JP2012240508A - Pneumatic tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire for a motorcycle in which in particular, center wear is reduced.SOLUTION: The pneumatic tire includes: a carcass 5 formed of at least one carcass ply; at least one spiral belt layer 6 arranged on the outer peripheral side of a crown region of the carcass 5 and comprising cords extending in the circumferential direction of the tire; and a tread rubber 7 arranged on the outer peripheral side of the spiral belt layer 6 and forming a tread contact area. The tread rubber 7 comprises: a center region 7a disposed in a range of 50% of the tread contact area, centering a tire equatorial plane; and a pair of shoulder regions 7b including tread contact ends. An auxiliary belt layer 9 comprising the plurality of cords extending at 0-60° of an angle to the tire equatorial plane is arranged within the center region 7a. Tensile rigidity per unit width of the auxiliary belt layer 9 is the same or more than that of the spiral belt layer 6.

Description

  The present invention relates to a pneumatic tire for motorcycles, and more particularly to a pneumatic tire for motorcycles with improved wear resistance.

  In pneumatic tires for motorcycles, it is necessary to provide a camber angle that inclines the tire with respect to the road surface during cornering, so the crown portion of the tire has a smaller curvature than the tires for automobiles. Since the tire has a radius and has a round cross-sectional shape, the difference in diameter between the center region including the tire equator plane and the shoulder region including the tread ground contact edge becomes large during internal pressure filling.

  Such a pneumatic radial tire for a motorcycle is, for example, as shown in FIG. 5 (a), a carcass 35 composed of at least one carcass ply, and a diameter due to centrifugal force at the time of traveling radially outward. In order to prevent this increase, it is common to provide a spiral belt layer 36 in which the cord extends in the circumferential direction of the tire to ensure the durability and stability performance of the tire.

  Here, assuming that the tire is traveling straight at a constant speed, the speed of the tread surface is the same while being grounded on the road surface and any part is grounded, while the speed of the spiral belt layer 36 is The radius of the portion is multiplied by the angular velocity of the tire, and the center region having a large belt radius has a relatively high speed.

  For this reason, the belt in the center region is faster than the tread surface, so that the tread rubber in the center region is subject to shear deformation in the driving direction, while the belt speed is lower in the shoulder region. When the tread rubber is subjected to shear deformation in the braking direction, a difference in belt speed due to a difference in tire radius occurs.

  That is, the crossing belt layer is deformed like a pantograph, or the rubber stretches between the belt layers, so that the belt can stretch or shrink in the tire circumferential direction, and the speed difference between the tread rubber and the belt. Although the component can be relaxed, in a tire provided with a spiral belt layer, the spiral belt layer does not extend in the tire circumferential direction and the deformation amount of shear rigidity is small, so the diameter difference cannot be relaxed by belt expansion and contraction. The belt speed difference due to the tire radius difference greatly affects.

Therefore, in the tread portion of the pneumatic tire for motorcycles having a round crown shape, relative displacement occurs between the spiral belt layer and the tread surface, and the shear deformation of the tread rubber in the tire circumferential direction increases, and the driving force is applied to the tire. Is applied, especially in the center region that is subjected to shear deformation in the driving direction, it is easy to slip with the driving force, and when a large driving force is applied, it starts to slide from the center region, and in the center region, there is center wear. There was a risk of occurrence.
In particular, since driving force is applied to the rear wheel tire, there is a high risk that large center wear will occur early.

  An object of the present invention is to provide a pneumatic tire for a motorcycle with particularly reduced center wear.

As a result of intensive studies to achieve the above object, the present inventor has found that when the belt is subjected to compressive strain in the tire circumferential direction, the circumferential speed of the belt in the tread surface can be reduced. In other words, during rolling, the tire undergoes out-of-plane bending in the circumferential direction of the tire, causing compression distortion on the inner side of the bend from the neutral axis and tensile strain on the outer side. As shown in an enlarged view of a part of the circumferential cross section, the neutral axis n _{5 of the} curve indicated by the alternate long and short dash line is considered to be almost on the belt. Control, give the belt located in the center area compressive strain in the tire circumferential direction, reduce the speed of the belt, reduce the speed difference with the belt located in the shoulder area, and tread rubber in the center area It was found that the center wear can be reduced by changing the shearing force in the tire circumferential direction in the braking direction.

