JP2005007919A

JP2005007919A - Pneumatic radial tire for heavy load

Info

Publication number: JP2005007919A
Application number: JP2003170927A
Authority: JP
Inventors: Atsushi Gojo; 淳志五條
Original assignee: Yokohama Rubber Co Ltd
Current assignee: Yokohama Rubber Co Ltd
Priority date: 2003-06-16
Filing date: 2003-06-16
Publication date: 2005-01-13
Anticipated expiration: 2023-06-16
Also published as: JP4234502B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for a heavy load capable of enhancing partial wear resistance without degrading a traction property from a new condition to the end of its life due to wearing. <P>SOLUTION: In the pneumatic radial tire for a heavy load having main grooves 2 extending in the tire circumferential direction and a block 4 demarcated by lug grooves 3 across the main grooves 2, a raised bottom 5 is formed in the lug groove 3 to demarcate the block 4, a notched part 6 with both ends in the width direction open to the main grooves 2 is formed in the boundary between the bottom raised part 5 and the block 4. The notched part 6 and the bottom raised part 5 are formed so that (1) the ratio h/D of the depth h of the notched part 6 from the surface of the block 4 to the depth D of the main groove is set to be 0.5-1.0, (2) the ratio y/Y of the peripheral length y of the bottom raised part 5 to the peripheral length Y of the lug groove 3 is set to be ≥ 0.7 and < 1.0, (3) the ratio x/X of the width x of the bottom raised part 5 to the width X on the lug groove 3 side of the block 4 is set to be 0.5-1.0, and (4) the ratio d/D of the height d of the bottom raised part 5 from the bottom surface of the main groove 2 to the depth D of the main groove is set to be 0.5-0.8. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は重荷重用空気入りラジアルタイヤに関し、さらに詳しくは、新品時から摩耗末期までのトラクション性を低下させることなく耐偏摩耗性を向上させた重荷重用空気入りラジアルタイヤに関する。
