JP2002029226A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve running performance on ice and snow. SOLUTION: The contour of a block 20 is formed by a pair of longitudinal sides 20A respectively extending in the circumferential direction R of a tread 14 and a pair of lateral sides 20B respectively extending in the direction orthogonal to the circumferential direction R of the tread 14. The block 20 is disposed on the tread surface part of the tread 14. The block tread surface 20C forming the top of the block 20 is provided with plural sipes 26 formed extending radially around the center G of gravity of the block tread surface 20A. When the sipe length of each sipe 26 projected on the longitudinal side 20A is taken as X, the sipe length of each sipe 26 projected on the lateral side 20B is taken as Y, the length of the longitudinal side 20A is taken as A, and the length of the lateral side 20B is taken as B, and the value of (X/A)/(Y/B) is taken as α, the value α satisfies the condition of 0.8<=α<=1.2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having improved running performance on ice and snow, and is particularly suitable for a winter tire used for running on ice and snow.

[0002]

2. Description of the Related Art Conventionally, as a pneumatic tire used for a passenger car traveling in a cold region, for example, a block type tread pattern in which a block row is arranged on a tread of a tire serving as a tread portion in contact with a road surface is used. Winter tires are known. And
Conventionally, a plurality of sipes, which are narrow grooves, are provided on a land portion which is a block formed on a tread of such a pneumatic tire. In addition, most of the conventional sipe extending directions formed in the block almost extend in a direction substantially perpendicular to the tire rotation direction so as to be generally the same as each other.

However, in the case of a structure in which the direction in which the sipe extends is substantially constant, the contact pressure distribution in the block at the time of contact with the tire becomes uneven, so that a sufficient grip cannot be obtained during running on ice. In other words, in such a structure in which the direction in which the sipe extends is substantially constant, for example, during running on ice and snow, although the effect of the sipe is sufficiently exerted against the longitudinal force applied along the tire rotation direction,
There is a drawback that the sipe has little effect on the lateral force of the tire from the lateral direction and loses grip when cornering,
It was not possible to cope with various external forces applied to the tires when traveling on snow and ice.

[0004]

Although the running performance of winter tires on ice and snow has been remarkably improved in recent years, it is still slippery when running on ice and snow, especially on ice, and only the starting acceleration performance and braking performance are improved. But not
There is a need for further improvements in all driving performances such as cornering performance. The present invention takes into account the above facts,
It is an object of the present invention to provide a pneumatic tire capable of improving running performance on ice and snow.

[0005]

The pneumatic tire according to claim 1 is a pneumatic tire having a plurality of block rows each including a plurality of blocks provided on a tread portion in contact with a road surface of an annular tread. The block has a plurality of sipes radially extending from the center of gravity of the block tread surface serving as the top surface of the block, and the length of the sipe projected on the vertical side constituting the block is X, and the block intersects with this vertical side. Let Y be the length of the sipe projected on the horizontal side of
When the length of the vertical side is A and the length of the horizontal side is B, (X
/ A) / (Y / B) is α, where α is 0.8 ≦ α
It satisfies the condition of .ltoreq.1.2.

The operation of the pneumatic tire according to claim 1 will be described below. The present invention is used for a pneumatic tire in which a plurality of block rows each including a plurality of blocks are provided on a tread portion in contact with a road surface of a tread formed in an annular shape, and centered on a center of gravity of a block tread surface serving as a top surface of the block. It has a plurality of sipes extending radially. further,
X is the length of the sipe projected on the vertical side of the block
And the length of the sipe projected on the horizontal side that intersects the vertical side to form the block is Y, the length of the vertical side is A,
Assuming that the value of (X / A) / (Y / B) when the length of the horizontal side is B is α, α satisfies the condition of 0.8 ≦ α ≦ 1.2.

In other words, the sipe is made denser at the center of the block and the sipe is made sparse at the periphery of the block, so that the rigidity of the block and the effect of sipe (edge effect,
Since it is known from past knowledge that both water removal effects can be achieved, a plurality of sipes are arranged so as to extend radially around the center of gravity of the block tread surface.

The value α of (X / A) / (Y / B), which is an expression relating to the direction in which each sipe extends with respect to the block, satisfies the condition of 0.8 ≦ α ≦ 1.2. ,
The anisotropy in the direction in which the sipe extends is reduced, the distribution of the ground pressure in the block is made uniform, and the coefficient of friction, especially on smooth road surfaces such as on ice, is increased, and the grip force is improved.
Along with this, the effect of the sipe on external force such as a wider range of longitudinal force and lateral force is enhanced, so that the effect of the sipe on the lateral force of the tire from the lateral direction is surely obtained, The running stability when cornering on ice and snow is improved. As described above, according to the pneumatic tire of the present invention, the running performance on ice and snow is improved.

