JP2002147536A - Metallic endless timing belt and producing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin metallic endless timing belt and a producing method thereof capable of achieving working movement at high speed and high accuracy, excellent in durability, usable as a transmission means at a low cost, and capable of preventing enlargement of driving torque and generation of noise. SOLUTION: Plural engagement holes are provided on the metallic thin endless belt along a peripheral direction at regular intervals, and a bending part in a slight height is formed at least on front and rear end parts of a periphery of the engagement hole along the peripheral direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal endless timing belt which is incorporated in a high-precision device such as an arm portion or an actuator mechanism of an industrial robot, and is suitable for use as a transmission means of a power transmission mechanism. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, as a driving force transmitting body for transmitting a driving force from a prime mover, a flat belt, a gear,
There are those employing various transmission systems such as chains and toothed belts. Driving force transmission elements employing these various transmission methods have advantages and disadvantages depending on the transmission method, and are used taking advantage of their respective characteristics.However, methods that can be used naturally are limited depending on the purpose of use. . Especially for precision power transmission which is indispensable for driving inside high precision equipment such as arms and actuator mechanisms of industrial robots, the method used is still the timing belt made of rubber / synthetic resin, metal or resin. A gear formed by a mold or the like is generally used. In recent years, high precision equipment such as arms of industrial robots is required to have high responsiveness, high controllability, simple structure, high speed, space saving, energy saving, etc. ing. In addition, there is a tendency that demands for use in a special environment such as a clean room or a vacuum environment, or a high temperature or high humidity environment are increasing. In particular, for high-definition responsiveness that is strongly required, vibration, rotation unevenness, backlash, and angular velocity fluctuation caused by the viscoelastic material itself in a rubber / synthetic resin timing belt become barriers, It is impossible to achieve power transmission. Also, gears have backlash, and if the distance between the input and output shafts is long, not only will the weight become excessive and the cost will increase, but also speed fluctuations will occur due to fluctuations in meshing between gears. Had.

[0003]

As described above, when the prior art transmission system is used for a high-precision device such as an industrial robot that requires high-precision transmission characteristics, the following problems are encountered. Have. Elongation occurs due to rubber or synthetic resin. There is backlash during forward / reverse rotation. Vibration occurs due to fluctuations in angular velocity and the like, resulting in uneven rotation. There is dust generation because it is made of rubber or synthetic resin. Gas or dust generation due to rubber or synthetic resin (cannot be used in a vacuum or clean room). Since it is made of rubber or synthetic resin, there is a limit on the operating temperature. Noise occurs during high-speed operation. Since it is made of rubber or synthetic resin, viscoelastic slip cannot be avoided, and high-precision transmission that achieves an accurate rotation ratio cannot be obtained.

From the above problems, when a conventional timing belt is used as a transmission method for a high-precision device such as a robot arm, transmission unevenness easily occurs, responsiveness is poor, and high-speed and high-precision At present, no working action has been obtained. In addition, the material is rubber or synthetic resin, so there is dust and dirt due to rubbing, and there are many restrictions in the use environment such that use in a vacuum, in a clean room, or in a high temperature or high humidity environment is impossible. Had problems.

[0005] Therefore, the above-mentioned problems (1) to (4) are solved,
The use of a metal timing belt is considered as one that can obtain a high-speed and high-precision work operation, has high durability, and can be used as a low-cost transmission means. As a technique related to the metal timing belt, for example, techniques disclosed in Japanese Utility Model Laid-Open No. 62-113112 and Japanese Utility Model Laid-Open No. 1-75644 have already been proposed.

The conveyor belt disclosed in Japanese Utility Model Application Laid-Open No. 62-113112 is made by rolling special steel such as stainless steel into a thin steel strip having flexibility, joining both ends of the belt to an endless endless belt. Along with forming the belt,
In the longitudinal direction of the endless belt, meshing holes are formed at the same intervals as a plurality of projections formed at equal intervals on the outer periphery of the pulley, and a flange that is bent outward is provided on the periphery of the meshing hole. It is composed.

