Friction transmission belt and method for manufacturing the same

Abstract

The present invention provides a V-belt for power transmission that ensures a friction coefficient that provides the same level of appropriate slippage and noise resistance during driving as a wrapped V-belt, while maintaining transmission performance without a decrease in the friction coefficient during driving. [Solution] A surface rubber layer is formed from a crosslinked rubber composition containing rubber components and short fibers, covering at least a portion of the side surface of the belt body and forming a friction transmission surface, and the short fibers are oriented in a direction parallel to the friction transmission surface. The static friction coefficient in the belt movement method on the friction transmission surface may be 1.2 to 1.4. The proportion of the short fibers may be 15 to 50 parts by mass per 100 parts by mass of the rubber component. The average thickness of the surface rubber layer may be 1 to 2 mm. The entire side surface of the belt body (especially the entire surface) may be covered with the surface rubber layer. The short fibers may be oriented in a direction perpendicular to the length of the belt on the friction transmission surface.

Description

[Technical Field]

[0001] The present invention relates to a friction transmission belt that can be used as a substitute for wrapped V-belts in similar applications, and to a method for manufacturing the same. [Background technology]

[0002] Friction transmission belts such as V-belts, V-ribbed belts, and flat belts are widely known as power transmission belts. V-belts include raw-edge type belts (raw-edge V-belts), in which the friction transmission surface (V-shaped side) is exposed rubber layer, and wrapped type belts (wrapped V-belts), in which the friction transmission surface is covered with an outer fabric (cover fabric). They are used differently depending on the application due to the difference in the surface properties of the friction transmission surface (coefficient of friction between the rubber layer and the cover fabric).

[0003] Wrapped V-belts are widely used in general industrial machinery such as compressors, generators, and pumps, as well as agricultural machinery such as combine harvesters, rice transplanters, and harvesters. Features of wrapped V-belts include a relatively low coefficient of friction, which allows for moderate slippage during operation, preventing excessive stress on the transmission mechanism, and low noise levels. In particular, in mechanisms susceptible to shock loads (overloads) caused by shock loading (sudden stops) due to entanglement of straw, stones, wood, etc., the moderate slippage of the V-belt mitigates the impact. Wrapped V-belts are ideally suited for applications requiring such shock load resistance.

[0004] One of the required characteristics for wrapped V-belts is wear resistance. When the cover fabric of a wrapped V-belt wears down, it can lead to a decrease in tension and excessive slippage, resulting in reduced power transmission and heat generation. Therefore, there is a demand for increased wear resistance of the cover fabric of wrapped V-belts.

[0005] In response to such demands, Japanese Patent Publication No. 2024-58593 (Patent Document 1) discloses a friction transmission belt that is excellent in productivity and economy, as well as in wear resistance, by adjusting the minimum viscosity of Mooney scorch at 125°C and the rubber hardness Hs of the rubber composition contained in the cover cloth that covers the friction transmission surface of the friction transmission belt. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2024-58593 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, in the friction transmission belt described in Patent Document 1, the friction transmission surface is covered with a cover cloth (friction canvas) containing a rubber composition (so-called friction rubber). Although the coefficient of friction is relatively high at the beginning of operation due to the friction rubber, as friction with the pulley during operation causes wear of the friction rubber (particularly adhesive wear that occurs as if tearing at the interface between the friction rubber and the canvas), the canvas is gradually exposed and the coefficient of friction decreases. As the coefficient of friction decreases, the friction transmission surface becomes slippery, and the transmission performance of the belt also decreases. Thus, a problem with wrapped V-belts in which the friction transmission surface is covered with friction canvas is that the coefficient of friction decreases with operation, making it impossible to maintain transmission performance.

[0008] Therefore, the object of the present invention is to provide a friction transmission belt and a method for manufacturing the same that can maintain transmission performance without a decrease in the coefficient of friction during driving, while ensuring a coefficient of friction that provides the same level of appropriate slippage and noise resistance during driving as a wrapped V-belt.

[0009] Another object of the present invention is to provide a friction transmission belt with less variation in the coefficient of friction and excellent manufacturing quality, and a method for manufacturing the same. [Means for solving the problem]

[0010] To achieve the above objectives, the present inventors have found that by covering at least a portion of the side surface of the belt body with a surface rubber layer formed from a crosslinked rubber composition containing rubber components and short fibers, and oriented the short fibers in a direction parallel to the friction transmission surface, it is possible to maintain a coefficient of friction that provides the same level of appropriate slippage and noise resistance during driving as a wrapped V-belt, without the coefficient of friction decreasing during driving, thereby maintaining transmission performance, and thus completing the present invention.

[0011] In other words, the present invention includes the following embodiments.

[0012] Embodiment [1]: A friction transmission belt (or V-belt) comprising a belt body (V-belt body) whose sides are inclined in a V-shape, and a surface rubber layer that covers at least a part of the sides of the belt body and forms a friction transmission surface, The surface rubber layer is formed of a crosslinked rubber composition containing rubber components and short fibers. A friction transmission belt in which the short fibers are oriented in a direction parallel to the friction transmission surface.

[0013] Embodiment [2]: The friction transmission belt according to Embodiment [1], wherein the static friction coefficient in the belt movement method on the friction transmission surface is 1.2 to 1.4.

[0014] Embodiment [3]: The friction transmission belt according to Embodiment [1] or [2], wherein the proportion of the short fibers is 15 to 50 parts by mass per 100 parts by mass of the rubber component.

[0015] Embodiment [4]: ​​A friction transmission belt according to any of Embodiments [1] to [3], wherein the average thickness of the surface rubber layer is 1 to 2 mm.

[0016] Embodiment [5]: A friction transmission belt according to any of Embodiments [1] to [4], wherein the entire side surface of the belt body is covered with the surface rubber layer.

[0017] Aspect [6]: The friction transmission belt according to any one of the aspects [1] to [5], wherein the entire surface of the belt body is covered with the surface rubber layer.

[0018] Aspect [7]: The friction transmission belt according to any one of the aspects [1] to [6], wherein the short fibers are oriented in a direction perpendicular to the belt length direction on the friction transmission surface.

[0019] Aspect [8]: The friction transmission belt according to any one of the aspects [1] to [7], wherein the short fibers are at least one selected from the group consisting of polyalkylene arylate short fibers, nylon short fibers, and cellulose short fibers.

[0020] Aspect [9]: A method for manufacturing the friction transmission belt according to any one of the aspects [1] to [8], including a rolling process of rolling a rubber composition containing a rubber component and short fibers to obtain a surface rubber layer precursor, and a covering process of covering the belt body precursor with the surface rubber layer precursor.

[0021] 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.

Advantages of the Invention

[0022] In the present invention, at least a part of the side surface of the belt body is covered with a surface rubber layer formed of a crosslinked rubber composition containing a rubber component and short fibers, and the short fibers are oriented in a direction parallel to the friction transmission surface. Therefore, while ensuring a friction coefficient (appropriate slidability) that gives appropriate slippage and sound resistance during running at the same level as a wrapped V-belt, the friction coefficient does not decrease during running, and the transmission performance can be maintained. Furthermore, by finely adjusting the type and ratio of the short fibers contained in the crosslinked rubber composition forming the friction transmission surface, the friction coefficient of the friction transmission surface can be easily finely adjusted. Also, by adjusting the fiber length of the short fibers, the variation in the friction coefficient of the friction transmission surface can be suppressed, and the manufacturing quality can be improved.

Brief Description of the Drawings

[0023] [Figure 1] Figure 1 is a schematic partial cross-sectional perspective view of a conventional wrapped V-belt. [Figure 2] Figure 2 is a schematic partial cross-sectional perspective view of a conventional low-edge cogged V-belt. [Figure 3] Figure 3 is a schematic partial cross-sectional perspective view of an example of the V-belt of the present invention. [Figure 4] Figure 4 is a schematic partial cross-sectional perspective view of another example of the V-belt of the present invention. [Figure 5] Figure 5 is a schematic diagram illustrating the method for measuring the friction coefficient of the belt obtained in the example. [Figure 6] Figure 6 shows the layout of the belt transmission performance test obtained in the embodiment. [Figure 7] Figure 7 is a graph showing the torque changes during the belt transmission performance test obtained in the embodiment. [Figure 8] Figure 8 is a schematic diagram illustrating the method for measuring the flexibility of the belt obtained in the example. [Modes for carrying out the invention]

[0024] [Friction transmission belt] The friction transmission belt of the present invention is a V-belt in which the belt body is covered with a surface rubber layer containing short fibers, instead of the cover cloth (friction canvas) of a wrapped V-belt. The area covered with the surface rubber layer may be at least a part of the side surface of the belt body (friction transmission surface), but from the viewpoint of productivity, the entire side surface is preferred, and the entire surface of the belt body is particularly preferred. As mentioned above, V-belts can be broadly classified into wrapped V-belts and raw edge V-belts, but the V-belt of the present invention is positioned between the two. Therefore, the configuration of the V-belt of the present invention will be explained with reference to the drawings, in comparison with conventional wrapped V-belts and conventional raw edge V-belts.

