Patent Publication Number: US-2019195182-A1

Title: Fuel injection valve

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a Divisional of U.S. application Ser. No. 15/551,459, filed Aug. 16, 2017, which is the U.S. National Stage of International Application No. PCT/JP2016/053505, filed Feb. 5, 2016, and claims priority to Japanese Patent Application No. 2015-050291, filed Mar. 13, 2015, each of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a fuel injection valve that injects fuel. 
     BACKGROUND ART 
     As a background technique of this technical field, the fuel injection valve described in Japanese Laid-open Patent Application 2011-144731(Patent Document-1) is known. The known fuel injection valve of the publication is equipped with a needle valve that is connected to a movable core (movable iron core) by press fitting and welding (paragraph 0047). For communicating an internal space of the movable iron core with an internal space of the needle valve, a connected part between the movable iron core and the needled valve is formed with an inlet opening (paragraph 0044). In a shaft portion of the needle valve, there are formed both a communication hole and another communication hole that are respectively arranged in upstream and downstream sides with respect to a flow direction of fuel. The upstream-side communication hole comprises a plurality of circular openings that are formed near an end (upstream side end portion) of the shaft portion that is connected to the movable iron core. The downstream-side communication hole comprises a plurality of oval openings that are formed near an end (upstream side end portion) of the shaft portion that is sealed. The upstream-side communication hole and the downstream-side communication hole are so constructed that the interior of the shaft portion is communicated with an interior space that is formed in a nozzle holder and a nozzle body through which the needled valve is received (paragraph 0044). With this construction, fuel led into the fuel injection valve from a fuel inlet portion (fuel supply opening) is led into an inner circumference side of the movable iron core, the inlet opening and then into an inner circumference side of the shaft portion of the needle valve. The fuel led into the shaft portion is led into the space formed between the needle valve and a unit of the nozzle holder and nozzle body after passing through the upstream-side communication hole and the downstream-side communication hole (paragraph 0056). 
     In the fuel injection valve disclosed in Patent Document-1, the shaft portion is constructed of a cylindrical member and fuel in the shaft portion is led into the outside through the communication holes. In this case, however, the interior of the shaft portion tends to generate a dead fuel flow region (stagnation) and a part where the fuel flow speed is lowered. 
     In fuel injection valves, for dealing with a case in which a foreign thing is accidently mixed into a fuel flow passage of the fuel injection valve during the production process, the fuel injection valves produced are subjected to a running-in operation for discharging the foreign thing to the outside. Thus, if the above-mentioned dead fuel flow region (stagnation) and the lowered fuel speed region are present, discharging the foreign thing to the outside takes time and thus the running-in operation of the valves has to be carried out for a long time. Production efficiency is lowered as the running-in operation takes a longer time. Furthermore, energy and cleaning liquid consumed by the running-in operation are increased. 
     PRIOR ART DOCUMENT 
     Patent Document 
     Patent Document-1 : Japanese Laid-open Patent Application (tokkai) 2011-144731 
     SUMMARY OF INVENTION 
     An object of the present invention is to provide a fuel injection valve that is able to discharge a foreign thing to the outside with a shorter running-in operation time even if the foreign thing has been mixed into the fuel flow passage of the fuel injection valve at the production process. 
     In order to achieve the above-mentioned object, the present invention provides a fuel injection valve which comprises a valve seat and a valve body, which cooperate with each other to open and close a fuel passage, a movable element having the valve body provided at one end thereof and having a fuel passage formed therein, a valve seat member having the valve seat formed thereon, an upstream-side communication hole located upstream of the flow of fuel and connecting the inside and outside of the movable element and a downstream-side communication hole located downstream of the flow of fuel and connecting the inside and outside of the movable element, wherein a guide section of the valve body, where the valve seat member and the valve body are in sliding contact with each other, is provided downstream of the downstream-side communication hole and wherein a fuel passage for connecting the upstream side and downstream side of the guide section in the center axis direction is provided at the same angular position in the circumferential direction of the movable element as the downstream-side communication hole. 
     In order to achieve the above-mentioned object, the present invention provides a fuel injection valve which includes a valve seat and a valve body that cooperate with each other to open and close a fuel passage and an electromagnetic drive section that drives the valve body, in which the electromagnetic drive section includes a fixed iron core and a movable iron core that is fixed to the valve body to drive the valve body in the open/close direction with the aid of magnetic attraction force generated between the fixed iron core and the movable iron core, and in which the valve body and the movable iron core are connected through a rod portion that has a fuel passage formed therein, and in which the rod portion is provided with an upstream-side communication hole that is located upstream of the flow of fuel and connects the inside and outside of the rod portion, and a downstream-side communication hole that is located downstream of the flow of fuel and connects the inside and outside of the rod portion; and an area ratio ((S 1 +S 2 )/S 3 ) wherein S 1  is a sectional area of the upstream-side communication hole, S 2  is a sectional area of the downstream-side side communication hole and S 3  is a sectional area of a fuel passage provided in an inlet part of a fuel passage formed in the rod portion is smaller than 3.5. 
     According the present invention, due to provision of the communication holes formed in the movable element, the flow speed of fuel that flows from the inside of the movable element to the outside of the same can be increased. Thus, even if a foreign thing is mixed into the fuel passage, the foreign thing can be speedily discharged from the fuel passage and thus, the running-in operation time of the vehicle can be shortened. 
     Other effects of the present invention will be described in the explanation of embodiments. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a vertically sectional view of an embodiment of a fuel injection valve of the present invention, which is provided by vertically sectioning the valve along a valve shaft axis (center axis line). 
