Title of Invention	A FUEL INJECTION VALVE
Abstract	ABSTRACT "A FUEL INJECTION VALVE" A fuel injection valve (10) has a cylinder member (11), a utilized movable core (33) and a valve needle (24), a fixed core (40) and a spring (39). The cylinder member has a fuel passage (26) to flow a fuel from an inlet port to an injection port (23). The movable portion (33) is slidably installed in the cylinder member. The fixed core (40) generates a magnetic force to draw up the movable core (33) to open the fuel passage. The fixed core has a body portion (41) press-fitted in the cylinder member (11) and an engaging portion (42) protruding from the body portion (41). The spring (39) is interposed between the movable core (33) and the engaging portion (42) to push the valve needle (24) to close the fuel passage (26). A restitutive force of the spring (26) is adjusted by plastically deforming the engaging portion (42). /c:™,..^ £

Title of Invention

A FUEL INJECTION VALVE

Abstract

ABSTRACT "A FUEL INJECTION VALVE" A fuel injection valve (10) has a cylinder member (11), a utilized movable core (33) and a valve needle (24), a fixed core (40) and a spring (39). The cylinder member has a fuel passage (26) to flow a fuel from an inlet port to an injection port (23). The movable portion (33) is slidably installed in the cylinder member. The fixed core (40) generates a magnetic force to draw up the movable core (33) to open the fuel passage. The fixed core has a body portion (41) press-fitted in the cylinder member (11) and an engaging portion (42) protruding from the body portion (41). The spring (39) is interposed between the movable core (33) and the engaging portion (42) to push the valve needle (24) to close the fuel passage (26). A restitutive force of the spring (26) is adjusted by plastically deforming the engaging portion (42). /c:™,..^ £

