Electromagnetic fuel injection valve

Abstract: The invention relates to a valve structure which can be easily worked, does not increase a producing cost, can reduce a dispersion in a side gap by restricting an eccentricity and an incline of a valve body and can maintain an injection accuracy high. In particular, the invention relates to an electromagnetic fuel injection valve (1) which is advantageous in view of production even in a narrow valve structure. In the electromagnetic fuel injection valve (1), at least one guide portion having one end fixed to an injection valve main body and guiding an axial sliding motion of the valve member in the inner portion is provided, and a nozzle guide body (5) constituting a magnetic passage portion formed so as to surround a magnetic member connected and fixed to one end of the valve member by the same material is provided. Accordingly, it is possible to reduce a dispersion of a side gap constituting the magnetic passage, and it is possible to stabilize an axial motion of the valve member, whereby an injection accuracy is maintained high and an inexpensive injection valve is obtained.

Description: BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to an electromagnetic fuel injection valve which is used in an internal combustion engine and drives a valve body due to an electromagnetic force so as to inject a fuel. DESCRIPTION OF THE PRIOR ART In an electromagnetic operating type injection valve described in Japanese Patent Unexamined Publication No. 10-122085, a valve body is constituted by a valve closing body 10 connected to an end portion of a connection tube 11 by a welding and a movable element 12, and is guided by a guide flange 15 provided in an intermediate member 6. On the contrary, a magnetic passage is constituted by a fuel inflow tube piece 1 serving as a core surrounded by an electromagnetic coil 4, at least one guide element 16 serving as a ferromagnetic element formed as a yoke, a connection member 14 brought into contact with another end portion of the guide element 16, and the movable element 12. At this time, a gap portion (a void portion) in a direction crossing a valve axis (in a diametrical direction) is formed between an outer peripheral surface of the movable element 12 and an inner peripheral surface of the connection member 14, and a side magnetic passage (refer to as a side gap in the present invention) is formed in the gap portion. In the electromagnetic fuel injection valve in accordance with the conventional structure, in order to restrict a dispersion in the side gap, it is necessary to secure a coaxiality between the intermediate member 6 and the connection member 14 and a coaxiality between a seat surface of a seat body 8 and the connection member 14 at each of parts levels, and it is also necessary to assemble the parts with securing both of them at a high accuracy. Accordingly, a working process becomes hard and a cost therefor becomes expensive. These problems become significant as the injection valve becomes narrower, so that a working accuracy becomes hard to be kept and it becomes hard to maintain a required injection accuracy due to an eccentricity and an incline of the valve body. SUMMARY OF THE INVENTION An object of the present invention is to provide an electromagnetic fuel injection valve which can be easily worked, does not increase a producing cost, can reduce a dispersion in a side gap by restricting an eccentricity and an incline of a valve body and can maintain an injection accuracy high. The object is solved according to the features of the independent claim. The dependent claims relate to advantageous embodiments of the invention. An electromagnetic fuel injection valve in accordance with the present invention has a gap portion (a side gap portion) in a direction crossing a valve axis (in a diametrical direction) in a magnetic passage for driving a valve body. In accordance with the present invention, the structure is made such that the gap portion and a guide portion for guiding a movement in a direction of the valve axis of the valve body are constructed within the same member (one member). That is, the member corresponds to a member provided in an outer peripheral portion of the valve body along the valve axis, and may be a nozzle body in which a fuel injection hole and a valve seat are formed or may be an independent member for supporting the nozzle body, for example, a nozzle guide body. