Abstract:
A fuel injector including a jacket, a valve seat, and a needle valve apparatus mounted within the jacket and engagable with the valve seat. The needle valve apparatus includes a plurality of holes for filtering fuel flowing through the injector. Each of the holes has a diameter sized to prevent passage therethrough of particles having widths of approximately 0.050 millimeters and larger. In one aspect of the invention, the needle valve apparatus includes a needle valve assembly having at least one transverse aperture through which fuel can flow and a generally tubular filter surrounding at least a portion of the needle valve assembly. The plurality of holes for filtering fuel is formed in the tubular filter. In another aspect, the needle valve apparatus includes a needle valve assembly having a needle valve with a wall that includes the plurality of holes.

Description:
BACKGROUND OF INVENTION  
         [0001]    The invention relates to fuel injectors, and more particularly to fuel filters in fuel injectors.  
           [0002]    In modern fuel-injected internal combustion engines, electromagnetic fuel injectors deliver fuel to the engine in metered pulses that are appropriately timed to the engine operation. To produce the metered pulses of fuel, electromagnetic fuel injectors typically include a valve member that is actuated by an electromagnetic coil to open and close the fuel valve. When the fuel valve is open, fuel is injected into the air/fuel mixing chamber and then into the combustion chamber to power the vehicle as is commonly understood. Of course, the fuel can also be injected directly into the combustion chamber.  
           [0003]    It is desirable to filter the fuel as it enters the fuel injector to help insure the smooth operation of the fuel injector. Primary fuel filters are commonly used to filter debris contained in the fuel and to prevent the debris from getting stuck between the valve needle and the valve seat, which would cause the injector to remain stuck in the open position. For example, U.S. Pat. Nos. 4,798,329, 5,238,192, 5,330,649, and 5,335,863 disclose various primary fuel filter arrangements in which a fuel filter is located at or near the point at which the fuel enters the fuel injector.  
           [0004]    Aside from the debris originally contained within the fuel, the fuel can pick up additional debris as it passes through the fuel injector. This additional debris is produced during the manufacturing of the fuel injector and includes extremely small particles that cannot be completely removed after the manufacturing process is complete. This additional debris is also capable of hampering the proper operation of the fuel injector and should be filtered. Various secondary fuel filters have been used in an attempt to filter the additional debris picked up by the fuel as the fuel travels through the fuel injector.  
         SUMMARY OF INVENTION  
         [0005]    With known secondary filter assemblies, particulate contaminants within the fuel may pass through the filter or bypass the filter completely to lodge between the valve needle and the valve seat, causing the valve to stick open and deliver fuel to an engine throughout the combustion cycle. This often occurs due to the improper or incomplete seal between the secondary filter and the supporting components of the fuel injector. The poor sealing characteristics can be inherent in the design of the secondary filter, can be caused by improper assembly of the secondary fuel filter in the fuel injector, or can be attributed to a combination of the design and the assembly. Efforts to improve the sealing characteristics have resulted in prior art secondary filter assemblies that are difficult and expensive to manufacture and assemble.  
           [0006]    The present invention provides an improved secondary filter assembly for a fuel injector. The secondary filter assembly of the present invention is located as close to the downstream end of the fuel injector as possible to capture substantially all of the additional debris. In light of the downstream location, the design of the secondary filter assembly has been optimized to minimize the pressure drop across the secondary filter, thereby substantially preventing fuel vaporization the could otherwise result in hot restart problems.  
           [0007]    In one embodiment of the present invention, the secondary filter assembly includes a tubular filter in the form of a screen that surrounds the needle portion of the needle valve assembly. Fuel is filtered as it passes through the apertures in the needle, just prior to injection. This first embodiment is easier and less expensive to manufacture and assemble than prior art secondary filter assemblies, yet does a substantially better job of filtering particulate and maintaining the proper operation of the fuel injector. One reason for the improvement is that the filter screen is designed to be self-sealing upon assembly. More specifically, the filter includes at least one end that is forced against and deflected by a surface of the needle valve assembly to form a seal between the end of the filter and the needle valve assembly. Preferably, the end of the filter includes a plurality of finger-like tabs that are deflected by the surface of the needle valve assembly to substantially seal and secure the end of the filter to the needle valve assembly.  
