Toothed belt

Abstract

Provided is a toothed belt in which the tensile modulus of elasticity of a rubber composition constituting belt teeth satisfies the following relationships (1) and (2). (1) Tensile elastic modulus X in belt width direction < tensile elastic modulus Y in belt length direction; (2) Tensile elastic modulus X in belt width direction < tensile elastic modulus Z in belt thickness direction

Description

Toothed belt

[0001] The present application claims priority to Japanese Patent Application No. 2023-116201, filed on July 14, 2023, and incorporates by reference all of the contents of said Japanese application.

[0002] Toothed belts are suitable for applications requiring synchronous rotation and are used in a variety of fields, such as as a power transmission means for motorcycles (see, for example, Patent Document 1 listed below).

[0003] Japanese Patent Application Publication No. 9-290467

[0004] The toothed belt used for rear-wheel drive of electric motorcycles is a toothed belt used for high-load transmission. Toothed belts used for high-load transmission are prone to damage such as tooth chipping. In order to avoid tooth chipping and extend the durability life, it is possible to consider increasing the tooth shear strength of the toothed belt. In order to increase the tooth shear strength, it is possible to consider increasing the elastic modulus of the belt teeth. Furthermore, the elastic modulus of the rubber composition can be increased by increasing the amount of reinforcing material contained in the rubber composition that constitutes the belt teeth. On the other hand, if the content of reinforcing material is increased, the viscosity of the uncrosslinked rubber composition increases, and it may be impossible to mold the tooth portion of the toothed belt.

[0005] An object of the present disclosure is to provide a toothed belt that is less likely to have chipped belt teeth and has good durability.

[0006] A toothed belt according to one embodiment of the present invention is a toothed belt in which the tensile modulus of the rubber composition constituting the belt teeth satisfies the following relationships (A) and (B): (A) Tensile modulus of elasticity in the width direction of the belt X<Tensile modulus of elasticity in the length direction of the belt Y (B) Tensile modulus of elasticity in the width direction of the belt X<Tensile modulus of elasticity in the thickness direction of the belt Z

[0007] The toothed belt according to one aspect of the present invention is a toothed belt that is less likely to have chipped belt teeth and has good durability.

[0008] FIG. 1 is a perspective view showing an example of a toothed belt. FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1. FIG. 3 is an end view taken along line B-B in FIG. 1. FIG. 4 is a diagram illustrating a method for measuring the tensile modulus X in the belt width direction. FIG. 5 is a diagram illustrating a method for measuring the tensile modulus Y in the belt length direction. FIG. 6 is a diagram illustrating a method for measuring the tensile modulus Z in the belt thickness direction. FIG. 7 is a diagram illustrating a manufacturing method 1 of a toothed belt. FIG. 8 is a diagram illustrating a manufacturing method 1 of a toothed belt. FIG. 9 is a diagram illustrating a manufacturing method 1 of a toothed belt. FIG. 10 is a diagram illustrating a manufacturing method 1 of a toothed belt. FIG. 11 is a diagram illustrating a manufacturing method 1 of a toothed belt. FIG. 12 is a diagram illustrating a manufacturing method 2 of a toothed belt. FIG. 13 is a diagram illustrating a manufacturing method 2 of a toothed belt. FIG. 14 is a diagram illustrating a manufacturing method 2 of a toothed belt. FIG. 15 is a diagram illustrating the dimensions of the toothed belts manufactured in the examples and comparative examples. FIG. 16 is a diagram illustrating the pulley layout of the transmission system used in the running tests in the examples and comparative examples.

[0009] The outline of the embodiments of the present invention will be described below. (1) A toothed belt in which the tensile modulus of the rubber composition constituting the belt teeth satisfies the following relationships (A) and (B): (A) Tensile modulus of elasticity in the belt width direction X<Tensile modulus of elasticity in the belt length direction Y (B) Tensile modulus of elasticity in the belt width direction X<Tensile modulus of elasticity in the belt thickness direction Z

[0010] As described above, increasing the elastic modulus of the belt teeth can increase the tooth shear strength of a toothed belt. The inventors of the present invention conducted detailed studies on this point and found that, while the tensile elastic modulus in the belt width direction does not significantly affect the tooth shear strength, increasing the tensile elastic modulus in the belt length direction and the tensile elastic modulus in the belt thickness direction increases the tooth shear strength. The toothed belt described in (1) above is a toothed belt developed based on this finding, and because the tensile elastic modulus of the rubber composition constituting the belt teeth satisfies the relationships (A) and (B) above, the tooth shear strength is high and tooth chipping is unlikely to occur.

[0011] (2) In the toothed belt of (1) above, the rubber composition preferably contains short fibers, which makes it easier to mold belt teeth that satisfy the above relationships (A) and (B) without impairing the moldability of the belt teeth.

