Friction drive belt

Abstract

Provided is a friction drive belt (B) wherein a power transmission surface is formed with a crosslinked rubber composition obtained by crosslinking an uncrosslinked rubber composition which includes para-aramid short fibers, pulp fiber, and a rubber component that includes a chloroprene rubber and / or an ethylene-α-olefin elastomer as the main component. The ratio of the content of the pulp fiber to the content of the para-aramid short fibers in the uncrosslinked rubber composition is not less than 0.15 but less than 1. The total content of the pulp fiber and the para-aramid short fibers in the uncrosslinked rubber composition is 20-50 parts by mass with respect to 100 parts by mass of the rubber component.

Description

Friction transmission belt

[0001] The present invention relates to a friction power transmission belt.

[0002] Friction power transmission belts having a power transmission surface formed of a crosslinked rubber composition containing pulp fibers and para-aramid short fibers are known (Patent Documents 1 and 2).

[0003] Patent No. 6918047 Patent No. 6529327

[0004] The present invention provides a friction transmission belt having a power transmission surface formed of a crosslinked rubber composition obtained by crosslinking a rubber component containing chloroprene rubber and / or ethylene-α-olefin elastomer as a main component and an uncrosslinked rubber composition containing pulp fibers and para-aramid short fibers, wherein the ratio of the content of the pulp fibers in the uncrosslinked rubber composition to the content of the para-aramid short fibers is 0.15 or more and less than 1, and the total content of the pulp fibers and the para-aramid short fibers in the uncrosslinked rubber composition is 20 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the rubber component.

[0005] 1A and 1B are perspective views of a section of a cogged V-belt according to an embodiment, cross-sectional views of a cogged V-belt according to an embodiment along the belt width direction, and cross-sectional views of a cogged V-belt according to an embodiment along the belt length direction.

[0006] The embodiments will be described in detail below.

[0007] 1 to 3 show a cog V-belt B according to an embodiment. This cog V-belt B is an endless frictional power transmission belt made of rubber and used in transmissions for motorcycles such as scooters. The cog V-belt B has a belt length of, for example, 200 mm or more and 5000 mm or less. The cog V-belt B has a maximum belt width of, for example, 10 mm or more and 30 mm or less. The cog V-belt B has a maximum belt thickness of, for example, 7.0 mm or more and 14.0 mm or less.

[0008] The cogged V-belt B according to the embodiment includes a V-belt body 10, a core wire 20, an inner reinforcing cloth 30, and an outer reinforcing cloth 40.

[0009] The V-belt body 10 has an isosceles trapezoidal cross section along the belt width direction. The angle between both sides of the V-belt body 10 is, for example, 24° to 42°. The V-belt body 10 has a compression rubber layer 11 provided on the inner periphery of the belt, an adhesive rubber layer 12 provided in the middle, and a tension rubber layer 13 provided on the outer periphery of the belt. On the inner periphery of the compression rubber layer 11, bottom cog forming portions 11a, each having a sine curve cross section along the belt length direction, are arranged at a constant pitch.

[0010] The compressed rubber layer 11 is formed of a crosslinked rubber composition X, which is obtained by heating and pressurizing an uncrosslinked rubber composition X', which is obtained by blending and kneading various rubber compounding ingredients, including pulp fiber and para-aramid short fiber, with a rubber component, and crosslinking the uncrosslinked rubber composition X' with a crosslinking agent. From the viewpoint of achieving high power transmission efficiency, the crosslinked rubber composition X is preferably provided so that the grain direction is in the belt width direction. In the cogged V-belt B according to the embodiment, both side surfaces of the compressed rubber layer 11 constitute power transmission surfaces, which are made of the crosslinked rubber composition X and contact the pulleys to transmit power.

[0011] The rubber components of the uncrosslinked rubber composition X' and the crosslinked rubber composition X contain chloroprene rubber (hereinafter referred to as "CR") and / or ethylene-α-olefin elastomer as the main component. The content of CR and / or ethylene-α-olefin elastomer in the rubber component is more than 50% by mass, and from the viewpoint of obtaining high power transmission efficiency, it is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 100% by mass. The rubber component is preferably 100% by mass of CR or 100% by mass of ethylene-α-olefin elastomer. In addition to CR and ethylene-α-olefin elastomer, the rubber component may contain chlorosulfonated polyethylene rubber (CSM), hydrogenated acrylonitrile rubber (H-NBR), etc.

