V-belts and belt transmission mechanisms for power transmission

Abstract

To provide a transmission V-belt that can suppress exothermic heat even when being used for a small-sized belt type stepless speed change device, and can suppress peeling of a core wire and generation of cracks in a compressed rubber layer.SOLUTION: A core wire of a transmission V-belt is formed by Lang' lay cords obtained by doubling and ply-twisting a plurality of aramid fiber-containing first twist yarns, and a total fineness of the core wire is adjusted to 1,000-3,500 dtex. Tensile strength per wire of the core wire may be 500-1,000 N. A pitch of the core wire may be larger by 0.05-0.25 mm than an average diameter of the core wire, and an average diameter of the core wire may be 0.4-1 mm. An elongation rigidity per mm pitch width of the belt may be 6,500-20,000 N, and a flexural rigidity per mm pitch width of the belt may be 40-260 N (mm)2. A thickness of the transmission V-belt may be 5-12 mm, and a pitch width may be 10-25 mm. The transmission V-belt may be a low edge V-belt having a cog at least on the inner peripheral surface side, and the transmission V-belt may be a gear change belt to be used for a small-sized belt type stepless speed change device.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a V-belt for power transmission used in small belt-type continuously variable transmissions and the like, and a belt transmission mechanism equipped with this V-belt. [Background technology]

[0002] Power transmission belts used in power transmission mechanisms of machinery and other equipment are broadly classified into friction belts and meshing belts based on the method of power transmission. Examples of friction belts include V-belts, V-ribbed belts, and flat belts, while toothed belts are a well-known example of meshing belts.

[0003] One example of a V-belt is the low-edge type belt (low-edge V-belt), which is a rubber layer with an exposed friction transmission surface (V-shaped side). Low-edge type belts include low-edge V-belts without cogs, low-edge cogged V-belts which have cogs only on the inner circumference to improve flexibility, and low-edge cogged V-belts (low-edge double cogged V-belts) which have cogs on both the inner and outer circumferences to improve flexibility.

[0004] One application for these V-belts (especially raw-edge cogged V-belts) is a belt-type continuously variable transmission (CVT). As shown in Figure 1, the belt-type CVT 30 is a device that continuously changes the gear ratio by winding a V-belt 1A around a drive pulley 31 and a driven pulley 32. Each pulley 31, 32 consists of fixed sheaves 31a, 32a whose axial movement is restricted or fixed, and movable sheaves 31b, 32b that can move in the axial direction. The pulleys 31, 32 have a structure that allows the width of the V-groove formed by these fixed sheaves 31a, 32a and movable sheaves 31b, 32b to be continuously changed. The V-belt 1A has tapered surfaces at both ends in the width direction that match the inclination of the opposing surfaces of the V-grooves of each pulley 31, 32, and fits into any position in the pulley radial direction according to the adjusted width of the V-groove. For example, by narrowing the width of the V-groove on the drive pulley 31 and widening the width of the V-groove on the driven pulley 32, the state shown in Figure 1(a) is changed to the state shown in Figure 1(b). This causes the V-belt 1A to move towards the outer circumference in the radial direction of the pulley on the drive pulley 31 side and towards the inner circumference in the radial direction of the pulley on the driven pulley 32 side. As a result, the winding radius around each pulley 31 and 32 changes continuously, allowing for stepless adjustment of the gear ratio.

[0005] V-belts (variable speed belts) used in such applications require high resistance to lateral pressure (high rigidity in the width direction) to suppress deformation of the belt due to lateral pressure from the pulleys, high flexibility (low bending rigidity) to reduce the wrapping radius around the pulleys, and low elongation rigidity to suppress slippage and obtain the desired gear ratio.

[0006] As a solution to these requirements, Japanese Patent Publication No. 2010-196888 (Patent Document 1) discloses a power transmission belt in which the compression rubber layer consists of two layers: an upper layer close to the core wire and a lower layer on the inner circumferential surface side, with the hardness of the upper layer in the range of 93 to 99 and the hardness of the lower layer in the range of 80 to 88. This document also states that when the upper width of the belt is W and the thickness of the belt is T, the relationship between these two may be 0.3W ≤ T ≤ 0.6W. Furthermore, this document states that the effects of the invention include improving the deformation resistance of the belt with the upper layer having high hardness, providing excellent bending fatigue resistance and making it less prone to cracking with the lower layer having low hardness, and reducing deformation during bending and suppressing crack occurrence by making the belt thickness thinner.

[0007] Japanese Patent Publication No. 2005-265106 (Patent Document 2) aims to provide a double cogged V-belt that does not accelerate fatigue of the para-aramid fiber core and has excellent bending fatigue resistance, having a para-aramid fiber core and a belt bending rigidity of 600 to 1200 N / mm². 3 A double cogged V-belt is disclosed in which the dynamic compression spring constant in the belt width direction is 15,000 N / mm or more.

[0008] Japanese Patent Publication No. 2014-209029 (Patent Document 3) describes a core wire formed of aramid fiber with a width of 2.0 N / mm². 2 A power transmission belt is disclosed in which the strain when compressed with a stress is 0.5-0.8%, and the strain when pulled with a load of 2kN in the longitudinal direction is 0.35-0.7%. The document states that, as an effect of the invention, compared to conventional products, the rigidity in the belt width direction is slightly lower and the elongation in the belt longitudinal direction is slightly higher, so even if a large misalignment occurs during speed changes, the occurrence of pop-out, where the core wires protrude from the belt body, is suppressed. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2010-196888 [Patent Document 2] Japanese Patent Publication No. 2005-265106 [Patent Document 3] Japanese Patent Publication No. 2014-209029 [Overview of the project] [Problems that the invention aims to solve]

[0010] While the belt configurations disclosed in Patent Documents 1 to 3 demonstrate some effectiveness in meeting the performance requirements of V-belts, the demands for miniaturization of belt-type continuously variable transmissions and improved durability of transmission belts are becoming increasingly stringent, necessitating further improvements. In particular, when the winding radius around the pulley decreases, the heat generated when the belt is bent and stretched increases, accelerating thermal degradation of the rubber. This makes the rubber more prone to cracking and delamination of the core wires, leading to a decrease in belt durability.

[0011] Therefore, the object of the present invention is to provide a transmission V-belt and a belt transmission mechanism equipped with this transmission V-belt that can suppress heat generation and prevent peeling of the core wires and cracking of the compression rubber layer, even when used in a small belt-type continuously variable transmission. [Means for solving the problem]

[0012] As a result of diligent research to achieve the above objectives, the inventors have found that by forming the core wire of a transmission V-belt with a Lang twist cord, which is made by combining multiple under-twisted yarns containing aramid fibers and then over-twisting them, and by adjusting the total fineness of the core wire to 1000 to 3500 dtex, heat generation can be suppressed even when used in a small belt-type continuously variable transmission, and the peeling of the core wire and the occurrence of cracks in the compression rubber layer can also be suppressed, thus completing the present invention.

[0013] In other words, the present invention includes the following embodiments.

[0014] Aspect [1]: A V-belt for transmission, formed of a lang-twist cord that is obtained by combining and upper-twisting a plurality of lower-twisted yarns containing aramid fibers, and having a core wire with a total fineness of 1000 to 3500 dtex.

[0015] Aspect [2]: The V-belt for transmission according to Aspect [1], wherein the tensile strength per single core wire is 500 to 1000 N.

[0016] Aspect [3]: The V-belt for transmission according to Aspect [1] or [2], wherein in the core wire, the twist coefficient of the lower-twisted yarn is 0.5 to 3, and the twist coefficient of the lang-twist cord is 0.5 to 5.

[0017] Aspect [4]: The V-belt for transmission according to any one of Aspects [1] to [3], wherein the pitch of the core wire is 0.05 to 0.25 mm larger than the average diameter of the core wire.

[0018] Aspect [5]: The V-belt for transmission according to any one of Aspects [1] to [4], wherein the average diameter of the core wire is 0.4 to 1 mm.

[0019] Aspect [6]: The V-belt for transmission according to any one of Aspects [1] to [5], wherein the elongation rigidity per 1 mm of the pitch width of the V-belt for transmission is 6500 to 20000 N.

[0020] Aspect [7]: The V-belt for transmission according to any one of Aspects [1] to [6], wherein the bending rigidity per 1 mm of the pitch width of the V-belt for transmission is 40 to 260 N(mm) 2 and is the V-belt for transmission according to any one of Aspects [1] to [6].

