JP3831024B2

JP3831024B2 - Method for producing pneumatic tire for rehabilitation heavy load and rehabilitation tire

Info

Publication number: JP3831024B2
Application number: JP26052796A
Authority: JP
Inventors: 健治金子
Original assignee: Bridgestone Corp
Current assignee: Bridgestone Corp
Priority date: 1996-10-01
Filing date: 1996-10-01
Publication date: 2006-10-11
Anticipated expiration: 2016-10-01
Also published as: JPH10100283A

Description

【０００１】
【発明の属する技術分野】
この発明は、更生重荷重用空気入りタイヤの製造方法及び更生タイヤ、より詳細には高速走行に伴う発熱を抑制し高速耐久性を向上させるための更生重荷重用空気入りタイヤの製造方法及びこの製造方法により製造した更生重荷重用空気入りタイヤに関し、特に航空機の使途を典型例とする重荷重下での使途に適合した更生重荷重用空気入りタイヤの製造方法及び更生タイヤに関するものである。
【０００２】
【従来の技術】
走行に伴いトレッドゴムが摩耗した重荷重用空気入りタイヤは、航空機用を典型例とする他にトラック−バス用、その他産業車両用を問わず更生を実施し、再使用するのが一般であり、なかでも航空機用タイヤはランディング時におけるトレッドゴムの急速摩耗が顕著である一方、その他の構成部分は再使用に十分耐えるに足る強度や耐久性を保持しているので、再三にわたる更生を実施するのが通例である。
【０００３】
この更生にあたり台タイヤ（更生に用いる摩耗タイヤ）に所定の処理、例えば残ったトレッドゴムの除去や必要とする部分修理、ときには後に故障を生じるうれいがあるブレーカやベルトのコード層の剥ぎ取りを施し、その後新しい未加硫部材、例えば未加硫トレッドゴムや半加硫トレッドゴムを張合せて更生対象タイヤとし、新品タイヤの性能を保持するため、新品用加硫成形金型と同じ内面形状をもつ更生用加硫成形金型により更生対象タイヤに加硫成形を施すのが一般である。
【０００４】
重荷重用空気入りタイヤのうち航空機用空気入りタイヤについては、高速走行の上、他の種のタイヤと対比してサイズに対する負荷荷重は極端に大きく、よってショルダ部の発熱をなるべく抑制する必要から、いわゆるラウンドショルダを広い領域にわたり採用する必要があり、実際に新品タイヤ、更生タイヤを問わず殆ど全ての航空機用空気入りタイヤがこの大きなラウンドショルダ形状を有する。
【０００５】
その反面、踏面中央領域に負荷荷重が集中し易くなり、その結果この中央領域のリブ部分が高温度になる傾向を有する。特にこの中央領域リブ部分の高温度走行の履歴をもつ更生対象タイヤのカーカス、特に熱収縮率が大きい６ナイロンコード又は６６ナイロンコードを用いたバイアスカーカスではショルダ部の熱収縮に比し踏面中央領域の熱収縮が大きくなるのは不可避であり、その結果新品用加硫成形金型と同じ内面形状をもつ更生用加硫成形金型を用いた更生タイヤでは踏面中央領域のトレッドゴムゲージが厚くなる。
【０００６】
【発明が解決しようとする課題】
厚いトレッドゴムゲージ部分は実機（航空機に装着した状態）で高速走行すると発熱量が増してより高温度となり、カット受傷の機会が増大する。カット受傷部分の接着力はその他の部分の接着力に比しより低く、これに高温度が加わるためセパレーション故障が発生し易くなることを解明した。
【０００７】
従って、この発明の請求項１〜４に記載した発明は、タイヤ更生後における踏面中央領域の発熱量を抑制することによりカット受傷の機会を減らする共にセパレーション故障発生を抑制して高速耐久性を向上させた更生重荷重用空気入りタイヤの製造方法を提供することを目的とするものである。
【０００８】
【課題を解決するための手段】
上記目的を達成するため、まずこの発明の請求項１に記載した発明は、走行により摩耗したトレッドゴムの残ゴムを除去したタイヤトレッド部に未加硫トレッドゴム又は半加硫トレッドゴムの更生用部材を張合せた更生対象タイヤを更生用加硫成形金型により加硫成形するに際し、
更生用加硫成形金型と、更生対象タイヤの新品用加硫成形金型とに関し、
