Raw-edge cogged v-belt, use method thereof, 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 raw-edge cog V-belt used in a belt-type continuously variable transmission, a method for using the same, and a belt transmission mechanism. [Background technology]

[0002] V-belts, which transmit power through friction, come in two types: raw-edge V-belts, which have a rubber layer with an exposed friction transmission surface (V-shaped side), and wrapped V-belts, whose friction transmission surface is covered with a cover fabric. They are used for different purposes based on the surface properties of the friction transmission surface (the coefficient of friction between the rubber layer and the cover fabric). Raw-edge V-belts include raw-edge V-belts without cogs, raw-edge cogged V-belts with cogs only on the inner circumferential surface of the belt to improve flexibility, and raw-edge cogged V-belts (raw-edge double cogged V-belts) with cogs on both the inner and outer circumferential surfaces to improve flexibility.

[0003] Raw edge V-belts are primarily used to drive general industrial machinery, agricultural machinery, and automotive engine accessories. Among these, raw edge cog V-belts are also used as variable speed belts (CVT belts) in belt-type continuously variable transmissions (CVT) for motorcycles (scooters), snowmobiles (small snow vehicles), and all-terrain vehicles (ATVs).

[0004] 1 is a schematic diagram illustrating the transmission mechanism of a CVT. As shown in FIG. 1, a belt-type CVT 20 has a mechanism for continuously changing the gear ratio by wrapping a V-belt 23 around a drive pulley 21 and a driven pulley 22. Each pulley 21, 22 has a fixed sheave 21a, 22a whose axial movement is restricted or fixed, and a movable sheave 21b, 22b that is movable in the axial direction, and the inner peripheral walls of the fixed sheaves 21a, 22a and the movable sheaves 21b, 22b form inclined opposing surfaces with a V-groove shape. Each pulley 21, 22 has a structure that allows the width of the V-groove of the pulley 21, 22 formed by the fixed sheaves 21a, 22a and the movable sheaves 21b, 22b to be continuously changed. Both widthwise end faces of the V-belt 23 are formed with tapered surfaces whose inclinations match the V-groove-shaped inclined opposing surfaces of the pulleys 21 and 22, and fit into any vertical position on the opposing surfaces of the V-grooves depending on the changed width of the V-grooves. For example, if the width of the V-groove of the drive pulley 21 is narrowed and the width of the V-groove of the driven pulley 22 is widened, thereby changing from the state shown in Fig. 1(a) to the state shown in Fig. 1(b), the V-belt 23 moves above the V-groove on the drive pulley 21 side and below the V-groove on the driven pulley 22 side, and the winding diameter around each of the pulleys 21 and 22 changes continuously, allowing the gear ratio to be changed continuously.

[0005] For example, a CVT for a motorcycle includes a drive pulley fixed around the crankshaft of the engine, a driven pulley connected to the drive shaft of the rear wheel via a gear or the like, and a V-belt wound 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 winding diameter of the drive pulley, while the movable sheave of the driven pulley moves closer to the fixed sheave, increasing the winding diameter of the driven pulley. This allows the rear wheels to be driven with high torque at low speeds. At high speeds, the movable sheave of the drive pulley moves closer to the fixed sheave, increasing the winding diameter of the drive pulley, while the movable sheave of the driven pulley moves away from the fixed sheave, reducing the winding diameter of the driven pulley. This allows the rear wheels to be driven with low torque at high speeds.

[0007] On the other hand, there is a difference between motorcycles and snowmobiles or four-wheeled buggies in the clutch mechanism (a mechanism that temporarily interrupts the transmission of power) when idling.

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

[0009] On the other hand, CVTs used in snowmobiles and all-terrain vehicles (ATVs) do not have an automatic centrifugal clutch. Instead, when idling, the movable sheave is moved until the side of the V-belt is completely separated from the movable or fixed sheave, thereby interrupting torque transmission from the drive pulley to the V-belt. In other words, in such CVTs, when idling, the V-belt drops into the bottom of the pulley groove (shaft), causing the underside (inner peripheral surface) of the V-belt to come into contact with the shaft, acting as a belt clutch that temporarily interrupts power transmission (the shaft of the drive pulley acts as an idler pulley). This type of transmission is called a belt clutch-in type CVT.

[0010] Figure 2 is a schematic diagram showing the state of a belt clutch-in type CVT when idling. 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 of the drive pulley 31, but rather contacts the pulley shaft 31c of the drive pulley 31. That is, in an automatic centrifugal clutch type CVT for a motorcycle, the V-belt contacts the sheave of the pulley even when idling, as shown in Figure 1, whereas in a belt clutch-in type CVT for a snowmobile or four-wheeled buggy, the inner peripheral surface of the V-belt contacts the outer peripheral surface of the pulley shaft of the drive pulley (a typical pulley shaft with a smooth outer peripheral surface).

[0011] The following belts are known as variable speed belts specialized for belt clutch-in type CVTs, that is, belts whose bottom surface (inner peripheral surface) comes into contact with a pulley shaft when the engine is idling, etc.

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

[0013] Japanese Patent Application Laid-Open Publication No. 2006-2836 (Patent Document 2) discloses a raw edge belt in which the bottom surface of the belt that slides in contact with the sheave shaft is made of canvas with no rubber glue applied, resulting in a friction coefficient of the bottom surface of 0.1 or less and no rubber falling off (rubber powder falling off), meaning there is no risk of fallen rubber getting into the gaps around the sheave shaft and causing problems.

[0014] Japanese Patent Application Laid-Open 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 comes into contact with the pulley recess, and no rubber adheres to the canvas at the contact point with the pulley recess, thereby eliminating rubber from adhering to the belt surface that comes into contact with the pulley recess, thereby lowering the coefficient of friction and preventing noise.

[0015] Japanese Patent Application Laid-Open 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 Application Laid-Open Publication No. 2009-51204 (Patent Document 5) discloses a cog V-belt that can be manufactured without attaching rubber 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 a mold and temporarily fixing it, and that can suppress the scattering of rubber dust even when the belt is dropped into a belt clutch-in type CVT.

[0017] Japanese Patent Application Laid-Open 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, the belt clutch-in method has lower engine braking performance than the automatic centrifugal clutch method, so a mechanism is being considered that takes advantage of the contact between the idler pulley and the inner surface of the speed change belt when idling and uses this friction force to act as an engine braking system (EBS) that brakes the driven pulley (rear wheel).

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

[0020] Japanese Patent Application Laid-Open Publication No. 2023-169113 (Patent Document 9) discloses a brake system for a belt clutch-in type continuously variable transmission that uses a low-edge cog V-belt as a variable speed belt, the compressed rubber layer being constructed by combining the main body of the compressed rubber layer with an inner surface layer that covers the inner peripheral surface of the main body of the compressed rubber layer and has a surface with a higher friction coefficient than the main body surface of the compressed rubber layer. [Prior art documents] [Patent documents]

[0021] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-188776 [Patent Document 2] Japanese Patent Application Laid-Open 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 Publication No. 2023-169113 Summary of the Invention [Problem to be solved by the invention]

[0022] The V-belts in Patent Documents 1 to 6 are designed to make the bottom surface of the belt slippery (lower the coefficient of friction) to prevent problems (such as abnormal noise, driving force, and rubber scattering) caused by the bottom surface of the belt rubbing against the pulley shaft, but do not describe engine braking performance (braking function) in belt clutch-in systems. Furthermore, the V-belts in Patent Documents 1 to 6 do not provide sufficient frictional force to achieve sufficient braking function, and therefore are unable to demonstrate braking function. Therefore, achieving and maintaining braking function by shortening braking distance and time has become an issue, and there is a demand for the development of a V-belt with advanced braking function (high frictional force).

[0023] On the other hand, the continuously variable speed engine brake systems of Patent Documents 7 and 8 require a pulley with a special shape.

