JPS607139B2 - Manufacturing method of electromagnetic fuel injection valve - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an electromagnetic fuel injection valve, and particularly to a method of manufacturing an electromagnetic fuel injection valve suitable for high-speed opening/closing and prevention of fuel leakage for internal combustion engines.

Generally, in high-speed engines such as internal combustion engines for automobiles, electromagnetic fuel injection valves are used in the fuel injection system.

Since such fuel injection valves open and close in extremely short cycles, they are required to have durability of 1M or more cycles.
In addition, it is necessary to have clean injection characteristics without dripping, and it is also required that fuel leakage is extremely small. Conventionally, a pintle-type needle valve is generally used as a valve in such a fuel injection system, and a nozzle portion is opened and closed by reciprocating a needle-shaped valve body. However, in the above-mentioned electromagnetic fuel injection valve with a needle valve structure, from the viewpoint of durability, it is necessary to use hardened steel for the valve body and valve seat, and to machine the valve body and valve seat with a high degree of precision. However, there are manufacturing difficulties.

Furthermore, even if the valve body and valve seat are precisely machined, fuel will leak if the valve body tilts with respect to the valve seat, so it is necessary to align the valve body accurately with the valve seat. The difference in diameter between the outer diameter of the needle and the part that guides the needle must be a few microns, and there are also drawbacks such as the need for secondary machining adjustment to polish the outer diameter of the needle to match the inner diameter of the guide part. ing. From this point of view, it is desirable to use a spherical valve structure instead of a needle valve structure, and an example of such a structure is disclosed in Japanese Patent Application Laid-open No. 10016/1983.

In order to prevent fuel leakage by adopting this type of spherical valve structure, it is difficult to create a highly durable electromagnetic fuel injection valve structure while ensuring a highly rounded spherical valve body. In particular, it is difficult to manufacture a spherical valve body without causing distortion.
As a prior art of this type, there is Japanese Patent Publication No. 56-60853.

As shown in FIG. 4, this is a combination of a spherical valve body 3, which is a partially cut-out sphere, and a plunger 32.
When processing a sphere with a part cut out in this way, there are two methods: one is to create a perfect sphere and then cut out a part, and the other is to finish the cutout into a perfect sphere. In the first method, cutting out the already hardened ball in order to maintain roundness and increase durability increases processing time and increases costs.In addition, in the second method, Processing the outer circumferential surface of a cutout as part of a true spherical surface is ``very difficult compared to simply manufacturing a true sphere.On the other hand,
There is a valve with a spherical valve structure, as in Japanese Utility Model Application No. 55-46576.

With this type of valve body consisting only of balls, it is not possible to increase the surface area of the part where the main magnetic pole and the sphere face each other, and the amount of magnetic flux passing from the main magnetic pole to the sphere is extremely limited, so it is not possible to increase the attractive force of the sphere. do not have. This is because the force of attraction is proportional to the opposing surface area and the acceleration is inversely proportional to the weight, but the sphere is the shape with the smallest surface area/volume ratio, which is a huge disadvantage.
Therefore, the effect of reducing weight by making it spherical is offset by the reduction in suction force, resulting in a decrease in acceleration.
Therefore, it is desirable to increase the suction force and increase the acceleration while suppressing the increase in weight as much as possible by adding a plunger. An object of the present invention is to provide a valve body that is highly effective in preventing fuel leakage and has sufficient durability for high-speed opening and closing operations in an electromagnetic fuel injection valve that employs a spherical valve structure in order to eliminate the drawbacks of a needle valve structure. The purpose of the present invention is to propose a method of manufacturing an electromagnetic fuel injection valve that can be manufactured while preventing the occurrence of distortion.

In order to achieve the above object, the present invention includes a connecting rod that is attached to a plunger that is reciprocated along the central axis direction of an exciting coil by an exciting action, and a valve housing that is fixed to the tip of the connecting rod and has a valve seat. In the method for manufacturing an electromagnetic fuel injection valve having a spherical valve body slidably housed in the connecting rod, a recess having a circular inner periphery is formed on the end face of the connecting rod, and the inner periphery of the recess and the spherical valve are connected to each other. The structure is such that the valve body is in linear contact with the valve body, and is integrally joined by resistance welding along this contact line, eliminating the risk of fuel leakage due to the inclination of the valve body, as well as ensuring sufficient pressure without distortion. It is designed to have sufficient strength while ensuring a perfect roundness.

Embodiments of the present invention will be described in detail below with reference to the drawings. First, a structural example of an electromagnetic fuel injection valve manufactured by the method of this embodiment is shown in the diagram.

