JP6530184B2 - Pneumatic tire - Google Patents

Pneumatic tire Download PDF

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JP6530184B2
JP6530184B2 JP2014256651A JP2014256651A JP6530184B2 JP 6530184 B2 JP6530184 B2 JP 6530184B2 JP 2014256651 A JP2014256651 A JP 2014256651A JP 2014256651 A JP2014256651 A JP 2014256651A JP 6530184 B2 JP6530184 B2 JP 6530184B2
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tire
groove
tread portion
tread
radial direction
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JP2016117329A (en
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聖二 横枕
聖二 横枕
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Toyo Tire Corp
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Toyo Tire Corp
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Description

本発明は、空気入りタイヤに関する。   The present invention relates to a pneumatic tire.

一般に、インフレート状態での空気入りタイヤのトレッド部の外周面のプロファイルは、空気入りタイヤに対してタイヤ径方向内側に曲率中心が位置する円弧形状（アール形状）である。これに対し、特許文献１に開示された空気入りタイヤのトレッド部の外周面のプロファイルは、空気入りタイヤに対してタイヤ径方向外側に曲率中心が位置する円弧形状（逆アール形状）を有する。特許文献２に開示された空気入りタイヤには、トレッド部のタイヤ幅方向の端部からサイド部に向けて延びるバットレス部に、タイヤ周方向に沿って延びる溝が形成されている。   In general, the profile of the outer peripheral surface of the tread portion of the pneumatic tire in an inflated state is an arc shape (round shape) in which the center of curvature is positioned on the inner side in the tire radial direction with respect to the pneumatic tire. On the other hand, the profile of the outer peripheral surface of the tread portion of the pneumatic tire disclosed in Patent Document 1 has an arc shape (reverse curve shape) in which the center of curvature is located on the outer side in the tire radial direction with respect to the pneumatic tire. In the pneumatic tire disclosed in Patent Document 2, a groove extending along the circumferential direction of the tire is formed in a buttress portion extending from an end portion in the tire width direction of the tread portion toward the side portion.

インフレート状態でのトレッド部の外周面のプロファイルがアール形状であると、トレッド部の中央部でタイヤ外径が最大となるので、車両走行時にはトレッド部の中央部で接地圧が高くなり、トレッド部の中央部で偏摩耗が生じやすい。   When the profile of the outer peripheral surface of the tread portion in the inflated state is a rounded shape, the tire outer diameter is maximum at the central portion of the tread portion, so the contact pressure becomes high at the central portion of the tread portion when the vehicle is traveling. Uneven wear is likely to occur at the center of the part.

トレッド部の外周面のプロファイルを逆アール形状とすると、トレッド部の中央部での接地圧を低減できるが、トレッド部のタイヤ幅方向の端部における接地圧が高くなる。つまり、トレッド部の外周面のプロファイルを単に特許文献１に開示されているような逆アール形状としても、接地圧分布を均一化できない。また、特許文献２では、接地圧分布の均一化について、特に検討されていない。   If the profile of the outer peripheral surface of the tread portion is a reverse radius shape, the contact pressure at the central portion of the tread portion can be reduced, but the contact pressure at the end portion in the tire width direction of the tread portion becomes high. In other words, even if the profile of the outer peripheral surface of the tread portion is simply the reverse radius shape as disclosed in Patent Document 1, the contact pressure distribution can not be made uniform. Moreover, in patent document 2, it does not consider in particular about equalization | homogenization of ground pressure distribution.

特開平１０−３２９５１１号公報Japanese Patent Application Laid-Open No. 10-329511 特開２００２−２９２１７号公報JP, 2002-29217, A

本発明は、空気入りタイヤにおける接地圧分布の均一化を課題とする。   An object of the present invention is to make contact pressure distribution uniform in a pneumatic tire.

本明細書において、「バッドレス部」とは、空気入りタイヤのトレッド部のタイヤ幅方向端部からタイヤ最大幅部までの領域を言う。また、「ショルダー部」とは、トレッド部がサイド部に対して接続されている領域を言い、トレッド部のタイヤ幅方向端部を含む。さらに、ショルダー部はバッドレス部のうち、トレッド部のタイヤ幅方向端部側の領域を含む。   In the present specification, the "badless portion" refers to the region from the tire width direction end of the tread portion of the pneumatic tire to the tire maximum width portion. Moreover, a "shoulder part" means the area | region where the tread part is connected with respect to the side part, and the tire width direction edge part of a tread part is included. Furthermore, the shoulder portion includes the area of the end portion in the tire width direction of the tread portion in the padless portion.

