Fuel injection device

Abstract

To provide a fuel injection device that exhibits high valve closing detection performance and is manufactured easily.SOLUTION: An upper housing 70 is formed to have a C-shaped cross section and is provided between a fixation core 50 and a housing 20. A coil 55 is provided on a nozzle hole side of the upper housing 70 between the fixation core 50 and the housing 20, and forms a magnetic circuit in the fixation core 50, the upper housing 70, the housing 20, a nozzle part 10 and a movable core 40 through electric conduction to enable attraction of the movable core 40 and the needle 30 to the fixation core 50 side. The upper housing 70 is separated from an outer peripheral wall of the fixation core 50. When the size in the axial direction of the upper housing 70 is defined as A and the size in the axial direction of a portion where an outer peripheral wall of the movable core 40 and an inner peripheral wall of the nozzle part 10 oppose to each other during closing of the valve as B, setting is performed to satisfy A / B≥1.2.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fuel injection device. [Background technology]

[0002] Fuel injection devices that perform minute injection amount control are known. To improve the accuracy of minute injection amount control, it is necessary to detect the valve closing timing of the fuel injection device. However, in conventional fuel injection devices, the signal generated when the valve closes is small, making it difficult to detect the valve closing timing.

[0003] Therefore, in the fuel injection device of Patent Document 1, in order to reduce magnetic resistance in the magnetic circuit, the upper housing is assembled by press-fitting into the annular space between the fixed core and the housing, and the inner wall of the upper housing is tightly fitted to the outer wall of the fixed core, and the outer wall of the upper housing is tightly fitted to the inner wall of the housing, eliminating any gaps and improving valve closure detectability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-162020 Summary of the Invention [Problem to be solved by the invention]

[0005] In the fuel injection device of Patent Document 1, the upper housing is press-fit into the annular space between the fixed core and the housing to tightly fit the inner peripheral wall of the upper housing to the outer peripheral wall of the fixed core, and the outer peripheral wall of the upper housing to the inner peripheral wall of the housing, eliminating any gaps. However, this raises the risk of the housing on the radially outer side of the upper housing expanding radially outward. To prevent the housing from expanding radially outward, special assembly equipment capable of maintaining the outer diameter of the housing is required.

[0006] An object of the present invention is to provide a fuel injection device that has high valve closure detectability and is easy to manufacture. [Means for solving the problem]

[0007] The fuel injection device according to the present invention includes a nozzle portion (10), a housing (20), a needle (30), a movable core (40), a fixed core (50), a magnetic restriction portion (15), an upper housing (70), and a coil (55). The nozzle portion has a nozzle hole (13) through which fuel is injected and a valve seat (14) formed around the nozzle hole. The cylindrical housing is connected to the nozzle portion on the side opposite the nozzle hole. The needle can open and close the nozzle hole by moving one end away from or into contact with the valve seat.

[0008] The movable core is attached to the needle so that a portion of the axial direction is located radially inside the end of the nozzle portion opposite the injection hole. The cylindrical fixed core is attached to the movable core opposite the injection hole, and at least a portion of the axial direction is located radially inside the housing. The magnetic throttling portion is provided between the end of the nozzle portion and the end of the fixed core, and is capable of throttling the magnetic field between the nozzle portion and the fixed core. The upper housing is formed in a cylindrical, annular, or C-shaped cross section and is provided between the fixed core and the housing.

[0009] The coil is provided on the injection hole side of the upper housing between the fixed core and the housing, and when energized, forms a magnetic circuit among the fixed core, the upper housing, the housing, the nozzle portion, and the movable core, and is capable of attracting the movable core together with the needle toward the fixed core. The upper housing is spaced apart from the outer peripheral wall of the fixed core or the inner peripheral wall of the housing.

[0010] If the axial size of the upper housing is A and the axial size of the part where the outer peripheral wall of the movable core and the inner peripheral wall of the nozzle portion face each other when the valve is closed is B, then: A / B≧1.2 It is set to be.

[0011] This reduces the magnetic resistance between the upper housing and the outer peripheral wall of the fixed core and between the upper housing and the inner peripheral wall of the housing, thereby reducing the magnetic resistance of the entire magnetic circuit, thereby increasing the induced electromotive force and improving valve closure detectability.

[0012] In the present invention, the upper housing is spaced apart from the outer peripheral wall of the fixed core or the inner peripheral wall of the housing. Therefore, when the upper housing is assembled into the annular space between the fixed core and the housing, the housing on the radially outer side of the upper housing is prevented from expanding radially outward. This eliminates the need for special assembly equipment capable of maintaining the outer diameter of the housing, making it easy to manufacture the fuel injection device. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view showing a fuel injection device according to a first embodiment. [Figure 2] 2 is a cross-sectional view showing an upper housing and its periphery of the fuel injection device according to the first embodiment. FIG. [Figure 3] FIG. 2 is a plan view showing an upper housing of the fuel injection device according to the first embodiment. [Figure 4] 5 is a cross-sectional view illustrating an assembly process of the upper housing of the fuel injection device according to the first embodiment. FIG. [Figure 5] FIG. 10 is a graph showing the relationship between A / B and the detectable flow rate when the valve is closed. [Figure 6] FIG. 10 is a cross-sectional view showing an upper housing and its periphery of a fuel injection device according to a second embodiment. [Figure 7] 10 is a cross-sectional view illustrating an assembly process of the upper housing of the fuel injection device according to the second embodiment. FIG. [Figure 8] FIG. 10 is a cross-sectional view showing an upper housing and its periphery of a fuel injection device according to a third embodiment. [Figure 9] FIG. 10 is a cross-sectional view showing an upper housing and its periphery of a fuel injection device according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, fuel injection devices according to a number of embodiments will be described with reference to the drawings. Note that substantially the same components in the number of embodiments will be denoted by the same reference numerals, and descriptions thereof will be omitted. <1> A number enclosed in "<" and ">" indicates the beginning of a section describing the content of an embodiment (including related matters) corresponding to the claimed invention having the item number (at the time of filing) in question.

