JP3933495B2 - Pneumatic radial tire - Google Patents

Description

【００２３】
表中、ｈは第一の隆起部５ａの最大高さ、Ｈはタイヤ幅方向中央部に位置するブロック列４ｃを区画する副溝３の最大溝深さ、ａは小ブロック８の大ブロック７上での配設領域、Ｗはショルダーブロック幅、ｂは小ブロック８の高さ、Ｌは大ブロック７の高さをそれぞれ示すものである。
【００２４】
なお、耐ブロックもげ性については、テストコースにて５００００ｋｍ走行した際のブロックもげの有無を観察して評価するとともに、ヒールアンドトウ偏摩性については、室内にて偏摩耗ドラム試験機を用い、タイヤ周方向に見て隣合うブロック同士間において、ヒール部（蹴り出し部）とトウ部（踏み込み部）との間に生じる段差量（ｍｍ）を測定して評価し、ウェット性については、テストコースにてウェットトラクションブレーキング試験により、トレッド部踏面の約７０％摩耗時について評価し、そしてトラクション性については、テストコースにて牽引力試験により、トレッド部踏面の約７０％摩耗時について評価した。
ここでは、耐ブロックもげ性以外に関する評価についての評価指数は、従来例タイヤをコントロール（１００）とし、ヒールアンドトウ偏摩耗性については、指数値が小さいほど優れた結果を示すものとし、ウェット性およびトラクション性については、指数値が大きいほど優れた結果を示すものとした。
なお、ウェット性およびトラクション性については、評価指数が９０以上で市場走行品として十分に耐え得る程度にあるといえる。
以下表２に、各評価結果を示す。
【００２５】
【表２】

【００２６】
表２によれば、実施例タイヤは、タイヤ幅方向中央部におけるブロックもげ性については、他の供試タイヤのいずれに対しても遜色なく優れた結果を示し、また、ショルダーブロック列のヒールアンドトウ偏摩耗性については、他の供試タイヤのいずれと比較しても、格段に優れた結果を示すことが判る。
また、実施例タイヤは、ウェット性およびトラクション性については、市場走行品として十分に耐え得る優れた結果を示すことが判る。
【００２７】
【発明の効果】
かくして、この発明によれば、重荷重用空気入りラジアルタイヤのトレッド部について、トレッドゴムがある程度摩耗した状態にあっても、ウェット性およびトラクション性を急激に低下させず、またタイヤ幅方向中央部でのブロックもげと、ショルダーブロックでのヒールアンドトウ偏摩耗とを、ともに抑制することができる。
【図面の簡単な説明】
【図１】 この発明に従う空気入りラジアルタイヤのトレッド部の一部の展開図である。
【図２】 （ａ）は、図１のＡ−Ａ線上の断面図であり、（ｂ）は、図１のＢ−Ｂ線上の断面図である。
【図３】 従来タイヤのトレッド部の一部の展開図であり、（ａ）はタイヤ新品時の場合、（ｂ）はトレッド７０％摩耗時の場合を示す。
【符号の説明】
１ トレッド部
２ 主溝
３ 副溝
３ａ，３ｂ 副溝の溝底
４ａ〜４ｅ ブロック列
５ 隆起部
５ａ 第一の隆起部
５ｂ 第二の隆起部
６ 周方向細溝
７ 大ブロック
８ 小ブロック
ａ 小ブロックの幅
ｂ 小ブロックの高さ
Ｈ ブロック列４ｃを区画する副溝３の最大溝深さ
ｈ 第一の隆起部の最大高さ
Ｌ 大ブロックの高さ
Ｗ ショルダーブロック幅[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire, and in particular, the tread portion of a heavy-duty pneumatic radial tire does not rapidly reduce wetness and traction even when the tread rubber is worn to some extent. In addition, the block baldness at the center portion in the tire width direction and the heel and toe uneven wear at the shoulder block are both suppressed.
[0002]
[Prior art]
Conventionally, as a tread pattern employed in a heavy-duty pneumatic radial tire, a rib pattern in which a land portion is defined by only a plurality of grooves extending substantially in the tire circumferential direction and a plurality of grooves extending substantially in the tire circumferential direction A block pattern in which a land portion is partitioned into a plurality of blocks by a plurality of grooves and a plurality of grooves extending substantially in the tire width direction is typical.