A core 4 is disposed at the center of the fuel injection valve, the coil 2 and the coil holder 3, and the upper end surface of the holder 3 is covered with a flange portion 5 integrated with the core mother.
A yoke 6 surrounds the outer and lower surfaces of the yoke 6. Further, a plunger 8 is connected to the coil 2 through a spring 7, facing the end face of the core 4 inserted into the center of the holder 3.
is housed so as to be movable in the direction of its central axis. The plunger 81 has a connecting rod 9 configuring the valve mechanism fixed,
Further, a spherical valve body 10 is fixed to the tip of the rod 9. The connecting rod 91 and the spherical valve body 10 are accommodated in the guide hole 2 of the valve housing q attached to the lower surface of the yoke 6, and are connected to a fuel inlet passage 3 and an outflow passage formed in the housing 1. As if to make a quick decision between the government and the government,
It reciprocates along the central axis direction of the coil 2. A conical valve seat part 15 is formed in the valve housing 11 at the opening to the outflow passage turtle 4, and the passage is blocked by coming into close contact with the spherical valve element IQ moving within the guide hole 12. A flange 16 is formed on the connecting rod 9, and a stopper IT interposed between the housing 11 and the plunger 8 defines the stroke of the valve body 10.

The electromagnetic fuel injection valve 1 configured in this manner has a reciprocating motion of several Hz to several hundred days 2 against the connecting rod 9 and the spherical valve body 10' while the engine is operating. Durability is required, and in order to prevent fuel leakage, the spherical valve body 0 must maintain sufficient roundness to connect the connecting rod 9.
It is required that it be fixed to.

Therefore, the conditions associated with the manufacturing method according to this embodiment are as follows.

That is, "Hardened steel or stainless steel materials are selected as the materials for the spherical valve body 10 and the valve seat portion 15 from the viewpoint of wear resistance that can withstand high-speed opening and closing operations.

Due to the characteristics of the injection valve 1, the stroke of the spherical valve body 10 is generally 0.05 to cover the fuel flow rate of the internal combustion engine.
~0.3 seconds are required, and the time from fully closed to fully open is required to be approximately 0.3 seconds. Therefore, the acceleration of the plunger 8 is on the order of several hundred grams, and the plunger 8 requires a lifespan of about 1 billion operations. Furthermore, it is desirable that the connecting rod 9 and the spherical valve body 10 be joined together by welding, since it is necessary to reliably join them together to improve durability.

Therefore, from the viewpoint of acid-soluble properties, both materials are required to be of the same quality. On the other hand, when joining together by welding, since the connecting rod 9 and the spherical valve body are made of fairly hard materials, there is a risk of cracking if the welded portion is heated or cooled too quickly. Furthermore, in order to prevent fuel leakage from the valve seat portion 15, both the spherical valve body 10 and the valve seat portion 15 need to have a roundness of several microns or less. For this reason, the welding between the connecting rod 9 and the spherical valve body 10 is performed on the valve seat portion 15 and the guide hole 12 of the spherical valve body ID.
This must be done using a method that does not cause distortion or softening of the material due to heating due to thermal effects on the parts that come into contact with the material. Therefore, the optimal welding method is resistance welding, which is low cost and has little thermal influence. Furthermore, since the stroke of the valve body 10 is short, the connection rod 9 and the spherical valve body 10 are
When welding with the valve body, a method must be adopted that will keep the length of the valve body structure (see Figure 1) constant after welding.

A manufacturing method that satisfies the above-mentioned required conditions is as follows. That is, as shown in FIGS. 2 and 3, first, a recess 18 having a circular inner circumferential edge is formed on the distal end surface of the connecting rod 9, which is one joint, and the recess 18 is inserted into the spherical valve body 1. and bring the two into linear contact.

This makes the welding part a circumferential edge along the inner green,
This is because it is necessary to minimize the thermal influence on areas other than the welded area. In addition, since both of these are given high-speed reciprocating motion and require high durability, the concave portion
The relationship between the inner diameter d of 8 and the diameter D of the spherical valve body 10 needs to be set as follows. First, from the viewpoint of bonding strength, it is desirable that the circumference to be welded be as large as possible. However, if the diameter of the contact circle is too large, the relative position of the connecting rod 9 and the spherical valve body 10 during welding, that is, its dimension (first
(see figure) becomes more variable. If this variation is large, the fuel injection valve 1 with a small stroke cannot perform proper fuel injection. For this reason, there is a limit to increasing the contact circle, and it has been experimentally confirmed that the contact angle 8 of the contact circle that covers one river of the spherical valve body increases when it exceeds 100 degrees, and the maximum contact angle 8 = The limit is 100 degrees. On the other hand, from the viewpoint of strength, when the angle a becomes 40 degrees or less, the effect of contact with the inner periphery of the recess 18 decreases, the strength decreases even though the thermal influence increases, and when the welding length shortens, the The bonding force becomes smaller. From the above,
A contact angle of 40 to 100 degrees is suitable, which means that
The diameter d of the recess 18 is 35 with respect to the diameter D of the spherical valve body 10.
This corresponds to ~75%. As shown in FIG. 3, electrodes 19 and 20 are brought into contact with the connecting rod 9 and the spherical valve body 10, which are connected in this way, and resistance welding is performed.

