V-belt for power transmission

Abstract

The present invention provides a V-belt for power transmission that offers excellent tension retention and reduces the need for tension checks and readjustments during use. [Solution] In a power transmission V-belt having a rubber layer with embedded core wires, the core wires are formed from a twisted cord containing aliphatic polyamide fibers, and the difference in the POC change rate shown below is adjusted to 0.3% or more in the power transmission V-belt. POC change rate: This refers to the change rate of POC when tension is applied to a belt by separating the flat pulleys, when the total length of the belt, which is wrapped around a pair of flat pulleys with the inner and outer circumferences reversed, is defined as the POC. However, the initial length of the POC used as the basis for the change rate is the POC when a tension of 15N is applied.

Description

[Technical Field]

[0001] This invention relates to V-belts for power transmission, such as wrapped V-belts and raw-edge V-belts. [Background technology]

[0002] Power transmission belts are broadly classified into friction belts and meshing belts. Examples of friction belts include flat belts, V-belts, and V-ribbed belts, while examples of meshing belts include toothed belts. V-belts include raw-edge type belts (raw-edge V-belts), in which the rubber layer with the friction transmission surface (V-shaped side) is exposed, and wrapped type belts (wrapped V-belts), in which the friction transmission surface is covered with an outer fabric (cover fabric). The type is used depending on the application based on the difference in the surface properties of the friction transmission surface (coefficient of friction between the rubber layer and the cover fabric).

[0003] When using these power transmission belts, it is necessary to apply the appropriate tension to the belt. If the belt is not tensioned sufficiently, toothed belts may experience tooth skipping (jumping), where the teeth of the belt jump over the tooth grooves of the pulley and move to the adjacent tooth groove, and friction transmission belts may experience excessive slippage, leading to overheating or even the inability to transmit power. In particular, V-belts are formed in a V-shape (inverted trapezoid) cross-section to increase the frictional force with the pulley, and even slight wear can cause a large drop in the inner circumference of the pulley, making them prone to tension loss. Therefore, tension management is crucial when using V-belts. When using conventional V-belts, it was necessary to periodically measure the tension and, if the tension fell below a predetermined lower limit, to re-tension the belt (by moving the pulley in the direction that stretches the belt), which reduced convenience for the user.

[0004] As an attempt to eliminate the need to readjust V-belt tension, Patent Document 1 (Japanese Patent Publication No. 54-141943) discloses an adjustable V-belt with an embedded rope tension member having high thermal shrinkage stress. This adjustable V-belt is described as being able to maintain a constant tension while running by manufacturing the compression rubber layer, adhesive rubber layer, cover canvas, and rope tension member in a specific procedure. Patent Document 1 also states that the rope tension member with high thermal shrinkage stress may be polyester fiber or polyamide fiber. In the embodiment of Patent Document 1, a V-belt manufactured using a polyester fiber tension member in a specific procedure is compared with a V-belt manufactured by a conventional method in an actual vehicle running test. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Unexamined Patent Publication No. 54-141943 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, while Patent Document 1 states that a rope tensioner with high thermal shrinkage stress shrinks in response to the heat generated by the belt's movement, automatically tensioning the belt and thus eliminating the need for belt re-tensioning, the examples in Patent Document 1 only involve comparative experiments using belts with the same core wire. Furthermore, the examples in Patent Document 1 show that the belt tension changes significantly depending on the manufacturing method, indicating that simply limiting the core wire material does not necessarily eliminate the need for re-tensioning.

[0007] Furthermore, using aliphatic polyamide fibers (nylon fibers) with a lower modulus of elasticity than the polyester fibers used in the examples of Patent Document 1 results in a disadvantage of reduced transmission capacity. For this reason, conventional V-belts using core wires containing nylon fibers have not yet been put into practical use.

[0008] Therefore, the object of the present invention is to provide a power transmission V-belt that has excellent tension retention properties and can reduce the need for checking and readjusting tension during use, as well as its applications. [Means for solving the problem]

[0009] To achieve the above objectives, the present inventors have discovered that in a power transmission V-belt equipped with a rubber layer in which a core wire is embedded, the core wire is formed with a twisted cord containing aliphatic polyamide fibers, and the difference in the rate of change of POC when the belt tension is changed from 50 N to 100 N is adjusted to 0.3% or more, thereby providing excellent tension retention and reducing the work of checking and readjusting the tension during use, thus completing the present invention.

[0010] In other words, the present invention includes the following embodiments.

[0011] Embodiment [1]: A power transmission V-belt having a rubber layer in which a core wire is embedded, wherein the core wire is formed of a twisted cord containing aliphatic polyamide fibers, and the difference in the rate of change of POC when the belt tension is changed from 50 N to 100 N is 0.3% or more at the POC change rates shown below.

[0012] POC Change Rate: This refers to the rate of change of the total length of a belt, where the inner and outer circumferences are reversed and the belt is wrapped around a pair of flat pulleys, when the flat pulleys are separated and tension is applied to the belt. However, the initial length (initial position) of the POC used as the basis for the rate of change is the POC when a tension of 15N is applied.

[0013] Embodiment [2]: A V-belt for power transmission according to Embodiment [1], wherein the tension retention rate is 80% or more when an initial tension of 150 N is applied to the core wire layer test specimen shown below and then held at 150°C for 30 minutes.

[0014] Core wire layer test piece: It means a test piece obtained by cutting out five core wire layers arranged in parallel in the belt width direction from an endless belt obtained by cutting a transmission V-belt to a length of 300 mm. However, in the core wire layer test piece, the thickness of each covering rubber layer covering the inner peripheral surface and the outer peripheral surface of the five parallel core wire groups is 0.5 mm or less.

[0015] Aspect [3]: The transmission V-belt according to Aspect [2] described above, in which, after applying an initial tension of 150 N to the core wire layer test piece and holding it at 150 °C for 30 minutes, the tension changes so as to increase between 15 minutes and 30 minutes after applying the initial tension.

[0016] Aspect [4]: The transmission V-belt according to any one of Aspects [1] to [3] described above, in which the total fineness of the core wire is 4000 to 16000 dtex.

[0017] Aspect [5]: The transmission V-belt according to any one of Aspects [1] to [4] described above, in which the twisted cord is a twisted cord composed of a lower-twisted yarn with a lower twist coefficient of 2 to 6 and an upper-twisted yarn obtained by upper-twisting the lower-twisted yarn with an upper twist coefficient of 2 to 6.

[0018] Aspect [6]: The transmission V-belt according to any one of Aspects [1] to [5] described above, which is a wrapped V-belt in which at least the belt side surface is covered with a cover cloth.

[0019] Aspect [7]: The transmission V-belt according to Aspect [6] described above, in which the cover cloth contains polyester-based fibers and / or polyamide-based fibers.

[0020] Aspect [8]: The transmission V-belt according to Aspect [6] or [7] described above, in which the cover cloth has a crosslinked rubber composition rubbed into the surface in contact with the pulley by a friction treatment.

[0021] Aspect [9]: The transmission V-belt according to any one of Aspects [1] to [8] described above, which is an M-shaped or A-shaped V-belt defined in JIS K 6323 (2008).

[0022] In the present application, the numerical range represented by "A to B" means "A or more and B or less", and is used in the sense of including the numerical values A and B at both ends thereof. [Advantages of the Invention]

[0023] In the present invention, in a transmission V-belt provided with a rubber layer in which a core wire is embedded, the core wire is formed of a twisted cord containing an aliphatic polyamide fiber, and the difference in the POC change rate when the belt tension is changed from 50 N to 100 N is adjusted to 0.3% or more. Therefore, the tension maintenance property is excellent, and the confirmation of the tension and the work of re-tensioning during use can be reduced. [Brief Description of the Drawings]

[0024] [Figure 1] FIG. 1 is a schematic partial cross-sectional perspective view of a wrapped V-belt, which is an example of the transmission V-belt of the present invention, cut. [Figure 2] FIG. 2 shows the layout of the belt running test of the wrapped V-belt obtained in the example. [Figure 3] FIG. 3 is a graph showing the relationship between the POC change rate and the tension in the wrapped V-belts obtained in Examples 1 to 4 and Comparative Example 1. [Figure 4] FIG. 4 is a graph showing the tension maintenance rate of the core wire layer test piece in the wrapped V-belts obtained in Examples 1 to 4 and Comparative Example 1. [Figure 5] FIG. 5 is a graph showing the tension maintenance rate during belt running in the wrapped V-belts obtained in Examples 1 to 4 and Comparative Example 1. [Modes for Carrying Out the Invention]

[0025] [Transmission V-belt] The power transmission V-belt of the present invention is characterized by having a rubber layer in which a core wire is embedded, the core wire being formed of a twisted cord containing aliphatic polyamide fibers, and the difference in the rate of change of POC when the belt tension is changed from 50 N to 100 N in the power transmission V-belt being 0.3% or more. The mechanism by which the power transmission V-belt of the present invention has excellent tension retention can be estimated as follows.

[0026] Currently, polyethylene terephthalate (PET) is commonly used as the core material for V-belts in low-load applications, while aramid resin is used in high-load applications. Aramid cores, made from aramid resin, have high tensile strength, allowing for higher belt tension settings and increased friction between the belt and pulley, enabling high-load power transmission. On the other hand, PET cores, made from PET, have high thermal shrinkage, which can compensate for tension loss due to belt wear, resulting in excellent tension retention. For this reason, PET cores are commonly used in low-load power transmission. However, even with PET cores, tension retention is not entirely sufficient, and it is necessary to periodically check whether the tension is being properly maintained and to readjust the tension (by moving the pulley in the direction that stretches the belt) if the tension falls below a predetermined lower limit.

