JP4208123B2 - Pneumatic radial tire - Google Patents

Pneumatic radial tire Download PDF

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JP4208123B2
JP4208123B2 JP2003090651A JP2003090651A JP4208123B2 JP 4208123 B2 JP4208123 B2 JP 4208123B2 JP 2003090651 A JP2003090651 A JP 2003090651A JP 2003090651 A JP2003090651 A JP 2003090651A JP 4208123 B2 JP4208123 B2 JP 4208123B2
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tire
protrusion
protrusions
radial direction
height
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JP2004291937A (en
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将明 小原
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Toyo Tire Corp
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Toyo Tire and Rubber Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C13/00—Tyre sidewalls; Protecting, decorating, marking, or the like, thereof
    • B60C13/02—Arrangement of grooves or ribs

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Description

【０００１】
【発明の属する技術分野】
本発明は、悪路走行を目的とした空気入りラジアルタイヤに関し、より詳しくは、泥濘地などの悪路走破性と耐久性・耐外傷性の向上に関する。
【０００２】
【従来の技術】
悪路走行を目的とした空気入りタイヤ（いわゆるオフロード用タイヤ）においては、平坦な舗装路や未舗装路を走行することのみならず、泥濘地を含む不整地悪路を走行することをも考慮している。そのため、通常は接地しないが悪路走行時に接地するバットレス部にも突起を設け、該突起による剪断力により悪路におけるトラクションを得ている。例えば、特許文献１に開示された悪路走行用空気入りタイヤがある。
【０００３】
【特許文献１】
特開平１１−２９１７１８号公報（第１〜２頁、第１〜２図）
【０００４】
【発明が解決しようとする課題】
かかるバットレス部の突起の高さが高ければ悪路走破性は向上するので、バイアス構造を有する空気入りタイヤでは、１０ｍｍ程度の突起とすることも可能である。しかし、突起を設けることによりバットレス部のゴムの量が不均一となり、加硫成型時に突起の下部にあるカーカスに対して応力が発生する。特にラジアル構造を有する空気入りタイヤでは、カーカスコードがタイヤ半径方向の放射状に延在しているので、該応力により間隔が均一であったカーカスコード間に疎密が発生したり、カーカスコードが蛇行したり、カーカスの耐久性が低下するおそれがあった。そのため、ラジアルタイヤにおいては、かかる応力を低減するためその突起の高さを２〜３ｍｍ程度としかできず、十分な悪路走破性を得ることができなかった。
【０００５】
また、該突起の高さを低くせざるを得ないので、突起による耐外傷性の低下も懸念されていた。単に突起の高さを高くするだけでは突起の剛性が確保できず、該突起による十分な剪断力が得られず、満足な悪路走破性を得ることができないこともあった。
【０００６】
本発明の目的は、悪路走行を目的とした空気入りラジアルタイヤにおいて、悪路走破性を向上させると共に、耐久性・耐外傷性との両立を図ることにある。
【０００７】
【課題を解決するための手段】
上記課題を解決するため、鋭意検討した結果、請求項１に記載の発明は、一対のビードコアと、前記ビードコアを巻回しトロイダル形状を成すカーカスと、前記カーカスのクラウン部のタイヤ半径方向外側に配置されたベルト層と、前記ベルト層よりタイヤ半径方向外側に配置されたトレッドゴムとを備えた空気入りラジアルタイヤにおいて、
バットレス部に高さが５ｍｍ以上の複数の突起がタイヤ周方向に間隔をおいて配置され、隣接する前記突起の間に前記突起を連結する１又は複数のリブが配置され、前記リブの高さが前記突起の高さの５０％〜１００％であり、前記リブの表面から底面にかけてタイヤ半径方向の長さが増大し、隣接する前記突起の間において前記リブの底面のタイヤ半径方向の長さの総和が前記突起の表面のタイヤ半径方向の長さの４０％以上である空気入りラジアルタイヤとした。
【０００８】
請求項１に記載の発明によれば、バットレス部に高さが５ｍｍ以上の複数の突起がタイヤ周方向に間隔をおいて配置されているので、悪路走行時においては、バットレス部も接地するので該突起によりトラクションを増大させることができる。また、突起の間に１又は複数のリブが設けられ、該リブの高さが突起の高さの５０％〜１００％であるので、突起自体のタイヤ周方向の剛性が高められ、該突起の剪断力による十分なトラクションを得ることができる。なお、該リブの高さが突起の高さの５０％未満であると、該突起の剛性を十分に高めることができない。