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a vertical cross sectional view of a fuel injection valve which shows an embodiment in accordance with the present invention; Fig. 2 is an enlarged cross sectional view in a periphery of a front end portion of the fuel injection valve; Fig. 3 is an enlarged cross sectional view in a periphery of a front end portion which shows another embodiment; and Fig. 4 is a cross sectional view taken along a direction of C in Fig. 3. DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be give below of an embodiment in accordance with the present invention with reference to Figs. 1 and 2. At first, a description will be given of a structure of a fuel injection valve 1 with reference to Fig. 1. Fig. 1 is a vertical cross sectional view of the fuel injection valve 1 which shows an embodiment in accordance with the present invention. The electromagnetic fuel injection valve 1 opens and closes a seat portion in accordance with an ON-OFF signal of a duty calculated by a control unit so as to inject a fuel. A magnetic circuit has a fuel introduction portion 2a, and is constituted by a core 2 having a column portion 2b extending in an axial direction in a center portion thereof, a bottomed cylindrical yoke 3 connected and fixed to the core 2, a plunger 4 opposing to the core 2 at an interval, and a nozzle guide body 5 having an inner diameter expanding portion in such a manner as to surround the plunger 4. An end surface outer peripheral portion of the column portion 2b in the core 2 and an end surface inner peripheral portion of the nozzle guide portion 5 are provided with a seal ring 6 for mechanically connecting and fixing each of them, thereby preventing a fuel from flowing out to a coil 16 side. further, the seal ring 6 is formed by a nonmagnetic material so as not to serve as a magnetic passage. The coil 16 exciting the magnetic circuit is wound around a bobbin 17, however, since the fuel is prevented by the seal ring 6 from flowing into the coil side, a comparatively inexpensive structure can be obtained by only taking an insulating property into consideration. A terminal 19 of a coil assembly 18 structured in the manner mentioned above is inserted into a hole 20 provided in the bottomed portion of the yoke 3. The terminal 19 is connected to a terminal of a control unit (not shown). A hole for inserting and holding a spring 14 corresponding to an elastic member pressing a movable valve 4A comprising a plunger 4 and a rod 7 connected to the plunger 4 by welding to a seat surface 10 disposed upstream side of a fuel injection hole 9 formed in a nozzle body 12 and allowing the fuel to pass through is provided at a center of the column portion 2b in the core 2. An upper end of the spring 14 is brought into contact with a lower end of a spring adjuster 15 inserted to a center of the core 2 for adjusting a set load. Further, a nozzle guide body 5 is fixed to a free end of the yoke 3 by welding. The movable valve 4A is constituted by the plunger 4 made of a magnetic material and the rod 7 having one end bonded to the plunger 4 by welding, however, a hollow portion 7A constituting a fuel passage is provided in an inner portion in the plunger 4 side of the rod 7. The hollow portion 7A has a fuel outflow port 7B below (in a downstream side of) a portion in which an outer diameter of the rod 7 is expanded (hereinafter, refer to as an expanded portion). Further, an outer periphery of the expanded portion 8 is brought into contact with an inner wall surface of a portion 5B in which an inner diameter of the nozzle guide body 5 is reduced (hereinafter, refer to as a contracted portion), whereby an axial motion of the movable valve 4A is guided. The nozzle body 12 having the seat surface 10 and the fuel injection hole 9 allowing the fuel to pass through and disposed at a center of the seat surface 10 is inserted to the end surface side of the contracted portion 5B of the nozzle guide body 5 so as to be mechanically bonded thereto. A stroke (a moving amount to an axial upper portion) of the movable valve 4A is determined in accordance with a height of the nozzle body 12. As a method of adjusting the height, it can be considered to control sizes in level of parts, however, in order to use the parts for a mass production with no loss, a shim may be inserted between the nozzle guide body 5 and the nozzle body 12. Here, reference numeral 21 denotes a filter. The filter 21 is provided for preventing dusts or foreign materials in the tube from entering to the seat side during a combustion. A description will be in detail given of a structure and a function of the