RU2840559C2 - Toothed v-belt with raw edge, method of its use and belt transmission mechanism - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: toothed V-belt with a raw edge comprises a tooth at least on the side of the inner peripheral surface and a rubber compression layer on the side of the inner peripheral surface. Rubber compression layer comprises a main body of the rubber compression layer and an inner surface layer covering the inner peripheral surface of the main body of the rubber compression layer, coefficient of friction of the surface of said inner surface layer is higher than that of the main body of the rubber compression layer which not coated by inner surface layer. Also disclosed is a belt drive system comprising such a belt, and a method of using a toothed V-belt with a raw edge.

EFFECT: higher efficiency of engine braking when using belt.

8 cl, 9 dwg, 5 tbl

Description

AREA OF TECHNOLOGY

[0001] The present invention relates to a toothed V-belt with a raw edge for use in a continuously variable transmission of a belt type, a method for using the same and a belt power transmission system.

LEVEL OF TECHNOLOGY

[0002] A V-belt for transmitting power by friction power transmission includes a raw edge type (raw edge V-belt), which is a rubber layer in which the friction power transmission surface (V-shaped side surface) is exposed, and a wrapped type (wrapped V-belt), in which the friction power transmission surface is covered with a cover fabric and is used selectively according to the use depending on the difference in the surface properties (friction coefficient between the rubber layer and the cover fabric) of the friction power transmission surface itself. Examples of a V-belt of the raw-edge type include a raw-edge V-belt on which no teeth are provided, a toothed V-belt with raw-edge on which teeth are provided only on the lower surface (inner peripheral surface) of the belt to improve flexibility, and a toothed V-belt with raw-edge (a double-sided toothed V-belt with raw-edge) on which teeth are provided on both the lower surface (inner peripheral surface) and the upper surface (outer peripheral surface) of the belt to improve flexibility.

[0003] The V-belt with a raw edge and the toothed V-belt with a raw edge are mainly used for driving the general industrial machine and the agricultural machine, for driving the auxiliary units in the engine of the automobile, and the like. In other applications, there is a toothed V-belt with a raw edge called a CVT belt, which is used in a belt-type continuously variable transmission (CVT) for a motorcycle (scooter), a snowmobile (snow groomer), an all-terrain vehicle (ATV), and the like.

[0004] As shown in FIG. 1, the belt-type CVT 20 is a system that continuously changes the transmission ratio by tensioning a V-belt 23 around a driving pulley 21 and a driven pulley 22. The pulleys 21 and 22 respectively include fixed pulley discs 21a and 22a that are fixed or limited in movement in the axial direction, and movable pulley discs 21b and 22b that can move in the axial direction, wherein the inner peripheral walls of the fixed pulley discs 21a and 22a and the inner peripheral walls of the movable pulley discs 21b and 22b form inclined opposite surfaces of a V-shaped groove. The pulleys 21 and 22, respectively, have a structure in which the width of the V-shaped groove of the pulleys 21 and 22 formed by these fixed pulley disks 21a and 22a and the movable pulley disks 21b and 22b can be continuously changed. Both end surfaces in the width direction of the V-belt 23 are formed in the form of converging cone surfaces having an inclination corresponding to the inclined opposite surfaces of the V-shaped groove of the corresponding pulleys 21 and 22, and they engage in any position in the up-down direction on the opposite surfaces of the V-shaped grooves according to the changing widths of the V-shaped grooves. For example, when the state illustrated by position (a) in FIG. 1 changes to the state illustrated by position (b) in FIG. 1, by decreasing the width of the V-shaped groove of the driving pulley 21 and increasing the width of the V-shaped groove of the driven pulley 22, the toothed V-belt 23 with an unprocessed edge rises in the V-shaped groove on the side of the driving pulley 21 and falls in the V-shaped groove on the side of the driven pulley 22, and the wrap radius on the corresponding pulleys 21 and 22 changes continuously, which makes it possible to continuously change the gear ratio.

[0005] For example, a CVT for a motorcycle includes a drive pulley fixed around a crankshaft of an engine, a driven pulley connected to a drive shaft of a rear wheel via a gear transmission or the like, and a V-belt tensioned around the drive pulley and the driven pulley.

[0006] At a low speed, the movable pulley disc of the driving pulley moves away from the fixed pulley disc, the wrapping radius on the driving pulley becomes smaller, and the movable pulley disc of the driven pulley approaches the fixed pulley disc, and the wrapping radius on the driven pulley becomes larger. Thus, the rear wheel is driven with a large torque at a low speed. On the other hand, at a high speed, the movable pulley disc of the driving pulley moves toward the fixed pulley disc, the wrapping radius on the driving pulley becomes larger, and the movable pulley disc of the driven pulley moves away from the fixed pulley disc, and the wrapping radius on the driven pulley becomes smaller. Thus, the rear wheel is driven with a small torque at a high speed.

[0007] On the other hand, the difference between a motorcycle and a snowmobile or all-terrain vehicle is the clutch system (a system that temporarily interrupts the transmission of power) at idle.

[0008] That is, in a motorcycle, an automatic centrifugal clutch is provided between the rear wheel and the driven pulley. This clutch blocks the transmission of torque from the driven pulley to the rear wheel at idle speed. Thus, even if the driven pulley rotates at idle speed, the rear wheel does not rotate.

[0009] On the other hand, in the case of a CVT on a snowmobile or an off-road vehicle, an automatic centrifugal clutch is not provided, but the movable pulley disk moves during idling until the side surface of the V-belt is completely separated from the movable or fixed pulley disk, thereby blocking the transmission of torque from the drive pulley to the V-belt. That is, the V-belt dropped into the lower part of the groove (shaft section) of the pulley during idling, that is, the lower surface (inner peripheral surface) of the V-belt coming into contact with the shaft section acts as a belt clutch that temporarily interrupts the transmission of power (the shaft section of the drive pulley acts as an idler pulley). Such a transmission is called a CVT with a belt clutch type.

[0010] FIG. 2 is a schematic diagram illustrating a state of a CVT with a belt type clutch at idle speed. As shown in FIG. 2, in the CVT 30 with a belt type clutch, the V-belt 33 does not contact with either the movable pulley disc 31b or the fixed pulley disc 31a of the drive pulley 31, but contacts with a pulley shaft portion 31c of the actual drive pulley 31. That is, in the CVT with an automatic centrifugal clutch type of a motorcycle, the V-belt contacts the pulley discs of the pulleys even during idle speed, which is illustrated in FIG. 1, whereas in the CVT with a belt type clutch, the CVT itself in a snowmobile or an all-terrain vehicle, the inner peripheral surface of the V-belt comes into contact with the outer peripheral surface of the pulley shaft portion of the drive pulley itself (the ordinary pulley shaft portion has a smooth outer peripheral surface).

[0011] The following belts are known as vane belts, which are specially designed for CVT with a belt type clutch, that is, a belt whose lower surface (inner peripheral surface) comes into contact with the pulley shaft during engine idling.

[0012] JP2004-188776A (Patent Literature 1) discloses a method for producing a V-belt as a variable speed belt used in a transmission of a two-wheeled vehicle, an all-terrain vehicle, a snowmobile or the like, in which a canvas fabric is attached to the bottom surface through a rubber layer to avoid the rubber bottom surface, thereby preventing the rubber underneath from sticking to the shaft.

[0013] JP2006-2836A (Patent Literature 2) discloses a belt with a raw edge in which the lower surface of the belt that slides in contact with the pulley disc shaft is formed as a canvas surface not coated with rubber paste, so that the friction coefficient of the lower surface is 0.1 or less and the rubber does not fly off (rubber powder does not fly off), so that there is no risk of the flown off rubber entering the gap around the pulley disc shaft and causing a malfunction.

[0014] JP2006-226420A (Patent Literature 3) discloses a power transmission belt in which a canvas fabric is provided on a surface of a compression rubber layer that comes into contact with a recess of a pulley, and no rubber is attached to the canvas fabric at the contact point with the recess of the pulley, which makes it possible to eliminate the attachment of rubber to the surface of the belt that comes into contact with the recess of the pulley, reduce the coefficient of friction, and prevent noise.

[0015] JP2007-144714A (Patent Literature 4) discloses a V-belt in which the lower surface of the belt is covered with a canvas fabric that is applied only to the main body side of the belt, thereby preventing rubber from leaking onto the surface of the canvas fabric and preventing the occurrence of abnormal noise and driving force.

[0016] JP2009-51204A (Patent Literature 5) discloses a toothed V-belt that can be manufactured without attaching rubber to a canvas fabric by using a circular knit canvas fabric with elastic threads as threads in the circumferential direction of the belt in a process of winding the canvas fabric onto a mold to temporarily fix the canvas fabric, which can prevent the scattering of rubber particles even when the belt is lowered in a CVT with a belt-type clutch.

[0017] JP2009-156289A (Patent Literature 6) discloses a V-belt in which Teflon (registered trademark) is applied to a lower canvas fabric, and the rubber used for bonding the lower canvas fabric to the rubber base is prevented from penetrating through the surface, thereby reducing the coefficient of friction with the crankshaft and reducing the torque transmitted from the crankshaft to the V-belt at idle speed.

[0018] On the other hand, compared with the automatic centrifugal type clutch, the belt type clutch has poor engine braking performance, and therefore a mechanism is being studied that uses the contact between the idler pulley and the inner peripheral surface of the CVT belt during idling to act as an engine braking system (EBS) that brakes the driven pulley (rear wheel) by frictional force.

[0019] WO2011/046740 (Patent Literature 7) and WO2019/209739 (Patent Literature 8) disclose an engine braking system with a continuously variable transmission that adds a braking function by engaging with an idler pulley (shaft section) that has a projection and a recess corresponding to a projection and a recess (tooth) on the inner peripheral surface of a V-belt.

LIST OF CITIONS

PATENT LITERATURE

[0020] Patent Literature 1: JP2004-188776A

Patent Literature 2: JP2006-2836A

Patent Literature 3: JP2006-226420A

Patent Literature 4: JP2007-144714A

Patent Literature 5: JP2009-51204A

Patent Literature 6: JP2009-156289A

Patent Literature 7: WO2011/046740

Patent Literature 8: WO2019/209739

ESSENCE OF THE INVENTION

TECHNICAL TASK

[0021] The purpose of the V-belt in each Patent Literature 1 to 6 is to ensure the slipperiness of the lower surface of the belt (reduce the coefficient of friction) to prevent problems (such as the occurrence of abnormal noise or driving force, and rubber scattering) caused by the friction of the lower surface of the belt with the pulley shaft, and the engine braking performance (braking function) of the belt type clutch is not mentioned. In addition, the V-belts described in Patent Literature 1 to 6 do not provide sufficient friction force to obtain a sufficient braking function, and therefore they cannot realize the braking function. Therefore, realizing the braking function by shortening the braking distance and time and maintaining the braking function become problems, and it is necessary to develop a V-belt having a high-level braking function (high friction force).

[0022] On the other hand, the engine braking system with a continuously variable transmission according to each of Patent Documents 7 and 8 requires a pulley of a special shape.