本発明は、トレッド部の外周面は、非インフレート状態において、中央部における外径よりも端部における外径が大きい逆アール形状を有し、前記トレッド部の前記端部からタイヤ最大幅部までの領域であるバッドレス部に、タイヤ周方向に沿って設けられた溝と、前記トレッド部に形成された主溝とを備え、前記溝は、タイヤ幅方向において前記トレッド部の前記端部と重複する位置まで延びており、かつ、前記主溝の底壁よりもタイヤ内径側に形成されている、空気入りタイヤである。 In the present invention, in the non-inflated state, the outer peripheral surface of the tread portion has a reverse radius shape in which the outer diameter at the end portion is larger than the outer diameter at the central portion, and the tire maximum width portion from the end portion of the tread portion And a main groove formed in the tread portion, the groove being the end portion of the tread portion in the tire width direction It is a pneumatic tire which extends to an overlapping position and is formed on the tire inner diameter side with respect to the bottom wall of the main groove .

トレッド部の外周面を逆アール形状とすることで、インフレート時にトレッド部の外周面を平坦に近い形状にできる。そのため、トレッド部の中央部における接地圧上昇を抑制し、この部分の偏摩耗を防止できる。バッドレス部にタイヤ径方向に沿って延びる溝を設けることで、トレッド部の外周面を逆アール形状としたことによるトレッド部の端部における接地圧の過度な上昇を抑制できる。つまり、トレッド部の外周面を逆アール形状とし、かつバッドレス部にタイヤ径方向に沿って延びる溝を設けることで、接地圧分布を均一化し、トレッド部の中央部での偏摩耗を抑制できる。   By forming the outer peripheral surface of the tread portion in a reverse radius shape, the outer peripheral surface of the tread portion can be made nearly flat when inflated. Therefore, it is possible to suppress an increase in contact pressure at the central portion of the tread portion and to prevent uneven wear of this portion. By providing the groove extending in the tire radial direction in the padless portion, it is possible to suppress an excessive rise in the contact pressure at the end portion of the tread portion due to the outer circumferential surface of the tread portion being in the reverse radius shape. That is, by forming the outer peripheral surface of the tread portion in a reverse radius shape and providing the groove extending in the tire radial direction in the padless portion, the contact pressure distribution can be made uniform and partial wear at the central portion of the tread portion can be suppressed.

インフレート時にトレッド部の中央部の接地圧上昇を効果的に抑制するには、タイヤ中心軸からの前記中央部までのタイヤ径方向の距離と、前記タイヤ中心軸から前記端部までのタイヤ径方向の距離との差は、前記中央部における前記トレッド部のゴム厚の０．０５倍以上０．２倍以下であることが好ましい。
In order to effectively suppress the contact pressure increase at the central portion of the tread portion at the time of inflation, the distance from the tire central axis to the central portion in the tire radial direction and the tire diameter from the tire central axis to the end portion It is preferable that the difference with the distance of the direction is 0.05 times or more and 0.2 times or less of the rubber thickness of the said tread part in the said center part.

前記溝は、タイヤ周方向に連続的に設けられても良いし、タイヤ周方向に断続的に設けられても良い。   The groove may be provided continuously in the tire circumferential direction or may be provided intermittently in the tire circumferential direction.

トレッド部の端部の接地圧上昇を効果的に抑制するには、前記溝のタイヤ径方向断面の断面積は、トレッド部のタイヤ径方向断面における前記トレッド部の前記中央部からタイヤ幅方向外側に延びる仮想線よりも前記端部側の領域の断面積の０．８倍以上１．２倍以下であることが好ましい。   In order to effectively suppress the contact pressure increase at the end portion of the tread portion, the cross-sectional area of the groove in the tire radial direction cross section of the groove is the tire width direction outer side from the central portion of the tread portion in the tire radial direction cross section of the tread portion It is preferable that the cross-sectional area of the area on the end side is 0.8 or more times and 1.2 or less times the virtual line extending in

トレッド部を逆アール形状とし、かつバッドレス部にタイヤ周方向に沿って延びる溝を設けることで、接地圧分布を均一化し、トレッド部の中央部での偏摩耗を抑制できる。   By forming the tread portion in a reverse radius shape and providing a groove extending in the circumferential direction of the tire in the padless portion, the contact pressure distribution can be made uniform and uneven wear in the central portion of the tread portion can be suppressed.

本発明の第１実施形態に係る空気入りタイヤの子午線方向の部分断面図。BRIEF DESCRIPTION OF THE DRAWINGS The fragmentary sectional view of the meridian direction of the pneumatic tire concerning 1st Embodiment of this invention. 本発明の第２実施形態に係る空気入りタイヤの子午線方向の部分断面図。The fragmentary sectional view of the meridian direction of the pneumatic tire concerning a 2nd embodiment of the present invention.

