Transmission belt

Abstract

A transmission belt according to the present invention comprises a belt body composed of a rubber composition and a core wire embedded in the belt body, wherein an adhesion treatment layer is provided on the surface the core wire, the rubber composition has a 20% modulus at 100°C of 10.0 MPa or more, and the ratio of the push-in elastic modulus of the adhesion treatment layer to the push-in elastic modulus of the rubber composition is 2.0 or more.

Description

Power transmission belt

[0001] This application claims priority to Japanese Patent Application No. 2023-115014, filed on July 13, 2023, and incorporates by reference the entire disclosure of said Japanese application.

[0002] BACKGROUND ART Known power transmission belts include toothed belts and friction power transmission belts, and some of these power transmission belts include a belt body made of a rubber composition and a core wire embedded in the belt body (see, for example, Patent Document 1).

[0003] WO2016 / 170747

[0004] A power transmission belt, which includes a belt body and a core wire embedded in the belt body, is required to have strong adhesion between the belt body and the core wire. A power transmission belt with weak adhesion between the belt body and the core wire is prone to separation between the belt body and the core wire, and has poor durability.

[0005] An object of the present disclosure is to provide a power transmission belt in which separation between the belt body and the core wires is unlikely to occur.

[0006] A transmission belt according to one embodiment of the present invention is a transmission belt having a belt body made of a rubber composition and a core wire embedded in the belt body, wherein the core wire has an adhesive treatment layer on its surface, the rubber composition has a 20% modulus at 100°C of 10.0 MPa or more, and the ratio of the indentation elastic modulus of the adhesive treatment layer to the indentation elastic modulus of the rubber composition is 2.0 or more.

[0007] In the power transmission belt according to one aspect of the present invention, the belt body and the core wire are strongly bonded to each other, so that separation between the belt body and the core wire is unlikely to occur, and therefore the power transmission belt has excellent durability.

[0008] Fig. 1 is a perspective view showing a part of a toothed belt. Fig. 2A is a cross-sectional view taken along line A-A in Fig. 1, and Fig. 2B is a partially enlarged view of Fig. 2A. Figs. 3A to 3D are schematic diagrams for explaining a method for producing an evaluation sample. Figs. 4A and 4B are schematic diagrams for explaining a method for producing an evaluation sample. A perspective view showing an evaluation sample.

[0009] The outline of the embodiments of the present invention will be described below: (1) A power transmission belt having a belt body made of a rubber composition and a core wire embedded in the belt body, wherein the core wire has an adhesive treatment layer on a surface thereof, the rubber composition has a 20% modulus at 100°C of 10.0 MPa or more, and the ratio of the indentation modulus of the adhesive treatment layer to the indentation modulus of the rubber composition is 2.0 or more.

[0010] The power transmission belt is resistant to separation between the belt body and the core wire embedded in the belt body, and has excellent durability.

[0011] (2) In the transmission belt of (1), the indentation modulus of the adhesive treatment layer is preferably 1,000 MPa or more. (3) In the transmission belt of (1) or (2), the core wire is preferably composed of carbon fiber. (4) In the transmission belt of (3), the number of filaments of the carbon fiber is preferably 3,000 to 50,000. In these cases, it is easy to increase the ratio of the indentation modulus of the adhesive treatment layer to the indentation modulus of the rubber composition.

[0012] (5) In the power transmission belt according to any one of (1) to (4), the rubber composition is preferably a crosslinked rubber composition containing a rubber component, and the rubber component is preferably any one of hydrogenated nitrile rubber, chloroprene rubber, and ethylene-α-olefin rubber.

[0013] (6) In the power transmission belt according to any one of (1) to (5), it is preferable that the outer diameter of the core wires in the belt thickness direction is 0.90 mm or more and 1.70 mm or less, and the outer diameter in the belt width direction is 0.90 mm or more and 1.70 mm or less.

[0014] (7) In the transmission belt according to any one of (1) to (6) above, it is preferable that the adhesive treatment agent for providing the adhesive treatment layer is a chlorinated rubber adhesive or a chlorosulfonated polyethylene adhesive. (8) The transmission belt according to any one of (1) to (7) above may be a toothed belt.

