Patent Abstract:
A solenoid valve is provided which may be used to inject fuel into an internal combustion engine for automotive vehicles. The solenoid valve includes an armature and stator attracting the armature to open a fluid passage. The solenoid valve also includes a retaining nut and an end body. The retaining nut engages a housing to retain a hollow cylindrical stator casing in the housing. The end body is joined to the casing in alignment therewith to hold the stator within the casing without subjecting the stator to the pressure produced by the engagement of the retaining nut with the housing. This minimizes undesirable loads on the stator.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     The present invention relates generally to a solenoid valve and a fuel injector which may be used to inject fuel into an internal combustion engine for automotive vehicles, and more particularly to an improved structure of a solenoid valve designed to minimizing undesirable loads on parts of the solenoid valve and a fuel injector using the same. 
     2. Background Art 
     In general, solenoid valves are used in fuel injectors of internal combustion engines. Such solenoid valves are designed to magnetically energize a stator installed in a housing to attract an armature, lifting up a valve member to open a valve hole. A maximum amount of lift of the valve member is fixed upon installation of the stator within the housing. For example, Japanese Patent First Publication No. 10-122086 discloses such a solenoid valve. FIG. 6 shows one example of conventional solenoid valves for use in fuel injectors. The shown solenoid valve is constructed to be installed in a holder body  113  of a fuel injector. A control valve  106  is press fit within an armature  105 . The control valve  106  is disposed slidably in a bearing  110  and moved to open a valve hole  108  formed in a plate  111  when the armature  105  is attracted to a stator  104 . The bearing  110  is screwed into the holder body  113  to nip the plates  111  and  112  between the holder body  113  and the bearing  110 . The stator  104  is welded at portions, as indicated by A and B, to a casing  114 . A retaining nut  102  is screwed on a threaded cylinder  107  of the holder body  113  to hold the casing  114  and a spacer  109  between the end body  101  and the bearing  110 , thereby positioning the stator  104  relative to the plate  111 . This fixes the interval between the stator  104  and the valve hole  108 , thereby setting the maximum amount of lift of the control valve  106 . 
     The positioning of the stator  104  relative to the plate  111 , however, requires welding of the casing  114  and the stator  104 . The stator  104 , thus, needs to be made of a heat resisting material If the stator  104  is positioned in direct contact with the end body  101  and the spacer  109  in order to avoid thermal loads on the stator  104 , the compressive pressure produced by tightening the retaining nut  102  acts on the stator  104 . The stator  104 , thus, needs to be made of material which is tough and hard. Specifically, it is necessary to make the stators  104  of limited materials, which will be disadvantages in increasing the attractive force produced by the stator  104  and which may result in undesirable thermal deformation and physical breakage of the stator  104 . 
     SUMMARY OF THE INVENTION 
     It is therefore a principal object of the invention to avoid the disadvantages of the prior art. 
     It is another object of the invention to provide an improved structure of a solenoid valve designed to minimize undesirable loads on a stator and a fuel injector using the same. 
     According to one aspect of the invention, there is provided a solenoid valve which comprises: (a) a housing in which a fluid passage and a valve seat is formed; (b) a valve member disposed in the housing, when resting on the valve seat, the valve member closing the fluid passage, when leaving the valve seat, the valve member opening the fluid passage; (c) an armature connected to the valve member, the armature being movable in the same direction as that of movement of the valve member; (d) a stator attracting the armature to move the valve member, opening the fluid passage; (e) a coil producing an attractive force in the stator electromagnetically when the coil is energized; (f) a pressure-receiving mechanism provided in contact with the housing; (g) a fixing mechanism engaging the housing in contact with the pressure-receiving mechanism to press the pressure-receiving mechanism against the housing; and (h) an engaging mechanism holding the stator in engagement with the pressure-receiving mechanism without transmitting an external force acting on the pressure-receiving mechanism from the fixing mechanism and the housing. 