[0012] Examples of ethylene-α-olefin elastomers include ethylene-propylene copolymer, ethylene-propylene-diene terpolymer (hereinafter referred to as "EPDM"), ethylene-octene copolymer, ethylene-butene copolymer, etc. When the rubber component contains an ethylene-α-olefin elastomer, the ethylene-α-olefin elastomer preferably contains one or more of these, and more preferably contains EPDM from the viewpoint of obtaining high power transmission efficiency.

[0013] When the rubber component contains an ethylene-α-olefin elastomer, the ethylene content thereof is preferably 40% by mass or more and 70% by mass or less, more preferably 50% by mass or more and 60% by mass or less, and even more preferably 51% by mass or more and 53% by mass or less, from the viewpoint of obtaining high power transmission efficiency.

[0014] When the rubber component contains EPDM, examples of the diene component include ethylidene nobornene (ENB), dicyclopentadiene, and 1,4-hexadiene. Among these, ethylidene nobornene (ENB) is preferred as the diene component from the viewpoint of obtaining high power transmission efficiency. In this case, the ENB (diene) content of the EPDM is preferably 4% by mass or more and 12% by mass or less, more preferably 5% by mass or more and 10% by mass or less, and even more preferably 7% by mass or more and 9% by mass or less.

[0015] The pulp fibers are dispersed in the rubber component and oriented in the grain direction. Examples of pulp fibers include kraft pulp, non-wood pulp, and recycled paper pulp. Examples of kraft pulp include chemical pulp and mechanical pulp. Examples of chemical pulp include bleached hardwood kraft pulp (LBKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), unbleached softwood kraft pulp (NUKP), semi-bleached hardwood kraft pulp (LSBKP), semi-bleached softwood kraft pulp (NSBKP), sulfite hardwood pulp, and sulfite softwood pulp. Examples of mechanical pulp include stone ground pulp (SGP), pressed stone ground pulp (TGP), chemi-ground pulp (CGP), groundwood pulp (GP), and thermomechanical pulp (TMP). Examples of non-wood pulps include kenaf pulp, abaca pulp, cotton linter pulp, straw pulp, bamboo pulp, etc. Examples of waste paper pulp include disintegrated waste paper pulp, disintegrated and deinked waste paper pulp (DIP), disintegrated, deinked and bleached waste paper pulp, etc. The pulp fiber preferably contains one or more of these, and from the viewpoint of obtaining high power transmission efficiency, it is more preferable that the pulp fiber contains kraft pulp.

[0016] From the viewpoint of obtaining high power transmission efficiency, the average fiber diameter D1 of the pulp fibers is preferably 10 μm or more and 50 μm or less, more preferably 20 μm or more and 40 μm or less. From the same viewpoint as above, the average fiber length L1 of the pulp fibers is preferably 20 μm or more and 1000 μm or less, more preferably 400 μm or more and 600 μm or less. From the same viewpoint as above, the ratio of the average fiber length L1 to the average fiber diameter D1 of the pulp fibers (L1 / D1) is preferably 1 or more and 50 or less, more preferably 10 or more and 20 or less.

[0017] From the viewpoint of obtaining high power transmission efficiency, the content A of pulp fibers in the uncrosslinked rubber composition X' is preferably 3 parts by mass or more and 25 parts by mass or less, more preferably 10 parts by mass or more and 20 parts by mass or less, and even more preferably 12 parts by mass or more and 18 parts by mass or less, per 100 parts by mass of the rubber component.

[0018] The para-aramid staple fibers are also dispersed in the rubber component and oriented in the grain direction. Examples of para-aramid staple fibers include polyparaphenylene terephthalamide staple fibers and copolyparaphenylene-3,4'-oxydiphenylene terephthalamide staple fibers. Commercially available polyparaphenylene terephthalamide staple fibers include Kevlar (registered trademark) manufactured by DuPont-Toray Co., Ltd. and Twaron (registered trademark) manufactured by Teijin Limited. Commercially available copolyparaphenylene-3,4'-oxydiphenylene terephthalamide staple fibers include Technora (registered trademark) manufactured by Teijin Limited. The para-aramid staple fibers preferably contain one or both of these, and more preferably contain copolyparaphenylene-3,4'-oxydiphenylene terephthalamide staple fibers from the viewpoint of obtaining high power transmission efficiency.

