Toothed belt drive

Abstract

This invention relates to a toothed belt drive device, comprising a toothed belt and two or more toothed pulleys. The toothed belt has a core wire embedded extending along its length and two or more belt teeth arranged at predetermined intervals along its length. The toothed pulleys have two or more pulley teeth on their outer circumferences opposite to the belt teeth and are wound around the toothed belt. The core wire comprises a carbon fiber rope formed by combining and re-twisting two or more initially twisted yarns containing carbon fibers. The initial twist of the initially twisted yarns is in the same direction as the re-twisted yarns. The initial twist coefficient of the initially twisted yarns is 0.62 to 1.30, and the re-twisted yarns are 2.06 to 3.95. The tooth pitch of the toothed belt relative to the tooth pitch of the toothed pulleys wound around the toothed belt is in the range of -0.4% to +0.1%.

Description

Technical Field

[0001] This invention relates to a toothed belt drive for synchronous transmission of a device that transmits high loads via a belt. Background Technology

[0002] Power transmission belts are broadly classified into friction belts and meshing belts. Examples of friction belts include flat belts, V-belts, and multi-ribbed belts, while examples of meshing belts include toothed belts. Toothed belts have: a back with core wires embedded approximately parallel to the belt's length direction; teeth spaced at predetermined intervals along the belt's length direction; and a toothed cloth covering the teeth. Power is transmitted by the teeth of the toothed belt engaging with pulleys that have corresponding grooves. Because toothed belts do not slip with pulleys, they can reliably transmit high loads, and therefore, their use in recent years as a replacement for chains for rear-wheel drive applications in two-wheeled motorcycles is increasing.

[0003] Toothed belts used in high-load transmission applications such as rear-wheel drive for two-wheeled motorcycles are known to include toothed belts with twisted cords incorporating carbon fiber in the core wire. For example, Patent Document 1 discloses a toothed belt in which a core wire containing co-twisted carbon fiber with a diameter of 1.1 mm or more and 2.5 mm or less is embedded. Furthermore, it is described that by forming the above structure, bending stiffness is reduced, preventing tooth loss due to excessive elongation of the core wire, and preventing core wire breakage due to reduced bending fatigue resistance (particularly paragraph 0009). It is also described that the initial twist coefficient of the core wire can be 0.65 to 1.61, and the re-twist coefficient can be 1.14 to 3.61 (paragraph 0021). In an embodiment, a toothed belt with a tooth profile (tooth shape) of H14M (tooth pitch 14 mm) was made using a core wire with an initial twist coefficient of 0.97 and a re-twist coefficient of 2.07.

[0004] The toothed belt with a core wire disclosed in Patent Document 1 shows a certain degree of durability for use in the rear-wheel drive of two-wheeled motorcycles. However, due to the large tooth shape with a 14mm pitch, it cannot cope with compactness issues, and its durability is insufficient due to the increase in power transmission in recent years. In particular, if the meshing with the pulley deteriorates, the wear of the toothed cloth is accelerated, thereby easily reducing the belt's durability.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2015-64103

[0008] Patent Document 2: Japanese Patent Application Publication No. 4-331844 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] Therefore, the first object of the present invention is to provide a toothed belt that can carry high loads and improve durability even in a compact layout.

[0011] However, when discussing the meshing of toothed belts and pulleys, their respective tooth pitches and PLD (Pitch Line Differential) are important. For example, Patent Document 2 discloses a toothed belt drive device characterized in that the pitch line differential (PLD) of the synchronous belt (toothed belt) is 10-20% higher than the designed PLD of the pulley, and the pitch (tooth pitch of the toothed belt) is 0.02-0.15% larger than the designed pitch (tooth pitch of the pulley).

[0012] Furthermore, existing technology discloses the following: Typically, the tooth pitch of the toothed belt is made to match the tooth pitch of the pulley, and the PLD of the belt is made to match the PLD of the pulley. On the other hand, when the pitch difference between the belt and the pulley is a slightly negative value (the tooth pitch of the toothed belt is slightly smaller than the tooth pitch of the pulley), the service life is extended. The reason for this is explained as follows: because the toothed belt elongates when a load torque is applied, the tooth pitch of the toothed belt matches the tooth pitch of the pulley.

[0013] As disclosed in Patent Document 2, although it is known that meshing can sometimes be optimized by making the tooth pitch of the toothed belt slightly smaller than that of the pulley, there are other factors affecting meshing in transmissions used in rear-wheel drive applications of two-wheeled motorcycles. For two-wheeled motorcycles that travel outdoors, foreign objects such as gravel can easily become embedded and accumulate between the toothed belt and the pulley (stone or sand inclusion). If sand inclusion occurs, it results in a situation similar to the toothed belt's PLD (pulse density) increasing, thus worsening the meshing between the toothed belt and the pulley. That is, even if the toothed belt and pulley mesh ideally in the initial stages of operation (when the vehicle is new), the meshing will worsen as the travel distance increases, increasing the likelihood of reduced toothed belt durability.

[0014] Therefore, the second objective of this application is to provide a toothed belt drive that can maintain an ideal meshing state even in the presence of factors such as sand inclusions that worsen the meshing between the toothed belt and the pulley, thereby improving the life of the toothed belt.

[0015] Methods for solving problems

[0016] To address the aforementioned problems, the present invention provides a toothed belt drive device comprising a toothed belt and two or more toothed pulleys. The toothed belt has a core wire extending and embedded in the belt length direction and two or more belt teeth arranged at predetermined intervals in the belt length direction. The toothed pulleys have two or more pulley teeth on their outer periphery opposite to the belt teeth and are wound around the toothed belt. The toothed belt drive device is characterized in that the core wire comprises a carbon fiber rope formed by combining and re-twisting two or more initially twisted yarns containing carbon fibers, the initial twist direction of the initially twisted yarns being the same as the re-twisted yarns, the initial twist coefficient of the initially twisted yarns being 0.62 to 1.30, the re-twisted yarns being 2.06 to 3.95, and the tooth pitch of the toothed belt relative to the tooth pitch of the toothed pulleys wound around the toothed belt being in the range of -0.4% to +0.1%.

[0017] According to the above structure, by including carbon fiber in the core wire embedded in the toothed belt, the tensile strength is improved and the durability under high load transmission is improved.

[0018] In addition, regarding the core yarn, by combining two or more initial twisted yarns for retwisting, and making the twist direction of the initial twist the same as that of the retwisting (co-twisting), the bending fatigue resistance is improved.

[0019] Furthermore, by keeping the initial twist coefficient and the retwist coefficient within the aforementioned range, it is possible to suppress the elongation of the core wire and the toothed belt while ensuring resistance to bending fatigue, thereby improving durability. When the initial twist coefficient and the retwist coefficient are less than the aforementioned range, the resistance to bending fatigue decreases; conversely, when the initial twist coefficient and the retwist coefficient are greater than the aforementioned range, the tensile strength decreases, and the elongation of the toothed belt increases, resulting in reduced durability.

[0020] If the tooth pitch of the toothed belt is outside the range of -0.4% to +0.1% relative to the tooth pitch of the toothed pulley around which the toothed belt is wrapped, the meshing between the teeth of the toothed belt and the teeth of the toothed pulley may deteriorate, and the durability of the toothed belt may decrease. Therefore, by placing it within the above range, the deterioration of the meshing between the teeth of the toothed belt and the teeth of the toothed pulley can be suppressed, and the durability of the toothed belt can be prevented from decreasing.

[0021] In addition, in this invention, the toothed belt drive device is characterized in that the tooth pitch of the toothed belt is in the range of -0.2% to +0.1% relative to the tooth pitch of the toothed pulley.

[0022] By setting the tooth pitch of the toothed belt relative to the toothed pulley to a larger range than existing products (toothed belts with a tooth pitch smaller than the tooth pitch of the toothed pulley to cope with the elongation of the toothed belt due to use), it is possible to suppress the deterioration of meshing caused by sand inclusion and further improve the durability of the toothed belt.

[0023] In addition, the toothed belt drive device described above can be used for rear-wheel drive applications in two-wheeled motorcycles.

