JP2004130881A

JP2004130881A - Pneumatic tire

Info

Publication number: JP2004130881A
Application number: JP2002295999A
Authority: JP
Inventors: Hironori Kobayashi; 小林　弘典; Takumi Hatakeyama; 畠山　拓未; Keita Rachi; 良知　啓太
Original assignee: Yokohama Rubber Co Ltd
Current assignee: Yokohama Rubber Co Ltd
Priority date: 2002-10-09
Filing date: 2002-10-09
Publication date: 2004-04-30
Anticipated expiration: 2022-10-09
Also published as: JP4255262B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of enhancing the durability of a bead part when the bead part is reinforced with a steel code reinforcing layer. <P>SOLUTION: Bead cores 2 are embedded in a left and a right bead part 1, 1, and bead filler 3 is installed at the periphery of each bead core 2, and the two ends of a carcass layer 4 set over between the two bead parts 1 are turned up round the bead cores 2 from inside the tire to the outside, and also the reinforcing layer in which a plurality of steel codes are pulled in alignment is embedded in each bead part 1 along the carcass layer 4. In this pneumatic tire, the reinforcing layer consisting of steel codes is divided into an inner layer 5A and an outer layer 5B about each bead core 2 as the boundary, and the inner reinforcing layer 5A is arranged between the body part 4A of the carcass layer 4 and the bead filler 3, while the outer reinforcing layer 5B is arranged outside in the tire width direction more than the turned-up part 4B of the carcass layer 4. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、耐久性に優れた空気入りタイヤに関し、さらに詳しくは、ビード部に埋設する補強層の配置及び構成を適正化することにより、ビード部の耐久性を向上するようにした空気入りタイヤに関する。
【０００２】
【従来の技術】
重荷重用空気入りラジアルタイヤにおいては、ビード部におけるカーカス層の巻き上げ端を起点とするセパレーションを抑制するために、複数本のスチールコードを引き揃えてなる補強層をカーカス層に沿って埋設することが行われている（例えば、特許文献１及び特許文献２参照。）。
【０００３】
即ち、従来の重荷重用空気入りラジアルタイヤにおいては、図７や図８に示すように、ビード部１にビードコア２が埋設され、ビードコア２の外周側にビードフィラー３が配置され、カーカス層４の端部がビードコア２の廻りにタイヤ内側から外側へ巻き上げられている。そして、複数本のスチールコードを引き揃えてなる補強層５はカーカス層４を包み込むように配置されている。
【０００４】
このようにビード部にスチールコード補強層を追加することにより、ビード部のタイヤ外側への倒れ込みを抑制し、カーカス層の巻き上げ端に作用する歪を低減し、その巻き上げ端を起点とするセパレーションを抑制することができる。しかしながら、ビード部にスチールコード補強層を追加した場合、その補強層に起因する故障を生じるため、耐久性の改善効果が必ずしも十分ではなかった。
【０００５】
【特許文献１】
特開平１１−２０４２３号公報
【特許文献２】
特開平７−１６４８３７号公報
【０００６】
【発明が解決しようとする課題】
本発明の目的は、スチールコード補強層によってビード部を補強するに際し、ビード部の耐久性を向上することを可能にした空気入りタイヤを提供することにある。
【０００７】
【課題を解決するための手段】
上記目的を達成するための本発明の空気入りタイヤは、左右一対のビード部にそれぞれビードコアを埋設し、各ビードコアの外周側にビードフィラーを配置し、前記左右一対のビード部間に装架されたカーカス層の両端部を前記ビードコアの廻りにタイヤ内側から外側へ巻き上げると共に、複数本のスチールコードを引き揃えてなる補強層を前記カーカス層に沿って前記ビード部に埋設した空気入りタイヤにおいて、前記スチールコードからなる補強層を前記ビードコアを堺にして内側補強層と外側補強層とに分割し、内側補強層を前記カーカス層の本体部と前記ビードフィラーとの間に配置し、外側補強層を前記カーカス層の巻き上げ部よりタイヤ幅方向外側に配置したことを特徴とするものである。
【０００８】
このようにスチールコード補強層をビードコアを堺にして内側補強層と外側補強層とに分割し、内側補強層をカーカス層の本体部とビードフィラーとの間に配置し、外側補強層をカーカス層の巻き上げ部よりタイヤ幅方向外側に配置したことにより、従来のようにカーカス層を包み込むようにスチールコード補強層を配置した場合に比べて、ビード部の耐久性を向上することができる。また、必要以上の重量増加を回避するために、スチールコードからなる補強層は上記位置だけに配置すると良い。
【０００９】
本発明では、カーカス層の巻き上げ端と内側補強層の上端と外側補強層の上端のタイヤ径方向の高さ位置を互いに異ならせ、カーカス層の巻き上げ端を内側補強層の上端よりも高くし、外側補強層の上端をカーカス層の巻き上げ端よりも高くすることが好ましい。或いは、カーカス層の巻き上げ端と内側補強層の上端と外側補強層の上端のタイヤ径方向の高さ位置を互いに異ならせ、カーカス層の巻き上げ端を外側補強層の上端よりも高くし、内側補強層の上端を前記カーカス層の巻き上げ端よりも高くすることが好ましい。いずれの場合も、ビード部の剛性変化が滑らかになるので、耐久性の面で有利である。
【００１０】
また、リム径の基準位置からのリムフランジの高さをＨとし、該リムフランジの頂点からの外側補強層の上端の高さをｈ１とし、該リムフランジの頂点からの内側補強層の上端の高さをｈ２とし、リム径の基準位置からの内側補強層の下端の高さをｈ３とし、リム径の基準位置からの外側補強層の下端の高さをｈ４としたとき、これら高さｈ１〜ｈ４をリムフランジ高さＨに対して適切に設定することが好ましい。
【００１１】
本発明では、スチールコード補強層を内側補強層と外側補強層に分割した構成を備えているので、この分割構造を有効に利用し、それによって、耐久性の向上のみならず、軽量化や操縦安定性の向上を図ることも可能である。より具体的には、内側補強層及び外側補強層のタイヤ周方向に対するコード絶対角度を互いに異ならせると良い。この場合、内側補強層及び外側補強層のタイヤ周方向に対するコード絶対角度の差を５〜６５度にすると良い。また、内側補強層及び外側補強層の単位幅当たりのコード打ち込み本数やコード撚り構造を互いに異ならせても良い。
【００１２】
【発明の実施の形態】
以下、添付図面を引用して本発明の実施形態を説明する。各図において、同一の構成要素は同一の符号を付し、重複した説明は省略する。
【００１３】