[0003]
In recent years, as with other pneumatic tires, both heavy-duty pneumatic tires ensure both block edge components in the tire front-rear direction and block edge components in the tire width direction to improve wettability and traction. For example, a raised portion 11 having a flat upper surface at the bottom of each sub-groove 10 extending in the tire width direction (a hatched line in FIG. 3 (a)), for example, as in the block pattern shown in FIG. A pattern has been proposed which comprises a portion (showing the upper surface of the raised portion).
[0004]
When the tire having such a block pattern is new as shown in FIG. 3 (a), it realizes excellent wet properties and traction properties as the original characteristics of the block pattern. When the tread portion tread shown in FIG. 3b is worn at about 70% wear, the upper surface of the raised portion 11 shown by hatching in FIG. 3A is exposed, and adjacent blocks in the tire circumferential direction are connected to form a block. By changing to a substantial rib, it is possible to suppress raised block block flaking and block uneven wear.
[0005]
[Problems to be solved by the invention]
In a tire having such a pattern, as described above, since the structure is based on a block pattern, when the tire is new, it can realize excellent wettability and traction, but the tread. When the rubber is worn to some extent, the ridge 11 shown in FIG. 3 (a) is not modified in any way and its upper surface is usually flat. May be exposed all at once, and a new problem that does not become a problem with tires that do not have ridges, such as a drastic decrease in wetness and traction, has emerged. The wettability and traction properties should not be drastically reduced until the end of tread rubber wear. It had been.
[0006]
Further, in the tire having the above pattern, block flaking is more likely to occur in the center portion of the tread than in the past due to off-road driving that is becoming increasingly severe today, and therefore it is possible to sufficiently prevent the occurrence of block flaking. It was requested.
[0007]
And in the tire having the above pattern, due to the above-mentioned severe off-road running, heel and toe uneven wear is likely to occur in the tread shoulder portion as compared with the conventional one, and thus the heel and toe uneven wear is reduced. Was also requested.
[0008]
The present invention has been made in view of these demands, and the object of the present invention is that even if the tread rubber is worn to some extent, the wettability and traction property do not rapidly deteriorate, and it is severe. The present invention also proposes a pneumatic radial tire that sufficiently prevents block flaking from occurring in the center portion of the tread, and reduces heel and toe uneven wear at the tread shoulder portion even during off-road driving.
[0009]
[Means for Solving the Problems]
In the pneumatic radial tire of the present invention, at least three main grooves extending in the tire circumferential direction are disposed in the tread portion, and a plurality of tires that intersect with the main grooves and extend in the tire width direction are provided. In the pneumatic radial tire in which the sub-grooves are arranged to divide four or more block rows, and a raised portion is provided at the groove bottom of each sub-groove that divides each block row, the shoulder located at the outermost edge of the tread Provided at the groove bottom of the sub-groove that defines the block row other than the block row is a first raised portion that connects blocks adjacent in the tire circumferential direction, and this first raised portion is within a cross section along the sub-groove. , A shape substantially in the shape of a bowl, and the maximum height of the raised portion is 0.2 to 0.5 times the maximum groove depth of the auxiliary groove, on the groove bottom of the auxiliary groove defining the shoulder block row, Connect adjacent blocks in the tire circumferential direction A second bulge is provided, and the second bulge is made higher in the cross section along the sub-groove than the tread edge side compared to the tread central part side, and is mounted on a large trapezoidal block. The small block is mounted on the tread edge side portion of the large block and has a width of 0.2 to 0.5 times the shoulder block width. At the same time, the height of the small block is 0.2 to 1.0 times the height of the large block.
Here, the shoulder block row means a block row formed closest to the tread edge among the block rows partitioned by grooves extending substantially in the tire circumferential direction on the tread surface, and the shoulder block width is In the tread shoulder, it means the block width measured in parallel with the road surface at the groove bottom position of the groove extending almost in the tire width direction, and the small block width means the width measured on the large block. .
