Friction transmission belt

Abstract

This friction transmission belt B is provided with a compression rubber layer 11 constituting a contact portion with a pulley. The compression rubber layer 11 is provided with a rubber layer body 14 and a fiber member layer 15. The fiber member layer 15 is composed of a fiber member 19, and a rubber member 21 existing in a gap S of the fiber member 19. The fiber member layer 15 has a contact surface 15a in contact with the pulley. The rubber member 21 forms a part of the contact surface 15a. The rubber member 21 consists of a crosslinked product of a rubber composition of the rubber layer body 14 having permeated into the gap S. The rubber composition contains a raw material rubber component and a liquid compounding agent. The total of the amount of the low molecular weight component having a molecular weight of 5000 g / mol or less, which is obtained by gel permeation chromatography analysis of the raw material rubber component, and the amount of the liquid compounding agent is 5.0 mass% or less of the total amount of the rubber composition.

Description

Friction transmission belt

[0001] The present application claims priority to Japanese Patent Application No. 2023-097418, filed on June 14, 2023, and incorporates by reference the entire disclosure of said Japanese application.

[0002] Conventionally, as a means for transmitting rotational power from an engine, motor, or the like, a method has been widely used in which pulleys are fixed to the respective rotating shafts of the driving and driven sides, and a friction transmission belt such as a V-ribbed belt is stretched across each pulley.

[0003] It is known that in a friction transmission belt (hereinafter referred to as a transmission belt), the pulley contact surface is covered with a covering fabric in order to control the friction coefficient of the contact portion with the pulley (for example, see Patent Document 1 listed below).

[0004] International Publication No. 2019 / 193881

[0005] For example, serpentine drive belts in which a single V-ribbed belt is wound around three or more pulleys, including a crankshaft pulley (drive ribbed pulley), a power steering pulley, and an air conditioning pulley (driven ribbed pulley), are widely used as accessory drive belt transmission devices for automobiles. As automobile performance continues to improve, further improvements in the friction and wear resistance of V-ribbed belts are required.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a friction transmission belt that can achieve improved friction and wear resistance.

[0007] The compressed rubber layer of the friction transmission belt is obtained by coating a fibrous member with a rubber composition that constitutes the main body of the rubber layer. Because a portion of the rubber composition permeates the fibrous member, a rubber portion consisting of a cross-linked product of the rubber composition that has permeated the fibrous member exists on the surface of the compressed rubber layer. The inventors have conducted extensive research focusing on this rubber portion and have found that the friction and wear resistance of the friction transmission belt can be improved by reducing the total amount of low-molecular-weight components of the raw rubber components and liquid compounding agents contained in the rubber composition, and that the presence of low-molecular-weight components with a molecular weight of 5,000 g / mol or less is particularly important in improving the friction and wear resistance, leading to the completion of the present invention.

[0008] The friction transmission belt of the present invention comprises a compressed rubber layer that forms a contact portion with a pulley. The compressed rubber layer comprises a rubber layer main body made of a cross-linked product of a rubber composition, and a fibrous material layer laminated on the rubber layer main body. The fibrous material layer is composed of a fibrous material made of fabric and a rubber material present in gaps between the fibrous materials. The fibrous material layer has a contact surface that contacts the pulley. The rubber material forms part of the contact surface. The rubber material is made of a cross-linked product of the rubber composition that has soaked into the gaps. The rubber composition includes a raw rubber component and a liquid compounding agent. The total amount of the liquid compounding agent and the amount of low-molecular-weight components having a molecular weight of 5,000 g / mol or less, as determined by gel permeation chromatography analysis of the raw rubber component, is 5.0 mass % or less of the total amount of the rubber composition.

[0009] In the above-mentioned friction transmission belt, a portion of the rubber composition constituting the rubber layer main body permeates the fibrous member constituting the fibrous member layer. The rubber composition permeated into the fibrous member forms a rubber portion, which is a part of the contact surface that comes into contact with the pulley. In this friction transmission belt, the total amount of the low-molecular-weight component of the raw rubber component and the liquid compounding agent contained in the rubber composition is kept low, at 5 mass % or less of the total amount of the rubber composition. In this friction transmission belt, the friction and wear resistance properties are improved.

[0010] In the friction transmission belt, the kinematic viscosity of the liquid compounding agent measured at 40°C in accordance with JIS K 2230 is 480 mm ２In this case, the friction and wear resistance is further improved.

[0011] In the above-mentioned friction transmission belt, the raw rubber component preferably contains an ethylene-α-olefin elastomer as a main component, which further improves the friction and wear resistance.

[0012] In the above-mentioned friction transmission belt, it is preferable that the fibrous members are knitted fabrics and the gaps between the fibrous members are stitches of the knitted fabrics, thereby further improving the friction and wear resistance.

[0013] The friction transmission belt is preferably a V-ribbed belt. The V-ribbed belt having the above-described compressed rubber layer further improves friction and wear resistance. This V-ribbed belt can exhibit stable water transmission capability.

[0014] The friction transmission belt of the present invention can achieve improved friction and wear resistance.

[0015] FIG. 2 is a diagram schematically showing a part of a V-ribbed belt according to one embodiment of the present invention. FIG. 3 is a cross-sectional view of a cross-linking device. FIG. 4 is a diagram for explaining a manufacturing method of the V-ribbed belt shown in FIG. 1. FIG. 5 is a diagram for explaining a manufacturing method of the V-ribbed belt shown in FIG. 1. FIG. 6 is a diagram showing an example of a fiber member constituting a fiber member layer. FIG. 7 is a conceptual diagram for explaining the surface state of a fiber member layer. FIG. 8 is a conceptual diagram for explaining the molecular weight distribution of a raw rubber component. FIG. 9 is a diagram showing the pulley layout of a belt running tester for evaluating water-injected power transmission capacity. FIG. 10 is a diagram showing the pulley layout of a belt running tester for a durability test.

