JPH07228109A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To provide a tire which can reduce the abnormal wear to a shoulder land part in a tread. CONSTITUTION:This tire is provided with a shoulder part where a row of peripheral land parts in a block shape which is classified by a peripheral groove 2 and a lug groove 3 is formed at least, and treads consisting of at least two types of blocks where a row of land parts are different from each other in the peripheral length. At a position which is out of place outwards in the axial direction from a contact end, thin grooves or sipes 6 which extend in the roughly peripheral direction are provided for a block 4 whose peripheral length is shorter in the row of land parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for passenger vehicles having a block-shaped row of land portions on a shoulder portion of a tread.

[0002]

2. Description of the Related Art Pneumatic tire treads are
In particular, for the purpose of preventing slippage on a wet road surface, it has a plurality of grooves having a lateral component and a land portion divided by these grooves. In the case of passenger car tires, four to five linear tires are provided at substantially equal intervals, and a large number of lug grooves extending so as to intersect these circumferential grooves are used. Is a rib that extends endlessly only in the central part and the remaining area is an independent block.

On the other hand, it is known that when the tire runs, the tread on the road surface produces noise or noise (pattern noise) due to the vibration of the air discharged from the groove. Of the various grooves applied in the tread design, this noise is a particular problem for lug grooves that extend across the tread. Therefore, usually, a plurality of pitches (2 to 5 types) having different lengths are used, and these pitches are arranged at random in the circumferential direction or with a certain regularity, so-called pitch variation is performed, and thereby specified. It is designed to disperse the frequency of high-pitched sounds and make noise inconspicuous.

[0004]

The noise reduction effect by the pitch variation becomes great by increasing the ratio of the length of the short pitch to the length of the long pitch. In that case, a block having a short circumferential length (hereinafter, referred to as (Abbreviated as short block)
And blocks having a long circumferential length (hereinafter abbreviated as long blocks) are mixed on the circumference of the tread, which is likely to cause abnormal wear or irregular wear. Since the short block has a lower rigidity than the long block, the shoulder block is largely deformed during cornering and braking, and the amount of slippage is increased, so that the short block is easily worn. This is because the amount of wear at the kick-out end of the block at the time of touchdown is greater than the amount of wear at the step-in end, so-called heel-and-toe wear, and the progress of this heel-and-toe wear causes the entire block to be depressed relative to the long block. Polygonal wear where the circumference of the tread has a polygonal shape as a whole,
There is a problem that it spreads in the width direction and develops into diagonal wear. As a result, not only the appearance of wear deteriorates, but also noise and vibration levels deteriorate, making it impossible to exhibit the expected tire performance when new.

A detailed analysis of the progress of wear revealed that when a slip angle was applied to the tire and a braking force was applied, the short block had a low rigidity in the initial stage, so that it collapsed in the front-rear direction, resulting in a more contact with the ground. As the length increases, the axial force and slippage increase, and at the same time, the buttress portion (upper sidewall upper portion) adjacent to the shoulder block flexes laterally, or the compression force that falls due to deformation causes the block to collapse. Is pushed toward the center of the tread, causing heel and toe wear. This tendency is remarkable especially in a tire having a small radius of curvature in the shoulder portion. On the other hand, in the long block, the collapse deformation in the front-rear direction is small, and the change in the ground contact length is small compared to the short block, so the above tendency is small.

It is an object of the present invention to provide a tire that advantageously solves the above problems.

[0007]

According to the present invention, at least a shoulder portion is provided with a block-shaped circumferential land portion row which is divided by a circumferential groove and a lug groove, and the land portion rows have different circumferential lengths. A tire having a tread composed of at least two types of blocks, and a narrow groove extending substantially circumferentially at a position axially outside from a ground contact end of the block having a short circumferential length in the land portion row or A pneumatic tire having a sipe.

Here, when the long block is also provided with the narrow groove or sipe, the short block is larger per volume of the narrow groove or sipe, and the width, the depth and the length of each volume. It is preferable that the buttresses are provided with the narrow groove or the sipe, respectively, by changing them individually or by combining them. In addition, in the buttress portion, it is actually preferable to provide a thin groove or sipe 5 to 15 mm axially outside from the ground contact end.

Further, although the present invention originates from the problem of wear of a tire subjected to pitch variability, the scope of application of the present invention is not limited to this, and in short, it is sufficient that the blocks have different circumferential lengths.