[0010]
In general, a plurality of main grooves extending substantially in the tire circumferential direction and a plurality of sub-grooves extending substantially in the tire width direction are arranged in the tread portion to partition the block row. In the pneumatic radial tire, the block edge component in the tire front-rear direction and the block edge component in the tire width direction can both be ensured, thus realizing excellent wetness and traction. However, as described above, it is important that these characteristics are not drastically reduced even at the end of wear of the tread rubber.
Of the influence of block edge components on these wet and traction properties, the influence of the edge component of the block located in the center portion of the tire width direction such as the center block is particularly large, and therefore this is located in the center portion of the tire width direction. It is important that the edge component of the block is not rapidly reduced even at the end of the tread rubber wear. According to the present invention, the groove bottom of the sub-groove that defines the block row other than the shoulder block row located at the outermost edge of the tread. By providing a first raised portion that connects blocks adjacent to each other in the tire circumferential direction, the shape of the first raised portion is substantially a bowl-like shape in the cross section along the sub-groove, At the end of the tread rubber wear, it is possible to gradually expose the surface of the first raised part, and the wetness and traction characteristics are sharp. It is possible to prevent the bottom.
On the contrary, in the above cross section, when the shape of the first raised portion is, for example, substantially trapezoidal, the surface of the first raised portion is strongly exposed at a stroke at the end of wear of the tread rubber, For this reason, since wet property and traction property will fall rapidly, it is unpreferable.
[0011]
In addition, in order to solve the problem of block peeling of the center block and the like during off-road driving, which is one of the problems of the present invention, the blocks constituting the center block row and the like require a considerable block rigidity. However, according to the present invention, the maximum height of the first raised portion is set to 0.2 times or more the maximum groove depth of the sub-groove, thereby sufficiently securing the height of the first raised portion. Thus, the block rigidity of the center block row or the like can be sufficiently secured, and the block peeling can be sufficiently prevented.
On the other hand, if the height of the first raised portion is too high, the first raised portion will be exposed at an early stage due to wear of the tread rubber. According to the present invention, the maximum height of the first raised portion is 0.5 times or less of the maximum groove depth, resulting in wear on the tread rubber. This does not lead to early exposure of the first raised portion, and thus can sufficiently prevent the wetness and traction from being deteriorated early.
[0012]
In order to solve the other problem of the present invention, that is, to reduce the uneven heel and toe wear enough to withstand even the increasingly severe off-road driving today, as a result of applicant's earnest research, It has been found that it is particularly advantageous to increase the block rigidity of the block row, and in particular, to increase the block rigidity on the tread edge side of each block constituting the shoulder block row to suppress the slippage at the time of kicking. According to the present invention, the second raised portion that connects the adjacent blocks in the tire circumferential direction is provided at the groove bottom of the auxiliary groove that defines the shoulder block row, and the shape of the second raised portion is Within the cross-section along the sub-groove, the tread edge side is made higher than the tread center side, and the trapezoidal large block is mounted on the trapezoidal large block. Moreover, the arrangement area of the small block is on the tread edge side portion of the large block, and is an area having a width of 0.2 to 0.5 times the shoulder block width. On the premise of increasing the block rigidity of the shoulder block row by setting it to 0.2 to 1.0 times the height, especially by increasing the block rigidity on the tread edge side of the shoulder block, it is becoming increasingly severe today Heel and toe uneven wear can be reduced to such an extent that it can withstand even during road running.
[0013]
As described above, according to the present invention, the optimization of the shape of the first raised portion prevents the wet property and the traction property from rapidly decreasing at the end of wear of the tread rubber, and optimizes the height of the first raised portion. The block located at the center in the tire width direction during off-road driving sufficiently prevents block peeling and reduces the heel and toe uneven wear by optimizing the structure of the second ridge. All can be realized.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a part of a tread surface of a pneumatic radial tire according to the present invention. In the tread portion 1, four main grooves 2 extending substantially in the tire circumferential direction are disposed. A plurality of sub-grooves 3 intersecting with the main grooves 2 and extending substantially in the tire width direction are arranged to partition the five block rows 4a to 4e, and the sub-grooves partitioning the block rows 4a to 4e. 3 Each of the groove bottoms is provided with a raised portion 5 (indicated by hatching in the figure).
