JP2000238514A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire improving stability and controllability while driving on a wet road. SOLUTION: In a block 18 of this tire, a sipe 20 comprising a thick and deep central sipe 22 and a plurality of a thin and shallow peripheral sipes 24 is formed. The peripheral sipes 24 stem from both ends of the central sipe 22 in the tire width direction and connects to circumferential direction grooves. Water absorbed by the sipe 20 is drained efficiently through the peripheral sipes 24 out to the circumferential grooves. Further, since the sipe 20 does not deteriorate rigidity of the block 18 because of the thin and shallow peripheral sipes 24, its stability and controllability on a wet road is improved.

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 steering stability when running on a wet road surface.

[0002]

2. Description of the Related Art Conventionally, tread patterns have been used to improve the performance in rainy weather, that is, when running on a wet road surface. The arrangement and design of the grooves in the tire circumferential or width direction of the tread portion improve the performance in rainy weather.

[0003] The major aim is drainage from the tire contact surface, and it is known that the volume of the groove should be increased.

However, an increase in the volume of the groove leads to a decrease in the ground contact area, which lowers the steering stability performance in fine weather.

[0005] Improvements in sipes (narrow grooves) have also been made for the purpose of minimizing the decrease in ground contact area and ensuring drainage.

[0006] The sipes ensure the contact with the road surface by draining water from the block ground surface.

[0007] Therefore, it is considered that drainage is improved by arranging more sipes in the block.

In order to ensure the drainage function, it is desirable that the sipe be connected to the periphery of the block and connected to the groove outside the block to secure a water channel.

However, when many sipes are arranged in a block and all of them are connected to grooves outside the block, the rigidity of the block is greatly reduced.

[0010] This causes a deterioration in the steering stability performance during fine weather and rainy weather.

[0011]

A sufficient drainage effect cannot be obtained if the groove width is reduced.

Further, since the way of inserting the sipe has a very large balance with the rigidity of the block, the contribution to the performance from the time of new article to the time of wear is large.

An object of the present invention is to provide a pneumatic tire capable of satisfying the performance required for a tire by further improving the sipe and further improving the steering stability during running on a wet road surface by further improving the drainage performance. It is in.

[0014]

According to a first aspect of the present invention, there is provided a pneumatic tire in which a plurality of blocks formed by a plurality of main grooves intersecting with each other are provided in a tread, and a sipe is formed in the blocks. The sipe includes a central sipe disposed at a central portion of the block, and a plurality of peripheral sipees branched from the central sipe and extending toward the peripheral edge of the block, wherein at least one peripheral sipe includes the main groove. The central sipe is thicker than the peripheral sipe, the central sipe is deeper than the peripheral sipe, and the number of sipes is set to be larger at the periphery of the block than at the center of the block. It is characterized by having.

In the pneumatic tire according to the first aspect, a plurality of peripheral sipes are branched from a central sipe provided at a central part of the block, and at least one of the peripheral sipes is formed in a main groove outside the block. Because of the connection, the water taken in the central sipe can be sequentially discharged to the main groove, and the drainage of the central sipe can be prevented from lowering.

Since the sipe has a small contribution to the reduction of the block rigidity at the central portion of the block, a central sipe thicker and deeper than the peripheral sipe can be arranged at the central portion of the block, and the drainage efficiency is good.

In addition, since the peripheral sipe is formed thinner and shallower than the central sipe at the peripheral portion of the block, the rigidity of the block can be prevented from lowering, and the ground area can be secured.

If the number of the peripheral sipes is too large, the rigidity of the block is reduced, and the ground area is reduced. Therefore, it is preferable that the number of peripheral sipes per block be suppressed to 8 or less, and 6 More preferably, the number is not more than the number. However, since this number varies depending on the size of the block, it is fundamental to reduce the number so as not to impair the drainage.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the sipe has a thickness of the thickest portion / thickness of the thinnest portion of 1.5 to 5.0. Is within the range.

The thickness dimension of the thickest part / thickness dimension of the thinnest part is less than 1.5, more specifically, the thickness dimension of the central sipe / the thickness dimension of the peripheral sipe is less than 1.5 Is not preferable because the drainage capacity is insufficient.

On the other hand, when the thickness of the thickest portion / thickness of the thinnest portion exceeds 5.0, more specifically, the thickness of the central sipe / the thickness of the peripheral sipe becomes larger. If it exceeds 5.0, the thickness of the central sipe becomes excessively large, and the ground contact area is reduced, so that the steering stability is deteriorated.