[0019] From the viewpoint of obtaining high power transmission efficiency, the fiber diameter D2 of the para-aramid staple fibers is preferably 5 μm or more and 70 μm or less, more preferably 10 μm or more and 50 μm or less, even more preferably 11 μm or more and 20 μm or less, and still more preferably 11 μm or more and 13 μm or less. From the same viewpoint as above, the fiber diameter D2 of the para-aramid staple fibers is preferably smaller than the average fiber diameter D1 of the pulp fibers. From the same viewpoint as above, the ratio (D1 / D2) of the average fiber diameter D1 of the pulp fibers to the fiber diameter D2 of the para-aramid staple fibers is preferably 1.5 or more and 5 or less, more preferably 2.5 or more and 3.5 or less. From the same viewpoint as above, the filament fineness of the para-aramid staple fibers is preferably 1 dtex or more and 5 dtex or less, more preferably 1.4 dtex or more and 1.6 dtex or less.

[0020] From the viewpoint of obtaining high power transmission efficiency, the fiber length L2 of the para-aramid short fibers is preferably 0.5 mm or more and 5 mm or less, more preferably 1 mm or more and 3 mm or less. From the same viewpoint as above, the fiber length L2 of the para-aramid short fibers is preferably longer than the average fiber length L1 of the pulp fibers. From the same viewpoint as above, the ratio (L1 / L2) of the average fiber length L1 of the pulp fibers to the fiber length L2 of the para-aramid short fibers is preferably 0.01 or more and 0.25 or less, more preferably 0.1 or more and 0.2 or less. From the same viewpoint as above, the ratio (L2 / D2) of the fiber length L2 to the fiber diameter D2 of the para-aramid short fibers is preferably 80 or more and 400 or less, more preferably 200 or more and 300 or less.

[0021] The content B of the para-aramid short fibers in the uncrosslinked rubber composition X' is preferably 10 to 40 parts by mass, more preferably 15 to 35 parts by mass, even more preferably 20 to 30 parts by mass, and still more preferably 23 to 28 parts by mass, per 100 parts by mass of the rubber component, from the viewpoint of obtaining high power transmission efficiency. The ratio (A / B) of the pulp fiber content A to the para-aramid short fiber content B in the uncrosslinked rubber composition X' is 0.15 or more and less than 1, and from the same viewpoint as above, is preferably 0.2 to 0.9, more preferably 0.55 to 0.7. The total content (A+B) of the pulp fibers and the para-aramid short fibers in the uncrosslinked rubber composition X' is 20 to 50 parts by mass, and from the same viewpoint as above, is preferably 25 to 48 parts by mass, more preferably 35 to 45 parts by mass.

[0022] Examples of other rubber compounding agents include carbon black, crosslinking agents, softening agents, vulcanization accelerators, processing aids, co-crosslinking agents, and antioxidants.

[0023] 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. From the viewpoint of obtaining high power transmission efficiency, it is preferable to contain HAF when the rubber component contains CR, and it is preferable to contain FEF when the rubber component contains an ethylene-α-olefin elastomer. From the same viewpoint as above, the content of carbon black in the uncrosslinked rubber composition X' is preferably 20 parts by mass or more and 80 parts by mass or less, more preferably 40 parts by mass or more and 60 parts by mass or less, per 100 parts by mass of the rubber component.

[0024] When the rubber component contains CR, the crosslinking agent is preferably a metal oxide such as zinc oxide or magnesium oxide, from the viewpoint of obtaining high power transmission efficiency. The content of the metal oxide crosslinking agent in the uncrosslinked rubber composition X' is, for example, 10 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the rubber component. When the rubber component contains an ethylene-α-olefin elastomer, the crosslinking agent is preferably an organic peroxide, from the same viewpoint as above. The content of the organic peroxide crosslinking agent in the uncrosslinked rubber composition X' is, for example, 3 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component.

