JP3876156B2

JP3876156B2 - Pneumatic tire

Info

Publication number: JP3876156B2
Application number: JP2001374834A
Authority: JP
Inventors: 祐二遠松
Original assignee: Yokohama Rubber Co Ltd
Current assignee: Yokohama Rubber Co Ltd
Priority date: 2001-12-07
Filing date: 2001-12-07
Publication date: 2007-01-31
Anticipated expiration: 2021-12-07
Also published as: JP2003170709A

Description

【０００１】
【発明の属する技術分野】
本発明は、空気入りタイヤに関し、さらに詳しくは、パターンノイズを低減した空気入りタイヤに関する。
【０００２】
【従来の技術】
従来、タイヤの偏摩耗を抑制するために、トレッド踏面に周方向細溝を形成してトレッドの剛性を調整することが行われていた。また、トレッドのパターンから生じる種々のノイズを低減させることを目的として、横方向に副細溝を形成することがある。これらの周方向と横方向の副細溝の両者を例えば図５に示すように設け、耐偏摩耗性と低騒音性をともに向上させようとすると、周方向細溝１と横方向の副細溝２との交差部分３の隣接するエッジ部４同士が、タイヤ走行中に接触し擦れ合ってノイズの発生原因となってしまうという問題があった。これは、周方向細溝１と副細溝２がともに細溝であるが故に、エッジ部４間の距離が小さく接触しやすくなるためである。
【０００３】
【発明が解決しようとする課題】
従って、本発明の課題は、パターンノイズを低減した空気入りタイヤを提供することにある。
【０００４】
【課題を解決するための手段】
本発明によれば、トレッド踏面部に周方向細溝およびこれに交差する副細溝を有し、前記周方向細溝と前記副細溝の交差部分の全てのエッジ部を踏面部にて直線状に面取りして面取り部を形成した空気入りタイヤが提供される。
【０００５】
また、本発明によれば、前記周方向細溝および前記副細溝の溝幅が０．３〜２．５ｍｍである前記空気入りタイヤが提供される。
【０００６】
また、本発明によれば、前記副細溝の溝深さが前記周方向細溝の溝深さの６０〜９０％である前記空気入りタイヤが提供される。
【０００７】
また、本発明によれば、前記面取り部の深さが、前記周方向細溝の溝深さの１０〜４０％である前記空気入りタイヤが提供される。
【０００８】
また、本発明によれば、前記面取り部の総面積が、トレッド接地部の溝面積の０．５〜５％である前記空気入りタイヤが提供される。
【０００９】
また、本発明によれば、タイヤ赤道線から車両外側の溝面積比が、車両内側の溝面積比よりも小さく、前記周方向細溝と前記副細溝がタイヤ赤道線から車両外側に設けられている前記空気入りタイヤが提供される。
【００１０】
また、本発明によれば、タイヤ赤道線から車両内側がブロック基調で車両外側がリブ基調の非対称パターンであり、前記周方向細溝と前記副細溝がタイヤ赤道線から車両外側に設けられている前記空気入りタイヤが提供される。
【００１１】
また、本発明によれば、さらに周方向細溝がタイヤ赤道線から車両内側にも設けられている前記空気入りタイヤが提供される。
【００１２】
また、本発明によれば、タイヤ赤道線から車両内側のブロックの鋭角部を面取りした前記空気入りタイヤが提供される。
【００１３】
また、本発明によれば、タイヤ赤道線から車両外側の最外リブ列にラグ溝をリブの途中で止まるように配置した前記空気入りタイヤが提供される。
【００１４】