[0024] Based on the above structure, even when the toothed belt stretches due to the high load caused by the rear wheel drive of a two-wheeled motorcycle, either the toothed pulley on the driving side (small diameter pulley) or the toothed pulley on the driven side (large diameter pulley) can maintain good meshing of their teeth, and a toothed belt drive device that improves the durability of the toothed belt can be manufactured.

[0025] Invention Effects

[0026] Toothed belts can provide high-load transmission even with a compact layout, improve durability, and maintain ideal meshing even in the presence of factors such as sand inclusions that worsen the meshing between the toothed belt and pulley, thus extending the life of the toothed belt. Attached Figure Description

[0027] Figure 1 This is a three-dimensional cross-sectional view of the toothed belt in the embodiment.

[0028] Figure 2 This is a cross-sectional view of the toothed belt according to the embodiment, and a diagram showing the relationship between the core wire and the PLD.

[0029] Figure 3 This is an explanatory diagram showing the names of the toothed belt and drive pulley (driven pulley) configuration (dimensions) of the embodiment.

[0030] Figure 4 This is an explanatory diagram regarding the measurement of PLD in toothed belts.

[0031] Figure 5 It is a cross-sectional view of the toothed belt, showing the relationship between the core wire and the PLD when the core wire diameter and the thickness of the toothed cloth are varied.

[0032] Figure 6 This is a schematic diagram of the toothed belt drive device of the embodiment (and also a schematic diagram of the traveling test machine of the embodiment). Detailed Implementation

[0033] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

[0034] (toothed belt 3 and toothed belt drive device 21)

[0035] like Figure 1 and Figure 2 As shown, the toothed belt 3 is arranged at a predetermined interval along the belt length direction (X direction), and is composed of two or more teeth 7 whose surface is covered by toothed cloth 11 and a back 4 in which the core wire 9 is embedded and extends in the belt length direction.

[0036] The aforementioned toothed belt 3 is wound between two or more pulleys and is widely used as a power transmission mechanism. For example, the toothed belt 3 is used in high-load transmission applications such as rear-wheel drive in two-wheeled motorcycles. Specifically, such as... Figure 6 and Figure 3 As shown, a toothed belt 3 is wound around the drive pulley 22 (toothed pulley) and the driven pulley 23 (toothed pulley). Figure 3 The toothed belt drive 21 between (not shown in the figure) is implemented in the form of a toothed belt drive device.

[0037] like Figure 3 As shown, two or more drive pulley teeth 221 (equivalent to pulley teeth) are provided on the outer periphery of the drive pulley 22, which are opposite to the teeth 7 (equivalent to belt teeth) of the toothed belt 3. Two or more driven pulley teeth 231 (equivalent to pulley teeth) (not shown) are also provided on the outer periphery of the driven pulley 23, which are opposite to the teeth 7 of the toothed belt 3.

[0038] The drive pulley 22 of this embodiment is envisioned for use in medium-sized (approximately 500cc displacement) two-wheeled motorcycles, with an outer diameter ranging from 67mm to 90mm, and is smaller than the drive pulley of Patent Document 1. Specifically, the drive pulley of Patent Document 1 has a tooth profile of H14M and 33 teeth (outer diameter approximately 144mm), and is intended for use in large two-wheeled motorcycles. In contrast, the drive pulley 22 of this embodiment is envisioned for use in medium-sized (approximately 500cc displacement) two-wheeled motorcycles, with a tooth profile of H11M and 26 teeth (outer diameter approximately 89mm), and is a small pulley (with a small tooth pitch PP and pulley outer diameter for compactness requirements).

[0039] It should be noted that the outer diameter OD of the driven pulley 23 is larger than the outer diameter OD of the driving pulley 22. Therefore, the number of teeth 231 of the driven pulley 23 is greater than the number of teeth 221 of the driving pulley 22. However, the pitch PLD (pitch distance) of the driving pulley 22 is the same as that of the driven pulley 23. In addition, the tooth pitch PP of the driving pulley 22 is the same as that of the driven pulley 23.

[0040] Here, for reference Figure 2 and Figure 3 The names of the toothed belt 3 and the drive pulley 22 (driven pulley 23) are defined.

[0041] The tooth pitch BP of the toothed belt 3 is the distance between adjacent teeth 7. (It should be noted that the tooth pitch BP of the toothed belt 3 varies depending on the tensile force and bending diameter, so it is defined as "the length (circumference) of the toothed belt 3 / the number of teeth 7").

[0042] PL (Pitch Wire) of Toothed Belt 3: The wire connecting the center position of the core wire 9 of Toothed Belt 3.

[0043] PLD (pitch distance) of toothed belt 3: The distance from the bottom of tooth 7 to PL (center of core wire 9) of toothed belt 3.

[0044] The outer diameter OD of the pulley: the diameter of the addendum circle of the pulley teeth.

[0045] Pulley pitch circumference PPL: With the toothed belt 3 wound around the pulley, the line connecting the center position of the core wire 9 of the toothed belt 3 on the outer circumference of the pulley.

[0046] Pitch diameter PD: The diameter of the pulley pitch circumference PPL

[0047] Pulley pitch PP: The distance (length of the arc) between adjacent teeth along the circumference of the pulley pitch.

[0048] PLD (Pitch Point Distance): The distance from the tooth tip of the pulley to the circumference of the pulley pitch (defined as "(Pitch Diameter PD - Pulley Outer Diameter OD) / 2").

[0049] (Details of toothed band 3: core wire 9)

[0050] On the back 4, the core wire 9 is embedded in a spiral shape along the length of the strip, and is arranged at specified intervals in the cross-sectional view along the width direction (Y direction) (refer to...). Figure 1 ).

[0051] The core wire 9 is a carbon fiber rope with the initial twist direction and the retwist twist direction being the same. By making the core wire 9 co-twisted, compared with ply twisting or unidirectional twisting, the bending stiffness is reduced, and excellent bending fatigue resistance can be obtained. For example, carbon fiber manufactured by Toray Industries, Ltd. under the trade name "Treka" is used. The co-twisted carbon fiber rope can be formed as follows: First, a multifilament yarn of carbon fiber with a fineness of 300-1000 tex is impregnated with a treatment liquid obtained by dissolving rubber latex and epoxy resin in a solvent such as toluene to produce a bonded yarn. Then, the bonded yarn is initially twisted in the S or Z direction with an initial twist coefficient of 0.62-1.30 to produce an initial twist yarn. Two to four initial twist yarns are combined and further retwisted in the same direction as the initial twist with a retwisting coefficient of 2.06-3.95. Thus, a co-twisted carbon fiber rope is obtained. Here, the twist coefficient TF is defined as TF = (fineness (tex)). 1 / 2 ×T / 960 (T: number of twists per 1m) indicates the number of times the twisting process is performed.

[0052] Carbon fiber multifilament yarns can be selected from multifilament yarns with different filament counts, such as 6K and 12K. 6K indicates multifilament yarn with 6,000 filaments, and 12K indicates multifilament yarn with 12,000 filaments. The fineness of 6K multifilament yarn is approximately 400 tex, and the fineness of 12K multifilament yarn is approximately 800 tex.

[0053] When the fineness of the carbon fiber multifilament yarn is greater than 1000 tex, its flexural fatigue resistance may decrease. Conversely, when the fineness of the carbon fiber multifilament yarn is less than 300 tex, material costs increase, and the number of initial twisted yarns required to produce the core yarn 9 with sufficient tensile strength increases, thus leading to increased processing time. Therefore, to adequately ensure both flexural fatigue resistance and appropriate cost / processing time, the lower limit of the fineness range for carbon fiber multifilament yarn is preferably 500 tex or 700 tex, and the upper limit is preferably 900 tex.

[0054] In this embodiment, a single 12K multifilament yarn (with a fineness of approximately 800 tex) is initially twisted to create a tufted yarn. Four such tufted yarns are then combined and retwisted. The resulting straight-twisted carbon fiber rope (12K-1 / 4) is used as the core thread 9. It should be noted that "12K-1 / 4" indicates a twisted rope formed by initially twisting a single 12K multifilament yarn to create a tufted yarn and then combining four such tufted yarns for retwisting. Similarly, "12K-1 / 3" indicates a twisted rope formed by initially twisting a single 12K multifilament yarn to create a tufted yarn and then combining three such tufted yarns for retwisting. Furthermore, "12K-4 / 0" indicates a twisted rope formed by combining four 12K multifilament yarns and unidirectionally twisting them.