[0015] (First embodiment) A fuel injection device according to a first embodiment is shown in Figure 1. The fuel injection device 1 is applied to, for example, a gasoline engine (hereinafter simply referred to as "engine") as an internal combustion engine mounted on a vehicle (not shown). The fuel injection device 1 injects gasoline as fuel and supplies it to the engine.

[0016] <1> The fuel injection device 1 includes a nozzle portion 10, a housing 20, a needle 30, a movable core 40, a fixed core 50, a magnetic restriction portion 15, an upper housing 70, a coil 55, etc. The nozzle portion 10 has an injection hole 13 from which fuel is injected, and a valve seat 14 formed around the injection hole 13. The cylindrical housing 20 is provided so as to connect to the side of the nozzle portion 10 opposite the injection hole 13. The needle 30 can open and close the injection hole 13 by moving one end away from or into contact with the valve seat 14.

[0017] The movable core 40 is provided in the needle 30 so that a portion of its axial direction is located radially inside the end of the nozzle portion 10 opposite the injection hole 13. The cylindrical fixed core 50 is provided on the opposite side of the movable core 40 from the injection hole 13, and at least a portion of its axial direction is located radially inside the housing 20. The magnetic throttling portion 15 is provided between the end of the nozzle portion 10 and the end of the fixed core 50, and is capable of throttling the magnetism between the nozzle portion 10 and the fixed core 50. The upper housing 70 has a C-shaped cross section and is provided between the fixed core 50 and the housing 20.

[0018] The coil 55 is provided between the fixed core 50 and the housing 20 on the injection hole 13 side of the upper housing 70, and when energized, forms a magnetic circuit among the fixed core 50, upper housing 70, housing 20, nozzle portion 10, and movable core 40, and is able to attract the movable core 40 together with the needle 30 toward the fixed core 50. The upper housing 70 is spaced apart from the outer peripheral wall of the fixed core 50.

[0019] More specifically, the nozzle portion 10 has a nozzle end portion 11 and a nozzle tube portion 12. The nozzle end portion 11 is formed, for example, from metal in the shape of a tube with a bottom. The nozzle end portion 11 has an injection hole 13 and a valve seat 14. A plurality of injection holes 13 are formed so as to penetrate the bottom portion of the nozzle end portion 11 from the inside to the outside. The valve seat 14 is formed in an annular shape around the injection hole 13 inside the bottom portion of the nozzle end portion 11.

[0020] The nozzle tube portion 12 is formed into a cylindrical shape from a magnetic material such as metal. The nozzle tube portion 12 is provided integrally with the nozzle end portion 11 so that the inner peripheral wall of one axial end thereof fits into the outer peripheral wall of the nozzle end portion 11. Here, the nozzle tube portion 12 and the nozzle end portion 11 are joined together by, for example, welding.

[0021] The housing 20 is formed into a cylindrical shape from a magnetic material such as metal, etc. The housing 20 is provided so as to be connected to the nozzle portion 10 on the side opposite to the injection hole 13.

[0022] More specifically, the housing 20 has an outer cylindrical portion 21, an outer annular portion 22, an inner cylindrical portion 23, and an inner annular portion 24 (see FIG. 2).

[0023] The outer cylindrical portion 21 is formed in a cylindrical shape. The outer annular portion 22 is formed in a ring shape so as to extend radially inward from one axial end of the outer cylindrical portion 21. The inner cylindrical portion 23 is formed in a cylindrical shape so as to extend from the inner edge of the outer annular portion 22 to the side opposite the outer cylindrical portion 21. The inner annular portion 24 is formed in a ring shape so as to extend radially inward from the end of the inner cylindrical portion 23 opposite the outer annular portion 22.

[0024] An annular housing recess 201 recessed radially outward is formed in the inner peripheral wall of the end of the outer cylindrical portion 21 opposite to the outer annular portion 22. Two housing recesses 201 are formed in the axial direction of the outer cylindrical portion 21.

[0025] An annular nozzle step surface 121 is formed on the outer peripheral wall of the nozzle tube portion 12 of the nozzle part 10 on the side opposite to the nozzle end portion 11. The housing 20 is provided so as to be connected to the nozzle tube portion 12 on the side opposite to the injection hole 13, so that the end face of the inner annular portion 24 abuts against the nozzle step surface 121 and the inner peripheral wall of the inner tube portion 23 abuts against the outer peripheral wall of the nozzle tube portion 12.

[0026] The needle 30 is made of, for example, a non-magnetic metal and has a needle body 31 and a flange 34.

[0027] The needle body 31 is formed in a rod shape. The flange portion 34 is formed in an annular shape so as to extend radially outward from the end of the needle body 31. The needle 30 is provided inside the nozzle portion 10 so as to be able to reciprocate in the axial direction inside the nozzle tube portion 12 and the nozzle end portion 11.

[0028] The needle 30 is formed with an axial flow passage 301 and a radial flow passage 302. The axial flow passage 301 is formed to extend in the axial direction from the end face of the needle body 31 opposite the nozzle end 11. The radial flow passage 302 is formed to extend in the radial direction of the needle body 31 and connect the axial flow passage 301 to the outer wall of the needle body 31. As a result, fuel on the side of the needle 30 opposite the nozzle end 11 can flow between the outer peripheral wall of the needle body 31 and the inner wall of the nozzle cylindrical portion 12 via the axial flow passage 301 and the radial flow passage 302.

