JPS58192755A - Processing method of improving fatigue strength of coil spring - Google Patents

Abstract

PURPOSE:To perform the processing so as to obtain a uniform quality, by contacting a coil spring with the surface of a drum, holding both ends thereof by rotary wheels at a specified interval, and thereafter hitting shot particles together with compressed air with the spring being rotated. CONSTITUTION:At fist, a coil spring is mounted on holding bodies 13 and 13, which are fixed to rotary wheels 12 and 12 of a processing device 10, and the rotary wheels 12 and 12 are rotated at a specified speed. Then, the coil spring begins the rotation under the state the spring is contacted with the outer surface of the drum 11. Then, the coil spring revolves around the drum 11 following the rotary wheels 12 and 12. Under this state, minute steel balls are made to hit the coil spring together with compressed air through a jetting hole 16 from a jetting gun 15, which is located in the vicinity of the coil spring. At this time, since the jetting hole 16 has a shape of long and thin hole, which is extended in one direction, the steel balls are made to flow along the entire length of the coil spring and to hit the spring uniformly, the surface layer is hardened, residual stress by the compression is increased, and the fatigue strength is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a process for improving the fatigue strength of a coil spring using a device that uniformly collides particles with compressed air on both the inner and outer surfaces of the coil spring in order to improve the fatigue strength. Regarding the method.

Conventionally, in compression springs or tension springs, during operation, the maximum stress value is concentrated at the end or inner diameter of the coiled part, and the concentrated part is the starting point for fatigue failure of the spring, leading to a coil spring breakage accident. Ta.

Therefore, in order to prevent these breakage accidents, a method of heating small diameter steel parts with compressed air has been adopted.

By performing this yacht beaning process, small scratches, etc. on the spring surface are removed, and at the same time, a thin hardened film layer is formed on the processed surface, and this hardened layer generates compressive residual stress on the coil spring surface layer. However, this has led to a demand for highly durable fill springs with improved fatigue strength, that is, fatigue life. Even if the outer surface of the coil spring is evenly pressed, the inner surface I will not be sufficiently pressed, especially if the spatial distance between the wire diameters of the coil spring is relatively small. In this case, the most important inner diameter part was not sufficiently peened, so it was not possible to expect much improvement in fatigue strength, and therefore, a sufficient effect in preventing breakage accidents could not be obtained.

The present invention has been devised in view of the above-mentioned drawbacks, and the object of the PJT is to bring a coil spring into contact with the surface of a circular drum, hold both ends of the coil spring on a rotating wheel at a predetermined distance, and then rotate the coil spring. The present invention aims to provide a treatment method for improving the fatigue strength of a coil spring by colliding yacht particles with compressed air against the inner and outer surfaces of the coil spring without rotating the wheel.

Hereinafter, the present invention will be explained according to an embodiment shown in FIG.

FIG. 1 is a perspective view showing a part of the processing apparatus according to the present invention, in which a cylindrical drum 0υ having the same width as the free length of the spring is placed at the center, and both sides of the drum 0L have a diameter larger than the diameter of the drum aυ. A rotating wheel α202 having a large diameter is provided with a holder [13Q3, .

In this figure, one rotating wheel aa is shown separated for convenience of explanation.

A rotating shaft α4 that can rotate the rotating wheel 040 at a constant speed is inserted into the center of the processing device 0, and the rotating shaft α4 is rotated by the power of an electric element (not shown). It has become.

Then, when the coil spring is fitted into the holding body Q3σ31@..., the outer circumferential surface of the coil spring comes into contact with the circumferential surface of the drum σD, and at the same time as the rotating wheel uz rotates, the attached coil spring also rotates. It rotates around the circumferential surface of the drum αυ.

The processing method for improving fatigue strength using the processing device configured as described above will be described in detail with reference to FIGS.
It is attached to the holding body +13α3 fixed to 3.

Next, the rotary wheel uQ is adjusted to a predetermined speed and rotated by a separate electric element.

