JP4076711B2

JP4076711B2 - Pneumatic tire manufacturing method

Info

Publication number: JP4076711B2
Application number: JP2000191514A
Authority: JP
Inventors: 英司東
Original assignee: Toyo Tire and Rubber Co Ltd
Current assignee: Toyo Tire Corp
Priority date: 2000-06-26
Filing date: 2000-06-26
Publication date: 2008-04-16
Anticipated expiration: 2020-06-26
Also published as: JP2002001834A

Description

【０００１】
【発明の属する技術分野】
本発明は導電性に優れた空気入りタイヤ及びその製造方法に関する。
【０００２】
【従来の技術】
近年、自動車の低燃費化への要請が高まっている。これに伴い、タイヤの転がり抵抗を小さくするためトレッドゴム組成物としてカーボンブラックの配合割合を少なくして珪酸を多く含むシリカ主配合系ゴム組成物からなるトレッドゴムを配した空気入りタイヤが提案されている。
【０００３】
このような空気入りタイヤは、トレッドゴム層には導電性の良いカーボンブラックの配合割合が少なく、導電性の悪い珪酸が多く含まれるため、車体から発生する静電気をタイヤリムからビード部、サイドウォール部、バットレス部及びタイヤトレッド部を経て踏面へ逃がすことができず、車体に静電気が蓄積されることがある。従って、従来より、導電性が良く、それでいて転がり抵抗の小さい空気入りタイヤの提供が望まれており、その開発が進められている。
【０００４】
従来、かかる観点から、導電性液状ゴム糊組成物をトレッドの接地端相当部付近からバットレス相当部にかけて塗布して加硫成形する方法が試行されている。
【０００５】
【発明が解決しようとする課題】
しかし、加硫成形前のグリーンタイヤは、ドーナツ形状をしていて、溝部は形成されておらず、加硫成形後の製品時の溝部に該当する部分は加硫成形金型の凸部によって加硫成形時にグリーンタイヤ時の面積の数倍に拡張される。
【０００６】
従って、導電性液状ゴム糊組成物をグリーンタイヤのトレッドの接地端相当部付近からバットレス相当部にかけて塗布して加硫成形した空気入りタイヤの場合、図８に示すように、タイヤショルダー部の横溝１７において、導電性導電性ゴム組成物の薄膜１９が当該溝表面に被覆されない部分１９０が発生する。その結果、導電性が十分発揮できない問題が生じる。なお、図８において、１４は陸部、１５は溝壁部、１６は溝底部、１８は踏面部である。
【０００７】
本発明の目的は、導電性の悪いタイヤトレッド面に導電性液状ゴム糊組成物をグリーンタイヤのトレッドの接地端相当部付近からバットレス相当部にかけて塗布して加硫成形しても、タイヤショルダー部の横溝の溝面全体を導電性ゴム薄膜で被覆することができ、導電性を十分発揮することができる空気入りタイヤの製造方法、前記タイヤ製造方法に用いることができる部材としての加硫成形前の押し出しトレッド及び、タイヤショールダー部の陸部と横溝の凹凸面に沿ってタイヤ周方向にほぼ均一な厚みで連続的に導電性皮膜が形成される空気入りタイヤを提供するところにある。
【０００８】
上記課題を解決するために、本製造方法の発明は、ベースゴムとキャップゴムで構成され、かつ、シリカ主配合系ゴム組成物で構成された加硫成形前のトレッドのタイヤショルダー部から、該トレッドの両側又は片側に配された導電性トレッドストリップゴムにかけて、これらの範囲内の表面を被覆するようにして導電性液状ゴム糊組成物を塗布して加硫成形し、タイヤショルダー部の陸部と横溝の凹凸面に沿ってタイヤ周方向に上記導電性液状ゴム糊組成物で構成された導電性被膜を形成してなる空気入りタイヤの製造方法において、
上記加硫成形前のトレッドは、そのタイヤショルダー部の表面から内面に向けて、その深さが上記加硫成形前のトレッドの上記キャップゴムの厚みの５０〜９０％である導電性液状ゴム糊組成物の溜穴がタイヤ周方向に複数形成されており、上記導電性液状ゴム糊組成物を、このトレッドの溜穴に充填しつつタイヤ周方向に塗布して、加硫成形したことを特徴とする空気入りタイヤの製造方法である。
