JP2008241031A - Belt for power transmission - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide method of manufacturing a belt for power transmission which can prevent such a problem that a rubber is exposed and thus crack is caused in joint of a cover canvas because of being adapted to overlap and adjoin ends of the cover canvas with each other which laminates on center belt surface and which can easily dispose the joint of the cover canvas on a concave grooved portion of the center belt. <P>SOLUTION: In the belt for the power transmission which comprises the center belt 3 and a plurality of blocks which engages with the concave grooved portion 17 of the center belt 3 and are provided along longitudinal direction at predetermined pitch and of which the cover canvas 10 is coated on at least one surface of the center belt 3, it is configured so as to use the cover canvas including uneven shape in the vicinity of the joint in advance so that the ends of the cover canvas 10 are overlapped and adjoined with each other and simultaneously the joint is disposed on the concave grooved portion 18 of the center belt. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a power transmission belt in which blocks are fitted and fixed at a predetermined pitch along a longitudinal direction of a center belt, and more specifically, a block is formed by arranging a joint position of a cover canvas in a center belt at a predetermined position. The present invention relates to a method of manufacturing a power transmission belt in which rattling between the belt and the center belt is suppressed.

  The belt used in the belt type continuously variable transmission is used by being wound around a transmission pulley that changes the effective diameter of the pulley by adjusting the V groove width of the pulley and adjusts the transmission gear ratio. Because the side pressure from the belt increases, the belt must withstand a large side pressure. In addition to continuously variable speed applications, it is necessary to use a belt that can withstand a particularly large load in applications for power transmission where the life of conventional rubber belts is too short.

  Among such belts, there is a tension transmission type power transmission belt in which a block is fixed to the center belt to increase the strength in the belt width direction. A block made of an elastomer that is relatively harder than the elastomer used for the center belt is fixed to the center belt embedded in the elastomer using a fixing material such as a bolt or a rivet.

  The center belt of such a power transmission belt is made of an elastomer such as rubber, and the block is fitted and fixed. By running the belt, the center belt repeatedly receives compressive and shearing forces from the block, generating permanent distortion in the elastomer forming the center belt, weakening the fixing force between the block and the center belt, and wobbling the block This can lead to rattling, which can lead to increased noise when the belt travels, and can cause the center belt to crack and cut.

  In particular, when the belt is wound around a small pulley diameter, the inner peripheral surface side of the center belt is sandwiched between the blocks, stress is concentrated and a large frictional force is generated, and the rubber constituting the center belt deteriorates. Cracks occurred or belts were cut.

  Therefore, in order to protect such a center belt and prevent loosening between the center belt and the block, Patent Document 1 provides a cover canvas on the surface of the center belt, and the material is aramid fiber. It is made of canvas.

  Further, Patent Document 2 discloses a belt in which a lap joint is used as a cover canvas joint on the surface of the center belt, and the wrap margin is 1 mm or less. By setting the lapping margin to 1 mm or less, the thickness change due to lapping is suppressed to reduce the influence on the block, and the problem of rocking of the block, generation of noise, and cracking of the center belt are prevented. It is intended.

JP 2000-291743 A JP 11-325191 A

  However, as disclosed in Patent Document 1, the cover canvas provided on the center belt is a canvas made of aramid fibers, so that it can withstand power transmission and wears the center belt even if friction occurs with the block. The belt life can be greatly extended.

  The center belt has a concavo-convex shape such as a concave portion provided at a predetermined pitch for meshing with the block. In the butt joint, the rubber is exposed, so that cracks are generated from the rubber, and the life of the center belt is shortened. In addition, since the aramid fiber is thicker and thicker than other fibers in the case of lap-joined, if the joint part between the end parts is lap-joined, it becomes a particularly thick part, and the center belt There is a problem that it is difficult to follow the uneven shape. Moreover, it is difficult to arrange the joint portion of the cover canvas at a predetermined position when manufacturing the belt.

  Therefore, a method of manufacturing a power transmission belt capable of allowing the joint portion of the cover canvas, which are overlap-joined, to follow the mold having the unevenness forming the center belt and arranging the joint portion at a predetermined position. The purpose is to provide.

