Joint v-belt and method of producing the same

Abstract

To provide a low-edge joint V-belt with high transmission efficiency.SOLUTION: In a joint V-belt 1 in which a plurality of low-edge V-belt parts 1a each having outer peripheral cog parts arranged in a belt length direction on an outer peripheral surface side, and inner peripheral cog parts arranged in the belt length direction on an inner peripheral surface side, each low-edge V-belt part 1a is formed of a core body layer 3 including a core wire 3a, an extended rubber layer 2 formed on an outer peripheral side of the core body layer 3, and a compressed rubber layer 4 formed on an inner peripheral side of the core body layer 3, with the low-edge V-belt parts 1a being connected via the extended rubber layer 2. The extended rubber layer 2 has either a single-layer structure formed of a first crosslinked rubber composition or a laminated structure including an inner peripheral rubber layer in contact with the core body layer 3, formed of a second crosslinked rubber composition. The first and second crosslinked rubber compositions have a rubber hardness Hs (type A) which is adjusted to a range between 60 and 90 degrees.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a joined V-belt formed by joining together a plurality of raw-edge cogged V-belts having cogs on both the inner and outer peripheral surfaces of the belt in the belt width direction, and a method for manufacturing the same. [Background technology]

[0002] Power transmission belts used in power transmission mechanisms such as machinery can be broadly classified into friction transmission belts and meshing transmission belts based on the type of power transmission. Known friction transmission belts include V-belts, V-ribbed belts, and flat belts, while meshing transmission belts include toothed belts. V-belts are classified into two types: raw-edge type (raw-edge V-belts), which have a rubber layer with an exposed friction transmission surface (V-shaped side), and wrapped type (wrapped V-belts), whose friction transmission surface is covered with an outer fabric. These types are used differently depending on their surface properties (friction coefficients). Raw-edge V-belts include raw-edge V-belts without cogs, raw-edge cogged V-belts, which have cogs only on the inner circumferential surface of the belt for improved flexibility, and raw-edge cogged V-belts (raw-edge double-cogged V-belts), which have cogs on both the inner and outer circumferential surfaces for improved flexibility.

[0003] These V-belts are sometimes used in parallel to increase transmission capacity. That is, a pulley with multiple V-grooves is used, with an individual V-belt wound around each V-groove, creating a multi-belt setup. When individual V-belts are used in this multi-belt setup, the tension and load on each V-belt can become uneven, potentially increasing the risk of vibration and overturning. To address this issue, the use of a combined V-belt, in which multiple V-belt sections are combined at the back (outer periphery) side, is recommended.

[0004] The combined V-belts can be broadly divided into wrapped combined V-belts, which have a wrapped V-belt portion, and raw edge combined V-belts, which have a raw edge V-belt portion.

[0005] As disclosed in Japanese Patent Publication No. 47-34432 (Patent Document 1), the wrapped connected V-belt has a structure in which the outer peripheral surfaces of each V-belt portion covered with an outer covering fabric are connected with a tie band made of canvas.

[0006] On the other hand, an example of a raw edge bonded V-belt is the structure disclosed in Japanese Patent Laid-Open Publication No. 10-47437 (Patent Document 2). Patent Document 2 discloses a bonded V-belt in which short-fiber-mixed rubber is arranged in a compression rubber layer and a tension rubber layer, the tension rubber layer and compression rubber layer have cogs, canvas is embedded in the tension rubber layer and compression rubber layer, and V-shaped grooves that fit into the convex portions of the pulley are cut at regular intervals from the compression rubber layer to the tension rubber layer. That is, in the bonded V-belt of Patent Document 2, the tension rubber layer of each V-belt portion has a structure that is continuous in the width direction of the bonded V-belt, and the tension rubber layer also serves to bond each V-belt portion. Patent Document 2 describes the effect of this configuration as being that by arranging small cogs without using a tie band made of canvas, cracks can be prevented from occurring in the tension rubber layer, thereby extending the belt's lifespan. It also states that by arranging canvas embedded in the tension rubber layer along the cog portion, shear forces and tearing forces can be dispersed, and that the cog pitch of the upper cog portion (the outer cog portion formed in the tension rubber layer) may be 3 to 6 mm and the cog depth may be 1.5 to 4.0 mm. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 47-34432 [Patent Document 2] Japanese Patent Application Publication No. 10-47437 Summary of the Invention [Problem to be solved by the invention]

[0008] When a raw-edge bonded V-belt like that described in Patent Document 2 is wound around the outer periphery of a pulley with multiple V-grooves, the compression rubber layer primarily comes into contact with the pulley's V-grooves, while the tension rubber layer has little contact with the pulley's V-grooves. In other words, the primary role of the tension rubber layer in a raw-edge bonded V-belt is to connect the V-belt sections, and it has been thought that its impact on the power transmission mechanism, such as bending stress and power transmission efficiency, is small. Therefore, in conventional technology, it is difficult to say that sufficient consideration has been given to the shape and dimensions of the tension rubber layer in raw-edge bonded V-belts, or the properties of the rubber composition that forms the tension rubber layer. The bonded V-belt described in Patent Document 2 also lacked sufficient power transmission efficiency.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a raw edge bonded V-belt with high power transmission efficiency and a method for manufacturing the same. [Means for solving the problem]

[0010] In order to achieve the above object, the inventors of the present invention conducted extensive research into the tension rubber layer of raw edge bonded V-belts and unexpectedly discovered that the tension rubber layer has a significant effect on the transmission efficiency of raw edge bonded V-belts, leading to the completion of the present invention.

[0011] That is, the present invention includes the following aspects.

[0012] Aspect [1]: A joined V-belt in which a plurality of raw edge V-belt portions are arranged (side by side) in the belt width direction, The raw edge V-belt portion has outer circumferential cog portions arranged in the belt length direction on the outer circumferential surface side and inner circumferential cog portions arranged in the belt length direction on the inner circumferential surface side, The raw edge V-belt portion includes a core layer including a core wire, a tension rubber layer formed on the outer peripheral side of the core layer, and a compression rubber layer formed on the inner peripheral side of the core layer, Each raw edge V-belt portion is connected in the belt width direction by the tension rubber layer, the tension rubber layer has a single layer structure formed of a first crosslinked rubber composition or a laminated structure including an inner rubber layer formed of a second crosslinked rubber composition and in contact with the core layer; and The bonded V-belt, wherein the first crosslinked rubber composition and the second crosslinked rubber composition have a rubber hardness Hs (type A) of 60 to 90 degrees.

[0013] Aspect [2]: The joined V-belt of aspect [1], wherein each raw edge V-belt portion is continuously connected in at least a partial region in the belt thickness direction in the tension rubber layer.

[0014] Aspect [3]: The combined V-belt of aspect [1] or [2], wherein the outer circumferential valley thickness, which is the distance between the center axis of the core wire and the groove bottom of the outer circumferential cog portion, is 0.5 to 3 mm.

[0015] Aspect [4]: ​​A combined V-belt according to any one of aspects [1] to [3], wherein the outer circumferential valley thickness, which is the distance between the center axis of the core wire and the groove bottom of the outer circumferential cog portion, is 0.11 to 0.3 times the total belt thickness.

[0016] Aspect [5]: A bonded V-belt according to any one of aspects [1] to [4], wherein the tension rubber layer comprises the inner rubber layer and an outer rubber layer formed of a third crosslinked rubber composition and laminated on the inner rubber layer, and the second crosslinked rubber composition and the third crosslinked rubber composition have different hardnesses.

[0017] Aspect [6]: The bonded V-belt of aspect [5], wherein the hardness of the second crosslinked rubber composition is lower than the hardness of the third crosslinked rubber composition.

[0018] Aspect [7]: A method for manufacturing a bonded V-belt according to any one of aspects [1] to [6], comprising: a cross-linked belt sleeve forming step for manufacturing a cross-linked belt sleeve having cog portions formed on its outer and inner peripheral surfaces; and a grinding step for grinding the cross-linked belt sleeve to form the shape of each raw edge V-belt portion.

