JP7536731B2 - Connected V-belt - Google Patents

Description

The present invention relates to a combined V-belt (multi-V belt, banded belt) in which multiple V-belts are wound around pulleys or the like and used simultaneously in high-load, long-span (long axle distance) layouts such as large-scale agricultural machinery, as well as a manufacturing method for the same and a method for preventing longitudinal tears.

V-belts that transmit power by friction transmission are available in two types: raw-edge type (raw-edge V-belts), which are rubber layers with an exposed friction transmission surface (V-shaped side), and wrapped type (wrapped V-belts), whose friction transmission surface is covered with a cover cloth. Different types are used depending on the application due to the difference in the surface properties of the friction transmission surface (friction coefficient between the rubber layer and the cover cloth). These V-belts are used in a wide range of fields, such as large automobiles such as trucks and buses, and industrial machinery, and are used under high loads due to increased transmission capacity and larger equipment. Thin V-ribbed belts are widely used in applications that do not require a large transmission capacity, such as for driving accessories in ordinary automobiles, but large V-belts are used for high-load applications where the transmission capacity of V-ribbed belts is insufficient. Belts used in high-load environments, such as large V-belts, require different material selection and product design than V-ribbed belts in order to withstand high loads, such as high rigidity in the belt width direction (resistance to lateral pressure) to prevent buckling deformation (dishing).

When these V-belts are capable of transmitting power on their own, they are used individually; however, in environments where greater power needs to be transmitted, such as large-scale agricultural machinery used in Europe and the United States, multiple V-belts must be used simultaneously.

However, when multiple V-belts are wound in parallel around the pulleys of a rotating device, tension differences can occur between the belts, compromising stable power transmission. Furthermore, contact can occur between adjacent belts, which can cause the inner and outer sides of the belt to flip over and become reversed, resulting in overturning. In addition, the layout of large-scale agricultural machinery used in Europe and the United States has a very long axis distance between the pulleys around which the V-belt is wound, which makes it easy for the V-belt to vibrate significantly while traveling, and can even cause vibration if the lengths of the multiple belts are not uniform.

Therefore, in such an operating environment, a combined V-belt is used, which is made up of multiple annular V-belt sections that have the same or corresponding configuration as the above V-belt. This combined V-belt is made up of multiple V-belt sections arranged in parallel, with the outer periphery of each V-belt section connected and combined with a connecting member (tie band) such as a reinforcing cloth.

For example, Japanese Patent Publication No. 47-34432 (Patent Document 1) discloses a combined V-belt with a connecting band having a fabric layer with threads that cross diagonally with respect to the belt longitudinal direction. It also describes that the belt has high load transmission capacity because it acts as thread tension when transmitting load between each belt body, and that the crossing angle of the threads may be in the range of 90° or 95-155°.

Japanese Utility Model Publication No. 55-45082 (Patent Document 2) discloses a structure including a connecting member in which at least two layers of rubber-backed sudare records are cross-laminated. It also states that the cross angle may be 95 to 150 degrees, and that this can provide good longitudinal and lateral elasticity as well as rigidity.

JP 55-135244 (Patent Document 3) discloses a combined V-belt that is connected and integrated with elastic canvas with rubber. It also describes that the weft thread of the elastic canvas may be woolly processed crimped nylon thread, and that this crimped nylon thread may be arranged in an oblique direction of 0 to 40 degrees to the longitudinal direction of the belt.

Patent Publication No. 47-34432 Published in Japanese JP 55-135244 A

In a combined V-belt, the challenge is to improve the durability of the connecting member. The connecting member of a combined V-belt is subjected to tensile forces in the belt width direction and shear forces in the belt length direction. In addition, the connecting member may be damaged if a foreign object such as a pebble gets caught between the belt and the pulley. As a result, a crack occurs in the connecting member, and the crack propagates in the belt length direction, causing the connection between the V-belt parts to be lost, resulting in a phenomenon known as a ring break (vertical tear), in which the V-belt is separated into individual V-belts.

However, the configuration described in the above-mentioned patent document is not effective enough in preventing breakage of the connected V-belt in recent years, when transmission capacity has continued to increase, and further improvement is required.

The object of the present invention is therefore to provide a bonded V-belt that can effectively prevent wheel breakage even in a high-load environment, a method for manufacturing the same, and a method for preventing wheel breakage.

As a result of extensive research into achieving the above-mentioned objective, the inventors discovered that forming a joined V-belt using tie bands that contain a specific fiber structure and that are oriented in a specific direction relative to the belt can effectively prevent ring breakage even in high-load environments, and thus completed the present invention.

That is, the combined V-belt of the present invention includes a plurality of V-belt portions (base belts) arranged in the belt width direction, and a tie band for connecting the outer circumferential surfaces of the plurality of V-belt portions; each V-belt portion includes a core layer including a core, a tension layer laminated on the outer circumferential belt side of the core layer, and a compression rubber layer laminated on the inner circumferential belt side of the core layer,
The tie band has a connecting reinforcing layer including a fiber structure (fiber aggregate), the fiber structure includes a plurality of first filaments extending at least in the width direction of the belt, and the first filaments are arranged at least spaced apart in the length direction of the belt. The adjacent first filaments may be arranged at intervals of about 0.5 to 7.5 mm in the length direction of the belt.

The density of the first filaments may be about 5 to 50 filaments/50 mm (e.g., 10 to 39 filaments/50 mm), and the fineness of the first filaments may be about 100 to 1000 dtex. The cover factor of the first filaments may be about 150 to 1200 (filaments/50 mm) x (dtex) ^1/2 . The connecting reinforcing layer may further contain a rubber component, and this rubber component may be interposed between the first filaments adjacent in the belt length direction. The first filaments may be a non-twisted yarn having a twist number of less than 1 turn/100 mm (0 turns/100 mm or more, less than 1 turn/100 mm), or a loosely twisted yarn having a twist number of 1 to 29 turns/100 mm. The first filaments may include synthetic fibers and/or inorganic fibers, and the synthetic fibers may include at least one synthetic fiber selected from polypropylene-based fibers, polyvinyl alcohol-based fibers, polyester-based fibers, and polyamide-based fibers. The fiber structure may be a net including a plurality of second filaments extending in a direction intersecting the belt width direction and connected to at least the first filaments. The tie band may further include a protective layer laminated on the outer circumferential side of the connecting reinforcing layer and including a fabric.

The present invention includes a method for manufacturing the joined V-belt by connecting the outer peripheral surfaces of multiple V-belt sections aligned in the belt width direction to a tie band having the connecting reinforcement layer, and a method for connecting multiple V-belt sections with the tie band to prevent the resulting joined V-belt from breaking.

The bonded V-belt of the present invention contains a specific fiber structure and is formed by a tie band that is oriented in a specific direction relative to the belt, so that even when used in high-load environments, such as applications requiring a large transmission capacity, it can effectively prevent loop breakage.

FIG. 1 is a schematic cross-sectional perspective view, partially cut away, showing an example of a joined V-belt of the present invention. FIG. 2 is a schematic cross-sectional view of an example of a V-belt portion constituting a combined V-belt of the present invention. FIG. 3 is a schematic cross-sectional view for explaining a process of connecting a plurality of uncrosslinked V-belt portions with a tie band. FIG. 4 is a schematic diagram for explaining a method for measuring the friction coefficient of the V-belt portion of the joined V-belt obtained in the examples. FIG. 5 is a schematic cross-sectional view for explaining a running test of the combined V-belts obtained in the examples and the comparative examples.

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 components) that are identical or have the same functions.

As an example of the combined V-belt of the present invention, a partially cutaway schematic cross-sectional perspective view of a wrapped combined V-belt is shown in FIG. 1. As shown in FIG. 1, this combined V-belt 10 has three V-belt parts V arranged parallel to each other in the belt width direction (direction B in FIG. 1) at intervals, and the outer circumferential surfaces of the three V-belt parts V are connected by a tie band (connecting member) T having a connecting reinforcing layer 1 in which a fiber structure 2 formed of a plurality of first filaments (filament bodies) 2a extending toward the belt width direction at intervals in the belt length direction (circumferential direction, direction A in FIG. 1) and a plurality of second filaments (filament bodies) 2b extending toward the belt length direction at intervals in the belt width direction is embedded in a rubber component (crosslinked rubber composition), and a protective layer 3 laminated on the connecting reinforcing layer 1 and formed of a fabric.

Each V-belt section V, like a conventional wrapped V-belt, is made up of an endless belt body in which, from the outer periphery of the belt, a tension layer (tension rubber layer) 4, a core body 5 [in this example, core wires (twisted cords) arranged at a predetermined interval in the belt width direction] are embedded in a crosslinked rubber composition, a core layer (bonded rubber layer) 6, and a compression rubber layer 7 are laminated in this order, and an outer cover fabric 8 (woven fabric, knitted fabric, nonwoven fabric, etc.) that covers the periphery of the belt body over the entire circumferential length of the belt.

In this example, the fiber structure 2 in the connecting reinforcement layer 1 is a net (net or net-like structure) having a structure in which warp threads (second threads 2b) are arranged alternately above and below weft threads (first threads 2a), and the intersections (contact points or intersections) of the warp threads (second threads 2b) and the weft threads (first threads 2a) are bonded (joined or joined) with resin. In this example, adjacent weft threads (first threads 2a) are arranged with a gap of about 0.5 to 7.5 mm between them in the belt length direction. Furthermore, in this example, the warp yarn (second filament 2b) and weft yarn (first filament 2a) are both polyethylene terephthalate (PET) fibers (untwisted yarn, multifilament yarn) with a fineness (total fineness) of 100 to 1000 dtex, and the density (yarn density) of each yarn is adjusted to 10 to 39 yarns/50 mm.

In conventional joined V-belts, in order to achieve both improved flexibility in the belt length direction and stretchability in the belt width direction (improved ease of fitting around pulleys), canvas or sudarekord, in which threads (filaments) are arranged diagonally (bias) relative to the belt width direction, are typically used as tie bands (joining members). In these canvas and sudarekord, the threads are generally arranged with almost no gaps and at high density (for example, thread density of about 70 to 80 threads/50 mm) to prevent damage from foreign objects from the back of the belt and to improve the mechanical properties of the tie band.

On the other hand, in the combined V-belt 10 of the present invention as described above, a fiber structure (net or mesh structure) 2 in which weft threads (first filament 2a) extending in the belt width direction are arranged at a low density is used as the tie band T that connects the back surface of each V-belt portion V, but unexpectedly, it is possible to effectively prevent circular breakage (vertical tearing). Although the reason why circular breakage can be prevented in this way is unclear, it is believed that not only is it possible to prevent thread breakage by improving the resistance to the tensile force acting in the belt width direction because the weft threads (first filament 2a) are arranged parallel to the belt width direction, thereby preventing thread breakage, but also that the configuration in which the weft threads (first filament 2a) are arranged at intervals at a low density has a large impact. Specifically, as in the case of the tie bands in the conventional combined V-belts, it was thought that a higher yarn density would improve the mechanical properties of the tie bands and make them less likely to break, but the inventors have found that arranging the yarns at a higher density actually tends to cause breaks, possibly because when a yarn breaks, stress is concentrated on the yarns adjacent to the broken yarn, and defects (or cracks) tend to propagate (or grow) continuously. That is, in the case of the present invention in which the yarns extending in the width direction are arranged with a certain gap therebetween (or when the yarn density is low), even if a weft yarn (first filamentous body 2a) breaks, the distance between the broken weft yarn and the adjacent weft yarn is large, so stress is less likely to concentrate on the adjacent weft yarns, and the propagation of cracks is suppressed, and it is presumed that breaks can be effectively suppressed despite the low yarn density. Furthermore, in this example, since a rubber component (crosslinked rubber composition) is present between adjacent weft yarns (first filamentous bodies 2a), it is believed that the stress is dispersed to the rubber component, making it even more difficult for defects to propagate and effectively suppressing peeling of the fiber structure (net or mesh structure) 2.

In addition, by forming a tie band (connecting member) T by laminating a protective layer 3 made of fabric on the connecting reinforcement layer 1, it is possible to effectively prevent the fiber structure (net or mesh structure) 2 in the connecting reinforcement layer 1 from being damaged by foreign objects from the back of the belt.

[Tie band (connecting member)]
The tie band in the combined V-belt of the present invention is sufficient to have at least a connecting reinforcement layer containing a specific fiber structure, and may also have a protective layer laminated on the outer circumferential side of the connecting reinforcement layer, as necessary.

[Connecting reinforcement layer]
(Fiber structure)
The fiber structure in the connecting reinforcement layer includes a plurality of first filaments (filaments) extending at least in the width direction of the belt, and the first filaments are arranged at least at intervals in the length direction of the belt.

In this application, the first filament (thread) needs only to extend approximately parallel to the belt width direction, and this means that the angle between the extension direction of the first filament (thread) and the belt width direction is, for example, approximately 10° or less (e.g., 0 to 5°), preferably 3° or less (e.g., 0 to 1°, particularly approximately 0°).