図１及び図２は、それぞれ本発明の第１及び第２実施形態からなる重荷重用空気入りラジアルタイヤのビード部を示す断面図である。図１及び図２において、ビード部１にはビードコア２が埋設され、ビードコア２の外周側にはビードフィラー３が配置されている。左右一対のビード部１，１間に装架されたカーカス層４は、その両端部がそれぞれビードコア２の廻りにタイヤ内側から外側へ巻き上げられている。即ち、カーカス層４はビードコア２を堺にして本体部４Ａと巻き上げ部４Ｂとから構成されている。そして、複数本のスチールコードを引き揃えてなる補強層は、ビードコア２を堺にして内側補強層５Ａと外側補強層５Ｂとに分割され、その内側補強層５Ａがカーカス層４の本体部４Ａとビードフィラー３との間に配置され、その外側補強層５Ｂがカーカス層４の巻き上げ部４Ｂよりタイヤ幅方向外側に配置されている。
【００１４】
上記ビード部の補強構造において、カーカス層４の巻き上げ端４ＢＵと内側補強層５Ａの上端５ＡＵと外側補強層５Ｂの上端５ＢＵのタイヤ径方向の高さ位置は互いに相違しており、カーカス層４の巻き上げ端４ＢＵは内側補強層５Ａの上端５ＡＵよりも高く、外側補強層５Ｂの上端５ＢＵはカーカス層４の巻き上げ端４ＢＵよりも高くなっている。
【００１５】
ここで、リム径の基準位置Ｒからのリムフランジの高さをＨとし、該リムフランジの頂点からの外側補強層５Ｂの上端５ＢＵの高さをｈ１とし、該リムフランジの頂点からの内側補強層５Ａの上端５ＡＵの高さをｈ２とし、リム径の基準位置Ｒからの内側補強層５Ａの下端５ＡＬの高さをｈ３とし、リム径の基準位置Ｒからの外側補強層５Ｂの下端５ＢＬの高さをｈ４としたとき、これら高さｈ１〜ｈ４をリムフランジ高さＨに対して適切に設定すると良い。但し、ここで言うリムとは、ＪＡＴＭＡ規定による標準リムである。
【００１６】
図１の実施形態のように、内側補強層５Ａの下端５ＡＬをビードコア２の内側近傍に配置し、外側補強層５Ｂの下端５ＢＬをビードコア２の外側近傍に配置した補強構造とする場合、下記条件を選択することにより、耐久性の向上効果が顕著に得られる。
１．９０＜ｈ１／Ｈ＜２．７０
１．１５＜ｈ２／Ｈ＜１．８５
０．５０＜ｈ３／Ｈ＜１．１０
０．１５＜ｈ４／Ｈ＜０．７０
【００１７】
図２の実施形態のように、内側補強層５Ａの下端５ＡＬをビードコア２の内側近傍に配置し、外側補強層５Ｂをビードコア２の下側に廻り込ませて該外側補強層５Ｂの下端５ＢＬをビードコア２の内側近傍に配置した補強構造とする場合、下記条件を選択することにより、耐久性の向上効果が顕著に得られる。
１．９０＜ｈ１／Ｈ＜２．７０
１．１５＜ｈ２／Ｈ＜１．８５
０．５０＜ｈ３／Ｈ＜１．１０
０．１０＜ｈ４／Ｈ＜０．５０
【００１８】
図３及び図４は、それぞれ本発明の第３及び第４実施形態からなる重荷重用空気入りラジアルタイヤのビード部を示す断面図である。図３及び図４において、ビード部１にはビードコア２が埋設され、ビードコア２の外周側にはビードフィラー３が配置されている。左右一対のビード部１，１間に装架されたカーカス層４は、その両端部がそれぞれビードコア２の廻りにタイヤ内側から外側へ巻き上げられている。即ち、カーカス層４はビードコア２を堺にして本体部４Ａと巻き上げ部４Ｂとから構成されている。そして、複数本のスチールコードを引き揃えてなる補強層は、ビードコア２を堺にして内側補強層５Ａと外側補強層５Ｂとに分割され、その内側補強層５Ａがカーカス層４の本体部４Ａとビードフィラー３との間に配置され、その外側補強層５Ｂがカーカス層４の巻き上げ部４Ｂよりタイヤ幅方向外側に配置されている。
【００１９】
上記ビード部の補強構造において、カーカス層４の巻き上げ端４ＢＵと内側補強層５Ａの上端５ＡＵと外側補強層５Ｂの上端５ＢＵのタイヤ径方向の高さ位置は互いに相違しており、カーカス層４の巻き上げ端４ＢＵは外側補強層５Ｂの上端５ＢＵよりも高く、内側補強層５Ａの上端５ＡＵはカーカス層４の巻き上げ端４ＢＵよりも高くなっている。
【００２０】
ここで、リム径の基準位置Ｒからのリムフランジの高さをＨとし、該リムフランジの頂点からの外側補強層５Ｂの上端５ＢＵの高さをｈ１とし、該リムフランジの頂点からの内側補強層５Ａの上端５ＡＵの高さをｈ２とし、リム径の基準位置Ｒからの内側補強層５Ａの下端５ＡＬの高さをｈ３とし、リム径の基準位置Ｒからの外側補強層５Ｂの下端５ＢＬの高さをｈ４としたとき、これら高さｈ１〜ｈ４をリムフランジ高さＨに対して適切に設定すると良い。但し、ここで言うリムとは、ＪＡＴＭＡ規定による標準リムである。
【００２１】
図３の実施形態のように、内側補強層５Ａの下端５ＡＬをビードコア２の内側近傍に配置し、外側補強層５Ｂの下端５ＢＬをビードコア２の外側近傍に配置した補強構造とする場合、下記条件を選択することにより、耐久性の向上効果が顕著に得られる。
０．４０＜ｈ１／Ｈ＜１．２０
２．２０＜ｈ２／Ｈ＜２．９０
０．５０＜ｈ３／Ｈ＜１．１０
０．１５＜ｈ４／Ｈ＜０．７０
【００２２】
図４の実施形態のように、内側補強層５Ａの下端５ＡＬをビードコア２の内側近傍に配置し、外側補強層５Ｂをビードコア２の下側に廻り込ませて該外側補強層５Ｂの下端５ＢＬをビードコア２の内側近傍に配置した補強構造とする場合、下記条件を選択することにより、耐久性の向上効果が顕著に得られる。
０．４０＜ｈ１／Ｈ＜１．２０
２．２０＜ｈ２／Ｈ＜２．９０
０．５０＜ｈ３／Ｈ＜１．１０
０．１０＜ｈ４／Ｈ＜０．５０
【００２３】
上述した内側補強層５Ａ及び外側補強層５Ｂについて、コード角度やコード打ち込み本数やコード撚り構造は特に限定されるものではない。
【００２４】
ところで、上記タイヤはスチールコード補強層を内側補強層５Ａと外側補強層５Ｂに分割した構成を備えているので、この分割構造を有効に利用し、それによって、耐久性の向上のみならず、軽量化や操縦安定性の向上を図ることが可能である。
【００２５】
図５及び図６は、内側補強層５Ａと外側補強層５Ｂを構成するスチールコードのタイヤ周方向に対する角度を説明するための展開図である。図５及び図６は、カーカス層４の本体部４Ａと内側補強層５Ａをビードコア２の左側に展開し、カーカス層４の巻き上げ部４Ｂと外側補強層５Ｂをビードコア２の右側に展開した状態を示している。図５及び図６において、内側補強層５Ａのタイヤ周方向に対するコード絶対角度βと外側補強層５Ｂのタイヤ周方向に対するコード絶対角度αとは互いに異なっている。ここで、スチールコードの傾斜方向はいずれであっても良い。
【００２６】
例えば、内側補強層５Ａのコード絶対角度βを外側補強層５Ｂのコード絶対角度αよりも大きくし、そのコード絶対角度の差を５〜６５度にすることにより、ビード部の耐久性を阻害することなく操縦安定性を向上することができる。なお、コード絶対角度の差が５度未満であると操縦安定性の向上効果が不十分になり、逆に６５度超であるとビード部の耐久性が低下することになる。
【００２７】
また、内側補強層５Ａの単位幅当たりのコード打ち込み本数を外側補強層５Ｂの単位幅当たりのコード打ち込み本数よりも少なくした場合、操縦安定性やビード部の耐久性を良好にしたまま軽量化を図ることができる。
【００２８】
更に、内側補強層５Ａ及び外側補強層５Ｂのコード撚り構造を互いに異ならせ、内側補強層５Ａのコードを外側補強層５Ｂのコードよりも軽くした場合、操縦安定性やビード部の耐久性を良好にしたまま軽量化を図ることができる。
【００２９】
【実施例】
〔実験Ａ〕
重荷重用空気入りラジアルタイヤ（サイズ：１１Ｒ２２．５）において、図１に示すビード部の補強構造を有し、内側補強層及び外側補強層の寸法を表１の通り種々異ならせた１２種類の本発明タイヤ（実施例１〜１２）、及び、図７に示すビード部の補強構造を有する従来タイヤ（従来例１）をそれぞれ製作した。従来例１において、補強層のカーカス層巻き上げ部側の上端の高さｈ５及びカーカス層本体部側の上端の高さｈ６を、リムフランジ高さＨに対して、ｈ５／Ｈ＝２．３０，ｈ６／Ｈ＝１．５０とした。
【００３０】
これら本発明タイヤ及び従来タイヤについて、以下の方法により耐久性を評価した。
【００３１】
〔耐久性〕
リムサイズ：２２．５×８．２５、空気圧：７００ｋＰａ（規定空気圧）、荷重：規定荷重の１６０％、速度：５０ｋｍ／ｈの条件で、各タイヤをドラム（直径：１７００ｍｍ）上で回転し、ビード部が故障に至るまでの距離を測定した。評価結果は、従来例１を１００とする指数により表１に示した。この指数値が大きいほどビード部の耐久性が優れている。
【００３２】
【表１】