[0055] The rubber latex in the treatment solution used to form the twisted carbon fiber rope is preferably composed of the same type of rubber composition as the rubber composition constituting the back 4 and the teeth 7. As the epoxy resin, one or more of the following can be used: ethylene glycol diglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether, hexanediol diglycidyl ether, etc.

[0056] The core wire diameter of core wire 9 is preferably 1.1 mm or more and 2.5 mm or less. When the core wire diameter is less than 1.1 mm, the elongation of core wire 9 increases, which easily leads to missing teeth (damage to the tooth 7). When the core wire diameter exceeds 2.5 mm, the core wire is prone to breakage due to the reduced bending fatigue resistance of core wire 9. Furthermore, the PLD of the toothed band 3... Figure 5 (a) shows the relationship between the thickness of the toothed cloth 11 and the diameter of the core wire 9. Therefore, when the core wire diameter is less than 1.1 mm, as shown... Figure 5 (b) shows that only small PLDs can be set, making it difficult to obtain a suitable PLD. Furthermore, even with a small core wire diameter, if the toothed cloth 11 is thickened, as shown... Figure 5(c) This results in a larger PLD, but reduces the volume of the rubber in the tooth 7, leading to reduced resistance to tooth breakage. The lower limit of the core wire diameter of the core wire 9 is preferably 1.2 mm or more, more preferably 1.6 mm or more, particularly preferably 1.9 mm or more, and the upper limit is preferably 2.4 mm or less, more preferably 2.2 mm or less.

[0057] Here, considering both bending fatigue resistance and tooth chipping resistance, the PLD of the toothed belt 3 can be 0.8–2.0 mm, preferably 0.9–1.5 mm, and more preferably 1.0–1.2 mm. Furthermore, it is preferable that the PLD of the toothed belt 3 is approximately the same as that of the drive pulley 22. Specifically, if the PLD of the toothed belt 3 is in the range of -5% to +5% relative to the PLD of the drive pulley 22, it can be said to be approximately the same.

[0058] (Back 4)

[0059] The backing material 4 is composed of a rubber composition with a JIS-A hardness of 80 to 89. Here, JIS-A hardness refers to the hardness measured using a Type A durometer, based on JIS K 6253 (2012), on the surface of the backing material 4 of the toothed belt 3. By achieving a JIS-A hardness of 80 to 89, the flexural stiffness of the backing material 4 is reduced, resulting in excellent resistance to flexural fatigue. When the JIS-A hardness of the backing material 4 is less than 80, cracks may occur in the backing material 4 due to impacts from foreign objects. When the JIS-A hardness of the backing material 4 exceeds 89, the resistance to flexural fatigue decreases, and cracks are more likely to occur in the backing material 4.

[0060] The rubber composition constituting the back 4 (rubber composition (B), hereinafter referred to as "back rubber") is preferably a mixture of hydrogenated nitrile butadiene rubber (hereinafter referred to as "HNBR") and hydrogenated nitrile butadiene rubber containing an unsaturated carboxylic acid metal salt (hereinafter referred to as "HNBR containing an unsaturated carboxylic acid metal salt"). The hardness can be adjusted by changing the mixing ratio of the two. Specifically, in order to obtain a hardness of 80 degrees or more and 89 degrees or less, it is preferable to set the mass ratio of "HNBR" to "HNBR containing an unsaturated carboxylic acid metal salt" to 40:60 to 100:0. As the HNBR containing an unsaturated carboxylic acid metal salt, for example, a substance in which zinc methacrylate, as an unsaturated carboxylic acid metal salt, is highly microdispersed in the HNBR (e.g., the trade name "Zeoforte (ZSC)" manufactured by Zeon in Japan).

[0061] HNBR refers to a substance whose heat resistance is improved by chemically hydrogenating the unsaturated bonds (carbon-carbon double bonds) of existing nitrile rubber to maintain its oil resistance, an advantage of existing nitrile rubber, and to prevent the aging of rubber elasticity caused by the recombination reaction of sulfur during heat aging. Unsaturated carboxylic acid metal salts are substances formed by the ionic bonding of unsaturated carboxylic acids with one or more carboxyl groups to a metal. Examples of unsaturated carboxylic acids include monocarboxylic acids such as acrylic acid and methacrylic acid, and dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid. Examples of metals include magnesium, titanium, iron, copper, zinc, aluminum, lead, and nickel.

[0062] The HNBR used in this invention is an unsaturated rubber with an iodine value ranging from 7 to 30 mg / 100 mg, preferably from 11 to 28 mg / 100 mg. Here, unsaturated rubber refers to rubber having unsaturated bonds, including carbon-carbon double bonds (C=C bonds), in its polymer molecular chain. Furthermore, the iodine value is an indicator of the amount of unsaturated bonds; a higher iodine value indicates a greater amount of unsaturated bonds in the polymer molecular chain. The iodine value is determined by adding excess iodine to the test sample to allow it to react completely (the reaction of iodine with unsaturated bonds) and then quantifying the amount of residual iodine through redox titration. When the iodine value of the HNBR is less than 7 mg / 100 mg, the cross-linking reaction between the HNBRs may be insufficient, reducing the rigidity of the teeth and causing defects such as missing teeth during wear. On the other hand, when the iodine value of the HNBR exceeds 30 mg / 100 mg, the amount of unsaturated bonds may become excessive, leading to reduced heat resistance of the teeth or deterioration due to oxidation, thus shortening the belt life.

[0063] (Teeth 7)

[0064] The tooth 7 is composed of a rubber composition with a hardness of 60 to 66 degrees according to JIS-D hardness (value measured using a Type D hardness tester). Here, JIS-D hardness refers to the hardness according to JIS K 6253 (2012), which is the hardness of the side surface of the tooth 7 of the toothed band 3 as measured using a Type D hardness tester. It should be noted that the Type D hardness tester is a high-hardness testing machine; when the value measured using a Type A hardness tester exceeds 90 degrees, a Type D hardness tester is preferred. The hardness of the rubber composition constituting the tooth 7 is higher than that of the rubber composition constituting the back 4, with a JIS-A hardness exceeding 90 degrees. Therefore, the hardness of the rubber composition constituting the tooth 7 is set to the value measured using a Type D hardness tester.

[0065] The rubber composition constituting the tooth 7 (rubber composition (A), hereinafter referred to as "tooth rubber") is preferably a mixture of HNBR and HNBR containing an unsaturated carboxylic acid metal salt, just like the back 4. The hardness is adjusted by changing the mixing ratio of the two. Specifically, it is preferable to mix "HNBR" and "HNBR containing an unsaturated carboxylic acid metal salt" at a mass ratio of 50:50 to 0:100.

[0066] Furthermore, it is preferable to embed short fibers 5, such as aromatic polyamides, into the rubber composition constituting the tooth portion 7. The short fibers 5 are preferably oriented along the shape of the tooth portion 7 on the side closest to the toothed fabric 11, and are oriented approximately parallel to the core wire 9 as they approach it. The type of short fiber 5 is not particularly limited; for example, aromatic polyamide fibers, PBO (poly(p-phenylenebenzodioxane)) are preferred. High-modulus fibers such as azole fiber, polyvinyl alcohol fiber, and carbon fiber.

[0067] Furthermore, in the rubber composition constituting the tooth portion 7, the powdered reinforcing inorganic filler is preferably compounded in an amount of 10 parts by mass or less relative to 100 parts by mass of the total rubber component containing HNBR and HNBR containing unsaturated carboxylic acid metal salts, more preferably in the range of 0.1 to 8 parts by mass, 0.5 to 5 parts by mass, or 1 to 3 parts by mass. When the amount of the powdered reinforcing inorganic filler exceeds 10 parts by mass relative to 100 parts by mass of the total rubber component, the heat generation of the rubber composition constituting the tooth portion 7 may increase, and the heat resistance of the rubber composition may decrease. Therefore, tooth loss and cracking may occur due to heat aging.

