JPH11165508A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of maintaining ice performance stable even if the tire is worn. SOLUTION: A block 18 containing a siping 20 is formed in the tread surface of a pneumatic tire. The shape of the siping 20 comprises a straight line section 20a parallel with the width direction of a tire and a V-shaped section 20b projected in the peripheral direction of the tire and closing a V-shape toward the bottom of the siping 20 continuously connected to each other. Therefore, the V-shaped section 20b is exposed to a tread 18a along with being worn and gradually closing the V-shape (reducing an angle of γ). Since this constitution increases the edge length of the siping 20 exposing along with wearing and also serves to cut water film by the V-shaped edge of the siping 20 with ease, increasing gripping force, the deterioration of ice performance along with wearing can be restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pneumatic tire capable of maintaining excellent ice and snow performance even after wear.

[0002]

2. Description of the Related Art Conventionally, a block provided on a tread surface of a tire is provided with a sipe to exert an effect on wet performance and ice and snow performance. That is, the edge length is substantially increased by the sipe provided in the block,
The thin water film stretched on the road surface is cut to secure the grip force of the tire (the so-called edge effect). As a result, the wet performance and ice / snow performance of the pneumatic tire are well ensured.

[0003]

In such a pneumatic tire, the rubber deteriorates with wear, so that the grip force is reduced. In addition, since the volume of the sipe decreases with the wear, the drainage performance of the sipe decreases.

On the other hand, since the length of the sipe exposed on the tread surface of the block does not change with wear, the edge length of the block is constant. That is, the edge effect is constant without changing before the wear.

[0005] Therefore, although the edge effect of a pneumatic tire is constant before and after abrasion, there is a problem in that the rubber deteriorates and the drainage performance of the sipe deteriorates due to the abrasion, and the ice and snow performance of the tire decreases. Was.

[0006] In view of the above, it is an object of the present invention to provide a pneumatic tire that can maintain stable ice and snow performance even when worn.

[0007]

According to the first aspect of the present invention, there is provided a pneumatic tire having a plurality of sipe-containing block-like land portions formed by grooves provided on a tread surface. A straight portion formed substantially parallel to the tire width direction on the tread surface of the block-shaped land portion, and the sipe bottom portion continuous with the straight portion, and is convex in the tire circumferential direction on a plane orthogonal to the sipe depth direction. And a V-shaped portion forming an angle θ (0 ° <θ <180 °) at the vertex, and the angle θ from the tread surface of the block-shaped land portion toward the sipe bottom in the sipe depth direction. And the sipe length on the plane increases.

By mounting a pneumatic tire on a vehicle such that the convex (apex) side of the V-shaped portion is oriented in the tire rotation direction, the V-shaped portion exposed at the time of wear is grounded from the convex side. Therefore, the V-shaped portion of the sipe, that is, the V
The character-shaped edge makes it easier to cut a thin water film on the road surface. In particular, the V-shaped portion of the sipe, that is, the shape of the V-shaped edge sharpens (the angle θ becomes smaller) as the wear progresses, so that the water film is more easily cut. Therefore,
Even if the wear progresses, the grip force of the pneumatic tire is secured well, and the deterioration of the wet performance and the ice and snow performance is suppressed.

Further, the sipe has a structure in which the sipe shape changes from the tread surface of the block-shaped land portion toward the sipe bottom in the sipe depth direction and the exposed sipe length is extended. The edge length is increased, and the deterioration of wet performance and ice and snow performance is suppressed.

As described above, the change in the wet performance and the ice and snow performance of the pneumatic tire due to the wear due to the change in the shape and the change in the sipe length are suppressed.

[0011] According to the second aspect of the present invention, there is provided a pneumatic tire having a plurality of sipe-shaped block-shaped land portions defined by grooves provided on a tread surface, wherein the sipe is a tread of the block-shaped land portion. From the sipe bottom to the sipe bottom, it is convex in the tire circumferential direction on a plane orthogonal to the sipe depth direction, and has an angle θ (0 ° <θ <180) at the vertex.
°), the angle θ decreases from the tread surface of the block-shaped land portion toward the sipe bottom in the sipe depth direction, and the sipe length on the plane is reduced. It is characterized by increasing.

By mounting a pneumatic tire on a vehicle such that the convex (apex) side of the V-shaped portion faces the tire rotation direction, the V-shaped portion exposed at the time of wear is grounded from the convex side. Therefore, the V-shaped portion of the sipe, that is, the V
The character-shaped edge makes it easier to cut a thin water film on the road surface. In particular, the V-shaped portion of the sipe, that is, the shape of the V-shaped edge sharpens (the angle θ becomes smaller) as the wear progresses, so that the water film is more easily cut. Therefore,
Even if the wear progresses, the grip force of the pneumatic tire is secured well, and the deterioration of the wet performance and the ice and snow performance is suppressed.