In this case, the contact position of the electrode 19 on the connecting rod 9 side does not cause any inconvenience to the spherical valve body 10, but the contact position of the electrode 20 on the spherical valve body 10 side poses a problem. That is, if the position where the spherical valve body 10 contacts the valve seat portion 15 and the guide hole 12 is not avoided, the heat effect during welding will be exerted on this position, causing distortion etc. and impairing the valve function. Therefore, focusing on the small apex angle of the valve seat portion 15 (see FIG. 2), the ratio of increase in the cross-sectional area of the fuel passage of the seat portion 15 to the stroke of the spherical valve body 10 is greatest when it is 90 degrees.

This has the advantage of minimizing the stroke required to flow the same flow rate near ■=90 degrees. A small stroke is advantageous in shortening the time required for the valve to fully open from fully closed, and in reducing noise during opening and closing, and therefore, a small stroke of 90 degrees is desirable. On the other hand? = 60 degrees or less, and it is 110 degrees
The increase rate of the fuel passage cross-sectional area with respect to the stroke decreases rapidly at temperatures above 60 degrees and maximum 11 degrees.
It needs to be set to 0 degrees. In this way, the apex angle of the valve seat portion 15 is selected within the range of 60 to 110 degrees.
Therefore, the contact area of the electrode 20 is between the contact area between the valve seat part 15 and the guide hole 12 in the spherical valve body 10,
Alternatively, a portion facing the fuel outflow passage 14 may be considered. However, on the outflow passage 14 side, the contact area of the electrode 20 is 4.5 mm, and the spherical valve body 10 is distorted and unsuitable due to heat generation due to current concentration. For this reason, the contact position of the electrode 20 is limited to a location between the valve seat portion 15 and the guide hole 12 where the contact portion with the valve seat portion 15 is not affected by heat. Therefore, the shape of the electrode 20 is such that a concave portion 21 is provided so that the electrode 20 contacts the optimal position in a linear manner so as to prevent current concentration. Here, since the range affected by heat due to resistance welding is approximately 10 degrees in angle, the contact angle Q between the spherical valve body 10 and the electrode 20 (see Figure 3) is such that the range affected by heat is approximately 60 to 110 degrees. It is necessary to set Q=70 to 120 degrees or more, including the angle taking into account. On the other hand, if we focus on the contact area with the guide hole 12, since this contact point Q is 180 degrees, it is necessary to make Q=170 degrees or less so as not to be affected by heat. However, when welding is carried out by touching the electrode 20 having the recess 21, if the temperature exceeds Q=140 degrees, the spherical valve body 10 will dig into the electrode 20, accelerating the wear and tear of the electrode 20. It is necessary to do so. For this reason, the contact angle Q between the spherical valve body 10 and the electrode 20 is 7.
It is set in the range of 0 to 140 degrees, which corresponds to the fact that the diameter of the electrode recess 21 is also 55 to 95% of the diameter D of the spherical valve body 10.

As described above, according to this embodiment, the connecting rod 9 and the spherical valve body 10 are
Since the spherical valve body 1 is connected in a line contact state and is securely connected by resistance welding while avoiding heat influence on the contact portion with the guide hole 12 and the valve seat portion 15, the spherical valve body 1 does not cause any distortion. A strong valve body structure can be achieved.

Therefore, the connecting rod 9 is connected to the valve housing 1 by using the spherical valve body 10 which has sufficient durability as a valve body structure capable of high-speed reciprocating motion and is easy to manufacture. On the other hand, since the fuel can be sufficiently sealed even if the connecting rod 9 is tilted to some extent, it is possible to manufacture an electromagnetic fuel injection valve that does not require a large tolerance between the outer diameter of the connecting rod 9 and the inner diameter of the housing 11. As described above, according to the present invention, by adopting the spherical valve body structure, it is possible to obtain an electromagnetic fuel injection valve in which the thorns and the connecting rod are welded together without any thermal influence on the spherical valve body. The valve can effectively prevent leakage and have sufficient durability.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing the structure of an electromagnetic fuel injection valve, Fig. 2 is an enlarged sectional view of the valve body, Fig. 3 is a sectional view showing the welding state of the connecting rod and the spherical valve body, and Fig. 4 is It is a sectional view showing an example of a conventional valve body. 1...'Electromagnetic fuel injection valve, 2...Exciting coil, 8...Plunger, 9...-Connecting rod, 10...Spherical valve body, 11 . . . ~ valve housing, 12 . . . guide hole, 15 . . . valve seat portion, 19, 20 . . . electrode. Figure 4 Figure 1 Figure 2 Figure 3

Claims (1)

[Scope of Claims] 1. A connecting rod that is attached to a plunger that reciprocates along the central axis of the excitation coil and is movable in a reciprocating manner; In a method of manufacturing an electromagnetic fuel injection valve including a fixed spherical valve element, a recess having a circular inner periphery is formed on the end face of a connecting rod facing the spherical valve element, and the inner periphery of the recess and the spherical valve element are connected to each other. A method of manufacturing an electromagnetic fuel injector, which comprises bringing them into contact in a line-contact state and integrally welding them together along the line of contact by resistance welding. 2. The method of manufacturing an electromagnetic fuel injection valve according to claim 1, characterized in that the inner diameter of the recess formed in the connecting rod is 35 to 75% of the diameter of the spherical valve body.