Toothed belt and manufacturing method thereof

Abstract

The present invention pertains to a toothed belt provided with a back section in which a core wire extending in the circumferential direction of the belt is embedded, and two or more tooth sections formed on the inner circumferential surface of the back section at intervals in the circumferential direction of the belt, the toothed belt includes a back rubber layer formed on the outer circumferential side of the belt with respect to the core wire, and a first rubber layer and a second rubber layer formed on the inner circumferential side of the belt with respect to the core wire, the back portion includes the back rubber layer, the elastic modulus of the first rubber layer is greater than the elastic modulus of the second rubber layer, and the elastic modulus of the second rubber layer is greater than the elastic modulus of the first rubber layer. The first rubber layer is formed from a first cross-linked rubber composition containing a first rubber component and first short fibers, the ratio of the first short fibers being 5-60 parts by mass per 100 parts by mass of the first rubber component, and the first short fibers being oriented in the longitudinal direction of the belt along the outlines of the teeth. The core wire includes a high elastic modulus fiber, and the tooth portion includes the first rubber layer and the second rubber layer interposed between the first rubber layer and the core wire.

Description

Technical Field

[0001] The present invention relates to a rubber toothed belt (or a rubber toothed belt covered with a tooth cloth) useful for synchronously transmitting power under high load conditions in a motorcycle or the like by meshing with a toothed pulley, and a method for producing the same. Background Art

[0002] Power transmission belts are generally divided into friction transmission belts and meshing transmission belts. Examples of friction transmission belts include flat belts, V-belts, and multi-V belts, while examples of meshing transmission belts include toothed belts. A toothed belt has a back portion with a core wire embedded approximately parallel to the belt circumference, teeth arranged at predetermined intervals along the belt circumference, and a tooth cloth covering the surface of the teeth. The teeth of the toothed belt transmit power by engaging with a pulley having grooves opposite to the teeth. There is no slippage between the toothed belt and the pulley, and even high loads can be transmitted reliably. In recent years, the use of toothed belts for rear-wheel drive applications in industrial machinery, internal combustion engines of automobiles, and two-wheeled motorcycles has increased. In particular, with the miniaturization of machinery and vehicles, there is a demand for toothed belts that correspond to miniaturization (to cope with small-diameter pulleys and narrow widths). If a miniaturized toothed belt is used in the same environment as a conventional large toothed belt, a higher load will be applied to the toothed belt. Therefore, a toothed belt with high durability that can withstand use under conditions of higher loads while coping with miniaturization is required.

[0003] Among the important elements of the durability of a toothed belt is the rigidity (deformation resistance) of the tooth portion. During the process of meshing with the toothed pulley, if the tooth portion is repeatedly deformed due to contact with the toothed pulley, it will lead to faults such as poor meshing due to tooth slippage (tooth skipping) and missing teeth due to cracks in the tooth root portion. It is believed that the mechanism of missing teeth is that in the failure mode of the tooth portion falling off the belt body, in the process of stress concentrated on the root portion of the tooth portion due to repeated deformation of the tooth portion, first, tiny cracks are generated in the tooth root portion, and then the cracks grow. In particular, when the toothed belt is used under high load conditions, the stress concentrated in the tooth root portion is extremely large, and cracks are easily generated starting from the tooth root portion, resulting in missing teeth. In detail, the tiny cracks generated mainly on the tooth surface or near the surface of the tooth root portion often develop (grow) toward the inside of the tooth rubber forming the tooth portion, causing missing teeth.

[0004] Therefore, in order to suppress deformation of the teeth, it is necessary to increase the rigidity. On the other hand, if the rigidity of the teeth is increased, the bending rigidity of the belt will also increase, and the bendability will decrease. If the toothed pulleys are miniaturized (reduced in diameter) along with the miniaturization of machinery and vehicles, high bendability (flexibility) is also required to achieve good meshing performance when wound around small-diameter pulleys. On the other hand, even if small cracks occur, as long as the small cracks can be suppressed from growing into missing teeth, tooth loss can be prevented.

[0005] That is, in a toothed belt, since the rigidity (deformation resistance) and bending property (flexibility) of the tooth portion are in an antagonistic relationship and difficult to achieve both, a processing method is needed to achieve a balance between the two. In addition, when tiny cracks are generated due to long-term use, etc., the growth of the cracks needs to be suppressed.

[0006] In particular, when a toothed belt is used for high-load transmission in the rear-wheel drive of a two-wheeled motorcycle, the toothed belt is required to be narrowed in order to achieve compactness. Therefore, in high-load transmission in the rear-wheel drive of a two-wheeled motorcycle, it is necessary to maintain meshing performance under high load even if the belt is narrowed to ensure tooth skipping resistance (high tooth skipping torque). In addition, in high-load transmission in the rear-wheel drive of a two-wheeled motorcycle, tooth skipping occurs due to the reduction in tension caused by the elongation of the belt in the initial stage of running. Therefore, in order to suppress tooth skipping in the initial stage of running, it is also necessary to ensure tension maintenance. In addition, in high-load transmission in the rear-wheel drive of a two-wheeled motorcycle, in order to cope with small-diameter pulleys, it is also necessary to ensure bending fatigue resistance.

[0007] Japanese Patent Gazette No. 2021-188747 (Patent Document 1) discloses the following: In order to improve the durability of a toothed belt used for rear-wheel drive applications on a two-wheeled motorcycle, a core wire embedded in the toothed belt is formed by combining and final-twisting two or more primary-twisted yarns containing carbon fibers to form a specific carbon fiber rope.

[0008] Japanese Patent Application Laid-Open No. 2023-18654 (Patent Document 2) discloses a toothed belt having a tooth portion formed by a tooth cloth, a first rubber layer formed along the tooth cloth, and a second rubber layer formed between the first rubber layer and a core wire, wherein the elastic modulus of the first rubber layer is adjusted to be greater than the elastic modulus of the second rubber layer.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2021-188747

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 2023-18654 Summary of the Invention

[0013] Problems to be solved by the invention

[0014] However, the toothed belt disclosed in Patent Document 1 struggles to achieve both rigidity and flexibility in the tooth portion, resulting in cracks. Furthermore, the belt's resistance to chipping is insufficient. Even if cracks are minute, they quickly develop, starting from the minute cracks themselves and leading to chipping. Consequently, its durability is also low.

[0015] Furthermore, the toothed belt of Patent Document 2 not only has insufficient chipping resistance but also insufficient bending properties. When used for rear-wheel drive applications of motorcycles and the toothed belt is narrowed, it is impossible to ensure tooth skipping resistance, tension retention, and bending fatigue resistance.

[0016] Therefore, an object of the present invention is to provide a toothed belt that can achieve both rigidity (deformation resistance) and bendability (flexibility) of the tooth portion and is also excellent in chipping resistance (durability), and a method for manufacturing the same.

[0017] Another object of the present invention is to provide a toothed belt and a method for manufacturing the same that can ensure tooth skipping resistance, tension retention, and bending fatigue resistance even when narrowed for use in high-load transmission applications in rear-wheel drive motorcycles.

[0018] Methods used to solve problems

[0019] To achieve the above-mentioned objectives, the inventors focused on the layer structure (distribution of mechanical properties) of the rubber layer constituting the tooth portion. They conducted in-depth research on methods to achieve a balance between tooth rigidity (deformation resistance) and flexibility (flexibility), which are in conflicting relationships, while ensuring the rigidity required to withstand use under higher loads. Furthermore, they investigated the rubber layer's blending components and cords to improve chipping resistance and compatibility with rear-wheel drive motorcycles. As a result, they discovered that by forming the tooth portion of a toothed belt from a first rubber layer and a second rubber layer formed between the first rubber layer and the cord, adjusting the elastic modulus of the first rubber layer to be greater than that of the second rubber layer, forming the cord from high-elastic-modulus fibers, and blending the short fibers into the first rubber layer so that they are oriented along the tooth portion's contour in the belt's longitudinal direction, a balance between tooth rigidity and flexibility can be achieved, while also improving chipping resistance. This led to the completion of the present invention.

[0020] That is, the toothed belt as the embodiment [1] of the present invention comprises a back portion in which a core extending along the belt circumferential direction is embedded, and two or more teeth formed on the inner peripheral surface of the back portion at intervals in the belt circumferential direction, the toothed belt comprising a back rubber layer formed on the outer peripheral side of the belt relative to the core cord, and a first rubber layer and a second rubber layer formed on the inner peripheral side of the belt relative to the core cord, wherein the back portion comprises the back rubber layer, the elastic modulus of the first rubber layer is greater than the elastic modulus of the second rubber layer, the first rubber layer is formed from a first cross-linked rubber composition containing a first rubber component and first short fibers, the proportion of the first short fibers is 5 to 60 parts by mass relative to 100 parts by mass of the first rubber component, the first short fibers are oriented in the belt length direction along the contour of the teeth portion, the core cord comprises high elastic modulus fibers, and the teeth portion comprises the first rubber layer and the second rubber layer sandwiched between the first rubber layer and the core cord.

[0021] Mode [2] of the present invention is the following mode: in the above-mentioned mode [1], the area ratio of the above-mentioned first rubber layer relative to the total area of ​​the above-mentioned first rubber layer and the above-mentioned second rubber layer in the cross-sectional view in the belt circumferential direction is 10 to 80 area %.

[0022] Mode [3] of the present invention is the following mode: in the above-mentioned mode [1] or [2], the tensile strength of the above-mentioned first rubber layer in the belt circumferential direction is 40 to 90 MPa, the tensile elastic modulus of the above-mentioned first rubber layer in the belt width direction is 4 to 25 MPa, the tensile strength of the above-mentioned second rubber layer in the belt circumferential direction is 10 to 50 MPa, and the tensile elastic modulus of the above-mentioned second rubber layer in the belt width direction is 1 to 10 MPa.

[0023] Mode [4] of the present invention is the following mode: in any one of modes [1] to [3] above, the tensile elastic modulus of the first rubber layer in the belt width direction is 1.1 to 10 times the tensile elastic modulus of the second rubber layer in the belt width direction.

[0024] Aspect [5] of the present invention is the aspect described in any one of aspects [1] to [4], wherein the first short fibers are polyamide fibers.

[0025] Mode [6] of the present invention is as follows: in any one of modes [1] to [5] above, the first cross-linked rubber composition further contains a first cross-linking agent and a first co-cross-linking agent, the second rubber layer is formed by a second cross-linked rubber composition containing a second rubber component, a second cross-linking agent and a second co-cross-linking agent, the first rubber component contains a first composite polymer containing hydrogenated nitrile rubber and an unsaturated carboxylic acid metal salt, the second rubber component contains a second composite polymer containing hydrogenated nitrile rubber and an unsaturated carboxylic acid metal salt, the proportion of the first co-cross-linking agent is 1 to 40 parts by mass relative to 100 parts by mass of the first rubber component, and the proportion of the second co-cross-linking agent is 0.2 to 25 parts by mass relative to 100 parts by mass of the second rubber component.

[0026] Mode [7] of the present invention is the following mode: in the above-mentioned mode [6], the above-mentioned second cross-linked rubber composition further contains second short fibers, and in the above-mentioned second cross-linked rubber composition, the proportion of the above-mentioned second short fibers is 5 parts by mass or less relative to 100 parts by mass of the above-mentioned second rubber component.

[0027] Mode [8] of the present invention is the following mode: in the above-mentioned mode [6] or [7], the first cross-linked rubber composition further contains a first reinforcing inorganic filler, the second cross-linked rubber composition further contains a second reinforcing inorganic filler, the proportion of the first composite polymer in the first rubber component is 80 mass% or more, the proportion of the second composite polymer in the second rubber component is 30 mass% or more, the first cross-linking agent contains a first organic peroxide, the proportion of the first organic peroxide is 1 to 20 mass parts relative to 100 mass parts of the first rubber component, the second cross-linking agent contains a second organic peroxide, the proportion of the second organic peroxide is 0.5 to 5 mass parts relative to 100 mass parts of the second rubber component, the proportion of the first reinforcing inorganic filler is 10 mass parts or less relative to 100 mass parts of the first rubber component, and the proportion of the second reinforcing inorganic filler is 10 mass parts or less relative to 100 mass parts of the second rubber component.

[0028] Aspect [9] of the present invention is the aspect described in any one of aspects [1] to [8] above, wherein the value X of the arrangement density of the core wires is 5 to 25%.

[0029] Mode

[10] of the present invention is as follows: in any one of the modes [1] to [9] above, the tooth pitch of the tooth portion is 6 to 16 mm, when the tooth pitch is greater than 6 mm and less than 9.5 mm, the belt elastic modulus is 15 to 20 kN / mm, when the tooth pitch is greater than 9.5 mm and less than 12.5 mm, the belt elastic modulus is 42 to 60 kN / mm, and when the tooth pitch is 12.5 to 16 mm, the belt elastic modulus is 50 to 65 kN / mm.

[0030] Mode

[11] of the present invention is as follows: a toothed belt transmission mechanism, which is a toothed belt transmission mechanism having a toothed belt according to any one of the above modes [1] to

[10] , wherein the above toothed belt is used for transmission purposes in the rear wheel drive of a two-wheeled motorcycle.

[0031] In the present invention, as mode

[12] , there is also provided a method for manufacturing a toothed belt according to any one of the above modes [1] to

[11] , comprising: a first rubber layer precursor preparation step, wherein an uncrosslinked rubber sheet having first short fibers oriented in one direction on the sheet surface is prepared as a first rubber layer precursor for forming the first rubber layer; and a preforming step, wherein the first rubber layer precursor and a second rubber layer precursor as an uncrosslinked rubber sheet for forming the second rubber layer are stacked in a configuration in which the first short fibers are oriented in the belt length direction, to produce a preform in a semi-crosslinked state.

[0032] In the present application, the numerical range represented by “A to B” means “A or more and B or less” and is used to include the numerical values ​​A and B at both ends.

[0033] Effects of the Invention

[0034] In the present invention, the teeth of a toothed belt are formed from a first rubber layer and a second rubber layer formed between the first rubber layer and the core. The elastic modulus of the first rubber layer is adjusted to be greater than that of the second rubber layer. The first rubber layer is formed from a first crosslinked rubber composition containing 100 parts by mass of a first rubber component and 5 to 60 parts by mass of first short fibers. The core contains high-elastic-modulus fibers, and the first short fibers are oriented along the tooth profile (the profile of the first rubber layer or the tooth fabric surface) in the belt longitudinal direction. This ensures tooth rigidity sufficient to withstand use under higher loads, while achieving a balance between rigidity and flexibility in the teeth, even when in a reverse relationship, and improving chipping resistance. Consequently, the present invention provides a toothed belt that suppresses tooth skipping (tooth slippage) during travel and improves belt durability. This toothed belt also suppresses tooth chipping (chipping) caused by the growth of microcracks that develop during travel, thereby achieving a longer life under high-load travel. In particular, the toothed belt of the present invention can ensure tooth skipping resistance, tension retention, and bending fatigue resistance even when the belt is narrowed for use in high-load transmission applications in rear-wheel drive motorcycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a partially sectional perspective view showing an example of the toothed belt of the present invention.

[0036] Figure 2 yes Figure 1 Schematic cross-section of a toothed belt.

[0037] Figure 3 Is used to illustrate Figure 1 Schematic cross-sectional view of the function of the teeth of a toothed belt.

[0038] Figure 4 Is used to illustrate Figure 1 Schematic cross-sectional view of the orientation state of the short fibers of a toothed belt.

[0039] Figure 5 This is a schematic cross-sectional view for explaining a state in which cracks have occurred in a toothed belt.

[0040] Figure 6 This is a schematic diagram for explaining a method for measuring the X value (%) of the arrangement density.

[0041] Figure 7 It is a schematic diagram for explaining the measuring method of the tooth rigidity test in the embodiment.

[0042] Figure 8 This is a diagram showing an example of measurement data for explaining a measurement method of a tooth rigidity test according to an embodiment.

[0043] Figure 9 Schematic cross-sectional view of the tooth portion of the toothed belt obtained in Example. DETAILED DESCRIPTION

[0044] <Toothed belt>

[0045] Hereinafter, an example of the toothed belt of the present invention will be described in detail with reference to the drawings as needed.

[0046] Figure 1 1 is a partial cross-sectional perspective view showing an example of the toothed belt of the present invention. Figure 2 yes Figure 1 A schematic cross-sectional view of a toothed belt. The toothed belt 1 in this example is an endless meshing transmission belt comprising a back portion 1c embedded with a core 5 extending in the belt circumferential direction (lengthwise direction), and two or more teeth 1a arranged at predetermined intervals on the inner circumference of the back portion 1c and extending in the belt width direction. The belt surface (inner circumference) on the tooth portion side is formed by a tooth cloth 2. The back portion 1c has a back rubber layer 6 disposed on the belt outer circumference side of the core 5, forming the belt outer circumference. Furthermore, the toothed belt 1 of the present invention comprises a first rubber layer (surface rubber layer) 3 and a second rubber layer (inner rubber layer) 4 on the belt inner circumference side of the core 5, between the tooth cloth 2 and the core 5. The first rubber layer 3 is disposed on the belt inner circumference (contacting the tooth cloth 2) along the contour of the tooth cloth 2, and the second rubber layer 4 is sandwiched or disposed between the first rubber layer 3 and the core 5 (contacting the core 5). The first rubber layer 3 has a higher elastic modulus (particularly tensile elastic modulus) than the second rubber layer 4 .

[0047] Between adjacent teeth 1a, there are flat tooth bottoms 1b. These teeth 1a and tooth bottoms 1b are formed alternately along the inner circumference (belt length) of the belt. Specifically, the surfaces of the teeth 1a and the inner circumference of the back 1c (i.e., the surface of the tooth bottoms 1b) are formed from a continuous single tooth fabric 2.

[0048] It should be noted that in Figure 1 In the embodiment shown, the tooth cloth constituting the surface of the tooth portion is a constituent element of the tooth portion, while the tooth cloth constituting the surface of the tooth bottom portion is a constituent element of the back portion. In addition, each tooth cloth constituting the tooth portion is a portion of a continuous tooth cloth ( Figure 2 part of the tooth cloth 2 in the middle).

[0049] In this example, the tooth portion 1a has a substantially trapezoidal cross-sectional shape in the belt circumferential direction. Furthermore, the circumferential surface of the tooth portion 1a, which has a substantially trapezoidal cross-sectional shape, is formed by the tooth cloth 2, which comprises a first rubber layer 3 formed along the tooth cloth 2 and a second rubber layer 4 formed between the first rubber layer 3 and the core cord 5. Specifically, in the tooth portion 1a, the first rubber layer 3 is formed as a layer along the tooth cloth 2, and the second rubber layer 4 is formed as a layer between the first rubber layer 3 and the core cord 5.

[0050] It should be noted that in the tooth base 1b, a first rubber layer (surface rubber layer) and a second rubber layer (not shown) (inner rubber layer) are sandwiched between the tooth cloth 2 and the core wire 5. Compared to the thickness of the first rubber layer 3 and the second rubber layer 4 in the tooth base 1a, the thickness of the first and second rubber layers in the tooth base is extremely thin.

[0051] The cords 5 extend in the belt length direction (circumferential direction) and are spaced apart in the belt width direction. The gaps between adjacent cords 5 can be formed by the cross-linked rubber composition constituting the back rubber layer 6 and / or the second rubber layer (particularly the cross-linked rubber composition constituting the back rubber layer 6).

[0052] Toothed belts are used for high-load transmission applications in industrial machinery, automotive internal combustion engines, and rear-wheel drives of motorcycles, and are particularly suitable for rear-wheel drives of motorcycles. For example, a toothed belt, when wound between a drive pulley (toothed pulley) and a driven pulley (toothed pulley), transmits power from the drive pulley to the driven pulley as the drive pulley rotates.

[0053] It should be noted that the toothed belt of the present invention is not limited to Figure 1 and 2 For example, as long as two or more teeth can mesh with the toothed belt pulley, the cross-sectional shape of the teeth (the cross-sectional shape of the toothed belt in the belt circumferential direction) is not limited to being approximately trapezoidal, and may be, for example, semicircular, semi-elliptical, polygonal (triangular, quadrilateral (rectangular, trapezoidal, etc.)), etc. Of these, trapezoidal or approximately trapezoidal shapes are preferred from the perspective of meshing transmission performance.

[0054] In the toothed belt (on the inner circumference side of the core wire) of the present invention, the area ratio of the first rubber layer relative to the total area of ​​the first and second rubber layers in a cross-sectional view in the belt circumferential direction (belt longitudinal direction) is, for example, 10 to 80% by area, preferably 20 to 70% by area, more preferably 30 to 60% by area, and even more preferably 35 to 50% by area. If this area ratio is too small, the rigidity (deformation resistance) of the tooth portion may be insufficient. Conversely, if it is too large, the belt's flexural rigidity may be increased, resulting in insufficient bendability (flexibility).

[0055] In the toothed belt of the present invention, the average distance between the centers of the circumferentially adjacent teeth (tooth pitch, reference Figure 2 ) can be, for example, 2 to 25 mm depending on the shape of the toothed pulley. The value of the tooth pitch also corresponds to the size of the tooth portion (the length of the tooth portion in the belt circumferential direction and the tooth height of the tooth portion). That is, the larger the tooth pitch, the larger the size of the tooth portion. In particular, in applications where high loads are applied, large-sized teeth are required, and the tooth pitch can be 5 mm or more, preferably 8 mm or more. The tooth pitch can be appropriately selected according to the application, and can be 6 to 16 mm in high-end transmission applications in the rear-wheel drive of a two-wheeled motorcycle, for example, about 8 mm to about 14 mm (especially about 10 mm to about 14 mm). In the present invention, as described later, by adjusting the material (elastic modulus), twist coefficient, core wire diameter, spacing, and arrangement density of the core wire according to the tooth pitch, the elastic modulus of the toothed belt can be controlled, and a toothed belt suitable for high-load transmission applications in the rear-wheel drive of a two-wheeled motorcycle can be produced.

[0056] Furthermore, the average tooth height of the teeth is preferably 40 to 70%, more preferably 50 to 65%, of the average thickness of the entire belt.

[0057] It should be noted that in this application, Figure 2 As shown, the average tooth height of the teeth refers to the average height of the teeth protruding from the inner circumference of the belt (the average height of the teeth protruding from the tooth bottom).

[0058] [Tooth]

[0059] The tooth portion includes a first rubber layer arranged on the surface side (inner surface side) and a second rubber layer arranged on the inner side connected to the first rubber layer. The first rubber layer and the second rubber layer are formed of cross-linked rubber compositions with different compositions, the elastic modulus (modulus) of the first rubber layer is relatively large, and the elastic modulus (modulus) of the second rubber layer is relatively small. In the toothed belt of the present invention, by making the cross-linked rubber composition forming the tooth portion have such a two-layer structure, it is possible to take into account both the rigidity and the bending properties of the tooth portion. Regarding its mechanism, refer to Figure 3 For explanation. It should be noted that in this application, the rubber layer forming the tooth portion refers to the rubber layer sandwiched between the core wire and the tooth cloth when the tooth portion includes a tooth cloth, and refers to the rubber layer sandwiched on the inner peripheral side relative to the core wire when the tooth portion does not include a tooth cloth. In addition, the first rubber layer and the second rubber layer, which are the rubber layers forming the tooth portion, are collectively referred to as the tooth rubber layer. In the tooth rubber layer, the first rubber layer is a layer composed of a single phase formed using the first cross-linked rubber composition, and the second rubber layer is a layer composed of a single phase formed using the second cross-linked rubber composition.

[0060] The teeth may also include a tooth cloth forming the surface. If the teeth do not include a tooth cloth, the surface of the first rubber layer forms the inner circumference of the belt. If the teeth do include a tooth cloth, the surface of the tooth rubber layer is covered with the tooth cloth, and the inner circumference of the belt is formed by the tooth cloth. Specifically, if the teeth include a tooth cloth, the surface of the teeth is formed by the tooth cloth, and the teeth are arranged along the contour of the teeth, including a first rubber layer disposed on the surface side in contact with the tooth cloth, and a second rubber layer disposed on the inner side in contact with the first rubber layer.

[0061] The inventors have discovered that the area within the tooth that affects flexibility (flexibility) is the second rubber layer, specifically the C portion located below the core 5. Specifically, they discovered that if the rubber layer within the tooth, specifically the C portion, is a high-rigidity (high-elastic modulus) rubber layer, flexibility (flexibility) decreases. Therefore, in the toothed belt of the present invention, to ensure high flexibility, the second rubber layer located within the tooth, specifically the second rubber layer 4 containing the C portion, is adjusted to have a relatively low rigidity (low-elastic modulus).

