Toothed belt and manufacturing method of the same

Abstract

To provide a toothed belt which can be produced easily and is excellent in durability even when used as a high load application and made of polyurethane.SOLUTION: A toothed belt 1 having tooth parts 1 in each of which a tooth polymer layer 3 containing polyurethane is covered with a tooth cloth 2 containing fluororesin fibers and low melting point fibers is produced. The low melting point fibers include a low melting point component which may be melted or softened at 100 to 180°C. The low melting point component may be at least one selected from a group comprising a polyester resin, a polyamide resin, and a polyolefin resin. The tooth cloth 2 is a multiple-woven fabric including first wefts containing fluororesin fibers and second wefts which do not contain fluororesin fibers. The first wefts may be located closer to the surface side than the second wefts. A number of the second wefts may be larger than a number of the first wefts. The low melting point fibers may be composite fibers containing fibers having a melting point of 200°C or higher.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a polyurethane toothed belt whose tooth surface (the inner peripheral surface or the side that meshes with a toothed pulley) is covered with a tooth cloth, and a method for producing the same. [Background technology]

[0002] Known types of power transmission belts include friction power transmission belts such as flat belts, V-belts, and V-ribbed belts, as well as meshing power transmission belts such as toothed belts. While friction power transmission belts transmit power with a few percent of slippage between them and the pulley, meshing power transmission belts can reliably transmit the rotation of the driving pulley to the driven pulley, and so are used according to the application.

[0003] A toothed belt is formed of a back part made of an elastic material such as rubber, elastomer, or resin, teeth arranged at regular intervals in the belt length direction, and a core wire (twisted cord) embedded in a spiral shape in the back part. Examples of materials for forming the back part and teeth part of a toothed belt include rubber, thermosetting polyurethane (cast polyurethane), and thermoplastic polyurethane. Of these, thermoplastic polyurethane belts have the disadvantage that they cannot be used at high temperatures, and their applications are limited. Thermosetting polyurethane toothed belts are preferred for outdoor applications because they have high heat resistance and excellent weather resistance. In addition, unlike rubber toothed belts, which are limited to black in color because they contain carbon black, thermosetting polyurethane toothed belts can be colored in various colors and have high designability, and are increasingly being used instead of chains for rear wheel drive of bicycles. Thus, depending on the application, thermosetting polyurethane toothed belts may not be able to be replaced by rubber toothed belts or thermoplastic polyurethane toothed belts.

[0004] The surface (inner peripheral surface) of the toothed portion of rubber toothed belts is often covered with tooth cloth (reinforcing cloth). In contrast, the toothed portion of thermosetting polyurethane toothed belts often has no tooth cloth and the polyurethane is exposed. The difference is that toothed belts made of polyurethane, which is a material with excellent abrasion resistance, can easily ensure durability without tooth cloth, while it is difficult to provide tooth cloth to thermosetting polyurethane toothed belts due to the manufacturing method.

[0005] In the manufacture of rubber toothed belts, a laminated body of tooth cloth, cords, and uncrosslinked rubber sheets is pressed against the outer periphery of a mold having grooves from the outer periphery, whereby the highly viscous rubber passes between the cords and flows toward the mold, and the tooth cloth can be pressed into the tooth grooves of the mold, making it easy to manufacture a toothed belt whose inner periphery is covered with tooth cloth. Similarly, when using thermoplastic polyurethane, the tooth cloth can be pressed into the mold by thermoplastic polyurethane in a highly viscous and fluid state. In contrast, in the case of a toothed belt made of thermosetting polyurethane, the liquid urethane prepolymer passes through the weave of the tooth cloth, so the tooth cloth cannot be pressed into the tooth grooves of the mold, and the tooth cloth is buried in the polyurethane.

[0006] In order to cover the inner peripheral surface of a thermosetting polyurethane toothed belt with a tooth cloth, it is necessary to make the tooth cloth conform to the tooth grooves of a mold in advance. For example, Japanese Patent Application Laid-Open No. 58-33442 (Patent Document 1) discloses a method in which a reinforcing cloth coated with a polyurethane elastomer is shaped, the polyurethane elastomer is also attached to the tooth grooves of the mold, the shaped reinforcing cloth is wrapped around the outer periphery of the mold, and then the cloth is pressed and heated from the outside. In addition, Japanese Patent Application Laid-Open No. 6-213283 (Patent Document 2) discloses a method in which a reinforcing cloth having an elastomer-impermeable resin layer is shaped, a flexible adhesive with a short curing time is solidified and interposed at both ends of the reinforcing cloth to reinforce its shape, and the reinforcing cloth is then wrapped around the mold. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 58-33442 [Patent Document 2] Japanese Patent Application Publication No. 6-213283 Summary of the Invention [Problem to be solved by the invention]

[0008] However, when the methods disclosed in these documents are adopted, the reinforcing cloth is reinforced using a polyurethane elastomer or a resin layer, which causes a problem of a large increase in the number of steps required to manufacture the belt. Therefore, polyurethane toothed belts used in low-load applications in particular are often belts that do not have a toothed cloth. However, there is also a demand for polyurethane toothed belts that can be used in high-load applications, and a belt that can be manufactured more simply and has high durability even in high-load applications is desired.

[0009] SUMMARY OF THE PRESENT EMBODIMENTS Accordingly, an object of the present invention is to provide a polyurethane toothed belt which can be easily produced and has excellent durability even in high load applications, and a method for producing the same. [Means for solving the problem]

[0010] In order to achieve the above object, the present inventors discovered that a polyurethane toothed belt having excellent durability even in high-load applications can be easily manufactured by covering a tooth polymer layer containing polyurethane with a tooth cloth containing a fluororesin fiber and a specific low-melting point fiber, and thus completed the present invention.

[0011] That is, the toothed belt according to embodiment [1] of the present invention is as follows: A toothed belt in which a tooth polymer layer is covered with a tooth cloth, the tooth polymer layer comprises polyurethane; The tooth cloth contains fluororesin fibers and low melting point fibers, and The low melting point fiber contains a low melting point component that can be melted or softened at 100 to 180°C.

[0012] The aspect [2] of the present invention is an aspect in which, in the aspect [1], the low melting point component is at least one selected from the group consisting of polyester-based resins, polyamide-based resins, and polyolefin-based resins.

[0013] The embodiment [3] of the present invention is an embodiment of the tooth cloth according to the embodiment [1] or [2], wherein the tooth cloth is a multi-woven fabric including a first weft yarn containing a fluororesin fiber and a second weft yarn not containing a fluororesin fiber, and the first weft yarn is located closer to the surface than the second weft yarn.

[0014] The fourth aspect of the present invention is the third aspect, wherein the number of the second wefts is greater than the number of the first wefts.

[0015] Aspect [5] of the present invention is any one of aspects [1] to [4] above, wherein the low melting point fiber is a composite fiber containing a fiber having a melting point of 200° C. or higher.

[0016] An aspect [6] of the present invention is an aspect in which the toothed belt according to any one of the aspects [1] to [5] further includes a core wire, and the core wire includes a twisted cord of carbon fiber multifilament yarn.

[0017] Aspect [7] of the present invention is any one of aspects [1] to [6] above, wherein the polyurethane is a cured product of a thermosetting polyurethane.

[0018] An embodiment [8] of the present invention is any one of the above embodiments [1] to [7], wherein the tooth cloth is permeated with polyurethane.

