JP2001213123A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having a block pattern for showing the effect of sipes on a wide-range input, reducing the input-direction reliability of block rigidity, offering stable controllability and good lopsided wear resistance and keeping onice/snow performance and general-road performance highly balanced. SOLUTION: This pneumatic tire having the block pattern on the tread surface of a tread portion comprises sipes 2 provided in at least two places extending from the peripheral end of each block 1 of the block pattern to the cross direction of the block at a certain angle to the tire cross direction to substantially form V-shaped or λ-shaped or inversely λ-shaped patterns in the blocks. The angle of a front axial groove wall 3 in the block 1 to the radial direction is different from that of a rear groove wall 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to a technique for improving a sipe provided on a tread of a pneumatic tire having a block pattern on a tread surface.

[0002]

2. Description of the Related Art A sipe provided on a rib or block of a tread has a water removing effect of cutting a water film on a road surface in the same manner as an edge effect of a groove, and makes it easy to change a rib or block, thereby reducing a hysteresis loss of rubber. Has the effect of facilitating expression. For these reasons, they are widely used in studless tires and the like.

Conventionally, as shown in FIG. 6, usually, the sipe 12 mostly enters the block 11 in a direction substantially perpendicular to the tire rotation direction.

[0004]

However, when the sipe direction is constant on the tread surface as described above, there is a problem that the effect of the sipe on snow or ice works only in a fixed direction. In addition, the deformation of the block during traveling greatly differs depending on the input direction, and the rigidity of the block becomes anisotropic. This means that, for example, the front-rear force is sufficiently exerted when traveling on snow, but the effect of the sipe on the lateral force is small, and the grip at the corner may be lost. Furthermore, when traveling on dry or wet road surfaces, the block rigidity in the front-rear direction is weak,
There are problems such as impairing the stability at a small steering angle.

[0005] Further, even if the sipe direction with respect to the circumferential direction is changed in order to reduce the anisotropy of the block stiffness, a difference occurs in the stiffness in the longitudinal direction of the block. There was a problem that the performance was biased.

Accordingly, an object of the present invention is to provide a sipe effect over a wider range of input, less dependence of the block rigidity on the input direction, stable maneuverability and good uneven wear resistance, An object of the present invention is to provide a pneumatic tire having a block pattern in which performance and general road performance are highly balanced.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventor has made intensive studies on the relationship between the sipe arrangement and the groove wall of the block. And found that the present invention was completed. That is, the pneumatic tire of the present invention is as shown below.

(1) An annular tread portion, a pair of sidewall portions disposed radially inward from both ends of the tread portion in the tire radial direction, and a bead portion connected to the tire radially inward portion of the sidewall portion. In the pneumatic tire having a block pattern formed on the tread portion of the tread portion, the block width is inclined at a fixed angle with respect to the tire axial direction from each circumferential end of each block of the block pattern. At least one sipe extending in the direction and substantially forming a V-shape, a character shape, or a letter shape in the block, and wherein the angle of the axial groove wall of the block with respect to the radial direction is the front and rear. It is a pneumatic tire characterized in that it differs in a groove wall.

Thus, a sipe effect can be obtained for a wide range of inputs, the dependency of block rigidity on the input direction is small, and a high sipe density can be achieved. Further, anisotropy does not occur in one pattern block during braking and traction.

(2) The pneumatic tire according to (1), wherein the tread rubber is a foamed rubber having a foaming ratio of 10 to 50%. By combining the sipe according to the present invention with foamed rubber, it is possible to further improve the performance on snow and the performance on ice.

(3) The pneumatic tire according to (1) or (2), wherein the sipe has a waveform on a tread surface. Thereby, the edge effect of the sipe can be enhanced.

(4) The pneumatic tire according to any one of (1) to (3), wherein the block pattern is a directional pattern. Thus, by specifying the rotation direction and mounting the vehicle on the vehicle, the input directions of braking and driving are limited, so that the effects of the present invention can be maximized. When the sipe is provided to be inclined in the circumferential direction as in (6) below, it is easy to distinguish the inclination direction.

(5) The pneumatic tire according to any one of (1) to (4), wherein the sipe has a three-dimensional fitting portion. As a result, the effect of suppressing the falling of the block between the sipes can be obtained,
In particular, performance on ice and snow can be improved. Here, 3
Having a dimensional fitting portion means that the sipe has a bent portion in the depth direction and the block is in a fitted state between the sipe.

(6) The pneumatic tire according to any one of (1) to (5), wherein the sipe is inclined in a depth direction. Thereby, especially the performance on snow can be improved.