[0012] (3) In the toothed belt of (1) or (2), it is preferable that the ratios of the tensile modulus Y and the tensile modulus Z to the tensile modulus X are both 1.1 or more. In this case, the belt teeth are suitable for forming belt teeth that have high tooth shear strength and are easy to mold.

[0013] (4) In the toothed belt of any one of (1) to (3) above, the tensile modulus X is preferably 3.5 MPa or more. In this case, chipping of the belt teeth is even less likely to occur.

[0014] (5) In the toothed belt according to any one of (1) to (4) above, the pitch of the belt teeth is preferably 8 mm or more and 14 mm or less.

[0015] (6) It is preferable that any one of the toothed belts (1) to (5) above further satisfy the following relationship (C): (C) Tensile modulus of elasticity Y in the belt length direction < tensile modulus of elasticity Z in the belt thickness direction When the above relationship (C) is satisfied, the tooth shear strength is stronger and tooth chipping is less likely to occur.

[0016] (7) In the toothed belt of any one of (2) to (6) above, it is preferable that the rubber composition constituting the belt teeth is a crosslinked uncrosslinked rubber composition containing a rubber component and short fibers, and that the content of the short fibers is 1 part by mass or more and 7 parts by mass or less per 100 parts by mass of the rubber component.

[0017] (8) In the toothed belt of (7) above, the rubber component is preferably any one of hydrogenated nitrile rubber, chloroprene rubber, and ethylene-propylene-diene rubber.

[0018] (9) In the toothed belt according to any one of (1) to (8) above, it is preferable that the rubber composition constituting the belt teeth has a Duro-A hardness of 85 or more and 98 or less.

[0019] (10) It is preferable that the toothed belt according to any one of (1) to (9) above includes a reinforcing fabric that forms the inner peripheral surface of the belt.

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0021] (Toothed Belt) Fig. 1 is a perspective view showing a portion of a toothed belt 1 according to an embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. Fig. 3 is an end view taken along line B-B in Fig. 1. Fig. 1 shows a portion of the toothed belt 1. The toothed belt 1 is an endless meshing power transmission belt. The toothed belt 1 is a single-sided toothed belt.

[0022] 1 to 3, the direction indicated by the double-headed arrow X is the width direction of the toothed belt 1. The direction indicated by the double-headed arrow Y is the length direction of the toothed belt 1. The length direction is also the circumferential direction of the toothed belt 1. The direction indicated by the double-headed arrow Z is the thickness direction of the toothed belt 1. The upper side of each page is the outer circumferential side of the toothed belt 1, and the lower side is the inner circumferential side.

[0023] The belt length of the toothed belt 1 (belt length at the belt pitch line BL) is, for example, 225 mm or more and 6000 mm or less. The belt width Wb of the toothed belt 1 is, for example, 10 mm or more and 120 mm or less. The belt thickness Tb of the toothed belt 1 is, for example, 3.5 mm or more and 9.0 mm or less. The belt thickness Tb of the toothed belt 1 is the thickness of the thickest part of the toothed belt 1. The dimensions of the toothed belt according to the embodiment of the present invention are not limited to these ranges.

[0024] The toothed belt 1 has a back portion 11 and a plurality of belt teeth 12. The back portion 11 extends in the circumferential direction of the belt. The back portion 11 is in the form of an endless belt. In a cross section of the toothed belt 1 perpendicular to the circumferential direction of the belt, the cross-sectional shape of the back portion 11 is rectangular. The plurality of belt teeth 12 are provided on the inner circumferential side of the back portion 11. The plurality of belt teeth 12 are arranged at equal intervals in the circumferential direction of the belt. Each belt tooth 12 extends in the width direction of the belt. The pitch Pb of the belt teeth 12 is, for example, 8 mm or more and 14 mm or less. The tooth profile of the belt teeth 12 is, for example, an arc tooth profile.

[0025] (Configuration of Toothed Belt) The toothed belt 1 includes a belt body 2, a core wire 3, and a reinforcing cloth 4. The belt body 2, the core wire 3, and the reinforcing cloth 4 will be described below.

[0026] (Belt main body) The belt main body 2 has a belt shape. The belt main body 2 includes a base 21 and a plurality of toothed portions 22. The base 21 extends in the circumferential direction of the belt. A core wire 3 is embedded in the base 21. The plurality of toothed portions 22 are provided on the inner circumferential side of the base 21. The plurality of toothed portions 22 are integral with the base 21. The plurality of toothed portions 22 are arranged at equal intervals in the circumferential direction of the belt. The surface of the toothed portions 22 is covered with a reinforcing cloth 4.

[0027] The belt body 2 is made of, for example, a rubber composition obtained by crosslinking an uncrosslinked rubber composition containing a rubber component and a rubber compounding agent through heating and pressure (hereinafter also referred to as a crosslinked rubber composition). In the belt body 2, the base 21 and the toothed portion 22 are each made of a crosslinked rubber composition. In the toothed belt 1 shown in Fig. 1, the base 21 and the toothed portion 22 are made of different crosslinked rubber compositions. The crosslinked rubber composition making up the base 21 and the crosslinked rubber composition making up the toothed portion 22 may have the same composition.

