JP4054076B2 - Pneumatic radial tire - Google Patents

Description

【００４９】
本発明の第２の空気入りラジアルタイヤの実施形態を図５に示すところに基づいて以下に説明する。
なおここでは、第１の空気入りラジアルタイヤについて述べた部分と同様の構成部分については説明を省略する。
【００５０】
このラジアルタイヤでは、とくに、最大負荷能力に応じた規定空気圧の充填状態で、トラック・バス用タイヤにあっては規定荷重の負荷時の、またトラック・バス用タイヤより小型のタイヤにあっては規定荷重の７０％の荷重の負荷時における、タイヤの子午線断面内の最外接地端位置１２と、前記規定空気圧の充填下での、ビードコアからのカーカス高さＨ_０ に対し、ビードコアからそのカーカス高さＨ_０ の１／２の点１３との間の、それらの両位置１２，１３をも含む、タイヤの子午線断面内の、図に斜線を施して示す領域１４内に、トレッドゴムのゴム硬度に対し、ＪＩＳ Ａ硬度で３度以上、より好ましくは５度以上高い硬度の高硬度ゴム層１５を配設する。
【００５１】
上記領域１４は、それを図に示すところに従って言い換えれば、両最外接地端位置１２の幅をＣＷとした場合に、タイヤ幅方向の外側へ、タイヤ赤道面Ｘ−Ｘから幅ＣＷ／２以上離隔し、かつ、タイヤの半径方向外側へ、ビードコア５からＨ_０ ／２以上離隔した範囲となる。ここで、領域１４の、トレッド側の境界は、図示の断面内で、最外接地端位置１２でタイヤの外表面に立てた法線１６によって特定される。
【００５２】
このように構成してなるタイヤでは、それが、轍等の傾斜面上を図２に示すように負荷転動する場合には、領域１４内に配設した高硬度ゴム層１５のゴム硬度がトレッドゴムのそれより高いことに基づき、バットレス近傍部分の膨出変形bside が、接地端近傍部分、ひいてはトレッド部の接地端部分に伝達し易くなり、この結果として、迫出し変形bshoおよびトレッドゴム剪断変形Ｓ_S がともに増加されるので、キャンバースラストＦ_C の十分なる増大をもたらすことができる。
【００５３】
なおここにおいて、高硬度ゴム層１５の配設範囲を、上述した領域１４に限定するのは、前記膨出変形bside が、その領域内にてとくに大きく発生することによるものであり、また、高硬度ゴム層１５のゴム硬度をトレッドゴムのそれより、ＪＩＳ Ａ硬度で３度以上、好適には５度以上高くするのは、それが３度未満では、上述したような機能の十分なる発現を期し難いことによる。
【００５４】
ところで、上述したような膨出変形bside に伴う歪の大きさ、すなわち、その変形bside の伝達し易さは、タイヤの外表面側でとくに大きくなるので、高硬度ゴム層１５はその外表面に近づけて配設することが有利である。これがため好適には、規定空気圧の充填状態におけるタイヤの子午線断面内で、ラジアルカーカス４の法線方向に測った高硬度ゴム層１５の最大厚みの中点を、その最大厚み位置を通る法線上で測ったタイヤ総厚みの厚み中点よりタイヤの外表面側に位置させる。
そこで、図６に示すところでは、高硬度ゴム層１５を、それの、タイヤの外周側に向く表面を外側に露出させて配設している。
【００５５】
このような構成を有する空気入りラジアルタイヤの、ワンダリング現象の抑制機能に関する比較試験について以下に説明する。
供試タイヤ
サイズが１９５／８５ Ｒ１６ １１４／１１２Ｌ ＬＴの小型トラック用ラジアルタイヤであって、図６および図７に示す構成を有するそれぞれのタイヤを発明タイヤ５および６とし、図８に示す構成のタイヤを比較タイヤとした。
【００５６】
図６に示す発明タイヤ５は、タイヤ幅方向で、タイヤ赤道面Ｘ−Ｘから７０mmの位置を始端としてＪＩＳ Ａ硬度が７６度、厚さが２．５mm、幅が２５mmの高硬度ゴム層１５を、前述したように、タイヤ外表面に露出させて配設したものである。ここで、トレッドゴムのＪＩＳ Ａ硬度は６１度とした。
ところで、この高硬度ゴム層１５の、カーカス４の法線方向に測った最大厚みは２．８mmであり、それの厚み中点はタイヤ外表面から１．４mmの位置にある。また、同一の法線上で測ったタイヤの総厚みは１３．５mmであり、それの厚み中点は、タイヤ外表面から６．７５mmの位置にある。
【００５７】
また、図７に示す発明タイヤ６は、タイヤ赤道面Ｘ−Ｘから７０mmの位置を始端とする、幅が２５mm、最大厚さが１１mmのほぼ三角形断面形状を有する、ＪＩＳ Ａ硬度が６７度の高硬度ゴム層１５を、タイヤ外表面から０．５mmの深さ位置に配設した点を除いて発明タイヤ１０と同様に構成したものである。
このタイヤの高硬度ゴム層１５の、カーカス４の法線方向に測った最大厚みは１２．７mmであり、それの厚み中点はタイヤ外表面から６．３５mmの位置にある。そして、同一の法線上で測ったタイヤの総厚みは１３．５mmであり、それの厚み中点は、タイヤ外表面から６．７５mmの位置にある。
なお、図８に示す比較タイヤは、前述したタイヤから高硬度ゴム層１５を省いたものである。
【００５８】
このようなタイヤの、最大負荷能力（１１８０kg）に応じた規定内圧は６．０kgf/cm^２であり、最大負荷能力の７０％の荷重（８２６kg）を負荷したときの接地幅ＣＷは１２０mmである。また、規定内圧（６．０kgf/cm^２）を充填したときの、ビードコア５からのカーカス高さＨ_０ は１３６mmである。
【００５９】
試験方法
６．０kgf/cm^２の内圧を充填したそれぞれのタイヤを、後輪が複輪タイプの２t積小型トラックに装着し、その小型トラックを、そこへの最大積載荷重の積載下にて、轍を含む舗装路をテストドライバーによって走行したときの直進安定性を官能評価することにより行った。その結果を表２に示す。
ここで、直進安定性指数は、比較タイヤをコントロールとし、性能のすぐれたものほど大きい値で表わす。
表２に示すところによれば、この発明に従うタイヤはいずれも、直進安定性が顕著に改善されることが明らかである。
【００６０】
【表２】

【００６１】
図９は、第２の空気入りラジアルタイヤの他の実施形態を示すタイヤ子午線断面図であり、これは、高硬度ゴム層１５の、タイヤの内周側に向く表面を波線状としたものである。ここで、図９（ａ）に示すように、高硬度ゴム層１５を、領域１４内でゴム中に完全に埋込む場合には、タイヤの外周側に向く表面をも波線状とすることが可能である。
【００６２】
このことによれば、高硬度ゴム層１５と隣接ゴム層との接着面積が増加して接着強度が（接着力×接着面積）が大きくなることから、前述した実施形態のラジアルタイヤと同様のワンダリング現象抑制性能を確保しつつ、タイヤの負荷転動による、高硬度ゴム層１５への歪の繰返しの発生に対しても、すぐれた剥離強度をもたらすことができる。しかも、ここにおける波線は、剥離の進行方向に対して大きな角度で交差することになるので、剥離の進行に効果的に対抗することができる。
【００６３】
またここで波線状部分１７の平均波長を、その波線状部分１７の総延長の１／３以下とした場合には、多数の波形の付与の下で、高硬度ゴム層１５の接着強度を一層高めることができる。
そしてさらに、波線状部分１７の総延長を、図１０に一点鎖線で示すように、波の中点を通る線分１８の長さより２０％以上長くした場合には、接着面積のさらなる増加をもって、接着強度をより一層高めることができる。
【００６４】
このような実施形態の空気入りラジアルタイヤの、耐ワンダリング性能と、高硬度ゴム層の耐剥離性とのそれぞれについての比較試験について以下に説明する。
供試タイヤ
前記比較試験に用いた、図７に示す構成を有する発明タイヤをコントロールタイヤとし、図９（ａ）に示す構成を有するタイヤを発明タイヤ７とした。
ここで、コントロールタイヤの高硬度ゴム層１５は前述した通りの寸法、物性等を有するものとし、発明タイヤ７の高硬度ゴム層１５等は、形状の点においてのみコントロールタイヤと相違するも、それの配設位置、体積、物性等はコントロールタイヤと同一とした。なお、この発明タイヤ７の波線の総延長は、コントロールタイヤの対応部分の１２５％とした。
【００６５】
試験方法
耐ワンダリング性能の評価は、サイズが１９５／８５ Ｒ１６ １１４／１１２Ｌ ＬＴのそれぞれのラジアルタイヤに６．０kgf/cm^２の内圧を充填して、後輪が複輪タイプの２t 積小型トラックに装着し、その小型トラックを、そこへの最大積載荷重の積載下にて、轍路を含む舗装路をテストドライバーによって走行したときの直進安定性を官能評価することにより行った。その結果を表３に示す。
ここで、直進安定性指数は、コントロールタイヤを１００とし、性能のすぐれたものほど大きい値で表わす。
【００６６】
また、耐剥離性の評価は、最大負荷能力に応じた規定内圧（６．０kgf/cm^２）の充填下で、規定最大負荷能力を負荷して５０km/hの速度でドラム走行した場合に、剥離長さが５mmに成長するまでの走行距離を指数評価することにより行った。その結果を表３に併せて示す。
ここでも、指数値は大きいほどすぐれた結果を示すものとする。
【００６７】
【表３】

【００６８】
表３によれば、発明タイヤ７では、コントロールタイヤに比し、直進安定性の幾分の向上と併せて、耐剥離性を大きく高め得ることが明らかである。
【００６９】
図１１は、本発明の第３の空気入りラジアルタイヤを示す子午線断面図であり、小型トラック用の、１９５／８５ Ｒ１６のサイズのタイヤについて示すこの図では、発明タイヤを実線で、比較タイヤを破線でそれぞれ表わす。
【００７０】
ここではとくに、最大負荷能力に応じた規定空気圧の１０％の空気圧の充填状態で、ビードコア５からのカーカス高さＨの０．５〜０．８倍、より好適には０．５〜０．７倍の範囲内の少なくとも一部に、タイヤ子午線断面内でラジアルカーカス４の法線方向に測ったタイヤ総厚みが、タイヤサイド部の他の部分における同様のタイヤ総厚みの７５％以下の薄肉部１９を設ける。
この図に示すところでは、ビードコア５から０．６３Ｈの位置の薄肉部１９でのタイヤ総厚みを５．５mmとし、その厚みを、０．５Ｈ〜０．８Ｈ以外の領域の最小厚みである９．０mm（０．４９Ｈの位置）の６１％としている。
加えてここでは、ラジアルカーカス４の曲率が最大となる部分の８０％以上を、ビードコア５からカーカス高さＨの０．６５〜０．８５倍の範囲内に設ける。
これも図に示すところでは、最大曲率を１／２３とし、最大曲率部分の１００％を上記範囲内に位置させている。
【００７１】
このような構成によれば、前述したように、ビードコア５から０．５Ｈ〜０．８Ｈの範囲内の薄肉部１９の剛性が局部的に低くなり、タイヤの傾斜面上での負荷転動に際し、その薄肉部１９に、図示の断面内での曲げ変形が集中し、バットレス近傍部分の膨出変形bside が増加するので、接地端近傍部分での迫出し変形bshoもまた大きくなって、キャンバースラストＦ_C が有効に増大されることになる。
【００７２】
ここで、薄肉部１９を０．５Ｈ〜０．８Ｈの範囲内に設けるのは、その部分が、０．５Ｈよりビードコア側に存在しても、膨出変形bside の増大に十分に寄与させることができず、一方、０．８Ｈを越えた位置、いいかえればバットレス部にその薄肉部１９を設けた場合には、バットレス部の剛性低下により、膨出変形bside を、接地端近傍部分、ひいては、トレッド部接地端に有効に伝達できないことによる。
また、薄肉部１９の厚みを他の部分の厚みの７５％以下とするのは、それが７５％を越えると、厚みの差、ひいては、剛性差が小さくなって、膨出変形bsideの十分な増加を期し難いことによる。
【００７３】
かかるタイヤにおいてより好ましくは、ラジアルカーカス４の最大幅位置を、ビードコア５からカーカス高さＨの０．６〜０．８倍の範囲内に設ける。図に示すところでは、その最大幅位置を、０．６９Ｈに設けている。
【００７４】
