Power transmission belt

Abstract

To provide a transmission belt having excellent durability. [Solution] A power transmission belt (B) includes an elastomer belt body (11) and a carbon fiber core wire (12) embedded in the belt body (11) and arranged to form a spiral with a pitch in the belt width direction. When the core wire (12) is viewed from the side perpendicular to its longitudinal direction, the angle θ of the outermost filament (F) in the carbon fiber filament bundle constituting the core wire (12) with respect to the longitudinal direction of the core wire (12) is between 8° and 20°.

Description

[Technical Field]

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

[0002] BACKGROUND ART Power transmission belts using a core wire made of carbon fiber are known. For example, Patent Document 1 discloses a toothed belt in which a core wire made of carbon fiber is embedded in a belt body made of rubber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-24075 Summary of the Invention

[0004] The present invention provides a power transmission belt comprising an elastomer belt body and a carbon fiber core wire embedded in the belt body and arranged to form a spiral with a pitch in the belt width direction, wherein when the core wire is viewed from the side perpendicular to its longitudinal direction, the angle formed by the outermost filament in the carbon fiber filament bundle constituting the core wire with respect to the longitudinal direction of the core wire is 8° or more and 20° or less. [Brief explanation of the drawings]

[0005] [Figure 1A] FIG. 2 is a perspective view of one piece of a toothed belt according to the embodiment. [Figure 1B] FIG. 2 is a vertical cross-sectional view of a portion of a toothed belt according to an embodiment. [Figure 2] FIG. 2 is a front view of a core wire embedded in a toothed belt body as viewed from the side perpendicular to the longitudinal direction. [Figure 3A] FIG. 2 is a first explanatory diagram of a method for manufacturing a toothed belt according to an embodiment. [Figure 3B] FIG. 6 is a second explanatory diagram of the method for manufacturing a toothed belt according to the embodiment. [Figure 3C]FIG. 6 is a third explanatory view of the method for manufacturing a toothed belt according to the embodiment. [Figure 4] FIG. 2 is a layout diagram of pulleys in a belt running tester. DETAILED DESCRIPTION OF THE INVENTION

[0006] Hereinafter, the embodiments will be described in detail with reference to the drawings.

[0007] 1A and 1B show a toothed belt B according to an embodiment. The toothed belt B according to the embodiment is a meshing power transmission belt and is suitable for use in high-load power transmission applications such as machine tools, printing machines, textile machines, and injection molding machines. The belt length of the toothed belt B according to the embodiment is, for example, 500 mm or more and 3000 mm or less. The belt width is, for example, 10 mm or more and 200 mm or less. The belt thickness (maximum) is, for example, 3 mm or more and 20 mm or less.

[0008] The toothed belt B according to this embodiment includes an endless toothed belt main body 11 made of an elastomer formed from polyurethane resin. The toothed belt main body 11 has a flat belt portion 111 with a horizontally elongated rectangular cross section and a plurality of toothed portions 112 integrally formed on the inner circumferential side thereof. The plurality of toothed portions 112 are spaced apart at a constant pitch in the belt length direction.

[0009] Examples of the tooth profile of the toothed portion 112 in a side view include an STS tooth profile with both sides bulging outward in an arc shape, a trapezoidal tooth profile, etc. The number of teeth in the toothed portion 112 is, for example, 30 to 400. The tooth width (maximum dimension in the belt length direction) is, for example, 2 mm to 10 mm. The tooth height is, for example, 2 mm to 8 mm. The arrangement pitch is, for example, 8 mm to 14 mm.

[0010] The polyurethane resin forming the toothed belt body 11 is a urethane composition obtained by mixing a urethane prepolymer with compounding agents such as a curing agent and a plasticizer, and then curing the urethane composition by heating and pressurizing the urethane prepolymer.

[0011] A urethane prepolymer is a relatively low-molecular-weight urethane compound having multiple NCO groups at its terminals, obtained by reacting an isocyanate component with a polyol component. Examples of the isocyanate component include tolylene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI). Examples of the polyol component include polytetramethylene ether glycol (PTMG). The urethane prepolymer may be composed of a single urethane compound or a mixture of multiple urethane compounds.

