JPH11321245A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve maneuvering stability on a dry road surface without worsening riding comfort. SOLUTION: The groove area ratio of a tread part 1 differs between both side tread parts with a tire equator line (X-X) placed in between, and the groove area of one side tread part 1a positioned on the outside 3 of a vehicle when mounting a tire is smaller than that of the other side tread part 1b positioned on the inside 4 of the vehicle. In a pneumatic radial tire provided with such an asymmetric tread pattern, the cross-sectional thickness of a tire side wall part 5a positioned on the outside 3 of the vehicle at the time of mounting the tire, and the cross-sectional thickness of a tire side wall part 5b positioned on the inside 4 of the vehicle differ at least at partial corresponding parts between a spaced point 6 of a rim flange and a point 7 with the maximum width of the tire, and a corresponding part 51a of the tire side wall part 5a positioned on the outside 3 of the vehicle is formed as an asymmetric thickness part 8 thicker than the cross-sectional thickness in a corresponding part 51b of the tire side wall part 5b positioned on the inside 4 of the vehicle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire suitable for use in high-roof vehicles such as minivans and one-box vehicles, and more particularly to steering stability on dry road surfaces without deteriorating ride comfort. The present invention relates to a pneumatic radial tire having an improved tire.

[0002]

2. Description of the Related Art High-roof vehicles, such as minivans and one-box vehicles, are no different from ordinary passenger vehicles in that they require a comfortable ride. On the other hand, this type of vehicle has a problem in that, due to its high center of gravity, the load largely acts on the area outside the tread portion during traveling, and the steering stability on dry road surfaces is lacking.

Conventionally, in order to improve such steering stability, an asymmetrical tread pattern in which a tread groove area on one side located outside the vehicle when the tire is mounted is made smaller than a groove area on a side located inside the vehicle. There is provided a pneumatic radial tire provided with: Such a tire has a tread pattern in which the tread groove area on one side located on the outside of the vehicle when the tire is mounted is smaller than the groove area on the side located on the inside of the vehicle. The rigidity of the land portion of the tread is improved, and steering stability is ensured.

[0004]

However, in the case of a tire for a high-roof vehicle such as a minivan or a one-box vehicle, as described above, since the center of gravity is high, only the asymmetric tread pattern as described above is not always sufficient. Steering stability cannot be achieved. In particular, in the case of this type of tire, since high-speed running stability is also particularly required, a tire that is satisfactory in this respect has not yet been provided.

An object of the present invention is to provide a pneumatic radial tire capable of improving the steering stability on a dry road surface without deteriorating the riding comfort.

[0006]

As a result of intensive studies to solve the above-mentioned problems, the present invention has revealed that the groove area ratio of the tread portion is different between the tread portions on both sides of the tire equator line. In the pneumatic radial tire having an asymmetrical tread pattern in which the groove area of the tread portion on one side located on the outside is smaller than the groove area of the tread portion on the inside located on the inside of the vehicle, when the tire is mounted, the groove area is on the outside of the vehicle. The cross-sectional thicknesses of the tire side wall portion and the tire side wall portion located inside the vehicle are different in at least a part of each corresponding portion between the rim flange separation point and the point having the tire maximum width, The corresponding portion of the tire side wall portion located on the outer side has an asymmetric thickness portion thicker than the cross-sectional thickness of the corresponding portion of the tire side wall portion located on the inside of the vehicle. It was adopted pneumatic radial tire according to claim being configured.

That is, the inventor of the present invention has increased the cross-sectional thicknesses of both side walls of the pneumatic radial tire having the asymmetric tread pattern in order to further improve the steering stability on a dry road surface. However, although the steering stability on dry roads has improved,
Riding comfort has deteriorated. In consideration of this point, the pneumatic radial tire having the asymmetric tread pattern described above has been modified such that the cross-sectional thickness of the tire side wall portion located outside the vehicle when the tire is mounted is changed to the tire sidewall located inside. When the tire side wall is made thicker than the section thickness of the part, that is, asymmetry thickness, contrary to prediction, it has been found that the steering stability on dry road surface can be improved without deteriorating the riding comfort. .