ここで、カーカス４の最大幅位置を０．６Ｈ〜０．８Ｈの範囲、より好適には０．７Ｈ〜０．８Ｈの範囲に設けることにより、膨出変形bside を増加させることが可能となる他、その膨出変形bside の発生位置をバットレス域に有効に近づけて、膨出変形bside に基づいて生じる迫出し変形bshoをより効果的に増大させることも可能となる。この一方で、内圧充填時のカーカス張力を上記範囲内で十分小ならしめて、その範囲での膨出変形bside を一層増加させることができる。
【００７５】
ところで、最大幅位置を０．６Ｈ未満の位置としたときは、十分大きな膨出変形bside をもたらし得ないうれいがあり、０．８Ｈを越える位置としたときは、カーカス４の最大幅位置が、タイヤの負荷転動時の故障核となり易いベルト端部に接近し過ぎることになって、タイヤの発熱耐久性、ベルト耐久性等が低下するおそれがある。
【００７６】
また、カーカス曲率が最大となる部分の８０％以上を０．６５Ｈ〜０．８５Ｈの範囲、より好適には０．７Ｈ〜０．８５Ｈの範囲に位置させることにより、カーカス４の最大幅位置を０．６Ｈ〜０．８Ｈの範囲に選択した場合と同様に、膨出変形bsideおよび迫出し変形bshoのそれぞれをともに効果的に増加させることができる。
すなわち、０．６５Ｈ未満では、膨出変形bside を、満足し得るほどに増加させることが難しく、０．８５Ｈを越えると、発熱耐久性、ベルト耐久性等の低下のうれいがある。
【００７７】
さらにここでは、ビードコア５からカーカス高さＨの０．８５倍の位置において、タイヤの子午線断面内でラジアルカーカス４の法線方向に測ったタイヤ総厚みを、ベルト側縁位置での同様のタイヤ総合厚みの０．６４倍以上とすることが好ましく、このことによれば、バットレス域の補強効果を高め、併せて、第２トレド域の剛性を高めることもできる。すなわち、上記比が０．６４倍未満では、上述した機能の十分なる発揮を所期し難い。
【００７８】
ところでここで、ベルトの側縁位置と、０．８５Ｈの位置とのそれぞれの位置でのタイヤ総厚みを対比するのは、ベルト側縁位置でのタイヤ総厚みは、傾斜面上を転動時のタイヤのトレッド部剛性に大きく影響することになるも、そこでのタイヤ総厚みは、主には、タイヤの主要特性である発熱耐久性、耐摩耗性等を考慮して決定されているのに対し、前記膨出変形bside および迫出し変形bshoの増加のためには、０．８５Ｈの位置でのタイヤ総厚みの影響が、他の部分に比してとくに大きいとの知見を得たことによる。ちなみに、図に示すところでは、ベルト側縁位置での厚みを２２．９mm、０．８５Ｈの位置での厚みを１７．２mmとして、上記倍数を約０．７５倍としている。
【００７９】
そしてまた好ましくは、ビードコア５からカーカス高さＨの０．８〜０．８５倍の範囲内の少なくとも一部に、タイヤ子午線断面内の、ラジアルカーカス４の法線方向でのタイヤ総厚みが、ビードコア５からカーカス高さＨの０．７５倍の位置における同様のタイヤ総厚みの１．５倍以上の厚肉部を設ける。図の実施形態では、０．８５Ｈの位置を、タイヤ総厚みが１７．２mmの厚肉部２０とし、０．７５Ｈの位置のそれを１０．５mmとして上記倍数を約１．６４倍としている。
【００８０】
かかる構成によれば、厚肉部２０をもって、第２トレッド域の剛性を大きく高め、また、バットレス域を有効に補強することができる。従って、膨出変形bside および迫出し変形bshoのそれぞれをともに大きく増大させて、剪断変形Ｓ_S の効果的な増大をもたらすことができる。
なお、上記倍数が１．５倍未満では、上述したような効果の十分なる発現を担保することが困難である。
【００８１】
図１２は、第３の空気入りラジアルタイヤの他の実施形態を示す断面図であり、これは、０．５Ｈ〜０．８Ｈの範囲、好ましくは０．５〜０．７Ｈの範囲内の薄肉部２１を局所的に薄肉化したものであり、図では、その薄肉部２１の最小厚みを、０．６２Ｈの位置で５．５mmとする。
【００８２】
ここにおける薄肉部２１は、厚みが漸減する前述した薄肉部１９と同様に、キャンバースラストＦ_C の増大に効果的に機能し得ることはもちろん、とくには、厚みが急激に減少することに基づき、たとえば、路線バスの如くに、タイヤサイド部が道路の縁石等に擦れてそこに損傷を生じるおそれがある場合等に、それの局部的な薄肉化をもって、かかる損傷の発生を最小限に抑制することができる。
【００８３】
以上のような空気入りラジアルタイヤの、ワンダリング現象の抑制性能に関する比較試験について以下に説明する。
供試タイヤ
図１１に実線で示す構造に従う、サイズが１９５／８５ Ｒ１６ １１４／１１２Ｌ ＬＴの小型トラック用ラジアルタイヤの、サイド部の肉厚分布およびカーカスラインを表４に示すように種々変更して発明タイヤ１０，１１とするとともに、同図に破線で示すタイヤを比較タイヤとした。
【００８４】
試験方法
これらのタイヤに、最大負荷能力に応じた規定内圧６．０kgf/cm^２ を充填後、それらを２ トン積みの小型トラック（後輪が複輪タイプ）に装着し、該小型トラックに最大積載荷重を負荷した状態で、轍を含む舗装路をテストドライバーが走行し、直進安定性を官能評価した。
その結果を、比較タイヤとコントロールとする指数評価（指数は大きいほど良好）にて、表４に併記した。
同表によれば、発明タイヤでは、直進安定性が大きく向上したことが明らかである。
【００８５】
【表４】

【００８６】
【発明の効果】
以上に述べたところから明らかなように、本発明に係る空気入りラジアルタイヤは、乗用車、小型トラック、トラック・バス等の車両に適用してワンダリング現象の発生を効果的に抑制することができ、とくには車両の高速走行に際し、轍等の存在する路面においても、すぐれた直進安定性を実現することができる。
【図面の簡単な説明】
【図１】 ワンダリング現象の発生状態を例示する略線説明図である。
【図２】 キャンバースラストの発生態様を示す子午線断面図である。
【図３】 第１の空気入りラジアルタイヤの半部を示す子午線断面図である。
【図４】 第１の空気入りラジアルタイヤを示す図３と同様の断面図である。
【図５】 第２の空気入りラジアルタイヤを示す子午線断面図である。
【図６】 高硬度ゴム層の一の配設態様を示す要部断面図である。
【図７】 高硬度ゴム層の他の配設態様を示す要部断面図である。
【図８】 比較タイヤを示す子午線断面図である。
【図９】 第２の空気入りラジアルタイヤの他の実施形態を示す断面図である。
【図１０】 高硬度ゴム層の波線状部分を拡大して例示する図である。
【図１１】 第３の空気入りラジアルタイヤの半部を示す子午線断面図である。
【図１２】 第３の空気入りラジアルタイヤの他の実施形態を示す子午線断面図である。
【符号の説明】
bside 膨出変形
bsho 迫出変形
Ｆ_c キャンバースラスト
１ ビード部
２ サイドウォール部
３ トレッド部
４ ラジアルカーカス
５ ビード部
６ ベルト
７ 第１トレッド域
８ 第２トレッド域
１１ 補強部
１２ 最外接地端位置
１３ 点
１４ 領域
１５ 高硬度ゴム層
１６ 法線
１７ 波線状部分
１８ 線分
Ｈ カーカス高さ（１０％空気圧）
Ｈ_０ カーカス高さ（１００％空気圧）
ＴＷ_１ 第１トレッド域の半幅
ＴＷ_２ 第２トレッド域の半幅
Ｗ トレッド幅
ＳＥ タイヤ断面幅
Ｂ ベルト最大幅[0001]
BACKGROUND OF THE INVENTION
  The present invention effectively suppresses the occurrence of a so-called wandering phenomenon, which is complicated when a vehicle travels on an inclined surface of a road surface having irregularities such as eaves, and is unpredictable by the driver. The present invention relates to a pneumatic radial tire with greatly improved stability.
[0002]
[Prior art]
  A radial tire in which a carcass cord extends in a direction substantially perpendicular to the tire equatorial plane is excellent in wear resistance and steering stability. Radial tires are used more frequently than bias tires in passenger cars as well as vehicles such as small trucks, trucks and buses.
  However, in recent years when vehicles are traveling at high speed on a daily basis due to the development and expansion of the road network, etc., the wandering phenomenon that is more likely to occur in radial tires than bias tires is sufficiently suppressed, and straight running stability is improved. There has been a strong demand to further improve safety.
[0003]
  Here, regarding the occurrence of the wandering phenomenon in the radial tire, as illustrated in FIG. 1, when the tire T rolls on the inclined surface S such as a bag, the load T on the tire T from the road surface is reduced. Reaction force F_R And Camber Surat F_C Each of these acts, and the lateral force F as the resultant force of the horizontal component of each of these forces_Y When the tire has a radial structure, the tread rigidity is much higher than that of the side part due to the structure of the radial tire. Camber thrust F than biased tires_C For this reason, in the figure, the lateral force F directed downward of the inclined surface S is shown._Y But Camber Thrust F_C The wandering phenomenon that becomes relatively large corresponding to the decrease in the width of the tire T, and the tendency of slipping down the inclined surface of the tire T becomes strong, making it difficult to ride over the saddle.
[0004]
[Problems to be solved by the invention]
