JP7554232B2 - Combined hexagonal belt and its manufacturing method - Google Patents

Description

The present invention relates to a combined hexagonal belt in which multiple V-belts capable of double-sided transmission are connected in the width direction, and a method for manufacturing the same.

Friction transmission belts such as V-belts, V-ribbed belts, and flat belts are known as power transmission belts. There are two types of V-belts: raw-edge type (raw-edge V-belts), in which the friction transmission surface is an exposed rubber layer, and wrapped type (wrapped V-belts), in which the friction transmission surface (V-shaped side) is covered with an outer covering fabric. These V-belts are widely and commonly used in general industrial and agricultural machinery.

When a V-belt is used in an application where it is capable of transmitting power by itself, only one V-belt is used. For example, in high-load operating environments that require enormous power transmission while repeatedly rotating forward and backward on multiple shafts, such as large agricultural machinery used on large farms in Europe and the United States, it becomes necessary to use multiple V-belts simultaneously. In other words, it is necessary to wrap multiple V-belts in parallel around the pulleys of the belt transmission mechanism (multiple belts) and rotate them to run.

However, when multiple V-belts are used, tension differences can occur between the parallel V-belts, which can impair stable power transmission. Furthermore, contact between adjacent V-belts can cause the inner and outer periphery of the belt to reverse, resulting in an inverted structure, which can lead to overturning. In addition, the running layout of the belt transmission mechanism in large agricultural machinery in Europe and the United States has a very long axis distance between the pulleys around which the V-belt is wound, which means that the V-belt is prone to vibrating significantly while running, and if the belt lengths are not uniform, there is also a risk of vibration.

Therefore, in an environment where multiple V-belts are run in parallel, a combined belt (combined V-belt) is used, which is configured by connecting multiple annular V-belt sections in the belt width direction, each section having a similar configuration to a V-belt or a configuration corresponding to a V-belt. This combined belt is configured as a V-belt in which multiple belt sections are arranged in parallel and connected together with tie bands (connecting members such as fabric).

As for joined V-belts, for example, Figures 1 and 2 of JP 10-274290 A (Patent Document 1) and Figure 2 of JP 2001-241513 A (Patent Document 2) disclose raw edge joined V-belts, and Figure 1 of JP 04-351350 A (Patent Document 3) and Figure 1 of JP 2020-3061 A (Patent Document 4) disclose wrapped joined V-belts. These joined V-belts can transmit large power through multiple V-shaped protrusions while eliminating the above-mentioned problems that can occur when multiple V-belts are hung on pulleys.

On the other hand, in a belt transmission mechanism requiring multi-axis transmission using such a combined V-belt, power may be transmitted not only by the inner peripheral surface of the belt but also by the outer peripheral surface (back surface) of the belt. In such a transmission mechanism, in order to improve the transmission performance on the outer peripheral surface (back surface), it is preferable to have a V-belt portion with a V-shaped side that can come into contact with a V-pulley on the outer peripheral surface as well. In other words, if the belt is configured as an endless belt with a cross section that has V-shaped sides that can come into contact with a V-pulley on both the inner peripheral surface and the outer peripheral surface and has a roughly hexagonal cross section, it becomes a combined V-belt that can transmit power on both sides with high performance.

As for a V-belt capable of double-sided transmission (double-V belt, commonly known as a hexagonal belt), a single belt (not multiple-connected) is disclosed, for example, in JP 2018-059626 A (Patent Document 5) and JP 2019-032078 A (Patent Document 6). This hexagonal belt has V-shaped side faces that can come into contact with a V-pulley on both the inner and outer circumferential surfaces, and is configured as an endless V-belt with a hexagonal cross section. In addition, a core body is provided between the radially inner rubber layer part and the radially outer rubber layer part of the hexagonal belt.

Japanese Patent Application Publication No. 10-274290 JP 2001-241513 A Japanese Patent Application Publication No. 04-351350 JP 2020-3061 A JP 2018-059626 A JP 2019-032078 A

However, connecting multiple hexagonal belts in the width direction is difficult in terms of manufacturing, and has not yet been put to practical use.

The object of the present invention is therefore to provide a linked hexagonal belt capable of high-performance double-sided transmission and high-capacity transmission, and a method for manufacturing the same.

As a result of intensive research by the inventors to achieve the above object, it was discovered that a connected-type hexagonal belt can be provided that is capable of high-performance double-sided transmission and high-capacity transmission by covering the inner and outer circumferential surfaces of a connected hexagonal belt including multiple hexagonal belt sections with hexagonal cross sections aligned in the belt width direction with a fabric that may contain a cross-linked rubber composition and connecting adjacent hexagonal belt sections with a continuous piece of the fabric, thereby achieving the present invention.

That is, the combined hexagonal belt according to embodiment [1] of the present invention is as follows:
A combined hexagonal belt in which a plurality of hexagonal belt portions each having a hexagonal cross section are arranged in the belt width direction,
the hexagonal belt portion includes a core layer, an inner rubber layer laminated on the inner circumferential surface side of the core layer and having a trapezoidal cross section, an inner outer covering material covering the inner rubber layer and including an inner outer covering fabric, an outer rubber layer laminated on the outer circumferential surface side of the core layer and having a trapezoidal cross section, and an outer outer covering material covering the outer rubber layer and including an outer outer covering fabric,
Adjacent hexagonal belt portions are connected to each other via connecting portions, adjacent inner outer cover fabrics are formed of a continuous inner fabric, and adjacent outer outer cover fabrics are formed of a continuous outer fabric.

Aspect [2] of the present invention is an aspect of aspect [1], in which the connecting portion includes an inner connecting material that forms the inner circumferential surface of the belt and an outer connecting material that forms the outer circumferential surface of the belt, the inner connecting material includes an inner connecting fabric, the outer connecting material includes an outer connecting fabric, the inner fabric is a fabric in which the inner connecting fabric and the inner outer covering fabric are continuous, and the outer fabric is a fabric in which the outer connecting fabric and the outer outer covering fabric are continuous.

Aspect [3] of the present invention is an aspect of aspect [2], in which the connecting portion further contains a cross-linked rubber composition.

Aspect [4] of the present invention is any of aspects [1] to [3] above, in which an inner reinforcing material is interposed between the inner outer covering material and the inner rubber layer, and an outer reinforcing material is interposed between the outer outer covering material and the outer rubber layer.

Aspect [5] of the present invention is any of aspects [1] to [4], in which the inner rubber layer includes a first inner rubber layer laminated on the core layer side, and a second inner rubber layer having a lower rubber hardness than the first inner rubber layer and laminated on the inner circumferential side of the belt.

The present invention also includes, as aspect [6], a method for producing a combined hexagonal belt according to any one of the aspects [1] to [5], which includes a cross-linking molding step of cross-linking a combined hexagonal belt precursor placed in a press mold by heating and pressurizing it.

Aspect [7] of the present invention is an aspect of the manufacturing method of aspect [6], in which the connecting portion contains a cross-linked rubber composition, and in the cross-linking molding step, cross-linking molding of the hexagonal belt portion and cross-linking molding of the connecting portion are performed simultaneously.

Aspect [8] of the present invention is the manufacturing method of aspect [7], wherein the press mold is a combination of an inner press mold having an inner groove portion corresponding to the inner shape of the combined hexagonal belt and an outer press mold having an outer groove portion corresponding to the outer shape of the combined hexagonal belt,
The bonded hexagonal belt precursor includes an inner fabric precursor for forming an inner fabric, an outer fabric precursor for forming an outer fabric, and a hexagonal belt portion precursor including an uncrosslinked rubber composition,
In the crosslinking molding process, the inner fabric precursor is arranged along the inner groove portion, the hexagonal belt portion precursor is laminated onto the inner fabric precursor, the outer fabric precursor is arranged along the hexagonal belt portion precursor, and then the outer groove portion is brought into contact with the outer fabric precursor, and the combined hexagonal belt precursor is sandwiched between the inner press mold and the outer press mold.

Aspect [9] of the present invention is an aspect in which the manufacturing method of aspect [8] is a manufacturing method of a bonded hexagonal belt including an inner reinforcing material and an outer reinforcing material, the hexagonal belt portion precursor is a combination of an inner hexagonal belt portion precursor and an outer hexagonal belt portion precursor, and in the crosslinking molding process, the inner hexagonal belt portion precursor is laminated on the inner fabric precursor, and then the outer hexagonal belt portion precursor is laminated.

Aspect [10] of the present invention is the manufacturing method of aspect [9], further comprising a hexagonal belt portion precursor preparation step as a pre-step of the cross-linking molding step,
The hexagonal belt portion precursor manufacturing step includes a step of manufacturing an inner hexagonal belt portion precursor and a step of manufacturing an outer hexagonal belt portion,
a step of preparing the inner hexagonal belt portion precursor, comprising: laminating a core layer precursor for forming a core layer on a thin outer rubber layer precursor for forming a part of the outer rubber layer; laminating an inner rubber layer precursor for forming an inner rubber layer on the core layer precursor; and then cutting a side surface of the inner rubber layer precursor;
In this embodiment, the step of producing the outer hexagonal belt portion precursor is a step of cutting a side surface of a thick outer rubber layer precursor for forming the remaining portion of the outer rubber layer.

In the present invention, in a joined hexagonal belt including multiple hexagonal belt parts with hexagonal cross sections aligned in the belt width direction, the inner and outer circumferential surfaces of the belt are each covered with a fabric that may contain a cross-linked rubber composition, and adjacent hexagonal belt parts are connected to each other by a continuous piece of fabric, providing a joined type hexagonal belt that allows high-performance double-sided transmission and high-capacity transmission. Furthermore, although it was difficult to manufacture multiple hexagonal belts in the width direction, the present invention has succeeded in easily manufacturing a joined hexagonal belt with the above characteristics by using a specific manufacturing method.

FIG. 1 is a schematic, partially cutaway perspective view showing an example of a coupled hexagonal belt according to the present disclosure. FIG. 2 is a schematic cross-sectional view for explaining the hexagonal belt portion and the connecting portion in FIG. FIG. 3 is a schematic partial cross-sectional perspective view showing another example of a coupled hexagonal belt according to the present disclosure. FIG. 4 is a schematic cross-sectional view showing an example of a coupled hexagonal belt according to the present disclosure, and an enlarged view of a connecting portion in the cross-sectional view. FIG. 5 is a cross-sectional view of a hexagonal belt portion of the combined hexagonal belt of FIG. FIG. 6 is a cross-sectional view of the hexagonal belt portion of FIG. 5, in which the inner rubber layer and the outer rubber layer have a two-layer structure. FIG. 7 is a cross-sectional view of a hexagonal belt portion of the combined hexagonal belt of FIG. FIG. 8 is a cross-sectional view of the hexagonal belt portion of FIG. 7, in which the inner rubber layer and the outer rubber layer have a two-layer structure. FIG. 9 is a schematic diagram showing a cutting step for cutting the hexagonal belt portion precursor into rings. FIG. 10 is a schematic diagram showing a skiving process in which a cut hexagonal belt portion precursor is cut into a V-shape. FIG. 11 is a schematic diagram showing a cutting step of cutting the inner hexagonal belt portion precursor into rings. FIG. 12 is a schematic diagram showing the steps of producing an inner hexagonal belt portion precursor having a reinforcing material. FIG. 13 is a schematic diagram showing the steps of producing an outer hexagonal belt portion precursor having a reinforcing material. FIG. 14 is a schematic overall view showing the steps of connecting and cross-linking the hexagonal belt portion precursor. FIG. 15 is a cross-sectional view taken along line AB of FIG. 16 is a schematic perspective view of the protrusion of the inner press mold of FIG. 15 as viewed in the direction from C to D. FIG. FIG. 17 is a schematic diagram showing a process of aligning an inner fabric precursor with an inner groove of an inner press mold, and then fitting a part of a hexagonal belt portion precursor into the inner groove with the inner fabric precursor aligned. FIG. 18 is a cross-sectional view showing a state in which the hexagonal belt portion precursor is fitted into the inner groove of the inner press mold via the inner fabric precursor. FIG. 19 is a cross-sectional view showing a state in which an outer fabric precursor is disposed along the hexagonal belt portion precursor of FIG. 18 using a jig. FIG. 20 is a cross-sectional view showing a state in which the outer groove of the outer press mold is brought into contact with the outer fabric precursor of FIG. 19, and the combined hexagonal belt precursor is sandwiched between the inner press mold and the outer press mold. FIG. 21 is a cross-sectional view showing a state in which a part of a hexagonal belt portion precursor is fitted into an inner groove of an inner press mold via an inner fabric precursor. FIG. 22 is a cross-sectional view showing a state in which the remaining part of the hexagonal belt portion precursor is laminated on a part of the hexagonal belt portion precursor of FIG. 21. FIG. 23 is a cross-sectional view showing a state in which an outer fabric precursor is disposed along the hexagonal belt portion precursor of FIG. 22 using a jig. FIG. 24 is a cross-sectional view showing a state in which the outer groove portion of the outer press mold is brought into contact with the outer fabric precursor of FIG. 23, and the combined hexagonal belt precursor is sandwiched between the inner press mold and the outer press mold. FIG. 25 is a cross-sectional view showing the state in which the cross-linked hexagonal belt precursor obtained after removing the press mold is cut. FIG. 26 is a diagram showing a multi-axis layout which is an arrangement for a belt running test of the embodiment.