[0012] Examples of curing agents include amine compounds such as 1,4-phenylenediamine, 2,6-diaminotoluene, 1,5-naphthalenediamine, 4,4'-diaminodiphenylmethane, and 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA). The curing agent preferably contains one or more of these. The amine compound curing agent is preferably blended so that the α value (NH2 groups / NCO groups), which is the ratio of the number of moles of NH2 groups in the curing agent to the number of moles of NCO groups in the urethane prepolymer, is 0.70 or more and 1.10 or less.

[0013] Examples of plasticizers include dialkyl phthalates such as dibutyl phthalate (DBP) and dioctyl phthalate (DOP); dialkyl adipates such as dioctyl adipate (DOA); and dialkyl sebacates such as dioctyl sebacate (DOS). The plasticizer preferably contains one or more of these. The amount of plasticizer blended is, for example, 3 to 20 parts by mass per 100 parts by mass of the urethane prepolymer.

[0014] Examples of other compounding agents include colorants, antifoaming agents, stabilizers, etc.

[0015] The hardness of the polyurethane resin forming the toothed belt body 11 is, for example, 70° or more and 100° or less. The hardness of this polyurethane resin is measured based on JIS K7312:1996.

[0016] As shown in Fig. 2, the toothed belt B according to this embodiment includes a core wire 12 made of carbon fiber embedded in a flat belt portion 111 of a toothed belt main body 11. From the viewpoint of obtaining excellent durability, the outer diameter D of the core wire 12 is preferably 0.4 mm or more and 2.7 mm or less, and more preferably 0.5 mm or more and 2.4 mm or less.

[0017] From the viewpoint of obtaining excellent durability, the carbon fiber constituting the core wire 12 is preferably a PAN-based carbon fiber. From the same viewpoint, the outer diameter of the carbon fiber filament F is preferably 4 μm or more and 9 μm or less, more preferably 6 μm or more and 8 μm or less.

[0018] From the viewpoint of obtaining excellent durability, the total number of carbon fiber filaments F constituting the core wire 12 is preferably 3,000 (3K) to 60,000 (60K), more preferably 9,000 (9K) to 54,000 (54K), and even more preferably 12,000 (12K) to 48,000 (48K). From the same viewpoint, the fineness of the carbon fiber constituting the core wire 12 is preferably 200 tex to 4,000 tex, more preferably 600 tex to 3,600 tex, and even more preferably 800 tex to 3,200 tex.

[0019] From the viewpoint of obtaining excellent durability, the core wire 12 is preferably a twisted yarn. Examples of twisted yarns constituting the core wire 12 include single twisted yarns, double twisted yarns, and Lang twisted yarns. From the same viewpoint, the twisted yarn core wire 12 is preferably a single twisted yarn obtained by twisting a bundle of carbon fiber filaments in one direction. The single twisted yarn core wire 12 may be an S twisted yarn, a Z twisted yarn, or a combination of both.

[0020] When the total number of carbon fiber filaments F constituting the single twisted yarn core wire 12 is less than 24,000 (24K), the number of twists per 10 cm of the length is preferably 2.0 turns / 10 cm or more and 25.0 turns / 10 cm or less, more preferably 3.0 turns / 10 cm or more and 19.0 turns / 10 cm or less, and even more preferably 5.0 turns / 10 cm or more and 11.0 turns / 10 cm or less, from the viewpoint of obtaining excellent durability. When the total number of carbon fiber filaments F constituting the single twisted yarn core wire 12 is 24,000 (24K) or more, the number of twists per 10 cm of the length is preferably 1.5 turns / 10 cm or more and 7.5 turns / 10 cm or less, more preferably 2.3 turns / 10 cm or more and 6.6 turns / 10 cm or less, and even more preferably 3.5 turns / 10 cm or more and 5.5 turns / 10 cm or less, from the viewpoint of obtaining excellent durability.

[0021] When the core wire 12 is viewed from the side perpendicular to its longitudinal direction, the angle θ formed by the outermost filament F in the carbon fiber filament bundle constituting the core wire 12 with respect to the longitudinal direction of the core wire 12 is 8° or more and 20° or less. From the viewpoint of obtaining excellent durability, the angle θ formed by this filament F with respect to the longitudinal direction of the core wire 12 is preferably 8° or more and 20° or less, more preferably 10° or more and 19° or less.