[0021] Aspect [8]: The V-belt for transmission according to any one of Aspects [1] to [7], having a thickness of 5 to 12 mm and a pitch width of the V-belt for transmission of 10 to 25 mm.

[0022] Aspect [9]: The V-belt for transmission according to any one of Aspects [1] to [8], being a low-edge V-belt having cogs at least on the inner peripheral surface side.

[0023] Embodiment

[10] : A transmission V-belt according to any of the embodiments [1] to [9], which is a variable speed belt used in a small belt-type continuously variable transmission.

[0024] Embodiment

[11] : A belt transmission mechanism comprising a transmission V-belt according to any of the embodiments [1] to

[10] and a pulley.

[0025] Embodiment

[12] : The belt transmission mechanism of Embodiment

[11] , wherein the transmission V-belt is a low-edge V-belt having cogs on at least the inner circumferential surface side, and is a variable speed belt used in a small belt-type continuously variable transmission. [Effects of the Invention]

[0026] In this invention, the core wire of the transmission V-belt is formed from a Lang twist cord, which is made by twisting together multiple under-twisted yarns containing aramid fibers, and the total fineness of the core wire is adjusted to 1000 to 3500 dtex. As a result, even when used in a small belt-type continuously variable transmission, heat generation can be suppressed, and peeling of the core wire and cracking of the compression rubber layer can also be suppressed. [Brief explanation of the drawing]

[0027] [Figure 1] Figure 1 is a schematic cross-sectional view illustrating the transmission mechanism of a belt-type continuously variable transmission. [Figure 2] Figure 2 is a schematic partial cross-sectional perspective view showing an example of the low-edge cogged V-belt of the present invention. [Figure 3] Figure 3 is a schematic cross-sectional view of the raw-edge cogged V-belt shown in Figure 2, cut along the longitudinal direction of the belt. [Figure 4] Figure 4 is a schematic partial cross-sectional perspective view showing an example of the low-edge double-cogged V-belt of the present invention. [Figure 5] Figure 5 is a schematic cross-sectional view of the low-edge double-cogged V-belt shown in Figure 4, cut along the longitudinal direction of the belt. [Figure 6] Figure 6 is a schematic cross-sectional view illustrating the definition of the overall thickness of the low-edge double-cogged V-belt in the present invention. [Figure 7]Figure 7 is a schematic cross-sectional view illustrating the definition of the belt pitch width of the raw-edge cogged V-belt in the present invention. [Figure 8] Figure 8 is a schematic diagram illustrating the method for measuring the bending stiffness EI of the low-edge V-belt obtained in the embodiment. [Figure 9] Figure 9 shows the layout of the peel resistance test for the low-edge V-belt obtained in the example. [Figure 10] Figure 10 shows the layout of the crack resistance test for the low-edge V-belt obtained in the example. [Modes for carrying out the invention]

[0028] [V-belt for power transmission] The V-belt for power transmission of the present invention is not particularly limited as long as it is formed from a Lang twist cord made by splicing together multiple under-twisted yarns containing aramid fibers and twisting them over, and includes a core wire with a total fineness of 1000 to 3500 dtex. Furthermore, the V-belt for power transmission of the present invention is a friction transmission belt in which the friction transmission surface is V-shaped, and such a V-belt may be a raw-edge type belt (raw-edge V-belt) in which the friction transmission surface (V-shaped side surface) is an exposed rubber layer, or a wrapped type belt (wrapped V-belt) in which the friction transmission surface is covered with an outer fabric (cover fabric). Of these, the raw-edge V-belt is preferred in terms of superior power transmission performance.

[0029] Low-edge V-belts include low-edge V-belts without cogs and low-edge cogged V-belts with cogs. Furthermore, low-edge cogged V-belts include low-edge cogged V-belts in which cogs are formed only on the inner circumference and low-edge double cogged V-belts in which cogs are formed on both the inner and outer circumferences. In this application, low-edge V-belts without cogs, low-edge cogged V-belts, and low-edge double cogged V-belts are collectively referred to as low-edge V-belts. Of these, low-edge cogged V-belts and low-edge double cogged V-belts used in variable-speed transmission belts (CVT belts) are preferred due to their significant advantages in this invention.

[0030] Figure 2 is a schematic partial cross-sectional perspective view showing an example of the raw edge cogged V-belt of the present invention, and Figure 3 is a schematic cross-sectional view of the raw edge cogged V-belt of Figure 2 cut in the longitudinal direction of the belt.

[0031] In this example, the raw edge cogged V-belt 1 has a cog section on the inner circumference of the belt body in which cog peaks 1a and cog valleys 1b are formed alternately along the longitudinal direction of the belt (direction A in the figure). The cross-sectional shape of the cog peaks 1a 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 or direction B in the figure) is trapezoidal. That is, each cog peak 1a protrudes in an approximately semicircular shape from the cog valley 1b in the cross-section in direction A in the belt thickness direction. The raw edge cogged V-belt 1 has a laminated structure in which a reinforcing fabric 2, an elastic rubber layer 3, a core layer (adhesive rubber layer) 4, a compression rubber layer 5, and a reinforcing fabric 6 are sequentially laminated from the outer circumference to the inner circumference (the side where the cog section is formed). The cross-sectional shape in the belt width direction is trapezoidal, with the belt width decreasing from the outer circumference to the inner circumference. Furthermore, a core wire 4a is embedded within the adhesive rubber layer 4, and the cog portion is formed in the compressed rubber layer 5 by a cog-equipped molding die.

[0032] Figure 4 is a schematic partial cross-sectional perspective view showing an example of the raw edge double cogged V-belt of the present invention, and Figure 5 is a schematic cross-sectional view of the raw edge double cogged V-belt of Figure 4 cut in the longitudinal direction of the belt.

[0033] In this example, the low-edge double-cogged V-belt 11 has an inner circumferential cog section on the inner surface of the compression rubber layer 15, in which inner circumferential cog peaks 11a and inner circumferential cog valleys 11b are formed alternately along the longitudinal direction of the belt (direction A in the figure). The cross-sectional shape of the inner circumferential cog peaks 11a 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 or direction B in the figure) is trapezoidal. That is, each inner circumferential cog peak 11a protrudes approximately semicircularly from the inner circumferential cog valleys 11b in the cross-section in direction A in the belt thickness direction.

[0034] Furthermore, the outer surface also has an outer cog section in which outer cog peaks 11c and outer cog valleys 11d are formed alternately along the longitudinal direction of the belt. The cross-sectional shape of the outer cog peaks 11c in the longitudinal direction is approximately trapezoidal, and the cross-sectional shape in the direction perpendicular to the longitudinal direction (width direction or direction B in the figure) is approximately rectangular. That is, each outer cog peak 11c protrudes in a approximately trapezoidal shape in the cross-section in direction A from the outer cog valley 11d in the belt thickness direction.

[0035] The low-edge double-cogged V-belt has a laminated structure, with a stretchable rubber layer 13, a core layer (adhesive rubber layer) 14, a compression rubber layer 15, and a reinforcing fabric 16 being sequentially laminated from the outer circumference to the inner circumference of the belt. The cross-sectional shape in the belt width direction is approximately trapezoidal, with the belt width decreasing from the outer circumference to the inner circumference. Furthermore, a core wire 14a is embedded in the core layer 14, and the inner circumference cog portion and the outer circumference cog portion are formed in the compression rubber layer 15 and the stretchable rubber layer 13, respectively, by a cog-forming mold.

[0036] (Overall thickness of the V-belt for power transmission) In the power transmission V-belt of the present invention (particularly the low-edge V-belt), the overall thickness (average thickness) of the belt is, for example, 5 to 12 mm, preferably 7 to 11.5 mm, and more preferably 8 to 11 mm. In the present invention, when the thickness of the power transmission V-belt is within this range, the bending rigidity of the belt can be reduced, and even when used in a small belt-type continuously variable transmission, heat generation, core wire peeling, and rubber cracking can be suppressed.

[0037] Figure 6, based on Figure 5, shows the definition of the overall thickness of the raw edge double cogged V-belt in the present invention. Specifically, in Figure 6, in the raw edge double cogged V-belt 11, the outer circumference cog height H5 indicates the height of the outer circumference cog portion formed on the outer circumference surface, and the outer circumference pitch height H4 indicates the distance from the center of the core wire to the outer circumference surface (the top of the cog portion). In addition, the inner circumference cog height H2 indicates the height of the inner circumference cog portion formed on the inner circumference surface, and the core-to-valley thickness H3 indicates the distance from the center of the core wire to the deepest part of the inner circumference cog valley. In contrast, the overall thickness H1 means the sum of the inner circumference cog height H2, the core-to-valley thickness H3, and the outer circumference pitch height H4, and represents the thickness at the top of the cog portion (the maximum thickness of the belt).

