JPH08169208A - Motorcycle tires - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the high-speed performance by balancing the grip when going straight and turning. A carcass 6 and a belt layer 7 are provided, which are 0.125 times or more the total length W of the tread circumferential surface, which is the length between the tread edges along the tread surface 2A around the tire equator CO and 0.5. The crown rubber 10 forming the crown region C having the tread circumferential surface length W1 which is equal to or less than twice the length of the shoulder rubber 11 forming the shoulder regions S on both sides of the crown rubber 10 has loss loss {E ″ / (E *) ² } and The hardness and each are large.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a rubber in the crown region of the tread portion with a greater loss compliance and hardness than the rubber in the shoulder regions located on both sides of the tread portion. The present invention relates to a motorcycle tire that enhances grip balance and enhances high-speed driving performance.

[0002]

2. Description of the Related Art In recent years, as the performance of motorcycles has improved, tires have been required to have higher performance, especially grip performance.

Conventionally, by increasing the grip performance, there are problems in that the wear resistance is lowered and the tread rubber is greatly changed over time. Thus, there was an antinomy relationship between the two.

In order to solve a part of the above-mentioned problems, Japanese Patent Laid-Open No.
In JP-A-1-270707 and JP-B-61-23446, tread rubber is divided in the meridian direction of the tire, and rubber having high wear resistance is used in the central portion and rubber having high grip performance is used in the side portions. Has been proposed.

[0005]

However, in the tire having such a structure, the grip required for braking and driving when traveling straight is not sufficient, and the steering performance is impaired, so that the tire is improved in performance. Does not achieve. In addition, there is a safety problem because the braking performance during wet is sacrificed.

As a result of repeated research aimed at solving the above-mentioned problems, the inventor has found that the tread rubber must mainly absorb the braking energy in order to improve the braking performance. It has been found that the elastic modulus E ″ needs to be high, but the braking performance on an actual road has a higher correlation with the loss compliance (E ″ / (E *) ² ).

Further, during turning, the tread portion is partially slipped, but at both sides of the tread, if the loss conblance is too high, the reaction force that meets the stress of the rubber will be small, and the tread portion will be high during turning. It becomes impossible to support the shearing force. Therefore, the inventors have completed the present invention by finding that the rubber on both sides needs to have lower loss compliance than the rubber on the center.

In the present invention, the tread portion is divided into a crown region and a shoulder region, and the crown rubber forming the crown region has a higher loss compliance and a higher hardness than the shoulder rubber forming the shoulder region. It is an object of the present invention to provide a motorcycle tire capable of improving grip performance during high-speed running and improving grip performance at the time of turning and at the time of turning.

[0009]

According to the present invention, there is provided a carcass which folds around a bead core of a bead portion from a tread portion through a sidewall portion, and a belt layer which is arranged inside the tread portion and radially outside the carcass. And a tread surface having a circular arc shape that bulges convexly in the tire meridional section, the tread circumferential surface total length W being the length between the tread edges along the tread surface around the tire equator. The crown rubber having the tread peripheral surface length W1 of 0.125 times or more and 0.5 times or less of the crown region C is more loss loss {E ″ / than the shoulder rubbers forming the shoulder regions S on both sides thereof. (E
*) ² } and the hardness of rubber are respectively large, and it is a tire for a motorcycle.

The crown rubber has a loss loss
2.0 x 10^-3~ 10 x 10 ^-3cm²/ Kg of rubber
JISA hardness in the range of 35 to 65 degrees
The shoulder rubber has 1.0 × 10 loss loss.^-3
~ 8.0 x 10^-3cm²/ Kg, JISA hardness of rubber is 30
It is preferably in the range of to 55 degrees.

The crown rubber has a larger ratio {E ″ / (E *) ^3/2 } of the loss elastic modulus E ″ to the 3/2 power of the complex elastic modulus (E *) than that of the shoulder rubber. Is preferred.

The loss compliance is the ratio of the loss elastic modulus E ″ to the square of the complex elastic modulus (E *) {E ″ /
(E *) ² }, the dynamic characteristics of the rubber with complex elastic modulus (E *) and loss elastic modulus E ″ are as follows: sample length 30 mm, sample width 4 mm, sample It is a value obtained by measuring a sample having a thickness of 1.5 mm and taken out from a crown rubber and a shoulder rubber, respectively, under the conditions of a measurement temperature of 50 ° C., a frequency of 10 Hz, a vibration width of 2%, and an initial strain of 10%. JIS A hardness is a value measured at a measurement temperature of 50 ° C.