[0019] The present invention also includes, as an embodiment [9], a method for producing a toothed belt according to any one of the above embodiments [1] to [8], which includes a shaping step of shaping a tooth cloth precursor in advance. Effect of the Invention

[0020] In the present invention, since a tooth polymer layer containing polyurethane is covered with a tooth cloth containing a fluororesin fiber and a specific low melting point fiber, a polyurethane toothed belt having a low friction coefficient and excellent durability even in high load applications can be easily manufactured. [Brief description of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic, partially sectional perspective view showing an example of a toothed belt according to the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view of the toothed belt of FIG. [Diagram 3] FIG. 3 is a schematic diagram for explaining a method of pushing a tooth cloth precursor into tooth grooves of a lower molding plate in a molding step of the method for producing a toothed belt of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing a state in which a tooth cloth precursor is sandwiched between a pair of shaping plates in the shaping step of the method for producing a toothed belt of the present invention. [Diagram 5] FIG. 5 is a schematic diagram showing a running layout in the durability test of the embodiment. [Figure 6] FIG. 6 is a scanning electron microscope (SEM) photograph of a circumferential cross section of the toothed belt obtained in Example 1, enlarged 50 times. [Figure 7] FIG. 7 is a SEM photograph of a cross section in the belt width direction of the toothed belt obtained in Example 1, enlarged 50 times. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] <Toothed belt> An example of a toothed belt according to the present invention will be described in detail below with reference to the attached drawings as necessary. In the following description, the same reference numerals may be used to designate elements (or members) that are identical or have the same functions.

[0023] FIG. 1 is a schematic partial cross-sectional perspective view showing an example of a toothed belt of the present invention, and FIG. 2 is a schematic cross-sectional view of the toothed belt of FIG. 1. The toothed belt 1 of this example is an endless meshing power transmission belt, and includes a back portion 1c in which a core wire 4 extending in the belt circumferential direction (longitudinal direction) is embedded, and a plurality of teeth 1a provided at a predetermined interval in the circumferential direction on the inner peripheral surface of the back portion 1c and extending in the belt width direction, and the belt surface (inner peripheral surface) on the tooth portion side is composed of a tooth cloth 2. The back portion 1c is disposed on the belt outer peripheral surface side of the core wire 4 and has a back polymer layer 5 formed of polyurethane, and this back polymer layer 5 forms the belt outer peripheral surface. Furthermore, the toothed belt 1 has a tooth polymer layer (polymer layer forming a tooth portion) 3 formed of polyurethane between the tooth cloth 2 and the core wire 4 on the belt inner peripheral surface side of the core wire 4.

[0024] Between adjacent tooth portions 1a, flat tooth bottom portions 1b are present, and the tooth portions 1a and the tooth bottom portions 1b are alternately formed along the circumferential direction (belt longitudinal direction) on the inner peripheral surface of the belt. That is, the surface of the tooth portions 1a and the inner peripheral surface of the back portion 1c (i.e., the surface of the tooth bottom portions 1b) are formed of a single continuous tooth cloth 2.

[0025] In the embodiment shown in Fig. 1, the tooth cloth constituting the surface of the tooth part is a constituent element of the tooth part, while the tooth cloth constituting the surface of the tooth bottom part is a constituent element of the back part. Also, each tooth cloth constituting the tooth part is a part of a continuous tooth cloth (a part of tooth cloth 2 in Fig. 2).

[0026] In this example, the tooth portion 1a has a cross-sectional shape in the circumferential direction of the belt that is substantially trapezoidal. The tooth portion 1a having a cross-sectional shape in the substantially trapezoidal direction has a surface (inner peripheral surface) in the circumferential direction formed by the tooth cloth 2, and an inside formed by a tooth polymer layer 3 interposed between the tooth cloth 2 and the core wire 4.

[0027] In addition, even in the tooth bottom portion 1b, a tooth polymer layer 3 (not shown) is interposed between the tooth cloth 2 and the core wire 4. The thickness of the tooth polymer layer 3 in the tooth bottom portion 1b is extremely thinner than the thickness of the tooth polymer layer 3 in the tooth portion 1a.

[0028] The core wires 4 extend in the belt longitudinal direction (circumferential direction) and are arranged at intervals in the belt width direction. The gaps between adjacent core wires 4 may be formed by the polymer composition constituting the back polymer layer 5 and / or the tooth polymer layer 3 (particularly, the polymer composition constituting the back polymer layer 5).

[0029] Although toothed belts can be used for high-load transmission applications in industrial machines, internal combustion engines of automobiles, rear-wheel drives of motorcycles, etc., they are preferably used for high-load transmission applications in rear-wheel drives of motorcycles. For example, when a toothed belt is wound between a driving pulley (toothed pulley) and a driven pulley (toothed pulley), the rotation of the driving pulley transmits power from the driving pulley side to the driven pulley side.

[0030] The toothed belt of the present invention is not limited to the form and structure shown in Figures 1 and 2. For example, the multiple toothed portions may be capable of meshing with a toothed pulley, and the cross-sectional shape of the toothed portions (cross-sectional shape of the toothed belt in the belt circumferential direction) is not limited to a substantially trapezoidal shape, and may be, for example, a semicircular shape, a semi-elliptical shape, a polygonal shape [triangular, quadrilateral (rectangular, trapezoidal, etc.)], etc. Among these, a substantially trapezoidal or semicircular cross-sectional shape is preferable from the viewpoint of meshing power transmission, etc.

[0031] In the toothed belt of the present invention, the average distance between the centers of adjacent teeth in the circumferential direction (tooth pitch, see FIG. 2) may be, for example, about 2 to 25 mm depending on the shape of the toothed pulley. The value of the tooth pitch also corresponds to the size of the scale of the teeth (the length of the teeth in the belt circumferential direction and the tooth height of the teeth). That is, the larger the tooth pitch, the larger the scale of the teeth. In particular, in applications where a high load acts, teeth with a large scale are required, and the tooth pitch may be 5 mm or more, and preferably 8 mm or more. The tooth pitch can be appropriately selected depending on the application, and may be about 6 to 16 mm for power transmission applications in rear wheel drive of motorcycles, and may be, for example, about 8 to 14 mm (particularly 10 to 14 mm).

[0032] Furthermore, the average tooth height of the tooth portion is, for example, 40 to 70%, preferably 50 to 65%, of the average value of the total belt thickness [thickness (distance or height) from the back surface (outer peripheral surface) to the tooth top].

[0033] In the present application, as shown in FIG. 2, the average tooth height of the tooth portion means the average height of the protruding tooth portion on the inner circumferential surface of the belt [the average value of the thickness (distance or height) from the tooth bottom surface to the tooth top].

[0034] [Tooth] The tooth portion includes a tooth cloth arranged on the surface side (inner surface side) and a tooth polymer layer (polymer layer forming the tooth portion) arranged or interposed between the tooth cloth and the core wire. That is, the surface of the tooth portion is covered with a tooth cloth, and the tooth cloth forms the inner peripheral surface of the belt. In the toothed belt of the present invention, the tooth portion containing polyurethane (particularly, thermosetting polyurethane) is covered with a tooth cloth containing fluororesin fiber and a specific low melting point fiber, so that a toothed belt having a low friction coefficient and excellent durability even in high load applications can be easily manufactured. The details of this mechanism are unknown, but it is speculated as follows.

[0035] The toothed belt can improve its wear resistance by providing a tooth cloth, but in the present invention, the tooth cloth contains fluororesin fibers, which reduces the friction coefficient and further improves the wear resistance. Fluororesin fibers have the disadvantages of being weakly adhesive and brittle and easily scattering early, but polyurethane (particularly thermosetting polyurethane) for forming the tooth polymer layer in the manufacturing process of the toothed belt penetrates the tooth cloth and bonds between the fibers, reinforcing the fluororesin fibers and suppressing early scattering. Furthermore, since the melting point of the low melting point component of the low melting point fiber is adjusted to 100 to 180°C, it can be softened by the heat used for shaping the tooth cloth or curing the urethane prepolymer that forms the tooth polymer layer, and can retain its shape at room temperature, so that the molten low melting point fiber can easily adhere or be bonded to the fluororesin fiber, which is presumed to contribute to improving the adhesiveness of the fluororesin fiber.