Therefore, the tire according to the present invention has the above-mentioned structure, and even when applied to a high-roof vehicle such as a minivan or a one-box vehicle having a high center of gravity, the tire does not deteriorate the riding comfort and can be used on a dry road surface. , The steering stability can be improved.

[0009]

FIG. 1 is a schematic view showing a tread pattern of an embodiment of a pneumatic radial tire according to the present invention, and FIG. 2 is a schematic perspective view of a main part of the pneumatic radial tire according to the embodiment. 3 is an enlarged sectional view of the main part.

In FIG. 1, 1 is a tread portion, and 2 is a groove formed on the surface of the tread portion 1. The line XX indicates the tire equator line. The tire of this embodiment is
As shown in FIG. 1, the total groove area ratio of the tread portion 1 is different between the tread portion 1a and the tread portion 1b on both sides of the tire equator line (XX line).

The tread portion 1a is a tread portion located on the outside 3 of the vehicle when the tire is mounted, and the tread portion 1b is a tread portion located on the inside 4 of the vehicle when the tire is mounted. As shown, in this tire, the outside of the vehicle 3
Is smaller than the groove area of the tread portion 1b located on the inner side 4 of the vehicle, and as a result, in the present embodiment, an asymmetric tread pattern is obtained.

In FIG. 1, the line AA indicates the ground contact end of the tread portion 1a located on the outside 3 of the vehicle, and the line BB
The line indicates the ground end of the tread portion 1b located on the inside 4 of the vehicle.

As shown in FIG. 2, the tire according to the present embodiment has a tire side wall 5a located on the outside 3 of the vehicle and a tire side wall 5b located on the inside of the vehicle. Corresponding portions 51a and 51b having different cross-sectional thicknesses are formed between points 7 having the maximum width. That is, the corresponding portion 51a of the tire side wall portion 5a located on the outside of the vehicle is configured as an asymmetric thickness portion 8 which is thicker than the cross-sectional thickness of the corresponding portion 51b of the tire side wall portion 5b located on the inside.

In particular, in the tire of this embodiment, the asymmetrical thickness portion 8 is formed between the separation point 6 of the rim flange 9 and the outer end 10a of the bead apex 10, as shown in FIG. Further, the asymmetric thickness portion 8 is configured by a thickness from the winding side 11a of the carcass ply 11 to the surface 52a of the tire side wall portion 5a. In the drawing, reference numeral 12 denotes a bead core. In addition, the rim of the present invention
Although not particularly limited, flange symbols J and J
J rim is used.

Here, the thickness of the asymmetrical thickness portion 8 is preferably 1.5 to 3 times the cross-sectional thickness of the tire side wall portion 5b located on the inside 4 of the vehicle at the corresponding portion.
The thickness of the asymmetric thickness portion 8 is 1.5 times the cross-sectional thickness at the corresponding portion of the tire side wall portion 5b located inside the vehicle 4.
If it is less than twice, the cross-sectional thickness of the outer tire side wall portion 5a with respect to the inner side tire side wall portion 5b is insufficient, and the ride comfort can be secured, but the effect of improving the steering stability cannot be satisfied yet. On the other hand, when the thickness of the asymmetric thickness portion 8 exceeds three times the cross-sectional thickness of the corresponding portion of the tire side wall portion 5b located on the inner side 4 of the vehicle, the cross-sectional thickness of the outer tire side wall portion 5a becomes too thick, On the contrary, the ride quality deteriorates.

[0016]

[Example] Example 1 of tire size 215 / 65R15
Each tire of Comparative Examples 1 and 2 was prototyped, and a test was performed for each item of ride comfort and steering stability under the following conditions.

Each of the example tire and the comparative example tire has the asymmetric tread pattern shown in FIG. Each carcass is composed of two carcass plies reinforced with polyester cords arranged in the radial direction at a cord density of 23 strands / 25 mm with a two-ply twist of 1000 denier. The belt is 2 + 2 ×
0.25mm steel cord with a cord density of 19 cords / 2
Two belt layers reinforced with 5 mm were alternately stacked at a cord angle of 21 degrees with respect to the tire circumferential direction.

