Patent Publication Number: US-7712453-B2

Title: Depressurizing valve and fuel injection device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is based on Japanese Patent Application Nos. 2005-300318 filed on Oct. 14, 2005 and 2006-186665 filed on Jul. 6, 2006, disclosures of which are incorporated herein by reference. 
   FIELD OF THE INVENTION 
   The present invention relates to a depressurizing valve for decreasing fuel pressure in a common rail of a fuel injection device at a vehicle deceleration, and further relates to a fuel injection device having the depressurizing valve. 
   BACKGROUND OF THE INVENTION 
   A conventional fuel injection device for an internal combustion engine has; a common rail for storing a high pressure fuel; fuel injection valves for injecting the high pressure fuel from the common rail into respective cylinders of the engine; a fuel pump for sucking and pressurizing the fuel and supplying the high pressure fuel to the common rail; a fuel return path for returning a portion of the high pressure fuel from the common rail to a low pressure side (a fuel tank); an electromagnetic type depressurizing valve which will be operated to open the fuel return path when the vehicle is decelerated in order to quickly reduce the fuel pressure in the common rail. 
   The depressurizing valve is mounted to, for example, the common rail. In the fuel injection device, however, as disclosed in Japanese Patent Publication No. 2001-59459, the depressurizing valve is mounted to the fuel pump. The depressurizing valve has a flanged portion, at which a through hole is formed for inserting a bolt therethrough, and the depressurizing valve is fixed to the fuel pump by the bolt. 
   In the fuel injection device, as disclosed in Japanese Patent Publication No. H11-141428, a solenoid portion is fixed to a body member of a fuel injection valve by a retaining nut, wherein an electromagnetic valve portion thereof can be used as a depressurizing valve. 
   The depressurizing valve mounted to the common rail has a connector for receiving driving current. The connector is electrically connected to a driving circuit through a wire harness, when the common rail is mounted to the engine. It is, however, necessary to adjust a direction of the connector when the depressurizing valve is mounted to the common rail, because the common rail must be mounted to the engine in a limited space and thereby a position (direction) of the connector must be selected to a predetermined position (direction) with respect to the common rail. Nothing has been proposed so far, wherein a direction of the connector is adjusted in the depressurizing valve to be mounted to the common rail. 
   If the fixing structure of the depressurizing valve, as disclosed in the above mentioned prior art (No. 2001-59459), in which the flanged portion of the valve is fixed to the fuel pump by the bolt, was intended to be applied to a fixing structure for a depressurizing valve to be mounted to the common rail, a bolt hole should be formed in the common rail of a cylindrical shape. In such a fixing structure, the direction of the connector provided in the depressurizing valve can be adjusted to a predetermined desired direction. However, it is actually difficult to form the bolt hole in the common rail, because the common rail is generally formed as the cylindrical shape, and thereby there is no sufficient space for the bolt hole. 
   In the fuel injection device disclosed in Japanese Patent Publication No. H11-141428, a direction of a connector portion can be adjusted by loosening a retaining nut. However, if the retaining nut was loosened, positions of inside parts, such as a spacer for adjusting an air gap, an armature, and so on would be changed. As a result, there would be a problem that the air gap would be changed after the retaining nut was once loosened and then tightly screwed again. Furthermore, if the retaining nut was loosened, a position and a contacting condition of a sealing member which is disposed between the retaining nut and the valve housing would be also changed. Accordingly, it would be necessary to check a sealing performance once again after the retaining nut was tightly screwed again. 
   In the case that the structure of the above prior art (Japanese Patent Publication No. H11-141428) for fixing the solenoid portion of the electromagnetic coil to the valve housing was applied to the depressurizing valve to be mounted to the common rail, the direction of the connector portion can be adjusted by loosening the retaining nut. However, there are still problems in that the air gap might be changed and/or the sealing performance should be checked again, as in the fuel injection device of the above mentioned prior art. 
   SUMMARY OF THE INVENTION 
   The present invention is made in view of the above problems. An object of the present invention is, therefore, to provide a fuel injection device, more particularly a depressurizing valve mounted to a common rail for the fuel injection device, in which a direction of a connector for the depressurizing valve can be adjusted, without affecting an air gap and a sealing performance. 