[0029] The needle 30 opens and closes the injection hole 13 by moving one end of the needle body 31, which is the end on the nozzle end 11 side, away from (unseating) or abutting (seating) the valve seat 14. Hereinafter, the direction in which the needle 30 moves away from the valve seat 14 will be referred to as the valve opening direction, and the direction in which the needle 30 abuts against the valve seat 14 will be referred to as the valve closing direction, as appropriate.

[0030] The movable core 40 is formed into a cylindrical shape from a magnetic material such as metal. The movable core 40 is provided radially outward of the needle body 31 on the nozzle end 11 side of the flange 34 so as to be movable in the axial direction relative to the needle 30. The flange 34 restricts the movable core 40 from moving relative to the needle 30 in the valve-opening direction.

[0031] The fixed core 50 is formed into a cylindrical shape from a magnetic material such as metal. The fixed core 50 has a core recess 501 and a core recess 502. The core recess 501 is formed into an annular shape so as to be recessed radially inward from the outer circumferential wall at one axial end of the fixed core 50. The core recess 502 is formed into an annular shape so as to be recessed radially outward from the inner circumferential wall at one axial end of the fixed core 50.

[0032] The fixed core 50 is provided with a magnetic restrictor 15 and a sleeve 51 .

[0033] The magnetic restricting portion 15 is formed into a cylindrical shape from, for example, a non-magnetic metal. The magnetic restricting portion 15 is provided so as to fit into the core recess 501. Here, the magnetic restricting portion 15 and the fixed core 50 are joined together by, for example, welding.

[0034] The sleeve 51 is formed into a cylindrical shape from, for example, a non-magnetic metal. The sleeve 51 is provided so as to fit into the core recess 502.

[0035] The fixed core 50 is provided on the opposite side of the movable core 40 from the injection hole 13. Here, the end of the magnetic restricting portion 15 opposite to the core recess 501 is connected to the end of the nozzle tubular portion 12 opposite to the nozzle end 11. The magnetic restricting portion 15 and the nozzle tubular portion 12 are joined by, for example, welding.

[0036] The inner peripheral wall of the end of the sleeve 51 on the injection hole 13 side can slide against the outer peripheral wall of the flange portion 34. In addition, the end face of the sleeve 51 on the injection hole 13 side can abut against the end face of the movable core 40 on the opposite side to the injection hole 13.

[0037] The fixed core 50 has a portion in the axial direction, which is on the injection hole 13 side, located radially inside the outer cylindrical portion 21 of the housing 20 (see FIGS. 1 and 2).

[0038] A cylindrical adjusting pipe 62 is press-fitted inside the fixed core 50. The fuel injection device 1 has a spring 63. The spring 63 is, for example, a coil spring, and is provided inside the fixed core 50 between the adjusting pipe 62 and the needle 30. One end of the spring 63 abuts against the adjusting pipe 62. The other end of the spring 63 abuts against the needle 30. The spring 63 can urge the needle 30 and the movable core 40 toward the injection hole 13, i.e., in the valve closing direction. The urging force of the spring 63 is adjusted by the position of the adjusting pipe 62 relative to the fixed core 50.

[0039] The coil 55 is formed in a cylindrical shape and is provided between the fixed core 50 and the housing 20. The coil 55 is formed by winding a conducting wire around a cylindrical bobbin 551 made of resin.

[0040] More specifically, the coil 55 and the bobbin 551 are provided between the outer peripheral wall of the fixed core 50, the magnetic restrictor 15 and the nozzle cylindrical portion 12, and the inner peripheral wall of the outer cylindrical portion 21 of the housing 20 (see FIG. 2).

[0041] The upper housing 70 is made of a magnetic material such as metal and is formed in a generally C-shape (see FIG. 3). The upper housing 70 is disposed between the fixed core 50 and the housing 20 on the opposite side of the coil 55 from the injection hole 13 (see FIGS. 1 and 2). The outer peripheral wall of the upper housing 70 and the inner peripheral wall of the outer cylindrical portion 21 of the housing 20 are in close contact with each other. The inner peripheral wall of the upper housing 70 and the outer peripheral wall of the fixed core 50 are spaced apart.

[0042] When power is supplied (energized), the coil 55 generates a magnetic force. When the magnetic force is generated in the coil 55, a magnetic circuit is formed in the fixed core 50, the upper housing 70, the outer cylindrical portion 21, the outer annular portion 22, the nozzle cylindrical portion 12, and the movable core 40, avoiding the magnetic restricting portion 15 (see FIG. 2).

[0043] This generates a magnetic attraction force between the fixed core 50 and the movable core 40, and the movable core 40 is attracted toward the fixed core 50 together with the needle 30. This causes the needle 30 to move in the valve-opening direction, and the end of the needle 30 moves away from the valve seat 14, opening the valve. As a result, the injection hole 13 is opened and fuel is injected from the injection hole 13. In this way, when the coil 55 is energized, it is possible to attract the movable core 40 toward the fixed core 50 and move the needle 30 away from the valve seat 14, i.e., in the valve-opening direction.

[0044] When the movable core 40 is attracted toward the fixed core 50 (in the valve-opening direction) by magnetic attraction, the flange 34 of the needle 30 moves axially inside the sleeve 51. At this time, the outer peripheral wall of the flange 34 slides against the inner peripheral wall of the sleeve 51. Therefore, the reciprocating axial movement of the end of the needle 30 on the flange 34 side is guided by the sleeve 51.

[0045] Furthermore, when the movable core 40 is attracted toward the fixed core 50 (valve opening direction) by the magnetic attraction force, the end face on the fixed core 50 side collides with the end face on the nozzle hole 13 side of the sleeve 51. This restricts the movement of the movable core 40 in the valve opening direction.