  By the way, Camber Thrust F_C When the tire rolls on the inclined surface S, as shown in the meridian cross-sectional view of the tire in FIG._r However, it is strongly grounded on the upper side of the inclined surface S, that is, on the mountain side, and tends to float up on the valley side of the inclined surface S, and particularly on the mountain side, the tread portion T_r By the strong ground contact, the area near buttress B on the tire side_U Collapse, in other words, bulging deformation bside to the mountain side occurs, and this bulging deformation bside is caused by the tread portion T near the ground contact edge._r The bending deformation of this, in other words, the bulging deformation bsho is brought about._r In the tread rubber, the shear deformation S as shown by the broken line in the figure._S And this shear deformation S_S Is a lateral force F directed upward of the inclined surface S._CSWill be generated on the basis of
[0005]
  Such camber thrust F_C In the case of a bias tire having a relatively small rigidity difference between the components of the tire and having a relatively flexible structure, the bulging deformation bside and the bulging deformation bsho can be secured sufficiently large. F_C In contrast, in radial tires, the rigidity of the tread portion is significantly higher than the rigidity of the side portion, and as described above, the tire side portion is exaggerated by phantom lines in the figure. Tends to cause reverse escape deformation, so the tread rubber shear deformation S_S Becomes smaller, Camber Thrust F_C Will be forced to decline.
[0006]
  Therefore, in the pneumatic radial tire, the camber thrust F_C To bring about an increase in region B_U The tread rubber shear deformation S at the ground contact end portion is increased by increasing the bulging deformation bside of the belt, increasing the transmission efficiency of the bulge deformation bside, and increasing the bulging deformation bsho near the ground contact end._S Is effective, and the contact area of the tire with respect to the inclined surface S is increased, and the lateral force F directed upward of the inclined surface S is effective._CSIt is effective to increase the total generation amount of
[0007]
  Therefore, the present invention increases the camber thrust of the radial tire while maintaining the characteristic inherent to the radial tire, thereby sufficiently suppressing the occurrence of wandering on an inclined surface such as a narrow road and improving straight running stability. An object is to provide a pneumatic radial tire which is greatly improved.
[0008]
[Means for Solving the Problems]
  The first pneumatic radial tire of the present invention includes a pair of bead portions and sidewall portions, and a toroidal tread portion continuous with both sidewall portions, and a radial carcass that reinforces each portion. And a belt that reinforces the tread portion on the outer peripheral side of the radial carcass, wherein the tread portion projects to the side of the first tread region and the first tread region that contacts the flat road surface, and the inclined road surface And a second tread region that is in contact with the mountain-side slope of the first tread region.₁) For tires smaller than truck / bus tires when loaded with a specified load for truck / bus tires under the specified air pressure according to the maximum load capacity according to JATMA standards. The maximum contact width from the tire equatorial plane of the contact portion of the tire to the flat road surface when the load is 70% of the load, and the width of the second tread region (TW)₂) With a specified air pressure according to the maximum load capacity, a specified load for truck and bus tires and a load 70% of the specified load for tires smaller than truck and bus tires. In addition, when the camber angle of 10 ° is applied, the half width of the first tread region (TW) of the maximum contact width from the tire equatorial plane of the contact portion of the tire to the flat road surface (TW)₁) When the ground contact width is on the outside in the width direction,
  TW₂/ TW₁> 4.0 × 10^-2
The carcass height (H) from the bead core is 0.95 times the carcass height (H) from the bead core when the air pressure is 10% of the specified air pressure. The distance (b) from the side edge of the first tread region to the tire outer contour line at the position of the second tread region (TW)₂)
  b / TW₂> 1.2
This satisfies the following conditions.
  In the present specification, the carcass height refers to the height to the innermost carcass ply in the presence of a plurality of carcass plies.
[0009]
  In such a tire, preferably, in the tire meridian cross-section, the normal line of the radial carcass at the side center portion in the range of 0.5 to 0.8 times the carcass height (H) from the bead core in the tire side portion. The total tire thickness in the direction is made thinner than similar tire total thicknesses in other portions of the tire side portion, and preferably the radial carcass maximum width position is 0.6 to 0 of the carcass height (H) from the bead core. .Locate within 8 times range.