   According to a feature of the present invention, a depressurizing valve is composed of a valve unit having a valve body; and a coil unit for attracting the valve body in a valve opening direction when electric current is supplied to a cylindrical electromagnetic coil. 
   The valve unit has a valve housing of a cylindrical shape to be mounted to a common rail; an armature integrally formed with the valve body; a first space formed in the valve housing and connected to a fuel return path for accommodating the valve body and the armature; and a second space formed in the valve housing for accommodating the electromagnetic coil, such that the electromagnetic coil is rotatable with respect to the valve housing in a circumferential direction, and the second space is coaxially formed with the first space. The valve unit further has a stator core arranged in an inner peripheral space of the electromagnetic coil and axially opposing to the armature; a connecting member fluid tightly connected to the valve housing and to the stator core, for dividing, together with the stator core, an inside space of the valve housing into the first and second spaces; and a valve seat provided at one end of the first space and having a flow control port for operatively communicating the first space with a high pressure chamber of the common rail by an axial movement of the valve body, wherein the valve body and the armature are axially and movably held in the first space between the valve seat and the stator core. 
   The coil unit is detachably assembled to the valve unit and has a connector integrally formed with the electromagnetic coil; and a mounting member for detachably mounting the electromagnetic coil and the connector to the valve unit. 
   According to the above feature, the direction of the connector integrally formed with the electromagnetic coil can be adjusted, since the electromagnetic coil is accommodated in the second space, such that the electromagnetic coil is rotatable with respect to the valve housing in a circumferential direction. 
   Furthermore, an air gap formed between the armature and the stator core is not changed, even when the mounting member is loosened and tightened for the purpose of adjusting the direction of the connector. This is because the valve body and the armature is held between the valve seat and the stator core. 
   In addition, a sealing member (such as an O-ring) is not necessary between the first and second spaces, since the first space for accommodating the valve body and the armature is fluid tightly connected to the second space for accommodating the coil by the connecting member. As a result, it is not necessary to check the sealing performance again after the mounting member is loosened and tightened. 
   According to another feature of the present invention, the connecting member is made of a non-magnetic material. Due to the non-magnetic material, the magnetic flux is blocked between the valve housing and the stator core, so that the valve body and the armature can be surely attracted. 
   According to a further feature of the present invention, a depressurizing valve is composed of a valve unit having a valve body; and a coil unit for attracting the valve body in a valve opening direction when electric current is supplied to a cylindrical electromagnetic coil. 
   The valve unit has a valve housing of a cylindrical shape to be mounted to a common rail; an armature integrally formed with the valve body; a first space formed in the valve housing and connected to a fuel return path for accommodating the valve body and the armature; and a second space formed in the valve housing for accommodating the electromagnetic coil, such that the electromagnetic coil is rotatable with respect to the valve housing in a circumferential direction, and the second space is coaxially formed with the first space. 
   The valve unit further has a stator core arranged in an inner peripheral space of the electromagnetic coil and axially opposing to the armature; a connecting member integrally formed with one of the valve housing and the stator core, for fluid tightly dividing, together with the stator core, an inside space of the valve housing into the first and second spaces, wherein the connecting member restricts magnetic flux flow between the stator core and the valve housing; and a valve seat provided at one end of the first space and having a flow control port for operatively communicating the first space with a high pressure chamber of the common rail by an axial movement of the valve body, wherein the valve body and the armature are axially and movably held in the first space between the valve seat and the stator core. 
   The coil unit is detachably assembled to the valve unit and has a connector integrally formed with the electromagnetic coil; and a mounting member for detachably mounting the electromagnetic coil and the connector to the valve unit. 
   According to the above feature, the direction of the connector integrally formed with the electromagnetic coil can be adjusted, an air gap formed between the armature and the stator core is not changed, and it is not necessary to check the sealing performance again after the mounting member is loosened and tightened again. 
