Title of Invention	A FUEL INJECTION VALVE
Abstract	In a fuel injection valve whose injection amount is adjustable in shorter time, a fixed core (30) is press fitted to inner circumferences of a non-magnetic member (14) and a second magnetic member (15) of a pipe member (12). Inner circumferential wall of the fixed core (30) has large and small diameter portions (35 and 36) to form a step (37) at a boundary therebetween. An end of a spring (24) is retained by the step (37) and the other end thereof by a moving core (22). The spring (24) urges the moving core (22) and a valve member (20) in a direction in which the valve member (20) is seated on a valve seat (17). Upon energizing a coil (44), the valve member (20) and the moving core (22) move against biasing force of the spring (24) toward the fixed core (30) so that the valve member (20) leaves the valve seat (17), which allows to inject fuel from injection bores (18a).

Title of Invention

A FUEL INJECTION VALVE

Abstract

In a fuel injection valve whose injection amount is adjustable in shorter time, a fixed core (30) is press fitted to inner circumferences of a non-magnetic member (14) and a second magnetic member (15) of a pipe member (12). Inner circumferential wall of the fixed core (30) has large and small diameter portions (35 and 36) to form a step (37) at a boundary therebetween. An end of a spring (24) is retained by the step (37) and the other end thereof by a moving core (22). The spring (24) urges the moving core (22) and a valve member (20) in a direction in which the valve member (20) is seated on a valve seat (17). Upon energizing a coil (44), the valve member (20) and the moving core (22) move against biasing force of the spring (24) toward the fixed core (30) so that the valve member (20) leaves the valve seat (17), which allows to inject fuel from injection bores (18a).