[0024] Among raw-edge V-belts, CVT applications require the highest level of lateral pressure resistance, and for this application, the compression rubber layer must be more rigid than other applications. Therefore, CVT applications inevitably lack flexibility, necessitating the use of cogs. In other words, high-rigidity rubber and cogs are essential components for CVT applications. On the other hand, to ensure braking (friction) by contacting the inner circumferential surface of the belt with the pulley shaft, a belt with a flat inner circumferential surface (without cogs) is advantageous, as it increases the contact area. However, because cogs are required for CVT applications, only the tops of the cogs come into contact with the pulley shaft (the shaft of a typical pulley has a smooth outer surface without any irregularities for engagement with the belt), making it difficult to improve friction (braking function). In other words, raw-edge V-belts used in CVT applications have a trade-off between lateral pressure resistance and improved braking function, making it difficult to achieve both.

[0025] In response to this, Patent Document 9 strengthens the braking function of the inner peripheral surface of the V-belt by arranging an inner surface layer (rubber layer) with a high friction coefficient on the inner peripheral surface of the main body of the compressed rubber layer in the raw edge cog V-belt. However, even in the raw edge V-belt of Patent Document 9, the inner surface layer (rubber layer) is easily worn away by wear during operation, and at the same time, the braking function is also lost, so there was an issue with durability (wear resistance).

[0026] Therefore, an object of the present invention is to provide a raw-edge cog V-belt that can be applied to the brake system of a belt clutch-in type continuously variable transmission and that 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 extensive research into achieving the above-mentioned object, the inventors have discovered that in a raw-edge cog V-belt having a cog section, at least on the inner periphery, in which cog crests and cog valleys are arranged alternately in the belt longitudinal direction (belt length direction or circumferential direction), the cog section is formed from a compressed rubber layer and a fabric layer covering the inner periphery surface of the compressed rubber layer, the tops of the cog crests are formed flat, and the length of each top in the belt longitudinal direction is adjusted to 20 to 60% of the cog pitch, which makes it possible to apply the belt to the brake system of a belt clutch-in type continuously variable transmission, and also improve durability such as wear resistance, thereby completing the present invention.

[0028] That is, the present invention includes the following aspects.

[0029] Aspect [1]: A raw edge cogged V-belt having a cog portion on at least the inner circumferential side, in which cog crests and cog valleys are alternately arranged in the belt longitudinal direction, the cog portion on the inner circumferential side is formed by a compression rubber layer and a fabric layer covering the inner circumferential surface of the compression rubber layer, The tops of the inner cogs are flat, and A raw edge cog V-belt in which the length of each apex in the longitudinal direction of the belt is 18 to 65% of the cog pitch.

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

[0031] Aspect [3]: The raw edge cogged V-belt of aspect [1] or [2], wherein the fabric layer contains aramid fiber.

[0032] Aspect [4]: ​​The raw edge cog V-belt of any of Aspects [1] to [3], wherein the cross-sectional shape of the inner cog valley in the longitudinal direction of the belt has a bottom portion consisting of an arc with a curvature radius of 2 to 4 mm, and a side wall portion extending from the bottom portion at an angle with respect to the belt thickness direction or along the belt thickness direction.

[0033] Aspect [5]: The cross-sectional shape of the inner cog valley in the belt longitudinal direction has a bottom portion formed by combining a plurality of continuous arcs, and a side wall portion extending from the bottom portion at an angle with respect to the belt thickness direction or along the belt thickness direction, the plurality of arcs have a smaller radius of curvature as they move away from the deepest portion of the cog valley; The raw edge cogged V-belt of any of the above aspects [1] to [4], wherein the radius of curvature of a first arc passing through the deepest portion among the plurality of arcs is larger than the radius of an imaginary circle tangent to the deepest portion and both side wall portions, and is 2 to 4 mm.

[0034] Aspect [6]: A belt transmission mechanism comprising a raw-edge cog V-belt according to any one of aspects [1] to [5] and a pulley, wherein the raw-edge cog V-belt is a variable speed belt used in a belt clutch-in type continuously variable transmission.

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

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

[0037] Aspect [9]: A method of using the raw-edge cog V-belt of any of aspects [1] to [5] in a belt clutch-in type continuously variable transmission, in which the belt is involved in any of continuously variable transmission, clutch, and brake.

[0038] In the present application, a numerical range expressed as "A to B" means "A or more and B or less," and is used in the sense that both the numerical values ​​A and B at the both ends are included. [Effects of the Invention]

[0039] In the present invention, a raw edge cog V-belt has a cog section, at least on the inner side, in which cog crests and cog valleys are arranged alternately in the longitudinal direction of the belt. 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 crests are formed flat, and the length of each top in the longitudinal direction of the belt is adjusted to 18 to 65% (e.g., 20 to 60%) of the cog pitch. This makes the belt applicable to the brake system of a belt clutch-in type continuously variable transmission, and also improves durability such as wear resistance. [Brief explanation of the drawings]

[0040] [Figure 1] FIG. 1 is a schematic diagram for explaining the transmission mechanism of a belt-type continuously variable transmission. [Figure 2] FIG. 2 is a schematic diagram showing the belt clutch-in type continuously variable transmission in an idling state. [Figure 3] FIG. 3 is a schematic, partially sectional perspective view showing an example of a raw-edge double-cogged V-belt according to the present invention. [Figure 4] FIG. 4 is a schematic cross-sectional view of the raw-edge double-cogged V-belt of FIG. 3 cut in the belt longitudinal direction. [Figure 5] FIG. 5 is an enlarged view of FIG. 4 for explaining the shape of the inner cog valley. [Figure 6] FIG. 6 is a diagram showing the layout of a testing machine used in a durability running test (Top durability test) of the raw-edge double-cogged V-belt obtained in the example. [Figure 7] FIG. 7 is a diagram showing the layout of a testing machine used in a durability running test (Low durability test) of the raw edge double cogged V-belt obtained in the example. [Figure 8] FIG. 8 is a schematic diagram comparing the cross-sectional shapes of the raw-edge double-cogged V-belts obtained in Examples 1 to 8 and Comparative Examples 1 to 5. [Figure 9] FIG. 9 is an FEM analysis diagram showing the state of cog interference that occurs when the raw-edge double-cogged V-belt obtained in Comparative Example 4 is bent. [Figure 10]FIG. 10 is a schematic diagram comparing the cross-sectional shapes of the raw-edge double-cogged V-belts obtained in Examples 9 to 21 and Comparative Examples 6 and 7. DETAILED DESCRIPTION OF THE INVENTION

[0041] [Structure of raw edge cog V-belt] In the raw-edge cogged V-belt of the present invention, the cogs formed on the inner periphery are formed from a compressed rubber layer and a fabric layer covering the inner periphery of the compressed rubber layer. In the present invention, the inner periphery of the compressed rubber layer is covered with a fabric layer, thereby improving wear resistance. Furthermore, among raw-edge V-belts, those used for CVTs require the highest level of lateral pressure resistance, and for this application, the compressed rubber layer must have higher rigidity than those used for other applications. Therefore, in CVT applications, forming the cogs in the compressed rubber layer, which is made of high-rigidity rubber and formed on the inner periphery, improves flexibility.

[0042] As described above, the raw-edge cog-shaped V-belt of the present invention is used in CVT applications, where cogs are essential on the inner periphery. Therefore, the only portions of the inner periphery (bottom) of the belt that come into contact with the pulley shaft are the cog crests. Therefore, in the raw-edge cog-shaped V-belt of the present invention, the crests are formed flat (flat along a plane perpendicular to the belt thickness direction). Furthermore, in the present invention, the length of the crests in the belt longitudinal direction is adjusted to 18% or more of the cog pitch, thereby increasing the area of ​​the V-belt's inner periphery that can come into contact with the outer periphery of the pulley shaft, ensuring frictional braking performance. Furthermore, in the present invention, the length of the crests in the belt longitudinal direction is adjusted to 65% or less of the cog pitch, ensuring braking performance without compromising the belt's flexibility or durability.

[0043] The raw-edge cogged V-belt of the present invention is not particularly limited as long as it has such a shape, and may be a raw-edge cogged V-belt in which cogs are formed only on the inner circumferential side of the raw-edge V-belt, or a raw-edge double-cogged V-belt in which cogs are formed on both the inner and outer circumferential sides of the raw-edge V-belt. Of these, raw-edge double-cogged V-belts are particularly preferred because they are used in more severe conditions, are required to have high levels of both lateral pressure resistance and flexural fatigue resistance, and provide the greatest effects of the present invention.

