Patent Document

RELATIONSHIP TO OTHER APPLICATIONS AND PATENTS 
       [0001]    This application is a divisional application of U.S. Ser. No. 11/102,037, filed Apr. 8, 2005. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to fuel injectors for internal combustion engines; more particularly, to fuel injectors for injection of fuel through a perforated spray director plate; and most particularly, to an improved director plate for a fuel injector wherein fuel flow through the passages is streamlined, thus reducing the prior art tendency for deposits to form at the entrances and along the walls of the passages. 
       BACKGROUND OF THE INVENTION 
       [0003]    Fuel injected internal combustion engines are well known. In direct-injected engines, the injection tip of the fuel injector extends into the combustion chamber and includes a perforated plate, known in the art as a “spray director plate,” for dispersing and directing fuel injected from the injection valve. In a conventional engine fuel injection system, the injection tip of the injector extends into a plenum or rail of the engine&#39;s intake manifold where the injected fuel is mixed with intake air before being discharged into the engine&#39;s combustion chamber. 
         [0004]    As is well known in the automotive arts, the configuration and positioning of a director plate with respect to the injection valve ball and valve seat are critical elements in the most fuel-efficient distribution of fuel into the manifold or firing chamber. A typical fuel injection valve includes a beveled circular seat and a reciprocably-actuated ball that seals against the seat in a circular sealing line. 
         [0005]    The perforations through a director plate may be considered as fuel flow  5  passages. It is known in prior art director plates to form a passage by drilling or punching with a tool from either the flow-entrance or flow-exit side, either parallel to or at an angle to the plate axis, resulting in a cylindrical passage having an abrupt corner at the tool entrance and typically a ragged or torn corner at the tool exit. A known problem in prior art fuel injectors is that, over time in use, deposits may build up at the flow entrances and exits to the cylindrical passages, as well as on the sidewalls, adversely affecting the control of the volume and spray pattern of fuel. 
         [0006]    What is needed in the art is a fuel injector director plate having an improved configuration of flow passages that results in a reduced propensity to form deposits. 
         [0007]    It is a principal object of the present invention to reduce the forming of deposits in the flow passages of a fuel injector spray director plate. 
       SUMMARY OF THE INVENTION 
       [0008]    Briefly described, an improved fuel injection spray director plate in accordance with the invention includes conically chamfered entries to the flow passages through the plate. The conical entry defines a chamfer that may extend part way or all the way through the plate. In a currently preferred embodiment, the chamfer extends only part way through the plate, and the remaining cylindrical portion of the passage provides desirable directional capability for the spray. Preferably, each flow passage is positioned in the director plate such that the main flow direction of fuel exiting the fuel injector valve is included in the cone of the chamfer. In a further refinement of the currently preferred embodiment, a second chamfer having a greater cone angle is provided at the passage entrance to further smooth the flow transition into the passage. The chamfers are preferably formed by successive stamping with tapered punches having increasing cone angles. The last cone angle may be radiused to provide a still smoother fuel entry into the passage. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0009]    The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0010]      FIG. 1  is an elevational cross-sectional view of a prior art fuel injection valve assembly including a valve seat, a valve ball, and a director plate; 
           [0011]      FIG. 2  is an elevational cross-sectional view of a fuel injection valve assembly including a valve seat, a valve ball, and an improved director plate; 
           [0012]      FIG. 3  is a schematic drawing showing various configurations of flow passages through an improved director plate; 
           [0013]      FIGS. 4 through 10  are drawings illustrative of methods for forming flow passages through a director plate in accordance with the invention, wherein  FIG. 4  is a cross-sectional view of a director plate showing a preliminary cylindrical passage being punched from the upstream (flow entry) surface of the plate; 
           [0014]      FIG. 5  is a cross-sectional view of a director plate showing a preliminary cylindrical passage being punched from the downstream (flow exit) surface of the plate; 
           [0015]      FIG. 6  is a cross-sectional view showing a first conical punch being entered into the cylindrical passage shown in  FIG. 5 ; 
           [0016]      FIG. 7  is a cross-sectional view of the director plate and passage after first conical punching as shown in  FIG. 6 ; 
           [0017]      FIG. 8  is a cross-sectional view showing a second conical punch being entered into the passage shown in  FIG. 7 ; 
           [0018]      FIG. 9  is a cross-sectional view of the director plate and passage after second conical punching as shown in  FIG. 8 ; and 
           [0019]      FIG. 10  is a cross-sectional view of the director plate an alternative second conical punch having a radius for providing a radiused inlet to the flow passage. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Referring to  FIG. 1 , a prior art fuel injection valve and director plate assembly  10  comprises a valve seat  12 , a valve ball  14 , and a director plate  16 . As is well known in  10  the prior art and need not be shown here, valve seat  12  is adapted to be sealingly welded into a body (not shown) of a fuel injector  18 . Seat  12  is provided with an annular first conically beveled face  20  for receiving valve ball  14  in a circular sealing line  22  having a diameter  24  greater than the diameter of the injection opening in seat  12 . First beveled face  20  typically terminates in a second beveled face  21  reverse-beveled  15  from face  20  defining a conical exit opening to permit dispersal of fuel injected by the valve. Controllably varying the position of valve ball  14  with respect to face  20  controllably varies the flow of fuel across seat  12 . 
