JP5452386B2 - Pneumatic tire - Google Patents

Pneumatic tire Download PDF

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JP5452386B2
JP5452386B2 JP2010141315A JP2010141315A JP5452386B2 JP 5452386 B2 JP5452386 B2 JP 5452386B2 JP 2010141315 A JP2010141315 A JP 2010141315A JP 2010141315 A JP2010141315 A JP 2010141315A JP 5452386 B2 JP5452386 B2 JP 5452386B2
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tire
land portion
width
central
rib
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達也 冨田
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Bridgestone Corp
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本発明は、トレッド部に、タイヤの周方向及び幅方向に沿う溝により区画された複数の陸部を備える空気入りタイヤにおいて、タイヤの接地時の陸部の変形に起因した摩耗を有利に低減しようとするものであり、特に車両の駆動輪に装着して好適な空気入りタイヤに関するものである。   The present invention advantageously reduces wear caused by deformation of a land portion when the tire contacts the ground in a pneumatic tire having a plurality of land portions defined by grooves along the circumferential direction and the width direction of the tire in a tread portion. In particular, the present invention relates to a pneumatic tire suitable for being mounted on a driving wheel of a vehicle.

従来から、タイヤのトレッド部に、タイヤ周方向に沿って延びる複数本の周方向主溝を配設してリブを形成し、このリブをタイヤ幅方向に沿う向きに分断して小陸部とするリブパターンのタイヤが使用されている（特許文献１、２参照）。リブパターンのタイヤは排水性に優れるとともに高速での使用に適しており、乗用車用タイヤに限らず、モノレール等の軌道走行車両用タイヤとしても広く採用されている。   Conventionally, a plurality of circumferential main grooves extending along the tire circumferential direction are provided on the tread portion of the tire to form a rib, and the rib is divided in a direction along the tire width direction to form a small land portion. Rib pattern tires are used (see Patent Documents 1 and 2). Rib pattern tires are excellent in drainage and suitable for high-speed use, and are widely used not only for passenger car tires but also for track running vehicles such as monorails.

特開２００４−３１４７８７号公報JP 2004-314787 A 特開２００８−２０７６５９号公報JP 2008-207659 A

ところで、一般にタイヤはトレッド部に曲率を持つため、タイヤ幅方向に径差の分布が生じる。この径差によって上記小陸部に生じるタイヤ周方向の剪断変形は、タイヤの耐摩耗性能に影響を及ぼすことが知られている。この剪断変形を防止するためには、例えば陸部の大きさを大きくして剪断剛性（剪断方向の剛性）を高めることが有効であるが、陸部の大きさを大きくし過ぎると、図１（ａ）、（ｂ）で比較して示すように（図１（ｂ）に対して図１（ａ）は陸部が大きくなっている）、陸部が路面に接地する際に、ゴムが流動によってより大きく膨出して陸部の剪断変形が増大し、逆に十分な耐摩擦性能が得られなくなる場合がある。特に乗用車等の駆動輪に装着したタイヤにおいては、駆動力の影響により陸部の変形がより大きくなって摩耗量が増えることがあり、未だ改善の余地が残されていた。   By the way, since a tire generally has a curvature in a tread portion, a distribution of a diameter difference occurs in the tire width direction. It is known that the shear deformation in the tire circumferential direction generated in the small land portion due to the diameter difference affects the wear resistance performance of the tire. In order to prevent this shear deformation, it is effective to increase the shear rigidity (shear direction rigidity) by increasing the size of the land portion, for example. However, if the size of the land portion is too large, FIG. As shown in comparison with (a) and (b) (FIG. 1 (a) is larger in the land portion than in FIG. 1 (b)), when the land portion contacts the road surface, the rubber is In some cases, the bulge is larger due to the flow and shear deformation of the land portion is increased, and conversely, sufficient friction resistance is not obtained. In particular, in tires mounted on driving wheels such as passenger cars, the deformation of the land portion becomes larger due to the influence of the driving force and the amount of wear increases, and there is still room for improvement.

本発明の課題は、トレッド部に、タイヤの周方向及び幅方向に沿う溝により区画された複数の陸部を備える空気入りタイヤにおいて、タイヤの接地時の陸部の変形に起因した摩耗を有利に低減しようとするものであり、特に車両の駆動輪に装着して好適な新規な空気入りタイヤを提供することにある。   An object of the present invention is to provide a pneumatic tire having a plurality of land portions that are partitioned by grooves along the circumferential direction and the width direction of the tire in the tread portion, and is advantageous for wear caused by deformation of the land portion when the tire contacts the ground. In particular, it is an object of the present invention to provide a novel pneumatic tire suitable for being mounted on a driving wheel of a vehicle.