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Friction Power Transmission Belt) Fig. 1 schematically shows a portion of a friction power transmission belt B according to one embodiment of the present invention. This friction power transmission belt B is a V-ribbed belt used, for example, in an accessory drive belt transmission device installed in the engine compartment of an automobile. This V-ribbed belt B has, for example, a belt circumference of 700 mm or more and 3000 mm or less, a belt width of 10 mm or more and 36 mm or less, and a belt thickness of 3.5 mm or more and 5.0 mm or less.

[0017] This V-ribbed belt B comprises an endless belt body 10. The inner peripheral surface of the belt body 10 contacts a pulley. The belt body 10 comprises a compressed rubber layer 11 located on the inner peripheral side of the belt, an adhesive rubber layer 12 located in the middle, and a back reinforcing fabric 13 located on the outer peripheral side of the belt.

[0018] The compressed rubber layer 11 extends in the length direction of the belt. The compressed rubber layer 11 comes into contact with a pulley such as a drive pulley or a driven pulley. The compressed rubber layer 11 forms the contact portion with the pulley. The compressed rubber layer 11 includes a rubber layer main body 14 and a fiber member layer 15. In this V-ribbed belt B, the compressed rubber layer 11 is composed of the rubber layer main body 14 and the fiber member layer 15.

[0019] The rubber layer main body 14 is also referred to as a compressed rubber layer main body. The thickness of the rubber layer main body 14 is, for example, 2.0 mm or more and 3.2 mm or less. The rubber layer main body 14 is made of a cross-linked product of a rubber composition. In other words, the rubber layer main body 14 is a cross-linked rubber produced using the rubber composition. The rubber composition is produced by mixing various compounding agents with raw rubber components. The rubber composition contains the raw rubber components and various compounding agents.

[0020] Examples of raw rubber components contained in the rubber composition include ethylene-α-olefin elastomers such as ethylene-propylene-diene terpolymer (EPDM), ethylene-propylene copolymer (EPM), ethylene-butene copolymer (EBM), and ethylene-octene copolymer (EOM); chloroprene rubber (CR); chlorosulfonated polyethylene rubber (CSM); and hydrogenated acrylonitrile rubber (H-NBR). The raw rubber component preferably uses one or more of these, and more preferably contains an ethylene-α-olefin elastomer. In this case, the raw rubber component preferably contains an ethylene-α-olefin elastomer as the main component. The term "the main component of the raw rubber component is an ethylene-α-olefin elastomer" means that the amount of ethylene-α-olefin elastomer contained in the raw rubber component is 50% by mass or more of the total amount of the raw rubber component. When the main component of the raw rubber component is an ethylene-α-olefin elastomer, the amount of the ethylene-α-olefin elastomer contained in the raw rubber component is preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more of the total amount of the raw rubber component. It is particularly preferable that the raw rubber component is an ethylene-α-olefin elastomer. EPDM is preferably used as the ethylene-α-olefin elastomer.

[0021] Examples of compounding agents that can be contained in the rubber composition include crosslinking agents such as sulfur and organic peroxides, vulcanization accelerators, co-crosslinking agents, antioxidants, processing aids, plasticizers, process oils, reinforcing agents such as carbon black, fillers, etc. Among these compounding agents, those that exhibit liquid properties at a temperature of 40° C. are liquid compounding agents. Of the above-mentioned compounding agents, plasticizers and process oils are liquid compounding agents.

[0022] Examples of plasticizers include dialkyl phthalates such as dibutyl phthalate (DBP) and dioctyl phthalate (DOP), dialkyl adipates such as dioctyl adipate (DOA), and dialkyl sebacates such as dioctyl sebacate (DOS). The rubber composition may contain one or more of these as the plasticizer. When the rubber composition contains a plasticizer, the content of the plasticizer is preferably 0.1 parts by mass or more and 40 parts by mass or less, more preferably 0.1 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of the raw rubber component.

[0023] Examples of process oils include paraffinic oils, naphthenic oils, and aromatic oils. The rubber composition may contain one or more of these as the process oil. When the rubber composition contains the process oil, the content of the process oil is preferably 0.1 parts by mass or more and 40 parts by mass or less, more preferably 0.1 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of the raw rubber component.

[0024] When the main component of the raw rubber component is an ethylene-α-olefin elastomer, the main component of the liquid compounding agent is preferably process oil. The liquid compounding agent being main component is process oil means that the amount of process oil contained in the liquid compounding agent is 50% by mass or more of the total amount of the liquid compounding agent. When the main component of the liquid compounding agent is process oil, the amount of process oil contained in the liquid compounding agent is preferably 70% by mass or more of the total amount of the liquid compounding agent, more preferably 90% by mass or more, and even more preferably 95% by mass or more. It is particularly preferable that the liquid compounding agent is process oil. When EPDM is used as the ethylene-α-olefin elastomer, paraffinic oil is preferred as the process oil.

[0025] As described above, the rubber layer main body 14 is a cross-linked product of a rubber composition. The cross-linked product of the rubber composition, in other words, the cross-linked rubber, is obtained by mixing raw rubber components with various compounding agents to prepare a rubber composition, pressurizing and heating this rubber composition in a mold, and cross-linking the raw rubber components with a cross-linking agent.

[0026] The fiber member layer 15 is laminated on the inner peripheral surface of the rubber layer main body 14. The fiber member layer 15 constitutes the inner peripheral surface of the belt main body 10. The thickness of the fiber member layer 15 is, for example, 0.1 mm or more and 1.5 mm or less. In this V-ribbed belt B, the fiber member layer 15 covers the entire inner peripheral surface of the rubber layer main body 14. The fiber member layer 15 may be laminated on the inner peripheral surface so as to cover a portion of the inner peripheral surface.

