Electromagnetic fuel injection valve

Abstract

Provided is an electromagnetic fuel injection valve with which good performance can be ensured and size reduction can be facilitated while avoiding deterioration in yield. An electromagnetic fuel injection valve (1) comprises a coil housing (6) surrounding a coil (5) provided around the outer periphery of a fixed core (2), and a resin (7) filled between the coil (5) and the coil housing (6). The coil housing (6) comprises a pair of coil housing halves (31) each having a partial cylindrical part (32). Two communication holes (33) having a predetermined diameter φ and penetrating in the radial direction are provided in the cylindrical parts (32) at a predetermined gap d apart in the axial direction.

Description

[Technical Field]

[0001] The present invention relates to an electromagnetic fuel injection valve in which a movable core is driven by controlling the energization of a coil around a fixed core, thereby repeatedly opening and closing the valve. [Background technology]

[0002] Conventionally, there has been known an electromagnetic fuel injection valve that includes a movable core that faces a fixed core and moves in conjunction with a valve body, a coil housing that surrounds a coil provided on the outer periphery of the fixed core and functions as a yoke that forms a magnetic circuit that passes through the fixed core and the movable core, and resin filled between the coil housing and the coil, in which the movable core and the valve body are driven together by controlling the flow of electricity to the coil, and the valve body alternates between an open state and a closed state (see, for example, Patent Document 1).

[0003] In the electromagnetic fuel injection valve of Patent Document 1, the coil housing includes two yokes arranged on either side of the coil in the radial direction. Each yoke has a partially cylindrical large-diameter portion whose inner surface faces the cylindrical side surface of the coil and has an obtuse central angle. A recess is formed in the large-diameter portion. A filling hole is provided in the recess of the large-diameter portion, penetrating the recess.

[0004] The space between the coil housing and the coil is filled with resin when the coating layer that covers the main parts of the electromagnetic fuel injection valve, including the coil housing, is injection molded using the main parts as insert parts. That is, at this time, the space between the two yokes serves as a filling port through which the resin is filled. Resin can also be filled through a filling hole.

[0005] When the resin is filled into this space, the recesses and filling holes function to enhance the filling of the resin into the space, thereby enabling the coating layer to be injection molded at lower pressure or in a shorter time, thereby improving production efficiency. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5546667 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the electromagnetic fuel injection valve of Patent Document 1, a recess is provided in the large-diameter portion of the yoke that constitutes the magnetic circuit, but this measure is not necessarily appropriate from the perspective of promoting miniaturization while avoiding performance degradation and a decrease in yield due to injection molding. In other words, although this recess improves the filling efficiency of the resin, it may adversely affect the magnetic path in the yoke, degrading performance, or may increase the diameter of the yoke.

[0008] In view of the problems with the conventional technology, an object of the present invention is to provide an electromagnetic fuel injection valve that can ensure good performance and promote miniaturization while avoiding the deterioration of yield caused by injection molding. [Means for solving the problem]

[0009] The first air-fuel ratio control device of the present invention comprises: A fixed core; a movable core facing the fixed core; a valve body that moves in conjunction with the movable core; a coil provided on the outer periphery of the fixed core; a coil housing that encloses the coil and forms a magnetic circuit that passes through the fixed core and the movable core; a resin filled between the coil and the coil housing; The coil housing includes a pair of coil housing halves disposed on both radial sides of the coil, In the electromagnetic fuel injection valve, the movable core and the valve element are driven by controlling the energization of the coil to repeat a valve open state and a valve closed state, Each coil housing half is a diameter larger than both axial ends of the coil housing half, The inner surface is the cylindrical side of the coil. At a certain interval Opposed partial cylindrical portions having an obtuse central angle, Each coil housing half in the partial cylindrical portion The circumferential center of the side wall The bearing has two communicating holes with a predetermined diameter that penetrate in the radial direction and are spaced apart in the axial direction by a predetermined distance. and positioned at one end and the other end of the coil, respectively. It is characterized in that it is provided.

[0010] In this configuration, the resin that forms the insulating portion between the coil housing and the coil can be filled at the same time as the coating layer that covers the main parts, including the coil housing of the electromagnetic fuel injection valve, is injection molded using the main parts as insert parts. In this case, the space between the two coil housing halves and the two communication holes serve as filling ports for the resin between the coil housing and the coil.

