Patent Publication Number: US-7581711-B2

Title: Electromagnetic fuel injection valve

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a National Stage entry of International Application No. PCT/JP2005/010652, filed Jun. 10, 2005, the entire specification claims and drawings of which are incorporated herewith by reference. 
     TECHNICAL FIELD 
     The present invention relates to an electromagnetic fuel injection valve that includes a valve housing formed from a valve seat member having a valve seat and a cylindrical magnetic body having a front end thereof coaxially connected to the valve seat member, a valve assembly formed from a valve body housed in the valve housing so that the valve body can be seated on the valve seat and a movable core coaxially connected to the valve body with the rear end face of the movable core as a movable side attracting face, the valve assembly being spring-biased in a direction that seats the valve body on the valve seat, a cylindrical non-magnetic body having the front end thereof coaxially joined to the rear end of the cylindrical magnetic body so as to surround a part of the movable core, and a fixed core that has at a front end thereof a fixed side attracting face facing the movable side attracting face and has a front portion thereof fitted into and fixed to a rear portion of the cylindrical non-magnetic body. 
     BACKGROUND ART 
     Such an electromagnetic fuel injection valve is already known form, for example, Patent Document 1.
     Patent Document 1:   

     Japanese Patent Application Laid-open No. 2000-8990 
     DISCLOSURE OF THE INVENTION 
     Problem To Be Solved By the Invention 
     However, in the above-mentioned conventional arrangement, the movable core is provided with an annular sliding-contact projection, which is in sliding contact with an inner face of the cylindrical non-magnetic body, a side gap between the cylindrical magnetic body and the movable core is relatively large, it cannot be said that the efficiency with which magnetic flux is passed is excellent, and it cannot be said that the valve-opening responsiveness is excellent. 
     The present invention has been accomplished under the above-mentioned circumstances, and it is an object thereof to provide an electromagnetic fuel injection valve that has enhanced efficiency in passing magnetic flux between a movable core and a cylindrical magnetic body and an improved valve-opening responsiveness. 
     Means For Solving the Problem 
     In order to attain these objects, in accordance with a first aspect of the present invention, there is provided an electromagnetic fuel injection valve comprising: a valve housing comprising a valve seat member having a valve seat and a cylindrical magnetic body having a front end thereof coaxially connected to the valve seat member; a valve assembly comprising a valve body housed in the valve housing so that the valve body can be seated on the valve seat and a movable core coaxially connected to the valve body with a rear end face of the movable core as a movable side attracting face, the valve assembly being spring-biased in a direction that seats the valve body on the valve seat; a cylindrical non-magnetic body having the front end thereof coaxially joined to the rear end of the cylindrical magnetic body so as to surround a part of the movable core; and a fixed core having at a front end thereof a fixed side attracting face facing the movable side attracting face and having a front portion thereof fitted into and fixed to a rear portion of the cylindrical non-magnetic body; characterized in that the movable core comprises a tubular sliding portion having an outer peripheral face that is in sliding contact with an inner peripheral face of a rear portion of the cylindrical magnetic body over a predetermined length along the axis of the cylindrical magnetic body, a rear tubular opposing portion that has the movable side attracting face at a rear end thereof, is connected coaxially and integrally to the rear end of the tubular sliding portion, and has the outer periphery thereof facing the inner periphery of the cylindrical magnetic body, and a front tubular opposing portion that has the outer periphery thereof facing the inner periphery of the cylindrical magnetic body and is connected coaxially and integrally to the front end of the tubular sliding portion, and when the diameter of the rear tubular opposing portion is D 1 , the diameter of the front tubular opposing portion is D 2 , and the diameter of the tubular sliding portion is D 3 , they are set so that D 1 &lt;D 2 &lt;D 3 . 
     Further, in addition to the arrangement of the first aspect, in accordance with a second aspect of the present invention, there is provided an electromagnetic fuel injection valve, wherein the predetermined length is set to be equal to or less than 1 mm. 
