JP2002120151A - Manufacturing method for endless metal belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for an endless metal belt capable of manufacturing the endless metal belt having high circumferential length accuracy with high productivity as compared to before. SOLUTION: This manufacturing method for the endless metal belt 6 has a shot peening process applying the shot peening to the belt 6 and adjusts a circumferential length of the belt 6 by controlling the shot peening. By measuring the circumferential length of the belt 6 before the shot peening and setting conditions of the shot peening on the basis of the measured result, the circumferential length of the belt 6 is adjusted. Otherwise, the circumferential length of the belt 6 during the shot peening is measured, and the shot peening is completed on the basis of the measured result.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for manufacturing an endless metal belt. The present invention relates to, for example, CVT (Contin
uously Variable Transmission) Can be used to adjust the circumference in the production of belts and the like.

[0002]

2. Description of the Related Art An endless metal belt is wound around, for example, two rollers and rolled, so that when the belt passes through a roller portion, a tensile bending stress is generated on the outer peripheral side of the belt, and the belt passes through the roller portion. Until the next roller portion, the belt becomes straight, and the tensile stress due to the bending on the outer peripheral side of the belt is eliminated. Therefore, it is desired that the outer circumferential surface of the belt is repeatedly subjected to tensile stress due to bending during the rotation of the belt, thereby improving the fatigue strength. JP-A-61-42402, JP-A-63-96
No. 258 proposes an endless metal belt in which shot peening is performed only on the outer peripheral surface of an endless metal belt to generate a compressive residual stress on the outer peripheral surface and improve the fatigue strength of the outer peripheral surface.

[0003]

However, in the case of an endless metal belt made of a thin plate, the thickness of the plastically deformed layer on the surface (about 2 mm) is required.
0 to 25 μm) is a level that cannot be ignored compared to the belt plate thickness (approximately 0.2 mm), so that the endless metal belt changes its overall shape, for example, increases in circumference (approximately 720 mm) (increases by approximately 2 mm), and crowning R Cause changes. Here, the crowning R is a curvature of a cross section perpendicular to the circumferential direction as shown in FIG. In metal belts, these values are often required to have high shape accuracy, and if conventional shot peening processing is performed in the prior art, the variation in shot peening processing is added to the accuracy variation of the processed product existing before the processing. Is a problem in product functions. In particular, in many cases, endless metal belts are laminated and used as a multilayer (for example, 9 layers) in products, and in this case, the circumference accuracy is extremely important. For example, when the permissible clearance between the laminated belts is 10 μm, the permissible range of the perimeter difference is 2π
60 μm. Conventionally, many endless metal belts have been produced, and a belt with a difference in length within the allowable range is selected from the belts and assembled to form a laminated belt. It is an extremely inefficient production method. An object of the present invention is to use a shot peening process, which was only one of the causes of a decrease in accuracy in the past, as a fine adjustment method of belt circumference accuracy, to achieve higher productivity and higher endless accuracy than in the past. An object of the present invention is to provide a method for manufacturing an endless metal belt that can manufacture a metal belt.

[0004]

The present invention to achieve the above object is as follows. (1) A method of manufacturing an endless metal belt having a shot peening step of performing a shot peening process on the endless metal belt, wherein a peripheral length of the endless metal belt is adjusted by adjusting the shot peening process. Manufacturing method. (2) The circumference of the endless metal belt is measured by measuring the circumference of the endless metal belt before the shot peening process, and setting the conditions of the shot peening process based on the measurement result. Manufacturing method of endless metal belt. (3) The endless metal belt according to (1), wherein the circumference of the endless metal belt is measured during the shot peening process and the circumference of the endless metal belt is adjusted by terminating the shot peening process based on the measurement result. Belt manufacturing method.