[0038] In this application, the total thickness of a power transmission V-belt (especially a low-edge V-belt) refers to the thickness from the outer circumferential surface to the inner circumferential surface (the thickness at the thickest point of the belt). If a cog is present, as shown in Figure 6, the top of the cog will be on either the inner or outer circumferential surface. Therefore, in a low-edge cogged V-belt with cogs only on the inner circumferential surface, the total thickness is the distance from the outer circumferential surface to the top of the cog on the inner circumferential surface. In other words, the total thickness refers to the distance from the top of the cog in the compression rubber layer (the convex top on the inner circumferential side) to the back of the belt in the case of a low-edge cogged V-belt, and the distance from the top of the cog in the compression rubber layer (the convex top on the inner circumferential side) to the top of the cog in the stretch rubber layer (the convex top on the outer circumferential side) in the case of a low-edge double cogged V-belt.

[0039] (Belt pitch width of V-belt for power transmission) In the power transmission V-belt of the present invention (particularly the low-edge V-belt), the belt pitch width is, for example, 10 to 25 mm, preferably 12 to 24.5 mm, and more preferably 15 to 24 mm. In the present invention, when the belt pitch width of the power transmission V-belt is within this range, the bending rigidity of the belt can be reduced, and even when used in a small belt-type continuously variable transmission, heat generation, core wire peeling, and rubber cracking can be suppressed. In particular, when the overall thickness of the belt is within the above range and the belt pitch width is within this range, the thickness becomes thin and the pitch width becomes narrow, which is especially preferable as it enhances the effects of the present invention.

[0040] Figure 7 shows the definition of the belt pitch width of the raw edge cogged V belt in the present invention. Specifically, Figure 7 is a schematic cross-sectional view of a raw edge cogged belt 1 in which a reinforcing fabric 2, a stretchable rubber layer 3, a core layer 4, a compression rubber layer 5, and a reinforcing fabric 6 are sequentially laminated, and the belt pitch width W means the width of the belt at the belt pitch line L (position on the line connecting the centers of the core wires 4a embedded at equal intervals in the core layer 4).

[0041] (Extensional stiffness of V-belts for power transmission) In the power transmission V-belt of the present invention (particularly the low-edge V-belt), the tensile stiffness per 1 mm of belt pitch width (belt tensile stiffness EA) is, for example, 6200 to 25000 N, preferably 6500 to 20000 N, more preferably 7000 to 18000 N, more preferably 7500 to 15000 N, and most preferably 8000 to 12000 N. In the present invention, because the belt tensile stiffness EA is within this range, heat generation caused by slippage can be suppressed. If the belt tensile stiffness EA is too small, there is a risk that the belt will stretch significantly under heavy loads, making it prone to slippage. On the other hand, if the belt tensile stiffness EA is too large, there is a risk that the belt will not be able to absorb load fluctuations through stretching, making it prone to slippage.

[0042] In this application, the tensile stiffness EA of the belt represents the relationship between the tensile force and strain (elongation rate) when the belt is stretched in the longitudinal direction. A high tensile stiffness of the belt means it is difficult to stretch, while a low tensile stiffness means it is easy to stretch.

[0043] In this application, the tensile stiffness EA of the belt is defined as the proportionality constant of the belt tension to the rate of change of belt length in the range of belt tension from 200 to 600 N. That is, in this application, the tensile stiffness EA of the belt can be determined as the slope of the approximate straight line of the measured values ​​for every 100 N between belt tensions of 200 N and 600 N in a graph plotting the rate of change of belt length (%) on the horizontal axis and belt tension (N) on the vertical axis, and can be measured in detail by the method described in the examples below.

[0044] (Bending stiffness of V-belts for power transmission) In the power transmission V-belt of the present invention (particularly the low-edge V-belt), the bending stiffness per 1 mm of belt pitch width (belt bending stiffness EI) is, for example, 40 to 260 N (mm). 2 Preferably 60-250 N (mm) 2 More preferably 80-240 N (mm) 2 , more preferably 100~235N(mm) 2 Most preferably 120-230 N (mm) 2 Therefore, in this invention, since the bending stiffness EI of the belt is within this range, heat generation caused by bending can be suppressed. If the bending stiffness EI of the belt is too small, there is a risk that the belt will vibrate and make noise, and conversely, if it is too large, there is a risk that internal heat generation due to bending and stretching of the belt will increase.

[0045] In this application, the bending stiffness EI of the belt represents the relationship between the compressive force required to deform an annular belt into a barrel shape by compressing it from the outer circumference and the pitch diameter (the diameter of the arc drawn by the pitch line connecting the centerlines of the core wires) when the bent portion of the belt is considered as an arc. A high bending stiffness of the belt makes it difficult to bend, while a low bending stiffness makes it easy to bend.

[0046] In this application, the bending stiffness EI of the belt can be measured using an autograph, and in detail, it can be measured by the method described in the examples below.

[0047] [Heart wire] The power transmission V-belt of the present invention is characterized in that the core wire is formed of a Lang twist cord, which is made by twisting together multiple under-twisted threads containing aramid fibers, and has a total fineness of 1000 to 3500 dtex. In the present invention, the heat generation during use of the power transmission V-belt can be suppressed due to the core wire having these characteristics, and the peeling of the core wire and the occurrence of cracks in the compression rubber layer can be suppressed, but it is particularly effective when used as a variable speed belt in a small belt-type continuously variable transmission with a relatively small load. The reason why it is particularly effective when used as a variable speed belt can be presumed to be as follows.

[0048] Common failure modes for variable speed belts include cog valley cracks and core wire delamination, both of which are more likely to occur when the belt temperature is high. Therefore, suppressing belt heat generation is key to improving the durability of variable speed belts. Causes of belt heat generation include slippage (frictional heat from rubbing between the belt and pulley) and bending (internal heat generation from bending and stretching the belt).

[0049] Generally, power transmission belts are designed with high tensile rigidity in mind, and therefore tend to use materials with high tensile modulus, such as aramid fibers or carbon fibers, for the core wire, and also tend to have a thicker core wire diameter. In contrast, the power transmission V-belt of the present invention is characterized by its thin core wire, but it is presumed that by using aramid fibers with high tensile modulus as the core wire, the tensile rigidity of the belt can be ensured even with a thin diameter. Furthermore, because the belt's tensile rigidity can be maintained at a relatively high level, belt elongation can be suppressed, reducing slippage and thus suppressing heat generation. In addition, because the belt's bending rigidity can be reduced due to its thin diameter, it is presumed that heat generation caused by bending can also be suppressed.

[0050] In other words, in the present invention, the core wire contains aramid fibers and is small in diameter, so the high elastic modulus of aramid increases the tensile rigidity of the belt, which can suppress heat generation caused by slippage. Furthermore, the small diameter reduces the bending rigidity of the belt, which can suppress heat generation caused by bending.

[0051] In a Lang twisted cord that constitutes such a core wire, the undertwisted yarn may be an aramid multifilament yarn containing multiple aramid fibers. The aramid multifilament yarn may also contain other fibers (such as polyester fibers) if necessary. The proportion of aramid fibers may be 50% by mass or more (particularly 80-100% by mass) of the total multifilament yarn, and preferably, all filaments are composed of aramid fibers. In the present invention, by including aramid fibers in the core wire, the tensile rigidity of the belt can be improved and heat generation caused by slippage can be suppressed. Therefore, if the proportion of aramid fibers is too small, there is a risk of heat generation.

[0052] The aramid multifilament yarn may contain multiple aramid filaments, for example, 100 to 5000 filaments, preferably 300 to 2000, more preferably 600 to 1500, and more preferably 800 to 1200 filaments. The average fineness of the aramid filaments is, for example, 0.8 to 10 dtex, preferably 1 to 5 dtex, more preferably 1.1 to 2 dtex, and more preferably 1.5 to 1.7 dtex.

[0053] Para-aramid fibers are preferred due to their excellent mechanical strength. Specifically, they may be para-aramid fibers consisting of a single repeating unit (for example, "Twaron" (registered trademark) manufactured by Teijin Limited, which is a poly-para-phenylene terephthalamide fiber, or "Kevlar" (registered trademark) manufactured by Toray DuPont Co., Ltd.), or copolymerized para-aramid fibers containing multiple repeating units (for example, "Technora" manufactured by Teijin Limited, which is a copolymerized aramid fiber of poly-para-phenylene terephthalamide and 3,4'-oxydiphenylene terephthalamide). Of these, copolymerized para-aramid fibers are particularly preferred.