Therefore, considering the balance of performance, it is preferable that the thickness of the thickest part / thickness of the thinnest part is in the range of 1.5 to 5.0.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the sipe has a depth of the deepest portion / a depth of the shallowest portion of 2.0 to 2.0.
8.0.

The sipe is preferably the deepest in the vicinity of the center of the block, and the sipe in the peripheral portion must be suppressed to such a depth that the rigidity of the portion is not significantly reduced.

Usually, the depth dimension (maximum) of the sipe is set to be smaller than the depth dimension of the main groove (smaller than the block height dimension). More specifically, the fact that the depth dimension of the shallowest part is less than 2.0 means that the depth dimension of the central sipe / the peripheral dimension of the peripheral sipe is less than 2.0. . That is, the depth of the peripheral sipe becomes excessively large, which is not preferable in terms of the rigidity of the block.

On the other hand, when the depth of the deepest portion / the depth of the shallowest portion exceeds 8.0, more specifically, the depth of the central sipe / the depth of the peripheral sipe becomes 8 If it exceeds 0.0, the drainage capacity is undesirably reduced. Here, the reason why the drainage capacity decreases is that, as described above, the depth dimension (maximum) of the sipe is set smaller than the depth dimension of the main groove (smaller than the block height dimension). Under these conditions, the fact that the depth dimension of the deepest part / the depth dimension of the shallowest part exceeds 8.0 means that the depth dimension of the shallowest part is relatively smaller than the depth dimension of the deepest part. That is, the depth dimension of the peripheral sipe is reduced, and the cross-sectional area of the water passage (the cross-sectional area perpendicular to the longitudinal direction of the peripheral sipe) is reduced.

According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects,
The sipe is characterized by being formed by a blade in which a plurality of bent plate materials are stuck together.

The blade (metal plate provided in the mold for molding the pneumatic tire) required for the sipe of the pneumatic tire according to any one of claims 1 to 3 is obtained by laminating a plurality of bent plate materials. Can be manufactured.

In particular, when the thickness of the metal plate is not locally changed by using a high-pressure press or the like, for example, a bent thin plate material having a constant thickness is bonded, and the portion forming the central sipe and the peripheral sipe are joined together. When the portion to be formed is constituted, the thickness of the portion forming the central portion sipe is obtained by adding the thickness of the portion forming the peripheral portion sipe by the number of the laminated portions. Thereby, a sipe for a pneumatic tire in which the central sipe is thicker than the peripheral sipe can be easily manufactured.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a pneumatic tire according to 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 S).
), And a plurality of blocks 18 defined by a plurality of lateral grooves 16 extending along the tire width direction (arrow L direction and arrow R direction).

Each block 18 has a sipe 20 formed therein.

As shown in FIG. 2 and FIG.
Has a central sipe 22 extending in the tire width direction at the block central portion.

Two peripheral sipes 24 are branched off from both ends of the central sipes 22 in the tire width direction.

As shown in FIGS.
Is a first portion 24A extending along the tire width direction in the present embodiment, and a second portion 24A inclined with respect to the tire width direction.
24B, and is connected to the circumferential groove 14 (not shown in FIGS. 2 and 3).

Here, as shown in FIGS. 2 and 3, the thickness of the central sipe 22 is T1, and the thickness of the peripheral sipe 24 is T2.
When the thickness T1 is greater than the thickness T2, the thickness T1 /
It is preferable that the thickness T2 be in the range of 1.5 to 5.0.

As shown in FIG. 4, when the depth (the deepest portion) of the central sipe 22 is D1 and the depth (the shallowest portion) of the peripheral sipe 24 is D2, the depth D1> the depth D2 And
It is preferable that the depth D1 / the depth D2 be in the range of 2.0 to 8.0.

In the peripheral sipe 24 of the present embodiment, the first portion 24A extending along the tire width direction is set to the deepest at a certain depth (D2), and the second portion 24 following this is set.
B gradually increases in depth toward the central sipe 22. The central sipe 22 has a constant depth (D
1).

FIG. 5 shows an example of a blade 26 for forming the sipe 20.

The blade 26 is formed by arranging blade pieces 28 formed of a metal plate having a constant thickness (T1) bent by a press or the like in opposite directions to each other and fixing a central portion thereof.

