JPH0825921A - Pneumatic radial tire for heavy load - Google Patents

Abstract

PURPOSE:To improve the durability of a tire bead part and prevent the separation trouble of a carcass ply end part by coating end part cords at both end parts of a carcass every one or plural cords with coating rubber independent every one or plural cords. CONSTITUTION:Layers with organic fiber cords or metallic fiber cords 2 placed parallelly in the almost right-angled direction to the tire equator face and embedded in coating rubber are laminated with the cord direction made almost the same to form a carcass ply 1 in annular shape. Depth cuts 4 are provided every two cords 2 in the longitudinal direction of the cords 2 from both end parts of the carcass ply 1. The cords 2 are thereby covered two by two with the same coating rubber 3 so as to form one group unit. The propagation of a micro crack generated to the cord end at the end part of the carcass ply 1 is thereby suppressed so as to improve the bead durability of a tire and to facilitate the folding work of both end parts of the carcass ply 1 at the time of forming the tire.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は、トラックやバスなどに
使用される重荷重用空気入りラジアルタイヤのビ−ド部
の耐久性能の改良に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of durability of a bead portion of a heavy duty pneumatic radial tire used for trucks and buses.

【０００２】[0002]

【従来技術】従来よりトラック、バスなどの大型車両に
供される重荷重用ラジアルタイヤを製造する場合のカ−
カス成形工程は以下に記述する方法が一般的である。即
ち、先ず図４（ａ）に示す如く、円筒状の成形ドラム１
０の上に巻回されて貼着されたインナ−ライナ−ゴム１
１の上部に、等間隔に並列されたコ−ドが被覆ゴム中に
埋設されたカ−カスプライ１２がタイヤ一本分に相当す
る長さに切断されて巻き付けられ貼着されて所謂バンド
１３が成形される。次に、この様にして出来た円筒状の
バンドの中央部分１４がバンド軸に直角方向外側に拡径
膨張される。次に、該バンドの両端部１５をバンド軸に
直角方向内側に絞り込んで縮径しその上の所定位置にス
ティフナ−ゴム１６を載置した一対のリング状のビ−ド
コア１７が嵌着される。次に、図４（ｂ）に示す如く、
該バンドの両端部１５とスティフナ−ゴム１６とが内圧
を充填されたサイドブラダ−１８によってビ−ドコア１
７の回りに折り返されてカ−カスプライ１の本体側１９
に貼着されて円筒状のカ−カス２０が形成される。2. Description of the Related Art Conventionally, a car for manufacturing a heavy-duty radial tire used for a large vehicle such as a truck or a bus.
The following method is generally used for the dust forming process. That is, first, as shown in FIG. 4A, the cylindrical forming drum 1
Inner-liner-rubber 1 wound and pasted on 0
A so-called band 13 is formed by cutting a carcass ply 12 in which cords juxtaposed at equal intervals are embedded in a coated rubber on the upper part of the sheet 1 and cutting and winding it to a length corresponding to one tire. Molded. Next, the central portion 14 of the cylindrical band thus formed is expanded and expanded outward in the direction perpendicular to the band axis. Next, a pair of ring-shaped bead cores 17 each having a stiffener rubber 16 mounted thereon are fitted in a predetermined position on the both ends 15 of the band by squeezing both ends 15 inward in a direction perpendicular to the band axis and reducing the diameter. . Next, as shown in FIG.
The bead core 1 is formed by a side bladder 18 in which both ends 15 of the band and a stiffener rubber 16 are filled with internal pressure.
The main body side 19 of the carcass ply 1 is folded back around 7
To form a cylindrical carcass 20.

【０００３】なお、上記の円筒状のカ−カスは、以後の
工程において必要な部材が追加貼着され、また円環体に
変形されて後、常法により加硫処理されて製品タイヤと
される。The above-mentioned cylindrical carcass is made into a product tire by vulcanizing by a conventional method after additional members necessary for the subsequent steps are additionally attached and after being transformed into an annular body. It

【０００４】[0004]

