Friction transmission belt

Abstract

A friction transmission belt 2 comprises a compression rubber layer 10 that constitutes a section of contact with a pulley. The compression rubber layer 10 comprises a rubber layer body 12 that comprises a crosslinked product of a rubber composition. The acetone-extracted fraction of the rubber layer body 12 as calculated by acetone extraction according to JIS K6229:2015 is 5.0 mass% or less.

Description

Friction transmission belt

[0001] The present application claims priority to Japanese Patent Application No. 2023-097420, 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 type devices 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 conditioner 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 has an object to provide a friction transmission belt that can achieve improved friction and wear resistance based on an idea different from conventional ones.

[0007] (1) The friction transmission belt of the present invention is a friction transmission belt including a compressed rubber layer that forms a contact portion with a pulley, wherein the compressed rubber layer includes a rubber layer main body made of a cross-linked rubber composition, and the acetone extractable content of the rubber layer main body is 5.0 mass % or less as determined by acetone extraction in accordance with JIS K6229:2015.

[0008] In the above friction transmission belt, the amount of solvent-extractable components contained in the rubber layer main body is maintained at an appropriate level. The rubber layer main body can effectively suppress the occurrence of adhesive wear caused by solvent-extractable components. The wear resistance of the rubber layer main body is improved. As a result, a stable contact state between the compressed rubber layer including the rubber layer main body and the pulley is maintained. The friction transmission belt can exhibit stable friction and wear resistance characteristics. The friction transmission belt can achieve improved friction and wear resistance characteristics.

[0009] (2) Preferably, in the friction transmission belt, the compressed rubber layer further includes a fibrous member layer laminated on the rubber layer main body, the fibrous member layer including a woven fabric, and the fibrous member contacting the pulley. In this case, friction and wear resistance is further improved.

[0010] (3) Preferably, in the friction transmission belt, the fibrous member layer further includes a rubber member present in gaps between the fibrous members, and the rubber member is made of a crosslinked product of the rubber composition that has permeated the gaps. In this case, friction and wear resistance is further improved.

[0011] (4) Preferably, in the friction transmission belt, the rubber member contacts the pulley, which further improves the friction and wear resistance.

[0012] (5) Preferably, in the friction transmission belt, the rubber composition contains a raw rubber component, and the raw rubber component is mainly composed of an ethylene-α-olefin elastomer. In this case, further improvement in friction and wear resistance is achieved.

[0013] (6) Preferably, the friction transmission belt is a V-ribbed belt. The V-ribbed belt having the above-described compressed rubber layer further improves the friction and wear resistance.

[0014] According to the present invention, it is possible to provide a friction transmission belt that can achieve improved friction and wear resistance.

[0015] Fig. 2 is a diagram schematically showing a part of a friction transmission belt according to an embodiment of the present invention. Fig. 3 is a cross-sectional view showing an example of a cross-linking device. Fig. 4 is a diagram for explaining a method for manufacturing the friction transmission belt shown in Fig. 1. Fig. 5 is a diagram for explaining a method for manufacturing the friction transmission 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 diagram showing the pulley layout of a belt running tester for evaluating water-injected power transmission capacity. Fig. 9 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, but the present invention is not limited to the embodiments described below.

[0017] 1 shows an example of a friction power transmission belt 2 according to an embodiment of the present invention. The friction power transmission belt 2 is a V-ribbed belt. The V-ribbed belt 2 is used, for example, in an accessory drive belt transmission device provided in the engine compartment of an automobile.

[0018] The V-ribbed belt 2 is an endless belt. The V-ribbed belt 2 has a belt circumference of, for example, 700 mm or more and 3000 mm or less, a belt width of, for example, 10 mm or more and 36 mm or less, and a belt thickness of, for example, 3.5 mm or more and 5.0 mm or less.

[0019] The V-ribbed belt 2 comprises a belt body 4 and a plurality of ribs 6 located on the inner circumferential side of the belt body 4. The belt body 4 extends in the belt length direction. The plurality of ribs 6 are aligned in the belt width direction. Each rib 6 is a protrusion that hangs inward from the inner circumferential surface of the belt body 4. The ribs 6 taper inward. The ribs 6 have a cross-sectional shape that is approximately an inverted triangle. The ribs 6 are also called V-ribs.

[0020] The rib height of the ribs 6 is, for example, 2.0 mm or more and 3.0 mm or less. The width between the base ends is, for example, 1.0 mm or more and 3.0 mm or less. The number of ribs 6 is, for example, 3 or more and 10 or less. The V-ribbed belt 2 shown in FIG. 1 has six ribs 6. The inner circumferential side of the V-ribbed belt 2 contacts a pulley such as a drive pulley or a driven pulley. Ribs 6 are provided on the inner circumferential side of the V-ribbed belt 2. The ribs 6 contact the pulley. Below, a specific configuration of a friction drive belt 2 according to one embodiment of the present invention will be described using this V-ribbed belt 2 as an example.