双方金型の中心軸線を含む平面による断面にあらわれるトレッド部踏面形成のための円弧のうち少なくとも踏面中央領域の円弧はタイヤ内側に曲率中心をもつ半径により形成され、更生用加硫成形金型の上記踏面中央領域の円弧の曲率半径が、新品用加硫成形用金型の該曲率半径に比しより大きな曲率半径を有し、
かつ金型中心軸線からタイヤ赤道面に該当する位置における踏面形成用金型内面までの高さにつき、更生用加硫成形金型の該高さｈが、新品用加硫成形用金型の高さＨに比しより低い更生用加硫成形用金型を用いて更生対象タイヤを加硫成形することを特徴とする更生重荷重用空気入りタイヤの製造方法である。
【０００９】
次に前記目的を達成するため、この発明の請求項２に記載した発明は、走行により摩耗したトレッドゴムの残ゴムを除去したトレッド部に未加硫トレッドゴム又は半加硫トレッドゴムの更生用部材を張合せた更生対象タイヤを更生用加硫成形金型により加硫成形するに際し、
更生用加硫成形金型と、更生対象タイヤの新品用加硫成形金型とに関し、
双方金型の中心軸線を含む平面による断面にあらわれるトレッド部踏面形成のための形状のうち少なくとも踏面中央領域の形状が、新品用加硫成形金型はタイヤ内側に曲率中心をもつ半径により形成された円弧からなり、更生用加硫成形金型は金型中心軸線と平行に延びる直線からなり、
かつ金型中心軸線から測った、タイヤ赤道面に該当する位置における踏面形成用金型内面までの高さにつき、更生用加硫成形金型の該高さｈが、新品用加硫成形用金型の高さＨに比しより低い更生用加硫成形用金型を用いて更生対象タイヤを加硫成形することを特徴とする更生重荷重用空気入りタイヤの製造方法である。
【００１０】
ここに踏面中央領域とは、新品用及び更生用の両加硫成形金型内においてタイヤのサイドウォール部最大幅を形成する位置の幅の０．４倍を最大とする幅を、タイヤ赤道面に該当する金型の踏面形成位置から両側に等分に振り分けた領域を指すものとする。
【００１１】
なぜなら従来更生タイヤのこの中央領域におけるトレッドゴム厚さが過大になるからであり、従って請求項１に記載した発明では、更生用加硫成形用金型の中央領域における断面での曲率半径を新品用加硫成形用金型の同じ断面における曲率半径より大きく採り、請求項２に記載した発明では、更生用加硫成形用金型の中央領域における断面での形状を直線とし、かつ請求項１、２に記載した発明は共に、更生用加硫成形金型の該高さｈを、新品用加硫成形用金型の高さＨに比しより低くすることにより、更生タイヤの中央領域におけるトレッドゴムゲージの厚さが高速走行により発生する発熱量を適度に抑制し、その結果カット受傷の機会が減少し、併せてセパレーション故障の発生が抑制される。
【００１２】
上記の効果を実際上確かなものとするには、まず請求項３に記載した発明のように、更生用加硫成形金型の前記断面にて、踏面中央領域の直線長さＦの、金型内におけるタイヤサイドウォール部最大幅形成位置の幅Ｗに対する比Ｆ／Ｗの値を０．４以下とするのが有効である。
【００１３】
次に、た請求項４に記載した発明のように、新品用加硫成形金型の内面高さＨから更生用加硫成形金型の内面高さｈを差し引いた値Δｈの高さＨに対する比Δｈ／Ｈの値の百分率を、０．２〜１．０％の範囲内とするのが適合する。
【００１６】
以上請求項１〜４に記載した発明は、特に重荷重、高内圧の更生航空機用空気入りタイヤに最適に適合し、なぜならこの種のタイヤは他のジャンルのタイヤに比し極端に高い荷重を支持するので、ショルダ部の発熱を抑制するため大きなラウンドショルダ部を備え、それ故踏面中央領域のトレッドゴムの発熱量が増大する傾向が強いためである。
【００１７】
またカーカスは有機繊維コ─ド、特に６ナイロンコード又は６６ナイロンコードのゴム引き布の多数プライからなるバイアス構造に適合する。なお更生時に使用するトレッドゴムは航空機用更生タイヤの場合に未加硫ゴムが一般であるが、ときに加硫度が０．５未満の、いわゆる半加硫ゴムの使用を可とする。
【００１８】
【発明の実施の形態】
以下、この発明の実施の形態の一例を図１に基づき説明する。
図１は、更生用及び新品用加硫成形金型の中心軸線Ｘを含む平面による左半断面と、更生用加硫成形金型内で加硫成形され収容されている更生航空機用空気入りタイヤの左半断面（細い実線で輪郭のみ示す）とを合せ示す説明図である。
【００１９】
