Patent Publication Number: US-2006016418-A1

Title: Fuel injector and a method of sealing the same

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to fuel injectors for internal combustion engines and a method of sealing the same.  
      2. Description of the Related Art  
      Typically, electromagnetic fuel injectors are used as fuel injectors for internal combustion engines.  
      An example of a known electromagnetic fuel injector is disclosed in Japanese non-examined laid-open patent publication No. 6-50235 and is reproduced in  FIG. 10 , which shows a sectional view of a fuel injector  210 .  
      The fuel injector  210  includes a fixed core  221 , a movable core  230 , a bobbin  251  and a body  270 . A coil  252  is wound on the bobbin  251  and develops electromagnetic force for driving the movable core  230 . A fuel injector of this type is provided with a seal for preventing fuel from leaking to the outside. For example, a seal is provided in order to prevent fuel from leaking to the outside via a connecting wire  225  for supplying electric power to the coil  252 . In the fuel injector  210  shown in  FIG. 10 , an O-ring  260   a  is disposed between the bobbin  251  and the fixed core  221 , and an O-ring  260   b  is disposed between the bobbin  251  and the body  270 .  
      When an O-ring is used as a seal, in order to achieve desirable characteristics, it is necessary to increase the outside diameter of the bobbin  251 , accordingly the outside diameter of the body  270  which is disposed over the bobbin  251 . To this end, the maximum diameter B 1  of the body  270  is increased.  
      As shown in  FIG. 10 , the fuel injector  210  is installed into a mounting hole  282  of an intake manifold  280 . The tip end of the fuel injector  210  must be located in a predetermined position such that the fuel that is injected through the fuel jet opening is mixed with air that is supplied via an intake passage  281  of the intake manifold  280  and such that the injected fuel is prevented from adhering to the inner wall of the intake manifold  280 .  
      The maximum outside diameter B 1  of the known fuel injector  210 , which is at a portion that the bobbin  251  is disposed, is larger than the minimum inside diameter A of the mounting hole  282  of the intake manifold  280 . Therefore, as shown in  FIG. 10 , a stepped mounting portion  270  is formed on the periphery of the fuel injector  210  below the portion having the bobbin  251  inside. Further, the length (“valve length”) H 1  of the movable core  230  is increased so that the tip end of the fuel injector  210  is placed in position.  
      However, the movable core  230  increases in weight as it increases in length, so that the operating characteristics of the fuel injector  210  is impaired.  
      On the other hand, fuel injectors of another type are also known in which sealing is provided without using an O-ring. An example of the known fuel injector of this type is disclosed in Japanese non-examined laid-open patent publication No. 9-42110 and is reproduced in  FIG. 9 , which shows a sectional view of a fuel injector  110 .  
      The fuel injector  110  includes a movable core  131 . A ball valve  132  is mounted on the tip end of the movable core  131  and serves to open and close a fuel jet opening  141   c  of a valve seat body  141 . A spring  134  is disposed between the movable core  131  and a spring adjuster  133  and normally urges the movable core  131  in the direction that causes the ball valve  132  to close the fuel jet opening  141   c.    
      A radially outwardly protruding flange  121   a  is formed on the outer surface of the fixed core  121  in a predetermined position. A bobbin  151  is disposed around the fixed core  121  and a coil  152  is wound on the bobbin  151 . A body  122  is disposed over the bobbin  151  and partially covers the periphery of the flange  121   a  of the fixed core  121 . A hole  121   b  is formed through the flange  121   a  of the fixed core  121 . A connecting wire  125  is placed in the hole  121   b . One end of the connecting wire  125  is connected to the coil  152 . A seal  127  is formed of glass and is disposed between the inner peripheral surface of the hole  121   b  and the connecting wire  125 .  
      A connector  124  is formed of resin and is disposed around the fixed core  121 . A socket  124   a  is formed in the connector  124  so that it can receive a connecting terminal which is connected to an external electric power source. The other end of the connecting wire  125  of which one end is connected to the coil  152  is located in the socket  124   a.    
      In the known fuel injector  110  shown in  FIG. 9 , the connecting wire  125  runs through the hole  121   b  of the flange  121   a  of the fixed core  121 . Further, the seal  127  is provided between the inner peripheral surface of the hole  121   b  and the connecting wire  125 . Thus, the need for an O-ring is eliminated, so that the maximum outside diameter of the body  122  can be made smaller than that of a fuel injector using an O-ring.  
      However, the outside diameter of the flange  121  of the fixed core  121 , or the outside diameter of a portion of the body  122  which covers the periphery of the flange  121   a  of the fixed core  121 , can be reduced only to a limited extent, because the seal  127  is provided in the hole  121   b  of the flange  121   a  of the fixed core  121 . Accordingly, the length of the body  122  which is inserted into the mounting hole  282  of the intake manifold  280 , or the length of the movable core  131 , can not be decreased.  
      Further, it is necessary to provide an additional sealing mechanism between the flange  121   a  of the fixed core  121  and the body  122 .  
     SUMMARY OF THE INVENTION  
      Accordingly, it is an object of the present invention to provide a fuel injector and a method of sealing the same, in which the maximum outside diameter of the body of the fuel injector can be reduced and the sealing structure can be made simpler.  
      In one aspect of the invention, a seal is provided in a region that is surrounded by a fixed core, a body and a connector, in the state in which a connecting wire is connected to a coil and runs through the region. Thus, it is not necessary to provide a seal in a flange of the fixed core. Therefore, the outside diameter of the flange of the fixed core, or the outside diameter of a portion of the body which contacts the flange (the maximum outside diameter of the body), can be reduced.  
