Abstract:
A method of setting a distance between a first body and a second body in a fuel injector is disclosed. The method includes providing an intermediate body having a first end, a second end and a longitudinal axis, the first end being fixedly connected to the first body and the second end being fixedly connected to the second body. The intermediate body is compressed toward the longitudinal axis. The compression axially elongates the intermediate body, such that the first body is separated from the second body. An apparatus used to set the distance is also disclosed.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention is directed to a method of setting armature/needle lift in a fuel injector by plastic deformation of a structural component of the fuel injector.  
         BACKGROUND OF THE INVENTION  
         [0002]    Fuel injectors are commonly employed in internal combustion engines to provide precise metering of fuel for introduction into each combustion chamber. Additionally, the fuel injector atomizes the fuel during injection, breaking the fuel into a large number of very small particles, increasing the surface area of the fuel being injected and allowing the oxidizer, typically ambient air, to more thoroughly mix with the fuel prior to combustion. The precise metering and atomization of the fuel reduces combustion emissions and increases the fuel efficiency of the engine.  
           [0003]    An electro-magnetic fuel injector typically utilizes a solenoid assembly to supply an actuating force to a fuel metering valve. Typically, the fuel metering valve is a plunger style needle valve which reciprocates between a closed position, when the needle is seated in a valve seat along a sealing diameter to prevent fuel from escaping through a metering orifice disc into the combustion chamber, and an open position, where the needle is lifted from the valve seat, allowing fuel to discharge through the metering orifice for introduction into the combustion chamber.  
           [0004]    Accurate lift set for the needle is important because the lift height affects the static flow of fuel through the injector. The previously known process of “direct lift set” requires very accurate machines and metering components, and special geometry between a lower subassembly and an upper subassembly of the injector to form a “lock” which holds the relative positions of the assemblies during connection of the subassemblies. The lower subassembly is generally comprised of a valve body, a seat/guide assembly, and an armature/needle assembly. The upper subassembly is generally comprised of a coil, an inlet tube, a housing, a non-magnetic shell, and a valve body shell.  
           [0005]    The upper and lower subasssemblies are pressed together to set the lift, with the interface occurring between the valve body and the valve body shell. This press involves shearing metal, causing a “chip” to shear off the valve body shell into a groove in the valve body. When attempting to push the two subassemblies together, the motion required to force the desired relationship is quite variable. For example, a 1000 Newton force may cause no motion, but a 1005 Newton force may cause the subassemblies to move 100 microns with respect to each other. It is seen, therefore, that control of the relative motions is difficult. For example, if the tooling used to set the lift pushes the subassemblies 20 microns closer together, the individual parts in each subassembly may compress some unknown amount, and the relative position of the parts may move some other, also unknown, amount. There is no absolute control of the relative positions of the parts, which makes direct lift setting a less than perfect process.  
           [0006]    It would be beneficial to develop a method of setting lift height by a method that ensures producing the desired lift height.  
         BRIEF SUMMARY OF THE INVENTION  
         [0007]    Briefly, the present invention provides a method of setting a distance between a first body and a second body. The method comprises providing an intermediate body having a first end, a second end and a longitudinal axis, the first end being fixedly connected to the first body and the second end being fixedly connected to the second body; and compressing the intermediate body toward the longitudinal axis and axially elongating the intermediate body, the first body being separated from the second body.  
           [0008]    Further, the present invention provides a method of setting armature/needle lift in a fuel injector. The method comprises providing a non-magnetic shell having a first end, a second end and a longitudinal axis; fixedly connecting the first end with a first subassembly; inserting an second subassembly into the second end, the second subassembly engaging the first subassembly; fixedly connecting the second subassembly to the non-magnetic shell; and compressing the non-magnetic shell toward the longitudinal axis and axially elongating the non-magnetic shell, the first subassembly being separated from the second subassembly.  
           [0009]    Additionally, the present invention provides an armature/needle assembly lift setting apparatus. The apparatus comprises a plurality of punches. Each punch has a longitudinal axis intersecting at a common point and a contact end. The apparatus also includes an interior perimeter generally formed by the engagement ends of the plurality of punches. The interior perimeter is sized to accept a working piece therein, with the working piece including a working piece longitudinal axis. The apparatus also includes an actuator operatively connected to the plurality of punches such that operation of the actuator moves each of the plurality of punches along each respective longitudinal axis. The engagement end of each of the plurality of punches engages the working piece and compresses the working piece in a plane of the longitudinal axes and lengthens the working piece along the working piece longitudinal axis.  