図において、符号１は航空機用タイヤの更生用加硫成形金型（以降更生用金型と略す）の例であり、これを太い実線にて示し、新品用加硫成形金型（以降新品用金型と略す）を破線で示し、後者の金型の数値符号付与は省略した。更生用金型１に関し、符号２は更生タイヤ１１の踏面１２を形成する内周面であり、符号３は更生タイヤ１１のサイドウォール部１３の外側表面を形成するサイドウォール用内面であり、そして符号４は更生タイヤ１１のビード部１４の外側表面を形成するビード用内面である。なお符号Ｅは金型１及び更生タイヤ１１を中心軸線Ｘ方向に２分する平面であり、タイヤでいえば赤道面に該当する。
【００２０】
踏面１２形成用内周面２とサイドウォール用内面３との間に符号５を付した部分が、タイヤでいうところのショルダ部を形成するショルダ用内面であり、航空機用タイヤではこのショルダ部のトレッドゴム１５の厚さを成るべく薄くする必要からショルダ用内面５は、他の種のタイヤに比し大幅に小さな曲率面（図の断面では大きな曲率半径）で形成する。それ故ここでいう踏面１２の中央領域とは、中心軸線Ｘ方向でみてサイドウォール部最大幅位置Ａ−Ａ（図１参照）相互間距離Ｗの０．４倍を最大とする幅を赤道面Ｅの両側に等分に振り分けた領域を指し、図では片側を符号ｆで示す範囲の領域である。。
【００２１】
また更生用金型１の内周面２には、更生タイヤ１１のトレッドゴム１５に溝を形成するため複数本のリブ６を設け、図１に示す更生タイヤ１１は航空機用であるからリブ６は内周面２の円周に沿って延びる（以下円周方向と略記する）直状リブであり、勿論これらリブ６部分は内周面２の範囲外である。
【００２２】
ここで、前記踏面１２の中央領域はＦ＝ｆ×２の幅をもち、更生タイヤを金型１内に収容した状態であるから幅ｆ領域はすなわち金型１の内周面２、そして破線で示す新品用金型の内周面の中央領域の半幅である。この金型の中央領域は、金型１及び新品用金型共に断面にてタイヤ１１内側に曲率中心Ｃ、Ｃ_Oをもつ半径Ｒ、Ｒ_Oにより形成するものとし、金型１の半径Ｒと、新品用金型の半径Ｒ_Oとの間で、Ｒ＞Ｒ_Oの関係を満たすものとする。
【００２３】
また、上記の半径Ｒ、Ｒ_Oの関係をさらに発展させた金型１の別の形態例は、図１に示す断面にて、新品用金型の半径Ｒ_Oは有限の所定値をもつ一方、金型１の半径Ｒに相当する中央領域を中心軸線Ｘに平行な直線とするものである。すなわち金型１の中央領域は全体として中心軸線Ｘを共有する円筒面を有するということである。
【００２４】
いずれにしても、中央領域の幅Ｆ（直線長さ）の、タイヤサイドウォール部１３の最大幅形成位置Ａ−Ａ相互間距離Ｗに対する比Ｆ／Ｗの値を０．４以下としたのは、０．４を超えるとショルダ部はトレッドゴム１５のゲージが厚くなり過ぎて発熱量の増加が著しく、またショルダ部の曲率が大きくなり過ぎ、その結果カーカスプライ相互間にセパレーションが発生し易くなるからである。
【００２５】
また比Ｆ／Ｗの上限値が０．４までなら、金型１の内周面は新品用金型に比しよりフラット化するものの、加硫成形時に更生タイヤ１１の内側を高圧にすることで更生タイヤ１１のショルダ部とその近傍のカーカス１７も同時にフラット化させることが可能であるから、タイヤショルダ部へのトレッドゴム１５の溜まり過ぎ（厚ゲージ化）を回避することが可能となり、ショルダ部の発熱性を新品同様に保持することができる。なお符号１６はサイドウォールゴムである。
【００２６】
さらに、中心軸線Ｘから測った赤道面Ｅ位置での金型１の内周面２の高さｈと、同様に測った同位置での新品用金型の内周面の高さＨとは、Ｈ＞ｈの関係を満たすことが発熱耐久性確保の点で望ましい。また（Ｈ−ｈ）＝Δｈとしたとき、（Δｈ／Ｈ）×１００（％）が０．２〜１．０％であるのが発熱耐久性確保の点で望ましい。
【００２７】
以上述べた金型１による更生対象のタイヤは航空機用空気入りタイヤ、それもバイアスタイヤが有利に適合するが、ラジアルタイヤにも適用可能であり、その他の種類のタイヤで踏面中央領域の発熱量が無視し得ない重荷重用空気入りタイヤの更生にも金型１を用いることができる。
【００２８】
【実施例】
航空機用空気入りタイヤの、サイズが４９×１７のバイアスタイヤであり、カーカス１７は１２６０Ｄ／２の６，６ナイロンコードをゴム引きした１８プライからなり、その外周に２層のブレーカを備える台タイヤを用いた。まず慣例に従い台タイヤはトレッド部の摩耗残ゴムなど余分な部材を切削除去し、必要な接着処理を施した後、新たに未加硫トレッドゴム部材を張合せて更生対象タイヤとし、これに図１に従う金型１のうち、内周面の中央領域が円筒面を有する金型１を適用して加硫成形を施した。
【００２９】