【００３３】
この結果から、本発明タイヤは従来タイヤに比べて耐久性が向上していることを確認した。特に、内側補強層及び外側補強層の寸法をリムフランジ高さＨに対して適正化した実施例５〜８の本発明タイヤは耐久性の向上効果が顕著であった。
【００３４】
〔実験Ｂ〕
重荷重用空気入りラジアルタイヤ（サイズ：１１Ｒ２２．５）において、図２に示すビード部の補強構造を有し、内側補強層及び外側補強層の寸法を表２の通り種々異ならせた１２種類の本発明タイヤ（実施例１３〜２４）をそれぞれ製作し、実験Ａと同じ方法により耐久性を評価し、その結果を従来例１を１００とする指数により表２に示した。
【００３５】
【表２】

【００３６】
この結果から、本発明タイヤは従来タイヤに比べて耐久性が向上していることを確認した。特に、内側補強層及び外側補強層の寸法をリムフランジ高さＨに対して適正化した実施例１７〜２０の本発明タイヤは耐久性の向上効果が顕著であった。なお、実施例２４の本発明タイヤは内側補強層及び外側補強層が重複しているため従来タイヤよりも重量が増加していた。
【００３７】
〔実験Ｃ〕
重荷重用空気入りラジアルタイヤ（サイズ：１１Ｒ２２．５）において、図３に示すビード部の補強構造を有し、内側補強層及び外側補強層の寸法を表３の通り種々異ならせた１２種類の本発明タイヤ（実施例２５〜３６）、及び、図８に示すビード部の補強構造を有する従来タイヤ（従来例２）をそれぞれ製作した。従来例２において、補強層のカーカス層巻き上げ部側の上端の高さｈ５及びカーカス層本体部側の上端の高さｈ６を、リムフランジ高さＨに対して、ｈ５／Ｈ＝０．８０，ｈ６／Ｈ＝２．５０とした。
【００３８】
これら本発明タイヤ及び従来タイヤについて、実験Ａと同じ方法により耐久性を評価し、その結果を従来例２を１００とする指数により表３に示した。
【００３９】
【表３】