Full Text	The present application is a divisional application of Indian Patent Application No. 1190/CHE/2005 entitled "Fuel Injection Valve and Manufacturing Method of the same" The present invention relates to a fuel injection valve for an internal combustion engine (the internal combustion engine hereinafter referred to as "engine") and a manufacturing method of the fuel injection valve. BACKGROUND OF THE INVENTION Conventionally, a fuel injection valve that electromagnetically drives a vaive member to open and close an injection port is known. In this kind of fuet injection valve, a fuel injection amount is adjusted by varying a restitutive force of an elastic member such as a spring to push the valve member. The restitutive force of the elastic member is adjusted by an adjusting member such as an adjusting pipe pushing the elastic member (refer to United States Pat. No. 5,165,656 and its counterpart JP-05-87264-A). In such a case of adjusting the restitutive force of the elastic member by the adjusting member, it is proposed to adjust the restitutive force by varying the press-fitting amount of the adjusting member into a fixed core and to caulk the adjusting member and the fixed core after adjusting the restitutive force. However, a use of the adjusting member such as the adjusting pipe, which is separately formed from the fixed core, causes issues such as an increase of parts and a complicated structure. Further, in fixing the adjusting member on the fixed core, a contact between the fixed core and the adjusting member may generate burrs and foreign matters. a . Further, in the fuel injection valve having the above configuration, a magnetic drawing force is generated between a fixed core and a movable core that are installed in a cylinder member. The fixed core is fixed in the cylinder member, and the movable core is slidably installed in the cylinder member to be moved by the magnetic drawing force in the cylinder member (refer to United States Pat. No. 6,616,073 and its counterpart JP-2003-166452-A, for example). Here, a distance between the fixed core and the movable portion, which face with each other, corresponds to a lift amount of a valve member. Thus, in order to set the fuel injection amount accurately, the distance between the fixed core and the movable portion must be adjusted with high accuracy. The fixed core is fixed inside the cylinder member such by press-fitting. However, when the fixed core has a protruding portion protruding radially inward, a portion of the fixed core in which the protruding portion is formed has a \arger stiffness than other portions of the fixed core. Thus, in press-fitting the fixed core inside the cylinder member, a force necessary to press-fitting varies corresponding to a position of the fixed core, namely a press-fitting amount of the fixed core, so that an adjusting accuracy of the distance between the fixed core and the movable portion decreases. Further, a variance of the press-fitting force occurs an abnormal contact between the fixed core and the cylinder member and a generation of burrs and/or abrasion particles. SUMMARY OF THE INVENTION The present invention, in view of the above-described issue, has an object to provide a fuel injection valve in which a number of parts are decreased .5 and which is free from complicated structure and generation of foreign matters and easy to adjust a restitutive force of an elastic member. Another object of the present invention is to provide a manufacturing method of a fuel injection valve capable of adjusting a restitutive force of an elastic member easily and with high accuracy. Still another object of the present invention is to provide a fuel injection valve having a large adjusting accuracy of a distance between a fixed core and a movable portion and preventing generations of burrs and abrasion particles. The fuel injection valve has a cylinder member, a movable portion, a fixed core and an elastic member. The cylinder member is formed in an approximately cylindrical shape and has a fuel passage to flow a fuel from an inlet port to an injection port. The movable portion is slidably installed in the cylinder member to reciprocate in an axial direction of the cylinder member to open and close the fuel passage. The fixed core is for generating a magnetic force to draw up the movable portion to open the fuel passage. The fixed core has a body portion fixed in the cylinder member, and an engaging portion protruding from the body portion. The elastic member is interposed between the movable portion and the engaging portion to push the movable portion to close the fuel passage. The engaging portion is plastically deformed to adjust a restitutive force of the elastic member. BRIEF DESCRIPTION OF THE DRAWINGS Features and advantages of embodiments will be appreciated, as well as methods of operation and the function of the related parts, from a study of the foliowing detailed description, the appended claims, and the drawings, all of which form a part of this application. In the drawings: FIG. 1 is a cross-sectional view showing a fuel injection valve according to a first embodiment of the present invention; FIG. 2 is a cross-sectional view showing a fixed core of the fuel injection valve according to the first embodiment; FIG. 3 is a cross-sectional view showing a first step of a manufacturing process of the fuel injection valve according to the first embodiment; FIG. 4 is a cross-sectional view showing a second step of the manufacturing process of the fuel injection valve according to the first embodiment; FIG. 5 is a cross-sectional view showing a third step of the manufacturing process of the fuel injection valve according to the first embodiment; FfG. 6 is a cross-sectional view showing a fuel injection valve according to a second embodiment of the present invention; FIG. 7 is a cross-sectional view showing a periphery of a fixed core and a cylinder member of the fuel injection valve according to the second embodiment; FIG. 8 is a cross-sectional view showing a fixed core of a fuef injection valve according to a third embodiment of the present invention; FIG. 9 is a cross-sectional view showing a fixed core of a fuel injection valve according to a fourth embodiment of the present invention; FIG. 10 is a cross-sectional view showing a fixed core of a fuel injection valve according to a fifth embodiment of the present invention; FIG. 11 is a cross-sectional view showing a periphery of a fixed core and a cylinder member of a fuel injection valve according to a sixth embodiment of the present invention; FIG. 12 is a cross-sectional view showing a periphery of a fixed core and a cylinder member of a fuel injection valve according to a seventh embodiment of the present invention; FIG. 13 is a cross-sectional view showing a periphery of a fixed core and a cylinder member of a fuel injection valve according to an eighth embodiment of the present invention; and FIG. 14 is a cross-sectional view showing a periphery of a fixed core and a cylinder member of a fuel injection valve according to a ninth embodiment of the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Embodiments of the present invention are described in the following with reference to drawings. Each of the embodiments describes a fuel Injection valve (hereinafter referred to as "injector") for injecting fuel into intake air taken in a combustion chamber in a gasoline engine, for example. The injector 10 may also be applied to a direct injection gasoline engine, in which the injector injects fuel directly into a combustion chamber thereof, or to a diesel engine. (First embodiment) FIG. 1 depicts an injector 10 according to a first embodiment of the present invention. The injector 10 has a holder pipe 11 formed in a thin-walled and approximately cylindrical shape. The holder pipe 11 includes a first magnetic portion 12, a nonmagnetic portion 13 and a second magnetic portion 14. The nonmagnetic portion 13 prevents a magnetic short circuit between the first magnetic portion 12 and the second magnetic portion 14. The first magnetic portion 12 and the nonmagnetic portion 13 are integrally connected with each other such by laser welding. Ditto for the nonmagnetic portion 13 and the second magnetic portion 14. Alternatively, the first magnetic portion 12, the non magnetic portion 13 and the second magnetic portion 14 may be integrally made of magnetic material and the like. In this case, a part of the holder pipe 11 corresponding to the nonmagnetic portion 13 is nonmagnetized by thermal processing and the like. The holder pipe 11 has a fuel inlet port 15 at an end portion in an axial direction thereof. A fuel pump, which is not shown, supplies the injector 10 with fuel through the fuel inlet port 15. The fuel supplied to the fuel inlet port 15 flows through a fuel filter 16 into an inner space of the holder pipe 11. The fuel filter 16 is disposed at the end portion of the holder pipe 11 and removes foreign matters included in the fuel. A valve body 20 is set at another end portion of the holder pipe 11 opposite from the fuel inlet port 15, namely inside the first magnetic portion 12. The valve body 20 is formed in an approximately cylindrical shape and fixed on an inner circumferential face of the first magnetic portion 12. The valve body 20 has a valve seat 21 formed such that an inner diameter thereof becomes shorter as closer to a tip end. An injection port plate 22 is fixed on an end face of the vatve body 20 opposite from the holder pipe 11. The injection port plate 22 is provided with an injection port 23 to connect a valve body 20-side end face and a counter valve body 20-side end face thereof. A valve needle 24 is installed inside the first magnetic portion 12 and the valve body 20 to be able to reciprocate in the axial direction. The valve needle 24 is disposed approximately coaxial to the holder pipe 11 and the valve body 20. The valve needle 24 has a seal portion 25 at a proximity to an injection port plate 22-side end portion thereof. The seal portion 25 is to come in contact with the valve seat 21 of the valve body 20. The valve needle 24 and the valve body 20 form a fuel passage 26 therebetween to flow fuel. The fuel passage 26 is communicated with the injection port 23 when the seal portion 25 of the valve needle 24 lifts off the valve seat 21. The injector 10 has a driving portion 30 to drive the valve needle 24. The driving portion 30 is an electromagnetic actuator including a coil 31, a housing 32, a movable core 33 and a fixed core 40. The coil 31 is wound on a spool 34 made of resin and formed in a cylindrical shape. The housing 32 is made of magnetic material and covers an outer face of the coi! 31. Outer faces of the coil 31, the housing 32 and the holder pipe 11 are covered by a resinous mold 35. The coil 31 is electrically connected via a wiring member 36 to a terminal 38 disposed in a connector 37. The connector 37 is integrally formed with the resinous mold 35. The movable core 33 is installed inside the holder pipe 11 to be able to reciprocate in the axial direction. The movable core 33 faces the fixed core 40 at a counter injection port 23-side end portion thereof. The movable core 33 reciprocates in the axial direction being guided by an inner circumferential face of the holder pipe 11. The movable core 33 is made of magnetic material such as iron and formed in an approximately cylindrical shape. The movable core 33 has a bore portion 331 in which a counter seal portion 25-side end portion of the valve needle 24 is fixed. The valve needle 24 is fixed to the bore portion 331 by press-fitting, welding and the like. Thus, the valve needle 24 and the movable core 33 forms a movable portion that integrally reciprocates in the axial direction. The movable core 33 further has a fuel bore 332 that communicates the bore portion 331 and the fuel passage 26. The movable core 33 is in contact with a spring (elastic member) 36 at the counter injection port 23-side end portion thereof. The spring 39 is in contact with the movable core 33 at one end portion and with the fixed core 40 at another end portion thereof. The spring 39 exerts a force to extend in the axial direction. Thus, the valve needle 24 integral with the movable core 33 is pressed by the spring 39 to seat on the valve seat 21, namely toward the injection port 23. The fixed core 40 is fixed inside the coil 31 to interpose the holder pope 11 therebetween. The fixed core 40 is made of magnetic material such as iron and formed in an approximately cylindrical shape. The fixed core 40 and the movable core 33 form a gap having a distance g therebetween. The distance g between the fixed core 40 and the movable core 33 corresponds to a lift amount of the valve needle 24. The fixed core 40, as shown in FIG. 2, is formed in a cup-like shape having a cylindrical portion 41 and a bottom portion (engaging portion) 42. The cylindrical portion 41 extends in the axial direction. An outer circumferential face of the cylindrical portion is in contact with the inner circumferential face of the holder pipe 11. The bottom portion 42 protrudes radially inward from an inner circumference of a counter moving core 33-side end portion of the cylindrical portion 41. The bottom portion 42 has a bore portion 43 at a radial center thereof that is connected to an inner space of the cylindrical portion 41 to flow fuel therethrough. Another end portion of the spring 39, namely a counter movable portion 33-side end portion thereof is in direct contact with the'bottom portion of the fixed core 40. A radially inside peripheral portion of the bottom portion 42 is deformed toward the movable core 33 as shown in FIG. 1. Next, an assembly of the injector 10 having above-described structure will be described. As shown in FIG. 3, the holder pipe 11, the valve body 20 and the coil 31 are assembled, and then the resinous mold 35 is formed. The injection port plate 22 is fixed on the valve body 20. The unitized movable core 33 and valve needle 24 are installed inside the holder pipe 11 and the valve body 20. An inner diameter of the holder pipe 11 is slightly larger than an outer diameter of the movable core 33. Thus, the unitized movable core 33 and valve needle 24 can reciprocate in an axial direction inside the holder pipe 11. After installing the unitized movable core 33 and valve needle 24 inside the holder pipe 11, the spring 39 is disposed at a counter valve needle 24-side of the movable core 33. The spring 39 is inserted inside the holder pipe 11 and one end portion thereof in the axial direction is in contact with the movable core 33. In this state, the spring 39 is in neither compressed nor tensile state and has a natural entire IO length L. After installing the spring 39 inside the holder pipe 11, a fixed core 40 is installed at the counter movable core 33-side of the spring 39. The fixed core 40 is press-fitted inside the holder pipe 11. The fixed core 40, as shown in FIG. 4, is press-fitted until a gap between itself and the movable core 33 becomes g. In this state, an end portion of the spring 39 opposite from the movable core 33 is in contact with the bottom portion 42. Thus, the spring 39 is compressed by press-fitting the fixed core 40 to have an entire length L1 shorter