本発明は、トレッド部に、タイヤの回転する向きに沿う複数本の周溝によって区画されたリブを有する空気入りタイヤにおいて、
前記リブは、タイヤの幅方向の中央域に位置し、前記リブをタイヤの回転する向きに間隔をおいて分断して短尺陸部（以下、中央陸部という）の集合体を形成する複数本の細溝を備えた中央リブと、前記中央リブを両側に挟み、前記リブをタイヤの回転する向きに間隔をおいて分断して短尺陸部（以下、ショルダー陸部という）の集合体を形成する複数本のラグ溝を備えたショルダーリブからなり、
前記中央陸部は、
接地面の面積が、４５０ｍｍ２以下であり、
タイヤの回転する向きに沿う寸法（以下、長さという）が、前記周溝の溝幅の１．５倍以上であってかつ前記ショルダー陸部の長さよりも短く、
タイヤの幅方向に沿う寸法（以下、幅という）が、前記ショルダー陸部の幅よりも短い、ことを特徴とする空気入りタイヤである。 The present invention provides a pneumatic tire having ribs defined by a plurality of circumferential grooves along a rotating direction of the tire in a tread portion.
The ribs are located in a central region in the width direction of the tire, and a plurality of ribs that divide the ribs at intervals in the rotation direction of the tire to form an aggregate of short land portions (hereinafter referred to as central land portions). A central rib with a narrow groove and a central portion of the central rib on both sides, and the rib is divided at intervals in the direction of rotation of the tire to form a short land portion (hereinafter referred to as a shoulder land portion). Consisting of shoulder ribs with multiple lug grooves
The central land portion is
The area of the ground plane is 450 mm 2 or less,
The dimension along the direction of rotation of the tire (hereinafter referred to as length) is 1.5 times or more the groove width of the circumferential groove and shorter than the length of the shoulder land portion,
The pneumatic tire is characterized in that a dimension along the tire width direction (hereinafter referred to as a width) is shorter than a width of the shoulder land portion.

前記細溝の溝幅が、０．２〜１．０ｍｍであることが好ましい。   It is preferable that the narrow groove has a groove width of 0.2 to 1.0 mm.

前記中央リブは、タイヤの幅方向中心から該中央リブの幅端に至るまでの寸法が、前記タイヤの幅方向中心から前記トレッド部の幅端に至るまでの寸法の２０〜４０％になることが好ましい。   The dimension between the center rib in the width direction of the tire and the width end of the center rib is 20 to 40% of the dimension from the center in the width direction of the tire to the width end of the tread portion. Is preferred.

前記中央リブの幅が、１０〜２０ｍｍであることが好ましい。   It is preferable that the width of the central rib is 10 to 20 mm.

トレッド部にタイヤの幅方向の中央域に位置する中央陸部と、タイヤの幅方向外側両端に位置するショルダー陸部を形成し、中央陸部の接地面の面積が、４５０ｍｍ２以下であり、中央陸部の長さが、周溝の溝幅の１．５倍以上であってかつショルダー陸部の長さよりも短く、中央陸部の幅が、ショルダー陸部の幅よりも短くなるようにしたので、中央陸部においては、陸部の大きさの最適化と陸部のタイヤ周方向の近接配置によってゴム流動量の増加による剪断変形が抑えられるとともに、ショルダー陸部においては、中央陸部よりも大きい陸部を配置して高い剪断剛性で径差による剪断変形を抑制することができ、タイヤの耐摩耗性能を向上させることが可能となる。 The tread portion is formed with a central land portion located in a central region in the tire width direction and a shoulder land portion located at both outer ends in the width direction of the tire, and the area of the ground contact surface of the central land portion is 450 mm 2 or less, The length of the central land is 1.5 times the groove width of the circumferential groove and shorter than the length of the shoulder land, and the width of the central land is shorter than the width of the shoulder land. Therefore, in the central land portion, shear deformation due to an increase in the rubber flow rate is suppressed by optimizing the size of the land portion and the proximity of the land portion in the tire circumferential direction, and in the shoulder land portion, the central land portion A larger land portion can be arranged to suppress shear deformation due to a difference in diameter with high shear rigidity, and the wear resistance performance of the tire can be improved.

中央陸部を形成する細溝の溝幅を０．２〜１．０ｍｍとしたので、中央陸部の剪断変形をより有利に抑制することができる。   Since the groove width of the narrow groove forming the central land portion is 0.2 to 1.0 mm, the shear deformation of the central land portion can be more advantageously suppressed.

中央リブのタイヤの幅方向中心から該中央リブの幅端に至るまでの寸法が、前記タイヤの幅方向中心から前記トレッド部の幅端に至るまでの寸法の２０〜４０％になるようにしたので、タイヤの幅方向に応じて陸部の大きさを最適化することができ、剪断変形の抑制をより効果的に図ることができる。   The dimension from the center of the tire in the width direction of the center rib to the width end of the center rib is 20 to 40% of the dimension from the center of the tire in the width direction to the width end of the tread portion. Therefore, the size of the land portion can be optimized according to the width direction of the tire, and the shear deformation can be more effectively suppressed.

中央陸部の幅を１０〜２０ｍｍとすることで陸部の大きさがより最適化され、タイヤの性能を確保しつつ耐摩耗性能を十分に向上させることができる。   By setting the width of the central land portion to 10 to 20 mm, the size of the land portion is further optimized, and the wear resistance performance can be sufficiently improved while ensuring the performance of the tire.

