RUN-FLAT TIRE

• Main Authors: MIYABE NAOAKI, TAMADA SATOSHI, OHASHI SHOICHI, SUGIMARU SATOSHI, YOKOYAMA TAKASHI
• Format: Patent
• Language: English; Japanese
• Published: 17.12.2015
• Subjects: CABLES OTHER THAN ELECTRIC; DEVICES OR ARRANGEMENTS RELATED TO TYRES; PERFORMING OPERATIONS; REPAIRING, OR CONNECTING VALVES TO, INFLATABLE ELASTIC BODIESIN GENERAL; ROPES; ROPES OR CABLES IN GENERAL; TEXTILES; TRANSPORTING; TYRE CHANGING OR REPAIRING; TYRE INFLATION; VEHICLE TYRES; VEHICLES IN GENERAL

PROBLEM TO BE SOLVED: To improve steering stability without impairing run-flat durability and riding comfortableness.SOLUTION: A run-flat tire includes side reinforcement rubber parts 7 which reinforce sidewall parts 2. The side reinforcement rubber parts are formed of a rubber composition in which the ratio (M50H/M50N) of a tensile stress (M50H) at the time of 50% elongation at 100°C to a tensile stress (M50N) at the time of 50% elongation at 23°C is 1.0 to 1.3. Belts 9 are formed of a main filament bundle 22 made by arranging main filaments 21 in a row. A wrapping filament 23 is configured in such a manner that a flat steel cord 20 has an n+1 structure (where n is 3 to 6) formed by winding the wrapping filament 23 around the main filament bundle 22. In the steel cord, the ratio (Da/Db) of a cord short diameter (Da) after pressing to a cord short diameter (Db) before pressing is 0.80 or less, and the ratio (R1/R2) of an in-plate rigidity (R1) to an out-of-plate rigidity (R2) is 10 to 30. 【課題】ランフラット耐久性及び乗り心地性を損なうことなく操縦安定性を改善する。【解決手段】サイドウォール部２を補強するサイド補強ゴム部７を備えたランフラットタイヤにおいて、サイド補強ゴム部を、２３℃での５０％伸張時の引張応力（Ｍ５０Ｎ）に対する１００℃での５０％伸張時の引張応力（Ｍ５０Ｈ）の比（Ｍ５０Ｈ／Ｍ５０Ｎ）が１．０以上１．３以下であるゴム組成物を用いるとともに、ベルト９は、主フィラメント２１を一列に引き揃えて主フィラメント束２２とし、その周囲にラッピングフィラメント２３を巻き付けてなるｎ＋１構造（但し、ｎ＝３〜６）の扁平なスチールコード２０を用いて構成する。スチールコードは、押圧前のコード短径（Ｄｂ）に対する押圧後のコード短径（Ｄａ）の比（Ｄａ／Ｄｂ）が０．８０以下であり、かつ、面外剛性（Ｒ２）に対する面内剛性（Ｒ１）の比（Ｒ１／Ｒ２）が１０以上３０以下である。【選択図】図１