[0015] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments.

[0016] (First embodiment) A power transmission belt according to this embodiment is a toothed belt. Toothed belts can be used in general industrial machines such as automobiles, motorcycles, machine tools, printing machines, textile machines, and injection molding machines. In particular, they can be suitably used in applications that require transmission capacity and durability under high-load environments, such as rear-wheel drive applications for electric motorcycles.

[0017] Fig. 1 is a perspective view showing a portion of a toothed belt 10 according to an embodiment of the present invention. Fig. 2A is a cross-sectional view taken along line A-A in Fig. 1, and Fig. 2B is a partially enlarged view of Fig. 2A. Fig. 2B shows an enlarged view of region B in Fig. 2A. Although Fig. 1 shows only a portion of the toothed belt 10, the toothed belt 10 is an endless meshing power transmission belt. In addition, the toothed belt 10 is a single-sided toothed belt.

[0018] The toothed belt 10 has a plurality of belt teeth 12 on its inner circumferential side. A core wire 13 is embedded in the toothed belt 10. The tooth profile of the belt teeth 12 is, for example, a circular arc tooth profile. In an embodiment of the present invention, the tooth profile of the belt teeth may be a trapezoidal tooth profile. The belt teeth 12 of the toothed belt 10 are straight teeth. In an embodiment of the present invention, the belt teeth may be helical teeth.

[0019] 1 and 2A, the toothed belt 10 includes a belt body 11, core wires 13, and a reinforcing fabric 14. The belt body 11 has a strip shape and includes a base portion 11a having a rectangular cross section perpendicular to the belt longitudinal direction, and a plurality of teeth 11b provided on the inner circumferential side of the base portion 11a. The plurality of teeth 11b are integrated with the base portion 11a. The plurality of teeth 11b are provided at equal intervals at predetermined intervals along the belt longitudinal direction.

[0020] The core wire 13 is embedded in the base portion 11a of the belt body 11. As shown in Fig. 2B, the core wire 13 has a core wire body 13A and an adhesive treatment layer 13B provided around the core wire 13. The adhesive treatment layer 13B is provided on the surface of the core wire 13.

[0021] The core wires 13 are arranged to have a pitch in the belt width direction and to form a spiral. The core wires 13 may be composed of two core wires, one having an S-twisted yarn core body and the other having a Z-twisted yarn core body, and these core wires may be arranged to form a double spiral.

[0022] The core wires 13 are arranged to extend parallel to each other at intervals in the belt width direction. In this case, the number of core wires 13 per 10 mm of belt width is preferably 5 / 10 mm or more and 20 / 10 mm or less. A toothed belt 10 having the core wires 13 arranged in this manner is suitable for ensuring excellent durability and excellent tension maintenance in high-load transmission. From the same viewpoint, the number of core wires 13 is more preferably 6 / 10 mm or more and 10 / 10 mm or less. The dimension of the gap between adjacent core wires 13 is, for example, 0.1 mm or more and 0.7 mm or less.

[0023] The reinforcing cloth 14 is provided so as to cover the inner peripheral surface of the toothed portion 11b. In the toothed belt 10, the belt teeth 12 are composed of the toothed portion 11b and the reinforcing cloth 14. In the embodiment of the present invention, the toothed belt does not necessarily have to include the reinforcing cloth.

[0024] The belt body 11 is made of a rubber composition. The core wire 13 has a core wire body 13A and an adhesive treatment layer 13B provided around the core wire body 13A. The rubber composition constituting the belt body 11 has a 20% modulus at 100°C of 10.0 MPa or more. In this case, the durability of the toothed belt 10 is good. There is no particular upper limit to the 20% modulus at 100°C of the rubber composition, but it is, for example, 30 MPa.

[0025] The applicant's research has revealed that toothed belts used for rear-wheel drive applications of electric motorcycles, etc., experience strain of about 20% at the meshing portion with the pulley. Therefore, it is important to set the 20% modulus of the rubber composition constituting the belt body to a predetermined value. Furthermore, toothed belts used for rear-wheel drive applications of electric motorcycles experience a maximum belt temperature of about 100°C during use. Therefore, it is important to set the evaluation temperature of the 20% modulus to 100°C.