     In addition to the arrangement of the first or second aspect, in accordance with a third aspect of the present invention, there is provided an electromagnetic fuel injection valve, wherein the diameter D 1  of the rear tubular opposing portion, the diameter D 2  of the front tubular opposing portion, and the diameter D 3  of the tubular sliding portion are set so as to satisfy (D 3 −D 2 )/(D 3 −D 1 )≦0.5. 
     In addition to the arrangement of any one of the first to third aspect, in accordance with a fourth aspect of the present invention, there is provided an electromagnetic fuel injection valve, wherein the movable side attracting face is formed at the rear end of the rear tubular opposing portion at substantially right angles to the outer peripheral face of the rear tubular opposing portion, and when the diameter of the fixed side attracting face is D 4 , it is set so that D 1 ≦D 4 . 
     Furthermore, in addition to the arrangement of any one of the first to fourth aspect, in accordance with a fifth aspect of the present invention, there is provided an electromagnetic fuel injection valve, wherein the movable core and the valve body are formed integrally from a high hardness ferrite magnetic material, the cylindrical magnetic body is formed from a high hardness ferrite magnetic material, and a journal portion provided in the valve body is slidably fitted into an inner peripheral face of the valve seat member 
     Effect of the Invention 
     In accordance with the arrangement of the first aspect of the present invention, since the tubular sliding portion of the movable core is in sliding contact with the inner peripheral face of the cylindrical magnetic body over the predetermined length along the axis of the cylindrical magnetic body, a side gap between the movable core and the cylindrical magnetic body becomes substantially ‘0’ in part and, furthermore, since the diameter D 1  of the rear tubular opposing portion, which forms part of the movable core so that the outer periphery of the rear tubular opposing portion faces the inner periphery of the cylindrical non-magnetic body, is smaller than the diameter D 2  of the front tubular opposing portion, which forms part of the movable core so that the outer periphery of the front tubular opposing portion faces the inner periphery of the cylindrical magnetic body, it is possible to enhance the efficiency of passing magnetic flux between the movable core and the cylindrical magnetic body and improve the valve-opening responsiveness. 
     Furthermore, in accordance with the arrangement of the second aspect of the present invention, the tubular sliding portion is in sliding contact with the inner peripheral face of the rear portion of the cylindrical magnetic body over the relatively short length of equal to or less than 1 mm, thereby reducing to a low level the magnetic holding power generated between the cylindrical magnetic body and the movable core after stopping energization, and it is thus possible to avoid a deterioration in the valve-closing responsiveness. Moreover, the length of the front tubular opposing portion is made relatively long, thus making it easy to maintain a constant side gap between the front tubular opposing portion and the cylindrical magnetic body, and it is thereby possible to prevent variations in individual performance from being caused and to avoid as far as possible variations in the side gap affecting the valve-closing responsiveness. 
     In accordance with the arrangement of the third aspect of the present invention, the distance between the front tubular opposing portion and the cylindrical magnetic body is set to be no more than half the distance between the rear tubular opposing portion and the cylindrical non-magnetic body so that the outer periphery of the front tubular opposing portion is made closer to the inner periphery of the cylindrical magnetic body, and it is thereby possible to yet further enhance the valve-opening responsiveness. 
     In accordance with the arrangement of the fourth aspect of the present invention, the magnetic flux can be passed between the fixed core and the movable core efficiently even when the axis of the movable core is eccentric to the axis of the fixed core, thus utilizing the area of the movable side attracting face effectively and thereby enhancing the attracting force with which the movable core is attracted to the fixed core. 
