JP2013052789A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having sipes in rib-like land part, and suppressing the generation of cracks originating from the bottoms of the sipes while securing partial wear resistance.SOLUTION: The pneumatic tire includes the sipes 4 in the rib-like land part 3. The sipes 4 are properly shaped.

Description

  The present invention relates to a pneumatic tire, and more particularly to a heavy duty pneumatic tire.

A tire having one or more rib-like land portions on a tread surface is known. The rib-like land portion has high wear resistance because it has higher rigidity than the block land portion.
However, the rib-like land portion has a problem that uneven wear called river wear, in which the vicinity of the edge is locally worn in the circumferential direction, is likely to occur. This river wear is caused by the lateral force applied to the tire during driving, resulting in a minute step near the edge of the rib. The amount of wear on the edge side of this is larger than the amount of wear on the center side of the rib-like land portion, resulting in uneven wear.

  For example, Patent Document 1 describes a tire in which uneven wear is suppressed while securing traction performance on a wet road surface by providing a sipe having an appropriate shape in a rib-like land portion.

JP 2010-18154 A

  However, the tire of Patent Document 1 has a problem that a rigidity step is generated at the sipe bottom raised to the bottom, and therefore, there is a problem that a crack starting from the sipe bottom raised at the bottom may occur particularly in the middle of wear.

  Accordingly, an object of the present invention is to provide a pneumatic tire capable of suppressing the occurrence of cracks starting from the sipe bottom while ensuring uneven wear resistance in a tire having a sipe in a rib-like land portion. There is to do.

The present invention has been made to solve the above problems, and the gist of the present invention is as follows.
(1) A pneumatic tire having one or more rows of ribs in a tread portion of the tire and having sipes in the rib-like land portion,
The sipe has at least a groove depth at a width direction end portion on a shoulder side smaller than a depth of a remaining portion,
When the tread width direction region where the groove bottom of the sipe is the shallowest is the width direction outer region, and the width direction inner region from the width direction outer region is the width direction inner region,
The pneumatic tire according to claim 1, wherein an inclination angle of the sipe with respect to the tread width direction in the width direction outer region is larger than an inclination angle of the sipe with respect to the tread width direction in the width direction inner region.

  (2) The pneumatic tire according to (1), wherein an inclination angle of the sipe with respect to a tread width direction in the width direction outer region is 10 ° to 60 °.

  (3) The pneumatic tire according to (1) or (2), wherein in the tread width direction region where the groove bottom of the sipe is deepest, the sipe has a flask shape in a circumferential cross section.

(4) The direction of rotation of the tire is specified,
The pneumatic tire according to any one of (1) to (3), wherein in the outer region in the width direction, the sipe is inclined with respect to the tread width direction toward the designated tire rotation direction. .

  ADVANTAGE OF THE INVENTION According to this invention, in the tire which has a sipe in a rib-shaped land part, the pneumatic tire which can suppress generation | occurrence | production of the crack starting from a sipe bottom can be provided, ensuring uneven wear resistance. .

It is a tread development view of the pneumatic tire concerning one embodiment of the present invention. It is sectional drawing and a tread figure of a block for explaining the shape of a sipe. It is a tread for demonstrating the shape of a sipe. It is a schematic diagram for demonstrating the effect of this invention. It is a tread circumferential direction sectional view for explaining a suitable shape of a sipe. It is sectional drawing and tread figure of the block of each tire.

Hereinafter, a pneumatic tire of the present invention (hereinafter referred to as a tire) will be described in detail with reference to the drawings.
FIG. 1 is a developed tread view of a tire according to an embodiment of the present invention.
As shown in FIG. 1, the tire of the present invention has a plurality of circumferential grooves 2 extending in the tread circumferential direction in the tread portion 1, and a plurality of rows of ribs are formed by the circumferential grooves 2 and the tread ends TE. The land part 3 is partitioned. Note that the rib-like land portion includes a land portion continuous in the circumferential direction, a groove and a sipe extending in the width direction, and a portion in which these grooves and sipes are closed at the time of ground contact.
The rib-shaped land portion 3 is provided with a sipe 4 that communicates the two circumferential grooves 2 adjacent to the rib-shaped land portion 3 in the tire width direction. Is divided into a plurality of blocks 5.

