JP4085621B2 - Manufacturing method of endless metal belt - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing an endless metal belt in which the circumference of the endless metal belt is adjusted. The present invention can be used for peripheral length adjustment in the manufacture of, for example, a CVT (Continuously Variable Transmission) belt.
[0002]
[Prior art]
Since the endless metal belt is wound around a roller and is rotated, it is desirable that a repeated stress is applied between the bending stress when passing through the roller and the disappearance of the bending stress at the linear portion to improve the fatigue strength. It is.
Fatigue strength is usually improved by performing shot peening on the surface portion of the endless metal belt. In order to further improve the fatigue strength, as proposed in JP-A-2000-225567, the surface of the endless metal belt is subjected to surface hardening treatment and then shot peened.
In improving fatigue strength by shot peening, the endless metal belt is made of a thin plate, and the thickness of the plastic deformation layer due to shot peening on the surface becomes a level that cannot be ignored compared to the plate thickness. Cause the circumference to increase. If the circumference is changed by the shot peening process, there is a problem in terms of product function, particularly when a ring belt is laminated and used as a multilayer. Conventionally, a method has been adopted in which a large number of belts are produced, and ones having circumferential lengths similar to each other are selected and stacked, but this is an extremely inefficient production method.
The present applicant has found that the circumference of the endless metal belt increases with the shot projection time and the increase rate of the circumference shows a gradual decrease with time, but the applied compressive residual stress is saturated early. In Japanese Patent Application No. 2000-312829, it has been proposed to adjust the circumference of an endless metal belt by shot peening. There, the circumference of the endless metal belt before the shot peening process was measured, and the circumference of the endless metal belt was adjusted by setting shot conditions such as shot projection time based on the measurement result.
[0003]
[Problems to be solved by the invention]
However, in the proposal of Japanese Patent Application No. 2000-312829, when shot peening is performed after the surface of the endless metal belt is subjected to surface hardening treatment, the elongation characteristic of the peripheral length of the endless metal belt by shot peening is influenced by the surface hardening treatment. Therefore, it has been found that there is a problem that accuracy of the circumference adjusted using shot peening deteriorates.
An object of the present invention is to improve the accuracy of adjusting the peripheral length of an endless metal belt using shot peening in a method for manufacturing an endless metal belt that is shot peened after surface hardening treatment to improve fatigue strength.
[0004]
[Means for Solving the Problems]
The present invention for achieving the above object is as follows.
(1) A method for producing an endless metal belt in which a surface hardening process is performed on the surface of an endless metal belt and then a shot peening process is performed,
Measure the circumferential length of the endless metal belt before and after the surface hardening treatment, calculate the amount of elongation of the surface hardening treatment from the measured results, and the endless metal belt after the surface hardening treatment and before the shot peening treatment. The required elongation amount of the endless metal belt in the shot peening process is calculated from the circumference, and the shot condition of the shot peening process is set based on the surface hardening process elongation amount and the required elongation amount, and the circumference of the endless metal belt is determined. A method of manufacturing an endless metal belt in which the length is adjusted.
(2) The method for manufacturing an endless metal belt according to (1), wherein the shot condition includes a shot projection time.
(3) The method for manufacturing an endless metal belt according to (1), wherein the shot condition includes a projection air pressure.
(4) The method for producing an endless metal belt according to (1), wherein the shot condition includes a projected particle diameter.
(5) The method for producing an endless metal belt according to (1), wherein the shot condition includes shot grain hardness.
[0005]
In the method for producing an endless metal belt of the present invention of the above (1)-(5), when variation occurs in the curing of the surface part of the endless metal belt in the surface hardening process, the plastic deformation resistance of the surface part changes, and the shotning process is performed. The circumferential elongation characteristics of the endless metal belt change. Since the above-described variation in the surface hardening process has a strong correlation with the circumferential length change amount before and after the surface hardening process, the circumferential elongation characteristic of the endless metal belt during the shot peening process can be predicted from the circumferential length change amount. Therefore, by setting the shot condition of the shot peening process based on the above-described circumference change amount in addition to the circumference before the shot peening process, the circumference of the endless metal belt can be adjusted with high accuracy.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Below, the manufacturing method of the endless metal belt of this invention Example is demonstrated with reference to FIGS.
In the endless metal belt manufacturing method of the present invention, as shown in FIG. 1, the start and end of a thin metal belt are welded to form an endless metal belt 1. In order to improve the fatigue strength of the endless metal belt 1, the endless metal belt 1 is subjected to surface hardening treatment (for example, nitriding treatment or soft nitriding treatment), and then shot peening is performed.
In the shot peening process, the circumference of the endless metal belt 1 is extended. Therefore, the shot peening process is used not only for improving the fatigue strength but also for adjusting the circumference.