[0019] Aspect [8]: The manufacturing method of aspect [7], wherein the cog portion formed on the outer peripheral surface of the cross-linked belt sleeve is a cog portion having a shape corresponding to the inner cog portion of the raw edge V-belt portion. [Effects of the Invention]

[0020] In the present invention, in a bonded V-belt in which multiple low-edge double-cogged V-belt portions are arranged in the belt width direction, the rubber hardness Hs (Type A) of the cross-linked rubber composition in contact with the core layer is adjusted to 60 to 90 degrees, thereby improving the transmission efficiency of the low-edge bonded V-belt. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a schematic, partially sectional perspective view showing an example of a raw edge bonded V-belt of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view of a portion of the raw edge bonded V-belt of FIG. [Figure 3] FIG. 3 is a schematic cross-sectional view of the raw edge V-belt portion of the raw edge bonded V-belt of FIG. 1 cut in the belt length direction. [Figure 4] FIG. 4 is a schematic cross-sectional view showing the definitions of the overall thickness, cog height, valley thickness, etc. of the raw edge V-belt portion of the present invention. [Figure 5] FIG. 5 is a schematic cross-sectional view of a raw edge V-belt portion of another example of the raw edge bonded V-belt of the present invention, cut in the belt length direction. [Figure 6] FIG. 6 is a schematic diagram for explaining a method for measuring the bending rigidity EI of the belt obtained in the example. [Figure 7] FIG. 7 is a schematic diagram for explaining a method for measuring the lateral pressure rigidity of the belt obtained in the example. [Figure 8] FIG. 8 shows the layout of the transmission efficiency test for the belt obtained in the example. DETAILED DESCRIPTION OF THE INVENTION

[0022] [Raw Edge Bonded V-Belt] The raw-edge bonded V-belt of the present invention has a structure in which multiple raw-edge V-belt segments are arranged in the belt width direction. The raw-edge V-belt segments have outer cogs arranged in the belt length direction (longitudinal or circumferential direction) on the outer peripheral surface and inner cogs arranged in the belt length direction on the inner peripheral surface, and may have the same structure as a conventional raw-edge double-cogged V-belt. Furthermore, the raw-edge V-belt segments include a core layer containing cords, a tension rubber layer formed on the outer peripheral side of the core layer, and a compression rubber layer formed on the inner peripheral side of the core layer. Each raw-edge V-belt segment is connected by the tension rubber layer, and a V-shaped groove is formed between adjacent raw-edge V-belt segments. In other words, the raw-edge bonded V-belt of the present invention functions as a tie band (connecting member) connecting the raw-edge V-belt segments in addition to the function of a tension rubber layer in a raw-edge V-belt. Therefore, the tension rubber layer in the raw-edge bonded V-belt of the present invention is required to have a different function than the tension rubber layer in a raw-edge V-belt. Furthermore, in raw edge bonded V-belts having such a structure, the pulley engages (or fits) into the V-shaped groove, so the tension rubber layer does not come into contact with the pulley very often. Perhaps because the tension rubber layer is considered to have little effect on the power transmission efficiency of raw edge bonded V-belts, the relationship between the tension rubber layer and the belt power transmission efficiency has not been studied much until now.

[0023] Factors that affect power transmission efficiency include the belt's bending rigidity and lateral pressure rigidity. In raw edge-connected V-belts, bending rigidity is literally related to bending, and high bending rigidity increases the energy consumed to bend the belt, resulting in reduced power transmission efficiency. On the other hand, lateral pressure rigidity is the resistance required to suppress dishing deformation, which occurs when tension is applied to the V-belt and the belt receives lateral pressure from the pulley, causing the center of the belt to collapse toward the inner periphery. Therefore, if lateral pressure rigidity is low, the belt is more susceptible to dishing deformation, increasing the slip ratio and reducing power transmission efficiency.

[0024] In this way, to improve transmission efficiency, it is necessary to reduce bending rigidity and increase lateral pressure rigidity, but for example, while it is advantageous to reduce rubber hardness or belt thickness to reduce bending rigidity, it is advantageous to increase rubber hardness or belt thickness to increase lateral pressure rigidity. In other words, because both bending rigidity and lateral pressure rigidity are common to the rigidity of a belt, there is a trade-off between reducing bending rigidity and increasing lateral pressure rigidity, making it difficult to achieve both.

[0025] In contrast to this, the present invention surprisingly improves the belt transmission efficiency by adjusting the hardness of the tension rubber layer, which was previously thought to have little effect on the transmission efficiency.

[0026] The combined V-belt of the present invention will be described in detail below with reference to the accompanying drawings as necessary. In the following description, the same reference numerals may be used to designate identical or functionally common elements (or members).

[0027] FIG. 1 is a schematic partial cross-sectional perspective view showing an example of a raw edge bonded V-belt (raw edge double cog bonded V-belt) of the present invention, FIG. 2 is a schematic cross-sectional view showing a portion of the raw edge bonded V-belt of FIG. 1, and FIG. 3 is a schematic cross-sectional view of the raw edge V-belt portion of the raw edge bonded V-belt of FIG. 1 cut in the belt length direction.

[0028] As shown in FIG. 1, this raw edge bonded V-belt 1 (embodiment 1) has three raw edge V-belt portions 1a extending in the belt longitudinal direction (circumferential direction, direction A in the figure) and arranged in parallel, and a V-shaped groove 1b is formed between adjacent raw edge V-belt portions 1a.

[0029] Each raw edge V-belt portion 1a has a laminated structure, in which a tension rubber layer 2, a core layer (adhesive rubber layer) 3, a compression rubber layer 4, and a reinforcing fabric 5 are laminated in this order from the outer periphery to the inner periphery of the belt. The cross section in the belt width direction is a generally trapezoidal shape, with the belt width decreasing from the outer periphery to the inner periphery of the belt. Furthermore, core wires 3a are embedded in the core layer 3.

[0030] In this application, as shown in Figure 2, the position of the central axis of the cords 3a in the belt thickness direction (the position on the line connecting the centers of the cords 3a embedded at equal intervals in the core layer 3) is the reference position for the outer and inner cog heights, and is referred to as the pitch line L in each figure. Also, the pitch width W of the raw edge V-belt portion means the width of the raw edge V-belt portion at the pitch line L.

[0031] The raw edge bonded V-belt 1 has a peripheral cog portion formed on the outer peripheral surface of the raw edge V-belt portion 1a (i.e., the entire outer peripheral surface of the raw edge bonded V-belt 1) in which peripheral cog crests 1c and peripheral cog valleys 1d are alternately arranged along the belt length direction (direction A in the figure). The cross-sectional shape of the peripheral cog crests 1c in the belt length direction is approximately trapezoidal, and the cross-sectional shape in the direction perpendicular to the belt length direction (the width direction or direction B in the figure) is approximately rectangular. That is, each peripheral cog crest 1c protrudes in the belt thickness direction from the peripheral cog valley 1d in a substantially trapezoidal shape in the cross section in direction A.

[0032] The raw edge V-belt portion 1a has an inner cog portion in which inner cog crests 1e and inner cog valleys 1f are alternately formed on the inner circumferential surface of the compressed rubber layer 4 in each raw edge V-belt portion 1a along the belt length direction (direction A in the figure). The cross section of each inner cog crest 1e in the belt length direction is generally trapezoidal, and the cross section in a direction perpendicular to the belt length direction is also trapezoidal. That is, each inner cog crest 1e protrudes from the inner cog valley 1f in the belt thickness direction in a generally trapezoidal shape in the cross section along direction A.

[0033] The three raw-edge V-belt portions 1a are connected by the continuous tension rubber layers 2 located on each outer surface. That is, the V-shaped groove 1b formed between adjacent raw-edge V-belt portions 1a penetrates the core layer 3 and extends to the tension rubber layer 2, but does not penetrate the tension rubber layer 2. Therefore, the tension rubber layer 2 forms a connecting portion 2a at the boundary between adjacent raw-edge V-belt portions 1a. The thickness t of the connecting portion 2a (the shortest distance between the bottom of the V-shaped groove 1b and the apex of the outer peripheral cog crest 1c) is approximately 0.87 times the thickness of the tension rubber layer 2 (the shortest distance from the boundary between the core layer 3 and the tension rubber layer 2 to the apex of the outer peripheral cog crest 1c). In particular, the apex (groove bottom) of the V-shaped groove 1b is located in a position that does not reach the bottom of the outer peripheral cog valley 1d, so the connecting portion 2a also has a high reinforcing function.

[0034] The tension rubber layer 2 has a single layer structure formed from a crosslinked rubber composition, and the hardness of the crosslinked rubber composition is adjusted to 60 to 90, thereby improving the belt transmission efficiency.

[0035] (Raw edge bonded V-belt shape) In the raw edge bonded V-belt of the present invention, adjacent raw edge V-belt portions may be connected by a tension rubber layer, and more specifically, they may be connected by at least a partial region of the tension rubber layer in the belt thickness direction being continuous. The connecting portion that forms the boundary between adjacent raw edge V-belt portions may be formed in at least a partial region of the tension rubber layer that connects the adjacent raw edge V-belt portions in the belt thickness direction, and the entire region of the tension rubber layer in the belt thickness direction may be connected, but from the viewpoint of improving power transmission efficiency, connecting only a partial region is preferred, and from the viewpoint of improving productivity and belt durability, forming the connecting portion in a partial region on the outer peripheral surface side of the tension rubber layer is particularly preferred.

[0036] The thickness t of the connecting portion (the shortest distance between the bottom of the V-shaped groove and the top of the outer cog) is, for example, 0.5 to 1 time, preferably 0.7 to 0.95 time, further preferably 0.8 to 0.9 time, further preferably 0.85 to 0.89 time, and most preferably 0.86 to 0.88 time the thickness of the tension rubber layer (the shortest distance from the boundary between the core layer and tension rubber layer to the top of the outer cog). If the thickness t of the connecting portion is too small, the durability of the belt may decrease, and if it is too large, the transmission efficiency may decrease.

[0037] In the outer peripheral cog portion, the cross-sectional shape in the length direction of the outer peripheral cog crest is not limited to a substantially trapezoidal shape, but may be, for example, a square shape, a rectangular shape, a substantially semicircular shape (curved or wavy), etc. Of these, a substantially trapezoidal shape and a substantially semicircular shape are preferred, and a substantially trapezoidal shape is particularly preferred.