[0025] (Wrapped V-belt) Figure 1 is a schematic partial cross-sectional perspective view of a conventional wrapped V-belt. As shown in Figure 1, the wrapped V-belt 21 is formed of an endless belt body consisting of an stretchable rubber layer 22 on the outer circumference of the belt, a compression rubber layer 24 on the inner circumference of the belt, and a core wire 23 embedded between the stretchable rubber layer 22 and the compression rubber layer 24 along the longitudinal direction of the belt (circumferential direction, direction A in the figure), and a cover cloth 25 that covers the periphery of this belt body over the entire length in the circumferential direction of the belt. That is, in a wrapped V-belt, as described in Patent Document 1, the friction transmission surface is formed of a cover cloth (friction canvas) containing a rubber composition (so-called friction rubber). Therefore, in a wrapped V-belt, the form of the surface that contacts the pulley is canvas (woven fabric) to which friction rubber is attached. Although the coefficient of friction is relatively large in the initial stages of running due to the friction rubber, as the friction rubber wears down (disappears) due to friction with the pulley during running, the canvas is gradually exposed and the coefficient of friction decreases. When the coefficient of friction decreases, the friction transmission surface becomes more slippery, which reduces the transmission performance of the belt.

[0026] In applications requiring moderate slipperiness (such as shock resistance), a state where the coefficient of friction is reduced to a certain extent due to wear (disappearance) of the friction rubber is preferable, even considering the balance with transmission performance. However, since the coefficient of friction decreases further during operation, it is not possible to maintain this preferable state in the long term (the coefficient of friction cannot be stabilized).

[0027] (Raw edge V-belt) Figure 2 is a schematic partial cross-sectional perspective view of a raw edge cogged V-belt, a type of conventional raw edge V-belt. As shown in Figure 2, the raw edge cogged V-belt 31 has cog sections on the inner circumferential surface of the belt body, in which cog peaks 31a and cog valleys 31b are formed alternately along the longitudinal direction of the belt. The cross-sectional shape of the cog peaks 31a in the longitudinal direction is approximately semicircular (curved or wave-shaped), and the cross-sectional shape in the direction perpendicular to the longitudinal direction (width direction) is trapezoidal. The raw edge cogged V-belt 31 has a laminated structure, in which a reinforcing fabric 32, an stretchable rubber layer 33 containing short fibers 33a, an adhesive rubber layer 34 in which core wires 34a are embedded, a compression rubber layer 35 containing short fibers 35a, and a reinforcing fabric 36 are sequentially laminated from the outer circumferential side to the inner circumferential side (the side where the cog sections are formed). In this low-edge cogged V-belt 31, short fibers 33a and 35a are oriented along the belt width direction within the compression rubber layer 35 and the stretch rubber layer 33, respectively.

[0028] In low-edge V-belts, the friction transmission surface is formed from the rubber composition of exposed compressed and stretched rubber layers. Therefore, compared to wrapped V-belts where the friction transmission surface is formed from fibers such as cloth, the friction coefficient of the friction transmission surface formed from the rubber composition is higher in low-edge V-belts (resulting in better grip and less slippage). However, in many low-edge V-belts (especially variable-speed belts), short fibers are oriented in the belt width direction (approximately perpendicular to the friction transmission surface), as shown in Figure 2, to improve resistance to lateral pressure. Therefore, in the friction transmission surface of a low-edge V-belt containing short fibers, the friction coefficient is slightly reduced due to the short fibers being exposed only at their tips. Furthermore, even if the surface wears down during operation, the same configuration is maintained, so the friction coefficient remains unchanged and can be maintained during operation. In other words, while low-edge V-belts operate with a stable friction coefficient, the friction coefficient itself remains relatively high during operation.

[0029] (V-belt of the present invention) The V-belt of the present invention is a V-belt that can simultaneously achieve the maintenance of transmission performance, which is difficult to achieve with wrapped V-belts, and moderate sliding properties, which is difficult to achieve with low-edge V-belts. The V-belt of the present invention will be described based on Figures 3 and 4, which show an embodiment in which the entire surface of the belt body is covered with a surface rubber layer (or cover rubber layer).

[0030] Figure 3 is a schematic partial cross-sectional perspective view of an example of the V-belt of the present invention, and Figure 4 is a schematic partial cross-sectional perspective view of another example of the V-belt of the present invention.

[0031] As shown in Figure 3, the V-belt 1 is formed from an endless belt body consisting of an stretchable rubber layer (or upper core rubber layer) 2 on the outer circumference of the belt, a compression rubber layer (or V-core rubber layer) 4 on the inner circumference of the belt, and an adhesive rubber layer 3 interposed between the stretchable rubber layer 2 and the compression rubber layer 4, and a surface rubber layer 5 that covers the periphery of the belt body along its entire length in the circumferential direction. In this V-belt 1, the cross-sectional shape is an inverted trapezoid (V-shape), and the surface rubber layers 5 on both sides that are inclined in a V-shape form a friction transmission surface that contacts the inner wall of the V-groove of the pulley.

[0032] Core wires 3a are embedded in the adhesive rubber layer 3 along the longitudinal direction of the belt (circumferential direction, direction A in the figure). The core wires 3a are core wires (twisted cords) arranged at predetermined intervals in the belt width direction (direction B in the figure).

[0033] The surface rubber layer 5 contains short fibers 5a oriented along the plane direction of the surface rubber layer 5.

[0034] In this example, all short fibers 5a are oriented along the plane direction of the surface rubber layer 5. More specifically, the short fibers 5a are oriented in a direction along the plane direction of the surface rubber layer 5 (parallel to the friction transmission surface on the friction transmission surface) and perpendicular to the belt length direction (circumferential direction). In this application, this orientation direction of short fibers is referred to as "pattern V".

[0035] On the other hand, the V-belt 11 shown in Figure 4 is a V-belt that differs from the V-belt 1 shown in Figure 3 only in the orientation direction of the short fibers 15a in the surface rubber layer 15, while the stretch rubber layer 12, the adhesive rubber layer 13 including the core wires 13a, and the compression rubber layer 14 are the same as those of the V-belt 1.

[0036] In this example as well, the short fibers 15a are oriented along the planar direction of the surface rubber layer 15, just as in the V-belt 1 shown in Figure 3. However, as shown in Figure 4, the short fibers 15a are oriented in a direction along the planar direction of the surface rubber layer 15 (parallel to the friction transmission surface on the friction transmission surface) and parallel to the belt length direction (circumferential direction). In this application, this orientation direction of the short fibers is referred to as "pattern P".

[0037] In other words, the V-belts shown in Figures 3 and 4 can be manufactured by covering the belt body precursor with a friction canvas in the wrapped V-belt process with an "uncrosslinked rubber sheet mixed with short fibers," and then crosslinking the rubber during the crosslinking molding (vulcanization) process, while the covering material integrates with the V-belt body. When manufactured in this way, the covering layer of the finished V-belt becomes a surface rubber layer containing short fibers, and this layer becomes the friction transmission surface. In the present invention, the short fibers are arranged in a direction parallel to the friction transmission surface. "Direction parallel to the friction transmission surface" means the direction in which the short fibers are oriented in the plane direction of the friction transmission surface, which corresponds to the side surface in Figures 3 and 4. The orientation direction of the short fibers does not need to be in the plane direction of the friction transmission surface, and it may be oriented in any direction relative to the belt length direction, and is not limited to pattern V in Figure 3 and pattern P in Figure 4. However, from the viewpoint of productivity, pattern V perpendicular to the belt length direction and pattern P parallel to the belt length direction are preferred, and pattern V is particularly preferred because it does not impair the flexibility of the belt. In contrast, in a low-edge V-belt, the orientation direction of the short fibers is perpendicular to the belt thickness direction (approximately perpendicular to the friction transmission surface), which is significantly different from the orientation direction of the short fibers in the present invention.

[0038] In other words, the difference between the V-belt of the present invention, the conventional wrapped V-belt, and the conventional raw-edge V-belt lies in the shape of the friction transmission surface (V-shaped side surface). Therefore, these friction transmission belts are distinguished by the difference in the surface morphology of the surface that contacts the pulley, and the difference in surface morphology results in a difference in the coefficient of friction, which is an indicator of the degree of slippage (slipability, gripability) against the pulley, and this difference results in a difference in sliding properties (degree of slippage) against the pulley. Furthermore, the difference in surface morphology also results in a difference in wear resistance (retention of the coefficient of friction). Table 1 shows a summary of these differences when comparing each belt.

[0039] [Table 1]

[0040] As shown in Table 1, the V-belt of the present invention has a lower coefficient of friction than a raw-edge V-belt because the area ratio of the fiber component occupying the friction transmission surface is larger, bringing it closer to the cover fabric surface of a wrapped V-belt (a state in which a certain amount of friction rubber has disappeared). On the other hand, unlike a wrapped V-belt, the V-belt of the present invention maintains the same shape even when the surface wears down during driving, so the coefficient of friction does not change and can be maintained while driving (it runs with a stable coefficient of friction while maintaining a relatively small coefficient of friction). Therefore, the V-belt of the present invention is positioned as a V-belt that can replace a wrapped V-belt in applications where a moderate amount of slippage (such as shock load resistance) is required, as it can provide equivalent moderate slippage and also has excellent friction coefficient maintenance (it can eliminate the decrease in the coefficient of friction during driving, which was a drawback of wrapped V-belts).

[0041] The V-belt of the present invention may have a friction coefficient on its friction transmission surface that is similar to the friction coefficient of the design value of a wrapped V-belt. Specifically, the static friction coefficient (apparent friction coefficient) of the V-belt of the present invention in the belt movement method is, for example, 1.1 to 1.5, preferably 1.15 to 1.45, more preferably 1.2 to 1.4, and more preferably 1.25 to 1.35. Furthermore, the static friction coefficient after travel can also be selected from the above range, including a preferred range. If the friction coefficient of the friction transmission surface is too low, there is a risk that the slippage will become too large and the transmission performance will be insufficient, and if it is too high, there is a risk that the mitigation of shock due to appropriate slippage (shock load resistance) will not function.

