JP2001277814A - Pneumatic tire for winter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To balance the abrasion of the block line on the center side and the block line on the shoulder side of a pneumatic tire for winter with block patterns, reducing the abrasion of the block line on the center side, and controlling the heel-and-toe abrasion of the block line on the shoulder side in the snowless season without deteriorating the performance of the pneumatic tire in the snow season. SOLUTION: In the pneumatic tire for winter whose flatness ratio is at least 80 with plural blocks formed on the surface of the tread, raised bottom parts of grooves are formed to connect the blocks in the circumferential direction of the tire. When the total surface areas of the raised bottom parts of grooves in the block line on the center side and in the block line on the shoulder side are SCE and SSH respectively, the ratio of SSH to SCE is at least 1.5, and the height of the raised bottom parts of grooves is 20-60% of the depth of a main groove.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a winter pneumatic tire having a block pattern that exhibits stable performance throughout the year.

[0002]

2. Description of the Related Art Conventional pneumatic tires used for light trucks are mainly classified into winter pneumatic tires used mainly on icy and snowy roads and summer pneumatic tires used in other cases. Can be classified.

[0003] In general, a usage form is generally adopted in which a pneumatic tire for summer is used and in winter, it is replaced with a pneumatic tire for winter to cope with a change in road surface conditions according to the season. At the beginning of the year, the use of winter pneumatic tires mounted on small trucks and used after the snowfall period is over, without replacing them with summer pneumatic tires, will continue to be used until the tire usage limit is reached I have. For this reason, a winter pneumatic tire that exhibits stable performance throughout the year and can be used continuously has been required.

In general, in the case of a block pattern for a light-duty truck for winter, the blocks in the center side block row that firmly contact the ground wear, but do not wear much near the shoulder side block row due to low ground pressure and low block rigidity. In addition, as a form of wear, so-called heel-and-toe wear, in which the block wears with a step in the tire circumferential direction, tends to occur. For this reason, there have been many problems that the shoulder-side row of blocks cannot be used due to wear of the center-side row of blocks even though the shoulder-side row of blocks has not been worn yet.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above problem, and does not impair the performance of a winter pneumatic tire having a block pattern during a snowfall season, without affecting the center side during a non-snowfall season. An object of the present invention is to balance wear of a block row and a shoulder block row to reduce wear of a center block row and to suppress heel and toe wear of a shoulder block row.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method of connecting a plurality of blocks formed on a tread surface in the circumferential direction of a tire so as to raise the bottom of a groove (hereinafter, referred to as a groove).
The rigidity of the shoulder-side block row is increased by reducing the ratio of the center-side block row and increasing the ratio of the shoulder-side block row, thereby increasing the rigidity of the shoulder-side block row. The point is to solve.

That is, the present invention provides a pneumatic winter tire having a flatness of 80 or more in which a plurality of blocks are formed on a tread surface, wherein a raised portion is provided so as to connect the blocks in the tire circumferential direction. When the total surface area of the bottom raised portion of the center block row and the bottom raised portion of the shoulder side block row are SCE and SSH, respectively, SS
A pneumatic winter tire, wherein the ratio of H / SCE is 1.5 or more, and the height of the raised bottom portion is 20 to 60% of the depth of the main groove.

Further, the present invention provides a pneumatic winter tire having a flatness of 80 or more in which a plurality of blocks are formed on a tread surface, wherein a bottom raising portion is provided so as to connect the blocks in the tire circumferential direction. The bottom raising part is installed only on the shoulder side block row of the tread surface,
A pneumatic winter tire, wherein the height of the raised portion is 20 to 60% of the depth of the main groove.

Further, the present invention provides a winter pneumatic tire in which the total surface area of the raised portion is 5% or more of the total surface area of the block.

[0010] The present invention also provides a pneumatic winter tire in which the raised portion is installed in all lateral grooves between blocks in the tire circumferential direction.

Further, the present invention provides a pneumatic winter tire in which the raised portion is installed in a part of a lateral groove between blocks in the tire circumferential direction.

Further, the present invention provides a pneumatic winter tire for a light truck having the above-mentioned raised portion.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a state of a raised portion installed on a center-side block row and a shoulder-side block row on the tread surface of a winter pneumatic tire for a light truck according to the present invention.