In particular, since the sipe exposed on the tread surface of the block-shaped land portion when it is new is also a V-shaped portion forming an angle θ, the grip force is increased by the shape of the sipe from the beginning, and the wet performance in the initial stage of wear is increased.・ Ice and snow performance is better.

Further, the sipe has a structure in which the sipe shape changes from the tread surface of the block-shaped land portion toward the sipe bottom in the sipe depth direction and the exposed sipe length is extended. The edge length is increased, and the deterioration of wet performance and ice and snow performance is suppressed.

As described above, a change in the sipe shape and a change in the sipe length suppresses a decrease in wet performance and ice / snow performance due to wear.

According to the third aspect of the present invention, the first or second aspect is provided.
In the invention described, when the block-shaped land portion wears 50% of its height, the angle θ formed by the V-shaped portion of the sipe exposed on the tread surface of the block-shaped land portion is set to 60 ° ≦ θ ≦
It is characterized by 170 °.

In order to explain the operation of the present invention, the relationship between the angle θ formed by the V-shaped portion of the sipe and the coefficient of friction on ice was examined using a sample block.

As shown in FIG. 2, the sipe 20 provided on the sample block has a straight portion 20a parallel to the tire width direction on the tread surface 18a of the block 18 and an angle θ extending from the straight portion 20a to the sipe bottom 21. And a V-shaped V-shaped portion 20b. That is, the sipe 20 is formed such that the angle θ formed by the V-shaped portion 20 b decreases toward the sipe bottom 21.

The sample block has a block height H of 5
At 0%, a plurality of types were prepared at intervals of 10 ° within an angle θ formed by the sipe in the range of 10 ° to 180 °, and a test was performed in a state where the block was worn down to 50% of the height H.

In the friction test on ice, the contact pressure was 2.5 kgf / c.
The sample block was pressed against an ice plate rotating at a speed of 20 km / h at m ² , and the friction coefficient on ice was calculated from the resistance generated at that time.

As shown in FIG. 7, 60 ° ≦ θ ≦ 170 °
It was confirmed that the coefficient of friction on ice increased. In particular, the maximum value is obtained at θ = 90 °.

As described above, at the position where the block wear amount is 50%, the angle θ formed by the V-shaped portion of the sipe is 60 ° ≦ θ.
By setting ≦ 170 °, the coefficient of friction on ice is improved.
Therefore, the coefficient of friction on ice is increased at a position where the amount of wear of the block is 50%, which is near the limit of use in a studless tire or the like, that is, at a position where the ice / snow performance is most reduced due to deterioration of rubber or the like, thereby suppressing the decrease in the ice / snow performance. be able to.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pneumatic tire according to a first embodiment of the present invention will be described with reference to FIGS.

As shown in FIG. 1, the tread 12 of the pneumatic tire 10 of the present embodiment has a tire circumferential direction (arrow A).
Direction, hereinafter referred to as A direction).
A plurality of blocks 18 defined by lug grooves 16 extending along the tire width direction (arrow B direction, hereinafter referred to as B direction) are formed.

In block 18, as shown in FIG.
Sipe 2 with both ends opened on side faces 18b and 18c
0 is provided. As shown in FIG. 3A, the sipe 20 includes a straight portion 20a formed as a straight line parallel to the direction B on the new tread surface 18a, and a sipe bottom 21 extending from the tread surface 18a to the straight portion 20a. V that is convex in the A1 direction on a plane parallel to the tread surface 18a and forms an angle θ
It has a shape connected to a V-shaped portion 20b. That is, the V-shaped portion 20b is located at the midpoint 22 of the linear portion 20a.
Ridge line 24 extending perpendicular to block tread surface 18a
Has a V-shape with the vertex at the top. V-shaped part 20b
Has a shape in which the V-shape is closed (the angle θ decreases) from the block tread surface 18a toward the sipe bottom 21.

In particular, as shown in FIG. 3B, the angle θ formed by the V-shaped portion 20b is 90 ° when the wear amount is 50%. Here, the wear amount is a ratio of the wear depth to the main groove depth (block height) H (hereinafter the same).

The pneumatic tire 10 constructed as described above
The operation of will be described below. First, the tire rotation direction is A1
The pneumatic tire 10 is mounted on the vehicle so as to be in the direction (see FIG. 1). The pneumatic tire 10 thus mounted exhibits an edge effect due to the linear portion 20a exposed on the tread surface 18a of the block 18 when new, and exhibits good ice and snow performance. In the pneumatic tire 10, the V-shaped portion 20b of the sipe 20 is exposed on the tread surface 18a with wear. V of small blocks 26 and 28 divided by V-shaped portion 20b
The letter-shaped edge easily cuts the thin water film stretched on the road surface,
Grip the road. In particular, in the V-shaped portion 20b, the V-shaped shape is sharpened (the angle θ decreases) as the wear progresses, so that the water film is more easily cut.