以下、本発明に係る実施形態を添付図面に従って説明する。以下の説明は、本質的に例示に過ぎず、本発明、その適用物、あるいは、その用途を制限することを意図するものではない。図面は模式的なものであり、各寸法の比率等は現実のものとは相違している場合がある。   Hereinafter, an embodiment according to the present invention will be described according to the attached drawings. The following description is merely exemplary in nature and is not intended to limit the present invention, its applications, or its applications. The drawings are schematic, and proportions of dimensions may be different from actual ones.

（第１実施形態）
図１に示す本発明の第１実施形態に係るゴム製の空気入りタイヤ（以下、単にタイヤという）１は、トレッド部２、一対のサイド部３、及び一対のビード部（図示せず）を備える。個々のビード部はサイド部３のタイヤ径方向の内側端部（トレッド部２とは反対側の端部）に設けられている。一対のビード部間には、カーカス４が設けられている。本実施形態では、カーカス４は１枚のカーカスプライ５を備える。タイヤ１の最内周面にはインナーライナー６が設けられている。また、トレッド部２では、カーカス４のタイヤ径方向外側にベルト７が設けられている。本実施形態では、ベルト７は３枚のベルトプライ１１，１２，１３を備える。最外層のベルトプライ１３の外側にさらに、補強プライ１４が配置されている。 First Embodiment
A rubber pneumatic tire (hereinafter simply referred to as a tire) 1 according to a first embodiment of the present invention shown in FIG. 1 comprises a tread portion 2, a pair of side portions 3 and a pair of bead portions (not shown). Prepare. Each bead portion is provided at the tire radial inner end (the end opposite to the tread portion 2) of the side portion 3. A carcass 4 is provided between the pair of bead portions. In the present embodiment, the carcass 4 includes one carcass ply 5. An inner liner 6 is provided on the innermost circumferential surface of the tire 1. Further, in the tread portion 2, a belt 7 is provided on the tire radial direction outer side of the carcass 4. In the present embodiment, the belt 7 comprises three belt plies 11, 12, 13. A reinforcing ply 14 is further disposed outside the outermost belt ply 13.

以下の説明では、トレッド部２のタイヤ幅方向の端部２ａからサイド部３のタイヤ最大幅部までの領域を、バッドレス部１５という。また、トレッド部２がサイド部３に対して接続されている領域をショルダー部１６という。ショルダー部１６は、トレッド部２の端部２ａを含む。また、ショルダー部１６は、バッドレス部１５のうち、トレッド部２の端部２ａ側の領域を含む   In the following description, a region from the end portion 2 a in the tire width direction of the tread portion 2 to the tire maximum width portion of the side portion 3 is referred to as a baddless portion 15. Further, a region in which the tread portion 2 is connected to the side portion 3 is referred to as a shoulder portion 16. The shoulder portion 16 includes an end 2 a of the tread portion 2. Further, the shoulder portion 16 includes a region on the end portion 2 a side of the tread portion 2 in the padless portion 15.

トレッド部２の外周面２ｂのタイヤ径方向断面は、タイヤ幅方向の中央部２ｃにおける外径Ｒｃよりも端部２ａにおける外径Ｒｅが大きい逆アール形状を有する。言い換えれば、トレッド部２の外周面２ｂのタイヤ径方向断面での断面形状は、曲率中心がタイヤ１に対してタイヤ径方向外側に位置する円弧状である。本実施形態では、トレッド部２の外周面２ｂの曲率は、中央部２ｃから端部２ａまで概ね均一である。しかし、トレッド部２の外周面２ｂの曲率は、タイヤ幅方向に分布を有していてもよい。 The cross section in the tire radial direction of the outer peripheral surface 2 b of the tread portion 2 has a reverse radius shape in which the outer diameter R e at the end portion 2 a is larger than the outer diameter R c at the central portion 2 c in the tire width direction. In other words, the cross-sectional shape of the outer peripheral surface 2 b of the tread portion 2 in the tire radial direction cross section is an arc shape in which the center of curvature is located outside the tire 1 in the tire radial direction. In the present embodiment, the curvature of the outer peripheral surface 2b of the tread portion 2 is substantially uniform from the central portion 2c to the end portion 2a. However, the curvature of the outer peripheral surface 2b of the tread portion 2 may have a distribution in the tire width direction.