陸部の大きさと陸部の剪断変形の関係を示した図であり、（ａ）に対して（ｂ）は、陸部の大きさが小さい場合の剪断変形の状態を示す図である。It is the figure which showed the relationship between the magnitude | size of a land part and the shear deformation of a land part, (b) with respect to (a) is a figure which shows the state of the shear deformation in case the magnitude | size of a land part is small. 本発明にしたがう空気入りタイヤの実施の形態につき、（ａ）はタイヤのトレッドパターンを示す平面展開図であり、（ｂ）は中央陸部の幅Ｗａ２と中央陸部の高さＨａ２とを示す図である。(A) is a plan development view showing a tread pattern of a tire according to an embodiment of a pneumatic tire according to the present invention, and (b) shows a width Wa 2 of the central land portion and a height Ha 2 of the central land portion. FIG. 中央陸部の長さ及び幅と中央陸部の膨出変形との関係を示した図である。It is the figure which showed the relationship between the length and width of a central land part, and the bulging deformation of a central land part. （ａ）は、タイヤ周方向の断面において、タイヤに駆動力が入力した際のクラウン部に配置した前記ベルトの変形による陸部の剪断変形を模式的に示した図であり、（ｂ）は、このときの細溝での陸部の剪断変形を模式的に示した図である。(A) is the figure which showed typically the shear deformation of the land part by the deformation | transformation of the said belt arrange | positioned in the crown part at the time of a driving force input into a tire in the cross section of a tire circumferential direction, (b) It is the figure which showed typically the shear deformation of the land part in the narrow groove at this time. 陸部のアスペクト比ＢＡｓと陸部の剪断剛性との関係を示す図である。It is a figure which shows the relationship between the aspect-ratio BAs of a land part, and the shear rigidity of a land part. 陸部の縦横比Ａｓと陸部の膨出量との関係を説明するための模式図であり、（ａ）は縦横比Ａｓ＜１の状態を、（ｂ）は縦横比Ａｓ＞１の状態をそれぞれ示した図である。It is a schematic diagram for demonstrating the relationship between the aspect ratio As of a land part, and the bulging amount of a land part, (a) is a state of aspect ratio As <1, (b) is a state of aspect ratio As> 1. FIG.

以下、図面を参照して、本発明をより具体的に説明する。
図２（ａ）、（ｂ）は本発明にしたがう空気入りタイヤの実施の形態を示した図であり、（ａ）はタイヤのトレッドパターンを示す平面展開図であり、（ｂ）は中央陸部の幅Ｗａ２と中央陸部の高さＨａ２とを示す図である。なお図２（ａ）において、Ｙ方向（タイヤ赤道面に沿った方向）がタイヤの回転する向き（以下、タイヤ周方向という）であり、Ｘ方向（タイヤ赤道面Ｅに直交する方向）がタイヤの幅方向（以下、タイヤ幅方向という）である。 Hereinafter, the present invention will be described more specifically with reference to the drawings.
2 (a) and 2 (b) are views showing an embodiment of a pneumatic tire according to the present invention, (a) is a plan development view showing a tread pattern of the tire, and (b) is a central land. is a diagram showing a height Ha 2 width Wa 2 and the central land portion parts. 2A, the Y direction (the direction along the tire equator plane) is the direction in which the tire rotates (hereinafter referred to as the tire circumferential direction), and the X direction (the direction perpendicular to the tire equator plane E) is the tire. In the width direction (hereinafter referred to as the tire width direction).

本発明に従うタイヤは、図示を省略するが、左右一対のビードコア間でトロイダル状に延在するカーカスと、このカーカスのクラウン部のタイヤ径方向外側に配置したベルトと、このベルトのタイヤ径方向外側に配置したトレッド部１とを具える慣例に従ったタイヤ構造を有し、トレッド部１に図２（ａ）に示したトレッドパターンを有するものである。   Although the tire according to the present invention is not illustrated, a carcass extending in a toroidal shape between a pair of left and right bead cores, a belt disposed on the outer side in the tire radial direction of the crown portion of the carcass, and an outer side in the tire radial direction of the belt 2 has a tread pattern as shown in FIG. 2 (a).

図２（ａ）に示すように、トレッド部１は、タイヤ周方向に伸延する複数の周溝２を有しており、この周溝２によって区画された複数のリブ３を備えている。   As shown in FIG. 2A, the tread portion 1 has a plurality of circumferential grooves 2 extending in the tire circumferential direction, and includes a plurality of ribs 3 partitioned by the circumferential grooves 2.

周溝２は、図示の例ではタイヤの赤道Ｅを通る１本の中央周溝２ａと、この中央周溝２ａを挟んでタイヤ幅方向の両側に各２本の外側周溝２ｂからなっている。中央周溝２ａは、タイヤの赤道Ｅから間隔をあけて、タイヤ幅方向両側に複数配置するものであってもよい。また中央周溝２ａの溝幅Ｗ１と外側周溝２ｂの溝幅Ｗ２は、図示の例ではＷ１とＷ２が等しい寸法になっているが、異なっていてもよい。 In the illustrated example, the circumferential groove 2 includes one central circumferential groove 2a passing through the equator E of the tire and two outer circumferential grooves 2b on both sides in the tire width direction across the central circumferential groove 2a. . A plurality of central circumferential grooves 2a may be arranged on both sides in the tire width direction with a space from the equator E of the tire. The groove width W 2 of the groove width W 1 and the outer circumferential groove 2b of the central circumferential groove 2a is W 1 and W 2 is in the same size in the illustrated example, it may be different.

