Electromagnetic fuel injection valve

Abstract

Provided is an electromagnetic fuel injection valve that is not affected by shrinkage deformation that occurs in a magnetic cylindrical body (4) following cooling after welding of a non-magnetic cylindrical body (6) and the magnetic cylindrical body (4), and that does not require post-processing. A sliding guide surface (49) that guides sliding of a movable core (12) on an inner peripheral surface of the non-magnetic cylindrical body (6) is provided on the inner peripheral surface of the non-magnetic cylindrical body (6), and on the other hand, a tapered surface (50) that forms a large diameter toward the rear end side from the middle portion to the rear end of the magnetic cylindrical body (4) is provided on the inner peripheral surface of the magnetic cylindrical body (4) that opposes the movable core (12).

Description

Technical Field

[0001] This invention relates primarily to an electromagnetic fuel injection valve used in an engine fuel supply system, and particularly to an improvement of such an electromagnetic fuel injection valve, comprising: a valve body formed by coaxially joining a magnetic cylinder to the rear end of a valve seat component having a valve seat; a valve core housed within the valve body and cooperating with the valve seat; a non-magnetic cylinder coaxially joined to the rear end of the magnetic cylinder; a fixed core coaxially joined to the rear end of the non-magnetic cylinder; a movable core joined to the rear end of the valve core, with its rear end face facing the front end face of the fixed core and disposed within the magnetic and non-magnetic cylinders; 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 a closing direction when the coil is de-energized, wherein the magnetic and non-magnetic cylinders are joined together by welding. Background Technology

[0002] According to the contents disclosed in Patent Document 1 below, such an electromagnetic fuel injection valve is known.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-240733 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the aforementioned electromagnetic fuel injection valve, when combining the magnetic cylinder, non-magnetic cylinder, and fixed core, the non-magnetic cylinder and fixed core are first butt-welded together, followed by butt-welding together the non-magnetic and magnetic cylinders. At this point, due to the thick wall of the fixed core, the integrated fixed core and non-magnetic cylinder have a large heat capacity, while the thin-walled magnetic cylinder has a small heat capacity. Therefore, after welding with the non-magnetic cylinder, significant shrinkage and deformation occur with cooling. In particular, the inner periphery of the rear end near the welded portion of the non-magnetic cylinder deforms radially inward, forming a bulge. This bulge interferes with the movable core, hindering its operation. Therefore, in the past, to remove this bulge, not only was the inner circumferential surface of the magnetic cylinder precision-machined, but the inner circumferential surface of the non-magnetic cylinder adjacent to it was also precision-machined—a post-processing. However, this post-processing contributes to the increased manufacturing cost of the electromagnetic fuel injection valve.

[0008] The present invention was made in view of the above circumstances, and its object is to provide an electromagnetic fuel injection valve that is unaffected even when shrinkage deformation occurs on the magnetic cylinder due to cooling after welding of the non-magnetic cylinder and the magnetic cylinder, and does not require the above-mentioned post-processing, thereby reducing manufacturing costs.

[0009] Methods for solving problems

[0010] To achieve the above objectives, the first feature of the present invention is as follows. An electromagnetic fuel injection valve comprises: a valve housing formed by coaxially joining a magnetic cylindrical body to the rear end of a valve seat component having a valve seat; a valve core housed within the valve housing and cooperating with the valve seat; a non-magnetic cylindrical body coaxially joined to the rear end of the magnetic cylindrical body; a fixed core coaxially joined to the rear end of the non-magnetic cylindrical body; and a movable core joined to the rear end of the valve core, with its rear end face facing the front end face of the fixed core and disposed on the magnetic cylindrical body and the non-magnetic cylindrical body. The cylinder contains: a coil disposed on the outer periphery of the fixed core, which generates 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 closing direction when the energization of the coil is de-energized, wherein the magnetic cylinder and the non-magnetic cylinder are joined together by welding, and the electromagnetic fuel injection valve is characterized in that a tapered surface with a larger diameter toward the rear end is provided from the middle portion of the inner circumferential surface of the magnetic cylinder opposite to the movable core.

[0011] Furthermore, the second feature of the present invention is as follows. Based on the first feature described above, a sliding guide surface is provided on the inner circumferential surface of the non-magnetic cylindrical body. This sliding guide surface guides the sliding of the movable core relative to the inner circumferential surface. On the other hand, the inner circumferential surface of the magnetic cylindrical body, excluding the conical surface, is formed such that its inner diameter is larger than the inner diameter of the sliding guide surface.