than the natural entire length L. After completion of press-fitting the fixed core 40, as shown in FIG. 5, a force is applied to the bottom portion 42 of the fixed core 40 by an adjusting punch 50. The adjusting punch 50 is inserted into the holder pipe 11 from the counter injection port 23-side end portion thereof, then presses the counter injection port 23-side end face of the bottom portion 42 toward the injection port 23. Thus, the bottom portion 42 protruding radially inward in the fixed core 40 is plastically deformed and bended toward the injection port 23. By deforming the bottom portion 42, the deformed bottom portion 42 pushes the spring 39 toward the injection port 23. As a result, an entire length of the spring 39 is decreased to be L2 shorter than the entire length L1. The bottom portion 42 is pressure-inserted by the adjusting punch 50 until the restitutive force of the spring 39, namely the force pushing the unitized movable core 33 and valve needle 24 toward the injection port 23 reaches a certain value. The bottom portion 42 is configured so that a wall thickness t satisfies a relation of 0.1 mm^t^LO mm. Thus, the bottom portion 42 is deformed by a force smaller than the force applied to the fixed core 40 in press-fitting the fixed core 40 into the holder pipe 11. As the wall thickness t becomes large, the strength against the restitutive force of the spring 39 decreases. Accordingly, as the wall thickness t is large, a post-deformation of the bottom portion 42 of the fixed core 40 is decreased after adjusting the restitutive force of the spring 39, to stabilize the restitutive force of the spring 39. However, when the wall thickness t is too large, a larger strength of force is necessary to deform the bottom portion 42 plastically than a force applied to the fixed core 40 to press-fit that. As a result, when the wall thickness t is too large, in deforming the bottom portion 42 of the fixed core 40, the fixed core 40 moves toward the injection port 23 to make it difficult to adjust the distance g between the fixed core 40 and the movable core 33 to with accuracy. Thus, it is desirable that the wall thickness t of the bottom portion 42 is configured to be able to deform by a strength of force smaller than that required for press-fitting the fixed core 40. Accordingly, in the first embodiment, the wall thickness t of the bottom portion 42 is set to be 1.0 mm or smaller. When the wall thickness t is too large, a strength of the bottom portion 42 against the restitutive of the spring 39 is decreased to cause a possibility of deforming after adjusting the restitutive force of the spring 39. Thus, the wall thickness t of the bottom portion 42 is required to have enough strength to bear the restitutive force of the spring 39. Accordingly, in the first embodiment, the wall thickness t of the bottom portion 42 is set to be 0.1 mm or larger. After completing an adjustment of the restitutive force of the spring 39, the fuel filter 16 is installed at the counter valve body 20-side end portion of the 12- holder pipe 11. Thus, the assembly of the injector 10 is completed. Next, an operation of the injector 10 having above-described structure will be described. When the coil 31 is not energized, no magnetic drawing force generates between the fixed core 40 and the movable core 33. Thus, a pushing force of the spring 39 moves the movable core 33 away from the fixed core 40, and the valve needle 24 integrally connected to the movable core 33 also moves away from the fixed core 40. As a result, when the coil 33 is not energized, the seal portion 25 of the valve needle 24 seats on the valve seat 21. Accordingly, no fuel is injected from the injection port 23. When the coil 31 is energized, a magnetic field generated in the coil 31 forms a magnetic circuit to pass a magnetic flux in the housing 32, the first magnetic portion, the movable core 33, the fixed core 40 and the second magnetic portion 14. Thus, a magnetic drawing force generates by energizing the coil 31 between the fixed core 40 and the movable core 33 which are separated by the pushing force of the spring 39. When the magnetic drawing force generated between the fixed core 40 and the movable core 33 exceeds the pushing force of the spring 39, the unitized movable core 33 and valve needle 24 move toward the fixed core 40. Thus, the seal portion 25 of the valve needle 24 lifts off the ^/a\ve seat 21. The unitized movable portion 33 and valve needle 24 move upward in FIG. 1 until the movable core 33 comes in contact with the fixed core 40. The fuel flowing from the fuel inlet 15 into the injector 10 further flows via the fuel filter 16, the inner space of the holder pipe 11, the inner space of the (3 fixed core 40, a bore portion 331 and fuel bore 332 of the movable portion 33 and the clearance between the holder pipe 11 and the valve needle 24 into the fuel passage 26. The fuel flowing into the fuel passage 26 further flows via a clearance between the valve needle 24 lifting off the valve seat 21 and the valve body 20 into the fuel port 23 formed in the fuel port plate 22. Thus, the fuel is injected from the injection port 23. When the coil 31 is not energized again, the magnetic drawing force between the fixed core 40 and the movable core 33 ceases. Thus, the pushing force of the spring 39 moves the movable core 33 integrally connected to the valve needle 24 away from the fixed core 40. Thus, the seal portion 25 seats on the valve seat 21 again to interrupt a fuel flow between the fuel passage 26 and the injection port 23. Thus, the fuel injection stops. In the above-described first embodiment, the spring 39 is in direct contact at the counter movable core 33-side end portion thereof with the fixed core 40. The restitutive force of the spring 39 is adjusted by plastically deforming the bottom portion 42 of the fixed core 40. Thus, no particular member is necessary to adjust the restitutive force of the spring 39. Further, in adjusting the restitutive force of the spring 39, members of the fuel injector 10 do not come in contact with each other. Accordingly, it is possible to decrease the number of parts to simplify the structure of the fuel injector 10 and to prevent foreign matter generation caused by contacts between the members. Further, by preventing foreign matter generation, the valve needle 24 and the valve body 20 pinch no foreign matter therebetween to prevent non-scheduled fuel injection. In the first embodiment, the restitutive force of the spring 38 is adjusted by plastically deforming the bottom portion 42 of the fixed core 40. Thus, the restitutive force of the spring 38 can be adjusted with high accuracy in accordance with a deformation amount of the bottom portion 42. Accordingly, regardless of tolerances of members, the restitutive force of the spring 39 can be easily adjusted with high accuracy to be a certain value. Further, the bottom portion 42 is disposed at the counter movable core 33-side end portion of the fixed core 40. Thus, the fixed core 40 can install the spring 39 having a large entire length therein. Then, even when the spring 39 has a large entire length, the spring 39 is installed inside the fixed core 40 without increasing an entire length of the injector 10. Accordingly, the body can be downsized. Still further, by restricting upsizing of the fuel injector 10 in accordance with an increase of the entire length of the spring 39, the spring 39 can be provided with a required enough entire length. Accordingly, the restitutive force of the spring 39 has a large flexibility. (Second embodiment) FIG. 6 depicts an injector 10 according to a second embodiment of the present invention. In the second embodiment, components of the injector 10 configured substantially as same as those in the first embodiment are assigned common referential numerals and descriptions of those are omitted. The injector 10 according to the second embodiment, as shown in FIG. 6, has a fixed core 50 differently shaped from the fixed core 40 in the first embodiment. As shown in FIGS. 6 and 7, the fixed core 50 has a small diameter portion 54 in addition to a cylindrical portion 51 and a bottom portion (engaging portion) 52. The outer diameter of the small diameter portion 54 is smaller than that of a cylindrical portion 51. The small diameter portion 54 is formed at a counter movable core 33-side end portion of the fixed core 50. The bottom portion 52 protrudes radially inward from an inner circumference of the small diameter portion 54. The bottom portion 52 has a bore portion 53 at a radial center thereof that is connected to an inner space of the cylindrical portion 51 and the small diameter portion 54 to flow fuel therethrough. A radially inside peripheral portion of the bottom portion 42 is deformed toward the movable core 33 as shown in FIG. 6 and by broken lines in FIG. 7. The small diameter portion 54 of the fixed core 50 provides a clearance 17 between an outer circumferential face of the fixed core 50 and an inner circumferential face of the holder pipe 11. The small diameter portion 54 is shaped so that an outer circumferential face thereof is approximately in parallel to and coaxial with the inner circumferential face of the holder pipe 11. The clearance 17 formed between the small diameter portion 54 and the holder pipe 11 extends over a certain length corresponding to a length of the small diameter portion 54 in an axial direction thereof. Representing a waif thickness of the bottom portion 52 as t and a length of the small diameter portion 54 in the axial direction as x, a relation of x^t is satisfied. Thus, the small diameter portion 54 is disposed radially outside the bottom portion 52. Accordingly, the clearance 17 is disposed between an outer peripheral portion of the bottom portion 52 and the holder pipe 11. In assembling the injector 10, a unitized valve needle 24 and movable core 33, which form the movable portion, are installed inside the holder pipe 11. After installing the unitized movable core 33 and valve needle 24, the spring 39 is disposed at a counter valve needle 24-side of the movable core 33. In this state, the spring 39 is in neither compressed nor tensile state and has a natural entire length L. After installing the spring 39, a fixed core 50 is installed at a counter movable core 33-side of the spring 39. The fixed core 50 is press-fitted inside the holder pipe 11. Accordingly, one end portion of the spring 39 is in contact with the movable core 33 and another end portion of the spring 39 is in contact with the bottom portion 52 of the fixed core 50. Then, the fixed core 50 is press-fitted further into the holder pipe 11 in a direction toward the movable core 33. By press-fitting the fixed core 50, the spring 39 being in contact with the bottom portion 52 of the fixed core 50 is compressed. As described above, the fixed core 50 has the small diameter portion 54 at the counter movable portion 33-side end portion thereof, and the bottom portion 52 protrudes radially inward from the small diameter portion 54. Thus, in installing the fixed core 50 inside the holder pipe 11, only the cylindrical portion 51 of the fixed core 50 is press-fitted in the holder pipe 11. That is, the small diameter portion 54 is not in contact with the holder pipe 11 and is not associated with press-fitting the fixed core 50. Here, by providing the fixed core 50 with the bottom portion 52 protruding radially inward, the fixed core 50 has a larger stiffness at a portion in which the bottom portion 52 is formed than other portion thereof, namely the cylindrical portion 51. In a case that a fixed core is provided with no small diameter portion 54, a force necessary to press-fit the portion of the fixed core 50 with the bottom portion 52 is larger than a force necessary to press-fit the 17 cylindrical portion 51. Accordingly, the force necessary to press-fit the fixed core 50 is varied corresponding to positions of the fixed core 50, namely a press-fitting amount of the fixed core 50. Contrastively, in the second embodiment, only the cylindrical portion 51 of the fixed core 50 having a constant wall thickness is press-fitted into the holder pipe 11. That is, the bottom portion 52 protrudes from the small diameter portion 54, however, as described above, the small diameter portion 54 is not associated with press-fitting the fixed core 50. Thus, the force necessary to press-fit the fixed core 50 is not varied corresponding to the press-fitting amount of the fixed core 50. Accordingly, the fixed core 50 is press-fitted into the holder pipe 11 by applying an approximately constant strength of force. The fixed core 50 is press-fitted until a gap between itself and the movable core 33 reaches a distance g. After completion of press-fitting the fixed core 50, the bottom portion 52 of the fixed core 50 is bent toward the movable core 33 as shown in FIG. 6 and by broken lines in FIG. 7. Thus, the entire length of the spring 39 can be adjusted with high accuracy. That is, the restitutive force of the spring 39, namely the force pushing the unitized valve needle 24 and movable core 33 is adjusted. In the above-described second embodiment, the bottom portion 52 of the fixed core 50 is formed to protrude radially inward from the small diameter portion 54. Thus, in press-fitting the fixed core 50 into the holder pipe 11, only the cylindrical portion 51 is associated with press-fitting the fixed core 50 into the holder pipe 11, and the small diameter portion 54 is not associated with the press-fitting. As a result, the small diameter portion 54, which has a large stiffness by a protrusion of the bottom portion 52, is not press-fitted into the holder pipe 11. Thus, the force necessary to press-fit the fixed portion 50 into the holder pipe 11 is approximately constant regardless of the press-fitting amount of the fixed core 50. Accordingly, it is possible to set the distance g of the clearance formed between the fixed core 50 and the movable core 33 with high accuracy. Further, in press-fitting the fixed core 40, the force applied to the fixed core 50 is approximately constant. This prevents irregular contact between the fixed portion 50 and the holder pipe 11. Accordingly, generations of burrs and abrasion particles can be prevented. Further, in the second embodiment, the bottom portion 52 protruding radially inward from the small diameter portion 54 serves the engaging portion of the fixed core 50 to be in contact with the spring 39. That is, the spring 39 pushing the unitized valve needle 24 and movable core 33 is in direct contact with the counter movable core 33-side end portion of the fixed core 50. Then, the restitutive force of the spring 39 is adjusted by bending, namely plastic deformation the bottom portion 52 of the fixed core 50. Thus, no particular member is necessary to adjust the restitutive force of the spring 39. Accordingly, it is possible to decrease the number of parts to simplify the structure. Further, by adjusting the restitutive force of the spring 39 by plastic deformation of the bottom portion 52 of the fixed core 50, the restitutive force of the spring 39 can be adjusted with high accuracy corresponding to the deformation amount of the bottom portion 42. Accordingly, regardless of tolerances of members, the restitutive force of the spring 39 can be adjusted easily and with high accuracy to be a certain value. {Third embodiment) FIG. 8 depicts a fixed core 60 of a fuel injector 10 according to a third embodiment of the present invention is shown in FIG. 8. Here, components of the injector 10 configured substantially as same as those in the first embodiment are assigned common referential numerals and descriptions of those are omitted. In the third embodiment, as shown in FIG. 8, the fixed core 60 has an engaging portion 62 on a way of a cylindrical portion 71 in the axial direction thereof. The engaging portion 62 is formed to protrude radially inward from an inner circumference of the cylindrical portion 61 of the fixed core 60. The engaging portion 62 is provided with a bore portion 63 at a radial center thereof to flow fuel therethrough. A counter movable core 33-side end portion of the spring 39 is in contact with the engaging portion 62. In the third embodiment, in press-fitting the fixed core 60 into the holder pipe 11, the press-fitting force is applied to a counter movable core 33-side end face 64 of the fixed core 60. In adjusting the restitutive force of the spring 39, the engaging portion 62 is plastically deformed by applying force to the engaging portion 62. Thus, in the fixed core 60, a position to which the press-fitting force is applied differs from a position to which a force to adjust the restitutive force of the spring 39 is applied. In the third embodiment, the position to apply the press-fitting force for the fixed core 60 differs from the position to apply the force to adjust the restitutive force of the spring 39. Thus, the movement of the fixed core 60 in p\astica))y deforming the engaging portion 62 and unnecessary deformation of the engaging portion 62 in the press-fitting is prevented. Accordingly, it is possible to increase accuracies of the position of the fixed core 60 and the distance g between the fixed core 60 and the movable portion 33. 