[0007]
However, since the elongation during shot peening changes depending on the surface hardening process (for example, nitriding or soft nitriding) that is performed before shot peening, the change is predicted from the change in circumference before and after surface hardening. Thus, shot conditions (for example, shot projection time) are set to improve the accuracy of circumference adjustment.
[0008]
More specifically, between the shot projection time T and the shot elongation amount ΔL _S , as shown in FIG. 2, the endless metal belt circumference increases with the shot projection time, and therefore the circumference change amount increases with the projection time. There is a relationship that the rate of increase in circumference increases gradually with time. Although the compressive residual stress of the surface portion of the endless metal belt increases with time, it is saturated early (about 12 seconds after the start of shot projection), and the residual stress does not change even if shots are further projected. When the saturation stress is reached, the effect of improving fatigue strength does not change even if more shots are projected (18 seconds and 36 seconds are continued after the start of shot projection) (the SN diagrams match, see FIG. 3). . Therefore, the shot projection after 12 seconds after the start of the shot projection works not as an improvement in durability but as a circumference adjustment.
[0009]
Further, there is a strong correlation between the surface hardening treatment depth and the surface hardening treatment elongation amount ΔL _H (= L ₂ −L ₁ ). When the surface treatment depth is deep, the surface treatment elongation increases, and the surface treatment depth. The larger the is, the greater the plastic deformation resistance in the shot, and the longer the shot projection time T required to obtain the required shot elongation. Therefore, between the surface hardening treatment elongation amount ΔL _H (= L ₂ −L ₁ ) and the shot projection time T, the larger the surface treatment elongation amount ΔL _H (= L ₂ −L ₁ ), the longer the shot projection time T is. There is a relationship of becoming longer.
By statistically examining these relationships, the relationship between the shot elongation amount ΔL _S , the surface hardening treatment elongation amount ΔL _H (= L ₂ −L ₁ ) and the shot projection time T is three-dimensional as shown in FIG. The relationship of characteristics is summarized in advance.
[0010]
Before the surface hardening treatment, the circumferential length L ₁ of each endless metal belt ₁ was measured.
Next, the endless metal belt 1 is subjected to a surface hardening process including nitriding or soft nitriding.
After the surface hardening treatment and before the shot peening treatment, the circumferential length L ₂ of each endless metal belt 1 was measured.
[0011]
By measuring the circumference of each endless metal belt 1 with a surface hardening treatment before and after the endless in respective endless metal belt 1, the circumferential length L ₂ and the surface hardening treatment before and after the endless metal belt 1 before the shot peening The amount of change in the circumferential length of the metal belt (L ₂ −L ₁ ) was determined.
More specifically, the required shot elongation ΔL _S of the endless metal belt 1 is calculated from the circumferential length L ₂ of the endless metal belt 1 after the surface hardening treatment, and the elongation amount ΔL _H of the endless metal belt 1 by the surface hardening treatment is calculated. Calculated. The required shot elongation amount ΔL _S is obtained as the elongation amount of the other belt to match the length of the longest belts laminated together. Further, the elongation amount ΔL _H of the endless metal belt 1 during the surface hardening process is obtained from the difference in the circumferential length of the endless metal belt before and after the surface hardening process (L ₂ −L ₁ ).
[0012]
Next, shot conditions (conditions including shot time T) for the shot peening process were set based on the circumference L ₂ and the circumference change amount (ΔL _H = L ₂ −L ₁ ).
More specifically, from the relationship between the shot elongation amount, the surface hardening treatment elongation amount and the shot projection time in FIG. 4, the required shot elongation amount ΔL _S of the endless metal belt 1 and the elongation amount ΔL _H of the endless metal belt by the surface hardening treatment are obtained. A shot projection time T corresponding to (= L ₂ −L ₁ ) was obtained.
[0013]
Next, the endless metal belt 1 was subjected to shot peening treatment for the shot projection time T obtained above. The shot peening process after 12 seconds mainly works for adjusting the circumference, and the projection time is longer than that when the surface hardening process is not performed due to the amount of elongation ΔL _H of the endless metal belt by the surface hardening process. .
[0014]
The shot conditions including the shot projection time T set above are set based on the measurement results outside the shot peening machine because they are the circumference measurement results before and after nitriding or soft nitriding, It is not set by circumference measurement in the shot machine. Therefore, there is no problem in measuring the circumference in the shot machine due to the measurement error caused by the engagement of the shot grains between the roller and the belt, the wear of the roller surface over time, and the engagement of the shot grains on the roller bearing. Therefore, the accuracy of the circumference adjustment is increased.
[0015]
A specific example is as follows.
The endless metal belt 1 used was 30 maraging steels having a plate thickness of about 0.2 mm, a plate width of about 12 mm, and a circumferential length of about 720 mm.
Prior to the shot peening treatment, surface hardening treatment (referred to as nitriding treatment) was performed. The depth of the nitride layer was about 20-30 μm.