In addition, although the circumferential direction fine groove 6 was provided in the center part of the tread part tread surface separately from the said four main grooves 2, this fine groove 6 is contained in the groove | channel which divides a block row here. Absent.
[0015]
FIG. 2A is a cross-sectional view taken along line AA in FIG.
[0016]
In FIG. 2 (a), the main groove 2 extending substantially in the tire circumferential direction (direction perpendicular to the paper surface in FIG. 2 (a)) intersects with the main groove 2, and the tire width direction (FIG. 2 (a)). In the right and left directions of the paper surface), the block row 4c is defined, and the first ridge is connected to the groove bottom 3a of the sub groove 3 and adjacent blocks in the tire circumferential direction. A portion 5 a is provided, and the shape of the first raised portion 5 a is a substantially bowl-like shape in the cross section along the auxiliary groove 3, and the maximum height h of the first raised portion 5 a is set to the auxiliary groove 3. The maximum groove depth H is 0.2 to 0.5 times.
[0017]
According to such a pneumatic radial tire, the shape of the first raised portion 5a provided in each of the groove bottoms 3a of the sub-groove 3 is formed in a substantially bowl-like shape in the cross section along the sub-groove 3. This makes it possible to gradually expose the surface of the first raised portion 5a even in the last stage of wear of the tread rubber, thereby preventing a sudden decrease in wetness and traction, and the first By ensuring that the maximum height h of the raised portion 5a is 0.2 times or more the maximum groove depth H of the sub-groove 3, sufficient block rigidity is ensured by sufficiently securing the height of the first raised portion 5a. By ensuring that the maximum height h of the first raised portion 5a is 0.5 times or less the maximum groove depth H of the secondary groove 3, First raised part 5 due to tread rubber wear Without causing premature exposure, early reduction in wet resistance and traction properties can be sufficiently prevented.
In the example shown in FIG. 1, the block rows 4 b and 4 d adjacent to both sides in the tire width direction of the block row 4 c defined by the sub-groove 3 described as A-A are also included in the block rows 4 b and 4 d. The structure of the 1st protruding part 5a arrange | positioned in the subgroove 3 which divides 4d is the same as the structure of the 1st protruding part 5a shown to Fig.2 (a).
[0018]
FIG. 2B is a cross-sectional view along the line BB in FIG.
[0019]
In FIG. 2B, the main groove 2 extending in the tire circumferential direction (direction perpendicular to the paper surface in FIG. 2B) intersects the main groove 2, and the tire width direction (paper surface in FIG. 2B). The left and right direction) are provided with auxiliary grooves 3 extending to define shoulder block rows 4a and 4e, and in the tire circumferential direction on the groove bottom 3b of the auxiliary grooves 3 that define the shoulder block rows 4a and 4e. A second raised portion 5b for connecting adjacent blocks is provided, and the shape of the second raised portion 5b is within the cross section along the sub-groove 3 (on the right side in FIG. 2 (b)). The side of the tread is made higher than the side of the central portion of the tread (left side in the figure), and the trapezoidal small block 8 is mounted on the trapezoidal large block 7. The shoulder block on the tread edge side portion 7a of the large block 7 With a region having a width of 0.2 to 0.5 times the W, the height b of the small block 8 0.2-1.0 times the height L of the large block 7. In addition, in FIG.2 (b), although the case where the 1st block 7 and the small block 8 which comprise the 2nd protruding part 5b are comprised by another member is shown, it can also comprise integrally with the same member. .
[0020]
According to such a pneumatic radial tire, on the premise of increasing the block rigidity of the shoulder block rows 4a and 4e, particularly by increasing the block rigidity on the tread edge side of the shoulder block, under off-road driving which is becoming increasingly severe today. Heel and toe uneven wear can be reduced to such an extent that it can sufficiently withstand.
[0021]
【Example】
Next, the applicant actually made a test tire and evaluated the block baldness resistance at the center in the tire width direction, the heel-and-toe uneven wear resistance of the shoulder block, the wetness and the traction property. explain.