      Preferably, the seal may be elastic. The seal may be preferably provided in a region that is surrounded by the fixed core, the flange that is formed on the surface of the fixed core and protrudes radially outward, the body and the connector.  
      In order to form the seal of a sealing material having low viscosity, preferably, the region may be first formed and then the sealing material is filled into the region. For example, the fixed core and the connector are positioned with respect to the body such that the region surrounded by the fixed core, the connector and the body communicates with an inlet hole formed in the body. After the sealing material has been filled into the region, the fixed core and the connector are positioned with respect to the body such that the region does not communicate with the inlet hole. In this case, preferably, the fixed core and the connector may be positioned with respect to the body by press-fitting. Of course, the body can be positioned with respect to the fixed core and the connector.  
      In another aspect of the invention, a seal is provided in a region that is surrounded by the body and the connector, in the state in which the connecting wire is connected to the coil and runs through the region. In this manner, too, it is not necessary to provide a seal in the flange of the fixed core. Therefore, the outside diameter of the flange of the fixed core, or the outside diameter of a portion of the body which contacts the flange (the maximum outside diameter of the body), can be reduced.  
      Preferably, the seal may be elastic. The seal may be preferably provided in a region that is surrounded by the body and a recess formed on the outer peripheral surface of the connector.  
      In order to form the seal of a sealing material having low viscosity, preferably, the region may be first formed and then the sealing material is filled into the region. For example, the connector is positioned with respect to the body such that the region that is surrounded by the body and the recess formed on the outer peripheral surface of the connector communicates with the inlet hole formed in the body. After the sealing material has been filled into the region, the connector is positioned with respect to the body such that the region does not communicate with the inlet hole. In this case, preferably, the connector may be positioned with respect to the body by press-fitting. Of course, the body can be positioned with respect to the connector.  
      In another aspect of the invention, the maximum outside diameter of the body of the fuel injector is smaller than the minimum inside diameter of a mounting hole of an intake manifold. In this case, the greater part of the body of the fuel injector can be inserted into the mounting hole of the intake manifold. Therefore, the length of the movable core of the fuel injector can be shortened, so that the operating characteristics of the fuel injector can be improved. Further, the coil is cooled by the intake air within the intake manifold, so that the operating characteristics of the fuel injector  10  is stabilized.  
      Other objects, features and advantages of the present invention will be readily understood after reading the following detailed description together with the accompanying drawings and the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a sectional view showing a fuel injector according to an embodiment of the invention.  
       FIG. 2  is a sectional view taken along line II-II in  FIG. 1 .  
       FIG. 3  is a sectional view taken along line III-III in  FIG. 1 .  
       FIG. 4  shows an example of a method of providing a seal in the fuel injector according to the embodiment of the invention.  
       FIG. 5  shows the example of the method of providing the seal in the fuel injector according to the embodiment of the invention.  
       FIG. 6  is a sectional view showing a fuel injector according to another embodiment of the invention.  
       FIG. 7  is a sectional view taken along line VII-VII in  FIG. 6 .  
       FIG. 8  shows an example of a method of providing a seal in the fuel injector according to the second embodiment of the invention.  
       FIG. 9  is a sectional view showing a prior art fuel injector.  
       FIG. 10  is a sectional view showing a prior art fuel injector mounted to an intake manifold.  
       FIG. 11  is a sectional view showing the fuel injector of the present invention which is mounted to an intake manifold. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      According to the present invention, a representative fuel injector may includes a fixed core, a movable core that can move with respect to the fixed core, a coil holding element that is disposed around the fixed core, a connector that is disposed around the fixed core and in which a connecting wire is embedded, the connecting wire being connected to the coil on the coil holding element, and a body that is disposed around the coil holding element.  
      Typically, the fixed core has a radially outwardly protruding flange. The coil holding element is disposed on the downstream side of the flange of the fixed core with respect to the direction of fuel flow. Further, the connector is formed of resin.  
      In one embodiment of the present invention, a seal is provided in a region that is surrounded by the fixed core, the body and the connector, with the connecting wire running through the region. Specifically, in this embodiment, the connecting wire that is connected to the coil on the coil holding element runs through the flange of the fixed core, the seal provided in the region, and the connector. In this embodiment, it is not necessary to provide a seal for sealing the connecting wire in the flange of the fixed core. Therefore, the outside diameter of the flange of the fixed core, or the outside diameter of a portion of the body which contacts the flange, can be reduced.  
      Suitably, the seal is provided in a region that is surrounded by the fixed core, the flange of the fixed core, the body and the connector, with the connecting wire running through the region. In this case, the region for the seal can be readily formed.  
      The seal and the connector may be formed of the same material or of different materials. Further, the seal and the connector may be formed separately or integrally.  
      Further, in this embodiment, it is not necessary to provide an additional seal between the fixed core and the body. Therefore, the sealing structure can be made simpler and the work for sealing can be made more easily.  
      Further, it is not necessary to provide an additional seal (particularly on the downstream side). Therefore, the coil (the coil holding element that holds the coil) can be freely positioned with respect to the boundary between the fixed core and the movable core. For example, the boundary between the fixed core and the movable core can be positioned in the middle of the coil in the axial direction. In this case, the efficiency and the operating characteristics of the fuel injector can be improved.  
      Various methods may be used to place the seal in the region.  
      For example, in one method, the seal is formed, in advance, with the connecting wire extending through the seal, and the seal is placed in the region. In another method, first, the region is formed, and thereafter, sealing material is filled into the region.  