     Moreover, in accordance with the arrangement of the fifth aspect of the present invention, since the integral movable core and valve body and the cylindrical magnetic body are formed from a high hardness ferrite magnetic material, it is unnecessary to subject the movable core and the cylindrical magnetic body to a surface treatment such as chromium plating, and no non-magnetic film that would be formed by the surface treatment is formed; it is therefore possible to yet further enhance the efficiency with which the magnetic flux is passed between the movable core and the cylindrical magnetic body, enhance the attracting force for the movable core, and markedly improve the valve-opening responsiveness, and this is advantageous in terms of production cost. Moreover, since the valve assembly is in sliding contact at two axially separated positions with the valve seat member and the cylindrical magnetic body, which form the valve housing, it is possible to prevent as far as possible the axis of the valve assembly from tilting within the valve housing, thus enabling a small and substantially uniform side gap to be set along the entire periphery between the movable core and the cylindrical magnetic body, the efficiency of passing the magnetic flux to be enhanced, and the valve-opening responsiveness to be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a vertical sectional view of an electromagnetic fuel injection valve (first embodiment). 
         FIG. 2  is an enlarged view of a part shown by arrow  2  in  FIG. 1  (first embodiment). 
     
    
    
     DESCRIPTION OF THE REFERENCE NUMERALS AND CHARACTERS 
     
         
           8  valve housing 
           9  cylindrical magnetic body 
           10  valve seat member 
           13  valve seat 
           17  valve assembly 
           18  movable core 
           18   a  tubular sliding portion 
           18   b  rear tubular opposing portion 
           18   c  front tubular opposing portion 
           20  valve body 
           20   a  journal portion 
           22  fixed core 
           26  cylindrical non-magnetic body 
           41  movable side attracting face 
           42  fixed side attracting face 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     A mode for carrying out the present invention is explained below by reference to one embodiment of the present invention shown in the attached drawings. 
     Embodiment 1 
     One embodiment of the present invention is explained by reference to  FIG. 1  and  FIG. 2 ; firstly in  FIG. 1  an electromagnetic fuel injection valve for injecting fuel into an engine (not illustrated) includes a valve section  5  in which a valve body  20  is housed within a valve housing  8  having a valve seat  13  at the front end thereof, the valve body  20  being spring-biased in a direction that seats the valve body  20  on the valve seat  13 , a solenoid section  6  in which a coil assembly  24  is housed in a solenoid housing  25  provided so as to be connected to the valve housing  8 , the coil assembly  24  being capable of exhibiting an electromagnetic force for operating the valve body  20  so as to make it separate from the valve seat  13 , and a synthetic resin covering section  7  having an integral coupler  40 , connecting terminals  38  connected to a coil  30  of the coil assembly  24  facing the coupler  40 , and at least the coil assembly  24  and the solenoid housing  25  being embedded in the covering section  7 . 
     The valve housing  8  is formed from a cylindrical magnetic body  9  made of a magnetic metal and a valve seat member  10  that is joined in a liquid-tight manner to the front end of the cylindrical magnetic body  9 . The valve seat member  10  is welded to the cylindrical magnetic body  9  in a state in which a rear end portion of the valve seat member  10  is fitted into a front end portion of the cylindrical magnetic body  9 , and this valve seat member  10  is coaxially provided with a fuel outlet hole  12  opening on the front end face thereof, a tapered valve seat  13  connected to the inner end of the fuel outlet hole  12 , and a guide hole  14  connected to a large diameter portion at the rear end of the valve seat  13  so as to guide the valve body  20 . An injector plate  16  made of a steel plate is welded in a liquid-tight manner along its entire periphery to the front end of the valve seat member  10 , the injector plate  16  having a plurality of fuel injection holes  15  communicating with the fuel outlet hole  12 . 
     The solenoid section  6  includes a movable core  18 , a cylindrical fixed core  22  facing the movable core  18 , a return spring  23  exhibiting a spring force that urges the movable core  18  away from the fixed core  22 , a coil assembly  24  disposed so as to surround a rear portion of the valve housing  8  and the fixed core  22  while being capable of exhibiting an electromagnetic force that allows the movable core  18  to be attracted to the fixed core  22  side against the spring force of the return spring  23 , and a solenoid housing  25  surrounding the coil assembly  24  so that a front end portion of the solenoid housing  25  is connected to the valve housing  8 . 