         FIG. 2  is an enlarged sectional view of a portion in the vicinity of a nozzle part  8  shown in  FIG. 1 . 
         FIG. 3  is an enlarged sectional view of a portion in the vicinity of a movable element  27 . 
         FIG. 4  is an analysis diagram showing the flow speed variation that appears at respective outlet portions of communication holes  27   boa  and  27   bob  when the ratio ((S 1 +S 2 )/S 3 ) between the sum (S 1 +S 2 ) of the sectional area S 1  of an upstream-side communication hole  27   boa  and the sectional area S 2  of a downstream-side communication hole  27   bob  and the sectional area S 3  of an open portion  27   af  through which a movable iron core  27   a  is communicated with a rod portion  27   b  is varied. 
         FIG. 5  is an analysis diagram showing a flow speed distribution that appears when the area ratio ((S 1 +S 2 )/S 3 ) is 3.0, 7.5 or 12.0. 
         FIG. 6  is an analysis diagram showing the flow speed variation that appears at the respective outlet portions of the communication holes  27   boa  and  27   bob  when the ratio (S 1 /S 2 ) between the sectional area S 1  of the upstream-side communication hole  27   boa  and the sectional area S 2  of the downstream-side communication hole  27   bob  is varied. 
         FIG. 7  is an analysis diagram showing flow speed distribution that appears when the area ratio (S 1 /S 2 ) is 0.3, 1.0 or 1.6. 
         FIG. 8  is a sectional view of an internal combustion engine that has a fuel injection valve  1  mounted thereon. 
         FIG. 9  is an analysis diagram showing a performance of an comparative example with respect to the fuel flow speed distribution appearing near the rod portion  27   b.    
     
    
    
     EMBODIMENT OF INVENTION 
     In the following, an embodiment of the present invention will be described with reference to  FIGS. 1 to 3 . 
     An entire construction of a fuel injection valve  1  will be described with reference to  FIG. 1 .  FIG. 1  is a vertically sectional view of an embodiment of the fuel injection valve of the present invention, which is provided by vertically sectioning the valve along a valve shaft axis (center axis line). It is to be noted that the center axis line  1   a  is matched with an axis (valve axis) of a movable element  27  that has a valve body  27   c , a rod portion (connecting portion)  27   b  and a movable iron core  27   a  integrally provided thereto, and the center axis line is matched with the central axis line of a cylindrical body  5 . 
     In the following, an upper end portion (upper end side) of the fuel injection valve  1  shown in  FIG. 1  will be sometimes called as a base end portion (base end side), and a lower end portion (lower end side) of the valve  1  will be sometimes called as a top end portion (top end side). Naming of the base end portion (base end side) and the top end portion (top end side) is based on a direction in which fuel flows or a mounting structure of the fuel injection valve  1  relative to a fuel piping. Upper and lower relation terms used in the specification are based on  FIG. 1 , and thus, such upper and lower relation terms have no connection with upper and lower relation terms that are used in an actual structure in which the fuel injection valve  1  is mounted in the internal combustion engine. 
     In the fuel injection valve  1 , there is provided, by a cylindrical body  5  of metal, a fuel passage (fuel flow passage)  3  that extends generally along a center axis line  1   a.  The cylindrical body  5  is made of a metallic material such as magnetic stainless steel or the like, and produced through press working such as deep draw processing or the like, so that the produced cylindrical body has a stepped portion in a direction along the center axial line  1   a . With this, the diameter of the base end portion of the cylindrical body  5  is larger than that of the top end portion of the same. 
     The base end portion of the cylindrical body  5  is formed with a fuel inlet opening  2  and a fuel filter  13  is fitted to the fuel inlet opening  2  to remove foreign matter mixed into fuel. 
     The base end portion of the cylindrical body  5  is radially outwardly expanded to form a flange portion (radially outwardly expanded portion)  5   d , and an O-ring  11  is put in an annular recessed portion (annular groove portion) provided between the flange portion  5   d  and a base end side end portion  47   a  of a cover  47 . 
     The top end portion of the cylindrical body  5  is provided with a valve portion  7  that includes a valve body  27   c  and a valve seat member  15 . The valve seat member  15  is inserted into the top end side of the cylindrical body  5  and secured to the cylindrical body  5  by laser welding  19 . The laser welding  19  is applied to the whole periphery of the outer cylindrical surface of the cylindrical body  5  from an outer circumference side. If desired, the valve seat member  15  may be secured to the cylindrical body  5  by laser welding after the valve seat member  15  is pressed into the top end side of the cylindrical body  5 . 
     In a middle portion of the cylindrical body  5 , there is arranged a drive section  9  for driving the valve body  27   c . The drive section  9  is constituted by an electromagnetic actuator (electromagnetic drive section). More specifically, the drive section  9  is constructed by using a fixed iron core  25  that is fixed to an interior (inner circumference side) of the cylindrical body  5 , a movable element (movable member)  27  that is arranged inside the cylindrical body  5  at the top end side relative to the fixed iron core  25  and movable in a direction along the center axis line  1   a , an electromagnetic coil  29  that is mounted around the cylindrical body  5  at a position where the fixed iron core  25  and a movable iron core  27   a  provided by the movable element  27  face each other with a fine gap δ 1  kept therebetween, and a yoke  33  that covers the electromagnetic coil  29  from an outer circumference side of the electromagnetic coil  29 . 