      When sealing material of low viscosity is used, the latter method is preferably used. For example, the fixed core and the connector are positioned with respect to the body such that the region that is surrounded by the fixed core, the connector and the body communicates with the inlet hole formed in the body. Then the sealing material is filled into the region. Thereafter, the fixed core and the connector are positioned with respect to the body such that the region does not communicate with the inlet hole. In order to position the fixed core and the connector with respect to the body, suitably, the fixed core, the coil holding element, the coil and the connector are assembled together into one piece such that a fixed core body is made and the fixed core body is positioned with respect to the body by press-fitting. Of course, the body can be positioned with respect to the fixed core body.  
      In another embodiment of the present invention, a seal is provided in a region that is surrounded by the body and the connector, with the connecting wire running through the region. In this embodiment as well, the connecting wire that is connected to the coil on the coil holding element runs through the flange of the fixed core, the seal provided in the region, and the connector. Thus, it is not necessary to provide a seal in the flange of the fixed core. Therefore, the outside diameter of the flange of the fixed core, or the outside diameter of a portion of the body which contacts the flange, can be reduced.  
      Suitably, the seal is provided in a region that is surrounded by the body and a recess formed on the outer peripheral surface of the connector, with the connecting wire running through the region. In this case, the region for the seal can be readily formed simply by forming the recess on the outer peripheral surface of the connector.  
      In this embodiment as well, it is not necessary to provide an additional seal between the fixed core and the body. Thus, the sealing structure can be made simpler and the work for sealing can be made more easily. Further, the coil can be freely positioned with respect to the boundary between the fixed core and the movable core.  
      The above-mentioned method can be available to place the seal in the region.  
      When sealing material of low viscosity is used, for example, the connector is positioned with respect to the body such that the region that is surrounded by the connector and the body communicates with the inlet hole formed in the body. Then the sealing material is filled into the region. Thereafter, the connector is positioned with respect to the body such that the region does not communicate with the inlet hole. In order to position the connector with respect to the body, suitably, the fixed core, the coil holding element, the coil and the connector are assembled together into one piece such that a fixed core body is made and the fixed core body is positioned with respect to the body by press-fitting. Of course, the body can be positioned with respect to the fixed core body.  
      Typically, a fuel injector is installed into a mounting hole of an intake manifold.  
      In a preferred embodiment of this invention, the outside diameter of a portion of the body which contacts the flange (the maximum outside diameter of the body) is smaller than the minimum inside diameter of the mounting hole of the intake manifold. In this case, the greater part of the body of the fuel injector can be inserted into the mounting hole of the intake manifold. Therefore, the length of the movable core (“the valve length”) can be shortened. Accordingly, the weight of the movable core can be reduced, so that the operating characteristics of the fuel injector can be improved.  
      Further, when the greater part of the body of the fuel injector is inserted into the mounting hole, the coil of the fuel injector is placed within the intake manifold. Thus, the coil of the fuel injector is cooled by the intake air within the intake manifold. Therefore, the influence of heat can be alleviated, so that the operating characteristics of the fuel injector is stabilized.  
      Each of the additional features and method steps disclosed above and below may be utilized separately or in conjunction with other features and method steps to provide improved fuel injectors and methods of sealing such fuel injectors. Representative examples of the present invention, which examples utilized many of these additional features and method steps in conjunction, will now be described in detail with reference to the drawings. This detailed description is merely intended to teach a person skilled in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Only the claims define the scope of the claimed invention. Therefore, combinations of features and steps disclosed within the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe some representative examples of the invention.  
       FIG. 1  shows a fuel injector  10  according to an embodiment of the present invention, in sectional view.  
      The fuel injector  210  includes an injector body  20 , a valve  30 , a valve seat  40  and a driving section  50 .  
      The injector body  20  has a generally cylindrical shape. The inner space of the injector body  20  serves as a fuel passage  21   h . Fuel flows through the fuel passage  21   h  from top to bottom in  FIG. 1 . The injector body  20  has a fixed core  21  on the upstream side and a body  22  on the downstream side with respect to the direction of fuel flow. The fixed core  21  and the body  22  are formed of magnetic material. A fuel filter  23  is mounted in the upstream portion of the fuel passage  21   h . A flange  21   a  is formed on the outer peripheral surface of the fixed core  21  in a predetermined position and protrudes radially outward.  
      The valve  30  includes a movable core  31  and a ball valve  32  that is disposed on the downstream side of the movable core  31 . The movable core  31  is formed of magnetic material. The movable core  31  has a generally cylindrical shape. The inner space of the movable core  31  serves as a fuel passage  31   a . Further, a communication hole  31   b  is formed through the side wall of the movable core  31  and serves to communicate the fuel passage  31   a  with a fuel passage  41   a  of a valve seat body  41  which will be described below. The ball valve  32  has a spherical shape. The valve  30  is disposed such that it can move in the axial direction of the fuel injector  10  (vertically as viewed in  FIG. 1 ) with respect to the injector body  20  and the valve seat  40 . In this embodiment, the movable core  31  is disposed such that it can slide along the inner peripheral surface of the body  22 .  
