Abstract:
A fuel injector comprising a pumping chamber pressurized by an actuator responsive to an engine controller for delivering pressurized fuel from the pumping chamber to a control valve module to control pressure applied at the outlet of an injector nozzle. The control valve module includes at least one control valve. Valve actuators are in a stator core plate that is independent of the control valve module. Machining operations during manufacture of the injector are simplified by a separation of the stator core plate and the control valve module. Mating, juxtaposed surfaces of the control valve module and the stator core plate are fixed by an indexer.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to a control valve assembly with either one or two control valves designed as an independent modular unit for a high-pressure fuel injector for an internal combustion engine, particularly diesel engines.  
           [0003]    2. Background Art  
           [0004]    A fuel injector for an internal combustion engine such as a diesel engine, which includes a unitary control valve module with a single control valve and a single stator core in aligned, stacked relationship with respect to an injector body and a nozzle assembly, is disclosed in copending U.S. patent application Ser. No. 10/197,317, filed Jul. 16, 2002. That application is assigned to the assignee of the present invention. Injectors of this kind comprise precisely machined components or modules that can be assembled with minimum fuel leakage using efficient assembly steps during manufacture. The injector precisely controls the quantity and the timing of the fuel injected into the combustion chamber of an internal combustion engine under the control of an electronic engine controller. The injection events are matched to the engine cycle to provide minimum brake specific fuel consumption and to reduced undesirable exhaust gas emissions.  
           [0005]    Fuel injectors of the kind disclosed in the copending patent application identified above include a high-pressure pump plunger that is stroked by a cam follower driven by a camshaft for the engine. The plunger cooperates with a plunger bore in a pump body to define a pumping chamber that is in communication with a control valve. The control valve is movable between an open position and a closed position to establish pressure pulses in a nozzle assembly of the injector. The valve is carried by an actuator armature situated adjacent an electromagnetic stator in a stator core plate. As the engine controller varies the current of stator windings, variable forces are transmitted to the control valve to effect appropriate shaping of fuel flow rate during each injection event to achieve optimum engine performance with reduced undesirable engine exhaust emissions.  
           [0006]    German Patent Publication WO 02/3142 A1 and copending U.S. patent application Ser. No. 10/196,894, filed Jul. 16, 2002, disclose fuel injectors having two control valves, each of which is controlled by a separate electromagnetic valve actuator. That copending application also is assigned to the assignee of the present invention. The manufacture of such dual valve injectors, as well as single valve actuators, requires precise, close-tolerance machining of valve body surfaces and drilling of multiple pressure passages. The passages typically are relatively long, which increases the manufacturing difficulties. In dual valve injector assemblies of the kind shown in copending U.S. patent application serial No. 10/196,894, the actuators are assembled within a common control valve body. This presents a further manufacturing problem because of the difficulty in accessing critical surfaces of the control valve body that must be machined.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention simplifies the manufacture of an injector by replacing costly and highly demanding grinding operations in bores by easily manufacturable flat grinding operations. Since the now shorter control valve module allows for different drilling angles, sharp deflections of fuel columns with the resulting hydraulic disadvantages can also be avoided. Further, unlike manufacture of known injector designs, ECM operations are not required to smooth and round the intersections of connecting bores. This contributes significantly to module strength and durability.  
           [0008]    Particularly with dual control valve designs, routing and attaching electrical coil lead wires to an external connector is not as challenging with the design of the present invention. A separate stator core plate facilitates this because the magnet cores are still accessible after installing the stator core plate into the injector body. The coil lead wires then can be readily attached to external connector wires; e.g., by crimping or welding.  
           [0009]    With the design of the present invention, each control valve seat is closer to the control valve module surface. This allows for the use of more rigid grinding tools, resulting possibly in smaller tolerances of the control valve seat geometry in the control valve module. Because the stator core plate is separate from the control valve module, it is also possible to integrate the stator core plate into the injector body. This would eliminate another demanding grinding process in a bore. However, the control valve stroke of at least one control valve would need to be set with a categorized shim during the assembly process rather than grinding the stroke into the valve during the grinding process.  
