Abstract:
A lower filter for a fuel injector includes a disk having an annular shape and including a plurality of filter holes. The disk is positioned upstream of a valve guide of an internal valve assembly without contacting the valve guide. The disk prevents internally generated contaminants contained in fuel flowing through the filter holes from reaching a valve guide area and a sealing area of the internal valve assembly. By installing the lower filter upstream of the valve guide and without contact to the valve guide, interference with the guidance and reciprocal movement of the valve is avoided. Application of the lower filter in fuel injectors may reduce the occurrence of injector failures by reducing the number of stuck open conditions in injectors and by reducing the number of hydro lock engine incidents without interference with the valve guide.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to fuel injection systems of internal combustion engines; more particularly, to fuel injectors; and most particularly, to an internal lower filter of a fuel injector. 
       BACKGROUND OF THE INVENTION 
       [0002]    Fuel injected internal combustion engines are well known. Fuel injection is a way of metering fuel into an internal combustion engine. Fuel injection arrangements may be divided generally into multi-port fuel injection (MPFI), wherein fuel is injected into a runner of an intake manifold ahead of a cylinder intake valve, and direct injection (DI), wherein fuel is injected directly into the combustion chamber of an engine cylinder, typically during or at the end of the compression stroke of the piston. 
         [0003]    A typical fuel injector includes an internal valve assembly that may include a reciprocably actuated ball that seals against a beveled circular seat in a circular sealing line. A guide that assists in positioning the ball relative to the seat may further be included in the internal valve assembly. 
         [0004]    It is most desirable, in a modern internal combustion engine, to precisely control the flow of fuel to the combustion chamber in order to meet performance requirements as well as emission regulations. Therefore, it is desirable to ensure that the ball completely seals against the seat when the valve assembly is in a closed position to avoid fuel passage when not needed. It is known to position an upper filter proximate to a fuel inlet of the injector. While the upper filter may capture contaminants generated upstream of the fuel injector, it cannot capture contaminants that may be generated during the assembly and/or operation of the fuel injector. It is important to prevent contamination of the area between the ball and the seat. Contamination between the ball and seat may be caused by internally generated particles which may lead to a malfunction of the injector. Malfunction of the injector due to contamination could result in a stuck open condition of one or multiple injectors. With the injector stuck open, uncontrolled amounts of fuel may enter the engine&#39;s combustion chamber, which may cause a hydraulic lock of the engine. Contaminants may be generated within the fuel injector, for example during injector assembly operations, due to insufficient cleaning of the fuel injector parts prior to assembly, or during operation of the fuel injector, for example, due to friction and wear of the contacting surfaces. It is currently not possible to completely eliminate such internal contamination of a fuel injector. 
         [0005]    A stuck open condition can lead to a severe failure mode for the injector and, therefore, injector manufacturing companies try, from both a design and a process stand point, to prevent such a failure mode by eliminating contamination as much as possible. In order to further reduce contamination of the fuel flowing through the injector with particles of internal origin, filters have been disposed internally of the fuel injector between the fuel inlet and the fuel outlet in the prior art. While such internal filters may prevent internally generated contaminants from reaching the internal valve assembly and from getting stuck between the ball and the seat, such prior art internal filters are typically supported by the valve guide, which may interfere with the accurate positioning of the ball relative to the seat. 
         [0006]    What is needed in the art is an internal filter for a fuel injector that is positioned in close proximity to the fuel outlet and that does not interfere with the accurate positioning of the ball relative to the seat. 
         [0007]    It is a principal object of the present invention to provide a self-supporting internal lower filter for a fuel injector that is assembled in the seat above a ball guide of an internal valve assembly of the fuel injector. 
       SUMMARY OF THE INVENTION 
       [0008]    Briefly described, a lower fuel filter is assembled internally of a fuel injector downstream of a fuel inlet and upstream of a valve guide. The lower filter may be, for example, a stainless steel filter with photo chemically etched holes. By positioning the lower filter upstream of the guide, contrary to the known prior art, contact of the filter with the guide is eliminated. Thus, interference with the positioning function of the guide is avoided while, at the same time, particulates that may be generated internally in the injector are captured before reaching the valve guide area and the sealing area between the seat and the ball. 
         [0009]    In one aspect of the invention, the lower filter is a self-supporting annular disk that may be welded, for example by laser welding or by resistance welding, to a shoulder integral with the seat. The shoulder is integrated into the seat such that the annular disk is positioned in close proximity to the guide without contacting the guide. 
