Transmission system

Abstract

Provided is a transmission system that comprises a toothed belt, a first toothed pulley, and a second toothed pulley having a diameter larger than that of the first toothed pulley, the toothed belt being wound around the first toothed pulley and the second toothed pulley. The nominal pitch of the belt teeth is 2 mm. The belt teeth are helical teeth having a tooth trace angle of 5.0° to 9.0° and a speed ratio of 2.0 or more to less than 5.0. Formula (1) is satisfied by: the toothed belt and the first toothed pulley; and the toothed belt and the second toothed pulley.　(1): 1.5X - 0.31 < Y < X - 0.03 In formula (1), X is the PLD of the toothed belt, and Y is the value calculated by using formula (2).　(2): Y = ((the nominal pitch of the toothed belt × the number of pulley teeth T / π) - tooth tip diameter) / 2

Description

Transmission system

[0001] This application claims priority from Japanese Patent Application No. 2024-012996, filed January 31, 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 toothed pulleys is known as a power transmission system. A power transmission system equipped with a toothed belt can perform stable synchronous transmission with low tension. Therefore, it is suitable for use in general industrial machinery such as machine tools and textile machines, as well as in electric power steering devices. However, the above-mentioned power transmission system has a problem in that it generates noise (running noise) during operation.

[0003] Methods for reducing noise generated when a toothed belt engages with a toothed pulley have been proposed. For example, Patent Document 1 discloses a helical tooth belt having a back portion in which core wires are embedded and a plurality of teeth provided on one surface of the back portion at predetermined intervals along the belt longitudinal direction and each tooth is inclined with respect to the belt width direction, wherein the surfaces of the tooth portions and a portion of the one surface of the back portion are made of tooth cloth, the tooth pitch of the plurality of teeth is 2 mm or more and less than 4 mm, the thickness of the back portion is 0.4 mm or more and 1.8 mm or less, the core wires are twisted cords containing high-strength glass fiber or carbon fiber and having a diameter of 0.2 mm or more and 0.6 mm or less, and the core wires are arranged so that the core wire pitch between the adjacent core wires is in the range of 0.45 mm or more and 0.6 mm or less.

[0004] Japanese Patent Application Laid-Open No. 2019-178776

[0005] Transmission systems consisting of toothed belts and toothed pulleys are required to reduce running noise (noise suppression), and this demand will never go away. Noise suppression is particularly important in applications where quietness is required.

[0006] An object of the present disclosure is to provide a noise-suppressed transmission system that is specified from a new perspective different from conventional ones.

[0007] A transmission system according to one aspect of the present invention comprises: a toothed belt having a plurality of belt teeth provided on its inner periphery; a first toothed pulley having a plurality of pulley grooves on its outer periphery that mesh with the belt teeth; and a second toothed pulley having a larger diameter than the first toothed pulley and having a plurality of pulley grooves on its outer periphery that mesh with the belt teeth, wherein the toothed belt is wound around the first toothed pulley and the second toothed pulley, wherein the nominal pitch of the belt teeth is 2 mm, the belt teeth are helical teeth with a tooth trace angle of 5.0 degrees or more and 9.0 degrees or less, the speed ratio is 2.0 or more and less than 5.0, and the toothed belt and the first toothed pulley, and the toothed belt and the second toothed pulley each satisfy the following formula (1): 1.5X - 0.31 < Y ​​< X - 0.03 (1) In formula (1), X is the PLD of the toothed belt, and Y is a value calculated by the following formula (2): Y = ((nominal pitch of toothed belt × number of pulley teeth T / π) - tip diameter) / 2 (2)

[0008] According to the present disclosure, a transmission system with reduced noise can be provided.

[0009] 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 an end view taken along line B-B in FIG. 2. FIG. 5 is a plan view showing a part of the inner peripheral surface of the toothed belt 10 in FIG. 2. FIG. 6 is a diagram illustrating a method for manufacturing a toothed belt. FIG. 7 is a diagram illustrating a method for manufacturing a toothed belt. FIG. 8 is a diagram illustrating a method for manufacturing a toothed belt. FIG. 9 is a diagram illustrating the dimensions of belt teeth. FIG. 10 is a diagram illustrating the dimensions of pulley grooves. FIGS. 11A and 11B are diagrams schematically showing a transmission system for evaluating noise. FIG. 12 is a graph showing the evaluation results of examples and comparative examples.