[0044] FIG. 3 is a schematic, partially sectional perspective view showing an example of a raw edge double cogged V-belt of the present invention, and FIG. 4 is a schematic sectional view of the raw edge double cogged V-belt of FIG. 3 cut in the belt longitudinal direction.

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

[0046] The outer circumferential surface also has an outer circumferential cog portion formed with outer circumferential cog peaks 1c and outer circumferential cog valleys 1d arranged alternately along the belt longitudinal direction, and the outer circumferential cog peaks 1c have a generally trapezoidal cross section in the belt longitudinal direction, and a generally rectangular cross section in the direction perpendicular to the belt longitudinal direction (the belt width direction or direction B in the figure). That is, each outer circumferential cog peak 1c protrudes from the outer circumferential cog valley 1d in the belt thickness direction in a generally trapezoidal shape in the cross section in direction A.

[0047] The raw edge double cog V-belt has a layered structure, in which a tension rubber layer 2, a core layer (adhesive rubber layer) 3, a compression rubber layer 4, and a fabric layer 5 are layered in this order from the outer periphery to the inner periphery of the belt. The cross section in the width direction of the belt is a generally inverted trapezoid shape, with the belt width decreasing from the outer periphery to the inner periphery of the belt. Furthermore, a core 3a is embedded within the core layer 3, and the inner cogs are formed in the compression rubber layer 4 covered with the fabric layer 5 using a cog-equipped molding die, and the outer cogs are formed in the tension rubber layer 2 using a cog-equipped molding die.

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

[0049] In the present invention, the apex 11 is formed flat (a flat shape having a surface approximately perpendicular to the belt thickness direction), thereby ensuring the friction area with the pulley shaft portion and thereby ensuring the friction force. As shown in FIG. 4, the ratio (proportion) of the length L of the apex (flat apex) 11 to the inner cog pitch P is an index of the area of ​​the flat shape (flat portion) of the apex 11 for ensuring the friction force.

[0050] In other words, when there are no cogs on the inner peripheral surface of the belt, the concept of "cog pitch" equals "circumferential length of the flat portion," and the area of ​​the flat portion is maximized. However, in the present invention, since cogs are essential, the area of ​​the flat portion cannot be maximized; the provision of cogs (valleys) results in loss of flat surfaces, reducing the area of ​​the flat portion. The ratio of the area of ​​the remaining flat portion when the maximum area is set to 100 is an index of the area of ​​the flat portion, and has the same meaning as "the ratio (proportion) of the circumferential length of the flat tops of the cog ridges to the cog pitch."

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

[0052] On the other hand, from the perspective of ensuring braking performance (frictional force on the inner peripheral surface), it is preferable to maximize the area of ​​the inner peripheral surface of the V-belt that can come into contact with the outer peripheral surface of the pulley shaft (i.e., the inner peripheral flatness ratio). Increasing the contact area with the pulley shaft requires narrowing the inner peripheral cog pitch to increase the number of cogs, or reducing the cog angle to increase the inner peripheral flatness ratio. However, these methods result in a smaller cog (recess) width. On the other hand, if the cog (recess) width is made too small, the cogs will interfere with each other during bending, hindering flexibility, and the increased stress generated in the cog valleys will make them more susceptible to cracking. Premature cog valley cracking will shorten the durability life.

[0053] In other words, in the braking system of a belt clutch-in type continuously variable transmission, the expression of braking function and durability (resistance to cog valley cracks) are in a trade-off relationship, so the area of ​​the inner circumferential surface of the belt must be set within a range that is appropriate for achieving both.

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

[0055] The inner cog pitch P is, for example, 6 to 17 mm, preferably 7 to 15 mm, further preferably 8 to 14 mm, even more preferably 9 to 13 mm, and most preferably 10 to 12.5 mm. If the inner cog pitch P is too small, the cogs (recesses) may not be sufficiently secured, which may result in impaired flexibility, while if it is too large, the inner circumferential flatness may decrease, which may result in insufficient braking performance (frictional force on the inner circumferential surface).

[0056] 4 and 5, in this example, the cross-sectional shape of the cog valley 1b includes a bottom portion 13 formed by combining three arcs, a first arc 13a and a pair of second arcs 13b, 13b, and sidewall portions 12, 12 extending from the bottom portion 13 and inclined at a cog angle θ (the inclination angle of one sidewall) in a direction in which the diameter of the cog valley 1b increases inward relative to the belt thickness direction (the direction indicated by the dashed line in FIGS. 4 and 5). As shown in FIGS. 4 and 5, when the raw edge cogged V-belt 1 is not bent, the radii of curvature of the multiple arcs (first arc 13a and second arc 13b) that make up the bottom portion 13 decrease with increasing distance from the deepest portion A of the cog valley 1b.

[0057] Specifically, the first arc 13a is represented by a circle C1 having a center O1 on a vertical line VL (belt thickness direction) perpendicular to the belt longitudinal direction, but is formed with a larger diameter than an imaginary circle VC (dotted circle with a curvature radius R0 in FIG. 5) which has a center O0, passes through the deepest part A of the cog valley 1b, and is tangent to the deepest part A of the cog valley 1b and both side wall parts 12 at three points (a total of three points: the deepest part A and the contact points B on the pair of side wall parts). Note that in the present application, when an arc whose base is formed by a single arc is defined as an imaginary circle, the circle equivalent to this imaginary arc is referred to as an imaginary circle.

[0058] 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 cog valley is not limited to a shape combining a first circular arc and a pair of second circular arcs, and may be a shape formed by a single circular arc. However, from the viewpoint of improving durability (resistance to cog valley cracking), a shape combining multiple consecutive circular arcs is preferred, and a shape combining a first circular arc and a pair of second circular arcs is particularly preferred.

[0060] When the bottom of the cog valley is formed by combining multiple consecutive 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 make the radius of curvature smaller as the distance from the deepest part increases. By using such multiple arcs, stress at the bottom of the cog valley, where stress due to bending deformation tends to concentrate, is alleviated and dispersed, thereby suppressing the occurrence of cracks in the cog valley. Furthermore, compared to when the bottom is formed by a single arc (corresponding to a virtual arc), the length of the cog portion in the circumferential direction of the belt (the length of the flat top) can be increased, ensuring a larger contact area with the pulley shaft.

[0061] The radius of curvature R1 of the first circular arc is, for example, 1 to 5 mm, preferably 1.5 to 4.8 mm (e.g., 1.5 to 4.5 mm), even more preferably 2 to 4.7 mm (e.g., 2 to 4 mm), even 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 be reduced, while if it is too large, the inner periphery flatness may be reduced, making it difficult to ensure sufficient braking performance (frictional force on the inner periphery). The range of the radius of curvature R1 of these first circular arcs may be the range of the radius of curvature of a single circular arc forming the bottom of the cog valley.

[0062] The radius of curvature R2 of the second circular arc is, for example, 0.1 to 3 mm, preferably 0.15 to 2 mm, further preferably 0.2 to 1.5 mm, even 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, there is a risk that the flex resistance will decrease and durability will decrease, while if it is too large, there is a risk that the inner periphery flatness will decrease and sufficient braking performance (friction force on the inner periphery surface) will not be ensured.

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

[0064] The cog angle θ of the sidewall portion may be 30° or less (particularly 25° or less), for example 20° or less, preferably 15° or less (e.g., 1 to 15°), further preferably 12° or less (e.g., 3 to 12°), and even more preferably 10° or less (e.g., 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 rate decreases, and there is a risk that sufficient braking performance (friction force on the inner circumference surface) cannot be ensured.