     Within the cylindrical body  5 , there is installed the movable element  27 . The cylindrical body  5  faces or surrounds an outer cylindrical surface of the movable iron core  27   a  to form a housing that covers the movable iron core  27   a.    
     The movable iron core  27   a , the fixed iron core  25  and the yoke  33  constitute a closed magnetic circuit through which a magnetic flux flows when the electromagnetic coil  29  is energized. The magnetic flux is able to pass through the fine gapδ 1 . However, in order to reduce a leakage flux flowing in the cylindrical body  5  at the position where the fine gapδ 1  is provided, a non-magnetic section or a weak magnetic section  5   c  that is weaker in magnetism than other parts of the cylindrical body  5  is provided at a position corresponding to the fine gapδ 1  of the cylindrical body  5 . In the following explanation, the non-magnetic section or the weak magnetic section  5   c  will be called just non-magnetic section  5   c . The non-magnetic section  5   c  can be produced by applying a non-magnetizing treatment to the cylindrical body  5  that is magnetized. For such non-magnetizing treatment, heat treatment can be used. Or, by providing the outer cylindrical surface of the cylindrical body  5  with an annular recess at the portion corresponding to the non-magnetic section  5   c , such non-magnetic section  5   c  can be produced. 
     The electromagnetic coil  29  is wound around a bobbin  31  that is made of resin and cylindrically shaped, and the bobbin is disposed around the cylindrical body  5 . The electromagnetic coil  29  is electrically connected to terminals  43  provided in a connector  41 . To the connector  41 , there is connected an external drive circuit, so that a drive current is applied to the electromagnetic coil  29  through the terminals  43 . 
     The fixed iron core  25  is made of a magnetic metallic material. The fixed iron core  25  is shaped cylindrical and has a through hole  25   a  that passes and extends through a central portion in a direction along the center axis line  1   a . The fixed iron core  25  is press-fitted to a base end side of a smaller diameter portion  5   b  of the cylindrical body  5  and positioned at a middle portion of the cylindrical body  5 . Since a larger diameter portion  5   a  is provided at the base end side of the smaller diameter portion  5   b , assembling work for the fixed iron core  25  is facilitated. The fixed iron core  25  may be fixed to the cylindrical body  5  by welding, or fixed to the cylindrical body  5  by both of welding and press-fitting. 
     The movable element  27  is constructed by using the movable iron core  27   a , the rod portion (connecting portion)  27   b  and the valve body  27   c . The movable iron core  27   a  is of an annular member. The valve body  27   c  is a member contactable with the valve seat  15   b  (see  FIG. 2 ). The valve seat  15   b  and the valve body  27   c  cooperate with each other to open and close a fuel passage. The rod portion  27   b  has a slender cylindrical shape and constitutes a connecting portion through which the movable iron core  27   a  and the valve body  27   c  are connected. The movable iron core  27   a  is connected to the valve body  27   c  to constitute a member that drives the valve body  27   c  in open/close direction by using a magnetic attraction force applied between the movable iron core and the fixed iron core  25 . 
     In this embodiment, the rod portion  27   b  and the valve body  27   c  are constructed by different materials and the valve body  27   c  is connected to the rod portion  27   b . The connection between the rod portion  27   b  and the valve body  27   c  is made through press-fitting or welding. If desired, the rod portion  27   b  and the valve body  27   c  may be integrally constructed by one member. 
     The rod portion  27   b  is shaped cylindrically and has a hole  27   ba  that extends therein in an axial direction to be exposed to the outside through an opening at the upper end of the rod portion  27   b . The rod portion  27   b  is formed with connection openings (open portions)  27   boa  and  27   bob  each connecting the inside and outside of the rod portion. Between the outer cylindrical surface of the rod portion  27   b  and the inner cylindrical surface of the cylindrical body  5 , there is defined a back pressure chamber  37 . An upper end portion  27   bc  of the rod portion  27   b  is inserted into a through hole  25   a  of the fixed iron core  25 , and the fuel passage  3  in the through hole  25   a  is connected to the back pressure chamber  37  through the hole  27   ba  and the connection openings  27   boa  and  27   bob . The hole  27   ba  and the connection openings  27   boa  and  27   bob  constitute the fuel passage  3  through which the fuel passage  3  in the through hole  25   a  and the back pressure chamber  37  are connected or communicated. 
     The through hole  25   a  of the fixed iron core  25  is provided with a coil spring  39 . One end of the coil spring  39  is in contact with a spring seat  27   ag  that is provided inside the movable iron core  27   a . The other end of the coil spring  39  is in contact with an adjuster (adjusting element)  35  that is arranged inside the through hole  25   a  of the fixed iron core  25 . The coil spring  39  is arranged to be compressed between the spring seat  27   ag  provided by the movable iron core  27   a  and a lower end (top end side end surface) of the adjuster (adjusting element)  35 . 
     The coil spring  39  serves as a biasing member that biases the movable element  27  in a direction (valve close direction) to cause the valve body  27   c  to contact the valve seat  15   b  (see  FIG. 2 ). By adjusting the position of the adjuster  35  in the through hole  25   a  in a direction along the center axis line  1   a , the biasing force applied from the coil spring  39  to the movable element  27 , which is a mover element having magnetic material can be adjusted. 
     The adjuster  35  is formed with a fuel passage  3  that passes through a center portion thereof in a direction along the center axis line  1   a . Fuel supplied from the fuel inlet opening  2  flows in the fuel passage  3  of the adjuster  35 , then flows in the fuel passage  3  of the top end side portion of the through hole  25   a  of the fixed iron core  25 , and then flows in the fuel passage  3  provided by the movable element  27 . 