Full Text	FUEL INJECTION VALVE AND METHOD OF ADJUSTING INJECTION AMOUNT OF SAME Description The present invention relates to a fuel injection valve for an internal combustion engine (hereinafter called "engine") and a method of adjusting injection amount of the fuel injection valve. It is necessary for adjusting injection amount of a fuel injection valve to adjust both of a static injection amount and a dynamic injection amount. The static injection amount is decided by a gap between a fixed core and a moving core. The dynamic injection amount is decided by a biasing force of a spring urging a valve member reciprocatingly movable with the moving core. As disclosed in JP-A-4-231672, it is well known that an adjusting pipe for retaining the spring is disposed in the fixed core and the biasing force of the spring is adjusted by changing a position of the adjusting pipe relative to the fixed core. In the fuel injection valve as disclosed in JP-A-4-231672, it is common to adjust the position of the adjusting pipe for adjusting ti\e dynamic in j action amount after the gap between the fixed core and the moving core is adjusted for adjusting the static injection amount. However, if the adjusting pipe is, for example, press fitted in the fixed core for positioning the adjusting pipe and the position of the fixed core is displaced due to pressing force of the adjusting pipe, a value of the gap between the fixed core and the moving core is likely changed so that the static injection amount is changed. To prevent the change of the gap between the fixed core and the moving core, fixed strength of the fixed core has to be reinforced. Further, to fix the adjusting pipe in the fixed core without applying an excessive pressing force to the fixed core, it is necessary to manufacture the fixed core and the adjusting pipe whose dimensions, shapes and surface roughness are highly accurate, which results in a higher manufacturing cost. Further, the conventional adjusting method, in that the biasing force of the spring is adjusted with the adjusting pipe, needsa longer adjusting time, since two step adjustments, that J.S, adjustments of the static injection amount and the dynamic injection amount, are required for adjusting the injection amount. An object of the present invention is to provide a fuel injection valve which is easily manufactured with less parts and in which injection amount is adjustable with shorter time. It is another object to provide a method of adjusting injection amount of the fuel injection valve mentioned above- To achieve the above object, ^in a fuel injection valve comprising a valve body having a valve seat, a valve member for interrupting fuel injection on seating on the valve seat and allowing the fuel injection on leaving the valve seat, a moving core positioned on an opposite side of the valve seat with respect to the valve member and reciprocatingly movable together with the valve member, a fixed core facing to an end of the moving core positioned on a side of one of directions inwhichthemoving core reciprocatingly moves, abiasingmember urging the valve member in the other of directions in which the moving core reciprocatingly moves, and a coil, when energized, generating a magnetic attracting force of urging the moving core against the biasing force of the biasing member toward the f ixedcore, the fuel injection valve is characterized in that the fixed core is provided at an inner wall with a protrusion by which the biasing member is retained. According to the fuel injection valve mentioned above, since the biasing member urging the valve member toward the valve seat is directly retained by the fixed core, a number of pats constituting the fuel injection valve is reduced. Further, static and dynamic injection amounts are adjustable simultaneously by adjusting position of the fixed core so that a time necessary for adjusting the injection amount is reduced. Position of the protrusion of the fixed core governs the biasing force of the biasing member for urging the valve member. Accordingly, on adjusting the dynamic injection amount, it is required to control to secure the position of the protrusion whose dimension is accurate to some extent. However, this dimensional control is not severer than that for the fixed core and the adjusting pipe to be press fitted into the fixed core as in the conventional fuel injection valve. Accordingly, fabrication of the fixed core of the present invention is easier than that of the conventional fuel injection valve. Further, once the fixed core is assembled and the gap between the fixed core and the moving core is adjusted, outer force larger than the pressing force required for press fitting of the fixed core is not applied to the fixed core so that the gap between the fixed core and the moving core is hardly changed. Accordingly, it is not necessary to rigidly fix the fixed core so that assembly of the fixed core is easier. Furthermore, by changing the assembly position of the fixed core, the gap between the fixed core and the moving core is adjustable and the biasing force of the biasing member is also adjustable, that is, the static and dynamic injection amounts can be adjusted. Accordingly, if the assembly position of th§ fixed core is controlled with higher accuracy, the gap between the fixed core and the moving core and the biasing force of the biasing member can be highly accurately adjusted, which results in adjusting highly accurately the static and dynamic injection amounts- It is preferable that the fixed core and the moving core are accommodated in a pipe member comprising a first magnetic member, a magnetism resistant member and a second magnetic member or the valve body, the f axed core and the moving core are accommodated in a pipe member having a magnetic member covering an outer circumference of the moving core- With this structure, the fixed core is press fitted into the pipe member. According to the fuel injection valve, assembly of the fixed core is easier since the fixed core is press fitted into the pipe member. Further, positioning of the fixed core relative to the pipe member is accurate since the fixed core is press fitted into the pipe member. Accordingly, the gap between the moving core and the fixed core is uniform (not fluctuated) in each of the fuel injection valves, which results in easily adjusting the injection amount of the fuel injection valve. Further, once the fixed core is press fitted in the pipe member, larger outer force like a force necessary for press fitting the adjusting pipe in the conventional fuel injection valve is not applied to the fixed core so that the fixed core may be press fitted into the pipe member with smaller pressing f ore Accordingly, it is not necessary to fabricate the fixed core with higher accuracy in order to secure a limited range of pressing force necessary for press fitting the fixed core into the pipe member so that the fabrication of the fixed core is easier. Furthermore, the pressing force necessary for press fitting the fixed core into the pipe member is smaller and an amount of scraps or chips produced by press fitting the fixed core into the pipe member is reduced. Preferably, the protrusion of the fixed core is formed by machining a part of the inner circumferential wall thereof so as to form a step or by cold forging or pressing the fixed core so as to form a single or plurality of projections protruding radially inward. In an engine having a plurality of cylinders, an air/fuel mixture ratio is adjusted by changing the average of the respective injection amounts of the fuel injection valves installed in the cylinders. The change of the average of the respective injection amount is executed by changing with a uniform ratio the respective currents supplied to the fuel injection valves• Accordingly, if the injection amount of one of the fuel injection valves is displaced out of a given range, the air/fuel mixture ratio is not accurately corrected. Therefore, it is preferable that the injection amount of each fuel injection valve falls within the given range. To this end, after defining the static injection amount with a gap between the moving core and the fixed core, position of an adjusting pipe, which is a separate member from the fixed core and retains the biasing member for urging the valve member, is adjusted so as to adjust the dynamic injection amount with higher accuracy. However, in an engine having a single cylinder, to correct the air/fuel mixture ratio, it is sufficient to adjust the injection amount of a single fuel injection valve so that it is not necessary to strictly control the static and dynamic injection amounts. Accordingly, it is preferable that the fuel injection valve, in which the static and dynamic injection amounts are simultaneously adjusted by adequately positioning the fixed core that directly retains the biasing member urging the valve member so as to accurately correct the air/fuel mixture ratio, is applied to the single cylinder engine. If the member retaining the biasing member or the biasing member itself has dimensional fluctuation due to manufacturing errors in a state that the fixed core is press fitted into the pipe member to secure a predetermined value of the gap between the fixed core and the moving core, the biasing force of the biasing member is apt to be fluctuated, which causes to fluctuate the dynamic injection amount. Accordingly, it is preferable to have a method comprising the following steps of adjusting the injection amount of the fuel injection valve. The first step is to form a housing assembly comprising members including the coils arranged outside outer circumference of the pipe member. The next step is to form a pipe shaped assembly in which the valve body, valvemember, the moving core, the biasing member and the fixed core ^re accommodated in such a manner that a gap between the moving core and the fixed core has a predetermined value. The final step is to adjust a distance by which the pipe shaped assembly is pushed into the housing assembly. If the position of the gap relative to the coil is changed by adjusting the distance by which the pipe shaped assembly is pushed into the housing assembly, a magnetic attracting force is changed. Further, if the housing assembly has a magnetic member positioned outside outer circumference of the pipe member so as to radially face to the moving core, an area of the magnetic member radially facing to the moving core is changed. Since the magnetic attracting force is adjusted by adjusting the distance by which the pipe shaped assembly is pushed into the housing assembly, the dynamic injection amount fluctuation due to the fluctuation of the magnetic attracting force can be adjusted and corrected with higher accuracy. other features and advantages of the present invention will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following 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 of a fuel injection valve according to a first embodiment of the present invention; Fig. 2 is an enlarged cross sectional view of a part in a vicinity of a fixed core of the fuel injection valve of Fig. 1; Fig. 3 is a schematic view showing an installation position of the fuel injection valve of Fig.l; Fig. 4 is a schematic view explaining a process of assembling the fixed core to the injection control valve; Fig. 5 is a time chart showing a change per time of an injection amount; Fig. 6 is a graph showing a relationship between a magnetic attracting force and a gap; Fig. 7 is a graph showing a relationship between a valve opening time and a gap; Fig. 8 is a graph showing a relationship between a valve closing time and a gap; Fig. 9 is a graph showing a relationship between an ineffective injection time and a gap; Figs. lOA and lOB are views explaining a method of adjusting a dynamic injection amount according to a second embodiment of the present invention; Figs . 1 lA and 1 IB are another views explaining the method of adjusting the dynamic injection amount according to the second embodiment; Fig. 12 is a further view explaining the method of adjusting the dynamic injection amount according to the second embodiment; Fig. 13 is a flowchart showing the method of adjusting the dynamic injection amount according to the second embodiment; Fig. 14 is a cross sectional view of a part of a fuel injection valve in a vicinity of a fixed core according to a third embodiment of the present invention; Fig. 15 is a cross sectional view of a fuel injection valve according to a fourth embodiment of the present invention; and Fig. 16 is a cross sectional view of a fuel injection valve according to a fifth embodiment of the present invention. Embodiments of the present invention are described with reference to drawings, (first embodiment) A fuel injection valve 10 according to a first embodiment of the present invention, which is shown in Fig. 1, is installed in a single cylinder engine for automotive two wheel vehicle shown in Fig. 3. As shown in Fig. 1, a pipe member 12, which is composed of a magnetic member and a non-magnetic member, is formed in shape of a cylinder. The pipe member 12 is provided inside with a fuel passage 300 . A valve body 16, a valve member 20, a moving core 22, a spring 24 as a biasing member, and a fixed core 30 are accommodated in the fuel passage 300. The pipe member 12 has a first magnetic member 13, a non-magnetic member 14 as a magnetism resistant member and a second magnetic member 15 which are arranged in series upward from a vicinity of the valve body 16 on a lower side of Fig. 1. Connection between the first magnetic member 13 and the non-magnetic member 14 and connection between the non-magnetic member 14 and the second magnetic member 15 are conducted by welding, for example, by laser welding. The non-magnetic member 14 prevents magnetic flux from short circuiting between the first and second magnetic members 13 and 15- The valve body 16 isbondedby welding to an interior of the first magnetic member 13 on a side of an injection bore. The valve body 16 is provided on an inner circumferential wall thereof with a valve seat 17 on which the valve member 20 can be seated. A cup shaped injection bore plate 18 is fixed by welding on an outer circumferential wall of the valve body 16. The injection bore plate 18 is formed in shape of a thin plate and provided at a center part thereof with a plurality of injection bores 18a. The valve member 20 is formed in shape of a cylinder having a bottom and provided on a bottom side