JP7368082B2 - V-belt for power transmission - Google Patents

Description

The present invention relates to a transmission V-belt such as a low-edge V-belt or a low-edge cogged V-belt, and more particularly to a transmission V-belt with excellent wear resistance.

V-belts (transmission V-belts) that transmit power by friction transmission include the raw-edge type (Raw-Edge V-belt), which is a rubber layer with an exposed friction transmission surface (V-shaped side surface); There is a wrapped type (wrapped V-belt) whose surface is covered with a cover cloth, and it can be used depending on the application depending on the surface properties of the friction transmission surface (such as the coefficient of friction between the rubber layer and the cover cloth). There is. In addition, low edge type belts have cogs installed on only the bottom surface (inner circumferential surface) of the belt, or on both the bottom surface (inner circumferential surface) and the top surface (outer circumferential surface) of the belt to improve flexibility. There's a belt.

Low-edge V-belts and raw-edge cogged V-belts are mainly used to drive general industrial machinery, agricultural machinery, and drive auxiliary equipment in automobile engines. Further, a part of the raw edge cogged V-belt is called a speed change belt, and is used in belt-type continuously variable transmission devices such as motorcycles.

As shown in FIG. 1, the belt type continuously variable transmission device 30 is a device that continuously changes the gear ratio by winding a transmission V-belt 10 around a driving pulley 31 and a driven pulley 32. Each pulley 31, 32 includes a fixed pulley piece 31a, 32a whose movement in the axial direction is restricted or fixed, and a movable pulley piece 31b, 32b which is movable in the axial direction. and the inner peripheral walls of the movable pulley pieces 31b and 32b form a V-groove-shaped inclined opposing surface. Each pulley 31, 32 has a structure in which the width of the V groove of the pulley 31, 32 formed by these fixed pulley pieces 31a, 32a and movable pulley pieces 31b, 32b can be continuously changed. Both end surfaces in the width direction of the transmission V-belt 10 are formed with tapered surfaces whose inclinations match the V-groove-shaped inclined opposing surfaces of the respective pulleys 31 and 32. Then, it fits into any vertical position on the opposing surface of the V-groove. For example, if the state shown in FIG. 1(a) is changed to the state shown in FIG. 1(b) by narrowing the width of the V-groove of the driving pulley 31 and widening the width of the V-groove of the driven pulley 32, The transmission V-belt 10 moves above the V-groove on the driving pulley 31 side and below the V-groove on the driven pulley 32 side, and the winding radius around each pulley 31 and 32 changes continuously, resulting in speed change. The ratio can be changed steplessly.

In this way, the speed change belt is used in a harsh environment where it is repeatedly bent and moved in the radial direction of the pulley while receiving high lateral pressure from the pulley. In order to meet the demands for improved fuel efficiency and durability in belt-type continuously variable transmissions, the transmission belt has flexibility (ease of bending), lateral pressure resistance (resistance to deformation due to lateral pressure), Improvements in properties such as wear resistance are required. In response to such demands, short fibers are commonly blended into the rubber composition constituting the V-belt for power transmission.

For example, Japanese Patent Application Laid-open No. 2003-314619 (Patent Document 1) discloses that 100 parts by weight of the rubber component contains 5 to 35 parts by weight of short fibers, and the short fibers have a tensile modulus of 15 to 300 GPa. A high-load power transmission cogged V-belt made of a rubber composition containing organic fibers is disclosed, and wholly aromatic polyester is exemplified as the organic fibers. It is also stated that by blending short fibers, the rubber hardness can be increased while suppressing heat generation when the belt is bent, thereby increasing the belt transmission ability. In the examples, various properties of the cogged V belt were evaluated for a cogged V belt in which the stretch rubber layer and the compressed rubber layer were formed from a rubber composition containing nylon staple fibers and technora staple fibers. , polyparaphenylenebenzbisoxazole short fibers, polyvinyl alcohol short fibers, and wholly aromatic polyester short fibers have been evaluated for their belt heat generation temperatures.

However, even this belt is not sufficient to meet the recent strict requirements regarding fuel efficiency and durability, and further improvements in flexibility, lateral pressure resistance, and abrasion resistance have been required.

JP2003-314619A (Claims 1 and 3-4, paragraph [0022], Examples)

An object of the present invention is to provide a power transmission V-belt that can improve flexibility and lateral pressure resistance.

Still another object of the present invention is to provide a power transmission V-belt that can improve wear resistance and durability.

As a result of intensive studies to achieve the above object, the present inventors discovered that the flexibility and lateral pressure resistance of a power transmission V-belt can be improved by incorporating liquid crystalline polyester short fibers into the compressed rubber layer, and the present invention completed.

That is, the transmission V-belt of the present invention includes a compressed rubber layer containing a first rubber component and a first liquid crystal polyester staple fiber. The transmission V-belt may further include a stretchable rubber layer containing a second rubber component and a second liquid crystalline polyester staple fiber. A mass ratio of the first liquid crystal polyester short fibers to the first rubber component may be larger than a mass ratio of the second liquid crystal polyester short fibers to the second rubber component. The proportion of the first liquid crystal polyester short fibers may be about 5 to 50 parts by mass based on 100 parts by mass of the first rubber component. The single fiber fineness of the first and second liquid crystalline polyester short fibers may be about 1 to 12 dtex, respectively. The average fiber length of the first and second liquid crystal polyester short fibers may be about 1 to 6 mm, respectively. The first and second liquid crystalline polyester staple fibers may each be wholly aromatic liquid crystalline polyester staple fibers. The short fibers contained in the compressed rubber layer and the stretchable rubber layer may be short fibers made of first and second liquid crystal polyester fibers, respectively. The first and second rubber components may each be a rubber component made of an ethylene-α-olefin elastomer. The transmission V-belt further includes an adhesive rubber layer containing a third rubber component, and the proportion of short fibers in the adhesive rubber layer is less than 5 parts by mass based on 100 parts by mass of the third rubber component. You can. The transmission V-belt may be a low-edge type V-belt (particularly a low-edge cogged V-belt in which cogs are formed at least on the inner circumferential side), which is a rubber layer with an exposed friction transmission surface.