[0021] The friction transmission belt 2 includes a compressed rubber layer 10, an adhesive rubber layer 20, and a back reinforcement fabric 30. The friction transmission belt 2 is configured by combining the compressed rubber layer 10, the adhesive rubber layer 20, and the back reinforcement fabric 30.

[0022] The compressed rubber layer 10 is located on the inner circumferential side of the belt. The back reinforcing fabric 30 is located on the outer circumferential side of the belt. The adhesive rubber layer 20 is located between the compressed rubber layer 10 and the back reinforcing fabric 30. The compressed rubber layer 10, adhesive rubber layer 20, and back reinforcing fabric 30 are arranged in this order in the thickness direction of the belt.

[0023] The compressed rubber layer 10 extends in the length direction of the belt. The compressed rubber layer 10 comes into contact with the pulley. The compressed rubber layer 10 constitutes the contact portion with the pulley. When the friction drive belt 2 is a V-ribbed belt, ribs 6 are provided on the inner circumferential side of the V-ribbed belt 2. In the V-ribbed belt 2, the ribs 6 are formed in the compressed rubber layer 10.

[0024] The compressed rubber layer 10 includes a rubber layer main body 12. The rubber layer main body 12 is formed using a rubber composition. The rubber layer main body 12 of the compressed rubber layer 10 is also called a compressed rubber layer main body.

[0025] A rubber composition is produced by mixing a raw rubber component with various compounding agents. The rubber composition contains the raw rubber component and various compounding agents.

[0026] Examples of compounding agents that can be contained in the rubber composition include crosslinking agents such as sulfur and organic peroxides, vulcanization accelerators such as zinc oxide, co-crosslinking agents, antioxidants, processing aids such as stearic acid, softeners such as process oil, plasticizers such as dioctyl phthalate (DOP), reinforcing agents such as carbon black, and fillers.

[0027] The rubber layer main body 12 is made of a cross-linked product of the rubber composition. In other words, the rubber layer main body 12 is a cross-linked rubber produced using the rubber composition. The cross-linked rubber is obtained by pressurizing and heating the rubber composition in a mold and cross-linking the raw rubber components with a cross-linking agent as a compounding agent.

[0028] Examples of raw rubber components contained in the rubber composition for the rubber layer main body 12 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 rubber composition preferably uses one or more of these as the raw rubber component, and more preferably contains an ethylene-α-olefin elastomer. In this case, it is preferable that the main component of the raw rubber component is an ethylene-α-olefin elastomer.

[0029] The raw rubber component containing an ethylene-α-olefin elastomer as a main component 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.

[0030] 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.

[0031] When the raw rubber component is mainly composed of an ethylene-α-olefin elastomer, the rubber composition preferably contains process oil in an amount of preferably 0.1 to 40 parts by mass, more preferably 0.1 to 20 parts by mass, per 100 parts by mass of the raw rubber component.

[0032] Examples of process oils include paraffinic oil, naphthenic oil, and aromatic oil. The rubber composition may contain one or more of these as the process oil. When EPDM is used as the ethylene-α-olefin elastomer, paraffinic oil is preferred as the process oil.

[0033] Examples of cross-linking agents include sulfur and organic peroxides such as dicumyl peroxide. When the main component of the raw rubber component is an ethylene-α-olefin elastomer, the rubber composition preferably contains at least sulfur as a cross-linking agent. In this case, the blending amount of sulfur is preferably 0.5 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the raw rubber component.

[0034] As shown in Fig. 1, a fiber member layer 14 is formed on the inner circumferential surface of the rubber layer main body 12. The compressed rubber layer 10 shown in Fig. 1 is formed of the rubber layer main body 12 and the fiber member layer 14. The compressed rubber layer 10 of the friction transmission belt 2 may further include the fiber member layer 14.

[0035] The fibrous material layer 14 forms the inner circumferential surface of the friction power transmission belt 2. The thickness of the fibrous material layer 14 is, for example, not less than 0.1 mm and not more than 1.5 mm.

[0036] 1 covers the entire inner circumferential surface of the rubber layer main body 12. The fiber material layer 14 is laminated on the inner circumferential surface of the rubber layer main body 12. The compression rubber layer 10 may be configured so that the fiber material layer 14 covers a portion of the inner circumferential surface of the rubber layer main body 12.