A sipe 20 which is a sipe having both sides open is provided.
Is gradually transformed into a V-shaped portion 20b having a smaller angle θ as it approaches the sipe bottom 21.
The edge lengths of 6, 28 increase, and the edge effect increases.

As described above, in the pneumatic tire 10 of the present embodiment, the V-shaped portion 20b, which is convex in the tire rotation (A1) direction, is exposed on the tread surface 18a due to wear, so that the sipe shape (small size) of the V-shaped portion 20b is reduced. Due to the change in the edge shape of the blocks 26 and 28), a thin water film on the road surface is easily cut and the grip force is increased, and the edge length is increased to increase the grip force. Suppress.

Further, at a position where the wear amount is 50%, which is near the limit of use of a studless tire or the like, as shown in FIG. 3B, the angle θ formed by the V-shaped portion 20b is 90 °. The coefficient of friction on ice of the block 18 is maximized (see FIG. 7), and a decrease in ice and snow performance can be suppressed.

The size of the block 18 in the present embodiment is such that length L × width W × height H is 30 mm × 20 mm.
× 10 mm, and the distance F from the end of the block to the ridge line 24 (straight line portion 20a) is 10 mm. The depth D of the sipe 20 is 8 mm. The angle α that the sipe 20 makes with the perpendicular to the tread surface 18a on the side surfaces 18b and 18c of the block 18 is 63.4 °.

Next, a pneumatic tire according to a second embodiment will be described with reference to FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

Since the difference from the first embodiment is only the sipe shape, only the sipe 40 will be described.

The sipe 40 is a tread 18a of the block 18.
A point on the ridge line 24 that is a perpendicular line from the midpoint 22 in the B direction from the sipe bottom 41 to the sipe bottom 41 has only a V-shaped portion 40b having a vertex and an angle θ. That is, block 18
The V-shape of the sipe 40 gradually closes (the angle θ decreases) from the tread surface 18a toward the sipe bottom 41.

The operation of the pneumatic tire according to the second embodiment configured as described above will be described below.

First, a pneumatic tire is mounted on a vehicle such that the tire rotation direction is the A1 direction. In the pneumatic tire of the present embodiment mounted as described above, the V-shaped portion 40 that is convex in the tire rotation (A1) direction with the progress of wear.
b is gradually exposed to the tread surface 18a while decreasing the angle θ. Therefore, the shape change of the V-shaped portion 40b (V
The sharpened character makes it easier to cut a thin water film on the road surface and increases the edge length to increase the gripping force, thereby suppressing the deterioration of ice and snow performance due to rubber deterioration and the like.

In particular, when new, the tread surface 18a of the block 18
V-shaped part 40 forming an angle θ1 (0 ° <θ1 <180 °)
Since b is exposed, the effect of increasing the grip force due to the sipe shape acts from the beginning, and the ice and snow performance in the early stage of wear is further improved.

The size of the block 18 in the present embodiment is as follows: length L × width W × height H is 30 mm × 20 mm.
× 10 mm, and the distance F from the end of the block to the ridge line 24 is 10 mm. Also, the depth D of the sipe 40
Is 8 mm. Side 18 of block 18 of sipe 40
The angle α between the vertical line at b and 18c is 61.3 °.
The angle θ1 formed by the sipe 40 on the tread surface 18a of the block 18 is 170 °. When the amount of wear is 50% (half of the block height H), the angle θ formed by the sipe 40 is 90 °.

The following test was conducted to confirm the operation of the pneumatic tire of the present invention thus configured.

First, using a sample block, the relationship between the amount of wear of the block and the coefficient of friction on ice was examined and used as a substitute for ice and snow performance.

Here, the first and second embodiments correspond to the first and second embodiments, respectively.
This is block 18 of the second embodiment. As shown in FIG. 5, the block of the comparative example has a length L × width W × height H of 30 mm × 20 mm × 10, as in the first and second embodiments.
mm, and a straight sipe 50 is formed. The distance F from the end of the block to the sipe 50 is 10 mm
It is. The depth D of the sipe 50 is 8 mm.

In the friction test on ice, the contact pressure was 2.5 kgf / c.
The sample block was pressed against an ice plate rotating at a speed of 20 km / h at m ² , and the friction coefficient on ice was calculated from the resistance generated at that time.

The friction coefficient on ice at a wear amount of 0% (when the block is new) in the comparative example is set to 100 and indexed as shown in FIG. The larger the index, the better the ice and snow performance (the larger the coefficient of friction on ice).