[0026] The ratio (B / A) of the indentation elastic modulus B of the adhesive treatment layer 13B to the indentation elastic modulus A of the rubber composition constituting the belt body 11 is 2.0 or more. In this case, the belt body 11 and the cords 13 are less likely to separate, and the toothed belt 10 has good durability. On the other hand, if the ratio (B / A) is less than 2.0, separation between the belt body 11 and the cords 13 is likely to occur early. The reason for this is presumed to be as follows. The cord body 13A usually has a very high indentation elastic modulus compared to the rubber composition constituting the adhesive treatment layer 13B and the belt body 11. It is believed that the greater the ratio of the indentation elastic modulus of the cord body 13A to the indentation elastic modulus of the adhesive treatment layer 13B, the more likely separation between the belt body 11 and the cords 13 is. On the other hand, when the ratio (B / A) is 2.0 or more, the ratio of the indentation elastic modulus of the core wire body 13A to the indentation elastic modulus of the adhesive treatment layer 13B tends to be small, and as a result, it is speculated that peeling between the belt body 11 and the core wire 13 is less likely to occur.

[0027] The indentation elastic modulus is measured using a nanoindenter (ultra-microindentation hardness tester). In this embodiment, the nanoindenter used is an ENT-NEXUS manufactured by ELIONIX.

[0028] The indentation modulus A of the rubber composition constituting the belt body 11 is measured by pressing the indenter of a nanoindenter against the belt body 11. The indentation modulus B of the adhesive treatment layer 13B is measured by pressing the indenter of a nanoindenter against the adhesive treatment layer 13B.

[0029] The specific method for measuring the indentation elastic modulus A and the indentation elastic modulus B of the toothed belt 10 is as follows. First, an arbitrary location of the toothed belt 10 is cut along a plane perpendicular to the belt length direction. As a result, the cut surfaces of the core wires 13 (the cut surface of the core wire main body 13A and the cut surface of the adhesive treatment layer 13B) are exposed on the cut surface of the toothed belt 10. Then, the indenter of a nanoindenter is pressed against the exposed cut surface of the adhesive treatment layer 13B to measure the indentation elastic modulus B. The indenter of the nanoindenter is also pressed against the exposed cut surface of the belt main body to measure the indentation elastic modulus A. At this time, the indenter of the nanoindenter is pressed against the belt main body in the peripheral portion of the core wires 13 (a region 100 μm or more and 200 μm or less from the outer periphery of the core wires). In measuring the indentation elastic modulus in this manner, after cutting the toothed belt 10, the cut surface of the exposed toothed belt 10 may be subjected to cutting processing using a microtome to make the cut surface smoother.

[0030] The test conditions for the measurements using the nanoindenter are as shown in Table 1.

[0031]

[0032] Indentation elastic modulus E ＩＴ , are calculated using the following formulas (1) to (5).

[0033]

[0034] In the above formulas (1) to (5), the symbols have the following meanings: ＩＴ : Indentation elastic modulus E ｒ : Converted elastic modulus by indentation contact V ｓ : Poisson's ratio of the test piece V ｉ : Poisson's ratio of the indenter E ｉ : Elastic modulus of the indenter C: Contact compliance (reciprocal of contact stiffness S) S: Contact stiffness: Slope of the tangent at Fmax of the unloading curve A ｐ (h ｃ ): Projected contact area ・h ｍａｘ : Maximum indentation depth h ｃ : Contact indentation depth h ｒ:Intersection of tangent and indentation depth ・F ｍａｘ : Test load

[0035] The indentation modulus B of the adhesive treatment layer 13B is preferably 1000 MPa or more. In this case, it is easy to increase the ratio (B / A) of the indentation modulus B of the adhesive treatment layer 13B to the indentation modulus A of the rubber composition, which is more suitable for suppressing peeling between the belt body 11 and the core wires 13.

