Toothed belts and transmission systems

Abstract

A toothed belt having multiple belt teeth arranged at a constant pitch in the longitudinal direction of the belt, wherein the belt teeth mesh with pulley grooves provided at a constant pitch on the periphery of the toothed pulley, wherein the area Sb of the backlash of the belt teeth with respect to the pulley groove and the area Sp of one of the pulley grooves are 7.26 × 10 -2 ≥Sb / Sp ≥ 3.46 × 10 -2 ...(1) and the tooth height Hb of the belt teeth and the tooth groove bottom depth Hp of the pulley groove are 1.04 ≥ Hb / Hp ≥ 0.91 ...(2) A toothed belt.

Description

[Technical Field]

[0001] This invention relates to a toothed belt and a power transmission system. This application claims priority under Japanese application No. 2024-132082, filed on August 8, 2024, and incorporates all the provisions of the said Japanese application. [Background technology]

[0002] A power transmission system equipped with a toothed belt and toothed pulleys is known as a power transmission system. Such power transmission systems are required to be usable for extended periods without the need to replace the toothed belt. In other words, the toothed belts in these power transmission systems must have excellent durability.

[0003] Patent Document 1 proposes a polyurethane power transmission belt in which at least the belt surface layer in contact with the pulley is formed from a polyurethane elastic body in which powdered fullerenes are dispersed as a filler. Patent Document 1 describes how the lifespan of the power transmission belt can be improved by lowering the tanδ of the belt body and reducing internal heat generation. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2007-309476 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The method described in Patent Document 1 had the problem of increasing the manufacturing cost of toothed belts. [Means for solving the problem]

[0006] This disclosure is made in view of these circumstances and aims to provide a toothed belt with good durability based on a different concept than before.

[0007] (1) A toothed belt according to one aspect of the present invention is A toothed belt having multiple belt teeth arranged at a constant pitch along the longitudinal direction of the belt, wherein the belt teeth mesh with pulley grooves arranged at a constant pitch along the outer circumference of the toothed pulley, The area Sb of the backlash of the belt teeth relative to the pulley groove and the area Sp of one of the pulley grooves are, 7.26 × 10 -2 ≥Sb / Sp ≥ 3.46 × 10 -2 ...(1) And, The tooth height Hb of the belt teeth and the groove depth Hp of the pulley groove are 1.04 ≥ Hb / Hp ≥ 0.91 ···(2) That is the case.

[0008] This toothed belt allows for reduced heat generation from the belt teeth during operation while maintaining transmission performance. As a result, the toothed belt is less prone to delamination at the interface between the belt body and the core wire, delamination at the interface between the belt body and the covering fabric, and wear of the belt teeth, thus providing excellent durability.

[0009] (2) A transmission system according to one aspect of the present invention is: A toothed belt having multiple belt teeth arranged at a constant pitch in the longitudinal direction of the belt, A transmission system comprising a toothed pulley having pulley grooves that mesh with the belt teeth provided along its outer circumference at a constant pitch, The area Sb of the backlash and the area Sp of one of the pulley grooves are, 7.26 × 10 -2 ≥Sb / Sp ≥ 3.46 × 10 -2 ...(1) And, The tooth height Hb of the belt teeth and the groove depth Hp of the pulley groove are 1.04 ≥ Hb / Hp ≥ 0.91 ···(2) It is as follows.

[0010] According to this transmission system, the toothed belt constituting the transmission system is less likely to generate heat and has excellent durability. Therefore, this transmission system can be used without replacing the toothed belt for a long period of time.

Advantages of the Invention

[0011] According to an aspect of the present invention, a toothed belt having good durability can be provided. Further, a transmission system provided with this toothed belt can be provided.

Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 is a side view schematically showing a transmission system. [Figure 2] FIG. 2 is a perspective view schematically showing a toothed belt. [Figure 3] FIG. 3 is a cross-sectional view taken along line A-A of FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view taken along line B-B of FIG. 2. [Figure 5] FIG. 5 is a diagram for explaining the area Sp of the pulley groove. [Figure 6] FIG. 6 is a diagram for explaining the area Sb of the backlash. [Figure 7] FIG. 7 is a diagram for explaining a manufacturing method of a toothed belt. [Figure 8] FIG. 8 is a diagram for explaining a manufacturing method of a toothed belt. [Figure 9] FIG. 9 is a diagram showing the toothed pulley layout of a belt running tester for a load endurance test.

Best Mode for Carrying Out the Invention

[0013] The outline of the embodiment of the present invention will be listed and described. [1] A toothed belt having multiple belt teeth arranged at a constant pitch in the longitudinal direction of the belt, wherein the belt teeth mesh with pulley grooves arranged at a constant pitch along the outer circumference of the toothed pulley, The area Sb of the backlash of the belt teeth relative to the pulley groove and the area Sp of one of the pulley grooves are, 7.26 × 10 -2 ≥Sb / Sp ≥ 3.46 × 10 -2 ...(1) And, The tooth height Hb of the belt teeth and the groove depth Hp of the pulley groove are 1.04 ≥ Hb / Hp ≥ 0.91 ···(2) That is, a toothed belt.