In the present invention, since the compressed rubber layer contains short liquid crystalline polyester fibers, the flexibility and lateral pressure resistance of the transmission V-belt can be improved. In particular, when used in a low edge type V-belt, which has a rubber layer with an exposed friction transmission surface, the wear resistance and durability of the belt can be improved.

FIG. 1 is a schematic diagram for explaining a speed change mechanism of a belt type continuously variable transmission. FIG. 2 is a schematic perspective view showing an example of the transmission V-belt of the present invention. FIG. 3 is a schematic cross-sectional view of the transmission V-belt of FIG. 2 taken in the belt longitudinal direction. FIG. 4 is a schematic diagram for explaining a method of measuring the friction coefficient of the belt obtained in the example. FIG. 5 is a schematic diagram for explaining a durability running test of the belt obtained in the example.

[Transmission V-belt]
The V-belt for power transmission of the present invention is not particularly limited as long as it includes a compressed rubber layer containing short liquid crystalline polyester fibers. From the viewpoint of a large effect, it is preferable to use a V-belt (such as a low-edge type V-belt or a V-ribbed belt) in which the friction transmission surface is an exposed rubber layer and is formed inclined in a V-shape (at a V angle). Low-edge type V-belts are particularly preferred because they are used in harsh environments and there is a strong demand for improved flexibility, lateral pressure resistance, and abrasion resistance. That is, the low edge type V-belt performs frictional transmission in the gap between the V-shaped pulleys, and therefore receives high side pressure from the pulleys. Therefore, if the lateral pressure resistance of the belt is low, the belt will buckle into a dish-like shape (dishing), and stress will concentrate at the interface of each component material such as the core wire and rubber, causing delamination. There is a risk that the belt life will be shortened. In this way, wrapped V-belts have relatively high wear resistance even without adding short fibers to the compressed rubber layer because the friction transmission surface is covered with a cover cloth, whereas low-edge type V-belts have short fibers It is highly necessary to increase the abrasion resistance of the exposed rubber layer by blending fibers, and the effects of the present invention are effectively exhibited.

The low edge type V belt includes a low edge V belt and a low edge cogged V belt. Furthermore, the raw edge cogged V belt is divided into the raw edge cogged V belt, in which cogs are formed only on the inner circumferential side of the raw edge V belt, and the raw edge cogged V belt, in which cogs are formed on both the inner circumferential side and the outer circumferential side of the raw edge belt. It can be roughly divided into V-belts. Among these, a low-edge cogged V-belt in which cogs are formed at least on the inner peripheral side of the low-edge V-belt is preferred because it is used as a speed change belt and the effects of the present invention are particularly effectively exhibited.

FIG. 2 is a schematic perspective view showing an example of the transmission V-belt (low edge cogged V-belt) of the present invention, and FIG. 3 is a schematic cross-sectional view of the transmission V-belt of FIG. 2 cut in the belt longitudinal direction. be.

In this example, the raw edge cogged V-belt 1 has a plurality of cog parts 1a formed on the inner peripheral surface of the belt main body at predetermined intervals along the longitudinal direction of the belt (direction A in the figure). The cross-sectional shape in the longitudinal direction of this cog portion 1a is approximately semicircular (curved or wavy), and the cross-sectional shape in the direction perpendicular to the longitudinal direction (width direction or B direction in the figure) is approximately semicircular (curved or wavy). is trapezoidal. That is, each cog portion 1a protrudes from the cog bottom portion 1b in a substantially semicircular shape in the cross section in the A direction in the belt thickness direction. The raw edge cogged V-belt 1 has a laminated structure, and from the outer circumferential side of the belt toward the inner circumferential side (the side where the cog portion 1a is formed), a reinforcing cloth 2, a stretchable rubber layer 3, an adhesive rubber layer 4 , a compressed rubber layer 5, and a reinforcing cloth 6 are sequentially laminated. The cross-sectional shape in the belt width direction is a trapezoid in which the belt width decreases from the outer circumferential side to the inner circumferential side. Further, a core body 4a is embedded in the adhesive rubber layer 4, and the cog portion 1a is formed in the compressed rubber layer 5 by a mold with a cog.

[Compressed rubber layer]
In the transmission V-belt of the present invention, the compressed rubber layer is formed of a rubber composition (vulcanized rubber composition) containing a first rubber component and a first liquid crystal polyester short fiber.

(First rubber component)
As the first rubber component, a vulcanizable or crosslinkable rubber may be used, such as diene rubber [natural rubber, isoprene rubber, butadiene rubber, chloroprene rubber, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber ( (nitrile rubber), hydrogenated nitrile rubber, etc.], ethylene-α-olefin elastomer, chlorosulfonated polyethylene rubber, alkylated chlorosulfonated polyethylene rubber, epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, fluororubber, etc. It will be done. These rubber components can be used alone or in combination of two or more.

Among these, ethylene-α-olefin elastomer and chloroprene rubber are preferred, as they can improve fuel efficiency by reducing belt weight, and improve durability such as ozone resistance, heat resistance, cold resistance, and weather resistance. From this point of view, ethylene-α-olefin elastomers [ethylene-propylene copolymer (EPM), ethylene-propylene-diene terpolymer (EPDM), etc.] are particularly preferred.