Here, as shown in FIG. 2, the sipe 4 has a depth from the tread portion tread surface 6 to the groove bottom 7 of the sipe 4 toward the shoulder side end portion P rather than the end portion on the tire equatorial plane CL side. Is small, that is, the groove bottom 7 on the shoulder side is shallow.
When the width direction region where the groove bottom is the shallowest is the width direction outer region T1, and the remaining width direction region (the region inside the width direction outer region T1) is T2, the sipe 4 is In the width direction outer side area | region T1, it inclines and inclines with the inclination-angle (alpha) (degree) with respect to the tread width direction toward the one direction side of the tread circumferential direction. In the illustrated example, the sipe 4 extends in the tread width direction in the width direction inner region T2 (the inclination angle with respect to the tread width direction is 0 °).
As shown in FIG. 2, the inclination angle α is a boundary when the boundary between the width direction outer region T1 and the width direction inner region T2 is O, and the width direction length of the width direction inner region T1 is a. An angle formed by a straight line connecting the point a / 2 on the outer side in the width direction from O and the outer end point in the width direction of the sipe with respect to the width direction. In addition, the inclination angle b is a width of a straight line connecting a point b / 2 on the inner side in the width direction from the boundary O and the inner end point in the width direction of the sipe when the width direction length of the groove bottom inclined portion is b. An angle made with respect to a direction.
Thus, in the present invention, the inclination angle α (°) with respect to the tread width direction of the sipe 4 in the width direction outer region T1 is equal to the inclination angle β with respect to the tread width direction of the sipe 4 in the width direction inner region T2. It is important that it is larger than (°).
As shown in FIG. 3, the inclination angles α and β are always considered as positive signs and are acute angles.
Hereinafter, the effects of the present invention when the direction of the arrow R in FIGS. 1 and 2 is designated as the rotation direction of the tire and the tire is mounted on the vehicle will be described.

First, by adopting such a configuration and reducing the depth of the sipe 4 provided in the rib-like land portion 3 on the shoulder side, the rigidity of the edge portion 8 on the outer side in the tire width direction of the rib-like land portion 3 is improved.
Therefore, even when a lateral force is greatly applied to the edge portion 8 on the outer side in the tire width direction of the rib-like land portion 3 during cornering traveling, the lateral force can be sufficiently resisted, and the edge portion 8 on the outer side in the tire width direction can be resisted. Slip wear is suppressed.
As a result, the wear difference between the edge portion 8 on the outer side in the tire width direction and the central portion 9 of the rib-like land portion 3 is reduced, and uneven wear can be suppressed.

Further, as schematically shown in FIG. 4A, when the sipe extends in the width direction, the sipe opens in response to an input from the road surface when the tire rolls, and a crack is generated at the bottom of the sipe groove. Or, this may cause the block to break.
On the other hand, in the present invention, as described above, the inclination angle of the sipe with respect to the tread width direction in the width direction outer region T1 is larger than the inclination angle of the sipe with respect to the tread width direction in the width direction inner region T2. For this reason, as schematically shown in FIG. 4B, the sipe has a shape extending in parallel with the input from the road surface, thereby suppressing the sipe from being opened by the input from the road surface. Therefore, generation of cracks from the sipe bottom can be prevented.

Furthermore, as shown in FIG. 2, it is preferable that the minimum depth H1 in the depth of the sipe 4 is in a range of 0.50 to 0.95 times the maximum depth H2.
When the minimum depth H1 is less than 0.50 times the maximum depth H2, the rigidity of the edge portion 8 on the outer side in the tire width direction of the rib-like land portion 3 is sufficiently improved, and uneven wear is suppressed. However, the traction performance on the wet road surface due to the sipe 4 may be lowered.
On the other hand, when the minimum depth H1 exceeds 0.95 times the maximum depth H2, the traction performance on the wet road surface by arranging the sipe 4 is sufficiently secured, but the rib-like land portion 3 Since the rigidity of the edge portion 8 on the outer side in the tire width direction is not sufficiently improved, there is a possibility that uneven wear cannot be effectively suppressed.
From such a viewpoint, it is more preferable that the minimum depth H1 in the depth of the sipe 4 is in a range of 0.60 to 0.85 times the maximum depth H2.

