JP2002361558A - Method of shot-peening for coiled spring - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shot peening method capable of uniformly adding a compressive residual stress by shot peening to the inside and outside of a coiled spring. SOLUTION: In this shot peening method, shot particles 2 are projected from nozzles 1 and 1 while the coiled spring 3 is rotated around a spring center shaft 31. A projection angle γ for projecting the shot particles 2 from the nozzle 1 is set at a position deflected by 30 deg. or more, 37 deg. or below, and -30 deg. or more, and -37 deg. or below from a surface F orthogonal to the spring center axis 31.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a shot peening method for uniformly applying a compressive residual stress to the entire surface of a coil spring.

[0002]

2. Description of the Related Art In order to improve the fatigue strength of a coil spring, a compressive residual stress is applied by shot peening. In this shot peening, it is important to improve the durability by uniformly applying shot particles to the entire surface of the coil spring and applying the impact energy of the shot particles uniformly to the entire surface to form a uniform compressive residual stress layer. It is.

In conventional shot peening, as shown in FIG. 2, a shot grain 2 is projected by a nozzle from a direction perpendicular to the central axis while rotating the coil spring 3 about the central axis and moving the coil spring 3 in the central axis direction at the same time. That is being done. In this method, the shot particles collide with the outside of the coil spring 3 in a large amount and collide with the inside in a small amount. Therefore, the inner compressive residual stress layer becomes thinner than the outer compressive residual stress layer. In addition, since a roller or a conveyor is used to transport the coil spring 3, fine frictional scratches are likely to occur due to sliding with the roller or the like on the side surface of the coil spring 3 due to movement in the center axis direction. As a result, in the conventional shot peening method, the durability of the coil spring 3 was insufficient.

[0004]

Problems to be Solved by the Invention
No. 3 proposes a shot peening method in which shot grains are projected from a direction having an inclination (projection) angle β (α <β) with respect to the center axis of a coil spring having a spiral (pitch) angle α. However, in this shot peening method, it is necessary to rotate the coil spring in a drum shape, which causes a problem that the work moving device becomes complicated.

An object of the present invention is to provide a shot peening method capable of uniformly applying a compressive residual stress by shot peening to the inside and outside of a coil spring. A second object of the present invention is to provide a shot peening method capable of reducing a difference in collision energy between the inside and the outside of a coil spring, and preventing frictional flaws caused by sliding of a side of the coil spring with a roller of a conveying device. In the offer. The object of the invention described in claim 3 is that in the shot peening method according to claim 1 or 2, the efficiency can be improved,
An object of the present invention is to provide a shot peening method having excellent productivity.

[0006]

According to the present invention, in a shot peening method for projecting shot grains from a nozzle while rotating a coil spring around a spring center axis, a projection angle γ for projecting shot grains from the nozzle is defined as: It is characterized by being set at a position deflected by 30 degrees or more and 37 degrees or less from an orthogonal plane orthogonal to the spring center axis.

[0007]

According to the present invention, the projection angle γ of the nozzle with respect to the spring center axis is set to 30 degrees or more and 37 degrees or less. Therefore, it is possible to uniformly apply a compressive residual stress by shot peening to the inside and outside of the coil spring.

According to the second aspect of the present invention, the coil spring is rolled around the central axis while being transported in a direction perpendicular to the spring central axis. As a result, it is possible to prevent frictional damage due to sliding with a transfer device such as a roller or a conveyor on the side surface of the coil spring, and to make uniform the collision energy between the inside and the outside.

According to the third aspect of the present invention, a plurality of nozzles are provided, and the projection angle γ with respect to the center axis of the spring is 30 degrees or more and 37 degrees or less, and -30 degrees or more and minus 37 degrees or less. With this configuration, the efficiency of shot peening can be improved, and the productivity is improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1A and 1B are schematic views of a shot peening method according to the present invention, in which shot grains 2, 2 are projected from a pair of nozzles 1, 1 to a coil spring 3. FIG. Perform shot peening. The coil spring 3 is transferred to the projection area 20 of the shot grains 2 and 2 one by one by the transport device 4.
Transported to The transport device 4 includes a conveyor 41, a carrier 42 formed of thin horizontal bars arranged in a row on the conveyor 41, and a friction plate 43 provided in the projection area 20.