[0010]

[0013] An outline of an embodiment of the present invention will be described below. [1] A power transmission system comprising: a toothed belt having a plurality of belt teeth provided on an inner periphery thereof; a first toothed pulley having a plurality of pulley grooves on its outer periphery that mesh with the belt teeth; and a second toothed pulley having a larger diameter than the first toothed pulley and having a plurality of pulley grooves on its outer periphery that mesh with the belt teeth, wherein the toothed belt is wound around the first toothed pulley and the second toothed pulley, wherein the nominal pitch of the belt teeth is 2 mm, the belt teeth are helical teeth with a tooth trace angle of 5.0 degrees or more and 9.0 degrees or less, and the speed ratio is 2.0 or more and less than 5.0, and wherein the toothed belt and the first toothed pulley, and the toothed belt and the second toothed pulley, respectively, satisfy the following formula (1): 1.5X - 0.31 < Y ​​< X - 0.03 (1) In formula (1), X is the PLD of the toothed belt, and Y is a value calculated by the following formula (2): Y = ((nominal pitch of toothed belt × number of pulley teeth T / π) - tip diameter) / 2 (2)

[0011] This transmission system satisfies formula (1), ensuring smooth meshing between the toothed belt and toothed pulley, and suppressing noise.

[0012] [2] In the transmission system of [1] above, it is preferable that the PLD of the toothed belt is 0.280 mm or more and 0.360 mm or less. [3] In the transmission system of either [1] or [2] above, it is preferable that the PLD of the first toothed pulley and the second toothed pulley is 0.180 mm or more and 0.280 mm or less.

[0013] [4] In the transmission system according to any one of the above [1] to [3], it is preferable that the toothed belt has a belt width of 20 mm or more.

[0014] [5] In the power transmission system according to any one of the above [1] to [4], it is preferable that the toothed belt has an overlap ratio ε of the belt teeth of 0.80 or more.

[0015] [6] In the transmission system according to any one of the above [1] to [5], it is preferable that the toothed belt has belt teeth with an arc tooth profile.

[0016] [7] In the transmission system according to any one of [1] to [6] above, it is preferable that the toothed belt has a belt tooth width of 0.8 mm or more and 1.8 mm or less.

[0017] [8] In any of the transmission systems [1] to [7] above, the toothed belt preferably comprises: a belt body having a belt-like shape and including a base portion having a rectangular cross section perpendicular to the longitudinal direction of the belt, and a plurality of tooth portions which are disposed on the inner circumferential side of the base portion at equal intervals at predetermined intervals and which are integrated with the base; a core wire embedded in the belt body; and a reinforcing cloth provided so as to cover the inner circumferential surfaces of the tooth portions; and the toothed belt preferably has a belt thickness of 1.1 mm or more, a thickness of the base portion of 0.30 mm or more and 1.6 mm or less, and a tooth height of the belt teeth of 0.50 mm or more and 1.0 mm or less.

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (Transmission System) Fig. 1 is a side view schematically showing a transmission system 1 according to an embodiment of the present invention. The transmission system 1 is suitably used in general industrial machines such as machine tools, printing machines, textile machines, and injection molding machines, and in electric power steering devices. As shown in Fig. 1, the transmission system 1 includes a drive pulley (first toothed pulley) 22, a driven pulley (second toothed pulley) 24, and a toothed belt 10. The drive pulley 22 is a small-diameter pulley with a relatively small diameter, and the driven pulley 24 is a large-diameter pulley with a relatively large diameter.

[0019] 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 ) on its inner periphery that mesh with the pulley grooves 21. The toothed belt 10 has a core wire 13 embedded therein. The toothed belt 10 is wound around the drive pulley 22 and the driven pulley 24.

[0020] 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.

[0021] The speed ratio of the transmission system 1 (number of teeth of the driven pulley 24 / number of teeth of the drive pulley 22) is equal to or greater than 2.0 and less than 5.0. This is suitable for reducing noise while keeping the motor size small. On the other hand, if the speed ratio is less than 2.0, the motor must be made larger in size in order to ensure the desired assist force. This makes it difficult to reduce the size of a device that includes the transmission system 1. Furthermore, if the speed ratio exceeds 5.0, it becomes necessary to increase the motor's rotation speed, making it difficult to reduce noise.

[0022] 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, 0 m / s or more and 33 m / s or less. In the transmission system 1, the transmission capacity is, for example, 0.1 kW or more and 10 kW or less.

[0023] (Toothed Belt) Fig. 2 is a perspective view showing a portion of a toothed belt 10. This toothed belt 10 constitutes a power transmission system 1 according to an embodiment of the present invention. Fig. 3 is a cross-sectional view taken along line A-A in Fig. 2. Fig. 4 is an end view taken along line B-B in Fig. 2. Fig. 5 is a plan view showing a portion of the inner peripheral surface of the toothed belt 10 in Fig. 2. Although only a portion of the toothed belt 10 is shown in Fig. 2, the toothed belt 10 is an endless meshing power transmission belt. The toothed belt 10 is a single-sided toothed belt.