In the present application, the first filament (filament) extending at least in the belt width direction does not necessarily have to extend in a straight line in the belt width direction, as long as it can exhibit resistance to the tensile force acting in the belt width direction and suppress breakage. For example, in the case where the fiber structure is a woven fabric formed of warp and weft threads, the filament may have a curved portion that is partially bent or curved (for example, curved in a wavy shape in the belt thickness direction, etc.) at the intersection (intersection or intersection point) of the warp and weft threads. The first filament is preferably formed to extend linearly over 50% or more, preferably 90% or more, and more preferably almost the entire belt width (or tie band width). If the proportion of the straight portion is within such a range, the rigidity in the belt width direction is less likely to decrease, and it is also easier to suppress breakage of the thread due to wear at the intersection.

The thread density of the first filament (number of threads per 50 mm in the belt length direction) may be, for example, about 5 to 50 threads/50 mm (e.g., 8 to 45 threads/50 mm), but may be lower than conventional tie bands made of canvas or sudarekord, and may be selected from a range of, for example, about 10 to 39 threads/50 mm (e.g., 12 to 35 threads/50 mm, preferably 20 to 32 threads/50 mm), preferably about 15 to 30 threads/50 mm (e.g., 18 to 27 threads/50 mm), and more preferably about 20 to 25 threads/50 mm. The range may be the average value of the thread density. If the lower limit of the density of the first filaments is within this range, the effect of increasing the rigidity (resistance to tensile force) in the width direction of the belt is sufficient, making it easier to prevent breakage. If the upper limit of the density of the first filaments is within this range, even if the first filaments break, the defect (crack or cut) is unlikely to continue to propagate in the length direction of the belt, and breakage tends to be prevented. In particular, if the connecting reinforcement layer contains a rubber component (crosslinked rubber composition), the rubber component is likely to get between adjacent first filaments, and the stress acting near the defect is dispersed to the rubber component, making it even more difficult for the defect to propagate and effectively preventing peeling of the fiber structure.

The fineness of the first filament (total fineness in the case of a multifilament yarn, etc.) can be selected, for example, from a range of about 100 to 1000 dtex (e.g., 200 to 900 dtex), preferably about 300 to 800 dtex (e.g., 400 to 700 dtex), and more preferably about 500 to 600 dtex. If the lower limit of the fineness of the first filament is in this range, the effect of increasing the rigidity (resistance to tensile force) in the belt width direction can be sufficiently obtained, making it easier to prevent breakage, and if the upper limit of the fineness of the first filament is in this range, the distance between adjacent first filaments can be adjusted to an appropriate range, making it easier to prevent breakage.

In order to effectively prevent ring breakage, it is preferable to arrange adjacent first filaments with a predetermined gap in the belt length direction. The gap between adjacent first filaments (the shortest distance in the belt length direction between the first filaments) may be selected from a range of, for example, about 0.5 to 7.5 mm (e.g., 0.8 to 6 mm), preferably about 1 to 5 mm (e.g., 1.1 to 4.5 mm), more preferably about 1.2 to 4 mm (e.g., 1.3 to 3.5 mm), and particularly about 1.4 to 3 mm (e.g., 1.4 to 2.5 mm, particularly 1.4 to 2.1 mm). The range may be the average value of the gap. If the upper limit of the gap between the first filaments is within this range, the effect of increasing the rigidity (resistance to tensile force) in the width direction of the belt is sufficient, making it easier to prevent breakage. If the lower limit of the density of the first filaments is within this range, even if the first filaments break, the defect (crack or cut) is unlikely to continue to propagate in the length direction of the belt, which tends to prevent breakage. In particular, if the connecting reinforcement layer contains a rubber component (crosslinked rubber composition), the rubber component is likely to get between adjacent first filaments, and the stress acting near the defect is dispersed to the rubber component, making it even more difficult for the defect to propagate and effectively preventing peeling of the fiber structure.

In this application, the "gap" between adjacent threads (filaments) that extend in the same direction in a fiber structure means the distance (shortest distance) from the surface of one thread to the surface of the other thread.

The first filament may have a predetermined cover factor (or coverage, hereinafter also referred to as CF) in order to effectively prevent breakage. The cover factor (CF) is an index that indicates the density of the yarn (first filament) in the fiber structure [or the degree to which the yarn (first filament) covers the plane of the fiber structure], and is expressed in the present application by the following formula.

CF=n×(N) ^1/2

[In the formula, n indicates the yarn density of the yarn (first filament) [strands/50 mm], and N indicates the fineness (total fineness) of the yarn (first filament) [dtex].]

The CF [unit: (lines/50 mm)×(dtex) ^1/2 ] of the first filament may be selected, for example, from the range of about 150 to 1200 (e.g., 180 to 1100), preferably about 200 to 1000 (e.g., 300 to 900), more preferably about 400 to 800 (e.g., 450 to 750), and particularly preferably about 500 to 720. When the lower limit value of the CF of the first filament is within this range, the effect of increasing the rigidity (resistance to tensile force) in the width direction of the belt is sufficiently obtained, making it easier to suppress breakage, and when the upper limit value of the density of the first filament is within this range, even if the first filament breaks, the defect (crack or cut) is less likely to propagate continuously in the length direction of the belt, tending to suppress breakage. In particular, when the connecting reinforcement layer contains a rubber component (crosslinked rubber composition), perhaps because the rubber component is likely to penetrate between adjacent first filaments, the stress acting near the defect site is dispersed to the rubber component, making it even more difficult for the defect to propagate and effectively suppressing peeling of the fiber structure.

The first filament may be, for example, a spun yarn, a filament yarn, a composite yarn, etc., with a filament yarn (monofilament yarn, multifilament yarn, etc.) being preferred, and a multifilament yarn being even more preferred.

When the first filament is a multifilament yarn, the multifilament yarn may contain, for example, about 10 to 1000 filaments (e.g., 30 to 700 filaments), about 50 to 500 filaments (e.g., 60 to 300 filaments), preferably about 70 to 200 filaments (e.g., 80 to 150 filaments), and more preferably about 85 to 120 filaments (e.g., 90 to 110 filaments).

The first filament may be untwisted or twisted yarn, but in order to increase the rigidity in the belt width direction, untwisted yarn or loosely twisted yarn with a twist count of 1 to 29 times/100 mm is preferred, with untwisted yarn being particularly preferred. In such filaments with a low twist count, adhesive components and rubber components (crosslinked rubber composition) from the adhesive treatment described below can easily penetrate between the fibers, effectively improving adhesion and making it easier to prevent the fiber structure from peeling off.

In this application, untwisted yarn means yarn with a twist count of 0 turns/100 mm or more (i.e., including yarn with no twist at all) and less than 1 turn/100 mm, which is essentially no twist.

The average diameter of the first filament may be, for example, about 0.01 to 3 mm (e.g., 0.05 to 1 mm), preferably about 0.08 to 0.5 mm (e.g., 0.1 to 0.4 mm), and more preferably about 0.15 to 0.3 mm (e.g., 0.2 to 0.25 mm).

The material of the first filament is not particularly limited, and examples of the material that can be used include synthetic fibers such as polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), vinyl alcohol fibers (polyvinyl alcohol fibers, ethylene-vinyl alcohol copolymer fibers, vinylon fibers, etc.), polyester fibers (polyalkylene arylate fibers, etc.), polyamide fibers (aliphatic polyamide fibers such as polyamide 6 fibers, polyamide 66 fibers, and polyamide 46 fibers, aramid fibers, etc.), and polyparaphenylene benzobisoxazole (PBO) fibers; cellulose fibers (cellulose fibers derived from natural plants, animals, bacteria, and algae; cellulose ester fibers, regenerated cellulose fibers, and other cellulose derivative fibers; natural fibers such as wool; and inorganic fibers such as carbon fibers, glass fibers, and metal fibers. These fibers may be used alone as a single yarn, or may be used as a composite yarn (mixed yarn) by combining two or more types.

Among these fibers, it is preferable to include a fiber having high heat resistance, for example, a fiber that is not completely melted at the crosslinking temperature in the crosslinking step and can retain the shape (or mechanical strength) of the filament to a certain degree (for example, a fiber made of a material having a melting point or softening point of 160°C or higher (for example, about 170 to 200°C)), in terms of excellent moldability (productivity). Examples of such a fiber having high heat resistance include inorganic fibers and at least one synthetic fiber selected from polypropylene-based fibers (such as polypropylene fibers), polyvinyl alcohol-based fibers, polyester-based fibers, and polyamide-based fibers. Therefore, it is preferable for the first filament to include such a fiber having high heat resistance (the synthetic fiber and/or inorganic fibers), and more preferably, synthetic fibers (for example, polyester-based fibers, polyamide-based fibers such as aramid fibers, etc.), and in particular, polyester-based fibers.

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.

The proportion of highly heat-resistant fibers (e.g., polyester fibers, polyamide fibers such as aramid fibers, and particularly polyester fibers) in the first filament may be, for example, 50% by mass or more (e.g., 70 to 90% by mass), preferably 90% by mass or more, and more preferably substantially 100% by mass. If it is in this range, not only is there an effect of suppressing breakage, but moldability (productivity) also tends to be improved.

The fiber structure is formed in a substantially planar shape (sheet shape) and may contain at least the first filament. For example, the fiber structure may be one in which the threads are aligned in one direction, such as the fibers in Suda Records or UD prepregs. However, in order to stabilize the arrangement of the multiple first filaments and efficiently orient them in the belt width direction, and to improve moldability (handleability or productivity), it is preferable that the fiber structure further contains, in addition to the first filaments, multiple second filaments that are at least connected (joined or intertwined) to the first filaments and extend in a direction intersecting the belt width direction.

The thread density of the second filament extending in a predetermined direction [the number of threads per 50 mm in the direction in which the second filaments extending in the same direction are arranged (the direction perpendicular to the extension direction of the second filaments, preferably the belt width direction)] may be, for example, about 5 to 50 threads/50 mm (for example, 8 to 45 threads/50 mm), and may be higher in density than the first filament (for example, arranged without any space between the second filaments), but from the viewpoint of improving the flexibility of the belt, it is preferable that the thread density is low like the first filament (particularly, the thread density of the second filament is equal to or lower than the thread density of the first filament), and may be selected from a range of, for example, about 10 to 39 threads/50 mm (for example, 12 to 35 threads/50 mm), preferably 15 to 30 threads/50 mm (for example, 18 to 27 threads/50 mm), and more preferably about 20 to 25 threads/50 mm. The range may be the average value of the thread density. If the lower limit of the density of the second filament is within this range, it becomes easier to improve the orientation and moldability of the first filament in the belt width direction, and if the upper limit of the density of the second filament is within this range, not only does it become easier to prevent the thread from being cut at the contact point (intersection or crossover point) with the first filament, but when the connecting reinforcement layer contains a rubber component (crosslinked rubber composition), the rubber component easily penetrates between adjacent threads, which seems to effectively prevent peeling of the fiber structure.

The fineness of the second filament (total fineness in the case of a multifilament yarn, etc.) can be selected, for example, from the range of about 100 to 1000 dtex (e.g., 200 to 900 dtex), preferably about 300 to 800 dtex (e.g., 400 to 700 dtex), and more preferably about 500 to 600 dtex.

The arrangement of the second filaments is not particularly limited, but from the viewpoint of improving the flexibility, moldability, durability, etc. of the belt, it is preferable that adjacent second filaments are arranged with a predetermined gap in a direction perpendicular to the extension direction (e.g., the belt width direction). The gap between adjacent second filaments (e.g., the shortest distance in the belt width direction between the second filaments) may be selected, for example, from a range of about 0.1 to 30 mm (e.g., 0.3 to 20 mm), or may be selected, for example, from a range of about 0.5 to 10 mm (e.g., 0.8 to 7.5 mm), preferably about 1 to 5 mm (e.g., 1.2 to 3 mm), and more preferably about 1.3 to 2.5 mm (e.g., 1.4 to 2.1 mm). The range may be the average value of the gap. If the upper limit of the gap of the second filament is within this range, it becomes easier to improve the orientation and moldability of the first filament in the belt width direction, and if the lower limit of the gap of the second filament is within this range, not only does it become easier to prevent the thread from being cut at the contact point (intersection or crossover point) with the first filament, but if the connecting reinforcement layer contains a rubber component (crosslinked rubber composition), the rubber component easily penetrates between adjacent threads, which seems to effectively prevent peeling of the fiber structure.