thereof with a contact portion 21. The contact portion 21 comes in contact with the valve seat 17 formed in the valve body 16. When the contact portion 21 is seated on the valve seat 17, the injection bores 18a are closed so that fuel injection is interrupted. The moving core 22 is bonded by welding to the valve member 2 0 on an opposite side to the valve body 16. The valve member 20 is provided on an upstream side of the contact portion 21 withapluralityof fuel apertures 20apenetrating a sidewall thereof. Fuel flowed in the valve member 20 passes through the fuel apertures 20a from an inside to an outside and flows toward a valve portion formed by the contact portion 21 and the valve seat 17. The fixed core 30 is formed in a cylindrical shape. The fixed core 30 is fixed into the pipe member 12 in such a manner that the fixed pore 30 is press fitted to inner circumferences of the non-magnetic member 14 and the second magnetic member 15 of the pipe member 12 after being inserted into the pipe member 12 from an opening thereof, as shown in Fig. 4. As shown in Fig. 1, the fixed core 30, which is positioned on an opposite side to the valve body 16 with respect to the moving core 22 in one of directions in which the valve member 20 moves reciprocatingly, is opposed to the moving core 22. An end of the fixed core 30 opposed to the moving core 22 is coated with non-magnetic material. * As shown in Fig. 2, the fixed core 30 has a first small diameter portion 31, a press fitting portion 32, a second small diameter portion 33 and a large diameter portion 34 which are arranged in series from a vicinity of the moving core 22. An outer diameter of the press fitting portion 32 is equal to that of the large diameter portion 34 - Each outer diameter of the first and second small diameter portions 31 and 33 is smaller than each outer diameter of the press fitting portion 32 and the large diameter portion 34 and the first and second small diameter portions 31 and 33 are not in contact with the inner circumferential wall of the pipe member 12. The press fitting portion 32 is press fitted to an inner circumferential wall of the non-magnetic member 14 and an inner circumferential wall of the second magnetic member 15. An inner circumferential wall of the fixed core 30 has a large diameter portion 35 and a small diameter portion 36 whose inner diameter is smaller than that of the large diameter portion 35 tha-^ is arranged in order from a side of the moving core 22. A boundary between the large diameter portion 35 and the small diameter portion 36 is provided with a step 37 constituting a protrusion. An end of a spring 24 is retained by the step 37.and the other end of the spring 24 is retained by the moving core 22. The spring 24 urges themoving core 22 and the valve member 20 in a direction in which the valve member 20 moves to seat on the valve seat 17, that is, in the other of the directions in which the valve member 20 moves reciprocatingly. Magnetic members 40 and 42 are magnetically connected and arranged radially outside a coil 44 . The magnetic member 40 is magnetically connected with the first magnetic member 13 and the magnetic member 42 is magnetically connected with the second magnetic member 15. The fixed core 30, the moving core 22, the first magnetic member 13, the magnetic members 40 and 42 and the secondmagnetic member 15 constitute a magnetic circuit. A spool 45, on which the coil 44 is mound, mounted on outer circumference of the pipe member 12. As shown in Fig, 1, a resin housing 50 covers the outer circumferences of the pipe member 12 and the coil 44. A terminal 52 is connected in circuit with the coil 44 and supplies driving current to the coil 44. Fuel flowed into the fuel passage 300 from a portion of the pipe member 12 on an upper side of Fig. 1 is injected from the injection bores 18a via a fuel passage inside the fixed core 30, a fuel passage inside the moving core 22, a fuel passage inside the valve member 20, the fuel apertures 20a and an opening formed between the contact portion 21 and the valve seat 17 when the contact portion 21 leaves the valve seat 17. In the fuel injection valve mentioned above, when the current to the coil 44 is turned off, the valve member 20 is moved by the spring 24 in a lower direction in Fig. 1, that is, in a valve closing direction, so that the contact portion 21 comes in contact with the valve seat 17. Accordingly, the injection bores 18a are closed for interrupting the fuel injection. When the current to the coil 44 is turned on, magnetic flux flows through the magnetic circuit constituted by the fixed core 30, the moving core 22, the first magnetic member 13, the magnetic members 40 and 42 and the second magnetic member 15 so that a magnetic attracting force generates between V^ the fixed core 30 and the moving core 22. 'Accordingly, the valve member 20 moves together with the moving core 22 against the biasing force of the spring 24 toward the fixed core 30 so that the contact portion 21 leaves the valve seat 17, which allows to inject fuel from the injection bores 18a. A maximum lift amount of the valve member 20 is defined in such a manner that the moving core 22 is stopped by the fixed core 30. A method of adjusting the dynamic injection amount of the fuel injection valve 10 is described below. First of all, when the fuel injection valve 10 injects fuel, an injection amount is changed according to a lapse of time. As shown in Fig. 5, when an injection pulse signal is applied to the coil during a given pulse time Ti, the magnetic attracting force generates between the fixed core 30 and the moving core 22 . Since there is a time delay after the injection pulse signal is turned on until the magnetic attracting force causing the moving core 22 to move toward the fixed core 30 generates, the valve member 20 is moved to leave the valve seat 17 and stopped by the fixed core 30 with a time delay after the rising of the injection pulse signal. A valve opening time To represents a time necessary for the valve member 20 to move away from the valve seat 17 until being stopped by the fixed core, that is, to show a maximum lift after the injection pulse signal for instructing the injection is turned on. When the injection pulse signal is turned off, there is still a time delay after the falling of the injection pulse signal until the moving core 22 leaves the fixed core 30 and the valve member 20 is seated on the valve seat 17. A valve closing time Tc represents a time necessary for the valve member 2 0 to be seated on the valve seat 17 for interrupting the injection after the injection pulse signal is turned off. As shown in Fig. 5, it is presumed that an area SO covering an amount of fuel to be injected until the valve member 20 is stopped by the fixed core 30 after leaving the valve seat 17 is substantially equal to an area SI covering an amount of fuel to be injected until the valve member 20 is seated on the valve J seat 17 after leaving the fixed core 30. Accordingly, if the dynamic injection amount shown in Fig. 5 is injected in a fully opened valve state in which the moving core 22 is stopped by the fixed core 30, an effective injection time of the fuel injection valve 10 necessary for the injection is presumed to satisfy the following formula (1), Ti + Tc - To = Ti - (To -Tc) (1) The static injection amount is obtained by measuring the injection amount upon applying to the fuel injection valve 10 an injection instruction signal having, for example, 1 minute pulse width. If injected in a fully opened valve state in which the moving core 22 is stopped by the fixed core 30, an injection amount per unit time [msec] of the dynamic injection amount q [mm /str] is presumed to be equal to an injection amount per unit time [mm /msec] into which the static injection amount Q [cm min] is converted. Accordingly, the injection amount per unit time [msec] of the dynamic injection amount q [mm^/str] can be expressed as Q/60. Further, when the injection signal having the pulse time Ti is applied to the coil 44, the dynamic injection amount q [mm /str] can be expressed in use of the effective injection time of the formula (1) as the following formula (2) , in which (To-Tc) is expressed as an ineffective injection time Tv, Q = (Q/60) X (ti- (to -Tc)) = (Q/60) X (Ti - Tv) (2) As shown in Fig. 4, the static injection amount and the dynamic injection amount of the fuel injection valve 10 are defined at the same time by press fitting the fixed core 30 into the pipe member 12 so that a gap between the moving core 22 and the fixed core 30 is a predetermined value. However, due to manufacturing fluctuations of the moving core 22, the fixed core 30 by which the spring 24 is retained and the spring 24 itself, the biasing force of the spring 24 is likely to be fluctuated so that the dynamic injection amount tends to vary every fuel injection valve. A method of adjusting the dynamic injection amount with less fluctuation is described below. To begin with, a relationship between the gap- and the magnetic attracting force, the valve opening time To or the valve closing time tc is described. As shown in Fig. 6, as the gap is larger, the magnetic attracting force of attracting the moving core 22 toward the fixed core is smaller. As the gap is larger and the attracting force is smaller, the valve opening time To is longer, as shown in Fig. 7. As shown in Fig. 8, as the gap is larger, the valve closing time tc is longer. However, a ratio of a time by which the valve opening time To becomes longer to a distance by which the gap becomes larger is larger than a ratio of a time by which the valve closing time Tc becomes longer to a distance by which the gap becomes larger. Accordingly, as shown in Fig. 9, the ineffective injection time Tv, which is a difference between the valve opening time To and the valve closing time Tc, is longer, as the gap is larger. It is understood from the formula (2) that the dynamic injection amour)t q is variable according to a change of the ineffective injection time Tv, that is, a change of the difference between the valve opening time To and the valve closing time Tc. Though the ineffective injection time Tv is changed according to a change of the gap, the dynamic injection amount of the fuel injection valve 10 can be adjusted to have a given value by measuring the static injection amount, while the fixed core 30 is press fitted to the pipe member 12, so that the static injection amount, which varies with the change of the gap, falls within an allowable range. 4 According to the first embodiment, a part of the fixed core 30 on an axial end side in a press fitting direction is press fitted to the inner circumferential wall of the pipe member 12. Axial length of the part of the fixed core 30 to be press fitted to the pipe member 12 is relatively short so that the fixed core 30 is easily press fitted to the pipe member 12 with less pressing force. (Second embodiment) A method of adjusting a dynamic injection amount according to a second embodiment is described with references to Figs. 10 to 13. A structure of a fuel injection valve, to which the method of adjusting the dynamic injection amount according to the second embodiment is applicable, is substantially same as the first embodiment. Fig. 13 is a flowchart showing the method of adjusting the dynamic in j act ion amount according to the second embodiment. As shown in Fig. lOA, a housing assembly 200 is formed by connecting the magnetic members 40 and 42 and the coil 44 through resin material (Step 400 in Fig. 13). The magnetic members 40 and 42 and the coil 44 are members mounted on an outer circumference of the pipe member 12. Further, as shown in Fig. lOB, the pipe member 12 formed by bonding the first magnetic material 13, the non-magnetic material 14 and the second magnetic material 15 to one another by welding. As shown in Figs. IIA, the pipe member 12 is press fitted into the housing assembly 200 until a distance d between the step 15a of the second magnetic member 15 and the magnetic member 42 becomes a given value (Step 402). The valve body 16 to which the injection bore plate 18 is bonded by welding is inserted into and bonded by welding to the first magnetic member 13. The spring 24 and the valve member 20 to which the moving core 22 is bonded by welding are inserted into the pipe member 12. Then, as shown in Fig. IIB, the fixed core 30 is press fitted in the pipe member 12 so as to secure a predetermined gap between the moving core 22 and the fixed core 30. The pipe member 12 is press fitted in the magnetic member 42 of the housing assembly 200. This pressing force is larger than the pressing force with which the fixed core 30 is press fitted in the pipe member 12. Accordingly, even if the fixed core 30 is press fitted in the pipe member 12, the distance d between the step 15a of the second magnetic member 15 of the pipe member 12 and the magnetic member 42 of the housing assembly 200 is hardly changed. As shown in Fig. 12, the fuel filter 22 is mounted on the pipe member 12 on a fuel inlet side thereof so that a pipe shaped assembly 210, which is composed of the pipe member 12, the valve body 16, the injection bore plate 18, the valve member 20, the moving core 22, the spring 24, the fixed core 30 and the fuel filter 60, is formed (Step 404). Then, the pipe shaped assembly 210 is pushed into the housing assembly 200 while a push amount is adjusted to achieve the distance d falling within a given range. According to the first embodiment, the dynamic injection amount of the fuel injection valve 10 is variable according to changes of the 4 valve opening time To and the valve closing time Tc, as understood from the formula (2) . Accordingly, to adjust the dynamic injection amount in the first embodiment, the gap between the moving core 22 and the fixed core 30 is adjusted so that the valve opening time To and the valve closing time Tc are changed. According to the second embodiment, to adjust the dynamic injection amount, the valve opening time To and the valve closing time Tc are changed by adjusting the distance (the push amount) by which the pipe shaped assembly 210 is pushed into the housing assembly 200. A change of the push amount by which the pipe shaped assembly 210 is pushed into the housing assembly 200 causes not only to change a position of the gap between the moving core 22 and the fixed core 30 relative to the coil 44 but also to change an area of the moving core 22 radially facing to the magnetic member 4 0 so that the