[0042] In this application, the static friction coefficient of the friction transmission surface in the V-belt (and the static friction coefficient of the friction transmission surface in the V-belt after travel) refers to the average of the static friction coefficients measured by the belt movement method, and can be measured in detail by the method described in the embodiments below.

[0043] In the V-belt of the present invention, in the examples shown in Figures 3 and 4, the surface rubber layer covers the entire surface of the belt body. However, as mentioned above, it may also cover only the entire side surface of the belt, or only the friction transmission surface of the belt side surface. In other words, considering productivity and other factors, the configuration in which the entire outer surface of the belt is covered, as shown in Figures 3 and 4, is preferable, but the upper surface (outer surface) and lower surface (inner surface) of the belt do not necessarily need to be covered with a surface rubber layer containing short fibers.

[0044] Furthermore, the V-belt of the present invention is not limited to the structure shown in Figures 3 and 4. For example, in the examples shown in Figures 3 and 4, the core wire is embedded in the adhesive rubber layer, but the core wire may be interposed between the stretch rubber layer and the compression rubber layer without providing an adhesive rubber layer, or the core wire may be embedded in the compression rubber layer or the stretch rubber layer.

[0045] The following describes in detail the surface rubber layer and belt body constituting the V-belt of the present invention, as well as the manufacturing method of the V-belt. Conventional pulleys can be used as pulleys, and in the case of a V-belt, a pulley equipped with a V-groove corresponding to the V-shape of the belt's friction transmission surface can be used.

[0046] [Surface rubber layer] In the V-belt of the present invention, the surface rubber layer is formed of a crosslinked rubber composition (first crosslinked rubber composition) containing a rubber component (first rubber component) and short fibers (first short fibers).

[0047] The average thickness of the surface rubber layer can be appropriately selected depending on the type of belt, for example, 0.2 to 5 mm, preferably 0.3 to 4 mm, more preferably 0.4 to 3 mm, more preferably 0.5 to 2.5 mm, and most preferably 0.8 to 2.2 mm. If the average thickness of the surface rubber layer is too small, this layer may disappear prematurely due to wear during driving, and the coefficient of friction may increase prematurely. Conversely, if the average thickness is too large, the flexibility will decrease, which may make the belt more prone to cracking.

[0048] In this application, the average thickness of each layer is determined as the average value of any 10 points.

[0049] (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 components can be used individually or in combination of two or more.

[0050] Of these rubber components, diene rubbers (natural rubber, chloroprene rubber, hydrogenated nitrile rubber, etc.) and ethylene-α-olefin elastomers [ethylene-propylene copolymer (EPM), ethylene-propylene-non-conjugated diene terpolymer (EPDM), ethylene-1-butene-non-conjugated diene copolymer (EBDM), etc.] are preferred, and chloroprene rubber is particularly preferred because it is relatively inexpensive while offering excellent abrasion resistance, heat resistance, and adhesion to fabrics.

[0051] The proportion of the first rubber component can be selected from a range of about 10 to 90% by mass in the first crosslinked rubber composition, for example, 20 to 85% by mass, preferably 30 to 80% by mass, more preferably 50 to 75% by mass, more preferably 55 to 70% by mass, and most preferably 60 to 65% by mass. If the proportion of the first rubber component is too low, the abrasion resistance may decrease, and conversely, if it is too high, the sliding properties may decrease.

[0052] (1B) First short fiber Examples of the first short fibers include polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers (polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers, aramid fibers, etc.), and polyalkylene arylate fibers [polyethylene terephthalate (PET) fibers, polyethylene naphthalate (PEN) fibers, etc.]. 2-4 Alkilen C 6-14 Synthetic fibers such as arylate fibers, vinylon fibers, polyvinyl alcohol fibers, and poly(p-phenylenebenzobisoxazole) (PBO) fibers; natural fibers such as cotton, linen, and wool; and inorganic fibers such as carbon fibers are commonly used. These short fibers can be used individually or in combination of two or more types.

[0053] As mentioned above, the first short fibers only need to be oriented in the direction of the friction transmission surface, and the material is not particularly limited and can be selected according to the belt's characteristics (coefficient of friction and strength). Among these, synthetic fibers such as polyamide fibers and polyalkylene arylate fibers, and cellulose fibers such as cotton are commonly used. The present invention is characterized by the ability to fine-tune the characteristics of the V-belt by fine-tuning the type and amount of the first short fibers. In particular, when used in the applications of conventional wrapped V-belts, the present invention makes it easy to fine-tune the coefficient of friction of the belt side surface, which is the contact surface with the pulley. In contrast, with conventional wrapped V-belts, fine-tuning of the coefficient of friction is difficult because the friction transmission surface is a cover cloth.

[0054] In applications where sliding properties are important, the first short fiber is preferably at least one selected from the group consisting of polyalkylene arylate fibers such as PET fibers, nylon fibers such as polyamide 6 fibers, and cellulose fibers such as cotton, due to its excellent flexibility (crack resistance). A combination of polyalkylene arylate fibers and / or nylon fibers with cellulose fibers is more preferable, and a combination of nylon fibers and cellulose fibers is most preferable.

[0055] When polyalkylene arylate fibers and / or nylon fibers are combined with cellulose fibers, the mass ratio of the two is 90 / 10 to 1 / 99, preferably 80 / 20 to 10 / 90, more preferably 70 / 30 to 20 / 80, and more preferably 50 / 50 to 30 / 70.

[0056] For applications where strength is critical, aramid fibers are preferred as the first staple fiber.

[0057] The average fiber diameter of the first short fibers is, for example, 1 to 1000 μm, preferably 3 to 100 μm, more preferably 5 to 50 μm, more preferably 10 to 30 μm, and most preferably 20 to 30 μm. If the average fiber diameter is too large, the mechanical properties of the surface rubber layer may deteriorate, and if it is too small, it may be difficult to disperse it uniformly.

[0058] The average fiber length of the first short fibers is, for example, 0.1 to 20 mm (particularly 1 to 20 mm), preferably 0.2 to 10 mm (particularly 1.5 to 10 mm), and more preferably 0.3 to 9 mm (particularly 2 to 7 mm), more preferably 0.4 to 8 mm (particularly 2.5 to 6 mm), and most preferably 0.5 to 7 mm, in order to suppress variations in the coefficient of friction on the friction transmission surface. If the average length of the first short fibers is too short, the sliding properties may decrease, and conversely, if it is too long, the dispersibility may decrease.

[0059] From the viewpoint of dispersibility and adhesion of the first short fibers in the first crosslinked rubber composition, it is preferable that at least the short fibers be bonded (or surface-treated). However, it is not necessary for all short fibers to be bonded; bonded short fibers and unbonded short fibers (untreated short fibers) may be mixed or used in combination.

[0060] In the bonding treatment of the first short fibers, various bonding treatments can be used, such as a treatment solution containing an initial condensate of phenols and formalin (such as a prepolymer of novolac or resol-type phenolic resin), a treatment solution containing a rubber component (or latex), a treatment solution containing the initial condensate and a rubber component (latex), a silane coupling agent, an epoxy compound (such as epoxy resin), or a reactive compound (adhesive compound) such as an isocyanate compound. In a preferred bonding treatment, the short fibers are treated with a treatment solution containing the initial condensate and a rubber component (latex), particularly with at least a resorcinol-formaldehyde-latex (RFL) solution. Such treatment solutions may be used in combination; for example, the short fibers may be pretreated with a conventional adhesive component, such as an epoxy compound (such as epoxy resin) or a reactive compound (adhesive compound) such as an isocyanate compound, and then treated with an RFL solution.

[0061] The proportion of the first short fibers may be 10 parts by mass or more (particularly 30 parts by mass or more) per 100 parts by mass of the first rubber component, for example 10 to 100 parts by mass, preferably 12 to 80 parts by mass (particularly 20 to 80 parts by mass), more preferably 13 to 60 parts by mass (particularly 30 to 60 parts by mass), more preferably 15 to 50 parts by mass (particularly 40 to 50 parts by mass), and most preferably 18 to 48 parts by mass (particularly 20 to 45 parts by mass), in order to ensure appropriate slip and noise resistance during driving while maintaining transmission performance. If the proportion of the first short fibers is too low, the coefficient of friction will become too high compared to conventional wrapped V-belts, which may result in the mitigation of impact through appropriate slip (shock load resistance) not working. Conversely, if it is too high, the coefficient of friction will become too low, which may result in excessive slip and insufficient transmission performance.

[0062] (1C) First cross-linking compound The first crosslinked rubber composition may further contain a first crosslinking compound. Examples of the first crosslinking compound include a first crosslinking agent (vulcanizing agent) for crosslinking the first rubber component, as well as a first co-crosslinking agent, a first crosslinking aid (vulcanization aid), a first crosslinking accelerator (vulcanization accelerator), and a first crosslinking retarder (vulcanization retarder). Of these, it is preferable to include a first crosslinking agent, and the first crosslinking agent is particularly preferred.

[0063] As the first crosslinking agent, conventional components can be used depending on the type of first rubber component, and examples include organic peroxides, sulfur-based crosslinking agents, and metal oxides.

[0064] Examples of organic peroxides include di-t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, 1,1-t-butylperoxy-3,3,5-trimethylcyclohexane, 1,3-bis(t-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyn-3, 1,3-bis(t-butylperoxy-di-isopropyl)benzene, 2,5-di-methyl-2,5-di(benzoylperoxy)hexane, t-butylperoxybenzoate, and t-butylperoxy-2-ethyl-hexyl carbonate. These organic peroxides can be used individually or in combination of two or more.

