Raw edge cogged V-belt, its usage method, and belt transmission mechanism

Abstract

To provide a raw-edge cogged V-belt capable of being applied to a braking system of a belt clutch-in type continuously variable transmission, and having excellent durability such as abrasion resistance.SOLUTION: In a raw-edge cogged V-belt (1) having on at least an inner peripheral side, a cog part in which cog crests 1a and cog valleys 1b are arranged alternately in a longitudinal direction of the belt, the cog part on the inner peripheral side is formed of a compressed rubber layer 4, and a fabric layer 5 covering an inner peripheral surface of the compressed rubber layer (4). The peaks of the cog crests 1a on the inner peripheral side are formed flat, and a length of each peak in the longitudinal direction of the belt is adjusted to 18 to 65% of a cog pitch. The cog pitch may be 6 to 17 mm. The fabric layer may contain aramid fiber. The raw-edge cogged V-belt (1) may be a transmission belt used in a belt clutch-in type continuously variable transmission.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a low-edge cogged V-belt used for a belt-type continuously variable transmission, a method of using the same, and a belt transmission mechanism.

Background Art

[0002] V-belts that transmit power by friction transmission include a raw-edge type V-belt (raw-edge V-belt) in which a rubber layer with a friction transmission surface (V-shaped side surface) is exposed, and a wrapped type V-belt (wrapped V-belt) in which the friction transmission surface is covered with a cover cloth. They are used according to the application depending on the difference in the surface properties (friction coefficient between the rubber layer and the cover cloth) of the friction transmission surface. Among raw-edge V-belts, in addition to raw-edge V-belts without cogs, there are raw-edge cogged V-belts with cogs provided only on the inner peripheral surface of the belt to improve flexibility, and raw-edge cogged V-belts (raw-edge double-cogged V-belts) with cogs provided on both the inner and outer peripheral surfaces of the belt to improve flexibility.

[0003] Raw-edge V-belts are mainly used for driving general industrial machines, agricultural machines, and auxiliary machine drives in automobile engines. Among them, raw-edge cogged V-belts are applied as a transmission belt (CVT belt) used for a belt-type continuously variable transmission (CVT) such as a motorcycle (scooter), a snowmobile, and an all-terrain vehicle (ATV).

[0004] Figure 1 is a schematic diagram illustrating the transmission mechanism of a CVT. As shown in Figure 1, the belt-type CVT 20 has a mechanism that continuously changes the gear ratio by wrapping a V-belt 23 around a drive pulley 21 and a driven pulley 22. Each pulley 21, 22 is equipped with a fixed sheave 21a, 22a whose axial movement is restricted or fixed, and a movable sheave 21b, 22b that can move in the axial direction. The inner circumferential walls of the fixed sheaves 21a, 22a and the inner circumferential walls of the movable sheaves 21b, 22b form a V-groove-shaped inclined opposing surface. Each pulley 21, 22 has a structure that allows the width of the V-groove formed by these fixed sheaves 21a, 22a and movable sheaves 21b, 22b to be continuously changed. The widthwise end faces of the V-belt 23 are formed with tapered surfaces whose inclination matches that of the V-groove-shaped inclined opposing surfaces of each pulley 21 and 22, and they fit into any vertical position on the opposing surfaces of the V-grooves according to the changed width of the V-grooves. For example, by narrowing the width of the V-groove of the drive pulley 21 and widening the width of the V-groove of the driven pulley 22, the state shown in Figure 1(a) is changed to the state shown in Figure 1(b), causing the V-belt 23 to move upward on the drive pulley 21 side and downward on the driven pulley 22 side, so that the winding diameter on each pulley 21 and 22 changes continuously, and the gear ratio can be changed steplessly.

[0005] For example, a CVT in a motorcycle comprises a drive pulley fixed around the engine's crankshaft, a driven pulley connected to the rear wheel's drive shaft via gears or the like, and a V-belt wrapped around the drive pulley and the driven pulley.

[0006] At low speeds, the movable sheave of the drive pulley moves away from the fixed sheave, reducing the drive pulley's winding diameter, while the movable sheave of the driven pulley moves closer to the fixed sheave, increasing the driven pulley's winding diameter. As a result, the rear wheels are driven with high torque at low speeds. On the other hand, at high speeds, the movable sheave of the drive pulley moves closer to the fixed sheave, increasing the drive pulley's winding diameter, while the movable sheave of the driven pulley moves away from the fixed sheave, reducing the driven pulley's winding diameter. As a result, the rear wheels are driven with low torque at high speeds.

[0007] On the other hand, there are differences in the clutch mechanism (a mechanism that temporarily interrupts power transmission) during idling between motorcycles and snowmobiles or ATVs.

[0008] In other words, in a motorcycle's CVT, an automatic centrifugal clutch is provided between the rear wheel and the driven pulley. This clutch interrupts torque transmission from the driven pulley to the rear wheel during idling. Therefore, even if the driven pulley rotates during idling, the rear wheel does not rotate.

[0009] On the other hand, in the case of CVTs in snowmobiles and ATVs, instead of having an automatic centrifugal clutch, torque transmission from the drive pulley to the V-belt is interrupted during idling by moving the movable sheave until the side of the V-belt is completely separated from the movable or fixed sheave. In other words, in the aforementioned CVT, during idling, the V-belt is dropped into the bottom of the pulley groove (shaft portion), causing the lower surface (inner circumferential surface) of the V-belt to contact the shaft portion, acting as a belt clutch that temporarily interrupts power transmission (the shaft portion of the drive pulley acts as an idler pulley). Such a transmission is called a belt clutch-in type CVT.

[0010] Figure 2 shows a schematic diagram of the idling state of a belt-clutch-in type CVT. As shown in Figure 2, in this belt-clutch-in type CVT 30, the V-belt 33 does not contact either the movable sheave 31b or the fixed sheave 31a on the drive pulley 31, but contacts the pulley shaft portion 31c of the drive pulley 31. In other words, in the automatic centrifugal clutch type CVT of motorcycles, the V-belt is in contact with the pulley sheave even at idle, as shown in Figure 1, whereas in the belt-clutch-in type CVT of snowmobiles and ATVs, the inner circumferential surface of the V-belt is in contact with the outer circumferential surface of the pulley shaft portion of the drive pulley (a general pulley shaft portion with a smooth outer surface).

[0011] The following belts are known as transmission belts specifically designed for belt-clutch type CVTs, that is, for applications where the bottom surface (inner circumference) of the belt contacts the pulley shaft, such as when the engine is idling.

[0012] Japanese Patent Publication No. 2004-188776 (Patent Document 1) discloses a method for manufacturing a V-belt used in transmissions of motorcycles, buggies, snowmobiles, etc., which prevents the bottom surface from becoming rubber by attaching canvas to the bottom surface via a rubber layer, thereby preventing the bottom surface rubber from adhering to the shaft.

[0013] Japanese Patent Publication No. 2006-2836 (Patent Document 2) discloses a low-edge belt in which the bottom surface of the belt that slides while in contact with the sheave shaft is made of canvas surface without adhesive rubber coating, resulting in a coefficient of friction of 0.1 or less on the bottom surface, and there is no rubber shedding (falling of rubber powder), so there is no risk of fallen rubber entering the gap around the sheave shaft and causing problems.

[0014] Japanese Patent Publication No. 2006-226420 (Patent Document 3) discloses a power transmission belt in which canvas is exposed on the surface of a compressed rubber layer that contacts the pulley recess, and rubber is not allowed to adhere to the canvas at the contact point with the pulley recess. This eliminates the rubber adhering to the belt surface that contacts the pulley recess, thereby lowering the coefficient of friction and preventing noise.

[0015] Japanese Patent Publication No. 2007-144714 (Patent Document 4) discloses a V-belt in which the bottom surface of the belt is covered with canvas that has been coated only on the belt body side, thereby preventing rubber from seeping out onto the canvas surface and suppressing the generation of abnormal noise and driving force.

[0016] Japanese Patent Publication No. 2009-51204 (Patent Document 5) discloses a cogged V-belt that can be manufactured without rubber adhering to the canvas by using a tubular canvas with elastic threads as the threads in the circumferential direction of the belt in the process of wrapping the canvas around the mold and temporarily fixing it, and which can suppress the scattering of rubber debris even when the belt is dropped into a belt clutch-in type CVT.

[0017] Japanese Patent Publication No. 2009-156289 (Patent Document 6) discloses a V-belt that reduces the coefficient of friction with the crankshaft and reduces the torque transmitted from the crankshaft to the V-belt during idling by applying Teflon (registered trademark) to the lower canvas and preventing the rubber used to adhere the lower canvas to the bottom rubber from penetrating the surface.

[0018] On the other hand, because the belt clutch-in system has lower engine braking performance compared to the automatic centrifugal clutch system, a mechanism is being considered that utilizes the contact between the idler pulley and the inner surface of the transmission belt during idling to act as an engine braking system (EBS) that brakes the driven pulley (rear wheel) with the resulting friction.

[0019] WO2011 / 046740 (Patent Document 7) and WO2019 / 209739 (Patent Document 8) disclose a continuously variable transmission engine brake system that adds a braking function by engaging with an idler pulley (shaft portion) which has irregularities corresponding to the irregularities (cogs) provided on the inner circumferential surface of a V-belt.

[0020] Japanese Patent Publication No. 2023-169113 (Patent Document 9) discloses a brake system for a belt clutch-in type continuously variable transmission in which a low-edge cogged V-belt is used as the variable belt, the low-edge cogged V-belt being composed of a compression rubber layer consisting of a compression rubber layer body and an inner surface layer that covers the inner circumferential surface of the compression rubber layer body and has a surface with a higher coefficient of friction than the surface of the compression rubber layer body. [Prior art documents] [Patent Documents]

[0021] [Patent Document 1] Japanese Patent Publication No. 2004-188776 [Patent Document 2] Japanese Patent Publication No. 2006-2836 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-226420 [Patent Document 4] Japanese Patent Application Laid-Open No. 2007-144714 [Patent Document 5] Japanese Patent Application Laid-Open No. 2009-51204 [Patent Document 6] Japanese Patent Application Laid-Open No. 2009-156289 [Patent Document 7] WO2011 / 046740 [Patent Document 8] WO2019 / 209739 [Patent Document 9] Japanese Patent Application Laid-Open No. 2023-169113 [Summary of the Invention] [Problems to be Solved by the Invention]

[0022] In the V-belts of Patent Documents 1 to 6, in order to prevent problems (such as abnormal noise, generation of driving force, and scattering of rubber) caused by the rubbing of the belt bottom surface against the pulley shaft, the belt bottom surface is made slippery (the friction coefficient is lowered). Regarding the engine brake performance (braking function) in the belt clutch-in method, there is no description. Furthermore, in the V-belts of Patent Documents 1 to 6, a frictional force sufficient to obtain a sufficient braking function cannot be obtained, and the braking function cannot be exhibited. Therefore, the manifestation of the braking function by shortening the braking distance and time, and the maintenance of the braking function have become problems, and the development of a V-belt with an advanced braking function (high frictional force) is required.