[0010]
  And preferably, in the meridian cross section of the tire, in the normal direction to the radial carcass at a position 0.85 times the carcass height (H) and a position 0.4 times from the bead core in the tire side portion. The total thickness of each tire isMosquitoThe thickness exceeds 1.65 times the same total tire thickness at the maximum width position of the tire.
  Further, in this tire, it is preferable that the tread width is in a range of 80 to 95% of the tire cross-sectional width in a state where the air pressure is 10% of the specified air pressure. In the filled state, the maximum belt width is preferably in the range of 60 to 90% of the tire cross-sectional width.
[0011]
  In the first pneumatic radial tire, compared to a conventional general radial tire, the tread portion protrudes greatly in the width direction of the tire by an amount corresponding to the second tread region. As shown in FIG. 2, since the ground contact area when rolling on the inclined surface of the tire is larger than that of the conventional tire, the lateral force F directed upward of the inclined surface S by itself._CSThe total amount of generation can be increased.
[0012]
  Here, the second tread region protruding in the tire width direction is the tread portion T._r As part of the tread part T_r As shown in FIG. 2, exaggerated deformation is effectively prevented from the vicinity of the ground contact edge to the tire side, while the bulging deformation bside increases. In addition, the bulging deformation bsho based on the bulging deformation bside can be transmitted over a wide range of the second tread region that is in contact with the inclined surface S, and thereby, the tread portion T_r Shear deformation S_S , Eventually Camber Thrust F_C Is effectively increased.
[0013]
  On the other hand, in a radial tire that does not have the second tread region, the grounding end position cannot be shifted to the upper side of the slope when contacting a sloping surface such as a saddle. When the pressure is greatly increased, the rigidity from the ground contact end portion to the tire side portion is low, so that the escape deformation as shown in FIG. 2 is inevitably generated.
[0014]
  Therefore, the tire having the second tread region is a tire having a radial structure, and still has a lateral force F._CS, By extension, Camber Thrust F_C Can be effectively increased.
[0015]
  By the way, even if a conventional radial tire has a shoulder shape such as a round shoulder or a tapered shoulder, when the camber angle of 10 ° is given, the side area of the tread portion is about 5 mm or less. The grounding portion may be grounded in width, but the grounding portion in this case is not a tread surface portion having high rigidity, and therefore it is impossible to bring about the desired effect of the present invention.
[0016]
  In this tire, the half width of the first tread region (TW)₁) And the width of the second tread area (TW)₂) Relative to
  TW₂/ TW₁> 4.0 × 10^-2
In particular, when the tire rolls on an inclined surface such as a saddle, the ground contact width of the second tread region is sufficiently secured, and the camber thrust F_C Effective increase in the distance from the side edge of the first tread region to the outer contour of the tire (b) and the width of the second tread region (TW).₂) Relative to
  b / TW₂> 1.2
In particular, the buttress portion and the second tread area restrain the deformation in the escape direction as shown by the phantom line in FIG. 2, while the second tread area bulges due to the bulging deformation bside. The deformation bsho is increased, and at the same time, the rigidity of the second tread region is increased, and when the second tread region is brought into contact with the ground, a large shear force is generated on the road surface._C Can be effectively increased.
[0017]
  The second pneumatic radial tire of the present invention is filled with a specified air pressure according to the maximum load capacity, particularly for truck and bus tires when a specified load is applied, and for trucks and buses. In the case of a tire smaller than the tire, the position of the outermost ground contact end in the meridian section of the tire and the height of the carcass from the bead core under the specified air pressure when the load is 70% of the specified load. On the other hand, only in the region in the meridian cross section of the tire, including both of the positions between the bead core and ½ point of the carcass height, the rubber hardness of the tread rubber is JIS A hardness. A high hardness rubber layer having a hardness of 3 degrees or more is disposed.
[0018]
  In the tire, preferably, in the meridian cross section of the tire, the surface of the high-hardness rubber layer facing at least the inner peripheral side of the tire has a wavy shape, and preferably, the average wavelength of the wavy portion is the wavy shape. The total extension of the part is set to 1/3 or less, and more preferably, the total extension of the wavy line part is made 20% or more longer than the length of the line segment passing through the midpoint of the wave.
[0019]
  More preferably, the middle point of the maximum thickness of the hard rubber layer measured in the radial direction of the radial carcass in the meridional section of the tire in the filled state with the specified air pressure is on the normal passing through the maximum thickness position. It is located on the outer surface side of the tire from the thickness midpoint of the measured total tire thickness.
[0020]
  In this pneumatic radial tire, the high-hardness rubber layer embedded in the area near the buttress increases the transmission efficiency of the bulging deformation bside in that area to the area near the ground contact edge, and enlarges the bulging deformation bsho there. In addition, the tread rubber also contributes to an increase in the shearing force on the road surface. As a result, the camber thrust F_C Will be increased.
[0021]
  Here, when the surface of the high-hardness rubber layer facing at least the inner circumference of the tire is configured in a wavy shape in the meridian section of the tire, the adhesion strength of the high-hardness rubber layer to the adjacent rubber layer is increased. Thus, the possibility of peeling off the high hardness rubber layer can be sufficiently removed.
[0022]
  The third pneumatic radial tire according to the present invention has a carcass height from the bead core (H) with respect to the carcass height (H) from the bead core, particularly in a filled state of 10% of the specified air pressure corresponding to the maximum load capacity. The tire total thickness measured in the radial direction of the radial carcass in the meridian cross section of the tire is at least partially within a range of 0.5 to 0.8 times the height (H) in the other portions of the tire side portion. A thin portion that is 75% or less of the same total tire thickness is provided, and 80% or more of the portion where the radius of curvature of the radial carcass is maximum in the meridian section of the tire is 0.65 of the carcass height (H) from the bead core. It is located within a range of ˜0.85 times.
[0023]
  Here, preferably, the maximum width position of the radial carcass is positioned within a range of 0.6 to 0.8 times the carcass height (H) from the bead core.
[0024]
  In addition, it is preferable that the carcass height (H) from the bead core is 0.5 to the carcass height (H) from the bead core, particularly when the air pressure is 10% of the specified air pressure corresponding to the maximum load capacity. The tire total thickness measured in the radial direction of the radial carcass within the meridional section of the tire is at least part of the range of 0.8 times less than 75% of the similar tire total thickness in other portions of the tire side portion. The thickness of the tire measured in the radial direction of the radial carcass in the meridian cross section of the tire at a position 0.85 times the carcass height (H) from the bead core is measured at the side edge position of the belt. The same total tire thickness at 0.64 times or more.
  It is also preferable that the carcass height (H) from the bead core is 0.5% of the carcass height (H) from the bead core, particularly when the air pressure is 10% of the specified air pressure corresponding to the maximum load capacity. The tire total thickness measured in the radial direction of the radial carcass in the meridian cross section of the tire is 75% of the similar tire total thickness in the other portions of the tire side portion at least in a range of ~ 0.8 times. A tire in the radial direction of the radial carcass in the tire meridian cross section at least partially within the range of 0.8 to 0.85 times the carcass height (H) from the bead core while providing the following thin-walled portion A thick part having a total thickness of 1.5 times or more the same total tire thickness at a position 0.75 times the carcass height (H) from the bead core is provided.
[0025]
    According to this pneumatic radial tire, the total thickness of the thin portion within the range of 0.5 to 0.8 times the carcass height (H) is particularly thin compared to the other portions of the tire side portion. Since the bending rigidity of the thin wall portion is locally reduced, the bending deformation concentrates on the rolling on the inclined surface of the tire, and the bulging deformation bside in the vicinity of the buttress increases. As the bulging deformation bsho in the vicinity of the ground contact end is also increased, the caber thrust F_C Is effectively increased.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
    Embodiments of the present invention will be described below based on the drawings.
    FIG. 3 shows an embodiment of the first pneumatic radial tire in a meridian section of a half thereof.
    In the figure, the solid line indicates the invention tire, and the broken line indicates the conventional tire. In the figure, reference numerals 1 and 2 respectively denote a bead portion and a sidewall portion that make a pair, and reference numeral 3 denotes a toroidal tread portion that is continuous with both sidewall portions 2.
    In this specification, the tire side portion or the side portion includes each of the bead portion 1 and the sidewall portion 2.
    Reference numeral 4 denotes a radial carcass that continuously extends from one bead portion 1 to the other bead portion 1, and this radial carcass 4 reinforces the above-described portions 1, 2, and 3.
    A belt 6 is disposed on the outer peripheral side of the crown portion of the radial carcass 4, thereby reinforcing the tread portion 3.
[0027]
    Here, in this tire, the tread portion 3 protrudes to the side of the first tread region 7 and the first tread region 7 that contacts the flat road surface when the tire is subjected to load rolling of the tire, and the mountain side slope of the inclined road surface. And a second tread region 8 that contacts the ground.