On the surface of the tread 1, there are provided a plurality of main grooves 2 extending in the tire circumferential direction and transverse grooves 3 extending in the tire radial direction arranged at predetermined intervals in the tire circumferential direction. Block 4 is formed. The center-side block row (width-wise central block row on the tread surface) 5 and the shoulder-side block row (shoulder block row on the tread surface) 6 have raised bottoms of the lateral grooves 3 and raised the groove bottoms to be shallower. Part 7 (shown with diagonal lines)
Are provided so as to connect the blocks 4 in the tire circumferential direction.

According to the present invention, as shown in FIG. 2, the bottom raising portion 7 is installed only on the shoulder side block row 6, or as shown in FIG. The object of the present invention can be achieved by adopting a configuration in which the shoulder-side block row 6 is small and large. In the latter, the center side block row 5
When the total surface area of the bottom raised portion 7 and the bottom raised portion 7 of the shoulder side block row 6 are SCE and SSH, respectively, it is preferable that the ratio of SSH / SCE is 1.5 or more. In this way, the bottom raising portion 7 is provided only on the shoulder side block row 6 or the ratio of the total height of the bottom raising portion of the shoulder side block row 6 to the total surface area of the center side block row 5 is 1.5 or more. Thereby, the block rigidity of the shoulder side block row 6 can be greatly increased as compared with the block rigidity of the center side block row 5.

Further, in the present invention, the height H of the raised bottom 7 is 20 to 60% of the depth D of the main groove in the height H of the raised bottom 7 and the depth D of the main groove shown in FIG. Preferably 25 to
It is better to be 50%. If the height H of the raised bottom portion 7 is less than 20% of the main groove depth D, the block rigidity cannot be sufficiently increased, and if it exceeds 60%, the effect of further increasing the block rigidity is obtained. The performance as a tire will be worse.

As described above, the ratio of the total surface area of the shoulder-side block rows 6 to the total surface area of the shoulder-side block rows 6 to the total surface area of the bottom-up sections of the center-side block rows 5 is 1.5 or more. And the height H of the raised portion 7 is set to 20 to less than the main groove depth D.
By setting it to 60%, the block rigidity of the shoulder side block row 6 can be increased more than that of the center side block row 5. As a result, during running, the sliding of the shoulder side block row 6 is reduced, the wear rate of the shoulder side block row 6 is increased, and the wear of the center side block row 5 can be reduced correspondingly, and the wear of both can be balanced. Thus, the problem that the tire cannot be used early due to the uneven center wear as described above is solved. Further, since the block rigidity of the shoulder-side block row 6 is increased, the movement of the block 4 is suppressed, and heel-and-toe wear can be suppressed. In addition, since the center-side block row 5 that greatly contributes to the tire performance during the snowfall period has a small rise in the center-side block row 5 as described above, the performance during the snowfall season is not impaired.

The total surface area of the raised portion 7 of the present invention is preferably at least 5% of the total surface area of the block 4. By setting the total surface area of the raised portion 7 to 5% or more of the total surface area of the block 4, the block rigidity of the shoulder side block row 6 and the performance as a winter pneumatic tire can be maintained in a well-balanced manner.

The shape of the bottom raising portion 7 in the present invention in the AA cross section shown in FIG. 4 is not particularly limited, and may be an appropriate shape such as a square or a trapezoid.

In the present invention, even if the raised portion is provided in all the lateral grooves between the blocks in the tire circumferential direction, if the initial target can be achieved, it may be provided in some of the lateral grooves between the blocks in the tire circumferential direction. .

[0022]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it goes without saying that the scope of the present invention is not limited by these Examples.

A tire having a tire size of 185R148PR and a tread pattern shown in FIG. 1 was used. The main groove depth D is 12 mm.

In common with the above, six types of tires of Examples 1 to 3, Comparative Examples 1 and 2, and a conventional example in which the raised portion is not arranged at all were manufactured with the raised portion in the lateral groove between the blocks as shown in Table 1. . These tires are mounted on the front and rear wheels of a one-box car, and a performance test on snow is performed as a performance test as a pneumatic tire for winter. A performance test as a pneumatic tire for summer is performed on a pavement road (non-ice and snow road). A wear test and a heel and toe wear test were performed. Table 1 shows the results.
Shown in The test vehicle used was a one-box car with a displacement of 2,000 cc.