[0068] In this embodiment, it is not necessarily necessary to incorporate powdered reinforcing inorganic fillers such as carbon black and silica into the rubber composition constituting the tooth portion 7. Specifically, the carbon black only needs to be incorporated to a degree sufficient to color the rubber composition constituting the tooth portion 7 black; preferably, it is 10 parts by mass or less relative to the total amount of the rubber component containing HNBR and HNBR containing unsaturated carboxylic acid metal salts, and more preferably, it is in the range of 0.1 to 8 parts by mass, 0.5 to 5 parts by mass, or 1 to 3 parts by mass. The carbon black is used as a colorant, and it is most suitable for coloring the rubber composition black.

[0069] Furthermore, it is preferable to incorporate a non-reinforcing filler into the rubber composition constituting the tooth 7. Examples of non-reinforcing fillers include: polyvalent metal carbonates (calcium carbonate, magnesium carbonate, etc.), polyvalent metal hydroxides (aluminum hydroxide, etc.), polyvalent metal sulfates (barium sulfate, etc.), silicates (natural or synthetic silicates where a portion of silicon is replaced by polyvalent metal atoms, such as aluminum silicate, magnesium silicate, magnesium aluminum silicate, etc.; or minerals with silicates as the main component, such as clay containing aluminum silicate, talc and mica containing magnesium silicate, etc.), zinc barium white, silica sand, etc. These non-reinforcing fillers can be used alone or in combination of two or more. Preferred non-reinforcing fillers are at least one selected from calcium carbonate, magnesium carbonate, aluminum hydroxide, barium sulfate, silicates (aluminum silicate, magnesium silicate, magnesium aluminum silicate, etc., or silicate minerals (talc, clay, mica, etc.)). Furthermore, from the viewpoint of greatly improving the processability and dispersibility of the compounding agent and minimizing the risk of poor dispersion of the compounding agent, the non-reinforcing filler preferably contains at least one of calcium carbonate, magnesium silicate or talc containing magnesium silicate, aluminum silicate or clay containing aluminum silicate, and particularly preferably contains calcium carbonate. Commercially available powdered fillers used as rubber fillers can be used as non-reinforcing fillers.

[0070] The average particle size (average primary particle size) of the non-reinforced filler can be selected from, for example, a range of about 0.01 μm to about 25 μm (e.g., about 0.2 μm to about 20 μm), preferably about 0.5 μm to about 17 μm (e.g., about 1 μm to about 15 μm). The average particle size (average primary particle size) of the non-reinforced filler can be, for example, about 0.01 μm to about 3 μm (e.g., about 0.02 μm to about 2 μm), preferably about 0.05 μm to about 1.5 μm (e.g., about 0.1 μm to about 1 μm), or it can be larger. For example, the average particle size (average primary particle size) of the non-reinforced filler can be about 0.2 μm to about 5 μm (e.g., about 0.3 μm to about 3 μm), preferably about 0.5 μm to about 2.5 μm (e.g., about 1 μm to about 2 μm). It should be noted that, depending on the type of unreinforced filler, such as magnesium silicate or its minerals, the unreinforced filler may sometimes break or fragment during the mixing process with rubber components. The average particle size of such fragmented or fragmentable unreinforced fillers can be the average particle size before mixing with rubber components. Unreinforced fillers in the tooth or its rubber composition typically have an average particle size within the aforementioned range (e.g., 0.1–10 μm, preferably 0.5–5 μm, more preferably 1–3 μm). The average particle size of the unreinforced filler can be determined as a volume average particle size using a laser diffraction particle size distribution measuring device. Furthermore, the average particle size of nanoscale fillers can be calculated as an arithmetic mean particle size using image analysis of electron microscope images, including scanning electron microscope images, with an appropriate number of samples (e.g., 50 samples).

[0071] The proportion of non-reinforcing filler relative to 100 parts by weight of the total rubber component can be about 3 parts by weight to about 50 parts by weight (e.g., about 5 parts by weight to about 40 parts by weight), preferably about 5 parts by weight to about 30 parts by weight (e.g., about 6 parts by weight to about 25 parts by weight), and more preferably about 7 parts by weight to about 20 parts by weight (e.g., about 8 parts by weight to about 15 parts by weight). If the content of non-reinforcing filler is too low, the processability of the belt and the dispersibility of the compounding agents may not be sufficiently improved; if the content of non-reinforcing filler is too high, the dispersibility of the compounding agents may be poor.

[0072] Using a higher proportion of non-reinforcing fillers can improve the dispersibility of various compounding agents (zinc oxide, reinforcing fillers, short fibers, etc.) in rubber compounding, enhance the uniformity of the rubber composition, and avoid significantly increasing the loss coefficient Tanδ. It can also suppress heat generation caused by rubber deformation. Therefore, it can inhibit both the initiation and growth of cracks, and significantly improve the toothed belt's resistance to chipped teeth.

[0073] Furthermore, the vulcanizate of the rubber composition used in the toothed portion 7 of this embodiment preferably has a storage modulus (E′) of 200–300 MPa and a loss coefficient (Tanδ) of 0.1–0.2 at an ambient temperature of 70°C, as determined by JIS K6394 (2007). If it falls within such a range, defects such as missing teeth are less likely to occur, deformation of the toothed portion 7 is suppressed, and thus it will not hinder meshing with the toothed pulleys (drive pulley 22, driven pulley 23), thereby improving durability.

[0074] E′ refers to the elastic modulus obtained from a test of a dynamic state under periodic vibration, defined as the ratio of deformation to elastic stress in the same phase. The higher the E′, the less easily the object deforms; even under strong external forces such as high load conditions, the deformation is small, and therefore, it is less prone to cracking or breaking. On the other hand, the lower the E′, the more easily the object deforms; therefore, even small external forces can easily cause the object to break or break.

[0075] Tanδ, obtained by dividing the loss modulus (E″) by E′, is a measure of the ratio of energy dissipated as heat to the maximum stored energy during one vibration cycle. In other words, Tanδ represents the ease with which vibrational energy applied to a rubber composition is dissipated as heat. A larger Tanδ indicates that most of the externally applied energy is converted into heat, causing the rubber composition to heat up and reducing its heat resistance. Conversely, a smaller Tanδ indicates that heat generation is suppressed, thus improving the heat resistance of the rubber composition.

[0076] (Tooth cloth 11)

[0077] The toothed fabric 11 uses a fibrous fabric woven from warp yarns 6 extending in the width direction and weft yarns 8 extending in the length direction as its base material. This fibrous fabric can include plain weave, twill weave, satin weave, etc. As the fiber material constituting this fibrous fabric, for example, aramid fibers, polyurethane elastic yarns, aliphatic fibers (nylon 6, nylon 66, polyester, polyvinyl alcohol, etc.) can be used. It should be noted that the toothed fabric 11 may also be omitted.

[0078] As the fiber fabric of this embodiment, a multi-layer (double-layer) woven structure can be used, which is woven from two types of weft yarns 8 and one type of warp yarn 6. In this case, it is preferable that the warp yarn 6 is made of nylon fiber and the weft yarn 8 is made of fluorinated fiber, nylon fiber, and polyurethane elastic yarn. In addition, as the weft yarn 8 located on the surface side of the toothed cloth 11 (the side that meshes with the toothed pulley), in order to reduce the friction between the toothed cloth 11 and the toothed pulley, it is preferable to use fluorinated fiber (e.g., PTFE fiber) with a low coefficient of friction. On the other hand, by using fibers other than fluorinated fibers (nylon fiber, polyurethane elastic yarn) in the weft yarn 8 located on the back side of the toothed cloth 11 (the adhesive side with the teeth 7), the adhesive force between the toothed cloth 11 and the rubber constituting the teeth 7 can be improved.

[0079] Furthermore, it is preferable to arrange low-melting-point fibers, which have a melting point that melts at the vulcanization temperature of the teeth 7 and back 4, which are based on rubber, around the fluorinated fibers. Specifically, this includes forms such as twisting the fluorinated fibers with the low-melting-point fibers or covering the fluorinated fibers with the low-melting-point fibers. It should be noted that the vulcanization conditions (vulcanization temperature and vulcanization time) of the teeth 7 and back 4 are not particularly limited, and are usually determined by referring to the vulcanization curve measured using a Mooney viscometer or other vulcanization behavior testing machine, taking into account the type of vulcanizing agent and vulcanization accelerator, as well as the vulcanization method. The typical vulcanization conditions thus determined are a vulcanization temperature of 100 to 200°C and a vulcanization time of about 1 minute to about 5 hours. Secondary vulcanization can be performed if necessary.