<Combined hexagonal belt>
The combined hexagonal belt of the present invention is a friction drive belt capable of transmitting power on both the outer and inner sides, and for example, a fabric covering the surface of a plurality of hexagonal belts (a plurality of hexagonal belt parts aligned in the belt width direction) aligned in parallel with their longitudinal directions is divided into an outer circumferential side and an inner circumferential side, and each of them is connected in the width direction while also serving as a tie band (connecting member). That is, the fabric has a function of covering the surface of the hexagonal belt parts and a function of connecting adjacent hexagonal belt parts, and by the fabric having such a structure, it is possible to successfully provide a robust combined hexagonal belt, which can transmit power on both sides with high performance and transmit a high capacity.

The coupled hexagonal belt of the present invention will be described in detail below, with reference to the attached drawings as necessary. In the following description, the same reference numerals may be used to designate elements (or members) that are identical or have the same functions.

An example of the combined hexagonal belt of the present invention is shown in Figures 1 and 2. As shown in Figures 1 and 2, this combined hexagonal belt 1 has two hexagonal belt parts arranged in parallel with their tops facing each other and spaced apart in the belt width direction, and the outer periphery (surface) of these two hexagonal belt parts is covered with an inner outer covering material 4 and an outer outer covering material 6. The inner outer covering material 4 and the outer outer covering material 6 are formed of a fabric containing a crosslinked rubber composition.

In the joined hexagonal belt 1, adjacent hexagonal belt parts are connected by a connecting part including an inner connecting material 7 and an outer connecting material 8. The inner connecting material 7 and the outer connecting material 8 are also formed of a fabric containing a crosslinked rubber composition. The fabric of the inner connecting material 7 is continuous with the fabric of the inner outer covering material 4, forming an inner fabric integrated with the inner circumferential surface of the belt. The fabric of the outer connecting material 8 is also continuous with the fabric of the outer outer covering material 6, forming an outer fabric integrated with the outer circumferential surface of the belt. Furthermore, in addition to the fabric, the inner connecting material 7 and the outer connecting material 8 contain a crosslinked rubber composition that has permeated the fabric in advance and a crosslinked rubber composition that has flowed in from the hexagonal belt part and crosslinked, and are integrated with the fabric together with the crosslinked rubber composition present between the inner connecting material 7 and the outer connecting material 8. Therefore, the connecting part is a strong composite in which the fabric and the crosslinked rubber composition are integrated.

The inside of the hexagonal belt portion, which is covered with an inner outer covering material 4 and an outer outer covering material 6, has a structure in which, from the inner circumference side of the belt, an inner rubber layer 3, a core layer 2 including a core wire 2a, and an outer rubber layer 5 are layered.

The combined hexagonal belt 10 shown in FIG. 3 is a combined hexagonal belt of the same form as the combined hexagonal belt of FIG. 1, except that a reinforcing material is interposed between the inner and outer covering materials and the inner and outer rubber layers. That is, in this combined hexagonal belt, the surfaces of the inner rubber layer 13, the core layer 12 including the core wire 12a, and the outer rubber layer 15 are covered with a reinforcing material 11, and the inner and outer covering materials 14 and 16 are laminated on the reinforcing material 11, and the fabrics of the inner and outer covering materials 14 and 16 are continuous with the fabrics of the inner connecting material 17 and the outer connecting material 18, respectively. By interposing the reinforcing material 11, the combined hexagonal belt 10 has a reinforced friction transmission surface, improving durability (abrasion resistance).

The structure and size of the combined hexagonal belt of the present disclosure will be described in more detail using Figure 4. The combined hexagonal belt 1 in Figure 4 is a schematic cross-sectional view of a combined hexagonal belt without any reinforcing material, as in Figure 1, but H in the figure indicates the thickness of the hexagonal belt part (height in the belt thickness direction), W in the figure indicates the width of the hexagonal belt part, and P in the figure indicates the pitch (distance between the centers of adjacent hexagonal belt parts). Furthermore, in the enlarged view of the connecting part, d in the figure indicates the thickness of the connecting part (minimum thickness), and e in the figure indicates the width of the connecting part (spacing between adjacent hexagonal belt parts). Regarding these sizes, the dimensions of AA type, BB type, and CC type, which are representative examples of combined hexagonal belts, are shown in Table 1.

In the combined hexagonal belt of the present invention, the thickness H (average thickness) of the hexagonal belt portion (combined hexagonal belt) is, for example, 5 to 30 mm, preferably 7 to 20 mm, and more preferably 10 to 18 mm.

The width W (average width) of the hexagonal belt portion is, for example, 7 to 40 mm, preferably 10 to 30 mm, and more preferably 12 to 25 mm.

The pitch P (average distance) of the hexagonal belt portion is, for example, 5 to 50 mm, preferably 8 to 40 mm, and more preferably 10 to 30 mm.

The connected hexagonal belt of the present invention is sufficient if multiple hexagonal belt portions are aligned parallel to each other in the width direction, and is not limited to being aligned at intervals as shown in Figures 1 to 4, but may be aligned without any intervals. In an embodiment in which the hexagonal belt portions are aligned without any intervals, the connecting portions are the boundaries between adjacent inner outer covering materials and the boundaries between adjacent outer outer covering materials. Of these, from the standpoint of productivity, etc., it is preferable to line up adjacent connected hexagonal belt portions with intervals.

The thickness d (average thickness) of the connecting portion is, for example, 0.5 to 5 mm, preferably 0.8 to 4 mm, and more preferably 1 to 3 mm. If the thickness d of the connecting portion is too thin, durability may decrease, and conversely, if it is too thick, power transmission may decrease.

When the hexagonal belt parts are spaced apart, the width e of the connecting part may be 0.5 mm or more, for example, 0.5 to 8 mm, preferably 1 to 5 mm, and more preferably 1.5 to 4 mm. If the width e of the connecting part is too small, there is a risk of reduced productivity.

In this example, a layer formed of a crosslinked rubber composition is present between the inner and outer connecting members that form the connecting portion. The inner and outer connecting members are not limited to fabrics containing a crosslinked rubber composition, i.e., fabrics in which the crosslinked rubber composition has permeated between the internal fibers, as shown in Figures 1 and 2, and may be fabrics that do not contain a crosslinked rubber composition, but fabrics containing a crosslinked rubber composition are preferred in terms of improving the mechanical properties of the connecting members. As shown in Figure 4, in the connecting portion, a layer formed of a crosslinked rubber composition is usually present between the inner and outer connecting members. The layer formed of the crosslinked rubber composition may be an integral structure as shown in Figure 4, or may be a structure in which the inner and outer connecting members are separated by contact at the center of the connecting portion.

The number of hexagonal belt parts is not limited to 2-3 as shown in Figures 1-4, but may be any number, for example 2-10, preferably 2-8, and more preferably 2-6.

[Hexagonal belt part]
The shape (external shape) of the hexagonal belt part is not particularly limited as long as it is the same as the shape of a conventional hexagonal belt, that is, it is endless and the cross-sectional shape perpendicular to the belt longitudinal direction is approximately hexagonal. The structure (internal structure) of the hexagonal belt part is also not particularly limited as long as it is the same as the structure of a conventional hexagonal belt, and includes a core layer (bonded rubber layer) including a core body, an outer rubber layer laminated on the outer periphery side of the core layer, and an inner rubber layer laminated on the inner periphery side of the core layer, and is a structure equivalent to a wrapped V-belt part in which the entire surface of the belt including the friction transmission surface is covered with an outer covering cloth (cover cloth) over the entire circumference. In such a hexagonal belt part, both left and right side surfaces of the V-shaped cross section facing the core layer (both side surfaces of the cross-section trapezoidal shape) form the friction transmission surface. Examples of the structure of the hexagonal belt part include the structures shown in Figures 5 to 8.

Figure 5 is a cross-sectional view of the hexagonal belt portion of the joined hexagonal belt of Figure 1. The hexagonal belt portion shown in Figure 5 is formed of a core layer 2 formed of adhesive rubber 2b including a core (core wire) 2a, an inner rubber layer 3 laminated on the inner peripheral surface side of the core layer 2 and having a trapezoidal cross section, an inner outer covering material 4 covering the inner rubber layer 3 and including an inner outer covering fabric, an outer rubber layer 5 laminated on the outer peripheral surface side of the core layer 2 and having a trapezoidal cross section, and an outer outer covering material 6 covering the outer rubber layer 5 and including an outer outer covering fabric. That is, from the inner periphery of the belt, the belt is made up of an endless belt body in which an inner rubber layer 3, a core layer 2, and an outer rubber layer 5 are layered in this order, and an inner outer covering material 4 and an outer outer covering material 6 that cover the periphery of the belt body over the entire length in the circumferential direction of the belt. The core layer 2, the inner rubber layer 3, and the inner outer covering material 4 form an inner hexagonal belt portion, and the outer rubber layer 5 and the outer outer covering material form an outer hexagonal belt portion.

Figure 6 is a cross-sectional view of the hexagonal belt part of Figure 5, in which the inner rubber layer and the outer rubber layer have a two-layer structure. That is, in the hexagonal belt part of Figure 5, the inner rubber layer and the outer rubber layer have a single-layer structure, whereas in the hexagonal belt part of Figure 6, the inner rubber layer has a two-layer structure of a first inner rubber layer 3a that is laminated on the inner peripheral surface side of the core layer 2 and has a trapezoidal cross section, and a second inner rubber layer 3b that is laminated on the inner rubber layer 3a and has a trapezoidal cross section, and the outer rubber layer has a two-layer structure of a first outer rubber layer 5a that is laminated on the outer peripheral surface side of the core layer 2 and has a trapezoidal cross section, and a second outer rubber layer 5b that is laminated on the outer rubber layer 5a and has a trapezoidal cross section. Except for this, the hexagonal belt part of Figure 5 is the same as the hexagonal belt part of Figure 5. By adjusting the inner rubber layer and the outer rubber layer to a two-layer structure with different rubber hardness, the lateral pressure resistance of the belt can be improved.

Figure 7 is a cross-sectional view of the hexagonal belt portion of the combined hexagonal belt of Figure 3. The hexagonal belt portion shown in Figure 7 is formed of a core layer 12 formed of adhesive rubber 12b including a core (core wire) 12a, a reinforcing material 11a covering the side surface of the core layer 12, an inner rubber layer 13 laminated on the inner peripheral surface side of the core layer 12 and having a trapezoidal cross section, an inner reinforcing material 11b covering the inner rubber layer 13, an inner outer covering material 14 covering the inner reinforcing material 11b and including an inner outer covering fabric, an outer rubber layer 15 laminated on the outer peripheral surface side of the core layer 12 and having a trapezoidal cross section, an outer reinforcing material 11c covering the outer rubber layer 15, and an outer outer covering material 16 covering the outer reinforcing material 11c and including an outer outer covering fabric. That is, from the inner periphery of the belt, the endless belt body is made up of an inner rubber layer 13 covered with an inner reinforcing material 11b, a core layer 12 in which a core 12a is embedded in an adhesive rubber 12b, and an outer rubber layer 15 covered with an outer reinforcing material 11c, which are laminated in this order, and an inner outer covering material 14 and an outer outer covering material 16 that cover the periphery of the belt body over the entire circumferential length of the belt.

Figure 8 is a cross-sectional view of the hexagonal belt part of Figure 7, in which the inner rubber layer and the outer rubber layer have a two-layer structure. That is, while the inner rubber layer and the outer rubber layer in the hexagonal belt part of Figure 7 have a single-layer structure, the hexagonal belt part of Figure 8 has a two-layer structure of the inner rubber layer, which is laminated on the inner peripheral surface side of the core layer 12 and has a trapezoidal cross section, and the second inner rubber layer 13b, which is laminated on the inner rubber layer 13a and has a trapezoidal cross section, and the outer rubber layer is laminated on the outer peripheral surface side of the core layer 12 and has a trapezoidal cross section, and the hexagonal belt part of Figure 8 is the same as the hexagonal belt part of Figure 7, except that it has a two-layer structure of the first outer rubber layer 15a, which is laminated on the outer rubber layer 15a and has a trapezoidal cross section.

In these examples, the core is a cord (twisted cord) arranged at a predetermined interval in the belt width direction. The core layer is formed of a crosslinked rubber composition (bonded rubber layer) in which the core is embedded, but the core layer may be formed only of a core disposed at the interface between the inner rubber layer and the outer rubber layer. In this application, when the core layer is formed only of a core, the core disposed at intervals in the belt body is referred to as the core layer, and such a core layer includes not only a form in which the core is disposed at the interface between the inner rubber layer and the outer rubber layer, but also a form in which a part or all of the core disposed at the interface between the inner rubber layer and the outer rubber layer is embedded in the inner rubber layer or the outer rubber layer during the manufacturing process.

(Inner and outer rubber layers)
The inner rubber layer is a rubber layer disposed radially inward (inner periphery of the belt) of the core layer in the annular hexagonal belt portion, and the outer rubber layer is a rubber layer disposed radially outward (outer periphery of the belt) of the core layer. The inner rubber layer and the outer rubber layer each extend in the circumferential direction (have the same length as the hexagonal belt portion) and have a substantially trapezoidal cross section perpendicular to the belt longitudinal direction.

