Toothed belt

Abstract

To provide a toothed belt having excellent tension maintainability.SOLUTION: In the toothed belt in which the core wire is embedded, a ratio of a core wire diameter in a belt thickness direction to a core wire diameter in a belt width direction is a core wire flattening ratio, and an absolute value X1 of a difference between a distance LA from a dedendum line to a center of the core wire in a dedendum and a core wire diameter X2 in the dedendum in the belt thickness direction and an absolute value Y of a difference between a core wire flattening ratio C in the dedendum and a core wire flattening ratio D in the belt teeth satisfies a relational expression of 2X + Y ≤ 0.096.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a toothed belt. This application claims priority from Japanese Application No. 2023-172917, filed October 4, 2023, and incorporates by reference all of the contents of said Japanese application. [Background technology]

[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). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-290467 Summary of the Invention [Problem to be solved by the invention]

[0004] The toothed belt used for rear-wheel drive of electric motorcycles is a toothed belt used for high-load transmission applications, and toothed belts used for high-load transmission applications are prone to tension reduction. When the tension of the belt decreases, noise increases, teeth skipping occurs, and the belt teeth are more likely to break. [Means for solving the problem]

[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 in which a core wire is embedded, 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, The ratio X (X = X1 / X2) of the absolute value X1 of the difference between the distance LA from the tooth bottom line to the center of the core wire at the tooth bottom and the distance LB from the tooth bottom line to the center of the core wire at the belt tooth to the core wire diameter X2 in the belt thickness direction at the tooth bottom, The absolute value Y of the difference between the center wire flatness ratio C at the tooth bottom and the center wire flatness ratio D at the belt tooth is 2X+Y≦0.96 A toothed belt that satisfies the following relationship. [Effects of the Invention]

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

[0008] [Figure 1] FIG. 1 is a perspective view showing an example of a toothed belt. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line BB in FIG. [Figure 4] FIG. 4 is an end view taken along line CC in FIG. [Figure 5] FIG. 5 is a diagram illustrating a method 1 for manufacturing a toothed belt. [Figure 6] FIG. 6 is a diagram illustrating a method 1 for manufacturing a toothed belt. [Figure 7] FIG. 7 is a diagram illustrating a method 1 for manufacturing a toothed belt. [Figure 8] FIG. 8 is a diagram illustrating a method 1 for manufacturing a toothed belt. [Figure 9] FIG. 9 is a diagram illustrating a method 1 for manufacturing a toothed belt. [Figure 10] FIG. 10 is a diagram illustrating a second method for manufacturing a toothed belt. [Figure 11] FIG. 11 is a diagram illustrating a second method for manufacturing a toothed belt. [Figure 12] FIG. 12 is a diagram illustrating a second method for manufacturing a toothed belt. [Figure 13]FIG. 13 is a diagram for explaining the dimensions of the toothed belts manufactured in the examples and comparative examples. [Figure 14] FIG. 14 is a diagram illustrating the method of the tensile test carried out in the examples and comparative examples. [Figure 15] FIG. 15 is a diagram showing the layout of pulleys in the transmission system used in the running tests in the example and comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0009] The outline of the embodiments of the present invention will be listed and explained. (1) A toothed belt with an embedded core wire, 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, The ratio X (X = X1 / X2) of the absolute value X1 of the difference between the distance LA from the tooth bottom line to the center of the core wire at the tooth bottom and the distance LB from the tooth bottom line to the center of the core wire at the belt tooth to the core wire diameter X2 in the belt thickness direction at the tooth bottom, The absolute value Y of the difference between the center wire flatness ratio C at the tooth bottom and the center wire flatness ratio D at the belt tooth is 2X+Y≦0.96 A toothed belt that satisfies the following relationship.

[0010] The toothed belt can ensure good tension maintenance. The inventors investigated the cause of the decrease in belt tension and found that the cause is that the distance L from the belt tooth root line to the cord center varies depending on the location, and that the cord flatness ratio (cord diameter in the belt thickness direction / cord diameter in the belt width direction) varies 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 above-mentioned toothed belt was discovered. In the toothed belt, the X and Y satisfy a predetermined relationship, and therefore the tension is unlikely to decrease.

