transmission belt

Abstract

The toothed belt 1, as a power transmission belt of the present invention, has an endless strip-shaped back portion 11 and belt teeth 12 provided on the inner circumference side of the back portion 11. The back portion 11 comprises a base portion 21 made of rubber material and a core wire 3 embedded in the base portion 21. The core wire 3 is a twisted yarn made by twisting together filaments 31, a part of the base portion 21 is contained within the core wire 3, and the bending rigidity of the core wire 3 taken from the toothed belt 1 is 0.15 g·cm 2 / dtex or more 0.30g cm 2 It is below / dtex.

Description

[Technical Field]

[0001] This invention relates to a power transmission belt. This application claims priority under Japanese application No. 2024-100176, filed on June 21, 2024, and incorporates all the provisions of the said Japanese application. [Background technology]

[0002] Transmission belts, such as toothed belts and V-ribbed belts, have a belt body made of rubber or elastomer. A core wire is embedded in this belt body. The core wire extends substantially in the circumferential direction of the belt. Typically, a twisted yarn made by twisting filaments together is used for the core wire (for example, Patent Document 1 below). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-148238 [Overview of the project] [Problems that the invention aims to solve]

[0004] In power transmission belts, bending and unbending are repeated cycles. From the perspective of extending lifespan, power transmission belts require improved resistance to bending fatigue. [Means for solving the problem]

[0005] This invention was made in view of these circumstances. The purpose of this invention is to provide a transmission belt that can achieve improved bending fatigue resistance.

[0006] Incidentally, power transmission belts are used with a set tension. For example, studies are underway to improve performance by focusing on the tensile modulus of elasticity and the twist coefficient of the core wires. As mentioned earlier, the core wire uses twisted yarn made by twisting filaments together. Since the twisted yarn contains gaps, a portion of the belt body covering the core wire may be embedded within the core wire of the transmission belt. The greater the amount of belt body embedded within the core wire, the more the movement of the filaments is restricted. This ease (or difficulty) of movement of the filaments affects the performance of the core wire's properties. In other words, if the amount of belt body embedded within the core wire can be determined, the core wire can be positioned within the transmission belt in a way that allows it to fully perform its properties. However, power transmission belts are configured so that the belt body and the core wires are sufficiently joined. Because the belt body is also joined around the core wires, it is difficult to accurately determine the amount of belt body contained within the core wires. As mentioned above, the belt body inherent in the core wire restrains the movement of the filaments within the cross-section of the core wire. Therefore, in order to improve the bending fatigue resistance of the transmission belt, the inventor focused on the bending stiffness of the core wire taken from the transmission belt, rather than the tensile modulus of elasticity or twist coefficient of the core wire mentioned above, and completed the following invention.

[0007] (1) The power transmission belt of the present invention has an endless strip-shaped back portion and belt teeth provided on the inner circumference side of the back portion, wherein the back portion comprises a base portion made of rubber material and a core wire embedded in the base portion, wherein the core wire is a twisted yarn made by twisting filaments together, a part of the base portion is embedded in the core wire, and the bending rigidity of the core wire taken from the power transmission belt is 0.15 g·cm 2 / dtex or more 0.30g cm 2 It is below / dtex.

[0008] In this power transmission belt, the base inherent in the core wire effectively restrains the movement of the filaments. This power transmission belt can suppress buckling of the filaments and friction between filaments while maintaining the flexibility of the core wire. This power transmission belt can improve bending fatigue resistance.

[0009] (2) In the transmission belt of (1) above, it is preferable that the filament is an inorganic fiber filament. This is suitable for improving the tension maintenance property of the transmission belt.

[0010] (3) In the transmission belt of (2) above, it is preferable that the inorganic fiber filament is a carbon fiber filament. This is suitable for improving the durability and tension maintenance property of the transmission belt.

[0011] (4) In any of the transmission belts of (1) to (3) above, it is preferable that the core wire is a single-twisted yarn or a combined-twisted yarn. This is suitable for improving the flexure fatigue resistance of the transmission belt.

[0012] (5) In the transmission belt of (4) above, it is preferable that the core wire is a single-twisted yarn, and the twist number of the single-twisted yarn is 40 turns / m or more and 120 turns / m or less. This is more suitable for improving the flexure fatigue resistance of the transmission belt.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a transmission belt capable of achieving an improvement in flexure fatigue resistance.

Brief Description of the Drawings

[0014] [Figure 1] It is a perspective view schematically showing a toothed belt which is a transmission belt. [Figure 2] It is a cross-sectional view taken along line A-A of FIG. 1. [Figure 3] It is a cross-sectional view taken along line B-B of FIG. 1. [Figure 4] It is a diagram for explaining a core wire. [Figure 5] It is a diagram for explaining a method of manufacturing a toothed belt. [Figure 6] It is a diagram for explaining a method of manufacturing a toothed belt. [Figure 7] It is a diagram showing a pulley layout of a transmission system used for evaluating flexure fatigue resistance.

