JPH061120A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve traveling performance on snow and that on ice while keeping them well-balanced. CONSTITUTION:A tread face TS is divided into a tread center area 11 and tread shoulder areas 12 and 12 by main grooves G1 and G2 whose groove width GW ranges from 8 to 15mm. A pneumatic tire is constituted in such a way that the center area width CW of the tread center area 11 in the axial direction of a tire may be 0.4 to 0.6 times of ground contact width W, and the shoulder area width SW of the tread shoulder area 12 in the axial direction of a tire may be 0.2 to 0.3 times of the ground contact width W. The land area ratio CL1/C1 of the tread center area 11 included in a ground contact face K may be 0.65 to 0.75 and the land area ratio SL1/S1 of the tread shoulder area 12 included in the ground contact face K should be 0.5 to 0.6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of improving snow running performance and ice running performance in a well-balanced manner.

[0002]

2. Description of the Related Art In recent years, so-called studless tires have been widely used as tires that can run on ice and snow roads.

In general, this type has a block pattern with a small land area ratio formed on the tread surface, and as shown in FIG. 5, the shearing force is obtained from the snow compacted in the groove a to improve the performance on snow. ing. On the other hand, for the performance on ice, the tread portion is made of a soft rubber material while each block b
It has been practiced to form siping d in the tire axial direction on each of the tires to enhance the adhesive frictional force with the ice road surface and the ice road surface scratching effect (shown in FIG. 6) due to the siping edge and the like.

[0004]

However, while the land area ratio can be improved by improving the snow performance, the actual contact area with the road surface (the area where the block surface and the road surface actually contact) is small. Therefore, there is a tendency that the adhesive frictional force of the entire tire is reduced and the performance on ice is deteriorated. Thus, there is a trade-off between performance on snow and performance on ice.
Conventionally, it has been difficult to improve both in a well-balanced manner.

An object of the present invention is to provide a pneumatic tire which can improve the performance on snow and the performance on ice in a well-balanced manner.

[0006]

In order to achieve the above object, the pneumatic tire of the present invention has a tread including the tire equator on the tread surface by extending both sides of the tire equator in the tire circumferential direction. A main groove having a groove width of 8 mm or more and 15 mm or less that divides the center region and a tread shoulder region including a tread edge, and extends in a direction intersecting with the main groove, and divides the tread center region and the tread shoulder region into a plurality of blocks. A tire having a block pattern including a lateral groove that has a center area width CW in the tire axial direction of the tread center area in a normal state in which the tire is mounted on a normal rim, a normal internal pressure is filled, and a normal load is applied. The width of the grounding surface of the grounding surface where the tread surface touches is greater than 0.4 times and less than 0.6 times, and The shoulder region width SW in the tire axial direction of the shoulder region is set to be larger than 0.2 times and smaller than 0.3 times the width W of the contact surface, while the width of the contact center area which is a tread center area included in the contact surface. The ratio CL1 / C1 of the total area C1 to the total surface area CL1 of the block in the ground contact center area is larger than 0.65 and smaller than 0.75, and further, in the ground contact shoulder area which is a tread shoulder area included in the ground contact surface area. The ratio SL1 / S1 between the total area S1 and the total surface area SL1 of the block in the grounded shoulder region is set to be larger than 0.5 and smaller than 0.6.

[0007]

With the main groove in the tire circumferential direction, the tread surface is provided with a tread center region having a width CW of 0.4 to 0.6 times the ground contact surface width W, and a tread center area of 0. It is divided into a tread shoulder region having a width SW of 2 to 0.3 times.

The tread center region is a region having a high performance on snow such that the block is deeply inserted into the snow surface. Therefore, the tread center region has a ratio of CL1 / C.
By forming a block pattern with a large land area ratio of 1 to 0.65 to 0.75, the actual ground contact area (the area where the block surface and the road surface actually contact) is increased, and the performance on ice is also compatible. Can be improved.

The tread shoulder area has a ratio SL1 / S1.
A block pattern with a small land area ratio of 0.5 to 0.6 is adopted. As a result, the snow compaction effect in the groove is enhanced, and the snow performance can be improved. As described above, the present invention focuses on the difference in the ground contact pressure in each region, and the land area ratio is different in each region. Therefore, the performance on ice and the performance on snow can be improved in a well-balanced manner for the entire tire.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In the drawings, a pneumatic tire 1 of the present invention includes bead portions 3 and 3 on both sides through which a bead core 2 passes, a sidewall portion 4 extending outward from each bead portion 3 in a tire radial direction,
In the present example, which is provided with a tread portion 5 connecting between the upper ends thereof, it is formed as a heavy-duty tire. In addition, a carcass 6 that folds around the bead core 2 from the tread portion 5 through the sidewall portion 4 is bridged between the bead portions 3 and 3, and the carcass 6 is radially outward and inside the tread portion 5. The tough belt layer 7 is wound.