[0011] (2) In the toothed belt of (1) above, the above relational expression is: 2X+Y≦0.90 is preferred.

[0012] (3) The toothed belt of (1) or (2) above has a rubber belt body in which the core wire is embedded, The JIS A hardness of the tooth portion of the belt body is preferably 84A or more and 98A or less.

[0013] (4) In the toothed belt of (3) above, the belt body is preferably made of a crosslinked product of an uncrosslinked rubber composition containing a rubber component and a rubber compounding agent. (5) In the toothed belt of (4) above, the rubber component is preferably hydrogenated nitrile rubber (HNBR) or ethylene-propylene-diene rubber (EPDM).

[0014] (6) In any one of the toothed belts (1) to (5) above, the core wire is preferably a carbon core wire or a steel core wire. (7) In any one of the toothed belts (1) to (6) above, it is preferable that the core wire diameter in the belt width direction and the core wire diameter in the belt thickness direction are each independently 0.80 mm or more and 2.30 mm or less.

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (toothed belt) FIG. 1 is a perspective view showing a part of a toothed belt 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line AA in FIG. FIG. 3 is a cross-sectional view taken along line BB in FIG. FIG. 4 is an end view taken along line CC in FIG. Fig. 1 shows a part of a toothed belt 1. The toothed belt 1 is an endless meshing power transmission belt. The toothed belt 1 is a single-sided toothed belt.

[0016] In Figure 1, the direction indicated by the double arrow X is the belt width direction of the toothed belt 1. The direction indicated by the double 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 arrow Z is the belt thickness direction of the toothed belt 1. The upper side of each page is the outer periphery of the toothed belt 1, and the lower side is the inner periphery.

[0017] The belt length of the toothed belt 1 (the 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 toothed belt 1 at its thickest portion. The dimensions of the toothed belt according to the embodiment of the present invention are not limited to this range.

[0018] 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 section of the back portion 11 is rectangular. A 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, not less than 8 mm and not more than 14 mm. The belt teeth 12 have a tooth profile, for example, a circular arc tooth profile.

[0019] The toothed belt 1 includes a belt body 2, a core wire 3, and a reinforcing cloth 4. The belt body 2 has a belt shape. The belt body 2 includes a base portion 21 and a plurality of teeth 22 . The base portion 21 extends in the circumferential direction of the belt. The core wire 3 is embedded in the base portion 21. The plurality of tooth portions 22 are provided on the inner circumferential side of the base portion 21. The plurality of tooth portions 22 are integral with the base portion 21. The plurality of tooth portions 22 are arranged at equal intervals in the circumferential direction of the belt. The surfaces of the tooth portions 22 are covered with a reinforcing cloth 4.

[0020] The belt body 2 is made of, for example, a crosslinked product of an uncrosslinked rubber composition containing a rubber component and a rubber compounding agent (hereinafter also referred to as a crosslinked rubber composition). The uncrosslinked rubber composition is crosslinked by, for example, heating and pressurizing to become the crosslinked product. The belt body 2 has a base portion 21 and a tooth portion 22 each made of a crosslinked rubber composition. 1, the base portion 21 and the toothed portion 22 are made of different cross-linked rubber compositions. The cross-linked rubber composition constituting the base portion 21 and the cross-linked rubber composition constituting the toothed portion 22 may have the same composition.

[0021] The core wire 3 is embedded in the base 21 . The core wire 3 has a pitch in the belt width direction and is provided to form a spiral.

[0022] The core wire 3 of the toothed belt 1 satisfies the following configuration. The ratio X (X = X1 / X2) of the absolute value X1 of the difference between the distance LA from the tooth root line BL to the center of the core wire at the tooth root 24 and the distance LB from the tooth root line BL to the center of the core wire at the belt tooth 12 to the core wire diameter X2 in the belt thickness direction at the tooth root 24; The absolute value Y of the difference between the core wire flatness ratio C at the tooth bottom 24 and the core wire flatness ratio D at the belt tooth 12 is 2X+Y≦0.96 (1) The relation (1) is satisfied.