【０００９】
従って、加硫成形時にタイヤショルダー部の横溝に該当する部分のトレッド表面がタイヤ成形金型により成形されて残りの部分よりも拡張されても、その拡張に対応して、溜穴に貯蔵されている導電性液状ゴム糊組成物が上記溜穴から延ばされてタイヤショルダー部の溝部の溝面全体に満遍なく供給され、タイヤショルダー部の陸部表面と同じく、タイヤショルダー部の溝部の溝面全体に均一な導電性被膜が連続的に形成されるものである。
【００１０】
前記タイヤ製造方法に用いることができる部材としての加硫成形前の押し出しトレッドの発明は、陸部と横溝の凹凸面をタイヤ周方向に繰り返すタイヤショルダー部を有し、ベースゴムとキャップゴムで構成され、かつ、シリカ主配合系ゴム組成物で構成された加硫成形前の押し出しトレッドであって、当該トレッドのタイヤショルダー部に、その表面から内面に向けて、その深さが上記加硫成形前のトレッドの上記キャップゴムの厚みの５０〜９０％である導電性液状ゴム糊組成物の溜穴がタイヤ周方向に複数形成されているトレッドである。
【００１１】
本発明の空気入りタイヤは、シリカ主配合系ゴム組成物で構成され、陸部と横溝の凹凸面をタイヤ周方向に繰り返すタイヤショルダー部を有するタイヤトレッドと、このトレッドの両側又は片側に配された導電性トレッドストリップゴムとを備えた空気入りタイヤにおいて、上記トレッドのタイヤショルダー部から上記導電性トレッドストリップゴムにかけて、これらの範囲内の表面が導電性液状ゴム糊組成物からなる導電性被膜で被覆されており、且つ上記導電性被膜は、タイヤショルダー部の陸部と横溝の凹凸面に沿ってタイヤ周方向にほぼ均一厚みで連続的に形成されている空気入りタイヤである。
【００１２】
【発明の実施の形態】
図１は、本発明に係るグリーンタイヤのトレッドの部分断面概略斜視図である。図２は導電性液状ゴム糊組成物が塗布された状態を示す図１のトレッドの概略断面図である。
【００１３】
図１において、１はトレッド、２はベースゴム、３はキャップゴム、４はトレッドの両側に設けられた導電性のトレッドストリップゴム、５はトレッド１の両タイヤショルダー部に沿ってタイヤ周方向に設けられた導電性液状ゴム糊組成物の溜穴、６は液状ゴム糊組成物である。なお、Ｒはタイヤ周方向である。
【００１４】
この溜穴５は、図示の通り、各タイヤショルダー部ＳＨともに２列に周方向に設けられており、かつ当該２列の溜穴５は１列ごとに周方向に向かって交互に千鳥状に配置されている。
【００１５】
この溜穴５の穴形状は、格別限定されるものではないが、図３に示される様な円錐状、または図４に示される様な三角柱状が好ましい。またその円または三角状の底面積即ち開口面積は２ｍｍ^２〜５ｍｍ^２が好ましい。また、図２〜４に示す様に、その溜穴５の穴の先端５ａまでの深さＤＨは、浅いと効果がなく、深すぎると加硫成形時にゴム流れ不良が発生し、タイヤ走行中に前記ゴム流れ不良部を起点としてゴムクラックに発展するので、トレッドのベースゴム２に至らない深さが好ましい。具体的には、前記トレッドのキャップゴム３の厚さＴＣの５０〜９０％の範囲内、好ましくは６０〜８０％の範囲内であり、数値で示せば３〜１５ｍｍが最適である。また、図１、図３及び図４に示す様に、タイヤ周方向に隣接する溜穴５の穴の先端５ａ同士の周方向間隔ＩＨは５〜２０ｍｍが好ましく、最適には９〜１５ｍｍである。また、タイヤショルダー部のそれぞれの２列の溜穴５の列同士の間隔ＩＬは、広いと効果がなく、近すぎると加硫成形時にゴム流れ不良が発生し、タイヤ走行中に前記ゴム流れ不良部を起点としてゴムクラックに発展するので、５〜１０ｍｍが好適範囲である。また、１つの溜穴５の容積は３〜１５ｍｍ³が好適であるが限定されない。本実施形態の溜穴５の穴形状は、図１及び図２に示す様に、円錐状で構成されている。なお、図４に示す三角柱状の上辺ＷＨは１ｍｍ〜５ｍｍ、上辺ＷＭは１ｍｍ〜５ｍｍが好ましい。
【００１６】
また、図１の点線で示される様に、導電性液状ゴム糊組成物６は、トレッド５のタイヤショルダー部ＳＨから、該トレッド１の両側に配された導電性トレッドストリップゴム４にかけて、これらの範囲内の表面を被覆するように塗布される。この導電性液状ゴム糊組成物の塗布範囲ＩＣは、格別限定されるものではないが、接地端相当部ｉｇよりさらにタイヤ中央側にまで塗布することが望ましい。具体的には、この導電性液状ゴム糊組成物の塗布範囲ＩＣは３０〜５０ｍｍ程度の範囲にわたって塗布することが望ましいが、上記接地端相当部ｉｇのタイヤ中央側寄り１０ｍｍから、導電性トレッドストリップゴム４の外端からタイヤ中央寄り５ｍｍ程度が最適である。
