JPH09309301A - Radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire which is restrained from deflected abrasion of a shoulder part without sacrificing wet performance, etc. SOLUTION: 1.0<=p<=1.7 is satisfied in case of P=(L80-L6)/(W6-W80) on the assumption that (1) a ratio of circumferential grounding length L80 at a position W80 of 80% of a distance from a tire equator line to tread both ends and circumferential grounding length Le on the tire equator line is 0.72-0.85 and (2) circumferential grounding length at W6 positioned inward in the tire shaft direction 3mm from a position of the maximum grounding width W on the tread both ends from the tire equator line is L6 in the shape of a grounding surface at the time of assembling a radial tire furnished with at least one layer of a radial carcass on a standard applicable rim, filling the maximum internal pressure specified in a JATMA standard and loading a load of the maximum load capacity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circumferential direction on the tire equator along with a circumferential contact length L80 at a position W80 which is 80% of a distance from a tire equator line to a maximum contact width W at both ends of a tread in a tire contact surface shape. The present invention relates to preventing early wear of a shoulder portion of a tire having a ratio with a ground contact length Le, which is a so-called “80% rectangular ratio” of 0.72 to 0.85.

[0002]

2. Description of the Related Art In recent years, in order to improve wet performance, especially wet performance at high speed, it has been attempted to set a so-called "80% rectangular ratio" to 0.75 to 0.85. The average lateral acceleration of the tire, especially the front tire, during normal driving in the market is 0.05 to 0.
When subjected to 08 gravitational acceleration, there is a problem that a nucleus of wear is generated in the shoulder portion near the tread end of the tire and the wear progresses from there. In such a case, not only the tire dynamic performance and the tire appearance are deteriorated, but also the tire life itself is significantly decreased. For this reason,
Attempts have been made to suppress the generation of wear nuclei in the shoulder by changing the tread compound or the belt structure.

Here, the terms used in the present specification will be described. The "ground contact surface shape" is a tire surface painted with black ink and transferred onto paper under a predetermined internal pressure and load. The "ground contact length" is the ground contact length in the circumferential direction at a predetermined position in the tire axial direction, and is the ground contact length measured by adjusting so as not to include a groove at the ground contact end in the circumferential direction. In places other than the tire equator line, the average value on the left and right is often used to represent.

[0004]

However, in the case described above, there is a trade-off problem that the tire dynamic performance and durability are deteriorated, and it cannot be said to be a drastic improvement.
Therefore, the present invention is to provide a tire in which uneven wear of the shoulder portion is suppressed by suppressing generation of wear nuclei in the shoulder portion without sacrificing other performance.

[0005]

To achieve the above object, in the present invention, a radial tire having at least one layer of radial carcass is mounted on a standard application rim, and JATM is used.
80% of the distance from the tire equatorial line to the maximum contact width W at both ends of the tread in the contact surface shape when the maximum internal pressure specified in the A standard is filled and the maximum load capacity is applied.
The ratio of the circumferential ground contact length L80 at the width W80 position to the circumferential ground contact length Le on the tire equator line is 0.72 to 0.85, and (2) the maximum ground contact width W at both ends of the tread from the tire equator line. L3 is the circumferential ground contact length at the position of width W6 3 mm in the tire axial direction from the position of P = (L80-L6
) / (W6-W80), 1.0≤P≤1.7
It adopts a configuration that satisfies.

A tire having a so-called 80% rectangular ratio of 0.72 to 0.85 has excellent wet performance, but the average lateral acceleration that a front tire receives during normal driving in the market is 0.05 to 0. It has been pointed out that when subjected to 08 gravitational acceleration, a core of wear is generated in the shoulder portion near the tread end of the tire, and the wear progresses from there. This is because the tire has a radius difference from the tire rotation axis from the tire center (tire equator line) to the shoulder portion as shown in FIG. The part is generated by sliding and advancing while being dragged. That is, so-called 8
The smaller the 0% rectangular ratio, the greater the sliding behavior.