[0023] X1 is the absolute value of the difference between the distance LA from the tooth root line BL at the tooth bottom 24 to the center of the core wire 3 (hereinafter referred to as the core wire center) and the distance LB from the tooth root line BL to the core wire center at the belt tooth 12 (see Figure 4). The larger X1 is, the greater the amount of variation in the distance L from the tooth root line BL to the core wire center in the belt length direction. If the amount of variation in distance L is large, the tension of the toothed belt is likely to decrease while it is running.

[0024] The distances LA and LB for calculating the above X1 are obtained at adjacent portions. That is, when the distance LA is obtained at one tooth bottom, the distance LB is obtained at the 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 distance LA and the distance LB is obtained at three locations along the belt length direction, and the average of the absolute values ​​of the differences is calculated to be the evaluation value X1. 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.

[0025] The distances LA and LB are measured by capturing an image of a cross section (see FIGS. 2 and 3) perpendicular to the belt length direction of the toothed belt 1. Specifically, the distances are captured 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 line 24, and a cross-sectional image such as that shown in Fig. 2 is obtained. Next, based on this cross-sectional image, the distance LA from the tooth bottom line BL to the center of the core wire is measured. 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.

[0026] Next, 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 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 bottom 24 is selected to obtain the distance LA. Next, based on this cross-sectional image, the distance LB from the tooth bottom line BL to the center of the core wire is measured. As the core wire cross section to be measured, a core wire cross section that is adjacent in the length direction to the core wire cross section selected to obtain the distance LA is selected. In measuring the distance LB, first, a virtual root line VBL is set as shown in Fig. 3. The virtual root line VBL is a virtual line located at a distance LC from the back surface 11 of the toothed belt 1. This distance LC is obtained based on the cross-sectional image (see Fig. 2) obtained to measure the distance LA. Then, the distance LB from the set virtual root line VBL to the center of the core wire is measured.

[0027] The above X2 is the diameter of the core wire in the thickness direction of the belt at the tooth bottom. The cord diameter X2 in the belt thickness direction is measured 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. In this case, the cord diameter X2 is calculated for the cord closest to the center in the belt width direction. The image used to acquire the cord diameter X2 in the belt thickness direction is the same as the image used to acquire the distance LA described above. The cord diameter X2 is obtained by measuring the cord diameter in the belt thickness direction at three locations along the belt length and calculating the average value. Here, the cord diameters are obtained at three locations spaced at approximately equal intervals.

[0028] The X is the ratio of the absolute value X1 to the core diameter X2, i.e., X=X1 / X2. If the above X is large, the amount of variation in the distance L from the root line BL to the center of the core wire in the belt length direction is large. Note that the above X1 may be 0. Therefore, the above X may be 0.

[0029] The above Y is the absolute value of the difference between the core wire flattening ratio C at the tooth bottom and the core wire flattening ratio D at the belt tooth. The above-mentioned 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.

[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 diameter φTA in the belt thickness direction is the same as X2 above. 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 targeted in acquiring 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 in the belt tooth 12. The cord flatness ratio D is determined by acquiring an image of a cross section (see Figure 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 larger the value of Y, the greater the difference between the cross-sectional shape of the core wire at the tooth bottom and the cross-sectional shape of the core wire at the belt tooth. If the cross-sectional shape of the core wire varies depending on the location, the toothed belt is likely to have low tension maintenance ability.

[0033] The ratio X of the absolute value X1 to the core wire diameter X2 and the absolute value Y of the difference between the core wire flatness ratio C and the core wire flatness ratio D are 2X+Y≦0.96 (1) The following relation is satisfied.