Furthermore, the tire width direction length W1 of the portion having the maximum depth H2 in the sipe 4 may be in a range of 0.1 to 0.9 times the tire width direction length W2 of the rib-like land portion 3. preferable.
When the tire width direction length W1 of the portion having the maximum depth H2 exceeds 0.9 times the tire width direction length W2 of the rib-like land portion 3, the wet road surface by disposing the sipe 4 Although the traction performance at is effectively improved, the rigidity at the edge portion 8 on the outer side in the tire width direction of the rib-like land portion 3 is not sufficiently improved, so that there is a possibility that uneven wear cannot be effectively suppressed.
On the other hand, when the tire width direction length W1 of the portion having the maximum depth H2 is less than 0.1 times the tire width direction length W2 of the rib-like land portion 3, the tire width of the rib-like land portion 3 is as follows. Although rigidity at the edge portion 8 on the outer side in the direction is effectively ensured and uneven wear is suppressed, there is a possibility that the traction performance on the wet road surface due to the sipe 4 is not sufficiently improved.

Furthermore, the tire width direction length W3 of the sipe 4 is preferably 0.80 or more times the tire width direction length W2 of the rib-like land portion 3.
This is because when the length W3 of the sipe 4 in the tire width direction is less than 0.80 times the length W2 of the rib-like land portion 3 in the tire width direction, the traction on the wet road surface even if the sipe 4 is provided. This is because the performance may not be improved sufficiently.
At this time, the depth of the sipe 4 is preferably 0.30 or more times the depth of the circumferential groove 2 sandwiching the rib-like land portion 3.
Because, when the depth of the sipe 4 is less than 0.30 times the depth of the circumferential groove 2 sandwiching the rib-like land portion 3, even if the sipe 4 is provided, the traction performance on the wet road surface is improved. This is because there is a possibility that it will not be improved sufficiently.
When the depths of the two circumferential grooves 2 sandwiching the rib-like land portion 3 are different, the depth of the sipe 4 is 0.30 of the depth of the circumferential groove 2 having a larger depth. It is preferable that it is twice or more.

Here, as shown in FIG. 2, the boundary between the width direction outer side region T1 and the width direction inner side region T2 is defined as O. In the illustrated example, the groove bottom depth is constant in the width direction outer region T1. Further, the width direction inner region T2 has a portion where the groove bottom is inclined and a portion where the depth of the groove bottom is constant.
As shown in FIG. 2, the width direction length of the width direction outer side area | region T1 is set to a, and the width direction length of the part where the groove bottom inclines in the width direction inner side area | region T2 is set to b.
At this time, as described above, the bent portion A (see FIG. 2), which is the starting point at which the sipe 4 is inclined with respect to the tread width direction toward one direction in the tread circumferential direction, is located outward in the width direction around the boundary O. It is preferable to set the range up to a / 2 or up to b / 2 in the width direction centering on O.
It is because it can suppress that a sipe opens by input from a road surface more reliably by setting it as this range.

In order to further extend the sipe 4 in the direction along the direction of the input from the road surface, an angle α (°) at which the sipe 4 is inclined with respect to the tread width direction is
10 ° ≦ α ≦ 60 °
It is preferable to set it as the range.

Furthermore, as shown in FIG. 2, it is preferable that the radius of curvature R of the sipe 4 when viewed from the tread surface at the bent portion A is 4 mm or more.
This is to suppress the cracking of the block land portion starting from the bent portion A by curving with a curvature radius of 4 mm or more.

FIG. 5 is a cross-sectional view in the tread circumferential direction for explaining a preferred sipe shape.
As shown in FIG. 5, in the region of the tread width direction where the groove bottom 7 of the sipe 4 is deepest (the width direction region where the bottom of the sipe is not raised), the sipe 4 has a flask shape (sipe bottom portion) in the circumferential cross section. And a shape in which the groove width is enlarged).
This is because the occurrence of cracks at the sipe bottom can be further suppressed.
In the present embodiment, the sipe is formed in the rib-like land portion, but it is not necessary to form the sipe on the surface. For example, the sipe can be formed on the groove bottom of a shallow groove having a depth of about 2 to 3 mm.