バッドレス部１５のうちショルダー部１６に該当する部分に、タイヤ周方向に沿って延びる溝１７が設けられている。具体的には、溝１７は、トレッド部２に形成された主溝１８の底壁１８ａとベルト７（補強プライ１４）との間のタイヤ高さ方向Ｈ（トレッド部２とビード部が対向する方向）の領域に設けられている。本実施形態における溝１７は、タイヤ周方向に連続的に設けられ、タイヤ幅方向から見ると無端環状である。しかし、溝１７は、タイヤ周方向に断続的に設けられていてもよい。また、タイヤ幅方向から見て放熱溝１７が延びる方向は、タイヤ周方向に完全に一致している必要はなく、実質的にタイヤ周方向に沿っていればよい。   A groove 17 extending along the circumferential direction of the tire is provided in a portion corresponding to the shoulder portion 16 in the padless portion 15. Specifically, in the groove 17, the tire height direction H (the tread portion 2 and the bead portion) between the bottom wall 18 a of the main groove 18 formed in the tread portion 2 and the belt 7 (the reinforcing ply 14) Direction) is provided. The grooves 17 in the present embodiment are continuously provided in the tire circumferential direction and have an endless annular shape when viewed from the tire width direction. However, the grooves 17 may be provided intermittently in the tire circumferential direction. Further, the direction in which the heat dissipation grooves 17 extend as seen from the tire width direction does not have to completely coincide with the tire circumferential direction, and may be substantially along the tire circumferential direction.

本実施形態における溝１７の溝壁１７ａは、溝１７の開口１７ｂ側からタイヤ径方向内側に延びる側壁１７ｃ，１７ｄと、開口１７ｂと対向する奥壁１７ｅとを備える。本実施形態では、側壁１７ｃ，１７ｄは円弧面状であり、側壁１７ｃ，１７ｄ間の間隔は、溝１７の深さ方向に概ね一定である。また、奥壁１７ｅはタイヤ径方向断面が円形の曲面である。そのため、本実施形態における溝１７のタイヤ径方向断面の断面形状は、概ねＵ字状である。溝１７の断面形状は、例えば円形、楕円形、又は三角形のような多角形状であってもよいが、応力や歪みの集中とそれに起因するクラックの発生を防止するために、鋭いエッジを有しない形状であることが好ましい。   The groove wall 17a of the groove 17 in the present embodiment includes side walls 17c and 17d extending inward in the tire radial direction from the opening 17b side of the groove 17, and a back wall 17e opposed to the opening 17b. In the present embodiment, the side walls 17 c and 17 d are arc-shaped, and the distance between the side walls 17 c and 17 d is substantially constant in the depth direction of the groove 17. Further, the back wall 17 e is a curved surface having a circular cross section in the tire radial direction. Therefore, the cross-sectional shape in the tire radial direction cross section of the groove 17 in the present embodiment is substantially U-shaped. The cross-sectional shape of the groove 17 may be, for example, a circular shape, an oval shape, or a polygonal shape such as a triangle, but does not have sharp edges in order to prevent concentration of stress and strain and generation of cracks resulting therefrom. It is preferable that it is a shape.

仮にトレッド部２の外周面２ｂのタイヤ径方向断面が、逆アール形状ではなく、タイヤ１に対してタイヤ径方向内側に曲率中心が位置する円弧形状（アール形状）や平坦形状であるとする。この仮定の下では、インフレート時のトレッド部２の外周面２ｂのタイヤ径方向断面はアール形状となり、中央部２ｃでタイヤ１の外径が最大となるので、車両走行時には中央部２ｃで接地圧が高くなり、この部分で偏摩耗が生じやすい。   It is assumed that the cross section in the tire radial direction of the outer peripheral surface 2b of the tread portion 2 is not a reverse radius shape, but an arc shape (a radius shape) or a flat shape whose center of curvature is located inside the tire 1 in the tire radial direction. Under this assumption, the cross section in the tire radial direction of the outer peripheral surface 2b of the tread portion 2 at the time of inflation becomes a rounded shape, and the outer diameter of the tire 1 becomes maximum at the central portion 2c. The pressure is high and uneven wear is likely to occur in this part.

これに対して、本実施形態では、トレッド部２の外周面２ｂのタイヤ径方向断面を逆アール形状とすることで、インフレート時にトレッド部２の外周面を平坦に近い形状にできる。そのため、トレッド部２の中央部２ｃにおける接地圧上昇を抑制し、この部分の偏摩耗を防止できる。   On the other hand, in the present embodiment, by forming the cross section in the tire radial direction of the outer peripheral surface 2b of the tread portion 2 in a reverse radius shape, the outer peripheral surface of the tread portion 2 can be made nearly flat. Therefore, the contact pressure increase at the central portion 2c of the tread portion 2 can be suppressed, and partial wear of this portion can be prevented.

