Toothed belt, and method for manufacturing a toothed belt

Abstract

A toothed belt comprising a belt body having a base and a plurality of teeth integrated on the inner circumference of the base, and a core wire embedded in the base, wherein the tooth pitch is 8 mm or more and 14 mm or less, the distance L from the root line to the center of the core wire varies along the length of the belt, the absolute value X of the difference between the distance LA from the root line to the center of the core wire at the root of the tooth and the distance LB from the root line to the center of the core wire at the belt tooth is 0.20 mm or more, the hardness of the teeth measured with a Type D durometer is 46 or more and 52 or less, and the diameter of the core wire is 1.0 mm or more and 2.4 mm or less.

Description

Technical Field

[0001] The present invention relates to a toothed belt and a method for manufacturing the toothed belt. This application claims priority based on Japanese Application No. 2025-003429 filed on January 9, 2025, and incorporates all the descriptions set forth in the above Japanese application.

Background Art

[0002] Toothed belts are suitable for applications that require synchronous rotation and are widely used in automotive applications and general industrial applications. In recent years, the number of cases where they are used in injection molding machines and industrial robots that are subject to high loads has been increasing (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is required to increase the skip torque (also called jumping torque) of the toothed belt so that tooth skipping does not occur during use.

Means for Solving the Problems

[0005] In view of such circumstances, the present disclosure has been made, and an object thereof is to provide a toothed belt in which tooth skipping is unlikely to occur.

[0006] A toothed belt according to one aspect of the present invention is a toothed belt having a belt body including a base portion and a plurality of tooth portions integrally formed on the inner peripheral side of the base portion, and a core wire embedded in the base portion, where the tooth pitch is 8 mm or more and 14 mm or less, The distance L from the root line to the center of the core line varies along the length of the belt. The absolute value X of the difference between the distance LA from the root line to the center of the core wire at the root of the tooth and the distance LB from the root line to the center of the core wire at the belt tooth is 0.20 mm or more. The above tooth portion has a hardness of 46 to 52 as measured by a Type D durometer. The diameter of the above-mentioned core wire is between 1.0 mm and 2.4 mm.

[0007] A method for manufacturing a toothed belt according to one aspect of the present invention is a method for manufacturing a toothed belt having a belt body comprising a base portion, a plurality of teeth integrated on the inner circumference side of the base portion, and a core wire embedded in the base portion, (A) A process of winding a core wire around the outer circumference of a cylindrical mold having a cross-sectional shape corresponding to belt teeth, with axially extending recesses and axially extending protrusions provided between adjacent recesses on its outer circumference, (B) A step of wrapping at least one layer of uncrosslinked rubber sheet around the mold on which the core wire is wound, (C) A step of integrally molding the base and the teeth by placing a rubber sleeve over the mold on which the core wire and at least one layer of uncrosslinked rubber sheet are wound, and then heating the uncrosslinked rubber sheet while pressing it toward the mold, Includes, The Mooney viscosity of the above uncrosslinked rubber sheet is between 45 MS(1+4)100°C and 60 MS(1+4)100°C. [Effects of the Invention]

[0008] According to an aspect of the present invention, a toothed belt that is less prone to tooth skipping can be provided. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a perspective view showing an example of a toothed belt. [Figure 2] Figure 2 is a cross-sectional view taken along line AA in Figure 1. [Figure 3] Figure 3 is a cross-sectional view along line BB in Figure 1. [Figure 4] Figure 4 is an end view taken along line C-C of Figure 1. [Figure 5] Figure 5 is a diagram for explaining a method of manufacturing a toothed belt. [Figure 6] Figure 6 is a diagram for explaining a method of manufacturing a toothed belt. [Figure 7] Figure 7 is a diagram for explaining a method of manufacturing a toothed belt. [Figure 8] Figure 8 is a diagram for explaining the dimensions of the toothed belts manufactured in the examples and comparative examples. [Figure 9] Figure 9 is a diagram for explaining a method of manufacturing a toothed belt of Comparative Example 5. [Figure 10] Figure 10 is a diagram for explaining a method of manufacturing a toothed belt of Comparative Example 5. [Figure 11] Figure 11 is a diagram for explaining a method of manufacturing a toothed belt of Comparative Example 5. [Figure 12] Figure 12 is a diagram for explaining a method of manufacturing a toothed belt of Comparative Example 5. [Figure 13] Figure 13 is a diagram for explaining a method of manufacturing a toothed belt of Comparative Example 5. [Figure 14] Figure 14 is a diagram showing the pulley layout of the transmission system used in the running tests in the examples and comparative examples. <000008!>

Best Mode for Carrying Out the Invention

[0010] The outline of the embodiments of the present invention will be listed and described. [1] A toothed belt having a belt body including a base portion and a plurality of tooth portions integrated on the inner peripheral side of the base portion, and a core wire embedded in the base portion, wherein the tooth pitch is 8 mm or more and 14 mm or less, the distance L from the tooth bottom line to the center of the core wire varies along the belt length direction, the absolute value X of the difference between the distance LA from the tooth bottom line to the center of the core wire at the tooth bottom and the distance LB from the tooth bottom line to the center of the core wire at the belt tooth is 0.20 mm or more, The hardness of the tooth part, measured by a Type D durometer, is 46 or more and 52 or less, A toothed belt in which the diameter of the core wire is 1.0 mm or more and 2.4 mm or less.

[0011] Since the toothed belt has a tooth part with a sufficiently high hardness and a core wire diameter that can optimize the meshing with the toothed pulley, it has a high skip torque and is less likely to experience tooth skipping.

[0012] [2] In the toothed belt of [1] above, it is preferable that the core wire is embedded so as to form a helix having a pitch in the belt width direction, and the gap dimension between adjacent core wires is 0.1 mm or more and 0.5 mm or less.

[0013] [3] In the toothed belt of [1] or [2] above, it is preferable that the belt body is composed of a crosslinked molded product of an uncrosslinked rubber sheet having a Mooney viscosity of 45 MS(1+4) 100°C or more and 60 MS(1+4) 100°C or less before molding.

[0014] [4] A method for manufacturing a toothed belt having a belt body including a base portion and a plurality of tooth portions integrated on the inner peripheral side of the base portion, and a core wire embedded in the base portion, (A) A step of winding a core wire around the outer periphery of a cylindrical mold provided with a concave portion extending in the axial direction and a convex portion extending in the axial direction provided between adjacent concave portions, which have a cross-sectional shape corresponding to the belt teeth, (B) A step of winding at least one layer of an uncrosslinked rubber sheet around the mold around which the core wire is wound, (C) After covering the mold around which the core wire and at least one layer of the uncrosslinked rubber sheet are wound with a rubber sleeve, heating while pressing the uncrosslinked rubber sheet toward the mold side to integrally form the base portion and the tooth portion, including A method for manufacturing a toothed belt, wherein the Mooney viscosity of the uncrosslinked rubber sheet is 45 MS(1+4) 100°C or more and 60 MS(1+4) 100°C or less.