[0065] Examples of sulfur-based crosslinking agents include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and sulfur chloride (sulfur monochloride, sulfur dichloride, etc.). These sulfur-based crosslinking agents can be used individually or in combination of two or more.

[0066] Examples of metal oxides include magnesium oxide, zinc oxide, and lead oxide. These metal oxides can be used individually or in combination of two or more.

[0067] The first crosslinking agent can be appropriately selected depending on the type of the first rubber component, and metal oxides are particularly preferred.

[0068] The proportion of the first crosslinking compound is, for example, 1 to 20 parts by mass, preferably 1.5 to 15 parts by mass, more preferably 2 to 10 parts by mass, and more preferably 3 to 5 parts by mass, per 100 parts by mass of the first rubber component. If the proportion of the first crosslinking compound is too low, the modulus and hardness of the first crosslinked rubber composition will decrease, and if it is too high, the flexibility of the belt will decrease.

[0069] (1D) First other additive The first crosslinked rubber composition may further contain other additives (first other additives), which are conventional additives used in rubber formulations.

[0070] Conventional additives include, for example, first-stage filling agents (first-stage reinforcing fillers such as carbon black and silica; first-stage non-reinforcing fillers such as calcium carbonate), softeners (oils such as paraffin oil and naphthenic oil), processing agents or processing aids (stearic acid or its metal salts, waxes, paraffin, fatty acid amides, etc.), plasticizers [aliphatic carboxylic acid plasticizers (adipate ester plasticizers, sebacate ester plasticizers, etc.), aromatic carboxylic acid esters]. Examples of additives include tellate plasticizers (phthalate ester plasticizers, trimellitic acid ester plasticizers, etc.), oxycarboxylic acid ester plasticizers, phosphate ester plasticizers, ether plasticizers, ether ester plasticizers, etc.), antioxidants (oxidants, heat aging inhibitors, flex crack inhibitors, ozone degradation inhibitors, etc.), colorants, adhesion improvers, tackifiers, plasticizers, coupling agents (silane coupling agents, etc.), stabilizers (UV absorbers, heat stabilizers, etc.), flame retardants, and antistatic agents. These additives can be used individually or in combination of two or more.

[0071] In particular, the proportion of the first softening agent is, for example, 1 to 20 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 first rubber component.

[0072] The proportion of the first processing agent or processing aid is, for example, 1 to 20 parts by mass, preferably 2 to 10 parts by mass, and more preferably 3 to 7 parts by mass, per 100 parts by mass of the first rubber component.

[0073] The total proportion of the first other compounding agent is, for example, 0.1 to 50 parts by mass, preferably 0.5 to 30 parts by mass, and more preferably 1 to 20 parts by mass, per 100 parts by mass of the first rubber component.

[0074] [Belt body] The belt body typically includes a compression rubber layer, an adhesive rubber layer containing a core wire, and a stretch rubber layer. Depending on the type of belt, the stretch rubber layer may be replaced with a backing fabric. On the other hand, the adhesive rubber layer is not an essential layer in the belt body, and the belt may be configured to include an adhesive rubber layer or not.

[0075] (Compressed rubber layer) The compression rubber layer is formed from a second crosslinked rubber composition (rubber composition for compression rubber layer) containing a second 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 25 mm, more preferably 2 to 20 mm, more preferably 2.5 to 10 mm, and most preferably 3 to 5 mm.

[0076] (2A) Second rubber component The second rubber component can be selected from the rubber components exemplified as the first rubber component, including preferred embodiments. The second rubber component is preferably of the same series or type as the first rubber component, and more preferably of the same type, in order to improve adhesion with the surface rubber layer.

[0077] The proportion of the second rubber component may be 10 to 95% by mass in the second crosslinked rubber composition, preferably 30 to 90% by mass, more preferably 40 to 85% by mass, more preferably 50 to 80% by mass, and most preferably 60 to 70% by mass.

[0078] (2B) Second crosslinking compound The second crosslinked rubber composition may further contain a second crosslinking compound. The second crosslinking compound can be selected from the crosslinking compound exemplified as the first crosslinking compound, including preferred embodiments.

[0079] The proportion of the second crosslinking compound is, for example, 1 to 30 parts by mass, preferably 2 to 25 parts by mass, more preferably 3 to 20 parts by mass, and more preferably 5 to 15 parts by mass, per 100 parts by mass of the second rubber component. If the proportion of the second crosslinking compound is too low, the modulus and hardness of the second crosslinked rubber composition will decrease, and if it is too high, the flexibility of the belt will decrease.

[0080] (2C) Second Other Additives The second crosslinked rubber composition may further contain other additives (second other additives), which are conventional additives used in rubber formulations. Examples of the second other additives include the conventional additives exemplified as the first other additives.

[0081] In particular, the proportion of the second reinforcing filler (especially carbon black) is, for example, 5 to 100 parts by mass, preferably 10 to 50 parts by mass, and more preferably 20 to 40 parts by mass, per 100 parts by mass of the second rubber component.

[0082] The proportion of the second plasticizer is, for example, 1 to 50 parts by mass, preferably 2 to 30 parts by mass, and more preferably 3 to 10 parts by mass, per 100 parts by mass of the second rubber component.

[0083] The proportion of the second processing agent or processing aid is, for example, 0.3 to 10 parts by mass, preferably 0.5 to 3 parts by mass, and more preferably 0.8 to 1.5 parts by mass, per 100 parts by mass of the second rubber component.

[0084] The total proportion of the second other compounding agent is, for example, 0.1 to 50 parts by mass, preferably 0.5 to 30 parts by mass, and more preferably 1 to 20 parts by mass, per 100 parts by mass of the second rubber component.

[0085] (Adhesive rubber layer) The adhesive rubber layer is formed from a third crosslinked rubber composition (rubber composition for adhesive rubber layer) containing a third rubber component. The average thickness of the adhesive rubber layer can be appropriately selected depending on the type of belt, but is, for example, 0.3 to 20 mm, preferably 0.5 to 10 mm, more preferably 1 to 7 mm, more preferably 1.5 to 5 mm, and most preferably 2 to 4 mm.

[0086] (3A) Third rubber component The third rubber component can be selected from the rubber components exemplified as the first rubber component, including preferred embodiments. The third rubber component is preferably of the same series or type as the second rubber component, and more preferably of the same type, in order to improve adhesion with the compression rubber layer.

[0087] The proportion of the third rubber component may be 10 to 95% by mass in the third crosslinked rubber composition, preferably 30 to 90% by mass, more preferably 40 to 80% by mass, more preferably 50 to 70% by mass, and most preferably 55 to 60% by mass.

[0088] (3B) Third crosslinking compound The third crosslinked rubber composition may further contain a third crosslinking compound. The third crosslinking compound can be selected from the crosslinking compound exemplified as the first crosslinking compound. Of the crosslinking compound, it is preferable to include a third crosslinking agent, and a combination of the third crosslinking agent and a third crosslinking accelerator is particularly preferred.

[0089] The third crosslinking agent can be selected from the crosslinking agents exemplified as the first crosslinking agent, including preferred embodiments.

[0090] Examples of third crosslinking accelerators include thiram-based accelerators such as tetramethylthiuram disulfide (TMTD); sulfenamide-based accelerators such as N-cyclohexyl-2-benzothiadylsulfenamide (CBS); and thiazole-based accelerators such as 2-mercaptobenzothiazole (MBT) and dibenzothiadyl disulfide (MBTS). These crosslinking accelerators can be used individually or in combination of two or more. Of these, thiram-based accelerators are preferred.

[0091] The proportion of the third crosslinking compound is, for example, 1 to 30 parts by mass, preferably 2 to 25 parts by mass, more preferably 3 to 20 parts by mass, and more preferably 5 to 15 parts by mass, per 100 parts by mass of the third rubber component. If the proportion of the third crosslinking compound is too low, the modulus and hardness of the first crosslinked rubber composition will decrease, and if it is too high, the flexibility of the belt will decrease.

[0092] The proportion of the third crosslinking agent is, for example, 1 to 30 parts by mass, preferably 2 to 25 parts by mass, more preferably 3 to 20 parts by mass, and more preferably 5 to 15 parts by mass, per 100 parts by mass of the third rubber component.

[0093] The proportion of the third crosslinking accelerator is, for example, 0.1 to 5 parts by mass, preferably 0.3 to 3 parts by mass, and more preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the third rubber component.

[0094] (3C) Third Other Additives The third crosslinked rubber composition may further contain other additives (third other additives), which are conventional additives used in rubber formulations. Examples of the third other additives include the conventional additives exemplified as the first other additives.

[0095] In particular, the proportion of carbon black is, for example, 5 to 100 parts by mass, preferably 10 to 50 parts by mass, and more preferably 20 to 40 parts by mass, per 100 parts by mass of the third rubber component.

[0096] The proportion of silica is, for example, 1 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 third rubber component.

[0097] The proportion of the third plasticizer is, for example, 1 to 50 parts by mass, preferably 2 to 30 parts by mass, and more preferably 3 to 10 parts by mass, per 100 parts by mass of the third rubber component.

[0098] The proportion of the third processing agent or processing aid is, for example, 0.3 to 10 parts by mass, preferably 0.5 to 3 parts by mass, and more preferably 0.8 to 1.5 parts by mass, per 100 parts by mass of the third rubber component.

[0099] The proportion of the third anti-aging agent is, for example, 1 to 30 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.

[0100] The total proportion of the third other compounding agent is, for example, 1 to 100 parts by mass, preferably 5 to 80 parts by mass, and more preferably 10 to 70 parts by mass, per 100 parts by mass of the third rubber component.