[0080] In this case, during the vulcanization of the teeth 7 and the back 4, the low-melting-point fibers melt, flow into the spaces between the fibers constituting the toothed cloth 11, and cool below their melting point, thereby crystallizing. Therefore, the breakage and scattering of fluorinated fibers caused by impact or wear on the surface of the toothed cloth 11 during engagement with or disengagement from the toothed pulley are suppressed. This provides longer-lasting protection for the teeth 7 and the back 4, prevents tooth loss in the belt, and enables extended service life under high-load conditions.

[0081] Here, as a low-melting-point fiber, a fiber with a melting point preferably below 165°C, more preferably below 150°C, such as polyamide fiber, polyester fiber or olefin fiber can be used.

[0082] Polyamide fibers, which can be used as low-melting-point fibers, include copolyamide fibers formed by a combination of W-aminocarboxylic acid components or dicarboxylic acid components and diamines.

[0083] As a polyester fiber suitable for use as a low-melting-point fiber, a core-sheath type composite fiber is preferably composed of a core polymer having a melting point higher than the vulcanization temperature of the toothed portion 7 and the back portion 4, and a sheath polymer having a melting point lower than the vulcanization temperature of the toothed portion 7 and the back portion 4. Examples of core polymers with melting points higher than the vulcanization temperatures of the toothed portion 7 and the back portion 4 include polyethylene terephthalate, polybutylene terephthalate, and copolymers thereof. Copolymers of the sheath polymer having melting points lower than the vulcanization temperatures of the toothed portion 7 and the back portion 4 are obtained through a polycondensation reaction of a diacid with a glycol. Examples of copolymers based on terephthalic acid and diethylene glycol include isophthalic acid, adipic acid, sebacic acid, butanediol, hexanediol, polyethylene glycol, neopentyl glycol, etc., and the melting point can be adjusted by their combination and copolymerization ratio.

[0084] Examples of olefin fibers that can be used as low-melting-point fibers include polypropylene fibers and polyethylene fibers (such as high-density polyethylene fibers, medium-density polyethylene fibers, low-density polyethylene fibers, linear low-density polyethylene fibers, and ultra-high molecular weight polyethylene fibers).

[0085] Alternatively, it can be a substance copolymerized from these fibers. Furthermore, as long as the fibers melt at the vulcanization temperature of the tooth section 7 and the back section 4, there are no particular limitations on their twisting method or composition. In addition, to improve the affinity with adhesives, the surface of these low-melting-point fibers can be subjected to plasma treatment, etc.

[0086] The toothed cloth 11 is bonded to the rubber constituting the tooth 7 through a series of adhesive processes including, for example, the following steps.

[0087] (1) The fiber fabric constituting the toothed cloth 11 is immersed in resorcinol-formalin-rubber latex treatment solution (hereinafter referred to as RFL treatment solution) and then dried.

[0088] Here, the RFL treatment solution preferably contains at least one of the following vulcanizing aids: an aqueous dispersion of a sulfur compound, a quinone oxime compound, a methacrylate compound, a maleimide compound, or a substance obtained by dispersing these vulcanizing aids in water.

[0089] As aqueous dispersions of sulfur compounds, examples include aqueous dispersions of sulfur and tetramethylthiuram disulfide. As quinone oximes, examples include p-quinone dioxime. As methacrylates, examples include ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate. As maleimides, examples include N,N′-m-phenylene bismaleimide and N,N′-(4,4′-diphenylmethane bismaleimide).

[0090] It should be noted that the "water" in the above-mentioned "substance obtained by dispersing the vulcanizing aid in water" may, for example, contain a certain amount of alcohol such as methanol. Therefore, even if the "vulcanizing aid" is insoluble in water, the affinity of the "vulcanizing aid" for water is increased, thus making the "vulcanizing aid" easier to disperse.

[0091] Thus, by adding a vulcanizing aid to the RFL treatment solution, the following effects are expected. That is, by strengthening the interlayer chemical bonding force between the rubber latex component contained in the RFL treatment solution and the outer rubber (referring to the rubber paste or calendered rubber used in the rubber paste treatment in (2) and the coating treatment in (3) described later. If the coating treatment is omitted, it refers to the rubber constituting the tooth 7), the adhesiveness is improved, and the peeling of the tooth cloth 11 is suppressed. As a more desirable effect, it is believed that the chemical bonding force (crosslinking force) of the rubber latex component contained in the RFL treatment solution itself is strengthened, resulting in peeling caused by the destruction of the aforementioned outer rubber, which is the object of adhesion, taking precedence over peeling caused by the cohesion and destruction of the adhesive layer (i.e., interlayer peeling).

[0092] Alternatively, when a vulcanizing agent is added to the RFL treatment solution, the impregnation treatment of the fibrous fabric can be performed in two steps. In this case, firstly, in the first RFL impregnation treatment, no vulcanizing agent is added to the RFL treatment solution. This is to ensure that the thermal curing of the RF component takes precedence over the crosslinking of the rubber latex component in the first treatment step.

[0093] On the other hand, in the second RFL impregnation treatment, compared with the first RFL treatment solution, an RFL treatment solution is used that contains a large amount of rubber latex components and at least one vulcanizing aid selected from sulfur compounds, quinone oxime compounds, methacrylate compounds, and maleimide compounds, or a substance obtained by dispersing a vulcanizing aid in water. It should be noted that the difference in the proportion of rubber latex components in the RFL treatment solution between the first and second impregnation treatments is intended to improve the adhesion of the RFL layer to fibers and rubber with different affinities.

[0094] (2) Two rubber paste treatments (P1 treatment, S1 treatment) are performed, in which an adhesive treatment agent containing a rubber paste obtained by dissolving a rubber composition in a solvent is applied to a fiber fabric and then baked.

[0095] (3) Rubber paste and calendered rubber are sequentially coated onto the surface of the fiber fabric. This process is also called coating treatment. Specifically, "sequentially" means "from the fiber fabric toward the toothed portion 7". Here, if a vulcanizing agent is added to the RFL treatment solution, it is preferable to add the same vulcanizing agent added to the RFL treatment solution to both the rubber paste and the calendered rubber used in this coating treatment. As a result, it is expected that the adhesive strength between the fiber fabric treated with the RFL treatment solution and the rubber paste can be significantly improved.

[0096] It should be noted that the above treatments (1) to (3) do not need to be performed in their entirety. Any one or more of them can be performed as needed. For example, in the case of adding a vulcanizing agent to the RFL treatment solution in treatment (1), since this treatment alone can significantly improve the adhesive strength between the fiber fabric and the rubber, the rubber paste treatment in (2) can be omitted.

[0097] The toothed belt 3 in this embodiment is manufactured using a pre-forming process. The pre-forming process involves the following steps: First, the toothed fabric 11 and the toothed portion 7 are pre-formed using a mold with a toothed die to obtain a pre-formed body. Next, the obtained pre-formed body is rolled onto the mold, and the core yarn 9 is spun in a spiral shape on it. Then, unvulcanized rubber constituting the back 4 is rolled onto it, and the entire assembly is vulcanized in a vulcanizing tank. In this pre-forming process, since the toothed fabric 11 and the toothed portion 7 are pre-formed before vulcanization, it is not necessary to allow the unvulcanized rubber constituting the back 4 to flow inwards (ventral side) between the core yarns 9 and to tighten the toothed fabric 11 to form the toothed portion 7 during vulcanization. Therefore, the distance (pitch) between the core yarns can be narrowed.

[0098] (Tooth profile and tooth pitch BP of tooth section 7)

[0099] The tooth profile of the tooth 7 can be any of the trapezoidal tooth profiles (MXL, XXL, XL, L, H, XH, XXH) specified in JISB1856 (2018) and ISO5294 (1989) and the circular arc tooth profiles (H, P, S, R, G) specified in JISB1857-1 (2015) and ISO13050 (2014). From the viewpoint of reducing the interference between the toothed belt 3 and the toothed pulleys (driving pulley 22, driven pulley 23) and improving the durability of the toothed belt 3, the circular arc tooth profile is preferred.