The outer and inner rubber layers constituting each hexagonal belt section may be a single layer (one layer) as shown in Figures 5 and 7, or may have a layered structure including two types of rubber layers as shown in Figures 6 and 8, with the rubber hardness and strength of each layer adjusted.

Among these, from the viewpoint of achieving both lateral pressure resistance and flexibility, it is preferable that the hexagonal belt portion has an inner rubber layer having a laminated structure of two or more layers including a first inner rubber layer laminated on the core layer side and a second inner rubber layer having a lower rubber hardness than the first inner rubber layer and laminated on the inner circumference side of the belt. It is also preferable that the hexagonal belt portion has an outer rubber layer having a laminated structure of two or more layers including a first outer rubber layer laminated on the core layer side and a second outer rubber layer having a lower rubber hardness than the first outer rubber layer and laminated on the outer circumference side of the belt. It is not necessary for the inner rubber layer and the outer rubber layer to have the same laminated structure, and it is sufficient to combine these embodiments as necessary.

Considering the balance between lateral pressure resistance and productivity, it is particularly preferable that the inner rubber layer has a two-layer structure (first inner rubber layer and second inner rubber layer) and the outer rubber layer has a single-layer structure or a two-layer structure (first outer rubber layer and second outer rubber layer).

In the case of a single-layer structure, the rubber hardness Hs of the inner rubber layer and the outer rubber layer can each be selected from a range of, for example, about 60 to 90°, and is preferably 72 to 80°, more preferably 73 to 78°, even more preferably 74 to 78°, and most preferably 75 to 77°. If the rubber hardness is too low, there is a risk of reduced resistance to lateral pressure, and conversely, if it is too high, there is a risk of reduced flexibility.

In this application, the rubber hardness of each rubber layer refers to the value Hs (Type A) measured using a Type A durometer in accordance with the spring type durometer hardness test specified in JIS K6253 (2012) (Vulcanized rubber and thermoplastic rubber - Determination of hardness), and may be referred to simply as rubber hardness. In more detail, it can be measured by the method described in the examples below.

The tensile strength of the inner rubber layer and the outer rubber layer in the belt width direction is, for example, 12 to 20 MPa, preferably 13 to 18 MPa, and more preferably 14 to 17 MPa. If the tensile strength is too small, there is a risk of reduced resistance to lateral pressure, and conversely, if it is too large, there is a risk of reduced flexibility.

In this application, the tensile strength of each rubber layer is measured by a method conforming to JIS K6251 (2017), and the tensile strength T of each rubber layer is used as an index value of the tensile strength. In detail, the tensile strength can be measured by the method described in the examples below.

When using a two-layer structure to improve lateral pressure resistance, it is preferable that the first inner rubber layer and the first outer rubber layer arranged on the core layer side are high hardness rubber layers. The rubber hardness Hs of the first inner rubber layer and the first outer rubber layer can each be selected from a range of, for example, about 80 to 100°, and is preferably 85 to 95°, more preferably 87 to 94°, even more preferably 90 to 93°, and most preferably 92 to 93°. If the rubber hardness is too low, there is a risk of reduced lateral pressure resistance, and conversely, if it is too high, there is a risk of reduced fit with the pulley groove and reduced flexibility.

On the other hand, the rubber hardness Hs of the second inner rubber layer and the second outer rubber layer may be approximately the same as the rubber hardness Hs shown in the case of the single layer structure described above.

Furthermore, the difference in rubber hardness Hs between the first inner rubber layer and the second inner rubber layer (rubber hardness of the first inner rubber layer - rubber hardness of the second inner rubber layer) may be, for example, 1° or more (particularly 5° or more), and is preferably 5 to 30° (e.g. 7 to 27°), more preferably 10 to 25° (e.g. 12 to 20°), even more preferably 14 to 20° (e.g. 15 to 19°), and most preferably 14 to 17° (particularly 15 to 17°). If the difference in rubber hardness between the second inner rubber layer and the first inner rubber layer is too small, there is a risk of reduced flexibility.

The difference in rubber hardness Hs between the first outer rubber layer and the second outer rubber layer can be selected from the same range as the difference in rubber hardness Hs between the first inner rubber layer and the second inner rubber layer, including the preferred range.

The tensile strength of the first inner rubber layer in the belt width direction is, for example, 25 to 50 MPa, preferably 25 to 40 MPa, more preferably 26 to 35 MPa, and most preferably 28 to 32 MPa. If the tensile strength is too small, there is a risk of reduced resistance to lateral pressure, and conversely, if it is too large, there is a risk of reduced flexibility. The tensile strength of the second inner rubber layer may be approximately the same as the tensile strength shown in the case of the single layer structure described above.

The tensile strengths of the first outer rubber layer and the second outer rubber layer can be selected from the same ranges, including the preferred ranges, as the tensile strengths of the first inner rubber layer and the second inner rubber layer, respectively.

The average thickness of the entire inner rubber layer and the average thickness of the entire outer rubber layer are, for example, 1 to 12 mm, preferably 2 to 10 mm, more preferably 2.5 to 9 mm, and even more preferably 3 to 8 mm.

The average thickness of the first inner rubber layer can be selected from the range of, for example, about 95 to 30% of the average thickness of the entire inner rubber layer, and is preferably 90 to 50%, more preferably 85 to 55%, even more preferably 80 to 60%, and most preferably 75 to 70%. This ratio may be the ratio when the inner rubber layer consists of only the first inner rubber layer and the second inner rubber layer (two-layer structure). If the thickness ratio of the first inner rubber layer is too small, there is a risk that the lateral pressure resistance will decrease, and conversely, if it is too large, there is a risk that the flexibility will decrease.

The ratio of the first outer rubber layer to the average thickness of the entire outer rubber layer can be selected from the same range as the ratio of the first inner rubber layer to the average thickness of the entire inner rubber layer, including the preferred range.

In addition to the first and second inner rubber layers, the inner rubber layer may further include other rubber layers having different rubber hardness. The other rubber layers may be a single layer or multiple layers. The other rubber layers may be laminated on either the upper or lower surfaces of the first inner rubber layer or the lower surface of the second inner rubber layer. The average thickness of the other rubber layers may be, for example, 30% or less, preferably 10% or less, and more preferably 5% or less, of the average thickness of the entire inner rubber layer. That is, it is preferable that the inner rubber layer includes the first and second inner rubber layers as main layers, and the average thickness of the total of the first and second inner rubber layers may be, for example, 70% or more, preferably 90% or more, and more preferably 95% or more, of the average thickness of the entire inner rubber layer. It is particularly preferable that the inner rubber layer consists of only the first and second inner rubber layers.

The outer rubber layer may further include other rubber layers having different rubber hardness in addition to the first outer rubber layer and the second outer rubber layer. The other rubber layers may be a single layer or multiple layers. The other rubber layers may be laminated on either the upper or lower surfaces of the first outer rubber layer or the lower surface of the second outer rubber layer. The average thickness of the other rubber layers may be, for example, 30% or less, preferably 10% or less, and more preferably 5% or less, of the average thickness of the entire outer rubber layer. That is, it is preferable that the outer rubber layer includes the first outer rubber layer alone as a main layer, or includes a combination of the first outer rubber layer and the second outer rubber layer as a main layer, and the average thickness of the total of the first outer rubber layer and the second outer rubber layer may be, for example, 70% or more, preferably 90% or more, and more preferably 95% or more, of the average thickness of the entire outer rubber layer. It is particularly preferable that the outer rubber layer consists of only the first outer rubber layer alone, or only the combination of the first inner rubber layer and the second inner rubber layer.

The inner rubber layer and the outer rubber layer may each be formed of a crosslinked rubber composition that is commonly used as a rubber composition for hexagonal belts. The crosslinked rubber composition may be a crosslinked rubber composition containing a rubber component, and by appropriately adjusting the composition of the composition, it is possible to adjust the rubber hardness of each layer constituting the inner rubber layer and the outer rubber layer, particularly the rubber hardness of the first inner rubber layer and the second inner rubber layer, and the rubber hardness of the first outer rubber layer and the second outer rubber layer. The method of adjusting the rubber hardness, etc. is not particularly limited, and may be adjusted by changing the composition and/or type of the components constituting the composition, and from the standpoint of simplicity, etc., it is preferable to adjust by changing the proportion and/or type of short fibers and fillers.

(A) Rubber Component The rubber component contained in the crosslinked rubber composition of the inner rubber layer and the outer rubber layer can be selected from known vulcanizable or crosslinkable rubbers and/or elastomers, such as diene rubbers [natural rubber, isoprene rubber, butadiene rubber, chloroprene rubber (CR), styrene butadiene rubber (SBR), vinylpyridine-styrene-butadiene copolymer rubber, acrylonitrile butadiene rubber (nitrile rubber); hydrogenated products of the diene rubbers such as hydrogenated nitrile rubber (including a mixed polymer of hydrogenated nitrile rubber and an unsaturated carboxylic acid metal salt)], olefin rubbers [e.g. ethylene-α-olefin rubbers (ethylene-α-olefin elastomers), polyoctenylene rubbers, ethylene-vinyl acetate copolymer rubbers, chlorosulfonated polyethylene rubbers, alkylated chlorosulfonated polyethylene rubbers], epichlorohydrin rubbers, acrylic rubbers, silicone rubbers, urethane rubbers, fluororubbers, etc. These rubber components can be used alone or in combination of two or more.

Among these, ethylene-α-olefin elastomers [ethylene-α-olefin rubbers such as ethylene-propylene copolymer (EPM) and ethylene-propylene-diene terpolymer (EPDM)] and chloroprene rubber are widely used because crosslinking agents and crosslinking accelerators diffuse easily, and chloroprene rubber and EPDM are preferred because they provide an excellent balance of mechanical strength, weather resistance, heat resistance, cold resistance, oil resistance, and adhesiveness, particularly when used in high-load environments. Furthermore, chloroprene rubber is particularly preferred because it has excellent abrasion resistance in addition to the above properties. The chloroprene rubber may be either sulfur-modified or non-sulfur-modified.

When the rubber component contains chloroprene rubber, the proportion of chloroprene rubber in the rubber component may be, for example, 50% by mass or more (particularly about 80 to 100% by mass), with 100% by mass (only chloroprene rubber) being particularly preferred.

(B) Short Fibers The crosslinked rubber composition may further contain short fibers in addition to the rubber component. Examples of short fibers include polyolefin fibers (e.g., polyethylene fibers, polypropylene fibers, etc.), polyamide fibers (e.g., polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers, aramid fibers, etc.), polyalkylene arylate fibers [e.g., _C2-4 alkylene _C8-14 arylate fibers such as polyethylene terephthalate (PET) fibers, polytrimethylene terephthalate (PTT) fibers, polybutylene terephthalate (PBT) fibers, polyethylene naphthalate (PEN) fibers, etc.], vinylon fibers, polyvinyl alcohol fibers, polyparaphenylene benzobisoxazole (PBO) fibers, and other synthetic fibers; natural fibers such as cotton, hemp, and wool; and inorganic fibers such as carbon fibers. These short fibers can be used alone or in combination of two or more.

Among these short fibers, synthetic fibers and natural fibers, particularly synthetic fibers such as polyester fibers (polyalkylene arylate fibers) whose main constituent unit is a _C2-4 alkylene _C8-14 arylate such as ethylene terephthalate and ethylene-2,6-naphthalate, polyamide fibers (aramid fibers, etc.), and inorganic fibers such as carbon fibers are widely used, and among them, fibers that are rigid and have high strength and modulus, such as polyester fibers (particularly polyethylene terephthalate fibers and polyethylene naphthalate fibers) and polyamide fibers (particularly aramid fibers), are preferred. Aramid fibers also have high abrasion resistance. Therefore, the short fibers preferably contain at least fully aromatic polyamide fibers such as aramid fibers. The aramid fibers may be commercially available products such as those under the trade names "Conex", "Nomex", "Kevlar", "Technora", and "Twaron (registered trademark)".

The average fiber diameter of the short fibers is, for example, 2 μm or more, preferably 2 to 100 μm, more preferably 3 to 50 μm (e.g., 5 to 50 μm), more preferably 7 to 40 μm, and most preferably 10 to 30 μm. The average length of the short fibers is, for example, 1 to 20 mm, preferably 1.5 to 10 mm, more preferably 2 to 5 mm, and more preferably 2.5 to 4 mm.

From the viewpoint of dispersibility and adhesion of the short fibers in the crosslinked rubber composition, the short fibers may be subjected to an adhesion treatment (or surface treatment) by a conventional method. Examples of the surface treatment method include a method of treating with a treatment liquid containing a conventional surface treatment agent. Examples of the surface treatment agent include an RFL liquid containing resorcinol (R), formaldehyde (F), and rubber or latex (L) [for example, an RFL liquid containing a condensate (RF condensate) formed by resorcinol (R) and formaldehyde (F), and the rubber or latex is, for example, a vinylpyridine-styrene-butadiene copolymer rubber], an epoxy compound, a polyisocyanate compound, a silane coupling agent, a crosslinked rubber composition (for example, a crosslinked rubber composition containing a wet-process white carbon containing hydrated silica as the main component, which contains surface silanol groups and is advantageous for increasing the chemical bonding strength with rubber), and the like. These surface treatment agents may be used alone or in combination, and the short fibers may be treated multiple times with the same or different surface treatment agents.