[0027] The fiber member layer 15 includes a fiber member. The fiber member is made of a fabric. Examples of the fabric include woven fabric and knitted fabric. Examples of the weave of the woven fabric include plain weave, twill weave, satin weave, and variations thereof. Examples of the knitted fabric include plain knit, rib knit, purl knit, and other variations in the weft knit, and single Denbigh knit, single Van Dyke knit, and other variations in the warp knit. From the viewpoint of being highly elastic and being able to uniformly cover the rubber layer main body 14, it is preferable that the fiber member be a knitted fabric.

[0028] When the fibrous member is composed of a woven fabric, warp and weft yarns are used to form the fibrous member. When the fibrous member is composed of a knitted fabric, knitting yarns are used to form the fibrous member. Examples of fibers that constitute the yarns used to form the woven or knitted fabric include natural fibers such as cellulose-based fibers, wool, and silk; and synthetic fibers such as polyurethane fibers, aliphatic polyamide fibers (nylon 66 fibers), aromatic polyamide fibers (para-type, meta-type), polyester fibers, acrylic fibers, and polyvinyl alcohol fibers. The woven or knitted fabric may be formed from one type of fiber or two or more types of fibers. From the viewpoint of good water absorption performance, cellulose-based fibers are preferred as the fibers that constitute the fibrous member.

[0029] When forming the fiber material layer 15, a fiber material that has been subjected to an adhesive treatment may be used, or a fiber material that has not been subjected to an adhesive treatment may be used. Examples of adhesive treatments include a treatment in which a fiber material is immersed in an epoxy resin solution or an isocyanate resin solution and heated, a treatment in which a fiber material is immersed in an RFL aqueous solution and heated, and a treatment in which a fiber material is immersed in rubber cement and dried.

[0030] The adhesive rubber layer 12 is a band extending in the belt length direction and having a horizontally elongated rectangular cross section. The thickness of the adhesive rubber layer 12 is, for example, 1.0 mm to 2.5 mm. The adhesive rubber layer 12 is composed of an adhesive rubber layer main body 16 and a cord 17 covered by the adhesive rubber layer main body 16.

[0031] The adhesive rubber layer main body 16 is a crosslinked rubber made of a rubber composition. In this V-ribbed belt B, the compressed rubber layer main body 14 and the adhesive rubber layer main body 16 may be made of the same rubber composition or different rubber compositions.

[0032] The cord 17 is located in the middle in the belt thickness direction of the adhesive rubber layer 12. The cord 17 is wound so as to form a spiral having a pitch in the belt width direction, and is embedded in the adhesive rubber layer main body 16.

[0033] The core wires 17 are made of twisted yarns of polyamide fiber, polyester fiber, aramid fiber, polyamide fiber, or the like. The diameter of the core wires 17 is, for example, 0.5 mm or more and 2.5 mm or less. The shortest distance between adjacent core wires 17 in the cross section of the adhesive rubber layer 12 is, for example, 0.05 mm or more and 0.20 mm or less. Preferably, the core wires 17 are subjected to one or more of the following adhesion treatments: an adhesion treatment in which the core wires 17 are immersed in an epoxy resin solution or an isocyanate resin solution and heated; an adhesion treatment in which the core wires 17 are immersed in an RFL aqueous solution and then heated; and an adhesion treatment in which the core wires 17 are immersed in rubber cement and then dried.

[0034] The back reinforcement fabric 13 is made of, for example, a plain weave, twill weave, satin weave, or other woven fabric, knitted fabric, or nonwoven fabric using yarns such as cotton, polyamide fiber, polyester fiber, or aramid fiber. The thickness of the back reinforcement fabric 13 is, for example, 0.4 mm to 1.2 mm. To impart adhesion to the adhesive rubber layer 12, the back reinforcement fabric 13 may be subjected to an adhesion treatment in which the fabric is immersed in an RFL aqueous solution and heated before molding, and / or an adhesion treatment in which rubber cement is coated on the outer peripheral surface of the adhesive rubber layer 12 and dried. The back reinforcement fabric 13 may be attached to the adhesive rubber layer 12 via a rubber layer (not shown).

[0035] In this V-ribbed belt B, a back rubber layer having a thickness of, for example, 0.4 mm to 0.8 mm may be used instead of the back reinforcing fabric 13. In this case, the texture of the woven fabric is preferably transferred to the surface of the back rubber layer in order to suppress noise generation during back drive. In order to suppress adhesion caused by contact between the back surface of the belt and a flat pulley, the back rubber layer is preferably composed of a rubber composition that is slightly harder than the adhesive rubber layer main body 16. Furthermore, when a back rubber layer is provided, the back rubber layer may be composed of the same rubber composition as one or both of the compressed rubber layer main body 14 and the adhesive rubber layer main body 16, or may be composed of a rubber composition different from both the compressed rubber layer main body 14 and the adhesive rubber layer main body 16. When the back rubber layer is composed of a different rubber composition from the adhesive rubber layer main body 16, the back rubber layer is preferably composed of a rubber composition that is slightly harder than the adhesive rubber layer main body 16 in order to suppress adhesion caused by contact between the back surface of the belt and a flat pulley.

[0036] As shown in FIG. 1 , in this V-ribbed belt B, a plurality of V-ribs 18 are formed on the compressed rubber layer 11 of the belt body 10, hanging down toward the inner periphery. The V-ribs 18 are ridges extending in the belt length direction and having a cross section of a generally inverted triangle. The V-ribs 18 are arranged side by side in the belt width direction. For example, each V-rib 18 has a rib height of 2.0 mm or more and 3.0 mm or less, and a base-to-base width of 1.0 mm or more and 3.6 mm or less. The number of V-ribs 18 is, for example, 3 to 10 (6 in FIG. 1 ).