     In the preferred mode of the invention, the engaging mechanism includes a holding member which is formed integrally with the pressure-receiving mechanism on a side of a surface of the pressure-receiving mechanism opposite a housing-contacting surface and which has formed therein a groove with which the stator is fitted. 
     The pressure-receiving mechanism includes a cylindrical member having a flange which is formed on a valve seat side of the holding member integrally with the holding member and which is nipped between the housing and the fixing mechanism. 
     The stator has formed thereon a portion tapered toward the valve seat. The holding member is made of a cylinder which has an end portion remote from the valve seat, bent inwardly and a shoulder formed on an inner wall thereof, inclined to contact with the tapered portion of the stator. 
     The engaging mechanism includes a stopper made of cylindrical member which hits on one of the armature and the control valve when the armature is attracted by the stator and which has a damper flange. The stator is made of a hollow cylindrical member in which the stopper is disposed in contact of an end remote from the armature with the damper flange. 
     According to the second aspect of the invention, there is provided a fuel injector which comprises: (a) a nozzle valve working to open and close a spray hole selectively; (b) a nozzle body supporting the nozzle valve slidably; (c) a pressure chamber formed in the nozzle body, producing therein a fuel pressure working to urge the nozzle valve in a spray hole-closing direction; and (d) a solenoid valve working to control the fuel pressure in the pressure chamber. The solenoid valve includes: (a) a housing in which a fluid passage and a valve seat is formed; (b) a valve member disposed in the housing, when resting on the valve seat, the valve member closing the fluid passage, when leaving the valve seat, the valve member opening the fluid passage; (c) an armature connected to the valve member, the armature being movable in the same direction as that of movement of the valve member; (d) a stator attracting the armature to move the valve member, opening the fluid passage; (e) a coil producing an attractive force in the stator electromagnetically when the coil is energized; (f) a pressure-receiving mechanism provided in contact with the housing; (g) a fixing mechanism engaging the housing in contact with the pressure-receiving mechanism to press the pressure-receiving mechanism against the housing; and (h) an engaging mechanism holding the stator in engagement with the pressure-receiving mechanism without transmitting an external force acting on the pressure-receiving mechanism from the fixing mechanism and the housing. 
     In the preferred mode of the invention, the engaging mechanism includes a holding member which is formed integrally with the pressure-receiving mechanism on a side of a surface of the pressure-receiving mechanism opposite a housing-contacting surface and which has formed therein a groove with which the stator is fitted. 
     The pressure-receiving mechanism includes a cylindrical member having a flange which is formed on a valve seat side of the holding member integrally with the holding member and which is nipped between the housing and the fixing mechanism. 
     The stator has formed thereon a portion tapered toward the valve seat. The holding member is made of a cylinder which has an end portion remote from the valve seat, bent inwardly and a shoulder formed on an inner wall thereof, inclined to contact with the tapered portion of the stator. 
     The engaging mechanism includes a stopper made of cylindrical member which hits on one of the armature and the control valve when the armature is attracted by the stator and which has a damper flange. The stator is made of a hollow cylindrical member in which the stopper is disposed in contact of an end remote from the armature with the damper flange. 
     According to the third aspect of the invention, there is provided a solenoid valve which comprises: (a) a housing in which a fluid passage and a valve seat is formed; (b) a valve member disposed in the housing, when resting on the valve seat, the valve member closing the fluid passage, when leaving the valve seat, the valve member opening the fluid passage; (c) an armature connected to the valve member, the armature being movable in the same direction as that of movement of the valve member; (d) a stator attracting the armature to move the valve member, opening the fluid passage; (e) a coil producing an attractive force in the stator electromagnetically when the coil is energized; (f) a stator-mounting member; (g) a pressing member engaging the housing to produce a nipping pressure working to nip the stator-mounting member between the pressure member and the housing; and (h) a stator-holding member holding the stator in the stator-mounting member without subjecting the stator to the nipping pressure produced by the pressure member. 