The proportion of the ethylene-α-olefin elastomer in the first rubber component may be 50% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more, from the viewpoint of improving fuel efficiency and durability. % by mass or more (especially 90 to 100% by mass), and most preferably 100% by mass (ethylene-α-olefin elastomer only).

(First liquid crystal polyester staple fiber)
In the present invention, since the compressed rubber layer contains the first liquid crystal polyester short fibers as short fibers, flexibility, lateral pressure resistance, and abrasion resistance can be simultaneously improved. Specifically, when blending cotton or nylon short fibers, which have conventionally been widely used as short fibers in compressed rubber layers, they have low elastic modulus and abrasion resistance, so it is difficult to improve lateral pressure resistance and abrasion resistance. Not enough. Furthermore, when aramid short fibers are blended, the lateral pressure resistance and abrasion resistance are considerably improved, but this is still not sufficient, and when a large amount is blended for further improvement, problems such as a decrease in processability and flexibility occur. On the other hand, when liquid crystalline polyester short fibers are blended, flexibility, lateral pressure resistance, and abrasion resistance can be improved at the same time. Liquid crystalline polyester short fibers have better abrasion resistance than aramid short fibers, so they do not need to be blended in large amounts and can suppress deterioration in processability and flexibility.

The first liquid crystal polyester short fiber is a short fiber made of polyester that has a mesogen group and exhibits liquid crystal-like properties in a molten state, and is a liquid crystal polyester made of a rigid aromatic polyester called engineering plastic. Short fibers are preferred.

The liquid crystalline polyester constituting the liquid crystalline polyester staple fiber has mesogenic groups (groups capable of forming liquid crystals) such as p-substituted aromatic rings, linear biphenyl groups, and substituted naphthyl groups as basic structural units. Any aromatic polyester that has linear ester bonds with various units may be used. Specifically, polyesters containing at least p-hydroxybenzoic acid as a polymerization component, such as p-hydroxybenzoic acid and diols (aromatic diols such as hydroquinone and dihydroxybiphenyl, C _2-6 alkanediols such as ethylene glycol, etc.) ), aromatic dicarboxylic acids (such as arene dicarboxylic acids such as terephthalic acid), and other aromatic hydroxycarboxylic acids (such as arene hydroxycarboxylic acids such as 6-hydroxy-2-naphthoic acid). An example is a copolymer with a polymer. More specifically, copolymers of p-hydroxybenzoic acid units and 4,4'-dihydroxybiphenyl units, copolymers of p-hydroxybenzoic acid units, 4,4'-dihydroxybiphenyl units, and terephthalic acid units. Examples include a copolymer of p-hydroxybenzoic acid units and ethylene terephthalate units, a copolymer of p-hydroxybenzoic acid units and 6-hydroxy-2-naphthoic acid units, and the like. Commercially available liquid crystal polyester products include "Zexion (registered trademark)" manufactured by KB Seiren Co., Ltd., "Vectran (registered trademark)" manufactured by Kuraray Co., Ltd., and "Sumika Super (registered trademark) LCP" manufactured by Sumitomo Chemical Co., Ltd. etc. can be exemplified. These liquid crystal polyesters can be used alone or in combination of two or more.

The liquid crystal polyester preferably has a large proportion of aromatic units such as para-hydroxybenzoic acid units from the viewpoint of excellent flexibility, lateral pressure resistance, and abrasion resistance, and the proportion of aromatic units is 50 mol among all structural units. % or more, preferably 80 mol% or more, more preferably 90 mol% or more, and may be 100 mol% (wholly aromatic liquid crystal polyester). Further, the liquid crystal polyester is preferably a wholly aromatic liquid crystal polyester containing parahydroxybenzoic acid units.

The first liquid crystal polyester short fibers may be short fibers obtained by cutting the first liquid crystal polyester fibers drawn into a fibrous shape into a predetermined length. The first liquid crystal polyester short fibers are preferably oriented in the width direction of the belt and embedded in the compressed rubber layer in order to suppress compressive deformation of the belt due to lateral pressure from the pulley (to increase lateral pressure resistance). In addition, it is preferable to make the short fibers protrude from the surface of the compressed rubber layer because it is possible to reduce the coefficient of friction on the surface to suppress noise (sounding) and to reduce wear due to friction with the pulley.

The average fiber length of the first liquid crystal polyester short fibers is, for example, 0.1 to 20 mm, preferably 0.5 to 15 mm (for example, 0 .5 to 10 mm), more preferably 1 to 6 mm (particularly 2 to 4 mm). If the average length of the first liquid crystalline polyester short fibers is too short, the mechanical properties in the grain direction may not be sufficiently enhanced and the lateral pressure resistance and abrasion resistance may decrease; However, there is a possibility that flexibility may be reduced due to a reduction in the orientation of the short fibers in the rubber composition. In particular, if the average fiber length is adjusted to 8 mm or less, for example 0.5 to 8 mm, preferably 1 to 5 mm, more preferably 1.5 to 4 mm, the dispersibility and orientation of the short fibers can be improved. Side pressure resistance and abrasion resistance (especially abrasion resistance) can be highly improved.

The single yarn fineness of the first liquid crystal polyester short fiber is, for example, 1 to 12 dtex, preferably 1.2 to 10 dtex (for example, 1.5 to 8 dtex), from the viewpoint that a high reinforcing effect can be imparted without reducing flexibility. More preferably, it is about 2 to 5 dtex (particularly 2 to 3 dtex). If the single yarn fineness is too large, there is a risk that the lateral pressure resistance and abrasion resistance per compounded amount will decrease, and if the single yarn fineness is too small, there is a risk that the flexibility will decrease due to a decrease in dispersibility in rubber. .