     The yoke  33  is made of a magnetic metallic material and serves both as yoke and a housing of the fuel injection valve  1 . The yoke  33  is shaped like a stepped cylindrical member including a larger diameter portion  33   a  and a smaller diameter portion  33   b . The larger diameter portion  33   a  is shaped cylindrical to cover an outer cylindrical surface of the electromagnetic coil  29  and has at the top end side thereof the smaller diameter portion  33   b  whose diameter is smaller than that of the larger diameter portion  33   a . The smaller diameter portion  33   b  is press-fitted to or tightly disposed on the smaller diameter portion  5   b  of the cylindrical body  5 . With this, the inner cylindrical surface of the smaller diameter portion  33   b  is intimately contact with the outer cylindrical surface of the cylindrical body  5 . Under this condition, at least one part of the inner cylindrical surface of the smaller diameter portion  33   b  faces the outer cylindrical surface of the movable iron core  27   a  through the cylindrical body  5 , and thus, the magnetic resistance of magnetic path produced at the opposed portions is reduced. 
     The top end side end portion of the yoke  33  is formed at its outer cylindrical surface with an annular recessed portion  33   c  that extends in a circumferential direction. At a thin wall part provided behind a bottom surface of the annular recessed portion, the yoke  33  and the cylindrical body  5  are joined to each other by laser welding all over the circumference. 
     Onto the top end portion of the cylindrical body  5 , there is disposed a cylindrical protector  49  that has a flange part  49   a  formed thereon, and thus the top end portion of the cylindrical body  5  is protected by the protector  49 . The protector  49  covers an upper part of a laser weld portion  24  of the yoke  33 . 
     The flange part  49   a  of the protector  49 , the diameter smaller portion  33   b  of the yoke  33  and a step surface defined between the larger and smaller diameter portions  33   a  and  33   b  of the yoke  33  constitute an annular groove  34  into which an O-ring  46  is received. At the time when the fuel injection valve  1  is going to be fitted to the internal combustion engine, the O-ring  46  serves as a sealing means that effects a liquid tight and airtight function against an annular space defined between an inner cylindrical surface of a valve mounting hole formed in the internal combustion engine and the outer cylindrical surface of the smaller diameter portion  33   b  of the yoke  33 . 
     A given area of the fuel injection valve  1  from a middle portion thereof to a portion near the base end side thereof is covered with a molded resin cover  47 . A top end side end portion of the resin cover  47  covers a part of the base end side of the larger diameter portion  33   a  of the yoke  33 . By the resin that forms the resin cover  47 , the connector  41  is integrally formed or provided. 
     In the following, construction of the nozzle part  8  will be described in detail with reference to  FIG. 2 .  FIG. 2  is an enlarged sectional view of a portion in the vicinity of the nozzle part  8  shown in  FIG. 1 . 
     The valve seat member  15  is formed with a through hole  15   d ,  15   c ,  15   v  and  15   e  that extends or penetrates in a direction along the center axis line  1   a . This through hole has at a part thereof a conical surface  15   v  whose diameter reduces as approaching toward the downstream side. The conical surface  15   v  forms thereon the valve seat  15   b , and when the valve body  27   c  is released from and put on the valve seat  15   b , the fuel passage is opened and closed. In the following explanation, the conical surface  15   v  forming the valve seat  15   b  may be called as a valve seat surface. The valve seat  15   b  and a portion of the valve body  27   c  that contacts the valve seat  15   b  are called as a seal portion. 
     An upper hole portion  15   d ,  15   c  and  15   v , which is placed above the conical surface  15   v  in the through hole  15   d ,  15   c ,  15   v  and  15   e , forms a valve body receiving hole for holding the valve body  27   c . An inner cylindrical surface of the valve body receiving hole is formed with a guide surface  15   c  for guiding the valve body  27   c  to move in a direction along the center axis line  1   a . The guide surface  15   c  is one of two guide surfaces that guide the movement of the movable element  27 , and the guide surface  15   c  serves as a downstream side guide surface placed at a downstream side. 
     The downstream side guide surface  15   c  and a slide surface  27   cb  of the valve body  27   c  that slides on the downstream side guide surface  15   c  constitute a downstream side guide portion  50 A that guides displacement or movement of the movable element  27 . 
     At an upstream side of the guide surface  15   c , there is provided a conical surface  15   d  whose diameter increases as approaching toward the upstream side. By the presence of the conical surface  15   d , assembling work for the valve body  27   c  is facilitated and enlargement of sectional area of the fuel passage is assured. A lower end portion of the valve body receiving hole  15   d ,  15   c  and  15   v  is connected to a fuel introducing hole  15   e , and a lower end surface of the fuel introducing hole  15   e  is exposed to a top end surface  15   t  of the valve seat member  15 . 
     To the top end surface  15   t  of the valve seat member  15 , there is connected a nozzle plate  21   n . The nozzle plate  21   n  is fixed to the valve seat member  15  by laser welding  23 . The laser weld portion  23  extends around an injection hole forming area to enclose fuel injection openings  110  provided within the injection hole forming area. 
     The nozzle plate  21   n  is constructed of a plate member (flat plate) of uniform thickness and has at its central portion a projected portion  21   na  that projects outward. The projected portion  21   na  is shaped by a curved surface (for example, spherical surface). Inside the projected portion  21   na , there is defined a combustion chamber  21   a . The combustion chamber  21   a  is connected to the fuel introducing hole  15   e  formed in the valve seat member  15 , so that fuel is supplied to the combustion chamber  21   a  through the fuel introducing hole  15   e.    
