Toothed belt and transmission system

Abstract

Provided is a toothed belt in which a plurality of belt teeth are provided at a constant pitch in a belt longitudinal direction, and the belt teeth mesh with pulley grooves provided at a constant pitch on a peripheral edge of a toothed pulley. A backlash area Sb of the belt teeth relative to the pulley grooves and an area Sp of one of the pulley grooves satisfy (1): 7.26 × 10-2 ≥ Sb / Sp ≥ 3.46 × 10-2, and a tooth height Hb of each belt tooth and a tooth groove bottom depth Hp of each pulley groove satisfy (2): 1.04 ≥ Hb / Hp ≥ 0.91.

Description

Toothed belts and transmission systems

[0001] The present application claims priority to Japanese Patent Application No. 2024-132082, filed on August 8, 2024, and incorporates by reference all of the contents of the above-mentioned Japanese application.

[0002] A power transmission system equipped with a toothed belt and a toothed pulley is known as a power transmission system. Such a power transmission system is required to be able to be used for a long period of time without replacing the toothed belt. In other words, the toothed belt provided in the power transmission system is required to have excellent durability.

[0003] Patent Document 1 proposes a polyurethane transmission belt in which at least the belt surface layer that contacts the pulley is formed from a polyurethane elastomer in which powdered fullerenes are dispersed as a filler. Patent Document 1 describes that the life of the transmission belt is improved by lowering the tan δ of the belt body and thereby reducing internal heat generation.

[0004] Japanese Patent Application Laid-Open No. 2007-309476

[0005] The technique described in Patent Document 1 has the problem of increasing the manufacturing cost of the toothed belt.

[0006] The present disclosure has been made in view of the above circumstances, and has an object to provide a toothed belt having good durability based on an idea different from that which has hitherto existed.

[0007] (1) A toothed belt according to one aspect of the present invention is a toothed belt having a plurality of belt teeth arranged at a constant pitch in the belt longitudinal direction, and the belt teeth mesh with pulley grooves arranged at a constant pitch along the outer periphery of a toothed pulley, wherein a backlash area Sb of the belt tooth with respect to the pulley groove and an area Sp of one of the pulley grooves are less than 7.26×10 －２ ≧Sb / Sp≧3.46×10 －２ ...(1) and the tooth height Hb of the belt tooth and the tooth groove bottom depth Hp of the pulley groove satisfy the following relationship: 1.04≧Hb / Hp≧0.91 ...(2).

[0008] This toothed belt can suppress heat generation in the belt teeth during driving while maintaining power transmission performance. As a result, the toothed belt is less susceptible to peeling at the interface between the belt body and the core wire, peeling at the interface between the belt body and the covering fabric, and wear of the belt teeth, and has good durability.

[0009] (2) A transmission system according to one aspect of the present invention is a transmission system including: a toothed belt having a plurality of belt teeth arranged at a constant pitch in the belt longitudinal direction; and a toothed pulley having pulley grooves that mesh with the belt teeth arranged at a constant pitch along the outer periphery, wherein the backlash area Sb and the area Sp of one of the pulley grooves are less than 7.26×10 －２ ≧Sb / Sp≧3.46×10 －２ ...(1) and the tooth height Hb of the belt tooth and the tooth groove bottom depth Hp of the pulley groove satisfy the following relationship: 1.04≧Hb / Hp≧0.91 ...(2).

[0010] According to this power transmission system, the toothed belt that constitutes the power transmission system does not easily generate heat and has excellent durability, so this power transmission system can be used for a long period of time without replacing the toothed belt.

[0011] According to the aspects of the present invention, it is possible to provide a toothed belt having good durability, and also to provide a transmission system including this toothed belt.

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

[0013]

[0023] The outline of the embodiments of the present invention will be described below. [1] A toothed belt having a plurality of belt teeth provided at a constant pitch in the belt longitudinal direction, the belt teeth meshing with pulley grooves provided at a constant pitch along the outer periphery of a toothed pulley, wherein a backlash area Sb of the belt tooth with respect to the pulley groove and an area Sp of one of the pulley grooves are 7.26 x 10 －２ ≧Sb / Sp≧3.46×10 －２ ...(1) wherein a tooth height Hb of the belt teeth and a tooth groove bottom depth Hp of the pulley groove satisfy the following relationship: 1.04≧Hb / Hp≧0.91 ...(2).