As shown in FIG. 6, in Example 1, as compared with the comparative example, the V-shape of the sipe shape becomes sharper (the angle θ becomes smaller) as the wear progresses, so that the ice and snow performance decreases. Is suppressed. In Example 2, since the V-shaped sipe shape was exposed from the tread surface of the block from the beginning, better ice and snow performance was maintained compared to the comparative example from the beginning of wear.

Next, a test of braking performance on ice was performed by mounting a pneumatic tire on the vehicle.

Here, the first and second embodiments correspond to the first and second embodiments, respectively.
The pneumatic tire according to the second embodiment is a pneumatic tire according to a first comparative example, in which the block illustrated in FIG. 5 is formed on a tread surface.
2 is a pneumatic tire having the same shape as FIG. Tire size is 1
85 / 70R14.

In the test, a pneumatic tire was mounted on the vehicle, and sudden braking was applied while driving on ice at a speed of 20 km / h.
The braking distance until stopping is measured, and the reciprocal thereof is shown in Table 1 as the braking performance on ice. Both when new and worn, the index is indexed with the brake performance on ice of the pneumatic tire of the comparative example being 100. The larger the numerical value, the better the brake performance on ice. Here, “wear” means that the wear amount is 50
It is the time of%.

[0048]

[Table 1]

As shown in Table 1, in Examples 1 and 2, the brake performance on ice was remarkably improved at the time of wear as compared with the comparative example. This is probably because the sipe shape is V-shaped and the edge length is increased. Especially,
Since the sipe is formed so that the angle θ formed by the V-shape becomes 90 ° at the time of 50% wear near the usage limit of studless tires, the wear depth at which the performance on ice greatly decreases due to wear, and the coefficient of friction on ice It is considered that the decrease in the on-ice performance was suppressed by the best (see FIG. 7).

[0050]

According to the first aspect of the present invention, the ice and snow performance is prevented from deteriorating due to wear, and good ice and snow performance can be maintained.

Since the present invention according to claim 2 has the above-described configuration, it is possible to suppress a decrease in ice and snow performance due to abrasion and maintain good ice and snow performance. In particular, better ice and snow performance can be obtained from the beginning of wear.

According to the third aspect of the present invention, since the above-described configuration is employed in the first or second aspect, the wear amount of the block-shaped land portion near the service limit where the ice and snow performance is greatly reduced with wear is reduced by 50%. In this case, it is possible to suppress a decrease in the ice and snow performance due to an increase in the coefficient of friction on ice.

[Brief description of the drawings]

FIG. 1 is a tread plan view of a pneumatic tire according to a first embodiment.

FIG. 2 is a perspective view of a block according to the first embodiment.

FIG. 3A is a plan view of the block according to the first embodiment when it is new, and FIG. 3B is a plan view of the block according to the first embodiment when it is worn by 50%.

FIG. 4 is a perspective view of a block according to a second embodiment.

FIG. 5 is a perspective view of a block according to a comparative example.

FIG. 6 Amount of wear of a block and ice and snow performance (friction coefficient on ice)
6 is a graph showing the relationship of.

FIG. 7 is a graph showing the relationship between the angle formed by a V-shaped sipe and the snow and ice performance (friction coefficient on ice) when the block is worn by 50%.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 14 Main groove (groove) 16 Lug groove (groove) 18 Block (block-shaped land portion) 20, 40 Sipe 20a Linear portion 20b, 40b V-shaped portion

Claims (3)

[Claims] 1. A pneumatic tire having a plurality of sipe-containing block land portions defined by grooves provided on a tread surface, wherein the sipe is substantially arranged in a tire width direction on a tread surface of the block land portion. A straight line portion formed in parallel with the straight line portion, the sipe bottom portion is convex in the tire circumferential direction on a plane perpendicular to the sipe depth direction, and has an angle θ (0 ° <θ <180) at a vertex. °), the angle θ decreases from the tread surface of the block-shaped land portion toward the sipe bottom in the sipe depth direction, and the sipe length on the plane The pneumatic tire is characterized by increasing in size. 2. A pneumatic tire having a plurality of sipe-containing block-shaped land portions defined by grooves provided on a tread surface, wherein the sipe is a sipe from a tread surface of the block-shaped land portion to a sipe bottom. It is convex in the tire circumferential direction on a plane orthogonal to the depth direction, and has an angle θ (0 ° <θ <
180 °), and the angle θ decreases from the tread surface of the block-shaped land portion toward the sipe bottom in the sipe depth direction, and the sipe length on the plane The pneumatic tire is characterized by increasing numbers. 3. The block-like land portion has a height of 50% of its height.
The angle θ formed by the V-shaped portion of the sipe exposed on the tread surface of the block-shaped land portion at the time of wear is 60 ° ≦ θ ≦ 170.
3. The pneumatic tire according to claim 1 or 2, wherein