      The valve seat  40  has a valve seat body  41 . The valve seat body  41  is mounted with the body  22 , for example, by press-fitting. The valve seat body  41  has a generally cylindrical shape with a bottom. A sealing surface (contact surface)  41   b  and a fuel jet opening  41   c  are formed in the bottom of the valve seat body  41 . The inner space of the valve seat body  41  serves as a fuel passage  41   a . A groove  41   d  is formed in a portion of the inner peripheral surface of the valve seat body  41  which faces the ball valve  32  and extends in the axial direction (vertically as viewed in  FIG. 1 ). Fuel can be led from the fuel passage  41   a  to the fuel jet opening  41   c  via the groove  41   d . The fuel jet opening  41   c  is closed when the ball valve  32  is in contact with the sealing surface  41   b , while the fuel jet opening  41   c  is opened when the ball valve  32  is not in contact with the sealing surface  41   b.    
      Further, a spring  34  is disposed between a spring adjuster  33  and the valve  30  (the movable core  31 ) and normally urges the valve  30  toward the valve seat  40  (in the direction that closes the fuel jet opening  41   c ).  
      As shown in  FIG. 2 , the spring adjuster  33  has a generally C-shaped cross section and is fixedly fitted in a predetermined position within the fixed core  21 , for example, by press-fitting or caulking. The biasing force that urges the valve  30  toward the valve seat  40  can be adjusted by adjusting the position of the spring adjuster  33  to be fixed. The spring adjuster  33  may have various configurations.  
      The inner space of the spring adjuster  33  serves as a fuel passage  33   a . Thus, fuel can pass through the fuel filter  23  and the fuel passages  21   h ,  33   a ,  31   a ,  41   a  and then be led to the fuel jet opening  41   c  via the groove  41   d.    
      The fixed core  21  and the movable core  31  are arranged such that a slight clearance is formed between the fixed core  21  and the movable core  31  when the ball valve  32  of the valve  30  is in contact with the sealing surface  41   b  of the valve seat body  41 .  
      The driving section  40  for driving the valve  30  includes the fixed core  21 , a coil  52  and the body  22 . A bobbin  51  is disposed around the fixed core  21  and the coil  52  is wound on the bobbin  51 . The bobbin  51  is a feature that corresponds to the “coil holding element” according to this invention. The bobbin  51  on which the coil  52  is wound is typically covered with resin. An end portion of a connecting wire  25  of which end is connected to the coil  52  is embedded in the resin, for example, by insert molding.  
      The body  22  has a generally cylindrical shape. The body  22  is disposed over the bobbin  51  such that the outer peripheral surface of the flange  21   a  of the fixed core  21  contacts the inner peripheral surface of the body  22 . For example, the body  22  is press fitted over the fixed core  21 . Further, the body  22  and the fixed core  21  are arranged such that the upstream end (upper end as viewed in  FIG. 1 ) of the body  22  is located on the upstream side of the flange  21   a.    
      A connector  24  is formed of resin and disposed over the fixed core  21 . A socket  24   a  is formed in the connector  24  and can receive a connecting terminal which is connected to an external electric power source. One end of the connecting wire  25  is connected to the coil  52  and the other end is placed in the socket  24   a . Thus, the coil  52  can be connected to the external electric power source via the connecting wire  25 . The connecting wire  25  for connection between the coil  52  and the external electric power source may be composed of one or more connecting wires. A plurality of the connecting wires may be connected in series.  
      The fixed core  21 , the body  22  and the connector  24  are arranged so as to define a region  26 . In this embodiment, the region  26  is defined by the fixed core  21 , the flange  21   a  of the fixed core  21 , a portion of the body  22  which protrudes upstream from the flange  21   a , and the connector  24 .  
      The connecting wire  25  and a seal  27  are placed in the region  26 . For example, the seal  27  may be provided in the region  26  with the connecting wire  25  running through the region  26 . The seal  27  can be formed of various sealing materials, and preferably of elastic sealing materials, such as rubber. Sealing effectiveness of the seal  27  can be enhanced by using elastic materials. Further, the seal  27  is formed of insulating material. The seal  27  may be formed of materials having any additional characteristic as necessary.  
       FIG. 2  is a sectional view taken along line II-II in  FIG. 1  and shows the state in which the connecting wire  25  and the seal  27  are placed in the region  26 . As shown in  FIG. 2 , the connecting wire  25  runs through the region  26  that is defined by the outer peripheral surface of the fixed core  21  and the inner peripheral surface of the body  22 , and the seal  27  is provided in the region  26 . In this embodiment, the region  26  is defined into a cylindrical (doughnut-like) shape by the outer peripheral surface of the fixed core  21  that is circular in section and the inner peripheral surface of the body  22  that is also circular in section. The seal  27  having a cylindrical (doughnut-like) shape is provided in the region  26 . The connecting wire  25  runs through the seal  27  in the axial direction.  
      Further, the connecting wire  25  is running through the flange  21   a  of the fixed core  21 . This state is shown in  FIG. 3 , which is a sectional view taken along line III-III in  FIG. 1 . As shown in  FIG. 3 , a recess  21   b  is formed in the outer peripheral surface of the flange  21   a  of the fixed core  21 . The recess communicates in the axial direction (in the vertical direction as viewed in  FIG. 1 ).  
      Various methods may be used to place the connecting wire  25  in the region of the flange  21   a  of the fixed core  21 .  
      In one method, one end portion of the connecting wire  25  which juts out of the bobbin  51  with the one end connected to the coil  52  is placed in the recess  21   b  of the flange  21   a  of the fixed core  21 . Then the recess  21   b  is filled with resin, so that the connecting wire  25  is fixed in the recess  21   b.    