【０００９】
ラジアルタイヤにおいてかかる突起を設けると、突起の有無によりバットレス部のゴム量が変化し、突起の下部のカーカスに対して応力が発生する。該応力により、カーカスコードの間隔に疎密が発生したり、カーカスコードが蛇行したりして、タイヤの耐久性を低下させることがある。本発明では、突起の間にリブを設け、該リブの表面から底面にかけてタイヤ半径方向の長さが増大し、隣接する該突起の間において該リブの底面のタイヤ半径方向の長さの総和が該突起の表面のタイヤ半径方向の長さの４０％以上としている。その結果、バットレス部のゴム量の急激な変化が緩和されるので、応力の発生を抑制し、タイヤの耐久性を向上させることができる。なお、当該長さの総和が５０％以上であればさらに好ましいが、４０％未満であるとゴム量の変化が緩和の程度が低く十分に応力が低減できない。
【００１０】
請求項２に記載の発明は、前記突起は、接地面から１５ｍｍ〜７０ｍｍの位置にある請求項１に記載の空気入りラジアルタイヤとした。
【００１１】
請求項２に記載の発明によれば、突起が接地面から１５ｍｍ〜７０ｍｍの位置にあり、悪路走行時に接地する頻度の高い範囲であるので、突起によるトラクション増大効果が期待できる。
【００１２】
請求項３に記載の発明は、隣接する前記突起のタイヤ周方向の間隔が１０ｍｍ〜８０ｍｍである請求項１又は２に記載の空気入りラジアルタイヤとした。
【００１３】
請求項３に記載の発明によれば、隣接する前記突起のタイヤ周方向の間隔が１０ｍｍ〜８０ｍｍであることが好ましい。突起の間隔が１０ｍｍ未満であると間隔が狭すぎて路面の凹凸に対するグリップ性が低下し、８０ｍｍを越えると突起の密度が小さくなり、いずれも十分なトラクションが得られない。
【００１４】
請求項４に記載の発明は、前記突起の少なくともタイヤ半径方向の長さが前記突起の表面から底面にかけて増大している請求項１乃至３のいずれかに記載の空気入りラジアルタイヤとした。
【００１５】
請求項４に記載の発明によれば、突起の少なくともタイヤ半径方向の長さが該突起の表面から底面にかけて増大しているので、さらに、バットレス部のゴム量の急激な変化が緩和され、応力の発生を抑制しタイヤの耐久性を向上させることができる。
【００１６】
【発明の実施の形態】
以下、図面を用いて、本発明に係る空気入りラジアルタイヤの実施形態を説明する。図１は、空気入りラジアルタイヤ１の断面を含む要部斜視図である。空気入りラジアルタイヤ１は、一対のビードコア２、ビードコア２を巻回しトロイダル形状を成すカーカス３、カーカス３のクラウン部のタイヤ半径方向外側に配置された補強ベルト層４、補強ベルト層４のタイヤ半径方向外側に配置されたトレッドゴム５を備えている。トレッドゴム５には、タイヤ周方向に連なる主溝１０や主溝１０を連通する横溝１１が刻まれ、主溝１０及び横溝１１によりブロック１２が形成されている。なお、主溝１０のみで形成されたリブ構造としてもよい。また、横溝１１のみにより形成されたラグ構造としてもよい。
【００１７】
カーカス３はラジアル構造を有し、カーカスコード（図示しない）はタイヤ半径方向の放射状に延在している。カーカスコードは特に限定されないが、ポリアミドなどの有機繊維コードやスチールコードが好適に使用される。
【００１８】
トレッドゴム５の接地端１３からタイヤ回転軸方向の幅が最大となる点１４に至るバットレス部６に突起７が間隔をおいてタイヤ周方向Ｒに連続して配置され、突起７の間はリブ２０により連結されている。平坦な舗装路や未舗装路を走行している時は、バットレス部６は接地しない。しかし、泥濘地など悪路（不整地）走行時においては、路面の状態によって、バットレス部６は接地するが、突起７の路面に対する剪断力によりトラクションを増大することができる。
【００１９】
次に、突起７及びリブ２０の形状について説明する。図２（ａ）は、突起７と突起７とを連結する２本のリブ２０を拡大した斜視図である。なお、連結するリブは１本又は３本以上であってもよい。突起７のバットレス部６からの高さａは、５ｍｍ以上としている。突起７の高さａが５ｍｍ未満であると、悪路路面に対する十分なトラクションを得ることができない。また、突起７の高さが低いので石などの突起物からの損傷を受けやすく、バットレス部６の耐外傷性も低下する。
【００２０】
リブ２０のバットレス部６からの高さｂは、突起７の高さａの５０％〜１００％としているので、リブ２０による突起７間の連結効果が得られ、突起７の剛性が高められ、十分なトラクションを得ることができる。なお、高さｂが高さａの５０％未満であると、十分な連結効果が得られず突起７の剛性が高められず、突起７自体が撓んでしまう。その結果、十分な剪断力を得ることができず、必要なトラクションを得ることができない。
【００２１】
突起７の表面７ａのタイヤ周方向の長さＬ、リブ２０の底面２０ｂのタイヤ周方向の長さの総和ＬＳ（図ではＬ１＋Ｌ２）として、ＬＳがＬの４０％以上、好ましくは５０％以上としている。かかる構造としたため、バットレス部６の突起７によるゴム量の変化が小さくなり、加硫成形時におけるカーカス３に対する応力が低減される。その結果、カーカスコード間の疎密やカーカスコードの蛇行の発生が抑制され、タイヤの耐久性が向上する。
【００２２】
なお、図２（ｂ）のＢ−Ｂ’断面図に示すように、突起７は傾斜部８を有し、表面７ａから底面７ｂにかけて、少なくともタイヤ半径方向Ａの長さが徐々に増大する構造とすることが好ましい。かかる構造であれば、よりゴム量の変化を小さくでき、応力を低減できる。また、突起７の剛性も高められる。