また、本発明によれば、４本の周方向主溝と２本の周方向細溝とを有し、タイヤ赤道線から車両内側で前記周方向主溝と交差する傾斜ラグ溝により３列のブロック列を形成し、少なくともセンター側２列のブロック列のブロックの鋭角部を面取りした前記空気入りタイヤが提供される。
【００１５】
また、本発明によれば、前記周方向主溝が、タイヤ赤道線から車両内側のタイヤ外側にトレッド接地幅の２０〜４０％および４０〜７０％の範囲と、タイヤ赤道線から車両外側のタイヤ外側にトレッド接地幅の５〜２０％および２０〜５０％の範囲に位置する前記空気入りタイヤが提供される。
【００１６】
さらに、本発明によれば、前記周方向細溝が、タイヤ赤道線から車両内側のタイヤ外側にトレッド接地幅の１〜１０％の範囲と、タイヤ赤道線から車両外側のタイヤ外側にトレッド接地幅の６０〜９０％の範囲に位置する前記空気入りタイヤが提供される。
【００１７】
【発明の実施の形態】
以下、本発明の構成について図面を参照しながら詳細に説明する。図１は、本発明の空気入りタイヤの踏面に形成されたトレッドパターンの一例を示す平面視説明図である。図１の左方のタイヤ赤道線Ｃから車両外側Ｏには、耐偏摩耗性を向上させるための周方向細溝１が設けられている。また、周方向細溝１と交差して交差部分３を形成するようにノイズを低減するための副細溝２が、トレッド幅方向または傾斜した方向に複数本設けられている。この交差部分３の各角部に形成される４つの全てのエッジ部４は、踏面部にて直線状となるように面取りして面取り部５を形成している。この交差部分３を拡大して側面から示した図１のＡ−Ａ線矢視方向部分断面図である図２のように、全エッジ部４が平面的に斜め方向に面取りされ、面取り部５を形成しているが、必ずしも面取りが平面的でなくてもよい。
【００１８】
このように、全てのエッジ部４を面取りすることによって、隣接するエッジ部４同士が、タイヤ走行中に擦れ合ってノイズが発生するのを抑制し、パターンノイズを低減することができる。また、踏面部にて直線状となるように面取りするのは、上記のエッジ部４同士の接触をより効果的に防ぐためであり、例えば、踏面部にて曲線状に突出した形状にした場合には、その突出した部分同士で接触しやすくなってしまいノイズの発生の抑制効果が低減してしまう。
【００１９】
本発明の周方向細溝１および副細溝２の溝幅は、例えば、０．３〜２．５ｍｍであるのが好ましい。また、副細溝２の溝深さが周方向細溝１の溝深さの６０〜９０％となるようにするのが好ましい。上記の溝深さの差が６０％未満であると副細溝２が浅すぎて摩耗によって早期に消滅してしまい、逆に９０％を超えると耐偏摩耗性の向上効果が小さくなるために好ましくない。
【００２０】
面取り部５の深さは、特に限定されないが、図２に示されるように周方向細溝１や副細溝２の溝深さよりも浅く設定するのがブロックやリブの剛性が小さくなりすぎず操縦安定性の低下を抑えるために好ましく、例えば、面取り部５の深さを周方向細溝１の溝深さの１０〜４０％とすればよい。
【００２１】
また、面取り部５の面取りの大きさも特に限定されないが、面取り部５の総面積が、トレッド接地部の溝面積の０．５〜５％となるように設定するのが好ましい。この面積比を０．５％以上とすることで、本発明の効果を有効に発現させることができ、５％以下とすることで、ブロックやリブの剛性が小さくなりすぎず操縦安定性の低下を抑えるために好ましい。また、面取り部５の面取りのサイズとしては、例えば、踏面にて細溝に沿う一辺が２〜４ｍｍとなるように面取りすればよい。なお、トレッド接地部とは、ＪＡＴＭＡ２００１年規格に準じて最大空気圧の８０％でリム組みし、最大荷重の８０％を負荷したタイヤが接地する接地幅のタイヤ全周にわたる領域を示す。
【００２２】