           [0008]    In a second embodiment of the present invention, the secondary filter is integrally formed in the needle by laser drilling or otherwise forming thousands of small holes directly in the needle itself, thereby eliminating the need for a separate filter screen surrounding the needle.  
           [0009]    Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0010]    [0010]FIG. 1 is a partially cut away elevation view of a fuel injector embodying the invention.  
         [0011]    [0011]FIG. 2 is an enlarged section view of the needle valve assembly of the fuel injector illustrated in FIG. 1.  
         [0012]    [0012]FIG. 3 is an enlarged partial section view of the needle valve assembly illustrated in FIG. 2.  
         [0013]    [0013]FIG. 4 is an enlarged partial view of the unrolled fuel filter screen illustrated in FIGS. 1 and 2.  
         [0014]    [0014]FIG. 5 is a partial cross-section view of the needle valve shown in FIG. 2.  
         [0015]    [0015]FIG. 6 is a partial side view of a needle apparatus that is an alternative embodiment of the present invention. 
     
    
       [0016]    Before one embodiment of the invention is explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.  
       DETAILED DESCRIPTION  
       [0017]    [0017]FIG. 1 illustrates a fuel injector  10  embodying the invention. The fuel injector  10  includes a jacket  14 . The jacket  14  has a lower end  18  with an opening  22  for communicating with a combustion chamber (not shown). The opening  22  can communicate directly with the combustion chamber (i.e., a direct injection system), or indirectly via an air/fuel mixing chamber (not shown) (i.e., a port injection system). As used herein and in the appended claims, the terms “upper,” “lower,” “above,” and “below” are used only for purposes of illustration and do not imply any particular orientation or configuration. An orifice plate  24  is positioned adjacent or inside the lower end  18  of the jacket  14 . The orifice plate  24  includes an orifice  25  that is coaxial with the opening  22 . Together, the orifice  25  in the orifice plate  24  and the opening  22  in the lower end  18  of the jacket  14  provide fluid communication between the fuel injector  10  and the combustion chamber or the fuel injector  10  and the air/fuel mixing chamber.  
         [0018]    The jacket  14  also houses a valve seat  26  having an opening  28  adjacent the lower end  18 . Additionally, the jacket  14  houses (see FIGS. 1 and 2) a needle valve apparatus with a needle valve assembly  30  having a tubular needle valve  34 , a ball member  38  connected to a lower end  42  of the needle valve  34 , and an armature  46  connected to an upper end  50  of the needle valve  34 . As seen in FIG. 2, the needle valve  34  also includes a central body portion  54  having at least one, and preferably a plurality of holes or apertures  58  that provide fluid communication between a bore  60  of the tubular needle valve  34  and the interior space of the jacket  14 . The needle valve  34  also includes an outer surface  62  that extends along the length of the needle valve  34  from the lower end  42  to the upper end  50 . Features of the outer surface  62  of the needle valve  34  will be described in more detail below.  
         [0019]    The ball member  38  is mounted on the lower end  42  of the needle valve  34  in any suitable manner to form the needle valve assembly  30  that is movable relative to the jacket  14 . Typically the needle valve  34  and the ball member  38  are both metallic and the ball member  38  is welded to the needle valve  34  such that the ball member  38  seals the lower end  42  of the needle valve  34 . Other suitable methods for securing the ball member  38  to the needle valve  34  are also contemplated. The ball member  38  is appropriately sized to be received in the valve seat  26 . Together, the needle valve assembly  30  and the valve seat  26  operate as a fuel valve that selectively opens and closes the injector  10 .  
         [0020]    The armature  46  has a lower end  66 , an upper end  70 , and an inner surface  72  defining a bore  74 . The upper end  50  of the needle valve  34  is received in the bore  74  and can be secured via a weld  78 . Of course, any other suitable method of securing can be used, including using a press-fit or using adhesives. Features of the inner surface  72  of the armature  46  will be described in more detail below.  
