JP4433804B2 - Pneumatic radial tire - Google Patents

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire that improves uneven wear resistance, braking performance on snow on shallow snow roads, and wet road turning performance in a well-balanced manner.

  All-season radial tires are designed to provide good exercise performance not only on dry roads but also on light snowy roads. As a tread pattern for that purpose, a block pattern is generally used to secure traction performance on a shallow snow road surface and turning performance on a wet road surface, and sipes extending in the width direction are provided on the block. However, in these all-season patterns, uneven wear due to slippage (heel and toe wear) is likely to occur due to the softening caused by the formation of the sipe, particularly in the shoulder area block where the ground contact length is shortened, When the sipe opens during traveling, there is a problem that cracks are likely to occur at the bottom of the sipe after the middle stage of wear.

Conventionally, as a technique for suppressing the uneven wear due to the formation of the sipe described above, there is a proposal that the sipe shape configuration is a three-dimensional structure having a bent portion in the depth direction, thereby increasing the block rigidity (for example, , See Patent Document 1). However, especially in all-season tires, the blocks are relatively large, so if all of the sipes are made into a three-dimensional structure, the rigidity of the blocks placed in the center area will become too high, resulting in a shallow snow road surface. There was a problem that the traction performance and the turning performance on a wet road surface deteriorated.
Japanese Patent Laid-Open No. 2001-1722

  An object of the present invention is to solve the problems of a tire having a block pattern provided with such a conventional three-dimensional structure sipe, and to substantially reduce the uneven wear resistance, while braking on snow and turning on a wet road. An object of the present invention is to provide a pneumatic radial tire with improved balance.

The pneumatic radial tire of the present invention for achieving the above object, a number of blocks arranged in the tread surface, the pneumatic radial tire provided with a sipe having a three-dimensional structure extending in the tire width direction to the blocks, wherein Three-dimensional sipe is arranged in the center area and shoulder area blocks of the tread surface, and the number of three-dimensional sipe arranged in the shoulder area block of the tread surface is set in the center area block of the tread surface. More than 50% of the sipe of the three-dimensional structure arranged, and more than 50% of the total sipe length of the sipe arranged in the shoulder area block is made into a three-dimensional sipe and arranged in the block of the center area The total sipe length of the sipe of the three-dimensional structure is calculated as the sipe length of the three-dimensional structure of the block in the shoulder region. And characterized in that 70% or less of the type length summation.

In the pneumatic radial tire of the present invention, the number of three-dimensional structural sipes (hereinafter referred to as three-dimensional sipes) provided in the block is increased in the shoulder region block than in the center region block, and is disposed in the shoulder region block. More than 50% of the total sipe length of the sipe is made into a three-dimensional sipe, and the total sipe length of the three-dimensional sipe placed in the center block is changed to the three-dimensional sipe of the shoulder block. Since the total length is 70% or less , the shoulder block blocks moderate wear by suppressing moderate wear such as heel and toe wear by moderately improving rigidity, and the block rigidity is moderately reduced in the center area. The braking performance on the road and the turning performance on the wet road can be ensured. Therefore, uneven wear resistance, braking performance on snow on shallow snow roads and turning performance on wet roads can be improved in a well-balanced manner.

  In the present invention, the center area of the tread surface refers to an area occupied by two central sections when the tread development width is divided into four equal parts, and the shoulder area refers to both areas occupied by one outer section. Say.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. In each drawing, the same constituent elements are given the same reference numerals, and redundant description is omitted.

  FIG. 1 is a partially developed plan view showing a tread surface of a pneumatic radial tire according to an embodiment of the present invention.

  In FIG. 1, the tread surface 1 of a pneumatic radial tire has a block pattern in which a large number of blocks 4 partitioned by a plurality of vertical grooves 2 extending in the tire circumferential direction T and a plurality of horizontal grooves 3 intersecting the tire are arranged. Become.

Each block 4 in the center region C occupying two sections on the center side obtained by dividing the development width W of the tread surface 1 into four equal parts includes two two-dimensional sipes 5a having two- dimensional structures extending in the tire width direction and two blocks. A three-dimensional sipe 5b is formed. Further, three three-dimensional sipes 5b extending in the tire width direction are formed in each block 4 in both shoulder regions S, S outside the center region C. In this way, the number of three-dimensional sipes 5b provided in each block 4 is arranged in the block 4 in the shoulder area S more than in the block 4 in the center area C. In the figure, a sipe marked with Δ indicates a three-dimensional sipe 5b, and a sipe not marked with Δ indicates a two-dimensional sipe 5a (the same applies to the following drawings).

  The three-dimensional sipe 5b is composed of curved surfaces having different inclination angles in two or more directions in the depth direction of the sipe, and has both the side surfaces of the sipe 5b interspersed with concave portions and convex portions. The block 4 in which the dimensional sipe 5b is formed has higher rigidity than the block 4 in which the two-dimensional sipe 5a is formed.

By increasing the number of three-dimensional sipes provided in the block to the shoulder area block rather than the center area block , the shoulder area block 4 has a moderate improvement in rigidity, thereby causing unevenness such as heel and toe wear. Abrasion is suppressed, and in the center region C, the block rigidity is appropriately reduced, so that braking performance on a shallow snow road and turning performance on a wet road are ensured. Therefore, uneven wear resistance, braking performance on snow on shallow snow roads and turning performance on wet roads can be improved in a well-balanced manner.