         [0021]    Prior art director plate  16  is coplanar with axial face  26  of seat  12  over both a peripheral portion  17  and a central portion  19  of plate  16 . Central portion  19  is provided with a plurality of exemplary cylindrical distribution passages  28   a , 28   b  through plate  16  for discharging into manifold or firing chamber  30  fuel having passed across seat  12 . Exemplary axis  29   a  of passage  28   a  is inclined to plate axis  31  such that fuel passing through passage  28   a  is discharged away from plate axis  31 . Exemplary axis  29   b  of passage  28   b  is parallel to plate axis  31  such that fuel passing through passage  28   b  is discharged parallel to plate axis  31 . 
         [0022]    Referring to  FIG. 2 , an improved fuel injection valve and director plate assembly  110  in accordance with the invention comprises a valve seat  12  and a valve ball  14  as in prior art assembly  10 . Novel assembly  110  differs from prior art assembly  10  in that fuel flow passages  128  through improved director plate  116  between an upstream surface  106  and a downstream surface  108  are chamfered  150  at the upstream end, such chamfering being preferably conical. The chamfering of each passage may extend only part way through ( 128   a ), the remainder of the passage being cylindrical ( 152 ), or completely through ( 128   b ) plate  16 . A second conical chamfer may also be imposed on top of the first chamfer, as discussed further, below (see  FIG. 9 ). The axes  129   b  of the passages may be parallel to plate axis  31 . 
         [0023]    A serious disadvantage of prior art director plate  16  is that areas of low fuel flow or flow stagnation occur at the entrances and along the walls of passages  28 . The relatively low fuel velocity in these areas permits deposits from fuel to form gradually. Flow visualization studies have shown that formation of deposits can be reduced or eliminated by eliminating such stagnation zones through the use of a taper at the entrance of the passage. Thus, in improved director plate  116 , the entrances to the passages are chamfered as described above to increase the velocity of the fuel across the entrance of the passage along director plate surface  106  and to eliminate eddies and stagnant areas near the entrances within the passages. An especially useful placement of the chamfered entrances in the director plate is such that fuel flowing from the valve seat and ball in a main direction of flow  154  is received into the chamfered entrances  150  of passages  128 . Thus, the walls of the chamfered portions are washed directly by fuel flowing at high velocity, preventing deposits from forming. 
         [0024]    A currently-preferred embodiment of a passage  128  in accordance with the invention is passage  128   a  comprising a chamfered upstream portion  150  and a cylindrical downstream portion  152  where the diameter of portion  152  is sized to control the volume of fuel exiting the director plate passage, and the length  156  of portion  152  is minimal, preferably less than the diameter of portion  152 . Referring to  FIG. 3 , flow passages  128   a  may take any of several forms within the scope of the invention, some of which are exemplarily shown. 
         [0025]    In passage  160 , the conical axis  162  and the cylindrical axis  164  are both parallel with axis  31  of plate  116 , as in passage  128   a  shown in  FIG. 2 . 
         [0026]    In passage  170 , the conical axis  172  is parallel with plate axis  31  and the cylindrical axis  174  is non-parallel with plate axis  31 . 
         [0027]    In passage  180 , the conical axis  182  is non-parallel with plate axis  31  and the cylindrical axis  184  is parallel with plate axis  31 . 
         [0028]    In passage  190 , both the conical axis  192  and the cylindrical axis  194  are non-parallel with plate axis  31 . 