[0100] Additionally, the tooth pitch BP of tooth 7 (the distance between tooth 7 and tooth 7 along the length direction (X direction) of the belt, refer to...) Figure 2The tooth pitch BP can be selected within the range of 8mm to 14mm. Corresponding circular arc tooth profiles include H8M, P8M, S8M, R8M, G8M (each with a tooth pitch BP of 8mm), H14M, P14M, S14M, G14M (each with a tooth pitch BP of 14mm), etc. Alternatively, a manufacturer-specific tooth profile not specified in the above standards can be used, such as H11M (tooth pitch BP of 11mm). When the tooth pitch BP is less than 8mm, the transmission capacity may be insufficient, and the durability of the toothed belt 3 may decrease. Conversely, when the tooth pitch BP is greater than 14mm, the toothed belt drive device 21 may become larger, and the bending fatigue resistance of the toothed belt 3 may decrease. Considering both the durability of the toothed belt 3 and the miniaturization of the toothed belt drive device 21, a tooth pitch BP of 11mm is preferred, and the tooth profile H11M is preferred.

[0101] Furthermore, the tooth pitch BP of the toothed belt 3 is in the range of -0.4% to +0.1% relative to the tooth pitch PP of the drive pulley 22. More preferably, the tooth pitch BP of the toothed belt 3 is in the range of -0.2% to +0.1% (particularly -0.1% to +0.1%) relative to the tooth pitch PP of the drive pulley 22. That is, it is preferable that the tooth pitch BP of the toothed belt 3 is the same as the tooth pitch PP of the drive pulley 22. It should be noted that, considering the elongation of the toothed belt 3 after use in the toothed belt drive device 21, the tooth pitch BP of the toothed belt 3 can be smaller than the tooth pitch PP of the drive pulley 22.

[0102] Based on the toothed belt 3 constructed as described above, by including carbon fiber in the core wire 9 embedded in the toothed belt 3, the tensile strength is improved and the durability under high load transmission is improved.

[0103] In addition, for core yarn 9, two or more initial twisted yarns are combined and re-twisted so that the twist direction of the initial twist is the same as that of the re-twisted yarn (co-twisting), thereby improving the resistance to bending fatigue.

[0104] In addition, the initial twist coefficient of the core wire 9 of the toothed belt 3 is 0.62 to 1.30 (preferably 0.75 to 1.15, more preferably 0.90 to 1.00), and the retwisting coefficient is 2.06 to 3.95 (preferably 2.45 to 3.55, more preferably 2.80 to 3.20).

[0105] Therefore, while ensuring resistance to bending fatigue, the elongation of the core wire 9 and the toothed belt 3 can be suppressed, thus improving durability. When the initial twist coefficient and the retwist coefficient are less than the above range, the resistance to bending fatigue decreases; conversely, when the initial twist coefficient and the retwist coefficient are greater than the above range, the tensile strength decreases, and the elongation of the toothed belt 3 increases, resulting in reduced durability.

[0106] Furthermore, according to the aforementioned toothed belt drive 21, the tooth pitch BP of the toothed belt 3 is designed to be in the range of -0.4% to +0.1% relative to the tooth pitch PP of the drive pulley 22. With this configuration, even when the toothed belt 3 stretches due to the high load of the toothed belt drive 21 (rear wheel drive of a two-wheeled motorcycle), either the drive pulley 22 (small diameter pulley) or the driven pulley 23 (large diameter pulley) can maintain good meshing between their teeth, thus improving the durability of the toothed belt 3. Outside of this range, sometimes the meshing between the teeth 7 of the toothed belt 3 and the drive pulley teeth 221 of the drive pulley 22 or the driven pulley teeth 231 of the driven pulley 23 deteriorates, reducing the durability of the toothed belt 3.

[0107] Furthermore, the tooth pitch BP of the toothed belt 3 is set to a range of -0.2% to +0.1% (particularly -0.1% to +0.1%) relative to the tooth pitch PP of the drive pulley 22. By making the tooth pitch BP of the toothed belt 3 as consistent as possible with the tooth pitch PP of the drive pulley 22, this range is set to be larger than that of existing products (toothed belts where the tooth pitch BP is smaller than the tooth pitch PP of the toothed pulley to cope with the elongation of the toothed belt due to use). As a result, the deterioration of meshing caused by sand inclusion can be suppressed, and the durability of the toothed belt 3 can be further improved.

[0108] Furthermore, based on the above configuration, even when the outer diameter OD of the drive pulley 22 of the toothed belt drive device 21 is relatively small, ranging from 67mm to 90mm, the durability of the toothed belt 3 can be improved while maintaining a high transmission capacity, thus enabling the toothed belt drive device 21 to be miniaturized.

[0109] Example

[0110] (toothed band)

[0111] In Examples 1-6 and Comparative Examples 1-7, toothed belts with a belt size of 120H11M25 (number of teeth: 120 teeth, tooth shape: H11M, tooth pitch BP: approximately 11 mm, belt width: 25 mm) were manufactured using the following components.

[0112] In addition, in Examples 7 to 10 and Comparative Examples 8 to 9, toothed belts with a belt size of 144H14M21 (number of teeth: 144 teeth, tooth shape: H14M, tooth pitch BP: approximately 14 mm, belt width: 21 mm) were manufactured using the following components.

[0113] (Rubber composition: back teeth)

[0114] [Table 1]

[0115] Table 1

[0116] teeth back Coating treatment HNBR - 80 50 HNBR containing unsaturated carboxylic acid metal salts 100 20 50 Aromatic polyamide short fibers 1 - - stearic acid 1 1 1 Carbon black SRF 2 2 - silicon dioxide - 40 50 calcium carbonate 10 - - Zinc oxide 5 2 2 plasticizer - 10 10 Anti-aging agents 2 2 2 Organic peroxides 2 2 2 total 123 159 167

[0117] Unit: parts by weight

[0118] (Materials used in the rubber composition)

[0119] HNBR: "Zetpol2010" manufactured by Zeon Corporation of Japan, with an iodine value of 11mg / 100mg.

[0120] HNBR containing unsaturated carboxylic acid metal salt: "Zeoforte ZSC2295CX" manufactured by Zeon Co., Ltd., Japan; HNBR: unsaturated carboxylic acid metal salt (mass ratio) = 100:110; iodine value of basic HNBR 28 mg / 100 mg

[0121] Aromatic polyamide staple fiber: "Cornex" manufactured by Teijin Corporation, with an average fiber length of 3mm and an average fiber diameter of 14μm.

[0122] Stearic acid: "Stamanic acid つばき" manufactured by NOF Co., Ltd.

[0123] Carbon black SRF: "Stone S" manufactured by Tokai Carbon Co., Ltd., with an average particle size of 66 nm and an iodine adsorption capacity of 26 mg / g.

[0124] Silica: "Ultrasil VN-3" manufactured by Evonik Degussa Japan Co., Ltd., with a specific surface area of ​​155-195 m². 2 / g

[0125] Calcium carbonate: "Super #1500" manufactured by Maruo Calcium Co., Ltd., with an average particle size of 1.5 μm.

[0126] Zinc oxide: Two types of zinc oxide manufactured by Sakai Chemical Industry Co., Ltd., with an average particle size of 0.55 μm.

[0127] Plasticizer: ADK CIZER RS700 manufactured by ADEKA Co., Ltd.

[0128] Anti-aging agent: p,p'-dioctyldiphenylamine ("Noncondiphenylamine OD3" manufactured by Seiko Chemical Co., Ltd.)

[0129] Organic peroxide: 1,3-bis(tert-butylperoxyisopropyl)benzene, theoretical active oxygen content 9.45%

[0130] (The multifilament yarn that makes up the carbon fiber core)

[0131] The "Treka T700SC-12000" manufactured by Toray Industries, Ltd. has a tensile modulus of elasticity of 230 GPa, a filament fineness of 0.67 tex, a filament count of 12000, and a fineness of 800 tex.

[0132] (Core wire processing)

[0133] It is immersed in a treatment solution obtained by dissolving rubber latex and epoxy resin in toluene.

[0134] (Toothed cloth and its treatment)

[0135] The toothed cloth has the same structure as in Patent Document 1. Furthermore, it undergoes the same RFL treatment (B-1 and B-2) and coating treatment as in Patent Document 1. It should be noted that the P1 and S1 treatments are not performed.