Best Mode for Carrying Out the Invention

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

[0016] (Transmission Belt) FIG. 1 is a perspective view showing an example of a transmission belt 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1. FIG. 3 is an end view taken along line B-B of FIG. 1. The transmission belt 1 in FIG. 1 is a toothed belt as an engaging transmission belt. FIG. 1 shows a part of the toothed belt 1. The toothed belt 1 shown in FIG. 1 is a single-sided toothed belt. The toothed belt 1 is endless and belt-shaped. In FIGS. 1 to 3, the direction indicated by the double-headed arrow X is the width direction of the toothed belt 1. The direction indicated by the double-headed arrow Y is the circumferential direction of the toothed belt 1. The belt circumferential direction is also the length direction of the toothed belt 1. The direction indicated by the double-headed arrow Z is the thickness direction of the toothed belt 1. The upper side of each paper surface is the outer peripheral side of the toothed belt 1, and the lower side is the inner peripheral side.

[0017] The belt length of the toothed belt 1 is, for example, 500 mm or more and 3000 mm or less. The belt width Wb of the toothed belt 1 is, for example, 10 mm or more and 200 mm or less. The belt thickness Tb of the toothed belt 1 is, for example, 3 mm or more and 20 mm or less. The belt thickness Tb of the toothed belt 1 is the thickness of the thickest part of the toothed belt 1. The dimensions of the toothed belt according to the embodiment of the present invention are not limited to this range.

[0018] The toothed belt 1 has a back 11 and a plurality of belt teeth 12. The back 11 extends in the belt circumferential direction. The back 11 is endless and belt-shaped. In a cross-section perpendicular to the belt circumferential direction of the toothed belt 1, the cross-sectional shape of the back 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. The pitch Pb of the belt teeth 12 is, for example, 8 mm or more and 14 mm or less. Each belt tooth 12 extends in the belt width direction. In this embodiment, the belt teeth 12 are straight teeth. The belt teeth 12 may also be helical teeth. The tooth profile of the belt teeth 12 is, for example, an arc tooth profile. The tooth profile of the belt teeth 12 may also be an S tooth profile or a trapezoidal tooth profile. The tooth height H of the belt teeth 12 is, for example, 2 mm or more and 8 mm or less.

[0019] (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.

[0020] (Belt body) The belt body 2 is made of rubber material. In other words, the rubber material forms the belt body 2. The rubber material is a crosslinked product of a rubber composition containing raw rubber components. Examples of raw rubber components include ethylene-α-olefin elastomers such as urethane (U), ethylene-propylene-diene terpolymer (EPDM), and ethylene-propylene copolymer (EPM); chloroprene rubber (CR); and nitrile rubbers such as acrylonitrile rubber (NBR) and hydrogenated acrylonitrile rubber (H-NBR).

[0021] Rubber compositions for rubber materials may contain rubber compounding agents in addition to raw rubber components. Examples of rubber compounding agents include crosslinking agents such as sulfur and organic peroxides, reinforcing agents such as carbon black, fillers, antioxidants, softeners, vulcanization accelerators, vulcanization accelerator aids, co-crosslinking agents, and short fibers.

[0022] As will be described later, in the manufacture of the toothed belt 1, the rubber composition for the rubber material is pressurized and heated together with the core wire 3 and reinforcing fabric 4 in a cavity formed between the inner mold and the outer mold. The rubber composition is fluid. A portion of the rubber composition penetrates the core wire 3 and reinforcing fabric 4. A toothed belt 1 is obtained in which a portion of the belt body 1 penetrates the core wire 3 and reinforcing fabric 4.

[0023] In a toothed belt 1 in which a portion of the belt body 2 is embedded in the core wire 3 and reinforcing fabric 4, the belt teeth 12 are less prone to chipping or wear. Separation of the core wire 3 from the belt body 2 is also less likely. This toothed belt 1 can have good durability.

[0024] The rubber material is preferably a crosslinked rubber composition containing urethane as a raw rubber component, i.e., made of polyurethane. As mentioned above, the belt body 2 is formed of a rubber material. The belt body 2 is preferably made of polyurethane. If the belt body 2 is made of polyurethane, it is more preferable that the belt body 2 is made of thermosetting polyurethane. Thermosetting polyurethane is a cured product of a thermosetting urethane composition obtained by blending a curing agent, an optional component such as a plasticizer, with a urethane prepolymer. Thermosetting polyurethane is more preferable as the material for the belt body 2 because, for example, the thermosetting urethane composition is easily impregnated into the core wire 3 and reinforcing fabric 4. The thermosetting urethane composition is suitable for manufacturing a toothed belt 1 in which a portion of the belt body 2 is embedded in the core wire 3 and reinforcing fabric 4.

[0025] The above-mentioned urethane prepolymer is a relatively low molecular weight urethane compound having multiple NCO groups at its terminals. The above-mentioned urethane prepolymer is obtained by the reaction of an isocyanate component with a polyol component. Examples of the above-mentioned isocyanate components include tolylene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI). Examples of the polyol components mentioned above include polytetramethylene ether glycol (PTMG). The above-mentioned urethane prepolymer may be composed of one type of urethane compound, or it may be composed of a mixture of multiple types of urethane compounds.