[0028] In the toothed belt 1 according to this embodiment, the rubber composition constituting the toothed portion 22 of the belt main body 2 has a tensile modulus of elasticity of the rubber composition that satisfies the following relationships (A) and (B): (A) Tensile modulus of elasticity X in the belt width direction < Tensile modulus of elasticity Y in the belt length direction (B) Tensile modulus of elasticity X in the belt width direction < Tensile modulus of elasticity Z in the belt thickness direction In the toothed belt 1, the tensile modulus of elasticity Y in the belt length direction and the tensile modulus of elasticity Z in the belt thickness direction are greater than the tensile modulus of elasticity X in the belt width direction, making it less likely for belt teeth to chip. In toothed belts, the tensile modulus of elasticity X does not have much effect on belt tooth chipping, whereas the tensile moduli Y and Z have a significant effect on belt tooth chipping. Therefore, in the toothed belt 1, the tensile moduli Y and Z, which have a significant effect on belt tooth chipping, are increased to suppress the occurrence of belt tooth chipping. Furthermore, since the tensile modulus of elasticity of the toothed belt 1 is not large in all directions (width direction, length direction, and thickness direction), it is not necessary to include a large amount of reinforcing material, and the moldability of the belt teeth is less likely to be impaired.

[0029] In the toothed belt 1, the ratio of the tensile modulus Y to the tensile modulus X is preferably 1.1 or more. Also, the ratio of the tensile modulus Z to the tensile modulus X is preferably 1.1 or more. In these cases, the tooth shear strength of the toothed belt 1 is likely to be improved. The ratio of the tensile modulus Y to the tensile modulus X is at most about 8, and is usually preferably 3 or less. Also, the ratio of the tensile modulus Z to the tensile modulus X is at most about 8, and is usually preferably 3 or less.

[0030] The tensile modulus X is preferably 3.5 MPa or more, which further reduces the risk of chipping of the belt teeth and improves the durability of the toothed belt 1. The upper limit of each of the tensile modulus Y and the tensile modulus Z is preferably 30 MPa.

[0031] It is preferable that the toothed belt 1 further satisfies the following relationship (C): (C) Tensile modulus of elasticity Y in the belt length direction < Tensile modulus of elasticity Z in the belt thickness direction By satisfying the above relationship (C), the tooth shear strength of the toothed belt 1 tends to be stronger. Therefore, the durability of the toothed belt 1 tends to be improved.

[0032] The tensile moduli X, Y, and Z are measured by the following method. (Method for Measuring Tensile Modulus X) FIG. 4 is a diagram illustrating a method for measuring the tensile modulus X. (1) First, a piece corresponding to one belt tooth 112 is cut out from the toothed belt 101. (2) Next, a cutting blade is inserted along the belt width direction to cut out a slice 161 having a width of approximately 1 mm and including the tooth tip. (3) Next, a strip having a length of approximately 2 mm in the Z direction is cut out from near the center of the part of the slice 161 corresponding to the tooth, and this is used as a test piece 162. The dimensions of the test piece 162 are approximately 1 mm in the Y direction and approximately 2 mm in the Z direction. The dimension in the X direction depends on the width of the toothed belt. Both ends of this test piece 162 in the longitudinal direction (X direction) are gripped, and a tensile test is performed to measure the tensile modulus X.

[0033] <Tensile Test> The tensile test is performed at room temperature using a universal testing machine (Instron). One end of the test piece 162 is held by the upper chuck of the Instron, and the other end of the test piece 162 is held by the lower chuck, so that the longitudinal direction of the test piece 162 is aligned vertically. The test piece 162 is set in the universal testing machine. At this time, the distance between the chucks is 1 mm. The tensile test is performed at a tensile speed of 10 mm / min to obtain an S-S curve (stress-strain curve), and the tensile modulus X is calculated based on the slope at 0 to 20% elongation.

[0034] (Method for Measuring Tensile Modulus Y) FIG. 5 is a diagram illustrating a method for measuring the tensile modulus Y. (1) First, a piece corresponding to one belt tooth 112 is cut out from the toothed belt 101. (2) Next, a cutting blade is inserted along the belt length direction to cut out a slice 171 having a width of approximately 2 mm from near the center in the width direction. (3) Next, a strip having a length of approximately 1 mm in the Z direction is cut out from a portion of the slice 171 near the base of the portion corresponding to the tooth, and this is used as a test piece 172. The dimensions of the test piece 172 are approximately 2 mm in the X direction and approximately 1 mm in the Z direction. The dimension in the Y direction depends on the tooth width of the belt tooth. The test piece 172 is gripped at both ends in the longitudinal direction (Y direction), and a tensile test is performed to calculate the tensile modulus Y. The tensile test method is the same as that used to measure the tensile modulus X. In measuring the tensile modulus Y, the test piece 172 is set in the Instron so that the crosslinked rubber composition constituting the teeth 122 is positioned between the upper and lower chucks. In Fig. 5, 104 denotes a reinforcing fabric.