【０００２】
【従来の技術】
重荷重用空気入りラジアルタイヤでは、トレッド面にタイヤ周方向の主溝とこれに交差するラグ溝とによりブロックを形成したトレッドパターンが多く使用され、これによりウェットグリップ性やトラクション性を高めるようにしている。しかしながら、ブロックを形成したタイヤは走行時におけるブロックの倒れ込みにより、ブロック表面にヒール・アンド・トウ摩耗と称する偏摩耗が生じ、トラクション性が低下する問題がある。
【０００３】
かかる問題を解消するため、従来から、ラグ溝にプラットフォームを隆起させてブロックの剛性を高めることによりブロックの倒れ込みを防止し、偏摩耗やトラクション性の低下を防止する対策が多数提案されている（例えば、特許文献１参照。）。
【０００４】
【特許文献１】
特開平２−２０４０７号公報
【０００５】
【発明が解決しようとする課題】
しかしながら、何れも新品時から摩耗末期まで初期の性能を維持できるようにしたものはなく、摩耗の進行と共に摩耗中期以降にはトラクション性の低下が見られたり、ブロックの倒れ込みを充分には防止できないなど、対策としては必ずしも充分なものとはいえなかった。
【０００６】
本発明の目的は、かかる従来の問題点を解消し、新品時から摩耗末期に至るまでトラクション性を低下させることなく耐偏摩耗性を向上させるようにした重荷重用空気入りラジアルタイヤを提供することにある。
【０００７】
【課題を解決するための手段】
上記の目的を達成するための本発明の重荷重用空気入りラジアルタイヤは、タイヤ周方向に延びる主溝と該主溝に交わるラグ溝とによって区画されるブロックを有する重荷重用空気入りラジアルタイヤにおいて、前記ブロックを区画する前記ラグ溝に底上げ部を形成し、該底上げ部と前記ブロックとの境界に幅方向の両端部が前記主溝に開放する切り欠き部を形成し、該切り欠き部及び底上げ部を、（１）切り欠き部のブロック表面からの深さｈと主溝の深さＤとの比ｈ／Ｄが０．５〜１．０、（２）底上げ部の周長ｙとラグ溝の周長Ｙとの比ｙ／Ｙが０．７以上、１．０未満、（３）底上げ部の幅ｘとブロックのラグ溝側の幅Ｘとの比ｘ／Ｘが０．５〜１．０、（４）底上げ部の主溝底面からの高さｄと主溝の深さＤとの比ｄ／Ｄが０．５〜０．８、となるように定めたことを特徴とする。
【０００８】
このように、ブロックを区画するラグ溝に底上げ部を形成すると共に、この底上げ部とブロックとの境界に幅方向の両端部が主溝に開放する切り欠き部を形成し、底上げ部及び切り欠き部における寸法比をそれぞれ特定したので、底上げ部がブロック剛性を高めてブロックの倒れ込みを防止して偏摩耗の発生を防止する新品時の機能を摩耗が進行した摩耗中期以降の段階においても維持し、摩耗中期以降は切り欠き部のエッジ効果によりトラクション性の低下を抑制する。
【０００９】
【発明の実施の形態】
以下、添付図面を参照して本発明の実施形態を説明する。各図において、同一の構成要素は同一の符号を付し、重複した説明は省略する。
【００１０】
図１は本発明の重荷重用空気入りラジアルタイヤのトレッド面の一例を示す一部平面図である。重荷重用空気入りラジアルタイヤは、トレッド面１にタイヤ周方向に延びる４本の主溝２と、これに交差するタイヤ幅方向に延びる複数のラグ溝３とにより多数のブロック４を形成している。