     The movable core  18  is slidably fitted into the rear portion within the valve housing  8 , and the movable core  18  is coaxially connected to the valve body  20 , which can be seated on the valve seat  13  so as to block the fuel outlet hole  12 , thus forming a valve assembly  17 . In this embodiment, the valve assembly  17  is formed from the movable core  18 , a valve shaft  19  connected integrally to the movable core  18 , and the valve body  20  formed integrally with the front end of the valve shaft  19 , a through hole  21  is formed coaxially in this valve assembly  17 , the through hole  21  communicating with the interior of the valve housing  8  and having a bottomed shape with its front end blocked, and the valve assembly  17  is urged by the return spring  23  in a direction that seats the valve body  20  on the valve seat  13 . 
     Referring in addition to  FIG. 2 , the rear end of the cylindrical magnetic body  9  of the valve housing  8  is coaxially joined to the front end of the fixed core  22  via a cylindrical non-magnetic body  26 , which is made of a non-magnetic material or a material that is more weakly magnetic than that of the fixed core  22 , that is, a non-magnetic metal such as stainless steel in this embodiment, the rear end of the cylindrical magnetic body  9  is butt-welded to the front end of the cylindrical non-magnetic body  26 , and the rear end of the cylindrical non-magnetic body  26  is welded to the fixed core  22  in a state in which a front end portion of the fixed core  22  is fitted into the cylindrical non-magnetic body  26 . 
     A tubular retainer  27  is coaxially press-fitted into the fixed core  22 , the tubular retainer  27  having one slit  27   a  extending in the axial direction and having a substantially C-shaped cross-section, and the return spring  23  is disposed between the retainer  27  and the movable core  18 . In order to avoid the movable core  18  from being in direct contact with the fixed core  22 , a ring-shaped stopper  28  made of a non-magnetic material is press-fitted into the inner periphery of a rear end portion of the movable core  18  so that the ring-shaped stopper  28  projects slightly from a rear end face of the movable core  18  toward the fixed core  22 . Furthermore, the coil assembly  24  is formed by winding a coil  30  around a bobbin  29  surrounding a rear portion of the valve housing  8 , the cylindrical non-magnetic body  26 , and the fixed core  22 . 
     The solenoid housing  25  is formed from a cylindrical magnetic frame  31  and a flange portion  22   a , the cylindrical magnetic frame  31  being made of a magnetic metal in a cylindrical shape having at one end thereof an annular end wall  31   a  facing an end portion of the coil assembly  24  on the valve section  5  side and surrounding the coil assembly  24 , the flange portion  22   a  protruding radially outward from a rear end portion of the fixed core  22  and facing an end portion of the coil assembly  24  on the side opposite to the valve section  5 , and the flange portion  22   a  being magnetically coupled to the other end portion of the magnetic frame  31 . Moreover, a tubular mating portion  31   b  is coaxially provided on the inner periphery of the end wall  31   a  of the magnetic frame  31 , the cylindrical magnetic body  9  of the valve housing  8  being fitted into the tubular mating portion  31   b , and the solenoid housing  25  is provided so as to be connected to the valve housing  8  by fitting the valve housing  8  into the tubular mating portion  31   b.    
     A cylindrical inlet tube  33  is integrally and coaxially connected to the rear end of the fixed core  22 , and a fuel filter  34  is mounted on a rear portion of the inlet tube.  33 . Moreover, a fuel passage  35  is coaxially provided in the inlet tube  33 , the retainer  23 , and the fixed core  22 , the fuel passage  35  communicating with the through hole  21  of the movable core  18 . 
     The covering section  7  is formed so as to embed not only the solenoid housing  25  and the coil assembly  24  but also a part of the valve housing  8  and a majority of the inlet tube  33  while filling in a gap between the solenoid housing  25  and the coil assembly  24 , and a cutout portion  36  is provided in the magnetic frame  31  of the solenoid housing  25 , the cutout portion  36  allowing an arm portion  29   a formed integrally with the bobbin  29  of the coil assembly  24  to be disposed outside the solenoid housing  25 . 