[0027] As mentioned above, the present invention aims to reduce the work of checking and readjusting tension when using V-belts, and employs a core wire containing aliphatic polyamide fibers as a means to achieve this. The reason why a core wire containing aliphatic polyamide fibers can be obtained with high tension retention is presumed to be due to its low tensile modulus and high thermal shrinkage force. Regarding thermal shrinkage force, it is similar to that of commonly used PET core wires, and it is presumed that the decrease in tension caused by the belt falling towards the inner circumference of the pulley due to wear is offset by the increase in tension caused by the shrinkage of the core wire due to heat generated during operation. Regarding tensile modulus, as is clear from the SS curve (stress-strain curve) in Figure 3 (comparison of nylon core wire and PET core wire) measured in the example described later, when the belt is worn by the same amount [when the POC (strain) changes by the same amount], the change in tension (stress) is large for the PET core wire (Comparative Example 1) with a steep SS curve, while the change in tension is small for the nylon core wire (Example 1) with a gentle SS curve. In other words, the decrease in tension due to wear is suppressed in belts using nylon core wires.

[0028] Thus, in this invention, the tension retention of the transmission V-belt can be improved by the two characteristics of the core wire containing aliphatic polyamide fibers: "low tensile modulus (small slope of the SS curve)" and "high thermal shrinkage force." In contrast, the prior art, Patent Document 1, only describes the magnitude of the thermal shrinkage stress, and does not describe the tensile modulus.

[0029] (Types and structure of V-belts for power transmission) The power transmission V-belt of the present invention is a friction transmission belt having a rubber layer in which a core wire is embedded, and the friction transmission surface is V-shaped, but is not particularly limited. Examples of such V-belts include wrapped V-belts and raw edge V-belts (for example, raw edge V-belts without cogs, raw edge cogged V-belts in which cogs are formed on the inner circumference side of the raw edge V-belt, and raw edge double cogged V-belts in which cogs are formed on both the inner and outer circumference sides of the raw edge V-belt).

[0030] The power transmission V-belt of the present invention is preferably a small V-belt used under low loads. Specifically, examples of small V-belts used under low loads include M-type, A-type, and B-type V-belts specified in JIS, with M-type or A-type V-belts being particularly preferred.

[0031] Of these V-belts, wrapped V-belts are preferred due to their high tension retention rate, and wrapped V-belts of type M, A, and B as specified in JIS are even more preferred, with wrapped V-belts of type M or A as specified in JIS being even more preferred.

[0032] A wrapped V-belt is preferable in which at least a portion of the friction transmission surface (for example, the entire friction transmission surface) is covered with a cover cloth (reinforcement cloth), a wrapped V-belt in which at least the sides of the belt are covered with a cover cloth is more preferable, and a wrapped V-belt in which the entire surface is covered with a cover cloth is even more preferable from the viewpoint of productivity and other factors.

[0033] Figure 1 shows a schematic partial cross-sectional perspective view of a wrapped V-belt, which is an example of a power transmission V-belt according to the present invention.

[0034] As shown in Figure 1, the wrapped V-belt 1 is formed from an endless belt body consisting of an extension layer (extension rubber layer or upper core rubber layer) 2 on the outer circumference of the belt, a compression layer (compression rubber layer or V-core rubber layer) 5 on the inner circumference of the belt, and an adhesive layer (adhesive rubber layer) 4 interposed between the extension layer 2 and the compression layer 5, and a cover cloth (outer covering cloth) 6 that covers the periphery of the belt body over its entire length in the circumferential direction. Core wires 3 are embedded in the adhesive layer 4 along the longitudinal direction of the belt (circumferential direction, direction A in the figure), and the core wires 3 are core wires (twisted cords) arranged at predetermined intervals in the belt width direction (direction B in the figure) when viewed in cross-sectional view in the belt width direction. In the wrapped V-belt of Figure 1, the cross-sectional shape is an inverted trapezoid (V-shape), and the cover cloth 6 on both sides that slope in a V-shape forms a friction transmission surface that contacts the inner wall of the V-groove of the pulley.

[0035] The wrapped V-belt is not limited to this structure. For example, in the example shown in Figure 1, the wrapped V-belt has a stretch layer, but the wrapped V-belt may also be a wrapped V-belt in which the belt body consists of an adhesive layer and a compression layer (a wrapped V-belt without a stretch layer).

[0036] Furthermore, in the example shown in Figure 1, the core wire is embedded in the adhesive layer, which is an adhesive rubber layer. However, the core wire may be interposed between the stretch layer and the compression layer, or embedded in the compression layer, without providing an adhesive layer. When the core wire is interposed between the stretch layer and the compression layer, the belt body corresponds to the rubber layer containing the core wire. When the core wire is embedded in the compression layer, the compression layer corresponds to the rubber layer containing the core wire.

[0037] The following describes the details of the belt body and cover fabric that constitute the power transmission V-belt, as well as the manufacturing method of the power transmission V-belt. Conventional pulleys can be used, and any pulley equipped with a V-groove corresponding to the V-shape of the belt's friction transmission surface can be used.

[0038] [Belt body] The belt body is characterized by comprising a rubber layer including a core wire, the core wire being formed of a twisted cord containing aliphatic polyamide fibers.

[0039] (Core wire) The core wires are arranged at predetermined intervals in the belt width direction and extend along the belt length direction (circumferential direction), embedded in the rubber layer. These core wires act as tensile members and may be arranged in parallel at a predetermined pitch parallel to the belt length direction, but from the viewpoint of productivity, they are usually arranged spirally in parallel at a predetermined pitch approximately parallel to the belt length direction. When arranged spirally, the angle of the core wires with respect to the belt length direction may be, for example, 5° or less, and from the viewpoint of belt runnability, it is preferable that it be as close to 0° as possible. Furthermore, the pitch or spacing (particularly the spinning pitch of the core wires), which is the distance between the centers of adjacent core wires, is preferably set in the range of 0.5 to 2 mm, more preferably in the range of 0.6 to 2 mm (particularly 1 to 1.9 mm), and even more preferably in the range of 0.7 to 1.5 mm (particularly 0.9 to 1.3 mm).

[0040] In this application, the number of core wires (especially the number of core wires in a core wire layer test specimen) refers to the apparent number of core wires arranged at a predetermined core wire pitch in the belt width direction in a cross-sectional view, as shown in Figure 1. That is, the number of core wires refers to the number of spirals when a single core wire is embedded in a spiral. However, in reality, since the core wires are embedded in a spiral, the arrangement of the core wires differs depending on the part of the endless wrapped V-belt from which the cross-section is taken. Therefore, for practical purposes, when the core wire pitch is a constant value, the value obtained by dividing the belt width by the core wire pitch and truncating the decimal part is considered as an approximate "number of core wires" (effective number).

[0041] The core wire may be formed from a twisted cord obtained by twisting together multiple under-twisted yarns containing aliphatic polyamide fibers. The under-twisted yarns may be nylon multifilament yarns containing multiple aliphatic polyamide fibers.

[0042] Examples of aliphatic polyamide fibers include polyamide 46 fibers, polyamide 6 fibers, polyamide 66 fibers, polyamide 610 fibers, polyamide 612 fibers, polyamide 11 fibers, and polyamide 12 fibers. These aliphatic polyamide fibers can be used individually or in combination of two or more types. Among these, polyamide 6 fibers, polyamide 66 fibers, etc. 4-8 Nylon fibers having alkylene chains are preferred.

[0043] The nylon multifilament yarn may contain other fibers in addition to aliphatic polyamide fibers, as long as the effects of the present invention are not impaired. Examples of other fibers include synthetic fibers such as polyester fibers (polyalkylelelate fibers, poly(p-phenylene naphthalate) fibers), polybenzoxazole fibers, acrylic fibers, and aramid fibers; and inorganic fibers such as glass fibers, carbon fibers, and metal fibers (steel fibers). These other fibers can be used individually or in combination of two or more types.

[0044] The proportion of other fibers may be 50% by mass or less in the nylon multifilament yarn, preferably 30% by mass or less, more preferably 10% by mass or less, and more preferably 5% by mass or less.

[0045] The proportion of aliphatic polyamide fibers may be 50% by mass or more in the nylon multifilament yarn, preferably 70% by mass or more, more preferably 90% by mass or more, more preferably 95% by mass or more, and most preferably 100% by mass. If the proportion of aliphatic polyamide fibers is too low, the tension retention may decrease.

[0046] The number of filaments in the nylon multifilament yarn may be, for example, 100 to 5000, preferably 200 to 3000, and more preferably 300 to 1000. The fineness of the nylon multifilament yarn may be, for example, 100 to 2000 dtex, preferably 300 to 1700 dtex, and more preferably 500 to 1250 dtex.

[0047] The fineness of each undertwist yarn is 3000 dtex or less, preferably 500 to 3000 dtex, more preferably 1000 to 2500 dtex, more preferably 1300 to 2000 dtex, and most preferably 1500 to 1900 dtex. If the fineness is too low, the transmission capacity will decrease and economic efficiency may also decrease, and if it is too high, the bending fatigue resistance may decrease.