In the present invention, the problem due to the sliding behavior of the shoulder portion is the portion near the tread edge,
It is based on the fact that if this part becomes the core of wear, the subsequent progress of wear becomes faster. And, it is based on the finding that it can be achieved by optimizing the change in the circumferential ground contact length from W80 close to the shoulder end to the maximum width W. Here, in the present invention, since the circumferential contact length at the maximum width W cannot be accurately measured, the value thereof is represented as a representative value, and the value of the contact length L6 at W6 located 3 mm axially inward of the value is represented. I am using. That is, L6 is the circumferential contact length at the position of the width W6 that is 3 mm inward in the tire axial direction from the position of the maximum contact width W at both ends of the tread from the tire equator line, and P = (L80-L6) / (W6-W8
In the case of 0), it is sufficient to satisfy 1.0 ≦ P ≦ 1.7. Here, the value of P is set to 1.0 or more because
If it is less than 1.0, the wet performance cannot be obtained as originally intended, and if it is more than 1.7, the slippage of the shoulder portion near the tread edge becomes large, and the nucleus of wear easily occurs. is there.

As a means for setting the value of P as in the present invention, specifically, the crown shape of the shoulder portion may be slightly raised as shown by the dotted line in FIG.
For example, there is a relationship between the belt structure and the tread pattern, and it can be said that there is some trial and error.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A radial tire of an embodiment according to the present invention and radial tires of a conventional example and a comparative example will be described below. The tire size is 205 / 65R15 for passenger car tires. As shown in Table 1, tires having different values of 5 types of P were prepared. These tires have the same other structures and shapes except for the ground contact shape.

The radial tires of Examples 1 and 2 according to the present invention, the radial tires of Comparative Examples 1 and 2 and the conventional tires were evaluated by the following tests. Regarding wet performance, straight running on a road surface with a water depth of 5 mm was carried out to measure the critical speed of hydroplaning, and the speed of conventional tires was evaluated as 100.
The vehicle was mounted on a taxi and traveled in and around Tokyo for about 15,000 km, and the uneven wear of front wheels was evaluated. In the evaluation, the wear difference between the position 3 mm in the tire axial direction from the ground contact end and the position of 80% of the distance to the ground contact width was evaluated with the conventional tire as 100. For the sake of convenience, the larger the numerical value, the smaller the difference in wear (good). The evaluation results are also shown in Table 1.

[0011]

[Table 1]

From the above results, it is understood that the tire of the present invention has a hydroplaning generation rate equivalent to that of the conventional tire, and the uneven wear is greatly improved. Although the tire of Comparative Example 1 was significantly improved in uneven wear, it resulted in a low hydroplaning generation rate.

[0013]

As described above, the radial tire according to the present invention can suppress uneven wear with almost no deterioration in wet performance.

[Brief description of drawings]

FIG. 1 is a diagram showing a contact surface shape of a radial tire according to the present invention.

FIG. 2 is a diagram showing a crown shape according to the present invention and a crown shape according to a conventional example.

FIG. 3 is a diagram showing that there is a radius difference with respect to a rotation axis in the tire width direction.

[Explanation of symbols]

 T tire crown portion E tire equatorial line 1 crown shape according to the present invention 2 conventional crown shape

Claims (1)

[Claims] 1. A radial tire having at least one layer of a radial carcass mounted on a standard application rim, and JATMA.
In the contact surface shape when the maximum internal pressure specified in the standard is filled and the maximum load capacity is applied, (1) the circumference at the position W80 of 80% of the distance from the tire equatorial line to the maximum contact width W at both ends of the tread. The ratio of the direction ground contact length L80 to the circumferential ground contact length Le on the tire equator line is 0.72 to 0.85, and (2) 3 mm from the position of the maximum ground contact width W at both ends of the tread to the tire axial direction from the tire equator line. Let L6 be the circumferential contact length at W6 located inward, and P = (L80-L6) /
A radial tire characterized by satisfying 1.0 ≦ P ≦ 1.7 when (W6-W80).