[0014] [2] A transmission system comprising a toothed belt in which a plurality of belt teeth are provided at a constant pitch in the belt longitudinal direction, and a toothed pulley in which pulley grooves that mesh with the belt teeth are provided at a constant pitch along the outer periphery, wherein the backlash area Sb and the area Sp of one of the pulley grooves are less than 7.26×10 －２ ≧Sb / Sp≧3.46×10 －２ ...(1) and a tooth height Hb of the belt tooth and a tooth groove bottom depth Hp of the pulley groove satisfy the following relationship: 1.04≧Hb / Hp≧0.91 ...(2).

[0015] Hereinafter, details of embodiments of the present invention will be described with reference to the drawings.

[0016] (Transmission System) Fig. 1 is a side view schematically illustrating a 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 machines, injection molding machines, robots, rear-wheel drives for motorcycles, and camshaft drives for automobile engines. As shown in Fig. 1, the transmission system 1 includes 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 Fig. 2) that mesh with the pulley grooves 21, and is stretched over the drive pulley 22 and the driven pulley 24.

[0017] The drive pulley 22 and the driven pulley 24 each have pulley grooves 21 that mesh with the belt teeth 12 of the toothed belt 10 and are evenly spaced at a predetermined pitch along the outer periphery. The pulley grooves 21 of the drive pulley 22 and the pulley grooves 21 of the driven pulley 24 have the same shape. Hereinafter, the drive pulley 22 and the driven pulley 24 will collectively be referred to simply as toothed pulleys 20.

[0018] The transmission system 1 transmits power from a drive source to a driven side. In the transmission system 1, the belt running 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) Fig. 2 is a perspective view showing a portion of a toothed belt 10 according to an embodiment of the present invention. This toothed belt 10 constitutes a power transmission system 1. Fig. 3 is a cross-sectional view taken along line A-A in Fig. 2. Fig. 4 is a cross-sectional view taken along line B-B in Fig. 2. Although Fig. 2 shows only a portion of the toothed belt 10, the toothed belt 10 is an endless meshing power transmission belt.

[0020] The belt length of the toothed belt 10 is, for example, 500 mm or more and 3000 mm or less. The belt width of the toothed belt 10 is, for example, 5 mm or more and 300 mm or less. The belt 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 these ranges.

[0021] The toothed belt 10 has a plurality of belt teeth 12 on its inner circumferential surface. As shown in Fig. 2, the toothed belt 10 includes 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 includes a belt body 11 made of an elastomer. The elastomer constituting the belt body 11 is, for example, polyurethane. The belt body 11 has a strip shape and includes a base 11a having a rectangular cross section perpendicular to the belt longitudinal direction, and a plurality of toothed portions 11b provided on the inner periphery of the base 11a. The toothed portions 11b are integrated with the base 11a. The toothed portions 11b are provided at equal intervals along the belt longitudinal direction. In the toothed belt 10, a reinforcing fabric 14 is provided so as to cover the inner periphery of the toothed portions 11b. In the toothed belt 10, the belt teeth 12 are composed of the toothed portions 11b and the reinforcing fabric 14.

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

[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 as the distance from the tooth bottom 15 between a pair of belt teeth 12 adjacent to each other in the belt length direction to the tip of the belt tooth 12 (see Hb in FIG. 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 as the distance between the tooth tips of a pair of adjacent belt teeth in the belt length direction (see P in FIG. 4).

[0025] Polyurethane is a preferred material for the belt body 11. Thermosetting polyurethane is a more preferred material for the belt body 11. The thermosetting polyurethane is a cured product of a thermosetting urethane composition in which a urethane prepolymer is blended with a curing agent and an optional plasticizer.

[0026] When thermosetting polyurethane is used as the material for the belt body 11, the thermosetting urethane composition easily impregnates the core wires and reinforcing fabric, making it suitable for manufacturing a toothed belt in which the core wires and reinforcing fabric are impregnated with the thermosetting polyurethane that constitutes the belt body 11. A toothed belt in which the core wires and reinforcing fabric are impregnated with the component (thermosetting polyurethane) that constitutes the belt body 11 is less likely to suffer from chipping or wear of the belt teeth, and the core wires are less likely to peel off from the belt body. Therefore, a toothed belt with this configuration has good durability.

