V-belt for transmission and belt transmission mechanism

Abstract

The present invention relates to a V-belt for transmission, said V-belt comprising a core wire which is formed from a Lang's lay cord obtained by combining and twisting a plurality of preliminarily twisted strands that contain aramid fibers, and which has a total fineness of 1000-3500 dtex.

Description

Transmission V-belt and belt transmission mechanism

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

[0002] Power transmission belts used in power transmission mechanisms of machinery and the like are broadly classified into friction transmission belts and meshing transmission belts based on the form of power transmission. Known friction transmission belts include V-belts, V-ribbed belts, and flat belts, while known meshing transmission belts include toothed belts.

[0003] One example of a V-belt is a raw-edge type belt (raw-edge V-belt), which is a rubber layer with an exposed friction transmission surface (V-shaped side surface).Raw-edge type belts include raw-edge V-belts without cogs, raw-edge cogged V-belts with improved flexibility due to cogs only on the inner peripheral surface of the belt, and raw-edge cogged V-belts (raw-edge double-cogged V-belts) with improved flexibility due to cogs on both the inner and outer peripheral surfaces of the belt.

[0004] One application of these V-belts (particularly raw-edge cog V-belts) is a belt-type continuously variable transmission. As shown in FIG. 1, the belt-type continuously variable transmission 30 is a device that continuously changes the gear ratio by wrapping a V-belt 1A around a drive pulley 31 and a driven pulley 32. Each pulley 31, 32 includes a fixed sheave 31a, 32a whose axial movement is restricted or fixed, and a movable sheave 31b, 32b that is movable in the axial direction. The V-belt 1A has a structure that allows the width of the V-groove of the pulleys 31, 32, formed by the fixed sheaves 31a, 32a and the movable sheaves 31b, 32b, to be continuously variable. Both widthwise end surfaces of the V-belt 1A are formed with tapered surfaces that match the inclination of the opposing surfaces of the V-grooves of each pulley 31, 32, and can fit into any radial position of the pulleys depending on the adjusted V-groove width. For example, by narrowing the width of the V-groove of the drive pulley 31 and widening the width of the V-groove of the driven pulley 32, changing from the state shown in FIG. 1(a) to the state shown in FIG. 1(b), the V-belt 1A moves radially outward on the drive pulley 31 side and radially inward on the driven pulley 32 side, causing the winding radius around each pulley 31, 32 to change continuously, thereby enabling the gear ratio to be adjusted continuously.

[0005] V-belts (variable speed belts) used in such applications are required to be able to handle not only the rotational running of the belt around two axes, a drive pulley and a driven pulley, but also the movement in the radial direction of the pulleys and the repeated bending motion caused by continuous changes in the winding radius. In order to do this, they are required to have high lateral pressure resistance (high widthwise rigidity) to suppress deformation of the belt due to the lateral pressure received from the pulleys, high flexibility (low bending rigidity) to reduce the winding radius around the pulleys, and resistance to stretch of the belt (high elongation rigidity) to suppress slippage and obtain the desired speed ratio.

[0006] As a proposal to meet these demands, Japanese Patent Application Laid-Open Publication No. 2010-196888 (Patent Document 1) discloses a power transmission belt in which the compression rubber layer is composed of two layers, an upper layer close to the core and a lower layer on the inner peripheral surface side, the upper layer having a hardness in the range of 93 to 99 and the lower layer having a hardness in the range of 80 to 88. This document also describes that, when the upper width of the belt is W and the thickness of the belt is T, the relationship between these may be 0.3W≦T≦0.6W. This document further describes, as effects of the invention, that the upper layer with high hardness improves the deformation resistance of the belt, that the lower layer with low hardness provides excellent resistance to bending fatigue and makes cracks less likely to occur, and that reducing the thickness of the belt reduces deformation during bending and suppresses the occurrence of cracks.

[0007] Japanese Patent Application Laid-Open No. 2005-265106 (Patent Document 2) discloses a double-cogged V-belt having a para-aramid fiber core wire and a belt bending stiffness of 600 to 1200 N / mm, with the aim of providing a double-cogged V-belt that is excellent in flex fatigue resistance and does not accelerate fatigue of the para-aramid fiber core wire. ３ and a double-cogged V-belt having a dynamic compression spring constant in the belt width direction of 15,000 N / mm or more.

[0008] Japanese Patent Application Laid-Open No. 2014-209029 (Patent Document 3) describes a method in which the core wire is made of aramid fiber and has a strength of 2.0 N / mm in the width direction. ２ The document discloses a power transmission belt that has a strain of 0.5 to 0.8% when compressed with a stress of 0.5 kN and a strain of 0.35 to 0.7% when pulled in the longitudinal direction with a load of 2 kN. This document describes, as an effect of the invention, that the rigidity in the belt width direction is slightly lower and the elongation in the belt longitudinal direction is slightly greater than that of conventional belts, thereby suppressing the occurrence of pop-out, in which the core wires pop out from the belt body, even if a large misalignment occurs during gear shifting.

[0009] Japanese Patent Publication No. 2010-196888 Japanese Patent Publication No. 2005-265106 Japanese Patent Publication No. 2014-209029

[0010] While the belt configurations disclosed in Patent Documents 1 to 3 exhibit a certain degree of effectiveness in terms of the performance required of a V-belt, the demands for downsizing of belt-type continuously variable transmissions and improvement of the durability of power transmission belts are becoming increasingly stringent, and further improvements are required. In particular, when the winding radius around the pulley becomes smaller, heat generation increases when the belt is bent and stretched, accelerating thermal degradation of the rubber, making it more likely that cracks will occur in the rubber or the core wires will peel off, resulting in a problem of reduced durability of the belt.

[0011] Therefore, an object of the present invention is to provide a transmission V-belt that can suppress heat generation even when used in a small belt-type continuously variable transmission, and that can also suppress peeling of the core wire and cracks in the compressed rubber layer, and a belt transmission mechanism equipped with this transmission V-belt.

[0012] As a result of extensive research to achieve the above object, the present inventors have found that by forming the core wire of a power transmission V-belt from a Lang twist cord made by doubling and then twisting a plurality of first twist yarns containing aramid fiber together, and by adjusting the total fineness of the core wire to 1000 to 3500 dtex, heat generation can be suppressed even when the belt is used in a small belt-type continuously variable transmission, and peeling of the core wire and cracking of the compression rubber layer can also be suppressed, thereby completing the present invention.

[0013] That is, the present invention includes the following aspects.

[0014] Aspect [1]: A power transmission V-belt including a core wire formed of a Lang twist cord obtained by doubling and second twisting a plurality of first twist yarns containing aramid fibers, and having a total fineness of 1000 to 3500 dtex.