         [0010]    In another aspect of the invention, the lower filter is attached to a retaining ring that is then assembled in the seat either by a press fit into the inner diameter of the seat or by a snap fit into a groove integrated into the inner diameter of the seat. It may further be possible to capture the retaining ring with the attached filter between the body of the fuel injector and the seat during injector assembly. The retaining ring, with the filter attached, may be assembled in the seat upstream of the guide to avoid interference with the guidance of the ball. 
         [0011]    In still another aspect of the invention, the filter is attached to an annular support ring containing fuel flow holes. The annular support ring and filter assembly is then assembled into the inner diameter of the seat with a close tolerance fit to the valve shaft outer diameter to prevent built in contaminants from flowing down to the ball and seat interface. The annular support ring and filter subassembly are assembled in the seat either by a press fit into the inner diameter of the seat or by a snap fit into a groove integrated into the inner diameter of the seat. It may further be possible to capture the annular support ring and filter subassembly between the body of the fuel injector and the seat during injector assembly. 
         [0012]    The lower filter in accordance with the invention may be used preferably in multi-port fuel injection (MPFI) injectors, but may be applicable in direct injection (DI) fuel injectors as well. Integration of a lower internal filter into MPFI injectors is desirable, since due to the lower fuel pressure compared to DI, there is a higher possibility for contaminants getting trapped between the ball seat and the ball. Thus, without interfering with the guidance of the valve, the application of the lower filter above a valve guide in accordance with the invention in fuel injectors may reduce the occurrence of injector failure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0014]      FIG. 1   a  is an isometric view of a lower filter, in accordance with the invention; 
           [0015]      FIG. 1   b  is an enlarged partial view of a filter area enclosed by circle  1   b  in  FIG. 1   a , in accordance with the invention; 
           [0016]      FIG. 1   c  is a partial cross-sectional view along line  1   c - 1   c  in  FIG. 1   a , in accordance with the invention; 
           [0017]      FIG. 1   d  is a partial cross-sectional view of a dimpled lower filter, in accordance with the invention; 
           [0018]      FIG. 2  is a cross-sectional view of a cartridge assembly of a fuel injector, in accordance with the invention; 
           [0019]      FIG. 3  is a cross-sectional view of a detail of the fuel injector shown in  FIG. 2 , in accordance with the invention; 
           [0020]      FIG. 4  is a cross-sectional view of a second internal valve assembly, in accordance with the invention; 
           [0021]      FIG. 5  is a cross-sectional view of the second internal valve assembly, in accordance with another aspect of the invention; 
           [0022]      FIG. 6  is a cross-sectional view of the second internal valve assembly, in accordance with still another aspect of the invention; 
           [0023]      FIG. 7  is a cross-sectional view of a third internal valve assembly, in accordance with the invention; 
           [0024]      FIG. 8  is a cross-sectional view of the third internal valve assembly, in accordance with another aspect of the invention; 
           [0025]      FIG. 9   a  is an isometric top view of an annular support ring, in accordance with the invention; 
           [0026]      FIG. 9   b  is an isometric bottom view of the annular support ring, in accordance with the invention; and 
           [0027]      FIG. 9   c  is an isometric cross-sectional view of the annular support ring, in accordance with the invention. 
       
    
    
       [0028]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates preferred embodiments of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
       DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0029]    Referring to  FIGS. 1   a  through  1   d , a lower filter  100  is a disk  110  that has an annular shape including an inner diameter  112  and an outer diameter  114 . Lower filter  100  includes a circular filter hole area  116  extending for a width  118  between inner diameter  112  and outer diameter  114 . Disk  110  has a thickness  122  that is preferably the same in an area  124  adjacent to inner diameter  112  and in an area  126  adjacent to outer diameter  114 . Circular filter hole area  116  may have a reduced thickness  128  and is positioned between the areas  124  and  126  as shown in  FIG. 1   c . Thickness  122  and reduced thickness  128  of disk  110  are preferably chosen such that stability of disk  110  is ensured and such that disk  110  is self-supporting. While filter hole area  116  is shown in  FIGS. 1   a  through  1   d  to have a reduced thickness  128 , it may be possible that filter hole area  116  has the same thickness  122  as adjacent areas  124  and  126 . Area  126  adjacent to outer diameter  114  may be designed to have a larger width than area  124  adjacent to inner diameter  112 . Area  126  may be primarily used to assemble lower filter  100  in a fuel injector as shown in  FIGS. 2 through 8 . Dimples  132  may be formed in area  126  as shown in  FIG. 1   d  enabling resistance weld retention of lower filter  100 . Dimples  132  may be formed, for example, in three places preferably 120 degrees spaced apart. Disk  110  may be, for example, formed from stainless steel. 