[0038] In the inner cog portion, the cross-sectional shape in the length direction of the inner cog ridge is not limited to a generally trapezoidal shape, but may be, for example, a square shape, a rectangular shape, a generally semicircular shape (curved or wavy), etc. Of these, a generally trapezoidal shape and a generally semicircular shape are preferred, and a generally trapezoidal shape is particularly preferred.

[0039] FIG. 4 shows definitions of the overall thickness, cog height, valley thickness, etc. of the raw edge V-belt portion (raw edge double cog V-belt portion) in the present invention.

[0040] The overall belt thickness H1 (average thickness) of the raw edge V-belt portion of the present invention is, for example, 5 to 20 mm, preferably 6 to 15 mm, further preferably 7 to 12 mm, and even more preferably 8 to 11 mm. If the thickness is too small, there is a risk of reduced lateral pressure resistance, while if the thickness is too large, there is a risk of reduced flexibility, reduced power transmission efficiency, and reduced resistance to bending fatigue.

[0041] 4, in this application, the thickness of the entire belt means the thickness at the top of the cog (maximum thickness of the belt). That is, the thickness H1 of the raw edge V-belt portion (i.e., the thickness of the raw edge bonded V-belt) means the shortest distance (distance parallel to the thickness direction) from the top of the cog (convex top on the inner periphery) of the compression rubber layer (or reinforcing fabric) to the top of the cog (convex top on the outer periphery) of the tension rubber layer (or reinforcing fabric).

[0042] In this application, the outer cog valley of the outer cog portion refers to the portion that forms the thin-walled portion of the tension rubber layer having the outer cog portion, and usually refers to a curved or flat valley or groove portion (a curved groove portion or a planar groove portion parallel to the outer circumferential surface of the belt) between adjacent outer cog peaks that protrude toward the outer periphery of the belt. The same applies to the inner cog valley of the inner cog portion.

[0043] In the raw edge bonded V-belt of the present invention, by adjusting the outer circumferential valley thickness H4 (the shortest distance in the belt thickness direction from the center axis of the core wire (pitch line L) to the bottom of the groove of the outer cog portion (the deepest part of the outer cog valley)) shown in Figure 4 within a specific range, it is possible to reduce bending rigidity while maintaining lateral pressure rigidity, thereby improving the belt transmission efficiency.

[0044] The outer circumferential valley thickness H4 (average thickness) can be selected from a range of approximately 0.3 to 4 mm, for example, 0.5 to 3 mm, preferably 1 to 2.8 mm, further preferably 1.2 to 2.5 mm, even more preferably 1.5 to 2.3 mm, and most preferably 1.7 to 2.1 mm. If the outer circumferential valley thickness H4 is too small, the lateral pressure rigidity may be reduced, and the transmission efficiency may decrease. On the other hand, if the outer circumferential valley thickness H4 is too large, the bending rigidity may be increased, and the transmission efficiency may decrease.

[0045] Furthermore, in the raw edge bonded V-belt of the present invention, by adjusting the outer circumferential valley thickness H4 relative to the overall belt thickness H1 within a specific range, it is possible to reduce bending rigidity while maintaining lateral pressure rigidity, thereby improving the belt's transmission efficiency.

[0046] The outer circumferential valley thickness H4 (average thickness) can be selected from a range of approximately 0.11 to 0.35 times the overall belt thickness H1, for example, 0.11 to 0.3 times, preferably 0.11 to 0.28 times, further preferably 0.11 to 0.25 times, even more preferably 0.13 to 0.23 times, and most preferably 0.15 to 0.21 times. If the outer circumferential valley thickness H4 ratio is too small, the lateral pressure rigidity may decrease, and the transmission efficiency may decrease. On the other hand, if the outer circumferential valley thickness ratio is too large, the bending rigidity may increase, and the transmission efficiency may decrease.

[0047] The height H5 of the outer circumferential rubber portion formed on the outer circumferential surface (outer circumferential cog height) is, for example, 2 to 5 mm, preferably 2.3 to 4 mm, and more preferably 2.5 to 3 mm.

[0048] The inner circumferential valley thickness [shortest distance from the central axis of the core wire (pitch line L) to the groove bottom of the inner circumferential cog portion (or the deepest part of the inner circumferential cog valley)] H3 is, for example, 0.5 to 3 mm, preferably 1 to 2 mm, and more preferably 1.2 to 1.6 mm.

[0049] The height H2 of the inner cog portion formed on the inner peripheral surface (inner cog height) is, for example, 3 to 8 mm, preferably 3.5 to 5 mm, and more preferably 3.7 to 4.5 mm.

[0050] (Tension rubber layer) The tension rubber layer may have a single-layer structure (a structure consisting of a single homogeneous phase) or a laminated structure (a structure consisting of multiple homogeneous phases). The laminated structure may be a laminated structure of two or more layers, preferably a two- to four-layer structure, and more preferably a two- or three-layer structure. Of these structures, the laminated structure is preferred because it can improve the belt's power transmission efficiency by increasing the lateral pressure rigidity while maintaining a low bending rigidity. The single-layer and two-layer structures are preferred because they can improve the belt's productivity, and the two-layer structure is particularly preferred because it can improve the belt's productivity and power transmission efficiency.

[0051] The shape of the laminated structure of the tension rubber layer is not particularly limited, but from the standpoint of productivity, etc., it may have a shape having an outer rubber layer that conforms to the surface shape of the outer cog portion, and in the case of a two-layer structure, it may be a combination of such an outer rubber layer and an inner rubber layer.

[0052] FIG. 5 is a schematic cross-sectional view of a raw edge V-belt portion of a raw edge bonded V-belt 11 of the present invention, which has a two-layer tension rubber structure, cut in the belt length direction.

[0053] In this example, the raw edge V-belt portion is layered from the outer periphery of the belt toward the inner periphery, with a tension rubber layer 12, a core layer 13 consisting only of cords, and a compression rubber layer 14, with no reinforcing fabric layered on the surface of the compression rubber layer 14. The tension rubber layer 12 is formed of an inner rubber layer 12a that contacts the core layer 13 and an outer rubber layer 12b that is layered on top of this inner rubber layer 12a. The inner rubber layer 12a has a shape similar to (or conforms to) the outer cog portion, and the outer rubber layer 12b has a layer shape that follows the surface shape of the outer cog portion. Furthermore, the layer shape of the outer rubber layer 12b is such that the layer thickness corresponding to the outer cog crest 11c of the outer cog portion is thick, and the layer thickness corresponding to the outer cog valley 11d from the side of the outer cog portion is thin.

[0054] In a raw edge bonded V-belt having such a raw edge V-belt portion, the rubber hardness Hs (type A) of the inner circumferential rubber layer 12a of the tension rubber layer 12 is adjusted to 60 to 90 degrees, thereby improving the power transmission efficiency of the belt.

[0055] In the tension rubber layer, the layer shape of the peripheral rubber layer is not limited to a shape in which the layer thickness corresponding to the peripheral cog ridges is thick, and the layer shape may be a layer shape with a uniform thickness. However, from the standpoint of productivity, a layer shape with a non-uniform thickness is preferable, and the layer shape of Figure 5 (a layer shape in which the layer thickness corresponding to the peripheral cog ridges of the peripheral cog part is thick, and the layer thickness corresponding to the peripheral cog valleys from the side of the peripheral cog part is thin) is particularly preferable.

[0056] In the tension rubber layer, the shape of the inner rubber layer is not limited to a shape similar to that of the outer cog portion, and may be a layer of uniform thickness or a layer dissimilar to that of the outer cog portion. However, from the standpoint of productivity, a shape similar to that of the outer cog portion as shown in FIG. 5 is preferred.

[0057] When the tension rubber layer has a two-layer structure consisting of an outer rubber layer and an inner rubber layer, the mass proportion of the inner rubber layer is preferably greater than that of the outer rubber layer in order to maintain low bending rigidity. The proportion of the inner rubber layer can be selected from a range of approximately 10 to 99 mass% (particularly 15 to 80 mass%) of the total mass of the outer rubber layer and the inner rubber layer, for example, 30 to 98 mass%, preferably 50 to 95 mass% (particularly 50 to 80 mass%), even more preferably 55 to 90 mass%, more preferably 60 to 85 mass%, and most preferably 70 to 80 mass%. If the mass of the inner rubber layer is too small, bending rigidity may increase, potentially reducing transmission efficiency. If it is too large, lateral pressure rigidity may decrease, potentially reducing transmission efficiency.

[0058] In the raw edge bonded V-belt of the present invention, the rubber hardness Hs (Type A) of the crosslinked rubber composition in contact with the core of the tension rubber layer is adjusted to 60 to 90 degrees, thereby ensuring lateral pressure rigidity while reducing bending rigidity and improving power transmission efficiency. Specifically, when the tension rubber layer has a single-layer structure formed from a first crosslinked rubber composition, the rubber hardness Hs (Type A) of the first crosslinked rubber composition should be 60 to 90 degrees. On the other hand, when the tension rubber layer has a laminated structure formed from a second crosslinked rubber composition and including an inner rubber layer in contact with the core layer (particularly, a two-layer structure consisting of the inner rubber layer and an outer rubber layer formed from a third crosslinked rubber composition and laminated on the inner rubber layer), the rubber hardness Hs (Type A) of the second crosslinked rubber composition should be 60 to 90 degrees.