           [0010]    The injector of the present invention comprises a control valve module that is independent of actuators of an actuator module or stator core plate. The control valve module is situated in stacked, adjacent relationship with respect to a guide plate adjacent a nozzle nut assembly. The stator core plate, the control valve module, the guide plate and the nozzle nut assembly are assembled together with an injector body to form an integrated fuel injector.  
           [0011]    The control valve module can be machined prior to assembly of the injector in a separate machining operation. The guide plate is interposed between the nozzle nut assembly and the control valve module, the relative angular position of one with respect to the other being indexed so that passages formed in the control valve module are aligned with passages formed in the guide plate, the latter being separately machined. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    [0012]FIG. 1 is a cross-sectional assembly view of a dual valve injector of the kind disclosed in copending patent application Ser. No. 10/196,894, previously identified;  
         [0013]    [0013]FIG. 2 is a cross-sectional view of a control valve module and a stator core plate, which may be assembled in a manner similar to the assembly of the design of FIG. 1; and  
         [0014]    [0014]FIG. 3 is an end view of the valve body of FIG. 2 as seen from the plane of section line  3 - 3  of FIG. 2, wherein the underside of the valve module body is illustrated. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    To provide an understanding of the mode of operation of the fuel injector of the invention, reference first will be made to the injector of FIG. 1. The injector of FIG. 1 does not include the features of the invention illustrated in FIG. 2, but the mode of operation of the injector of FIG. 1 is generally common to the mode of operation of the injector of the invention.  
         [0016]    The design of FIG. 1 includes an injector body  10 , which has a cylindrical plunger bore  12  in which a pump plunger  14  is situated. The upper end of the plunger  14  carries a cam follower assembly  16 , which is engaged by an engine camshaft-operated actuator (not shown). A spring seat  18  formed on body  10  is engaged by plunger spring  20 , the upper end of which engages cam follower  16 . Cam follower guide  22  is located within the spring  20 .  
         [0017]    The cylindrical bore  12  and the plunger  14  define a high pressure pumping chamber  24 , which is in fluid communication with high pressure delivery passage  26 . This passage communicates with passage  44  in guide plate  42 , with passage  28  in spring cage  30 , with passage  43  in stop plate  45  and with nozzle passage  32  in nozzle body  34 .  
         [0018]    Fuel injection orifices  36  are formed in the tip of nozzle body  34 . They are opened and closed by a nozzle needle valve  38 . A nozzle spring  40 , which is seated on guide plate  42 , urges needle valve  38  in a downward direction as viewed in FIG. 1. Guide plate  42  has a passage  44 , which communicates with the previously described high pressure delivery passage  26 .  
         [0019]    A first control valve  46 , hereinafter referred to as the main control valve, is positioned in a valve bore  48  in control valve body  50 . A second control valve  52 , hereinafter referred to as the nozzle control valve, is positioned in valve bore  54 .  
         [0020]    Passage  26  communicates with annular space  56  adjacent main control valve  46  through internal passage  57 . Main control valve  46  carries an armature  58  positioned directly adjacent a stator  60  with an air gap there between. When the actuator for main control valve  46  is de-energized, the valve is open and the valve stroke is limited by a stop  62  on the upper side of the armature  58 . Annular space  56  has a valve seat  64  on control valve body  50 . When the stator  60  is activated, main control valve  46  is urged against the valve seat  64 . When the stator  60  is deactivated, spring  66  shifts main control valve  46  to the open position, thereby allowing pressurized fluid in passage  26  to be connected to a spill passage  68 . The solenoid windings for the stator  60  are shown at  70 .  
         [0021]    Nozzle control valve  52  is connected to second armature  72 , which is situated directly adjacent second stator 74 . The windings for stator  74  are shown at  76 . Valve spring  78 , seated on stator valve plate  80 , urges the armature  72  and the nozzle control valve  52  in a downward direction, which closes the control valve  52  against valve seat  82 . Thus, the control valve  52  normally is closed by the valve spring  78  against the valve seat  82  when the windings  76  are de-energized.  