         [0030]    Filter hole area  116  shown in detail in  FIG. 1   b  includes a plurality of filter holes  140 . Filter holes  140  may be, for example, chemically etched holes. It may further be possible to form filter holes  140  in disk  110  by laser drilling, stamping, or other machining operations. Filter holes  140  may be formed in a strip of material before disk  110  is, for example, stamped off the strip. 
         [0031]    To maximize fuel flow through a fuel injector and the filter efficiency of lower filter  100 , as many filter holes  140  as desired without reducing the stability of disk  110  may be formed in reduced thickness area  128 . Filter holes  140  have a diameter  142  that may be the same for each of the filter holes  140  or that may not be the same for each of the filter holes  140 . The diameter  142  of filter holes  140  is preferably smaller than the largest possible distance between a ball, such as ball  214 ,  314 , or  414 , and a seat, such as seat  212 ,  312 , or  412 , when a valve assembly, such as valve assembly  210 ,  310 , or  410  (shown in  FIGS. 2 ,  4 , and  7 , respectively) is in an open position. Filter holes  140  may be grouped and/or arranged in a pattern, for example in a rhombus as shown in  FIG. 1   b . Other patterns are possible and the pattern of filter holes  140  may depend on the forming process of filter holes  140  in disk  110 . 
         [0032]    Referring to  FIG. 2 , a cartridge assembly of a fuel injector  200  is illustrated. Fuel injector  200  extends axially from a fuel inlet end  202  to a fuel outlet end  204 , encloses a fuel passage  206 , and includes a first internal valve assembly  210  positioned upstream of and proximate to fuel outlet end  204  within fuel injector  200 . Fuel injector  200  may be a fuel injector for multi-port fuel injection as shown in  FIG. 2 . Fuel injector  200  may further be a fuel injector for direct injection. 
         [0033]    A body  224  of fuel injector  200  houses internal valve assembly  210 . Internal valve assembly  210  includes a valve seat, such as beveled circular seat  212 , a reciprocably actuated valve, such as ball  214 , that seals against seat  212 , for example, in a circular sealing area  216 , and a shaft  218  extending axially from ball  214 . Shaft  218  may be hollow. Internal valve assembly  210  regulates the fuel flow through fuel outlet end  204 . A guide  230  that directs ball  214  is positioned in close proximity to and upstream of sealing area  216  within seat  212 . Lower filter  100 , as shown in detail in  FIGS. 1   a  through  1   d , is positioned upstream of guide  230  without contacting guide  230  to avoid interference with the positioning function of guide  230  while particulates that may be generated internally in the injector and that may be harmful to the injector operation are captured before reaching a valve guide area  232  between guide  230  and ball  214  and sealing area  216  between the seat  212  and the ball  214 . Lower filter  100  may be assembled in fuel injector  200  in close proximity of guide  230  and with a close tolerance fit to the outer circumference of ball  214  as shown in  FIG. 2 . 
         [0034]    Referring to  FIG. 3 , guide  230  and lower filter  100  are shown assembled in seat  212  of fuel injector  200 . As can be seen, seat  212  includes a shoulder  222  that supports lower filter  100 . Lower filter  100  is assembled into seat  212  until disk  110  makes contact with shoulder  222 . Outer diameter  114  of disk  110  of lower filter  100  fits closely into an inner circumferential contour of seat  212 . Inner diameter  112  of disk  110  is designed to closely fit around ball  214  as shown in  FIG. 1 , precluding particles or internal contaminants from entering valve guide area  232  and sealing area  216 . Shoulder  222  is adapted to receive area  126  of disk  110 . When lower filter  100  is installed in seat  212 , filter hole area  116  is preferably positioned axially above a fuel passage  234  of guide  230 . Shoulder  222  is designed such that lower filter  100  is positioned upstream of guide  230 , in close proximity to guide  230 , and such that contact between lower filter  100  and guide  230  is avoided. Preferably, lower filter  100  is positioned at least about 100 μm above guide  230 . However, this position may be varied. 