The first liquid crystalline polyester short fibers may be subjected to a general-purpose adhesive treatment in order to increase the adhesive strength with the first rubber component. Examples of such adhesive treatment include a method of dipping in a treatment liquid containing an epoxy compound or a polyisocyanate compound, a method of dipping in an RFL treatment liquid containing resorcinol, formaldehyde, and latex, and a method of dipping in rubber glue. These treatments may be applied alone or in combination of two or more types.

The proportion of the first liquid crystalline polyester short fibers is, for example, 5 to 50 parts by mass, preferably 5 to 40 parts by mass (for example, 8 to 35 parts by mass), and more preferably 10 parts by mass, based on 100 parts by mass of the first rubber component. ~30 parts by mass (particularly 20 to 30 parts by mass). If the amount of the first liquid crystal polyester short fibers is too small, the lateral pressure resistance and abrasion resistance will be reduced, and if the amount is too large, the processability may be reduced, and the flexibility of the belt may be reduced, leading to a decrease in durability.

(Other short fibers)
The rubber composition forming the compressed rubber layer may further contain other short fibers. Other short fibers include polyamide short fibers (polyamide 6 short fibers, polyamide 66 short fibers, polyamide 46 short fibers, aramid short fibers, etc.), polyalkylene arylate short fibers (for example, polyethylene terephthalate short fibers, polyethylene naphthalate short fibers) ), polyarylate short fibers (amorphous wholly aromatic polyester short fibers, etc.), vinylon short fibers, polyvinyl alcohol short fibers, polyparaphenylenebenzobisoxazole (PBO) short fibers, and other synthetic short fibers; cotton, linen , natural short fibers such as wool; and inorganic short fibers such as carbon short fibers. These other short fibers can be used alone or in combination of two or more. Among these, aramid staple fibers and PBO staple fibers are preferred.

The rubber composition forming the compressed rubber layer may contain these other short fibers, but it is preferable that the proportion of the first liquid crystal polyester short fibers is high, and the rubber composition does not substantially contain other short fibers. is preferred. Specifically, the proportion of the first liquid crystal polyester short fibers in the short fibers of the compressed rubber layer may be 30% by mass or more (for example, 30 to 100% by mass), for example, 40% by mass or more. , preferably 50% by mass or more (for example, 80% by mass or more), more preferably 90% by mass or more (especially 100% by mass). If the first liquid crystalline polyester short fiber, which has a greater effect of improving lateral pressure resistance and abrasion resistance than conventional short fibers, is used alone, there is no need to blend a large amount of short fiber, so the flexibility is improved. It is possible to improve lateral pressure resistance and wear resistance while suppressing deterioration.

(other ingredients)
The rubber composition forming the compressed rubber layer contains a vulcanizing agent or a crosslinking agent (or a crosslinking agent system) (sulfur-based vulcanizing agent, etc.), a co-crosslinking agent (bismaleimides, etc.), a vulcanization aid, or a vulcanization accelerator. agents (thiuram accelerators, etc.), vulcanization retarders, metal oxides (zinc oxide, magnesium oxide, calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, aluminum oxide, etc.), reinforcing agents (e.g. carbon black, silicon oxide such as hydrated silica), fillers (clay, calcium carbonate, talc, mica, etc.), softeners (oils such as paraffin oil and naphthenic oil, etc.), processing agents or processing aids ( stearic acid, metal stearate, wax, paraffin, fatty acid amide, etc.), antioxidants (antioxidants, heat aging inhibitors, flex cracking inhibitors, ozone deterioration inhibitors, etc.), colorants, tackifiers, Examples include plasticizers, coupling agents (silane coupling agents, etc.), stabilizers (ultraviolet absorbers, heat stabilizers, etc.), flame retardants, antistatic agents, and the like. These additives can be used alone or in combination of two or more. Note that the metal oxide may act as a crosslinking agent.

[Stretch rubber layer]
The transmission V-belt of the present invention may further include a stretched rubber layer formed of a rubber composition (vulcanized composition) containing a second rubber component and a second liquid crystalline polyester staple fiber.

(Second rubber component)
As the second rubber component, the rubber components exemplified for the first rubber component can be used, and preferred embodiments are also the same as those of the first rubber component. The second rubber component may be a different rubber component from the first rubber component, but is usually the same as the first rubber component.

(Second liquid crystal polyester staple fiber)
In the present invention, it is sufficient that the liquid crystalline polyester short fibers are included at least in the compressed rubber layer, but in order to further improve lateral pressure resistance and abrasion resistance (especially abrasion resistance), in addition to the compressed rubber layer, the liquid crystal polyester short fibers are It is preferable that the rubber layer also contains liquid crystalline polyester short fibers. When not only the compressed rubber layer but also the stretchable rubber layer contains the second liquid crystal polyester short fibers as short fibers, the lateral pressure resistance and abrasion resistance (especially abrasion resistance) are further improved. As the second liquid crystal polyester staple fiber, the liquid crystal polyester staple fibers exemplified in the first liquid crystal polyester staple fiber can be used, and preferable aspects such as type, average fiber length, and single yarn fineness are also the same as those of the first liquid crystal polyester staple fiber. is the same as The second liquid crystal polyester staple fibers may be different staple fibers from the first liquid crystal polyester staple fibers, but are usually the same as the first liquid crystal polyester staple fibers.