[0037] In this V-ribbed belt B, the surface of the compression rubber layer 11 is made up of a fiber material layer 15. The surfaces of the V-ribs 18 are made up of a fiber material layer 15. In this V-ribbed belt B, the fiber material layer 15 comes into contact with the pulley. The surface of the fiber material layer 15 is a contact surface 15a that comes into contact with the pulley. In other words, the fiber material layer 15 has a contact surface 15a that comes into contact with the pulley.

[0038] (Method of Manufacturing V-ribbed Belt B) Next, a method of manufacturing the V-ribbed belt B will be described with reference to the drawings. The V-ribbed belt B according to one embodiment of the present invention is manufactured by a conventionally known method. Figure 2 is a diagram illustrating a cross-linking device 30 used in the manufacture of the V-ribbed belt B.

[0039] The cross-linking device 30 includes a base 31, an expansion drum 32, and a mold 33. The expansion drum 32 is cylindrical. The expansion drum 32 is provided upright on the base 31. The mold 33 is cylindrical. The mold 33 is provided outside the expansion drum 32.

[0040] The expansion drum 32 has a drum body 32a and an expansion sleeve 32b. Both the drum body 32a and the expansion sleeve 32b are cylindrical. The expansion sleeve 32b is located on the outside of the drum body 32a. The expansion sleeve 32b is made of rubber. The expansion sleeve 32b is fitted onto the outer periphery of the drum body 32a. The drum body 32a has a number of vent holes 32c. Each vent hole 32c connects the inside and outside of the drum body 32a. Both ends of the expansion sleeve 32b are fixed by fixing rings 34. The fixing rings 34 seal the gaps between the drum body 32a and the ends of the expansion sleeve 32b.

[0041] Although not shown, the cross-linking device 30 has a pressurizing means. The pressurizing means introduces pressure-adjusted air into the drum body 32a. The air passes through the air vents 32c and is introduced between the drum body 32a and the expansion sleeve 32b. The expansion sleeve 32b expands radially outward. This pressurizes the uncross-linked slab, as will be described later.

[0042] The mold 33 is detachable from the base 31. The mold 33 attached to the base 31 is provided concentrically on the outside of the expansion drum 32. The mold 33 is a mold used to manufacture the V-ribbed belt B. A plurality of V-rib forming grooves 33a extending in the circumferential direction are provided on the inner peripheral surface of the mold 33 to shape the V-ribs 18 of the V-ribbed belt B. The plurality of V-rib forming grooves 33a are arranged side by side in the axial direction (groove width direction). Each V-rib forming groove 33a is formed so that its width narrows from the groove opening toward the groove bottom. The shape of the V-rib forming groove 33a corresponds to the shape of the V-rib 18.

[0043] Although not shown, the cross-linking device 30 includes a heating means and a cooling means for the mold 33. The temperature of the mold 33 is controlled by the heating means and the cooling means.

[0044] 3A and 3B are diagrams for explaining a method for manufacturing the V-ribbed belt B. FIG.

[0045] In the manufacturing method of the V-ribbed belt B according to the embodiment, first, the raw rubber components are blended with the compounding ingredients, and then the blended components are kneaded in a kneader, Banbury mixer, or other kneading machine to obtain a rubber composition. The rubber composition is formed into a sheet by calendar molding or the like to produce an uncrosslinked rubber sheet 14' for the rubber layer main body 14 of the compressed rubber layer 11. Similarly, an uncrosslinked rubber sheet 16' for the rubber layer main body 16 of the adhesive rubber layer 12 is also prepared. A fibrous member 19 for the fibrous member layer 15 and a back reinforcing fabric 13 are prepared, and an adhesive treatment is applied to the fibrous member 19 or the back reinforcing fabric 13 as needed. In this manufacturing method, the fibrous member 19 is formed into a cylindrical shape in advance. The back reinforcing fabric 13 may also be formed into a cylindrical shape in advance. A cord 17 is prepared, and an adhesive treatment is applied to the cord 17 as needed.

[0046] Next, the back reinforcing fabric 13 and the uncrosslinked rubber sheet 16' for the adhesive rubber layer main body 16 are wound in this order around a cylindrical drum (not shown) covered with a rubber sleeve 37. After the core wire 17 is spirally wound around the uncrosslinked rubber sheet 16', the uncrosslinked rubber sheet 16' for the adhesive rubber layer main body 16 and the uncrosslinked rubber sheet 14' for the compressed rubber layer main body 14 are further wound in this order. A tubular fiber member 19 is placed on the uncrosslinked rubber sheet 14' to obtain an uncrosslinked slab S'.

[0047] Next, the uncrosslinked slab S' is removed from the cylindrical drum together with the rubber sleeve 37. As shown in Fig. 3A, the uncrosslinked slab S' is placed on the inner peripheral surface side of the mold 33 together with the rubber sleeve 37. As a result, the uncrosslinked slab S' is set between the mold 33 and the expansion drum 32.

[0048] Next, the mold 33 is heated, and air is introduced through the air vent 32c between the drum body 32a and the expansion sleeve 32b of the expansion drum 32, as shown in FIG. 3B. The expansion sleeve 32b is expanded, and the uncrosslinked slab S' is pressed against the mold 33. The uncrosslinked rubber sheet 14' flows into the V-rib forming groove 33a while stretching the fibrous material 19. The fibrous material 19, the uncrosslinked rubber sheet 14', the uncrosslinked rubber sheet 16', the cord 17, and the back reinforcing fabric 13 are integrated, and crosslinking of the raw rubber components of the uncrosslinked rubber sheets 14' and 16' progresses. This forms a cylindrical belt slab S. The belt slab S is a crosslinked product of the uncrosslinked slab S'. The molding temperature for the belt slab S is, for example, 100°C or higher and 180°C or lower. The molding pressure for the belt slab S is, for example, 0.5 MPa or higher and 2.0 MPa or lower. The forming time of the belt slab S is, for example, 10 minutes or more and 60 minutes or less.

[0049] Then, the belt slab S is taken out from the bridging device 30, cut into rings each having a predetermined number of ribs 18, and turned over to obtain a V-ribbed belt B.