[0025] From the viewpoint of obtaining high power transmission efficiency, the storage modulus E' of the crosslinked rubber composition X in the grain direction at 25°C is preferably 600 MPa or more and 1300 MPa or less, more preferably 800 MPa or more, and even more preferably 1000 MPa or more. This storage modulus E' is measured in accordance with JIS K6394:2007 under the measurement conditions of a temperature of 25°C, a static strain of 1.5%, a dynamic strain of 0.1%, and a frequency of 10 Hz.

[0026] The adhesive rubber layer 12 and the tension rubber layer 13 are also formed of a crosslinked rubber composition in which an uncrosslinked rubber composition, which is obtained by mixing a rubber component with various rubber compounding agents, is heated and pressurized to be crosslinked with a crosslinking agent. The adhesive rubber layer 12 and the tension rubber layer 13 may be formed of the same crosslinked rubber composition X as the compression rubber layer 11, or may be formed of a different crosslinked rubber composition.

[0027] The core wires 20 are embedded in the intermediate portion of the thickness direction of the adhesive rubber layer 12 of the V-belt body 10 so as to form a spiral having a pitch in the belt width direction. The core wires 20 are made of, for example, twisted yarn. Examples of fiber materials for the core wires 20 include polyester fiber and aramid fiber. In order to impart adhesion to the adhesive rubber layer 12, the core wires 20 are preferably subjected to one or more of the following adhesion treatments before molding: immersion in a surface treatment agent containing an epoxy compound or an isocyanate compound followed by heating; immersion in an RFL aqueous solution followed by heating; and immersion in rubber cement followed by drying.

[0028] The inner reinforcing fabric 30 is provided to cover the inner peripheral surface of the compressed rubber layer 11 of the V-belt main body 10. The inner reinforcing fabric 30 is made of, for example, a woven fabric, a knitted fabric, a nonwoven fabric, or the like. Examples of fiber materials for the inner reinforcing fabric 30 include nylon fiber, polyester fiber, cotton, and aramid fiber. To impart adhesion to the compressed rubber layer 11, the inner reinforcing fabric 30 is preferably subjected to one or more of the following bonding processes prior to molding: immersion in a primer containing an epoxy compound or an isocyanate compound followed by heating; immersion in an RFL aqueous solution followed by heating; immersion in rubber cement followed by drying; or coating the surface facing the V-belt main body 10 with high-viscosity rubber cement and drying. In the cogged V-belt B according to the embodiment, the lower cog 14 is formed by covering the lower cog-forming portion 11a of the compressed rubber layer 11 with the inner reinforcing fabric 30.

[0029] The outer reinforcing fabric 40 is provided so as to cover the outer peripheral surface of the tension rubber layer 13 of the V-belt main body 10. The outer reinforcing fabric 40 is made of, for example, a woven fabric, a knitted fabric, a nonwoven fabric, etc. Examples of fiber materials that form the outer reinforcing fabric 40 include nylon fiber, polyester fiber, cotton, and aramid fiber. In order to impart adhesion to the tension rubber layer 13, the outer reinforcing fabric 40 is preferably subjected to one or more of the following adhesion treatments before molding: an adhesion treatment in which the outer reinforcing fabric 40 is immersed in a primer containing an epoxy compound or an isocyanate compound and then heated; an adhesion treatment in which the outer reinforcing fabric 40 is immersed in an RFL aqueous solution and then heated; an adhesion treatment in which the outer reinforcing fabric 40 is immersed in rubber cement and then dried; and an adhesion treatment in which a high-viscosity rubber cement is coated on the surface that faces the V-belt main body 10 and then dried.

[0030] In the cogged V-belt B according to the embodiment having the above configuration, the uncrosslinked rubber composition X′ before crosslinking of the crosslinked rubber composition X forming the power transmission surface of the compressed rubber layer 11 contains a rubber component containing CR and / or an ethylene-α-olefin elastomer as a main component, pulp fibers, and para-aramid short fibers, and the ratio (A / B) of the pulp fiber content A to the para-aramid short fiber content B in the uncrosslinked rubber composition X′ is 0.15 or more and less than 1, and the total content (A+B) of the pulp fibers and the para-aramid short fibers in the uncrosslinked rubber composition X′ is 20 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the rubber component, thereby achieving high power transmission efficiency.