[0024] The belt length of the toothed belt 10 (belt length at the belt pitch line BL) is, for example, 400 mm or less. A preferred belt length is 100 mm or more and 400 mm or less. A more preferred belt length is 150 mm or more and 380 mm or less. The belt width Wb of the toothed belt 10 is, for example, 20 mm or more and 45 mm or less. The belt thickness Tb of the toothed belt 10 is, for example, 1.1 mm or more and 3.0 mm or less. The belt thickness Tb of the toothed belt 10 is the thickness of the thickest part of the toothed belt 10. The dimensions of the toothed belt according to the embodiment of the present invention are not limited to these ranges.

[0025] The toothed belt 10 has a plurality of belt teeth 12 on its inner peripheral surface. The belt teeth 12 of the toothed belt 10 have a nominal pitch of 2 mm. Here, the nominal pitch has the same meaning as the "nominal pitch" used in JIS B 1857-1 and the like. In the embodiment of the present invention, the range of the nominal pitch (tooth pitch Pb) of the toothed belt 10 is 2±0.005 mm. The tooth profile of the belt teeth 12 is, for example, a circular-arc tooth profile.

[0026] 4, the double-headed arrow Wt indicates the width of the belt tooth 12. The width of the belt tooth 12 is defined by the dimension between the ends of a pair of tooth roots 15 adjacent to each other and sandwiching the belt tooth 12 in the circumferential direction of the belt. The width Wt of the belt tooth 12 is, for example, not less than 0.8 mm and not more than 1.8 mm.

[0027] (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 and are formed at a predetermined pitch along its outer periphery. In the toothed pulley 20, the number of teeth of the drive pulley 22 is, for example, 20 to 50. The number of teeth of the driven pulley 24 is, for example, 100 to 150. The tooth profile of the pulley groove 21 is, for example, a circular arc tooth profile. The tooth profile of the pulley groove 21 corresponds to the tooth profile of the belt teeth 12. The toothed pulley 20 may be provided with, for example, a flange.

[0028] (Relationship between Toothed Belt and Toothed Pulley) In the transmission system 1, the belt teeth 12 of the toothed belt 10 are configured to smoothly mesh with the pulley groove 21 of the toothed pulley 20. In the transmission system 1, the toothed belt 10 and the driving pulley 22, and the toothed belt 10 and the driven pulley 24 each satisfy the following formula (1): 1.5X-0.31<Y<X-0.03 (1)

[0029] In formula (1), X is the PLD (Pitch Line Differential) of the toothed belt 10. The PLD of the toothed belt 10 is the distance between the pitch line and the tooth bottom surface of the toothed belt 10. A preferable PLD of the toothed belt 10 is 0.280 mm or more and 0.360 mm or less. In this case, smooth meshing between the toothed belt 10 and the toothed pulley 20 is easily ensured, which is more suitable for suppressing noise. On the other hand, if the PLD of the toothed belt 10 is less than 0.280 mm, interference between the belt teeth and the pulley teeth is strong on the side in the belt travel direction when they mesh, resulting in increased noise. On the other hand, if the PLD of the toothed belt 10 exceeds 0.360 mm, interference between the belt teeth and the pulley teeth is strong on the side opposite to the belt travel direction when they mesh, resulting in increased noise. The PLD of the toothed belt 10 is more preferably 0.300 mm or more and 0.340 mm or less.

[0030] In formula (1), Y is a value calculated by the following formula (2): Y = ((nominal pitch of toothed belt × number of pulley teeth T / π) - tip diameter) / 2 (2) Y expressed in formula (2) above is a value similar to the PLD of the toothed pulley 20. In the transmission system 1, there is a predetermined relationship between X, which is the PLD of the toothed belt 10, and Y, which is similar to the PLD of the toothed pulley 20, so smooth meshing between the toothed belt 10 and the toothed pulley 20 is ensured, and noise is suppressed.

[0031] The nominal pitch of the toothed belt 10 is 2 mm. Therefore, the above formula (2) can be rewritten as the following formula (2'): Y = ((2 × number of pulley teeth T / π) - tip diameter) / 2 (2')

[0032] In the above formula (2), the value of Y is preferably 0.180 mm or more and 0.280 mm or less, which is more likely to ensure smooth meshing between the toothed belt 10 and the toothed pulley 20 and is more suitable for suppressing noise.

[0033] In the transmission system 1, the PLD of each of the drive pulley 22 and the driven pulley 24 is preferably 0.180 mm or more and 0.280 mm or less. In this case, smooth meshing between the toothed belt 10 and the toothed pulley 20 is more likely to be ensured, which is more suitable for noise suppression. On the other hand, if the PLD of the toothed pulley 20 is less than 0.180 mm, the pulley tooth gaps become narrower, the interference position when the toothed belt 10 and the toothed pulley 20 mesh together becomes higher, and the interference state worsens. On the other hand, if the PLD of the toothed pulley 20 exceeds 0.280 mm, the pulley tooth gaps become wider, the interference position when the toothed belt 10 and the toothed pulley 20 mesh together becomes lower, and the interference state worsens. The PLD of the toothed pulley 20 is more preferably 0.200 mm or more and 0.260 mm or less.