The carcass 6 is a radial direction arrangement body using at least one carcass ply in which the carcass cords are arranged at an angle of 75 to 90 degrees with respect to the tire equator CO. The carcass cords include steel cords,
Fiber cords such as nylon, polyester and rayon are used.

The belt layer 7 is formed of a belt ply 7A in which belt cords are arranged at an angle of 30 to 70 degrees with respect to the tire equator CO. In each belt ply 7A, the belt cords cross each other. It is piled up in different directions. As a belt cord, carcass 6
Similarly to metal fiber cords such as steel and nylon,
Organic fiber cords such as polyester and rayon are used.

The tread surface TS, which is the outer surface of the tread portion 5, has a radius of curvature TR centered on the tire equatorial plane in the meridional section of the tire that is assembled to the regular rim and filled with the regular internal pressure. It bends with a single arc of 300 to 800 mm. The tire 1 has the tread surface T
S is the buttress surface BS extending from the sidewall portion 4.
A so-called square shoulder that intersects with the buttress surface BS forms a tread edge e.

On such a tread surface TS, as shown in FIG. 2, main grooves G1 and G extending in the tire circumferential direction are formed.
A block pattern is formed which is divided by 2 and the lateral grooves Y ...

The main grooves G1 and G2 are, for example, zigzag grooves arranged on both sides of the tire equator CO and having a groove width GW of 8 mm or more and 15 mm or less.
The main grooves G1 and G2 are formed substantially symmetrically with respect to the tire equator CO by having zigzag pitches that are equal to each other and being arranged with a phase shift in the frequency dividing direction of approximately 1/2 pitch. To be done.

The main grooves G1 and G2 extend continuously in the circumferential direction so that the tread surface includes the tire equator CO and the tread center region 11 disposed between the main grooves G1 and G2 and the tread edge e. And each main groove G1, G
The tire is divided into three regions, that is, the tread shoulder regions 12 and 12 arranged on the outer side in the tire axial direction.

The center region width CW, which is the distance in the tire axial direction of the tread center region 11, is greater than 0.4 times and less than 0.6 times the ground contact surface width W, and the tread shoulder region 12 is also included. In the shoulder region, which is the distance in the tire axial direction, is larger than 0.2 times and smaller than 0.3 times the ground contact surface width W. Therefore, in the tread center region 11 divided by such a width ratio, the tread surface TS is curved in an arc shape as described above, and thus the ground contact pressure becomes large, and conversely, the tread shoulder region 12 becomes small in ground contact pressure. .

The contact surface width W means the tire axial direction of the contact surface K with which the tread surface TS contacts the ground in a normal state in which the tire is mounted on the regular rim and is filled with the regular internal pressure and a regular load defined by JIS or the like is added. Distance, in this example the tread has a square shoulder,
The ground contact surface width W matches the tread width TW.

In the tread center region 11 and the tread shoulder region 12 having different ground pressures,
Block patterns having different land area ratios CL1 / C1 and land area ratios SL1 / S1 are formed.

That is, the tread center area 11 is
In this example, a sub-main groove g passing over the tire equator CO and a plurality of lateral grooves Y1 that cross the sub-main groove g and extend between the main grooves G1 and G2 are provided, whereby the tread center region is 2 A block pattern having column block columns R1 and R1 is formed.

The sub-main groove g is, in this example, the main grooves G1 and G2.
The zigzag groove has a narrower groove width gw than that of the main groove G1 and G2 and is arranged with a phase shift of approximately 1/3 pitch from the main grooves G1 and G2. Further, each block B1 forming the block row R1 is formed with a siping 13 that extends in a Z shape from the outer edge in the tire axial direction toward the inner edge and closes the opening at the time of contact with the ground to maintain the block rigidity. Enhances the scratching effect on icy roads.

In the present embodiment, the tread shoulder region 12 is provided with a Y-shaped lateral groove Y2 having an inner end communicating with the main grooves G1 and G2 and an outer end opening at the buttress surface. The tread shoulder region 12 forms a block row R2 in which an outer block B2 contacting the tread edge e and an inner block B3 spaced inward from the tread edge e are alternately arranged.

The blocks B2 and B3 are also formed with sipings 14 and 15 extending in the tire axial direction, and the number, length, shape, etc. of the sipings 13, 14 and 15 are determined according to the required tire performance. .

