JP7688501B2 - Transmission belt - Google Patents

Description

The present invention relates to a transmission belt.

It is known that nanofibers with a fiber diameter of 1 μm or less are used as reinforcing materials. For example, Patent Document 1 discloses that the compressed rubber layer that constitutes the V-side of a V-belt is formed from a cross-linked rubber composition that contains a rubber component, nanofibers of polyethylene terephthalate fibers, and short para-aramid fibers.

Patent No. 6145170

The objective of the present invention is to provide a high-performance transmission belt.

The present invention relates to a power transmission belt having at least a portion of a belt body formed from a crosslinked rubber composition, the crosslinked rubber composition being composed of a crosslinked product of an uncrosslinked rubber composition containing a rubber component, nanofibers having a fiber diameter of 1 μm or less, short fibers having a fiber diameter of 5 μm or more, and an amylphenol disulfide polymer, the nanofibers and the short fibers being oriented in the belt width direction in the crosslinked rubber composition, and the content of the amylphenol disulfide polymer in the uncrosslinked rubber composition being 5 parts by mass or less per 100 parts by mass of the rubber component.

According to the present invention, the cross-linked rubber composition forming at least a part of the belt body is composed of a cross-linked product of an uncross-linked rubber composition containing a rubber component, nanofibers having a fiber diameter of 1 μm or less, short fibers having a fiber diameter of 5 μm or more, and an amylphenol disulfide polymer. In this cross-linked rubber composition, the nanofibers and short fibers are oriented in the belt width direction. Since the content of the amylphenol disulfide polymer in the uncross-linked rubber composition is 5 parts by mass or less per 100 parts by mass of the rubber component, high performance can be obtained.

FIG. 2 is a perspective view of a piece of a double cogged V-belt according to an embodiment. 1 is a vertical cross-sectional view of a portion of a double-cogged V-belt according to an embodiment. FIG. 2 is a cross-sectional view of a double-cogged V-belt according to an embodiment. FIG. 1 is a perspective view of a composite material. 1 is a cross-sectional view showing the configuration of a transmission using a double-cogged V-belt according to an embodiment. 1 is a vertical cross-sectional view showing the configuration of a transmission using a double-cogged V-belt according to an embodiment. FIG. 2 is a first explanatory diagram of a molding and cross-linking step in the manufacturing method of the double-cogged V-belt according to the embodiment. FIG. 4 is a second explanatory diagram of the molding and cross-linking step in the manufacturing method of the double-cogged V-belt according to the embodiment. FIG. 4 is a third explanatory diagram of the molding and cross-linking step in the manufacturing method of the double-cogged V-belt according to the embodiment. FIG. 4 is a fourth explanatory diagram of the molding and cross-linking step in the manufacturing method of the double-cogged V-belt according to the embodiment. FIG. 5 is a fifth explanatory diagram of the molding and cross-linking step in the manufacturing method of the double-cogged V-belt according to the embodiment. FIG. 6 is a sixth explanatory diagram of the molding and cross-linking step in the manufacturing method of the double-cogged V-belt according to the embodiment. FIG. 7 is a seventh explanatory diagram of the molding and cross-linking step in the manufacturing method of the double-cogged V-belt according to the embodiment. FIG. 8 is an eighth explanatory diagram of the molding and cross-linking step in the manufacturing method of the double-cogged V-belt according to the embodiment. FIG. 4 is a first explanatory diagram of a width cutting/V-side forming step in the manufacturing method of the double-cogged V-belt according to the embodiment. FIG. 4 is a second explanatory diagram of the width cutting and V-side forming step in the manufacturing method of the double-cogged V-belt according to the embodiment. FIG. 1 is a diagram showing a low-speed layout of a belt running test machine. FIG. 1 is a diagram showing a high-speed layout of a belt running test machine.

The following describes the embodiments in detail.

1A to 1C show a double cogged V-belt B (power transmission belt) according to an embodiment. The double cogged V-belt B according to the embodiment is an endless power transmission member used, for example, in a transmission device of a two-wheeled motor vehicle, a four-wheeled motor vehicle, or other general-purpose machine.

The cross-sectional shape of the double cogged V-belt B according to the embodiment is a trapezoid in which the inner peripheral portion is shorter at the bottom than at the top, and a rectangular shape in which the outer peripheral portion is elongated horizontally. The belt length of the double cogged V-belt B according to the embodiment is, for example, 700 mm or more and 1000 mm or less. The belt width is, for example, 10 mm or more and 36 mm or less. The belt thickness is, for example, 13 mm or more and 16 mm or less.

On the inner periphery of the double cogged V-belt B according to the embodiment, lower cogs _CL are arranged at a constant pitch along the belt length direction. The outer contour of the lower cogs _CL is formed in a sinusoidal shape in vertical cross section. On the outer periphery of the double cogged V-belt B according to the embodiment, upper cogs _CU are arranged at a constant pitch along the belt length direction. The outer contour of the upper cogs _CU is formed in a trapezoidal shape in vertical cross section.

The double cogged V-belt B according to the embodiment includes a belt body 11 made of a rubber material, a reinforcing cloth 12 made of a fiber material, and a core wire 13. The belt body 11 has a compressed rubber layer 111 on the inner circumferential side, a tension rubber layer 112 on the outer circumferential side, and an adhesive rubber layer 113 therebetween. The reinforcing cloth 12 is provided so as to cover the inner circumferential surface of the compressed rubber layer 111 and form the lower cog C _L. The core wire 13 is embedded in the middle part of the adhesive rubber layer 113 in the belt thickness direction, and is provided so as to form a spiral having a pitch in the belt width direction.

