Toothed belt

Abstract

A toothed belt in which a core wire is embedded, wherein the core wire is a carbon core wire, the core wire has a core wire diameter of 1.30-1.45 mm, the carbon core wire is a twisted yarn obtained by twisting carbon filaments, the twist of the core wire is single twist, the core wire has a twist number of 30-50 tpm, the core wire has an occupancy rate of 80-95% per belt unit width, the belt has a PLD of 1.25-1.60 mm, and the belt has a nominal pitch of the belt teeth is 11 mm.

Description

Toothed belt

[0001] This application claims priority from Japanese Patent Application No. 2024-056700, filed March 29, 2024, and incorporates by reference all of the contents of the above-mentioned Japanese application.

[0002] Toothed belts are suitable for applications requiring synchronous rotation and are used in a variety of fields, for example, as a power transmission means for motorcycles (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2021-188747

[0004] The toothed belt used for rear-wheel drive of electric motorcycles is a toothed belt used for high-load transmission. When used in high-load transmission applications, tooth chipping and belt breakage easily occur. Therefore, toothed belts used in high-load transmission applications are required to have a high level of durability.

[0005] The present disclosure has been made in view of the above circumstances, and has an object to provide a toothed belt that is excellent in durability and can be suitably used in high-load transmission applications.

[0006] A toothed belt according to one embodiment of the present invention is a toothed belt having an embedded core wire, wherein the core wire is a carbon core wire, the core wire diameter is 1.30 mm or more and 1.45 mm or less, the carbon core wire is a twisted yarn made by twisting together carbon filaments, the core wire is a single twist, the twist number of the core wire is 30 tpm or more and 50 tpm or less, the occupancy rate of the core wire per unit width of the belt is 80% or more and 95% or less, the belt PLD is 1.25 mm or more and 1.60 mm or less, and the nominal pitch of the belt teeth is 11 mm.

[0007] According to the present invention, a toothed belt having excellent durability can be provided.

[0008] FIG. 1 is a perspective view showing an example of a toothed belt. FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1. FIG. 3 is an end view taken along line B-B in FIG. 1. FIG. 4 is a diagram illustrating a method for manufacturing a toothed belt. FIG. 5 is a diagram illustrating a method for manufacturing a toothed belt. FIG. 6 is a diagram illustrating a method for manufacturing a toothed belt. FIG. 7 is a diagram illustrating a pulley layout used in belt running test A. FIG. 8 is a diagram illustrating a pulley layout used in belt running test B.

[0009] The outline of the embodiments of the present invention will be described below. [1] A toothed belt having an embedded core wire, wherein the core wire is a carbon core wire, the core wire diameter is 1.30 mm or more and 1.45 mm or less, the carbon core wire is a twisted yarn formed by twisting together carbon filaments, the core wire is a single twist, the twist number of the core wire is 30 tpm or more and 50 tpm or less, the occupancy rate of the core wire per unit belt width is 80% or more and 95% or less, the belt PLD is 1.25 mm or more and 1.60 mm or less, and the nominal pitch of the belt teeth is 11 mm.

[0010] [2] In the toothed belt of [1] above, the number of carbon filaments is preferably 24,000.

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Toothed Belt) Fig. 1 is a perspective view showing a portion of a toothed belt 1 according to an embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. Fig. 3 is an end view taken along line B-B in Fig. 1. Fig. 1 shows a portion of the toothed belt 1. The toothed belt 1 is an endless meshing power transmission belt. The toothed belt 1 is a single-sided toothed belt.

[0012] In Fig. 1, the direction indicated by the double-headed arrow X is the width direction of the toothed belt 1. The direction indicated by the double-headed arrow Y is the length direction of the toothed belt 1. The length direction is also the circumferential direction of the toothed belt 1. The direction indicated by the double-headed arrow Z is the thickness direction of the toothed belt 1. The upper side of each page is the outer circumferential side of the toothed belt 1, and the lower side is the inner circumferential side.

[0013] The belt length of the toothed belt 1 (belt length at the belt pitch line) is, for example, 225 mm or more and 6000 mm or less. The belt width Wb of the toothed belt 1 is, for example, 5 mm or more and 120 mm or less. The belt thickness Tb of the toothed belt 1 is, for example, 3.5 mm or more and 9.0 mm or less. The belt thickness Tb of the toothed belt 1 is the thickness of the thickest part of the toothed belt 1. The dimensions of the toothed belt according to the embodiment of the present invention are not limited to these ranges.