【００４０】
この結果から、本発明タイヤは従来タイヤに比べて耐久性が向上していることを確認した。特に、内側補強層及び外側補強層の寸法をリムフランジ高さＨに対して適正化した実施例２９〜３２の本発明タイヤは耐久性の向上効果が顕著であった。
【００４１】
〔実験Ｄ〕
重荷重用空気入りラジアルタイヤ（サイズ：１１Ｒ２２．５）において、図４に示すビード部の補強構造を有し、内側補強層及び外側補強層の寸法を表４の通り種々異ならせた１２種類の本発明タイヤ（実施例３７〜４８）をそれぞれ製作し、実験Ａと同じ方法により耐久性を評価し、その結果を従来例２を１００とする指数により表４に示した。
【００４２】
【表４】

【００４３】
この結果から、本発明タイヤは従来タイヤに比べて耐久性が向上していることを確認した。特に、内側補強層及び外側補強層の寸法をリムフランジ高さＨに対して適正化した実施例４１〜４４の本発明タイヤは耐久性の向上効果が顕著であった。なお、実施例４８の本発明タイヤは内側補強層及び外側補強層が重複しているため従来タイヤよりも重量が増加していた。
【００４４】
〔実験Ｅ〕
重荷重用空気入りラジアルタイヤ（サイズ：１１Ｒ２２．５）において、図４に示すビード部の補強構造を有し、内側補強層及び外側補強層のコード角度、単位幅当たりのコード打ち込み本数、コード撚り構造を表５の通り種々異ならせた７種類の本発明タイヤ（実施例４９〜５５）、及び、図８に示すビード部の補強構造を有する従来タイヤ（従来例３）をそれぞれ製作した。従来例３において、補強層のコード角度を２０度とし、コード打ち込み本数を２３本／５０ｍｍとし、コード撚り構造を３＋８×０．２２とした。
【００４５】
これら本発明タイヤ及び従来タイヤについて、実験Ａと同じ方法により耐久性の試験を行い、その結果を従来例３を１００とする指数により表５に示した。また、以下の方法によりタイヤ重量及び操縦安定性を評価した。
【００４６】
〔タイヤ重量〕
各タイヤの重量を測定した。評価結果は、従来例３を１００とする指数により表５に示した。この指数値が小さいほど軽量である。
【００４７】
〔操縦安定性〕
リムサイズ：２２．５×７．５０、空気圧：７００ｋＰａ（規定空気圧）、荷重：規定荷重の１００％の条件で、各タイヤを車両に装着し、テストコースにおいて専門パネラー３名によるフィーリング評価を行った。評価結果は、従来例３を１００とする指数にて示した。この指数値が大きいほど操縦安定性が優れている。
【００４８】
【表５】

