Patent Publication Number: US-6655612-B2

Title: Needle/armature rotation limiting feature

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to needle/armature assemblies for fuel injectors and more particularly to a needle/armature assembly for a fuel injector with a rotation limiting feature. 
     The assembly of fuel injectors, in particular, the lift setting, of fuel injectors with an off-center impact point between the armature and inlet tube is believed to be more difficult and time consuming than those fuel injectors designed without an off-center impact point between the armature and inlet tube. The needle/armature assembly of the off-center impact injector appears to demonstrate a tendency to rotate due to the armature and inlet tube surfaces being non-parallel. These off-center impact point injectors have demonstrated to be lift sensitive to the rotational location of the needle/armature assembly relative to the inlet tube. It is believed that this sensitivity is due to the impact surface of the armature and inlet tube being non-parallel. This sensitivity to needle/armature position may result in reduced manufacturer yield of the fuel injector due to failures of the injector with respect to lift and static flow testing. This sensitivity may also contribute to injector lift shift, and resulting flow shift over durability cycling. 
     It would be beneficial to provide a needle/armature rotational limiting device that overcomes the aforementioned rotational problems in the needle/armatures of offset impact fuel injectors. 
     BRIEF SUMMARY OF THE INVENTION 
     Briefly, the present invention provides a solenoid actuated fuel injector with a repeatable stroke. The fuel injector comprises, a housing having a fuel inlet, a fuel outlet, and a fuel passageway extending from the fuel inlet to the fuel outlet along a longitudinal axis. The fuel injector further comprises, a valve body disposed proximate the fuel outlet. The valve body includes an inlet portion and an armature guide eyelet that is disposed in the inlet portion of the valve body within the fuel passageway. The armature guide eyelet is sized to direct and support reciprocal motion of the needle/armature assembly within the fuel passageway along the longitudinal axis. 
     The solenoid actuated fuel injector also comprises a needle/armature assembly that is reciprocally disposed in and axially aligned with the fuel passageway. The needle/armature assembly includes an upper bearing guide fixedly connected to a needle stem portion. The upper bearing guide comprises a bearing portion and a contacting portion. The armature guide eyelet comprises a first portion that circumscribes the upper bearing guide bearing portion, and a second portion engaging the upper bearing guide contacting portion. 
     The present invention also provides a method of mechanically insuring a repeatable stroke of a needle/armature assembly within a solenoid actuated fuel injector. The method comprises, providing a housing that includes a fuel inlet, a fuel outlet, and a fuel passageway that extends from the fuel inlet to the fuel outlet along a longitudinal axis. The method further comprises, providing a valve body disposed proximate the fuel outlet. The method additionally comprises, providing a needle/armature assembly reciprocally disposed in and axially aligned with the fuel passageway. 
     The needle/armature assembly includes an upper bearing guide fixedly connected to a needle stem portion. The method includes, providing an armature guide eyelet disposed in an inlet portion of the valve body within the fuel passageway. The armature guide eyelet is sized to direct and support the reciprocal motion of the needle/armature assembly within the fuel passageway along the longitudinal axis. The method further includes, forming a bearing portion and a contacting portion on the upper bearing guide of the needle/armature assembly. The method also includes, forming a first portion of the armature guide eyelet that circumscribes the upper bearing guide bearing portion and forming a second portion of the armature guide eyelet that abuts the upper bearing guide contacting portion. The method additionally includes, engaging the second portion of the armature guide eyelet and the contacting portion of the upper bearing guide of the needle/armature assembly. 
     The present invention further provides a method of operating a needle/armature assembly within a solenoid actuated fuel injector. The method comprises actuating reciprocal motion of the needle/armature assembly within a valve body of the solenoid actuated fuel injector. The method further comprises limiting the axial rotation of the needle/armature assembly within the valve body of the solenoid actuated fuel injector. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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: 
     FIG. 1 is a side view, in section, of an offset impact fuel injector of the present invention. 
     FIG. 2 is a sectional view of the fuel injector taken along line  4 - 4  of FIG. 1, showing an assembly of the armature upper bearing guide and armature guide eyelet according to the first preferred embodiment of the present invention. 
     FIG. 3 is an enlarged view of the engagement of the abutting contact portions of the armature upper bearing guide and armature guide eyelet assembly according to the first preferred embodiment of the present invention. 
     FIG. 4 is a top plan view of a second preferred embodiment of the present invention showing an assembly of the armature upper bearing guide and armature guide eyelet assembly. 