[0014] [2] A toothed belt having multiple belt teeth arranged at a constant pitch in the longitudinal direction of the belt, A transmission system comprising a toothed pulley having pulley grooves that mesh with the belt teeth provided along its outer circumference at a constant pitch, The area Sb of the backlash and the area Sp of one of the pulley grooves are, 7.26 × 10 -2 ≥Sb / Sp ≥ 3.46 × 10 -2 ...(1) And, The tooth height Hb of the belt teeth and the groove depth Hp of the pulley groove are 1.04 ≥ Hb / Hp ≥ 0.91 ···(2) This is a transmission system.

[0015] The embodiments of the present invention will be described in detail below with reference to the drawings.

[0016] (Transmission system) Figure 1 is a schematic side view showing a power transmission system 1 according to an embodiment of the present invention. The transmission system 1 is suitable for use in high-load transmission applications such as machine tools, printing machines, textile machinery, injection molding machines, robots, rear-wheel drive for motorcycles, and camshaft drive for automobile engines. As shown in Figure 1, the transmission system 1 comprises a drive pulley 22, a driven pulley 24, and a toothed belt 10. The drive pulley 22 and the driven pulley 24 each have a plurality of pulley grooves 21 formed therein. The toothed belt 10 has a plurality of belt teeth 12 (see Figure 2) that mesh with the pulley grooves 21 and is stretched over the drive pulley 22 and the driven pulley 24.

[0017] Both the drive pulley 22 and the driven pulley 24 have pulley grooves 21 that mesh with the belt teeth 12 of the toothed belt 10, provided at a predetermined pitch and evenly spaced along the outer circumference. The pulley grooves 21 of the drive pulley 22 and the pulley grooves 21 of the driven pulley 24 are identical in shape. Hereinafter, both the drive pulley 22 and the driven pulley 24 will be simply referred to as the toothed pulley 20.

[0018] The transmission system 1 transmits power from the drive source to the driven side. In the transmission system 1, the belt travel speed is, for example, 10 to 2000 m / min. In the transmission system 1, the transmission capacity is, for example, 0.1 to 600 kW.

[0019] (Toothed belt) Figure 2 is a perspective view showing a part of a toothed belt 10 according to an embodiment of the present invention. This toothed belt 10 constitutes a power transmission system 1. Figure 3 is a cross-sectional view taken along line AA in Figure 2. Figure 4 is a cross-sectional view along line BB in Figure 2. Figure 2 shows only a portion of the toothed belt 10, which is an endless interlocking power transmission belt.

[0020] The length of the toothed belt 10 is, for example, 500 mm or more and 3000 mm or less. The width of the toothed belt 10 is, for example, 5 mm or more and 300 mm or less. The thickness (maximum thickness) of the toothed belt 10 is, for example, 3 mm or more and 20 mm or less. The dimensions of the toothed belt according to the embodiment of the present invention are not limited to this range.

[0021] The toothed belt 10 has a plurality of belt teeth 12 on its inner circumferential surface. As shown in Figure 2, the toothed belt 10 comprises a belt body 11, a core wire 13, and a reinforcing fabric 14. In this embodiment, the belt teeth 12 of the toothed belt 10 are straight teeth.

[0022] The toothed belt 10 comprises a belt body 11 made of elastomer. The elastomer constituting the belt body 11 is, for example, polyurethane. The belt body 11 has a strip shape and comprises a base portion 11a with a rectangular cross-section perpendicular to the longitudinal direction of the belt, and a plurality of teeth 11b provided on the inner circumference side of the base portion 11a. These plurality of teeth 11b are integrated with the base portion 11a. The plurality of teeth 11b are provided at equal intervals along the length of the belt, with predetermined intervals between them. In the toothed belt 10, the reinforcing fabric 14 is provided to cover the inner circumferential surface of the teeth 11b. In the toothed belt 10, the belt teeth 12 are composed of the teeth 11b and the reinforcing fabric 14.

[0023] The tooth profile of the belt teeth 12 is, for example, an arc tooth profile. The number of teeth on the belt teeth 12 is, for example, between 30 and 400. The intermediate width W of the belt teeth 12 is, for example, 1 mm or more and 10 mm or less. The intermediate width W of the belt teeth 12 of the toothed belt 10 refers to the distance in the belt length direction (see W in Figure 4) at the point where the distance from the tip of the belt teeth 12 is h, in a cross section perpendicular to the width direction of the toothed belt 10. Here, distance h is a value calculated from the shape of the pulley groove 21 of the toothed pulley 20 that meshes with the belt teeth 12 of the toothed belt 10. Specifically, in a side view of the pulley groove 21, it is half the distance between the imaginary straight line (see VL in Figures 5 and 6) that is perpendicular to the center line CL of the pulley groove 21 and tangent to the tooth tip 26 of the toothed pulley 20, and the bottom of the tooth groove of the pulley groove 21 (see 2h in Figures 5 and 6) (see h in Figure 6).