The short fibers may be oriented in the width direction of the belt and embedded in the inner and outer rubber layers to suppress compressive deformation of the belt due to pressure from the pulleys.

The proportion of short fibers can be selected from a range of about 50 parts by mass or less per 100 parts by mass of the rubber component, for example 30 parts by mass or less, and preferably 10 to 30 parts by mass. If the proportion of short fibers is too low, the rubber hardness of the inner rubber layer and the outer rubber layer may decrease, and conversely, if the proportion is too high, the rubber hardness may be too high, resulting in reduced flexibility.

When the outer rubber layer and the inner rubber layer have a two-layer structure, the proportion of short fibers in the first inner rubber layer and the first outer rubber layer is, for example, 5 to 50 parts by mass, preferably 10 to 30 parts by mass, more preferably 15 to 25 parts by mass, and more preferably 18 to 22 parts by mass, per 100 parts by mass of the rubber component (first rubber component). The proportion of short fibers in the second inner rubber layer and the second outer rubber layer is, for example, 30 parts by mass or less, preferably 20 parts by mass or less, and more preferably 10 parts by mass or less, per 100 parts by mass of the rubber component (second rubber component).

(C) Filler The crosslinked rubber composition may further contain a filler in addition to the rubber component. Examples of the filler include carbon black, silica, clay, calcium carbonate, talc, and mica. The filler often contains a reinforcing filler, and such a reinforcing filler may be carbon black, reinforcing silica, or the like. Note that the reinforcing property of silica is usually smaller than that of carbon black. These fillers may be used alone or in combination of two or more kinds. In the present disclosure, in order to improve lateral pressure resistance, it is preferable to contain a reinforcing filler, and it is particularly preferable to contain carbon black.

The average particle size (number average primary particle size) of carbon black is, for example, 5 to 200 nm, preferably 10 to 150 nm, and more preferably 15 to 100 nm. In terms of high reinforcing effect, the particle size may be small, for example, 5 to 38 nm, preferably 10 to 35 nm, and more preferably 15 to 30 nm. Examples of small particle size carbon black include SAF, ISAF-HM, ISAF-LM, HAF-LS, HAF, and HAF-HS. These carbon blacks can be used alone or in combination of two or more kinds.

The proportion of the filler (particularly carbon black) is, for example, 10 to 100 parts by mass, preferably 12 to 80 parts by mass, more preferably 15 to 70 parts by mass, and even more preferably 20 to 60 parts by mass, per 100 parts by mass of the rubber component.

When the outer rubber layer and the inner rubber layer have a two-layer structure, the ratio of the filler (particularly, carbon black) in the first inner rubber layer and the first outer rubber layer is, for example, 10 to 100 parts by mass, preferably 20 to 80 parts by mass, more preferably 30 to 70 parts by mass, and more preferably 40 to 60 parts by mass, per 100 parts by mass of the rubber component (first rubber component). The ratio of the filler (particularly, carbon black) in the second inner rubber layer and the second outer rubber layer is, for example, 5 to 80 parts by mass, preferably 10 to 60 parts by mass, more preferably 15 to 50 parts by mass, and more preferably 20 to 40 parts by mass, per 100 parts by mass of the rubber component (second rubber component).

The proportion of carbon black may be, for example, 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and may be 100% by mass, based on the total filler. If the proportion of carbon black based on the total filler is too low, the rubber hardness of the inner rubber layer and the outer rubber layer may decrease.

(D) Other Additives The crosslinked rubber composition may contain, as necessary, a crosslinking agent (or vulcanizing agent), a co-crosslinking agent (crosslinking assistant), a crosslinking accelerator, a crosslinking retarder, a metal oxide (calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, aluminum oxide, etc.), a softener (oils such as paraffin oil and naphthenic oil), a processing agent or processing assistant (for example, fatty acid such as stearic acid, fatty acid metal salt such as metal stearate, fatty acid amide such as stearic acid amide, wax, paraffin, etc.), an adhesion improver [for example, resorcinol-formaldehyde cocondensate (RF condensate), amino resin (condensate of nitrogen-containing cyclic compound and formaldehyde, for example, melamine such as hexamethylol melamine, hexaalkoxymethyl melamine (hexamethoxymethyl melamine, hexabutoxymethyl melamine, etc.)], resin, urea resin such as methylol urea, benzoguanamine resin such as methylol benzoguanamine resin, etc.), co-condensates thereof (resorcin-melamine-formaldehyde co-condensates, etc.)], anti-aging agents (antioxidants, heat anti-aging agents, flex crack inhibitors, anti-ozonants, etc.), plasticizers [aliphatic carboxylic acid ester plasticizers (adipate ester plasticizers, sebacate ester plasticizers, etc.), aromatic carboxylic acid ester plasticizers (phthalate ester plasticizers, trimellitate ester plasticizers, etc.), oxycarboxylic acid ester plasticizers, phosphate ester plasticizers, ether plasticizers, ether ester plasticizers, etc.], colorants, tackifiers, lubricants, coupling agents (silane coupling agents, etc.), stabilizers (ultraviolet ray absorbers, heat stabilizers, etc.), flame retardants, antistatic agents, etc. may be included. The metal oxide may act as a crosslinking agent. In the adhesion improver, the resorcin-formaldehyde cocondensate and the amino resin may be an initial condensation product (prepolymer) of resorcin and/or a nitrogen-containing cyclic compound (such as melamine) with formaldehyde.

As the crosslinking agent, conventional components can be used depending on the type of rubber component. For example, metal oxides (magnesium oxide, zinc oxide, lead oxide, etc.), organic peroxides (diacyl peroxide, peroxy ester, dialkyl peroxide, etc.), sulfur-based crosslinking agents, etc. can be exemplified. As the sulfur-based crosslinking agent, for example, powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, sulfur chlorides (sulfur monochloride, sulfur dichloride, etc.) can be exemplified. These crosslinking agents can be used alone or in combination of two or more. When the rubber component is chloroprene rubber, metal oxides (magnesium oxide, zinc oxide, etc.) can be used as the crosslinking agent. Note that metal oxides can be used in combination with other crosslinking agents (sulfur-based crosslinking agents, etc.), and metal oxides and/or sulfur-based crosslinking agents can be used alone or in combination with a crosslinking accelerator.

The proportion of the crosslinking agent can be selected from a range of, for example, about 1 to 20 parts by mass per 100 parts by mass of the rubber component, calculated as solid content, depending on the type of crosslinking agent and rubber component. For example, the proportion of the metal oxide as the crosslinking agent is, for example, 1 to 20 parts by mass, preferably 3 to 17 parts by mass, more preferably 5 to 15 parts by mass, and more preferably 7 to 13 parts by mass per 100 parts by mass of the rubber component. When a metal oxide as the crosslinking agent is combined with a sulfur-based crosslinking agent, the proportion of the sulfur-based crosslinking agent is, for example, 0.1 to 50 parts by mass, preferably 1 to 30 parts by mass, and more preferably about 3 to 10 parts by mass per 100 parts by mass of the metal oxide. The proportion of the organic peroxide is, for example, 1 to 8 parts by mass, preferably 1.5 to 5 parts by mass, and more preferably 2 to 4.5 parts by mass per 100 parts by mass of the rubber component.

Examples of the co-crosslinking agent (crosslinking aid or co-vulcanizing agent) include known crosslinking aids, such as polyfunctional (iso)cyanurates [e.g., triallyl isocyanurate (TAIC), triallyl cyanurate (TAC), etc.], polydienes (e.g., 1,2-polybutadiene, etc.), metal salts of unsaturated carboxylic acids [e.g., (meth)acrylic acid polyvalent metal salts such as zinc (meth)acrylate and magnesium (meth)acrylate], oximes (e.g., quinone dioxime, etc.), guanidines (e.g., diphenyl guanidine, etc.), polyfunctional (meth)acrylates [e.g., alkane diol di(meth)acrylate such as ethylene glycol di(meth)acrylate and butane diol di(meth)acrylate, trimethylol propane tri(meth)acrylate, pentaerythritol tetraacetate, etc.], and the like. alkane polyol poly(meth)acrylates such as cyclohexyl (meth)acrylate, bismaleimides (aliphatic bismaleimides such as alkylene bismaleimides such as N,N'-1,2-ethylene dimaleimide, N,N'-hexamethylene bismaleimide, and 1,6'-bismaleimide-(2,2,4-trimethyl)cyclohexane; arene bismaleimides or aromatic bismaleimides such as N,N'-m-phenylene dimaleimide, 4-methyl-1,3-phenylene dimaleimide, 4,4'-diphenylmethane dimaleimide, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, 4,4'-diphenylether dimaleimide, 4,4'-diphenylsulfone dimaleimide, and 1,3-bis(3-maleimidophenoxy)benzene). These crosslinking aids can be used alone or in combination of two or more. Among these cross-linking aids, polyfunctional (iso)cyanurates, polyfunctional (meth)acrylates, and bismaleimides (arene bismaleimides such as N,N'-m-phenylenedimaleimide or aromatic bismaleimides) are preferred, and bismaleimides are often used. The addition of a cross-linking aid (e.g., bismaleimides) can increase the degree of cross-linking and prevent adhesion wear, etc.

The ratio of the co-crosslinking agent (crosslinking assistant) such as bismaleimides is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 8 parts by mass, more preferably 1 to 5 parts by mass, and even more preferably 2 to 4 parts by mass, per 100 parts by mass of the rubber component, calculated as solid content.

Examples of crosslinking accelerators (vulcanization accelerators) include thiuram accelerators [e.g., tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), dipentamethylenethiuram tetrasulfide (DPTT), N,N'-dimethyl-N,N'-diphenylthiuram disulfide, etc.], thiazole accelerators [e.g., 2-mercaptobenzothiazole, submersible 2-mercaptobenzothiazole, etc.], Lead salts, 2-mercaptothiazoline, dibenzothiazyl disulfide, 2-(4'-morpholinodithio)benzothiazole, etc.], sulfenamide accelerators [e.g., N-cyclohexyl-2-benzothiazylsulfenamide (CBS), N,N'-dicyclohexyl-2-benzothiazylsulfenamide, etc.], guanidines (diphenylguanidine, di-o-tolylguanidine, etc.), urea or thiourea accelerators (e.g., ethylenethiourea, etc.), dithiocarbamates, xanthogenates, etc. These crosslinking accelerators can be used alone or in combination of two or more. Of these crosslinking accelerators, TMTD, DPTT, CBS, etc. are commonly used.

The proportion of the crosslinking accelerator, calculated as solid content, may be 15 parts by mass or less (e.g., 0 to 15 parts by mass) per 100 parts by mass of the rubber component, for example, 0.1 to 10 parts by mass, preferably 0.2 to 5 parts by mass, more preferably 0.3 to 3 parts by mass, and even more preferably 0.5 to 1.5 parts by mass.

The proportion of the softener (oils such as naphthenic oils) may be 30 parts by mass or less (e.g., 0 to 30 parts by mass) per 100 parts by mass of the rubber component, calculated as solid content, and is, for example, 1 to 30 parts by mass, preferably 3 to 20 parts by mass, and more preferably 3 to 10 parts by mass.

When the outer rubber layer and the inner rubber layer have a two-layer structure, the ratio of the softener in the first inner rubber layer and the first outer rubber layer is, for example, 1 to 30 parts by mass, preferably 3 to 20 parts by mass, and more preferably 3 to 10 parts by mass, per 100 parts by mass of the rubber component (first rubber component). In the second inner rubber layer and the second outer rubber layer, the ratio of the softener is, for example, 20 parts by mass or less, preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component (second rubber component).

The proportion of the processing agent or processing aid (such as stearic acid) may be 10 parts by mass or less (e.g., 0 to 10 parts by mass) per 100 parts by mass of the rubber component, calculated as solid content, and is, for example, 0.1 to 5 parts by mass, preferably 0.5 to 3 parts by mass, and more preferably 1 to 3 parts by mass.

The proportion of the antioxidant, calculated as solid content, is, for example, 0.5 to 15 parts by mass, preferably 1 to 10 parts by mass, more preferably 2.5 to 7.5 parts by mass, and even more preferably 3 to 7 parts by mass, per 100 parts by mass of the rubber component.

The proportion of the plasticizer, calculated as solid content, may be 30 parts by mass or less (e.g., 0 to 30 parts by mass) per 100 parts by mass of the rubber component, for example, 0.5 to 20 parts by mass, preferably 1 to 10 parts by mass, and more preferably 3 to 7 parts by mass.

When the outer rubber layer and the inner rubber layer have a two-layer structure, the ratio of the plasticizer in the first inner rubber layer and the first outer rubber layer is, for example, 20 parts by mass or less, preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component (first rubber component). In the second inner rubber layer and the second outer rubber layer, the ratio of the plasticizer is, for example, 1 to 30 parts by mass, preferably 3 to 20 parts by mass, and more preferably 3 to 10 parts by mass, per 100 parts by mass of the rubber component (second rubber component).