magnetic attracting force is changed, which results in changing the valve opening^ time To and the valve closing time Tc. Accordingly, the dynamic injection amount is adjusted by pushing the pipe shaped assembly 210 into the housing assembly 200 so that predetermined values of the valve opening time To and the valve closing time Tc are secured. The valve opening time To is determined by measuring a time duration from a time when the injection pulse signal applied to the coil 44 rises to a time when an acceleration sensor 230, which is mounted, for example, on a basement 200 as shown in Fig. 12, detects a shock due to hitting of the moving member 22 against the fixed core 30 . The valve closing time Tc is detected by measuring a time duration from a time when the injection pulse signal applied to the coil 44 falls to a time when an acceleration sensor 230 detects a shock due to seating of the valve member 20 on the valve seat 17. As soon as the valve opening time To and the valve closing time Tc reach the predetermined values (Step 408), pushing of the pipe shaped assembly 210 into the housing assembly 200 is terminated. Then, the pipe shaped member 210 is fixed to the housing assembly 200 by bonding the magnetic member 40 and the first magnetic member 13 to each other (Step 410). In the method of adjusting the injection amount according to the second embodiment, it is preferable in view of preventing foreign materials from entering into the fuel injection valve 10 that all processes up to Step 404 at which the pipe shaped assembly 210 is formed by mounting the fuel filter on the pipe member 12 on a fuel inlet side thereof are performed in a clean room. It is not necessary to perform in the clean room the processes of measuring the leakage amount at Steps 406 and 408 and the process of adjusting the push amount of the pipe shaped assembly 210 into the housing assembly 200 so that all processes until the injection amount adjustment of the fuel injection valve 10 is finished after the fuel filter has been mounted on the pipe member 12 on a fuel inlet side thereof may be carried out in a usual working room. In the second embodiment, the valve body 16 and the injection bore plate 18 are attached to the pipe member 12 after the pipe member 12 has been press fitted to the housing assembly 200, since the injection bore plate 18 is formed in shape of a cup whose outer diameter is larger than inner diameter of the magnetic member 40 . However, if an injection bore plate 18, which is formed in shape of a thin plate, is fixed to a bottom outer wall of the valve body, as shown in third and fourth embodiments described later, the pipe shaped assembly the moving core 22, the spring 24 and the fixed core 30 are accommodated in the pipe member 12 so that the gap between: 210, in which, after the valve body 16 and the injection plate 18 are mounted on the pipe member 12, the valve member 20, the moving core 22, the spring 24 and the fixed core 30 are the moving core 22 and the fixed core 30 has the predetermined value, may be inserted into the housing assembly 200. (Third embodiment) A third embodiment of the present invention is described in Fig. 14. The same reference number as that of the first embodiment is assigned to a substantially similar functional component. , A fixed core 70 is press fitted into the pipe member 12. The fixed core 70 is provided on an inner circumference thereof with a plurality of projections 72 circumferentially spaced or a ring shaped projection 72 which are or is formed by cold forging or pressing (punching) so as to protrude radially inward. The single or plurality of projections 72 constitute the protrusion. Inner diameter of the fixed core 70 is smaller at the projection 72. The spring 24 is retained by the projection 72. 4 In the fuel injection valve according to the third embodiment, the static and dynamic injection amounts may be simultaneously decided by adjusting the gap between the moving core 22 and the fixed core 7 0 to the predetermined value. Further, the given value of the dynamic injection amount may be secured by measuring the injection amount while the fixed core 70 is press fitted into the pipe member 12. Moreover, after forming the housing assembly by connecting the members including the coil 44 which are mounted on the outer circumference of the pipe member 12 and forming the pipe shaped assembly by accommodating the valve body 16, the injection bore plate 18, the valve member 20, the moving core 22, the spring 24 and the fixed core 70 in the pipe member 12 so that the gap between the moving core 22 and the fixed core 70 has the predetermined value, the dynamic injection amount may be adjusted by adjusting the push amount of the pipe shaped assembly into the housing assembly. (Fourth and fifth embodiments) Fourth and fifth embodiments of the present invention are described with reference to Figs. 15 and 16, respectively. As shown in Fig. 15, a pipe member 82 of a fuel injection valve 80 according to the fourth embodiment has a magnetic member 83 and a non-magnetic member 84 which are arranged in order from a side of a valve body 86 positioned at a lower part of Fig. 15. The magnetic member is inserted into and bonded by welding to an inner circumference of the non-magnetic member 84. A thin thickness injection bore plate 88 is fixed by welding to a bottom outer wall of the valve body 86. The injection bore plate 88 is provided with a plurality of injection bores. A valve member 90 is formed in shape of a cylinder having a bottom. The valve member 90 has a contact portion 91 which comes in contact with a valve seat 87 formed on the valve body 86 . The valve member 90 is provided in a side wall on an upstream side of the contact portion 91 with a plurality of fuel apertures 90a penetrating through the side wall. Fuel flowed in the valve member 90 flows radially from an inside of the fuel apertures 90a to an outside thereof and, then, flows toward a valve portion formed by the contact portion 91 and the valve seat 87. A moving core 92 is fixed by welding to the valve member 90 on an opposite side to the valve body 86. An end of a spring 94 as the biasing member is retained by the valve member 90 and the other end thereof is retained by a step 101 formed by the protrusion of a fixed core 100. The fixed core 100 is press flitted in the pipe member 82. A coil 102 is arranged on an outer circumference of the non-magnetic member 84 . Magnetic member 104 covers the outer circumference of the coil 102 and is connected to the magnetic member 83 at a position radially outside, the moving core 92 and to the non-magnetic member 8 4 at a position radially outside the fixed core 100. A resin housing 110 covers outsides of the pipe member 82, the coil 102 and the magnetic member 104. A fuel filter 112 is mounted on the pipe member 82 on a fuel inlet side thereof. In a fuel injection valve 120 according to the fifth embodiment, as shown in Fig. 16, a fixed core 122 is press fitted to the pipe member 82. The fixed core 122 is provided on an inner circumference thereof with a plurality of projections 123 circumferentially spaced and formed by cold forging or punching to protrude radially inward, which constitute the protrusion. Inner diameter of the fixed core 122 is smaller at the projections 72. A spring 94 is retained by the projections 123. The other structure of the fuel injection valve 120 is substantially same as that of the fourth embodiment. In each of the fuel injection valves 80 and 120, the static and dynamic injection amounts may be simultaneously decided by adjusting the gap between the moving core and the fixed core to the predetermined value. Further, the given value of the dynamic injection amount may be secured by measuring the injection amount while the fixed core is press fitted into the pipe member. Moreover, after forming the housing assembly by connecting the members including the coil 102 which are mounted on the outer circumference of the pipe member 82 and forming the pipe shaped assembly by accommodating the valve body, the injection bore plate, the valve member, the moving core, the spring and the fixed core in the pipe member so that the gap between the moving core and the fixed core has the predetermined value, the dynamic injectionamountmaybeadjustedby adjusting the push amount of the pipe shaped'assembly into the housing assembly. In the embodiments mentioned above, the fixed core directly retains the spring 24, 94. Since members other than the fixed core for retaining the spring 24, 94, the fuel injection valve is manufacture with less parts. Further, on defining a position where the fixed core is press fitted to the pipe member, the gap between the moving core and the fixed core and the biasing force of the spring 24, 94 for urging the moving core and the valve member can be decided at the same time. That is, both of the static and dynamic injection amounts can be decided simultaneously, which results in reducing a time for adjusting the fuel injection amount. As a larger outer force is not applied to the fixed core, once the fixed core is press fitted to the pipe member, pressing force required for the fixed core to be press fitted into the pipe member is smaller so that press fitting of the fixed core is easy and an amount of scraps or chips produced by press fitting the f IXd core into the pipe member is reduced. Further, it is not necessary strictly control the pressing f orcerequired for the fixed core to be press fitted into the pipe member and, since the adjusting pipe for retaining the spring 24, 94 is not press fitted into the fixed core, fabrication of the fixed core is easy. In the embodiments mentioned above, the position of the fixed core is decided by being press fitted so that positioning accuracy of the fixed core is higher. The gap between the moving core and the fixed core is decided with high accuracy, * accuracy of the static injection amount is higher. Dimensional control for forming the inner protruding of the fixed core by which the spring 24, 94 is retained is more rough than dimensional control for forming the fixed core to which the adjusting pipe is press fitted. Accordingly, positioning accuracy of the fixed core is higher and the biasing force of the spring 24, 94 can be adjusted with higher accuracy, which results in adjusting the dynamic injection amount with higher accuracy. As mentioned above, if the fixed core is positioned with higher accuracy, adjusting accuracy of the static and dynamic injection amounts of the fuel injection valve is higher so that fluctuation of the injection amount is smaller. Accordingly, the fuel injection valve of the present invention may be applied to the engine provided with a plurality of cylinders among which fuel injection amount fluctuations are higher. To further reduce the dynamic injection amount fluctuations, the injection amount may be measured, while adjusting pressing distance by which the fixed core is press fitted, so as to adjust the dynamic injection amount to the predetermined value, as described in the first embodiment. Further, as described in the second embodiment, the valve opening time may be adjusted to the given value, while adjusting the push amount of the pipe shaped assembly into the housing assembly, so as to adjust the dynamic injection amount to the predetermined value. Instead of press fitting the fixed core into the pipe member, the fixed core may be fixed by welding to the pipe member. Further, the fixed core may be assembled without using the pipe member. Claims 1. A fuel injection valve (10, 80, 120) having a valve body (16, 86) having a valve seat (17, 87), a valve member (20, 90) for interrupting fuel injection on seating on the valve seat and allowing the fuel injection on leaving the valve seat, a moving core (22, 92) reciprocating movable together with the valve member, the moving core being positioned on an opposite side of the valve seat with respect to the valve member, a fixed core (30, 70, 100, 122) facing to an end of the moving core positioned on a side of one of directions in which the moving core reciprocatingly moves, a biasing member (24, 94) urging the valve member in the other of directions in which the moving core reciprocatingly moves, and a coil (44, 102) , when energized, generating a magnetic attracting force of urging the moving core against the biasing force of the biasing member toward the fixed core, characterized in that: the fixed core is provided at an inner wall with a protrusion (37, 72, 101, 123) by which the biasing member is retained. 2. The fuel injection valve according to claim 1, further having, a pipe member (12) comprising a first magnetic member (13) , a magnetism resistant member (14) and a second magnetic member (15) which are axially arranged in series from a side of the valve body (16), the fixed core (30, 70) and the moving core (22) being accommodated in the pipe member, wherein the fixed core is press fitted into the pipe member. 3. The fuel injection valve according to claim 1, further having, a pipe member (82) in which the valve body (86), the fixed core (100, 122) and the moving core ( 92 ) are accommodated, the pipe member comprising a magnetic member (83) covering an outer circumference of the moving core, wherein the fixed core is press fitted into the pipe member. 4. The fuel injection valve according to any one of claims 1 to 3, wherein the protrusion constitutes a step (37, 101). 5. The fuel injection valve according to any one of claims 1 to 3, wherein the protrusion is a single or a plurality of projections (72, 123). 6. The fuel injection valve according to any one of claims 1 to 3, wherein the fuel injection valve is applied to a single cylinder internal combustion engine. 7. A method of adjusting a fuel injection amount of the fuel injection valve recited in claim 2 or 3 , characterized in steps of forming a housing assembly (200) comprising members including the coils (44, 102) arranged outside outer circumference of the pipe member, forming a pipe shaped assembly (210) in which the valve body (16, 86), valve member (20, 90), the moving core (22, 92), the biasing member (24, 94) and the fixed core (30, 70, 100, 122) are accommodated in such a manner that a gap between the moving core and the fixed core has a predetermined value, and , adjusting a distance by which the pipe shaped assembly is pushed into the housing assembly. 8. A fuel injection valve substantially as herein described with reference to the accompanying drawings.