Further, in the present invention, among the sipes arranged in the shoulder region S, 50% or more of the total sipe length is made into the three-dimensional sipe 5b . If it is less than 50%, the effect of suppressing uneven wear cannot be sufficiently obtained. In addition, the total sipe length of the three-dimensional sipe 5b arranged in the block 4 of the center area C is set to 70% or less of the total sipe length of the three-dimensional sipe 5b arranged in the block 4 of both shoulder areas S and S. ing. If it exceeds 70%, the effect of improving the braking performance on snow on a snowy road and the turning performance on a wet road cannot be obtained sufficiently. Here, the sipe length sum means the sum of the lengths on the tire circumference obtained when the sipe on the surface of the block 4 is linearly extended in the longitudinal direction.

In the present invention, when the sizes of the blocks 4 arranged in the center area C are different, the number of the three-dimensional sipes 5b arranged in each block 4 may be larger than that of the large block in the small block. Thereby, the block rigidity in the center area C can be improved further advantageously.

FIG. 2 is a developed plan view corresponding to FIG. 1 showing a tread surface of a pneumatic radial tire according to another embodiment of the present invention.

The embodiment of FIG. 2 is 1 in that, the one sipe of the center of the three sipes formed in the blocks 4 in the shoulder area S constituted by two-dimensional sipes 5a, blocks in Center region S One of the four sipes formed in 4 is a three-dimensional sipe 5b. In this way, by adjusting the balance of rigidity of each block 4 in the shoulder region S and the center region C, according to the configuration of the tread pattern, uneven wear resistance, snow braking performance on shallow snow roads and wet road turning performance Can be improved in a balanced manner.

  In the embodiment described above, the case where the longitudinal groove 2 is formed at the boundary between the center region C and the shoulder region S of the tread surface 1 is shown, but the tread pattern of the pneumatic radial tire of the present invention is limited to this. The block pattern which arrange | positioned the block 4 straddling the center area | region C and the shoulder area S may be sufficient. Further, both ends of the sipes 5 a and 5 b may be held in the block 4, and both ends or one end may be extended to the end of the block 4.

  As described above, in the pneumatic radial tire of the present invention, the number of three-dimensional sipes provided in the block 4 is arranged more in the block 4 in the shoulder region S than in the block 4 in the center region C, thereby preventing uneven wear resistance. For improving the braking performance on snow and turning performance on wet roads in a well-balanced manner, the block 4 arranged on the tread surface 1 has a relatively large groove area ratio of 25 to 50%, preferably 30 to 40%. Especially effective for tires.

The tire size is 195 / 70R15C104 / 102R, and the tread pattern excluding the sipe arrangement form is the same as in FIG. 1, and the ratio (%) of the total length of the three-dimensional sipe to the total sipe length of all the sipes, Comparison of conventional tires (conventional example 1), in which the ratio (%) of the total length of 3D sipes in the center area to the total length of 3D sipes in the shoulder area is different as shown in Table 1 A tire (Comparative Example 1) and a tire of the present invention ( Examples 1 to 4 ) were produced. In addition, the depth of all the sipes was made common with 10.0 mm respectively.

These six types of tires are mounted on a 2-B1BOX type vehicle, and the uneven wear resistance, snow braking performance and wet road turning performance are evaluated by the following methods. This is also shown in Table 1. The larger the value, the better.
[Evaluation of uneven wear resistance]
After traveling 10,000 km on the asphalt road surface with a normal load, the amount of heel and toe wear was measured and evaluated based on the results.
[Snow braking performance evaluation]
The braking distance was measured by lock braking at a braking speed of 40 km / h on a snowy road and evaluated based on the result.
[Wet road turning performance evaluation]
A wet skid pad road having a radius of 30 m was circulated at high speed with a normal load applied, and the time required for this was measured, and the evaluation was made based on the result.

  As a result, the tire according to the present invention has a braking performance on snow and a wet road turning performance without substantially reducing the uneven wear resistance performance as compared with the conventional example 1 in which all the sipes are formed of three-dimensional sipes. It turns out that it is improving.

1 is a partially developed plan view showing a tread surface of a pneumatic radial tire according to an embodiment of the present invention. FIG. 3 is a developed plan view corresponding to FIG. 1 showing a tread surface of a pneumatic radial tire according to another embodiment of the present invention.

Explanation of symbols

1 Tread surface 2 Vertical groove 3 Horizontal groove 4 Block 5a 2D sipe 5b 3D sipe C Center area S Shoulder area W Tread width

Claims (3)

In a pneumatic radial tire in which a large number of blocks are arranged on the tread surface and a sipe having a three-dimensional structure extending in the tire width direction is provided on these blocks.
A three-dimensional sipe is arranged in each of the center region and shoulder region blocks of the tread surface, and the number of the three-dimensional structure sipe arranged in the shoulder region block of the tread surface is set to the center region block of the tread surface. More than 50% of the sipe of the three-dimensional structure arranged in the shoulder area, and more than 50% of the total sipe length of the sipe arranged in the shoulder area block is made into a three-dimensional sipe, and arranged in the block of the center area A pneumatic radial tire in which the total sipe length of the three-dimensional sipe is 70% or less of the total sipe length of the three-dimensional sipe of the block in the shoulder region . The pneumatic radial tire according to claim 1, wherein the number of sipes having a three-dimensional structure arranged in the block in the center area is larger than that in a large block with respect to a small block. The pneumatic radial tire according to claim 1 or 2, wherein a groove area ratio in the tread surface is 25 to 50%.

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