    Here, more specifically, the first tread region 7 is a tire for trucks and buses in a state in which a tire mounted on an applicable rim is filled with a specified air pressure corresponding to the maximum load capacity based on the JATMA standard. For tires smaller than truck and bus tires under the specified load, that is, the maximum load, when the load of 70% of the specified load is applied, A large area.
[0028]
    By the way, all the load conditions here are determined in consideration of the magnitude of load actually applied to the tire and the load frequency, and in trucks and buses, the maximum load is often applied. This is based on the fact that in other vehicles, a load of about 70% of the maximum load is applied in many cases.
[0029]
    Also, the second tread region is filled with the above specified air pressure, and when the above-mentioned load conditions are applied to the tires for trucks and buses and the other tires, both give a 10 ° camber angle to the tires. Of the maximum width region of the contact portion to the flat road surface of the tire, the region outside the first tread region in the width direction is referred to.
    In this case, the camber angle of 10 ° is given to each tire because the tire behavior when rolling the saddle is examined in detail, and the deformation mode on the inclined surface of the saddle is 10 ° to the tire. It is because the knowledge that it is almost equivalent to the case where the camber angle is given is obtained.
[0030]
    Moreover, in this tire, the half width TW of the first tread region 7₁And the width TW of the second tread area 8₂In other words, in the state of filling with the specified air pressure according to the maximum load capacity, in the case of truck and bus tires under the specified load, and in the case of small tires with truck and bus tires Is the half-width TW of the first tread region 7, which is the maximum contact width from the tire equator surface of the contact portion of the tire to the flat road surface when a load of 70% of the specified load is applied₁In the state of filling with the above-mentioned specified air pressure, a specified load is applied to a truck / bus tire, and a load of 70% of the specified load is applied to a tire smaller than a truck / bus tire. In addition, when the camber angle of 10 ° is applied, the half width TW of the first tread region of the maximum contact width from the tire equatorial plane of the contact portion of the tire to the flat road surface.₁The width TW of the second tread region which is the ground contact width on the outer side in the width direction.₂Relative to
    TW₂/ TW₁> 4.0 × 10^-2
  And
[0031]
    In addition, here, 0.95 times the carcass height H from the bead core 5 to the carcass height H from the bead core 5 in a state filled with 10% of the prescribed air pressure to the innermost carcass ply. The intersection of the imaginary line segment drawn at the height position and the perpendicular line extending from the side edge of the first tread region 7 to the imaginary line segment is defined as P, and the imaginary line segment and the outside of the tire The distance b between the two points P and Q and the width TW of the second tread area, where Q is the intersection with the contour line₂Relative to
    b / TW₂> 1.2
  And
[0032]
    In the tire having such a configuration, when the load rolls on the inclined surface S as shown in FIG. 2, because of the presence of the second tread region 8, the tire has the conventional contact width region. Compared to radial tires, the contact area can be increased, whereby a lateral force F directed upward of the inclined surface S is obtained._CS, By extension, Camber Thrust F_C Can be increased directly.
    In addition, as described above, the highly rigid second tread region 8 prevents the escape deformation in the vicinity of the buttress and actively contributes to the increase in the bulging deformation bsho in the vicinity of the ground contact end. Also from Camber Thrust F_c Can be effectively increased.
[0033]
    Here, the width TW of the second tread region 8₂Is the half width TW of the first tread region 7₁4.0 × 10 for^-2In the case of the following, when the load rolling on the inclined surface of the tire, the contact width of the second tread region 8 cannot be sufficiently secured, and the camber thrust F_CIt may not be possible to expect an increase according to the requirements.
    Here, in order to sufficiently ground the second tread region 8, it is preferable that the radius of curvature thereof in the meridian section is 30 mm or more.
[0034]
    By the way, when observing the deformation behavior of the second tread region 8 when rolling such a tire on an inclined surface, in order to generate a large bulging deformation bsho based on the bulging deformation bside, Usually, it is effective to increase the rigidity of the portion in the vicinity of the point P described above. Therefore, from the point P, the rubber thickness of the outer portion in the axial direction of the tire is sufficiently increased, and the second rubber thickness b is set. Tread area 8 width TW₂ By making the ratio with respect to a value exceeding 1.2, it is possible to effectively reinforce the buttress portion directly and indirectly the second tread region 8 as a result, and as a result, the second tread region. The camber thrust F is increased by effectively increasing the squeeze deformation bsho of 8 and generating a large shearing force against the road surface at the contact portion of the second tread region 8 together._C Can be greatly increased.
    In other words, if the ratio is less than 1.2, the reinforcing effect is low, and it is difficult to expect a large bulging deformation bsho due to the bulging deformation bside.
[0035]
    This is particularly true when the tire outer contour line passing through the point Q is used to define a reinforcing portion 11 that protrudes further laterally from the tread end, that is, from the side edge of the second tread region 8, as shown. This reinforcing part 11 functions to increase the strength and rigidity of the second tread region 8 and the buttress part, resulting in an increase in the bulging deformation bside under the excellent reinforcing action, and the caber thrust F_C It is possible to effectively contribute to further increase of
[0036]
    In addition, when the reinforcing portion 11 is provided continuously in a ring shape in the tire circumferential direction or when provided with a slight interval in the circumferential direction through a narrow-width slit or the like, The original function can be exhibited particularly effectively.
    On the other hand, in order to ensure the reinforcing effect by the reinforcing portion 11 and to effectively suppress the increase in the tire weight, a plurality of reinforcing portions 11 are arranged at relatively large intervals in the tire circumferential direction. It is preferable that the rib is constituted by a book.
[0037]
    In such a tire, more preferably, in the tire meridian cross section, the radial carcass of the radial center portion in the side center portion in the range of 0.5 to 0.8 times the carcass height H from the bead core 5 in the tire side portion. The total tire thickness in the normal direction is made thinner than the similar total tire thickness in other portions of the tire side portion, and preferably, the maximum width position of the radial carcass is set to 0.6 to 0. 0 of the carcass height H. It is located within the range of 8 times.
[0038]
    Here, according to the former, by making the thickness of the side center portion of the tire side portion smaller than the thickness of each of the buttress portion and the bead portion, particularly ensuring high rigidity in the buttress portion, In addition to ensuring the increase in deformation bsho, it is also possible to increase the bulging deformation bside by concentrating the bulging deformation bside in the vicinity of the buttress in the central portion by reducing the rigidity of the side central portion in particular. With each of these, Camber Thrust F_C Can effectively contribute to the increase of.
[0039]
    By the way, as for these things, the tire total thickness of each position 0.85 times and 0.4 times the carcass height H from the bead core 5 is 1 of the tire total thickness in the maximum width position of the carcass. This is particularly noticeable when the value exceeds 65 times. In other words, if it is 1.65 times or less, it is difficult to sufficiently increase the bulging deformation bside.
[0040]
    Here, each of 0.85 times and 0.4 times the carcass height HofThe position is specified in order to concentrate the deformation on the side center portion in the range of 0.5 to 0.8 times the carcass height H. This is due to the finding that it is advantageous to sufficiently reduce the thickness at the positions of 0.85H and 0.4H that are in the vicinity of the outside.
[0041]
    In the latter case, when the maximum width position of the carcass is specified in the range of 0.6H to 0.8H, the radius of curvature of the carcass from the tread end area to the buttress area is reduced, and the tire inclined surface In addition to increasing the bulging deformation bside at the time of load rolling, it is also possible to increase the bulging deformation bsho by bringing the position of the bulging deformation bside closer to the buttress area. In addition, since the carcass tension at the time of internal pressure filling is reduced within the above range, it is possible to ensure further increase of the bulging deformation bside in that range.
[0042]
    In such a tire, it is more preferable that the tread width is in the range of 80 to 95% of the tire cross-sectional width and the maximum belt width is equal to the tire cross-sectional width under a 10% air pressure filling of the specified internal pressure. The range is 60 to 90%.
[0043]
    That is, when the tread width is less than 80% of the tire cross-sectional width, the camber thrust F_C If it exceeds 95%, Camber Thrust F may not be increased sufficiently._C As the increase of the limit reaches the limit, the risk of breakage of the tread edge increases. Further, when the maximum belt width is less than 60% of the tire cross-sectional width, there is a risk that effective transmission of the bulging deformation bside in the vicinity of the buttress to the vicinity of the ground contact end may be impaired, which reduces 90%. Beyond, Camber Thrust F_C As the increase of the limit reaches the limit, separation of the belt end portion is likely to occur.
[0044]
    In addition, when the tread width exceeds 95% of the tire cross-sectional width, there is a high risk of deterioration in heat durability due to an increase in the rubber thickness at the belt end portion. When it exceeds 90% of the width, there is a high possibility that the belt durability and the heat generation durability are lowered due to an increase in strain at the belt end portion.
[0045]
    The embodiment of the first pneumatic radial tire has been described above with respect to the size of TBR 11R 22.5 14PR shown in FIG. 3, and these are shown in FIG. 4 and the size is TBR 215/70. The same applies to R17.5 tires. Here again, the solid line indicates the inventive tire, and the broken line indicates the conventional tire.
