JPS5843582B2 - Ninenkikanyounenriyoufunshiyaki - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a fuel injector for an internal combustion engine.

Conventionally, there are various types of fuel injectors.

The injector used in combination with a fuel injection device that injects fuel is used to atomize the fuel by opening the valve to which the fuel is pumped from the injection device to form a spray, and to open the valve when the pumping of fuel is stopped. It is necessary to close the valve to prevent fuel leakage.

For this purpose, it is necessary to finish the valve head and valve seat with particularly high precision, but for parts that are mass produced such as automobile parts,
It is not easy to carry out the above-mentioned high-precision processing, and therefore the product has the disadvantage of being expensive.

In other words, in the past, the valve head and shaft member were manufactured integrally from the same material, and in order to improve the sealing performance between the valve head and valve seat of a needle valve manufactured using such a method. Generally, the valve head side is finished by grinding, and it is also customary to perform hardening or the like to reduce wear on the valve head.

However, with grinding finishing, the accuracy is limited to about 0.5μ, and it is not possible to obtain greater roundness and surface smoothness.

Since there is no other way to perform such grinding and finishing one by one, there is a problem in that the manufacturing process is very time-consuming and leads to an increase in cost.

In addition, when hardening is performed, since the valve stem is a thin rod with a diameter of several millimeters, the valve stem is thermally deformed due to hardening.
Therefore, after quenching, additional processing is required to remove the thermal deformation mentioned above, and due to these problems,
Conventionally, manufacturing fuel injectors has been extremely difficult, and a countermeasure has been desired, especially for parts that need to be mass-produced, such as automobile parts.

This invention has been developed in view of the above-mentioned conventional problems. Firstly, the present invention provides a steel ball for ball bearings with a valve head having a high degree of roundness and hardened hardness. is used.

The reason why steel balls for ball bearings are used in this way is as follows.

That is, as mentioned above, in normal grinding and finishing, the processing limit is to obtain a roundness of about 0.5μ.

However, since steel balls for ball bearings have a spherical shape, they can be subjected to highly accurate lapping, and a roundness of about 0.1 μm can be obtained through this lapping.

Furthermore, since this paraping process processes a large amount of steel ball material at once, the dimensional difference between each finished steel ball is extremely small.

Therefore, if such a high-precision steel ball for a bearing is used as a valve head and brought into contact with the valve seat, the fuel will be sealed very well and the surface finish will be good, resulting in extremely good fuel flow. Become.

On the other hand, steel balls for ball bearings are hardened to obtain sufficient hardness to prevent rolling wear, and are used in frequent contact and separation motions, such as the valve head and valve seat of a fuel injector. It has good abrasion resistance even when repeated use, and is easy to handle because it does not leave dents or other damage on the valve head during processing.

The second aspect of the present invention is to weld and fix a bearing steel ball to one end of a valve shaft member by electron beam welding, spot welding, or the like.

This type of welding method joins the parts by generating the minimum necessary amount of heat, so there is little thermal deformation of the shaft member and valve head, and the hardened steel ball is tempered, reducing its hardness. There is no fear.

In particular, the valve head and shaft member of this type of fuel injector are approximately several millimeters in diameter, and unless the welding method described above is used, they are not suitable for practical use due to thermal deformation or reduction in the hardness of the steel ball.

Thirdly, after the bearing steel balls are welded to the shaft, a portion is cut out to form an annular edge at a position where the fuel spray from the steel balls spreads in a conical flare shape.

The contact part of the bearing steel ball used as the valve head with the valve seat is
The roundness and surface precision of the steel balls for bearings are used as they are, and a portion is cut away to form an annular edge in order to obtain a predetermined conical flare.

During this notching process, since the bearing steel ball has sufficient quenching hardness, the valve head will not be damaged by dents or the like, making it easy to handle.

In addition, no sliding guide is provided between the valve shaft member and the outer cylinder or valve seat, and the ball passes through the annular gap between the surface of the high-precision bearing steel ball and the valve seat. Self-alignment is achieved by balancing the pressure of the injected fuel.

The present invention closely combines the above-mentioned main technical means, and has good workability, high efficiency, and great cost advantages.

The structure of the present invention will be explained below according to the embodiment shown in FIGS. 1 to 5.

Fig. 1 shows a fuel injector to which the present invention is applied, in which 1 is a valve head formed by cutting a part 1a of a steel ball, and 2 is a valve head 1 formed by electron beam welding or spot welding at the shaft end. 3 is a valve seat whose contact surface 3a with the valve head 1 forms a tapered surface; 4 is an O-ring for sealing;
5 is a spring for pushing the shaft member to the right and bringing the valve head 1 into contact with the valve seat 3; 6 is a nut; 7 is a filter; 8 is an outer cylinder; 9 is a connector for connecting an injector to a fuel injection device to supply fuel. The tube for feeding, 10 is a fitting for connecting the tube to the injector.

Note that the protrusion 1c of the valve head 1 plays an auxiliary role when adjusting the spring pressure with the nut 6, and may be omitted from a functional point of view.

Further, the valve head 1 is in line contact with the tapered surface of the valve seat 3.

And <BOB=β is the apex angle of a conical shape with the steel ball center O as the apex and including the contact line.

The relationship between the valve seat 3 and the shaft member 2 is designed so that the shaft member 2 can be inserted through the valve seat without contacting the inner peripheral surface 3b.