[0022] The core wires 12 are arranged to form a spiral having a pitch in the belt width direction. The core wires 12 may be composed of two threads, an S-twisted thread and a Z-twisted thread, and arranged to form a double spiral. The core wires 12 are arranged to extend parallel to each other at intervals in the belt width direction. In this case, the number of core wires 12 per 10 mm of belt width is preferably 3 / 10 mm to 16 / 10 mm, more preferably 4 / 10 mm to 15 / 10 mm, from the viewpoint of obtaining excellent durability. Since the core wires 12 are arranged to form a spiral having a pitch in the belt width direction, their length direction is inclined with respect to the belt length direction. However, since the inclination angle is small, the angle θ formed by the outermost filament F in the carbon fiber filament bundle constituting the core wires 12 with respect to the length direction of the core wires 12 is substantially the same as the angle formed by the filament F with respect to the belt length direction.

[0023] The core wires 12 are preferably subjected to an adhesive treatment such as immersion in a liquid adhesive and then drying before molding.

[0024] The toothed belt B according to the embodiment includes a nonwoven fabric 13 embedded along the belt length direction, on the inner circumferential side of the position where the core wires 12 are embedded in the belt thickness direction in the toothed belt main body 11. The nonwoven fabric 13 may be made up of either a single layer or multiple layers.

[0025] The nonwoven fabric 13 contains the polyurethane resin that forms the toothed belt main body 11, and is provided so as to form a layer in a side view. The portions of the nonwoven fabric 13 that correspond to the tooth portions 112 penetrate into the tooth portions 112 so as to bulge outward in a side view, and expand thickly in the belt thickness direction. The portions of the nonwoven fabric 13 that correspond to the spaces between the tooth portions 112 come into contact with the core wires 12 and are compressed thinly in the belt thickness direction.

[0026] Examples of fiber materials that can be used to form the nonwoven fabric 13 include nylon fibers, polyester fibers, aramid fibers, polyketone fibers, and carbon fibers. The nonwoven fabric 13 may be made of either a single type of fiber or multiple types of fibers.

[0027] It is preferable that the nonwoven fabric 13 is subjected to an adhesive treatment such as immersing it in a liquid adhesive and then drying it before molding.

[0028] Belt tension T per 1 mm of belt width when the belt elongation rate of toothed belt B according to the embodiment is 0.1% 0.1 From the viewpoint of obtaining excellent durability, the strength is preferably 30 N / mm or more, more preferably 45 N / mm or more, and from the viewpoint of avoiding an increase in bending rigidity that would impair bending fatigue resistance, the strength is preferably 50 N / mm or less, more preferably 45 N / mm or less.

[0029] This belt tension T 0.1 is calculated as follows. First, in an atmosphere of 25°C, the toothed belt B according to the embodiment is wound around a pair of flat pulleys, each with a pulley diameter of 95.4 mm, of a belt tension tester so that the back surfaces of the belt are in contact. Next, one flat pulley is moved away from the other flat pulley at a speed of 50 mm / min. At this time, the occurrence of tension detected through one of the pair of flat pulleys is taken as the starting point, and the relationship between the displacement between the pair of flat pulleys and the detected tension is recorded. Next, the displacement between the pair of flat pulleys is doubled to calculate the belt elongation amount, and this is divided by the belt length of the toothed belt B according to the embodiment in an unloaded state to convert the displacement between the pair of flat pulleys into a belt elongation rate. The detected tension is also divided by 2 to calculate the belt tension, and this is then divided by the belt width of the toothed belt B according to the embodiment to convert the detected tension into a belt tension per mm of belt width. Then, from the relationship between the belt elongation rate and the belt tension, the belt tension T 0.1 Ask for.

[0030] According to the toothed belt B of the embodiment configured as described above, when the core wire 12 is viewed from the side perpendicular to its longitudinal direction, the angle θ formed by the outermost filaments F in the carbon fiber filament bundle constituting the core wire 12 with respect to the longitudinal direction of the core wire 12 is 8° or more and 20° or less, thereby achieving excellent durability. This is presumably because excessive strain can be prevented from occurring in the carbon fiber filaments F, which are a brittle material constituting the core wire 12.

[0031] Next, a method for manufacturing the toothed belt B according to the embodiment will be described.