[0012] The effects of the invention

[0013] According to a first feature of the invention, a cross-sectional triangular space is defined between the conical surface formed on the inner circumferential surface of the magnetic cylinder and the outer circumferential surface of the movable core. This space absorbs the raised portion, wherein the raised portion is generated at the inner circumferential edge of the rear end of the magnetic cylinder after welding the magnetic cylinder and the non-magnetic cylinder. Therefore, the raised portion does not interfere with the movable core. Consequently, after performing the welding, there is no need to perform the conventional post-processing on the inner circumferential surfaces of the magnetic cylinder and the non-magnetic cylinder, thereby reducing manufacturing costs.

[0014] According to a second feature of the invention, a sliding guide surface is formed on the inner circumference of the magnetic cylinder to guide the movable core to slide relative to the inner circumference of the magnetic cylinder. Furthermore, the inner diameter of the inner circumferential surface of the magnetic cylinder, excluding the aforementioned conical surface, is larger than the inner diameter of the sliding guide surface. Therefore, even when the outer circumferential surface of the magnetic cylinder is covered with a synthetic resin coating, its inner circumferential surface will not extend further radially inward than the sliding guide surface, even if the inner circumferential surface of the magnetic cylinder shrinks due to cooling. Thus, smooth sliding of the movable core relative to the sliding guide surface can be ensured. Attached Figure Description

[0015] Figure 1 This is a longitudinal sectional view showing an embodiment of the electromagnetic fuel injection valve for internal combustion engines according to the present invention.

[0016] Figure 2 yes Figure 1 An enlarged view of the part indicated by arrow 2. Detailed Implementation

[0017] 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.

[0018] 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 member 43 is sandwiched between the electromagnetic fuel injection valve I and the cylinder head 40.

[0019] The valve housing 2 of the aforementioned electromagnetic fuel injection valve I is composed of a cylindrical valve seat component 3, a magnetic cylindrical body 4 which is fitted into the outer peripheral surface of the rear end of the valve seat component 3 and is liquid-tightly welded, a non-magnetic cylindrical body 6 which abuts against the rear end of the magnetic cylindrical body 4 and is liquid-tightly welded, a 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.

[0020] 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.

[0021] The front end of the non-magnetic cylindrical body 6 retains a portion that does not engage with the fixed core 5. From this portion to the magnetic cylindrical body 4, a hollow cylindrical movable core 12 is fitted. The movable core 12 faces the front end of the fixed core 5, and the valve core 13 is connected to the movable core 12. The hollow cylindrical fixed core 5 and the movable core 12 are thicker than the magnetic cylindrical body 4 and the non-magnetic cylindrical body 6.

[0022] 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.

[0023] The valve stem 15 is made of a tube with a groove 15a, and its interior is connected to the hollow part of the movable core 12. The inside and outside of the valve stem 15 are connected via the groove 15a. In addition, a plurality of flat surfaces 17 are formed around the spherical valve part 14 to allow fuel to pass through.

[0024] 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.

[0025] 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 is subjected to a force from the fixed core 5 in a downward direction opposite to the direction in which the valve core 13 sits on the valve seat 8, 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.

[0026] 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.

[0027] On the outer periphery of the valve housing 2, a coil assembly 28 is fitted 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, where it is fitted onto 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.

[0028] 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.

[0029] 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).

[0030] Furthermore, when the coil 30 is de-energized, the movable core 12 and the valve core 13 are pushed forward by the force of the valve spring 22, so that the valve part 14 of the valve core 13 sits on the valve seat 8.

[0031] When coil 30 is energized, the magnetic flux generated by coil 30 passes sequentially through magnetic yoke 31, magnetic cylinder 4, movable core 12, and fixed core 5. The attraction caused by the magnetic force generated between the two cores 5 and 12 causes movable core 12 to compress valve spring 23 while being attracted to fixed core 5, causing valve part 14 of valve core 13 to detach from valve seat 8, thus opening valve orifice 7. Then, high-pressure fuel pumped by fuel pump (not shown) to fuel inlet cylinder 26 passes through fuel flow path 18 of valve housing 2 and is directly injected into combustion chamber 42 of engine E from fuel injection orifice 11.

[0032] 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, resulting in good valve closing response of the valve core 13.

[0033] When coil 30 is energized and disconnected, movable core 12 is released from the attractive force from fixed core 5. Therefore, valve spring 23 uses its set load to move movable core 12 away from fixed core 5, thereby closing valve core 13 and stopping fuel injection from fuel injection hole 11.