【００１１】
ブロック４を区画するラグ溝３には、ブロック４の幅方向中央位置に底上げ部５が形成されている。底上げ部５のブロック４との境界部分には、図２に示すように、幅方向の両端部が主溝２に開放する切り欠き部６が形成され、周方向に隣り合うブロック４、４が切り欠き部６、６を介して底上げ部５に連結されている。このように底上げ部５を形成することにより、ブロック４の剛性が強化され、走行時におけるブロック４の倒れ込みを防いでいる。
【００１２】
本発明の重荷重用空気入りラジアルタイヤは、上記のように底上げ部５と切り欠き部６とを設けたことを基本として、切り欠き部６のブロック４表面からの深さｈと主溝の深さＤとの比ｈ／Ｄが０．５〜１．０に設定されている。このように切り欠き部６を形成することにより、摩耗が進行した段階においても切り欠き部６によるエッジ効果によりトラクション性の低減を抑制する。ｈ／Ｄが０．５未満では摩耗中期以降のトラクション効果が不足し、１．０超では切り欠き部６の底面からトレッド部にクラックが発生する原因となる。
【００１３】
また、底上げ部５の周長ｙとラグ溝３の周長Ｙとの比ｙ／Ｙが０．７以上、１．０未満に設定される。このように設定することによりブロック４の倒れ込み防止効果を確実にする。ｙ／Ｙが０．７未満ではブロック４の倒れ込みが大きくなり偏摩耗の発生を充分に抑制することができない。
【００１４】
上記する底上げ部５は、図３に図１のＢーＢ矢視断面を示すように、ブロック４の幅方向中央部に位置することが望ましく、底上げ部５の幅ｘとブロック４のラグ溝３側の幅Ｘとの比ｘ／Ｘが０．５〜１．０、好ましくは０．７〜１．０となるように設定する。また、底上げ部５の主溝２底面からの高さｄと主溝の深さＤとの比ｄ／Ｄは０．５〜０．８に設定される。このように設定することによりブロック４の倒れ込み防止効果を一層確実にする。ｘ／Ｘ又はｄ／Ｄが０．５未満ではブロック４の倒れ込みを充分支えられず偏摩耗の発生原因となる。また、ｄ／Ｄが０．８超では新品時のトラクション効果が得難くなる。
【００１５】
なお、底上げ部５の総幅が、ブロック４のラグ溝３側の幅Ｘとの関係で上記の範囲内である限りにおいて、底上げ部５を幅方向に２以上に分割して形成することができる。
【００１６】
図１の本発明の重荷重用空気入りラジアルタイヤのトレッド面１には、ラグ溝３がタイヤ幅方向に傾斜する直線状の溝である場合を例示したが、ラグ溝３がヒール・アンド・トウ摩耗の原因となるような曲線状又は折線状の溝である場合にも本発明の構成を適用することができる。
【００１７】
【実施例】
実施例１〜３、比較例１〜３
トレッドパターン（図１）とタイヤサイズ（２９５／７５Ｒ２２．５）を共通にして、ラグ溝に底上げ部を形成しない従来タイヤ（従来例）と、底上げ部と切り欠き部を形成し該底上げ部におけるｈ／Ｄ、ｙ／Ｙ、ｘ／Ｘ、ｄ／Ｄの値をそれぞれ表１のように異ならせた本発明タイヤ（実施例１〜３）及び比較タイヤ（比較例１〜３）とをそれぞれ作製した。
【００１８】
これら７種類のタイヤについて、以下の方法により耐偏摩耗性と新品時及び７５％摩耗時におけるトラクション性を調べ、その結果を従来例を１００とする指数表示により表１に併記した。数値は大きい方が優れていることを示す。
【００１９】
〔耐偏摩耗性評価〕
各タイヤをトラックタイプ（装着車両：６×４）の車両の駆動軸に装着して試験路を３万マイル（４８２７９ｋｍ）走行させ、走行後のタイヤのヒール・アンド・トゥ摩耗の発生状況を調べた。
【００２０】
〔トラクション性評価〕
新品時及び７５％摩耗時における各タイヤをトラックタイプ（装着車両：６×４）の車両の駆動軸に装着して湿潤試験路を走行させ、ドライバーのフィーリングにより評価した。
【００２１】
【表１】