[0015] The above method for manufacturing a toothed belt uses an uncrosslinked rubber sheet having a specific Mooney viscosity and is suitable for manufacturing toothed belts with high rubber hardness, such as the toothed belt described in [1] above.

[0016] [5] The method for manufacturing the toothed belt described in [4] above is preferably: The above-mentioned core wire is wound so as to form a spiral having a pitch in the axial direction, The diameter of the above-mentioned core wire is 1.0 mm or more and 2.4 mm or less. The gap between adjacent core wires is 0.1 mm or more and 0.5 mm or less. We manufacture toothed belts with a tooth pitch of 8mm to 14mm. In this case, it is suitable for manufacturing the toothed belt described in [2] above.

[0017] The embodiments of the present invention will be described in detail below with reference to the drawings.

[0018] (Toothed belt) Figure 1 is a perspective view showing a part of a toothed belt 1 according to an embodiment of the present invention. Figure 2 is a cross-sectional view taken along line AA in Figure 1. Figure 3 is a cross-sectional view along line BB in Figure 1. Figure 4 is a line cross-section view of Figure 1. Figure 1 shows a portion of the toothed belt 1. The toothed belt 1 is an endless interlocking transmission belt. The toothed belt 1 is a single-sided toothed belt. The toothed belt 1 according to this embodiment can be used in general industrial applications such as machine tools, printing machines, textile machinery, and injection molding machines, as well as in automotive and motorcycle applications. Particularly preferred applications are industrial robots where repeatable positioning accuracy is required.

[0019] In Figure 1, the direction indicated by the double-headed arrow X is the belt width direction of the toothed belt 1. The direction indicated by the double-headed arrow Y is the belt length direction of the toothed belt 1. The belt length direction is also the belt circumference direction of the toothed belt 1. The direction indicated by the double-headed arrow Z is the belt thickness direction of the toothed belt 1. The upper side of each plane is the outer circumference side of the toothed belt 1, and the lower side is the inner circumference side.

[0020] The belt length of toothed belt 1 (belt length in the belt pitch line) is, for example, 225 mm or more and 6000 mm or less. The belt width Wb of the toothed belt 1 is, for example, 5 mm or more and 120 mm or less. The belt thickness Tb of the toothed belt 1 is, for example, between 3.5 mm and 9.0 mm. The belt thickness Tb of the toothed belt 1 is the thickness of the thickest part of the toothed belt 1. The dimensions (belt length, belt width Wb, and belt thickness Tb) of the toothed belt according to the embodiment of the present invention are not limited to this range.

[0021] The toothed belt 1 has a back portion 11 and a plurality of belt teeth 12. The back portion 11 extends in the circumferential direction of the belt. The back portion 11 is an endless band. In a cross-section perpendicular to the circumferential direction of the toothed belt 1, the cross-sectional shape of the back portion 11 is rectangular. Multiple belt teeth 12 are provided on the inner circumference side of the back portion 11. The multiple belt teeth 12 are arranged at equal intervals in the circumferential direction of the belt. Each belt tooth 12 extends in the belt width direction. The portion sandwiched between adjacent belt teeth 12 is the tooth root 24. The tooth pitch Pb of the belt teeth 12 is between 8 mm and 14 mm. The tooth profile of the belt teeth 12 is, for example, an arc tooth profile.

[0022] (Mechanism of toothed belt) The toothed belt 1 comprises a belt body 2, a core wire 3, and a reinforcing fabric 4. The belt body 2, core wire 3, and reinforcing fabric 4 are described below.

[0023] (Belt body) The belt body 2 has a strip-like shape. The belt body 2 comprises a base portion 21 and a plurality of teeth portions 22. The base portion 21 extends in the circumferential direction of the belt. The core wire 3 is embedded in the base portion 21. Multiple teeth 22 are provided on the inner circumferential side of the base portion 21. Multiple teeth 22 are integral with the base portion 21. Multiple teeth 22 are arranged at equal intervals in the circumferential direction of the belt. The surface of the teeth 22 is covered with reinforcing fabric 4.

[0024] The belt body 2 is made of a rubber composition (hereinafter also referred to as the crosslinked rubber composition) which is formed by crosslinking an uncrosslinked rubber composition containing rubber components and rubber compounding agents by heating and pressurizing. The belt body 2 consists of a base portion 21 and a tooth portion 22, both made of a cross-linked rubber composition. The toothed belt 1 shown in Figure 1 has a base 21 and teeth 22 made of the same cross-linked rubber composition. In other words, the belt body 2 is made of one type of cross-linked rubber composition. The belt body 2 may be made of two or more types of cross-linked rubber compositions.

[0025] As described above, the belt body 2 is composed of a crosslinked rubber composition in which an uncrosslinked rubber composition containing, for example, a rubber component and a rubber compounding agent is crosslinked. Examples of the above rubber components include hydrogenated nitrile rubber (HNBR), alloys in which at least one of metal acrylate, metal methacrylate, metal polyacrylate, and metal polymethacrylate is finely dispersed in hydrogenated nitrile rubber (HNBR), ethylene-α-olefin elastomers such as chloroprene rubber (CR) and ethylene-propylene-diene rubber (EPDM), chlorosulfonated polyethylene rubber, styrene-butadiene rubber, and epichlorohydrin rubber. These may be used individually or in combination of two or more.

[0026] Preferred rubber components include hydrogenated nitrile rubber and an alloy in which at least one of zinc acrylate, zinc methacrylate, zinc polyacrylate, and zinc polymethacrylate is finely dispersed in hydrogenated nitrile rubber. In this specification, hydrogenated nitrile rubber (HNBR) and an alloy in which at least one of the following is finely dispersed in hydrogenated nitrile rubber (HNBR): metal acrylate, metal methacrylate, metal polyacrylate, and metal polymethacrylate, are collectively referred to as "HNBR-based rubber components."

[0027] As for the above HNBR-based rubber component, a low viscosity type is preferred. For example, an HNBR-based rubber component with a Mooney viscosity of 50ML(1+4)100℃ or higher and 72ML(1+4)100℃ or lower is preferred. Commercially available HNBR-based rubber components can also be used. Examples of commercially available HNBR-based rubber components include Zetpol 2000L, Zetpol 2010L, Zetpol 2011L, Zetpol 2020L, Zetpol 2030L, Zeoforte 2195LCX, Zeoforte 2295L, and Zeoforte 2395 (all manufactured by ZEON). These may be used individually or in combination of two or more types.