[0031] The cogged V-belt B according to this embodiment can be manufactured by a known method.

[0032] In the above embodiment, the cogged V-belt B is provided with both the inner reinforcing cloth 30 and the outer reinforcing cloth 40, but this is not particularly limited to this, and the V-belt may be provided with only one of the inner reinforcing cloth 30 and the outer reinforcing cloth 40.

[0033] In the above embodiment, a cog V-belt B has only lower cogs 14, but this is not limited to this and may be a double cog V-belt that also has upper cogs, or a low-edge V-belt that has no cogs, or even other types of friction transmission belts such as flat belts or V-ribbed belts.

[0034] (Cogged V-belt) The following cogged V-belts were produced in Examples 1-1 to 1-5, Comparative Examples 1-1 to 1-3, Examples 2-1 to 2-2, and Comparative Example 2. These cogged V-belts had the same configuration as the above-described embodiment except that they did not have an inner reinforcing fabric. Tables 1A and 1B show the formulations of the uncrosslinked rubber compositions used to form each compression rubber layer.

[0035] Example 1-1 Sulfur-modified CR (manufactured by Tosoh Corporation) was used as a rubber component. Relative to 100 parts by mass of the rubber component, 50 parts by mass of HAF (manufactured by Tokai Carbon Co., Ltd.), 5 parts by mass of DOS (manufactured by Taoka Chemical Co., Ltd.), 5 parts by mass of zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd.), 9 parts by mass of magnesium oxide (manufactured by Kyowa Chemical Industry Co., Ltd.), 1 part by mass of stearic acid (manufactured by Kao Corporation), 5 parts by mass of antioxidant (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 10 parts by mass of inorganic filler-containing processing aid (manufactured by Lanxess AG), 10 parts by mass of zinc powder (manufactured by Hakusui Tech Co., Ltd.), 15 parts by mass of pulp fiber P (ARBOCEL PWC500, manufactured by JRS, average fiber diameter D1: 35 μm, average fiber length L1: 500 μm, L1 / D1: 14.3), and para-aramid short fiber (Technora (registered trademark) An uncrosslinked rubber composition sheet was prepared containing 26 parts by mass of a rubber composition manufactured by Teijin Ltd. (fiber diameter D2: 12 μm, fiber length L2: 3 mm, L2 / D2: 250). This uncrosslinked rubber composition sheet was placed with the grain direction aligned with the belt width direction, and a cogged V-belt was produced in which a compression rubber layer was formed with the crosslinked rubber composition, which was designated Example 1-1.

[0036] The adhesive rubber layer and tension rubber layer were formed from different EPDM cross-linked rubber compositions. The core wire was composed of twisted polyester fiber yarn. The outer reinforcing fabric was composed of a woven fabric made of nylon 66 fiber. The ratio (D1 / D2) of the average fiber diameter D1 of the pulp fiber P to the fiber diameter D2 of the para-aramid short fiber was 2.92. The ratio (L1 / L2) of the average fiber length L1 of the pulp fiber P to the fiber length L2 of the para-aramid short fiber was 0.17.

[0037] Examples 1-2 to 1-6 and Comparative Examples 1-1 to 1-3 A cog V-belt having the same configuration as Example 1-1 was produced, except that the blending amount of pulp fiber P was 10 parts by mass per 100 parts by mass of the rubber component, and this was designated Example 1-2.

[0038] A cogged V-belt having the same configuration as that of Example 1-1 was produced, except that the blending amount of pulp fiber P was 5 parts by mass per 100 parts by mass of the rubber component, and this was designated Example 1-3.

[0039] A cogged V-belt having the same configuration as that of Example 1-1 was produced, except that the compounding amount of para-aramid short fibers was 20 parts by mass per 100 parts by mass of the rubber component, and this was designated Example 1-4.

[0040] A cog V-belt having the same configuration as Example 1-1 was produced, except that the blending amounts of pulp fiber P and para-aramid short fiber were 10 parts by mass and 20 parts by mass, respectively, per 100 parts by mass of the rubber component, and this was designated Example 1-5.