[0036] The indentation elastic modulus A is preferably 100 MPa or more and 1000 MPa or less, while satisfying that the ratio (B / A) of the indentation elastic modulus B of the adhesive treatment layer 13B to the indentation elastic modulus A is 2.0 or more. The indentation elastic modulus A is more preferably 200 MPa or more and 600 MPa or less, and even more preferably 270 MPa or more and 400 MPa or less, while satisfying that the ratio (B / A) is 2.0 or more.

[0037] In the toothed belt 10 of this embodiment, the belt body 11 is made of one type of rubber composition. However, in the toothed belt according to the embodiment of the present invention, the belt body may be made of two or more types of rubber compositions. For example, the base portion 11a of the belt body 11 and the tooth portion 11b of the belt body 11 may be made of different rubber compositions. When the belt body of the toothed belt is made of two or more types of rubber compositions, the 20% modulus of the rubber composition making up the belt body is evaluated based on the rubber composition making up the tooth portion (the rubber composition making up the tooth portion 11b in the belt body 11), and the indentation modulus A of the rubber composition making up the belt body is evaluated based on the rubber composition in which the cords are embedded (the rubber composition making up the base portion 11a in the belt body 11).

[0038] The rubber composition constituting the belt body 11 is, for example, an uncrosslinked rubber composition containing a rubber component that has been crosslinked by heating and pressurization. The uncrosslinked rubber composition may further contain a rubber compounding agent. Examples of the rubber component include hydrogenated nitrile rubber (HNBR), chloroprene rubber (CR), ethylene-α-olefin rubbers such as ethylene-propylene-diene rubber (EPDM), ethylene-propylene rubber (EPM), and ethylene-butene-diene rubber (EBM), chlorosulfonated polyethylene rubber, styrene-butadiene rubber, and epichlorohydrin rubber. Among these, HNBR, CR, and EPDM are preferred.

[0039] As the rubber compounding agent, conventionally known rubber compounding agents can be used, examples of which include a vulcanization accelerator, an antioxidant, a reinforcing agent, a plasticizer, a co-crosslinking agent, and a crosslinking agent.

[0040] Examples of the vulcanization accelerator aid include metal oxides, metal carbonates, fatty acids, and derivatives thereof. Examples of the metal oxide include zinc oxide (zinc white) and magnesium oxide. These vulcanization accelerator aids may be used alone or in combination of two or more. The content of the vulcanization accelerator aid is, for example, 1 part by mass or more and 15 parts by mass or less per 100 parts by mass of the rubber component.

[0041] Examples of the antioxidant include benzimidazole-based antioxidants, aromatic secondary amine-based antioxidants, and amine-ketone-based antioxidants. These antioxidants may be used alone or in combination of two or more. The content of the antioxidant is, for example, 1.5 parts by mass or more and 3.5 parts by mass or less per 100 parts by mass of the rubber component.

[0042] Examples of the reinforcing material include carbon black and silica. The reinforcing material may be a combination of carbon black and silica. Examples of the carbon black include channel black, furnace black, thermal black, and acetylene black. Examples of the furnace black include SAF, ISAF, N-339, HAF, N-351, MAF, FEF, SRF, GPF, ECF, and N-234. Examples of the thermal black include FT and MT. Only one type of carbon black may be used, or two or more types may be used in combination.

[0043] When carbon black is used, the content thereof is, for example, 10 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the rubber component.When silica is used, the content thereof is, for example, 5 parts by mass or more and 40 parts by mass or less per 100 parts by mass of the rubber component.

[0044] Examples of the plasticizer include dialkyl sebacate, dialkyl phthalate, and dialkyl adipate. Examples of the dialkyl sebacate include polyether ester and dioctyl sebacate (DOS). Examples of the dialkyl phthalate include dibutyl phthalate (DBP) and dioctyl phthalate (DOP). Examples of the dialkyl adipate include dioctyl adipate (DOA). These plasticizers may be used alone or in combination of two or more. The content of the plasticizer is, for example, 5 to 15 parts by mass per 100 parts by mass of the rubber component.