図１に示すように、タイヤ赤道線Ｃから車両外側Ｏの溝面積比が、車両内側Ｉの溝面積比よりも小さく、面取り部５を有する交差部分３を形成する周方向細溝１と副細溝２がタイヤ赤道線Ｃから車両外側に設けられているのが好ましい。このように車両外側Ｏの溝面積比を小さくしたうえで、その部分に周方向細溝１を設けたために、この二つの要因によってタイヤの耐偏摩耗性をより向上させることができるうえに、車両内側Ｉの溝面積比が大きいので排水性能を確保できウェット性能にも優れる。また、タイヤ赤道線Ｃから車両外側Ｏの溝面積比が、車両内側Ｉの溝面積比の０．７０〜０．９０倍となるようにするのがさらに好ましい。
【００２３】
さらに、図１のように、タイヤ赤道線Ｃから車両内側Ｉをブロック基調のトレッドパターンとし、車両外側Ｏをリブ基調のトレッドパターンとする非対称パターンとし、面取り部５を有する交差部分３を形成する周方向細溝１と副細溝２がタイヤ赤道線Ｃから車両外側Ｏに設けられているのが好ましい。このようにリブ基調のトレッドパターンを車両外側Ｏに配し、その部分に周方向細溝１を設けることで、耐偏摩耗性をより向上させることができるからである。また、図１に示すように、さらにもう一本の周方向細溝１ａをタイヤ赤道線Ｃから車両内側Ｉにも設け、タイヤ赤道線Ｃから車両内側Ｉがブロック基調のトレッドパターンになるように構成してもよく、リブ基調の部分が耐偏摩耗性能を発揮し、ブロック基調の部分でウェット性能を発揮するので好ましい。
【００２４】
さらには、図１に示すように、タイヤ赤道線Ｃから車両内側Ｉのブロックの鋭角部６を面取りすることによって、剛性の弱い鋭角部６がもぎれて偏摩耗するのを抑制することができるために好ましい。
【００２５】
また、図１のように、タイヤ赤道線Ｃから車両外側Ｏの最外リブ列にラグ溝をリブの途中で止まるように配置するのが、ショルダー部の段差摩耗を抑え、耐偏摩耗性を向上させるので好ましい。
【００２６】
また、図１のように、４本の周方向主溝８と２本の周方向細溝１，１ａとを有し、タイヤ赤道線Ｃから車両内側Ｉで周方向主溝８と交差する傾斜ラグ溝９により３列のブロック列を形成し、少なくともセンター側２列のブロック列のブロックの鋭角部６を面取りした本発明の空気入りタイヤとするのが、ウェット性能を向上しつつ、偏摩耗とタイヤ騒音を有効に抑制することができるために特に好ましい。
【００２７】
また、この４本の周方向主溝８は、２本をタイヤ赤道線Ｃから車両内側Ｉのタイヤ外側にトレッド接地幅の２０〜４０％および４０〜７０％の範囲に位置するように配置し、他の２本をタイヤ赤道線Ｃから車両外側Ｏのタイヤ外側にトレッド接地幅の５〜２０％および２０〜５０％の範囲に位置するように配置するのが好ましい。２本の周方向細溝１ａおよび１は、タイヤ赤道線Ｃから車両内側Ｉのタイヤ外側にトレッド接地幅の１〜１０％の範囲と、タイヤ赤道線Ｃから車両外側Ｏのタイヤ外側にトレッド接地幅の６０〜９０％の範囲にそれぞれ位置するように配置するのが好ましい。
【００２８】
【実施例】
以下、実施例によって本発明をさらに説明するが、本発明の範囲をこれらの実施例に限定するものではない。
実施例１〜２及び比較例１〜５
トレッドパターンを図１および図３〜図６のように変更して、下記表１のような構成としたタイヤサイズ２１５／６５Ｒ１５の各タイヤを作製し、６．５ＪＪのリムに内圧２００ｋＰａでリム組み後、３０００ｃｃの後輪駆動車の４輪に装着し、以下の各試験に供した。
【００２９】
ウェット性能
タイヤテストコースを走行し、水深が平均約１０ｍｍの平地を半径６０ｍの円弧を描きながら速度を上げてゆき、限界速度を測定し、比較例１を１００とする指数で評価した。数値が大きい程良好である。
耐偏摩耗性能
一般道及び高速道路を合計８０００ｋｍ走行させて、車両外側の最大摩耗量と車両内側の最大摩耗量とを測定し、両者の差を比較例１を１００とする指数で評価した。数値が大きいほど良好である。
騒音性能
タイヤテストコースを速度６０ｋｍ／ｈにて走行させ、車内音圧レベル（ｄＢ）を測定し、比較例１を１００とする指数で評価した。数値が大きいほど良好である。
【００３０】
【表１】