[0046] When the power supply to the coil 55 is stopped while the movable core 40 is attracted to the fixed core 50, the needle 30 and the movable core 40 are urged toward the valve seat 14 by the urging force of the spring 63. This causes the needle 30 to move in the valve closing direction, and the end of the needle 30 comes into contact with the valve seat 14, closing the valve. As a result, the injection hole 13 is closed.

[0047] The fuel injection device 1 has a spring 65. The spring 65 is, for example, a coil spring, and is provided with one end abutting against the surface of the movable core 40 on the injection hole 13 side and the other end abutting against an annular nozzle step surface 122 formed on the inner circumferential wall of the nozzle tube portion 12 (see FIG. 2). The spring 65 can bias the movable core 40 toward the fixed core 50, i.e., in the valve opening direction. The biasing force of the spring 65 is smaller than the biasing force of the spring 63. Therefore, when the coil 55 is not energized, the needle 30 is pressed against the valve seat 14 by the spring 63, and the movable core 40 is pressed against the flange portion 34.

[0048] In this embodiment, the needle 30 is provided with a stopper 66. The stopper 66 is formed in an annular shape from, for example, a non-magnetic metal. The stopper 66 is press-fitted into the movable core 40 on the injection hole 13 side so that the inner peripheral wall thereof fits into the outer peripheral wall of the needle body 31. The movable core 40 is movable in the axial direction relative to the needle body 31 between the flange 34 and the stopper 66. The stopper 66 abuts against the surface of the movable core 40 on the injection hole 13 side, thereby restricting movement of the movable core 40 in the valve-closing direction relative to the needle 30.

[0049] 1, the periphery of the coil 55 and the bobbin 551, and the outer peripheral wall of the fixed core 50 are molded with a molded portion 56 made of resin. Here, the inner peripheral wall of the upper housing 70 faces but is spaced apart from the outer peripheral wall of the fixed core 50. Resin forming the molded portion 56 exists between the inner peripheral wall of the upper housing 70 and the outer peripheral wall of the fixed core 50 (see FIG. 2).

[0050] The fuel injection device 1 includes a connector portion 57. The connector portion 57 is formed integrally with the molded portion 56 from resin so as to protrude radially outward from the molded portion 56.

[0051] Terminals 553 are insert-molded into connector portion 57 and molded portion 56. Terminals 553 are formed of a conductor such as metal, one end of which is connected to coil 55 and the other end of which is located inside connector portion 57.

[0052] The end of terminal 553 on the coil 55 side is molded with bobbin extension 552. Bobbin extension 552 is formed integrally with bobbin 551 so as to extend from bobbin 551 in the direction opposite to nozzle hole 13 (see FIG. 1).

[0053] A fuel flow path 100 is formed inside the fixed core 50, the magnetic restrictor portion 15, and the nozzle portion 10. The fuel flow path 100 is connected to the injection hole 13.

[0054] A pipe (not shown) is connected to the end of the fixed core 50 opposite to the injection hole 13. As a result, fuel from a fuel supply source (fuel pump) flows into the fuel flow path 100 via the pipe. The fuel flow path 100 guides the fuel to the injection hole 13.

[0055] The fuel that flows into the fuel flow passage 100 from the end of the fixed core 50 opposite the injection hole 13 flows through the inside of the fixed core 50 and the adjusting pipe 62, the axial flow passage 301, the radial flow passage 302, and between the needle 30 and the nozzle portion 10, and is led to the injection hole 13.

[0056] A filter 2 is provided on the inside of the end of the fixed core 50 opposite to the injection hole 13. The filter 2 is capable of capturing foreign matter in the fuel flowing through the fuel flow passage 100.

[0057] An electronic control unit (hereinafter referred to as "ECU") (not shown) is connected to terminal 553. The ECU is a small computer having a CPU as a calculation unit, ROM and RAM as storage units, I / O as an input / output unit, etc. The ECU controls the operation of the engine, devices, and equipment mounted on the vehicle based on information from various sensors provided in various parts of the vehicle, and controls the running of the vehicle, etc.

[0058] The ECU controls the supply of electricity to the coil 55 via the terminal 553, thereby controlling the operation of the fuel injection device 1 and the engine and controlling the vehicle. When the ECU supplies electricity to the coil 55, a magnetic attraction force is generated between the fixed core 50 and the movable core 40, and the movable core 40 and the needle 30 move in the valve opening direction against the biasing force of the spring 63. As a result, the needle 30 moves away from the valve seat 14, opening the valve. As a result, the fuel in the fuel flow path 100 is injected through the injection hole 13 into the combustion chamber of the engine, which is outside the fuel injection device 1.

[0059] If the axial size of the upper housing 70 is A and the axial size of the portion where the outer peripheral wall of the movable core 40 and the inner peripheral wall of the nozzle portion 10 face each other when the valve is closed is B, then: A / B≧1.2 Here, "when the valve is closed" refers to a state in which the coil 55 is not energized, the needle 30 is in contact with the valve seat 14, and the movable core 40 is in contact with the flange portion 34. Furthermore, when the valve is closed, the axial size B of the portion where the outer circumferential wall of the movable core 40 faces the inner circumferential wall of the nozzle portion 10 corresponds to the distance between the end face of the movable core 40 on the injection hole 13 side and the boundary surface between the nozzle cylinder portion 12 and the magnetic throttle portion 15.

[0060] As shown in Figure 5, as the value of A / B increases, the detectable flow rate when the valve is closed decreases, improving the detectability of the valve being closed. When the value of A / B is 1.2 or higher, the detectable flow rate when the valve is closed becomes almost constant. In other words, A / B = 1.2 corresponds to the critical value of the effect.

