Toothed belt

Abstract

In a toothed belt in which a core wire is embedded, a distance L from a tooth bottom line to a center line center varies along a belt length direction, and the absolute value X of the difference between a distance LA from the tooth bottom line to the center line center at a tooth bottom and a distance LB from the tooth bottom line to the center line center at a belt tooth is 0.35 mm or less.

Description

Toothed belt

[0001] The present application claims priority to Japanese Patent Application No. 2023-172854, filed on October 4, 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, for example, as a power transmission means for motorcycles (see, for example, Patent Document 1).

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

[0004] The toothed belts used for rear-wheel drive of electric motorcycles are toothed belts used for high-load transmission. Toothed belts used for high-load transmission are prone to a decrease in tension. When the belt tension decreases, it is likely to cause increased noise, tooth skipping, and damage to the belt teeth.

[0005] An object of the present disclosure is to provide a toothed belt having good tension maintenance properties.

[0006] A toothed belt according to one aspect of the present invention is a toothed belt having an embedded core wire, wherein the distance L from the tooth root line to the center of the core wire varies along the length direction of the belt, and the absolute value X of the difference between the distance LA from the tooth root line to the center of the core wire at the tooth root and the distance LB from the tooth root line to the center of the core wire at the belt tooth is 0.35 mm or less.

[0007] According to the present disclosure, a toothed belt with good tension maintenance properties can be provided.

[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 a cross-sectional view taken along line B-B in FIG. 1. FIG. 4 is an end view taken along line C-C in FIG. 1. FIG. 5 is a diagram illustrating a first manufacturing method of a toothed belt. FIG. 6 is a diagram illustrating a first manufacturing method of a toothed belt. FIG. 7 is a diagram illustrating a first manufacturing method of a toothed belt. FIG. 8 is a diagram illustrating a first manufacturing method of a toothed belt. FIG. 9 is a diagram illustrating a first manufacturing method of a toothed belt. FIG. 10 is a diagram illustrating a second manufacturing method of a toothed belt. FIG. 11 is a diagram illustrating a second manufacturing method of a toothed belt. FIG. 12 is a diagram illustrating a second manufacturing method of a toothed belt. FIG. 13 is a diagram illustrating the dimensions of the toothed belts manufactured in the examples and comparative examples. FIG. 14 is a diagram illustrating the method of tensile testing conducted in the examples and comparative examples. FIG. 15 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 having an embedded core wire, wherein a distance L from a tooth root line to a center of the core wire varies along the belt length direction, and an absolute value X of a difference between a distance LA from the tooth root line to the center of the core wire at a tooth root and a distance LB from the tooth root line to the center of the core wire at a belt tooth is 0.35 mm or less.

[0010] The toothed belt described above can ensure good tension maintenance. The inventors investigated the causes of belt tension degradation and found that one of the causes is that the distance L from the tooth root line to the core center of the belt is not constant along the belt length but varies (fluctuations) depending on the location. Based on this finding, the inventors further investigated methods for maintaining tension over long periods of time. As a result, the toothed belt described above was discovered. The toothed belt described above has an absolute value X of the difference between the distance LA from the tooth root line to the core center at the tooth root and the distance LB from the tooth root line to the core center at the belt tooth, which is 0.35 mm or less. Therefore, tension does not decrease easily even when used in high-load power transmission applications. On the other hand, the distance L from the tooth root line to the core center of the toothed belt described above is preferably constant, and therefore the absolute value X is preferably small. Although there is no problem with the performance of the toothed belt even if the absolute value X is 0 mm, a toothed belt with X = 0 mm is not easy to manufacture. Therefore, in the toothed belt, the distance L from the tooth root line to the center of the core wire varies along the belt length direction. In other words, in the toothed belt in which the absolute value X is not 0 mm, the distance L varies along the belt length direction.

[0011] (2) In the toothed belt of (1) above, the absolute value X is preferably 0.03 mm or more and 0.35 mm or less. (3) In the toothed belt of (1) or (2) above, the ratio of the cord diameter in the belt thickness direction to the cord diameter in the belt width direction is the cord flatness ratio, and the absolute value Y of the difference between the cord flatness ratio C at the tooth bottom and the cord flatness ratio D at the belt tooth is preferably 0.30 or less. (4) In any of the toothed belts of (1) to (3) above, the cord is embedded in a rubber belt body, and the JIS A hardness of the tooth portion of the belt body is preferably 84A or more and 98A or less.

