JP4107915B2

JP4107915B2 - Method for forming a bead core having a hexagonal cross section

Info

Publication number: JP4107915B2
Application number: JP2002243293A
Authority: JP
Inventors: 勉佐伯
Original assignee: Bridgestone Corp
Current assignee: Bridgestone Corp
Priority date: 2002-08-23
Filing date: 2002-08-23
Publication date: 2008-06-25
Anticipated expiration: 2022-08-23
Also published as: JP2004082375A

Description

【０００１】
【発明の属する技術分野】
本発明は、トラック、バス等の重荷重用ラジアルタイヤを製造する際に用いて好適な六角断面を有するビードコアの成形方法に関するものであり、該ビードコアを構成するワイヤの規則的な配置を実現し、該ビードコアが本来もつ特性（曲げ剛性、引張力、ねじり剛性等）をより有利に発揮させようとするものである。
【０００２】
【従来の技術】
トラック、バス等の重荷重用ラジアルタイヤは高い耐久性を確保する観点から六角断面になるビードコアが採用されている。
【０００３】
かかるビードコアは、胴部の周りに所定の断面形状を有する溝部を有するフォーマを使用し、インシュレーションを施したワイヤを該溝部内でその幅方向に沿い一定のピッチ送り量で送給しながら螺旋状に巻回して配列層を形成し、さらにその巻回し動作を連続的に往路、復路で交互に繰り返して該配列層を複数段に積み重ねることで六角断面をなすビードコアに成形している。
【０００４】
ところで、従来方式に従って成形されたビードコアは、一定のピッチ送り量で送給しながら積み重ねているにもかかわらず、コアの幅方向におけるワイヤ相互の中心間距離が不揃いになる場合があり、また、かかるビードコアを使用した加製品タイヤの調査結果によれば、ビードコアの成形直後のワイヤの配列状況（加硫前）と加硫後におけるワイヤの配列状況に大きな違いが発生するのが避けられない状況にあった（製品タイヤのビードコアの幅方向におけるワイヤ相互の中心間距離が加硫前のワイヤ相互の中心間距離の９５％以上圧縮された状態にある）。
【０００５】
ここに、ワイヤの配列状況が不均一な場合、製品タイヤの入力に対して局所的に歪みが集中するのが不可避であり、ビードコアを構成するそれぞれのワイヤの利用率が低下しビードコアが本体もつ特性を十分に発揮することができない懸念があり、加硫前と加硫後でワイヤの配列状況が変動する場合には、曲げ剛性、ねじり剛性等、ビードコアが本来有する性能を十分に発揮できる状態にあるとはいえず、ワイヤの利用率の低下も避けられない。
【０００６】
【発明が解決しようとする課題】
本発明の課題は、ワイヤをフォーマで巻回しながら六角断面を有するビードコアを成形するに当たって巻回しにかかるワイヤを全列、全段で均一に配列させることができる新規な法を提案するところにある。