[0023] On the other hand, in the continuously variable transmission engine brake systems of Patent Documents 7 and 8, special-shaped pulleys are required.

[0024] Furthermore, among low-edge V-belts, CVT applications require the highest level of lateral pressure resistance, and to meet this requirement, the compression rubber layer needs to be more rigid than in other applications. Therefore, in CVT applications, flexibility is inevitably insufficient, making cogs essential. In other words, high-rigidity rubber and the cog section are essential components for CVT applications. On the other hand, in order to exert a braking effect (frictional force) by bringing the inner surface of the belt into contact with the pulley shaft, a belt with a flat inner surface (without cogs) that has a larger contact area is advantageous. However, since it is a CVT application and cogs are essential, the only part of the belt's inner surface (bottom surface) that contacts the pulley shaft (the shaft part of a typical pulley that has a smooth outer surface without grooves for fitting with the belt) is the top of the cog, making it difficult to improve frictional force (braking function). In other words, in low-edge V-belts used in CVT applications, there is a trade-off relationship between improved lateral pressure resistance and improved braking function, which is difficult to achieve simultaneously.

[0025] In contrast, Patent Document 9 describes a method for enhancing the braking function of the inner surface of a V-belt by arranging an inner surface layer (rubber layer) with a high coefficient of friction on the inner surface of the main body of the compressed rubber layer in a low-edge cogged V-belt. However, even in the low-edge V-belt of Patent Document 9, the inner surface layer (rubber layer) is prone to disappearing due to wear during operation, and the braking function is also lost at the same time, so there was a problem with durability (wear resistance).

[0026] Therefore, the object of the present invention is to provide a low-edge cogged V-belt that can be applied to the braking system of a belt-clutch type continuously variable transmission and also has excellent durability such as wear resistance, as well as a method of using the same and a belt transmission mechanism. [Means for solving the problem]

[0027] As a result of diligent research to achieve the above objectives, the inventors have found that in a low-edge cogged V-belt having a cog portion on at least the inner circumference side in which cog peaks and cog valleys are alternately arranged in the longitudinal direction of the belt (belt length direction or circumferential direction), the cog portion is formed from a compressed rubber layer and a fabric layer covering the inner surface of the compressed rubber layer, the tops of the cog peaks are formed flat, and the length of each top in the longitudinal direction of the belt is adjusted to 20-60% of the cog pitch, thereby making it applicable to the brake system of a belt clutch-in type continuously variable transmission, and improving durability such as wear resistance, and thus completing the present invention.

[0028] In other words, the present invention includes the following embodiments.

[0029] Embodiment [1]: A low-edge cogged V-belt having cog portions on at least the inner circumference side in which cog peaks and cog valleys are arranged alternately in the longitudinal direction of the belt, The cog portion on the inner circumference is formed of a compressed rubber layer and a fabric layer covering the inner surface of the compressed rubber layer. The top of the cog peak on the inner circumference is flat, and A low-edge cogged V-belt in which the length of each vertex in the longitudinal direction of the belt is 18-65% of the cog pitch.

[0030] Embodiment [2]: The low-edge cogged V-belt of Embodiment [1], wherein the cog pitch is 6 to 17 mm.

[0031] Embodiment [3]: A raw-edge cogged V-belt according to Embodiment [1] or [2], wherein the fabric layer comprises aramid fibers.

[0032] Embodiment [4]: ​​A low-edge cogged V-belt according to any of Embodiments [1] to [3], wherein the cross-sectional shape of the cog valley on the inner circumference in the longitudinal direction of the belt comprises a bottom portion consisting of a circular arc with a radius of curvature of 2 to 4 mm and a side wall portion extending from the bottom portion inclined with respect to the belt thickness direction or along the belt thickness direction.

[0033] Embodiment [5]: The cross-sectional shape of the cog valley on the inner circumference in the longitudinal direction of the belt is such that it comprises a bottom portion formed by combining a plurality of continuous arcs and a side wall portion extending from the bottom portion inclined with respect to the belt thickness direction or along the belt thickness direction, As the plurality of arcs move away from the deepest part of the cog valley, the radius of curvature decreases. A low-edge cogged V-belt according to any of the embodiments [1] to [4], wherein the radius of curvature of the first arc passing through the deepest part of the plurality of arcs is larger in diameter than the virtual circle tangent to the deepest part and the side walls on both sides, and is 2 to 4 mm.

[0034] Embodiment [6]: A belt transmission mechanism comprising a low-edge cogged V-belt according to any of Embodiments [1] to [5] and a pulley, wherein the low-edge cogged V-belt is a variable speed belt used in a belt clutch-in type continuously variable transmission.

[0035] Embodiment [7]: The belt transmission mechanism of Embodiment [6], wherein the belt clutch-in type continuously variable transmission is a continuously variable transmission in which the inner surface of the belt contacts the pulley shaft portion during idling.

[0036] Embodiment [8]: The belt transmission mechanism of Embodiment [6] or [7], wherein the belt clutch-in type continuously variable transmission is a continuously variable transmission equipped with a braking system that utilizes the frictional force between the inner surface of the belt and the pulley shaft portion.

[0037] Embodiment [9]: A method of using any of the raw edge cogged V-belts described in Embodiments [1] to [5] in a belt clutch-in type continuously variable transmission, which is involved in any of the continuously variable transmission, clutch, or brake.

[0038] In this application, the numerical range represented by "A~B" means "A or greater and B or less," and is used to include the values ​​A and B at both ends of that range. [Effects of the Invention]

[0039] In the present invention, a low-edge cogged V-belt having a cog portion on at least the inner circumference side in which cog peaks and cog valleys are alternately arranged in the longitudinal direction of the belt, wherein the cog portion is formed of a compressed rubber layer and a fabric layer covering the inner surface of the compressed rubber layer, the tops of the cog peaks are formed flat, and furthermore, the length of each top in the longitudinal direction of the belt is adjusted to 18-65% (for example, 20-60%) of the cog pitch, so that it can be applied to the brake system of a belt clutch-in type continuously variable transmission, and durability such as wear resistance can also be improved. [Brief explanation of the drawing]

[0040] [Figure 1] Figure 1 is a schematic diagram illustrating the transmission mechanism of a belt-type continuously variable transmission. [Figure 2] Figure 2 is a schematic diagram showing the idling state of a belt-clutch type continuously variable transmission. [Figure 3] Figure 3 is a schematic partial cross-sectional perspective view showing an example of the low-edge double-cogged V-belt of the present invention. [Figure 4] Figure 4 is a schematic cross-sectional view of the low-edge double-cogged V-belt shown in Figure 3, cut along the longitudinal direction of the belt. [Figure 5] Figure 5 is an enlarged view of Figure 4 to illustrate the shape of the inner cog valley. [Figure 6] Figure 6 shows the layout of the test machine used in the endurance running test (Top endurance test) of the low-edge double-cogged V-belt obtained in the example. [Figure 7] Figure 7 shows the layout of the test machine used in the durability running test (Low durability test) of the low-edge double-cogged V-belt obtained in the example. [Figure 8] Figure 8 is a schematic diagram comparing the cross-sectional shapes of the low-edge double-cogged V-belts obtained in Examples 1-8 and Comparative Examples 1-5. [Figure 9] Figure 9 is an FEM analysis diagram showing the state of cog interference that occurs when the low-edge double-cogged V-belt obtained in Comparative Example 4 is bent. [Figure 10]Figure 10 is a schematic diagram comparing the cross-sectional shapes of the low-edge double-cogged V-belts obtained in Examples 9-21 and Comparative Examples 6-7. [Modes for carrying out the invention]

[0041] [Structure of a low-edge cogged V-belt] In the raw edge cogged V-belt of the present invention, the cog portion formed on the inner circumference is made of a compression rubber layer and a fabric layer covering the inner surface of the compression rubber layer. In the present invention, since the inner surface of the compression rubber layer is covered with a fabric layer, wear resistance can be improved. Furthermore, among raw edge V-belts, CVT applications require the highest level of lateral pressure resistance, and to meet this requirement, the compression rubber layer needs to be more rigid than in other applications. Therefore, in CVT applications, flexibility can be improved by forming the cog portion in the compression rubber layer made of high-rigidity rubber formed on the inner circumference.

[0042] As described above, the raw edge cogged V-belt of the present invention is used in CVT applications, and since the cog portion is essential on the inner circumference side, the only part of the inner surface (bottom surface) of the belt that comes into contact with the pulley shaft portion is the top of the cog teeth. Therefore, in the raw edge cogged V-belt of the present invention, the top of the cog teeth is formed into a flat shape (a flat shape along a plane perpendicular to the belt thickness direction). Furthermore, in the present invention, the length of the top of the cog teeth in the longitudinal direction of the belt is adjusted to 18% or more of the cog pitch, so that the area of ​​the inner surface of the V-belt that can come into contact with the outer surface of the pulley shaft portion can be increased, and braking performance due to friction can be ensured. Furthermore, in the present invention, the length of the top of the cog teeth in the longitudinal direction of the belt is adjusted to 65% or less of the cog pitch, so that braking performance can be ensured without impairing belt flexibility or durability.

[0043] The raw edge cogged V-belt of the present invention is not particularly limited as long as it has the shape described above. It may be a raw edge cogged V-belt in which cogs are formed only on the inner circumference, or a raw edge double cogged V-belt in which cogs are formed on both the inner and outer circumferences. Of these, the raw edge double cogged V-belt is particularly preferred because it is used in more severe conditions, requires a high level of both lateral pressure resistance and bending fatigue resistance, and offers greater benefits from the present invention.