[0012] (5) In the toothed belt of (4), the belt body is preferably made of a crosslinked product of an uncrosslinked rubber composition containing a rubber component and a rubber compounding agent. (6) In the toothed belt of (5), the rubber component is preferably hydrogenated nitrile rubber (HNBR) or ethylene-propylene-diene rubber (EPDM).

[0013] (7) In the toothed belt of any one of (1) to (6), the core wire is preferably a carbon core wire or a steel core wire. (8) In the toothed belt of any one of (1) to (7), the core wire preferably has a core wire diameter in the belt width direction and a core wire diameter in the belt thickness direction that are each independently 0.80 mm or more and 2.30 mm or less.

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. (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 a cross-sectional view taken along line B-B in Fig. 1. Fig. 4 is an end view taken along line CC 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.

[0015] In Fig. 1, the direction indicated by the double-headed arrow X is the belt width direction of the toothed belt 1. The direction indicated by the double-headed arrow Y is the belt length direction of the toothed belt 1. The belt length direction is also the belt circumferential direction of the toothed belt 1. The direction indicated by the double-headed arrow Z is the belt 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.

[0016] The belt length of the toothed belt 1 (belt length at the belt pitch line) is, for example, 225 mm or more and 6000 mm or less. The belt width Wb of the toothed belt 1 is, for example, 5 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.

[0017] 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 portion sandwiched between adjacent belt teeth 12 is a tooth bottom 24. The tooth 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, a circular arc tooth profile.

[0018] The toothed belt 1 comprises a belt body 2, a core wire 3, and a reinforcing cloth 4. The belt body 2 has a band shape. The belt body 2 comprises a base 21 and a plurality of tooth portions 22. The base 21 extends in the circumferential direction of the belt. The core wire 3 is embedded in the base 21. The plurality of tooth portions 22 are provided on the inner circumferential side of the base 21. The plurality of tooth portions 22 are integral with the base 21. The plurality of tooth portions 22 are arranged at equal intervals in the circumferential direction of the belt. The surface of the tooth portions 22 is covered with the reinforcing cloth 4.

[0019] The belt main body 2 is made of, for example, a cross-linked product of an uncross-linked rubber composition containing a rubber component and a rubber compounding agent (hereinafter also referred to as a cross-linked rubber composition). The uncross-linked rubber composition is cross-linked, for example, by heating and pressurizing, to become the cross-linked product. In the belt main body 2, the base 21 and the toothed portion 22 are each made of a cross-linked rubber composition. In the toothed belt 1 shown in FIG. 1, the base 21 and the toothed portion 22 are made of different cross-linked rubber compositions. The cross-linked rubber composition making up the base 21 and the cross-linked rubber composition making up the toothed portion 22 may have the same composition.

[0020] The core wire 3 is embedded in the base portion 21. The core wire 3 has a pitch in the belt width direction and is provided to form a spiral.

[0021] The distance L from the root line BL to the center of the core wire 3 (hereinafter referred to as the core wire center) of the core wire 3 varies along the belt length direction. In other words, the distance L from the root line BL to the core wire center is not constant along the belt length direction.

[0022] A preferred range for the distance L from the tooth root line BL to the center of the core wire is, for example, 0.55 to 1.15 mm when the nominal pitch of the belt teeth 12 is 8 mm, and 1.15 to 1.75 mm when the nominal pitch of the belt teeth 12 is 14 mm. Therefore, it is preferable that the distance L of the toothed belt 1 varies within this range. In this specification, the nominal pitch has the same meaning as the "nominal pitch" used in JIS B 1857-1 and the like. In an embodiment of the present invention, the range of the tooth pitch Pb of the toothed belt 1 is 8±0.03 mm when the nominal pitch is 8 mm, and 14±0.03 mm when the nominal pitch is 14 mm.

[0023] It is preferable that the distance L of the cord 3 varies periodically along the belt length direction. Here, "the distance L varies periodically" means that when the distance L at each position along the belt length direction of the cord 3 is plotted on a graph with an arbitrary point on the cord 3 as the origin, the distance from the origin as the horizontal axis, and the distance L as the vertical axis, minimum values ​​appear at approximately regular intervals along the horizontal axis on the obtained graph. Here, "approximately regular intervals" means that all intervals are between 0.95 and 1.05 times the median value.