In order to confirm the effect of the present invention, tires according to Invention Examples 1 and 2 having a tread pattern shown in FIG. 1 and having a tire size of 275 / 80R22.5 were manufactured.
As schematically shown in FIG. 6, the tires according to Invention Examples 1 and 2 are provided with a bottom raised portion in the sipe, and the sipe has an inclination angle α with respect to the tread width direction in the outer region in the width direction. It is larger than the inclination angle β with respect to the tread width direction in the inner region in the width direction.
Specifically, the inclination angle α is 20 ° in Invention Example 1 and 45 ° in Invention Example 2.
Further, as a tire according to a comparative example, Invention Example 1 except that an inclination angle α with respect to the tread width direction in the outer region in the width direction is equal to an inclination angle β with respect to the tread width direction in the inner region in the width direction. A tire having the same configuration as that of No. 2 was made on a trial basis.
Furthermore, as a tire according to the conventional example, a tire having the same configuration as that of the comparative example was prepared except that the sipe did not have a bottom raised portion.

For tires according to Invention Examples 1, 2, Comparative Example, and Conventional Example, the sipe width (width extending length) W2 is 20 mm, the sipe thickness (sipe groove width) is 0.7 mm, The groove depth (maximum depth) H2 is 16 mm, which is common.
Further, as shown in FIGS. 2 and 6, the inventive examples 1 and 2 and the comparative example are common in that the width w of the bottom raised portion is 14 mm and the bottom raised width (maximum raised width) d is 3 mm.

The following tests for evaluating tire performance were performed on each of the above tires.
<Wet performance>
The starting acceleration on the test course (wet iron plate road) was evaluated. Expressed as an index when the evaluation result of the tire according to the conventional example is 100, the larger the value, the better the performance.
<Riverwear wear>
Abrasion evaluation was performed by field tests. The occurrence of river wear was confirmed when the wear rate was 70%.
<Sipe bottom crack level>
The degree of occurrence in the field test was visually checked. The visual check was performed when the wear rate was 40%.
The evaluation results of these tests are shown in Table 1 below.

As shown in Table 1, river wear was not generated in the tires according to Invention Examples 1 and 2, whereas river wear was generated in the tires according to the conventional examples.
In the tires according to the conventional example and the comparative example, cracks at the sipe bottom were confirmed, whereas in the tires according to Invention Examples 1 and 2, no cracks were generated.
Furthermore, the tires according to Invention Examples 1 and 2 have the same wet performance as the tires according to the conventional example and the comparative example.
From the above, it can be seen that the tires according to Invention Examples 1 and 2 are comprehensively excellent in uneven wear resistance, crack resistance, and wet performance.

1 tread tread 2 circumferential groove 3 rib-like land 4 sipe 5 block 6 tread tread 7 groove bottom 8 edge 9 block center TE tread edge

Claims (4)

A pneumatic tire having one or more rows of ribs in a tread portion of the tire and having sipes on the rib-like land portion,
The sipe has at least a groove depth at a width direction end portion on a shoulder side smaller than a depth of a remaining portion,
When the tread width direction region where the groove bottom of the sipe is the shallowest is the width direction outer region, and the width direction inner region from the width direction outer region is the width direction inner region,
The pneumatic tire according to claim 1, wherein an inclination angle of the sipe with respect to the tread width direction in the width direction outer region is larger than an inclination angle of the sipe with respect to the tread width direction in the width direction inner region.   2. The pneumatic tire according to claim 1, wherein an inclination angle of the sipe with respect to a tread width direction in the width direction outer region is 10 ° to 60 °.   The pneumatic tire according to claim 1 or 2, wherein the sipe has a flask shape in a circumferential cross section in a region in a tread width direction where the groove bottom of the sipe is deepest. The direction of rotation of the tire is specified,
The pneumatic tire according to any one of claims 1 to 3, wherein in the outer region in the width direction, the sipe is inclined with respect to the tread width direction toward the designated tire rotation direction.

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