[0024] The tooth height of the belt teeth 12 is, for example, 0.7 mm or more and 8 mm or less. The tooth height of the belt teeth 12 is defined by the distance from the tooth root 15 between a pair of mutually adjacent belt teeth 12 in the belt length direction to the tip of the belt teeth 12 (see Hb in Figure 4). The pitch of the belt teeth 12 is, for example, 2 mm or more and 14 mm or less. The pitch of the belt teeth 12 is defined by the distance between the tips of two adjacent belt teeth in the length direction of the belt (see P in Figure 4).

[0025] The preferred material for the belt body 11 is polyurethane. A more preferred material for the belt body 11 is thermosetting polyurethane. The above-mentioned thermosetting polyurethane is a cured product of a thermosetting urethane composition in which a curing agent and optional components such as plasticizers are blended with a urethane prepolymer.

[0026] When thermosetting polyurethane is used as the material for the belt body 11, the thermosetting polyurethane composition easily impregnates the core wire and reinforcing fabric, making it suitable for manufacturing toothed belts in which the thermosetting polyurethane constituting the belt body 11 impregnates the core wire and reinforcing fabric. A toothed belt in which the components constituting the belt body 11 (thermosetting polyurethane) impregnate the core wire and reinforcing fabric is less prone to tooth chipping and wear, and also less prone to the core wire separating from the belt body. Therefore, toothed belts with such a configuration have good durability.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] The above thermosetting polyurethane may further contain a lubricant. Examples of the above-mentioned lubricants include fatty acid esters, hydrocarbon resins, paraffin, higher fatty acids, fatty acid amides, aliphatic alcohols, metal soaps, and modified silicones. These lubricants may be used individually or in combination of two or more types. When the above-mentioned lubricant is included, the amount of the lubricant is, for example, 3 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the above-mentioned urethane prepolymer.

[0031] The above thermosetting urethane composition may further contain, for example, a colorant, an antifoaming agent, a stabilizer, and the like.

[0032] The JIS-A hardness of the polyurethane constituting the belt body 11 is preferably between 85 and 100. More preferably between 90 and 100. By setting the JIS-A hardness of the polyurethane to 90 or higher, good abrasion resistance can be easily ensured. The JIS-A hardness of the above polyurethane is measured using a Type A hardness test based on JIS K7312:1996. A Type A durometer is used for this measurement.

[0033] The toothed belt 10 is equipped with a core wire 13. The core wire 13 is embedded in the base 11a of the belt body 11. The core wire 13 is made of carbon fiber. The outer diameter of the core wire 13 is preferably 0.6 mm to 2.2 mm, from the viewpoint of ensuring excellent durability and excellent tension retention in high-load transmission. The outer diameter of the core wire 13 is more preferably 0.8 mm to 1.2 mm.

[0034] The carbon fibers constituting the core wire 13 are preferably PAN-based carbon fibers. The use of PAN-based carbon fibers is suitable for ensuring excellent durability in high-load transmission and excellent tension retention in high-load transmission. The filament diameter of the carbon fiber described above is preferably 4 μm to 9 μm. In this case, it is suitable for obtaining excellent durability in high-load transmission. For the same reason, the filament diameter of the carbon fiber described above is more preferably 6 μm to 8 μm.

[0035] The total number of filaments of the carbon fibers constituting the core wire 13 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 filaments of the carbon fibers is more preferably 9,000 (9K) or more and 18,000 (18K) or less. A more preferable total number of filaments of the carbon fibers is 12,000 (12K).

[0036] The fineness of the carbon fibers constituting the core wire 13 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 fibers is more preferably 600 tex or more and 1200 tex or less. A more preferable fineness of the carbon fibers is 800 tex.

[0037] The core wire 13 is preferably a twisted yarn. In this case, the toothed belt 10 equipped with the core wire 13 is suitable for ensuring excellent durability and excellent tension retention in high-load transmission. Examples of twisted yarns that make up the core wire 13 include single-ply yarn, double-ply yarn, and Lang-ply yarn.

[0038] The core wire 13 of the twisted yarn is preferably a single-twist yarn in which a bundle of carbon fiber filaments is twisted in one direction, because it is easier to ensure excellent durability and excellent tension retention in high-load transmission. When the core wire 13 is a single-ply yarn, the number of twists of the core wire 13 is preferably 4 turns / 10cm or more and 12 turns / 10cm or less. In this case, the toothed belt 10 is better suited to ensuring excellent durability and excellent tension retention in high-load transmission. From a similar viewpoint, a more preferable number of twists for the core wire 13 is 6 turns / 10cm or more and 10 turns / 10cm or less. As the single-ply yarn core wire 13, an S-twist yarn may be used, a Z-twist yarn may be used, or both may be used.

