Patent Publication Number: US-8523090-B2

Title: Fuel injection systems and armature housings

Description:
TECHNICAL FIELD 
     This disclosure relates generally to fuel injection systems and improved armatures and armature housings for electrically operated fuel injectors. 
     BACKGROUND 
     Fuel injected engines employ fuel injectors, each of which delivers a metered quantity of fuel to an associated engine cylinder during each engine cycle. Prior fuel injectors were of the mechanically or hydraulically actuated type with either mechanical or hydraulic control of fuel delivery. More recently, electronically controlled fuel injectors have been developed. In the case of an electronic injector, fuel is supplied to the injector by a transfer pump. The injector may include various mechanisms for pressurizing the fuel delivered by the transfer pump. An electrically operated mechanism either carried outside the injector body or disposed within the injector body is then actuated to cause fuel delivery to the associated engine cylinder. 
     Prior fuel injector designs have included high pressure fuel passages extending around a central recess containing a solenoid coil and a solenoid armature. One such fuel injection system that delivers pressurized fuel from a high pressure pump and through a common rail to fuel injectors with solenoid valves is illustrated in U.S. Pat. No. 5,975,437. In such systems, the high pressure fuel passage includes turns and bends in order not to intersect the solenoid recess, thereby complicating formation of the passages and requiring the use of plugs to seal off portions of the passages after formation. 
     Because the overall size of the fuel injector is small, the size of the solenoid is also small, thereby undesirably reducing the available solenoid force on the armature. As a result, the armature should be placed accurately with respect to the solenoid to provide the reliable movement of the armature during the opening and closing the high pressure fuel injector valve. 
     SUMMARY OF THE DISCLOSURE 
     One aspect of this disclosure involves an improved armature housing and armature for a fuel injector that provides for a more reliable and consistent movement of the armature when its corresponding solenoid coil is activated. The disclosed armature is coupled to an armature pin. The armature housing includes a first cylindrical portion that slidably accommodates the armature pin. The armature housing also includes a second cylindrical portion that is coupled to the first cylindrical portion. The second cylindrical portion slidably accommodates the armature. Using appropriate manufacturing tolerances for the outer diameters of the armature pin and armature and the inner diameters of the first and second cylindrical portions respectively, the disclosed armature housing provides for more reliable and consistent movement of the armature when the solenoid is energized. 
     In another aspect of this disclosure, a fuel injector is disclosed that includes an armature coupled to an armature pin. The fuel injector also includes an armature housing that includes a first cylindrical portion for slidably accommodating the armature pin and a second cylindrical portion coupled to the first cylindrical portion. The second cylindrical portion slidably accommodates the armature. The fuel injector also includes a solenoid including a stator and a coil that engages the second cylindrical portion of the armature housing. The armature pin includes a distal end that includes or is coupled to a closure element. The closure element engages a first orifice of an orifice plate when the armature is in a relaxed position. The closure element is lifted off of the first orifice and the orifice plate when the solenoid is energized and the armature pin and closure element are moved away from the orifice plate. 
     In another aspect of this disclosure, a fuel injection system is provided. The disclosed fuel injection system includes a common rail containing high pressure fuel. The fuel injection system also includes a plurality of fuel injectors fluidly connected to the common rail. Each of the fuel injectors includes an armature coupled to an armature pin. Each fuel injector also includes an armature housing including a first cylindrical portion for slidably accommodating the armature pin and a second cylindrical portion coupled to the first cylindrical portion for slidably accommodating the armature. Each fuel injector of the system also includes a solenoid including a stator and a coil that engages the second cylindrical portion of the armature housing. The armature pin of each injector has a distal end that includes or is coupled to a closure element. The closure element engages a first orifice of an orifice plate when the armature is in a relaxed position. The closure element is lifted off of the first orifice and orifice plate when the solenoid is energized and the armature, armature pin and closure element are moved away from the orifice plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial sectional view of a disclosed fuel injector illustrating a disclosed armature housing, armature, armature pin, solenoid assembly and injector body. 
         FIG. 2  is a perspective view of a disclosed armature housing. 
         FIG. 3  is a sectional view of the armature housing, armature, armature pin and armature spring as shown in  FIG. 1 . 
         FIG. 4  is a sectional view of a disclosed fuel injector. 