nozzle guide body 5 and the nozzle body 12 connected and fixed to the nozzle guide body 5 in accordance with the present embodiment, and a structure of the fuel passage with reference to Fig. 2. Fig. 2 is a vertical cross sectional view of a main portion and shows the valve portion in an enlarged manner. The nozzle guide body 5 has an inner diameter expanded portion 5A and a contracted portion 5B. The plunger 4 is opposed to the inner diameter expanded portion 5A, and a side gap sg constituting a magnetic passage is formed between an inner wall surface of the inner diameter expanded portion 5A and an outer peripheral surface of the plunger 4. On the contrary, the expanded portion 8 of the rod 7 connected to the plunger 4 is coaxially opposed to the inner diameter contracted portion 5B, and an axial motion of the movable valve 4A is guided at the portion. Further, the nozzle body 12 is connected and fixed to the end of the inner diameter contracted portion 5B, and a cylindrical fuel swirling member 13 is mechanically fixed within the nozzle body 12. In continuous with the fuel swirling member 13, the seat surface 10 and the fuel injection hole 9 are integrally formed in the nozzle body 12. A ball 11 corresponding to a valve closing body is connected to the front end portion of the rod 7 by welding. An outer peripheral surface of the ball 11 is coaxially assembled to an inner diameter side of the fuel swirling member 13 at a little interval, thereby guiding the axial motion of the movable valve 4A as assist. In accordance with the structure mentioned above, the side gap sg corresponding to the magnetic passage formed between the plunger 4 and the inner diameter expanded portion 5A of the nozzle guide body 5 is produced so as to have a significantly reduced dispersion and a high accuracy. That is, since the guiding portion of the nozzle guide body 5 opposing to the expanded portion 8 of the rod 7 and the inner diameter expanded portion 5A in which the side gap sg is formed are disposed within the same member, it becomes easy to work the elements with keeping the coaxiality of the elements at a high accuracy (in accordance with the same working procedure, that is, the member does not require any change of clamping). Further, since no accurate work in accordance with a combination of the parts is required, the accuracy is not reduced even in the case of a narrow valve body. Accordingly, since an accurate work can be easily performed, the structure can be inexpensively produced and a size dispersion due to a mass production can be restricted, so that a mass production can be performed. In this case, in the nozzle guide body 5, a high-frequency induction hardening is applied to the contracted portion 5B side except the inner diameter expanded portion 5A. A hardening is applied to a range of an X portion shown in Fig. 2. This hardened portion increases a hardness of the portion for guiding the movable valve 4A and reduces a friction generated by a sliding operation between the contracted portion 5B and the expanded portion 8 of the rod 7. Returning to Fig. 1, a description will be given of a motion of the fuel injection valve 1 in accordance with the present invention. The fuel injection valve 1 drives the movable valve 4A in accordance with an electrical ON-OFF signal applied to the electromagnetic coil 16 so as to open and close the seat surface 10, thereby controlling the fuel injection. When the electrical signal is applied to the coil 16, a magnetic circuit is formed in the core 2, the yoke 3, the plunger 4 and the nozzle guide body 5, and the plunger 4 is sucked to the core 2b side. When the plunger 4 is moved, the movable valve 4A integrally formed therewith is also moved so as to be apart from the seat surface 10 in the seat of the nozzle body 12 and open the fuel injection hole 9. The fuel is pressurized and adjusted via a fuel pump (not shown) and a regulator for adjusting a fuel pressure, flows into an inner portion of the fuel injection valve 1 from the filter 21, and flows downward via the outflow port 7B from the hollow portion 7A provided in the movable valve 4A. Thereafter, the fuel is sufficiently rectified before reaching an upstream side of the fuel swirling member 13 provided in the nozzle body 12 and moves to the fuel injection hole 8 disposed downstream via an axial passage 13A and a diametrical passage 13B of the fuel swirling member 13. At this time, the fuel is eccentrically introduced from the axial center by the diametrical passage 13B. That is, a swirling motion is