【発明が解決しようとする課題】しかるに、上記の様に
して円筒状のカ−カスが形成される際に、カ−カスプラ
イの両端部のコ−ド端末部分は、頭初の円筒状の成形ド
ラム上の外径ΦＡから前述の如くビ−ドコア回りに折り
返されてカ−カスプライの本体側に貼着された時の外径
ΦＢまで拡径されることとなる（尚、以後外径ΦＡに対
する外径ΦＢの比率を拡張率と呼称する）。従って、前
記コ−ド端末部分はこの拡径によってコ−ド間隔が大き
く引き伸ばされてコ−ドを被覆するゴムの厚さが薄くな
り、被覆ゴムの本来の役目であるコ−ドとゴム間の接着
機能が低下される。また、従来のタイヤでは、カ−カス
プライの両端部の各コ−ドは同一の被覆ゴムで一体的に
被覆されているので、タイヤが長期間走行して前記カ−
カスプライの両端部のコ−ドの一部の被覆ゴム２１に走
行疲労によって微小亀裂２２が万一発生した場合には、
図５に示す様に隣接するコ−ド２３の被覆ゴム２１に容
易に伝播してカ−カスプライ端部の剥離故障に進展する
可能性が増大するという懸念があった。However, when the cylindrical carcass is formed as described above, the cord end portions at both ends of the carcass ply are formed into a cylindrical shape at the beginning of the head. From the outer diameter ΦA on the drum, it is folded back around the bead core to the outer diameter ΦB when it is attached to the body side of the carcass ply as described above (hereinafter, with respect to the outer diameter ΦA. The ratio of the outer diameter ΦB is called the expansion rate). Therefore, in the cord end portion, due to the diameter expansion, the cord interval is greatly expanded and the thickness of the rubber covering the cord is thinned, and the original function of the covering rubber is between the cord and the rubber. The adhesive function of is reduced. Further, in the conventional tire, since the cords at both ends of the carcass ply are integrally covered with the same covering rubber, the tire is run for a long time and the car
In the unlikely event that a minute crack 22 occurs in the coating rubber 21 at a part of the cords at both ends of the dregs ply due to running fatigue,
As shown in FIG. 5, there is a concern that the possibility of easy propagation to the covering rubber 21 of the adjacent code 23 and progressing to peeling failure at the end of the carcass ply increases.

【０００５】更に、従来のタイヤでは同一の被覆ゴムで
カ−カスプライの両端部の各コ−ドが埋設され連繋され
ているので、前記折り返し部分の高さ（ビ−ドコアの底
面即ち内周面から折り返し端末までの距離）が高い構造
が採用されて前記の拡張率が大きく成る様な場合や、被
覆ゴムの硬度が高くコ−ド間のゴムが伸び難くコ−ド間
隔が引き伸ばされにくい場合では、前記した折り返し作
業が困難となりタイヤ成形能率が極めて悪くなるという
問題があった。Further, in the conventional tire, since the respective cords at both ends of the carcass ply are buried and connected by the same covering rubber, the height of the folded-back portion (the bottom surface of the bead core, that is, the inner peripheral surface). The distance between the cord and the turn-up terminal) is high, and the expansion ratio becomes large, or the hardness of the coated rubber is high and the rubber between the cords is hard to stretch and the cord spacing is difficult to stretch. However, there has been a problem that the above-mentioned folding operation becomes difficult and the tire molding efficiency becomes extremely poor.

【０００６】上記の事情を鑑みて、本発明の目的は、タ
イヤビ−ド部の耐久性能、特にカ−カスプライの端末部
分の剥離故障を効果的に防止し、しかもタイヤ成形工程
での折り返し作業性を向上する重荷重用空気入りラジア
ルタイヤを提供することである。In view of the above circumstances, it is an object of the present invention to effectively prevent the durability performance of the tire bead portion, particularly the peeling failure of the end portion of the carcass ply, and the workability of folding back in the tire molding process. It is to provide a pneumatic radial tire for heavy load, which improves

【０００７】[0007]

【課題を解決するための手段】上記の目的を達成するた
めに、本発明の重荷重用空気入りラジアルタイヤでは、
特許請求項１に記載の如く、複数の有機繊維コ−ド、又
は金属繊維コ−ドがタイヤ赤道面にほぼ直角方向に並列
されて被覆ゴム中に埋設された層が該コ−ド方向をほぼ
同一にして少なくとも一層以上積層されて円環状に形成
されたタイヤカ−カスの両端部がタイヤの左右に配置さ
れる一対のビ−ドコアの回りに各々巻回されて折り返さ
れている重荷重用空気入りラジアルタイヤにおいて、前
記タイヤカ−カスの両端部の端末部分のコ−ドが１本毎
に、または複数本毎に、さらに１本及び複数本ごとに独
立した被覆ゴムで被覆されていることを特徴としてい
る。In order to achieve the above object, the heavy-duty pneumatic radial tire of the present invention comprises:
As described in claim 1, a layer in which a plurality of organic fiber cords or metal fiber cords are juxtaposed in a direction substantially perpendicular to the tire equatorial plane and embedded in the coated rubber is arranged in the cord direction. Air for heavy load in which both ends of a tire carcass, which are formed substantially in the same manner and are laminated in at least one layer, are wound around and folded back around a pair of bead cores arranged on the left and right of the tire. In the filled radial tire, the cords of the terminal portions at both end portions of the tire carcass are coated one by one, or by a plurality of sheets, and further by one and a plurality of independent coating rubbers. It has a feature.