     In the preferred mode of the invention, the stator-holding member is disposed in alignment with the stator to urge the stator into constant engagement with the stator-mounting member. 
     The stator-mounting member is made of a hollow cylindrical member which has a flange which is nipped between a step formed on an inner wall of the pressing member and an end of the housing. 
     The stator-mounting member has disposed therein the stator. The stator-mounting member has formed on an inner wall thereof a tapered surface. The stator has formed on an outer wall a tapered surface which engages the tapered surface of the stator-mounting member. 
     The stator-mounting member is made of a hollow cylindrical member which has an end portion bent inward to engage a groove formed on an outer wall of the stator-holding member to hold the stator within the stator-mounting member tightly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be understood more fully from the detailed description given hereinbelow and from the accompanying drawings of the preferred embodiments of the invention, which, however, should not be taken to limit the invention to the specific embodiments but are for the purpose of explanation and understanding only. 
     In the drawings: 
     FIG. 1 is a vertical sectional view which shows a fuel injector equipped with a solenoid valve according to the embodiment of the invention; 
     FIG. 2 is a partial sectional view which shows an internal structure of the solenoid valve installed in the fuel injector of FIG. 1; 
     FIG. 3 is a partial sectional view which shows a stator and an armature of the solenoid valve of FIG. 2; 
     FIG. 4 is an exploded perspective view which shows an end body, a stator, and a casing of the solenoid valve of FIG. 2; 
     FIG. 5 is an exploded perspective view which shows assembling processes of parts of the solenoid valve of FIG. 2; and 
     FIG. 6 is a partial sectional view which shows a conventional solenoid valve. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, wherein like reference numbers refer to like parts in several views, particularly to FIGS. 1 and 2, there is shown a fuel injector  1  according to the invention. 
     The fuel injector  1  is installed in a head of an internal combustion engine (not shown) and inject fuel directly into one of cylinders of the engine. 
     The fuel injector  1  includes a holder body  11  (i.e., an injector body) and a nozzle body  12  which are joined by a retaining nut  14 . 
     The holder body  11  has a needle chamber  11   d  formed therein. Similarly, the nozzle body  12  has a needle chamber  12   e  formed therein. A nozzle valve  20  is disposed within the needle chambers  11   d  and  12   e.    
     The holder body  11  has an inlet  11   f  which works as a connector to a fuel pump (not shown) The inlet  11   f  has a fuel inlet passage  11   a  formed therein. A bar filter  13  is installed in the fuel inlet passage  11   a.  The fuel inlet passage  11   a  communicates with a fuel passage  12   d  formed in the nozzle body  12  through a fuel passage  11   b.  The fuel passage  12   d  communicates with the needle chamber  12   e  through a fuel sump  12   c.  The needle chamber  12   e  communicates with spray holes  12   b  formed in a head of the nozzle body  12 . The fuel supplied from the fuel pump to the inlet  11   f  flows through the bar filter  13  to the fuel inlet passage  11   a,  the fuel passages  11   b  and  12   d,  the fuel sump  12   c,  and the needle chamber  12   e  and is injected from the spray holes  12   b  into a cylinder of the engine. The holder body  11  also has a leak passage  11   c  leading to the needle chamber  11   d.    
     The nozzle valve  20  consists of a needle  20   c,  a rod  20   b,  and a control piston  20   a.  The needle  20   c  is made up of a seating portion (i.e., a valve head), a small-diameter portion, a tapered portion, and a large-diameter portion. The large-diameter portion is disposed hermetically within the needle chamber  12   e  to be movable in a lengthwise direction of the nozzle valve  20 . The tapered portion is urged upward, as viewed in FIG. 1, by the fuel pressure in the fuel sump  12   c.  An annular gap is formed between an outer wall of the small-diameter portion and an inner wall of the needle chamber  12   e.  The seating portion is of a conical shape and rests on a valve seat  12   a  to close the spray holes  12   b.  The rod  20   b  abuts at one end on the needle  20   c  and at the other end on the control piston  20   a.  A coil spring  15  is disposed around the rod  20   b  and urges the needle  20   c  through the rod  20   b  into constant engagement with the valve seat  12   a.  The control piston  20   a  is disposed within the needle chamber  11   d  hermetically to be movable in the lengthwise direction thereof. 