Full Text

FUEL INJECTION VALVE AND METHOD OF ADJUSTING INJECTION AMOUNT OF SAME Description
The present invention relates to a fuel injection valve for an internal combustion engine (hereinafter called "engine") and a method of adjusting injection amount of the fuel injection valve.
It is necessary for adjusting injection amount of a fuel injection valve to adjust both of a static injection amount and a dynamic injection amount. The static injection amount is decided by a gap between a fixed core and a moving core. The dynamic injection amount is decided by a biasing force of a spring urging a valve member reciprocatingly movable with the moving core. As disclosed in JP-A-4-231672, it is well known that an adjusting pipe for retaining the spring is disposed in the fixed core and the biasing force of the spring is adjusted by changing a position of the adjusting pipe relative to the fixed core. In the fuel injection valve as disclosed in JP-A-4-231672, it is common to adjust the position of the adjusting pipe for adjusting ti\e dynamic in j action amount after the gap between the fixed core and the moving core is adjusted for adjusting the static injection amount.
However, if the adjusting pipe is, for example, press fitted in the fixed core for positioning the adjusting pipe and the position of the fixed core is displaced due to pressing force of the adjusting pipe, a value of the gap between the fixed core and the moving core is likely changed so that the

static injection amount is changed. To prevent the change of the gap between the fixed core and the moving core, fixed strength of the fixed core has to be reinforced. Further, to fix the adjusting pipe in the fixed core without applying an excessive pressing force to the fixed core, it is necessary to manufacture the fixed core and the adjusting pipe whose dimensions, shapes and surface roughness are highly accurate, which results in a higher manufacturing cost.
Further, the conventional adjusting method, in that the biasing force of the spring is adjusted with the adjusting pipe, needsa longer adjusting time, since two step adjustments, that J.S, adjustments of the static injection amount and the dynamic injection amount, are required for adjusting the injection amount.
An object of the present invention is to provide a fuel injection valve which is easily manufactured with less parts and in which injection amount is adjustable with shorter time.
It is another object to provide a method of adjusting injection amount of the fuel injection valve mentioned above-
To achieve the above object, ^in a fuel injection valve comprising a valve body having a valve seat, a valve member for interrupting fuel injection on seating on the valve seat and allowing the fuel injection on leaving the valve seat, a moving core positioned on an opposite side of the valve seat with respect to the valve member and reciprocatingly movable together with the valve member, a fixed core facing to an end of the moving core positioned on a side of one of directions

inwhichthemoving core reciprocatingly moves, abiasingmember urging the valve member in the other of directions in which the moving core reciprocatingly moves, and a coil, when energized, generating a magnetic attracting force of urging the moving core against the biasing force of the biasing member toward the f ixedcore, the fuel injection valve is characterized in that the fixed core is provided at an inner wall with a protrusion by which the biasing member is retained.
According to the fuel injection valve mentioned above, since the biasing member urging the valve member toward the valve seat is directly retained by the fixed core, a number of pats constituting the fuel injection valve is reduced. Further, static and dynamic injection amounts are adjustable simultaneously by adjusting position of the fixed core so that a time necessary for adjusting the injection amount is reduced. Position of the protrusion of the fixed core governs the biasing force of the biasing member for urging the valve member. Accordingly, on adjusting the dynamic injection amount, it is required to control to secure the position of the protrusion whose dimension is accurate to some extent. However, this dimensional control is not severer than that for the fixed core and the adjusting pipe to be press fitted into the fixed core as in the conventional fuel injection valve. Accordingly, fabrication of the fixed core of the present invention is easier than that of the conventional fuel injection valve.
Further, once the fixed core is assembled and the gap

between the fixed core and the moving core is adjusted, outer force larger than the pressing force required for press fitting of the fixed core is not applied to the fixed core so that the gap between the fixed core and the moving core is hardly changed. Accordingly, it is not necessary to rigidly fix the fixed core so that assembly of the fixed core is easier.
Furthermore, by changing the assembly position of the fixed core, the gap between the fixed core and the moving core is adjustable and the biasing force of the biasing member is also adjustable, that is, the static and dynamic injection amounts can be adjusted. Accordingly, if the assembly position of th§ fixed core is controlled with higher accuracy, the gap between the fixed core and the moving core and the biasing force of the biasing member can be highly accurately adjusted, which results in adjusting highly accurately the static and dynamic injection amounts-
It is preferable that the fixed core and the moving core are accommodated in a pipe member comprising a first magnetic member, a magnetism resistant member and a second magnetic member or the valve body, the f axed core and the moving core are accommodated in a pipe member having a magnetic member covering an outer circumference of the moving core- With this structure, the fixed core is press fitted into the pipe member.
According to the fuel injection valve, assembly of the fixed core is easier since the fixed core is press fitted into the pipe member. Further, positioning of the fixed core

relative to the pipe member is accurate since the fixed core is press fitted into the pipe member. Accordingly, the gap between the moving core and the fixed core is uniform (not fluctuated) in each of the fuel injection valves, which results in easily adjusting the injection amount of the fuel injection valve.
Further, once the fixed core is press fitted in the pipe member, larger outer force like a force necessary for press fitting the adjusting pipe in the conventional fuel injection valve is not applied to the fixed core so that the fixed core may be press fitted into the pipe member with smaller pressing f ore Accordingly, it is not necessary to fabricate the fixed core with higher accuracy in order to secure a limited range of pressing force necessary for press fitting the fixed core into the pipe member so that the fabrication of the fixed core is easier. Furthermore, the pressing force necessary for press fitting the fixed core into the pipe member is smaller and an amount of scraps or chips produced by press fitting the fixed core into the pipe member is reduced.
Preferably, the protrusion of the fixed core is formed by machining a part of the inner circumferential wall thereof so as to form a step or by cold forging or pressing the fixed core so as to form a single or plurality of projections protruding radially inward.
In an engine having a plurality of cylinders, an air/fuel mixture ratio is adjusted by changing the average of the respective injection amounts of the fuel injection valves

installed in the cylinders. The change of the average of the respective injection amount is executed by changing with a uniform ratio the respective currents supplied to the fuel injection valves• Accordingly, if the injection amount of one of the fuel injection valves is displaced out of a given range, the air/fuel mixture ratio is not accurately corrected. Therefore, it is preferable that the injection amount of each fuel injection valve falls within the given range. To this end, after defining the static injection amount with a gap between the moving core and the fixed core, position of an adjusting pipe, which is a separate member from the fixed core and retains the biasing member for urging the valve member, is adjusted so as to adjust the dynamic injection amount with higher accuracy.
However, in an engine having a single cylinder, to correct the air/fuel mixture ratio, it is sufficient to adjust the injection amount of a single fuel injection valve so that it is not necessary to strictly control the static and dynamic injection amounts. Accordingly, it is preferable that the fuel injection valve, in which the static and dynamic injection amounts are simultaneously adjusted by adequately positioning the fixed core that directly retains the biasing member urging the valve member so as to accurately correct the air/fuel mixture ratio, is applied to the single cylinder engine. If the member retaining the biasing member or the biasing member itself has dimensional fluctuation due to manufacturing errors in a state that the fixed core is press fitted into the pipe

member to secure a predetermined value of the gap between the fixed core and the moving core, the biasing force of the biasing member is apt to be fluctuated, which causes to fluctuate the dynamic injection amount.
Accordingly, it is preferable to have a method comprising the following steps of adjusting the injection amount of the fuel injection valve. The first step is to form a housing assembly comprising members including the coils arranged outside outer circumference of the pipe member. The next step is to form a pipe shaped assembly in which the valve body, valvemember, the moving core, the biasing member and the fixed core ^re accommodated in such a manner that a gap between the moving core and the fixed core has a predetermined value. The final step is to adjust a distance by which the pipe shaped assembly is pushed into the housing assembly.
If the position of the gap relative to the coil is changed by adjusting the distance by which the pipe shaped assembly is pushed into the housing assembly, a magnetic attracting force is changed. Further, if the housing assembly has a magnetic member positioned outside outer circumference of the pipe member so as to radially face to the moving core, an area of the magnetic member radially facing to the moving core is changed. Since the magnetic attracting force is adjusted by adjusting the distance by which the pipe shaped assembly is pushed into the housing assembly, the dynamic injection amount fluctuation due to the fluctuation of the magnetic attracting force can be adjusted and corrected with higher accuracy.

other features and advantages of the present invention will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following 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 of a fuel injection valve according to a first embodiment of the present invention;
Fig. 2 is an enlarged cross sectional view of a part in a vicinity of a fixed core of the fuel injection valve of Fig. 1;
Fig. 3 is a schematic view showing an installation position of the fuel injection valve of Fig.l;
Fig. 4 is a schematic view explaining a process of assembling the fixed core to the injection control valve;
Fig. 5 is a time chart showing a change per time of an injection amount;
Fig. 6 is a graph showing a relationship between a magnetic attracting force and a gap;
Fig. 7 is a graph showing a relationship between a valve opening time and a gap;
Fig. 8 is a graph showing a relationship between a valve closing time and a gap;
Fig. 9 is a graph showing a relationship between an ineffective injection time and a gap;
Figs. lOA and lOB are views explaining a method of adjusting a dynamic injection amount according to a second embodiment of the present invention;