Further, the metal belt for power transmission according to Japanese Utility Model Application Laid-Open No. 1-75644 is a metal belt for power transmission wound around a toothed belt wheel, and a pair of peripheral members is provided on a sheet metal endless belt body. An engaging portion composed of a cantilevered cut-and-raised piece facing in the direction and a hole of a trace of the cut-and-raised piece is provided at regular intervals in the circumferential direction, and each pair of cut-and-raised pieces is It is configured such that it is folded in the direction of opposition and separation, and the folded edge forms a contact curved surface with the teeth of the belt wheel inserted into the hole.

However, the above-mentioned Japanese Utility Model Application Laid-Open No.
In the case of the conveyor belt according to Japanese Patent Publication No. 12, since a flange that bends outward is provided on the peripheral edge of the meshing hole formed in the endless belt, the belt is provided on the peripheral edge of the meshing hole. Due to the provided flange, the bending rigidity of the endless belt is increased, and in particular, when the endless belt is driven by a small-diameter pulley, the driving torque becomes excessively large.

In the case of the metal belt for power transmission according to Japanese Utility Model Laid-Open No. 1-75644, a pair of circumferentially opposed cantilever cut-and-raised pieces are provided on a thin metal endless belt body. Therefore, the formation of the cantilevered cut-and-raised piece becomes complicated, the manufacturing cost increases, and when the thin metal endless belt is driven to rotate at high speed, the cantilever-shaped cut-and-raised piece vibrates. Therefore, there is a problem that noise may be generated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to solve the above-mentioned problems (1) to (2) to achieve a high-speed and high-precision work operation. And it can be used as a low cost transmission means with good durability and
It is an object of the present invention to provide a thin metal endless timing belt and a method of manufacturing the same, in which there is no fear that a driving torque becomes excessive or noise is generated.

[0011]

In order to achieve the above object, according to the first aspect of the present invention, a plurality of meshing holes are formed at equal intervals along a circumferential direction of a thin metal endless belt. A metal endless timing belt, wherein a bent portion having a minute height is formed at least in front and rear ends of a peripheral edge of the engagement hole along a circumferential direction.

A meshing hole formed in the metal endless timing belt meshes with a plurality of sprocket pins (projections) formed at equal intervals on an outer periphery of a pulley around which the metal endless timing belt is wound. Power can be transmitted to the driven side accurately and with high definition. In addition, even if the belt circumference slightly expands or contracts or slips occur between the belt and the pulley, the meshing hole of the belt and the sprocket of the pulley are securely meshed with each other so that accurate transmission can be performed. A bent portion having a minute height is formed outside the peripheral edge.

Further, since the present invention is made of metal, it has a long service life, has no stains due to dust generation, and has extremely high maintainability. It can be used in a vacuum, clean room, high temperature or high humidity environment. Furthermore, since the belt is thin, the diameter of the pulley can be reduced, and the structure of the transmission mechanism itself can be made simple, lightweight, and compact. Therefore, power consumption can be reduced, and energy saving and resource saving can be realized as a high precision device such as a robot arm.

Further, in the metal endless timing belt according to the present invention, since the bent portion having a minute height is formed at least at the front and rear ends along the circumferential direction of the peripheral edge of the engagement hole, Even when an excessive load is applied to the meshing hole when meshing with a sprocket pin (projection) formed on the outer circumference of the pulley, the strength of the peripheral portion of the meshing hole can be improved by the bent portion. Cracks and the like can be reliably prevented from being generated at the periphery of the engagement hole, and the life of the belt can be extended.

According to a second aspect of the present invention, there is provided a metal endless timing belt according to the first aspect, wherein a bent portion having a minute height is formed over the entire periphery of the engagement hole. It is.

Further, according to a third aspect of the present invention, there is provided a method of manufacturing a metal endless timing belt, wherein both ends of a strip-shaped metal plate which can be subjected to plastic working are joined to each other to form a ring-shaped endless belt. A heat treatment step of heat-treating the endless belt, if necessary, a rolling step of thinning and elongating the endless belt to a predetermined thickness by a belt rolling machine, and Along the circumferential direction of the endless belt, a plurality of meshing holes are formed at equal intervals, and a bent portion having a minute height is formed at least at the front and rear ends of the circumferential edge of the meshing hole along the circumferential direction. Forming a metal endless timing belt.