金型１の中央領域の幅Ｆの、位置Ａ−Ａ相互間距離Ｗに対する比Ｆ／Ｗの値は実施例１が０．３４、実施例２が０．１５であり（比Ｆ／Ｗの値は０．４０〜０．１５の範囲内が望ましい）、また従来例に適用した新品用金型（図１の破線にて示す）の中央領域における曲率半径Ｒ_Oは３１５ｍｍであり、この金型の内面高さＨから金型１の内面高さｈを差し引いた値Δｈの高さＨに対する比Δｈ／Ｈの値の百分率は０．５５％である。
【００３０】
ほぼ同じ状態の更生対象タイヤを従来の新品用金型と上記金型１とにより更生を実施し、実施例１、２及び従来例それぞれの更生タイヤをRated Pressureの内圧充填下で供試タイヤとし、以下に述べる試験条件にてドラムによる高速耐久性試験及び発熱温度測定を実施した。
【００３１】
供試タイヤを１．２×Rated Loadの荷重にてドラムに押し当て、ドラムの回転速度（表面速度）を８０秒の時間でゼロからRated Speed まで直線勾配で加速し、８０秒経過直前から荷重を急速に解放し、８０秒経過時に荷重はゼロとなり供試タイヤはドラムから離れる。この試験条件を１サイクルとするオン−オフ試験を繰り返し、供試タイヤに異常が発見された時点で試験を終了させ、試験終了までに要したサイクル数をもって高速耐久性の良否を評価する。
【００３２】
また発熱温度は上記試験終了後、直ちに踏面中央位置（赤道面Ｅ位置）、第二リブ（図１にて２個のリブ６に挟まれるトレッドゴム部分）幅中央位置及びショルダ部のトレッドゴム最深部の温度を円周上４箇所で計測し、その平均値を求めた。評価は上記サイクル数も含め全て従来例を１００とする指数にてあらわした。サイクル数は数値が大なるほど良く、発熱温度は小なるほど良い。これらの試験結果を表１に示す。
【００３３】
【表１】

【００３４】
表１から、従来例の更生タイヤに対し実施例１、２の更生タイヤは、第二リブ及びショルダ部の発熱温度が同等以下である上、踏面中央部の発熱温度が顕著に低下し、かつ高速耐久性が大幅に向上していることがわかり、このことはとりもなおさず踏面中央領域にカット傷を受ける機会を減らすことにつながり、仮にカットを受傷しても比較的浅い傷に止まり、結局のところ耐セパレーション性が大幅に向上することを保証することに他ならない。
【００３５】
【発明の効果】
この発明の請求項１〜４に記載した発明は、従来の更生重荷重用空気入りタイヤの弱点とされていたトレッド部の踏面中央領域の著しい発熱量を大幅に低減し、これにより更生重荷重用空気入りタイヤのカット受傷の機会を減らし、同時にカット損傷の度合いを軽微なものとし、その結果高速耐久性を顕著に向上させることができ製造方法を提供することができる。
【図面の簡単な説明】
【図１】この発明による製造方法の一実施例及び更生タイヤ例の断面を示す説明図である。
【符号の説明】
１更生用金型
２内周面
３サイドウォール用内面
４ビード用内面
５ショルダ用内面
６リブ
１１更生タイヤ
１２踏面
１３サイドウォール部
１４ビード部
１５トレッドゴム
１６サイドウォールゴム
１７カーカス
Ｅ赤道面
Ｘ中心軸線
Ｒ更生用金型内周面の断面の曲率半径
Ｒ_O新品用金型内周面の断面の曲率半径
Ｃ半径Ｒの曲率中心
Ｃ_O半径Ｒ_Oの曲率中心
Ａ最大幅形成位置
ＷＡ−Ａ間距離
ｆ内周面中央領域の半幅
ｈ金型１の内周面高さ
Ｈ新品用金型の内周面高さ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a regenerative heavy load pneumatic tire and a regenerated tire, and more specifically, a method for manufacturing a regenerative heavy load pneumatic tire for suppressing heat generation associated with high speed running and improving high speed durability, and the method for manufacturing the same. In particular, the present invention relates to a method for manufacturing a rehabilitated heavy load pneumatic tire suitable for use under heavy loads, typically a use of an aircraft, and a regenerated tire.