[0028] Examples of the rubber compounding agents mentioned above include, for example, short fibers, vulcanization accelerators, antioxidants, reinforcing agents, plasticizers, co-crosslinking agents, crosslinking agents, and processing aids. Examples of the above-mentioned short fibers include aramid short fibers, nylon short fibers, polyester short fibers, and the like. Para-aramid short fibers are preferred as the above-mentioned aramid short fibers. These short fibers may be of one type only, or two or more types may be used in combination.

[0029] The length of the short fibers mentioned above is, for example, between 0.5 mm and 3.5 mm. The diameter of the above short fibers is, for example, between 5 μm and 50 μm. The preferred content of the above-mentioned short fibers is 1 part by mass or more and 7 parts by mass or less per 100 parts by mass of the rubber component.

[0030] Examples of the above-mentioned vulcanization accelerators include metal oxides, metal carbonates, fatty acids, and their derivatives. Examples of the above-mentioned metal oxides include zinc oxide (zinc oxide) and magnesium oxide. These vulcanization accelerators may be used individually or in combination of two or more types. The amount of the above-mentioned vulcanization accelerator is, for example, 3 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the rubber component.

[0031] Examples of the above-mentioned anti-aging agents include benzimidazole-based anti-aging agents, aromatic secondary amine-based anti-aging agents, and amine-ketone-based anti-aging agents. These anti-aging agents may be used individually or in combination of two or more types. The amount of the above-mentioned anti-aging agent is, for example, 1.5 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the rubber component.

[0032] Examples of the reinforcing materials mentioned above include carbon black and silica. The reinforcing materials may also include carbon black and silica in combination. Examples of the carbon blacks mentioned above include channel black, furnace black, thermal black, and acetylene black. Examples of furnace blacks mentioned above include SAF, ISAF, N-339, HAF, N-351, MAF, FEF, SRF, GPF, ECF, and N-234. Examples of the above-mentioned thermal blacks include FT and MT. You may use only one type of carbon black, or you may use two or more types in combination.

[0033] When carbon black is used, its content is, for example, 5 to 50 parts by mass per 100 parts by mass of rubber component. When silica is used, its content is, for example, 10 parts by mass or more and 30 parts by mass or less per 100 parts by mass of rubber component.

[0034] Examples of the plasticizers mentioned above include dialkyl sebacate, dialkyl phthalate, and dialkyl adipate. Examples of the above-mentioned dialkyl sebacates include polyether esters and dioctyl sebacate (DOS). Examples of the above-mentioned dialkyl phthalates include dibutyl phthalate (DBP) and dioctyl phthalate (DOP). Examples of the above-mentioned dialkyl adipates include dioctyl adipate (DOA). These plasticizers may be used individually or in combination of two or more types. The content of the plasticizer is, for example, 5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of rubber component.

[0035] Examples of the above-mentioned co-crosslinking agents include trimethylolpropane trimethacrylate, m-phenylenedimaleimide, zinc dimethacrylate, and triallyl isocyanurate. These co-crosslinking agents may be used individually or in combination of two or more. The content of the above-mentioned co-crosslinking agent is, for example, 3 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component.

[0036] Examples of the crosslinking agents mentioned above include sulfur and organic peroxides. Sulfur and organic peroxides may be used in combination. Of course, either one may be used alone. When sulfur and organic peroxide are used in combination as the crosslinking agent, it is preferable that the total amount of the crosslinking agent is, for example, 0.1 parts by mass or more and 3 parts by mass of sulfur and 1 part by mass or more and 5 parts by mass of organic peroxide per 100 parts by mass of rubber component.

[0037] Examples of the processing aids mentioned above include stearic acid, polyethylene wax, and metal salts of fatty acids. These processing aids may be used individually or in combination of two or more. The content of the processing aids is, for example, 0.5 parts by mass or more and 2 parts by mass per 100 parts by mass of the rubber component.

[0038] The belt body 2 is composed of a crosslinked rubber composition in which such an uncrosslinked rubber composition is crosslinked. The belt body 2 has a hardness of 46 to 52 (hereinafter also referred to as Duro-D hardness) measured with a Type D durometer on the teeth 22. Therefore, the toothed belt 1 has high hardness in the teeth 22, making it less prone to tooth skipping. On the other hand, if the Duro-D hardness of the teeth 22 is less than 46, the skip torque is small, and tooth skipping cannot be sufficiently suppressed. Furthermore, toothed belts 1 with a Duro-D hardness of the teeth 22 exceeding 52 are difficult to manufacture using a single-stage manufacturing process.

[0039] In this invention, the reason why the hardness of the tooth portion is defined by a measurement using a Type D durometer is that if the hardness of the tooth portion 22 is measured using a Type A durometer, the measurement value will be 90 or higher, making it difficult to accurately measure the hardness of the tooth portion 22.

[0040] The hardness of the teeth 22 is measured by pressing a Type D durometer specified in JIS-K6253-3 (2012) against the side surface of the teeth 22 of the belt body 2 (the end face of the teeth 22 in the belt width direction). The ambient temperature during measurement shall be the standard test temperature of 23±2℃ as specified in JIS-K6250.

[0041] In the belt body 2, it is preferable that the hardness of the base portion 21 is the same as or lower than the hardness of the teeth portion 22. A toothed belt 1 in which the hardness of the base portion 21 is lower than the hardness of the teeth portion 22 has the effect of being less prone to backside cracks.

[0042] (Core wire) The core wire 3 is embedded in the base 21. Examples of the core wire 3 include glass core wire, aramid core wire, carbon core wire, and steel core wire. These core wires are preferably composed of twisted threads. As the core wire 3, carbon wire and steel wire are preferred. Carbon and steel are materials with high elastic modulus. Therefore, in toothed belts with carbon wire or steel wire, the length does not change easily when a load is applied, and the change in tooth pitch is small. For this reason, toothed belts with carbon wire or steel wire tend to maintain a good meshing state with toothed pulleys.

[0043] The diameter of the core wire 3 is between 1.0 mm and 2.4 mm. Here, the diameter of the core wire 3 is the outer diameter φW of the core wire 3 in the belt width direction at the tooth root 24 of the toothed belt 1. In a toothed belt 1 with a tooth pitch Pb of 8 mm to 14 mm, tooth skipping is less likely to occur if the diameter of the core wire 3 is within this range. The outer diameter φW of the core wire 3 can be measured at the cross-section of the tooth root 24 of the toothed belt 1 (see Figure 2).