[0035] (Method for Measuring Tensile Modulus Z) FIG. 6 is a diagram illustrating a method for measuring the tensile modulus Y. (1) A slice 171 of one belt tooth 112 is cut out in the same manner as in steps (1) and (2) of the method for measuring the tensile modulus Y. (2) Next, a strip approximately 1 mm long in the Y direction is cut out from near the center of the portion of the slice 171 corresponding to the tooth portion, and this is used as the test piece 173. The dimensions of the test piece 173 are approximately 2 mm in the X direction and approximately 1 mm in the Y direction. The dimension in the Z direction depends on the thickness of the toothed belt. Both ends of the test piece 173 in the longitudinal direction (Z direction) are gripped, and a tensile test is performed to calculate the tensile modulus Z. The tensile test method is the same as when measuring the tensile modulus X. Note that, in measuring the tensile modulus Z, the tester 173 is set in the universal testing machine so that the crosslinked rubber composition constituting the tooth portion 122 is positioned between the upper and lower chucks. In FIG. 6, 103 denotes a cord and 104 denotes a reinforcing cloth.

[0036] The Duro-A hardness of the crosslinked rubber composition constituting the belt teeth is preferably 85 or more and 98 or less. In this case, chipping of the belt teeth is less likely to occur, and the durability of the toothed belt is improved.

[0037] As described above, the belt body 2 is made of a cross-linked rubber composition obtained by cross-linking an uncross-linked rubber composition containing a rubber component and a rubber compounding agent. Examples of the rubber component include hydrogenated nitrile rubber (HNBR), chloroprene rubber (CR), ethylene-α-olefin elastomers such as ethylene-propylene-diene rubber (EPDM), chlorosulfonated polyethylene rubber, styrene-butadiene rubber, and epichlorohydrin rubber. Among these, HNBR, CR, and EPDM are preferred.

[0038] The uncrosslinked rubber composition preferably contains short fibers as a rubber compounding agent. The short fibers contained in the crosslinked rubber composition are preferably oriented in the Y and Z directions, not in the X direction. In other words, the length directions of the short fibers are preferably oriented in the Y and Z directions, not in the X direction. In these cases, the tensile modulus of the crosslinked rubber composition constituting the tooth portion 22 can easily satisfy the above-mentioned relationships (A) and (B). Furthermore, the tensile modulus of the crosslinked rubber composition constituting the tooth portion can easily be increased without reducing the moldability of the belt teeth.

[0039] Furthermore, by orienting the short fibers in the Z direction rather than the Y direction, the above relationship (C) is more easily satisfied. For example, when manufacturing a toothed belt by the two-stage manufacturing method described below, if the amount of short fibers added to the rubber composition constituting the tooth portion is increased, the short fibers are more easily oriented in the Z direction rather than the Y direction.

[0040] Examples of the short fibers include aramid short fibers, nylon short fibers, and polyester short fibers. Para-aramid short fibers are preferred as the aramid short fibers. Only one type of these short fibers may be used, or two or more types may be used in combination. The length of the short fibers is, for example, 0.5 mm or more and 3.5 mm or less. The diameter of the short fibers is, for example, 5 μm or more and 50 μm or less. The content of the short fibers is preferably 1 part by mass or more and 7 parts by mass or less per 100 parts by mass of the rubber component. If the content of the short fibers exceeds 7 parts by mass, cracks are likely to occur in the tooth portion. The content of the short fibers is more preferably 1 part by mass or more and 3 parts by mass or less per 100 parts by mass of the rubber component.

[0041] Examples of rubber compounding agents other than the short fibers include, for example, vulcanization accelerators, antioxidants, reinforcing materials, plasticizers, co-crosslinking agents, crosslinking agents, and processing aids. Examples of the vulcanization accelerators include metal oxides, metal carbonates, fatty acids, and derivatives thereof. Examples of the metal oxides include zinc oxide (zinc oxide) and magnesium oxide. These vulcanization accelerators may be used alone or in combination of two or more. The content of the vulcanization accelerator is, for example, 3 to 20 parts by mass per 100 parts by mass of the rubber component.

[0042] Examples of the reinforcing material include carbon black and silica. The reinforcing material may be a combination of carbon black and silica. 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.

[0043] When carbon black is used, the content thereof is, for example, 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the rubber component.When silica is used, the content thereof 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.

[0044] 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. The content of the plasticizer is, for example, 5 to 20 parts by mass per 100 parts by mass of the rubber component.