[0023] Among the V-belts with untreated edges, the highest level of lateral pressure resistance is required for use in CVT, and in order to be applicable for such use, a higher rigidity in the compression rubber layer is required than in other applications. Therefore, when using CVT, the flexibility is inevitably insufficient, and therefore a tooth becomes necessary. That is, high-rigidity rubber and a toothed portion are essential components for using CVT. On the other hand, in order to bring the inner circumferential surface of the belt into contact with the pulley shaft portion to generate a braking effect (friction force), it is appropriate to use a belt with a flat inner circumferential surface (without a tooth), in which the contact area is increased. However, since the tooth is important for the use of CVT, the only part of the inner circumferential surface (bottom surface) of the belt that comes into contact with the pulley shaft part (the part of the shaft of the ordinary pulley that has a smooth outer circumferential surface without any protrusion or recess formed to engage with the belt) is the upper part of the tooth, which makes it difficult to improve the friction force (braking function). That is, in the V-belt with untreated edge used in CVT, both the resistance to lateral pressure and the improvement of the braking function are properties in a compromise relationship, which is difficult to achieve.

[0024] Accordingly, an object of the present invention is to provide a toothed V-belt with a rough edge that can be used as a braking system for a continuously variable transmission with a belt-type clutch, a method for using the same, and a belt power transmission system.

SOLVING THE PROBLEM

[0025] In order to achieve the above object, the inventors found that a toothed V-belt with a raw edge can be used as a braking system of a continuously variable transmission with a belt-type clutch by configuring a compression rubber layer of the toothed V-belt with a raw edge as a combination of a main body of the compression rubber layer and an inner surface layer that covers an inner peripheral surface of the main body of the compression rubber layer and has a surface with a coefficient of friction greater than that of the surface of the main body of the compression rubber layer, and made the present invention.

[0026] Thus, the toothed V-belt with a raw edge according to aspect [I] of the present invention is a toothed V-belt with a raw edge, including:

a tooth at least on the side of the inner peripheral surface; and

a rubber compression layer located on the side of the inner peripheral surface, wherein

the rubber compression layer comprises a main body of the rubber compression layer and an inner surface layer covering the inner peripheral surface of the main body of the rubber compression layer, and

the coefficient of friction of the surface of the inner surface layer is higher than the coefficient of friction of the surface of the main body of the rubber compression layer not covered by the inner surface layer.

[0027] Aspect [II] of the present invention is the aspect according to aspect [I], wherein the surface friction coefficient of the inner surface layer is from 0.4 to 0.7.

[0028] Aspect [III] of the present invention is the aspect according to aspect [I] or [II], wherein the average thickness of the inner surface layer is from 0.3 mm to 2 mm.

[0029] Aspect [IV] of the present invention is the aspect according to any one of aspects [I] to [III], wherein the hardness Hs (Type A) of the rubber of the inner surface layer is 82° or less, and the hardness Hs (Type A) of the rubber of the main body of the compression rubber layer is 89° or more.

[0030] The present invention also includes, as aspect [V], a belt power transmission system including a toothed V-belt with a raw edge according to any one of aspects [I] to [IV] and a pulley, wherein the toothed V-belt with a raw edge is a CVT belt used in a continuously variable transmission with a belt-type clutch.

[0031] Aspect [VI] of the present invention is the aspect according to aspect [V], wherein the continuously variable transmission with a belt-type clutch is a continuously variable transmission in which the inner peripheral surface of the belt comes into contact with a portion of the pulley shaft during idling.

[0032] Aspect [VII] of the present invention is the aspect according to aspect [V] or [VI], wherein the continuously variable transmission with a belt-type clutch is a continuously variable transmission having a braking system that uses the frictional force between the inner peripheral surface of the belt and said portion of the pulley shaft.

[0033] The present invention also includes, as aspect [VIII], a method of using a toothed V-belt with a raw edge according to any one of aspects [I] to [IV], wherein the toothed V-belt with a raw edge is used in all of a continuously variable transmission, a clutch and a brake in a continuously variable transmission with a belt-type clutch.

BENEFICIAL EFFECTS OF THE INVENTION

[0034] In the present invention, since the compression rubber layer of the toothed V-belt with a raw edge is configured as a combination of a main body of the compression rubber layer and an inner surface layer that covers the inner peripheral surface of the main body of the compression rubber layer and has a surface with a coefficient of friction greater than that of the surface of the main body of the compression rubber layer, a braking function (with a high friction force) can be added to the inner peripheral surface of the belt, and the toothed V-belt with a raw edge can be applied as a braking system of a continuously variable transmission with a belt-type clutch mounted on a snowmobile, an all-terrain vehicle or the like. That is, in the present invention, the friction force of the inner peripheral surface of the belt can be improved while maintaining the bending fatigue resistance and lateral pressure resistance, and thus the braking function (high friction force) can be ensured even for a part of the pulley shaft. In particular, since the inner peripheral surface of the main body of the compression rubber layer is covered with a certain surface layer (high friction rubber composition), the braking function can be added while maintaining the heat resistance, lateral pressure resistance and bending fatigue resistance of the CVT belt.

BRIEF DESCRIPTION OF THE FIGURES

[0035] FIG. 1 is a schematic view illustrating a transmission system of a belt-type continuously variable transmission itself.

FIG. 2 is a schematic diagram illustrating a state of a continuously variable transmission with a belt type clutch during idling.

FIG. 3 is a schematic partial sectional perspective view illustrating an example of a double-sided toothed V-belt with a raw edge according to the present invention.

FIG. 4 is a schematic cross-sectional view in which the double-sided toothed V-belt with a raw edge according to FIG. 3 is cut in the longitudinal direction of the belt.

FIG. 5 is a schematic sectional view in which another example of a double-sided toothed V-belt with a raw edge according to the present invention is cut in the longitudinal direction of the belt.

FIG. 6 is a schematic sectional view illustrating the definitions of the overall thickness, the toothed portion height, the valley portion thickness, and the like of the double-sided toothed V-belt with a raw edge in the present application.

FIG. 7 is a schematic view illustrating a method for measuring the coefficient of friction of the inner peripheral surface of a double-sided toothed V-belt with a rough edge obtained in Example.

FIG. 8 is a diagram showing the arrangement of a testing machine used in the performance durability test (top durability test) of the double-sided toothed V-belt with a raw edge obtained in Example.

FIG. 9 is a diagram showing the arrangement of a testing machine used in the performance durability test (bottom durability test) of the double-sided toothed V-belt with a raw edge obtained in Example.

DESCRIPTION OF IMPLEMENTATION OPTIONS

[0036] [Configuration of toothed V-belt with raw edge]

The toothed V-belt with a raw edge according to the present invention is not particularly limited as long as the toothed V-belt with a raw edge includes a compression rubber layer having a specific two-layer structure including a main body of a compression rubber layer and a surface layer (inner surface layer). The toothed V-belt with a raw edge can be roughly divided into a toothed V-belt with a raw edge in which a tooth is formed only on the inner periphery side of the V-belt with a raw edge, and a double-sided toothed V-belt with raw edges in which teeth are formed on both the inner periphery side and the outer periphery side of the V-belt with a raw edge. Among them, the double-sided toothed V-belt with raw edges is particularly preferable from the viewpoint of use under more severe conditions and the need to ensure both lateral pressure resistance and bending fatigue resistance at a high level.

[0037] FIG. 3 is a schematic partial sectional view in perspective illustrating an example of a double-sided toothed V-belt with a raw edge according to the present invention, and FIG. 4 is a schematic sectional view in which the double-sided toothed V-belt with a raw edge of FIG. 3 is cut in the longitudinal direction of the belt.

[0038] In the example, the double-sided toothed V-belt 1 with a raw edge has a toothed inner periphery portion formed by alternately disposing an inner periphery tooth ridge 1a and an inner periphery tooth valley 1b along the belt longitudinal direction (direction A in the figure) on the inner peripheral surface of the compression rubber layer 4, the sectional shape in the longitudinal direction of the inner periphery tooth ridge 1a is substantially a semicircle shape (a curved shape or a wave shape), and the sectional shape in the direction (width direction or direction B in the figure) orthogonal to the longitudinal direction is a trapezoid shape. That is, each inner periphery tooth ridge 1a projects substantially in a semicircle shape in the section in the direction A from the inner periphery tooth valley 1b in the belt thickness direction.

[0039] In addition, the outer peripheral side also has an outer peripheral toothed portion formed by alternately disposing an outer peripheral tooth ridge 1c and an outer peripheral tooth valley 1d along the longitudinal direction of the belt, and the sectional shape in the longitudinal direction of the outer peripheral tooth ridge 1c is substantially a trapezoid shape, and the sectional shape in the direction (width direction or direction B in the figure) perpendicular to the longitudinal direction is substantially a rectangular shape. That is, each outer peripheral tooth ridge 1c projects substantially in a trapezoid shape in the section in the direction A from the outer peripheral tooth valley 1d in the thickness direction of the belt.

[0040] A double-sided toothed V-belt with a raw edge has a layered structure in which a tension rubber layer 2, a tension member layer 3 (adhesive rubber layer), a main body 4a of a compression rubber layer, and an inner surface layer 4b of a compression rubber layer are stacked in layers in the specified order from the outer peripheral side to the inner peripheral side of the belt. The cross-sectional shape in the width direction of the belt is essentially a trapezoid shape in which the width of the belt decreases from the outer peripheral side to the inner peripheral side of the belt. Furthermore, the tension member 3a is embedded in the tension member layer 3, and the inner peripheral toothed portion and the outer peripheral toothed portion are respectively formed in the compression rubber layer 4 and the tension rubber layer 2 by a toothed mold.

[0041] FIG. 5 is a schematic sectional view in which another example of a double-sided toothed V-belt with a raw edge according to the present invention is cut in the longitudinal direction of the belt. The double-sided toothed V-belt with a raw edge of FIG. 5 includes a tension rubber layer 12, a tension member layer 13 (an adhesive rubber layer), and a compression rubber layer 14. In this example, in the compression rubber layer 14 including the main body 14a, the inner surface layer 14b is formed thicker than that of the double-sided toothed V-belt with a raw edge of FIG. 1. In this example, compared with the double-sided toothed V-belt with a raw edge of FIG. 1, the lateral pressure resistance is slightly lower, but the braking performance constancy is slightly improved.

[0042] Based on FIG. 4, the definitions of the overall thickness, the heights of the toothed portions, the thicknesses of the valley portions and the like of the toothed V-belt with a raw edge according to the present invention are shown in FIG. 6. The thickness H1 (average thickness) of the entire belt of the toothed V-belt with a raw edge according to the present invention is, for example, from 8 mm to 19 mm, preferably from 10 mm to 19 mm, more preferably from 13 mm to 19 mm, and still more preferably from 14 mm to 16 mm. If the thickness is too small, the lateral pressure resistance may decrease, and if the thickness is too large, the bendability may decrease, the power transmission efficiency may decrease, and the bending fatigue resistance may decrease.

[0043] As shown in FIG. 6, in the present application, in the case where the rubber tension layer and/or the rubber compression layer has a toothed portion, the thickness of the entire belt means the thickness (maximum belt thickness) with the top of the toothed portion.

[0044] In the present application, the inner periphery tooth groove of the inner periphery toothed portion means a portion that forms a thin portion of the compression rubber layer having the inner periphery toothed portion, and generally means a curved or flat portion of the groove or a groove portion (a curved portion of the groove or a flat portion of the groove parallel to the surface direction of the belt) between adjacent ridges of the inner periphery teeth that project in the direction of the inner periphery side of the belt.

[0045] The height H2 (the height of the inner periphery tooth) of the inner periphery toothed portion formed on the inner peripheral surface may be selected from a range of, for example, 4 mm to 8 mm, and preferably 5 mm to 7 mm. The height H5 (the height of the outer periphery tooth) of the outer periphery toothed portion formed on the outer peripheral surface may be selected from a range of, for example, 2 mm to 5 mm, and preferably 3 mm to 4 mm.

