Abstract:
A nozzle assembly of a fuel injector extends along a main axis and includes a nozzle body provided with an inner space divided in upstream chamber and downstream chamber and also with, a valve needle including a main elongated shaft slidably guided in said inner space and extending through-out both upstream and downstream chambers. The nozzle body and the valve needle cooperate to define throttle fluid communication means between upstream and downstream chambers inducing, in use, a pressure drop when fuel flows through. The nozzle assembly is further provided with a tubular sleeve arranged between the upstream chamber and the downstream chamber in abutment against a face of the body and being radially self-centred guided by a cylindrical face of the needle, the throttle means being arranged in said sleeve.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a national stage application under 35 USC 371 of PCT Application No. PCT/EP2015/058549 having an international filing date of Apr. 21, 2015, which is designated in the United States and which claimed the benefit of GB Patent Application No. 1408422.2 filed on May 13, 2014 the entire disclosures of each are hereby incorporated by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a fuel injector and more particularly to a nozzle motion control feature arranged in said injector. 
       BACKGROUND OF THE INVENTION 
       [0003]    Fuel injector of the prior art are disclosed in EP0844383 and in EP0971118 and, a known embodiment is also partially presented on  FIGS. 1 and 2 . This fuel injector  10  extends along a main axis A and it is provided with a nozzle assembly  12  comprising a hydraulically controlled valve needle  14  slidably arranged in a nozzle body  16 . The valve needle  14  axially A displaces under the influence of fuel pressure differences inducing forces on upstream faces  18 ,  20 , and downstream faces  22 ,  24 , of the needle  14 . To induce said pressure difference the injector  10  is provided with a control valve, not shown, closing or opening an outlet of a control chamber  26  wherein pressure alternatively builds-up and down, the upper part of the valve needle  14  protruding in said control chamber  26  and also, with a throttle orifice  28  through which the pressurized fuel flows toward injection holes  30 , said throttle  28  generating a pressure drop. 
         [0004]    In the injector of  FIG. 1 , the throttle  28  is an annular clearance between the inner face  32  of the nozzle body  16  and the outer edge  34  of a collar  36 , also known as “boost flange” or “NMC” (nozzle motion control), radially extending from the valve needle  14 . 
         [0005]    In use, upon the operating condition of an internal combustion engine, the pressure of the fuel flowing in the injectors  10  varies in a large range extending from few bars to several thousands of bars and, consequently the nozzle body  16  expends slightly reducing or increasing the throttle  28  and, affecting the operating performances of the injector  10 . 
       SUMMARY OF THE INVENTION 
       [0006]    Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing a nozzle assembly of a fuel injector. The nozzle assembly extends along a main axis from upstream end to downstream end, in reference to the fuel flow direction in an injector, said nozzle assembly comprising a nozzle body provided with an inner space divided in upstream chamber and downstream chamber and also with, a valve needle comprising a main elongated shaft slidably guided in said inner space. The needle extends through-out both upstream and downstream chambers, the nozzle body and the valve needle advantageously cooperating to define throttle fluid communication means between upstream and downstream chambers inducing, in use, a pressure drop when fuel flows through said throttle means. 
         [0007]    The nozzle assembly is further provided with a tubular sleeve, having a central hole through which extends the needle, the sleeve, being arranged between the upstream chamber and the downstream chamber in abutment against a face of the body, respectively of the needle, and being radially self-centred guided by a cylindrical face of the needle, respectively the body, the throttle means being arranged in said sleeve. 
         [0008]    The valve needle is provided with a collar radially outwardly extending from its main shaft to a peripheral edge, the sleeve being providing with a central hole and being in axial abutment against a face of the nozzle body. The sleeve being also radially self-centred guided by said peripheral edge. The throttle means is an orifice drilled through the sleeve and extending from an upstream orifice opening in the upstream chamber to a downstream orifice opening in the downstream chamber. 
         [0009]    The sleeve is tubular and axially elongated, the throttle being drilled through the lateral wall of the tubular sleeve, the upstream orifice being arranged in the outer cylindrical face of the sleeve and, the downstream orifice being arranged in the inner cylindrical face of the sleeve. 
         [0010]    Alternatively, the sleeve may be provided with a multitude of fine through holes so that, the sleeve provides, in use, pressure drop and, is also a fuel filter retaining foreign matters and particles flowing in the fuel. 
         [0011]    Also, the downstream end of the tubular sleeve is bevelled so that the abutting portion of the sleeve against the face of the nozzle body is reduced. 