         [0035]    Fuel flowing from fuel inlet end  202  to fuel outlet end  204  through fuel injector  200  (all shown in  FIG. 2 ) passes through lower filter  100  before passing through guide  230  and entering sealing area  216 . Any particles or contaminants in the fuel flow that are generated downstream of fuel inlet end  202  within fuel injector  200 , for example during the assembly process or during operation, that have a size that may be harmful for injector operation, and that are larger than diameter  142  of filter holes  140  are captured by lower filter  140  and, therefore, precluded from entering valve guide area  232  and sealing area  216 . 
         [0036]    Lower filter  100  may be retained in seat  212 , for example, by welding, such as spot welding, area  126  of disk  110  to shoulder  222 . This could be done, for example by laser welding or resistance welding. In the case of laser welding, disk  110  could be spot welded to shoulder  222 , for example, in three spots positioned in area  126  and spaced apart by 120 degrees. In the case of resistance welding, disk  110  need to include dimples  132  as shown in  FIG. 1   d.    
         [0037]    While lower filter  100  is shown in  FIG. 3  as being assembled in seat  212  with filter hole area  116  facing guide  230 , it may be possible to assemble lower filter  100  with filter hole area  116  facing away from guide  230  and facing fuel inlet end  202 . 
         [0038]    Referring to  FIGS. 4 through 6 , a second internal valve assembly  310  includes a seat  312 , a reciprocably actuated ball  314 , that seals against seat  312 , for example, in a circular sealing area  316 , and a shaft  318  extending axially from ball  314 . A guide  330  that directs ball  314  is positioned in close proximity to and upstream of sealing area  316  within seat  312 . Lower filter  100 , as shown in detail in  FIGS. 1   a  through  1   d , is positioned upstream of guide  330  and upstream of ball  314  to avoid interference with the guidance of ball  314  while particulates that may be generated internally within a fuel injector, such as fuel injector  200  as shown in  FIG. 2 , and that may be harmful to the injector operation are captured before reaching a valve guide area  332  between guide  330  and ball  314  and sealing area  316  between the seat  312  and the ball  314 . Second internal valve assembly  310  may replace internal valve assembly  210  in fuel injector  200  as shown in  FIGS. 2 and 3 . 
         [0039]    Lower filter  100  is attached to an annular retaining ring  350  that is assembled into seat  312 . Lower Filter  100  is preferably attached to retaining ring  350  prior to assembly of retaining ring  350  in seat  312  forming a sub-assembly. Retaining ring  350  may be formed, for example, of a stainless steel. Retaining ring  350  is attached to area  126  of disk  110  of lower filter  100  such that an outer circumferential contour of disk  110  overlaps with an inner circumferential contour of retaining ring  350 . For example, an outer diameter  352  of retaining ring  350  extends beyond outer diameter  114  of disk  110  and an inner diameter  354  of retaining ring  350  does not extend beyond area  126 . Accordingly, retaining ring  350  does not cover filter hole area  116  of lower filter  100 . 
         [0040]    Retaining ring  350  is assembled in seat  312  preferably such that lower filter  100  is positioned upstream of ball  314  such that inner diameter  112  of disk  110  surrounds shaft  318  of valve assembly  310 . Outer diameter  114  of disk  110  is adapted to loosely fit into an inner circumferential contour of seat  312 . Inner diameter  112  of lower filter  100  is designed to closely fit around an outer diameter of shaft  318  without interfering with the reciprocating movement of shaft  318 , precluding particles or internal contaminants from entering valve guide area  332  and sealing area  316 . Seat  312  may include a shoulder  322  integrated into the inner circumferential contour that may assist in positioning retaining ring  350 . Retaining ring  350  with lower filter  100  attached is inserted into seat  312  until it makes contact with shoulder  322 . Shoulder  322  may have a smaller width than shoulder  222  shown in  FIG. 3 . 
         [0041]    Retaining ring  350  may be retained within seat  312  by either a press fit into an inner circumferential contour of seat  312  as shown in  FIG. 4  or by a snap fit into a groove  326  incorporated into the inner circumferential contour of seat  312  as shown in  FIG. 5 . It may be further possible to capture retaining ring  350  between a body  324  of a fuel injector and shoulder  322  of seat  312  during assembly of seat  312  and body  324  as shown in  FIG. 6 . This may be achieved in two ways, first (as shown in  FIG. 6 ) by designing retaining ring  350  to have a larger thickness compared to the retaining ring  350  shown in  FIGS. 4 and 5  or by designing seat  312  to have a smaller axial length above shoulder  322  than seat  312  shown in  FIGS. 4 and 5 . 