【００４９】
この結果から、内側補強層及び外側補強層の構造を互いに異ならせることにより、耐久性の向上のみならず、軽量化や操縦安定性の向上を図ることが可能であった。
【００５０】
【発明の効果】
以上説明したように本発明によれば、スチールコードからなる補強層をビードコアを堺にして内側補強層と外側補強層とに分割し、内側補強層をカーカス層の本体部とビードフィラーとの間に配置し、外側補強層をカーカス層の巻き上げ部よりタイヤ幅方向外側に配置したから、従来のようにカーカス層を包み込むようにスチールコード補強層を配置した場合に比べて、ビード部の耐久性を向上することができる。
【図面の簡単な説明】
【図１】本発明の第１実施形態からなる重荷重用空気入りラジアルタイヤのビード部を示す断面図である。
【図２】本発明の第２実施形態からなる重荷重用空気入りラジアルタイヤのビード部を示す断面図である。
【図３】本発明の第３実施形態からなる重荷重用空気入りラジアルタイヤのビード部を示す断面図である。
【図４】本発明の第４実施形態からなる重荷重用空気入りラジアルタイヤのビード部を示す断面図である。
【図５】本発明の空気入りタイヤにおける内側補強層と外側補強層を構成するスチールコードの配列の一例を示す展開図である。
【図６】本発明の空気入りタイヤにおける内側補強層と外側補強層を構成するスチールコードの配列の他の例を示す展開図である。
【図７】従来の重荷重用空気入りラジアルタイヤのビード部を示す断面図である。
【図８】従来の重荷重用空気入りラジアルタイヤのビード部の変形例を示す断面図である。
【符号の説明】
１　ビード部
２　ビードコア
３　ビードフィラー
４　カーカス層
４Ａ　カーカス層の本体部
４Ｂ　カーカス層の巻き上げ部
４ＢＵ　カーカス層の巻き上げ端
５Ａ　内側補強層
５Ｂ　外側補強層
５ＡＵ　内側補強層の上端
５ＡＬ　内側補強層の下端
５ＢＵ　外側補強層の上端
５ＢＬ　外側補強層の下端
Ｈ　リムフランジ高さ
Ｒ　リム径の基準位置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pneumatic tire having excellent durability, and more particularly, to a pneumatic tire having improved durability of a bead portion by optimizing an arrangement and a configuration of a reinforcing layer embedded in the bead portion. About.
[0002]
[Prior art]
In a heavy-duty pneumatic radial tire, in order to suppress the separation from the winding end of the carcass layer in the bead portion, a reinforcing layer formed by aligning a plurality of steel cords may be embedded along the carcass layer. (For example, see Patent Documents 1 and 2).
[0003]
That is, in a conventional pneumatic radial tire for heavy load, as shown in FIGS. 7 and 8, a bead core 2 is embedded in a bead portion 1, a bead filler 3 is arranged on an outer peripheral side of the bead core 2, and a carcass layer 4 is formed. The end is wound up around the bead core 2 from the inside to the outside of the tire. The reinforcing layer 5 formed by aligning a plurality of steel cords is disposed so as to surround the carcass layer 4.
[0004]
By adding the steel cord reinforcing layer to the bead portion in this way, the bead portion is prevented from falling down to the outside of the tire, the strain acting on the winding end of the carcass layer is reduced, and the separation starting from the winding end is reduced. Can be suppressed. However, when a steel cord reinforcing layer is added to a bead portion, a failure due to the reinforcing layer occurs, and the effect of improving durability is not always sufficient.
[0005]
[Patent Document 1]
JP-A-11-20423 [Patent Document 2]
JP-A-7-164837
[Problems to be solved by the invention]
An object of the present invention is to provide a pneumatic tire capable of improving the durability of a bead portion when reinforcing the bead portion with a steel cord reinforcing layer.
[0007]
[Means for Solving the Problems]
To achieve the above object, the pneumatic tire of the present invention embeds a bead core in each of a pair of left and right bead portions, arranges a bead filler on an outer peripheral side of each bead core, and is mounted between the pair of left and right bead portions. While winding both ends of the carcass layer around the bead core from the inside of the tire to the outside, a pneumatic tire having a reinforcing layer formed by aligning a plurality of steel cords embedded in the bead portion along the carcass layer, The reinforcing layer made of the steel cord is divided into an inner reinforcing layer and an outer reinforcing layer using the bead core as a rim, and the inner reinforcing layer is disposed between the main body of the carcass layer and the bead filler. Are arranged on the outer side in the tire width direction from the winding portion of the carcass layer.
[0008]
In this way, the steel cord reinforcing layer is divided into an inner reinforcing layer and an outer reinforcing layer using the bead core as a sakai, the inner reinforcing layer is disposed between the main body of the carcass layer and the bead filler, and the outer reinforcing layer is formed as the carcass layer. By arranging the steel cord reinforcing layer so as to surround the carcass layer as in the related art, the durability of the bead portion can be improved by arranging the steel cord reinforcing layer so as to surround the carcass layer. Further, in order to avoid an unnecessary increase in weight, the reinforcing layer made of a steel cord is preferably disposed only at the above-mentioned position.
[0009]
In the present invention, the height of the winding end of the carcass layer, the upper end of the inner reinforcing layer and the upper end of the outer reinforcing layer in the tire radial direction are different from each other, and the winding end of the carcass layer is higher than the upper end of the inner reinforcing layer, It is preferable that the upper end of the outer reinforcing layer is higher than the winding end of the carcass layer. Alternatively, the heights in the tire radial direction of the winding end of the carcass layer, the upper end of the inner reinforcing layer, and the upper end of the outer reinforcing layer are made different from each other, and the winding end of the carcass layer is higher than the upper end of the outer reinforcing layer, so that the inner reinforcement is performed. Preferably, the upper end of the layer is higher than the winding end of the carcass layer. In any case, the change in rigidity of the bead portion is smooth, which is advantageous in terms of durability.
[0010]
The height of the rim flange from the reference position of the rim diameter is H, the height of the upper end of the outer reinforcing layer from the top of the rim flange is h1, and the height of the upper end of the inner reinforcing layer from the top of the rim flange is h1. When the height is h2, the height of the lower end of the inner reinforcing layer from the reference position of the rim diameter is h3, and the height of the lower end of the outer reinforcing layer from the reference position of the rim diameter is h4, these heights h1 It is preferable that h4 to h4 be appropriately set with respect to the rim flange height H.
[0011]
In the present invention, since the steel cord reinforcing layer is provided with a structure in which the steel cord reinforcing layer is divided into an inner reinforcing layer and an outer reinforcing layer, this split structure is effectively used, thereby not only improving the durability but also reducing the weight and controlling the steering. It is also possible to improve the stability. More specifically, it is preferable to make the cord absolute angles of the inner reinforcing layer and the outer reinforcing layer relative to the tire circumferential direction different from each other. In this case, the difference between the absolute cord angles of the inner reinforcing layer and the outer reinforcing layer with respect to the tire circumferential direction is preferably 5 to 65 degrees. Further, the number of cords per unit width of the inner reinforcing layer and the outer reinforcing layer and the cord twisting structure may be different from each other.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In each drawing, the same components are denoted by the same reference numerals, and redundant description will be omitted.
[0013]
1 and 2 are cross-sectional views showing a bead portion of a heavy-duty pneumatic radial tire according to the first and second embodiments of the present invention, respectively. 1 and 2, a bead core 2 is embedded in a bead portion 1, and a bead filler 3 is arranged on an outer peripheral side of the bead core 2. Both ends of the carcass layer 4 mounted between the pair of right and left bead portions 1 and 1 are wound around the bead core 2 from the inside of the tire to the outside. That is, the carcass layer 4 is composed of a main body portion 4A and a winding portion 4B with the bead core 2 serving as a rim. The reinforcing layer formed by aligning a plurality of steel cords is divided into an inner reinforcing layer 5A and an outer reinforcing layer 5B using the bead core 2 as a rim, and the inner reinforcing layer 5A and the main body 4A of the carcass layer 4 are separated. The outer reinforcing layer 5B is disposed between the bead filler 3 and the outer reinforcing layer 5B is disposed outside the winding portion 4B of the carcass layer 4 in the tire width direction.
[0014]
In the reinforcing structure of the bead portion, the height positions in the tire radial direction of the raised end 4BU of the carcass layer 4, the upper end 5AU of the inner reinforcing layer 5A, and the upper end 5BU of the outer reinforcing layer 5B are different from each other. The winding end 4BU is higher than the upper end 5AU of the inner reinforcing layer 5A, and the upper end 5BU of the outer reinforcing layer 5B is higher than the winding end 4BU of the carcass layer 4.
[0015]