[0027] The urethane prepolymer is a relatively low-molecular-weight urethane compound having multiple terminal NCO groups. The urethane prepolymer is obtained by reacting an isocyanate component with a polyol component. Examples of the isocyanate component include tolylene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI). Examples of the polyol component include polytetramethylene ether glycol (PTMG). The urethane prepolymer may be composed of one type of urethane compound or a mixture of multiple types of urethane compounds.

[0028] Examples of the curing agent 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-diaminobenzoic acid isobutyl. These curing agents may be used alone or in combination of two or more. The amine compound as the curing agent has an α value (NH ２ It is preferable that the α value is set to 0.70 or more and 1.10 or less.２ The ratio of moles of NCO groups to moles of NCO groups in the urethane prepolymer.

[0029] Examples of the plasticizer 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). Only one type of plasticizer may be used, or two or more types may be used in combination. The blending amount of the plasticizer is, for example, 3 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the urethane prepolymer.

[0030] The thermosetting polyurethane may further contain a lubricant. Examples of the lubricant include fatty acid esters, hydrocarbon resins, paraffins, higher fatty acids, fatty acid amides, aliphatic alcohols, metal soaps, and modified silicones. These lubricants may be used alone or in combination of two or more. When the lubricant is contained, 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 urethane prepolymer.

[0031] The 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 85 or more and 100 or less. The JIS-A hardness of the polyurethane is more preferably 90 or more and 100 or less. By making the JIS-A hardness of the polyurethane 90 or more, good abrasion resistance is easily ensured. The JIS-A hardness of the polyurethane is measured by a Type A hardness test based on JIS K7312:1996. A Type A durometer is used for this measurement.

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

[0034] The carbon fiber constituting the core wire 13 is preferably a PAN-based carbon fiber. The use of a PAN-based carbon fiber is suitable for ensuring excellent durability and excellent tension retention in high-load transmission. The filament diameter of the carbon fiber is preferably 4 μm or more and 9 μm or less. 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 is more preferably 6 μm or more and 8 μm or less.

[0035] The total number of carbon fiber filaments constituting the core wire 13 is preferably 6,000 (6K) or more and 48,000 (48K) or less. This is suitable for obtaining excellent durability and excellent tension retention under high load transmission. For the same reason, the total number of carbon fiber filaments is more preferably 9,000 (9K) or more and 18,000 (18K) or less. An even more preferable total number of carbon fiber filaments 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. This is suitable for obtaining excellent durability and excellent tension retention under 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. An even 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 including the core wire 13 is suitable for ensuring excellent durability and excellent tension retention in high load transmission. Examples of the twisted yarn constituting the core wire 13 include single twisted yarn, double twisted yarn, and Lang twisted yarn.

[0038] The twisted core wire 13 is preferably a single-twisted yarn obtained by twisting a bundle of carbon fiber filaments in one direction, because this facilitates ensuring excellent durability and excellent tension maintenance in high-load transmission. When the core wire 13 is a single-twisted yarn, the twist number of the core wire 13 is preferably 4 turns / 10 cm or more and 12 turns / 10 cm or less. In this case, the toothed belt 10 is more suitable for ensuring excellent durability and excellent tension maintenance in high-load transmission. From the same viewpoint, the twist number of the core wire 13 is more preferably 6 turns / 10 cm or more and 10 turns / 10 cm or less. As the single-twisted core wire 13, an S-twisted yarn, a Z-twisted yarn, or both may be used.

[0039] The core wires 13 are arranged with a pitch in the belt width direction to form a spiral. The core wires 13 may be composed of two core wires, an S-twisted yarn and a Z-twisted yarn, and arranged to form a double spiral. The core wires 13 are arranged to extend parallel to each other at intervals in the belt width direction. In this case, the number of core wires 13 per 10 mm of belt width is preferably 6 / 10 mm or more and 10 / 10 mm or less. The toothed belt 10 having the core wires 13 arranged in this manner is suitable for ensuring excellent durability and excellent tension retention in high-load transmission. From the same viewpoint, the number of core wires 13 is more preferably 7 / 10 mm or more and 9 / 10 mm or less.

[0040] The core wires 13 are preferably subjected to an adhesive treatment. For example, the adhesive treatment may involve immersing the core wires 13 in a liquid adhesive and then drying the liquid. This adhesive treatment is performed before winding the core wires 13 around a mold in the method for manufacturing a toothed belt, which will be described later.