     A first annular plate  16 , as shown in FIG. 2, is disposed within a cylindrical end chamber which is formed in an end portion of the holder body  11  in communication with an upper end of the needle chamber  11   d.  The first plate  16  has formed therein a through hole  16   a  leading to the needle chamber  11   d  and an inlet orifice  16   b  communicating between the through hole  16   a  and the fuel inlet passage  11   a  through a fuel passage  11   j.  A pressure chamber  16   c  is defined by the end of the control piston  20   a,  the inner wall of the needle chamber  11   d,  and an inner wall of the through hole  16   a.    
     A second annular plate  18  and a third annular plate  17  are laid on the first plate  16  to overlap each other. The second annular plate  18  has a seat  18   a  formed on a flat surface thereof facing the third annular plate  17 . The third plate  17  is screwed into the end chamber of the holder body  11  to hold the first plate  16  and the second plate  18  therewithin. The third plate  17  has through holes  17   a  and  17   b  formed therein. A bushing  60  is press fit within the through hole  17   a . The bushing  60  is made of a thin-walled hollow cylindrical member having a relatively high hardness and defines a valve chamber  70  between a lower end thereof and the second plate  18 . The second plate  18  has formed therein a valve hole  18   b  which establishes communication between the pressure chamber  16   c  and the valve chamber  70 . A clearance  11   e  is, as clearly shown in FIG. 2, formed in a circumferential direction between side walls of the first and second plates  16  and  18  and the inner wall of the end chamber of the holder body  11 . The clearance  11   e  leads to the leak passage  11   c  and to the hole  17   b  through a recess  17   c  formed in a surface of the third plate  17  facing the second plate  18 . The holder body  11  has a cylindrical threaded portion  11   g.  The cylindrical threaded portion  11   g,  the second plate  18 , and the third plate  17  form a housing for a solenoid valve  2  as will be described below. 
     The solenoid valve  2  has a stator  31  disposed within a hollow cylindrical casing  33 . The casing  33  has, as shown in FIG. 2, formed on an inner wall thereof an inner shoulder  33   b  which has a conical surface inclined downward, as viewed in the drawing. The casing  33  has formed on an outer wall thereof below the inner shoulder  33   b  a flange  33   a  which is held between an inner step  52   a  of a retaining nut  52 , as clearly shown in FIG. 5, and the end of the threaded portion  11   g  of the holder body  11  through an annular spacer  19  to join the casing  33  to the holder body  11 . Specifically, the retaining nut  52  is tightened on the threaded portion  11   g  of the holder body  11 , thereby nipping the flange  33   a  between the inner step  52   a  of the retaining nut  52  and the end of the threaded portion  11   g  of the holder body  11  through the annular spacer  19  to secure the casing  33  on the holder body  11  firmly. The annular spacer  19  is made of a disc whose thickness is so selected as to adjust a maximum lift of the control valve  40  to a desired value. The maximum lift may alternatively be adjusted by changing the thickness of the flange  33   a  without use of the annular spacer  19 . Instead of the spacer  19 , a disc spring may also be disposed between the flange  33   a  and the end of the threaded portion  11   g  to adjust the amount of lift of the control valve  40  by turning the retaining nut  52 . The casing  33  has an upper opening closed by an end body  53 . The casing  33  has a thin-walled end  33   c  curved inwardly to engage an annular groove  53   a  formed in an outer wall of the end body  53 . The outer wall of the end body  53  is opposed to the inner wall of the retaining nut  52  in a radius direction thereof, and not in a longitudinal direction thereof. 