リブ３は、タイヤの赤道Ｅの周辺であるタイヤ幅方向の中央域に位置する中央リブ３ａと、この中央リブ３ａを両側に挟み、トレッド部１のタイヤ幅方向最外部に位置するショルダーリブ３ｂを備えている。中央リブ３ａは、タイヤ幅方向に沿う複数の細溝（サイプ）３ａ１でタイヤの回転する向きに間隔をおいて分断して中央陸部３ａ２を形成しており、ショルダーリブ３ｂは、タイヤ幅方向に沿う複数のラグ溝３ｂ１でタイヤの回転する向きに間隔をおいて分断してショルダー陸部３ｂ２を形成している。図示の例で細溝３ａ１及びラグ溝３ｂ１は、タイヤ幅方向に対して平行に延びており、中央陸部３ａ２及びショルダー陸部３ｂ２の接地面は矩形状となっているが、細溝３ａ１、ラグ溝３ｂ１は、タイヤ幅方向に傾斜していても、またジグザグ状であってもよい。また中央陸部３ａ２は、この中央陸部３ａ２を含む中央リブ３ａと、この中央リブ３ａと隣り合う他の中央リブ３ａとの関係において、中央陸部３ａ２がタイヤ幅方向にタイヤ幅方向に一列に並ぶようにした格子状の配置であってもよいし、図示のようにタイヤ周方向に半ピッチずれた千鳥状の配置であってもよい。千鳥状の配置とした場合には、中央陸部３ａ２の接地タイミングをタイヤ幅方向にずらすことができ、パターンノイズの低減に有利となる。 The rib 3 includes a central rib 3a located in a central region in the tire width direction around the equator E of the tire, and a shoulder rib 3b located on the outermost side in the tire width direction of the tread portion 1 with the central rib 3a sandwiched between both sides. It has. The central rib 3a is divided into a plurality of narrow grooves (sipes) 3a 1 along the tire width direction at intervals in the tire rotating direction to form the central land portion 3a 2. The shoulder rib 3b A plurality of lug grooves 3b 1 along the width direction are divided at intervals in the direction of rotation of the tire to form a shoulder land portion 3b 2 . In the illustrated example, the narrow groove 3a 1 and the lug groove 3b 1 extend in parallel to the tire width direction, and the ground contact surfaces of the central land portion 3a 2 and the shoulder land portion 3b 2 are rectangular. The narrow groove 3a 1 and the lug groove 3b 1 may be inclined in the tire width direction or zigzag. In addition, the central land portion 3a 2 is configured so that the central land portion 3a 2 has a tire width in the tire width direction in the relationship between the central rib 3a including the central land portion 3a 2 and another central rib 3a adjacent to the central rib 3a. It may be a grid-like arrangement arranged in a line in the direction, or may be a zigzag arrangement shifted by a half pitch in the tire circumferential direction as shown. In the case of a staggered arrangement, the ground contact timing of the central land portion 3a 2 can be shifted in the tire width direction, which is advantageous in reducing pattern noise.

中央陸部３ａ２は、接地面の面積Ｓｂを約４５０ｍｍ２以下（図２（ａ）の例では約３６０ｍｍ２）とすることで耐摩耗性能を向上させることができる。この点につき図３を参照して説明する。図３は中央陸部３ａ２の幅Ｗａ２及び長さＬａ２を様々に変化させたときの、陸部の膨出量（ゴム流動量）の検討結果を示したものである。本発明者が耐摩耗性能について鋭意検討を重ねたところ、中央陸部３ａ２の摩耗の原因は、中央陸部３ａ２が路面に接してから離れるまでの間で、中央陸部３ａ２の膨出による剪断変形の寄与が大きいことを見出した。さらに検討を重ねたところ、中央陸部３ａ２の接地面の面積Ｓｂとゴムの膨出変形（ゴム流出量）との間に、図３に示す一定の関係を見出すに至った。図３から明らかなように、中央陸部３ａ２の接地面の面積Ｓｂが小さいほどゴムの膨出変形が小さくなる。そしてこの図３のＳ２〜Ｓ７の領域、特に中央陸部３ａ２の接地面の面積Ｓｂを４５０ｍｍ２以下とした場合に、摩耗を有利に低減させることができることが明らかとなった。 The center land portion 3a 2 can improve the wear resistance performance by setting the area Sb of the contact surface to about 450 mm 2 or less (about 360 mm 2 in the example of FIG. 2A). This point will be described with reference to FIG. FIG. 3 shows the examination results of the bulge amount (rubber flow amount) of the land portion when the width Wa 2 and the length La 2 of the central land portion 3a 2 are variously changed. The present inventor has conducted extensive study for wear resistance, causes wear of the central land portion 3a 2 is between the central land portion 3a 2 is to away from contact with the road surface, the central land portion 3a 2 Rise It has been found that the contribution of shear deformation due to protrusion is large. As a result of further studies, a certain relationship shown in FIG. 3 was found between the contact surface area Sb of the central land portion 3a 2 and the rubber bulge deformation (rubber outflow amount). As apparent from FIG. 3, the smaller the area Sb of the ground contact surface of the central land portion 3a 2 is, the smaller the rubber bulge deformation becomes. And it became clear that the wear can be advantageously reduced when the area Sb of S2 to S7 in FIG. 3, particularly the area Sb of the ground contact surface of the central land portion 3a 2 is 450 mm 2 or less.