      In another method, in the process of covering the bobbin  51  on which the coil  52  is wound, with resin, a protrusion which protrudes from the bobbin  51  and has a shape corresponding to the shape of the recess  21   b  is formed of resin with a portion of the connecting wire  25  of which end is connected to the coil  52  being embedded in the protrusion. And, when the bobbin  51  is disposed around the fixed core  21 , the protrusion in which the connecting wire  25  is embedded is fitted in the recess  21   b  so as to fix the connecting wire  25  in the recess  21   b.    
      Various methods may be used to place the connecting wire  25  and the seal  27  in the region  26 .  
      In one method, first, the bobbin  51  is fitted onto the fixed core  21  with the coil  52  which is wound on the bobbin  51  being covered with the resin and a portion of the connecting wire  25  of which end is connected to the coil  52  being embedded in the resin. At this time, the bobbin  51  is aligned in the circumferential direction such that the connecting wire  25  running from the bobbin  51  is placed in the recess  21   b  of the flange  21   a . Then, the body  22  is fitted over the bobbin  51 . At this time, the connecting wire  25  that runs from the bobbin  51  via the flange  21   a  is placed in a region (corresponding to the region  26 ) which is defined by the fixed core  21 , the flange  21   a  of the fixed core  21 , and the portion of the body  22  which extends upstream from the flange  21   a . Subsequently, the sealing material is filled into this region. Then, the connector  24  is formed of resin over the fixed core  21 .  
      The seal  27  and the connector  24  may be formed independently at different times or at about the same time. In either way, the seal  27  is provided in the region  26 , which is defined by the fixed core  21 , the flange  21   a  of the fixed core  21 , the portion of the body  22  which extends upstream from the flange  21   a , and the connector  24 , with the connecting wire  25  running through the region  26 .  
      In another method, first, the bobbin  51  is fitted onto the fixed core  21  with the coil  52  which is wound on the bobbin  51  being covered with the resin and a portion of the connecting wire  25  of which end is connected to the coil  52  being embedded in the resin. At this time, the bobbin  51  is aligned in the circumferential direction such that the connecting wire  25  is placed in a predetermined position. Then, in this state, the connector  24  is formed of resin over the fixed core  21  such that a region is defined by the fixed core  21 , the flange  21   a , of the fixed core  21  and the connector  24 . In this manner, the connecting wire  25  is embedded in the connector  24 . Then, the body  22  is fitted over the bobbin  51 . Subsequently, sealing material is filled, through an inlet hole formed in the body  22 , into the region  26  which is defined by the fixed core  21 , the flange  21   a  of the fixed core  21 , the portion of the body  22  which extends upstream from the flange  21   a , and the connector  24 . The sealing material is then hardened. Thus, the seal  27  is provided in the region  26  with the connecting wire  25  running through the region  26 .  
      In a further different method, first, the bobbin  51  is fitted onto the fixed core  21  with the coil  52  which is wound on the bobbin  51  being covered with the resin and a portion of the connecting wire  25  of which end is connected to the coil  52  being embedded in the resin. Then, the body  22  is fitted over the bobbin  51 . Subsequently, sealing material is filled into a region which is defined by the fixed core  21 , the flange  21   a  of the fixed core  21  and the portion of the body  22  which extends upstream of the flange  21   a  and into a region in which the connector  24  is to be formed. In this manner, the seal  27  is provided in the region  26  with the connecting wire  25  running through the region  26 , and at the same time, the connector  24  is formed over the fixed core  21 . In this method, the seal  27  and the connector  24  are integrally formed of the sealing material. In this embodiment, a portion of the integrally formed body which is corresponding to the region  26  is a feature that corresponds to the “seal provided in a region that is surrounded by the fixed core, the body and the connector” in this invention.  
      A sealing material having low viscosity may be used to form the seal  27 . In such a case, it is difficult to provide the seal in the above-mentioned methods. An example of the method of providing the seal  27  in the region  26  which is surrounded by the fixed core  21 , the body  22  and the connector  24 , by using a sealing material having a low viscosity, will now be described with reference to  FIGS. 4 and 5 .  
      When sealing material of low viscosity is used, the body  22  as shown in  FIGS. 4 and 5  is used. An upstream end  22   c  of the body  22  is located on the upstream side of the normal position of the region  26  which is surrounded by the fixed core  21 , the body  22  and the connector  24 . Further, an inlet hole  22   a  through which the sealing material is injected into the region  26  is formed through the body  22  on the upstream side of the normal position of the region  26 . The inlet hole  22   a  may be of any design and configuration through which the sealing material can be injected into the region  26 , and its shape, size, location and number can be appropriately chosen.  
      First, the bobbin  51  is fitted onto the fixed core  21  with the coil  52  which is wound on the bobbin  51  being covered with the resin and with a portion of the connecting wire  25  of which end is connected to the coil  52  being embedded in the resin. At this time, the bobbin  51  is aligned in the circumferential direction such that the connecting wire  25  is placed in a predetermined position. Then, in this state, the connector  24  is formed of resin over the fixed core  21  such that a region is defined by the fixed core  21 , the flange  21   a  of the fixed core  21 , and the connector  24 . Thus, the coil  52 , the bobbin  51 , the connecting wire  25 , the fixed core  21  and the connector  24  are assembled together into one piece (hereinafter referred to as a “fixed core body”). In this state, a recess is defined by the fixed core  21 , the flange  21   a  of the fixed core  21 , and the connector  24 .  