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

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

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

[0018] Aspect [5]: The power transmission V-belt 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 power transmission V-belt according to any one of aspects [1] to [5], wherein the elongation stiffness per mm of pitch width of the power transmission V-belt is 6,500 to 20,000 N.

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

[0021] Aspect [8]: The power transmission V-belt according to any one of aspects [1] to [7], wherein the thickness is 5 to 12 mm, and the pitch width of the power transmission V-belt is 10 to 25 mm.

[0022] Aspect [9]: The power transmission V-belt according to any one of aspects [1] to [8], which is a raw edge V-belt having cogs at least on the inner peripheral surface side.

[0023] Aspect

[10] : The power transmission V-belt according to any one of aspects [1] to [9], which is a variable speed belt used in a small-sized belt-type continuously variable transmission.

[0024] Aspect

[11] : A belt transmission mechanism including the transmission V-belt according to any one of aspects [1] to

[10] and a pulley.

[0025] Aspect

[12] : The belt transmission mechanism of aspect

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

[0026] In the present invention, the core wire of the power transmission V-belt is formed from a Lang twist cord formed by doubling and then twisting a plurality of first twist yarns containing aramid fiber together, and the total fineness of the core wire is adjusted to 1000 to 3500 dtex. Therefore, even when the belt is 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.

[0027] FIG. 1 is a schematic cross-sectional view illustrating the transmission mechanism of a belt-type continuously variable transmission. FIG. 2 is a schematic, partially sectional, perspective view showing an example of a raw-edge cogged V-belt of the present invention. FIG. 3 is a schematic cross-sectional view of the raw-edge cogged V-belt of FIG. 2 cut in the belt longitudinal direction. FIG. 4 is a schematic, partially sectional, perspective view showing an example of a raw-edge double-cogged V-belt of the present invention. FIG. 5 is a schematic cross-sectional view of the raw-edge double-cogged V-belt of FIG. 4 cut in the belt longitudinal direction. FIG. 6 is a schematic cross-sectional view illustrating the definition of the overall thickness of a raw-edge double-cogged V-belt of the present invention. FIG. 7 is a schematic cross-sectional view illustrating the definition of the belt pitch width of a raw-edge cogged V-belt of the present invention. FIG. 8 is a schematic view illustrating a method for measuring the bending rigidity EI of raw-edge V-belts obtained in Examples. FIG. 9 shows the layout of a peel resistance test of raw-edge V-belts obtained in Examples. FIG. 10 shows the layout of a crack resistance test of raw-edge V-belts obtained in Examples.

[0028] [Power Transmission V-Belt] The power transmission V-belt of the present invention is not particularly limited as long as it is formed of a Lang twist cord obtained by doubling and second-twisting a plurality of first-twist yarns containing aramid fibers, and includes a core wire having a total fineness of 1,000 to 3,500 dtex. The power transmission V-belt of the present invention is a friction transmission belt having a V-shaped friction transmission surface. A V-belt having such a shape 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 sheath (cover fabric). Of these, raw-edge V-belts are preferred because of their excellent power transmission properties.

[0029] Raw-edge V-belts include raw-edge V-belts without cogs and raw-edge cogged V-belts with cogs. Furthermore, raw-edge cogged V-belts include raw-edge cogged V-belts with cogs formed only on the inner periphery of the raw-edge V-belt and raw-edge double-cogged V-belts with cogs formed on both the inner and outer periphery of the raw-edge V-belt. In this application, raw-edge V-belts without cogs, raw-edge cogged V-belts, and raw-edge double-cogged V-belts are collectively referred to as raw-edge V-belts. Of these, raw-edge cogged V-belts and raw-edge double-cogged V-belts used as variable-speed belts (CVT belts) are preferred due to the significant effects of the present invention.

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

[0031] In this example, the raw-edge cogged V-belt 1 has a cog portion formed on the inner peripheral surface of the belt body, with cog crests 1a and cog valleys 1b arranged alternately along the longitudinal direction of the belt (direction A in the figure). The longitudinal cross-section of the cog crests 1a is approximately semicircular (curved or wavy), and the cross-section in the direction perpendicular to the longitudinal direction (the width direction or direction B in the figure) is trapezoidal. That is, each cog crest 1a protrudes approximately semicircularly from the cog valleys 1b in the belt thickness direction in the cross section along direction A. The raw-edge cogged V-belt 1 has a layered structure, in which a reinforcing fabric 2, a tension rubber layer 3, a core layer (adhesive rubber layer) 4, a compression rubber layer 5, and a reinforcing fabric 6 are layered in this order from the outer periphery of the belt toward the inner periphery (the side where the cogs are formed). The cross-sectional shape in the width direction of the belt is trapezoidal, with the belt width narrowing from the outer periphery to the inner periphery. Furthermore, the core wires 4a are embedded in the adhesive rubber layer 4, and the cog portion is formed in the compression rubber layer 5 by a cog-forming mold.

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

[0033] In this example, the raw-edge double-cogged V-belt 11 has an inner cog portion formed on the inner surface of the compressed rubber layer 15 along the longitudinal direction of the belt (direction A in the figure), with inner cog peaks 11a and inner cog valleys 11b arranged alternately, and the inner cog peaks 11a have a substantially semicircular (curved or wavy) cross-sectional shape in the longitudinal direction, and a trapezoidal cross-sectional shape in the direction perpendicular to the longitudinal direction (the width direction or direction B in the figure). That is, each inner cog peak 11a protrudes in a substantially semicircular shape from the inner cog valleys 11b in the belt thickness direction in a cross section along direction A.

[0034] The outer circumferential surface also has a circumferential cog portion formed with circumferential cog crests 11c and circumferential cog valleys 11d arranged alternately along the longitudinal direction of the belt, and the circumferential cog crests 11c have a substantially trapezoidal cross section in the longitudinal direction and a substantially rectangular cross section in the direction perpendicular to the longitudinal direction (the width direction or direction B in the figure). That is, each circumferential cog crest 11c protrudes from the circumferential cog valleys 11d in the belt thickness direction in a substantially trapezoidal shape in the cross section in direction A.

[0035] The raw-edge double-cogged V-belt has a layered structure, with a tension rubber layer 13, a core layer (adhesive rubber layer) 14, a compression rubber layer 15, and a reinforcing fabric 16 layered in that order from the outer periphery to the inner periphery. The cross-sectional shape in the belt width direction is a generally trapezoidal shape, with the belt width decreasing from the outer periphery to the inner periphery. Furthermore, cords 14a are embedded in the core layer 14, and the inner and outer cogs are formed in the compression rubber layer 15 and the tension rubber layer 13, respectively, using a cog-forming mold.