On both sides of the compression rubber layer 111, V-shaped sides 111a are formed, which become the pulley contact surfaces. The V-angle in the cross section formed by the V-shaped sides 111a is, for example, 27° or more and 33° or less.

The compressed rubber layer 111, which constitutes the V-shaped side surface 111a, is formed of cross-linked rubber composition X. Cross-linked rubber composition X is composed of a cross-linked product of uncross-linked rubber composition Y.

The uncrosslinked rubber composition Y contains a rubber component, nanofibers, short fibers, and an amylphenol disulfide polymer serving as a co-crosslinking agent.

Examples of rubber components include ethylene-α-olefin elastomers (EPDM, EPR), chloroprene rubber (CR), chlorosulfonated polyethylene rubber (CSM), hydrogenated acrylonitrile rubber (H-NBR), etc. The rubber component preferably contains one or more of these, and from the viewpoint of obtaining excellent durability, it is more preferable to contain ethylene-α-olefin elastomers (EPDM, EPR) or chloroprene rubber (CR).

When the rubber component contains an ethylene-α-olefin elastomer, the ethylene content is preferably 45% by mass or more and 55% by mass or less, more preferably 50% by mass or more and 53% by mass or less, from the viewpoint of obtaining excellent durability. When the rubber component contains an EPDM, the diene component is preferably ethylidene norbornene (ENB) from the viewpoint of obtaining excellent durability, and the diene content (ENB content) is preferably 6% by mass or more and 12% by mass or less, more preferably 7% by mass or more and 8% by mass or less, from the same viewpoint.

The nanofibers are fine fibers having a fiber diameter _d1 of 1 μm or less (1000 nm or less). From the viewpoint of obtaining excellent durability, the fiber diameter _d1 of the nanofibers is preferably 10 nm or more and 1000 nm or less, more preferably 300 nm or more and 900 nm or less, and even more preferably 500 nm or more and 800 nm or less. From the same viewpoint, the fiber length _l1 of the nanofibers is preferably 0.3 mm or more and 5 mm or less, more preferably 0.5 mm or more and 1.5 mm or less. From the same viewpoint, the ratio of the fiber length _l1 of the nanofibers to the fiber diameter _d1 ( _l1 / _d1 : aspect ratio) is preferably 300 or more and 100,000 or less, more preferably 1000 or more and 5,000 or less, even more preferably 1200 or more and 2,000 or less, and even more preferably 1350 or more and 1500 or less.

Examples of nanofibers include synthetic nanofibers such as polyethylene terephthalate fibers (hereinafter referred to as "PET fibers") and polyamide fibers (6-nylon fibers, 6,6-nylon fibers); and naturally derived nanofibers such as cellulose nanofibers. It is preferable for the nanofibers to contain one or more of these, and from the viewpoint of obtaining excellent durability, it is more preferable for the nanofibers to contain PET nanofibers.

The content A of nanofibers in the uncrosslinked rubber composition Y is preferably 1 part by mass or more and 5 parts by mass or less, more preferably 2 parts by mass or more and 3 parts by mass or less, per 100 parts by mass of the rubber component, from the viewpoint of obtaining excellent durability.

In the uncrosslinked rubber composition Y, the nanofibers are preferably blended in the rubber component in the form of a composite material M having a sea-island structure of a sea of thermoplastic resin R and numerous islands of nanofiber F bundles as shown in FIG. 2. In this case, the uncrosslinked rubber composition Y contains the nanofibers F dispersed in the rubber component because the thermoplastic resin R melts and diffuses into the rubber component when kneaded.

This composite material M is obtained by cutting into rod-like conjugate fibers in which the nanofibers F are present in parallel and independent islands in a sea polymer of a thermoplastic resin R. The outer diameter of the composite material M is, for example, 10 μm or more and 100 μm or less. The length of the composite material M is the same as the fiber length _l1 of the nanofibers F, and is preferably 0.3 mm or more and 5 mm or less, more preferably 0.5 mm or more and 1.5 mm or less.

Examples of the thermoplastic resin R include polyethylene resin, ethylene vinyl acetate copolymer resin, nylon resin, urethane resin, etc. The thermoplastic resin R preferably contains one or more of these. Since the thermoplastic resin R diffuses into the rubber component during kneading, it is preferable that the thermoplastic resin R has high compatibility with the rubber component. Therefore, when the rubber component has low polarity, the thermoplastic resin R preferably contains low polarity polyethylene resin, ethylene vinyl acetate copolymer resin, etc. In particular, when the rubber component contains ethylene-α-olefin elastomer (EPDM, EPR), the thermoplastic resin R preferably contains polyethylene resin. In addition, when the rubber component has high polarity such as nitrile rubber (NBR), the thermoplastic resin R preferably contains a highly polar polyethylene resin modified by introducing a polar group such as maleic acid, a nylon resin, a urethane resin, etc.

The content of nanofibers F in the composite material M is, for example, 30% by mass or more and 95% by mass or less. The number of nanofibers F in the composite material M is, for example, 10 to 2000.

Examples of short fibers include para-aramid short fibers, meta-aramid short fibers, polyparaphenylene benzobisoxazole short fibers, nylon 6 short fibers, nylon 6,6 short fibers, nylon 4,6 short fibers, polyethylene terephthalate short fibers, polyethylene naphthalate short fibers, etc. It is preferable that the short fibers contain one or more of these, and from the viewpoint of obtaining excellent durability, it is more preferable that the short fibers contain para-aramid short fibers.