[0054] The tensile modulus of aramid fibers can be selected from a range of approximately 50 to 100 GPa, for example, 50 to 90 GPa, preferably 60 to 90 GPa, more preferably 65 to 85 GPa, and more preferably 70 to 80 GPa. In applications requiring high flexural fatigue resistance, the aramid fibers may be high-elongation aramid fibers with a tensile modulus of approximately 50 to 70 GPa. If the tensile modulus is too low, the tensile stiffness of the belt will decrease, which may cause heat generation due to slippage. Conversely, if it is too high, the flexural fatigue resistance may decrease.

[0055] In this application, the tensile modulus refers to the apparent Young's modulus measured in accordance with the method for measuring initial tensile resistance described in Section 8.10 of JIS L 1013 (2021).

[0056] The fineness of each under-twist yarn is 2000 dtex or less, preferably 500 to 2000 dtex, more preferably 1000 to 1900 dtex, more preferably 1300 to 1800 dtex, and most preferably 1500 to 1700 dtex. If the fineness is too low, the elongation will increase, and the tensile strength and tensile modulus will decrease, which may also reduce economic efficiency. Conversely, if the fineness is too high, the flexural fatigue resistance may decrease.

[0057] The number of under-twisted yarns can be multiple, but preferably 2 to 6, more preferably 2 to 4, more preferably 2 to 3, and most preferably 2. Too many yarns may reduce the flexural fatigue resistance.

[0058] The twist coefficient (under-twist coefficient) of each under-twist yarn can be selected from a range of approximately 0.3 to 5, for example, 0.5 to 3, preferably 0.6 to 2.5, more preferably 0.7 to 2, even more preferably 0.8 to 1.5, and most preferably 0.9 to 1.2. If the under-twist coefficient is too small, the bending stiffness of the belt may increase or the bending fatigue resistance may decrease, while if it is too large, the tensile stiffness of the belt may decrease.

[0059] In the present invention, the lower-twisted yarn is produced by applying twist in one direction to a multifilament yarn. However, the twisted cord obtained by aligning and applying upper twist to a plurality of obtained lower-twisted yarns is a Lang-twisted cord in which the upper twist is applied in the same direction as the direction of the lower twist. Since the Lang-twisted cord has a large inclination angle of the filaments with respect to the longitudinal direction of the twisted cord, it has excellent flexibility and can reduce the bending rigidity of the belt.

[0060] The twist coefficient (upper twist coefficient of the upper-twisted yarn) of the Lang-twisted cord can be selected from the range of about 0.5 to 5, for example, 1 to 4.5, preferably 1.5 to 4, more preferably 2 to 3.8, still more preferably 2.5 to 3.5, and most preferably 2.8 to 3.2. If the upper twist coefficient is too small, the bending rigidity of the belt may increase or the flexural fatigue resistance may decrease. On the contrary, if it is too large, the elongation rigidity of the belt may decrease.

[0061] The ratio of the upper twist coefficient to the lower twist coefficient (upper twist coefficient / lower twist coefficient) is, for example, 0.5 to 10, preferably 1 to 8, more preferably 1.5 to 5, still more preferably 2 to 4, and most preferably 2.5 to 3.5.

[0062] In the present application, each twist coefficient of the lower twist coefficient and the upper twist coefficient can be calculated based on the following formula.

[0063] TF = TN × D 0.5 / 960 [In the formula, TF: twist coefficient, TN: number of twists per meter, D: fineness (tex) of the yarn is shown]

[0064] The total fineness of the Lang-twisted cord is 1000 to 3500 dtex. In the present invention, since the total fineness of the core wire formed of the Lang-twisted cord is relatively small, the bending rigidity of the belt is low and heat generation due to bending can also be suppressed. If the total fineness is less than 1000 dtex, the elongation rigidity of the belt may decrease. If the total fineness exceeds 3500 dtex, the bending rigidity of the belt may increase. The total fineness of the Lang-twisted cord is preferably 2000 to 3450 dtex, and more preferably 3000 to 3400 dtex.

[0065] The top-twisted Lang-twisted cord may be treated with adhesive (or surface treatment) to improve its adhesion to the rubber component. As for the bonding treatment method, conventional methods can be used, for example, the method described in Japanese Patent Publication No. 6349369, which includes a step of treating with a first treatment agent consisting of a rubber composition (a) containing a condensate of resorcinol and formaldehyde (a1), a rubber component containing carboxyl-modified latex (a2), and a curing agent (a3) ​​containing a polycarbodiimide resin having a plurality of carbodiimide groups, and a hydrophilic solvent (b). In particular, a method is preferred that includes a first treatment step of treating with a first treatment agent consisting of a rubber composition (a) containing a curing agent (a3) ​​containing a polycarbodiimide resin having a plurality of carbodiimide groups, and a hydrophilic solvent (b); a second treatment step of treating the first treated yarn treated in the first treatment step with a second treatment agent containing resorcinol, formaldehyde, and latex; and a third treatment step of treating the second treated yarn treated in the second treatment step with a third treatment agent containing rubber. By permeating the spaces between the undertwisted yarns or between the single fibers that make up the undertwisted yarns with adhesive components, and attaching these components to the surface of the fibers, the ability of the fibers to bundle together can be improved.

[0066] The adhesion rate of the adhesive component (solid content adhesion rate) is, for example, 1 to 50% by mass, preferably 3 to 30% by mass, more preferably 5 to 25% by mass, and more preferably 10 to 20% by mass, relative to the Lang twisted cord before bonding treatment. If the proportion of the adhesive component is too low, the adhesion between fibers will be insufficient, which may cause friction between fibers during bending and reduce bending fatigue resistance. If the proportion of the adhesive component is too high, the core wire diameter may become too large.

[0067] The average diameter of the core wire (Lang twisted cord after bonding treatment) is, for example, 0.1 to 1.2 mm, preferably 0.3 to 1.1 mm, more preferably 0.4 to 1 mm, more preferably 0.5 to 0.9 mm, and most preferably 0.6 to 0.8 mm.

[0068] In this application, the average diameter of the core wires refers to the average diameter of the core wires within the belt. The average diameter of the core wires is determined by taking a cross-sectional image of the belt in the width direction using a scanning electron microscope (SEM), measuring the length of all core wires in the belt in the width direction in the captured image, and calculating the arithmetic mean. However, if a portion of the core wire is missing on the side of the belt, it will be excluded from the measurement.

[0069] In this invention, compared to, for example, the tensile strength of the core wire in the embodiment of Patent Document 2 (tensile strength of aramid core wire with a total fineness of 9900 dtex, 1300 N), the total fineness of the core wire is relatively small, and the tensile strength per core wire is low. Therefore, by reducing the core wire pitch and arranging them more densely, the tensile rigidity of the belt can be improved. From the viewpoint of increasing the tensile rigidity of the belt, it is considered preferable to have a higher tensile strength per core wire. However, if the core wire is made thicker to increase the tensile strength per core wire, there is a risk of reduced flexibility, and it is also necessary to increase the core wire pitch, so the tensile rigidity of the belt will not be dramatically increased. In this invention, the core wire diameter is reduced and they are arranged more densely while ensuring that the tensile strength per core wire is not excessively low, so that the bending rigidity of the belt can be reduced while maintaining the tensile rigidity of the belt.

[0070] The tensile strength per core wire is, for example, 300 to 1200 N, preferably 500 to 1000 N, more preferably 550 to 800 N, even more preferably 580 to 700 N, and most preferably 600 to 650 N. If the tensile strength per core wire is too low, the belt's elongation stiffness may be low, and if the tensile strength per core wire is too high, the belt's bending stiffness may be high.

[0071] In this application, the tensile strength per core wire can be measured in accordance with JIS L 1017 (2002).

[0072] The core wires are arranged at predetermined intervals in the belt width direction and extend along the belt length direction (circumferential direction), embedded in the core layer. These core wires act as tensile members and may be arranged in parallel at a predetermined pitch parallel to the belt length direction, but from the viewpoint of productivity, they are usually arranged spirally in parallel at a predetermined pitch approximately parallel to the belt length direction. When arranged spirally, the angle of the core wires with respect to the belt length direction may be, for example, 5° or less, and from the viewpoint of belt running performance, it is preferable that it is as close to 0° as possible.