[0011] By using the two communication holes as resin filling ports in this way, the resin flows faster from the outside to the inside of the coil housing half, and welds can be prevented from forming at both ends of the coil, preventing welds from causing winding disturbances at both ends of the coil and improving yield.

[0012] Furthermore, this improvement in yield is achieved by simply providing two communication holes in the coil housing halves that form the magnetic circuit, minimizing the change in cross-sectional area of ​​the coil housing halves and without increasing the diameter of the coil housing. Therefore, according to the present invention, it is possible to provide an electromagnetic fuel injection valve that can ensure good performance and promote miniaturization while achieving an improvement in yield.

[0013] In the present invention, the thickness of the coil housing halves may be uniform, which can prevent a decrease in the magnetic force between the fixed core and the movable core due to the magnetic flux being restricted in the portions of the coil housing halves where the thickness is not uniform.

[0014] In the present invention, the diameter of the opening on the coil side of each communication hole may be larger than the diameter of the opening on the opposite side. With this, when resin is filled from the outside of the coil housing half through the communication hole during injection molding of the coating layer of the electromagnetic fuel injection valve, the resin is well diffused from the coil-side opening of the communication hole to the inside of the coil housing half, so that the occurrence of welds at both ends of the coil can be more effectively suppressed. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view showing an electromagnetic fuel injection valve according to an embodiment of the present invention. [Figure 2] 2 is an enlarged cross-sectional view showing a part of the coil assembly in the electromagnetic fuel injection valve of FIG. 1. FIG. [Figure 3] 2 is a perspective view showing a coil housing half of the electromagnetic fuel injection valve of FIG. 1. FIG. [Figure 4A] 10 is a diagram showing the results of a resin flow analysis on the occurrence of welds when resin is filled between the coil housing and the coil when there are no communication holes in the coil housing halves. FIG. [Figure 4B] 10 is a diagram showing the results of a resin flow analysis on the occurrence of the weld when one communication hole is present in the coil housing half. FIG. [Figure 4C] FIG. 10 is a diagram showing the results of a resin flow analysis regarding the occurrence of the weld in an embodiment of the present invention in which two communication holes exist in the coil housing half. [Figure 4D] FIG. 10 is a diagram showing the results of a resin flow analysis regarding the occurrence of the weld when three communication holes are present in the coil housing half. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an electromagnetic fuel injection valve according to one embodiment of the present invention. As shown in FIG. 1, this electromagnetic fuel injection valve 1 includes a fixed core 2, a movable core 3 facing the fixed core 2, a valve element 4 interlocking with the movable core 3, a coil 5 provided on the outer periphery of the fixed core 2, a coil housing 6 surrounding the coil 5 and forming a magnetic circuit passing through the fixed core 2 and the movable core 3, and resin 7 filled between the coil 5 and the coil housing 6. The electromagnetic fuel injection valve 1 alternates between an open state and a closed state by controlling the supply of current to the coil 5, thereby driving the movable core 3 and the valve element 4.

[0017] The valve housing 8 of the electromagnetic fuel injection valve 1 is made up of a cylindrical valve seat member 9, a magnetic cylinder 10 fitted onto the outer peripheral surface of the rear end of the valve seat member 9 and welded liquid-tightly, a non-magnetic cylinder 11 abutted against the rear end of the magnetic cylinder 10 and welded liquid-tightly, the above-mentioned hollow cylindrical fixed core 2 whose small-diameter front end is fitted onto the inner peripheral surface of the non-magnetic cylinder 11 and welded liquid-tightly, and a fuel inlet tube 12 fitted onto the outer peripheral surface of the rear end of the fixed core 2 and welded liquid-tightly.

[0018] The valve seat member 9 has a valve hole 13 that opens at its front end surface, a conical valve seat 14 that connects to the inner circumferential end of the valve hole 13, and a cylindrical guide hole 15 that connects to the large diameter portion of the valve seat 14. A steel injector plate 16 that has a plurality of fuel injection holes that communicate with the valve hole 13 is welded to the front end surface of the valve seat member 9 in a liquid-tight manner.

[0019] A portion of the front end of the non-magnetic cylinder 11 is left that does not fit with the fixed core 2, and the hollow cylindrical movable core 3 described above is fitted from this portion to the magnetic cylinder 10, facing the front end face of the fixed core 2, and the valve body 4 is connected to the movable core 3. The hollow cylindrical fixed core 2 and movable core 3 are thicker than the magnetic cylinder 10 and non-magnetic cylinder 11.