[0044] Increasing the diameter of the core wire embedded in a toothed belt tends to increase the belt's longitudinal modulus, thereby improving its ability to suppress tooth skipping (hereinafter also referred to as tooth skipping suppression performance). However, if the core wire diameter is made too large, interference between the toothed belt and the toothed pulley occurs, resulting in a decrease in tooth skipping suppression performance. On the other hand, if the diameter of the core wires embedded in a toothed belt is small, even if the spacing between adjacent core wires is the same as when using larger diameter core wires, the tooth skipping prevention performance tends to be inferior compared to when using larger diameter core wires. This is because, when the core wire diameter is small, the proportion of the total cross-sectional area of ​​the core wires in the cross section perpendicular to the length direction of the toothed belt is smaller compared to when using larger diameter core wires, resulting in a lower Young's modulus of elasticity for the toothed belt. From this perspective, the toothed belt 1 ensures excellent tooth skipping suppression performance while maintaining proper meshing with the toothed pulley by setting the diameter of the core wire 3 to 1.0 mm or more and 2.4 mm or less. The preferred diameter of the core wire 3 is 1.0 mm or more and 2.0 mm or less.

[0045] From the viewpoint of ensuring excellent tooth skipping suppression performance while maintaining proper meshing with the toothed pulley, it is preferable that the ratio of the diameter of the core wire 3 to the tooth pitch Pb (φW / Pb) is 0.100 or more and 0.175 or less for the toothed belt 1. The meshing between a toothed belt and a toothed pulley is influenced by the PLD (PITCH LINE DIFFERENTIAL), and the diameter of the core wire is an important factor in determining the PLD. For a toothed belt 1 with a core wire diameter of 1.0 mm to 2.4 mm and a tooth pitch Pb of 8 mm to 14 mm, if the ratio (φW / Pb) is within the above range, it is easier to maintain proper meshing with the toothed pulley and to ensure tooth skipping prevention performance.

[0046] Furthermore, in the toothed belt 1, as described below, the distance L from the tooth root line BL to the center of the core wire 3 (hereinafter also referred to as the core wire center) fluctuates along the belt length direction. Specifically, as described below, the absolute value X of the difference between distance LA and distance LB is 0.20 mm or more. Therefore, in the toothed belt 1, the PLD fluctuates along the belt length direction. In such a toothed belt 1, in order to maintain proper meshing with the toothed pulley while ensuring excellent tooth skipping suppression performance, it is appropriate to set the above ratio (φW / Pb) to 0.100 or more and 0.175 or less.

[0047] The core wires 3 have a pitch in the belt width direction and are arranged to form a spiral. For example, a core wire pair consisting of an S-twisted core wire 3 and a Z-twisted core wire 3 may be arranged to have a pitch in the belt width direction and form a spiral.

[0048] The core wires 3 are arranged so as to extend parallel to each other with spacing in the belt width direction. Visually, multiple core wires 3 are arranged side by side in the belt width direction. The gap between adjacent core wires 3 is preferably 0.1 mm or more and 0.5 mm or less. If this gap is less than 0.1 mm, defects in the tooth formation are likely to occur when manufacturing the toothed belt using the method described later, and if it exceeds 0.5 mm, it is difficult to increase the skip torque.

[0049] In the case of core wire 3, the distance L from the root line BL to the center of core wire 3 (core wire center) varies along the belt length direction. In other words, the distance L from the root line BL to the core wire center is not constant along the belt length direction.

[0050] The preferred range for the distance L from the tooth root line BL to the core wire center is, for example, 0.65 mm to 0.86 mm when the nominal pitch of the belt teeth 12 is 8 mm, and 1.40 mm to 1.60 mm when the nominal pitch of the belt teeth 12 is 14 mm. Therefore, it is preferable that the distance L of the toothed belt 1 varies within this range. In this specification, "nominal pitch" has the same meaning as "nominal pitch" as used in JIS B 1857-1 and other standards. In embodiments of the present invention, the range of the tooth pitch Pb of the toothed belt 1 is 8 ± 0.03 mm when the nominal pitch is 8 mm, and 14 ± 0.03 mm when the nominal pitch is 14 mm.

[0051] The distance L of the core wire 3 preferably fluctuates periodically along the length of the belt. Here, the statement that the distance L fluctuates periodically means that when the distance L at each position along the belt length of the core wire 3 is plotted on a graph with any point on the core wire 3 as the origin, the distance from the origin on the horizontal axis, and the distance L on the vertical axis, the resulting graph shows that local minimums appear at approximately constant intervals along the horizontal axis. Here, "approximately constant intervals" means that all intervals are between 0.95 and 1.05 times the median value.

[0052] A toothed belt in which the above-mentioned distance L fluctuates periodically along the belt length can be manufactured by the toothed belt manufacturing method (one-stage method) described later. In other words, a toothed belt manufactured by the toothed belt manufacturing method (one-stage method) described later has the above-mentioned distance L fluctuating periodically along the belt length.

[0053] In the toothed belt 1, the absolute value X of the difference between the distance LA (see Figure 4) from the root line BL to the center of the core wire at the root of the tooth 24 and the distance LB (see Figure 4) from the root line BL to the center of the core wire at the belt tooth 12 is 0.20 mm or more. When a toothed belt 1 is manufactured using a single-stage process, the absolute value X is usually 0.20 mm or greater. In the toothed belt 1, the above-mentioned X is 0.60 mm or less. If the above-mentioned X exceeds 0.60 mm, the core wire 3 is greatly wavy along the length direction of the belt. As a result, the elongation when tension is applied to the toothed belt 1 increases, the belt tension decreases significantly, and the tooth skipping prevention performance is impaired.

[0054] (How to calculate X) To calculate the above X, distances LA and LB are obtained from adjacent parts. That is, if distance LA is obtained from the root of one tooth, distance LB is obtained from the belt tooth adjacent to this root, and the difference is calculated based on the obtained LA and LB. Furthermore, in this invention, the difference between distance LA and distance LB is obtained at three locations along the length of the belt, and the average of the absolute values ​​of these differences is calculated to obtain the evaluation value X. Here, distances LA and LB are obtained at three locations that are spaced approximately equally apart. In this invention, the three locations that are spaced approximately equally apart on the toothed belt 1 refer to three locations selected such that the difference in the number of belt teeth between each selected location is one or less.