[0041] A cogged V-belt having the same configuration as that of Example 1-1 was produced, except that pulp fiber Q (ARBOCEL BE600-30 manufactured by JRS, average fiber diameter D1: 18 μm, average fiber length L1: 30 μm, L1 / D1: 1.67) was used instead of pulp fiber P, and this was designated Example 1-6. The ratio (D1 / D2) of the average fiber diameter D1 of pulp fiber Q to the fiber diameter D2 of the para-aramid short fibers was 1.5. The ratio (L1 / L2) of the average fiber length L1 of pulp fiber Q to the fiber length L2 of the para-aramid short fibers was 0.01.

[0042] A cogged V-belt having the same structure as that of Example 1-1 except that pulp fiber P was not blended was produced and designated Comparative Example 1-1.

[0043] A cog V-belt having the same configuration as Example 1-1 was produced, except that the blending amount of pulp fiber P was 25 parts by mass per 100 parts by mass of the rubber component, and the total content of pulp fiber P and para-aramid short fiber was 51 parts by mass per 100 parts by mass of the rubber component, and this was designated Comparative Example 1-2.

[0044] A cog V-belt having the same configuration as Example 1-1 was produced, except that the blending amounts of pulp fiber P and para-aramid short fiber were 25 parts by mass and 20 parts by mass, respectively, per 100 parts by mass of the rubber component, and the ratio of the content of pulp fiber P to the content of para-aramid short fiber was 1.25. This was designated Comparative Example 1-3.

[0045] Example 2-1 An uncrosslinked rubber composition sheet was prepared by blending EPDM (EP33 manufactured by ENEOS Materials Corporation, ethylene content: 52% by mass, ENB (diene) content: 8.1% by mass) as a rubber component with 100 parts by mass of the rubber component, 40 parts by mass of FEF (manufactured by Tokai Carbon Co., Ltd.), 10 parts by mass of paraffinic process oil (manufactured by Japan Sun Oil Co., Ltd.), 5 parts by mass of zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd.), 1.5 parts by mass of stearic acid (manufactured by Kao Corporation), 7.5 parts by mass of organic peroxide (manufactured by NOF Corporation), 4 parts by mass of N,N′-m-phenylenedimaleimide (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), 12 parts by mass of zinc methacrylate (manufactured by Kawauchi Chemical Industry Co., Ltd.), 10 parts by mass of pulp fiber P, and 28 parts by mass of para-aramid short fiber. This uncrosslinked rubber composition sheet was placed so that the grain direction was in the belt width direction, and crosslinked to form a compression rubber layer with the crosslinked rubber composition to produce a cogged V-belt, which was designated Example 2-1.

[0046] Example 2-2 and Comparative Example 2 A cog V-belt having the same configuration as Example 2-1 was produced, except that the compounding amount of para-aramid short fibers was 22 parts by mass per 100 parts by mass of the rubber component, and this was designated Example 2-2.

[0047] A cogged V-belt having the same structure as that of Example 2-1 except that pulp fiber P was not blended was produced and designated Comparative Example 2.

[0048]

[0049]

[0050] (Test Evaluation) The following test evaluation was carried out, and the results are shown in Tables 2A and 2B.

[0051] <Storage Modulus E'> For each of Examples 1-1 to 1-5, Comparative Examples 1-1 to 1-3, Examples 2-1 to 2-2, and Comparative Example 2, the storage modulus E' in the grain direction of the crosslinked rubber composition forming the compression rubber layer at 25°C was measured according to JIS K6394: 2007. The measurement conditions were a temperature of 25°C, a static strain of 1.5%, a dynamic strain of 0.1%, and a vibration frequency of 10 Hz.

