Electromagnetic fuel injection valve

Abstract

By providing a guide portion (50) on the inner circumferential surface of the valve housing (2), the movable core (12) can be supported regardless of whether it is tilted, allowing it to slide smoothly at all times. An annular guide portion (50) is provided on the inner circumferential surface of the valve housing (2), with a convex curved surface (50a) as its inner circumferential surface. The convex curved surface (50a) supports the movable core (12), allowing it to slide and tilt.

Description

Technical Field

[0001] This invention relates primarily to electromagnetic fuel injection valves used in the fuel supply system of an engine. Background Technology

[0002] Conventionally, as an electromagnetic fuel injection valve for engines, there is a known electromagnetic fuel injection valve as described in Patent Document 1. This electromagnetic fuel injection valve comprises: a valve body coaxially formed by connecting a magnetic cylinder to the rear end of a valve seat member having a valve seat at its front end, connecting a non-magnetic cylinder to the rear end of the magnetic cylinder, and connecting a fixed core to the rear end of the non-magnetic cylinder; a valve core cooperating with the valve seat within the valve body; a movable core connected to the rear end of the valve core, facing the front end of the fixed core, and supported by the valve body, allowing it to slide axially; a coil disposed on the outer periphery of the fixed core, generating an attractive force between the fixed core and the movable core when energized; and a valve spring that applies force to the movable core and the valve core toward the valve core in the valve-closing direction when the coil is de-energized.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2003-206820 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, in the aforementioned electromagnetic fuel injection valve, ensuring smooth axial sliding of the movable core is a crucial issue for stabilizing fuel injection characteristics. To address this issue, in the device described in Patent Document 1, an annular guide portion with a cylindrical inner circumferential surface is provided protruding from the inner circumferential surface of the valve housing. This guide portion supports the movable core so that it can slide axially (hereinafter referred to as "sliding").

[0008] However, a sliding gap needs to be provided between the guide portion and the movable core. As a result, the movable core may tilt slightly due to this sliding gap. The outer peripheral surface of the movable core will come into contact with the end edge of the cylindrical inner peripheral surface of the guide portion due to this tilt. The surface pressure at the contact point increases excessively, causing the fuel oil film present at the contact point to break. Therefore, not only is the smooth sliding of the movable core impaired, but the wear resistance of the movable core is also reduced.

[0009] The present invention was made in view of the above circumstances, and its object is to provide an electromagnetic fuel injection valve in which the movable core is supported by a guide portion provided on the inner circumferential surface of the valve housing regardless of whether the movable core is tilted, so that the movable core always slides smoothly and freely, and the fuel injection characteristics are stable and the durability is high.

[0010] Methods for solving problems

[0011] To achieve the above objectives, the first feature of the present invention is as follows. An electromagnetic fuel injection valve comprises: a valve housing coaxially formed by connecting a magnetic cylindrical body to the rear end of a valve seat component having a valve seat at its front end, connecting a non-magnetic cylindrical body to the rear end of the magnetic cylindrical body, and connecting a fixed core to the rear end of the non-magnetic cylindrical body; a valve core cooperating with the valve seat within the valve housing; a movable core connected to the rear end of the valve core and facing the front end of the fixed core, and simultaneously supported by the valve housing to allow axial sliding; a coil disposed on the outer periphery of the fixed core and generating an attractive force between the fixed core and the movable core when energized; and a valve spring that, when the coil is de-energized, applies force to the movable core and the valve core in a valve-closing direction. The electromagnetic fuel injection valve is characterized in that an annular guide portion is provided on the inner circumferential surface of the valve housing, the guide portion having a convex curved surface as its inner circumferential surface, the convex curved surface supporting the movable core in a manner that allows it to slide and tilt.

[0012] Furthermore, the second feature of the present invention is as follows. Based on the first feature described above, the convex curved surface is formed along the arc surface of the inner circumference of the virtual ring, and the virtual ring is formed by arranging a large circle center on the center line of the valve housing and a small circle center on the outer side of the valve housing.

[0013] The effects of the invention

[0014] According to a first feature of the invention, in order to support the movable core in a sliding and tilting manner, the inner peripheral surface of the guide portion is provided as a convex curved surface. Thus, regardless of whether the movable core is tilted or not, the movable core and the guide portion are always in curved surface contact, and no excessive increase in surface pressure occurs at the curved surface contact portion, thereby maintaining a fuel oil film at the curved surface contact portion. As a result, the guide portion can support the movable core, allowing it to slide smoothly and freely, and can maintain the wear resistance of the movable core, thereby contributing to improving the stability and durability of the fuel injection characteristics of the electromagnetic fuel injection valve.