Here, the height of the rim flange from the reference position R of the rim diameter is H, the height of the upper end 5BU of the outer reinforcing layer 5B from the top of the rim flange is h1, and the inside reinforcement from the top of the rim flange is h1. The height of the upper end 5AU of the layer 5A is h2, the height of the lower end 5AL of the inner reinforcing layer 5A from the rim diameter reference position R is h3, and the lower end 5BL of the outer reinforcing layer 5B from the rim diameter reference position R is h3. Assuming that the height is h4, the heights h1 to h4 are preferably set appropriately with respect to the rim flange height H. However, the rim referred to here is a standard rim specified by JATMA.
[0016]
When the lower end 5AL of the inner reinforcing layer 5A is arranged near the inside of the bead core 2 and the lower end 5BL of the outer reinforcing layer 5B is arranged near the outside of the bead core 2 as in the embodiment of FIG. By selecting, a remarkable effect of improving durability can be obtained.
1.90 <h1 / H <2.70
1.15 <h2 / H <1.85
0.50 <h3 / H <1.10.
0.15 <h4 / H <0.70
[0017]
2, the lower end 5AL of the inner reinforcing layer 5A is arranged near the inner side of the bead core 2, the outer reinforcing layer 5B is wrapped under the bead core 2, and the lower end 5BL of the outer reinforcing layer 5B is fixed. In the case where the reinforcing structure is arranged near the inside of the bead core 2, the effect of improving the durability can be remarkably obtained by selecting the following conditions.
1.90 <h1 / H <2.70
1.15 <h2 / H <1.85
0.50 <h3 / H <1.10.
0.10 <h4 / H <0.50
[0018]
FIG. 3 and FIG. 4 are cross-sectional views showing a bead portion of the heavy duty pneumatic radial tire according to the third and fourth embodiments of the present invention, respectively. 3 and 4, a bead core 2 is buried in a bead portion 1, and a bead filler 3 is arranged on an outer peripheral side of the bead core 2. Both ends of the carcass layer 4 mounted between the pair of right and left bead portions 1 and 1 are wound around the bead core 2 from the inside of the tire to the outside. That is, the carcass layer 4 is composed of a main body portion 4A and a winding portion 4B with the bead core 2 serving as a rim. The reinforcing layer formed by aligning a plurality of steel cords is divided into an inner reinforcing layer 5A and an outer reinforcing layer 5B using the bead core 2 as a rim, and the inner reinforcing layer 5A and the main body 4A of the carcass layer 4 are separated. The outer reinforcing layer 5B is disposed between the bead filler 3 and the outer reinforcing layer 5B is disposed outside the winding portion 4B of the carcass layer 4 in the tire width direction.
[0019]
In the reinforcing structure of the bead portion, the height positions in the tire radial direction of the raised end 4BU of the carcass layer 4, the upper end 5AU of the inner reinforcing layer 5A, and the upper end 5BU of the outer reinforcing layer 5B are different from each other. The winding end 4BU is higher than the upper end 5BU of the outer reinforcing layer 5B, and the upper end 5AU of the inner reinforcing layer 5A is higher than the winding end 4BU of the carcass layer 4.
[0020]
Here, the height of the rim flange from the reference position R of the rim diameter is H, the height of the upper end 5BU of the outer reinforcing layer 5B from the top of the rim flange is h1, and the inside reinforcement from the top of the rim flange is h1. The height of the upper end 5AU of the layer 5A is h2, the height of the lower end 5AL of the inner reinforcing layer 5A from the rim diameter reference position R is h3, and the lower end 5BL of the outer reinforcing layer 5B from the rim diameter reference position R is h3. Assuming that the height is h4, the heights h1 to h4 are preferably set appropriately with respect to the rim flange height H. However, the rim referred to here is a standard rim specified by JATMA.
[0021]
As in the embodiment of FIG. 3, when the lower end 5AL of the inner reinforcing layer 5A is arranged near the inside of the bead core 2 and the lower end 5BL of the outer reinforcing layer 5B is arranged near the outside of the bead core 2, the following conditions are satisfied. By selecting, a remarkable effect of improving durability can be obtained.
0.40 <h1 / H <1.20
2.20 <h2 / H <2.90
0.50 <h3 / H <1.10.
0.15 <h4 / H <0.70
[0022]
As in the embodiment of FIG. 4, the lower end 5AL of the inner reinforcing layer 5A is arranged near the inner side of the bead core 2, the outer reinforcing layer 5B is wrapped under the bead core 2, and the lower end 5BL of the outer reinforcing layer 5B is connected. In the case where the reinforcing structure is arranged near the inside of the bead core 2, the effect of improving the durability can be remarkably obtained by selecting the following conditions.
0.40 <h1 / H <1.20
2.20 <h2 / H <2.90
0.50 <h3 / H <1.10.
0.10 <h4 / H <0.50
[0023]
Regarding the inner reinforcing layer 5A and the outer reinforcing layer 5B described above, the cord angle, the number of cords to be driven, and the cord twist structure are not particularly limited.
[0024]
By the way, since the tire has a structure in which the steel cord reinforcing layer is divided into the inner reinforcing layer 5A and the outer reinforcing layer 5B, this divided structure is effectively used, thereby not only improving the durability but also reducing the weight. It is possible to improve the steering and steering stability.
[0025]
FIGS. 5 and 6 are developed views for explaining the angles of the steel cords forming the inner reinforcing layer 5A and the outer reinforcing layer 5B with respect to the tire circumferential direction. FIGS. 5 and 6 show a state in which the main body portion 4A of the carcass layer 4 and the inner reinforcing layer 5A are developed on the left side of the bead core 2, and the winding portion 4B of the carcass layer 4 and the outer reinforcing layer 5B are developed on the right side of the bead core 2. Is shown. 5 and 6, a cord absolute angle β of the inner reinforcing layer 5A with respect to the tire circumferential direction and a cord absolute angle α of the outer reinforcing layer 5B with respect to the tire circumferential direction are different from each other. Here, the inclination direction of the steel cord may be any.
[0026]
For example, by making the cord absolute angle β of the inner reinforcing layer 5A larger than the cord absolute angle α of the outer reinforcing layer 5B and making the difference in the cord absolute angle 5 to 65 degrees, the durability of the bead portion is impaired. The steering stability can be improved without the need. If the difference between the cord absolute angles is less than 5 degrees, the effect of improving the steering stability will be insufficient, and if it exceeds 65 degrees, the durability of the bead portion will decrease.
[0027]
When the number of cords per unit width of the inner reinforcing layer 5A is smaller than the number of cords per unit width of the outer reinforcing layer 5B, the weight can be reduced while maintaining the steering stability and the durability of the bead portion. Can be planned.
[0028]
Furthermore, when the cord twist structure of the inner reinforcing layer 5A and the outer reinforcing layer 5B is made different from each other, and the cord of the inner reinforcing layer 5A is made lighter than the cord of the outer reinforcing layer 5B, the steering stability and the durability of the bead portion are good. The weight can be reduced while maintaining the above.
[0029]
【Example】
[Experiment A]
Twelve kinds of pneumatic radial tires for heavy loads (size: 11R22.5) having the bead portion reinforcement structure shown in FIG. 1 and the dimensions of the inner reinforcement layer and the outer reinforcement layer were varied as shown in Table 1. Invention tires (Examples 1 to 12) and a conventional tire (Conventional Example 1) having a bead portion reinforcing structure shown in FIG. 7 were manufactured. In Conventional Example 1, the height h5 of the upper end of the reinforcing layer on the side of the carcass layer winding-up portion and the height h6 of the upper end of the side of the carcass layer main body portion are defined as h5 / H = 2.30 with respect to the rim flange height H. h6 / H = 1.50.
[0030]
The durability of each of the tire of the present invention and the conventional tire was evaluated by the following method.
[0031]
〔durability〕
Each tire is rotated on a drum (diameter: 1700 mm) under the following conditions: rim size: 22.5 × 8.25, air pressure: 700 kPa (specified air pressure), load: 160% of the specified load, and speed: 50 km / h. The distance until the part failed was measured. The evaluation results are shown in Table 1 using an index with Conventional Example 1 being 100. The larger the index value, the better the durability of the bead portion.
[0032]
[Table 1]