[0059] When the tension rubber layer has a single layer structure, the rubber hardness Hs (Type A) of the first crosslinked rubber composition may be 60 to 90 degrees, preferably 70 to 90 degrees, more preferably 75 to 90 degrees, even more preferably 80 to 90 degrees, and most preferably 85 to 89 degrees. If the rubber hardness Hs of the crosslinked rubber composition is too low, the lateral pressure rigidity may be reduced, which may result in a decrease in power transmission efficiency. If the rubber hardness Hs of the crosslinked rubber composition is too high, the flexural rigidity may be increased, which may result in a decrease in power transmission efficiency.

[0060] When the tension rubber layer has a two-layer structure consisting of the inner rubber layer and the outer rubber layer, adjusting the rubber hardness Hs (Type A) of the second crosslinked rubber composition forming the inner rubber layer to be smaller than the rubber hardness Hs (Type A) of the third crosslinked rubber composition forming the outer rubber layer makes it possible to increase the lateral pressure rigidity while maintaining a small bending rigidity, thereby improving the power transmission efficiency. In the present invention, when the tension rubber layer has a single-layer structure, as described above, adjusting the rubber hardness Hs of the first crosslinked rubber composition within the above range can improve the power transmission efficiency of the belt, but in a tension rubber layer with a two-layer structure, adjusting the rubber hardness Hs of the second crosslinked rubber composition within the above range can further improve the power transmission efficiency of the belt.

[0061] If the entire tension rubber layer is made of rubber with a low rubber hardness Hs, there is a risk that the lateral pressure rigidity will be low. On the other hand, if the entire tension rubber layer is made of rubber with a high rubber hardness Hs, there is a risk that the bending rigidity will be high. In contrast, by using a two-layer structure with different rubber hardness Hs, although the mechanism is not clear, it is possible to increase the lateral pressure rigidity while maintaining a low bending rigidity, possibly due to the influence of the layer structure, compared to simply adjusting the rubber hardness Hs of a single layer, thereby improving the belt's power transmission efficiency. Furthermore, contrary to the present invention, if the rubber hardness Hs of the inner rubber layer is made higher than the rubber hardness Hs of the outer rubber layer, the bending rigidity will be increased and the power transmission efficiency will be reduced.

[0062] When the tension rubber layer has a two-layer structure, the rubber hardness Hs (Type A) of the second crosslinked rubber composition may be 60 to 90 degrees, preferably 60 to 80 degrees, preferably 63 to 78 degrees, further preferably 65 to 77 degrees, even more preferably 68 to 75 degrees, and most preferably 70 to 73 degrees. If the rubber hardness Hs of the crosslinked rubber composition is too low, the lateral pressure rigidity may be reduced, which may result in a decrease in power transmission efficiency. If the rubber hardness Hs of the crosslinked rubber composition is too high, the flexural rigidity may be increased, which may result in a decrease in power transmission efficiency.

[0063] When the tension rubber layer has a two-layer structure consisting of the inner rubber layer and the outer rubber layer, the rubber hardness Hs (Type A) of the third crosslinked rubber composition may be 60 to 90 degrees, for example, 65 to 90 degrees, preferably 75 to 90 degrees, further preferably 78 to 90 degrees, even more preferably 80 to 90 degrees, and most preferably 85 to 89 degrees. If the rubber hardness Hs of the crosslinked rubber composition is too low, the lateral pressure rigidity may be reduced, which may result in a decrease in power transmission efficiency. If the rubber hardness Hs of the crosslinked rubber composition is too high, the flexural rigidity may be increased, which may result in a decrease in power transmission efficiency.

[0064] The rubber hardness Hs of each of the first to third crosslinked rubber compositions can be adjusted by the type, presence or absence, and amount of the crosslinking agent, co-crosslinking agent, softener, short fiber, and reinforcing agent (for example, carbon black).

[0065] In this application, the rubber hardness of the crosslinked rubber composition refers to the value Hs (Type A) measured using a Type A durometer in accordance with the spring type durometer hardness test specified in JIS K 6253 (2012) (Vulcanized rubber and thermoplastic rubber - Determination of hardness), and may be simply referred to as rubber hardness. In detail, it can be measured by the method described in the examples below.

[0066] (A1) First rubber component The first to third cross-linked rubber compositions each contain a first rubber component. The first rubber component may be a vulcanizable or cross-linkable rubber, such as a diene rubber (natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), or hydrogenated nitrile rubber (H-NBR)), an ethylene-α-olefin elastomer (ethylene-propylene copolymer (EPM), ethylene-propylene-diene terpolymer (EPDM), or the like), a chlorosulfonated polyethylene rubber, an alkylated chlorosulfonated polyethylene rubber, an epichlorohydrin rubber, an acrylic rubber, a silicone rubber, a urethane rubber, or a fluororubber. These rubber components may be used alone or in combination.

[0067] Of these, ethylene-α-olefin elastomer and chloroprene rubber are preferred, with chloroprene rubber being particularly preferred due to its excellent balance of heat resistance, abrasion resistance, oil resistance, etc. and high productivity.

[0068] When the first rubber component contains chloroprene rubber, the proportion of the chloroprene rubber in the first rubber component may be 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more (particularly 90 to 100% by mass), and most preferably 100% by mass (chloroprene rubber only), in order to improve the above-mentioned properties and productivity. When the first rubber component contains an ethylene-α-olefin elastomer, the proportion of the ethylene-α-olefin elastomer in the first rubber component is the same as the proportion of the chloroprene rubber.

[0069] The proportion of the first rubber component in the first to third crosslinked rubber compositions is, for example, 10 to 90 mass%, preferably 20 to 80 mass%, further preferably 30 to 70 mass%, even more preferably 40 to 65 mass%, and most preferably 50 to 60 mass%.

[0070] (A2) First short fiber The first to third crosslinked rubber compositions may further contain first staple fibers. Examples of the first staple fibers include polyamide staple fibers (aliphatic polyamide staple fibers such as polyamide 6 staple fibers, polyamide 66 staple fibers, and polyamide 46 staple fibers; aramid staple fibers, etc.), polyester staple fibers (polyalkylene arylate staple fibers such as polyethylene terephthalate (PET) staple fibers and polyethylene naphthalate (PEN) staple fibers; liquid crystal polyester staple fibers; polyarylate staple fibers (amorphous wholly aromatic polyester staple fibers, etc.)), synthetic staple fibers such as vinylon staple fibers, polyvinyl alcohol staple fibers, and polyparaphenylene benzobisoxazole (PBO) staple fibers; natural staple fibers such as cotton, hemp, and wool; and inorganic staple fibers such as carbon staple fibers. These staple fibers can be used alone or in combination. Among these, polyamide staple fibers such as aramid staple fibers and aliphatic polyamide staple fibers are preferred, and aramid staple fibers are particularly preferred.

[0071] The aramid fibers constituting the aramid short fibers may be para-aramid fibers or meta-aramid fibers.

[0072] Examples of para-aramid fibers include polyparaphenylene terephthalamide fibers (e.g., Twaron (registered trademark) from Teijin Limited, Kevlar (registered trademark) from Toray DuPont Co., Ltd., etc.), and copolymer fibers of polyparaphenylene terephthalamide and 3,4'-oxydiphenylene terephthalamide (e.g., Technora (registered trademark) from Teijin Limited, etc.).

[0073] Examples of meta-aramid fibers include polymetaphenylene isophthalamide fibers (such as "Conex (registered trademark)" from Teijin Limited).

[0074] These aramid fibers can be used alone or in combination of two or more. Among these, para-aramid fibers are preferred because they can easily improve both wear resistance and power transmission efficiency at the same time.

[0075] The first short fibers have an average fiber diameter of 2 μm or more, for example, 2 to 100 μm, preferably 3 to 50 μm, more preferably 7 to 40 μm, and even more preferably 10 to 30 μm.The first short fibers have an average fiber length of, for example, 1 to 20 mm, preferably 1.3 to 15 mm, more preferably 1.5 to 10 mm, more preferably 2 to 5 mm, and most preferably 2.5 to 4 mm.

[0076] The first short fibers may be embedded in the compression rubber layer while being oriented substantially parallel to the belt width direction in order to suppress compressive deformation of the belt due to pressure from the pulley.

[0077] The first short fibers may be subjected to a conventional adhesive treatment to enhance adhesion to the first rubber component. Conventional adhesive treatment methods can be used, including treatment with a treatment solution containing a precondensate of phenols and formalin (e.g., a prepolymer of novolac or resol-type phenolic resin); a treatment solution containing a rubber component (or latex); a treatment solution containing the precondensate and a rubber component (latex); or a treatment solution containing a reactive compound (adhesive compound) such as a silane coupling agent, an epoxy compound (e.g., an epoxy resin), an isocyanate compound, or a bismaleimide compound. These methods can be used alone or in combination. Among these methods, treatment with a treatment solution containing the precondensate and a rubber component (latex) is preferred, and treatment with at least a resorcinol-formalin-latex (RFL) solution is particularly preferred.