  In the pneumatic tire for a motorcycle according to the present invention, the carcass formed by at least one carcass ply and the cord disposed on the outer peripheral side of the crown area of the carcass and extending in the circumferential direction of the tire Comprising at least one spiral belt layer and a tread rubber disposed on the outer peripheral side of the spiral belt layer and forming a tread ground surface, wherein the tread rubber is centered on a tire equator surface. And a pair of shoulder regions including the tread contact end, and extends within the center region at an angle in the range of 0 to 60 ° with respect to the tire equator plane. Auxiliary belt layer composed of a plurality of cords is disposed, and the tensile rigidity per unit width of the spiral belt layer and the auxiliary belt layer is equal to or greater than It is an butterfly.

Here, “50% range of the tread contact surface” means JATMA (Japan Automobile Tire Association) YEAR BOOK in Japan, ETRTO (European Tire and Rim Technical Organization) STANDARDDS MANUAL in Europe, TRA (THE TIRE AND THE TIRE TIRE in the United States). ASSOCIATION INC.) Periphery length in the tread width direction measured along the tread surface under the condition that the tire is assembled to the applicable rim specified in YEAR BOOK and filled with the highest air pressure specified in JATMA etc. Of the entire tread surface to the peripheral length is 50%.
“Tensile rigidity per unit width” is defined as the cord tensile strength per unit width × the number of driven wires.

  In such a pneumatic tire for a motorcycle, more preferably, the tensile rigidity per unit width of the auxiliary belt layer is 40% or more of the tensile rigidity per unit width of the spiral belt layer.

  Preferably, the reinforcing cord layer is disposed between the carcass and the spiral belt layer, either radially inward of the carcass or radially outward of the spiral belt layer.

  Further, another pneumatic tire for a motorcycle according to the present invention includes a carcass formed by at least one carcass ply and a tread rubber disposed on the outer peripheral side of the crown area of the carcass to form a tread grounding surface. The tread rubber comprises a center region in a range of 50% of the tread ground contact surface centering on the tire equator surface, and a pair of shoulder regions including a tread ground contact end. At least one spiral belt layer made of a cord extending in the circumferential direction of the tire is disposed radially inward of the inner carcass and radially outward of the carcass in the shoulder region. It is characterized by.

  Any of the tires described above is preferably used as a tire for mounting a rear wheel of a motorcycle.

  In the present invention, an auxiliary belt layer composed of a plurality of cords extending at an angle in the range of 0 to 60 ° with respect to the tire equatorial plane is disposed in the center region, and the spiral belt layer and the auxiliary belt layer are arranged. By making the tensile rigidity per unit width equal to or greater, the position of the neutral axis of the bend of the tread is controlled, and compressive strain in the tire circumferential direction is given to the spiral belt layer located in the center region, and the belt layer The speed can be reduced and, as a result, center wear can be reduced.

  In another tire of the present invention, at least one spiral belt layer made of a cord extending in the circumferential direction of the tire is provided radially inward of the carcass in the center region and radially outward of the carcass in the shoulder region. By arranging it, the neutral axis of the bend of the tread can be controlled, the belt located in the center area can be compressed and strained in the tire circumferential direction, and the speed of the belt can be reduced, resulting in center wear. Can be reduced.

1A is a cross-sectional view in the width direction in a tire posture in which a pneumatic tire for a motorcycle is assembled to an applicable rim and filled with a maximum air pressure according to an embodiment of the present invention, and FIG. It is the enlarged view to which a part of circumferential direction cross section of the tread part of this was expanded. It is the enlarged view which expanded a part of cross section of the width direction of a tread part about other embodiment of this invention. It is the enlarged view which expanded a part of cross section of the width direction of a tread part about other embodiment of this invention. (A) is width direction sectional drawing in the tire attitude | position which assembled | attached the pneumatic tire for motorcycles to the application rim, and filled the highest air pressure with other embodiment of this invention, (b) is (a). It is the enlarged view to which a part of cross section of the tread part of the width direction was expanded. (A) is the width direction sectional view in the tire attitude | position which assembled | attached the conventional pneumatic tire for motorcycles to the application rim, and was filled with the highest air pressure, (b) is the width direction cross section of the tread part of (a). It is the enlarged view which expanded a part.

Hereinafter, a pneumatic tire for a motorcycle according to the present invention will be described in detail with reference to the drawings.
In FIG. 1, 1 is a tread portion, 2 is a pair of sidewall portions extending radially inward continuously to the respective side portions of the tread portion 1, and 3 is radially inward of the sidewall portion 2. Each bead portion is shown.