   Furthermore, the number of connecting portions can be reduced, because the connecting member is integrally formed with one of the valve housing and the stator core. 
   According to a still further feature of the present invention, a depressurizing valve is composed of a valve unit having a valve body; and a coil unit for attracting the valve body in a valve opening direction when electric current is supplied to a cylindrical electromagnetic coil. 
   The valve unit has a valve housing of a cylindrical shape to be mounted to a common rail; an armature integrally formed with the valve body; a first space formed in the valve housing and connected to a fuel return path for accommodating the valve body and the armature; and a second space formed in the valve housing for accommodating the electromagnetic coil, such that the electromagnetic coil is rotatable with respect to the valve housing in a circumferential direction, and the second space is coaxially formed with the first space. 
   The valve unit further has a stator core arranged in an inner peripheral space of the electromagnetic coil and axially opposing to the armature; a connecting member integrally formed with and arranged between the valve housing and the stator core, wherein the connecting member and the stator core divide an inside space of the valve housing into the first and second spaces, and wherein the connecting member restricts magnetic flux flow between the stator core and the valve housing; and a valve seat provided at one end of the first space and having a flow control port for operatively communicating the first space with a high pressure chamber of the common rail by an axial movement of the valve body, wherein the valve body and the armature are axially and movably held in the first space between the valve seat and the stator core. 
   The coil unit is detachably assembled to the valve unit and has a connector integrally formed with the electromagnetic coil; and a mounting member for detachably mounting the electromagnetic coil and the connector to the valve unit. 
   According to the above feature, the direction of the connector integrally formed with the electromagnetic coil can be likewise adjusted, an air gap formed between the armature and the stator core is not changed, and it is not necessary to check the sealing performance again after the mounting member is loosened and tightened again. 
   Furthermore, the first and second spaces can be fluid tightly separated without any connecting process, such as, the welding, soldering and the like, since the valve housing, the stator core and the connecting member are integrally formed as one unit. 
   According to an additional feature of the present invention, a recessed portion is formed in the stator core and opening to the first space, and a spring is arranged in the recessed portion for biasing the valve body in the valve closing direction. 
   According to such a feature, the spring is not dropped out from the valve unit, even when the coil unit is detached from the valve unit. 
   According to a further feature of the present invention, the coil unit has a plate member made of a magnetic material, which is arranged between the electromagnetic coil and the connector, and which is integrally molded with the connector. 
   As a result, any sealing member is not necessary for preventing water from entering into the electromagnetic coil, because the electromagnetic coil and the connector are integrally molded. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings: 
       FIG. 1  is a schematic diagram showing a system structure of a common rail type fuel injection device having a depressurizing valve; 
       FIG. 2  is a cross sectional view showing the depressurizing valve  9  in  FIG. 1 ; 
       FIG. 3  is an exploded cross sectional view of the depressurizing valve  9 ; 
       FIG. 4  is a cross sectional view showing the depressurizing valve  9  mounted to a common rail  1 ; 
       FIG. 5  is a cross sectional view showing a depressurizing valve according to a second embodiment; 
       FIG. 6  is a cross sectional view showing a depressurizing valve according to a third embodiment; 
       FIG. 7  is a cross sectional view showing a depressurizing valve according to a fourth embodiment; and 
       FIG. 8  is a cross sectional view showing a depressurizing valve according to a fifth embodiment. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   First Embodiment 
   A first embodiment of the present invention will be disclosed.  FIG. 1  is a schematic diagram showing a system structure of a common rail type fuel injection device having a depressurizing valve according to the first embodiment. The fuel injection device has a common rail  1 , which is formed into almost a cylindrical shape and in which a high-pressure fuel is stored. Multiple fuel injection valves  2  are connected to the common rail  1 , wherein the fuel injection valves  2  are mounted to respective engine cylinders of a diesel engine (not shown) so that the high pressure fuel stored in the common rail  1  is injected into the engine cylinders through the respective fuel injection valves  2 . A valve opening timing as well as a valve opening period for the respective fuel injection valves  2  is controlled by an electronic control unit (ECU) which is not shown in the drawing. 