[0045] Examples of the co-crosslinking agent include trimethylolpropane trimethacrylate, m-phenylenedimaleimide, zinc dimethacrylate, and triallyl isocyanurate. One type of co-crosslinking agent may be used alone, or two or more types may be used in combination. The amount of the co-crosslinking agent is, for example, 3 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the rubber component.

[0046] Examples of the crosslinking agent include sulfur and organic peroxides. Sulfur and organic peroxides may be used in combination. Of course, either one may be used alone. When sulfur and organic peroxides are used in combination as the crosslinking agent, the total compounding amount of the crosslinking agents is, for example, 0.1 part by mass or more and 1.0 part by mass or less of sulfur and 1 part by mass or more and 10 parts by mass or less of organic peroxide per 100 parts by mass of the rubber component.

[0047] Examples of the core wire body 13A constituting the core wire 13 include glass core wire, aramid core wire, carbon core wire, and steel core wire. These core wire bodies 13A are preferably made of twisted yarn. The twisted yarn may be single twist, double twist, or Lang twist. Among these twisting methods, single twist is preferred.

[0048] Carbon core wires are preferred for the core wire body 13A because they are suitable for high-load power transmission applications and can easily secure sufficient tension even when thin. Furthermore, carbon core wires have a high indentation modulus and tend to easily separate from the belt body. Therefore, carbon core wires are suitable for use in the toothed belt according to the embodiment of the present invention, which is designed to be less susceptible to separation between the belt body and the core wire.

[0049] The carbon core wire contains carbon fiber as a constituent material. The carbon core wire may be composed of carbon fiber alone, or may be composed of a composite of carbon fiber and other types of fiber, with carbon fiber as the main component. Here, "composed mainly of carbon fiber" means that the carbon fiber content exceeds 50% by mass. When carbon fiber is composited with other types of fiber, the higher the proportion of the carbon fiber (for example, 90% by mass or more) is, the more preferable it is.

[0050] The carbon fibers may be PAN-based, pitch-based, or a mixture of both. A sizing agent such as an epoxy resin may be attached to the carbon fibers. Examples of other types of fibers include inorganic fibers such as glass fibers and metal fibers, and organic fibers such as aramid fibers, polyester fibers, PBO fibers, nylon fibers, and polyketone fibers.

[0051] The carbon fiber has a filament diameter of, for example, 4 μm or more and 6 μm or less. When the carbon core wire is composed of only carbon fiber, the number of filaments of the carbon fiber is preferably 3,000 to 50,000. By using such a carbon core wire as the core wire body 13A, the toothed belt 10 becomes a toothed belt with excellent positioning accuracy and suitable for high-load power transmission applications.

[0052] The outer diameters of the core wires 13, φT in the belt thickness direction and φW in the belt width direction, are preferably 0.90 mm or more and 1.70 mm or less. More preferably, φT and φW are 1.00 mm or more and 1.60 mm or less. The outer diameter φT in the belt thickness direction and the outer diameter φW in the belt width direction may be the same or different.

[0053] An adhesive treatment layer 13B is provided on the surface of the core wire 13. Examples of adhesive treatment agents for providing the adhesive treatment layer 13B include chlorinated rubber adhesives and CSM (chlorosulfonated polyethylene) adhesives. The adhesive treatment agents may be commercially available products. Examples of commercially available products include Chemlok 233X, Chemlok 6108, and Chemlok 402X manufactured by Lord Corporation, and Metalok F-112, Metalok F-116, and Metalok R-146 manufactured by Toyo Kagaku Kenkyusho.

[0054] The adhesive treatment layer 13B may be formed, for example, by immersing the core wire body 13A in a solution containing the adhesive treatment agent and then drying it. The core wire body 13A may be subjected to a surface treatment before the adhesive treatment layer is provided.

[0055] The reinforcing fabric 14 is made of, for example, a woven fabric, a knitted fabric, a nonwoven fabric, etc. Examples of fibers that make up the reinforcing fabric 14 include polyamide fibers (nylon fibers), polyester fibers, aramid fibers, polyparaphenylenebenzobisoxazole (PBO) fibers, cotton, etc.