[0026] Examples of the curing agents mentioned above include amine compounds such as 1,4-phenylenediamine, 2,6-diaminotoluene, 1,5-naphthalenediamine, 4,4'-diaminodiphenylmethane, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), and 4-chloro-3,5-diaminobenzoate isobutyl. These curing agents may be used individually or in combination of two or more. The amine compound used as the curing agent is preferably blended such that its α-value (NH2 group / NCO group) is between 0.70 and 1.10. The α-value is the ratio of the number of moles of NH2 groups in the curing agent to the number of moles of NCO groups in the urethane prepolymer.

[0027] Examples of the above plasticizers include dialkyl phthalates such as dibutyl phthalate (DBP) and dioctyl phthalate (DOP); dialkyl adipates such as dioctyl adipate (DOA); and dialkyl sebacates such as dioctyl sebacate (DOS). One or more of these plasticizers may be used. The amount of the plasticizer used is, for example, 3 parts by mass or more and 20 parts by mass or less per 100 parts by mass of urethane prepolymer.

[0028] The thermosetting urethane composition may further contain a lubricant. Examples of lubricants include fatty acid esters, hydrocarbon resins, paraffins, higher fatty acids, fatty acid amides, aliphatic alcohols, metal soaps, and modified silicones. It is preferable that the lubricant contains one or more of these. If a lubricant is included, the amount is, for example, 3 parts by mass or more and 20 parts by mass or less per 100 parts by mass of urethane prepolymer.

[0029] The thermosetting urethane composition may further contain, for example, colorants, defoamers, stabilizers, etc.

[0030] If the belt body 2 is made of polyurethane, the JIS-A hardness of the belt body 2 (specifically, the polyurethane constituting the belt body 2) is, for example, 85 or more and 100 or less. The JIS-A hardness of the polyurethane is preferably between 90 and 100. Polyurethane having a JIS-A hardness of 90 or higher can effectively contribute to improving the abrasion resistance of the belt body 2. The JIS-A hardness of polyurethane is measured using a Type A hardness test based on JIS K7312:1996. JIS-A hardness is measured using a Type A durometer.

[0031] 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. As mentioned above, the belt body 2 is made of rubber material. Therefore, the base 21 and teeth 22 that make up the belt body 2 are made of rubber material. If the belt body 2 is made of polyurethane, the base 21 and teeth 22 are also made of polyurethane. The base 21 and teeth 22 are made of the same polyurethane.

[0032] As described above, the toothed belt 1 has a back portion 11 and a plurality of belt teeth 12. The back portion 11 of the toothed belt 1 in the part where the belt teeth 12 are provided is composed of a base portion 21 and a core wire 3. The back portion 11 of the toothed belt 1 in the part where the belt teeth 12 are not provided is composed of a base portion 21, a core wire 3, and a reinforcing fabric 4. The belt teeth 12 are composed of teeth 22 and a reinforcing fabric 4.

[0033] (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.

[0034] Examples of fibers that make up the reinforcing fabric 4 include nylon fibers such as nylon 6,6, nylon 4,6, and nylon 6, chemical fibers such as polyketone fibers, aramid fibers, and polyester fibers, and natural fibers such as cotton. The reinforcing fabric 4 may be composed of a single type of fiber or of multiple types of fibers.

[0035] The reinforcing fabric 4 may be woven or knitted. It is preferable that the reinforcing fabric 4 is woven.

[0036] Examples of fabrics used as reinforcing fabric 4 include canvases such as 2 / 2 twill canvas, 3 / 1 twill canvas, plain weave canvas, and satin weave canvas, which are formed by warp and weft threads. When canvas is used as the reinforcing fabric 4, the fineness of the warp and weft threads is preferably 44 to 933 dtex, and more preferably 44 to 470 dtex. The yarn density of the warp and weft threads is preferably 74 to 430 threads / 5cm width, and more preferably 132 to 250 threads / 5cm width. The basis weight of the reinforcing fabric 4 is preferably 90 to 600 g / m². 2 And more preferably 200-450 g / m² 2 That is the case.

[0037] The reinforcing fabric 4 is preferably provided such that, for example, one of the warp threads or the weft threads coincides with the length direction of the belt. The stretch properties of the reinforcing fabric 4, which uses a stretch-processed yarn such as woolly yarn as the weft, are anisotropic. When the reinforcing fabric 4 has anisotropic stretch properties, it is preferable that the weft is arranged to coincide with the length of the belt so that the stretch properties in the length direction of the belt are high.

[0038] The reinforcing fabric 4 may be subjected to an adhesive treatment before forming the toothed belt 1, for example, by immersing it in an epoxy adhesive and then drying it.