[0033]
From these results, it was confirmed that the tire of the present invention had improved durability as compared with the conventional tire. In particular, the effects of the present invention tires of Examples 5 to 8 in which the dimensions of the inner reinforcing layer and the outer reinforcing layer were adjusted to the rim flange height H were remarkable.
[0034]
[Experiment B]
In a pneumatic radial tire for heavy loads (size: 11R22.5), 12 types of books having a bead portion reinforcement structure shown in FIG. 2 and having variously different dimensions of an inner reinforcement layer and an outer reinforcement layer as shown in Table 2. Inventive tires (Examples 13 to 24) were manufactured, and the durability was evaluated by the same method as in Experiment A. The results are shown in Table 2 by using an index with Conventional Example 1 being 100.
[0035]
[Table 2]

[0036]
From these results, it was confirmed that the tire of the present invention had improved durability as compared with the conventional tire. In particular, the effects of the present invention tires of Examples 17 to 20 in which the dimensions of the inner reinforcing layer and the outer reinforcing layer were adjusted to the rim flange height H were remarkable. The tire of Example 24 of the present invention was heavier than the conventional tire because the inner reinforcing layer and the outer reinforcing layer overlapped.
[0037]
[Experiment C]
A pneumatic radial tire for heavy loads (size: 11R22.5) has a bead portion reinforcement structure shown in FIG. 3, and 12 types of books in which dimensions of an inner reinforcement layer and an outer reinforcement layer are variously changed as shown in Table 3. Invention tires (Examples 25 to 36) and a conventional tire (Conventional Example 2) having a bead portion reinforcement structure shown in FIG. 8 were manufactured. In Conventional Example 2, the height h5 of the upper end of the reinforcing layer on the side of the carcass layer winding-up portion and the height h6 of the upper end of the side of the carcass layer main body are defined as h5 / H = 0.80 with respect to the rim flange height H. h6 / H was set to 2.50.
[0038]
The durability of these tires of the present invention and conventional tires was evaluated by the same method as in Experiment A, and the results are shown in Table 3 by using an index with Conventional Example 2 being 100.
[0039]
[Table 3]

[0040]
From these results, it was confirmed that the tire of the present invention had improved durability as compared with the conventional tire. In particular, in the tires of Examples 29 to 32 in which the dimensions of the inner reinforcing layer and the outer reinforcing layer were optimized with respect to the rim flange height H, the effect of improving the durability was remarkable.
[0041]
[Experiment D]
In a heavy-duty pneumatic radial tire (size: 11R22.5), 12 kinds of books having a bead portion reinforcing structure shown in FIG. 4 and having variously different dimensions of an inner reinforcing layer and an outer reinforcing layer as shown in Table 4. Inventive tires (Examples 37 to 48) were manufactured, and the durability was evaluated by the same method as in Experiment A. The results are shown in Table 4 using an index with Conventional Example 2 being 100.
[0042]
[Table 4]

[0043]
From these results, it was confirmed that the tire of the present invention had improved durability as compared with the conventional tire. In particular, in the tires of Examples 41 to 44 in which the dimensions of the inner reinforcing layer and the outer reinforcing layer were optimized with respect to the rim flange height H, the effect of improving the durability was remarkable. The tire of Example 48 of the present invention was heavier than the conventional tire because the inner reinforcing layer and the outer reinforcing layer overlapped.
[0044]
[Experiment E]
The pneumatic radial tire for heavy loads (size: 11R22.5) has a bead portion reinforcement structure shown in FIG. 4, the cord angle of the inner reinforcement layer and the outer reinforcement layer, the number of cords per unit width, the cord twist structure. The tires of the present invention (Examples 49 to 55), which differed from each other as shown in Table 5, and a conventional tire having a bead portion reinforcing structure shown in FIG. In Conventional Example 3, the cord angle of the reinforcing layer was set to 20 degrees, the number of cords to be driven was set to 23/50 mm, and the cord twist structure was set to 3 + 8 × 0.22.
[0045]
A durability test was performed on these tires of the present invention and the conventional tire in the same manner as in Experiment A, and the results are shown in Table 5 by using an index with Conventional Example 3 being 100. The tire weight and steering stability were evaluated by the following methods.
[0046]
[Tire weight]
The weight of each tire was measured. The evaluation results are shown in Table 5 using an index with Conventional Example 3 being 100. The smaller the index value, the lighter the weight.
[0047]
(Driving stability)
Rim size: 22.5 × 7.50, air pressure: 700 kPa (specified air pressure), load: 100% of the specified load, each tire was mounted on a vehicle, and a feeling evaluation was performed by three expert panelists on a test course. Was. The evaluation results were indicated by an index with Conventional Example 3 being 100. The larger the index value, the better the steering stability.
[0048]
[Table 5]

[0049]
From these results, it was possible to improve not only the durability but also the weight reduction and the steering stability by making the structures of the inner reinforcing layer and the outer reinforcing layer different from each other.
[0050]
【The invention's effect】
As described above, according to the present invention, a reinforcing layer made of a steel cord is divided into an inner reinforcing layer and an outer reinforcing layer using a bead core as a sacrificial layer. And the outer reinforcement layer is placed outside the carcass layer roll-up part in the tire width direction, so that the durability of the bead part is higher than when a steel cord reinforcement layer is placed so as to wrap the carcass layer as before. Can be improved.
[Brief description of the drawings]
FIG. 1 is a sectional view showing a bead portion of a pneumatic radial tire for heavy loads according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a bead portion of a pneumatic radial tire for heavy loads according to a second embodiment of the present invention.
FIG. 3 is a sectional view showing a bead portion of a pneumatic radial tire for heavy loads according to a third embodiment of the present invention.
FIG. 4 is a sectional view showing a bead portion of a pneumatic radial tire for heavy loads according to a fourth embodiment of the present invention.
FIG. 5 is a development view showing an example of an arrangement of steel cords constituting an inner reinforcing layer and an outer reinforcing layer in the pneumatic tire of the present invention.
FIG. 6 is a development view showing another example of the arrangement of the steel cords constituting the inner reinforcing layer and the outer reinforcing layer in the pneumatic tire of the present invention.
FIG. 7 is a sectional view showing a bead portion of a conventional pneumatic radial tire for heavy load.
FIG. 8 is a cross-sectional view showing a modified example of a bead portion of a conventional pneumatic radial tire for heavy load.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 bead portion 2 bead core 3 bead filler 4 carcass layer 4A carcass layer main body 4B carcass layer winding portion 4BU carcass layer winding end 5A inner reinforcing layer 5B outer reinforcing layer 5AU inner reinforcing layer upper end 5AL inner reinforcing layer lower end 5BU Upper end 5BL of outer reinforcement layer Lower end H of outer reinforcement layer Rim flange height R Rim diameter reference position