  In order to solve the above-mentioned problems, claim 1 of the present invention provides a center belt having at least one surface formed with ridges and recesses in the belt width direction alternately, and the recesses of the center belt. In a method for manufacturing a power transmission belt comprising a plurality of blocks provided at a predetermined pitch along a longitudinal direction to be engaged, and at least one surface of a center belt is covered with a cover canvas, the cover canvas is overlapped at the ends. It is characterized in that the joint belt is shaped and formed in advance with the concave and convex shape of the center belt at the joint, and the joint is disposed on the concave portion of the center belt. To do.

  According to a second aspect of the present invention, in the method for manufacturing a power transmission belt according to the first aspect, the cover canvas is a canvas made of aramid fibers.

  In the third aspect, the outermost end portion of the cover canvas, which is overlapped on the outside, is disposed within one third of the height of the ridge from the concave bottom of the center belt. The power transmission belt manufacturing method according to claim 1 or 2.

  In claim 4, the outermost end portion of the cover canvas overlapped on the outside is overlapped with the end portions, and the upper end portion is within 1/3 of the height of the ridge from the concave bottom of the center belt, and The power transmission belt manufacturing method according to claim 1, wherein the power transmission belt is disposed in front of the concave bottom in the belt traveling direction.

  As in the first aspect of the present invention, as the cover canvas covering the surface of the center belt, the joint portion is previously formed with a concavo-convex shape along the shape of the center belt, and the thickness is increased by overlapping and joining. Even if it is increased, it is easy to follow, and the position of the joint portion can be easily arranged at a predetermined position of the center belt, so that a product free from variations in quality due to the shift of the position of the joint portion can be obtained.

  In claim 2, the material of the cover canvas is an aramid fiber, but the aramid fiber is a material that is rigid and difficult to conform to the uneven shape, and this tendency is particularly noticeable in a joined portion that is overlapped. By pre-forming the belt, it is possible to sufficiently conform to the uneven shape, and it is possible to manufacture a belt having no difference from the other portions even at the joint portion in the entire circumference of the belt.

  According to the third aspect of the present invention, since the outermost portion of the cover canvas overlapped on the outer side is positioned near the concave bottom of the center belt, the power transmission belt that is unlikely to cause the problem of peeling of the cover canvas pressed by the block is provided. Can be manufactured.

  According to the fourth aspect, the outermost end portion of the cover canvas overlapped on the outer side is disposed on the front side of the concave bottom with respect to the belt traveling direction, and is disposed at a position where the load is less when the belt is traveling. The problem of the center belt being damaged due to the peeling off of the cover canvas can be made difficult.

  FIG. 1 is a schematic perspective view showing an example of a power transmission belt 1 manufactured by the manufacturing method of the present invention, and FIG. 2 is a side sectional view thereof. The power transmission belt 1 of the present invention is attached to two center belts 3 of the same width formed by embedding a rope-shaped core body 5 in an elastomer 4 in a spiral shape, and attached to the center belt 3 at a predetermined pitch. It is composed of a plurality of blocks 2. The side faces 6 and 7 of the block have fitting grooves 8 and 9, and the center belt 3 is mounted in the fitting grooves. Both side surfaces 6 and 7 of the block 2 are inclined surfaces that come into contact with the V-grooves of the pulley, receive power from the driven pulley, pull the center belt 3 that is locked and fixed, and drive pulley Is transmitted to the driven pulley. A cover canvas 10 which is a feature of the present invention is laminated on the surface of the center belt 3 integrally with the center belt 3.

  As shown in FIG. 1, the block 2 includes an upper beam portion 11 and a lower beam portion 12, and a center pillar 13 in which the central portions of the upper and lower beam portions 11 and 12 are connected to each other. As described above, the fitting grooves 8 and 9 of the center belt 3 are formed, and the groove upper surface and the groove lower surface in the fitting grooves 8 and 9 are formed on the groove 15 and the lower surface provided on the upper surface of the center belt 3. Convex ridges 17 and 18 that engage with the provided concave ridges 16 are provided.

  FIG. 3 is an example of another belt, and a pair of side pillars 22 and 23 extend upward from both ends of the beam portion 21, and the upper ends of the side pillars 22 and 23 respectively extend toward the center of the block 2. The extending lock portions 24 and 25 are provided to face each other. The beam portion 21, the side pillars 22 and 23, and the lock portions 24 and 25 form a fitting groove 20 into which the center belt 3 is fitted. The center belt 3 is inserted into the fitting groove 20 through the opening between the lock portions 24 and 25 and attached. Further, convex portions 27 are respectively provided on the side of the fitting grooves 20 of the lock portions 24 and 25, and the convex portions 27 are fitted to the concave strip portions 26 provided on the center belt 3 at a predetermined pitch. To do. As a result, the center belt 3 is not easily removed from the block 2 after being mounted. A cover canvas 10 is laminated on the surface of the center belt 3 integrally with the center belt 3.