[0014] The toothed belt 1 has a back portion 11 and a plurality of belt teeth 12. The back portion 11 extends in the circumferential direction of the belt. The back portion 11 is in the form of an endless band. In a cross section of the toothed belt 1 perpendicular to the circumferential direction of the belt, the cross section of the back portion 11 is rectangular. The plurality of belt teeth 12 are provided on the inner circumferential side of the back portion 11. The plurality of belt teeth 12 are arranged at equal intervals in the circumferential direction of the belt. Each belt tooth 12 extends in the width direction of the belt. The portion sandwiched between adjacent belt teeth 12 is the tooth bottom 24.

[0015] The belt teeth 12 of the toothed belt 1 have a nominal pitch of 11 mm. Here, the nominal pitch has the same meaning as the "nominal pitch" used in JIS B 1857-1 and the like. In the embodiment of the present invention, the tooth pitch Pb of the toothed belt 1 is in the range of 11±0.03 mm. The tooth profile of the belt teeth 12 is, for example, a circular arc tooth profile.

[0016] By setting the nominal pitch of the belt teeth 12 to 11 mm, the toothed belt 1 can be suitably used as a power transmission means for motorcycles, including electric motorcycles. The reason for this is that a toothed belt with a nominal pitch of belt teeth of 11 mm is easier to design to be strong and less likely to break than a toothed belt with a nominal pitch of 8 mm, and because the pulley diameter can be made smaller than a toothed belt with a nominal pitch of 14 mm, it is easier to contribute to making motorcycles smaller and lighter.

[0017] The toothed belt 1 comprises a belt body 2, a core wire 3, and a reinforcing cloth 4. The belt body 2 has a band shape. The belt body 2 comprises a base 21 and a plurality of tooth portions 22. The base 21 extends in the circumferential direction of the belt. The core wire 3 is embedded in the base 21. The plurality of tooth portions 22 are provided on the inner circumferential side of the base 21. The plurality of tooth portions 22 are integral with the base 21. The plurality of tooth portions 22 are arranged at equal intervals in the circumferential direction of the belt. The surface of the tooth portions 22 is covered with the reinforcing cloth 4.

[0018] The belt body 2 is made of, for example, a rubber composition obtained by crosslinking an uncrosslinked rubber composition containing a rubber component and a rubber compounding agent through heating and pressure (hereinafter also referred to as a crosslinked rubber composition). In the belt body 2, the base 21 and the toothed portion 22 are each made of a crosslinked rubber composition. In the toothed belt 1 shown in FIG. 1, the base 21 and the toothed portion 22 are made of the same crosslinked rubber composition. The crosslinked rubber composition making up the base 21 and the crosslinked rubber composition making up the toothed portion 22 may have different compositions. Details of the crosslinked rubber composition will be described later.

[0019] In the belt main body 2 made of the crosslinked rubber composition, for example, the JIS A hardness of the toothed portion 22 is 84A or more and 98A or less. In this case, the belt main body 2 is less likely to deform, and the toothed portion 22 is less likely to be damaged by cracks. The JIS A hardness of the toothed portion 22 is measured by pressing a rubber hardness tester perpendicularly against the side surface of the toothed portion 22 of the belt main body 2 (the end surface of the toothed portion 22 in the belt width direction). As the rubber hardness tester, a Type A durometer specified in JIS-K6253-3 (2012) is used. The ambient temperature during measurement is 23°C.

[0020] The core wire 3 is embedded in the base portion 21. The core wire 3 has a pitch in the belt width direction and is provided to form a spiral.

[0021] The core wire diameter of the core wire 3 is 1.30 mm or more and 1.45 mm or less. This is suitable for providing a toothed belt with good durability. If the core wire diameter is less than 1.30 mm, the elastic modulus and breaking strength of the core wire itself may be low, and the durability of the toothed belt may not be ensured. On the other hand, if the core wire diameter exceeds 1.45 mm, bending fatigue resistance may decrease and it may become difficult to wind the core wire around a small-diameter pulley. In the present invention, the core wire diameter of the core wire is the core wire diameter φWT in the belt thickness direction of the core wire. The core wire diameter of the core wire 3 is preferably 1.35 mm or more and 1.40 mm or less. The core wire diameter φWA in the belt width direction of the core wire 3 is preferably 1.30 mm or more and 1.45 mm or less. The core wire diameter φWT in the belt thickness direction and the core wire diameter φWA in the belt width direction may be the same or different, but it is preferable that the difference between the two dimensions is as small as possible.

