JPH07108803A - Radial tire for motorcycle - Google Patents

Abstract

PURPOSE:To increase both a high-speed stability and turning performance by providing a rubber layer containing specified short fibers between carcusses inside a belt layer formed of plies in which organic fiber belt cord is covered with topping rubber. CONSTITUTION:A belt layer 7 inside a tread part 2 and outside carcusses 6 in the radial direction is formed with ply pieces made by winding wide and long band plies 7A in which organic fiber cords are covered with topping rubber are wound spirally approximately in parallel with a tire equator C. Also a rubber layer 9 between the carcusses 6 on the inner side of the belt layer 7 in the radial direction is formed of a rubber compound containing a 20 to 50 pts.wt. of carbon black of 35 to 120mgr/gr in iodine adsorption amount and 10 to 40 pts.wt. of short fibers relative to 100 of rubber component. Thus the rigidity of the tread part 2 can be increased uniformly to increase both a high- speed stability and turning stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire for a motorcycle capable of improving both high speed running stability and turning stability.

[0002]

2. Description of the Related Art Motorcycles, unlike four-wheeled vehicles such as passenger cars, buses and trucks, turn with a large bank angle. Therefore, the tires used in motorcycles are
Unlike the four-wheeled vehicle, the radius of curvature of the tread surface in the tire axial direction is extremely small.

On the other hand, for motorcycles, structures such as X-ply tires, belted bias tires and radial ply tires are used properly according to the purpose of use such as improvement of high-speed running stability and ride comfort. It was

With the recent maintenance of highways, high-speed performance is required for motorcycles as well, and the use of radial-ply tires, which have relatively good stability for high-speed running, is increasing.

[0005]

In the tire having the radial ply structure, as shown in FIG. 7, for example, a belt layer b is arranged outside a carcass a in a radial arrangement, and the belt layer b is straight running. In many cases, a small band-shaped ply is spirally wound in the tire circumferential direction in order to improve the tire resistance.

However, the tire having the above structure has a radial structure, so that the cornering power is low and the rigidity of the tread portion is low. Therefore, the tire is inferior in performance when traveling at an extremely high speed and when turning with a bank angle. There is a problem. Therefore, it became necessary to improve high-speed stability and turn performance.

As a result of earnest research aimed at achieving both high-speed stability and turning performance, the inventors of the present invention have found that: (a) based on a radial ply structure, (b) a sheet-shaped rubber layer between the inside of the belt layer and the carcass. The present invention has been completed based on the finding that it is effective to form the sheet layer from a rubber composition containing short fibers.

It is an object of the present invention to provide a radial tire for a motorcycle that can achieve both high speed stability and turning performance.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a tread width, which is a distance in the tire axial direction between tread portion edges, has a maximum tire width, and a tread surface is curved in a convex arc shape in the tire axial direction. A radial tire for a motorcycle, which has a toroidal carcass having a cord in a radial arrangement and folding around a bead core of a bead part through a sidewall part from a tread part, and an outer side in a radial direction of the carcass inside the tread part. And a rubber layer interposed between the carcass and the inner side in the radial direction of the belt layer. The belt layer is a long and small belt cord made of organic fibers covered with a topping rubber. The rubber layer is composed of a ply piece formed by spirally winding a strip-shaped ply of a width substantially parallel to the tire equator.
The iodine adsorption amount is 35 to 1 with respect to 100 parts by weight of the rubber component.
A radial tire for a motorcycle, comprising a rubber composition containing 20 to 50 parts by weight of carbon black of 20 mgr / gr and 10 to 40 parts by weight of short fibers.

In the rubber layer, short fibers are 4 with respect to the tire equator.
It is preferable to orient at an angle of 5 to 90 °.

The rubber layer may be formed of one sheet piece, or may be formed of two sheet pieces that overlap inward and outward in the radial direction. When formed from two sheet pieces, the fibers of each sheet piece are preferably oriented in directions intersecting with each other.

[0012]

Since the carcass is arranged in a radial arrangement and the belt layer is formed by spirally winding the band-shaped plies, the traveling stability is excellent when traveling straight ahead, and high-speed traveling becomes possible.

Further, since the rubber layer is interposed between the inside of the belt layer and the carcass, the rigidity of the tread portion is increased over substantially the entire area of the tread surface. As a result, the turning stability when turning with a bank angle is improved. improves.

The rubber layer not only regulates the compounding ratio of carbon black and short fibers in the rubber composition, but also regulates the iodine adsorption amount of the carbon black itself.

The specific surface area of carbon black per unit weight of the carbon black can be determined by measuring the amount of adsorbed iodine. As a characteristic of carbon black, the bond between particles tends to increase as the specific surface area increases, that is, as the iodine adsorption amount increases. The iodine adsorption amount is measured according to JIS K6221.