[0048] The number of under-twisted yarns can be multiple, but preferably 2 to 6, more preferably 2 to 4, more preferably 2 to 3, and most preferably 3. Too many yarns may reduce the bending fatigue resistance.

[0049] The twist coefficient (under-twist coefficient) of each under-twist yarn can be selected from a range of approximately 1 to 7, for example, 2 to 6, preferably 2.2 to 5, more preferably 2.3 to 4, more preferably 2.5 to 3.5, and most preferably 2.8 to 3.2. If the under-twist coefficient is too small, it will become difficult to stretch, which may reduce tension retention, and if it is too large, the tensile strength will decrease, which may reduce durability.

[0050] Twisted cords may be single-twisted, double-twisted, or Lang-twisted, but in twisted cords, it is preferable that the undertwisted yarn is made by twisting a multifilament yarn in one direction, and the twisted cord obtained by aligning multiple undertwisted yarns and twisting them together is preferably a double-twisted cord in which the upper twist is applied in the opposite direction to the undertwist. Double-twisted cords have a small inclination angle of the filaments with respect to the longitudinal direction of the twisted cord, so they can achieve both tension retention and durability.

[0051] The twist coefficient of the twisted cord (the upper twist coefficient of the upper twisted yarn) can be selected from a range of about 1 to 7, for example, 2 to 6, preferably 2.2 to 5, more preferably 2.3 to 4, more preferably 2.5 to 3.5, and most preferably 2.8 to 3.2. If the upper twist coefficient is too small, it will become difficult to stretch, which may reduce its tension retention, and if it is too large, the tensile strength will decrease, which may reduce its durability.

[0052] The ratio of the upper twist coefficient to the lower twist coefficient (upper / lower twist coefficient) is, for example, 0.3 to 3, preferably 0.5 to 2, more preferably 0.7 to 1.5, even more preferably 0.8 to 1.2, and most preferably 0.9 to 1.1.

[0053] In this application, the twist coefficients (TF) for the under-twist coefficient and the over-twist coefficient can be calculated based on the following formulas.

[0054] TF = TN × D 0.5 / 960 [In the formula, TN represents the number of twists per meter, and D represents the fineness (tex) of the yarn.]

[0055] The total fineness of the twisted cord is, for example, 1000 to 20000 dtex (particularly 1000 to 10000 dtex), preferably 2000 to 18000 dtex (particularly 3000 to 9000 dtex), more preferably 3000 to 17000 dtex (particularly 4000 to 8000 dtex), more preferably 4000 to 16000 dtex (particularly 4500 to 7000 dtex), and most preferably 5000 to 15000 dtex (particularly 5000 to 6000 dtex). If the total fineness is too low, the transmission capacity may decrease, and if it is too high, the bending fatigue resistance may decrease.

[0056] The core wire may be treated with an adhesive to enhance its adhesion to the rubber component. For example, the adhesive treatment may involve immersing the stranded cord in a resorcinol-formaldehyde-latex treatment solution (RFL treatment solution), followed by heating and drying to form a uniform adhesive layer on the surface of the stranded cord. The RFL treatment solution is a mixture of latex and an initial condensate of resorcinol and formalin. The latex may be, for example, chloroprene rubber, natural rubber, styrene-butadiene-vinylpyridine terpolymer (VP latex), nitrile rubber, or hydrogenated nitrile rubber. Furthermore, the adhesive treatment may involve pre-treating with an epoxy compound or isocyanate compound before treatment with the RFL treatment solution.

[0057] The average diameter (average wire diameter) of the stranded cord (or core wire) is, for example, 0.2 to 2.5 mm, preferably 0.5 to 2 mm, more preferably 0.5 to 1.8 mm (particularly 0.7 to 1.5 mm), more preferably 0.7 to 1.7 mm (particularly 0.8 to 1.2 mm), and most preferably 1 to 1.6 mm. If the core wire diameter is too thin, the transmission capacity may decrease, and if it is too thick, the bending fatigue resistance may decrease.

[0058] (Rubber layer) In the rubber layer including the core wire, the rubber composition excluding the core wire can be any conventional rubber composition used in V-belts and is not particularly limited. For example, if the belt body is formed of an elastic rubber layer on the outer circumference of the belt, a compression rubber layer on the inner circumference of the belt, and an adhesive rubber layer in which the core wire is embedded and which is interposed between the elastic rubber layer and the compression rubber layer, the crosslinked rubber composition of each rubber layer may be in the following forms. Note that, as mentioned above, the belt body is not limited to the following forms, and in any form, the form of each layer can be selected from the following forms, including preferred forms. Therefore, for example, even in a form where the belt body does not have an elastic rubber layer, the following forms can be applied to the compression rubber layer and the adhesive rubber layer.

[0059] (Compressed rubber layer) The compression rubber layer is formed from a first crosslinked rubber composition containing a first rubber component. The average thickness of the compression rubber layer can be appropriately selected depending on the type of belt, for example, 1 to 30 mm, preferably 1.5 to 20 mm, and more preferably 2 to 10 mm.

[0060] (1A) First rubber component Examples of the first rubber component include diene rubbers [natural rubber, isoprene rubber, butadiene rubber, chloroprene rubber, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (nitrile rubber), hydrogenated nitrile rubber (including a mixed polymer of hydrogenated nitrile rubber and an unsaturated carboxylic acid metal salt)], ethylene-α-olefin elastomer, chlorosulfonated polyethylene rubber, alkylated chlorosulfonated polyethylene rubber, epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, and fluororubber. These rubber components can be used individually or in combination of two or more.

[0061] Of these rubber components, diene-based rubbers are preferred, with combinations of natural rubber and styrene-butadiene rubber, and chloroprene rubber being preferred. The mass ratio of natural rubber to styrene-butadiene rubber is 1 / 99 to 90 / 10, preferably 5 / 95 to 80 / 20, more preferably 10 / 90 to 50 / 50, and more preferably 20 / 80 to 30 / 70.

[0062] The proportion of the first rubber component is 20 to 80% by mass, preferably 30 to 75% by mass, more preferably 40 to 70% by mass, more preferably 45 to 65% by mass, and most preferably 50 to 60% by mass in the first crosslinked rubber composition.

[0063] (1B) 1st Carbon Black The first crosslinked rubber composition may contain carbon black (first carbon black) as a reinforcing filler. The average particle size (average primary particle size) of the carbon black is, for example, 5 to 200 nm, preferably 10 to 150 nm, more preferably 20 to 100 nm, more preferably 23 to 80 nm (particularly 30 to 80 nm), and most preferably 25 to 70 nm (particularly 50 to 70 nm). If the average particle size of the carbon black is too small, workability may decrease, and conversely, if it is too large, durability may decrease.

[0064] In this application, the average particle diameter of carbon black can be measured using, for example, a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and can be calculated as the arithmetic mean particle diameter of an appropriate number of samples (e.g., 50 samples) through image analysis.

[0065] The amount of iodine adsorbed by carbon black is, for example, 5 to 200 g / kg, preferably 10 to 100 g / kg, more preferably 15 to 80 g / kg, more preferably 20 to 50 g / kg, and most preferably 23 to 30 g / kg. If the amount of iodine adsorbed is too low, durability may decrease, and conversely, if it is too high, workability may decrease.

[0066] In this application, the amount of iodine adsorbed by the first carbon black can be measured in accordance with the standard test method of ASTM D1510-17.

[0067] The proportion of the first carbon black is, for example, 10 to 100 parts by mass, preferably 30 to 80 parts by mass, more preferably 40 to 70 parts by mass, more preferably 45 to 65 parts by mass, and most preferably 50 to 60 parts by mass, per 100 parts by mass of the first rubber component.

[0068] (1C) First crosslinking agent The first crosslinked rubber composition may further contain a first crosslinking agent. Examples of the first crosslinking agent include metal oxides (magnesium oxide, zinc oxide, lead oxide, etc.), sulfur-based crosslinking agents [powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, sulfur chloride (sulfur monochloride, sulfur dichloride, etc.)], oximes (quinone dioxime, etc.), guanidines (diphenylguanidine, etc.), and organic peroxides [diasyl peroxide, peroxyester, dialkyl peroxide (e.g., dicumyl peroxide, t-butylcumyl peroxide, 1,1-di-butylperoxy-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexane, 1,3-bis(t-butylperoxy-isopropyl)benzene, di-t-butyl peroxide, etc.)]. These crosslinking agents can be used alone or in combination of two or more. Of these, it is preferable that a sulfur-based crosslinking agent is included, and a combination of a metal oxide and a sulfur-based crosslinking agent is particularly preferred.

[0069] The proportion of the first crosslinking agent is, for example, 1 to 15 parts by mass, preferably 3 to 13 parts by mass, and more preferably 5 to 10 parts by mass, per 100 parts by mass of the first rubber component. The proportion of the metal oxide as the first crosslinking agent is, for example, 1 to 15 parts by mass, preferably 2 to 10 parts by mass, more preferably 2 to 9 parts by mass, and more preferably 3 to 8 parts by mass, per 100 parts by mass of the first rubber component. When a metal oxide and a sulfur-based crosslinking agent are combined as the first crosslinking agent, the proportion of the sulfur-based crosslinking agent is, for example, 10 to 2000 parts by mass (particularly 10 to 100 parts by mass), preferably 30 to 1500 parts by mass (particularly 30 to 70 parts by mass), and more preferably 40 to 1000 parts by mass (particularly 40 to 60 parts by mass), per 100 parts by mass of the metal oxide.