[0022] The belt PLD of the toothed belt 1 in which the core wires 3 are embedded is 1.25 mm or more and 1.60 mm or less. In this case, good durability of the toothed belt can be ensured. On the other hand, if the belt PLD is outside the above range, the toothed belt is more likely to suffer from tooth chipping at an early stage. From the viewpoint of making tooth chipping less likely to occur in the toothed belt, the belt PLD is preferably 1.38 mm or more and 1.60 mm or less. The belt PLD is the distance between the pitch line and the tooth bottom surface in the toothed belt 1. The belt PLD can be adjusted, for example, by changing the diameter of the core wires 3 or the thickness of the reinforcing fabric 4.

[0023] The carbon core wire is a twisted yarn made by twisting together carbon filaments. The carbon filaments are filaments made of carbon fibers. The twist of the core wire is single twist. By twisting the carbon filaments of the core wire 3 single twist, the elastic modulus of the core wire is increased, and good durability of the toothed belt can be ensured. On the other hand, if the twist of the carbon core wire is a double twist or a Lang twist, the durability of the toothed belt using these core wires is poor.

[0024] In the toothed belt 1, the cords 3 may be S-twisted yarns or Z-twisted yarns, or both S-twisted yarns and Z-twisted yarns may be used. The cords 3 are preferably arranged such that the S-twisted cords 3 and the Z-twisted cords 3 are alternately positioned at a pitch in the belt width direction.

[0025] The twist number of the core wire is 30 tpm (turns per meter) or more and 50 tpm or less. In this case, good durability of the toothed belt can be ensured. On the other hand, if the twist number of the core wire is less than 30 tpm, the performance of the core wire cannot be ensured. Furthermore, if the twist number of the core wire exceeds 50 tpm, tooth chipping of the toothed belt becomes more likely to occur, and the durability of the toothed belt decreases. The preferred twist number of the core wire is 35 tpm or more and 45 tpm or less.

[0026] The number of carbon filaments (also referred to as filament count) is preferably 24,000 (24K). This is suitable for providing a toothed belt with good durability. Here, 24,000 (24K) carbon filaments does not strictly mean that the number of carbon filaments is 24,000, but rather that it is sufficient if the number is approximately 24,000. In the field of carbon fibers, carbon fibers containing approximately 24,000 filaments are traded as "24K."

[0027] The carbon filaments may be PAN-based carbon filaments or pitch-based carbon filaments. PAN-based carbon filaments are preferred as the carbon filaments, as they are more likely to improve the durability of toothed belts used for high-load transmission applications. The filament diameter of the carbon filaments is, for example, 5 μm or more and 7 μm or less.

[0028] The cords 3 are arranged so as to extend parallel to each other at intervals in the belt width direction. Apparently, multiple cords 3 are arranged side by side in the belt width direction. The occupancy rate of the cords 3 per unit belt width is 80% or more and 95% or less. This is suitable for providing a toothed belt with good durability. If the occupancy rate is outside the above range, the belt longitudinal elastic modulus decreases, making the belt more susceptible to early tooth chipping.

[0029] The occupancy rate (%) of the core wires 3 per unit width of the belt is the percentage of the "sum of the core wire diameters of the core wires 3" to the "belt width" in a cross section (Figure 2) cut perpendicular to the belt length direction so as to pass through the center of the belt tooth 12 in the belt length direction.

[0030] The core wires 3 may be subjected to an adhesive treatment to increase the adhesive strength with the belt body 2. Examples of the adhesive treatment include an RFL treatment in which the core wires are immersed in an RFL aqueous solution and then heated, and a rubber cement treatment in which the core wires are immersed in rubber cement and then dried. Only one of these adhesive treatments may be performed, or both may be performed. The core wires 3 may be subjected to a surface treatment before the adhesive treatment. Examples of the surface treatment include a treatment in which the core wires are immersed in an epoxy solution or an isocyanate solution and then heated. These adhesive treatments and surface treatments are performed before winding the core wires around a mold in the manufacturing method of a toothed belt described below.