[0036] (Total Thickness of Transmission V-Belt) In the transmission V-belt of the present invention (particularly, the raw edge V-belt), the total belt thickness (average thickness) 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 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, separation of the cord, and cracking of the rubber can be suppressed.

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

[0038] In this application, the total thickness of a power transmission V-belt (particularly a raw-edge V-belt) refers to the thickness from the outer peripheral surface to the inner peripheral surface (the thickness at the thickest point of the belt). In the case of a V-belt with cogs, the tops of the cogs are on the inner or outer peripheral surface, as shown in Figure 6. Therefore, in a raw-edge cogged V-belt with cogs only on the inner peripheral surface, the total thickness is the distance from the outer peripheral surface to the tops of the cogs on the inner peripheral surface. That is, in the case of a raw-edge cogged V-belt, the total thickness refers to the distance from the tops of the cogs (convex tops on the inner peripheral side) in the compression rubber layer to the back surface of the belt. In the case of a raw-edge double-cogged V-belt, the total thickness refers to the distance from the tops of the cogs (convex tops on the inner peripheral side) in the compression rubber layer to the tops of the cogs (convex tops on the outer peripheral side) in the tension rubber layer.

[0039] (Belt Pitch Width of Power Transmission V-Belt) In the power transmission V-belt (particularly, the raw 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, separation of the cord, and the occurrence of cracks in the rubber can be suppressed. In particular, when the overall belt thickness is within the above range and the belt pitch width is within this range, the thickness is thin and the pitch width is narrow, which is preferable because the effects of the present invention are particularly enhanced.

[0040] Fig. 7 shows the definition of the belt pitch width of a raw-edge cogged V-belt according to the present invention. Fig. 7 is a schematic cross-sectional view of a raw-edge cogged belt 1 in which a reinforcing fabric 2, a tension rubber layer 3, a core layer 4, a compression rubber layer 5, and a reinforcing fabric 6 are laminated in that order. The belt pitch width W refers to the width of the belt at the pitch line L (the position on the line connecting the centers of the cords 4a embedded at equal intervals in the core layer 4).

[0041] (Extensional Rigidity of Transmission V-Belt) In the transmission V-belt (particularly, the raw edge V-belt), the extensional rigidity per 1 mm of the belt pitch width (the belt extensional rigidity EA) is, for example, 6,200 to 25,000 N, preferably 6,500 to 20,000 N, further preferably 7,000 to 18,000 N, even more preferably 7,500 to 15,000 N, and most preferably 8,000 to 12,000 N. In the present invention, since the belt extensional rigidity EA is within this range, heat generation due to slippage can be suppressed. If the belt extensional rigidity EA is too small, the belt may elongate significantly under heavy loads, making it more likely to slip. On the other hand, if the belt extensional rigidity EA is too large, the belt may not be able to absorb load fluctuations due to its elongation, making it more likely to slip.

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

[0043] In the present application, the elongation stiffness EA of the belt is defined as a proportional constant of the belt tension with respect to the rate of change in belt length in the belt tension range of 200 to 600 N. That is, in the present application, the elongation stiffness EA of the belt can be determined as the slope of an approximate straight line of measured values ​​for every 100 N of the belt tension between 200 N and 600 N in a graph in which measured values ​​are plotted with the rate of change in belt length (%) on the horizontal axis and the belt tension (N) on the vertical axis, and in detail, can be measured by the method described in the examples below.

[0044] (Bending Rigidity of Transmission V-Belt) In the transmission V-belt of the present invention (particularly, the raw edge V-belt), the bending rigidity per 1 mm of the pitch width of the belt (belt bending rigidity EI) is, for example, 40 to 260 N (mm). ２ , preferably 60 to 250 N (mm) ２ , more preferably 80 to 240 N (mm) ２ , more preferably 100 to 235 N (mm) ２ , most preferably 120 to 230 N (mm) ２ In the present invention, since the bending rigidity EI of the belt is within this range, heat generation due to bending can be suppressed. If the bending rigidity EI of the belt is too small, there is a risk that the vibration and noise of the belt will increase, 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 rigidity EI of a belt represents the relationship between the compressive force required to compress a circular belt from the outer periphery and deform it into a bale shape, and the pitch diameter (the diameter of the arc drawn by the pitch line connecting the center lines of the core wires) when the bent portion of the belt is considered to be an arc.When the bending rigidity of a belt is high, the belt is difficult to bend, and when the bending rigidity of a belt is low, the belt is easy to bend.

[0046] In the present application, the bending rigidity EI of the belt can be measured using an autograph, and more specifically, can be measured by the method described in the examples below.

[0047] [Core Wire] The power transmission V-belt of the present invention is characterized in that the core wire is formed of a Lang twist cord obtained by doubling and then twisting a plurality of first twist yarns containing aramid fibers, and has a total fineness of 1,000 to 3,500 dtex. By providing the core wire with these characteristics, heat generation during use of the power transmission V-belt can be suppressed, and separation of the core wire and cracking of the compression rubber layer can be suppressed. This is particularly effective when used as a speed-change belt in a small, belt-type continuously variable transmission that is subject to a relatively small load. The reason why this is particularly effective when used as a speed-change belt can be presumed as follows.

[0048] The failure modes of speed change belts include cog valley cracks and cord separation, both of which are more likely to occur as the belt temperature rises. Therefore, suppressing belt heat generation is the key to improving the durability of speed change belts. The causes of belt heat include slippage (frictional heat caused by the belt rubbing against the pulley) and bending (internal heat generation caused by the bending and stretching of the belt).

[0049] Based on the idea that high tensile rigidity is fundamentally desirable for power transmission belts, there is a tendency to use materials with high tensile modulus of elasticity, such as aramid fiber or carbon fiber, for the core wires, and to increase the core wire diameter. In contrast, the power transmission V-belt of the present invention is characterized by a small-diameter core wire. However, by using aramid fiber with a high tensile modulus of elasticity as the core wire, it is presumed that the tensile rigidity of the belt can be ensured even with a small diameter. Furthermore, since the tensile rigidity of the belt can be maintained relatively high, it is presumed that belt elongation can be suppressed, slippage can be reduced, and heat generation can be suppressed. Furthermore, since the small diameter reduces the flexural rigidity of the belt, it is presumed that heat generation due to bending can also be suppressed.

[0050] That is, in the present invention, the core wire contains aramid fiber and has a small diameter, and therefore the high elastic modulus of aramid increases the elongation rigidity of the belt, making it possible to suppress heat generation due to slippage, and the small diameter reduces the bending rigidity of the belt, making it possible to suppress heat generation due to bending.