[0056] The reinforcing fabric 14 may be subjected to an adhesive treatment to enhance adhesive strength with the belt body 11. The reinforcing fabric 14 may be subjected to a surface treatment before the adhesive treatment.

[0057] The toothed belt 10 having such a configuration may be manufactured by a known manufacturing method.

[0058] (Other Embodiments) The power transmission belt according to the embodiment of the present invention is not limited to a toothed belt as long as the core wire and the belt body satisfy a predetermined relationship. The power transmission belt according to the embodiment of the present invention may be a friction power transmission belt such as a flat belt, a V-belt, or a V-ribbed belt.

[0059] As described above, in the power transmission belt according to the embodiment of the present invention, the core wire and the belt body in which the core wire is embedded satisfy a predetermined relationship, so that the core wire and the belt body are less likely to separate and the belt has excellent durability. The results of the performance evaluation that demonstrate this are shown below.

[0060] Here, evaluation samples No. 1 to No. 11 were prepared in which a core wire was embedded in a rubber composition (a vulcanizate of a raw rubber composition). Using the obtained evaluation samples, the indentation modulus A of the rubber composition and the indentation modulus B of the adhesive treatment layer were measured. Furthermore, a fracture test was conducted on each evaluation sample, and the fracture life was measured as an index of durability. The 20% modulus was also measured for the vulcanizate of the raw rubber composition used to prepare the evaluation samples. The material combinations and evaluation results for evaluation samples No. 1 to No. 11 are shown in Table 2.

[0061] [Materials of Evaluation Samples] (1) Raw Rubber Composition (a) Raw Rubber Composition A: 100 parts by mass of sulfur-modified chloroprene rubber (CR) (manufactured by Tosoh Corporation) was used as a base rubber. To 100 parts by mass of this base rubber, 60 parts by mass of carbon black HAF (manufactured by Tokai Carbon Co., Ltd., product name: Seast 3), 4.2 parts by mass of an antioxidant, 1.5 parts by mass of stearic acid, 7.3 parts by mass of an organic peroxide crosslinking agent (manufactured by NOF Corporation, product name: Perhexa 25B40), 4 parts by mass of magnesium oxide, 8 parts by mass of a co-crosslinking agent (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name: Valnoc PM), and 10 parts by mass of a co-crosslinking agent (manufactured by Kawaguchi Chemical Industry Co., Ltd., product name: Actor ZMA) were blended and kneaded to form an unvulcanized rubber composition, which was used as Raw Rubber Composition A.

[0062] (b) Raw rubber composition B: 100 parts by mass of sulfur-modified chloroprene rubber (CR) (manufactured by Tosoh Corporation) was used as the base rubber. To 100 parts by mass of this base rubber, 70 parts by mass of carbon black HAF (manufactured by Tokai Carbon Co., Ltd., product name: SEAT 3), 4.5 parts by mass of an antioxidant, 1 part by mass of stearic acid, 6.5 parts by mass of magnesium oxide, 2 parts by mass of a vulcanization accelerator (manufactured by Sanshin Chemical Industry Co., Ltd., product name: Suncerar TT-G), 0.6 parts by mass of a vulcanization accelerator (manufactured by Sanshin Chemical Industry Co., Ltd., product name: Suncerar DM), 2 parts by mass of a vulcanization accelerator (manufactured by Sanshin Chemical Industry Co., Ltd., product name: Suncerar M), 15 parts by mass of a co-crosslinking agent (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name: Valnoc PM), and 5 parts by mass of zinc oxide were blended and kneaded to form an unvulcanized rubber composition, which was used as raw rubber composition B.

[0063] (c) Raw rubber composition C: Raw rubber composition C was prepared in the same manner as raw rubber composition A, except that the co-crosslinking agent (Actor ZMA) and the organic peroxide crosslinking agent were not blended, and 5 parts by mass of zinc oxide was blended.

[0064] (d) Raw rubber composition D: Raw rubber composition D was prepared in the same manner as in the preparation of raw rubber composition A, except that the co-crosslinking agent (Actor ZMA) was not compounded.