[0032] 3A, a cylindrical inner mold 31 is covered with a nonwoven fabric 13, and then the core wire 12 is spirally wound thereon. At this time, the outer periphery of the inner mold 31 is provided with axially extending grooves 32 whose cross sections correspond to the tooth portions 112 and are spaced apart at regular intervals in the circumferential direction, and axially extending ridges 33 are formed between each groove 32. Therefore, the nonwoven fabric 13 and the core wire 12 are supported by the ridges 33.

[0033] 3B, the inner mold 31 is placed inside a cylindrical outer mold 34. At this time, a cavity C for molding the toothed belt main body is formed between the inner mold 31 and the outer mold 34.

[0034] Next, as shown in FIG. 3C, a liquid urethane composition made by blending a compounding agent with a urethane prepolymer is injected into the sealed cavity C, filling it, and heated. At this time, the urethane composition flows and hardens, forming a toothed belt main body 11 made of polyurethane resin. Also, tooth portions 112 are formed in the recessed grooves 32. The core wires 12 are adhered to and embedded in the toothed belt main body 11. Furthermore, the nonwoven fabric 13 is impregnated with the urethane composition and hardens, and is also adhered to and embedded in the toothed belt main body 11. In this way, the toothed belt main body 11, the core wires 12, and the nonwoven fabric 13 are integrated to form a cylindrical belt slab S.

[0035] Finally, the belt slab S is removed from the inner mold 31 and the outer mold 34 and cut into rings to obtain the toothed belt B according to the embodiment.

[0036] In the above embodiment, the toothed belt B is composed of the toothed belt main body 11, the core wire 12, and the nonwoven fabric 13, but this is not particularly limited to this, and a reinforcing fabric may be provided on the toothed portion side surface on the inner periphery of the toothed belt main body and / or on the back surface on the outer periphery of the toothed belt main body.

[0037] In the above embodiment, the toothed belt B has the toothed belt main body 11 formed from a polyurethane resin, but this is not particularly limited to this, and the toothed belt main body may also be formed from a cross-linked rubber composition.

[0038] In the above embodiment, the toothed belt B is used as the power transmission belt, but it is not particularly limited to this, and may be a flat belt, a V-belt, a V-ribbed belt, or the like. [Example]

[0039] [Test Evaluation 1] (toothed belt) Toothed belts were produced for Example 1 and Comparative Examples 1-1 and 1-2. The configurations of each are also shown in Table 1.

[0040] Example 1 A toothed belt with an STS tooth profile having the same configuration as the above embodiment was used as Example 1. The toothed belt of Example 1 had a belt length of 1400 mm, a belt width of 14 mm, and a belt thickness (maximum) of 8.6 mm. The tooth portion was S14M as specified in ISO13050:2014(E).

[0041] The urethane composition used to form the toothed belt body was a blend of 100 parts by mass of urethane prepolymer, 13 parts by mass of 3,3'-dichloro-4,4'-diaminodiphenylmethane as a curing agent, and 10 parts by mass of dioctyl phthalate as a plasticizer. The hardness of the polyurethane resin forming the toothed belt body, measured according to JIS K7312, was 92°.

[0042] The core wire was made of a single-twisted yarn, which was a filament bundle (total number of filaments: 48,000, total fineness: 3,200 tex) consisting of four 12,000 carbon fiber strands (Toray T700SC-12000, manufactured by Toray Industries, Inc., 12K, 800 tex, outer diameter of filament: 7 μm) twisted together in one direction at four twists per 10 cm. The angle of the outermost filament in the carbon fiber filament bundle constituting the core wire with respect to the longitudinal direction of the core wire was 10°. For the single-twisted yarn core wire, S-twisted yarn and Z-twisted yarn were prepared, and these were subjected to an adhesive treatment by immersing in adhesive and then drying. The S-twisted and Z-twisted single-twisted yarn core wires were arranged alternately across the belt width to form a double helix. The number of core wires per 10 mm of belt width was four. The outer diameter of the core wire was 2.0 mm.

[0043] The nonwoven fabric used was made of nylon fibers and produced without pressure by the needle punch method. The nonwoven fabric was not subjected to any adhesive treatment.

[0044] The belt strength per 1 mm of belt width of the toothed belt of Example 1 was 1302 N / mm. Belt tension T 0.1 was 40.0 N / mm.