[0046] The design height H4 of the outer periphery, which is the distance from the center of the tension member to the outer peripheral surface (the upper portion of the toothed portion), is, for example, 4 mm to 8 mm, and preferably 5 mm to 7 mm, and the thickness H3 of the recess in the center, which is the distance from the center of the tension member to the deepest portion of the recess of the tooth of the inner periphery, is, for example, 1 mm to 9 mm, and preferably 2 mm to 8 mm.

[0047] [Rubber Compression Layer]

The rubber compression layer includes a main body of the rubber compression layer (the main body of the rubber compression layer) formed of a rubber composition (a crosslinked rubber composition), and a surface layer (an inner surface layer) that covers the inner peripheral surface of the belt of the main body and has a surface with a higher coefficient of friction than the surface of the main body. It is sufficient that the rubber compression layer includes the main body of the rubber compression layer and the inner surface layer, and the rubber compression layer may include another layer (for example, another rubber layer located between the main body of the rubber compression layer and the inner surface layer), but a two-layer structure including the main body of the rubber compression layer and the inner surface layer is preferable from the viewpoint of the mechanical properties and performance of the rubber compression layer. In the present invention, the rubber compression layer is formed into a two-layer structure including a main body and an inner surface layer, so that a braking function (high friction force) can be added to the inner peripheral surface of the belt, while maintaining the heat resistance, lateral pressure resistance and bending fatigue resistance required for a CVT belt.

[0048] The average thickness of the compression rubber layer (common to the main body and the inner surface layer) can be appropriately selected according to the type of belt, and is, for example, 7 mm to 13 mm, preferably 8 mm to 12 mm, and more preferably 9 mm to 11 mm. In the present application, the thickness of the compression rubber layer means the thickness of the upper portion of the toothed portion of the inner periphery.

[0049] (Main Body of Compression Rubber Layer)

In the toothed V-belt with a raw edge according to the present invention, the main body of the rubber compression layer is formed from a rubber composition (crosslinked rubber composition) containing a first rubber component.

[0050] (A1) First Rubber Component

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

[0051] Among them, ethylene-α-olefin elastomer and chloroprene rubber are preferable, and chloroprene rubber is particularly preferable from the viewpoint of excellent balance of heat resistance, abrasion resistance, oil resistance and the like, and high performance.

[0052] When the first rubber component contains chloroprene rubber, from the viewpoint of the possibility of improving the properties and performance, the proportion of chloroprene rubber in the first rubber component may be 50 mass% or more, preferably 80 mass% or more, more preferably 90 mass% or more (particularly 90 mass% to 100 mass%), and most preferably 100 mass% (only chloroprene rubber). If the first rubber component contains ethylene-α-olefin elastomer, the proportion of ethylene-α-olefin elastomer in the first rubber component is the same as the proportion of chloroprene rubber.

[0053] (A2) First Short Fiber

The rubber composition forming the main body of the rubber compression layer may additionally contain a first short fiber. Examples of the first short fiber include a synthetic short fiber such as a polyamide short fiber (such as an aliphatic polyamide short fiber such as polyamide 6 short fiber, polyamide 66 short fiber and polyamide 46 short fiber, an aramid short fiber), a polyalkylene arylate short fiber (such as polyethylene terephthalate (PET) short fiber and polyethylene naphthalate short fiber), a liquid crystal polyester short fiber, a polyarylate short fiber (such as an amorphous entirely aromatic polyester short fiber), a vinylone short fiber, a polyvinyl alcohol short fiber and a polyparaphenylene benzobisoxazole (PBO) short fiber; a natural short fiber such as cotton, hemp and wool; and inorganic short fiber such as carbon short fiber. These first short fibers can be used singly or in combination of two or more kinds thereof. Among them, aramid short fiber and PBO short fiber are preferable, and aramid short fiber is particularly preferable.

[0054] The first short fiber may be a short fiber obtained by cutting a fiber stretched to a fibrous form of a predetermined length. The first short fiber is preferably embedded in the main body of the rubber compression layer in a state oriented in the width direction of the belt, so as to prevent the belt from being deformed when compressed by the lateral pressure of the pulley (to increase the lateral pressure resistance). Since the friction coefficient of the surface in contact with the pulley can be reduced, which makes it possible to prevent noise (sound), and wear due to friction with the pulley can be reduced, it is preferable that the short fiber protrudes from the surface of the main body of the rubber compression layer.

[0055] The average fiber length of the first short fiber is, for example, 0.1 mm to 20 mm, preferably 0.5 mm to 15 mm (for example, 0.5 mm to 10 mm), and more preferably 1 mm to 6 mm (particularly 2 mm to 4 mm) from the viewpoint of improving the lateral pressure resistance and the abrasion resistance without reducing the flexibility. If the length of the first short fiber is too short, the mechanical properties in the fiber direction cannot be sufficiently improved, and the lateral pressure resistance and the abrasion resistance may decrease. Conversely, if the fiber length is too long, the orientation of the short fiber in the rubber composition may deteriorate, which may result in a decrease in flexibility.

[0056] The fineness of a single filament of the first short fiber is, for example, 1 dtex to 12 dtex, preferably 1.2 dtex to 10 dtex (for example, 1.5 dtex to 8 dtex), and more preferably 2 dtex to 5 dtex (particularly 2 dtex to 3 dtex) from the viewpoint of providing a strong reinforcing effect without reducing the bendability. If the fineness of a single filament is too large, the lateral pressure resistance and the abrasion resistance based on the amount of the mixture may decrease, and if the fineness of a single filament is too small, the bendability may decrease due to a decrease in dispersibility in rubber.

[0057] The first short fiber may be subjected to a general-purpose adhesive treatment to enhance the adhesive strength with the first rubber component. Examples of such an adhesive treatment include a method of dipping the first short fiber into a treatment liquid containing an epoxy compound or a polyisocyanate compound, a method of dipping the first short fiber into an RFL treatment liquid containing resorcinol, formaldehyde and latex, and a method of dipping the first short fiber into a rubber adhesive. These treatment methods may be used individually or in combination of two or more kinds.

[0058] The proportion of the first short fiber is, for example, 5 parts by mass to 50 parts by mass, preferably 5 parts by mass to 40 parts by mass (for example, 8 parts by mass to 35 parts by mass), more preferably 10 parts by mass to 30 parts by mass, and still more preferably 15 parts by mass to 25 parts by mass, relative to 100 parts by mass of the first rubber component. If the amount of the first short fibers is too small, the lateral pressure resistance and the abrasion resistance may decrease, and if the amount is too large, the processability may deteriorate or the flexibility of the belt may decrease, which may lead to a decrease in durability.

[0059] (A3) Other Components

The rubber composition forming the main body of the rubber compression layer may contain a generally used additive. Examples of the additive include a cross-linking agent or a vulcanizing agent (such as a sulfur-based cross-linking agent and an organic peroxide), a co-cross-linking agent (such as bismaleimides), a cross-linking additive or cross-linking accelerator (such as a thiuram accelerator), a cross-linking retarder, a metal oxide (such as zinc oxide, magnesium oxide, calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide and aluminum oxide), a filler [such as a reinforcing agent (reinforcing filler) such as carbon black and a silicon oxide (such as silicon hydroxide); and a diluent (non-reinforcing filler or inert filler) such as clay, calcium carbonate, talc and mica], a plasticizer (or softener) [such as oils (such as paraffin oil and naphthenic oil), an aliphatic carboxylic acid plasticizer, an aromatic carboxylic acid ester plasticizer, an hydroxycarboxylic acid ester plasticizer, a phosphate ester plasticizer, an ester plasticizer and an ester plasticizer], a processing agent or processing additive (such as stearic acid, metal stearate, wax, paraffin and fatty acid amide), an antiaging agent (such as an antioxidant, a thermal antiaging agent, a flex cracking anti-aging agent and an antiozonant), an adhesion improver, a colorant, a tackifier, a coupling agent (such as a silane coupling agent) agent), stabilizer (such as ultraviolet absorber and heat stabilizer), flame retardant and antistatic agent. These additives can be used singly or in combination of two or more kinds. Metal oxide can act as a cross-linking agent.

[0060] The proportion of a filler (first filler), such as carbon black or silica, is, for example, from 10 parts by mass to 200 parts by mass, preferably from 20 parts by mass to 100 parts by mass, more preferably from 30 parts by mass to 80 parts by mass, and even more preferably from 40 parts by mass to 70 parts by mass, relative to 100 parts by mass of the first rubber component.

[0061] The proportion of the plasticizer (first plasticizer) may be 10 parts by mass or less, for example, 0.1 parts by mass to 10 parts by mass, preferably 1 part by mass to 8 parts by mass, and more preferably 3 parts by mass to 7 parts by mass, relative to 100 parts by mass of the first rubber component. If the proportion of the plasticizer is too high, the rubber compression layer may become too soft, which may reduce the lateral pressure resistance.

[0062] The total proportion of the other components (A3) is, for example, from 5 parts by mass to 300 parts by mass, preferably from 10 parts by mass to 200 parts by mass, more preferably from 30 parts by mass to 150 parts by mass, and even more preferably from 50 parts by mass to 100 parts by mass, based on 100 parts by mass of the first rubber component.

[0063] (A4) Properties of the Main Body of the Rubber Compression Layer

The main body of the rubber compression layer has a high rubber hardness because a rubber composition with high rigidity (high elastic modulus) is used to obtain lateral pressure resistance. The rubber hardness may be 89° or more, for example, 90° to 99°, preferably 91° to 98°, more preferably 92° to 97°, and even more preferably 93° to 96°. If the rubber hardness of the main body of the rubber compression layer is too low, the lateral pressure resistance may decrease, and if the rubber hardness is too high, the bending fatigue resistance and durability may decrease.

[0064] In the present application, the rubber hardness of each rubber layer is indicated by the Hs value (Type A) measured using a Type A durometer in accordance with the spring durometer hardness test specified in JIS K6253 (2012) (Vulcanized rubber and thermoplastic rubber - Hardness testing method -), and may be simply referred to as the rubber hardness. Specifically, the measurement can be performed by the method described in the Examples that will be described below.

[0065] The tensile strength of the main body of the rubber compression layer is, for example, 25 MPa to 50 MPa, preferably 30 MPa to 40 MPa, and more preferably about 30 MPa to 35 MPa in the belt width direction. If the tensile strength is too low, the lateral pressure resistance may decrease. Conversely, if the tensile strength is too high, the bending fatigue resistance may decrease.

[0066] In the present application, with regard to the tensile strength of each rubber layer, the tensile strength value T of each rubber layer, which can be measured by a method in accordance with JIS K6251 (2017), is used as the index value of the tensile strength. In particular, the measurement can be performed by the method described in the Examples that will be described below.

[0067] The coefficient of friction of the surface of the main body of the rubber compression layer may be less than 0.40, for example 0.20 or more and less than 0.40, preferably from 0.30 to 0.39, and more preferably from 0.32 to 0.38. If the coefficient of friction of the surface of the main body of the rubber compression layer is too small, the power transmission efficiency may decrease. Conversely, if the coefficient of friction is too large, problems such as abnormal noise and sticking and scattering of rubber may occur.

[0068] In the present application, the friction coefficients (average friction coefficients) of the main body of the rubber compression layer and the inner surface layer can be calculated by pulling a cut belt on a flat pulley at an angle of 90° and measuring the friction force (load) when the inner peripheral surface of the belt comes into contact with the outer peripheral surface of the flat pulley and moves, and in particular, this measurement can be performed in the manner described in the Examples that will be described below.

[0069] In the present application, the coefficient of friction of the surface of the main body of the compression rubber layer means the coefficient of friction of the surface of the main body of the compression rubber layer which is not covered by the inner surface layer, and means the coefficient of friction of the toothed V-belt with a rough edge of the present invention in the form in which the inner surface layer is not covered.