[0044] Figure 3 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 4 is a schematic cross-sectional view of the raw edge double cogged V-belt of Figure 3 cut in the longitudinal direction of the belt.

[0045] In this example, the low-edge double-cogged V-belt 1 has an inner cog section formed on the inner surface of the compressed rubber layer 4, in which inner cog peaks 1a and inner cog valleys 1b are alternately arranged along the longitudinal direction of the belt (direction A in the figure). The cross-sectional shape of the inner cog peaks 1a in the longitudinal direction of the belt is approximately an inverted trapezoid, and the cross-sectional shape in the direction perpendicular to the longitudinal direction of the belt (width direction or direction B in the figure) is also approximately an inverted trapezoid.

[0046] On the other hand, the outer surface also has an outer cog section in which outer cog peaks 1c and outer cog valleys 1d are formed alternately along the longitudinal direction of the belt. The cross-sectional shape of the outer cog peaks 1c in the longitudinal direction of the belt is approximately trapezoidal, and the cross-sectional shape in the direction perpendicular to the longitudinal direction of the belt (width direction or direction B in the figure) is approximately rectangular. That is, each outer cog peak 1c protrudes in a approximately trapezoidal shape in the cross-section in direction A from the outer cog valley 1d in the belt thickness direction.

[0047] The low-edge double-cogged V-belt has a laminated structure, with a stretchable rubber layer 2, a core layer (adhesive rubber layer) 3, a compression rubber layer 4, and a fabric layer 5 sequentially laminated from the outer circumference to the inner circumference of the belt. The cross-sectional shape in the belt width direction is a roughly inverted trapezoid shape, where the belt width decreases from the outer circumference to the inner circumference. Furthermore, a core 3a is embedded in the core layer 3, the inner circumference cog portion is formed in the compression rubber layer 4 covered with the fabric layer 5 by a cog-equipped molding die, and the outer circumference cog portion is formed in the stretchable rubber layer 2 by a cog-equipped molding die.

[0048] In particular, each inner circumference cog peak 1a protrudes in a substantially inverted trapezoidal shape in the cross-section in direction A from the inner circumference cog valley 1b in the belt thickness direction. That is, in the present invention, the top portion 11 of the inner circumference cog peak 1a is formed in a flat shape along the belt longitudinal direction, and the length L of the top portion 11 in the belt longitudinal direction (circumferential direction) is adjusted to 20-60% of the inner circumference cog pitch P (the shortest distance between the deepest parts of adjacent cog valleys).

[0049] In this invention, frictional force is ensured by securing a friction area with the pulley shaft portion by forming the top portion 11 flat (a flat shape having a surface substantially perpendicular to the belt thickness direction). As shown in Figure 4, the ratio (percentage) of the length L of the top portion (flat top portion) 11 to the inner circumference cog pitch P serves as an indicator of the area of ​​the flat shape (flat portion) of the top portion 11 necessary to ensure frictional force.

[0050] In other words, when there are no cogs on the inner circumference of the belt, the concept of "cog pitch" becomes equal to "circumferential length of the flat area," and the area of ​​the flat area is maximized. However, in this invention, since cogs are essential, it is not possible to maximize the area of ​​the flat area, and the flat surface is lost by providing cogs (valleys), thus reducing the area of ​​the flat area. When the above-mentioned maximum area is set to 100, the ratio of the area of ​​the remaining flat portion is an indicator of the area of ​​the flat area, and has the same meaning as "the ratio (percentage) of the circumferential length of the flat top of the cog peaks to the cog pitch."

[0051] In other words, multiplying this ratio by the number of cogs in the belt gives the "sum of the circumferential lengths of all flat tops relative to the total circumferential length of the inner surface if there were no cogs," and further multiplying this ratio by the belt width gives the "total area of ​​the flat tops relative to the total area of ​​the inner surface if there were no cogs." Therefore, in this application, the ratio of the length L of the tops (flat tops) to the inner cog pitch P is also called the inner flatness ratio.

[0052] On the other hand, from the perspective of ensuring braking performance (frictional force on the inner circumference), it is preferable to maximize the area of ​​the inner circumference of the V-belt that can contact the outer circumference of the pulley shaft (i.e., the inner circumference flatness ratio). In order to increase the area in contact with the pulley shaft, it is necessary to increase the number of cogs by narrowing the inner circumference cog pitch or to increase the inner circumference flatness ratio by reducing the cog angle. However, these methods result in reducing the width of the cogs (recesses). On the other hand, if the width of the cogs (recesses) is made too small, the cogs will interfere with each other when bending, impairing flexibility, and the stress generated in the cog valleys will increase, making them more prone to cracking. As a result, the durability life will be shortened due to the premature occurrence of cog valley cracks.

[0053] In other words, in the braking system of a belt-clutch type continuously variable transmission, the performance of the braking function and durability (resistance to cog valley cracks) are inversely related, so it is necessary to set the surface area of ​​the inner circumference of the belt to a range that is suitable for achieving both.

[0054] From this viewpoint, in the present invention, the length L in the longitudinal direction of each apex of the belt is adjusted to 18-65% (particularly 20-60%) of the inner circumference cog pitch P, preferably 25-63%, more preferably 30-62%, more preferably 35-61%, and most preferably 38-60%. Alternatively, the length L may be preferably 25-55%, more preferably 30-50%, more preferably 35-45%, and most preferably 35-40% of the inner circumference cog pitch P. If the ratio of the length L to the inner circumference cog pitch P (inner circumference flatness ratio) is less than the lower limit of 18%, the contact area will be insufficient and a sufficient braking function will not be achieved. If it exceeds the upper limit of 65%, the width of the inner circumference cog (recess) will be too small and the durability (resistance to cog valley cracks) will decrease.

[0055] The inner circumference cog pitch P is, for example, 6 to 17 mm, preferably 7 to 15 mm, more preferably 8 to 14 mm, more preferably 9 to 13 mm, and most preferably 10 to 12.5 mm. If the inner circumference cog pitch P is too small, the cogs (recesses) may not be sufficiently secured, which may impair flexibility. If it is too large, the inner circumference flatness ratio may decrease, which may prevent sufficient braking performance (frictional force on the inner surface).

[0056] Figure 5 is an enlarged view of Figure 4 to illustrate the shape of the inner circumference cog valley. As shown in Figures 4 and 5, in this example, the cross-sectional shape of the cog valley 1b is a bottom 13 formed by combining three arcs: a first arc 13a and a pair of second arcs 13b, 13b, and side wall portions 12, 12 extending from the bottom 13, inclined at a cog angle θ (angle of inclination of one side wall) in the direction in which the diameter of the cog valley 1b expands toward the inner circumference with respect to the belt thickness direction (indicated by the dashed line in Figures 4 and 5). As shown in Figures 4 and 5, when the raw edge cogged V belt 1 is not bent, the radius of curvature of the multiple arcs (first arc 13a and second arc 13b) constituting the bottom 13 decreases as it moves away from the deepest part A of the cog valley 1b.

[0057] Specifically, the first arc 13a is represented by a circle C1 having its center O1 on a vertical line VL (belt thickness direction) perpendicular to the longitudinal direction of the belt. However, it is formed with a larger diameter than a virtual circle VC (a dotted circle with a radius of curvature R0 in Figure 5) which has its center O0, passes through the deepest part A of the cog valley 1b, and tangent to the deepest part A of the cog valley 1b and the side walls 12 on both sides at three points (a total of three points: the deepest part A and the contact points B on the pair of side walls). In this application, a virtual circle is defined as a circle corresponding to a virtual arc when the bottom is composed of a single arc.

[0058] Furthermore, the second arc 13b is interposed between the first arc 13a and the side wall portion 12. The radius of curvature R2 of the second arc 13b is smaller than the radius of curvature R1 of the first arc 13a.

[0059] In the present invention, the shape of the bottom of the inner circumference cog valley is not limited to a shape formed by combining a first arc and a pair of second arcs, but may be a shape formed by a single arc. However, a shape formed by combining multiple consecutive arcs is preferred in terms of improving durability (resistance to cog valley cracking), and a shape formed by combining a first arc and a pair of second arcs is particularly preferred.

[0060] When the bottom of the cog valley is formed by combining multiple continuous arcs, it is preferable to make the radius of curvature of the first arc located at the deepest part of the cog valley larger than that of the virtual arc, and to decrease the radius of curvature as it moves away from the deepest part. By using such multiple-stage arcs, the stress at the bottom of the cog valley, where stress tends to concentrate due to bending deformation, can be relaxed and dispersed, thereby suppressing the occurrence of cracks in the cog valley. Furthermore, compared to the case where the bottom is formed by a single arc (corresponding to a virtual arc), the length in the belt circumferential direction of the cog section (length of the flat top section) can be increased, and a wider contact area with the pulley shaft can be secured.

[0061] The radius of curvature R1 of the first arc is, for example, 1 to 5 mm, preferably 1.5 to 4.8 mm (e.g., 1.5 to 4.5 mm), more preferably 2 to 4.7 mm (e.g., 2 to 4 mm), more preferably 2.5 to 4.6 mm (e.g., 2.5 to 4 mm), and most preferably 3 to 4.5 mm (e.g., 3 to 4 mm). If the radius of curvature R1 is too small, durability (resistance to cog valley cracking) may decrease, and if it is too large, the inner circumference flatness may decrease, and sufficient braking performance (frictional force of the inner circumference) may not be ensured. The range of the radius of curvature R1 of the first arc may also be the range of the radius of curvature of the arc in which the bottom of the cog valley is formed by a single arc.

[0062] The radius of curvature R2 of the second arc is, for example, 0.1 to 3 mm, preferably 0.15 to 2 mm, more preferably 0.2 to 1.5 mm, more preferably 0.25 to 1.3 mm, and most preferably 0.5 to 1.2 mm. If the radius of curvature R2 is too small, the bending resistance may decrease and durability may be reduced, and if it is too large, the inner circumference flatness may decrease and sufficient braking performance (frictional force of the inner circumference) may not be ensured.

[0063] In the cross-sectional shape of the cog valley, the side wall portion is not limited to a shape that extends from the bottom at a cog angle θ in a direction that increases the diameter of the cog valley toward the inner circumference with respect to the belt thickness direction, but may also be a shape that extends from the bottom along (parallel to) the belt thickness direction.