     The coupler  40  is provided integrally with the covering section  7 , the connecting terminals  38  connected to opposite ends of the coil  30  of the coil assembly  24  facing the coupler  40 , the base end of the connecting terminal  38  being embedded in the arm portion  29   a , and coil ends  30   a  of the coil  30  being welded to the connecting terminals  38 . 
     The covering section  7  is formed from a first resin molded layer  7   a  covering the solenoid housing  25  and forming part of the coupler  40 , and a second resin molded layer  7   b  covering the first resin molded layer  7   a . The first resin molded layer  7   a  on the extremity side relative to a middle portion of the coupler  40  is not covered by the second resin molded layer  7   b  but exposed to the outside, a rear portion of the inlet tube  33  is not covered by the second resin molded layer  7   b  but exposed to the outside and, furthermore, a portion of the first resin molded layer  7   a  corresponding to a rear portion of the valve housing  8  is not covered by the second resin molded layer  7   b  but exposed to the outside. Endless engagement channels  48  and  49  are formed in portions of the first resin molded layer  7   a  corresponding to the middle portion of the coupler  40  and the rear portion of the valve housing  8 , end portions of the second resin molded layer  7   b  being engaged with the engagement channels  48  and  49 , and an endless engagement channel  50  is provided on the outer periphery of a middle portion of the inlet tube  33 , an end portion of the second resin molded layer  7   b  being engaged with the engagement channel  50 . That is, the end portions of the second covering section  7   b  are made to interlock with the first covering section  7   a  and the inlet tube  33  via concavo-convex engagement. 
     In  FIG. 2 , the front end of the cylindrical non-magnetic body  26  is coaxially joined by butt-welding to the rear end of the cylindrical magnetic body  9  of the valve housing  8  so as to surround a part of the movable core  18 , which has a rear end face thereof as a movable side attracting face  41 , and a front portion of the fixed core  22 , which has a front end face thereof as a fixed side attracting face  42 , is fitted into and fixed to a rear portion of the cylindrical non-magnetic body  26  so that the fixed side attracting face  42  faces the movable side attracting face  41 . 
     The front portion of the fixed core  22  is coaxially provided with a small diameter mating portion  22   b  forming, on the outer peripheral side, an annular step portion  43  facing forward so that the front end of the small diameter mating portion  22   b  forms the fixed side attracting face  42 , and this small diameter mating portion  22   b  is fitted into the rear portion of the cylindrical non-magnetic body  26  until the. step portion  43  abuts against the rear end of the cylindrical non-magnetic body  26  while a portion of the small diameter mating portion  22   b  corresponding to the fixed side attracting face  42  is in intimate contact with the inner periphery of a middle portion of the cylindrical non-magnetic body  26 , and in this state the fixed core  22  is fixed by welding to the cylindrical non-magnetic body  26 . 
     Moreover, provided on the inner face of the cylindrical non-magnetic body  26  is an annular depression  44  having a flat portion  44   a  that is flush with the outer periphery of the fixed side attracting face  42  of the fixed core  22 , thus forming an annular chamber  45  between the annular depression  44  and the outer periphery of a rear portion of the movable core  18 . 
     Furthermore, a center hole  46  is formed in the inner periphery of the cylindrical non-magnetic body  26  forward of the annular depression  44 , the center hole  46  having an inner diameter that is larger than the outer diameter of the fixed side attracting face  42 , and the inner periphery of the cylindrical magnetic body  9  is provided with a guide hole  47  that has a larger diameter than that of the guide hole  14  of the valve seat member  10  so that the guide hole  47  is flush with the center hole  46 . 