【００１７】
なお、図２において、７ａは溜穴５内における導電性液状ゴム糊組成物６の充填部、７ｂはトレッド表面に塗布された導電性液状ゴム糊組成物６の塗布部である。
【００１８】
図５は前記トレッドを用いてグリーンタイヤを加硫成形した空気入りタイヤの概略部分断面図である。図６は、図５において矢印方向ＡＤ１から見た要部拡大概略側面図である。図７は図５において矢印方向ＡＤ２即ちタイヤ側面方向からから見た要部拡大概略斜視図である。図５〜図７において、ＳＨはタイヤショルダー部、ＩＧは接地端である。また図６において、８は陸部、９は溝壁、１０は溝底、１１は横溝、１２は踏面部、１３は導電性ゴム組成物からなる導電性被膜である。本実施形態のタイヤは、タイヤショルダー部ＳＨにおいてタイヤ周方向Ｒに向かって陸部８と横溝１１とが繰り返して凹凸面を形成する構成で成形されている。なお、本発明において「横溝」とは、タイヤ幅方向の溝、スリット、斜め溝をすべて含む概念である。なお、Ｒはタイヤ周方向である。
【００１９】
すなわち、図５〜図７より、前記トレッドに塗布された導電性液状ゴム糊組成物は、タイヤの加硫成形とともに、上記トレッドのタイヤショルダー部ＳＨから、該トレッド１の両側に配されサイドウォール部２０に連なる導電性トレッドストリップゴム４にかけてこれらの範囲内の表面を被覆して導電性被膜１３を形成している。そして図６に示す様に、上記導電性被膜１３は、タイヤショルダー部の陸部と横溝の凹凸面に沿ってタイヤ周方向にほぼ均一厚みで連続的に形成されている。
【００２０】
本実施形態の空気入りタイヤは、上述の構成を有していることから、トレッド１のゴム層に導電性の良いカーボンブラックの配合割合が少なく、導電性の悪い珪酸が多く含まれていても、図５に示す様に、車体から発生する静電気を、タイヤリムからビード部２１、サイドウォール部２０、そして導電性トレッドストリップゴム４が配置されているバットレス部２２、及び、トレッド接地端ＩＧを超えてタイヤ中央側のトレッド面にまで伸びている導電性被膜１３を通じて踏面へ逃がすことができ、車体に静電気が蓄積されることがない。
【００２１】
また、走行とともにタイヤトレッド面が摩耗して、陸部８の表面に形成されている導電性被膜１３が摩耗しても、導電性トレッドストリップ４に連なる導電性被膜１３は連続した厚みが確保されて横溝１１の溝壁９及び溝底１０にも形成されていることから、摩耗された陸部８の表面には必ず横溝１１の溝壁９から連なる導電性被膜１３がタイヤ表面に露出している。従って、タイヤが摩耗しても車体から発生する静電気はこの導電性被膜１３を通じて地面に放電される。
【００２２】
なお、溜穴を除く液状ゴム糊組成物の塗布は、格別限定されるものではないが、０．０１ｍｍ〜０．３ｍｍの厚さとなる様に塗布するのが好ましい。
【００２３】
【実施例】
図１に示すトレッドを有したタイヤサイズＰ２０５／５５Ｒ１６（成形後のタイヤサイズ）の前記実施形態に係るグリーンタイヤに、既述の通り、導電性液状ゴム糊組成物を塗布した後、加硫成形し、これを実施例タイヤとした。なお、導電性液状ゴム糊組成物は、表１に示すゴム組成物１kgをゴム用揮発油９リットルに攪拌溶解して作成されている。
【００２４】
また、溜穴を有しない以外は、本実施例と同じグリーンタイヤを加硫成形して、これを比較例タイヤとした。比較例１は溜穴は有していないが導電性液状ゴム糊組成物を実施例と同様にして塗布したタイヤ、比較例２は導電性液状ゴム糊組成物を塗布しないタイヤである。
【００２５】
なお、液状ゴム糊組成物の塗布範囲は、実施例及び比較例２共に図１の点線に示す範囲であり、接地端相当部ｉｇのタイヤ中央側寄り１０ｍｍから、導電性トレッドストリップゴムの外端からタイヤ中央寄り５ｍｍの範囲である。溜穴を除く液状ゴム糊組成物の塗布の厚みは約０．０５ｍｍである。また、溜穴の穴形状は円錐状であり、その円の底面積即ち開口面積は３ｍｍ^２、溜穴５の穴の先端５ａまでの深さＤＨは４ｍｍ、タイヤ周方向に隣接する溜穴の穴の先端同士の周方向間隔ＩＨは１００ｍｍ、またタイヤショルダー部のそれぞれの２列の溜穴の列同士の間隔ＩＬは１０ｍｍである。
【００２６】
【表１】