  A material used as the elastomer 4 of the center belt 3 is a single material such as chloroprene rubber, natural rubber, nitrile rubber, styrene-butadiene rubber, hydrogenated nitrile rubber, chlorosulfonated polyethylene, alkylated chlorosulfonated polyethylene or the like. And rubber or polyurethane rubber blended appropriately. And as the core 5, a rope selected from polyester fiber, polyamide fiber, aramid fiber, glass fiber, steel wire and the like is used. The core body 5 may be made of a woven fabric, a knitted fabric, a metal thin plate, or the like of the above-mentioned fiber other than a rope embedded in a spiral shape.

  In the present embodiment, the case where the two center belts 3 and 3 are used and mounted in the fitting groove 20 of the block 2 is described. However, another center belt is used. It doesn't matter.

  As shown in FIG. 2, the center canvas 3 is provided with cover canvases 10 on both upper and lower sides, so that the center belt is protected from friction between the center belt and the block that occurs during belt running. By adopting such a configuration, wear of the center belt 3 due to friction with the block 2 is prevented. In particular, when a whisker-like reinforcing material such as zinc oxide whisker is blended in the block 2, the wear on the center belt side tends to become very large due to the whisker while rubbing against the center belt. Can be prevented. Further, by using an aramid fiber as the material for the cover canvas 10, the effect of preventing wear can be further enhanced, and failure due to cutting of the belt can be reduced.

  Examples of the cover canvas 10 that can be used include plain woven fabrics, twill woven fabrics, and satin woven fabrics. All of them need not be aramid fibers, and for example, a form using aramid fibers in the wefts in the longitudinal direction of the belt can be mentioned. The aramid fiber may be either a para aramid fiber or a meta aramid fiber, but it is preferable to use a multifilament yarn obtained by converging an original yarn of 0.3 to 1.2 denier. In addition to the aramid fiber, a yarn in which a polyamide fiber or a urethane elastic yarn is mixed and twisted can be used, but the ratio of the aramid fiber is preferably 20 to 80% of the total weight of the weft yarn. If the thickness of the raw yarn is less than 0.3 denier, the tensile strength of the cover canvas 10 in the longitudinal direction of the belt is lowered and the wear resistance is inferior. Conversely, if the thickness exceeds 1.2 denier, the rigidity of the cover canvas 10 becomes too high after weaving, which may cause the balance between the warp and weft to become unbalanced or cause wrinkles in the canvas. It is not preferable.

  Examples of the para-aramid fiber include Kevlar, Technora and Twaron as trade names, and examples of the meta-aramid fiber include Nomex and Conex as trade names.

  Further, the warp in the belt width direction may be filament yarn made of aramid fibers such as para-aramid fibers and meta-aramid fibers in the same manner as the weft yarns, and other polyamide fibers such as 6 nylon, 6, 6-nylon and 12 nylon. Filament yarns such as polyvinyl alcohol fiber and polyester fiber can be used.

  Adhesion treatment is performed in order to laminate and bond the cover canvas 10 having such a configuration to the surface of the center belt. Examples of the adhesion treatment include treatment with an RFL solution, an isocyanate solution, or an epoxy solution. The RFL solution is a mixture of an initial condensate of resorcin and formalin mixed with latex. Examples of latex used here include styrene / butadiene / pyridine terpolymers, hydrogenated nitrile rubber, chlorosulfonated polyethylene, epichlorohydrin, and the like. The latex. In addition, a glueing process, a soaking process, and a coaching process in which a rubber paste dissolved in a solvent is attached to the surface of the cover canvas 10 can also be cited as an adhesive process.