[0039] The core wire 13 has a pitch in the belt width direction and is provided so as to form a helix. The core wire 13 may be composed of two wires, an S-twisted yarn and a Z-twisted yarn, and they may be provided so as to form a double helix. The core wires 13 are arranged at intervals in the belt width direction and extend in parallel. At this time, the number of core wires 13 per 10 mm of the belt width is preferably 6 wires / 10 mm or more and 10 wires / 10 mm or less. The toothed belt 10 with the core wires 13 arranged in this way is suitable for ensuring excellent durability in high-load transmission and excellent tension maintenance in high-load transmission. From the same viewpoint, a more preferable number of core wires 13 is 7 wires / 10 mm or more and 9 wires / 10 mm or less.

[0040] The core wire 13 is preferably subjected to an adhesion treatment. Examples of the adhesion treatment include a treatment of immersing in a liquid adhesive and then drying. This adhesion treatment is performed before winding the core wire 13 around a mold in the method for manufacturing a toothed belt described later.

[0041] The reinforcing cloth 14 is provided so as to cover the inner peripheral surface of the tooth portion 11b. The durability of the belt teeth 12 is also improved by providing the reinforcing cloth 14. The reinforcing cloth 14 may be a woven fabric or a knitted fabric. The woven fabric is preferred for the reinforcing cloth 14.

[0042] Examples of the reinforcing cloth 14 made of a woven fabric include a 2 / 2 twill woven canvas, a 3 / 1 twill woven canvas, a plain woven canvas, a satin woven canvas, etc. formed by warp and weft yarns. When the reinforcing cloth 14 is made of these canvases, the preferred fineness of the warp and the weft is 44 dtex or more and 933 dtex or less. A more preferable fineness is 44 dtex or more and 235 dtex or less. The yarn density of the warp and the weft is preferably 74 yarns / 5 cm width or more and 430 yarns / 5 cm width or less. A more preferable yarn density is 132 yarns / 5 cm width or more and 174 yarns / 5 cm width or less. The basis weight of the reinforcing cloth 14 is 90 g / m 2 or more and 600 g / m2 The following is preferable. A more preferable basis weight is 300 g / m². 2 More than 450g / m 2 The following applies:

[0043] It is preferable that the reinforcing fabric 14, which is made of woven fabric, is provided such that the direction of one of the warp threads and the weft threads coincides with the direction of the belt length. The weft yarn of the reinforcing fabric 14 may be an elastic yarn such as a false-twist yarn. When the weft yarn is an elastic yarn, the reinforcing fabric 14 has anisotropic elasticity, meaning that the elasticity characteristics differ between the weft and warp directions. In this case, it is preferable that the weft yarn of the reinforcing fabric 14 is aligned with the belt length direction so that the elasticity characteristics in the belt length direction are high.

[0044] Examples of fibrous materials that make up the reinforcing fabric 14 include nylon fibers such as nylon 6,6 fibers, nylon 4,6 fibers, and nylon 6 fibers, chemical fibers such as polyketone fibers, aramid fibers, and polyester fibers, and natural fibers such as cotton. The reinforcing fabric 14 may be composed of one type of fiber or multiple types of fibers.

[0045] The reinforcing fabric 14 may be subjected to an adhesive treatment. For example, the adhesive treatment may involve immersing the fabric in an epoxy adhesive and then drying it. This adhesive treatment is performed before winding the reinforcing fabric 14 onto the mold in the toothed belt manufacturing method described later.

[0046] The reinforcing cloth 14 may be subjected to wear modification treatment. Examples of wear modification treatments include applying a binder containing the wear modifier dispersed in it to the reinforcing cloth before it is wrapped around the mold, or immersing the reinforcing cloth in the binder before it is wrapped around the mold.

[0047] Examples of the above-mentioned wear modifiers include ultra-high molecular weight polyethylene (UHMWPE), polytetrafluoroethylene (PTFE), perfluoroalkoxyalkanes (PFA), perfluoroethylene propene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), polyvinylidene fluoride (PVDF), and other fluororesins.

[0048] In the belt teeth 12 of the toothed belt 10, cured material of the thermosetting urethane composition has penetrated into the gaps in the reinforcing fabric 14. Therefore, not only the reinforcing fabric 14 but also the cured material of the thermosetting urethane composition is exposed on the surface (inner circumferential surface) of the belt teeth 12.

[0049] (Toothed pulley) The toothed pulley 20 is made of, for example, stainless steel. The toothed pulley 20 has pulley grooves 21 along its outer circumference that mesh with the belt teeth 12 of the toothed belt 10 at a predetermined pitch. The outer diameter of the toothed pulley 20 is, for example, 20 to 700 mm. The tooth profile of the pulley groove 21 is, for example, an arc tooth profile. The toothed pulley 20 may, for example, have a flange.