[0020] The valve element 4 is composed of a spherical valve portion 17 that can slide in the guide hole 15 to open and close the valve hole 13 in cooperation with the valve seat 14, and a valve rod 18 whose front end is fixed to the valve portion 17. The rear end of the valve rod 18 is press-fitted and welded to the inner peripheral surface of the movable core 3. Therefore, the valve element 4 can move up and down within the valve housing 8 together with the movable core 3.

[0021] The valve rod 18 is made of a pipe material with a slot 19, and its interior communicates with the hollow portion of the movable core 3, and the inside and outside of the valve rod 18 communicate with each other via the slot 19. In addition, a plurality of flat surfaces are formed around the spherical valve portion 17 to allow the passage of fuel.

[0022] Thus, the fuel inlet tube 12, the fixed core 2, the retainer 20 described below, the hollow portions of the movable core 3 and the valve rod 18, the slot 19 in the valve rod 18, the guide hole 15 in the valve seat member 9, the valve hole 13, and the fuel nozzle holes in the injector plate 16 form a continuous fuel flow path F within the valve housing 8.

[0023] A retainer 20 made of slotted pipe material is press-fitted and fixed to the middle of the hollow portion of the fixed core 2, with its front end forming the first spring seat. Meanwhile, the rear end of the valve rod 18 terminates midway through the hollow portion of the movable core 3, with its upper end forming the second spring seat. A valve spring 21 is compressed between the first and second spring seats. The set load of the valve spring 21 urges the movable core 3 in a direction away from the fixed core 2 downward, i.e., in the direction of seating the valve disc 4 on the valve seat 14. The set load of the valve spring 21 is adjusted by the depth of fit of the retainer 20 into the fixed core 2.

[0024] A ring-shaped stopper member 22 made of a non-magnetic material is embedded in the inner peripheral surface of the movable core 3 and protrudes slightly from the rear end face. A coil assembly 23 is fitted onto the outer periphery of the valve housing 8 in correspondence with the fixed core 2 and the movable core 3.

[0025] The coil assembly 23 comprises a bobbin 24 made of synthetic resin that is fitted onto the outer circumferential surface of the magnetic cylindrical body 10 from the rear end of the magnetic cylindrical body 10 to the fixed core 2, and the coil 5 wound around the bobbin. A terminal support arm 26 is integrally formed at the rear end of the bobbin 24 to support the base end of a power supply terminal 25 that protrudes to one side. An end of the coil 5 is connected to the power supply terminal 25. Approximately half of the circumferential surface of the coil assembly 23 is covered by the coil housing (yoke) 6 described above.

[0026] A synthetic resin coating layer 27 is injection molded to cover the outer surfaces of the magnetic cylinder 10 and the fuel inlet tube 12 and to embed the coil assembly 23. At this time, a coupler 28 that houses and holds the power supply terminal 25 and protrudes from one side of the coil assembly 23 is molded integrally with the coating layer 27. The resin 7 filled between the coil 5 and the coil housing 6 is formed as part of the coating layer 27.

[0027] A fuel filter 29 is attached to the inlet of the fuel inlet tube 12. A fuel cap connected to a fuel pump (not shown) is fitted onto the outer periphery of the upper end of the fuel inlet tube 12 via a seal member 30.

[0028] Fig. 2 shows an enlarged view of the vicinity of the coil assembly 23. As shown in Fig. 2, the coil housing 6 is composed of a pair of coil housing halves 31 arranged on either side of the coil assembly 23 in the radial direction. The space between the coil 5 and the coil housing halves 31 is filled with the above-mentioned resin 7 that forms an insulating portion therebetween.

[0029] FIG. 3 shows the coil housing half 31. As shown in FIG. 3, the coil housing half 31 has a partially cylindrical portion 32 whose inner surface faces the cylindrical side surface of the coil and is a partially cylindrical portion with an obtuse central angle θ. The central angle can be, for example, 145°. The coil housing half 31 has a constant thickness t. For example, the thickness t can be 1 mm.

[0030] As shown in Fig. 2, the partial cylindrical portion 32 is provided with two communicating holes 33 that penetrate radially and have a predetermined diameter φ, spaced a predetermined distance d apart in the axial direction, with the center point between the communicating holes 33 positioned at the center of the partial cylindrical portion 32. The predetermined diameter φ is, for example, 2 mm. The predetermined distance d is, for example, 8.4 mm.