[0062] Furthermore, the inventors have discovered that, within the tooth portion, the areas that influence deformation resistance are the tooth cloth (or inner circumference) corresponding to the first rubber layer, particularly the portion A located on the side of the tooth portion and the portion B located near the bottom of the tooth. Specifically, it has been discovered that if portions A and B are rubber layers with low rigidity (low elastic modulus), deformation resistance decreases. Specifically, portion A, which is the side of the tooth portion, is the area that contacts the pulley and bears the maximum load (impact), so it is effective that the cross-linked rubber composition of portion A has high rigidity (high elastic modulus). On the other hand, portion B, which is the root near the bottom of the tooth, is the area where tiny cracks first occur due to repeated deformation (the starting point for missing teeth), so it is effective that the cross-linked rubber composition of portion B has high rigidity (high elastic modulus). Therefore, in the toothed belt of the present invention, in order to ensure deformation resistance, the first rubber layer 3 having portions A and B inside is adjusted to have relatively high rigidity (high elastic modulus).

[0063] From the perspective of deformation resistance, as long as at least the A and B portions of the teeth are formed of high-rigidity rubber, the top portion of the teeth (the tooth tip portion) need not be formed of high-rigidity rubber. In contrast, in the toothed belt of the present invention, the first rubber layer, including the top portion, is formed of high-rigidity rubber from the perspective of high productivity and achieving a high degree of deformation resistance.

[0064] The tensile strength of the first rubber layer in the belt circumferential direction is, for example, 40 to 90 MPa, preferably 45 to 85 MPa, more preferably 50 to 83 MPa, more preferably 55 to 80 MPa, and most preferably 60 to 70 MPa. If the tensile strength is too low, the rigidity of the tooth portion may be reduced, thereby reducing deformation resistance. Conversely, if the tensile strength is too high, the belt's flexibility, particularly its ability to wind around (mesh) small-diameter pulleys, may be reduced.

[0065] The tensile strength of the second rubber layer in the belt circumferential direction is, for example, 10 to 50 MPa, preferably 20 to 45 MPa, more preferably 25 to 40 MPa, even more preferably 25 to 35 MPa, and most preferably 30 to 34 MPa. If the tensile strength is too low, deformation resistance may be reduced. Conversely, if it is too high, the belt's flexibility, particularly its ability to wind around (mesh) small-diameter pulleys, may be reduced.

[0066] In the belt circumferential direction, the tensile strength of the first rubber layer is greater than that of the second rubber layer. The ratio of the tensile strength of the first rubber layer to the tensile strength of the second rubber layer (tensile strength of the first rubber layer / tensile strength of the second rubber layer) can be 1.3 to 3.5, preferably 1.4 to 3.0, more preferably 1.5 to 2.5, more preferably 1.6 to 2.0, and most preferably 1.7 to 1.9. By maintaining the tensile strength ratio of the two layers within this range, a balance can be achieved between the rigidity (deformation resistance) and bendability (flexibility) of the teeth, which are in an antagonistic relationship, achieving both.

[0067] In this application, the tensile strength of the first and second rubber layers is determined by measuring the "tensile strength T" of each rubber layer using a method according to JIS K 6251 (2017). Specifically, the tensile strength can be measured using the method described in the Examples below.

[0068] The tensile modulus (modulus) of the first rubber layer in the belt width direction can be selected from a range of, for example, about 4 MPa to about 25 MPa, for example, 5 to 20 MPa, preferably 6 to 18 MPa, more preferably 8 to 16 MPa, more preferably 10 to 15 MPa, and most preferably 12 to 15 MPa. If the tensile modulus is too low, the rigidity of the tooth portion may be reduced, thereby reducing the deformation resistance. Conversely, if it is too high, the bending properties of the belt, especially the winding (meshing) properties around small-diameter pulleys, may be reduced.

[0069] The tensile modulus (modulus) of the second rubber layer in the belt width direction is, for example, 1.0 to 10.0 MPa, preferably 1.5 to 5.0 MPa, more preferably 1.6 to 4.0 MPa, more preferably 1.8 to 3.0 MPa, and most preferably 1.9 to 2.5 MPa. If the tensile modulus is too low, deformation resistance may be reduced. Conversely, if it is too high, the belt's flexibility, particularly its ability to wind around (mesh) a small-diameter pulley, may be reduced.

[0070] In the belt width direction, the tensile modulus of the first rubber layer is greater than that of the second rubber layer. The ratio of the tensile modulus of the first rubber layer to the tensile modulus of the second rubber layer (tensile modulus of the first rubber layer / tensile modulus of the second rubber layer) can be 1.1 to 15.0, for example, 1.1 to 10.0, preferably 2.0 to 10.0, more preferably 4.0 to 9.5, more preferably 5.0 to 9.0 (for example, 5.5 to 8.5), even more preferably 6.0 to 8.0, and most preferably 6.0 to 7.5. By setting the ratio of the tensile moduli of the two layers within this range, a balance can be achieved between the rigidity (deformation resistance) and the bendability (flexibility) of the tooth portion, which are in an antagonistic relationship, thereby achieving both.

[0071] In this application, the tensile modulus (modulus) of the first and second rubber layers is determined by measuring the tensile stress at 2% elongation of each rubber layer using a method according to JIS K 6251 (2017). Specifically, the tensile modulus (modulus) can be measured using the method described in the Examples below.

[0072] Furthermore, in the tooth portion, the first rubber layer is formed of a first cross-linked rubber composition containing a first rubber component and first short fibers, and the first short fibers are oriented in the belt length direction (belt circumferential direction) along the contour of the tooth portion. In the toothed belt of the present invention, by adjusting the tooth portion to a two-layer structure as described above, it is possible to take both rigidity and flexibility into account, and it is possible to suppress microcracks mainly generated at the tooth roots. Even in the case where microcracks are generated due to long-term use, etc., the first short fibers are oriented in the above-mentioned direction in the first rubber layer, and it is possible to suppress the toothed belt from being chipped, and the tooth chipping resistance (durability) of the belt can be improved. Regarding the mechanism of improved tooth chipping resistance, refer to Figure 4 and Figure 5 Provide explanation.

[0073] Figure 4 Is used to illustrate Figure 1 Schematic cross-sectional view of the orientation state of the short fibers of the toothed belt, Figure 5 This is a schematic cross-sectional view for explaining a state in which cracks have occurred in a toothed belt.

[0074] like Figure 5 As shown, the toothed belt 11 is formed by a tooth cloth 12, a tooth rubber layer 13 covered by the tooth cloth 12, a back rubber layer 16, and a core 15 sandwiched between the tooth rubber layer 13 and the back rubber layer 16. However, micro cracks are easily generated on the rubber surface of the tooth roots of the tooth rubber layer 13 and near the surface. The generated micro cracks extend from the rubber surface toward the inside of the tooth rubber layer 13 in a direction substantially perpendicular to the tooth rubber layer 13. Figure 5The crack 13a develops in the direction of arrow A in the figure and grows into a crack 13a until the tooth is broken.

[0075] In contrast, Figure 4 As shown, in the toothed belt 1 of the present invention, the first rubber layer 3 located on the tooth cloth 2 side contains first short fibers 3a. Figure 4 This figure schematically shows the dispersion state of the first short fibers 3a in the first rubber layer 3 for understanding the orientation direction of the first short fibers 3a. Inside the first rubber layer 3, the first short fibers 3a are oriented in the belt length direction along the contour of the tooth cloth 2 (the surface direction of the tooth cloth). In other words, the first short fibers 3a are oriented in the first rubber layer 3 in a direction roughly parallel to the surface direction of the tooth cloth. The orientation direction of the first short fibers 3a is relative to the direction of development of microcracks ( Figure 5 The first short fibers 3a are arranged in a direction intersecting (particularly, approximately perpendicular to) the tooth cloth surface (e.g., the direction extending inward from the tooth cloth surface, or the direction approximately perpendicular to the tooth cloth surface, such as the direction of arrow A in the figure). Therefore, if the first rubber layer 3 contains the first short fibers 3a at a specified ratio, the first short fibers 3a will always be present in a pattern intersecting or approximately perpendicular to the direction of growth of microcracks that form on the surface or within the first rubber layer 3. Therefore, in the first rubber layer 3 of the toothed belt 1 of the present invention, the first short fibers 3a have the function of preventing (protecting) the growth of microcracks. Even if microcracks form due to repeated deformation, they can be prevented from growing, thereby improving the tooth chipping resistance of the toothed belt. The proportion of the first short fibers to demonstrate this function is approximately 5 to 60 parts by mass, particularly approximately 10 to 60 parts by mass, per 100 parts by mass of the first rubber component. In contrast, toothed belts containing a smaller proportion of short fibers in the tooth rubber layer cannot effectively prevent the growth of cracks, cannot improve tooth chipping resistance, and, because the moduli of the tooth rubber layer and the adhesive rubber layer are not adjusted, microcracks themselves are more likely to form.

[0076] It should be noted that, in the present application, the state in which the first staple fibers are oriented along the contour of the tooth portion refers not only to the state in which the first staple fibers are oriented approximately parallel to the contour of the tooth portion, but also to the state in which the first staple fibers are oriented approximately parallel to the contour of the tooth cloth (or inner circumferential surface). The same applies to the state in which the first staple fibers are oriented in the longitudinal direction of the belt.

[0077] In the present application, the "profile of the tooth portion" may refer to the profile of the first rubber layer. If the tooth portion includes a tooth cloth, it may refer to the tooth cloth surface or the interface between the tooth cloth and the first rubber layer, or the interface between the first rubber layer and the second rubber layer. In particular, whether the first short fibers are oriented along the profile of the tooth portion can be determined based on the interface between the first rubber layer and the second rubber layer. For example, if the first short fibers are substantially parallel to the corresponding interface (the corresponding portion of the interface at the shortest distance from the first short fibers), they can be determined to be oriented along the profile of the tooth portion.

[0078] The shape of the first rubber layer is not particularly limited as long as it is a layer formed along the tooth cloth. Figures 1 to 3 The layer shape shown as having uneven thickness (i.e., a shape in which the thickness of the layer is greatest at the top or center of the tooth portion and decreases toward the bottom of the tooth portion in a cross-sectional view of the tooth portion in the belt length direction) may be a layer shape having uniform thickness. However, from the perspective of productivity, etc., a layer shape having uneven thickness (particularly a shape in which the thickness of the layer is greatest at the top or center of the tooth portion and decreases toward the bottom of the tooth portion in a cross-sectional view of the tooth portion in the belt length direction) is preferred.

[0079] In the tooth portion, the area ratio of the first rubber layer relative to the total area of ​​the first rubber layer and the second rubber layer in the cross-sectional view in the belt length direction (circumferential direction) can be selected from the range of about 5 area % to about 85 area %, for example, 10 to 80 area %, preferably 20 to 70 area %, more preferably 30 to 60 area %, and more preferably 35 to 50 area %. If this area ratio is too small, the rigidity (deformation resistance) of the tooth portion may be insufficient, and the running performance and durability of the belt may be reduced. Conversely, if it is too large, the bending rigidity of the belt may become high, the bending performance (flexibility) may be insufficient, and the durability of the belt may be reduced. In applications where belt durability is important, the above-mentioned area ratio is preferably 15 to 65 area %, and more preferably 20 to 60 area %.

[0080] The shape of the second rubber layer, in a cross-sectional view of the tooth portion in the belt length direction, is not limited to a substantially trapezoidal shape formed between the first rubber layer and the core cord. It may also be a layered shape formed along the first rubber layer, a substantially trapezoidal shape formed along the first rubber layer and between another rubber layer and the core cord, or the like. Of these, from the perspective of improving the flexibility of the tooth portion, a shape that contacts the core cord, that is, a substantially trapezoidal shape formed between the first rubber layer and the core cord, or a substantially trapezoidal shape formed between another rubber layer and the core cord, is preferred. A substantially trapezoidal shape formed between the first rubber layer and the core cord is particularly preferred.

[0081] The rubber hardness Hs of the first rubber layer (the first cross-linked rubber composition constituting the first rubber layer) is, for example, 65 to 80 degrees, preferably 68 to 78 degrees, more preferably 70 to 76 degrees, and most preferably 72 to 74 degrees, as measured by the D-type durometer. If the hardness is too low, the rigidity of the tooth portion may be reduced, thereby reducing deformation resistance. Conversely, if the hardness is too high, the belt's flexibility, particularly its winding (meshing) properties around a small-diameter pulley, may be reduced.

[0082] The rubber hardness Hs of the second rubber layer (the second cross-linked rubber composition constituting the second rubber layer) is, for example, 50 to 66 degrees, preferably 53 to 65 degrees, more preferably 54 to 62 degrees, more preferably 55 to 60 degrees, and most preferably 56 to 59 degrees, as measured by the D-type durometer. If the hardness is too low, deformation resistance may be reduced, while if it is too high, the belt's flexibility, particularly its durability against reverse bending, may be reduced.

[0083] In this application, the D-type hardness of the first and second rubber layers refers to the value Hs(D-type) measured using a D-type durometer according to the spring durometer hardness test specified in JIS K 6253 (2012) (Vulcanized and thermoplastic rubbers - Determination of hardness), and is sometimes referred to simply as rubber hardness. Specifically, it can be measured by the method described in the Examples below, and can be measured as the hardness of a rubber sheet obtained by cross-linking the rubber composition used to form the belt.

[0084] Typically, the rubber hardness of a rubber composition is often measured using a Type A hardness (a value measured using a Type A durometer). However, if the value measured using a Type A durometer exceeds 90 degrees, it is preferable to use a Type D durometer. In the toothed belt of the present invention, the hardness of the rubber layer constituting the teeth is higher than that of the back rubber layer (described later), and the Type A hardness exceeds 90 degrees. Therefore, the hardness of the rubber layer constituting the teeth is evaluated using the Type D hardness.

[0085] In the tooth portion, as a tooth rubber layer, other rubber layers may be included in addition to the first rubber layer and the second rubber layer, as long as the effect of the present invention is not impaired. As other rubber layers, for example, an adhesive rubber layer sandwiched between the tooth cloth and the first rubber layer, an intermediate rubber layer sandwiched between the first rubber layer and the second rubber layer, etc. can be listed. The adhesive rubber layer can be a layer for improving the adhesion between the tooth cloth and the first rubber layer. In addition, the intermediate rubber layer can be a layer having a tensile elastic modulus smaller than that of the first rubber layer and larger than that of the second rubber layer. Among them, the adhesive rubber layer (third rubber layer) is preferred. The thickness of the adhesive rubber layer is a thickness that can improve the adhesion between the tooth cloth and the first rubber layer. Specifically, the thickness of the third rubber layer (adhesive rubber layer) at the top of the tooth portion is preferably less than 0.5 mm, and more preferably less than 0.3 mm. If the thickness of the third rubber layer is too thick, the rigidity of the tooth portion may be reduced.

[0086] As the structure of the tooth portion, a structure in which the tooth rubber layer includes only an adhesive rubber layer as another layer is preferred. A structure not including any other layer, that is, a structure consisting of a first rubber layer and a second rubber layer formed between the first rubber layer and the above-mentioned core cord is particularly preferred; a structure consisting of a tooth cloth covering the circumferential surface of the belt, a first rubber layer formed along the tooth cloth, and a second rubber layer formed between the first rubber layer and the above-mentioned core cord is particularly preferred.

[0087] (Crosslinked rubber composition)

[0088] The toothed belt of the present invention is characterized in that the first rubber layer is formed from a first crosslinked rubber composition containing first short fibers as an essential component. However, both the first and second rubber layers may be formed from crosslinked rubber compositions commonly used as rubber compositions for toothed belts. The crosslinked rubber composition may contain a rubber component. By appropriately adjusting the composition, the mechanical properties, such as the elastic modulus (modulus), of each rubber layer, particularly the first and second rubber layers, can be adjusted. The method for adjusting the elastic modulus (modulus) and other properties is not particularly limited and can be achieved by varying the composition and / or types of the components of the composition. For simplicity, it is preferred to adjust the ratio and / or types of the crosslinking compounding agent, short fibers, and filler.

[0089] (A) Rubber component

[0090] Examples of the rubber components (first and second rubber components) of the cross-linked rubber composition forming the first and second rubber layers include diene rubbers (natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), styrene-butadiene rubber (SBR), vinylpyridine-styrene-butadiene rubber, acrylonitrile-butadiene rubber (nitrile rubber: NBR), acrylonitrile-chloroprene rubber, hydrogenated nitrile rubber (HNBR), etc.), ethylene-α-olefin elastomers (ethylene-propylene copolymer (EPM), ethylene-propylene-diene terpolymer (EPDM), etc.), chlorosulfonated polyethylene rubber (CSM), alkylated chlorosulfonated polyethylene rubber (ACSM), epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, and fluororubber. These rubber components may be carboxylated, such as carboxylated SBR and carboxylated NBR. These rubber components may be used alone or in combination of two or more.

[0091] A particularly preferred rubber component is hydrogenated nitrile rubber (HNBR), and chloroprene rubber (CR) and ethylene-propylene-diene terpolymer (EPDM) are also preferably used. In particular, the preferred rubber component for applications with high loads is a rubber with high heat aging resistance, especially hydrogenated nitrile rubber (HNBR) that can be carboxylated (hereinafter, also including carboxylated hydrogenated nitrile rubber, sometimes simply referred to as hydrogenated nitrile rubber). In the rubber component, the proportion of the above-mentioned preferred rubber component is preferably 50% by mass or more (for example, about 80% by mass to about 100% by mass), and particularly preferably 100% by mass. The hydrogenated nitrile rubber that can be carboxylated can be partially hydrogenated nitrile rubber or fully hydrogenated nitrile rubber. The hydrogenation rate of the hydrogenated nitrile rubber that can be carboxylated can be selected from the range of about 50% to about 100%, and can be 70% to 100%.

[0092] It should be noted that, in the present application, HNBR refers to a rubber in which the unsaturated bonds (carbon-carbon double bonds) possessed by conventional nitrile rubber are chemically hydrogenated in order to prevent aging of the rubber elasticity due to the recombination reaction of sulfur during heat aging while maintaining the advantage of conventional nitrile rubber, namely, oil resistance, thereby improving heat resistance by making it less susceptible to recombination reactions during heat aging.

[0093] The iodine value (unit: mg / 100 mg) of HNBR is, for example, 5 to 60 (for example, 7 to 50), preferably 8 to 40 (for example, 8 to 35), and more preferably 10 to 30.

[0094] It should be noted that, in the present application, iodine value is an index representing the amount of unsaturated bonds, and the higher the iodine value, the more the amount of unsaturated bonds represented in the polymer molecular chain. Iodine value is obtained by adding excessive iodine to the test sample to make its complete reaction (making iodine and unsaturated bonds react) and utilizing redox titration to quantitatively obtain the amount of remaining iodine. When the iodine value of HNBR is small, the cross-linking reaction of HNBR is likely to be insufficient, and the rigidity of cross-linked rubber decreases, and therefore, deformation resistance decreases when belt travels. On the other hand, if the iodine value of HNBR is large, the amount of unsaturated bonds is likely to increase excessively, and thermal degradation and oxidative degradation of cross-linked rubber are carried out, and belt life shortens.

[0095] The rubber component preferably contains at least a hydrogenated nitrile rubber which may be carboxylated. The proportion of such a hydrogenated nitrile rubber in the rubber component may be 80 to 100% by mass, preferably 90 to 100% by mass, and more preferably 100% by mass.

[0096] The rubber component preferably contains a composite polymer comprising hydrogenated nitrile rubber and an unsaturated carboxylic acid metal salt (hereinafter referred to as "HNBR / unsaturated carboxylic acid metal salt composite polymer"). The composite polymer may also be a polymer alloy. It should be noted that, in the present application, the composite polymer contained in the first rubber component is referred to as the first composite polymer, and the composite polymer contained in the second rubber component is referred to as the second composite polymer. The polymer can increase the elastic modulus (modulus) and hardness of the tooth portion, and can suppress deformation of the rubber and the growth of cracks.

[0097] The unsaturated carboxylic acid metal salt may be a compound in which an unsaturated carboxylic acid having one or two or more carboxyl groups is ionically bonded to a metal.

[0098] Examples of the unsaturated carboxylic acid of the unsaturated carboxylic acid metal salt include monocarboxylic acids such as (meth)acrylic acid and crotonic acid, dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid, and monoalkyl esters of these dicarboxylic acids. These unsaturated carboxylic acids can be used alone or in combination of two or more. A preferred unsaturated carboxylic acid is (meth)acrylic acid.

[0099] Examples of the metal of the unsaturated carboxylic acid metal salt include polyvalent metals such as elements of Group 2 of the Periodic Table (such as magnesium and calcium), elements of Group 4 of the Periodic Table (such as titanium and zirconium), and elements of Groups 8 to 14 of the Periodic Table (such as iron, cobalt, nickel, copper, zinc, aluminum, tin, and lead). These metals may be used alone or in combination of two or more. Preferred metals include elements of Group 2 of the Periodic Table (such as magnesium) and elements of Group 12 of the Periodic Table (such as zinc).

[0100] Preferred examples of the unsaturated carboxylic acid metal salt include zinc (meth)acrylate, magnesium (meth)acrylate, etc. The unsaturated carboxylic acid metal salt may be used alone or in combination of two or more.

[0101] It should be noted that commercially available HNBR / unsaturated carboxylic acid metal salt composite polymers can be used. For example, a product obtained by highly finely dispersing zinc methacrylate as an unsaturated carboxylic acid metal salt in HNBR (e.g., manufactured by Zeoforte Co., Ltd., trade name "Zeoforte (ZSC)") can be used.

[0102] In addition, HNBR / unsaturated carboxylic acid metal salt composite polymer can also be the mixture of the composite polymer that unsaturated carboxylic acid metal salt is micro-dispersed in the HNBR and the hydrogenated acrylonitrile-butadiene rubber (HNBR) that does not contain unsaturated carboxylic acid metal salt.That is, in HNBR / unsaturated carboxylic acid metal salt composite polymer, the mass ratio of hydrogenated acrylonitrile-butadiene rubber and unsaturated carboxylic acid metal salt can be mixed with commercially available hydrogenated acrylonitrile-butadiene rubber that comprises unsaturated carboxylic acid metal salt and adjust.The adjustment of elastic modulus (modulus), hardness can be adjusted by changing both mixing ratios.

[0103] In the HNBR / unsaturated carboxylic acid metal salt composite polymer, the mass ratio of hydrogenated nitrile rubber to unsaturated carboxylic acid metal salt can be selected from the range of about 100 / 70 to 100 / 180, preferably 100 / 80 to 100 / 175, and more preferably 100 / 90 to 100 / 175. In the first rubber layer, this mass ratio is 100 / 90 to 100 / 170, preferably 100 / 95 to 100 / 150, and more preferably 100 / 100 to 100 / 120. In the second rubber layer, this mass ratio is 100 / 70 to 100 / 110, preferably 100 / 75 to 100 / 100, and more preferably 100 / 80 to 100 / 90. If the proportion of the unsaturated carboxylic acid metal salt is too low, the elastic modulus (modulus) and hardness of the cross-linked rubber composition (or tooth portion) may decrease. Conversely, if it is too high, the processability and bendability of the belt may decrease.

[0104] The proportion of the HNBR / unsaturated carboxylic acid metal salt composite polymer in the rubber component can be 10% by mass or greater, preferably 30% by mass or greater, more preferably 50% by mass or greater, more preferably 80% by mass or greater, most preferably 90% by mass or greater, and may also be 100% by mass. In particular, the proportion of the HNBR / unsaturated carboxylic acid metal salt composite polymer in the first rubber layer is preferably 80% by mass or greater (particularly 100% by mass) of the rubber component (first rubber component), and in the second rubber layer is preferably 30% by mass or greater (particularly 100% by mass) of the rubber component (second rubber component). These proportions may be those in the commercial product "Zeoforte (ZSC)."

[0105] The other rubber component combined with the HNBR / unsaturated carboxylic acid metal salt composite polymer is preferably at least one rubber component selected from the group consisting of EPDM and CR. The proportion of the other rubber component in the rubber component is, for example, 70% by mass or less, preferably 50% by mass or less, more preferably 30% by mass or less, and most preferably 10% by mass or less.

[0106] To ensure interlayer adhesion, the first rubber layer and the second rubber layer preferably contain the same series or the same type of rubber component, more preferably the same type of rubber component, and even more preferably the same rubber component.

[0107] (B) Short fibers

[0108] As described above, the first cross-linked rubber composition contains the first short fibers as an essential component, and the second cross-linked rubber composition forming the second rubber layer may also contain the second short fibers.