[0070] The average thickness of the main body of the compression rubber layer can be appropriately selected depending on the type of the belt, and is, for example, from 4 mm to 13 mm, preferably from 5 mm to 12 mm, more preferably from 6 mm to 11 mm, even more preferably from 7 mm to 10 mm, and most preferably from 7.5 mm to 9 mm. In the present application, the thickness of the main body of the compression rubber layer means the thickness of the upper portion of the toothed portion.

[0071] (Inner Surface Layer of Rubber Compression Layer)

In the present application, the inner peripheral surface of the belt of the main body of the compression rubber layer is covered with a surface layer (inner surface layer). The reason for forming the inner surface layer in the present invention is as follows.

[0072] That is, when a V-belt with a raw edge, not limited to a CVT belt, is pulled onto the pulleys, only the two V-shaped side surfaces come into contact with the pulleys, and the inner peripheral surface (lower surface, surface below) does not come into contact with the pulleys, or even if the inner peripheral surface comes into contact with the pulleys, only light contact occurs. Therefore, in most cases, the friction force on the inner peripheral surface of the V-belt with a raw edge is not required. On the contrary, as described above, in the application related to the CVT variable speed belt with belt type clutch, the inner peripheral surface of the V-belt with untreated edge is not only used in contact with the pulley (pulley shaft part), but also exerts a pressing force on the pulley (pulley shaft part), which serves as a braking function, and the performance is greatly affected by the friction force of the inner peripheral surface of the V-belt with untreated edge. Therefore, the fact that the friction force is required on the inner peripheral surface of the V-belt with untreated edge itself is a special circumstance. In this regard, Patent Literatures 1 to 6 described above only disclose the idea of how to make the inner peripheral surface of the belt slippery (reducing the coefficient of friction), and the opposite idea of requiring a friction force on the inner peripheral surface of the belt (increasing the coefficient of friction) is unique (unexpected) with respect to the related art. That is, in the related art, the inner peripheral surface is preferably made of fabric (no rubber is used) to reduce the coefficient of friction, while the present invention is characterized by an aspect in which a rubber layer (a rubber composition with a high coefficient of friction) is disposed on the inner peripheral surface.

[0073] In particular, in the present invention, the coefficient of friction of the surface of the inner surface layer is made larger than the coefficient of friction of the surface of the main body of the rubber compression layer. The method of adjusting the coefficient of friction of the inner surface layer can be performed by adjusting the components of the rubber composition forming the inner surface layer. However, as described above, in the case of a toothed V-belt with an untreated edge, it is difficult to achieve both the lateral pressure resistance and the improvement of the braking performance. Therefore, in the present invention, the rubber composition is selected from the following points, taking into account the properties of the toothed V-belt with an untreated edge.

[0074] That is, although there is a need to increase the thickness of the entire belt for a V-belt with a raw edge in terms of improving the lateral pressure resistance and the power transmission capability, there is also a need to maintain good bendability by, for example, reducing the thickness of the entire belt in terms of improving the bending fatigue resistance and the power transmission efficiency. A toothed V-belt with a raw edge can satisfy these two conflicting needs by providing a tooth in the V-belt with a raw edge. That is, in the toothed V-belt with a raw edge, the crest of the tooth increases the power transmission friction surface to improve the lateral pressure resistance and the power transmission capability, while the tooth valley is designed to maintain good bendability, and when the toothed V-belt with a raw edge is pulled on the pulleys, the bendability of the tooth valley is larger than the bendability of the tooth valley. As a result, the fatigue of the rubber compression layer, which is repeatedly flexed in the tooth valley, increases, and cracks in the rubber compression layer are more likely to appear in the tooth valley than in the tooth crest.

[0075] The inner peripheral surface of the toothed V-belt with a raw edge is formed with a toothed portion in which a tooth crest and a tooth valley are arranged alternately, but in the present use, only the upper portion of the inner periphery tooth crest comes into contact with a pulley shaft portion. The inner surface layer with a high friction coefficient may be arranged only on the upper portion of the inner periphery tooth crest, but in view of performance, it is preferable to arrange the inner surface layer as a continuous layer that continuously connects the inner periphery tooth crest and the inner periphery tooth valley. When forming a continuous layer, the rubber composition that forms the inner surface layer also affects the cracks (bending fatigue resistance) of the tooth valley. In addition, an increase in the thickness of the inner surface layer in the rubber compression layer reduces the proportion of the main body, and thus also affects the rigidity (resistance to lateral pressure) of the entire rubber compression layer. That is, although the inner surface layer has the function of improving the braking performance (high friction force) of the inner peripheral surface of the belt, the inner surface layer also affects the reduction of the lateral pressure resistance and the bending fatigue resistance of the belt. Therefore, it is necessary to add a braking function (high friction coefficient) of the inner peripheral tooth ridge to the rubber composition forming the inner surface layer, while ensuring the lateral pressure resistance and the bending fatigue resistance. From this point of view, in the present invention, when adjusting the rubber composition, it is more preferable to adjust the surface friction coefficient of the inner surface layer so that it is higher than the surface friction coefficient of the main body of the rubber compression layer, and further adjust the value of the friction coefficient and/or the thickness of the inner surface layer.

[0076] From this viewpoint, the inner surface layer can be formed from a rubber composition (cross-linked rubber composition) containing a second rubber component. Furthermore, in the present invention, by adjusting the combination of the main body of the compression rubber layer and the inner surface layer in addition to the friction coefficient value and/or the thickness of the inner surface layer, it is possible to improve the braking performance (high friction force) of the inner peripheral surface of the belt while maintaining the heat resistance, lateral pressure resistance and bending fatigue resistance required for a CVT belt.

[0077] (B1) Second Rubber Component

The second rubber component may be selected from the rubber components exemplified by the first rubber component, including the preferred aspects. 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.

[0078] (B2) Other Components and Component for Increasing the Coefficient of Friction

The rubber composition forming the inner surface layer may further comprise other components. The other components may be those presented as an example as other components (A3) in the main body of the rubber compression layer.

[0079] It is sufficient that the rubber composition forming the inner surface layer has a higher coefficient of friction than that of the rubber composition forming the main body of the rubber compression layer, but the method for increasing the coefficient of friction is not particularly limited. The components given as examples of the other components (A3) can be used as friction-regulating agents for increasing the viscosity of the rubber composition for the purpose of regulating the coefficient of friction. Examples of friction-regulating agents are plasticizers, adhesion promoters, and tackifiers.

[0080] Examples of the plasticizer (second plasticizer) include oils (such as paraffin oil and naphthenic oil), an aliphatic carboxylic acid plasticizer (such as an adipic acid ester plasticizer and a sebacic acid ester plasticizer), an aromatic carboxylic acid ester plasticizer (such as a phthalic acid ester plasticizer and a trimellitic acid ester plasticizer), an oxycarboxylic acid ester plasticizer, a phosphate ester plasticizer, an ester plasticizer (such as a polyoxyalkylene glycol such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol) and an ester plasticizer [such as a poly-C _2-4 alkylene glycol ester of a di-C _2-18 fatty acid such as an ester polyethyleneglycol dibutanoic acid, polyethyleneglycol ester of diisobutanoic acid, polyethyleneglycol ester of di-2-ethylbutanoic acid, polyethyleneglycol ester of di-2-ethylhexanoic acid and polyethyleneglycol ester of didecanoic acid; a poly C _2-4 alkylene oxide adduct of a C _2-12 aliphatic dicarboxylic acid such as a polyethyleneoxide adduct of adipic acid; and a di(C _1-12 alkoxy C _2-4 alkyl) C _2-12 aliphatic dicarboxylic acid ester such as a mono- or di(butoxyethyl) adipic acid ester, a di(2-ethylhexyloxyethyl) adipic acid ester and a di(octoxyethyl) adipic acid ester]. These plasticizers may be used singly or in combination of two or more kinds.

[0081] Examples of the adhesion promoter include a co-condensate of resorcinol and formaldehyde (RF condensate) and an amino resin [a condensate of a nitrogen-containing cyclic compound and formaldehyde, for example, a melamine resin such as hexamethylol melamine and hexaalkoxymethyl melamine (such as hexamethoxymethyl melamine and hexabutoxymethyl melamine), a urea resin such as methylol urea, and a benzoguanamine resin such as methylol benzoguanamine resin]. These adhesion promoters may be used singly or in combination of two or more kinds.

[0082] Examples of the tackifier include terpene resin, rosin resin such as natural rosin and modified rosin, petroleum resin, and modified olefin polymer. These tackifiers may be used singly or in combination of two or more kinds.

[0083] Among these friction coefficient adjusting agents, a plasticizer such as an ester-based plasticizer and an ester-based plasticizer is preferable, and the ester-based plasticizer is particularly preferable. The ester-based plasticizer may be a poly-C _2-4 alkylene glycol di-C _4-12 fatty acid ester such as polyethylene glycol di-2-ethylhexanoic acid ester.

[0084] The proportion of the friction coefficient regulating agent (particularly the second plasticizer) is, for example, 1 part by mass to 30 parts by mass, preferably 3 parts by mass to 20 parts by mass, and more preferably 10 parts by mass to 20 parts by mass, relative to 100 parts by mass of the second rubber component. If the proportion of the friction coefficient regulating agent is too small, the effect of increasing the friction coefficient will be small, and if the proportion is too large, the rubber compression layer may become too soft and the lateral pressure resistance may decrease.

[0085] The proportion of the filler (second filler) such as carbon black is, for example, from 10 parts by mass to 200 parts by mass, preferably from 20 parts by mass to 100 parts by mass, more preferably from 30 parts by mass to 100 parts by mass, and even more preferably from 40 parts by mass to 70 parts by mass, relative to 100 parts by mass of the first rubber component.

[0086] The total proportion of the other components (B2) is, for example, from 5 parts by mass to 300 parts by mass, preferably from 10 parts by mass to 200 parts by mass, more preferably from 30 parts by mass to 150 parts by mass, and even more preferably from 50 parts by mass to 100 parts by mass, relative to 100 parts by mass of the second rubber component.

[0087] Since short fiber is a component that reduces the coefficient of friction, it is preferable that the rubber composition forming the inner surface layer substantially does not contain short fiber, and it is particularly preferable that the rubber composition does not contain short fiber.

[0088] (B3) Inner Surface Layer Properties

The coefficient of friction of the surface of the inner surface layer of the rubber compression layer can be selected from a range of approximately 0.35 to 0.75, and is, for example, 0.40 to 0.70 (particularly 0.45 to 0.58), preferably 0.50 to 0.60, and more preferably 0.53 to 0.60. The coefficient of friction can be 0.40 or more. The rubber composition forming the inner surface layer is formed from a composition that does not contain a short fiber, so that the coefficient of friction can be adjusted to 0.40 or more, preferably 0.45 or more, and even more preferably 0.50 or more. If the coefficient of friction of the inner surface layer is too small, the braking performance may be insufficient, and if the coefficient of friction is too large, problems such as abnormal noise and sticking and scattering of rubber may occur.

[0089] In the present application, the coefficient of friction can be measured by the method described in the Examples, which will be described below.

[0090] The difference in the coefficient of friction between the main body of the rubber compression layer and the inner surface layer (the coefficient of friction of the surface of the inner surface layer - the coefficient of friction of the surface of the main body) may be 0.03 or more, and is, for example, from 0.05 to 0.3, preferably from 0.1 to 0.27, more preferably from 0.12 to 0.25, even more preferably from 0.13 to 0.22, and most preferably from 0.15 to 0.2. If the difference in the coefficient of friction between the inner surface layer and the main body is too small, the braking performance may decrease. Conversely, if the difference in the coefficient of friction is too large, problems such as abnormal noise and sticking and scattering of rubber may occur.