On the other hand, in Comparative Example 1, the thickness of the tire side wall portions is the same at the corresponding portions of the tire side wall portions on both the inner and outer sides. In Comparative Example 2, the thickness of the tire side wall on the winding side of the carcass ply between the rim flange separation point and the point having the maximum width of the tire was twice as large as that of Comparative Example 1 at the corresponding portion, and the thickness was changed on both the inner and outer sides. At the corresponding portion of the tire side wall portion. On the other hand, in Example 1, the thickness of the tire side wall portion on the winding side of the carcass ply between the rim flange separation point and the point having the maximum width of the tire is set to the thickness of the corresponding portion of the outer tire side wall portion. The thickness was twice as large and the thickness of the inner side wall of the tire was the same as that of Comparative Example 1.

(Ride Comfort Test) A domestic minivan (2400 CC) equipped with each of the prototype tires of the Examples and Comparative Examples was run on an actual vehicle and evaluated by a feeling test by three drivers. The evaluation was performed by giving each driver a type of a prototype tire and running the vehicle, giving a score out of 5 out of 5 points, and performing an index evaluation with the average value of the tire of Comparative Example 1 being 100. Table 1 shows the results. Each numerical value in the table indicates that the larger the value, the better the riding comfort.

(Driving Stability Test) A domestic minivan (2400 CC) equipped with each of the prototype tires of the Examples and Comparative Examples was run on an actual vehicle and evaluated by a feeling test by three drivers. The evaluation was performed by giving each driver a type of a prototype tire and running the vehicle, giving a score out of 5 out of 5 points, and performing an index evaluation with the average value of the tire of Comparative Example 1 being 100. Table 1 shows the results. Each numerical value in the table indicates that the larger the value, the better the steering stability.

[0021]

[Table 1]

From the results shown in Table 1, the steering stability of the tire of Comparative Example 2 in which the tire side walls having the thickness twice that of Comparative Example 1 are formed on both the inner and outer sides of the vehicle is recognized as compared with Comparative Example 1. However, the ride is getting worse. On the contrary,
In the tire of Example 1, the riding comfort was almost maintained, and an improvement in steering stability was also recognized.

[0023]

As described above, the pneumatic radial tire of the present invention can improve the steering stability on a dry road surface without deteriorating the riding comfort. Therefore, although not particularly limited, the pneumatic radial tire of the present invention can be suitably used even when applied to a high-roof vehicle such as a minivan or a one-box vehicle having a high center of gravity.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a tread pattern of an embodiment of a pneumatic radial tire according to the present invention.

FIG. 2 is a schematic partial perspective view of the pneumatic radial tire according to the embodiment.

FIG. 3 is an enlarged sectional view of the main part.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tread part 1a Tread part 1b Tread part 2 Groove 3 Outside 4 Inside 5a Tire side wall part 5b Tire side wall part 51a Corresponding part 52a Surface 51b Corresponding part 6 Separation point 7 Point having maximum tire width 8 Asymmetric thickness part 9 Rim flange Reference Signs List 10 Bead Apex 11 Carcass ply 11a Winding side 12 Bead core

Claims (4)

[Claims] 1. The groove area ratio of the tread portion differs between the tread portions on both sides of the tire equator line, and the groove area of one tread portion located outside the vehicle when the tire is mounted is located inside the vehicle. In a pneumatic radial tire having an asymmetric tread pattern smaller than a groove area of one tread portion, a tire side wall portion located outside the vehicle when the tire is mounted,
Each cross-sectional thickness of the tire side wall portion located inside the vehicle is different at least in each corresponding portion between the rim flange separation point and the point having the tire maximum width, and the tire side wall located outside the vehicle is provided. The corresponding part of the part,
A pneumatic radial tire, wherein the pneumatic radial tire is configured as an asymmetrically thick portion that is thicker than a cross-sectional thickness at a portion corresponding to a tire side wall portion located inside a vehicle. 2. The pneumatic radial tire according to claim 1, wherein the asymmetric thickness portion is formed between the rim flange separation point and the outer end of the bead apex. 3. The pneumatic radial tire according to claim 1, wherein the thickness of the asymmetric thickness portion is constituted by the thickness from the winding side of the carcass ply or the outer ply to the surface of the tire side wall. . 4. The tire according to claim 1, wherein the thickness of the asymmetric thickness portion is 1.5 to 3 times the cross-sectional thickness of a corresponding portion of the tire side wall located inside the vehicle. The described pneumatic radial tire.