【０００８】また、本発明の効果を確実にしまた実用性
を高めるために、特許請求項２に記載のごとく、前記独
立した被覆ゴムで被覆されるタイヤカ−カスの両端部の
端末部の範囲が、前記タイヤカ−カスの両端部のコ−ド
端末よりタイヤ径方向内側に１０ないし３０ｍｍとされ
る特許請求項１に記載の重荷重用空気入りラジアルタイ
ヤとしている。Further, in order to secure the effect of the present invention and enhance the practicality, the range of the end portions of both ends of the tire carcass covered with the independent coating rubber is set as described in claim 2. The pneumatic radial tire for heavy load according to claim 1, wherein the radial distance is 10 to 30 mm inward in the tire radial direction from the code terminals at both ends of the tire carcass.

【０００９】[0009]

【作用】本発明の重荷重用空気入りラジアルタイヤで
は、上記の如く、タイヤカ−カスプライの両端部の端末
部のコ−ドが１本または複数本ごとに被覆ゴムで被覆さ
れて言わば群単位に独立しているので、タイヤの成形工
程において、成形ドラム上で円筒状に形成されたタイヤ
カ−カスプライの両端部が折り返されて拡径される場合
に、１本または複数本ごとに独立した群単位の個々の間
に存在する空隙の間が拡張して前記拡径による前記両端
部の周長の変化に対応するので、従来タイヤの如く両端
部の被覆ゴムの伸張が殆ど発生しない。従って、両端部
の端末部のコ−ドを被覆する被覆ゴムが折り返し成形を
された後もその厚さが頭初の設定値と変わらず十分に維
持され、次工程の加硫時に加硫圧力によって多数のフィ
ラメントが撚り合わさって成るコ−ドの該フィラメント
間に被覆ゴムが十分に浸透してコ−ドとゴムとの接着が
向上される。As described above, in the heavy duty pneumatic radial tire of the present invention, one or more cords at the end portions of both ends of the tire carcass ply are covered with the covering rubber, so to speak, independently of each other. Therefore, in the tire forming process, when both ends of the tire carcass ply formed into a cylindrical shape on the forming drum are folded back to be expanded in diameter, one or more individual tires are separated into groups. Since the spaces between the individual spaces expand to accommodate the change in the circumferential length of the both ends due to the diameter expansion, the extension of the coated rubber at both ends hardly occurs unlike the conventional tire. Therefore, the thickness of the coated rubber that coats the cords at the end portions at both ends is maintained at the same value as the initial setting even after being folded and molded, and the vulcanization pressure at the time of vulcanization in the next step Thus, the coating rubber is sufficiently penetrated between the filaments of the cord formed by twisting a large number of filaments, and the adhesion between the cord and the rubber is improved.

【００１０】又、製品タイヤが長期間使用され走行疲労
によってタイヤカ−カスプライの両端部のコ−ド末端で
被覆ゴムに微小亀裂が発生した場合において、前記空隙
に充填された別ゴムによって、該亀裂の伝播が前記１本
または複数本ごとに独立した個々の群単位の被覆ゴムの
中の伝播で一旦停止して亀裂伝播速度が遅くなるので、
コ−ド端末の剥離故障の発生が起こり難くなりタイヤの
耐久性が向上する。Further, when the product tire is used for a long period of time and a minute crack is generated in the coated rubber at the cord ends of both ends of the tire carcass ply due to running fatigue, the crack is caused by another rubber filled in the void. Of the above-mentioned one or a plurality of the independent independent rubber in the rubber unit of each group is temporarily stopped by the propagation, the crack propagation speed becomes slow,
The peeling failure of the cord terminal is less likely to occur, and the durability of the tire is improved.