Examples of para-aramid short fibers include polyparaphenylene terephthalamide short fibers and copolyparaphenylene-3,4'-oxydiphenylene terephthalamide short fibers. Examples of commercially available polyparaphenylene terephthalamide short fibers include Twaron manufactured by Teijin Limited, and Kevlar 29, Kevlar 49, and Kevlar 119 manufactured by DuPont. Examples of commercially available copolyparaphenylene-3,4'-oxydiphenylene terephthalamide short fibers include Technora manufactured by Teijin Limited. It is preferable that the short fibers be fibrillated to exhibit a high reinforcing effect, and from this viewpoint, it is even more preferable that the short fibers include polyparaphenylene terephthalamide short fibers that are easily fibrillated.

From the viewpoint of obtaining excellent durability, the fiber diameter _d2 of the short fibers is preferably 5 μm or more and 50 μm or less, more preferably 11 μm or more and 13 μm or less. From the same viewpoint, the ratio ( _d2 / _d1 ) of the fiber diameter _d2 of the short fibers to the fiber diameter _d1 of the nanofibers is preferably 10 to 70, more preferably 15 to 20. From the same viewpoint, the filament fineness of the short fibers is preferably 1 dtex to 5 dtex, more preferably 1.4 dtex to 1.6 dtex.

From the viewpoint of obtaining excellent durability, the fiber length _l2 of the short fibers is preferably 1 mm or more and 10 mm or less, more preferably 2 mm or more and 3.5 mm or less. From the same viewpoint, the fiber length _l2 of the short fibers is preferably longer than the fiber length _l1 of the nanofibers. From the same viewpoint, the ratio ( _l2 / _l1 ) of the fiber length _l2 of the short fibers to the fiber length _l1 of the nanofibers is preferably 1.1 or more and 5 or less, more preferably 2.5 or more and 3.5 or less.

From the viewpoint of obtaining excellent durability, the ratio of the fiber length _l2 of the short fibers to the fiber diameter _d2 ( _{l2 / d2} :aspect ratio) is preferably 20 to 700, more preferably 200 to 300. From the same viewpoint, the aspect ratio of the short fibers (l2/ _d2 ) is preferably smaller than the aspect ratio of the nanofibers ( _l1 / _d1 ). From the same viewpoint, the ratio of the aspect ratio of the short fibers ( _l2 / _d2 ) to the aspect ratio of the nanofibers _{( l1} / _d1 ) ( _l2 / _d2 /l1/ _d1 ) is preferably 0.1 to 0.5, more preferably 0.15 to 0.2.

The short fiber content B in the uncrosslinked rubber composition Y is preferably 20 parts by mass or more and 40 parts by mass or less, more preferably 25 parts by mass or more and 30 parts by mass or less, per 100 parts by mass of the rubber component, from the viewpoint of obtaining excellent durability.

From the viewpoint of obtaining excellent durability, the short fiber content E in the uncrosslinked rubber composition Y is preferably greater than the nanofiber content A. From the same viewpoint, the ratio (B/A) of the short fiber content B to the nanofiber content A is preferably 10 or more and 16 or less, more preferably 11 or more and 12 or less.

The sum of the contents of nanofibers and short fibers in the uncrosslinked rubber composition Y (A+B) is preferably 24 parts by mass or more and 45 parts by mass or less, more preferably 29 parts by mass or more and 33 parts by mass or less, per 100 parts by mass of the rubber component, from the viewpoint of obtaining excellent durability.

The content C of amylphenol disulfide polymer in the uncrosslinked rubber composition Y is 5 parts by mass or less per 100 parts by mass of the rubber component, and from the viewpoint of obtaining excellent durability, is preferably 0.2 parts by mass or more and 3 parts by mass or less, more preferably 0.5 parts by mass or more and 1.5 parts by mass or less.

From the viewpoint of obtaining excellent durability, the content C of amylphenol disulfide polymer in the uncrosslinked rubber composition Y is preferably less than the content A of nanofiber. From the similar viewpoint, the ratio (C/A) of the content C of amylphenol disulfide polymer to the content A of nanofiber is preferably 0.08 or more and 2 or less, more preferably 0.3 or more and 0.5 or less.

From the viewpoint of obtaining excellent durability, the content C of amylphenol disulfide polymer in the uncrosslinked rubber composition Y is preferably less than the content B of short fibers. From the same viewpoint, the ratio (C/B) of the content C of amylphenol disulfide polymer to the content B of short fibers is preferably 0.007 or more and 0.18 or less, more preferably 0.03 or more and 0.04 or less.

From the viewpoint of obtaining excellent durability, the uncrosslinked rubber composition Y preferably contains zinc dimethacrylate as a co-crosslinking agent. From the viewpoint of obtaining excellent durability, the content D of zinc dimethacrylate in the uncrosslinked rubber composition Y is preferably 10 parts by mass or more and 40 parts by mass or less, more preferably 15 parts by mass or more and 25 parts by mass or less, per 100 parts by mass of the rubber component.

From the viewpoint of obtaining excellent durability, the zinc dimethacrylate content D in the uncrosslinked rubber composition Y is preferably greater than the nanofiber content A. From the same viewpoint, the ratio (D/A) of the zinc dimethacrylate content D to the nanofiber content A is preferably 4 or more and 16 or less, more preferably 6 or more and 10 or less.

From the same viewpoint, the ratio (D/B) of the zinc dimethacrylate content D to the short fiber content B in the uncrosslinked rubber composition Y is preferably 0.5 or more and 1.1 or less, more preferably 0.6 or more and 0.8 or less. From the same viewpoint, it is preferable that the zinc dimethacrylate content D is less than the short fiber content B.