Therefore, the coil spring begins to rotate in the state X while in contact with the periphery of the drum αυ, and continues to rotate.

It follows the wheels a'a aa and rotates around the drum αυ.

When this state is reached, the micro steel balls are ejected from the injection gun α, which has come close to the coil spring, into the injection nozzle QI along with compressed air.
The coil spring f collides with the coil spring f via 19.

The injection port 06) is not circular but is an elongated hole extending in one direction, so that the steel balls are scattered over the entire length f of the coil spring.

Figure 3 shows another embodiment, in which the injection gun (15)
as (151a... is a thin tube and is composed of a plurality of tubes, and in order to eject simultaneously and collide with the inner diameter part, it is moved in the vertical direction to the positions α!ila', α51al...
...(Adjust so that it moves.)

In any case, when the steel balls are ejected by the above-mentioned injection gun, the coil spring itself rotates and rotates.The steel balls collide uniformly over the entire inner and outer surfaces, and therefore, according to this method, the metal waves on the surface layer The membrane is cut, resulting in minute surface scratches,
At the same time as skin scale is removed, the surface layer is hardened and compressive residual stress is generated and increased.

That is, according to this method 1, on the one hand, stress concentration is prevented by removing surface scratches and skin scale, and on the other hand, fatigue strength is improved by increasing compressive residual stress.

As a result, the coil spring is provided with a hardened layer over the entire inner and outer surfaces, and strong compressive residual stress is generated.

Now, if we explain this state with reference to Figures 4 and 5, Figure 4 shows the outer surface l with the coil spring in the free state.
This is a diagram showing the distribution of residual stress when a steel ball collides with the steel ball. In the figure, the symbol 0 indicates the part of zero stress, the symbol 0 indicates the tensile stress, and the symbol - indicates the compressive stress, which indicates the stress of the coil spring. Since the inner diameter surface is not pressurized, the residual stress is in a tensile state.
However, since a hardened layer is developed from the intermediate part to the outer surface of the wire due to the Nyosoto particles, a compressive stress part C is formed.

However, by colliding with the steel ball also on the inner diameter surface, compressive stress is generated as shown in FIG. 5, forming part A.

Then, as it reaches the middle part of the wire, the hardened layer becomes dispersed, resulting in tensile stress, forming part B, and then, the hardened layer due to the steel ball collision on the outer surface forms part C, again having compressive stress.

As described above, the present invention provides a coil that is formed by bringing a coil spring into contact with the surface of a drum, holding both ends of the coil spring on a rotating wheel at a predetermined distance, and then colliding micro steel balls with compressed air against the inner and outer surfaces of the coil spring. Since it is based on a treatment method for improving the fatigue strength of springs, it has been difficult to treat steel ball collisions on the inner and outer surfaces of coil springs at the same time and uniformly, but with this method mass production has been established. At the same time, remarkable effects such as being able to process to completely uniform quality in terms of quality control were obtained.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of an apparatus for carrying out the processing method of the present invention, with a part of the apparatus being exploded, and FIG. 2 is a diagram showing an embodiment for carrying out the processing method of the present invention. FIG. 3 is a partially enlarged view showing another example, FIGS. 4 and 5 are stress distribution diagrams after treatment, and FIG. 4 is a stress distribution diagram when the outer surface of the coil spring is pressurized. FIG. 5 shows a stress distribution diagram when the entire inner and outer surfaces are pressurized. OI...Fatigue strength improvement treatment device UυΦ・Φ...Drum Gz...Rotating wheel q...Holding body α4...Rotating shaft α... Injection gun No. 1 C Fig. 2-15 Part 11, n No. 32 Zo No. 4 Fig. 53

Claims (1)

[Claims] After the coil spring is brought into contact with the drum surface and both terminals of the coil spring are held at a predetermined distance by the rotating wheel, the rotating wheel is not rotated and the terminal is collided with the compressed air against the inner and outer surfaces of the coil spring. Treatment method for improving fatigue strength of coil springs.