[0064] The cog angle θ of the side wall may be 30° or less (particularly 25° or less), for example 20° or less, preferably 15° or less (e.g., 1 to 15°), more preferably 12° or less (e.g., 3 to 12°), and more preferably 10° or less (particularly 4 to 10°). The cog angle θ is, for example, 8° or less, preferably 5° or less. If the cog angle θ is too small, cog interference is likely to occur, and if it is too large, the inner circumference flatness ratio will decrease, and there is a risk that sufficient braking performance (frictional force of the inner circumference) cannot be ensured.

[0065] In the low-edge cogged V-belt of the present invention, it is preferable to apply a C-chamfer of C0.5mm to C2.0mm or an R-chamfer of R0.5mm to R2.0mm to the intersection of the flat top portion 11 and the side wall portion 12, in order to prevent chipping of the edge portion. In the present invention, the inner circumferential flatness ratio may be adjusted by C-chamfering and R-chamfering the intersection. For example, in the case of R-chamfering, the inner circumferential flatness ratio may be adjusted by adjusting the radius of curvature R3 of the R-chamfer within the range (0.5 to 2.0mm). That is, the inner circumferential flatness ratio may be decreased by adjusting the radius of curvature R3 to a large value, or increased by adjusting it to a small value. Furthermore, in the present invention, the inner circumferential flatness ratio may be adjusted by combining such adjustments with C-chamfering or R-chamfering with adjustments to the radius of curvature R1, the radius of curvature R2, or the cog angle θ.

[0066] Figure 4 shows the definitions of the overall thickness, cog height, and valley thickness of the raw edge cogged V-belt (raw edge double cogged V-belt) of the present invention.

[0067] The overall thickness H (average thickness) of the raw-edge cogged V-belt of the present invention is, for example, 8 to 19 mm, preferably 10 to 19 mm, more preferably 13 to 18 mm, and more preferably 14 to 17 mm. If the thickness is too small, the lateral pressure resistance may decrease, and if the thickness is too large, the flexibility may decrease, reducing the transmission efficiency and the bending fatigue resistance may decrease.

[0068] As shown in Figure 4, in this application, when the compression rubber layer 4 and the stretch rubber layer 2 have cogs, the overall belt thickness H refers to the thickness at the top of the cogs (the maximum thickness of the belt). In other words, the thickness H of the raw edge cogged V belt 1 refers to the shortest distance (distance perpendicular to the thickness direction) from the top of the cogs of the fabric layer 5 (the top on the inner circumference side) to the top of the cogs of the stretch rubber layer 2 (the top on the outer circumference side).

[0069] Furthermore, in this application, the inner cog valley of the inner cog portion refers to the portion that forms the thin-walled portion of the fabric layer and the compression rubber layer having the inner cog portion, and usually refers to a curved valley or groove (curved groove) located between adjacent inner cog peaks that protrude on the inner circumference side of the belt.

[0070] The height H1 of the inner circumferential cog portion formed on the inner circumferential surface (the shortest distance from the deepest part of the inner circumferential cog valley to the top of the inner circumferential cog portion in the belt thickness direction) may be selected from a range of, for example, 4 to 8 mm, preferably 5 to 7 mm, and the height H4 of the outer circumferential cog portion formed on the outer circumferential surface (the shortest distance from the deepest part of the outer circumferential cog valley to the top of the outer circumferential cog portion in the belt thickness direction) may be selected from a range of, for example, 2 to 5 mm, preferably 3 to 4 mm.

[0071] The inner circumference core valley thickness H2 on the inner circumference surface (the shortest distance from the central axis of the core wire to the deepest part of the inner circumference cog valley in the belt thickness direction) may be selected from a range of, for example, 2 to 7 mm, preferably 3 to 5 mm, and the outer circumference core valley thickness H3 on the outer circumference surface (the shortest distance from the central axis of the core wire to the deepest part of the outer circumference cog valley in the belt thickness direction) may be selected from a range of, for example, 0.5 to 4 mm, preferably 1 to 3 mm.

[0072] In the raw-edge cogged V-belt of the present invention, the belt width and V-angle are not particularly limited and can be appropriately selected according to the design circumstances of the belt transmission mechanism. Typically, the upper width (belt width on the outer circumference) can be selected from a range of, for example, 20 to 50 mm, preferably 30 to 44 mm. The V-angle, which is the angle of the V-shaped side surface, can be selected from a range of, for example, 20 to 35°, preferably 24 to 32°.

[0073] [Compressed rubber layer] In the low-edge cogged V-belt of the present invention, the compression rubber layer body is formed of a rubber composition (crosslinked rubber composition) containing a first rubber component.

[0074] (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 can be used individually or in combination of two or more.

[0075] 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.

[0076] 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.

[0077] (A2) First short fiber The rubber composition forming the compression 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, polyamide 46 short fibers, etc., aramid short fibers, etc.), polyalkylene arylate short fibers (e.g., polyethylene terephthalate (PET) short fibers, polyethylene naphthalate short fibers, etc.), liquid crystal polyester short fibers, polyarylate short fibers (amorphous all-aromatic polyester short fibers, etc.), vinylon short fibers, polyvinyl alcohol-based short fibers, poly-p-phenylene benzobisoxazole (PBO) short fibers, and other synthetic short fibers; natural short fibers such as cotton, linen, and wool; and inorganic short fibers such as carbon short fibers. These first short fibers can be used alone or in combination of two or more. Of these, aramid short fibers and PBO short fibers are preferred, and aramid short fibers are particularly preferred.

[0078] The first short fibers may be short fibers obtained by cutting fibers that have been stretched into a fibrous shape to a predetermined length. The first short fibers are preferably embedded in the compression rubber layer body oriented in the belt width direction in order to suppress the compression deformation of the belt due to lateral pressure from the pulley (to improve lateral pressure resistance). Furthermore, it is preferable to have the short fibers protrude from the surface of the compression rubber layer in order to reduce the coefficient of friction of the surface in contact with the pulley, thereby suppressing noise (sound generation) and reducing wear due to friction with the pulley.

[0079] The average fiber length of the first short fibers is, for example, 0.1 to 20 mm, preferably 0.5 to 15 mm (for example, 0.5 to 10 mm), and more preferably 1 to 6 mm (particularly 2 to 4 mm), in order to improve lateral pressure resistance and abrasion resistance without reducing flexibility. If the fiber length of the first short fibers is too short, the mechanical properties in the direction of grain cannot be sufficiently improved, which may reduce lateral pressure resistance and abrasion resistance. Conversely, if it is too long, the orientation of the short fibers in the rubber composition may decrease, which may reduce flexibility.

[0080] The single filament fineness of the first short fiber is, for example, 1 to 12 dtex, preferably 1.2 to 10 dtex (e.g., 1.5 to 8 dtex), and more preferably 2 to 5 dtex (particularly 2 to 3 dtex), in order to provide a high reinforcing effect without reducing flexibility. If the single filament fineness is too high, the lateral pressure resistance and abrasion resistance per unit amount may decrease, and if the single filament fineness is too low, the flexibility may decrease due to reduced dispersibility in the rubber.

[0081] The first short fibers may be subjected to a general adhesive treatment to enhance their adhesion to the first rubber component. Examples of such adhesive treatments include immersion in a treatment solution containing an epoxy compound or a polyisocyanate compound, immersion in an RFL treatment solution containing resorcinol, formaldehyde, and latex, and immersion in rubber adhesive. These treatments may be applied individually or in combination of two or more.

[0082] The proportion of the first short fibers is, for example, 5 to 50 parts by mass, preferably 5 to 40 parts by mass (for example, 8 to 35 parts by mass), more preferably 10 to 30 parts by mass, and more preferably 15 to 25 parts by mass, per 100 parts by mass of the first rubber component. If there are too few first short fibers, the lateral pressure resistance and abrasion resistance may decrease, and if there are too many, the processability may decrease and the flexibility of the belt may decrease, which may reduce durability.

[0083] (A3) Other ingredients The rubber composition forming the compression rubber layer may contain conventional additives, 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 oxides (zinc oxide, magnesium oxide, calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, aluminum oxide, etc.), fillers [reinforcing agents such as carbon black and silicon oxide (hydrated silica, etc.) (reinforcing fillers); bulking agents such as clay, calcium carbonate, talc, mica (non-reinforcing fillers or inert fillers), etc.], plasticizers (or softeners). Examples of additives include plasticizers (oils (such as paraffin oil and naphthenic oil), 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 stearic acid 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.

[0084] The proportion of fillers such as carbon black and silica (first filler) 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.

[0085] The proportion of the plasticizer (first plasticizer) may be 10 parts by mass or less per 100 parts by mass of the first rubber component, for example, 0.1 to 10 parts by mass, preferably 1 to 8 parts by mass, and more preferably 3 to 7 parts by mass. If the proportion of plasticizer is too high, the compression rubber layer may soften too much, which may reduce its resistance to lateral pressure.

[0086] The total proportion of the other components (A3) 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.

[0087] (A4) Characteristics of the compressed rubber layer The compression rubber layer uses a high-rigidity (high-modulus) rubber composition and has high rubber hardness to enhance lateral pressure resistance. The rubber hardness may be 89° or higher, for example, 90-99°, preferably 91-98°, more preferably 92-97°, and more preferably 93-96°. If the rubber hardness of the compression rubber layer is too low, the lateral pressure resistance may decrease, and if it is too high, the flexibility may be insufficient, and the durability (resistance to cog valley cracking) may decrease.

[0088] In this application, the rubber hardness of each rubber layer is expressed as the value Hs (Type A) measured using a Type A durometer in accordance with the spring durometer hardness test specified in JIS K 6253 (2012) (Vulcanized rubber and thermoplastic rubber - Method for determining hardness -), and may simply be referred to as rubber hardness. In detail, it can be measured by the method described in the examples below.

[0089] The tensile strength of the compression rubber layer is, for example, 25 to 50 MPa, preferably 30 to 40 MPa, and more preferably 30 to 35 MPa in the belt width direction. If the tensile strength is too low, the lateral pressure resistance may decrease, and conversely, if it is too high, the flexibility may be insufficient, and the durability (resistance to cog valley cracking) may decrease.

[0090] In this application, the tensile strength of each rubber layer is measured using the tensile strength T value of each rubber layer, which can be measured by a method compliant with JIS K 6251 (2017), as the index value of tensile strength. In detail, it can be measured by the method described in the examples below.