[0015] Furthermore, according to the second feature of the present invention, the convex curved surface of the guide portion is formed along the arc surface of the inner circumference of the virtual ring, which is formed by arranging a large circle center on the center line of the valve housing and a small circle center on the outer side of the valve housing. Thus, the curvature of the convex curved surface is constant, and the contact state between the movable core and the curved surface of the guide portion is always stable regardless of whether the movable core is tilted or not, thereby ensuring smoother sliding of the movable core. Attached Figure Description

[0016] Figure 1 This is a longitudinal sectional view showing an embodiment of the electromagnetic fuel injection valve for engines according to the present invention.

[0017] Figure 2 yes Figure 1 An enlarged view of the part indicated by arrow 2. Detailed Implementation

[0018] Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. In the electromagnetic fuel injection valve I of the present invention, the fuel injection side is set as the front, and the fuel inlet side is set as the rear.

[0019] First of all, Figure 1 In this engine, the cylinder head 40 has a mounting hole 41 that opens into the combustion chamber 42, and an electromagnetic fuel injection valve I capable of injecting fuel into the combustion chamber 42 is installed in the mounting hole 41. At this time, a buffer component 43 is sandwiched between the fuel injection valve I and the cylinder head 40.

[0020] The valve housing 2 of the electromagnetic fuel injection valve I described above is composed of a cylindrical valve seat component 3, a magnetic cylindrical body 4 which is fitted into and liquid-tightly welded to the outer peripheral surface of the rear end of the valve seat component 3, a non-magnetic cylindrical body 6 which abuts against the rear end of the magnetic cylindrical body 4 and is liquid-tightly welded, a thick-walled and hollow cylindrical fixing core 5 which has a small-diameter front end 5a fitted into the inner peripheral surface of the non-magnetic cylindrical body 6 and is liquid-tightly welded, and a fuel inlet cylinder 26 which is fitted into the outer peripheral surface of the rear end of the fixing core 5 and is liquid-tightly welded.

[0021] The valve seat component 3 has a valve hole 7 open at its front end face, a conical valve seat 8 connected to the inner circumferential end of the valve hole 7, and a cylindrical guide hole 9 connected to the large diameter portion of the valve seat 8. A steel plate injector plate 10 is liquid-tightly welded to the front end face of the valve seat component 3. The injector plate 10 has a plurality of fuel injection holes 11 communicating with the valve hole 7.

[0022] The front end of the non-magnetic cylindrical body 6 has a portion that is not fitted with the fixed core 5. A hollow cylindrical movable core 12 is fitted from this portion to the magnetic cylindrical body 4. The movable core 12 faces the front end of the fixed core 5. The valve core 13 is connected to the movable core 12.

[0023] The valve core 13 consists of a spherical valve portion 14 and a valve stem 15. The valve portion 14 can slide in the guide hole 9, thereby cooperating with the valve seat 8 to open and close the valve hole 7. The front end of the valve stem 15 is fixed to the valve portion 14, and the rear end of the valve stem 15 is pressed into and welded to the inner circumferential surface of the movable core 12. Therefore, the valve core 13 can move up and down within the valve housing as an integral part of the movable core 12.

[0024] The valve stem 15 is made of a tube with a groove 15a, and its interior communicates with the hollow portion of the movable core 12. The inside and outside of the valve stem 15 are also connected via the groove 15a. In addition, a plurality of flat surfaces 17 are formed around the spherical valve portion 14 to allow fuel to pass through.

[0025] Furthermore, the fuel inlet cylinder 26, the fixed core 5, the retainer 20, the movable core 12 and the hollow parts of the valve stem 15, the groove 15a of the valve stem 15, the guide hole 9 of the valve seat component 3, the valve hole 7 and the fuel injection hole 11 constitute a series of fuel flow paths 18 within the valve housing 2.