[0050] (Relationship between toothed belt 10 and toothed pulley 20) Each tooth 12 of the toothed belt 10 meshes with a pulley groove 21 provided on the outer circumference of the drive pulley 22 and a pulley groove 21 provided on the outer circumference of the driven pulley 24. In the toothed belt 10 and toothed pulley 20, the area Sb of the backlash and the area of ​​one pulley groove 21 have a predetermined relationship.

[0051] Figure 5 shows one of the pulley grooves 21 of the toothed pulley 20. Figure 5 shows the side view shape of the pulley groove 21. The side view shape of the pulley groove 21 is the same as the shape of the pulley groove 21 in a cross section perpendicular to the axial direction of the pulley 20. Figure 6 shows the state in which one belt tooth 12 of the toothed belt 10 and one pulley groove 21 of the toothed pulley 20 are engaged. Figure 6 shows the side view shapes of the belt tooth 12 and the pulley groove 21.

[0052] The area Sp of one pulley groove 21 is the area of ​​the shaded portion in Figure 5. This area Sp is the area enclosed by the imaginary straight line VL and the tooth surface of the pulley groove 21. Here, the imaginary line VL is a straight line perpendicular to the center line CL and is an imaginary straight line tangent to the tooth tip 26 of the toothed pulley 20.

[0053] The area Sb of the backlash of the toothed belt 10 relative to the toothed pulley 20 is the area of ​​the shaded portion in Figure 6. This backlash area Sb is the backlash area Sb in a static state where no load is applied to the toothed belt 10.

[0054] The backlash area Sb is determined by the following conditions: With the center line CL of the belt teeth 12 aligned with the center line CL of the pulley groove 21, the belt teeth 12 are moved from the outside of the pulley groove 21 toward the pulley groove 21 until the belt teeth 12 make contact with the toothed pulley 20, thereby overlapping the belt teeth 12 and the pulley groove 21. In this state, the area enclosed by the imaginary line VL, the belt teeth 12, and the pulley groove 21 is the backlash area Sb. When the belt teeth 12 are moved toward the pulley groove 21 as described above, initially, the tips of the belt teeth 12 may contact the pulley groove, or the tooth surfaces of the belt teeth 12 may contact the pulley groove. When overlapping the belt teeth 12 and the pulley groove 21 in order to calculate the backlash area Sb, the belt teeth 12 are moved until the belt teeth 12 or any part of its vicinity (the tooth roots close to the tooth roots of the belt teeth 12) contacts the toothed pulley 20, at which point the two are overlapped.

[0055] The backlash area Sb can be measured using CAD. Specifically, for example, the shapes of the belt teeth and pulley grooves can be measured using a contour tracer (contour shape measuring instrument) or a 3D scanner, and the resulting drawings can be used to perform measurements using CAD functions.

[0056] The transmission system 1, comprising a toothed belt 10 and a toothed pulley 20, satisfies the following equation (1) for the backlash area Sb relative to the area Sp of one pulley groove 21. 7.26 × 10 -2 ≥Sb / Sp ≥ 3.46 × 10 -2 ...(1) By satisfying the above equation (1), the toothed belt can be made less prone to overheating during operation. Therefore, the toothed belt can be made to have excellent durability. On the other hand, if the Sb / Sp ratio falls outside the above range, the amount of heat generated when the belt teeth are driven increases. As a result, the lifespan of the toothed belt is shortened, and its durability is reduced. The reason why the amount of heat generated when the belt teeth are driven increases when the Sb / Sp ratio falls outside the above range is thought to be because the sliding work (shear stress × amount of sliding) with the pulley groove that occurs when the belt teeth mesh at the tooth root, pressure surface, and tooth tip increases.

[0057] Also, Sb / Sp is 7.26 × 10 -2 If the value exceeds this limit, the meshing between the toothed belt 10 and the toothed pulley 20 becomes incomplete, and the power transmission capacity is not achieved.

[0058] In the toothed belt 10 and toothed pulley 20, the tooth height Hb of the belt teeth 12 and the tooth groove bottom depth Hp of the pulley groove 21 have a predetermined relationship. The tooth height Hb of a belt tooth 12 is the distance from the tooth root 15 to the tip of a pair of mutually adjacent belt teeth 12 in the belt length direction, as shown in Figure 3. For example, in belt teeth of G8M and G14M as specified in ISO 13050:2014(E), it is denoted as hg. The tooth groove bottom depth Hp of the pulley groove 21 is the distance from the tip circle Cp of the toothed pulley 20 to the tooth groove bottom on the center line CL of the pulley groove 21 (see Figure 5).

[0059] In the transmission system 1, the ratio of the tooth height Hb of the belt teeth 12 to the tooth groove bottom depth Hp of the pulley groove 21 satisfies the following equation (2). 1.04 ≥ Hb / Hp ≥ 0.91 ···(2) By satisfying equation (2) above, the shear stress generated in the belt teeth when they mesh with the pulley groove can be distributed. Therefore, the concentration of heat in the belt teeth can be avoided, and the toothed belt becomes less prone to breakage.