【００２７】
この実施例及び比較例のタイヤについて、導電性の評価を実施した。その結果を表２に示す。なお、導電性の評価は、タイヤを１５×６−ＪＪのホイールに組付け、内圧２００ｋＰａとし、支持軸によりホイール部で支持して鉄板上に設置し、４５０ｋｇｆの荷重をかけた状態で、鉄板とホイール間に１０００Ｖの電圧をかけて電気抵抗値を測定することによって評価した。○は電気抵抗値が１×１０⁻ ¹⁰ＭΩ以下、△は１×１０⁻ ⁸〜１×１０⁻ ¹⁰ＭΩ、×は１×１０⁻ ⁸ＭΩ以上である。
【００２８】
【表２】

【００２９】
表２から、本発明によって造られたタイヤは導電性が満足できるレベルにあることが分かる。
【００３０】
【発明の効果】
本発明の空気入りタイヤの製造方法は、上述の通りであるので、導電性液状ゴム糊組成物をグリーンタイヤのトレッドの接地端相当部付近からバットレス相当部にかけて塗布して加硫成形しても、タイヤショルダー部の横溝の溝面全体を導電性ゴム薄膜で被覆することができ、導電性を十分発揮することができる。
【図面の簡単な説明】
【図１】本発明に係る加硫成形前のトレッドの部分断面概略斜視図である。
【図２】導電性液状ゴム糊組成物が塗布された状態を示す図１のトレッドの概略断面図である。
【図３】隣接している円錐状の溜穴を概念的に示す概略斜視図である。
【図４】隣接している三角柱状の溜穴を概念的に示す概略斜視図である。
【図５】図１のトレッドを用いて加硫成形してなる空気入りタイヤの概略部分断面図である。
【図６】図５において矢印方向ＡＤ１から見た要部拡大概略斜視図である。
【図７】図５において矢印方向ＡＤ２から見た要部拡大概略側面図である。
【図８】図５と同方向から見た従来タイヤの要部拡大概略側面図である。
【符号の説明】
１トレッド
２ベースゴム
３キャップゴム
４トレッドストリップゴム
５溜穴
６液状ゴム糊組成物
７ａ充填部
７ｂ塗布部
８陸部
９溝壁
１０溝底
１１横溝
１２踏面部
１３導電性被膜[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire excellent in conductivity and a method for manufacturing the same.
[0002]
[Prior art]
In recent years, there has been an increasing demand for lower fuel consumption of automobiles. Along with this, a pneumatic tire was proposed in which a tread rubber comprising a silica main compounded rubber composition containing a large amount of silicic acid with a reduced proportion of carbon black as a tread rubber composition was arranged to reduce the rolling resistance of the tire. ing.
[0003]
In such a pneumatic tire, the tread rubber layer has a low blending ratio of carbon black with good conductivity and contains a lot of silicic acid with poor conductivity, so that static electricity generated from the vehicle body is discharged from the tire rim to the bead portion and sidewall portion. In some cases, it is impossible to escape to the tread through the buttress portion and the tire tread portion, and static electricity may accumulate in the vehicle body. Therefore, it has been desired to provide a pneumatic tire having good conductivity and yet low rolling resistance, and development thereof has been promoted.
[0004]
Conventionally, from such a viewpoint, a method of applying and vulcanizing a conductive liquid rubber paste composition from the vicinity of the grounded end corresponding portion to the buttress corresponding portion of the tread has been tried.
[0005]
[Problems to be solved by the invention]
However, the green tire before vulcanization has a donut shape and no groove is formed, and the portion corresponding to the groove in the product after vulcanization is vulcanized by the convex part of the vulcanization mold. It is expanded to several times the area of green tires during sulfur molding.
[0006]
Therefore, in the case of a pneumatic tire in which the conductive liquid rubber paste composition is applied from the vicinity of the grounded end equivalent portion of the green tire to the equivalent portion of the buttress and vulcanized, as shown in FIG. 17, a portion 190 is generated in which the groove surface is not covered with the thin film 19 of the conductive conductive rubber composition. As a result, there arises a problem that the conductivity cannot be sufficiently exhibited. In FIG. 8, 14 is a land portion, 15 is a groove wall portion, 16 is a groove bottom portion, and 18 is a tread surface portion.
[0007]
The object of the present invention is to apply a conductive liquid rubber paste composition to a tire tread surface having poor conductivity from the portion corresponding to the grounding end of the tread of the green tire to the portion corresponding to the buttress and vulcanize the tire shoulder portion. The entire groove surface of each lateral groove can be covered with a conductive rubber thin film, and a method for manufacturing a pneumatic tire capable of sufficiently exhibiting conductivity, before vulcanization molding as a member that can be used in the tire manufacturing method The present invention provides a pneumatic tire in which a conductive film is continuously formed with a substantially uniform thickness in the tire circumferential direction along the land surface of the tire shawl and the uneven surface of the lateral groove.
[0008]