[0039] As mentioned above, when the belt body 2 is made of thermosetting polyurethane, the thermosetting polyurethane composition hardens while it is penetrating the gaps in the reinforcing fabric 4. Therefore, the surface (inner circumferential surface) of the belt teeth 12 is not made up of the reinforcing fabric 4 alone, but rather of the reinforcing fabric 4 and thermosetting polyurethane.

[0040] (Core wire) The core wires 3 are embedded in the base 21 of the belt body 2. The core wires 3 extend substantially in the circumferential direction of the belt. For example, as shown in Figure 1, the core wires 3 are spaced apart in the belt width direction. The outer diameter of the core wire 3 is, for example, between 0.45 mm and 3.0 mm.

[0041] Figure 4 is a cross-sectional view of the core wire 3. Figure 4 shows an example of the core wire 3. The core wire 3 contains numerous filaments 31. The core wire 3 is a twisted yarn formed by twisting the filaments 31 together. The core wire 3 shown in Figure 4 is a single-ply yarn. A single-ply yarn is a twisted yarn in which a bundle of filaments 31 is twisted in one direction. Although not shown, the core wire 3 may also be a double-ply yarn. A double-ply yarn is a twisted yarn in which, for example, multiple strands (not shown) obtained by under-twisting a bundle of filaments 31 in one direction are gathered together and then over-twisted in the opposite direction to the under-twist.

[0042] In this toothed belt 1, if the core wire 3 is a single-ply yarn, the number of twists of the single-ply yarn is preferably, for example, 40 twists / m or more and 120 twists / m or less. If the core wire 3 is a multi-ply yarn, the number of undertwists of the multi-ply yarn is preferably, for example, 40 twists / m or more and 120 twists / m or less. The number of overtwists of the multi-ply yarn is more preferably, for example, 40 twists / m or more and 120 twists / m or less.

[0043] As mentioned above, the core wires 3 are arranged 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. From the viewpoint of obtaining excellent durability and excellent tension retention in high-load transmission, the number of core wires 3 per 10 mm of belt width is preferably 6 or more and 10 or less per 10 mm, and more preferably 7 or more and 9 or less per 10 mm.

[0044] The core wire 3 has a pitch in the belt width direction and is arranged to form a spiral. The core wire 3 may consist of two strands, an S-twisted yarn and a Z-twisted yarn, arranged to form a double helix.

[0045] As mentioned above, the core wire 3 is a twisted yarn made by twisting together filaments 31. From the viewpoint of obtaining excellent durability under high load transmission and excellent tension retention under high load transmission, it is preferable that the filaments 31 are inorganic fiber filaments (hereinafter also called inorganic filaments). Examples of inorganic filaments include carbon fiber filaments and glass fiber filaments. From the viewpoint of obtaining excellent durability under high load transmission and excellent tension retention under high load transmission, it is more preferable that the filament 31 is a carbon fiber filament (hereinafter also called a carbon filament). In this case, from the viewpoint of obtaining excellent durability under high load transmission, the diameter of the carbon filament is preferably 4 μm to 9 μm, and more preferably 6 μm to 8 μm. If the filament 31 is a carbon filament, the core wire 3 is a single-ply yarn, and it is even more preferable that the number of twists of the single-ply yarn is 40 turns / m or more and 120 turns / m or less.

[0046] Examples of carbon filaments include PAN-based carbon filaments and pitch-based carbon filaments. From the standpoint of flexibility, if the filament 31 constituting the core wire 3 is a carbon filament, in other words, if the core wire 3 is a carbon core wire, then it is preferable that the carbon filament is a PAN-based carbon filament.

[0047] When the filament 31 is a carbon filament, the total number of carbon filaments constituting the core wire 3 is preferably 6,000 (6K) or more and 48,000 (48K) or less. In this case, it is suitable for obtaining excellent durability in high-load transmission and excellent tension retention in high-load transmission. For the same reason, the total number of carbon filaments is more preferably 9,000 (9K) or more and 18,000 (18K) or less. A more preferable total number of carbon filaments is 12,000 (12K).

[0048] The fineness of the carbon filament constituting the core wire 3 is preferably 400 tex or more and 3200 tex or less. In this case, it is suitable for obtaining excellent durability in high-load transmission and excellent tension retention in high-load transmission. For the same reason, the fineness of the carbon filament is more preferably 600 tex or more and 1200 tex or less. A more preferable fineness of the carbon filament is 800 tex.

[0049] In this toothed belt 1, the core wire 3 is pre-treated to increase the adhesion strength with the belt body 2. The pre-treatment is performed using a treatment agent. In the pre-treatment, the treatment agent (specifically, the main agent described later) is applied to the filament 31 or core wire 3 and dried, thereby adhering the treatment agent to the filament 31 or core wire 3.

[0050] Pretreatment may be performed when twisting the filaments 31 to form the core wire 3. Pretreatment may be performed on the core wire 3 formed by twisting the filaments 31. Pretreatment may be performed when twisting the filaments 31 to form the core wire 3, and also on the core wire 3 formed by twisting the filaments 31.