[0031] The resin is filled between the coil housing 6 and the coil 5 at the same time as the coating layer 27 is injection molded. This injection molding is performed using the main parts of the electromagnetic fuel injection valve 1, including the assembled coil housing 6, valve housing 8, power supply terminal 25, etc., as insert parts. At this time, when filling the resin between the coil housing 6 and the coil 5, the space between the two coil housing halves 31 and the two communication holes 33 serve as the resin filling ports.

[0032] In the completed electromagnetic fuel injection valve 1 with the coating layer 27 formed in this manner, when the coil 5 is not energized, the valve portion 17 is pressed forward by the valve spring 21 and is in a closed state where it is seated on the valve seat 14. In this state, when fuel is pressure-fed from a fuel pump (not shown) through a fuel distribution pipe to the fuel inlet tube 12, the fuel fills the fuel flow path F in the valve housing 8 and applies further fluid pressure to the valve portion 17.

[0033] In this state, when the coil 5 is excited by passing current through the coupler 28, the resulting magnetic flux passes through the coil housing 6, the magnetic cylinder 10, the movable core 3, and the fixed core 2, generating a magnetic attractive force between the movable core 3 and the fixed core 2. As a result, the movable core 3 is attracted to the fixed core 2 against the set load of the valve spring 21, and the movable core 3 comes into contact with the fixed core 2.

[0034] As a result, the valve portion 17 is lifted off the valve seat 14, and the electromagnetic fuel injection valve 1 is placed in an open state. In response to this, high-pressure fuel in the fuel flow path F passes through the valve hole 13 and is injected in the form of a mist from the fuel nozzle of the injector plate 16 into the intake pipe of the internal combustion engine. Then, when the power supply to the coil 5 is cut off, the valve portion 17 returns to a closed state in which it is seated on the valve seat 14.

[0035] Therefore, by controlling the energization of the coil 5, the electromagnetic fuel injection valve 1 alternates between a closed state and an open state, and an appropriate supply of fuel can be performed to the internal combustion engine to which the electromagnetic fuel injection valve 1 is attached.

[0036] As described above, according to this embodiment, two communication holes 33 are provided in the coil housing half 31, which minimizes adverse effects on the magnetic circuit in the coil housing half 31 and improves yield without increasing the diameter of the coil housing 6. Therefore, it is possible to provide an electromagnetic fuel injection valve that can ensure good performance and promote miniaturization while improving yield.

[0037] That is, the resin can be filled between the coil housing 6 and the coil 5 simultaneously when the coating layer 27 is formed of resin by injection molding using the main parts of the electromagnetic fuel injection valve 1, including the coil housing 6, as insert parts. At this time, the space between the two coil housing halves 31 and the two communication holes 33 in each half serve as filling ports for the resin between the coil housing 6 and the coil 5.

[0038] This increases the speed at which resin flows into the coil housing half 31 from the outside to the inside of the coil housing half 31, and prevents welds from occurring at both ends of the coil 5, thereby preventing winding irregularities at both ends of the coil 5 due to welds and improving yield.

[0039] This improvement in yield can be achieved simply by providing two communication holes 33 in the coil housing half 31, without providing any recesses or the like. Therefore, it is possible to avoid increasing the diameter of the coil housing 6 while minimizing adverse effects on the magnetic circuit in the coil housing half 31.

[0040] 4A to 4D are diagrams showing the results of resin flow analysis to explain the effect of these two communication holes 33. 4A to 4D show how welds 34 occur when resin is filled between the coil housing 6 and the coil 5 during injection molding of the above-described coating layer 27. 4A to 4D show how welds 34 occur when the number of communication holes 33 provided in the coil housing half 31 is "0" (none), "1," "2" (in the present embodiment), and "3," respectively.

[0041] 4A, when the number of communication holes 33 is "0" (none), resin is filled only between the two coil housing halves 31, resulting in a weld 34 that is approximately linear along the length of the coil housing halves 31. Therefore, the end of this weld 34 coincides with the coil wire transfer position at the end of the coil 5, and it can be understood that this causes disorder in the coil wire.

[0042] 4B, when the number of communicating holes 33 is "1," the resin filling through the communicating holes 33 causes the welds 34 to expand around the communicating holes 33, and the expanded welds 34 close at both ends of the coil 5. Therefore, it is understood that the formation of welds 34 cannot be avoided at the coil wire transfer positions at both ends of the coil 5, causing disturbances in the coil wire.