[0050] FIG. 4 shows an example of a fiber member 19 that constitutes the fiber member layer 15. The fiber member 19 shown in FIG. 4 is a knitted fabric called plain knit or jersey knit. Knitted fabric is made by knitting yarn 20 (knitting yarn). This forms stitches. Stitches are gaps that are created when the yarn 20 is knitted. Although not shown, woven fabric is made by combining yarns (warp threads) and yarns (weft threads). This forms weave patterns. Weave patterns are gaps in woven fabric. Nonwoven fabric is made by entangling many fibers. In nonwoven fabric, the entanglement of fibers forms gaps. In this way, the fiber member 19 has many gaps. In other words, many gaps exist in the fiber member 19.

[0051] A large number of gap openings are present on the surface of the fibrous material 19. The portions indicated by the symbol S in Fig. 4 are the gaps in the fibrous material 19 shown in Fig. 4. The gaps S penetrate the fibrous material 19. In the following description, for convenience of explanation, the gaps S are represented as cylindrical holes penetrating the fibrous material 19.

[0052] As described above, in the manufacturing method of the friction transmission belt B, the crosslinked slab S' is pressed against the cylindrical mold 33, and the uncrosslinked rubber sheets 14', 16' flow into the V-rib forming grooves 33a while pressing and stretching the fibrous member 19. For example, as shown in FIG. 3A , the fibrous member 19 is laminated on the uncrosslinked rubber sheet 14', i.e., the rubber composition of the rubber layer main body 14. The rubber composition has fluidity. As the rubber composition presses the fibrous member 19, a portion of the rubber composition permeates the gaps S between the fibrous member 19. Subsequently, the raw rubber components of the rubber composition crosslink, forming rubber members 21 composed of the crosslinked rubber composition permeating the gaps S in the fibrous member 19, as shown in FIG. 3B . The fibrous member layer 15 is composed of the fibrous member 19 and the rubber members 21 present in the gaps S between the fibrous member 19. The rubber members 21 stretch by threading through the gaps S between the fibrous member 19.

[0053] 5 is a schematic diagram showing the surface state of the fiber material layer 15. As described above, numerous gaps S are present on the surface of the fiber material 19. In the manufacturing method of the friction transmission belt B, the rubber composition presses the fiber material 19, so that part of the rubber composition that has soaked into the gaps S seeps out onto the surface of the fiber material 19. The surface of the fiber material layer 15 is composed of a fiber portion 19a made of the fiber material 19 and a rubber portion 21a made of the rubber material 21. The surface of the fiber material layer 15, i.e., the contact surface 15a that comes into contact with the pulley, is equipped with the fiber portion 19a and the rubber portion 21a. The rubber member 21 forms part of the contact surface 15a.

[0054] While the rubber composition has a predetermined fluidity, the stronger the force with which the rubber composition presses the fibrous component 19, the longer the time the rubber composition presses the fibrous component 19, the higher the fluidity of the rubber composition, and the larger the size of the gaps S in the fibrous component 19, the greater the amount of rubber composition that seeps out to the surface. When a large amount of rubber composition has seeped out to the surface, the rubber portions 21a cover the gaps S. When a small amount of rubber composition is present, the rubber portions 21a are formed inside the gaps S. If the rubber composition does not reach the openings, the rubber portions 21a will not be formed on the contact surface 15a. The proportion of the rubber portions 21a that occupy the contact surface 15a varies depending on the molding conditions, the fluidity of the rubber composition, the specifications of the fibrous component 19, and the like. The proportion of the rubber portions 21a that occupy the contact surface 15a is set appropriately according to the specifications of the friction transmission belt.

[0055] The surface state of the fiber material layer 15 shown in Fig. 5 is a state in which rubber portions 21a are formed in some of the gaps S of the fiber material 19 shown in Fig. 4. In Fig. 5, the gaps S where the rubber composition did not reach the openings and the rubber portions 21a were not formed are not shown as part of the fiber portions 19a.

[0056] The proportion of the rubber portion 21a occupying the contact surface 15a (hereinafter referred to as the rubber occupied area ratio) can be obtained, for example, as follows. An observation sample including a portion of the surface is taken from the fiber material layer 15 of the V-ribbed belt. There are no particular restrictions on the size of the surface to be sampled, but for example, an observation sample including a rectangular surface measuring 5 mm in the belt longitudinal direction and 2 mm in the belt width direction is prepared. The observation sample is set on the stage of a microscope (for example, a Keyence VHX-6000 digital microscope), and the surface is focused. A glass slide is pressed against the observation sample from above, and an image of the surface of the fiber material layer 15 is captured. Based on the captured surface image, the area of ​​each rubber portion 21a included in the observation region is measured using software built into the microscope. The ratio of the total area of ​​the rubber portions 21a to the entire area of ​​the observation region is then obtained as the rubber occupied area ratio. In measuring this rubber occupied area ratio, the load with which the glass slide is pressed against the surface sample is appropriately set so as not to exceed 1 kg for a surface size of 5 mm x 2 mm. This load is preferably set to about 500 g (more specifically, 450 g or more and 550 g or less). The rubber occupied area ratio thus obtained is preferably 3% or more and 50% or less, from the viewpoint of obtaining good friction and wear resistance characteristics.

[0057] As described above, the rubber composition forming the rubber layer main body 14 of the compressed rubber layer 11 contains a raw rubber component. The raw rubber component is usually an aggregate of polymers having different molecular weights. The raw rubber component has a molecular weight distribution.

