube  12 , as by welding, after adjustment to set the proper gap. Before or after this step, the spring  62  may be installed and the adjusting sleeve  64  is forced into magnetic pole  54  in the proper position for providing suitable compression of the spring  62  for biasing the injection valve toward the closed position. 
     The external members are then assembled on the outside of the injector tube  12 , sliding them over the tube from the inlet end  16 . First, the seal  48  is slid into position against the flange of the expanded diameter portion  50 . Split spacer ring  46  may then be positioned against the seal or it may be added later. The coil body  24  is preferably made in two pieces which are assembled about the central portions of the coil assembly and the combined coil assembly and coil body are then slid over the inlet end of the tube and down into position with the lower end  28  of the two piece coil body received within the spacer ring  46  or around which the ring is subsequently installed. The ends  26 ,  28  of the coil body may be, but are not required to be, welded or otherwise fixed to the tube  12  at this time. Subsequently, the tubular support element  30  is slid over the inlet end of the tube with its lower end surrounding the upper end  26  of the body  24  and the seal ring  36  and push-on seal retainer  38  are finally applied. The assembled injector is then calibrated by adjusting the spring tension to obtain the desired fuel flow. Finally, fuel filter  52  is installed in the inlet end  16  of tube  12 , completing assembly of the injector. 
     It may be seen that, preassembly of certain of the components and the use of the continuous tube as a skeleton in and on which the components of the injector are assembled provide considerable simplification of the final assembly process of the injector, thereby reducing the cost of manufacture. In addition, the imperforate continuous tube itself separates the fuel bathed elements within the tube from all of the external components including, particularly, the coil assembly. Thus, fuel is prevented from contacting the coil and the other external elements, thereby providing an extended life for the coil and preventing leakage of fuel other than at the connections at opposite ends of the injector with an associated fuel rail and an engine inlet runner or port of a manifold or cylinder head. The dual functions of support element  30  of providing seal backup as well as a clip groove, the preassembled structure of the coil assembly, and the dual function of the magnetic pole  54  as both a concentrator of magnetic force and an adjustable stop for the injection valve  56 , along with various alternative embodiments of press fitted or otherwise retained spray directors and simple push-on seal retainers, all combine to provide a simplified and economical injector construction suitable for use in engines. Some of the various novel features included in the injector combination may, of course, also be utilized in other forms of injectors than those of the specific type shown, so that no limitation as to the scope of application of the various features is intended in their description as part of the previously described embodiments. 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.