5 (Fourth and Fifth embodiments) FIGS. 9 and 10 respectively depict fixed cores 40, 60 of injectors 10 according to a fourth and a fifth embodiments of the present invention. Here, components of the injectors 10 configured substantially as same as those in the first or third embodiment are assigned common referential numerals and 10 descriptions of those are omitted. The fourth embodiment is a modified example of the first embodiment. As shown in FIG. 9, the fixed core 40 has a thin-walled portion 45 at a movable core 33-side portion of the bottom portion 42. The thin-walled portion 45 is configured to have a wall thickness smaller than that of the cylindrical portion 41. 15 Thus, the bottom portion 42 can be deformed by relatively small strength of force. The fifth embodiment is a modified example of the third embodiment. As shown in FIG. 10, the fixed core 60 has a thin-walled portion 65 at a movable core 33-side portion of the engaging portion 62 that is disposed 20 between both end portions of the fixed core 60 in an axial direction. Thus, the engaging portion 62 is easily deformed by a relatively small strength of force. Both in the fourth and fifth embodiments, by providing the fixed core 40, 70 with the thin-walled portion 45, 75, the bottom portion 42 or the engaging portion 72 is easily deformed by relatively small strength of force. Accordingly, 2.1 it is possible to adjust the restitutive force of the spring 39 easily and with high accuracy. (Sixth embodiment) FIG. 11 depicts a fixed core 70 of an injector 10 according to a sixth embodiment of the present invention. Here, components of the injector 10 configured substantially as same as those in the second embodiment are assigned common referential numerals and descriptions of those are omitted. In the sixth embodiment, as shown in FIG. 11, the fixed core 70 has a tapered portion 72 having an outer diameter smaller than that of a counter movable core 33-side end portion of the cylindrical portion 71. The tapered portion 72 is inclined radially inward as going away from the movable core 33 at a counter movable core 33-side end portion of the tapered portion 70. Thus, a distance between the outer circumferential face of the tapered portion 72 of the fixed core 70 and an inner circumferential face of the holder pipe 11 increases as going away from the movable core 33. A wall thickness t of the tapered portion 72 is set to satisfy a relation of t^1/2h, wherein h denotes a wall thickness of the cylindrical portion 71. Thus, the tapered portion 72 has a larger stiffness than that of the cylindrical portion 71. By providing the fixed core 70 with the tapered portion 72, a clearance 17 is formed between the outer circumferential face of the tapered portion 72 and the inner circumferential face of the holder pipe 11. The outer circumferential face of the tapered portion 72 and the inner circumferential face of the holder portion 11 form a certain angle with each other. The tapered portion 72 is formed to have a certain length in an axial direction of the fixed X2- core 70. Thus, the tapered portion 72 and the holder pipe 11 forms the clearance 17 over a certain length in the axial direction. Further, because the tapered portion 72 is inclined, the clearance 17 becomes wider in a radial direction as going away from the movable core 33. Still further, because the i tapered portion 72 is inclined radially inward, the tapered portion 72 protrudes radially inward from the cylindrical portion 71. Thus, the tapered portion 72 provides the small diameter portion forming the clearance 17 between itself and the holder pipe 11 and the protruding portion protruding from the cylindrical portion 71. Furthermore, a counter movable portion 33-side end portion of the ) spring 39 is in contact with the inner circumferential face of the tapered portion 72. Thus, the tapered portion 72 serves the engaging portion. In the sixth embodiment, in adjusting the restitutive force of the spring 39, the tapered portion 72 is bent to be shrunk radially inward as shown by broken lines in FIG. 11. As the tapered portion 72 is bent to be shrunk radially 5 inward, the end portion of the spring 39 in contact with the tapered portion 72 moves toward the movable core 33. Thus, an entire length of the spring 39 changes, so that the restitutive force of the spring 39 can be adjusted easily and with high accuracy. In the sixth embodiment, the tapered portion 72 of the fixed core 70, 0 which has a diameter smaller than that of the cylindrical portion 71, is not in contact with the holder pipe 11. Thus, only the cylindrical portion 71 is associated with the press-fitting, and the tapered portion 72 is not associated with the press-fitting. Then, only the cylindrical portion 71 of the fixed core 70, which has an approximately constant wall thickness, is press-fitted into the ^2.3 holder pipe 11. Accordingly, the force applied in press-fitting the fixed core 70 can be approximately constant and the distance g between the fixed core 70 and the movable core 33 can have high accuracy. Further, in the sixth embodiment, in press-fitting the fixed core 70 into the holder pipe 11, a force to press-fit the fixed core 70 is applied to a step portion 74 between the cylindrical portion 71 and the tapered portion 72. Thus, a position to apply the force to press-fit the fixed core 70 is the step portion 74, and a position to apply the force to adjust the restitutive force of the spring 39 is the tapered portion 72. As a result, both the positions differs from each other and it is possible to prevent the motion of the fixed core 70 in deforming the tapered portion 72 and unnecessary deformation of the tapered portion 72 in press-fitting the fixed core 70. Accordingly, it is possible to increase accuracies of the position of the fixed core 70 and the distance g between the fixed core 70 and the movable core 33. (Seventh, Eighth and Ninth embodiments) FIGS. 12 to 14 respectively depict fixed cores 40 of fuel injectors 10 according to a seventh, eighth and ninth embodiments of the present invention. Here, components of the injectors 10 configured substantially as same as those in the second embodiment are assigned common referential numerals and descriptions of those are omitted. In each the seventh, eighth and ninth embodiments, in order to form a clearance between the fixed core 40 and the holder pipe 11, the holder pipe 11 has a diameter expanding portion 11a, 11b or 11c. In the seventh embodiment, the holder pipe 11 has a large diametei portion (diameter expanding portion) 11a radially outside the bottom portion 42 of the fixed core 40. The large diameter portion 11a has an inner diameter larger than portions in contact with the cylindrical portion 41 of the fixed core 40. Thus, at the large diameter portion 11a of the holder pipe 11, a clearance 17 is formed between the outer circumferential face of the fixed core 40 and the inner circumferential face of the holder pipe 1.1. In the eighth embodiment, the holder pipe 11 has a tapered portion (diameter expanding portion) 11b radially outside the bottom portion 42 of the fixed core 40. An inner diameter of the tapered portion11b extends as going from a position of the fixed core 40 in contact with the cylindrical portion 41 toward the fuel inlet port 15. Thus, at the tapered portion 11b of the holder pipe 11, a clearance 17 is formed between the outer circumferential face of the fixed core 40 and the innercircumferential face of the holder pipe 11. In the ninth embodiment, the holder pipe 11 has a depressed portion (diameter expanding portion) 11c radially outside the bottom portion 42 of the fixed core 40. The depressed portion 11c is formed to extend in a circumferential direction of the holder pipe 11. The depressed portion 11c has an inner diameter larger than the portion of the fixed core 40 in contact with the cylindrical portion 41. That is, the depressed portion 11c is depressed radially outward with respect to the portion in contact with the cylindrical portion 41 of the fixed core 40. Thus, at the depressed portion 11c of the holder pipe 11, a clearance 17 is formed between the outer circumferential face of the fixed core 40 and the inner circumferential face of the holder pipe 11. In the seventh, eighth and ninth embodiments, by providing the holder pipe 11 with the large diameter portion 11a, the tapered portion 11b or the depressed portion 11c, the clearance 17 is formed between the holder pipe 11 and the fixed core 40. That is, in order to form the clearance 17, not only the fixed core 40 but also the holder pipe 11 may be processed.* In these embodiments, the outer circumferential face of the bottom portion 42 of the fixed core 40 is not in contact with the holder pipe 11. Thus, only the cylindrical portion 41 is associated with the press-fitting, and the outer circumferential face of the bottom portion 42 is not associated with the press-fitting. Then, only the cylindrical portion 41 of the fixed core 40 is press-fitted into the holder pipe 11. Accordingly, the force applied in press-fitting the fixed core 40 becomes constant and the accuracy of the distance g between the fixed core 40 and the movable core 33 is increased. The above-described embodiments describe examples in which the movable portion includes separately formed movable core 33 and the valve needle 24. However, the movable core 33 and the valve needle 24 may be integrally formed. In some of the embodiments, the injection port plate 22 having the injection port 23 is fixed on the valve body 20, however, the valve body 20 itself may be provided with an injection port. Further, some of the embodiments describe examples in which the spring 39 is in direct contact with the fixed core or the movable core, however, another member may be disposed between the spring 39 and the fixed core and/or the movable core. Still further, some of the several embodiments describe examples in which the holder pipe 11 forms a magnetic circuit by a magnetic field generated in the coil 31. However, the holder pipe 11 is not limited to a member capable of forming a magnetic circuit, and the present invention may be applied to any member that can install the fixed core therein. In the above-described embodiments, the embodiments in which the present invention is applied are described individually, however, a plurality of the embodiments may be combined. This description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. WE CLAIM: 1. A fuel injection valve (10) comprising: a cylinder member (11) formed in an approximately cylindrical shape and having a fuel passage (26) to flow a fuel from an inlet port (15) to an injection port (23); a movable portion (33) made of magnetic material and slidably installed in the cylinder member (11) to reciprocate in an axial direction of the cylinder member (11) to open and close the fuel passage (26); a fixed core (50, 70) for generating a magnetic force to move the movable portion (33) to open the fuel passage and having a body portion (51, 71) fixed in the cylinder member, and a protruding portion (52, 72) protruding radially inward from the body portion (51, 71), and wherein a clearance (17) is formed between an inner circumferential face of the cylinder member (11) and at least a portion of an outer circumferential face of the fixed core (50, 70) which is radially outside the protruding portion (42). 2. The fuel injection valve (10) according to claim 1, wherein: the body portion (51) has a small diameter portion (54) in which an outer circumferential face of the body portion (51) is depressed radially inward; and the clearance (17) is formed radially outside the small diameter portion (54). 3. The fuel injection valve (10) according to claim 2, wherein an outer circumferential face of the small diameter portion (54) is approximately in parallel to the inner circumferential face of the cylinder member (11). 4. The fuel injection valve (10) according to claim 1, wherein: the protruding portion (72) extends to be inclined radially inward from the end portion of the body portion (71); and the clearance (17) is formed radially outside the protruding portion (72). 28 5. The fiiel injection valve (IU) according to oaim t, wucicm uiw p.v»v.w«...to portion (72) is formed so that a distance between an outer circumferential face of the protruding portion (72) and the inner circumferential face of the cylinder member (11) increases as going away from the movable portion (33). 6. The fuel injection valve (10) according to claim 1, wherein: the cylinder member (11) has a diameter expanding portion (11a, lib, lie) in which the inner circumferential face of the cylinder member (11) is depressed radially outward; and the clearance (17) is formed radially inside the diameter expanding portion (11a, lib, lie). 7. The fuel injection valve (10) according to any one of claims 1 to 5, wherein it comprises an elastic member (39) interposed between the movable portion (33) and the protruding portion (42, 72) to push the movable portion (33) in a direction to close the fuel passage (26). 8. The fuel injection valve (10) according to claim 7, wherein the protruding portion (42, 72) is plastically deformed to adjust a restitutive force of the elastic member (39).