         [0012]    The collar is guided toward the upstream end of the tubular sleeve, the downstream opening of the throttle being toward the downstream end of the sleeve, downstream the collar. 
         [0013]    In an alternative embodiment, the sleeve may be a thick disc-plate radially extending from the central hole. The throttle is drilled through the thickness of the sleeve and, its upstream orifice is arranged in the upper face of the sleeve and, its downstream orifice being arranged in the lower face of the sleeve. 
         [0014]    The lower face of the disc-place sleeve is provided with a recess defining a circular bevelled protrusion, such as a peripheral lip, so that the abutting portion of the sleeve is reduced or, alternatively, the face of the nozzle body against which abuts the sleeve is provided with a circular bevelled protrusion, such as a peripheral lip upwardly protruding, so that the abutting portion of the sleeve is reduced. 
         [0015]    In another embodiment, the sleeve is a thick disc-plate having a central hole larger than the needle shaft, the sleeve radially extending from said hole to an outer peripheral face slidably guided and self-centred by the inner cylindrical face of the nozzle. The valve needle is provided with a radially extending face which outer edge is larger than the central hole of the sleeve so that, the sleeve is received in axial abutment against said radial face of the needle. The throttle means comprise an orifice drilled through the thickness of said disc-sleeve and extending from the upper face to the lower face of the sleeve. 
         [0016]    In any embodiment, the nozzle assembly may further comprise biasing means arranged to axially bias the sleeve, downstream against the face, of the body, or of the needle. 
         [0017]    The biasing means can be a compression spring coiled around the needle shaft and compressed between the sleeve, and an upper radial face of the needle or, it can be a spring compressed between the sleeve, and the inner face of the upstream chamber, the spring having a larger section upstream, where it is stuck against said inner face, than downstream, where it is in contact with the sleeve. 
         [0018]    In any embodiment, the throttle means may comprise a plurality of orifices provided through the sleeve also, the upstream orifice of the throttle can be of a larger section that the downstream orifice. 
         [0019]    The invention further extends to a fuel injector provided with a nozzle assembly as previously described. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The present invention is now described by way of example with reference to the accompanying drawings in which: 
           [0021]      FIG. 1  is an axial section of a nozzle assembly of a fuel injector of the prior art. 
           [0022]      FIG. 2  is a magnified view of the nozzle motion control feature of the injector of  FIG. 1 . 
           [0023]      FIG. 3  is a first embodiment of a nozzle motion control feature as per the invention. 
           [0024]      FIG. 4  is an alternative to the first embodiment of  FIG. 3 . 
           [0025]      FIG. 5  is a second embodiment of a nozzle motion control feature as per the invention. 
           [0026]      FIG. 6  is an alternative construction of the second embodiment of  FIG. 5 . 
           [0027]      FIG. 7  is a third embodiment of a nozzle motion control feature as per the invention. 
           [0028]      FIG. 12  is yet another alternative for fixing the electrical terminal in the connector body. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0029]    To ease and clarify the following description the top-down orientation of the figures is arbitrarily chosen and, words and expressions such as “above, under, over, below . . . ” may be utilized without any intention to limit the invention. Also, similar features full filling similar functions in different embodiments may be identified with same reference numbers. 
         [0030]    In reference to  FIG. 3  is described a first embodiment of a nozzle assembly  12  wherein a nozzle body  16  extends along a main axis A and is provided with an internal cylindrical bore defining inner volume V in which is slidably arranged a valve needle  14 . 
         [0031]    The inner volume V of the nozzle body  16  comprises an upstream chamber  38 , represented on the upper side of the figure, having an upstream diameter D 38  and, a downstream chamber  40 , on the lower side of the figure, having a downstream diameter D 40 , smaller than the upstream diameter D 38 . The bottom face of the upstream chamber  38  is a disc-face  42  wherein centrally opens the downstream chamber  40 . 