[0109] Examples of the short fibers (first short fibers and second short fibers) include polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers [aliphatic polyamide fibers (nylon fibers) such as polyamide 6 fibers, polyamide 66 fibers, and polyamide 46 fibers, and aramid fibers, etc.], polyester fibers [polyalkylene arylate fibers (e.g., polyethylene terephthalate (PET) fibers, polypropylene terephthalate (PTT) fibers, polybutylene terephthalate (PBT) fibers, polyethylene naphthalate (PEN) fibers, etc.] 2-4 Alkylene C 8-14 Aromatic ester fibers); polyarylate fibers, liquid crystal polyester fibers and other completely aromatic polyester fibers, etc.], vinylon fibers, polyvinyl alcohol fibers, polyparaphenylene benzobis(2-phenylene) fibers The short fibers may be synthetic fibers such as polyamide (PBO) fibers; natural fibers such as cotton, linen, and wool; regenerated cellulose fibers such as rayon and cellulose ester fibers; and inorganic fibers such as carbon fibers and glass fibers. These short fibers may be used alone or in combination of two or more. In particular, fibers with a high elastic modulus (modulus) such as polyamide fibers, PBO fibers, glass fibers, and carbon fibers are preferably used. More preferred are polyamide fibers such as aliphatic polyamide fibers (nylon fibers) or aramid fibers, and PBO fibers. Aliphatic polyamide fibers are most preferred as the first short fibers, and aramid fibers are most preferred as the second short fibers.

[0110] The average fiber diameter of the short fibers is, for example, 1 to 100 μm (for example, 3 to 70 μm), preferably 5 to 50 μm (for example, 7 to 30 μm), and more preferably 10 to 25 μm (particularly 12 to 20 μm). The average fiber length of the short fibers is, for example, 0.3 to 10 mm (for example, 0.5 to 7 mm), preferably 1 to 5 mm (particularly 2 to 4 mm). If the average fiber diameter of the short fibers is too small or the average fiber length is too long, the short fibers may not be uniformly dispersed or may be difficult to orient in a predetermined direction. If the average fiber diameter is too large or the average fiber length is too short, the mechanical properties of each rubber layer may be reduced.

[0111] In addition, the staple fibers are preferably subjected to a conventional adhesive treatment (or surface treatment) to adhere an adhesive component to at least a portion of the surface of the staple fibers. This adhesive treatment improves the adhesion between the staple fibers and the rubber component, thereby suppressing the formation of microcracks originating from the interface between the staple fibers and the rubber component. Examples of adhesive treatments include treatments using adhesive components such as epoxy compounds (or epoxy resins), polyisocyanates, silane coupling agents, and resorcinol-formalin-latex (RFL).

[0112] In the first crosslinked rubber composition, the proportion of the first short fibers can be 5 to 60 parts by mass (particularly 10 to 60 parts by mass), preferably 8 to 55 parts by mass (e.g., 10 to 50 parts by mass), more preferably 15 to 45 parts by mass, more preferably 20 to 40 parts by mass, and most preferably 25 to 35 parts by mass, relative to 100 parts by mass of the first rubber component, as described above. If the proportion of the first short fibers is too low, the chipping resistance is reduced. Conversely, if it is too high, not only is the effect of the short fibers reduced, but the mechanical properties of the first rubber layer are also reduced.

[0113] The second cross-linked rubber composition may not contain the second short fibers, but preferably contains the second short fibers from the viewpoint of improving the mechanical properties of the second rubber layer.

[0114] In order to improve chipping resistance, the proportion of the second short fibers relative to the second rubber component is preferably smaller than the proportion of the first short fibers relative to the first rubber component. The proportion of the second short fibers relative to 100 parts by mass of the second rubber component can be 10 parts by mass or less (0 to 10 parts by mass), particularly 5 parts by mass or less (e.g., 3 parts by mass or less), preferably 0.1 to 5 parts by mass (e.g., 0.3 to 4 parts by mass), further preferably 0.5 to 3.5 parts by mass, more preferably 1 to 3 parts by mass, and most preferably 1.5 to 2.5 parts by mass. If the proportion of the second short fibers is too high, while the elastic modulus (modulus) and hardness of the second cross-linked rubber composition can be increased, on the other hand, microcracks may be easily generated at the interface between the second rubber component and the second short fibers, reducing chipping resistance.

[0115] When the second cross-linked rubber composition contains second short fibers, the orientation direction of the second short fibers is not particularly limited, but they are preferably arranged in the belt longitudinal direction, similar to the first short fibers. Furthermore, when the second cross-linked rubber composition contains second short fibers, the second short fibers are preferably arranged so that the side closer to the tooth cloth follows the contour of the teeth, and the second short fibers become substantially parallel to the core wire as they approach the core wire.

[0116] (C) Filling ingredients

[0117] The crosslinked rubber composition (the first crosslinked rubber composition and the second crosslinked rubber composition) may further contain a filler. Examples of the filler (the first filler and the second filler) include reinforcing inorganic fillers and non-reinforcing fillers.

[0118] Examples of the reinforcing inorganic filler (the first reinforcing inorganic filler and the second reinforcing inorganic filler) include carbon black and silica. These reinforcing inorganic fillers can be used alone or in combination of two or more. The reinforcing inorganic filler can be in powder form.

[0119] The average particle size (average primary particle size) of carbon black is, for example, 5 to 200 nm, preferably 10 to 150 nm, more preferably 20 to 100 nm, and even more preferably 30 to 80 nm. The iodine adsorption capacity of carbon black is, for example, 5 to 200 mg / g, preferably 10 to 150 mg / g, more preferably 15 to 100 mg / g, and even more preferably 20 to 80 mg / g.

[0120] Silica comprises dry silica, wet silica, surface treated silica etc. In addition, silica can also be classified into such as dry process white carbon black, wet process white carbon black, colloidal silica, precipitated silica etc. according to the preparation method. These silicas can be used alone or in combination of two or more. Among these silicas, preferably there is silica (silicic anhydride, hydrous silicic acid) with surface silanol groups, and the chemical bonding strength of the hydrous silicic acid with many surface silanol groups and rubber component is strong.

[0121] The average particle size (average primary particle size) of silica is, for example, 1 to 500 nm, preferably 3 to 300 nm, more preferably 5 to 100 nm, and further preferably 10 to 50 nm.

[0122] The nitrogen adsorption specific surface area of ​​silica obtained by the BET method is, for example, 50 to 400 m 2 / g, preferably 100 to 300 m 2 / g, more preferably 150 to 200m 2 / g.

[0123] In the present application, the average particle size of the reinforcing inorganic filler can be calculated as the arithmetic average particle size of an appropriate number of samples (eg, 50 samples) by image analysis of electron micrographs including scanning electron micrographs.

[0124] The proportion of the reinforcing inorganic filler per 100 parts by mass of the rubber component can be 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 1 part by mass or less, and even more preferably 0 parts by mass. If a reinforcing inorganic filler is used as needed, the proportion can be, for example, 0.1 to 8 parts by mass, preferably 0.5 to 5 parts by mass, and even more preferably 1 to 3 parts by mass per 100 parts by mass of the rubber component. If the proportion of the reinforcing inorganic filler is too high, the rubber composition will generate increased heat and reduce heat resistance, potentially causing cracks and chipping due to thermal degradation.

[0125] Examples of non-reinforcing fillers (first non-reinforcing filler and second non-reinforcing filler) include polyvalent metal carbonates (calcium carbonate, magnesium carbonate, etc.), polyvalent metal hydroxides (aluminum hydroxide, etc.), polyvalent metal sulfates (barium sulfate, etc.), silicates (natural or synthetic silicates in which a portion of silicon is replaced by polyvalent metal atoms, such as aluminum silicate, magnesium silicate, and magnesium aluminum silicate; minerals containing silicates as main components, such as clay containing aluminum silicate, talc containing magnesium silicate, and mica, etc.), lithopone, and silica sand. These non-reinforcing fillers can be used alone or in combination of two or more.

[0126] Preferred non-reinforcing fillers are at least one selected from calcium carbonate, magnesium carbonate, aluminum hydroxide, barium sulfate, and silicates (such as aluminum silicate, magnesium silicate, and magnesium aluminum silicate; and silicate minerals (such as talc, clay, and mica)). Furthermore, from the perspective of significantly improving the processability of the tape and the dispersibility of the compounding ingredients, and minimizing the occurrence of poor dispersion of the compounding ingredients, the non-reinforcing filler preferably includes at least one selected from calcium carbonate, magnesium silicate, or talc containing magnesium silicate, and aluminum silicate or clay containing aluminum silicate, with calcium carbonate being particularly preferred. Powdered fillers commercially available as rubber fillers can be used as non-reinforcing fillers.

[0127] The average particle size (average primary particle size) of the non-reinforcing filler can be selected from the range of, for example, about 0.01 μm to about 25 μm (for example, about 0.2 μm to about 20 μm), preferably about 0.5 μm to about 17 μm (for example, about 1 μm to about 15 μm). The average particle size (average primary particle size) of the non-reinforcing filler can be, for example, 0.01 to 3 μm (for example, 0.02 to 2 μm), preferably 0.05 to 1.5 μm (especially 0.1 to 1 μm), and can be larger. In addition, the average particle size (average primary particle size) of the non-reinforcing filler can be, for example, 0.2 to 5 μm (for example, 0.3 to 3 μm), preferably 0.5 to 2.5 μm (especially 1 to 2 μm). It should be noted that, depending on the type of non-reinforcing filler, such as magnesium silicate or its minerals, the non-reinforcing filler may be crushed or broken during the kneading process with the rubber component, etc. The average particle size of such a pulverizable or crushable non-reinforcing filler may be the average particle size before kneading with the rubber component, etc. The non-reinforcing filler in each cross-linked rubber composition generally has an average particle size within the above-mentioned range (e.g., 0.1 to 10 μm, preferably 0.5 to 5 μm, and more preferably 1 to 3 μm).

[0128] It should be noted that, in the present application, the average particle size of non-reinforcing fillers can be measured as a volume average particle size using a laser diffraction particle size distribution analyzer. Alternatively, the average particle size of nano-sized fillers can be calculated as the arithmetic average particle size of an appropriate number of samples (e.g., 50 samples) by image analysis of electron micrographs, including scanning electron micrographs.

[0129] The proportion of the non-reinforcing filler is, for example, 70 parts by mass or less, preferably 40 parts by mass or less, and more preferably 30 parts by mass or less, per 100 parts by mass of the rubber component. If a non-reinforcing filler is used as needed, the proportion is, for example, 3 to 70 parts by mass, preferably 5 to 40 parts by mass, and more preferably 10 to 30 parts by mass per 100 parts by mass of the rubber component. If the proportion of the non-reinforcing filler is too high, the dispersibility of the compounding agent may be impaired.

[0130] The proportion of the filler compounding agent is, for example, 3 to 70 parts by mass, preferably 5 to 50 parts by mass, more preferably 10 to 40 parts by mass, and further preferably 20 to 30 parts by mass per 100 parts by mass of the rubber component.

[0131] (D) Cross-linking agents

[0132] The rubber composition is formulated with a crosslinking agent (vulcanizing agent) for crosslinking the rubber component, and may contain, as needed, a co-crosslinking agent, a crosslinking aid (vulcanizing aid), a crosslinking accelerator (vulcanization accelerator), a crosslinking retarder (vulcanization retarder), etc. Among these, the crosslinking ingredients (first crosslinking ingredient and second crosslinking ingredient) preferably include at least a crosslinking agent and a co-crosslinking agent (crosslinking aid), and a combination of a crosslinking agent and a co-crosslinking agent is particularly preferred.

[0133] As the crosslinking agent (first crosslinking agent and second crosslinking agent), conventional ones can be used depending on the type of the rubber component, and examples thereof include organic peroxides, sulfur-based crosslinking agents, and metal oxides.

[0134] Examples of the organic peroxides (first organic peroxide and second organic peroxide) include di-tert-butyl peroxide, dicumyl peroxide, tert-butylcumyl peroxide, 1,1-tert-butylperoxy-3,3,5-trimethylcyclohexane, 1,3-bis(tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, 1,3-bis(tert-butylperoxy-diisopropyl)benzene, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, tert-butylperoxybenzoate, and tert-butylperoxy-2-ethyl-hexyl carbonate. These organic peroxides may be used alone or in combination of two or more.

[0135] Examples of the sulfur-based crosslinking agent include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and sulfur chloride (sulfur monochloride, sulfur dichloride, etc.). These sulfur-based crosslinking agents can be used alone or in combination of two or more.

[0136] Examples of the metal oxide include magnesium oxide, zinc oxide, and lead oxide. These metal oxides may be used alone or in combination of two or more.

[0137] The crosslinking agent can be appropriately selected according to the type of rubber component, and is preferably an organic peroxide or a metal oxide, with an organic peroxide being particularly preferred. The crosslinking agent may also be a combination of an organic peroxide and a metal oxide.

[0138] The ratio of the crosslinking agent is, for example, 1 to 20 parts by mass, preferably 3 to 15 parts by mass, and more preferably 5 to 10 parts by mass per 100 parts by mass of the rubber component. If the ratio of the crosslinking agent is too low, the elastic modulus (modulus) and hardness of the rubber composition decrease, while if it is too high, the flexibility of the belt decreases.

[0139] The proportion of the organic peroxide can be selected from a range of approximately 0.5 to 20 parts by mass (e.g., approximately 1 to 10 parts by mass) per 100 parts by mass of the rubber component, and is typically 1 to 5 parts by mass (e.g., 1.2 to 4.5 parts by mass), preferably 1.5 to 4 parts by mass, and more preferably 2 to 3 parts by mass. In the first rubber layer, the proportion of the first organic peroxide is, for example, 1 to 20 parts by mass, preferably 1.5 to 10 parts by mass, and more preferably 1.5 to 4 parts by mass per 100 parts by mass of the first rubber component. In the second rubber layer, the proportion of the second organic peroxide is, for example, 0.5 to 5 parts by mass, preferably 0.8 to 4 parts by mass, and more preferably 1 to 3 parts by mass per 100 parts by mass of the second rubber component.

[0140] The ratio of the metal oxide is, for example, 0.1 to 30 parts by mass, preferably 0.5 to 20 parts by mass, more preferably 1 to 15 parts by mass, further preferably 2 to 10 parts by mass, and most preferably 3 to 7 parts by mass per 100 parts by mass of the rubber component.

[0141] Examples of the co-crosslinking agent (crosslinking aid or co-vulcanizing agent) include known crosslinking aids, such as polyfunctional (iso)cyanurates [e.g., triallyl isocyanurate (TAIC), triallyl cyanurate (TAC), etc.], polydienes (e.g., 1,2-polybutadiene), metal salts of unsaturated carboxylic acids [e.g., polyvalent metal salts of (meth)acrylate such as zinc (meth)acrylate and magnesium (meth)acrylate], oximes (e.g., quinone dioxime), guanidines (e.g., diphenylguanidine), polyfunctional (meth)acrylates [e.g., alkanediol di(meth)acrylates such as ethylene glycol di(meth)acrylate and butanediol di(meth)acrylate, alkanediol di(meth)acrylates such as trimethylolpropane tri(meth)acrylate and pentaerythritol tetra(meth)acrylate], and polyfunctional (meth)acrylates. hydrocarbon polyol poly(meth)acrylate], bismaleimides (aliphatic bismaleimides, such as N,N'-1,2-ethylenebismaleimide, N,N'-hexamethylenebismaleimide, 1,6'-bismaleimide-(2,2,4-trimethyl)cyclohexane and other alkylene bismaleimides; aromatic hydrocarbon bismaleimides or aromatic bismaleimides, such as N,N'-m-phenylenedimaleimide, 4-methyl-1,3-phenylenedimaleimide, 4,4'-diphenylmethanedimaleimide, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, 4,4'-diphenyletherdimaleimide, 4,4'-diphenylsulfonedimaleimide, 1,3-bis(3-maleimidophenoxy)benzene, etc.), etc. These co-crosslinking agents can be used alone or in combination of two or more. Among these co-crosslinking agents, polyfunctional (iso)cyanurates, polyfunctional (meth)acrylates, and bismaleimides (aromatic bismaleimides or aromatic bismaleimides such as N,N'-m-phenylenedimaleimide) are preferred, with bismaleimides being particularly preferred. By adding a co-crosslinking agent (such as bismaleimides), the degree of crosslinking can be increased, thereby increasing the elastic modulus.

[0142] The proportion of a co-crosslinking agent (crosslinking aid) such as bismaleimide is, for example, 0.2 to 40 parts by mass, preferably 0.5 to 30 parts by mass, more preferably 0.8 to 20 parts by mass, and even more preferably 1 to 15 parts by mass, relative to 100 parts by mass of the rubber component, calculated on a solids basis. In the first rubber layer, the proportion of the co-crosslinking agent (first co-crosslinking agent) is, for example, 1 to 40 parts by mass, preferably 2 to 30 parts by mass (e.g., 5 to 20 parts by mass), more preferably 2.5 to 18 parts by mass (e.g., 8 to 15 parts by mass), more preferably 3 to 14 parts by mass (e.g., 4 to 12 parts by mass), and most preferably 5 to 11 parts by mass (e.g., 5 to 7 parts by mass), relative to 100 parts by mass of the first rubber component. The proportion of the co-crosslinking agent (second co-crosslinking agent) in the second rubber layer can be selected from a range of approximately 0.2 to 25 parts by mass, for example, 0.3 to 20 parts by mass (e.g., 0.5 to 10 parts by mass), preferably 0.5 to 7 parts by mass (e.g., 0.5 to 6 parts by mass), further preferably 0.8 to 5 parts by mass, more preferably 0.8 to 3 parts by mass, and most preferably 0.8 to 2 parts by mass, relative to 100 parts by mass of the second rubber component. In particular, when the proportion of the first co-crosslinking agent in the first rubber component is adjusted to 3 parts by mass or greater (particularly 5 parts by mass or greater), the tooth chipping resistance of the toothed belt can be significantly improved through the combined effect of the first short fibers oriented in a predetermined direction.

[0143] The proportion of the cross-linking compounding agent, calculated on a solids basis, is, for example, 0.2 to 50 parts by mass, preferably 0.5 to 40 parts by mass, more preferably 1 to 30 parts by mass, and even more preferably 2 to 20 parts by mass, relative to 100 parts by mass of the rubber component. In the first rubber layer, the proportion of the cross-linking compounding agent (first cross-linking compounding agent) is, for example, 1 to 40 parts by mass, preferably 5 to 20 parts by mass, and even more preferably 10 to 15 parts by mass, relative to 100 parts by mass of the first rubber component. In the second rubber layer, the proportion of the cross-linking compounding agent (second cross-linking compounding agent) is, for example, 0.3 to 25 parts by mass, preferably 0.5 to 10 parts by mass, and even more preferably 1 to 8 parts by mass, relative to 100 parts by mass of the second rubber component.

[0144] (E) Other compounding agents

[0145] The crosslinked rubber composition may further contain additives conventionally used in rubber compositions for toothed belts. Examples of conventional additives include metal oxides (calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, aluminum oxide, etc.), softeners (oils such as paraffin oil and cycloparaffin oil), processing agents or processing aids (stearic acid or its metal salts, wax, paraffin, fatty acid amide, etc.), plasticizers [aliphatic carboxylic acid plasticizers (adipate plasticizers, sebacate plasticizers, etc.), aromatic carboxylic acid ester plasticizers (phthalate plasticizers, trimellitic acid plasticizers, etc.), hydroxycarboxylic acid ester plasticizers, phosphate plasticizers, ether plasticizers, ether ester plasticizers, etc.], antioxidants (antioxidants, heat aging agents, flex cracking agents, ozone degradation inhibitors, etc.), colorants, tackifiers, plasticizers, coupling agents (silane coupling agents, etc.), stabilizers (ultraviolet absorbers, heat stabilizers, etc.), flame retardants, antistatic agents, etc. Furthermore, the crosslinked rubber composition may contain an adhesiveness improver (resorcinol-formaldehyde co-condensate, amino resin, etc.) as needed. These additives may be used alone or in combination of two or more.

[0146] In particular, the proportion of the processing agent or processing aid can be selected from the range of, for example, about 0.1 to 10 parts by mass relative to 100 parts by mass of the rubber component, and can be 0.3 to 3 parts by mass (particularly 0.5 to 1.5 parts by mass) in the first rubber layer and 0.1 to 2 parts by mass (particularly 0.3 to 1 part by mass) in the second rubber layer.

[0147] The ratio of the antioxidant is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass, and more preferably 1 to 3 parts by mass, relative to 100 parts by mass of the rubber component.

[0148] (Preferred Combination of the First Rubber Layer and the Second Rubber Layer)

[0149] The elastic modulus (modulus) of the first and second rubber layers can be adjusted by varying the ratio of specific components that influence the elastic modulus of the rubber layers and their amounts. For example, the content of at least one component selected from short fibers, fillers, and crosslinking agents (crosslinkers, co-crosslinkers (such as bismaleimides)) can be increased in the first rubber layer compared to the second rubber layer. In particular, in the toothed belt of the present invention, since the first rubber layer contains a specific amount of first short fibers as an essential component, adjusting the ratio of second short fibers in the second rubber layer allows for easy adjustment of the elastic modulus. Furthermore, by making the ratio of second short fibers in the second rubber layer smaller than that of first short fibers in the first rubber layer, the occurrence of microcracks in the second rubber layer can be suppressed, thereby improving chipping resistance. Furthermore, by adjusting the content of the co-crosslinking agent (particularly bismaleimides) in addition to the ratio of short fibers, the elastic modulus (tensile elastic modulus) of the first rubber layer and the second rubber layer can be balanced and appropriately adjusted, and the rigidity (deformation resistance) and bendability (flexibility) of the teeth in an inverse relationship can be achieved, and the chipping resistance can be greatly improved.

[0150] Furthermore, in the toothed belt of the present invention, in order to obtain the rigidity of the teeth that can withstand use under conditions with higher loads and have a high elastic modulus, and in order to balance the rigidity (deformation resistance) and bendability (flexibility) of the teeth in an inverse relationship, the following combination is set as a preferred method.

[0151] A preferred embodiment may be as follows: in the first rubber layer, the first rubber component contains 80% by mass or more of HNBR containing an unsaturated carboxylic acid metal salt, the proportion of the first short fibers is 5 to 60 parts by mass, the proportion of the first reinforcing inorganic filler is 10 parts by mass or less, the proportion of the first co-crosslinking agent is 1 to 40 parts by mass, and the proportion of the organic peroxide is 1 to 20 parts by mass, relative to 100 parts by mass of the first rubber component. Moreover, in the second rubber layer, the second rubber component contains 30% by mass or more of HNBR containing an unsaturated carboxylic acid metal salt, the proportion of the second short fibers is 5 parts by mass or less, the proportion of the second reinforcing inorganic filler is 10 parts by mass or less, the proportion of the second co-crosslinking agent is 0.2 to 25 parts by mass, and the proportion of the organic peroxide is 0.5 to 5 parts by mass, relative to 100 parts by mass of the second rubber component.

[0152] (tooth cloth)

[0153] In the case where the tooth portion includes a tooth cloth, the tooth cloth constituting the inner peripheral surface of the belt (the surface of the tooth portion and the tooth bottom) can be formed of, for example, a woven fabric, a knitted fabric, a non-woven fabric, or the like. Conventionally, most of them are woven fabrics (canvas), which are composed of a woven fabric formed by weaving warp yarns extending in the width direction of the belt and weft yarns extending in the circumferential direction of the belt. The fabric structure of the woven fabric is not particularly limited as long as the warp yarns and the weft yarns are regularly crossed in the longitudinal and transverse directions. It can be any one of plain weave, twill weave (or twill weave), satin weave (satin weave), etc., or a fabric structure formed by combining these structures. Preferred woven fabrics have twill weave and satin weave structures.

[0154] As the fiber of the weft and warp yarn forming the tooth cloth, in addition to the fiber same as the above-mentioned staple fiber, polyphenylene ether fibers, polyether ether ketone fibers, polyether sulfone fibers, polyurethane fibers etc. can also be exemplified.These fibers can be used alone or in combination of two or more.Among these fibers, general organic fibers, preferably cellulose fibers such as cotton or rayon, polyester fibers (PET fibers etc.), polyamide fibers (aliphatic polyamide fibers such as polyamide 66 fibers, aromatic polyamide fibers etc.), PBO fibers, fluororesin fibers [polytetrafluoroethylene (PTFE) fibers etc.] etc.In addition, also preferably these fibers and composite yarn with elastic yarn (for example, elastic fibers formed by polyurethane with elastic polyurethane elastic yarn, stretch processing (for example, wool processing, crimping processing etc.) processing yarn etc.).

[0155] The warp and weft yarns are not particularly limited in form and may be monofilament yarns, multifilament yarns formed by combining or twisting filaments (long fibers), or spun yarns (spun staple yarns) formed by twisting short fibers. The multifilament yarns or spun staple yarns may be twisted or blended yarns made from two or more fibers. The weft yarns preferably contain the aforementioned stretchable elastic yarns. For weaving performance, the warp yarns typically do not contain elastic yarns. To ensure the circumferential stretchability of the tooth cloth, the weft yarns containing the elastic yarns extend in the circumferential direction of the belt, while the warp yarns extend in the width direction of the belt.