【００１１】更に、タイヤ成形工程において、成形ドラ
ム上で円筒状に形成されたタイヤカ−カスプライの両端
部がビ−ドコア回りに折り返されて前記両端部の周長が
拡張される場合に、本発明のタイヤでは両端部に設けら
れている前記１本または複数本ごとに独立した群単位の
各々の間に存在する空隙が単に拡大することで対応出
来、従来構造のタイヤの如く被覆ゴムを伸張させるに要
する大きな力を必要としないので前記折り返し作業が容
易となり成形作業の能率が向上すると共に成形装置の複
雑化が防止出来る。Further, in the tire molding process, when both ends of the tire carcass ply formed in a cylindrical shape on the molding drum are folded back around the bead core to expand the circumferential length of the both ends, the present invention In the tire of No. 1, it is possible to deal with it by simply expanding the voids existing between each of the independent group units for each of the one or a plurality of tires provided at both ends, and to extend the coated rubber like the tire of the conventional structure. Since a large force required for the molding is not required, the folding operation can be facilitated, the efficiency of the molding operation is improved, and the molding apparatus can be prevented from becoming complicated.

【００１２】また、本発明では、タイヤカ−カスプライ
の両端部の端末部分のコ−ドが１本または複数本ごとに
被覆ゴムで被覆されて言わば群単位に独立する範囲は、
コ−ドの長手方向に前記両端部の端末部分のコ−ド端末
からカ−カスプライの内側に向かって１０乃至３０ｍｍ
の範囲であることが好ましい。過去の多くの実験結果を
調査した結果から、走行疲労によって前記コ−ド端末の
微小亀裂が発生する範囲は前記コ−ド端末からカ−カス
プライの内側に向かって１０ｍｍ以下の範囲であること
が確認されたので、隣接コ−ドの被覆ゴムから独立する
範囲は少なくともコ−ド長手方向に前記コ−ド端末から
１０ｍｍの範囲が好ましい。また、前記独立する範囲が
コ−ド長手方向に前記コ−ド端末から３０ｍｍを越える
と、その範囲がビ−ドコアの底部即ち内周面まで到達し
て、タイヤ内面のタイヤ径方向外側からこの部分にまで
延設されているタイヤ内圧保持用インナ−ライナ−ゴム
が前記空隙内に没入されて、インナ−ライナ−ゴムの設
定厚さが減少することによるタイヤ内圧の漏洩や、プラ
イコ−ド配列の乱れなどの別のトラブルを誘起する懸念
が生ずる。Further, according to the present invention, the range in which the cords at the end portions of both ends of the tire carcass ply are covered with the coating rubber for each one or a plurality of cords, so to speak, in a group unit,
10 to 30 mm toward the inside of the carcass ply from the cord ends at the end portions of the both ends in the longitudinal direction of the cord.
It is preferably in the range of. From the results of many past experiments, it is found that the range in which the micro-cracks of the cord end are generated by running fatigue is 10 mm or less from the cord end toward the inside of the carcass ply. Since it was confirmed, the range independent of the covering rubber of the adjacent code is preferably at least 10 mm from the code end in the longitudinal direction of the code. Further, when the independent range exceeds 30 mm from the code end in the longitudinal direction of the code, the range reaches the bottom portion of the bead core, that is, the inner peripheral surface, and the inner surface of the tire from the outer side in the tire radial direction. The tire inner pressure retaining inner liner rubber extended to a portion is immersed in the gap to reduce the set thickness of the inner liner rubber, thereby leaking the tire inner pressure and ply cord arrangement. There is a concern that it may induce other troubles such as disorder of the.

【００１３】なお、上記の如く、タイヤカ−カスプライ
の両端部の端末部のコ−ドが１本または複数本ごとに被
覆ゴムで被覆されて言わば群単位に独立する場合におい
て、一つの群に属するコ−ドの本数は１０本以下とする
のが好ましい。１０本を越えると走行疲労によるコ−ド
端末の微小亀裂が一気に伝播する範囲が広くなりビ−ド
部の剥離故障で走行不能となる時期を早める。As described above, when the cords at the end portions at both ends of the tire carcass ply are covered with the coating rubber for each one or a plurality of cords and are independent of each other, so to speak, belong to one group. The number of cords is preferably 10 or less. When the number exceeds 10, the range in which the microcracks of the code terminal propagate at a stretch due to running fatigue is widened, and the time at which the vehicle cannot run due to peeling failure at the bead portion is shortened.