[0091] The average thickness of the compression rubber layer is, for example, 7 to 13 mm, preferably 8 to 12 mm, and more preferably 9 to 11 mm. In this application, the thickness of the compression rubber layer refers to the thickness at the top of the cog portion.

[0092] [Fabric layer] In this invention, the inner surface of the compressed rubber belt is covered with a fabric layer to ensure braking performance and improve durability (resistance to cog valley cracking) and abrasion resistance. The fabric layer may be made of conventional fabric.

[0093] Examples of commonly used fabrics include woven fabrics, knitted fabrics (weft knitted fabrics, warp knitted fabrics), and nonwoven fabrics. Of these, woven fabrics such as plain weave, twill weave, and satin weave, and woven and knitted fabrics with intersection angles exceeding 90° but not exceeding 120° are preferred. Particularly preferred are woven fabrics commonly used as cover fabrics for transmission belts in general industrial and agricultural machinery [plain weave fabrics with right-angle intersections, and plain weave fabrics with intersection angles exceeding 90° but not exceeding 120° (wide-angle canvas)]. Furthermore, in applications where durability is required, the fabric may be wide-angle canvas.

[0094] Examples of fibers constituting the fabric include the fibers exemplified as constituting the first short fibers of the compression rubber layer. The fibers may be single yarns using only one type of fiber, or composite yarns (such as blended yarns) combining two or more types of fibers. Among the fibers, aramid fibers are preferred because they can improve abrasion resistance.

[0095] The aramid fiber may be a para-aramid fiber or a meta-aramid fiber.

[0096] Examples of para-aramid fibers include poly(p-phenylene terephthalamide) fibers (e.g., Teijin Limited's "Twaron®" and Toray DuPont's "Kevlar®"), and copolymer fibers of poly(p-phenylene terephthalamide) and 3,4'-oxydiphenylene terephthalamide (e.g., Teijin Limited's "Technora®").

[0097] Examples of meta-aramid fibers include polymetaphenylene isophthalamide fibers (for example, Teijin Limited's "Conex®").

[0098] These aramid fibers can be used individually or in combination of two or more types. Of these, para-aramid fibers are preferred.

[0099] The fabric layer may be a single layer or multiple layers (for example, two to five layers, preferably two to four layers), but from the standpoint of productivity, a single layer (1 ply) or two layers (2 plies) is preferred.

[0100] The fabric layer may be subjected to adhesive treatment, such as treatment with RFL liquid (such as immersion treatment), if necessary, or friction treatment by rubbing adhesive rubber onto the fabric, or the adhesive rubber and the fabric may be laminated and then laminated or embedded in the compression rubber layer in a laminated form.

[0101] The average thickness of the fabric layer is, for example, 0.1 to 1.5 mm, preferably 0.2 to 1 mm, and more preferably 0.3 to 0.7 mm. If the fabric layer is too thin, there is a risk that the braking performance cannot be adequately ensured due to premature wear of the fabric, and if it is too thick, there is a risk that the flexibility will decrease.

[0102] [Stretchable rubber layer] The raw edge cogged 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.

[0103] 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.

[0104] The rubber composition forming the stretchable rubber layer also preferably contains a second short fiber, as this can further improve lateral pressure resistance and abrasion resistance. Including the second short fiber not only in the compression rubber layer but also in the stretchable rubber layer further improves lateral pressure resistance and abrasion resistance. The second short fiber can be selected from the short fibers exemplified in the first short fiber example, including preferred embodiments. The second short fiber may be a different short fiber from the first short fiber, but is usually the same as the first short fiber. The proportion of the second short fiber can be selected from the proportion of the first short fiber, including preferred proportions.

[0105] The rubber composition forming the stretchable rubber layer may further contain other components exemplified in the rubber composition forming the compression rubber layer.

[0106] The properties of the stretchable rubber layer can be selected from the aforementioned properties of the compression rubber layer (hardness, tensile strength, coefficient of friction, etc.), including within a preferred range.

[0107] The average thickness of the stretchable rubber layer is, for example, 2 to 10 mm, preferably 2.5 to 8 mm, and more preferably 3 to 7 mm. In this application, the thickness of the stretchable rubber layer refers to the thickness at the top of the cog portion.

[0108] [Core layer] The core layer may contain a core, or it may be a core layer formed solely of a core. However, it is preferable that the core layer (adhesive rubber layer) be made of a cross-linked rubber composition in which a core 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 main body of the compression rubber layer to bond the stretchable rubber layer and the main body of the compression rubber layer, and the core is embedded in the adhesive rubber layer.

[0109] (Adhesive rubber layer) The raw edge cogged 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.

[0110] 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.

[0111] The rubber composition forming the adhesive rubber layer may further contain short fibers and other components as exemplified in the rubber composition forming the compression rubber layer.

[0112] The adhesive rubber layer preferably has a lower hardness than the compression rubber layer. The rubber hardness of the adhesive rubber layer is, for example, 60 to 85°, preferably 65 to 84°, more preferably 70 to 83°, and more preferably 75 to 82°. If the rubber hardness is too low, there is a risk of insufficient resistance to lateral pressure, and if it is too high, there is a risk of reduced adhesion. By adjusting the adhesive rubber layer to such a low hardness, it becomes possible to deform significantly when shear stress is applied, and delamination between the core body and the compression rubber layer and stretch rubber layer can be suppressed.

[0113] 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.

[0114] (Core body) The core is not particularly limited, but typically, stranded cords arranged at predetermined intervals in the belt width direction can be used. The strands are arranged extending in the longitudinal direction of the belt, and multiple strands may be arranged parallel to the longitudinal direction of the belt. However, from the viewpoint of productivity, they are usually arranged spirally, extending in parallel at a predetermined pitch, approximately parallel to the longitudinal direction of the low-edge cogged V-belt. When arranged spirally, the angle of the strands 18 with respect to the longitudinal direction of the belt may be, for example, 5° or less, and from the viewpoint of belt runnability, it is preferable that it be as close to 0° as possible. The pitch of the strands is preferably set in the range of 1.5 to 2.5 mm, and more preferably in the range of 1.8 to 2.2 mm. The pitch of the strands is the distance between the centers of adjacent strands.

[0115] The core wire only needs to be in contact with the adhesive rubber layer at least in part, and may be embedded in any of the following configurations: the adhesive rubber layer embeds the core wire, the core wire is embedded between the adhesive rubber layer and the stretchable rubber layer, or the core wire is embedded between the adhesive rubber layer and the compression rubber layer. Of these, the configuration in which the adhesive rubber layer embeds the core wire is preferred because it can improve durability.

[0116] Examples of fibers constituting the core wire include those exemplified as fibers constituting the first short fibers. Among the aforementioned fibers, those with high modulus include ethylene terephthalate, ethylene-2,6-naphthalate, and other C3 fibers. 2-4 Alkylene-C 6-12 Polyester fibers (polyalkylene arylate fibers) with arylate as the main constituent unit, synthetic fibers such as aramid fibers, and inorganic fibers such as carbon fibers are commonly used, with polyester fibers (polyethylene terephthalate fibers, polyethylene naphthalate fibers, etc.) and aramid fibers being preferred. The fibers may also be multifilament yarns. The multifilament yarn may contain, for example, 100 to 5000 monofilament yarns, preferably 500 to 4000, and more preferably about 1000 to 3000 monofilament yarns.

[0117] As the core wire, a twisted cord using multifilament yarn (e.g., multi-ply, single-ply, Lang-ply, etc.) can usually be used. The average diameter of the core wire (diameter of the twisted cord) may be, for example, 0.5 to 3 mm, preferably 0.6 to 2 mm, and more preferably about 0.7 to 1.5 mm. The total fineness of the core wire (twisted cord) may be, for example, 2000 to 17000 dtex, preferably 4000 to 15000 dtex, and more preferably 5000 to 13000 dtex (especially about 6000 to 8000 dtex).

[0118] The core wire may be bonded (or surface-treated) in the same manner as the first short fiber to improve adhesion with the rubber component. Preferably, the core wire is bonded with at least RFL liquid.

[0119] [Reinforcement fabric] The raw-edge cogged V-belt of the present invention may include a reinforcing fabric. Examples of the reinforcing fabric include being laminated on the outer surface of the stretchable rubber layer or being embedded in the stretchable rubber layer.

[0120] The reinforcing fabric may be made of conventional fabric. Examples of conventional fabrics include the fabrics exemplified as fabrics for the fabric layer. The reinforcing fabric may also be treated with adhesive, for example, by treatment with RFL liquid (such as immersion treatment), or by friction treatment in which adhesive rubber is rubbed into the fabric, or by laminating the adhesive rubber and the fabric together and then laminating or embedding them in the compression rubber layer in a laminated form.

[0121] The average thickness of the reinforcing fabric is, for example, 0.1 to 1.5 mm, preferably 0.2 to 1 mm, and more preferably 0.3 to 0.7 mm.

[0122] [Manufacturing method for raw edge cogged V-belts] 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.

[0123] The following describes a typical manufacturing method for a raw-edge cogged V-belt. First, a laminate of a fabric layer precursor and a sheet for the compression rubber layer (uncrosslinked rubber sheet) is placed with the fabric layer precursor facing downwards and in contact with a flat cogged mold in which teeth and grooves corresponding to the inner circumference cog portion are arranged alternately. The laminate is then pressed at a temperature of 60-120°C (especially 80-100°C) to form a cog pad (a pad that is not completely crosslinked but in a semi-crosslinked state) with the inner circumference cog portion. The ends of this cog pad are then cut vertically at appropriate points (especially the tops of the cog peaks) to obtain the required length.

[0124] Next, an inner mold, which has teeth and grooves arranged alternately to correspond to the inner cog portion, is placed over the outer circumference of the 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). After laminating a first adhesive rubber layer sheet (lower adhesive rubber: uncrosslinked rubber sheet) around the outer circumference of the cog pad, a core wire (twisted cord) that will form the core is spun in a spiral shape, and a second adhesive rubber layer sheet (upper adhesive rubber: uncrosslinked rubber sheet) and a stretchable rubber layer sheet (uncrosslinked rubber sheet) are sequentially wrapped around its outer circumference to produce an uncrosslinked molded body.