In order to solve the above problems, the invention of the present production method comprises a tire shoulder portion of a tread before vulcanization molding composed of a base rubber and a cap rubber and composed of a silica main compounded rubber composition. The conductive liquid rubber paste composition is applied to the conductive tread strip rubber disposed on both sides or one side of the tread, and the surface within these ranges is coated and vulcanized to form a land portion of the tire shoulder portion. In the manufacturing method of a pneumatic tire formed by forming a conductive coating composed of the conductive liquid rubber paste composition in the tire circumferential direction along the uneven surface of the lateral groove,
The tread before vulcanization molding is a conductive liquid rubber paste whose depth is 50 to 90% of the thickness of the cap rubber of the tread before vulcanization molding from the surface of the tire shoulder portion toward the inner surface. A plurality of reservoir holes in the composition are formed in the tire circumferential direction, and the conductive liquid rubber paste composition is applied in the tire circumferential direction while being filled in the reservoir hole of the tread and vulcanized and molded. It is a manufacturing method of a pneumatic tire.
[0009]
Therefore, even if the tread surface of the portion corresponding to the lateral groove of the tire shoulder portion is molded by the tire molding mold and expanded more than the remaining portion during vulcanization molding, it is stored in the reservoir corresponding to the expansion. The conductive liquid rubber paste composition extending from the reservoir hole is uniformly supplied to the entire groove surface of the tire shoulder portion, and the entire groove surface of the tire shoulder portion is the same as the land surface of the tire shoulder portion. A uniform conductive film is continuously formed.
[0010]
The invention of the extruded tread before vulcanization molding as a member that can be used in the tire manufacturing method has a tire shoulder portion that repeats the land portion and the uneven surface of the lateral groove in the tire circumferential direction, and is composed of a base rubber and a cap rubber And an extruded tread composed of a silica main compound-based rubber composition before vulcanization molding , the depth of which is the vulcanization molding from the surface to the inner surface of a tire shoulder portion of the tread. In the tread, a plurality of reservoir holes of the conductive liquid rubber paste composition that is 50 to 90% of the thickness of the cap rubber of the previous tread are formed in the tire circumferential direction.
[0011]
The pneumatic tire of the present invention is composed of a tire main tread rubber composition, and has a tire tread having a tire shoulder portion that repeats uneven surfaces of a land portion and a lateral groove in the tire circumferential direction, and is disposed on both sides or one side of the tread. In the pneumatic tire provided with the conductive tread strip rubber, the surface in these ranges from the tire shoulder portion of the tread to the conductive tread strip rubber is a conductive coating made of a conductive liquid rubber paste composition. The electrically conductive coating is a pneumatic tire that is continuously formed in a substantially uniform thickness in the tire circumferential direction along the land portion of the tire shoulder portion and the uneven surface of the lateral groove.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a partial cross-sectional schematic perspective view of a tread of a green tire according to the present invention. FIG. 2 is a schematic cross-sectional view of the tread of FIG. 1 showing a state where the conductive liquid rubber paste composition is applied.
[0013]
In FIG. 1, 1 is a tread, 2 is a base rubber, 3 is a cap rubber, 4 is a conductive tread strip rubber provided on both sides of the tread, and 5 is a tire circumferential direction along both tire shoulder portions of the tread 1. A reservoir hole 6 of the conductive liquid rubber paste composition provided is a liquid rubber paste composition. R is the tire circumferential direction.
[0014]
As shown in the drawing, the reservoir holes 5 are provided in two rows in the circumferential direction for each tire shoulder SH, and the two rows of reservoir holes 5 are alternately staggered in the circumferential direction for each row. Has been placed.
[0015]
The hole shape of the reservoir hole 5 is not particularly limited, but a conical shape as shown in FIG. 3 or a triangular prism shape as shown in FIG. 4 is preferable. The bottom area of the circle or triangle, that is, the opening area, is preferably ²