From the viewpoint of obtaining excellent durability, the zinc dimethacrylate content D in the uncrosslinked rubber composition Y is preferably greater than the amylphenol disulfide polymer content C. From the same viewpoint, the ratio (D/C) of the zinc dimethacrylate content D to the amylphenol disulfide polymer content C is preferably 4 or more and 100 or less, more preferably 15 or more and 25 or less.

The sum of the contents of amylphenol disulfide polymer and zinc dimethacrylate in the uncrosslinked rubber composition Y (C+D) is preferably 10 parts by mass or more and 45 parts by mass or less, more preferably 15 parts by mass or more and 25 parts by mass or less, per 100 parts by mass of the rubber component, from the viewpoint of obtaining excellent durability.

From the viewpoint of obtaining excellent durability, the uncrosslinked rubber composition Y preferably contains carbon black. Examples of carbon black include furnace blacks such as ISAF, HAF, MAF, FEF, SRF, GPF, and ECF. The carbon black preferably contains one or more of these, and from the viewpoint of obtaining excellent durability, it is more preferable that the carbon black contains ISAF.

From the viewpoint of obtaining excellent durability, the arithmetic mean particle diameter of carbon black is preferably 18 nm or more and 30 nm or less, more preferably 20 nm or more and 23 nm or less. The arithmetic mean particle diameter of carbon black is determined as the number average of the particle diameters of 100 carbon black particles measured by observation with an electron microscope.

From the viewpoint of obtaining excellent durability, the nitrogen adsorption specific surface area of carbon black is preferably 95 m ² /g or more and 150 m ² /g or less, more preferably 115 ^{m 2} /g or more and 125 m ² /g or less. The nitrogen adsorption specific surface area of carbon black is measured based on JIS K6217-2:2017.

The carbon black content E in the uncrosslinked rubber composition Y is 25 parts by mass or more and 70 parts by mass or less per 100 parts by mass of the rubber component, and from the viewpoint of obtaining excellent durability, is preferably 30 parts by mass or more and 60 parts by mass or less, and more preferably 35 parts by mass or more and 45 parts by mass or less.

From the viewpoint of obtaining excellent durability, the carbon black content E in the uncrosslinked rubber composition Y is preferably greater than the nanofiber content A. From the same viewpoint, the ratio (E/A) of the carbon black content E to the nanofiber content A is preferably 8 or more and 24 or less, more preferably 14 or more and 18 or less.

From the viewpoint of obtaining excellent durability, the carbon black content E in the uncrosslinked rubber composition Y is preferably greater than the short fiber content B. From the same viewpoint, the ratio (E/B) of the carbon black content E to the short fiber content B is preferably 1.05 or more and 2 or less, more preferably 1.3 or more and 1.5 or less.

From the viewpoint of obtaining excellent durability, the carbon black content E in the uncrosslinked rubber composition Y is preferably greater than the amylphenol disulfide polymer content C. From the same viewpoint, the ratio (E/C) of the carbon black content E to the amylphenol disulfide polymer content C is preferably 8 or more and 200 or less, more preferably 30 or more and 50 or less.

When the uncrosslinked rubber composition Y contains both zinc dimethacrylate and carbon black, the carbon black content E is preferably equal to or greater than the zinc dimethacrylate content D from the viewpoint of obtaining excellent durability. From the same viewpoint, the ratio (E/D) of the carbon black content E to the zinc dimethacrylate content D is preferably 1 or more and 3 or less, more preferably 1.5 or more and 2.5 or less.

When the uncrosslinked rubber composition Y contains both zinc dimethacrylate and carbon black, the sum of the contents of zinc dimethacrylate and carbon black (D+E) is preferably 40 parts by mass or more and 70 parts by mass or less, more preferably 50 parts by mass or more and 65 parts by mass or less, and even more preferably 57 parts by mass or more and 63 parts by mass or less, per 100 parts by mass of the rubber component, from the viewpoint of obtaining excellent durability.

The uncrosslinked rubber composition Y may contain sulfur as a crosslinking agent, or may contain an organic peroxide, or may contain both sulfur and an organic peroxide. When the rubber component contains CR, the uncrosslinked rubber composition Y may contain a metal oxide such as magnesium oxide as a crosslinking agent.

The uncrosslinked rubber composition Y may also contain thermoplastic resin R, plasticizer, processing aid, etc., which constitute the portion of the composite material M other than the nanofiber F.

The contents of nanofibers, carbon black, and para-aramid short fibers in the uncrosslinked rubber composition Y are substantially the same as those in the crosslinked rubber composition X. However, in the crosslinked rubber composition X, the co-crosslinking agent and the crosslinking agent are incorporated into the rubber component for crosslinking or consumed for crosslinking the rubber component. Therefore, the contents of the co-crosslinking agent and the crosslinking agent are specified only in the uncrosslinked rubber composition Y before crosslinking.

The crosslinked rubber composition X that forms the compressed rubber layer 111 is arranged so that its grain direction corresponds to the belt width direction and its anti-grain direction corresponds to the belt length direction. Therefore, in the crosslinked rubber composition X, the nanofibers and short fibers are dispersed in the rubber component and oriented in the grain direction.

The elongation at break EB in the anti-grain direction of the crosslinked rubber composition X at 25°C is preferably 60% or more and 100% or less, more preferably 65% or more and 95% or less, from the viewpoint of obtaining excellent durability. This elongation at break EB is measured based on JIS K6251:2017.

From the viewpoint of obtaining excellent durability, the storage modulus E' of the crosslinked rubber composition X in the grain direction at 25°C is preferably 900 MPa or more, more preferably 920 MPa or more. This storage modulus E' is measured by a tensile method based on JIS K6394:2007, where the average strain is the strain when a load 1.3 times the load at a strain of 1%, the strain amplitude is 0.1%, the frequency is 10 Hz, and the test temperature is 25°C.