Full Text

The present application is a divisional application of Indian Patent Application No. 1190/CHE/2005 entitled "Fuel Injection Valve and Manufacturing Method of the same"
The present invention relates to a fuel injection valve for an internal combustion engine (the internal combustion engine hereinafter referred to as "engine") and a manufacturing method of the fuel injection valve.
BACKGROUND OF THE INVENTION
Conventionally, a fuel injection valve that electromagnetically drives a vaive member to open and close an injection port is known. In this kind of fuet injection valve, a fuel injection amount is adjusted by varying a restitutive force of an elastic member such as a spring to push the valve member. The restitutive force of the elastic member is adjusted by an adjusting member such as an adjusting pipe pushing the elastic member (refer to United States Pat. No. 5,165,656 and its counterpart JP-05-87264-A). In such a case of adjusting the restitutive force of the elastic member by the adjusting member, it is proposed to adjust the restitutive force by varying the press-fitting amount of the adjusting member into a fixed core and to caulk the adjusting member and the fixed core after adjusting the restitutive force.
However, a use of the adjusting member such as the adjusting pipe, which is separately formed from the fixed core, causes issues such as an increase of parts and a complicated structure. Further, in fixing the adjusting member on the fixed core, a contact between the fixed core and the adjusting member may generate burrs and foreign matters.
a .

Further, in the fuel injection valve having the above configuration, a magnetic drawing force is generated between a fixed core and a movable core that are installed in a cylinder member. The fixed core is fixed in the cylinder member, and the movable core is slidably installed in the cylinder member to be moved by the magnetic drawing force in the cylinder member (refer to United States Pat. No. 6,616,073 and its counterpart JP-2003-166452-A, for example). Here, a distance between the fixed core and the movable portion, which face with each other, corresponds to a lift amount of a valve member. Thus, in order to set the fuel injection amount accurately, the distance between the fixed core and the movable portion must be adjusted with high accuracy.
The fixed core is fixed inside the cylinder member such by press-fitting. However, when the fixed core has a protruding portion protruding radially inward, a portion of the fixed core in which the protruding portion is formed has a \arger stiffness than other portions of the fixed core. Thus, in press-fitting the fixed core inside the cylinder member, a force necessary to press-fitting varies corresponding to a position of the fixed core, namely a press-fitting amount of the fixed core, so that an adjusting accuracy of the distance between the fixed core and the movable portion decreases. Further, a variance of the press-fitting force occurs an abnormal contact between the fixed core and the cylinder member and a generation of burrs and/or abrasion particles.
SUMMARY OF THE INVENTION
The present invention, in view of the above-described issue, has an object to provide a fuel injection valve in which a number of parts are decreased
.5

and which is free from complicated structure and generation of foreign matters and easy to adjust a restitutive force of an elastic member.
Another object of the present invention is to provide a manufacturing method of a fuel injection valve capable of adjusting a restitutive force of an elastic member easily and with high accuracy.
Still another object of the present invention is to provide a fuel injection valve having a large adjusting accuracy of a distance between a fixed core and a movable portion and preventing generations of burrs and abrasion particles.
The fuel injection valve has a cylinder member, a movable portion, a fixed core and an elastic member. The cylinder member is formed in an approximately cylindrical shape and has a fuel passage to flow a fuel from an inlet port to an injection port. The movable portion is slidably installed in the cylinder member to reciprocate in an axial direction of the cylinder member to open and close the fuel passage. The fixed core is for generating a magnetic force to draw up the movable portion to open the fuel passage. The fixed core has a body portion fixed in the cylinder member, and an engaging portion protruding from the body portion. The elastic member is interposed between the movable portion and the engaging portion to push the movable portion to close the fuel passage. The engaging portion is plastically deformed to adjust a restitutive force of the elastic member.
BRIEF DESCRIPTION OF THE DRAWINGS
Features and advantages of embodiments will be appreciated, as well as methods of operation and the function of the related parts, from a study of

the foliowing detailed description, the appended claims, and the drawings, all of which form a part of this application. In the drawings:
FIG. 1 is a cross-sectional view showing a fuel injection valve according to a first embodiment of the present invention;
FIG. 2 is a cross-sectional view showing a fixed core of the fuel injection valve according to the first embodiment;
FIG. 3 is a cross-sectional view showing a first step of a manufacturing process of the fuel injection valve according to the first embodiment;
FIG. 4 is a cross-sectional view showing a second step of the manufacturing process of the fuel injection valve according to the first embodiment;
FIG. 5 is a cross-sectional view showing a third step of the manufacturing process of the fuel injection valve according to the first embodiment;
FfG. 6 is a cross-sectional view showing a fuel injection valve according to a second embodiment of the present invention;
FIG. 7 is a cross-sectional view showing a periphery of a fixed core and a cylinder member of the fuel injection valve according to the second embodiment;
FIG. 8 is a cross-sectional view showing a fixed core of a fuef injection valve according to a third embodiment of the present invention;
FIG. 9 is a cross-sectional view showing a fixed core of a fuel injection valve according to a fourth embodiment of the present invention;
FIG. 10 is a cross-sectional view showing a fixed core of a fuel injection

valve according to a fifth embodiment of the present invention;
FIG. 11 is a cross-sectional view showing a periphery of a fixed core and a cylinder member of a fuel injection valve according to a sixth embodiment of the present invention;
FIG. 12 is a cross-sectional view showing a periphery of a fixed core and a cylinder member of a fuel injection valve according to a seventh embodiment of the present invention;
FIG. 13 is a cross-sectional view showing a periphery of a fixed core and a cylinder member of a fuel injection valve according to an eighth embodiment of the present invention; and
FIG. 14 is a cross-sectional view showing a periphery of a fixed core and a cylinder member of a fuel injection valve according to a ninth embodiment of the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Embodiments of the present invention are described in the following with reference to drawings. Each of the embodiments describes a fuel Injection valve (hereinafter referred to as "injector") for injecting fuel into intake air taken in a combustion chamber in a gasoline engine, for example. The injector 10 may also be applied to a direct injection gasoline engine, in which the injector injects fuel directly into a combustion chamber thereof, or to a diesel engine. (First embodiment)
FIG. 1 depicts an injector 10 according to a first embodiment of the

present invention.
The injector 10 has a holder pipe 11 formed in a thin-walled and approximately cylindrical shape. The holder pipe 11 includes a first magnetic portion 12, a nonmagnetic portion 13 and a second magnetic portion 14. The nonmagnetic portion 13 prevents a magnetic short circuit between the first magnetic portion 12 and the second magnetic portion 14. The first magnetic portion 12 and the nonmagnetic portion 13 are integrally connected with each other such by laser welding. Ditto for the nonmagnetic portion 13 and the second magnetic portion 14. Alternatively, the first magnetic portion 12, the non magnetic portion 13 and the second magnetic portion 14 may be integrally made of magnetic material and the like. In this case, a part of the holder pipe 11 corresponding to the nonmagnetic portion 13 is nonmagnetized by thermal processing and the like. The holder pipe 11 has a fuel inlet port 15 at an end portion in an axial direction thereof. A fuel pump, which is not shown, supplies the injector 10 with fuel through the fuel inlet port 15. The fuel supplied to the fuel inlet port 15 flows through a fuel filter 16 into an inner space of the holder pipe 11. The fuel filter 16 is disposed at the end portion of the holder pipe 11 and removes foreign matters included in the fuel.
A valve body 20 is set at another end portion of the holder pipe 11 opposite from the fuel inlet port 15, namely inside the first magnetic portion 12. The valve body 20 is formed in an approximately cylindrical shape and fixed on an inner circumferential face of the first magnetic portion 12. The valve body 20 has a valve seat 21 formed such that an inner diameter thereof becomes shorter as closer to a tip end. An injection port plate 22 is fixed on an end face

of the vatve body 20 opposite from the holder pipe 11. The injection port plate 22 is provided with an injection port 23 to connect a valve body 20-side end face and a counter valve body 20-side end face thereof.
A valve needle 24 is installed inside the first magnetic portion 12 and the valve body 20 to be able to reciprocate in the axial direction. The valve needle 24 is disposed approximately coaxial to the holder pipe 11 and the valve body 20. The valve needle 24 has a seal portion 25 at a proximity to an injection port plate 22-side end portion thereof. The seal portion 25 is to come in contact with the valve seat 21 of the valve body 20. The valve needle 24 and the valve body 20 form a fuel passage 26 therebetween to flow fuel. The fuel passage 26 is communicated with the injection port 23 when the seal portion 25 of the valve needle 24 lifts off the valve seat 21.
The injector 10 has a driving portion 30 to drive the valve needle 24. The driving portion 30 is an electromagnetic actuator including a coil 31, a housing 32, a movable core 33 and a fixed core 40. The coil 31 is wound on a spool 34 made of resin and formed in a cylindrical shape. The housing 32 is made of magnetic material and covers an outer face of the coi! 31. Outer faces of the coil 31, the housing 32 and the holder pipe 11 are covered by a resinous mold 35. The coil 31 is electrically connected via a wiring member 36 to a terminal 38 disposed in a connector 37. The connector 37 is integrally formed with the resinous mold 35.
The movable core 33 is installed inside the holder pipe 11 to be able to reciprocate in the axial direction. The movable core 33 faces the fixed core 40 at a counter injection port 23-side end portion thereof. The movable core 33

reciprocates in the axial direction being guided by an inner circumferential face of the holder pipe 11. The movable core 33 is made of magnetic material such as iron and formed in an approximately cylindrical shape. The movable core 33 has a bore portion 331 in which a counter seal portion 25-side end portion of the valve needle 24 is fixed. The valve needle 24 is fixed to the bore portion 331 by press-fitting, welding and the like. Thus, the valve needle 24 and the movable core 33 forms a movable portion that integrally reciprocates in the axial direction. The movable core 33 further has a fuel bore 332 that communicates the bore portion 331 and the fuel passage 26.
The movable core 33 is in contact with a spring (elastic member) 36 at the counter injection port 23-side end portion thereof. The spring 39 is in contact with the movable core 33 at one end portion and with the fixed core 40 at another end portion thereof. The spring 39 exerts a force to extend in the axial direction. Thus, the valve needle 24 integral with the movable core 33 is pressed by the spring 39 to seat on the valve seat 21, namely toward the injection port 23.
The fixed core 40 is fixed inside the coil 31 to interpose the holder pope 11 therebetween. The fixed core 40 is made of magnetic material such as iron and formed in an approximately cylindrical shape. The fixed core 40 and the movable core 33 form a gap having a distance g therebetween. The distance g between the fixed core 40 and the movable core 33 corresponds to a lift amount of the valve needle 24. The fixed core 40, as shown in FIG. 2, is formed in a cup-like shape having a cylindrical portion 41 and a bottom portion (engaging portion) 42. The cylindrical portion 41 extends in the axial direction.