[0070] (1D) First crosslinking agent The first crosslinked rubber composition may further contain a first crosslinking aid. Examples of the first crosslinking aid include a first crosslinking accelerator and a first cocrosslinking agent.

[0071] Examples of first crosslinking promoters include thiram-based promoters [e.g., tetramethylthiram monosulfide (TMTM), tetramethylthiram disulfide (TMTD), tetraethylthiram disulfide (TETD), tetrabutylthiram disulfide (TBTD), dipentamethylenethiram tetrasulfide (DPTT), N,N'-dimethyl-N,N'-diphenylthiram disulfide (MPTD), etc.], sulfenamide-based promoters [e.g., N-cyclohexyl-2-benzothiadylsulfenamide (CBS), N,N'-dicyclohexyl-2-benzothiadylsulfenamide (DCBS), Nt-butyl-2-benzothiadylsulfenamide (TBBS), etc.], and thiomorpholine-based promoters [e.g., 4,4'-dithiodimorpholine (DTDM), 2-(4' Examples include -morpholinodithio)benzothiazole (MBSS), thiazole-based accelerators [e.g., 2-mercaptobenzothiazole (MBT), zinc salt of MBT (ZMBT), dibenzothiadyl disulfide (MBTS), etc.], urea-based or thiourea-based accelerators [e.g., ethylenethiourea (ETU), trimethylthiourea (TMU), diethylthiourea (DETU), etc.], guanidine-based accelerators [e.g., diphenylguanidine (DPG), di-o-tolylguanidine (DOTG), etc.], dithiocarbamate-based accelerators [e.g., sodium dimethyldithiocarbamate (SDMC), zinc diethyldithiocarbamate (ZDEC), zinc dibutyldithiocarbamate (ZDBC), etc.], and xanthogenic acid-based accelerators [e.g., zinc isopropylxanthogenic acid (ZIX)]. These crosslinking accelerators can be used individually or in combination of two or more.

[0072] Among these crosslinking accelerators, TMTD, DPTT, CBS, and MBTS are commonly used, with thiazole-based accelerators such as MBTS being preferred.

[0073] The proportion of the first crosslinking accelerator is, for example, 0.1 to 5 parts by mass, preferably 0.2 to 4 parts by mass, more preferably 0.3 to 3 parts by mass, more preferably 0.5 to 2.5 parts by mass, and most preferably 1 to 2 parts by mass, per 100 parts by mass of the first rubber component.

[0074] The first co-crosslinking agent (co-vulcanizing agent) is a known co-crosslinking agent, for example, polyfunctional (iso)cyanurates [e.g., triallyl isocyanurate (TAIC), triallyl cyanurate (TAC), etc.], polydienes (e.g., 1,2-polybutadiene, etc.), metal salts of unsaturated carboxylic acids [e.g., polyvalent metal salts of (meth)acrylic acids such as zinc (meth)acrylate and magnesium (meth)acrylate], oximes (e.g., quinone dioxime, etc.), guanidines (e.g., diphenylguanidine, etc.), polyfunctional (meth)acrylates [e.g., ethylene glycol di(meth)acrylate, alkanediol di(meth)acrylate such as butanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra( Examples include alkane polyols such as meth)acrylates, bismaleimides (aliphatic bismaleimides, e.g., alkylene bismaleimides such as N,N'-1,2-ethylenedimaleimide, N,N'-hexamethylenebismaleimide, 1,6'-bismaleimide-(2,2,4-trimethyl)cyclohexane; arene bismaleimides or aromatic bismaleimides, e.g., N,N'-m-phenylenedimaleimide, 4-methyl-1,3-phenylenedimaleimide, 4,4'-diphenylmethanedimaleimide, 2,2-bis[4-(4-maleimoidphenoxy)phenyl]propane, 4,4'-diphenyletherdimaleimide, 4,4'-diphenylsulfonedimaleimide, 1,3-bis(3-maleimoidphenoxy)benzene, etc.). These cocrosslinking agents can be used alone or in combination of two or more.

[0075] Among these cocrosslinking agents, polyfunctional (iso)cyanurates, polyfunctional (meth)acrylates, and bismaleimides (arene bismaleimides such as N,N'-m-phenylenedimaleimide or aromatic bismaleimides) are preferred, with bismaleimides being particularly preferred.

[0076] The proportion of the first co-crosslinking agent is, for example, 0.1 to 5 parts by mass, preferably 0.3 to 4 parts by mass, more preferably 0.5 to 3.5 parts by mass, more preferably 1 to 3 parts by mass, and most preferably 1.5 to 2.5 parts by mass, per 100 parts by mass of the first rubber component.

[0077] The proportion of the first crosslinking aid is, for example, 0.1 to 5 parts by mass, preferably 0.2 to 4 parts by mass, more preferably 0.3 to 3.5 parts by mass, more preferably 0.5 to 3 parts by mass, and most preferably 1 to 2.5 parts by mass, per 100 parts by mass of the first rubber component.

[0078] (1E) First plasticizer The first crosslinked rubber composition may further contain a first plasticizer. Examples of the first plasticizer include oil-based plasticizers [paraffinic oils, alicyclic oils (naphthenic oils), aromatic oils, etc.], aliphatic carboxylic acid-based plasticizers (adipate ester plasticizers, sebacate ester plasticizers, etc.), aromatic carboxylic acid-based plasticizers (phthalate ester plasticizers, trimellitic ester plasticizers, etc.), oxycarboxylic acid-based plasticizers, phosphate ester plasticizers, ether-based plasticizers, and ether ester plasticizers. These plasticizers can be used alone or in combination of two or more. Of these plasticizers, oil-based plasticizers are preferred, and aromatic oils are particularly preferred.

[0079] The proportion of the first plasticizer is, for example, 1 to 50 parts by mass, preferably 3 to 30 parts by mass, more preferably 5 to 25 parts by mass, and more preferably 10 to 20 parts by mass, per 100 parts by mass of the first rubber component.

[0080] (1F) 1st Other Additives The first crosslinked rubber composition may further contain other additives (first other additives), which are conventional additives used in rubber formulations.

[0081] Commonly used additives include, for example, short fibers (cellulose fibers such as cotton and rayon, polyester fibers such as polyethylene terephthalate, and polyamide fibers such as nylon and aramid), fillers (silicon oxide such as silica; metal carbonates such as calcium carbonate; metal oxides such as calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, and aluminum oxide; metal carbides such as silicon carbide and tungsten carbide; metal nitrides such as titanium nitride, aluminum nitride, and boron nitride; zeolite, diatomaceous earth, calcined diatomaceous earth, activated clay, alumina, mica, kaolin, and sericite). Examples of additives include mineral materials such as bentonite, montmorillonite, smectite, and clay; processing agents or processing aids (fatty acids or their metal salts such as stearic acid and metal stearic acid salts; fatty acid esters such as stearic acid esters; fatty acid amides such as stearate amides); antioxidants (antioxidants, heat aging inhibitors, flex crack inhibitors, ozone degradation inhibitors, etc.); adhesion improvers (phenol resins, amino resins, etc.); crosslinking retarders; colorants; coupling agents (silane coupling agents, etc.); stabilizers (UV absorbers, heat stabilizers, etc.); lubricants; flame retardants; and antistatic agents. These additives can be used individually or in combination of two or more. Of these, processing agents or processing aids and antioxidants are commonly used.

[0082] The total proportion of the first other additive is, for example, 0.01 to 100 parts by mass, preferably 0.1 to 50 parts by mass, more preferably 1 to 30 parts by mass, and more preferably 2 to 10 parts by mass, per 100 parts by mass of the first rubber component.

[0083] (Stretchable rubber layer) The stretchable rubber layer is formed of a second crosslinked rubber composition containing a second rubber component. The second crosslinked rubber composition may be a different rubber composition from the first crosslinked rubber composition, or it may be the same rubber composition. From the viewpoint of productivity and other factors, it is preferable that the first crosslinked rubber composition and the second crosslinked rubber composition are the same rubber composition. Even if the second crosslinked rubber composition is a different rubber composition from the first crosslinked rubber composition, it is preferable that it is a rubber composition selected from preferred embodiments of the first crosslinked rubber composition.

[0084] The average thickness of the stretchable rubber layer can be appropriately selected depending on the type of belt, but is, for example, 0.5 to 5 mm, preferably 0.6 to 3 mm, and more preferably 0.6 to 2 mm.

[0085] (Adhesive rubber layer) The adhesive rubber layer in which the core wire is embedded is formed of a third crosslinked rubber composition containing a third rubber component. The third crosslinked rubber composition is not particularly limited as long as it is a composition that enhances the adhesive function compared to the first crosslinked rubber composition. From the viewpoint of improving interlayer adhesion, the third crosslinked rubber composition is preferably a rubber composition obtained by adding a third tackifier to the composition of the first crosslinked rubber composition and adjusting the composition ratio.