The crown rubber is a shoulder rubber,
The tread surface of the crown region may be formed so as to be in contact with a boundary surface inclined in the tire axial direction toward the tire axial direction outside as shown in FIG. 1 from the tire axial direction outer end point toward the tire radial direction inward direction, or As shown in FIG. 2, they may be formed so as to contact each other at a boundary surface extending from the outer end point in the tire radial direction.

[0014]

The length of the tread surface forming the crown region C is W
In No. 1, it is necessary for the tire to cover the ground contact surface when the tire travels in the camber angle range of 0 to 10 degrees. The tread circumferential surface length W1 is 0.12 of the tread circumferential surface total length W.
If it is less than 5 times, the above-mentioned ground contact surface cannot be sufficiently covered and the grip performance during straight running becomes unstable, while if it exceeds 0.5 times, the grip performance at the time of turning cannot be secured. is there.

In order to increase the grip force, particularly the braking force, it is necessary to absorb the energy generated during braking by the rubber forming the tread portion, that is, the tread rubber. It is known that the loss elastic modulus E ″ of the rubber must be increased in order to allow this energy to be efficiently absorbed by the rubber. However, when traveling on an actual road surface, the loss compliance has a better braking property. The correlation is high, and the loss compliance is related in the present invention.

Further, when the vehicle turns, since the vehicle travels with a large bank angle, the shoulder region comes into contact with the ground and a large shearing force acts. This shear force causes the tread rubber to partially slide, but if the loss compliance of the crown rubber is too high, the reaction force against the stress of the rubber will be small, and the tread rubber will not be able to support the shearing force at the time of turning and will wear in a splayed shape. There is a danger of so-called abrasion. Therefore, it is necessary to make the loss compliance of the shoulder rubber smaller than that of the crown rubber.

On the other hand, the actual contact area of the motorcycle with respect to the road surface is in the range of 20% (rough road surface) to 60% (fine road surface) of the apparent contact area in the slick tire having no tread pattern. The force by which the tread rubber bites into and gets caught in the unevenness of the road surface acts as a stress during turning.

It is effective to reduce the hardness of the rubber in order to make it penetrate into the unevenness. However, in the crown rubber, when the loss compliance is increased and the hardness of the rubber is decreased, the rubber strength is lowered and the wear resistance is greatly impaired.

By combining these relationships, by increasing the loss compliance and the hardness of the rubber of the crown rubber in comparison with the shoulder rubber, the braking force is high at the time of going straight and the turning force is high at the time of turning. Of tires can be provided.

Further, in the circuit running in a race or the like, the running becomes more severe as compared with running on a general road surface, and the tire temperature generated during running becomes higher. Under such a condition, the ratio {E ″ / (E *) ^3/2 } has a high correlation with the braking performance.

Therefore, in order to expand the use so as to be suitable for running on a circuit, the above ratio of crown rubber {E ″ /
(E *) ^3/2 } is preferably higher than that of the shoulder rubber, and in order to increase the heat resistance of the crown rubber, the glass transition temperature of the crown rubber is preferably higher than that of the shoulder rubber.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a motorcycle tire 1 includes a tread portion 2, a sidewall portion 3 extending from both ends thereof inward in the tire radial direction, and a bead portion 4 located at an inner end of the sidewall portion 3 in the tire radial direction. The tread surface 2A has an arc shape that bulges convexly in the meridional section of the tire. In addition, the tire 1 for a motorcycle includes the tread portion 2
A carcass 6 which passes through the sidewall part 3 and folds back the bead core 5 of the bead part 4 from the inner side to the outer side in the tire axial direction, and the belt layer 7 which is arranged inside the tread part 2 and on the outer side in the radial direction of the carcass 6. Further, a bead apex 8 having a triangular cross section is erected on the outside of the bead core in the tire radial direction.

The carcass 5 has a tire equator C in this example.
One or more sheets having radial arrangement carcass cords inclined at an angle of 70 to 90 ° with respect to O, and in this embodiment, 1 sheet
The carcass ply consists of a sheet of carcass, and the carcass cord is made of an organic fiber cord such as nylon, aramid, or aromatic polyamide.