(Core layer)
The core layer may contain a core, and may be a core layer formed only of a core as described above, but is preferably a core layer (adhesive rubber layer) formed of a crosslinked rubber composition in which a core is embedded, from the viewpoint of suppressing interlayer peeling and improving belt durability. A core layer formed of a crosslinked rubber composition in which a core is embedded is usually called an adhesive rubber layer, and an adhesive rubber layer in which a core may be embedded in a layer formed of a crosslinked rubber composition containing a rubber component is preferably interposed between the inner rubber layer and the outer rubber layer to bond the inner rubber layer and the outer rubber layer, and the core is preferably embedded in the adhesive rubber layer.

The average thickness of the core layer (particularly the adhesive rubber layer) is, for example, 0.2 to 5 mm, preferably 0.3 to 4 mm, even more preferably 0.5 to 3.5 mm, even more preferably 0.8 to 3 mm, and most preferably 1 to 2.5 mm.

(A) Crosslinked Rubber Composition The rubber hardness Hs of the crosslinked rubber composition forming the core layer (particularly the adhesive rubber layer) is, for example, 72 to 80°, preferably 73 to 78°, and more preferably 75 to 77°. If the rubber hardness is too low, there is a risk that the lateral pressure resistance will decrease, and conversely, if the rubber hardness is too high, the crosslinked rubber composition around the core will become rigid, making it difficult for the core to bend, and there is a risk that heat deterioration (cracks) of the core layer, bending fatigue of the core, and the like will occur, causing the core to peel off.

The tensile strength of the crosslinked rubber composition forming the core layer (particularly the adhesive rubber layer) is, for example, 12 to 20 MPa, preferably 13 to 18 MPa, and more preferably 14 to 17 MPa in the belt width direction. If the tensile strength is too small, there is a risk of reduced resistance to lateral pressure, and conversely, if it is too large, there is a risk of reduced flexibility.

As the rubber component (A1) constituting the crosslinked rubber composition forming the core layer, the rubber components exemplified as the rubber component (A) of the inner rubber layer and the outer rubber layer can be used, and preferred embodiments can be selected from the preferred embodiments of the rubber component (A).

The crosslinked rubber composition of the core layer may further contain a filler (A2) in addition to the rubber component (A1). As the filler (A2), the fillers exemplified as the filler (C) of the inner rubber layer and the outer rubber layer can be used. Among the above fillers, carbon black and reinforcing silica are preferred, and a combination of carbon black and reinforcing silica is particularly preferred.

In the core layer, the proportion of the filler (A2) is, for example, 1 to 100 parts by mass, preferably 10 to 80 parts by mass, more preferably 30 to 70 parts by mass, and even more preferably 40 to 60 parts by mass, per 100 parts by mass of the rubber component (A1). When carbon black and reinforcing silica are combined, the proportion of the reinforcing silica is, for example, 10 to 200 parts by mass, preferably 30 to 100 parts by mass, and even more preferably 50 to 80 parts by mass, per 100 parts by mass of the carbon black.

The crosslinked rubber composition of the core layer may further contain other additives (A3) in addition to the rubber component (A1). As the other additives (A3), the additives exemplified as the other additives (D) of the inner rubber layer and the outer rubber layer can be used, and crosslinking agents, crosslinking accelerators, processing agents or processing aids, plasticizers, anti-aging agents, etc. can be preferably used. The proportion of the other additives (A3) can be selected from the same range as that of the additives (D) of the inner rubber layer and the outer rubber layer, including the preferred range.

(B) Core The core contained in the core layer is not particularly limited, but is usually a core wire (twisted cord) arranged at a predetermined interval in the belt width direction. The core wire is arranged extending in the longitudinal direction of the belt, and may be arranged parallel to the longitudinal direction of the belt at a predetermined pitch, but from the viewpoint of productivity, it is usually arranged in a spiral shape extending parallel to the longitudinal direction of the belt at a predetermined pitch. When arranged in a spiral shape, the angle of the core wire with respect to the longitudinal direction of the belt may be, for example, 5° or less, and from the viewpoint of belt running property, the closer to 0° the more preferable. In addition, the pitch or interval (particularly the spinning pitch of the core wire), which is the distance between the centers of adjacent cores, is preferably set in the range of 1.0 to 3.6 mm, more preferably set in the range of 1.2 to 3 mm, and even more preferably set in the range of 1.4 to 2.4 mm.

When the core is embedded in the adhesive rubber that constitutes the core layer, it is sufficient that a portion of the core is embedded in the adhesive rubber. From the viewpoint of improving durability, it is preferable that the core is not exposed on the surface of the core layer (the entire core is completely embedded in the adhesive rubber). A core wire is preferable as the core.

Examples of fibers constituting the core wire include synthetic fibers such as polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers [aliphatic polyamide fibers (nylon fibers) such as polyamide 6 fibers, polyamide 66 fibers, and polyamide 46 fibers, and aramid fibers, etc.], polyester fibers (polyalkylene arylate fibers) [poly _C2-4 alkylene- _C8-14 arylate fibers such as polyethylene terephthalate (PET) fibers and polyethylene naphthalate (PEN) fibers, etc.], vinylon fibers, polyvinyl alcohol fibers, and polyparaphenylene benzobisoxazole (PBO) fibers; natural fibers such as cotton, hemp, and wool; and inorganic fibers such as carbon fibers. These fibers can be used alone or in combination of two or more.

Among these fibers, from the viewpoint of high modulus, polyester fibers (polyalkylene arylate fibers) having a _C2-4 alkylene- _C8-14 arylate, such as ethylene terephthalate or ethylene-2,6-naphthalate, as a main constituent unit, synthetic fibers such as polyamide fibers (aramid fibers, etc.), and inorganic fibers such as carbon fibers are generally used, with polyester fibers (particularly polyethylene terephthalate fibers and polyethylene naphthalate fibers) and polyamide fibers (particularly aramid fibers) being preferred.

The fiber may be in the form of a multifilament yarn. The fineness of the multifilament yarn may be, for example, 2000 to 10000 denier (particularly 4000 to 8000 denier). The multifilament yarn may contain, for example, about 100 to 5000 filaments, preferably 500 to 4000 filaments, and more preferably 1000 to 3000 filaments.

The core wire can usually be a twisted cord (e.g., double twist, single twist, Lang twist, etc.) using multifilament yarn. The average diameter of the core wire (fiber diameter of the twisted cord) can be, for example, 0.5 to 3 mm, preferably 0.6 to 2.5 mm, more preferably 0.7 to 2 mm, and even more preferably 1.1 to 2 mm.

When the core wire is embedded in the adhesive rubber, it may be surface-treated to improve adhesion to the crosslinked rubber composition that forms the adhesive rubber. Examples of the surface treatment agent include the surface treatment agents exemplified as the surface treatment agents for the short fibers (B) of the inner rubber layer and the outer rubber layer. The surface treatment agents may be used alone or in combination of two or more types, and the core wire may be treated sequentially multiple times with the same or different surface treatment agents. It is preferable to adhesively treat the core wire with at least RFL liquid.

(Inner and outer covering materials)
The inner and outer covering materials include an inner and outer covering fabric, respectively. The inner and outer covering fabrics (cover fabrics) are each formed of a conventional fabric (A). Examples of the fabric (A) include woven fabrics, knitted fabrics (weft knitted fabrics, warp knitted fabrics), nonwoven fabrics, and other fabric materials. Among these, woven fabrics woven in the form of plain weave, twill weave, satin weave, and other forms, woven fabrics woven at a wide angle of more than 90° and less than 120°, and knitted fabrics, etc. are preferred, and woven fabrics commonly used as cover fabrics for transmission belts for general industry and agricultural machines [plain weave fabrics in which the warp and weft cross at a right angle, and plain weave fabrics (wide-angle canvas) in which the warp and weft cross at a wide angle of more than 90° and less than 120°] are particularly preferred. Furthermore, in applications requiring durability, wide-angle canvas may be used.

Fibers constituting the fabric (A) include, for example, synthetic fibers such as polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers (polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers, aramid fibers, etc.), polyester fibers (polyalkylene arylate fibers, etc.), vinyl alcohol fibers (polyvinyl alcohol fibers, ethylene-vinyl alcohol copolymer fibers, vinylon fibers, etc.), and polyparaphenylene benzobisoxazole (PBO) fibers; cellulose fibers (cellulose fibers, cellulose derivative fibers, etc.), natural fibers such as wool; and inorganic fibers such as carbon fibers. These fibers may be used alone as a single yarn, or may be a blended yarn in which two or more types are combined.

Of these fibers, blended yarns of polyester and cellulosic fibers are preferred because of their excellent mechanical properties and economical efficiency.

The polyester fiber may be a polyalkylene arylate fiber, such as a polyC _2-4 alkylene-C _8-14 arylate fiber, for example, a polyethylene terephthalate (PET) fiber or a polyethylene naphthalate (PEN) fiber.

Cellulosic fibers include cellulose fibers (cellulose fibers derived from plants, animals, bacteria, etc.) and fibers of cellulose derivatives. Examples of cellulose fibers include cellulose fibers (pulp fibers) derived from natural plants such as wood pulp (coniferous and broadleaf pulp, etc.), bamboo fiber, sugarcane fiber, seed hair fibers (cotton fibers (cotton linters), kapok, etc.), ginseng bark fibers (hemp, paper mulberry, Mitsumata, etc.), and leaf fibers (Manila hemp, New Zealand hemp, etc.); cellulose fibers derived from animals such as sea squirt cellulose; bacterial cellulose fibers; and algae cellulose. Examples of cellulose derivative fibers include cellulose ester fibers and regenerated cellulose fibers (rayon, cupra, lyocell, etc.).

The mass ratio of polyester fibers to cellulosic fibers is, for example, the former/latter = 90/10 to 10/90, preferably 80/20 to 20/80, more preferably 70/30 to 30/70, and even more preferably 60/40 to 40/60.

The average fineness of the fibers constituting the fabric (A) is, for example, 5 to 30 count, preferably 10 to 25 count, and more preferably 10 to 20 count.

The fabric (raw fabric) (A) has a basis weight of, for example, 100 to 500 g/m ² , preferably 200 to 400 g/m ² , and more preferably 250 to 350 g/m ² .

When the fabric (raw fabric) (A) is a woven fabric, the thread density of the fabric (density of warp and weft threads) is, for example, 60 to 100 threads/50 mm, preferably 70 to 90 threads/50 mm, and more preferably 75 to 85 threads/50 mm.

The inner and outer covering fabrics may each be a single layer or multiple layers (e.g., 2 to 5 layers, preferably 2 to 4 layers, and more preferably 2 to 3 layers), but from the standpoint of productivity, a single layer (1 ply) or two layers (2 plies) is preferred.

In order to improve adhesion to the belt body (inner rubber layer and outer rubber layer) or the reinforcing material described later, the inner and outer covering materials may further contain a crosslinked rubber composition as a rubber component in addition to the inner and outer covering fabrics, respectively. The rubber component may permeate the inner and outer covering materials, may permeate near the surface, or may be attached to the surface. Examples of methods for manufacturing the inner and outer covering materials containing a crosslinked rubber composition include a method of soaking the inner and outer covering fabrics in a rubber paste in which the rubber composition is dissolved in a solvent, and a method of rubbing a solid rubber composition into the inner and outer covering fabrics. The rubber component may be attached to at least one surface of the inner and outer covering fabrics, and is preferably attached to at least the surface that comes into contact with the belt body.

The rubber components exemplified as rubber component (A) for the inner rubber layer and the outer rubber layer can be used as the rubber component (a) constituting the crosslinked rubber composition contained in each of the inner and outer covering materials (hereinafter referred to as the "crosslinked rubber composition of the covering material"). The preferred embodiment can also be selected from the preferred embodiments for the rubber component (A).

The crosslinked rubber composition of the covering material may further contain a filler (b) in addition to the rubber component (a). As the filler (b), the fillers exemplified as the filler (C) of the inner rubber layer and the outer rubber layer can be used, and the preferred embodiment and the proportion of carbon black in the filler can be selected from the embodiment and proportion of the filler (C).

In the crosslinked rubber composition of the covering material, the proportion of filler (b) (particularly carbon black) is, for example, 5 to 80 parts by mass, preferably 10 to 75 parts by mass, more preferably 30 to 70 parts by mass, and even more preferably 40 to 60 parts by mass, per 100 parts by mass of rubber component (a).

The crosslinked rubber composition of the outer covering material may further contain a plasticizer (c) in addition to the rubber component (a). As the plasticizer (c), the plasticizers exemplified as the plasticizers for the inner rubber layer and the outer rubber layer can be used. Of the plasticizers, ether ester plasticizers are preferred. The proportion of the plasticizer (c) is, for example, 3 to 50 parts by mass, preferably 5 to 40 parts by mass, more preferably 10 to 30 parts by mass, and even more preferably 15 to 25 parts by mass, per 100 parts by mass of the rubber component (a).

The crosslinked rubber composition of the outer covering material may further contain other additives (d) in addition to the rubber component (a). As the other additives (d), the additives exemplified as other additives (D) for the inner rubber layer and the outer rubber layer can be used, and crosslinking agents, crosslinking accelerators, processing agents or processing aids, anti-aging agents, etc. can be preferably used. The proportion of the other additives (d) can be selected from the same range as the additives (D) for the inner rubber layer and the outer rubber layer, including the preferred range.