The tension rubber layer 112 and the adhesive rubber layer 113 are formed of a cross-linked rubber composition. The tension rubber layer 112 and the adhesive rubber layer 113 may be formed of the same cross-linked rubber composition X as the compression rubber layer 111.

The reinforcing fabric 12 is made of, for example, a woven fabric, knitted fabric, or nonwoven fabric made of synthetic or natural fibers. It is preferable that the reinforcing fabric 12 is subjected to an adhesive treatment to impart adhesion to the belt body 11. Note that a reinforcing fabric of a similar configuration may also be provided to cover the outer peripheral surface of the tension rubber layer 112.

The core wire 13 is composed of twisted yarn made of synthetic fibers. It is preferable that the core wire 13 is subjected to an adhesive treatment to give it adhesiveness to the belt body 11.

According to the double cogged V-belt B of the embodiment having the above configuration, the crosslinked rubber composition X forming the compressed rubber layer 111 which is the part constituting the V-side surface 111a is composed of a crosslinked product of the uncrosslinked rubber composition Y containing a rubber component, nanofibers, short fibers, and an amylphenol disulfide polymer, and in the crosslinked rubber composition X, the nanofibers and short fibers are oriented in the belt width direction, and the content of the amylphenol disulfide polymer in the uncrosslinked rubber composition Y is 5 parts by mass or less per 100 parts by mass of the rubber component, thereby obtaining high performance. Specifically, excellent durability can be obtained whether the belt is run at a low speed or a high speed.

Figures 3A and 3B show a transmission 20 for a motorcycle or the like that uses a double-cogged V-belt B according to an embodiment.

This transmission 20 includes a drive pulley 21 and a driven pulley 22 that are arranged so that their rotation axes are parallel. The double-cogged V-belt B according to the embodiment is wound between the drive pulley 21 and the driven pulley 22.

The driving pulley 21 and the driven pulley 22 each have a fixed sheave 211, 221 that cannot move in the axial direction, and a movable sheave 212, 222 that can move in the axial direction. A V-groove 23 into which the double-cogged V-belt B of the embodiment fits is formed between the fixed sheave 211, 221 and the movable sheave 212, 222 of the driving pulley 21 and the driven pulley 22, respectively.

When the movable sheaves 212, 222 move closer to the fixed sheaves 211, 221, the V groove 23 narrows in width. At this time, the double cogged V-belt B according to the embodiment is pushed up toward the outer periphery inside the V groove 23, and the winding diameter of the belt pitch lines L1, L2, i.e., the pulley diameter, increases. On the other hand, when the movable sheaves 212, 222 move away from the fixed sheaves 211, 221, the V groove 23 widens in width. At this time, the double cogged V-belt B according to the embodiment sinks toward the inner periphery inside the V groove 23, and the pulley diameter decreases.

With the above configuration, in this speed change device 20, the ratio of the pulley diameters of the drive pulley 21 and the driven pulley 22 is changed between a low-speed mode in which the drive pulley 21 has a small pulley diameter and the driven pulley 22 has a large pulley diameter, and a high-speed mode in which the drive pulley 21 has a large pulley diameter and the driven pulley 22 has a small pulley diameter, thereby continuously changing and transmitting the rotational speed of the drive pulley 21 to the driven pulley 22 via the double cog V-belt B.

Next, the manufacturing method of the double-cogged V-belt B according to the embodiment will be described with reference to Figures 4A to H and Figures 5A to B.

<Component preparation process>
In the member preparation step, first, a composite material M having a sea-island structure of a sea of thermoplastic resin R and numerous islands of bundles of nanofibers F as shown in Fig. 2 is blended and kneaded with a rubber component. At this time, the thermoplastic resin R of the composite material M melts and diffuses into the rubber component, and the nanofibers F are dispersed in the rubber component. Thereafter, carbon black, zinc dimethacrylate, and other rubber compounding agents are further blended and kneaded to prepare a block of uncrosslinked rubber composition Y.

Next, the block of uncrosslinked rubber composition Y is rolled to produce an uncrosslinked rubber sheet for forming the compressed rubber layer 111. Note that the uncrosslinked rubber sheet has nanofibers oriented in the grain direction, which is the rolling direction.

Similarly, an uncrosslinked rubber sheet for forming the tension rubber layer 112 and an uncrosslinked rubber sheet for forming the adhesive rubber layer 113 are also prepared. In addition, a predetermined adhesive treatment is performed on the reinforcing fabric 12 and the core wire 13.

<Molding/crosslinking process>
In the molding and cross-linking process, first, as shown in Fig. 4A, the reinforcing cloth 12 and the uncross-linked rubber sheet 111' for forming the compressed rubber layer 111 are wound in order on the outer circumferential surface of the first cylindrical mold 311 to mold the lower cog molded body 40'. At this time, the reinforcing cloth 12 is provided so as to be aligned with the lower cog forming grooves 311a that are continuously provided in the circumferential direction on the outer periphery of the first cylindrical mold 311. In addition, the uncross-linked rubber sheet 111' is provided so that its grain direction is the axial direction of the first cylindrical mold 311, and therefore the belt width direction.

Next, as shown in Fig. 4B, the lower cog molded body 40' on the first cylindrical mold 311 is covered with a first rubber sleeve 312 having a smooth inner surface, which is then placed in a vulcanizing can and sealed, and the vulcanizing can is filled with high-temperature, high-pressure steam and maintained in this state for a predetermined period of time. At this time, the uncrosslinked rubber sheet 111' flows and is pressed into the lower cog forming groove 311a, and the crosslinking proceeds to about half and is combined with the reinforcing cloth 12, forming a cylindrical lower cog composite 40 with the lower cog C _L formed on the inner periphery as shown in Fig. 4C.