[0086] Examples of third tackifiers include factis [sulfur factis (black sub) obtained by crosslinking oils and fats (such as linseed oil, rapeseed oil, castor oil, cottonseed oil, soybean oil, etc.) with sulfur or hydrogen sulfide, sulfur chloride factis (white sub) obtained by crosslinking the oils and fats with sulfur monochloride or sulfur dichloride, sulfur-free factis obtained by crosslinking the oils and fats with isocyanate compounds or organic peroxides, etc.], terpene resins (polyterpene resins or their hydrogenated products, terpene phenol resins or their hydrogenated products, etc.), rosin resins (natural rosin, cured rosin, disproportionated rosin, polymerized rosin, rosin esters, rosin phenol resins, etc.), petroleum resins (C 5-9Examples include aliphatic petroleum resins mainly composed of higher olefinic hydrocarbons such as fractions, dicyclopentadiene petroleum resins mainly composed of dicyclopentadiene or their hydrogenated products, aromatic petroleum resins mainly composed of aromatic hydrocarbons such as vinyltoluene or indene or their hydrogenated products, coumarone resins such as coumarone-indene resin and coumarone-indene-styrene copolymer or their hydrogenated products), and modified olefin polymers [ethylene-(meth)acrylic acid copolymer, ethylene-2-hydroxyethyl (meth)acrylate copolymer, ethylene-glycidyl (meth)acrylate copolymer, ethylene-vinyl acetate-(meth)acrylic acid copolymer, ethylene-ethyl (meth)acrylate-(anhydride) maleic acid copolymer, partially saponified ethylene-vinyl acetate copolymer, etc.].

[0087] These tackifiers can be used individually or in combination of two or more. Of the tackifiers, petroleum resins are preferred.

[0088] The proportion of the third tackifier is, for example, 0.1 to 30 parts by mass, preferably 0.3 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and more preferably 1 to 3 parts by mass, per 100 parts by mass of the third rubber component.

[0089] Regarding the adjustment of the composition ratio, the proportions of the third carbon black, the third crosslinking agent, and the third crosslinking accelerator may be adjusted.

[0090] The third carbon black can be selected from the carbon blacks exemplified as the first carbon black, including preferred embodiments.

[0091] The third crosslinking agent can be selected from the crosslinking agents exemplified as the first crosslinking agent, including preferred embodiments.

[0092] Examples of the third crosslinking aid include the third crosslinking accelerator and the third cocrosslinking agent. Of these, the third crosslinking accelerator is preferred. The third crosslinking accelerator can be selected from the crosslinking accelerators exemplified as the first crosslinking accelerator, including preferred embodiments.

[0093] The proportion of the third carbon black is, for example, 30 to 100 parts by mass, preferably 50 to 80 parts by mass, more preferably 55 to 75 parts by mass, and more preferably 60 to 70 parts by mass, per 100 parts by mass of the third rubber component.

[0094] The proportion of the third crosslinking agent is, for example, 1 to 12 parts by mass, preferably 2 to 10 parts by mass, and more preferably 3 to 8 parts by mass, per 100 parts by mass of the third rubber component. When a metal oxide and a sulfur-based crosslinking agent are combined as the third crosslinking agent, the proportion of the sulfur-based crosslinking agent is, for example, 3 to 50 parts by mass, preferably 5 to 40 parts by mass, and more preferably 10 to 30 parts by mass, per 100 parts by mass of the metal oxide.

[0095] The proportion of the third crosslinking aid is, for example, 0.1 to 4 parts by mass, preferably 0.2 to 3 parts by mass, more preferably 0.3 to 2 parts by mass, and more preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the third rubber component.

[0096] The average thickness of the adhesive rubber layer can be appropriately selected depending on the type of belt, but is, for example, 0.2 to 5 mm, preferably 0.3 to 3 mm, and more preferably 0.5 to 2 mm.

[0097] [Cover Fabric] The cover fabric (reinforcement fabric) only needs to cover at least a portion of the friction transmission surface. As mentioned above, this is the case for wrapped V-belts, but for other V-belts such as raw edge V-belts, the cover fabric may cover not only at least a portion of the friction transmission surface but also areas other than the friction transmission surface. For example, in a raw edge V-belt, the non-friction transmission surface may be covered with a cover fabric as a backing fabric (backing fabric corresponding to the stretchable rubber layer). Of these, a reinforcement fabric that covers the friction transmission surface, such as the side of a wrapped V-belt, is preferred, and a cover fabric as the outer covering of a wrapped V-belt (a V-belt in which the entire area, including the non-contact surface with the pulley, is covered with reinforcement fabric) is particularly preferred.

[0098] (fabric) The cover fabric includes woven fabrics. Examples of woven fabrics include woven fabrics, knitted fabrics (weft-knitted fabrics, warp-knitted fabrics), and nonwoven fabrics. Of these, woven fabrics produced in forms such as plain weave, twill weave, and satin weave, and woven fabrics and knitted fabrics produced with a wide angle where the intersection angle between the warp and weft threads exceeds 90° and is about 120° or less are preferred. Particularly preferred are woven fabrics that are commonly used as cover fabrics for transmission belts for general industrial and agricultural machinery [plain weave fabrics where the intersection angle between the warp and weft threads is a right angle, and plain weave fabrics (wide-angle canvas) where the intersection angle between the warp and weft threads exceeds 90° and is about 120° or less].

[0099] Commonly used fibers for fabrics include, for example, polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers (polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers, aramid fibers, etc.), polyester fibers [polyalkylene arylate fibers such as polyethylene terephthalate (PET) fibers and polyethylene naphthalate (PEN) fibers], vinyl alcohol fibers (polyvinyl alcohol, ethylene-vinyl alcohol copolymer fibers, vinylon fibers, etc.), poly(p-phenylene benzobisoxazole) (PBO) fibers, and other synthetic fibers; cellulose fibers (cellulose fibers, cellulose derivative fibers, etc.), natural fibers such as wool, and inorganic fibers such as carbon fibers. These fibers may be used individually as single yarns or as blended yarns combining two or more types.

[0100] Of these fibers, synthetic fibers are preferable because they can enhance abrasion resistance and improve tension retention, and composite yarns (especially blended yarns) of synthetic fibers and cellulose fibers are even more preferable because they offer an excellent balance with economic efficiency.

[0101] As synthetic fibers, polyolefin fibers, polyamide fibers, and polyester fibers are preferred, and polyester fibers are even more preferred, and polyester fibers are even more preferred, because they can enhance abrasion resistance and improve tension retention.

[0102] Polyester fibers may also be polyalkylene arylate fibers. Examples of polyalkylene arylate fibers include PET fibers, polybutylene terephthalate (PBT) fibers, PEN fibers, and other polycrystalline C 2-4 Alkylene-C 8-14 Examples include arylate-based fibers.

[0103] Polyamide fibers may also be aliphatic polyamide fibers. Examples of aliphatic polyamide fibers include polyamide 6 fibers, polyamide 66 fibers, etc. 4-8 Examples include nylon fibers containing alkylene chains.

[0104] Cellulosic fibers include cellulose fibers (cellulose fibers derived from plants, animals, or bacteria, etc.) and cellulose derivative fibers. Examples of cellulose fibers include natural plant-derived cellulose fibers (pulp fibers) such as wood pulp (coniferous and hardwood pulp, etc.), bamboo fibers, sugarcane fibers, seed hair fibers (cotton fibers (cotton linters), kapok, etc.), ginseng fibers (hemp, paper mulberry, mitsumata, etc.), and leaf fibers (Manila hemp, New Zealand hemp, etc.); animal-derived cellulose fibers such as ascidian cellulose; bacterial cellulose fibers; and algal cellulose. Examples of cellulose derivative fibers include cellulose ester fibers and regenerated cellulose fibers (rayon, cupro, lyocell, etc.).

[0105] When the fabric contains synthetic fibers, the proportion of synthetic fibers (particularly polyester fibers and / or polyamide fibers) may be 10% by mass or more of the total fibers, preferably 30% by mass or more, more preferably 50% by mass or more, and more preferably 60% by mass or more, from the viewpoint of improving tension retention. Furthermore, from the viewpoint of economy and abrasion resistance, the proportion of synthetic fibers is, for example, 30 to 90% by mass, preferably 50 to 80% by mass, and more preferably 60 to 70% by mass of the total fibers.

[0106] In a composite yarn of a synthetic fiber and a cellulose-based fiber, the mass ratio of the synthetic fiber (particularly, a polyester-based fiber and / or a polyamide-based fiber) to the cellulose-based fiber is, for example, the former / latter = 99 / 1 to 10 / 90, preferably 95 / 5 to 20 / 80, more preferably 90 / 10 to 30 / 70, still more preferably 80 / 20 to 50 / 50, and most preferably 70 / 30 to 60 / 40.

[0107] The average fineness of the fibers constituting the fabric is, for example, 5 to 30 denier, preferably 10 to 25 denier, and more preferably about 10 to 20 denier. If the fineness (denier) is too small, it may be difficult to uniformly penetrate the rubber composition between the fibers, and if it is too large, the mechanical strength of the reinforcing fabric may decrease.

[0108] The basis weight of the fabric (raw fabric) is, for example, 100 to 500 g / m 2 , preferably 200 to 400 g / m 2 , more preferably 250 to 350 g / m 2 . If the basis weight is too large, the flexibility of the belt may decrease, and if it is too small, the reinforcing effect by the cover fabric may decrease.

[0109] When the fabric (raw fabric) is a woven fabric, the yarn density of the fabric (the density of warp and weft yarns) is, for example, 60 to 100 threads / 50 mm, preferably 70 to 90 threads / 50 mm, and more preferably about 75 to 85 threads / 50 mm. If the density is too high, it may be difficult to uniformly penetrate the rubber composition between the fibers, and conversely, if the density is too low, the adhesion amount of the rubber composition may increase and the abrasion resistance may decrease.