In the present invention, by setting the iodine adsorption amount of carbon black to 35 to 120 mg / gr,
The bond between the particles of the carbon black is optimized. Examples of the types of carbon black that satisfy the regulation of the iodine adsorption amount include GPF, FEF, HAF, ISAF and the like, as shown in Table 1 below.

The rubber layer contains 20 to 50 parts by weight of carbon black whose iodine adsorption amount is regulated as described above and 10 to 40 parts by weight of short fibers per 100 parts by weight of the rubber component.

If the carbon black and the short fibers are less than the lower limits of the above numerical values, the strength of the rubber layer is lowered, the rigidity of the tread portion is insufficient, and the steering stability is lowered.
On the other hand, when the carbon black and the short fibers are more than the upper limits of the above numerical values, the heat-generating property of the rubber layer becomes large, and the belt layer is liable to peel due to heat generation, and conversely the strength may be lowered.

As described above, according to the present invention, a rubber layer made of the rubber composition regulated as described above is interposed between the inside of the belt layer and the carcass to form a belt layer in which a belt-shaped ply is spirally wound. By being integrated organically, it is possible to improve both high-speed running stability and turning stability.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 4, a radial tire 1 for a motorcycle
Includes a sidewall portion 3 extending inward in the radial direction from both ends of the tread portion 2 and a bead portion 4 continuous inward in the radial direction of the sidewall portion 3, and between the edges E, E of the tread portion 2. The tread width WT, which is the distance in the tire axial direction, forms the maximum tire width, and the tread surface 2A is curved in an arc shape that is convex in the tire axial direction.

Further, the radial tire 1 for a motorcycle includes a carcass 6 which is folded back from the tread portion 2 through a sidewall portion and around a bead core 5 of a bead portion 4, and inside the tread portion 2 and radially outward of the carcass 6. And a rubber layer 9 interposed between the carcass 6 and the inside of the belt layer 7 in the radial direction.

A bead apex 8 having a triangular cross-section and made of hard rubber is provided on the outer side of the bead core 5 in the radial direction of the bead part 4 and between the main part of the carcass 6 and the folded part.

The carcass 6 is composed of one or more carcass plies in which radial or semi-radial arrangement carcass cords inclined at an angle of 75 to 90 ° with respect to the tire equator C are arranged, and in this example, one carcass ply. As the cord, an organic fiber cord such as nylon, rayon, polyester or aromatic polyamide is used.

The belt layer 7 is a ply piece 7 formed by spirally winding a narrow and long strip-shaped ply 10.
It consists of A. As shown in FIG. 2, the belt-shaped ply 10 has one belt cord 11 or two belt cords 11, 11 arranged in parallel, embedded in a topping rubber 12 in this embodiment.
As the belt cord 11, a steel cord is used in addition to an organic fiber cord such as nylon, polyester, and aromatic polyamide. As the belt cord 11, the aromatic polyamide fiber having tensile strength and elastic modulus substantially equal to that of steel and having a weight smaller than that of steel can be preferably used.

The belt-shaped ply 10 extends from left to right in FIG. 1 and the tire equator C from a starting point H1 which is an outer edge F of the belt layer 7 located near one end edge E of the tread portion 2.
The ply piece 7A can be formed by spirally winding at a small angle of 5 ° or less with respect to the tire equator C until reaching the end point H2 forming the outer edge F of the belt layer 7 in the vicinity of the other end edge E. . Further, in the present embodiment, when the strip-shaped ply 10 is wound, as shown in FIG. 3, the vicinity of the opposite side edges 10a, 10a of the strip-shaped ply 10 are wrapped around each other and wound to prevent the strip-shaped ply 10 from loosening. ing. The belt layer 7 may be formed of two or more ply pieces having the above-described configuration, that is, a plurality of layers of two or more spiral windings of the strip ply 10.

The belt width WB, which is the width of the belt layer 7 in the tire axial direction, is set in the range of 0.8 to 1.0 times the tread width WT.

In the present embodiment, the rubber layer 9 has a width dimension WG of 0.5 to 0.95 times the belt width WB and 0.3 to 1.
It is formed by a piece of sheet of rubber having a rubber thickness of 5 mm. The rubber layer 9 is a rubber containing 20 to 50 parts by weight of carbon black having an iodine adsorption amount in the range of 35 to 120 mgr / gr and 10 to 40 parts by weight of short fibers with respect to 100 parts by weight of the rubber component. It consists of a composition.

The short fibers are organic fibers such as nylon and polyester, and have a diameter d of 0.3 to 0.5 μm and a length l of 300 to 500 μm. Therefore, the aspect ratio 1 / d is 10.
It is an ultrafine short fiber body around 00. This short fiber is 45 to 90 ° with respect to the tire equator C, preferably 85 to 90.
Oriented at angles in the range of °. The angle of the orientation is
It is stated that 70% of all the short fibers contained should be oriented at the angle.