[0036] Although it is sufficient that at least a part of the fluororesin fiber of the tooth cloth is fixed with polyurethane, it is preferable that the tooth cloth is entirely permeated with polyurethane because the reinforcing effect of the fluororesin fiber is large and the durability of the belt can be improved. The polyurethane permeated entirely into the tooth cloth hardens the periphery of the fluororesin fiber present in large amounts on the surface side of the teeth, thereby compensating for the drawback of the fluororesin fiber being brittle and easily scattered.

[0037] Furthermore, it is particularly preferable that the tooth cloth is permeated with polyurethane throughout and has a thin polyurethane film (polyurethane layer) on the surface of the tooth cloth. When the polyurethane that has permeated to the surface side of the tooth cloth forms a thin film on the surface of the tooth cloth, the fluororesin fiber can be reinforced by being wrapped around the surface of the tooth cloth, thereby further enhancing the reinforcing effect of the fluororesin fiber.

[0038] The average thickness of such a polyurethane layer is, for example, 10 to 100 μm, preferably 20 to 50 μm, and more preferably 30 to 40 μm. If the polyurethane layer is too thin, the fluororesin fibers may easily scatter, whereas if it is too thick, the coefficient of friction may become high.

[0039] In the present application, the average thickness of the polyurethane layer can be determined as the average value of any 10 points on a scanning microscope photograph.

[0040] (Tooth cloth) The tooth cloth contains a fluororesin fiber and a low melting point fiber. The tooth cloth contains the fluororesin fiber, which reduces the friction coefficient and improves the wear resistance of the toothed belt, and the tooth cloth contains the low melting point fiber, which makes it possible to perform shaping using the tooth cloth alone without blending a urethane elastomer or an adhesive.

[0041] (A) Fluorine resin fiber Examples of fluororesin fibers (or fluorine-based fibers) include polytetrafluoroethylene (PTFE) fibers, polychlorotrifluoroethylene (PCTFE) fibers, polyvinylidene fluoride (PVDF) fibers, polyvinyl fluoride (PVF) fibers, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) fibers, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) fibers, ethylene-tetrafluoroethylene copolymer (ETFE) fibers, and ethylene-chlorotrifluoroethylene copolymer (ECTFE) fibers. These fluororesin fibers can be used alone or in combination. Of these, PTFE fibers are preferred.

[0042] (B) Low melting point fiber The low melting point fiber contains a low melting point component that can be melted (dissolved) or softened at 100 to 180° C., so that shaping can be easily performed. The low melting point component is preferably a component that can be melted (dissolved) or softened at a temperature equal to or lower than the molding temperature of the toothed belt (for example, a temperature described in the manufacturing method described later).

[0043] The melting point or softening point (particularly the melting point) of the low melting point component may be in the range of 100 to 180° C., and is preferably 120 to 175° C., further preferably 130 to 170° C., further preferably 140 to 165° C., and most preferably 155 to 165° C. If the melting point of the low melting point component is too low, the heat resistance of the belt may decrease, whereas if it is too high, the moldability (productivity) may decrease or molding may become difficult.

[0044] Examples of the low melting point component include polyolefin resins, polyester resins, and polyamide resins.

[0045] Examples of polyolefin resins include poly-α-C such as linear olefin resins, specifically polyethylene resins (e.g., high-density polyethylene resin, medium-density polyethylene resin, low-density polyethylene resin, linear low-density polyethylene resin, ultra-high molecular weight polyethylene resin, etc.), and polypropylene resins (isotactic polypropylene resin, syndiotactic polypropylene resin, atactic polypropylene resin, etc.). 2-6 Olefin resin (α-C 2-6 Olefin homopolymers or copolymers, etc.

[0046] The polyester resin may be a polyester resin obtained by a polycondensation reaction between a dibasic acid (or dicarboxylic acid) and a diol, for example, a polyester resin containing terephthalic acid as a dibasic acid and diethylene glycol as a diol as polymerization components, and preferably a polyester resin containing terephthalic acid and diethylene glycol as the base polymerization components and further containing other copolymerization components different from these. Examples of the other copolymerization components include aliphatic dicarboxylic acids (e.g., C 2 , such as adipic acid and sebacic acid). 2-12 alkane-dicarboxylic acids, etc.), benzenedicarboxylic acids which may have an alkyl group (e.g., C 1-12 (e.g., benzenedicarboxylic acid which may have an alkyl group), ethylene glycol, butanediol, neopentyl glycol, hexanediol, polyethylene glycol, and other (mono- or poly)C 2-12 Alkanediols and the like can be used. The dibasic acid (dicarboxylic acid) may be a derivative capable of forming an ester bond with the diol (for example, an alkyl ester of a dibasic acid, an acid halide such as an acid chloride, an acid anhydride, and the like). These copolymerization components can be used alone or in combination of two or more. The melting point of the polyester resin can be adjusted by the combination of the polymerization components and the copolymerization ratio.

[0047] The polyamide resin may be a polymer (homopolymer or copolymer) obtained by a polycondensation reaction between a dibasic acid (or dicarboxylic acid) and a diamine, a polycondensation reaction of an ω-aminocarboxylic acid, a ring-opening reaction of a lactam, or a combination thereof. These polymerization components (dibasic acid, diamine, ω-aminocarboxylic acid, lactam) may be aliphatic components, such as alkylene groups (e.g., C 8-16 Alkylene group, preferably C 10-12 It is preferable that the polymer component has a cyclic alkylene group, and a typical polymer component is, for example, C 8-16 Alkane-dicarboxylic acids (e.g., 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, etc.) 10-12 Alkane-dicarboxylic acids, etc.), C 8-16 Alkanediamines (e.g., C1,2-dodecanediamine, 1,10-decanediamine, etc.) 10-12 Alkanediamines, etc.), C 8-16 Aminoalkane-carboxylic acids [e.g., 11-aminoundecanoic acid, 12-aminolauric acid (12-aminododecanoic acid) and other C 10-12 These polymerization components can be used alone or in combination of two or more. Representative polyamide resins include aliphatic polyamide resins such as polyamide 1010, polyamide 1012, polyamide 1212, polyamide 11, and polyamide 12. 8-16 Alkylene group, preferably C 10-12 and aliphatic polyamide resins having alkylene groups.

[0048] These low melting point components may be used alone or in combination of two or more kinds. Among these low melting point components, it is preferable to include a polyester resin.

[0049] The low melting point fiber may contain a low melting point component on at least a part of the surface, and may be a fiber formed of the low melting point component alone, or may be a composite fiber formed of a low melting point component and a high melting point component. Among these, composite fibers are preferred from the viewpoint of improving durability. The composite fiber may be a core-sheath type composite fiber, a conjugate fiber, or the like.

[0050] Among these, sheath-core composite fibers (especially filament yarns of sheath-core composite fibers) are preferred because the low-melting point component in the sheath melts with the heat during shaping of the tooth cloth or hardening treatment of the belt, thereby improving adhesion and suppressing scattering of the fluororesin fibers, and the fibers in the core that remain unmelted maintain the texture of the tooth cloth and improve abrasion resistance.

[0051] As the core-sheath type composite fiber, it is preferable that the sheath portion is formed of the low melting point component (for example, polyolefin-based resin, polyamide-based resin and / or polyester-based resin, preferably polyester-based resin), and the core portion is formed of fibers (high melting point fibers) that cannot melt (dissolve) or soften at a temperature equal to or lower than the molding temperature of the toothed belt (for example, the temperature described in the manufacturing method described later). The melting point (or softening temperature) of the high melting point fiber is not particularly limited as long as it is above 180°C, but may be preferably 200°C or higher (for example, 200 to 300°C). When the sheath portion is formed of a polyester-based resin, the high melting point fiber is a polyester-based fiber [for example, a polyalkylene arylate-based fiber (for example, a C fiber such as PET fiber, PTT fiber, PBT fiber, PEN fiber, etc. 2-4 Alkylene C 8-14 arylate fibers; completely aromatic polyester fibers such as liquid crystal polyester fibers; or copolymer fibers thereof.