[0046]
    Incidentally, in the invention tire shown in FIG.₁× 2 = 185.0 mm, TW₂= 9.6 mm, b = 19.7 mm, b / TW₂= 2.05, TW₂/ TW₁= 10.38 × 10^-2In the conventional tire shown in FIG.₁× 2 = 185.0mm, TW₂= 0.0 mm, b = 15.5 mm.
    In the invention tire shown in FIG.₁× 2 = 167.0 mm, TW₂= 8.0 mm, b = 15.4 mm, b / TW₂= 1.93, TW₂/ TW₁= 9.58 × 10^-2In the conventional tire shown in FIG.₁× 2 = 167.0mm, TW₂= 0.0 mm, b = 12.1 mm.
[0047]
  Below, the comparative test of the suppression performance of the wandering phenomenon of the invention tire shown in FIG. 3 and the conventional tire will be described.
Test tire
  In the tire having a size of 11R22.5 14PR, inventive tires 1 to 4 having the dimensions shown in Table 1 and conventional tires were prepared.
  Here, in the inventive tire, the outer contour line of the tread portion has a radius of curvature of 580 mm from the tire equatorial plane to the tire width direction outer side 62.8 mm, and between the tire equatorial plane and the tire width direction outer side 62.8 to 91.5 mm. Has a radius of curvature of 200 mm, and the outer side in the width direction is an arc having a radius of curvature of 40 mm.
  In this case, the first tread region 7 exists between the tire equatorial plane and both outer sides in the tire width direction up to 92.5 mm, and the second tread region 8 exists outside the first tread region 7 in the width direction. To do.
  Further, in the conventional tire, the tread portion includes only the first tread region and does not have the second tread region.
Test method
  Each of these tires is mounted on a 7.50 × 22.5 rim and the specified internal pressure is 7.0 kgf / cm.²After loading the air pressure of 11.5t, load it on a normal truck (wheel array 2-D ・ 4) and drive the pavement including the rutted road with a test driver with a maximum load on it. Sensory evaluation of stability was performed.
  The results are also shown in Table 1 in an index evaluation with a conventional tire set to 100 (the larger the index value, the better the result).
  According to the table, it is clear that any of the inventive tires can greatly improve the straight running stability.
[0048]
[Table 1]

[0049]
  An embodiment of the second pneumatic radial tire of the present invention will be described below based on the place shown in FIG.
  In addition, description is abbreviate | omitted here about the component similar to the part described about the 1st pneumatic radial tire.
[0050]
  Especially in this radial tire, in the state of filling with the specified air pressure corresponding to the maximum load capacity, in the case of truck and bus tires under the specified load, and in the case of tires smaller than the truck and bus tires When a load of 70% of the specified load is applied, the outermost ground contact end position 12 in the meridian section of the tire and the carcass height H from the bead core under the specified air pressure filling₀ In contrast, the carcass height H from the bead core₀ In the meridian cross section of the tire, including both of the positions 12 and 13 between the half point 13 and the region 14 shown by hatching in the figure, the rubber hardness of the tread rubber is A high hardness rubber layer 15 having a JIS A hardness of 3 degrees or more, more preferably 5 degrees or more is provided.
[0051]
  In other words, the region 14 has a width CW / 2 or more from the tire equatorial plane XX to the outside in the tire width direction when the width of both outermost ground contact end positions 12 is CW. Separated and radially outward of the tire from the bead core 5 to H₀ / 2 or more apart. Here, the boundary on the tread side of the region 14 is specified by a normal 16 standing on the outer surface of the tire at the outermost ground contact end position 12 in the illustrated cross section.
[0052]
  In the tire configured as described above, when it rolls on an inclined surface such as a heel as shown in FIG. 2, the rubber hardness of the high hardness rubber layer 15 disposed in the region 14 is high. Based on the fact that it is higher than that of the tread rubber, the bulging deformation bside in the vicinity of the buttress becomes easy to be transmitted to the vicinity of the grounding end, and consequently to the grounding end of the tread. As a result, the bulging deformation bsho and the tread rubber shear Deformation S_S Since both are increased, Camber Thrust F_C A sufficient increase in.
[0053]
  Here, the reason why the high hardness rubber layer 15 is disposed in the above-described region 14 is that the bulging deformation bside is particularly greatly generated in the region. Hardness The rubber layer 15 has a JIS A hardness of 3 degrees or more, preferably 5 degrees or more higher than that of the tread rubber. Because it is difficult to expect.
[0054]
  By the way, since the magnitude of the strain associated with the bulging deformation bside as described above, that is, the ease of transmission of the deformation bside, is particularly great on the outer surface side of the tire, the high hardness rubber layer 15 is formed on the outer surface. It is advantageous to arrange them close together. For this reason, preferably, the midpoint of the maximum thickness of the hard rubber layer 15 measured in the normal direction of the radial carcass 4 in the meridional section of the tire in the filled state with the prescribed air pressure is on the normal passing through the maximum thickness position. It is located on the outer surface side of the tire from the midpoint of the total thickness of the tire as measured in.
  Therefore, as shown in FIG. 6, the high-hardness rubber layer 15 is arranged with its surface facing the outer peripheral side of the tire exposed to the outside.
[0055]
  A comparative test regarding the function of suppressing the wandering phenomenon of the pneumatic radial tire having such a configuration will be described below.
Test tire
  Radial tires for light trucks having a size of 195/85 R16 114 / 112L LT and having the configurations shown in FIGS. 6 and 7 are the inventive tires 5 and 6, and the tires having the configurations shown in FIG. 8 are compared. Tire.
[0056]
  The inventive tire 5 shown in FIG. 6 has a high hardness rubber layer 15 having a JIS A hardness of 76 degrees, a thickness of 2.5 mm, and a width of 25 mm starting from a position 70 mm from the tire equatorial plane XX in the tire width direction. As described above, is exposed on the outer surface of the tire. Here, the JIS A hardness of the tread rubber was 61 degrees.
  By the way, the maximum thickness of the high hardness rubber layer 15 measured in the normal direction of the carcass 4 is 2.8 mm, and the midpoint of the thickness is 1.4 mm from the outer surface of the tire. Further, the total thickness of the tire measured on the same normal line is 13.5 mm, and the midpoint of the thickness is 6.75 mm from the tire outer surface.
[0057]
  The invention tire 6 shown in FIG. 7 has a substantially triangular cross-sectional shape with a width of 25 mm and a maximum thickness of 11 mm starting from a position 70 mm from the tire equatorial plane XX, and has a JIS A hardness of 67 degrees. The high hardness rubber layer 15 is configured in the same manner as the inventive tire 10 except that the high hardness rubber layer 15 is disposed at a depth of 0.5 mm from the outer surface of the tire.
  The maximum thickness of the hard rubber layer 15 of this tire measured in the normal direction of the carcass 4 is 12.7 mm, and the midpoint of the thickness is from the outer surface of the tire.6.35It is in the position of mm. And the total thickness of the tire measured on the same normal line is 13.5 mm, The middle point of the thickness exists in the position of 6.75 mm from the tire outer surface.
  The comparative tire shown in FIG. 8 is obtained by omitting the high hardness rubber layer 15 from the tire described above.
[0058]
  The specified internal pressure according to the maximum load capacity (1180 kg) of such a tire is 6.0 kgf / cm.²The contact width CW when a load (826 kg) of 70% of the maximum load capacity is applied is 120 mm. Also, the specified internal pressure (6.0kgf / cm²) The carcass height H from the bead core 5 when filling₀ Is 136 mm.
[0059]
Test method
  6.0kgf / cm²Each tire filled with the internal pressure is mounted on a 2-ton truck that has a double-wheeled rear wheel, and the small truck is loaded with the maximum load on it. It was carried out by sensory evaluation of the straight running stability when traveling. The results are shown in Table 2.
  Here, the straight running stability index is expressed as a larger value as the performance is better with the comparative tire as a control.
  According to the results shown in Table 2, it is clear that the straight running stability is remarkably improved in any of the tires according to the present invention.
[0060]
[Table 2]

[0061]
  FIG. 9 is a tire meridian cross-sectional view showing another embodiment of the second pneumatic radial tire, in which the surface of the high hardness rubber layer 15 facing the inner peripheral side of the tire is wavy. is there. Here, as shown in FIG. 9A, when the high hardness rubber layer 15 is completely embedded in the rubber in the region 14, the surface facing the outer peripheral side of the tire may be wavy. Is possible.
[0062]
  According to this, since the adhesion area between the high-hardness rubber layer 15 and the adjacent rubber layer is increased and the adhesion strength is increased (adhesive force × adhesion area), the wander similar to the radial tire of the above-described embodiment is achieved. While ensuring the ring phenomenon suppression performance, it is possible to provide excellent peel strength even against repeated occurrence of strain on the high-hardness rubber layer 15 due to load rolling of the tire. In addition, since the wavy line here intersects with the progress direction of the peeling at a large angle, it can effectively counter the progress of the peeling.