[0091] The hardness of the rubber of the inner surface layer of the rubber compression layer may be 85° or less, preferably 82° or less, and more preferably 80° or less, and may be selected from a range of, for example, about 40° to 85° (particularly 50° to 80°), and is, for example, 51° to 80° (for example, 51° to 70°), preferably 52° to 80° (for example, 52° to 60°), more preferably 60° to 79°, even more preferably 70° to 78°, and most preferably 73° to 77°. If the hardness of the rubber of the inner surface layer is too low, the lateral pressure resistance may be insufficient, and if the hardness of the rubber is too high, the bending fatigue resistance may be insufficient.

[0092] The difference in rubber hardness between the main body of the rubber compression layer and the inner surface layer (rubber hardness of the main body - rubber hardness of the inner surface layer) is, for example, from 10° to 50°, preferably from 12° to 45°, and more preferably from 15° to 40°. If the difference in rubber hardness between the main body and the inner surface layer is too small, the bending fatigue resistance may decrease. Conversely, if this difference in rubber hardness is too large, the lateral pressure resistance may decrease.

[0093] The tensile strength of the inner surface layer of the rubber compression layer is, for example, 10 MPa to 25 MPa, preferably 11 MPa to 20 MPa, and more preferably 12 MPa to 15 MPa. If the tensile strength is too small, the lateral pressure resistance may be insufficient, and if the tensile strength is too large, the bending fatigue resistance may be insufficient.

[0094] The difference in tensile strength between the main body of the rubber compression layer and the inner surface layer (tensile strength of the main body - tensile strength of the inner surface layer) is, for example, 5 MPa to 30 MPa, preferably 10 MPa to 25 MPa, and more preferably 15 MPa to 20 MPa. If the difference in tensile strength between the main body and the inner surface layer is too small, the bending fatigue resistance may decrease. Conversely, if this difference in tensile strength is too large, the lateral pressure resistance may decrease.

[0095] The thickness of the inner surface layer is preferably adjusted to a proper thickness of the inner surface layer that ensures high braking performance while maintaining lateral pressure resistance and bending fatigue resistance. In particular, the average thickness of the inner surface layer is from 0.2 mm to 2.5 mm, preferably from 0.3 mm to 2 mm (for example, from 0.5 mm to 2 mm), more preferably from 0.3 mm to 1.5 mm, even more preferably from 0.4 mm to 1.2 mm, and most preferably from 0.5 mm to 1 mm. If the thickness of the inner surface layer is too small, the inner surface layer may wear out prematurely, and the stability of the braking performance may be insufficient. If the thickness of the inner surface layer is too large, the proportion of the main body of the rubber compression layer may decrease, and the lateral pressure resistance may be insufficient. That is, the range described above is the proper range that ensures high braking performance (consistency) while maintaining lateral pressure resistance. The thickness of the inner surface layer should be in the range of the thickness of H3 in the center of the groove due to the structure of the toothed V-belt with untreated edge.

[0096] The average thickness of the inner surface layer can be measured using a microscope, and in particular, this measurement can be performed in the manner described in the Examples that will be described below.

[0097] The average thickness of the inner surface layer is, for example, from 1% to 19%, and preferably from 3% to 13% of the average thickness of the entire belt. The average thickness of the inner surface layer is, for example, from 1% to 25%, preferably from 3% to 20%, more preferably from 4% to 15%, and even more preferably from 5% to 10% of the average thickness of the rubber compression layer (common to the main body and the inner surface layer).

[0098] [Rubber Tension Layer]

The toothed V-belt with a raw edge according to the present invention may further include a rubber tension layer formed from a rubber composition (crosslinked rubber composition) containing a third rubber component.

[0099] The third rubber component may be selected from the rubber components exemplified by the first rubber component, including the preferred aspects. The third rubber component may be a rubber component different from the first rubber component, but is typically the same as the first rubber component.

[0100] The rubber composition forming the rubber tension layer also preferably contains a second short fiber from the viewpoint of further improving the lateral pressure resistance and the abrasion resistance. If the rubber tension layer and the main body of the rubber compression layer contain the second short fiber as the mentioned short fiber, the lateral pressure resistance and the abrasion resistance are further improved. The second short fiber can be selected from the short fibers exemplified by the first short fiber, including the preferred aspect. The second short fiber may be a short fiber different from the first short fiber, but it is usually the same as the first short fiber. The proportion of the second short fiber can be selected from the proportion of the first short fiber, including the preferred proportion.

[0101] The rubber composition forming the rubber tension layer may further contain other components exemplified for the rubber composition forming the main body of the rubber compression layer.

[0102] The properties of the rubber tension layer can be selected from the properties (such as hardness, tensile strength, coefficient of friction) of the main body of the rubber compression layer described above, including the preferred ranges.

[0103] [Tension Element Layer]

The tension member layer may include the tension member and may be a tension member layer formed only from the tension member, but it is preferable that the tension member layer is a tension member layer (adhesive rubber layer) formed from a crosslinked rubber composition in which the tension member is embedded, from the viewpoint of preventing peeling between layers and improving the durability of the belt. The adhesive rubber layer is arranged 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 tension member is embedded in the adhesive rubber layer.

[0104] [Adhesive Rubber Layer)

The toothed V-belt with a raw edge according to the present invention may further include an adhesive rubber layer formed from a curable product (crosslinkable rubber composition) of a rubber composition containing a fourth rubber component.

[0105] The fourth rubber component may be selected from the rubber components exemplified by the first rubber component, including the preferred aspects. The fourth rubber component may be a rubber component different from the first rubber component, but is usually the same as the first rubber component.

[0106] The rubber composition forming the adhesive rubber layer may further contain short fibers or other components exemplified for the rubber composition forming the main body of the compression rubber layer.

[0107] It is preferable that the adhesive rubber layer has a rubber hardness lower than that of the main body of the compression rubber layer. The rubber hardness of the adhesive rubber layer is, for example, from 60° to 85°, preferably from 65° to 84°, more preferably from 70° to 83°, and even more preferably from 75° to 82°. If the rubber hardness is too low, the lateral pressure resistance may be insufficient, and if the rubber hardness is too high, the adhesive ability may decrease. By adjusting the adhesive rubber layer to such a low hardness, it becomes possible to deform it significantly under the action of shear stress, and peeling of the tension member from the main body of the compression rubber layer and the tension rubber layer is prevented.

[0108] The average thickness of the adhesive rubber layer is, for example, from 0.8 mm to 3 mm, preferably from 1.2 mm to 2.8 mm, and even more preferably from 1.5 mm to 2 mm.

[0109] (Tension Element]

The tension member is not particularly limited, and a cord (twisted cord) arranged at a predetermined interval in the belt width direction may generally be used. The cords are arranged in the longitudinal direction of the belt, and although a plurality of cords may be arranged parallel to the longitudinal direction of the belt, from the viewpoint of efficiency, the cords are generally arranged in parallel in a spiral shape extending substantially parallel to the longitudinal direction of the belt of the toothed V-belt with a predetermined pitch. In the case of spiral arrangement, the angle of the cord 18 with respect to the longitudinal direction of the belt may be, for example, 5° or less, and it is preferable that this angle is closer to 0° from the viewpoint of belt performance. The pitch of the cords is preferably set in the range of 1.5 mm to 2.5 mm, and more preferably in the range of 1.8 mm to 2.2 mm.

[0110] It is sufficient that at least a part of the cord is in contact with the adhesive rubber layer, and the cord may be in any form from a form in which the cord is embedded in the adhesive rubber layer, a form in which the cord is embedded between the adhesive rubber layer and the tension rubber layer, and a form in which the cord is embedded between the adhesive rubber layer and the compression rubber layer. Among these, the form in which the cord is embedded in the adhesive rubber layer is preferable from the viewpoint of improving durability.

[0111] Examples of the fiber forming the cord include the same fiber as the short fiber. Among the fibers, synthetic fiber such as polyester fiber (polyalkylene arylate fiber) having _C2-4 alkylene- _C6-12 allylate such as ethylene terephthalate and ethylene 2,6-naphthalate as a main structural unit, as well as aramid fiber, inorganic fiber such as carbon fiber and the like are widely used in terms of high elastic modulus, but polyester fiber (such as polyethylene terephthalate fiber and polyethylene naphthalate fiber) and aramid fiber are preferable. The fiber may be a multifilament yarn. The multifilament yarn may comprise monofilament yarns, for example, from 100 fibers to 5000 fibers, preferably from 500 fibers to 4000 fibers, and more preferably from 1000 fibers to 3000 fibers.

[0112] As the cord, a twisted cord comprising a multifilament yarn (for example, a folded cord, a single twisted cord or a Lang twisted cord) can be used as a rule. The average wire diameter of the cord (the twisted cord diameter) can be, for example, about 0.5 mm to 3 mm, preferably about 0.6 mm to 2 mm, and more preferably about 0.7 mm to 1.5 mm. The total fineness of the cord (twisted cord) can be, for example, from 2,000 dtex to 17,000 dtex, preferably from 4,000 dtex to 15,000 dtex, and more preferably from 5,000 dtex to 13,000 dtex (particularly from about 6,000 dtex to 8,000 dtex).

[0113] In order to improve the adhesion to the rubber component, the cord may be subjected to an adhesion treatment (or surface treatment) in the same manner as the short fibers. It is preferable that the cord is subjected to an adhesion treatment with at least an RFL liquid.

[0114] [Reinforcing Fabric]

The toothed V-belt with a raw edge according to the present invention may include a reinforcing fabric. Examples of the form of the reinforcing fabric include a form in which a layer of the reinforcing fabric is provided on the outer peripheral surface of the rubber tension layer, a form in which the reinforcing fabric is embedded in the main body of the rubber compression layer and/or the rubber tension layer, and a form in which the reinforcing fabric is embedded between the main body of the rubber compression layer and the inner surface layer.

[0115] The reinforcing fabric may be formed by, for example, a fabric material (particularly a woven fabric) such as a woven fabric, a wide-angle canvas fabric, a knitted fabric or a non-woven fabric, and, if necessary, a reinforcing fabric layer may be provided on or it may be embedded in the compression rubber layer and/or the tension rubber layer in the above-mentioned forms after an adhesive treatment such as an RFL liquid treatment (such as a dip treatment), a friction treatment in which an adhesive rubber is rubbed into a fabric material, or lamination of an adhesive rubber and a fabric material.

[0116] [Method of Manufacturing Toothed V-Belt with Raw Edge]

The method for producing the toothed V-belt with a raw edge according to the present invention is not particularly limited, and a generally accepted method can be used for the lamination process of each layer (the wicket production method) depending on the type of belt.