この結果、本発明タイヤは新品時及び７５％摩耗時におけるトラクション性を低下させることなく耐偏摩耗性が向上していることがわかる。
【００２２】
【発明の効果】
上述したように、本発明の重荷重用空気入りラジアルタイヤは、ブロックを区画するラグ溝に底上げ部と共に、この底上げ部とブロックとの境界に幅方向の両端部が主溝に開放する切り欠き部を形成し、底上げ部及び切り欠き部における寸法比をそれぞれ特定したので、底上げ部がブロック剛性を高めてブロックの倒れ込みを防止して偏摩耗の発生を防止する新品時における機能を摩耗が進行した摩耗中期以降の段階においても維持し、摩耗中期以降は切り欠き部のエッジ効果によりトラクション性の低下を抑制する。
【図面の簡単な説明】
【図１】本発明の重荷重用空気入りラジアルタイヤのトレッド面の一例を示す一部平面図である。
【図２】図１のＡ−Ａ矢視断面図である。
【図３】図１のＢーＢ矢視断面図である。
【符号の説明】
１トレッド面２主溝
３ラグ溝４ブロック
５底上げ部６切り欠き部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heavy-duty pneumatic radial tire, and more particularly, to a heavy-duty pneumatic radial tire having improved uneven wear resistance without reducing traction from new to the end of wear.
[0002]
[Prior art]
In heavy-duty pneumatic radial tires, a tread pattern in which a block is formed on the tread surface by a main groove in the tire circumferential direction and a lug groove intersecting this is used to improve wet grip and traction. Yes. However, a tire having a block has a problem that traction is deteriorated due to a partial wear called heel-and-toe wear on the surface of the block due to the collapse of the block during running.
[0003]
In order to solve such a problem, conventionally, a number of measures have been proposed to prevent the block from collapsing by raising the platform in the lug groove and increasing the rigidity of the block, thereby preventing uneven wear and deterioration of traction ( For example, see Patent Document 1.)
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2-20407
[Problems to be solved by the invention]
However, none of them has been able to maintain the initial performance from the new product to the end of wear, and as the wear progresses, the traction performance is lowered and the collapse of the block cannot be prevented sufficiently. As a countermeasure, it was not always sufficient.
[0006]
An object of the present invention is to provide a heavy-duty pneumatic radial tire that eliminates the conventional problems and improves uneven wear resistance without reducing traction from new to the end of wear. It is in.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a heavy-duty pneumatic radial tire of the present invention is a heavy-duty pneumatic radial tire having a block defined by a main groove extending in the tire circumferential direction and a lug groove intersecting the main groove. A bottom raised portion is formed in the lug groove defining the block, and a notch portion in which both end portions in the width direction are opened to the main groove at a boundary between the bottom raised portion and the block is formed. (1) The ratio h / D of the depth h from the block surface of the notch to the depth D of the main groove is 0.5 to 1.0, and (2) the peripheral length y of the bottom raised portion and the lug The ratio y / Y to the circumferential length Y of the groove is 0.7 or more and less than 1.0. (3) The ratio x / X of the width x of the bottom raised portion and the width X on the lug groove side of the block is 0.5 to 1.0, (4) The ratio d / D between the height d of the bottom raised portion from the bottom surface of the main groove and the depth D of the main groove is 0.5. 0.8, and wherein the set things so that.
[0008]
In this way, a bottom raised portion is formed in the lug groove that defines the block, and a notch portion in which both end portions in the width direction are opened to the main groove at the boundary between the bottom raised portion and the block is formed. Since the dimensional ratio in each part is specified, the raised function of the bottom part increases the block rigidity and prevents the block from collapsing to prevent the occurrence of uneven wear. In the middle of the wear, the traction is prevented from lowering by the edge effect of the notch.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. In each drawing, the same constituent elements are given the same reference numerals, and redundant description is omitted.
[0010]
FIG. 1 is a partial plan view showing an example of a tread surface of a heavy duty pneumatic radial tire of the present invention. The heavy-duty pneumatic radial tire forms a large number of blocks 4 on the tread surface 1 by four main grooves 2 extending in the tire circumferential direction and a plurality of lug grooves 3 extending in the tire width direction intersecting therewith. .
[0011]
In the lug groove 3 that partitions the block 4, a bottom raised portion 5 is formed at the center in the width direction of the block 4. As shown in FIG. 2, a notch portion 6 having both ends in the width direction opened to the main groove 2 is formed at a boundary portion between the bottom raised portion 5 and the block 4, and the