[0031] The reinforcing fabric 4 covers the surface of the tooth portion 22. The reinforcing fabric 4 forms the inner circumferential surface of the toothed belt 1. The inner circumferential surface of the toothed belt 1 includes the reinforcing fabric 4. The reinforcing fabric 4 is a woven fabric. Examples of fibers that form the reinforcing fabric 4 include polyamide fibers (nylon fibers), polyester fibers, aramid fibers, polyparaphenylene benzobisoxazole (PBO) fibers, cotton, etc. A woven fabric of polyamide fibers is preferred as the reinforcing fabric 4. The thickness of the reinforcing fabric 4 is, for example, 0.50 mm or more and 1.00 mm or less. The reinforcing fabric 4 preferably has elasticity, such as a woven fabric in which the weft yarns have been subjected to a wooly finish, for example.

[0032] The reinforcing fabric 4 may be subjected to an adhesive treatment to enhance adhesion to the belt body 2. Examples of the adhesive treatment include an RFL treatment in which the reinforcing fabric 4 is immersed in an RFL aqueous solution and then heated, a soaking treatment in which the reinforcing fabric 4 is immersed in a low-viscosity rubber cement and then dried, and a coating treatment in which a high-viscosity rubber cement is applied to the surface of the belt body side and then dried. Only one of these treatments may be performed, or two or more may be performed. Prior to the adhesive treatment, the reinforcing fabric 4 may be subjected to a surface treatment in which the reinforcing fabric 4 is immersed in an epoxy solution or an isocyanate solution and then heated. These adhesive treatments and surface treatments are performed before winding the reinforcing fabric 4 around a mold in the manufacturing method of a toothed belt described below.

[0033] Next, the cross-linked rubber composition constituting the belt body 2 will be described. As described above, the belt body 2 is composed of a cross-linked rubber composition obtained by cross-linking an uncross-linked rubber composition containing a rubber component and a rubber compounding agent. Examples of the rubber component include hydrogenated nitrile rubber (HNBR), an alloy of hydrogenated nitrile rubber (HNBR) with at least one of a metal acrylate, a metal methacrylate, a metal polyacrylate, and a metal polymethacrylate finely dispersed therein, chloroprene rubber (CR), an ethylene-α-olefin elastomer such as ethylene-propylene-diene rubber (EPDM), chlorosulfonated polyethylene rubber, styrene-butadiene rubber, and epichlorohydrin rubber. These may be used alone or in combination of two or more.

[0034] The rubber component is preferably HNBR, an alloy of HNBR with at least one of zinc acrylate, zinc methacrylate, zinc polyacrylate, and zinc polymethacrylate finely dispersed therein, or EPDM.The belt body 2 is particularly preferably made of a crosslinked product of an uncrosslinked rubber composition containing hydrogenated nitrile rubber (HNBR).

[0035] Examples of the rubber compounding agents include short fibers, vulcanization accelerators, antioxidants, reinforcing materials, plasticizers, co-crosslinking agents, crosslinking agents, and processing aids. Examples of the short fibers include aramid short fibers, nylon short fibers, and polyester short fibers. Para-aramid short fibers are preferred as the aramid short fibers. These short fibers may be used alone or in combination of two or more.

[0036] The short fibers have a length of, for example, 0.5 mm or more and 3.5 mm or less, a fiber diameter of, for example, 5 μm or more and 50 μm or less, and a preferred content of the short fibers is 1 part by mass or more and 7 parts by mass or less per 100 parts by mass of the rubber component.

[0037] 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 oxide) 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, 3 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the rubber component.

[0038] 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 5.0 parts by mass or less per 100 parts by mass of the rubber component.

[0039] 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.

[0040] When carbon black is used, the content thereof is, for example, 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the rubber component.When silica is used, the content thereof is, for example, 10 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the rubber component.

[0041] 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 20 parts by mass per 100 parts by mass of the rubber component.

[0042] Examples of the co-crosslinking agent include trimethylolpropane trimethacrylate, m-phenylenedimaleimide, zinc dimethacrylate, and triallyl isocyanurate. These co-crosslinking agents may be used alone or in combination of two or more. The content of the co-crosslinking agent is, for example, 3 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component.