All of the test tires are pneumatic radial tires for heavy loads with a tire size of 295 / 80R22.5. Applicable rim, filling air pressure and load load conform to ETRTO, conventional tires, comparative tires 1 to 7 and implementation Each of the example tires had the specifications shown in Table 1, and the other tires had the same structure as that of a normal pneumatic radial tire.
Table 1 shows specifications relating to the raised portions 5a and 5b of each of the test tires.
[0022]
[Table 1]

[0023]
In the table, h is the maximum height of the first raised portion 5 a, H is the maximum groove depth of the sub-groove 3 that defines the block row 4 c located at the center in the tire width direction, and a is the large block 7 of the small block 8. The upper arrangement area, W is the width of the shoulder block, b is the height of the small block 8, and L is the height of the large block 7.
[0024]
The block peeling resistance is evaluated by observing the presence or absence of block peeling when running on the test course at 50,000 km, and the heel and toe uneven wear resistance is measured using an uneven wear drum tester indoors. Measures and evaluates the amount of step (mm) between the heel part (kicking part) and the toe part (stepping part) between adjacent blocks as seen in the tire circumferential direction. The course was evaluated for about 70% wear on the tread surface by a wet traction braking test, and the traction property was evaluated for about 70% wear on the tread section by a traction test on the test course.
Here, the evaluation index for evaluations other than the block peeling resistance is that the conventional tire is the control (100), and the heel and toe uneven wear performance is better as the index value is smaller. As for the traction property, the larger the index value, the better the result.
In addition, about wet property and traction property, it can be said that the evaluation index is 90 or more and it can be sufficiently endured as a market running product.
Table 2 below shows each evaluation result.
[0025]
[Table 2]

[0026]
According to Table 2, the example tires showed excellent results comparable to any of the other test tires in terms of block flaking at the center in the tire width direction. It can be seen that the toe uneven wear property shows significantly superior results compared to any of the other test tires.
Moreover, it turns out that an Example tire shows the outstanding result which can fully endure as a market running goods about wet property and traction property.
[0027]
【The invention's effect】
Thus, according to the present invention, even if the tread rubber is worn to some extent with respect to the tread portion of the heavy-duty pneumatic radial tire, the wet property and the traction property are not drastically reduced, and the tire width direction central portion is not affected. Both block baldness and uneven heel and toe wear on the shoulder block can be suppressed.
[Brief description of the drawings]
FIG. 1 is a development view of a part of a tread portion of a pneumatic radial tire according to the present invention.
2A is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line BB in FIG.
FIG. 3 is a development view of a part of a tread portion of a conventional tire, where (a) shows a case when the tire is new, and (b) shows a case when the tread is 70% worn.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tread part 2 Main groove 3 Subgroove 3a, 3b Groove bottoms 4a-4e of subgroove Block row 5 Raised part 5a First raised part 5b Second raised part 6 Circumferential narrow groove 7 Large block 8 Small block a Small Block width b Small block height H Maximum groove depth h of sub-groove 3 that defines block row 4c Maximum height of first raised portion L Large block height W Shoulder block width

Claims (1)

At least three main grooves extending substantially in the tire circumferential direction are disposed in the tread portion, and a plurality of sub grooves extending substantially in the tire width direction are disposed so as to intersect with the main grooves. In the pneumatic radial tire which divides the block row more than the row, and has a raised portion at the groove bottom of each of the sub grooves which divide each block row,
A first ridge for connecting adjacent blocks in the tire circumferential direction is provided at the groove bottom of the secondary groove that defines a block row other than the shoulder block row located at the outermost edge of the tread. In the cross-section along the sub-groove, it has a substantially bowl-shaped shape, and the maximum height of the raised portion is 0.2 to 0.5 times the maximum groove depth of the sub-groove,
A second ridge is provided at the groove bottom of the secondary groove that divides the shoulder block row to connect blocks adjacent in the tire circumferential direction. The part side is made higher than the center part of the tread, and a trapezoidal small block is mounted on the large trapezoidal block. The small block is arranged on the tread edge side of the large block. And a region having a width of 0.2 to 0.5 times the width of the shoulder block, and the height of the small block is 0.2 to 1.0 times the height of the large block. Radial tire.

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