[0041] The reinforcing fabric 14 is provided so as to cover the inner peripheral surface of the tooth portion 11b. The provision of the reinforcing fabric 14 also improves the durability of the belt teeth 12. The reinforcing fabric 14 may be a woven fabric or a knitted fabric. The reinforcing fabric 14 is preferably a woven fabric.

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

[0043] The reinforcing fabric 14 made of woven fabric is preferably arranged so that one of the warp and weft threads faces the belt length direction. The weft thread of the reinforcing fabric 14 may be a stretch-processed yarn such as a false-twisted yarn. When the weft thread is a stretch-processed yarn, the reinforcing fabric 14 has anisotropic stretch characteristics, in which the stretch characteristics differ between the weft and warp directions. In this case, the reinforcing fabric 14 is preferably arranged so that the weft thread of the reinforcing fabric 14 faces the belt length direction, so that the stretch characteristics in the belt length direction are high.

[0044] Examples of fiber materials constituting the reinforcing fabric 14 include nylon fibers such as nylon 6,6 fiber, nylon 4,6 fiber, and nylon 6 fiber, chemical fibers such as polyketone fiber, aramid fiber, and polyester fiber, and natural fibers such as cotton. The reinforcing fabric 14 may be made 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 reinforcing fabric 14 in an epoxy adhesive and then drying the same. This adhesive treatment is performed before winding the reinforcing fabric 14 around a mold in the method for manufacturing a toothed belt, which will be described later.

[0046] The reinforcing fabric 14 may be subjected to a wear modification treatment. Examples of the wear modification treatment include a treatment in which a binder having the wear modifier dispersed therein is applied to the reinforcing fabric before being wrapped around the mold, or a treatment in which the reinforcing fabric before being wrapped around the mold is immersed in the binder.

[0047] Examples of the wear modifier include ultra-high molecular weight polyethylene (UHMWPE), fluororesins such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylenepropene copolymer (FEP), ethylene-tetrafluoroethylene copolymer (ETFE), and polyvinylidene fluoride (PVDF).

[0048] In the belt teeth 12 of the toothed belt 10, the cured product of the thermosetting urethane composition penetrates into the gaps in the reinforcing fabric 14. Therefore, not only the reinforcing fabric 14 but also the cured product of the thermosetting urethane composition are exposed on the surface (inner peripheral surface) of the belt tooth 12.

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

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

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

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

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

[0054] The backlash area Sb is determined by the following condition. With the center line CL of the belt tooth 12 and the center line CL of the pulley groove 21 aligned, the belt tooth 12 is moved from the outside of the pulley groove 21 toward the pulley groove 21 until the belt tooth 12 contacts the toothed pulley 20, causing the belt tooth 12 and the pulley groove 21 to overlap. In this state, the area surrounded by the imaginary line VL, the belt tooth 12, and the pulley groove 21 is the backlash area Sb. Note that when the belt tooth 12 is moved toward the pulley groove 21 as described above, there are cases where the tip of the belt tooth 12 first contacts the pulley groove, and cases where the tooth surface of the belt tooth 12 first contacts the pulley groove. When overlapping the belt tooth 12 with the pulley groove 21 to calculate the backlash area Sb, the belt tooth 12 is moved until the belt tooth 12 and any part of the belt tooth 12 or its vicinity (the tooth bottom portion close to the tooth base of the belt tooth 12) come into contact with the toothed pulley 20, and the two are overlapped.

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

[0056] In the transmission system 1 including the toothed belt 10 and the toothed pulley 20, the backlash area Sb relative to the area Sp of one pulley groove 21 satisfies the following formula (1): 7.26×10 －２ ≧Sb / Sp≧3.46×10 －２ ... (1) By satisfying the above formula (1), the toothed belt is less likely to generate heat when driven. Therefore, the toothed belt has excellent durability. On the other hand, if the Sb / Sp ratio is outside the above range, the amount of heat generated when the belt teeth are driven increases. As a result, the toothed belt has a shorter lifespan and poor durability. The reason why the amount of heat generated when the belt teeth are driven increases when the Sb / Sp ratio is outside the above range is believed to be because the sliding work (shear stress x sliding amount) with the pulley groove that occurs when the belt teeth mesh with each other increases at least at one of the root, pressure surface, and tip of the belt teeth.