   The ECU comprises a well known microcomputer having CPU, ROM, RAM and so on, and carries out various kinds of calculations and processes which are memorized in the microcomputer. The ECU controls respective operations of the fuel injection valves  2 , a fuel amount control valve  7 , a depressurizing valve  9 , and so on, upon receiving information, such as an engine rotational speed, a pedal stroke of an acceleration pedal (not shown), and so on. 
   The high pressure fuel is supplied from a fuel pump  3  to the common rail  1 , and the high pressure fuel is stored in a high pressure chamber  1   e  of the common rail  1  at such a pressure corresponding to a fuel injection pressure. A well known fuel pump of a variable capacitor type is used as the fuel pump  3 . The fuel is fed by a feed pump  5  from a fuel tank  4  to the fuel pump  3 , and the fuel is pressurized by the fuel pump  3 . The ECU receives a pressure signal from a pressure sensor  6  provided at the common rail  1 , and controls the fuel amount control valve  7  provided to the fuel pump  3 , such that the fuel injection pressure is adjusted at a predetermined value determined by an engine load and an engine rotational speed. 
   The common rail  1  is connected to the fuel tank  4  through a leak pipe  8 , which forms a fuel return path. The depressurizing valve  9  is attached at one longitudinal end of the common rail  1 , for opening and closing the fuel return path. The ECU controls the depressurizing valve  9  in accordance with the engine operational condition, such that the fuel pressure in the common rail  1  is adjusted at (reduced to) a target value by opening the depressurizing valve  9  to return a portion of the high pressure fuel from the common rail  1  to the fuel tank  4  through the fuel return path. 
   The depressurizing valve  9  will be further explained with reference to  FIGS. 2 to 4 .  FIG. 2  shows a cross sectional view of the depressurizing valve  9 ,  FIG. 3  shows an exploded view thereof, and  FIG. 4  shows the depressurizing valve  9  mounted to the common rail  1 . 
   The depressurizing valve  9  is composed of a valve unit  10  and a coil unit  30 , wherein the coil unit  30  is detachably assembled to the valve unit  10 . The valve unit  10  has a valve body  11  for opening and closing the fuel return path, whereas the coil unit  30  has a cylindrical coil  31  of an electromagnetic type for attracting the valve body  11  in a valve opening direction when the coil  31  is energized. 
   The valve unit  10  has a cylindrical valve housing  12  made of a magnetic metal and screwed into the common rail  1 . A first cylindrical space  121  and a second cylindrical space  122  are formed in the inside of the valve housing  12 , which are longitudinally connected to each other. The valve body  11  and an armature  13  are accommodated in the first cylindrical space  121 . The coil  31  of the coil unit  30  is accommodated in the second cylindrical space  122 , such that the coil  31  can rotate in a circumferential direction. 
   A cylindrical guide member  14  is press fitted into the first cylindrical space  121  for slidably supporting the valve body  11 . The armature is made of a magnetic metal and fixed to the valve body  11  by a press fit or a welding. 
   A valve seat  15  is fixed to one end of the valve housing  12  by the press-fit or caulking. The first cylindrical space  121  is operatively communicated with the inside of the common rail  1  through a flow control port  151  formed in the valve seat  15 . The first cylindrical space  121  is further communicated with a fuel return port  1   a  formed in the common rail  1  through a communication port  141  formed in the guide member  14  and a communication port  123  formed in the valve housing  12 . The fuel return port  1   a  is connected to the leak pipe  8 . 
   A first male screw portion  124  is formed at an outer peripheral surface of the valve housing  12 , such that the male screw portion  124  will be screwed into a female screw portion  1   b  formed in the common rail  1 . An annular groove  125  is also formed at the outer peripheral surface of the valve housing  12  between the first male screw portion  124  and the communication port  123 , for accommodating a sealing member  16 , such as an O-ring. A hexagon head portion  126  is further formed at a middle portion of the valve housing  12 , wherein the hexagon head portion  126  is positioned at an outside of the common rail  1  when the valve housing  12  is mounted (screwed) to the common rail  1 . A second male screw portion  127  is formed at a rear end of the valve housing  12 , which will be engaged with (screwed into) a retaining nut  34  (also referred to as a mounting member). 