  The tire shown here is embedded in a pair of bead portions 3, and in the figure, between the hexagonal bead cores 4, the main body portion 5 a of the carcass 5 extends in a toroidal shape, and each side portion around the bead core 4. And it has the folding | returning part 5b turned back toward the outer side from the tire width direction inner side. In the figure, the carcass 5 is constituted by a single carcass ply, but a carcass can also be constituted by a plurality of carcass plies. When the carcass layer is composed of two carcass plies, a radial structure in which the cord angle constituting the carcass ply is 90 ° with respect to the tire circumferential direction, and the cord angle with respect to the tire circumferential direction is 30 to 85 °. A bias structure in which the plies in the range are used while being crossed with each other can be obtained.

A so-called spiral belt structure in which at least one, in the figure, for example, one or a plurality of cords, for example, one cord or a plurality of cords are continuously wound around the outer side in the tire radial direction of the carcass 5 in an extending posture in the tire circumferential direction. A spiral belt layer 6 is provided.
Further outward of the spiral belt layer 6 in the radial direction, a tread rubber 7 that extends in an arc shape to the maximum width position of the tire and forms a contact area of the tread portion 1 is provided, for example, in a single layer structure. Further, side rubbers 8 that form side portions are provided on both sides of the tread rubber 7.
Furthermore, although omitted in FIG. 1, a required groove is formed on the surface of the tread rubber 7.

  The tread rubber 7 is formed by a center region 7a in a range of 50% of the tread contact surface centered on the tire equator surface and a pair of shoulder regions 7b including a tread contact end. The shoulder region 7b sandwiches the equator surface. A pair is formed at symmetrical positions.

In the center region, an auxiliary belt layer 9 in which a plurality of cords extended at an angle in the range of 0 to 60 ° with respect to the tire equatorial plane is covered with rubber, preferably, a carcass 5 and a spiral belt layer. 6 are arranged in a single layer in the figure, and the tensile rigidity per unit width of the spiral belt layer 6 and the auxiliary belt layer 9 is equal to or higher than that.
In such an embodiment, the neutral axis n ₅ positioned on the conventional belt is shifted to the radially inward neutral axis n ₁ of the spiral belt layer 6, and is positioned radially outward of the tire from the neutral axis n _1. In the region where compression is applied, compressive strain is applied, the speed of the spiral belt layer 6 is reduced, and center wear can be reduced.

  Preferably, the tensile rigidity per unit width of the auxiliary belt layer is 40% or more of the tensile rigidity per unit width of the spiral belt layer, and this configuration can enhance the effect of reducing center wear.

  Here, the inside of the center region can be in a range of 40 to 100% of the circumferential cross section of the center region 7a.

  Further, the cord constituting the auxiliary belt layer 9 can be composed of a steel cord or an organic fiber cord. In the case of organic fiber cords, for example, twisted cords such as aromatic polyamide, nylon and aromatic polyketone can be used. In the case of a steel cord, it can be used as it is without twisting a single steel wire or a single steel wire.

FIG. 2 is an enlarged view of another embodiment of the present invention in which a part of the circumferential cross section of the tread portion is enlarged. In this embodiment, the auxiliary belt layer 19 is disposed radially inward of the carcass 5. Arrange.
In such an arrangement, the neutral axis n ₅ positioned on the conventional belt is shifted to the neutral axis n ₂ in the radial direction of the spiral belt layer 6, and is positioned outward in the tire radial direction from the neutral axis n _2. By applying compressive strain in the region, the speed of the spiral belt layer 6 can be reduced, and the center wear can be reduced.

FIG. 3 is an enlarged view of another embodiment of the present invention, in which a part of the circumferential cross section of the tread portion is enlarged. In this embodiment, the auxiliary belt layer 29 is disposed outside the spiral belt layer 6 in the radial direction. It arranges in the direction.
In such an arrangement, the neutral axis n ₅ positioned on the conventional belt is shifted to the neutral axis n ₃ radially outward of the spiral belt layer 6, and is positioned radially outward of the tire from the neutral axis n _3. By applying compressive strain in the region, the speed of the spiral belt layer 6 can be reduced, and the center wear can be reduced.

  FIG. 4A is a cross-sectional view in the width direction in a tire posture in which another embodiment of the present invention is assembled with a pneumatic tire for a motorcycle mounted on an applied rim and filled with a maximum air pressure, and FIG. It is the enlarged view to which a part of circumferential cross section of the tread part of a) was expanded. In addition, the same code | symbol is attached | subjected to the element similar to the tire shown in the previous figure, and the description is abbreviate | omitted.

  In this embodiment, one center spiral belt layer 16a is disposed radially inward of the carcass in the center region, and one shoulder spiral belt layer 16b is disposed radially outward of the carcass in the shoulder region, Each spiral belt layer 16a, 16b consists of a cord extending in the circumferential direction of the tire.