[0051] In the Lang twist cord constituting such a core, the first twist yarn may be an aramid multifilament yarn containing a plurality of aramid fibers. The aramid multifilament yarn may contain other fibers (such as polyester fibers) if necessary. The proportion of aramid fibers may be 50% by mass or more (particularly 80 to 100% by mass) of the entire multifilament yarn, and preferably, all filaments are composed of aramid fibers. In the present invention, by including aramid fibers in the core, the elongation rigidity of the belt can be improved and heat generation due to slippage can be suppressed. Therefore, if the proportion of aramid fibers is too small, there is a risk that the belt may be more susceptible to heat generation.

[0052] The aramid multifilament yarn may contain a plurality of aramid filaments, for example, 100 to 5000 filaments, preferably 300 to 2000 filaments, more preferably 600 to 1500 filaments, 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] The aramid fiber is preferably a para-aramid fiber because of its excellent mechanical strength. Specifically, it may be a para-aramid fiber having a single repeating unit (for example, a polyparaphenylene terephthalamide fiber such as "Twaron (registered trademark)" manufactured by Teijin Limited or "Kevlar (registered trademark)" manufactured by DuPont-Toray Co., Ltd.), or a copolymerized para-aramid fiber having a plurality of repeating units (for example, a copolymerized aramid fiber of polyparaphenylene terephthalamide and 3,4'-oxydiphenylene terephthalamide such as "Technora" manufactured by Teijin Limited). Of these, copolymerized para-aramid fibers are particularly preferred.

[0054] The tensile modulus of the aramid fiber can be selected from a range of about 50 to 100 GPa, for example, 50 to 90 GPa, preferably 60 to 90 GPa, further preferably 65 to 85 GPa, and even more preferably 70 to 80 GPa. In applications requiring high resistance to flex fatigue, the aramid fiber may be a high-elongation aramid fiber having a tensile modulus of about 50 to 70 GPa. If the tensile modulus is too small, the elongation rigidity of the belt may decrease, which may cause heat generation due to slippage. Conversely, if the tensile modulus is too large, there is a risk that the resistance to flex fatigue 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 first twist yarn is 2000 dtex or less, preferably 500 to 2000 dtex, further preferably 1000 to 1900 dtex, even more preferably 1300 to 1800 dtex, and most preferably 1500 to 1700 dtex. If the fineness is too small, the elongation will be large and the tensile strength and tensile modulus will be reduced, which may also reduce economic efficiency. Conversely, if the fineness is too large, there is a risk that the flexural fatigue resistance will be reduced.

[0057] The number of first twist yarns may be more than one, but is preferably 2 to 6, more preferably 2 to 4, even more preferably 2 to 3, and most preferably 2. If the number is too large, there is a risk that bending fatigue resistance will decrease.

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

[0059] In the present invention, the first twist yarn is produced by twisting the multifilament yarn in one direction, and the resulting twisted cord, which is made by aligning and twisting the multiple first twist yarns, is a Lang twist cord, in which the second twist is applied in the same direction as the first twist. Lang twist cords have excellent flexibility due to the large inclination angle of the filaments with respect to the longitudinal direction of the twisted cord, and can reduce the bending rigidity of the belt.

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

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

[0062] In the present application, the twist coefficients of the first twist and the second twist can be calculated based on the following formula.

[0063] TF = TN x D ０．５ / 960 [wherein TF is the twist factor, TN is the number of twists per meter, and D is the yarn fineness (tex)]

[0064] The total fineness of the Lang twist cord is 1000 to 3500 dtex. In the present invention, since the total fineness of the cord formed from the Lang twist 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 be low, and if the total fineness exceeds 3500 dtex, the bending rigidity of the belt may be high. The total fineness of the Lang twist cord is preferably 2000 to 3450 dtex, and more preferably 3000 to 3400 dtex.

[0065] The Lang twisted cord may be subjected to an adhesive treatment (or surface treatment) to improve adhesion to the rubber component. As the adhesive treatment method, a conventional method can be used, and examples thereof include the method described in Japanese Patent No. 6,349,369, which includes a step of treating with a first treating agent consisting of a rubber composition (a) containing a condensate of resorcinol and formaldehyde (a1), a rubber component (a2) containing a carboxyl-modified latex, and a curing agent (a3) ​​containing a polycarbodiimide resin having multiple carbodiimide groups, and a hydrophilic solvent (b). Among these, a method including a first treating step of treating with a first treating agent consisting of a rubber composition (a) containing a curing agent (a3) ​​containing a polycarbodiimide resin having multiple carbodiimide groups and a hydrophilic solvent (b), a second treating step of treating the first-treated yarn treated in the first treating step with a second treating agent containing resorcinol, formaldehyde, and latex, and a third treating step of treating the second-treated yarn treated in the second treating step with a third treating agent containing rubber is preferred. The bundling ability of the fibers can be improved by allowing the adhesive component to penetrate between the first twisted yarns or between the individual fibers that make up the first twisted yarns and attaching the adhesive component to the surfaces of the fibers.

[0066] The adhesion rate of the adhesive component (solid content adhesion rate) is, for example, 1 to 50 mass %, preferably 3 to 30 mass %, further preferably 5 to 25 mass %, and even more preferably 10 to 20 mass %, of the Lang twist cord before the adhesive treatment. If the proportion of the adhesive component is too small, adhesion between the fibers will be insufficient, and friction between the fibers will occur when the cord is bent, which may result in a decrease in bending fatigue resistance. If the proportion of the adhesive component is too large, there is a risk that the cord diameter will become too large.

[0067] The average diameter of the core wire (Lang twisted cord after adhesive treatment) is, for example, 0.1 to 1.2 mm, preferably 0.3 to 1.1 mm, further preferably 0.4 to 1 mm, even 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 cords refers to the average diameter of the cords in the belt. The average diameter of the cords is determined by photographing a cross section of the belt in the width direction with a scanning electron microscope (SEM), measuring the lengths of all the cords in the belt in the photographed image in the width direction, and then calculating the arithmetic average value. However, if some of the cords are missing on the side of the belt, they are not included in the measurement.