   An annular connecting member  17 , made of a non-magnetic metal, is arranged a boundary portion between the first and second spaces  121  and  122 . A stator core  18  made of a magnetic metal is arranged in the second space  122 , such that the stator core  18  opposes to the armature  13 . The connecting member  17  is fluid-tightly fixed to the valve housing  12  and to the stator core  18  by welding, soldering and the like. The first and second spaces  121  and  122  are thus fluid-tightly separated by the connecting member  17  and the stator core  18 . 
   A recessed portion  181  opening to the first space  121  is formed in the stator core  18 . A spring  19  is arranged in the recessed portion  181 , so that the valve body  11  and the armature  13  are biased by the spring  19  in a direction toward the valve seat  15 , namely a valve closing direction. 
   The valve seat  15  is press-fitted into or fixed by caulking to the open end (the end of the left-hand side) of the valve housing  12 , after the valve body  11 , the armature  13 , the guide member  14  and the spring  19  are inserted into the first space  121 . As above, the valve body  11 , the armature  13 , and the spring  19  are held in the first space  121  between the valve seat  15  and the stator core  18 . 
   The coil unit  30  is composed of the coil  31 , a connector  32 , a plate  33 , and the retaining nut  34 , wherein the coil  31 , the plate  33  and a terminal  321  are integrally molded in the connector  32 . The plate  33  is arranged at a right-hand side of the coil  31 , and an outer peripheral portion of the plate  33  is projecting outwardly from the connector  32 . The terminal  321  is connected at its one end to the coil  31 . 
   The coil  31  is formed into a cylindrical shape. The coil  31  is accommodated in the cylindrical space formed by the valve housing  12 , the stator core  18  and the connecting member  17 , such that the coil  31  is rotatable in its circumferential direction. In other words, a circumferential position of the coil  31  with respect to the valve housing  12  can be freely selected. Accordingly, a direction of the terminal  321  of the connector  32  can be selectively decided. 
   The plate  33  is made of a magnetic metal and formed into a circular disc shape. The plate  33  is arranged to oppose to the valve housing  12  and the stator core  18 , to form a magnetic circuit together with the valve housing  12  and the stator core  18 . 
   The retaining nut (fixing means)  34  is composed of a cylindrical portion  342  and a flanged portion  343  inwardly extending from one longitudinal end of the cylindrical portion  342 . A female screw portion  341  is formed at an inner peripheral surface of the cylindrical portion  342 , such that the female screw portion  341  will be engaged with the second screw portion  127  formed at the valve housing  12 . The retaining nut  34  is assembled to the connector  32  after the coil  31  and the plate  33  are integrally molded in the connector  32 , such that an inner end of the flanged portion  343  holds the outer peripheral portion of the plate  33 , wherein the retaining nut  34  can be rotatable with respect to the connector  32 . 
   A process for assembling the depressurizing valve  9  to the common rail  1  will be explained. The coil unit  30  is at first tentatively assembled to the valve unit  10 . Namely, the coil  31  is inserted into the cylindrical second space  122 , and the retainer  34  is screwed onto the second screw portion  127  until the outer peripheral portion of the plate  33  is interposed between and held by the longitudinal end of the valve housing  12  and the flanged portion  343  of the retaining nut  34 . 
   Then, the male screw portion  124  of the valve housing  12  is screwed into the female screw portion  1   b  of the common rail  1 , to firmly fix the depressurizing valve  9  (more specifically, the valve housing  12 ) to the common rail  1 . In this screwed position of the valve housing  12 , a front surface  152  of the valve seat  15  is brought into contact with and pressed against a seal surface  1   c  of the common rail  1 , so that a space between the front surface  152  and the seal surface  1   c  is sealed. Further, the sealing member  16  is in contact with an inner peripheral sealing surface  1   d  of the common rail  1 , to prevent the fuel from leaking through a gap between the valve housing  12  and the common rail  1   
   Then, the retaining nut  34  is loosened from the valve housing  12  in order that the direction of the connector  32  is adjusted with respect to the common rail  1 . Thereafter, the retaining nut  34  is tightly screwed again to the valve housing  12 , to finish the process of assembling the depressurizing valve  9  to the common rail  1 . 