【００１４】[0014]

【実施例】通常のトラックやバスに使用されるタイヤサ
イズ１０００Ｒ２０のラジアルタイヤに本発明を適用し
た一実施例を以下に説明する。図１において、本実施例
のカ−カスプライ１は、複数のフィラメントを撚り合わ
せた直径が１．１ｍｍのスチ−ルコ−ド２が２８本／５
０ｍｍの打ち込みで被覆ゴム３内に並列して埋設されて
いる。カ−カスプライのコ−ド長手方向に相当する幅は
５１０ｍｍとされて、その両端部からコ−ド長手方向に
１５ｍｍの範囲を、図１に示す如く、コ−ド２本毎に幅
０．７ｍｍの細い切り込み４が設けられる。該細い切り
込み４は、タイヤ一本分の長さに亙って並列された複数
個のリングカッタ−またはプレスカッタ−（図示省略）
によって形成される。この様にして制作されたカ−カス
プライ１の中央部分５の断面は、図２（ａ）に示される
形状となり、また、カ−カスプライの両端部６の前記切
り込み４を入れた部分の断面は、図２（ｂ）に示すごと
くコ−ドが２本づつ同一の被覆ゴムで被覆されて一つの
群単位７を形成した形状となっている。EXAMPLES An example in which the present invention is applied to a radial tire having a tire size of 1000R20 used for ordinary trucks and buses will be described below. In FIG. 1, the carcass ply 1 of the present embodiment has 28/5 steel rods 2 having a diameter of 1.1 mm obtained by twisting a plurality of filaments together.
It is embedded in the coated rubber 3 side by side with a driving of 0 mm. The width of the carcass ply corresponding to the longitudinal direction of the cord is 510 mm, and the range of 15 mm from the both ends in the longitudinal direction of the cord is a width of 0. A fine cut 4 of 7 mm is provided. The thin notch 4 has a plurality of ring cutters or press cutters (not shown) arranged in parallel over the length of one tire.
Formed by. The cross section of the central portion 5 of the carcass ply 1 thus produced has the shape shown in FIG. 2 (a), and the cross section of the both ends 6 of the carcass ply with the notches 4 is As shown in FIG. 2B, two cords are coated with the same coated rubber to form one group unit 7.

【００１５】上記の様にして制作されたカ−カスプライ
をタイヤ一本分に相当する所定長さに切り取って矩形平
板状のシ−トとしたものを一層、外径が拡縮可能な円筒
状の成形ドラムに巻回されたインナ−ライナ−ゴムの上
部に巻回貼着して円筒部材（バンド）が成形される。次
に、前記成形ドラムを拡径して前記円筒部材の中央部分
を拡張した後、前記円筒部材の両端部をビ−ドコアの内
径よりやや小さい径まで絞り込んで縮径し前記円筒部材
の中央部との間に段差部が形成される。次に、前記のご
とく縮径された円筒部材の両端部の上部に成形ドラムの
左右から断面三角形状のスティフナ−ゴムを載置した一
対のビ−ドコアが嵌着される。The carcass ply produced as described above is cut into a sheet having a rectangular flat plate shape by cutting it into a predetermined length corresponding to one tire, and the sheet has a cylindrical shape whose outer diameter can be expanded and contracted. A cylindrical member (band) is formed by winding and adhering the inner-liner-rubber on the forming drum. Next, after expanding the diameter of the forming drum to expand the central portion of the cylindrical member, both end portions of the cylindrical member are narrowed down to a diameter slightly smaller than the inner diameter of the bead core to reduce the diameter to the central portion of the cylindrical member. A step portion is formed between and. Next, a pair of bead cores on which stiffener rubbers having a triangular cross-section are mounted are fitted from the left and right of the molding drum onto the upper portions of both ends of the cylindrical member whose diameter has been reduced as described above.

【００１６】次に、該ビ−ドコア下に絞り込まれている
前記円筒部材の両端部が、前記ビ−ドコアの回りを巻回
して前記スティフナ−ゴムと共に前記段差部の上に折り
返されて、前記段差部上の円筒部材（カ−カスプライ）
とスティフナ−ゴムと前記円筒部材の両端部とが互いに
接着される。Next, both ends of the cylindrical member which is narrowed under the bead core are wound around the bead core and folded back together with the stiffener rubber onto the stepped portion, Cylindrical member (carcass ply) on the step
The stiffener rubber and both ends of the cylindrical member are adhered to each other.