[0034] The toothed belt 1 satisfies the above relational expression (1), and therefore has good tension maintaining properties. The above X is the ratio of the absolute value X1 to the core wire diameter X2. The larger the above X, the more likely the core wire 3 will have a wavy shape along the belt length direction. Therefore, the larger the above X, the more likely the tension of the toothed belt 1 will decrease while it is running. The above Y is the absolute value of the difference between the cord flatness ratio C and the cord flatness ratio D. The larger the above Y, the greater the difference in the cross-sectional shape of the cord 3 at each location along the belt length, and the more likely the tension of the toothed belt 1 to decrease while running. Furthermore, according to the study by the present inventors, the value of X has a greater effect on the tension maintaining ability of the toothed belt than the value of Y. Therefore, the toothed belt 1 ensures good tension maintenance by setting "2X+Y" to 0.96 or less.

[0035] In the toothed belt 1, the relationship between X and Y is preferably 2X+Y≦0.90, and more preferably 2X+Y≦0.45, from the viewpoint of improving the ability to maintain tension.

[0036] Either or both of X and Y may be 0. However, it is not easy to manufacture a toothed belt where X = 0 or Y = 0. Therefore, from the viewpoint of ensuring productivity, it is preferable that the toothed belt 1 has both X and Y greater than 0.

[0037] The above X1 is the absolute value of the difference between the distance LA and the distance LB, and specifically, the above X1 is preferably 0.35 mm or less, which makes it easier to ensure good tension maintenance. The above X1 is more 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 X1 is controlled to less than 0.03 mm. When the nominal pitch of the toothed belt 1 is 8 mm, X1 is more preferably 0.03 mm or more and 0.15 mm or less.When the nominal pitch of the toothed belt 1 is 14 mm, X1 is more preferably 0.03 mm or more and 0.25 mm or less.

[0038] In the toothed belt 1, a preferred range of 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, when X1 is not 0, it is preferred 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, etc. 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.

[0039] In the toothed belt 1, the above Y is preferably 0.30 or less. Setting Y to 0.30 or less is suitable for ensuring good tension retention. On the other hand, in a toothed belt where Y exceeds 0.30, the cross-sectional shapes of the core wire at the tooth bottom and the core wire at the belt teeth are significantly different, which may result in poor tension retention.

[0040] In the toothed belt 1, the outer diameter of the core wire 3, the core wire diameter φWA in the belt width direction at the tooth bottom 24, and the core wire diameter φTA (=X2) 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 diameter φWA and the outer diameter 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.

[0041] 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 the same as possible.

[0042] The configurations 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, for example, a crosslinked product (crosslinked rubber composition) of an uncrosslinked 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. Of these, HNBR and EPDM are preferred.

[0043] 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. The aramid short fibers are preferably para-aramid short fibers. These short fibers may be used alone or in combination of two or more kinds.

[0044] 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 amount 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.

[0045] Examples of the vulcanization accelerator include metal oxides, metal carbonates, fatty acids and derivatives thereof, etc. Examples of the metal oxide include zinc oxide (zinc white), magnesium oxide, etc. These vulcanization accelerators 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.

[0046] Examples of the antiaging agent include benzimidazole-based antiaging agents, aromatic secondary amine-based antiaging agents, amine-ketone-based antiaging agents, etc. These antiaging agents may be used alone or in combination of two or more. The content of the antioxidant relative to 100 parts by mass of the rubber component is, for example, 1.5 parts by mass or more and 5.0 parts by mass or less.

[0047] Examples of the reinforcing material include carbon black, silica, etc. Carbon black and silica may be used in combination as the reinforcing material. Examples of the carbon black include channel black, furnace black, thermal black, and acetylene black. Examples of the furnace black include SAF, ISAF, N-339, HAF, N-351, MAF, FEF, SRF, GPF, ECF, and N-234. Examples of the thermal black include FT and MT. Only one type of carbon black may be used, or two or more types may be used in combination.

[0048] 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.

[0049] 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 amount of the plasticizer is, for example, 5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the rubber component.