      Subsequently, the fixed core body is fitted to the body  22 . In this embodiment, as shown in  FIG. 4 , the fixed core body is press fitted into the body  22  from upstream (from above as viewed in  FIG. 4 ). At this state, an outer peripheral surface  21   c  of the flange  21   a  and a downstream-side outer peripheral surface  24   e  of the connector  24  contact an inner peripheral surface  22   b  of the body  22 . Consequently, the region  26  is defined by an outer peripheral surface  21   e  of the fixed core  21 on the upstream side of the flange  21   a , an upstream end surface  21   d  of the flange  21   a , a downstream end surface  24   d  of the connector  24 , and the inner peripheral surface  22   b  of the body  22 .  
      In order to mount the fixed core body to the body  22 , first, the fixed core body is positioned with respect to the body  22  in a position in which the sealing material can be injected into the region  26 . In this embodiment, as shown in  FIG. 4 , the fixed core body is press fitted into the body  22  in the direction of the arrow until the region  26  reaches a position (“temporary press-fitted position”) in which the region  26  communicates with the inlet hole  22   a  of the body  22 . At this state, as shown in  FIG. 4 , a predetermined axial extent of clearance is formed between a stepped end surface  24   f  of the connector  24  and the upstream-side end surface  22   c  of the body  22  and between a downstream-side end surface  51   a  of the bobbin  51  and a stepped surface  22   d  of the body  22 . An appropriate position in which the region  26  communicates with the inlet hole  22   a  can be chosen as the temporary press-fitted position.  
      In the state in which the fixed core body is positioned in the temporary press-fitted position and the region  26  communicates with the inlet hole  22   a , sealing material is filled into the region  26  through the inlet hole  22   a . Thereafter, the inlet hole  22   a  is closed and then the region  26  is placed in the normal position.  
      In this embodiment, the fixed core body is further press fitted downstream (in the direction of the arrow) from the temporary press-fitted position to a position (“press-fitted position”) in which the stepped end surface  24   f  of the connector  24  contacts the upstream-side end surface  22   c  of the body  22 . Thus, the fixed core body is positioned with respect to the body  22  in the press-fitted position. The downstream-side outer peripheral surface  24   e  of the connector  24  closes the inner end of the inlet hole  22   a  of the body  22  by the time that the fixed core body is positioned in the press-fitted position.  
      At this state, as shown in  FIG. 5 , the stepped end surface  24   f  of the connector  24  abuts on the upstream-side end surface  22   c  of the body  22 , and the downstream-side end surface  51   a  of the bobbin  51  abuts on the stepped surface  22   d  of the body  22 . An appropriate position in which the region  26  does not communicate with the inlet hole  22   a  can be chosen as the press-fitted position.  
      This press-fitted position corresponds to above “the normal position of the region  26 ”.  
      In this manner, even if the sealing material to be filled into the region  26  has low viscosity, the sealing material is prevented from flowing out of the region  26 . Further, the sealing material which has been hardened is not squeezed out of the region  26  even if the fuel pressure is applied onto the sealing material.  
      Preferably, the fixed core body is moved from the temporary press-fitted position to the press-fitted position before the sealing material in the region  26  is hardened. Of course, the body  22  can be moved with respect to the fixed core body from the temporary press-fitted position to the press-fitted position.  
      Further, the fixed core body may be mounted to the body  22  by a method other than press-fitting.  
      Operation of this embodiment will now be explained.  
      When current is supplied to the coil  52 , magnetic flux flows through the fixed core  21 , the movable core  31  and the body  22  and thus a force to move the valve  30  (the movable core  31  and the ball valve  32 ) toward the fixed core  21  is generated. As a result, the valve  30  moves in a direction away from the valve seat  40  (upward as viewed in  FIG. 1 ) against the biasing force of the spring  34 . The valve  30  then stops in a position in which the movable core  31  contacts the fixed core  21 .  
      At this state, the ball valve  32  separates from the sealing surface  41   b  of the valve seat body  41 . Thus, the fuel jet opening  41   c  is opened and fuel is injected through the fuel jet opening  41   c.    
      When the supply of current to the coil  52  is stopped in this state, the valve  30  moves in a direction toward the valve seat  40  (downward as viewed in  FIG. 1 ) by the biasing force of the spring  34 . The valve  30  then stops in a position in which the ball valve  32  contacts the sealing surface  41   b  of the valve seat body  41 .  
      At this state, the fuel jet opening  41   c  is closed and the fuel injection from the fuel jet opening  41   c  is stopped.  
      As mentioned above, in this embodiment, the seal  27  is provided in the region  26  which is surrounded by the fixed core  21 , the flange  21   a  of the fixed core  21 , the body  22  and the connector  24 , with the connecting wire  25  running through the region  26 .  
      In this regard, in the prior art shown in  FIG. 9 , the seal  127  is provided in the hole  121   b  of the flange  121   a  of the fixed core  121 , with the connecting wire  125  running through the hole  121   b . Therefore, in the prior art, the outside diameter of the flange  121   a  of the fixed core  121 , or the outside diameter of a portion of the body  122  which contacts the flange  121   a  (the maximum outside diameter of the body  122 ), can be reduced only to a limited extent. Further, it is necessary to provide an additional sealing mechanism between the flange  121   a  of the fixed core  121  and the body  122 .  
      In contrast to this prior art, in this embodiment, the seal  27  is not provided in the flange  21   a  of the fixed core  21 . Therefore, the outside diameter of the flange  21   a  of the fixed core  21  can be reduced to the smallest possible diameter with which the connecting wire  25  does not contact the fixed core  21  and the body  22 . Further, the flange  21   a  can have about the same outside diameter as the bobbin  51 . Therefore, compared with the prior art, it is possible to make smaller the outside diameter of the flange  21   a  of the fixed core  21 , or the outside diameter of a portion of the body  22  which contacts the flange  21   a  (the maximum outside diameter of the body  122 ). Further, it is not necessary to provide an additional seal between the fixed core  21  and the body  22 .  