【００１７】この時前記円筒部材の両端部は、前記拡縮
前の成形ドラムの外径ΦＡ＝１６００ｍｍから前記円筒
部材の両端部が前記段差部上に折り返されてスティフナ
−上に貼着された時のコ−ド端末の外径ΦＢ＝１７２０
ｍｍまで略７．５％の拡張率で伸張を受けるが、本発明
のカ−カスプライでは前述のごとく両端部が２本づつの
群単位として独立して被覆ゴムで被覆されているので、
各群単位間の前記空隙が上記の拡張率に相当して拡大さ
れて被覆ゴムは殆ど伸張せず被覆ゴム厚さが薄くなるこ
とがない。また、前記折り返し作業に当たって、前記円
筒部材の両端部の拡径時に被覆ゴムを伸張させるに要す
る力を必要とせず、従って折り返し作業が容易に行え作
業能率が向上する。At this time, when both ends of the cylindrical member are folded back from the outer diameter ΦA = 1600 mm of the molding drum before expansion and contraction to both ends of the cylindrical member and attached to the stiffener. Code terminal outer diameter ΦB = 1720
Although it is stretched up to about 7.5 mm at an expansion rate of about 7.5%, in the carcass ply of the present invention, both ends are independently coated with the coating rubber as two group units as described above.
The gap between each group unit is expanded corresponding to the above expansion rate, the coated rubber is hardly expanded, and the coated rubber thickness is not thinned. Further, in the folding operation, the force required to extend the covering rubber when expanding the diameters of both ends of the cylindrical member is not required, and therefore, the folding operation can be performed easily and the work efficiency is improved.

【００１８】また、前記折り返し端部の両側に、図３
（ａ）の如く、硬質の薄いシ−ト状のコ−ド端被覆ゴム
８をコ−ド端部の補強部材として貼着するときは、次工
程の加硫工程において該コ−ド端被覆ゴム８が加硫圧力
によって前記各群単位間の空隙９内に圧入されて加硫後
製品タイヤとなった際の折り返し端部の断面は図３
（ｂ）の断面図の様に形成される。この様に折り返し端
部が形成された場合では、タイヤが走行疲労によってコ
−ド端部に微小亀裂が発生すると、その亀裂の伝播は前
記のごとく空隙９内に圧入された硬いコ−ド端被覆ゴム
によって阻止されて、伝播速度が低下するためビ−ド部
の剥離故障の発生が遅れタイヤの耐久性能が一層向上す
る。Also, on both sides of the folded-back end portion, as shown in FIG.
As shown in (a), when the hard thin sheet-shaped cord end coating rubber 8 is attached as a reinforcing member for the cord end, the cord end coating is applied in the vulcanization step of the next step. The rubber 8 is press-fitted into the voids 9 between the respective group units by the vulcanization pressure to form a product tire after vulcanization.
It is formed as shown in the sectional view of FIG. In the case where the folded-back end portion is formed in this way, when a small crack is generated at the code end portion due to running fatigue of the tire, the propagation of the crack is caused by the hard cord end pressed into the void 9 as described above. It is blocked by the covering rubber and the propagation speed is lowered, so that the occurrence of peeling failure at the bead portion is delayed and the durability performance of the tire is further improved.

【００１９】次に、上記の本発明の効果を実際に確認す
るために、タイヤサイズ及び使用材料を同一として本実
施例のタイヤと従来構造の比較例のタイヤとを各々試作
して、タイヤビ−ド部耐久力試験を実施した。試験方法
及び試験条件は、室温３８±３℃に設定された室内に設
置された直径３ｍの鋼鉄製のドラムの内周面にＪＩＳ正
規内圧を充填したタイヤをＪＩＳ正規荷重の２倍の荷重
で押し付けて走行させてタイヤビ−ド部に故障が発生す
るまでの走行距離を比較するものである。Next, in order to actually confirm the above-mentioned effects of the present invention, a tire of the present example and a tire of a comparative example having a conventional structure were made as trials, using the same tire size and the same material, and tire tires were prepared. The end portion durability test was carried out. The test method and test conditions are as follows: A tire with a JIS regular internal pressure filled on the inner peripheral surface of a steel drum with a diameter of 3 m installed in a room set at a room temperature of 38 ± 3 ° C. under twice the JIS regular load. This is to compare the traveling distance until the tire bead portion is broken by pressing and traveling.