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

[0058] In the toothed belt 10 and the 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. As shown in FIG. 3 , the tooth height Hb of the belt tooth 12 is the distance from the tooth bottom 15 between a pair of belt teeth 12 adjacent to each other in the belt length direction to the tip of the belt tooth 12. For example, in the case of belt teeth of G8M and G14M defined in ISO 13050:2014(E), this is expressed as hg. The tooth groove bottom depth Hp of the pulley groove 21 is the distance from the tooth tip circle Cp of the toothed pulley 20 to the tooth groove bottom on the center line CL of the pulley groove 21 (see FIG. 5 ).

[0059] In the transmission system 1, the ratio of the tooth height Hb of the belt tooth 12 to the tooth groove bottom depth Hp of the pulley groove 21 satisfies the following formula (2): 1.04 ≥ Hb / Hp ≥ 0.91 (2) By satisfying the above formula (2), it is possible to disperse the shear stress generated in the belt tooth when the belt tooth meshes with the pulley groove. This prevents heat from concentrating on the belt tooth, making the toothed belt less susceptible to damage.

[0060] On the other hand, if Hb / Hp is less than 0.91, shear stress is concentrated at the base of the belt tooth, and heat is likely to be concentrated at the base of the belt tooth. Also, if Hb / Hp exceeds 1.04, shear stress is concentrated at the tip of the belt tooth, and heat is likely to be concentrated at the tip of the belt tooth. In either case, localized heat is likely to be generated at the belt tooth, resulting in poor durability of the toothed belt.

[0061] In the transmission system 1, when the tips of the belt teeth 12 are in contact with the tooth groove bottoms of the pulley grooves 21, the tooth bottoms 15 between the belt teeth 12 may be in contact with the tips of the pulley teeth, or may have a gap between them. If there is a gap, the gap is preferably 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 belt tooth 12 and the pulley groove 21 at the measurement position of the mid-width W of the belt tooth 12 is preferably 2.0% to 10.0% of the mid-width W of the belt tooth 12. This gap dimension is measured with the belt tooth 12 and the pulley groove 21 overlapped to determine the backlash area Sb. The gap dimension is the sum of distances g between the tooth surface of the belt tooth 12 and the tooth surface of the pulley groove 21 in the direction perpendicular to the center line CL at the measurement position of the mid-width W (see FIG. 6). Since there are usually two gaps between the tooth surface of the belt tooth and the tooth surface of the pulley groove per belt tooth, the gap dimension is calculated as the sum of distances g, as described above.

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

[0064] (1) A toothed belt molding die 30 is prepared. This toothed belt molding die 30 includes a cylindrical inner die 31 and a cylindrical outer die 34. The outer periphery of the inner die 31 is provided with axially extending recesses 32 and axially extending protrusions 33. The recesses 32 have a cross-sectional shape corresponding to the belt teeth 12 and are grooves extending in the axial direction (direction perpendicular to the paper surface of FIG. 7). The recesses 32 are provided at a constant pitch and spaced apart in the circumferential direction. The protrusions 33 are provided between adjacent recesses 32. The inner periphery of the outer die 34 has a smooth surface.

[0065] (2) First, the cylindrical reinforcing cloth 14 is placed over the cylindrical inner mold 31. Next, the core wires 13 are spirally wound around the reinforcing cloth 14. The cylindrical reinforcing cloth 14 is molded in advance to fit 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 at a predetermined position inside the cylindrical outer mold 34. As a result, a cavity C for molding the belt main body is formed between the inner mold 31 and the outer mold 34 (see FIG. 7).

[0067] (4) Next, a thermosetting urethane composition 111 containing a urethane prepolymer or the like is poured into the sealed cavity C and heated (see FIG. 8 ). The thermosetting urethane composition 111 hardens within the cavity C. As a result, belt teeth are formed in the recesses 32, and belt tooth bottoms are formed in the protrusions 33. In this process, the thermosetting urethane composition 111 hardens while penetrating into gaps in the reinforcing fabric 14 (not shown). As a result, the cured thermosetting urethane composition 111, along with the reinforcing fabric 14, is exposed on the inner circumferential surfaces of the formed belt teeth 12.