The proportion of the second liquid crystalline polyester short fibers may be 50 parts by mass or less, for example 1 to 50 parts by mass, preferably 5 to 40 parts by mass, and more preferably is about 10 to 30 parts by mass (especially 15 to 25 parts by mass). If the amount of the second liquid crystal polyester short fiber is too small, lateral pressure resistance and abrasion resistance (especially abrasion resistance) will decrease, and if it is too large, the processability will decrease, and the flexibility of the belt will decrease, resulting in a decrease in durability. There is a risk that this may decrease.

In the present invention, when the first and second liquid crystal polyester short fibers are included in both the compressed rubber layer and the stretched rubber layer, the mass ratio of the first liquid crystal polyester short fibers to the first rubber component (first The liquid crystal polyester staple fiber content) is preferably larger than the mass ratio of the second liquid crystal polyester staple fibers to the second rubber component (second liquid crystal polyester staple fiber content). By making the content of the first liquid crystal polyester short fibers larger than the content of the second liquid crystal polyester short fibers, it is possible to improve the lateral pressure resistance and abrasion resistance of the belt while suppressing a decrease in flexibility. On the other hand, if the content of the second liquid crystal polyester staple fibers is higher than the content of the first liquid crystal polyester staple fibers, the rigidity of the entire belt becomes too large, the flexibility tends to decrease, and the contact with the pulleys becomes uneven. Perhaps because of this, wear resistance tends to decrease.

As a specific short fiber content ratio of both layers, the content of the second liquid crystal polyester short fiber is preferably less than 1 times (0.95 times or less) the content of the first liquid crystal polyester short fiber, for example, 0.9. (e.g. 0.1 to 0.9 times), preferably 0.8 times or less (e.g. 0.3 to 0.8 times), more preferably 0.7 times or less (e.g. 0.5 to 0.7 times) 2 times).

(Other short fibers and other ingredients)
The rubber composition forming the stretchable rubber layer may also further contain other short fibers and other components exemplified in the rubber composition forming the compressed rubber.

The rubber composition forming the stretchable rubber layer may also contain other short fibers for the same reason as the compressed rubber layer, but it is preferable that the proportion of the second liquid crystal polyester short fibers is high, and substantially Preferably, it does not contain other short fibers. The proportion of the second liquid crystalline polyester short fibers is also similar to the rubber composition forming the compressed rubber.

[Adhesive rubber layer]
The transmission V-belt of the present invention may further include an adhesive rubber layer formed of a rubber composition (vulcanized rubber composition) containing a third rubber component.

As the third rubber component, the rubber components exemplified for the first rubber component can be used, and preferred embodiments are also the same as those of the first rubber component. The third rubber component may be a different rubber component from the first rubber component, but is usually the same as the first rubber component.

The rubber composition forming the adhesive rubber layer may contain short fibers. Examples of short fibers include the liquid crystal polyester short fibers exemplified as the first liquid crystal polyester short fibers, and the short fibers exemplified as other short fibers that may be included in the composition forming the compressed rubber layer. . These short fibers can be used alone or in combination of two or more. Among these short fibers, liquid crystal polyester short fibers are preferred.

In the rubber composition forming the adhesive rubber layer, the proportion of short fibers is set to 100% by mass of the third rubber component in order to improve the adhesive force between the core and the third rubber component and improve the durability of the belt. The amount may be less than 5 parts by weight, for example, 3 parts by weight or less (for example, 0.01 to 3 parts by weight), preferably 2 parts by weight or less, and more preferably 1 part by weight or less. In particular, the rubber composition forming the adhesive rubber layer preferably does not substantially contain short fibers. Here, "substantially not containing" means allowing short fibers to be unavoidably mixed, and the amount thereof is less than 1 part by mass per 100 parts by mass of the third rubber component.

The rubber composition forming the adhesive rubber layer may also further contain other components exemplified in the rubber composition forming the compressed rubber layer.

[Core body]
The core body is not particularly limited, but usually core wires (twisted cords) arranged at predetermined intervals in the belt width direction can be used. The core wires are arranged to extend in the longitudinal direction of the belt, and are usually arranged in parallel with each other at a predetermined pitch in parallel to the longitudinal direction of the belt. The core wire only needs to have at least a part of it in contact with the adhesive rubber layer, and may be in a form in which the core wire is buried in the adhesive rubber layer, in a form in which the core wire is buried between the adhesive rubber layer and the stretchable rubber layer, or in a form in which the core wire is buried in the adhesive rubber layer. Any form may be used in which the core wire is embedded between the layer and the compressed rubber layer. Among these, a form in which the core wire is embedded in the adhesive rubber layer is preferred from the viewpoint of improving durability.

Examples of the fibers constituting the core wire include the same fibers as the short fibers. Among the above fibers, from the viewpoint of high modulus, polyester fibers (polyalkylene arylate fibers) containing _C2-4 alkylene-arylates such as ethylene terephthalate and ethylene-2,6-naphthalate as the main constituent units, aramid fibers, etc. Synthetic fibers, inorganic fibers such as carbon fibers, etc. are commonly used, and polyester fibers (polyethylene terephthalate fibers, polyethylene naphthalate fibers) and polyamide fibers are preferred. The fibers may be multifilament yarns. The fineness of the multifilament yarn may be, for example, about 2,000 to 10,000 deniers (particularly 4,000 to 8,000 deniers). The multifilament yarn may include, for example, 100 to 5,000 monofilament yarns, preferably 500 to 4,000, and more preferably 1,000 to 3,000 monofilament yarns.

As the core wire, a twisted cord (for example, plied, single-twisted, rung-twisted, etc.) using multifilament yarn can usually be used. The average wire diameter of the core wire (fiber diameter of the twisted cord) may be, for example, 0.5 to 3 mm, preferably 0.6 to 2 mm, and more preferably about 0.7 to 1.5 mm. good.