In the inner covering material, the proportion of the crosslinked rubber composition is, for example, 10 to 200 parts by mass, preferably 50 to 100 parts by mass, and more preferably 70 to 90 parts by mass, per 100 parts by mass of the inner covering fabric. The proportion of the crosslinked rubber composition in the outer covering material can also be selected from the proportion in the inner covering material, including the preferred range.

The average thickness of the inner and outer covering materials (the average thickness of each layer in the case of multiple layers) is, for example, 0.4 to 2 mm, preferably 0.5 to 1.4 mm, and more preferably 0.6 to 1.2 mm. If the covering fabric is too thin, there is a risk of reduced abrasion resistance, and if it is too thick, there is a risk of reduced flex resistance of the belt.

(Inner and outer reinforcements)
The inner reinforcing material and the outer reinforcing material each include an inner reinforcing fabric and an outer reinforcing fabric. The inner reinforcing fabric and the outer reinforcing fabric are each formed of a conventional fabric (A1). As the fabric (A1), the fabrics exemplified as the fabric (A) of the inner outer covering material and the outer outer covering material can be used, and can be selected from the same aspects as the fabric (A), including preferred aspects.

The inner reinforcing material may further contain a cross-linked rubber composition in addition to the inner reinforcing fabric to improve adhesion between the inner rubber layer and the inner outer covering material, and the outer reinforcing material may further contain a cross-linked rubber composition to improve adhesion between the outer rubber layer and the outer covering material.

The crosslinked rubber composition contained in each of the inner reinforcing material and the outer reinforcing material can be the same as the crosslinked rubber composition of the outer covering material, and preferred embodiments can be selected from the preferred embodiments of the crosslinked rubber composition of the outer covering material.

The average thickness of the inner reinforcement and the outer reinforcement (the average thickness of each layer in the case of multiple layers) is, for example, 0.4 to 2 mm, preferably 0.5 to 1.4 mm, and more preferably 0.6 to 1.2 mm. If the reinforcing fabric is too thin, the reinforcing effect of the friction transmission surface may be reduced, and if it is too thick, the flex resistance of the belt may be reduced.

One of the inner reinforcement and the outer reinforcement may cover the side of the core layer, and it is preferable that the inner reinforcement cover the side of the core layer.

[Connection part]
The connecting portion connects adjacent hexagonal belt portions to each other. In an embodiment in which the hexagonal belt portions are arranged without any gaps, the connecting portion is a boundary between adjacent inner outer covering materials and a boundary between adjacent outer covering materials. On the other hand, in an embodiment in which the hexagonal belt portions are arranged with gaps, the connecting portion includes an inner connecting member that forms the inner circumferential surface of the belt and an outer connecting member that forms the outer circumferential surface of the belt.

The inner connecting material and the outer connecting material each include an inner connecting fabric and an outer connecting fabric. The inner connecting fabric and the outer connecting fabric are each formed of a conventional fabric (A2). The fabric (A2) may be any of the fabrics exemplified as the fabric (A) of the inner outer covering material and the outer outer covering material, and may be selected from the embodiments of the fabric (A), including preferred embodiments.

The inner connecting material and the outer connecting material may further contain a cross-linked rubber composition in addition to the inner connecting fabric and the outer connecting fabric, respectively, in order to improve adhesion with the cross-linked rubber composition. The cross-linked rubber composition of the outer covering material can be used as the cross-linked rubber composition contained in the inner connecting material and the outer connecting material, respectively, and preferred embodiments can be selected from the preferred embodiments of the cross-linked rubber composition of the outer covering material.

The average thickness of the inner connecting material and the outer connecting material (the average thickness of each layer in the case of multiple layers) is, for example, 0.4 to 2 mm, preferably 0.5 to 1.4 mm, and more preferably 0.6 to 1.2 mm. If the connecting material is too thin, the connecting effect may be reduced, and if it is too thick, the flex resistance of the belt may be reduced.

The connecting portion may include a rubber layer formed of a cross-linked rubber composition between the inner connecting material and the outer connecting material. The cross-linked rubber composition forming the rubber layer may be a cross-linked rubber composition from which a part of the rubber composition for forming the inner rubber layer, the core layer, and the outer rubber layer (particularly the rubber composition of the core layer) has flowed out. Therefore, the cross-linked rubber composition of the rubber layer may be the same as the cross-linked rubber composition of the core layer.

Manufacturing method of joined hexagonal belt
The combined hexagonal belt of the present disclosure is obtained by a manufacturing method including a crosslinking molding step of heating and pressurizing a combined hexagonal belt precursor disposed in a press mold to crosslink it. The manufacturing method of the present disclosure can manufacture a combined hexagonal belt through the crosslinking molding step, and does not require connecting each hexagonal belt after crosslinking in advance. Therefore, the manufacturing method of the present disclosure can easily manufacture a combined hexagonal belt, which is difficult to manufacture, with high production efficiency. In detail, in the manufacturing method of the present disclosure, the combined hexagonal belt precursor disposed in a press mold is heated and pressurized, so that the crosslinking reaction of the uncrosslinked rubber component contained in the combined hexagonal belt precursor progresses, and the constituent materials of the combined hexagonal belt precursor are integrated (adhered) and molded into the desired shape at the same time. In particular, when the connecting portion contains a crosslinked rubber composition, the crosslinking molding of the hexagonal belt portion and the crosslinking molding of the connecting portion can be performed simultaneously in the crosslinking molding step. That is, in the manufacturing method of the present disclosure, the following three steps 1 to 3 are performed simultaneously in the crosslinking molding step, so that the crosslinking molding of each hexagonal belt portion and the connection of a plurality of hexagonal belt portions can be completed in one step.

Step 1 for crosslinking the uncrosslinked rubber component contained in the bonded hexagonal belt precursor
Step 2: bonding and integrating the materials constituting the bonded hexagonal belt precursor (by a crosslinking reaction of the uncrosslinked rubber components contained in each material)
Step 3: forming the outer shape of the joined hexagonal belt into a predetermined shape (including forming the predetermined joint structure).

The press mold is preferably a combination of an inner press mold having an inner groove that corresponds to the inner shape of the joined hexagonal belt, and an outer press mold having an outer groove that corresponds to the outer shape of the joined hexagonal belt.

The bonded hexagonal belt precursor preferably includes an inner fabric precursor for forming the inner fabric, an outer fabric precursor for forming the outer fabric, and a hexagonal belt portion precursor containing an uncrosslinked rubber composition.

When the combined hexagonal belt precursor of the present disclosure includes the hexagonal belt portion precursor, the manufacturing method of the combined hexagonal belt of the present disclosure may further include a hexagonal belt portion precursor manufacturing process as a process preceding the cross-linking molding process.

[Hexagonal belt part precursor manufacturing process]
In the hexagonal belt portion precursor preparation step, the hexagonal belt portion precursor (uncrosslinked hexagonal belt portion) may be prepared by a method conforming to a conventional method used in the manufacture of wrapped V-belts, etc. Examples of the method for preparing the hexagonal belt portion precursor include a method conforming to the method for producing a V-belt described in WO2015/104778.

In particular, in the manufacturing method disclosed herein, the method for producing the hexagonal belt portion may be a method for producing a precursor of the entire hexagonal belt portion, which is a laminate of an inner rubber layer precursor (inner rubber layer sheet) for forming the inner rubber layer, a core layer precursor for forming the core layer, and an outer rubber layer precursor (outer rubber layer sheet) for forming the outer rubber layer (integrated manufacturing method), or a method for producing a precursor in which the hexagonal belt portion is divided (split-type manufacturing method), that is, a method for separately producing the inner hexagonal belt portion precursor and the outer hexagonal belt portion precursor. Of these, in the embodiment not including a reinforcing material, the integrated manufacturing method is preferred from the viewpoint of simplicity, and in the embodiment including a reinforcing material, the split-type manufacturing method is preferred from the viewpoint of easily forming a strong connection portion.

(No reinforcement material included)
In an embodiment not including a reinforcing material, a method (preparation process) for producing a precursor of the entire hexagonal belt portion may be a method (process) for laminating a core layer precursor for forming a core layer on an outer rubber layer precursor for forming an outer rubber layer, laminating an inner rubber layer precursor for forming an inner rubber layer on the core layer precursor, and then cutting the sides of the inner rubber layer precursor and the outer rubber layer precursor.

The specific manufacturing process will be explained with reference to the drawings. In the embodiment that does not include a reinforcing material, as shown in FIG. 9, the uncrosslinked outer rubber layer sheet 25 obtained by rolling is set on a mantle, and the uncrosslinked adhesive rubber layer sheet 22b is wound around the outer periphery of the outer rubber layer sheet 25. Then, the core body 22a is wound around the outer periphery of the wound adhesive rubber layer sheet 22b, and the uncrosslinked adhesive rubber layer sheet 22b and the inner rubber layer sheet 23 are wound around the outer periphery of the wound core body 22a in order in a winding process, a cutting process in which the obtained annular laminate (uncrosslinked sleeve) 20 is cut (sliced) in a state in which it is arranged around the outer periphery of the mantle, and a skiving process in which the cut annular laminate 20a is hung on a pair of pulleys and cut into a V shape while rotating as shown in FIG. 10 (a process of removing the excess part 23a of the inner rubber layer sheet 23 and the excess part 25a of the outer rubber layer sheet) is performed to obtain a hexagonal belt portion precursor (uncrosslinked hexagonal belt portion).

(Aspects including reinforcing material)
In an embodiment including a reinforcing material, the method (production process) for producing the inner hexagonal belt portion precursor may be a method (process) for laminating a core layer precursor for forming a core layer on a thin outer rubber layer precursor for forming a part of the outer rubber layer, laminating an inner rubber layer precursor for forming an inner rubber layer on the core layer precursor, and then cutting the side of the inner rubber layer precursor.

The method (production process) for producing the outer hexagonal belt portion precursor may be a process for cutting the side of the thick outer rubber layer precursor for forming the remaining portion of the outer rubber layer.

Specific manufacturing steps will be described with reference to the drawings. In an embodiment that does not include a reinforcing material, as shown in FIG. 11, a release sheet (such as a nylon film) 36a is set on the mantle, and an uncrosslinked thin outer rubber layer sheet (a thin sheet that forms part of the outer rubber layer) 35a and an uncrosslinked adhesive rubber layer sheet 32b are wound around the outer periphery of the release sheet 36a, and then a core body 32a is wound around the outer periphery of the wrapped adhesive rubber layer sheet 32b, and an uncrosslinked adhesive rubber layer sheet 32b and an inner rubber layer sheet 33 are wound around the outer periphery of the wrapped core body 32a in a winding step, and the resulting annular laminate (uncrosslinked sleeve) 30 is cut (sliced) while placed on the outer periphery of the mantle, to obtain an annular laminate 30a.

As shown in FIG. 12, the cut annular laminate 30a is placed over a pair of pulleys and cut into a V shape while rotating in a skiving process (a process for removing excess portion 33a) to obtain a skived annular laminate. At this point, the resulting annular laminate includes a release sheet 36a.

Next, the reinforcing material precursor 31a is covered over the entire surface of the skived annular laminate over the entire length. As a method for covering the reinforcing material precursor 31a, known methods such as those described in JP-A-10-323915 and JP-A-2016-87885 can be used. The number of reinforcing material precursors to be covered can be selected as needed.

Furthermore, the reinforcing material precursor on the rear side of the precursor is peeled off (removed) from the annular laminate covered with the reinforcing material precursor 31a. There are no limitations to this method, but from the viewpoint of productivity, a preferred method is to perform a trim cut (reverse skive) on both ends on the rear side (remove the end 37a to remove the release sheet), peel off the laminate 37b of the reinforcing material precursor and the release sheet (upper reinforcing material peeling), and peel off the reinforcing material precursor together with the release sheet. This process results in an inner hexagonal belt portion precursor (uncrosslinked inner hexagonal belt portion).

As shown in FIG. 13, the outer hexagonal belt part precursor (uncrosslinked outer hexagonal belt part) can be obtained through a winding process in which a release sheet (such as a nylon film) 36b and an uncrosslinked thick outer rubber layer sheet 35b are wound around the mantle in this order, a cutting process in which the obtained annular laminate is cut (sliced into rings) on the mantle, a skiving process in which the cut annular laminate is placed over a pair of pulleys and cut into a V shape while rotating (a process for removing excess parts 35c), a covering process in which a reinforcing material precursor 31b is applied to the skived annular laminate so as to cover the entire surface over the entire length, a reverse skiving process in which a trim cut (reverse skiving) is performed at both ends on the back side (a process for removing excess parts 38a), and a peeling process in which the laminate 38b of the reinforcing material precursor and the release sheet is peeled off (upper reinforcing material peeling) to peel off the reinforcing material precursor together with the release sheet.

In the embodiment including the reinforcing material, by using a split-type manufacturing method for producing the hexagonal belt portion, in the cross-linking molding step described below, a portion of the rubber composition (particularly the rubber composition of the core layer) for forming the inner rubber layer, the core layer, and the outer rubber layer flows into the connecting portion from the gap between the reinforcing material precursor (inner reinforcing material precursor) 31a and the reinforcing material precursor (outer reinforcing material precursor) 31b, and the connecting fabric and the rubber composition are integrated at the connecting portion to form a strong connecting portion.