[0050] Examples of the co-crosslinking agent include trimethylolpropane trimethacrylate, m-phenylenedimaleimide, zinc dimethacrylate, triallyl isocyanurate, etc. These co-crosslinking agents may be used alone or in combination of two or more. The content of the co-crosslinking agent is, for example, 3 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component.

[0051] Examples of the crosslinking agent include sulfur and organic peroxides. Sulfur and organic peroxides may be used in combination, or, of course, either one may be used alone. When sulfur and an organic peroxide are used in combination as the crosslinking agent, the total compounding amount of the crosslinking agent is preferably, for example, 0.1 part 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.

[0052] 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 to 2 parts by mass per 100 parts by mass of the rubber component.

[0053] The belt body 2 is made of a crosslinked rubber composition obtained by crosslinking such an uncrosslinked rubber composition. In the belt body 2, for example, the JIS A hardness of the tooth portion 22 is 84A or more and 98A or less. In this case, the belt body 2 is less likely to deform and breakage due to cracks in the tooth portion is less likely to occur. In particular, when the belt width is 8mm or more, it is preferable that the JIS A hardness of the tooth portion 22 is in 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). A type A durometer specified in JIS-K6253-3 (2012) is used as the rubber hardness tester. The ambient temperature during measurement is 23°C.

[0054] (core wire) Examples of the core wire 3 include a glass core wire, an aramid core wire, a carbon core wire, a steel core wire, etc. These core wires are preferably made of twisted yarn. Carbon and steel core wires are preferred for 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 or steel core wires are less likely to change length when subjected to load, and the tooth pitch changes only slightly. Therefore, toothed belts equipped with carbon or steel core wires can easily maintain a good meshing state with toothed pulleys.

[0055] 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.

[0056] The core wires 3 are arranged so as to extend in parallel at intervals in the belt width direction. A plurality of core wires 3 appear to be arranged side by side in the belt width direction. 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 with core wires 3 arranged in this manner is suitable for ensuring excellent durability and excellent tension retention in high load transmission. From the same perspective, the more preferable number of core wires 3 is 6 / 10 mm or more and 10 / 10 mm or less. The dimension of the gap between adjacent core wires 3 is, for example, not less than 0.0 mm and not more than 0.45 mm.

[0057] The cords 3 may be subjected to an adhesive treatment to increase the adhesive strength between the cords 3 and the belt body 2. Examples of the adhesive treatment include an RFL treatment in which the substrate is immersed in an RFL aqueous solution followed by heating, a rubber cement treatment in which the substrate is immersed in rubber cement followed by drying, etc. Either one of these adhesive treatments may be performed, or both may be performed. Prior to the bonding treatment, the core wire 3 may be subjected to a surface treatment, such as immersion in an epoxy solution or an isocyanate solution followed by heating. These adhesive treatments and surface treatments are carried out before winding the core wire around a mold in the method of manufacturing a toothed belt, which will be described later.

[0058] (reinforced fabric) The reinforcing cloth 4 covers the surface of the toothed portion 22. The reinforcing cloth 4 forms the inner peripheral surface of the toothed belt 1. The inner peripheral surface of the toothed belt 1 includes the reinforcing cloth 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, and cotton. The reinforcing fabric 4 is preferably, for example, a woven fabric of polyamide fiber. The thickness of the reinforcing fabric 4 is, for example, not less than 0.5 mm and not more than 2.0 mm. The reinforcing fabric 4 is preferably stretchable, for example, like a woven fabric in which the weft yarns have been subjected to a wooly process.

[0059] The reinforcing fabric 4 may be subjected to an adhesive treatment to enhance adhesive strength with the belt body 2. Examples of the adhesion treatment include an RFL treatment in which the belt is immersed in an RFL aqueous solution and then heated, a soaking treatment in which the belt is immersed in a low-viscosity rubber cement and then dried, and a coating treatment in which a high-viscosity rubber cement is applied to the surface of the belt body side and then dried. Only one of these treatments may be performed, or two or more of them may be performed. Before the adhesive treatment, the reinforcing fabric 4 may be subjected to a surface treatment in which the fabric is immersed in an epoxy solution or an isocyanate solution and then heated. These adhesive treatments and surface treatments are carried out before the reinforcing fabric 4 is wound around a mold in the method of manufacturing a toothed belt, which will be described later.