         [0029]    Referring to  FIGS. 4 through 10 , a method in accordance with the invention is disclosed for forming one or more director plate chamfered flow passages. 
         [0030]    In  FIGS. 4 and 5 , a director plate blank  216  has an upstream surface  206  and a downstream surface  208 . An exemplary cylindrical fuel flow passage  228   a  extends through plate  216 . Axis  229   a  of passage  228   a  is inclined to plate axis  231  by a first angle  270 . Passage  228   a  is formed preferably by stamping or punching (not shown) in a direction  272  entering from the downstream surface  208 , as shown in  FIG. 5 , rather than from upstream surface  206 , as shown in  FIG. 4 . This is principally because the punch-entering surface is left with a clean, sharp corner  274 , rather than a torn-out corner  276  as tends to occur on the punch-exiting surface (omitted from surface  208  in  FIG. 4 ). When the passage is formed as in  FIG. 5 , torn-out corner  276  and associated debris is eliminated in the next forming step as described below. The result of forming cylindrical passage  228   a  by punching or stamping in either direction is a first stage director plate  216   a.    
         [0031]    Referring to  FIGS. 6 and 7 , a first punch tool  278  having a frusto-conical portion  280  of a first included cone angle  282  is entered into passage  228   a  to a first depth  284 . The axis  286  of frusto-conical portion  280  may be coincident with cylindrical axis  229   a but preferably is inclined from axis  229   a  toward axis  231  by a second angle  288 . The result of punching by tool  278  is a second stage director plate  216   a  having a residual portion of cylindrical passage  228   a  and a newly-formed conical passage portion  228   b , as shown in  FIG. 7 . 
         [0032]    Referring to  FIGS. 8 and 9 , a second punch tool  290  having a frusto-conical portion  292  of a second included cone angle  294  is entered into conical passage portion  228   b  to a second depth  296 . The axis  298  of frusto-conical portion  292  is preferably inclined to cylindrical axis  229   a  by an angle  300  which is larger than angle  288  and may equal angle  270  ( FIGS. 4 and 5 ). The result of punching by tool  290  is a third stage director plate  216   b  having a residual portion of cylindrical passage  228   a , a residual portion of first conical passage portion  228   b , and a second conical passage portion  228   c , as shown in  FIG. 9 . 
         [0033]    Note that in some cases the use of second punch tool  290  may be omitted, for example, when the declination of first punch tool axis  286  from plate axis  231  is less than about 10-15°. 
         [0034]    In some applications, the director plate at third stage  216   b  is ready for use. However, for maximum performance, a secondary process may be used to eliminate any burrs from the multiple stamping process just described, which process may include exemplarily fluid honing, electrochemical treatment, and the like. 
         [0035]    For clarity of explanation, first and second conical portions  228   b , 228   c  are shown as being formed in two separate punching steps by two separate punch tools  278 , 290 . It should be obvious to one of ordinary skill in the art of punch tools, however, that the shapes of the two punches can be formed in a single compound punch tool (not shown), and that director plate  216   b  may be formed from plate  216  in a single punching step. It is further possible to devise a multiply compound punch tool which punches portions  228   a , 228   b , 228   c  in a single stroke; the disadvantage of such a tool is that portion  228   a  then must be formed by punching in the same direction as portions  228   b , 228   c , which has been shown to cause significant tear-out damage to the downstream corner  274  ( FIG. 5 ). Thus it is a preferred method in accordance with the invention that cylindrical portion  228   a  is formed by punching or stamping in a first direction, and that conical portions  228   b , 228   c  are formed by punching in a second direction generally opposite to the first direction. 
         [0036]    Referring to  FIG. 10 , in a radiusing punch tool  320 , conical portion  292 , shown previously in tool  290  is merged into a concave radius portion  322  to provide an even smoother fuel entrance into the fuel flow passage. Preferably, tool  320  includes a convex radius portion  324  outboard of portion  322  to laterally position residual plate material  326 , removed from the flow passage during formation thereof, at a distance from the entrance to the flow passage. The result of using tool  320  is a director plate  216   c  having both a radiused entry into either a single conical or a doubly-conical and cylindrical fuel flow passage. 
         [0037]    While the invention has been described by reference to various specific embodiments, it should be understood that numerous changes may be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the described embodiments, but will have full scope defined by the language of the following claims.

Technology Category: 2