Still further, the invention described in claim 4 is as follows.
A method for producing a metal endless timing belt, wherein a cutting step of forming a ring-shaped endless belt by cutting a cylindrical raw tube made of a metal capable of plastic working into a desired width, and A heat treatment step of heat treating the endless belt,
A rolling step of reducing the thickness of the endless belt to a predetermined thickness and elongating the endless belt by a belt rolling machine, and piercing a plurality of meshing holes at equal intervals along a circumferential direction of the thinned endless belt, And a pressing step of forming a bent portion having a minute height at least at the front and rear ends of the peripheral edge of the meshing hole along the circumferential direction. It is.

Further, the invention as set forth in claim 5 is a method of manufacturing a metal endless timing belt, which comprises reducing the thickness of a cylindrical tube made of metal capable of plastic working to a predetermined thickness and elongating the tube. Thinning step, and, if necessary, a heat treatment step of heat-treating the cylindrical tube before or after or during the thinning step, and cutting the thinned cylindrical tube into a desired width, A cutting step of forming a ring-shaped endless belt, and a plurality of meshing holes are formed at regular intervals along a circumferential direction of the thinned endless belt, and at least along a circumferential direction of a periphery of the meshing hole. And forming a bent portion having a very small height at the front and rear ends of the metal endless timing belt.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 shows a power transmission device to which a metal endless timing belt according to Embodiment 1 of the present invention is applied.
The power transmission device is incorporated in a high-precision device such as an arm portion or an actuator mechanism of an industrial robot, for example, but is not limited to this, and it is needless to say that the power transmission device can be applied to other devices.

In FIG. 1, reference numeral 1 denotes a metal endless timing belt. The metal endless timing belt 1 is wound around a pulley 3 and a pulley 4. The metal endless timing belt 1 is provided with a plurality of meshing holes 2 along its entire length along the circumferential direction. The meshing holes 2 are formed on the outer circumferences of the pulleys 3 and 4 with which the timing belt 1 meshes at equal intervals with sprocket pins 5 and 6 (projections) formed at equal intervals over the entire circumference. I have.

In this embodiment, a bent portion having a minute height is formed at least at the front and rear ends of the periphery of the engagement hole along the circumferential direction.

That is, in this embodiment, FIG.
As shown in (b), the shape of the meshing hole 2 is a circular hole, and a bent portion 7 having a minute height is formed outside the entire peripheral edge of the meshing hole 2. The height h of the bent portion 7 is set to substantially the same size as the plate thickness.

The bent portion 7 does not necessarily need to be provided outside the entire peripheral edge of the meshing hole 2, and as shown in FIG. The bent portion 7 having a minute height may be provided outside only the peripheral edge of the end. In the case of such a configuration, the bent portion 7 is not provided along the circumferential direction of the metal endless timing belt 1 in the outer periphery of the meshing hole 2,
The rigidity of the metal endless timing belt 1 along the circumferential direction is almost the same as that without the bent portion 7.

The shape of the meshing hole 2 is determined by pulleys 3, 4
The shape of the sprocket pins 5 and 6 is determined according to the shape thereof. In the illustrated example, the shape is circular, but may be another shape, for example, an elliptical shape. In the embodiment shown in FIG. 1B, the shape of the sprocket pins 5, 6 is hemispherical, but is not limited to this. FIG. 1 (c)
FIG. 1 (b) shows an enlarged cross-sectional shape between the air holes in FIG. 1 (b). Similarly, FIG. 1 (e) shows an enlarged cross-sectional shape between the air holes in FIG. 1 (d). It is shown.

Embodiment 2 FIG. 2 shows Embodiment 2 of the present invention. A method of manufacturing a metal endless timing belt according to Embodiment 2 is a method of manufacturing a strip-shaped metal plate which can be subjected to plastic working. Joining both ends of each other to form a ring-shaped endless belt, and a heat treatment step of heat-treating the endless belt if necessary, and reducing the thickness of the endless belt to a predetermined thickness by a belt rolling machine. A rolling process for elongating, and a plurality of meshing holes are formed at equal intervals along a circumferential direction of the thinned endless belt, and front and rear end portions of at least a circumferential edge of the meshing hole along the circumferential direction. And a pressing step of forming a bent portion having a minute height.

Next, a method of manufacturing the metal endless timing belt according to the second embodiment will be specifically described.