[0051] As a pretreatment agent, for example, an emulsion in which an epoxy group-containing compound and a curing agent are dispersed in water can be used. From the viewpoint of increasing the adhesion to the belt body 2, it is preferable that the treatment agent is an emulsion containing an epoxy group-containing compound and a curing agent as the main component, with a solid content ratio of 80% by mass or more of the main component. The solid content ratio of the main component is expressed as the ratio of the mass of the main component to the total mass of solids obtained by drying the treatment agent.

[0052] Examples of epoxy group-containing compounds include sorbitol polyglycidyl ether, glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, and trimethylolpropane polyglycidyl ether. Among these, polyglycerol polyglycidyl ether is preferred.

[0053] Examples of curing agents include isocyanate-based curing agents and amine-based curing agents. In this toothed belt 1, any of these may be used alone, or two or more may be used in combination. Examples of isocyanate-based curing agents include naphthalene diisocyanate, isophorone diisocyanate, 4,4'-diphenylmethane diisocyanate, toluene-2,4-diisocyanate, xylylene diisocyanate, tolylene diisocyanate, polymethylene polyphenyl diisocyanate, and hexamethylene diisocyanate. Among these, 4,4'-diphenylmethane diisocyanate is preferred. Commercially available isocyanate-based curing agents can also be used. An example of a commercially available isocyanate-based curing agent is "Grilbond IL-6" manufactured by EMS. Examples of amine-based curing agents include imidazole compounds, diamine compounds, and compounds having an oxazole ring. Among these, imidazole compounds are preferred. Commercially available amine-based curing agents can be used. An example of such a commercially available amine-based curing agent is "Curesol" manufactured by Shikoku Chemicals Co., Ltd.

[0054] As described above, in the pretreatment, a treatment agent is applied to the filament 31 or core wire 3. The degree of treatment agent application is determined by the application rate of the treatment agent to a core wire 3 of a predetermined length. This application rate is expressed as the ratio of the mass of the core wire 3 after treatment to the mass of the core wire 3 before treatment. In this toothed belt 1, the adhesion rate of the treatment agent is adjusted to a range of, for example, 1% to 30%. A preferred range for the adhesion rate is 2% to 17%.

[0055] In this toothed belt 1, instead of the emulsion containing an epoxy group-containing compound and a curing agent as described above, an aqueous solution containing, for example, resorcinol and formaldehyde, with a solid content ratio of 80% by mass or more, can be used as the treatment agent. This aqueous solution is also called RF solution, and the solid content ratio of the main component is expressed as the solid content ratio of the initial condensate of resorcinol and formaldehyde. For the initial condensate (RF) of resorcinol (R) and formaldehyde (F) in RF solution, the molar ratio of resorcinol (R) to formaldehyde (F) (R / F) is, for example, 1 / 3 to 1 / 0.5.

[0056] In this toothed belt 1, the RF liquid used as a processing agent may contain chemicals such as latex, as long as it does not impair the function. Examples of these latexes include vinylpyridine-styrene-butadiene rubber latex (VP-SBR), styrene-butadiene rubber latex (SBR), natural rubber latex (NR), chloroprene rubber latex (CR), chlorosulfonated polyethylene rubber latex (CSM), 2,3-dichlorobutadiene rubber latex (2,3-DCB), hydrogenated nitrile rubber latex (H-NBR), carboxylated hydrogenated nitrile rubber latex, butadiene rubber latex (BR), and nitrile rubber latex (NBR). The treatment agent may contain one or more of these.

[0057] When the treatment agent is an aqueous solution containing the initial condensate of resorcinol and formaldehyde and the aforementioned latex, this treatment agent is also called an RFL aqueous solution. In this case, the solid content ratio, which is the sum of the content of the initial condensate of resorcinol and formaldehyde and the content of the latex-derived solids in the RFL aqueous solution, is, for example, 10% by mass or more and 30% by mass or less. For the initial condensate (RF) of resorcinol (R) and formaldehyde (F) in an RFL aqueous solution, the molar ratio of resorcinol (R) to formaldehyde (F) (R / F) is, for example, 1 / 3 to 1 / 0.5. The mass ratio (RF / L) of the initial condensate (RF) of resorcinol (R) and formaldehyde (F) in the RFL aqueous solution to the latex-derived solids (L) is, for example, 1 / 10 to 1 / 0, preferably around 1 / 6. A mass ratio (RF / L) of 1 / 0 means that the RFL aqueous solution contains only the initial condensate (RF) and does not contain the latex-derived solids (L).

[0058] The mass of the treated core wire 3 is measured as follows: An initial load of 1 / 20 of the total decitex number of the untreated core wire 3 is applied to the treated core wire 3, and a 1m long sample is taken. After drying this sample in a desiccator for 24 hours or more, the mass of this sample is measured. The mass of the sample obtained in this way is used as the mass of the treated core wire 3. The mass of the untreated core wire 3 is the mass per 1m of the untreated core wire 3.