[0037] The fiber member layer 14 forms the surface of the compressed rubber layer 10. In the friction transmission belt 2, the fiber member layer 14 comes into contact with the pulley. The surface of the fiber member layer 14 is a contact surface 14a that comes into contact with the pulley. The fiber member layer 14 has the contact surface 14a that comes into contact with the pulley. As described above, in the V-ribbed belt 2, the ribs 6 are formed on the compressed rubber layer 10, and the ribs 6 come into contact with the pulley. The surface of the ribs 6 is formed by the fiber member layer 14.

[0038] The fibrous member layer 14 includes a fibrous member. The fibrous member is made of a fabric. Examples of fabrics include woven fabrics and knitted fabrics. Examples of weaves of woven fabrics include plain weave, twill weave, satin weave, and variations thereof. Examples of knitted fabric weaves include plain knit, rib knit, purl knit, and other variations in the weft knitting, and single Denbigh knit, single Van Dyke knit, and other variations in the warp knitting. From the viewpoint of being able to uniformly cover the rubber layer main body 12, it is preferable that the fibrous member be a highly elastic knitted fabric.

[0039] 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 among these, or may be formed from two or more types of fibers. From the viewpoint of having good water absorption performance, cellulose-based fibers are preferred as the fibers that constitute the fibrous member.

[0040] When forming the fiber material layer 14, 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.

[0041] The adhesive rubber layer 20 extends in the belt length direction. The adhesive rubber layer 20 has a horizontally elongated rectangular cross section. The thickness of the adhesive rubber layer 20 is, for example, 1.0 mm or more and 2.5 mm or less.

[0042] The adhesive rubber layer 20 includes a rubber layer main body 22 and a core wire 24. The adhesive rubber layer 20 of this friction transmission belt 2 is composed of the rubber layer main body 22 and the core wire 24.

[0043] The rubber layer main body 22 of the adhesive rubber layer 20 is also referred to as an adhesive rubber layer main body. The adhesive rubber layer main body 22 is made of a rubber composition. The adhesive rubber layer main body 22 is made of a cross-linked product of the rubber composition. In this friction transmission belt 2, the adhesive rubber layer main body 22 may be made of the same rubber composition as the rubber composition of the compressed rubber layer main body 12, or may be made of a rubber composition different from the rubber composition of the compressed rubber layer main body 12.

[0044] The cord 24 is located in the middle of the adhesive rubber layer 20 in the belt thickness direction. The cord 24 is covered with the rubber layer main body 22. The cord 24 extends in the belt length direction. As shown in Figure 1, in the cross section of the adhesive rubber layer 20, cross sections of multiple cords 24 (hereinafter referred to as cord cross sections) are aligned in the belt width direction. In the adhesive rubber layer 20, one or more cords 24 are wound spirally at regular intervals in the belt width direction.

[0045] The core wires 24 are made of twisted yarns of polyamide fiber, polyester fiber, aramid fiber, polyamide fiber, etc. The diameter of the core wires 24 is, for example, 0.5 mm or more and 2.5 mm or less. The distance between adjacent core wire cross sections in the cross section of the adhesive rubber layer 20 is, for example, 0.05 mm or more and 0.20 mm or less.

[0046] The core wire 24 may be subjected to an adhesive treatment. Examples of adhesive treatments include immersion in an epoxy resin solution or an isocyanate resin solution followed by heating, immersion in an RFL aqueous solution followed by heating, and immersion in rubber cement followed by drying. It is preferable that the core wire 24 be subjected to one or more of these adhesive treatments.

[0047] The back reinforcing fabric 30 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 reinforcing fabric 30 is, for example, 0.4 mm to 1.2 mm. To impart adhesion to the adhesive rubber layer 20, the back reinforcing fabric 30 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 surface of the adhesive rubber layer 20 and dried. The back reinforcing fabric 30 may be attached to the adhesive rubber layer 20 via a rubber layer (not shown).

[0048] In this friction transmission belt 2, a back rubber layer (not shown) having a thickness of, for example, 0.4 mm to 0.8 mm may be used instead of the back reinforcement fabric 30. 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 due to contact between the back surface of the belt and the flat pulley, the back rubber layer is preferably composed of a rubber composition slightly harder than that of the adhesive rubber layer main body 22. 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 12 and the adhesive rubber layer main body 22, or may be composed of a rubber composition different from that of either the compressed rubber layer main body 12 or the adhesive rubber layer main body 22. When the back rubber layer is composed of a different rubber composition from that of the adhesive rubber layer main body 22, the back rubber layer is preferably composed of a rubber composition slightly harder than that of the adhesive rubber layer main body 22 in order to suppress adhesion due to contact between the back surface of the belt and the flat pulley.