The core wire may be subjected to adhesive treatment (or surface treatment) in the same manner as short fibers in order to improve adhesion with the rubber component. Preferably, the core wire is also adhesively treated with at least an RFL liquid.

[Reinforcement cloth]
In the power transmission V-belt of the present invention, when a reinforcing cloth is used, the reinforcing cloth is not limited to the form in which the reinforcing cloth is laminated on the surface of the compressed rubber layer. A reinforcing cloth may be laminated thereon, or a reinforcing layer may be embedded in a compressed rubber layer and/or an elongated rubber layer (for example, as described in JP-A No. 2010-230146). The reinforcing fabric can be formed of a fabric material (preferably a woven fabric) such as a woven fabric, a wide-angle canvas, a knitted fabric, or a non-woven fabric, and if necessary, the reinforcing fabric may be subjected to the adhesive treatment described above, for example, treated with an RFL liquid (dipping treatment). etc.), friction may be applied by rubbing the adhesive rubber into the cloth material, or the adhesive rubber and the cloth material may be laminated (coated) and then laminated on the surface of the compressed rubber layer and/or the stretchable rubber layer.

[Manufacturing method of transmission V-belt]
The method for manufacturing the power transmission V-belt of the present invention is not particularly limited, and a conventional method can be used for the step of laminating each layer (method for manufacturing a belt sleeve).

For example, in the case of a cogged V-belt, a laminate consisting of a reinforcing cloth (lower cloth) and a compressed rubber layer sheet (unvulcanized rubber) is arranged with the reinforcing cloth facing down and teeth and grooves arranged alternately. A cog pad (not fully vulcanized, but in a semi-vulcanized state) is placed in a flat mold with a cog and pressed at a temperature of about 60 to 100 degrees Celsius (especially 70 to 80 degrees Celsius) to form the cog part. After producing a certain pad), both ends of this cog pad may be cut perpendicularly from the top of the cog crest. Furthermore, an inner mold having teeth and grooves arranged alternately is placed on the cylindrical mold, and a cog pad is wound around the teeth and grooves, and the cog pad is joined at the top of the cog crest. After laminating the first adhesive rubber layer sheet (lower adhesive rubber: unvulcanized rubber) on the cog pad, the core wire is spun in a spiral shape, and the second adhesive rubber layer sheet is layered on top of the cog pad. A molded body may be prepared by sequentially wrapping a sheet (upper adhesive rubber: same as the first adhesive rubber layer sheet), a stretchable rubber layer sheet (unvulcanized rubber), and a reinforcing cloth (upper cloth). After that, the mold is placed in a vulcanizing can with a jacket over it, and the belt sleeve is prepared by vulcanizing at a temperature of about 120 to 200 degrees Celsius (especially 150 to 180 degrees Celsius). May be cut.

The present invention will be explained in more detail below based on Examples, but the present invention is not limited by these Examples. The details of the materials used in the examples and the evaluation methods of the measured evaluation items are shown below.

[Materials used]
EPDM: "NORDEL (registered trademark) IP4640" manufactured by DowDuPont, ethylene content 55%, ethylidenenorbornene content 4.9%
Liquid crystalline polyester short fiber 1: “Zexion (registered trademark)” manufactured by KB Seiren Co., Ltd., fineness 2.3 dtex, fiber length 3 mm
Liquid crystalline polyester short fiber 2: “Zexion (registered trademark)” manufactured by KB Seiren Co., Ltd., fineness 2.3 dtex, fiber length 10 mm
Aramid short fiber: "Twaron (registered trademark)" manufactured by Teijin Ltd., modulus 88 cN, fineness 2.2 dtex, fiber length 3 mm
Naphthenic oil: “Diana (registered trademark) process oil NS-90S” manufactured by Idemitsu Kosan Co., Ltd.
Carbon black HAF: "SEAST (registered trademark) 3" manufactured by Tokai Carbon Co., Ltd.
Anti-aging agent: “Nocrac (registered trademark) AD-F” manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Vulcanization accelerator DM: “Noxeler (registered trademark) DM” manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Vulcanization accelerator TT: “Noxeler (registered trademark) TT” manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Vulcanization accelerator CZ: “Noxeler (registered trademark) CZ” manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
Silica: "ULTRASIL (registered trademark) VN3" manufactured by Evonik Japan Co., Ltd., BET specific surface area 175 m ² /g
Cord: A fiber made by adhering a cord with a total denier of 6,000, which is made by plying 1,000 denier PET fibers in a 2x3 twist configuration with a top twist coefficient of 3.0 and a final twist coefficient of 3.0.

[Measurement of physical properties of vulcanized rubber]
(1) Hardness The compressed rubber layer sheet was press-vulcanized at a temperature of 170° C. for 20 minutes to produce a vulcanized rubber sheet (length 100 mm x width 100 mm x thickness 2 mm). The orientation direction of the short fibers was parallel to the width direction of the vulcanized rubber sheet. The hardness was measured in accordance with JIS K6253 (2012) using a laminate of three vulcanized rubber sheets as a sample using a durometer type A hardness tester.