applied to the fuel and the fuel is introduced to the fuel injection hole 9, whereby the fuel is atomized and injected. Next, a description will be given of another embodiment in accordance with the present invention with reference to Figs. 3 and 4. Fig. 3 is a vertical cross sectional view of a main portion in which a valve portion is enlarged, and Fig. 4 is a cross sectional view taken along a direction of C in Fig. 3. A description will be given of a structure and an operation with reference to respective drawings. In the present embodiment, a rod 7' connected and fixed to the plunger 4 is produced by a drawn material. In this case, since a dimensional accuracy can be secured by grinding an outer shape, an inexpensive movable valve 4'A can be provided. Further, the valve closing body is not formed in a ball shape and has a spherical surface connected to a contracted portion of the rod 7', thereby being constituted by a spherical surface conical valve 11' obtained by closing so as to form a conical shape in subsequent to the spherical R surface. Accordingly, since no mechanical fixing means by welding or the like is added, an inexpensive structure can be provided. A nozzle guide body 5' has an inner diameter expanded portion 5'A, a contracted portion 5'B and an expanded portion 5'C a little greater than the contracted portion 5'B. The plunger 4 is opposed to the inner diameter expanded portion 5'A and a side gap sg constituting a magnetic passage is formed. Further, a guide hole opposing to the rod 7' portion is formed in the contracted portion 5'B, and a nozzle body 120 is inserted and fixed to the expanded portion 5'C. In the structure mentioned above, a dispersion of the side gap sg constituting the magnetic passage can be restricted by securing an coaxiality between the guide hole opposing to the rod 7' portion and the inner diameter expanded portion 5'A of the nozzle guide body 5'. That is, since the guide hole guiding the valve body and the inner diameter expanded portion 5'A constituting the side gap sg are constructed by the same material, an accurate working process can be easily performed. A nozzle body 12' has a fuel inflow passage 22, an axial passage 13'A communicating with the inflow passage 22 and a diametrical passage 13', and is integrally provided with a seat surface 10 for the spherical surface conical valve 11' corresponding to the valve closing body and a fuel injection hole 9' in a downstream portion thereof. In this case, also in the present embodiment, a high-frequency induction hardening is applied to the contracted portion 5'B side in the nozzle guide body 5' except the inner diameter expanded portion 5'A. A hardening is applied to a range of a Y portion shown in Fig. 3. This hardened portion increases a hardness of the portion for guiding the movable valve 4'A and reduces a friction generated by a sliding operation between the contracted portion 5'B and the expanded portion 8' of the rod 7'. The pressurized fuel flows into the nozzle body 12' from a plurality of recess-shaped axial passages 7'A (illustrated in Fig. 4 and communicating between the inner diameter expanded portion 5'A and the contracted portion 5'B) formed in the rod 7', however, the fuel sufficiently rectified before reaching here flows downstream from the axial passage 13'A via the diametrical passage 13'B. At this time, the fuel is eccentrically introduced from the axial center by the diametrical passage 13'B. That is, a swirling force is applied to the fuel and the fuel is introduced to the fuel injection hole 9', whereby an atomization of the fuel is promoted and the fuel is injected. In this case, an axial moving amount of the rod 7' constituting the valve body is determined by a height of the nozzle body 12' also in the present embodiment, however, in order to reduce a dispersion of the size, it is possible to insert a shim between the nozzle body 12' and the nozzle guide body 5' so as to adjust. The embodiment mentioned above can be easily produced in the case of being applied to a fuel injection valve in which a nozzle body having a small diameter and formed in a narrow shape is required, and a great advantage can be obtained. In the former embodiment, the nozzle guide body 5 and the nozzle body 12 may be constructed as the present embodiment. Further, in place of the ball valve 11, the spherical surface conical valve 11 may be employed. In two embodiments mentioned above, in order to work a coaxiality between the guide portion for guiding the rod and the inner wall surface forming the