[0125] Subsequently, the uncrosslinked molded body is covered with a jacket and placed in a known crosslinking apparatus (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.

[0126] In the case of a raw edge double cogged V-belt, a jacket is placed over the outer circumference of the uncrosslinked molded body with an outer matrix having teeth and grooves arranged alternately to correspond to the outer cog portion, and crosslinking is performed, resulting in a crosslinked belt sleeve in which the outer cog portion is also formed on the outer surface, and a raw edge double cogged V-belt is obtained by cutting it into a V shape.

[0127] 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 stacking order of the multiple adhesive rubber layer sheets, depending on the embedding position in the adhesive rubber layer. [Examples]

[0128] 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, the method for producing the uncrosslinked rubber sheet, and the methods for measuring or evaluating each physical property are shown below.

[0129] [Materials used] Chloroprene rubber: "PM-40" manufactured by DENKA Co., Ltd. Magnesium oxide: "Kyowa Mag 30" manufactured by Kyowa Chemical Industry Co., Ltd. Stearic acid: "Stearic acid Tsubaki" manufactured by NOF Corporation. Anti-aging agent: "Nonflex OD-3" manufactured by Seiko Chemical Co., Ltd. Carbon Black: "Seast 3" manufactured by Tokai Carbon Co., Ltd. Silica: "ULTRASIL(registered trademark) VN3" manufactured by Evonik Japan Co., Ltd., BET specific surface area 175 m² 2 / g Plasticizer 1: Naphthenic oil, "NS-900" manufactured by Idemitsu Kosan Co., Ltd. Plasticizer 2: "RS-700" manufactured by ADEKA Corporation Crosslinking accelerator: Tetramethylthiuram disulfide (Noxellar TT, manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Zinc Oxide: "Zinc Oxide 3 Types" manufactured by Seido Chemical Industry Co., Ltd. Sulfur: "Sulfur" manufactured by Migen Chemical Co., Ltd. N,N'-m-phenylenedimaleimide: "Balnock PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Resorcinol-formaldehyde copolymer (resorcinol resin): A resorcinol-formaldehyde copolymer containing less than 20% by mass of resorcinol and less than 0.1% by mass of formalin. Hexamethoxymethylolmelamine: "POWERPLAST PP-1890S" manufactured by Singh Plasticisers & Resins Pvt. Ltd. Aramid short fibers: "Conex short fibers" manufactured by Teijin Limited, with an average fiber length of 3 mm and an average fiber diameter of 14 μm. Short fibers with a solid content adhesion rate of 6% obtained by bonding with RFL solution (resorcinol 2.6 parts by mass, 37% formalin 1.4 parts by mass, vinylpyridine-styrene-butadiene copolymer latex (manufactured by Nippon Zeon Co., Ltd.) 17.2 parts by mass, water 78.8 parts by mass). Core wire: A twisted cord with a total fineness of 6600 dtex, made by twisting aramid fibers with a fineness of 1100 dtex in a 2x3 twist configuration with an upper twist coefficient of 3.0 and a lower twist coefficient of 3.0, and then adhesive treatment is applied (core wire diameter 1.28 mm). Fabric (reinforcement): Aramid canvas (thickness 0.30~0.50mm) bonded with RFL liquid.

[0130] [Preparation of uncrosslinked rubber sheets for rubber layers] The rubber compositions for forming the compression rubber layer, stretch rubber layer, and adhesive rubber layer were prepared according to the mixing ratios shown in Table 1 below. Each rubber composition for forming a layer was mixed using a Banbury mixer, and the resulting mixed rubber was passed through a calender roll to produce a rolled rubber sheet (uncrosslinked rubber sheet). In this specification, each rubber composition is denoted by R1 to R7.

[0131] [Table 1]

[0132] [Rubber hardness Hs of cross-linked rubber] Uncrosslinked rubber sheets for each rubber layer were press-heated at 160°C for 30 minutes to produce crosslinked rubber sheets (100mm x 100mm x 2mm thickness). A laminate of three crosslinked rubber sheets was used as a sample, and the hardness of the crosslinked rubber sheets was measured using a Type A durometer in accordance with the spring-type durometer hardness test specified in JIS K 6253 (2012).

[0133] [Tensile strength of cross-linked rubber] Cross-linked rubber sheets prepared for measuring the rubber hardness Hs of cross-linked rubber were used as samples, and dumbbell-shaped (Type 5) test specimens were prepared in accordance with JIS K 6251 (2017). For samples containing short fibers, dumbbell-shaped test specimens were taken so that the direction of arrangement of the short fibers (arrangement direction) was the tensile direction. Then, both ends of the test specimen were grasped with a chuck (gripping device), and the test specimen was pulled at a speed of 500 mm / min until it broke. The tensile strength was defined as the value obtained by dividing the maximum tensile force recorded by the initial cross-sectional area of ​​the test specimen (tensile strength T).

[0134] [Fabrication of low-edge double-cogged V-belts] A low-edge double-cogged V-belt (size: top width 38.5 mm, thickness (H) 16.7 mm, cog height (inner circumference side: H1) 6.8 mm, cog height (outer circumference side: H4) 3.8 mm, pitch height (H3 + H4) 5.4 mm, inner circumference core valley thickness (H2) 4.5 mm, belt outer circumference length 1158 mm, V angle 26°) was manufactured using the method described in the above embodiment.

[0135] [Analysis using the 3D Finite Element Method (FEM)] Based on the method described in the embodiment of Japanese Patent Publication No. 7256249, a three-dimensional finite element model was created for the obtained raw edge double cogged V-belt (two types: a belt in an untensioned state and a belt with a tension of 1000 N applied). The model was used to check whether interference between adjacent cog sections (cog interference) occurred when the belt bent. If cog interference did not occur, the finite element model was used to analyze the maximum value of the Mises stress generated at the deepest part of the inner circumference cog valley. On the other hand, if cog interference occurred, the evaluation of the raw edge double cogged V-belt was not performed.

[0136] [Evaluation of low-edge double-cogged V-belts] (1) Endurance driving test (Top endurance test) To confirm the resistance to cog valley cracking (flexural fatigue resistance), a two-axis running test machine was used, as shown in Figure 6, which was equipped with a drive (DR) pulley with a diameter (pitch diameter) of 178 mm and a driven (DN) pulley with a diameter (pitch diameter) of 140 mm. A low-edge double-cogged V-belt was mounted on each pulley, the drive pulley rotation speed was set to 6,000 rpm, the shaft load (dead weight) to 1.2 kN, and a load of 60 Nm was applied by a load device (power generator). The belt was run at an ambient temperature of 115°C, and the running time until a crack that had formed in the cog valley reached the core wire and the belt reached the end of its lifespan was measured as the running life.

[0137] (Criteria for judging endurance driving tests (Top Endurance Test)) a: Driving life of 130 hours or more (passed) b: Driving life of 110 hours or more, but less than 130 hours (passed) c: Driving life is less than 110 hours (failed)

[0138] (2) Endurance driving test (Low endurance test) To confirm the resistance to core wire peeling (resistance to lateral pressure), a two-axis running test machine equipped with a drive (DR) pulley with a diameter (pitch diameter) of 92 mm and a driven (DN) pulley with a diameter (pitch diameter) of 208 mm was used, as shown in Figure 7. A low-edge double-cogged V-belt was mounted on each pulley, the rotation speed of the drive pulley was set to 5,000 rpm, the shaft load (dead weight) to 2.2 kN, and a load of 50 Nm was applied by a load device (power generator). The belt was run at an ambient temperature of 60°C, and the running time until core wire peeling occurred was measured as the running life.

[0139] (Criteria for judging endurance driving tests (Low endurance tests)) a: Driving life of 30 hours or more (passed) b: Driving life of 10 hours or more but less than 30 hours (pass) c: Driving life is less than 10 hours (failed)

[0140] (3) Brake performance test (engine braking performance in an actual vehicle) A 1,000cc four-wheeled buggy (off-road vehicle) was fitted with a low-edge double-cogged V-belt in its CVT and subjected to real-world testing. While the vehicle was running, the throttle was released from its top speed, and the time it took for the driven pulley's rotation speed to decrease from 478 rpm to 0 rpm without applying the brakes was measured.

[0141] (Criteria for evaluating brake performance tests) a: The time it takes for the rotation speed to return to 0 rpm is 7 seconds or less (Pass) b: The time it takes for the rotation speed to reach 0 rpm is between 7 and 8 seconds (pass). c: Time taken for the rotation speed to reach 0 rpm exceeds 8 seconds (failed).

[0142] (4) Brake duration test (engine braking duration in an actual vehicle) After the aforementioned brake performance test was performed on a vehicle that had traveled 500 miles on rough terrain (off-road), the brake performance was checked using the same method as in the brake performance test. Brake durability was judged based on the following criteria, considering whether the brake performance after 500 miles of travel maintained a high level of performance compared to the initial (before 500 miles of travel) brake performance, or whether the level had deteriorated. In addition, if the brake performance test was unsuccessful (rating C), the brake durability test was not performed.

[0143] (Criteria for evaluating brake durability test) a: Brake performance remains at a high level after approximately 500 miles of driving (maintains an A rating). b: Brake performance after 500 miles of driving is rated b (downgraded from a to b, but remains at a b rating). c: Brake performance after 500 miles of driving is rated c (a decrease from a or b rating to a c rating).

[0144] (5) Overall Judgment Based on the results of endurance driving tests (Top endurance test, Low endurance test), brake performance tests, and brake durability tests, the overall superiority (ranking) of the belts was determined using the criteria shown in Table 2, considering whether they provided sufficient flexural fatigue resistance (resistance to cog valley cracking) and lateral pressure resistance (resistance to core wire delamination) while also demonstrating adequate brake performance. From the perspective of product practicality, ranks A, B, and C were considered pass, and rank D was considered fail. If cog interference was confirmed in the FEM analysis, the overall judgment was immediately set to rank D (fail).

[0145] [Table 2]

[0146] <Belts with a cog pitch of 11.8 mm (Comparative Examples 1-5 and Examples 1-8)> [Comparative Example 1] In a belt with an inner circumference cog pitch of 11.8 mm and a radius of curvature of 2.3 mm for the arc forming the bottom of the inner circumference cog valley, a belt was fabricated in which the cog peaks were formed as curves (arcs with a radius of curvature of 2.8 mm) and no flat tops were formed.

