JP2003267004A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire allowing improvement of ice performance and snow performance by designing a block shape. <P>SOLUTION: In the pneumatic tire, a block row formed of a plurality of blocks 3 arranged in the tread 1 along the circumference direction of the tire is formed, and a plurality of studs 4 are driven in blocks 3. Length L of the block 3 in the tire width direction is changed, thereby setting a ratio of maximum to minimum of the block length L in the block row at 1.5 to 1.8. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire suitable as a stud tire for competition, and more particularly to a pneumatic tire with improved on-ice performance and on-snow performance.

[0002]

2. Description of the Related Art Conventionally, a stud tire for competition has a structure in which a block row composed of a plurality of blocks arranged along the tire circumferential direction is formed on a tread, and a plurality of studs are driven into these blocks. Generally, in a stud tire for competition, the length and width of the blocks included in the block row are substantially constant, and blocks having the same area are merely arranged continuously. Therefore, the transmission of traction force on ice and snow was unitary, and the performance on ice and the performance on snow were not always sufficient.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire capable of improving on-ice performance and on-snow performance by devising a block shape.

[0004]

A pneumatic tire of the present invention for achieving the above-mentioned object forms a block row composed of a plurality of blocks arranged along a tire circumferential direction on a tread, and a plurality of blocks are formed in these blocks. In a pneumatic tire in which studs are driven, the length of the block in the tire width direction is changed in the tire circumferential direction, and the maximum / minimum ratio of the block length in the block row is 1.5 to
It is characterized by having been set to 1.8.

The inventors of the present invention change the length of the block in the tire width direction in the tire circumferential direction and define the maximum and minimum ratio of the block length in the block row within the above range, so that the traction force by the block is moderated. Therefore, the inventors have found that the maximum traction force can be obtained as a tire, and have arrived at the present invention. That is, according to the present invention, the performance on ice and the performance on snow can be improved by periodically changing the block length in the block row.

In the present invention, in order to increase the traction force on ice and snow, the studs driven into the blocks adjacent in the tire circumferential direction are preferably displaced from each other in the tire width direction. Further, it is preferable that the contour of the contact surface formed by the blocks on the outer side in the tire width direction is non-linear. Furthermore, it is preferable that the tread pattern based on the shape of the block has directionality.

In order to sufficiently secure the holding force of the stud, it is preferable to dispose the center of the stud at a position separated by 5 mm or more from the side wall of the block. The width of the block in the tire circumferential direction is preferably 13 mm or more. Furthermore, the rubber composition of the tread has a JI at 0 ° C.
The SA hardness is preferably 74 or more.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The structure of the present invention will be described in detail below with reference to the accompanying drawings.

1 to 3 show a pneumatic tire according to an embodiment of the present invention. 1 to 3,
The tread 1 is provided with a plurality of blocks 3 divided by the grooves 2. These blocks 3 form a plurality of block rows arranged in the tire circumferential direction. The block 3 is provided with a plurality of stud display portions 5 for displaying the driving positions of the studs 4. The structure of the stud display portion 5 is not particularly limited as long as it displays the driving position of the stud 4, but it is preferably a circular recess. The stud 4 is driven into the block 3 based on the stud display portion 5. The stud 4 is normally driven into all the positions of the stud display portion 5, but may not be driven into a part thereof.

In the above pneumatic tire, the block 3
The length L in the tire width direction changes in a tire circumferential direction in a substantially sinusoidal cycle, and the maximum / minimum ratio of the block length L in each block row is in the range of 1.5 to 1.8. That is, for the block length L, the ratio (L _max / L _min ) of the maximum value L _max to the minimum value L _min is in the above range. When the width W of the block 3 in the tire circumferential direction is substantially constant, the maximum / minimum ratio of the block areas in each block row is in the range of 1.5 to 1.8.

In this way, the length L of the block 3 in the tire width direction is changed in the tire circumferential direction, and the maximum and minimum ratios of the block length L in each block row are regulated within the above range, so that the block length on ice and snow can be reduced. Since the traction force is moderate and the tire has the maximum traction force, the performance on ice and the performance on snow can be improved.

If the maximum / minimum ratio of the block length L in each block row deviates from the above range, the effect of improving on-ice performance and on-snow performance cannot be obtained. However, as long as the above range is satisfied, part of the block 3 May extend over the tread center line CL.

In the pneumatic tire, the studs 4 driven into the blocks 3 adjacent to each other in the tire circumferential direction are preferably displaced from each other in the tire width direction. By arranging these studs 4 at positions displaced from each other when viewed in the tire circumferential direction, the traction force on ice and snow is increased. When the length of the block in the tire width direction is constant as in the conventional case, when the studs driven into the blocks adjacent to each other in the tire circumferential direction are attempted to be displaced in the tire width direction from each other, part of the stud is located at the block edge. It was difficult to approach and secure its holding power. However, in the above pneumatic tire, since the length L of the block 3 in the tire width direction is changed in the tire circumferential direction,
It is possible to separate all the studs 4 from the block edge and sufficiently secure their holding force.

The contour of the ground contact surface formed by the block 3 on the outer side in the tire width direction is preferably non-linear. That is, as shown in FIG. 2, it is desirable that the contour of the contact surface formed by the block 3 on the outer side in the tire width direction, that is, the outer edge of the block 3 does not coincide with the straight line E indicated by the broken line. By making the contour of the ground contact surface outside in the tire width direction non-linear in this way, the traction force on ice and snow is increased.