     The projected portion  21   na  is formed with the plurality of fuel injection openings  110 . Each of the fuel injection openings  110  can employ any form. For example, each fuel injection opening may have at an upstream part thereof a swirling chamber for providing fuel with swirling power. A center axis line  110   a  of each fuel injection opening may be in parallel with the center axis line  1   a  of the fuel injection valve, or the center axis line  110   a  may be inclined relative to the line  1   a . Furthermore, the projected portion  21   na  may be of a type that has no projected portion. 
     In the embodiment, the valve portion  7  that opens and closes the fuel injection openings  110  comprises the valve seat member  15  and the valve body  27   c , and a fuel injection portion that decides the form of fuel spray comprises the nozzle plate  21   n . The valve portion  7  and the fuel injection portion constitute a nozzle portion  8  that makes a fuel injection. That is, in the nozzle portion  8  of the embodiment, the nozzle plate  21   n  is connected to a top end surface  15   t  of a body side (valve seat member  15 ) of the nozzle portion  8 . 
     Furthermore, in the embodiment, the valve body  27   c  is a ball valve having a spherical shape. Accordingly, a portion of the valve body  27   c , which faces the guide face  15   c , is formed with a plurality of circumferentially spaced cut surfaces  27   ca  by which a fuel passage  15   h  (see  FIG. 3 ) is formed. The valve body  27   c  may be constructed of a valve body other than the ball body. For example, needle valve is usable. 
     A construction in the vicinity of the movable element  27  will be described in detail with reference to  FIG. 3 .  FIG. 3  is an enlarged sectional view of a portion in the vicinity of the movable element  27 . 
     In the embodiment, the movable iron core  27   a  and the rod portion  27   b  are integrally constructed from one member. A central portion of an upper end surface  27   ab  of the movable iron core  27   a  is formed with a recessed portion  27   aa  that is recessed downward. At a bottom of the recessed portion  27   aa , there is formed a valve seat  27   ag  by which one end of a coil spring  39  is supported. Furthermore, at the bottom of the recessed portion  27   aa , there is provided an open portion  27   af  that communicates with the interior of the rod portion  27   b . The open portion  27   af  constitutes a fuel passage that allows fuel, which has come to a space  27   ai  in the recessed portion  27   aa  from the through hole  25   a  of the fixed iron core  25 , to flow to a space  27   bi  in the rod portion  27   b.    
     Although, in the embodiment, the rod portion  27   b  and the movable iron core  27   a  are integrally constructed from one member, they may be constructed from separate members and thereafter they may be integrally connected to each other. 
     The upper end surface  27   ab  of the movable iron core  27   a  is a surface that faces a lower end surface  25   b  of the fixed iron core  25 . The upper end surface  27   ab  and the lower end surface  25   b  respectively constitute magnetic attracting surfaces against which magnetic attracting force is applied respectively. An outer cylindrical surface  27   ac  of the movable iron core  27   a  is constructed to slide on an inner cylindrical surface  5   e  of the cylindrical body  5 . The inner cylindrical surface  5   e  constitutes an upstream side guide surface, and the outer cylindrical surface  27   ac  slides on the upstream side guide surface  5   e . The upstream side guide surface  5   e  and the outer cylindrical surface  27   ac  of the movable iron core  27   a  constitute an upstream side guide portion  50 B that guides displacement or movement of the movable element  27 . 
     The movable element  27  is guided by two points that are the upstream side guide portion  50 B and the afore-mentioned downstream side guide portion  50 A, and moved forward and backward along the center axis line  1   a.    
     As is mentioned hereinabove, the rod portion  27   b  is formed with the communication holes  27   boa  and  27   bob  through which the inside and outside of the rod portion  27   b  are communicated. The communication hole  27   boa  is provided at an upper part of the rod portion  27   b  and arranged near the movable iron core  27   a . The communication hole  27   bob  is provided at a lower part of the rod portion  27   b  and arranged near the valve body (seal portion)  27   c . In the embodiment, the communication holes  27   boa  and  27   bob  are provided to suppress generation of a dead fuel flow region (stagnation) that would appear near the rod portion  27   b  of the movable element  27 . 
     In the following, a fuel flow appearing near the rod portion  27   b  will be described with reference to a comparative example of  FIG. 9 .  FIG. 9  is an analysis diagram showing a performance of the comparative example with respect to the fuel flow speed distribution appearing near the rod portion  27   b . In  FIG. 9 , there are shown a sectional view taken along the line A-A that passes through the communication holes  27   bo  and another sectional view taken along the line B-B that is perpendicular to the line A-A and does not pass through the communication holes  27   bo . It is to be noted that the communication holes  27   bo  are respectively provided at two positions of the rod portion  27   b  that are spaced from each other by 180 degrees in a circumferential direction. 
     In the comparative example, the rod portion  27   b  is formed at a middle part thereof with an axially extending communication hole (open portion)  27   bo . However, in this case, the outer cylindrical surface side of the rod portion  27   b  tends to generate a dead fuel flow region (upper dead fuel flow region) at an area between the lower end portion of the movable iron core  27   a  and an upper end portion of the communication hole  27   bo . The dead fuel flow region extends to an upper area of the communication hole  27   bo . Furthermore, in the inner cylindrical surface side (inside) of the rod portion  27   b , the lower end part of the rod portion  27   b  to which the valve body  27   c  constituting the seal portion is connected tends to generate a dead fuel flow region (lower dead fuel flow region). 