[0156] The average diameter of the fibers (or yarns) is, for example, 1 to 100 μm (e.g., 3 to 50 μm), preferably 5 to 30 μm, and more preferably 7 to 25 μm. Regarding the average fiber diameter (thickness) of the yarns (twisted yarns), the weft yarns can be, for example, approximately 100 to 1000 dtex (particularly approximately 300 to 700 dtex), and the warp yarns can be, for example, approximately 50 to 500 dtex (particularly approximately 100 to 300 dtex). The density (pieces / cm) of the weft yarns can be, for example, approximately 5 to 50 (particularly approximately 10 to 30), and the density (pieces / cm) of the warp yarns can be, for example, approximately 10 to 300 (particularly approximately 20 to 100).

[0157] Woven fabrics may have a multilayer weave structure (e.g., a double weave structure). In a fabric structure comprising warp and weft yarns, at least a portion of the weft yarns may be formed from low-friction fibers (or low-friction fibers) such as fibers containing fluororesins (e.g., composite yarns containing fibers made of fluororesins such as PTFE). For example, the warp yarns may be formed from polyamide fibers such as nylon 66, polyester fibers, or the like, while the weft yarns may be formed solely from fibers made of the fluororesin. The weft yarns may be formed from composite yarns made from the fluororesin fibers and a second fiber such as polyamide fibers or polyurethane fibers (elastane). The weft yarns may be formed from composite yarns made from the composite yarns and a second composite yarn made from two or more of the second fibers.

[0158] In this method, the weft yarns located on the surface (exposed) side of the tooth cloth (the side meshing with the toothed pulley) are preferably made of fluorinated fibers (e.g., PTFE fibers) with a low coefficient of friction to reduce friction between the cloth and the toothed pulley. On the other hand, the weft yarns located on the back side of the tooth cloth (the side bonded to the first rubber layer) are made of fibers other than fluorinated fibers to improve the adhesion between the cloth and the rubber forming the teeth. This tooth cloth reduces friction during meshing with the toothed pulley, thus suppressing noise generation.

[0159] In addition, when using fluorine-based fibers, it is preferred to arrange low-melting-point fibers with a rubber base material having a melting point that melts at the crosslinking (vulcanization) temperature of the teeth and back around the fluorine-based fibers. Specifically, among the forms of composite yarns containing fluorine-based fibers, there are forms in which fluorine-based fibers and low-melting-point fibers are twisted together, and forms in which fluorine-based fibers are covered with low-melting-point fibers. It should be noted that the crosslinking (vulcanization) conditions of the teeth and back are not particularly limited, and the crosslinking (vulcanization) time is generally about 1 minute to about 5 hours at a crosslinking (vulcanization) temperature of 100 to 200°C.

[0160] In a configuration where low-melting-point fibers are arranged around the fluorocarbon fibers, the low-melting-point fibers melt during crosslinking (vulcanization) of the teeth and back, flow between the fibers forming the tooth cloth, and then cool below their melting point, crystallizing. This prevents the fluorocarbon fibers from being cut or scattered due to impact or abrasion on the tooth cloth surface during insertion into or removal from the toothed pulley. Using this type of weft yarn as the tooth cloth for a toothed belt protects the teeth and back for a longer period of time, preventing tooth chipping and extending the belt's life even under high loads.

[0161] The average thickness of the tooth cloth (tooth cloth in the toothed belt) is, for example, 0.1 to 2 mm, preferably 0.2 to 1.5 mm. The average thickness of the raw material tooth cloth (tooth cloth before forming) is, for example, 0.5 to 3 mm, preferably 0.75 to 2.5 mm.

[0162] To improve adhesion to the first rubber layer, the fabric forming the tooth cloth can be subjected to an adhesive treatment. Examples of adhesive treatments include: immersing the fabric in an RFL treatment solution and then heating and drying; treating the fabric with an epoxy compound or isocyanate compound; dissolving a rubber composition in an organic solvent to form a rubber paste, immersing the fabric in the rubber paste, and then heating and drying; or a combination of these treatments. These methods can be performed individually or in combination, and the order and number of treatments are not limited. For example, the fabric can be immersed in an RFL treatment solution and then further immersed in a rubber paste and then heated and dried.

[0163] Furthermore, to improve the adhesion between the tooth cloth and the first rubber layer, an uncrosslinked rubber sheet formed by rolling a rubber composition can be laminated onto the back side of the fabric forming the tooth cloth (the side that adheres to the first rubber layer). This rubber composition (third crosslinked rubber composition) can be appropriately selected from the crosslinked rubber compositions exemplified as the crosslinked rubber compositions forming the first and second rubber layers, and can be a conventional adhesive rubber composition. It should be noted that the uncrosslinked rubber sheet obtained from this rubber composition can form a third rubber layer (adhesive rubber layer) sandwiched between the tooth cloth and the first rubber layer in the toothed belt. The fabric subjected to the above adhesive treatment is referred to as a tooth cloth precursor.

[0164] [Tooth bottom]

[0165] When the tooth portion includes a tooth cloth, the tooth cloth constitutes the surface of the tooth portion and also constitutes the surface of the back portion on the tooth portion side (the surface of the tooth bottom).

[0166] When the tooth portion includes a tooth cloth, a first rubber layer and a second rubber layer may be interposed between the tooth cloth and the core wire at the back portion corresponding to the tooth base. However, only the first rubber layer may be interposed, or the tooth cloth may be in contact with the core wire without interposing the first and second rubber layers. In either case, whether the first rubber layer or the second rubber layer is interposed at the back portion corresponding to the tooth base, the thickness of the first rubber layer and the thickness of the first and second rubber layers are formed thinner than that of the tooth portion.

[0167] When the tooth portion does not include a tooth cloth, the back portion corresponding to the tooth base may be formed of the first rubber layer and the second rubber layer, or may be formed of only the first rubber layer. In either case, the thickness of the first rubber layer and the thickness of the first rubber layer and the second rubber layer in the back portion corresponding to the tooth base are formed thinner than those of the tooth portion.

[0168] [Back rubber layer]

[0169] The back portion is formed with the above-mentioned teeth and tooth bottom on the inner peripheral surface, and has a back rubber layer forming the outer peripheral surface of the belt on its outer peripheral surface side. In addition, the above-mentioned back rubber layer is formed by a cross-linked rubber composition (the fourth cross-linked rubber composition). Figures 1 to 3 In the embodiment, the other surface (belt back) on the side where the teeth are not formed is not covered with a fabric (woven fabric, knitted fabric, non-woven fabric, etc.), but it can be covered as needed. Including the preferred embodiment, the fabric can be selected from the fabrics exemplified as the tooth cloth.

[0170] (Fourth crosslinked rubber composition)

[0171] From the viewpoint of reducing the belt's bending rigidity, ensuring bendability (windability around pulleys), and bending fatigue resistance, the fourth crosslinked rubber composition preferably has a lower hardness than the first and second crosslinked rubber compositions constituting the teeth.

[0172] Specifically, the rubber hardness Hs of the fourth crosslinked rubber composition is, for example, 80 to 89 degrees on a Type A durometer. Alternatively, it can be approximately 20 to 30 degrees on a Type D durometer. By adjusting the hardness of the back rubber layer within this range, the flexural rigidity of the back portion is reduced, resulting in excellent flexural fatigue resistance. If the Type A hardness of the fourth crosslinked rubber composition is too low, cracks may form on the back portion due to collisions with foreign objects, for example. Conversely, if it is too high, flexural fatigue resistance may be reduced, potentially leading to cracks on the back portion.

[0173] It should be noted that in the present application, the type A hardness refers to the hardness of the back rubber layer surface, and can be measured using a type A durometer in accordance with the spring durometer hardness test specified in JIS K6253 (2012).

[0174] The fourth cross-linked rubber composition is not particularly limited as long as it does not impair the adhesion between the back rubber layer and the teeth. For example, it can be selected from the cross-linked rubber compositions exemplified as the cross-linked rubber compositions for the first and second rubber layers, and can be appropriately adjusted so that the rubber hardness falls within the above range.

[0175] In the fourth cross-linked rubber composition, from the viewpoint of improving the adhesion between the back rubber layer and the teeth, the rubber component (fourth rubber component) preferably contains a rubber component of the same series or the same type as that of the second rubber layer (inner rubber layer), and more preferably the same type of rubber component.

[0176] The fourth rubber component preferably comprises an HNBR / unsaturated carboxylic acid metal salt composite polymer. The proportion of the HNBR / unsaturated carboxylic acid metal salt composite polymer in the fourth rubber component may be 5% by mass or greater, for example, 5 to 50% by mass, preferably 10 to 30% by mass, and more preferably 15 to 25% by mass.

[0177] The filler compounding ingredient may be a reinforcing inorganic filler (fourth reinforcing inorganic filler), preferably a combination of carbon black and silica. The proportion of carbon black is, for example, 1 to 50 parts by mass, preferably 2 to 30 parts by mass, and more preferably 3 to 10 parts by mass per 100 parts by mass of silica. The proportion of the fourth reinforcing inorganic filler is, for example, 10 to 100 parts by mass, preferably 20 to 80 parts by mass, and more preferably 30 to 50 parts by mass per 100 parts by mass of the fourth rubber component.

[0178] The crosslinking agent (fourth crosslinking agent) may be a combination of an organic peroxide (fourth organic peroxide) and a metal oxide (fourth metal oxide). The proportion of the fourth organic peroxide is, for example, 0.5 to 5 parts by mass, preferably 0.8 to 4 parts by mass, and more preferably 1 to 3 parts by mass, relative to 100 parts by mass of the fourth rubber component. The proportion of the fourth metal oxide is, for example, 1 to 15 parts by mass, preferably 2 to 10 parts by mass, and more preferably 2 to 8 parts by mass, relative to 100 parts by mass of the fourth rubber component.

[0179] The co-crosslinking agent (fourth co-crosslinking agent) may be a bismaleimide. The proportion of the fourth co-crosslinking agent is, for example, 0.2 to 10 parts by mass, preferably 0.5 to 5 parts by mass, and more preferably 1 to 3 parts by mass per 100 parts by mass of the fourth rubber component.

[0180] The fourth crosslinked rubber composition may contain a plasticizer. The plasticizer may be selected from the plasticizers exemplified for the first rubber layer and the second rubber layer. These plasticizers may be used alone or in combination of two or more. Of these plasticizers, ether ester plasticizers are preferred.

[0181] The proportion of the plasticizer relative to 100 parts by mass of the fourth rubber component is, for example, 1 to 50 parts by mass, preferably 2 to 30 parts by mass, more preferably 3 to 20 parts by mass, and further preferably 5 to 15 parts by mass.

[0182] The average thickness of the back rubber layer is, for example, 0.3 to 3 mm, preferably 0.5 to 2 mm. The average thickness of the back portion (average thickness of the back portion of the tooth bottom) is, for example, 1 to 5 mm, preferably 1.5 to 4 mm.

[0183] [Core Wire]

[0184] On the back, on the inner circumference of the above-mentioned back rubber layer, a core wire extending along the circumferential direction of the belt is buried. This core wire acts as a tensile member, which can improve the running stability and strength of the toothed belt. In addition, on the back, the core wire, which is a twisted rope extending along the circumferential direction of the belt, is usually buried at a predetermined interval in the width direction of the belt. Two or more core wires can be arranged parallel to the longitudinal direction. From the perspective of productivity, they are usually buried in a spiral shape. When arranged in a spiral shape, the angle of the core wire relative to the longitudinal direction of the belt can be, for example, less than 5°. From the perspective of the running performance of the belt, the closer to 0°, the more preferred.

[0185] In more detail, Figure 1 As shown, the core wires can be embedded at predetermined intervals (or pitches) (or at equal intervals) from one end to the other in the width direction of the back. The distance between the centers of adjacent core wires, i.e., the pitch, can be greater than the core wire diameter. Depending on the core wire diameter, it is, for example, 0.5 to 3.5 mm, preferably 0.8 to 3 mm, and more preferably 0.9 to 2.8 mm.

[0186] The core yarn can be formed from a twisted rope made by twisting two or more strands or multifilament yarns. A twisted rope of strands is preferred, and a single strand can be formed by bundling filaments (long fibers). There are no particular restrictions on the thickness of the filaments forming the twisted rope, the number of filaments in the rope, the number of strands, or the twisting method.

[0187] The twisted rope forming the core can be a unidirectional twist, a ply twist, or a straight twist. Unidirectional twist and straight twist are preferred, with straight twist being particularly preferred. By setting the core to a straight twist with the twist direction of the initial twist and the final twist in the same direction, the bending stiffness is reduced compared to ply twist or unidirectional twist, resulting in excellent bending fatigue resistance.

[0188] In the present invention, by adjusting the elastic modulus, twist coefficient, core diameter D, core pitch P, and arrangement density of the core wire, the elastic modulus of the toothed belt described later is controlled. Even when the belt is narrowed for high-load transmission applications in the rear-wheel drive of a two-wheeled motorcycle, it is possible to ensure tooth skipping resistance, tension maintenance, and bending fatigue resistance.

[0189] In the present invention, regarding the elastic modulus of the core wire, by making the core wire contain high elastic modulus fibers, the elastic modulus (modulus) of the belt can be improved, and the tooth skipping resistance in the above-mentioned applications can be improved. As high elastic modulus fibers, for example, carbon fibers, aramid fibers, glass fibers, metal fibers (steel fibers), etc. can be cited. These high elastic modulus fibers can be used alone or in combination of two or more. Among these high elastic modulus fibers, carbon fibers and aramid fibers are preferred, and carbon fibers are most preferred. The proportion of high elastic modulus fibers can be more than 10% by mass of all the fibers constituting the core wire, preferably more than 50% by mass, more preferably more than 80% by mass, more preferably more than 90% by mass, and most preferably 100% by mass.

[0190] The core wire may contain other fibers in addition to the above-mentioned high elastic modulus fibers within the scope of not impairing the effect of the present invention. Examples of other fibers include polyester fibers (polyalkylene arylate fibers, poly(p-phenylene naphthalene dicarboxylate) fibers), polybenzoic acid fibers, and poly(vinyl alcohol) fibers. Synthetic fibers such as azole fibers, acrylic fibers, and aliphatic polyamide fibers, etc. The proportion of other fibers may be 50% by mass or less, preferably 20% by mass or less, and more preferably 10% by mass or less of all fibers constituting the core yarn.

[0191] That is, the core wire of the present invention only needs to contain these high elastic modulus fibers, and is preferably formed of these high elastic modulus fibers. In high-load transmission applications such as rear-wheel drive motorcycles, it is particularly preferably formed of carbon fibers.

[0192] Examples of carbon fibers include pitch-based carbon fibers, polyacrylonitrile (PAN)-based carbon fibers, phenolic resin-based carbon fibers, cellulose-based carbon fibers, and polyvinyl alcohol-based carbon fibers. Commercially available carbon fibers include, for example, "Toray Industries (registered trademark)" manufactured by Toray Industries, Inc., "Tenax (registered trademark)" manufactured by Toho Tenax Co., Ltd., and "Diaryl (registered trademark)" manufactured by Mitsubishi Chemical Corporation. These carbon fibers can be used alone or in combination of two or more. Among these carbon fibers, pitch-based carbon fibers and PAN-based carbon fibers are preferred, and PAN-based carbon fibers are particularly preferred.

[0193] In particular, carbon fiber multifilament yarns are preferably used for high-load transmission applications in rear-wheel drive motorcycles. Carbon fiber multifilament yarns can be selected from 6K and 12K multifilament yarns with varying filament counts. 6K refers to a multifilament yarn with 6,000 filaments, while 12K refers to a multifilament yarn with 12,000 filaments. The fineness of 6K multifilament yarns is approximately 400 tex, while the fineness of 12K multifilament yarns is approximately 800 tex.

[0194] When the fineness of the carbon fiber multifilament yarn exceeds 1000 tex, the bending fatigue resistance may be reduced. Conversely, when the fineness of the carbon fiber multifilament yarn is less than 300 tex, the material cost increases, and the number of primary twist yarns required to produce a core wire with sufficient tensile strength increases, resulting in an increase in working hours. In the present invention, by using carbon fibers with a diameter of 1000 tex or less, a toothed belt with excellent tooth skipping resistance can be produced even when the belt is narrowed for high-load transmission applications in rear-wheel drives of motorcycles.

[0195] Specific examples of the carbon fiber ropes used for the core wire include the carbon fiber ropes (twisted ropes) shown in Table 1.

[0196] [Table 1]

[0197]

[0198] The core wire diameter D, which represents the average diameter (average wire diameter) of the core wire (or twisted rope), can be selected from a range of approximately 0.2 mm to approximately 2.5 mm, for example, 0.8 to 2.4 mm. If the core wire diameter is too thin, the elongation of the core wire may increase, resulting in tooth chipping (loss of teeth). If the core wire diameter is too thick, the bending fatigue resistance of the core wire may decrease, resulting in the core wire being cut.

[0199] In particular, in high-load transmission applications in rear-wheel drive motorcycles, the core wire diameter D of the core wire formed of carbon fibers is preferably adjusted according to the tooth pitch.

[0200] In a toothed belt having a tooth pitch of 6 mm or more and less than 9.5 mm (for example, 7 to 9 mm, particularly 8 mm), the core wire diameter D of the core wire formed by carbon fiber can be adjusted to, for example, approximately 0.8 mm to approximately 1.2 mm, preferably 0.9 to 1.1 mm, further preferably 0.9 to 1.05 mm, and even more preferably 0.9 to 1.0 mm.

[0201] In a toothed belt having a pitch of 9.5 mm or more and less than 12.5 mm (e.g., 10-12 mm, particularly 11 mm), the core wire diameter D of the core wire formed of carbon fiber can be adjusted to, for example, 1.3-1.8 mm (particularly 1.4-1.8 mm).

[0202] In addition, in a toothed belt with a tooth pitch of 12.5 to 16 mm (for example, 13 to 15 mm, especially 14 mm), the core wire diameter D of the core wire formed by carbon fiber can be adjusted to a range of, for example, about 1.7 mm to about 2.4 mm (for example, about 1.9 mm to about 2.4 mm), preferably to 1.8 to 2.2 mm (especially 1.9 to 2.2 mm), further preferably to 1.8 to 2.1 mm, and more preferably to 1.8 to 2.0 mm.

[0203] The core wire spacing P, which represents the spacing between the core wires (the distance between the centers of two adjacent core wires in the belt), can be selected from the range of about 0.2 mm to about 2.5 mm, for example, 0.9 to 2.5 mm, preferably 1.2 to 2.4 mm, further preferably 1.5 to 2.3 mm, more preferably 1.9 to 2.2 mm, and most preferably 2.0 to 2.1 mm.

[0204] In particular, in high-load transmission applications in rear-wheel drive motorcycles, the core pitch P of the carbon fiber core wires is preferably adjusted according to the tooth pitch.

[0205] In a toothed belt having a tooth pitch of 6 mm or more and less than 9.5 mm (for example, 7 to 9 mm, particularly 8 mm), the core wire spacing P of the core wire formed by the carbon fiber can be adjusted to, for example, 0.9 to 1.3 mm, preferably 1.0 to 1.3 mm, further preferably 1.05 to 1.2 mm, and more preferably 1.1 to 1.15 mm.

[0206] In addition, in a toothed belt having a pitch of 9.5 mm or more and less than 12.5 mm (for example, 10 to 12 mm, particularly 11 mm), the core wire pitch P of the core wires formed of carbon fibers can be adjusted to, for example, 1.4 to 2.0 mm (particularly 1.5 to 1.9 mm).

[0207] In addition, in a toothed belt with a tooth pitch of 12.5 to 16 mm (for example, 13 to 15 mm, especially 14 mm), the core wire spacing P of the core wire formed by carbon fiber can be adjusted to a range of, for example, about 1.8 mm to about 2.5 mm (for example, about 2.0 mm to about 2.5 mm), for example, it can be adjusted to 1.8 to 2.4 mm (especially 2.0 to 2.3 mm), preferably adjusted to 1.9 to 2.3 mm, and further preferably adjusted to 1.9 to 2.2 mm.

[0208] In the present invention, by adjusting the core diameter D and the core spacing P, and controlling the core arrangement density (X%), a toothed belt suitable for high-load transmission applications in rear-wheel drive motorcycles can be produced. In particular, even with a narrowed belt width, the elastic modulus (modulus) of the belt can be increased, thereby improving tooth skipping resistance. In this application, the arrangement density (X%) refers to "the ratio of the area without cores (the sum of the spacings d) to the belt width W," that is, "the ratio of the sum of the spacings d between adjacent cores to the belt width W." A smaller X value indicates a denser belt.

[0209] In detail, Figure 6 : is a diagram showing the belt width W, core wire diameter D, core wire interval d, and core wire pitch P of the toothed belt of the present invention, as shown in FIG. Figure 6 As shown, in the belt 1 having the tooth cloth 2, two or more cores 5 are arranged in the back rubber layer 6 with a predetermined interval d in the belt width direction. The interval d includes not only the intervals between adjacent cores 5 but also the intervals between the cores 5 at both ends and the belt ends ( Figure 6 It should be noted that the above-mentioned tape end refers to the end located on the line connecting the center of the core wire 5 ( Figure 6 The left or right end of the strip is shown in the figure. That is, in this application, the total value of the spacing d refers to the value obtained by subtracting the value of "the total core wire diameter D (core wire diameter D × the number of core wires)" from the value of "tape width" W. Therefore, as shown in the following formula, the above-mentioned X value (%) can be replaced by the relationship between the core wire diameter D and the core wire pitch P.

[0210] X = (total of intervals d / tape width W) × 100

[0211] =[(Total of tape width W - core wire diameter D) / tape width W]×100

[0212] ={[Tape width W - (core wire diameter D × number of core wires)] / Tape width W} × 100

[0213] =<{Tape width W-[core wire diameter D×(Tape width W / core wire spacing P)]} / Tape width W>×100

[0214] =[1-(core wire diameter D / core wire spacing P)]×100.

[0215] It should be noted that in this application, the tape width W, the core diameter D, the spacing d, and the core spacing P are obtained based on a cross-sectional view perpendicular to the length direction of the tape (cross-sectional view). The core spacing P is as follows: Figure 6 Shown is the distance between the centers of adjacent core wires in the above cross-sectional view.

[0216] The X value of the arrangement density of the core wires is, for example, 5 to 25%, preferably 5 to 20%, more preferably 5.1 to 15%, more preferably 5.2 to 13%, and most preferably 5.2 to 10%. If the X value is too small, the arrangement of the core wires may become too dense (the interval d between adjacent core wires becomes too narrow), and the rubber will not easily flow around the core wires during the manufacture of the belt, resulting in poor forming (the core wires are not loaded by the rubber). On the other hand, if the X value is too large, the arrangement of the core wires may become too sparse, especially if the width is narrowed, the number of core wires will be insufficient and the elastic modulus of the belt will be insufficient, which will damage the meshing transmission performance (tooth skipping resistance) and cannot ensure durability.

[0217] In the present invention, by adjusting the twist coefficient of the twisted cord constituting the core wire, a toothed belt suitable for high-load transmission in rear-wheel drive motorcycles can be produced, and in particular, tension retention and bending fatigue resistance can be improved even when the width is narrowed.

[0218] It should be noted that twist coefficient is a value that replaces the angle formed by the fiber with respect to the longitudinal direction of the core yarn and is used as an indicator to compare the twist strength of twisted yarns of different finenesses. A larger twist coefficient indicates a larger angle formed by the fiber with respect to the longitudinal direction of the core yarn, and thus a stronger twist. In this application, twist coefficient is calculated using the following formula, taking into account the specific gravity of the carbon fiber.

[0219] Twist coefficient = [twist (times / m) × √fineness (tex)] / 960.

[0220] In the present invention, the final twist coefficient of a straight-twist rope or a ply-twist rope can be evaluated in the same way as the twist coefficient of a unidirectional twist rope. Therefore, in this application, the final twist coefficient is used to include the twist coefficient of a unidirectional twist rope. The final twist coefficient of the core wire can be selected from the range of about 1.1 to about 3 (especially about 1.1 to about 2.7), for example, 1.1 to 2.5, preferably 1.2 to 2.5, more preferably 1.5 to 2.4, more preferably 1.7 to 2.3, and most preferably 1.8 to 2.2. If the twist coefficient is too small, when used in high-load transmission applications in the rear-wheel drive of a two-wheeled motorcycle, the bending fatigue resistance may be reduced. Conversely, if it is too large, the tension maintenance may be reduced.