仮に、単にトレッド部２の外周面２ｂの逆アール形状とするだけであると、トレッド部２の端部２ａにおける接地圧が過度に高くなる。しかし、本実施形態では、ショルダー部１６にタイヤ径方向に沿って延びる溝１７を設けることで、トレッド部２の外周面２ｂを逆アール形状としたことによるトレッド部２の端部２ａにおける接地圧の過度な上昇を抑制できる。具体的には、ショルダー部１６の溝１７を設けた部分では、他の部分と比較してゴム体積が減少するので剛性を低下させることができる。溝１７の断面積や配置によってショルダー部１６の剛性を適切に調整することで、トレッド部２の端部２ａにおける接地圧の過度な上昇を抑制できる。   The contact pressure at the end portion 2a of the tread portion 2 becomes excessively high if the outer circumferential surface 2b of the tread portion 2 is merely formed in the reverse radius shape. However, in the present embodiment, by providing the groove 17 extending in the tire radial direction in the shoulder portion 16, the contact pressure at the end portion 2 a of the tread portion 2 by making the outer circumferential surface 2 b of the tread portion 2 into a reverse radius shape. Can prevent excessive rise in Specifically, at the portion where the groove 17 of the shoulder portion 16 is provided, the rubber volume is reduced as compared with the other portions, so that the rigidity can be reduced. By appropriately adjusting the rigidity of the shoulder portion 16 by the cross-sectional area and the arrangement of the groove 17, it is possible to suppress an excessive rise in the contact pressure at the end portion 2 a of the tread portion 2.

以上のように、本実施形態の空気入りタイヤ１では、トレッド部２の外周面２ｂを逆アール形状とし、かつショルダー部１６にタイヤ径方向に沿って延びる溝１７を設けることで、接地圧分布を均一化し、トレッド部２の中央部２ｃでの偏摩耗を抑制できる。   As described above, in the pneumatic tire 1 of the present embodiment, the contact pressure distribution is obtained by forming the outer circumferential surface 2 b of the tread portion 2 in a reverse radius shape and providing the groove 17 extending in the tire radial direction in the shoulder portion 16. Can be made uniform and uneven wear at the central portion 2c of the tread portion 2 can be suppressed.

インフレート時にトレッド部２の中央部２ｃの接地圧上昇を効果的に抑制するには、逆アール形状の曲率がある程度の値を有することが好ましい。例えば、トレッド部２の中央部２ｃから端部２ａまでのタイヤ高さ方向Ｈの距離Ｐが、中央部２ｃにおけるトレッド部２のゴム厚ｈ（補強プライ１４からトレッド部２の外周面２ｂまでのタイヤ径方向の距離）の０．０５倍以上０．２倍以下であることが好ましい。つまり、中央部２ｃの接地圧上昇を効果的に抑制するには、距離Ｐとゴム厚ｈの間に以下の式（１）の関係が成立することが好ましい。   In order to effectively suppress an increase in the contact pressure of the central portion 2c of the tread portion 2 at the time of inflation, it is preferable that the curvature of the reverse curve has a certain value. For example, the distance P between the central portion 2c of the tread portion 2 and the end portion 2a in the tire height direction H is the rubber thickness h of the tread portion 2 at the central portion 2c (from the reinforcing ply 14 to the outer peripheral surface 2b of the tread portion 2 It is preferable that the distance in the tire radial direction be 0.05 times or more and 0.2 times or less. That is, in order to effectively suppress the contact pressure increase of the central portion 2c, it is preferable that the relationship of the following equation (1) be established between the distance P and the rubber thickness h.

［数１］
０．０５ｈ≦Ｐ≦０．２ｈ （１） [Equation 1]
0.05 h ≦ P ≦ 0.2 h (1)

溝１７のタイヤ径方向断面での断面積Ｓが過度に小さいと、トレッド部２の端部２ａにおける接地圧の過度な上昇を抑制できない。一方、溝１７の断面積Ｓが過度に大きいと、ショルダー部１６の強度が低下し、例えば、溝１７よりもタイヤ高さ方向Ｈのトレッド部２側の部分で、ショルダー部１６の欠けが生じる。トレッド部２のタイヤ径方向断面において、トレッド部２の中央部２ｃからタイヤ幅方向外側に延びる仮想線Ｌよりも端部２ａ側の領域の断面積Ｔとすると、溝１７の断面積Ｓは断面積Ｔの０．８倍以上１．２倍以下であることが好ましい。つまり、ショルダー部１６の必要な剛性を確保しつつトレッド部２の端部２ａにおける接地圧の過度な上昇を抑制するには、断面積Ｓ，Ｔの間に以下の式（２）の関係が成立することが好ましい。   If the cross-sectional area S in the tire radial direction cross section of the groove 17 is excessively small, an excessive rise in the contact pressure at the end portion 2 a of the tread portion 2 can not be suppressed. On the other hand, if the cross-sectional area S of the groove 17 is excessively large, the strength of the shoulder portion 16 is reduced, and for example, the shoulder portion 16 is chipped at a portion on the tread portion 2 side in the tire height direction H than the groove 17 . Assuming that in the tire radial direction cross section of the tread portion 2 a cross sectional area T of a region closer to the end 2 a than a virtual line L extending from the central portion 2 c of the tread 2 to the outer side in the tire width direction The area T is preferably 0.8 times or more and 1.2 times or less. That is, in order to suppress an excessive rise in the contact pressure at the end portion 2a of the tread portion 2 while securing the necessary rigidity of the shoulder portion 16, the relationship of the following formula (2) is satisfied between the cross sectional areas S and T: It is preferable to hold.