[0034] The PLD of the toothed pulley 20 is the radial distance between the pitch diameter and the tip diameter. In the transmission system 1, the PLD of the drive pulley 22 and the driven pulley 24 preferably have the same value.

[0035] As shown in FIG. 5 , the belt teeth 12 of the toothed belt 10 are helical teeth. In FIG. 5 , θ is the tooth trace angle of the belt teeth 12. The tooth trace angle θ of the helical teeth belt teeth 12 is 5.0 degrees or more and 9.0 degrees or less. In this case, when the toothed belt 10 and the toothed pulley 20 mesh, the belt teeth 12 gradually mesh with the pulley groove 21 from one side to the other along the tooth trace, thereby reducing meshing impact noise. This suppresses noise in the transmission system 1. On the other hand, if the tooth trace angle is less than 5.0 degrees, the noise reduction effect of employing helical teeth is poor. Furthermore, vibration of the toothed belt is also likely to occur. If the tooth trace angle exceeds 9.0 degrees, the bias force due to the helical teeth becomes excessive, which can cause wear on the side of the toothed belt due to contact between the side of the toothed belt and the flange of the pulley, etc. Furthermore, the increased bias force increases the rubbing noise with the flange and the rubbing noise caused by meshing while being subjected to the bias force, resulting in increased noise. The toothed pulley 20 that meshes with the toothed belt 10 also has helical teeth.

[0036] The overlap ratio ε of the belt teeth 12 of the toothed belt 10, which is a helical tooth, is preferably 0.80 or more. The reason for this is that in the case of a helical toothed belt, the tooth trace of the belt teeth is inclined (not at 90°) relative to the belt traveling direction, so the helical teeth mesh sequentially from the teeth at the belt end, and before the meshing ends, the next tooth begins to mesh, which stabilizes the running state of the belt.

[0037] The belt tooth overlap ratio ε is the ratio of the period during which one belt tooth meshes with a pulley tooth groove to the period during which the next belt tooth meshes with the pulley tooth groove, and is calculated using the following formula (3): ε=Wb·tan θ / Pb (3) (where Wb is the width of the toothed belt, θ is the tooth trace angle, and Pb is the tooth pitch of the toothed belt.)

[0038] (Configuration of Toothed Belt) As shown in Fig. 2, the toothed belt 10 includes a belt body 11, core wires 13, and a reinforcing fabric 14. The belt body 11 has a band shape and includes a base portion 11a having a rectangular cross section perpendicular to the belt longitudinal direction, and a plurality of teeth 11b provided on the inner circumferential side of the base portion 11a. The plurality of teeth 11b are integrated with the base portion 11a. The plurality of teeth 11b are provided at equal intervals at predetermined intervals along the belt longitudinal direction.

[0039] In Fig. 4, the double-headed arrow Sb indicates the thickness of the base portion 11a. The thickness of the base portion 11a is, for example, 0.30 mm or more and 1.6 mm or less. The thickness of the base portion 11a is preferably 0.50 mm or more and 1.40 mm or less.

[0040] In the toothed belt 10, the reinforcing fabric 14 is provided so as to cover the inner peripheral surface of the toothed portion 11b. In the toothed belt 10, the belt tooth 12 is composed of the toothed portion 11b and the reinforcing fabric 14.

[0041] In Fig. 4, the double-headed arrow Hb indicates the tooth height of the belt tooth 12 (the tooth height of the belt tooth 12). The tooth height Hb of the belt tooth 12 is, for example, 0.50 mm or more and 1.0 mm or less. Here, the tooth height Hb of the belt tooth 12 refers to the distance in the belt thickness direction from the adjacent tooth bottom portion 15 to the apex of the tooth tip of the belt tooth 12 (see Hb in Fig. 4). In the toothed belt 10, at the tooth bottom portion 15, the core wires 13 embedded in the inner peripheral portion of the base portion 11a of the belt main body 11 are arranged just inside the reinforcing fabric 14 (on the outer peripheral side of the belt).

[0042] The belt body 11 is made of a rubber composition (crosslinked rubber composition) obtained by crosslinking an uncrosslinked rubber composition containing a rubber component and a rubber compounding agent through heating and pressure. Examples of the rubber component include hydrogenated nitrile rubber (HNBR), chlorosulfonated polyethylene rubber, chloroprene rubber (CR), and ethylene-α-olefin elastomers such as ethylene-propylene-diene rubber (EPDM).