[0136] (Manufacturing of toothed belts)

[0137] In the fabrication of the toothed belts using the preforming process in Examples 1-6 and Comparative Examples 1-7, firstly, an uncured rubber sheet (thickness: 2.55 mm) forming the toothed fabric and teeth was placed in a mold with a toothed die and pressed at 120°C for 160 seconds at a pressing pressure of 4.51 MPa (surface pressure) to produce a preform. Next, the preform was rolled onto the mold, and the core yarn 9 was spun in a spiral pattern on it at a spinning tension of 460-700 N / yarn, a spinning pitch of 2.2 mm / yarn, and a spinning speed of 1.5 m / s. After rolling an uncured rubber sheet (thickness: 1.35 mm) forming the back onto it, the entire assembly was vulcanized in a vulcanizing tank at a vulcanization temperature of 179°C, a vulcanization time of 40 minutes, and a vapor pressure of 0.83 MPa to produce the toothed belt.

[0138] In addition, in the fabrication of the toothed belts using the preforming process in Examples 7-10 and Comparative Examples 8-9, firstly, an uncured rubber sheet (thickness: 2.90 mm) forming the toothed fabric and teeth was placed in a toothed mold and pressed at 120°C for 160 seconds at a pressing pressure of 4.51 MPa (surface pressure) to produce a preform. Next, the preform was rolled onto the mold, and the core yarn 9 was spun in a spiral pattern on it at a spinning tension of 300-960 N / yarn, a spinning pitch of 2.2 mm / yarn, and a spinning speed of 1.5 m / s. After rolling an uncured rubber sheet (thickness: 2.10 mm) forming the back onto it, the entire assembly was vulcanized in a vulcanizing tank at a vulcanization temperature of 179°C, a vulcanization time of 40 minutes, and a vapor pressure of 0.83 MPa to produce the toothed belt.

[0139] (Determination of PLD of toothed belt)

[0140] The PLD (distance from the bottom of the teeth to the center of the core wire) of the toothed belt is measured as follows. First, the toothed belt is cut parallel to its width, and the cross-section is observed under a microscope at 20x magnification. Figure 4As shown, the distances (t1) from the bottom of the tooth to the top of the core wire and (t2) from the bottom of the tooth to the bottom of the core wire are measured. These distances are averaged ((t1+t2) / 2) to calculate the distance (t3) from the bottom of the tooth to the center of the core wire. This distance (t3) is calculated for all core wires cut in the cross-section, and the arithmetic mean of these distances (t3) is then calculated as the PLD of the toothed belt. At this point, the core wires subject to measurement are limited to those from which the entire cross-section can be observed; core wires from which the entire cross-section cannot be observed (partially covering the end face of the belt) are excluded from the measurement.

[0141] (Determination of tooth pitch BP in toothed bands)

[0142] The tooth pitch BP of the toothed belts in Examples 1-6 and Comparative Examples 1-7 was calculated by dividing the overall length (pitch circle circumference) of the toothed belt, as measured by a measuring machine, by the number of teeth on the toothed belt. Both measuring pulleys had 30 teeth each, and the measuring load was set to 966 N. The length of the toothed belt was measured as follows: the drive pulley was rotated at 30 rpm, and after 10 seconds of running-in between the toothed belt and the measuring pulley, the measurement was performed.

[0143] The tooth pitch BP of the toothed belts in Examples 7-10 and Comparative Examples 8-9 was calculated by dividing the overall length (pitch circle circumference) of the toothed belt, as measured by a measuring machine, by the number of teeth on the toothed belt. Both measuring pulleys had 30 teeth each, and the measuring load was set to 1186 N. The length of the toothed belt was measured as follows: the drive pulley was rotated at 30 rpm, and after 10 seconds of running-in between the toothed belt and the measuring pulley, the measurement was performed.

[0144] (Endurance running test)

[0145] Next, the toothed belts of Examples 1-10 and Comparative Examples 1-9 were subjected to comparison with... Figure 6 The toothed belt drive device 21 shown was subjected to a high-load running test using a biaxial high-load running test machine with the same layout, and the technical effect of the toothed belts in Examples 1 to 10 was verified (test results: see Tables 2 and 3).

[0146] (Test conditions: Examples 1-6 and Comparative Examples 1-7 (Examples 7-10 and Comparative Examples 8-9))

[0147] Testing machine: Biaxial high-load traveling testing machine (refer to) Figure 6 )

[0148] Pulley tooth profile (drive pulley, driven pulley): H11M (H14M)

[0149] PLD of pulleys (drive pulley, driven pulley): 1.10mm (1.10mm)

[0150] Pulley pitch (drive pulley, driven pulley): 11.000mm (14.000mm)

[0151] Drive pulley teeth: 26 teeth (30 teeth)

[0152] Driven pulley teeth: 59 teeth (70 teeth)

[0153] Initial tension: 1050N (1150N)

[0154] • Control mode of drive pulley speed:

[0155] (1) Increase from 0 rpm to 3150 rpm in 25 seconds.

[0156] (2) Maintain at 3150 rpm for 230 seconds

[0157] (3) Reduce from 3150rpm to 0rpm in 15 seconds.

[0158] (4) Increase the speed from 0 rpm to 3150 rpm in 20 seconds.

[0159] (5) Reduce from 3150 rpm to 0 rpm in 20 seconds.

[0160] (6) Repeat (4) to (5) 5 times.

[0161] Set the above as one loop and repeat.

[0162] • Control mode for load torque:

[0163] (1) Increase from 0 N·m to 690 N·m in 2 seconds

[0164] (2) Descend from 690 N·m to 220 N·m in 5 seconds.

[0165] (3) Maintain at 220 N·m for 230 seconds

[0166] (4) Descend from 220 N·m to 0 N·m in 15 seconds.

[0167] (5) Increase from 0 N·m to 690 N·m in 2 seconds.

[0168] (6) Descend from 690 N·m to 0 N·m in 35 seconds.

[0169] (7) Repeat (5) to (6) 5 times.

[0170] Set the above as one loop and repeat.

[0171] Sand addition conditions: Type of sand: A mixture of silica sand and cement sand.

[0172] The location for adding sand: the meshing inlet of the driven pulley.

[0173] Amount and frequency of sand addition: Perform 5 cycles at 5g / cycle, then perform 35 cycles without adding sand. Repeat this process afterward.

[0174] (Example 1)

[0175] Four initial-twist yarns are produced by initially twisting 800 tex carbon fiber multifilament yarns along the S direction at 32 twists / meter. These four initial-twist yarns are then combined and re-twisted along the S direction at 51 twists / meter to produce a straight-twist rope with a total fineness of 3200 tex. The twisted rope is then glued using the above method to create a treated rope. Using this treated rope as the core yarn, a toothed belt is manufactured by setting the spinning tension to 630 N / yarn using the method described in the toothed belt manufacturing method above. The tooth pitch of the toothed belt is 10.964 mm, and the PLD (parts density) of the toothed belt is 1.10 mm.

[0176] (Example 2)

[0177] The spinning tension was set to 500 N / spindle, and the toothed belt was manufactured in the same manner as in Example 1. The tooth pitch of the toothed belt was 11.000 mm, and the PLD of the toothed belt was 1.10 mm.

[0178] (Example 3)

[0179] Four initial twisted yarns were made by first twisting 800 tex carbon fiber multifilament yarns along the S direction at 44 twists / meter. The four initial twisted yarns were then combined and re-twisted along the S direction at 67 twists / meter to make a straight twist rope with a total fineness of 3200 tex. Otherwise, a toothed belt was made in the same manner as in Example 2.

[0180] (Example 4)

[0181] Four initial twisted yarns were made by first twisting 800 tex carbon fiber multifilament yarns along the S direction at 21 twists / meter. The four initial twisted yarns were then combined and re-twisted along the S direction at 35 twists / meter to make a straight twist rope with a total fineness of 3200 tex. Otherwise, a toothed belt was made in the same manner as in Example 2.

[0182] (Example 5)

[0183] The spinning tension was set to 580 N / spindle, and the toothed belt was manufactured in the same manner as in Example 1. The tooth pitch of the toothed belt was 10.978 mm.