         [0032]    Further means to delimit the upstream chamber  38  from the downstream chamber  40  is provided by a collar  36  integral, or independent and fixed, to the valve needle  14 , said collar  36  cooperating with a tubular cylindrical sleeve  44 . As shown on  FIG. 3 , the sleeve  44  is axially placed on the bottom disc-face  42  and is radially set and self-centred by the peripheral face  34  of the collar  36 . The wall  46  of the sleeve  44  defines an inner cylindrical face  48 , against which slides the collar  36 , and an outer cylindrical face  50 . The wall  46  axially extends between an upper face  52  and a lower face  54  positioned on the bottom disc-face  42 . In the bottom part of the wall  46  the sleeve  44  is provided with a throttle orifice  56  drilled through the wall  46  and extending from an upstream orifice  58  opening in the outer face  50  of the wall  46  to a downstream orifice  60  opening in the inner face  48  of the wall  46 , in the downstream chamber  40  below the collar  36 . While other arrangements can be derived from this example, in the present embodiment the upstream opening  58  has a larger section than the downstream opening  60  and, the lower face  54  of the sleeve is provided with a bevelled shape  62  that reduces the contacting area between the sleeve  44  and the bottom disc-face  42 . Furthermore, on  FIG. 3  the throttle is represented as radially extending through the wall of the sleeve. Alternative orientations can be chosen. For instance an horizontal tilt of the throttle axis may create a swirl to the flow going through said throttle, avoiding to induce direct radial forces on the needle. 
         [0033]    In an alternative and symmetrical design, not represented, the bevelled portion of the sleeve is provided on the lower-inner face of said sleeve, while on  FIG. 3  it is represented on the lower-outer face. 
         [0034]    Sliding of the outer face  34  of the collar  36  against the inner face  48  of the sleeve  46  still manages a minor functional clearance between the two cylindrical surfaces. Said functional clearance is so much smaller than the throttle orifice  56  then no fuel is able to flow through said clearance. All fuel flowing from the upstream chamber  38  to the downstream chamber  40  flows through the throttle orifice  56 . 
         [0035]    In use, pressurized fuel fills the upstream chamber  38  then flows through the throttle orifice  56  to enter the downstream chamber  40  where from it exits via injection holes  30 . The valve needle  14  axially slides between open and closed position of the injection holes  30  and so, the collar  36  slides inside the sleeve  44 . 
         [0036]    The throttle  56  induces a pressure drop so the pressure in the downstream chamber  40  is lower than it is in the upstream chamber  38 . Consequently the higher pressure of the upstream chamber  38  induces on the upper face  52  of the sleeve  44  downwardly oriented forces biasing the sleeve  44  in abutment against the bottom disc-face  42 . For securing the axial abutment of the sleeve  44  against the bottom disc-face  42 , one can add biasing means  64  inducing further downward forces on the sleeve  44 . Examples are illustrated on  FIG. 4  where, on the left side of the figure, the biasing means  64  is a coil spring compressed between the upper face  52  of the sleeve and a downwardly oriented radial face  66  of the valve needle  14 , said radial face  66  being in this example, the under face of the main spring seat. The main spring downwardly biases the needle with high force and, the biasing means  64  upwardly biases the needle with much smaller forces just sufficient to hold the sleeve in place. 
         [0037]    In an alternative embodiment illustrated on the right side of  FIG. 4 , the biasing means  64  is a spring that upwardly enlarges toward its upper end that is stuck against the inner face of the upstream chamber  38 . Here again, the forces generated by said biasing means  64  are relatively minor and just sufficient to secure the axial positioning of the sleeve  44 . Also, although only one throttle orifice  56  is shown, the sleeve could be provided with a plurality, two, three or more, throttle orifices. 
         [0038]    In an alternative embodiment, not represented, the few throttle orifices described above are replaced by a large number of very fine holes arranged through the wall of the sleeve. Said multitude of holes provides a similar pressure drop as the few orifices described above. As an additional combined function, said multitude of fine holes create a filter stopping foreign matters, particles and other contaminants that may be in the fuel and prevent said foreign matters to flow toward the injection holes. 
         [0039]    A second embodiment of the invention is now described in reference to  FIG. 5  where further means to delimit the upstream chamber  38  from the downstream chamber  40  is provided by a collar  36  of the valve needle  14  cooperating with a thick disc-plate sleeve  68 . As shown on  FIG. 5 , said thick sleeve  68  is axially set in abutment on the bottom disc-face  42  and is radially set as self-centred by the peripheral face  34  of the collar  36 . The throttle orifice  56  is drilled through the thickness of the sleeve  68  and extends from the upper face  52  of the sleeve to the opposed lower face  54 . Also, the upper end of the downstream chamber  40  is chamfered enlarging its section and, the opening of said downstream chamber  40  in the bottom disc-face  42  is surrounded by a small inverted V-shape protrusion  70  on the top of which is placed the thick sleeve  68 . 