[0055] Distances LA and LB are measured by acquiring images of a cross-section of the toothed belt 1 perpendicular to the belt length direction (see Figures 2 and 3). Specifically, the images are acquired using the following method. First, the toothed belt 1 is cut perpendicular to the length of the belt so as to pass through the center of the tooth root 24 in the belt length direction, and a cross-sectional image as shown in Figure 2 is obtained. Next, the distance LA from the tooth root line BL to the center of the core wire is measured based on this cross-sectional image. At this time, the core wire cross-section to be measured is selected to be the cross-section of the core wire closest to the center in the belt width direction.

[0056] Next, the toothed belt 1 is cut perpendicular to the length of the belt so as to pass through the center of the belt teeth 12 in the length direction of the belt, and a cross-sectional image as shown in Figure 3 is obtained. At this time, the belt tooth 12 to be cut is selected to be adjacent to the tooth root 24 that was cut in order to obtain the distance LA. Next, based on this cross-sectional image, the distance LB from the tooth root line BL to the center of the core wire is measured. At this time, the core wire cross-section to be measured is selected to be close in the length direction of the core wire to the core wire cross-section selected to obtain the distance LA. In measuring distance LB, first, a virtual root line VBL is set as shown in Figure 3. The virtual root line VBL is a virtual line located at distance LC from the back surface 11a of the toothed belt 1. This distance LC is obtained based on the cross-sectional image (see Figure 2) acquired to measure distance LA. Next, the distance LB from the established virtual root line VBL to the center of the core wire is measured.

[0057] The core wire 3 may be a core wire that has been treated with adhesive to enhance its adhesion to the belt body 2. A toothed belt 1 having a core wire 3 that has been bonded can be manufactured in the toothed belt manufacturing method described later by using a core wire that has been bonded as described below before being wound onto a mold. Adhesion treatments applied to the core wire before winding it onto the mold include, for example, RFL treatment, which involves immersing the wire in an aqueous solution containing an initial condensate of resorcinol and formaldehyde and latex (also called RFL aqueous solution) and then drying it, and rubber cement treatment, which involves immersing the wire in rubber cement and then drying it. These adhesion treatments may be applied individually or in combination. The core wire may be subjected to a surface treatment before being wrapped around the mold. Examples of such surface treatments include immersion in an epoxy solution or an isocyanate solution followed by drying.

[0058] Furthermore, the following bonding treatment may be applied to the core wire before it is wrapped around the mold. For example, the process may involve coating each filament in the core wire with a converging agent and then drying it to form a coating, or coating a twisted set of filaments with an adhesive and then drying it to form a coating. In this case, examples of converging agents and adhesives used include RFL liquid, an aqueous solution containing the initial condensate of resorcinol and formaldehyde (also called RF aqueous solution), an emulsion in which an epoxy group-containing compound and a curing agent are dispersed in water, etc. Alternatively, compositions can be used as the above-mentioned converging agents and adhesives that include uncrosslinked rubber such as chlorosulfonated polyethylene and hydrogenated nitrile rubber (HNBR), and crosslinking agents that undergo crosslinking by heat treatment, such as diisocyanate compounds, aromatic nitroso compounds, and maleimide-based crosslinking agents.

[0059] (Reinforcement fabric) The reinforcing fabric 4 covers the surface of the teeth 22. The reinforcing fabric 4 constitutes the inner circumferential surface of the toothed belt 1. The inner circumferential surface of the toothed belt 1 includes the reinforcing fabric 4. Reinforcement fabric 4 is a woven fabric. Examples of fibers that make up the reinforcing fabric 4 include polyamide fibers (nylon fibers), polyester fibers, aramid fibers, poly(p-phenylenebenzobisoxazole) (PBO) fibers, and cotton. For the reinforcing fabric 4, a woven fabric of polyamide fibers is preferred, for example. The thickness of the reinforcing fabric 4 is, for example, 0.5 mm or more and 2.0 mm or less. The reinforcing fabric 4 preferably has elasticity, such as a woven fabric in which the weft threads have been treated with a woolly finish. The value of X can be adjusted by adjusting the thickness of the reinforcing fabric 4.

[0060] The reinforcing fabric 4 may be treated with an adhesive to enhance its adhesion to the belt body 2. Examples of the bonding treatments mentioned above include RFL treatment, which involves immersing the belt in an RFL aqueous solution and then heating it; soaking treatment, which involves immersing the belt in a low-viscosity rubber adhesive and then drying it; and coating treatment, which involves applying a high-viscosity rubber adhesive to the surface of the belt body and then drying it. One of these treatments may be performed, or two or more may be performed. The reinforcing fabric 4 may be subjected to a pre-treatment before the bonding process, which involves immersing it in an epoxy solution or isocyanate solution followed by heating. These bonding and surface preparation processes are performed before wrapping the reinforcing cloth 4 around the mold in the toothed belt manufacturing method described later.

[0061] (Manufacturing method for toothed belts) Next, we will explain the manufacturing method of the toothed belt 1. The toothed belt 1 is manufactured, for example, by a method for manufacturing a toothed belt according to an embodiment of the present invention.

[0062] A method for manufacturing a toothed belt according to an embodiment of the present invention is: (A) A process of winding a core wire around the outer circumference of a cylindrical mold having a cross-sectional shape corresponding to belt teeth, with axially extending recesses and axially extending protrusions provided between adjacent recesses on its outer circumference, (B) A step of wrapping at least one layer of uncrosslinked rubber sheet around the mold on which the core wire is wound, (C) A step of integrally molding the base and the teeth by placing a rubber sleeve over the mold on which the core wire and at least one layer of uncrosslinked rubber sheet are wound, and then heating the uncrosslinked rubber sheet while pressing it toward the mold, Includes, The Mooney viscosity of the above uncrosslinked rubber sheet is between 45 MS(1+4)100°C and 60 MS(1+4)100°C.

[0063] In this method of manufacturing toothed belts, an uncrosslinked rubber sheet with a Mooney viscosity within a predetermined range is used. As a result, the formability of the teeth is good, and the teeth can be formed with a predetermined range of Duro-D hardness. In this method of manufacturing toothed belts, the base and teeth of the belt body are integrally molded. In this manufacturing method, the base and teeth are molded simultaneously in a single process.

[0064] Two methods are known for manufacturing toothed belts: one in which the base and teeth are integrally molded (also referred to as the one-stage method in this specification), and another in which only the teeth are partially molded first, and then the base is molded and the base and teeth are integrated (also referred to as the two-stage method in this specification). Comparing the two manufacturing methods, the one-stage method is more economically advantageous because it has fewer steps and can be manufactured in a shorter time. On the other hand, the one-stage method may have inferior moldability of the teeth compared to the two-stage method.