      Thus, as shown in  FIG. 11 , in this embodiment, the maximum outside diameter B 2  of the body  22  of the fuel injector  10  can be made smaller than the minimum inside diameter A of a mounting hole of an intake manifold  80 .  
      In this case, the greater part of the body  22  of the fuel injector  10  can be inserted into the mounting hole  82 . Therefore, the length of the movable core  31 , or the valve length H 2 , can be made shorter than the valve length H 1  of the prior art shown in  FIG. 10 . Accordingly, the weight of the movable core  31  is reduced, so that the operating characteristics of the fuel injector  10  can be improved.  
      Further, the fuel injector  10  can be mounted to the intake manifold  80  such that the coil  52  is inserted into the intake manifold  80 . Thus, the coil  52  can be cooled by the intake air within the intake manifold  80 . Therefore, the influence of heat can be alleviated, so that the operating characteristics of the fuel injector  10  is stabilized.  
      Further, in  FIG. 11 , a stepped mounting portion  70  is provided on the outer peripheral surface of the fuel injector  10  and serves to position the tip end (e.g. the fuel jet opening) of the fuel injector  10 . When the stepped mounting portion  70  is provided, the maximum outside diameter of a portion of the body  22  excluding the mounting portion  70  corresponds to the “the maximum outside diameter of the body” according to this invention.  
      Further, in this embodiment, an O-ring or any other similar seal is not provided on the downstream side of the flange  11   a . Therefore, the degree of freedom in design of the position of the coil  52  with respect to the boundary between the fixed core  21  and the movable core  31  can be increased. For example, the boundary between the fixed core  21  and the movable core  31  can be positioned in the middle of the coil  52  in the axial direction. In this case, the efficiency and the operating characteristics of the fuel injector  10  can be improved.  
      In the above-mentioned embodiment, the region  26  for the seal has been described as being defined by the fixed core (the fixed core  21  and the flange  21   a  of the fixed core  21 ), the body (a portion of the body  22  which protrudes upstream from the flange  21   a  of the fixed core  21 ) and the connector  24 , but a method of forming the region  26  for the seal is not limited to this. Further, the region  26  can be formed partially along the circumferential direction around the fixed core  21 .  
      Another embodiment of the present invention will now be described. In this embodiment, the region for the seal is defined by the connector and the body.  
       FIG. 6  is a sectional view showing the fuel injector  10  according to this embodiment of this invention. Components identical to those shown in  FIG. 1  are given like numerals as in  FIG. 1 . The embodiment shown in  FIG. 6  is different from the embodiment shown in  FIG. 1  in configuration of the fixed core  21  and the connector  24 . Therefore, only the different points will now be described.  
      In this embodiment, a recess  24   c  is formed on the outer peripheral surface of the connector  24  along the circumferential direction. Further, the connector  24  has an end wall  24   b  formed between the recess  24   c  and a downstream-side end surface  24   d  of the connector  24  on the side of the flange  21   a . The downstream-side end surface  24   d  (lower end surface as viewed in  FIG. 6 ) of the connector  24  is in contact with the upstream-side surface  21   d  (upper surface as viewed in  FIG. 6 ) of the flange  21   a.    
      Further, the body  22  is disposed such that the inner peripheral surface  22   b  of the body  22  contacts the outer peripheral surface  21   c  of the flange  21   a  and the outer peripheral surface of the end wall  24   b  of the connector  24 .  
      Thus, the region  26  is defined by the connector  24  (the recess  24   c  of the connector  24 ) and the body  22  (a portion of the body  22  which protrudes upstream from the flange  21   a ).  
      In this embodiment, too, the seal  27  is provided in the region  26  which is defined by the connector  24  and the body  22 , with the connecting wire  25  running through the region  26 .  FIG. 7  is a sectional view taken along line VII-VII in  FIG. 6  and shows the state in which the connecting wire  25  and the seal  27  are provided in the region  26 .  
      Further, in this embodiment, the inner space of the fixed core  21  and the inner space of the connector  24  form the fuel passage  21   h . Specifically, the inner space of the connector  24  forms the upstream portion of the fuel passage  21   h  and the inner space of the fixed core  21  forms the downstream portion of the fuel passage  21   h . However, it may be configured such that the fuel passage  21   h  is formed by the inner space of the fixed core  21  alone as shown in  FIG. 1 .  
      Various methods may be used to place the connecting wire  25  and the seal  27  in the region  26 .  
      In one method, first, the bobbin  51  is fitted onto the fixed core  21  with the coil  52  which is wound on the bobbin  51  being covered with the resin and with a portion of the connecting wire  25  of which end is connected to the coil  52  being embedded in the resin. At this time, the bobbin  51  is aligned in the circumferential direction such that the connecting wire  25  running from the bobbin  51  is placed in the recess  21   b  of the flange  21   a . Then, with the connecting wire  25  in a predetermined position, the connector  24  is formed of resin on the outer peripheral side of the fixed core  21  such that the recess  24   c  is formed in the outer peripheral surface of the connector  24 . Thus, the connecting wire  25  is embedded in the connector  24 . Then, the body  22  is fitted over the bobbin  51 . Subsequently, sealing material is filled, through an inlet hole formed in the body  22 , into the region  26  that is defined by the recess  24   c  of the connector  24  and the portion of the body  22  which protrudes upstream from the flange  21   a . The sealing material is then hardened. Thus, the seal  27  is provided in the region  26  with the connecting wire  25  running through the region  26 .  