[0045] Examples of the co-crosslinking agent include trimethylolpropane trimethacrylate, m-phenylenedimaleimide, zinc dimethacrylate, and triallyl isocyanurate. 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 10 parts by mass or less per 100 parts by mass of the rubber component.

[0046] 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 compounding amount of the crosslinking agents is preferably, for example, 0.1 parts by mass or more and 3 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.

[0047] Examples of the processing aid include stearic acid, polyethylene wax, and metal salts of fatty acids. These processing aids may be used alone or in combination of two or more. The content of the processing aid is, for example, 0.5 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the rubber component.

[0048] (Core Wire) As described above, the core wire 3 is embedded in the base 21. Examples of the core wire 3 include glass core wire, aramid core wire, carbon core wire, and steel core wire. These core wires are preferably made of twisted yarn. Carbon core wire and steel core wire are preferred as the core wire 3. Carbon and steel are materials with high elastic moduli. Therefore, toothed belts equipped with carbon core wire or steel core wire are less likely to change in length when a load is applied, and the change in tooth pitch is small. Therefore, toothed belts equipped with carbon core wire or steel core wire are more likely to maintain a good meshing state with toothed pulleys.

[0049] The outer diameters of the core wires 3, φT in the belt thickness direction and φW in the belt width direction, are preferably 0.90 mm or more and 1.70 mm or less. More preferably, φT and φW are 1.00 mm or more and 1.60 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.

[0050] The core wires 3 are arranged to form a spiral with a pitch in the belt width direction. For example, a core wire pair composed of an S-twisted core wire 3 and a Z-twisted core wire 3 may be arranged to form a spiral with a pitch in the belt width direction.

[0051] The core wires 3 are arranged so as to extend in parallel with a gap in the belt width direction. A plurality of core wires 3 are arranged side by side in the belt width direction in appearance. In this case, the number of core wires 3 per 10 mm of belt width is preferably 5 / 10 mm or more and 20 / 10 mm or less. A toothed belt 1 having the core wires 3 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 3 is more preferably 6 / 10 mm or more and 10 / 10 mm or less. Furthermore, the dimension of the gap between adjacent core wires 3 is, for example, 0.1 mm or more and 0.7 mm or less.

[0052] The core wires 3 may be subjected to an adhesive treatment to increase the adhesive strength with the belt body 2. Examples of the adhesive treatment include an RFL treatment in which the core wires are immersed in an RFL aqueous solution and then heated, and a rubber cement treatment in which the core wires are immersed in rubber cement and then dried. Only one of these adhesive treatments may be performed, or both may be performed. The core wires 3 may be subjected to a surface treatment before the adhesive treatment. Examples of the surface treatment include a treatment in which the core wires are immersed in an epoxy solution or an isocyanate solution and then heated. 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.

[0053] (Reinforcing Fabric) The reinforcing fabric 4 covers the surface of the toothed portion 22. The reinforcing fabric 4 forms the inner circumferential surface of the toothed belt 1. The inner circumferential surface of the toothed belt 1 includes the reinforcing fabric 4. The reinforcing fabric 4 is a woven fabric. Examples of fibers that form the reinforcing fabric 4 include polyamide fibers (nylon fibers), polyester fibers, aramid fibers, polyparaphenylenebenzobisoxazole (PBO) fibers, cotton, etc. A woven fabric of polyamide fibers is preferred as the reinforcing fabric 4. The thickness of the reinforcing fabric 4 is, for example, 0.5 mm or more and 2.0 mm or less. The reinforcing fabric 4 preferably has elasticity, such as a woven fabric in which the weft yarns have been subjected to a wooly process or the like.

[0054] The reinforcing fabric 4 may be subjected to an adhesive treatment to enhance adhesive strength with the belt main body 2. Examples of the adhesive treatment include an RFL treatment in which the reinforcing fabric 4 is immersed in an RFL aqueous solution and then heated, a soaking treatment in which the reinforcing fabric 4 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 main body side and then dried. Only one of these treatments may be performed, or two or more may be performed. Prior to the adhesive treatment, the reinforcing fabric 4 may be subjected to a surface treatment in which the reinforcing fabric 4 is immersed in an epoxy solution or an isocyanate solution and then heated. These adhesive treatments and surface treatments are performed before winding the reinforcing fabric 4 around a mold in the manufacturing method of a toothed belt described below.

[0055] (Method of Manufacturing Toothed Belt) Next, a description will be given of a method of manufacturing the toothed belt 1. The toothed belt 1 can be manufactured by, for example, a toothed belt manufacturing method 1 or a toothed belt manufacturing method 2, which will be described later.

[0056] (Manufacturing Method 1 of Toothed Belt) Figures 7 to 11 are diagrams for explaining manufacturing method 1 of toothed belt 1. Figures 7 to 11 show only a belt molding die 5 and a part of the belt (including the belt material). The manufacturing method of a toothed belt described with reference to Figures 7 to 11 is also called a two-stage manufacturing method because the tooth portion and the base portion are molded separately.