[0024] On the other hand, in the toothed belt 1, the amount of variation in the distance L from the tooth root line BL to the core center along the belt length is kept small. Specifically, the absolute value X of the difference between the distance LA from the tooth root line BL to the core center at the tooth root 24 (see FIG. 4) and the distance LB from the tooth root line BL to the core center at the belt tooth 12 (see FIG. 4) is 0.35 mm or less. In this way, by setting the absolute value X to 0.35 mm or less, good tension maintenance can be ensured. Furthermore, a smaller absolute value X is preferable from the perspective of tension maintenance, but a smaller absolute value X makes manufacturing more difficult and may result in reduced productivity.

[0025] The distances LA and LB used to calculate the above X are obtained at adjacent portions. That is, when the distance LA is obtained at one tooth bottom, the distance LB is obtained at a belt tooth adjacent to this tooth bottom, and the difference is calculated based on the obtained LA and LB. Furthermore, in the present invention, the difference between the distances LA and LB is obtained at three locations along the belt length direction, and the average of the absolute values ​​of the differences is calculated to obtain the evaluation value X. Here, the distances LA and LB are obtained at three locations spaced at approximately equal intervals. Note that in the present invention, the three locations spaced at approximately equal intervals on the toothed belt 1 refer to three locations selected so that the difference in the number of belt teeth included between the selected locations is one or less.

[0026] Distances LA and LB are measured using an image of a cross section (see FIGS. 2 and 3) of the toothed belt 1 perpendicular to the belt length direction. Specifically, the images are obtained using the following method. First, the toothed belt 1 is cut perpendicular to the belt length direction so as to pass through the center of the belt length direction of the tooth bottom 24, and a cross-sectional image such as that shown in FIG. 2 is obtained. Next, the distance LA from the tooth bottom line BL to the center of the core wire is measured based on this cross-sectional image. At this time, the cross section of the core wire closest to the center in the belt width direction is selected as the cross section of the core wire to be measured.

[0027] Next, the toothed belt 1 is cut perpendicular to the belt length direction so as to pass through the center of the belt length of the belt tooth 12, and a cross-sectional image such as that shown in FIG. 3 is obtained. As the belt tooth 12 to be cut, a belt tooth adjacent to the cut tooth root 24 is selected to obtain the distance LA. Next, based on this cross-sectional image, the distance LB from the tooth root line BL to the core wire center is measured. As the core wire cross section to be measured, a core wire cross section that is closest in the length direction to the core wire cross section selected to obtain the distance LA is selected. To measure the distance LB, first, a virtual tooth root line VBL is set as shown in FIG. 3. The virtual tooth root line VBL is a virtual line located a distance LC from the back surface 11 of the toothed belt 1. This distance LC is obtained based on the cross-sectional image obtained to measure the distance LA (see FIG. 2). Then, the distance LB from the set virtual tooth root line VBL to the core wire center is measured.

[0028] The above X is preferably 0.03 mm or more and 0.35 mm or less. It is not easy to manufacture a toothed belt in which the above X is controlled to less than 0.03 mm. When the nominal pitch of the toothed belt 1 is 8 mm, the above X is more preferably 0.03 mm or more and 0.15 mm or less. Furthermore, when the nominal pitch of the toothed belt 1 is 14 mm, the above X is more preferably 0.03 mm or more and 0.25 mm or less.

[0029] Furthermore, in the toothed belt 1, the absolute value Y of the difference between the cord flatness ratio C at the tooth bottom and the cord flatness ratio D at the belt tooth is preferably 0.30 or less. The cord flatness ratio is the average value of the ratio of the cord diameter φT in the belt thickness direction to the cord diameter φW in the belt width direction. Setting Y to 0.30 or less is suitable for ensuring good tension maintenance. On the other hand, a toothed belt with Y exceeding 0.30 may have poor tension maintenance due to a large difference in cross-sectional shape between the cord at the tooth bottom and the cord in the belt tooth. Y may also be 0.

[0030] The cord flatness ratio C is the average value of the ratio (φTA / φWA) of the cord diameter φTA in the belt thickness direction to the cord diameter φWA in the belt width direction at the tooth bottom 24. The cord flatness ratio C is determined by acquiring an image of a cross section (see Figure 2) of the toothed belt 1 perpendicular to the belt length direction, passing through the center of the tooth bottom 24 in the belt length direction, and using this image to measure the cord diameter φWA in the belt width direction and the cord diameter φTA in the belt thickness direction. The image used to acquire the cord flatness ratio C is the same as the image used to acquire the distance LA described above. The cord measured to acquire the cord flatness ratio C is the same as the cord used to acquire the distance LA described above. The images used to acquire the cord flatness ratio C are acquired at three locations spaced approximately equally apart along the belt length direction.