中央陸部３ａ２の長さＬａ２は、中央陸部３ａ２を挟む周溝２（左右の周溝の溝幅が異なる場合は、溝幅が小さい側の周溝をいう）の溝幅の１．５倍以上であり、かつショルダー陸部３ｂ２の長さＬｂ２よりも短く、中央陸部３ａ２の幅Ｗａ２は、ショルダー陸部３ｂ２の幅Ｗｂ２よりも狭くなっている。中央陸部３ａ２の接地面の面積Ｓｂを小さくしすぎると、中央陸部３ａ２の倒れ込み(座屈)により摩耗しやすくなることがあるが、中央陸部３ａ２の長さＬａ２を周溝２の溝幅の１．５倍以上とすることで、接地面積Ｓｂが大きくなって剪断剛性が高くなり、中央陸部３ａ２が倒れ込みにくくなる。またトレッド部１は、タイヤの中央部から幅方向外側に向けてタイヤの径が小さくなる曲率を有しており、タイヤ幅方向に径差の分布が生じているが、ショルダー陸部３ｂ２の大きさは中央陸部３ａ２よりも大きく、高い剪断剛性を備えているため、径差の影響による摩耗を十分に低下させることができる。 The length La 2 of the central land portion 3a 2 are circumferential grooves 2 sandwiching the central land portion 3a 2 (if the groove width of the circumferential groove of the left and right are different, refers to a circumferential groove of the groove width is smaller side) of the groove width of is 1.5 times or more, and less than the length Lb 2 of the shoulder land portion 3b 2, the width Wa 2 of the central land portion 3a 2 is narrower than the width Wb 2 of the shoulder land portion 3b 2. If the area Sb of the ground contact surface of the central land portion 3a 2 is made too small, the central land portion 3a 2 may be easily worn due to collapse (buckling), but the length La 2 of the central land portion 3a 2 may be reduced. By setting it to 1.5 times or more the groove width of the groove 2, the ground contact area Sb is increased, the shear rigidity is increased, and the central land portion 3 a 2 is not easily collapsed. Further, the tread portion 1 has a curvature with which the diameter of the tire decreases from the center portion of the tire toward the outer side in the width direction, and a distribution of the diameter difference occurs in the tire width direction, but the shoulder land portion 3b 2 Since the size is larger than that of the central land portion 3a 2 and high shear rigidity is provided, wear due to the influence of the diameter difference can be sufficiently reduced.

上記の構成となるタイヤについてさらに検討を進めたところ、特に乗用車等の駆動輪に装着した場合には、陸部の剪断変形が大きくなり耐摩耗性能が低下する傾向が見られた。この点につき図４（ａ）、（ｂ）を参照して説明する。図４（ａ）に示すように、タイヤに駆動力が入力された際には、ベルトは踏み込み側（図に示す、タイヤの回転方向を示す矢印の先端側）で浮き上がり、蹴り出し側（図に示す、タイヤの回転方向を示す矢印の根元側）で沈み込む変形を引き起こすため、蹴り出しの際には陸部がより強い力で押し込まれることになる。またタイヤに駆動力が入力されると、図４（ｂ）に示すように細溝の溝底ではタイヤの変形が助長されるため、陸部におけるゴム流動がさらに増えて剪断変形は一段と大きくなる。細溝３ａ１の溝幅が０．２〜１．０ｍｍであれば、駆動時における溝底でのタイヤの変形が抑制されるとともに、剪断変形する中央陸部３ａ２が、この中央陸部３ａ２よりも前方（タイヤの回転方向を示す矢印の先端側）に位置する中央陸部３ａ２と、細溝３ａ１において接触して剪断変形が抑えられるので、耐摩耗性能を向上させることが可能となる。上記範囲であれば溝幅が極端に狭くなりすぎず、タイヤの生産性が損なわれることもない。 Further examination of the tire having the above-described configuration revealed that, particularly when mounted on a driving wheel of a passenger car or the like, the shear deformation of the land portion increased and the wear resistance performance tended to decrease. This point will be described with reference to FIGS. 4 (a) and 4 (b). As shown in FIG. 4 (a), when a driving force is input to the tire, the belt is lifted on the stepping side (the tip side of the arrow indicating the rotation direction of the tire shown in the figure) and kicked out (see FIG. 4). In this case, the land portion is pushed in with a stronger force when kicking out. When a driving force is input to the tire, the deformation of the tire is promoted at the bottom of the narrow groove as shown in FIG. 4 (b), so that the rubber flow in the land portion is further increased and the shear deformation is further increased. . If the groove width of the narrow groove 3a 1 is 0.2 to 1.0 mm, deformation of the tire at the groove bottom during driving is suppressed, and the central land portion 3a 2 that undergoes shear deformation is the central land portion 3a. Since the center land portion 3a 2 positioned in front of the tire 2 (the tip side of the arrow indicating the rotation direction of the tire) and the narrow groove 3a 1 come into contact with each other and shear deformation is suppressed, it is possible to improve wear resistance. It becomes. If it is the said range, a groove width will not become extremely narrow, and productivity of a tire will not be impaired.

周溝２の深さＨａ２は、６．０〜８．０ｍｍ程度であり、細溝３ａ１の深さＨａ１は、
Ｈａ２を基準とする比率にて０．５以上１以下とすることが好ましい。上記範囲であれば中央陸部３ａ２の倒れ込みが大きくなりすぎることがなく、剪断変形を抑制することができる。 Depth Ha 2 of circumferential grooves 2 is about 6.0～8.0Mm, depth Ha 1 of the thin groove 3a 1 is
The ratio based on Ha 2 is preferably 0.5 or more and 1 or less. Without falling in the central land portion 3a 2 is too large if the above-mentioned range, it is possible to suppress the shear deformation.