[0043] 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 preferably, for example, 0.1 parts by mass or more and 3 parts by mass or less of sulfur and 1 part by mass or more and 12 parts by mass or less of organic peroxide per 100 parts by mass of the rubber component.

[0044] Examples of the processing aid include stearic acid, polyethylene wax, and metal salts of fatty acids. These processing aids may be used alone or in combination of two or more. The content of the processing aid is, for example, 0.5 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the rubber component.

[0045] (Method of Manufacturing Toothed Belt) Figures 4 to 6 are diagrams for explaining a method of manufacturing the toothed belt 1. Figures 4 to 6 show only a part of the belt (including the belt material) and a mold 5 for forming the belt.

[0046] In manufacturing the toothed belt 1, a belt molding die 5 is used. The die 5 is cylindrical. The outer periphery of this die 5 is provided with recesses 51 extending in the axial direction and protrusions 52 extending in the axial direction. The recesses 51 have a cross-sectional shape corresponding to the belt teeth 12 and are grooves extending in the axial direction (a direction perpendicular to the paper surface of FIG. 5 ). The recesses 51 are provided at regular intervals in the circumferential direction. The protrusions 52 are provided between adjacent recesses 51.

[0047] (1) Materials are prepared. The rubber components are masticated, and then rubber compounding agents are added and kneaded to obtain an uncrosslinked rubber composition. The obtained uncrosslinked rubber composition is molded to produce an uncrosslinked rubber sheet 23. In this case, calendar molding, for example, can be used as a molding method for the uncrosslinked rubber sheet 23.

[0048] The core wires 3 and the reinforcing cloth 4 are prepared, and if necessary, are subjected to adhesive treatment and surface treatment, and then the reinforcing cloth 4 is formed into a cylindrical shape.

[0049] (2) As shown in Figure 4, first, a cylindrically molded reinforcing cloth 4 is placed on the outer periphery of a mold 5. Next, the cords 3 are spirally wound around the reinforcing cloth 4. At this time, it is preferable that the cords 3 are spirally wound in pairs of S-twisted cords and Z-twisted cords. After the cords 3 are wound, an uncrosslinked rubber sheet 23 is further wound around the mold 5. Multiple uncrosslinked rubber sheets 23 (two in Figure 4) are wound around the mold 5. This forms an uncrosslinked molded body 13C in which the reinforcing cloth 4, the cords 3, and the uncrosslinked rubber sheet 23 are laminated around the outer periphery of the mold 5. When multiple uncrosslinked rubber sheets 23 are wound around the mold 5, the uncrosslinked rubber sheets may have the same composition or different compositions.

[0050] (3) As shown in FIG. 5 , a rubber sleeve 6 is placed over the uncrosslinked molded body 13C on the mold 5. The uncrosslinked molded body 13 covered with the rubber sleeve 6 is placed inside a vulcanization can (not shown) together with the mold 5, and the vulcanization can is sealed. High-temperature, high-pressure steam is filled into the vulcanization can. This state is maintained for a predetermined time. As a result, the uncrosslinked molded body 13C is pressed against the mold 5 and heated. The uncrosslinked rubber sheet 23 flows within the cavity formed between the mold 5 and the rubber sleeve 6. The uncrosslinked rubber sheet 23 passes between the cords 3. The uncrosslinked rubber sheet 23 flows into each of the multiple recesses 51 formed in the mold 5 while pressing against the reinforcing fabric 4. As the uncrosslinked rubber sheet 23 flows within the cavity in this manner, it becomes integrated with the cords 3 and the reinforcing fabric 4 and is crosslinked. As a result, a cylindrical belt slab 14B is formed, as shown in FIG. 6 .

[0051] (4) The pressure inside the vulcanizer is reduced to release the seal. The belt slab 14B formed between the mold 5 and the rubber sleeve 6 is demolded. The demolded belt slab 14B is sliced ​​into rings. The toothed belt 1 can also be obtained by going through these steps.

[0052] Hereinafter, the embodiments of the present invention will be described in more detail with reference to examples, but the embodiments of the present invention are not limited to the following examples. Here, a plurality of toothed belts were manufactured and their performance was evaluated.