Since the blade 26 of the present embodiment can be constructed by combining one type of blade piece 28 formed by pressing or the like, it can be easily manufactured regardless of its relatively complicated shape. (Operation) Next, the operation of the pneumatic tire 10 of the present embodiment will be described. (1) In the pneumatic tire 10 of the present embodiment, since the thick and deep central sipe 22 is provided at the central portion of the block 18, a large amount of water in the ground contact surface when traveling on a wet road surface is absorbed and a large amount of water is absorbed. Can be drained from In addition, since the contribution of the sipe 20 to the reduction of the block rigidity is small in the central portion of the block, the block rigidity is ensured even if the groove depth of the central sipe 22 is increased. (2) Since the peripheral sipe 24 connected to the circumferential groove 14 is connected to the central sipe 22, the water absorbed by the central sipe 22 receives the water from the peripheral groove 14 via the peripheral sipe 24. , The water absorption capacity of the central sipe 22 does not saturate. (3) Thickness T1 / central sipe 2 of central sipe 22
Since the thickness T2 of No. 4 is in the range of 1.5 to 5.0, high steering stability during running on a wet road surface can be obtained.

Here, the thickness T1 of the central sipe 22
If the thickness T2 of the peripheral sipe 24 is less than 1.5, the drainage capacity of the peripheral sipe 24 to the circumferential groove 14 is insufficient, which is not preferable.

On the other hand, the thickness dimension T1 /
When the thickness T2 of the peripheral sipe 24 exceeds 5.0,
The thickness dimension of the central sipe 22 is excessively large, which is not preferable from the viewpoint of securing a ground contact area. (4) Since the depth (the deepest portion) D1 of the central sipe 22 and the depth (the shallowest portion) D2 of the peripheral sipe 24 are within the range of 2.0 to 8.0, the block rigidity and drainage performance are improved. Can be balanced.

If the depth dimension D2 of the central sipe 24 / the depth dimension D2 of the peripheral sipe 24 is less than 2.0, the peripheral sipe 24 will have an excessively large depth, which is undesirable in terms of the rigidity of the block. .

On the other hand, if the depth dimension D2 of the central sipe 24 / the depth dimension D2 of the peripheral sipe 24 exceeds 8.0, the peripheral sipe 24 will be shallow and the drainage capacity will decrease, which is not preferable. .

As described above, the pneumatic tire 10 of the present embodiment can improve the steering stability when traveling on a wet road surface by the operations described in (1) to (4) above. (Test Example) In order to confirm the effect of the present invention, a conventional tire, an example tire to which the present invention was applied, and a comparative example tire were prepared, and a steering stability test on a wet road surface was performed. .

First, in order to confirm that a combination relating to the sipe thickness and the sipe depth was necessary, a test was performed by changing the sipe thickness and the sipe depth, respectively.

Table 1 shows the evaluation score of the steering stability performance by the test driver. The larger the number, the better the performance.

Next, a test was performed by changing the ratio of the maximum sipe thickness (Tmax) to the minimum thickness (Tmin) to see the effect of the sipe thickness change.

Table 2 shows the evaluation score of the steering stability performance by the test driver. The larger the number, the better the performance.

Further, in order to see the effect of the sipe depth change, a test was conducted by changing the ratio between the maximum sipe depth (Dmax) and the minimum sipe depth (Dmin).

Table 3 shows the evaluation score of the steering stability performance by the test driver. The larger the number, the better the performance.

Next, the test tire will be described below.

Conventional example 1 tire: A tire having a pattern (same as the example) and a sipe shape shown in FIG. As shown in FIG. 6, the block 18 is formed with two sipes 30 extending linearly in the tire width direction.

Tires of Comparative Examples 1 to 5, Tires of Examples 1 to 10, Tires of Examples 1-1 to 1-5, Tires of Examples 2-1 to 2-5, Comparative Example 1 -1 and tires of Comparative Example 2-1: tires having a pattern and a sipe shape (having different dimensions) of the above-described embodiment in a tread.

In each of the conventional example, the comparative example and the example, the size of the square block on the center side of the tread is 30 mm (dimension in the tire circumferential direction L) × 30 mm (dimension in the tire width direction W) × height 8
mm, the size of the rectangular block on the shoulder side is 30 mm (tire circumferential dimension L) × 50 mm (tire width dimension W) × height 8 mm, and the circumferential groove width and the lateral groove width are each 5 mm.
mm (see FIGS. 2 and 3 for W and L).

