Abstract:
A fuel injector that comprises a parallel circuit fuel filtration circuit providing filtered fuel to the control valve. Specifically, a fuel filter is positioned inside the injector within the passage leading to the control valve. Debris is removed from the fuel and filtered fuel is allowed to pass through to the control valve. Unfiltered fuel may be purged from the fuel injector during injection. Alternatively, unfiltered fuel may be removed from the injector via the drain.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to a fuel filtration device and more specifically, a fuel injector with a parallel circuit fuel filtration circuit. 
       BACKGROUND 
       [0002]    Increased emission standards have lead fuel injector manufacturers to operate at higher injection pressures. For example, typical common rail injectors are now injecting fuel at pressures between 250 and 300 MPa. In order to reach these higher injection pressures, control valves within fuel injectors must operate with precision in an environment free from fuel debris and contaminants. Thus, it is increasingly important fuel to be filtered before being delivered to control valves. 
         [0003]    Control valves within injectors perform a myriad of tasks related to injection. In order to repeatedly perform these tasks, control valves are assembled to exacting standards. These standards make control valves susceptible to and more affected by damage from debris that may be contained within the fuel supplied thereto. It has been recognized that debris from fuel damages control valves much more than any other valves (e.g., check valves) within the injector. Damaged control valves ultimately lead to injector failure. 
         [0004]    Previous attempts to filter fuel within an injector have always been in “series.” In other words, said attempts have stubbornly sought to filter all fuel delivered to the injector and ultimately both the control and check valves. This has typically been done by inserting a filter at or near the high-pressure fuel inlet of the injector. Inserting filter at this point ultimately fails and allows debris into the injector for at least two reasons. First, by attempting to filter all high-pressure fuel provided to the injector, the limits of the filter efficiency dictate that at least a small percentage of debris will ultimately get through the filter and potentially have access to the control valve. Secondly, when a filter in series becomes inundated with debris such that the filter can catch no more debris, a pressure drop across the filter occurs. The increasing pressure behind the filter eventually overcomes the blockages and pushes debris through the filter; into the injector; and ultimately to the sensitive control valve. 
         [0005]    By counter-intuitively realizing that not all valves need the same level of protection by the filter, the present disclosure seeks primarily to protect the sensitive control valve. It does this by filtering the fuel within the injector in “parallel” as opposed to in “series.” In other words, fuel delivered to the control valve is filtered while the fuel provided to the check valve may or may not be filtered. The filter in the present disclosure is positioned adjacent the control valve and downstream of the fuel supply inlet. In so doing, the disclosed fuel injector is directed to overcoming one or more of the problems set forth above. 
       SUMMARY OF THE INVENTION 
       [0006]    In one embodiment the fuel injector has an injector body, a control valve assembly positioned within the injector body, a check valve positioned within the injector body, a fuel supply line with an inlet, a first passage in fluid communication with the control valve assembly, and a second passage in fluid communication with the check valve, and a filter positioned within the first passage of the fuel supply line. 
         [0007]    In another embodiment a fuel system has a fuel supply, a pump fluidly connected to the fuel supply, at least one fuel injector fluidly connected to the pump and wherein the at least one fuel injector has an injector body, a control valve assembly positioned within the injector body, a check valve positioned within the injector body, a fuel supply line with an inlet, a first passage in fluid communication with the control valve assembly, and a second passage in fluid communication with the check valve, and a filter positioned within the first passage of the fuel supply line. 
         [0008]    In another embodiment a method of filtering fuel having the steps of supplying a fuel injector that has an injector body, a control valve assembly positioned within the injector body, a check valve positioned within the injector body, a fuel supply line with an inlet, a first passage in fluid communication with the control valve assembly, and a second passage in fluid communication with the check valve, and a filter positioned within the first passage of the fuel supply line; delivering fuel to the fuel injector via the inlet of the fuel supply line; diverting a portion of the fuel within the fuel supply line to the first passage, and another portion of fuel to the second passage; and filtering the fuel delivered to the control valve assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a diagrammatic schematic of a fuel system using a common rail fuel injector; 
           [0010]      FIG. 2  is a diagrammatic cross section of a fuel injector according to one embodiment of the present disclosure; and 
           [0011]      FIG. 3  is a detail of the diagrammatic cross section of a fuel injector according to one embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    Referring to  FIG. 1 , a fuel system utilizing a common rail fuel injector  22  is shown. A reservoir  10  contains fuel at an ambient pressure. A transfer pump  12  draws low-pressure fuel through fuel supply line  13  and provides it to high-pressure pump  14 . High-pressure pump  14  then pressurizes the fuel to desired fuel injection pressure levels and delivers the fuel to the fuel rail  16 . The pressure in fuel rail  16  is controlled in part by safety valve  18 , which spills fuel to the fuel return line  20  if the pressure in the rail  16  is above a desired pressure. The fuel return line  20  returns fuel to low pressure reservoir  10 . 
         [0013]    Fuel injector  22  draws fuel from rail  16  and injects it into a combustion cylinder of the engine (not shown). Fuel not injected by injector  22  is spilled to fuel return line  20 . Electronic Control Module (ECM)  24  provides general control for the system. ECM  24  receives various input signals, such as from pressure sensor  26  and a temperature sensor  28  connected to fuel rail  16 , to determine operational conditions. ECM  24  then sends out various control signals to various components including the transfer pump  12 , high-pressure pump  14 , and fuel injector  22 . 