[0052] That is, the low melting point fiber may be a composite fiber containing a high melting point fiber (particularly, a fiber having a melting point of 200°C or higher). When the low melting point fiber is made of only a low melting point resin, the wear resistance of the tooth cloth is likely to decrease. In contrast, by making the low melting point fiber a composite fiber containing a fiber having a melting point of 200°C or higher, the wear resistance of the tooth cloth can be improved while allowing the tooth cloth to be shaped.

[0053] Specific examples of commercially available low melting point fibers include "Melset," "Cornetta," and "Esporan" manufactured by Unitika Ltd., which are composite yarns with a core of normal polyester and a sheath of low melting point polyester, "Bell Couple" manufactured by KB Seiren Ltd., "Flor M" manufactured by Unitika Ltd., which is made of low melting point nylon, "Elder" manufactured by Toray Industries, Inc., and "Izanas" manufactured by Toyobo Co., Ltd., which is made of polyethylene.

[0054] (C) Other fibers The fibers forming the tooth cloth may contain the fluororesin fibers and low melting point fibers, but may further contain other fibers.

[0055] The other fibers may be organic fibers or inorganic fibers. Examples of organic fibers include polyamide fibers [aliphatic polyamide fibers (nylon fibers) such as polyamide 6 fibers, polyamide 66 fibers, and polyamide 46 fibers, and aramid fibers], polyester fibers [polyalkylene arylate fibers (e.g., polyethylene terephthalate (PET) fibers, polytrimethylene terephthalate (PTT) fibers, polybutylene terephthalate (PBT) fibers, polyethylene naphthalate (PEN) fibers, and other C fibers], and the like. 2-4 Alkylene C 8-14 arylate fibers); completely aromatic polyester fibers such as polyarylate fibers and liquid crystal polyester fibers; or copolymer fibers thereof, etc.], synthetic fibers such as vinylon fibers, polyvinyl alcohol fibers, polyparaphenylene benzobisoxazole (PBO) fibers, polyphenylene ether fibers, polyether ether ketone fibers, polyether sulfone fibers, and polyurethane fibers; natural fibers such as cotton, hemp, and wool, regenerated cellulose fibers such as rayon, cellulose ester fibers, etc. Examples of inorganic fibers include carbon fibers and glass fibers.

[0056] The other fibers can be used alone or in combination of two or more. Among these fibers, organic fibers are widely used, and preferred are cellulose-based fibers such as cotton and rayon, polyester-based fibers (PET fibers, etc.), polyamide-based fibers (aliphatic polyamide fibers such as polyamide 66 fibers, aramid fibers, etc.), PBO fibers, polyurethane-based fibers, etc., and particularly preferred are polyamide-based fibers (aliphatic polyamide fibers such as polyamide 66 fibers, etc.) and / or polyurethane-based fibers.

[0057] (D) Shape of tooth cloth The tooth cloth constituting the inner peripheral surface of the belt (the surface of the tooth portion and the tooth bottom portion) may be formed of, for example, a woven fabric, a knitted fabric, a nonwoven fabric, or the like, and is preferably formed of a woven fabric from the viewpoint of moldability (or productivity), etc. The tooth cloth is often conventionally formed of a woven fabric (canvas), and is often composed of a fabric woven with warp threads extending in the belt width direction and weft threads extending in the belt circumferential direction.

[0058] Each thread (warp and / or weft) forming the fabric may be a fluororesin fiber, a low melting point fiber, or another fiber, and may be formed by using two or more of them alone. The form of the warp and weft is not particularly limited, and may be a monofilament yarn, which is a single long fiber, a multifilament yarn obtained by arranging or twisting filaments (long fibers), a spun yarn (spun yarn) obtained by twisting staples (short fibers), or a flat slit yarn obtained by forming a thin, cut sheet into a thread shape by thermal drawing or the like. The multifilament yarn or the spun yarn may be a composite yarn (mixed yarn) using multiple types of fibers, such as a mixed twist yarn, a mixed spun yarn, a mixed fiber yarn, or a covered yarn. Of these, the fluororesin fiber is preferably a monofilament yarn or a slit yarn.

[0059] Furthermore, each yarn (warp yarn and / or weft yarn) forming the fabric may form a composite yarn with, for example, an elastic yarn having elasticity [for example, polyurethane-based elastic yarn having elasticity such as spandex formed from polyurethane, processed yarn that has been stretched (for example, woolly processing, shrink processing, etc.)], and when the composite yarn contains polyurethane fiber, it is preferable to form a composite yarn (mixed yarn) with the polyurethane-based elastic yarn formed from polyurethane fiber and the fiber [preferably the polyester-based fiber (PET fiber, fiber containing polyester-based resin as a low melting point component, etc.), the polyamide-based fiber (aliphatic polyamide fiber such as polyamide 66 fiber, aramid fiber, etc.), the fluororesin fiber (PTFE fiber, etc.)].

[0060] The weft preferably contains the elastic yarn having the above-mentioned stretchability, and the warp usually does not contain the elastic yarn from the viewpoint of weaving. In order to ensure the stretchability of the tooth cloth in the circumferential direction of the belt, the weft containing the elastic yarn extends in the circumferential direction of the belt, and the warp extends in the width direction of the belt.

[0061] The average diameter of the fibers is, for example, 1 to 100 μm (e.g., 3 to 50 μm), preferably 5 to 30 μm, and more preferably 7 to 25 μm. With regard to the average fineness (thickness) of the yarns, the weft yarn may be, for example, about 100 to 1000 dtex (particularly, 300 to 700 dtex), and the warp yarn may be, for example, about 50 to 500 dtex (particularly, 100 to 300 dtex). The density of the weft yarn (pieces / cm) may be, for example, about 5 to 50 (particularly, 10 to 40), and the density of the warp yarn (pieces / cm) may be, for example, about 10 to 300, preferably about 15 to 100 (particularly, 20 to 60).

[0062] When the fabric is a woven fabric, the weave structure is not particularly limited as long as the warp and weft threads are regularly crossed in the vertical and horizontal directions, and may be any of plain weave, twill weave (or twill weave), satin weave (satin weave, satin), etc., or a combination of these weave structures. Preferred woven fabrics have twill and satin weave structures (particularly twill weaves such as 1 / 3 twill and 2 / 2 twill). The woven fabric may have a single-layer structure or a multi-layer structure (such as a double-weave structure). A single-layer structure may be used because it is easily applicable to small toothed belts, and a double-weave structure (particularly a two-color double-weave structure with weft threads) is preferred because it can improve durability, and a double-weave structure is particularly preferred.

[0063] In a weave having warp and weft threads, in order to reduce friction between the tooth cloth and the toothed pulley, it is preferable to form the (exposed) warp and / or weft threads (preferably the weft threads) located on the surface side (inner peripheral side) of the belt from a fiber with a low friction coefficient (or a low friction fiber) such as the fluororesin fiber (PTFE fiber, etc.) or a composite yarn thereof, as necessary, and it is particularly preferable to form the weft thread located on the surface side (inner peripheral side, i.e., the side that meshes with the toothed pulley) of the belt from a composite yarn containing a fluororesin fiber and a low melting point fiber. In such an embodiment, it is possible to reduce friction at the meshing between the tooth cloth and the toothed pulley and improve abrasion resistance.