blocks

4, 4 adjacent in the circumferential direction are formed. It is connected to the bottom raising part 5 through the

notches

6 and 6. By forming the bottom raised portion 5 in this way, the rigidity of the block 4 is strengthened, and the block 4 is prevented from falling during traveling.
[0012]
The heavy-duty pneumatic radial tire of the present invention is based on the provision of the bottom raised portion 5 and the cutout portion 6 as described above, and the depth h of the cutout portion 6 from the surface of the block 4 and the depth of the main groove. The ratio h / D with the thickness D is set to 0.5 to 1.0. By forming the cutout portion 6 in this way, reduction of traction is suppressed by the edge effect by the cutout portion 6 even at the stage where wear has progressed. If h / D is less than 0.5, the traction effect after the middle stage of wear is insufficient, and if it exceeds 1.0, cracks occur from the bottom surface of the notch 6 to the tread.
[0013]
Further, the ratio y / Y between the circumferential length y of the bottom raised portion 5 and the circumferential length Y of the lug groove 3 is set to 0.7 or more and less than 1.0. By setting in this way, the fall prevention effect of the block 4 is ensured. When y / Y is less than 0.7, the block 4 is greatly collapsed and the occurrence of uneven wear cannot be sufficiently suppressed.
[0014]
The above-described bottom raised portion 5 is preferably located at the center in the width direction of the block 4 as shown in FIG. The ratio x / X to the width X on the 3 side is set to 0.5 to 1.0, preferably 0.7 to 1.0. The ratio d / D between the height d of the bottom raised portion 5 from the bottom surface of the main groove 2 and the depth D of the main groove is set to 0.5 to 0.8. By setting in this way, the effect of preventing the block 4 from falling down is further ensured. If x / X or d / D is less than 0.5, the block 4 cannot be sufficiently tilted down, causing uneven wear. On the other hand, if d / D is more than 0.8, it is difficult to obtain a traction effect when new.
[0015]
In addition, as long as the total width of the bottom raised portion 5 is within the above range in relation to the width X on the lug groove 3 side of the block 4, the bottom raised portion 5 may be formed by being divided into two or more in the width direction. it can.
[0016]
Although the case where the lug groove 3 is a linear groove inclined in the tire width direction is illustrated on the tread surface 1 of the heavy-duty pneumatic radial tire of the present invention in FIG. 1, the lug groove 3 is a heel and toe. The configuration of the present invention can also be applied to a curved or polygonal groove that causes wear.
[0017]
【Example】
Examples 1-3, Comparative Examples 1-3
A conventional tire (conventional example) in which the tread pattern (FIG. 1) and the tire size (295 / 75R22.5) are used in common and the bottom raised portion is not formed in the lug groove, and the bottom raised portion and the cutout portion are formed. The tires of the present invention (Examples 1 to 3) and comparative tires (Comparative Examples 1 to 3) in which the values of h / D, y / Y, x / X, and d / D are different as shown in Table 1 are shown. Produced.
[0018]
About these seven types of tires, the uneven wear resistance and the traction properties at the time of new article and 75% wear were examined by the following method, and the results are also shown in Table 1 by index display with the conventional example as 100. Larger numbers indicate better values.
[0019]
[Evaluation of uneven wear resistance]
Each tire is mounted on the drive shaft of a truck type (equipped vehicle: 6 x 4) and the test road is run for 30,000 miles (48279 km), and the occurrence of heel and toe wear on the tire after running is investigated. It was.
[0020]
[Evaluation of traction]
Each tire when new and 75% worn was mounted on a drive shaft of a truck type (equipped vehicle: 6 × 4) vehicle and traveled on a wet test road, and evaluated by the driver's feeling.
[0021]
[Table 1]

As a result, it can be seen that the tire according to the present invention has improved uneven wear resistance without deteriorating the traction properties when new and 75% worn.
[0022]
【The invention's effect】
As described above, the heavy-duty pneumatic radial tire according to the present invention includes a notch portion in which both end portions in the width direction open to the main groove at the boundary between the bottom raised portion and the block, along with the bottom raised portion in the lug groove defining the block. Since the dimensional ratios of the bottom raised part and the notch part were specified, the bottom raised part increased the block rigidity and prevented the block from collapsing to prevent the occurrence of uneven wear. It is maintained even in the stage after the middle stage of wear, and after the middle stage of wear, the reduction in traction is suppressed by the edge effect of the notch.
[Brief description of the drawings]
FIG. 1 is a partial plan view showing an example of a tread surface of a heavy duty pneumatic radial tire of the present invention.
FIG. 2 is a cross-sectional view taken along the line AA in FIG.
3 is a cross-sectional view taken along line BB in FIG.
[Explanation of symbols]
1 tread surface 2 main groove 3 lug groove 4 block 5 bottom raised portion 6 notch

Claims

In a heavy-duty pneumatic radial tire having a block defined by a main groove extending in the tire circumferential direction and a lug groove intersecting the main groove,
A bottom raised portion is formed in the lug groove defining the block, and a notch portion in which both end portions in the width direction are opened to the main groove at a boundary between the bottom raised portion and the block is formed. A heavy-duty pneumatic radial tire with the following parts:
(1) The ratio h / D of the depth h from the block surface of the notch to the depth D of the main groove is 0.5 to 1.0.
(2) The ratio y / Y between the circumferential length y of the raised bottom portion and the circumferential length Y of the lug groove is 0.7 or more and less than 1.0 (3) The width x of the raised bottom portion and the width X of the block on the lug groove side Ratio x / X of 0.5 to 1.0
(4) The ratio d / D between the height d of the bottom raised portion from the bottom surface of the main groove and the depth D of the main groove is 0.5 to 0.8.