The belt layer 7 is composed of a plurality of belt plies, and the belt plies have belt cords arranged so as to intersect with each other between the plies, and the belt cords are made of nylon, rayon, aromatic polyamide organic fibers or It is formed using a steel cord.

In the tread portion 2, a tread rubber 9 forming a tread surface 2A on the outer side in the radial direction of the belt layer 7 is formed.
Are arranged.

The tread rubber 9 has a tread edge E extending along the tread surface 2A with the tire equator CO as the center,
A crown rubber 10 forming a crown region C having a crown region W1 having a tread circumferential surface length W of 0.125 times or more and 0.5 times or less of a tread circumferential surface total length W which is a length between E, and It is formed by the shoulder rubber 11 forming the shoulder regions S on both sides.

The crown rubber 10 has shoulder rubbers 11 and 11 on both sides thereof and boundary surfaces 12 and 12 inclined outward in the tire radial direction from the tire axial direction outer end points P and P on the tread surface 2A of the crown region C, respectively. Touching. The crown rubber 10 and the shoulder rubber 11 have different rubber characteristics as described later.

By inclining the boundary surface 12 in this manner, the length of the boundary surface 12 becomes longer, and the crown rubber 10
By increasing the joint area between the shoulder rubbers 11 to disperse the force acting between the two rubbers having different rubber characteristics to prevent adhesive failure and uneven wear, and to gradually increase the camber angle during turning, the rubber characteristics It helps to reduce the discomfort caused by the difference.

In this embodiment, the crown rubber 10
Has a loss-priority of 2.0 × 10 ⁻³ to 10 × 1
In the range of 0 ^-3 cm ² / kg and the JIS A hardness of 35 to 65 degrees, the shoulder rubber 11 has a loss priance of 1.0 x 10 ^-3 to 8 x 10 ^-3 cm ² / kg. And the JISA hardness is in the range of 30 to 55 degrees.

Crown rubber 10 and shoulder rubber 11
For each of the above, the optimum range of the loss brilliance and the hardness of the rubber is set as described above, and the crown rubber 10
Has a greater loss brilliance and a higher rubber hardness than the shoulder rubber 11.

In the crown rubber 10, when the loss priance is less than 2.0 × 10 ⁻³ cm ² / kg, the grip performance in straight running is poor, and the loss priance is 10 ×.
If it exceeds 10 ^-3 cm ² / kg, the grip performance during straight running becomes sensitive, and the grip feels uncomfortable during straight running turning time, resulting in poor maneuverability.

In the shoulder rubber 11, if the loss priance is less than 1.0 × 10 ^-3 cm ² / kg, the grip performance during turning is inferior, while the loss priance is 8.0 × 10 ^-3 cm ² / kg or more. If it becomes too large, the shearing force at the time of turning becomes high, which promotes wear.

Further, if the rubber hardness of the crown rubber 10 is less than 35 degrees, abrasion resistance is inferior such as so-called abrasion in which the surface wears in a wrinkle shape, and if it exceeds 65 degrees, the biting with the road surface in the crown region is small. Insufficient grip when driving straight ahead.

If the rubber hardness of the shoulder rubber 10 is less than 30 degrees, the shoulder region will be worn early and the tread groove will be reduced in a short period of time, resulting in a marked decrease in durability.
On the other hand, if the rubber hardness exceeds 55 degrees, the grip force at the time of turning becomes insufficient, so that the turning stability becomes poor.

Further, in this embodiment, the crown rubber 10
Is the ratio {E ″ / (E *) of the loss elastic modulus E ″ to the 2/3 power of the complex elastic modulus (E *) compared to the shoulder rubber 11.
^3/2 } is a big one. Further, the crown rubber 10 has a glass transition temperature higher than that of the shoulder rubber 11.

The reason for this is that when used for high-speed straight running or high-speed turning running such as circuit running for the purpose of racing, tires are more harsh than running on general road surfaces. The heat generated by the tires during running will also be large. For this purpose, the glass transition temperature of the rubber is increased, the heat resistance is improved, and the above-mentioned ratio {E ″ / (E
*) ^3/2 } has a high correlation with braking performance.