【００３１】
上記表１に示すように、周方向細溝１と副細溝２を有さない比較例１（図３）、副細溝２を有さない比較例２（図４）、交差部分３の全てのエッジ部４を面取りしなかった比較例３（図５）および比較例４（図６）については、騒音性能の充分な改善が見られなかった。また、周方向細溝１および副細溝２の溝幅が広すぎて、もはや細溝とは言えない比較例５（図１）については、溝が広すぎて溝面積が大きくなり、リブの剛性が小さくなってしまい、耐偏摩耗性が悪化してしまった。それに対して、周方向細溝１と副細溝２の交差部分３の全てのエッジ部４を踏面部にて直線状に面取りした本発明の実施例１〜２（図１）の空気入りタイヤは、パターンノイズが低減し良好な騒音性能が得られた。また、タイヤ赤道線Ｃから車両外側Ｏの溝面積比が、車両内側Ｉの溝面積比よりも小さく、車両内側Ｉがブロック基調で車両外側Ｏがリブ基調の非対称パターンを採用しているので、耐偏摩耗性とウェット性能も優れている。
【００３２】
【発明の効果】
本発明に従って、空気入りタイヤのトレッド踏面部に周方向細溝およびこれに交差する副細溝を有し、前記周方向細溝と前記副細溝の交差部分の全てのエッジ部を踏面部にて直線状に面取りして面取り部を形成することによって、パターンノイズを低減した空気入りタイヤを得ることができる。
【図面の簡単な説明】
【図１】本発明の空気入りタイヤのトレッドパターンの平面視説明図である。
【図２】交差部分を示す図１のＡ−Ａ線矢視方向部分断面図である。
【図３】比較例１の空気入りタイヤのトレッドパターンの平面視説明図である。
【図４】比較例２の空気入りタイヤのトレッドパターンの平面視説明図である。
【図５】比較例３の空気入りタイヤのトレッドパターンの平面視説明図である。
【図６】比較例４の空気入りタイヤのトレッドパターンの平面視説明図である。
【符号の説明】
１周方向細溝
１ａ周方向細溝
２副細溝
３交差部分
４エッジ部
５面取り部
６鋭角部
７ラグ溝
８周方向主溝
９傾斜ラグ溝
Ｃタイヤ赤道線
Ｉ車両内側
Ｏ車両外側[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire with reduced pattern noise.
[0002]
[Prior art]
Conventionally, in order to suppress uneven wear of the tire, a circumferential narrow groove is formed on the tread surface to adjust the rigidity of the tread. Further, in order to reduce various noises generated from the tread pattern, a sub-fine groove may be formed in the lateral direction. For example, when both the circumferential and lateral sub-grooves are provided as shown in FIG. 5 to improve both uneven wear resistance and low noise resistance, the circumferential narrow groove 1 and the lateral sub-grooves are improved. There is a problem that adjacent edge portions 4 of the intersecting portion 3 with the groove 2 come into contact with each other and rub against each other during running of the tire and cause noise. This is because both the circumferential narrow groove 1 and the secondary narrow groove 2 are narrow grooves, and therefore, the distance between the edge portions 4 is small, and the contact is easy.
[0003]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a pneumatic tire with reduced pattern noise.
[0004]
[Means for Solving the Problems]
According to the present invention, the tread tread has a circumferential narrow groove and a sub-thin groove that intersects the circumferential narrow groove, and all the edge portions of the intersection of the circumferential narrow groove and the sub-thin groove are straight at the tread. A pneumatic tire that is chamfered in a shape to form a chamfered portion is provided.
[0005]
Moreover, according to this invention, the said pneumatic tire whose groove width of the said circumferential direction fine groove and the said subfine groove is 0.3-2.5 mm is provided.
[0006]
In addition, according to the present invention, there is provided the pneumatic tire in which a groove depth of the sub-fine grooves is 60 to 90% of a groove depth of the circumferential fine grooves.
[0007]
Moreover, according to this invention, the depth of the said chamfer part is 10-40% of the groove depth of the said circumferential direction fine groove, The said pneumatic tire is provided.
[0008]
Moreover, according to this invention, the said pneumatic tire whose total area of the said chamfering part is 0.5 to 5% of the groove area of a tread grounding part is provided.
[0009]
Further, according to the present invention, the groove area ratio on the vehicle outer side from the tire equator line is smaller than the groove area ratio on the vehicle inner side, and the circumferential narrow groove and the auxiliary narrow groove are provided on the vehicle outer side from the tire equator line. The pneumatic tire is provided.
[0010]
Further, according to the present invention, an asymmetrical pattern in which the vehicle inner side from the tire equator line is a block key tone and the vehicle outer side is a rib key tone pattern, and the circumferential narrow groove and the auxiliary narrow groove are provided on the vehicle outer side from the tire equator line. The pneumatic tire is provided.
[0011]
In addition, according to the present invention, there is provided the pneumatic tire in which a circumferential narrow groove is further provided on the vehicle inner side from the tire equator line.
[0012]
Moreover, according to this invention, the said pneumatic tire which chamfered the acute angle part of the block inside a vehicle from a tire equator line is provided.
[0013]
In addition, according to the present invention, there is provided the pneumatic tire in which the lug groove is arranged from the tire equator line to the outermost rib row outside the vehicle so as to stop in the middle of the rib.
[0014]
Further, according to the present invention, there are three circumferential main grooves and two circumferential narrow grooves, and three rows of inclined lug grooves intersecting the circumferential main grooves on the vehicle inner side from the tire equator line. The pneumatic tire is provided that forms a block row and chamfers at least the acute angle portions of the blocks of the two row rows on the center side.
[0015]
Further, according to the present invention, the circumferential main grooves are in the range of 20 to 40% and 40 to 70% of the tread ground contact width from the tire equator line to the outer tire side of the vehicle, and from the tire equator line to the outer tire of the vehicle. The pneumatic tire is provided on the outer side in the range of 5 to 20% and 20 to 50% of the tread contact width.
[0016]