     A stopper  35  is disposed in the cylindrical stator  31  in contact with the lower end of the end body  53 . The stopper  35  consists of a hollow cylinder  35   b  and a damper flange  35   a  formed on an end of the cylinder  35   b.  A small annular gap is provided between the inner wall  31   a  of the stator  31  and the outer wall of the stopper  35 . Specifically, the stator  31  is not in direct contact with the stopper  35 . The stator  31  consists of a large-diameter portion, a tapered portion (i.e., a shoulder)  31   b,  as clearly shown in FIG. 4, a small-diameter portion. The end  31   c  of the large-diameter portion is in contact with the damper flange  35   a.  The outer diameter of the large-diameter portion is substantially equal to that of the damper flange  35   a.  The tapered portion  31   b  is in contact with the inner shoulder  33   b  of the casing  33 . In the stator  31 , a bobbin  34  and a coil  32  wound around the bobbin  34  are fixed through resin. The coil  32  leads electrically to a terminal  51  extending into a connector  50 . 
     A control valve  40  is disposed slidably within the stator  31  and the third plate  17 . The control valve  40  consists of a spherical member  40   a,  a stem  40   b,  and a spring seat  40   c.  The spherical member  40   a,  the stem  40   b,  and the spring seat  40   c  may be connected together in press-fits or formed by machining a single member. The spherical member  40   a  has a flat surface which works to close the valve hole  18   b.  The stem  40   b  is press fit at a base thereof within a central hole formed in an armature  41  to be slidable along with the armature  41  in contact with the inner wall of the bush  60 . The armature  41  is disposed between the stator  31  and the third plate  17 . The armature  41 , as clearly shown in FIG. 3, has an annular protrusion  41   a  formed on the center of the end surface facing the stator  31 . The protrusion  41   a  projects from the end surface of the armature  41  by approximately 50 μm in order to establish an air gap H between the armature  41  and the stator  31  when the armature  41  is lifted up fully. The protrusion  41   a  is located in co-axial alignment with the cylinder  35   b  of the stopper  35  so that the end of the protrusion  41   a  hits on the lower end of the cylinder  35   b  when the armature  41  is lifted up fully. 
     A second coil spring  38  is, as shown in FIG. 2, disposed in the cylinder  35   b  of the stopper  35  between an end of a spring pressure-adjusting pipe  37  forced into the end body  53  and the spring seat  40   c  to urge the spherical member  40   a  into constant engagement with the second plate  18  through the stem  40   b  to close the valve hole  18   b.    
     The manner in which the casing  33 , the stator  31 , the stopper  35 , the end body  53 , and the retaining nut  52  are joined to the holder body  11  will be discussed below with reference to FIGS. 4 and  5 . 
     First, the stator  31  equipped with the coil  32  and the terminal  51  is inserted into the casing  33  until the tapered portion  31   b  hits on the inner shoulder  33   b  of the casing  33 , thereby positioning the stator  31  coaxially with the casing  33 . The stopper  35  is inserted into the stator  31  until the damper flange  35   a  hits on the end  31   c  of the stator  31 . The cylinder  35   b  of the stopper  35  is fitted in contact with the inner wall  31   a  of the stator  31 , thereby positioning the stopper  35  coaxially with the stator  31 . The terminal  51  is inserted into a hole (not shown) formed in the end body  53 . 
     The end body  53  is placed on the damper flange  35   a  of the stopper  35 . The edge  33   d  of the thin-walled end  33   c  of the casing  33  is located on a level with the groove  53   a  of the end body  53 . The edge  33   d  of the thin-walled end  33   c  of the casing  33  is pressed inwardly into the groove  53   a  to join the casing  33  to the end body  53 . When the edge  33   d  of the casing  33  is forced into the groove  53   a  of the end body  53 , it will cause the end body  53  to be shifted downwardly, as viewed in FIGS. 4 and 5, to move the damper flange  35   a  and the stator  31  in the same direction. This causes the tapered portion  31   b  of the stator  31  to be pressed against the inner shoulder  33   b  of the casing  33 , thus positioning the stator  31  in the longitudinal direction thereof within the casing  33 . The damper flange  35   a  is nipped between the end body  53  and the stator  31 . 