[0064] As a representative embodiment of the warp and weft yarns, the warp yarns may be formed, for example, from the polyamide-based fibers, polyester-based fibers, preferably polyamide-based fibers such as nylon 66; the weft yarns are preferably yarns having at least the fluororesin fibers, and may be formed, for example, from a fiber containing the fluororesin fiber alone, but are preferably formed from a composite yarn (mixed yarn) containing the fluororesin fiber and the low-melting point fiber, and more preferably from a composite yarn containing the fluororesin fiber, the low-melting point fiber, and the polyurethane-based fiber (elastic yarn).

[0065] In addition, when the yarn is a composite yarn (mixed yarn) containing the fluororesin fiber and the low melting point fiber, it is preferable that the low melting point fiber is arranged around the fluororesin fiber. Specific composite yarn configurations include a configuration in which the fluororesin fiber and the low melting point fiber are mixed and twisted, and a configuration in which the fluororesin fiber is covered with the low melting point fiber.

[0066] In the embodiment in which the low melting point fiber is arranged around the fluororesin fiber, the low melting point component of the low melting point fiber melts (dissolves) or softens when the tooth portion and the back portion are hardened, and after bonding with the surface of the fluororesin fiber, the low melting point fiber is crystallized by cooling to below the melting point. As a result, when the tooth portion is engaged with the toothed pulley or disengaged from the toothed pulley, the fluororesin fiber is prevented from being cut or scattered due to the impact or wear that occurs on the surface of the tooth portion. Therefore, when the weft yarn of this embodiment is used as the tooth cloth (tooth cloth precursor) of the toothed belt, the tooth portion and the back portion are protected for a longer period of time due to the above-mentioned action, so that the belt can be prevented from chipping and the life of the belt can be extended during high-load running. Furthermore, as described above, the polyurethane for forming the tooth polymer layer also penetrates into the tooth cloth to reinforce the fluororesin fiber, so in the present invention, the durability of the belt can be further improved by both actions. In this way, in the present invention, the presence of polyurethane and low melting point fiber eliminates the need for resin components and adhesives for maintaining the shape of the tooth cloth precursor, so the productivity of the toothed belt can also be improved. That is, since the present invention contains both low melting point fibers and fluororesin fibers, it is possible to achieve both a reduction in the friction coefficient and improved productivity of the toothed belt, and to easily manufacture a toothed belt with excellent durability.

[0067] When the tooth cloth precursor for forming the tooth cloth contains fluororesin fiber and low melting fiber, the ratio (proportion) of the low melting fiber may be, for example, 20 to 70 mass%, preferably 30 to 69 mass% (for example, 40 to 68 mass%), more preferably 50 to 67 mass% (for example, 55 to 66.5 mass%), and particularly 60 to 66.5 mass% (for example, 62 to 66 mass%) based on the total amount of the fluororesin fiber and the low melting fiber. If the ratio of the low melting fiber is too small, the productivity of the toothed belt may decrease, and if it is too large, the friction coefficient may increase and the wear resistance may decrease.

[0068] When the woven fabric has a multiple weave structure such as a double weave structure, the fluororesin fibers are preferably contained in threads (particularly as weft threads) that are exposed on the surface side of the belt (the inner surface side, i.e., the side that engages with the toothed pulley).

[0069] In particular, when the tooth cloth is a multi-woven fabric including a first weft yarn containing fluororesin fiber and a second weft yarn not containing fluororesin fiber, the first weft yarn is preferably located closer to the surface side of the belt than the second weft yarn. By forming the tooth cloth into a multi-woven fabric having such a configuration, the exposure of the fluororesin fiber on the back side of the tooth cloth (the side adhering to the tooth polymer layer) can be reduced, improving the adhesion. At the same time, the exposure of the fluororesin fiber on the front side of the tooth cloth (the side meshing with the toothed pulley) can be increased, reducing the friction coefficient. Here, it is not necessary for all the weft yarns containing fluororesin fiber to be located closer to the surface side than the weft yarns not containing fluororesin fiber, and it is sufficient that the average positions of the respective threads in the front-back direction of the tooth cloth are in the above-mentioned positional relationship.

[0070] The number of the second weft is preferably greater than the number of the first weft, and the ratio of the number of the two is 1 / 10 to 10 / 11, preferably 1 / 5 to 2 / 3, and more preferably 1 / 3 to 1 / 2. Fluorine resin fibers have poor adhesion, and when exposed to the back side of the tooth cloth (the side adhering to the tooth polymer layer), the adhesion decreases and the tooth cloth becomes easy to peel off. By making the number of the second wefts not containing fluororesin fibers greater than the number of the first wefts containing fluororesin fibers, it is possible to reliably prevent the wefts containing fluororesin from being exposed to the back side of the tooth cloth (the side adhering to the tooth polymer layer), and to suppress peeling of the tooth cloth. If the ratio of the number of the second wefts is too large, there is a risk that the friction coefficient will increase.

[0071] In addition, when the woven fabric has a two-color double weft weave structure, the weft yarn located on the front side (inner peripheral side) of the belt is preferably a first weft yarn containing fluororesin fiber, and the weft yarn located (not exposed) on the back side (tooth polymer layer side or core wire side) of the tooth cloth (fabric) is preferably a second weft yarn not containing fluororesin fiber, and the second weft yarn may contain low melting point fiber but does not necessarily have to. In particular, the first weft yarn preferably contains fluororesin fiber and low melting point fiber, and particularly preferably contains fluororesin fiber, low melting point fiber and polyurethane fiber (elastic yarn).

[0072] Furthermore, by forming the weft yarn (not exposed) located on the back side (tooth polymer layer side or core wire side) of the tooth cloth (fabric) from fibers other than low-friction fibers such as fluororesin fibers, the adhesiveness (adhesion) between the tooth cloth (tooth cloth precursor) and the tooth polymer layer can be effectively improved. Therefore, the weft yarn located on the tooth polymer layer side of the tooth cloth (tooth cloth precursor) may be formed from, for example, a thread containing the polyamide fiber or polyester fiber (preferably a polyamide fiber such as nylon 66), or preferably a composite thread containing a polyamide fiber such as nylon 66 and the polyurethane fiber (elastic thread). In particular, it is preferable that the second weft yarn contains a composite thread containing a polyamide fiber and a polyurethane fiber (elastic thread).

[0073] The tooth cloth (tooth cloth in the toothed belt) has an average thickness of, for example, 0.1 to 2 mm, preferably 0.2 to 1.5 mm. The tooth cloth as a raw material (tooth cloth precursor before molding) has an average thickness of, for example, 0.5 to 3 mm, preferably 0.75 to 2.5 mm.

[0074] In order to enhance the adhesion with the tooth polymer layer, the fabric (tooth fabric precursor) forming the tooth fabric may be subjected to an adhesive treatment. Examples of the adhesive treatment include a method of immersing the fabric in a resorcin-formalin-latex treatment liquid (RFL treatment liquid) and then drying by heating; a method of treating with an epoxy compound or an isocyanate compound; and a method of combining these treatment methods. These methods can be performed alone or in combination of two or more kinds, and the order of treatment and the number of treatments are not limited.

[0075] (Tooth polymer layer) The tooth polymer layer may contain polyurethane, and may be formed of a crosslinked polymer composition (first crosslinked polymer composition) containing polyurethane. The tooth polymer layer may be a layer (polymer layer) formed of a single phase of the crosslinked polymer composition. The crosslinked polymer composition may be a crosslinked product of a hardenable polymer composition (particularly a thermosetting polymer composition).

[0076] (a) Polyurethane The polyurethane (or urethane elastomer) is not particularly limited, and any conventional polyurethane can be used, but from the standpoint of moldability, it may be a cured product of a urethane prepolymer and a curing agent (two-component curing polyurethane).