Figs . 1 lA and 1 IB are another views explaining the method of adjusting the dynamic injection amount according to the second embodiment;
Fig. 12 is a further view explaining the method of adjusting the dynamic injection amount according to the second embodiment;
Fig. 13 is a flowchart showing the method of adjusting the dynamic injection amount according to the second embodiment;
Fig. 14 is a cross sectional view of a part of a fuel injection valve in a vicinity of a fixed core according to a third embodiment of the present invention;
Fig. 15 is a cross sectional view of a fuel injection valve according to a fourth embodiment of the present invention; and
Fig. 16 is a cross sectional view of a fuel injection valve according to a fifth embodiment of the present invention. Embodiments of the present invention are described with reference to drawings, (first embodiment)
A fuel injection valve 10 according to a first embodiment of the present invention, which is shown in Fig. 1, is installed in a single cylinder engine for automotive two wheel vehicle shown in Fig. 3. As shown in Fig. 1, a pipe member 12, which is composed of a magnetic member and a non-magnetic member, is formed in shape of a cylinder. The pipe member 12 is provided inside with a fuel passage 300 . A valve body 16, a valve member

20, a moving core 22, a spring 24 as a biasing member, and a fixed core 30 are accommodated in the fuel passage 300.
The pipe member 12 has a first magnetic member 13, a non-magnetic member 14 as a magnetism resistant member and a second magnetic member 15 which are arranged in series upward from a vicinity of the valve body 16 on a lower side of Fig. 1. Connection between the first magnetic member 13 and the non-magnetic member 14 and connection between the non-magnetic member 14 and the second magnetic member 15 are conducted by welding, for example, by laser welding. The non-magnetic member 14 prevents magnetic flux from short circuiting between the first and second magnetic members 13 and 15- The valve body 16 isbondedby welding to an interior of the first magnetic member 13 on a side of an injection bore. The valve body 16 is provided on an inner circumferential wall thereof with a valve seat 17 on which the valve member 20 can be seated. A cup shaped injection bore plate 18 is fixed by welding on an outer circumferential wall of the valve body 16. The injection bore plate 18 is formed in shape of a thin plate and provided at a center part thereof with a plurality of injection bores 18a.
The valve member 20 is formed in shape of a cylinder having a bottom and provided on a bottom side thereof with a contact portion 21. The contact portion 21 comes in contact with the valve seat 17 formed in the valve body 16. When the contact portion 21 is seated on the valve seat 17, the injection bores 18a are closed so that fuel injection is interrupted.

The moving core 22 is bonded by welding to the valve member 2 0 on an opposite side to the valve body 16. The valve member
20 is provided on an upstream side of the contact portion
21 withapluralityof fuel apertures 20apenetrating a sidewall
thereof. Fuel flowed in the valve member 20 passes through
the fuel apertures 20a from an inside to an outside and flows
toward a valve portion formed by the contact portion 21 and
the valve seat 17.
The fixed core 30 is formed in a cylindrical shape. The fixed core 30 is fixed into the pipe member 12 in such a manner that the fixed pore 30 is press fitted to inner circumferences of the non-magnetic member 14 and the second magnetic member 15 of the pipe member 12 after being inserted into the pipe member 12 from an opening thereof, as shown in Fig. 4. As shown in Fig. 1, the fixed core 30, which is positioned on an opposite side to the valve body 16 with respect to the moving core 22 in one of directions in which the valve member 20 moves reciprocatingly, is opposed to the moving core 22. An end of the fixed core 30 opposed to the moving core 22
is coated with non-magnetic material.
*
As shown in Fig. 2, the fixed core 30 has a first small diameter portion 31, a press fitting portion 32, a second small diameter portion 33 and a large diameter portion 34 which are arranged in series from a vicinity of the moving core 22. An outer diameter of the press fitting portion 32 is equal to that of the large diameter portion 34 - Each outer diameter of the first and second small diameter portions 31

and 33 is smaller than each outer diameter of the press fitting portion 32 and the large diameter portion 34 and the first and second small diameter portions 31 and 33 are not in contact with the inner circumferential wall of the pipe member 12. The press fitting portion 32 is press fitted to an inner circumferential wall of the non-magnetic member 14 and an inner circumferential wall of the second magnetic member 15.
An inner circumferential wall of the fixed core 30 has a large diameter portion 35 and a small diameter portion 36 whose inner diameter is smaller than that of the large diameter portion 35 tha-^ is arranged in order from a side of the moving core 22. A boundary between the large diameter portion 35 and the small diameter portion 36 is provided with a step 37 constituting a protrusion. An end of a spring 24 is retained by the step 37.and the other end of the spring 24 is retained by the moving core 22. The spring 24 urges themoving core 22 and the valve member 20 in a direction in which the valve member 20 moves to seat on the valve seat 17, that is, in the other of the directions in which the valve member 20 moves reciprocatingly.
Magnetic members 40 and 42 are magnetically connected and arranged radially outside a coil 44 . The magnetic member 40 is magnetically connected with the first magnetic member 13 and the magnetic member 42 is magnetically connected with the second magnetic member 15. The fixed core 30, the moving core 22, the first magnetic member 13, the magnetic members 40 and 42 and the secondmagnetic member 15 constitute a magnetic

circuit.
A spool 45, on which the coil 44 is mound, mounted on outer circumference of the pipe member 12. As shown in Fig, 1, a resin housing 50 covers the outer circumferences of the pipe member 12 and the coil 44. A terminal 52 is connected in circuit with the coil 44 and supplies driving current to the coil 44.
Fuel flowed into the fuel passage 300 from a portion of the pipe member 12 on an upper side of Fig. 1 is injected from the injection bores 18a via a fuel passage inside the fixed core 30, a fuel passage inside the moving core 22, a fuel passage inside the valve member 20, the fuel apertures 20a and an opening formed between the contact portion 21 and the valve seat 17 when the contact portion 21 leaves the valve seat 17.
In the fuel injection valve mentioned above, when the current to the coil 44 is turned off, the valve member 20 is moved by the spring 24 in a lower direction in Fig. 1, that is, in a valve closing direction, so that the contact portion 21 comes in contact with the valve seat 17. Accordingly, the injection bores 18a are closed for interrupting the fuel injection.
When the current to the coil 44 is turned on, magnetic flux flows through the magnetic circuit constituted by the fixed core 30, the moving core 22, the first magnetic member 13, the magnetic members 40 and 42 and the second magnetic member 15 so that a magnetic attracting force generates between

V^
the fixed core 30 and the moving core 22. 'Accordingly, the valve member 20 moves together with the moving core 22 against the biasing force of the spring 24 toward the fixed core 30 so that the contact portion 21 leaves the valve seat 17, which allows to inject fuel from the injection bores 18a. A maximum lift amount of the valve member 20 is defined in such a manner that the moving core 22 is stopped by the fixed core 30.
A method of adjusting the dynamic injection amount of the fuel injection valve 10 is described below.
First of all, when the fuel injection valve 10 injects fuel, an injection amount is changed according to a lapse of time. As shown in Fig. 5, when an injection pulse signal is applied to the coil during a given pulse time Ti, the magnetic attracting force generates between the fixed core 30 and the moving core 22 . Since there is a time delay after the injection pulse signal is turned on until the magnetic attracting force causing the moving core 22 to move toward the fixed core 30 generates, the valve member 20 is moved to leave the valve seat 17 and stopped by the fixed core 30 with a time delay after the rising of the injection pulse signal. A valve opening time To represents a time necessary for the valve member 20 to move away from the valve seat 17 until being stopped by the fixed core, that is, to show a maximum lift after the injection pulse signal for instructing the injection is turned on.
When the injection pulse signal is turned off, there is still a time delay after the falling of the injection pulse

signal until the moving core 22 leaves the fixed core 30 and the valve member 20 is seated on the valve seat 17. A valve closing time Tc represents a time necessary for the valve member 2 0 to be seated on the valve seat 17 for interrupting the injection after the injection pulse signal is turned off. As shown in Fig. 5, it is presumed that an area SO covering an amount of fuel to be injected until the valve member 20 is stopped by the fixed core 30 after leaving the valve seat 17 is substantially equal to an area SI covering an amount of fuel to be injected until the valve member 20 is seated on the valve J seat 17 after leaving the fixed core 30. Accordingly, if the dynamic injection amount shown in Fig. 5 is injected in a fully opened valve state in which the moving core 22 is stopped by the fixed core 30, an effective injection time of the fuel injection valve 10 necessary for the injection is presumed to satisfy the following formula (1),
Ti + Tc - To = Ti - (To -Tc) (1)
The static injection amount is obtained by measuring the injection amount upon applying to the fuel injection valve 10 an injection instruction signal having, for example, 1 minute pulse width. If injected in a fully opened valve state in which the moving core 22 is stopped by the fixed core 30, an injection amount per unit time [msec] of the dynamic injection amount q [mm /str] is presumed to be equal to an injection amount per unit time [mm /msec] into which the static injection amount Q [cm min] is converted. Accordingly, the injection amount per unit time [msec] of the dynamic injection amount