The cover factor (CF) [unit: (lines/50 mm)×(dtex) ^1/2 ] of the second filaments is not particularly limited and may be selected, for example, from the range of about 10 to 1500 (e.g., 100 to 1300). From the viewpoint of improving the flexibility, moldability, durability, etc. of the belt, it may be selected, for example, from the range of about 150 to 1200 (e.g., 180 to 1100), preferably about 200 to 1000 (e.g., 300 to 900), more preferably about 400 to 800 (e.g., 450 to 750), and particularly preferably about 500 to 720. When the lower limit of the CF of the second filament is within this range, it becomes easier to improve the belt width direction orientation and moldability of the first filament, and when the upper limit of the CF of the second filament is within this range, not only does it become easier to prevent the thread from breaking at the contact point (intersection or intersection) with the first filament, but when the connecting reinforcement layer contains a rubber component (crosslinked rubber composition), the rubber component easily penetrates between adjacent threads, which seems to effectively prevent peeling of the fiber structure.

The second filament may be, for example, a spun yarn, a filament yarn, a composite yarn, etc., with a filament yarn (monofilament yarn, multifilament yarn, etc.) being preferred, and a multifilament yarn being even more preferred.

When the second filament is a multifilament yarn, the multifilament yarn may contain, for example, about 10 to 1000 filaments (e.g., 30 to 700 filaments), about 50 to 500 filaments (e.g., 60 to 300 filaments), preferably about 70 to 200 filaments (e.g., 80 to 150 filaments), and more preferably about 85 to 120 filaments (e.g., 90 to 110 filaments).

The second filament may also be an untwisted yarn or a twisted yarn, but like the first filament, it is preferably an untwisted yarn with a twist number of 0 turns/100 mm or more and less than 1 turn/100 mm, or a loosely twisted yarn with a twist number of 1 to 29 turns/100 mm, with an untwisted yarn being particularly preferred. In such filaments with a low twist number, adhesive components and rubber components (crosslinked rubber composition) from the adhesive treatment described below can easily penetrate between the fibers, effectively improving adhesion and making it easier to suppress peeling of the fiber structure.

The average diameter of the second filament may be, for example, about 0.01 to 3 mm (e.g., 0.05 to 1 mm), preferably about 0.08 to 0.5 mm (e.g., 0.1 to 0.4 mm), and more preferably about 0.15 to 0.3 mm (e.g., 0.2 to 0.25 mm).

The material of the second filament is not particularly limited, and may be, for example, the same as the preferred embodiment of the material of the first filament. In addition, the proportion of highly heat-resistant fibers (e.g., polyester fibers, polyamide fibers such as aramid fibers, and particularly polyester fibers) in the second filament may be, for example, 50% by mass or more (e.g., 70 to 90% by mass), preferably 90% by mass or more, and more preferably substantially 100% by mass. If it is in such a range, moldability (productivity) tends to be improved.

The second filament is not particularly limited as long as it extends in a direction intersecting the belt width direction. For example, it may extend in the thickness direction of the belt (tie band), but it is preferable for it to extend toward the back surface of the belt (the surface direction of the tie band). The crossing angle between the second filament and the first filament may be, for example, about 20 to 160° (e.g., 30 to 150°), preferably 45 to 135° (e.g., 60 to 120°), and more preferably 75 to 105° (e.g., 80 to 100°, particularly approximately a right angle).

The second filament may extend in multiple directions, not just one specific direction, as long as it intersects with the belt width direction. That is, the fiber structure may be a multiaxial fiber structure formed with three or more axial threads, such as a triaxial woven fabric, triaxial net, or honeycomb net (honeycomb mesh). From the standpoint of availability or productivity, a biaxial fiber structure (such as a sudarekord, woven fabric, or net formed with warp and weft threads) formed with a first filament extending in the belt width direction and a second filament extending in a specific direction (preferably the belt length direction) is preferred.

In the Suda record, woven fabric, or net formed of warp and weft threads, either the warp thread or the weft thread may be the first filament, and from the viewpoint of productivity, it is preferable to make the weft thread the first filament in the belt width direction. In addition, when forming a net with the weft thread as the first filament and the warp thread as the second filament, the structure of the net may be a structure in which the warp threads 2b arranged at intervals in the belt width direction are arranged alternately above and below each weft thread 2a extending in the belt width direction, as in the fiber structure 2 shown in FIG. 1; instead of the above and below alternating, a structure in which two warp threads are used to sandwich each weft thread above and below may also be used, but the former structure shown in FIG. 1 is preferable from the viewpoint of improving the flexibility of the belt.

As the fiber structure, a woven fabric or a net (network structure or mesh) formed from a first filament and a second filament is preferable, and among them, a net is more preferable because it is easy to improve the strength (mechanical properties) of the tie band (connecting member). In particular, a net formed without weaving the threads or tying the threads (forming knots) (a non-interlaced net without a woven structure or knots) tends to easily suppress the decrease in rigidity due to meandering of the filaments (or the curved portion), and also tends to suppress breakage due to wear at the contact point (intersection) between the first filament and the second filament. Representative nets include "Crenet (registered trademark)" manufactured by Kurabo Industries Ltd. and "Sof (registered trademark)" manufactured by Sumika Sekisui Film Co., Ltd.

In addition, in the fiber structure (woven fabric or net, particularly the non-interlaced net), the contact points (intersections) between the first and second filaments are preferably bonded (joined or glued). When the contact points are bonded, the relative arrangement, such as the spacing between the filaments, can be stabilized, allowing efficient orientation in the belt width direction and improving moldability. There are no particular restrictions on the form of bonding at the contact points, and they may be fused by heat fusion or the like, but it is preferable that they are bonded with an adhesive (such as a resin) because they can be easily bonded regardless of the material of the thread and can improve productivity. There are no particular restrictions on the adhesive, and a conventional adhesive can be used, and it may be the same as the adhesive component used in the adhesive treatment of the fiber structure described below.

The fiber structure may be subjected to a conventional adhesive treatment (or surface treatment) [e.g., treatment with a treatment liquid containing an adhesive component] in order to improve adhesion to a rubber component (crosslinked rubber composition) or the like. Examples of adhesive components (or surface treatment agents) used in the adhesive treatment include isocyanates (polyisocyanate compounds), epoxy resins (epoxy compounds), silane coupling agents, amino resins, rubber latex or rubber paste, and RFL liquids containing resorcin (R), formaldehyde (F), and rubber or latex (L) [e.g., RFL liquids containing a condensate (RF condensate) formed by resorcin (R) and formaldehyde (F) and the rubber component, e.g., vinylpyridine-styrene-butadiene copolymer rubber]. These may be used alone or in combination of two or more kinds, and may be treated sequentially multiple times with the same or different adhesive components. Among these, adhesive components containing the same type (preferably the same) of rubber component as the rubber component in the connecting reinforcing layer, such as rubber latex (e.g., chloroprene latex), are preferred.

The fiber structure may have a basis weight of, for example, 10 to 120 g/m ² (e.g., 20 to 100 g/m ² ), preferably 30 to 90 g/m ² (40 to 80 g/m ² ), and more preferably about 50 to 70 g/m ^2. The fiber structure may have an average thickness of, for example, 0.1 to 1 mm, preferably 0.2 to 0.5 mm, and more preferably about 0.25 to 0.3 mm.

The connecting reinforcement layer may also have multiple layers (e.g., 2 to 3 layers) of the above-mentioned substantially planar (sheet-like) fiber structure as necessary, but from the standpoint of the flexibility and productivity of the belt, it is preferably a single layer.

(Crosslinked Rubber Composition (Rubber Component))
The connecting reinforcement layer may contain at least a fiber structure, but preferably further contains a rubber component (crosslinked rubber composition), and in particular, it is preferable that the fiber structure is embedded in the rubber component. When the rubber component is interposed between the filaments constituting the fiber structure, peeling of the fiber structure can be effectively suppressed, and when the rubber component is interposed between the first filaments adjacent in the belt length direction, in particular, stress is dispersed in the rubber component, making it even more difficult for defects to propagate.

The rubber hardness Hs of the crosslinked rubber composition forming the connecting reinforcement layer is, for example, about 56 to 64°, preferably about 58 to 62°, and more preferably about 59 to 61°. If the rubber hardness is too low, durability may decrease, and conversely, if it is too high, flexibility may decrease.

In this application, the rubber hardness of each rubber layer is the value Hs (JIS A) measured using a durometer A-type hardness tester in accordance with JIS K6253 (2012) (vulcanized rubber and thermoplastic rubber - Determination of hardness), and may be referred to simply as rubber hardness.

The tensile modulus of the crosslinked rubber composition forming the connecting reinforcing layer is, for example, about 10 to 25 MPa, preferably about 15 to 20 MPa, and more preferably about 16 to 18 MPa. If the tensile modulus is too small, durability may decrease, and conversely, if it is too large, flexibility may decrease.

In this application, the tensile modulus of each rubber layer can be measured by a method conforming to JIS K6251 (2017).

The rubber component constituting the crosslinked rubber composition that may be contained in the connecting reinforcement 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 of the ease with which the vulcanizing agent and vulcanization accelerator diffuse. In particular, when used in a high-load environment, chloroprene rubber and EPDM are preferred because of their excellent balance of mechanical strength, weather resistance, heat resistance, cold resistance, oil resistance, and adhesiveness. Furthermore, chloroprene rubber is particularly preferred because, in addition to the above properties, it also has excellent abrasion resistance. The chloroprene rubber may be either a sulfur-modified type or a non-sulfur-modified type.

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.

The crosslinked rubber composition of the connecting reinforcing layer 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. Of these fillers, 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 about 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 about 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.

The proportion of the filler (particularly carbon black) may be, for example, 1 to 100 parts by mass, preferably 10 to 70 parts by mass, and more preferably 20 to 60 parts by mass (particularly 30 to 50 parts by mass) per 100 parts by mass of the rubber component. If the proportion of the filler is too small, the elastic modulus may be insufficient, resulting in reduced durability, whereas if the proportion is too high, the elastic modulus may be too high, resulting in reduced flexibility.

The cross-linked rubber composition of the connecting reinforcing layer may contain other additives as necessary, for example, short fibers (e.g., synthetic fibers such as polyolefin fibers, polyamide fibers, polyalkylene arylate fibers, polyvinyl alcohol fibers, and polyparaphenylene benzobisoxazole (PBO) fibers; natural fibers such as cotton, hemp, and wool; inorganic fibers such as carbon fibers, etc.), vulcanizing agents or cross-linking agents, co-cross-linking agents (cross-linking assistants or co-vulcanizing agents) [e.g., polyfunctional (iso)cyanurates, polydiene, metal salts of unsaturated carboxylic acids, oximes, guanidines, polyfunctional (meth)acrylates, bismaleimides, etc.], vulcanizing assistants or cross-linking assistants, vulcanization accelerators or cross-linking accelerators, vulcanization retarders or cross-linking retarders, metal oxides (calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, aluminum oxide, etc.), softeners (paraffin oil, naphthenic oils, etc.), processing agents or processing aids, adhesion improvers [for example, resorcin-formaldehyde co-condensates (RF condensates), amino resins (condensates of nitrogen-containing cyclic compounds and formaldehyde, for example, melamine resins such as hexamethylol melamine, hexaalkoxymethyl melamine (hexamethoxymethyl melamine, hexabutoxymethyl melamine, etc.), urea resins such as methylol urea, benzoguanamine resins such as methylol benzoguanamine resins, etc.), co-condensates thereof (resorcin-melamine-formaldehyde co-condensates, etc.)], antioxidants (antioxidants, heat aging inhibitors, flex crack inhibitors, ozone degradation inhibitors, etc.), colorants, tackifiers, plasticizers, lubricants, coupling agents (silane coupling agents, etc.), stabilizers (ultraviolet absorbing agents, heat stabilizers, etc.), flame retardants, antistatic agents, etc. may be included. The metal oxide may act as a crosslinking agent. In addition, in the adhesion improver, the resorcinol-formaldehyde co-condensate and the amino resin may be an initial condensate (prepolymer) of a nitrogen-containing cyclic compound such as resorcinol and/or melamine with formaldehyde.

These other additives may be used alone or in combination of two or more. Of these, the connecting reinforcing layer preferably contains, in addition to the rubber component, a vulcanizing agent or crosslinking agent, a vulcanization accelerator or crosslinking accelerator, a processing agent or processing aid, an antiaging agent, and a plasticizer.

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

The proportion of the vulcanizing agent or 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 vulcanizing agent or crosslinking agent and rubber component. For example, the proportion of the metal oxide as the crosslinking agent is, for example, about 1 to 20 parts by mass, preferably 3 to 17 parts by mass, and more preferably 5 to 15 parts by mass (particularly 7 to 13 parts by mass) per 100 parts by mass of the rubber component. When a metal oxide is combined with a sulfur-based vulcanizing agent, the proportion of the sulfur-based vulcanizing agent is, for example, about 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, about 1 to 8 parts by mass, preferably 1.5 to 5 parts by mass, and more preferably about 2 to 4.5 parts by mass per 100 parts by mass of the rubber component.