[0077] The urethane prepolymer may be any prepolymer that can be cured with a curing agent, and any conventional prepolymer can be used, but prepolymers having an isocyanate group at the end (for example, a prepolymer having two or more isocyanate groups at the end) are commonly used.

[0078] The prepolymer having an isocyanate group at its end may be a polyurethane prepolymer obtained by reacting an excess amount of polyisocyanates with polyols.

[0079] Examples of polyols include polyester polyols, polyether polyols, polyether ester polyols, polycarbonate polyols, polyester amide polyols, and acrylic polymer polyols. These polyols can be used alone or in combination. Among these polyols, polyester diols and polyether diols are widely used, and polyether diols such as polytetramethylene glycol ether are preferred from the viewpoints of flexibility and water resistance.

[0080] Examples of polyisocyanates include aliphatic polyisocyanates [aliphatic diisocyanates such as propylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMDI), and lysine diisocyanate (LDI), and aliphatic triisocyanates such as 1,6,11-undecane triisocyanate methyl octane and 1,3,6-hexamethylene triisocyanate], alicyclic polyisocyanates [cyclohexane 1,4-diisocyanate, isophorone diisocyanate (IPDI), hydrogenated xylitol, and the like]. alicyclic diisocyanates such as diisocyanate, hydrogenated bis(isocyanatophenyl)methane, and alicyclic triisocyanates such as bicycloheptane triisocyanate], aromatic polyisocyanates [aromatic diisocyanates such as phenylene diisocyanate, tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), naphthalene diisocyanate (NDI), bis(isocyanatophenyl)methane (MDI), tolidine diisocyanate (TODI), and 1,3-bis(isocyanatophenyl)propane], etc.

[0081] These polyisocyanates can be used alone or in combination of two or more. Among these polyisocyanates, aliphatic diisocyanates such as HDI, alicyclic diisocyanates such as IPDI, aromatic aliphatic diisocyanates such as XDI, and aromatic diisocyanates such as MDI and TDI are widely used, and aromatic polyisocyanates such as TDI are particularly preferred from the viewpoint of mechanical properties, etc.

[0082] (b) Hardener The curable polymer composition may contain a curing agent. As the curing agent, polyols and polyamines, which are conventional curing agents, can be used and can be selected depending on the type of prepolymer, but polyamines are preferred from the viewpoint of reactivity and the like.

[0083] Examples of polyamines include aliphatic diamines (e.g., ethylenediamine, propylenediamine, tetramethylenediamine, etc.), alicyclic diamines (e.g., 1,4-cyclohexylenediamine, isophoronediamine, etc.), aromatic diamines (e.g., 4,4'-diaminodiphenylmethane, 3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA), phenylenediamine, etc.), aromatic aliphatic diamines (e.g., m-xylylenediamine, etc.), triamines (diethylenetriamine, triethylenetetramine, tetraethylenepentamine, etc.), and the like.

[0084] These polyamines may be used alone or in combination of two or more. Among these polyamines, aromatic polyamines such as MOCA are particularly preferred in terms of reactivity and mechanical properties.

[0085] The urethane prepolymer and the curing agent are usually combined and used in a ratio (isocyanate group / active hydrogen atom=about 0.8 / 1 to 1.2 / 1) in which the isocyanate group and the active hydrogen atom (e.g., amino group) are approximately equal in amount. The ratio of the curing agent can be selected, for example, from the range of about 1 to 50 parts by mass, preferably 3 to 30 parts by mass, and more preferably about 5 to 20 parts by mass, relative to 100 parts by mass of the urethane prepolymer.

[0086] (c) Other ingredients The curable polymer composition may further contain other components. Examples of the other components include plasticizers, stabilizers (weather stabilizers, antioxidants, heat stabilizers, light stabilizers, etc.), fillers, short fibers, lubricants, colorants, solvents, etc. These other components can be used alone or in combination of two or more. The total proportion of the other components is, for example, 30 parts by mass or less, preferably 1 to 20 parts by mass, and more preferably about 3 to 15 parts by mass, relative to 100 parts by mass of the urethane prepolymer.

[0087] [Tooth bottom] The tooth cloth constitutes the surface of the tooth portion and also constitutes the surface of the back portion on the tooth portion side (the surface of the tooth bottom portion).

[0088] In the back portion corresponding to the tooth bottom portion, a tooth polymer layer may be interposed between the tooth cloth and the core wire, or the tooth cloth and the core wire may be in contact with each other without the tooth polymer layer. When a tooth polymer layer is interposed in the back portion corresponding to the tooth bottom portion, the thickness of the tooth polymer layer is formed to be thinner than that of the tooth portion.

[0089] [Back polymer layer] The back portion has the teeth and tooth bottoms formed on the inner peripheral surface, and has a back polymer layer that forms the outer peripheral surface of the belt on the outer peripheral surface side. Furthermore, the back polymer layer is formed of a crosslinked polymer composition (second crosslinked polymer composition). In the embodiment of Figs. 1-2, the other surface (back surface of the belt) on the side where the teeth are not formed is not covered with a fabric (woven fabric, knitted fabric, nonwoven fabric, etc.), but may be covered as necessary. This fabric can be selected from the fabrics exemplified as tooth fabrics, including the preferred embodiments.

[0090] (Second Crosslinked Polymer Composition) The second crosslinked polymer composition is not particularly limited as long as the adhesion between the back polymer layer and the teeth is not impaired, and can be selected from, for example, the crosslinked polymer compositions exemplified as the crosslinked polymer composition of the tooth polymer layer (first polymer layer). In the second crosslinked polymer composition, the polyurethane (second polyurethane) preferably contains the same series or type of polyurethane as the tooth polymer layer (first polymer layer), more preferably the same type of polyurethane, and even more preferably the same polyurethane, in order to improve the adhesion between the back polymer layer and the teeth.

[0091] The average thickness of the back polymer layer is, for example, 0.3 to 3 mm, preferably 0.5 to 2 mm. The average thickness of the back portion (average thickness of the back portion at the tooth bottom) is, for example, 1 to 5 mm, preferably 1.5 to 4 mm.

[0092] [Core] In the back portion, a core wire extending along the belt circumferential direction is embedded on the inner periphery side of the back polymer layer. This core wire acts as a tension member and can improve the running stability and strength of the toothed belt. Furthermore, in the back portion, the core wire, which is a twisted cord extending along the belt circumferential direction, is usually embedded in the belt width direction at a predetermined interval, and although multiple core wires parallel to the longitudinal direction may be arranged, from the viewpoint of productivity, it is usually embedded in a spiral shape. When arranged in a spiral shape, the angle of the core wire with respect to the belt longitudinal direction may be, for example, 5° or less, and from the viewpoint of belt running property, the closer to 0° the more preferable.

[0093] More specifically, the core wires may be embedded at a predetermined interval (or pitch) (or at equal intervals) from one end to the other end in the belt width direction of the back part, as shown in Fig. 1. The distance between the centers of adjacent core wires (spinning pitch) should be larger than the diameter of the core wire, and is, for example, 0.5 to 3.5 mm, preferably 0.8 to 3 mm, and more preferably 0.9 to 2.8 mm depending on the diameter of the core wire.

[0094] The core wire may be formed of a twisted cord made by twisting together a plurality of strands or multifilament yarns. Of these, a twisted cord made of strands is preferred, and one strand may be formed by bundling filaments (long fibers). There are no particular limitations on the thickness of the filaments forming the twisted cord, the number of filaments bundled together, the number of strands, and the twisting configuration.

[0095] The twisted cord forming the core wire may be a single-twisted, double-twisted, or rung-twisted cord. By using a rung-twisted core wire in which the twist direction of the first twist is the same as that of the top twist, the bending stiffness is lower than that of a double-twisted or single-twisted cord, and excellent resistance to bending fatigue is obtained.