Next, the steam is released from the vulcanizer to release the seal, the first cylindrical mold 311 is removed, the first rubber sleeve 312 is removed, and the mold is cooled. As shown in FIG. 4D, the outer periphery of the lower cog complex 40 molded on the first cylindrical mold 311 is then cut with a blade to adjust the thickness.

Next, after the lower cog complex 40 is removed from the first cylindrical die 311, it is fitted onto the second cylindrical die 321 as shown in FIG. 4E. At this time, the lower cog complex 40 is provided so that its lower cogs _CL are fitted into the lower cog fitting grooves 321a arranged continuously in the circumferential direction on the outer periphery of the second cylindrical die 321.

Next, as shown in FIG. 4F, an uncrosslinked rubber sheet 113' for forming the adhesive rubber layer 113 is wound around the lower cog composite 40 on the second cylindrical mold 321, the core wire 13 is wound spirally around the uncrosslinked rubber sheet 113' for forming the adhesive rubber layer 113, and an uncrosslinked rubber sheet 112' for forming the tension rubber layer 112 are wound around the uncrosslinked rubber sheet 113' in this order to form the uncrosslinked slab S'.

Next, as shown in FIG. 4G, the uncrosslinked slab S' is covered with the second rubber sleeve 322, which is placed in a vulcanizer and sealed, and the vulcanizer is filled with high-temperature, high-pressure steam and maintained in this state for a specified time. At this time, the main crosslinking of the lower cog complex 40 progresses. At the same time, the uncrosslinked rubber sheet 113' for forming the adhesive rubber layer 113 also crosslinks and is compounded with the core wire 13. In addition, the uncrosslinked rubber sheet 112' for forming the tension rubber layer 112 flows and is pressed into the upper cog forming grooves 322a arranged in a circumferential direction on the inner circumference of the second rubber sleeve 322, and the crosslinking progresses. Then, as shown in FIG. 4H, the entire assembly is integrated to form a cylindrical belt slab S.

<Width cutting and V-side forming process>
Steam is discharged from the vulcanizer to release the seal, the second cylindrical mold 321 is taken out, the second rubber sleeve 322 is removed, and after cooling, the belt slab S is removed from the second cylindrical mold 321.

Then, as shown in FIG. 5A, the belt slab S is cut to a predetermined width, and then, as shown in FIG. 5B, both sides are cut with a blade to form the V-side 111a, thereby obtaining the double-cogged V-belt B according to the embodiment.

In the above embodiment, the double-cogged V-belt B is shown, but the present invention is not limited thereto. It may be a single-cogged V-belt having only the lower cog, or a low-edge V-belt having no cog. In addition, the V-ribbed belt may be formed of the crosslinked rubber composition X as a portion constituting the V-side of the V-rib, and the same effect as the above embodiment can be obtained. Furthermore, at least a portion of the belt body may be a toothed belt or a flat belt formed of the crosslinked rubber composition X, and high performance can be obtained. Specifically, in these cases, the crosslinked rubber composition X has nanofibers and short fibers oriented in the belt width direction, and has relatively high rigidity in the belt width direction, so that warping in the belt width direction can be suppressed, and has relatively low rigidity in the belt length direction, so that it can be bent with a small force and wound around a pulley, and as a result, stable belt running performance can be obtained over a long period of time.

(Crosslinked rubber composition and double cogged V-belt)
The crosslinked rubber compositions and double cogged V-belts were prepared in the following Examples 1 to 5 and Comparative Examples 1 to 6. The configurations of each are also shown in Tables 1 and 2.

Example 1
An EPDM rubber component (T7241, manufactured by JSR Corporation, ethylene content: 52 mass%, ENB content: 7.7 mass%) was charged into a Banbury mixer, and 3.6 parts by mass of a polyethylene resin-PET nanofiber composite material (Nanofront, manufactured by Teijin Frontier Corporation) was charged per 100 parts by mass of this rubber component, and they were kneaded at a temperature higher than the melting point of the polyethylene resin contained in the composite material. Thereafter, 40 parts by mass of ISAF carbon black (SEAST 6, manufactured by Tokai Carbon Co., Ltd., arithmetic mean particle size: 22 nm, nitrogen adsorption specific surface area: 119 ^m2 /g), 10 parts by mass of process oil (SUMPAR 2280, manufactured by Sun Oil Co., Ltd.), 0.25 parts by mass of stearic acid as a processing aid (STEARIC ACID S50, manufactured by New Japan Chemical Co., Ltd.), 5 parts by mass of zinc oxide as a vulcanization accelerator aid (Zinc Oxide 3, manufactured by Sakai Chemical Co., Ltd.), 20 parts by mass of zinc dimethacrylate as a co-crosslinking agent (ACTOR ZMA, manufactured by Kawaguchi Chemical Industry Co., Ltd.), 1 part by mass of amylphenol disulfide polymer as a co-crosslinking agent (SANCELAR AP, manufactured by Sanshin Chemical Industry Co., Ltd.), and 4 parts by mass of N,N'-m-phenylene bismaleimide as a co-crosslinking agent (Bulnoc PM, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) were further added and kneaded relative to 100 parts by mass of the rubber component.