[0221] In particular, for high-load transmission applications in rear-wheel drive motorcycles, the twist coefficient of the carbon fiber core is preferably adjusted according to the tooth pitch. In toothed belts with a tooth pitch of 6 mm or more and less than 9.5 mm (e.g., 7 to 9 mm, particularly 8 mm), the final twist coefficient of the carbon fiber core (particularly the twist coefficient of unidirectional lay ropes) is preferably adjusted to, for example, 1.1 to 2.0 (particularly 1.5 to 1.8). Furthermore, in toothed belts with a tooth pitch of 9.5 mm or more and less than 12.5 mm (e.g., 10 to 12 mm, particularly 11 mm), the final twist coefficient of the carbon fiber core (particularly the final twist coefficient of straight lay ropes or the twist coefficient of unidirectional lay ropes) is preferably adjusted to, for example, 1.2 to 2.5 (particularly 1.7 to 2.5), and the initial twist coefficient of the carbon fiber core (particularly the initial twist coefficient of straight lay ropes) is preferably adjusted to, for example, 0.7 to 1.8 (particularly 0.7 to 1.5). In addition, in a toothed belt with a tooth pitch of 12.5 to 16 mm (for example, 13 to 15 mm, especially 14 mm), the final twist coefficient of the core wire formed by carbon fiber (especially the final twist coefficient of the forward twist rope or the twist coefficient of the unidirectional twist rope) is preferably adjusted to, for example, 1.4 to 2.4 (especially 1.7 to 2.4), and the initial twist coefficient of the core wire formed by carbon fiber (especially the initial twist coefficient of the forward twist rope) is preferably adjusted to, for example, 0.7 to 1.8 (especially 0.7 to 1.5).

[0222] To improve adhesion to the fourth crosslinked rubber composition, the core wire may be subjected to an adhesive treatment. For example, the adhesive treatment method may be as follows: the twisted cord is immersed in a resorcinol-formalin-latex treatment solution (RFL treatment solution), followed by heating and drying to form a uniform adhesive layer on the surface of the twisted cord. The RFL treatment solution is a mixture of an initial condensate of resorcinol and formalin mixed with latex. The latex may be, for example, chloroprene rubber, styrene-butadiene-vinyl pyridine terpolymer (VP latex), nitrile rubber, hydrogenated nitrile rubber, or the like. Alternatively, the adhesive treatment method may be a method in which the twisted cord is pretreated with an epoxy compound or isocyanate compound and then treated with the RFL treatment solution.

[0223] [Elastic modulus of toothed belt]

[0224] The toothed belt of the present invention controls the elastic modulus (modulus) by adjusting the elastic modulus, twist factor, core diameter D, core pitch P, and arrangement density of the core wires, thereby enabling the production of a toothed belt suitable for high-load transmission applications in rear-wheel drive motorcycles. Specifically, the elastic modulus of the toothed belt is significantly influenced by the elastic modulus of the arranged core wires (fibers). Therefore, in the present invention, by using specific high-elastic modulus fibers as the core wires and adjusting the arrangement density appropriately, the belt's elastic modulus is adjusted to an appropriate range suitable for such applications.

[0225] In this application, the Young's modulus of the toothed belt is set to E (N / mm 2 ), let the cross-sectional area of ​​the toothed belt be A (mm 2 ), when the tensile force applied to the toothed belt is set to F (N) and the strain (rate of change of belt length) is set to ε (dimensionless), the elastic modulus (tensile elastic modulus) of the toothed belt is defined as the value of EA[E (Young's modulus of the belt) × A (cross-sectional area of ​​the belt)] (unit: N), and is derived as EA=F / ε.

[0226] It should be noted that the tensile stress of the toothed belt is set to σ (N / mm 2 ), the relationship σ = F / A = E × ε naturally holds. However, the toothed belt of the present invention is a composite of a rubbery elastic body (a rubber composition in this embodiment) and a core (a cord in this embodiment), making it difficult to specify the cross-sectional area. Therefore, in this application, the belt elastic modulus (tensile elastic modulus) of the toothed belt of the present invention is defined as EA (N). Specifically, the belt elastic modulus (tensile elastic modulus) of the toothed belt of the present invention can be measured as the tensile elastic modulus per 1 mm using the method described in the Examples below.

[0227] The elastic modulus (tensile modulus) of the toothed belt of the present invention is, for example, 15 to 65 kN / mm, preferably 30 to 64 kN / mm, more preferably 40 to 63 kN / mm, even more preferably 45 to 62 kN / mm, and most preferably 55 to 60 kN / mm. If the elastic modulus of the toothed belt is too low, tooth skipping resistance, tension retention, and chipping resistance may be reduced when used in high-load transmission applications such as rear-wheel drive motorcycles. Conversely, if the elastic modulus is too high, bending fatigue resistance and belt installation efficiency may be reduced.

[0228] In particular, in high-load transmission applications such as rear-wheel drive motorcycles, the elastic modulus of the toothed belt is preferably adjusted according to the tooth pitch.

[0229] In a toothed belt having a tooth pitch of 6 mm or more and less than 9.5 mm (eg, 7 to 9 mm, particularly 8 mm), the elastic modulus (tensile elastic modulus) of the toothed belt is, for example, 15 to 20 kN / mm (particularly 16 to 19 kN / mm).

[0230] In addition, in a toothed belt having a tooth pitch of 9.5 mm or more and less than 12.5 mm (for example, 10 to 12 mm, particularly 11 mm), the elastic modulus (tensile elastic modulus) of the toothed belt is, for example, 42 to 60 kN / mm, preferably 42 to 50 kN / mm, and further preferably 42 to 48 kN / mm.

[0231] Furthermore, in a toothed belt having a tooth pitch of 12.5 to 16 mm (e.g., 13 to 15 mm, particularly 14 mm), the elastic modulus (tensile elastic modulus) of the toothed belt is, for example, 50 to 65 kN / mm, preferably 53 to 65 kN / mm, and more preferably 54 to 60 kN / mm.

[0232] <Method for Manufacturing Toothed Belt>

[0233] The toothed belt of the present invention can be produced, for example, by the following process (preforming process).

[0234] [First rubber layer precursor preparation step]

[0235] When the tooth portion includes a tooth cloth, first, a tooth cloth precursor forming the tooth cloth, an uncrosslinked rubber sheet forming two or more rubber layers, for example, an uncrosslinked rubber sheet forming the first rubber layer (surface rubber layer), namely a first rubber layer precursor, an uncrosslinked rubber sheet forming the second rubber layer (inner rubber layer), namely a second rubber layer precursor, and an unvulcanized rubber sheet forming the back rubber layer, namely a back rubber layer precursor, are prepared.

[0236] In particular, the first rubber layer precursor is preferably subjected to the first rubber layer precursor preparation step described below because it orients the first short fibers in a predetermined direction.

[0237] In the first rubber layer precursor preparation step, the first short fibers can be oriented (arranged) in a predetermined direction during the process of preparing an uncrosslinked rubber sheet by rolling the rubber composition kneaded using a Banbury mixer or the like using a roller or a calender. Specifically, methods for orienting the first short fibers in a predetermined direction (one direction on the sheet surface) include conventional methods, such as a method of rolling a rubber sheet by passing it between a pair of calendering rolls with a predetermined gap, thereby producing a rolled sheet in which the first short fibers are oriented in the rolling direction.

[0238] When the second rubber layer and the back rubber layer contain short fibers (particularly when the second rubber layer contains second short fibers), the short fibers can also be oriented by the same method.

[0239] [Preforming process]

[0240] Next, a tooth cloth precursor is wound around the outer circumference of a cylindrical mold having two or more grooves (concave lines) corresponding to the teeth of the toothed belt. Next, a laminate is formed around the outer circumference of the mold. The laminate is formed by sequentially winding an uncrosslinked rubber sheet (first rubber precursor) for forming the first rubber layer (surface rubber layer) and an uncrosslinked rubber sheet (second rubber layer precursor) for forming the second rubber layer (inner rubber layer), with the first short fibers of the first rubber precursor oriented in the belt length direction. The laminate is then heated to a temperature at which the rubber composition softens (e.g., approximately 70°C to 90°C) using a predetermined device. Simultaneously, pressure is applied from the outer circumference to press the rubber composition of the uncrosslinked rubber sheet and the tooth cloth precursor into the grooves (concave lines) of the cylindrical mold, forming the teeth. This results in a semi-crosslinked preform. During this press-fitting process, the teeth are formed into a layered structure: the tooth cloth is positioned on the outermost surface, extending along the tooth contour. A first rubber layer is positioned within the tooth cloth, also along the tooth contour. Furthermore, the first short fibers are aligned along the tooth contour, also oriented in the belt's longitudinal direction. Furthermore, a second rubber layer is positioned within the tooth cloth. If the teeth do not include a tooth cloth, a first rubber precursor is wound around the outer circumference of the cylindrical mold in place of the tooth cloth precursor.

[0241] It should be noted that a method for obtaining a semi-crosslinked preform can also be a method using a flat pressing die (flat die) having two or more grooves (concave lines) corresponding to the teeth, instead of a cylindrical die, and pressing the uncrosslinked rubber sheet rubber composition and the tooth cloth precursor into the grooves (concave lines) of the flat die by heating and pressing in accordance with the above steps to form the teeth. In this method, after the preform is released from the flat die, the preform is wound around a cylindrical die having two or more grooves (concave lines) corresponding to the teeth (so that the teeth fit into the grooves), and then the process proceeds to the next step.

[0242] [Cross-linking molding process]

[0243] The twisted cord constituting the core is helically wound at a predetermined pitch (a predetermined pitch in the axial direction of the cylindrical mold) around the outer circumference of the resulting preform. Furthermore, an uncrosslinked rubber sheet, i.e., a back rubber layer precursor, which will form the back rubber layer, is wound around the outer circumference to form an uncrosslinked belt forming body (uncrosslinked laminate).

[0244] Next, with the uncrosslinked belt molded body positioned around the outer periphery of the cylindrical mold, it is further coated with a rubber jacket serving as a vapor barrier. The jacketed belt molded body and the cylindrical mold are then housed within a crosslinking molding apparatus, such as a vulcanizer. Within the crosslinking molding apparatus, the belt molded body is heated and pressurized to form the desired shape. The crosslinking reaction of the uncrosslinked and semi-crosslinked rubber components within the belt molded body causes the various components to bond and solidify into a single body, forming a sleeve-shaped crosslinked molded body (crosslinked belt sleeve).

[0245] [Cutting process]

[0246] Finally, the cross-linked belt sleeve released from the cylindrical mold is cut into a predetermined width to obtain two or more toothed belts.

[0247] Example

[0248] Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to these Examples.

[0249] [Rubber composition]

[0250]

[0251]

[0252] [Materials used in the rubber composition]

[0253] HNBR: "Zetpol 2010" manufactured by Zeon Co., Ltd. of Japan, iodine value 11mg / 100mg

[0254] HNBR containing an unsaturated carboxylic acid metal salt: Zeoforte ZSC2295CX manufactured by Zeon Co., Ltd., base HNBR: unsaturated carboxylic acid metal salt (mass ratio) = 100:110, iodine value of base HNBR 28 mg / 100 mg

[0255] Nylon staple fiber: "Leona" manufactured by Asahi Kasei Corporation, polyamide 66, average fiber length 3 mm, average fiber diameter 27 μm

[0256] Aramid staple fiber 1: "Conex" manufactured by Teijin Limited, average fiber length 3 mm, average fiber diameter 14 μm

[0257] Aramid staple fiber 2: "Towaron (registered trademark)" manufactured by Teijin Limited, average fiber length 3 mm, average fiber diameter 12 μm

[0258] PBO staple fibers: "Sailon" manufactured by Toyobo Co., Ltd., average fiber length 3 mm, average fiber diameter 12 μm

[0259] Stearic acid: "Stamanic acid つばき" manufactured by NOF Co., Ltd.

[0260] Carbon black SRF: "Steel S" manufactured by Tokai Carbon Co., Ltd., average particle size 66 nm, iodine adsorption 26 mg / g

[0261] Silica: "Ultrasil VN-3" manufactured by Evonik Degussa Japan Co., Ltd., with a specific surface area of ​​155 to 195 m 2 / g

[0262] Calcium carbonate: "Super #1500" manufactured by Maruo Calcium Co., Ltd., average particle size 1.5 μm

[0263] Zinc oxide: "Zinc oxide type 2" manufactured by Sakai Chemical Industry Co., Ltd., average particle size 0.55 μm

[0264] Anti-aging agent: p,p'-dioctyldiphenylamine, "Noncondiphenylamine OD3" manufactured by Seiko Chemical Co., Ltd.

[0265] Organic peroxide: 1,3-bis(tert-butylperoxyisopropyl)benzene, theoretical active oxygen content 9.45%

[0266] Co-crosslinking agent: N,N'-m-phenylene bismaleimide, "Valnock PM" manufactured by Ouchi Shinko Chemical Co., Ltd.

[0267] Plasticizer: "ADK CIZER RS700" manufactured by ADEKA Corporation.

[0268] [Core Wire]

[0269] In Examples 1 to 33 and Comparative Examples 1 to 10, a 12K multifilament yarn ["Toreka T700SC-12000" manufactured by Toray Industries, Ltd., single yarn fineness 0.67 dtex, total fineness 800 tex] is used to form a unidirectionally twisted carbon fiber rope (12K-1 / 0, tensile elastic modulus 230 GPa), which is adhesively treated with an HNBR-based coating agent to obtain a core wire with a core wire diameter of 1.1 mm.

[0270] In Examples 34 to 75 and Comparative Examples 11 to 13, various carbon fiber ropes shown in Tables 13 to 16 and 18 to 20 were produced using the above-mentioned 12K multifilament yarn or 6K multifilament yarn, and adhesive treatment was performed using an HNBR-based coating agent to obtain various core wires.

[0271] [Tooth cloth and tooth cloth handling]

[0272] The woven fabrics shown in Table 4 were dipped in RFL treatment liquids and rubber cement to produce tooth cloth precursors. Specifically, the RFL treatment was performed using the two RFL treatment liquids (RFL1 and RFL2) shown in Table 5, with the dip treatment performed in the order of RFL1 and RFL2. Furthermore, the rubber cement treatment was also performed using the two rubber cements (Rubber Cement 1 and Rubber Cement 2) shown in Table 6, with the dip treatment performed in the order of Rubber Cement 1 and Rubber Cement 2.

[0273] [Table 4]

[0274]

[0275] *1: PTFE fiber [Toyoflon 1330 pttex, manufactured by Toray Industries, Inc.]

[0276] *2: Polyester fiber [Unitika Co., Ltd., "Cornetta," a core-sheath composite fiber with a core melting point of 256°C and a sheath melting point of 160°C]

[0277] [Table 5]

[0278]

[0279] [Table 6]

[0280]

[0281] [Production of uncrosslinked rubber sheets]

[0282] The uncrosslinked rubber sheets used to form the teeth and back (back rubber layer) were prepared by mixing the rubber compositions listed in Tables 2 and 3 using a Banbury mixer. The resulting mixed rubber was then rolled to a specified thickness using calendering rollers to produce the uncrosslinked rubber sheets. The short fibers contained in the uncrosslinked rubber sheets were oriented in the rolling direction. In this application, the rubber compositions are designated R1 to R30.

[0283] [Hardness (Type D)]

[0284] Uncrosslinked rubber sheets were pressed and heated at 165°C for 30 minutes to produce crosslinked rubber sheets (100 mm x 100 mm x 2 mm thick). A laminate of three crosslinked rubber sheets was used as a sample, and the hardness (Type D) of the crosslinked rubber sheets was measured using a Type D durometer in accordance with the spring durometer hardness test specified in JIS K 6253 (2012) (Rubber, vulcanized and thermoplastic - Determination of hardness).

[0285] [Tensile strength]

[0286] The uncrosslinked rubber sheet was pressed and heated at a temperature of 165°C for 30 minutes to produce a crosslinked rubber sheet (100mm×100mm×2mm thickness). According to JIS K 6251 (2017), a test piece punched into a dumbbell shape (No. 5 shape) was made. In the sample containing short fibers, the dumbbell-shaped test piece was cut in such a way that the arrangement direction of the short fibers (the direction parallel to the texture) became the tensile direction. Then, the two ends of the test piece were clamped with a chuck (clamp), and the test piece was stretched at a speed of 50mm / min until it was cut. The value obtained by dividing the maximum tensile force recorded at this time by the initial cross-sectional area of ​​the test piece (tensile strength T) was used as the tensile strength. The tensile strength of each rubber composition is shown in Tables 2 and 3.

[0287] [Tensile elastic modulus]

[0288] By the same method as the above-mentioned tensile strength, a dumbbell-shaped test piece (shape 5) according to JIS K 6251 (2017) was prepared. In the sample containing short fibers, the dumbbell-shaped test piece was cut in such a way that the perpendicular direction (texture perpendicular direction) relative to the arrangement direction (texture parallel direction) of the short fibers became the tensile direction. Then, the two ends of the test piece were clamped with a chuck (clamp), and the test piece was stretched at a speed of 50 mm / min. The tensile force at the specified elongation (2%) was divided by the initial cross-sectional area of ​​the test piece (tensile stress at 2% elongation) as the tensile modulus (modulus). The tensile modulus of each rubber composition is shown in Tables 2 and 3.

[0289] <Examples 1 to 33 and Comparative Examples 1 to 10>

[0290] [Manufacturing of toothed belts]

[0291] In Examples 1 to 33 and Comparative Examples 1 to 10, as shown below, a toothed belt having a total thickness of 5.6 mm, a tooth profile of G8M, a tooth height (including tooth cloth) of 3.5 mm, a tooth pitch of 8 mm, a number of teeth of 140, a circumference of 1120 mm, and a width of 12 mm was produced using the preforming process described in this embodiment.

[0292] Tables 8 to 12 show the configuration (layer structure) of the toothed belts produced in Examples 1 to 33 and Comparative Examples 1 to 10, and the rubber compositions used in the respective rubber layers.

[0293] (Comparative Example 1)

[0294] A tooth cloth precursor to form the tooth cloth, an uncrosslinked rubber sheet (R3, sheet thickness 0.70 mm) to form the first rubber layer, and an uncrosslinked rubber sheet (R2, sheet thickness 1.00 mm) to form the second rubber layer were sequentially stacked on a pressing mold (flat mold) having two or more grooves (concave strips) corresponding to the teeth of the toothed belt. The layers were pressed at a temperature of 90°C and a pressing pressure (surface pressure) of 20.2 MPa for 160 seconds to produce a semi-crosslinked preform.

[0295] Next, a preform is wound around a cylindrical mold with two or more grooves (recessed lines) corresponding to the teeth (so that the teeth fit into the grooves). A twisted cord forming the core is spirally wound around the outer circumference of the preform (tension: 150-250 N / strand, pitch: 1.25 mm, winding speed: 1.5 m / s). Furthermore, an uncrosslinked rubber sheet (R30, sheet thickness 0.90 mm) forming the back rubber layer is wound around the outer circumference to form an uncrosslinked belt mold (uncrosslinked laminate). The uncrosslinked rubber sheet is wound so that the short fibers contained in the sheet are oriented in the longitudinal direction of the belt.

[0296] Next, cross-linking molding was performed using a vulcanizer at a heating temperature of 179° C. and a steam pressure of 0.83 MPa for 40 minutes to produce a cross-linked molded body (cross-linked belt sleeve).

[0297] Finally, the cross-linked belt sleeve released from the cylindrical mold was cut into a width of 12 mm to obtain a toothed belt.

[0298] (Comparative Examples 2 to 5)

[0299] Toothed belts were produced in the same manner as in Comparative Example 1 except that R4 was used in Comparative Example 2, R5 was used in Comparative Example 3, R6 was used in Comparative Example 4, and R7 was used in Comparative Example 5 as the uncrosslinked rubber sheet forming the first rubber layer.

[0300] (Examples 1 to 6)

[0301] A toothed belt was produced in the same manner as in Comparative Example 1, except that R8 was used in Example 1, R9 was used in Example 2, R10 was used in Example 3, R11 was used in Example 4, R12 was used in Example 5, and R13 was used in Example 6 as the uncrosslinked rubber sheet forming the first rubber layer.

[0302] (Comparative Example 6)

[0303] A toothed belt was produced by the same method as in Comparative Example 1 except that the uncrosslinked rubber sheet forming the teeth was only R2 (sheet thickness 1.70 mm).

[0304] (Comparative Example 7)

[0305] A toothed belt was produced by the same method as in Comparative Example 1 except that the uncrosslinked rubber sheet forming the teeth was only R10 (sheet thickness 1.70 mm).

[0306] (Comparative Example 8)

[0307] A toothed belt was produced in the same manner as in Example 3 except that the uncrosslinked rubber sheet forming the first rubber layer was R2 (sheet thickness 0.85 mm) and the uncrosslinked rubber sheet forming the second rubber layer was R10 (sheet thickness 0.85 mm).

[0308] (Example 7)

[0309] A toothed belt was produced in the same manner as in Example 3 except that the thickness of the uncrosslinked rubber sheet forming the first rubber layer was 0.20 mm and the thickness of the uncrosslinked rubber sheet forming the second rubber layer was 1.50 mm.

[0310] (Example 8)

[0311] A toothed belt was produced in the same manner as in Example 3 except that the thickness of the uncrosslinked rubber sheet forming the first rubber layer was 0.35 mm and the thickness of the uncrosslinked rubber sheet forming the second rubber layer was 1.35 mm.

[0312] (Example 9)

[0313] A toothed belt was produced in the same manner as in Example 3 except that the thickness of the uncrosslinked rubber sheet forming the first rubber layer was 1.00 mm and the thickness of the uncrosslinked rubber sheet forming the second rubber layer was 0.70 mm.

[0314] (Example 10)

[0315] A toothed belt was produced in the same manner as in Example 3 except that the thickness of the uncrosslinked rubber sheet forming the first rubber layer was 1.35 mm and the thickness of the uncrosslinked rubber sheet forming the second rubber layer was 0.35 mm.

[0316] (Examples 11 to 15)

[0317] Toothed belts were produced in the same manner as in Example 3 except that R14 was used in Example 11, R15 was used in Example 12, R16 was used in Example 13, R17 was used in Example 14, and R18 was used in Example 15 as the uncrosslinked rubber sheet forming the first rubber layer.

[0318] (Examples 16 to 21)

[0319] A toothed belt was produced by the same method as in Example 3 except that R20 was used in Example 16, R21 was used in Example 17, R22 was used in Example 18, R23 was used in Example 19, R24 was used in Example 20, and R25 was used in Example 21 as the uncrosslinked rubber sheet forming the first rubber layer.

[0320] (Example 22)

[0321] A toothed belt was produced in the same manner as in Example 3 except that the uncrosslinked rubber sheet forming the first rubber layer was R14 (sheet thickness 0.20 mm) and the uncrosslinked rubber sheet forming the second rubber layer was R2 (sheet thickness 1.50 mm).

[0322] (Example 23)

[0323] A toothed belt was produced in the same manner as in Example 3 except that the uncrosslinked rubber sheet forming the first rubber layer was R17 (sheet thickness 1.00 mm) and the uncrosslinked rubber sheet forming the second rubber layer was R2 (sheet thickness 0.70 mm).

[0324] (Example 24)

[0325] A toothed belt was produced in the same manner as in Example 3 except that the uncrosslinked rubber sheet forming the first rubber layer was R17 (sheet thickness 1.35 mm) and the uncrosslinked rubber sheet forming the second rubber layer was R2 (sheet thickness 0.35 mm).

[0326] (Examples 25 to 27, Comparative Example 9)

[0327] Toothed belts were produced in the same manner as in Example 3 except that R1 was used in Example 25, R4 was used in Example 26, R5 was used in Example 27, and R7 was used in Comparative Example 9 as the uncrosslinked rubber sheet forming the second rubber layer.

[0328] (Examples 28-29)

[0329] A toothed belt was produced by the same method as in Example 25 except that R8 was used in Example 28 and R13 was used in Example 29 as the uncrosslinked rubber sheet forming the first rubber layer.

[0330] (Example 30, Comparative Example 10)

[0331] A toothed belt was produced by the same method as in Comparative Example 9 except that the uncrosslinked rubber sheet forming the first rubber layer was R8 in Comparative Example 10 and R13 in Example 30.

[0332] (Example 31)

[0333] A toothed belt was produced by the same method as in Example 3 except that the uncrosslinked rubber sheet forming the first rubber layer was designated as R27 and the uncrosslinked rubber sheet forming the second rubber layer was designated as R26.

[0334] (Examples 32 and 33)

[0335] In Examples 32 and 33, toothed belts were produced by the same methods as in Examples 3 and 14, except that a preform was produced without using a tooth cloth precursor for forming the tooth cloth. These toothed belts had no tooth cloth provided on the surfaces of the teeth or tooth bottoms of the belts and had a tooth height of 3.5 mm (excluding the tooth cloth).

[0336] [Bending rigidity test]

[0337] (Bending rigidity test conditions)

[0338] The bending stiffness E of the toothed belt was determined by a bending test using an Olsen bending tester in accordance with JIS K 7106 (1995). r The obtained Er is multiplied by the secondary moment of cross section I of the toothed belt calculated by the following formula (1): r The bending rigidity E of the toothed belt is calculated by the following formula (2): r I r . Here, the dimensions of the toothed belt test piece are set to length: 80 mm, width: 12 mm, back thickness: 2.1 mm, the distance S between the pillars is set to 25.4 mm, and the oscillator moment M at 100% of the load scale is set to 0.343 N·m. In addition, the test is carried out under the conditions of temperature 23±2°C and humidity 65±5%. The smaller the value of bending rigidity, the better the bending (flexibility). The following shows the judgment criteria for bending rigidity.