[0073] The core wire pitch (the average distance between the centers of adjacent core wires in the belt widthwise cross-section) is preferably larger than the average core wire diameter within a predetermined range. Specifically, the value obtained by subtracting the core wire diameter from the core wire pitch (the value of "core wire pitch - average core wire diameter," which represents the width of each section in the belt widthwise cross-section where no core wires exist) can be selected from a range of approximately 0.03 to 0.3 mm, for example, 0.05 to 0.25 mm, preferably 0.08 to 0.23 mm, more preferably 0.1 to 0.22 mm, and more preferably 0.15 to 0.21 mm. If the above value is too small, the core wires may ride up or rub against each other, which may reduce the tensile strength of the belt. Conversely, if it is too large, the tensile rigidity of the belt may decrease. In other words, from the viewpoint of increasing the tensile rigidity of the belt, a smaller value is preferable, but if it is too small, the core wires may ride up or rub against each other, which may reduce the strength.

[0074] In this application, the number of core wires refers to the apparent number of core wires in a cross-sectional view, arranged at a predetermined core wire pitch in the belt width direction, as shown in Figure 2. That is, the number of core wires refers to the number of spirals when a single core wire is embedded in a spiral. However, in reality, since the core wires are embedded in a spiral, the arrangement of the core wires differs depending on the part of the cross-section taken within a single endless V-belt for power transmission. Therefore, for practical purposes, when the core wire pitch is a constant value, the value obtained by dividing the belt width by the core wire pitch and truncating the decimal part is considered as an approximate "number of core wires" (effective number).

[0075] [Compressed rubber layer] In the power transmission V-belt of the present invention, the compression rubber layer is formed of a rubber composition (crosslinked rubber composition) containing a first rubber component.

[0076] (A1) First rubber component The first rubber component may be a vulcanizable or crosslinkable rubber, such as diene rubber [natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), hydrogenated nitrile rubber (H-NBR), etc.], ethylene-α-olefin elastomer [ethylene-propylene copolymer (EPM), ethylene-propylene-diene ternary copolymer (EPDM), etc.], chlorosulfonated polyethylene rubber, alkylated chlorosulfonated polyethylene rubber, epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, fluororubber, etc. These rubber components can be used individually or in combination of two or more.

[0077] Of these, ethylene-α-olefin elastomer and chloroprene rubber are preferred, with chloroprene rubber being particularly preferred due to its excellent balance of heat resistance, abrasion resistance, and oil resistance, as well as its high productivity.

[0078] When the first rubber component contains chloroprene rubber, the proportion of chloroprene rubber in the first rubber component may be 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more (particularly 90-100% by mass), and most preferably 100% by mass (chloroprene rubber only), from the viewpoint of improving the above properties and productivity. When the first rubber component contains ethylene-α-olefin elastomer, the proportion of ethylene-α-olefin elastomer in the first rubber component is the same as the proportion of chloroprene rubber.

[0079] (A2) First short fiber The rubber composition forming the compression rubber layer may further contain first short fibers. Examples of first short fibers include polyamide short fibers (aliphatic polyamide short fibers such as polyamide 6 short fibers, polyamide 66 short fibers, and polyamide 46 short fibers; aramid short fibers, etc.), polyester short fibers [polyalkylene arylate fibers such as polyethylene terephthalate (PET) short fibers and polyethylene naphthalate (PEN) short fibers; liquid crystal polyester short fibers; polyarylate short fibers (amorphous all-aromatic polyester short fibers, etc.)], synthetic short fibers such as vinylon short fibers, polyvinyl alcohol-based short fibers, and poly(p-phenylene benzobisoxazole (PBO)) short fibers; natural short fibers such as cotton, linen, and wool; and inorganic short fibers such as carbon short fibers. These short fibers can be used individually or in combination of two or more types. Of these, polyamide short fibers such as aramid short fibers and aliphatic polyamide short fibers are preferred, and a combination of aramid short fibers and aliphatic polyamide short fibers is particularly preferred.

[0080] The average fiber diameter of the first short fibers is 2 μm or more, for example, 2 to 100 μm, preferably 3 to 50 μm, more preferably 7 to 40 μm, and more preferably 10 to 30 μm. The average fiber length of the first short fibers is, for example, 1 to 20 mm, preferably 1.3 to 15 mm, more preferably 1.5 to 10 mm, more preferably 2 to 5 mm, and most preferably 2.5 to 4 mm.

[0081] The first short fibers may be embedded in the compression rubber layer oriented substantially parallel to the belt width direction in order to suppress the compression deformation of the belt in response to pressure from the pulley.

[0082] The first short fibers may be subjected to conventional bonding treatments to enhance their adhesion to the first rubber component. Conventional bonding treatments can be used, for example, by using 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 the rubber component (latex); or a treatment solution containing a reactive compound (adhesive compound) such as a silane coupling agent, epoxy compound (such as epoxy resin), isocyanate compound, or bismaleimide compound. These methods can be used individually or in combination of two or more. Of these methods, the method of treatment with a treatment solution containing the initial condensate and the rubber component (latex) is preferred, and the method of treatment with at least a resorcinol-formaldehyde-latex (RFL) solution is particularly preferred.

[0083] The proportion of the first short fibers is, for example, 5 to 50 parts by mass, preferably 5 to 40 parts by mass, more preferably 10 to 35 parts by mass, and more preferably 20 to 30 parts by mass, per 100 parts by mass of the first rubber component.

[0084] (A3) Other ingredients The rubber composition forming the compression rubber layer may contain conventional additives as other components (first other component), such as crosslinking agents or vulcanizing agents (sulfur-based crosslinking agents, organic peroxides, etc.), co-crosslinking agents (bismaleimides, etc.), crosslinking aids or crosslinking accelerators (thiuram-based accelerators, etc.), crosslinking retarders, metal powders (zinc powder, etc.), metal oxides (zinc oxide, magnesium oxide, lead oxide, calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, aluminum oxide, etc.), fillers [reinforcing agents such as carbon black, silicon oxide (hydrated silica, etc.) (reinforcing fillers); bulking agents such as clay, calcium carbonate, talc, mica (non-reinforcing fillers or inert fillers)]. Examples of additives include fillers, plasticizers (or softeners) [oils (paraffin oil, naphthenic oil, etc.), aliphatic carboxylic acid plasticizers, aromatic carboxylic acid ester plasticizers, oxycarboxylic acid ester plasticizers, phosphate ester plasticizers, ether plasticizers, ether ester plasticizers, etc.], processing agents or processing aids (stearic acid, metal stearate salts, waxes, paraffin, fatty acid amides, etc.), anti-aging agents (antioxidants, heat aging inhibitors, flex crack inhibitors, ozone degradation inhibitors, etc.), adhesion improvers, colorants, tackifiers, 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. Metal oxides may also act as crosslinking agents.

[0085] The proportion of the crosslinking agent (first crosslinking agent) is, for example, 1 to 20 parts by mass, preferably 2 to 15 parts by mass, more preferably 3 to 12 parts by mass, and more preferably 4 to 10 parts by mass, per 100 parts by mass of the first rubber component.

[0086] The proportion of the filler (first filler), such as carbon black, is, for example, 10 to 200 parts by mass, preferably 20 to 100 parts by mass, more preferably 30 to 80 parts by mass, and more preferably 40 to 70 parts by mass, per 100 parts by mass of the first rubber component.

[0087] The proportion of metal powder is, for example, 1 to 30 parts by mass, preferably 3 to 20 parts by mass, and more preferably 5 to 15 parts by mass, per 100 parts by mass of the first rubber component.

[0088] The total proportion of the other components (first other components) is, for example, 5 to 300 parts by mass, preferably 10 to 200 parts by mass, more preferably 30 to 150 parts by mass, and more preferably 50 to 100 parts by mass, per 100 parts by mass of the first rubber component.

[0089] [Stretchable rubber layer] The power transmission V-belt of the present invention may further include an stretchable rubber layer formed of a rubber composition (crosslinked rubber composition) containing a second rubber component.

[0090] The second rubber component can be selected from the rubber components exemplified as the first rubber component, including preferred embodiments. 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.

[0091] The rubber composition may further contain short fibers (second short fibers), and the second short fibers can be selected from the short fibers exemplified as the first short fibers, including in preferred embodiments. The average fiber diameter and average fiber length of the second short fibers can also be selected from the range of the first short fibers, including in preferred embodiments. The second short fibers may be different from the first short fibers, but are usually the same as the first short fibers.