[0043] Conventionally known rubber compounding agents can be used as the rubber compounding agent. Examples of the rubber compounding agent include vulcanization accelerators, antioxidants, reinforcing materials, plasticizers, co-crosslinking agents, crosslinking agents, etc. Examples of the vulcanization accelerators include metal oxides, metal carbonates, fatty acids and derivatives thereof, etc. Examples of the metal oxides include zinc oxide (zinc oxide) and magnesium oxide, etc. These vulcanization accelerators may be used alone or in combination of two or more. The content of the vulcanization accelerator is, for example, 3 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the rubber component.

[0044] Examples of the antiaging agent include benzimidazole-based antiaging agents, aromatic secondary amine-based antiaging agents, and amine-ketone-based antiaging agents. These antiaging agents may be used alone or in combination of two or more. As the antiaging agent, it is preferable to use a benzimidazole-based antiaging agent and an aromatic secondary amine-based antiaging agent in combination. The content of the antiaging agent is, for example, 1.5 parts by mass or more and 3.5 parts by mass or less per 100 parts by mass of the rubber component.

[0045] Examples of the reinforcing material include carbon black and silica. It is preferable to use a combination of carbon black and silica as the reinforcing material. Examples of the carbon black include channel black, furnace black, thermal black, and acetylene black. Examples of the furnace black include SAF, ISAF, N-339, HAF, N-351, MAF, FEF, SRF, GPF, ECF, and N-234. Examples of the thermal black include FT and MT. Only one type of carbon black may be used, or two or more types may be used in combination. It is preferable to use HAF alone or in combination with other carbon black.

[0046] The amount of the carbon black is, for example, 10 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the rubber component. The amount of the silica is, for example, 10 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the rubber component.

[0047] Examples of the plasticizer include dialkyl sebacate, dialkyl phthalate, and dialkyl adipate. Examples of the dialkyl sebacate include polyether ester and dioctyl sebacate (DOS). Examples of the dialkyl phthalate include dibutyl phthalate (DBP) and dioctyl phthalate (DOP). Examples of the dialkyl adipate include dioctyl adipate (DOA). These plasticizers may be used alone or in combination of two or more. As the plasticizer, it is preferable to use polyether ester alone or in combination with another plasticizer. The content of the plasticizer is, for example, 5 to 15 parts by mass per 100 parts by mass of the rubber component.

[0048] Examples of the co-crosslinking agent include trimethylolpropane trimethacrylate, m-phenylenedimaleimide, zinc dimethacrylate, triallyl isocyanurate, etc. These co-crosslinking agents may be used alone or in combination of two or more. The content of the co-crosslinking agent is, for example, 3 parts by mass or more and 8 parts by mass or less per 100 parts by mass of the rubber component.

[0049] Examples of the crosslinking agent include sulfur and organic peroxides. Sulfur and organic peroxides may be used in combination. Of course, either one may be used alone. When sulfur and organic peroxides are used in combination as the crosslinking agent, the total content of the crosslinking agents is preferably, for example, 0.1 parts by mass or more and 0.7 parts by mass or less of sulfur and 1 part by mass or more and 5 parts by mass or less of organic peroxide per 100 parts by mass of the rubber component.

[0050] Examples of the core wire 13 include a glass core wire, an aramid core wire, a carbon core wire, a steel core wire, etc. These core wires are preferably made of twisted yarn.

[0051] The outer diameters of the core wires 13, φT in the belt thickness direction and φW in the belt width direction, are preferably 0.15 mm or more and 0.80 mm or less. More preferably, φT and φW are 0.25 mm or more and 0.50 mm or less. The outer diameter φT in the belt thickness direction and the outer diameter φW in the belt width direction may be the same or different.

[0052] The core wires 13 are arranged to have a pitch in the belt width direction and to form a spiral. The core wires 13 may be composed of two strands, an S-twisted yarn and a Z-twisted yarn, which are arranged to form a double spiral.

[0053] 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 10 / 10 mm or more and 26 / 10 mm or less. A toothed belt 10 having the core wires 13 arranged in this manner is suitable for ensuring excellent durability and excellent tension maintenance in high-load transmission. From the same viewpoint, the number of core wires 13 is more preferably 14 / 10 mm or more and 24 / 10 mm or less. Furthermore, the dimension of the gap between adjacent core wires 13 is, for example, 0.1 mm or more and 0.7 mm or less.

[0054] The cords 13 may be subjected to an adhesive treatment to enhance adhesive strength with the belt body. Examples of the adhesive treatment include an RFL treatment in which the cords are immersed in an RFL aqueous solution and then heated, and a rubber cement treatment in which the cords are immersed in rubber cement and then dried. Only one of these adhesive treatments may be performed, or both may be performed.

[0055] The core wires 13 may be subjected to a surface treatment before the adhesive treatment. Examples of the surface treatment include a treatment of immersing the core wires in an epoxy solution followed by heating, a treatment of immersing the core wires in an isocyanate solution followed by heating, etc. These adhesive treatments and surface treatments are performed before winding the core wires around a mold in the manufacturing method of a toothed belt described below.