[0010]

According to the present invention, the lateral stress exerted on the block can be alleviated by the narrow groove or the sipe extending in the substantially circumferential direction at a position axially outward from the grounded end of the land portion row. , By arranging this narrow groove or sipe in the short block, or when also arranging in the long block, the narrow groove or sipe volume arranged in the short block is made larger than the narrow groove or sipe volume in the long block. By doing so, the influence of lateral stress on the short block or the long block can be equalized, and abnormal wear such as heel-and-toe wear can be advantageously reduced. And that position is actually in the buttress section,
The lateral stress can be effectively relieved by setting the position apart from the ground contact end in the axially outward direction within a range of 5 to 15 mm and relatively close to the ground contact end.

[0011]

The tire of the present invention will be described below with reference to the drawings. 1 is a sectional view of a tire showing a first embodiment of the present invention, and FIG. 2 is a partial perspective view of a shoulder block in FIG. In FIG. 1, the tread portion 1 is an equatorial plane O
On the other hand, the left half is omitted, but it has a symmetrical cylindrical shape. The tread 1 has a plurality of, in this embodiment, two linear circumferential grooves 2 extending in parallel to each other on one side, and a circumferential groove 2 ₂ , 2 ₁ extending from the position of the equatorial plane O to a grounding end E. The independent blocks 4 ₃ , 4 ₂ and 4 ₁ are divided by a large number of lug grooves 3 ₃ , 3 ₂ and 3 ₁ that are curved and bowed, and the shoulder-land portion row 5 ₁ and intermediate land are arranged from the tread end E side. It forms a row 5 ₂ and a central land row 5 ₃ .

The circumferential groove 2 is located at a position where the tread 1 is substantially equally divided in the axial direction, or when two treads are used on one side of the tread, the groove 2 ₁ near the tread end E as shown in FIG. For the groove 2 ₂ which is provided at the 1/4 point or slightly near the tread edge E, and also near the equatorial plane O, the above-mentioned both grooves 2 ₁ ,
It can be provided so as to divide the central portion divided into. The ground contact end E is the ground contact end when the tire is assembled into a rim and a regular internal pressure and load (JATMA standard) are applied, and is, so to speak, a position that limits the effective width of the tread.

The blocks 4 in the land portion row 5 are subjected to pitch variation at a plurality of pitches having different lengths in the circumferential direction. In this embodiment, in the shoulder block row 51, _one of the circumferential direction (see FIG. block 4 ₁₁ pitch P _1, including lug groove 3 ₁ adjacent to the lower side) on 1, likewise the pitch P ₂ of the blocks 4 ₁₂ comprising lug grooves 3 _1, and the lug 4 ₁₃ comprising lug grooves 3 ₁ The three types of pitches have a length relationship of P ₁ <P ₂ <P ₃ . The relationship between the pitch length, the intermediate block 4 _2,
The same applies to the middle block 4 _3. And the relationship of the circumferential length of each block also follows this. For land row, can be provided with ribs extending endlessly in the circumferential direction in place of the block by dividing lug grooves 3 _3.

[0014] In the present invention, the shoulder - the block 4 ₁₁ included in the short pitch P ₁ of the land row 5 _1, deviated by a predetermined distance v toward axially outward from the ground contact edge E position (v =. 5 to
15 mm) with a narrow groove or sipe for lateral stress relaxation 6 ₁
Shall be provided. If the distance v is too small, the outer side of the narrow groove in the axial direction also comes into contact with the ground to cause step wear. On the other hand, if it is too large, the lateral stress is not sufficiently relaxed, which is not preferable. In this embodiment, the shoulder - no rounded shape side edge portions of the blocks 4 _1, also includes also the depth to the intermediate block 4 ₁₂ different (d _1> d ₂₎ narrow grooves or sipes 6 ₂ As a result, with respect to the long block 4 ₁₃ included in the long pitch p ₃ , the intermediate block 4 ₁₂ and the short block 4 ₁₁ are sequentially relaxed in order to largely relieve the lateral stress. Note it is possible to provide a shallow narrow grooves or sipes than even the depth d ₂ in the long block 4 _13.

FIG. 3 is a perspective view of a shoulder block showing a second embodiment of the present invention. The feature of this embodiment is the shoulder - the short blocks 4 ₁₁ and the intermediate block 4 _{1 2} rows of blocks, the narrow grooves or sipes 6 _1, 6 ₂ has a width w ₁ and w ₂
The point is that each is provided. The width relationship is w ₁ > w ₂ , and the groove depths d are the same. Also in the case of this embodiment, a long block
Although 4 ₁₃ has no narrow groove or sipe, it goes without saying that a narrow groove or sipe narrower than the width of the narrow groove of the intermediate block can be provided.