[0147] [Comparative Example 2] A belt was fabricated in which a flat top portion with a circumferential length of 1.1 mm was added to the inner circumference cog peaks of the belt of Comparative Example 1, and the inner circumference flatness ratio was adjusted to 9%. Two consecutive arcs were formed as the arcs that form the bottom of the cog valleys, based on a virtual arc R0 = 2.5 mm (the first arc at the deepest point R1 = 3.9 mm, and a pair of second arcs R2 = 1.0 mm).

[0148] [Comparative Example 3] Compared to Comparative Example 2, a belt was fabricated in which the radius of curvature of the cog peak R chamfer was reduced to R3 = 2.1 mm, thereby increasing the circumferential length of the flat top portion to 1.8 mm and adjusting the inner circumferential flatness ratio to 15%.

[0149] [Example 1] Compared to Comparative Example 2, a belt was fabricated in which the radius of curvature of the cog peak R chamfer was reduced to R3 = 1.8 mm, thereby adjusting the circumferential length of the flat top to 2.4 mm and adjusting the inner circumferential flatness to 20%.

[0150] [Example 2] Compared to Comparative Example 2, a belt was fabricated in which the circumferential length of the flat top portion was increased to 4.5 mm and the inner circumferential flatness ratio was increased to 38%.

[0151] [Example 3] In Example 2, where the inner circumference flatness ratio was adjusted to 38%, a belt was fabricated in which the radius of curvature of the first arc at the deepest part of two consecutive arcs, based on the radius of curvature R0 = 2.5 mm of a virtual arc, was changed to R1 = 3.0 mm to form the bottom of the cog valley.

[0152] [Example 4] In Example 2, where the inner circumference flatness ratio was adjusted to 38%, a belt was fabricated in which the radius of curvature of the first arc at the deepest part of two consecutive arcs, based on the radius of curvature R0 = 2.5 mm of a virtual arc, was changed to R1 = 4.0 mm to form the bottom of the cog valley.

[0153] [Example 5] In Example 2, where the inner circumference flatness ratio was adjusted to 38%, a belt was fabricated in which the radius of curvature of the first arc at the deepest part of two consecutive arcs, based on the radius of curvature R0 = 2.5 mm of a virtual arc, was changed to R1 = 4.5 mm to form the bottom of the cog valley.

[0154] [Example 6] Compared to Example 2, a belt was fabricated in which the radius of curvature of the virtual arc that forms the basis of the two consecutive arcs that form the bottom of the cog valley (radius of curvature R1 = 3.9 mm for the first arc at the deepest point, and radius of curvature R2 = 1.0 mm for the pair of second arcs) was reduced to R0 = 1.1 mm, and the cog angle was changed to θ = 20°, thereby adjusting the inner circumference flatness ratio to 38%.

[0155] [Example 7] Compared to Example 2, a belt was fabricated in which the radius of curvature of the virtual arc was reduced to R0 = 0.5 mm, the radius of curvature of the second arc was changed to R2 = 0.5 mm, and the cog angle was changed to θ = 24°, thereby adjusting the inner circumference flatness ratio to 38%.

[0156] [Example 8] Compared to Example 2, the radius of curvature of the virtual arc was reduced to R0 = 1.5 mm and the cog angle was reduced to θ = 4°, thereby adjusting the circumferential length of the flat top to 7.1 mm and creating a belt with an increased inner circumferential flatness ratio of 60%.

[0157] [Comparative Example 4] Compared to Example 2, the radius of curvature of the virtual arc was reduced to R0 = 1.4 mm and the cog angle was reduced to θ = 1°, thereby adjusting the circumferential length of the flat top to 7.9 mm and creating a belt with an increased inner circumferential flatness ratio of 67%.

[0158] [Comparative Example 5] A belt was manufactured in the same manner as in Example 2, except that a fabric layer covering the inner surface of the belt was not provided.

[0159] Table 3 shows the evaluation results of the belts obtained in Comparative Examples 1-5 and Examples 1-8. Figure 8 shows the schematic cross-sectional shapes of the belts obtained in the Comparative Examples and Examples.

[0160] [Table 3]

[0161] The belt in Comparative Example 1 had low stress in the cog valleys and received an A rating for durability (resistance to cog valley cracking), but because it lacked flat sections, its engine braking performance received a C rating, resulting in an overall D rank.

[0162] Compared to Comparative Example 1, the belts of Comparative Examples 2 and 3 had less stress generated in the cog valleys and received an A rating for durability (resistance to cog valley cracking). However, because their inner circumference flatness was small (9% for Comparative Example 2 and 15% for Comparative Example 3), their engine braking performance received a C rating, resulting in an overall D rank.

[0163] The belt in Example 1 performed at the same level as Comparative Examples 2 and 3, with low stress in the cog valleys and a durability rating of A for resistance to cog valley cracking. However, because the inner circumference flatness ratio increased to 20%, the engine braking performance improved to a B rating, and the engine braking persistence was also good (B rating), resulting in an overall rating of B.

[0164] Furthermore, the belt in Example 2 exhibited low stress in the cog valleys, resulting in a durability rating of A (resistance to cog valley cracking). In addition, its inner circumference flatness ratio increased to 38%, leading to improved engine braking performance (rated A) and good engine braking persistence (rated A), resulting in an overall rating of A.

[0165] In Example 2, where the inner circumference flatness ratio was increased to 38%, the same results as in Example 2 were obtained in Examples 3 (R1=3.0mm), 4 (R1=4.0mm), and 5 (R1=4.5mm), in which the radius of curvature R1 of the first arc at the deepest part of two consecutive arcs, based on a virtual arc R0=2.5mm, was changed as the arc forming the bottom of the cog valley, and the same results as in Example 2 were obtained.

[0166] Compared to Example 2, in which the inner circumference flatness ratio was increased to 38%, Example 6, in which the radius of curvature of the virtual arc that forms the basis of the two consecutive arcs that form the bottom of the cog valley was reduced to R0=1.1 mm (and the cog angle was changed to θ=20° to adjust the inner circumference flatness ratio to 38%), the engine braking performance was rated A, but the stress generated in the cog valley increased, causing the durability (resistance to cog valley cracking) to decrease to a B rating, resulting in an overall rating of B. Furthermore, in Example 7, in which the radius of curvature of the virtual arc was reduced to R0=0.5 mm (and the cog angle was changed to θ=24° to adjust the inner circumference flatness ratio to 38%), the engine braking performance was rated A, but the stress generated in the cog valley increased, causing the durability (resistance to cog valley cracking) to decrease to a C rating, resulting in an overall rating of C.

[0167] On the other hand, in Example 8, where the inner circumference flatness was increased to 60% by reducing the radius of curvature R0 of the virtual arc and the cog angle θ (R0=1.5mm, θ=4°), the stress generated in the cog valleys was small, and both durability (resistance to cog valley cracking) and engine braking performance received an A rating, resulting in an overall A rank. However, in Comparative Example 4, where the inner circumference flatness was increased to 67% by further reducing the radius of curvature R0 of the virtual arc and the cog angle θ (R0=1.4mm, θ=1°), FEM analysis revealed interference between adjacent cog sections (cog interference) when the belt bent, resulting in a D rank (failure). Figure 9 shows the FEM analysis diagram of the low-edge double-cogged V-belt obtained in Comparative Example 4, which shows the state in which the inner circumference cog sections interfere with each other. As is clear from Figure 9, in the belt of Comparative Example 4, the upper inner circumference cog section deforms due to bending, causing adjacent inner circumference cog sections to come into contact.

[0168] Based on these results, the belts of Examples 1 to 8, with an inner circumference flatness ratio of 20-60%, were ranked A, B, and C respectively, indicating that they meet the acceptable standards from the perspective of product practicality. It can be said that setting the inner circumference flatness ratio within this range is suitable for achieving both "brake function" and "durability (resistance to cog valley cracks)," which are often conflicting requirements.

[0169] Furthermore, compared to Example 2, which had an inner circumference flatness ratio of 38% and received an overall rating of A, Comparative Example 5, which did not have a fabric layer covering the inner circumference surface of the belt, showed an A rating for braking performance in the initial stages of driving (before 500 miles of driving), but after driving, it deteriorated to a C rating, resulting in an A rating for engine braking sustainability. In addition, durability (resistance to cog valley cracks) also deteriorated to a C rating. As a result, the overall rating was D. From these results, it can be seen that the fabric layer covering the inner circumference surface of the belt is effective in terms of engine braking sustainability and durability (resistance to cog valley cracks).

[0170] <Belt with a cog pitch of 9.44 mm (Comparative Examples 6-7 and Examples 9-21)> [Comparative Example 6] A belt was fabricated with an inner circumference cog pitch of 9.44 mm, and a flat top portion with a circumferential length of 1.4 mm (radius of curvature R3 = 2.4 mm for the R chamfer of the cog peak) was provided on the inner circumference cog peak, and the inner circumference flatness ratio was adjusted to 15%. As the arcs forming the bottom of the cog valleys, two consecutive arcs were formed based on the radius of curvature R0 = 1.1 mm of a virtual arc (radius of curvature R1 = 2.5 mm for the first arc at the deepest point, and radius of curvature R2 = 0.3 mm for the pair of second arcs).

[0171] [Example 9] Compared to Comparative Example 6, a belt was fabricated in which the radius of curvature of the cog peak R chamfer was reduced to R3 = 2.0 mm, thereby adjusting the circumferential length of the flat top portion to 1.9 mm and adjusting the inner circumferential flatness ratio to 20%.

[0172] [Example 10] Compared to Comparative Example 6, a belt was fabricated in which the radius of curvature of the cog peak R chamfer was reduced to R3 = 0.5 mm, thereby adjusting the circumferential length of the flat top to 4.6 mm and adjusting the inner circumferential flatness ratio to 48%.

[0173] [Example 11] In Example 10, in which the inner circumference flatness ratio was adjusted to 48%, a belt was fabricated in which the radius of curvature of the first arc at the deepest part of two consecutive arcs was changed to R1 = 1.5 mm to form the bottom of the cog valley.

[0174] [Example 12] In Example 10, where the inner circumference flatness ratio was adjusted to 48%, a belt was manufactured with the radius of curvature of the first arc changed to R1 = 2.0 mm (radius of curvature of the second arc R2 = 0.75 mm).