【００２３】
図３に示すように、突起７及びリブ２０のタイヤ半径方向Ａの位置は、底面７ｂ及び２０ｂを含めて接地面９より垂直な方向に１５ｍｍ〜７０ｍｍの位置とすることが好ましい。当該範囲に突起があれば、悪路走行時に突起が路面に接地する頻度が高いためトラクションが増大するので、悪路走破性が向上する。また、接地面９より１５ｍｍ未満の位置は、横溝１１が開口しているので、突起７の配置が困難となる。
【００２４】
タイヤ周方向Ｒに隣接する突起７の間隔は、１０ｍｍ〜８０ｍｍとすることが好ましい。１０ｍｍ未満であると間隔が狭すぎて路面の凹凸に対するグリップ性が低下し、８０ｍｍを越えると突起７の密度が小さくなり、いずれも十分なトラクションが得られない。ここでいう突起７の間隔は、突起７の表面７ａの間隔であり、等間隔である必要はなく、１０ｍｍ〜８０ｍｍの範囲にあればよい。また、当該間隔は３０ｍｍ〜５０ｍｍであればより好ましい。
【００２５】
また、突起７の形状は互いに同じ大きさや形状でなくてもよい。上述の条件を備えていればよい。例えば、図４（ａ）は突起７間のリブを３本とした例であり、図４（ｂ）は突起７の形状を平行四辺形とし、傾斜方向を交互に異なるように配置した例であり、図４（ｃ）は突起７の形状を台形に切り込みを入れた形状とした例である。
【００２６】
【実施例】
表１に示す実施例及び比較例に係るタイヤを試作し、性能評価を行った。タイヤサイズは、３５×１２．５０Ｒ１７とした。突起の形状は、図１に示したように突起は矩形で、周方向間隔は５０ｍｍ、接地面から３０ｍｍ〜５０ｍｍの位置に配置した。カーカスコード不良は、タイヤ加硫成型後、タイヤゴム層を解体除去、もしくはＸ線撮影によりカーカスの配置（カーカスコード間隔の疎密やカーカスコードの蛇行）を確認し、不良が発生しているか否かを確認した結果である。悪路走破性は、泥濘地走行時のフィーリング評価を実施し、パネラー３名による評価点の平均点で、比較例１を１００とした指数であり、数字が大きいほど良好であることを示す。
【００２７】
【表１】

Figure 0004208123
【００２８】
表1によれば、比較例１ではリブ底面の半径方向長さの総和が突起の底面のそれに比べ短いため応力低減効果が小さく、カーカスコードの不良が発生している。比較例２では、リブ高さが低いため突起の剛性が不足し十分なトラクションが得られず悪路走破性が低下している。これに対して、実施例では、悪路走破性が向上し、しかもカーカスコードの不良が発生していない。
【００２９】
【発明の効果】
以上の通り、本発明の空気入りラジアルタイヤにおいて、バットレス部に複数の突起をタイヤ周方向に間隔をおいて配置し、該突起をリブにより連結し、該突起及び該リブを所定の構造としたので、悪路走行時のトラクションを増大させ、耐久性・耐外傷性との両立を図ることができる。
【図面の簡単な説明】
【図１】本発明に係る空気入りラジアルタイヤの断面を含む要部斜視図である。
【図２】（ａ）は突起及びリブを拡大した斜視図、（ｂ）はＢ−Ｂ’断面図である。
【図３】好ましい突起及びリブの位置を示すタイヤ断面図である。
【図４】（ａ）〜（ｃ）は、他の突起の形状の例を示す図である。
【符号の説明】
１ 空気入りラジアルタイヤ
２ ビードコア
３ カーカス
４ 補強ベルト
５ トレッド
７ 突起
２０ リブ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire for running on rough roads, and more particularly, to improving bad road running performance and durability / trauma resistance such as muddy ground.
[0002]
[Prior art]
Pneumatic tires (so-called off-road tires) intended for driving on rough roads not only drive on flat and unpaved roads, but also run on rough roads including muddy areas. I am considering. Therefore, a projection is also provided on the buttress portion that is not normally grounded but is grounded when traveling on a rough road, and the traction on the rough road is obtained by the shearing force of the protrusion. For example, there is a pneumatic tire for running on rough roads disclosed in Patent Document 1.
[0003]
[Patent Document 1]
JP-A-11-291718 (pages 1 and 2, FIGS. 1 and 2)
[0004]
[Problems to be solved by the invention]