[0059] As mentioned above, the core wire 3 is a twisted yarn made by twisting together filaments 31. Since the twisted yarn contains gaps, a part of the base 21 that covers the core wire 3 fits into the core wire 3 embedded in the base 21 of the belt body 2. In this toothed belt 1, a part of the base 21 is embedded within the core wire 3. The base 21 (i.e., the belt body 2) embedded within the core wire 3 restrains the movement of the filaments 31 within the cross-section of the core wire 3. The greater the amount of belt body 2 contained within the core wire 3, the more the movement of the filament 31 within the cross-section of the core wire 3 is constrained, thus increasing the bending rigidity of the core wire 3.

[0060] Therefore, the inventor focused on the fact that the amount of belt body inherent in the core wire and the bending stiffness of the core wire are mutually related, and investigated the bending fatigue resistance of a toothed belt by controlling the bending stiffness of the core wire by adjusting the amount of belt body inherent in the core wire. (1) The bending stiffness of the core wire taken from the toothed belt was 0.15 g·cm 2 If the denier count is less than / dtex, the filament is more likely to move within the cross-section of the core wire, which can lead to filament buckling and friction between filaments, and (2) The bending stiffness of the core wire taken from the toothed belt was 0.30 g·cm 2 When the dtex limit is exceeded, the toothed belt experiences repeated bending and unbending, resulting in a large force being applied to it. This fatigue significantly reduces the strength of the toothed belt. This discovery led to the completion of the present invention. In other words, in this toothed belt 1, the bending stiffness of the core wire 3 taken from the toothed belt 1 is 0.15 g·cm. 2 / dtex or more 0.30g cm 2 It is below / dtex. In this toothed belt 1, the belt body 2, which is embedded in the core wire 3, effectively restrains the movement of the filaments 31. This toothed belt 1 can suppress buckling of the filaments 31 and friction between the filaments 31 while maintaining the flexibility of the core wire 3. This toothed belt 1 can improve bending fatigue resistance.

[0061] In the present invention, the bending rigidity of the core wire collected from the transmission belt is represented by the bending rigidity of the core wire collected from the base portion of the transmission belt in an unused state. A core wire is collected as a test piece (length = 50 mm) from the base portion of the transmission belt in an unused state, and the bending rigidity of this test piece is measured. The base portions adhering to the surface of the test piece are removed until the small base portions are scattered. The small base portion means a base portion having a size that does not protrude from a circle with a diameter of 0.1 mm. The measurement of the bending rigidity is carried out in accordance with JIS K7106 under the conditions of a temperature of 23 ± 5°C and a humidity of 50 ± 5% using a bending stiffness tester of the bending method by a single cantilever (for example, "Olzen type stiffness tester (light load type)" manufactured by YASUDA). The weight is 4 ounces, the load attachment position is 3 inches, the deflection angle scale is 5 degrees, and the distance between the fulcrums is set to 1 inch.

[0062] In this toothed belt 1, from the viewpoint of effectively improving the flexural fatigue resistance, the bending rigidity of the core wire 3 collected from the toothed belt 1 is 0.15 g·cm 2 / dtex or more and 0.22 g·cm 2 / dtex or less is preferable.

[0063] In this toothed belt 1, there is no particular limitation on the method of controlling the amount of the belt body 2 inherent in the core wire 3. For example, by adjusting molding conditions such as the molding temperature, molding pressure, and molding time, the amount of the belt body 2 inherent in the core wire 3 may be controlled. By adjusting the adhesion rate of the aforementioned treatment agent, the amount of the belt body 2 inherent in the core wire 3 may be controlled. When controlling the amount of the belt body 2 inherent in the core wire 3 by adjusting the adhesion rate of the treatment agent, the adhesion rate of the treatment agent is preferably 3% or more and 16% or less, more preferably 3.9% or more and 15.7% or less, and even more preferably 3.9% or more and 11.7% or less.

[0064] (Manufacturing method) The manufacturing method for the toothed belt 1 will be explained using the example of a case where the belt body 2 is made of thermosetting polyurethane. The toothed belt can be manufactured by conventionally known methods. Figures 5 and 6 illustrate the manufacturing method of the toothed belt 1. Figures 5 and 6 show only a portion of the mold and the belt (including the belt material).

[0065] (1) Prepare a toothed belt forming die 50. This toothed belt forming die 50 comprises a cylindrical inner die 51 and a cylindrical outer die 54. The outer circumference of the inner mold 51 is provided with recesses 52 extending in the axial direction and protrusions 53 extending in the axial direction. The recesses 52 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 52 are provided at regular intervals in the circumferential direction. The protrusions 53 are provided between adjacent recesses 52. The inner circumference of the outer mold 54 has a smooth surface.

[0066] (2) First, the cylindrical inner mold 51 is covered with the reinforcing cloth 4 which has been processed into a cylindrical shape. Next, the core wire 3 is wrapped spirally around the reinforcing cloth 4. The reinforcing fabric 4, which has been processed into a tubular shape, is pre-formed to conform to the shape of the recess 52 of the inner mold 51.