[0026] exist Figure 1 and Figure 2 In this structure, a retainer 20, made of a grooved tube, is pressed and fixed into the middle of the hollow portion of the fixed core 5, with its front end forming a first spring seat 21. On the other hand, the rear end of the valve stem 15 terminates midway in the hollow portion of the movable core 12, with its upper end forming a second spring seat 22. A valve spring 23 is compressed between the first spring seat 21 and the second spring seat 22. The movable core 12 applies force from the fixed core 5 in a forward-facing direction, i.e., the valve body 13's closing direction, using the set load of the valve spring 23. The set load of the valve spring 23 is adjusted by the engagement depth of the retainer 20 into the fixed core 5.

[0027] An annular stop component 35 made of non-magnetic material, which protrudes slightly from its rear end face, is embedded in the inner circumferential surface of the movable core 12.

[0028] Return to Figure 1 In the valve housing 2, a coil assembly 28 is embedded on the outer periphery, corresponding to the fixed core 5 and the movable core 12. The coil assembly 28 consists of a synthetic resin tube 29 and a coil 30 wound around it. The tube 29 extends from the rear end of the magnetic cylinder 4 to the fixed core 5, which is embedded on their outer periphery. A terminal support arm 29a is integrally formed at the rear end of the tube 29, supporting the base end of a power supply terminal 33 protruding to one side of the tube 29. The end of the coil 30 is connected to the power supply terminal 33. Approximately half of the circumference of the coil assembly 28 is covered by a magnetic yoke 31.

[0029] A synthetic resin coating 27 is injection molded, which covers the outer circumference of the magnetic cylinder 4 to the fuel inlet cylinder 26 and embeds the coil assembly 28. At this time, a connector 34 that houses and holds the power supply terminal 33 and protrudes to one side of the coil assembly 28 is integrally formed with the coating 27.

[0030] A fuel filter 36 is installed at the inlet of the aforementioned fuel inlet cylinder 26. Additionally, a fuel cap 46 is fitted onto the outer periphery of the upper end of the fuel inlet cylinder 26 via a sealing member 47. This fuel cap 46 is one of a plurality of fuel distribution caps formed by branches of a fuel guide 45 connected to the outlet of a fuel pump (not shown).

[0031] like Figure 2 As shown, an annular guide portion 50 is provided on the inner circumferential surface of the non-magnetic cylindrical body 6 that protrudes forward toward the fixed core 5. The inner circumferential surface of the guide portion 50 is formed by a convex curved surface 50a, thereby supporting the movable core 12 in a way that allows it to slide and tilt.

[0032] When forming the aforementioned convex surface 50a, a virtual annulus T is set with a large circle center Ob on the center line Y of the valve housing 2 (the line passing through the center of the valve seat 8) and a small circle center Os on the outer side of the non-magnetic cylindrical body 6 in the radial direction. The aforementioned convex surface 50a is formed along the arc surface of the inner circumference of the virtual annulus T. The inner circumference surface of the aforementioned magnetic cylindrical body 4 is recessed in the radial direction beyond the aforementioned convex surface 50a.

[0033] Next, the function of this embodiment will be explained.

[0034] With the coil 30 de-energized, the movable core 12 and valve core 13 are pushed forward by the force of the valve spring 23, causing the valve portion 14 of the valve core 13 to sit on the valve seat 8, thereby closing the valve orifice 7. Furthermore, high-pressure fuel, pumped by a fuel pump (not shown), is delivered to the fuel inlet cylinder 26 and fills a series of fuel flow paths 18 upstream of the valve orifice 7 within the valve housing 2, where it awaits its arrival.

[0035] When the coil 30 is energized, the magnetic flux generated by the coil 30 passes through the magnetic yoke 31, the magnetic cylinder 4, the movable core 12, and the fixed core 5 in sequence. The attraction caused by the magnetic force generated between the two cores 5 and 12 causes the movable core 12 to overcome the set load of the valve spring 23 and be attracted by the fixed core 5, causing the valve part 14 of the valve core 13 to leave the valve seat 8. Once the valve hole 7 is opened, the high-pressure fuel waiting in the fuel flow path 18 is directly injected into the combustion chamber 42 of the engine E through the fuel injection hole 11 via the valve hole 7.

[0036] At this time, the stop member 35 protruding from the rear end face of the movable core 12 abuts against the front end face of the fixed core 5, thereby leaving a specified gap between the opposite end faces of the fixed core 5 and the movable core 12. Therefore, when the coil 30 is de-energized as described later, the residual magnetism between the two cores 5 and 12 is reduced, which plays a role in achieving good valve closing response of the valve core 13.