[0031] The cord flatness ratio D is the average value of the ratio (φTB / φWB) of the cord diameter φTB in the belt thickness direction to the cord diameter φWB in the belt width direction at a belt tooth 12. The cord flatness ratio D is determined by acquiring an image of a cross section (see FIG. 3) of the toothed belt 1 perpendicular to the belt length direction, passing through the center of the belt length direction of the belt tooth 12, and using this image to obtain the cord diameter φWB in the belt width direction and the cord diameter φTB in the belt thickness direction. The image used to obtain the cord flatness ratio D is the same as the image used to obtain the distance LB described above. Therefore, the image used to obtain the cord flatness ratio D is acquired at a belt tooth adjacent to the tooth bottom from which the image used to obtain the cord flatness ratio C was acquired. The cord measured to obtain the cord flatness ratio D is the same as the cord used to obtain the distance LB described above. The images used to obtain the cord flatness ratio D are acquired at three locations spaced approximately equally apart along the belt length direction.

[0032] The outer diameters of the core wire 3, φWA in the belt width direction at the tooth bottom 24 and φTA in the belt thickness direction at the tooth bottom 24, are preferably 0.80 mm or more and 2.30 mm or less. More preferably, the outer diameters φWA and φTA are 0.90 mm or more and 1.60 mm or less. The outer diameter φTA in the belt thickness direction and the outer diameter φWA in the belt width direction may be the same or different.

[0033] It is preferable that the core wire diameter φWA in the belt width direction at the tooth bottom 24 and the core wire diameter φWB in the belt width direction at the belt tooth 12, and the core wire diameter φTA in the belt thickness direction at the tooth bottom 24 and the core wire diameter φTB in the belt thickness direction at the belt tooth 12 are as close to identical as possible.

[0034] The configuration of each of the belt body 2, the cords 3, and the reinforcing fabric 4 will be described below. (Belt Body) As described above, the belt body 2 is made of a cross-linked product (cross-linked rubber composition) of an uncross-linked rubber composition containing, for example, 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. Of these, HNBR and EPDM are preferred.

[0035] Examples of the rubber compounding agents include short fibers, vulcanization accelerators, antioxidants, reinforcing materials, plasticizers, co-crosslinking agents, crosslinking agents, and processing aids. 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. These short fibers may be used alone or in combination of two or more.

[0036] The short fibers have a length of, for example, 0.5 mm or more and a diameter of, for example, 5 μm or more and 50 μm or less, and 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.

[0037] Examples of the vulcanization accelerator aid include metal oxides, metal carbonates, fatty acids, and derivatives thereof. Examples of the metal oxide include zinc oxide (zinc oxide) and magnesium oxide. These vulcanization accelerator aids may be used alone or in combination of two or more. The content of the vulcanization accelerator aid is, for example, 3 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the rubber component.

[0038] Examples of the antioxidant include benzimidazole-based antioxidants, aromatic secondary amine-based antioxidants, and amine-ketone-based antioxidants. These antioxidants may be used alone or in combination of two or more. The content of the antioxidant is, for example, 1.5 parts by mass or more and 5.0 parts by mass or less per 100 parts by mass of the rubber component.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] The belt body 2 is made of a cross-linked rubber composition obtained by cross-linking such an uncross-linked rubber composition. For example, the JIS A hardness of the toothed portion 22 of the belt body 2 is 84A or more and 98A or less. In this case, the belt body 2 is less likely to deform and less likely to break due to cracks in the toothed portion. In particular, when the belt width is 8 mm or more, it is preferable that the JIS A hardness of the toothed portion 22 be within the above range. The JIS A hardness of the toothed portion 22 is measured by pressing a rubber hardness tester perpendicularly against the side surface of the toothed portion 22 of the belt body 2 (the end surface of the toothed portion 22 in the belt width direction). As the rubber hardness tester, a Type A durometer specified in JIS-K6253-3 (2012) is used. The ambient temperature during measurement is 23°C.

[0046] (Core wire) 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, they have excellent tension retention. Furthermore, 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.