[0053] (Belt Raw Materials) (1) Uncrosslinked Rubber Composition An uncrosslinked rubber composition was prepared having the compounding composition (parts by mass) shown in Table 1. The uncrosslinked rubber composition was prepared by masticating the rubber component, and then adding and kneading the rubber compounding agents.

[0054]

[0055] In Table 1, HNBR (1) is ZP2010 (manufactured by Zeon Corporation), and HNBR (2) is ZSC2195CX (manufactured by Zeon Corporation). In addition, in Table 1, the aramid staple fibers are para-aramid staple fibers having a fiber length of 1 mm, and the organic peroxide is Peroximon F40 (manufactured by NOF Corporation).

[0056] (2) Core Wire Carbon core wires (1) to (8) were prepared with the configurations shown in Table 2. Toray T700SC-12K carbon filaments were prepared as carbon filaments for producing carbon core wires (1) to (8), and the carbon core wires were produced by twisting these filaments with a predetermined filament count, twisting method, and number of twists. S-twisted and Z-twisted carbon core wires were produced.

[0057]

[0058] (3) Reinforcing Fabric A woven fabric having warp and weft threads made of polyamide fiber was subjected to the following adhesive treatment. The adhesive treatments included a soaking treatment in which the woven fabric was immersed in low-viscosity rubber cement and then dried, and a coating treatment in which high-viscosity rubber cement was applied to the surface of the woven fabric that would become the belt body and then dried. The thickness of the reinforcing fabric during preparation was adjusted so that the thickness of the reinforcing fabric in the completed toothed belt would be the thickness shown in Tables 3 and 4.

[0059] [Examples 1 to 6, Comparative Examples 1 to 13] Toothed belts were manufactured by a manufacturing method that performed the above-mentioned steps (1) to (4). In the obtained toothed belt, S-twisted cords 3 and Z-twisted cords 3 were arranged alternately at a pitch in the belt width direction. The configuration of the toothed belt is shown in Tables 3 and 4. In step (3) of the toothed belt manufacturing method, the vulcanization conditions were 170°C and 30 minutes. The obtained toothed belts were evaluated by belt running test A and belt running test B.

[0060] (Dimensions of toothed belt) Types of toothed belts called H11M, H8M, and H14M were manufactured. The manufactured toothed belts had a belt width of 10 mm. The H8M and H14M toothed belts conform to JIS B1857-1 (2015). The H11M toothed belt has a tooth pitch of 11±0.03 mm.

[0061] (Evaluation) The toothed belts manufactured in the examples and comparative examples were subjected to belt running test A and belt running test B. The results are shown in Table 3.

[0062] (1) Belt Running Test A (Tooth Chipping Test) This test is a test to evaluate the durability of a toothed belt against tooth chipping. FIG. 7 shows the pulley layout of a belt running tester 90 used in Belt Running Test A. The belt running tester 90 includes a drive pulley 91 and a driven pulley 92 provided on the left side of the drive pulley 91. The driven pulley 92 is provided so as to be movable left and right so that an axial load (SW) can be applied. Belt Running Test A is performed by wrapping the toothed belt to be evaluated around each pulley.

[0063] In belt running test A, when the toothed belt to be evaluated is a toothed belt with a tooth pitch of 11 mm (toothed belts other than Comparative Examples 6 and 7), a toothed pulley with 28 teeth and a tooth groove shape of H11M is used as the drive pulley 91, and a toothed pulley with 62 teeth and a tooth groove shape of H11M is used as the driven pulley 92. Furthermore, when the toothed belt to be evaluated is a toothed belt with a tooth pitch of 8 mm (Comparative Example 6), a toothed pulley with 38 teeth and a tooth groove shape of H8M is used as the drive pulley 91, and a toothed pulley with 84 teeth and a tooth groove shape of H8M is used as the driven pulley 92. Furthermore, when the toothed belt to be evaluated is a toothed belt with a tooth pitch of 14 mm (Comparative Example 7), a toothed pulley with 22 teeth and a tooth groove shape of H14M is used as the drive pulley 91, and a toothed pulley with 48 teeth and a tooth groove shape of H14M is used as the driven pulley 92.