[0096] The fibers forming the core wire are not particularly limited, and examples thereof include synthetic fibers such as polyester fibers (polyalkylarylate fibers, polyparaphenylene naphthalate fibers), polybenzoxazole fibers, acrylic fibers, and polyamide fibers (aliphatic polyamide fibers, aramid fibers, etc.), and inorganic fibers such as glass fibers, carbon fibers, and metal fibers (steel fibers). These fibers can be used alone or in combination of two or more. As the fibers forming the core wire, synthetic fibers such as polyester fibers and polyamide fibers, and inorganic fibers such as glass fibers and carbon fibers are commonly used from the viewpoint of low elongation and high strength.

[0097] In particular, in applications where a high load is applied, multifilament carbon fiber yarn is preferably used. For example, the carbon fiber manufactured by Toray Industries, Inc. under the trade name "TORAYCA" is used.

[0098] Carbon fiber multifilament yarns can be selected from multifilament yarns with different filament counts, such as 6K and 12K. 6K represents a multifilament yarn with 6,000 filaments, and 12K represents a multifilament yarn with 12,000 filaments. The fineness of 6K multifilament yarn is approximately 400 tex, and that of 12K multifilament yarn is approximately 800 tex.

[0099] If the fineness of the multifilament carbon fiber yarn is greater than 1000 tex, the bending fatigue resistance may decrease. Conversely, if the fineness of the multifilament carbon fiber yarn is less than 300 tex, the material cost increases and the number of first twisted yarns required to produce a cord with sufficient tensile strength increases, resulting in an increase in the number of work steps.

[0100] In one embodiment of the toothed belt of the present invention, the core wire is a carbon fiber cord (12K-1 / 0) made by single-twisting one 12K multifilament yarn (fineness of about 800 tex). Alternatively, the core wire may be a rung-twisted carbon fiber cord (12K-1 / 4) made by first twisting one 12K multifilament yarn (fineness of about 800 tex) to make a first twisted yarn, and then top-twisting four of the first twisted yarns. Note that "12K-1 / 0" indicates a twisted cord made by single-twisting one 12K multifilament yarn, and "12K-1 / 4" indicates a twisted cord made by first twisting one 12K multifilament yarn to make a first twisted yarn, and then top-twisting four of the first twisted yarns. Similarly, for example, "12K-1 / 3" indicates a twisted cord made by first twisting one 12K multifilament yarn to create a first twisted yarn, and then twisting three of the first twisted yarns together, while "12K-4 / 0" indicates a twisted cord made by first twisting four 12K multifilament yarns together.

[0101] The core wire may be subjected to an adhesive treatment in order to enhance adhesion to the crosslinked polymer composition. The adhesive treatment may be, for example, a method in which the twisted cord is immersed in an RFL treatment liquid, and then heated and dried to form a uniform adhesive layer on the surface of the twisted cord. The RFL treatment liquid is a mixture of a precondensate of resorcin and formalin mixed with latex, and the latex may be, for example, chloroprene rubber, styrene-butadiene-vinylpyridine terpolymer (VP latex), nitrile rubber, hydrogenated nitrile rubber, or the like. Furthermore, the adhesive treatment may be a method in which the twisted cord is pretreated with an epoxy compound or an isocyanate compound, and then treated with the RFL treatment liquid.

[0102] The average diameter (average wire diameter) of the twisted cord (or core wire) is, for example, 0.2 to 2.5 mm, preferably 0.5 to 2.3 mm, and more preferably 0.7 to 2.2 mm, and is preferably 0.8 to 2.1 mm for applications where a particularly high load is applied. If the core wire diameter is too small, the core wire may stretch too much, which may cause tooth chipping (loss of teeth). If the core wire diameter is too large, the core wire may break due to a decrease in bending fatigue resistance. In one embodiment of the present invention, the core wire diameter is adjusted to 1.1 mm.

[0103] (Method of Manufacturing Toothed Belt) The method for manufacturing a toothed belt of the present invention is not particularly limited as long as it includes a shaping step of shaping a tooth cloth precursor in advance as an essential step. In the present invention, since the tooth cloth contains low melting point fibers, a treatment for retaining the shape of the tooth cloth precursor is not required in the shaping step, and the productivity of the toothed belt can be improved. In detail, the low melting point fibers contained in the tooth cloth are softened by heating, and then hardened when the temperature drops to retain the shape, so that there is no need to apply a resin component such as a polyurethane elastomer as in Patent Document 1, and the number of steps for manufacturing the toothed belt can be reduced.

[0104] In the shaping step, the tooth cloth precursor is shaped using a pair of shaping plates on which tooth profiles are engraved. By shaping, the tooth cloth precursor is molded in advance into the tooth profile of the toothed belt, so that the toothed belt can be manufactured using thermosetting polyurethane, which has a low raw material viscosity.

[0105] In the shaping process, as shown in FIG. 3, the tooth cloth precursor 12 placed on the lower shaping plate 13 on which the tooth profile of the toothed belt is engraved is pressed into the tooth grooves 13a of the lower shaping plate 13 by rotating the pinion roll 11 so as to conform to the tooth profile of the lower shaping plate 13. In the present invention, before the tooth cloth precursor 12 is clamped by the upper shaping plate described later, the tooth cloth precursor 12 is aligned with the tooth profile of the lower shaping plate 13 using the pinion roll 11, so that a tooth cloth having a uniform thickness can be formed and abrasion resistance can be improved. That is, if the tooth cloth precursor 12 is placed on the lower shaping plate 13 without being aligned with the tooth grooves, the tooth cloth precursor 12 is stretched and thinned when it is clamped by the upper shaping plate and pressure-molded as described later, but thinning can be prevented by aligning it with the tooth grooves in advance.

[0106] The tooth cloth precursor 12 is pressed into the tooth grooves 13a of the lower shaping plate 13 by the pinion roll 11, and as shown in FIG. 4, an upper shaping plate 14 having the tooth profile engraved thereon is fitted into the tooth profile of the lower shaping plate 13, and the tooth cloth precursor 12 is shaped by applying pressure under heat.

[0107] When the tooth cloth precursor 12 is an elastic cloth, it is preferable to arrange the elastic direction of the cloth perpendicular to the extension direction (direction in which the grooves of the tooth cloth extend) of the tooth form of the lower molding plate 13. When the elastic cloth is a woven fabric containing elastic yarn in the weft, it is preferable to arrange the weft in the direction perpendicular to the extension direction of the tooth form of the lower molding plate 13.

[0108] The heating temperature is, for example, 60 to 200° C., preferably 80 to 180° C., more preferably 100 to 160° C., and more preferably 120 to 150° C. The pressure is, for example, 0.1 to 5.0 MPa, preferably 0.5 to 4.0 MPa, more preferably 1.0 to 3.0 MPa, and more preferably 1.5 to 2.5 MPa.

[0109] The method of manufacturing a toothed belt using a shaped tooth cloth precursor is not particularly limited, and a conventional method can be used. For example, a method of manufacturing the toothed belt using a mold that combines an inner mold having an outer peripheral surface with a plurality of grooves corresponding to the tooth shape extending in the axial direction and a cylindrical outer mold may be used. The method of winding the shaped tooth cloth precursor around the inner mold is not particularly limited, and examples thereof include a method of joining both ends of the tooth cloth precursor to form a cylindrical shape and then covering the outer periphery of the inner mold, and a method of winding the tooth cloth precursor around the outer periphery of the inner mold and then joining the ends. The joining method is also not particularly limited, and examples thereof include sewing, a method of overlapping the ends of the tooth cloth precursor and fixing them with an adhesive, and a method of butting the ends of the tooth cloth precursor and fixing them with a joint sheet.