Further, according to the present invention, the circumferential narrow groove has a range of 1 to 10% of the tread ground contact width from the tire equator line to the outer tire side of the vehicle, and the tread ground contact width from the tire equator line to the outer tire end of the vehicle. The pneumatic tire located in the range of 60 to 90% of the above is provided.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory plan view showing an example of a tread pattern formed on the tread surface of the pneumatic tire of the present invention. A circumferential narrow groove 1 for improving uneven wear resistance is provided on the vehicle outer side O from the left tire equator line C in FIG. Further, a plurality of sub-fine grooves 2 for reducing noise are provided in the tread width direction or the inclined direction so as to intersect with the circumferential-direction fine grooves 1 to form the intersecting portions 3. All four edge portions 4 formed at each corner of the intersecting portion 3 are chamfered so as to be linear at the tread surface portion to form a chamfered portion 5. As shown in FIG. 2 which is a partial cross-sectional view in the direction of arrows AA in FIG. However, the chamfering is not necessarily flat.
[0018]
Thus, by chamfering all the edge parts 4, it can suppress that the adjacent edge parts 4 mutually rub against each other during tire driving | running | working, and can reduce pattern noise. Further, the chamfering so as to be linear at the tread portion is to more effectively prevent the contact between the edge portions 4 described above, for example, when the shape is projected in a curved shape at the tread portion. In this case, the protruding portions are easily brought into contact with each other, and the effect of suppressing noise generation is reduced.
[0019]
The groove widths of the circumferential narrow grooves 1 and the secondary narrow grooves 2 of the present invention are preferably 0.3 to 2.5 mm, for example. Moreover, it is preferable that the groove depth of the sub-fine groove 2 is 60 to 90% of the groove depth of the circumferential fine groove 1. If the above groove depth difference is less than 60%, the sub-fine groove 2 is too shallow and disappears early due to wear. Conversely, if it exceeds 90%, the effect of improving uneven wear resistance is reduced. It is not preferable.
[0020]
The depth of the chamfered portion 5 is not particularly limited. However, setting the depth of the chamfered portion shallower than the groove depths of the circumferential narrow grooves 1 and the sub-fine grooves 2 as shown in FIG. For example, the depth of the chamfered portion 5 may be 10 to 40% of the groove depth of the circumferential narrow groove 1.
[0021]
The size of the chamfered portion 5 is not particularly limited, but it is preferable that the total area of the chamfered portion 5 is set to 0.5 to 5% of the groove area of the tread grounding portion. By making this area ratio 0.5% or more, the effect of the present invention can be effectively exhibited, and by making it 5% or less, the rigidity of the block or rib does not become too small, and the steering stability is lowered. Is preferable in order to suppress this. Moreover, as a chamfering size of the chamfered portion 5, for example, the chamfered surface may be chamfered so that one side along the narrow groove is 2 to 4 mm. Note that the tread contact portion indicates a region over the entire circumference of the tire with a contact width where the tire is grounded by 80% of the maximum load and the rim is assembled at 80% of the maximum air pressure according to the JATMA 2001 standard.
[0022]
As shown in FIG. 1, the groove area ratio from the tire equator line C to the vehicle outer side O is smaller than the groove area ratio from the vehicle inner side I, and the circumferential narrow groove 1 and the secondary groove forming the intersecting portion 3 having the chamfered portion 5. It is preferable that the narrow groove 2 is provided on the vehicle outer side from the tire equator line C. In this way, since the groove area ratio on the vehicle outer side O is reduced and the circumferential narrow groove 1 is provided in that portion, the uneven wear resistance of the tire can be further improved by these two factors. Since the groove area ratio on the vehicle inner side I is large, the drainage performance can be secured and the wet performance is also excellent. More preferably, the groove area ratio from the tire equator line C to the vehicle outer side O is 0.70 to 0.90 times the groove area ratio from the vehicle inner side I.
[0023]
Further, as shown in FIG. 1, an intersection portion 3 having a chamfered portion 5 is formed from the tire equator line C to an asymmetric pattern in which the vehicle inner side I is a block-tread tread pattern and the vehicle outer side O is a rib-based tread pattern. It is preferable that the circumferential narrow groove 1 and the secondary narrow groove 2 are provided on the vehicle outer side O from the tire equator line C. This is because the uneven wear resistance can be further improved by arranging the tread pattern of the rib base tone on the vehicle outer side O and providing the circumferential narrow groove 1 in that portion. Further, as shown in FIG. 1, another circumferential narrow groove 1a is also provided from the tire equator line C to the vehicle inner side I so that the vehicle inner side I from the tire equator line C has a block-tread tread pattern. It may be configured, and the rib base part exhibits uneven wear resistance, and the block base part exhibits wet performance, which is preferable.
[0024]
Furthermore, as shown in FIG. 1, by chamfering the acute angle portion 6 of the block on the vehicle inner side I from the tire equator line C, it is possible to prevent the acute angle portion 6 having low rigidity from being broken and causing partial wear. Therefore, it is preferable.
[0025]
In addition, as shown in FIG. 1, the lug grooves are arranged from the tire equator line C to the outermost rib row on the vehicle outer side O so as to stop in the middle of the ribs, thereby suppressing the step wear of the shoulder portion and improving the uneven wear resistance. Since it improves, it is preferable.
[0026]
Further, as shown in FIG. 1, there are four circumferential main grooves 8 and two circumferential