[0060] (Method of manufacturing toothed belt) Next, a method for manufacturing the toothed belt 1 will be described. 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.

[0061] (Toothed Belt Manufacturing Method 1) 5 to 9 are diagrams for explaining a manufacturing method 1 of a toothed belt 1. In Fig. 5 to Fig. 9, only a part of a mold 5 for forming the belt and a belt (including a belt material) are shown. 5 to 9, the method for manufacturing a toothed belt is also called a two-stage method because the tooth portion and the base portion are molded separately. This two-stage method makes it easy to manufacture a toothed belt with small X and Y.

[0062] In manufacturing the toothed belt 1, a belt forming mold 5 is used. The mold 5 is cylindrical. On the outer periphery of this mold 5, recessed portions 51 extending in the axial direction and protruding portions 52 extending in the axial direction are provided. The recessed portions 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 recessed portions 51 are provided at regular intervals in the circumferential direction. The protruding portions 52 are provided between adjacent recessed portions 51.

[0063] (1) Prepare the ingredients. The rubber component is 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.

[0064] The core wires 3 and the reinforcing fabric 4 are prepared, and if necessary, they are subjected to adhesive treatment and surface treatment. Furthermore, the reinforcing fabric 4 is formed into a cylindrical shape.

[0065] (2) As shown in FIG. 5, first, a cylindrically formed reinforcing cloth 4 is placed on the outer peripheral surface of a mold 5 . Next, the uncrosslinked rubber sheet 23A is wrapped around the reinforcing fabric 4. At this time, only one uncrosslinked rubber sheet 23A may be wrapped around, or multiple uncrosslinked rubber sheets 23A may be wrapped around. As a result, a first uncrosslinked molded body 13A in which the reinforcing fabric 4 and the uncrosslinked rubber sheet 23A are laminated on the mold 5 is molded. The uncrosslinked rubber sheet 23A wound in this step is an uncrosslinked rubber sheet for forming the teeth portion. When a plurality of uncrosslinked rubber sheets 23A are wound, the uncrosslinked rubber sheets may have the same composition or different compositions.

[0066] 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 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 recesses 51 of the mold 5 while pressing 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, as shown in FIG. 7, a plurality of teeth 122 in a semi-bridged state are formed.

[0067] (3) Next, as shown in FIG. 8, the core wire 3 is wound spirally around the outer periphery of the molded tooth portion 122. Furthermore, an uncrosslinked rubber sheet 23B is wound on top of that. 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 cords 3 and the uncrosslinked rubber sheets 23B are laminated is molded on the mold 5 (on the tooth portion 122).

[0068] At this time, it is preferable that the core wire 3 is wound while applying a tension of 49N or more and 490N or less. The uncrosslinked rubber sheet 23B wound in this step is an uncrosslinked rubber sheet that forms the base.

[0069] (4) As shown in Figure 9, a rubber sleeve 6 is placed over the second uncrosslinked molded body 13B 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 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, which has integrated and completely crosslinked tooth portions 22 and base portion 21.

[0070] (5) The pressure inside the vulcanization can 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.

[0071] (Toothed Belt Manufacturing Method 2) The method for manufacturing the toothed belt 1 is not limited to the two-stage manufacturing method described above, but it can also be manufactured by the following method. 10 to 12 are diagrams for explaining a method 2 for manufacturing a toothed belt 1. In Fig. 10 to 12, only a part of a mold 5 for forming the belt and a belt (including a belt material) are shown. The method for producing a toothed belt, which will be explained with reference to FIGS. 10 to 12, is also called a one-stage method because the tooth portion and the base portion are cross-linked at the same time. In this manufacturing method 2, the same belt-forming mold 5 as in manufacturing method 1 is used.