[0068] By going through steps (1) to (4) as described above, a cylindrical slab is formed in which the belt body 11, the cords 13, and the reinforcing fabric 14 are integrated. The molding conditions in step (4) may be appropriately selected taking into consideration the composition of the thermosetting urethane composition, and may be set, for example, at a molding temperature of 170°C, a molding pressure of 12 MPa, and a molding time of 20 minutes.

[0069] (5) Finally, the slab is removed from the inner mold 31 and the outer mold 34, and the resulting slab is sliced ​​into rings, thereby obtaining the toothed belt 10 according to this embodiment.

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

[0071] Other Embodiments The belt teeth of the toothed belt according to the embodiment of the present invention are not limited to straight teeth, but may be helical teeth.

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

[0073] The following examples further illustrate embodiments of the present invention, but the present invention is not limited to these examples. Toothed belts were produced for each of Examples 1 to 3 and Comparative Examples 1 and 2. Furthermore, G8M pulleys conforming to ISO 13050:2014(E) were produced as toothed pulleys (drive pulley and driven pulley) to be meshed with the toothed belts. The tooth groove bottom depth Hp of the pulley grooves of these toothed pulleys was measured and found to be 3.545 mm.

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

[0075] The thermosetting urethane composition used to form the belt body was a blend of 100 parts by mass of a urethane prepolymer (PTMEG-TDI) with tolylene diisocyanate as the isocyanate component and polytetramethylene ether glycol as the polyol component, and 16 parts by mass of a curing agent (4-chloro-3,5-diaminobenzoic acid isobutyl). The cured product of the thermosetting urethane composition had a JIS-A hardness of 95.

[0076] The core wire was made of single-twisted yarn that had been subjected to an adhesive treatment. The single-twisted yarn was made by twisting a filament bundle of 12,000 carbon fibers (Tenax-J UTS50 F22, manufactured by Teijin Limited, 12K, 800 tex, filament diameter: 7.0 μm) in one direction at a twist rate of 90 tpm per meter. S-twisted yarn and Z-twisted yarn were prepared as the single-twisted yarns used for the core wire. The adhesive treatment involved immersing the yarn in an adhesive and then drying it. A phenol-based adhesive was used as the adhesive.

[0077] The cords using S-twisted yarns and the cords using Z-twisted yarns were used so that double helices were formed in the obtained toothed belt, arranged alternately in the belt width direction. The number of cords was 8 per 10 mm of belt width.

[0078] The canvas (reinforcing fabric) was a 2 / 2 twill canvas formed with one weft yarn made of nylon 6,6 fiber bundles with a fineness of 235 dtex and three warp yarns with a fineness of 235 dtex. The canvas was arranged so that the weft yarn was aligned in the belt length direction. The canvas was not subjected to an adhesive treatment. The canvas had a thickness of 1.2 mm, a warp yarn density of 113 threads / 5 cm width, a weft yarn density of 120 threads / 5 cm width, and a basis weight of 385 g / m. ２ It was.

[0079] Example 2 A toothed belt was produced in the same manner as in Example 1, except that the shape of the belt teeth was changed as follows. 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 FIG. 4) was 3.62 mm, the intermediate width W (see FIG. 4) was 4.38 mm, and the tooth width bg was 5.23 mm. The obtained toothed belt had a backlash area Sb of 0.58 mm when meshed with a G8M pulley specified in ISO 13050:2014(E). ２ is.

[0080] Example 3 A toothed belt was produced in the same manner as in Example 1, except that the shape of the belt teeth was changed as follows. 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 FIG. 4) was 3.62 mm, the intermediate width W (see FIG. 4) was 4.34 mm, and the tooth width bg was 5.25 mm. The obtained toothed belt had a backlash area Sb of 0.82 mm when meshed with a G8M pulley specified in ISO 13050:2014(E). ２ is.

[0081] Comparative Example 1 A toothed belt was produced in the same manner as in Example 1, except that the shape of the belt teeth was changed as follows. 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 FIG. 4) was 3.20 mm, the intermediate width W (see FIG. 4) was 4.03 mm, and the tooth width bg was 5.44 mm. The obtained toothed belt had a backlash area Sb of 0.52 mm when meshed with a G8M pulley specified in ISO 13050:2014(E). ２ is.