[0101] (Core wire) While not particularly limited, twisted cords arranged at predetermined intervals in the belt width direction can typically be used as the core wires. The core wires may be arranged extending in the length direction of the belt, or in parallel at a predetermined pitch parallel to the length direction of the belt, but from the viewpoint of productivity, they are usually arranged spirally in parallel at a predetermined pitch approximately parallel to the length direction of the belt. When arranged spirally, the angle of the core wires with respect to the length direction of the belt may be, for example, 5° or less, and from the viewpoint of belt running performance, it is preferable that it be as close to 0° as possible. Furthermore, the pitch or spacing (especially 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 1.5 to 2.5 mm, and more preferably in the range of 1.8 to 2.2 mm.

[0102] The fibers that make up the core include, for example, ethylene terephthalate and ethylene-2,6-naphthalate.2-4 Alkylene-C 8-14 Polyester fibers (polyalkylene arylate fibers) with arylate as the main constituent unit, synthetic fibers such as aramid fibers, and inorganic fibers such as carbon fibers are commonly used. Polyester fibers (polyethylene terephthalate fibers, polyethylene naphthalate fibers, etc.) and aramid fibers are preferred, and aramid fibers are particularly preferred.

[0103] These fibers may be used as multifilament yarn, which is made by drawing together a large number of fibers (filaments). The number of filaments in the multifilament yarn may be, for example, 100 to 5000, preferably 200 to 3000, and more preferably 300 to 1000. The fineness of the multifilament yarn may be, for example, 100 to 2000 dtex, preferably 300 to 1700 dtex, and more preferably 500 to 1250 dtex.

[0104] As the core wire, a twisted cord using multifilament yarn (e.g., multi-ply, single-ply, Lang-ply, etc.) can usually be used. The average diameter of the core wire (diameter of the twisted cord) may be, for example, 0.5 to 3 mm, preferably 0.6 to 2.5 mm, and more preferably 0.7 to 2 mm. The total fineness of the core wire (twisted cord) may be, for example, 2000 to 30000 dtex, preferably 5000 to 25000 dtex, and more preferably 10000 to 20000 dtex. The number of filaments contained in the core wire (twisted cord) may be, for example, 2000 to 20000, preferably 3000 to 12000, and more preferably 5000 to 8000.

[0105] The core wire may be bonded (or surface-treated) using conventional methods (such as bonding with RFL solution, epoxy compounds, or isocyanate compounds) to improve adhesion with the rubber component.

[0106] (Stretchable rubber layer) The fourth crosslinked rubber composition (rubber composition for the stretchable rubber layer) that forms the stretchable rubber layer may be a different rubber composition from the second crosslinked rubber composition (rubber composition for the compression rubber layer), or it may be the same rubber composition. From the viewpoint of productivity and other factors, it is preferable that the rubber composition for the compression rubber layer and the rubber composition for the stretchable rubber layer are the same rubber composition. Even if the rubber composition for the stretchable rubber layer is a different rubber composition from the rubber composition for the compression rubber layer, it is preferable that it is a rubber composition selected from preferred embodiments of the rubber composition for the compression rubber layer.

[0107] The average thickness of the stretchable rubber layer can be appropriately selected depending on the type of belt, but for example, it is 0.5 to 10 mm, preferably 0.6 to 5 mm, more preferably 0.6 to 4 mm, more preferably 0.7 to 3 mm, and most preferably 0.8 to 2 mm.

[0108] [Manufacturing method for V-belts] The V-belt of the present invention can be manufactured in the same manner as the conventional method for manufacturing a wrapped V-belt, except that in the covering step (the step of covering the belt body precursor with friction canvas) in the conventional method for manufacturing a wrapped V-belt, a surface rubber layer precursor (an uncrosslinked rubber sheet mixed with short fibers) is used instead of friction canvas.

[0109] In other words, the V-belt of the present invention can be obtained by a manufacturing method that includes a rolling step of rolling a first uncrosslinked rubber composition containing a first rubber component and first short fibers to obtain a surface rubber layer precursor, and a covering step of covering the belt body precursor with the surface rubber layer precursor.

[0110] In the rolling process, an uncrosslinked rubber composition is prepared by kneading the components, including the first rubber component and the first short fibers, in a conventional manner. Then, a surface rubber layer precursor can be obtained by a conventional rolling method, for example, by passing the rubber between a pair of calender rolls with a predetermined gap between them and rolling it into a sheet, thereby obtaining a rolled sheet in which the short fibers are oriented in the rolling direction. As such a manufacturing method, for example, the manufacturing method described in Japanese Patent Application Publication No. 2003-14054 can also be used.

[0111] Furthermore, the V-belt of the present invention can also be obtained by a manufacturing method that includes, for example, a rolling step of rolling various uncrosslinked rubber compositions to obtain various sheet-like precursors (compression rubber layer precursor, adhesive rubber layer precursor, stretch rubber layer precursor, surface rubber layer precursor); a winding step of cutting the compression rubber layer precursor and adhesive rubber layer precursor and setting them on a mantle, winding a core wire around them, and then winding the stretch rubber layer precursor on top of the wound core wire; a cutting step of cutting (slicing) the obtained annular laminate on the mantle; a skiving step of placing the cut annular laminate on a pair of pulleys and cutting it into a V shape while rotating to obtain a belt body precursor; a covering step of covering the obtained belt body precursor with the surface rubber layer precursor to obtain a belt precursor; and a crosslinking molding (vulcanization) step of crosslinking the obtained belt precursor. As a method for manufacturing such a wrapped V-belt, for example, the methods described in Japanese Patent Application Publication No. 6-137381 and WO2015 / 104778 can also be used. In the covering process, the surface rubber layer precursor is positioned relative to the belt body precursor such that the first short fibers contained in the surface rubber layer precursor are oriented in a predetermined direction. [Examples]

[0112] 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.

[0113] [Raw materials for rubber composition] Chloroprene rubber: "PM-40" manufactured by Denka Co., Ltd. Cotton staple fiber A: "Cotton staple fiber" manufactured by Hashimoto Co., Ltd., average fineness (cotton count) 8 count, average fiber length 3 mm Cotton staple fiber B: "Cotton staple fiber" manufactured by Hashimoto Co., Ltd., average fineness (cotton count) 8 count, average fiber length 0.1 mm Cotton staple fiber C: Manufactured by Hashimoto Co., Ltd., "Cotton Staple Fiber," average fineness (cotton count) 8, average fiber length 0.5 mm Cotton staple fiber D: Manufactured by Hashimoto Co., Ltd., "Cotton Staple Fiber," average fineness (cotton count) 8, average fiber length 7mm Cotton staple fiber E: Manufactured by Hashimoto Co., Ltd., "Cotton Staple Fiber," average fineness (cotton count) 8, average fiber length 10 mm Nylon staple fiber A: "Leona" (registered trademark) manufactured by Asahi Kasei Corporation, average fiber diameter 27 μm, average fiber length 3 mm Nylon staple fiber B: "Leona" manufactured by Asahi Kasei Corporation, average fiber diameter 27 μm, average fiber length 0.1 mm Nylon staple fiber C: "Leona" manufactured by Asahi Kasei Corporation, average fiber diameter 27 μm, average fiber length 0.5 mm Nylon staple fiber D: "Leona" manufactured by Asahi Kasei Corporation, average fiber diameter 27 μm, average fiber length 7 mm Nylon staple fiber E: "Leona" manufactured by Asahi Kasei Corporation, average fiber diameter 27 μm, average fiber length 10 mm Polyester staple fibers: "Tetron®" manufactured by Teijin Limited, average fiber diameter 25 μm, average fiber length 3 mm Aramid short fibers: "Twaron®" manufactured by Teijin Limited, average fiber diameter 12 μm, average fiber length 3 mm PBO short fibers: "Zylon®" manufactured by Toyobo Co., Ltd., average fiber diameter 12 μm, average fiber length 3 mm Magnesium oxide: "Kyowa Mag 150" manufactured by Kyowa Chemical Co., Ltd. Carbon black: "Seas S" manufactured by Tokai Carbon Co., Ltd., average primary particle size 66nm Silica: Manufactured by Evonik Japan Co., Ltd., "ULTRASIL® VN3", BET specific surface area 175 m² 2 / g Plasticizer: ADEKA Corporation's "ADEKA Sizer RS-700" Naphthenic oil: "NS-900" manufactured by Idemitsu Kosan Co., Ltd. Anti-aging agent: "Nonflex OD-3" manufactured by Seiko Chemical Co., Ltd. Zinc Oxide: "Zinc Oxide 3 Types" manufactured by Seido Chemical Industry Co., Ltd. N,N'-m-phenylenedimaleimide: "Balnock PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: "Stearic acid Tsubaki" manufactured by NOF Corporation. Crosslinking accelerator: "Noxellar TT" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Sulfur: Powdered sulfur manufactured by Migen Chemical Co., Ltd.

[0114] [Heart wire] Three bundles of 1670 dtex (1000 filaments) aramid fibers were joined together and twisted in the S direction with a twist coefficient of 3.0 to produce a base twist yarn. Five of these base twist yarns were then joined together and twisted in the Z direction with a twist coefficient of 3.0 to produce a twisted cord (multi-twisted yarn) with a total fineness of 25050 dtex (15000 filaments) and a diameter of 1.9 mm. This treated cord was then bonded and used as the core wire. The twist coefficient TF is calculated using the following formula.

[0115] 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.]