[0092] The rubber composition may further contain other components (second other components), and the second other component can be selected from the other components exemplified as the first other component, including preferred embodiments. The second other component may be a different component from the first other component, but is usually the same as the first other component.

[0093] [Core layer] The core layer may include the core wire as a core, or it may be a core layer formed only of the core wire. However, it is preferable that the core layer (adhesive rubber layer) be made of a crosslinked rubber composition in which the core wire is embedded, as this suppresses delamination between layers and improves belt durability. The adhesive rubber layer is interposed between the stretchable rubber layer and the compression rubber layer body to bond the stretchable rubber layer and the compression rubber layer, and the core wire is embedded in the adhesive rubber layer.

[0094] (Adhesive rubber layer) The power transmission V-belt of the present invention may further include an adhesive rubber layer formed of a cured product (crosslinked rubber composition) of a rubber composition containing a third rubber component.

[0095] The third rubber component can be selected from the rubber components exemplified as the first rubber component, including preferred embodiments. 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.

[0096] The rubber composition may further contain other components (third other components), and the third other component can be selected from the other components exemplified as the first other component.

[0097] The proportion of the crosslinking agent (third crosslinking agent) is, for example, 1 to 20 parts by mass, preferably 2 to 15 parts by mass, more preferably 3 to 12 parts by mass, and more preferably 4 to 10 parts by mass, per 100 parts by mass of the third rubber component.

[0098] The proportion of fillers such as carbon black and silica (third fillers) is, for example, 10 to 200 parts by mass, preferably 20 to 100 parts by mass, more preferably 30 to 80 parts by mass, and more preferably 40 to 70 parts by mass, per 100 parts by mass of the third rubber component.

[0099] The proportion of the adhesion improver is, for example, 1 to 20 parts by mass, preferably 2 to 15 parts by mass, and more preferably 3 to 10 parts by mass, per 100 parts by mass of the third rubber component.

[0100] The total proportion of the third other component is, for example, 5 to 300 parts by mass, preferably 10 to 200 parts by mass, more preferably 30 to 150 parts by mass, and more preferably 50 to 100 parts by mass, per 100 parts by mass of the third rubber component.

[0101] The average thickness of the adhesive rubber layer is, for example, 0.8 to 3 mm, preferably 1.2 to 2.8 mm, and more preferably 1.5 to 2 mm.

[0102] [Reinforcement fabric] The power transmission V-belt of the present invention may further include a reinforcing fabric. Examples of the form of the reinforcing fabric include laminating it on the inner surface of the compression rubber layer, laminating it on the outer surface of the stretch rubber layer, or embedding it in the compression rubber layer and / or stretch rubber layer.

[0103] The reinforcing fabric can be formed from, for example, fabric materials such as woven fabric, wide-angle canvas, knitted fabric, or nonwoven fabric (especially woven fabric), and if necessary, it may be subjected to adhesive treatment, such as treatment with RFL liquid (such as immersion treatment), friction treatment by rubbing adhesive rubber into the fabric material, or the adhesive rubber and the fabric material may be laminated and then laminated or embedded in the compression rubber layer and / or stretch rubber layer in the above form.

[0104] [Manufacturing method for V-belts for power transmission] The method for manufacturing the power transmission V-belt (especially the raw edge V-belt) of the present invention is not particularly limited. For example, the method for manufacturing the raw edge cogged V-belt of the present invention is not particularly limited, and conventional methods can be used for the lamination process of each layer (method for manufacturing the belt sleeve) depending on the type of belt. For example, a typical method for manufacturing a raw edge cogged V-belt is described below.

[0105] First, a laminate of reinforcing fabric (bottom fabric) and a sheet for the compression rubber layer body (uncrosslinked rubber sheet) is placed with the reinforcing fabric facing downwards and in contact with a flat cog mold in which teeth and grooves corresponding to the inner circumference cog portion (cog peaks 1a and cog bottoms 1b shown in Figure 2) are alternately arranged. The inner circumference cog portion is then molded by pressing at a temperature of 60-100°C (especially 70-80°C) to produce a cog pad (a pad that is not completely crosslinked, but in a semi-crosslinked state). Then, both ends of this cog pad are cut vertically at appropriate points (especially the tops of the cog peaks) to obtain the required length.

[0106] Next, an inner mold, in which teeth and grooves corresponding to the cog portion are arranged alternately, is placed over the outer circumference of a cylindrical mold. The cog pad is wrapped around the inner mold, engaging with the teeth and grooves, and joined at both ends (especially the tops of the cog peaks). A sheet for the first adhesive rubber layer (lower adhesive rubber: uncrosslinked rubber sheet) is laminated around the outer circumference of the cog pad. Then, a core wire (twisted cord) that will form the core body is spun spirally, and a sheet for the second adhesive rubber layer (upper adhesive rubber: uncrosslinked rubber sheet) and a sheet for the stretch rubber layer (uncrosslinked rubber sheet) are sequentially wrapped around its outer circumference to produce an uncrosslinked molded body. Furthermore, if necessary, a reinforcing cloth (upper cloth) may be laminated on top of the stretch rubber layer.

[0107] Subsequently, the uncrosslinked molded body is covered with a jacket and placed in a known crosslinking device (such as a vulcanizing vessel), where crosslinking is performed at a temperature of 120-200°C (especially 150-180°C) to produce a crosslinked belt sleeve. Then, it is cut into a V-shape using a cutter or the like to obtain an endless low-edge cogged V-belt.

[0108] In the case of a low-edge double-cogged V-belt, an outer matrix with teeth and grooves corresponding to the outer cog portion arranged alternately is placed over the outer circumference of the uncrosslinked molded body, and a jacket is placed over it to perform crosslinking molding, thereby obtaining a crosslinked belt sleeve in which cog portions are also formed on the outer surface, and cutting it into a V shape yields a low-edge double-cogged V-belt.

[0109] Furthermore, the adhesive rubber layer can be formed from multiple adhesive rubber layer sheets, and the core wire (stranded cord) forming the core body may be spun in relation to the lamination order of the multiple adhesive rubber layer sheets, depending on the embedding position in the adhesive rubber layer. [Examples]

[0110] 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 and comparative examples, and the evaluation methods for the examples and comparative examples are shown below.

[0111] [Materials used] (Rubber component) Chloroprene rubber: "PM-40" manufactured by Denka Co., Ltd. Carboxylate-modified NBR latex (COOH-modified NBR): "Nipol 1571CL" manufactured by Nippon Zeon Co., Ltd., 38% by mass of active ingredient, high nitrile type.

[0112] (Hardening agent) Polycarbodiimide dispersion: "Carbodilite E-02" manufactured by Nisshinbo Chemical Co., Ltd., active ingredient 40% by mass, NCN (carbodiimide) equivalent 445 Polymeric isocyanate (polymeric MDI): "Millionate® MR-200" manufactured by Tosoh Corporation, NCO content 30% by mass

[0113] (Short fibers) The following short fibers were used. Each short fiber was subjected to an adhesive treatment by immersion in RFL solution [a mixture of 2.6 parts by mass of resorcinol, 1.4 parts by mass of 37% formalin, 17.2 parts by mass of vinylpyridine-styrene-butadiene copolymer latex (manufactured by Nippon Zeon Co., Ltd.), and 78.8 parts by mass of water] and then dried. The adhesion rate of the adhesive component (solid content) was adjusted to 6% by mass relative to the short fiber before treatment.

[0114] Para-aramid short fibers: "Twaron" manufactured by Teijin Limited, fiber length 3mm Nylon 66 staple fibers: "Leona" manufactured by Asahi Kasei Corporation, fiber length 3mm

[0115] (Filler) Carbon Black FEF: "Seast SO" manufactured by Tokai Carbon Co., Ltd. Silica: "NipsilVN3" manufactured by Tosoh Silica Co., Ltd.