     After the stator  31 , the stopper  35 , and the end body  53  are installed in the casing  33  in the above manner, the casing  33  is put in the threaded portion  11   g  of the holder body  11  through the spacer  19 . Next, the retaining nut  52  is put on the casing  33  and the end body  53  and then screwed on the threaded portion  11   g  to holding the spacer  19  and the flange  33   a  between the inner step  52   a  of the retaining nut  52 , as shown in FIG. 5, and the end surface  11   h  of the threaded portion  11   g  of the holder body  11 , thereby positioning the assembly of the casing  33 , the stator  31 , the stopper  35 , and the end body  53  within the holder body  11 . This fixes the interval between the second plate  18  installed in the body holder  11  and the stator  31 , setting a maximum amount of lift of the control valve  40 . 
     A fuel injection operation of the fuel injector  1  will be discussed below. 
     When it is required to inject the fuel into the internal combustion engine, an ECU (electronic control unit), not shown, actuates a fuel injection pump and delivers the fuel to an accumulator pipe. The fuel is stored in the accumulator pipe at a constant high pressure level and supplied to the fuel injector  1  through a supply pipe connected to the inlet  11   f.    
     The ECU produces a control valve-actuating current as a function of an operating condition of the engine and outputs it to the coil  32  of the stator  31  in the form of a pulse signal. When the coil  32  is energized, it will cause the stator  31  to produce an attractive force. When the sum of the attractive force and the fuel pressure within the pressure chamber  16   c  acting on the control valve  40  exceeds the spring pressure of the second spring  38 , the armature  41  is attracted to the stator  31 , thereby causing the control valve  40  to be lifted upward, as viewed in FIGS. 1,  2 , and  3  until the protrusion  41   a  of the armature  41  hits on the end of the cylinder  35   b  of the stopper  35 ,  50  that the spherical member  40  a of the control valve  40  leaves the seat  18   a  to open the valve hole  18   b.  When the valve hole  18   a  is opened, it establishes the fluid communication between the pressure chamber  16   c  and the valve chamber  70 , thereby causing the fuel to flow from the pressure chamber  16   c  to the valve chamber  70 . The fuel entering the valve chamber  70  is drained to a fuel tank through the through hole  17   b , the inside of the cylinder  35   b  of the stopper  35 , and the inside of the adjusting pipe  37 . 
     When the pressure chamber  16   c  communicates with the valve chamber  70 , it will cause the fuel flowing out of the pressure chamber  16   c  through the valve hole  18   b  to be greater than that flowing into the pressure chamber  16   c  from the inlet orifice  16   b , so that the fuel pressure within the pressure chamber  16   c  drops. When the fuel pressure in the pressure chamber  16   c  decreases, and the sum of the spring pressure of the first spring  15  and the fuel pressure in the pressure chamber  16   c  urging the needle  20   c  in the spray hole-closing direction overcomes the fuel pressure in the fuel sump  12   c  urging the needle  20   c  in the spray hole-opening direction, it will cause the needle  20   c  to be moved away from the valve seat  12   a  to open the spray holes  12   b,  thereby producing a fuel jet. 
     When it is required to stop the fuel injection, the ECU deenergizes the coil.  32 . When the coil  32  is deenergized, it will cause the attractive force to disappear from the stator  31 , so that the spring pressure of the second spring  38  overcomes the fuel pressure in the pressure chamber  16   c  to move the control valve  40  downward, thereby closing the valve hole  18   b  through the spherical member  40   a.  The fuel continues flowing into the pressure chamber  16   c  through the inlet orifice  16   b,  so that the fuel pressure in the pressure chamber  16   c  is elevated. When the sum of the spring pressure of the first spring  15  and the fuel pressure in the pressure chamber  16   c  acting on the needle  20   c  in the spray hole-closing direction overcomes the fuel pressure in the fuel sump  12   c  in the spray hole-opening direction, it will cause the needle  20   c  to move downward, as viewed in FIG. 1, so that the needle  20   c  rests on the valve seat  12   a  to close the spray holes  12   b,  thereby stopping the fuel injection. 