[0117] For example, a conventional method for producing a toothed V-belt with an unprocessed edge will be described below. First, a laminated body including an inner surface layer sheet (an unstitched rubber sheet) of a compression rubber layer and a main body sheet of a compression rubber layer (an unstitched rubber sheet) is arranged so that the inner surface layer sheet is in contact with a flat toothed mold in which toothed portions and groove portions corresponding to the toothed portions of the inner periphery are alternately arranged, and pressing is performed at a temperature of 60°C to 120°C (particularly, 80°C to 100°C) to obtain a toothed lining having a molded toothed portion (a lining that is not completely stitched and is in a semi-stitched state). Then, both edges of the toothed lining may be cut perpendicularly from a proper position (particularly, the upper portion of the tooth ridge portion proper). Then, the outer periphery of the cylindrical mold is covered with an inner mother mold having toothed portions and groove portions alternately arranged, the toothed lining is wound by engaging with the toothed portions and groove portions of the inner mother mold to be connected at both edges (particularly, the top of the tooth ridge portion), the second sheet of the adhesive rubber layer (lower adhesive rubber: uncrosslinked rubber sheet) can be laminated onto the outer periphery of the toothed lining, and then the cord (twisted cord) for forming a tension member can be braided in a spiral, and the first sheet of the adhesive rubber layer (upper adhesive rubber: uncrosslinked rubber sheet) and the sheet of the tension rubber layer (uncrosslinked rubber sheet) can be sequentially wound onto the outer periphery thereof to obtain an uncrosslinked molded article.

[0118] After this, the unstitched molded article is covered with a jacket and placed in a well-known stitching device (such as a vulcanization tank), and stitching molding is carried out at a temperature of 120°C to 200°C (particularly, 150°C to 180°C) to obtain a stitched wickel. Then, using a cutter or the like, the stitched wickel is cut into a V-shape to obtain an endless toothed V-belt with a raw edge.

[0119] In the case of a double-sided toothed V-belt with a raw edge, while the outer periphery of the unstitched molded article is covered with an outer mother mold having alternately arranged toothed portions and groove portions corresponding to the toothed portions of the outer periphery, the outer periphery is covered with a jacket, and stitching is performed to obtain a stitched serrated part with a toothed portion formed on the outer peripheral surface, and the stitched serrated part is cut with a V-shape to obtain a double-sided toothed V-belt with a raw edge.

[0120] The adhesive rubber layer may be formed by a plurality of sheets of adhesive rubber layers, and the cord (twisted cord) that forms the tension member may be woven in accordance with the lamination order of the sheets of adhesive rubber layers of said plurality depending on the embedding position in the adhesive rubber layer.

Examples

[0121] Next, the present invention will be described in more detail based on Examples, but the present invention is not limited to these Examples. Detailed information on the materials used in the Examples, the method for producing the non-crosslinked rubber sheet, and the method for measuring or evaluating each of the physical properties are given below.

[0122] [Materials Used]

Chloroprene rubber: "PM-40" produced by DENKA Co., Ltd.

Magnesium oxide: "KyowaMag 30" manufactured by Kyowa Chemical Industry Co., Ltd.

Stearic acid: "TSUBAKI Stearic Acid" by NOF Corporation

Anti-aging agent: "Nonflex OD-3" manufactured by Seiko Chemical Co., Ltd.

Carbon black: "Seast 3" by Tokai Carbon Co., Ltd.

Silicon dioxide: "ULTRASIL (registered trademark) VN3" manufactured by Evonik Japan Co., Ltd., BET specific surface area: 175 ^m2 /g

Plasticizer 1: naphthenic oil, "NS-900" from Idemitsu Kosan Co., Ltd.

Plasticizer 2: "RS-700" manufactured by ADEKA Co., Ltd.

Crosslinking accelerator: tetramethylthiuram disulfide ("Nocceler TT" manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.)

Zinc Oxide: "Third Grade Zinc Oxide" produced by Seido Chemical Industry Co., Ltd.

Sulfur: "Sulfur" produced by Miwon Chemical Co., Ltd.

N,N'-m-phenylenedimaleimide: "Vulnoc PM" manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.

Resorcinol-formaldehyde copolymer (resorcinol resin): resorcinol-formaldehyde copolymer with a resorcinol content of less than 20% by weight and a formalin content of less than 0.1% by weight

Hexamethoxymethylolmelamine: "POWERPLAST PP-1890S" manufactured by Singh Plasticisers & Resins Pvt. Ltd.

Aramid short fiber: “Conex Short Fiber” produced by Teijin Co., Ltd., short fiber with an average fiber length of 3 mm, an average fiber diameter of 14 μm, an adhesion coefficient of solid content of 6 mass%, subjected to adhesive treatment with RFL liquid (resorcinol: 2.6 parts by mass, 37% formalin: 1.4 parts by mass, vinylpyridine, styrene and butadiene copolymer latex (produced by Zeon Corporation, Japan): 17.2 parts by mass, water: 78.8 parts by mass)

Cord: treated cord (cord diameter 1.28 mm) obtained by carrying out adhesive treatment on twisted cord having a total fineness of 6600 dtex, in which aramid fibers having a fineness of 1100 dtex are twisted in a 2×3 configuration to obtain organzine with a primary twist coefficient of 3.0 and a secondary twist coefficient of 3.0

Reinforcement fabric: Nylon canvas 2/2 twill fabric (thickness: 0.30mm to 0.50mm), subjected to adhesive treatment with RFL liquid.

[0123] [Production of Non-Stitched Rubber Sheet for Rubber Layer]

Rubber compositions for forming a compression rubber layer (main body, inner surface layer), a tension rubber layer and an adhesive rubber layer were prepared in the mixing ratios shown in Tables 1 and 2 below. The rubber compositions for forming each layer were kneaded using a Banbury mixer, and the resulting kneaded rubber was passed through a calender roll to obtain a roll rubber sheet (non-crosslinked rubber sheet). In this application, the rubber compositions are designated as R1 to R7, respectively.

[0124]

Table 1

Main body rubber compression layer and rubber tension layer Adhesive rubber layer R1 R2 Composition (mass part) Chloroprene rubber 100 100 Aramid short fiber 20 - Plasticizer 1 5 - Plasticizer 2 - 5 Magnesium oxide 4 4 Carbon black 50 40 Silicon dioxide - 20 Anti-aging agent 4 4 Zinc oxide 5 5 N,N'-m-phenylenedimaleimide 3 2 Stearic acid 2 2 Sulfur 0.5 - Stitching accelerator - 1 Copolymer of resorcinol and formalin - 1 Hexamethoxymethylolmelamine - 3 Hardness Hs (type A) (°) 93 82 Tensile strength (MPa) [parallel to grain direction] 30.5 19.0

[0125]

Table 2

Inner surface layer R3 R4 R5 R6 R7 Composition (mass part) Chloroprene rubber 100 100 100 100 100 Aramid short fiber - - - - 5 Plasticizer 1 - - - - 5 Plasticizer 2 5 20 10 30 - Magnesium oxide 4 4 4 4 4 Carbon black 40 50 50 40 40 Silicon dioxide 20 - - - - Anti-aging agent 4 4 4 4 4 Zinc oxide 5 5 5 5 5 N,N'-m-phenylenedimaleimide 2 - - - - Stearic acid 2 - - 1 2 Sulfur - 1 1 - 0.5 Stitching accelerator 1 1 1 1 - Copolymer of resorcinol and formalin 1 - - - - Hexamethoxymethylolmelamine 3 - - - - Hardness Hs (type A) (°) 82 54 76 46 84 Tensile strength (MPa) [parallel to grain direction] 19.0 12.3 14.5 11.5 23.0

[0126] [Hardness Hs of rubber of cross-linked rubber itself]

The uncrosslinked rubber sheet for each rubber layer was subjected to heat pressing at 160°C for 30 minutes to obtain a crosslinked rubber sheet (100 mm × 100 mm × 2 mm (thickness)). A laminate obtained by laminating three crosslinked rubber sheets was used as a sample, and the hardness of the crosslinked rubber sheet was measured using a type A durometer in accordance with the spring type durometer hardness test specified in JIS K6253 (2012).

[0127] [Tensile strength of cross-linked rubber]

A cross-linked rubber sheet prepared for measuring the rubber hardness Hs of the cross-linked rubber itself was used as the specimen, and a dumbbell-shaped test specimen (No. 5 mold) was produced in accordance with JIS K6251 (2017). In a specimen containing a short fiber, the dumbbell-shaped test specimen was selected so that the arrangement direction of the short fiber (fiber direction) was the tensile direction. The value (tensile strength T) obtained by dividing the maximum tensile force recorded when both ends of the test specimen were clamped with a chuck (clamp) and the test specimen was stretched at a speed of 500 mm/min until the test specimen broke, by the initial cross-sectional area of the test specimen was determined as the tensile strength.

[0128] [Production of Double-Sided Toothed V-Belt with Raw Edge]

The method described in the above embodiment was used to produce a double-sided toothed V-belt with a raw edge (size: top width 38.5 mm, V angle: 26 degrees, thickness (H1): 15.5 mm, tooth height (inner periphery side: H2): 6.8 mm, tooth height (outer periphery side: H5): 3.8 mm, pitch height (H4): 5.3 mm, thickness at the center of the groove (H3): 3.4 mm, belt outer periphery length: 1109 mm).

[0129] [Measurement of Inner Surface Layer Thickness]

The double-sided toothed V-belt with untreated edge was cut parallel to the belt width direction at the top of the tooth, and its cross section was examined using a microscope at 20 times magnification to measure the thickness of the inner surface layer. The thickness was measured at 5 points in such a way that the belt was approximately divided into 5 equal parts in the length direction, and the arithmetic mean of the thickness values at 5 points was taken as the thickness of the inner surface layer of the belt.

[0130] [V-belt evaluation]

(1) Coefficient of Friction of the Inner Peripheral Surface of the Belt

As shown in FIG. 7, one end of the test piece 40 of the belt 40, which had ends due to being cut, was fixed to the load cell 41, and a load 42 of 3 kgf (test load Ts) was suspended from the other end, and the inner peripheral surface of the test piece of the belt was placed in contact with a flat pulley 43 (diameter: 47.6 mm, material: SUS304, surface roughness Ra: 1.6 μm in accordance with JIS B 0601) such that the winding angle θ was 90°. The load (measured load Tt) detected by the load cell was read when the test piece of the belt on the side of the load cell 41 was pulled at a speed of 42 mm/s for about 15 seconds, and the static friction coefficient μ was calculated using the following formula (1). The friction coefficient (average friction coefficient) of the inner peripheral surface of the belt was taken as the average value of the static friction coefficients obtained from the results of three measurements. The flat pulley was fixed so as not to rotate during this measurement.

[0131] μ=ln (Tt/Ts)/θ (1)

(In this formula μ: coefficient of static friction

Tt [N]: measured load

Ts [N]: test load

θ [rad]: winding angle (contact angle)).

[0132] (2) Durability Performance Test (Upper Durability Test)

As shown in FIG. 8, a two-axle performance test machine including a driving (DR) pulley with a diameter (pitch circle diameter) of 178 mm and a driven (DN) pulley with a diameter (pitch circle diameter) of 140 mm was used to conduct a test to confirm the tooth root crack resistance (bending fatigue resistance). A double-sided toothed V-belt with a raw edge was tensioned on pulleys, and the driving pulley was rotated at 6000 rpm, the axial load (dead weight) was 1.2 kN, and a load of 60 Nm was applied by a loading device (power generation device), after which the belt was operated at an ambient temperature of 115 °C, and the operating time until the cracks formed in the tooth valley reached the cord and the life cycle ended was measured as the service life.

[0133] (Determination Criteria for Performance Durability Test (Upper Durability Test))

a: service life of 130 hours or more (successful completion)

b: service life of 110 hours or more but less than 130 hours (pass)

c: service life less than 110 hours (failure).

[0134] (3) Durability Performance Test (Bottom Durability Test)

As shown in FIG. 9, a two-axle performance test machine including a driving (DR) pulley with a diameter (pitch circle diameter) of 92 mm and a driven (DN) pulley with a diameter (pitch circle diameter) of 208 mm was used to conduct a cord peeling resistance (side pressure resistance) confirmation test. A double-sided toothed belt with a raw edge was pulled onto the pulleys, and the driving pulley was rotated at a speed of 5,000 rpm, the axial load (dead weight) was 2.2 kN, and a load of 50 Nm was applied by a loading device (power generation device), after which the belt was operated at an ambient temperature of 60 °C, and the operating time until cord peeling occurred was measured as the service life.