FIG. 2 shows another embodiment in which the boundary surfaces 12A, 12A between the crown rubber 10 and the shoulder rubber 11 are formed so as to be substantially parallel to the tire equatorial plane CO from the outer end points P, P. As described above, the motorcycle tire of the present invention can be modified into various modes.

[0038]

SPECIFIC EXAMPLE A tire having a tire size of 170/60 HR17 and having the configuration shown in FIG. 1 was experimentally manufactured (Example) and its performance was tested.
Tests were also performed on tires having a conventional configuration (conventional example) and tires having configurations other than the present application (comparative examples 1 to 4).

The test conditions are as follows. 1) Braking performance and turning performance when traveling straight ahead Each test tire was attached to the rear wheel of a motorcycle with a displacement of 750 cc, and each race circuit was run 10 laps. The braking performance when going straight is evaluated by the driver's feeling, and the turning performance is evaluated by the driver's feeling at the limit speeds that can be controlled for 2 to 4 laps and 8 to 10 laps. It is indicated by an index of 100. The larger the value, the better.

2) Abrasion resistance After the test of the item 1) was completed, it was visually judged. The test results are shown in Table 1.

[0041]

[Table 1]

As shown in Comparative Example 1, when only the loss convance is increased as compared with the conventional example, the turning performance in the latter half is deteriorated, and so-called abrasion occurs in which the shoulder rubber is worn in a wavy shape. It was

Further, in Comparative Example 3 in which the loss concurrence is almost the same and the hardness of the rubber is low, the breaking strength of the rubber is insufficient and abrasion occurs in the crown rubber.

Further, as in Comparative Example 2, when a rubber having a low loss convulence and a low rubber hardness is used as the crown rubber, the braking force at the time of straight traveling becomes insufficient.

It is in the embodiment according to the constitution of the present invention that good results are obtained in all of braking performance, turning performance and abrasion resistance when traveling straight ahead.

[0046]

As described above, the motorcycle tire according to the present invention is, as described above, characterized in that the crown rubber has a larger loss priance and a greater hardness than the shoulder rubber. By balancing the grip with time and preventing the occurrence of appreciation, the high-speed running performance of the tire can be improved.

[Brief description of drawings]

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

FIG. 2 is a cross-sectional view showing another embodiment.

[Explanation of symbols]

 2 tread portion 2A tread surface 3 sidewall portion 4 bead portion 5 bead core 6 carcass 7 belt layer 10 crown rubber 11 shoulder rubber 12, 12A boundary surface C crown area CO tire equator E tread edge P outer edge point S shoulder area W tread circumference Surface overall length W1 tread circumference

Claims (5)

[Claims] 1. A carcass which folds around a bead core of a bead part from a tread part through a side wall part, and a belt layer arranged inside the tread part and radially outside the carcass, and the tread surface is a tire meridian. A motorcycle tire having an arcuate shape that bulges convexly in a cross section, wherein the tread circumferential surface total length W is 0.125, which is the length between tread edges along the tread surface centering on the tire equator.
The crown rubber having the tread circumferential length W1 of not less than twice and not more than 0.5 times and forming the crown region C has a loss loss {E ″ / (E *) compared to the shoulder rubbers forming the shoulder regions S on both sides thereof. ² } and the hardness of rubber are respectively large, a tire for a motorcycle. 2. The crown rubber has a loss priance of 2.0 × 10 ⁻³ to 10 × 10 ⁻³ cm ² / kg, and a J value of the rubber.
The ISA hardness is in the range of 35 to 65 degrees, and the shoulder rubber has a loss priance of 1.0 × 10 ⁻³ to.
8.0 × 10 ^-3 cm ² / kg, rubber JISA hardness of 30 ~
The tire for a motorcycle according to claim 1, wherein the tire has a range of 55 degrees. 3. The crown rubber is in contact with the shoulder rubber at a boundary surface inclined outward in the tire axial direction from the outer end point in the tire axial direction on the tread surface of the crown region toward the inner side in the tire radial direction. A motorcycle tire according to 1. 4. The crown rubber has a loss elastic modulus E ″ with respect to the 3/2 power of the complex elastic modulus (E *) as compared with the shoulder rubber.
The tire for motorcycles according to claim 1, wherein the ratio {E ″ / (E *) ^3/2 } is large. 5. The tire for a motorcycle according to claim 1, wherein the crown rubber has a glass transition temperature higher than that of the shoulder rubber.