［数２］
０．８Ｔ≦Ｓ≦１．２Ｔ （２） [Equation 2]
0.8T ≦ S ≦ 1.2T (2)

次に、溝１７の具体的な配置について説明する。   Next, the specific arrangement of the grooves 17 will be described.

溝１７の開口１７ｂのタイヤ径方向の最も外側（タイヤ高さ方向Ｈの最もトレッド部２側）の位置、言い換えれば溝壁１７ａのうち側壁１７ｃがショルダー部１６の外周面と接続する位置を、溝１７の上端１７ｆという。また、溝１７の開口１７ｂのタイヤ径方向の最も内側（タイヤ高さ方向Ｈの最もビード部側）の位置、言い換えれば溝壁１７ａのうち側壁１７ｄがショルダー部１６の外周面と接続する位置を、溝１７の下端１７ｇという。トレッド部２の端部２ａから上端１７ｆ及び下端１７ｇまでのタイヤ高さ方向Ｈの距離Ａ，Ｂは、トレッド部２に形成された主溝１８の最大の深さｇに対して、以下のように設定している。   The position of the opening 17b of the groove 17 on the outermost side in the tire radial direction (most tread 2 side in the tire height direction H), in other words, the position where the side wall 17c of the groove wall 17a is connected to the outer peripheral surface of the shoulder portion 16, is The upper end 17 f of the groove 17 is called. Further, the innermost position (the most bead side in the tire height direction H) of the opening 17b of the groove 17 in the tire radial direction, in other words, the position where the side wall 17d of the groove wall 17a is connected to the outer peripheral surface of the shoulder portion 16 , And the lower end 17g of the groove 17. The distances A and B in the tire height direction H from the end 2a of the tread portion 2 to the upper end 17f and the lower end 17g are as follows with respect to the maximum depth g of the main groove 18 formed in the tread portion 2: It is set to.

まず、距離Ａは、深さｇの１．０倍以上１．５倍以下に設定している。つまり、距離Ａはと深さｇの間には、以下の関係がある。   First, the distance A is set to at least 1.0 times and not more than 1.5 times the depth g. That is, there is the following relationship between the distance A and the depth g.

［数３］
ｇ≦Ａ≦１．５ｇ （３） [Equation 3]
g ≦ A ≦ 1.5 g (3)

次に、距離Ｂは、深さｇの１．３倍以上２．５倍以下に設定している。つまり、距離Ｂと深さｇの間には、以下の関係がある。   Next, the distance B is set to 1.3 times or more and 2.5 times or less of the depth g. That is, the following relationship exists between the distance B and the depth g.

［数４］
１．３ｇ≦Ｂ≦２．５ｇ （４） [Equation 4]
1.3 g ≦ B ≦ 2.5 g (4)

溝１７の開口１７ｂと奥壁１７ｅの間のタイヤ幅方向の最大距離である溝１７の深さＣは、トレッド部２の中央部２ｃと端部２ａとの間のタイヤ幅方向の距離Ｗに対して０．０８倍以上０．２倍以下の範囲に設定している。つまり、深さＣと距離Ｗの間には、以下の関係がある。   The depth C of the groove 17 which is the maximum distance in the tire width direction between the opening 17b of the groove 17 and the back wall 17e is the distance W in the tire width direction between the central portion 2c and the end portion 2a of the tread portion 2. On the other hand, it is set in the range of 0.08 times or more and 0.2 times or less. That is, there is the following relationship between the depth C and the distance W:

［数５］
０．０８Ｗ≦Ｃ≦０．２Ｗ （５） [Equation 5]
0.08 W ≦ C ≦ 0.2 W (5)

溝１７が延びる方向がタイヤ幅方向となす角度である溝１７の傾斜角度θは、０°から６０°の範囲に設定している。つまり、傾斜角度θについて、以下の関係がある。   The inclination angle θ of the groove 17 which is an angle formed by the direction in which the groove 17 extends with the tire width direction is set in the range of 0 ° to 60 °. In other words, the following relationship exists for the inclination angle θ.