narrow grooves

1, 1 a, and an inclination that intersects the circumferential main groove 8 on the vehicle inner side I from the tire equator line C. The pneumatic tire of the present invention, in which three rows of blocks are formed by the lug grooves 9 and at least the acute angle portions 6 of the blocks of the two rows on the center side are chamfered, improves the wet performance and causes uneven wear. And tire noise can be effectively suppressed.
[0027]
Further, the four circumferential main grooves 8 are arranged so that the two are located in the range of 20 to 40% and 40 to 70% of the tread ground contact width from the tire equator line C to the outside of the tire on the vehicle inner side I. The other two are preferably arranged from the tire equator line C to the outer side of the vehicle outside O so as to be located in the range of 5 to 20% and 20 to 50% of the tread contact width. The two circumferential

narrow grooves

1a and 1 are in the range of 1 to 10% of the tread contact width from the tire equator line C to the tire outer side of the vehicle inner side I, and from the tire equator line C to the tire outer side of the vehicle outer side O. It is preferable to arrange so as to be located in the range of 60 to 90% of the width.
[0028]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.
Examples 1-2 and Comparative Examples 1-5
The tread pattern was changed as shown in FIG. 1 and FIGS. 3 to 6 to produce tires of tire size 215 / 65R15 having the structure shown in Table 1 below, and the rim was assembled on a 6.5 rim rim at an internal pressure of 200 kPa. After that, it was mounted on four wheels of a 3000 cc rear wheel drive vehicle and subjected to the following tests.
[0029]
Wet performance Running on a tire test course, increasing the speed while drawing an arc with a radius of 60m on a flat surface with an average water depth of about 10mm, measuring the critical speed, and evaluating Comparative Example 1 with an index of 100 did. The larger the value, the better.
Uneven wear resistance performance Traveling a total of 8000 km on a general road and a highway, measuring the maximum wear amount on the outside of the vehicle and the maximum wear amount on the inside of the vehicle. It was evaluated with. The larger the value, the better.
Noise performance A tire test course was run at a speed of 60 km / h, an in-vehicle sound pressure level (dB) was measured, and an evaluation with an index of Comparative Example 1 being 100 was evaluated. The larger the value, the better.
[0030]
[Table 1]