[0056] The reinforcing fabric 14 is made of, for example, woven fabric, knitted fabric, nonwoven fabric, etc. Examples of fibers that make up the reinforcing fabric 14 include polyamide fiber (nylon fiber), polyester fiber, aramid fiber, polyparaphenylenebenzobisoxazole (PBO) fiber, cotton, etc. As the reinforcing fabric 14, for example, a woven fabric of polyamide fiber is preferable.

[0057] The reinforcing fabric 14 is preferably stretchable. For example, a woven fabric using woolly processed weft yarns has stretchability. In this case, the reinforcing fabric 14 is preferably provided so that the direction in which it stretches most easily coincides with the length direction of the belt. The thickness of the reinforcing fabric 14 is, for example, 0.05 mm or more and 0.3 mm or less.

[0058] The reinforcing fabric 14 may be subjected to an adhesive treatment to enhance adhesion to the belt body 11. Examples of the adhesive treatment include an RFL treatment in which the reinforcing fabric 14 is immersed in an RFL aqueous solution and then heated, a soaking treatment in which the reinforcing fabric 14 is immersed in a low-viscosity rubber cement and then dried, and a coating treatment in which a high-viscosity rubber cement is applied to the surface of the belt body side and then dried. Only one of these treatments may be performed, or two or more of them may be performed.

[0059] Prior to the adhesive treatment, the reinforcing fabric 14 may be subjected to a surface treatment in which the fabric is immersed in an epoxy solution and then heated, or in which the fabric is immersed in an isocyanate solution and then heated. These adhesive treatments and surface treatments are performed before the reinforcing fabric 14 is wound around a mold in the method for manufacturing a toothed belt, which will be described later.

[0060] (Method of Manufacturing Toothed Belt) A method of manufacturing the toothed belt 10 will be described in the order of steps. Figures 6 to 8 are diagrams for explaining the method of manufacturing the toothed belt 10. Figures 6 to 8 show only a mold 30 for forming the belt and a part of the belt (including the belt material).

[0061] A belt molding die 30 is used to manufacture the toothed belt 10. The die 30 is cylindrical. The outer periphery of this die 30 is provided with axially extending recessed portions 31 and axially extending protruding portions 32. The recessed portions 31 have a cross-sectional shape corresponding to the belt teeth 12 and are grooves extending in the axial direction (a direction perpendicular to the paper surface of FIG. 6 ). The recessed portions 31 are provided at regular intervals in the circumferential direction. The protruding portions 32 are provided between adjacent recessed portions 31.

[0062] (1) Materials are prepared. The rubber components are masticated, and then rubber compounding agents are added and kneaded to obtain an uncrosslinked rubber composition. The obtained uncrosslinked rubber composition is molded to produce an uncrosslinked rubber composition sheet 111. In this case, calendar molding, for example, can be used as a molding method for the uncrosslinked rubber composition sheet 111.

[0063] The core wires 13 and the reinforcing cloth 14 are prepared, and if necessary, are subjected to an adhesive treatment, and then the reinforcing cloth 14 is formed into a cylindrical shape.

[0064] (2) The materials are layered in order. As shown in FIG. 6 , first, a cylindrically formed reinforcing cloth 14 is placed on the outer peripheral surface of a mold 30. Next, the cord 13 is spirally wound around the reinforcing cloth 14. Furthermore, an uncrosslinked rubber composition sheet 111 is wrapped around the reinforcing cloth 14. Multiple uncrosslinked rubber composition sheets 111 (two sheets in FIG. 6 ) are wrapped around the reinforcing cloth 14. In this way, an uncrosslinked slab 135 in which the reinforcing cloth 14, the cord 13, and the uncrosslinked rubber composition sheet 111 are layered is molded on the mold 30. At this time, it is preferable to layer the uncrosslinked rubber composition sheet 111 so that the grain direction corresponds to the length direction of the belt.

[0065] (3) As shown in FIG. 7 , a rubber sleeve 34 is placed over the uncrosslinked slab 135 on the mold 30, and the resulting product is placed in a vulcanizer and sealed. Next, high-temperature, high-pressure steam is filled into the vulcanizer. This state is maintained for a predetermined time. As a result, the uncrosslinked slab 135 is pressed against the mold 30 and heated. At this time, the uncrosslinked rubber composition sheet 111 passes between the cords 13 and flows into each of the multiple recesses 31 of the mold 30 while pressing the reinforcing fabric 14, and is crosslinked, forming the crosslinked rubber composition 11 that constitutes the belt body. At the same time, the cords 13 and reinforcing fabric 14 are integrated with the crosslinked rubber composition 11. As a result, a cylindrical belt slab 35 is molded, as shown in FIG. 8 .