[0339] I r =b×h 3 / 12 (1)

[0340] [Wherein, I r Indicates the secondary moment of area of ​​the test piece (mm 4 ), b represents the width of the test piece (mm), and h represents the thickness of the back of the test piece (mm)]

[0341] E r I r =[(S×M) / 300]×[N / (D×0.01745)] (2)

[0342] [Where, E r Indicates the bending stiffness of the test piece (N / mm 2), Ir represents the secondary moment of cross section of the test piece (mm 4 ), S represents the distance between the fulcrums (mm), M represents the oscillator moment (N·m), D represents the bending angle (degrees) (1 degree = π / 180 = 0.01745 radians), and N represents the load scale reading corresponding to the bending angle (degrees) (%)]

[0343] (Bending rigidity criteria)

[0344] a: Bending rigidity less than 700MPa (qualified)

[0345] b: Flexural rigidity is 700 MPa or more and less than 800 MPa (qualified)

[0346] c: Flexural rigidity is 800 MPa or more (unacceptable).

[0347] Tables 8 to 12 show the test results of the toothed belts of Examples 1 to 33 and Comparative Examples 1 to 10.

[0348] [Tooth rigidity test]

[0349] (Tooth rigidity test conditions)

[0350] like Figure 7 As shown, the teeth of the toothed belt 1 are hung on the protrusion 21a of a tooth shearing jig (a rigid body shaped like the teeth of a toothed pulley) 21. While pressing each tooth with a constant pressure (0.98 cN·m of tightening torque per 1 mm of width), the tooth load per 12 mm of width relative to displacement when stretched at a rate of 1 mm / min using a universal testing machine is defined as the tooth rigidity (tooth rigidity) and evaluated. The tooth load relative to displacement is the value obtained after the third cycle of numerical stability, as shown in the figure. Figure 8 The values ​​are obtained by linear approximation in the tooth load range of 50 to 400 N. A larger value of tooth rigidity indicates better rigidity (deformation resistance) of the tooth portion. The following is a criterion for determining tooth rigidity.

[0351] (Criteria for determining tooth rigidity)

[0352] a: Tooth rigidity is 1300N / mm or more (qualified)

[0353] b: Tooth rigidity is 1100N / mm or more and less than 1300N / mm (qualified)

[0354] c: Tooth rigidity is less than 1100N / mm (unqualified)

[0355] Tables 8 to 12 show the test results of the toothed belts of Examples 1 to 33 and Comparative Examples 1 to 10.

[0356] [Tooth skipping test]

[0357] (Running test conditions)

[0358] Using a biaxial torque tester, a toothed belt was wound between a drive pulley (number of teeth: 22) and a driven pulley (number of teeth: 22). The interaxial distance between the pulleys was adjusted to maintain a belt tension of 230 N. The drive pulley was then rotated at 1800 rpm to move the belt forward while the load on the driven pulley was continuously increased. The load torque applied to the driven pulley when tooth skipping (tooth slippage) occurred was measured as the tooth skipping torque. The tooth skipping torque value is used as an indicator of tooth skipping resistance; higher tooth skipping torque values ​​indicate a higher toothed belt resistance to tooth slippage.

[0359] Note that the values ​​for the tooth skipping torque are calculated relative to those of Comparative Example 2, which has a low ratio of short fibers in the first rubber layer (2 parts by mass) and exhibits the best endurance among the comparative examples (112 N·m), as 1.00. A value of 1.00 or less indicates no reinforcement effect relative to the toothed belt of Comparative Example 2. A value exceeding 1.00 indicates an improvement in tooth rigidity (deformation resistance) due to the reinforcement effect. A higher value indicates a greater degree of reinforcement.

[0360] (Criteria for tooth skipping test)

[0361] a: Tooth skipping torque exceeds 1.00 (qualified)

[0362] b: Tooth skipping torque is 1.00 (qualified)

[0363] c: Tooth skipping torque is 0.95 or more and less than 1.00 (qualified)

[0364] d: Tooth skipping torque is less than 0.95 (unqualified).

[0365] [Durability running test]

[0366] (Running test conditions)

[0367] A toothed belt was installed on a biaxial running tester equipped with a drive pulley (number of teeth: 22) and a driven pulley (number of teeth: 22). The running life was measured as the time the belt ran until failure (tooth failure) occurred. The toothed belt installation tension was set to 230N, the drive pulley speed was set to 1800rpm, the driven pulley load was set to 9.0kW, and the ambient temperature was 25°C (room temperature).

[0368] Note that the running time until failure (hereinafter referred to as running time) is calculated as a relative value, assuming that the running time (159 hours) of Comparative Example 2, which has a low ratio of short fibers (2 parts by mass) in the first rubber layer and exhibits the best durable running performance among the comparative examples, is set to 1.00. A value of 1.00 or less indicates no reinforcement effect relative to the toothed belt of Comparative Example 2. A value exceeding 1.00 indicates improved durable running performance due to the reinforcement effect. It can be said that a larger value indicates a greater degree of reinforcement effect.

[0369] (Judgment criteria for the endurance running test)

[0370] a: The travel time until failure is 1.25 or more (with enhanced effect)

[0371] b: The travel time until failure is greater than 1.10 and less than 1.25 (with enhanced effect)

[0372] c: The travel time until failure is greater than 1.00 and less than 1.10 (with an enhancement effect)

[0373] d: The travel time until failure is less than 1.00 (no enhancement effect).

[0374] [Comprehensive judgment]

[0375] Comprehensive evaluation was performed based on the criteria shown in Table 7, taking into account the levels of enhancement effects on both the tooth skipping torque and the durable running performance relative to Comparative Example 2 serving as a reference.

[0376] [Table 7]

[0377]

[0378] The test results of the toothed belts of Examples 1 to 33 and Comparative Examples 1 to 10 are shown in Tables 8 to 12. Figure 9 2 and 3 show cross-sectional views of the tooth portions of the toothed belts in Examples 3, 8, and 9 and Comparative Examples 6 to 8.

[0379]

[0380] [Table 9]

[0381]

[0382]

[0383] [Table 11]

[0384]

[0385]

[0386] (Comparative Examples 1 to 5)

[0387] Comparative Example 1 is a toothed belt with a two-layer structure consisting of a first rubber layer (surface rubber layer) positioned on the surface side of the teeth along the tooth contour, and a second rubber layer (inner rubber layer) positioned within the teeth. The first rubber layer is made of R3 (cross-linked rubber) with a tensile modulus of 6.0 MPa, and the second rubber layer is made of R2 (cross-linked rubber) with a tensile modulus of 3.8 MPa. The ratio of the tensile modulus of the first rubber layer to the tensile modulus of the second rubber layer is 1.6. This ratio (tensile modulus of the first rubber layer / tensile modulus of the second rubber layer) is hereinafter referred to as the "tensile modulus ratio of the two layers."

[0388] Comparative Examples 2 to 5 are examples in which the tensile modulus is increased by increasing the amount of the first co-crosslinking agent in the first rubber layer of Comparative Example 1. As the amount increases, the tensile modulus increases to 9.4 MPa in Comparative Example 2, to 10.9 MPa in Comparative Example 3, to 13.7 MPa in Comparative Example 4, and to 16.8 MPa in Comparative Example 5.

[0389] As a result, the bending rigidity was 602N / mm (Comparative Example 1: a judgment), 652N / mm (Comparative Example 2: a judgment), 660N / mm (Comparative Example 3: a judgment), 676N / mm (Comparative Example 4: a judgment), and 724N / mm (Comparative Example 5: b judgment), all of which were qualified levels.

[0390] In addition, the tooth rigidity is 1185MPa (Comparative Example 1: b judgment), 1362MPa (Comparative Example 2: a judgment), 1410MPa (Comparative Example 3: a judgment), 1454MPa (Comparative Example 4: a judgment), and 1527MPa (Comparative Example 5: a judgment), which are all qualified levels.

[0391] In addition, regarding dynamic performance, the tooth skipping torque (relative value) was 0.95 (Comparison Example 1: judgment c), 1.00 (Comparison Example 2: judgment b), 1.03 (Comparison Example 3: judgment a), 1.06 (Comparison Example 4: judgment a), and 1.07 (Comparison Example 5: judgment a), all of which were acceptable levels. Following the same trend as tooth rigidity, it increased as the tensile modulus of the first rubber layer increased.

[0392] However, the endurance running (running time until failure (relative value)) was 0.53 (Comparative Example 1: d determination), 1.00 (Comparative Example 2: d determination), 0.80 (Comparative Example 3: d determination), 0.86 (Comparative Example 4: d determination), and 0.69 (Comparative Example 5: d determination), resulting in an overall unacceptable rating (D grade). It is presumed that in these cases, microcracks generated by long-term running grew, causing tooth chipping.

[0393] (Examples 1 to 6)

[0394] Example 1 is an example in which the co-crosslinking agent content in the first rubber layer of Comparative Example 1 is reduced to 1 part by mass (the same amount as in the second rubber layer), but the amount of the first short fibers is increased to 20 parts by mass. Specifically, the first rubber layer is formed from R8 (crosslinked rubber) with a tensile modulus of 5.3 MPa, and the second rubber layer is formed from R2 (crosslinked rubber) with a tensile modulus of 3.8 MPa. The ratio of the tensile moduli of the two layers is 1.4.

[0395] Regarding dynamic performance, it is at the same level as Comparative Example 1, where the tooth skipping torque (relative value) is 0.95 (c judgment), but compared with Comparative Example 1, where the endurance running (running time until failure (relative value)) is 0.53 (c judgment), the endurance running (running time until failure (relative value)) is improved to 1.43 (a judgment), and the overall judgment is qualified (C grade).

[0396] Example 2 is an example in which the amount of first short fibers in the first rubber layer of Comparative Example 1 is increased to 20 parts by mass while maintaining the co-crosslinking agent content at the same level (3 parts by mass). Specifically, the first rubber layer is formed from R9 (crosslinked rubber) having a tensile elastic modulus of 9.0 MPa, and the second rubber layer is formed from R2 (crosslinked rubber) having a tensile elastic modulus of 3.8 MPa. The ratio of the tensile elastic moduli of the two layers is 2.4.

[0397] Example 3 is an example in which the amount of first short fibers in the first rubber layer of Comparative Example 2 is increased to 20 parts by mass while maintaining the co-crosslinking agent content at the same level (6 parts by mass). Specifically, the first rubber layer is formed from R10 (crosslinked rubber) having a tensile elastic modulus of 14 MPa, and the second rubber layer is formed from R2 (crosslinked rubber) having a tensile elastic modulus of 3.8 MPa. The ratio of the tensile elastic moduli of the two layers is 3.7.

[0398] Example 4 is an example in which the amount of first short fibers in the first rubber layer of Comparative Example 3 is increased to 20 parts by mass while maintaining the co-crosslinking agent content at the same level (8 parts by mass). Specifically, the first rubber layer is formed from R11 (crosslinked rubber) having a tensile elastic modulus of 14.3 MPa, and the second rubber layer is formed from R2 (crosslinked rubber) having a tensile elastic modulus of 3.8 MPa. The ratio of the tensile elastic moduli of the two layers is 3.8.

[0399] Example 5 is an example in which the amount of first short fibers in the first rubber layer of Comparative Example 4 is increased to 20 parts by mass while maintaining the co-crosslinking agent content at the same level (11 parts by mass). Specifically, the first rubber layer is formed from R12 (crosslinked rubber) having a tensile elastic modulus of 19.2 MPa, and the second rubber layer is formed from R2 (crosslinked rubber) having a tensile elastic modulus of 3.8 MPa. The ratio of the tensile elastic moduli of the two layers is 5.1.

[0400] Example 6 is an example in which the amount of first short fibers in the first rubber layer of Comparative Example 5 is increased to 20 parts by mass while maintaining the content of the first co-crosslinking agent at the same level (14 parts by mass). Specifically, the first rubber layer is formed from R13 (crosslinked rubber) having a tensile elastic modulus of 23.5 MPa, and the second rubber layer is formed from R2 (crosslinked rubber) having a tensile elastic modulus of 3.8 MPa. The ratio of the tensile elastic moduli of the two layers is 6.2.

[0401] Regarding Examples 2 to 6, when compared with the corresponding comparative examples (comparisons in which the content of the first co-crosslinking agent is the same and the amount of the first short fiber is increased), in any comparison, the tooth skipping torque (relative value) is equal to or higher than that of the comparative example, and is judged as a. In the endurance running (running time until failure (relative value)), compared with the comparative example which is at the unqualified level, it is improved to 1.64 (Example 2; a judgment), 2.08 (Example 3; a judgment), 1.50 (Example 4; a judgment), 1.55 (Example 5; a judgment), and 1.54 (Example 6; a judgment), and the overall judgment is qualified (A grade).

[0402] In particular, Example 3 (R10, 6 parts by mass of the first co-crosslinking agent) achieved excellent results in both tooth skipping torque and endurance running. Even increasing the amount of the first co-crosslinking agent further showed no improvement in running life. These results confirm that increasing the amount of the first short fiber is effective in improving durability (extending life).

[0403] (Comparative Examples 6 to 8)

[0404] Comparative Example 6 is a toothed belt in which the entire rubber layer forming the teeth is composed solely of R2 (cross-linked rubber) with a tensile modulus of 3.8 MPa (relatively low modulus) forming the second rubber layer of Examples 1 to 6. While the flexural rigidity was 553 MPa (a rating), which was better than the examples, the tooth rigidity was 1092 N / mm (c rating), failing. Regarding dynamic performance, the tooth skipping torque (relative value) was 0.90 (d rating), and the endurance running (running time until failure (relative value)) was also 0.33 (d rating), resulting in an overall failure (D grade).

[0405] Comparative Example 7 is a toothed belt in which the entire rubber layer forming the teeth is composed solely of R10 (cross-linked rubber) with a tensile modulus of 14 MPa (relatively high modulus) that formed the first rubber layer of Example 3. While the tooth rigidity was 1750 N / mm (a rating), which was better than the example, the bending rigidity was 825 MPa (c rating), failing. Regarding dynamic performance, the tooth skipping torque (relative value) was 1.35 (a rating), but the endurance running (running time until failure (relative value)) was 0.43 (d rating), resulting in an overall failure rating (D grade).

[0406] Comparative Example 8 is an example in which the tooth portion has a two-layer structure consisting of a first rubber layer and a second rubber layer, similar to the example, but with the elastic moduli of the first and second rubber layers reversed. Specifically, the first rubber layer uses R2 (cross-linked rubber) with a tensile modulus of 3.8 MPa (relatively low elastic modulus), while the second rubber layer uses R10 (cross-linked rubber) with a tensile modulus of 14 MPa (relatively high elastic modulus). It should be noted that in the cross-sectional view of the tooth portion, the proportion of the first rubber layer relative to the area of ​​all rubber layers constituting the tooth portion is set to 50%. The result is a tooth rigidity of 1275 N / mm (b evaluation), which is acceptable, but a bending rigidity of 820 MPa (c evaluation), which is unacceptable. Regarding dynamic performance, the tooth skipping torque (relative value) is 1.07 (a evaluation), but the endurance running (running time until failure (relative value)) is 0.75 (d evaluation), resulting in an overall unacceptable rating (D grade).

[0407] If the entire tooth portion is formed from a rubber layer with a low elastic modulus, as in Comparative Example 6, the tooth portion's rigidity (deformation resistance) is insufficient. If the entire tooth portion is formed from a rubber layer with a high elastic modulus, as in Comparative Example 7, the tooth portion's bendability (low bending rigidity) is insufficient. Furthermore, if the tooth portion is formed from a two-layered rubber layer, as in Comparative Example 8, but the inner portion is formed from a rubber layer with a higher elastic modulus than the outer portion, not only is the bendability (low bending rigidity) insufficient, but the tooth portion's rigidity (deformation resistance) is also reduced. Furthermore, the absence of a first rubber layer with the specified amount of short fiber orientation results in low durability.

[0408] In contrast, the method of this embodiment is a method that obtains a tooth portion with rigidity (high elastic modulus) that can withstand use under conditions with higher loads, and is able to balance the rigidity (deformation resistance) and bending properties (low bending rigidity: softness) of the tooth portion that is in an inverse relationship, and also has excellent durability.

[0409] (Examples 7 to 10)

[0410] Compared to the toothed belt of Example 3, in which the first rubber layer is formed of R10 (cross-linked rubber) having a tensile elastic modulus of 14 MPa and the second rubber layer is formed of R2 (cross-linked rubber) having a tensile elastic modulus of 3.8 MPa, Examples 7 to 10 are examples of toothed belts in which the ratio of the area occupied by the first rubber layer relative to the area of ​​all rubber layers constituting the tooth portion in a cross-sectional view of the tooth portion is set to a variable ratio.

[0411] In Examples 7 to 10 and Example 3, the ratio of the area occupied by the first rubber layer relative to the area of ​​all rubber layers constituting the tooth portion in a cross-sectional view of the tooth portion was set to 10% (Example 7), 20% (Example 8), 40% (Example 3), 60% (Example 9), and 80% (Example 10).

[0412] As a result, the tooth rigidity was 1275 N / mm (Example 7: judgment b), 1347 N / mm (Example 8: judgment a), 1442 N / mm (Example 3: judgment a), 1527 N / mm (Example 9: judgment a), and 1561 N / mm (Example 10: judgment a), all of which were acceptable levels. The rigidity increased as the area ratio of the first rubber layer increased.

[0413] On the other hand, the flexural rigidity was 601 MPa (Example 7: judgment a), 633 MPa (Example 8: judgment a), 671 MPa (Example 3: judgment a), 692 MPa (Example 9: judgment a), and 743 MPa (Example 10: judgment b), all of which were acceptable levels, and increased as the area ratio of the first rubber layer increased.

[0414] In addition, regarding dynamic performance, the tooth skipping torque (relative value) was 1.00 (Example 7: judgment b), 1.10 (Example 8: judgment a), 1.11 (Example 3: judgment a), 1.26 (Example 9: judgment a), and 1.31 (Example 10: judgment a), all of which were acceptable levels. Following the same trend as tooth rigidity, it increased as the proportion of the area of ​​the first rubber layer increased.

[0415] In addition, the endurance running (running time until failure (relative value)) was 1.41 (Example 7: a judgment), 1.82 (Example 8: a judgment), 2.08 (Example 3: a judgment), 1.69 (Example 9: a judgment), and 1.07 (Example 10: c judgment), all of which were qualified levels, and increased particularly when the proportion of the area of ​​the first rubber layer was within the range of 20% to 60%.

[0416] According to the above comprehensive evaluation, the toothed belts of Examples 7 to 10 were of acceptable quality (grades A to C).

[0417] (Examples 11 to 15)

[0418] Compared to the structure of Example 3 (20 parts by mass of first short fibers, 6 parts by mass of first co-crosslinking agent, and 40% of the area occupied by the first rubber layer relative to the total area of ​​the rubber layers constituting the tooth portion in the cross-sectional view of the tooth portion) which has the best durable running performance among Examples 1 to 6, Examples 11 to 15 are examples of toothed belts using a rubber composition in which the first short fibers contained in the first rubber layer are set as variables. The first rubber layer was formed using R14 (5 parts by mass of short fibers, tensile modulus of 10.8 MPa) in Example 11, R15 (10 parts by mass of short fibers, tensile modulus of 12.6 MPa) in Example 12, R10 (20 parts by mass of short fibers, tensile modulus of 14 MPa) in Example 3, R16 (30 parts by mass of short fibers, tensile modulus of 13.7 MPa) in Example 13, R17 (50 parts by mass of short fibers, tensile modulus of 14.0 MPa) in Example 14, and R18 (60 parts by mass of short fibers, tensile modulus of 13.9 MPa) in Example 15. The rubber composition of R19 (65 parts by mass of short fibers) could not be kneaded, and therefore could not be used to produce a toothed belt.

[0419] As a result, the tooth rigidity was 1271N / mm (Example 11: b judgment), 1367N / mm (Example 12: a judgment), 1442N / mm (Example 3: a judgment), 1430N / mm (Example 13: a judgment), 1432N / mm (Example 14: a judgment), and 1425N / mm (Example 15: a judgment), all of which were qualified levels.

[0420] On the other hand, the flexural rigidity was 648 MPa (Example 11: judgment a), 662 MPa (Example 12: judgment a), 671 MPa (Example 3: judgment a), 687 MPa (Example 13: judgment a), 706 MPa (Example 14: judgment b), and 713 MPa (Example 15: judgment b), increasing as the elastic modulus of the first rubber layer increased.

[0421] In addition, regarding dynamic performance, the tooth skipping torque (relative value) is 1.03 (Example 11: a judgment), 1.05 (Example 12: a judgment), 1.11 (Example 3: a judgment), 1.07 (Example 13: a judgment), 1.07 (Example 14: a judgment), and 1.06 (Example 15: a judgment), all of which are qualified levels, showing the same tendency as tooth rigidity.

[0422] On the other hand, the endurance running (running time until failure (relative value)) was 1.24 (Example 11: b judgment), 1.86 (Example 12: a judgment), 2.08 (Example 3: a judgment), 1.30 (Example 13: a judgment), 1.25 (Example 14: a judgment), and 1.21 (Example 15: b judgment), all of which were qualified levels.

[0423] According to the above comprehensive judgment, the toothed belts of Examples 3 and 11 to 15 showed an enhancement effect in both tooth skipping torque and durable running performance, and in this respect, they were highly qualified (A or B grade). In particular, in Example 12 (10 parts by mass of short fibers, 12.6 MPa tensile elastic modulus) and Example 3 (20 parts by mass of short fibers, 14.0 MPa tensile elastic modulus), the tooth skipping torque was excellent, and the effect of durable running performance (extended life) was large. In Example 3 in particular, the tensile strength of the rubber composition (R10) was significantly large, which can be said to be a method with a large enhancement effect. On the other hand, in Examples 13 to 15 in which the amount of the first short fibers was further increased, the effect of extended life as in Examples 12 and 3 did not appear. Therefore, as the enhancement effect brought about by the first short fibers, the content of about 10 parts by mass to about 30 parts by mass, with a peak of about 20 parts by mass, can be said to be a particularly preferred range.

[0424] Based on the above results, the physical properties of the first rubber layer can be appropriately determined to have a tensile modulus in the belt width (cross-grain) direction of 4 to 25 MPa (particularly 10 to 15 MPa). Furthermore, the proportion of short fibers in the first rubber layer can be appropriately determined to be 5 to 60 parts by mass (particularly 10 to 30 parts by mass).

[0425] (Example 16)

[0426] Compared to the configuration of Example 1 (R8: 20 parts by mass of first short fibers, 1 part by mass of first co-crosslinking agent), Example 16 is an example of a toothed belt in which the amount of first short fibers contained in the first rubber layer is reduced to 10 parts by mass. Example 16 examines the influence of the first short fibers and first co-crosslinking agent contents on the elastic modulus (reinforcement) of the first rubber layer at a level near the lower limit of the reinforcing effect. Specifically, the first rubber layer is formed from R20 (crosslinked rubber) with a tensile modulus of 4.3 MPa, and the second rubber layer is formed from R2 (crosslinked rubber) with a tensile modulus of 3.8 MPa. The ratio of the tensile moduli of the two layers is 1.1. Regarding dynamic performance, while it is comparable to Comparative Example 1, with a tooth skipping torque (relative value) of 0.95 (c judgment), the endurance running (running time until failure (relative value)) reaches an acceptable level of 1.24 (b judgment), resulting in an overall acceptable rating (C grade), confirming the reinforcing effect.

[0427] (Examples 17 and 18)

[0428] Compared to the structure of Example 1 (R8: 20 parts by mass of first short fibers, 1 part by mass of first co-crosslinking agent), Example 17 is an example of a toothed belt in which the amount of first short fibers contained in the first rubber layer is increased to 50 parts by mass. That is, the first rubber layer is formed from R21 (cross-linked rubber) with a tensile elastic modulus of 9.5 MPa, and the second rubber layer is formed from R2 (cross-linked rubber) with a tensile elastic modulus of 3.8 MPa, and the ratio of the tensile elastic moduli of the two layers is 2.5. Regarding dynamic performance, the tooth skipping torque (relative value) was 1.00 (b judgment), and the endurance running (running time until failure (relative value)) reached the acceptable level of 1.30 (a judgment), and the overall judgment was acceptable (B grade).

[0429] Furthermore, Example 18 is a toothed belt in which the type of the first staple fiber in Example 17 is changed to meta-aramid fiber. Specifically, the first rubber layer is formed from R22 (cross-linked rubber) with a tensile modulus of 10 MPa, and the second rubber layer is formed from R2 (cross-linked rubber) with a tensile modulus of 3.8 MPa. The ratio of the tensile moduli of the two layers is 2.6. Regarding dynamic performance, the tooth skipping torque (relative value) is 1.00 (b-criteria), and the endurance running (running time until failure (relative value)) reaches a passing level of 1.51 (a-criteria), resulting in an overall passing rating (B grade). This indicates that changing the type of staple fiber does not significantly affect the reinforcing effect.