[0175] [Example 13] In Example 10, where the inner circumference flatness ratio was adjusted to 48%, a belt was manufactured in which the radius of curvature of the first arc was changed to R1 = 2.75 mm.

[0176] [Example 14] In Example 10, where the inner circumference flatness ratio was adjusted to 48%, a belt was manufactured with the radius of curvature of the first arc changed to R1 = 3.0 mm (radius of curvature of the second arc R2 = 0.25 mm).

[0177] [Example 15] In Example 10, where the inner circumference flatness ratio was adjusted to 48%, a belt was fabricated with the radius of curvature of the first arc changed to R1 = 3.9 mm.

[0178] [Example 16] In Example 10, where the inner circumference flatness ratio was adjusted to 48%, a belt was manufactured in which the radius of curvature of the first arc was changed to R1 = 4.5 mm.

[0179] [Example 17] Compared to Example 10, a belt was fabricated in which the radius of curvature of the virtual arcs that form the basis of the two consecutive arcs that form the bottom of the cog valley was increased to R0 = 1.5 mm, and the radius of curvature of the first arc was changed to R1 = 3.9 mm and the radius of curvature of the second arc to R2 = 1.0 mm, thereby adjusting the inner circumference flatness ratio to 41%.

[0180] [Example 18] Compared to Example 17, a belt was fabricated in which the radius of curvature of the virtual arc that forms the basis of the two consecutive arcs that form the bottom of the cog valley was increased to R0 = 1.8 mm, and the cog angle was reduced to θ = 1°, thereby adjusting the inner circumference flatness to 41%.

[0181] [Example 19] Compared to Example 17, a belt was fabricated in which the radius of curvature of the virtual arc that forms the basis of the two consecutive arcs that form the bottom of the cog valley was reduced to R0 = 0.5 mm, and the cog angle was increased to θ = 17°, thereby adjusting the inner circumference flatness to 41%.

[0182] [Example 20] Compared to Example 17, a belt was fabricated in which the radius of curvature of the virtual arc that forms the basis of the two consecutive arcs that form the bottom of the cog valley was increased to R0 = 1.9 mm, and the cog angle was reduced to θ = 0°, thereby adjusting the inner circumference flatness to 49%.

[0183] [Example 21] Compared to Example 10, a belt was fabricated in which the circumferential length of the flat top portion was adjusted to 5.6 mm by reducing the radius of curvature of the virtual arc to R0 = 0.5 mm, the radius of curvature of the first arc to R1 = 1.5 mm, and the radius of curvature of the second arc to R2 = 0.25 mm, thereby increasing the inner circumferential flatness ratio to 59%.

[0184] [Comparative Example 7] Compared to Example 21, a belt was fabricated in which the circumferential length of the flat top portion was adjusted to 6.3 mm by reducing the cog angle to θ = 6°, thereby increasing the inner circumferential flatness ratio to 67%.

[0185] Table 4 shows the evaluation results of the belts obtained in Comparative Examples 6-7 and Examples 9-21. Figure 10 shows the schematic cross-sectional shapes of the belts obtained in Comparative Examples 6-7 and Examples 9-21.

[0186] [Table 4]

[0187] The belt in Comparative Example 6 had low stress in the cog valleys and received an A rating for durability (resistance to cog valley cracking), but its inner circumference flatness ratio was low at 15%, resulting in a C rating for engine braking performance, and an overall rating of D.

[0188] The belt in Example 9 was at the same level as Comparative Example 6, with low stress generated in the cog valleys and a durability rating of A for resistance to cog valley cracking. However, because the inner circumference flatness ratio increased to 20%, the engine braking performance improved to a B rating, and the engine braking persistence was also good (B rating), resulting in an overall rating of B.

[0189] Furthermore, the belt in Example 10 has low stress in the cog valleys and a durability rating of A (resistance to cog valley cracking), and its inner circumference flatness ratio is 48%, resulting in improved engine braking performance (rated A) and good engine braking persistence (rated A), thus improving the overall rating to A.

[0190] In Example 10, where the inner circumference flatness ratio was increased to 48%, the radius of curvature R1 of the first arc at the deepest part of two consecutive arcs based on a virtual arc R0=1.1mm was changed as the arc forming the bottom of the cog valley in Examples 12 (R1=2.0mm), 13 (R1=2.75mm), 14 (R1=3.0mm), 15 (R1=3.9mm), and 16 (R1=4.5mm). In all of these cases, durability (resistance to cog valley cracking), engine braking performance, and engine braking persistence were all good (rated a or b), resulting in an overall rating of A or B. Even in Example 11 (R1=1.5mm), where R1 was the smallest, although durability (resistance to cog valley cracking) decreased (rated c), the overall rating was a passing C.

[0191] Compared to Example 10, in Example 17, where the radius of curvature of the virtual arc was increased to R0=1.5 mm, and the radius of curvature of the first arc was changed to R1=3.9 mm and the radius of curvature of the second arc to R2=1.0 mm, the inner circumference flatness ratio was adjusted to 41%, the same good results as in Example 10 were obtained. Furthermore, in Example 18, where the radius of curvature of the virtual arc was increased to R0=1.8 mm (and the cog angle was reduced to θ=1° to adjust the inner circumference flatness ratio to 41%), the same good results as in Example 17 were obtained. Furthermore, in Example 19, in which the radius of curvature of the virtual arc was reduced to R0 = 0.5 mm compared to Example 17 (and the cog angle was increased to θ = 17° to adjust the inner circumference flatness to 41%), although the stress generated in the cog valleys increased, the durability (resistance to cog valley cracking) was rated as B, and the overall rating was B.

[0192] Furthermore, in Example 20, in which the radius of curvature of the virtual arc was increased to R0 = 1.9 mm (and the cog angle was reduced to θ = 0° to adjust the inner circumference flatness ratio to 49%) compared to Example 17, results as good as those of Example 17 were obtained.

[0193] On the other hand, in Example 21, in which the radius of curvature of the virtual arc and the first arc was reduced (R0=0.5mm, R1=1.5mm) compared to Examples 10 and 17, thereby increasing the inner circumference flatness to 59%, the stress generated in the cog valleys was large, resulting in a durability (cog valley crack resistance) rating of C, but the overall rating was a passing grade of C. However, in Comparative Example 7, in which the inner circumference flatness was increased to 67% by further reducing the cog angle (θ=6°), FEM analysis revealed interference between adjacent cog sections (cog interference) when the belt bent, resulting in a D rank (failure).

[0194] Based on these results, the belts of Examples 9-21, with an inner circumference flatness ratio of 20-59%, were ranked A, B, and C respectively, indicating that they meet the acceptable standards in terms of product practicality. It can be said that setting the inner circumference flatness ratio within this range is suitable for achieving both "brake function" and "durability (resistance to cog valley cracks)," which are often conflicting requirements.

[0195] From the above, it was confirmed that a low-edge cogged V-belt, having a cog section at least on the inner circumference side in which cog peaks and cog valleys are alternately arranged in the longitudinal direction of the belt, wherein the cog section is formed of a compressed rubber layer and a fabric layer covering the inner surface of the compressed rubber layer, the tops of the cog peaks are formed flat, and furthermore, the length of each top in the longitudinal direction of the belt is adjusted to 20-60% of the cog pitch, can be applied to the brake system of a belt clutch-in type continuously variable transmission, and its durability, such as wear resistance, can also be improved. [Industrial applicability]

[0196] The raw-edge cogged V-belt of the present invention is suitable as a transmission V-belt used in transmission mechanisms that require high frictional force on the inner circumference. In particular, it can be used as a transmission belt in belt-clutch-in type CVTs such as snowmobiles (small snow vehicles) and four-wheel buggies (ATVs), and is suitable as a transmission belt used in belt-clutch-in type CVTs where the inner circumference of the belt contacts the pulley shaft during idling. It can also be used as a transmission belt in a belt-clutch-in type continuously variable transmission that is involved in stepless shifting, clutching, and braking. [Explanation of Symbols]

[0197] 1… Raw edge cogged V-belt 1a... Inner circumference cog mountain 1b...Inner circumference cog valley 1c... Outer perimeter cog peak 1d... Outer Cog Valley 2…Stretchable rubber layer 3…Core layer (adhesive rubber layer) 3a… Core body (core wire) 4…Compressed rubber layer 5...Fabric layer

Claims

1. A belt transmission mechanism used in a belt clutch-in type continuously variable transmission equipped with a brake system that utilizes the frictional force of the inner surface of the belt, The system comprises a pulley and a low-edge cogged V-belt having cog portions on at least the inner circumference side in which cog peaks and cog valleys are arranged alternately in the longitudinal direction of the belt, wherein the cog portions on the inner circumference side are formed of a compression rubber layer and a fabric layer covering the inner surface of the compression rubber layer. The aforementioned brake system is a system that utilizes the frictional force generated by the contact between the inner surface of the belt and the pulley shaft portion having a smooth outer surface during idling. A belt transmission mechanism wherein the tops of the cog teeth on the inner circumferential surface of the belt that contact the pulley shaft portion are flat and covered with the fabric layer, and the length of each top in the longitudinal direction of the belt is 20 to 60% of the cog pitch.

2. The belt transmission mechanism according to claim 1, wherein the cog pitch is 6 to 17 mm.

3. The belt transmission mechanism according to claim 1 or 2, wherein the fabric layer contains aramid fibers.

4. The belt transmission mechanism according to claim 1 or 2, wherein the cross-sectional shape of the cog valley on the inner circumference side in the longitudinal direction of the belt has a bottom portion consisting of a circular arc with a radius of curvature of 2 to 4 mm and a side wall portion extending from the bottom portion inclined with respect to the belt thickness direction or along the belt thickness direction.

5. In the low-edge cogged V-belt, The cross-sectional shape of the cog valley on the inner circumference in the longitudinal direction of the belt is such that it comprises a bottom portion formed by combining a plurality of continuous arcs, and a side wall portion that is inclined with respect to the belt thickness direction or extends from the bottom portion along the belt thickness direction, As the plurality of arcs move away from the deepest part of the cog valley, the radius of curvature decreases. The belt transmission mechanism according to claim 1 or 2, wherein, among the plurality of arcs, the radius of curvature of the first arc passing through the deepest part is larger in diameter than the virtual circle tangent to the deepest part and the side walls on both sides, and is 2 to 4 mm.

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