Examples of vulcanization accelerators or crosslinking 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 vulcanization accelerators can be used alone or in combination of two or more. Of these vulcanization accelerators, TMTD, DPTT, CBS, etc. are commonly used.

The proportion of the vulcanization accelerator or crosslinking accelerator, calculated as solid content, is, for example, about 0.1 to 15 parts by mass, preferably about 0.3 to 10 parts by mass (e.g., 0.5 to 5 parts by mass), and more preferably about 0.5 to 3 parts by mass (particularly 0.5 to 1.5 parts by mass) per 100 parts by mass of the rubber component.

Examples of processing agents or processing aids include fatty acids such as stearic acid, fatty acid metal salts such as metal stearates, fatty acid amides such as stearic acid amide, waxes, and paraffins.

The proportion of the processing agent or processing aid (such as stearic acid) is, in terms of solid content, for example 10 parts by mass or less (e.g., 0 to 10 parts by mass), preferably 0.1 to 5 parts by mass (e.g., 0.5 to 3 parts by mass), and more preferably about 1 to 3 parts by mass (particularly 1.5 to 2.5 parts by mass) per 100 parts by mass of the rubber component.

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

Examples of plasticizers include aliphatic carboxylic acid ester plasticizers (adipate ester plasticizers, sebacic acid ester plasticizers, etc.), aromatic carboxylic acid ester plasticizers (phthalate ester plasticizers, trimellitic acid ester plasticizers, etc.), oxycarboxylic acid ester plasticizers, phosphate ester plasticizers, ether plasticizers, and ether ester plasticizers. These plasticizers can be used alone or in combination of two or more. Of these, ether ester plasticizers are preferred.

The proportion of the plasticizer is, for example, about 1 to 30 parts by mass, preferably about 3 to 20 parts by mass, and more preferably about 3 to 10 parts by mass (particularly about 3 to 8 parts by mass) per 100 parts by mass of the rubber component.

The average thickness of the connecting reinforcement layer is, for example, 0.1 to 2 mm, preferably 0.3 to 1.5 mm, and more preferably 0.5 to 1 mm. If the connecting reinforcement layer is too thin, the effect of preventing breakage may be reduced, and if it is too thick, the bending fatigue resistance (flexibility) of the belt may be reduced.

The tie band (connecting member) may also have multiple layers (e.g., 2 to 3 layers) of the connecting reinforcement layer as described above if necessary, but from the standpoint of the flexibility of the belt and productivity, it is preferably a single layer.

[Protective Layer]
The tie band (connecting member) may be formed only by the connecting reinforcement layer, but may also be provided with a protective layer laminated on top of the connecting reinforcement layer (on the outer peripheral surface side of the belt or the outermost layer) in order to effectively suppress damage to the fiber structure in the connecting reinforcement layer (e.g., damage caused by foreign objects from the back surface of the belt).

The protective layer may be formed of a rubber sheet (preferably a rubber sheet of a rubber composition containing at least short fibers) of a conventional cross-linked rubber composition [e.g., a composition containing a rubber component exemplified as the cross-linked rubber composition that the connecting reinforcing layer may contain], or may be formed of a conventional cloth. These protective layers may be used alone or in combination of two or more kinds. Of these protective layers, a protective layer formed of cloth is preferred.

Examples of fabrics 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, etc., and woven fabrics and knitted fabrics woven at a wide angle between the warp and weft threads exceeding 90° and not exceeding 120° are preferred, and woven fabrics widely used as cover fabrics for transmission belts for general industry and agricultural machinery [plain weave fabrics in which the warp and weft threads cross at a right angle, and plain weave fabrics (wide-angle canvas) in which the warp and weft threads cross at a wide angle between 90° and not exceeding 120°] are particularly preferred.

When the protective layer includes a fabric (particularly a woven fabric), it is preferable to arrange the threads constituting the fabric so that they are oblique to the belt width direction (for example, at an angle of about 15° or more to the belt width direction). In particular, when the fabric is a woven fabric composed of warp and weft threads, it is preferable to arrange the warp and weft threads so that the directions in which they extend are approximately symmetrical to the belt length direction (the bisector of the crossing angle of the warp and weft threads is approximately parallel to the belt length direction). When a protective layer arranged in this way is combined with the connecting reinforcement layer, it is possible to effectively protect the fiber structure and suppress ring breakage, while ensuring elasticity in the belt length direction and making it easier to suppress vibration, overturning, and separation of the belt, which further improves the durability of the belt and tends to transmit power more efficiently.

Fibers constituting the fabric 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 used in combination of two or more types as a composite yarn (blended yarn, etc.).

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. Examples of the polyalkylene arylate fiber include poly _C2-4 alkylene- _C8-14 arylate fibers such as polyethylene terephthalate (PET) fiber and polyethylene naphthalate (PEN) fiber. These polyester fibers may be used alone or in combination.

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 fiber (cotton fiber (cotton linter), kapok, etc.), ginseng bark fiber (hemp, paper mulberry, Mitsumata, etc.), and leaf fiber (Manila hemp, New Zealand hemp, etc.); cellulose fibers derived from animals such as sea squirt cellulose; bacterial cellulose fiber; and algae cellulose. Examples of cellulose derivative fibers include cellulose ester fibers; and regenerated cellulose fibers (rayon, cupra, lyocell, etc.). These cellulose fibers can be used alone or in combination of two or more. Of these, cotton fiber is preferred.

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, and more preferably 70/30 to 30/70 (particularly 60/40 to 40/60).

The average fineness of the yarn that constitutes the fabric is, for example, about 5 to 30 count, preferably about 10 to 25 count, and more preferably about 10 to 20 count.

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

The average thickness of the fabric (raw fabric) is, for example, about 0.1 to 1.5 mm, preferably about 0.2 to 1 mm, and more preferably about 0.3 to 0.7 mm.

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

The protective layer may be a fabric having a rubber component (rubber composition) attached thereto in order to improve adhesion to the connecting reinforcement layer. The fabric having a rubber component attached thereto may be a fabric that has been subjected to an adhesive treatment, such as a treatment of soaking (immersing) in a rubber paste prepared by dissolving a rubber composition in a solvent, or a treatment of friction (rubbing) a solid rubber composition. The adhesive treatment may be performed on at least one surface of the fabric, and it is preferable to treat at least the surface that comes into contact with the connecting reinforcement layer, and it is particularly preferable to treat both surfaces.

The rubber hardness Hs of the rubber composition used in the adhesive treatment of the protective layer is, for example, about 50 to 60°, preferably about 52 to 56°, and more preferably about 53 to 55°. If the rubber hardness is too low, durability may decrease, and conversely, if it is too high, flexibility may decrease.

The tensile modulus of the rubber composition used in the adhesive treatment of the protective layer is, for example, 5 to 20 MPa, preferably 10 to 15 MPa, and more preferably about 11 to 13 MPa. If the tensile modulus is too small, durability may decrease, and conversely, if it is too large, flexibility may decrease.

The rubber components in the rubber composition used in the adhesive treatment of the protective layer are the same as those exemplified as the cross-linked rubber composition of the connecting reinforcing layer, including the preferred embodiments.

The rubber composition used in the adhesive treatment of the protective layer may further contain a filler in addition to the rubber component. As the filler, the fillers exemplified as the cross-linked rubber composition of the connecting reinforcing layer can be used. These fillers can be used alone or in combination of two or more. Among these fillers, it is preferable to contain a reinforcing filler, and it is particularly preferable to contain carbon black.

The proportion of the filler (particularly carbon black) is, for example, 5 to 80 parts by mass, preferably 10 to 75 parts by mass, and more preferably about 30 to 70 parts by mass (particularly 40 to 60 parts by mass) per 100 parts by mass of the rubber component. If the proportion of the filler is too low, the elastic modulus may be insufficient, resulting in reduced durability, whereas if the proportion is too high, the elastic modulus may be too high, resulting in reduced flexibility.

The rubber composition used in the adhesive treatment of the protective layer may contain other additives as necessary, such as the other additives exemplified as the crosslinked rubber composition of the connecting reinforcing layer. These other additives may be used alone or in combination of two or more. Of these, the rubber composition used in the adhesive treatment of the protective layer preferably contains a vulcanizing agent or crosslinking agent, a vulcanization accelerator or crosslinking accelerator, a processing agent or processing aid, an antiaging agent, and a plasticizer.

The proportions of the vulcanizing agent or crosslinking agent, vulcanization accelerator or crosslinking accelerator, and antioxidant are the same as those exemplified for the crosslinked rubber composition of the connecting reinforcing layer, including the preferred embodiments.

The proportion of the processing agent or processing aid (such as stearic acid) is, for example, 10 parts by mass or less (e.g., 0 to 5 parts by mass), preferably 0.1 to 3 parts by mass, and more preferably 0.3 to 2 parts by mass (particularly 0.5 to 1.5 parts by mass) per 100 parts by mass of the rubber component, calculated as solid content.

The proportion of plasticizer (such as an ether ester plasticizer) is, for example, about 3 to 50 parts by mass, preferably 5 to 40 parts by mass, and more preferably about 10 to 30 parts by mass (particularly 15 to 25 parts by mass) per 100 parts by mass of the rubber component.

The average thickness of the protective layer is, for example, about 0.4 to 2 mm, preferably about 0.5 to 1.4 mm, and more preferably about 0.6 to 1.2 mm. If the protective layer is too thin, the effect of suppressing damage to the fiber structure may be reduced, and if it is too thick, the flexibility of the belt may be reduced.

In addition, the direction of the threads that make up the fabric (or the orientation of the fabric) is not particularly limited, but it is preferable to arrange them diagonally relative to the belt width direction.

The tie band (connecting member) may have multiple protective layers (e.g., 2-3 layers) as described above if necessary, but preferably has one layer.

[V-belt section]
The V-belt portion connected to the tie band (connecting member) is not particularly limited, and may be any conventional V-belt portion other than the V-belt portion shown in Fig. 1, that is, it may include a core layer (bonded rubber layer) including a core (core wire), a tension layer (tension rubber layer) laminated on the outer circumferential side of the core layer, and a compression rubber layer laminated on the inner circumferential side of the core layer, and have an endless V-shaped cross section. Note that both the left and right sides of the V-shaped cross section are friction transmission surfaces, and in the V-shaped cross section, the side with the wider belt width is the outer circumferential side, and the side with the narrower belt width is the inner circumferential side.

The conventional V-belt portion may be, for example, a wrapped V-belt in which the entire belt surface, including the friction transmission surface, is covered with an outer covering cloth (cover cloth), or a raw edge V-belt (including a raw edge cogged V-belt) in which the transmission surface is exposed without being covered. In applications such as agricultural machinery, the belt and the entire transmission mechanism are easily damaged by the high friction coefficient of the transmission surface and stress or impact due to the inclusion of waste straw, stones, wood, etc., so a wrapped V-belt with a small friction coefficient on the transmission surface and moderate slippage that can mitigate stress or impact is often used as the V-belt portion. In such high-load applications, high rigidity (resistance to lateral pressure) in the belt width direction is also required to prevent buckling deformation (dishing). Therefore, the V-belt portion may be, for example, a wrapped V-belt portion with excellent resistance to lateral pressure described in JP 2020-3061 A, that is, a wrapped V-belt portion in which the compressed rubber layer has a laminated structure including two types of compressed rubber layers with different rubber hardness, and the rubber hardness of each layer is adjusted. Combining the V-belt section, which has excellent resistance to lateral pressure, with the tie band can further improve the wheel breakage prevention effect.

In detail, FIG. 2 shows a schematic cross-sectional view of an example of a V-belt portion constituting the combined V-belt of the present invention (a drawing in which the tie band is omitted and only the V-belt portion is shown in close-up). The wrapped V-belt portion V1 shown in FIG. 2 is formed of an endless belt body in which, from the outer periphery of the belt, a tension rubber layer 14, a core layer (bonded rubber layer) 16 in which a core 15 is embedded in a vulcanized rubber composition, a first compressed rubber layer 17a, and a second compressed rubber layer 17b are laminated in this order, an outer cover fabric 18 (woven fabric, knitted fabric, nonwoven fabric, etc.) that covers the periphery of the belt body over the entire length in the belt circumferential direction, and a reinforcing fabric layer 19 interposed between the second compressed rubber layer 17b and the outer cover fabric 18.

In this example, the core layer 16 is formed of a vulcanized rubber composition in which the core 15 is embedded, but the core layer may be formed only of a core disposed at the interface between the tension rubber layer and the compression 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 tension rubber layer and the compression rubber layer, but also a form in which a part or all of the core disposed at the interface between the tension rubber layer and the compression rubber layer is embedded in the tension rubber layer or the compression rubber layer during the manufacturing process.

The components and materials (rubber composition, core cord, fabric, etc.) of each component of the V-belt portion [first compressed rubber layer, second compressed rubber layer, tension rubber layer, core layer (bonded rubber layer, core), outer cover fabric, reinforcing fabric layer, etc.] and their ratios, the thickness and characteristics of each layer (hardness Hs of each rubber layer and its relationship, tensile modulus (modulus), etc.), and combinations of these are the same as the examples and preferred embodiments described in JP 2020-3061 A.