In the method (1) for producing an endless metal belt, the shot peening process is used not only for improving the fatigue strength but also for fine adjustment of the belt circumference, and the shot peening condition (for example, shot peening) is used. Since the circumference of the endless metal belt is adjusted by adjusting the processing time and the like, an endless metal belt having higher productivity and higher circumference accuracy than conventional ones can be manufactured. Assuming that the shot peening processing conditions include, for example, shot peening processing time, as a result of examining the change in the circumference of the endless metal belt due to the shot peening processing, the circumference of the endless metal belt increases with the shot projection time, and the circumference increases. It was found that the rate showed a decreasing tendency with time. On the other hand, the compressive residual stress on the surface applied to the endless metal belt is early (for example, in 9 seconds) as the shot time elapses.
It has been found that because of saturation, fatigue strength having a strong correlation with the compressive residual stress can be secured by shot peening in a relatively short time (for example, in 9 seconds). Therefore,
The projection time required to ensure fatigue strength (for example, 9
Seconds) or more,
It is possible to finely adjust the circumferential length of the endless metal belt in the direction of increasing the circumferential length of the endless metal belt with high accuracy in a region where the circumferential length increase rate is gentle while maintaining the improved fatigue strength. However, the shot peening processing time must be adjusted within a range that is equal to or longer than the projection time (for example, 9 seconds) necessary to secure the fatigue strength. Since the method of the present invention is a method of adjusting the perimeter of each belt itself by adjusting the shot peening process, as in the conventional case where a plurality of belts are produced and a belt having a similar length is selected. There is no need to produce a large number of extra belts, and high productivity is achieved. In the method (2) for manufacturing an endless metal belt, the circumference of the endless metal belt before the shot peening treatment is measured. As a result of the measurement, it is known how many millimeters of the circumference must be increased, and the required projection time can be determined from, for example, a relationship between the amount of change in the circumference and the projection time (for example, a graph of FIG. 3 described later) that is obtained in advance. Therefore, shot peening is performed for that time to set the circumference of the endless metal belt to the target circumference. In the method for manufacturing an endless metal belt according to the above (3), the circumference of the endless metal belt during the shot peening process is continuously measured, and the shot peening process ends when the circumference of the endless metal belt reaches a target value. . In the case of the above method (2), if a constant relationship is used for the relationship between the circumferential change and the projection time, the relationship between the circumferential change and the projection time is determined depending on conditions such as nitriding or nitrocarburizing before shot peening. When the relationship changes, the perimeter of the endless metal belt changes. According to the method (3), the perimeter of the endless metal belt is continuously measured during the shot peening process, and the measurement result reaches a target value. Then, since the shot is stopped, the final belt circumference is not affected by conditions such as nitriding or soft nitriding before the shot peening, and the belt circumference is adjusted to the target circumference with high accuracy. be able to.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for producing an endless metal belt according to the present invention will be described below with reference to FIGS. It is to be noted that parts common to all embodiments of the present invention are denoted by the same reference numerals throughout all embodiments of the present invention.

First, portions common to all embodiments of the present invention will be described. In the method for manufacturing an endless metal belt according to the present invention, the start and end of the thin metal belt are welded to form an endless metal belt 6. The endless metal belt 6 has, for example, a thickness of about 0.2 mm, a width of about 12 mm, and a circumference of about 720 m.
m maraging steel. Next, the endless metal belt 6 is subjected to a surface hardening treatment such as a nitriding treatment or a nitrocarburizing treatment. The depth of the nitride layer is, for example, about 25 μm. Next, the endless metal belt 6 is subjected to shot peening to improve the fatigue strength. The shot peening is performed on both the outer circumferential surface and the inner circumferential surface of the belt to prevent the endless metal belt from being subjected to multiplex deformation when the shot peening is performed. It is desirable that the shot peening is so-called stress peening performed by applying a pre-tensile stress to the surface, but is not limited to stress peening. The shot peening conditions are, for example, a preload radius of curvature of R20 mm, a projection air pressure of 0.3 MPa, a projection particle diameter of Φ70 μm, a shot grain hardness of HV700, and the same inner and outer projection processing conditions. In the shot peening process, the peripheral length of the endless metal belt 6 is adjusted by adjusting the shot peening process conditions (shot peening process time, air pressure, projection amount, particle size, grain hardness, etc., particularly the shot peening process time). Make fine adjustments.