[0052] <Dynamic Friction Coefficient> For each of Examples 1-1 to 1-5, Comparative Examples 1-1 to 1-3, Examples 2-1 to 2-2, and Comparative Example 2, 5 mm square test specimens were prepared from the crosslinked rubber composition forming the compressed rubber layer. The test specimens were set in a pin-on-disc friction and wear tester. The surface of the test specimen perpendicular to the grain direction was used as the sliding surface, and the sliding surface was abutted against the surface of a disk-shaped mating member made of S45C so that the direction perpendicular to the grain direction and anti-grain direction was the sliding direction. A load of 19.6 N was applied from above to the test specimen, and the mating member was rotated at 80 rpm in a room temperature atmosphere of 25°C. The steady-state value of the friction force acting on the test specimen was measured, and the dynamic friction coefficient was calculated by dividing it by the load of 19.6 N (resistance). The dynamic friction coefficients of Examples 1-1 to 1-5 and Comparative Examples 1-2 to 1-3 were evaluated relative to the dynamic friction coefficient of Comparative Example 1-1, which was set to 100. Examples 2-1 and 2-2 were evaluated relative to the coefficient of dynamic friction of Comparative Example 2, which was set at 100.

[0053] <Transmission efficiency> For each of Examples 1-1 to 1-5, Comparative Examples 1-1 to 1-3, Examples 2-1 to 2-2, and Comparative Example 2, the belt was wound around a drive pulley and a driven pulley with variable winding diameters, and the drive pulley was rotated at 3000 rpm with a drive shaft torque of 4 N m to run the belt. The input rotation speed (N １ ), input torque (Tｒ１ ), output rotation speed (N ２ ) and output torque (T ｒ２ ) was measured, and the transmission efficiency was calculated based on the following formula (1). Examples 1-1 to 1-5 and Comparative Examples 1-2 to 1-3 were evaluated relative to the transmission efficiency of Comparative Example 1-1, which was set to 100. Examples 2-1 and 2-2 were evaluated relative to the transmission efficiency of Comparative Example 2, which was set to 100.

[0054]

[0055]

[0056]

[0057] The present invention is useful in the technical field of friction transmission belts.

[0058] B Cogged V-belt (friction transmission belt) 10 V-belt body 11 Compression rubber layer 11a Lower cog forming portion 12 Adhesive rubber layer 13 Tension rubber layer 14 Lower cog 20 Cord 30 Inner reinforcing fabric 40 Outer reinforcing fabric

Claims

1. A friction transmission belt having a power transmission surface formed of a crosslinked rubber composition obtained by crosslinking an uncrosslinked rubber composition containing a rubber component containing chloroprene rubber and / or ethylene-α-olefin elastomer as a main component, pulp fiber, and para-aramid short fiber, a ratio of the content of the pulp fibers to the content of the para-aramid short fibers in the uncrosslinked rubber composition is 0.15 or more and less than 1, and a total content of the pulp fibers and the para-aramid short fibers in the uncrosslinked rubber composition is 20 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the rubber component.

2. 2. The friction power transmission belt according to claim 1, The friction transmission belt, wherein the content of the pulp fibers in the uncrosslinked rubber composition is 3 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the rubber component.

3. 2. The friction power transmission belt according to claim 1, The friction transmission belt has a content of the para-aramid short fibers in the uncrosslinked rubber composition of 10 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the rubber component.

4. 2. The friction power transmission belt according to claim 1, A friction power transmission belt, wherein the pulp fibers include kraft pulp.

5. 2. The friction power transmission belt according to claim 1, The para-aramid staple fibers comprise copolyparaphenylene-3,4'-oxydiphenylene terephthalamide staple fibers.

6. 2. The friction power transmission belt according to claim 1, The pulp fibers have an average fiber length of 20 μm or more and 1000 μm or less.

7. 2. The friction power transmission belt according to claim 1, The para-aramid short fibers have a fiber length of 0.5 mm or more and 5 mm or less.

8. 2. The friction power transmission belt according to claim 1, The para-aramid short fibers have a fiber length longer than the average fiber length of the pulp fibers.

9. 2. The friction power transmission belt according to claim 1, The pulp fibers have an average fiber diameter of 10 μm or more and 50 μm or less.

10. 2. The friction power transmission belt according to claim 1, The para-aramid short fibers have a fiber diameter of 5 μm or more and 70 μm or less.

11. 2. The friction power transmission belt according to claim 1, The para-aramid short fibers have a fiber diameter smaller than the average fiber diameter of the pulp fibers.

12. 2. The friction power transmission belt according to claim 1, The crosslinked rubber composition has a storage modulus in the grain direction at 25°C of 600 MPa or more and 1300 MPa or less.