[0065] The method for manufacturing a toothed belt according to an embodiment of the present invention uses an uncrosslinked rubber sheet with a Mooney viscosity within a predetermined range, and therefore, despite being a one-step manufacturing process, it exhibits good moldability of the teeth. According to this method for manufacturing a toothed belt, the toothed belt 1 can be manufactured at low cost and in a short time. Figures 5-7 illustrate the manufacturing method of the toothed belt 1. Figures 5-7 show only the mold 5 for belt forming and a portion of the belt (including the belt material). The manufacturing method for the toothed belt 1, as explained with reference to Figures 5-7, is a one-step manufacturing method in which the teeth and base are integrally molded in a single process.

[0066] In the manufacture of the toothed belt 1, a belt molding die 5 is used. The mold 5 is cylindrical. The outer circumference of the mold 5 is provided with recesses 51 extending in the axial direction and protrusions 52 extending in the axial direction. The recesses 51 have a cross-sectional shape corresponding to the belt teeth 12 and are grooves extending in the axial direction (the direction perpendicular to the plane of the paper in Figure 5). The recesses 51 are provided at regular intervals in the circumferential direction. The protrusions 52 are provided between adjacent recesses 51.

[0067] (1) Prepare the materials. An uncrosslinked rubber composition is obtained by kneading the rubber components and then adding and kneading the rubber compounding agent. An uncrosslinked rubber sheet 23 is produced by molding the obtained uncrosslinked rubber composition. At this time, a method such as calendering can be used to mold the uncrosslinked rubber sheet 23.

[0068] Prepare the core wire 3 and reinforcing fabric 4, and apply adhesive treatment or surface preparation to each as needed. Furthermore, the reinforcing fabric 4 is formed into a cylindrical shape.

[0069] The uncrosslinked rubber sheet 23 used in the embodiments of the present invention has a Mooney viscosity of 45 MS(1+4)100°C or higher and 60 MS(1+4)100°C or lower. A Mooney viscosity within this range is suitable for molding tooth portions with a Duro-D hardness within the above range. In contrast, when the Mooney viscosity is 45 MS(1+4) 100°C or lower, it is not easy to increase the Duro-D hardness to the above range. On the other hand, when the Mooney viscosity exceeds 60, defects in the tooth formation are likely to occur when manufacturing toothed belts. The Mooney viscosity described above is measured according to the method compliant with JIS K6300-1 (2013).

[0070] (2) As shown in Figure 5, first, a cylindrical reinforcing cloth 4 is placed over the outer surface of the mold 5. The core wire 3 is then wound spirally over the reinforcing cloth 4. At this time, it is preferable to wind the core wire 3 while applying a tension of 98N to 490N.

[0071] After winding the core wire 3, the uncrosslinked rubber sheet 23 is then wound around it. Multiple sheets of the uncrosslinked rubber sheet 23 (two sheets in Figure 5) are wound around it. As a result, an uncrosslinked molded body 13 is formed on the outer circumference of the mold 5, in which the reinforcing fabric 4, core wire 3, and uncrosslinked rubber sheet 23 are laminated. In this case, it is preferable to laminate the uncrosslinked rubber sheets 23 so that the row direction corresponds to the belt length direction. In particular, if the uncrosslinked rubber sheets 23 contain short fibers, it is preferable to laminate the uncrosslinked rubber sheets 23 so that the row direction corresponds to the belt length direction. When multiple uncrosslinked rubber sheets 23 are wrapped around the material, each uncrosslinked rubber sheet may have the same composition or a different composition. In the case where uncrosslinked rubber sheets with different compositions are wrapped around the material, the Mooney viscosity of each uncrosslinked rubber sheet must be between 45 MS(1+4)100°C and 60 MS(1+4)100°C. When multiple uncrosslinked rubber sheets 23 are wrapped around the belt, for example, the uncrosslinked rubber sheet wrapped around the inner circumference (the uncrosslinked rubber sheet that mainly forms the teeth after molding) can be an uncrosslinked rubber sheet containing short fibers, while the uncrosslinked rubber sheet wrapped around the outer circumference (the uncrosslinked rubber sheet that mainly forms the base after molding) can be an uncrosslinked rubber sheet that does not contain short fibers. In this case, flexibility on the back side is ensured, and a toothed belt that is less prone to cracking on the back side can be manufactured.

[0072] (3) As shown in Figure 6, the rubber sleeve 6 is placed over the uncrosslinked molded body 13 on the mold 5. The uncrosslinked molded body 13 with the rubber sleeve 6 is placed inside a vulcanizing can (not shown) together with the mold 5, and the vulcanizing can is sealed. High-temperature and high-pressure steam is filled into the vulcanizing can. This state is maintained for a predetermined time. As a result, the uncrosslinked molded body 13 is pressed towards the mold 5 and heated. The uncrosslinked rubber sheet 23 flows within the cavity formed between the mold 5 and the rubber sleeve 6. The uncrosslinked rubber sheet 23 passes between the core wires 3. The uncrosslinked rubber sheet 23 flows into each of the multiple recesses 51 provided in the mold 5 while pressing against the reinforcing fabric 4. As the uncrosslinked rubber sheet 23 flows within the cavity in this manner, it integrates with the core wires 3 and the reinforcing fabric 4 and becomes crosslinked. As a result, a cylindrical belt slab 14 is formed, as shown in Figure 7. In this process, the base and the teeth are vulcanized simultaneously. In this process, the base and the teeth are integrally molded to obtain the belt body.

[0073] (4) The inside of the vulcanizing can is depressurized to release the seal. The belt slab 14 formed between the mold 5 and the rubber sleeve 6 is demolded. The demolded belt slab 14 is cut into slices. The toothed belt 1 is obtained by going through these steps.

[0074] The method for manufacturing a toothed belt according to the embodiment of the present invention is a one-step process in which the base and the teeth are integrally molded in a single step. Therefore, the method for manufacturing a toothed belt according to the embodiment of the present invention allows for the manufacture of toothed belts in a shorter time and at a lower cost compared to a two-step process. [Examples]

[0075] The embodiments of the present invention will be described in more detail below with reference to examples, but the embodiments of the present invention are not limited to the following examples. Here, we manufactured several toothed belts and evaluated their performance.

[0076] (Belt raw material) (1) Uncrosslinked rubber sheet Uncrosslinked rubber compositions A to H with the formulations shown in Table 1 were prepared. The uncrosslinked rubber compositions were prepared by kneading the rubber components and then adding and kneading the rubber compounding agent. Using each of the uncrosslinked rubber compositions A to H, uncrosslinked rubber sheets A to H with a thickness of 1.0 mm were produced by calendering.