Further, the short fibers intersect the belt cord 11 of the belt layer 7, so that the both have a hoop effect and further enhance the rigidity of the tread portion.

An example of the rubber composition of the rubber layer 9 is shown in Table 1.
Table 2 shows an example of the rubber composition of each part forming the tire.

[0031]

[Table 1]

[0032]

[Table 2]

A rubber layer 9 is shown in FIGS.
The other aspect formed using A and 9B is shown. In this example, the sheet pieces 9A and 9B are superposed inward and outward in the radial direction, and the short fibers of the sheet pieces 9A and 9B are 4 with respect to the tire equator C.
The short fibers are inclined and oriented in the range of 5 to 90 °, preferably 45 to 80 °, and the short fibers intersect each other between the sheet pieces.

Therefore, the short fibers of both the sheet pieces 9A and 9B and the belt cord 11 of the belt layer 7 have a triangular orientation, so that the rigidity of the tread portion 2 can be further increased over substantially the entire area.

[0035]

SPECIFIC EXAMPLES Tires (Examples 1 to 5) having a tire size of 180 / 55R17 and having the configuration shown in FIG. 1 were prototyped according to the specifications shown in Table 3 and tested for their performance. Conventional tires without a rubber layer (Comparative Examples 1 and 2) and tires having configurations other than those of the present invention (Comparative Examples 3 to 3)
A test was also conducted for 10) to compare the performance.

The test conditions are as follows. High-speed stability, turning stability, and a feeling of being stiff. Each test tire was mounted on an actual vehicle, and straight running and turning were repeated on a test road to make a judgment based on a driver's feeling, and an index was set to 100 as Comparative Example 1. . In each case, the larger the value, the better. The test results are shown in Table 3.

[0037]

[Table 3]

As a result of the test, it was confirmed that the working example of the present invention had less feeling than that of the comparative example and that the high-speed stability and the turning stability could be improved in a well-balanced manner.

[0039]

As described above, in the radial tire for a motorcycle of the present invention, short fibers are provided between the belt layer formed by spirally winding the belt-shaped ply and the carcass inside the belt layer. Since the rubber layer including the rubber containing the rubber is interposed, the rigidity of the tread portion can be uniformly increased and both high-speed stability and cornering stability can be improved even though the tire has a radial arrangement.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a developed plan view showing an arrangement of the carcass, a belt layer, and a rubber layer.

FIG. 3 is a perspective view showing an example of a strip ply.

FIG. 4 is a cross-sectional view showing an example of the winding.

FIG. 5 is a cross-sectional view schematically showing another arrangement of the carcass, the belt layer, and the rubber layer.

FIG. 6 is a developed plan view thereof.

FIG. 7 is a cross-sectional view showing a conventional technique.

[Explanation of symbols] 2 tread portion 3 sidewall portion 4 bead portion 5 bead core 6 carcass 7 belt layer 9 rubber layer 9A, 9B sheet piece 10 belt-shaped ply 11 belt cord 12 topping rubber C tire equator E edge WB belt width WG width WT tread width

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[Procedure amendment]

[Submission date] March 17, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

[0031]

[Table 1]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

[0032]

[Table 2]

Claims (4)

[Claims] 1. A radial tire for a motorcycle, wherein a tread width, which is a distance in the tire axial direction between end edges of the tread portion, has a maximum tire width, and a tread surface is curved in a convex arc shape in the tire axial direction. A toroidal carcass that has a cord of radial arrangement while folding around the bead core of the bead part from the tread part through the sidewall part,
A belt layer disposed inside the tread portion and radially outward of the carcass; and a rubber layer interposed between the belt layer radially inside and the carcass, and the belt layer is made of an organic fiber. The rubber layer is composed of a ply piece formed by spirally winding a long and narrow band-shaped ply in which a belt cord is covered with a topping rubber, the rubber layer being based on 100 parts by weight of a rubber component. A radial tire for a motorcycle, comprising a rubber composition containing 20 to 50 parts by weight of carbon black having an iodine adsorption amount of 35 to 120 mgr / gr and 10 to 40 parts by weight of short fibers. 2. The radial tire for a motorcycle according to claim 1, wherein the rubber layer has short fibers oriented at an angle of 45 to 90 ° with respect to the tire equator. 3. The rubber layer has a rubber thickness of 0.3 to 1.5.
The radial tire for motorcycles according to claim 1 or 2, wherein the radial width is 0.5 mm to 0.95 times the belt width of the belt layer. 4. The rubber layer is composed of two sheet pieces that overlap inward and outward in the radial direction, and the short fibers between the sheet pieces are oriented in directions intersecting with each other.
The radial tire for motorcycle according to 2 or 3.