[0069] In the present invention, the total fineness of the core wires is relatively small compared to the tensile strength of the core wires in the examples of Patent Document 2 (1,300 N tensile strength of aramid core wires with a total fineness of 9,900 dtex), for example. Therefore, the tensile strength per core wire is low, and the tensile rigidity of the belt can be improved by narrowing the cord pitch and arranging the cords densely. From the viewpoint of increasing the tensile rigidity of the belt, a higher tensile strength per cord is considered preferable. However, thickening the cords to increase the tensile strength per cord may reduce flexibility, and the cord pitch must be increased, which does not result in a dramatic increase in the tensile rigidity of the belt. In the present invention, the cord diameter is narrowed and the cords are arranged densely, while preventing the tensile strength per cord from becoming excessively low, thereby reducing the flexural rigidity of the belt 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, further 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 elongation rigidity of the belt may be low, whereas if the tensile strength per core wire is too high, the bending rigidity of the belt may be high.

[0071] In the present 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, extend along the belt length direction (circumferential direction), and are embedded in the core layer. These core wires act as tension members and may be arranged parallel to the belt length direction at a predetermined pitch. However, from the viewpoint of productivity, they are usually arranged spirally, extending parallel to the belt length direction at a predetermined pitch. When arranged spirally, the angle of the core wire with respect to the belt length direction may be, for example, 5° or less, and from the viewpoint of belt running performance, the closer to 0° the angle is, the better.

[0073] The core wire pitch (the average distance between the centers of adjacent core wires in the belt width direction cross section) is preferably larger than the average core wire diameter by a predetermined range. Specifically, the value obtained by subtracting the core wire diameter from the core wire pitch (the "core wire pitch - average core wire diameter" value, meaning the width per section of the belt width direction where no core wires are present) 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 even more preferably 0.15 to 0.21 mm. If the value is too small, the core wires may be prone to climbing over or rubbing against each other, resulting in a decrease in the tensile strength of the belt. Conversely, if the value is too large, the elongation rigidity of the belt may be reduced. That is, from the viewpoint of increasing the elongation rigidity of the belt, a smaller value is preferable, but if the value is too small, the core wires may be prone to climbing over or rubbing against each other, resulting in a decrease in 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. In other words, the number of core wires refers to the number of spirals when one core wire is embedded in a spiral shape. However, since the core wires are actually embedded in a spiral shape, the arrangement of the core wires varies depending on the location from which the cross section is taken, even within an endless power transmission V-belt. Therefore, in practice, when each core wire pitch is a constant value, the value calculated by dividing the belt width by the core wire pitch and rounding down to the nearest whole number is considered to be the approximate "number of core wires" (effective number).

[0075] [Compressed Rubber Layer] In the power transmission V-belt of the present invention, the compressed rubber layer is formed of a rubber composition (crosslinked rubber composition) containing the 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 terpolymer (EPDM), etc.), chlorosulfonated polyethylene rubber, alkylated chlorosulfonated polyethylene rubber, epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, fluororubber, etc. These rubber components may be used alone 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 from the viewpoints of excellent balance of heat resistance, abrasion resistance, oil resistance, etc. and high productivity.

[0078] When the first rubber component contains chloroprene rubber, the proportion of the 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 to 100% by mass), and most preferably 100% by mass (chloroprene rubber only), in order to improve the above-mentioned properties and productivity. When the first rubber component contains an ethylene-α-olefin elastomer, the proportion of the ethylene-α-olefin elastomer in the first rubber component is the same as the proportion of the chloroprene rubber.

[0079] (A2) First Short Fibers The rubber composition forming the compressed rubber layer may further contain first short fibers. Examples of the 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 wholly aromatic polyester short fibers, etc.)), synthetic short fibers such as vinylon short fibers, polyvinyl alcohol short fibers, and polyparaphenylene benzobisoxazole (PBO) short fibers; natural short fibers such as cotton, hemp, and wool; and inorganic short fibers such as carbon short fibers. These short fibers can be used alone or in combination. Among 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 first short fibers have an average fiber diameter of 2 μm or more, for example, 2 to 100 μm, preferably 3 to 50 μm, more preferably 7 to 40 μm, and even more preferably 10 to 30 μm.The first short fibers have an average fiber length of, 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 while being oriented substantially parallel to the belt width direction in order to suppress compressive deformation of the belt due to pressure from the pulley.

[0082] The first short fibers may be subjected to a conventional adhesive treatment to enhance adhesion to the first rubber component. Conventional adhesive treatment methods can be used, including treatment with a treatment liquid containing a precondensate of phenols and formalin (e.g., a prepolymer of novolac or resol-type phenolic resin); a treatment liquid containing a rubber component (or latex); a treatment liquid containing the precondensate and a rubber component (latex); or a treatment liquid containing a reactive compound (adhesive compound) such as a silane coupling agent, an epoxy compound (e.g., an epoxy resin), an isocyanate compound, or a bismaleimide compound. These methods can be used alone or in combination. Among these methods, treatment with a treatment liquid containing the precondensate and a rubber component (latex) is preferred, and treatment with at least a resorcinol-formalin-latex (RFL) solution is particularly preferred.

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

[0084] (A3) Other Components The rubber composition that forms the compression rubber layer may contain conventional additives as other components (first other components). Examples of the additives include 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 (reinforcing fillers) such as carbon black and silicon oxide (hydrated silica, etc.)]; extenders (non-reinforcing fillers or inert fillers) such as clay, calcium carbonate, talc, and mica]. fillers, etc.), 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 stearates, wax, paraffin, fatty acid amides, etc.), antiaging agents (antioxidants, heat-aging inhibitors, flex crack inhibitors, antiozonants, etc.), adhesion improvers, colorants, tackifiers, coupling agents (silane coupling agents, etc.), stabilizers (ultraviolet absorbers, heat stabilizers, etc.), flame retardants, antistatic agents, etc. These additives can be used alone or in combination of two or more. Note that metal oxides may also function as crosslinking agents.

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

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

[0087] The amount of the metal powder relative to 100 parts by mass of the first rubber component 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.

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

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

[0090] The second rubber component, including preferred embodiments thereof, can be selected from the rubber components exemplified as the first rubber component. The second rubber component may be a rubber component different 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), which can be selected from the short fibers exemplified as the first short fibers, including preferred embodiments. The average fiber diameter and average fiber length of the second short fibers can also be selected from the ranges of the first short fibers, including 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 another component (second other component), and the second other component, including preferred embodiments, can be selected from the other components exemplified as the first other component. The second other component may be a component different from the first other component, but is usually the same as the first other component.

[0093] [Core Layer] The core layer may contain the core wires as the core, and may be a core layer formed only of the core wires, but from the viewpoint of suppressing interlayer delamination and improving belt durability, it is preferable that the core layer be a core layer (adhesive rubber layer) formed of a crosslinked rubber composition with the core wires embedded in it. The adhesive rubber layer is interposed between the tension rubber layer and the main body of the compression rubber layer to bond the tension rubber layer and the compression rubber layer together, and the core wires are 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, including preferred embodiments thereof, can be selected from the rubber components exemplified as the first rubber component. The third rubber component may be a rubber component different from the first rubber component, but is usually the same as the first rubber component.