An outer circumferential face of the cylindrical portion is in contact with the inner circumferential face of the holder pipe 11. The bottom portion 42 protrudes radially inward from an inner circumference of a counter moving core 33-side end portion of the cylindrical portion 41. The bottom portion 42 has a bore portion 43 at a radial center thereof that is connected to an inner space of the cylindrical portion 41 to flow fuel therethrough. Another end portion of the spring 39, namely a counter movable portion 33-side end portion thereof is in direct contact with the'bottom portion of the fixed core 40. A radially inside peripheral portion of the bottom portion 42 is deformed toward the movable core 33 as shown in FIG. 1.
Next, an assembly of the injector 10 having above-described structure will be described.
As shown in FIG. 3, the holder pipe 11, the valve body 20 and the coil 31 are assembled, and then the resinous mold 35 is formed. The injection port plate 22 is fixed on the valve body 20. The unitized movable core 33 and valve needle 24 are installed inside the holder pipe 11 and the valve body 20. An inner diameter of the holder pipe 11 is slightly larger than an outer diameter of the movable core 33. Thus, the unitized movable core 33 and valve needle 24 can reciprocate in an axial direction inside the holder pipe 11. After installing the unitized movable core 33 and valve needle 24 inside the holder pipe 11, the spring 39 is disposed at a counter valve needle 24-side of the movable core 33. The spring 39 is inserted inside the holder pipe 11 and one end portion thereof in the axial direction is in contact with the movable core 33. In this state, the spring 39 is in neither compressed nor tensile state and has a natural entire
IO

length L.
After installing the spring 39 inside the holder pipe 11, a fixed core 40 is installed at the counter movable core 33-side of the spring 39. The fixed core 40 is press-fitted inside the holder pipe 11. The fixed core 40, as shown in FIG. 4, is press-fitted until a gap between itself and the movable core 33 becomes g. In this state, an end portion of the spring 39 opposite from the movable core 33 is in contact with the bottom portion 42. Thus, the spring 39 is compressed by press-fitting the fixed core 40 to have an entire length L1 shorter than the natural entire length L.
After completion of press-fitting the fixed core 40, as shown in FIG. 5, a force is applied to the bottom portion 42 of the fixed core 40 by an adjusting punch 50. The adjusting punch 50 is inserted into the holder pipe 11 from the counter injection port 23-side end portion thereof, then presses the counter injection port 23-side end face of the bottom portion 42 toward the injection port 23. Thus, the bottom portion 42 protruding radially inward in the fixed core 40 is plastically deformed and bended toward the injection port 23. By deforming the bottom portion 42, the deformed bottom portion 42 pushes the spring 39 toward the injection port 23. As a result, an entire length of the spring 39 is decreased to be L2 shorter than the entire length L1. The bottom portion 42 is pressure-inserted by the adjusting punch 50 until the restitutive force of the spring 39, namely the force pushing the unitized movable core 33 and valve needle 24 toward the injection port 23 reaches a certain value.
The bottom portion 42 is configured so that a wall thickness t satisfies a relation of 0.1 mm^t^LO mm. Thus, the bottom portion 42 is deformed by a

force smaller than the force applied to the fixed core 40 in press-fitting the fixed core 40 into the holder pipe 11. As the wall thickness t becomes large, the strength against the restitutive force of the spring 39 decreases. Accordingly, as the wall thickness t is large, a post-deformation of the bottom portion 42 of the fixed core 40 is decreased after adjusting the restitutive force of the spring
39, to stabilize the restitutive force of the spring 39. However, when the wall
thickness t is too large, a larger strength of force is necessary to deform the
bottom portion 42 plastically than a force applied to the fixed core 40 to press-fit
that. As a result, when the wall thickness t is too large, in deforming the
bottom portion 42 of the fixed core 40, the fixed core 40 moves toward the
injection port 23 to make it difficult to adjust the distance g between the fixed
core 40 and the movable core 33 to with accuracy. Thus, it is desirable that
the wall thickness t of the bottom portion 42 is configured to be able to deform
by a strength of force smaller than that required for press-fitting the fixed core
40. Accordingly, in the first embodiment, the wall thickness t of the bottom
portion 42 is set to be 1.0 mm or smaller. When the wall thickness t is too
large, a strength of the bottom portion 42 against the restitutive of the spring 39
is decreased to cause a possibility of deforming after adjusting the restitutive
force of the spring 39. Thus, the wall thickness t of the bottom portion 42 is
required to have enough strength to bear the restitutive force of the spring 39.
Accordingly, in the first embodiment, the wall thickness t of the bottom portion
42 is set to be 0.1 mm or larger.
After completing an adjustment of the restitutive force of the spring 39, the fuel filter 16 is installed at the counter valve body 20-side end portion of the
12-

holder pipe 11. Thus, the assembly of the injector 10 is completed.
Next, an operation of the injector 10 having above-described structure will be described.
When the coil 31 is not energized, no magnetic drawing force generates between the fixed core 40 and the movable core 33. Thus, a pushing force of the spring 39 moves the movable core 33 away from the fixed core 40, and the valve needle 24 integrally connected to the movable core 33 also moves away from the fixed core 40. As a result, when the coil 33 is not energized, the seal portion 25 of the valve needle 24 seats on the valve seat 21. Accordingly, no fuel is injected from the injection port 23.
When the coil 31 is energized, a magnetic field generated in the coil 31 forms a magnetic circuit to pass a magnetic flux in the housing 32, the first magnetic portion, the movable core 33, the fixed core 40 and the second magnetic portion 14. Thus, a magnetic drawing force generates by energizing the coil 31 between the fixed core 40 and the movable core 33 which are separated by the pushing force of the spring 39. When the magnetic drawing force generated between the fixed core 40 and the movable core 33 exceeds the pushing force of the spring 39, the unitized movable core 33 and valve needle 24 move toward the fixed core 40. Thus, the seal portion 25 of the valve needle 24 lifts off the ^/a\ve seat 21. The unitized movable portion 33 and valve needle 24 move upward in FIG. 1 until the movable core 33 comes in contact with the fixed core 40.
The fuel flowing from the fuel inlet 15 into the injector 10 further flows via the fuel filter 16, the inner space of the holder pipe 11, the inner space of the
(3

fixed core 40, a bore portion 331 and fuel bore 332 of the movable portion 33 and the clearance between the holder pipe 11 and the valve needle 24 into the fuel passage 26. The fuel flowing into the fuel passage 26 further flows via a clearance between the valve needle 24 lifting off the valve seat 21 and the valve body 20 into the fuel port 23 formed in the fuel port plate 22. Thus, the fuel is injected from the injection port 23.
When the coil 31 is not energized again, the magnetic drawing force between the fixed core 40 and the movable core 33 ceases. Thus, the pushing force of the spring 39 moves the movable core 33 integrally connected to the valve needle 24 away from the fixed core 40. Thus, the seal portion 25 seats on the valve seat 21 again to interrupt a fuel flow between the fuel passage 26 and the injection port 23. Thus, the fuel injection stops.
In the above-described first embodiment, the spring 39 is in direct contact at the counter movable core 33-side end portion thereof with the fixed core 40. The restitutive force of the spring 39 is adjusted by plastically deforming the bottom portion 42 of the fixed core 40. Thus, no particular member is necessary to adjust the restitutive force of the spring 39. Further, in adjusting the restitutive force of the spring 39, members of the fuel injector 10 do not come in contact with each other. Accordingly, it is possible to decrease the number of parts to simplify the structure of the fuel injector 10 and to prevent foreign matter generation caused by contacts between the members. Further, by preventing foreign matter generation, the valve needle 24 and the valve body 20 pinch no foreign matter therebetween to prevent non-scheduled fuel injection.