The coil spring 3 is mounted on the carrier 4 of the transfer device 4.
2 and rolls around the spring central axis 31 on the friction plate 43 in the projection area 20. The nozzles 1 and 1 are arranged symmetrically with respect to the coil spring 3 as shown in FIG.
On the other hand, the shot grains 2 and 2 are projected obliquely downward at a projection angle γ of 30 degrees or more and 37 degrees or less.

The axes of the nozzles 1 and 1 (shot grains 2 and
The projection direction of (2) may be set to a plane inclined forward and backward from a plane F orthogonal to the spring center axis 31. In this case, it is possible to solve the problem that the carrier 42 formed of a thin horizontal bar hinders the collision of the shot particles 2 with the inside of the coil spring 3.

As shown in FIGS. 2A and 2B, the coil spring 3 has a pitch angle α, a coil diameter D, a wire diameter d, and a pitch P. 3A shows directions B and C in which the wire diameter d is disturbed by the pitch angle α and the shot particles 2 hardly hit the point A inside the coil spring 3. (B) of FIG.
The shot grain 2 is formed inside the coil spring 3 by the projection angle β in the direction B where the shot grain hardly hits the point A and the wire diameter d.
3 shows a range of the projection angle が where it is difficult to hit.

FIG. 4 shows a formula (1) for calculating the projection angle β and a formula (2) for calculating the projection angle い at which the shot particles 2 hardly hit the point A. The projection angle γn of the nozzle 1 to be avoided is
Equation (3) is obtained. On the other hand, the approximate expression of the optimum projection angle γ at which the shot particles 2 are evenly applied to the entire coil spring is calculated by Expression (4). FIG. 5A is a graph in which the projection angle at which the variation in the collision energy is minimized for each pitch angle α is determined as the optimum projection angle γ. The calculation formula (4) expresses the characteristic curve of FIG.

Therefore, the optimum projection angle γ is calculated by the following equation (3).
It is desirable that both of equation (4) and equation (4) be satisfied. From the above, the optimum projection angle γ determined according to the pitch angle α is in the range of 30 degrees to 37 degrees, and in a general coil spring 3 having a pitch angle α of 20 degrees or less, the optimum projection angle γ is 35 degrees. It turns out that it is about 37 degrees.

For this reason, the nozzles 1 and 1 are shown in FIG.
When the projection angle γ is 30 degrees or more and 37 degrees or less and -30 degrees or more and minus 37 degrees or less from the angle perpendicular to the spring center axis 31 as shown in FIG. Collide. As a result, a compressive residual stress layer having a uniform thickness can be formed on all surfaces including the outside and inside of the coil spring 1.

FIG. 6C shows the energy applied to the inside and outside of the coil spring 3 by the direction of the spring center axis 31 of the coil spring 3 being conveyed and the shot particles 2 projected from the nozzle 1. It is a graph which shows the relationship of a ratio. FIG.
(A) conveys the coil spring 3 of the conventional shot peening method in the direction of the spring center axis 31. (b) of FIG.
The case where the coil spring 3 is transported in a direction orthogonal to the spring shaft 31 in the shot peening method of the present invention is shown.

When the coil spring 3 is transported in the direction perpendicular to the spring center axis 31 in the shot peening method of the present invention, it is found that the difference between the collision energies inside and outside the coil spring 3 is small.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a shot peening method of the present invention.

FIG. 2 is an enlarged view of a coil spring.

FIG. 3 shows projection angles β and い at which shot particles hardly collide with the inside.
FIG.

FIG. 4 is a formula for calculating the projection angles β, ξ, γn and the optimum projection angle γ.

FIG. 5 is a graph and a sectional view of an optimum projection angle γ.

FIG. 6 is a graph showing a moving direction of a coil spring and an inner / outer collision energy ratio.

[Explanation of symbols]

 1 Nozzle 2 Shot grain 3 Coil spring

Claims (3)

[Claims] 1. A shot peening method for projecting shot particles from a nozzle while rotating a coil spring about a spring center axis, wherein a projection angle γ for projecting shot particles from the nozzle is
30 degrees or more from an orthogonal plane orthogonal to the spring center axis, 37
A shot peening method for a coil spring, wherein the shot peening method is set at a position deviated by less than one degree. 2. The shot peening method according to claim 1, wherein the coil spring is transported in a direction perpendicular to a center axis of the spring. 3. The shot peening method according to claim 1, wherein the number of the nozzles is plural, and the projection angle γ is 30 degrees or more and 37 degrees or less, -30 degrees or more, and minus 37 degrees. A shot peening method for a coil spring, wherein shot grains are projected from both of the following.