  In these adhesion treatments, the friction coefficient between the block and the center belt cover canvas can be lowered by blending a friction coefficient reducing material with an adhesion treatment agent such as an RFL solution, an isocyanate solution, an epoxy solution, or rubber glue. Further, it is possible to prevent wear due to friction between the block containing the whisker such as zinc oxide and the center belt. Specific examples of the friction coefficient reducing material include polytetrafluoroethylene, polytrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, tetrafluoroethylene-ethylene copolymer. Fluorine resin such as polymer, ceramic powder, glass beads, ultra high molecular weight polyethylene, graphite, molybdenum disulfide, phenol resin, glass fiber, carbon fiber, aramid fiber, etc., at least one of these, Preferably, ceramic powder, glass beads, ultrahigh molecular weight polyethylene, graphite, molybdenum disulfide, polytetrafluoroethylene and other fluororesins, and at least one of phenolic resins, more preferably polytetrafluoroethylene. It is preferable to use a fluorocarbon resin such as La fluoroethylene.

  Examples of the method for producing the power transmission belt of the present invention include the following methods. The cover canvas 10 and the elastomer sheet 4 are placed on a mold 100 having projections and depressions and pressed to create a composite sheet 101 with a canvas serving as an inner layer having projections and depressions including a concave portion on one side (FIG. 4). ). The composite sheet 101 is cut so as to have a predetermined circumferential length, and is wound around a cylindrical mold 102 using, for example, a spinning device as shown in FIG. A rubber layer (not shown) is wound and vulcanized to form a sleeve.

  The side without the irregularities of the removed sleeve 103 is polished as necessary to have a predetermined thickness, and the elastomer sheet 4 as the outer layer and the cover canvas 10 are laminated (FIG. 6). Pressing between the lower mold 100 having an uneven shape meshing with the unevenness created above and the upper mold 104 having an uneven shape for providing unevenness on the newly laminated elastomer sheet 4 to the outer layer side As well as forming the recesses and protrusions including the recess 18, the elastomer is vulcanized (FIG. 7). The entire circumference of the belt sleeve can be vulcanized by vulcanizing the unvulcanized portion in order. Then, the center belt can be manufactured by cutting to a predetermined width.

  In the step of placing the cover canvas 10 in the above-described process on the mold 100 having irregularities, the mold is used to place the joint S between the ends of the cover canvas in the concave portion of the center belt as shown in FIG. It is necessary to arrange on the convex part. In the present invention, a concavo-convex shape is formed in the vicinity of the joint S of the cylindrical canvas with the ends joined together, and when the shape is placed in accordance with the shape of the mold, the joint is just the mold. It is characterized in that the canvas arranged on the ridge is used as a cover canvas. By adopting such a configuration, it is possible to very easily align the joint portion S in the cover canvas.

  Examples of a method for forming a concavo-convex shape in advance in the joint portion S of the cover canvas 10 include the following method, which can be shaped relatively easily. The ends of the canvas are overlapped with each other by a predetermined width, and the ends are heat-sealed by using a press mold having a desired concavo-convex shape, and at the same time shaping is performed. Concave and convex shapes are also formed at the same time as heat fusion, but this may be performed in a separate process. In this way, the cover canvas having an uneven shape at the joint is fitted to the unevenness of the mother mold, and the cylindrical cover canvas is attached to the mold.

  A power transmission belt can be finally obtained by fitting the block into the concave portion of the center belt obtained as described above.

  In the above description, an example of the process of pressing the cover canvas and the rubber sheet to form the composite sheet 101 with the cover canvas is described, but a cylindrical mold having irregularities on the peripheral surface is used. It is also possible to place the joint portion in a desired position by fitting the cover canvas having a concave and convex shape in the joint portion with the concave and convex portions of the cylindrical mold, and similarly, the position of the joint portion in the cover canvas of the present invention There is an effect that the matching can be easily performed.

  FIG. 8 is a side view of a center belt showing an aspect according to claim 3 of the present invention. According to claim 3 of the present invention, the cover canvases 10 are overlapped to form the joint portion S, and the outermost end portion 10a of the canvas overlapped on the outer side is the bottom in the concave strip portion 16 of the center belt 3. It arrange | positions in the concave bottom part 16a vicinity, and, specifically, the said most end part 10a is arrange | positioned in the position within 1/3 of the protruding item | line height H from the concave bottom part 16a.