[0016]
Next, as shown in FIG. 5, a shot peening process was performed. Shot peening is applied to both the outer peripheral surface and the inner peripheral surface of the belt so that the endless metal belt does not undergo multiple deformation when shot peening is performed. The shot peening was so-called stress peening performed by applying a pre-tension stress to the surface. However, it is not limited to stress peening.
In the shot peening process, the endless metal belt 1 is subjected to a pre-tension stress (a first roller 2 that applies a pretension stress (preload) to the inner peripheral surface of the endless metal belt 1 and a pretension stress ( The first end of the endless metal belt 1 from the projection nozzle 5 from the inner peripheral side of the endless metal belt 1. The shot grain 6 is projected toward the winding part around the roller 2, and the shot grain 8 is directed from the outer peripheral side of the endless metal belt 1 toward the part where the endless metal belt 1 is wound around the second roller 3 from the projection nozzle 7. Projected. A preload curvature in the direction opposite to the projection position on the outer peripheral side was given at the projection position on the inner peripheral side. Reference numerals 9 and 10 are shutters which control the projection time by opening and closing the shutters.
The preload radius of curvature R was 20 mm, the projection air pressure was 0.3 MPa, the projection particle diameter Φ70 μm, the shot grain hardness was HV700, and the inner and outer projection processes were performed under the same conditions.
[0017]
The peripheral length adjustment of the endless metal belt 1 by the shot peening treatment after the surface hardening treatment and the results were as follows.
The peripheral length of the endless metal belt 1 before the shot peening treatment has a variation of about ± 150 μm (0.021% relative to the peripheral length value, the standard deviation is 50 μm). The projection time was adjusted between 12 seconds and 36 seconds in the direction of canceling out.
[0018]
As a result, the variation amount is about ± 25 μm (about ± 0.0035% with respect to the circumference value, standard deviation 9 μm), and the variation amount is estimated by about 1/6 of the conventional time without considering the surface hardening treatment elongation. Even when compared with the case (variation amount: about ± 51 μm), it could be suppressed to ½. Furthermore, this result was superior in accuracy compared with the case where the measurement was performed directly in the machine (variation amount: about ± 30 μm). This is considered to be because the measurement error factor caused by the above-described shot particle entrapment or the like could be eliminated by measuring outside the apparatus.
[0019]
【The invention's effect】
According to the manufacturing method of the endless metal belt of the present invention of claim 1-5 , the circumference is measured before and after the surface hardening treatment, and the circumference elongation characteristic at the time of shot peening is predicted from the amount of change in the circumference, Since the shot conditions including the shot time are set based on this, it is possible to improve the accuracy of the circumferential length adjustment regardless of the shot peening process after the surface hardening process is applied to the surface of the endless metal belt. .
In addition, by measuring the circumference before and after the surface hardening treatment, it is possible to set shot conditions from the measurement results outside the machine, eliminate error factors such as biting of shot grains, and the circumference adjustment accuracy equal to or better than direct measurement inside the machine Can be secured.
[Brief description of the drawings]
FIG. 1 is a perspective view of an endless metal belt manufactured by the method of manufacturing an endless metal belt of the present invention and a partial cross-sectional view thereof.
FIG. 2 is a graph showing changes in circumferential length and residual stress with respect to projection time in an endless metal belt manufacturing method of the present invention.
FIG. 3 is a stress amplitude-repetition number diagram (SN diagram) when the shot time is changed in the method of manufacturing an endless metal belt of the present invention.
FIG. 4 is a three-dimensional summary of the relationship between the required shot elongation (mm), surface hardening treatment elongation (mm) and shot projection time (sec) used in the endless metal belt manufacturing method of the present invention. FIG.
FIG. 5 is a side view of a shot peening machine during execution of shot peening.
[Explanation of symbols]
1 Endless metal belt 2, 3, 4 Roller 5, 7 Projection nozzle 6, 8 Shot grain 9, 10 Shutter

Claims (5)

A method for producing an endless metal belt that is subjected to surface peening after the surface of the endless metal belt is subjected to surface hardening treatment,
Measure the circumference of the endless metal belt before and after the surface hardening treatment, calculate the amount of elongation of the surface hardening treatment from the measured results, and The necessary elongation amount of the endless metal belt in the shot peening process is calculated from the circumference, and the shot condition of the shot peening process is set based on the surface hardening treatment elongation amount and the necessary elongation amount, and the circumference of the endless metal belt is determined. A method of manufacturing an endless metal belt that is adjusted in length. The method of manufacturing an endless metal belt according to claim 1, wherein the shot condition includes a shot projection time. The method for manufacturing an endless metal belt according to claim 1, wherein the shot condition includes a projection air pressure. The method for manufacturing an endless metal belt according to claim 1, wherein the shot condition includes a projected particle diameter. The method for manufacturing an endless metal belt according to claim 1, wherein the shot condition includes shot grain hardness.

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