Step 1 First, as shown in FIG. 2 (a), a strip-shaped plate material 11 made of a metal material capable of being subjected to plastic working as a material of the metal endless timing belt 1 is prepared. As the belt-shaped plate material 11, for example, a stainless steel plate having a plate thickness of about 0.2 to 0.4 mm is used.
Of course, metal materials such as alloys, Al alloys, Cu alloys, and Fe can be used. In the first embodiment, stainless steel plate (SUS) is used as the material of the endless timing belt 1 made of metal.
4 is preferred.

Step 2 Next, the endless belt 12 shown in FIG. 2B is obtained by rolling the strip-shaped plate material 11 into a ring shape, butting both ends thereof, and welding. The type of this welding is, for example, plasma welding, TIG welding or laser beam welding.

Step 3 After heat-treating the endless belt 12 as necessary to improve the workability of the welded portion to at least the same level as that of the base metal, the endless belt 12 is subjected to belt rolling as shown in FIG. The entire circumference is rolled by the mill 13 to reduce the wall thickness to a predetermined thickness and a perimeter, and at the same time, to lengthen the wall. Usually, in a mechanism such as a robot arm, the pulley diameter is about φ15 to φ100 mm.
The thickness of the thinned endless belt 12 is 0.05 to 0.5 mm.
2 mm is desirable.

Step 4 After that, as shown in FIG. 2D, meshing holes 14 are formed at equal intervals along the circumferential direction of the endless belt 12 by, for example, press working. A bent portion 16 having a height substantially equal to the thickness of the sheet is pressed on the outer periphery to produce a metal endless timing belt 16. FIG. 2 (e)
5 shows an enlarged cross-sectional shape of the bent portion 16. Further, as shown in FIG. 2 (f), the bent portion 16 has a diameter slightly larger than the diameter of the meshing holes 14 formed at regular intervals along the circumferential direction of the endless belt 12. It is formed by press working using an upper die 17 and a lower die 18 of a press machine.

It should be noted that the formation of the engagement hole 14 and the bending portion 1
6 may be formed by one press working.

The metal endless timing belt 16 manufactured as described above has no thickness unevenness and has a perfect circle without distortion. This makes it possible to obtain high-precision transmission characteristics free from vibration, backlash, rotation unevenness, and the like due to the high elasticity and high rigidity, which are the characteristics of the metal, and the thinness thereof. Further, the engagement hole 14 having a bent portion 16 having a minute height on the periphery of the hole.
By making the contact hole, the contact strength with the pulley is increased, and it is optimal as a meshing frictional power transmission member capable of transmitting the power of the driving pulley to the driven pulley accurately and precisely without slipping.

The other constructions and operations are the same as those of the first embodiment, and the description is omitted.

Third Embodiment FIG. 3 shows a third embodiment of the present invention. The method of manufacturing a metal endless timing belt according to the third embodiment is a cylindrical endless belt made of a metal which can be subjected to plastic working. Cutting the raw tube to a desired width, a cutting step of forming a ring-shaped endless belt, a heat treatment step of heat-treating the endless belt as necessary, and a step of rolling the endless belt to a predetermined thickness by a belt rolling mill. A rolling step of thinning and lengthening, and a plurality of meshing holes are formed at regular intervals along a circumferential direction of the thinned endless belt, and at least along a circumferential direction of a periphery of the meshing hole. And a pressing step of forming a bent portion having a minute height at the front and rear ends.

Next, a method for manufacturing the metal endless timing belt according to the third embodiment will be specifically described.

Step 1 First, as shown in FIG. 3 (a), a cylindrical raw tube 21 made of a metal material which can be subjected to plastic working, which is a material of the metal endless timing belt 1, is cut into a desired width and a ring is formed. An endless belt 22 is formed. As the cylindrical raw tube 21,
It is desirable to use a seamless pipe that has no seams in the axial direction.

Step 2 Next, after heat-treating the endless belt 12 as necessary to improve the workability of the welded portion to a level equal to or higher than that of the base material, FIG.
As shown in (b), the endless belt 22 is
The entire circumference is rolled by 3 and the thickness is reduced to a predetermined thickness and the circumference at the same time as the elongation.

Step 3 After that, as shown in FIG. 3C, meshing holes 24 are formed at equal intervals along the circumferential direction of the endless belt 22 by, for example, press working. Fig. 2
In the same manner as shown in (e), the bent portion 16 having a height substantially equal to the plate thickness is pressed to manufacture a metal endless timing belt 25.