(2) Amount of wear The compressed rubber layer sheet was press-vulcanized at a temperature of 170° C. for 20 minutes to produce a vulcanized rubber sheet (length 50 mm x width 50 mm x thickness 8 mm). The orientation direction of the short fibers was parallel to the thickness direction of the vulcanized rubber sheet (perpendicular to the polished surface). The vulcanized rubber sheet was cut out in the thickness direction using a hollow drill with an inner diameter of 16.2 mm to produce a cylindrical test piece with a diameter of 16.2±0.2 mm and a thickness of 8 mm. The amount of wear was measured using a DIN abrasion tester (rotating cylindrical abrasion tester) in accordance with JIS K6264 (2005). The abrasive cloth was attached to a rotating drum using an abrasive cloth presser, and the test method was Method A, in which the test piece was measured without rotating it, and the applied force on the test piece was 10N. The weight change of the test piece before and after the test was measured, and the amount of wear (wear volume) was calculated from the specific gravity of the test piece measured in advance.

(3) Compressive stress The sheet for the compressed rubber layer was press-vulcanized at a temperature of 170° C. for 20 minutes to produce a vulcanized rubber molded body (length 25 mm, width 25 mm, thickness 12.5 mm). The orientation direction of the short fibers was parallel to the thickness direction of the vulcanized rubber molded body (perpendicular to the compression surface). This vulcanized rubber molded body is sandwiched between a pair of metal compression plates from above and below (in the thickness direction of the vulcanized rubber molded body), and while the vulcanized rubber molded body and compression plates are in contact but are not pressed, The position of the upper compression plate was taken as the initial position. By lowering the upper compression plate at a speed of 10 mm/min, the vulcanized rubber molded body is pressed (pressing surface 25 mm x 25 mm) to distort the vulcanized rubber molded body by 20% in the thickness direction, and in this state is held for 1 second. After holding, the upper compression plate was raised and returned to the initial position (preliminary compression). After repeating this pre-compression three times, the stress-strain curve was measured while pressing at a speed of 10 mm/min in the same way as in the pre-compression. The stress was defined as compressive stress. It can be determined that the higher the measured compressive stress, the higher the lateral pressure resistance of the belt. Note that the preliminary compression was performed three times in order to suppress variations in measurement data.

[Belt evaluation]
(1) Friction coefficient As shown in Fig. 4, one end of the cut belt 11 is fixed to the load cell 12, a load 13 of 3 kgf is attached to the other end, and the belt is wrapped at a winding angle of 45°. 11 was wound around pulley 14. Pulley 14 is fixed and does not rotate. Then, the belt 11 was pulled from the load cell 12 side at a speed of 30 mm/sec for about 15 seconds, and the load T1 acting on the load cell 12 was measured. The friction coefficient μ was determined by the following formula.

μ=ln(T1/T2)/(π/4)
(In the formula, μ: friction coefficient, T1: load (N) acting on the load cell 12, T2: load (N) due to the load 13).

(2) Durability running test As shown in Fig. 5, the durability running test was carried out using a two-axis running test machine equipped with a driving (Dr.) pulley 22 with a diameter of 50 mm and a driven (Dn.) pulley 23 with a diameter of 125 mm. I went. A low edge cogged V-belt 21 is hung around each pulley 22, 23, the driving pulley 22 is rotated at 5000 rpm, the driven pulley 23 is applied a load of 10 Nm, and the belt 21 is run for 24 hours at an ambient temperature of 80°C. I let it happen. The side surface of the belt after running was observed visually and with a microscope to check for peeling of the core wire and cracks in the rubber layer, and if there was no peeling or cracks in the rubber layer, it was determined that there was no abnormality. In addition, the amount of wear was evaluated from the amount of change in the upper width of the belt before and after running, and the relative values are listed in the table, taking the amount of wear of Comparative Example 1 as 100.

Examples 1 to 7 and Comparative Examples 1 to 2
(Formation of rubber layer)
The rubber compositions in Table 1 (compressed rubber layer, stretchable rubber layer) and Table 2 (adhesive rubber layer) are rubber-kneaded using a known method such as a Banbury mixer, and the kneaded rubber is passed through a calendar roll. Rolled rubber sheets (sheets for compressed rubber layers, sheets for stretched rubber layers, and sheets for adhesive rubber layers) were produced. The short fibers were adhesively treated with RFL liquid (containing resorcinol, formaldehyde, and vinylpyridine-styrene-butadiene rubber latex as latex), and the short fibers had a solid content adhesion rate of 6% by mass. As the RFL liquid, 2.6 parts by mass of resorcin, 1.4 parts by mass of 37% formalin, 17.2 parts by mass of vinylpyridine-styrene-butadiene copolymer latex, and 78.8 parts by mass of water were used.

Table 3 shows the results of evaluating the physical properties of the vulcanized rubber of the obtained compressed rubber layer sheet.

As is clear from Table 3, when comparing the physical properties of vulcanized rubber, rubber compositions A to E containing liquid crystalline polyester short fibers had higher wear resistance than rubber composition F containing aramid short fibers. . In particular, rubber composition B, in which 30 parts by mass of liquid crystalline polyester short fibers is blended alone with respect to 100 parts by mass of the polymer component, has the highest compressive stress in addition to hardness and abrasion resistance, and has the highest compressive stress in the rubber layer of the power transmission V-belt. It had characteristics suitable for Furthermore, rubber composition E with liquid crystalline polyester short fibers having a fiber length of 10 mm had slightly lower abrasion resistance and compressive stress than rubber composition A with fiber length 3 mm.

[Manufacture of belts]
A laminate of the reinforcing fabric and the sheet for the compressed rubber layer (unvulcanized rubber) was placed in a flat cog-equipped mold with alternating teeth and grooves with the reinforcing fabric facing down, and pressed at 75°C. A cog pad (not completely vulcanized, but in a semi-vulcanized state) with a cog portion molded by pressing was produced. Next, both ends of this cog pad were cut perpendicularly from the top of the cog crest.