mm

^{2 to} 5 mm ² . Also, as shown in FIGS. 2 to 4, the depth DH to the tip 5a of the reservoir hole 5 is not effective if it is shallow, and if it is too deep, poor rubber flow occurs during vulcanization molding, and the tire is running. In addition, since it develops into a rubber crack starting from the defective rubber flow portion, a depth that does not reach the base rubber 2 of the tread is preferable. Specifically, it is in the range of 50 to 90% of the thickness TC of the cap rubber 3 of the tread, preferably in the range of 60 to 80%. Moreover, as shown in FIG.1, FIG3 and FIG.4, the circumferential direction space | interval IH of the front-end | tip 5a of the hole 5 of the reservoir hole 5 adjacent to a tire circumferential direction is preferable 5-20 mm, and optimally 9-15 mm. . Further, if the distance IL between the two rows of the reservoir holes 5 in the tire shoulder portion is wide, there is no effect, and if it is too close, a rubber flow failure occurs during vulcanization molding, and the rubber flow failure occurs during tire running. Since it develops into a rubber crack starting from the part, 5 to 10 mm is a preferable range. Further, the volume of one reservoir 5 is preferably ³ to 15 mm ^3, but is not limited. As shown in FIG. 1 and FIG. 2, the hole shape of the reservoir hole 5 of the present embodiment is conical. Note that the upper side WH of the triangular prism shape shown in FIG. 4 is preferably 1 mm to 5 mm, and the upper side WM is preferably 1 mm to 5 mm.
[0016]
Further, as shown by the dotted lines in FIG. 1, the conductive liquid rubber paste composition 6 extends from the tire shoulder portion SH of the tread 5 to the conductive tread strip rubber 4 disposed on both sides of the tread 1. It is applied to cover the surface within the range. The application range IC of the conductive liquid rubber paste composition is not particularly limited, but it is desirable to apply the conductive liquid rubber paste composition further to the tire center side than the ground contact end equivalent part ig. Specifically, it is desirable that the conductive liquid rubber paste composition is applied over a range of about 30 to 50 mm, but the conductive tread strip starts from 10 mm closer to the tire center side of the ground contact end equivalent part ig. The optimal distance from the outer edge of the rubber 4 to the center of the tire is about 5 mm.
[0017]
In FIG. 2, 7a is a filling portion of the conductive liquid rubber paste composition 6 in the