[0116] (Additives) Naphthenic oil: "Diana Process Oil NS-90S" manufactured by Idemitsu Kosan Co., Ltd. Adhesion improver A (resorcinol-formaldehyde co-condensate): "POWERPLAST PP-1860" manufactured by Singh Plasticisers & Resins. Adhesion improver B (hexamethoxymethylmelamine): "POWERPLAST PP-1890S" manufactured by Singh Plasticisers & Resins. Magnesium oxide: "Kyowa Mag 150" manufactured by Kyowa Chemical Industry Co., Ltd. Crosslinking accelerator MBTS (dibenzothiadyl disulfide): "Noxellar DM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Crosslinking accelerator TMTD (tetramethylthiuram disulfide): "Noxellar TT" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Anti-aging agent A (octyl diphenylamine): "Nonflex OD-3" manufactured by Seiko Chemical Co., Ltd. Anti-aging agent B (4,4'-bis(α,α-dimethylbenzyl)diphenylamine): "Nonflex DCD" manufactured by Seiko Chemical Co., Ltd. Anti-aging agent C (microcrystalline wax): "SunTight C" manufactured by Seiko Chemical Co., Ltd. Zinc powder: "M-11" manufactured by Sakai Chemical Industry Co., Ltd. Softening agent: "ADEKA Sizer C-8" manufactured by ADEKA Corporation Stearic acid: "Bead Stearic Acid Camellia" manufactured by NOF Corporation. Zinc Oxide: "Zinc Oxide (JIS Standard Type 2)" manufactured by Hakusui Tech Co., Ltd. Co-crosslinking agent (N,N'-m-phenylenedimaleimide): "Balnock PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0117] (Core wire) The following types of core wires were used. All of the core wires were bonded using the following processing method. The adhesion rate of the adhesive component (solid content) (final adhesion rate after the third processing step) was adjusted to 15% by mass relative to the core wire before processing (before the first processing step).

[0118] Aramid core wires in Examples 1-3: Two under-twisted yarns, each made from a 1670dtex aramid fiber bundle (Teijin Limited's "Technora"), were combined and then over-twisted in the same direction as the under-twist with a twist coefficient of 3.0 to create a Lang twisted cord with a total fineness of 3340dtex (the diameter of the processed cord is approximately 0.70mm and the tensile strength per core wire is 620N).

[0119] Polyester core used in Comparative Examples 1-3: Two bundles of 1100dtex PET fiber (Toray Industries, Inc.'s "Tetron") were combined and twisted with a twist coefficient of 3.0 to create three under-twisted yarns. These under-twisted yarns were then combined and twisted in the opposite direction to the under-twist with a twist coefficient of 3.0 to create a double-twisted cord with a total fineness of 6600dtex (the diameter of the processed cord is approximately 1.00 mm and the tensile strength per core is 440N).

[0120] Aramid core wire used in Comparative Examples 4, 7, and 10: Two under-twisted yarns, each made from a 1670 dtex aramid fiber bundle (Teijin Limited's "Technora") twisted with a twist coefficient of 1.0, were combined and then over-twisted in the opposite direction to the under-twist with a twist coefficient of 3.0 to create a double-twisted cord with a total fineness of 3340 dtex (the diameter of the processed cord is approximately 0.71 mm and the tensile strength per core wire is 620 N).

[0121] Aramid core used in Comparative Examples 5, 8, and 11: Two aramid fiber bundles (Teijin Limited's "Technora") with a density of 1100 dtex were combined and twisted with a twist coefficient of 1.0 to create three under-twisted yarns. These under-twisted yarns were then combined and over-twisted in the same direction as the under-twist with a twist coefficient of 3.0 to create a Lang twisted cord with a total density of 6600 dtex (the diameter of the processed cord is approximately 0.94 mm and the tensile strength per core is 1300 N).

[0122] Aramid core used in Comparative Examples 6, 9, and 12: Two aramid fiber bundles (Teijin Limited's "Technora") with a density of 1100 dtex were combined and twisted with a twist coefficient of 1.0 to create three under-twisted yarns. These under-twisted yarns were then combined and twisted in the opposite direction to the under-twist with a twist coefficient of 3.0 to create a multi-twisted cord with a total density of 6600 dtex (the diameter of the processed cord is approximately 0.95 mm and the tensile strength per core is 1300 N).

[0123] Table 1 summarizes the details of the core wires used in Examples 1-3 and Comparative Examples 1-12.

[0124] [Table 1]

[0125] (Method for bonding core wires) (A) Preparation of the first treatment agent A polycarbodiimide dispersion and water were mixed with the RFL solution with the composition shown in Table 2 in the proportions shown in Table 3, and the mixture was stirred at room temperature for 10 minutes to prepare the first treatment agent with the composition shown in Table 3.

[0126] [Table 2]

[0127] [Table 3]

[0128] (B) Preparation of the second treatment agent The RFL solution with the composition shown in Table 2 and water were mixed in the proportions shown in Table 4, and the mixture was stirred at room temperature for 10 minutes to prepare the second treatment agent with the composition shown in Table 4.

[0129] [Table 4]

[0130] (C) Preparation of the third treatment agent The rubber composition for the adhesive rubber layer, described later, was dissolved in toluene in the proportions shown in Table 5, and polymeric isocyanate was added to prepare the third treatment agent (rubber glue).

[0131] [Table 5]

[0132] (D) Adhesion treatment Untreated twisted cord was immersed in a first treatment agent for 10 seconds and dried at 150°C for 2 minutes (first treatment step). Next, the twisted cord treated with the first treatment agent was immersed in a second treatment agent for 10 seconds and dried at 230°C for 2 minutes (second treatment step). Finally, the twisted cord treated with the second treatment agent was immersed in a third treatment agent for 3 seconds and dried at 100°C for 1 minute. This immersion and drying process was repeated three times, and then the cord was further heated at 230°C for 2 minutes to obtain the core wire (third treatment step).

[0133] (Reinforcement fabric) Canvas made from 10-count cotton yarn, plain woven at a yarn density of 70 threads / 50mm (weight 180g / m²) 2 A treated canvas (approximately 0.5 mm thick, approximately 450 g / m²) was obtained by rubbing the adhesive rubber composition onto the canvas. 2 The same reinforcing fabric was used on both the inner and outer circumferences of the belt.

[0134] [Belt stretch stiffness EA] The test specimen's belt was placed on a measuring machine (belt length measuring device) with a pair of V-groove pulleys of equal pitch diameter positioned vertically, and a load was applied to the lower pulley in a direction that separated the two pulleys. In this case, the belt tension (the tension acting on one span of the belt located between the two pulleys) was half the load applied to the lower pulley.

[0135] In detail, the belt length at a belt tension of 200N was set as the reference length (0% change in belt length), and the belt tension was varied from 200N to 600N, with the percentage change in belt length relative to the reference length recorded. The measurement temperature was adjusted to 25°C.

[0136] For the measurement results, a graph was created with the belt length change rate (%) on the horizontal axis and belt tension (N) on the vertical axis. The values ​​at five points where the belt tension was 200N, 300N, 400N, 500N, and 600N were approximated by a straight line, and the slope of the approximated line was defined as the belt's tensile stiffness EA (unit: N). The tensile stiffness EA was expressed as a value per belt, or as a value per 1 mm of pitch width obtained by dividing by the belt's pitch width.

[0137] [Belt bending stiffness EI] By attaching an upper plate 42 and a lower plate 43 to the Autograph for compressing the test specimen's belt from the back, an annular belt 41 was positioned between the upper and lower plates 42 and 43, as shown in Figure 8. The distance between the plates was narrowed at a speed of 100 mm / min, and the compressive force (bending load) was measured and recorded at six points when the pitch diameter D was 110 mm, 100 mm, 90 mm, 80 mm, 70 mm, and 60 mm, at a measurement temperature of 25°C. The bending stiffness EI at the six points was calculated using the following formula, and its average value (arithmetic mean) was obtained.

[0138] Bending stiffness EI = (Compressive force × (Pitch diameter D / 2)) 2 ) / 2 (Unit: N(mm) 2 )

[0139] Bending stiffness EI is expressed as a value per belt, or as a value per 1 mm of pitch width, calculated by dividing EI by the belt's pitch width.

[0140] [Durability Test 1 (Peeling Resistance Test)] The peel resistance test was performed using a two-axis running test machine consisting of a 60 mm diameter drive (Dr.) pulley and a 140 mm diameter driven (Dn.) pulley, as shown in Figure 9. A low-edge V-belt was mounted on these two pulleys, and the belt was run with an axial load of 700 N, a drive pulley rotation speed of 6000 rpm, and a drive pulley torque of 15 N·m at an ambient temperature of 80°C. The side temperature of the belt during running was measured using a non-contact thermometer ("THI-500" manufactured by Ichinen TASCO Co., Ltd.), and the time until peeling occurred on the underside of the core wire (inner circumference side of the belt) was compared.