[0058] FIG. 6 is a conceptual diagram showing the molecular weight distribution of a raw rubber component. The horizontal axis of FIG. 6 represents molecular weight (g / mol), with the molecular weight increasing toward the right. The vertical axis of FIG. 6 represents the abundance ratio, with the abundance ratio increasing toward the top. A raw rubber component usually has the molecular weight distribution shown in FIG. 6. This molecular weight distribution can be obtained, for example, by performing gel permeation chromatography analysis (hereinafter, GPC analysis). In the present disclosure, a "High Temperature GPC (Alliance GPC / V2000)" manufactured by Nippon Waters is used as the measuring instrument, and the molecular weight distribution measured under the following conditions in terms of polystyrene is used as the molecular weight distribution of the raw rubber component. Temperature: 140°C Solvent: 1,2,4-trichlorobenzene (TCB) Flow rate: 1 mL / min Sample concentration: 0.1% Detector: Differential refractometer

[0059] In Figure 6, arrow L indicates the left tail of the molecular weight distribution. This indicates the presence of polymers with low molecular weights (hereinafter referred to as low molecular weight components) among the polymers constituting the raw rubber component. The raw rubber component contains low molecular weight components.

[0060] As described above, the pulley contact surface 15a of the friction transmission belt B has a rubber portion 21a made of a cross-linked product of the rubber composition that has soaked into the fiber member 19. This rubber portion 21a is made of a cross-linked product of the rubber composition for the rubber layer main body 14. The inventors have conducted extensive research focusing on this rubber portion 21a and have found that the friction and wear resistance of the friction transmission belt B is improved by reducing the total amount of low-molecular-weight components of the raw rubber components and the liquid compounding agent contained in the rubber composition of the rubber layer main body 14, and that the presence of low-molecular-weight components having a molecular weight of 5000 g / mol or less is particularly closely related to the friction and wear resistance, thereby completing the present invention.

[0061] In this friction transmission belt B, the total amount of the low-molecular-weight component having a molecular weight of 5000 g / mol or less, as determined by GPC analysis of the raw rubber components, and the amount of the liquid compounding agent is 5.0 mass% or less of the total rubber composition of the rubber layer main body 14. In other words, the total amount ratio, expressed as the ratio of the amount of the low-molecular-weight component having a molecular weight of 5000 g / mol or less and the amount of the liquid compounding agent to the total rubber composition of the rubber layer main body 14, is 5.0 mass% or less. This results in a friction transmission belt B in which the rubber portion 21a forming part of the contact surface 15a has appropriate strength. Since change in the state of the contact surface 15a is suppressed, the friction coefficient imparted by coating the fibrous member 19 is stably maintained. This friction transmission belt B has good water-injection power transmission capability, and this good water-injection power transmission capability is stably maintained. This friction transmission belt B can achieve improved friction and wear resistance.

[0062] From the viewpoint of friction and wear resistance, the smaller the total amount of the low molecular weight component and the liquid compounding agent, the better. However, the low molecular weight component and the liquid compounding agent contribute to improving the processing characteristics of the rubber composition. From this viewpoint, the total amount of the low molecular weight component and the liquid compounding agent is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and even more preferably 1.6% by mass or more of the total rubber composition of the rubber layer main body 14. From the viewpoint of improving friction and wear resistance, this total amount is preferably 4.9% by mass or less, more preferably 4.2% by mass or less of the total rubber composition.

[0063] In this friction transmission belt B, the rubber composition of the rubber layer main body 14 has a kinematic viscosity of 480 mm as measured at 40°C in accordance with JIS K 2230. ２ / s or less. ２ A liquid compounding agent having a kinematic viscosity of 1 / s or less effectively improves the fluidity of the rubber composition. In this friction transmission belt B, the rubber portion 21a is stably formed on the contact surface 15a with the pulley. As described above, the total amount of the low-molecular-weight component of the raw rubber component and the amount of the liquid compounding agent is kept to 5.0 mass% or less. This friction transmission belt B can achieve further improvement in friction and wear resistance.

[0064] As described above, in this friction transmission belt B, when the raw rubber component of the rubber layer main body 14 is primarily an ethylene-α-olefin elastomer, the liquid compounding agent is preferably a process oil. In this case, from the viewpoint of further improving friction and wear resistance, the total amount of the low-molecular-weight component having a molecular weight of 5000 g / mol or less contained in the ethylene-α-olefin elastomer and the process oil is preferably 5.0 mass% or less. When the raw rubber component is EPDM and the process oil is paraffinic oil, the total amount of the low-molecular-weight component having a molecular weight of 5000 g / mol or less contained in the EPDM and the paraffinic oil is preferably 5.0 mass% or less, from the viewpoint of further improving friction and wear resistance.

[0065] Up to this point, a V-ribbed belt has been described as an embodiment of the friction transmission belt according to the present invention, but the friction transmission belt according to the embodiment of the present invention is not limited to this and may be a V-belt, a flat belt, or the like.

[0066] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. V-ribbed belts of Examples 1 to 6 and Comparative Examples 1 to 4 were produced and evaluated.

[0067] <Materials for the Fiber Component Layer> A knitted fabric was prepared as the fiber component for forming the fiber component layer. The knitted fabric used was a plain knit (plain knit) fabric made of a urethane elastic yarn covered with a 6-nylon yarn. The urethane elastic yarn had a fineness of 22 denier (24.4 dtex), and the 6-nylon yarn had a fineness of 78 denier (86.7 dtex) and 52 filaments. The knitted fabric had a knit density of 66 wales / 2.54 cm and 70 courses / 2.54 cm. The thickness of the knitted fabric was 0.52 mm. As an adhesive treatment for this knitted fabric, the knitted fabric was immersed in an RFL aqueous solution and heated and dried to form an RFL coating on the surface of the knitted fabric. The RFL aqueous solution was prepared as follows. Resorcinol (R) and formalin (F) were mixed, and an aqueous sodium hydroxide solution was added and stirred to obtain an RF precondensate (R / F molar ratio = 1 / 1.5). VP latex (L) was then mixed with the RF precondensate to give an RF / L mass ratio of 1 / 8, and water was further added to adjust the solid concentration to 20%, followed by stirring for 24 hours to obtain an RFL aqueous solution.