[0116] [Preparation of rubber composition] Rubber compositions R1 to R22 having the compositions shown in Tables 2 to 6 were kneaded in a Banbury mixer to prepare a lump of uncrosslinked rubber composition. The obtained uncrosslinked rubber composition was passed through a calender roll to produce a rolled rubber sheet of a predetermined thickness, thereby producing uncrosslinked rubber sheets that form each rubber layer except for the friction rubber. In the case of uncrosslinked rubber sheets containing short fibers, the sheets were manufactured so that the short fibers were oriented in the rolling direction.

[0117] [Table 2]

[0118] [Table 3]

[0119] [Table 4]

[0120] [Table 5]

[0121] [Table 6]

[0122] [Woven fabric for cover and reinforcement fabrics] Woven fabric made from a blend of polyester and cotton fibers (polyester fiber / cotton = 50 / 50 mass ratio) (120° wide-angle weave, fineness: 20 count warp and 20 count weft, warp and weft yarn density: 75 threads / 50mm, basis weight: 280g / m²) 2 Using the uncrosslinked rubber composition for friction rubber (rubber composition R4 in Table 3), the uncrosslinked rubber composition and the woven fabric were simultaneously passed between rolls with different surface speeds on a calender roll. Then, a friction treatment (performed once on each side of the woven fabric) was carried out to rub the uncrosslinked rubber composition into the weave of the fabric, thereby preparing a cover fabric precursor and a reinforcing fabric precursor.

[0123] [Manufacturing of V-belts] (Comparative Example 1) A wrapped V-belt was fabricated using the following steps (1) to (3).

[0124] (1) An uncrosslinked rubber sheet for the compression rubber layer made of rubber composition R1, an uncrosslinked rubber sheet for the adhesive rubber layer made of rubber composition R3, a core wire, and an uncrosslinked rubber sheet for the stretch rubber layer made of rubber composition R1 were sequentially laminated and attached to the outer surface of a cylindrical mantle to form a cylindrical uncrosslinked sleeve in which the uncrosslinked rubber sheets and core wires were laminated. The obtained uncrosslinked sleeve was cut in the circumferential direction while it was placed on the outer surface of the cylindrical mantle to produce an annular uncrosslinked rubber belt.

[0125] (2) Next, the uncrosslinked rubber belt was removed from the cylindrical mantle, 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 twice with the cover cloth precursor (thickness 0.6 mm) to produce an uncrosslinked belt molded body in which the belt body was double-covered with the cover cloth precursor (total thickness 1.2 mm).

[0126] (3) The obtained uncrosslinked belt molded body was inserted into the groove of the ring mold. Furthermore, with cylindrical rubber sleeves (jackets) fitted onto the outer surfaces of the ring mold and the uncrosslinked belt molded body, they were placed in a vulcanizing can and pressurized to 0.83 MPa at a temperature of 177°C to crosslink the rubber components, thereby obtaining a crosslinked wrapped V-belt.

[0127] (Example 1) In step (2) above, instead of using a cover cloth precursor, an uncrosslinked rubber sheet (0.6 mm thick) for the surface rubber layer made from rubber composition R5 was wrapped around twice as a covering material (covering layer), and joined on the lower surface (inner circumferential surface) of the belt to form an uncrosslinked belt molded body in which the periphery of the belt body was covered with an uncrosslinked rubber sheet for the surface rubber layer (total thickness 1.2 mm). The V-belt was manufactured in the same manner as in Comparative Example 1. The uncrosslinked rubber sheet for the surface rubber layer was arranged so that the orientation direction (rolling direction) of the short fibers was in the direction of pattern V in Figure 3 (a direction perpendicular to the belt length direction).

[0128] (Example 2) A V-belt was manufactured in the same manner as in Example 1, except that the wrapping of the uncrosslinked rubber sheet (0.6 mm thick) for the surface rubber layer was changed to one turn, and the total thickness of the covering material around the belt was changed to 0.6 mm.

[0129] (Example 3) A V-belt was manufactured in the same manner as in Example 1, except that the thickness of the uncrosslinked rubber sheet for the surface rubber layer was changed to 0.75 mm and the total thickness of the covering material around the belt was changed to 1.5 mm.

[0130] (Example 4) A V-belt was manufactured in the same manner as in Example 1, except that the number of turns of the uncrosslinked rubber sheet (0.6 mm thick) for the surface rubber layer was changed to three, and the total thickness of the uncrosslinked rubber sheet for the surface rubber layer around the belt was changed to 1.8 mm.

[0131] (Example 5) A V-belt was manufactured in the same manner as in Example 1, except that the number of turns of the uncrosslinked rubber sheet (0.6 mm thick) for the surface rubber layer was changed to 5 turns, and the total thickness of the uncrosslinked rubber sheet for the surface rubber layer around the belt was changed to 3.0 mm.

[0132] (Example 6) A V-belt was manufactured in the same manner as in Example 1, except that the orientation direction (rolling direction) of the short fibers in the uncrosslinked rubber sheet for the surface rubber layer was arranged to be in the direction of pattern P in Figure 4 (parallel to the belt length direction).

[0133] (Reference example 1) The low-edge V-belt was manufactured using the following procedure (1) to (2).

[0134] (1) On the outer surface of a cylindrical drum, a reinforcing fabric (bottom fabric) precursor (total thickness 1.2 mm), an uncrosslinked rubber sheet for the compression rubber layer made from rubber composition R2, an uncrosslinked rubber sheet for the adhesive rubber layer made from rubber composition R3, a core wire, an uncrosslinked rubber sheet for the stretch rubber layer made from rubber composition R2, and a reinforcing fabric (top fabric) precursor (total thickness 1.2 mm) were sequentially laminated and attached to form a cylindrical uncrosslinked sleeve in which the reinforcing fabric precursor, uncrosslinked rubber sheet, and core wire were laminated. Then, a jacket was placed over the uncrosslinked belt sleeve and the mold was placed in a vulcanizing can, and a crosslinked belt sleeve was obtained by crosslinking molding at a temperature of 177°C and a pressure of 0.83 MPa.

[0135] (2) The obtained cross-linked belt sleeve was cut into sections of a predetermined width using a cutter, and then the sides were further cut into a V-shape to achieve the same V-angle (40°) as in Comparative Example 1, thereby obtaining a low-edge V-belt with the same shape as Comparative Example 1 and Examples 1 to 23 (endless with V-shaped sides).

[0136] (Example 7) A V-belt was prepared in the same manner as in Example 3, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R6 (the ratio of short fibers to 10 parts by mass per 100 parts by mass of rubber component was changed to 10 parts by mass).

[0137] (Example 8) A V-belt was prepared in the same manner as in Example 3, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R7 (the ratio of short fibers to 100 parts by mass of rubber component was changed to 20 parts by mass).

[0138] (Example 9) A V-belt was prepared in the same manner as in Example 3, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R8 (the ratio of short fibers to 100 parts by mass of rubber component was changed to 30 parts by mass).

[0139] (Example 10) A V-belt was prepared in the same manner as in Example 3, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R9 (the ratio of short fibers to 100 parts by mass of rubber component was changed to 60 parts by mass).

[0140] (Example 11) A V-belt was manufactured in the same manner as in Example 3, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R10 (short fibers were changed to cotton fibers).

[0141] (Example 12) A V-belt was manufactured in the same manner as in Example 3, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R11 (short fibers were changed to nylon fibers).

[0142] (Example 13) A V-belt was manufactured in the same manner as in Example 3, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R12 (short fibers were changed to polyester fibers).

[0143] (Example 14) A V-belt was manufactured in the same manner as in Example 3, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R13 (short fibers were changed to aramid fibers).

[0144] (Example 15) A V-belt was manufactured in the same manner as in Example 3, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R14 (short fibers were changed to PBO fibers).

[0145] (Example 16) A V-belt was prepared in the same manner as in Example 11, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R15 (the ratio of short fibers to 10 parts by mass per 100 parts by mass of rubber component was changed to 10 parts by mass).

[0146] (Example 17) A V-belt was prepared in the same manner as in Example 11, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R16 (the ratio of short fibers to 100 parts by mass of rubber component was changed to 60 parts by mass).

[0147] (Example 18) A V-belt was prepared in the same manner as in Example 14, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R17 (the ratio of short fibers to 10 parts by mass per 100 parts by mass of rubber component was changed to 10 parts by mass).

[0148] (Example 19) A V-belt was prepared in the same manner as in Example 14, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R18 (the ratio of short fibers to 100 parts by mass of rubber component was changed to 60 parts by mass).

[0149] (Example 20) A V-belt was manufactured in the same manner as in Example 3, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R19 (the fiber length of the short fibers was changed to 0.1 mm).

[0150] (Example 21) A V-belt was manufactured in the same manner as in Example 3, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R20 (the fiber length of the short fibers was changed to 0.5 mm).

[0151] (Example 22) A V-belt was manufactured in the same manner as in Example 3, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R21 (the fiber length of the short fibers was changed to 7 mm).

[0152] (Example 23) A V-belt was manufactured in the same manner as in Example 3, except that the rubber composition used for the uncrosslinked rubber sheet for the surface rubber layer was changed to rubber composition R2221 (the fiber length of the short fibers was changed to 10 mm).

[0153] Table 7 shows the results of the thickness of each layer (excluding the belt covering layer) for Comparative Example 1, Examples 1-23, and Reference Example 1.

[0154] [Table 7]

[0155] [Evaluation and Judgment] For each test specimen (example, comparative example, reference example), the coefficient of friction, manufacturing quality, transmission performance (slip ratio), and flexibility (crack resistance) were verified to determine whether a V-belt capable of solving the problem of the present invention was obtained.