         [0021]    Referring to FIG. 1, the jacket  14  also houses a support tube  86 . The support tube  86  includes a lower end  90  adjacent the upper end  70  of the armature  46  and an upper end  94  having a fuel inlet opening  98 . The support tube  86  also includes a bore that houses a primary fuel filter  100  (shown hidden in FIG. 1), at least a portion of an adjustment sleeve  102 , and at least a portion of a spring  106 . The spring  106  is constrained between the lower end of the adjustment sleeve  102  and the upper end  50  of the needle valve  34  and/or a seat in the armature bore  74 . The adjustment sleeve  102  is adjustable relative to the support tube  86  and biases the spring  106  against the needle valve  34  and/or armature  46 , thereby biasing the needle valve assembly  30  into a first or closed position, wherein the ball member  38  rests in the valve seat  26  and blocks fluid communication between the fuel injector  10  and the combustion chamber or the fuel injector  10  and the air/fuel mixing chamber.  
         [0022]    The injector  10  further includes an electromagnetic coil assembly  110  that encircles a portion of the jacket  14  and is housed inside a support frame  114 . The electromagnetic coil assembly  110  can be selectively charged to create a magnetic field that attracts the armature  46 , and thus the needle valve assembly  30 , toward the lower end  90  of the support tube  86  (upward in FIG. 1) and into a second or open position. The biasing force of the spring  106  is overcome such that the ball member  38  is raised from the valve seat  26 , allowing fuel to flow through the opening  28 , through the orifice  25  in the orifice plate  24 , and into the combustion chamber or the air/fuel mixing chamber. While in the open position, the upper end  70  of the armature  46  contacts the lower end  90  of the support tube  86 . The needle valve assembly  30  remains in the open position until the charge is removed from the electromagnetic coil assembly  110 , at which point the spring  106  biases the needle valve assembly  30  back into the closed position.  
         [0023]    The bore of the support tube  86  defines the upper-most portion of a fuel passageway  118  that provides a path for fuel to travel through the fuel injector  10  and into the combustion chamber or the air/fuel mixing chamber. Fuel flows into the fuel inlet opening  98 , through the primary fuel filter  100 , the bore of the support tube  86 , the bore in the adjustment sleeve  102 , the armature bore  74 , the needle valve bore  60 , the apertures  58  in the needle valve  34 , and into the interior space of the jacket  14 . When the ball member  38  becomes unseated from the valve seat  26 , the opening  28  is exposed. Fuel passes through the opening  28  and exits the injector  10  through the orifice  25 . While not shown in the pictured embodiment, the injector  10  can also include an extension tube (not shown) that is press-fit and welded into the upper end of the jacket  14  or the upper end of the support tube  86 .  
         [0024]    The fuel injector  10  also includes a housing or overmolding  122  that surrounds portions of the support tube  86 , the support frame  114  and the jacket  14 . The housing  122  is preferably plastic and is preferably molded over the injector  10 . In the preferred embodiment, the housing  122  is nylon or polyester, but any other suitable material can be used. The housing  122  protects the injector  10  from the environment. Additionally, the housing  122  is molded to form an electrical connection socket  126  around an external power lead (not shown) that extends from the electromagnetic coil assembly  110 . An end cap  124  snaps onto the lower portion of the jacket  14 . O-rings  130  are mounted adjacent both ends of the fuel injector  10  to seal the connections between the injector  10  and the injector sockets in the manifold (not shown).  
         [0025]    As shown in FIGS.  1 - 5 , the fuel injector  10  further includes a fuel filter screen  134  mounted on the needle valve assembly  30 . The fuel filter screen  134  surrounds much of the needle valve  34  and filters fuel after the fuel passes through the apertures  58 . The filter  134  is generally rectangular after manufacture and is then rolled into a generally tubular shape for assembly onto the needle valve assembly  30 . The filter  134  includes (see FIG. 4) thousands of apertures or holes  136  preferably sized to stop particles larger than 0.050 millimeters in width. It is important to note that the holes  136  can be sized differently depending upon the specific filtering requirements. The holes  136  are preferably formed by chemical etching or other suitable techniques. The filter  134  is burr-free, durable, and easy and inexpensive to manufacture, preferably from stainless steel. Alternatively, the filter  134  can be made from other suitable chemically resistive materials.  