[0002]
[Prior art]
Heavy duty pneumatic tires with worn tread rubber during travel are generally re-used after being rehabilitated for trucks, buses and other industrial vehicles, in addition to aircraft. In particular, aircraft tires are prone to rapid tread rubber wear during landing, while other components retain sufficient strength and durability to withstand reuse. Is customary.
[0003]
For this rehabilitation, the base tires (wear tires used for rehabilitation) should be treated in a predetermined manner, for example, removing the remaining tread rubber, repairing the necessary parts, and stripping the cord layers of breakers and belts that may later fail. After that, new unvulcanized parts such as unvulcanized tread rubber and semi-cured tread rubber are laminated to make the tires subject to rehabilitation, and the same inner surface shape as new vulcanization molds to maintain the performance of new tires Generally, retreaded tires are vulcanized and molded using a vulcanization mold for retreading.
[0004]
Among pneumatic tires for heavy loads, pneumatic tires for aircraft, on high speed running, the load on the size is extremely large compared to other types of tires, so it is necessary to suppress the heat generation of the shoulder as much as possible, So-called round shoulders need to be employed over a wide area, and virtually all pneumatic pneumatic tires for aircraft, whether new tires or retreaded tires, have this large round shoulder shape.
[0005]
On the other hand, the load load tends to concentrate on the center area of the tread surface, and as a result, the rib portion of the center area tends to become high temperature. In particular, in the carcass of the tire to be rehabilitated with a history of high-temperature running in the central region rib portion, particularly in the bias carcass using the 6 nylon cord or 66 nylon cord having a large thermal contraction rate, the center region of the tread surface compared to the thermal contraction of the shoulder portion. It is inevitable that the heat shrinkage of the tire will increase, and as a result, the tread rubber gauge in the center area of the tread becomes thicker in the retreaded tire using the vulcanization mold for rehabilitation having the same inner surface shape as the new vulcanization mold .
[0006]
[Problems to be solved by the invention]
When the thick tread rubber gauge part is driven at high speed with an actual machine (installed in an aircraft), the amount of heat generation increases and the temperature becomes higher, and the chance of cut damage increases. It was clarified that the adhesive strength of the cut-scratched part is lower than that of the other parts, and that a high temperature is applied to this, so that a separation failure is likely to occur.
[0007]
Therefore, the invention described in claims 1 to 4 of the present invention reduces the chance of cut damage by suppressing the amount of heat generated in the center area of the tread after tire retreading, and at the same time suppresses the occurrence of separation failure and increases the high-speed durability. is to shall aims to provide a method for producing a retreaded pneumatic tire for heavy load having enhanced.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, first, the invention described in claim 1 of the present invention is used to regenerate unvulcanized tread rubber or semi-vulcanized tread rubber on a tire tread portion from which the remaining rubber of the tread rubber worn by running is removed. When vulcanizing and molding a tire to be rehabilitated with components using a vulcanization mold for rehabilitation,
Regarding vulcanization molds for rehabilitation and vulcanization molds for new tires for rehabilitation,
Of the arcs for forming the tread part tread that appear in the cross section of the plane including the central axis of both molds, at least the arc in the center area of the tread is formed by a radius having a center of curvature inside the tire. The radius of curvature of the arc in the center region of the tread has a larger radius of curvature than the radius of curvature of the vulcanization mold for new article,
In addition, the height h of the vulcanization mold for rehabilitation is the height of the mold for vulcanization molding for new products, with respect to the height from the mold center axis to the inner surface of the tread surface molding mold at the position corresponding to the tire equatorial plane. A method for producing a pneumatic tire for rehabilitation heavy load, characterized in that a rehabilitation target tire is vulcanized using a mold for vulcanization for rehabilitation that is lower than the length H.
[0009]
Next, in order to achieve the above object, the invention described in claim 2 of the present invention is for rehabilitation of unvulcanized tread rubber or semi-vulcanized tread rubber in the tread portion from which the remaining rubber of the tread rubber worn by running is removed. When vulcanizing and molding a tire to be rehabilitated with components using a vulcanization mold for rehabilitation,
Regarding vulcanization molds for rehabilitation and vulcanization molds for new tires for rehabilitation,
Of the shapes for forming the tread surface tread that appear in the cross section of the plane including the center axis of both molds, at least the shape of the tread center region is formed by the radius of the new vulcanization mold with the center of curvature inside the tire. The vulcanization mold for rehabilitation consists of a straight line extending parallel to the mold center axis,
In addition, the height h of the vulcanization mold for rehabilitation measured from the mold center axis to the inner surface of the tread surface mold at the position corresponding to the tire equatorial plane is the vulcanization mold for new parts. It is a method for producing a rehabilitation heavy load pneumatic tire, characterized in that a rehabilitation target tire is vulcanized and molded using a rehabilitation vulcanization mold lower than the mold height H.