Furthermore, the role of the spring 5 is that it is installed between the valve seat 3 and the nut 6, and when the pressure feeding of fuel is stopped, the spring 5 moves the valve head 1 to the valve seat 3.
When the fuel is forced into the injector and the pressure inside the injector reaches a preset valve opening pressure, the valve is pushed to the left against the spring pressure to perform injection. It is for.

The valve opening pressure is adjusted by adjusting the amount of deflection of the spring 5, that is, the spring pressure, using the nut 6.

Figure 2 shows the state of the fuel jet when the steel ball of valve head 1 is installed without cutting in Figure 1. In this case, the fuel does not spread out in a conical curtain shape. Undesirable.

3 and 4 respectively show the main parts of this invention,
It is a drawing showing the relationship between a valve head 1 of a steel ball cut on a small circle perpendicular to the axis and a tapered surface 3a of a valve seat 3 that comes into contact with the valve head 1.

In the case of Fig. 3, the edge 1b of the valve head 1 is outside the edge 3c of the valve seat 3, and the fluid flies in the direction of the tangent to the edge 1b of the spherical surface, so the position X of the edge 1b is selected appropriately. This makes it possible to easily adjust the divergence angle α of the jet.

In addition, in the case of FIG. 4, the edge 1b of the valve head 1 is the edge 3 of the valve seat 3.
c, the jet flow will fly in the direction of inclination of the contact surface (tapered surface) 3a of the valve seat 3.

FIG. 5 shows another embodiment of the invention, in which the valve seat 3
The abutment surface 3a is finished into a spherical surface with approximately the same radius as the valve head 1,
The valve head 1 and the contact surface 3a are in surface contact with each other.

In this case, the sealing performance is even better than when the valve head 1 is in line contact with the contact surface 3a of the valve seat 3.

The abutment surface 3a can be easily formed by cold forming.

As explained above, this invention is a type in which the main components are an outer cylinder, a valve seat, a valve, and a spring, and there is no sliding guide between the valve shaft member and the outer cylinder or valve seat. In a fuel injector for an internal combustion engine, a hardened and surface-finished steel ball for a bearing is used as the valve head, and the hardened steel ball for the bearing is attached to one end of the valve shaft member by electron beam welding or A hardened steel ball for a bearing is welded and fixed by a method with little heat effect such as spot welding, and then a hardened steel ball for a bearing is welded and fixed to one end of the shaft member of the above valve, and when the valve is opened, the fuel A part is notched on the opposite side of the shaft member to form an annular edge at the position where the spray spreads to the conical frame, and the surface of the hardened steel ball for the bearing is brought into contact with the valve seat as it is without any post-processing. Since it is a flat surface, it is possible to extremely easily obtain good sealing between the valve head and the valve seat, which is essential for a fuel injection valve.

In other words, if the valve head is finished by normal grinding, extremely sophisticated processing technology is required to obtain a roundness of 0.5μ, but currently steel balls for bearings can be finished with a roundness of about 0.1μ. It is easy to finish and mass-produced.

Therefore, by using a steel ball for the valve head, extremely good sealing performance can be obtained.

Further, as long as the same degree of sealing performance as the conventional valve seat is obtained, the roundness of various parts of the conical surface of the valve seat may be slightly inferior to that of the conventional valve seat, so that machining is easy.

Further, the fuel is scattered in a conical flare by cutting a portion of the steel ball, and since the spray angle depends on the cut position of the steel ball, it is extremely easy to adjust the spray angle.

Furthermore, steel balls that can be mass-produced, have small mutual differences, and have good roundness are commercially available and can be easily obtained.

Further, the work of welding and fixing the steel balls to the end face of the shaft member itself is extremely easy, so the workability is good, the efficiency is high, and the cost advantage is large.

[Brief explanation of drawings]

Figure 1 is an overall sectional view showing a typical embodiment of this invention, and Figure 2 is a main part for explaining the state of fuel injection flow when the steel balls used in this invention are applied without being cut. Partially enlarged sectional views, Figures 3 and 4 are respectively
FIG. 2 is an enlarged sectional view of a main part of the figure. FIG. 5 is an enlarged sectional view of a main part showing another embodiment of the present invention. 1...Valve head, 1a...Cut part, 1b
...Edge, 1c...Protrusion, 2...
- Shaft member, 3... Valve seat, 3a... Contact surface (tapered surface), 3c... Edge.

Claims (1)

[Claims] 1. In a fuel injector for an internal combustion engine of a type in which an outer cylinder, a valve seat, a valve, and a spring are the main components, and no sliding guide is provided between the valve shaft member and the outer cylinder or valve seat. A hardened and surface-finished steel ball for bearings is used as the valve head, and the steel ball is welded and fixed to one end of the valve shaft member by a method with little heat effect such as electron beam welding or spot welding. Next, a steel ball welded and fixed to one end of the shaft member of the above-mentioned valve is attached to the valve seat so as to form an annular edge at a position where the fuel spray spreads in a conical flare shape when the valve is opened. A valve for a fuel injector of an internal combustion engine, characterized in that a portion of the steel ball is notched on the opposite side, and the surface of the steel ball other than the partially notched portion is used as a contact surface to the valve seat without any post-processing. Method of manufacturing parts.