[0430] (Examples 19 to 21)

[0431] Compared to the structure of Example 3 (R10: 20 parts by mass of nylon staple fibers, 6 parts by mass of the first co-crosslinking agent), which exhibited the best durability, Example 19 is an example of a toothed belt in which the type of the first staple fibers is changed to meta-aramid fibers. Specifically, the first rubber layer is formed from R23 (crosslinked rubber) with a tensile modulus of 14 MPa, and the second rubber layer is formed from R2 (crosslinked rubber) with a tensile modulus of 3.8 MPa. The ratio of the tensile moduli of the two layers is 3.7. Regarding dynamic performance, the tooth skipping torque (relative value) was 1.12 (a-judgment), and the durable running (running time until failure (relative value)) reached an acceptable level of 2.11 (a-judgment), resulting in an overall acceptance rating (A grade) comparable to that of Example 3.

[0432] Example 20 is a toothed belt in which the type of the first short fiber is changed to para-aramid fiber. Specifically, the first rubber layer is formed from R24 (cross-linked rubber) with a tensile modulus of 14.8 MPa, and the second rubber layer is formed from R2 (cross-linked rubber) with a tensile modulus of 3.8 MPa. The ratio of the tensile moduli of the two layers is 3.9. Regarding dynamic performance, the tooth skipping torque (relative value) is 1.15 (a-level evaluation), and the endurance running (running time until failure (relative value)) reaches an acceptable level of 1.39 (a-level evaluation), resulting in an overall passing rating (A grade).

[0433] Example 21 is a toothed belt in which the type of the first short fiber is changed to PBO fiber. Specifically, the first rubber layer is formed from R25 (cross-linked rubber) with a tensile modulus of 13 MPa, and the second rubber layer is formed from R2 (cross-linked rubber) with a tensile modulus of 3.8 MPa. The ratio of the tensile moduli of the two layers is 3.4. Regarding dynamic performance, the tooth skipping torque (relative value) is 1.12 (a-level evaluation), and the endurance running (running time until failure (relative value)) reaches the acceptable level of 1.85 (a-level evaluation), resulting in an overall passing rating (A grade).

[0434] It was confirmed that even when the type of short fibers was changed, the effects of enhancing both the tooth skipping torque and the durable running performance (extending the service life) could be obtained.

[0435] (Examples 22 to 24)

[0436] Examples 22 to 24 are examples that verify the relationship between the ratio of the area occupied by the first rubber layer relative to the total rubber layer constituting the tooth portion (hereinafter referred to as the "area ratio") and the elastic modulus of the first rubber layer (the proportion of the first short fibers contained in the first rubber layer) in a cross-sectional view of the tooth portion. Example 22 is an example near the lower limit of the reinforcing effect (where the area ratio is small and the proportion of the first short fibers is also small), with an area ratio of 10% and 5 parts by mass of the first short fibers (tensile modulus of 10.8 MPa). Conversely, Examples 23 and 24 are examples near the upper limit of the reinforcing effect (where the area ratio is large and the proportion of the first short fibers is also large). In Example 23, the area ratio is 60% and the first short fibers are 50 parts by mass (tensile modulus of 14 MPa), and in Example 24, the area ratio is 80% and the first short fibers are 50 parts by mass (tensile modulus of 14 MPa).

[0437] Regarding dynamic performance, the tooth skipping torque (relative value) was 1.00 (Example 22: judgment b), 1.28 (Example 23: judgment a), and 1.35 (Example 24: judgment a), all of which were at a qualified level.

[0438] On the other hand, the endurance running (running time until failure (relative value)) is 1.13 (Example 22: b judgment), 1.28 (Example 23: a judgment), and 1.05 (Example 24: c judgment), all of which are qualified levels and can be said to have an enhancement effect.

[0439] According to the above comprehensive evaluation, the toothed belts of Examples 22 to 24 were of acceptable quality (grades A to C).

[0440] (Examples 25 to 27, Comparative Example 9)

[0441] Compared to the configuration of Example 3, which exhibited the best endurance performance among Examples 1-6, Examples 25-27 and Comparative Example 9 employ toothed belts with rubber compositions having different tensile moduli in the second rubber layer. Specifically, while Example 3 employed R2 (tensile modulus of 3.8 MPa, ratio of the two layers of tensile modulus of 3.7), Example 25 employed R1 (tensile modulus of 2.4 MPa, ratio of the two layers of tensile modulus of 5.8), Example 26 employed R4 (tensile modulus of 9.4 MPa, ratio of the two layers of tensile modulus of 1.5), Example 27 employed R5 (tensile modulus of 10.9 MPa, ratio of the two layers of tensile modulus of 1.3), and Comparative Example 9 employed R7 (tensile modulus of 16.8 MPa, ratio of the two layers of tensile modulus of 0.8) to form the second rubber layer.

[0442] Regarding dynamic performance, the tooth skipping torque (relative value) is 1.09 (Example 25: a judgment), 1.14 (Example 26: a judgment), 1.14 (Example 27: a judgment), and 1.37 (Comparative Example 9: a judgment), all of which are qualified levels and can be said to have an enhancement effect.

[0443] Endurance running (relative running time until failure) was 1.88 (Example 25: judgment a), 1.14 (Example 26: judgment b), 1.08 (Example 27: judgment c), and 0.42 (Comparative Example 9: judgment d). Examples 25 to 27 were at acceptable levels, indicating a strengthening effect. Comparative Example 9, on the other hand, failed.

[0444] Based on the above comprehensive evaluation, the toothed belts of Examples 25 to 27 demonstrated enhanced effects on both tooth skipping torque and durable running performance, achieving acceptable performance (grades A to C). In particular, Examples 25 (tensile modulus 2.4 MPa) and 26 (tensile modulus 9.4 MPa), which had a relatively low second rubber layer tensile modulus, achieved a highly acceptable performance (grades A or B). Example 27 (tensile modulus 10.9 MPa), which had a relatively high second rubber layer tensile modulus, showed little effect on extending life, achieving a grade of C. Comparative Example 9, in which the second rubber layer tensile modulus was further increased to exceed that of the first rubber layer, exhibited a short running life and failed the test (grade D).

[0445] (Examples 28 and 29)

[0446] Examples 28 and 29 are examples of toothed belts in which the rubber composition of the first rubber layer is modified compared to Example 25 (R1: tensile modulus 2.4 MPa), where the second rubber layer has a lower tensile modulus. Example 28 features a first rubber layer made of R8 (cross-linked rubber) with a tensile modulus of 5.3 MPa, and the ratio of the tensile moduli of the two layers is 2.2. The tooth skipping torque (relative value) was 1.02 (a assessment), and the endurance running (running time to failure (relative value)) reached an acceptable level of 1.23 (b assessment), resulting in an overall acceptance rating (B grade).

[0447] Furthermore, Example 29 is a toothed belt in which the first rubber layer is formed of R13 (cross-linked rubber) with a tensile modulus of 23.5 MPa, and the ratio of the tensile moduli of the two layers is 9.8. The tooth skipping torque (relative value) was 1.16 (a evaluation), and the endurance running (running time until failure (relative value)) was 1.24 (b evaluation), resulting in an overall passing level (B grade).

[0448] (Example 30, Comparative Example 10)

[0449] Example 30 and Comparative Example 10 are examples of toothed belts in which the rubber composition of the first rubber layer is changed compared to Comparative Example 9 (R7: tensile modulus 16.8 MPa, ratio of tensile modulus of the two layers 0.8), in which the tensile modulus of the second rubber layer is larger. Comparative Example 10 is a toothed belt in which the first rubber layer is formed of R8 (cross-linked rubber) with a tensile modulus of 5.3 MPa, and the ratio of the tensile modulus of the two layers is 0.3. The tooth skipping torque (relative value) was 1.19 (a judgment), but the endurance running (running time until failure (relative value)) was 0.74 (d judgment), which was unqualified. As in Comparative Example 9, the tensile modulus of the second rubber layer was greater than the tensile modulus of the first rubber layer, and the overall judgment was unqualified (D grade).

[0450] On the other hand, Example 30 is a toothed belt in which the first rubber layer is made of R13 (cross-linked rubber) with a tensile modulus of 23.5 MPa, and the ratio of the tensile moduli of the two layers is 1.4. The tooth skipping torque (relative value) was 1.59 (a-criteria), and the endurance running (running time until failure (relative value)) was 1.01 (c-criteria), reaching the acceptable level and receiving an overall acceptance rating (C grade).

[0451] (Example 31)

[0452] Example 31 is an example of a toothed belt that, unlike Example 3 (R10 for the first rubber layer and R2 for the second rubber layer), which exhibited the best durability among Examples 1-30, does not use a reinforcing inorganic filler (carbon black). Specifically, the toothed belt is formed from a crosslinked rubber composition in which the first rubber layer is R27 (tensile modulus of 13.9 MPa), which is the composition obtained by removing carbon black from R10, and the second rubber layer is R26 (tensile modulus of 3.8 MPa), which is the composition obtained by removing carbon black from R2. The tooth skipping torque (relative value) was 1.10 (a rating), and the durability (travel time until failure (relative value)) was 2.07 (a rating), resulting in an overall pass rating (A grade), comparable to Example 3.

[0453] (Examples 32 and 33)

[0454] Examples 32 and 33 are examples of toothed belts in which, compared to Example 3 (20 parts by mass of the first staple fiber) and Example 14 (50 parts by mass of the first staple fiber), tooth cloth is not provided on the surface of the tooth portion and tooth bottom of the belt. In Example 32, the tooth skipping torque (relative value) was 1.15 (a judgment), and the endurance running (running time until failure (relative value)) was 2.03 (a judgment), and the overall judgment was equivalent to the passing level (A grade) of Example 3. In addition, in Example 33, the tooth skipping torque (relative value) was 1.10 (a judgment), and the endurance running (running time until failure (relative value)) was 1.29 (a judgment), and the overall judgment was equivalent to the passing level (A grade) of Example 14.

[0455] Based on the above results, it can be confirmed that by forming the belt from a first rubber layer formed along the tooth cloth and a second rubber layer formed between the first rubber layer and the core wire, the elastic modulus of the first rubber layer is adjusted to be greater than the elastic modulus of the second rubber layer, and the short fibers are oriented in the first rubber layer along the contour of the tooth portion in the length direction of the belt, the rigidity and flexibility of the teeth in a back-to-back relationship can be taken into account, tooth skipping (tooth slippage) during belt running can be suppressed, and tooth defects (tooth missing) can be suppressed, which can adapt to long service life during high-load running.

[0456] <Examples 34 to 44 and Comparative Example 11>

[0457] [Manufacturing of toothed belts]

[0458] In Examples 34 to 44 and Comparative Example 11, as shown below, a toothed belt having a total thickness of 7.0 mm, a tooth profile of G8M, a tooth height (including tooth cloth) of 3.5 mm, a tooth pitch of 8 mm, a number of teeth of 140, a circumference of 1120 mm, and a width of 17 mm was produced using the preforming process described in this embodiment.

[0459] Table 13 shows the configuration (layer structure) of the tooth portion of the toothed belts produced in Examples 34 to 44 and Comparative Example 11, the rubber composition used in each rubber layer, and the twisted cord used in the core wire.

[0460] (Comparative Example 11)

[0461] A tooth cloth precursor for forming the tooth cloth and an uncrosslinked rubber sheet (R28, sheet thickness 1.70 mm) for forming the rubber layer of the tooth portion are sequentially stacked on a pressing mold (flat mold) having two or more grooves (concave strips) corresponding to the teeth of the toothed belt. The sheets are then pressed for 160 seconds at a temperature of 90°C and a pressing pressure (surface pressure) of 20.2 MPa to produce a semi-crosslinked preform.

[0462] Next, a preform was wound around a cylindrical mold having two or more grooves (recessed strips) corresponding to the teeth (so that the teeth and grooves fit together). The twisted cords forming the core yarns shown in Table 13 were spirally wound around the outer circumference of the preform under the conditions shown in Table 13 (tension: 150-250 N / strand, pitch: 1.15 mm, winding speed: 1.5 m / s). Furthermore, an uncrosslinked rubber sheet (R30, sheet thickness 0.90 mm) forming the back rubber layer was wound around the outer circumference to form an uncrosslinked belt mold (uncrosslinked laminate). The uncrosslinked rubber sheet was wound so that the short fibers contained in the sheet were oriented in the longitudinal direction of the belt.

[0463] Next, cross-linking molding was performed using a vulcanizer at a heating temperature of 179° C. and a steam pressure of 0.83 MPa for 40 minutes to produce a cross-linked molded body (cross-linked belt sleeve).

[0464] Finally, the cross-linked belt sleeve released from the cylindrical mold was cut into a width of 17 mm to obtain a toothed belt.

[0465] (Examples 34 to 44)

[0466] Toothed belts were produced in the same manner as in Comparative Example 11, except that two types of uncrosslinked rubber sheets, an uncrosslinked rubber sheet (R16, sheet thickness 0.70 mm) forming the first rubber layer and an uncrosslinked rubber sheet (R29, sheet thickness 1.00 mm) forming the second rubber layer, were laminated in this order as the rubber layers forming the teeth, and the cords shown in Table 13 were wound under the conditions shown in Table 13. In all cases, the area ratio of the first rubber layer to the total area of ​​the rubber layers forming the teeth was 40%.

[0467] [Belt elastic modulus]

[0468] The elastic modulus (tensile elastic modulus) of the tape was measured at room temperature of 23±2°C and humidity of 50±5%. Specifically, the test tape was left under these conditions for 24 hours or more and then measured by the following method.

[0469] First, a pair of toothed pulleys (20 teeth) are installed on the lower fixing part and the upper load cell connection part of the universal testing machine ["AGS-J10kN" manufactured by Shimadzu Corporation], and the toothed belt (test belt) is hung between the pulleys. Next, the upper pulley is raised, and an initial tension T0 is applied to the toothed belt to eliminate the deflection in the longitudinal direction (for example, about 5N in the case of a toothed belt with a belt width of 10mm). The position of the upper pulley in this state is set as the initial position, the belt circumference is set as the belt reference circumference (L0) (mm), the belt length change rate (dimensionless) is set to 0 (origin), the upper pulley is raised at a speed of 10mm / min, and the relationship between the belt length change rate (dimensionless) (horizontal axis) and the belt tension (N) (vertical axis) (SS line graph) is recorded on a PC (personal computer). It should be noted that the belt length change rate (dimensionless) on the horizontal axis is equal to the change rate (dimensionless) of the interaxial distance between the pulleys. The belt tension (N) in the longitudinal axis is a value obtained by dividing the axial load (N) corresponding to the load detected by the load cell of a tensile testing machine (universal testing machine) by 2.

[0470] Regarding the belt elastic modulus EA of the total width of the test belt within the specified installation tension range, the belt circumference (mm) when stretched to the belt tension T1 (N) corresponding to the lower limit of the installation tension is defined as L1, and the passing point on the SS line diagram at this time is defined as P1. The belt circumference (mm) when stretched to the belt tension T2 (N) corresponding to the upper limit of the installation tension is defined as L2, and the passing point on the SS line diagram at this time is defined as P2. The value (N) (equivalent to the so-called "belt tensile stiffness") obtained by dividing the increase in belt tension T (N) between P1 and P2 (T2-T1) (N) by the belt length change rate between P1 and P2 [(L2-L1) / L1] (dimensionless) is calculated. This value is converted to a value per 1 mm of belt width and is used as the belt elastic modulus (N / mm).

[0471] In this application, for the above-mentioned installation tension range (T1~T2), the belt elastic modulus is measured in the range of 10~60kN / mm for a belt with a tooth pitch of 8mm, the belt elastic modulus is measured in the range of 20~100kN / mm for a belt with a tooth pitch of 11mm, and the belt elastic modulus is measured in the range of 50~175kN / mm for a belt with a tooth pitch of 14mm.

[0472] It should be noted that the unit of the belt elastic modulus can be expressed in (N / %). In this case, the horizontal axis of the SS line graph is not the value of the belt length change rate [(L2-L1) / L1] (dimensionless), but rather the percentage (%) of the belt length change rate [(L2-L1) / L1] (so-called "belt elongation (%)"). If the value of the belt elastic modulus (N / %) is set to 100, it can be converted to the value of the belt elastic modulus EA (N) defined in this application.

[0473] [Tooth skipping test]

[0474] (Running test conditions)

[0475] Using a biaxial torque tester, a toothed belt was wound between a drive pulley (number of teeth: 24) and a driven pulley (number of teeth: 59). The distance between the pulley axes was adjusted to maintain a belt tension of 400 N. The belt was then rotated at 1200 rpm while the load on the driven pulley was continuously increased. The load torque applied to the driven pulley when tooth skipping (tooth slippage) occurred was measured as the tooth skipping torque. The tooth skipping torque value is used as an indicator of tooth skipping resistance; higher tooth skipping torque values ​​indicate a higher toothed belt resistance to tooth slippage.

[0476] Note that the values ​​of the tooth skipping torque are shown as relative values, with the tooth skipping torque value of Comparative Example 11 (250 N·m) set to 1.00. A value of 1.00 or less indicates no reinforcement effect relative to the toothed belt of Comparative Example 11. A value exceeding 1.00 indicates an improvement in tooth rigidity (deformation resistance) due to the reinforcement effect. A larger value indicates a greater degree of reinforcement effect.

[0477] (Criteria for tooth skipping test)

[0478] a: Tooth skipping torque exceeds 1.10 (qualified)

[0479] b: Tooth skipping torque exceeds 1.00 and is less than 1.10 (qualified)

[0480] c: Tooth skipping torque is 1.00 (unqualified)

[0481] d: Tooth skipping torque is less than 1.00 (unqualified).

[0482] [Durability running test]

[0483] (Running test conditions)

[0484] A toothed belt was installed on a biaxial running tester equipped with a drive pulley (number of teeth: 24) and a driven pulley (number of teeth: 59). The running life was measured as the time it took for the belt to fail (tooth failure). The toothed belt installation tension was set to 400N, the drive pulley speed was set to 1000rpm, the driven pulley load was set to 283N·m, and the ambient temperature was 25°C (room temperature).

[0485] It should be noted that if the maintenance rate of the tension after 100 hours of running relative to the initial tension (hereinafter referred to as the "tension maintenance rate") exceeds 50%, it means that the elongation of the belt caused by the reduction in tension is suppressed due to the reinforcement effect. It can be said that the larger the value, the higher the reinforcement effect.

[0486] (Criteria for judging the tension maintenance rate)

[0487] a: The tension maintenance rate after 100 hours is more than 80% of the initial value (qualified)

[0488] b: The tension maintenance rate after 100 hours is 70% or more and less than 80% of the initial value (qualified)

[0489] c: The tension maintenance rate after 100 hours exceeds 50% of the initial value and is less than 70% (qualified)

[0490] d: The tension maintenance rate after 100 hours was 50% or less of the initial value (failed).

[0491] Furthermore, regarding the running time until failure (hereinafter referred to as "lifetime"), the running time of each example is converted into a relative value, with the running time of Comparative Example 11 (241 hours) being set to 1.00. A value of 1.00 or less indicates no reinforcement effect relative to the toothed belt of Comparative Example 11. A value exceeding 1.00 indicates improved durability due to the reinforcement effect. It can be said that a larger value indicates a greater degree of reinforcement effect.

[0492] (Lifespan Criteria)

[0493] a: The running time until failure is 1.25 or more (qualified)

[0494] b: The travel time until failure is greater than 1.10 and less than 1.25 (qualified)

[0495] c: The travel time until failure is greater than 1.00 and less than 1.10 (qualified)

[0496] d: The running time until failure is less than 1.00 (unqualified).

[0497] [Comprehensive judgment]

[0498] The overall quality (grading) was determined based on the following criteria, taking into account the tooth skipping torque in the tooth skipping test, the tension retention rate in the endurance running test, and the level of reinforcement effect in terms of life span. From the perspective of product practicality, grades A, B, and C were considered acceptable, and grade D was considered unacceptable.

[0499] Level A: All three tests above are judged as A

[0500] Level B: The above three items are judged as b (excluding judgements c and d)

[0501] Level C: The three tests above include a judgment of c (excluding judgment of d)

[0502] Level D: The three tests above include a judgment of d.

[0503] Table 13 shows the verification results for the toothed belts of Examples 34 to 44 and Comparative Example 11.

[0504]

[0505] (Examples 37 to 41)

[0506] In Examples 37 to 41, the toothed belts having a toothed portion with a specific two-layer structure had their core wire diameter D, pitch P, and arrangement density X adjusted within specific ranges. This resulted in an appropriate belt elastic modulus, resulting in excellent tooth skipping resistance and durable running performance, as required for rear-wheel drive transmission applications in motorcycles, and were rated A or B overall. In particular, Examples 37 to 40, with a core wire pitch P of 1.10 to 1.15 mm, achieved an A grade.

[0507] (Comparative Example 11)

[0508] Comparative Example 11 is an example in which the entire rubber layer of the tooth portion has a single-layer structure and the belt elastic modulus is as low as 14.7 kN / mm. However, the tooth skipping resistance and tension retention rate are low, and the life span is also short, so it is comprehensively judged as D grade.

[0509] (Examples 34 to 36 and 42 to 44)

[0510] Example 34 is an example in which the core wire diameter D is 0.7 mm and the core wire spacing P is as small as 0.85 mm, so the belt elastic modulus is as high as 22.2 kN / mm. However, compared with Examples 37 to 41, the tension maintenance rate is low and the life time is also short, so it is comprehensively judged as C grade.

[0511] In Example 35, the X value of the core arrangement density was as low as 4.76%, and thus the belt elastic modulus was as low as 13.4 kN / mm. However, compared with Examples 37 to 41, the life was shorter, and therefore the overall evaluation was C grade.

[0512] Example 36 is an example in which the twist coefficient of the core wire is as low as 0.94. However, compared with Examples 37 to 41, the life time is shorter, and therefore the overall evaluation is C grade.

[0513] Example 42 has a high twist coefficient of 2.21 for the core wire and a low elastic modulus of 14.0 kN / mm for the tape. However, compared with Examples 37 to 41, the life span is shorter and therefore the overall evaluation results in a C grade.

[0514] Example 43 is an example in which the X value of the core arrangement density is as high as 25.93%, resulting in a high belt elastic modulus of 21.4 kN / mm. However, compared with Examples 37 to 41, the life is shorter and therefore the overall evaluation is C grade.

[0515] Example 44 is an example in which the core wire diameter D is as large as 1.3 mm, so the belt elastic modulus is as low as 13.8 kN / mm. However, compared with Examples 37 to 41, the tension maintenance rate is low and the life time is also short, so it is comprehensively judged as C grade.

[0516] Based on these results, Table 14 shows the results of summarizing particularly appropriate ranges of the core wire and belt elastic modulus for the toothed belt of tooth profile G8M with a tooth pitch of 8 mm.

[0517] [Table 14]

[0518]

[0519] <Examples 45 to 57 and Comparative Example 12>

[0520] [Manufacturing of toothed belts]

[0521] In Examples 45 to 57 and Comparative Example 12, as shown below, the preforming process described in this embodiment is used to produce a toothed belt having a total thickness of 8.5 mm, a tooth profile of H11M, a tooth height (including tooth cloth) of 5.1 mm, a tooth pitch of 11 mm, a number of teeth of 113, a circumference of 1243 mm, and a width of 25 mm.

[0522] Table 15 shows the configuration (layer structure) of the tooth portion of the toothed belts produced in Examples 45 to 57 and Comparative Example 12, the rubber composition used in each rubber layer, and the twisted cord used in the core wire.

[0523] (Comparative Example 12)

[0524] A tooth cloth precursor for forming the tooth cloth and an uncrosslinked rubber sheet (R28, sheet thickness 2.7 mm) for forming the rubber layer of the tooth portion are sequentially stacked on a pressing mold (flat mold) having two or more grooves (concave strips) corresponding to the teeth of the toothed belt. The sheets are then pressed for 160 seconds at a temperature of 90°C and a pressing pressure (surface pressure) of 20.2 MPa to produce a semi-crosslinked preform.

[0525] Next, a preform was wound around a cylindrical mold having two or more grooves (recessed strips) corresponding to the teeth (so that the teeth and grooves fit together). A twisted cord constituting the core wires shown in Tables 15 and 16 was spirally wound around the outer circumference of the preform under the conditions shown in Tables 15 and 16 (tension: 250-600 N / strand, pitch: 2.20 mm, winding speed: 1.5 m / s). Furthermore, an uncrosslinked rubber sheet (R30, sheet thickness 1.3 mm) forming the back rubber layer was wound around the outer circumference to form an uncrosslinked belt mold (uncrosslinked laminate). The uncrosslinked rubber sheet was wound so that the short fibers contained in the sheet were oriented in the longitudinal direction of the belt.