[0072] (1) Prepare materials in the same manner as in Manufacturing Method 1. That is, an uncrosslinked rubber sheet 23, adhesively treated core wires 3, and adhesively treated reinforcing cloth 4 formed into a cylindrical shape are prepared.

[0073] (2) As shown in Fig. 10, first, a cylindrically formed reinforcing cloth 4 is placed on the outer periphery of a mold 5. The core wire 3 is wound spirally around the reinforcing cloth 4. After the cords 3 are wound, an uncrosslinked rubber sheet 23 is further wound around the mold 5. A plurality of uncrosslinked rubber sheets 23 (two sheets in FIG. 10) are wound around the mold 5. As a result, an uncrosslinked molded body 13C is formed on the outer periphery of the mold 5, in which the reinforcing fabric 4, the cords 3, and the uncrosslinked rubber sheet 23 are laminated. When a plurality of uncrosslinked rubber sheets 23 are wound, the uncrosslinked rubber sheets may have the same composition or different compositions.

[0074] (3) As shown in FIG. 11, a rubber sleeve 6 is placed on the uncrosslinked molded body 13C on the mold 5. The uncrosslinked molded body 13C 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 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 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.

[0075] (4) The pressure inside the vulcanization can 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 cut into rings. The toothed belt 1 can also be obtained by going through these steps. [Example]

[0076] Hereinafter, the embodiments of the present invention will be described in more detail with reference to examples. Here, a number of toothed belts were manufactured and their performance was evaluated.

[0077] (Belt material) (1) Uncrosslinked rubber composition Uncrosslinked rubber compositions A to C having the compounding compositions (parts by mass) shown in Table 1 were prepared. Each of the uncrosslinked rubber compositions A to C was prepared by masticating the rubber component, and then adding and kneading the rubber compounding ingredients.

[0078] [Table 1]

[0079] 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 short fibers are para-aramid short fibers with a fiber length of 1 mm, and the organic peroxide is Peroximon F40 (manufactured by NOF Corporation).

[0080] (2) Core wire A carbon core wire was used, and 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 width direction were both 1.10 mm.

[0081] (3) Reinforcement fabric The following adhesive treatment was applied to a woven fabric having warp and weft threads made of polyamide fibers. The adhesive treatments included a soaking treatment in which the fabric was immersed in low-viscosity rubber glue and then dried, and a coating treatment in which high-viscosity rubber glue was applied to the surface of the 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, which was the thickness of the woven fabric before the adhesive treatment.

[0082] (Toothed belt dimensions) 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 are indicated by the symbols shown in FIG. 13 as follows: Pb=8.00mm, Tb=5.00mm, h1=2.05mm, h2=2.95mm, R=5.20mm, W=5.20mm, a=0.00mm, r1=0.80mm, r2=0.80mm, PLD(PITCH LINE DIFFERENTIAL)=0.686mm. The toothed belt has a belt length of 800 mm and a belt width of 8 mm or 10 mm.

[0083] [Examples 1 to 3, 6] A toothed belt was manufactured by the above-mentioned 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 157N or 98N. The vulcanization conditions for the teeth (steam temperature and holding time in step (2) of production 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 production method 1) were 170°C and 30 minutes.

[0084] [Examples 4 to 5, Comparative Examples 1 to 2] A toothed belt was manufactured by the above-mentioned manufacturing method 2. 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 set to 59N or 157N. The overall vulcanization conditions (steam temperature and holding time in step (3) of production method 2) were 170°C and 30 minutes.

[0085] (evaluation) The toothed belts manufactured in the examples and comparative examples were evaluated as follows, and the results are shown in Table 2. Of the following evaluations, evaluations (1) to (4) were performed using a toothed belt with a belt width of 10 mm, and evaluation (5) was performed using a toothed belt with a belt width of 8 mm.

[0086] (1) Absolute value X1 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 calculation was performed using the acquired image. An average value of three locations was calculated. The results are shown in Table 2.

[0087] (2) Absolute value Y of the difference between the wire flatness ratio C and the wire flatness 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 calculation was performed using the acquired image. An average value of three locations was calculated. The results are shown in Table 2.