[0045] <Comparative Example 1-1> Comparative Example 1-1 was a toothed belt having the same configuration as Example 1, except that a carbon fiber plied yarn (total number of filaments: 48,000, total fineness: 3,200 tex) was used as the core. The plied yarn was produced by twisting a carbon fiber filament bundle, the same number of filaments as used in Example 1, in one direction at four twists per 10 cm to form a first twist yarn, collecting four of these filaments and twisting them together, and then twisting this in the opposite direction to the first twist yarn at four twists per 10 cm. The angle formed by the outermost filament in the carbon fiber filament bundle constituting the core of the plied yarn with respect to the longitudinal direction of the core wire was 7°.

[0046] The belt strength per mm of the belt width of the toothed belt of Comparative Example 1-1 was 1267 N / mm. Belt tension T 0.1 was 38.5N / mm.

[0047] <Comparative Example 1-2> Comparative Example 1-2 was a toothed belt having the same configuration as Example 1, except that the number of twists per 10 cm of the core wire length was 6 times / 10 cm. The angle formed by the outermost filament in the carbon fiber filament bundle constituting the core wire with respect to the longitudinal direction of the core wire was 21°.

[0048] The belt strength per mm of the belt width of the toothed belt of Comparative Example 1-2 was 640 N / mm. Belt tension T 0.1 was 41.0 N / mm.

[0049] [Table 1]

[0050] (Belt durability test) 4 shows the pulley layout of a belt running tester 40 used in the belt durability test. This belt running tester 40 has a drive pulley 41 with 22 teeth and a driven pulley 42 with 33 teeth located to the right of the drive pulley 41. The driven pulley 42 is configured to be movable left and right so that it can apply an axial load and also a load torque.

[0051] For each of the toothed belts B of Example 1 and Comparative Examples 1-1 and 1-2, the toothed belts B were wound around a drive pulley 41 and a driven pulley 42 in an atmosphere of 60°C, and a fixed shaft load (SW) of 1960 N was applied to the driven pulley 42 to apply a tension of 1000 N to the toothed belt B, and a load torque of 120 N m was applied, and under these conditions, the drive pulley 41 was rotated at a rotation speed of 1800 rpm. The time until the toothed belt B broke was then measured, and this time was defined as the belt durability life.

[0052] (Test results) The test results are shown in Table 1. From this, it can be seen that Example 1 is much more durable than Comparative Examples 1-1 and 1-2.

[0053] [Test evaluation 2] (toothed belt) Toothed belts of Examples 2-1 and 2-2 and Comparative Examples 2-1 and 2-2 were produced. The configurations of each are also shown in Table 2.

[0054] <Example 2-1> Example 2-1 was a toothed belt with an STS tooth profile similar to that of the above embodiment. The toothed belt of Example 2-1 had a belt length of 800 mm, a belt width of 8 mm, and a belt thickness (maximum) of 4.8 mm. The toothed belt was S8M as specified in ISO13050:2014(E).

[0055] The core wire was a single-twisted yarn obtained by twisting a carbon fiber filament bundle, the same as that used in Example 1, with 12,000 filaments in length in one direction at 6 twists per 10 cm. The angle of the outermost filament in the carbon fiber filament bundle constituting the core wire with respect to the longitudinal direction of the core wire was 9°. For the single-twisted yarn core wire, S-twisted yarn and Z-twisted yarn were prepared, and these were subjected to an adhesive treatment by immersing in an adhesive and then drying. The single-twisted S-twisted yarn and Z-twisted yarn core wire were arranged alternately in the belt width direction to form a double helix. The number of core wires per 10 mm of belt width was 8. The outer diameter of the core wire was 0.9 mm.

[0056] The urethane composition and nonwoven fabric for forming the toothed belt body were the same as those used in Example 1.

[0057] The belt strength per 1 mm of belt width of the toothed belt of Example 2-1 was 1150 N / mm. Belt tension T 0.1 was 44.4N / mm.

[0058] <Example 2-2> Example 2-2 was a toothed belt having the same configuration as Example 2-1, except that the number of twists per 10 cm of the core wire was 10 / 10 cm. The angle formed by the outermost filament in the carbon fiber filament bundle constituting the core wire with respect to the longitudinal direction of the core wire was 19°.

[0059] The belt strength per mm of belt width of the toothed belt of Example 2-2 was 738 N / mm. Belt tension T 0.1 was 40.5N / mm.