         FIG. 5  is an enlarged view of the nozzle, needle valve and distal end of the valve casing. 
         FIG. 6  is a schematic view of a disclosed fuel injection system. 
     
    
    
     DETAILED DESCRIPTION 
     Turning first to  FIG. 1 , a partial view of a disclosed fuel injector  10  is illustrated. The fuel injector  10  includes a solenoid case  11  which is coupled to an injector body  12 . The solenoid case  11  houses the solenoid assembly  18  which includes a stator  13 , coil or magnet  14 , guideposts  15 ,  16  and an upper cap  17 . The stator  13  may also include a central aperture  21  which accommodates a guide pin  22  to facilitate the upward movement of the stator  13  and coils  14  when the solenoid assembly  18  is energized causing the armature  24  to push against the stator  13  and causing the stator  13  and coil  14  to move towards the upper cap  17  to an energized or open position. The armature  24  is accommodated within an armature housing  25 . 
     As shown in  FIGS. 2-3 , the armature housing  25  includes a first cylindrical portion  26  and a second cylindrical portion  27 . The first cylindrical portion  26  slidably accommodates the armature pin  28  which includes a proximal end  29  that is connected to the armature  24  and a distal end  31  that may include or be coupled to a closure element  32  as shown in  FIG. 1 . The first cylindrical portion  26  may be coupled to the second cylindrical portion  27  by an annular disk  30 . The annular disk  30  may include one or more drain openings  33  as best seen in  FIG. 2 . The second cylindrical portion  27  slidably accommodates the armature  24 . The second cylindrical portion  27  is non-carburized and the first cylindrical portion  26  is carburized to maximize the magnetic flux across the armature  24  when the coil  14  is energized. 
     Turning back to  FIG. 1 , the armature housing  25  may be held in place in the injector body  12  by a snap ring  36  received in the circumferential slot  37  in the first cylindrical portion  26  as shown in  FIG. 3 . Other means for securing the armature housing  25  to the injector body  12  are available as will be apparent to those skilled in the art. For example, the second cylindrical portion  27  could be secured to the injector body  12 . Thus, the armature housing  25  is stationary within the injector body  12 ; the armature  24  and armature pin  28  move under the influence of the solenoid assembly  18 . 
     Specifically, the armature pin  28  is connected to a collar  38  that traps the armature spring  39  between the collar  38  and the lower surface  41  of the first cylindrical portion  26 . The armature spring  39  acts to pull the armature pin  28  and armature  24  away from the solenoid assembly  18  or downward in the perspective of  FIG. 1  so the closure element  32  closes the orifice  42  in the orifice plate  43  as shown in  FIGS. 1 and 4 . Thus, the armature spring  39  biases the armature  24  and armature pin  28  downward in the relaxed or closed position shown in  FIGS. 1 and 4 . 
       FIGS. 1 and 4  also illustrate a fuel passageway  45 . The fuel passageway  45  contains high pressure fuel which is delivered below the orifice plate  43  and into the valve chamber  46  (see  FIG. 4 ). The high pressure fuel is provided by the common rail  47  shown in  FIG. 6 . With the closure element  32  blocking the orifice  42  of the orifice plate  43 , high pressure fuel entering the chamber  46  establishes an equilibrium pressure in the chamber  46  and may circulate through the unblocked slanted orifice  44 . In this high-pressure equilibrium condition, the bias of the spring  54  maintains the distal nose  55  of the needle valve  48  against the seat  59  of the nozzle  57  and in the closed position shown in  FIGS. 4 and 5 . 
     The needle valve  48  includes a proximal end  51  disposed opposite the orifice  42  from the closure element  32 . The needle valve  48  may also include a collar or shoulder  52  to support an end or collar  53  of the valve spring  54 . In the position shown in  FIGS. 4-5 , the needle valve  48  is biased downward by the spring  54  so that the distal nose  55  rests on the seat  59  and blocks fluid from exiting the nozzle  57  through the orifice  58  that are more easily seen in  FIG. 5 . 