The shape of the block 3 is not particularly limited, but as shown in FIG. 2, the block 3 is rotated in the tire rotation direction R from the tread center side toward the shoulder side.
It is preferable that the tread pattern based on the shape of the block 3 has directionality by being bent or inclined in the opposite direction. Such a directional pattern is effective in increasing the traction on ice and snow.

The center position of the stud 4 is not particularly limited, but it is preferable that it is located at a position 5 mm or more away from the side wall of the block 3. If the distance between the center position of the stud 4 and the edge of the block 3 is less than 5 mm, the holding force of the stud 4 embedded in the block 3 becomes insufficient,
As a result, it becomes difficult to maximize the effect of improving the performance on ice and the performance on snow.

The width W of the block 3 in the tire circumferential direction is not particularly limited, but is preferably 13 mm or more, more preferably 13 to 21 mm. If the block width W is less than 13 mm, the holding force of the stud 4 embedded in the block 3 becomes insufficient, and as a result, it becomes difficult to maximize the effect of improving the performance on ice and the performance on snow. . In the present embodiment, the block width W is 13 mm, and the block width W is substantially constant in each block row.

The JIS-A hardness at 0 ° C. of the rubber composition constituting the tread 1 is not particularly limited, but is 74
As mentioned above, it is good that it is more preferably 74 to 82. This JI
If the SA hardness is less than 74, the holding force of the stud 4 embedded in the block 3 becomes insufficient, and as a result,
It becomes difficult to maximize the effect of improving the performance on ice and the performance on snow.

The pneumatic tire of the present invention is a tire which is premised on driving a stud into a block. Therefore, not only the tire in which the stud is driven into the block but also the tire in which the stud display portion for displaying the position where the stud is driven is provided in the block is included in the present invention.

[0020]

EXAMPLE A tire size of 110 / 650R15, a tread is provided with a plurality of block rows made up of a plurality of blocks arranged along the tire circumferential direction, and a plurality of studs are driven into these blocks. Comparative Examples 1 to 4 and Examples 1 and 2 in which the maximum and minimum ratios of the block lengths in Table 1 were variously changed as shown in Table 1 were manufactured. In each tire, the width of the block in the tire circumferential direction was 13 mm, and the center of the stud was arranged at a position separated from the side wall of the block by 5 mm or more. The JIS-A hardness of the tread rubber at 0 ° C was 74.

For these test tires, the performance on ice and the performance on snow were evaluated by the following methods, and the results are shown in Table 1.
Are also shown.

Performance on ice and on snow: 20 test tires
It was mounted on a 00cc class 4WD vehicle, and a trained test driver performed sensory evaluation and time required for section driving on ice and snow, and scored the superiority and inferiority. The evaluation results are shown by an index with the score of Comparative Example 1 (conventional tire) being 100. The larger this index value, the better the performance.

[0023]

[Table 1] As can be seen from Table 1, in Examples 1 and 2, the maximum-minimum ratio of the block lengths in each block row was in the range of 1.5 to 1.8, so that the performance on ice and the performance on snow were remarkably improved. .

Next, using the tread pattern which was the best in the above evaluation, JIS-A at 0 ° C. of the tread rubber was adopted.
Each of the racing tires of Examples 3 to 8 in which only the hardness was varied as shown in Table 2 was manufactured. Then, the performance on ice and the performance on snow were evaluated by the same method as described above, and the results are also shown in Table 2. However, the evaluation result is shown by an index with the score of Example 3 being 100.

[0025]

[Table 2] As can be seen from Table 2, especially in Examples 6 to 8, the JIS-A hardness of the tread rubber was 74 or more, so that the performance on ice and the performance on snow were remarkably improved.

[0026]

As described above, according to the present invention, a block row composed of a plurality of blocks arranged along the tire circumferential direction is formed on the tread, and a plurality of studs are driven into these blocks. In the tire, the length of the block in the tire width direction is changed in the tire circumferential direction, and the maximum / minimum ratio of the block length in the block row is set to 1.5 to 1.8, so that the maximum traction force as a tire is obtained. Therefore, the performance on ice and the performance on snow can be improved.

[Brief description of drawings]

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

FIG. 2 is a partially enlarged view of FIG.

3 is a cross-sectional view taken along the line XX of FIG.

[Explanation of symbols]

1 tread 2 grooves 3 blocks 4 studs 5 Stud display L block length W block width

Claims (7)

[Claims] 1. A pneumatic tire in which a block row composed of a plurality of blocks arranged along a tire circumferential direction is formed on a tread, and a plurality of studs are driven into these blocks, in which the length of the blocks in the tire width direction is measured. Pneumatic tire in which the maximum / minimum ratio of the block lengths in the block row is set to 1.5 to 1.8 by changing the height in the tire circumferential direction. 2. The pneumatic tire according to claim 1, wherein the studs driven into the blocks adjacent to each other in the tire circumferential direction are at positions displaced from each other in the tire width direction. 3. The pneumatic tire according to claim 1, wherein the contour of the ground contact surface formed by the block on the outer side in the tire width direction is non-linear. 4. The pneumatic tire according to claim 1, wherein the tread pattern based on the shape of the block has directionality. 5. The pneumatic tire according to claim 1, wherein the center of the stud is arranged at a position distant from the side wall of the block by 5 mm or more. 6. The tire circumferential width of the block is 13
The pneumatic tire according to any one of 1 to 5 having a size of at least mm. 7. The rubber composition constituting the tread is 0
The pneumatic tire according to any one of 1 to 6, which has a JIS-A hardness of 74 or higher at 74 ° C.