The operation of the pneumatic tire according to claim 2 will be described below. The present invention has the same configuration as that of the first aspect and operates in the same manner, but further has at least one sipe penetrating near the center of gravity of the block tread, which is the top surface of the block, and has the center of gravity of the block tread as a center. The sipe extends radially from the center of the block tread surface at a distance of at least 1.5 mm. That is, in the present invention, instead of providing a sipe penetrating near the center of gravity of the block tread, a sipe extending radially is not arranged at the center of gravity of the block tread, and the rigidity of the block near the center of gravity of the block tread is maintained. .

The operation of the pneumatic tire according to claim 3 will be described below. The present invention has the same configuration as that of the first and second aspects and operates in the same manner, but further has a configuration in which a block having a plurality of radially extending sipes occupies at least 5% of all blocks. are doing. That is, in the present invention, since the block having a plurality of radially extending sipes of claim 1 occupies at least 5% of all blocks, the operation of claim 1 can be reliably achieved.

The operation of the pneumatic tire according to claim 4 will be described below. The present invention has a configuration similar to that of the first to third aspects and operates in the same manner, but further has a configuration in which each sipe is formed in a linear shape or a wavy shape. That is, in the present invention, not only each sipe is formed in a linear shape but also in a wavy shape, the same effect as in the first embodiment is exerted. In the case of this wavy sipe, the length of the sipe center line projected on the vertical side is X, and the length of the sipe center line projected on the horizontal side is Y, and (X / A) / The value of (Y / B) can be calculated.

The operation of the pneumatic tire according to claim 5 will be described below. The present invention has the same configuration as that of the first to fourth aspects and operates in the same manner, but further has a configuration having a bent portion in the middle of the sipe in the depth direction. In other words, according to the present invention, the sipe having a bend is arranged in the block, so that the inner wall surface of the sipe supports the force from the lateral direction like a key, thereby increasing the rigidity of the block. Thus, the effect of the sipe can be expected to be further enhanced.

The operation of the pneumatic tire according to claim 6 will be described below. The present invention has the same configuration as that of the first to fifth aspects and operates in the same manner, but further has a configuration in which the tread rubber constituting the tread is formed of foamed rubber. That is, in the present invention, the tread rubber constituting the tread is formed by the foamed rubber having fine bubbles inside, so that it is suitable as the tread rubber of the winter tire.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic tire according to one embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a diagram illustrating a typical example of a tread pattern of a pneumatic tire 10 according to the present embodiment. Here, the pneumatic tire 10
1B, a carcass 12 which is a radial carcass having bead portions (not shown) at both ends and a crown portion of the carcass 12, as shown in FIG. 1B. This type of pneumatic tire is a general combination of a highly rigid belt (not shown) and a tread 14 which is formed in an annular shape with tread rubber on the outer peripheral surface of the belt and is arranged. In the following description, description is omitted.

Further, as shown in FIG. 1, the outer surface of the pneumatic tire 10 which is in contact with the road surface is formed by a tread portion of the above-described tread 14 having an outer surface formed in an arcuate crown shape. The tread 14 is formed symmetrically with respect to a center line CL which is an equatorial plane, and shoulder portions 16 form both end portions of the tread 14 connected to the sidewall portion 18, respectively. The tread rubber constituting the tread 14 is formed of foam rubber.

The tread 14 of the pneumatic tire 10 has a pair of vertical sides 20A extending in the circumferential direction R of the tread 14 and each extending in a direction perpendicular to the circumferential direction R of the tread 14. A pair of horizontal sides 20B
Thus, the block 20 on which the contour is formed is arranged. In the present embodiment, a plurality of these blocks 20 are arranged at equal intervals around one circumference of the tread 14, and a plurality of block rows composed of these blocks 20 are formed side by side in the tire width direction. A groove 22 is formed between each of the blocks 20, and the tread pattern of the pneumatic tire 10 according to the present embodiment has a structure in which a plurality of blocks 20 are combined.