The kneaded mass of uncrosslinked rubber composition was then discharged from the Banbury mixer and cooled once, after which it was again charged into the Banbury mixer together with 28 parts by mass of polyparaphenylene terephthalamide short fibers (Kevlar 119, manufactured by DuPont) of para-aramid short fibers, 0.5 parts by mass of sulfur (Seimi OT, manufactured by Nippon Kanretsu Kogyo Co., Ltd.) as a crosslinking agent, and 7 parts by mass (2.8 parts by mass of active ingredient) of organic peroxide (Peroximon F-40, manufactured by Nippon Oil & Fats Co., Ltd., purity 40% by mass) as a crosslinking agent, per 100 parts by mass of the rubber component, and kneaded.

Next, the kneaded mass of uncrosslinked rubber composition was discharged from the Banbury mixer and rolled using a calendar roll to obtain an uncrosslinked rubber sheet.

The uncrosslinked rubber sheet thus obtained was press molded to produce a sheet-shaped crosslinked rubber composition. The uncrosslinked rubber sheet thus obtained was used to produce a double-cogged V-belt having the same configuration as the above embodiment, in which a compressed rubber layer was formed. These sheet-shaped crosslinked rubber compositions and double-cogged V-belts were designated as Example 1.

Here, the composite material used above has a sea-island structure with a sea of polyethylene resin and an island of 1,200 PET nanofibers.

The composite material contains 30% polyethylene resin by mass and 70% nanofiber by mass. Therefore, the polyethylene resin content is 1.1 parts by mass and the nanofiber content is 2.5 parts by mass per 100 parts by mass of the rubber component.

The outer diameter of the composite material is 30 μm and the length is 1 mm. Therefore, the fiber length l ₁ of the PET fiber nanofiber is 1 mm. The fiber diameter d ₁ is 700 nm. The fiber diameter d ₂ of the polyparaphenylene terephthalamide short fiber of the para-aramid short fiber is 12 μm. The fiber length l ₂ is 3 mm.

The tension rubber layer and adhesive rubber layer of the double cogged V-belt were formed from a cross-linked rubber composition with EPDM as the rubber component. The core wire was made of twisted PET fiber yarn. The reinforcing fabric was made of woven PET fiber fabric.

Example 2
A sheet-shaped crosslinked rubber composition and a double-cogged V-belt were prepared in the same manner as in Example 1, except that N,N'-m-phenylenebismaleimide was not used. These were designated as Example 2.

Example 3
A sheet-shaped cross-linked rubber composition and a double-cogged V-belt were prepared in the same manner as in Example 1, except that the content of ISAF carbon black was 30 parts by mass per 100 parts by mass of the rubber component, and the content of the co-crosslinking agent zinc dimethacrylate was also 30 parts by mass per 100 parts by mass of the rubber component, and these were designated Example 3.

Example 4
A sheet-shaped crosslinked rubber composition and a double-cogged V-belt were prepared in the same manner as in Example 1, except that the content of the amylphenol disulfide polymer was 0.2 parts by mass per 100 parts by mass of the rubber component, and these were designated as Example 4.

Example 5
A sheet-shaped crosslinked rubber composition and a double-cogged V-belt were prepared in the same manner as in Example 1, except that the content of the amylphenol disulfide polymer was 5 parts by mass per 100 parts by mass of the rubber component, and these were designated as Example 5.

<Comparative Example 1>
A sheet-shaped crosslinked rubber composition and a double-cogged V-belt were prepared in the same manner as in Example 1, except that no amylphenol disulfide polymer or sulfur was used. These were designated Comparative Example 1.

<Comparative Example 2>
A sheet-shaped crosslinked rubber composition and a double-cogged V-belt were prepared in the same manner as in Example 1, except that the polyethylene resin-PET nanofiber composite material, the amylphenol disulfide polymer, and sulfur were not used, and these were designated Comparative Example 2.

<Comparative Example 3>
A sheet-shaped crosslinked rubber composition and a double-cogged V-belt were prepared in the same manner as in Example 1, except that no polyparaphenylene terephthalamide short fibers were used. These were designated Comparative Example 3.

<Comparative Example 4>
A sheet-shaped crosslinked rubber composition and a double-cogged V-belt were prepared in the same manner as in Example 1, except that the content of zinc dimethacrylate was 40 parts by mass per 100 parts by mass of the rubber component and that amylphenol disulfide polymer and sulfur were not used. These were designated Comparative Example 4.

<Comparative Example 5>
A sheet-shaped cross-linked rubber composition and a double-cogged V-belt were prepared in the same manner as in Example 1, except that the content of ISAF carbon black was 20 parts by mass per 100 parts by mass of the rubber component, the content of zinc dimethacrylate was 40 parts by mass per 100 parts by mass of the rubber component, and amylphenol disulfide polymer and sulfur were not used. These were designated Comparative Example 5.

<Comparative Example 6>
A sheet-shaped crosslinked rubber composition and a double-cogged V-belt were prepared in the same manner as in Example 1, except that the content of the amylphenol disulfide polymer was 10 parts by mass per 100 parts by mass of the rubber component, and these were designated Comparative Example 6.

(Test Method)
<Elongation at break EB>
For each of the sheet-shaped crosslinked rubber compositions of Examples 1 to 5 and Comparative Examples 1 to 6, the elongation at break (EB) in the anti-grain direction at 25° C. was measured based on JIS K6251:2017.

<Storage vertical elastic modulus E'>
For each of the sheet-shaped crosslinked rubber compositions of Examples 1 to 5 and Comparative Examples 1 to 6, the fresh storage elastic modulus E' at 25°C was measured by a tensile method based on JIS K6394: 2007. The measurement conditions were as follows: average strain was defined as the strain when a load 1.3 times the load at a strain of 1%, strain amplitude was 0.1%, frequency was 10 Hz, and test temperature was 25°C.