[0110] Specific methods for manufacturing a toothed belt can be, for example, those described in JP 2017-025191 A, JP 2017-129277 A, JP 2019-59232 A, and Japanese Patent No. 4,596,296 A. EXAMPLES

[0111] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The raw materials used, preparation methods, evaluation methods, etc. are shown below.

[0112] [Tooth cloth processing] A tooth fabric precursor was produced by immersing the woven fabric shown in Table 2 in the RFL treatment liquid. In detail, the RFL treatment was carried out using two types of RFL treatment liquid (RFL1 and RFL2) shown in Table 1, and the immersion treatment was carried out in the order of RFL1 and RFL2.

[0113] [Table 1]

[0114] [Fibers that make up the tooth cloth] PTFE fiber A: "Toyoflon" manufactured by Toray Industries, Inc., filament yarn PTFE fiber B: "Yumiflon" manufactured by YMT, slit yarn Polyester fiber: "Melset" manufactured by Unitika Co., Ltd., a core-sheath type composite filament with a core melting point of 256°C and a sheath melting point of 154°C 66 nylon fiber: "Leona" manufactured by Asahi Kasei Corporation

[0115] [Polymer composition (liquid polyurethane raw material)] A mixture of 100 parts by mass of polyether-based urethane prepolymer and 17 parts by mass of a curing agent (3,3'-dichloro-4,4'-diaminodiphenylmethane (MOCA)).

[0116] [Core] A carbon fiber cord (12K-1 / 0, tensile modulus 230 GPa) was produced by single-twisting a single 12K multifilament yarn (Toray Industries, Inc., "TORAYCA T700SC-12000", single yarn fineness 0.67 dtex, total fineness 800 tex) to obtain a core wire with a diameter of 1.1 mm.

[0117] [Durability test] The test was carried out using a two-axis running test machine consisting of a drive (Dr.) pulley with 55 teeth and a driven (Dn.) pulley with 25 teeth, with the layout shown in Fig. 5. A toothed belt was hung between these two pulleys, and the belt was run at room temperature (25°C) with an axial load of 1000 N, a drive pulley rotation speed of 500 rpm, and a driven pulley torque of 31 N m.

[0118] Example 1 As described below, the tooth cloth was shaped using a double-woven fabric, and then a toothed belt was molded. That is, the treated tooth cloth was placed on a flat grooved mold plate (lower mold plate) in which teeth and grooves corresponding to the shape of the toothed belt were alternately arranged, and the treated tooth cloth was pressed between the tooth grooves of the grooved mold plate by a pinion roll having a protrusion on the outer periphery, and the treated tooth cloth shown in Table 2 was pressed between the upper mold plate and the lower mold plate at a temperature of 140°C. At this time, the low melting point polyester fiber contained in the weft yarn softened and adhered to the surface of the fluororesin fiber. In addition, when the mold plate was opened and the temperature decreased, the low melting point polyester hardened, and the tooth shape was molded into the treated tooth cloth. The shaped treated tooth cloth was removed from the mold plate, wrapped around the outer periphery of the inner mold for belt molding, and then both ends were joined. The above-mentioned core wire was spirally wound around the outer periphery of the inner mold around which the treated tooth cloth was wound, with an interval (spinning pitch) of 1.2 mm. Then, a toothed belt having a belt size of 125G8M1256 (tooth profile G8M, number of teeth 157, width 12.5 mm) was manufactured by injecting the polymer composition into a mold and curing it using a general-purpose method described in JP 2019-59232 A. The toothed belt obtained had a tooth surface covered with a tooth cloth containing fluororesin fibers and had a low friction coefficient, but such a toothed belt could be manufactured by a simple method. The results of the durability running test of this toothed belt are shown in Table 2. As shown in Table 2, the toothed belt obtained in Example 1 showed high durability with no tooth chipping even after 1372 hours.

[0119] Example 2 A toothed belt was produced in the same manner as in Example 1, except that the tooth cloth shown in Table 2 (the tooth cloth in which the type of PTFE fiber contained in the weft yarn was changed) was used.

[0120] Examples 3 to 4 A toothed belt was produced in the same manner as in Example 1, except that the tooth fabric shown in Table 2 (the double-layered woven fabric was changed to a single-layered woven fabric) was used.

[0121] Comparative Example 1 A conventional toothed belt was manufactured in accordance with JP-A-7-156288. The tooth tops of this toothed belt are not covered with fabric, and the 66 nylon nonwoven fabric is intended to protect the core wires at the tooth bottoms. It is wound around the outer periphery of an inner die for belt molding without being shaped, and is embedded near the core wires (near the tooth base) after the belt is hardened. The results of a durability running test of this toothed belt are shown in Table 2. As shown in Table 2, the toothed belt obtained in Comparative Example 1 suffered from chipped teeth in a short period of time.

[0122] Comparative Example 2 A toothed belt was produced in the same manner as in Example 1, except that the tooth cloth shown in Table 2 (the tooth cloth in Example 3 in which the PTFE fiber A contained in the weft was changed to 66 nylon fiber) was used.

[0123] [Table 2]

[0124] SEM photographs of the circumferential cross section and width cross section of the toothed belt obtained in Example 1 are shown in Figures 6 and 7, respectively. The white parts in the upper parts of Figures 6 and 7 are fluororesin fibers, which are located on the surface of the tooth cloth, which is a double-woven fabric, and a thin film with a thickness of about 30 to 50 μm can be observed between the fluororesin fibers and the surface. Since this thin film is a polymer composition (polyurethane), it was confirmed that the polyurethane for forming the tooth polymer layer permeates the entire tooth cloth. [Industrial Applicability]

[0125] The toothed belt (meshing power transmission belt or toothed power transmission belt) of the present invention can be used in combination with a toothed pulley in various fields where synchronization between input and output is required, for example, power transmission mechanisms in vehicles such as automobiles and motorcycles, power transmission mechanisms in industrial machine motors, pumps, automatic doors, automated machines, and other machinery, office automation equipment parts, coin transport devices, copiers, printers, etc. In particular, it can be used as a power transmission belt (timing belt or toothed belt) for industrial machines with high load (high horsepower) applications and rear wheel drive of motorcycles. [Explanation of symbols]

[0126] 1...Toothed belt 1a...teeth part 1b…Tooth bottom 1c...back 2…Tooth cloth 3…Tooth polymer layer 4…Core wire 5…Back polymer layer

Claims

1. A toothed belt in which a tooth polymer layer is covered with a tooth cloth, the tooth polymer layer comprises polyurethane; The tooth cloth contains fluororesin fibers and low melting point fibers, and The low melting point fiber includes a low melting point component that can be melted or softened at 100 to 180°C.

2. 2. The toothed belt according to claim 1, wherein the low melting point component is at least one resin selected from the group consisting of polyester resins, polyamide resins and polyolefin resins.

3. 3. The toothed belt according to claim 1, wherein the tooth cloth is a multi-woven fabric including a first weft yarn containing a fluororesin fiber and a second weft yarn not containing a fluororesin fiber, and the first weft yarn is located closer to a surface than the second weft yarn.

4. 4. The toothed belt according to claim 3, wherein the number of said second weft threads is greater than the number of said first weft threads.

5. 3. The toothed belt according to claim 1, wherein the low melting point fiber is a composite fiber containing a fiber having a melting point of 200° C. or higher.

6. 3. The toothed belt according to claim 1, further comprising a core wire, said core wire comprising twisted cords of carbon fiber multifilament yarn.

7. 3. The toothed belt according to claim 1, wherein said polyurethane is a cured product of a thermosetting polyurethane.

8. 3. The toothed belt according to claim 1, wherein the tooth cloth is permeated with polyurethane.

9. 3. The method for producing a toothed belt according to claim 1, further comprising a shaping step of shaping the tooth cloth precursor in advance.

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