         [0026]    As seen in FIG. 5, the filter  134  has body portion  138 , a first edge portion  142 , and a second edge portion  146 . The filter  134  is sized such that when rolled up, the first and second edge portions  142  and  146  overlap one another and can be connected together to form the generally tubular configuration. The edge portions  142  and  146  can be connected together by welding or by any other suitable method. As shown in FIG. 5, the edge portions  142  and  146  each have a thickness that is approximately half the thickness of the body portion  138 . When the filter  134  is rolled into a tubular shape, the combined thickness of the overlapped edges  142  and  146  is substantially equal to the thickness of the body portion  138 .  
         [0027]    As best seen in FIGS. 2 and 4, the filter  134  also includes lower and upper or first and second ends  150  and  154 , respectively. The ends  150  and  154  are substantially mirror images of one another and could be reversed without changing the operation of the injector  10 . Each of the ends  150  and  154  includes a plurality of finger-like tabs  158 . The purpose of the tabs  158  will be described in more detail below.  
         [0028]    The needle valve assembly  30  includes several features that cooperate with the filter  134  to help substantially seal and secure the filter  134  to the needle valve assembly  30  and to facilitate proper filtering. Referring to FIG. 2, the outer surface  62  of the needle valve  34  includes a tapered portion  162  adjacent the lower end  42 . The tapered portion  162  tapers outwardly in the direction extending from the central body portion  54  to the lower end  42 . The tapered portion  162  tapers to a circumference that is larger than the original circumference of the rolled filter  134  so that the lower end  150  of the filter  134 , and more specifically the tabs  158  on the lower end  150 , must deflect outwardly, thereby forming a tight fit with the tapered portion  162 . The tight fit between the lower end  150  of the filter  134  and the tapered portion  162  of the needle valve  34  substantially seals and secures the lower end  150  of the filter  134  to the lower end  42  of the needle valve  34 .  
         [0029]    The tapered portion  162  terminates at a circumferential shoulder  166  that can act as a security stop during assembly, as described below. The outer surface  62  also includes a circumferential step  170  between the central body portion  54  and the upper end  50  that creates the necessary flow area between the central body portion  54  and the filter  134 . The tapered portion  162 , the circumferential shoulder  166 , and the circumferential step  170  of the needle valve  34  can be formed using any suitable machining or forming techniques.  
         [0030]    Referring to FIG. 3, the inner surface  72  of the armature  46  also includes a tapered portion  174  adjacent the lower end  66 . The tapered portion  174  tapers inwardly in the direction extending from the lower end  66  to the upper end  70 . The tapered portion  174  tapers to a circumference that is smaller than the original circumference of the rolled filter  134  so that the upper end  154  of the filter  134 , and more specifically the tabs  158  on the upper end  154 , must deflect inwardly, thereby forming a tight fit with the tapered portion  174 . The tight fit between the upper end  154  of the filter  134  and the tapered portion  174  of the armature  46  substantially seals and secures the upper end  154  of the filter  134  to the lower end  66  of the armature  46 . The tapered portion  174  of the armature  46  can also be formed using any suitable machining or forming techniques.  
         [0031]    The filter  134  is preferably installed in the following manner. First, the filter  134  is rolled into its tubular configuration by overlappingly connecting the first and second edge portions  142  and  146 . Next, the rolled filter  134  is slid over (downwardly in FIGS. 1 and 2) the upper end  50  of the needle valve  34  so that the filter  134  slides over the circumferential step  170  and the outer surface  62  until the lower end  150  of the filter  134  engages the tapered portion  162  of the outer surface  62 . The tapered portion  162  centers the filter  134  with respect to the needle valve  34  during assembly. As the filter  134  is forced further onto the tapered portion  162  and the fit becomes tighter between the lower end  150  and the tapered portion  162 , the lower end  150 , and more specifically the tabs  158  on the lower end  150 , deflect outwardly.  
         [0032]    The outward deflection of the tabs  158  on the lower end  150  substantially seals and secures the lower end  150  of the filter  134  on the lower end  42  of the needle valve  34 . During normal assembly, the lower end  150  will become sealed against the tapered portion  162  prior to engaging the circumferential shoulder  166 . Only when the filter  134  is advanced too far will the lower end  150  engage the circumferential shoulder  166 , thereby substantially prohibiting further advancement of the filter  134 . The circumferential shoulder  166  therefore acts as a security stop to substantially prevent improper assembly of the fuel injector  10 .  