【０００７】
【課題を解決するための手段】
本発明は、インシュレーション済のワイヤをフォーマの溝部内でその幅方向に沿い螺旋状に巻回して配列層を形成するとともにその巻回し動作を往路と復路で交互に繰返して該配列層を複数段に積み重ねて六角断面をなすビードコアに成形するに当たり、
螺旋状に巻回す際のワイヤのピッチ送り量を下記の条件に従って制御することを特徴とする六角断面を有するビードコアの成形方法である。
記
（Ｐｄ−Ｐｕ）／Ｄ≧０．００４
Ｐｕ：往路におけるワイヤのピッチ送り量
Ｐｄ：復路におけるワイヤのピッチ送り量
Ｄ：インシュレーション済みのワイヤの直径
【０００８】
また、本発明は、インシュレーション済のワイヤをフォーマの溝部内でその幅方向に沿い螺旋状に巻回して配列層を形成するとともにその巻回し動作を往路と復路で交互に繰返して該配列層を複数段に積み重ねて六角断面をなすビードコアを成形するに当たり、
螺旋状に巻回して配列層を形成する際のワイヤのピッチ送り量をフォーマの溝部内と該フォーマの溝部より露出した領域で変更すべく、下記の条件に従って制御することを特徴とする六角断面を有するビードコアの成形方法である。
記
（Ｐｉ−Ｐｆ）／Ｄ≧０．００２
Ｐｉ：フォーマの溝部内でのワイヤのピッチ送り量
Ｐｆ：フォーマの溝部より露出した領域でのワイヤのピッチ送り量
Ｄ：インシュレーション済のワイヤの直径
【０００９】
さらに本発明はインシュレーション済のワイヤをフォーマの溝部内でその幅方向に沿い螺旋状に巻回して配列層を形成するとともにその巻回し動作を往路と復路で交互に繰返して該配列層を複数段に積み重ねて六角断面をなすビードコアを成形するに当たり、
前記フォーマの溝部の底壁及び側壁にそれぞれ互いに間隔をおいて配列された区画凹所を設け、この区画凹所に沿ってワイヤを螺旋状に巻回すことを特徴とする六角断面を有するビードコアの成形方法であり、区画凹所は、その深さをｔ、相互間隔をＬ、インシュレーション済みのワイヤの直径をＤとした場合に、
ｔ≦１／２・Ｄ
Ｌ＝１．０５Ｄ〜１．１０Ｄ
とするのが望ましい。
【００１０】
フォーマの溝部については、該溝部の幅方向に傾斜した底壁と、該底壁に向けて狭幅になる一対の溝壁を備えたものとするのがよい。
【００１１】
【発明の実施の形態】
以下、図面を用いて本発明をより具体的に説明する。
【００１２】
フォーマの溝部はその幅方向に角度が１５°程度になる傾斜を有する底壁とこの底壁に向けて狭幅になる図１に示すような断面形状になっており、かかる溝部１を有するフォーマｆを使用して六角断面をなすビードコア２を形成する場合、一定のピッチ送り量でワイヤの巻回しを行っても、底壁１ａが傾斜しているため巻回し動作の往路、復路（上り、下り）でワイヤＷの位置が変動すること、また、ワイヤの巻回しの際、フォーマの溝部内（固定域）ではワイヤの配列層が側壁によって拘束されるが該溝部１から露出した巻回し領域（フリー域）では巻回しにかかるワイヤの配列層は拘束されることはないので、同一のピッチ送り量でワイヤを巻回しても図２に示すように固定域とフリー域でワイヤ相互の中心間距離に差がでてくるのは避けられない（固定域におけるワイヤの配列層はビードコアをフォーマから取り外した時、ワイヤの戻り力の影響を受ける）。