     The pressure produced by fastening the retaining nut  52  acting on the flange  33   a  of the casing  33  exerts the compressive stress on the upper and lower surfaces  33   e  and  33   f  of the flange  33   a,  as clearly shown in FIG. 5, but does not substantially act on the thin-walled portion  33   c  of the casing  33 . Specifically, the pressure produced by the retaining nut  52  acting on the flange  33   a  of the casing  33  is not transmitted to the stator  31 . Therefore, external pressures substantially acting on the stator  31  when the control valve  40  is at rest are only the pressure exerted by the stopper  35  on the stator  31  toward the nozzle body  12  which is produced by staking the edge  33   d  of the casing  33  and the reactive pressure from the surface of the inner shoulder  33   b.  The outer diameter of the tapered portion  31   b  of the stator  31  and the inner diameter of the inner shoulder  33   b  of the casing  33  are decreased in a direction in which the stator  31  is pressed, that is, downward, as viewed in FIG. 5, therefore, the pressure exerted by the end body  53  on the stator  31  does not concentrate on a specified portion of the tapered portion  31   b  of the stator  31 . Moreover, the pressure exerted on the stator  31  by pressing or staking the edge  33   d  of the casing on the end body  53  is much smaller than the pressure exerted on the flange  33   a  of the casing  33  by fastening the retaining nut  52 . The stator  31  is not welded to any parts of the solenoid valve  2  and thus not subjected to the thermal stress during the assembly. 
     Further, the maximum lift of the control valve  40  is, as described above, set by the contact of the protrusion  41   a  of the armature  41  with the end of the cylinder  35   b  of the stopper  35 . The impact acting on the stopper  35  when the protrusion  41   a  hits on the cylinder  35   b  of the stopper  35  is transmitted to the casing  33  from the damper flange  35   a  through the end body  53  and to the body holder  11  from the flange  33   a  of the casing  33  through the retaining nut  52 . The impact is, however, not exerted on the stator  31  because the stopper  35  is disposed only within the stator  31  and not joined directly to the stator  31  at all. 
     Specifically, the static load acting on the stator  31  is very low, and the impact load is not exerted on the stator  31 , thereby allowing the stator  31  to be made of a relatively low tenacity material. Additionally, the stator  31  is not welded to any parts of the solenoid valve  2  and thus may be made of a low thermal resistance material. 
     While, in the above embodiment, the casing  33 , the stator  31 , the stopper  35 , and the end body  53  are joined by bending or staking the edge  33   d  of the casing  33  into the groove  53   a  of the end body  53 , it may be accomplished by fastening screws into the side walls of the casing  33  and the end body  53  in the lateral direction thereof. 
     The maximum lift of the control valve  40  is restricted by the direct engagement of the armature  41  with the stopper  35 , however, it may be set by providing a flange on the stem  40   b  of the control valve  40  which hits on a member fixed on a given portion of the holder body  11  when the control valve  40  is lifted up to a desired level. 
     The stator  31  is not joined to the casing  33 , however, may be connected directly to the casing  33  by staking or using screws. 
     While the present invention has been disclosed in terms of the preferred embodiments in order to facilitate better understanding thereof, it should be appreciated that the invention can be embodied in various ways without departing from the principle of the invention. Therefore, the invention should be understood to include all possible embodiments and modifications to the shown embodiments witch can be embodied without departing from the principle of the invention as set forth in the appended claims.

Technology Classification (CPC): 5