[0065] In the raw-edge cog V-belt of the present invention, the intersections between the flat crests 11 and the sidewalls 12 are preferably chamfered with a radius of 0.5 mm to 2.0 mm or rounded with a radius of 0.5 mm to 2.0 mm to prevent chipping of the edges. In the present invention, the inner circumferential flatness may be adjusted by chamfering the intersections with a radius of 0.5 mm to 2.0 mm. For example, in the case of rounded chamfers, the radius of curvature R3 of the rounded chamfer may be adjusted within the aforementioned range (0.5 to 2.0 mm). That is, the radius of curvature R3 may be increased to decrease the inner circumferential flatness, or decreased to increase the inner circumferential flatness. Furthermore, in the present invention, the inner circumferential flatness may be adjusted by combining adjustment of the radius of curvature R1, the radius of curvature R2, or the cog angle θ with adjustment of the radius of curvature R1 or R2.

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

[0067] The overall belt 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, further preferably 13 to 18 mm, and even more preferably 14 to 17 mm. If the thickness is too small, there is a risk of reduced lateral pressure resistance, whereas if the thickness is too large, there is a risk of reduced flexibility, resulting in reduced power transmission efficiency and reduced resistance to bending fatigue.

[0068] 4, in the present application, when the compression rubber layer 4 and the tension rubber layer 2 have cogs, the overall belt thickness H refers to the thickness at the top of the cog (maximum belt thickness). 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 cog (top on the inner periphery) of the fabric layer 5 to the top of the cog (top on the outer periphery) of the tension rubber layer 2.

[0069] In addition, in this application, the inner cog valley of the inner cog portion means the portion that forms the thin-walled portion of the fabric layer and compression rubber layer having the inner cog portion, and usually means a curved valley or groove portion (curved groove portion) located between adjacent inner cog peaks that protrude toward the inner periphery of the belt.

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

[0071] The inner circumferential valley thickness H2 on the inner surface (the shortest distance from the central axis of the core wire to the deepest part of the inner circumferential cog valley in the belt thickness direction) may be selected, for example, from the range of 2 to 7 mm, preferably 3 to 5 mm, and the outer circumferential valley thickness H3 on the outer circumferential surface (the shortest distance from the central axis of the core wire to the deepest part of the outer circumferential cog valley in the belt thickness direction) may be selected, for example, from the range of 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 depending on the design circumstances of the belt transmission mechanism. Typically, the upper width (belt width on the outer circumferential side) of the belt width can be selected, for example, from a range of 20 to 50 mm, and preferably from 30 to 44 mm. The V-angle, which is the angle of the V-shaped side surface, can be selected, for example, from a range of 20 to 35°, and preferably from 24 to 32°.

[0073] [Compressed rubber layer] In the raw-edge cogged V-belt of the present invention, the compressed rubber layer main 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 may be used alone or in combination.

[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, oil resistance, etc. and high productivity.

[0076] When the first rubber component contains chloroprene rubber, the proportion of the chloroprene rubber in the first rubber component may be 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more (particularly 90 to 100% by mass), and most preferably 100% by mass (chloroprene rubber only), in order to improve the above-mentioned properties and productivity. When the first rubber component contains an ethylene-α-olefin elastomer, the proportion of the ethylene-α-olefin elastomer in the first rubber component is the same as the proportion of the chloroprene rubber.

[0077] (A2) First short fiber The rubber composition forming the compressed rubber layer may further contain first staple fibers. Examples of the first staple fibers include synthetic staple fibers such as polyamide staple fibers (aliphatic polyamide staple fibers such as polyamide 6 staple fibers, polyamide 66 staple fibers, and polyamide 46 staple fibers, and aramid staple fibers), polyalkylene arylate staple fibers (e.g., polyethylene terephthalate (PET) staple fibers and polyethylene naphthalate staple fibers), liquid crystal polyester staple fibers, polyarylate staple fibers (e.g., amorphous wholly aromatic polyester staple fibers), vinylon staple fibers, polyvinyl alcohol staple fibers, and polyparaphenylene benzobisoxazole (PBO) staple fibers; natural staple fibers such as cotton, hemp, and wool; and inorganic staple fibers such as carbon staple fibers. These first staple fibers can be used alone or in combination. Among these, aramid staple fibers and PBO staple fibers are preferred, and aramid staple fibers are particularly preferred.

[0078] The first short fibers may be short fibers obtained by cutting stretched fibers to a predetermined length. The first short fibers are preferably oriented in the belt width direction and embedded in the main body of the compressed rubber layer to suppress compressive deformation of the belt due to lateral pressure from the pulleys (to increase lateral pressure resistance). Furthermore, it is preferable to have the short fibers protrude from the surface of the compressed rubber layer, since this reduces the coefficient of friction of the surface that comes into contact with the pulleys, thereby suppressing noise and reducing wear due to friction with the pulleys.

[0079] The average fiber length of the first short fibers is, for example, 0.1 to 20 mm, preferably 0.5 to 15 mm (e.g., 0.5 to 10 mm), and more preferably 1 to 6 mm (particularly 2 to 4 mm), from the viewpoint of improving 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 grain direction may not be sufficiently improved, which may reduce lateral pressure resistance and abrasion resistance. Conversely, if the fiber length is too long, the orientation of the short fibers in the rubber composition may be reduced, which may reduce flexibility.

[0080] The single fiber 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), so as to provide a high reinforcing effect without reducing flexibility. If the single fiber fineness is too large, the lateral pressure resistance and abrasion resistance per blend amount may decrease, while if the single fiber fineness is too small, the dispersibility in rubber may decrease, resulting in reduced flexibility.

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

[0082] The proportion of the first short fibers relative to 100 parts by mass of the first rubber component is, for example, 5 to 50 parts by mass, preferably 5 to 40 parts by mass (e.g., 8 to 35 parts by mass), further preferably 10 to 30 parts by mass, and further preferably 15 to 25 parts by mass. If the amount of the first short fibers is too small, the lateral pressure resistance and abrasion resistance may decrease, whereas if the amount is too large, the processability may decrease and the flexibility of the belt may decrease, resulting in a decrease in 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 (reinforcing fillers) such as carbon black and silicon oxide (hydrated silica, etc.); extenders (non-reinforcing fillers or inert fillers) such as clay, calcium carbonate, talc, and mica, etc.], plasticizers (or softeners), and the like. Examples of additives include 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, and ether ester plasticizers), processing agents or processing aids (such as stearic acid, metal stearates, waxes, paraffins, and fatty acid amides), antioxidants (such as antioxidants, heat-resistant agents, flex crack inhibitors, and antiozonants), adhesion improvers, colorants, tackifiers, coupling agents (such as silane coupling agents), stabilizers (such as ultraviolet absorbers and heat stabilizers), flame retardants, and antistatic agents. These additives can be used alone or in combination. Metal oxides may also function as crosslinking agents.

[0084] The proportion of the filler (first filler) such as carbon black or silica relative to 100 parts by mass of the first rubber component is, for example, 10 to 200 parts by mass, preferably 20 to 100 parts by mass, further preferably 30 to 80 parts by mass, and further preferably 40 to 70 parts by mass.

[0085] The proportion of the plasticizer (first plasticizer) may be 10 parts by mass or less, 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, per 100 parts by mass of the first rubber component. If the proportion of the plasticizer is too high, the compression rubber layer may become too soft, resulting in a decrease in lateral pressure resistance.

[0086] The total proportion of the other components (A3) relative to 100 parts by mass of the first rubber component is, for example, 5 to 300 parts by mass, preferably 10 to 200 parts by mass, further preferably 30 to 150 parts by mass, and even more preferably 50 to 100 parts by mass.

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

[0088] In this application, the rubber hardness of each rubber layer indicates the value Hs (Type A) measured using a Type A durometer in accordance with the spring type durometer hardness test specified in JIS K 6253 (2012) (Vulcanized rubber and thermoplastic rubber - Determination of hardness), and may be simply 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 in the belt width direction is, for example, 25 to 50 MPa, preferably 30 to 40 MPa, and more preferably about 30 to 35 MPa. If the tensile strength is too low, there is a risk that the lateral pressure resistance will decrease, whereas if it is too high, there is a risk that the flexibility will be insufficient and the durability (cog valley crack resistance) will decrease.

[0090] In the present application, the tensile strength of each rubber layer is measured by a method in accordance with JIS K 6251 (2017), and the value of the tensile strength T of each rubber layer is used as an index value of the tensile strength. In detail, the measurement can be performed by the method described in the examples below.