Snow Performance Test Each of these test tires was rim size 14 × 5 ・ 1 / 2J.
The tire pressure is 280 kPa for the front wheels and 40 for the rear wheels.
The vehicle was mounted at 0 kPa, and the braking distance was measured when the vehicle was running on a snowy road surface at a speed of 40 km / h and stopped by applying a brake. The evaluation results were obtained by calculating the reciprocal of the braking distance and using an index with the value of the conventional tire being 100. The larger the index value, the better the performance on snow.

Uneven wear resistance test Each of these test tires was rim size 14 × 5 ・ 1 / 2J.
The tire pressure is 280 kPa for the front wheels and 40 for the rear wheels.
After mounting at 0 kPa and traveling 20,000 km on a general pavement, the wear amount of each of the center-side block row and the shoulder-side block row was measured. The evaluation results were obtained by calculating the reciprocal of the difference in the amount of wear and setting the value of the conventional tire to 100 to indicate the index. The larger the index value is, the smaller the wear difference between the center-side block row and the shoulder-side block row is, and the uneven wear resistance is more excellent.

Heel and toe abrasion test Each of these test tires was rim size 14 × 5 ・ 1 / 2J.
The tire pressure is 280 kPa for the front wheels and 40 for the rear wheels.
After mounting at 0 kPa and traveling 20,000 km on a general pavement, the difference in the amount of wear between the kick-out side and the step-in side of each block was measured.
It was indicated by an index. The larger the index value, the more excellent the heel and toe wear performance.

[0028]

[Table 1]

As is clear from Table 1, the tire of the present invention maintains the same performance on snow as the conventional tire, and the difference in the amount of wear between the shoulder side block row and the center side block row is reduced. It can be seen that the wear of both parts has been balanced. Further, it can be seen that the heel-and-toe wear is reduced in the tire of the present invention as compared with the conventional tire.

[0030]

As described above, according to the present invention, a plurality of blocks formed on the tread surface are provided with raised bottom portions in the lateral grooves between the blocks so as to be connected in the tire circumferential direction. By increasing the bottom raising ratio, the block rigidity of the shoulder side block row is increased, and the wear of the shoulder side block row and the center side block row is balanced without deteriorating the tire performance during the snowfall period, so that the center side block row is It is possible to solve the problem that tires cannot be used early due to reduced center wear and uneven center wear. Further, heel and toe wear of the shoulder side block row can be suppressed.

[Brief description of the drawings]

FIG. 1 is an expanded plan view of a tread portion of the present invention.

FIG. 2 is an expanded plan view of a tread portion in which only the shoulder-side block row of the present invention is raised.

FIG. 3 is a sectional view taken along the line AA of FIG. 1;

[Explanation of symbols]

 Reference Signs List 1 tread 2 main groove 3 side groove 4 block 5 center side block row 6 shoulder side block row 7 bottom raised part D main groove depth H height of bottom raised part

Claims (6)

[Claims] 1. A winter pneumatic tire having a flatness of 80 or more and having a plurality of blocks formed on a tread surface, wherein a raised bottom portion of a groove is provided so as to connect the blocks in the tire circumferential direction. When the total area of the raised portions of the grooves in the side block row and the raised portions of the grooves in the shoulder side block row are SCE and SSH, respectively, SSH
A pneumatic winter tire, wherein the ratio of / SCE is 1.5 or more and the height of the raised bottom of the groove is 20 to 60% of the depth of the main groove. 2. A winter pneumatic tire having a flatness of 80 or more, in which a plurality of blocks are formed on a tread surface, wherein a raised bottom portion of a groove is provided so as to connect the blocks in a tire circumferential direction. A pneumatic winter tire, wherein the raised portion of the groove is provided only in the shoulder-side block row on the tread surface, and the height of the raised portion of the groove is 20 to 60% of the depth of the main groove. 3. The pneumatic winter tire according to claim 1, wherein the total surface area of the raised portion of the groove is 5% or more of the total surface area of the block. 4. The pneumatic winter tire according to claim 1, wherein the raised portion of the groove is provided in all the lateral grooves between the blocks in the tire circumferential direction. 5. The pneumatic winter tire according to claim 1, wherein the raised bottom of the groove is provided in a part of the lateral groove between blocks in the tire circumferential direction. 6. A pneumatic winter tire for a light truck according to claim 1.