reservoir hole

5, and 7b is an application portion of the conductive liquid rubber paste composition 6 applied to the tread surface.
[0018]
FIG. 5 is a schematic partial cross-sectional view of a pneumatic tire in which a green tire is vulcanized using the tread. FIG. 6 is an enlarged schematic side view of the main part viewed from the arrow direction AD1 in FIG. FIG. 7 is an enlarged schematic perspective view of a main part when viewed from the arrow direction AD2 in FIG. 5-7, SH is a tire shoulder part and IG is a grounding end. In FIG. 6, 8 is a land portion, 9 is a groove wall, 10 is a groove bottom, 11 is a lateral groove, 12 is a tread portion, and 13 is a conductive coating made of a conductive rubber composition. The tire of the present embodiment is formed with a configuration in which the land portion 8 and the lateral groove 11 are repeatedly formed in the tire shoulder portion SH in the tire circumferential direction R to form an uneven surface. In the present invention, the “lateral groove” is a concept including all the grooves, slits, and oblique grooves in the tire width direction. R is the tire circumferential direction.
[0019]
That is, from FIG. 5 to FIG. 7, the conductive liquid rubber paste composition applied to the tread is disposed on both sides of the tread 1 from the tire shoulder portion SH of the tread together with the vulcanization molding of the tire. A conductive coating 13 is formed by covering the surface within these ranges over the conductive tread strip rubber 4 connected to the portion 20. And as shown in FIG. 6, the said conductive film 13 is continuously formed in the tire circumferential direction with the substantially uniform thickness along the land part of a tire shoulder part, and the uneven surface of a horizontal groove.
[0020]
Since the pneumatic tire of the present embodiment has the above-described configuration, the rubber layer of the tread 1 has a small blending ratio of carbon black with good conductivity, and contains a lot of silicic acid with poor conductivity. As shown in FIG. 5, the static electricity generated from the vehicle body exceeds the bead portion 21, sidewall portion 20, buttress portion 22 where the conductive tread strip rubber 4 is disposed, and the tread grounding end IG from the tire rim. Thus, it is possible to escape to the tread surface through the conductive coating 13 extending to the tread surface on the tire center side, and static electricity is not accumulated in the vehicle body.
[0021]
Further, even when the tire tread surface is worn with traveling and the conductive coating 13 formed on the surface of the land portion 8 is worn, the conductive coating 13 connected to the conductive tread strip 4 has a continuous thickness. Since the groove wall 9 and the groove bottom 10 of the lateral groove 11 are also formed on the surface of the worn land portion 8, the conductive coating 13 connected to the groove wall 9 of the lateral groove 11 is always exposed on the tire surface. Yes. Therefore, even if the tire is worn, static electricity generated from the vehicle body is discharged to the ground through the conductive coating 13.
[0022]
The application of the liquid rubber paste composition excluding the reservoir hole is not particularly limited, but is preferably applied so as to have a thickness of 0.01 mm to 0.3 mm.
[0023]
【Example】
As described above, after applying the conductive liquid rubber paste composition to the green tire according to the embodiment having the tire size P205 / 55R16 (tire size after molding) having the tread shown in FIG. This was used as an example tire. The conductive liquid rubber paste composition is prepared by stirring and dissolving 1 kg of the rubber composition shown in Table 1 in 9 liters of volatile oil for rubber.
[0024]
In addition, the same green tire as in this example was vulcanized and molded except that it did not have a reservoir hole, and this was used as a comparative tire. Comparative Example 1 does not have a reservoir, but is a tire coated with a conductive liquid rubber paste composition in the same manner as in the Examples, and Comparative Example 2 is a tire without a conductive liquid rubber paste composition.
[0025]
Note that the application range of the liquid rubber paste composition is the range indicated by the dotted line in FIG. 1 in both the example and the comparative example 2, and the outer end of the conductive tread strip rubber from 10 mm closer to the tire center side of the contact end equivalent portion ig. To 5 mm near the tire center. The coating thickness of the liquid rubber paste composition excluding the reservoir hole is about 0.05 mm. Further, the hole shape of the reservoir hole is conical, the bottom area of the circle, that is, the opening area is 3 mm ² , the depth DH to the hole tip 5a of the reservoir hole 5 is 4 mm, and the adjacent reservoir hole in the tire circumferential direction is 4 mm. The circumferential interval IH between the tips of the holes is 100 mm, and the interval IL between the two rows of reservoir holes in the tire shoulder is 10 mm.
[0026]
[Table 1]

[0027]
Conductivity evaluation was performed on the tires of this example and comparative example. The results are shown in Table 2. In addition, evaluation of conductivity is performed by attaching the tire to a 15 × 6-JJ wheel, setting the internal pressure to 200 kPa, supporting the wheel portion by a support shaft on the iron plate, and applying a load of 450 kgf. The electrical resistance value was measured by applying a voltage of 1000 V between the wheel and the wheel. ○ the electrical resistance 1 × ¹⁰ ^- 10 MΩ or less, △ is 1 × 10 ^- is ⁸ M.OMEGA. Or more ^{^{^{^{- 8 ~1 × 10 - 10 MΩ}}}} , × is 1 × 10.
[0028]
[Table 2]