Further, as shown in FIG. 2, the block tread surface 20C serving as the top surface of the block 20 is provided with one sipe 24 which is a narrow groove passing through the vicinity of the center of gravity G of the block tread surface 20C. Block tread surface 2 at least 1.5 mm away from center of gravity G of 20C
A plurality of sipes 26, each of which is a narrow groove, extending radially around the center of gravity G of 0C, is provided.
26 are each formed in a linear shape.

As shown in FIG. 2, the sipe length of each radially extending sipe 26 projected on the vertical side 20A constituting these blocks 20 is represented by X, and the horizontal side constituting the block 20 intersects with the vertical side 20A. The sipe length of each sipe 26 extending radially projected onto the side 20B is represented by Y, and the vertical side 20A
Is A, and the length of the side 20B is B. Further, the value of (X / A) / (Y / B) at this time is α,
This α satisfies the condition of 0.8 ≦ α ≦ 1.2.

Next, the operation of the pneumatic tire 10 according to the present embodiment will be described below. The pneumatic tire 10 according to the present embodiment has a plurality of block rows each including a plurality of blocks 20 formed along a tire width direction on a tread portion that is a surface in contact with a road surface of a tread 14 formed in an annular shape. ing. Furthermore, the center of gravity G of the block tread 20C
In addition to having one sipe 24 penetrating the vicinity, the sipe 24 has a plurality of sipe 26 radially extending from the position at least 1.5 mm away from the center of gravity G of the block tread 20C and centering on the center of gravity G of the block tread 20C. X / A)
The value of // (Y / B) is α, where α is 0.8 ≦ α ≦ 1.
Condition 2 is satisfied.

That is, by making the sipe dense at the center of the block and sparse at the periphery of the block, the rigidity of the block and the effect of the sipe (edge effect,
Since it is known from the past knowledge that the water removal effect can be compatible, in the present embodiment, the center of gravity G of the block tread surface 20C is obtained.
And a plurality of sipes 26 are arranged so as to extend radially.

Further, each sipe 26
(X / A) / (Y / B)
Is satisfied by satisfying the condition of 0.8 ≦ α ≦ 1.2,
The anisotropy in the direction in which the sipe 26 extends is reduced, the distribution of the ground pressure in the block 20 is made uniform, and the coefficient of friction on a smooth road surface such as on ice is increased, thereby improving the grip force.

As a result, the effect of the sipe 26 on the input of a wider range of external force such as the longitudinal force and the lateral force is enhanced, so that the sipe 26 is also effective against the lateral force of the tire from the lateral direction.
The effect is reliably obtained, and running stability when cornering on ice and snow is improved. As described above, according to the pneumatic tire 10 according to the present embodiment, traveling performance on ice and snow is improved.

At this time, in the present embodiment, the block 20 having the plurality of sipes 26 extending radially occupies at least 5% of the entire block, so that the above-described operation can be reliably achieved. Further, in the present embodiment, the tread rubber constituting the tread 14 is formed of foamed rubber having fine bubbles inside, so that the tread rubber of the pneumatic tire 10 according to the present embodiment is the tread of the winter tire. It becomes suitable as rubber.

On the other hand, as shown in FIG. 3, the block 20 of the pneumatic tire 10 according to the present embodiment has at least four sipes 24 and 26 in a state where the sipes 24 and 26 have a bend in the middle of the depth direction. It may be arranged. In other words, the sipe 24, 26 having a bend is arranged in the block 20, so that the inner wall surfaces of the sipe 24, 26 support the force from the lateral direction like a key,
This has the effect of increasing the rigidity of the block 20, and the effects of the sipes 24, 26 can be expected to be further enhanced. FIG. 3A shows an example in which the sipe is formed by bending in a stepped manner, and FIG. 3B shows an example in which the sipe is formed by simply bending so as to be bent. However, the rigidity of the block 20 can be increased.

On the other hand, in the present embodiment, each sipe 24, 2
Although 6 is formed in a linear shape, the same operation as in the above-described embodiment can be achieved even if the sipes 24 and 26 are formed in a wavy shape as shown in FIG. At this time, in the case of the wavy sipe 26, the length of the sipe center line S projected on the vertical side 20A is defined as X, and the length of the sipe center line S projected on the horizontal side 20B is defined as Y ( X / A) /
The value of (Y / B) can be calculated.