The average thickness of the thin outer rubber layer sheet is, for example, 10 to 50%, preferably 20 to 40%, and more preferably 25 to 35% of the average thickness of the entire outer rubber layer sheet (the combined thickness of the first outer rubber layer sheet and the second outer rubber layer sheet).

When the inner rubber layer or the outer rubber layer has a laminated structure of two or more layers, the above-mentioned uncrosslinked outer rubber layer sheet or inner rubber layer sheet may be arranged by laminating multiple types of sheets as necessary.

[Crosslinking molding process]
The combined hexagonal belt precursor including the obtained hexagonal belt portion precursor is placed in a press mold and subjected to a crosslinking molding process. In the crosslinking molding process, when the press mold is a combination of an inner press mold and an outer press mold, the inner fabric precursor may be placed along the inner groove, the hexagonal belt portion precursor may be laminated on the inner fabric precursor, the outer fabric precursor may be placed along the hexagonal belt portion precursor, the outer groove may be brought into contact with the outer precursor, and the combined hexagonal belt precursor may be sandwiched between the inner press mold and the outer press mold. The crosslinking molding process will be described below with reference to the drawings.

Figure 14 shows an overall view of the cross-linking molding of a bonded hexagonal belt precursor using a cross-linking molding device 40. A number of uncross-linked annular bodies (inner fabric precursor, hexagonal belt portion precursor, and outer fabric precursor) 41 held in a wound state around a pair of pulleys 44a, 44b are clamped between the pair of pulleys 44a, 44b by two press molds.

As shown in Figs. 15 and 16, the two press molds each have a structure corresponding to the shape of the connecting hexagonal belt. The first press mold is a combination of an inner press mold 42a having an inner groove with a trapezoidal cross section and an outer press mold 42b having an outer groove with a trapezoidal cross section, and the second press mold is a combination of an inner press mold 43a having an inner groove with a trapezoidal cross section and an outer press mold 43b having an outer groove with a trapezoidal cross section. When the inner press molds 42a, 43a and the outer press molds 42b, 43b are combined, a cavity with a hexagonal cross section corresponding to the shape of the hexagonal belt is formed inside the press mold. A heating plate 45 is provided between the inner press mold 42a of the first press mold and the inner press mold 43a of the second press mold, and both press molds can be heated. Therefore, by disposing (fitting) a combined hexagonal belt precursor in the hollow portion and heating it, a portion of the annular body 41 can be molded into the shape of a combined hexagonal belt and cross-linked. Then, by rotating the pair of pulleys 44a, 44b, the annular body 41 can be moved in a sequential rotation, and when the annular body 41 is cross-linked in sequence around the entire circumference, the combined hexagonal belt is completed.

The cross-linking molding process using this device will be described in detail below. First, as shown in FIG. 17, the inner fabric precursor 41a is fitted into multiple grooves having an inverted trapezoidal cross section formed in the inner press mold 42a using a jig 46a having a shape corresponding to the grooves. The inner fabric precursor 41a may contain an uncross-linked rubber composition.

Next, in an embodiment that does not include a reinforcing material, as shown in FIG. 18, the hexagonal belt portion precursor 47 is fitted into each groove into which the inner fabric precursor 41a is fitted, and then, as shown in FIG. 19, the hexagonal belt portion precursor is arranged in each groove aligned in the width direction, and the outer fabric precursor 41b is placed on top of it (on the outer periphery), and the outer fabric precursor 41b is aligned to the contour of the hexagonal belt portion precursor by a jig 46b. The outer fabric precursor 41b may also contain an uncrosslinked rubber composition.

As shown in FIG. 20, an outer press mold 42b is disposed on the outer peripheral surface of the combined hexagonal belt precursor set in the inner press mold 42a, and the combined hexagonal belt precursor is subjected to a cross-linking molding process in which it is heated and pressurized while being sandwiched between the inner press mold 42a and the outer press mold 42b.

On the other hand, in the embodiment including the reinforcing material, as shown in FIG. 21, the inner hexagonal belt portion precursor 48 is fitted into each groove portion into which the inner fabric precursor 41a is fitted, and then, as shown in FIG. 22, the outer hexagonal belt portion precursor 49 is laminated on top of the inner hexagonal belt portion precursor 48 (outer peripheral surface), thereby forming the hexagonal belt portion precursor.

Furthermore, as shown in FIG. 23, with the hexagonal belt portion precursors aligned in each groove aligned in the width direction, the outer fabric precursor 41b is placed on top of them (on the outer periphery), and the outer fabric precursor 41b is aligned to the contour of the hexagonal belt portion precursor by a jig 46b. The outer fabric precursor 41b may also contain an uncrosslinked rubber composition.

As shown in FIG. 24, an outer press mold 42b is disposed on top (outer peripheral surface) of the combined hexagonal belt precursor set in the inner press mold 42a, and the combined hexagonal belt precursor is subjected to a cross-linking molding process in which it is heated and pressurized while being sandwiched between the inner press mold 42a and the outer press mold 42b.

In this cross-linking molding process, when the precursors are bonded and integrally cross-linked by the cross-linking reaction of the rubber components while molded into the formwork shape of the press mold, a cross-linked sleeve is formed in which multiple hexagonal belt portions are connected and bonded in the width direction. In this process, the connecting portion is formed by integrally cross-linking the inner connecting material, which is part of the inner fabric, the outer connecting material, which is part of the outer fabric, and the rubber composition that has flowed out from the rubber layer of the hexagonal belt portion precursor between the inner connecting material and the outer connecting material. In other words, the connecting portion is formed as a complex composed of three components: the inner connecting material, the cross-linked rubber composition, and the outer connecting material.

The inner and outer fabric precursors for forming the outer covering material and the connecting material can be treated (adhesive treatment) with an uncrosslinked rubber composition, so that the adhesive components attached to the inner and outer fabric precursors can firmly bond to each hexagonal belt portion precursor (uncrosslinked hexagonal belt portion). For example, when a woven fabric (woven fabric with rubber) that has been treated by friction (rubbing) a solid rubber composition is used as the inner and outer fabric precursors, they are bonded to each other by the crosslinking reaction of the friction rubber composition. That is, the process of setting the inner and outer fabric precursors to the hexagonal belt portion precursor includes an uncrosslinked belt bonding process of bonding multiple hexagonal belt portion precursors to each other via the inner and outer fabric precursors.

In the crosslinking molding process, the heating temperature can be selected according to the type of rubber component, and is, for example, 120 to 200°C, and preferably 150 to 180°C. The pressure can be selected according to the type of rubber component, and is, for example, 0.1 to 10 MPa, preferably 0.5 to 3 MPa, and more preferably 0.9 to 1.5 MPa. In this application, the pressure is a value converted into the press surface pressure. In addition, each rubber layer sheet containing short fibers can be rolled with a calendar roll or the like to align (orient) the short fibers in the rolling direction.

The bridging sleeve thus formed is cut to a predetermined width as shown in FIG. 25, forming a joined hexagonal belt having a predetermined number of hexagonal belt portions (six in FIG. 25). Note that FIG. 25 is an example of a joined hexagonal belt that does not include a reinforcing material.

The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. The raw materials used in the rubber composition, the method for preparing the rubber composition, the fiber materials used, and the methods for measuring or evaluating each physical property are also shown.

[Raw materials for rubber composition]
Chloroprene rubber: "PM-40" manufactured by DENKA Corporation
Magnesium oxide: Kyowa Mag 30 manufactured by Kyowa Chemical Industry Co., Ltd.
Stearic acid: "Camellia Stearate" manufactured by NOF Corporation
Anti-aging agent: "Nonflex OD-3" manufactured by Seiko Chemical Co., Ltd.
Carbon black: "Seat 3" manufactured by Tokai Carbon Co., Ltd.
Silica: "ULTRASIL (registered trademark) VN3" manufactured by Evonik Japan Co., Ltd., BET specific surface area 175 m ² /g
Plasticizer: "Adeka Cizer RS-700" manufactured by ADEKA Corporation
Crosslinking accelerator: "Noccela TT" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Zinc oxide: "Zinc oxide type 3" manufactured by Seido Chemical Industry Co., Ltd.
Naphthenic oil: "NS-900" manufactured by Idemitsu Kosan Co., Ltd.
N,N'-m-phenylenedimaleimide: "Vulnoc PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Aramid short fibers: Short fibers having a solid adhesion rate of 6 mass% obtained by bonding Teijin Limited's "Conex short fibers" (average fiber length 3 mm, average fiber diameter 14 μm) with an RFL liquid (2.6 parts by mass of resorcinol, 1.4 parts by mass of 37% formalin, 17.2 parts by mass of vinylpyridine-styrene-butadiene copolymer latex (manufactured by Zeon Corporation) and 78.8 parts by mass of water).

[Core wire]
Twisted aramid fiber cord, average wire diameter 1.190 mm.

[Rubber composition for adhesive rubber layer and friction rubber]
Rubber composition A having the composition shown in Table 2 was kneaded in a Banbury mixer, and the kneaded rubber was passed through a calendar roll to form a rolled rubber sheet of a predetermined thickness to prepare an uncrosslinked rubber sheet for an adhesive rubber layer. Rubber composition B shown in Table 2 was kneaded in a Banbury mixer to prepare a lump-shaped uncrosslinked rubber composition for friction. Furthermore, the hardness and tensile strength of the crosslinked product (crosslinked rubber) of each rubber composition were measured, and the results are also shown in Table 2.

[Rubber Composition for Inner Rubber Layer and Outer Rubber Layer]
Rubber compositions C to D having the formulations shown in Table 3 were kneaded in a Banbury mixer, and the kneaded rubber was passed through a calendar roll to form a rolled rubber sheet of a predetermined thickness, thereby producing an uncrosslinked rubber sheet for an inner rubber layer and an uncrosslinked rubber sheet for an outer rubber layer. Furthermore, the hardness and tensile strength of the crosslinked product (crosslinked rubber) of each rubber composition were measured, and the results are also shown in Table 3.

[Rubber hardness Hs of crosslinked rubber]
Each uncrosslinked rubber sheet for rubber layer was press-heated at 160°C for 30 minutes to prepare a crosslinked rubber sheet (100mm x 100mm x 2mm thick). A laminate of three crosslinked rubber sheets was used as a sample, and the hardness of the crosslinked rubber sheet was measured using a type A durometer in accordance with the spring durometer hardness test specified in JIS K6253 (2012). For the lump uncrosslinked rubber composition B for friction, a test specimen was sampled from the lump rubber and passed through a calendar roll to prepare an uncrosslinked rolled rubber sheet of a predetermined thickness.

[Tensile strength of crosslinked rubber]
A crosslinked rubber sheet prepared for measuring the rubber hardness Hs of crosslinked rubber was used as a sample, and a test piece was prepared by punching out into a dumbbell shape (No. 5 type) according to JIS K6251 (2017). For samples containing short fibers, dumbbell-shaped test pieces were taken so that the alignment direction of the short fibers (parallel to the grain direction) was the tensile direction. Then, both ends of the test piece were held with a chuck (gripping tool), and the test piece was pulled until it broke at a speed of 500 mm/min. The maximum tensile force recorded when the test piece was divided by the initial cross-sectional area of the test piece (tensile strength T) was defined as the tensile strength.

[Sheathing, connecting and reinforcing materials]
A woven fabric (120° wide angle weave, 20-count warp yarn and 20-count weft yarn, warp and weft yarn density 75 threads/50 mm, basis weight 280 g/ ^m2 ) of blended yarns of polyester fiber and cotton (polyester fiber/cotton = 50/50 mass ratio) was subjected to a friction treatment using rubber composition B in Table 2 by simultaneously passing the rubber composition B and the woven fabric between calendar rolls with different surface speeds and rubbing the rubber composition B into the weave of the woven fabric (once each on the front and back of the woven fabric) to prepare a reinforcing material precursor (woven fabric with rubber), and inner and outer fabric precursors (woven fabric with rubber) for forming an outer covering material and a connecting material.

[Preparation of Bonded Hexagonal Belt]
Example 1 (Inner rubber layer/outer rubber layer are single layers covered with a reinforcing material)
The rubber composition D in Table 3 was used as the outer rubber layer sheet and the inner rubber layer sheet. A release sheet (nylon film), an outer rubber layer sheet (thickness 0.5 mm), and an adhesive rubber layer sheet were wound in this order around the outer circumferential surface of the mantle, a core wire was spun in a spiral shape around the outer circumferential surface, and an adhesive rubber layer sheet and an inner rubber layer sheet were further wound in this order to form an uncrosslinked annular laminate (uncrosslinked sleeve). The obtained annular laminate was cut (sliced) in the circumferential direction at a predetermined width while being disposed around the outer periphery of the mantle, to form a plurality of annular laminates.

Next, the cut annular laminate was removed from the mantle and rotated around a pair of pulleys while cutting (skiving) both sides of the annular laminate at a specified angle, forming a V-shaped cross section of the annular laminate. Next, the skived annular laminate was covered all around its entire length with a reinforcing material precursor (woven fabric with rubber), after which a trim cut (reverse skiving) was performed on both ends on the back side, and the reinforcing material precursor was peeled off and removed together with the release sheet to form the inner hexagonal belt portion precursor.