     When the solenoid coil  14  is activated and the armature  24  and armature pin  28  move towards the stator  13  or upward in the orientation of  FIG. 4 , the closure element  32  moves away from the orifice  42  thereby creating a pressure drop from the chamber  46  to the orifice plate  43 . This pressure drop enables the fuel pressure in the chamber  46  to overcome the bias of the spring  54  and move the distal nose  55  of the needle valve  48  off of the seat  59  thereby permitting fuel to exit the nozzle  57  through the orifice  58 . 
     In the embodiment shown, the solenoid case  11  is connected to injector body  12  which, in turn, is connected to the valve body  61 . The distal end  62  of the valve body  61  is coupled to the nozzle  57 . The orifice plate  43  may be sandwiched between the fuel injector body  12  and a block  63 . The fuel passageway  45  may pass through the block  63  as well as the orifice plate  43 . The second cylindrical portion  27  of the armature housing  25  is supported by a spacer shown at  64  in  FIGS. 1 and 4 . Drain passages for fuel that is used as coolant as it circulates through the slanted orifice  44  are shown at  65 ,  66 . Thus, not only is the slanted orifice  44  of the orifice plate  43  used to establish a pressure equilibrium in the valve chamber  46  when the valve  48  is in a closed position, the high-pressure fuel that passes through the orifice  44  also spreads to other components of the fuel injector  10  and serves as a coolant medium. 
     Turning to  FIG. 6 , an engine  70  is disclosed that includes a fuel injection system  71 . The fuel injection system  71  includes the high pressure common rail  47  that is linked by passages  72  to the plurality of fuel injectors  10  described above in connection with  FIGS. 1-5 . A common drain passage is shown at  73 . A high pressure pump  74  delivers fuel to the common rail  47 . The pump  74  and fuel injectors  10  may be controlled by electronic control module (ECM)  75  via the communication lines  76 ,  77 . A fuel tank is shown at  80  which receives fuel from the drain line  73  and provides fuel to the filter  81  by the preliminary pump  82  which is in communication with the high pressure pump  74  via the supply passages  83 ,  84 . The high-pressure pump  74  is connected to the common rail  47  by the supply passage  85 . 
     Industrial Applicability 
     Improvements to fuel injectors and fuel injection systems are disclosed that are based on the disclosed armature housing  25 . The disclosed armature housing  25  includes a first cylindrical portion  26  that is designed with tight tolerances with respect to the armature pin  28 . The armature housing  25  also includes a second cylindrical portion  27  that is also designed with tight tolerances with respect to the armature  24 . The tolerances used for the armature pin  28 /first cylindrical portion  26  will typically be less than the tolerances used for the armature  24 /second cylindrical portion  27 . 
     More specifically, as shown in  FIG. 3 , the first cylindrical portion  26  has a inner minimum diameter D 2  that is 2-7 microns greater than the maximum outer diameter D 1  of the armature pin  28 , thereby providing a close, but free sliding fit between the armature pin  28  and the cylindrical portion  26 . Further, unwanted lateral movement of the armature  24  within the armature housing  25  is prevented by providing the cylindrical portion  27  with an inner minimum diameter D 4  that is 10-30 microns greater than the maximum outer diameter D 3  of the armature  24 . The difference between in minimum inner diameter D 2  of the first cylindrical portion  26  and the maximum outer diameter D 1  of the armature pin  28  will typically be less than the difference between the minimum inner diameter D 4  of the second cylindrical portion  27  and the maximum outer diameter D 3  of the armature  24 . 
     In one example, the tolerance used for the armature pin  28 /first cylindrical portion  26  may be about 4 microns and the tolerance used for the armature  24 /second cylindrical portion  27  may be about 10 microns, but the tolerances can vary, depending on the size of the fuel injector  10  and the materials used for the first and second cylindrical portions  26 ,  27  of the armature housing  25 , the armature  24  and the armature pin  28 . 
     Thus, the disclosed armature housing  25  provides a more reliable movement of the armature  24  and armature pin  28  when the solenoid assembly  18  is activated. By providing a more reliable movement of the armature  24  and armature pin  28 , the disclosed armature housing  25  provides a more reliable release of the closure element  32  from the orifice  42  and therefore a more reliable opening of the valve  48 . Conversely, by providing a more reliable movement of the armature  24  and armature pin  28 , the disclosed armature housing  25  provides a more reliable engagement of the closure element  32  on the orifice  42  and therefore a more reliable closing of the valve  48 .