[0049] (Method of Manufacturing Friction Power Transmission Belt) Next, a method of manufacturing the friction power transmission belt 2 will be described with reference to the drawings. The friction power transmission belt 2 according to one embodiment of the present invention is manufactured by a conventionally known method. Fig. 2 is a diagram for explaining a cross-linking device 40 used in manufacturing a V-ribbed belt as the friction power transmission belt 2.

[0050] The cross-linking device 40 includes a base 42, an expansion drum 44, and a mold 46. The expansion drum 44 is cylindrical. The expansion drum 44 is provided upright on the base 42. The mold 46 is cylindrical. The mold 46 is provided outside the expansion drum 44.

[0051] The expansion drum 44 has a drum body 48 and an expansion sleeve 50. Both the drum body 48 and the expansion sleeve 50 are cylindrical. The expansion sleeve 50 is located on the outside of the drum body 48. The expansion sleeve 50 is made of rubber. The expansion sleeve 50 is fitted onto the outer periphery of the drum body 48. The drum body 48 has a number of vent holes 48a. Each vent hole 48a communicates between the inside and outside of the drum body 48. Both ends of the expansion sleeve 50 are fixed by fixing rings 52. The fixing rings 52 seal the gaps between the drum body 48 and the ends of the expansion sleeve 50.

[0052] Although not shown, the cross-linking device 40 has a pressurizing means. The pressurizing means introduces pressure-adjusted air into the drum body 48. The air passes through the air vents 48a and is introduced between the drum body 48 and the expansion sleeve 50. The expansion sleeve 50 expands radially outward. This pressurizes the uncross-linked slab, which will be described later.

[0053] The mold 46 is detachable from the base 42. The mold 46 attached to the base 42 is provided concentrically on the outside of the expansion drum 44. The mold 46 is a mold used to manufacture the V-ribbed belt 2. A plurality of rib forming grooves 46a extending in the circumferential direction are provided on the inner peripheral surface of the mold 46 to form the ribs 6 of the V-ribbed belt 2. The plurality of rib forming grooves 46a are arranged in parallel in the axial direction (groove width direction). Each rib forming groove 46a is formed so that its width narrows from the groove opening toward the groove bottom. The shape of the rib forming groove 46a corresponds to the shape of the rib 6.

[0054] Although not shown, the cross-linking device 40 includes a heating means and a cooling means for the mold 46. The temperature of the mold 46 is controlled by the heating means and the cooling means.

[0055] 3A and 3B are diagrams for explaining a method of manufacturing a V-ribbed belt as the friction transmission belt 2. FIG.

[0056] In the manufacturing method of the V-ribbed belt 2 according to the embodiment, first, the raw rubber components are mixed with the compounding ingredients, and then the mixture is kneaded in a kneading machine such as a kneader or a Banbury mixer to obtain a rubber composition. The rubber composition is formed into a sheet by calendar molding or the like to prepare an uncrosslinked rubber sheet 12' for the rubber layer main body 12 of the compressed rubber layer 10. Similarly, an uncrosslinked rubber sheet 22' for the rubber layer main body 22 of the adhesive rubber layer 20 is also prepared. A fiber member 60 for the fiber member layer 14 and a back reinforcing fabric 30 are prepared, and an adhesive treatment is applied to the fiber member 60 or the back reinforcing fabric 30 as needed. In this manufacturing method, the fiber member 60 is formed into a cylindrical shape in advance. The back reinforcing fabric 30 may also be formed into a cylindrical shape in advance. A cord 24 is prepared, and an adhesive treatment is applied to the cord 24 as needed.

[0057] Next, the back reinforcing fabric 30 and the uncrosslinked rubber sheet 22' for the adhesive rubber layer main body 22 are wound in this order around a cylindrical drum (not shown) covered with a rubber sleeve. After the cord 24 is spirally wound around the uncrosslinked rubber sheet 22', the uncrosslinked rubber sheet 22' for the adhesive rubber layer main body 22 and the uncrosslinked rubber sheet 12' for the compressed rubber layer main body 12 are further wound in this order. A cylindrical fiber member 60 is placed on the uncrosslinked rubber sheet 12' to obtain an uncrosslinked slab S'.

[0058] Next, the uncrosslinked slab S' is removed from the cylindrical drum together with the rubber sleeve 54. As shown in Fig. 3A, the uncrosslinked slab S' is placed on the inner peripheral surface side of the mold 46 together with the rubber sleeve 54. As a result, the uncrosslinked slab S' is set between the mold 46 and the expansion drum 44.