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

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

[0098] The ratio of the filler (third filler) such as carbon black or silica relative to 100 parts by mass of the third rubber component is, for example, 10 to 200 parts by mass, preferably 20 to 100 parts by mass, further preferably 30 to 80 parts by mass, and further preferably 40 to 70 parts by mass.

[0099] The proportion of the adhesion improver relative to 100 parts by mass of the third rubber component 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.

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

[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] [Reinforcing Fabric] The power transmission V-belt of the present invention may further include a reinforcing fabric, which may be laminated on the inner circumferential surface of the compression rubber layer, laminated on the outer circumferential surface of the tension rubber layer, or embedded in the compression rubber layer and / or the tension rubber layer, for example.

[0103] The reinforcing fabric can be formed from fabric materials (especially woven fabrics) such as woven fabrics, wide-angle canvas, knitted fabrics, and nonwoven fabrics, and if necessary, can be subjected to an adhesive treatment, for example, treatment with RFL liquid (dipping treatment, etc.), a friction treatment in which adhesive rubber is rubbed into the fabric material, or the adhesive rubber and the fabric material can be laminated together and then laminated or embedded in a compression rubber layer and / or tension rubber layer in the above-mentioned form.

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

[0105] First, a laminate of a reinforcing fabric (lower fabric) and a sheet for the main body of the compressed rubber layer (an uncrosslinked rubber sheet) is placed, with the reinforcing fabric facing downward, in contact with a flat cog mold in which teeth and grooves corresponding to the inner cogs (cog crests 1a and cog bottoms 1b shown in FIG. 2) are alternately arranged, and the laminate is pressed at a temperature of 60 to 100°C (particularly 70 to 80°C) to produce a cog pad with shaped inner cogs (a pad that is not completely crosslinked but is in a semi-crosslinked state). Both ends of this cog pad are then cut vertically at appropriate points (particularly the tops of the cog crests) to obtain the required length.

[0106] Next, an inner matrix having alternating tooth and groove portions corresponding to the cogs is placed over the outer periphery of a cylindrical mold, and a cog pad is wound around the inner matrix by engaging the tooth and groove portions and bonding both ends (particularly the tops of the cog crests). A sheet for a first adhesive rubber layer (lower adhesive rubber: uncrosslinked rubber sheet) is then laminated around the outer periphery of this cog pad, and the cord (twisted cord) that forms the core is spun spirally, and a sheet for a second adhesive rubber layer (upper adhesive rubber: uncrosslinked rubber sheet) and a sheet for a tension rubber layer (uncrosslinked rubber sheet) are sequentially wound around the outer periphery to produce an uncrosslinked molded article. Furthermore, if necessary, a reinforcing fabric (upper fabric) may be laminated on the tension rubber layer.

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

[0108] In the case of a raw-edge double-cogged V-belt, an outer mold having teeth and grooves corresponding to the outer peripheral cogs arranged alternately is placed on the outer periphery of the uncrosslinked molded body, and then a jacket is placed over the uncrosslinked molded body and crosslinking molding is performed to obtain a crosslinked belt sleeve having cogs formed on the outer peripheral surface as well, which is then cut into a V shape to obtain a raw-edge double-cogged V-belt.

[0109] The adhesive rubber layer can be formed from multiple adhesive rubber layer sheets, and the core wire (twisted cord) forming the core body may be spun in association with the stacking order of the multiple adhesive rubber layer sheets, depending on the embedding position in the adhesive rubber layer.

[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. Carboxyl-modified NBR latex (COOH-modified NBR): "Nipol 1571CL" manufactured by Nippon Zeon Co., Ltd., active ingredient 38% by mass, high nitrile type

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

[0113] (Short fibers) The following short fibers were used. All short fibers were immersed in an RFL liquid [a mixed liquid of 2.6 parts by mass of resorcinol, 1.4 parts by mass of 37% by mass 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 dried to undergo an adhesion treatment. The adhesion rate of the adhesive component (solid content) was adjusted to 6% by mass relative to the short fibers before treatment.

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

[0115] (Filler) Carbon black FEF: "Seat SO" manufactured by Tokai Carbon Co., Ltd. Silica: "Nipsil VN3" 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 Co., Ltd. Adhesion improver B (hexamethoxymethyl melamine): "POWERPLAST PP-1890S" manufactured by Singh Plasticisers & Resins Co., Ltd. Magnesium oxide: "Kyowamag 150" manufactured by Kyowa Chemical Industry Co., Ltd. Crosslinking accelerator MBTS (dibenzothiazyl disulfide): "Noccela DM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Crosslinking accelerator TMTD (tetramethylthiuram disulfide): "Noccela TT" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant A (octyldiphenylamine): "Nonflex OD-3" manufactured by Seiko Chemical Co., Ltd. Antioxidant B (4,4'-bis(α,α-dimethylbenzyl)diphenylamine): "Nonflex DCD" manufactured by Seiko Chemical Co., Ltd. Antioxidant C (microcrystalline wax): "Suntite C" manufactured by Seiko Chemical Co., Ltd. Zinc powder: "M-11" manufactured by Sakai Chemical Industry Co., Ltd. Softener: "Adeka Cizer C-8" manufactured by ADEKA Corporation Stearic acid: "Camellia Stearate Beads" manufactured by NOF Corporation Zinc oxide: "Zinc Oxide (JIS Class 2)" manufactured by Hakusui Tech Co., Ltd. Co-crosslinking agent (N,N'-m-phenylenedimaleimide): "Valnoc PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

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

[0118] Aramid cord of Examples 1 to 3: A Lang-twisted cord having a total fineness of 3340 dtex, obtained by combining two first-twisted yarns made of 1670 dtex aramid fiber bundles ("Technora" manufactured by Teijin Limited) first twisted at a twist multiplier of 1.0, and then second-twisting the yarns in the same direction as the first twist at a twist multiplier of 3.0 (the diameter of the treated cord was approximately 0.70 mm, and the tensile strength per cord was 620 N).

[0119] Polyester core wire used in Comparative Examples 1 to 3: A plied cord with a total fineness of 6,600 dtex (the diameter of the treated cord was approximately 1.00 mm, and the tensile strength per core wire was 440 N) obtained by combining two 1,100 dex PET fiber bundles ("Tetron" manufactured by Toray Industries, Inc.) and first twisting them at a twist multiplying factor of 3.0 to form a first twist yarn, and combining three of these yarns and then second twisting them at a twist multiplying factor of 3.0 in the opposite direction to the first twist.