[0078] The proportion of the first short fibers can be selected within the range of 50 parts by mass or less per 100 parts by mass of the first rubber component.

[0079] In the first and third crosslinked rubber compositions, the proportion of the first short fibers may be 50 parts by mass or less per 100 parts by mass of the first rubber component, for example, 1 to 50 parts by mass, preferably 5 to 40 parts by mass, further preferably 7 to 30 parts by mass, and further preferably 10 to 20 parts by mass.

[0080] In the second crosslinked rubber composition, the proportion of the first short fibers is, for example, 30 parts by mass or less, preferably 20 parts by mass or less, further preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the first rubber component, and may be 0 parts by mass.

[0081] (A3) First inorganic filler The first to third crosslinked rubber compositions may further contain a first inorganic filler. Examples of the first inorganic filler (A3) include carbonaceous materials (carbon black, graphite, etc.), metal compounds or synthetic ceramics (metal oxides such as magnesium oxide, calcium oxide, barium oxide, iron oxide, copper oxide, zinc oxide, lead oxide, barium oxide, titanium oxide, and aluminum oxide; metal silicates such as calcium silicate and aluminum silicate; metal carbides such as silicon carbide and tungsten carbide; metal nitrides such as titanium nitride, aluminum nitride, and boron nitride; metal carbonates such as magnesium carbonate and calcium carbonate; and metal sulfates such as calcium sulfate and barium sulfate), and mineral materials (zeolite, diatomaceous earth, calcined diatomaceous earth, activated clay, alumina, silica, talc, mica, kaolin, sericite, bentonite, montmorillonite, smectite, clay, etc.). These inorganic fillers can be used alone or in combination.

[0082] Of these inorganic fillers, carbonaceous materials such as carbon black, metal oxides such as magnesium oxide and zinc oxide, and mineral materials such as silica are preferred, and carbonaceous materials and metal oxides are more preferred, with carbon black being particularly preferred because it can improve the hardness, modulus, and abrasion resistance of the crosslinked rubber composition.

[0083] Carbon black is generally classified into several grades based on differences in primary particle size, iodine adsorption capacity, and nitrogen adsorption specific surface area. ASTM classifies carbon black into grades N0** to N9** based on iodine adsorption capacity, but traditional classifications (SAF, HAF, GPF, etc.) based on the performance of compounded rubber products are also used. Grades with small primary particle sizes, such as N110 (SAF), N220 (ISAF), and N330 (HAF), are referred to as hard carbon, while grades with large primary particle sizes, such as N550 (FEF), N660 (GPF), and N762 (SRF), are sometimes referred to as soft carbon. Iodine adsorption capacity and primary particle size are closely related, with the smaller the primary particle size, the greater the iodine adsorption capacity. The classification of carbon black is shown in Table 1, using the Seast® series manufactured by Tokai Carbon Co., Ltd. as an example, along with the iodine adsorption capacity and average primary particle size.

[0084] [Table 1]

[0085] In this application, carbon black contained in a rubber composition is not classified by raw material, but carbon black having a primary particle diameter of 40 nm or more is referred to as soft carbon, and carbon black having a primary particle diameter of less than 40 nm is referred to as hard carbon.

[0086] In the present application, the primary particle size of carbon black can be measured using, for example, a transmission electron microscope.

[0087] The primary particle size of the soft carbon may be 40 nm or more, but the maximum primary particle size may be, for example, 300 nm or less, preferably 200 nm or less, and more preferably 100 nm or less. If the maximum primary particle size of the soft carbon is too large, there is a risk that the effect of improving wear resistance will not be achieved.

[0088] The average primary particle size of the soft carbon is, for example, 40 to 100 nm, preferably 45 to 90 nm, further preferably 50 to 80 nm, and even more preferably 60 to 70 nm. If the average primary particle size of the soft carbon is too small, there is a risk that the transmission efficiency (fuel economy) will decrease, and conversely, if it is too large, there is a risk that the effect of improving wear resistance will not be achieved.

[0089] The iodine adsorption amount of the soft carbon may be less than 60 g / kg, for example, 10 g / kg or more and less than 60 g / kg, preferably 20 to 58 g / kg, further preferably 30 to 55 g / kg, and further preferably 40 to 50 g / kg. If the iodine adsorption amount is too high, there is a risk of a decrease in transmission efficiency.

[0090] In the present application, the iodine adsorption amount of carbon black can be measured in accordance with the standard test method of ASTM D1510-17.

[0091] The primary particle diameter of the hard carbon may be less than 40 nm, but the maximum primary particle diameter may be, for example, 38 nm or less, preferably 35 nm or less, and more preferably 30 nm or less.

[0092] The average primary particle size of the hard carbon is, for example, 10 to 35 nm, preferably 12 to 33 nm, further preferably 15 to 30 nm, and even more preferably 20 to 25 nm.

[0093] The iodine adsorption amount of the hard carbon may be 60 g / kg or more, for example, 60 to 150 g / kg, preferably 80 to 130 g / kg, further preferably 100 to 130 g / kg, and further preferably 120 to 125 g / kg.

[0094] In the present invention, the carbon black preferably contains hard carbon in the first and second crosslinked rubber compositions, and preferably contains soft carbon in the third crosslinked rubber composition.

[0095] The proportion of carbon black in the inorganic filler (A3) may be 10% by mass or more, preferably 50% by mass or more, and more preferably 60% by mass or more.

[0096] The content of carbon black is 10 to 60 parts by mass, preferably 15 to 50 parts by mass, and more preferably 20 to 40 parts by mass, per 100 parts by mass of the first rubber component (A1) in the first and second crosslinked rubber compositions. The content of carbon black is 10 to 100 parts by mass, preferably 30 to 90 parts by mass, and more preferably 50 to 70 parts by mass, per 100 parts by mass of the first rubber component (A1) in the third crosslinked rubber composition.

[0097] In addition to carbon black, the inorganic filler (A3) may further contain a metal oxide such as magnesium oxide or zinc oxide, which may act as a crosslinking agent.

[0098] The ratio of the metal oxide is, for example, 1 to 100 parts by mass, preferably 10 to 50 parts by mass, and more preferably 20 to 40 parts by mass, relative to 100 parts by mass of carbon black in the first and second crosslinked rubber compositions.The ratio of the metal oxide is, for example, 1 to 50 parts by mass, preferably 5 to 30 parts by mass, and more preferably 10 to 20 parts by mass, relative to 100 parts by mass of carbon black in the third crosslinked rubber composition.

[0099] The proportion of the inorganic filler (first inorganic filler) (A3) is, for example, 10 to 100 parts by mass, preferably 20 to 70 parts by mass, and more preferably 30 to 50 parts by mass, per 100 parts by mass of the first rubber component (A1) in the first and third crosslinked rubber compositions. The proportion of the inorganic filler (A3) is, for example, 10 to 150 parts by mass, preferably 50 to 100 parts by mass, and more preferably 60 to 80 parts by mass, per 100 parts by mass of the first rubber component (A1) in the second crosslinked rubber composition.

[0100] (A4) Other ingredients The rubber composition forming the tension rubber layer may contain conventional additives as other components (first other components), and examples of the additives include crosslinking agents or vulcanizing agents (sulfur-based crosslinking agents, organic peroxides, the above-mentioned metal oxides, etc.), co-crosslinking agents (bismaleimides, etc.), crosslinking aids or crosslinking accelerators (thiuram-based accelerators, etc.), crosslinking retarders, metal powders (zinc powder, etc.), plasticizers (or softeners) [oils (paraffin oil, naphthenic oil, etc.), aliphatic carboxylic acid-based plasticizers, aromatic carboxylic acid ester-based plasticizers, etc.]. Examples of additives include plasticizers, hydroxycarboxylic acid ester plasticizers, phosphate ester plasticizers, ether plasticizers, ether ester plasticizers, etc., processing agents or processing aids (stearic acid, metal stearates, waxes, paraffins, fatty acid amides, etc.), antiaging agents (antioxidants, heat aging inhibitors, flex crack inhibitors, antiozonants, etc.), adhesion improvers, colorants, tackifiers, coupling agents (silane coupling agents, etc.), stabilizers (ultraviolet absorbers, heat stabilizers, etc.), flame retardants, and antistatic agents. These additives can be used alone or in combination. Metal oxides may also function as crosslinking agents.

[0101] The proportion of the crosslinking agent (first crosslinking agent) relative to 100 parts by mass of the first rubber component is, for example, 1 to 20 parts by mass, preferably 2 to 15 parts by mass, further preferably 3 to 12 parts by mass, and even more preferably 4 to 10 parts by mass.