[Compressed rubber layer]
The compressed rubber layer may be formed of a crosslinked rubber composition that is commonly used as a rubber composition for a V-belt [for example, a composition containing a rubber component exemplified as the crosslinked rubber composition that the connecting reinforcement layer may contain].

The compressed rubber layer constituting each V-belt portion may be a single layer as shown in FIG. 1, but it is preferable to have a laminated structure of two or more layers including a first compressed rubber layer laminated on the outer periphery of the belt and a second compressed rubber layer having a lower rubber hardness than the first compressed rubber layer and laminated on the inner periphery of the belt. By adjusting the rubber hardness of the tension rubber layer to be higher than that of the second compressed rubber layer and the rubber hardness of the first compressed rubber layer to be equal to or higher than that of the tension rubber layer, the lateral pressure resistance of the combined V-belt can be improved.

The compressed rubber layer may have a laminated structure of three or more layers as long as it includes a first compressed rubber layer and a second compressed rubber layer. However, from the standpoint of lateral pressure resistance and productivity, a two-layer structure consisting of a first compressed rubber layer and a second compressed rubber layer is preferred.

The rubber hardness of the first compressed rubber layer is equal to or greater than the rubber hardness of the stretched rubber layer, and the difference in rubber hardness Hs (JIS A) between the first compressed rubber layer and the stretched rubber layer (rubber hardness of the first compressed rubber layer - rubber hardness of the stretched rubber layer) may be 0° or greater. The rubber hardness of the first compressed rubber layer is preferably higher than that of the stretched rubber layer. The difference in rubber hardness Hs (JIS A) between the first compressed rubber layer and the stretched rubber layer can be selected from a range of, for example, 0 to 10° in order to achieve both lateral pressure resistance and flexibility of the belt, and is preferably 0 to 7°, more preferably 0 to 5° (for example, 0 to 4°), and even more preferably 0 to 3° (particularly 0 to 1°) in order to improve the lateral pressure resistance of the belt. If the difference in rubber hardness between the two layers is too large, the rubber hardness of the stretched rubber layer decreases, and the lateral pressure resistance may decrease.

The rubber hardness Hs of the first compression rubber layer can be selected, for example, from the range of about 80 to 100°, and is preferably about 85 to 95°, more preferably 87 to 93°, and even more preferably about 88 to 92° (particularly 89 to 91°). If the rubber hardness is too low, there is a risk that the resistance to lateral pressure will decrease, and conversely, if it is too high, there is a risk that the fit with the pulley groove and flexibility will decrease.

The rubber hardness Hs of the second compressed rubber layer is lower than the rubber hardness of either the first compressed rubber layer or the tension rubber layer, and the difference in rubber hardness Hs between the first compressed rubber layer and the second compressed rubber layer (rubber hardness of the first compressed rubber layer - rubber hardness of the second compressed rubber layer) may be, for example, 1° or more (particularly 5° or more), 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°). The difference in rubber hardness Hs between the tension rubber layer and the second compressed rubber layer (rubber hardness of the tension rubber layer - rubber hardness of the second compressed rubber layer) can also be selected from the same range as the difference in rubber hardness Hs between the first compressed rubber layer and the second compressed rubber layer. If the difference in rubber hardness between the second compressed rubber layer and the first compressed rubber layer or the tensioned rubber layer is too small, flexibility may decrease.

The rubber hardness Hs of the second compression rubber layer can be selected, for example, from the range of about 60 to 90°, and is preferably about 65 to 80°, more preferably 68 to 76°, even more preferably 70 to 74°, and most preferably about 71 to 73°. 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.

The tensile modulus of the first compression rubber layer in the belt width direction is, for example, about 25 to 50 MPa, preferably about 25 to 40 MPa, and more preferably about 26 to 35 MPa (particularly about 28 to 32 MPa). If the tensile modulus is too small, the lateral pressure resistance may decrease, and conversely, if it is too large, the flexibility may decrease.

The tensile modulus of the second compression rubber layer in the belt width direction is, for example, about 12 to 20 MPa, preferably about 13 to 18 MPa, and more preferably about 14 to 17 MPa. If the tensile modulus is too small, the lateral pressure resistance may decrease, and conversely, if it is too large, the flexibility may decrease.

The average thickness of the entire compressed rubber layer is, for example, about 1 to 12 mm, preferably about 2 to 10 mm, and more preferably about 2.5 to 9 mm (particularly about 3 to 5 mm).

The average thickness of the first compressed rubber layer can be selected from the range of, for example, about 95 to 30% of the average thickness of the entire compressed rubber layer, and is preferably about 90 to 50%, more preferably 85 to 55%, and even more preferably about 80 to 60% (particularly 75 to 70%). This ratio may be the ratio when the compressed rubber layer consists only of the first compressed rubber layer and the second compressed rubber layer (i.e., L2/L1 in Figure 2). If the thickness ratio of the first compressed rubber layer is too small, there is a risk of reduced lateral pressure resistance, and conversely, if it is too large, there is a risk of reduced flexibility.

In addition to the first and second compressed rubber layers, the compressed rubber layer may further include other compressed rubber layers having different rubber hardness. The other compressed rubber layers may be a single layer or multiple layers. The other compressed rubber layers may be laminated on either the upper or lower surface of the first compressed rubber layer or the lower surface of the second compressed rubber layer. The average thickness of the other compressed 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 compressed rubber layer. That is, it is preferable that the compressed rubber layer includes the first and second compressed rubber layers as main layers, and the average thickness of the total of the first and second compressed 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 compressed rubber layer. It is particularly preferable that the compressed rubber layer consists of only the first and second compressed rubber layers.

The compressed rubber layer may be formed of a cross-linked rubber composition that is commonly used as a rubber composition for V-belts. The cross-linked rubber composition may be a cross-linked rubber composition containing a rubber component, and the rubber hardness of each layer constituting the compressed rubber layer, particularly the first compressed rubber layer and the second compressed rubber layer, can be adjusted by appropriately adjusting the composition of the composition. The method for 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.

(First Compressed Rubber Layer)
The rubber component constituting the cross-linked rubber composition forming the first compressed rubber layer is the same as the rubber component exemplified in the section on the cross-linked rubber composition that the connecting reinforcement layer may contain, including preferred embodiments, and chloroprene rubber is particularly preferred.

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.

The crosslinked rubber composition forming the first compressed rubber layer may further contain short fibers in addition to the rubber component. Examples of short fibers include the material of the first filament and the fibers exemplified as the fibers constituting the fabric of the protective layer. These short fibers can be used alone or in combination of two or more. Among these short fibers, stiff fibers with 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 (registered trademark)", "Nomex (registered trademark)", "Kevlar (registered trademark)", "Technora (registered trademark)" and "Twaron (registered trademark)".

The average fiber diameter of the short fibers is, for example, 2 μm or more, and preferably about 5 to 100 μm. The average length of the short fibers is, for example, 1 to 20 mm, and preferably about 1.5 to 10 mm.

From the viewpoint of dispersibility and adhesion of the short fibers in the rubber composition, the short fibers may be subjected to a conventional adhesive treatment (or surface treatment) [such as the adhesive treatment of the fiber structure exemplified in the section on the connecting reinforcing layer].

The short fibers may be oriented in the width direction of the belt and embedded in the compression rubber layer to suppress compressive deformation of the belt due to pressure from the pulley.

The proportion of short fibers is, for example, 5 to 50 parts by mass, and preferably about 10 to 30 parts by mass, per 100 parts by mass of the rubber component. If the proportion of short fibers is too low, the rubber hardness of the first compression rubber layer may decrease, and conversely, if the proportion is too high, flexibility may decrease.

The crosslinked rubber composition forming the first compressed rubber layer may further contain a filler in addition to the rubber component. Examples of the filler include the same fillers, including preferred embodiments, as those exemplified in the section on the crosslinked rubber composition that the connecting reinforcing layer may contain. In order to improve resistance to lateral pressure, it is preferable to contain a reinforcing filler, and it is particularly preferable to contain carbon black.

Even when a large amount of carbon black is blended, the deterioration of processability can be suppressed, and the mechanical properties (elastic modulus) of the first compressed rubber layer can be improved. Furthermore, carbon black can reduce the friction coefficient of the first compressed rubber layer, and improve the abrasion resistance of the first compressed rubber layer.

The proportion of the filler (particularly carbon black) may be, for example, 10 to 100 parts by mass, and preferably about 20 to 80 parts by mass, per 100 parts by mass of the rubber component. If the proportion of the filler is too low, the elastic modulus may be insufficient, resulting in reduced resistance to lateral pressure and durability, whereas if the proportion is too high, the elastic modulus may be too high, resulting in reduced flexibility.

The proportion of carbon black may be, for example, 50% by mass or more, preferably 90% by mass or more, and may be 100% by mass, relative to the total filler. If the proportion of carbon black relative to the total filler is too low, the rubber hardness of the first compressed rubber layer may decrease.

The cross-linked rubber composition forming the first compressed rubber layer may contain, in addition to the rubber component, filler, and short fibers, other additives as necessary, such as the other additives exemplified in the section on the cross-linked rubber composition that the connecting reinforcement layer may contain.

The proportion of the vulcanizing 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 vulcanizing agent and rubber component. For example, the proportion of the metal oxide as the vulcanizing agent is, for example, about 1 to 20 parts by mass, and preferably about 3 to 17 parts by mass, per 100 parts by mass of the rubber component. When a metal oxide is combined with a sulfur-based vulcanizing agent, the proportion of the sulfur-based vulcanizing agent is, for example, about 0.1 to 50 parts by mass, and preferably about 1 to 30 parts by mass, per 100 parts by mass of the metal oxide. The proportion of the organic peroxide is, for example, about 1 to 8 parts by mass, and preferably about 1.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

The co-crosslinking agent (crosslinking aid or co-vulcanizing agent) may be a known crosslinking aid, such as the co-crosslinking agents exemplified as other additives to the crosslinked rubber composition in the connecting reinforcing layer, and may be used alone or in combination of two or more. Among these crosslinking 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 crosslinking aid (e.g., bismaleimides) can increase the degree of crosslinking and prevent adhesion wear, etc.

The proportion of co-crosslinking agents (crosslinking assistants) such as bismaleimides is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 8 parts by mass, per 100 parts by mass of the rubber component, calculated as solid content.

The proportion of the vulcanization accelerator is, for example, 0.1 to 15 parts by mass, preferably 0.3 to 10 parts by mass, per 100 parts by mass of the rubber component, calculated as solid content.

The proportion of the softener (oils such as naphthenic oils) is, for example, 1 to 30 parts by mass, and preferably 3 to 20 parts by mass, per 100 parts by mass of the rubber component, calculated as solid content.

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

The proportion of the adhesion improver (resorcinol-formaldehyde co-condensate, hexamethoxymethylmelamine, etc.) is, for example, 0.1 to 20 parts by mass, preferably 0.3 to 5 parts by mass, per 100 parts by mass of the rubber component, calculated as solid content.

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

(Second Compressed Rubber Layer)
As the rubber component constituting the cross-linked rubber composition forming the second compressed rubber layer, the rubber components exemplified in the section on the cross-linked rubber composition that the connecting reinforcement layer may contain can be used, and are the same as those of the first compressed rubber layer, including preferred embodiments.

The cross-linked rubber composition of the second compressed rubber layer may further contain a filler in addition to the rubber component. As the filler, the fillers exemplified in the section on the cross-linked rubber composition that the connecting reinforcement layer may contain can be used, and the preferred embodiment and the proportion of carbon black in the filler are the same as those of the filler of the first compressed rubber layer.

In the second compressed rubber layer, the proportion of the filler (particularly carbon black) may be, for example, 5 to 80 parts by mass, and preferably about 10 to 60 parts by mass, per 100 parts by mass of the rubber component. If the proportion of the filler is too small, the elastic modulus may be insufficient, resulting in reduced resistance to lateral pressure and durability, whereas if the proportion is too high, the elastic modulus may be too high, resulting in reduced flexibility.

The vulcanized rubber composition of the second compressed rubber layer may further contain a plasticizer in addition to the rubber component. Examples of the plasticizer include the plasticizers exemplified in the section on the crosslinked rubber composition that the connecting reinforcement layer may contain. These plasticizers may be used alone or in combination of two or more kinds. Of these, ether ester plasticizers are preferred.

The proportion of plasticizer is, for example, 1 to 30 parts by mass, preferably about 3 to 20 parts by mass, per 100 parts by mass of the rubber component.