[0057] In manufacturing the toothed belt 1, a belt molding die 5 is used. The die 5 is cylindrical. The outer periphery of this die 5 is provided with recesses 51 extending in the axial direction and protrusions 52 extending in the axial direction. The recesses 51 have a cross-sectional shape corresponding to the belt teeth 12 and are grooves extending in the axial direction (a direction perpendicular to the paper surface of FIG. 7 ). The recesses 51 are provided at regular intervals in the circumferential direction. The protrusions 52 are provided between adjacent recesses 51.

[0058] (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 sheet 23. In this case, calendar molding, for example, can be used as a molding method for the uncrosslinked rubber sheet 23.

[0059] The core wires 3 and the reinforcing cloth 4 are prepared, and if necessary, are subjected to adhesive treatment and surface treatment, and then the reinforcing cloth 4 is formed into a cylindrical shape.

[0060] (2) As shown in Fig. 7, first, a cylindrically formed reinforcing cloth 4 is placed on the outer peripheral surface of a mold 5. Next, an uncrosslinked rubber sheet 23A is wrapped around the reinforcing cloth 4. At this time, only one uncrosslinked rubber sheet 23A may be wrapped around, or multiple uncrosslinked rubber sheets 23A may be wrapped around. In this way, a first uncrosslinked molded body 13A in which the reinforcing cloth 4 and the uncrosslinked rubber sheet 23A are laminated on the mold 5 is molded. The uncrosslinked rubber sheet 23A wrapped around in this step is an uncrosslinked rubber sheet for forming teeth.

[0061] In this case, it is preferable to laminate the uncrosslinked rubber sheets 23A so that the grain direction corresponds to the belt length direction. In this case, it is easy to mold a crosslinked rubber composition in which the short fibers are oriented in the Y direction and the Z direction, but not in the X direction. When multiple uncrosslinked rubber sheets 23A are wound, the uncrosslinked rubber sheets may have the same composition or different compositions.

[0062] Thereafter, as shown in FIG. 8, a rubber sleeve 6 is placed over the first uncrosslinked molded body 13A on the mold 5, and this is then placed in a vulcanizer and sealed. Next, high-temperature, high-pressure steam is filled into the vulcanizer. This state is then maintained for a predetermined time. As a result, the first uncrosslinked molded body 13A is pressed against the mold 5 and heated. As a result, the uncrosslinked rubber sheet 23A flows into each of the multiple recesses 51 in the mold 5 while pressing against the reinforcing fabric 4, and is crosslinked. At this time, the uncrosslinked rubber sheet 23A is heated so as to be in a semi-crosslinked state. As a result, multiple teeth 122 in a semi-crosslinked state are molded, as shown in FIG. 9.

[0063] (3) Next, as shown in Figure 10, the cord 3 is wound spirally around the outer periphery of the molded tooth portion 122. Furthermore, an uncrosslinked rubber sheet 23B is wound thereon. One or more uncrosslinked rubber sheets 23B (one sheet in Figure 10) are wound. This results in a second uncrosslinked molded body 13B in which the cord 3 and the uncrosslinked rubber sheet 23B are laminated on the mold 5 (on the tooth portion 122). At this time, it is preferable to laminate the uncrosslinked rubber sheet 23B so that the grain direction corresponds to the belt length direction. The uncrosslinked rubber sheet wound in this step is the uncrosslinked rubber sheet that forms the base.

[0064] The composition of the uncrosslinked rubber sheet 23B may be the same as or different from the composition of the uncrosslinked rubber sheet 23A. When a plurality of uncrosslinked rubber sheets 23B are wound, the respective uncrosslinked rubber sheets may have the same composition or different compositions.

[0065] (4) As shown in Figure 11, a rubber sleeve 6 is placed over the second uncrosslinked molded body 13B on the mold 5, and the resultant is placed in a vulcanizer and sealed. Next, high-temperature, high-pressure steam is filled into the vulcanizer. This state is then maintained for a predetermined time. As a result, the second uncrosslinked molded body 13B is pressed against the mold 5 and heated. At this time, the uncrosslinked rubber sheet 23B passes between the cords 3 and is crosslinked while being pressed against the plurality of semi-crosslinked tooth portions 122 molded in the plurality of recesses 51. As a result, a cylindrical belt slab 14A is molded having integrated and completely crosslinked tooth portions 22 and base portion 21.

[0066] (5) The pressure inside the vulcanizer is reduced to release the seal. Then, the belt slab 14A molded between the mold 5 and the rubber sleeve 34 is demolded. The demolded belt slab 14A is then sliced ​​into rings. Through these steps, the toothed belt 1 is obtained.