[0526] Next, cross-linking molding was performed using a vulcanizer at a heating temperature of 179° C. and a steam pressure of 0.83 MPa for 40 minutes to produce a cross-linked molded body (cross-linked belt sleeve).

[0527] Finally, the cross-linked belt sleeve released from the cylindrical mold was cut into pieces with a width of 25 mm to obtain a toothed belt.

[0528] (Examples 45 to 57)

[0529] Toothed belts were produced in the same manner as in Comparative Example 12, except that two types of uncrosslinked rubber sheets, an uncrosslinked rubber sheet (R16, sheet thickness 1.1 mm) forming the first rubber layer and an uncrosslinked rubber sheet (R29, sheet thickness 1.6 mm) forming the second rubber layer, were laminated in this order, and the cords shown in Tables 15 and 16 were wound under the conditions shown in Tables 15 and 16. In all cases, the area ratio of the first rubber layer to the total area of ​​the rubber layers forming the teeth was 40%.

[0530] [Belt elastic modulus]

[0531] The belt elastic modulus was measured by the same method as in Examples 34 to 44 and Comparative Example 11.

[0532] [Tooth skipping test]

[0533] (Running test conditions)

[0534] Using a biaxial torque tester, a toothed belt was wound between a drive pulley (number of teeth: 26) and a driven pulley (number of teeth: 59). The distance between the pulley axes was adjusted to maintain a belt tension of 200 N. The belt was then rotated at 1200 rpm while the load on the driven pulley was continuously increased. The load torque applied to the driven pulley when tooth skipping (tooth slippage) occurred was measured as the tooth skipping torque. The tooth skipping torque value is used as an indicator of tooth skipping resistance; higher tooth skipping torque values ​​indicate a higher toothed belt resistance to tooth slippage.

[0535] Note that the values ​​of the tooth skipping torque are shown as relative values, with the tooth skipping torque value of Comparative Example 12 (700 N·m) set to 1.00. A value of 1.00 or less indicates no reinforcement effect relative to the toothed belt of Comparative Example 12. A value exceeding 1.00 indicates that the rigidity (deformation resistance) of the tooth portion is improved due to the reinforcement effect. A larger value indicates a greater degree of reinforcement effect.

[0536] (Criteria for tooth skipping test)

[0537] a: Tooth skipping torque exceeds 1.10 (qualified)

[0538] b: Tooth skipping torque exceeds 1.00 and is less than 1.10 (qualified)

[0539] c: Tooth skipping torque is 1.00 (unqualified)

[0540] d: Tooth skipping torque is less than 1.00 (unqualified).

[0541] [Durability running test]

[0542] (Running test conditions)

[0543] A toothed belt was installed on a biaxial running tester equipped with a drive pulley (number of teeth: 26) and a driven pulley (number of teeth: 59). The running life was measured as the time it took for the belt to fail (tooth failure). The toothed belt installation tension was set to 1000N, the drive pulley speed was set to 1200rpm, the driven pulley load was set to 668N·m, and the ambient temperature was 25°C (room temperature).

[0544] It should be noted that if the maintenance rate of the tension after 100 hours of running relative to the initial tension (hereinafter referred to as the "tension maintenance rate") exceeds 50%, it means that the elongation of the belt caused by the reduction in tension is suppressed due to the reinforcement effect. It can be said that the larger the value, the higher the reinforcement effect.

[0545] (Criteria for judging the tension maintenance rate)

[0546] a: The tension maintenance rate after 100 hours is more than 80% of the initial value (qualified)

[0547] b: The tension maintenance rate after 100 hours is 70% or more and less than 80% of the initial value (qualified)

[0548] c: The tension maintenance rate after 100 hours exceeds 50% of the initial value and is less than 70% (qualified)

[0549] d: The tension maintenance rate after 100 hours was 50% or less of the initial value (failed).

[0550] Furthermore, regarding the running time until failure (hereinafter referred to as "lifetime"), the running time of each example is converted into a relative value, with the running time of Comparative Example 12 (490 hours) being set to 1.00. A value of 1.00 or less indicates no reinforcement effect relative to the toothed belt of Comparative Example 12. A value exceeding 1.00 indicates improved durable running performance due to the reinforcement effect. It can be said that the larger the value, the greater the reinforcement effect.

[0551] (Lifespan Criteria)

[0552] a: The running time until failure is 1.25 or more (qualified)

[0553] b: The travel time until failure is greater than 1.10 and less than 1.25 (qualified)

[0554] c: The travel time until failure is greater than 1.00 and less than 1.10 (qualified)

[0555] d: The running time until failure is less than 1.00 (unqualified).

[0556] [Comprehensive judgment]

[0557] The overall quality (grading) was determined based on the following criteria, taking into account the tooth skipping torque in the tooth skipping test, the tension retention rate in the endurance running test, and the level of reinforcement effect in terms of life span. From the perspective of product practicality, grades A, B, and C were considered acceptable, and grade D was considered unacceptable.

[0558] Level A: All three tests above are judged as A

[0559] Level B: The above three items are judged as b (excluding judgements c and d)

[0560] Level C: The three tests above include a judgment of c (excluding judgment of d)

[0561] Level D: The three tests above include a judgment of d.

[0562] Tables 15 and 16 show the verification results for the toothed belts of Examples 45 to 57 and Comparative Example 12.

[0563]

[0564]

[0565] (Examples 45 to 50)

[0566] In Examples 45 to 50, the toothed belts having a toothed portion with a specific two-layer structure have their core wire diameter D, pitch P, and arrangement density X adjusted within specific ranges. This results in an appropriate belt elastic modulus. Consequently, the belts exhibit excellent tooth skipping resistance and durable running performance, which are required for rear-wheel drive transmission applications in motorcycles, and were rated A to B overall. Among these, Examples 45 and 48 to 49 received an A overall rating, indicating particularly good performance.

[0567] Example 51 is an example in which the final twist coefficient of the core yarn is as high as 2.92 and the belt elastic modulus is as low as 40.8 kN / mm compared with Examples 48 and 49. However, the tension maintenance rate is low compared with Examples 45 to 50, and the overall judgment is C grade.

[0568] (Comparative Example 12)

[0569] Comparative Example 12 is an example in which the rubber layer of the tooth portion is a single-layer structure as a whole, the final twist coefficient of the core wire is as high as 3.01, the core wire diameter D is 2.0, and the core wire spacing P is 2.20, all of which are relatively large. Therefore, the belt elastic modulus is as low as 40.8 kN / mm, but the tooth skipping resistance (tooth skipping torque) and tension maintenance rate are low, and the service life is also short, so it is comprehensively judged as D grade.

[0570] (Examples 52 to 57)

[0571] Example 52 is an example in which the core wire final twist coefficient is as high as 3.01, the core wire diameter D is 2.0, and the core wire spacing P is 2.20, all of which are relatively large, resulting in a low belt elastic modulus of 40.8 kN / mm. However, compared with Examples 45 to 50, the tension maintenance rate is low and the service life is also short, so it is comprehensively judged as C grade.

[0572] Example 53 is an example in which the core wire diameter D is as small as 1.0 mm and the core wire arrangement density X value is as high as 28.57%, resulting in a low belt elastic modulus of 18.5 kN / mm. However, compared with Examples 45 to 50, the tooth skipping resistance is low and the service life is short, so the overall judgment is C grade.

[0573] Example 54 is an example in which the final twist coefficient of the core yarn is as high as 3.01 and the belt elastic modulus is as low as 34.4 kN / mm. However, compared with Examples 45 to 50, the life time is shorter and therefore the overall evaluation is C grade.

[0574] Example 55 is an example in which the X value of the arrangement density of the core wires is as low as 2.70%. However, compared with Examples 45 to 50, the life span is shorter, and therefore the overall evaluation is C grade.

[0575] Example 56 is an example in which the core wire pitch P is as large as 2.10 mm and the belt elastic modulus is as high as 54.6 kN / mm. However, compared with Examples 45 to 50, the tooth skipping resistance is low and the service life is also short, so it is comprehensively judged as C grade.

[0576] Example 57 has a relatively large core wire diameter D of 2.1 mm and a core wire pitch P of 2.20 mm, and a low core wire arrangement density X value of 4.55%. However, compared with Examples 45 to 50, the life span is shorter, and therefore the overall evaluation results in a C grade.

[0577] Based on these results, Table 17 shows the results of summarizing the appropriate ranges of the core wire and belt elastic modulus for the toothed belt of tooth profile H11M with a tooth pitch of 11 mm.

[0578] [Table 17]

[0579]

[0580] <Examples 58 to 75 and Comparative Example 13>

[0581] [Manufacturing of toothed belts]

[0582] In Examples 58 to 75 and Comparative Example 13, as shown below, the preforming process described in this embodiment is used to produce a toothed belt having a total thickness of 10.6 mm, a tooth profile of H14M, a tooth height (including tooth cloth) of 6.2 mm, a tooth pitch of 14 mm, a number of teeth of 144, a circumference of 2016 mm, and a width of 21 mm.

[0583] Tables 18 to 20 show the configuration (layer structure) of the tooth portion of the toothed belts produced in Examples 58 to 75 and Comparative Example 13, the rubber composition used in each rubber layer, and the twisted cord used in the core wire.

[0584] (Comparative Example 13)

[0585] A tooth cloth precursor for forming the tooth cloth and an uncrosslinked rubber sheet (R28, sheet thickness 2.9 mm) for forming the rubber layer of the tooth portion are sequentially stacked on a pressing mold (flat mold) having two or more grooves (concave strips) corresponding to the teeth of the toothed belt. The sheets are then pressed for 160 seconds at a temperature of 90°C and a pressing pressure (surface pressure) of 20.2 MPa to produce a semi-crosslinked preform.

[0586] Next, a preform was wound around a cylindrical mold having two or more grooves (recessed strips) corresponding to the teeth (so that the teeth and grooves fit together). The twisted cords forming the core yarns shown in Table 19 were spirally wound around the outer circumference of the preform under the conditions shown in Table 19 (tension: 450-750 N / strand, pitch: 2.20 mm, winding speed: 1.5 m / s). Furthermore, an uncrosslinked rubber sheet (R30, sheet thickness 2.0 mm) forming the back rubber layer was wound around the outer circumference to form an uncrosslinked belt mold (uncrosslinked laminate). The uncrosslinked rubber sheet was wound so that the short fibers contained in the sheet were oriented in the longitudinal direction of the belt.

[0587] Next, cross-linking molding was performed using a vulcanizer at a heating temperature of 179° C. and a steam pressure of 0.83 MPa for 40 minutes to produce a cross-linked molded body (cross-linked belt sleeve).

[0588] Finally, the cross-linked belt sleeve released from the cylindrical mold was cut into a width of 21 mm to obtain a toothed belt.

[0589] (Examples 58 to 75)

[0590] Toothed belts were produced in the same manner as in Comparative Example 13, except that two types of uncrosslinked rubber sheets, an uncrosslinked rubber sheet (R16, sheet thickness 1.2 mm) forming the first rubber layer and an uncrosslinked rubber sheet (R29, sheet thickness 1.7 mm) forming the second rubber layer, were laminated in this order, and the cords shown in Tables 18 to 20 were wound under the conditions shown in Tables 18 to 20. In all cases, the area ratio of the first rubber layer to the total area of ​​the rubber layers forming the teeth was 40%.

[0591] [Belt elastic modulus]

[0592] The belt elastic modulus was measured by the same method as in Examples 34 to 44 and Comparative Example 11.

[0593] [Tooth skipping test]

[0594] (Running test conditions)

[0595] Using a biaxial torque tester, a toothed belt was wound between a drive pulley (number of teeth: 33) and a driven pulley (number of teeth: 61). The distance between the pulley axes was adjusted to maintain a belt tension of 200 N. The drive pulley was then rotated at 1200 rpm to move the belt forward while the load on the driven pulley was continuously increased. The load torque applied to the driven pulley when tooth skipping (tooth slippage) occurred was measured as the tooth skipping torque. The tooth skipping torque value is used as an indicator of tooth skipping resistance; higher tooth skipping torque values ​​indicate a higher toothed belt resistance to tooth slippage.

[0596] Note that the values ​​of the tooth skipping torque for each example are converted to relative values, with the tooth skipping torque value of Comparative Example 13 (540 N·m) set to 1.00. A value of 1.00 or less indicates no reinforcement effect relative to the toothed belt of Comparative Example 13. A value exceeding 1.00 indicates that the rigidity (deformation resistance) of the tooth portion is improved due to the reinforcement effect. It can be said that a larger value indicates a greater degree of reinforcement effect.

[0597] (Criteria for tooth skipping test)

[0598] a: Tooth skipping torque exceeds 1.10 (qualified)

[0599] b: Tooth skipping torque exceeds 1.00 and is less than 1.10 (qualified)

[0600] c: Tooth skipping torque is 1.00 (unqualified)

[0601] d: Tooth skipping torque is less than 1.00 (unqualified).

[0602] [Durability running test]

[0603] (Running test conditions)

[0604] A toothed belt was installed on a biaxial running tester equipped with a drive pulley (number of teeth: 33) and a driven pulley (number of teeth: 61). The running time until the belt failed (tooth damage) was measured as the running life. The toothed belt installation tension was set to 1150N, the drive pulley speed was set to 1200rpm, the driven pulley load was set to 910N·m, and the ambient temperature was 25°C (room temperature).

[0605] It should be noted that if the maintenance rate of the tension after 100 hours of running relative to the initial tension (hereinafter referred to as the "tension maintenance rate") exceeds 50%, it means that the elongation of the belt caused by the reduction in tension is suppressed due to the reinforcement effect. It can be said that the larger the value, the higher the reinforcement effect.

[0606] (Criteria for judging the tension maintenance rate)

[0607] a: The tension maintenance rate after 100 hours is more than 80% of the initial value (qualified)

[0608] b: The tension maintenance rate after 100 hours is 70% or more and less than 80% of the initial value (qualified)

[0609] c: The tension maintenance rate after 100 hours exceeds 50% of the initial value and is less than 70% (qualified)

[0610] d: The tension maintenance rate after 100 hours was 50% or less of the initial value (failed).

[0611] Furthermore, regarding the running time until failure (hereinafter referred to as the life time), the running time of each example is converted into a relative value and shown, with the running time of Comparative Example 13 (506 hours) being set to 1.00. If this value is 1.00 or less, it indicates that there is no reinforcement effect relative to the toothed belt of Comparative Example 13. If it exceeds 1.00, it indicates that the durable running performance is improved due to the reinforcement effect. It can be said that the larger the value, the greater the reinforcement effect.

[0612] (Lifespan Criteria)

[0613] a: The running time until failure is 1.25 or more (qualified)

[0614] b: The travel time until failure is greater than 1.10 and less than 1.25 (qualified)

[0615] c: The travel time until failure is greater than 1.00 and less than 1.10 (qualified)

[0616] d: The running time until failure is less than 1.00 (unqualified).

[0617] [Comprehensive judgment]

[0618] The overall quality (grading) was determined based on the following criteria, taking into account the tooth skipping torque in the tooth skipping test, the tension retention rate in the endurance running test, and the level of reinforcement effect in terms of life span. From the perspective of product practicality, grades A, B, and C were considered acceptable, and grade D was considered unacceptable.

[0619] Level A: All three tests above are judged as A

[0620] Level B: The above three items are judged as b (excluding judgements c and d)

[0621] Level C: The three tests above include a judgment of c (excluding judgment of d)

[0622] Level D: The three tests above include a judgment of d.

[0623] The verification results of the toothed belts of Examples 58 to 75 and Comparative Example 13 are shown in Tables 18 to 20.

[0624]

[0625]

[0626]

[0627] (Examples 58 to 64)

[0628] In Examples 58 to 64, the core wire diameter D, pitch P, and arrangement density X of the toothed belts having a specific two-layer structure were adjusted to specific ranges, and the belt elastic modulus was within an appropriate range. Therefore, the belts had excellent tooth skipping resistance and durable running performance required for transmission applications in rear-wheel drive of two-wheeled motorcycles, and were comprehensively judged to be A to B grades. Among them, Examples 58 to 60 and 64 were comprehensively judged to be A grade, which is particularly good. It should be noted that in Example 64, a smaller diameter core wire (3 twisted 12K-1 / 3) was used than in Examples 58 to 60, but by adjusting the arrangement density of the core wire to be larger (reducing X), the service life was improved compared to Examples 58 to 60, resulting in an A grade judgment.

[0629] (Comparative Example 13)

[0630] Comparative Example 13 is an example in which the entire rubber layer of the tooth portion has a single-layer structure and the final twist coefficient of the core wire is as high as 2.65, resulting in a low belt elastic modulus of 49.8 kN / mm. However, the tooth skipping resistance and tension retention rate are low, and the service life is also short, so the overall judgment is D grade.

[0631] (Examples 65 to 69)

[0632] Example 65 is an example in which the final twist coefficient of the core wire is as high as 2.65, so the belt elastic modulus is as low as 49.8 kN / mm. However, compared with Examples 58 to 64, the tension maintenance rate is low and the service life is also short, so it is comprehensively judged as C grade.

[0633] Example 66 is an example in which the final twist coefficient of the core wire is as high as 3.06, the core wire diameter D is 1.7 mm, and the core wire spacing P is 1.90 mm, all of which are relatively small, resulting in a low belt elastic modulus of 49.5 kN / mm. However, compared with Examples 58 to 64, the tension maintenance rate is low and the service life is short, so it is comprehensively judged as C grade.

[0634] Example 67 is an example in which the core wire diameter D is as small as 1.8 mm, so the belt elastic modulus is as low as 49.2 kN / mm. However, compared with Examples 58 to 64, the service life is shorter, so it is comprehensively judged as C grade.

[0635] Example 68 has a high core density X value of 25.93%, resulting in a low belt elastic modulus of 47.4 kN / mm. However, compared with Examples 58 to 64, the tension retention rate is low and the service life is short, so it was comprehensively judged as a C grade.

[0636] Example 69 is an example in which the core wire diameter D is as large as 2.5 mm and the core wire pitch P is as large as 2.70 mm. However, compared with Examples 58 to 64, the life time is shorter and therefore the overall evaluation is C grade.

[0637] (Examples 70 to 75)

[0638] In Example 64, which uses a thin-diameter core wire, the combination of the rubber composition is changed. However, since the core wire diameter D, spacing P, and arrangement density X of the core wire are adjusted to specific ranges, the belt elastic modulus is within an appropriate range. Therefore, the tooth skipping resistance, tension maintenance rate, and durable running performance required for transmission applications in the rear wheel drive of a two-wheeled motorcycle are excellent, and the overall judgment is A grade.

[0639] Based on these results, Table 21 shows the results of summarizing the appropriate ranges of the core wire and belt elastic modulus for the toothed belt of tooth profile H14M with a tooth pitch of 14 mm.

[0640] [Table 21]

[0641]

[0642] Industrial applicability

[0643] The toothed belt (meshing belt or toothed belt) of the present invention, when combined with a toothed pulley, can be used in various fields requiring input and output synchronization, such as power transmission mechanisms in vehicles such as automobiles and motorcycles, power transmission mechanisms for motors and pumps in industrial machinery, machinery such as automatic doors and automated machinery, copiers, and printing presses. In particular, it can be used as a power transmission belt (timing belt, toothed belt) for rear-wheel drives of industrial machinery and motorcycles in high-load (high-horsepower) applications.

[0644] While the present invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the present invention.

[0645] This application is based on Japanese Patent Application No. 2023-037874 filed on March 10, 2023 and Japanese Patent Application No. 2024-023084 filed on February 19, 2024, the contents of which are incorporated herein by reference.

[0646] Explanation of symbols

[0647] 1…Toothed belt

[0648] 1a…tooth

[0649] 1b…bottom of tooth

[0650] 1c…back

[0651] 2…tooth cloth

[0652] 3…First rubber layer

[0653] 3a…First short fiber

[0654] 4…Second rubber layer

[0655] 5…core wire

[0656] 6…Back rubber layer

Claims

1. A toothed belt comprising a back portion in which a core extending in the belt circumferential direction is embedded, and two or more teeth formed on the inner circumferential surface of the back portion at intervals in the belt circumferential direction, the toothed belt comprising a back rubber layer formed on the outer circumferential side of the belt relative to the core, and a first rubber layer and a second rubber layer formed on the inner circumferential side of the belt relative to the core, wherein: The back portion includes the back rubber layer, The elastic modulus of the first rubber layer is greater than the elastic modulus of the second rubber layer, The first rubber layer is formed of a first cross-linked rubber composition containing a first rubber component and first short fibers. The ratio of the first short fibers is 5 to 60 parts by mass relative to 100 parts by mass of the first rubber component. The first short fibers are oriented along the contour of the tooth portion in the belt length direction, The core wire comprises high elastic modulus fibers, and The tooth portion includes the first rubber layer and the second rubber layer interposed between the first rubber layer and the core wire.

2. The toothed belt according to claim 1, wherein The area ratio of the first rubber layer relative to the total area of ​​the first rubber layer and the second rubber layer in a cross-sectional view in the belt circumferential direction is 10 to 80 area %.

3. The toothed belt according to claim 1 or 2, wherein: The tensile strength of the first rubber layer in the belt circumferential direction is 40 to 90 MPa. The tensile elastic modulus of the first rubber layer in the belt width direction is 4 to 25 MPa. The tensile strength of the second rubber layer in the belt circumferential direction is 10 to 50 MPa, and The second rubber layer has a tensile elastic modulus in the belt width direction of 1 to 10 MPa.

4. The toothed belt according to any one of claims 1 to 3, wherein The tensile elastic modulus of the first rubber layer in the belt width direction is 1.1 to 10 times the tensile elastic modulus of the second rubber layer in the belt width direction.

5. The toothed belt according to any one of claims 1 to 4, wherein The first short fibers are polyamide fibers.

6. The toothed belt according to any one of claims 1 to 5, wherein The first cross-linked rubber composition further contains a first cross-linking agent and a first co-cross-linking agent, The second rubber layer is formed from a second cross-linked rubber composition containing a second rubber component, a second cross-linking agent, and a second co-cross-linking agent. The first rubber component contains a first composite polymer comprising hydrogenated nitrile rubber and an unsaturated carboxylic acid metal salt. The second rubber component contains a second composite polymer comprising hydrogenated nitrile rubber and an unsaturated carboxylic acid metal salt, The ratio of the first co-crosslinking agent is 1 to 40 parts by mass relative to 100 parts by mass of the first rubber component, and The ratio of the second co-crosslinking agent is 0.2 to 25 parts by mass relative to 100 parts by mass of the second rubber component.

7. The toothed belt according to claim 6, wherein: The second cross-linked rubber composition further contains second short fibers. In the second cross-linked rubber composition, the ratio of the second short fibers is 5 parts by mass or less relative to 100 parts by mass of the second rubber component.

8. The toothed belt according to claim 6, wherein: The first cross-linked rubber composition further contains a first reinforcing inorganic filler, The second crosslinked rubber composition further contains a second reinforcing inorganic filler, The proportion of the first composite polymer in the first rubber component is 80% by mass or more. The proportion of the second composite polymer in the second rubber component is 30% by mass or more. The first crosslinking agent includes a first organic peroxide, and the ratio of the first organic peroxide is 1 to 20 parts by mass relative to 100 parts by mass of the first rubber component. The second crosslinking agent includes a second organic peroxide, and the ratio of the second organic peroxide is 0.5 to 5 parts by mass relative to 100 parts by mass of the second rubber component. The ratio of the first reinforcing inorganic filler is 10 parts by mass or less relative to 100 parts by mass of the first rubber component, and The ratio of the second reinforcing inorganic filler is 10 parts by mass or less relative to 100 parts by mass of the second rubber component.

9. The toothed belt according to any one of claims 1 to 8, wherein The arrangement density X of the core wires is 5 to 25%.

10. The toothed belt according to any one of claims 1 to 9, wherein The tooth pitch of the tooth portion is 6 to 16 mm. When the tooth pitch is greater than 6 mm and less than 9.5 mm, the belt elastic modulus is 15 to 20 kN / mm. When the tooth pitch is greater than 9.5 mm and less than 12.5 mm, the belt elastic modulus is 42 to 60 kN / mm, and When the tooth pitch is 12.5 to 16 mm, the belt elastic modulus is 50 to 65 kN / mm.

11. A toothed belt transmission mechanism comprising the toothed belt according to any one of claims 1 to 10, wherein: The toothed belt is used for transmission in rear wheel drive of a motorcycle.

12. The method for manufacturing a toothed belt according to any one of claims 1 to 10, comprising: a first rubber layer precursor preparation step of preparing an uncrosslinked rubber sheet in which first short fibers are oriented in one direction on a sheet surface as a first rubber layer precursor for forming a first rubber layer; and The preforming step comprises laminating the first rubber layer precursor and a second rubber layer precursor as an uncrosslinked rubber sheet for forming a second rubber layer in an arrangement in which the first short fibers are oriented in the belt length direction to produce a semi-crosslinked preform.

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