[0015]

Embodiments of the present invention will be described below. FIG. 2 is an enlarged plan view (a) and a cross-sectional view (b) of the tread tread portion. In the block of the tread tread portion, all the sipes 2 forming a character shape are provided in the same direction, and an axial groove wall is provided. Is the same as α for both the front and rear groove walls with respect to the radial direction. By providing the sipe 2 in the block 1, a sipe effect can be obtained for a wider range of input, and a higher sipe density can be achieved.

However, the block 1 having the sipe 2 has a difference in rigidity with respect to the input of the tire rotation in the front-rear direction. That is, in the block shown in FIG. 2, the sipe closes due to block deformation in response to an input from above (arrow A) and opens in response to an input from below (arrow B). is there. As a result, the rigidity of the block is reduced during either braking or traction, which adversely affects uneven wear resistance.

Therefore, in the present invention, by making the angle of the axial groove wall of the block with respect to the radial direction different between the front and rear groove walls, the rigidity of the block is optimized, and stable maneuverability is obtained regardless of the input direction. And a tire having both good uneven wear resistance. That is, FIG.
As shown in the plan view (a) and the cross-sectional view (b) shown in
When the angle of the groove wall of the block is changed between 3 and 4 before and after and β> α, when there is no sipe, an input from above (arrow A) is more blocked than an input from below (arrow B) than an input from below (arrow B). Since the rigidity is reduced, the difference in rigidity in the direction of the groove walls 3 and 4 before and after the block caused by providing the above-described sipe such as a character shape can be offset. Here, the difference between the angles β and α in the groove walls 3 and 4 is preferably 3 ° or more.

The included angle θ when the sipes 2 form a human character shape or the like is preferably 15 to 90 °. When the included angle θ is less than 15 °, the blocks fall between the sipes become large. On the other hand, when the included angle θ exceeds 90 °, uneven wear such as heel and toe tends to occur depending on the use condition. The distance d between the adjacent sipes is preferably 2.5 to 10 mm. If the distance d is less than 2.5 mm, the rigidity of the block is reduced and the maneuverability on a dry road surface is reduced. If it exceeds, braking performance on icy roads will be reduced, and the tire will not function as an original studless tire.

Further, in the present invention, the sipe has a bent portion in the depth direction as shown in FIG. 1B, and the block between the sipe has a three-dimensional fitting portion. preferable. Even if such bent portions are not provided in all sipes, for example, as shown in the figure or provided alternately, it is possible to sufficiently suppress the blocks from falling between the sipes, and to improve the performance on ice and snow. Further, in the illustrated example, the sipe is linear on the tread surface.
The zigzag or waveform can enhance the edge effect of the sipe. Furthermore, the performance on snow can be improved by inclining the sipe in the depth direction.

Preferred embodiments of the tread pattern of the pneumatic tire of the present invention are shown in FIGS.

In the present invention, in the case of a studless tire, the tread rubber is preferably a foamed rubber having a foaming ratio of 10 to 50%. If the foaming ratio is less than 10%, the effect of improving the performance on ice is insufficient, while if it exceeds 50%, the abrasion resistance is reduced. Similarly, the average diameter of the closed cells is preferably 20 to 60 μm. If the average cell diameter of the closed cells is less than 20 μm, the water removal effect is not sufficient,
On the other hand, if it exceeds 60 μm, the wear resistance is reduced. The foaming ratio V _S is obtained by measuring the density ρ ₁ (g / m ³ ) of the block-shaped sample, and measuring the density ρ ₀ of the non-foamed rubber (solid rubber), by the following equation. . V _S = (ρ ₀ / ρ ₁ -1) × 100 (%)

In the production of foamed rubber, as a foaming agent,
For example, ammonium bicarbonate, sodium bicarbonate that generates carbon dioxide, and nitrososulfonylazo compounds that generate nitrogen, such as dinitrosopentamethylenetetramine (DPT), N, N′-dimethyl-N, N′-dinitrosophthal Amide, azodicarbonamide (ADC
A), N, N'-dinitrosopentamethylenetetramine, benzenesulfonylhydrazide, toluenesulfonylhydrazide, p, p'-oxy-bis (benzenesulfonylhydrazide) (OBSH), p-toluenesulfonyl semicarbazide, p, p'- Oxy-bis (benzenesulfonyl semicarbazide) and the like can be mentioned, and these are appropriately selected and used according to the vulcanization temperature. In addition, urea and the like are mentioned as the foaming aid. Of these, ADC
A, OBSH, and combinations of DBP and urea are preferred.