In the shot peening process, as shown in FIGS. 1 and 2, the endless metal belt 6 is joined to a first roller 3 for applying a pre-tension stress (preload) to the inner peripheral surface of the endless metal belt 6. And a second roller 2 for applying a pre-tension stress (preload) to the outer peripheral surface of the endless metal belt 6. From the projection nozzle 5 toward the portion where the endless metal belt 6 is wound around the first roller 3, and from the outer peripheral side of the endless metal belt 6, the shot particles 15 are projected from the projection nozzle 4 to the second end of the endless metal belt 6. The shot particles 15 are projected toward a portion where the roller 2 is wound. At the inner projection position, a preload curvature in the opposite direction to the outer projection position is given, and the projection timing of the inner and outer projection nozzles 4, 5 can be controlled independently.

[0009] Of the three rollers, 1 is a driving roller,
Reference numerals 2 and 3 denote driven rollers. Two projection nozzles 4 and 5 are set. The projection on the outer periphery is performed by the main nozzle 4, and the projection on the inner periphery is performed by the sub nozzle 5. The sub-nozzle 5 projects from an obliquely upper side or an obliquely lower side at an angle of about 30 ° with respect to a horizontal plane in order to prevent interference with the endless metal belt 6 at a position facing the circumferential direction. Is the effective component V · cos of the projection velocity V.
In order to increase θ, it is desirable that the distance be as small as possible without interfering with the endless metal belt 6. However, there is no particular requirement for equipment having a sufficient projection speed.

A tension is applied to the endless metal belt 6 by a spring 11. This tension is to obtain a frictional force for the endless metal belt 6 to rotate without slipping and to be fed, and to be compared with a tensile preload generated on the surface of the endless metal belt 6 due to the curvature of the rollers 2 and 3. And small enough.
The driven roller 2 is set on a slide base 10 and is designed so that a spring force acts as a tension of the endless metal belt 6. The driven roller 3 of the inner projection unit is fixed on the same fixed base 7 as the base of the drive shaft. Drive shaft 13
Are driven by a servo motor 12. When the required level of the shape accuracy of the product is low, another conventional motor type other than the servomotor may be used. As the shot grain projection mechanism, a normal direct pressure air blow type is used, but any other ventilation air blow type, impeller type, and other types may be used.

The shot peening used in the present invention includes shot peening (called stress peening) performed by applying a preload (prestress) to the endless metal belt 6. However, shot peening used in the present invention is not limited to stress peening. The principle of stress peening will be described with reference to FIG. When the endless metal belt 6 reaches the portion where the endless metal belt 6 is wound around the rollers 1, 2, and 3, the endless metal belt 6 is bent, and a preload A of tensile bending stress is applied to the outer peripheral side of the bend, and the inner peripheral side of the bend is applied. A preload of compressive bending stress is applied.
Shot peening is performed in this state. Shot grain 15
Is projected onto a portion of the endless metal belt 6 to which a preload of tensile bending stress is applied. V indicates the projection speed, and eV indicates the reflection speed. By projecting the shot grains 15, the endless metal belt 6
The surface of the substrate expands to generate a compressive residual stress B on the surface. Then, with the rotation of the endless metal belt 6, the endless metal belt 6 is rotated.
Preload of tensile bending stress is released when advancing from the winding portions of rollers 1, 2, and 3 into a linear portion, and a tensile preload A is applied, and a large compressive residual stress of A + B = C is applied to the surface of the endless metal belt. Is formed. That is, compared to shot peening without preload, stress peening provides a compressive residual stress greater by tensile preload A, which is advantageous in improving fatigue strength.

As shown in FIGS. 1 and 2, in the fine adjustment of the circumference of the endless metal belt 6, the change in the circumference of the endless metal belt 6 is measured by the distance between the drive shaft 13 and the driven shaft 14. I do. Specifically, the amount of movement of the arm 9 fixed on the slide base 10 is measured by the dial gauge 8 fixed on the fixed base 7, and the measured amount is extracted as an electric signal.

In the present invention, the reason why the shot peening treatment can be used not only to improve the fatigue strength but also to finely adjust the circumference of the endless metal belt 6 will be described. Generally, endless metal belts that require strength are subjected to a surface hardening treatment such as nitriding or nitrocarburizing. % Or less (± 0.144 mm or less with respect to the average circumference of 720 mm) is extremely difficult. If a process capable of adjusting the precision such as a normal tensile elongation process is performed after the surface hardening in order to suppress this variation, the surface hardened layer is cracked, the residual compressive stress is released, and the strength is greatly reduced.