      In another method, first, the fixed core  21 , the bobbin  51  and the body  22  are assembled together. In this state, sealing material is filled over the fixed core  21 , so that the connector  24  and the seal  27  are formed integrally. Thus, the seal  27  is provided in the region  26  which is defined by the connector  24  and the body  22 , with the connecting wire  25  running through the region  26 .  
      In this embodiment, the recess  24   c  which defines a part of the region  26  is formed of resin, so that the region  26  can be easily formed.  
      The outer peripheral surface of the end wall  24   b  may not be in contact with the inner peripheral surface  22   b  of the body  22 . For example, a clearance or seal may be formed between the outer peripheral surface of the end wall  24   b  and the inner peripheral surface  22   b  of the body  22 .  
      Further, the end wall  24   b  may not be provided. For example, the downstream-side surface of the seal  26  may contact the upstream-side surface  21   d  of the flange  21   a . In this case, like in the above-mentioned embodiment, the region for the seal is defined by the fixed core  21  (the flange  21   a  of the fixed core  21 ), the body  22  (a portion of the body  22  which protrudes upstream from the flange  21   a  of the fixed core  21 ) and the connector  24 .  
      In the above-mentioned methods, it is difficult to provide the seal  27  by filling sealing material having a low viscosity into the region  26  which is surrounded by the body  22  and the connector  24 . A method for providing the seal  27  in the region  26  which is surrounded by the body  22  and the connector  24 , by using a sealing material having a low viscosity, will now be described with reference to  FIG. 8 . This method is basically similar to the method described in the first embodiment, and therefore will be explained in brief.  
      When the sealing method of this embodiment is used, the body  22  as shown in  FIG. 8  is used. The upstream-side end surface  22   c  of the body  22  is located on the upstream side of the normal position of the region  26  which is surrounded by the body  22  and the connector  24 . Further, the inlet hole  22   a  for injecting the sealing material is formed through the body  22  on the upstream side of the normal position of the region  26 .  
      In order to provide the seal  27  in the region  26  which is surrounded by the body  22  and the connector  24 , first, the bobbin  51  is fitted onto the fixed core  21  with the coil  52  which is wound on the bobbin  51  being covered with the resin and with a portion of the connecting wire  25  of which end is connected to the coil  52  being embedded in the resin. At this time, the bobbin  51  is aligned in the circumferential direction such that the connecting wire  25  is placed in a predetermined position. Then, in this state, the connector  24  is formed of resin on the outer peripheral side of the fixed core  21  such that the recess  24   c  is formed in the outer peripheral surface of the connector  24 . In this manner, the coil  52 , the bobbin  51 , the connecting wire  25 , the fixed core  21 , and the connector  24  are assembled together into one piece (hereinafter referred to as a “fixed core body”). In this state, a region is defined by the recess  24   c  in the outer peripheral surface of the connector  24 .  
      Subsequently, the fixed core body is press fitted into the body  22  from upstream (from above as viewed in  FIG. 8 ). At this state, the downstream-side outer peripheral surface  24   e  of the connector  24  contacts the inner peripheral surface  22   b  of the body  22 , so that the region  26  is defined by the recess  24   c  of the connector  24  and the inner peripheral surface  22   b  of the body  22 .  
      Then, as shown in  FIG. 8 , the fixed core body is press fitted into the body  22  in the direction of the arrow until the region  26  reaches a temporary press-fitted position in which the region  26  communicates with the inlet hole  22   a  of the body  22 . Sealing material is then filled into the region  26  through the inlet hole  22   a . Thereafter, the fixed core body is further press fitted downstream (in the direction of the arrow) from the temporary press-fitted position to the press-fitted position in which the stepped end surface  24   f  of the connector  24  abuts on the upstream-side end surface  22   c  of the body  22 . The downstream-side outer peripheral surface  24   e  of the connector  24  closes the inner end of the inlet hole  22   a  of the body  22  by the time that the fixed core body is positioned with respect to the body  22  in the press-fitted position.  
      The present invention is not limited to the constructions that have been described as the representative embodiments, but rather, may be added to, changed, replaced with alternatives or otherwise modified without departing from the spirit and scope of the invention. For example, the seal  27  has been described as being arranged to fill the region  26 , but the seal  27  may be arranged in part of the region  26  as long as the inner and outer peripheral surfaces of the region  26  are in contact with the inner and outer peripheral surfaces of the seal  27 . The method of defining the region  26  by the fixed core  21 , the flange  21   a  of the fixed core  21 , the body  22  and the connector  24  or by the body  22  and the recess  24   c  of the connector  24  is not limited to the methods described in the representative embodiments, but various methods may be used. The seal  27  and the connector  24  may be formed of the same material or of different materials. The seal  27  and the connector  24  may be formed separately or integrally. The method of placing the connecting wire  25  in the connector  24 , the region  26  and the flange  21   a  is not limited to the methods described in the representative embodiments, but various methods may be used. The construction of the fuel injector is not limited to that of the embodiments. For example, the configurations of the fixed core  21 , the body  22 , the movable core  31 , the bobbin  51 , the connector  24 , the valve  30  and the valve seat  40  can be appropriately changed. Further, the mechanism for opening and closing the fuel jet opening is not limited to that described in the embodiments.  
      The fuel injector of this invention can be used as a fuel injector for injecting various kinds of fuel.  
      Further, the present invention can also be representative as a fuel supply system which includes a fuel tank, a fuel pump and the fuel injector according to the embodiment of this invention.