[0047] As described above, the core wires 3 are arranged to have a pitch in the belt width direction and to form a spiral. 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 have a pitch in the belt width direction and to form a spiral.

[0048] 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 15 / 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, 0.0 mm or more and 0.45 mm or less.

[0049] 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.

[0050] (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.

[0051] The reinforcing fabric 4 may be subjected to an adhesive treatment to enhance adhesion to the belt 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 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.

[0052] (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.

[0053] (Manufacturing Method 1 of Toothed Belt) Figures 5 to 9 are diagrams for explaining manufacturing method 1 of toothed belt 1. Figures 5 to 9 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 5 to 9 is also called a two-stage manufacturing method because the tooth portion and the base portion are molded separately. This two-stage manufacturing method makes it easy to manufacture toothed belts with small X and Y values.

[0054] 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. 5 ). The recesses 51 are provided at regular intervals in the circumferential direction. The protrusions 52 are provided between adjacent recesses 51.

[0055] (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.

[0056] 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.

[0057] (2) As shown in Figure 5, 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 is molded on the mold 5, in which the reinforcing cloth 4 and the uncrosslinked rubber sheet 23A are laminated. The uncrosslinked rubber sheet 23A wrapped around in this step is an uncrosslinked rubber sheet for forming teeth. When multiple uncrosslinked rubber sheets 23A are wrapped around, the respective uncrosslinked rubber sheets may have the same composition or different compositions.

[0058] Thereafter, as shown in FIG. 6, 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 can and sealed. Next, high-temperature, high-pressure steam is filled into the vulcanizer can. 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. 7.

[0059] (3) Next, as shown in Fig. 8, the core wire 3 is spirally wound 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 Fig. 8) are wound. In this way, a second uncrosslinked molded body 13B in which the core wire 3 and the uncrosslinked rubber sheet 23B are laminated is molded on the mold 5 (on the tooth portion 122).

[0060] At this time, it is preferable to wind the core wire 3 while applying a tension of 49 N or more and 490 N or less. The uncrosslinked rubber sheet 23B wound in this step is an uncrosslinked rubber sheet that forms the base.

[0061] (4) As shown in Figure 9, 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 23 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.

[0062] (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 6 is demolded. The demolded belt slab 14A is then sliced ​​into rings. Through these steps, the toothed belt 1 is obtained.

[0063] (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 10 to 12 are diagrams for explaining manufacturing method 2 for the toothed belt 1. Figures 10 to 12 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 10 to 12 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.

[0064] (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.

[0065] (2) As shown in Figure 10, first, a cylindrically formed 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 sheet 23 is further wound around the reinforcing cloth 4. Multiple uncrosslinked rubber sheets 23 (two in Figure 10) are wound around the mold 5. This results in an uncrosslinked molded body 13C in which the reinforcing cloth 4, the cord 3, and the uncrosslinked rubber sheet 23 are layered around the outer periphery of the mold 5. When multiple uncrosslinked rubber sheets 23 are wound around the mold 5, the uncrosslinked rubber sheets may have the same composition or different compositions.

[0066] (3) As shown in FIG. 11 , a rubber sleeve 6 is placed over the uncrosslinked molded body 13C on the mold 5. The uncrosslinked molded body 13C 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 sheet 23 flows within the cavity formed between the mold 5 and the rubber sleeve 6. The uncrosslinked rubber sheet 23 passes between the cords 3. The uncrosslinked rubber 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 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. 12 .

[0067] (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.

[0068] The embodiments of the present invention will be described in more detail below with reference to examples. In these examples, a number of toothed belts were manufactured and their performance was evaluated.

[0069] (Belt Raw Materials) (1) Uncrosslinked Rubber Composition Uncrosslinked rubber compositions A to C were prepared having the compounding compositions (parts by mass) shown in Table 1. Each of the uncrosslinked rubber compositions A to C was prepared by masticating the rubber component, and then adding and kneading the rubber compounding agents.

[0070]

[0071] In Table 1, HNBR (1) is ZP2010 (manufactured by Zeon Corporation), and HNBR (2) is ZSC2195CX (manufactured by Zeon Corporation). In addition, in Table 1, the aramid staple fibers are para-aramid staple fibers having a fiber length of 1 mm, and the organic peroxide is Peroximon F40 (manufactured by NOF Corporation).