         [0033]    With the lower end  150  of the filter  134  centered, sealed, and secured, the armature  46  is pressed onto the upper end  50  of the needle valve  34 . As the armature  46  is pressed onto the upper end  50  (downward in FIG. 2), the lower end  66  of the armature  46  approaches the upper end  154  of the filter  134  until the tapered portion  174  of the inner surface  72  engages the upper end  154  of the filter  134 . The tapered portion  174  of the armature  46  also helps center the filter  134  during assembly. As shown in FIG. 3, the tapered portion  174  causes the upper end  154 , and more specifically the tabs  158  on the upper end  154 , to deflect inwardly. The inward deflection of the tabs  158  on the upper end  154  substantially seals and secures the upper end  154  of the filter  134  in place on the needle valve assembly  30 . Finally, the armature  46  can be welded or otherwise secured in place on the needle valve  34 .  
         [0034]    With the lower end  150  secured on the lower end  42  of the needle valve  34  by the tight fit on the tapered portion  162 , and the upper end  154  secured in place on the needle valve assembly  30  by the armature  46 , the filter  134  is substantially prevented from moving upwardly or downwardly (as viewed with respect to FIGS. 1 and 2) relative to the needle valve assembly  30 . Because the upper and lower ends  150  and  154  are substantially sealed, fuel must pass through the holes  136  in the filter  134 . Debris too large to pass through the holes  136  will be successfully filtered and will not be permitted to pass around the sealed lower and upper ends  150  and  154 . The tab-and-taper arrangements result in a filter  134  that is largely self-sealing at both ends when assembled with the needle valve assembly  30 . In addition, the tab-and-taper arrangement results in a filter  134  that is largely self-centering during assembly with the needle valve assembly  30 . These advantages make assembly of the injector  10  easier and less expensive than the assembly of prior art injectors. Additionally, the filter  134  is positioned to filter fuel as close to the engine as possible.  
         [0035]    It is important to note that the invention described herein may be used with any type of fuel injector employing a needle valve, and should not be limited to the specific fuel injector configuration shown in the figures. It is also important to understand that other methods of assembling the filter  134  on the needle valve assembly  30  can be used. For example, instead of rolling the filter  134  into the substantially tubular configuration prior to sliding the filter  134  onto the needle valve  34 , it is possible to assemble the filter  134  onto the needle valve  34  by wrapping the filter  134  around the needle valve  34  and then connecting the first and second edge portions  142  and  146 . If this method is used, it is important that the filter  134  be wrapped tightly enough around the needle valve  34  so that the lower end  150  of the filter  134  is substantially sealed and secured to the needle valve  34  as described above.  
         [0036]    [0036]FIG. 6 illustrates a portion of a needle valve apparatus  200  that is an alternative embodiment of the present invention. The needle valve apparatus  200  does not include the fuel filter screen  134 . Rather, the needle valve apparatus  200  includes a tubular needle valve  204  that has thousands of holes  208  formed directly in the wall of the needle valve  204 . The holes  208  communicate between the bore of the needle valve  204  and the interior space of the jacket  14 . The thousands of holes  208  act as the secondary fuel filter, thereby eliminating the need for a separate fuel filter screen  134 . In other words, the needle valve  204  is substantially identical to the needle valve  34  with the exception that the holes  208  replace the apertures  58 . The functions previously performed separately by the apertures  58  and the holes  136  are therefore combined and performed simultaneously by the holes  208 . Like the holes  136  in the fuel filter screen  134 , the holes  208  are preferably sized to stop particles larger than 0.050 millimeters in width. The holes  208  are preferably laser-drilled in the wall of the needle valve  204  by spinning the needle valve  204  and rapidly firing a laser-drilling tool as the needle valve  204  spins. Of course, other suitable techniques can also be used to form the holes  208 . By forming the holes  208  directly in the needle valve  204 , and thereby eliminating the fuel filter screen  134 , the number of parts in the fuel injector  10  is reduced and assembly is simplified.  
         [0037]    Various features of the invention are set forth in the following claims.