[0066] (4) The pressure inside the vulcanization can is reduced to release the seal. Then, the belt slab 35 molded between the mold 30 and the rubber sleeve 34 is demolded. The demolded belt slab 35 is then sliced ​​into rings. Through these steps, the toothed belt 10 is obtained.

[0067] (Method of Manufacturing Toothed Pulley) The toothed pulley 20 can be manufactured by a conventionally known method. For example, the toothed pulley 20 can be manufactured by preparing a dedicated hob cutter according to the shape of the pulley groove of the toothed pulley, then subjecting a metal material to gear cutting using the hob cutter, and further performing drilling, contour processing, flange attachment, and the like as necessary.

[0068] Hereinafter, the embodiments of the present invention will be described in more detail with reference to examples, but the embodiments of the present invention are not limited to the following examples. Here, a transmission system including a toothed belt and a toothed pulley was fabricated, and a noise test was conducted on this transmission system.

[0069] (Toothed Belt) Toothed belts (A) to (J) were manufactured with a nominal pitch of 2 mm and a configuration similar to that of the toothed belt 10 shown in Figures 2 to 5. Each toothed belt was manufactured using the method described above (see Figures 6 to 8). Toothed belt (A) had a belt width Wb of 22 mm and a belt circumference of 330 mm at a compression rate of 0%. Toothed belt (A) had helical teeth with a tooth trace angle of 6.7 degrees as the belt teeth. In toothed belt (A), the helical tooth overlap ratio ε was 1.29.

[0070] The toothed belt (A) has a tooth height Hb of 0.76 mm and a total thickness Tb (Hb+Sb) of 2.1 mm. The belt tooth dimensions of the toothed belt (A) are as follows: S is 1.300 mm, A is 0.172 mm, r is 1.300 mm, and r is 0.172 mm. ｂｂ is 1.300 mm. In FIG. ｂｂ " is "S" and "r" listed in Table 4 of JIS B 1857-1 (2015) ｂｂ ", and "A" corresponds to "a-Y" derived from Table 4 of JIS B 1857-1 (2015).

[0071] In the toothed belts (A) to (J), the belt body 11 has a rubber component of EPDM. In the toothed belts (A) to (J), the core wire 13 is a glass core wire. The glass core wire has an outer diameter φT in the belt thickness direction and an outer diameter φW in the belt thickness direction of 0.33 mm.

[0072] In toothed belts (A) to (J), the reinforcing fabric 14 is a woven fabric. The warp and weft of this fabric are polyamide 66 fibers. The PLD of the toothed belt 10 is adjusted by adjusting the thickness of the reinforcing fabric 14 or the strength of the winding load of the core wire. In toothed belts (A) to (J), the belt body 11, the core wire 13, and the reinforcing fabric 14 are made of the same material.

[0073] (Toothed pulleys) Toothed pulleys (A1) to (F1) and toothed pulleys (A2) to (F2) were manufactured, each with a different shape of the pulley groove 21. Toothed pulleys with the same alphabetical designation, such as toothed pulley (A1) and toothed pulley (A2), are paired toothed pulleys. The toothed pulley with the number 1 after the alphabet is the driving pulley, and the toothed pulley with the number 2 after the alphabet is the driven pulley.

[0074] The toothed pulleys (A1) to (F1) and the toothed pulleys (A2) to (F2) were manufactured by a manufacturing process including gear cutting using a dedicated hob cutter manufactured according to the shape of the pulley groove of each pulley. Here, the groove shapes of the paired drive pulley and driven pulley are identical.

[0075] Toothed pulleys (A1) to (F1) have a tooth tip circle diameter shown in Table 1 and have 40 teeth (40T). Toothed pulleys (A2) to (F2) have a tooth tip circle diameter shown in Table 1 and have 110 teeth (40T). The width of each toothed pulley is the belt width + 4 mm. Each toothed pulley is made of stainless steel.

[0076] The dimensions of the pulley grooves of the toothed pulley (A1) and the toothed pulley (A2) are as shown in FIG. 10, with Hp being 0.760 mm and R １ is 1.325 mm, A is 0.172 mm, and B ｇ In FIG. 10, "Hp", "R １ " and "B ｇ " is "H" listed in Table 13 of JIS B 1857-2 (2015). ｇ "," "R １ " and "B ｇ ", and "A" corresponds to "a-Y" derived from Table 13 of JIS B 1857-2 (2015). １ ". Furthermore, toothed pulleys (B1) to (F1) are pulleys in which the PLD of toothed pulley (A1) has been changed, and toothed pulleys (B2) to (F2) are pulleys in which the PLD of toothed pulley (A2) has been changed.