[0077] The Mooney viscosity of each of the uncrosslinked rubber sheets A to H was measured using a method compliant with JIS K6300-1 (2013). Here, an S-rotor was used as the rotor. The sample dimensions were obtained by stacking six 1mm thick uncrosslinked rubber sheets, punching them out to a diameter of approximately 50mm, and forming two disc-shaped pieces as a pair.

[0078] [Table 1]

[0079] In Table 1, HNBR(1) is Zetpol 2010 (manufactured by Nippon Zeon Co., Ltd.), HNBR(2) is Zeoforte ZSC2195CX (manufactured by Nippon Zeon Co., Ltd.), HNBR(3) is Zetpol 2010L (manufactured by Nippon Zeon Co., Ltd.), and HNBR(4) is Zeoforte ZSC2195LCX (manufactured by Nippon Zeon Co., Ltd.). Also in Table 1, the aramid short fibers are para-aramid short fibers with a fiber length of 1 mm and a wire diameter of 12 μm, and the organic peroxide is peroximone F40 (manufactured by NOF Corporation).

[0080] (2) Core wire Carbon core wires with a diameter of 1.0 mm and carbon core wires with a diameter of 2.0 mm were used, which had been bonded with a converging agent and an adhesive. The converging agent and adhesive used were compositions containing HNBR and a maleimide-based crosslinking agent that is crosslinked by heat treatment.

[0081] (3) Reinforcement fabric The following bonding treatment was applied to a fabric in which the warp and weft threads are made of polyamide fibers. The bonding treatments involved a soaking process, in which the fabric was immersed in a low-viscosity rubber adhesive and then dried, and a coating process, in which a high-viscosity rubber adhesive was applied to the side of the fabric that would become the belt body and then dried. The thickness of the reinforcing fabric before molding was set to 1.2 mm, 1.4 mm, 1.7 mm, or 1.8 mm. The thickness of each reinforcing fabric was prepared to match the thickness of the fabric before bonding.

[0082] (Dimensions of toothed belt) We manufactured toothed belts of the type known as S8M and the type known as S14M. The dimensions of the toothed belt called S8M are as follows, indicated by the symbols shown in Figure 8. Pb=8.00mm, Tb=5.00mm, h1=1.95mm, h2=3.05mm, R=5.20mm, W=5.20mm, a=0.686mm, r1=0.80mm, r2=0.80mm, PLD(PITCH LINE DIFFERENTIAL)=0.686mm. Furthermore, this toothed belt has a length of 840 mm and a width of 10 mm.

[0083] The dimensions of the toothed belt called S14M are as follows, indicated by the symbols shown in Figure 8. Pb=14.00mm, Tb=10.20mm, h1=4.90mm, h2=5.30mm, R=9.10mm, W=9.10mm, a=1.397mm, r1=1.40mm, r2=1.40mm, PLD=1.397mm. Furthermore, this toothed belt has a length of 1400mm and a width of 14mm.

[0084] [Examples 1-5, Comparative Examples 1-4, and 6-7] The toothed belt was manufactured using the toothed belt manufacturing method described above (single-stage manufacturing method). The uncrosslinked rubber sheet, core wire, and reinforcing fabric are as described above. The selected uncrosslinked rubber composition, belt tooth pitch, core wire pitch (core wire gap dimension), and tension when winding the core wire are as shown in Table 2. The vulcanization conditions (steam temperature and holding time in step (3) of the toothed belt manufacturing method described above) were 120°C for 5 minutes, followed by 170°C for 15 minutes. Furthermore, the diameter of the core wire (the outer diameter φW of the core wire in the belt width direction at the tooth root) was calculated as the average value of three locations using cross-sectional images obtained in the calculation of the absolute value X described later. The result showed that it was the same as, or slightly larger than, the diameter of the core wire before winding.

[0085] [Comparative Example 5] Using the belt material combinations shown in Table 2, toothed belts were manufactured using the following manufacturing method (two-stage process). Figures 9 to 13 show the manufacturing method of the toothed belt in this comparative example.

[0086] (1) In the same manner as in the one-stage manufacturing method, an uncrosslinked rubber sheet 23 (uncrosslinked rubber sheets 23A, 23B), a core wire 3, and a reinforcing cloth 4 were prepared. Furthermore, the reinforcing fabric 4 was formed into a cylindrical shape.

[0087] (2) As shown in Figure 9, first, a cylindrical reinforcing cloth 4 was placed over the outer surface of the mold 5. Next, an uncrosslinked rubber sheet 23A was wrapped around the reinforcing fabric 4. The uncrosslinked rubber sheet 23A is a sheet made of uncrosslinked rubber composition A (see Table 2).

[0088] Subsequently, as shown in Figure 10, a rubber sleeve 6 was placed over the first uncrosslinked molded body 13A on the mold 5, and this was placed inside the vulcanizing can and sealed. Next, high-temperature (120°C) and high-pressure steam was filled into the vulcanizing can and held in this state for 5 minutes. As a result, the first uncrosslinked molded body 13A was pressed towards the mold 5 and heated. As a result, the uncrosslinked rubber sheet 23A flowed into each of the multiple recesses 51 of the mold 5 while pressing against the reinforcing fabric 4, and was crosslinked. At this time, the uncrosslinked rubber sheet 23A was heated to a semi-crosslinked state. As a result, multiple semi-bridged tooth portions 122 were formed, as shown in Figure 11.

[0089] (3) Next, as shown in Figure 12, the core wire 3 was spirally wrapped around the outer circumference of the formed tooth portion 122. Furthermore, one uncrosslinked rubber sheet 23B was wrapped around it to form the base. As a result, a second uncrosslinked molded body 13B was formed on the mold 5 (on the teeth portion 122), in which the core wire 3 and the uncrosslinked rubber sheet 23B were laminated. As shown in Table 2, the uncrosslinked rubber sheet 23B is a sheet made of uncrosslinked rubber composition B.

[0090] (4) As shown in Figure 13, the rubber sleeve 6 was placed over the second uncrosslinked molded body 13B on the mold 5, and this was placed inside the vulcanizing can and sealed. Next, high-temperature (170°C) and high-pressure steam was filled into the vulcanizing can. Furthermore, this state was maintained for 15 minutes. As a result, the second uncrosslinked molded body 13B was pressed towards the mold 5 and heated. At this time, the uncrosslinked rubber sheet 23B passed between the core wires 3 and was crosslinked while being pressed against the multiple semi-crosslinked teeth 122 formed in the multiple recesses 51. As a result, a cylindrical belt slab 14 was formed having integrated and fully crosslinked teeth 22 and base 21.