【００２０】上記試験の結果で得られた各々のタイヤの
故障発生までの走行距離を指数表示に直して評価する。
比較例のタイヤのカ−カスプライ端部の剥離故障が発生
した時点の走行距離を１００％とした場合に、本実施例
のタイヤの故障発生までの距離は１４０％となる結果が
得られ、本発明のタイヤではタイヤのビ−ド耐久性能が
著しく向上することが確認された。The mileage until the occurrence of a failure of each tire obtained from the results of the above test is converted into an index display and evaluated.
When the running distance at the time of peeling failure at the end of the carcass ply of the tire of the comparative example is 100%, the distance until the failure of the tire of this example is 140%. It was confirmed that in the tire of the invention, the bead durability performance of the tire was remarkably improved.

【００２１】なお、上記の実施例では、カ−カスプライ
は一層のスチ−ルコ−ド層からなるとしたが、カ−カス
プライのコ−ドはナイロンコ−ドやポリエステルコ−ド
または芳香族アラミド繊維などの有機繊維コ−ドであっ
ても良く、またカ−カスプライ層が２層以上の複数層で
あっても本発明が適当出来る。更に、上記実施例では、
タイヤサイズを通常のトラック、バスに使用される１０
００Ｒ２０としたが、本発明は、通常のトラック、バス
用のラジアルタイヤの他ライトトラック用、航空機用、
農耕用、更には建設機械用のラジアルタイヤにも同様に
適用出来る。また、上記の実施例では、タイヤの全周に
おいて、タイヤカ−カスプライの両端部の端末部でコ−
ドが２本ごとの群単位となっていたが、タイヤ１本内の
周方向で２本ごとの群単位、３本ごとの群単位を交互に
配置するなど群単位に含まれるコ−ド本数を、前記した
ごとく１０本内の範囲において、各種に組み合わせるこ
とが出来る。In the above embodiment, the carcass ply is composed of one steel cord layer, but the carcass ply is made of nylon cord, polyester cord or aromatic aramid fiber. The present invention can be applied to the present invention, even if it is a plurality of layers including two or more carcass ply layers. Further, in the above embodiment,
Tire size used for normal trucks and buses 10
However, the present invention is not limited to radial tires for ordinary trucks and buses, but also for light trucks, aircraft,
It is also applicable to radial tires for agricultural and construction machinery. Further, in the above-described embodiment, the entire circumference of the tire is covered by the end portions of both ends of the tire carcass ply.
The number of cords included in each group is such that every two tires have a group unit, but every two tires in the circumferential direction have a group unit, and every three tires have a group unit alternately. Can be variously combined within the range of 10 as described above.

【００２２】[0022]

【発明の効果】本発明の重荷重用ラジアルタイヤでは、
カ−カスプライの両端部の端末部分が、一本毎に、また
は複数本毎に、更に一本及び複数本ごとに独立した被覆
ゴムで被覆されているので、タイヤ製造時にカ−カスプ
ライコ−ドを被覆する被覆ゴムの厚さが薄くならず、コ
−ドと被覆ゴム間の接着が十分に担保され、更にタイヤ
走行疲労によって前記端末部分のコ−ド末端に発生する
微小亀裂の伝播が抑制されてタイヤのビ−ド耐久性が著
しく向上すると共に、タイヤ成形時のカ−カスプライ両
端部の折り返し作業が容易となりタイヤ成形能率がすこ
ぶる向上する。According to the radial tire for heavy load of the present invention,
Since the end portions of the both ends of the carcass ply are covered by independent rubber for each one or for every plural ones, and for each one or plurals, the carcass ply cord is provided at the time of tire production. The thickness of the coating rubber to be coated is not thin, the adhesion between the code and the coating rubber is sufficiently secured, and the propagation of microcracks generated at the cord end of the terminal portion due to tire running fatigue is suppressed. Thus, the bead durability of the tire is remarkably improved, and the work of folding back both ends of the carcass ply at the time of tire molding is facilitated, and the tire molding efficiency is greatly improved.

【図面の簡単な説明】[Brief description of drawings]

【図１】本発明の一実施例のタイヤのカ−カスプライの
構造を示す図である。FIG. 1 is a diagram showing a structure of a carcass ply of a tire according to an embodiment of the present invention.

【図２】本発明の一実施例のタイヤのカ−カスプライの
断面を示す図である。 （ａ）カ−カスプライの中央部分の断面を示す図であ
る。 （ｂ）カ−カスプライの両端部分の断面を示す図であ
る。FIG. 2 is a diagram showing a cross section of a carcass ply of a tire according to an embodiment of the present invention. (A) It is a figure which shows the cross section of the center part of a carcass ply. (B) It is a figure which shows the cross section of both ends of a carcass ply.