If the height of the projection of the buttress portion is high, the rough road running performance is improved. Therefore, in a pneumatic tire having a bias structure, it is possible to provide a projection of about 10 mm. However, by providing the protrusion, the amount of rubber in the buttress portion becomes non-uniform, and stress is generated on the carcass below the protrusion during vulcanization molding. Particularly in a pneumatic tire having a radial structure, since the carcass cords extend radially in the tire radial direction, due to the stress, the carcass cords having a uniform interval occur, and the carcass cords meander. Or the durability of the carcass may be reduced. Therefore, in the radial tire, in order to reduce such stress, the height of the protrusion can only be about 2 to 3 mm, and sufficient rough road running performance cannot be obtained.
[0005]
In addition, since the height of the protrusions has to be lowered, there is a concern that the damage resistance is lowered due to the protrusions. By simply increasing the height of the protrusion, the rigidity of the protrusion cannot be ensured, and sufficient shearing force by the protrusion cannot be obtained, and satisfactory rough road running performance may not be obtained.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to improve rough road running performance and achieve both durability and trauma resistance in a pneumatic radial tire intended for running on rough roads.
[0007]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-described problems, the invention according to claim 1 is arranged on the outer side in the tire radial direction of a pair of bead cores, a carcass wound around the bead core to form a toroidal shape, and a crown portion of the carcass. In a pneumatic radial tire comprising a belt layer formed and a tread rubber disposed on the outer side in the tire radial direction from the belt layer,
A plurality of protrusions having a height of 5 mm or more are arranged at intervals in the tire circumferential direction on the buttress portion, and one or a plurality of ribs connecting the protrusions are arranged between the adjacent protrusions, and the height of the ribs Is 50% to 100% of the height of the protrusion, the length in the tire radial direction increases from the surface to the bottom of the rib, and the length in the tire radial direction of the bottom surface of the rib between the adjacent protrusions A pneumatic radial tire having a total sum of 40% or more of the length of the surface of the protrusion in the tire radial direction.