<Belt running test>
6A and 6B show a belt running tester 50. The belt running tester 50 includes a driving pulley 51 and a driven pulley 52. Each of the driving pulley 51 and the driven pulley 52 is configured so that the winding diameter at the center position of the core wire of the double cogged V-belt B to be tested is variable. The driven pulley 52 is also configured so that a constant load DW (dead weight) can be applied to the double cogged V-belt B so as to generate a constant belt tension.

For each of the double cogged V-belts of Examples 1 to 5 and Comparative Examples 1 to 6, first, as shown in FIG. 6A, the double cogged V-belt B was wound around the driving pulley 51 so that the winding diameter at the center of the core was 99 mm, and the driven pulley 52 was wound so that the winding diameter at the center of the core was 263 mm. A constant load DW of 1800 N was applied to the driven pulley 52 to generate belt tension, forming a low-speed layout. Then, the driving pulley 51 was rotated at 7500 rpm at an ambient temperature of 30° C. to start low-speed belt running. The double cogged V-belt was run until it broke, and the time from the start of belt running to breaking was defined as the low-speed belt life. The longest belt running time was set to 200 hours.

As shown in FIG. 6B, the double cogged V-belt B was wound around the driving pulley 51 so that the winding diameter at the center of the core was 210 mm, and the driven pulley 52 was wound so that the winding diameter at the center of the core was 165 mm. A constant load DW of 2300 N was applied to the driven pulley 52 to generate belt tension, forming a high-speed layout. After that, the driving pulley 51 was rotated at 9400 rpm in an ambient temperature of 100°C to start high-speed belt running. The double cogged V-belt was run until it broke, and the time from the start of belt running to breaking was defined as the high-speed belt life. The longest belt running time was set to 50 hours.

(Test Results)
The test results are shown in Table 3. From Table 3, it can be seen that, according to Examples 1 to 5, excellent durability can be obtained at both low and high belt running speeds, whereas, in Comparative Examples 1 to 6, excellent durability cannot be obtained at both low and high belt running speeds.

The present invention is useful in the technical field of transmission belts.

B Double-cogged V-belt (power transmission belt)
C _L lower cog C _U upper cog M Composite material R Thermoplastic resin F Nanofiber S' Uncrosslinked slab S Belt slab 11 Belt body 111 Compressed rubber layer 111', 112', 113' Uncrosslinked rubber sheet 111a V-shaped side 112 Tension rubber layer 113 Adhesive rubber layer 12 Reinforcing cloth 13 Cord 20 Speed change device 21 Driving pulley 211, 221 Fixed sheave 212, 222 Movable sheave 22 Driven pulley 23 V-groove 311 First cylindrical mold 311a Lower cog forming groove 312 First rubber sleeve 321 Second cylindrical mold 321a Lower cog fitting groove 322 Second rubber sleeve 322a Upper cog forming groove 40' Lower cog molded body 40 Lower cog composite 50 Belt running tester 51 Driving pulley 52 Driven pulley

Claims (14)

A power transmission belt, at least a portion of a belt body being formed from a crosslinked rubber composition,
The crosslinked rubber composition is composed of a crosslinked product of an uncrosslinked rubber composition containing a rubber component, nanofibers having a fiber diameter of 1 μm or less, short fibers having a fiber diameter of 5 μm or more, and an amylphenol disulfide polymer,
In the crosslinked rubber composition, the nanofibers and the short fibers are oriented in the belt width direction,
The content of the amylphenol disulfide polymer in the uncrosslinked rubber composition is 5 parts by mass or less per 100 parts by mass of the rubber component. The power transmission belt according to claim 1,
The content of the nanofibers in the uncrosslinked rubber composition is 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of the rubber component. The power transmission belt according to claim 1 or 2,
The content of the short fibers in the uncrosslinked rubber composition is 20 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the rubber component. The power transmission belt according to any one of claims 1 to 3,
The uncrosslinked rubber composition of the power transmission belt contains zinc dimethacrylate. The power transmission belt according to claim 4,
a mass ratio of the content of the zinc dimethacrylate to the content of the amylphenol disulfide polymer in the uncrosslinked rubber composition is 4 or more and 100 or less. The power transmission belt according to claim 4 or 5,
The uncrosslinked rubber composition has a total content of the amylphenol disulfide polymer and the zinc dimethacrylate of 10 parts by mass or more and 45 parts by mass or less per 100 parts by mass of the rubber component. The power transmission belt according to any one of claims 1 to 6,
The uncrosslinked rubber composition of the power transmission belt contains carbon black. The power transmission belt according to claim 7,
a mass ratio of the content of the carbon black to the content of the amylphenol disulfide polymer in the uncrosslinked rubber composition is 8 or more and 200 or less. The power transmission belt according to any one of claims 1 to 8,
The power transmission belt is a V-belt or a V-ribbed belt. The power transmission belt according to any one of claims 1 to 8,
The power transmission belt is a toothed belt or a flat belt. The power transmission belt according to any one of claims 1 to 10,
The power transmission belt, wherein the nanofibers are synthetic nanofibers. The power transmission belt according to claim 11,
The power transmission belt, wherein the synthetic fiber nanofiber is a polyethylene terephthalate fiber nanofiber. The power transmission belt according to any one of claims 1 to 12,
a mass ratio of the content of the amylphenol disulfide polymer in the uncrosslinked rubber composition to the content of the nanofibers is 0.08 or more and 2 or less. The power transmission belt according to any one of claims 1 to 13,
A power transmission belt, wherein a mass ratio of a content of the amylphenol disulfide polymer in the uncrosslinked rubber composition to a content of the short fibers is 0.007 or more and 0.18 or less.

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