[0010]
Here, the center area of the tread surface is a tire equator plane having a maximum width 0.4 times the width of the position where the maximum width of the sidewall portion of the tire is formed in both the new and renewal vulcanization molds. It shall refer to the area equally distributed on both sides from the tread formation position of the mold corresponding to.
[0011]
This is because the thickness of the tread rubber in the central region of the conventional retread tire is excessive, and therefore, in the invention described in claim 1, the radius of curvature in the cross section in the central region of the vulcanization mold for retreading is set to a new one. The vulcanization molding die for use is larger than the radius of curvature in the same cross section, and in the invention described in claim 2, the shape of the cross section in the central region of the vulcanization molding die for rehabilitation is a straight line. In both of the inventions described in No. 2, the height h of the vulcanization mold for rehabilitation is made lower than the height H of the vulcanization mold for new articles, so that The thickness of the tread rubber gauge moderately suppresses the amount of heat generated by high-speed running, and as a result, the chance of cut damage is reduced, and the occurrence of separation failure is also suppressed.
[0012]
In order to make the above effect practically reliable, first, as in the invention described in claim 3, in the cross section of the vulcanization mold for rehabilitation, a metal having a linear length F in the center region of the tread surface is used. It is effective that the value of the ratio F / W to the width W of the tire sidewall maximum width forming position in the mold is 0.4 or less.
[0013]
Next, as in the invention described in claim 4, with respect to the height H of the value Δh obtained by subtracting the inner surface height h of the vulcanization molding die for rehabilitation from the inner surface height H of the new vulcanization molding die. Suitably, the percentage of the value of the ratio Δh / H is in the range of 0.2-1.0%.
[0016]
The inventions described in claims 1 to 4 are optimally adapted to pneumatic tires for rehabilitation aircraft, particularly heavy loads and high internal pressures, because this type of tire has an extremely high load compared to tires of other genres. This is because a large round shoulder portion is provided in order to suppress heat generation in the shoulder portion, and therefore, the heat generation amount of the tread rubber in the center region of the tread surface is likely to increase.
[0017]
Carcass is also compatible with bias structures consisting of multiple plies of rubberized fabric of organic fiber cords, especially 6 nylon cord or 66 nylon cord. The tread rubber used at the time of rehabilitation is generally unvulcanized rubber in the case of aircraft retreaded tires, but sometimes a so-called semi-vulcanized rubber having a vulcanization degree of less than 0.5 can be used.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described with reference to FIG.
FIG. 1 shows a left half cross-section of a rehabilitation and new vulcanization mold including a central axis X, and a retreaded aircraft pneumatic tire vulcanized and accommodated in the rehabilitation vulcanization mold. It is explanatory drawing which combines and shows the left half cross section (only an outline is shown with a thin continuous line).
[0019]
In the figure, reference numeral 1 is an example of a vulcanization molding die for aircraft tire rehabilitation (hereinafter abbreviated as a rehabilitation die), which is indicated by a thick solid line, and is a new vulcanization molding die (hereinafter referred to as a new product). (Abbreviated as a mold) is indicated by a broken line, and the numerical symbol of the latter mold is omitted. Regarding the rehabilitation mold 1, reference numeral 2 is an inner peripheral surface that forms the tread 12 of the rehabilitated tire 11, reference numeral 3 is an inner surface for the sidewall that forms the outer surface of the sidewall portion 13 of the rehabilitated tire 11, and Reference numeral 4 denotes an inner surface for beads forming the outer surface of the bead portion 14 of the retread tire 11. Note that E is a plane that bisects the mold 1 and the retreaded tire 11 in the direction of the central axis X, and corresponds to the equator plane in the case of a tire.
[0020]
A portion denoted by reference numeral 5 between the inner peripheral surface 2 for forming the tread surface 12 and the inner surface 3 for the sidewall is an inner surface for the shoulder that forms a shoulder portion in the sense of a tire, and in the tire for an aircraft, Because the thickness of the tread rubber 15 needs to be as thin as possible, the inner surface 5 for the shoulder is formed with a curvature surface (a large curvature radius in the cross section in the drawing) that is significantly smaller than that of other types of tires. Therefore, the central region of the tread 12 here refers to a width that maximizes 0.4 times the distance W between the sidewall portions maximum width position AA (see FIG. 1) when viewed in the direction of the central axis X. E indicates an area that is equally divided on both sides of E, and in the figure, one side is an area in a range indicated by reference numeral f. .
[0021]
Further, a plurality of ribs 6 are provided on the inner peripheral surface 2 of the rehabilitation mold 1 in order to form grooves in the tread rubber 15 of the rehabilitation tire 11, and the rehabilitation tire 11 shown in FIG. Is a straight rib extending along the circumference of the inner peripheral surface 2 (hereinafter abbreviated as “circumferential direction”). Of course, these ribs 6 are outside the range of the inner peripheral surface 2.