中央リブ３ａは、タイヤの幅方向中心（タイヤの赤道Ｅ）から中央リブ３ａのタイヤ幅方向最も外側となる幅端に至るまでの寸法Ｗ３が、タイヤの幅方向中心からトレッド部１のタイヤ幅方向最も外側となる幅端に至るまでの寸法Ｗ４の２０〜４０％の範囲に位置することが好ましい。図示の例でトレッド部１は、中央リブ３ａとショルダーリブ３ｂのみからなるものであるが、上記範囲に中央リブ３ａを配置し、この中央リブ３ａとショルダーリブ３ｂとの間に第２の中央リブ（複数であってもよい）を設ける場合には、各リブを構成するそれぞれの陸部の接地面の面積、長さ及び幅をタイヤの赤道Ｅからタイヤ幅方向外側に向けて次第に大きくなるように配置して、ゴムの流動量を抑制しつつ径差の影響も抑えることが可能となり、耐摩耗性能の最適化を図ることができる。 Central rib 3a are the dimensions W 3 from the widthwise center of the tire (the tire equator E) up to the tire width direction outermost become wide end of the central rib 3a, the tire from the widthwise center of the tire tread portion 1 is preferably located 20 to 40% of the dimension W 4 ranging in width direction outermost become wide end. In the illustrated example, the tread portion 1 is composed of only the central rib 3a and the shoulder rib 3b. However, the central rib 3a is disposed in the above range, and the second central portion is interposed between the central rib 3a and the shoulder rib 3b. When ribs (which may be plural) are provided, the area, length, and width of the ground contact surface of each land portion constituting each rib gradually increase from the equator E of the tire toward the outer side in the tire width direction. Thus, it is possible to suppress the influence of the diameter difference while suppressing the flow amount of rubber, and the wear resistance performance can be optimized.

中央陸部３ａ２の幅Ｗａ２は、１０〜２０ｍｍであることが好ましい。中央陸部３ａ２の長さＬａ２及び幅Ｗａ２のいずれか一方を大きくしすぎると、接地面の面積Ｓｂとの関係上、他方が小さくなりすぎるため、陸部の形状が極端に細長くなってしまい操縦安定性に影響を及ぼすおそれがあるが、上記の範囲であればタイヤの性能を維持したまま、優れた耐摩耗性能を得ることができる。 The width Wa 2 of the central land portion 3a 2 is preferably 10 to 20 mm. If either one of the length La 2 and the width Wa 2 of the central land portion 3a 2 is too large, the other portion becomes too small due to the relationship with the area Sb of the ground contact surface, so that the shape of the land portion becomes extremely elongated. However, if it is in the above range, excellent wear resistance performance can be obtained while maintaining the tire performance.

中央陸部３ａ２は、図２（ａ）、（ｂ）に示す長さＬａ２及び幅Ｗａ２が、溝深さ（中央陸部の３ａ２高さ）に対して１．５倍以上となっていることが好ましい。ここで溝深さとは、中央陸部３ａ２を取り囲む周溝２の深さＨａ２及び細溝３ａ１の深さＨａ１のうち、最も深いものをいう。この点につき、図５を参照して説明する。中央陸部３ａ２の接地面の面積Ｓｂが小さくなりすぎると、中央陸部３ａ２の剪断剛性が低下して倒れ込み（座屈）が生じ、中央陸部３ａ２の接地端での接地圧は非常に高くなる一方、接地面での接地圧は低くなるため、グリップ力が減少して摩耗の進行がし易くなることが判明した。図５に示す、陸部のアスペクト比ＢＡｓ（中央陸部３ａ２の高さ（溝深さ）に対する中央陸部３ａ２の周方向長さＬｂ又は幅方向長さＷｂの割合）と陸部の剪断剛性との関係は、陸部のアスペクト比ＢＡｓが比較的大きな数値の場合は陸部の剪断剛性が大きく変化していないが、約１．５未満となるところで急激に低下する。すなわち、中央陸部３ａ２の長さＬａ２及び幅Ｗａ２が、溝深さに対して１．５倍以上の場合には、所要とする陸部の剪断剛性が確保され、良好な接地性を得ることができる。 The central land portion 3a 2 has a length La 2 and a width Wa 2 shown in FIGS. 2A and 2B of 1.5 times or more with respect to the groove depth (3a 2 height of the central land portion). It is preferable that Here, the groove depth means the deepest of the depth Ha 2 of the circumferential groove 2 surrounding the central land portion 3a 2 and the depth Ha 1 of the narrow groove 3a 1 . This point will be described with reference to FIG. If the area Sb of the ground contact surface of the central land portion 3a 2 becomes too small, the shear rigidity of the central land portion 3a 2 is lowered, causing collapse (buckling), and the ground pressure at the ground contact end of the central land portion 3a 2 is On the other hand, it was found that the contact pressure on the contact surface was lowered while the contact surface was very low, so that the grip force was reduced and the wear progressed easily. As shown in FIG. 5, the aspect ratio BAs of the land portion (the ratio of the circumferential length Lb or the width direction length Wb of the central land portion 3a 2 to the height (groove depth) of the central land portion 3a 2 ) and the land portion The relationship between the shear rigidity and the shear rigidity of the land portion is a relatively large value, but the shear rigidity of the land portion does not change greatly. That is, when the length La 2 and the width Wa 2 of the central land portion 3a 2 are 1.5 times or more with respect to the groove depth, the required shear rigidity of the land portion is ensured, and good grounding property is achieved. Can be obtained.