[0156] [Coefficient of friction] The coefficient of friction of the belt was measured using the following method (belt movement method). As shown in Figure 5, one end of the belt test piece 41, which had been cut to create an end, was fixed to the load cell 42, and a load of 1.5 kgf (test load Ts) was suspended from the other end. The belt test piece was positioned so that both sides (friction transmission surface) were in contact with the V-pulley 43 so that the winding angle θ was 80°. The load detected from the load cell 42 (measured load Tt) when the belt test piece 41 on the load cell 42 side was pulled at a speed of 30 mm / second for about 10 seconds was read, and the static friction coefficient μ was calculated using the following formula (1). The average value of the static friction coefficient obtained from the three measurement results was taken as the coefficient of friction of the belt friction transmission surface (average friction coefficient). During measurement, the V-pulley 43 was fixed so as not to rotate. The coefficient of friction was measured and calculated for the test specimen before and after the transmission performance test (before and after running), and evaluated according to the judgment criteria shown in Table 8. Furthermore, in measuring the static friction coefficient μ, the number of evaluation samples (n) for each test specimen (example, comparative example, reference example) was set to 5, and the average value of all measured values ​​was calculated.

[0157] μ = ln(Tt / Ts) / θ···(1) (In the formula, μ: coefficient of static friction, Tt[N]: measured load, Ts[N]: test load, θ[rad]: wrapping angle (contact angle))

[0158] The design value for the friction coefficient of the wrapped V-belt in Comparative Example 1 is 1.3. If the friction coefficient is too low, the slippage will be excessive, and the designed transmission performance may not be ensured. Conversely, if it is too high, the shock absorption effect (shock load resistance) due to moderate slippage and the noise resistance may not be obtained. In other words, a friction coefficient of 1.3 for the V-belt in the example is preferable for use as a substitute in the same applications as Comparative Example 1 (wrapped V-belt). However, if the friction coefficient value drops sharply between before and after driving, it means that the designed friction coefficient cannot be maintained, which can impair the function (transmission performance) of the belt.

[0159] [Table 8]

[0160] [Product Quality (Variation in Friction Coefficient)] The maximum value μ of the static friction coefficient μ (static friction coefficient μ before running) in all five evaluation samples (n = 5) of each test specimen (Example, Comparative Example, Reference Example) used for the evaluation of the [friction coefficient] max and the minimum value μ min The difference between them (μ max - μ min ) was calculated and evaluated according to the criteria shown in Table 9. The smaller the μ max - μ min , the smaller the variation between the friction coefficient samples and the better the manufacturing quality can be judged.

[0161]

Table 9

[0162] [Transmission Performance Test] In the transmission performance test, the slip rate of the belt when the belt was run was evaluated using a two-axis running test machine with the layout shown in Fig. 6. The input torque pattern of the driving pulley in this transmission performance test is shown in Fig. 7.

[0163] Specifically, as shown in Fig. 6, the obtained V-belt was hung on each pulley of a two-axis running test machine consisting of a driving (Dr.) pulley with a diameter of 150.2 mm and a driven (Dn.) pulley with a diameter of 150.2 mm, and the belt was run for 20 minutes with an axial load of 1322 N, a rotational speed of the driving pulley of 2400 rpm, and a load torque of the driving pulley of 51.5 N·m (warm-up running). Then, after the load torque of the driving pulley was once reduced to 0 N·m (point A in Fig. 7), the load torque was gradually increased at a rate of 20 N·m / min, and the rotational speeds of the driving pulley and the driven pulley at the time when the input torque reached 100 N·m (point B in Fig. Ⅱ) were measured.

[0164] Then, from the rotational speeds of the driving pulley and the driven pulley at point A and point B, the slip rate was calculated according to the following formula and judged according to the criteria shown in Table 10. The smaller the slip rate, the better the transmission performance can be judged.

[0165] Slip ratio (%) = [(KA-KB) / KA] × 100 [In the formulas, KA = NA / RA and KB = NB / RB, where RA is the rotational speed (rpm) of the drive pulley during no-load operation (time A), NA is the rotational speed (rpm) of the driven pulley during no-load operation (time A), RB is the rotational speed (rpm) of the drive pulley during load operation (time B), and NB is the rotational speed (rpm) of the driven pulley during load operation (time B)]

[0166] [Table 10]

[0167] [Flexibility (reverse bending crack test)] (Test method) In the reverse bending crack test, as shown in Figure 8, a belt 51 with its inner and outer surfaces reversed was sandwiched between two parallel flat plates 52 and 53. The distance between plates 52 and 53 was gradually reduced at a speed of 50 mm / min, and the distance between the plates when a crack occurred in the belt was measured. A shorter distance between plates when a crack occurs indicates superior flexibility (crack resistance). The results were expressed as a relative evaluation with Comparative Example 1 as the baseline (value 100). A value of 105 or less was considered to be equivalent to Comparative Example 1, and was deemed suitable as a replacement belt for Comparative Example 1. The evaluation was performed in detail according to the criteria shown in Table 11.

[0168] [Table 11]

[0169] [Overall assessment] Based on the evaluation of each evaluation item, an overall evaluation was conducted according to the criteria shown in Table 12, and a rank of C or higher was considered a passing level.

[0170] [Table 12]

[0171] [Verification Results and Discussion] The verification results are shown in Tables 13-17.

[0172] [Table 13]

[0173] [Regarding Table 13] (Comparative Example 1) Comparative Example 1 is an example of a wrapped V-belt using friction canvas (a composite of canvas and friction rubber) as the covering material. In Comparative Example 1, the friction rubber wore down as the belt ran, gradually exposing the canvas. As a result, the coefficient of friction of the friction transmission surface decreased significantly with each run (a decrease of 0.7 before and after running), and the coefficient of friction was evaluated as d (fail). Furthermore, as the coefficient of friction decreased, the slip ratio increased, and the transmission performance was also evaluated as d (fail), resulting in an overall rating of D.

[0174] (Example 1) Example 1 uses rubber composition R5 as the covering material, forming a surface rubber layer with this crosslinked rubber composition, and setting its average thickness to 1.2 mm, the same level as the friction canvas of Comparative Example 1. By forming the friction transmission surface with a crosslinked rubber composition containing short fibers as a substitute for friction canvas, the friction coefficient of the friction transmission surface does not decrease even when the belt is running, the design friction coefficient (1.2 or more and 1.4 or less) is maintained, and the friction coefficient evaluation was rated as A. Furthermore, the transmission performance (slip ratio) was also at an acceptable level (rated as B), and the flexibility was also rated as A, the same as the belt of Comparative Example 1, so the overall evaluation was B rank.

[0175] (Examples 2-5) Examples 2 to 5 are based on the V-belt of Example 1, but with a modified average thickness of the surface rubber layer. In Example 2, where the average thickness of the surface rubber layer was reduced from 1.2 mm to 0.6 mm compared to Example 1, the friction coefficient was rated as 'a', but the slip ratio increased due to the decrease in lateral pressure rigidity, resulting in a transmission performance rating of 'c', and thus the overall rating was 'C'.

[0176] On the other hand, in Examples 3 (average thickness 1.5 mm), 4 (average thickness 1.8 mm), and 5 (average thickness 3.0 mm), where the average thickness of the surface rubber layer was increased, the friction coefficient and transmission performance (slip ratio) were all rated as A. Example 3 also had good flexibility, resulting in an overall rating of A. However, as the average thickness increased, flexibility tended to decrease and cracking became more likely. Due to the impact of flexibility, Example 4 received an overall rating of B, and Example 5 received a C.

[0177] Based on these results, V-belts with an average surface rubber layer thickness of 1.0 mm to 2.0 mm are considered to be well-balanced (B-rank or higher) in terms of friction coefficient, transmission performance, and flexibility. In particular, V-belts with an average thickness of 1.5 mm are considered to be the most well-balanced (A-rank) V-belts.

[0178] (Example 6) Example 6 is an example in which the orientation direction of the short fibers in the surface rubber layer was changed from the V-belt of Example 1 (where the orientation direction of the short fibers is pattern V) to the direction of pattern P (parallel to the belt length direction). The friction coefficient of the friction transmission surface was at the same level as Example 1, receiving an A rating. However, because the orientation direction of the short fibers became parallel to the belt length direction, the belt became less flexible, resulting in a decrease in the transmission performance (slip ratio) and flexibility (crack resistance) to a C rating, and thus the overall rating was C. From the results of Examples 1 and 6, it can be said that the orientation direction of the short fibers in the surface rubber layer should be in the direction of pattern V (perpendicular to the belt length direction).

[0179] (Reference example 1) Reference Example 1 is an example verified with a low-edge V-belt for comparison. On the friction transmission surface of the low-edge V-belt, short fibers are oriented in the belt width direction (a direction approximately perpendicular to the friction transmission surface), and there are short fibers in a form where only the tips are exposed. The coefficient of friction in this form is about 1.6, which is larger than the coefficient of friction of the V-belt in the example (about 1.4). Furthermore, even if the friction transmission surface wears down due to driving, the coefficient of friction does not change significantly and remains maintained while driving. In other words, the low-edge V-belt runs with a relatively large and stable coefficient of friction. The V-belt in the example can be said to be a V-belt that can run with a smaller coefficient of friction than the low-edge V-belt, but with a stable coefficient of friction similar to the low-edge V-belt.

[0180] [Table 14]

[0181] [Regarding Table 14] (Examples 7-10) This example is based on Example 3, but with the rubber composition forming the surface rubber layer changed from R5 to R6-R9, and the ratio of short fibers to the rubber component changed accordingly.