［数６］
０°≦θ≦６０° （６） [Equation 6]
0 ° ≦ θ ≦ 60 ° (6)

ベルトプライ１１，１２，１３の端部１１ａ，１２ａ，１３ａから溝１７までの最短距離Ｄ（図１において破線の円で概念的に示す）は、ショルダー部１６におけるゴム厚の最大値（最大ゴム厚）Ｅに対して３０％以上に設定している。つまり、最短距離Ｄと最大ゴム厚Ｅとの間には、以下の関係がある。   The shortest distance D from the end portions 11a, 12a, 13a of the belt plies 11, 12, 13 to the groove 17 (represented conceptually by a broken circle in FIG. 1) is the maximum value of the rubber thickness at the shoulder portion 16 (maximum rubber Thickness is set to 30% or more of E. That is, the following relationship exists between the shortest distance D and the maximum rubber thickness E.

［数７］
Ｄ≧０．３Ｅ （７） [Equation 7]
D 0.3 0.3 E (7)

溝１７について、下端１７ｇの距離Ｂ、深さＣ、傾斜角度θを、それぞれ式（４），（５），（６）のように設定し、さらに前述のように段積Ｓを式（２）のように設定することで、ショルダー部１６の必要な剛性を確保しつつトレッド部２の端部２ａにおける接地圧の過度な上昇をより確実に抑制できる。また、溝１７の上端１７ｆの距離Ａを式（３）のように設定することで、トレッド部２の外周面２ｂから溝１７までの間には、剛性確保上必要なゴム量があるので、溝１７よりもタイヤ高さ方向Ｈのトレッド部２側の部分におけるショルダー部１６の欠けを防止できる。さらに、ベルトプライ１１〜１３の端部１１ａ〜１３ａから溝１７までの最短距離Ｄを式（７）のように設定することで、製造公差に起因してベルトプライ１１〜１３の端部１１ａ〜１３ａが溝１７内に突出するのを防止できる。   With respect to the groove 17, the distance B of the lower end 17g, the depth C, and the inclination angle θ are set as in equations (4), (5) and (6), respectively, and the step area S is further By setting as in the above, it is possible to more reliably suppress an excessive rise in the contact pressure at the end 2 a of the tread portion 2 while securing the necessary rigidity of the shoulder portion 16. Further, by setting the distance A of the upper end 17f of the groove 17 as in the equation (3), the amount of rubber necessary for securing the rigidity exists between the outer peripheral surface 2b of the tread portion 2 and the groove 17. Chipping of the shoulder portion 16 at a portion on the tread portion 2 side in the tire height direction H relative to the groove 17 can be prevented. Furthermore, by setting the shortest distance D from the end portions 11a to 13a of the belt plies 11 to 13 to the groove 17 as in equation (7), the end portions 11a to 11 of the belt plies 11 to 13 due to manufacturing tolerances The protrusion of the groove 13 a into the groove 17 can be prevented.

（第２実施形態）
図２に示す本発明の第２実施形態に係るタイヤ１では、溝１７の溝壁１７ａの全体、つまり側壁１７ｃ，１７ｄと奥壁１７ｅの全体に凹部２１と凸部２２が設けられている。 Second Embodiment
In the tire 1 according to the second embodiment of the present invention shown in FIG. 2, the recess 21 and the protrusion 22 are provided in the entire groove wall 17a of the groove 17, that is, in the entire side walls 17c and 17d and the back wall 17e.

ショルダー部１６、特にベルトプライ１１〜１３の端部１１ａ〜１３ａ付近はゴム量が多いので、タイヤ１の他の部分と比較して走行中の発熱量が大きい。また、ベルトプライ１１〜１３の端部１１ａ〜１３ａの周辺では、タイヤ転動に伴って繰り返し歪みが発生しやすい。しかし、発生した熱は溝１７を介して放熱されるので、ベルトプライ１１〜１３の端部１１ａ〜１３ａ付近の熱劣化と、それに起因するセパレーションのような故障の発生を防止できる。凹部２１と凸部２２を設けることで、溝１７の溝壁１７ａの表面積、つまり放熱面積を拡げているので、より効果的にショルダー部１６における発熱を抑制できる。   Since the amount of rubber is large in the shoulder portion 16, particularly near the end portions 11 a to 13 a of the belt plies 11 to 13, the amount of heat generation during traveling is large compared to the other portions of the tire 1. In addition, around the end portions 11a to 13a of the belt plies 11 to 13, distortion is likely to occur repeatedly as the tire rolls. However, since the generated heat is dissipated through the grooves 17, it is possible to prevent the occurrence of a thermal deterioration near the end portions 11a to 13a of the belt plies 11 to 13 and a failure such as separation caused thereby. By providing the recess 21 and the protrusion 22, the surface area of the groove wall 17 a of the groove 17, that is, the heat radiation area is expanded, so that the heat generation in the shoulder portion 16 can be suppressed more effectively.