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

[0092] [Fabric layer] In the present invention, the inner peripheral surface of the compressed rubber layer 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 a conventional fabric.

[0093] Examples of conventional fabrics include woven fabrics, knitted fabrics (weft-knitted fabrics and warp-knitted fabrics), nonwoven fabrics, and the like. Of these, woven fabrics such as plain weave, twill weave, and satin weave, and woven and knitted fabrics with a crossing angle of more than 90° and not more than about 120° are preferred, and woven fabrics commonly used as cover fabrics for transmission belts in general industry and agricultural machinery [plain weave fabrics with a crossing angle of right angles, and plain weave fabrics (wide-angle canvas) with a crossing angle of more than 90° and not more than about 120°] are particularly preferred. Furthermore, for applications requiring durability, the fabric may be wide-angle canvas.

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

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

[0096] Examples of para-aramid fibers include polyparaphenylene terephthalamide fibers (e.g., Twaron (registered trademark) from Teijin Limited, Kevlar (registered trademark) from Toray DuPont Co., Ltd., etc.), and copolymer fibers of polyparaphenylene terephthalamide and 3,4'-oxydiphenylene terephthalamide (e.g., Technora (registered trademark) from Teijin Limited, etc.).

[0097] Examples of meta-aramid fibers include polymetaphenylene isophthalamide fibers (such as "Conex (registered trademark)" from Teijin Limited).

[0098] These aramid fibers can be used alone or in combination of two or more kinds. Among 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 ply) is preferred.

[0100] If necessary, the fabric layer may be subjected to an adhesive treatment, such as a treatment with an RFL liquid (dipping treatment, etc.), a friction treatment in which adhesive rubber is rubbed into the fabric, or the adhesive rubber and the fabric may be laminated together, and then laminated or embedded in a laminated form in a compressed rubber layer.

[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, the fabric may wear out prematurely, making it difficult to ensure sufficient braking performance, while if it is too thick, flexibility may decrease.

[0102] [Tension rubber layer] The raw-edge cogged V-belt of the present invention may further include a tension rubber layer formed of a rubber composition (crosslinked rubber composition) containing a second rubber component.

[0103] The second rubber component, including preferred embodiments, can be selected from the rubber components exemplified as the first rubber component. The second rubber component may be a rubber component different from the first rubber component, but is usually the same as the first rubber component.

[0104] The rubber composition forming the tension rubber layer also preferably contains second short fibers, as this can further improve lateral pressure resistance and abrasion resistance. When the second short fibers are contained as short fibers not only in the compression rubber layer but also in the tension rubber layer, the lateral pressure resistance and abrasion resistance are further improved. The second short fibers, including preferred embodiments, can be selected from the short fibers exemplified as the first short fibers. The second short fibers may be different from the first short fibers, but are usually the same as the first short fibers. The proportion of the second short fibers, including preferred proportions, can be selected from the proportion of the first short fibers.

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

[0106] The properties of the tension rubber layer, including the preferred ranges, can be selected from the properties of the compression rubber layer (hardness, tensile strength, coefficient of friction, etc.) described above.

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

[0108] [Core layer] The core layer need only contain a core, and may be a core layer formed only of a core, but from the viewpoint of suppressing interlayer delamination and improving belt durability, it is preferably a core layer (adhesive rubber layer) formed of a crosslinked rubber composition with a core embedded therein. The adhesive rubber layer is interposed between the tension rubber layer and the main body of the compression rubber layer to bond the tension rubber layer and the 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, including preferred embodiments, can be selected from the rubber components exemplified as the first rubber component. The third rubber component may be a rubber component different from the first rubber component, but is usually the same as the first rubber component.

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

[0112] The adhesive rubber layer preferably has a lower rubber hardness than the compressed rubber layer. The rubber hardness of the adhesive rubber layer is, for example, 60 to 85°, preferably 65 to 84°, further preferably 70 to 83°, and even more preferably 75 to 82°. If the rubber hardness is too low, there is a risk that the resistance to lateral pressure will be insufficient, while if it is too high, there is a risk that the adhesiveness will decrease. By adjusting the adhesive rubber layer to such a low hardness, it becomes possible for it to deform significantly when shear stress is applied, and peeling between the core and the compressed rubber layer and the tension 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, a core wire (twisted cord) arranged at a predetermined interval in the belt width direction can be used. The core wire is arranged extending in the belt longitudinal direction, and although multiple core wires parallel to the belt longitudinal direction may be arranged, from the viewpoint of productivity, the core wires are typically arranged in a spiral shape extending parallel to the belt longitudinal direction of raw-edge cogged V-belts at a predetermined pitch. When arranged in a spiral shape, the angle of the core wire 18 with respect to the belt longitudinal direction may be, for example, 5° or less, and from the viewpoint of belt running performance, an angle closer to 0° is preferable. The core wire pitch is preferably set in the range of 1.5 to 2.5 mm, more preferably in the range of 1.8 to 2.2 mm. The core wire pitch is the distance between the centers of adjacent core wires.

[0115] The core wires may be embedded in the adhesive rubber layer, embedded between the adhesive rubber layer and the tension rubber layer, or embedded between the adhesive rubber layer and the compression rubber layer, as long as at least a portion of the core wires is in contact with the adhesive rubber layer. Of these, the core wires are preferably embedded in the adhesive rubber layer in view of improving durability.

[0116] Examples of fibers constituting the core wire include the fibers exemplified as the fibers constituting the first short fibers. Among the above fibers, C fibers such as ethylene terephthalate and ethylene-2,6-naphthalate are preferred in terms of high modulus. 2-4 Alkylene-C 6-12 Polyester fibers (polyalkylene arylate fibers) having arylate as the main structural 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 be multifilament yarns. The multifilament yarns may contain, for example, 100 to 5,000 monofilament yarns, preferably 500 to 4,000 monofilament yarns, and more preferably about 1,000 to 3,000 monofilament yarns.

[0117] The core wire can usually be a twisted cord (e.g., double twist, single twist, Lang twist, etc.) using multifilament yarn. The average wire 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, 2,000 to 17,000 dtex, preferably 4,000 to 15,000 dtex, and more preferably 5,000 to 13,000 dtex (particularly about 6,000 to 8,000 dtex).

[0118] The core wires may be subjected to an adhesive treatment (or surface treatment) in the same manner as the first short fibers in order to improve adhesion to the rubber component. The core wires are preferably subjected to an adhesive treatment with at least an RFL liquid.

[0119] [Reinforcing fabric] The raw-edge cogged V-belt of the present invention may include a reinforcing fabric, which may be laminated on the outer peripheral surface of the tension rubber layer or embedded in the tension rubber layer, for example.

[0120] The reinforcing fabric may be made of a conventional fabric. Examples of conventional fabrics include the fabrics exemplified for the fabric layer. If necessary, the reinforcing fabric may also be subjected to an adhesion treatment, such as treatment with an RFL liquid (dipping treatment, etc.), or a friction treatment in which adhesive rubber is rubbed into the fabric, or the adhesive rubber and the fabric may be laminated together and then laminated or embedded in a compressed rubber layer.

[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 cog V-belts] The method for manufacturing the raw edge cogged V-belt of the present invention is not particularly limited, and for the lamination process of each layer (the method for manufacturing the belt sleeve), a conventional method can be used depending on the type of belt.

[0123] A typical manufacturing method for a raw-edge cog V-belt is described below. First, a laminate of a fabric layer precursor and a compression rubber layer sheet (uncrosslinked rubber sheet) is placed, with the fabric layer precursor facing downward, in contact with a flat cog mold in which teeth and grooves corresponding to the inner cogs are alternately arranged. Pressing is performed at a temperature of 60 to 120°C (particularly 80 to 100°C) to produce a cog pad (a pad that is not completely crosslinked, but is in a semi-crosslinked state) with the inner cogs shaped. Then, both ends of this cog pad are cut vertically from appropriate locations (particularly the tops of the cog peaks) to obtain the required length.