         [0040]    In use, the operation of this second embodiment is similar to the operation of the previously described first embodiment. The downwardly oriented forces induced by the pressure in the upstream chamber  38  maintain the sleeve  68  in place. Here again, should it be felt necessary to secure said position, biasing means  64  such as the compression springs of  FIG. 4  could easily be implemented in similar manners as described above. 
         [0041]    An alternative to the second embodiment is represented on  FIG. 6  where the only difference with the above description is the contact area between the sleeve  68  and the bottom disc-face  42 . Here, the bottom disc-face  42  is flat and the sleeve  68  is provided on its lower face  54  with a recess  72  externally surrounded by a small peripheral lip  74  minimizing the contact area between the sleeve  68  and the bottom disc-face  42 . An advantage of this alternative may reside in the manufacturing process where the recess  72  may be easier to make than the V-shape protrusion  70  described above. 
         [0042]    A third embodiment is now described in reference to  FIG. 7  where the thick disc-plate sleeve  68  is axially slidably externally guided by an inner cylindrical face  76  of body  16 . The sleeve  68  is provided with an axial central hole  78  through which freely extends the needle  14 , the sleeve  68  axially resting on a radially extending face  80  protruding from the needle  14 . Similarly as described above, the throttle  56  extends through the thickness of the sleeve  68 . An alternative to said third embodiment is to provide the radially extending face  80  against which abuts the thick sleeve  68  with one or more small passage creating a throttle restriction enabling the fuel to flow between the thick sleeve  68  and the abutting surface  80 . 
         [0043]    Also, in this embodiment again, biasing means such as the springs of  FIG. 4  could enable to secure the axial position of the sleeve  68  against the radial face  80 . Furthermore, as in any of the previous embodiments, the sleeve  68 , here represented be provided with a plurality of throttle openings. 
         [0044]    In use, the higher pressure of the upstream chamber  38  induces on the sleeve  68  downwardly oriented forces that bias said sleeve  68  on the radial face  80  of the needle  14 . As the needle  14  slides up and down between the open and closed position the sleeve  68  follows said motion. 
         [0045]    Furthermore, in an alternative embodiment, instead of having a throttle orifice drilled through the sleeve  44 , a throttle passage can be defined in providing the collar  36  with at least one flat portion axially extending on the outer surface of the collar  36 , a throttle passage being defined between said flat portion and the cylindrical inner face  48  of the sleeve  44 . Alternatively to a flat portion, the outer surface of the collar  36  could be provided with an under-cut, a slot or a hole intersecting said outer surface of the collar  36 , such as a semi-circular or triangular hole, defining the throttle passage  56 . Alternatively, said slots can be arranged on the inner face of the sleeve. 
         [0046]    The following references have been utilized in this description: 
         [0047]    A main axis 
         [0048]    V inner volume of the nozzle body 
         [0049]    d 34  edge diameter 
         [0050]    D 38  diameter of the upstream chamber 
         [0051]    D 40  diameter of the downstream chamber 
         [0052]      10  fuel injector 
         [0053]      12  nozzle assembly 
         [0054]      14  valve needle 
         [0055]      16  nozzle body 
         [0056]      18  upstream face of the needle 
         [0057]      20  upstream face of the collar 
         [0058]      22  downstream face of the collar 
         [0059]      24  downstream face of the needle 
         [0060]      26  control chamber 
         [0061]      28  throttle 
         [0062]      30  injection holes 
         [0063]      32  inner face of the body 
         [0064]      34  outer edge of a collar 
         [0065]      36  collar 
         [0066]      38  upstream chamber 
         [0067]      40  downstream chamber 
         [0068]      42  bottom face of the upstream chamber 
         [0069]      44  tubular sleeve 
         [0070]      46  wall of the sleeve 
         [0071]      48  inner cylindrical face of the sleeve 
         [0072]      50  outer cylindrical face of the sleeve 
         [0073]      52  upper face of the sleeve 
         [0074]      54  lower face of the sleeve 
         [0075]      56  throttle orifice 
         [0076]      58  upstream opening of the throttle 
         [0077]      60  downstream opening of the throttle 
         [0078]      62  bevelled shape of the sleeve 
         [0079]      64  biasing means 
         [0080]      66  downwardly oriented radial face 
         [0081]      68  disc-plate thick sleeve 
         [0082]      70  V-shaped protrusion 
         [0083]      72  recess in the lower face of the sleeve 
         [0084]      74  peripheral lip 
         [0085]      76  inner cylindrical face of the body axially guiding the sleeve 
         [0086]      78  central hole of the sleeve 
         [0087]      80  radial abutting face