[0022]
Here, the central region of the tread 12 has a width of F = f × 2, and the retread tire is accommodated in the mold 1, so the width f region is the inner peripheral surface 2 of the mold 1 and the broken line. It is the half width of the center area | region of the internal peripheral surface of a new mold shown by. The center region of the mold is formed by the radii R and R _O having the centers of curvature C and C _O inside the tire 11 in cross section in both the mold 1 and the new mold. It is assumed that the relationship R> R _O is satisfied with the radius R _O of the new mold.
[0023]
Further, in another embodiment of the mold 1 in which the relationship between the radii R and R _O is further developed, the radius R _O of the new mold has a finite predetermined value in the cross section shown in FIG. The central region corresponding to the radius R of the mold 1 is a straight line parallel to the central axis X. That is, the central region of the mold 1 has a cylindrical surface that shares the central axis X as a whole.
[0024]
In any case, the value of the ratio F / W of the width F (straight length) of the central region to the maximum width formation position A-A distance W of the tire sidewall portion 13 is set to 0.4 or less. If the value exceeds 0.4, the gauge of the tread rubber 15 becomes too thick in the shoulder portion, and the calorific value increases remarkably. Also, the curvature of the shoulder portion becomes too large, and as a result, separation between the carcass plies tends to occur. Because.
[0025]
If the upper limit of the ratio F / W is up to 0.4, the inner peripheral surface of the mold 1 will be flatter than that of a new mold, but the inside of the retread tire 11 will be at a high pressure during vulcanization molding. Since the shoulder portion of the retread tire 11 and the carcass 17 in the vicinity thereof can be flattened at the same time, it is possible to avoid the accumulation of the tread rubber 15 (thickness gauge) in the tire shoulder portion. The exothermic property of the part can be maintained as if it were new. Reference numeral 16 denotes a sidewall rubber.
[0026]
Further, the height h of the inner peripheral surface 2 of the mold 1 at the position of the equator plane E measured from the central axis X and the height H of the inner peripheral surface of the new mold at the same position measured in the same manner. , H> h is desirable from the viewpoint of securing heat generation durability. In addition, when (H−h) = Δh, (Δh / H) × 100 (%) is preferably 0.2 to 1.0% from the viewpoint of securing heat generation durability.
[0027]
The tires to be rehabilitated by the mold 1 described above are pneumatic tires for aircraft, and bias tires are also suitable, but they can also be applied to radial tires. However, the mold 1 can also be used to rehabilitate heavy-duty pneumatic tires that cannot be ignored.
[0028]
【Example】
A pneumatic tire for aircraft, a bias tire with a size of 49 × 17, and the carcass 17 is made of 18 ply rubberized 1260D / 2 6,6 nylon cord, and has two layers of breakers on its outer periphery. Was used. First, in accordance with conventional practice, the base tire is cut and removed excess members such as wear remaining rubber on the tread, and after applying the necessary adhesion treatment, a new unvulcanized tread rubber member is laminated to make the tire to be rehabilitated. Among the molds 1 according to No. 1, the mold 1 having a cylindrical surface in the central region of the inner peripheral surface was applied for vulcanization molding.
[0029]
The value of the ratio F / W of the width F of the central region of the mold 1 to the position A-A distance W is 0.34 in Example 1 and 0.15 in Example 2 (of the ratio F / W). The value is preferably within the range of 0.40 to 0.15), and the radius of curvature R _O in the central region of the new mold (shown by the broken line in FIG. 1) applied to the conventional example is 315 mm. The percentage of the value Δh / H relative to the height H of the value Δh obtained by subtracting the inner surface height h of the mold 1 from the inner surface height H of the mold is 0.55%.
[0030]
Rehabilitation of tires subject to rehabilitation in almost the same state is performed with the conventional new mold and the above-described mold 1, and the rehabilitated tires of Examples 1 and 2 and the conventional example are used as test tires under the internal pressure filling of the Rate Pressure. A high-speed durability test using a drum and measurement of heat generation temperature were performed under the test conditions described below.
[0031]
The test tire is pressed against the drum with a load of 1.2 × Rated Load, and the drum rotation speed (surface speed) is accelerated with a linear gradient from zero to Rated Speed over a period of 80 seconds. Is released rapidly, and after 80 seconds, the load becomes zero and the test tire leaves the drum. The on-off test with this test condition as one cycle is repeated. When an abnormality is found in the test tire, the test is terminated, and the quality of the high-speed durability is evaluated based on the number of cycles required until the end of the test.