【図３】本発明の一実施例のタイヤにコ−ド端被覆ゴム
を適用した図である。 （ａ）折り返し端部の両側にコ−ド端被覆ゴムが配置さ
れた状態の図である。 （ｂ）コ−ド端被覆ゴムを適用した折り返し端部の横断
平面図である。FIG. 3 is a diagram in which a cord end coating rubber is applied to a tire according to an embodiment of the present invention. FIG. 6A is a view showing a state in which the cord end covering rubber is arranged on both sides of the folded back end portion. (B) It is a cross-sectional top view of the folding | returning edge part to which the cord end coating rubber is applied.

【図４】タイヤの成形作業を示す図である。 （ａ）円筒状のバンドを成形する状態を示す図である。 （ｂ）カ−カスプライを成形ドラム上に折り返す状態を
示す図である。FIG. 4 is a diagram showing a tire forming operation. (A) It is a figure which shows the state which shape | molds a cylindrical band. FIG. 6B is a diagram showing a state in which the carcass ply is folded back onto the forming drum.

【図５】コ−ド端末の亀裂がカ−カスプライ端部に伝播
する状態を示す図である。FIG. 5 is a view showing a state in which a crack of a cord end propagates to a carcass ply end portion.

【符号の説明】[Explanation of symbols]

１ カ−カスプライ ２ スチ−ルコ−ド ３ 被覆ゴム ４ 細い切り込み ５ カ−カスプライの中央部分 ６ カ−カスプライの両端部 ７ 群単位 ８ コ−ド端被覆ゴム ９ 空隙 １０ 成形ドラム １１ インナ−ライナ−ゴム １２ カ−カスプライ １３ バンド １４ バンドの中央部分 １５ バンドの両端部 １６ スティフナ−ゴム １７ ビ−ドコア １８ サイドブラダ− １９ カ−カスプライの本体側 ２０ カ−カス ２１ 被覆ゴム ２２ 微小亀裂 ２３ コ−ド DESCRIPTION OF SYMBOLS 1 Carcass ply 2 Steel cord 3 Covering rubber 4 Fine cut 5 Central part of the carcass ply 6 Both ends of the carcass ply 7 Group unit 8 Code end coating rubber 9 Void 10 Molding drum 11 Inner liner Rubber 12 Carcass ply 13 Band 14 Band central part 15 Band both ends 16 Stiffener rubber 17 Bead core 18 Side bladder 19 Carcass ply main body side 20 Carcass 21 Cover rubber 22 Microcracks 23 Code

Claims (2)

【特許請求の範囲】[Claims] 【請求項１】複数の有機繊維コ−ド、又は金属繊維コ−
ドがタイヤ赤道面にほぼ直角方向に並列されて被覆ゴム
中に埋設された層が該コ−ド方向をほぼ同一にして少な
くとも一層以上積層されて円環状に形成されたタイヤカ
−カスの両端部がタイヤの左右に配置される一対のビ−
ドコアの回りに各々巻回されて折り返されている重荷重
用空気入りラジアルタイヤにおいて、前記タイヤカ−カ
スの両端部の端末部分のコ−ドが１本毎に、または複数
本毎に、さらに１本及び複数本ごとに独立した被覆ゴム
で被覆されていることを特徴とする重荷重用空気入りラ
ジアルタイヤ。1. A plurality of organic fiber cords or metal fiber cords
Both ends of a tire carcass formed in an annular shape by stacking at least one layer in which the cords are juxtaposed substantially at right angles to the equatorial plane of the tire and embedded in the coated rubber so that the cord directions are substantially the same. Are a pair of bees arranged on the left and right of the tire.
In a heavy-duty pneumatic radial tire that is wound around each core and folded back, one cord is provided at each end of the tire carcass at both ends, or a plurality of cords are provided at each end. And a pneumatic radial tire for heavy loads, characterized in that each of the plurality of rubbers is covered with an independent coating rubber. 【請求項２】前記独立した被覆ゴムで被覆されるタイヤ
カ−カスの両端部の端末部の範囲が、前記タイヤカ−カ
スの両端部のコ−ド端末よりタイヤ径方向内側に１０な
いし３０ｍｍとされる請求項１に記載の重荷重用空気入
りラジアルタイヤ。2. The range of the terminal portions at both ends of the tire carcass covered with the independent coating rubber is 10 to 30 mm inward in the tire radial direction from the cord terminals at both ends of the tire carcass. The pneumatic radial tire for heavy load according to claim 1.