[0120] Aramid cord used in Comparative Examples 4, 7, and 10: A plied cord having a total fineness of 3,340 dtex (the diameter of the treated cord was approximately 0.71 mm, and the tensile strength per cord was 620 N) obtained by combining two first twisted yarns made of 1,670 dtex aramid fiber bundles ("Technora" manufactured by Teijin Limited) with a twist multiplying factor of 1.0 and then second twisting the yarns in the opposite direction to the first twist with a twist multiplying factor of 3.0.

[0121] Aramid core wire used in Comparative Examples 5, 8, and 11: A Lang-twisted cord having a total fineness of 6,600 dtex (the diameter of the treated cord was approximately 0.94 mm, and the tensile strength per core wire was 1,300 N) obtained by combining two 1,100 dtex aramid fiber bundles ("Technora" manufactured by Teijin Limited) and first twisting them at a twist multiplier of 1.0 to form three first twisted yarns, which were then second twisted in the same direction as the first twist at a twist multiplier of 3.0.

[0122] Aramid core wire used in Comparative Examples 6, 9, and 12: A plied cord having a total fineness of 6,600 dtex (the diameter of the treated cord was approximately 0.95 mm, and the tensile strength per core wire was 1,300 N) obtained by combining two 1,100 dtex aramid fiber bundles ("Technora" manufactured by Teijin Limited) and first twisting them at a twist multiplying factor of 1.0, and combining three of these first twisted yarns and then second twisting them in the opposite direction to the first twist at a twist multiplying factor of 3.0.

[0123] Details of the core wires used in Examples 1 to 3 and Comparative Examples 1 to 12 are summarized in Table 1.

[0124]

[0125] (Method for adhesive treatment of core wire) (A) Preparation of first treatment agent A polycarbodiimide dispersion and water were mixed with an RFL liquid having 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 a first treatment agent having the composition shown in Table 3.

[0126]

[0127]

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

[0129]

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

[0131]

[0132] (D) Bonding Treatment An 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 a cord (third treatment step).

[0133] (Reinforcing fabric) Canvas (180 g / m2) plain woven with 10-count cotton yarn at a thread density of 70 threads / 50 mm ２ The rubber composition for the adhesive rubber layer was rubbed into the canvas to obtain a treated canvas (thickness: about 0.5 mm, basis weight: about 450 g / m ２ The same reinforcing fabric was used on both the inner and outer circumferential sides of the belt.

[0134] [Belt elongation stiffness EA] A test belt was hung on a measuring machine (belt length measuring machine) with a pair of V-grooved pulleys with the same pitch diameter arranged above and below, and a load was applied to the lower pulley in the direction of separating the two pulleys. At this time, the belt tension (the tension acting on one span of the belt located between the two pulleys) was half of the load applied to the lower pulley.

[0135] Specifically, the belt length when the belt tension was 200 N was taken as the reference length (belt length change rate 0%), and the belt tension was changed from 200 N to 600 N, and the belt length change rate relative to the reference length was recorded. The measurement temperature was adjusted to 25°C.

[0136] The measurement results were graphed with the belt length change rate (%) on the horizontal axis and the belt tension (N) on the vertical axis, and the values ​​at five belt tension points of 200 N, 300 N, 400 N, 500 N, and 600 N were linearly approximated, and the slope of the approximated line was taken as the elongation stiffness EA (unit: N) of the belt. The elongation stiffness EA was expressed as a value per belt, or a value per 1 mm of pitch width divided by the pitch width of the belt.

[0137] [Belt Bending Stiffness EI] An upper plate 42 and a lower plate 43 for compressing the test specimen belt from the back were attached to an autograph, and a circular belt 41 was placed between the upper and lower plates 42, 43 as shown in Fig. 8. The distance between the plates was narrowed at a rate 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 the average value (arithmetic mean value) was determined.

[0138] Bending rigidity EI = (compression force × (pitch diameter D / 2)) ２ ) / 2 (unit: N (mm) ２ )

[0139] The bending stiffness EI is expressed as a value per belt or a value per mm of pitch width divided by the pitch width of the belt.

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

[0141] [Durability Test 2 (Crack Resistance Test)] The crack resistance test was performed using a biaxial running tester consisting of a drive (Dr.) pulley with a diameter of 120 mm and a driven (Dn.) pulley with a diameter of 80 mm, as shown in Figure 10. A raw edge V-belt was hung between these two pulleys, and the belt was run at an ambient temperature of 120°C under an axial load of 400 N, a drive pulley rotation speed of 6000 rpm, and a drive pulley torque of 12 N m. The side temperature of the running belt was measured with 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] Example 1 and Comparative Examples 1 and 4 to 6 (Formation of Rubber Layers) For the rubber compositions in Table 6 (adhesive rubber layer) and Table 7 (compressed rubber layer and tensioned rubber layer), rubber kneading was carried out using a known method such as a Banbury mixer, and the kneaded rubber obtained was passed through a calendar roll to prepare rolled rubber sheets (sheet for adhesive rubber layer, sheet for compressed rubber layer, sheet for tensioned rubber layer).

[0143]

[0144]

[0145] (Belt Manufacturing) A laminate of a reinforcing fabric (lower fabric) and a sheet for a compression rubber layer (uncrosslinked rubber) was placed, with the reinforcing fabric facing down, on a flat cog mold in which teeth and grooves corresponding to the cogs were alternately arranged. The laminate was pressed at 75°C to produce a cog pad (not completely crosslinked, but in a semi-crosslinked state) with shaped cogs. Next, both ends of this cog pad were cut vertically from the tops of the cog peaks.

[0146] Next, an inner mold, with alternating tooth and groove portions corresponding to the cog portions, was placed over a cylindrical mold. The cog pad was wrapped around the inner mold by engaging the tooth and groove portions, and joined at the tops of the cog crests. A first adhesive rubber layer sheet (lower adhesive rubber, uncrosslinked rubber, the same as the adhesive rubber layer sheet) was then laminated around the outer periphery of the wrapped cog pad. The cord was then spirally spun, and a second adhesive rubber layer sheet (upper adhesive rubber, the same as the adhesive rubber layer sheet), a tension rubber layer sheet (uncrosslinked rubber), and a reinforcing cloth (upper cloth) were sequentially wrapped around the outer periphery to produce an uncrosslinked molded body. The short fibers were oriented in the belt width direction. The cord pitch was 0.9 mm in Example 1 and Comparative Example 4, and 1.1 mm in Comparative Examples 1, 5, and 6.