side gap at a high accuracy and in an easy manner, it is sufficient that these elements are within the same member, so that the nozzle guide body and the nozzle body 12 may be constituted by the same member. As mentioned above, in accordance with each of the embodiments mentioned above, in the fuel injection valve having the fuel passage in which the fuel is communicated is formed in an inner portion, the valve member for opening and closing the fuel passage, the valve seat portion with which the valve member is brought into contact at a time of closing the fuel passage, and the fuel injection hole allowing the fuel to pass through in the downstream side of the valve seat portion, there is provided at least one guide portion having one end fixed to the injection valve main body and guiding the axial sliding motion of the valve member in the inner portion, and the nozzle guide body constituting the magnetic passage portion formed so as to surround the magnetic member connected and fixed to one end of the valve member by the same material. Accordingly, it is possible to reduce a dispersion of the side gap constituting the magnetic passage by restricting the eccentricity and the incline of the valve member, it is possible to stabilize the axial motion of the valve member and it is possible to maintain the injection accuracy high. In particular, even in the narrow valve structure, the injection accuracy is not lowered. Further, since the working process is performed within the same member, the accurate working process can be easily realized, and the inexpensive production can be achieved and a mass production can be performed. Since the guide portion for guiding the axial sliding motion of the valve member and the member surrounding the magnetic member connected and fixed to the valve member so as to form the magnetic passage are provided within the same member, it is possible to restrict the eccentricity and the incline of the valve member and it is possible to reduce the dispersion of the side gap constituting the magnetic passage. Accordingly, it is possible to stabilize the axial motion of the valve member and it is possible to maintain the injection accuracy high.

Claims: An electromagnetic fuel injection valve comprising: a core (2) and a coil (16) wound around a bobbin (17), wherein upon energizing the coil (16) a movable valve (4A) is driven so as to open and close a seat surface (10) of the valve (4A), wherein the valve (4A) comprises a plunger (4) and a rod (7) connected to the plunger (4), the plunger (4) forms a gap (sg) to an inner diameter expanded portion (5A), an expanded portion (8) of the rod (7) is guided by an inner diameter contracted portion (5B) and the inner diameter expanded portion (5A) and the inner diameter contracted portion (5B) are formed within one member being a nozzle guide body (5). An electromagnetic fuel injection valve according to claim 1, wherein a nozzle body (12) having a valve seat (10) and a fuel injection hole (9) in a downstream side of said valve seat (10) is provided as an independent member form said nozzle guide body (5), and said nozzle body (12) is supported by said nozzle guide body (5). An electromagnetic fuel injection valve according to claim 2, wherein said valve seat (10) and said fuel injection hole (9) are formed in said nozzle guide body (5). An electromagnetic fuel injection valve according to at least one of claims 1 to 3, wherein said nozzle guide body (5) constitutes a magnetic passage portion formed so as to surround a magnetic member connected and fixed to one end of said valve (4A) and being made by the same material. An electromagnetic fuel injection valve according to at least one of claims 1 to 4, wherein a high-frequency hardening is applied to a portion of said nozzle guide body (5) except the magnetic passage portion.

Inventors: AMOU KIYOSHI, ISHIKAWA TOHRU, KADOMUKAI YUZO, MAEKAWA NORIYUKI, MIYAJIMA AYUMU, OKAMOTO YOSHIO, YAMAKADO MAKOTO, AMOU, KIYOSHI, ISHIKAWA, TOHRU, KADOMUKAI, YUZO, MAEKAWA, NORIYUKI, MIYAJIMA, AYUMU, OKAMOTO, YOSHIO, YAMAKADO, MAKOTO, Amou, Kiyoshi, Hitachi Ltd. Intell. Prop. Group, Ishikawa, Tohru, Hitachi Ltd. Intell. Prop. Group, Kadomukai, Yuzo, Hitachi Ltd. Intell. Prop. Group, Maekawa, Noriyuki, Hitachi Ltd. Intell.Prop. Group, Miyajima, Ayumu, Hitachi Ltd. Intell. Prop. Group, Okamoto, Yoshio, Hitachi Ltd. Intell Prop. Group, Yamakado, Makoto, Hitachi Ltd. Intell. Prop. Group
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 2000
Main classification: F02M51
IPC codes: F02M51, F02M61