[0008]
According to the first aspect of the invention, since the plurality of protrusions having a height of 5 mm or more are arranged at intervals in the tire circumferential direction on the buttress portion, the buttress portion is also grounded when traveling on a rough road. Therefore, the traction can be increased by the protrusion. In addition, since one or a plurality of ribs are provided between the protrusions, and the height of the ribs is 50% to 100% of the height of the protrusions, the rigidity of the protrusions in the tire circumferential direction can be increased. Sufficient traction by shearing force can be obtained. If the height of the rib is less than 50% of the height of the protrusion, the rigidity of the protrusion cannot be sufficiently increased.
[0009]
When such a protrusion is provided in the radial tire, the amount of rubber in the buttress portion changes depending on the presence or absence of the protrusion, and stress is generated on the carcass below the protrusion. Due to the stress, the carcass cords may be sparse or dense, or the carcass cords may meander, reducing the durability of the tire. In the present invention, a rib is provided between the protrusions, and the length in the tire radial direction increases from the surface of the rib to the bottom surface, and the total length of the bottom surface of the rib in the tire radial direction is between the adjacent protrusions. It is 40% or more of the length of the surface of the protrusion in the tire radial direction. As a result, a rapid change in the amount of rubber in the buttress portion is mitigated, so that the generation of stress can be suppressed and the durability of the tire can be improved. It is more preferable if the total length is 50% or more, but if it is less than 40%, the change in the amount of rubber is low and the stress cannot be sufficiently reduced.
[0010]
The invention according to claim 2 is the pneumatic radial tire according to claim 1, wherein the protrusion is located at a position of 15 mm to 70 mm from the ground contact surface.
[0011]
According to the second aspect of the present invention, since the protrusion is located at a position of 15 mm to 70 mm from the ground contact surface and is in a range where the ground contacts frequently when traveling on a rough road, the effect of increasing the traction by the protrusion can be expected.
[0012]
Invention of Claim 3 was set as the pneumatic radial tire of Claim 1 or 2 whose space | interval of the tire circumferential direction of the said adjacent protrusion is 10 mm-80 mm.
[0013]
According to invention of Claim 3, it is preferable that the space | interval of the tire circumferential direction of the said adjacent protrusion is 10 mm-80 mm. If the distance between the protrusions is less than 10 mm, the distance is too narrow, and the grip performance with respect to the road surface unevenness is lowered. If the distance exceeds 80 mm, the density of the protrusions decreases, and sufficient traction cannot be obtained in any case.
[0014]
The invention according to claim 4 is the pneumatic radial tire according to any one of claims 1 to 3, wherein at least a length of the protrusion in the tire radial direction increases from a surface to a bottom surface of the protrusion.
[0015]
According to the invention of claim 4, since at least the length in the tire radial direction of the protrusion increases from the surface to the bottom surface of the protrusion, a sudden change in the amount of rubber in the buttress portion is further alleviated and stress is increased. It is possible to suppress the occurrence of the tire and improve the durability of the tire.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a pneumatic radial tire according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a main part including a cross section of a pneumatic radial tire 1. The pneumatic radial tire 1 includes a pair of bead cores 2, a carcass 3 wound around the bead core 2 to form a toroidal shape, a reinforcing belt layer 4 disposed on the outer side in the tire radial direction of a crown portion of the carcass 3, and a tire radius of the reinforcing belt layer 4. A tread rubber 5 is provided on the outer side in the direction. In the tread rubber 5, a main groove 10 that continues in the tire circumferential direction and a lateral groove 11 that communicates with the main groove 10 are engraved, and a block 12 is formed by the main groove 10 and the lateral groove 11. In addition, it is good also as a rib structure formed only by the main groove 10. FIG. Moreover, it is good also as a lug structure formed only by the lateral groove 11. FIG.
[0017]
The carcass 3 has a radial structure, and carcass cords (not shown) extend radially in the tire radial direction. The carcass cord is not particularly limited, but an organic fiber cord such as polyamide or a steel cord is preferably used.
[0018]
Protrusions 7 are continuously arranged in the tire circumferential direction R at a distance from the ground contact end 13 of the tread rubber 5 to the point 14 where the width in the tire rotation axis direction is maximum. 20 are connected. The buttress portion 6 is not grounded when traveling on a flat paved road or an unpaved road. However, when traveling on rough roads (rough roads) such as muddy ground, the buttress portion 6 is grounded depending on the state of the road surface, but the traction can be increased by the shearing force of the protrusions 7 on the road surface.