  While the belt is running on the pulley, the block 2 is driven by the pulley in the driving pulley, and the center belt 3 is pulled by the block 2, and the center belt 3 fitted to the block 2 is pulled. In the recess 16, a shearing force is generated on the front side in the belt traveling direction. On the other hand, in the driven pulley, on the contrary, the center belt 3 pulls the block 2 held between the pulleys, so that the concave strip portion 16 of the center belt 3 fitted to the block 2 has a rear side in the belt traveling direction. A shearing force is generated. Since the influence of these truncation forces increases as the distance from the concave bottom portion 16a increases, if the extreme end portion 10a of the cover canvas 10 is disposed at a location where the shearing force is large, the cover belt 10 is liable to be peeled off from it, and the center belt 3 is damaged. Problems that lead to cutting and disconnection are likely to occur. Therefore, as described above, the position of the end 10a of the cover canvas 10 that is overlapped on the outside is arranged in the vicinity of the concave bottom portion 16a so that peeling does not easily occur.

  In addition, the driving pulley and the driven pulley, if any, have a larger shearing force generated in the driven pulley, and the center belt concave portion 16a has a failure in cracking at the rear position in the belt traveling direction. In view of the fact that it is easy to occur, it can be said that the cover canvas 10 most end portion 10a is more preferably disposed on the front side in the belt traveling direction as in the fourth aspect.

  The block 2 is a block basically made of a resin composition, and the resin material is formed on the surface of the block 2 made only of the resin composition and the surface of the insert material made of metal or the like in the resin composition and having the same general shape as the block. The one coated with may be used. In general, a block having no insert material has lower rigidity than a block having the insert material, and is greatly affected by the case where the joint portion S of the cover canvas 10 is in contact with the block 2. In that sense, it can be said that the problem in the case where the joint portion S is located in the concave strip portion 15 of the center belt 3 is a problem that appears remarkably in the case of the block 2 having no insert material. Therefore, the effect of the present invention is greater in the block having no insert material.

  The insert material is an insert material that provides the side pressure resistance and bending rigidity of the block 2, and the materials include aluminum alloys, ceramics, composite materials of ceramics and aluminum, materials such as carbon fiber reinforced resin and iron. Can be mentioned.

In terms of imparting lateral pressure resistance and bending rigidity, a metal material is preferable. Among the metal materials, the elastic modulus of aluminum alloy is 7000 kgf / mm ² and the specific gravity is 2.8, whereas iron has an elastic modulus of 22000 kgf. / Mm ² and a specific gravity of 7.8, and it can be said that iron is stronger in terms of strength. However, for belts that rotate at high speeds, the weight of the belt greatly affects the life of the aluminum, which is advantageous in terms of weight reduction. It is preferable to use an alloy. However, the metal material is excellent in terms of imparting side pressure resistance and bending rigidity, and it is preferable to use a block 2 in which a predetermined portion of the insert material is coated with a resin material.

  When the resin material is arranged at a predetermined location, if an insert material made of a metal material that is slightly smaller than the size of the block 2 is used to cover almost the entire surface with the resin material, the resin material is partially covered and arranged. Compared to the above, problems such as peeling of the resin material are less likely to occur, which is a preferable mode. However, even if it is the entire surface, the part where the insert material is fixed when the resin material is coated on the manufacturing process is in contact with the part where the insert material is exposed. There is no problem as long as the portion that comes into contact with the pulley and the portion where the blocks come into contact with each other are covered with resin.

  Of course, as described above, the block 2 may be made of only a resin material having no insert material as described above. When using the block 2 in which the insert material is not embedded, the weight can be reduced as compared with the belt using the block in which the insert material is embedded. However, it is suitable for applications with relatively light loads and high rotation, such as motorcycles.

  The resin material has a relatively large friction coefficient and excellent wear resistance, and has a higher rigidity than the elastomer 4 constituting the center belt 3, specifically, a hard rubber having a hardness of 90 ° JIS A or more, a hard polyurethane resin, Liquid crystal resin, phenol resin, epoxy resin, polyester resin, acrylic resin, methacrylic resin, polyamide resin, polyamideimide (PAI) resin, polyphenylene sulfide (PPS) resin, polybutylene terephthalate (PBT) resin, polyimide (PI) resin, Rubbers and synthetic resins such as polyether sulfone (PES) resin and polyether ether ketone (PEEK) resin are used.

  Among these, a thermoplastic resin such as a polyamide resin is used to manufacture the block by an injection molding method in order to efficiently manufacture the block. In addition, it is preferable to use a resin that has a low coefficient of friction, excellent wear resistance, is rigid, has elasticity in bending, and does not easily break. 6-nylon is preferred.