[0184] (Example 6)

[0185] The spinning tension was set to 460 N / spindle, and the toothed belt was fabricated in the same manner as in Example 1. The tooth pitch of the toothed belt was 11.011 mm.

[0186] (Comparative Example 1)

[0187] Three initial-twist yarns were made by initially twisting 800 tex carbon fiber multifilament yarns along the S direction at 32 twists / meter. These three initial-twist yarns were then combined and re-twisted along the S direction at 39 twists / meter to create a straight-twist rope with a total fineness of 2400 tex. Otherwise, a toothed belt was made in the same manner as in Example 1. The tooth pitch of the toothed belt was 10.964 mm, and the PLD (partial drop) of the toothed belt was 1.00 mm.

[0188] (Comparative Example 2)

[0189] Four initial-twist yarns were made by initially twisting 800 tex carbon fiber multifilament yarns along the S direction at 32 twists / meter. These four initial-twist yarns were then combined and re-twisted along the S direction at 34 twists / meter to create a straight-twist rope with a total fineness of 3200 tex. Otherwise, a toothed belt was manufactured in the same manner as in Example 1. The tooth pitch of the toothed belt was 10.964 mm, and the PLD (partial drop) of the toothed belt was 1.10 mm.

[0190] (Comparative Example 3)

[0191] Four 800 tex carbon fiber multifilament yarns were combined and twisted along the S direction at 16.2 twists / meter to produce a unidirectional twisted rope with a total fineness of 3200 tex. Otherwise, a toothed belt was manufactured in the same manner as in Example 1. The tooth pitch of the toothed belt was 10.964 mm, and the PLD of the toothed belt was 1.08 mm.

[0192] (Comparative Example 4)

[0193] Four initial-twist yarns were produced by initially twisting 800 tex carbon fiber multifilament yarns along the S direction at 32 twists / meter. These four initial-twist yarns were then combined and re-twisted along the Z direction at 51 twists / meter to produce a twisted rope with a total fineness of 3200 tex. Otherwise, a toothed belt was manufactured in the same manner as in Example 1. The tooth pitch of the toothed belt was 10.964 mm, and the PLD (partial drop) of the toothed belt was 1.11 mm.

[0194] (Comparative Example 5)

[0195] Four initial-twist yarns were made by initially twisting 800 tex carbon fiber multifilament yarns along the S direction at 32 twists / meter. These four initial-twist yarns were then combined and re-twisted along the S direction at 107 twists / meter to create a straight-twist rope with a total fineness of 3200 tex. Otherwise, a toothed belt was manufactured in the same manner as in Example 1. The tooth pitch of the toothed belt was 10.964 mm, and the PLD (partial drop) of the toothed belt was 1.11 mm.

[0196] (Comparative Example 6)

[0197] The spinning tension was set to 700 N / spindle, and the toothed belt was manufactured in the same manner as in Example 1. The tooth pitch of the toothed belt was 10.945 mm.

[0198] (Comparative Example 7)

[0199] The spinning tension was set to 420 N / spindle, and the toothed belt was manufactured in the same manner as in Example 1. The tooth pitch of the toothed belt was 11.022 mm.

[0200] (Experimental Results)

[0201]

[0202] (Examples 7-10 and Comparative Examples 8-9)

[0203] In Examples 7-10 and Comparative Examples 8-9, as described above, a toothed belt with a tooth profile of H14M was used, with the retwist coefficient (3.01) and initial twist coefficient (0.94) fixed, and only the spinning tension (tooth pitch of the toothed belt) was made a variable.

[0204] (Example 7)

[0205] The core yarn is the same as in Example 1, with the spinning tension set at 800 N / yarn and the tooth pitch of the toothed belt set at 13.944 mm.

[0206] (Example 8)

[0207] The spinning tension is set to 940 N / yarn, and the tooth pitch of the toothed belt is set to 13.972 mm.

[0208] (Example 9)

[0209] The spinning tension is set to 550N / yarn, and the tooth pitch of the toothed belt is set to 14.000mm.

[0210] (Example 10)

[0211] The spinning tension is set to 350N / yarn, and the tooth pitch of the toothed belt is set to 14.014mm.

[0212] (Comparative Example 8)

[0213] The spinning tension is set to 960 N / yarn, and the tooth pitch of the toothed belt is set to 13.930 mm.

[0214] (Comparative Example 9)

[0215] The spinning tension is set to 300N / yarn, and the tooth pitch of the toothed belt is set to 14.028mm.

[0216] (Experimental Results)

[0217] [Table 3]

[0218] Table 3

[0219]

[0220] (Inspection)

[0221] Examples 1-6 have a lifespan of over 80 hours, and since the failure mode is missing teeth, it is relatively easy to handle abnormalities such as replacing the toothed belt. On the other hand, Comparative Examples 1-7 have a lifespan of less than 70 hours, and the failure mode is unpredictable, such as disconnection.

[0222] In Comparative Example 1, it was considered that the tensile strength was insufficient because a thin core yarn with three strands of initial twist was used. In Comparative Example 2, it was considered that the bending fatigue resistance was insufficient because the retwist coefficient was too small. In Comparative Examples 3 and 4, it was considered that the bending fatigue resistance was insufficient because the core yarn was twisted in one direction or in a ply twisting manner. In Comparative Example 5, it was considered that the tensile strength was insufficient because the retwist coefficient was too large, or the elongation of the toothed belt increased, resulting in poor meshing. Comparative Examples 6 and 7 were examples from Example 1 where only the tooth pitch of the toothed belt was changed, but the tooth pitch of the toothed belt was outside the range of -0.4% to +0.1% relative to the tooth pitch of the toothed pulley, thus reducing the service life.

[0223] On the other hand, it is believed that Example 1 can simultaneously improve tensile strength and bending fatigue resistance, and also maintain meshing relatively well. Furthermore, in Example 2, it is believed that by matching the tooth pitch of the toothed belt with the tooth pitch of the pulley, the deterioration of meshing caused by sand inclusions can be suppressed, thus further improving the service life. In addition, Examples 5 and 6 are examples of Example 1 where only the tooth pitch of the toothed belt was changed; the tooth pitch of the toothed belt relative to the tooth pitch of the toothed pulley is within the range of -0.2% to +0.1%, and good results were obtained.

[0224] Regarding Examples 7-10, Example 9, where the toothed belt pitch is ±0% of the toothed pulley pitch, has the longest lifespan; as this difference increases, the lifespan decreases. On the other hand, regarding Comparative Examples 8 and 9, when the toothed belt pitch is outside the range of -0.4% to +0.1% of the toothed pulley pitch, the lifespan decreases significantly. Furthermore, the failure mode is unpredictable disconnection.

[0225] The present invention has been described in detail with reference to specific embodiments, but it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

[0226] This application is based on Japanese Patent Application No. 2020-094540 filed on May 29, 2020 and Japanese Patent Application No. 2021-083225 filed on May 17, 2021, the contents of which are incorporated herein by reference.

[0227] Symbol Explanation

[0228] 3. Toothed belt

[0229] 4. Back

[0230] 5 Short Fibers

[0231] 6 warp yarns

[0232] 7. Teeth

[0233] 8 weft yarns

[0234] 9-core wire

[0235] 11 Toothed Cloth

[0236] 21 Toothed belt drive device

[0237] 22 Drive pulley

[0238] 23 Driven pulley

Claims

1. A toothed belt drive device comprising a toothed belt and two or more toothed pulleys, wherein the toothed belt has a core wire extending and embedded in the belt length direction and two or more belt teeth arranged at predetermined intervals in the belt length direction, and the toothed pulleys have two or more pulley teeth on their outer periphery opposite to the belt teeth and are wound around the toothed belt, the toothed belt drive device being used for rear-wheel drive of a two-wheeled motorcycle, wherein... The core wire comprises a carbon fiber rope formed by combining and re-twisting two or more initially twisted yarns containing carbon fibers. The initial twist of the yarn is in the same direction as the retwisted yarn. The initial twist coefficient is 0.62 to 1.

30. The retwisting coefficient is 2.45–3.

55. The toothed belt has a pitch that is in the range of -0.2% to +0.1% relative to the toothed pulley around which it is wound. The toothed belt has the best durability when it is around ±0%.

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