[0124] Next, an inner mold having alternating tooth and groove portions corresponding to the inner cog portion is placed over the outer periphery of the cylindrical mold, and a cog pad is wrapped around it by engaging the tooth and groove portions of the inner mold and joining both ends (particularly the tops of the cog crests).A sheet for the first adhesive rubber layer (lower adhesive rubber: uncrosslinked rubber sheet) is then laminated around the outer periphery of this cog pad, and the core wire (twisted cord) that forms the core body is spun spirally, and a sheet for the second adhesive rubber layer (upper adhesive rubber: uncrosslinked rubber sheet) and a sheet for the tension rubber layer (uncrosslinked rubber sheet) are sequentially wrapped around the outer periphery to produce an uncrosslinked molded body.

[0125] The uncrosslinked molded body is then placed in a known crosslinking device (such as a vulcanizer) with the jacket on, and crosslinked at a temperature of 120 to 200°C (particularly 150 to 180°C) to produce a crosslinked belt sleeve.Then, using a cutter or the like, the crosslinked belt sleeve is cut into a V shape to obtain an endless raw-edge cog V-belt.

[0126] In the case of a raw-edge double-cogged V-belt, an outer mold having teeth and grooves corresponding to the outer cogs arranged alternately is placed on the outer periphery of the uncrosslinked molded body, and then a jacket is placed over the uncrosslinked molded body and crosslinked molding is performed to obtain a crosslinked belt sleeve having outer cogs also formed on the outer periphery, which is then cut into a V shape to obtain a raw-edge double-cogged V-belt.

[0127] The adhesive rubber layer can be formed from multiple adhesive rubber layer sheets, and the core wire (twisted cord) that forms 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. [Example]

[0128] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Details of the materials used in the examples, the method for producing an uncrosslinked rubber sheet, and the method for measuring or evaluating each physical property are shown below.

[0129] [Materials used] Chloroprene rubber: DENKA Corporation "PM-40" Magnesium oxide: Kyowa Mag 30 manufactured by Kyowa Chemical Industry Co., Ltd. Stearic acid: "Camellia Stearate" 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 m 2 / g Plasticizer 1: Naphthenic oil, "NS-900" manufactured by Idemitsu Kosan Co., Ltd. Plasticizer 2: ADEKA Corporation "RS-700" Crosslinking accelerator: tetramethylthiuram disulfide ("Noccela TT" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Zinc oxide: "Zinc oxide type 3" manufactured by Seido Chemical Industry Co., Ltd. Sulfur: "Sulfur" manufactured by Bigen Chemical Co., Ltd. N,N'-m-Phenylenedimaleimide: "Valnoc PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Resorcinol-formalin copolymer (resorcinol resin): Resorcinol-formalin 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 staple fiber: Teijin Co., Ltd.'s "Conex staple fiber," average fiber length 3 mm, average fiber diameter 14 μm, staple fiber with a solid adhesion rate of 6 mass% that was adhesively treated with RFL liquid (resorcinol 2.6 mass parts, 37% formalin 1.4 mass parts, vinylpyridine-styrene-butadiene copolymer latex (Zeon Corporation) 17.2 mass parts, water 78.8 mass parts). Core: A 2x3 twisted cord of 1100 dtex aramid fiber with a top twist coefficient of 3.0 and a bottom twist coefficient of 3.0, totaling 6600 dtex, and then adhesively treated (core diameter 1.28 mm). Fabric (reinforced fabric): Aramid canvas (thickness 0.30-0.50mm) adhesively treated with RFL liquid

[0130] [Preparation of uncrosslinked rubber sheet for rubber layer] The rubber compositions for forming the compression rubber layer, tension rubber layer, and adhesive rubber layer were prepared according to the compounding ratios shown in Table 1 below. The rubber compositions for forming each layer were kneaded using a Banbury mixer, and the resulting kneaded rubber was passed through a calendar roll to produce a rolled rubber sheet (uncrosslinked rubber sheet). In this specification, each rubber composition will be designated as R1 to R7.

[0131] [Table 1]

[0132] [Rubber hardness Hs of cross-linked rubber] The 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 thick). Three crosslinked rubber sheets were stacked to form a laminate, which was used as a sample. The hardness of the crosslinked rubber sheets was measured using a Type A durometer in accordance with the spring 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 (size 5) test specimens were prepared according to JIS K 6251 (2017). For samples containing short fibers, dumbbell-shaped test specimens were prepared so that the orientation direction of the short fibers (grain direction) was the tensile direction. Both ends of the test specimen were gripped with chucks (gripping tools), and the test specimen was pulled at a speed of 500 mm / min until it broke. The maximum tensile force recorded when the specimen was pulled by the initial cross-sectional area of ​​the test specimen was used as the tensile strength (T).

[0134] [Manufacturing raw edge double cog V-belts] Using the method described in the above embodiment, a raw-edge double-cogged V-belt (size: upper 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 valley thickness (H2) 4.5 mm, belt outer circumference length 1158 mm, V angle 26°) was produced.

[0135] [Analysis using the 3D finite element method (FEM)] Based on the method described in the examples of Japanese Patent No. 7256249, a three-dimensional finite element model was created for the obtained raw-edge double-cogged V-belt (two types: one with no tension and one with 1000 N tension applied). This model was used to check whether interference between adjacent cogs (cog interference) occurred when the belt was bent. Furthermore, when no cog interference occurred, analysis was performed using the finite element model to calculate the maximum value of the Mises stress generated at the deepest part of the inner cog valley. On the other hand, when cog interference occurred, the following evaluation of the raw-edge double-cogged V-belt was not performed.

[0136] [Raw Edge Double Cogged V-Belt Evaluation] (1) Endurance driving test (Top endurance test) Tests to confirm cog valley crack resistance (flex fatigue resistance) were conducted using a biaxial running test machine 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, as shown in Figure 6. A raw-edge double-cogged V-belt was hung on each pulley, and the drive pulley was set to a rotation speed of 6,000 rpm, with an axle load (deadweight) of 1.2 kN, and a load of 60 Nm was applied by a loading device (power generator) at an ambient temperature of 115°C. The running life was measured as the running time until a crack that had appeared in the cog valley reached the core wire and the belt's life expired.

[0137] (Criteria for endurance driving test (Top endurance test)) A: Running life is 130 hours or more (passed) b: Running life is 110 hours or more but less than 130 hours (pass) c: Running life is less than 110 hours (failed)

[0138] (2) Endurance driving test (Low endurance test) Tests to confirm resistance to core wire peeling (side pressure resistance) were conducted using a biaxial 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, as shown in Figure 7. A low-edge double-cogged V-belt was hung on each pulley, and the drive pulley was set to a rotation speed of 5,000 rpm, with an axle load (dead weight) of 2.2 kN, and a load of 50 Nm was applied by a loading device (power generator) at an ambient temperature of 60°C. The running time until core wire peeling occurred was measured as the running life.

[0139] (Durability test (Low durability test) criteria) A: Running life is 30 hours or more (passed) b: Running life is 10 hours or more but less than 30 hours (pass) c: Running life is less than 10 hours (failed)

[0140] (3) Braking performance test (engine braking performance on an actual vehicle) A low-edge double-cogged V-belt was fitted to the CVT of a 1,000cc four-wheeled buggy (off-road vehicle) and a real-world test was conducted. While the vehicle was running, the throttle was released from maximum speed and the time it took for the rotation speed of the driven pulley to drop from 478 rpm to 0 rpm was measured without applying the brakes.

[0141] (Brake performance test criteria) a: Time until the rotation speed reaches 0 rpm is 7 seconds or less (pass) b: Time until the rotation speed reaches 0 rpm is over 7 seconds and less than 8 seconds (pass) c: Time until the rotation speed reaches 0 rpm exceeds 8 seconds (failed)

[0142] (4) Braking durability test (engine braking durability in an actual vehicle) The vehicle on which the braking performance test was performed was driven 500 miles on a rough road (off-road), and then the braking performance was confirmed using the method described in the braking performance test. Braking durability was evaluated based on the following criteria, from the perspective of whether the braking performance after 500 miles of driving maintained a high level of the initial braking performance (before 500 miles of driving) or whether the level had deteriorated. Note that if the braking performance test was failed (evaluated as C), the braking durability test was not performed.