   In the above embodiment, the coil unit  30  is tentatively assembled to the valve unit  10 , and then the valve unit  10  is assembled to the common rail  1  together with the coil unit  30 . However, the valve unit  10  can be at first assembled to the common rail  1  without a tentative assembling of the coil unit  30 . In this case, the coil unit  30  will be firmly assembled to the valve unit  10 , after the valve unit  10  has been assembled to the common rail  1 . 
   In the above common rail type fuel injection device, electrical current supply to the coil  31  of the depressurizing valve  9  is cut off in the operational conditions of the vehicle other than a vehicle decelerating operation. Therefore, the valve body  11  and the armature  13  are biased by the spring toward the valve seat  15 , such that the valve body  11  is in contact with the valve seat  15  to close the flow control port  151 . As a result, the fuel return path is closed. 
   In the case that a pedal stroke of the acceleration pedal is rapidly decreased, namely in the deceleration of the vehicle, the ECU opens the depressurizing valve  9 , so that a portion of the high pressure fuel in the common rail  1  is drained to the fuel tank  4 . As a result, the fuel pressure in the common rail  1  is quickly decreased to a target pressure. 
   More exactly, when the electrical current is supplied to the coil  31  through the terminal  321  of the connector  32 , the magnetic flux is generated around the coil  31  to produce an attracting force between the stator core  18  and the armature  13 . Then, the armature  13  as well as the valve body  11  is displaced toward the stator core  18  against the spring force of the spring  19 . The valve body  11  is separated from the valve seat  15  to open the flow control port  151  of the valve seat. As a result, the high pressure fuel in the common rail  1  flows to the fuel tank  4  through the flow control port  151  of the valve seat  15 , the communication port  141  of the guiding member  14 , the communication port  123  of the valve housing  12 , the fuel return port  1   a  of the common rail  1 , and the leak pipe  8 . 
   In the above embodiment, the coil  31  is inserted into the second space  122  of the valve housing  12  such that the coil  31  is rotatable therein with respect to the valve housing  12 . Accordingly, the direction of the connector  32  integrally formed with the coil  31  can be adjusted. 
   Furthermore, in the above embodiment, the valve body  11  and the armature  13  are held by and between the valve seat  15  and the stator core  18 . Accordingly, even when the retaining nut  34  is loosened to adjust the direction of the connector  32 , an air gap between the armature  13  and the stator core  18  is not changed. 
   Furthermore, since the valve body  11 , the armature  13  and the spring  19  are held by and between the stator core  18  and the valve seat  15 , those parts  11 ,  13  and  19  may not be detached from the valve housing  12 , even when the coil unit  30  is disassembled from the valve unit  10 . 
   In addition, in the above embodiment, the first space  121  for the valve body  11  and the armature  13 , and the second space  122  for the coil  31  are fluid tightly sealed from each other by the connecting member  17  and the stator core  18 . Therefore, no additional sealing element (such as an O-ring) is necessary between the first and second spaces  121  and  122 . Furthermore, it is not necessary to check a seal performance after the retaining nut  34  is loosened and then screwed again. 
   The coil  31  is integrally molded in the connector  32 , it is not necessary to provide any sealing means for preventing water from entering into the coil. 
   Second Embodiment 
   A second embodiment of the present invention will be explained.  FIG. 5  shows a cross sectional view of the depressurizing valve according to the second embodiment. The same reference numerals are given to the same or similar parts to the first embodiment. 
   In the above first embodiment, the coil unit  30  is assembled to the valve unit  10  by the retaining nut  34 , wherein the female screw portion  341  of the retaining nut  34  is screwed with the male screw portion  127  of the valve housing  12 . The second embodiment differs from the first embodiment in the assembling method of the coil unit  30  to the valve unit  10 . 