[0029]
From Table 2, it can be seen that the tires made according to the present invention are at a satisfactory level of electrical conductivity.
[0030]
【The invention's effect】
Since the manufacturing method of the pneumatic tire of the present invention is as described above, the conductive liquid rubber paste composition is applied from the vicinity of the ground contact end portion of the green tire tread to the buttress equivalent portion and vulcanized. Further, the entire groove surface of the lateral groove of the tire shoulder portion can be covered with the conductive rubber thin film, and the conductivity can be sufficiently exhibited.
[Brief description of the drawings]
FIG. 1 is a partial perspective schematic perspective view of a tread before vulcanization molding according to the present invention.
FIG. 2 is a schematic cross-sectional view of the tread of FIG. 1 showing a state where a conductive liquid rubber paste composition is applied.
FIG. 3 is a schematic perspective view conceptually showing conical reservoirs adjacent to each other.
FIG. 4 is a schematic perspective view conceptually showing adjacent triangular prism-shaped reservoir holes.
FIG. 5 is a schematic partial cross-sectional view of a pneumatic tire formed by vulcanization molding using the tread of FIG. 1;
6 is an enlarged schematic perspective view of a main part viewed from an arrow direction AD1 in FIG.
FIG. 7 is an enlarged schematic side view of a main part when viewed from an arrow direction AD2 in FIG.
FIG. 8 is an enlarged schematic side view of a main part of a conventional tire viewed from the same direction as FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tread 2 Base rubber 3 Cap rubber 4 Tread strip rubber 5 Reservoir 6 Liquid rubber paste composition

7a Filling part

7b Application part 8 Land part 9 Groove wall 10 Groove bottom 11 Horizontal groove 12 Tread part 13 Conductive film

Claims

From the tire shoulder portion of the tread before vulcanization molding composed of a base rubber and a cap rubber and composed of a silica main compounded rubber composition, to a conductive tread strip rubber disposed on both sides or one side of the tread. The conductive liquid rubber paste composition is applied and vulcanized so as to cover the surface within these ranges, and the above-mentioned conductivity in the tire circumferential direction along the land portion of the tire shoulder portion and the uneven surface of the lateral groove. In the manufacturing method of the pneumatic tire formed by forming a conductive film composed of a liquid rubber paste composition,
The tread before vulcanization molding is a conductive liquid rubber paste whose depth is 50 to 90% of the thickness of the cap rubber of the tread before vulcanization molding from the surface of the tire shoulder portion toward the inner surface. A plurality of reservoir holes of the composition are formed in the tire circumferential direction, and the conductive liquid rubber paste composition is applied in the tire circumferential direction while filling the reservoir hole of the tread, and vulcanized and molded. A method for manufacturing a pneumatic tire.

The method for producing a pneumatic tire according to claim 1, wherein the reservoir hole of the conductive liquid rubber paste composition is a conical or triangular prismatic small hole.

It is an extruded tread before vulcanization molding that has a tire shoulder part that repeats the uneven surface of the land part and the lateral groove in the tire circumferential direction, is composed of a base rubber and a cap rubber, and is composed of a silica main compounded rubber composition The conductive liquid rubber paste composition having a depth of 50 to 90% of the thickness of the cap rubber of the tread before vulcanization molding is formed on the tire shoulder portion of the tread from the surface toward the inner surface. A tread in which a plurality of reservoir holes are formed in the tire circumferential direction.

A tire tread composed of a main rubber compounding system of silica and having a tire shoulder that repeats the uneven surface of the land and the lateral groove in the tire circumferential direction, and a conductive tread strip rubber disposed on both sides or one side of the tread. In the pneumatic tire provided, the surface within these ranges is covered with a conductive coating made of a conductive liquid rubber paste composition from the tire shoulder portion of the tread to the conductive tread strip rubber, and the conductive The pneumatic coating is a pneumatic tire that is continuously formed with a substantially uniform thickness in the tire circumferential direction along the land portion of the tire shoulder portion and the uneven surface of the lateral groove.