[0091] (5) The inside of the vulcanizing can was depressurized to release the seal, and then the belt slab 14 formed between the mold 5 and the rubber sleeve 6 was demolded. After that, as in the example, the demolded belt slab 14 was cut into sections to obtain a toothed belt. The diameter of the core wire of the resulting toothed belt was the same as the diameter of the core wire before winding.

[0092] [Table 2]

[0093] (evaluation) The toothed belts manufactured in the examples and comparative examples were evaluated as follows. The results are shown in Table 3.

[0094] (1) Belt formability The judgment was made based on whether the tooth height of the belt teeth (tooth portion) was within the tolerance range. If it was within the tolerance range, it was evaluated as "○"; if it was outside the tolerance range, it was evaluated as "×". The tooth height of the belt teeth described above was determined by selecting three belt teeth at approximately equal intervals from the entire circumference of the belt, obtaining a sample piece with a belt width of 5 mm including the selected teeth, magnifying and projecting the belt tooth shape at 10 to 20 times, and obtaining the tooth height as the distance between the tooth tip and tooth root line in the resulting projection.

[0095] (2) The absolute value X of the difference between distance LA and distance LB As described above, images of the toothed belt 1 perpendicular to the belt length were obtained, and the average value was calculated using the obtained images. The average value was calculated at three points. The results are shown in Table 3. Comparative Example 1 showed a "×" rating for belt formability, and therefore the absolute value X could not be calculated. The cross-sectional image obtained here was used to calculate the diameter of the core wire.

[0096] (3) Hardness of the belt teeth The hardness of the cross-linked rubber composition constituting the belt teeth was measured using the following method, based on Duro-D hardness. Measurements were taken using a commercially available Type D durometer. Here, the rubber hardness tester was pressed perpendicularly against the side surface of the belt teeth (the end face of the teeth in the belt width direction) during measurement. The ambient temperature during measurement was 23±2°C. Measurements were performed on three belt teeth, and the average value was used as the result. The results are shown in Table 3.

[0097] (4) Measurement of skip torque (durability evaluation) Using the power transmission system 90 with the pulley layout shown in Figure 14, a belt running test was performed according to the following procedures [1] to [7], and the skip torque was measured. In this test, the belt running test for the toothed belt called S8M was performed using a 24-tooth drive pulley and a 48-tooth driven pulley. Similarly, the belt running test for the toothed belt called S14M was performed using a 28-tooth drive pulley and a 45-tooth driven pulley.

[0098] [1] A belt is placed on two pulleys (drive pulley 91 and driven pulley 92), and with the drive shaft fixed, the driven shaft is slid (see arrow in the figure) to apply tension to the belt to a predetermined level. [2] Then rotate the belt a few times to allow it to settle in. [3] Check with a tension meter to see if the belt is under the specified tension. Repeat [1] and [2] until the specified tension is reached (350N for S8M, 400N for S14M). [4] When the specified tension is reached, the driven shaft is fixed. [5] Rotate the belt at a constant speed until it reaches a predetermined rotational speed. [6] While rotating at a constant speed, the load on the driven pulley 92 is gradually increased. [7] Increase the load and measure the torque (skip torque) when the belt skips teeth using a torque meter (not shown). The results are shown in Table 3. In this evaluation, for toothed belts called S8M, a skip torque of 90N or more is considered sufficiently high, and for toothed belts called S14M, a skip torque of 250N or more is considered sufficiently high.

[0099] [Table 3]

[0100] As shown in Table 3, the toothed belt according to the embodiment of the present invention was found to have high skip torque and be less prone to tooth skipping. Although Comparative Example 5 has a sufficiently high skip torque, it is manufactured using a two-stage process, resulting in a longer manufacturing time and higher manufacturing costs.

[0101] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims and is intended to include all modifications in the meaning and scope equivalent to the claims. [Explanation of symbols]

[0102] 1. Toothed belt 2. Belt body 3 core wires 4. Reinforcement fabric 5. Mold 6 Rubber sleeve 11 Back 12 belt teeth 13, 13A, 13B Uncrosslinked molded product 14 Belt Slab 21 Base 22, 122 Teeth 23, 23A, 23B Uncrosslinked Rubber Sheets 24 Root 51 Recess 52 Convex part 90 Transmission System 91 Drive pulley 92 Driven pulley

Claims

1. A toothed belt comprising a belt body having a base, a plurality of teeth integrated on the inner circumference side of the base, and a core wire embedded in the base, The tooth pitch is between 8 mm and 14 mm. The distance L from the root line to the center of the core line varies along the length of the belt. The absolute value X of the difference between the distance LA from the root line to the center of the core wire at the root of the tooth and the distance LB from the root line to the center of the core wire at the belt tooth is 0.20 mm or more. The tooth portion has a hardness of 46 or more and 52 or less, as measured by a Type D durometer. The diameter of the aforementioned core wire is 1.0 mm or more and 2.4 mm or less. The belt body is a toothed belt composed of a cross-linked molded product of an uncrosslinked rubber sheet having a Mooney viscosity of 45 MS (1 + 4) 100°C or higher and 60 MS (1 + 4) 100°C or lower before molding.

2. The aforementioned core wire is embedded so as to form a spiral having a pitch in the belt width direction, The toothed belt according to claim 1, wherein the gap between adjacent core wires is 0.1 mm or more and 0.5 mm or less.

3. The toothed belt according to claim 1 or 2, wherein the ratio of the diameter of the core wire to the tooth pitch is 0.100 or more and 0.175 or less.

4. A method for manufacturing a toothed belt having a base, a belt body comprising a base and a plurality of teeth integrated on the inner circumference of the base, and a core wire embedded in the base, (A) A process of winding a core wire around the outer circumference of a cylindrical mold having a cross-sectional shape corresponding to belt teeth, with axially extending recesses and axially extending protrusions provided between adjacent recesses on its outer circumference, (B) A step of winding at least one layer of uncrosslinked rubber sheet around the mold on which the core wire is wound, (C) A step of integrally molding the base portion and the teeth portion by placing a rubber sleeve over the mold around which the core wire and at least one layer of uncrosslinked rubber sheet are wound, and then heating the uncrosslinked rubber sheet while pressing it toward the mold, Includes, A method for manufacturing a toothed belt, wherein the Mooney viscosity of the uncrosslinked rubber sheet is 45 MS (1 + 4) 100°C or higher and 60 MS (1 + 4) 100°C or lower.

5. The core wire is wound to form a spiral having a pitch in the axial direction, The diameter of the aforementioned core wire is 1.0 mm or more and 2.4 mm or less. The gap between adjacent core wires is between 0.1 mm and 0.5 mm. A method for manufacturing a toothed belt according to claim 4, wherein the tooth pitch of the toothed belt is 8 mm or more and 14 mm or less.

Images