Claims

A bead core is buried in each of a pair of left and right bead portions, a bead filler is arranged on an outer peripheral side of each bead core, and both end portions of a carcass layer mounted between the pair of left and right bead portions are around the bead core from inside the tire. In a pneumatic tire in which a reinforcing layer formed by aligning a plurality of steel cords is buried in the bead portion along the carcass layer, the reinforcing layer made of the steel cord is wound inside the bead core, and The carcass layer was divided into a reinforcing layer and an outer reinforcing layer, the inner reinforcing layer was disposed between the main body of the carcass layer and the bead filler, and the outer reinforcing layer was disposed outside the rolled-up portion of the carcass layer in the tire width direction. Pneumatic tire.

The height of the winding end of the carcass layer, the upper end of the inner reinforcing layer, and the upper end of the outer reinforcing layer in the tire radial direction are different from each other, and the winding end of the carcass layer is higher than the upper end of the inner reinforcing layer. The pneumatic tire according to claim 1, wherein an upper end of the outer reinforcing layer is higher than a winding end of the carcass layer.

A reinforcing structure in which the lower end of the inner reinforcing layer is disposed near the inside of the bead core, and the lower end of the outer reinforcing layer is disposed near the outside of the bead core, and the height of the rim flange from the reference position of the rim diameter is reduced. H, the height of the upper end of the outer reinforcing layer from the apex of the rim flange is h1, the height of the upper end of the inner reinforcing layer from the apex of the rim flange is h2, and the reference position of the rim diameter is 3. The pneumatic pneumatic pump according to claim 2, wherein the following condition is satisfied, where h3 is the height of the lower end of the inner reinforcing layer and h4 is the height of the lower end of the outer reinforcing layer from a reference position of the rim diameter. tire.
1.90 <h1 / H <2.70
1.15 <h2 / H <1.85
0.50 <h3 / H <1.10.
0.15 <h4 / H <0.70

A reinforcing structure in which the lower end of the inner reinforcing layer is arranged near the inside of the bead core, the outer reinforcing layer is wrapped under the bead core, and the lower end of the outer reinforcing layer is arranged near the inside of the bead core. At the same time, the height of the rim flange from the reference position of the rim diameter is H, the height of the upper end of the outer reinforcing layer from the top of the rim flange is h1, and the height of the inner reinforcing layer from the top of the rim flange is h1. The height of the upper end is h2, the height of the lower end of the inner reinforcing layer from the reference position of the rim diameter is h3, and the height of the lower end of the outer reinforcing layer from the reference position of the rim diameter is h4. The pneumatic tire according to claim 2, wherein the following conditions are satisfied.
1.90 <h1 / H <2.70
1.15 <h2 / H <1.85
0.50 <h3 / H <1.10.
0.10 <h4 / H <0.50

The heights of the raised end of the carcass layer, the upper end of the inner reinforcing layer, and the upper end of the outer reinforcing layer in the tire radial direction are different from each other, and the raised end of the carcass layer is higher than the upper end of the outer reinforcing layer. The pneumatic tire according to claim 1, wherein an upper end of the inner reinforcing layer is higher than a winding end of the carcass layer.

A reinforcing structure in which the lower end of the inner reinforcing layer is disposed near the inside of the bead core, and the lower end of the outer reinforcing layer is disposed near the outside of the bead core, and the height of the rim flange from the reference position of the rim diameter is reduced. H, the height of the upper end of the outer reinforcing layer from the apex of the rim flange is h1, the height of the upper end of the inner reinforcing layer from the apex of the rim flange is h2, and the reference position of the rim diameter is 6. The pneumatic pneumatic pump according to claim 5, wherein the following condition is satisfied when a height of a lower end of the inner reinforcing layer is h3 and a height of a lower end of the outer reinforcing layer from a reference position of the rim diameter is h4. tire.
0.40 <h1 / H <1.20
2.20 <h2 / H <2.90
0.50 <h3 / H <1.10.
0.15 <h4 / H <0.70

A reinforcing structure in which the lower end of the inner reinforcing layer is arranged near the inside of the bead core, the outer reinforcing layer is wrapped under the bead core, and the lower end of the outer reinforcing layer is arranged near the inside of the bead core. At the same time, the height of the rim flange from the reference position of the rim diameter is H, the height of the upper end of the outer reinforcing layer from the top of the rim flange is h1, and the height of the inner reinforcing layer from the top of the rim flange is h1. The height of the upper end is h2, the height of the lower end of the inner reinforcing layer from the reference position of the rim diameter is h3, and the height of the lower end of the outer reinforcing layer from the reference position of the rim diameter is h4. The pneumatic tire according to claim 5, wherein the following conditions are satisfied.
0.40 <h1 / H <1.20
2.20 <h2 / H <2.90
0.50 <h3 / H <1.10.
0.10 <h4 / H <0.50

The pneumatic tire according to any one of claims 1 to 7, wherein the inner reinforcing layer and the outer reinforcing layer have different cord absolute angles with respect to the tire circumferential direction.

9. The pneumatic tire according to claim 8, wherein a difference between a cord absolute angle of the inner reinforcing layer and the outer reinforcing layer with respect to a tire circumferential direction is 5 to 65 degrees. 10.

The pneumatic tire according to any one of claims 1 to 9, wherein the number of cords per unit width of the inner reinforcing layer and the outer reinforcing layer is different from each other.

The pneumatic tire according to any one of claims 1 to 10, wherein cord twisting structures of the inner reinforcing layer and the outer reinforcing layer are different from each other.