[0088] (3) JIS A hardness of the 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 specified in JIS-K6253-3 (2012)) perpendicularly against the side of the toothed portion of the belt body (the end face of the toothed portion in the belt width direction). 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.

[0089] (4) Belt elasticity The belt elastic modulus (N / mm) evaluated here is a value obtained by dividing the load at 0.2% elongation in a tensile test carried out by the following method by the belt width (10 mm). FIG. 14 is a diagram illustrating the method of the tensile test.

[0090] <Tensile test> The tensile test is carried out 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.

[0091] In this test, first, as shown in FIG. 14, the toothed belt is wound around a pair of flat pulleys 81 and 82 of a belt tension tester 80 so that the back surface of the belt is in contact with the pulleys. 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. Subsequently, 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 carried out at an ambient temperature of 25±5°C.

[0092] Next, based on the recorded measurements, the load on the belt when the belt elongation is 0.2% is determined. Here, the belt elongation of 0.2% 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.

[0093] 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). Measurements are taken three times, changing the contact position between the toothed belt and the flat pulley, and the average value is taken as the result.

[0094] (5) Running test (evaluation of tension maintenance) A transmission system 90 was constructed by winding a toothed belt around two pulleys including a driving pulley (number of teeth: 22) 91 and a driven pulley (number of teeth: 33) 92 . FIG. 15 shows the transmission system 90 pulley layout. Using this transmission system, a running test is conducted with a drive speed of 4212 rpm, a driven speed of 2808 rpm, a driven load of 34.3 N·m, an axial load (SW) of 608 N, and an ambient temperature of 60°C. The initial tension is set using the axial load measured by the load cell. When setting, after setting the target tension, the pulley is rotated by hand three times to rotate the belt, and then the tension is adjusted to the target value again. In this running test, the initial tension (T0) is used as the standard, and the test is stopped after 100 hours of running, and the belt tension (T) when warm is measured with an ultrasonic tension meter. After the measurement, the tension maintenance rate is calculated using the following formula: Calculate. Tension maintenance rate (%)=T / T0×100 The results are shown in Table 2.

[0095] [Table 2]

[0096] As shown in Table 2, the toothed belt according to the embodiment of the present invention has good tension maintenance properties.

[0097] 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. [Explanation of symbols]

[0098] 1 Toothed belt 2 Belt body 3 core wire 4 Reinforcement fabric 5. Mold 6 Rubber sleeve 11 Back 12 belt teeth 13A, 13B Uncrosslinked molded product 14A Belt Slab 21 Base 22, 122 teeth 23 Uncrosslinked rubber sheet 24 Root 51 Recess 52 Convex part 90 Transmission System 91 Drive pulley 92 driven pulley

Claims

1. A toothed belt with an embedded core wire, 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, a ratio X of the absolute value X1 of the difference between the distance LA from the tooth bottom line to the center of the core wire at the tooth bottom and the distance LB from the tooth bottom line to the center of the core wire at the belt tooth to the core wire diameter X2 in the belt thickness direction at the tooth bottom; 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 2X + Y≦0.96 A toothed belt that satisfies the following relationship.

2. The relation is: 2X + Y≦0.90 2. The toothed belt according to claim 1, wherein:

3. a rubber belt body in which the core wires are embedded, 3. The toothed belt according to claim 1, wherein the JIS A hardness of the toothed portion of the belt body is 84A or more and 98A or less.

4. 4. The toothed belt according to claim 3, wherein the belt body is made of a crosslinked product of an uncrosslinked rubber composition containing a rubber component and a rubber compounding agent.

5. 5. The toothed belt according to claim 4, wherein the rubber component is hydrogenated nitrile rubber (HNBR) or ethylene-propylene-diene rubber (EPDM).

6. 6. The toothed belt according to claim 1, wherein the core wire is a carbon core wire or a steel core wire.

7. 7. The toothed belt according to claim 1, wherein the core wires have 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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