[0147] The uncrosslinked molded body was then covered with a jacket, and the mold was placed in a vulcanizer. The uncrosslinked molded body was crosslinked and molded at 160°C for 20 minutes to obtain a belt sleeve. This belt sleeve was cut into a V-shaped cross section with a predetermined width in the belt longitudinal direction using a cutter. This belt sleeve was then finished into a belt with the structure shown in Figure 2, i.e., a raw-edge cogged V-belt (size: upper width 24 mm, thickness 11 mm, V angle 30 degrees, outer periphery length 900 mm, pitch width 23 mm), which is a variable speed belt with cogs on the inner periphery of the belt.

[0148] The evaluation results of the belts obtained in Example 1 and Comparative Examples 1 and 4 to 6 are shown in Table 8.

[0149]

[0150] Example 2 and Comparative Examples 2 and 7 to 9: A raw edge double-cogged V-belt (size: upper width 25 mm, thickness 10 mm, V angle 30 degrees, outer periphery length 900 mm, pitch width 23 mm) was obtained in the same manner as in Example 1, except that no upper fabric was used and a crosslinked belt sleeve having cogs formed on the outer periphery was produced by covering the outer periphery of the crosslinked molded body with an outer matrix having alternating arrangement of teeth and grooves corresponding to the outer periphery cogs, and then crosslinking molding was performed. The cord pitch was 0.9 mm in Example 2 and Comparative Example 7, and 1.1 mm in Comparative Examples 2 and 8 to 9.

[0151] The evaluation results of the belts obtained in Example 2 and Comparative Examples 2 and 7 to 9 are shown in Table 9.

[0152]

[0153] Example 3 and Comparative Examples 3 and 10-12: A raw-edge double-cogged V-belt (size: upper width 25 mm, thickness 9 mm, V angle 30 degrees, outer periphery length 900 mm, pitch width 23 mm) was obtained in the same manner as in Example 1, except that no upper fabric was used and a crosslinked belt sleeve having cogs formed on the outer periphery was produced by covering the outer periphery of the crosslinked molded body with an outer matrix having alternating arrangement of teeth and grooves corresponding to the outer periphery cogs, and then crosslinking molding was performed. The cord pitch was 0.9 mm in Example 3 and Comparative Example 10, and 1.1 mm in Comparative Examples 3 and 11-12.

[0154] The evaluation results of the belts obtained in Example 3 and Comparative Examples 3 and 10 to 12 are shown in Table 10.

[0155]

[0156] As is clear from the results in Tables 8 to 10, for all types and sizes of belts, the Examples using Lang twisted cords made of aramid fibers with a total fineness of 3,500 dtex or less had higher elongation rigidity and lower flexural rigidity than the Comparative Examples. Furthermore, the belt side temperatures of the Example belts were maintained low, confirming that they had excellent peel resistance and crack resistance.

[0157] Specifically, in Comparative Examples 1 to 3, the core wires were formed of polyester fibers, the total fineness was large, and the twisting method was ply twist, so the bending rigidity was high, the belt temperature rose, and durability was low.

[0158] In Comparative Examples 4, 7, and 10, the twisting of the cords was ply twisted, which resulted in high bending rigidity, an increase in belt temperature, and low durability.

[0159] In Comparative Examples 5, 8, and 11, the total fineness of the cord was large, so that the bending rigidity was high, the belt temperature rose, and the durability was low.

[0160] In Comparative Examples 6, 9, and 12, the total fineness of the cord was large and the cord was plied, so the bending rigidity was high, the belt temperature rose, and the durability was low.

[0161] The power transmission V-belt of the present invention can be applied to raw-edge V-belts, raw-edge cogged V-belts having cogs, and the like. In particular, it can be suitably used as a V-belt (speed-change belt or CVT belt) used in a transmission (continuously variable transmission) in which the speed ratio changes continuously while the belt is running, such as a raw-edge cogged V-belt or raw-edge double-cogged V-belt used in continuously variable transmissions of motorcycles, ATVs (all-terrain vehicles), snowmobiles, and the like. In particular, it can be suitably used as a raw-edge cogged V-belt or raw-edge double-cogged V-belt used in continuously variable transmissions of scooters with small engine displacements (for example, 250 cc or less, preferably 160 cc or less).

[0162] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the present invention. This application is based on Japanese Patent Application No. 2023-215734 filed on December 21, 2023, and Japanese Patent Application No. 2024-206743 filed on November 27, 2024, the contents of which are incorporated herein by reference.

[0163] REFERENCE SIGNS LIST 1... Raw-edge cogged V-belt 11... Raw-edge double cogged V-belt 2, 6, 16... Reinforcing fabric 3, 13... Tension rubber layer 4, 14... Core layer 4a, 14a... Cord 5, 15... Compression rubber layer

Claims

1. A V-belt for power transmission, comprising a lange twisted cord made by doubling and twisting multiple first twisted yarns containing aramid fiber, and including a core wire with a total fineness of 1,000 to 3,500 dtex.

2. The power transmission V-belt according to claim 1, wherein the tensile strength of each of said core wires is 500 to 1000 N.

3. A power transmission V-belt according to claim 1 or 2, wherein in said core wire, the twist factor of said first twisted yarn is 0.5-3, and the twist factor of said Lang twisted cord is 0.5-5.

4. A transmission V-belt according to any one of claims 1 to 3, wherein the pitch of the core wires is 0.05 to 0.25 mm larger than the average diameter of the core wires.

5. The transmission V-belt according to any one of claims 1 to 4, wherein the average diameter of the core wire is 0.4 to 1 mm.

6. The transmission V-belt according to any one of claims 1 to 5, wherein the elongation stiffness per mm of the pitch width of the transmission V-belt is 6,500 to 20,000 N.

7. The bending stiffness of the transmission V-belt per 1 mm of pitch width is 40 to 260 N (mm). ２ The transmission V-belt according to any one of claims 1 to 6.

8. The transmission V-belt according to any one of claims 1 to 7, which has a thickness of 5 to 12 mm and a pitch width of 10 to 25 mm.

9. The transmission V-belt according to any one of claims 1 to 8, which is a raw edge V-belt having cogs at least on the inner peripheral surface side.

10. The transmission V-belt according to any one of claims 1 to 9, which is a variable speed belt used in a small-sized belt-type continuously variable transmission.

11. A belt transmission mechanism comprising the transmission V-belt according to any one of claims 1 to 10 and a pulley.

12. The belt transmission mechanism according to claim 11, wherein the transmission V-belt is a raw edge V-belt having cogs at least on the inner peripheral side, and is a variable speed belt used in a small belt type continuously variable transmission.

Images