The metal endless timing belt 25 manufactured in this manner also enables high-precision transmission similarly to that obtained in the second embodiment, and is suitable for an internal driving mechanism such as a robot arm. Become a transmission.

The other configuration and operation are the same as those of the first embodiment, and the description thereof is omitted.

Fourth Embodiment FIG. 4 shows a fourth embodiment of the present invention. A method of manufacturing a metal endless timing belt according to the fourth embodiment is a method of manufacturing a cylindrical endless belt made of a metal which can be subjected to plastic working. A thinning step of thinning and lengthening the tube to a predetermined thickness, a heat treatment step of heat-treating the cylindrical tube before or after or during the thinning step as necessary, A cutting step of cutting the cylindrical raw tube to a desired width to form a ring-shaped endless belt, and a plurality of meshing holes are formed at equal intervals along a circumferential direction of the thinned endless belt. And a pressing step of forming a bent portion having a minute height at least at the front and rear ends of the periphery of the engagement hole along the circumferential direction.

Next, a method for manufacturing a metal endless timing belt according to the fourth embodiment will be specifically described.

Step 1 First, as shown in FIG. 4A, a cylindrical raw tube 31 made of a metal material capable of being subjected to plastic working as a material of the metal endless timing belt 1 is formed. This cylindrical tube 31 is
A flat metal plate (not shown) may be formed by rolling a cylindrical metal plate into a cylindrical shape and welding both ends thereof, or a flat metal plate formed by deep drawing. However, the cylindrical tube 3
1 is preferable to form a flat metal plate by deep drawing since the cylindrical base tube 31 can be made seamless and there is no variation in strength along the circumferential direction.

Here, deep drawing is performed on a flat metal plate (not shown) by pressing using an upper die and a lower die of a deep drawing machine, and a cup-shaped metal plate as shown in FIG. A cylindrical tube 31 is formed. Desirable plate thickness of the cup-shaped cylindrical element tube 31 is 0.1 to 0.15 mm.
However, other plate thicknesses may be used.

Step 2 Next, as shown in FIG. 4B, the cylindrical raw tube 31 is driven to rotate while being fitted to the tip of the rotary base shaft 33 of the rotary drawing machine 32. Then, the external pressure roller 34 is brought into contact with the outer peripheral wall of the rotating cylindrical element tube 31, pressed uniformly, and moved in the direction of arrow B. In this manner, the cylindrical tube 31 is formed by the external pressure roller 34.
Is squeezed to reduce the thickness and length to a predetermined thickness. By this spinning, a thin metal sleeve 35 having a thickness of about 0.03 to 0.15 mm as shown in FIG. 4C is formed.

Step 3 If necessary, before or after or during the thinning step, in order to improve the workability of the cylindrical tube 31, an annealing treatment is performed for the purpose of removing internal stress and the like. Thereafter, the thin metal sleeve 35 having a reduced thickness and lengthened as described above is
As shown in FIG. 4D, a thin metal endless seamless belt 36 is formed by cutting into a ring shape with an arbitrary width.

Step 4 After that, as shown in FIG. 4 (e), meshing holes 37 are formed at equal intervals along the circumferential direction of the endless belt 36 by, for example, press working. Fig. 2
In the same manner as shown in (e), the bent portion 16 having a height substantially equal to the plate thickness is pressed to manufacture a metal endless timing belt 38.

The metal endless timing belt 38 manufactured in this manner also enables high-precision transmission similarly to that obtained in the second embodiment, and is suitable for an internal driving mechanism such as a robot arm. Become a transmission.

Other configurations and operations are the same as those of the first embodiment, and therefore, description thereof will be omitted.

[0051]

As described above, according to the present invention,
For high-speed and precise work operation required for high-precision equipment such as a robot arm, it is suitable as a meshing friction transmission element for a drive transmission mechanism that requires high-precision transmission characteristics. Therefore, maintenance is extremely high due to the long life of parts, and it is used in a vacuum or clean room without gas generation and dust generation.It is also used in high temperature or humid environment because of its high heat and moisture resistance. An endless timing belt made of metal and a method of manufacturing the same can be provided.