【００１３】
本発明では、螺旋状に巻回す際のワイヤのピッチ送り量を、
（Ｐｄ−Ｐｕ）／Ｄ≧０．００４
Ｐｕ：往路におけるワイヤのピッチ送り量
Ｐｄ：復路におけるワイヤのピッチ送り量
Ｄ：インシュレーション済みのワイヤの直径
の条件に従って制御するものであり、これによれば巻回し動作の往路と復路（上り、下り）にかかわりなくワイヤの配列状況をほぼ一定とすることができる。
【００１４】
また、溝部の固定域とフリー域でワイヤの配列状況に大きな差がでることが懸念される場合には、
（Ｐｉ−Ｐｆ）／Ｄ≧０．００２
Ｐｉ：フォーマの溝部内でのワイヤのピッチ送り量
Ｐｆ：フォーマの溝部より露出した領域でのワイヤのピッチ送り量
Ｄ：インシュレーション済のワイヤの直径
の条件でワイヤを巻回すことで固定域、フリー域にかかわりなしにワイヤの配列状況をほぼ一定にすることができる。
【００１５】
溝部の底壁が傾斜している上掲図１に示したようなフォーマでの巻回しにおいては、所定のピッチ送り量で配列層を形成していっても、底壁が傾斜しているためワイヤが図３に示すように底壁の傾斜に沿って滑ってゆき、ワイヤの配列状況にずれが生じるため六角断面になるビードコアの特性に悪影響を与えることもないとはいえず、このような滑りが生じなくとも、配列層の段数が増していくに従いその重みでもって下部域におけるワイヤの配列層が崩れてしまうおそれもある。
【００１６】
このため、図４に示すようにフォーマの溝部の底壁及び側壁にそれぞれ互いに間隔を開けて区画凹所を設けておき、この区画凹所にワイヤを配置しながら螺旋状に巻まわすのがよく、これによればワイヤ相互の中心間距離が均等になる。
【００１７】
区画凹所は、その深さをｔ、相互間隔をＬ、インシュレーション済みのワイヤの直径をＤとして、
ｔ≦１／２・Ｄ
Ｌ＝１．０５Ｄ〜１．１０Ｄ
とするのが望ましい。
【００１８】
本発明において区画凹所の相互間隔Ｌを１．０５Ｄ〜１．１０Ｄとするのが望ましいのは、加硫を施した製品タイヤのビードコアにつき、その幅方向距離をｘ、縦方向距離をｙとした場合（図４参照）に、Ｄｙ／Ｄｘとビードコアのねじり剛性との関係は図５に示すような分布になる一方、製品タイヤのワイヤ相互の中心間距離Ｄ xと区画凹所の相互間距離Ｌとは図６に示すような関係にあり、区画凹所の相互間距離Ｌが１．０５Ｄ〜１．１０Ｄ程度でＤｙ／Ｄｘがほぼ１すなわち、ビードコアのねじれり剛性が最大となるからである。
【００１９】
【実施例】
実施例１
直径が1.83mm(インシュレーション後の直径2.03mm)になるワイヤを用いフォーマにて成形した六角断面になるビードコア(58Ｔ(7-10- 7))を備えた重荷重用空気入りタイヤ(TBR 11Ｒ22.5Ｍ810Ｚ)を製作し、該タイヤの曲げ剛性について調査した。その結果を表１に示す。なお、表中番号１は従来法に従ってビードコアを成形した場合（ワイヤのピッチ送り量をすべて一定）であり、番号２は固定域とフリー域でワイヤのピッチ送り量を変更した場合であり、番号３は往路と復路でワイヤのピッチ送り量を変更した場合であり、番号４は、固定域とフリー域でワイヤのピッチ送り量を変更するとともに往路と復路でワイヤのピッチ送り量を変更した場合である。
【００２０】
【表１】