     Such dead fuel flow regions are caused by a stagnation of fuel flow produced when the fuel flow speed becomes very slow. In order to wash foreign things away from the dead fuel flow region with the slow speed fuel flow, it takes time. Accordingly, it is desirable to suppress generation of the dead fuel flow region or minimize area of the dead fuel flow region as small as possible. 
     Accordingly, in the embodiment, in order to suppress generation of the upper dead fuel flow region and lower dead fuel flow region or minimize the area of the upper dead fuel flow region and lower dead fuel flow region, communication holes are grouped into two, one being arranged at an upper end side of the rod portion  27   b  and the other being arranged at a lower end side of the rod portion  27   b . That is, the communication holes are divided into at least two and respectively arranged at axially spaced two portions of the rod portion  27   b . One (the upstream-side communication hole  27   boa ) of the two portions is positioned in the vicinity of the lower end portion of the movable iron core  27   a  (the upper end portion of the rod portion  27   b ), and the other one (the downstream-side communication hole  27   bob ) of the two portions is positioned in the vicinity of the valve body  27   c  (the lower end portion of the rod portion  27   b ). For example, the upstream-side communication hole  27   boa  is so arranged that an upper end portion of the hole  27   boa  is not placed apart from the lower end portion of the movable iron core  27   a  by a distance longer than an inner diameter of the rod portion  27   b . Furthermore, the downstream-side communication hole  27   bob  is so arranged that the lower end portion of the hole  27   bob  is not placed apart from the lower end of the rod portion  27   b  by a distance longer than the inner diameter of the rod portion  27   b.    
     The downstream side guide portion  50 A is formed with the fuel passage  15   h  that extends in the direction of the center axis line  1   a  to communicate the upstream side of the guide portion with the downstream side of the same. The fuel passage  15   h  is defined between the cut surfaces  27   ca  of the valve body  27   c  and the inner cylindrical surface (downstream side guide surface)  15   c  of the valve body receiving hole formed in the valve seat member  15 . The fuel passage  15   h  is arranged in the same angular position as the downstream-side communication hole  27   bob  with respect to a circumferential direction of the movable element  27  or the rod portion  27   b . A center axis line of the downstream-side communication hole  27   bob  and a center axis line of the cut surfaces  27   c  are parallel with each other and present in a single virtual plane. The center axis line  1   a  is also present in the virtual plane. 
     With the above-mentioned arrangement, fuel led into the back pressure chamber  37  from the downstream-side communication hole  27   bob  can smoothly flow into the fuel passage  15   h  formed in the downstream side guide portion  50 A. Thus, the fuel flow speed can be increased at the outlet portion of the downstream-side communication hole  27   bob , and thus, generation of dead fuel flow region can be suppressed. 
     Furthermore, a sectional area (opening area) S 1  of the upstream-side communication hole  27   boa  and a sectional area (opening area) S 2  of the downstream-side communication hole  27   bob  are so set as to increase the flow speed of fuel that flows in the vicinity of the rod portion  27   b . In the following, the results of analyzing the fuel flow in the vicinity of the rod portion  27   b  will be explained with reference to  FIGS. 4 to 7 . 
       FIG. 4  is an analysis diagram showing the flow variation that appeared at respective outlet portions of the communication holes  27   boa  and  27   bob  when the ratio ((S 1 +S 2 )/S 3 ) between the sum (S 1 +S 2 ) of the sectional area S 1  of the upstream-side communication hole  27   boa  and the sectional area S 2  of the downstream-side communication hole  27   bob  and the sectional area S 3  of the open portion  27   af  through which the movable iron core  27   a  is communicated with the rod portion  27   b  is varied. 
     The sectional area S 3  is a sectional area of the open portion  27   af  through which the movable iron core  27   a  is fluidly communicated with the rod portion  27   b . The sectional area S 3  is a sectional area of a fuel passage provided at an inlet part of the fuel passage  3  formed in the rod portion  27   b . In case where the fuel passage provided in the inner cylindrical portion  27   bs  is divided into a plurality of fuel passages, the sectional area S 3  is a total sum of the sectional areas of the plurality of fuel passages. The sectional area S 3  is a sectional area of a fuel passage that supplies the fuel which flows from the upstream-side communication hole  27   boa  and the downstream-side communication hole  27   bob.    
     In the embodiment, the upstream-side communication hole  27   boa  comprises two openings that are spaced from each other by 180 degrees in a circumferential direction of the rod portion  27   b . The sectional area S 1  of the upstream-side communication hole  27   boa  is the sum of the sectional areas of the two openings of the hole  27   boa . The downstream-side communication hole  27   bob  comprises two openings that are spaced from each other by 180 degrees in the circumferential direction of the rod portion  27   b . The sectional area S 2  of the downstream-side communication hole  27   bob  is the sum of the sectional areas of the two openings of the hole  27   bob.    
     As is seen from  FIG. 4 , in a range where the area ratio ((S 1 +S 2 )/S 3 ) is smaller than 4.0, the fuel flow speed at the outlet portions of the communication holes  27   boa  and  27   bob  increases as the sectional ratio becomes small. When the area ratio ((S 1 +S 2 )/S 3 ) is equal to or larger than 4.0, the fuel flow speed at the outlet portions of the communication holes  27   boa  and  27   bob  becomes generally constant and shows a value smaller than the value appearing when the sectional ratio ((S 1 +S 2 )/S 3 ) is smaller than 4.0. 