In the first embodiment, the restitutive force of the spring 38 is adjusted by plastically deforming the bottom portion 42 of the fixed core 40. Thus, the restitutive force of the spring 38 can be adjusted with high accuracy in accordance with a deformation amount of the bottom portion 42. Accordingly, regardless of tolerances of members, the restitutive force of the spring 39 can be easily adjusted with high accuracy to be a certain value.
Further, the bottom portion 42 is disposed at the counter movable core 33-side end portion of the fixed core 40. Thus, the fixed core 40 can install the spring 39 having a large entire length therein. Then, even when the spring 39 has a large entire length, the spring 39 is installed inside the fixed core 40 without increasing an entire length of the injector 10. Accordingly, the body can be downsized. Still further, by restricting upsizing of the fuel injector 10 in accordance with an increase of the entire length of the spring 39, the spring 39 can be provided with a required enough entire length. Accordingly, the restitutive force of the spring 39 has a large flexibility. (Second embodiment)
FIG. 6 depicts an injector 10 according to a second embodiment of the present invention. In the second embodiment, components of the injector 10 configured substantially as same as those in the first embodiment are assigned common referential numerals and descriptions of those are omitted.
The injector 10 according to the second embodiment, as shown in FIG. 6, has a fixed core 50 differently shaped from the fixed core 40 in the first embodiment. As shown in FIGS. 6 and 7, the fixed core 50 has a small diameter portion 54 in addition to a cylindrical portion 51 and a bottom portion

(engaging portion) 52. The outer diameter of the small diameter portion 54 is smaller than that of a cylindrical portion 51. The small diameter portion 54 is formed at a counter movable core 33-side end portion of the fixed core 50. The bottom portion 52 protrudes radially inward from an inner circumference of the small diameter portion 54. The bottom portion 52 has a bore portion 53 at a radial center thereof that is connected to an inner space of the cylindrical portion 51 and the small diameter portion 54 to flow fuel therethrough. A radially inside peripheral portion of the bottom portion 42 is deformed toward the movable core 33 as shown in FIG. 6 and by broken lines in FIG. 7.
The small diameter portion 54 of the fixed core 50 provides a clearance 17 between an outer circumferential face of the fixed core 50 and an inner circumferential face of the holder pipe 11. The small diameter portion 54 is shaped so that an outer circumferential face thereof is approximately in parallel to and coaxial with the inner circumferential face of the holder pipe 11. The clearance 17 formed between the small diameter portion 54 and the holder pipe 11 extends over a certain length corresponding to a length of the small diameter portion 54 in an axial direction thereof. Representing a waif thickness of the bottom portion 52 as t and a length of the small diameter portion 54 in the axial direction as x, a relation of x^t is satisfied. Thus, the small diameter portion
54 is disposed radially outside the bottom portion 52. Accordingly, the clearance 17 is disposed between an outer peripheral portion of the bottom portion 52 and the holder pipe 11.
In assembling the injector 10, a unitized valve needle 24 and movable core 33, which form the movable portion, are installed inside the holder pipe 11.

After installing the unitized movable core 33 and valve needle 24, the spring 39 is disposed at a counter valve needle 24-side of the movable core 33. In this state, the spring 39 is in neither compressed nor tensile state and has a natural entire length L. After installing the spring 39, a fixed core 50 is installed at a counter movable core 33-side of the spring 39. The fixed core 50 is press-fitted inside the holder pipe 11. Accordingly, one end portion of the spring 39 is in contact with the movable core 33 and another end portion of the spring 39 is in contact with the bottom portion 52 of the fixed core 50. Then, the fixed core 50 is press-fitted further into the holder pipe 11 in a direction toward the movable core 33. By press-fitting the fixed core 50, the spring 39 being in contact with the bottom portion 52 of the fixed core 50 is compressed.
As described above, the fixed core 50 has the small diameter portion 54 at the counter movable portion 33-side end portion thereof, and the bottom portion 52 protrudes radially inward from the small diameter portion 54. Thus, in installing the fixed core 50 inside the holder pipe 11, only the cylindrical portion 51 of the fixed core 50 is press-fitted in the holder pipe 11. That is, the small diameter portion 54 is not in contact with the holder pipe 11 and is not associated with press-fitting the fixed core 50.
Here, by providing the fixed core 50 with the bottom portion 52 protruding radially inward, the fixed core 50 has a larger stiffness at a portion in which the bottom portion 52 is formed than other portion thereof, namely the cylindrical portion 51. In a case that a fixed core is provided with no small diameter portion 54, a force necessary to press-fit the portion of the fixed core 50 with the bottom portion 52 is larger than a force necessary to press-fit the
17

cylindrical portion 51. Accordingly, the force necessary to press-fit the fixed core 50 is varied corresponding to positions of the fixed core 50, namely a press-fitting amount of the fixed core 50.
Contrastively, in the second embodiment, only the cylindrical portion 51 of the fixed core 50 having a constant wall thickness is press-fitted into the holder pipe 11. That is, the bottom portion 52 protrudes from the small diameter portion 54, however, as described above, the small diameter portion 54 is not associated with press-fitting the fixed core 50. Thus, the force necessary to press-fit the fixed core 50 is not varied corresponding to the press-fitting amount of the fixed core 50. Accordingly, the fixed core 50 is press-fitted into the holder pipe 11 by applying an approximately constant strength of force.
The fixed core 50 is press-fitted until a gap between itself and the movable core 33 reaches a distance g. After completion of press-fitting the fixed core 50, the bottom portion 52 of the fixed core 50 is bent toward the movable core 33 as shown in FIG. 6 and by broken lines in FIG. 7. Thus, the entire length of the spring 39 can be adjusted with high accuracy. That is, the restitutive force of the spring 39, namely the force pushing the unitized valve needle 24 and movable core 33 is adjusted.
In the above-described second embodiment, the bottom portion 52 of the fixed core 50 is formed to protrude radially inward from the small diameter portion 54. Thus, in press-fitting the fixed core 50 into the holder pipe 11, only the cylindrical portion 51 is associated with press-fitting the fixed core 50 into the holder pipe 11, and the small diameter portion 54 is not associated with the

press-fitting. As a result, the small diameter portion 54, which has a large stiffness by a protrusion of the bottom portion 52, is not press-fitted into the holder pipe 11. Thus, the force necessary to press-fit the fixed portion 50 into the holder pipe 11 is approximately constant regardless of the press-fitting amount of the fixed core 50. Accordingly, it is possible to set the distance g of the clearance formed between the fixed core 50 and the movable core 33 with high accuracy. Further, in press-fitting the fixed core 40, the force applied to the fixed core 50 is approximately constant. This prevents irregular contact between the fixed portion 50 and the holder pipe 11. Accordingly, generations of burrs and abrasion particles can be prevented.
Further, in the second embodiment, the bottom portion 52 protruding radially inward from the small diameter portion 54 serves the engaging portion of the fixed core 50 to be in contact with the spring 39. That is, the spring 39 pushing the unitized valve needle 24 and movable core 33 is in direct contact with the counter movable core 33-side end portion of the fixed core 50. Then, the restitutive force of the spring 39 is adjusted by bending, namely plastic deformation the bottom portion 52 of the fixed core 50. Thus, no particular member is necessary to adjust the restitutive force of the spring 39. Accordingly, it is possible to decrease the number of parts to simplify the structure. Further, by adjusting the restitutive force of the spring 39 by plastic deformation of the bottom portion 52 of the fixed core 50, the restitutive force of the spring 39 can be adjusted with high accuracy corresponding to the deformation amount of the bottom portion 42. Accordingly, regardless of tolerances of members, the restitutive force of the spring 39 can be adjusted

easily and with high accuracy to be a certain value. {Third embodiment)
FIG. 8 depicts a fixed core 60 of a fuel injector 10 according to a third embodiment of the present invention is shown in FIG. 8. Here, components of the injector 10 configured substantially as same as those in the first embodiment are assigned common referential numerals and descriptions of those are omitted.
In the third embodiment, as shown in FIG. 8, the fixed core 60 has an engaging portion 62 on a way of a cylindrical portion 71 in the axial direction thereof. The engaging portion 62 is formed to protrude radially inward from an inner circumference of the cylindrical portion 61 of the fixed core 60. The engaging portion 62 is provided with a bore portion 63 at a radial center thereof to flow fuel therethrough. A counter movable core 33-side end portion of the spring 39 is in contact with the engaging portion 62. In the third embodiment, in press-fitting the fixed core 60 into the holder pipe 11, the press-fitting force is applied to a counter movable core 33-side end face 64 of the fixed core 60. In adjusting the restitutive force of the spring 39, the engaging portion 62 is plastically deformed by applying force to the engaging portion 62. Thus, in the fixed core 60, a position to which the press-fitting force is applied differs from a position to which a force to adjust the restitutive force of the spring 39 is applied.
In the third embodiment, the position to apply the press-fitting force for the fixed core 60 differs from the position to apply the force to adjust the restitutive force of the spring 39. Thus, the movement of the fixed core 60 in

p\astica))y deforming the engaging portion 62 and unnecessary deformation of
the engaging portion 62 in the press-fitting is prevented. Accordingly, it is
possible to increase accuracies of the position of the fixed core 60 and the
distance g between the fixed core 60 and the movable portion 33.
5 (Fourth and Fifth embodiments)
FIGS. 9 and 10 respectively depict fixed cores 40, 60 of injectors 10
according to a fourth and a fifth embodiments of the present invention. Here,
components of the injectors 10 configured substantially as same as those in the
first or third embodiment are assigned common referential numerals and
10 descriptions of those are omitted.
The fourth embodiment is a modified example of the first embodiment.
As shown in FIG. 9, the fixed core 40 has a thin-walled portion 45 at a movable
core 33-side portion of the bottom portion 42. The thin-walled portion 45 is
configured to have a wall thickness smaller than that of the cylindrical portion 41.
15 Thus, the bottom portion 42 can be deformed by relatively small strength of
force.
The fifth embodiment is a modified example of the third embodiment.
As shown in FIG. 10, the fixed core 60 has a thin-walled portion 65 at a
movable core 33-side portion of the engaging portion 62 that is disposed
20 between both end portions of the fixed core 60 in an axial direction. Thus, the
engaging portion 62 is easily deformed by a relatively small strength of force.
Both in the fourth and fifth embodiments, by providing the fixed core 40, 70 with the thin-walled portion 45, 75, the bottom portion 42 or the engaging portion 72 is easily deformed by relatively small strength of force. Accordingly,
2.1

it is possible to adjust the restitutive force of the spring 39 easily and with high
accuracy.
(Sixth embodiment)
FIG. 11 depicts a fixed core 70 of an injector 10 according to a sixth embodiment of the present invention. Here, components of the injector 10 configured substantially as same as those in the second embodiment are assigned common referential numerals and descriptions of those are omitted.
In the sixth embodiment, as shown in FIG. 11, the fixed core 70 has a tapered portion 72 having an outer diameter smaller than that of a counter movable core 33-side end portion of the cylindrical portion 71. The tapered portion 72 is inclined radially inward as going away from the movable core 33 at a counter movable core 33-side end portion of the tapered portion 70. Thus, a distance between the outer circumferential face of the tapered portion 72 of the fixed core 70 and an inner circumferential face of the holder pipe 11 increases as going away from the movable core 33. A wall thickness t of the tapered portion 72 is set to satisfy a relation of t^1/2h, wherein h denotes a wall
thickness of the cylindrical portion 71. Thus, the tapered portion 72 has a larger stiffness than that of the cylindrical portion 71.
By providing the fixed core 70 with the tapered portion 72, a clearance 17 is formed between the outer circumferential face of the tapered portion 72 and the inner circumferential face of the holder pipe 11. The outer circumferential face of the tapered portion 72 and the inner circumferential face of the holder portion 11 form a certain angle with each other. The tapered portion 72 is formed to have a certain length in an axial direction of the fixed
X2-