[0060] On the other hand, if the Hb / Hp ratio is less than 0.91, shear stress concentrates at the tooth roots of the belt teeth, making it easier for heat to concentrate at the tooth roots of the belt teeth. Furthermore, when the Hb / Hp ratio exceeds 1.04, shear stress concentrates at the tips of the belt teeth, making it easier for heat to concentrate at the tips of the belt teeth. In either case, localized heat generation is likely to occur in the belt teeth, resulting in the toothed belt having inferior durability.

[0061] In the transmission system 1, with the tips of the belt teeth 12 in contact with the bottom of the tooth grooves of the pulley grooves 21, the tooth roots 15 between the belt teeth 12 may be in contact with the tips of the pulley teeth, or there may be a gap between them and the tips of the pulley teeth. If the above-mentioned gap exists, it is preferable that the gap be 4.1% or less of the tooth height Hb of the belt teeth 12.

[0062] In the transmission system 1, the gap dimension between the pulley groove 21 and the belt teeth 12 at the measurement position of the intermediate width W of the belt teeth 12 is preferably 2.0% or more and 10.0% or less of the intermediate width W of the belt teeth 12. This gap dimension is measured with the belt teeth 12 and pulley groove 21 overlapping in order to determine the backlash area Sb. The above gap dimension is the sum of the distances g perpendicular to the center line CL between the tooth surface of the belt teeth 12 and the tooth surface of the pulley groove 21 at the measurement position of the intermediate width W (see Figure 6). Since there are usually two gaps between the tooth surface of the belt teeth and the tooth surface of the pulley groove for each belt tooth, the above gap dimension is calculated as the sum of the distances g as described above.

[0063] (Manufacturing method) A method for manufacturing a toothed belt 10 will be described. A toothed belt can be manufactured by conventionally known methods. Figures 7 and 8 illustrate the manufacturing method of the toothed belt 10. Figures 7 and 8 show only a portion of the mold and the belt (including the belt material).

[0064] (1) Prepare a toothed belt forming die 30. This toothed belt forming die 30 comprises a cylindrical inner die 31 and a cylindrical outer die 34. The outer circumference of the inner mold 31 is provided with recesses 32 extending in the axial direction and protrusions 33 extending in the axial direction. The recesses 32 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 7). The recesses 32 are provided at regular intervals in the circumferential direction. The protrusions 33 are provided between adjacent recesses 32. The inner circumference of the outer mold 34 has a smooth surface.

[0065] (2) First, the cylindrical inner mold 31 is covered with the reinforcing cloth 14 which has been processed into a cylindrical shape. Next, the core wire 13 is wrapped spirally around the reinforcing cloth 14. The reinforcing fabric 14, which has been processed into a cylindrical shape, is pre-formed to conform to the shape of the recess 32 of the inner mold 31.

[0066] (3) Next, the inner mold 31 around which the core wire 13 is wound is placed in a predetermined position inside the cylindrical outer mold 34. This creates a cavity C for forming the belt body between the inner mold 31 and the outer mold 34 (see Figure 7).

[0067] (4) Next, a thermosetting urethane composition 111 containing a urethane prepolymer, etc., is poured into the sealed cavity C and heated (see Figure 8). The thermosetting urethane composition 111 hardens within the cavity C. As a result, the teeth of the belt are formed in the recessed portion 32, and the roots of the belt teeth are formed in the convex portion 33. In this process, the thermosetting urethane composition 111 hardens while penetrating into the gaps in the reinforcing fabric 14 (not shown). As a result, the hardened thermosetting urethane composition 111 is exposed on the inner circumferential surface of the formed belt teeth 12 along with the reinforcing fabric 14.

[0068] Through these steps (1) to (4), a cylindrical slab is formed in which the belt body 11, core wire 13, and reinforcing fabric 14 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.

[0069] (5) Finally, the slab is demolded from the inner mold 31 and the outer mold 34, and the toothed belt 10 according to this embodiment is obtained by cutting the obtained slab into sections.

[0070] The manufacturing method for the toothed pulley 20 will be described. The toothed pulley 20 can be manufactured using conventionally known methods. For example, the toothed pulley 20 can be manufactured by creating a dedicated hob cutter according to the tooth groove shape of the toothed pulley, then cutting the teeth on a metal material using this hob cutter, and further performing drilling, external shaping, flange attachment, etc., as necessary.

[0071] (Other embodiments) The teeth of the toothed belt according to the embodiment of the present invention are not limited to straight teeth, but may also be beveled teeth.

[0072] In the toothed belt according to an embodiment of the present invention, the tooth profile of the belt teeth may be trapezoidal. In the embodiment of the present invention, the toothed belt may be composed of a rubber composition, a resin other than polyurethane (such as olefin or nylon), or the like. The core wires constituting the toothed belt described above may be made of organic fibers such as aramid fibers, polyester fibers, PBO fibers, nylon fibers, and polyketone fibers, as well as glass fibers, metal fibers, and the like. [Examples]

[0073] 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. Toothed belts were fabricated in each of Examples 1-3 and Comparative Examples 1 and 2. Furthermore, toothed pulleys (drive pulley and driven pulley) that mesh with the toothed belt described above were manufactured using G8M pulleys in accordance with ISO 13050:2014(E). The tooth groove bottom depth Hp of these toothed pulleys was measured to be 3.545 mm.