【００２１】
表１より明らかなように、従来法に従って成形されたビードコアを備えるタイヤの曲げ剛性を100とした場合(指数表示)において、本発明にしたがって成形したビードコアを備えるタイヤ(番号２、３、４)についてはすべて良好な結果が得られることが確認された。
【００２２】
実施例２
溝部の底壁の傾斜角が１５°になるフォーマにて直径が1.83mm(インシュレーション後の直径2.03mm)のワイヤの巻回しによって成形した六角断面のビードコア(45Ｔ(7-9- 6))を備えた重荷重用空気入りタイヤ(TBR 11Ｒ22.5Ｍ810Ｚ)を製作してそのタイヤのビード耐久性(速度：60Km／h 一定、荷重：ステップロード、150％スタート)について調査を行った。その結果を表２に示す。
【００２３】
【表２】

【００２４】
区画凹所を設けたフォーマを使用してビードコアを成形した場合、それを構成するワイヤの配置が何れの場合もきわてめ良好であり、相互間隔Ｌが2.03mm(Ｄ)になるタイヤのビード耐久性を100としたとき、Ｌ＝1.05Ｄで108、Ｌ＝1.10Ｄで112、Ｌ＝1.30Ｄで92という結果が得られた。
【００２５】
【発明の効果】
本発明によればビードを構成するワイヤを全列、全段で均等に配置することが可能であり、ビードコアが本体もつべき特性をより有利に発揮させることができる。
【図面の簡単な説明】
【図１】フォーマの溝部の断面を示した図である。
【図２】ワイヤ相互の中心間距離とピッチ送り量の関係を示した図である。
【図３】ワイヤの巻回し状況を示した図である。
【図４】フォーマの溝部の断面を示した図である。
【図５】ねじり剛性とＤｙ／Ｄｘの関係を示した図である。
【図６】ワイヤ相互の中心間距離（Ｄｘ）と区画凹所相互間隔（Ｌ）の関係を示したグラフである。
【符号の説明】
１溝部
１ａ底壁
２ビードコア
３区画凹所
ｆフォーマ
Ｗワイヤ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a bead core having a hexagonal cross section suitable for use in manufacturing heavy duty radial tires such as trucks and buses, and realizes regular arrangement of wires constituting the bead core, The bead core is intended to exhibit the properties inherent to it (bending rigidity, tensile force, torsional rigidity, etc.) more advantageously.
[0002]
[Prior art]
A heavy duty radial tire for trucks, buses, etc. employs a bead core having a hexagonal cross section from the viewpoint of ensuring high durability.
[0003]
Such a bead core uses a former having a groove portion having a predetermined cross-sectional shape around the body portion, and spirals while feeding the insulated wire in the groove portion along the width direction at a constant pitch feed amount. An array layer is formed by winding the layers into a bead core having a hexagonal cross section by stacking the array layers in a plurality of stages by alternately repeating the winding operation in the forward path and the return path.
[0004]
By the way, the bead cores molded in accordance with the conventional method may be uneven in the distance between the centers of the wires in the width direction of the core, although they are stacked while being fed at a constant pitch feed amount. According to the survey results of product tires using such bead cores, it is inevitable that there will be a great difference between the wire arrangement immediately after molding the bead core (before vulcanization) and the wire arrangement after vulcanization. (The distance between the centers of the wires in the width direction of the bead core of the product tire was compressed 95% or more of the distance between the centers of the wires before vulcanization).
[0005]
Here, when the arrangement state of the wires is not uniform, it is inevitable that the strain is concentrated locally with respect to the input of the product tire, the utilization rate of each wire constituting the bead core is lowered, and the bead core has the main body. There is a concern that the characteristics cannot be fully exhibited, and when the wire arrangement varies before and after vulcanization, the bead core can fully demonstrate its inherent properties such as bending rigidity and torsional rigidity. In other words, the utilization rate of the wire is unavoidable.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to propose a novel method capable of uniformly arranging a wire for winding in all rows and all stages in forming a bead core having a hexagonal cross section while winding the wire with a former. .
[0007]
[Means for Solving the Problems]
In the present invention, an insulated wire is wound spirally along the width direction in a groove portion of a former to form an array layer, and the winding operation is alternately repeated in the forward path and the return path to form a plurality of array layers. When forming into a bead core that has a hexagonal cross-section by stacking in stages,
A method for forming a bead core having a hexagonal cross section, wherein a pitch feed amount of a wire when spirally wound is controlled according to the following conditions.
Record
(Pd−Pu) /D≧0.004
Pu : Pitch feed amount of the wire in the forward path
Pd : Pitch feed amount of wire on the return path
D: diameter of the insulated wire.
In addition, the present invention also forms an array layer by spirally winding the insulated wire along the width direction in the groove portion of the former and forming the array layer by alternately repeating the winding operation in the forward path and the return path. In forming a bead core having a hexagonal cross section by stacking
A hexagonal cross section that is controlled in accordance with the following conditions in order to change the pitch feed amount of the wire when forming the array layer by spirally winding in the groove portion of the former and the region exposed from the groove portion of the former A method for forming a bead core having
Record
(Pi−Pf) /D≧0.002
Pi: Pitch feed amount of wire in groove of former
Pf: Pitch feed amount of wire in the area exposed from the groove of the former
D: Diameter of the insulated wire
Furthermore, the present invention forms an array layer by spirally winding an insulated wire along the width direction in the groove portion of the former, and at the same time, repeating the winding operation alternately in the forward path and the return path, to form a plurality of the array layers. In forming a bead core that has a hexagonal cross-section by stacking in stages,