中央陸部３ａ２は、周方向に縦長の形状とすることが好ましい。この点について図６（ａ）、（ｂ）を参照して説明すると、図６（ｂ）に示すように周方向に縦長の形状の場合には、中央陸部３ａ２の側面において、タイヤ周方向を向く面Ｐ（自由表面Ｐ）の面積が、タイヤ幅方向を向く面Ｑ（自由表面Ｑ）の面積よりも小さくなり、荷重Ｆの負荷時にタイヤ周方向への膨出量に比べタイヤ幅方向への膨出量の割合を大きくすることができるので、図６（ａ）に示す場合に比べて中央陸部３ａ２の蹴り出し側の摩耗をより効率的に低減することが可能となる。特に幅Ｗａ２に対する長さＬａ２の比率である縦横比Ａｓを１以上２以下とすることが好ましい。縦横比Ａｓを１未満とした場合には、中央陸部３ａ２がタイヤ幅方向に細長い横長形状となって、タイヤ周方向の荷重入力に対抗する中央陸部３ａ２の剪断剛性が低下するおそれがあり、縦横比Ａｓが２を超える場合には、中央陸部３ａ２の接地面の面積Ｓｂとの関係上、中央陸部３ａ２の幅Ｗａ２が小さくなりすぎて操縦安定性が低下するおそれがあるが、上記の範囲であればタイヤの性能を維持したまま、優れた耐摩耗性能を得ることができる。 The central land portion 3a 2 is preferably a vertically long shape in the circumferential direction. FIGS. 6 (a) In this regard, with reference to (b), in the case of vertically long shape in the circumferential direction as shown in FIG. 6 (b), the side surfaces of the central land portion 3a 2, tire circumferential The area of the surface P (free surface P) facing the direction is smaller than the area of the surface Q (free surface Q) facing the tire width direction, and the tire width compared to the bulging amount in the tire circumferential direction when the load F is applied it is possible to increase the percentage of swelling of the direction, it is possible to more efficiently reduce the trailing side wear of the central land portion 3a 2 compared to the case shown in FIG. 6 (a) . In particular, the aspect ratio As, which is the ratio of the length La 2 to the width Wa 2, is preferably 1 or more and 2 or less. When the aspect ratio As is less than 1, the central land portion 3a 2 has a horizontally long shape in the tire width direction, and the shear rigidity of the central land portion 3a 2 that opposes load input in the tire circumferential direction may be reduced. There is, the aspect ratio as is the case of more than 2, the relationship between the area Sb of the ground plane of the central land portion 3a 2, the steering stability width Wa 2 of the central land portion 3a 2 becomes too small to decrease Although there is a possibility, if it is in the above range, excellent wear resistance performance can be obtained while maintaining the performance of the tire.

中央周溝２ａの溝幅Ｗ１は外側周溝２ｂの溝幅Ｗ２よりも幅が狭くなっていることが好ましい。タイヤの接地圧はタイヤの幅方向中央域において高く、幅方向外側に向かって徐々に低くなっている。溝幅が大きくなると陸部の接地面が減少し、各陸部の接地圧が上昇して剪断変形が大きくなるが、タイヤ幅方向中央域の溝幅Ｗ１をタイヤ幅方向外側の溝幅Ｗ２よりも幅を狭くしておけば、タイヤの全域に亘って接地圧を均等に近づけることができるので、耐摩耗性能の向上を図ることができる。 The groove width W 1 of the central circumferential groove 2a is preferably width than the groove width W 2 of the outer circumferential groove 2b is narrow. The contact pressure of the tire is high in the center region in the width direction of the tire and gradually decreases toward the outside in the width direction. As the groove width increases, the land contact surface of the land portion decreases and the contact pressure of each land portion increases to increase shear deformation. However, the groove width W 1 in the center region in the tire width direction is changed to the groove width W on the outer side in the tire width direction. If the width is made narrower than 2, the ground pressure can be made evenly distributed over the entire area of the tire, so that the wear resistance can be improved.

図２（ａ）に示すトレッドパターンであって、表１に示す組み合わせとなる、サイズが
１９５／６５Ｒ１５のタイヤを試作した。このタイヤをサイズが６Ｊ−１５となるリムに組み込み、乗用車の駆動輪、遊輪の両方に装着し、テストコースを走行して耐摩耗性能について調査を行った。
このときの空気圧は２１０ｋＰａであり、タイヤ負荷荷重は４．４１ｋＮであった。結果を表１に併せて示す。 A tire having a size of 195 / 65R15 having the combination shown in Table 1 and the tread pattern shown in FIG. This tire was incorporated into a rim having a size of 6J-15, mounted on both the driving wheel and the idle wheel of a passenger car, and traveled on a test course to investigate the wear resistance.
The air pressure at this time was 210 kPa, and the tire load was 4.41 kPa. The results are also shown in Table 1.

Figure 0005452386
Figure 0005452386

耐摩耗性能は、テストコースで乗用車を実走させ、１００００ｋｍ走行後の駆動輪と遊輪の摩耗量を所定位置においてそれぞれ測定し、これらの磨耗量を平均化してトレッド部全体の摩耗量として調査を行った。細溝の溝幅を２ｍｍに設定したタイヤ（比較タイヤ１）の摩耗量を１００として、結果を表１に指数で示した。数値が大きいほど耐摩耗性能が高いことを示す。   The wear resistance performance is measured as the wear amount of the entire tread by measuring the wear amount of the driving wheel and idler wheel at a predetermined position after running a passenger car on a test course and averaging the wear amount. went. The results are shown in Table 1 as an index with the amount of wear of the tire (comparative tire 1) having a groove width of 2 mm set to 2 mm as 100. A larger value indicates higher wear resistance.