[0067] (3) Next, the inner mold 51 around which the core wire 3 is wound is placed in a predetermined position inside the cylindrical outer mold 54. This creates a cavity C for forming the belt body between the inner mold 51 and the outer mold 54 (see Figure 5).

[0068] (4) Next, a thermosetting urethane composition 111 containing a urethane prepolymer is poured into the sealed cavity C, and the core wire 3 and reinforcing fabric 4 are pressurized and heated together (see Figure 6). The thermosetting urethane composition 111 hardens within the cavity C. As a result, the belt teeth 12 are formed in the recessed portion 52, and the back portion 11 of the belt is formed in the convex portion 53. In this process, the thermosetting urethane composition 111 hardens while penetrating into the gaps of the reinforcing fabric 4 (not shown). Therefore, the hardened thermosetting urethane composition 111 is exposed on the inner circumferential surface of the formed belt along with the reinforcing fabric 4. The thermosetting urethane composition 111 hardens while penetrating into the gaps of the core wires 3. Therefore, the hardened thermosetting urethane composition 111 is contained within the core wires 3.

[0069] Through these steps (1) to (4), a cylindrical slab is formed in which the belt body 2, core wire 3, and reinforcing fabric 4 are integrated. The molding conditions in step (4) can be appropriately selected considering the composition of the thermosetting urethane composition. For example, the molding temperature may be set to 170°C, the molding pressure to 12 MPa, and the molding time to 20 minutes.

[0070] (5) Finally, the slab is demolded from the inner mold 51 and the outer mold 54, and the toothed belt 1 according to this embodiment is obtained by cutting the obtained slab into sections.

[0071] Although the transmission belt of the present invention has been described using a single-sided toothed belt as an example, the transmission belt of the present invention is not limited to this. The present invention can be applied to double-toothed belts, which are also interlocking transmission belts, as well as to friction transmission belts such as flat belts, V-belts, and V-ribbed belts. [Examples]

[0072] 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.

[0073] (Toothed belt) Toothed belts (belt size: 100 S8M 800) of Examples 1-4 and Comparative Examples 1-3, having the same configuration as toothed belt 1 shown in Figure 1-3, were manufactured.

[0074] <Example 1> The toothed belt in Example 1 had a belt length of 800 mm, a belt thickness (maximum) of 4.8 mm, and a belt width of 10 mm. The belt teeth were S8M as specified in ISO 13050:2014(E), with a spacing of 8 mm.

[0075] For forming the belt body, a thermosetting urethane composition was used, comprising 100 parts by mass of a urethane prepolymer (PTMEG-TDI) in which the isocyanate component is tolylene diisocyanate and the polyol component is polytetramethylene ether glycol, blended with 16 parts by mass of a curing agent (isobutyl 4-chloro-3,5-diaminobenzoate) and 7.5 parts by mass of a lubricant (fatty acid ester). The JIS-A hardness of the cured product of the thermosetting urethane composition was 95. As mentioned above, the JIS-A hardness of the cured thermosetting urethane composition was measured using a Type A durometer in accordance with JIS K7312:1996.

[0076] A carbon core was used for the core wire. This carbon core wire is a single-ply yarn made by twisting a bundle of 12,000 carbon filaments (Tenax-J UTS50 F22, manufactured by Teijin, filament fineness: 800 tex, filament diameter: 7.0 μm) in one direction with 90 twists per meter of length. S-twist yarn and Z-twist yarn were prepared as single-ply yarns. The core wires were pre-treated. In the pre-treatment, a treatment agent was applied to the core wires, and then the treated core wires were dried to allow the treatment agent to adhere to the core wires. The adhesion rate of the treatment agent to the core wires was 6.4%. As a treatment agent, an aqueous solution containing an epoxy group-containing compound and an amine-based curing agent was prepared, with "Denacol EX-521" manufactured by Nagase Chemtec and "Curesol 2E4MZ-CN" manufactured by Shikoku Chemicals as the main components. In this treatment agent, the solid content ratio of the main components was 100% by mass. The amount of amine-based curing agent was 9.5 parts by mass per 100 parts by mass of epoxy group-containing compound.

[0077] The core wires of the single-twisted S-twist and Z-twist yarns were arranged so that they were alternately aligned in the belt width direction to form a double helix. The number of core wires per 10mm belt width was set at 8.

[0078] For the canvas (reinforcement fabric), a 2 / 2 twill weave canvas was used, where one weft thread of nylon 6,6 fibers with a fineness of 235 dtex was used, and three warp threads of the same fineness of 235 dtex were used for the warp threads. The canvas fabric was constructed so that the weft threads aligned with the length of the belt. The canvas was not treated with adhesive. The canvas fabric had a thickness of 1.2 mm, a warp thread density of 113 threads / 5 cm width, a weft thread density of 120 threads / 5 cm width, and a basis weight of 385 g / m2.

[0079] Core wires were taken from the manufactured toothed belts, and their bending stiffness was measured using the method described above, resulting in a value of 0.20 g·cm. 2 It was / dtex.