[0074] <Example 1> A toothed belt 10 with the same configuration as the first embodiment was manufactured. In this embodiment, a toothed belt with a belt width of 8 mm and a belt length of 800 mm was manufactured. The belt teeth 12 of this toothed belt are based on the G8M belt teeth specified in ISO 13050:2014(E), with the shape of the belt teeth adjusted so that the tooth height Hb (see Figure 4) is 3.47 mm, the intermediate width W (see Figure 4) is 4.28 mm, and the tooth width bg is 5.22 mm. Here, the tooth width bg is the dimension of the tooth root of the belt tooth as defined in ISO 13050:2014(E). The resulting toothed belt, when meshed with a G8M pulley as specified in ISO 13050:2014(E), has a backlash area Sb of 0.92 mm². 2 That is the case.

[0075] For forming the belt body, a thermosetting urethane composition was used, which consisted of 100 parts by mass of a urethane prepolymer (PTMEG-TDI) in which tolylene diisocyanate was used as the isocyanate component and polytetramethylene ether glycol was used as the polyol component, and 16 parts by mass of a curing agent (isobutyl 4-chloro-3,5-diaminobenzoate). The JIS-A hardness of the cured product of the thermosetting urethane composition was 95.

[0076] The core wire uses a single-ply yarn that has been treated with adhesive. For the single-ply yarn described above, a bundle of carbon fibers (Tenax-J UTS50 F22, manufactured by Teijin, 12K, 800tex, filament diameter: 7.0μm) with 12,000 filaments was used, twisted in one direction with 90 twists per meter of length. For the core wire, S-twist yarn and Z-twist yarn were prepared. The bonding treatment described above involved immersion in an adhesive followed by drying. A phenolic adhesive was used as the bonding agent.

[0077] The core wires using S-twist yarn and the core wires using Z-twist yarn were used in the resulting toothed belt in such a way that double helices were formed, arranged alternately in the belt width direction. 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 has 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. 2 That was the case.

[0079] <Example 2> A toothed belt was manufactured in the same manner as in Example 1, except that the shape of the belt teeth was changed as described below. In this example, the shape of the belt teeth was adjusted based on the G8M belt teeth specified in ISO 13050:2014(E), so that the tooth height Hb (see Figure 4) was 3.62 mm, the intermediate width W (see Figure 4) was 4.38 mm, and the tooth width bg was 5.23 mm. The resulting toothed belt, when meshed with a G8M pulley as specified in ISO 13050:2014(E), has a backlash area Sb of 0.58 mm². 2 That is the case.

[0080] <Example 3> A toothed belt was manufactured in the same manner as in Example 1, except that the shape of the belt teeth was changed as described below. In this example, the shape of the belt teeth was adjusted based on the G8M belt teeth specified in ISO 13050:2014(E), so that the tooth height Hb (see Figure 4) was 3.62 mm, the intermediate width W (see Figure 4) was 4.34 mm, and the tooth width bg was 5.25 mm. The resulting toothed belt, when meshed with a G8M pulley as specified in ISO 13050:2014(E), has a backlash area Sb of 0.82 mm². 2 That is the case.

[0081] <Comparative Example 1> A toothed belt was manufactured in the same manner as in Example 1, except that the shape of the belt teeth was changed as described below. In this comparative example, the shape of the belt teeth was adjusted based on the G8M belt teeth specified in ISO 13050:2014(E), so that the tooth height Hb (see Figure 4) was 3.20 mm, the intermediate width W (see Figure 4) was 4.03 mm, and the tooth width bg was 5.44 mm. The resulting toothed belt, when meshed with a G8M pulley as specified in ISO 13050:2014(E), has a backlash area Sb of 0.52 mm². 2 That is the case.

[0082] <Comparative Example 2> A toothed belt was manufactured in the same manner as in Example 1, except that the shape of the belt teeth was changed as described below. In this comparative example, the shape of the belt teeth was adjusted based on the G8M belt teeth specified in ISO 13050:2014(E), so that the tooth height Hb (see Figure 4) was 3.62 mm, the intermediate width W (see Figure 4) was 4.43 mm, and the tooth width bg was 5.20 mm. The resulting toothed belt, when meshed with a G8M pulley as specified in ISO 13050:2014(E), has a backlash area Sb of 0.42 mm². 2 That is the case.

[0083] <Comparative Example 3> A toothed belt was manufactured in the same manner as in Example 1, except that the shape of the belt teeth was changed as described below. In this comparative example, the shape of the belt teeth was adjusted based on the G8M belt teeth specified in ISO 13050:2014(E), so that the tooth height Hb (see Figure 4) was 3.71 mm, the intermediate width W (see Figure 4) was 4.41 mm, and the tooth width bg was 5.21 mm. The resulting toothed belt, when meshed with a G8M pulley as specified in ISO 13050:2014(E), has a backlash area Sb of 0.50 mm². 2 That is the case.