The cross-linked rubber composition of the second compressed rubber layer may further contain short fibers and other additives in addition to the rubber component. The short fibers may be the short fibers exemplified as the short fibers of the first compressed rubber layer, and the other additives may be the other additives exemplified in the section on the cross-linked rubber composition that the connecting reinforcement layer may contain. Of these, the second compressed rubber layer preferably contains a vulcanizing agent or cross-linking agent, a vulcanization accelerator, a processing agent or processing aid, and an anti-aging agent in addition to the rubber component.

The proportion of metal oxide as a vulcanizing agent is, for example, 1 to 20 parts by mass, preferably about 3 to 17 parts by mass, per 100 parts by mass of the rubber component.

The proportion of the vulcanization accelerator is, for example, 0.1 to 15 parts by mass, preferably 0.3 to 10 parts by mass, per 100 parts by mass of the rubber component, calculated as solid content.

The proportion of the processing agent or processing aid (such as stearic acid) is, for example, 10 parts by mass or less (e.g., 0 to 5 parts by mass), preferably about 0.1 to 3 parts by mass, per 100 parts by mass of the rubber component.

The proportion of the antioxidant is, for example, 0.5 to 15 parts by mass, and preferably about 1 to 10 parts by mass, per 100 parts by mass of the rubber component.

[Tension layer (tension rubber layer)]
The tension layer may be formed of a fabric (such as the fabrics exemplified for the protective layer) or the like, but is preferably a tension rubber layer. As described above, the rubber hardness of the tension rubber layer is preferably higher than that of the second compressed rubber layer and lower than that of the first compressed rubber layer.

The rubber hardness Hs of the tension rubber layer can be selected, for example, from the range of about 75 to 95°, for example, about 80 to 94° (e.g., 83 to 93°), preferably about 86 to 92°, and more preferably about 87 to 91° (particularly 89 to 91°). If the rubber hardness 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 modulus of the tension rubber layer in the belt width direction is, for example, about 25 to 50 MPa, preferably 25 to 40 MPa, and more preferably 26 to 35 MPa (particularly 28 to 32 MPa). If the tensile modulus is too small, the lateral pressure resistance may decrease, and conversely, if it is too large, the flexibility may decrease.

The average thickness of the tension rubber layer may be, for example, 0.5 to 10 mm (e.g., 0.5 to 1.5 mm), preferably about 0.6 to 5 mm.

The tension rubber layer may be formed of a cross-linked rubber composition that is commonly used as a rubber composition for V-belts. The cross-linked rubber composition may be a cross-linked rubber composition containing a rubber component, and the rubber hardness of the tension rubber layer can be adjusted by appropriately adjusting the composition of the composition. The method for adjusting the rubber hardness, etc. is not particularly limited, and may be adjusted by changing the composition and/or type of the components that make up 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.

As the rubber component constituting the cross-linked rubber composition forming the tension rubber layer, the rubber components exemplified in the section on the cross-linked rubber composition that the connecting reinforcement layer may contain can be used, and the preferred embodiment is the same as the rubber component of the first compression rubber layer.

The vulcanized rubber composition of the tension rubber layer may further contain short fibers in addition to the rubber component. The short fibers exemplified in the first compressed rubber layer section can be used as the short fibers, and the preferred embodiments and ratio to the rubber component are the same as those of the first compressed rubber layer.

The vulcanized rubber composition of the tension rubber layer may further contain a filler. As the filler, the fillers exemplified in the section on the crosslinked rubber composition that the connecting reinforcement layer may contain can be used, and the preferred embodiment and the proportion of carbon black in the filler are the same as those of the filler of the first compression rubber layer.

In the tension rubber layer, the proportion of filler (particularly carbon black) may be, for example, 5 to 100 parts by mass, and preferably about 10 to 80 parts by mass, per 100 parts by mass of the rubber component. If the proportion of filler is too small, the elastic modulus may be insufficient, resulting in reduced resistance to lateral pressure and durability, while if the proportion is too high, the elastic modulus may be too high, resulting in reduced flexibility.

The cross-linked rubber composition of the tension rubber layer may further contain other additives in addition to the rubber component. The other additives may be those exemplified in the section on the cross-linked rubber composition that the connection reinforcement layer may contain, and the preferred embodiments and ratios to the rubber component are the same as those of the first compression rubber layer.

[Core layer (adhesive rubber 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 the core is embedded in a layer formed of a crosslinked rubber composition containing a rubber component. The adhesive rubber layer is interposed between the tension rubber layer and the compression rubber layer (particularly the first compression rubber layer) to bond the tension rubber layer and the compression rubber layer, and the core is embedded in the adhesive rubber layer.

The average thickness of the adhesive rubber layer is, for example, about 0.2 to 5 mm, and preferably about 0.3 to 3 mm.

(Crosslinked Rubber Composition)
The rubber hardness Hs of the crosslinked rubber composition forming the adhesive rubber layer is, for example, about 72 to 80°, preferably about 73 to 78°, and more preferably about 75 to 77°. If the rubber hardness is too low, the lateral pressure resistance may decrease, and conversely, if the rubber hardness is too high, the crosslinked rubber composition around the core body becomes rigid, making the core body difficult to bend, which may cause heat deterioration (cracks) of the adhesive rubber layer, bending fatigue of the core body, and the like, and may cause the core body to peel off.

As the rubber component constituting the cross-linked rubber composition forming the adhesive rubber layer, the rubber components exemplified in the section on the cross-linked rubber composition that the connecting reinforcement layer may contain can be used, and the preferred embodiment is the same as the rubber component of the first compressed rubber layer.

The cross-linked rubber composition of the adhesive rubber layer may further contain a filler in addition to the rubber component. As the filler, the fillers exemplified in the section on the cross-linked rubber composition that the connecting reinforcement layer may contain can be used, and the preferred embodiment and the proportion of carbon black in the filler are the same as those of the first compressed rubber layer.

In the adhesive rubber layer, the proportion of the filler may be, for example, 1 to 100 parts by mass, preferably about 10 to 80 parts by mass, per 100 parts by mass of the rubber component. The proportion of the carbon black may be, for example, 1 to 50 parts by mass, preferably about 10 to 45 parts by mass, per 100 parts by mass of the rubber component.

The cross-linked rubber composition of the adhesive rubber layer may further contain a plasticizer in addition to the rubber component. The plasticizer may be any of the plasticizers exemplified in the section on the cross-linked rubber composition that the connecting reinforcement layer may contain, and the preferred embodiment and ratio to the rubber component are the same as those of the plasticizer of the second compressed rubber layer.

The vulcanized rubber composition of the adhesive rubber layer may further contain short fibers and other additives in addition to the rubber component. The short fibers may be the short fibers exemplified in the section on the first compressed rubber layer, and the other additives may be the additives exemplified in the section on the crosslinked rubber composition that the connecting reinforcement layer may contain. Of these, the adhesive rubber layer preferably contains a vulcanizing agent or crosslinking agent, a vulcanization accelerator, a processing agent or processing aid, and an anti-aging agent in addition to the rubber component. The ratio of these additives to the rubber component is the same as for the second compressed rubber layer.

(Core body)
The cores contained in the core layer are usually cords (twisted cords) arranged at a predetermined interval in the belt width direction. The cords are arranged extending in the belt length direction, and usually arranged in parallel to the belt length direction at a predetermined pitch. When the cores are embedded in the bonded rubber layer, it is sufficient that a part of the core is embedded in the bonded rubber layer, and from the viewpoint of improving durability, a form in which the cores are embedded in the bonded rubber layer (a form in which the entire core is completely embedded in the bonded rubber layer) is preferred. The core is preferably a cord.

The fibers constituting the core wire include, for example, the fibers exemplified as the material for the first filament, and may be used alone or in combination of two or more. Among these fibers, polyester fibers (particularly polyethylene terephthalate fibers and polyethylene naphthalate fibers) and polyamide fibers (particularly aramid fibers) are preferred in terms of high modulus.

The yarn constituting the core wire may be a multifilament yarn. The fineness of the multifilament yarn may be, for example, about 2000 to 10000 dtex (particularly 4000 to 8000 dtex). The multifilament yarn may contain, for example, about 100 to 5000 filaments, and preferably about 500 to 4000 filaments.

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

When the core wire is embedded in the adhesive rubber layer, it may be subjected to a conventional adhesive treatment (surface treatment) [such as the treatments exemplified as the adhesive treatment for the fiber structure of the connecting reinforcing layer] in order to improve adhesion to the crosslinked rubber composition that forms the adhesive rubber layer. The adhesive treatment may be performed alone or in combination of two or more types, and may be performed multiple times in sequence with the same or different surface treatment agents. It is preferable to adhesively treat the core wire with at least RFL liquid.

[Outer covering]
The outer cover fabric (cover fabric) is made of a conventional fabric. Examples of the fabric include the fabrics exemplified in the protective layer section. Among these, woven fabrics such as plain weave, twill weave, and satin weave, woven fabrics with a cross angle of more than 90° and not more than about 120°, and knitted fabrics are preferred, and woven fabrics commonly used as cover fabrics for transmission belts for general industrial and agricultural machines [plain weave fabrics with a cross angle of right angles, and plain weave fabrics (wide-angle canvas) with a cross angle of more than 90° and not more than about 120°] are particularly preferred. Furthermore, wide-angle canvas may be used for applications requiring durability.

The composition of the fabric, i.e., the type and fineness of the fibers that make up the fabric, the weight per unit area, the average thickness, the thread density, etc., are the same as those exemplified in the protective layer section above, including the preferred embodiments.

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

The outer covering fabric may be a fabric having a rubber component attached thereto in order to improve adhesion to the belt body. The outer covering fabric having a rubber component attached thereto may be a fabric that has been subjected to an adhesive treatment, such as a treatment of soaking (immersing) the fabric in a rubber paste prepared by dissolving a rubber composition in a solvent, or a treatment of friction (rubbing) a solid rubber composition. The adhesive treatment may be performed on at least one surface of the fabric, and it is preferable to treat at least the surface that comes into contact with the belt body.

The rubber components constituting the rubber composition to be attached to the outer cover fabric can be the rubber components exemplified in the section on the crosslinked rubber composition that the connecting reinforcing layer may contain, and the preferred embodiment is the same as the rubber component of the first compressed rubber layer.

The rubber composition to be attached to the outer cover fabric may further contain a filler in addition to the rubber component. As the filler, the fillers exemplified in the section on the crosslinked rubber composition that the connecting reinforcing layer may contain can be used, and the preferred embodiment and the proportion of carbon black in the filler are the same as those of the filler in the first compressed rubber layer.

In the rubber composition to be applied to the outer covering fabric, the proportion of filler (particularly carbon black) is, for example, 5 to 80 parts by mass, preferably about 10 to 75 parts by mass, per 100 parts by mass of the rubber component.

The rubber composition to be applied to the outer cover fabric may further contain a plasticizer in addition to the rubber component. The plasticizer may be any of the plasticizers listed in the section on the crosslinked rubber composition that may be contained in the connecting reinforcement layer, and the preferred embodiment is the same as the plasticizer in the second compressed rubber layer.

In the rubber composition to be applied to the outer covering fabric, the ratio of the plasticizer is, for example, about 3 to 50 parts by mass, and preferably about 5 to 40 parts by mass, per 100 parts by mass of the rubber component.

The rubber composition to be attached to the outer cover cloth may further contain short fibers and other additives in addition to the rubber component. The short fibers may be the short fibers exemplified in the section on the first compressed rubber layer, and the other additives may be the additives exemplified in the section on the crosslinked rubber composition that the connecting reinforcement layer may contain. Of these, the rubber composition to be attached to the outer cover cloth preferably contains, in addition to the rubber component, a vulcanizing agent or crosslinking agent, a vulcanization accelerator, a processing agent or processing aid, and an anti-aging agent. The ratio of these additives to the rubber component is the same as for the second compressed rubber layer.

The coefficient of friction of the outer covering fabric, which is the transmission surface, is, for example, about 0.9 to 1, preferably about 0.91 to 0.96, and more preferably about 0.92 to 0.95. In this application, the coefficient of friction can be measured by the method described in the examples below.

The average thickness of the outer covering fabric (the average thickness of each layer in the case of multiple layers) is, for example, 0.4 to 2 mm, and preferably about 0.5 to 1.4 mm. If the thickness of the outer covering fabric is too thin, the abrasion resistance may decrease, and if it is too thick, the flexibility of the belt may decrease.

[Reinforcing fabric layer]
Each V-belt portion may or may not further include a reinforcing fabric layer on the inner circumferential surface (the surface on the inner circumferential side) of the compressed rubber layer [between the inner circumferential surface of the compressed rubber layer and the outer covering fabric as shown in FIG. 2 when the V-belt portion is a wrapped V-belt] as necessary.

The reinforcing fabric layer is formed of a conventional fabric, similar to the outer covering fabric. The fabric may be any of the fabrics listed in the protective layer section above, and the preferred embodiments are the same as those of the protective layer and outer covering fabric.