[0068] <Materials for Compressed Rubber Layer Main Body> The following five types of EPDM were prepared as raw rubber components: EPDM1 (manufactured by Dow Chemical under the trade name "Nordel 4640") EPDM2 (manufactured by Mitsui Chemicals under the trade name "EPT 3070") EPDM3 (manufactured by Mitsui Chemicals under the trade name "EPT 3091") EPDM4 (manufactured by Mitsui Chemicals under the trade name "EPT X-4010M") GPC analysis was performed on each EPDM under the conditions described above, and the amount of low molecular weight components with a molecular weight of 5,000 g / mol or less contained in 100 parts by mass of EPDM was measured. As a result, EPDM1 contained 0 parts by mass of low molecular weight components, EPDM2 contained 0 parts by mass, EPDM3 contained 0 parts by mass, and EPDM4 contained 5 parts by mass. As compounding ingredients, carbon black (trade name "Asahi #60" manufactured by Asahi Carbon Co., Ltd.), process oil (trade name "Sunflex 2280" manufactured by Japan Sun Oil Co., Ltd.), zinc oxide (trade name "Zinc Oxide Type 2" manufactured by Sakai Chemical Industry Co., Ltd.), stearic acid (trade name "Stearic Acid" manufactured by Kao Corporation or "Beads Stearic Acid Camellia" manufactured by NOF Corporation), vulcanization accelerator A (trade name "Noccela MSA-G" manufactured by Ouchi Shinko Chemical Co., Ltd.), vulcanization accelerator B (trade name "Suncerer EM2" manufactured by Sanshin Chemical Industry Co., Ltd.), and sulfur (trade name "Oil Sulfur" manufactured by Hosoi Chemical Industry Co., Ltd.) were prepared. Of the materials for the compressed rubber layer main body, the compounding ingredient corresponding to the liquid compounding ingredient was process oil. Each material was blended and kneaded in the amounts shown in Table 1 below to prepare a rubber composition. The rubber composition was formed into a 0.7 mm thick sheet using a roll.

[0069]

[0070] <Materials for Adhesive Rubber Layer Main Body> EPDM (trade name "EP123" manufactured by JSR Corporation) was used as the raw rubber component, and 100 parts by mass of this raw rubber component contained 50 parts by mass of carbon black (trade name "Asahi #60" manufactured by Asahi Carbon Co., Ltd.), 8 parts by mass of process oil (trade name "Sunflex 2280" manufactured by Nippon Sun Oil Co., Ltd.), 10 parts by mass of stearic acid (trade name "Stearic Acid" manufactured by Kao Corporation or "Beads Stearic Acid" manufactured by NOF Corporation), and 100 parts by mass of EPDM (trade name "EP123" manufactured by JSR Corporation). A rubber composition was prepared by blending and kneading 1 part by mass of zinc oxide (trade name "Zinc Oxide Type 2" manufactured by Sakai Chemical Industry Co., Ltd.), 5 parts by mass of zinc methacrylate (trade name "Actor ZMA" manufactured by Kawaguchi Chemical Industry Co., Ltd.), 1 part by mass of vulcanization accelerator (trade name "Noccela MSA-G" manufactured by Ouchi Shinko Chemical Co., Ltd.), 3 parts by mass of vulcanization accelerator (trade name "Suncerer EM2" manufactured by Sanshin Chemical Industry Co., Ltd.), and 1.5 parts by mass of sulfur (trade name "Oil Sulfur" manufactured by Hosoi Chemical Industry Co., Ltd.). The rubber composition was formed into a sheet having a thickness of 0.45 mm using a roll.

[0071] <Material for Core Wire> As a material for the core wire, a twisted yarn of polyester fiber was prepared, which was immersed in an aqueous RFL solution and then subjected to an adhesion treatment of heating and drying.

[0072] <Material for Back Reinforcing Fabric> A woven fabric made of a cotton-polyester blend yarn was immersed in an aqueous RFL solution and then subjected to a bonding treatment of heating and drying to prepare a back reinforcing fabric.

[0073] Example 1 A V-ribbed belt having a width of 21.36 mm (the number of V-ribs is 6) and a circumferential length of 1,210 mm was produced using the same configuration as in the above-described embodiment, except that the rubber composition of Example 1 shown in Table 1 was used as the compressed rubber layer main body material, and the fiber member, compressed rubber layer main body material, adhesive rubber layer main body material, core wire, and back reinforcing fabric were as described above, by the manufacturing method described with reference to FIGS. 2 to 3B . This was designated as the V-ribbed belt of Example 1.

[0074] [Examples 2 to 6 and Comparative Examples 1 to 4] V-ribbed belts (width = 21.36 mm (number of V-ribs: 6), circumference = 1210 mm) of Examples 2 to 6 and Comparative Examples 1 to 4 were produced in the same manner as in Example 1, except that the compressed rubber layer main body material was as shown in Table 1 above.

[0075] <Total Amount of Low Molecular Weight Components and Liquid Compounding Agents> The sum of the amount of low molecular weight components having a molecular weight of 5000 g / mol or less contained in 100 parts by mass of EPDM and the amount of process oil compounded relative to 100 parts by mass of EPDM was calculated. This was taken as the total amount of the low molecular weight components having a molecular weight of 5000 g / mol or less and the amount of the liquid compounding agent obtained by GPC analysis of the raw rubber components. The total amount of each component shown in Table 1 above was calculated. This was taken as the total amount of the rubber composition, and the ratio of the total amount of the low molecular weight components having a molecular weight of 5000 g / mol or less and the amount of the liquid compounding agent to the total amount of the rubber composition was calculated. The results are shown in the "Total Amount Ratio" column in Tables 2 and 3 below.