[0084] <Comparative Example 4> A toothed belt was manufactured in the same manner as in Example 1, except that the shape of the belt teeth was changed as described below. In this comparative example, the shape of the belt teeth was adjusted based on the G8M belt teeth specified in ISO 13050:2014(E), so that the tooth height Hb (see Figure 4) was 3.62 mm, the intermediate width W (see Figure 4) was 4.32 mm, and the tooth width bg was 5.27 mm. The resulting toothed belt, when meshed with a G8M pulley as specified in ISO 13050:2014(E), has a backlash area Sb of 1.06 mm². 2 That is the case.

[0085] (evaluation) <Load endurance test> Figure 9 shows the toothed pulley layout of a belt running test machine for load endurance testing.

[0086] This belt running test machine 40 has a drive pulley 41 with 22 teeth and an outer diameter of 56.02 mm, and a driven pulley 42 with 33 teeth and an outer diameter of 84.03 mm, which are arranged laterally apart. The driven pulley 42 is configured to be able to be subjected to an axial load (SW) on the side. As described above, the drive pulley 41 and the driven pulley 42 have pulley grooves with dimensions of G8M as specified in ISO 13050:2014(E).

[0087] For each of the toothed belts in the examples and comparative examples, the belts were wrapped around the drive pulley 41 and driven pulley 42 of the belt running test machine 40, and a torque of 34.3 N·m was applied to the driven pulley 42 along with an axial load (SW) of 607.6 N. The axial load (SW) was set using a load cell. When setting the load, the target tension was set, the toothed pulley was rotated manually three times around the belt, and then the target tension was adjusted again. Then, at an ambient temperature of 60°C, the drive pulley 41 was rotated at a speed of 4200 rpm and the driven pulley 42 at a speed of 2800 rpm, and the belts were run. Then, the belt operation was stopped periodically and visually inspected, and the belt operation was continued until a malfunction occurred, such as chipping or wear of the belt teeth or separation between the belt body and the core wire. In addition, when a toothed belt malfunctioned, the temperature of the tooth roots of the belt was measured using an infrared thermometer. The results are shown in Table 1.

[0088] [Table 1]

[0089] As shown in Table 1, the toothed belt according to the embodiment of the present invention has been shown to be less prone to heat generation and to have excellent durability.

[0090] 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]

[0091] 1. Transmission System 10 Toothed belt 11 Belt body 11a base 11b Teeth 12 belt teeth 13 Core wires 14 Reinforcement fabric 15. Root of the tooth 20-tooth pulley 21 Pulley groove 22 Drive pulley 24 Driven pulley 26 Tooth tips of toothed pulley 20 30. Die for forming toothed belts 31 Internal mold 32 recesses 33 Convex part 34 Outer mold 40 Belt running test machine 41 Drive pulley 42 Driven pulley 111 Thermosetting urethane composition C Cavity

Claims

1. A toothed belt is stretched over a toothed pulley, which has multiple belt teeth arranged at a constant pitch in the longitudinal direction of the belt and multiple pulley grooves arranged at a constant pitch along its outer circumference, The toothed pulley is a toothed pulley with a G tooth shape as specified in ISO 13050:2014(E), The area Sb of the backlash of the belt teeth relative to the pulley groove and the area Sp of one of the multiple pulley grooves provided on the outer circumference of the toothed pulley are, 6.36 × 10⁻² ≥ Sb / Sp ≥ 4.01 × 10⁻² ... (1) The tooth height Hb of the belt teeth and the tooth groove bottom depth Hp of the pulley groove are 1.02 ≥ Hb / Hp ≥ 0.98 ... (2) That is, a toothed belt.

2. The toothed belt according to claim 1, wherein the toothed pulley is a G8M toothed pulley as defined in ISO 13050:2014(E).

3. A toothed belt having multiple belt teeth arranged at a constant pitch in the longitudinal direction of the belt, A transmission system comprising a toothed pulley having a plurality of pulley grooves that mesh with the belt teeth arranged along its outer circumference at a constant pitch, The toothed pulley is a toothed pulley with a G tooth shape as specified in ISO 13050:2014(E), The area Sb of the backlash of the belt teeth relative to the pulley groove and the area Sp of one of the multiple pulley grooves provided on the outer circumference of the toothed pulley are, 6.36 × 10⁻² ≥ Sb / Sp ≥ 4.01 × 10⁻² ... (1) The tooth height Hb of the belt teeth and the tooth groove bottom depth Hp of the pulley groove are 1.02 ≥ Hb / Hp ≥ 0.98 ... (2) This is a transmission system.

4. The transmission system according to claim 3, wherein the toothed pulley is a G8M toothed pulley as defined in ISO 13050:2014(E).

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