     FIG. 5 is an enlarged view of the interlocking engagement between the armature upper bearing guide and armature guide eyelet assembly according to the second preferred embodiment of the present invention. 
     FIG. 6 is a top plan view of an alternate version of the first embodiment of the present invention showing an assembly of the armature upper bearing guide and armature guide eyelet. 
     FIG. 7 is an enlarged view of the alternate version of the first preferred embodiment of the present invention showing the engagement of the abutting contact portions of the armature upper bearing guide and armature guide eyelet assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Fuel injectors are used to provide a metered amount of fuel in an internal combustion engine. Details of the operation of the fuel injector  100  in relation to the operation of the internal combustion engine (not shown) are well known and will not be described in detail herein, except as the operation relates to the preferred embodiments. Although the preferred embodiments are generally directed to injector valves for internal combustion engines, those skilled in the art will recognize from present disclosure that the preferred embodiments can be adapted for other applications in which precise metering of fluids is desired or required. 
     An offset impact fuel injector  100  into which the present invention can be incorporated is disclosed in U.S. patent application Ser. No. 09/470,983 filed Dec. 23,1999, owned by the assignee of the present invention, which is incorporated herein by reference in its entirety. 
     FIG. 1 shows an offset impact fuel injector  100 , according to the present invention. As used herein, like numerals indicate like elements throughout. The injector  100  includes a housing  20  having a fuel inlet  22 , a fuel outlet  24 , and a fuel passageway  30  extending from the fuel inlet  22  to the fuel outlet  24  along a longitudinal axis  500 . 
     The injector  100  includes a valve body  26  that is disposed proximate the fuel outlet  24  along the longitudinal axis  500 . The injector  100  additionally includes a needle/armature assembly  28  reciprocally disposed in the valve body  26  and axially aligned in the fuel passageway  30 . 
     An armature guide eyelet  32  is disposed and fixedly connected in an inlet portion  34  of the valve body  26 . The armature guide eyelet  32  is fabricated out of a non-magnetic steel material. Those skilled in the art should recognize that the armature guide eyelet  32  can be fabricated out of any other suitable non-magnetic material. The armature guide eyelet  32  is sized to direct and support the reciprocal motion of the needle/armature assembly  28  within the fuel passageway  30  along the longitudinal axis  500 . The needle/armature assembly  28  is comprised of an upper bearing guide  36  fixedly connected to a needle stem portion  38 . The needle/armature assembly  28  forms a closure assembly defining an outer perimeter about the longitudinal axis  500  that has a portion with a constant diameter contiguous to another portion with varying radii (as shown in FIGS. 2, and  4 - 7 ), which assembly  28  is free floating in the armature guide eyelet  32 , but is limited in rotation within the fuel passageway  30  along the longitudinal axis  500 . 
     FIG. 2 shows a cross sectional view of an upper bearing guide/armature eyelet guide assembly  120  according to a first preferred embodiment of the present invention. The bearing/guide assembly  120  is comprised of the armature guide eyelet  32  and the upper bearing guide  36 . 
     The upper bearing guide  36  comprises a contacting portion  42  that extends inward from a bearing portion  44  of the upper bearing guide  36 . The words “inward” and “outward” designate directions in the drawing to which reference is made. “Inward” is defined to mean in a direction toward the longitudinal axis  500  of the figure referred, and “outward” is defined to mean in a direction away from the longitudinal axis  500  of the figure referred. 
     The armature guide eyelet  32  comprises a first portion  40  that circumscribes the upper bearing guide  36  bearing portion  44 , and a second portion  45  that engages the upper bearing guide  36  contacting portion  42 . The first portion  40  is connected to the second portion  45  of the armature guide eyelet  32  by lateral projections  46  extending inward. 
     FIG. 3 shows an enlarged view of the engagement between the contacting portion  42  and the second portion  45 . The amount of clearance  47  between the armature guide eyelet  32  and the upper bearing guide  36  ranges from approximately 30 to 50 microns, with 40 microns being preferred. An abutting portion  43  on the contacting portion  42  of the upper bearing guide  36  interlocks an abutting portion  41  on the second portion  45  of the armature guide eyelet  32 . With the exception of the clearance  47 , the abutting engagement as shown in FIG. 3 limits the free rotational movement of the upper bearing guide  36  with respect to the fixed armature guide eyelet  32 . 