[0182] In these examples, the ratio of short fibers to 100 parts by mass of rubber component was varied from 10 parts by mass (Example 7), 20 parts by mass (Example 8), 30 parts by mass (Example 97), 45 parts by mass (Example 3), to 60 parts by mass (Example 10). As the ratio of short fibers increased, the coefficient of friction decreased, and a moderate shock absorption effect (shock load resistance) was obtained, but the transmission performance and flexibility tended to decrease. Specifically, Example 7, with a ratio of 10 parts by mass of short fibers, had a high coefficient of friction and was ranked C because it lacked a moderate shock absorption effect (shock load resistance). On the other hand, Example 10, with a ratio of 60 parts by mass of short fibers, had a coefficient of friction that was too low, resulting in a high slip ratio and insufficient transmission performance, which also resulted in a C rank. On the other hand, Examples 8, 9, and 3, which had a short fiber ratio of 20 to 45 parts by mass, achieved a balance between shock load resistance and transmission performance, and obtained an optimal coefficient of friction (1.2 to 1.4) that provided the same level of moderate slippage and noise reduction during driving as a wrapped V-belt. Since this coefficient of friction was maintained even after driving, they received an overall rating of A.

[0183] Therefore, from the viewpoint of achieving an excellent balance between the coefficient of friction (appropriate sliding properties), transmission performance, and flexibility (crack resistance), it can be said that the proportion of short fibers contained in the surface rubber layer is preferably about 20 to 45 parts by mass per 100 parts by mass of rubber component.

[0184] [Table 15]

[0185] [Regarding Table 15] (Examples 11-15) This example is based on Example 3, but with the rubber composition forming the surface rubber layer changed from R5 to R10-R14, and the type of short fibers included in the surface rubber layer changed.

[0186] Examples 11-13, which used cotton, nylon, and polyester as the short fibers, showed no significant difference in each evaluation item compared to Example 3, which used a 3:2 blend of cotton and nylon, and were ranked A. On the other hand, Examples 14-15, which used aramid and PBO as the short fibers, showed a slight decrease in flexibility (crack resistance) and were ranked B. Considering these results, it can be concluded that when the short fibers are selected from cotton, nylon, and polyester, the surface rubber layer is highly flexible and exhibits excellent bendability, while when aramid and PBO are used, the rubber composition becomes slightly more rigid, resulting in a slight decrease in flexibility and increased susceptibility to cracking. Therefore, from the viewpoint of excellent flexibility (crack resistance), it can be said that it is preferable to select the type of short fibers to be included in the surface rubber layer from cotton, nylon, and polyester.

[0187] [Table 16]

[0188] [Regarding Table 16] (Examples 16-19) This is an example of an investigation into the relationship between the types of short fibers contained in the surface rubber layer and the ratio of short fibers to the rubber component.

[0189] In these examples, focusing on the coefficient of friction and transmission performance, it was observed that as the proportion of short fibers increased, the coefficient of friction decreased, resulting in a moderate sliding effect that mitigated shock (shock load resistance), while the transmission performance tended to decrease. Furthermore, focusing on flexibility (crack resistance), it was observed that flexibility tended to be superior with a smaller proportion of short fibers, and when cotton or nylon were used for the short fibers.

[0190] In detail, Examples 7, 16, and 18, which contained 10 parts by mass of short fibers, were ranked C due to their high coefficient of friction and insufficient shock absorption (shock load resistance) from adequate sliding. On the other hand, Examples 10, 17, and 19, which contained 60 parts by mass of short fibers, were also ranked C due to their excessively low coefficient of friction, resulting in a high slip ratio and insufficient transmission performance. In contrast, Examples 3, 11, and 14, which contained 45 parts by mass of short fibers, achieved an optimal coefficient of friction (1.2 to 1.4) that balanced shock load resistance and transmission performance, and this coefficient of friction was maintained even after driving, resulting in an A rating for both coefficient of friction and transmission performance. However, Example 14, which used aramid for the short fibers, had slightly lower flexibility than Examples 3 and 11, which used cotton and nylon, and was ranked B, a slightly lower rank, from the perspective of flexibility (crack resistance).

[0191] Based on the above results, Examples 3 and 11, in which the proportion of short fibers contained in the surface rubber layer is 20 parts by mass or more and 50 parts by mass or less per 100 parts by mass of rubber component, and in which the short fibers are selected from cotton, nylon, and polyester, can be said to be the most suitable embodiment from the viewpoint of having the best balance (rank A) between the coefficient of friction (appropriate sliding properties), transmission performance, and flexibility (crack resistance).

[0192] [Table 17]

[0193] [Regarding Table 17] (Examples 20-23) This example is based on Example 3, but with the rubber composition forming the surface rubber layer changed from R5 to R19-R22, and the fiber length of the short fibers contained in the surface rubber layer was altered.

[0194] In Example 21, where the short fiber length was 0.5 mm, and Example 22, where it was 7 mm, there was no difference from Example 3 in all evaluation items, indicating that the fiber length of the short fibers included in the surface rubber layer can be appropriately selected from a relatively wide range. On the other hand, in Example 20, where the fiber length was 0.1 mm, and Example 23, where it was 10 mm, the variation in friction coefficient between samples was relatively large, resulting in a C rank from the perspective of manufacturing quality. Considering these results, in Example 20, where the short fiber length was extremely short at 0.1 mm, the orientation of the short fibers was disordered, and the orientation direction became somewhat random from pattern V, resulting in variation in the orientation of the short fibers on the belt surface between evaluation samples, which is thought to have caused variation in the friction coefficient. On the other hand, in Example 23, where the short fiber length was extremely long at 10 mm, the surface rubber layer became rigid, resulting in poor workability during manufacturing, making it difficult to repeatedly produce homogeneous samples, which is thought to have caused variation in the friction coefficient between evaluation samples.

[0195] Therefore, while the fiber length of the short fibers contained in the surface rubber layer can be appropriately selected from a relatively wide range, from the viewpoint of manufacturing quality, a range of approximately 0.5 to 7 mm is preferable.

[0196] (Effects obtained) From the above verification results, it was confirmed that the V-belts of Examples 1 to 23, in which the friction transmission surface is formed with a "surface rubber layer containing short fibers and with the short fibers oriented in a direction parallel to the friction transmission surface," have a lower coefficient of friction compared to the raw edge V-belt, and approach the coefficient of friction of the cover fabric surface of the wrapped V-belt (a state in which a certain amount of friction rubber has been lost). Furthermore, it was confirmed that even if the friction transmission surface wears down during driving, the coefficient of friction does not change and can be maintained while driving (driving with a stable coefficient of friction while maintaining a relatively small coefficient of friction). Therefore, it can be said that the V-belt of the present invention is a V-belt that can maintain transmission performance without the coefficient of friction decreasing during driving, while ensuring a coefficient of friction that provides the same level of appropriate slippage and noise resistance during driving as the wrapped V-belt.

[0197] In particular, regarding the surface rubber layer forming the friction transmission surface, it was found that if the average thickness is 1.0 mm or more and 2.0 mm or less, if the ratio of short fibers to 100 parts by mass of rubber component is 15 parts by mass or more and 50 parts by mass or less, if the short fibers are oriented perpendicular to the belt length direction, and if the short fibers are selected from cotton short fibers, nylon short fibers, and polyester short fibers, then a V-belt with an excellent balance in terms of friction coefficient (transmission performance and shock load resistance), manufacturing quality, maintenance of friction coefficient during driving, and flexibility can be provided. [Industrial applicability]

[0198] The friction transmission belt of the present invention can be used as a substitute for wrapped V-belts in similar applications, for example, in general industrial machinery such as compressors, generators, and pumps, as well as agricultural machinery such as combine harvesters, rice transplanters, and lawnmowers (harvesters). [Explanation of symbols]

[0199] 1…V-belt 2…Stretchable rubber layer 3…Adhesive rubber layer 3a…core wire 4…Compressed rubber layer 5…Surface rubber layer 5a...Short fibers

Claims

1. A friction transmission belt comprising a belt body with both sides inclined in a V-shape, and a surface rubber layer that covers at least a portion of the sides of the belt body and forms a friction transmission surface, The surface rubber layer is formed of a crosslinked rubber composition containing rubber components and short fibers. A friction transmission belt in which the short fibers are oriented in a direction parallel to the friction transmission surface.

2. The friction transmission belt according to claim 1, wherein the static friction coefficient in the belt movement method on the friction transmission surface is 1.2 to 1.

4.

3. The friction transmission belt according to claim 1 or 2, wherein the proportion of the short fibers is 15 to 50 parts by mass per 100 parts by mass of the rubber component.

4. The friction transmission belt according to claim 1 or 2, wherein the average thickness of the surface rubber layer is 1 to 2 mm.

5. The friction transmission belt according to claim 1 or 2, wherein the entire side surface of the belt body is covered with the surface rubber layer.

6. The friction transmission belt according to claim 1 or 2, wherein the entire surface of the belt body is covered with the surface rubber layer.

7. The friction transmission belt according to claim 1 or 2, wherein the short fibers are oriented in a direction perpendicular to the belt length direction on the friction transmission surface.

8. The friction transmission belt according to claim 1 or 2, wherein the short fibers are at least one selected from the group consisting of polyalkylene arylate short fibers, nylon short fibers, and cellulose short fibers.

9. A method for manufacturing a friction transmission belt according to claim 1 or 2, comprising: a rolling step of rolling a rubber composition containing rubber components and short fibers to obtain a surface rubber layer precursor; and a covering step of covering a belt body precursor with the surface rubber layer precursor.

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