[0059] Next, the mold 46 is heated, and air is introduced through the air vents 48a between the drum body 48 of the expansion drum 44 and the expansion sleeve 50, as shown in FIG. 3B. The expansion sleeve 50 is expanded, and the uncrosslinked slab S' is pressed against the mold 46. The uncrosslinked rubber sheet 12' flows into the rib-forming groove 46a while stretching the fibrous member 60. The fibrous member 60, the uncrosslinked rubber sheet 12', the uncrosslinked rubber sheet 22', the cord 24, and the back reinforcing fabric 30 are integrated, and crosslinking of the raw rubber components of the uncrosslinked rubber sheets 12' and 22' 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.

[0060] Then, the belt slab S is taken out from the cross-linking device 40, cut into rings each having a predetermined number of ribs 6, and turned over, thereby obtaining the V-ribbed belt 2.

[0061] In order to improve the friction and wear resistance of the friction transmission belt 2 described above, the present inventors focused on the wear resistance of the rubber layer main body 12 of the compressed rubber layer 10 that comes into contact with the pulley. If the wear resistance of the rubber layer main body 12 is improved, the contact state between the compressed rubber layer 10 and the pulley is maintained stably, which contributes to improving the friction and wear resistance of the friction transmission belt 2.

[0062] As described above, the rubber layer main body 12 is made of a cross-linked product of a rubber composition. The cross-linked product contains various components, including unreacted components from the cross-linking reaction. These components include components that can be extracted with a solvent. The rubber composition contains liquid compounding agents such as plasticizers and softeners. For example, increasing the amount of liquid compounding agents increases the solvent extractable content of the cross-linked product. The solvent extractable content of the cross-linked product also increases when the raw rubber components contain a large amount of low-molecular-weight components.

[0063] The solvent-extractable components can move within the matrix of the crosslinked product. The solvent-extractable components may be closely related to the occurrence of adhesive wear. If the solvent-extractable components are closely related to the occurrence of adhesive wear, it is thought that if the rubber layer main body 12 contains a large amount of solvent-extractable components, the wear resistance of the rubber layer main body 12 will decrease.

[0064] Therefore, based on the above-mentioned idea, the inventors conducted extensive research into the effect of solvent-extractable components on the abrasion resistance of the rubber layer main body 12 in order to improve the abrasion resistance of the rubber layer main body 12. As a result, they discovered that adjusting the solvent-extractable components of the rubber layer main body 12, rather than the amount of liquid compounding agent, is more effective in controlling the abrasion resistance of the rubber layer main body 12, and thus completed the present invention.

[0065] In a friction drive belt 2 according to one embodiment of the present invention, in order to determine the amount of solvent-extractable components contained in the rubber layer main body 12, the acetone extractable content of the rubber layer main body 12 determined by acetone extraction in accordance with JIS K6229:2015 is used as the solvent extractable content. To measure the acetone extractable content, a portion (approximately 3 g) of the rubber layer main body 12 is sampled from the compressed rubber layer 10 of the friction drive belt 2 as a test piece. Using acetone as the extraction solvent and an extraction time of 8 hours, the test piece is subjected to Soxhlet extraction. The acetone extractable content is determined according to Method A defined in JIS K6229:2015.

[0066] In this friction drive belt 2, the acetone extractable content of the rubber layer main body 12, as determined by acetone extraction in accordance with JIS K6229:2015, is 5.0 mass% or less. This maintains an appropriate amount of solvent-extractable components contained in the rubber layer main body 12. The rubber layer main body 12 can effectively suppress the occurrence of adhesive wear caused by solvent-extractable components. The wear resistance of the rubber layer main body 12 is improved. As a result, the contact state between the compressed rubber layer 10, including the rubber layer main body 12, and the pulley is stably maintained. The friction drive belt 2 can exhibit stable friction and wear resistance characteristics. The friction drive belt 2 can achieve improved friction and wear resistance characteristics.

[0067] In this friction transmission belt 2, from the viewpoint of more effectively improving the wear resistance of the rubber layer main body 12, the acetone extractables of the rubber layer main body 12 are preferably 4.9% by mass or less, and more preferably 4.1% by mass or less. From the viewpoint of improving the wear resistance, the lower the acetone extractables, the better, and therefore no preferred lower limit is set.

[0068] The acetone extractables are controlled by adjusting the composition of the rubber composition, including the selection of raw rubber components. The acetone extractables in the target rubber composition without any liquid compounding ingredients correspond to the lower limit of the acetone extractables in the composition of the rubber composition.