[0037] When the coil 30 is energized and disconnected, the movable core 12 is released from the attractive force from the fixed core 5. Therefore, the valve spring 23 uses its set load to move the movable core 12 away from the fixed core 5, thereby closing the valve core 13 and stopping the injection of fuel from the fuel injection hole 11.

[0038] Thus, the movable core 12, which performs the opening and closing action of the valve core 13, is supported by the inner circumferential surface, i.e., the convex curved surface 50a, of the guide portion 50 of the non-magnetic cylindrical body 6, making it slidable and tiltable. Therefore, the movable core 12 and the guide portion 50 are in a curved surface contact state with each other. Therefore, even if the movable core 12 tilts slightly due to the sliding gap between the movable core 12 and the guide portion 50, the curved surface contact state between the movable core 12 and the guide portion 50 is maintained, which can suppress the excessive rise of the surface pressure at the contact portion and prevent the fuel oil film at the contact portion from breaking.

[0039] In this way, the guide portion 50 supports the movable core 12 in a manner that allows the movable core 12 to slide and tilt smoothly at all times, and can maintain the wear resistance of the movable core 12, thereby helping to improve the stability and durability of the fuel injection characteristics of the electromagnetic fuel injection valve I.

[0040] In particular, when the convex surface 50a of the guide portion 50 is formed along the arc surface of the inner circumference of the aforementioned virtual ring T, if the curvature of the convex surface 50a is kept constant, the contact state between the movable core 12 and the curved surface of the guide portion 50 will not change even when the movable core 12 is tilted, thus ensuring smoother sliding of the movable core 12.

[0041] The embodiments of the present invention have been described above, but the present invention is not limited to the content described above. Various design changes can be made without departing from its spirit.

[0042] Symbol Explanation

[0043] I.... Electromagnetic fuel injection valve

[0044] Ob.... Center of the large circle

[0045] Os.... Center of the small circle

[0046] T....Virtual Ring

[0047] Y.... Centerline of valve body

[0048] 2....Valve housing

[0049] 3. Valve seat components

[0050] 4. Magnetic cylindrical body

[0051] 5....Fixing Core

[0052] 6. Non-magnetic cylindrical body

[0053] 8....valve seat

[0054] 12...Modible Core

[0055] 13...valve core

[0056] 30... coil

[0057] 50...Guide Section

[0058] 50a..Convex surface.

Claims

1. An electromagnetic fuel injection valve, comprising: The valve housing (2) is formed by coaxially connecting a magnetic cylinder (4) to the rear end of a valve seat component (3) having a valve seat (8) at the front end, connecting a non-magnetic cylinder (6) to the rear end of the magnetic cylinder (4), and connecting a fixed core to the rear end of the non-magnetic cylinder (6); the valve core (13) cooperates with the valve seat (8) within the valve housing (2); and the movable core (12) is connected to the rear end of the valve core (13). The part is combined with and faces the front end of the fixed core (5) and is supported by the non-magnetic cylindrical body (6) so as to be able to slide axially; a coil (30) is disposed on the outer periphery of the fixed core (5) and generates an attraction between the fixed core (5) and the movable core (12) when energized; a valve spring (23) applies force to the movable core (12) and the valve core (13) in the valve-closing direction when the energization of the coil (30) is disconnected. The electromagnetic fuel injection valve is characterized in that... The front of the fixed core (5) is formed into a hollow cylinder by liquid-tight welding of its small-diameter front end portion (5a) to the inner circumferential surface of the non-magnetic cylindrical body (6). The front end portion of the non-magnetic cylindrical body (6) has a portion that does not fit with the fixed core (5). An annular guide portion (50) is provided at the front end of the inner circumferential surface of the non-magnetic cylindrical body (6). The guide portion (50) has a convex curved surface (50a) as its inner circumferential surface. The convex curved surface (50a) supports the movable core (12), allowing it to slide and tilt. The convex surface (50a) is formed with constant curvature along the inner circumferential arc surface of the virtual ring (T). The virtual ring (T) has a large circle center (Ob) on the centerline (Y) of the valve body (2) and a small circle center (Os) on the outer side of the valve body (2). The inner circumferential surface of the magnetic cylinder (4) is formed in a manner that is recessed outward in the radial direction compared to the convex curved surface (50a), and the virtual ring (T) is set such that the center of the small circle (Os) is positioned outward in the radial direction of the non-magnetic cylinder (6).

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