In the present invention, when the tread center region 11 included in the ground plane K is defined as the ground center region 11K, the total area C1 including the groove area of the ground center region 11K and the ground center region 11K. The land area ratio CL1 / C1 which is the ratio with respect to the total surface area CL1 of the block B1 is set to be larger than 0.65 and smaller than 0.75.

Similarly, when the tread shoulder region 12 included in the ground contact surface K is defined as the ground shoulder region 12K, the total area S1 including the groove area of the ground shoulder region 12K is defined.
And blocks B2 and B3 in the grounding shoulder area 12K
The land area ratio SL1 / S1 which is the ratio of the total surface area SL1 of the above is larger than 0.5 and smaller than 0.6.

As a result of various experiments conducted by the inventor of the present invention, when the tread surface TS is divided into the tread center region 11 and the tread shoulder region 12 at the above-described width dimension ratio, for example, the tread center region 11 is landed. Area ratio C
When L1 / CL is constant, the on-snow performance of the entire tire is the land area ratio SL1 / S1 of the tread shoulder region 12.
However, it was found that the performance on ice was hardly affected. On the contrary, tread shoulder area 1
It was found that when the land area ratio SL1 / S1 of 2 is constant, the on-snow performance of the entire tire is hardly affected by the land area ratio CL1 / C1 of the tread center region 11, and the on-ice performance is greatly affected. Was done.

That is, the land area ratio CL1 / C1 is 0.6 as shown in FIGS.
When it is greater than 5, the tire exhibits excellent on-ice performance, and when the land area ratio SL1 / S1 is less than 0.6, it can exhibit excellent on-snow performance. The experimental results show that a heavy load tire having a tire size of 10.00R20 having the structure shown in FIG. 1 has a center area width CW / contact surface width W = 0.5, a shoulder area width SW / contact surface width W = 0.25. While making a trial with the value of, the trial tire has a rim size of 7.00 T and an internal pressure of 7.
It is an index value when mounted on an 8-ton truck under the condition of 25 ksc and traveling in a constant volume state.

When the land area ratio CL1 / C1 is 0.65 or less, the on-ice performance becomes insufficient, and conversely, when the land area ratio CL1 / C1 is 0.75 or more, the drainage performance becomes insufficient and the wet performance deteriorates. Land area ratio SL1
When / S1 is 0.6 or more, the on-snow performance is insufficient, while when it is 0.5 or less, the tread shoulder rigidity is reduced and the high-speed performance and turning performance on a dry road surface are deteriorated.

[0029]

As described above, in the pneumatic tire of the present invention, the land area ratio of the ground contact center area and the land area ratio of the ground contact shoulder area, which are divided by the main groove, are different within a predetermined range. The snow performance and ice performance can be improved in a balanced manner.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a tire according to an embodiment of the present invention.

FIG. 2 is a plan view showing an example of the tread pattern.

FIG. 3 is a diagram showing the relationship between the land area ratio CL1 / C1 and the performance on ice.

FIG. 4 is a diagram showing a relationship between a land area ratio SL1 / S1 and snow performance.

FIG. 5 is a diagram illustrating traction of a block on a snowy road surface.

FIG. 6 is a diagram illustrating an ice road surface scratching effect.

[Explanation of symbols]

 11 tread center area 11K ground contact center area 12 tread shoulder area 12K ground contact shoulder area CO tire equator e tread edge G1, G2 main groove Y, Y1, Y2 lateral groove K ground surface TS tread surface

Claims (1)

[Claims] 1. A groove width of 8 mm or more that divides the tread surface into a tread center area including a tire equator and a tread shoulder area including a tread edge by extending both sides of the tire equator in the tire circumferential direction on the tread surface. 15
A tire having a block pattern, which comprises a main groove of mm or less, and a lateral groove extending in a direction intersecting with the main groove and partitioning the tread center region and the tread shoulder region into a plurality of blocks, wherein the tire of the tread center region is provided. The center area width CW in the axial direction is set to 0. 0 of the contact surface width W of the contact surface where the tread surface contacts the ground in a normal state in which the tire is mounted on the regular rim, the regular internal pressure is filled, and the regular load is applied.
The width of the shoulder region SW in the tire axial direction of the tread shoulder region is set to be larger than 0.2 times and smaller than 0.3 times the ground contact surface width W, while being larger than 4 times and smaller than 0.6 times. The ratio CL1 / C1 of the total area C1 of the grounding center area, which is the tread center area included in the grounding surface, to the total surface area CL1 of the block in the grounding center area is 0.6.
The ratio SL1 / S1 of the total area S1 of the grounding shoulder area, which is a tread shoulder area included in the grounding surface and the total surface area SL1 of the block in the grounding shoulder area, is larger than 0.5 and smaller than 0.75. Greater than 5 and 0.6
A smaller pneumatic tire.