[0067] (Manufacturing Method 2 for Toothed Belt) The manufacturing method for the toothed belt 1 is not limited to the two-stage manufacturing method described above, and the toothed belt can also be manufactured by the following method. Figures 12 to 14 are diagrams for explaining manufacturing method 1 for the toothed belt 1. Figures 12 to 14 only show a belt-forming mold 5 and a portion of the belt (including the belt material). The manufacturing method for the toothed belt described with reference to Figures 12 to 14 is also called a one-stage manufacturing method because the tooth portion and the base portion are cross-linked simultaneously. Manufacturing method 2 uses the same belt-forming mold 5 as manufacturing method 1.

[0068] (1) Materials are prepared in the same manner as in Manufacturing Method 1. That is, an uncrosslinked rubber sheet 23, adhesively treated cords 3, and adhesively treated reinforcing cloth 4 formed into a cylindrical shape are prepared.

[0069] (2) As shown in Figure 12, first, a cylindrically molded reinforcing cloth 4 is placed on the outer periphery of a mold 5. A cord 3 is spirally wound around the reinforcing cloth 4. After the cord 3 is wound, an uncrosslinked rubber composition sheet 23 is further wound around the reinforcing cloth 4. Multiple uncrosslinked rubber composition sheets 23 (two sheets in Figure 12) are wound around the mold 5. This results in an uncrosslinked molded body 13C in which the reinforcing cloth 4, cord 3, and uncrosslinked rubber composition sheet 23 are laminated around the outer periphery of the mold 5. In laminating the materials, the uncrosslinked rubber composition sheets 23 are preferably laminated so that the grain direction corresponds to the circumferential direction of the belt. When multiple uncrosslinked rubber sheets 23 are wound around the mold 5, the uncrosslinked rubber sheets may have the same composition or different compositions.

[0070] (3) As shown in FIG. 13 , a rubber sleeve 6 is placed over the uncrosslinked molded body 13C on the mold 5. The uncrosslinked molded body 13 covered with the rubber sleeve 6 is placed inside a vulcanization can (not shown) together with the mold 5, and the vulcanization can is sealed. High-temperature, high-pressure steam is filled into the vulcanization can. This state is maintained for a predetermined time. As a result, the uncrosslinked molded body 13C is pressed against the mold 5 and heated. The uncrosslinked rubber composition sheet 23 flows within the cavity formed between the mold 5 and the rubber sleeve 6. The uncrosslinked rubber composition sheet 23 passes between the cords 3. The uncrosslinked rubber composition sheet 23 flows into each of the multiple recesses 51 formed in the mold 5 while pressing against the reinforcing fabric 4. As the uncrosslinked rubber composition sheet 23 flows within the cavity in this manner, it becomes integrated with the cords 3 and the reinforcing fabric 4 and is crosslinked. As a result, a cylindrical belt slab 14B is formed, as shown in FIG. 14 .

[0071] (4) The pressure inside the vulcanizer is reduced to release the seal. The belt slab 14B formed between the mold 5 and the rubber sleeve 6 is demolded. The demolded belt slab 14B is sliced ​​into rings. The toothed belt 1 can also be obtained by going through these steps.

[0072] 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 plurality of toothed belts were manufactured and their performance was evaluated.

[0073] (Belt Raw Materials) (1) Uncrosslinked Rubber Compositions Uncrosslinked rubber compositions A1 to A4 and B1 to B2 were prepared having the compounding compositions shown in Table 1. The uncrosslinked rubber compositions were prepared by masticating the rubber component, and then adding and kneading the rubber compounding agents.

[0074]

[0075] In Table 1, HNBR (1) is ZP2010 (manufactured by Zeon Corporation), HNBR (2) is ZSC2195CX (manufactured by Zeon Corporation), and CR (1) is Skyprene 505 (manufactured by Tosoh Corporation). In Table 1, the aramid staple fibers are para-aramid staple fibers having a fiber length of 1 mm and a fiber diameter of 12 μm, and the organic peroxide is Peroximon F40 (manufactured by NOF Corporation).

[0076] (2) Core Wire A carbon core wire was used. The outer diameter φT of the carbon core wire in the belt thickness direction and the outer diameter φW of the carbon core wire in the belt thickness direction were both 1.10 mm.

[0077] (3) Reinforcing Fabric A woven fabric having warp and weft threads made of polyamide fiber was subjected to the following adhesive treatments: a soaking treatment in which the woven fabric was immersed in low-viscosity rubber cement and then dried, and a coating treatment in which high-viscosity rubber cement was applied to the surface of the woven fabric that would become the belt body and then dried.

[0078] (Dimensions of Toothed Belt) A type of toothed belt called S8M was manufactured. The dimensions of this toothed belt, indicated by the symbols in FIG. 15, are as follows: Pb = 8.00 mm, Tb = 5.00 mm, h1 = 2.05 mm, h2 = 2.95 mm, R = 5.20 mm, W = 5.20 mm, a = 0.00 mm, r1 = 0.80 mm, r2 = 0.80 mm, PLD = 0.686 mm. This toothed belt had a belt length of 840 mm and a belt width of 8 mm.