Next, the results of running tests performed by comparing the pneumatic tires described in the present embodiment with the examples according to the prior art will be described based on Table 1 below. That is, in the conventional examples 1 and 2 shown in Table 1, not only the sipe was not formed to extend radially, but also the α value was 3.2 in the conventional example 1 and 7 in the conventional example 2. 0.7, which does not satisfy the condition of 0.8 ≦ α ≦ 1.2. On the other hand, in Example 1 and Example 2 shown in Table 1, the sipe 26 is formed so as to extend radially, and the α value is 1.
2 and 0.8 in the second embodiment, so that 0.8 ≦
The pneumatic tire satisfies the condition of α ≦ 1.2. Then, a running test was performed with each of these tires mounted on a vehicle, and the results in Table 1 below were obtained.

[0027]

[Table 1]

That is, as shown in Table 1, braking performance and cornering performance were evaluated as performance on ice and performance on snow as shown in Table 1. At this time, the braking performance on ice is obtained by indexing the distance from the speed of 20 km / h to the stop on ice, and the braking performance on snow is from the speed of 50 km / h on the snow until the vehicle stops. It is an index of distance, and the larger the numerical value, the better the evaluation. The cornering performance on ice and snow is a feeling evaluation of the driver and is expressed by an index on a scale of 1 to 10, and the larger the numerical value, the better the evaluation.

As a result of the above Table 1, the braking performance on ice was higher than that of Conventional Example 1 in both Examples 1 and 2, and the braking performance on snow was also higher in Conventional Example 1 than in Examples 1 and 2. The score was higher. On the other hand, the cornering property of each of Examples 1 and 2 was higher than those of Conventional Examples 1 and 2 under any conditions. For this reason, it turned out that the tires of Example 1 and Example 2 are overall better than the tires of Conventional Example 1 and Conventional Example 2.

Here, a sensory evaluation by a driver is adopted as an evaluation method of the running test, and the size of the tire used in the running test is 205 / 65R15.
The size of the rim is 6.5 JX15, and the vehicle used in the running test is Cam Riglia in a passenger car,
The internal pressure of the tire was 210 KPa for the front wheels and 230 KPa for the rear wheels.

In the above embodiment, the number of sipes is not limited to the number shown in the drawings, and may be larger or smaller than the number shown in the drawings. Further, in the above-described embodiment, the tread rubber constituting the tread is formed of foamed rubber, but may be another type of rubber material.

[0032]

The pneumatic tire of the present invention has the above-mentioned structure, and therefore has an excellent effect that the running performance on ice and snow can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a pneumatic tire according to an embodiment of the present invention, in which (A) is a plan view and (B) is a cross-sectional view taken along the line 1B-1B of (A). is there.

FIG. 2 is an enlarged plan view of the block in a state where the planar structure of the block is simplified.

FIG. 3 is an enlarged sectional view of a main part of a block showing an example in which a sipe is arranged so as to have a bend in the depth direction, and FIG. 3A shows an example in which the sipe is formed by being bent in a step shape. (B) shows an example in which the sipe is formed by being bent just to be bent.

FIG. 4 is an enlarged plan view of a main part of a block for explaining a wavy sipe;

[Explanation of symbols]

 10 Pneumatic tire 14 Tread 16 Shoulder part 20 Block 24 Sipe 26 Sipe

Claims (6)

[Claims] 1. A pneumatic tire in which a plurality of block rows each including a plurality of blocks are provided on a tread portion in contact with a road surface of an annular tread, wherein a center of gravity of a block tread surface serving as a top surface of the block is determined. It has a plurality of sipes that extend radially as the center, and the length of the sipes projected on the vertical sides of the block is X
And the length of the sipe projected on the horizontal side that intersects the vertical side to form the block is Y, the length of the vertical side is A,
The value of (X / A) / (Y / B) when the length of the horizontal side is B is α, and the α satisfies the condition of 0.8 ≦ α ≦ 1.2. Containing tires. 2. A block having at least one sipe penetrating near a center of gravity of a block tread, which is a top surface of the block, wherein a sipe extending radially from the center of gravity of the block tread is at least 1.5 mm away from the center of gravity of the block tread. The pneumatic tire according to claim 1, wherein the pneumatic tire extends radially from the position. 3. The pneumatic tire according to claim 1, wherein the block having a plurality of radially extending sipes occupies at least 5% of all blocks. 4. The pneumatic tire according to claim 1, wherein each sipe is formed in a linear shape or a wavy shape. 5. The pneumatic tire according to claim 1, wherein the pneumatic tire has a bent portion in the middle of the sipe in a depth direction. 6. The pneumatic tire according to claim 1, wherein the tread rubber constituting the tread is formed of foamed rubber.