[0143] (Criteria for braking durability test) A: High level of braking performance before and after 500 miles of driving (maintained as A rating) b: Braking performance after 500 miles is graded b (decreased from grade a to grade b, then remained grade b) C: Braking performance after 500 miles is graded C (deterioration from grade A or B to grade C)

[0144] (5) Overall Judgment Based on the results of the endurance driving tests (Top endurance test, Low endurance test), braking performance test, and braking durability test, the products were judged (ranked) based on the criteria shown in Table 2, from the perspective of demonstrating braking performance while maintaining the required levels of flex fatigue resistance (cog valley crack resistance) and lateral pressure resistance (core wire peeling resistance) for a transmission belt. From the perspective of product practicality, products were rated as passing (A, B, or C) and failing (D). If cog interference was confirmed in the FEM analysis, the overall rating was determined to be D (failure).

[0145] [Table 2]

[0146] <Belt with cog pitch of 11.8 mm (Comparative Examples 1 to 5 and Examples 1 to 8)> [Comparative Example 1] A belt was produced with an inner cog pitch of 11.8 mm and a 2.3 mm radius of curvature for the arc forming the bottom of the inner cog valley, in which the cog peaks were curved (arcs with a 2.8 mm radius of curvature) and no flat peaks were formed.

[0147] Comparative Example 2 A belt was produced in which the inner cog crests were provided with flat peaks measuring 1.1 mm in the circumferential direction, adjusting the inner circumferential flatness to 9%, in contrast to the belt of Comparative Example 1. The arcs forming the bottoms of the cog valleys were formed as two consecutive arcs (the deepest first arc R1 = 3.9 mm, and the pair of second arcs R2 = 1.0 mm) based on a virtual arc R0 = 2.5 mm.

[0148] Comparative Example 3 In comparison with Comparative Example 2, the radius of curvature of the cog crest R chamfer was reduced to R3 = 2.1 mm, the circumferential length of the flat top was increased to 1.8 mm, and a belt was produced in which the inner circumference flatness rate was adjusted to 15%.

[0149] [Example 1] In comparison with Comparative Example 2, the radius of curvature of the cog crest R chamfer was reduced to R3 = 1.8 mm, and the circumferential length of the flat top was adjusted to 2.4 mm, resulting in a belt with an inner circumference flatness rate adjusted to 20%.

[0150] [Example 2] In contrast to Comparative Example 2, a belt was produced 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, in which the inner circumference flatness ratio was adjusted to 38%, a belt was produced in which the radius of curvature of the first arc, the deepest of two consecutive arcs based on the virtual arc radius of curvature R0 = 2.5 mm, which forms the bottom of the cog valley, was changed to R1 = 3.0 mm.

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

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

[0154] [Example 6] In comparison with Example 2, the radius of curvature of the virtual arc that forms the two consecutive arcs that form the bottom of the cog valley (the radius of curvature of the deepest first arc R1 = 3.9 mm, and the radius of curvature of the pair of second arcs R2 = 1.0 mm) was reduced to R0 = 1.1 mm, and the cog angle was changed to θ = 20°, to produce a belt with an inner circumference flatness rate adjusted to 38%.

[0155] [Example 7] In comparison with Example 2, 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° to produce a belt with an inner circumference flatness rate adjusted to 38%.

[0156] [Example 8] In comparison with 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 producing a belt with an inner circumference flatness rate increased to 60%.

[0157] Comparative Example 4 In comparison with 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 producing a belt with an inner circumference flatness rate increased to 67%.

[0158] Comparative Example 5 A belt was produced in the same manner as in Example 2, except that no fabric layer was provided to cover the inner peripheral surface of the belt.

[0159] The evaluation results of the belts obtained in Comparative Examples 1 to 5 and Examples 1 to 8 are shown in Table 3. The schematic cross-sectional shapes of the belts obtained in the Comparative Examples and Examples are shown in FIG.

[0160] [Table 3]

[0161] The belt of Comparative Example 1 had small stress in the cog valleys and was rated a for durability (cog valley crack resistance), but had no flat portions and was rated c for engine braking performance, resulting in an overall rating of D.

[0162] The belts of Comparative Examples 2 and 3 generated less stress in the cog valleys than Comparative Example 1, and their durability (resistance to cog valley cracking) was rated A. However, because the inner circumference flatness rate was small at 9% (Comparative Example 2) and 15% (Comparative Example 3), their engine braking performance was rated C, and their overall rating was D.

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

[0164] Furthermore, the belt of Example 2 generated less stress in the cog valleys, resulting in durability (cog valley crack resistance) being rated a, and the inner circumference flatness rate was increased to 38%, so engine braking performance was improved to a rating, and engine braking durability was also good (rated a), resulting in an overall rating of A rank.

[0165] In Example 2, in which the inner circumference flatness ratio was increased to 38%, results equivalent to those of Example 2 were obtained in Examples 3 (R1 = 3.0 mm), 4 (R1 = 4.0 mm), and 5 (R1 = 4.5 mm), 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 = 2.5 mm was changed as the arc forming the bottom of the cog valley.

[0166] In Example 6, the radius of curvature of the virtual arc that forms 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 periphery flatness to 38%), compared to Example 2, in which the inner periphery flatness was increased to 38%. The engine braking performance was rated a, but the durability (cog valley crack resistance) was reduced to b due to increased stress in the cog valley, resulting in an overall rating of B. Furthermore, in Example 7, 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 periphery flatness to 38%), the engine braking performance was rated a, but the durability (cog valley crack resistance) was reduced to c due to increased stress in the cog valley, resulting in an overall rating of C.

[0167] On the other hand, in Example 8, where the radius of curvature R0 of the virtual arc and the cog angle θ were reduced (R0 = 1.5 mm, θ = 4°) to increase the inner circumference flatness ratio to 60%, the stress generated in the cog valleys was small, and durability (cog valley crack resistance) and engine braking performance were both rated "A," resulting in an overall rating of "A." However, in Comparative Example 4, where the radius of curvature R0 of the virtual arc and the cog angle θ were further reduced (R0 = 1.4 mm, θ = 1°) to increase the inner circumference flatness ratio to 67%, FEM analysis confirmed interference between adjacent cog portions (cog interference) when the belt was bent, resulting in a rating of "D" (failure). Figure 9 shows an FEM analysis diagram showing interference between the inner cog portions of the raw-edge double-cogged V-belt obtained in Comparative Example 4. As is clear from Figure 9, the upper inner cog portion of the belt in Comparative Example 4 is deformed by bending, causing adjacent inner cog portions to come into contact with each other.

[0168] From the above results, the belts of Examples 1 to 8, which had an inner circumference flatness ratio of 20 to 60%, were ranked A, B, or C, which are acceptable levels from the viewpoint of product practicality. Setting the inner circumference flatness ratio within this range is suitable for achieving both "expression of braking function" and "durability (resistance to cog valley cracks)," which are in a trade-off relationship.

[0169] In addition, compared to the belt of Example 2, which had an inner circumference flatness rate of 38% and received an overall rating of A, the belt of Comparative Example 5, which did not have a fabric layer covering the inner circumference surface of the belt, had braking performance rated A at the beginning of the run (before 500 miles of running), but after the run, it deteriorated to a level of C, resulting in a rating of C for engine braking durability. Furthermore, durability (cog valley crack resistance) also deteriorated to a level of C. As a result, the overall rating was D. These results demonstrate that the fabric layer covering the inner circumference surface of the belt is effective in terms of engine braking durability and durability (cog valley crack resistance).

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

[0171] [Example 9] In comparison with Comparative Example 6, the radius of curvature of the cog crest R chamfer was reduced to R3 = 2.0 mm, and the circumferential length of the flat top was adjusted to 1.9 mm, resulting in a belt with an inner circumference flatness rate adjusted to 20%.

[0172] [Example 10] In comparison with Comparative Example 6, the radius of curvature of the cog crest R chamfer was reduced to R3 = 0.5 mm, and the circumferential length of the flat top was adjusted to 4.6 mm, resulting in a belt with an inner circumference flatness rate adjusted to 48%.

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

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

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

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

[0177] [Example 15] In Example 10, in which the inner periphery flatness ratio was adjusted to 48%, a belt was produced in which the radius of curvature of the first circular arc was changed to R1=3.9 mm.