[0034] Next, in Figure 2 In this process, the outer circumferential surfaces of the magnetic cylindrical body 4, the non-magnetic cylindrical body 6, and the fixed core 5 are formed with the same diameter.

[0035] In addition, the inner circumferential surface of the non-magnetic cylindrical body 6 opposite to the movable core 12 is formed as a sliding guide surface 49 for the movable core 12 to slide freely into place.

[0036] In addition, on the inner circumferential surface of the magnetic cylinder 4 opposite to the movable core 12, a conical surface 50 with a larger diameter is formed from the middle part of the inner circumferential surface to the rear end.

[0037] Furthermore, the diameter D2 of the inner circumferential surface of the magnetic cylinder 4, excluding the aforementioned conical surface 50, is set to be larger than the diameter D1 of the aforementioned sliding guide surface 49. Therefore, the inner circumferential surface of the magnetic cylinder 4 is recessed radially outward compared to the sliding guide surface 49.

[0038] Next, the function of this embodiment will be explained.

[0039] When joining the magnetic cylinder 4, the non-magnetic cylinder 6, and the fixed core 5, firstly, the non-magnetic cylinder 6 and the fixed core 5 are butt-jointed and welded together. Then, the non-magnetic cylinder 6 and the magnetic cylinder 4 are butt-jointed and welded together. Furthermore, a weld seam b1 is formed between the non-magnetic cylinder 6 and the fixed core 5, and a weld seam b2 is formed between the non-magnetic cylinder 6 and the magnetic cylinder 4.

[0040] However, the non-magnetic cylindrical body 6, which is integrated with the thick-walled fixed core 5, has a large heat capacity, while the thin-walled magnetic cylindrical body 4 has a small heat capacity. Therefore, after welding the non-magnetic cylindrical body 6 and the magnetic cylindrical body 4, shrinkage deformation occurs on the magnetic cylindrical body 4 due to cooling, especially the inner periphery of the rear end near the weld b2, which deforms inward in the radial direction to form a bulge 52.

[0041] To address this issue, in this invention, since the aforementioned conical surface 50 is pre-formed on the inner circumferential surface of the magnetic cylinder 4, a cross-sectional triangular space 51 is defined between the conical surface 50 and the outer circumferential surface of the movable core 12. The aforementioned protrusion 52 is absorbed by this space 51, thus preventing interference between the protrusion 52 and the movable core 12. Consequently, after the aforementioned welding is performed, there is no need to perform the conventional post-processing on the inner circumferential surfaces of the magnetic cylinder 4 and the non-magnetic cylinder 6, thereby reducing manufacturing costs.

[0042] It should be noted that when the coil 30 is energized, the triangular cross-sectional space 51 between the aforementioned conical surface 50 and the movable core 12 can narrow the magnetic circuit between the movable core 12 and the magnetic cylinder 4, thereby reducing the attractive force between the fixed core 5 and the movable core 12 to some extent. Therefore, the axial length L of the aforementioned conical surface 50 is preferably set such that the triangular cross-sectional space 51 is sufficient to absorb the minimum size of the aforementioned protrusion 52. According to experiments, the axial length L of the conical surface 50 can be appropriately set to 1mm to 1.5mm.

[0043] Furthermore, when the synthetic resin coating layer 27 is injection molded, shrinkage deformation occurs in the coating layer 27 and the magnetic cylinder 4 during cooling, resulting in a slight reduction in the inner diameter of the magnetic cylinder 4. The coating layer 27 covers the outer circumferential surface of the magnetic cylinder 4 from the fuel inlet cylinder 26 and embeds the coil assembly 28 within it.

[0044] To address this issue, in this invention, a sliding guide surface 49 is formed on the inner circumferential surface of the magnetic cylinder 4 to guide the movable core 12 to slide relative to this inner circumferential surface. Furthermore, the inner diameter of the inner circumferential surface of the magnetic cylinder 4, excluding the aforementioned conical surface 50, is made larger than the inner diameter of the sliding guide surface 49. Therefore, the inner circumferential surface of the magnetic cylinder 4 recedes radially outward relative to the sliding guide surface 49. As a result, even if the inner circumferential surface of the magnetic cylinder 4 is slightly reduced in diameter as described above, the reduced-diameter inner circumferential surface will not extend further radially inward than the sliding guide surface 49.