The outer hexagonal belt precursor was formed by following the same process as the inner hexagonal belt precursor, except for the process of wrapping a release sheet (nylon film) and an uncrosslinked outer rubber layer sheet, in that order, around the outer periphery of the mantle to form an uncrosslinked annular laminate (uncrosslinked sleeve).

Then, using the method described in the embodiment, the inner fabric precursor (woven fabric with rubber), the six inner and outer hexagonal belt portion precursors, and the outer fabric precursor (woven fabric with rubber) were placed in a press mold, pressurized to 1.2 MPa, and heated to a temperature of 160°C to obtain a crosslinked sleeve in which six hexagonal belt portions (ARPM AA type, cross-sectional dimensions: width 13 mm x thickness 8.510.2 mm, belt length 122 inches) were connected and bonded. The resulting crosslinked sleeve was cut to form a bonded hexagonal belt having two hexagonal belt portions (hexagonal belt portions having the structure shown in Figure 7).

Example 2 (two inner rubber layers, one outer rubber layer, and a reinforcing material covering the rubber layer)
For the outer rubber layer sheet and the second inner rubber layer sheet, rubber composition D in Table 3 was used, and for the first inner rubber layer sheet, rubber composition C having high hardness was used.

In the manufacturing process of the inner hexagonal belt portion precursor, in the process of forming the uncrosslinked annular laminate (uncrosslinked sleeve), the core wire is spun into a spiral shape, and then the adhesive rubber layer sheet, the first inner rubber layer sheet, and the second inner rubber layer sheet are wound in that order. Except for this, a combined hexagonal belt having two hexagonal belt portions was formed in the same manner as in Example 1. The first inner rubber layer sheet, which contains short fibers, has the short fibers aligned in the belt width direction.

Example 3 (Inner rubber layer/outer rubber layer each having two layers covered with reinforcing fabric)
For the second outer rubber layer sheet and the second inner rubber layer sheet, rubber composition D in Table 3 was used, and for the first outer rubber layer sheet and the first inner rubber layer sheet, rubber composition C having high hardness was used.

In the manufacturing process of the inner hexagonal belt portion precursor, a first outer rubber layer sheet was used as an outer rubber layer sheet having a thickness of 0.5 mm in the process of forming an uncrosslinked annular laminate (uncrosslinked sleeve), and in the manufacturing process of the outer hexagonal belt portion precursor, a release sheet (nylon film), a first outer rubber layer sheet, and a second outer rubber layer sheet were wrapped around the outer circumferential surface of the mantle in that order in the process of forming an uncrosslinked annular laminate (uncrosslinked sleeve). In addition, a combined hexagonal belt having two hexagonal belt portions (hexagonal belt portions having the structure shown in FIG. 8) was formed in the same manner as in Example 2. In addition, the first outer rubber layer sheet and the first inner rubber layer sheet, which contain short fibers, had the short fibers aligned in the belt width direction.

Example 4 (two inner rubber layers, one outer rubber layer, not covered with a reinforcing material)
For the outer rubber layer sheet and the second inner rubber layer sheet, rubber composition D in Table 3 was used, and for the first inner rubber layer sheet, rubber composition C having high hardness was used.

A joined hexagonal belt having two hexagonal belt portions was formed using the manufacturing method described in the embodiment that does not include a reinforcing material.

Comparative Example 1
A wrapped bonded V-belt according to Example 5 of JP 2020-3061 A (Patent Document 4) was formed.

[Belt running test (durability performance)]
Using the combined hexagonal belt obtained in the embodiment and the wrapped combined V-belt obtained in the comparative example, the pulleys in the layout consisting of the driving pulley (Dr1), driven pulleys (Dn2 and Dn3), tension pulley (Ten4), and idler pulley (ID5) shown in Table 4 were arranged in the order of driving pulley (Dr1) 51, tension pulley (Ten4) 54, driven pulley (Dn3) 53, driven pulley (Dn2) 52, and idler pulley (ID5) 55 as shown in Figure 26. The belt was run under the conditions shown in Table 5, and the time until the belt broke was evaluated according to the following criteria. Note that, as for the load during running, as shown in Table 6, the test was performed under a condition in which a load of 9.5 kW was applied to the driven pulley (back driven pulley) Dn2 and 23.0 kW was applied to the driven pulley Dn3, for a total of 32.5 kW. In the examples, V-pulleys were used for Dr1, Dn2, and Dn3, and flat pulleys were used for Ten4 and ID5. In the comparative examples, V-pulleys were used for Dr1 and Dn3, and flat pulleys were used for Dn2, Ten4, and ID5.

(Judgment criteria)
◎: 240 hours completed, no cracks, peeling, or other abnormalities were observed. 〇: 240 hours completed, slight cracks or peeling was observed (not to the extent that it interfered with performance).
×: Abnormalities (cracks or peeling) occurred that impair performance.

[Belt running test (transmission performance)]
Whether or not high-performance double-sided transmission is possible can be judged from the viewpoint of how much the transmission performance on the outer circumferential side (back side) of the belt is improved compared to a wrapped-coupled V-belt (Comparative Example 1) in which the outer circumferential surface (back side) of the belt is formed flat. The transmission performance on the outer circumferential side (back side) of the belt is indexed by the slip ratio value between the friction transmission surface on the outer circumferential side of the belt and the back driven pulley Dn2, and it was determined that the smaller the slip ratio value, the better the transmission performance on the outer circumferential side (back side) of the belt and the higher the performance of high-performance double-sided transmission is.

Specifically, for Examples 1 to 4 and Comparative Example 1, a test machine with a multi-axis layout similar to that used in the durability performance test described above was used to run the belt under the loads shown in Table 6 (9.5 kW on driven pulley Dn2, 23.0 kW on driven pulley Dn3, a total of 32.5 kW) before and after the run to evaluate the durability performance (conditions in Table 5), and the rotation speed (rpm) of the driven pulley (rear driven pulley) Dn2 was measured to calculate the slip ratio according to the following formula. The rotation speeds of the drive pulley Dr1 and driven pulley Dn2 under no load, and the rotation speed of the drive pulley Dr1 under load in this measurement are shown in Table 7.

If the slip rate (%) after the run (after completing 240 hours) was less than 1%, it was evaluated as having excellent transmission performance on the outer periphery (back side) of the belt and capable of high-performance double-sided transmission, and was rated as A.
If the slip rate (%) after the run (after completing 240 hours) was 1% or more, the transmission performance on the outer periphery of the belt (back side) was evaluated as being inferior, and high-performance double-sided transmission was not possible, and the belt was given a rating of b.
From the viewpoint of suitability for practical use in this application, belts rated "a" were determined to be at the pass level.

Slip ratio (%) = [(K2 - K1) / K1] x 100
[In the formula, K1=R1/N1, K2=R2/N2, R1 is the rotation speed (rpm) of the drive pulley during unloaded operation, N1 is the rotation speed (rpm) of the driven pulley during unloaded operation, R2 is the rotation speed (rpm) of the drive pulley during loaded operation, and N2 is the rotation speed (rpm) of the driven pulley during loaded operation]

The results of the running evaluation of the resulting bonded hexagonal belt are shown in Table 8.

From the results in Table 8, each of the joined hexagonal belts of the examples showed no significant abnormalities by the 240-hour cutoff time and completed the run. It can be seen that, as in Examples 2 to 4, providing a high-hardness rubber layer on the core layer side of the inner (outer) rubber layer has an effect on durability.

On the other hand, the wrapped bonded V-belt of Comparative Example 1 also completed the 240-hour test without any significant abnormalities. The transmission performance (slip rate) was 1.00% (grade b) before the test and 1.30% (grade b) after the test.

In contrast, the transmission performance (slip rate) of the combined hexagonal belts of Examples 1 to 4 was 0.70% (a-judgment) before the endurance run in all cases, and 0.90% (a-judgment) after the endurance run. In other words, the combined hexagonal belt has a suppressed slip rate on the outer belt side (back side) compared to the wrapped combined V-belt, improving transmission performance. Therefore, it was confirmed that the combined hexagonal belt, which has a V-shaped side (friction transmission surface) that can come into contact with the V-pulley on the outer peripheral side in addition to the inner peripheral side, is capable of high-performance double-sided transmission.

The combined hexagonal belt of the present disclosure can be used as various friction transmission belts that require double-sided drive, for example, in general industrial machines such as compressors, generators, and pumps; textile machines such as spinning machines, spinning machines, looms, knitting machines, and dyeing and finishing machines; and agricultural machines such as tillers, rice planters, vegetable transplanters, transplanters, binders, combines, bean cutters, corn crushers, potato harvesters, beet harvesters, vegetable harvesters, grass cutters, threshers, rice hullers, and rice polishers. In particular, it is suitable for large, high-load agricultural machines used in Europe and the United States, for example, tillers, binders, combines, vegetable harvesters, threshers, bean cutters, corn crushers, potato harvesters, and beet harvesters.

Reference Signs List 1... Jointed hexagonal belt 2... Core layer 2a... Core wire 3... Inner rubber layer 4... Inner outer covering material 5... Outer rubber layer 6... Outer outer covering material 7... Inner connecting material 8... Outer connecting material

Claims (10)

A combined hexagonal belt in which a plurality of hexagonal belt portions each having a hexagonal cross section are arranged in the belt width direction,
the hexagonal belt portion includes a core layer, an inner rubber layer laminated on the inner circumferential surface side of the core layer and having a trapezoidal cross section, an inner outer covering material covering the inner rubber layer and including an inner outer covering fabric, an outer rubber layer laminated on the outer circumferential surface side of the core layer and having a trapezoidal cross section, and an outer outer covering material covering the outer rubber layer and including an outer outer covering fabric,
The adjacent hexagonal belt portions are connected to each other via connecting portions, and adjacent inner outer cover fabrics are formed of a continuous inner fabric, and adjacent outer outer cover fabrics are formed of a continuous outer fabric. The connecting portion includes an inner connecting member that forms an inner circumferential surface of the belt and an outer connecting member that forms an outer circumferential surface of the belt,
The inner connecting material includes an inner connecting fabric, and the outer connecting material includes an outer connecting fabric,
2. The joined hexagonal belt according to claim 1, wherein the inner fabric is a fabric in which the inner connecting fabric and the inner outer cover fabric are continuous, and the outer fabric is a fabric in which the outer connecting fabric and the outer outer cover fabric are continuous. The joined hexagonal belt according to claim 2, wherein the connecting portion further comprises a cross-linked rubber composition. The joined hexagonal belt according to any one of claims 1 to 3, in which an inner reinforcing material is interposed between the inner outer covering material and the inner rubber layer, and an outer reinforcing material is interposed between the outer outer covering material and the outer rubber layer. The combined hexagonal belt according to any one of claims 1 to 3, wherein the inner rubber layer includes a first inner rubber layer laminated on the core layer side, and a second inner rubber layer having a lower rubber hardness than the first inner rubber layer and laminated on the inner circumference side of the belt. A method for manufacturing a combined hexagonal belt according to any one of claims 1 to 3, comprising a cross-linking molding step in which a combined hexagonal belt precursor placed in a press mold is heated and pressurized to cross-link the combined hexagonal belt. The manufacturing method according to claim 6, wherein the connecting portion contains a cross-linked rubber composition, and in the cross-linking molding step, cross-linking molding of the hexagonal belt portion and cross-linking molding of the connecting portion are carried out simultaneously. The press mold is a combination of an inner press mold having an inner groove portion corresponding to the inner shape of the combined hexagonal belt and an outer press mold having an outer groove portion corresponding to the outer shape of the combined hexagonal belt,
The bonded hexagonal belt precursor includes an inner fabric precursor for forming an inner fabric, an outer fabric precursor for forming an outer fabric, and a hexagonal belt portion precursor including an uncrosslinked rubber composition,
8. The manufacturing method according to claim 7, wherein in the crosslinking molding process, the inner fabric precursor is arranged along the inner groove portion, the hexagonal belt portion precursor is laminated onto the inner fabric precursor, the outer fabric precursor is arranged along the hexagonal belt portion precursor, and then the outer groove portion is brought into contact with the outer fabric precursor, and the combined hexagonal belt precursor is sandwiched between the inner press mold and the outer press mold. A method for manufacturing a combined hexagonal belt including an inner reinforcement material and an outer reinforcement material, the hexagonal belt portion precursor is a combination of an inner hexagonal belt portion precursor and an outer hexagonal belt portion precursor, and the manufacturing method described in claim 8, in which the inner hexagonal belt portion precursor is laminated on the inner fabric precursor and then the outer hexagonal belt portion precursor is laminated on the inner hexagonal belt portion precursor in the crosslinking molding process. The method further includes a hexagonal belt portion precursor preparation step as a step prior to the crosslinking molding step,
The hexagonal belt portion precursor manufacturing step includes a step of manufacturing an inner hexagonal belt portion precursor and a step of manufacturing an outer hexagonal belt portion,
a step of preparing the inner hexagonal belt portion precursor, comprising: laminating a core layer precursor for forming a core layer on a thin outer rubber layer precursor for forming a part of the outer rubber layer; laminating an inner rubber layer precursor for forming an inner rubber layer on the core layer precursor; and then cutting a side surface of the inner rubber layer precursor;
10. The method according to claim 9, wherein the step of preparing the outer hexagonal belt portion precursor comprises cutting a side surface of a thick outer rubber layer precursor for forming the remaining portion of the outer rubber layer.

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