Further, when the metal endless timing belt according to the first and second aspects is incorporated in a high precision device such as a robot arm, the bending stress is reduced due to the reduction in the thickness of the belt, so that the pulleys around which the belt is wound are miniaturized. It is also possible to simplify the structure of the drive transmission mechanism, save space, and achieve the miniaturization and weight reduction of the entire device.
With the downsizing of the drive motor, etc., there is also obtained an effect that power costs can be reduced and cost can be significantly reduced as compared with the gear interlocking method.

In the metal endless timing belt according to the first and second aspects, a bent portion having a minute height is formed at least at the front and rear ends of the periphery of the meshing hole along the circumferential direction. The bent portion enhances the strength of the peripheral edge of the engagement hole, can reliably prevent the occurrence of a crack or the like at the peripheral edge of the bent portion, and can prolong the life of the metal endless timing belt. In addition, since the height of the bent portion is very small, the bending rigidity of the metal endless timing belt along the circumferential direction is hardly increased, so that the pulleys around which the belt is wound can be miniaturized. Becomes

Further, according to the third to fifth aspects of the present invention, a metal endless timing belt which is thin, has high fatigue strength, has no unevenness in thickness, and has no distortion in shape can be easily produced in large quantities. In addition, the effect of being able to manufacture at low cost is obtained.

[Brief description of the drawings]

FIGS. 1 (a) to 1 (e) are configuration diagrams each showing a power transmission device to which a metal endless timing belt according to Embodiment 1 of the present invention is applied.

FIGS. 2 (a) to 2 (e) are configuration diagrams respectively showing manufacturing steps of a method for manufacturing a metal endless timing belt according to Embodiment 2 of the present invention.

FIGS. 3 (a) to 3 (c) are configuration diagrams showing manufacturing steps of a method for manufacturing a metal endless belt according to Embodiment 3 of the present invention.

FIGS. 4 (a) to 4 (e) are configuration diagrams respectively showing manufacturing steps of a method for manufacturing a metal endless belt according to Embodiment 4 of the present invention.

[Explanation of Signs] 1: Endless metal timing belt, 2: Mesh hole, 3,
4: pulley, 5, 6: sprocket pins 5, 6, 7: bent portion.

Claims (5)

[Claims] 1. A plurality of meshing holes are formed at equal intervals along a circumferential direction of a thin metal endless belt, and minute meshes are formed at least on front and rear ends of the circumferential edge of the meshing hole along the circumferential direction. A metal endless timing belt, wherein a bent portion having a height is formed. 2. A bent portion having a minute height is formed over the entire periphery of the engagement hole.
The metal endless timing belt described. 3. A method for producing a metal endless timing belt, comprising: a joining step of joining both ends of a band-shaped plate material made of a metal capable of being subjected to plastic working to each other to form a ring-shaped endless belt; A heat treatment step of heat-treating the endless belt; a rolling step of reducing the thickness of the endless belt to a predetermined thickness and elongating the endless belt by a belt rolling machine; And a press step of forming a bent portion having a minute height at least at the front and rear ends of the periphery of the meshing hole along the circumferential direction. A method for producing a metal endless timing belt. 4. A method for producing a metal endless timing belt, comprising: cutting a cylindrical raw tube made of metal capable of plastic working into a desired width to form a ring-shaped endless belt; A heat treatment step of heat-treating the endless belt as necessary; a rolling step of reducing and elongating the endless belt to a predetermined thickness by a belt rolling machine; and a circumferential direction of the thinned endless belt. A press step of forming a plurality of engaging holes at equal intervals, and forming a bent portion having a minute height at least at the front and rear ends of the peripheral edge of the engaging hole along the circumferential direction. A method of manufacturing a metal endless timing belt. 5. A method for producing a metal endless timing belt, comprising: a step of thinning and lengthening a cylindrical tube made of metal capable of being plastically processed to a predetermined thickness; A heat treatment step of heat-treating the cylindrical tube before, during or after the thinning step; and a cutting step of cutting the thinned cylindrical tube into a desired width to form a ring-shaped endless belt. A plurality of interlocking holes are formed at equal intervals along the circumferential direction of the thinned endless belt, and a small height is provided at least at the front and rear end portions of the perimeter of the interlocking hole along the circumferential direction. And a pressing step of forming a bent portion having a bent portion.