[0045] As described above, without performing the post-processing as in the past, the smooth sliding of the movable core 12 relative to the sliding guide surface 49 of the non-magnetic cylindrical body 6 can be ensured. Therefore, the movable core 12 can always respond quickly and easily to the energization and de-energization of the coil 30 to reliably open and close the valve core 13.

[0046] 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.

[0047] Symbol Explanation

[0048] I... Electromagnetic fuel injection valve

[0049] D1...Diameter of the sliding guide surface

[0050] D2... Diameter of the inner circumference of the magnetic cylinder

[0051] 2....Valve housing

[0052] 3....Valve seat components

[0053] 4....Magnetic cylindrical body

[0054] 5...Fixed core

[0055] 6...Non-magnetic cylindrical body

[0056] 8...valve seat

[0057] 12...Modible Core

[0058] 13...valve core

[0059] 27...Covering layer

[0060] 30... coil

[0061] 49... Sliding guide surface

[0062] 50...conical surface

[0063] 51...triangular space

[0064] 52...protrusion.

Claims

1. An electromagnetic fuel injection valve, comprising: The valve housing (2) is formed by coaxially attaching a magnetic cylindrical body (4) to the rear end of a valve seat component (3) having a valve seat (8); The valve core (13) is housed within the valve housing (2) and cooperates with the valve seat (8); A non-magnetic cylindrical body (6) is coaxially connected to the rear end of the magnetic cylindrical body (4); A fixed core (5) is coaxially connected to the rear end of the non-magnetic cylindrical body (6); The movable core (12) is combined with the rear end of the valve core (13) so that the rear end face faces the front end face of the fixed core (5) and is disposed in the magnetic cylinder (4) and the non-magnetic cylinder (6). A coil (30), disposed on the outer periphery of the fixed core (5), generates an attractive force between the fixed core (5) and the movable core (12) when energized; and, The valve spring (23) applies force to the movable core (12) and the valve core (13) in the closing direction of the valve core (13) when the energization of the coil (30) is disconnected. The rear end face of the magnetic cylinder (4) and the front end face of the non-magnetic cylinder (6) are joined together by welding. The electromagnetic fuel injection valve is characterized in that... A conical surface (50) is provided on the inner circumferential surface of the magnetic cylinder (4) opposite to the movable core (12). The conical surface (50) increases in diameter from the middle of the inner circumferential surface toward the rear end face and is connected to the rear end face. The welding is a butt welding performed by connecting the rear end face of the magnetic cylinder (4) with the front end face of the non-magnetic cylinder (6). The magnetic cylinder (4) has a raised portion (52) that is formed by the inner circumference of the rear end deforming in the radial direction as the magnetic cylinder (4) cools after the butt welding. The raised portion (52) is housed in the space (51) between the conical surface (50) and the outer peripheral surface of the movable core (12) without interfering with the movable core (12).

2. An electromagnetic fuel injection valve, comprising: The valve housing (2) is formed by coaxially attaching a magnetic cylindrical body (4) to the rear end of a valve seat component (3) having a valve seat (8); The valve core (13) is housed within the valve housing (2) and cooperates with the valve seat (8); A non-magnetic cylindrical body (6) is coaxially connected to the rear end of the magnetic cylindrical body (4); A fixed core (5) is coaxially connected to the rear end of the non-magnetic cylindrical body (6); The movable core (12) is combined with the rear end of the valve core (13) so that the rear end face faces the front end face of the fixed core (5) and is disposed in the magnetic cylinder (4) and the non-magnetic cylinder (6). A coil (30), disposed on the outer periphery of the fixed core (5), generates an attractive force between the fixed core (5) and the movable core (12) when energized; and, The valve spring (23) applies force to the movable core (12) and the valve core (13) in the closing direction of the valve core (13) when the energization of the coil (30) is disconnected. The rear end face of the magnetic cylinder (4) and the front end face of the non-magnetic cylinder (6) are joined together by welding. The electromagnetic fuel injection valve is characterized in that... A conical surface (50) is provided on the inner circumferential surface of the magnetic cylinder (4) opposite to the movable core (12). The conical surface (50) increases in diameter from the middle of the inner circumferential surface toward the rear end face and is connected to the rear end face. A sliding guide surface (49) is provided on the inner circumferential surface of the non-magnetic cylindrical body (6), which guides the rear end circumferential surface of the movable core (12). On the other hand, the inner circumferential surface of the magnetic cylindrical body (4), except for the conical surface (50), is formed such that its inner diameter is larger than that of the sliding guide surface (49).

Images