The reinforcing fabric layer may be a fabric to which a rubber component is attached in order to improve adhesion to the compressed rubber layer and the outer cover fabric. The fabric to which the rubber component is attached may be a fabric that has been subjected to an adhesive treatment, such as a treatment of soaking (immersing) in a rubber paste in which a rubber composition is dissolved in a solvent, or a treatment of friction (rubbing) a solid rubber composition. As the rubber composition, the rubber compositions exemplified as the rubber composition for the outer cover fabric can be used, and the preferred embodiments are the same as those for the outer cover fabric. The adhesive treatment may be performed on at least one surface of the fabric, and it is preferable to treat at least the surface that comes into contact with the compressed rubber layer, and it is particularly preferable to treat both surfaces.

The average thickness of the reinforcing fabric layer is, for example, 0.4 to 2 mm, and preferably about 0.5 to 1.4 mm. If the reinforcing fabric layer is too thin, the effect of improving abrasion resistance may be reduced, and if it is too thick, the flexibility of the belt may be reduced.

[Method of manufacturing bonded V-belt]
The joined V-belt of the present invention is obtained by producing an uncrosslinked V-belt portion (belt main body portion) by a conventional method, and then connecting the resulting multiple uncrosslinked V-belt portions with tie bands.

First, a typical method for producing an uncrosslinked tie band (tie band precursor) is to prepare an uncrosslinked tie band precursor by laminating an uncrosslinked rubber sheet for the link reinforcement layer obtained by rolling on both sides of an adhesively treated fiber structure, and if necessary, further laminating an adhesively treated protective layer fabric on one side of this link reinforcement layer precursor to prepare an uncrosslinked tie band. During lamination, the directions of the fiber structure (first filament) in the link reinforcement layer precursor and the threads constituting the protective layer fabric may be adjusted. Alternatively, the link reinforcement layer precursor may be used as a tie band precursor without laminating the protective layer fabric.

In addition, the uncrosslinked V-belt portion can be manufactured, for example, by the methods described in JP-A-6-137381 and WO2015/104778. A specific method for manufacturing an uncrosslinked wrapped V-belt portion includes cutting a laminate of an adhesively treated reinforcing fabric and an uncrosslinked second compression rubber layer sheet and a first compression rubber layer sheet obtained by rolling, setting the laminate on a mantle, wrapping the uncrosslinked adhesive rubber layer sheet on the first compression rubber layer sheet, wrapping a core body on the wrapped adhesive rubber layer sheet, and further wrapping an uncrosslinked tension rubber layer sheet on the wrapped core body. A cutting process is performed to cut (slice) the resulting annular laminate on the mantle. A skiving process is performed to cut the cut annular laminate into a V shape while it is rotating, and a cover wrapping process is performed to cover the periphery of the resulting uncrosslinked belt body with an outer cover fabric precursor. The uncrosslinked wrapped V-belt portion can be obtained by the following steps.

The above is an example of a method for manufacturing an uncrosslinked wrapped V-belt portion, but the reinforcing fabric is not necessarily required, and the compressed rubber layer may be one layer or three or more layers. In addition, when the V-belt portion is a raw edge V-belt or a raw edge cogged V-belt, it can be manufactured by a conventional manufacturing method for these V-belts. For example, when the V-belt portion is a raw edge V-belt, it may be manufactured in the same manner as the manufacturing method for the uncrosslinked wrapped V-belt portion described above, except that the cover winding process of covering with the outer covering fabric precursor is not performed. When the V-belt portion is a raw edge cogged V-belt, a cog portion may be provided on the inner peripheral side of the compressed rubber layer sheet (a laminate with the reinforcing fabric if necessary) using a mold or the like.

A typical process for connecting a plurality of uncrosslinked V-belt parts with a tie band will be described with reference to FIG. 3. A plurality of uncrosslinked V-belt parts V1 are fitted into a groove having an inverted trapezoidal cross section formed in a cylindrical or annular lower crosslinking mold 21, and then a tie band T is set on the radially outer portion. In setting the tie band, the tie band T is wrapped around the plurality of uncrosslinked wrapped V-belt parts V1 arranged in the width direction along the circumferential direction, and the tie band T is set on the plurality of uncrosslinked wrapped V-belt parts V1. At this time, the tie band T is set so that the first filament forming the fiber structure in the connection reinforcement layer precursor extends in the belt width direction. The tie band T and the plurality of uncrosslinked V-belt parts V1 set in this way are subjected to a crosslinking process (vulcanization process) in which they are sandwiched between the upper crosslinking mold 22 and the lower crosslinking mold 21 and crosslinked while being pressurized. This cross-linking process (vulcanization process) forms a cross-linked sleeve in which multiple wrapped V-belt sections V1 are connected and joined with tie bands T. The cross-linked sleeve thus formed is cut to a predetermined width to form a joined V-belt having a predetermined number of V-belt sections.

In the crosslinking step, the crosslinking temperature can be selected according to the type of rubber component, and is, for example, about 120 to 200°C, and preferably about 150 to 180°C. 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 protective layer, the connecting reinforcement layer, and the V-belt portion are bonded to each other by the rubber component (rubber composition) and/or adhesive component on their surfaces (bonding interfaces). For example, when a laminate of a protective layer precursor formed of a fabric subjected to friction (rubbing) treatment of a solid rubber composition and an uncrosslinked connecting reinforcement layer precursor in which a fiber structure is embedded (or sandwiched) in an uncrosslinked connecting reinforcement layer sandwiched rubber sheet obtained by rolling treatment is used as the tie band precursor, the protective layer and the connecting reinforcement layer are bonded to each other by a crosslinking reaction of the friction rubber composition and the connecting reinforcement layer sandwiched rubber composition. Similarly, the process of setting the tie band precursor to the uncrosslinked V-belt portion includes an uncrosslinked belt bonding step of bonding a plurality of uncrosslinked V-belt portions to each other via the tie band precursor (connecting reinforcement layer precursor) as a connecting portion. In this step, for example, the connecting reinforcement layer and the V-belt portion are bonded to each other by a reaction between the connecting reinforcement layer sandwiched rubber composition on the inner periphery side of the tie band precursor and the rubber composition on the outer periphery side of the uncrosslinked V-belt portion. The shape of the outer periphery of the uncrosslinked V-belt part may be appropriately selected according to the V-belt part as long as it can be joined to the tie band precursor (connection reinforcement layer precursor), and may be, for example, an outer cover fabric precursor or an extension layer formed of a fabric obtained by friction-treating a rubber composition, or an uncrosslinked rubber sheet for an extension rubber layer. The uncrosslinked belt joining step is not limited to this method, and the connection reinforcement layer precursor may be wrapped alone, or a protective layer precursor formed of an uncrosslinked rubber sheet may be wrapped around the connection reinforcement layer precursor wrapped alone (outer periphery) to form a tie band precursor.

In the combined V-belt of the present invention, the number of V-belt parts is not limited to three as shown in FIG. 1, but may be two or more, for example, 2 to 10, preferably 2 to 8, and more preferably 2 to 6. The adjacent V-belt parts may be aligned parallel to each other in the longitudinal direction, and are not limited to the arrangement of the parts spaced apart as shown in FIG. 1, and may be aligned without any space between them. From the viewpoint of productivity, it is preferable to arrange the adjacent wrapped V-belt parts at intervals. The interval between the adjacent V-belt parts is, for example, about 1.7 to 4.3 mm, preferably 2 to 4.1 mm, and more preferably 2.3 to 3.9 mm. The tie band may be capable of connecting the V-belt parts, and is not limited to the arrangement of the V-belt parts by contacting and integrating the entire outer circumferential surface of each V-belt part as shown in FIG. 1, and may have an area where the outer circumferential surface of the V-belt part does not come into contact with the tie band. From the viewpoint of belt durability, it is preferable that the entire outer circumferential surface of each V-belt part comes into contact with the tie band and is integrated.

The combined V-belt of the present invention is suitable for high-load applications and is therefore suitable for high-horsepower machines, and the load (standard transmission capacity) on one V-belt portion may be 10 PS or more, preferably 20 PS or more, and more preferably 22 PS or more (for example, approximately 22 to 30 PS).

Furthermore, when the bonded V-belt is a wrapped bonded V-belt, it is preferable to use it in a high-load, long-span (long center-to-center distance) layout, such as in large-scale agricultural machinery. Since bonded V-belts are suitable for long-span layouts, the maximum span length (center-to-center distance between pulleys) may be 1000 mm or more, for example, about 2000 to 5000 mm.

The overall belt length of the combined V-belt may be, for example, 200 inches (508 cm) or more, for example, about 220 to 500 inches, or about 30 to 200 inches.

The width of the outer circumferential belt surface of each V-belt portion may be, for example, 15 to 35 mm (particularly, 16 to 25 mm), and the thickness of each V-belt portion may be, for example, 10 to 20 mm (particularly, 10 to 15 mm).

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 of the rubber composition, the method for preparing the rubber composition, the fiber materials used, and the measurement or evaluation methods for each physical property are shown below.

[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: "RS-700" manufactured by ADEKA Corporation
Vulcanization accelerator (or 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 fiber: "Conex short fiber" manufactured by Teijin Limited, short fiber having an average fiber length of 3 mm, an average fiber diameter of 14 μm, and a solid adhesion rate of 6 mass% that was subjected to an adhesion treatment with RFL liquid (resorcinol 2.6 parts, 37% formalin 1.4 parts, vinylpyridine-styrene-butadiene copolymer latex (manufactured by Zeon Corporation) 17.2 parts, water 78.8 parts).

[Core wire]
Twisted aramid fiber cord, average wire diameter 1.985 mm.

[Rubber composition for adhesive rubber layer, friction rubber, and rubber sandwiched between fiber structures]
Rubber composition A or C having the formulation shown in Table 1 was kneaded in a Banbury mixer, and the kneaded rubber was passed through a calendar roll to form an uncrosslinked rolled rubber sheet of a predetermined thickness, to prepare a sheet for an adhesive rubber layer and a sheet for a rubber sandwiched between fiber structures (a sheet for a connecting reinforcing layer). Rubber composition B shown in Table 1 was kneaded in a Banbury mixer to prepare a lump uncrosslinked rubber composition for friction. The results of measuring the hardness and tensile modulus of the crosslinked products of each rubber composition are also shown in Table 1.

[Rubber Compositions for First Compressed Rubber Layer, Second Compressed Rubber Layer, and Tension Rubber Layer]
The rubber compositions D to E having the formulations shown in Tables 2 and 3 were kneaded in a Banbury mixer, and the kneaded rubber was passed through a calendar roll to form uncrosslinked rolled rubber sheets of a predetermined thickness, thereby producing sheets for the first compressed rubber layer, the second compressed rubber layer, and the tension rubber layer. The results of measuring the hardness and tensile modulus of the crosslinked products of each rubber composition are also shown in Tables 2 and 3.

[Rubber hardness Hs of crosslinked rubber]
Each rubber layer sheet was press-crosslinked 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 was measured using a durometer A-type hardness tester in accordance with JIS K6253 (2012). For the friction lump uncrosslinked rubber composition B, 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 modulus 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 shape) in accordance with JIS K6251 (2017). For samples containing short fibers, the dumbbell shape was punched out so that the arrangement direction of the short fibers (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 at a speed of 500 mm/min, and the tensile stress (tensile modulus) until the test piece broke was measured.

[Fabrics for reinforcing fabric layer, outer cover fabric and protective layer]
A woven fabric (120° wide angle weave, warp yarn count 20 and weft yarn count 20, warp and weft yarn density 75 threads/50 mm, basis weight 280 g/ ^m2 , average thickness 0.50 mm) of polyester fiber and cotton blended yarn (polyester fiber/cotton = 50/50 mass ratio) was treated with rubber composition B in Table 1 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 fabric precursor, an outer covering fabric precursor and a protective layer precursor.

[Preparation of Uncrosslinked Wrapped V-Belt Part]
A laminate of a reinforcing fabric precursor, a sheet for a second compressed rubber layer shown in Table 3, and a sheet for a first compressed rubber layer shown in Table 2 was cut and placed on the outer circumferential surface of a cylindrical drum, and then a sheet for an adhesive rubber layer, a core wire, and a sheet for an tensile rubber layer shown in Table 2 were laminated and attached in order to form a cylindrical uncrosslinked sleeve in which the reinforcing fabric precursor, the uncrosslinked rubber layer, and the core wire were laminated. The obtained uncrosslinked sleeve was cut in the circumferential direction while being placed on the outer circumferential surface of the cylindrical drum to form a ring-shaped uncrosslinked rubber belt. In the first compressed rubber layer and the tensile rubber layer containing short fibers, the short fibers were arranged in the belt width direction. In addition, the thickness of each rubber layer sheet was adjusted so that the tensile rubber layer thickness, the first compressed rubber layer thickness L2, and the compressed rubber layer thickness L1 (all thicknesses after crosslinking) in the bonded V-belt were the average thicknesses shown in Table 4.