[0019]
Next, the shape of the protrusion 7 and the rib 20 will be described. FIG. 2A is an enlarged perspective view of the two ribs 20 that connect the protrusion 7 and the protrusion 7. Note that one or three or more ribs may be connected. The height a of the protrusion 7 from the buttress portion 6 is 5 mm or more. If the height a of the protrusion 7 is less than 5 mm, sufficient traction on the rough road surface cannot be obtained. Moreover, since the height of the protrusion 7 is low, the protrusion 7 such as a stone is easily damaged, and the damage resistance of the buttress portion 6 is also reduced.
[0020]
Since the height b of the rib 20 from the buttress portion 6 is 50% to 100% of the height a of the protrusion 7, the connection effect between the protrusions 7 by the rib 20 is obtained, and the rigidity of the protrusion 7 is increased. Sufficient traction can be obtained. If the height b is less than 50% of the height a, a sufficient connection effect cannot be obtained, the rigidity of the protrusion 7 cannot be increased, and the protrusion 7 itself bends. As a result, sufficient shearing force cannot be obtained and necessary traction cannot be obtained.
[0021]
As the total length LS (L1 + L2 in the figure) of the length L of the surface 7a of the protrusion 7 in the tire circumferential direction and the length of the bottom surface 20b of the rib 20 in the tire circumferential direction, LS is 40% or more, preferably 50% or more of L. Yes. With such a structure, the change in the rubber amount due to the protrusion 7 of the buttress portion 6 is reduced, and the stress on the carcass 3 during vulcanization molding is reduced. As a result, the density of the carcass cords and the meandering of the carcass cords are suppressed, and the durability of the tire is improved.
[0022]
As shown in the BB ′ cross-sectional view of FIG. 2 (b), the protrusion 7 has an inclined portion 8, and at least the length in the tire radial direction A gradually increases from the surface 7a to the bottom surface 7b. It is preferable that With such a structure, the change in the rubber amount can be further reduced, and the stress can be reduced. Further, the rigidity of the protrusion 7 can be increased.
[0023]
As shown in FIG. 3, the positions of the protrusions 7 and the ribs 20 in the tire radial direction A are preferably 15 mm to 70 mm in the direction perpendicular to the ground contact surface 9 including the bottom surfaces 7 b and 20 b. If there is a projection in the range, the traction increases because the projection contacts the road surface frequently when traveling on a rough road, so that the rough road running performance is improved. Further, since the lateral groove 11 is opened at a position less than 15 mm from the ground plane 9, it is difficult to arrange the protrusions 7.
[0024]
The interval between the protrusions 7 adjacent to each other in the tire circumferential direction R is preferably 10 mm to 80 mm. If the distance is less than 10 mm, the distance is too narrow and the grip performance against the unevenness of the road surface is lowered. If the distance exceeds 80 mm, the density of the protrusions 7 is reduced, and sufficient traction cannot be obtained in any case. The space | interval of the processus | protrusion 7 here is a space | interval of the surface 7a of the processus | protrusion 7, does not need to be equal intervals, and should just exist in the range of 10 mm-80 mm. Moreover, the said space | interval is more preferable if it is 30-50 mm.
[0025]
Further, the shapes of the protrusions 7 may not be the same size and shape. What is necessary is just to have the above-mentioned conditions. For example, FIG. 4A is an example in which three ribs are provided between the protrusions 7, and FIG. 4B is an example in which the protrusions 7 are parallelograms and are arranged so that the inclination directions are alternately different. FIG. 4C shows an example in which the shape of the protrusion 7 is a trapezoidal shape.
[0026]
【Example】
Tires according to the examples and comparative examples shown in Table 1 were prototyped and evaluated for performance. The tire size was 35 × 12.50R17. As shown in FIG. 1, the shape of the protrusions was rectangular, and the circumferential interval was 50 mm, and the protrusions were arranged at positions of 30 mm to 50 mm from the ground plane. For carcass cord defects, after tire vulcanization molding, the tire rubber layer is disassembled and removed, or X-ray photography confirms the carcass arrangement (the density of the carcass cords and the meandering of the carcass cords), and whether or not a defect has occurred. This is the result of confirmation. The rough road running performance is a feeling evaluation at the time of muddy road running, an average score of evaluation points by three panelists, an index with Comparative Example 1 being 100, and indicates that the larger the number, the better. .