           [0010]    Additionally, the present invention provides a fuel injector comprising an upstream end body having an inlet tube, a downstream body having a valve body, and a longitudinal axis extending therethrough. The fuel injector also includes a hollow shell having a first end connected to the inlet tube, a second end connected to the valve body, and a central portion therebetween being plastically deformable toward the longitudinal axis, such that the hollow shell elongates along the longitudinal axis to separate the upstream end from the downstream end. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The accompanying drawings, which are incorporated herein, and constitute part of this specification, illustrate the presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the invention. In the drawings:  
         [0012]    [0012]FIG. 1 is a side profile view, in section, of a portion of a fuel injector manufactured according to a preferred embodiment of the present invention;  
         [0013]    [0013]FIG. 2 is a side profile view, in section, of an inlet tube being inserted into a non-magnetic shell in the fuel injector shown in FIG. 1;  
         [0014]    [0014]FIG. 3 is a side profile view, in section, of the inlet tube having been fully inserted into the non-magnetic shell;  
         [0015]    [0015]FIG. 4 is a side profile view, in section, of the inlet tube having been fixedly connected to the non-magnetic shell;  
         [0016]    [0016]FIG. 5 is a side profile view, in section, of the non-magnetic shell being compressed by a lift setting apparatus to separate the inlet tube from an armature/needle assembly in the fuel injector;  
         [0017]    [0017]FIG. 6 is a sectional view of the non-magnetic shell and the lift setting apparatus taken along line  6 - 6  of FIG. 5; and  
         [0018]    [0018]FIG. 7 is a side profile view, in section, of the non-magnetic shell after being compressed by the lift setting apparatus to separate the inlet tube from the armature/needle assembly. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]    [0019]FIG. 1 shows a side profile view, in section, of a portion of a portion of a fuel injector  10  having an upstream end  12 , a downstream end  14 , and a longitudinal axis  16  extending therethrough, according to a preferred embodiment of the present invention. As used herein, like numbers indicate like elements throughout. Only the relevant portions of the fuel injector  10  will be shown and discussed, as those skilled in the art will recognize the interrelationship of these portions with the remaining, unshown portions of the fuel injector  10 .  
         [0020]    The fuel injector  10  includes a downstream body or subassembly  210 , and an upstream body or subassembly  220 . As used herein, the term “upstream” is defined to mean a direction toward the top of the figures, and “downstream” is defined to mean a direction toward the bottom of the figures. The downstream subassembly  220  is comprised of a valve body  230  which has an upstream end  232  and a downstream end  234 . The downstream subassembly  220  is also comprised of a seat/guide assembly  30 , and an armature/needle assembly  40 , which are located within the valve body  230 . The upstream subassembly  220  is comprised of an inlet tube  240 . The downstream subassembly  210  the upstream subassembly  220  and the elements comprising the downstream subassembly  210  and the upstream subassembly  220  are all located coaxial with the longitudinal axis  16 .  
         [0021]    The seat/guide assembly  30  includes a generally frusto-conical valve seat  310  located proximate to the downstream end  14  of the injector  10 . The armature/needle assembly  40  includes a needle  410  which has an upstream end  412  and a downstream end  414 . The downstream end  414  of the needle  410  is shaped and configured for a sealing engagement with the frusto-conical valve seat  310  when the needle is in a closed position, as will be described in more detail. The armature/needle assembly  40  also includes an armature  420 , which has an upstream end  422  having a contact face  423 , and a downstream end  424 . The downstream end  424  of the armature  420  is fixedly connected to the upstream end  412  of the needle  410 , so that the needle  410  and the armature  420  operate together as the armature/needle assembly  40 .  
         [0022]    The inlet tube  240  includes an upstream end  242  and a downstream end  244 . The downstream end  244  includes a contact face  245  which contacts the contact face  423  on the armature  420 , as will be described in more detail herein.  
         [0023]    The injector  10  also includes an intermediate body  50 , which connects the upstream end  232  of the valve body  230  with the downstream end  244  of the inlet tube  240 . Preferably, the intermediate body  50  is a non-magnetic hollow shell. Preferably, the intermediate body  50  is constructed from austenitic steel, and more preferably  304 L austenitic steel, although those skilled in the art will recognize that other, plastically deformable materials can be used. Preferably, the intermediate body  50  is connected to the valve body  230  with a weld  510  and to the inlet tube  240  with a weld  520 .  
         [0024]    The intermediate body  50  includes an upstream end  502 , a downstream end  504 , a central portion  506 , and a longitudinal axis  508  which is co-axial with the injector longitudinal axis  106 . Preferably, the body  50  is generally tubular, with a longitudinal channel  510  extending therethrough, generally co-axial with the longitudinal axis  508 . Preferably, the longitudinal channel  510  tapers generally outwardly through the central portion  506 , so that the longitudinal channel  510  is generally larger in the downstream portion  504  than in the upstream portion  502 . Additionally, the wall of the central portion  506  is preferably thicker than the walls of either the upstream or the downstream portions  502 ,  504 , respectively. The thicker central portion  506  provides a rigid support between the valve body  203  and the inlet tube  240  and improves the structural integrity of the fuel injector  10 . Preferably, the downstream end face  246  of the inlet tube  240  and the contact face  423  of the armature  420  engage each other within the central portion  506 .  