q [mm^/str] can be expressed as Q/60. Further, when the injection signal having the pulse time Ti is applied to the coil 44, the dynamic injection amount q [mm /str] can be expressed in use of the effective injection time of the formula (1) as the following formula (2) , in which (To-Tc) is expressed as an ineffective injection time Tv,
Q = (Q/60) X (ti- (to -Tc)) = (Q/60) X (Ti - Tv) (2)
As shown in Fig. 4, the static injection amount and the dynamic injection amount of the fuel injection valve 10 are defined at the same time by press fitting the fixed core 30 into the pipe member 12 so that a gap between the moving core 22 and the fixed core 30 is a predetermined value. However, due to manufacturing fluctuations of the moving core 22, the fixed core 30 by which the spring 24 is retained and the spring 24 itself, the biasing force of the spring 24 is likely to be fluctuated so that the dynamic injection amount tends to vary every fuel injection valve. A method of adjusting the dynamic injection amount with less fluctuation is described below.
To begin with, a relationship between the gap- and the

magnetic attracting force, the valve opening time To or the valve closing time tc is described. As shown in Fig. 6, as the gap is larger, the magnetic attracting force of attracting the moving core 22 toward the fixed core is smaller. As the gap is larger and the attracting force is smaller, the valve opening time To is longer, as shown in Fig. 7. As shown in Fig. 8, as the gap is larger, the valve closing time tc is

longer.
However, a ratio of a time by which the valve opening time To becomes longer to a distance by which the gap becomes larger is larger than a ratio of a time by which the valve closing time Tc becomes longer to a distance by which the gap becomes larger. Accordingly, as shown in Fig. 9, the ineffective injection time Tv, which is a difference between the valve opening time To and the valve closing time Tc, is longer, as the gap is larger.
It is understood from the formula (2) that the dynamic injection amour)t q is variable according to a change of the ineffective injection time Tv, that is, a change of the difference between the valve opening time To and the valve closing time Tc. Though the ineffective injection time Tv is changed according to a change of the gap, the dynamic injection amount of the fuel injection valve 10 can be adjusted to have a given value by measuring the static injection amount, while the fixed core 30 is press fitted to the pipe member 12, so that the static injection amount, which varies with the change of the gap, falls within an allowable range.
4
According to the first embodiment, a part of the fixed core 30 on an axial end side in a press fitting direction is press fitted to the inner circumferential wall of the pipe member 12. Axial length of the part of the fixed core 30 to be press fitted to the pipe member 12 is relatively short so that the fixed core 30 is easily press fitted to the pipe member 12 with less pressing force.

(Second embodiment)
A method of adjusting a dynamic injection amount according to a second embodiment is described with references to Figs. 10 to 13. A structure of a fuel injection valve, to which the method of adjusting the dynamic injection amount according to the second embodiment is applicable, is substantially same as the first embodiment. Fig. 13 is a flowchart showing the method of adjusting the dynamic in j act ion amount according to the second embodiment.
As shown in Fig. lOA, a housing assembly 200 is formed by connecting the magnetic members 40 and 42 and the coil 44 through resin material (Step 400 in Fig. 13). The magnetic members 40 and 42 and the coil 44 are members mounted on an outer circumference of the pipe member 12. Further, as shown in Fig. lOB, the pipe member 12 formed by bonding the first magnetic material 13, the non-magnetic material 14 and the second magnetic material 15 to one another by welding.
As shown in Figs. IIA, the pipe member 12 is press fitted into the housing assembly 200 until a distance d between the step 15a of the second magnetic member 15 and the magnetic member 42 becomes a given value (Step 402).
The valve body 16 to which the injection bore plate 18 is bonded by welding is inserted into and bonded by welding to the first magnetic member 13. The spring 24 and the valve member 20 to which the moving core 22 is bonded by welding are inserted into the pipe member 12. Then, as shown in Fig. IIB, the fixed core 30 is press fitted in the pipe member 12

so as to secure a predetermined gap between the moving core 22 and the fixed core 30. The pipe member 12 is press fitted in the magnetic member 42 of the housing assembly 200. This pressing force is larger than the pressing force with which the fixed core 30 is press fitted in the pipe member 12. Accordingly, even if the fixed core 30 is press fitted in the pipe member 12, the distance d between the step 15a of the second magnetic member 15 of the pipe member 12 and the magnetic member 42 of the housing assembly 200 is hardly changed. As shown in Fig. 12, the fuel filter 22 is mounted on the pipe member 12 on a fuel inlet side thereof so that a pipe shaped assembly 210, which is composed of the pipe member 12, the valve body 16, the injection bore plate 18, the valve member 20, the moving core 22, the spring 24, the fixed core 30 and the fuel filter 60, is formed (Step 404).
Then, the pipe shaped assembly 210 is pushed into the housing assembly 200 while a push amount is adjusted to achieve the distance d falling within a given range. According to the first embodiment, the dynamic injection amount of the fuel injection valve 10 is variable according to changes of the
4
valve opening time To and the valve closing time Tc, as understood from the formula (2) . Accordingly, to adjust the dynamic injection amount in the first embodiment, the gap between the moving core 22 and the fixed core 30 is adjusted so that the valve opening time To and the valve closing time Tc are changed.
According to the second embodiment, to adjust the dynamic

injection amount, the valve opening time To and the valve closing time Tc are changed by adjusting the distance (the push amount) by which the pipe shaped assembly 210 is pushed into the housing assembly 200. A change of the push amount by which the pipe shaped assembly 210 is pushed into the housing assembly 200 causes not only to change a position of the gap between the moving core 22 and the fixed core 30 relative to the coil 44 but also to change an area of the moving core 22 radially facing to the magnetic member 4 0 so that the magnetic attracting force is changed, which results in changing the valve opening^ time To and the valve closing time Tc. Accordingly, the dynamic injection amount is adjusted by pushing the pipe shaped assembly 210 into the housing assembly 200 so that predetermined values of the valve opening time To and the valve closing time Tc are secured.
The valve opening time To is determined by measuring a time duration from a time when the injection pulse signal applied to the coil 44 rises to a time when an acceleration sensor 230, which is mounted, for example, on a basement 200 as shown in Fig. 12, detects a shock due to hitting of the moving member 22 against the fixed core 30 . The valve closing time Tc is detected by measuring a time duration from a time when the injection pulse signal applied to the coil 44 falls to a time when an acceleration sensor 230 detects a shock due to seating of the valve member 20 on the valve seat 17. As soon as the valve opening time To and the valve closing time Tc reach the predetermined values (Step 408), pushing of the

pipe shaped assembly 210 into the housing assembly 200 is terminated. Then, the pipe shaped member 210 is fixed to the housing assembly 200 by bonding the magnetic member 40 and the first magnetic member 13 to each other (Step 410).
In the method of adjusting the injection amount according to the second embodiment, it is preferable in view of preventing foreign materials from entering into the fuel injection valve 10 that all processes up to Step 404 at which the pipe shaped assembly 210 is formed by mounting the fuel filter on the pipe member 12 on a fuel inlet side thereof are performed in a clean room. It is not necessary to perform in the clean room the processes of measuring the leakage amount at Steps 406 and 408 and the process of adjusting the push amount of the pipe shaped assembly 210 into the housing assembly 200 so that all processes until the injection amount adjustment of the fuel injection valve 10 is finished after the fuel filter has been mounted on the pipe member 12 on a fuel inlet side thereof may be carried out in a usual working room.
In the second embodiment, the valve body 16 and the injection bore plate 18 are attached to the pipe member 12 after the pipe member 12 has been press fitted to the housing assembly 200, since the injection bore plate 18 is formed in shape of a cup whose outer diameter is larger than inner diameter of the magnetic member 40 . However, if an injection bore plate 18, which is formed in shape of a thin plate, is fixed to a bottom outer wall of the valve body, as shown in third and fourth embodiments described later, the pipe shaped assembly

the moving core 22, the spring 24 and the fixed core 30 are accommodated in the pipe member 12 so that the gap between:
210, in which, after the valve body 16 and the injection plate 18 are mounted on the pipe member 12, the valve member 20, the moving core 22, the spring 24 and the fixed core 30 are
the moving core 22 and the fixed core 30 has the predetermined value, may be inserted into the housing assembly 200. (Third embodiment)
A third embodiment of the present invention is described in Fig. 14. The same reference number as that of the first embodiment is assigned to a substantially similar functional component. ,
A fixed core 70 is press fitted into the pipe member 12. The fixed core 70 is provided on an inner circumference thereof with a plurality of projections 72 circumferentially spaced or a ring shaped projection 72 which are or is formed by cold forging or pressing (punching) so as to protrude radially inward. The single or plurality of projections 72 constitute the protrusion. Inner diameter of the fixed core 70 is smaller at the projection 72. The spring 24 is retained by the projection 72.
4
In the fuel injection valve according to the third embodiment, the static and dynamic injection amounts may be simultaneously decided by adjusting the gap between the moving core 22 and the fixed core 7 0 to the predetermined value.
Further, the given value of the dynamic injection amount may be secured by measuring the injection amount while the fixed core 70 is press fitted into the pipe member 12.