[0110] The fabric may be subjected to an adhesion treatment [for example, an adhesion treatment such as immersion treatment in a resorcin - formalin - latex solution (RFL solution)].

[0111] The fabric may be single - layer or multi - layer (for example, 2 to 5 layers, preferably 2 to 4 layers, more preferably 2 to 3 layers), but from the viewpoint of productivity, etc., a single - layer (1 ply) or a two - layer (2 plies) is preferred, and a single - layer is particularly preferred.

[0112] (Fourth crosslinked rubber composition) The cover cloth may be formed solely from the aforementioned fabric, but it is preferable that the fourth crosslinked rubber composition is rubbed into at least one surface of the fabric by friction treatment, and it is even more preferable that the fourth crosslinked rubber composition is rubbed into the surface that contacts the pulley by friction treatment. The cover cloth may also have the fourth crosslinked rubber composition rubbed into both surfaces of the fabric by friction treatment.

[0113] The proportion of the fourth crosslinked rubber composition can be selected from a range of about 5 to 80% by mass in the cover fabric. Since the fabric and the rubber composition reinforce each other to improve abrasion resistance, for example, it is 10 to 70% by mass, preferably 20 to 60% by mass, more preferably 25 to 55% by mass, more preferably 30 to 50% by mass, and most preferably 35 to 45% by mass. If the proportion of the fourth crosslinked rubber composition is too low, the fabric may become more exposed, and abrasion resistance may decrease (the fabric may wear down easily). On the other hand, if it is too high, there will be a lot of "free and weak" rubber composition that does not penetrate the weave of the fabric, which may reduce abrasion resistance (the rubber may wear down easily).

[0114] The average thickness of the cover fabric (or the total average thickness of all layers in the case of multiple layers) is, for example, 0.4 to 2 mm, preferably 0.5 to 1.4 mm, and more preferably 0.6 to 1.2 mm. If the reinforcing fabric is too thin, the abrasion resistance may decrease, and if it is too thick, the flexibility of the belt may decrease.

[0115] In this application, the average thickness of the cover cloth can be measured based on scanning electron microscopy (SEM) images and determined as the average value of five or more arbitrary points through image analysis or the like.

[0116] (4A) Fourth rubber component The fourth crosslinked rubber composition contains a fourth rubber component. Examples of the fourth rubber component include the rubber components exemplified as the first rubber component. The rubber components can be used alone or in combination of two or more. Among the rubber components, diene rubbers (natural rubber, chloroprene rubber, hydrogenated nitrile rubber, etc.) and ethylene-α-olefin elastomers (ethylene-propylene copolymer (EPM), ethylene-propylene-diene ternary copolymer (EPDM), etc.) are preferred. For wrapped V-belts, chloroprene rubber is particularly preferred because it is relatively inexpensive while offering excellent abrasion resistance, heat resistance, and adhesion to fabrics.

[0117] The proportion of the fourth rubber component can be selected from a range of about 10 to 90% by mass in the fourth crosslinked rubber composition, for example, 20 to 80% by mass, preferably 25 to 70% by mass, more preferably 30 to 65% by mass, more preferably 40 to 60% by mass, and most preferably 45 to 55% by mass. If the proportion of rubber component (A) is too low, the adhesiveness may decrease, and conversely, if it is too high, the abrasion resistance may decrease.

[0118] (4B) 4th Carbon Black The fourth crosslinked rubber composition may further contain a fourth carbon black. The range of average particle size and iodine adsorption amount of the fourth carbon black can be selected from the range of average particle size and iodine adsorption amount of the first carbon black, including in preferred embodiments.

[0119] The proportion of the fourth carbon black is, for example, 10 to 100 parts by mass, preferably 15 to 80 parts by mass, more preferably 20 to 70 parts by mass, more preferably 25 to 60 parts by mass, and most preferably 30 to 50 parts by mass, per 100 parts by mass of the fourth rubber component.

[0120] (4C) Fourth tackifier The fourth crosslinked rubber composition may further contain a fourth tackifier. Examples of the fourth tackifier include the tackifiers exemplified as the third tackifier. The tackifiers can be used alone or in combination of two or more.

[0121] Among the aforementioned tackifiers, factis (vulcanized oils or sub-fuses) such as sulfur factis, and petroleum resins such as coumarone resin are preferred, and a combination of factis and petroleum resin is particularly preferred.

[0122] When combining factis and petroleum resin, the proportion of factis can be selected from a range of about 5 to 1000 parts by mass per 100 parts by mass of petroleum resin, for example, 10 to 100 parts by mass, preferably 20 to 80 parts by mass, and more preferably 30 to 50 parts by mass.

[0123] The proportion of the fourth tackifier is, for example, 1 to 50 parts by mass, preferably 5 to 30 parts by mass, more preferably 7 to 25 parts by mass, more preferably 8 to 20 parts by mass, and most preferably 10 to 15 parts by mass, per 100 parts by mass of the fourth rubber component. If the proportion of the fourth tackifier is too low, the effect of improving workability may decrease, and conversely, if it is too high, the abrasion resistance may decrease.

[0124] (4D) Fourth crosslinking agent The fourth crosslinked rubber composition may further contain a fourth crosslinking agent. The fourth crosslinking agent can be selected from the crosslinking agents exemplified as the first crosslinking agent, including preferred embodiments.

[0125] The proportion of the fourth crosslinking agent is, for example, 1 to 15 parts by mass, preferably 3 to 13 parts by mass, and more preferably 5 to 10 parts by mass, per 100 parts by mass of the fourth rubber component. The proportion of the metal oxide as the fourth crosslinking agent is, for example, 1 to 30 parts by mass, preferably 3 to 20 parts by mass, and more preferably 5 to 15 parts by mass, per 100 parts by mass of the fourth rubber component. When a metal oxide and a sulfur-based crosslinking agent are combined as the fourth crosslinking agent, the proportion of the sulfur-based crosslinking agent is, for example, 1 to 100 parts by mass, preferably 5 to 50 parts by mass, and more preferably 10 to 20 parts by mass, per 100 parts by mass of the metal oxide.

[0126] (4E) Fourth Plasticizer The fourth crosslinked rubber composition may further contain a fourth plasticizer. Examples of the fourth plasticizer include the plasticizers exemplified as the first plasticizer. The plasticizers can be used alone or in combination of two or more. Among the plasticizers, oil-based plasticizers are preferred, and alicyclic oils are particularly preferred.

[0127] The proportion of the fourth plasticizer is, for example, 1 to 100 parts by mass, preferably 5 to 50 parts by mass, more preferably 10 to 40 parts by mass, and more preferably 20 to 30 parts by mass, per 100 parts by mass of the fourth rubber component.

[0128] (4F) Fourth crosslinking agent The fourth crosslinked rubber composition may further contain a fourth crosslinking aid. Examples of the fourth crosslinking aid include a fourth crosslinking accelerator and a fourth cocrosslinking agent. Of these, the fourth cocrosslinking agent is preferred. The fourth cocrosslinking agent can be selected from the cocrosslinking agents exemplified as the first cocrosslinking agent, including preferred embodiments.

[0129] The proportion of the fourth crosslinking aid is, for example, 0.1 to 5 parts by mass, preferably 0.2 to 4 parts by mass, more preferably 0.3 to 3 parts by mass, more preferably 0.5 to 2 parts by mass, and most preferably 0.7 to 1.5 parts by mass, per 100 parts by mass of the fourth rubber component.

[0130] (4G) Fourth Adhesion Improvement Agent The fourth crosslinked rubber composition may further contain a fourth adhesion improver. Examples of the fourth adhesion improver include phenolic resins [such as resorcinol-formaldehyde cocondensates (RF condensates)], amino resins [such as melamine resins like hexamethylolmelamine and hexalokoxymethylmelamine (hexamethoxymethylmelamine, hexasubtoxymethylmelamine, etc.); urea resins like methylolurea; benzoguanamine resins like methylolbenzoguanamine resin, etc.], epoxy compounds, isocyanate compounds, and the like. These adhesion improvers can be used alone or in combination of two or more.

[0131] Of these, phenolic resin and amino resin are preferred, and melamine resin is particularly preferred.

[0132] The proportion of the fourth adhesion improver is, for example, 0.5 to 30 parts by mass, preferably 1 to 20 parts by mass, more preferably 1.5 to 10 parts by mass, more preferably 2 to 5 parts by mass, and most preferably 2.5 to 4 parts by mass, per 100 parts by mass of the fourth rubber component.

[0133] (4H) 4th Other Additives The fourth crosslinked rubber composition may further contain other additives (fourth other additives), which are conventional additives used in rubber formulations.

[0134] Conventional additives can be selected from the conventional additives exemplified as first other additives, including preferred embodiments.

[0135] The range of the total ratio of the fourth other additive to the fourth rubber component can be selected from the range of the total ratio of the first other additive to the first rubber component, including a preferred range.

[0136] [Characteristics of V-belts for power transmission] In the power transmission V-belt of the present invention, the difference in the rate of change of point of content (POC) when the belt tension is changed from 50 N to 100 N is 0.3% or more (for example, 0.3 to 1%), preferably 0.4% or more (for example, 0.4 to 0.8%), and more preferably 0.5% or more (for example, 0.5 to 0.7%). If the difference in the rate of change of POC is too small, there is a risk that the tension retention performance will decrease.