[0061] In this embodiment, A / B is set to, for example, approximately 1.7, which reduces the magnetic resistance between the upper housing 70 and the outer peripheral wall of the fixed core 50 and between the upper housing 70 and the inner peripheral wall of the housing 20, thereby reducing the magnetic resistance of the entire magnetic circuit.

[0062] In this embodiment, an efficient magnetic circuit with a small magnetic gap and magnetic resistance can be formed in the fixed core 50, upper housing 70, and housing 20, so that the induced electromotive force generated by the behavior of the movable core 40 can be increased, and controllability can be improved when the induced electromotive force is used as a signal.

[0063] As an example of control using induced electromotive force as a signal, for example, an example in which the closing of the needle 30 is detected based on the detected induced electromotive force (JP 2017-61882 A) can be adopted.

[0064] Next, the upper housing 70 will be described in detail.

[0065] As shown in FIG. 3, the upper housing 70 has a main body 71, a notch 72, and a recess 73.

[0066] The main body 71 is formed in an annular shape from a magnetic material such as metal. The cutout portion 72 is formed by cutting out a portion of the main body 71 in the circumferential direction. As a result, the main body 71 of the upper housing 70 is divided in the circumferential direction and is formed in a C-shape when viewed from the axial direction. In other words, the main body 71 is formed so that the cross section taken along a plane perpendicular to its axis has a C-shape.

[0067] The recesses 73 are formed so as to recess radially inward from the outer peripheral wall of the main body 71 and extend in the axial direction. Five recesses 73 are formed at equal intervals around the circumferential direction of the main body 71. As a result, the outer peripheral wall of the upper housing 70 is divided into six parts in the circumferential direction. By forming the recesses 73 in the main body 71, the resin that forms the molded portion 56 can flow from the side of the upper housing 70 opposite the coil 55 to the coil 55 side through the recesses 73. Furthermore, by forming the recesses 73 in the main body 71, the main body 71 can be easily deformed in the radial direction.

[0068] As shown in FIG. 3 , when the circumferential lengths of the outer peripheral wall of the upper housing 70 divided into six parts in the circumferential direction by the recessed portion 73 are respectively denoted as Lo1, Lo2, Lo3, Lo4, Lo5, and Lo6, and the circumferential length of the inner peripheral wall of the upper housing 70 is denoted as Li, Li=Lo1+Lo2+Lo3+Lo4+Lo5+Lo6 In other words, the area of ​​the outer peripheral wall of the upper housing 70 that is in close contact with the inner peripheral wall of the outer cylindrical portion 21 of the housing 20 is equal to the area of ​​the inner peripheral wall of the upper housing 70 that faces the outer peripheral wall of the fixed core 50. As a result, even if a recess 73 serving as a resin flow path is formed in the outer peripheral wall of the upper housing 70, the magnetic path area on the radially inner side of the upper housing 70 can be made equal to the magnetic path area on the radially outer side, and it is possible to prevent magnetic choking from occurring at the close contact area between the outer peripheral wall of the upper housing 70 and the inner peripheral wall of the outer cylindrical portion 21 of the housing 20. From this perspective, it is preferable that Li≦Lo1+Lo2+Lo3+Lo4+Lo5+Lo6.

[0069] Next, a method for assembling the upper housing 70 between the fixed core 50 and the housing 20, that is, a method for manufacturing the fuel injection device 1, will be described.

[0070] The method for manufacturing the fuel injection device 1 includes the following steps.

[0071] (Housing assembly process) After the nozzle end portion 11, nozzle cylindrical portion 12, spring 65, needle 30, movable core 40, stopper 66, magnetic restricting portion 15, fixed core 50, sleeve 51, etc. are assembled together, the housing 20 is assembled to the nozzle cylindrical portion 12. Specifically, the housing 20 is inserted into the nozzle portion 10 from the nozzle end portion 11 side, and the inner annular portion 24 is brought into contact with the nozzle step surface 121. Thereafter, the nozzle cylindrical portion 12 and the housing 20 are fixed by welding.

[0072] (Coil assembly process) After the housing assembly process, the coil 55, which is integral with the bobbin 551, the bobbin extension 552, and the terminal 553, is inserted between the fixed core 50 and the housing 20. Specifically, the coil 55 is inserted from the side of the fixed core 50 opposite to the injection hole 13, and the coil 55 is positioned between the magnetic restricting portion 15 and the housing 20.

[0073] (Upper housing assembly process) After the coil assembly process, the upper housing 70 is inserted between the fixed core 50 and the housing 20. Specifically, the upper housing 70 is inserted from the side opposite the injection hole 13 of the fixed core 50, and with the bobbin extension portion 552 positioned in the cutout portion 72 of the upper housing 70, the upper housing 70 is press-fitted into the housing 20.

[0074] <3> As shown in FIG. 4, before the upper housing 70 is provided between the fixed core 50 and the housing 20, the outer diameter Duo of the upper housing 70 is equal to or larger than the inner diameter Dhi of the housing 20, and the inner diameter Dui is larger than the outer diameter Dco of the fixed core 50.

[0075] When the upper housing 70 is press-fitted into the housing 20, the outer peripheral wall of the upper housing 70 first comes into contact with the inner peripheral wall of the end of the outer cylindrical portion 21 of the housing 20 opposite the injection hole 13. In this state, when the upper housing 70 is moved toward the injection hole 13, the outer peripheral wall of the upper housing 70 slides against the inner peripheral wall of the outer cylindrical portion 21 of the housing 20. At this time, the upper housing 70 deforms radially inward so that the inner and outer diameters are reduced.