As the rubber component of the matrix rubber of the foamed rubber, natural rubber (NR), polystyrene butadiene rubber (SBR), polybutadiene rubber (BR), polyisoprene rubber (IR), or a blend with other rubbers is used. And should not be particularly limited.

The foamed rubber of the present invention may further contain a filler such as carbon black, an antioxidant, a wax, a vulcanization accelerator, a vulcanizing agent, a silane coupling agent, a dispersant, Stearic acid, zinc white, a softener such as an aroma oil, a naphthenic oil, a paraffin oil, an ester plasticizer, a liquid polymer (a liquid polyisoprene rubber, a liquid polybutadiene rubber) and the like can be appropriately compounded.

In the pneumatic tire of the present invention, the structure and material other than the tread can be appropriately determined according to a common usage.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. As Examples 1 to 4 and Comparative Example, size 2 having a tread pattern shown in FIGS. 7 to 11 (where (A) is a plan view and (B) is a sectional view in the tire radial direction).
Each test tire of 25/50 R16 was manufactured under the sipe conditions shown in Table 1 below, mounted on a 7J rim, and subjected to a field running test under a tire air pressure of 200 kPa to perform on snow (acceleration, cornering). Feeling evaluation was performed on running performance (dry performance) such as on-ice performance, braking performance on dry roads, and steering stability, and running performance (wet performance) such as braking performance on wet roads and steering stability. The results were indexed with the tire of Comparative Example taken as 100. In each case, the larger the numerical value, the better the result. The results obtained are shown in Table 1 below.

[0027]

[Table 1]

[0028]

As described above, in the pneumatic tire of the present invention, a sipe effect can be obtained for a wide range of input, and the input direction dependence of the block rigidity is small.
Stable maneuverability and good uneven wear resistance are obtained. As a result, in the case of a studless tire, on-snow performance, particularly cornering performance, is improved. In addition, running stability on a dry road surface or a wet road surface, particularly when a small steering angle is input, is improved. Further, braking performance on ice is improved.

[Brief description of the drawings]

FIG. 1 is a plan view and a sectional view of a sipe-containing block according to the present invention.

FIG. 2 is a plan view and a sectional view of a block in which the angle of the axial groove wall with respect to the radial direction is the same for both front and rear groove walls.

FIG. 3 is a development view of a tread of a pneumatic tire according to a preferred embodiment of the present invention.

FIG. 4 is a development view of a tread of a pneumatic tire according to another preferred embodiment of the present invention.

FIG. 5 is a development view of a tread of a pneumatic tire according to still another preferred embodiment of the present invention.

FIG. 6 is a plan view of a conventional sipe-containing block.

FIG. 7 is a developed plan view and a sectional view of a tread of the pneumatic tire of Example 1.

FIG. 8 is a developed plan view and a sectional view of a tread of the pneumatic tire of Example 2.

FIG. 9 is a developed plan view and a sectional view of a tread of the pneumatic tire according to the third embodiment.

FIG. 10 is a developed plan view and a sectional view of a tread of the pneumatic tire of Example 4.

FIG. 11 is a developed plan view and a sectional view of a tread of a pneumatic tire of a comparative example.

[Explanation of symbols]

 1,11 blocks 2,12 sipes 3,4 groove walls

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B60C 11/11 B60C 11/04 D

Claims (6)

[Claims] An annular tread portion, a pair of sidewall portions disposed radially inward from both ends of the tread portion in the tire radial direction, and a bead portion connected to the sidewall radially inward in the tire radial direction. In the pneumatic tire having a block pattern formed on the tread portion of the tread portion, each block of the block pattern is inclined at a fixed angle with respect to the tire axial direction from a circumferential end of each block in the block width direction. And at least one or more sipes that form a V-shape, a character shape, or a letter shape in the block, wherein the angle of the axial groove wall of the block with respect to the radial direction is the front and rear grooves. A pneumatic tire characterized by being different at a wall. 2. The pneumatic tire according to claim 1, wherein the tread rubber is a foamed rubber having a foaming rate of 10 to 50%. 3. The pneumatic tire according to claim 1, wherein the sipe has a waveform on a tread surface. 4. The pneumatic tire according to claim 1, wherein the block pattern is a directional pattern. 5. The pneumatic tire according to claim 1, wherein the sipe has a three-dimensional fitting portion. 6. The pneumatic tire according to claim 1, wherein the sipe is inclined in a depth direction.