         [0025]    The process for setting the lift of the armature/needle assembly  40  is as follows. The seat assembly  30  is inserted into and fixedly connected to the downstream end  234  of the valve body  230 . The armature/needle assembly  40  is inserted into the upstream end  232  of the valve body  230 . The downstream end  412  of the needle  410  is engaged with the valve seat  310 , as the needle  410  would be engaged with the valve seat  310  in a closed position. The intermediate body  50  is then lowered over the upstream end  232  of the valve body  230  and secured to the valve body with weld  520 . As shown in FIGS. 2 and 3, the downstream end  244  of the inlet tube  240  is inserted into the intermediate body  50  until the downstream end face  246  engages the armature contact face  423 . The armature/needle assembly  40  is kept firmly against the valve seat  310  in this position for a predetermined period of time in order to minimize settlement movement between the parts involved in this insertion operation. With the inlet tube  240  pressed against the armature/needle assembly  40  in order to minimize any settling movement between the parts, the downstream end  244  of the inlet tube  240  is then connected to the intermediate body  50  by weld  510 , as shown in FIG. 4. Although welds  510 ,  520  are the preferred means for connecting the intermediate body  50  to the inlet tube  240  and the valve body  230 , respectively, those skilled in the art will recognize that other methods of permanently connecting the intermediate body  50  to the inlet tube  240  and the valve body  230 , respectively, such as furnace brazing, swaging, gluing, interference fit, or any other process typically used to permanently join the intermediate body  50  to the inlet tube  240  and the valve body  230  can be used.  
         [0026]    After the connection of the inlet tube to  240  to the intermediate body  50  is complete, the lift setting is performed. The portion of the fuel injector  10  is inserted into a lift setting apparatus  60 , as shown in FIG. 5. The lift setting apparatus  60  preferably includes four punches  610  which are generally symmetrically spaced about the longitudinal axis  16  ninety degrees apart from each other, as shown in FIG. 6, although those skilled in the art will recognize that more or less than four punches  610  can be used. Each of the four punches  610  includes a longitudinal axis  612 , which are all generally perpendicular to the longitudinal axis  16  of the injector  10  when the injector  10  is inserted into the lift setting apparatus  60 , and which intersect at the longitudinal axis  16 . The longitudinal axes  612  form a contact plane  614 . As can be seen from FIG. 5, the contact plane  614  is preferably along, or at least proximate to, the location of contact between the downstream end face  246  of the inlet tube  240  and the contact face  423  of the armature  420 . Each punch  610  also includes a contact face  616  which engages the fuel injector  10  during the lift setting operation. Prior to starting the lift setting operation, the punches  610  are generally spaced apart from each other so as to form an interior perimeter  618  which is sized to accept the portion of the fuel injector  10 . The portion of the fuel injector  10  is aligned with the punches  612  such that the intermediate body  50  is aligned in the contact plane  614 .  
         [0027]    When the lift setting operation is commenced, an actuator  620 , which is operatively connected to the punches  610 , moves the punches  610  perpendicularly to and toward the longitudinal injector axis  16 . The contact faces  616  on each punch  610  engage the central portion  506  of the intermediate body  50  and compress the central portion  506  along the contact plane  614  toward the longitudinal axis  106  in a crimping-type manner. This crimping operation plastically deforms the central portion  506  of the intermediate body  50  and elongates the intermediate body  50  along the longitudinal axis  106  a predetermined amount, as shown in FIG. 7, separating the inlet tube  240  from the armature/needle assembly  40 . The predetermined amount of the elongation is the value of the desired lift distance for the armature/needle assembly  40 .  
         [0028]    In order to guarantee a desired and repeatable lift as a result of the crimping operation, the punches  610  can be set to travel a preset stroke distance, or to contact the intermediate body  50  with a predetermined load. In order to verify the lift of the armature/needle assembly  40 , the armature/needle assembly  40  can be operated using a slave coil (not shown) with the lift amount being measured. In the event that the lift that is developed is not enough to meet the desired lift, the portion of the fuel injector  10  can be reinserted in the lift setting apparatus  60 . The stroke distance or the applied load can be reset and the punches  610  can be reapplied to the central portion  506  of the intermediate body  50  to further plastically deform the intermediate body  50  and increase the lift.  
         [0029]    Although the plastic deformation of the intermediate body  50  is preferably performed by the punches  610 , those skilled in the art will recognize that the deformation can be performed with any other symmetrical physically controlled force.  
         [0030]    It will be appreciated by those skilled in the art that changes could be made to the embodiment described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiment disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined in the appended claims.