[0064] Belt running test A was conducted under the following conditions: drive-side rotation speed 5000 rpm, driven-side rotation speed 2258 rpm, driven-side load 150 N·m, axial load (SW) 618 N, and ambient temperature 60°C. The axial load (SW) was set using a load cell. After setting the target tension, the pulley was manually rotated three times around the belt, and then the tension was adjusted again to the target tension. In this running test, the shortest time until belt tooth chipping, separation (peeling between the belt body and the core wire), or breakage occurred was measured. The results are shown in Tables 3 and 4.

[0065] (2) Belt Running Test B (Flex Fatigue Test) This test evaluates the flex fatigue resistance of a toothed belt. FIG. 8 shows the pulley layout of a belt running tester 100 used in Belt Running Test B. The belt running tester 100 includes one drive pulley 101 and three driven pulleys 102. The driven pulley 102a is disposed diagonally above and to the right of the drive pulley 101. The driven pulley 102b is disposed diagonally above and to the left of the driven pulley 102a and above the drive pulley 101. The driven pulley 102c is disposed diagonally below and to the left of the driven pulley 102b and to the left of the driven pulley 102a. The driven pulley 102b is configured to be movable up and down so that an axial load (DW) can be applied. In this belt running tester 100, the drive pulley 101 and three driven pulleys 102 are arranged so that the contact angle between the toothed belt and the drive pulley 101 is 120 degrees. Belt running test B is performed by wrapping the toothed belt to be evaluated around each pulley.

[0066] In Belt Running Test B, when the toothed belt to be evaluated has a tooth pitch of 11 mm (toothed belts other than Comparative Examples 6 and 7), toothed pulleys having 19 teeth, a tooth groove shape of H11M, and a pitch diameter of 66.5 mm are used as the drive pulley 101 and the driven pulley 102. When the toothed belt to be evaluated has a tooth pitch of 8 mm (Comparative Example 6), toothed pulleys having 26 teeth, a tooth groove shape of H8M, and a pitch diameter of 66.2 mm are used as the drive pulley 101 and the driven pulley 102. When the toothed belt to be evaluated has a tooth pitch of 14 mm (Comparative Example 7), toothed pulleys having 15 teeth, a tooth groove shape of H14M, and a pitch diameter of 66.8 mm are used as the drive pulley 101 and the driven pulley 102.

[0067] In belt running test B, the toothed belt to be evaluated was wound around the drive pulley 101 and three driven pulleys 102 of the belt running tester 100, and an upward axial load (DW) of 392 N was applied to the driven pulley 102b to apply belt tension, and the drive pulley 101 was rotated at a rotation speed of 5,500 revolutions per minute at room temperature to run the belt. The belt running was then stopped periodically to check for breaks in the core wire, and the number of revolutions the toothed belt made around the four pulleys before a break occurred in the core wire (the number of belt circulations) was measured.

[0068] In the belt running test B, the measurement results were ranked according to the following criteria. The results are shown in Tables 3 and 4. A: The belt circulation count was 5 x 10 ７ The core wire did not break even after more than 1 x 10 ７ More than 5 times x 10 ７ The cord broke after the belt was rotated 1×10 or less times. ７ The core wire broke after less than 100 revolutions of the belt.

[0069]

[0070]

[0071] As shown in Tables 3 and 4, the toothed belt according to the embodiment of the present invention has good durability.

[0072] 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.

[0073] REFERENCE SIGNS LIST 1 toothed belt 2 belt body 3 core wire 4 reinforcing fabric 5 mold 6 rubber sleeve 11 back portion 12 belt teeth 13C uncrosslinked molded body 14B belt slab 21 base portion 22 tooth portion 23 uncrosslinked rubber sheet 51 recessed portion 52 protruding portion 90, 100 belt running tester 91, 101 driving pulley 92, 102 driven pulley

Claims

1. A toothed belt having an embedded core wire, wherein the core wire is a carbon core wire, the core wire diameter is 1.30 mm or more and 1.45 mm or less, the carbon core wire is a twisted yarn made by twisting together carbon filaments, the core wire is twisted in one direction, the twist number of the core wire is 30 tpm or more and 50 tpm or less, the occupancy rate of the core wire per unit width of the belt is 80% or more and 95% or less, the belt PLD is 1.25 mm or more and 1.60 mm or less, and the nominal pitch of the belt teeth is 11 mm.

2. The toothed belt according to claim 1, wherein the number of carbon filaments is 24,000.

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