[0135] (Determination Criteria for Performance Durability Test (Bottom Durability Test))

a: service life of 30 hours or more (successful completion)

b: service life of 10 hours or more but less than 30 hours (pass)

c: service life less than 10 hours (failure to complete).

[0136] (4) Braking Performance Test (Engine Braking Performance in Real Vehicle)

A double-sided toothed V-belt with a raw edge was adopted for the CVT of a 1000cc all-terrain vehicle (off-road vehicle), and a test was conducted on an actual vehicle. The throttle was returned from the maximum acceleration position while the vehicle was still moving, and the time it took for the driven pulley speed to drop from 478 rpm to 0 rpm without applying the brake was measured.

[0137] (Determination Criteria for Braking Performance Test)

a: Time to reach 0 rpm is 7 seconds or less (pass)

b: Time to reach 0 rpm is more than 7 seconds but less than 8 seconds (pass)

c: The time to reach 0 rpm is more than 8 seconds (failure).

[0138] (5) Brake Consistency Test (Engine Braking Consistency in Real Vehicle)

After the vehicle on which the braking performance test was conducted had been driven for 500 miles on a rough road (off-road), the braking performance was confirmed using the method described for the braking performance test. The braking consistency was determined by the following criteria in terms of whether the braking performance after 500 miles had maintained the initial braking performance (before 500 miles) at a high level or whether this level had decreased. If the braking performance test failed (defined as c), the braking consistency test was not conducted.

[0139] (Determination Criteria for the Braking Continuity Test)

a: braking performance before and after 500 miles is high (definition a is maintained)

b: braking performance after 500 miles is defined as b (decrease from definition a to definition b, maintained as definition b)

c: The braking performance after 500 miles is defined as c (decrease from definition a or b to definition c).

[0140] (6) Complex definition

Based on the results of durability performance tests (upper durability test, lower durability test), braking performance test and braking consistency test, superiority or inferiority was determined (ranked) comprehensively according to the following criteria in terms of demonstrating braking performance while ensuring bending fatigue resistance (tooth valley crack resistance) and lateral pressure resistance (cord peeling resistance) at the level required for a CVT belt. From the viewpoint of product practicality, ranks A, B and C were determined to be successful, and rank D was determined to be unsuccessful.

[0141]

Table 3

Complex definition Engine braking efficiency Continuous engine braking Durability of the upper Durability of the bottom Rank A Definition of ‘a’ Definition of ‘a’ Definition of ‘a’ Definition of ‘a’ Rank B Definition of 'a' or 'b' Does not include definition 'c', but includes one definition 'b' Rank C Definition of 'a' or 'b' One definition of 'c' is included Definition of 'a' or 'b' Does not include definition 'c', but includes two or more definitions 'b' Rank D Definition of 'a' or 'b' Includes two or more definitions of 'c' Definition of ‘c’ All definitions

[0142] [Example 1]

R1 was used for the tension rubber layer, R2 was used for the adhesive rubber layer, R1 was used for the main body of the compression rubber layer, and R4 was used for the inner surface layer of the compression rubber layer to produce a double-sided toothed V-belt with raw edge in which the compression rubber layer was a two-layer structure. In the obtained belt, the thickness of the main body of the compression rubber layer was 9.3 mm, and the thickness of the inner surface layer was 0.2 mm.

[0143] [Example 2]

A double-sided toothed V-belt with a raw edge was produced in the same manner as in Example 1, except that the thickness of the main body of the compression rubber layer in the resulting belt was changed to 9.2 mm, and the thickness of the inner surface layer in the resulting belt was changed to 0.3 mm.

[0144] [Example 3]

A double-sided toothed V-belt with a raw edge was produced in the same manner as in Example 1 except that the thickness of the main body of the compression rubber layer in the resulting belt was changed to 9.0 mm, and the thickness of the inner surface layer in the resulting belt was changed to 0.5 mm.

[0145] [Example 4]

A double-sided toothed V-belt with a raw edge was produced in the same manner as in Example 1 except that the thickness of the main body of the compression rubber layer in the resulting belt was changed to 8.5 mm, and the thickness of the inner surface layer in the resulting belt was changed to 1.0 mm.

[0146] [Example 5]

A double-sided toothed V-belt with a raw edge was produced in the same manner as in Example 1 except that the thickness of the main body of the compression rubber layer in the resulting belt was changed to 7.5 mm, and the thickness of the inner surface layer in the resulting belt was changed to 2.0 mm.

[0147] [Example 6]

A double-sided toothed V-belt with a raw edge was produced in the same manner as in Example 1 except that the thickness of the main body of the compression rubber layer in the resulting belt was changed to 7.0 mm, and the thickness of the inner surface layer in the resulting belt was changed to 2.5 mm.

[0148] [Examples 7 through 12]

In Examples 7 through 12, double-sided cogged V-belts with raw edges were produced in the same manner as in Examples 1 through 6, except that R5 was used for the inner surface layer of the compression rubber layer instead of R4.

[0149] [Comparative Example 1]

R1 was used for the tension rubber layer, R2 was used for the adhesive rubber layer, and only R1 was used for the compression rubber layer to produce a double-sided toothed V-belt with a raw edge, in which the compression rubber layer was a single-layer structure. In the obtained belt, the thickness of the compression rubber layer was 9.5 mm. Namely, it is a form where each of the inner peripheral surfaces of the main bodies of the compression rubber layers in Examples 1 to 12 is not covered with an inner surface layer, and the inner peripheral surface of the belt is formed from R1.

[0150] [Comparative Example 2]

A double-sided toothed V-belt with a raw edge in which the compression rubber layer had a single-layer structure was produced in the same manner as in Comparative Example 1, except that only R4 was used for the compression rubber layer. That is, it is a mold in which not only the inner surface layer but also the main body of the compression rubber layer in each of Examples 1 to 6 were formed of R4. The entire compression rubber layer was formed of R4.

[0151] [Comparative Example 3]

A double-sided toothed V-belt with a raw edge in which the inner circumferential surface of the main body of the compression rubber layer was covered with a reinforcing fabric was produced in the same manner as in Example 1, except that the reinforcing fabric was used instead of the inner surface layer of the compression rubber layer. That is, the inner circumferential surface of the belt was formed by the reinforcing fabric. In this form, the thickness of the reinforcing fabric layer was 0.3 mm.

[0152] [Reference Example 1]

A rubber-bonded reinforcing fabric obtained by friction-treating the reinforcing fabric used in Comparative Example 3 with a rubber composition (R4) was produced. A double-sided toothed V-belt with an untreated edge in which the inner peripheral surface of the main body of the compression rubber layer was covered with a rubber-bonded reinforcing fabric was produced in the same manner as Example 1 except that the rubber-bonded reinforcing fabric was used instead of the inner surface layer of the compression rubber layer. That is, it is a mold in which the inner surface layer of the belt in each of the Examples was arranged as a rubber-bonded reinforcing fabric layer (the reinforcing fabric was embedded in the rubber composition). In this mold, the thickness of the rubber-bonded reinforcing fabric layer was 0.5 mm, and the outer surface of the rubber-bonded reinforcing fabric layer (the inner peripheral surface of the belt) was formed by an R4 thin film of 0.2 mm in thickness.

[0153] The evaluation results of the double-sided toothed V-belts with untreated edges obtained in Examples 1 to 12, Comparative Examples 1 to 3, and Reference Example 1 are shown in Table 4.

[0154]

Table 4

Example 1 2 3 4 5 6 7 8 9 10 11 12 Rubber compression layer Main body R1 Hardness Hs (type A) (°) 93 Inner surface layer R4 R5 Hardness Hs (type A) (°) 54 76 Thickness (mm) 0.2 0.3 0.5 1.0 2.0 2.5 0.2 0.3 0.5 1.0 2.0 2.5 Coefficient of friction of the inner peripheral surface of the belt 0.58 0.58 0.56 0.53 0.57 0.55 0.53 0.52 0.51 0.52 0.50 0.51 Durability performance test Upper durability: resistance to cracking in the tooth valleys
Service life (hours) 134 135 134 143 162 115 140 137 135 137 157 124 Definition a a a a a b a a a a a b Bottom Durability: Resistance to Cord Peeling
Service life (hours) 36 35 35 33 24 12 38 39 40 34 25 13 Definition a a a a b b a a a a b b Test on a real vehicle Engine braking efficiency Initial a a a a a a a a a a a a After the run c b a a a a c b a a a a Continuous engine braking c b a a a a c b a a a a Complex definition C B A A B C C B A A B C

Table 4 (continued)

Comparative Example Reference Example 1 2 3 1 Rubber compression layer Main body R1 R4 R1 R1 Hardness Hs (type A) (°) 93 54 93 93 Inner surface layer No No Reinforcing fabric Reinforcing fabric with attached R4 Hardness Hs (type A) (°) - - - 54 Thickness (mm) - - 0.3 0.5 Coefficient of friction of the inner peripheral surface of the belt 0.36 0.57 0.34 0.55 Durability performance test Upper durability: resistance to cracking in the tooth valleys
Service life (hours) 127 65 140 158 Definition b c a a Bottom Durability: Resistance to Cord Peeling
Service life (hours) 36 5 33 32 Definition a c a a Test on a real vehicle Engine braking efficiency Initial c a c a After the run - a - c Continuous engine braking - a - c Complex definition D D D C

[0155] In Comparative Example 1, the main body of the compression rubber layer is formed of R1, and the inner circumferential surface of the main body of the compression rubber layer is not covered with an inner surface layer. The friction coefficient of the inner circumferential surface of the belt formed of R1 was a low value of 0.36. In the durability performance test, for Bottom Durability (lateral pressure resistance; cord peeling resistance) it was determined to be ‘a’, for Top Durability (bending fatigue resistance, tooth valley crack resistance) it was determined to be ‘b’, which corresponded to the pass levels, but sufficient friction force was not obtained, the engine braking performance was determined to be ‘c’ (failure), and the comprehensive determination was assigned the rank of D.

[0156] In Comparative Example 2, not only the inner surface layer but also the main body of the compression rubber layer were formed of R4. Since the friction coefficient of the inner peripheral surface of the belt formed of R4 had a high value of 0.57, sufficient friction force was obtained, and the engine braking performance was determined to be ‘a’ (passable). On the other hand, since the entire rubber compression layer was formed of R4 which had low rigidity, in the durability performance test, the life cycle was prematurely terminated due to insufficient rigidity in both the bottom performance test (lateral pressure resistance; cord peel resistance) and the top performance test (flexural fatigue resistance, tooth valley crack resistance), and the determination was made as ‘c’ (failure) and the comprehensive determination was assigned rank D.

[0157] In Comparative Example 3, the inner circumferential surface of the main body of the compression rubber layer was covered with a reinforcing fabric, and the friction coefficient of the inner circumferential surface of the belt formed by the reinforcing fabric had a low value of 0.34. In the durability performance test, in the bottom durability test (lateral pressure resistance; cord peeling resistance) and the top durability test (bending fatigue resistance, tooth gullet crack resistance) it was determined to be ‘a’, but sufficient friction force was not obtained, the engine braking performance was determined to be ‘c’ (failure), and the comprehensive determination was assigned a rank of D.