[0043] 4C, when the number of communicating holes 33 is "2," the welds 34 are pushed out around the communicating holes 33 at one and the other ends of the coil 5 by the resin filled from each communicating hole 33, and this situation extends to both ends 35 of the coil 5. Therefore, it can be seen that the formation of welds 34 at the coil wire transfer positions at both ends 35 of the coil 5 is avoided, and the occurrence of disturbances in the coil wire is prevented.

[0044] As shown in Figure 4D, when the number of communicating holes 33 is "3," the welds 34 are pushed out around each communicating hole 33 by the resin filled from each communicating hole 33, and it can be seen that, as in the case where the number of communicating holes 33 is "2," the formation of welds 34 at the coil wire transfer positions at both ends of the coil 5 is avoided.

[0045] On the other hand, it has been confirmed that the greater the number of communication holes 33, the worse the magnetic properties of the coil housing half 31 become, and the lower the attractive force between the fixed core 2 and the movable core 3 becomes.

[0046] From the above, it can be seen that by arranging two communication holes 33 having an appropriate diameter φ at the middle position of the coil housing half 31 with an appropriate distance d along the length of the coil housing half 31, it is possible to avoid the formation of welds 34 at both ends of the coil 5 without causing deterioration of the magnetic properties. However, the diameter φ and distance d of the two communication holes 33 are selected so that welds do not form at the coil wire transfer positions at the ends of the coil 5, as shown in Figure 4C.

[0047] Furthermore, according to this embodiment, since the thickness of the coil housing half 31 is constant, the magnetic flux is restricted in the parts of the coil housing half where the thickness is uneven, which prevents a decrease in the magnetic force between the fixed core 2 and the movable core 3.

[0048] Although the embodiments of the present invention have been described above, the present invention is not limited to these. For example, the diameter of the opening of each communication hole 33 on the coil 5 side may be larger than the diameter of the opening on the opposite side. In this way, when resin is filled from the outside of the coil housing half 31 through the communication hole 33, the resin diffuses well from the communication hole 33 to the inside of the coil housing half 31, making it possible to more effectively prevent the formation of welds 34 at both ends of the coil 5. [Explanation of symbols]

[0049] 1...electromagnetic fuel injection valve, 2...fixed core, 3...movable core, 4...valve body, 5...coil, 6...coil housing, 7...resin, 8...valve housing, 9...valve seat member, 10...magnetic cylindrical body, 11...non-magnetic cylindrical body, 12...fuel inlet tube, 13...valve hole, 14...valve seat, 15...guide hole, 16...injector plate, 17...valve portion, 18...valve rod, 19...slot, 20...retainer, 21...valve spring, 22...stopper member, 23...coil assembly, 24...bobbin, 25...power supply terminal, 26...terminal support arm, 27...coating layer, 28...coupler, 29...fuel filter, 30...sealing member, 31...coil housing half, 32...partial cylindrical portion, 33...communicating hole, 34...weld, 35...both ends, F...fuel flow path.

Claims

1. A fixed core; a movable core facing the fixed core; a valve body that moves in conjunction with the movable core; a coil provided on the outer periphery of the fixed core; a coil housing that encloses the coil and forms a magnetic circuit that passes through the fixed core and the movable core; a resin filled between the coil and the coil housing; The coil housing includes a pair of coil housing halves disposed on both radial sides of the coil, In the electromagnetic fuel injection valve, the movable core and the valve element are driven by controlling the energization of the coil to repeat a valve open state and a valve closed state, Each coil housing half has a diameter larger than both axial end portions of the coil housing half, an inner surface of which faces the cylindrical side surface of the coil at a fixed interval, and a partial cylindrical portion having an obtuse central angle; an electromagnetic fuel injection valve, characterized in that two communicating holes having a predetermined diameter and penetrating radially are provided in a circumferential center portion of a side wall of the partial cylindrical portion of each coil housing half, the communicating holes being located on one end side and the other end side of the coil, with a predetermined axial distance between them.

2. 2. An electromagnetic fuel injection valve according to claim 1, wherein the thickness of said coil housing half is constant.

3. 2. The electromagnetic fuel injection valve according to claim 1, wherein the diameter of the opening on the coil side of each communication hole is larger than the diameter of the opening on the opposite side.

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