[0060] <Comparative Example 2-1> Comparative Example 2-1 was a toothed belt having the same configuration as Example 2-1, except that the number of twists per 10 cm of the core wire was 4 / 10 cm. The angle formed by the outermost filament in the carbon fiber filament bundle constituting the core wire with respect to the longitudinal direction of the core wire was 6°.

[0061] The belt strength per 1 mm of belt width of the toothed belt of Comparative Example 2-1 was 811 N / mm. Belt tension T 0.1 was 32.7N / mm.

[0062] <Comparative Example 2-2> Comparative Example 2-2 was a toothed belt having the same configuration as Example 2-1, except that the number of twists per 10 cm of the core wire was 12 / 10 cm. The angle formed by the outermost filament in the carbon fiber filament bundle constituting the core wire with respect to the longitudinal direction of the core wire was 21°.

[0063] The belt strength per mm of the belt width of the toothed belt of Comparative Example 2-2 was 694 N / mm. Belt tension T 0.1 was 42.8N / mm.

[0064] [Table 2]

[0065] (Belt durability test) A belt running test machine 40 having the same pulley layout as that used in Test Evaluation 1, shown in FIG. 4, was used, in which the drive pulley 41 and the driven pulley 42 were designed to mesh with the toothed portions of toothed belts B of Examples 2-1 and 2-2 and Comparative Examples 2-1 and 2-2, respectively.

[0066] For each of the toothed belts B of Examples 2-1 and 2-2 and Comparative Examples 2-1 and 2-2, the toothed belts B were wound around a drive pulley 41 and a driven pulley 42 in an atmosphere of 60°C, and a fixed shaft load (SW) of 608 N was applied to the driven pulley 42 to apply a tension of 306 N to the toothed belt B and a load torque of 34.5 N m. Under these conditions, the drive pulley 41 was rotated at a rotation speed of 4,218 rpm. The time until the toothed belt B broke was then measured, and this time was defined as the belt durability life.

[0067] (Test results) The test results are shown in Table 2. From this, it can be seen that Examples 2-1 and 2-2 are much more durable than Comparative Examples 2-1 and 2-2. [Industrial Applicability]

[0068] The present invention is useful in the technical field of power transmission belts. [Explanation of symbols]

[0069] B. Toothed belt (power transmission belt) C cavity F filament S Belt Slab 11 Toothed belt body 111 Flat belt 112 Tooth 12 core wires 13 Nonwoven fabric 31 Inner mold 32 Groove 33 protrusion 34 Outer mold 40 Belt running test machine 41 Drive pulley 42 driven pulley

Claims

1. A power transmission belt comprising: a belt body made of an elastomer; and a carbon fiber core wire embedded in the belt body and arranged to form a spiral having a pitch in the belt width direction, When the core wire is viewed from a side perpendicular to its longitudinal direction, the angle formed by the outermost filament in the carbon fiber filament bundle constituting the core wire with respect to the longitudinal direction of the core wire is 8° or more and 20° or less, the core wire is a single-twist yarn obtained by twisting the carbon fiber filament bundle in one direction, the core wire of the single twisted yarn has a total number of the carbon fiber filaments constituting the core wire of the single twisted yarn that is less than 24,000, and the number of twists per 10 cm of the length thereof is 5.0 turns / 10 cm or more and 11.0 turns / 10 cm or less; A power transmission belt having a belt tension T 0.1 per mm of belt width at a belt elongation rate of 0.1% of 30 N / mm or more and 50 N / mm or less.

2. A power transmission belt comprising an elastomer belt body and a carbon fiber core wire embedded in the belt body and arranged to form a spiral having a pitch in the belt width direction, When the core wire is viewed from a side perpendicular to its longitudinal direction, the angle formed by the outermost filament in the carbon fiber filament bundle constituting the core wire with respect to the longitudinal direction of the core wire is 8° or more and 20° or less, the core wire is a single-twist yarn obtained by twisting the carbon fiber filament bundle in one direction, The single twisted yarn core wire of the power transmission belt has a total number of filaments of the carbon fiber constituting the single twisted yarn core wire of 24,000 or more and 60,000 or less, and the number of twists per 10 cm of the length of the power transmission belt is 1.5 or more and 7.5 or less.

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