A bead core having a hexagonal cross section, characterized in that a partition recess arranged at a distance from each other is provided on the bottom wall and side wall of the groove portion of the former, and a wire is spirally wound along the partition recess. It is a forming method, and the partition recess is defined by assuming that the depth is t, the mutual interval is L, and the diameter of the insulated wire is D.
t ≦ 1/2 ・ D
L = 1.05D to 1.10D
Is desirable.
[0010]
About the groove part of a former | foamer, it is good to have the bottom wall inclined in the width direction of this groove part, and a pair of groove wall which becomes narrow toward this bottom wall.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described more specifically with reference to the drawings.
[0012]
A groove portion of the former has a bottom wall having an inclination with an angle of about 15 ° in the width direction and a cross-sectional shape as shown in FIG. When the bead core 2 having a hexagonal cross section is formed using f, even if the wire is wound at a constant pitch feed amount, the bottom wall 1a is inclined, so that the forward and backward paths (up, The position of the wire W fluctuates in the downward direction, and when the wire is wound, the wire arrangement layer is constrained by the sidewall in the groove portion (fixed region) of the former, but the winding region is exposed from the groove portion 1. In the (free zone), the wire arrangement layer is not constrained, so even if the wire is wound with the same pitch feed amount, the center of the wires in the fixed zone and the free zone as shown in FIG. Avoid differences in distance Never (when alignment layers of wire removal of the bead cores from the former in the stationary region, affected by the wire return force).
[0013]
In the present invention, the pitch feed amount of the wire when spirally wound,
(Pd−Pu) /D≧0.004
Pu : Pitch feed amount of the wire in the forward path
Pd : Pitch feed amount of wire on the return path
D: Control is performed according to the condition of the diameter of the insulated wire, and according to this, the arrangement state of the wires can be made almost constant regardless of the forward path and the return path (up and down) of the winding operation.
[0014]
Also, if you are concerned that there will be a big difference in the wire arrangement between the fixed area and free area of the groove,
(Pi−Pf) /D≧0.002
Pi: Pitch feed amount of wire in groove of former
Pf: Pitch feed amount of wire in the area exposed from the groove of the former
D: By winding the wire under the condition of the diameter of the insulated wire, the arrangement state of the wires can be made almost constant regardless of the fixed region and the free region.
[0015]
In winding with a former as shown in FIG. 1 in which the bottom wall of the groove portion is inclined, the bottom wall is inclined even if the array layer is formed with a predetermined pitch feed amount. As the wire slides along the inclination of the bottom wall as shown in FIG. 3, the wire arrangement state is shifted, so it cannot be said that it does not adversely affect the characteristics of the bead core having a hexagonal cross section. Even if slip does not occur, as the number of steps of the arrangement layer increases, there is a possibility that the arrangement layer of the wires in the lower region may collapse with the weight.
[0016]
For this reason, as shown in FIG. 4, it is preferable to provide a partition recess in the bottom wall and the side wall of the groove portion of the former so as to be spaced apart from each other, and to spirally wind the wire while placing the wire in the partition recess. According to this, the distance between the centers of the wires becomes equal.
[0017]
Compartmental recesses, where t is the depth, L is the mutual spacing, and D is the diameter of the insulated wire,
t ≦ 1/2 ・ D
L = 1.05D to 1.10D
Is desirable.
[0018]
In the present invention, it is desirable that the interval L between the compartment recesses is 1.05D to 1.10D. For the bead core of the vulcanized product tire, the width direction distance is x and the longitudinal direction distance is y. when (see Fig. 4), while the relationship between the torsional stiffness of Dy / Dx and the bead core becomes distributed as shown in FIG. 5, between the mutual center distance D x between compartments recess wire cross product tire The distance L has a relationship as shown in FIG. 6, and the distance L between the partition recesses is about 1.05D to 1.10D , and Dy / Dx is almost 1, that is, the torsional rigidity of the bead core is maximized. It is.
[0019]
【Example】
Example 1
Heavy duty pneumatic tire (TBR 11R22.) With a bead core (58T (7-10-7)) with a hexagonal cross section formed by a former using a wire with a diameter of 1.83mm (diameter after insulation 2.03mm). 5M810Z) was manufactured and the bending stiffness of the tire was investigated. The results are shown in Table 1. In the table, number 1 is when the bead core is molded according to the conventional method (the wire pitch feed amount is all constant), and number 2 is the case where the wire pitch feed amount is changed in the fixed range and the free range. 3 is a case where the pitch feed amount of the wire is changed in the forward path and the return path, and No. 4 is a case where the pitch feed amount of the wire is changed in the fixed area and the free area and the pitch feed amount of the wire is changed in the forward path and the return path. It is.
[0020]
[Table 1]