[0027]
[Table 1]
Figure 0004208123
[0028]
According to Table 1, in Comparative Example 1, the sum of the radial lengths of the rib bottom surfaces is shorter than that of the bottom surfaces of the protrusions, so that the stress reduction effect is small and the carcass cord is defective. In Comparative Example 2, since the rib height is low, the rigidity of the protrusion is insufficient, and sufficient traction cannot be obtained, resulting in poor road running performance. On the other hand, in the embodiment, the rough road running performance is improved and the carcass cord is not defective.
[0029]
【The invention's effect】
As described above, in the pneumatic radial tire of the present invention, a plurality of protrusions are arranged at intervals in the tire circumferential direction on the buttress portion, the protrusions are connected by ribs, and the protrusions and the ribs have a predetermined structure. Therefore, it is possible to increase the traction during driving on a rough road and to achieve both durability and trauma resistance.
[Brief description of the drawings]
FIG. 1 is a perspective view of a main part including a cross section of a pneumatic radial tire according to the present invention.
2A is an enlarged perspective view of protrusions and ribs, and FIG. 2B is a cross-sectional view taken along the line BB ′.
FIG. 3 is a tire cross-sectional view showing preferred protrusions and rib positions.
FIGS. 4A to 4C are diagrams showing examples of other protrusion shapes. FIGS.
[Explanation of symbols]
1 Pneumatic radial tire 2 Bead core 3 Carcass 4 Reinforcement belt 5 Tread 7 Protrusion 20 Rib

Claims (4)

一対のビードコアと、前記ビードコアを巻回しトロイダル形状を成すカーカスと、前記カーカスのクラウン部のタイヤ半径方向外側に配置されたベルト層と、前記ベルト層よりタイヤ半径方向外側に配置されたトレッドゴムとを備えた空気入りラジアルタイヤにおいて、
バットレス部に高さが５ｍｍ以上の複数の突起がタイヤ周方向に間隔をおいて配置され、隣接する前記突起の間に前記突起を連結する１又は複数のリブが配置され、前記リブの高さが前記突起の高さの５０％〜１００％であり、前記リブの表面から底面にかけてタイヤ半径方向の長さが増大し、隣接する前記突起の間において前記リブの底面のタイヤ半径方向の長さの総和が前記突起の表面のタイヤ半径方向の長さの４０％以上である空気入りラジアルタイヤ。A pair of bead cores, a carcass wound around the bead core to form a toroidal shape, a belt layer disposed on the outer side in the tire radial direction of the crown portion of the carcass, and a tread rubber disposed on the outer side in the tire radial direction from the belt layer In the pneumatic radial tire with
A plurality of protrusions having a height of 5 mm or more are arranged at intervals in the tire circumferential direction on the buttress portion, and one or a plurality of ribs connecting the protrusions are arranged between the adjacent protrusions, and the height of the ribs Is 50% to 100% of the height of the protrusion, the length in the tire radial direction increases from the surface to the bottom of the rib, and the length in the tire radial direction of the bottom surface of the rib between the adjacent protrusions Is a pneumatic radial tire in which the sum total is 40% or more of the length of the surface of the protrusion in the tire radial direction. 前記突起は、接地面から１５ｍｍ〜７０ｍｍの位置にある請求項１に記載の空気入りラジアルタイヤ。The pneumatic radial tire according to claim 1, wherein the protrusion is located at a position of 15 mm to 70 mm from the ground contact surface. 隣接する前記突起のタイヤ周方向の間隔が１０ｍｍ〜８０ｍｍである請求項１又は２に記載の空気入りラジアルタイヤ。The pneumatic radial tire according to claim 1 or 2, wherein an interval in the tire circumferential direction between adjacent protrusions is 10 mm to 80 mm. 前記突起の少なくともタイヤ半径方向の長さが前記突起の表面から底面にかけて増大している請求項１乃至３のいずれかに記載の空気入りラジアルタイヤ。The pneumatic radial tire according to any one of claims 1 to 3, wherein at least a length of the protrusion in a tire radial direction increases from a surface to a bottom surface of the protrusion.
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