     On the other hand, the movable side attracting face  41 , which has substantially the same outer diameter as that of the fixed side attracting face  42 , is formed on the rear end face of the movable core  18 , and this movable core  18  is formed from a tubular sliding portion  18   a  having an outer peripheral face that is in sliding contact with an inner face of the guide hole  47 , which is an inner peripheral face of the rear portion of the cylindrical magnetic body  9 , over a predetermined length L along the axis of the cylindrical magnetic body  9 , a rear tubular opposing portion  18   b  that has the movable side attracting face  42  at its rear end, is connected coaxially and integrally to the rear end of the tubular sliding portion  18   a , and has the outer periphery thereof facing the inner periphery of the cylindrical non-magnetic body  26 , and a front tubular opposing portion  18   c  that has the outer periphery thereof facing the inner periphery of the guide hole  47 , which is the inner periphery of the cylindrical magnetic body  9 , and is connected coaxially and integrally to the front end of the tubular sliding portion  18   a.    
     Moreover, when the diameter of the rear tubular opposing portion  18   b  is D 1 , the diameter of the front tubular opposing portion  18   c  is D 2 , and the diameter of the tubular sliding portion  18   a  is D 3 , they are set so that D 1 &lt;D 2 &lt;D 3 , and the predetermined length L is set to be equal to or less than 1 mm. 
     Furthermore, D 1  to D 3  are set so as to satisfy (D 3 −D 2 )/(D 3 −D 1 )≦0.5, and in order to satisfy this condition (D 3 −D 2 ) is for example 0.036 to 0.056 mm, and (D 3 −D 1 ) is for example 0.086 to 0.112 mm. By so doing, the difference in level between the outer periphery of the front tubular opposing portion  18   c  and the outer periphery of the tubular sliding portion  18   a  is 0.018 to 0.028 mm whereas the difference in level between the outer periphery of the rear tubular opposing portion  18   b  and the outer periphery of the tubular sliding portion  18   a  is 0.043 to 0.056 mm, and the distance between the front tubular opposing portion  18   c  and the cylindrical magnetic body  9  is no more than half the distance between the rear tubular opposing portion  18   b  and the cylindrical non-magnetic body  26 . 
     Furthermore, the movable side attracting face  42  is formed at the rear end of the rear tubular opposing portion  18   b  at substantially right angles to the outer peripheral face of the rear tubular opposing portion  18   b , and when the diameter of the fixed side attracting face  42  at the front end of the fixed core  22  is D 4 , it is set so that D 1 ≦D 4 . 
     Moreover, the valve assembly  17  formed integrally from the movable core  18  and valve body  20 , and the cylindrical magnetic body  9  are formed from a high hardness ferrite magnetic material, and the valve body  20  is provided with a journal portion  20   a  that is fitted slidably into the inner peripheral face of the valve seat member  10 , that is, the guide hole  14 . 
     The operation of this embodiment is now explained. The movable core  18  is formed from the tubular sliding portion  18   a , which has the outer peripheral face that is in sliding contact with the inner peripheral face of the rear portion of the cylindrical magnetic body  9  over the predetermined length L along the axis of the cylindrical magnetic body  9 , the rear tubular opposing portion  18   b , which has the movable side attracting face  42  at its rear end, is connected coaxially and integrally to the rear end of the tubular sliding portion  18   a , and has the outer periphery thereof facing the inner periphery of the cylindrical non-magnetic body  26 , and the front tubular opposing portion  18   c , which has the outer periphery thereof facing the inner periphery of the cylindrical magnetic body  9  and is connected coaxially and integrally to the front end of the tubular sliding portion  18   a , and when the diameter of the rear tubular opposing portion  18   b  is D 1 , the diameter of the front tubular opposing portion  18   c  is D 2 , and the diameter of the tubular sliding portion  18   a  is D 3 , they are set so that D 1 &lt;D 2 &lt;D 3 . 
     In accordance with the movable core  18  having such a shape, the tubular sliding portion  18   a  is in sliding contact with the inner peripheral face of the cylindrical magnetic body  9  over the predetermined length L along the axis of the cylindrical magnetic body  9 , a side gap between the movable core  18  and the cylindrical magnetic body  9  thus becomes substantially ‘0’ in part and, furthermore, since the diameter D 1  of the rear tubular opposing portion  18   b , which forms part of the movable core  18  so that the outer periphery thereof faces the inner periphery of the cylindrical non-magnetic body  26 , is smaller than the diameter D 2  of the front tubular opposing portion  18   c , which forms part of the movable core  18  so that the outer periphery thereof faces the inner periphery of the cylindrical magnetic body  9 , it is possible to enhance the efficiency of passing magnetic flux between the movable core  18  and the cylindrical magnetic body  9  and improve the valve-opening responsiveness. 