         [0022]    The guide plate  42  receives a needle piston or needle valve load pin  84  situated in a piston opening. Load pin  84  extends downwardly and engages a spring seat for nozzle needle valve  38 , as shown at  83 . A pressure chamber on the upper side of the needle valve load pin  84  communicates with high-pressure annular space  54  for nozzle control valve  52  through passage  86 .  
         [0023]    Passage  26  communicates, as explained before, with annular space  56  for main control valve  46 . It also communicates with the upper side of the needle valve load pin  84  through a flow restricting passage  88 .  
         [0024]    Unlike the design shown in FIG. 1, the design of FIG. 2, which incorporates the teachings of the invention, includes a control valve module body  90 , which is separate from actuator module body or stator core plate  92 . The control valve module body and the stator core plate are situated in face-to-face, juxtaposed relationship at an interface shown at  94  when they are assembled in the injector assembly. The interface at  94  can be machined by a single grinding operation throughout the entire width of the control valve module body  90 .  
         [0025]    A nozzle nut or nozzle housing of the kind shown at  87  in FIG. 1 encloses control valve module body  90  and stator core plate  92 .  
         [0026]    As seen in FIG. 2, a main control valve  96  is situated in valve bore  98 , and a nozzle control valve  100  is situated in valve bore  102 . Main control valve  96  has a valve land that engages valve seat  104 , and nozzle control valve  100  has a valve land that engages valve seat  106 . Main control valve  96  is connected to actuator armature  108 , and nozzle control valve  100  is connected to actuator armature  110 . Armature  108  is positioned adjacent the pole face of stator  111 , which has stator coil windings  112 . Armature  110  is situated adjacent the pole face of stator  114 , which has stator coil windings  116 .  
         [0027]    A valve shim  118  carried by nozzle control valve  100  at the upper end of the valve acts as a seat for valve spring  120 . Similarly, a valve shim  122  may be provided for main control valve  96  against which valve spring  124  is seated. A washer spring  126 , is seated against an injector body or against a stator valve plate corresponding to stator valve plate  80  of FIG. 1 when the stator core plate and the control valve module are assembled. It engages the top of stator  114 , as shown at  127 . Stator  114  thus is urged against a calibrated spacer shim  131  so that the armature  110  and the stator  114  are precisely positioned with respect to the ground surface  94  on the control valve module body. The injector body corresponds to the injector body  10  of FIG. 1. The outline of the injector body is shown in FIG. 3 at  162 .  
         [0028]    When the armature  108  is driven toward the pole face of stator  111  as the windings  112  are energized, the valve  96  is closed against the valve seat  104 . Annular space  128  for main control valve  96  is pressurized by high pressure. It is connected to a passage corresponding to passage  26  in the injector of FIG. 1 through internal passage structure (not shown in FIG. 2) in control valve module body  90 . Annular space  128  communicates with fuel injector nozzle feed passage  132 , which communicates with a passage corresponding to passage  28  seen in FIG. 1. Annular space  128  communicates also with passage  134 , which in turn communicates with passage  136  through recess  138  machined in the top surface of the valve module body at interface  94 . A flow restriction  140  in passage  136  is calibrated to provide a reduced and controlled pressure buildup in passage  142 , which in turn communicates with passage  144  extending from the annular space  130  for the nozzle control valve  100 . Passage  142  communicates with the upper surface of a needle load pin of the kind shown at  84  in FIG. 1.  
         [0029]    The stator core plate  92  has separate openings  146  and  148 , which receive, respectively, the stator and the armature for nozzle control valve  100  and the stator and armature for valve  96 . The stator for valve  100  has a central opening  150 , which receives the spring  120 , and the stator  111  for valve  96  has a central opening  152  for valve spring  124 .  
         [0030]    [0030]FIG. 3 illustrates the bottom of the valve module body. Alignment pin openings are shown in FIG. 3 at  154  and  172 . When the control valve module is assembled against a guide plate of the kind shown at  42  in FIG. 1, alignment pins will provide for proper indexing of the control valve module body relative to a guide plate corresponding to guide plate  42  in FIG. 1. Alignment pin openings, one of which is shown at  166 , are formed in control valve module body  98  for receiving alignment pins for indexing the control valve module body  90  relative to stator core plate  92 .  