       FIG. 5  is an analysis diagram showing a flow speed distribution that appeared when the area ratio ((S 1 +S 2 )/S 3 ) is 3.0, 7.5 or 12.0. Also in  FIG. 5 , like in  FIG. 9 , there is shown the flow speed distribution with respect to a sectional view taken along the line A-A and another sectional view taken along the line B-B. 
     When the area ratio ((S 1 +S 2 )/S 3 ) is 3.0, the lower side of the lower end face of the movable iron core  27   a  has no portion where the fuel flow speed is lowered to such a degree as to generate the dead fuel flow region in both the area of the sectional view of the line A-A and the area of the sectional view of the line B-B. As is mentioned in the description of  FIG. 4 , we consider that the fuel flow speed is increased at the outlet portions of the communication holes  27   boa  and  27   bob.    
     While, when the area ratio ((S 1 +S 2 )/S 3 ) is 7.5 or 12.0, the lower side of the lower end face of the movable iron core  27   a  has therearound a portion where the fuel flow speed is reduced to such a degree as to generate the dead fuel flow region in both the area of the sectional view of the line A-A and the area of the sectional view of the line B-B. We consider that generation of such dead fuel flow region is caused by a lowered fuel flow speed at the outlet portions of the communication holes  27   boa  and  27   bob.    
     When the area ratio ((S 1 +S 2 )/S 3 ) is 7.5, the opening area of the upstream-side communication hole  27   boa  is the same as that provided when the area ratio ((S 1 +S 2 )/S 3 ) is 3.0, and the opening area of the downstream-side communication hole  27   bob  is increased. In this case, the dead fuel flow region appears at a downstream side of the upstream-side communication hole  27   boa.    
     While, when the area ratio ((S 1 +S 2 )/S 3 ) is 12.0, the opening area of the downstream-side communication hole  27   bob  is the same as that provided when the area ratio ((S 1 +S 2 )/S 3 ) is 7.5, and the opening area of the upstream-side communication hole  27   boa  is increased. In this case, the dead fuel flow region appears at a side area of the upstream-side communication hole  27   boa . This may be because the fuel flow has a larger speed component in the axial direction of the rod portion  27   b , the fuel flow is discharged from a lower portion of the enlarged upstream side-communication hole  27   boa  and the discharging position of the fuel flow from the upstream-side communication hole  27   boa  is shifted toward the lower end side of the rod portion  27   b . Furthermore, it is considered that since the opening area of the downstream-side communication hole  27   bob  is increased, the fuel flow in the rod portion  27   b  toward the lower end portion thereof is easily made. 
     As is mentioned hereinabove, by setting the area ratio ((S 1 +S 2 )/S 3 ) to a range smaller than 4.0, it is possible to increase the fuel speed at the outlet portions of the communication holes  27   boa  and  27   bob . With this, it is possible to suppress generation of the dead fuel flow region in the vicinity of the rod portion  27   b.    
     It is to be noted that the lower limit value of the area ratio ((S 1 +S 2 )/S 3 ) is affected by a sectional area of a fuel passage that is provided at a downstream side of the upstream-side and downstream-side communication holes  27   boa  and  27   bob . In general, the fuel injection amount is decided by both the area of an annular space defined between the valve body  27   c  and the valve seat  15   b  and the total sectional area of the fuel injection hole. The area of the annular space defined between the valve body  27   c  and the valve seat  16   b  or the total sectional area of the fuel injection hole is the smallest in the fuel passage defined by the fuel injection valve. Thus, it is necessary to make the opening area (S 1 +S 2 ) of the communication holes  27   boa  and  27   bob  larger than the area of the annular space between the valve body  27   c  and the valve seat  15   b  and the total sectional area of the fuel injection hole. Thus, the opening area (S 1 +S 2 ) of the communication holes  27   boa  and  27   bob  is set larger than the area of the annular space defined between the valve body  27   c  and the valve seat  15   b  and the total sectional area of the fuel injection hole. By using the opening area (S 1 +S 2 ) thus set, the lower limit value of the area ratio ((S 1 +S 2 )/S 3 ) is decided. 
     Both the area (S 1 +S 2 ) and the area S 3  of the fuel passage are larger than the area of the annular space defined between the valve body  27   c  and the valve seat  15   b  and the total sectional area of the fuel injection hole. Accordingly, the lower limit valve of the area ratio ((S 1 +S 2 )/S 3 ) has a chance to be smaller than 1 (one). However, in order to smooth the flow out of fuel from the communication holes  27   boa  and  27   bob  by removing a pressure loss appearing at the rod portion  27   b , it is preferable to set the area ratio ((S 1 +S 2 )/S 3 ) to a value that is 1 (one) or larger than 1 (one). 
       FIG. 6  is an analysis diagram showing the flow speed variation that appears at the respect outlet portions of the communication holes  27   boa  and  27   bob  when the ratio (S 1 /S 2 ) between the sectional area S 1  of the upstream-side communication hole  27   boa  and the sectional area S 2  of the downstream-side communication hole  27   bob  is varied. 