  Here, the inside of the center region can be the same range as described above, and the inside of the shoulder region can be a range of 80 to 100% of the circumferential cross section of the shoulder region 7b.

In such an embodiment, the neutral axes n _4a and n _4b are positioned at the positions of the spiral belt layers 16a and 16b, respectively, and the position of the neutral axis is changed between the center region and the shoulder region, so that it is particularly positioned in the center region. The center wear can be reduced by applying compressive strain in a region located outward in the tire radial direction from the neutral axis n _4a to reduce the speed of the spiral belt layer 6.

  By the way, since a driving force is applied to the rear wheels of the motorcycle, it is preferable to employ the above-described configuration for the rear wheel mounting tire, which is advantageous for center wear.

Next, a rear tire having a structure as shown in FIG. 1A and having a rear tire size of 190 / 50ZR17, a radial tire provided with a steel monofilament spiral belt and a nylon carcass is arranged. Example tires 1 to 4 changed as shown in FIG. 1, and comparative tires having the same structure as shown in FIG. evaluated.
The front tire was a radial tire of 120 / 70ZR17.
In the present invention, since the tire structure other than the tread portion does not require modification, the tire structure is substantially the same as that of a conventional pneumatic tire for motorcycles.

Example tires 1 to 4 and comparative example tires were respectively mounted on a rim having a rim size of 6.0 × 17, an internal pressure of 290 kPa, a load of 150 kg, a test speed of 60 to 100 km / h, a travel distance of 5000 km, and a center groove. The difference in wear amount between the shoulder groove and the shoulder groove was evaluated as an index, and the results are shown in Table 2.
The value of the comparative example tire was set as 100 and displayed as an index. In addition, the value in a table | surface shows that a wear amount difference is so small that a center wear is reducing, so that a numerical value is small.

  From the results in Table 2, the center tire of the example tire 1 to the example tire 4 can be reduced compared to the comparative example tire.

DESCRIPTION OF SYMBOLS 1,31 Tread part 2,32 Side wall part 3,33 Bead part 4,34 Bead core 5,35 Carcass 5a Main part 5b Folding part 6,16a, 16b, 36 Spiral belt layer 7,37 Tread rubber 7a Center area 7b Shoulder Region 8, 38 Side rubber 9, 19, 29 Auxiliary belt layer

Claims (7)

A carcass formed of at least one carcass ply, at least one spiral belt layer comprising a cord disposed on the outer peripheral side of the crown area of the carcass and extending in the circumferential direction of the tire, and a spiral In a pneumatic tire for a motorcycle including a tread rubber disposed on the outer peripheral side of the belt layer and forming a tread ground surface,
The tread rubber is composed of a center region in the range of 50% of the tread contact surface centered on the tire equator surface, and a pair of shoulder regions including the tread contact end.
In the center region, an auxiliary belt layer composed of a plurality of cords extending at an angle in the range of 0 to 60 ° with respect to the tire equatorial plane is disposed, and per unit width of the spiral belt layer and the auxiliary belt layer. A pneumatic tire for a motorcycle, characterized by having a tensile rigidity equal to or greater than that of the motorcycle.   The pneumatic tire for a motorcycle according to claim 1, wherein the tensile rigidity per unit width of the auxiliary belt layer is 40% or more of the tensile rigidity per unit width of the spiral belt layer.   The pneumatic tire for a motorcycle according to claim 1 or 2, wherein the auxiliary belt layer is disposed between a carcass and a spiral belt layer.   The pneumatic tire for a motorcycle according to claim 1 or 2, wherein the auxiliary belt layer is disposed radially inward of the carcass.   The pneumatic tire for a motorcycle according to claim 1 or 2, wherein the auxiliary belt layer is disposed radially outward of the spiral belt layer. In a pneumatic tire for a motorcycle comprising a carcass formed of at least one carcass ply and a tread rubber disposed on the outer peripheral side of the crown area of the carcass to form a tread ground surface,
The tread rubber is composed of a center region in a range of 50% of the tread contact surface centered on the tire equator surface, and a pair of shoulder regions including the tread contact end.
At least one spiral belt layer made of a cord extending in the circumferential direction of the tire is disposed radially inward of the carcass in the center region and radially outward of the carcass in the shoulder region. A pneumatic tire for a motorcycle characterized by comprising   The pneumatic tire for a motorcycle according to any one of claims 1 to 6, which is a tire for mounting a rear wheel of a motorcycle.

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