[0076] When the upper housing 70 is further moved toward the injection hole 13, the outer edge of the end face of the upper housing 70 facing the injection hole 13 abuts against the annular stepped surface 205 formed on the inner peripheral wall of the outer cylindrical portion 21, completing the press-fit. In this state, the outer peripheral wall of the upper housing 70 and the inner peripheral wall of the outer cylindrical portion 21 of the housing 20 are in close contact with each other, and the outer diameter Duo of the upper housing 70 and the inner diameter Dhi of the housing 20 become the same. However, even in this state, the inner diameter Dui of the upper housing 70 is larger than the outer diameter Dco of the fixed core 50, so a cylindrical gap Sp1 is formed between the inner peripheral wall of the upper housing 70 and the outer peripheral wall of the fixed core 50. The size of this gap Sp1 is 10 to 150 μm.

[0077] (Molding process) After the upper housing assembly process, molten resin is poured between the fixed core 50 and the housing 20 and between the periphery of the fixed core 50 and the mold to form the molded portion 56 and the connector portion 57. At this time, the molten resin flows from the side opposite the injection hole 13 of the upper housing 70, through the recessed portion 73 and the notched portion 72, toward the coil 55. As a result, the periphery of the coil 55 is covered with resin. At this time, the resin also flows into the gap Sp1 between the inner circumferential wall of the upper housing 70 and the outer circumferential wall of the fixed core 50.

[0078] As explained above, <1> In this embodiment, if the axial size of the upper housing 70 is A and the axial size of the portion where the outer circumferential wall of the movable core 40 and the inner circumferential wall of the nozzle portion 10 face each other when the valve is closed is B, then: A / B≧1.2 It is set to be.

[0079] This reduces the magnetic resistance between the upper housing 70 and the outer peripheral wall of the fixed core 50 and between the upper housing 70 and the inner peripheral wall of the housing 20, thereby reducing the magnetic resistance of the entire magnetic circuit. This increases the induced electromotive force and improves valve closure detectability.

[0080] In this embodiment, the upper housing 70 is spaced apart from the outer peripheral wall of the fixed core 50. Therefore, when the upper housing 70 is assembled into the annular space between the fixed core 50 and the housing 20, the housing 20 on the radially outer side of the upper housing 70 is prevented from expanding radially outward. This eliminates the need for special assembly equipment or the like capable of maintaining the outer diameter of the housing 20, making it possible to easily manufacture the fuel injection device 1.

[0081] Also, <3> In this embodiment, before the upper housing 70 is provided between the fixed core 50 and the housing 20 , the outer diameter Duo of the upper housing 70 is equal to or larger than the inner diameter Dhi of the housing 20 , and the inner diameter Dui is larger than the outer diameter Dco of the fixed core 50 .

[0082] This allows the outer peripheral wall of the upper housing 70 and the inner peripheral wall of the housing 20 to be closely attached to each other, while forming a gap Sp1 as a cylindrical clearance between the inner peripheral wall of the upper housing 70 and the outer peripheral wall of the fixed core 50. Also, the size of the clearance, i.e., the gap Sp1, can be easily controlled. Therefore, when the upper housing 70 is assembled into the annular space between the fixed core 50 and the housing 20, the housing 20 on the radially outer side of the upper housing 70 can be more effectively prevented from expanding radially outward.

[0083] (Second embodiment) A part of a fuel injection device according to the second embodiment is shown in Figure 6. The second embodiment differs from the first embodiment in the configuration of the upper housing 70 and the like.

[0084] <1> In this embodiment, the inner peripheral wall of the upper housing 70 is in close contact with the outer peripheral wall of the fixed core 50 , and the outer peripheral wall is spaced apart from the inner peripheral wall of the outer cylindrical portion 21 of the housing 20 .

[0085] Next, the upper housing assembly process of this embodiment will be described.

[0086] <4> As shown in FIG. 7, before the upper housing 70 is provided between the fixed core 50 and the housing 20, the inner diameter Dui is equal to or smaller than the outer diameter Dco of the fixed core 50, and the outer diameter Duo is smaller than the inner diameter Dhi of the housing 20.

[0087] When the upper housing 70 is press-fitted into the housing 20, the inner peripheral wall of the upper housing 70 first comes into contact with the outer peripheral wall of the fixed core 50. In this state, when the upper housing 70 is moved toward the injection hole 13, the inner peripheral wall of the upper housing 70 and the outer peripheral wall of the fixed core 50 slide against each other. At this time, the upper housing 70 deforms radially outward so that the inner and outer diameters expand.

[0088] When the upper housing 70 is further moved toward the injection hole 13, the outer edge of the end face of the upper housing 70 on the injection hole 13 side abuts against the annular stepped surface 205 formed on the inner circumferential wall of the outer tubular portion 21, completing the press-fit. In this state, the inner circumferential wall of the upper housing 70 and the outer circumferential wall of the fixed core 50 are in close contact with each other, and the inner diameter Dui of the upper housing 70 and the outer diameter Dco of the fixed core 50 become the same. However, even in this state, the outer diameter Duo of the upper housing 70 is smaller than the inner diameter Dhi of the housing 20, so a cylindrical gap Sp2 is formed between the outer circumferential wall of the upper housing 70 and the inner circumferential wall of the outer tubular portion 21 of the housing 20. The size of this gap Sp2 is 10 to 150 μm.

[0089] As explained above, <4> In this embodiment, before the upper housing 70 is provided between the fixed core 50 and the housing 20 , the inner diameter Dui is equal to or smaller than the outer diameter Dco of the fixed core 50 , and the outer diameter Duo is smaller than the inner diameter Dhi of the housing 20 .