[0137] In this application, the POC change rate refers to the rate of change of the POC when tension is applied to a belt by separating the flat pulleys, where the POC is defined as the total length of the belt (the total length of the back surface of the belt or the length of the belt along the outer surface of the pulleys) in a belt that is wrapped around a pair of flat pulleys with its inner and outer circumferences reversed. In detail, this can be measured by the method described in the embodiments below.

[0138] The power transmission V-belt of the present invention may have a tension retention rate of 50% or more when an initial tension of 150 N is applied to a core wire layer test piece and then held at 150°C for 30 minutes, preferably 70% or more, more preferably 80% or more, and more preferably 90% or more.

[0139] In this application, such tension maintenance rate can be measured by the method described in the examples later.

[0140] Furthermore, in this application, the core wire layer test specimen refers to a test specimen obtained by cutting a V-belt for power transmission to a length of 300 mm and cutting out five core wire layers arranged in parallel in the belt width direction from an ended belt, and more specifically, a test specimen prepared by the method described in the examples described later.

[0141] In the present invention, when an initial tension of 150N is applied to a rubber layer having a width equivalent to five core wires, and then the belt is held at 150°C for 30 minutes, it is preferable that the tension increases between 15 minutes after the initial tension is applied and 30 minutes after the initial tension is applied.

[0142] Furthermore, in this application, such changes in tension can be confirmed by the method described in the examples below.

[0143] [Manufacturing method for V-belts for power transmission] The present invention provides a method for manufacturing a power transmission V-belt that can utilize conventional methods depending on the type of belt. For example, in the case of a wrapped V-belt, the method involves cutting an uncrosslinked compression rubber layer sheet and an adhesive rubber layer sheet obtained by rolling and setting them on a mantle, then winding a core wire around them, further winding an uncrosslinked adhesive rubber layer sheet and an stretch rubber layer sheet on top of the wound core, a cutting step in which the resulting annular laminate is cut (sliced) on the mantle, and a skiving step in which the cut annular laminate is placed on a pair of pulleys and cut into a V shape while rotating. Furthermore, the obtained belt body precursor may be wrapped with a cover cloth precursor and subjected to a crosslinking step. The cover cloth precursor may be a precursor obtained by friction-treating at least one side of a fabric with a rubber composition for cover cloth containing an uncrosslinked rubber component. Examples of such methods for manufacturing a wrapped V-belt include those described in Japanese Patent Application Publication No. 6-137381 and WO2015 / 104778. [Examples]

[0144] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. Details of the materials used in the examples are shown below.

[0145] [Raw materials for rubber composition] Chloroprene rubber: "PM-40" manufactured by Denka Co., Ltd. Natural rubber: SVR20 (standard Vietnamese rubber) SBR: "Nipol1502" manufactured by Nippon Zeon Co., Ltd. Magnesium oxide: "Kyowa Mag 150" manufactured by Kyowa Chemical Co., Ltd. Zinc oxide: "Zinc Oxide Type 2" manufactured by Sakai Chemical Industry Co., Ltd. Plasticizer A (naphthenic oil): "SUNTHENE410" manufactured by Nippon Sun Oil Co., Ltd. Plasticizer B (Aromatic oil): "Diana Process Oil AH-16" manufactured by Idemitsu Kosan Co., Ltd. Tackifier A: "Kuro Sub 21" manufactured by Tenma Sub Chemical Co., Ltd. Tackifier B: "Coumaron Indene Oil" manufactured by Kobe Oil Chemical Industry Co., Ltd. Tackifier C: ExxonMobil "Escorets 1102" Adhesion improver: Cyretz 964RPC, manufactured by Cytec Industries, a mixture of hexamethoxymethylmelamine (65% by mass) and amorphous silica (35% by mass). Carbon black SRF: "Seas S" manufactured by Tokai Carbon Co., Ltd., average primary particle size 66nm Carbon Black HAF: "Seas 3" manufactured by Tokai Carbon Co., Ltd., average primary particle size 28nm Carbon Black GPF: Manufactured by Nippon Steel Carbon Co., Ltd. "HTC#G" Anti-aging agent ODPA: "Nocrack AD-F" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: "Stearic acid Tsubaki" manufactured by NOF Corporation. Crosslinking accelerator MBTS: "Noxellar DM-P" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Co-crosslinking agent MPBM: "Balnock PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Sulfur: "MIDAS" manufactured by Migen Chemical Co., Ltd.

[0146] [Preparation of sheet-like rubber compositions] Rubber compositions having the compositions shown in Table 1 (composition for compression rubber layer, composition for adhesive rubber layer) were mixed in a Banbury mixer, and this mixed rubber was passed through a calender roll to produce uncrosslinked rolled rubber sheets of a predetermined thickness (sheet for compression rubber layer, sheet for adhesive rubber layer).

[0147] [Table 1]

[0148] [Preparation of friction rubber composition] Rubber compositions having the compositions shown in Table 2 were mixed in a Banbury mixer to prepare friction rubber compositions (lump-type uncrosslinked rubber compositions).

[0149] [Table 2]

[0150] [Cover fabric] Fabric A for cover cloth: Cotton woven fabric (plain weave, composed of 20 count warp and 20 count weft threads, warp and weft thread density 75 threads / 50mm, weight 280g / m) 2 ) Fabric B for cover cloth: Woven fabric made from a cotton and PET blend yarn (mass ratio of cotton to PET: cotton / PET = 35 / 65) (plain weave, composed of 20 count warp and 20 count weft threads, warp and weft thread density 75 threads / 50mm, weight 280g / m 2 )

[0151] [Preparation of cover cloth precursors by friction treatment] Using a calender roll with three rolls (top roll, center roll, and bottom roll) arranged vertically, a friction rubber composition was passed between the top roll and the center roll and rolled into a sheet-like rubber composition. This sheet-like rubber composition was then continuously passed between the center roll and the bottom roll, which rotated at different speeds, simultaneously with the fabric for the cover cloth. The rubber composition was rubbed into the fibers of the fabric to obtain a cover cloth precursor. The rotation speeds were 15 rpm for the top roll, 20 rpm for the center roll, and 10 rpm for the bottom roll, with a clearance of 1 mm between the center roll and the bottom roll. For the cover cloth fabric, Fabric A was used in Example 1 and Comparative Examples 1-2, while Fabric B was used in Examples 2-6.

[0152] [Heart wire] C1 (Nylon core): A double-twisted cord with a total fineness of 5640 dtex, made by combining two bundles of 940 dtex nylon 66 fibers and twisting them with a twist coefficient of 3.0, then combining three of these under-twisted threads and twisting them with a twist coefficient of 3.0, followed by adhesive treatment (diameter 1.00 mm). C2 (Nylon core): A double-twisted cord with a total fineness of 9400 dtex, made by combining two bundles of 940 dtex nylon 66 fibers and twisting them with a twist coefficient of 3.0, then combining five of these under-twisted threads and twisting them with a twist coefficient of 3.0, followed by adhesive treatment (diameter 1.30 mm). C3 (Nylon core): A double-twisted cord with a total fineness of 14100 dtex, made by combining three bundles of 940 dtex nylon 66 fibers and twisting them with a twist coefficient of 3.0, then combining five of these under-twisted threads and twisting them with a twist coefficient of 3.0, and finally applying adhesive treatment to the resulting cord (diameter 1.60 mm). C4 (PET core wire): A double-twisted cord with a total fineness of 16500 dtex, made by combining three PET fiber bundles (360 filaments each) with a twist coefficient of 3.0, then twisting five of these under-twisted threads together with a twist coefficient of 3.0, and finally bonding the resulting cord (diameter 1.55 mm).

[0153] [Fabrication of wrapped V-belts] A sheet for the compression rubber layer, a sheet for the first adhesive rubber layer, a core wire (spinning pitch of core wire C1 of Examples 1-2 and 5-6: 1.1 mm; spinning pitch of core wire C2 of Example 3: 1.5 mm; spinning pitch of core wire C3 of Example 4: 1.8 mm; spinning pitch of core wire C4 of Comparative Examples 1-2: 1.7 mm), and a sheet for the second adhesive rubber layer were sequentially laminated and attached to the outer surface of a cylindrical drum to form a cylindrical uncrosslinked sleeve in which the uncrosslinked rubber layer and core wire were laminated. The spinning tension of the core wire was set to 15 N. The obtained uncrosslinked sleeve was cut circumferentially while placed on the outer surface of the cylindrical drum to form an annular uncrosslinked rubber belt.

[0154] Next, the uncrosslinked rubber belt was removed from the drum, and both sides of the uncrosslinked rubber belt were cut (skived) at a predetermined angle to form a V-shaped cross-section. The V-shaped uncrosslinked rubber belt was then covered with the cover cloth precursor in a cover-wrapping process to form an uncrosslinked belt molded body in which the periphery of the belt body was covered with the cover cloth precursor. The side of the cover cloth precursor that had been friction-treated with the rubber composition was placed on the outer circumference of the belt.

[0155] The obtained uncrosslinked belt molded body was inserted into the groove of the ring mold. Furthermore, with cylindrical rubber sleeves fitted onto the outer surfaces of the ring mold and the uncrosslinked belt molded body, they were placed in a vulcanizing vessel and crosslinked by pressurizing them to 0.83 MPa at a temperature of 177°C to obtain a crosslinked belt. The obtained crosslinked belt was removed from the ring mold to obtain a wrapped V-belt with a belt size of M-26 [JIS M type, cross-sectional dimensions: width 10.0 mm x thickness 5.0 mm, belt length 660 mm, average thickness of cover cloth 0.55 mm].