[0072] (2) Core Wire A carbon core wire was used. The carbon core wire had an outer diameter φT in the belt thickness direction and an outer diameter φW in the belt width direction, both of which were 1.10 mm.

[0073] (3) Reinforcing Fabric The following adhesive treatment was performed on a woven fabric whose warp and weft were made of polyamide fiber. The adhesive treatment consisted of 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. The thickness of the reinforcing fabric before molding was 1.2 mm, 1.4 mm, or 1.7 mm. The thickness of each reinforcing fabric was adjusted to the thickness of the woven fabric before the adhesive treatment.

[0074] (Dimensions of Toothed Belt) A type of toothed belt called S8M was manufactured. Two types of toothed belts with different belt widths were manufactured. The dimensions of this toothed belt, indicated by the symbols in FIG. 13, 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 (Pitch Line Differential) = 0.686 mm. The toothed belt had a belt length of 800 mm and a belt width of 8 mm or 10 mm.

[0075] Examples 1 to 3, 6 Toothed belts were manufactured by the above-described manufacturing method 1. The combinations of the uncrosslinked rubber composition and the thickness of the reinforcing fabric are shown in Table 2. The tension when winding the core wire was 157 N or 98 N. The vulcanization conditions for the tooth portion (steam temperature and holding time in step (2) of manufacturing method 1) were 130°C for 15 minutes or 120°C for 10 minutes. The overall vulcanization conditions (steam temperature and holding time in step (4) of manufacturing method 1) were 170°C for 30 minutes.

[0076] [Examples 4 and 5, Comparative Examples 1 and 2] Toothed belts were produced by the above-mentioned Production Method 2. The combinations of the uncrosslinked rubber compositions and the thicknesses of the reinforcing fabrics are shown in Table 2. The tension when winding the cord was 59 N or 157 N. The overall vulcanization conditions (steam temperature and holding time in step (3) of Production Method 2) were 170°C and 30 minutes.

[0077] (Evaluation) The following evaluations were carried out on the toothed belts produced in the Examples and Comparative Examples. The results are shown in Table 2. Of the evaluations below, evaluations (1) to (4) were carried out using toothed belts with a belt width of 10 mm, and evaluation (5) was carried out using toothed belts with a belt width of 8 mm.

[0078] (1) Absolute Value X of the Difference Between Distance LA and Distance LB As described above, an image of a cross section perpendicular to the belt length direction of the toothed belt 1 was acquired, and the absolute value X of the difference between distances LA and LB was calculated using the acquired image. The average value of three locations was calculated. The results are shown in Table 2.

[0079] (2) Absolute Value Y of the Difference Between the Cord Flattening Ratio C and the Cord Flattening Ratio D As described above, an image of a cross section perpendicular to the belt length direction of the toothed belt 1 was acquired, and the absolute value Y of the difference between the cord flattening ratio C and the cord flattening ratio D was calculated using the acquired image. The average value of three locations was calculated. The results are shown in Table 2.

[0080] (3) JIS A Hardness of Belt Body The JIS A hardness of the crosslinked rubber composition constituting the belt body was measured by the following method. The results are shown in Table 2. The JIS A hardness was measured by pressing a rubber hardness tester (Type A durometer defined in JIS-K6253-3 (2012)) against the side surface of the tooth portion of the belt body (the end surface of the tooth portion in the belt width direction) perpendicularly to the side surface. The ambient temperature during measurement was 23°C. The measurement was performed on three belt teeth, and the average value was used as the result.

[0081] (4) Belt Elastic Modulus The belt elastic modulus (N / mm) evaluated here is the value obtained by dividing the load at 0.2% elongation by the belt width (10 mm) in a tensile test performed by the following method. Fig. 14 is a diagram illustrating the tensile test method.

[0082] <Tensile Test> This tensile test is performed using a belt tensile tester 80. The belt tensile tester 80 is equipped with a pair of flat pulleys 81 and 82, each having a pulley diameter of 95.4 mm. The flat pulley 82 is fixed, and the flat pulley 81 is configured to be movable relative to the flat pulley 82. The belt tensile tester 80 is equipped with a load cell (not shown) to measure the load applied to the flat pulley 81.