[0090] This allows the inner peripheral wall of the upper housing 70 and the outer peripheral wall of the fixed core 50 to be closely attached to each other, while forming a gap Sp2 as a cylindrical clearance between the outer peripheral wall of the upper housing 70 and the inner peripheral wall of the housing 20. Also, it is easy to manage the size of the clearance, i.e., the gap Sp2. Therefore, when the upper housing 70 is assembled into the annular space between the fixed core 50 and the housing 20, the housing 20 on the radially outer side of the upper housing 70 can be more effectively prevented from expanding radially outward.

[0091] (Third embodiment) A part of a fuel injection device according to the third embodiment is shown in Fig. 8. The third embodiment differs from the first embodiment in the configuration of the upper housing 70 and the like.

[0092] <2> In this embodiment, the upper housing 70 has a plurality of divided upper housings 710 arranged side by side in the axial direction.

[0093] In this embodiment, the upper housing 70 has three split upper housings 710. Here, the three split upper housings 710 are respectively referred to as split upper housing 711, split upper housing 712, and split upper housing 713. The split upper housing 711, split upper housing 712, and split upper housing 713 are arranged in this order, starting from the side opposite the injection hole 13 toward the injection hole 13 side.

[0094] The split upper housing 711 , split upper housing 712 , and split upper housing 713 all have outer peripheral walls that are in close contact with the inner peripheral wall of the outer cylindrical portion 21 of the housing 20 , and are spaced apart from the outer peripheral wall of the fixed core 50 .

[0095] In this embodiment, the divided upper housing 711 and the divided upper housing 712, and the divided upper housing 712 and the divided upper housing 713 are in close contact with each other, but they may be spaced apart.

[0096] In this embodiment, the upper housing 70 is made up of a plurality of divided upper housings 710, thereby reducing the axial size of each divided upper housing 710. Therefore, the divided upper housings 710 can be formed by press working, for example, improving the workability of the parts.

[0097] In this embodiment, if the axial size of the upper housing 70 is A and the axial size of the portion where the outer circumferential wall of the movable core 40 and the inner circumferential wall of the nozzle portion 10 face each other when the valve is closed is B, then: A / B≧1.2 It is set to be.

[0098] Here, A is the sum of the axial size A1 of the divided upper housing 711, the axial size A2 of the divided upper housing 712, and the axial size A3 of the divided upper housing 713.

[0099] In this embodiment, A1, A2, and A3 are the same, and are set so that A / B is, for example, approximately 1.7.

[0100] In this embodiment, by setting A / B≧1.2, similar to the first embodiment, the magnetic resistance between the upper housing 70 and the outer peripheral wall of the fixed core 50 and between the upper housing 70 and the inner peripheral wall of the housing 20 can be reduced, and the magnetic resistance of the entire magnetic circuit can be reduced. This increases the induced electromotive force, improving valve closure detectability.

[0101] Furthermore, in this embodiment, the divided upper housings 711-713 of the upper housing 70 are spaced apart from the outer peripheral wall of the fixed core 50. Therefore, when the upper housing 70 is assembled into the annular space between the fixed core 50 and the housing 20, the housing 20 on the radially outer side of the upper housing 70 can be prevented from expanding radially outward. This eliminates the need for special assembly equipment or the like capable of maintaining the outer diameter of the housing 20, making it possible to easily manufacture the fuel injection device 1.

[0102] (Fourth embodiment) A part of a fuel injection device according to the fourth embodiment is shown in Figure 9. The fourth embodiment differs from the first embodiment in the configuration of the upper housing 70 and the like.

[0103] <5> In this embodiment, the upper housing 70 has a first upper housing 721 and a second upper housing 722 provided on the injection hole 13 side of the first upper housing 721. The first upper housing 721, which is one of the first upper housing 721 and the second upper housing 722, has an inner circumferential wall that is in contact with the outer circumferential wall of the fixed core 50 while being spaced apart from the inner circumferential wall of the housing 20. The second upper housing 722, which is the other of the first upper housing 721 and the second upper housing 722, has an inner circumferential wall that is in contact with the inner circumferential wall of the housing 20 while being spaced apart from the outer circumferential wall of the fixed core 50.

[0104] Therefore, the first upper housing 721 and the second upper housing 722 have different press-fit surfaces, and when the first upper housing 721 is press-fitted, the influence of the press-fit surface of the second upper housing 722 after press-fitting can be reduced.

[0105] In this embodiment, the first upper housing 721 and the second upper housing 722 are spaced apart from each other, but they may be in close contact with each other.

[0106] In this embodiment, if the axial size of the upper housing 70 is A and the axial size of the portion where the outer circumferential wall of the movable core 40 and the inner circumferential wall of the nozzle portion 10 face each other when the valve is closed is B, then: A / B≧1.2 It is set to be.

[0107] Here, A is the sum of the axial size A1 of the first upper housing 721 and the axial size A2 of the second upper housing 722.

[0108] In this embodiment, A1 and A2 are the same, and A / B is set to be, for example, approximately 1.7.

[0109] In this embodiment, by setting A / B≧1.2, similar to the first embodiment, the magnetic resistance between the upper housing 70 and the outer peripheral wall of the fixed core 50 and between the upper housing 70 and the inner peripheral wall of the housing 20 can be reduced, and the magnetic resistance of the entire magnetic circuit can be reduced. This increases the induced electromotive force, improving valve closure detectability.

[0110] Furthermore, in this embodiment, the first upper housing 721 of the upper housing 70 is spaced apart from the inner circumferential wall of the housing 20. Furthermore, the second upper housing 722 of the upper housing 70 is spaced apart from the outer circumferential wall of the fixed core 50. Therefore, when the upper housing 70 is assembled into the annular space between the fixed core 50 and the housing 20, the housing 20 on the radially outer side of the upper housing 70 can be prevented from expanding radially outward. This eliminates the need for special assembly equipment or the like capable of maintaining the outer diameter of the housing 20, making it possible to easily manufacture the fuel injection device 1.