     Furthermore, since the predetermined length L is set to be equal to or less than 1 mm, the tubular sliding portion  18   a  is in sliding contact with the inner peripheral face of the rear portion of the cylindrical magnetic body  9  over the relatively short length of equal to or less than 1 mm, thereby reducing to a low level the magnetic holding power generated between the cylindrical magnetic body  9  and the movable core  18  after stopping energization, and it is thus possible to avoid a deterioration in the valve-closing responsiveness. Moreover, the length of the front tubular opposing portion  18   c  is made relatively long, thus making it easy to maintain a constant side gap between the front tubular opposing portion  18   c  and the cylindrical magnetic body  9 , and it is thereby possible to prevent variations in individual performance from being caused and to avoid as far as possible variations in the side gap affecting the valve-closing responsiveness. 
     Furthermore, since the diameter D 1  of the rear tubular opposing portion  18   b , the diameter D 2  of the front tubular opposing portion  18   c , and the diameter D 3  of the tubular sliding portion  18   a  are set so as to satisfy (D 3 −D 2 )/(D 3 −D 1 )≦0.5, the distance between the front tubular opposing portion  18   c  and the cylindrical magnetic body  9  is made to be no more than half the distance between the rear tubular opposing portion  18   b  and the cylindrical non-magnetic body  26 , thus enabling the outer periphery of the front tubular opposing portion  18   c  to be made closer to the inner periphery of the cylindrical magnetic body  9  and thereby yet further improving the valve-opening responsiveness. 
     Furthermore, since the movable side attracting face  41 , which faces the fixed side attracting face  42  at the front end of the fixed core  22 , is formed at the rear end of the rear tubular opposing portion  18   b  at substantially right angles to the outer peripheral face of the rear tubular opposing portion  18   b , and when the diameter of the fixed side attracting face  42  is D 4 , it is set so that D 1 ≦D 4 , the magnetic flux is passed between the fixed core  22  and the movable core  18  efficiently even when the axis of the movable core  18  is eccentric to the axis of the fixed core  22 , thus enabling the area of the movable side attracting face  41  to be utilized effectively and thereby enhancing the attracting force with which the movable core  18  is attracted to the fixed core  22 . 
     Moreover, since the movable core  18  and the valve body  20  are formed integrally from a high hardness ferrite magnetic material and the cylindrical magnetic body  9  is formed from a high hardness ferrite magnetic material, it is unnecessary to subject the movable core  18  and the cylindrical magnetic body  9  to a surface treatment such as chromium plating, and no non-magnetic film that would be formed by the surface treatment is formed; it is thus possible to yet further enhance the efficiency with which the magnetic flux is passed between the movable core  18  and the cylindrical magnetic body  9 , enhance the attracting force for the movable core  18 , and markedly improve the valve-opening responsiveness, and this is advantageous in terms of production cost. 
     Moreover, since the valve assembly  17  is in sliding contact at two axially separated positions with the valve seat member  10  and the cylindrical magnetic body  9 , which form the valve housing  8 , as a result of the journal portion  20   a  provided on the valve body  20  being slidably fitted into the inner peripheral face of the valve seat member  10 , the axis of the valve assembly  17  can be prevented as far as possible from tilting within the valve housing  8 , thus enabling a small and substantially uniform side gap to be set along the entire periphery between the movable core  18  and the cylindrical magnetic body  9 , the efficiency in passing the magnetic flux to be enhanced, and the valve-opening responsiveness to be improved. 
     An embodiment of the present invention is explained above, but the present invention is not limited to the above-mentioned embodiment and can be modified in a variety of ways without departing from the spirit and scope of the present invention described in the claims.