[0079] Examples 1 to 4, Comparative Example 1 Using the combinations of belt raw materials shown in Table 2, toothed belts were manufactured by the above-described two-stage manufacturing method.

[0080] Comparative Example 2 Using the combination of belt raw materials shown in Table 2, a toothed belt was manufactured by the one-stage manufacturing method described above.

[0081]

[0082] (Evaluation) The toothed belts produced in the Examples and Comparative Examples were evaluated as follows. The results are shown in Table 3. (1) Hardness of Belt Teeth Duro-A hardness was measured as the hardness of the crosslinked rubber composition constituting the belt teeth using the following method. A commercially available Type A durometer was used. Here, a rubber hardness tester was pressed perpendicularly against the side surface of the toothed portion of the belt body (the end surface of the toothed portion in the belt width direction) to measure the hardness.

[0083] (2) Tensile Modulus of Belt Tooth The crosslinked rubber composition constituting the belt tooth was measured for the tensile modulus in the X direction, the tensile modulus in the Y direction, and the tensile modulus in the Z direction. The method for measuring the tensile modulus in each direction was as described above.

[0084] (3) Tooth Shear Strength Measurement was performed in accordance with the tooth shear strength test described in 6.5 of "Toothed Belt Transmission - Physical Property Test Methods" in JIS B 1865 (2021). This evaluation was performed using an S-tooth shear tooth tip. The results were expressed as a relative value, with the measured value of Example 4 set to 100.

[0085] (4) Running Test (Durability Evaluation) A transmission system 90 was constructed by wrapping a toothed belt around two pulleys including a drive pulley 91 (number of teeth: 22, pitch diameter: 56.02 mm) and a driven pulley 92 (number of teeth: 33, pitch diameter: 84.03 mm). FIG. 16 shows the pulley layout of the transmission system 90. Using this transmission system, a running test was conducted under the following conditions: drive-side rotation speed: 4212 rpm, driven-side rotation speed: 2808 rpm, driven-side load: 34.3 N m, span tension: 304 N, set weight: 608 N, and ambient temperature: 60°C, and the time until chipping occurred in the belt teeth was measured. The results are expressed as a relative value, with the measured value for Example 4 set to 100.

[0086]

[0087] As shown in Table 4, it was revealed that the belt teeth according to the embodiment of the present invention are less susceptible to tooth chipping and have excellent durability.

[0088] 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.

[0089] REFERENCE SIGNS LIST 1, 101 Toothed belt 11 Back portion 12, 112 Belt teeth 13A, 13B, 13C Uncrosslinked molded body 14A, 14B Belt slab 2 Belt body 21 Base portion 22, 122 Tooth portion 23, 23A, 23B Uncrosslinked rubber sheet 3, 103 Core wire 4, 104 Reinforcing fabric 5 Mold 51 Concave portion 52 Convex portion 6 Rubber sleeve 90 Transmission system 91 Driving pulley 92 Driven pulley 161, 171 Slice 162, 172, 173 Test piece

Claims

1. A toothed belt in which the tensile modulus of the rubber composition constituting the belt teeth satisfies the following relationships (A) and (B): (A) Tensile modulus of elasticity in the belt width direction X < Tensile modulus of elasticity in the belt length direction Y (B) Tensile modulus of elasticity in the belt width direction X < Tensile modulus of elasticity in the belt thickness direction Z 2. The toothed belt according to claim 1, wherein the rubber composition contains short fibers.

3. The toothed belt according to claim 1 or 2, wherein the ratios of the tensile modulus Y and the tensile modulus Z to the tensile modulus X are each 1.1 or more.

4. The toothed belt according to any one of claims 1 to 3, wherein the tensile elastic modulus X is 3.5 MPa or more.

5. A toothed belt according to any one of claims 1 to 4, wherein the belt tooth pitch is 8 mm or more and 14 mm or less.

6. The toothed belt according to any one of claims 1 to 5, further satisfying the following relationship (C): (C) Tensile elastic modulus Y in the belt length direction < tensile elastic modulus Z in the belt thickness direction 7. A toothed belt according to any one of claims 2 to 6, wherein the rubber composition constituting the belt teeth is a crosslinked uncrosslinked rubber composition containing a rubber component and short fibers, and the content of the short fibers is 1 part by mass or more and 7 parts by mass or less per 100 parts by mass of the rubber component.

8. The toothed belt according to claim 7, wherein the rubber component is any one of hydrogenated nitrile rubber, chloroprene rubber, and ethylene-propylene-diene rubber.

9. The toothed belt according to any one of claims 1 to 8, wherein the rubber composition constituting the belt teeth has a Duro-A hardness of 85 or more and 98 or less.

10. The toothed belt according to any one of claims 1 to 9, further comprising a reinforcing fabric constituting the inner peripheral surface of the belt.

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