         [0042]    Referring to  FIGS. 7 through 9 , a third internal valve assembly includes a seat  412 , a reciprocably actuated ball  414 , that seals against seat  412 , for example, in a circular sealing area  416 , and a shaft  418  extending axially from ball  414 . A guide  430  that directs ball  414  is positioned in close proximity to and upstream of sealing area  416  within seat  412 . Lower filter  100 , as shown in detail in  FIGS. 1   a  through  1   d , is positioned upstream of guide  430  and ball  414  to avoid interference with the guidance of ball  414  while particulates that may be generated internally within a fuel injector and that may be harmful to the injector operation are captured before reaching a valve guide area  432  between guide  430  and ball  414  and sealing area  416  between the seat  412  and the ball  414 . Third internal valve assembly  410  may replace internal valve assembly  210  in fuel injector  200  as shown in  FIGS. 2 and 3 . 
         [0043]    Lower filter  100  is attached to an annular support ring  450  that includes a plurality of flow through holes  456 . Lower filter  100  is preferably attached to support ring  450  prior to assembly of support ring  450  in seat  412  thereby forming a sub-assembly. The support ring  450  and lower filter  100  sub-assembly is then installed into seat  412  eliminating the need to handle multiple parts during assembly. 
         [0044]    Annular support ring  450 , shown in detail in  FIGS. 9   a  through  9   c , may be formed, for example, of a stainless steel. Support ring  450  includes an outer diameter  452 , an inner diameter  454 , and a circular channel  458  positioned there between. Inner diameter  454  of support ring  450  is adapted to closely fit around shaft  418  without limiting the reciprocating movement of shaft  418 , thereby precluding particles or internal contaminants from entering valve guide area  432  and sealing area  416 . Outer diameter  452  is adapted to closely fit into an inner circumferential contour of seat  412 . Channel  458  is formed in one of the surfaces of support ring  450  and adapted to receive lower filter  100 . Since support ring  450  stabilizes lower filter  100 , it may be possible to form lower filter  100  to have a smaller overall thickness than thickness  122  as shown in  FIG. 1   c . When using support ring  450 , disk  110  ( FIGS. 1   a - 1   d ) may not need to be self-supporting. Flow through holes  456  may be formed above channel  458 . When attached to support ring  450 , filter hole area  116  of lower filter  100  is positioned below flow through holes  456 . The number and size of flow through holes  456  may be selected according to the desired fuel flow through support ring  450 . By assembling lower filter  100  in channel  458  of support ring  450 , possible assembly damage to filter hole area  116  is reduced. 
         [0045]    Seat  412  may include a shoulder  422  integrated into the inner circumferential contour that may assist in positioning support ring  450 . Support ring  450  with lower filter  100  attached is inserted into seat  412  until it makes contact with shoulder  422 . Shoulder  422  may have a smaller width than shoulder  222  shown in  FIG. 3 . While support ring  450  is shown in  FIGS. 7 and 8  assembled with channel  458  facing guide  430 , it may also be assembled with channel  458  facing away from guide  430 . 
         [0046]    Support ring  450  may be retained within seat  412  by either a press fit into an inner circumferential contour of seat  412  as shown in  FIG. 7  or by a snap fit into a groove incorporated into the inner circumferential contour of seat  312  in a similar way as shown in  FIG. 5  for retaining ring  350 . It may be further possible to capture support ring  450  between a body  424  of a fuel injector and shoulder  422  of seat  412  during assembly of seat  412  and body  424  as shown in  FIG. 8 . This may be achieved in two ways, first (as shown in  FIG. 8 ) by designing support ring  450  to have a larger thickness compared to the support ring  450  shown in  FIG. 7  or by designing seat  412  to have a smaller axial length above shoulder  422  than seat  412  shown in  FIG. 7 . 
         [0047]    By capturing particles or contaminants generated within a fuel injector, for example fuel injector  200 , with lower filter  100  in accordance with a preferred embodiment of the invention, failure modes of the injector, such as a stuck open condition that may lead to a hydraulic lock of the engine, can be reduced compared to prior art fuel injectors that are operated without an internal lower filter. By installing lower filter  100  upstream of a ball guide, such as guide  230 ,  330 , or  430 , and without contact to the ball guide, internally generated contaminants are captured before reaching the ball and guide interface and the ball and seat interface while avoiding interference with the guidance and reciprocal movement of the ball, such as ball  214 ,  314 , and  414 . 
         [0048]    While the lower filter  100  in accordance with the invention may be especially useful for applications in fuel injectors for multi-port fuel injection as described above, lower filter  100  may also be utilized in fuel injectors for direct injection. 
         [0049]    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.