[0102] The proportion of the co-crosslinking agent in the first and third crosslinked rubber compositions is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass, and more preferably 1 to 3 parts by mass, per 100 parts by mass of the first rubber component. Also, the proportion of the co-crosslinking agent in the second crosslinked rubber composition is, for example, 5 parts by mass or less, preferably 3 parts by mass or less, and more preferably 1 part by mass or less, per 100 parts by mass of the first rubber component.

[0103] The total proportion of the other components (first other components) relative to 100 parts by mass of the first rubber component is, for example, 0.1 to 100 parts by mass, preferably 1 to 50 parts by mass, and more preferably 5 to 30 parts by mass.

[0104] (Core layer) The core layer may contain a core wire, and may be a core layer formed only of a core wire, or may be a core layer containing a core wire and an adhesive rubber layer formed from a fourth crosslinked rubber composition.

[0105] When the core layer includes an adhesive rubber layer, the cord may be at least partially in contact with the adhesive rubber layer, and may be embedded in the adhesive rubber layer, embedded between the adhesive rubber layer and the tension rubber layer, or embedded between the adhesive rubber layer and the compression rubber layer. Of these, the core is preferably embedded in the adhesive rubber layer in view of improving durability.

[0106] The rubber hardness Hs (type A) of the fourth crosslinked rubber composition is, for example, 60 to 85 degrees, preferably 65 to 84 degrees, and more preferably 70 to 83 degrees.

[0107] The second rubber component contained in the fourth crosslinked rubber composition can be selected from the rubber components exemplified as the first rubber component (A1), including preferred embodiments. The second rubber component may be a rubber component different from the first rubber component (A1), but is usually the same type as the first rubber component (A1).

[0108] The fourth crosslinked rubber composition may also further contain inorganic fillers and other components, which can be selected from the inorganic fillers and other components exemplified as the inorganic filler (A3) and other components (A4), including preferred embodiments.

[0109] The average thickness of the adhesive rubber layer is, for example, 0.8 to 3 mm, preferably 1.2 to 2.8 mm, and more preferably 1.5 to 2 mm.

[0110] The core wires are not particularly limited, but typically twisted cords arranged at a predetermined interval in the width direction of the belt can be used. The core wires are arranged to extend in the length direction of the belt and may be arranged in parallel with the length direction of the belt at a predetermined pitch. However, from the viewpoint of productivity, they are usually arranged in a spiral shape, extending in parallel with the length direction of the belt at a predetermined pitch. When arranged in a spiral shape, the angle of the core wire with respect to the length direction of the belt may be, for example, 5° or less, and from the viewpoint of belt running performance, the closer to 0° the core wire is, the more preferable. Furthermore, the pitch or interval, which is the distance between the centers of adjacent core wires (particularly the spinning pitch of the core wires), is preferably set in the range of 0.5 to 3 mm, more preferably in the range of 1 to 2.5 mm, even more preferably in the range of 1.2 to 2 mm, and most preferably in the range of 1.5 to 1.8 mm.

[0111] Examples of fibers constituting the core wire include the same fibers as the short fibers. Among the fibers, C fibers such as ethylene terephthalate and ethylene-2,6-naphthalate are preferred in terms of high modulus. 2-4 Alkylene-C 8-14 Polyester fibers (polyalkylene arylate fibers) containing arylate as the main structural unit, synthetic fibers such as aramid fibers, and inorganic fibers such as carbon fibers are commonly used, with polyester fibers (polyethylene terephthalate fibers, polyethylene naphthalate fibers, etc.) and aramid fibers being preferred. These fibers may be used in the form of multifilament yarns containing multiple filaments. The fineness of the multifilament yarns is, for example, 200 to 5000 dtex (particularly 500 to 2000 dtex). The multifilament yarns may contain, for example, 50 to 1500 filaments, preferably 100 to 1000 filaments, and more preferably 150 to 300 filaments.

[0112] As the core wire, a twisted cord (for example, ply twist, single twist, Lang twist, etc.) using multifilament yarn can usually be used. Among these, ply twisted cords are preferred.

[0113] In the twisted cord, the first twist yarn may be a plurality of multifilament yarns. The fineness of each first twist yarn is, for example, 500 to 5000 dtex, preferably 1000 to 4000 dtex, and more preferably 2000 to 3800 dtex. The number of first twist yarns may be more than one, but is preferably 2 to 6, more preferably 3 to 5, and even more preferably 5.

[0114] The twist coefficient (first twist coefficient) of each first twisted yarn is, for example, 0.5 to 5, preferably 1 to 4, more preferably 2 to 3.5, and even more preferably 2.5 to 3.3.

[0115] The twist coefficient of the twisted cord (final twist coefficient of the final twisted yarn) is, for example, 0.5 to 5, preferably 1 to 4, more preferably 2 to 3.5, and even more preferably 2.5 to 3.3.

[0116] The ratio of the first twist coefficient to the final twist coefficient (first twist coefficient / final twist coefficient) is, for example, 0.3 to 3, preferably 0.4 to 2, more preferably 0.5 to 1.5, and most preferably 0.8 to 1.2.

[0117] In the present application, the twist coefficients of the first twist and the second twist can be calculated based on the following formula.

[0118] TF=TN×D 0.5 / 960 [wherein TF is the twist factor, TN is the number of twists per meter, and D is the yarn fineness (tex)]

[0119] The average wire diameter of the core wire (diameter of the twisted cord) may be, for example, 0.5 to 3 mm, preferably 0.6 to 2.5 mm, more preferably 0.7 to 2 mm, more preferably 1 to 2 mm, and most preferably 1.5 to 2 mm. The total fineness of the core wire (twisted cord) may be, for example, 2,000 to 30,000 dtex, preferably 5,000 to 25,000 dtex, more preferably 10,000 to 20,000 dtex, and more preferably 12,000 to 18,500 dtex.

[0120] The core wires may be subjected to an adhesive treatment (or surface treatment) in the same manner as the first short fibers (A2) in order to improve adhesion to the rubber component. The core wires are preferably subjected to an adhesive treatment with at least an RFL liquid.

[0121] From the viewpoint of productivity, the core layer is preferably formed only from a core wire.

[0122] (Compressed rubber layer) The fifth crosslinked rubber composition forming the compression rubber layer has a rubber hardness Hs (type A) of, for example, 80 to 90 degrees, preferably 83 to 90 degrees, and more preferably 85 to 89 degrees.

[0123] The third rubber component contained in the fifth crosslinked rubber composition can be selected from the polymer components exemplified as the first rubber component (A1), including preferred embodiments. The third rubber component may be a rubber component different from the first rubber component (A1), but is usually the same type as the first rubber component (A1).

[0124] The fifth crosslinked rubber composition may also further contain short fibers, inorganic fillers, and other components, which can be selected from the inorganic fillers and other components exemplified as the first short fibers (A2), the first inorganic filler (A3), and the first other component (A4) in the first to third crosslinked rubber compositions, including preferred embodiments.

[0125] (reinforced fabric) The raw edge bonded V-belt (or raw edge V-belt portion) of the present invention may further include a reinforcing fabric, which may be laminated on the inner circumferential surface of the compressed rubber layer, laminated on the outer circumferential surface of the tension rubber layer, embedded in the compressed rubber layer and / or tension rubber layer, or a combination of these.

[0126] The reinforcing fabric can be formed from fabric materials (especially woven fabrics) such as woven fabrics, wide-angle canvas, knitted fabrics, and nonwoven fabrics, and if necessary, can be subjected to an adhesive treatment, for example, treatment with RFL liquid (dipping treatment, etc.), a friction treatment in which adhesive rubber is rubbed into the fabric material, or the adhesive rubber and the fabric material can be laminated together and then laminated or embedded in the compression rubber layer and / or tension rubber layer in the above-mentioned form.

[0127] Of these, from the viewpoint of reducing the bending rigidity of the belt, a configuration in which a reinforcing fabric is laminated only on the inner peripheral surface of the compressed rubber layer and a configuration in which the raw edge bonded V-belt does not have a reinforcing fabric are preferred, and a configuration in which the raw edge bonded V-belt does not have a reinforcing fabric is particularly preferred.

[0128] (Characteristics of raw edge bonded V-belts) In the raw edge bonded V-belt of the present invention (specifically, each raw edge V-belt portion), the bending rigidity per raw edge V-belt portion (belt bending rigidity EI) is, for example, 5000 to 10000 N (mm). 2 , preferably 5500 to 9000 N (mm) 2 , more preferably 6000 to 8000 N (mm) 2 , more preferably 6500 to 7500 N (mm) 2 , most preferably 6800 to 7200 N (mm) 2 is.

[0129] In the raw edge bonded V-belt of the present invention, the bending rigidity (belt bending rigidity EI) per 1 mm of pitch width (W) of the raw edge V-belt portion is, for example, 300 to 700 N (mm). 2 , preferably 350 to 600 N (mm) 2 , more preferably 400 to 550 N (mm) 2 , more preferably 420 to 500N (mm) 2 , most preferably 440 to 480 N (mm) 2 is.

[0130] In the present invention, since the bending rigidity EI of the belt is within this range, the transmission efficiency can be improved. If the bending rigidity EI of the belt is too small, there is a risk that the belt will vibrate and make noise, whereas if it is too large, there is a risk that the energy loss due to bending and straightening of the belt will increase, resulting in a decrease in transmission efficiency.