The perimeter change due to the shot peening process is about 0.1 to 0.2%, but if the process is continued under constant conditions, the rate of increase shows a gradual decrease as shown in FIG. By adjusting the processing time in
Fine adjustment of the circumference of less than 2% is possible. In particular,
The circumferential change of the endless metal belt 6 having a circumferential length of 720 mm due to the shot peening process is about 1 to 3 mm, and the circumferential length increases with the projection time as shown in FIG. 3, and the rate of increase gradually decreases with the projection time. The increase rate of the circumference is relatively small after about 9 seconds from the start of the projection, and the order can be used for fine adjustment of the circumference of 0.02% or less.

On the other hand, as shown in FIG. 3, the residual compressive stress applied to the surface of the endless metal belt 6 is early after the elapse of the projection time, and the residual stress is saturated after about 9 seconds from the start of the projection. It was found that a fatigue strength having a very strong correlation with the residual stress can be ensured by a relatively short-time treatment. In FIG. 3, a minus sign indicates that the residual stress is a compressive stress. Further, the compressive residual stress of 200 kg / mm ² is a sufficiently large stress for improving the fatigue strength.

If the shot peening process is considered only from the viewpoint of improving fatigue strength, which is a conventional object, it is reasonable to set the projection time to the minimum level at which the fatigue strength can be secured. However, in the present invention, the tendency of FIG. 3 is used, that is, the shot peening is performed in a region where the circumferential length increase rate is smaller than the projection time necessary for securing the fatigue strength, without reducing the fatigue strength. Fine adjustment of the circumference of the endless metal belt 6 is performed. FIG. 4 shows that the projection times are 9, 18 and 36 seconds,
This shows that the fatigue characteristic curve hardly changes.
It can be seen that when the projection time is about 9 seconds or longer, the fatigue strength is hardly affected by the magnitude of the projection time. That is, there is no change in the fatigue strength after the compressive residual stress is saturated.

By applying surface compressive residual stress by shot peening, both improvement in fatigue strength and elongation in the circumferential direction can be obtained stably. Generally, when a material is strengthened by surface hardening such as nitriding or nitrocarburizing, embrittlement occurs at the same time as hardening, and especially for tensile deformation, cracks are generated from slight irregularities on the surface and brittle grain boundaries. However, even a small strain is destroyed at the weakest part. On the other hand, such surface defects are relatively insensitive to compressive strain as compared with the case of tension, and the original strength of the material is often obtained. Circumferential elongation caused by shot grain projection is
This is caused by the Poisson effect on plastic deformation due to compression, and the shot peening process allows local and uniform compression plastic deformation to occur continuously, enabling stable circumferential elongation without cracking. .

Next, parts unique to each embodiment of the present invention will be described. In Example 1 of the present invention, the circumference of the endless metal belt 6 before the shot peening was measured, and the circumference of the endless metal belt was adjusted by setting the conditions of the shot peening based on the measurement result.

A maraging steel endless metal belt 6 having a circumference of 720 mm, a thickness of about 0.2 mm, and a width of about 12 mm
I prepared them. The endless metal belt 6 has a perimeter variation of about ± 150 μm (0.021% for a perimeter value of 720 mm, a standard deviation of 50 μm) due to the nitriding treatment (the thickness of the nitride layer is about 25 μm) before the shot peening treatment. Had. From the value measured in advance, it is possible to know how many millimeters of the circumference must be increased, and from the relationship between the amount of change in circumference and the projection time obtained in advance (the graph of FIG. 3), the required projection time is set to 18 seconds or more. It was obtained within 36 seconds, and shot peening was performed for that time to finely adjust the circumference of the endless metal belt. The conditions of the shot peening process are the preload radius of curvature R
= 20mm, projected air pressure 0.3MPa, projected particle diameter Φ70
μm, shot grain hardness HV700, and inner and outer circumferences were the same. As a result, the variation amount was about ± 51 μm (about 0.007% with respect to the circumference value, the standard deviation was 17 μm), and the variation amount could be suppressed to about １ ／ of the conventional amount. As the shot peening condition, not only the shot time, but also the shot pressure, the shot grain size, and the like may be adjusted. It is desirable to adjust the shot time because the length can be easily adjusted.