[0076] <Evaluation of Abrasion Resistance> A Taber abrasion test was performed in accordance with JIS K6264-2 at room temperature under a load of 9.8 N, a rotation speed of 48 rpm, and a rotation time of 30 minutes to determine the amount of abrasion. Test pieces for the Taber abrasion test were prepared using rubber compositions shown in Table 1. The mass loss rate was calculated based on the amount of abrasion. The results are shown in Tables 2 and 3 below. The smaller the value, the better the abrasion resistance.

[0077] <Evaluation of Water-Injected Power Transmission Capacity> Fig. 7 shows the pulley layout of a belt running test machine 50 for evaluating water-injected power transmission capacity. In Fig. 7, symbol B denotes a V-ribbed belt.

[0078] This belt running tester 50 has a first drive pulley 51, a ribbed pulley with a pulley diameter of 121.6 mm, located at the lower left, and a second drive pulley 52, a ribbed pulley with a pulley diameter of 141.5 mm, located to the right of the first drive pulley 51. A first driven pulley 53, a ribbed pulley with a pulley diameter of 77.0 mm, is located diagonally above the right of the second drive pulley 52, and a second driven pulley 54, a ribbed pulley with a pulley diameter of 61.0 mm, is located above the second drive pulley 52. ​​A first idler pulley 55, a flat pulley with a pulley diameter of 76.2 mm, is located between the first drive pulley 51 and the second driven pulley 54, and a second idler pulley 56, a flat pulley with a pulley diameter of 76.2 mm, is located between the first driven pulley 53 and the second driven pulley 54. The second driven pulley 54 is movable up and down and is configured to be able to bear an axial load.

[0079] Each of the V-ribbed belts B produced in the examples and comparative examples was wound around first and second drive pulleys 51 and 52 and second and second driven pulleys 53 and 54 so that the V-rib sides were in contact, and around first and second idler pulleys 55 and 56 so that the tension rubber layer sides were in contact. An upward axial load (dead weight (DW)) of 706 N was applied to the second driven pulley 54 to apply belt tension. The winding angle of the V-ribbed belt B around the second drive pulley 52 was 39°. Next, in an atmosphere at a temperature of 21°C, the first drive pulley 51 and the second drive pulley 52 were rotated in the same direction at 800 rpm and 931 rpm, respectively, thereby forcibly slipping the V-ribbed belt B on the second drive pulley 52. ​​Water droplets were also dripped at a rate of 300 ml per minute onto the V-rib surface at the beginning of the winding of the V-ribbed belt B on the right side of the first drive pulley 51. The maximum value of the generated torque (maximum torque) was then measured using a torque meter attached to the second drive pulley 52. ​​This measurement was performed before and after the durability test described below. The absolute value of the difference between the maximum torque before the durability test and the maximum torque after the durability test was calculated to confirm the change in maximum torque. The results are shown in Tables 2 and 3 below. The smaller the change in maximum torque, the more stably the water-injected power transmission capacity is maintained and the more excellent the friction and wear resistance characteristics are.

[0080] 8 shows the pulley layout of a belt running tester 60 for a durability test. This belt running tester 60 is composed of a pair of drive ribbed pulley 61 and driven ribbed pulley 62, both of which have a pulley diameter of 60 mm and are arranged on the left and right.

[0081] For each of the V-ribbed belts produced in the examples and comparative examples, V-ribbed belt B was wound around drive ribbed pulley 61 and driven ribbed pulley 62 so that the V-rib sides were in contact, and drive ribbed pulley 61 was pulled sideways so that a dead weight (DW) of 1177 N was applied, while a rotational load of 3.8 kW was applied to driven ribbed pulley 62. A belt running test was conducted in which drive ribbed pulley 61 was rotated at a rotational speed of 3500 rpm for 96 hours in a room temperature environment (23±5°C).

[0082]

[0083]

[0084] As shown in Tables 2 and 3, the V-ribbed belt according to the embodiment of the present invention exhibits a small change in maximum torque and achieves improved friction and wear resistance.

[0085] The V-ribbed belt of the present disclosure is useful, for example, in an automotive accessory drive belt transmission system.

[0086] DESCRIPTION OF SYMBOLS 10 Belt body 11 Compressed rubber layer 12 Adhesive rubber layer 13 Back reinforcing fabric 14 Rubber layer body (compressed rubber layer body) 15 Fiber member layer 16 Adhesive rubber layer body 17 Core wire 18 V-rib 19 Fiber member 21 Rubber member 30 Crosslinking device 14', 16' Uncrosslinked rubber sheet 50, 60 Running test machine B Friction transmission belt (V-ribbed belt) S Gap

Claims

1. A friction transmission belt having a compressed rubber layer that forms a contact portion with a pulley, the compressed rubber layer includes a rubber layer main body made of a cross-linked product of a rubber composition, and a fiber member layer laminated on the rubber layer main body, the fiber member layer is composed of a fiber member made of a fabric and a rubber member present in gaps between the fiber members, the fiber material layer has a contact surface that contacts the pulley, the rubber member forms a part of the contact surface, the rubber member is made of a cross-linked product of the rubber composition that has permeated into the gap, The rubber composition includes a raw rubber component and a liquid compounding agent, the total amount of a low molecular weight component having a molecular weight of 5000 g / mol or less, as determined by gel permeation chromatography of the raw rubber component, and the amount of the liquid compounding agent is 5.0 mass% or less of the total amount of the rubber composition; Friction transmission belt.

2. The kinetic viscosity of the liquid compounding agent measured at 40°C in accordance with JIS K 2230 is 480 mm ２ / s or less, The friction power transmission belt according to claim 1.

3. The main component of the raw rubber component is an ethylene-α-olefin elastomer. The friction power transmission belt according to claim 1.

4. The fibrous member is a knitted fabric, and the gaps in the fibrous member are the stitches of the knitted fabric. The friction power transmission belt according to claim 1.

5. It is a V-ribbed belt. The friction power transmission belt according to any one of claims 1 to 4.