Next, the uncrosslinked rubber belt was removed from the drum, and both sides of the uncrosslinked rubber belt were cut (skived) at a specified angle to form the cross-sectional shape of the uncrosslinked rubber belt into a V-shaped cross section. As shown in FIG. 2, the uncrosslinked rubber belt with a V-shaped cross section (a belt consisting of an extension rubber layer 14, an adhesive rubber layer 16 in which a core body (core wire) 15 is embedded, a first compressed rubber layer 17a, a second compressed rubber layer 17b, and a reinforcing cloth layer 19) was wrapped around the periphery with a precursor of the outer cover cloth 18 to form an uncrosslinked wrapped V-belt portion.

[Example 1]
(Preparation of Connection Reinforcement Layer Precursor 1)
A fibrous structure (net for connecting reinforcement layer) having the structure shown in Table 5 [Kurabo Industries, Ltd.'s "Clenet (registered trademark)" (warp and weft: PET multifilament yarn (untwisted yarn), structure: TRT structure in which warp yarns are alternately arranged above and below the weft as shown in Figure 1, contact points of warp and weft: bonded with resin) was subjected to an adhesive treatment with chloroprene latex] was laminated on both sides with a fiber structure sandwiching rubber sheet formed from rubber composition C in Table 1, and pressed through a roll to prepare a connecting reinforcement layer precursor 1 in which the net was sandwiched between the sandwiching rubber.

(Preparation of Bonded V-Belt)
The six uncrosslinked wrapped V-belt parts obtained were fitted into an annular groove formed in a lower crosslinking mold, and then the linked reinforcement layer precursor 1 and the protective layer precursor laminated on the linked reinforcement layer precursor 1 were set as a tie band precursor on the radially outer portion. That is, in the setting of the tie band precursor, the linked reinforcement layer precursor 1 and the protective layer precursor were wound in this order along the circumferential direction (belt length direction) of the six uncrosslinked wrapped V-belt parts arranged in the width direction, and the tie band precursor was set on the six uncrosslinked wrapped V-belt parts. The linked reinforcement layer precursor 1 was arranged so that the warp yarns of the linked reinforcement layer net shown in Table 5 were approximately parallel to the belt length direction, and the weft yarns (first filament) were approximately parallel to the belt width direction. In addition, the protective layer precursor laminated on the linked reinforcement layer precursor 1 was arranged so that the direction of the yarns constituting the woven fabric was oblique to the belt width direction (both the warp yarns and the weft yarns were 30° to the belt width direction, i.e., both yarns were symmetrical with respect to the belt length direction).

The tie band precursor and six uncrosslinked wrapped V-belt portions thus set were sandwiched between an upper crosslinking mold and a lower crosslinking mold, pressurized to 1.2 MPa, and crosslinked at a crosslinking temperature of 160°C to obtain a crosslinked belt in which six wrapped V-belt portions (RMA B type, cross-sectional dimensions: width 16.5 mm x thickness 11 mm, belt length 71 inches, average thickness of outer cover fabric 1.2 mm) were connected and bonded with tie bands. The resulting crosslinked belt was cut to produce a bonded V-belt (wrapped bonded V-belt) with three wrapped V-belt portions.

The wrapped combined belt obtained in Example 1 was separated into three wrapped V-belt sections, and the friction coefficient of the wrapped V-belt alone was measured using the method described below, and was found to be 0.93.

[Examples 2 to 6 and Reference Examples 1 to 2]
(Preparation of Interconnect Reinforcement Layer Precursors 2 to 8)
Interconnect reinforcement layer precursors 2 to 8 were each prepared in the same manner as in Example 1, except that the fibrous structure (interconnect reinforcement layer net) in interconnect reinforcement layer precursor 1 was changed as shown in Table 5.

(Preparation of Bonded V-Belt)
A combined V-belt (a wrapped combined V-belt having three wrapped V-belt portions) was prepared in the same manner as in Example 1, except that the combined reinforcement layer precursors 2 to 8 were used instead of the combined reinforcement layer precursor 1.

[Comparative Example 1]
(Preparation of Connection Reinforcement Layer Precursor 9)
The woven fabric for the protective layer was used instead of the fibrous structure (net for the connection reinforcement layer) in the connection reinforcement layer precursor 1. That is, a woven fabric (120° wide-angle weave, warp yarn count 20 and weft yarn count 20, warp and weft yarn density 75 threads/50 mm, basis weight 280 g/m ² , average thickness 0.50 mm) of a polyester fiber and cotton blended yarn (polyester fiber/cotton = 50/50 mass ratio) was laminated with a fiber structure sandwiching rubber sheet formed of the rubber composition C in Table 1 on both sides thereof to prepare a connection reinforcement layer precursor 9 in which the woven fabric was sandwiched between the sandwiching rubber.

(Preparation of Bonded V-Belt)
A combined V-belt having three wrapped V-belt portions was manufactured in the same manner as in Example 1, except that a combined reinforcement layer precursor 9 was used instead of the combined reinforcement layer precursor 1 of Example 1, and the direction of the yarns constituting the woven fabric in this combined reinforcement layer precursor 9 was arranged in the same direction as the protective layer precursor, i.e., diagonally to the belt width direction (both warp and weft yarns were at 30° to the belt width direction, i.e., both yarns were symmetrical to the belt length direction).

[Belt friction coefficient]
As shown in Fig. 4, the friction coefficient of the belt was measured by fixing one end of a cut belt 31 to a load cell 32, placing a load 33 of 3 kgf on the other end, and winding the belt 31 around a pulley 34 with the belt winding angle of 45° around the pulley 34. The belt 31 on the load cell 32 side was then pulled at a speed of 30 mm/sec for about 15 seconds, and the average friction coefficient of the friction transmission surface was measured. During the measurement, the pulley 34 was fixed so as not to rotate.

[Driving test]
A biaxial layout test machine consisting of a driving pulley and a driven pulley was used to compare the time until a ring break or a crack occurred in the connecting member. As shown in FIG. 5, the driving pulley and the driven pulley were pulleys with a narrower central groove width than usual. When such a pulley is used, the central V-belt portion protrudes toward the outer periphery when wrapped around the pulley, so that a strong tensile force acts on the tie band (connecting member) in the belt width direction. The outer diameter (diameter) of the driving pulley and the driven pulley was 146 mm, the rotation speed of the driving pulley was 1750 rpm, the load of the driven pulley was 22.5 kW, the axial load was 300 kgf, and the test temperature (ambient temperature) was 25°C.

The results of the running evaluation of the resulting wrapped bonded V-belt are shown in Table 5.

In Table 5, the yarn density and gap (shortest distance between adjacent yarns) of the weft yarn (first filament) and warp yarn (second filament) are all average values. Also, the thickness of the fiber structure, the thickness of the connecting reinforcement layer, and the thickness of the protective layer are all average thicknesses.

As is clear from the results in Table 5, in the running test, in Comparative Example 1, where the threads were arranged to cross diagonally in the belt width direction (the fiber structure did not have the first filament), a loop break occurred after 90 hours. On the other hand, in Example 1, where the threads (weft threads) were arranged in the belt width direction (the fiber structure had the first filament), cracks were confirmed in the tie band (connecting member) after 500 hours, but no loop breakage occurred.

Examples 2 and 3 are examples in which the yarn density of the weft yarn (first filament) and warp yarn (second filament) of Example 1 is increased [or the gap between the yarns is reduced, or the cover factor (CF) is increased]. In Example 2, like Example 1, no breakage occurred even after 500 hours, whereas in Example 3, breakage occurred after 384 hours, resulting in a slight decrease in durability (although within the acceptable range). It is presumed that this result is due to the yarn density being too high [or the gap between the yarns being too small, or the CF being too large], which makes it easier for cracks (or defects) to propagate.

Example 4 and Reference Example 1 are examples in which the thread density is lower than in Example 1 [or the gaps between the threads are larger, or the CF is smaller], which is the opposite of Examples 2 and 3. In Example 4, breakage occurred after 312 hours, and durability was slightly lower than in Example 1, but was within the acceptable range. In Reference Example 1, in which the thread density was even lower than in Example 4, breakage occurred in a relatively short time (120 hours), and durability was low. Therefore, if the thread density is too low [or the gaps between the threads are too large, or the CF is too small], it is thought that even if the effect of suppressing crack propagation is high, the strength (or rigidity) of the connecting reinforcement layer will decrease and sufficient reinforcement effect will not be obtained.

In Reference Example 1, the yarn density of both the weft and warp yarns was changed to a smaller value [or the yarn gap was increased or the CF was decreased] compared to Example 1, whereas Example 5 and Reference Example 2 were examples in which only one of the yarns was changed. In Example 5, in which only the warp yarn was changed [weft yarn (first filament) was the same as in Example 1], no breakage occurred even after 500 hours, as in Example 1. On the other hand, in Reference Example 2, in which only the weft yarn was changed [warp yarn (second filament) was the same as in Example 1], breakage occurred after 96 hours, and durability was greatly reduced. From this, it was found that the form of the warp yarn (second filament) does not have much effect on preventing breakage, and that adjustment of the density [or yarn gap or CF] of the weft yarn (first filament) is important.

In Example 6, the material of the fiber structure was changed from PET to aramid, but like Example 1, no breakage occurred even after 500 hours.

Among Examples 1-2 and 5-6 in which no breakage occurred even after 500 hours, Example 5, in which the warp threads were arranged in a somewhat sparse state, had a fiber structure that was easily distorted in shape during the manufacture of the bonded belt and was somewhat difficult to handle. Therefore, taking into consideration the moldability and productivity, Examples 1-2 and 6 were preferred, with Example 1 being particularly preferred.

The combined V-belt of the present invention can be used in general industrial machines such as compressors, generators, and pumps, and agricultural machines such as combines, rice planters, and mowers, and can effectively prevent wheel breakage, making it suitable for use in high-load machines used in high-load environments. Examples of high-load machines include large agricultural machines used in Europe and the United States (e.g., cultivators, vegetable transplanters, transplanters, binders, combines, vegetable harvesters, threshers, bean cutters, corn harvesters, potato harvesters, beet harvesters, etc.) and other high-load machines used in long-span layouts with high loads.

T...Tie band (connecting member)
1...connecting reinforcing layer 2...fiber structure (net, mesh structure)
2a...first filament (weft)
2b: Second filament (warp)
3: Protective layer V, V1: V-belt portion 4, 14: Expansion layer (expansion rubber layer)
5, 15... Core body (core wire)
6, 16...Core layer (adhesive rubber layer)
7: Compressed rubber layer 8, 18: Outer cover fabric (cover fabric)
REFERENCE SIGNS LIST 10... Bonded V-belt 17a... First compressed rubber layer 17b... Second compressed rubber layer 19... Reinforcement fabric layer

Claims (8)

A combined V-belt including a plurality of V-belt portions arranged in the belt width direction and a tie band for connecting the outer peripheral surfaces of the plurality of V-belt portions; each V-belt portion including a core layer including a core, a tension layer laminated on the outer peripheral side of the core layer, and a compression rubber layer laminated on the inner peripheral side of the core layer,
The tie band has a connecting reinforcing layer including a fibrous structure; the fibrous structure includes a plurality of first filaments extending at least in a width direction of the belt; the first filaments are arranged at least at intervals in a length direction of the belt;
the adjacent first filaments are arranged with a gap of 1 to 4.8 mm in the belt length direction ;
the first filament includes at least one fiber selected from a polyester-based fiber and a polyamide-based fiber,
The first filament has an average diameter of 0.15 to 0.3 mm;
The first filament is a non-twisted yarn having a twist number of less than 1 turn/100 mm, or a loosely twisted yarn having a twist number of 1 to 29 turns/100 mm . The bonded V-belt according to claim 1, wherein the density of the first filament is 5 to 50 filaments/50 mm, and the fineness of the first filament is 100 to 1000 dtex. 3. The combined V-belt according to claim 1, wherein the cover factor of said first filament is 150 to 1200 (filaments/50 mm)×(dtex) ^1/2. The joined V-belt according to any one of claims 1 to 3, wherein the connecting reinforcing layer further contains a rubber component; this rubber component is interposed between the first filaments adjacent in the belt length direction. The combined V-belt according to any one of claims 1 to 4, wherein the fiber structure is a net including a plurality of second filaments extending in a direction intersecting the belt width direction and connected to at least the first filaments. 6. The joined V-belt according to claim 1 , wherein the tie band further comprises a protective layer that is laminated on an outer circumferential side of the connecting reinforcing layer and that contains a fabric. A method for manufacturing the joined V-belt according to any one of claims 1 to 6 , comprising connecting outer peripheral surfaces of a plurality of V-belt portions arranged in a belt width direction to a tie band having the connecting reinforcing layer. A method for connecting a plurality of V-belt portions with the tie band according to any one of claims 1 to 6 to prevent the resulting combined V-belt from breaking.

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