第２実施形態のその他の構成及び作用は、第１実施形態と同様である。   Other configurations and operations of the second embodiment are the same as those of the first embodiment.

１ タイヤ
２ トレッド部
２ａ 端部
２ｂ 外周面
２ｃ 中央部
３ サイド部
４ カーカス
５ カーカスプライ
６ インナーライナー
７ ベルト
１１，１２，１３ ベルトプライ
１４ 補強プライ
１５ バッドレス部
１６ ショルダー部
１７ 溝
１７ａ 溝壁
１７ｂ 開口
１７ｃ，１７ｄ 側壁
１７ｅ 奥壁
１７ｆ 上端
１７ｇ 下端
１８ 主溝
１８ａ 底壁
２１ 凹部
２２ 凸部
Ａ，Ｂ，Ｗ 距離
Ｃ 深さ
Ｄ 最短距離
ｇ 深さ
ｈ ゴム厚
Ｐ 距離
Ｓ，Ｔ 断面積
θ 傾斜角度 1 tire
Reference Signs List 2 tread portion 2a end portion 2b outer peripheral surface 2c central portion 3 side portion 4 carcass 5 carcass ply 6 inner liner 7 belt 11, 12, 13 belt ply 14 reinforcement ply 15 baddless portion 16 shoulder portion 17 groove 17 a groove wall 17 b opening 17 c, 17d side wall 17e back wall 17f upper end 17g lower end 18 main groove 18a bottom wall 21 recessed portion 22 convex portion A, B, W distance C depth D shortest distance g depth h rubber thickness P distance S, T sectional area θ inclination angle

Claims (5)

トレッド部の外周面は、非インフレート状態において、中央部における外径よりも端部における外径が大きい逆アール形状を有し、
前記トレッド部の前記端部からタイヤ最大幅部までの領域であるバッドレス部に、タイヤ周方向に沿って設けられた溝と、前記トレッド部に形成された主溝とを備え、
前記溝は、タイヤ幅方向において前記トレッド部の前記端部と重複する位置まで延びており、かつ、前記主溝の底壁よりもタイヤ内径側に形成されている、空気入りタイヤ。 In the non-inflated state, the outer peripheral surface of the tread portion has a reverse radius shape in which the outer diameter at the end portion is larger than the outer diameter at the central portion;
A groove which is a region from the end of the tread portion to the tire maximum width portion includes a groove provided along a tire circumferential direction and a main groove formed in the tread portion .
The pneumatic tire extends to a position overlapping the end of the tread portion in the tire width direction , and is formed on the tire inner diameter side with respect to a bottom wall of the main groove . タイヤ中心軸からの前記中央部までのタイヤ径方向の距離と、前記タイヤ中心軸から前記端部までのタイヤ径方向の距離との差は、前記中央部における前記トレッド部のゴム厚の０．０５倍以上０．２倍以下である、請求項１に記載の空気入りタイヤ。   The difference between the distance in the tire radial direction from the tire central axis to the central portion and the distance in the tire radial direction from the tire central axis to the end portion is 0. 0 of the rubber thickness of the tread portion at the central portion. The pneumatic tire according to claim 1, which is at least 05 times and at most 0.2 times. 前記溝は、タイヤ周方向に連続的に設けられている、請求項１又は請求項２に記載の空気入りタイヤ。   The pneumatic tire according to claim 1, wherein the groove is provided continuously in the tire circumferential direction. 前記溝は、タイヤ周方向に断続的に設けられている、請求項１又は請求項２に記載の空気入りタイヤ。   The pneumatic tire according to claim 1, wherein the groove is provided intermittently in the tire circumferential direction. 前記溝のタイヤ径方向断面の断面積は、トレッド部のタイヤ径方向断面における前記トレッド部の前記中央部からタイヤ幅方向外側に延びる仮想線よりも前記端部側の領域の断面積の０．８倍以上１．２倍以下である、請求項１から請求項４のいずれか１項に記載の空気入りタイヤ。   The cross-sectional area of the tire radial direction cross section of the groove is 0. 0 of the cross-sectional area of the end side region of the imaginary line extending outward from the central portion of the tread portion in the tire radial direction cross section of the tread portion. The pneumatic tire according to any one of claims 1 to 4, which is 8 times or more and 1.2 times or less.
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US3517720A (en) * 1969-04-29 1970-06-30 Armstrong Rubber Co Pneumatic tire
US3693690A (en) * 1970-06-29 1972-09-26 Goodyear Tire & Rubber Pneumatic aircraft tire
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