[0131] In this application, the bending rigidity EI of a belt represents the relationship between the compressive force required to compress a circular belt from the outer periphery and deform it into a bale shape, and the pitch diameter (the diameter of the arc drawn by the pitch line connecting the center lines of the core wires) when the bent portion of the belt is considered to be an arc. If the bending rigidity of the belt is high, the belt will be difficult to bend, and if the bending rigidity of the belt is low, the belt will be easy to bend.

[0132] In the present application, the bending rigidity EI of the belt can be measured using an autograph, and more specifically, can be measured by the method described in the examples below.

[0133] In the raw edge bonded V-belt of the present invention (more specifically, each raw edge V-belt portion), the belt lateral pressure rigidity may be 1500 N / mm or more, for example, 1500 to 5000 N / mm, preferably 2000 to 4500 N / mm, further preferably 2500 to 4000 N / mm, further preferably 2700 to 3500 N / mm, and most preferably 2800 to 3200 N / mm. In the present invention, since the belt lateral pressure rigidity is in this range, the transmission efficiency can be improved.

[0134] In the present application, the lateral pressure rigidity of the belt can be measured using an autograph, and more specifically, can be measured by the method described in the examples below.

[0135] [Manufacturing method for raw edge bonded V-belts] The method for manufacturing the raw edge bonded V-belt of the present invention includes a cross-linking sleeve forming step of manufacturing a cross-linking belt sleeve having cog portions formed on its outer and inner surfaces, and a polishing step of polishing the cross-linking belt sleeve to form the shape (V-shaped groove) of each raw edge V-belt portion.

[0136] In the bridging sleeve forming step, a method for manufacturing the bridging belt sleeve can be a conventional method for manufacturing a raw edge cogged V-belt.

[0137] Specifically, an inner mold having alternating tooth and groove portions corresponding to the outer cog portions is placed over the outer periphery of a cylindrical mold, and a sheet for a tension rubber layer (uncrosslinked rubber sheet) is wound around it. A core wire (twisted cord) is then spirally spun, and a sheet for a compression rubber layer (uncrosslinked rubber sheet) is then wound around the outer periphery to produce an uncrosslinked molded article. When the tension rubber layer has a laminated structure, multiple sheets for the tension rubber layer may be wound sequentially, or a pre-laminated laminate sheet may be wound around it. Furthermore, if necessary, an adhesive rubber layer sheet (uncrosslinked rubber sheet) or a reinforcing fabric may be laminated.

[0138] The uncrosslinked belt sleeve obtained in this manner is covered with a jacket (an outer mold in which teeth and grooves corresponding to the inner cog portions are alternately arranged), and placed in a known crosslinking device (such as a vulcanization can), where crosslinking molding is carried out at a temperature of 120 to 200°C (particularly 150 to 180°C) to produce a crosslinked belt sleeve.

[0139] The inner mold may be an inner mold in which teeth and grooves corresponding to the inner cog portions are arranged alternately, but from the standpoint of productivity, etc., an inner mold in which teeth and grooves corresponding to the outer cog portions are arranged alternately is preferred.

[0140] In the grinding process, the cross-linked belt sleeve is ground to form the shape of each raw-edge V-belt portion, and in an inner mold in which teeth and grooves corresponding to the outer cogs are alternately arranged, the outer peripheral surface of the resulting cross-linked sleeve corresponds to the inner peripheral surface of the target joined V-belt. Therefore, the cross-linked belt sleeve obtained in the cross-linked belt sleeve forming process can be ground directly from the outer peripheral surface side of the cross-linked belt sleeve to form the shape of each raw-edge V-belt portion (belt side shape and V-shaped groove shape).

[0141] On the other hand, in an inner mold in which teeth and grooves corresponding to the inner cog portions are alternately arranged, the outer peripheral surface of the obtained bridging sleeve corresponds to the outer peripheral surface of the target joined V-belt. Therefore, the inner and outer peripheral surfaces of the bridging belt sleeve obtained in the bridging belt sleeve forming process are turned inside out (inverted), and the inner peripheral surface of the target belt is made the outer peripheral surface of the bridging belt sleeve, and then the shape of each raw edge V-belt portion can be formed by grinding from the outer peripheral surface side of the bridging belt sleeve.

[0142] In the grinding step, before grinding the outer peripheral surface of the crosslinked belt sleeve, the crosslinked belt sleeve may be cut into rings using a cutter or the like depending on the number of raw-edge V-belt portions. Also, before grinding the outer peripheral surface of the crosslinked belt sleeve, a rough V-shaped groove shape may be formed by cutting. [Example]

[0143] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. Details of the materials used in the examples and comparative examples and the evaluation methods for the examples and comparative examples are shown below.

[0144] [Materials used] (Rubber composition) The materials compounded in the rubber composition are as follows:

[0145] Chloroprene rubber: Denka Co., Ltd. "PM-40" Magnesium oxide: Kyowa Mag 150 manufactured by Kyowa Chemical Industry Co., Ltd. Stearic acid: NOF Corporation "Camellia Stearate Beads" Zinc oxide: "Zinc oxide (JIS standard type 2)" manufactured by Hakusui Tech Co., Ltd. Carbon black ISAF: "Seast 6" manufactured by Tokai Carbon Co., Ltd. Carbon black SRF: "Seast S" manufactured by Tokai Carbon Co., Ltd. Para-aramid staple fiber: Twaron (registered trademark) manufactured by Teijin Limited, fiber length 3 mm Softener: ADEKA Cizer C-8 manufactured by ADEKA Corporation Crosslinking accelerator MBTS (dibenzothiazyl disulfide): "Noccela DM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant ODPA (octyldiphenylamine): "Nonflex OD-3" manufactured by Seiko Chemical Co., Ltd. Sulfur: "Powdered sulfur" manufactured by Bigen Chemical Co., Ltd. Co-crosslinking agent MPBM (N,N'-m-phenylenedimaleimide): "Valnoc PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0146] (core wire) The core wire was a plied cord with a total fineness of 16,500 dtex, which was made by combining five first-twisted yarns made by first twisting three 1,100 dtex PET fiber bundles together at a twist factor of 3.0, and then second-twisting them in the opposite direction to the first twist at a twist factor of 3.0. The diameter of the treated cord (treated cord after the adhesive treatment described below) was approximately 1.6 mm.

[0147] (Method for bonding short fibers and cords) The para-aramid short fibers and cords were each subjected to an adhesion treatment by immersing them in an RFL liquid [a mixed liquid of 2.6 parts by mass of resorcinol, 1.4 parts by mass of 37% by mass formalin, 17.2 parts by mass of vinylpyridine-styrene-butadiene copolymer latex (manufactured by Zeon Corporation), and 78.8 parts by mass of water] and drying. The adhesion rate of the adhesive component (solid content) was adjusted to 6% by mass of the short fibers or cords before treatment.

[0148] [Rubber hardness Hs of cross-linked rubber] A crosslinked rubber sheet (100 mm x 100 mm x 2 mm thick) was produced by press-heating a rubber sheet (uncrosslinked rubber sheet) for the tension rubber layer or compression rubber layer having the composition shown in Table 2 at a temperature of 160°C, a pressure of 2 MPa, and a time of 30 minutes. Three of the obtained crosslinked rubber sheets were stacked to form a laminate, which was used as a sample. The rubber hardness Hs (Type A) of the crosslinked rubber sheet was measured using a Type A durometer in accordance with the spring-type durometer hardness test specified in JIS K 6253 (2012) (Vulcanized rubber and thermoplastic rubber - Determination of hardness).

[0149] [Belt bending rigidity EI] An autograph (Shimadzu Corporation, "AGS-J10kN") was fitted with upper and lower plates for compressing the test belt from the back, and the circular belt 21 serving as the specimen was positioned between the upper and lower plates 22 and 23, as shown in Figure 6, so that the outer periphery of the circular belt 21 was in contact with the upper and lower plates 22 and 23. The distance between the plates was narrowed at a rate of 100 mm / min, and the compressive force (bending load) was measured and recorded at a measurement temperature of 25°C when the pitch diameter D (the shortest distance between the opposing pitch lines L of the upper and lower plates 22 and 23) reached 160 mm. The bending stiffness EI was calculated from the measurement results using the following formula.

[0150] Bending stiffness EI = (compression force x (pitch diameter D / 2) 2 ) / 2 (unit: N(mm) 2 )

[0151] For bonded V-belts, the bending stiffness EI was measured by cutting each raw edge V-belt section and expressed as a value per V-belt section or a value per mm of pitch width divided by the pitch width W of the V-belt section.

[0152] [Belt lateral pressure stiffness] First, a circular V-belt was cut (in the case of a joined V-belt, the V-belt was cut into each raw-edge V-belt section before cutting) to prepare a lateral pressure resistance evaluation sample S with a circumferential length of 70 mm. Then, as shown in FIG. 7, the sample S was sandwiched vertically between two metal jigs 31 and 32 so that the friction transmission surface of the sample S was in contact with the jigs. Using an autograph (Shimadzu Corporation, "AGS-J10kN"), the lower jig 32 was raised at a rate of 5 mm / min, and the travel distance and compressive force of the lower jig 32 were recorded. The lateral pressure stiffness was calculated using the following formula from the travel distance of the lower jig 32 when the compressive force was between 200 N and 1000 N.