A cylindrical mold is covered with an inner matrix having alternating teeth and grooves, and the cog pad is engaged with the teeth and grooves, and the cog pad is joined at the top of the cog ridge. After laminating an adhesive rubber layer sheet (unvulcanized rubber) on top, the core wire is spun into a spiral shape, and on top of this, an adhesive rubber layer sheet (same as the adhesive rubber layer sheet above) and a stretch rubber layer sheet are laminated. A molded body was prepared by sequentially wrapping sheets (unvulcanized rubber). Thereafter, the mold was placed in a vulcanizing can with a jacket placed over it, and the mold was vulcanized at a temperature of 160° C. for 20 minutes to obtain a belt sleeve. This sleeve was cut into a V shape with a cutter to produce a raw edge cogged V belt (size: top width 22.0 mm, thickness 11.0 mm, outer circumference 800 mm), which is a speed change belt having cogs on the inner circumference side of the belt. .

Table 4 shows the evaluation results of the obtained belt.

As is clear from Table 4, when comparing the belt evaluation results, Examples 1 to 7 in which the compressed rubber layer contains liquid crystal polyester short fibers have good lateral pressure resistance and abrasion resistance while maintaining good flexibility. it was high. In particular, in Examples 1 to 4, both the compressed rubber layer and the stretchable rubber layer contain liquid crystalline polyester short fibers with a fiber length of 3 mm, and the blending amount of the short fibers in the compressed rubber layer is equal to that of the short fibers in the stretchable rubber layer. It is considered that the lateral pressure resistance and abrasion resistance were high while maintaining good flexibility. In particular, in Example 3, the short fibers were composed of liquid crystal polyester alone and did not contain any short fibers other than liquid crystal polyester, so the lateral pressure resistance and abrasion resistance were particularly high.

In Example 5, since the stretchable rubber layer did not contain short liquid crystalline polyester fibers, the amount of wear increased, but the bending fatigue resistance was good and there was no problem in durability. In addition, in Example 6, since the amount of short fibers in the compressed rubber layer and the stretched rubber layer are the same, it is thought that the abrasion resistance can be further improved by increasing the amount of short fibers contained in the stretched rubber layer of Example 3. However, in reality, the amount of wear increased slightly, probably because the entire belt became rigid and contact with the pulleys became uneven. Furthermore, in Example 7, since the fiber length of the liquid crystal polyester short fibers in the stretchable rubber layer was 10 mm, both the friction coefficient and the amount of wear increased slightly, probably because the dispersibility and orientation of the short fibers decreased. Ta.

On the other hand, Comparative Example 1, in which the compressed rubber layer and the stretchable rubber layer did not contain liquid crystalline polyester short fibers but contained conventional aramid short fibers, had low abrasion resistance. In addition, Comparative Example 2, in which the amount of short fibers in the stretched rubber layer was greater than the amount of short fibers in the compressed rubber layer, had low abrasion resistance and poor flexibility, and the rubber layer A crack has occurred.

The transmission V-belt of the present invention can be applied to, for example, a low-edge type V-belt (low-edge V-belt, low-edge cogged V-belt), a V-ribbed belt, and the like. In particular, V-belts (variable transmission belts) used in transmissions (continuously variable transmissions) in which the gear ratio changes steplessly while the belt is running, such as motorcycles, ATVs (four-wheeled buggies), snowmobiles, etc. It is preferable to apply the present invention to low edge cogged V-belts and low-edge double cogged V-belts used in transmissions.

1... V-belt for power transmission 2, 6... Reinforcement cloth 3... Stretch rubber layer 4... Adhesive rubber layer 4a... Core body 5... Compressed rubber layer

Claims (10)

A low edge type V-belt having a rubber layer with an exposed frictional transmission surface, and a power transmission V-belt comprising a compressed rubber layer containing a first rubber component and a first liquid crystalline polyester short fiber ,
The first liquid crystalline polyester short fiber has a single yarn fineness of 1 to 12 dtex,
The average fiber length of the first liquid crystal polyester short fibers is 1 to 6 mm, and
A transmission V-belt, wherein the proportion of the first liquid crystalline polyester short fibers is 5 to 50 parts by mass based on 100 parts by mass of the first rubber component. The power transmission V-belt according to claim 1, further comprising a stretchable rubber layer containing a second rubber component and a second liquid crystalline polyester staple fiber. 3. The transmission V-belt according to claim 2, wherein the mass ratio of the first liquid crystal polyester short fibers to the first rubber component is larger than the mass ratio of the second liquid crystal polyester short fibers to the second rubber component. The power transmission V-belt according to claim 2 or 3, wherein the second liquid crystalline polyester staple fiber has a single fiber fineness of 1 to 12 dtex. The power transmission V-belt according to any one of claims 2 to 4, wherein the second liquid crystal polyester short fibers have an average fiber length of 1 to 6 mm. The power transmission V-belt according to any one of claims 2 to 5 , wherein the first and second liquid crystalline polyester staple fibers are each wholly aromatic liquid crystalline polyester staple fibers. The power transmission V-belt according to any one of claims 2 to 6 , wherein the short fibers contained in the compressed rubber layer and the stretchable rubber layer consist of first and second liquid crystal polyester fibers, respectively. The power transmission V-belt according to any one of claims 2 to 7 , wherein the first and second rubber components each comprise an ethylene-α-olefin elastomer. Any one of claims 1 to 8 , further comprising an adhesive rubber layer containing a third rubber component, wherein the proportion of short fibers in the adhesive rubber layer is less than 5 parts by mass based on 100 parts by mass of the third rubber component. Transmission V-belt described in . The transmission V-belt according to any one of claims 1 to 9 , which is a low-edge cogged V-belt having cogs formed at least on the inner circumferential side.

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