[0080] <Examples 2-4 and Comparative Examples 1-3> Except for adjusting the pretreatment conditions to change the adhesion rate of the treatment agent to the core wire as shown in Table 1 below, and thereby changing the amount of belt body contained within the core wire, toothed belts for Example 2-4 and Comparative Example 1-3 were manufactured in the same manner as in Example 1. The bending stiffness of the core wires taken from the toothed belts was measured for each example in the same manner as in Example 1. The results are shown in Table 1.

[0081] (evaluation) <Tensile Test> Tensile tests were performed on each of the toothed belts in the examples and comparative examples using a universal tensile testing machine to obtain their tensile strength. In the tensile test, a toothed belt was cut to prepare a test specimen measuring 10 mm in width and 290 mm in length. Next, the specimen was gripped by the chucks of a universal tensile testing machine up to 70 mm from the end, and the specimen was set in the universal tensile testing machine so that the distance between the chucks was 150 mm. Subsequently, the specimen was pulled at a tensile speed of 50 mm / min until it broke, and the load acting on the specimen was measured. The tensile strength of the toothed belt was obtained based on the load at which it broke. The tensile strength column in Table 1 below shows the tensile strength of the toothed belt in its unused state, i.e., before fatigue.

[0082] <Flexion fatigue test> Figure 7 shows the pulley layout of the belt running test machine 60 for flexural fatigue testing.

[0083] This belt-driven test machine 60 is equipped with a drive pulley 61, a first driven pulley 62, and a second driven pulley 63. The drive pulley 61 is located on the right side, the first driven pulley 62 is located diagonally below and to the left of the drive pulley 61, and the second driven pulley 63 is located above the first driven pulley 62 and diagonally above and to the left of the drive pulley 61. The first driven pulley 62 is movable up and down and is configured to be able to withstand an axial load. The arrow R in Figure 7 indicates the direction of rotation of the drive pulley 61.

[0084] For each of the toothed belts in the examples and comparative examples, the belts were wrapped around the drive pulley 61, first driven pulley 62, and second driven pulley 63 of the belt running test machine 60, and an axial load (DW) of 40 kg was applied to the first driven pulley 62. The axial load (DW) was set using an axial load measured by a load cell. When setting the load, the target tension was set, the pulley was manually rotated three times to rotate the belt, and then the target tension was adjusted again. Then, under room temperature conditions (23±5℃), the belts were run by rotating the drive pulley 61 at a speed of 5500 rpm, the first driven pulley 62 at a speed of 5500 rpm, and the second driven pulley 63 at a speed of 5500 rpm. Three bending cycles constitute one cycle, and the toothed belt is 1 x 10 8The belt was bent several times. After belt operation, the toothed belt was subjected to the aforementioned tensile test, and its fatigued tensile strength was measured. The ratio of the fatigued tensile strength to the pre-fatigue tensile strength was calculated. The results are shown in the "Remaining Strength Ratio" column of Table 1. The closer the value is to 100, the better the flexural fatigue resistance.

[0085] [Table 1]

[0086] As shown in Table 1, it is clear that the toothed belt according to the embodiment of the present invention can achieve improved bending fatigue resistance. [Explanation of Symbols]

[0087] 1. Power transmission belt (toothed belt) 11 Back 12 belt teeth 2. Belt body 21 Base 22 Teeth 3 core wires 31 Filaments 4. Reinforcement fabric 50 molds 51 Internal mold 52 grooves 53 Convex Strip 54 Outer mold 60 Belt running test machine 61 Drive pulley 62 First driven pulley 63 Second driven pulley 111 Thermosetting urethane composition

Claims

1. A transmission belt having an endless strip-shaped back portion and belt teeth provided on the inner circumference side of the back portion, wherein the back portion comprises a base made of rubber material and a core wire embedded in the base portion, The aforementioned core wire is a twisted yarn made by twisting together filaments, A portion of the base is contained within the core wire, The bending stiffness of the core wire taken from the aforementioned transmission belt is 0.15 g·cm. ２ / dtex or more 0.30g・cm ２ / dtex is below, Power transmission belt.

2. The aforementioned filament is an inorganic fiber filament. The transmission belt according to claim 1.

3. The inorganic fiber filament is a carbon fiber filament. The transmission belt according to claim 2.

4. The aforementioned core wire is a single-ply yarn or a double-ply yarn. A transmission belt according to any one of claims 1 to 3.

5. The core wire is a single-twist yarn, and the number of twists of the single-twist yarn is 40 turns / m or more and 120 turns / m or less. The transmission belt according to claim 4.

6. The core wire is a core wire to which a treatment agent is attached, The treatment agent adhering to the core wire comprises an epoxy group-containing compound and a curing agent, or an initial condensate of resorcinol and formaldehyde. The transmission belt according to claim 1.

7. The adhesion rate of the treatment agent attached to the core wire is 3% or more and 16% or less. The transmission belt according to claim 6.

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