[0141] [Durability Test 2 (Crack Resistance Test)] The crack resistance test was performed using a two-axis running test machine consisting of a 120 mm diameter drive (Dr.) pulley and an 80 mm diameter driven (Dn.) pulley, as shown in Figure 10. A low-edge V-belt was mounted on these two pulleys, and the belt was run with an axial load of 400 N, a drive pulley rotation speed of 6000 rpm, and a drive pulley torque of 12 N·m at an ambient temperature of 120 °C. The side temperature of the belt during running was measured using a non-contact thermometer (THI-500, manufactured by Ichinen TASCO Co., Ltd.), and the time until cracks appeared in the cog valleys was compared.

[0142] Examples 1 and Comparative Examples 1 and 4-6 (Formation of the rubber layer) The rubber compositions shown in Table 6 (adhesive rubber layer) and Table 7 (compression rubber layer and stretch rubber layer) were prepared by compounding the rubber using known methods such as a Banbury mixer, and the resulting compounded rubber was passed through a calender roll to produce rolled rubber sheets (sheet for adhesive rubber layer, sheet for compression rubber layer, and sheet for stretch rubber layer).

[0143] [Table 6]

[0144] [Table 7]

[0145] (Belt manufacturing) A laminate of reinforcing fabric (bottom fabric) and a sheet for the compression rubber layer (uncrosslinked rubber) was placed with the reinforcing fabric facing downwards on a flat cog mold in which teeth and grooves corresponding to the cog portion were arranged alternately. A cog pad (not fully crosslinked, but in a semi-crosslinked state) was produced by pressing the laminate at 75°C to form the cog portion. Next, both ends of this cog pad were cut vertically from the top of the cog peaks.

[0146] Next, an inner mold, in which teeth and grooves corresponding to the cog portion were arranged alternately, was placed over a cylindrical mold. The cog pad was then wrapped around the inner mold, engaging with the teeth and grooves, and joined at the top of the cog peaks. A first adhesive rubber layer sheet (lower adhesive rubber, uncrosslinked rubber, same as the adhesive rubber layer sheet) was laminated around the outer circumference of the wrapped cog pad. Then, the core wire was spun in a spiral shape, and a second adhesive rubber layer sheet (upper adhesive rubber, same as the adhesive rubber layer sheet), a stretchable rubber layer sheet (uncrosslinked rubber), and a reinforcing cloth (upper cloth) were sequentially wrapped around the outer circumference to produce an uncrosslinked molded body. The short fibers were oriented in the belt width direction. The core wire pitch was 0.9 mm for Example 1 and Comparative Example 4, and 1.1 mm for Comparative Examples 1 and 5-6.

[0147] Subsequently, a jacket was placed over the uncrosslinked molded body, and the mold was set in a vulcanizing can. Crosslinking was performed at a temperature of 160°C for 20 minutes to obtain a belt sleeve. This belt sleeve was then cut with a cutter into a V-shaped cross-section of a predetermined width along the longitudinal direction of the belt. This belt sleeve was then finished into a belt with the structure shown in Figure 2, namely a low-edge cogged V-belt (size: top width 24 mm, thickness 11 mm, V angle 30 degrees, outer circumference length 900 mm, pitch width 23 mm), which is a variable speed belt with cogs on the inner circumference of the belt.

[0148] Table 8 shows the evaluation results of the belts obtained in Example 1 and Comparative Examples 1 and 4-6.

[0149] [Table 8]

[0150] Example 2 and Comparative Examples 2 and 7-9 A low-edge double-cogged V-belt (size: top width 25 mm, thickness 10 mm, V angle 30 degrees, outer circumference length 900 mm, pitch width 23 mm) was obtained in the same manner as in Example 1, except that a cross-linked belt sleeve was manufactured in which cogs were formed on the outer surface by covering the outer matrix, which had teeth and grooves corresponding to the outer cog portion, with the outer matrix, which was arranged alternately on the outer circumference of the cross-linked molded body, with a jacket over it and performing cross-linking molding. The core wire pitch was 0.9 mm for Example 2 and Comparative Example 7, and 1.1 mm for Comparative Examples 2 and 8-9.

[0151] Table 9 shows the evaluation results of the belts obtained in Example 2 and Comparative Examples 2 and 7-9.

[0152] [Table 9]

[0153] Examples 3 and Comparative Examples 3 and 10-12 A low-edge double-cogged V-belt (size: top width 25 mm, thickness 9 mm, V angle 30 degrees, outer circumference length 900 mm, pitch width 23 mm) was obtained in the same manner as in Example 1, except that a cross-linked belt sleeve was manufactured in which cogs were formed on the outer circumference surface by covering the outer matrix, which had teeth and grooves corresponding to the outer circumference cogs arranged alternately on the outer circumference of the cross-linked molded body without using an outer fabric, and then covering it with a jacket and performing cross-linking molding. The core wire pitch was 0.9 mm for Example 3 and Comparative Example 10, and 1.1 mm for Comparative Examples 3 and 11-12.

[0154] Table 10 shows the evaluation results of the belts obtained in Example 3 and Comparative Examples 3 and 10-12.

[0155] [Table 10]

[0156] As is clear from the results in Tables 8-10, in all types and sizes of belts, the examples using Lang-twisted aramid fiber cords with a total fineness of 3500 dtex or less exhibited higher tensile rigidity and lower bending rigidity compared to the comparative examples. Furthermore, the belts in the examples maintained a low belt side temperature, and it was confirmed that they had excellent peel resistance and crack resistance.

[0157] In more detail, in Comparative Examples 1-3, the core wire was formed from polyester fibers, resulting in a high total fineness and a multi-twist method, which led to high bending rigidity, increased belt temperature, and low durability.

[0158] In comparative examples 4, 7, and 10, the twisting method of the core wires was multi-twisted, resulting in high bending rigidity, elevated belt temperature, and low durability.

[0159] In comparative examples 5, 8, and 11, the high total denier of the core wire resulted in high bending rigidity, increased belt temperature, and low durability.

[0160] In comparative examples 6, 9, and 12, the total fineness of the core wires was high, and due to the multi-strand construction, the bending rigidity was high, the belt temperature rose, and the durability was low. [Industrial applicability]

[0161] The power transmission V-belt of the present invention can be applied to low-edge V-belts, low-edge cogged V-belts having cog sections, and is particularly suitable for use in V-belts (gear belts or CVT belts) used in transmissions (continuously variable transmissions) where the gear ratio changes steplessly during belt operation. For example, it is suitable for use in continuously variable transmissions of motorcycles, ATVs (four-wheeled buggies), snowmobiles, etc., and is particularly suitable for use in continuously variable transmissions of scooters with small displacements (for example, 250cc or less, preferably 160cc or less), and is particularly suitable for use in continuously variable transmissions of scooters with small displacements, such as low-edge cogged V-belts and low-edge double cogged V-belts. [Explanation of Symbols]

[0162] 1… Raw edge cogged V-belt 11… Raw edge double cogged V-belt 2, 6, 16… Reinforcement fabric 3,13…Stretchable rubber layer 4,14…Core layer 4a, 14a... core wire 5,15... Compressed rubber layer

Claims

1. A low-edge V-belt having a thickness of 5 to 12 mm, a pitch width of 10 to 25 mm, and having cogs on at least the inner circumferential surface side, It contains a core wire formed from a Lang twist cord, which is made by splicing together 2 to 6 under-twisted threads containing aramid fibers and then twisting them together. The twist coefficient of the aforementioned under-twisted yarn is 0.5 to 3. The twist coefficient of the aforementioned Lang twisted cord is 0.5 to 5. The tensile strength of each of the aforementioned core wires is 500 to 1000 N, and A low-edge V-belt in which the fineness of the aforementioned core wires is 1000 to 3500 dtex.

2. The low-edge V-belt according to claim 1, wherein the pitch of the core wires is 0.05 to 0.25 mm larger than the average diameter of the core wires.

3. The low-edge V-belt according to claim 1 or 2, wherein the average diameter of the core wires is 0.4 to 1 mm.

4. The low-edge V-belt according to claim 1 or 2, wherein the elongation stiffness per 1 mm of pitch width is 6,500 to 20,000 N.

5. The bending stiffness of the low-edge V-belt is 40 to 260 N (mm) per 1 mm of pitch width. ２ The low-edge V-belt according to claim 1 or 2.

6. A low-edge V-belt according to claim 1 or 2, which is a variable speed belt used in a belt-type continuously variable transmission.

7. A belt transmission mechanism comprising a low-edge V-belt according to claim 1 or 2 and a pulley.

8. The belt transmission mechanism according to claim 7, wherein the low-edge V-belt is a variable speed belt used in a belt-type continuously variable transmission.

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