core 70. Thus, the tapered portion 72 and the holder pipe 11 forms the
clearance 17 over a certain length in the axial direction. Further, because the
tapered portion 72 is inclined, the clearance 17 becomes wider in a radial
direction as going away from the movable core 33. Still further, because the
i tapered portion 72 is inclined radially inward, the tapered portion 72 protrudes
radially inward from the cylindrical portion 71. Thus, the tapered portion 72 provides the small diameter portion forming the clearance 17 between itself and the holder pipe 11 and the protruding portion protruding from the cylindrical portion 71. Furthermore, a counter movable portion 33-side end portion of the
) spring 39 is in contact with the inner circumferential face of the tapered portion
72. Thus, the tapered portion 72 serves the engaging portion.
In the sixth embodiment, in adjusting the restitutive force of the spring 39, the tapered portion 72 is bent to be shrunk radially inward as shown by broken lines in FIG. 11. As the tapered portion 72 is bent to be shrunk radially
5 inward, the end portion of the spring 39 in contact with the tapered portion 72
moves toward the movable core 33. Thus, an entire length of the spring 39 changes, so that the restitutive force of the spring 39 can be adjusted easily and with high accuracy.
In the sixth embodiment, the tapered portion 72 of the fixed core 70,
0 which has a diameter smaller than that of the cylindrical portion 71, is not in
contact with the holder pipe 11. Thus, only the cylindrical portion 71 is associated with the press-fitting, and the tapered portion 72 is not associated with the press-fitting. Then, only the cylindrical portion 71 of the fixed core 70, which has an approximately constant wall thickness, is press-fitted into the
^2.3

holder pipe 11. Accordingly, the force applied in press-fitting the fixed core 70 can be approximately constant and the distance g between the fixed core 70 and the movable core 33 can have high accuracy. Further, in the sixth embodiment, in press-fitting the fixed core 70 into the holder pipe 11, a force to press-fit the fixed core 70 is applied to a step portion 74 between the cylindrical portion 71 and the tapered portion 72. Thus, a position to apply the force to press-fit the fixed core 70 is the step portion 74, and a position to apply the force to adjust the restitutive force of the spring 39 is the tapered portion 72. As a result, both the positions differs from each other and it is possible to prevent the motion of the fixed core 70 in deforming the tapered portion 72 and unnecessary deformation of the tapered portion 72 in press-fitting the fixed core 70. Accordingly, it is possible to increase accuracies of the position of the fixed core 70 and the distance g between the fixed core 70 and the movable core 33. (Seventh, Eighth and Ninth embodiments)
FIGS. 12 to 14 respectively depict fixed cores 40 of fuel injectors 10 according to a seventh, eighth and ninth embodiments of the present invention. Here, components of the injectors 10 configured substantially as same as those in the second embodiment are assigned common referential numerals and descriptions of those are omitted.
In each the seventh, eighth and ninth embodiments, in order to form a clearance between the fixed core 40 and the holder pipe 11, the holder pipe 11 has a diameter expanding portion 11a, 11b or 11c.
In the seventh embodiment, the holder pipe 11 has a large diametei

portion (diameter expanding portion) 11a radially outside the bottom portion 42 of the fixed core 40. The large diameter portion 11a has an inner diameter larger than portions in contact with the cylindrical portion 41 of the fixed core 40. Thus, at the large diameter portion 11a of the holder pipe 11, a clearance 17 is formed between the outer circumferential face of the fixed core 40 and the inner circumferential face of the holder pipe 1.1.
In the eighth embodiment, the holder pipe 11 has a tapered portion (diameter expanding portion) 11b radially outside the bottom portion 42 of the fixed core 40. An inner diameter of the tapered portion11b extends as going from a position of the fixed core 40 in contact with the cylindrical portion 41 toward the fuel inlet port 15. Thus, at the tapered portion 11b of the holder pipe 11, a clearance 17 is formed between the outer circumferential face of the fixed core 40 and the innercircumferential face of the holder pipe 11.
In the ninth embodiment, the holder pipe 11 has a depressed portion (diameter expanding portion) 11c radially outside the bottom portion 42 of the fixed core 40. The depressed portion 11c is formed to extend in a circumferential direction of the holder pipe 11. The depressed portion 11c has an inner diameter larger than the portion of the fixed core 40 in contact with the cylindrical portion 41. That is, the depressed portion 11c is depressed radially outward with respect to the portion in contact with the cylindrical portion 41 of the fixed core 40. Thus, at the depressed portion 11c of the holder pipe 11, a clearance 17 is formed between the outer circumferential face of the fixed core 40 and the inner circumferential face of the holder pipe 11.
In the seventh, eighth and ninth embodiments, by providing the holder

pipe 11 with the large diameter portion 11a, the tapered portion 11b or the depressed portion 11c, the clearance 17 is formed between the holder pipe 11 and the fixed core 40. That is, in order to form the clearance 17, not only the fixed core 40 but also the holder pipe 11 may be processed.* In these embodiments, the outer circumferential face of the bottom portion 42 of the fixed core 40 is not in contact with the holder pipe 11. Thus, only the cylindrical portion 41 is associated with the press-fitting, and the outer circumferential face of the bottom portion 42 is not associated with the press-fitting. Then, only the cylindrical portion 41 of the fixed core 40 is press-fitted into the holder pipe 11. Accordingly, the force applied in press-fitting the fixed core 40 becomes constant and the accuracy of the distance g between the fixed core 40 and the movable core 33 is increased.
The above-described embodiments describe examples in which the movable portion includes separately formed movable core 33 and the valve needle 24. However, the movable core 33 and the valve needle 24 may be integrally formed. In some of the embodiments, the injection port plate 22 having the injection port 23 is fixed on the valve body 20, however, the valve body 20 itself may be provided with an injection port. Further, some of the embodiments describe examples in which the spring 39 is in direct contact with the fixed core or the movable core, however, another member may be disposed between the spring 39 and the fixed core and/or the movable core. Still further, some of the several embodiments describe examples in which the holder pipe 11 forms a magnetic circuit by a magnetic field generated in the coil 31. However, the holder pipe 11 is not limited to a member capable of forming a

magnetic circuit, and the present invention may be applied to any member that can install the fixed core therein.
In the above-described embodiments, the embodiments in which the present invention is applied are described individually, however, a plurality of the embodiments may be combined.
This description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

WE CLAIM:
1. A fuel injection valve (10) comprising:
a cylinder member (11) formed in an approximately cylindrical shape and having a fuel passage (26) to flow a fuel from an inlet port (15) to an injection port (23);
a movable portion (33) made of magnetic material and slidably installed in the cylinder member (11) to reciprocate in an axial direction of the cylinder member (11) to open and close the fuel passage (26);
a fixed core (50, 70) for generating a magnetic force to move the movable portion (33) to open the fuel passage and having
a body portion (51, 71) fixed in the cylinder member, and a protruding portion (52, 72) protruding radially inward from the body portion (51, 71),
and wherein a clearance (17) is formed between an inner circumferential face of the cylinder member (11) and at least a portion of an outer circumferential face of the fixed core (50, 70) which is radially outside the protruding portion (42).
2. The fuel injection valve (10) according to claim 1, wherein:
the body portion (51) has a small diameter portion (54) in which an outer circumferential face of the body portion (51) is depressed radially inward; and
the clearance (17) is formed radially outside the small diameter portion (54).
3. The fuel injection valve (10) according to claim 2, wherein an outer circumferential face of the small diameter portion (54) is approximately in parallel to the inner circumferential face of the cylinder member (11).
4. The fuel injection valve (10) according to claim 1, wherein:
the protruding portion (72) extends to be inclined radially inward from the end portion of the body portion (71); and
the clearance (17) is formed radially outside the protruding portion (72).
28

5. The fiiel injection valve (IU) according to oaim t, wucicm uiw p.v»v.w«...to
portion (72) is formed so that a distance between an outer circumferential face of the
protruding portion (72) and the inner circumferential face of the cylinder member (11)
increases as going away from the movable portion (33).
6. The fuel injection valve (10) according to claim 1, wherein:
the cylinder member (11) has a diameter expanding portion (11a, lib, lie) in which the inner circumferential face of the cylinder member (11) is depressed radially outward; and
the clearance (17) is formed radially inside the diameter expanding portion (11a, lib, lie).
7. The fuel injection valve (10) according to any one of claims 1 to 5, wherein it comprises an elastic member (39) interposed between the movable portion (33) and the protruding portion (42, 72) to push the movable portion (33) in a direction to close the fuel passage (26).
8. The fuel injection valve (10) according to claim 7, wherein the protruding portion (42, 72) is plastically deformed to adjust a restitutive force of the elastic member (39).

Documents:

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Patent Number

268598

Indian Patent Application Number

1213/CHE/2009

PG Journal Number

37/2015

Publication Date

11-Sep-2015

Grant Date

07-Sep-2015

Date of Filing

26-May-2009

Name of Patentee

DENSO CORPORATION

Applicant Address

1-1, SHOWA-CHO, KARIYA-CITY, AICHI-PREF. 448-8661

Inventors:

#	Inventor's Name	Inventor's Address
1	SUGIYAMA, KOICHI,	C/O DENSO CORPORATION 1-1, SHOWA-CHO, KARIYA-CITY, AICHI-PREF. 448-8661

PCT International Classification Number

F02M69/54

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2004-247013	2004-08-26	Japan
2	2004-247014	2004-08-26	Japan