[0065] (2) Core wire provided with an adhesive treatment layer The core wire body was immersed in an adhesive treatment agent (for example, Chemlok, manufactured by Lord Industries, etc.) and then dried to prepare core wires A to E provided with a surface treatment layer. A Z-twisted carbon core wire was used as the core wire body. Specifically, carbon fiber (manufactured by Toray Industries, Inc., product name: Torayca T700SC-12000, number of filaments: 12,000) was used, and this was twisted 6 times per 10 cm to form a single-twisted yarn to form the core wire body. The twist of the core wire body was Z-twist. The core wire diameter was 1.10 mm.

[0066] [Fabrication of Evaluation Samples] Figures 3A to 3D and 4A to 4B are schematic diagrams for explaining a method for fabricating evaluation samples. Figure 5 is a diagram showing an evaluation sample. The material combinations are shown in Table 2. The fabrication method for evaluation samples will be explained below in the order of steps.

[0067] (1) A rectangular frame mold 51 is prepared, and multiple cords 31 are stretched across two parallel sides of the frame mold 51 (see FIG. 3A). Both ends of the cords 31 are fixed to the frame. (2) Separately from step (1), a mold 53 having a rectangular prism-shaped space (through-hole) 55 is prepared, and a raw rubber composition 57 is filled into the space 55 (see FIG. 3B). Four molds 53 filled with the raw rubber composition 57 are prepared.

[0068] (3) A mold 53 filled with raw rubber composition 57 is placed below the cord 31 prepared in step (1) (see FIG. 3C). Furthermore, a mold 53 filled with raw rubber composition 57 is placed above the cord 31 (see FIG. 3D). This results in the cord 31 being sandwiched between the upper and lower raw rubber compositions 57. (4) After step (3) is completed, the frame 51 and mold 53 are set in a press (not shown) with the mold 53 placed so as to sandwich the cord 31 from above and below, and press vulcanization is carried out under conditions of 170°C x 25 minutes.

[0069] (5) After press vulcanization, the mold 53 and the frame mold 51 are removed to obtain a molded product 61, as shown in Fig. 4A, in which a plurality of cords 31 penetrate a vulcanizate 59 of the raw rubber composition molded into a rectangular parallelepiped (hereinafter simply referred to as vulcanizate 59). (6) The cords 31 penetrating the vulcanizate 59 are cut to obtain a molded product 63 in which the cords 31 protrude only in one direction (downward in the figure) of the vulcanizate 59 (see Fig. 4B).

[0070] (7) Next, the molded product 63 was cut so as to have one core wire 31, and a molded product with the core wire 31 protruding in one direction was cut out from a 20 mm x 10 mm x 10 mm rectangular parallelepiped vulcanized product 59, as shown in Figure 5. Finally, the surface of the rectangular parallelepiped vulcanized product 59 opposite to the side from which the core wire 31 protruded was cut using a microtome to expose a smooth finished surface 65a, thereby completing the evaluation sample 65 (see Figure 5). The end face of the core wire body 31A and the end face of the adhesive treatment layer 31B constituting the core wire 31 were exposed on the finished surface 65a.

[0071] [Performance Evaluation] (1) Measurement of Indentation Elastic Modulus A and Indentation Elastic Modulus B The indentation elastic modulus A was measured by pressing the indenter of a nanoindenter (manufactured by ELIONIX (ENT-NEXUS)) against the vulcanizate 59 around the core wire 31 exposed on the finished surface 65a of the evaluation sample 65. The indentation elastic modulus B was measured by pressing the indenter of a nanoindenter (manufactured by ELIONIX (ENT-NEXUS)) against the end face of the adhesive treatment layer 31B of the core wire 31 exposed on the finished surface 65a of the evaluation sample 65. The test conditions for the measurements were as already described. In the measurement of the indentation elastic modulus A, 25 measurement points were measured in one measurement operation, and the average value was used as the result value. On the other hand, in the measurement of the indentation elastic modulus B, since it was difficult to measure 25 measurement points in one measurement operation, the measurement operation was performed multiple times to collect measurement values ​​for 25 points on the adhesive treatment layer, and the average value was used as the result value.