[0021]
As is apparent from Table 1, when the bending rigidity of a tire including a bead core formed according to the conventional method is 100 (index indication), the tire including a bead core formed according to the present invention (

numbers

2, 3, and 4) For all, it was confirmed that good results were obtained.
[0022]
Example 2
A bead core with a hexagonal cross section (45T (7-9-6)) formed by winding a wire with a diameter of 1.83mm (diameter 2.03mm after insulation) in a former with an inclination angle of the bottom wall of the groove of 15 ° A heavy-duty pneumatic tire (TBR 11R22.5M810Z) equipped with a tire was manufactured, and the bead durability of the tire (speed: 60 km / h constant, load: step load, 150% start) was investigated. The results are shown in Table 2.
[0023]
[Table 2]

[0024]
When a bead core is molded using a former provided with a compartment recess, the arrangement of the wires constituting the bead core is extremely good in any case, and the bead of the tire having a mutual interval L of 2.03 mm (D) When the durability was 100, L = 1.05D was 108, L = 1.10D was 112, and L = 1.30D was 92.
[0025]
【The invention's effect】
According to the present invention, the wires constituting the beads can be arranged uniformly in all rows and in all stages, and the characteristics that the bead core should have can be exhibited more advantageously.
[Brief description of the drawings]
FIG. 1 is a view showing a cross section of a groove portion of a former.
FIG. 2 is a diagram showing a relationship between a distance between centers of wires and a pitch feed amount.
FIG. 3 is a view showing a winding state of a wire.
FIG. 4 is a view showing a cross section of a groove portion of a former.
FIG. 5 is a diagram showing a relationship between torsional rigidity and Dy / Dx.
FIG. 6 is a graph showing the relationship between the distance between centers of wires (Dx) and the distance between partitioning recesses (L).
[Explanation of symbols]
1 groove 1a bottom wall 2 bead core 3 partitioning recess f former W wire

Claims

Insulated wire is spirally wound along the width direction in the groove of the former to form an array layer, and the winding operation is alternately repeated in the forward and return paths to stack the array layers in multiple stages. When forming a bead core with a hexagonal cross section,
A method for forming a bead core having a hexagonal cross section, characterized in that the pitch feed amount of a wire when spirally wound is changed according to the following conditions in order to change the forward path and the backward path.
Record
(Pd−Pu) /D≧0.004
Pu : Pitch feed amount of the wire in the forward path
Pd : Pitch feed amount of wire on the return path
D: Diameter of the insulated wire

Insulated wire is spirally wound along the width direction in the groove of the former to form an array layer, and the winding operation is alternately repeated in the forward and return paths to stack the array layers in multiple stages. In forming a bead core having a hexagonal cross section,
A hexagonal cross section that is controlled in accordance with the following conditions in order to change the pitch feed amount of the wire when forming the array layer by spirally winding in the groove portion of the former and the region exposed from the groove portion of the former A method for forming a bead core comprising:
Record
(Pi−Pf) /D≧0.002
Pi: Pitch feed amount of wire in groove of former
Pf: Pitch feed amount of wire in the area exposed from the groove of the former
D: Diameter of the insulated wire

Insulated wire is spirally wound along the width direction in the groove of the former to form an array layer, and the winding operation is alternately repeated in the forward and return paths to stack the array layers in multiple stages. In forming a bead core having a hexagonal cross section,
A bead core having a hexagonal cross section, characterized in that a partition recess arranged at a distance from each other is provided on the bottom wall and side wall of the groove portion of the former, and a wire is spirally wound along the partition recess. Molding method.

The method according to claim 1, wherein the groove portion of the former includes a bottom wall inclined in the width direction of the groove portion and a pair of groove walls narrowing toward the bottom wall. .