[0063]
  Further, here, when the average wavelength of the wavy line portion 17 is set to 1/3 or less of the total extension of the wavy line portion 17, the adhesion strength of the high hardness rubber layer 15 is further increased under the application of a large number of waveforms. Can be increased.
  Further, when the total extension of the wavy line portion 17 is made 20% or more longer than the length of the line segment 18 passing through the midpoint of the wave, as shown by a one-dot chain line in FIG. 10, with a further increase in the adhesion area, The adhesive strength can be further increased.
[0064]
  A comparative test for each of the wandering resistance and the peel resistance of the high hardness rubber layer of the pneumatic radial tire of such an embodiment will be described below.
Test tire
  The inventive tire having the configuration shown in FIG. 7 used in the comparative test was used as a control tire, and the tire having the configuration shown in FIG.
  Here, the high hardness rubber layer 15 of the control tire has the dimensions and physical properties as described above, and the high hardness rubber layer 15 of the inventive tire 7 differs from the control tire only in terms of shape, The position, volume, physical properties, etc. of the tire were the same as those of the control tire. The total extension of the wavy lines of the tire 7 of the present invention was 125% of the corresponding portion of the control tire.
[0065]
Test method
  Evaluation of anti-wandering performance is 6.0kgf / cm for each radial tire of size 195/85 R16 114 / 112L LT²The rear wheel is mounted on a 2t truck with double wheels and the rear wheel is mounted on a pavement including a narrow road with a maximum load. The straight running stability was evaluated by sensory evaluation. The results are shown in Table 3.
  Here, the straight-running stability index is represented by a larger value when the control tire is 100 and the performance is better.
[0066]
  In addition, the peel resistance was evaluated based on the specified internal pressure (6.0 kgf / cm) corresponding to the maximum load capacity.²) Specified maximum under fillingLoad capacityWhen the drum was run at a speed of 50 km / h under load, the running distance until the peel length grew to 5 mm was evaluated by index evaluation. The results are also shown in Table 3.
  Again, the larger the index value, the better the result.
[0067]
[Table 3]

[0068]
  According to Table 3, it is clear that the invention tire 7 can greatly improve the peel resistance in combination with some improvement in straight running stability as compared with the control tire.
[0069]
  FIG. 11 is a meridian cross-sectional view showing a third pneumatic radial tire of the present invention. In this figure showing a 195/85 R16 size tire for a light truck, the inventive tire is shown by a solid line and a comparative tire is shown. Represented by broken lines.
[0070]
  Here, in particular, in a state where the air pressure is 10% of the specified air pressure corresponding to the maximum load capacity, the carcass height H from the bead core 5 is 0.5 to 0.8 times, more preferably 0.5 to 0. At least a portion within the 7-fold range, the total tire thickness measured in the normal direction of the radial carcass 4 in the tire meridian cross section is 75% or less of the same total tire thickness in other portions of the tire side portion. A portion 19 is provided.
  As shown in this figure, the total tire thickness at the thin portion 19 at a position 0.63H from the bead core 5 is 5.5 mm, and the thickness is the minimum thickness in a region other than 0.5H to 0.8H. 61% of 0.0 mm (0.49H position).
  In addition, here, 80% or more of the portion where the curvature of the radial carcass 4 is maximum is provided within the range of 0.65 to 0.85 times the carcass height H from the bead core 5.
  Also in this figure, the maximum curvature is 1/23, and 100% of the maximum curvature portion is located within the above range.
[0071]
    According to such a configuration, as described above, the rigidity of the thin-walled portion 19 within the range of 0.5H to 0.8H from the bead core 5 is locally reduced, and during load rolling on the inclined surface of the tire. Since the bending deformation in the cross section shown in the figure concentrates on the thin wall portion 19 and the bulging deformation bside in the vicinity of the buttress increases, the bulging deformation bsho in the vicinity of the ground contact end also increases, and the camber thrust F_C Is effectively increased.
[0072]
    Here, providing the thin wall portion 19 within the range of 0.5H to 0.8H sufficiently contributes to the increase of the bulging deformation bside even if the portion exists on the bead core side from 0.5H. On the other hand, when the thin wall portion 19 is provided at a position exceeding 0.8H, in other words, in the buttress portion, due to a decrease in rigidity of the buttress portion, the bulging deformation bside may be This is because it cannot be effectively transmitted to the tread grounding end.
    In addition, the thickness of the thin portion 19 is set to 75% or less of the thickness of the other portions. If the thickness exceeds 75%, the difference in thickness and, in turn, the difference in rigidity becomes small, and the bulging deformation bside is sufficient. Because it is difficult to expect an increase.
[0073]
    More preferably, in this tire, the maximum width position of the radial carcass 4 is provided within a range of 0.6 to 0.8 times the carcass height H from the bead core 5. As shown in the figure, the maximum width position is set to 0.69H.
[0074]
    Here, by providing the maximum width position of the carcass 4 in the range of 0.6H to 0.8H, more preferably in the range of 0.7H to 0.8H, the bulging deformation bside can be increased. In addition, it is possible to effectively increase the bulging deformation bsho generated based on the bulging deformation bside by effectively bringing the position where the bulging deformation bside occurs to the buttress area. On the other hand, the carcass tension at the time of internal pressure filling can be made sufficiently small within the above range to further increase the bulging deformation bside within that range.
[0075]
    By the way, when the maximum width position is less than 0.6H, there is a possibility that a sufficiently large bulging deformation bside is not caused. When the position exceeds 0.8H, the maximum width position of the carcass 4 is Further, the belt end portion that tends to become a failure nucleus at the time of rolling rolling of the tire is too close, and there is a possibility that the heat generation durability of the tire, the belt durability, and the like are lowered.
[0076]
    Further, by positioning 80% or more of the portion having the maximum carcass curvature in the range of 0.65H to 0.85H, more preferably in the range of 0.7H to 0.85H, the maximum width position of the carcass 4 is set. Each of the bulging deformation bside and the bulging deformation bsho can be effectively increased in the same manner as when selected in the range of 0.6H to 0.8H.
    That is, if it is less than 0.65H, it is difficult to increase the bulging deformation bside to a satisfactory level, and if it exceeds 0.85H, there is a decrease in heat generation durability and belt durability.
[0077]
    Further, here, at a position 0.85 times the carcass height H from the bead core 5, the total tire thickness measured in the normal direction of the radial carcass 4 in the meridional section of the tire is the same tire at the belt side edge position. It is preferable that the total thickness is 0.64 times or more. According to this, the reinforcing effect of the buttress area can be enhanced and the rigidity of the second toled area can be enhanced. That is, when the ratio is less than 0.64, it is difficult to expect the above-described functions to be sufficiently exhibited.
[0078]
    By the way, the total tire thickness at each of the belt side edge position and the 0.85H position is compared with the tire total thickness at the belt side edge position when rolling on an inclined surface. However, the total tire thickness is mainly determined in consideration of the heat generation durability and wear resistance, which are the main characteristics of the tire. On the other hand, for the increase of the bulging deformation bside and the bulging deformation bsho, the fact that the influence of the total tire thickness at the position of 0.85H is particularly large compared to the other parts was obtained. . Incidentally, as shown in the figure, the thickness at the belt side edge position is 22.9 mm, the thickness at the position of 0.85H is 17.2 mm, and the multiple is about 0.75 times.
[0079]
    And preferably, the tire total thickness in the normal direction of the radial carcass 4 in the tire meridian cross section is at least partially within a range of 0.8 to 0.85 times the carcass height H from the bead core 5. A thick part of 1.5 times or more of the same total tire thickness at a position 0.75 times the carcass height H from the bead core 5 is provided. In the embodiment shown in the figure, the position of 0.85H is the thick portion 20 having a total tire thickness of 17.2 mm, the position of 0.75H is 10.5 mm, and the multiple is about 1.64 times.
[0080]
    According to this configuration, the thick portion 20 can greatly increase the rigidity of the second tread region, and can effectively reinforce the buttress region. Therefore, both the bulging deformation bside and the bulging deformation bsho are greatly increased, and the shear deformation S_S An effective increase of.
    In addition, if the said multiple is less than 1.5 times, it is difficult to ensure sufficient expression of the effects as described above.
[0081]
    FIG. 12 is a cross-sectional view showing another embodiment of the third pneumatic radial tire, which is a thin wall in the range of 0.5H to 0.8H, preferably in the range of 0.5 to 0.7H. The portion 21 is locally thinned, and in the figure, the minimum thickness of the thin portion 21 is set to 5.5 mm at a position of 0.62H.