[0069] As described above, the fiber material layer 14 includes a fiber material 60. FIG. 4 shows an example of a fiber material 60 that constitutes the fiber material layer 14. The fiber material 60 shown in FIG. 4 is a knitted fabric called a plain knit or jersey knit. Knitted fabric is made by knitting yarns 62 (knitting yarns). This forms stitches. Stitches are gaps that are created when the yarns 62 are 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 the woven fabric. In this way, the fiber material 60 has many gaps.

[0070] Numerous gap openings are present on the surface of the fibrous material 60. The portions indicated by the symbol S in Fig. 4 are the gaps in the fibrous material 60 shown in Fig. 4. The gaps S penetrate the fibrous material 60. In the following description, for convenience of explanation, the gaps S are represented as cylindrical holes penetrating the fibrous material 60.

[0071] As described above, the compressed rubber layer 10 includes a fibrous member layer 14, which includes a fibrous member 60. The fibrous member 60 forms the skeleton of the fibrous member layer 14 that contacts the pulley. The fibrous member 60 contacts the pulley. As described above, numerous gaps S exist in the fibrous member 60. If a liquid such as water is present between the compressed rubber layer 10 and the pulley, the numerous gaps S existing in the fibrous member 60 capture the liquid. This allows stable contact between the compressed rubber layer 10 and the pulley to be maintained. This friction transmission belt 2 can exhibit high water-injection power transmission capacity. The friction transmission belt 2 can achieve improved friction and wear resistance by further including a fibrous member layer 14 including the fibrous member 60 in the compressed rubber layer 10.

[0072] As described above, in the manufacturing method of the friction transmission belt 2, the uncrosslinked slab S' is pressed against the mold 46, and the uncrosslinked rubber sheet 12' flows into the rib forming grooves 46a while stretching the fibrous member 60. For example, as shown in FIG. 3B , the fibrous member 60 is laminated on the uncrosslinked rubber sheet 12', i.e., the rubber composition of the rubber layer main body 12. The rubber composition has fluidity. As the rubber composition presses the fibrous member 60, a portion of the rubber composition penetrates into the gaps S between the fibrous member 60. Subsequently, the raw rubber components of the rubber composition crosslink, forming rubber members 64 made of the crosslinked rubber composition that has penetrated into the gaps S in the fibrous member 60, as shown in FIG. 3B . The rubber members 64 stretch, weaving through the gaps S between the fibrous members 60. The fibrous member layer 14 is composed of the fibrous member 60 and the rubber members 64 present in the gaps S between the fibrous members 60. The fibrous member layer 14 includes the rubber members 64 in addition to the fibrous member 60.

[0073] The rubber members 64 function as anchors. The fiber members 60 are firmly bonded to the rubber layer main body 12. The fiber members 60 can continue to contribute to the water-injected power transmission capacity of the friction transmission belt 2. The friction transmission belt 2 can further improve the friction and wear resistance by further including rubber members 64 present in the gaps S between the fiber members 60 in the fiber member layer 14.

[0074] 5 is a schematic diagram showing the surface state of the fiber material layer 14. As described above, numerous gaps S are present on the surface of the fiber material 60. In the method for producing the friction transmission belt 2, the rubber composition presses the fiber material 60, so that some of the rubber composition that has soaked into the gaps S seeps out onto the surface of the fiber material 60. The surface of the fiber material layer 14 is composed of a fiber portion 60a made of the fiber material 60 and a rubber portion 64a made of the rubber material 64. The surface of the fiber material layer 14, i.e., the contact surface 14a that comes into contact with the pulley, is equipped with the fiber portion 60a and the rubber portion 64a. The rubber member 64 forms part of the contact surface 14a.

[0075] The rubber member 64 comes into contact with the pulley. When adhesive wear occurs in the rubber member 64 due to this contact, adhesive wear debris is generated. The wear debris adheres to the fibrous member 60. In particular, when the wear debris adheres to the gaps S of the fibrous member 60 and blocks the gaps S, the liquid capturing function of the fibrous member 60 decreases. Wear progresses gradually. It is expected that the water injection power transmission capacity of the friction drive belt 2 will gradually decrease.

[0076] However, the rubber member 64 is a cross-linked product of the rubber composition of the rubber layer main body 12 that has seeped into the gaps S of the fiber member 60. As described above, the acetone extractable content of the rubber layer main body 12 is 5.0 mass % or less. The rubber member 64 has excellent abrasion resistance. Even when the rubber member 64 comes into contact with a pulley, adhesive wear is unlikely to occur. Wear debris is effectively prevented from clogging the gaps S. The fiber member 60 can continue to perform its liquid capture function. In this friction transmission belt 2, deterioration of water transmission performance due to use is significantly suppressed. Because the rubber member 64 present in the gaps S of the fiber member 60 is a cross-linked product of the rubber composition of the rubber layer main body 12, the friction transmission belt 2 can continue to maintain good water transmission performance even when the rubber member 64 comes into contact with a pulley. This friction transmission belt 2 can further improve its friction and wear resistance.