The tire of Conventional Example 1 has a sipe depth of 8 mm,
The sipe width is 1 mm.

The dimensions of the sipe of the square block of the example and the comparative example are as follows: A: 10 mm; B: 15 mm; C: 5 mm;
Is 5 mm.

The dimensions of the sipes of the rectangular blocks of the example and the comparative example are about 16.6 mm for A, 15 mm for B, about 8.3 mm for C, and about 8.3 mm for E.

The thickness and depth of the sipe are different from each other, and the dimensions in each test are as described in the table.

The dimensions W, L, A, B, C, E, T1,
2 and 3 for T2, and FIG. 4 for dimensions D1 and D2.

The tire size of each of the tire of the example, the comparative example and the conventional tire is 205/5.
5R16.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

[Table 3]

As a result of the test, it was confirmed that the tire of the example to which the present invention was applied had improved steering stability during running on a wet road surface as compared with the tires of the conventional example and the comparative example.

The sipe shape formed in the block is
The shape is not limited to the shape described in the embodiment, and may be, for example, a shape as shown in FIGS.

In the embodiment, four peripheral sipes 24 are connected to one central sipes 22. However, the number of peripheral sipes 24 may be six as shown in FIG. As shown in FIG. 8A, the block end side may branch into a plurality.

Here, the sipe 20 formed in the block 18 shown in FIG. 7A is, as shown in FIG.
It is formed by a blade 26 sandwiching a straight blade piece 29 between two blade pieces 28.

In the block 18 shown in FIG. 8A, the two central sipes 22 are connected. As shown in FIG. 8B, the blades 28A and B are combined and joined. 26.

In the embodiment, the peripheral sipe 24 is connected to the circumferential groove 14. However, the present invention is not limited to this, and the peripheral sipe 24 may be connected to the lateral groove 16.

Although the shape of the block 18 in the embodiment is rectangular, it may be triangular, trapezoidal, other polygonal, or the like.

[0073]

As described above, the pneumatic tire of the present invention has the above-described structure, so that the water drainage between the block and the road surface is excellent, and the rigidity of the block is ensured. There is an excellent effect that the steering stability at the time can be improved as compared with the conventional case.

[Brief description of the drawings]

FIG. 1 is a plan view of a tread of a pneumatic tire according to one embodiment of the present invention.

FIG. 2 is an enlarged plan view of a block on the tread center side.

FIG. 3 is an enlarged plan view of a shoulder-side block.

FIG. 4 is a perspective view of a block.

FIG. 5 is a perspective view of a blade forming a sipe.

FIG. 6 is a plan view of a tread of a conventional pneumatic tire.

FIG. 7A is a plan view of a block of a pneumatic tire according to another embodiment, and FIG. 7B is a perspective view of a blade forming a sipe.

FIG. 8A is a plan view of a block of a pneumatic tire according to still another embodiment, and FIG. 8B is a perspective view of a blade forming a sipe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pneumatic tire 12 Tread 14 Circumferential groove (main groove) 16 Lateral groove (main groove) 18 Block 20 Sipe 22 Central part sipe 24 Peripheral part sipe 26 Blade 28 Blade piece (plate material)

Claims (4)

[Claims] 1. A pneumatic tire in which a plurality of blocks formed by a plurality of main grooves crossing each other are provided on a tread, and a sipe is formed in the block, wherein the sipe is a central sipe disposed in a block central portion. And a plurality of peripheral sipe branches from the central sipe and extending toward the block periphery, wherein at least one peripheral sipe is connected to the main groove, and the central sipe is the peripheral The pneumatic tire, wherein the thickness is larger than the partial sipe, the central sipe is deeper than the peripheral sipe, and the number of sipes is set to be larger at the periphery of the block than at the center of the block. 2. The pneumatic device according to claim 1, wherein the sipe has a thickness of the thickest portion / thickness of the thinnest portion in the range of 1.5 to 5.0. tire. 3. The pneumatic device according to claim 1, wherein the sipe has a depth of the deepest portion / a depth of the shallowest portion of 2.0 to 8.0. tire. 4. The pneumatic tire according to claim 1, wherein the sipe is formed by a blade formed by laminating a plurality of bent plate materials.