[0083] In this test, first, as shown in FIG. 14 , a toothed belt is wrapped around a pair of flat pulleys 81 and 82 of a belt tensile tester 80 so that the back surfaces of the belt are in contact. Next, the movable flat pulley 81 is moved away from the fixed flat pulley 82 at a constant speed. At this time, the moving speed of the flat pulley 81 is set to 50 mm / min. The position of the flat pulley 81 when the load applied to the flat pulley 81 reaches 1000 N is set to the initial position. Next, the flat pulley 81 is further moved away from the flat pulley 82 at a moving speed of 50 mm / min, and the displacement of the flat pulley 81 and the load applied to the flat pulley 81 are recorded. This test is performed at an ambient temperature of 25±5°C.

[0084] Next, based on the recorded measurements, the load on the belt when the belt elongation is 0.2% is determined. Here, 0.2% belt elongation refers to the time when twice the displacement of the flat pulley 81 from its initial position (belt elongation) is 0.2% of the belt length (800 mm) of the toothed belt in an unloaded state. In other words, this refers to the time when the displacement of the flat pulley 81 is 0.8 mm. The load on the belt is half the value of the load applied to the flat pulley 81.

[0085] Next, the belt elastic modulus (N / mm) is calculated by dividing the load on the belt when the belt elongation amount is 0.2% by the belt width (10 mm). The measurement is carried out three times while changing the contact position between the toothed belt and the flat pulley, and the average value is taken as the result value.

[0086] (5) Running Test (Evaluation of Tension Maintenance) A transmission system 90 was constructed by wrapping a toothed belt around two pulleys including a drive pulley 91 (number of teeth: 22) and a driven pulley 92 (number of teeth: 33). FIG. 15 shows the pulley layout of the transmission system 90. Using this transmission system, a running test was conducted at a drive-side rotation speed of 4212 rpm, a driven-side rotation speed of 2808 rpm, a driven-side load of 34.3 N m, an axial load (SW) of 608 N, and an ambient temperature of 60°C. The initial tension was set by the axial load measured by a load cell. After setting the target tension, the pulley was manually rotated three times to return to the target tension. In this running test, the tension was measured based on the initial tension: T0. After 100 hours of running, the belt was stopped, and the warm belt tension: T was measured using an ultrasonic tension meter. After the measurement, the tension retention rate is calculated using the following formula: Tension retention rate (%) = T / T0 x 100 The results are shown in Table 2.

[0087]

[0088] As shown in Table 2, the toothed belt according to the embodiment of the present invention has good tension maintenance properties.

[0089] 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.

[0090] REFERENCE SIGNS LIST 1 toothed belt 2 belt body 3 core wire 4 reinforcing fabric 5 mold 6 rubber sleeve 11 back portion 12 belt teeth 13A, 13B uncrosslinked molded body 14A belt slab 21 base portion 22, 122 tooth portion 23 uncrosslinked rubber sheet 24 tooth root 51 recess 52 protrusion 90 transmission system 91 driving pulley 92 driven pulley

Claims

1. A toothed belt having an embedded core wire, wherein the distance L from the tooth root line to the center of the core wire varies along the length of the belt, and the absolute value X of the difference between the distance LA from the tooth root line to the center of the core wire at the tooth root and the distance LB from the tooth root line to the center of the core wire at a belt tooth is 0.35 mm or less.

2. The toothed belt according to claim 1, wherein the absolute value X is equal to or greater than 0.03 mm and equal to or less than 0.35 mm.

3. A toothed belt as claimed in claim 1 or 2, wherein the ratio of the core wire diameter in the belt thickness direction to the core wire diameter in the belt width direction is the core wire flatness ratio, and the absolute value Y of the difference between the core wire flatness ratio C at the tooth bottom and the core wire flatness ratio D at the belt tooth is 0.30 or less.

4. A toothed belt as set forth in any one of claims 1 to 3, comprising a rubber belt body with the core wires embedded therein, the JIS A hardness of the teeth of the belt body being 84A or more and 98A or less.

5. The toothed belt according to claim 4, wherein the belt body is made of a crosslinked product of an uncrosslinked rubber composition containing a rubber component and a rubber compounding agent.

6. The toothed belt according to claim 5, wherein the rubber component is hydrogenated nitrile rubber (HNBR) or ethylene-propylene-diene rubber (EPDM).

7. A toothed belt according to any one of claims 1 to 6, wherein the core wire is a carbon core wire or a steel core wire.

8. A toothed belt according to any one of claims 1 to 7, wherein the core wire has a core wire diameter in the belt width direction and a core wire diameter in the belt thickness direction that are each independently 0.80 mm or more and 2.30 mm or less.

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