[0077] As described above, in the manufacturing method of the friction drive belt 2, the rubber composition presses against the fiber component 60, causing a portion of the rubber composition to seep into the gaps S between the fiber component 60. As long as the rubber composition has a predetermined fluidity, the stronger the force with which the rubber composition presses against the fiber component 60, the longer the time the rubber composition presses against the fiber component 60, the higher the fluidity of the rubber composition, and the larger the size of the gaps S between the fiber component 60, 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 64a cover the gaps S. When a small amount of rubber composition has seeped out, the rubber portions 64a are formed inside the gaps S. If the rubber composition does not reach the openings, the rubber portions 64a will not be formed on the contact surface 14a. The proportion of the rubber portions 64a that occupy the contact surface 14a varies depending on the molding conditions, the fluidity of the rubber composition, the specifications of the fiber component 60, and the like. The proportion of the rubber portions 64a that occupy the contact surface 14a is set appropriately according to the specifications of the friction drive belt.

[0078] The surface state of the fiber material layer 14 shown in Fig. 5 is a state in which rubber portions 64a are formed in some of the gaps S of the fiber material 60 shown in Fig. 4. In Fig. 5, the gaps S where the rubber composition did not reach the openings and the rubber portions 64a were not formed are not shown as part of the fiber material 60a.

[0079] The proportion of the rubber portion 64a occupying the contact surface 14a (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 14 of the V-ribbed belt 2. There are no particular limitations 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 14 is captured. Based on the captured surface image, the area of ​​each rubber portion 64a included in the observation region is measured using software built into the microscope. As a result, the ratio of the total area of ​​the rubber portions 64a to the area of ​​the entire observation region is 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.

[0080] 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.

[0081] 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.

[0082] <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.

[0083] <Materials for Compressed Rubber Layer Main Body> The following two types of EPDM were prepared as raw rubber components: EPDM1 (trade name "EP 123" manufactured by JSR Corporation) EPDM2 (trade name "Nordel 4640" manufactured by Dow Chemical Co., Ltd.) 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 "Nocceler MSA-G" manufactured by Ouchi Shinko Chemical Co., Ltd.), vulcanization accelerator B (trade name "Sunceler EM2" manufactured by Sanshin Chemical Industry Co., Ltd.), and sulfur (trade name "Oil Sulfur" manufactured by Hosoi Chemical Industry Co., Ltd.) were prepared. A rubber composition was prepared by blending and kneading each material in the amounts shown in Table 1. The rubber composition was formed into a sheet having a thickness of 0.7 mm using a roll.

[0084]

[0085] <Materials for Adhesive Rubber Layer Main Body> EPDM (trade name "EP123" manufactured by JSR Corporation) was used as a raw rubber component, and relative to 100 parts by mass of this raw rubber component, 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 Japan Sun Oil Co., Ltd.), 1 part by mass of stearic acid (trade name "Stearic Acid" manufactured by Kao Corporation or "Beads Stearic Acid Camellia" manufactured by NOF Corporation), 5 parts 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 "Nocceler MSA-G" manufactured by Ouchi Shinko Chemical Co., Ltd.), 3 parts by mass of vulcanization accelerator (trade name "Sunceler EM2" manufactured by Sanshin Chemical Industry Co., Ltd.), and sulfur (Hosoi Chemical Industry Co., Ltd.) were used. A rubber composition was prepared by compounding and kneading 1.5 parts by mass of a rubber composition manufactured by Nippon Oil & Energy Chemical Co., Ltd. (trade name "Oil Sulfur") with 1.5 parts by mass of a rubber composition manufactured by Nippon Oil & Energy Chemical Co., Ltd. The rubber composition was formed into a sheet having a thickness of 0.45 mm using a roll.

[0086] <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.

[0087] <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.

[0088] 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.

[0089] [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.

[0090] <Measurement of Acetone Extractables> As described above, the acetone extractables were measured in accordance with JIS K6229:2015. In this measurement, a portion (approximately 3 g) of the rubber layer main body was sampled from the compressed rubber layer of the friction transmission belt as a test piece. Using acetone as the extraction solvent and an extraction time of 8 hours, the test piece was subjected to Soxhlet extraction. The acetone extractables were measured according to Method A. The results are shown in the "Acetone Extractables" column in Tables 2 and 3 below.