     When the area ratio (S 1 /S 2 ) between the sectional area S 1  of the upstream-side communication hole  27   boa  and the sectional area S 2  of the downstream-side communication hole  27   bob  is 1.0, the fuel flow at the respective outlet portions of the communication holes  27   boa  and  27   bob  shows the highest speed. Then, by using a speed value (0.9m/s) in  FIG. 4 , which appears at the outlet portion of the upstream side-communication hole  27   boa  when the area ratio ((S 1 +S 2 )/S 3 ) is 4.0, as a reference, an allowable range of the area ratio (S 1 /S 2 ) is set. That is, by using the upstream-side communication hole  27   boa  where the fuel flow speed is lower than that of the downstream-side communication hole  27   bob  as a reference, a range where the fuel flow speed at the outlet portion of the upstream-side communication hole  27   boa  is higher than 0.9 m/s is set to the allowable range. 
     In the embodiment, the area ratio (S 1 /S 2 ) is set to a range or value that larger than 0.5 and smaller than 1.6. With this setting, it is possible to set both the sectional area S 1  of the upstream-side communication hole  27   boa  and the sectional area S 2  of the downstream-side communication hole  27   bob  in such a manner that the fuel flow speed at the respective outlet portions of the communication holes  27   boa  and  27   bob  shows a value near its maximum value and is set in a suitable range where generation of the dead fuel flow region is suppressed. 
       FIG. 7  is an analysis diagram showing flow speed distribution that appears when the area ratio (S 1 /S 2 ) is 0.3. 1.0 or 1.6. Also in  FIG. 7 , like in  FIG. 9 , there is shown the flow speed distribution with respect to a sectional view taken along the line A-A and another sectional view taken along the line B-B. 
     When the area ratio (S 1 /S 2 ) is 1.0, the lower side of the lower end face of the movable iron core  27   a  has no portion where the fuel flow speed is lowered to such a degree as to generate the dead fuel flow region in both the area of the sectional view of the line A-A and the area of the sectional view of the line B-B. 
     While, when the area ratio (S 1 /S 2 ) is 0.3, the lower side of the lower end face of the movable iron core  27   a  has therearound a portion where the fuel flow speed is reduced to such a degree as to generate the dead fuel flow region in both the area of the sectional view of the line A-A and the area of the sectional view of the line B-B. While, when the area ratio (S 1 /S 2 ) is 1.6, the lower side of the lower end face of the movable iron core  27   a  has a small portion where the fuel flow speed is reduced to generate the dead fuel flow region. We consider that generation of the dead fuel flow region in the case where the area ratio (S 1 /S 2 ) is 0.3 or 1.6 is caused by the fuel flow whose speed is reduced at the outlet portions of the communication holes  27   boa  and  27   bob.    
     In the embodiment, the area ratio ((S 1 +S 2 )/S 3 ) is set to a range smaller than 4.0 and the area ratio (S 1 /S 2 ) is set to a range larger than 0.5 and smaller than 1.6, so that the fuel flow speed at the outlet portions of the communication holes  27   boa  and  27   bob  can be increased. Thus, generation of dead fuel flow region near the rod portion  27   b  can be suppressed. 
     It is to be noted that the number of the upstream-side communication hole (holes)  27   boa  and the number of the downstream-side communication hole (holes)  27   bob  are not limited to two. That is, one or three and more are usable. However, when only one hole is provided in place of the two holes as each of the communication holes  27   boa  and  27   bob , a dead fuel flow region tends to be generated at a position that is spaced from the hole by 180 degrees in a circumferential direction. Accordingly, if possible, two or more communication holes  27   boa  and  27   bob  that are equally spaced from one another in a circumferential direction should be provided. 
     In the following, an internal combustion engine to which the fuel injection valve of the present invention is practically mounted will be explained with reference to  FIG. 8 .  FIG. 8  is a sectional view of the internal combustion engine to which the fuel injection valve  1  is practically mounted. 
     An engine block  101  of the internal combustion engine  100  is formed with cylinders  102 . Each cylinder  102  is formed at a head portion thereof with an intake port  103  and an exhaust port  104 . The intake port  103  is equipped with an intake valve  105  that opens and close the intake port  103 , and the exhaust port  104  is equipped with an exhaust valve  106  that opens and closes the exhaust port  104 . To an inlet side end portion  107   a  of an intake passage  107  that is formed in the engine block  101  and communicated with the intake port  103 , there is fixed an intake pipe  108 . 
     To a fuel supply opening  2  (see  FIG. 1 ) of the fuel injection valve  1 , there is connected a fuel line  111 . 
     The intake pipe  108  is formed with a mounting portion  109  to which the fuel injection valve  1  is mounted, and the mounting portion  109  is formed with an insertion hole  109   a  into which the fuel injection valve  1  is inserted. The insertion hole  109   a  extends to an inner wall surface (intake passage), so that fuel injected from the fuel injection valve  1  inserted in the insertion hole  109   a  is injected into the intake passage. If the internal combustion engine is of a two directional spray type, the engine block  101  is formed with two intake ports  103  and fuel injections from respective fuel injection valves are directed toward the intake ports  103  (intake valves  105 ). 
     As is described hereinabove, by suitably arranging the communication holes  27   boa  and  27   bob  and making the opening area of the communication holes  27   boa  and  27   bob  to a suitable size, the flow speed of fuel that flows out from the interior of the rod portion  27   b  to the outside of the same through the communication holes  27   boa  and  27   bob  can be increased, and thus, generation of dead fuel flow region in the vicinity of the rod portion  27   b  can be suppressed. Thus, even if a foreign thing is mixed into fuel in the fuel flow passage  3 , the foreign thing can be speedily removed from fuel flow passage  3 , and the time for running-in operation can be shortened. 
     The present invention is not limited to the above-mentioned embodiment. Deletion of part of the construction and addition of part to the construction are possible in the invention.