Moreover, after forming the housing assembly by connecting the members including the coil 44 which are mounted on the outer circumference of the pipe member 12 and forming the pipe shaped assembly by accommodating the valve body 16, the injection bore plate 18, the valve member 20, the moving core 22, the spring 24 and the fixed core 70 in the pipe member 12 so that the gap between the moving core 22 and the fixed core 70 has the predetermined value, the dynamic injection amount may be adjusted by adjusting the push amount of the pipe shaped assembly into the housing assembly. (Fourth and fifth embodiments)
Fourth and fifth embodiments of the present invention are described with reference to Figs. 15 and 16, respectively.
As shown in Fig. 15, a pipe member 82 of a fuel injection valve 80 according to the fourth embodiment has a magnetic member 83 and a non-magnetic member 84 which are arranged in order from a side of a valve body 86 positioned at a lower part of Fig. 15. The magnetic member is inserted into and bonded by welding to an inner circumference of the non-magnetic member 84. A thin thickness injection bore plate 88 is fixed

by welding to a bottom outer wall of the valve body 86. The injection bore plate 88 is provided with a plurality of injection bores.
A valve member 90 is formed in shape of a cylinder having a bottom. The valve member 90 has a contact portion 91 which comes in contact with a valve seat 87 formed on the valve body 86 . The valve member 90 is provided in a side wall on an upstream

side of the contact portion 91 with a plurality of fuel apertures 90a penetrating through the side wall. Fuel flowed in the valve member 90 flows radially from an inside of the fuel apertures 90a to an outside thereof and, then, flows toward a valve portion formed by the contact portion 91 and the valve seat 87. A moving core 92 is fixed by welding to the valve member 90 on an opposite side to the valve body 86. An end of a spring 94 as the biasing member is retained by the valve member 90 and the other end thereof is retained by a step 101 formed by the protrusion of a fixed core 100. The fixed core 100 is press flitted in the pipe member 82.
A coil 102 is arranged on an outer circumference of the non-magnetic member 84 . Magnetic member 104 covers the outer circumference of the coil 102 and is connected to the magnetic member 83 at a position radially outside, the moving core 92 and to the non-magnetic member 8 4 at a position radially outside the fixed core 100. A resin housing 110 covers outsides of the pipe member 82, the coil 102 and the magnetic member 104. A fuel filter 112 is mounted on the pipe member 82 on a fuel inlet side thereof.
In a fuel injection valve 120 according to the fifth embodiment, as shown in Fig. 16, a fixed core 122 is press fitted to the pipe member 82. The fixed core 122 is provided on an inner circumference thereof with a plurality of projections 123 circumferentially spaced and formed by cold forging or punching to protrude radially inward, which constitute the protrusion. Inner diameter of the fixed core

122 is smaller at the projections 72. A spring 94 is retained by the projections 123. The other structure of the fuel injection valve 120 is substantially same as that of the fourth embodiment.
In each of the fuel injection valves 80 and 120, the static and dynamic injection amounts may be simultaneously decided by adjusting the gap between the moving core and the fixed core to the predetermined value.
Further, the given value of the dynamic injection amount may be secured by measuring the injection amount while the fixed core is press fitted into the pipe member.
Moreover, after forming the housing assembly by connecting the members including the coil 102 which are mounted on the outer circumference of the pipe member 82 and forming the pipe shaped assembly by accommodating the valve body, the injection bore plate, the valve member, the moving core, the spring and the fixed core in the pipe member so that the gap between the moving core and the fixed core has the predetermined value, the dynamic injectionamountmaybeadjustedby adjusting the push amount of the pipe shaped'assembly into the housing assembly.
In the embodiments mentioned above, the fixed core directly retains the spring 24, 94. Since members other than the fixed core for retaining the spring 24, 94, the fuel injection valve is manufacture with less parts. Further, on defining a position where the fixed core is press fitted to the pipe member, the gap between the moving core and the fixed

core and the biasing force of the spring 24, 94 for urging the moving core and the valve member can be decided at the same time. That is, both of the static and dynamic injection amounts can be decided simultaneously, which results in reducing a time for adjusting the fuel injection amount.
As a larger outer force is not applied to the fixed core, once the fixed core is press fitted to the pipe member, pressing force required for the fixed core to be press fitted into the pipe member is smaller so that press fitting of the fixed core is easy and an amount of scraps or chips produced by press fitting the f IXd core into the pipe member is reduced. Further, it is not necessary strictly control the pressing f orcerequired for the fixed core to be press fitted into the pipe member and, since the adjusting pipe for retaining the spring 24, 94 is not press fitted into the fixed core, fabrication of the fixed core is easy.
In the embodiments mentioned above, the position of the fixed core is decided by being press fitted so that positioning accuracy of the fixed core is higher. The gap between the
moving core and the fixed core is decided with high accuracy,
*
accuracy of the static injection amount is higher. Dimensional control for forming the inner protruding of the fixed core by which the spring 24, 94 is retained is more rough than dimensional control for forming the fixed core to which the adjusting pipe is press fitted. Accordingly, positioning accuracy of the fixed core is higher and the biasing force of the spring 24, 94 can be adjusted with higher accuracy,

which results in adjusting the dynamic injection amount with higher accuracy.
As mentioned above, if the fixed core is positioned with higher accuracy, adjusting accuracy of the static and dynamic injection amounts of the fuel injection valve is higher so that fluctuation of the injection amount is smaller. Accordingly, the fuel injection valve of the present invention may be applied to the engine provided with a plurality of cylinders among which fuel injection amount fluctuations are higher.
To further reduce the dynamic injection amount fluctuations, the injection amount may be measured, while adjusting pressing distance by which the fixed core is press fitted, so as to adjust the dynamic injection amount to the predetermined value, as described in the first embodiment. Further, as described in the second embodiment, the valve opening time may be adjusted to the given value, while adjusting the push amount of the pipe shaped assembly into the housing assembly, so as to adjust the dynamic injection amount to the predetermined value.

Instead of press fitting the fixed core into the pipe member, the fixed core may be fixed by welding to the pipe member. Further, the fixed core may be assembled without using the pipe member.

Claims
1. A fuel injection valve (10, 80, 120) having
a valve body (16, 86) having a valve seat (17, 87),
a valve member (20, 90) for interrupting fuel injection on seating on the valve seat and allowing the fuel injection on leaving the valve seat,
a moving core (22, 92) reciprocating movable together with the valve member, the moving core being positioned on an opposite side of the valve seat with respect to the valve member,
a fixed core (30, 70, 100, 122) facing to an end of the moving core positioned on a side of one of directions in which the moving core reciprocatingly moves,
a biasing member (24, 94) urging the valve member in the other of directions in which the moving core reciprocatingly moves, and
a coil (44, 102) , when energized, generating a magnetic attracting force of urging the moving core against the biasing force of the biasing member toward the fixed core, characterized in that:
the fixed core is provided at an inner wall with a protrusion (37, 72, 101, 123) by which the biasing member is retained.
2. The fuel injection valve according to claim 1, further having,
a pipe member (12) comprising a first magnetic member

(13) , a magnetism resistant member (14) and a second magnetic member (15) which are axially arranged in series from a side of the valve body (16), the fixed core (30, 70) and the moving core (22) being accommodated in the pipe member, wherein the fixed core is press fitted into the pipe member.
3. The fuel injection valve according to claim 1, further having,
a pipe member (82) in which the valve body (86), the fixed core (100, 122) and the moving core ( 92 ) are accommodated, the pipe member comprising a magnetic member (83) covering an outer circumference of the moving core, wherein the fixed core is press fitted into the pipe member.
4. The fuel injection valve according to any one of claims 1 to 3, wherein the protrusion constitutes a step (37, 101).
5. The fuel injection valve according to any one of claims 1 to 3, wherein the protrusion is a single or a plurality of projections (72, 123).
6. The fuel injection valve according to any one of claims 1 to 3, wherein the fuel injection valve is applied to a single cylinder internal combustion engine.
7. A method of adjusting a fuel injection amount of

the fuel injection valve recited in claim 2 or 3 , characterized in steps of
forming a housing assembly (200) comprising members including the coils (44, 102) arranged outside outer circumference of the pipe member,
forming a pipe shaped assembly (210) in which the valve
body (16, 86), valve member (20, 90), the moving core (22,
92), the biasing member (24, 94) and the fixed core (30, 70,
100, 122) are accommodated in such a manner that a gap between
the moving core and the fixed core has a predetermined value,
and ,
adjusting a distance by which the pipe shaped assembly is pushed into the housing assembly.

8. A fuel injection valve substantially as herein described with reference to the accompanying drawings.

Documents:

153-che-2004-abstract.pdf

153-che-2004-claims filed.pdf

153-che-2004-claims granted.pdf

153-che-2004-correspondnece-others.pdf

153-che-2004-correspondnece-po.pdf

153-che-2004-description(complete) filed.pdf

153-che-2004-description(complete) granted.pdf

153-che-2004-drawings.pdf

153-che-2004-form 1.pdf

153-che-2004-form 19.pdf

153-che-2004-form 26.pdf

153-che-2004-form 3.pdf

153-che-2004-form 5.pdf

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Patent Number

201495

Indian Patent Application Number

153/CHE/2004

PG Journal Number

05/2007

Publication Date

02-Feb-2007

Grant Date

10-Aug-2006

Date of Filing

25-Feb-2004

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	OKUYAMA SYOUHEI	C/O DENSO CORPORATION 1-1, SHOWA-CHO, KARIYA-CITY AICHI-PREF 448-8661
2	SUGIYAMA KOICHI	C/O DENSO CORPORATION 1-1, SHOWA-CHO, KARIYA-CITY AICHI-PREF 448-8661

PCT International Classification Number

F02M061/16

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2003-52798	2003-02-28	Japan
2	2003-425202	2003-12-22	Japan