[0091] <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.

[0092] <Evaluation of Water-Injected Power Transmission Capacity> Fig. 6 shows the pulley layout of a belt running test machine 70 for evaluating water-injected power transmission capacity. In Fig. 7, symbol V indicates a V-ribbed belt.

[0093] This belt running tester 70 has a first drive pulley 71, a ribbed pulley with a pulley diameter of 121.6 mm, located at the lower left, and a second drive pulley 72, a ribbed pulley with a pulley diameter of 141.5 mm, located to the right of the first drive pulley 71. A first driven pulley 73, a ribbed pulley with a pulley diameter of 77.0 mm, is located diagonally above the right of the second drive pulley 72, and a second driven pulley 74, a ribbed pulley with a pulley diameter of 61.0 mm, is located above the second drive pulley 72. A first idler pulley 75, a flat pulley with a pulley diameter of 76.2 mm, is located between the first drive pulley 71 and the second driven pulley 74, and a second idler pulley 76, a flat pulley with a pulley diameter of 76.2 mm, is located between the first driven pulley 73 and the second driven pulley 74. The second driven pulley 74 is movable up and down and is configured to be able to bear an axial load.

[0094] Each of the V-ribbed belts fabricated in the examples and comparative examples was wound around first and second drive pulleys 71 and 72 and second and second driven pulleys 73 and 74 with the V-rib sides in contact, and around first and second idler pulleys 75 and 76 with the tension rubber layer sides in contact. An upward axial load (dead weight (DW)) of 706 N was applied to the second driven pulley 74 to apply belt tension. The winding angle of the V-ribbed belt around the second drive pulley 72 was 39°. Next, in an atmosphere at a temperature of 21°C, the first drive pulley 71 and the second drive pulley 72 were rotated in the same direction at 800 rpm and 931 rpm, respectively, to forcibly slip the V-ribbed belt on the second drive pulley 72. Water droplets were also dripped onto the V-rib surface at the beginning of the winding of the V-ribbed belt on the right side of the first drive pulley 71 at a rate of 300 ml per minute. The maximum value of the generated torque (maximum torque) was measured using a torque meter attached to the second drive pulley 72. This measurement was performed before and after the durability test described below. The absolute value of the difference between the maximum torque before and 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 transmission capacity is maintained and the more excellent the friction and wear resistance characteristics are.

[0095] 7 shows the pulley layout of a belt running tester 80 for a durability test. This belt running tester 80 is composed of a pair of drive ribbed pulley 81 and driven ribbed pulley 82, each with a pulley diameter of 60 mm, arranged on the left and right.

[0096] For each of the V-ribbed belts produced in the examples and comparative examples, the V-ribbed belt was wound around a drive ribbed pulley 81 and a driven ribbed pulley 82 so that the V-rib sides were in contact, and the drive ribbed pulley 81 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 the driven ribbed pulley 82. A belt running test was conducted in which the drive ribbed pulley 81 was rotated at a rotational speed of 3500 rpm for 96 hours in a room temperature environment (23±5°C).

[0097]

[0098]

[0099] As shown in Tables 2 and 3, it is clear that the friction transmission belt according to the embodiment of the present invention can achieve improved friction and wear resistance.

[0100] DESCRIPTION OF SYMBOLS 2 Friction power transmission belt (ribbed belt) 4 Belt body 6 Rib 10 Compressed rubber layer 12 Compressed rubber layer body (rubber layer body) 14 Fiber member layer 14a Contact surface 20 Adhesive rubber layer 22 Adhesive rubber layer body (rubber layer body) 24 Core wire 30 Back reinforcing fabric 40 Cross-linking device 46 Mold 46a Rib forming groove 60 Fiber member 64 Rubber member 70, 80 Running test machine B Friction power 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, The acetone extractable content of the rubber layer body, as determined by acetone extraction in accordance with JIS K6229:2015, is 5.0% by mass or less. Friction transmission belt.

2. The compressed rubber layer further includes a fiber member layer laminated on the rubber layer main body, The fiber material layer includes a fiber material made of a fabric, The fiber member contacts the pulley. The friction power transmission belt according to claim 1.

3. The fibrous material layer further includes a rubber material present in gaps between the fibrous materials, The rubber member is made of a crosslinked product of the rubber composition that has permeated into the gap. The friction power transmission belt according to claim 2.

4. The rubber member contacts the pulley. The friction power transmission belt according to claim 3.

5. The rubber composition includes a raw rubber component, The main component of the raw rubber component is an ethylene-α-olefin elastomer. The friction power transmission belt according to claim 1.

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