[0082] Comparative Example 2 A toothed belt was produced in the same manner as in Example 1, except that the shape of the belt teeth was changed as follows. 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 FIG. 4) was 3.62 mm, the intermediate width W (see FIG. 4) was 4.43 mm, and the tooth width bg was 5.20 mm. The obtained toothed belt had a backlash area Sb of 0.42 mm when meshed with a G8M pulley specified in ISO 13050:2014(E). ２ is.

[0083] Comparative Example 3 A toothed belt was produced in the same manner as in Example 1, except that the shape of the belt teeth was changed as follows. 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 FIG. 4) was 3.71 mm, the intermediate width W (see FIG. 4) was 4.41 mm, and the tooth width bg was 5.21 mm. The obtained toothed belt had a backlash area Sb of 0.50 mm when meshed with a G8M pulley specified in ISO 13050:2014(E). ２ is.

[0084] Comparative Example 4 A toothed belt was produced in the same manner as in Example 1, except that the shape of the belt teeth was changed as follows. 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 FIG. 4) was 3.62 mm, the intermediate width W (see FIG. 4) was 4.32 mm, and the tooth width bg was 5.27 mm. The obtained toothed belt had a backlash area Sb of 1.06 mm when meshed with a G8M pulley specified in ISO 13050:2014(E). ２ is.

[0085] (Evaluation) <Load Endurance Test> FIG. 9 shows the layout of toothed pulleys in a belt running tester for a load endurance test.

[0086] This belt running tester 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, arranged at a laterally spaced interval, and is configured so that a lateral shaft load (SW) can be applied to the driven pulley 42. As described above, the drive pulley 41 and the driven pulley 42 have pulley grooves with dimensions G8M specified in ISO 13050:2014(E).

[0087] Each toothed belt of the example and comparative example was wound around the drive pulley 41 and driven pulley 42 of the belt running tester 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. After setting the target tension, the belt was manually rotated three times around the toothed pulley, and then adjusted to the target tension again. The belt was then run at an ambient temperature of 60°C, with the drive pulley 41 rotating at 4,200 rpm and the driven pulley 42 at 2,800 rpm. The belt was then periodically stopped and visually observed, and continued running until failure occurred, such as chipped or worn belt teeth, or separation between the belt body and the core. When a failure occurred in the toothed belt, the belt's root temperature was measured using a radiation thermometer. The results are shown in Table 1.

[0088]

[0089] As shown in Table 1, it was clear that the toothed belt according to the embodiment of the present invention is less likely to generate heat and has excellent durability.

[0090] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, and it is intended to include all modifications within the meaning and scope of the claims.

[0091] DESCRIPTION OF SYMBOLS 1 Transmission system 10 Toothed belt 11 Belt body 11a Base 11b Toothed portion 12 Belt teeth 13 Core wire 14 Reinforcing fabric 15 Tooth bottom portion 20 Toothed pulley 21 Pulley groove 22 Driving pulley 24 Driven pulley 26 Tooth tip of toothed pulley 20 30 Toothed belt molding mold 31 Inner mold 32 Concave portion 33 Convex portion 34 Outer mold 40 Belt running tester 41 Driving pulley 42 Driven pulley 111 Thermosetting urethane composition C Cavity

Claims

1. A toothed belt having a plurality of belt teeth arranged at a constant pitch in the longitudinal direction of the belt, the belt teeth meshing with pulley grooves arranged at a constant pitch along the outer periphery of a toothed pulley, wherein the backlash area Sb of the belt tooth with respect to the pulley groove and the area Sp of one of the pulley grooves are less than 7.26 x 10 －２ ≧Sb / Sp≧3.46×10 －２ ...(1), and a tooth height Hb of the belt teeth and a tooth groove bottom depth Hp of the pulley groove satisfy the following relationship: 1.04≧Hb / Hp≧0.91...(2).

2. A transmission system comprising a toothed belt in which a plurality of belt teeth are provided at a constant pitch in the longitudinal direction of the belt, and a toothed pulley in which pulley grooves that mesh with the belt teeth are provided at a constant pitch along the outer periphery, wherein the backlash area Sb and the area Sp of one of the pulley grooves are less than 7.26 x 10 －２ ≧Sb / Sp≧3.46×10 －２ ...(1), wherein a tooth height Hb of the belt tooth and a tooth groove bottom depth Hp of the pulley groove satisfy the following relationship: 1.04≧Hb / Hp≧0.91...(2).

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