         [0031]    Annular space  128  for the main control valve  96 , seen in FIG. 2, communicates with spill bore  170 . This bore is only partially seen in the cross-sectional view of FIG. 2 since it generally runs radially outward at an obtuse angle from the axis of valve  96 . It communicates with annular space  128  when the valve  96  is open. When stator  114  is energized, nozzle control valve  100  is unseated from valve seat  106 , thereby allowing annular space  130  to communicate with spill passage  164 , which, like spill passage  170 , is only partially seen in FIG. 2.  
         [0032]    A high-pressure passage corresponding to passage  26  in FIG. 1 extends from a high-pressure pumping chamber corresponding to high-pressure pumping chamber  24  in FIG. 1. It communicates with angularly disposed passages  132  and  134 , seen in FIG. 2.  
         [0033]    As indicated above, FIG. 3 shows the bottom of the control valve module body  90 . The valve module body has two kidney-shaped recesses  174  and  176 , which prevent cross-flow between the valve bores. FIG. 3 shows the valve bore  102  for the nozzle control valve  100 . Likewise, the valve bore  98  for main control valve  96  can be seen in FIG. 3.  
         [0034]    Passage  144  in FIG. 2 extends from the annular space  130  for nozzle control valve  100 . It is an angularly drilled passage, seen also in FIG. 3. The end of the passage  144  is seen in FIG. 3.  
         [0035]    The kidney-shaped recess  174  has a flow-restricting orifice  178 , and the kidney-shaped recess  176  has a flow-restricting orifice  180 . These orifices communicate with a low-pressure port (not shown) in a needle valve housing or nut of the kind seen in FIG. 1 at  87 . That port would communicate with a low-pressure region, such as low-pressure region  182  seen in FIG. 1. The orifices  178  and  180  prevent a pressure buildup at the base of the control valves  96  and  100 . A pressure buildup, if it were to occur, would result in an undesirable leakage from one valve region to the other, thereby interfering with the proper functioning of the valves. The orifices further prevent spill pulses from getting into the kidney-shaped recesses. Any leakage from one valve bore thus will not influence the valve in the other bore.  
         [0036]    The recess shown at  138  at interface  94  in FIG. 2 is easily machined since the control valve module body is made as a separate element of the injector. The passages  134  and  132 , for example, also are easily machined using a drilling operation. Further, notwithstanding the awkward angle of the passage  144 , that passage can be easily machined prior to final assembly of injector.  
         [0037]    The passages in the control valve module can be strategically drilled at locations of maximum material cross-section and strength.  
         [0038]    Passages in the control valve module that intersect (e.g., passages  132  and  134 ) are disposed at a relative obtuse angle, which reduces the deflection of fluid passing through the passages. The drilling of these passages results in a smooth surface at the location of the intersection, and no special deburring operation (e.g. ECM) is needed. The resulting reduction of deflection of fluid in the passages improves fluid flow efficiency because of a reduction in flow disturbances.  
         [0039]    A minimum amount of grinding is required to achieve the desired flatness of the surfaces at interface  94 . The grinding operation is easier than a corresponding grinding operation for the design of FIG. 1 because the surface being ground is not at the base of a stator bore. Similarly, the desired flatness at the base surface  184 , seen in FIG. 2, can be achieved by a simple grinding operation.  
         [0040]    Complex grinding is not required in the valve bores, unlike the case of an integrated design such as that shown in FIG. 1. Further, the shims  131  and the shoulder shown at  186  in FIG. 2 facilitate fitting of the valves within the valve openings, thereby achieving a desired air gap at the armature and proper valve positioning with respect to the valve seats for the control valves  96  and  100 . Easier, faster and more precise drilling and valve grinding operations thus are possible because of the separate stator core plate and control valve module of the invention.  
         [0041]    The advantage in drilling operations is due in part to the shorter drilling distances that are needed.  
         [0042]    Although an embodiment of the invention has been described, modifications may be made by persons skilled in the art without departing from the scope of the invention. All such modifications and equivalents thereof are intended to be covered by the following claims.