[0077] (Examples 1 to 8, Comparative Examples 1 to 7) A transmission system 40 was constructed using the toothed belt 48, drive pulley 42, and driven pulley 44 in the combinations shown in Table 1. FIGS. 11A and 11B show the pulley layout of the transmission system 40. FIG. 11A is a top view of the transmission system 40, and FIG. 11B is a front view of the transmission system 40. The transmission system 40 was constructed by winding the toothed belt 48 around two pulleys having a drive pulley 42 and a driven pulley 44. In this transmission system 40, the SW (set weight) was fixed so that the belt tension was 100 N. The speed ratio of this transmission system 40 was 2.75.

[0078] In the transmission system 40, the toothed belt 48 was run, and the noise level during running was measured. The noise level measurement was performed using a precision sound level meter (manufactured by Rion Co., Ltd., product name NL-52) equipped with a sound collection microphone 45. At this time, the sound collection microphone 45 was installed 25 mm laterally (in the belt width direction) from the side surface of the toothed belt 48, and 20 mm away from the center of the driving pulley toward the center of the driven pulley. In this evaluation, the average noise level of the primary meshing sound measured while changing the rotation speed from 500 rpm to 2000 rpm was taken as the measured value.

[0079] Based on the measured values, the noise level was evaluated on a four-point scale from AA to C. AA: 64 dB or less A: Over 64 dB, 70 dB or less B: Over 70 dB, 75 dB or less C: Over 75 dB

[0080] The results are shown in Table 1 and Figure 12. Figure 12 shows the results of Examples 1 to 6 and Comparative Examples 1 to 4. In Figure 12, Examples / Comparative Examples showing results of AA are plotted with "◎", Examples / Comparative Examples showing results of A are plotted with "◯", Examples / Comparative Examples showing results of B are plotted with "△", and Examples / Comparative Examples showing results of C are plotted with "X".

[0081]

[0082] As shown in Table 1 and FIG. 12, it has become clear that noise in the transmission system can be suppressed by satisfying the above formula (1).

[0083] 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.

[0084] REFERENCE SIGNS LIST 1, 40 Transmission system 10, 48 Toothed belt 11 Belt body (crosslinked rubber composition) 11a Base 11b Toothed portion 12 Belt tooth 13 Core wire 14 Reinforcing fabric 15 Tooth root 20 Toothed pulley 21 Pulley groove 22, 42 Driving pulley 24, 44 Driven pulley 30 Mold 31 Concave portion 32 Convex portion 34 Rubber sleeve 35 Belt slab 111 Uncrosslinked rubber composition sheet 135 Uncrosslinked slab

Claims

1. A transmission system comprising: a toothed belt having a plurality of belt teeth on its inner circumference; a first toothed pulley having a plurality of pulley grooves on its outer circumference that mesh with the belt teeth; and a second toothed pulley having a larger diameter than the first toothed pulley and also having a plurality of pulley grooves on its outer circumference that mesh with the belt teeth, wherein the toothed belt is wound around the first toothed pulley and the second toothed pulley, wherein the nominal pitch of the belt teeth is 2 mm, the belt teeth are helical teeth with a tooth trace angle of 5.0 degrees or more and 9.0 degrees or less, and the speed ratio is 2.0 or more and less than 5.0, and wherein the toothed belt and the first toothed pulley, and the toothed belt and the second toothed pulley each satisfy the following formula (1). 1.5X - 0.31 < Y < X - 0.03 (1) In formula (1), X is the PLD of the toothed belt, and Y is a value calculated by the following formula (2): Y = ((nominal pitch of toothed belt × number of pulley teeth T / π) - tip diameter) / 2 (2) 2. The transmission system according to claim 1, wherein the PLD of the toothed belt is equal to or greater than 0.280 mm and equal to or less than 0.360 mm.

3. A transmission system according to claim 1 or 2, wherein the PLD of the first toothed pulley and the second toothed pulley is 0.180 mm or more and 0.280 mm or less.

4. A transmission system according to any one of claims 1 to 3, wherein the toothed belt has a belt width of 20 mm or more.

5. A transmission system according to any one of claims 1 to 4, wherein the toothed belt has an overlap ratio ε of the belt teeth of 0.80 or more.

6. A transmission system according to any one of claims 1 to 5, wherein the toothed belt has belt teeth with an arc tooth profile.

7. A transmission system according to any one of claims 1 to 6, wherein the toothed belt has a belt tooth width of 0.8 mm or more and 1.8 mm or less.

8. A transmission system according to any one of claims 1 to 7, wherein the toothed belt comprises: a belt body having a band-like base portion having a rectangular cross section perpendicular to the longitudinal direction of the belt; and a plurality of teeth portion integral with the base portion and spaced at equal intervals at predetermined intervals on the inner periphery of the base portion; a core wire embedded in the belt body; and a reinforcing cloth provided so as to cover the inner periphery of the teeth portion; wherein the toothed belt has a belt thickness of 1.1 mm or more; the thickness of the base portion is 0.30 mm or more and 1.6 mm or less; and the tooth height of the belt teeth is 0.50 mm or more and 1.0 mm or less.

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