   As shown in  FIG. 5 , a bolt  35  is used as a fixing means. More exactly, a female screw portion  182  is formed at the stator core  18 , a through hole  322  is formed in the connector  32  for inserting the bolt  35 , and a through hole  331  is formed in the plate  33  for also inserting a screwed portion of the bolt  35 . The bolt  35  can be formed as a hexagon head bolt, a bolt with a head having a hexagon recess, and so on. 
   The bolt  35  is screwed into the screw portion  182  to firmly hold the plate  33  between the stator core  18  and the head of the bolt  35 , so that the coil unit  30  is assembled to the valve unit  10 . 
   Third Embodiment 
   A third embodiment of the present invention will be explained.  FIG. 6  shows a cross sectional view of the depressurizing valve according to the third embodiment. The same reference numerals are given to the same or similar parts to the first embodiment. 
   In the first embodiment, the ring-shaped connecting member  17  is used for connecting the valve body  11  to the stator core  18 . According to the third embodiment, a pipe-shaped connecting member  17   a  having a thin wall is used. 
   If the connecting member  17  was made of the magnetic material in the first embodiment, the magnetic flux may not flow from the stator core  18  to the armature  13 , but flows from the stator core  18  to the valve housing  12  through the connecting member  17 . Then, the attracting force is not generated at the armature  13 . This is because the connecting member  17  must be made of the non-magnetic material in the first embodiment. 
   On the other hand, the connecting member  17   a  of the third embodiment is made of the magnetic material. As shown in  FIG. 6 , the connecting member  17   a  is formed into the pipe shape having a small thickness to make the flux flow area at a smaller amount, so that the magnetic flux flow is restricted between the stator core  18  and the valve housing  12 . As above, even when the magnetic material is used for the connecting member  17   a , the amount of the magnetic flux flowing through the connecting member  17   a  can be maintained at a smaller value, and the magnetic flux flows from the stator core  18  to the armature  13  to generate the attracting force. 
   As an alternative method for restricting the magnetic flux flow between the stator core  18  and the valve housing  12 , the connecting member  17  in the first embodiment as well as the connecting member  17   a  of the third embodiment is made of a stainless material having the magnetism, and the connecting member  17  or  17   a  is non-magnetized by a partial heat treatment or the like. 
   Fourth Embodiment 
   A fourth embodiment of the present invention will be explained.  FIG. 7  shows a cross sectional view of the depressurizing valve according to the fourth embodiment. The same reference numerals are given to the same or similar parts to the first embodiment. 
   As shown in  FIG. 7 , a connecting portion  17   b  of a thin wall is integrally formed with the stator core  18   b  made of the magnetic material. The connecting portion  17   b  is fluid tightly connected to the valve housing  12  by the welding, soldering or the like. 
   In the first to third embodiments, the connecting member  17  or  17   a  is connected to the valve housing  12  and to the stator core  18  by the welding, soldering and the like, namely at two boundaries between the connecting member  17  ( 17   a ) and the valve housing  12  and between the connecting member  17  ( 17   a ) and the stator core  18 . According to the fourth embodiment, however, the connecting portion  17   b  is connected at one boundary between the connecting portion  17   b  and the valve housing  12 , so that the number of process for the welding, soldering and the like can be reduced. 
   Alternatively, a cylindrical connecting portion of a thin wall may be integrally formed with the valve housing  12  made of the magnetic material, and the thin-walled connecting portion may be fluid tightly connected to the stator core  18  by the welding, soldering and the like. 
   Fifth Embodiment 
   A fifth embodiment of the present invention will be explained.  FIG. 8  shows a cross sectional view of the depressurizing valve according to the fifth embodiment. The same reference numerals are given to the same or similar parts to the first embodiment. 
   As shown in  FIG. 8 , a valve housing  12   c  and a stator core  18   c  is integrally formed into a unitary body made of the magnetic material, wherein the stator core  18   c  and the valve housing  12   c  are connected via a thin walled connecting portion  17   c . According to this embodiment, the first and second spaces  121  and  122  can be fluid tightly separated from each other without the connecting process by the welding, soldering or the like.