[0032]
Also, immediately after the above test, the exothermic temperature is the center position of the tread (equatorial plane E position), the second rib (the tread rubber portion sandwiched between the two ribs 6 in FIG. 1), the center position of the width and the deepest tread rubber of the shoulder portion. The temperature of the part was measured at four locations on the circumference, and the average value was obtained. All the evaluations including the number of cycles described above were expressed as an index with the conventional example as 100. The greater the number of cycles, the better, and the lower the exothermic temperature, the better. These test results are shown in Table 1.
[0033]
[Table 1]

[0034]
From Table 1, the retreaded tires of Examples 1 and 2 with respect to the retreaded tire of the conventional example have the heat generation temperatures of the second rib and the shoulder portion equal to or lower than those, and the heat generation temperature of the center portion of the tread surface is significantly reduced. It can be seen that the high-speed durability is greatly improved, and this leads to a reduction in the chance of receiving cut scratches in the center area of the tread, and even if cuts are received, they remain relatively shallow, After all, it is nothing other than ensuring that the separation resistance is greatly improved.
[0035]
【The invention's effect】
The invention described in claims 1 to 4 of the present invention greatly reduces the significant heat generation in the center region of the tread portion of the tread portion, which has been a weak point of conventional regenerative heavy load pneumatic tires. enters reduce the chance of cutting injury of the tire, at the same time the degree of cut damage was not significant, it is a result high-speed durability to be able to significantly improve Hisage manufacturing method Kyosu Rukoto.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a cross section of an embodiment of a manufacturing method according to the present invention and a retread tire example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rehabilitation metal mold 2 Inner peripheral surface 3 Side wall inner surface 4 Bead inner surface 5 Shoulder inner surface 6 Rib 11 Rehabilitation tire 12 Tread surface 13 Side wall portion 14 Bead portion 15 Tread rubber 16 Side wall rubber 17 Carcass E Equatorial plane X Center the center of curvature of the axis of curvature of the cross-section of the R rehabilitating mold inner circumferential surface radius R _O new of the cross section of the mold inner peripheral surface curvature C radius R C _O radius R _O of the curvature center a maximum width forming position W A- A distance f A half width in the central area of the inner peripheral surface h inner peripheral surface height H of the mold 1 inner peripheral surface height of a new mold

Claims

Rehabilitated tires with vulcanized tread rubber or vulcanized tread rubber bonded to the tire tread from which the remaining rubber of the tread rubber worn by running is vulcanized with a vulcanization mold for rehabilitation. When doing
Regarding vulcanization molds for rehabilitation and vulcanization molds for new tires for rehabilitation,
Of the arcs for forming the tread part tread that appear in the cross section of the plane including the central axis of both molds, at least the arc in the center area of the tread is formed by a radius having a center of curvature inside the tire. The radius of curvature of the arc in the center region of the tread has a larger radius of curvature than the radius of curvature of the vulcanization mold for new article,
And the height (h) of the vulcanization mold for rehabilitation is the height from the mold center axis to the inner surface of the tread forming mold at the position corresponding to the tire equatorial plane. A method for producing a pneumatic tire for rehabilitation heavy load, characterized in that a rehabilitation target tire is vulcanized using a mold for vulcanization for rehabilitation which is lower than the height (H).

The tire to be rehabilitated by rehabilitating the rehabilitation material of unvulcanized tread rubber or semi-vulcanized tread rubber to the tread part from which the remaining rubber of the tread rubber worn by running is removed is vulcanized by the vulcanization mold for rehabilitation. On the occasion
Regarding vulcanization molds for rehabilitation and vulcanization molds for new tires for rehabilitation,
Of the shapes for forming the tread surface tread that appear in the cross section of the plane including the center axis of both molds, at least the shape of the tread center region is formed by the radius of the new vulcanization mold with the center of curvature inside the tire. The vulcanization mold for rehabilitation consists of a straight line extending parallel to the mold center axis,
In addition, the height (h) of the vulcanization mold for rehabilitation is the vulcanization molding for a new article with respect to the height to the inner surface of the mold for forming the tread surface at the position corresponding to the tire equatorial plane, as measured from the mold center axis. A method for producing a pneumatic tire for rehabilitation heavy load, characterized in that a rehabilitation target tire is vulcanized using a rehabilitation vulcanization mold lower than the height (H) of the rehabilitation mold.

In the cross section of the vulcanization mold for rehabilitation, the ratio (F / W) of the linear length (F) of the center area of the tread to the width (W) of the tire sidewall maximum width formation position in the mold The manufacturing method according to claim 2 whose value is 0.4 or less.

The ratio (Δh / H) of the value (Δh) to the height (H) obtained by subtracting the inner surface height (h) of the vulcanization mold for rehabilitation from the inner surface height (H) of the new vulcanization mold The manufacturing method according to claim 1, 2 or 3, wherein the percentage of the value of is in the range of 0.2 to 1.0%.