         [0014]    Reference is now made to  FIGS. 2 and 3 . High-pressure fuel enters the injector through high-pressure supply inlet  30  and travels through a fuel supply passage  32 . The fuel supply line has a first passage  34  that leads to a control valve assembly  36  and a second passage/check control cavity line  38  that leads to a check control cavity  40 . The first passage may also include a fuel filter chamber  42  positioned within the first passage  34  and adjacent the control valve assembly  36 . The fuel filter chamber  42  may have a first shoulder  43  adjacent the control valve assembly  36 , and a second shoulder  45  within the first passage  34  but distal the control valve assembly  36 . Disposed within the fuel filter chamber  42  is a fuel filter  44 . The fuel filter  44  may be installed within the fuel filter chamber  42  by press fitting or any other installation means recognized by those skilled in the art. The fuel filter  44  depicted in  FIGS. 2 and 3  is a screen filter. However, as recognized by those skilled in the art, fuel filter  44  may be microfiltration device of any suitable design. For example, fuel filter  44  may be a screen filter, an edge filter, a media filter, or any other type of filter device. 
         [0015]    Control valve assembly  36  includes an electrical actuator, such as a piezo or a solenoid  46  (as illustrated in  FIGS. 2 and 3 ). Valve member  48  is movable in response to electrical actuator movement. Solenoid  46  controls the position of armature  50 , which attached to valve member  48 . Valve member  48  moves between upper seat  52  and lower seat  54  to control the flow of filtered fuel from the first passage  34  of the fuel supply line  32  to check line  56 . Although control valve assembly  36  is shown as a poppet valve, other valve types including spool valves, or combinations of various types of valves, etc., could be used. 
         [0016]    High pressure fuel in check line  56  travels through body  58  to fuel cavity  60  where it acts upon check valve  62  to push it in an upward direction against the biasing of check spring  64 . When check  62  moves upward, fuel exits injector  22  through at least one tip orifice  66 . 
         [0017]    The opening and closing of check valve  62  is controlled in part by the presence of high pressure fuel in check line  56  and by the valve opening pressure created by the check spring  64 . Additionally, a check control cavity  40  exists on top of the check valve  62 , and specifically on top of the upper portion  68  of check valve  62 , to control the opening of check valve  62 . When the top surface  70  of the upper portion  68  is exposed to pressure in check control cavity  40 , a force is exerted on check valve  62  biasing it in a closed position. The area of the top surface  70  is generally larger than the area of the check valve  62  exposed to fluid pressure in fuel cavity  60 , thereby biasing check valve  62  in the closed position. It should be noted that various check designs are possible. As shown in  FIG. 2 , a single piece check can be used. Alternatively, a multiple piece check (not shown) could be used. Further, a check piston (not shown) could be implemented. 
         [0018]    Pressurized fluid is provided to the check control cavity  40  through check control cavity line  56 . Check control cavity  40  is always fluidly connected to low-pressure drain line  72 . Focusing particularly on control valve assembly  36 , the actuation of control valve assembly  36  controls when injector  22  will inject. Specifically, control valve assembly  36  controls the flow of filtered high-pressure fuel from the first passage  34  of the fuel supply line  32  to check line  56 . Further it controls the venting of check line  56  and fuel cavity  60  when injection is over allowing check spring  64  to push check  62  closed. 
       INDUSTRIAL APPLICABILITY 
       [0019]    High-pressure fuel enters the fuel injector through the high-pressure fuel supply inlet  30 . At least a portion of the fuel delivered to the fuel supply inlet  30  is delivered through the fuel supply line  32  to the first passage  34  and the fuel filter chamber  42  and through the fuel filter  44  to control valve assembly  36 . In the non-energized state of the control valve assembly  36 , flow is blocked thereto. In this condition the injector  22  is in a non-injectable mode. When high-pressure fuel to be delivered to the control valve assembly  36  is blocked, it then seeks to travel through the second passage/check control cavity line  38  to check control cavity  40  and low pressure drain  72 . It should be noted that in this condition, both check line  56 , fuel cavity  60 , check control cavity line  38  and check control cavity  40  are all fluidly connected to low pressure drain  72  and subsequently fuel reservoir  10 . 
         [0020]    When injection is desired, control valve assembly  36  is actuated. Specifically, solenoid  46  is energized, thereby pulling up armature  50 . As armature  50  pulls up, valve member  48  is pulled off the lower seat  54 . Those skilled in the art will recognize that the control valve could be equipped with a piezo stack actuator. As soon as valve member  48  reaches the upper seat  52 , pressurized filtered fuel from the first passage  34  of the fuel supply line  32  is fluidly connected to check line  56 . Further, check control cavity  40  is allowed to drain to low pressure drain line  72  thereby removing pressure in the check control cavity  40  and allowing fuel pressure in fuel cavity  60  to push check valve  62  up against check spring  64  and inject into the cylinder (not shown). It should be noted that orifice  66  provides a flow restriction in a low-pressure drain line  72 . Low pressure drain line  72  is always open to reservoir  10 , therefore as soon as pressurized flow decreases enough that the flow can move through the orifice  66 , the pressure in check control cavity line  38 , can drain to low pressure. 
         [0021]    Once it is desirable to stop injection, control valve assembly  36  is de-energized allowing armature  50  back down to its original position thereby moving valve member  48  from the upper seat  52  to lower seat  54 . Finally, pressure decreases in fuel cavity  60 , check line  56 , check control cavity  40  and check control cavity line  38  to low pressure through low-pressure drain  72 . 
         [0022]    The above description is intended for illustration purposes only and is not intended to limit the scope of the present disclosure in any way. Thus, those who are skilled in the art will appreciate the various modifications that can be made in the illustrated embodiments without departing from the spirit and scope of the present disclosure, which is defined in the terms of the claims set forth below.