[0082]
    The thin-walled portion 21 here is similar to the above-described thin-walled portion 19 in which the thickness gradually decreases, and the camber thrust F_C Of course, the tire side portion is rubbed against the curb of the road and damaged, for example, like a route bus. When there is a possibility, the occurrence of such damage can be suppressed to a minimum by locally reducing the thickness thereof.
[0083]
    A comparative test regarding the performance of suppressing the wandering phenomenon of the pneumatic radial tire as described above will be described below.
  Test tire
    Inventive tire 10 with various changes in the thickness distribution and carcass line of the side portion of the radial tire for a small truck having a size of 195/85 R16 114 / 112L LT according to the structure shown by the solid line in FIG. 11, and the tire indicated by the broken line in FIG.
[0084]
  Test method
    These tires have a specified internal pressure of 6.0 kgf / cm depending on the maximum load capacity.² After loading, load them on a 2 ton load small truck (rear wheel is a multi-wheel type), and with the maximum load applied to the small truck, a test driver travels on the paved road including the eaves and goes straight Sensory evaluation of stability was performed.
    The results are shown in Table 4 together with the index evaluation (the larger the index, the better) as the comparative tire and the control.
    According to the table, it is clear that the straight running stability is greatly improved in the inventive tire.
[0085]
[Table 4]

[0086]
【The invention's effect】
  As is apparent from the above description, the pneumatic radial tire according to the present invention can be effectively applied to vehicles such as passenger cars, light trucks, trucks and buses, and the wandering phenomenon can be effectively suppressed. In particular, when the vehicle is traveling at high speed, excellent straight running stability can be realized even on a road surface where there is a hail or the like.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating the state of occurrence of a wandering phenomenon.
FIG. 2 is a meridian cross-sectional view showing how a camber thrust is generated.
FIG. 3 is a meridian cross-sectional view showing a half portion of a first pneumatic radial tire.
FIG. 4 is a cross-sectional view similar to FIG. 3, showing a first pneumatic radial tire.
FIG. 5 is a meridian cross-sectional view showing a second pneumatic radial tire.
FIG. 6 is a cross-sectional view of a principal part showing one arrangement mode of a high hardness rubber layer.
FIG. 7 is a cross-sectional view of the main part showing another arrangement of the high-hardness rubber layer.
FIG. 8 is a meridian cross-sectional view showing a comparative tire.
FIG. 9 is a cross-sectional view showing another embodiment of the second pneumatic radial tire.
FIG. 10 is an enlarged view illustrating a wavy line portion of a high hardness rubber layer.
FIG. 11 is a meridian cross-sectional view showing a half portion of a third pneumatic radial tire.
FIG. 12 is a meridian cross-sectional view showing another embodiment of a third pneumatic radial tire.
[Explanation of symbols]
  bside bulging deformation
  bsho
  F_c Camber thrust
  1 Bead section
  2 Side wall
  3 Tread
  4 Radial carcass
  5 Bead section
  6 Belt
  7 1st tread area
  8 Second tread area
  11 Reinforcement part
  12 Outermost ground contact position
  13 points
  14 areas
  15 High hardness rubber layer
  16 Normal
  17 Wavy lines
  18 line segments
  H Carcass height (10% air pressure)
  H₀ Carcass height (100% air pressure)
  TW₁  Half width of the first tread area
  TW₂  Half width of the second tread area
  W tread width
  SE tire cross-section width
  B Belt maximum width

Claims (15)

Both have a pair of bead portions and sidewall portions, and a toroidal tread portion connected to both sidewall portions, a radial carcass that reinforces each portion, and a belt that reinforces the tread portion on the outer peripheral side of the radial carcass In pneumatic radial tires with
The tread portion is composed of a first tread area that is grounded on a flat road surface, and a second tread area that projects to the side of the first tread area and is grounded on a mountain slope of the inclined road surface,
The half width (TW ₁ ) of the first tread region is smaller than that of a truck / bus tire when a specified load is applied to a truck / bus tire in a state of filling with a specified air pressure corresponding to the maximum load capacity. For a tire, the maximum contact width from the tire equatorial plane of the contact portion of the tire to a flat road surface when 70% of the specified load is applied,
The width (TW ₂ ) of the second tread region is filled with a specified air pressure corresponding to the maximum load capacity, and a specified load is applied to a tire smaller than that of a truck / bus tire. Of the maximum ground contact width from the tire equator surface of the tire to the flat road surface when a load of 70% of the specified load is applied and a camber angle of 10 ° is applied, the first When the ground contact width is on the outer side in the width direction from the half width (TW ₁ ) of the tread area,
TW ₂ / TW ₁ > 4.0 × 10 ⁻²
While satisfying the conditions of
The first tread region at a position 0.95 times the carcass height (H) from the bead core with respect to the carcass height (H) from the bead core in a state where 10% of the specified air pressure is filled. The distance (b) from the side edge of the tire to the outer contour of the tire with respect to the width (TW ₂ ) of the second tread region
b / TW ₂ > 1.2
Pneumatic radial tire that satisfies the above conditions.   In the tire meridian cross section, the tire total thickness in the normal direction of the radial carcass in the side center portion in the range of 0.5 to 0.8 times the carcass height (H) from the bead core in the tire side portion. The tire according to claim 1, wherein the tire is made thinner than a similar total tire thickness in other portions of the tire side portion.   The tire according to claim 1 or 2, wherein the maximum width position of the radial carcass is located within a range of 0.6 to 0.8 times the carcass height (H) from the bead core. In the tire meridian section, the total tire thickness in the normal direction to the radial radius at the position of 0.85 times the carcass height (H) and the position of 0.4 times the carcass height (H) in the tire side portion. tire according to any, one of claims 1 to 3 comprising a thickness exceeding 1.65 times the similar total tire thickness at the maximum width position of the car mosquitoes scan a.   The tire according to any one of claims 1 to 4, wherein a tread width is in a range of 80 to 95% of a tire cross-sectional width in a filling state of 10% of the specified air pressure.   The tire according to any one of claims 1 to 5, wherein a maximum belt width is in a range of 60 to 90% of a tire cross-sectional width in a state where the air pressure is 10% of the specified air pressure. Both have a pair of bead portions and sidewall portions, and a toroidal tread portion connected to both sidewall portions, a radial carcass that reinforces each portion, and a belt that reinforces the tread portion on the outer peripheral side of the radial carcass In pneumatic radial tires with
With a specified air pressure in accordance with the maximum load capacity, truck and bus tires with a specified load are loaded, and tires smaller than truck and bus tires have a load of 70% of the specified load. The outermost grounding end position in the meridian section of the tire when loaded,
The region in the meridian section of the tire, including both of the positions between the bead core and a half point of the carcass height with respect to the carcass height from the bead core under the specified air pressure filling A pneumatic radial tire in which a high hardness rubber layer having a JIS A hardness of 3 degrees or more with respect to the rubber hardness of the tread rubber is disposed only inside.   The tire according to claim 7, wherein a surface of the high-hardness rubber layer facing at least the inner peripheral side of the tire is wavy in a meridian cross section of the tire.   The tire according to claim 8, wherein an average wavelength of the wavy line portion is 1/3 or less of a total extension of the wavy line portion.   The tire according to claim 8 or 9, wherein the total length of the wavy line portion is 20% or more longer than the length of the line segment passing through the midpoint of the wave.   In the filled state of the specified air pressure, in the meridional section of the tire, the tire midpoint of the maximum thickness of the hard rubber layer measured in the radial direction of the radial carcass was measured on the normal passing through the maximum thickness position. The tire according to any one of claims 7 to 10, wherein the tire is positioned on the outer surface side of the tire from the thickness middle point of the thickness. Both have a pair of bead portions and sidewall portions, and a toroidal tread portion connected to both sidewall portions, a radial carcass that reinforces each portion, and a belt that reinforces the tread portion on the outer peripheral side of the radial carcass In pneumatic radial tires with
Range of 0.5 to 0.8 times the carcass height (H) from the bead core with respect to the carcass height (H) from the bead core when filled with 10% of the specified air pressure according to the maximum load capacity At least a portion of the tire is provided with a thin portion in which the total tire thickness measured in the radial carcass normal direction within the meridional section of the tire is 75% or less of the same total tire thickness in other portions of the tire side portion. Pneumatic radial tire.   The tire according to claim 12, wherein the maximum width position of the radial carcass is located in a range of 0.6 to 0.8 times the carcass height (H) from the bead core.   The portion where the radius of curvature of the radial carcass in the meridian section of the tire is at least 80% or more is located within a range of 0.65 to 0.85 times the carcass height (H) from the bead core. 13. The tire according to 13.   At a position 0.85 times the carcass height (H) from the bead core, the total tire thickness measured in the normal direction of the radial carcass in the meridian section of the tire is 0% of the same total tire thickness at the side edge position of the belt. The tire according to any one of claims 12 to 14, wherein the tire is 64 times or more.

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