その結果、中央陸部の接地面積が大きすぎるタイヤ(比較タイヤ１)、中央リブの範囲が好ましい設定より外れるタイヤ（比較タイヤ２、３）は、十分な耐摩耗性能を得ることができない。一方これらがともに好ましい設定となるタイヤ(適合タイヤ１、２)は、耐摩耗性能に優れていることが確認された。特に細溝の溝幅を０．５ｍｍとしたタイヤ(適合タイヤ１)は結果が特に良好であった。   As a result, tires (comparative tires 1) in which the contact area of the central land portion is too large and tires (comparative tires 2 and 3) in which the range of the central rib deviates from a preferable setting cannot obtain sufficient wear resistance. On the other hand, it was confirmed that the tires (compatible tires 1 and 2) in which both of these are preferable settings are excellent in wear resistance. In particular, the tire (conforming tire 1) in which the groove width of the narrow groove was 0.5 mm was particularly good.

本発明によれば、タイヤの接地時の陸部の変形に起因した摩耗を有利に低減でき、車両の駆動輪に装着しても十分な耐摩耗性能を備える空気入りタイヤを安定的に供給できる。   ADVANTAGE OF THE INVENTION According to this invention, the wear resulting from the deformation | transformation of the land part at the time of a tire grounding can be reduced advantageously, and even if it mounts | wears with the driving wheel of a vehicle, the pneumatic tire provided with sufficient wear-resistant performance can be supplied stably. .

１ トレッド部
２ 周溝
２ａ 中央周溝
２ｂ 外側周溝
３ リブ
３ａ 中央リブ
３ｂ ショルダーリブ
３ａ１ 細溝
３ａ２ 中央陸部
３ｂ１ ラグ溝
３ｂ２ ショルダー陸部
Ｗａ２ 中央陸部の幅
Ｌａ２ 中央陸部の長さ
Ｗｂ２ ショルダー陸部の幅
Ｌｂ２ ショルダー陸部の長さ
Ｗ１ 中央周溝の溝幅
Ｗ２ 外側周溝の溝幅 1 tread portion 2 circumferential groove 2a central circumferential groove 2b outer circumferential groove 3 rib 3a central rib 3b shoulder rib 3a 1 narrow groove 3a 2 central land portion 3b 1 lug groove 3b 2 shoulder land portion Wa 2 central land width La 2 center land portion of the length Wb 2 of width Lb 2 shoulder land portion of the shoulder land portion length W 1 central circumferential groove of the groove width W 2 outer circumferential groove of the groove width

Claims (4)

トレッド部に、タイヤの回転する向きに沿う複数本の周溝によって区画されたリブを有する空気入りタイヤにおいて、
前記リブは、タイヤの幅方向の中央域に位置し、前記リブをタイヤの回転する向きに間隔をおいて分断して短尺陸部の集合体を形成する複数本の細溝を備えた中央リブと、前記中央リブを両側に挟み、前記リブをタイヤの回転する向きに間隔をおいて分断して短尺陸部の集合体を形成する複数本のラグ溝を備えたショルダーリブからなり、
前記中央リブを形成する短尺陸部は、
接地面の面積が、４５０ｍｍ２以下であり、
タイヤの回転する向きに沿う寸法が、前記周溝の溝幅の１．５倍以上であってかつ前記ショルダーリブを形成する短尺陸部のタイヤの回転する向きに沿う寸法よりも短く、
タイヤの幅方向に沿う寸法が、前記ショルダーリブを形成する短尺陸部のタイヤの幅方向に沿う寸法よりも短い、
ことを特徴とする空気入りタイヤ。 In a pneumatic tire having ribs defined by a plurality of circumferential grooves along the rotating direction of the tire in the tread portion,
The rib is located in a central region in the width direction of the tire, and a central rib having a plurality of narrow grooves that form an aggregate of short land portions by dividing the rib at intervals in the direction of rotation of the tire And, sandwiching the central rib on both sides, consisting of a shoulder rib with a plurality of lug grooves that form an aggregate of short land portions by dividing the rib at intervals in the direction of rotation of the tire,
The short land portion forming the central rib is
The area of the ground plane is 450 mm 2 or less,
The dimension along the tire rotating direction is 1.5 times or more the groove width of the circumferential groove and shorter than the dimension along the tire rotating direction of the short land portion forming the shoulder rib,
The dimension along the width direction of the tire is shorter than the dimension along the width direction of the tire of the short land portion forming the shoulder rib,
A pneumatic tire characterized by that. 前記細溝の溝幅が、０．２〜１．０ｍｍである、請求項１記載の空気入りタイヤ。   The pneumatic tire according to claim 1, wherein a groove width of the narrow groove is 0.2 to 1.0 mm. 前記中央リブは、タイヤの幅方向中心から該中央リブの幅端に至るまでの寸法が、前記タイヤの幅方向中心から前記トレッド部の幅端に至るまでの寸法の２０〜４０％になる、請求項１又は２記載の空気入りタイヤ。   The center rib has a dimension from the center in the width direction of the tire to the width end of the center rib that is 20 to 40% of a dimension from the center in the width direction of the tire to the width end of the tread portion. The pneumatic tire according to claim 1 or 2. 前記中央リブの幅が、１０〜２０ｍｍである、請求項１〜３何れかに記載の空気入りタイヤ。   The pneumatic tire according to claim 1, wherein a width of the central rib is 10 to 20 mm.
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