In the second embodiment of the present invention, the circumference of the endless metal belt 6 is measured during the shot peening process, and the circumference of the endless metal belt 6 is adjusted by ending the shot peening process based on the measurement result. Was.

In the fine adjustment of the circumferential length in the first embodiment, the circumferential length variation after shot peening is one-third of the conventional one, but is present. This is due to variations in the state of the workpiece before the shot peening process and variations in shot conditions. Therefore, in order to further suppress variations in the circumference, the circumference is continuously measured even during the shot peening process, and the process is terminated when the target circumference is reached. The conditions of the endless metal belt 6 are the same as those of the first embodiment. The shot conditions are the same as those of the first embodiment except for the continuous measurement of the circumference during the shot and the stop of the shot when the target value is reached.
The same as above. For the projection time, the minimum projection time was set to 9 seconds, and the processing was terminated when the target circumference reached thereafter. The treatment was performed on 30 endless metal belts, and the perimeter of the treated product was separately measured with a measuring instrument. As a result, the variation of the circumference was about ± 30 μm (about 0.004% of the circumference, the standard deviation was 10 μm), which was about 1
Accuracy control with a variation amount of / 5 or less has become possible.

[0022]

According to the method for manufacturing an endless metal belt of the present invention, the circumference of the endless metal belt is adjusted by adjusting the shot peening process, so that the shot peening conditions can be adjusted while maintaining the fatigue strength. Simply by adjusting the circumference, the circumference of the endless metal belt can be adjusted. Compared to the conventional method of producing a large number of belts and selecting and assembling those with similar circumferences, high productivity and high circumference precision are achieved. Endless metal belts can now be manufactured. According to the method for manufacturing an endless metal belt according to claim 2, the circumference of the endless metal belt before the shot peening process is measured, and the shot peening condition is set based on the measurement result, and the circumference of the endless metal belt is finely adjusted. Since the adjustment is performed, the circumference can be adjusted with high accuracy. According to the method of manufacturing an endless metal belt according to the third aspect, the circumference of the endless metal belt during the shot peening is measured, and the shot peening is terminated based on the measurement result. It is not affected by the conditions of the previous nitriding treatment or nitrocarburizing treatment, and the circumference can be adjusted with higher precision than the method of claim 2.

[Brief description of the drawings]

FIG. 1 is a plan view of an apparatus in which a method for producing an endless metal belt according to the present invention is being performed.

FIG. 2 is a front view of the apparatus of FIG. 1;

FIG. 3 shows a method for producing an endless metal belt of the present invention.
It is a graph which shows the amount of circumference change and the change of residual stress with respect to projection time.

FIG. 4 shows a method for producing an endless metal belt according to the present invention.
It is a stress amplitude-repetition number diagram (SN diagram) at the time of changing a shot time.

FIG. 5 is a perspective view of an endless metal belt manufactured by the method for manufacturing an endless metal belt of the present invention and a partial cross-sectional view thereof.

FIG. 6 is a stress distribution diagram in a sheet thickness direction in each step of preload application, shot peening, and preload release in the method of manufacturing an endless metal belt according to the present invention.

[Explanation of symbols]

 1, 2, 3 rollers 1 drive roller 2 second roller (driven roller) 3 first roller (driven roller) 4 projection nozzle (outside projection) 5 projection nozzle (inside projection) 6 endless metal belt 7 fixed base 8 dial Gauge 9 Arm 10 Slide base 11 Spring 12 Servo motor 13 Drive shaft 14 Follower shaft 15 Shot grain

Claims (3)

[Claims] 1. A method of manufacturing an endless metal belt having a shot peening step of performing a shot peening process on an endless metal belt, wherein the peripheral length of the endless metal belt is adjusted by adjusting the shot peening process. Manufacturing method of metal belt. 2. The peripheral length of the endless metal belt is measured by measuring the peripheral length of the endless metal belt before the shot peening process and setting the conditions of the shot peening process based on the measurement result. A method for producing the endless metal belt according to the above. 3. The peripheral length of the endless metal belt is measured by measuring a peripheral length of the endless metal belt during the shot peening process and terminating the shot peening process based on the measurement result. Manufacturing method of endless metal belt.