[0156] [Measurement of SS curve] A pair of flat pulleys with an outer diameter of 76.2 mm were mounted on a tensile testing machine (Shimadzu Corporation's "Autograph AG-5000A"). The V-belt of the test specimen was wrapped around the outer circumference of these pulleys, with the inner and outer circumferences reversed. The two pulleys were moved apart until the belt tension reached 200 N, after which the expansion was released. The belt was then expanded again, and the position where the belt tension reached 15 N was defined as the initial position. Using the POC (total length of the back of the belt or the belt length along the outer circumference of the pulley) at the initial position as a reference, the rate of change of POC and the belt tension were recorded while the two pulleys were further separated at a speed of 50 mm / min. The measurement temperature was 25°C.

[0157] The POC change rate refers to the rate of change of POC under tension loading relative to the POC at the initial position with a tension of 15N (initial POC), and is expressed by the following formula.

[0158] POC change rate (%) = [(POC under tension load - initial POC) / initial POC] × 100

[0159] When using the POC change rate as a criterion, a smaller change in belt tension indicates superior tension retention, and when using the change in belt tension as a criterion, a larger POC change rate indicates superior tension retention. In this application, a difference in the POC change rate when the belt tension is changed from 50N to 100N (POC change rate at 100N tension - POC change rate at 50N tension) of 0.3% or more was considered acceptable (excellent tension retention).

[0160] [Measurement of tension changes in core wire layer test specimens] The adhesive layer of a 300mm long ended belt was sliced ​​and removed from both the top and bottom using a slicer, and the adhesive rubber layer with the embedded core wire was extracted. Note that in an endless belt, the core wire is a single wire extending continuously in a spiral, but in an ended belt after cutting, there are multiple core wires running parallel in the direction of the belt width.

[0161] Next, the unnecessary portions at both ends were cut off with a cutter along the space between the core wires so that the core wires would be embedded in the adhesive rubber layer, ensuring that the core wires were not exposed from the end faces. This created a core wire layer test specimen. Furthermore, in the obtained core wire layer test specimen, the thickness of each covering rubber layer covering the inner and outer surfaces of the group of five parallel core wires was adjusted to 0.5 mm or less. Note that since the elastic modulus of the core wires and the rubber are significantly different, the effect of the rubber covering the core wires can be ignored if the rubber thickness is around 0.5 mm.

[0162] The core wire layer specimen was gripped in a tensile testing machine equipped with a constant temperature chamber (Shimadzu Corporation's "Autograph AG-5000A") with a chuck distance of approximately 200 mm, and an initial tension of 150 N was applied. The change in tension was then recorded. The constant temperature chamber was set to 150°C. In this application, the tension retention rate of the core wire layer specimen is expressed as a ratio to the initial tension. The tension retention rate 30 minutes after the application of the initial tension was compared, and the increase or decrease in tension between 15 minutes and 30 minutes after the application of the initial tension was also compared.

[0163] [Belt running test] The wrapped V-belt was run under the following conditions to observe the change in tension and determine whether readjustment was necessary. As shown in Figure 2, the wrapped V-belt was mounted on a two-axis running test machine consisting of a 65mm diameter drive (Dr.) pulley and a 65mm diameter driven (Dn.) pulley. The drive pulley rotated at 3600 rpm, the driven pulley was loaded at 1.3 Nm, and the belt was run at an ambient temperature of 25°C. The initial belt tension was 51 N. To allow time for the belt to settle into the pulleys, the belt was run for 5 minutes after installation at 51 N, and the tension was adjusted back to 51 N. This process was repeated twice. Under these test conditions, a belt tension below 34 N was calculated to be a level where normal power transmission was impossible. Therefore, if the belt tension fell below 34 N, it was readjusted to 44 N.

[0164] [Belt wear rate] The weight of the belt was measured before and after the belt running test, and the belt wear rate was calculated based on the following formula. The belt running test was terminated after 260 hours.

[0165] Belt wear rate (%) = [(Belt weight before travel - Belt weight after travel) / Belt weight before travel] × 100

[0166] [Verification Results] Example 1 was a wrapped V-belt made of a nylon core wire and reinforcing fabric A, Example 2 was a wrapped V-belt made of a nylon core wire and reinforcing fabric B, Examples 3 and 4 were wrapped V-belts with a larger diameter nylon core wire than Example 2, Example 5 was a wrapped V-belt with a modified compression rubber layer compared to Example 2, Example 6 was a wrapped V-belt with a modified friction rubber compared to Example 2, Comparative Example 1 was a wrapped V-belt made of a PET core wire and reinforcing fabric A, and Comparative Example 2 was a wrapped V-belt with a modified friction rubber compared to Comparative Example 1. The test results for each are shown in Table 3, and the test results for the wrapped V-belts obtained in Examples 1 to 4 and Comparative Example 1 are shown in Figures 3 to 5.

[0167] [Table 3]

[0168] Examples 1-6 showed high differences in POC change rate and high tension retention rate of the core wire layer test specimens. In the belt running test, no re-tensioning was required until the test was terminated, and the tension trend was stable. In Example 1, no re-tensioning was required until the test was terminated in the belt running test, but the tension trend was slightly lower compared to Example 2.

[0169] Examples 3 and 4 are examples in which the core wire diameter was increased compared to Example 2. However, the difference in the POC change rate was similar in all of Examples 2 to 4, confirming that the effect of tension maintenance can be obtained even with different core wire diameters.

[0170] Example 5 is an example in which the rubber composition of the compression rubber layer is changed from that of Example 2, but the results are equivalent to those of Example 2, confirming that the compounding and physical properties of the compression rubber layer are not limited.

[0171] Example 6 is an example in which the friction rubber was changed compared to Example 2. Although the wear rate was reduced, no significant difference was observed in the tension retention rate. Unlike conventional techniques that use friction rubber with wear resistance to improve tension retention, it was confirmed that the tension retention was improved by the characteristics of the core wire.

[0172] On the other hand, Comparative Example 1 showed low differences in POC change rate and low tension retention rate of the core wire layer test specimen, requiring re-tensioning twice during the belt running test, at 45 hours and 170 hours.

[0173] Comparative Example 2 is an example in which the friction rubber was changed compared to Comparative Example 1. The wear rate was reduced, and the decrease in tension due to wear should have been suppressed. However, because it is a PET core wire, it was not possible to improve the overall tension retention. [Industrial applicability]

[0174] The power transmission V-belt of the present invention can be used for V-belts such as wrapped V-belts, raw edge V-belts, and raw edge cogged V-belts, and is particularly suitable for small wrapped V-belts of type M or A, and for wrapped V-belts used under low loads (for example, when the power transmission per belt is 10 to 2000W, preferably 12 to 1500W, more preferably 15 to 800W, and more preferably 20 to 500W). [Explanation of Symbols]

[0175] 1... Wrapped V-belt 2...Stretch layer 3… Core wire 4…Adhesive rubber layer 5…Compression layer 6…Cover cloth

Claims

1. A power transmission V-belt having a rubber layer in which a core wire is embedded, wherein the core wire is formed of a twisted cord containing aliphatic polyamide fibers, and the difference in the rate of change of POC when the belt tension is changed from 50 N to 100 N is 0.3% or more, as shown below for the rate of change of POC. POC change rate: This refers to the rate of change in the total length of a belt, where the inner and outer circumferences are reversed and the belt is wrapped around a pair of flat pulleys, when the flat pulleys are separated and tension is applied to the belt. However, the initial length of the POC used as the basis for the rate of change is the POC when a tension of 15 N is applied.

2. The V-belt for power transmission according to claim 1, wherein the tension retention rate is 80% or more when an initial tension of 150 N is applied to the core wire layer test specimen shown below and then held at 150°C for 30 minutes. Core wire layer test specimen: This refers to a test specimen cut from a V-belt for power transmission that has been cut to a length of 300 mm, from which five core wire layers arranged in parallel in the belt width direction have been cut out. However, in the core wire layer test specimen, the thickness of each covering rubber layer covering the inner and outer surfaces of the five parallel core wire groups shall be 0.5 mm or less.

3. The V-belt for power transmission according to claim 2, wherein when an initial tension of 150 N is applied to the core wire layer test piece and it is held at 150°C for 30 minutes, the tension increases from 15 minutes after the initial tension is applied until 30 minutes after the initial tension is applied.

4. A power transmission V-belt according to any one of claims 1 to 3, wherein the total fineness of the core wires is 4,000 to 16,000 dtex.

5. The V-belt for power transmission according to any one of claims 1 to 3, wherein the twisted cord is a multi-twist cord consisting of a lower twist yarn with a lower twist coefficient of 2 to 6 and a higher twist yarn obtained by twisting the lower twist yarn with a higher twist coefficient of 2 to 6.

6. A V-belt for power transmission according to any one of claims 1 to 3, wherein at least the sides of the belt are covered with a cover cloth.

7. The V-belt for power transmission according to claim 6, wherein the cover fabric comprises polyester fibers and / or polyamide fibers.

8. The V-belt for power transmission according to claim 6, wherein the cover cloth has a crosslinked rubber composition rubbed into the surface that contacts the pulley by friction treatment.

9. A power transmission V-belt according to any one of claims 1 to 3, which is an M-type or A-type V-belt as defined in JIS K 6323 (2008).

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