  In addition, these resins contain cotton yarn, chemical fibers such as polyamide fibers and aramid fibers, woven fabrics made of glass fibers, metal fibers, carbon fibers, etc., fillers, whiskers, silica, inorganic materials such as calcium carbonate, etc. Made of reinforced resin.

  In the present invention, it is possible to mix a fibrous reinforcing material or a whisker-shaped reinforcing material in the resin material forming the block as described above, and the fibrous reinforcing material is blended in the range of 15 to 40% by weight. To do. If it is less than 15% by weight, there is a problem that the reinforcing effect is small and the wear resistance of the block is not sufficient, and if it exceeds 40% by weight, it becomes difficult to blend into a resin or injection molding becomes difficult. Because there is a problem, it is not preferable.

  Examples of the fibrous reinforcing material to be blended with the synthetic resin include aramid fibers, carbon fibers, glass fibers, polyamide fibers, and polyester fibers. Among them, the resin that constitutes the block described above is a preferable example of using 4,6-nylon and carbon fiber in combination with carbon fiber to improve the water-absorbing defect of 4,6-nylon and greatly improve the rigidity. It is possible to make use of the wear resistance, impact resistance and fatigue resistance of 4,6-nylon. In addition to the organic fibers described above, inorganic fibers such as zinc oxide whisker, potassium titanate whisker, and aluminum borate whisker may be blended as the fibrous reinforcing material.

  In addition, the lubricity of the block 2 can be improved by mixing at least one selected from molybdenum disulfide, graphite, and fluorine resin. Examples of the fluorine-based resin include polytetrafluoroethylene (PTFE), polyfluorinated ethylene propylene ether (PFPE), tetrafluoroethylene hexafluoropropylene copolymer (PFEP), polyfluorinated alkoxyethylene (PFA), and the like. .

  The present invention can be applied to the manufacture of belts that change the effective diameter of pulleys and transmit large torque, such as continuously variable transmissions for automobiles, motorcycles, and agricultural machines.

It is a perspective schematic diagram showing an example of a power transmission belt according to the present invention. It is a sectional side view of a power transmission belt. It is a perspective schematic diagram showing other examples of the power transmission belt concerning the present invention. It is sectional drawing when the unevenness | corrugation of the inner layer side was shape | molded with the metal mold | die. It is a schematic diagram of spinning the core. It is sectional drawing of the place which laminated | stacked the rubber sheet and cover canvas of the outer layer side. It is sectional drawing of the place which shape | molds the unevenness | corrugation by the side of an outer layer with a metal mold | die. It is a side view of the center belt which shows the aspect concerning Claim 3. It is a side view of the center belt which shows the aspect concerning Claim 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power transmission belt 2 Block 3 Center belt 4 Rubber 5 Core body 6 Side surface 7 Side surface 8 Fitting groove 9 Fitting groove 10 Cover canvas 10a Endmost part 11 Upper beam part 12 Lower beam part 13 Center pillar 15 Concave part 16 Concave section 17 Convex section 18 Convex section 100 Mold 101 Composite sheet 102 Mold 103 Sleeve 104 Mold S Joint

Claims (4)

  A center belt in which ridges and recesses in the belt width direction are alternately formed on at least one surface, and a plurality of blocks provided at a predetermined pitch along the longitudinal direction engaging with the recesses of the center belt. In the method of manufacturing a power transmission belt in which at least one surface of the center belt is covered with a cover canvas, the end portions of the cover canvas are overlapped and joined to each other, and the uneven shape of the center belt is previously formed on the joint. A method for producing a power transmission belt, characterized in that the belt is shaped and used in such a manner that the joint portion is disposed in the concave portion of the center belt.   The method for manufacturing a power transmission belt according to claim 1, wherein the cover canvas is a canvas made of aramid fibers.   2. The outermost cover canvas overlapped on the outer side of the cover canvas with the end portions overlapped and joined is disposed within 1/3 of the height of the ridge from the concave bottom of the center belt. The manufacturing method of the power transmission belt of Claim-2.   Of the cover canvas with the ends overlapped and joined, the outermost end portion of the cover canvas overlapped on the outside is within 1/3 of the height of the ridge from the concave bottom of the center belt, and more than the concave bottom. The method for producing a power transmission belt according to claim 1, wherein the power transmission belt is disposed on the front side in the belt traveling direction.

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