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

[0179] [Example 17] In comparison with Example 10, the radius of curvature of the virtual arc that forms 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 was changed to R2 = 1.0 mm, resulting in a belt with an inner circumference flatness rate adjusted to 41%.

[0180] [Example 18] In comparison with Example 17, the radius of curvature of the virtual arc that forms 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°, resulting in a belt with an inner circumference flatness rate adjusted to 41%.

[0181] [Example 19] In comparison with Example 17, the radius of curvature of the virtual arc that forms 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°, resulting in a belt with an inner circumference flatness rate adjusted to 41%.

[0182] [Example 20] In comparison with Example 17, the radius of curvature of the virtual arc that forms 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 producing a belt with an inner circumference flatness rate adjusted to 49%.

[0183] [Example 21] In comparison with Example 10, the radius of curvature of the virtual arc was reduced 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 adjusting the circumferential length of the flat top to 5.6 mm and producing a belt with an inner circumference flatness ratio increased to 59%.

[0184] Comparative Example 7 In comparison with Example 21, the cog angle was reduced to θ=6°, and the circumferential length of the flat top was adjusted to 6.3 mm, resulting in a belt with an inner circumferential flatness ratio of 67%.

[0185] The evaluation results of the belts obtained in Comparative Examples 6 to 7 and Examples 9 to 21 are shown in Table 4. The schematic cross-sectional shapes of the belts obtained in Comparative Examples 6 to 7 and Examples 9 to 21 are shown in FIG.

[0186] [Table 4]

[0187] The belt of Comparative Example 6 had small stress in the cog valleys, and its durability (cog valley crack resistance) was rated A, but its inner circumference flatness rate was small at 15%, so its engine braking performance was rated C, and its overall rating was D.

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

[0189] Furthermore, the belt of Example 10 had low stress in the cog valleys, giving it an A rating for durability (cog valley crack resistance), and the inner circumference flatness rate was increased to 48%, improving engine braking performance to an A rating, and engine braking durability was also good (A rating), resulting in an overall rating of A rank.

[0190] In Example 10, in which the inner periphery flatness ratio was increased to 48%, the radius of curvature R1 of the deepest of two consecutive arcs based on a virtual arc R0 = 1.1 mm was changed as the arc forming the bottom of the cog valley. In Examples 12 (R1 = 2.0 mm), 13 (R1 = 2.75 mm), 14 (R1 = 3.0 mm), 15 (R1 = 3.9 mm), and 16 (R1 = 4.5 mm), durability (cog valley crack resistance), engine braking performance, and engine braking durability were all good (a or b rating), and the overall rating was A or B. In Example 11 (R1 = 1.5 mm), in which R1 was the smallest, durability (cog valley crack resistance) decreased (c rating), but the overall rating was C, which is acceptable.

[0191] In Example 17, in which 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, and the inner periphery flatness ratio was adjusted to 41%, compared to Example 10 in which the inner periphery flatness ratio was increased to 48%, good results equivalent to those of Example 10 were obtained. Also, in Example 18, in which 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 periphery flatness ratio to 41%) compared to Example 17, good results equivalent to those of 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 (and the cog angle was expanded to θ = 17° to adjust the inner circumference flatness rate to 41%) compared to Example 17, although the stress generated in the cog valley increased, durability (cog valley crack resistance) was rated B, and the overall rating was ranked 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 rate to 49%) compared to Example 17, results as good as those in 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 = 0.5 mm, R1 = 1.5 mm) compared to Examples 10 and 17, and the inner circumference flatness ratio was increased to 59%, the stress generated in the cog valleys was large, and durability (cog valley crack resistance) was rated C, but the overall rating was C, which is a pass level. However, in Comparative Example 7, in which the inner circumference flatness ratio was increased to 67% by further reducing the cog angle (θ = 6°), FEM analysis confirmed interference between adjacent cog portions (cog interference) when the belt was bent, so it was rated D (failed).

[0194] From the above results, the belts of Examples 9 to 21, which had an inner circumference flatness ratio of 20 to 59%, were ranked A, B, or C, which are acceptable levels from the viewpoint of product practicality. Setting the inner circumference flatness ratio within this range is suitable for achieving both "expression of braking function" and "durability (resistance to cog valley cracks)," which are in a trade-off relationship.

[0195] From the above, it has been confirmed that a raw edge cog V-belt having a cog portion on at least the inner side where cog peaks and cog valleys are arranged alternately in the longitudinal direction of the belt, the cog portion being 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 being formed flat, and the length of each top in the longitudinal direction of the belt being adjusted to 20 to 60% of the cog pitch can be applied to the brake system of a belt clutch-in type continuously variable transmission, and can also improve durability such as wear resistance. [Industrial Applicability]

[0196] The raw-edge cog V-belt of the present invention is suitable as a power transmission V-belt for use in a power transmission mechanism requiring high friction on the inner peripheral surface. In particular, it can be used as a speed-change belt in a belt-clutch-type CVT for snowmobiles (small snow vehicles) and all-terrain vehicles (ATVs), etc., in which the inner peripheral surface of the belt contacts the pulley shaft during idling. It can also be used as a speed-change belt involved in any of the stepless speed change, clutch, and brake in a belt-clutch-type continuously variable transmission. [Explanation of symbols]

[0197] 1...Raw edge cog V-belt 1a…Inner Cog Mountain 1b...Inner Cog Valley 1c...Outer Cog Mountain 1d...Outer Cog Valley 2...Tension rubber layer 3...Core layer (adhesive rubber layer) 3a… Core body (core wire) 4...Compressed rubber layer 5...Fabric layer

Claims

1. A raw-edge cogged V-belt having a cog portion on at least the inner circumferential side, in which cog crests and cog valleys are alternately arranged in the belt longitudinal direction, the cog portion on the inner circumferential side is formed by a compression rubber layer and a fabric layer covering the inner circumferential surface of the compression rubber layer, The tops of the inner cogs are flat, and A raw edge cog V-belt in which the length of each apex in the belt longitudinal direction is 18 to 65% of the cog pitch.

2. 2. The raw edge cogged V-belt according to claim 1, wherein the cog pitch is 6 to 17 mm.

3. 3. The raw-edge cogged V-belt according to claim 1, wherein the fabric layer contains aramid fibers.

4. 4. The raw edge cogged V-belt according to claim 1, wherein the cross-sectional shape of the inner cog valley in the belt longitudinal direction has a bottom portion formed of an arc with a curvature radius of 2 to 4 mm, and a side wall portion extending from the bottom portion at an angle with respect to the belt thickness direction or along the belt thickness direction.

5. The cross-sectional shape of the inner cog valley in the belt longitudinal direction has a bottom portion formed by combining a plurality of continuous arcs, and a side wall portion extending from the bottom portion at an angle with respect to the belt thickness direction or along the belt thickness direction, the plurality of arcs have a smaller radius of curvature as they move away from the deepest portion of the cog valley; 5. The raw edge cogged V-belt according to claim 1, wherein a first arc passing through the deepest portion among the plurality of arcs has a radius of curvature of 2 to 4 mm that is larger than a radius of an imaginary circle that is tangent to the deepest portion and the side wall portions on both sides.

6. 6. A belt transmission mechanism comprising the raw-edge cogged V-belt according to claim 1 and a pulley, wherein the raw-edge cogged V-belt is a variable speed belt used in a belt clutch-in type continuously variable transmission.

7. 7. The belt transmission mechanism according to claim 6, wherein the belt clutch-in type continuously variable transmission is a continuously variable transmission in which the inner peripheral surface of the belt contacts the pulley shaft portion during idling.

8. 8. The belt transmission mechanism according to claim 6, wherein the belt clutch-in type continuously variable transmission is a continuously variable transmission equipped with a brake system that utilizes friction between the inner peripheral surface of the belt and a pulley shaft portion.

9. 6. A method for using the raw-edge cogged V-belt according to claim 1, wherein the raw-edge cogged V-belt is used in a belt clutch-in type continuously variable transmission to involve any of a continuously variable transmission, a clutch, and a brake.

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