[0153] Lateral pressure stiffness = (1000 - 200) / travel distance of lower jig 32 (unit: N / mm)

[0154] [Transmission efficiency] As shown in Figure 8, the transmission efficiency test was performed using a two-axis running test machine consisting of a driving (Dr.) pulley with a diameter of 129 mm connected to a driving shaft and a driven (Dn.) pulley with a diameter of 129 mm connected to a driven shaft. The driving and driven shafts were connected to motors and equipped with torque meters and digital tachometers, allowing for adjustment of rotation speed and torque. Each pulley had two V-grooves, and a two-ribbed belt was suspended on the combined V-belt, while two belts were suspended on the single V-belt. The belts were then tensioned with an axle load of 1200 N. The driving pulley was adjusted to a rotation speed of 2,000 rpm and a torque of 30 Nm, and the torque and rotation speed of the driving and driven shafts were measured. The measurement temperature (ambient temperature) was 25°C.

[0155] As shown in the formula below, the power P1 of the drive shaft is calculated as the product of the torque T1 and the rotational speed ρ1 of the drive shaft. Similarly, the power P2 of the driven shaft is calculated as the product of the torque T2 and the rotational speed ρ2 of the driven shaft. The transmission efficiency η is calculated by dividing the power of the driven shaft by the power of the drive shaft.

[0156] P1=T1×ρ1 P2=T2×ρ2 η=P2 / P1=(T2×ρ2) / (T1×ρ1)

[0157] In Table 4, the transmission efficiency is expressed as a relative value with Comparative Example 1 being set at 100, and a relative value of the transmission efficiency exceeding 100 was judged to be acceptable, while one below 100 was judged to be unacceptable.

[0158] Examples 1 to 10 and Comparative Examples 1 to 3

[0159] (Formation of rubber layer) For the rubber compositions in Table 2 (tension rubber layer and compression rubber layer), rubber kneading was carried out using a known method such as a Banbury mixer, and the resulting kneaded rubber was passed through a calendar roll to produce rolled rubber sheets (sheets for the tension rubber layer and the compression rubber layer).

[0160] [Table 2]

[0161] (Belt manufacturing) An inner mold corresponding to the outer cog was placed on the outer periphery of a cylindrical mold, a sheet for a tension rubber layer was wound around the outer periphery, and then a cord was spirally spun around the outer periphery of the sheet for a tension rubber layer (or tension rubber sheet). A sheet for a compression rubber layer (or compression rubber sheet) was then wound around the outer periphery, and then an outer mold corresponding to the inner cog was placed on top to form an uncrosslinked belt sleeve. A jacket was then placed on the uncrosslinked belt sleeve, and the mold was placed in a vulcanizer, and crosslinked at 160°C for 20 minutes to obtain a crosslinked belt sleeve.

[0162] The outer periphery of the obtained crosslinked belt sleeve was ground with a grinder (a diamond electroplated wheel shaped to correspond to the V-shaped grooves of the raw-edge type bonded V-belt) to form multiple raw-edge double-cogged V-belt sections. After cutting into two raw-edge double-cogged V-belt sections, the inner and outer peripheral surfaces were inverted to obtain raw-edge double-cogged bonded V-belts.

[0163] In Examples 6 to 10 and Comparative Example 2, the sheet for the tension rubber layer was formed by laminating two sheets, a sheet for the outer rubber layer (or outer rubber sheet) and a sheet for the inner rubber layer (or inner rubber sheet), and in Comparative Example 1, the sheet was cut into single raw edge double cogged V-belts to form a single type raw edge double cogged V-belt.

[0164] Table 3 shows the belt size of the raw edge double cogged V-belt portion of the raw edge double cogged combined V-belt (or the single type raw edge double cogged V-belt of Comparative Example 1).

[0165] [Table 3]

[0166] Table 4 shows the evaluation results of the belts obtained in the examples and comparative examples.

[0167] [Table 4]

[0168] Examples 1 to 10 are combined-type raw edge double cog combined V-belts, and have high power transmission efficiency due to the hardness of the tension rubber layer being within a specific range.

[0169] Examples 1 to 4 are examples in which only the outer circumferential valley thickness H4 and the total belt thickness H1 differ, but when the outer circumferential valley thickness H4 is small, the transmission efficiency decreases, possibly due to a decrease in lateral pressure rigidity (particularly in Example 2), and when the outer circumferential valley thickness H4 is large, the transmission efficiency decreases, perhaps due to an increase in bending rigidity (particularly in Example 4). Of Examples 1 to 4, Example 3 had the highest transmission efficiency. Comparing Example 3 and Example 5, Example 3 had increased lateral pressure rigidity and higher transmission efficiency, possibly due to the higher hardness of the tension rubber layer.

[0170] Example 6 has the same outer circumferential valley thickness as Example 3 and two tension rubber layers, but although the lateral pressure rigidity is slightly reduced, the bending rigidity is significantly reduced, which may be why the transmission efficiency is higher than that of Example 3.

[0171] In Examples 7 and 8, the outer rubber sheet was thicker and the inner rubber sheet was thinner than in Example 6, but the transmission efficiency was slightly reduced, possibly due to the increased bending rigidity.

[0172] Example 9 is an example in which the inner and outer rubbers of Example 6 are interchanged. That is, Example 9 is an example in which the inner rubber layer is formed from rubber composition A with high hardness and the outer rubber layer is formed from rubber composition B with low hardness, but the transmission efficiency was slightly reduced, possibly due to an increase in bending rigidity.

[0173] In Example 10, the thickness of the inner rubber sheet was made thicker than in Example 7, thereby increasing the outer circumferential valley thickness H4. However, the transmission efficiency decreased, possibly due to the increased bending rigidity.

[0174] Comparative Example 2 is an example in which the rubber hardness is high, but the transmission efficiency decreased, possibly due to increased bending rigidity. Comparative Example 3 is an example in which the rubber hardness is low, but the transmission efficiency decreased, possibly due to decreased lateral pressure rigidity. [Industrial Applicability]

[0175] The raw edge bonded V-belt of the present invention can be suitably used in applications requiring energy saving performance by taking advantage of its high power transmission efficiency, and is used in air conditioners, blowers, exhaust fans, compressors, generators, gas heat pumps, etc. [Explanation of symbols]

[0176] 1,11...Raw edge bonded V-belt 2,12...Tension rubber layer 3,13…Core layer 3a…core wire 4,14...Compressed rubber layer 5...Reinforcing fabric

Claims

1. A combined V-belt in which a plurality of raw edge V-belt portions are arranged in the belt width direction, The raw edge V-belt portion has outer circumferential cog portions arranged in the belt length direction on the outer circumferential surface side and inner circumferential cog portions arranged in the belt length direction on the inner circumferential surface side, the raw edge V-belt portion includes a core layer including a core wire, a tension rubber layer formed on an outer peripheral side of the core layer, and a compression rubber layer formed on an inner peripheral side of the core layer, Each raw edge V-belt portion is connected in the belt width direction by the tension rubber layer, the tension rubber layer has a single layer structure formed of a first crosslinked rubber composition or a laminated structure including an inner rubber layer formed of a second crosslinked rubber composition and in contact with the core layer; and The bonded V-belt has a rubber hardness Hs (type A) of 60 to 90 degrees for the first crosslinked rubber composition and the second crosslinked rubber composition.

2. 2. The joined V-belt according to claim 1, wherein each raw edge V-belt portion is continuously connected in at least a partial area in the belt thickness direction of the tension rubber layer.

3. 3. The joined V-belt according to claim 1, wherein the outer circumferential valley thickness, which is the distance between the center axis of said core wire and the groove bottom of said outer circumferential cog portion, is 0.5 to 3 mm.

4. 3. The joined V-belt according to claim 1, wherein the outer circumferential trough thickness, which is the distance between the center axis of said core wire and the groove bottom of said outer circumferential cog portion, is 0.11 to 0.3 times the total belt thickness.

5. 3. The bonded V-belt according to claim 1, wherein the tension rubber layer comprises the inner rubber layer and an outer rubber layer formed of a third crosslinked rubber composition and laminated on the inner rubber layer, and the second crosslinked rubber composition and the third crosslinked rubber composition have different hardnesses.

6. 6. The bonded V-belt according to claim 5, wherein the hardness of said second crosslinked rubber composition is less than the hardness of said third crosslinked rubber composition.

7. 3. The method for manufacturing a joined V-belt according to claim 1, further comprising: a forming step of manufacturing a bridging belt sleeve having cog portions formed on its outer and inner peripheral surfaces; and a grinding step of grinding the bridging belt sleeve to form the shape of each raw edge V-belt portion.

8. 8. The manufacturing method according to claim 7, wherein the cog portion formed on the outer peripheral surface of the bridging belt sleeve has a shape corresponding to the inner cog portion of the raw edge V-belt portion.

Images