FIG. 4 is a perspective view of a block showing a third embodiment of the present invention. The feature of this embodiment, the shoulder - provided the short blocks in the land row, the intermediate block, and the long block 4 _11, 4 _12, 4 ₁₃ narrow grooves or sipes ₆₁ each length is different, the 6 _2, 6 ₃ There is a point. The relationship of these narrow grooves is l ₁ > l ₂ > l ₃ contrary to the block length. In the case of this embodiment, the width w and the depth d of the narrow groove are the same.

The depth, width, and length variations of the fine groove or sipe in the present invention have been described above, but these three mixed forms are also effective for side stress relaxation. It is desirable that the smaller the block length, the smaller the groove or the volume of the sipe formed on the block. The narrow grooves 6 may be provided in a zigzag shape or a wavy shape in addition to the straight shape shown in the figure, or may be arranged intermittently in the circumferential extension.

[0018]

[Effect] In order to confirm the effect of the tire of the present invention thus constructed, Examples 1, 2 and 3 shown in FIGS.
As a comparative example, a narrow groove with a uniform width is shouldered on the tire of
For all the short, medium and long blocks in the land row, a comparative test was conducted using an indoor tester for the tires provided over the entire longitudinal direction. In this case, the basic parts other than the narrow groove were commonly applied to each tire as follows. That is, the tire size is 185 / 70R14, the carcass is made of two polyester array radial arrangement plies, the belt layer is made of a non-stretch structure including two steel code plies, and the tread shown in FIG. 1 is used. I was there. Regarding the block length, the ratio of short, medium, and long blocks was set to 8.5: 9.0: 10.5. The details of the fine grooves and the test results are shown in Table 1.

[0019]

[Table 1]

The test method was as follows: A tire was mounted on a rim of 5.5J × 14 size, filled with an internal pressure of 1.9 Kgf / Cm ² , and then 45 to a drum having a safety work stuck on the surface.
It was crimped with a load of 0 Kgf. Then, give the tire a slip angle of 0.5 ° and a braking force of 50 Kgf, and apply 4 at a speed of 50 Km / H.
After running for 00 km, the state of wear after running was compared and evaluated.
In the test, the room temperature was set to 30 ° C.

As shown in the evaluation result column of Table 1, in the tire according to the present invention, the abnormal wear can be advantageously reduced by evenly relieving the stress in the shoulder-land portion row.

[Brief description of drawings]

FIG. 1 is a partial plan view of a tread according to a first embodiment of the present invention.

FIG. 2 is a partial perspective view of the shoulder block in FIG.

FIG. 3 is a perspective view of a shoulder block according to a second embodiment of the present invention.

FIG. 4 is a perspective view of a shoulder block according to a third embodiment of the present invention.

[Explanation of symbols]

 1 Tread portion 2 Circumferential groove 3 Lug groove 4 Block 5 Land row 6 Narrow groove or sipe P Pitch E Grounding end

Claims (6)

[Claims] 1. A tread comprising a block-shaped circumferential land portion row divided by a circumferential groove and a lug groove in at least a shoulder portion, and the land portion row is composed of at least two types of blocks having different circumferential lengths. And a narrow groove or sipe extending substantially in the circumferential direction at a position deviated to the outside in the axial direction from the ground contact end with respect to the block having a short circumferential length in the land portion row. Pneumatic tires. 2. A block having a long circumferential length is also provided with the above-mentioned narrow groove or sipe, and the narrow groove or sipe of the block having a short circumferential length is larger per volume of the narrow groove or sipe. The pneumatic tire according to claim 1, which is characterized in that. 3. The pneumatic tire according to claim 2, wherein the width of the narrow groove or sipe of the block having a short circumferential length is wider than the width of the narrow groove or sipe of the block having a long circumferential length. 4. The depth of the narrow groove or sipe of the block having a short circumferential length is deeper than the depth of the narrow groove or sipe of the block having a long circumferential length.
The pneumatic tire according to the item. 5. The length of the narrow groove or sipe of the block having a short circumferential length is longer than the length of the narrow groove or sipe of the block having a long circumferential length.
The pneumatic tire according to the item. 6. The pneumatic tire according to claim 1, wherein the narrow groove or sipe is provided in the buttress portion.