[0158] In Examples 1 to 6, the compression rubber layer had a two-layer structure in which R1 was used for the main body of the compression rubber layer, and R4 was used for the inner surface layer of the compression rubber layer. In any case, the friction coefficient of the inner circumferential surface of the belt formed from R4 was a high value of 0.53 to 0.58. Thus, sufficient friction force was obtained, and the engine braking performance was determined to be ‘a’ (passable).

[0159] Specifically, when the thickness of the inner surface layers was 0.5 mm (Example 3) and 1.0 mm (Example 4), all test items (bottom durability test, top durability test, engine braking performance, engine braking consistency) were determined to be ‘a’ (passed), and rank A was assigned in the comprehensive determination.

[0160] When the thickness of the inner surface layer was increased to 2.0 mm (Example 5), the lateral pressure resistance was reduced and a ‘b’ was determined in the bottom durability test and a B rank was assigned in the comprehensive definition. When the thickness of the inner surface layer was increased to 2.5 mm (Example 6), the life cycle in the bottom durability test (lateral pressure resistance) was further reduced (determined as ‘b’) and the life cycle in the upper durability test (flexural fatigue resistance; tooth valley crack resistance) was also reduced (determined as ‘b’) and a C rank was assigned in the comprehensive definition.

[0161] When the thickness of the inner surface layer was reduced to 0.3 mm (Example 2), the bottom durability test, the upper durability test and the engine braking performance were initially determined as ‘a’ at the same levels as those in Examples 3 and 4, but when the inner surface layer was worn out during operation, exposing the main body of the compression rubber layer, the braking performance became low, and thus the braking performance after running was determined as ‘b’, and the constancy of the braking performance decreased and was determined as ‘b’, and was assigned rank B in the comprehensive determination.

[0162] When the thickness of the inner surface layer was reduced to 0.2 mm (Example 1), the bottom durability test, the upper durability test and the engine braking performance were determined to be ‘a’ at the same levels as those in Examples 3 and 4, but when the inner surface layer was prematurely worn out, exposing the main body of the compression rubber layer, the braking performance became low, and thus the braking performance after a run was determined to be ‘c’, and the constancy of the braking performance could not be obtained and was determined to be ‘c’, and a rank of C was assigned in the comprehensive determination.

[0163] In Examples 7 to 12, the inner surface layers of the rubber compression layers in Examples 1 to 6 were changed from R4 to R5, and each rubber compression layer had a two-layer structure. In these Examples, the friction coefficients of the inner peripheral surfaces of the belt formed from R5 had high values of 0.50 to 0.53. Thus, sufficient friction force was obtained, and the engine braking performance was determined to be ‘a’ (passable).

[0164] When the thickness of the inner surface layer was changed to 0.2 mm (Example 7), 0.3 mm (Example 8), 0.5 mm (Example 9), 1.0 mm (Example 10), 2.0 mm (Example 11), and 2.5 mm (Example 12), the same levels and trend were observed as in Examples 1 through 6.

[0165] Reference Example 1 was a mold in which the inner peripheral surface of the main body of the compression rubber layer was covered with a reinforcing fabric with attached rubber, that is, a mold in which the inner surface layer of the belt in Example was arranged as a layer of reinforcing fabric with attached rubber (a reinforcing fabric embedded in a rubber composition). In this mold, the outer surface of the layer of reinforcing fabric with attached rubber (the inner peripheral surface of the belt) was formed by a thin film R4 of 0.2 mm in thickness, and thus the friction coefficient of the inner peripheral surface of the belt formed from R4 had a high value of 0.55. Thus, sufficient friction force was obtained, and the engine braking performance was determined to be ‘a’ (successful passing). However, when the R4 thin film (0.2mm thick) wore out prematurely, exposing the reinforcing fabric, the braking performance became low and thus the braking performance consistency was not obtained and was determined as ‘c’, and was assigned rank C in the comprehensive definition.

[0166] As described above, from the results of the durability performance test (upper durability test, lower durability test), braking performance test and braking consistency test, when superiority or inferiority was comprehensively determined (ranked) in terms of demonstrating the braking performance while ensuring the bending fatigue resistance (tooth valley crack resistance) and the lateral pressure resistance (cord peeling resistance) at the level required for the CVT belt, it can be said that it is effective to form a two-layer structure by providing an inner surface layer with a high coefficient of friction on the inner peripheral surface of the main body of the compression rubber layer. It can be confirmed that the braking function (high friction force) was exhibited when the coefficient of friction of the inner surface layer of the compression rubber layer was approximately 0.50 to 0.58.

[0167] It was confirmed that the braking function (high friction force) was exhibited when the average thickness of the inner surface layer was in the range of 0.2 mm to 2.5 mm, but from the viewpoint of the balance between the constancy of the braking performance and the lateral pressure resistance, it could be said that the range of 0.5 mm to 2.0 mm was particularly suitable.

[0168] [Example 13]

In Example 13, a double-sided toothed V-belt with a raw edge was produced in the same manner as in Example 3 except that R6 was used instead of R4 for the inner surface layer of the compression rubber layer.

[0169] [Example 14]

In Example 14, a double-sided toothed V-belt with a raw edge was produced in the same manner as in Example 3 except that R3 was used instead of R4 for the inner surface layer of the compression rubber layer.

[0170] [Example 15]

In Example 15, a double-sided raw-edge toothed V-belt was produced in the same manner as in Example 3 except that R7 was used for the inner surface layer of the compression rubber layer instead of R4.

[0171] The evaluation results of the double-sided toothed V-belts with untreated edges obtained in Examples 13 through 15 are shown in Table 5 together with the results of Examples 3 and 9.

[0172]

Table 5

Example 13 3 9 14 15 Rubber compression layer Main body R1 Hardness Hs (type A) (°) 93 Inner surface layer R6 R4 R5 R3 R7 Hardness Hs (type A) (°) 46 54 76 82 84 Thickness (mm) 0.5 Coefficient of friction of the inner peripheral surface of the belt 0.60 0.56 0.51 0.42 0.39 Durability performance test Upper durability: resistance to cracking in the tooth valleys
Service life (hours) 135 134 135 135 135 Definition a a a a a Bottom Durability: Resistance to Cord Peeling
Service life (hours) 36 35 40 38 38 Definition a a a a a Test on a real vehicle Engine braking efficiency Initial a a a b b After the run b a a b c Continuous engine braking b a a b c Complex definition B A A B C

[0173] In Example 13, the rubber composition of the inner surface layer in Example 3 was changed from R4 to R6. That is, it is a form where a rubber composition with a friction coefficient higher than that in Example 3 was used. Although the durability performance and engine braking performance were high (defined as ‘a’), the inner surface layer was formed of a rubber composition with low mechanical strength (rubber hardness, tensile strength), and therefore this layer disappeared relatively early due to wear, and the engine braking stability was defined as ‘b’, and was assigned a rank of B in the comprehensive definition.

[0174] In Examples 14 and 15, the rubber composition of the inner surface layer of Example 3 was changed from R4 to R3 and R7, respectively. That is, it is a form where a rubber composition with a coefficient of friction lower than that of Example 3 is used. Although the durability performance was determined as ‘a’, the engine braking performance was slightly lower (determined as ‘b’). In Example 14, in which the coefficient of friction of the inner circumferential surface of the belt was 0.42, the engine braking performance was maintained after 500 miles of running (the constancy was determined as ‘b’), and a B rank was assigned in the comprehensive determination. In Example 15, in which the coefficient of friction of the inner circumferential surface of the belt was 0.39, the engine braking performance decreased after 500 miles of running (the constancy was determined as ‘c’), and a C rank was assigned in the comprehensive determination.

[0175] From the above results, it is evident that the friction coefficient of the inner peripheral surface of the belt is preferably 0.40 or more, and even more preferably 0.50 or more from the viewpoint of the engine braking performance level.

[0176] In Table 5, the coefficient of friction decreases in the following order: Example 13 (coefficient of friction of 0.60), Example 3 (coefficient of friction of 0.56), Example 9 (coefficient of friction of 0.51), Example 14 (coefficient of friction of 0.42), and Example 15 (coefficient of friction of 0.39), and the comprehensive determination was rank A or B in the Examples having a coefficient of friction of 0.40 or more, and rank C in Example 15 having a coefficient of friction of 0.39. In the other examples, the short fiber is not contained, while in Example 15 the short fiber is contained and the coefficient of friction is less than 0.40, therefore, it is preferable not to arrange a fibrous material such as a short fiber on the inner peripheral surface of the belt.

INDUSTRIAL APPLICABILITY

[0177] The toothed V-belt with a raw edge according to the present invention is suitable as a power transmission V-belt used in a power transmission system requiring a high friction force on the inner peripheral surface. In particular, the toothed V-belt with a raw edge can be used as a CVT belt used in a CVT with a belt-type clutch for snowmobiles (small vehicles for driving on snow), all-terrain vehicles (ATV) and the like, and is suitable as a CVT belt used in a CVT with a belt-type clutch, in which the inner peripheral surface of the belt comes into contact with a portion of the pulley shaft during idling.

[0178] Although the present invention has been described in detail with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various modifications and changes can be made without departing from the spirit and scope of the present invention. The present application is based on Japanese Patent Application No. 2022-080410 filed on May 16, 2022, and Japanese Patent Application No. 2023-073007 filed on April 27, 2023, and the contents thereof are incorporated herein by this reference.

LIST OF POSITIONAL DESIGNATIONS

[0179] 1: Toothed V-belt with raw edge

1A: crest of the denticle of the inner periphery

1b: denticle of the inner periphery

1c: outer periphery denticle ridge

1d: outer periphery tooth depression

2: rubber tension layer

3: tension element layer (adhesive rubber layer)

3a: tension element (cord)

4: rubber compression layer

4a: main body of rubber compression layer

4b: inner surface layer.

Claims (15)

1. A toothed V-belt with a rough edge, comprising: a tooth at least on the side of the inner peripheral surface; and a rubber compression layer located on the side of the inner peripheral surface, wherein the rubber compression layer comprises a main body of the rubber compression layer and an inner surface layer covering the inner peripheral surface of the main body of the rubber compression layer, and the coefficient of friction of the surface of the inner surface layer is higher than the coefficient of friction of the surface of the main body of the rubber compression layer not covered by the inner surface layer. 2. A toothed V-belt with a rough edge according to claim 1, in which the coefficient of friction of the surface of the inner surface layer is from 0.4 to 0.7. 3. A toothed V-belt with a raw edge according to claim 1 or 2, in which the average thickness of the inner surface layer is from 0.3 mm to 2 mm. 4. A toothed V-belt with a raw edge according to any one of claims 1 to 3, wherein the hardness Hs (Type A) of the rubber of the inner surface layer is 82° or less, and the hardness Hs (Type A) of the rubber of the main body of the rubber compression layer is 89° or more. 5. A belt power transmission system comprising: a toothed V-belt with a raw edge according to any one of paragraphs 1-4; and pulley, while The toothed V-belt with raw edge is a variable speed belt used in continuously variable transmission with belt type clutch. 6. The belt power transmission system of claim 5, wherein the continuously variable transmission with a belt-type clutch is a continuously variable transmission in which an inner peripheral surface of the belt comes into contact with a portion of the pulley shaft during idle running. 7. A belt power transmission system according to claim 5 or 6, wherein the continuously variable transmission with a belt-type clutch is a continuously variable transmission having a braking system that uses the frictional force between the inner peripheral surface of the belt and the said section of the pulley shaft. 8. A method of using a toothed V-belt with a raw edge according to any one of claims 1 to 4, wherein the toothed V-belt with a raw edge is used in all of a continuously variable transmission, a clutch and a brake in a continuously variable transmission with a belt-type clutch.