[0111] (Other embodiments) In the above-described embodiment, an example was shown in which the "magnetically restricted portion" was formed from a non-magnetic material separate from the nozzle portion. However, in other embodiments, the end of the nozzle portion facing the fixed core may be thinned to form this portion into the "magnetically restricted portion." In this case, the axial size B of the portion where the outer circumferential wall of the movable core and the inner circumferential wall of the nozzle portion face each other when the valve is closed corresponds to the distance between the end face of the movable core facing the injection hole and the boundary surface between the nozzle cylinder portion and the magnetically restricted portion.

[0112] In the third embodiment, an example was shown in which the outer peripheral walls of all of the multiple divided upper housings are in close contact with the inner peripheral wall of the housing and are spaced apart from the outer peripheral wall of the fixed core. In contrast to this, in other embodiments, the inner peripheral walls of all of the multiple divided upper housings may be in close contact with the outer peripheral wall of the fixed core and are spaced apart from the inner peripheral wall of the housing. Also, among the multiple divided upper housings, some divided upper housings may have their outer peripheral walls in close contact with the inner peripheral wall of the housing and are spaced apart from the outer peripheral wall of the fixed core, while other divided upper housings may have their inner peripheral walls in close contact with the outer peripheral wall of the fixed core and are spaced apart from the inner peripheral wall of the housing.

[0113] In addition, in the fourth embodiment, an example was shown in which the first upper housing 721, which is one of the first upper housing 721 and the second upper housing 722, has an inner wall that contacts the outer wall of the fixed core 50 while the outer wall is spaced apart from the inner wall of the housing 20, and the second upper housing 722, which is the other of the first upper housing 721 and the second upper housing 722, has an inner wall that contacts the inner wall of the housing 20 while being spaced apart from the outer wall of the fixed core 50. In contrast to this, in other embodiments, the second upper housing 722, which is one of the first upper housing 721 and the second upper housing 722, may have its inner peripheral wall in contact with the outer peripheral wall of the fixed core 50 while being spaced apart from the inner peripheral wall of the housing 20, and the first upper housing 721, which is the other of the first upper housing 721 and the second upper housing 722, may have its inner peripheral wall in contact with the inner peripheral wall of the housing 20 while being spaced apart from the outer peripheral wall of the fixed core 50.

[0114] In the above-described embodiment, the upper housing has a notch in a portion of its circumferential direction and is C-shaped when viewed from the axial direction, i.e., has a C-shaped cross section. However, in other embodiments, the upper housing may be cylindrical or annular without having a notch in a portion of its circumferential direction.

[0115] As such, the present disclosure is not limited to the above-described embodiments, and can be implemented in various forms without departing from the spirit of the present disclosure. [Explanation of symbols]

[0116] 1 fuel injection device, 10 nozzle portion, 13 injection hole, 14 valve seat, 15 magnetic restriction portion, 20 housing, 30 needle, 40 moving core, 50 fixed core, 55 coil, 70 upper housing

Claims

1. a nozzle portion (10) having a nozzle hole (13) through which fuel is injected and a valve seat (14) formed around the nozzle hole; a cylindrical housing (20) provided to connect to the nozzle portion on the opposite side to the injection hole; a needle (30) whose one end is capable of opening and closing the injection hole by moving away from or contacting the valve seat; a movable core (40) provided in the needle such that a part of the axial direction thereof is located radially inside an end of the nozzle portion opposite to the injection hole; a cylindrical fixed core (50) provided on the opposite side of the movable core from the injection hole, at least a part of which in the axial direction is located radially inside the housing; a magnetic restricting portion (15) provided between an end of the nozzle portion and an end of the fixed core, capable of restricting magnetism between the nozzle portion and the fixed core; an upper housing (70) formed in a cylindrical, annular, or C-shaped cross section and provided between the fixed core and the housing; a coil (55) that is provided between the fixed core and the housing on the injection hole side of the upper housing, the coil forming a magnetic circuit through the fixed core, the upper housing, the housing, the nozzle portion, and the movable core when energized, and that is capable of attracting the movable core together with the needle toward the fixed core, the upper housing is spaced apart from an outer peripheral wall of the fixed core or an inner peripheral wall of the housing, Let A be the axial size of the upper housing, and B be the axial size of the portion where the outer peripheral wall of the movable core and the inner peripheral wall of the nozzle portion face each other when the valve is closed. A / B≧1.2 A fuel injection system that is set to:

2. 2. The fuel injection device according to claim 1, wherein the upper housing has a plurality of divided upper housings (710) arranged side by side in the axial direction.

3. 3. The fuel injection device according to claim 1, wherein the upper housing has an outer diameter equal to or larger than the inner diameter of the housing and an inner diameter larger than the outer diameter of the fixed core before being disposed between the fixed core and the housing.

4. 3. The fuel injection device according to claim 1, wherein the upper housing has an inner diameter equal to or smaller than the outer diameter of the fixed core and an outer diameter smaller than the inner diameter of the housing before being disposed between the fixed core and the housing.

5. The upper housing includes a first upper housing (721) and a second upper housing (722) provided on the injection hole side of the first upper housing, an inner peripheral wall of one of the first upper housing and the second upper housing is in contact with an outer peripheral wall of the fixed core, and the outer peripheral wall is spaced apart from the inner peripheral wall of the housing; 2. The fuel injection device according to claim 1, wherein the other of the first upper housing and the second upper housing has an inner peripheral wall that is spaced apart from the outer peripheral wall of the fixed core and has an outer peripheral wall that is in contact with the inner peripheral wall of the housing.

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