     It should be recognized by those skilled in the art that the direction of the contacting portion  42  on the upper bearing guide  36  and the second portion  45  on the armature guide eyelet  32  could be directed outward away from the longitudinal axis  500  of the fuel injector  100 . 
     For example, FIG. 4 shows a top plan view of a second preferred embodiment of a bearing/guide assembly  220  having outward protrusions. The bearing/guide assembly  220  is comprised of an armature guide eyelet  132  and an upper bearing guide  136 . The upper bearing guide  136  comprises a contacting portion  142  that extends outward from a bearing portion  144  of the upper bearing guide  136 . The contacting portion  142  is connected to the bearing portion  144  of the upper bearing guide  136  via lateral projections  149  that extend outward. 
     Additionally, FIG. 4 shows the detail of the armature guide eyelet  132 . The armature guide eyelet  132  comprises a first portion  140  that circumscribes the upper bearing guide  136  bearing portion  144 , and a second portion  145  that engages the upper bearing guide  136  contacting portion  142 . The first portion  140  is connected to the second portion  145  of the armature guide eyelet  132  via lateral projections  146  that extend outward. 
     FIG. 5 shows an enlarged view of the interlocking engagement between the contacting portion  142  and the second portion  140 . A abutting portion  143  on the lateral projection  149  of the upper bearing guide  136  interlocks an abutting portion  141  on the lateral projection  146  of the armature guide eyelet  132 . With the exception of the clearance  47 , the interlocking engagement as shown in FIG. 9 limits the free rotational movement of the upper bearing guide  136  with respect to the fixed armature guide eyelet  132 . 
     In addition to the direction of the protrusion, it should be recognized by those skilled in the art that the shape of the mating protrusions could be flat, square, triangular or any other shape as desired without departing from the sprit and scope of the claimed invention. 
     For example, FIG. 6 shows a bearing/guide assembly  320  that depicts an alternate version of the bearing/guide assembly  120  of the first embodiment as shown in FIG.  2 . The upper bearing guide  36  has been disclosed from the first preferred embodiment as shown in FIG.  3 . 
     Additionally, FIG. 6 shows an armature guide eyelet  232  that comprises a first portion  240  that circumscribes the upper bearing guide  36  bearing portion  44 , and a second portion  245  that engages the upper bearing guide  36  contacting portion  42 . The second portion  245  is flat. The first portion  240  is connected to the second portion  245  of the armature guide eyelet  232  via lateral projections  246  that extend inward. 
     FIG. 7 shows an enlarged view of the engagement between the contacting portion  42  and the second portion  245 . The contacting portion  43  on the flat protrusion  42  of the upper bearing guide  36  abuts a contacting portion  241  on the lateral projection  246  of the armature guide eyelet. With the exception of the clearance  47 , the abutting engagement as shown in FIG. 7 limits the free rotational movement of the upper bearing guide  36  with respect to the fixed armature guide eyelet  232 . 
     A method of mechanically limiting rotation of the needle/armature assembly  28  within the offset impact fuel injector  100  of the present invention will now be disclosed. According to the first preferred embodiment, the method comprises, engaging the upper bearing guide  36  within the armature guide eyelet  32 , thus guiding the reciprocal motion of the needle/armature assembly  28  within the passageway  30  of the fuel injector  100  along the longitudinal axis  500 . 
     In addition to guiding the reciprocal motion, the method comprises limiting rotation of the upper bearing guide  36  of the needle/armature assembly  28  by engaging the abutting portion  43  of the flat contacting portion  42  of the upper bearing guide  36  and the abutting portion  41  of the first portion  40  of the armature guide eyelet  32 . 
     A method of operating the needle/armature assembly  28  within the solenoid actuated fuel injector  100  will now be disclosed. The method comprises actuating reciprocal motion of the needle/armature assembly  28  within the valve body  26  of the solenoid actuated fuel injector  100 . As the needle/armature assembly  28  reciprocates within the valve body  26  the axial rotation of the needle/armature assembly  28  is limited. The axial rotation of the needle/armature assembly  28  is limited through engagement between the armature guide eyelet  32  and the upper bearing guide  36 . Further, a repeatable stroke (not shown) of the needle/armature  28  assembly is insured through engagement between the upper bearing guide  36  contacting portion  42  and the second portion  45  of the armature guide eyelet  32 . 
     It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but is intended to cover modifications within the spirit and scope of the present invention as defined in the appended claims.