[0072] (2) Breakdown Life For evaluation sample 65, vibrations were applied in an atmosphere of 120°C along the length of the cord 31 at a frequency of 10 Hz and a load of 98.1 N, and the number of vibrations (one reciprocation counted as one cycle) until the cord 31 came out of the vulcanizate 59 was measured. The measurement was performed on two samples, and the average value was taken as the result.

[0073] (3) Measurement of 20% modulus of vulcanizates (rubber compositions) of raw rubber compositions A to D Dumbbell-shaped No. 3 test pieces were prepared through the following steps (a) to (d).

[0074] (a) The raw rubber composition was sheeted to a thickness of 2.1 to 2.4 mm to obtain a rubber sheet. (b) The obtained rubber sheet was cut to a size of 150 mm x 150 mm. (c) The cut rubber sheet was set in a mold (150 mm x 150 mm x 2 mm thick) and press-vulcanized at 170°C for 20 minutes to obtain a rubber sheet. (d) The obtained rubber sheet was punched out to prepare a dumbbell-shaped No. 3 (JIS K6251 (2017)) test piece.

[0075] Using this test piece, the 20% modulus at 100° C. was measured by the following method. The results are shown in Table 2.

[0076] (Measurement of 20% modulus) Measurement was performed in accordance with JIS K6251 (2017) "Vulcanized rubber and thermoplastic rubber - Determination of tensile properties." Here, a universal material testing machine (Instron 3365) was used as the testing machine. The test conditions were temperature x time 100°C x 30 minutes, and a tensile speed of 500 mm / min. An S-S curve was obtained when the specimen was elongated until breakage, and the stress at 20% elongation was defined as the "20% modulus at 100°C."

[0077]

[0078] From the results shown in Table 2, it can be seen that the power transmission belt according to the embodiment of the present invention has excellent durability.

[0079] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, and it is intended to include all modifications within the meaning and scope of the claims.

[0080] DESCRIPTION OF SYMBOLS 10 Toothed belt 11 Belt body 11a Base portion 11b Tooth portion 12 Belt teeth 13, 31 Core wire 13A, 31A Core wire body 13B, 31B Adhesive treatment layer 14 Reinforcing fabric 51 Frame 53 Mold 55 Space 57 Raw rubber composition 59 Vulcanizate of raw rubber composition 61, 63 Molded product 65 Evaluation sample

Claims

1. A power transmission belt having a belt body made of a rubber composition and a core wire embedded in the belt body, The core wire has an adhesive treatment layer on its surface, The rubber composition has a 20% modulus at 100° C. of 10.0 MPa or more, The ratio of the indentation elastic modulus of the adhesive treatment layer to the indentation elastic modulus of the rubber composition is 2.0 or more. Transmission belt.

2. 2. The power transmission belt according to claim 1, wherein the adhesive treatment layer has an indentation elastic modulus of 1000 MPa or more.

3. 3. The power transmission belt according to claim 1, wherein the core wire is made of carbon fiber.

4. 4. The power transmission belt according to claim 3, wherein the number of filaments of the carbon fiber is 3,000 to 50,000.

5. 3. The power transmission belt according to claim 1, wherein the rubber composition is obtained by crosslinking an uncrosslinked rubber composition containing a rubber component, and the rubber component is any one of hydrogenated nitrile rubber, chloroprene rubber, and ethylene-α-olefin rubber.

6. 3. The power transmission belt according to claim 1, wherein the outer diameter of the core wire in the belt thickness direction is 0.90 mm or more and 1.70 mm or less, and the outer diameter in the belt width direction is 0.90 mm or more and 1.70 mm or less.

7. 3. The power transmission belt according to claim 1, wherein an adhesive treatment agent for providing the adhesive treatment layer is a chlorinated rubber adhesive or a chlorosulfonated polyethylene adhesive.

8. 3. The power transmission belt according to claim 1, which is a toothed belt.