[0031]
As shown in Table 1 above, Comparative Example 1 (FIG. 3) having no circumferential narrow groove 1 and sub-fine grooves 2, Comparative Example 2 (FIG. 4) having no sub-fine grooves 2, In Comparative Example 3 (FIG. 5) and Comparative Example 4 (FIG. 6) in which all the edge portions 4 were not chamfered, sufficient improvement in noise performance was not observed. Further, in Comparative Example 5 (FIG. 1), in which the groove widths of the circumferential narrow grooves 1 and the sub-fine grooves 2 are too wide and can no longer be said to be narrow grooves, the grooves are too wide to increase the groove area. Rigidity was reduced, and uneven wear resistance was deteriorated. On the other hand, the pneumatic tires of Examples 1 and 2 (FIG. 1) of the present invention in which all the edge portions 4 of the intersecting portions 3 of the circumferential narrow grooves 1 and the sub-fine grooves 2 are linearly chamfered at the tread portion. The pattern noise was reduced and good noise performance was obtained. Further, since the groove area ratio from the tire equator line C to the vehicle outer side O is smaller than the groove area ratio of the vehicle inner side I, the vehicle inner side I adopts an asymmetric pattern in which the block tone and the vehicle outer side O adopt a rib tone. Excellent uneven wear resistance and wet performance.
[0032]
【The invention's effect】
According to the present invention, the tread surface portion of the pneumatic tire has a circumferential narrow groove and a secondary narrow groove intersecting with the circumferential narrow groove, and all edge portions of the intersecting portion of the circumferential narrow groove and the secondary narrow groove are used as the foot surface portion. By forming the chamfered portion by chamfering linearly, a pneumatic tire with reduced pattern noise can be obtained.
[Brief description of the drawings]
FIG. 1 is a plan view explanatory view of a tread pattern of a pneumatic tire according to the present invention.
FIG. 2 is a partial cross-sectional view in the direction of arrows AA in FIG.
3 is a plan view explanatory view of a tread pattern of a pneumatic tire of Comparative Example 1. FIG.
4 is a plan view explanatory diagram of a tread pattern of a pneumatic tire of Comparative Example 2. FIG.
5 is a plan view explanatory view of a tread pattern of a pneumatic tire of Comparative Example 3. FIG.
6 is a plan view explanatory view of a tread pattern of a pneumatic tire of Comparative Example 4. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Circumferential narrow groove 1a Circumferential narrow groove 2 Subfine groove 3 Intersection part 4 Edge part 5 Chamfer part 6 Sharp corner part 7 Lug groove 8 Circumferential main groove 9 Inclined lug groove C Tire equator line I Vehicle inside O Vehicle outside

Claims

The tread tread has a circumferential narrow groove and a sub-thin groove intersecting this, and all the edges of the intersecting portion of the circumferential narrow groove and the sub-thin groove are chamfered linearly at the tread. Pneumatic tire that formed part.

2. The pneumatic tire according to claim 1, wherein a groove width of the circumferential narrow groove and the secondary narrow groove is 0.3 to 2.5 mm.

The pneumatic tire according to claim 1 or 2, wherein a groove depth of the sub-fine groove is 60 to 90% of a groove depth of the circumferential fine groove.

The pneumatic tire according to any one of claims 1 to 3, wherein a depth of the chamfered portion is 10 to 40% of a groove depth of the circumferential narrow groove.

The pneumatic tire according to any one of claims 1 to 4, wherein a total area of the chamfered portion is 0.5 to 5% of a groove area of the tread grounding portion.

The groove area ratio on the vehicle outer side from the tire equator line is smaller than the groove area ratio on the vehicle inner side, and the circumferential narrow groove and the sub narrow groove are provided on the vehicle outer side from the tire equator line. A pneumatic tire given in any 1 paragraph.

7. The tire according to claim 1, wherein the inner side of the vehicle has a block pattern and the outer side of the vehicle has a rib-based asymmetric pattern, and the circumferential narrow groove and the auxiliary narrow groove are provided on the outer side of the vehicle from the tire equator line. The pneumatic tire according to claim 1.

The pneumatic tire according to claim 7, further comprising a circumferential narrow groove provided on the inner side of the vehicle from the tire equator line.

The pneumatic tire according to claim 7 or 8, wherein an acute angle portion of a block inside the vehicle is chamfered from the tire equator line.

The pneumatic tire according to any one of claims 7 to 9, wherein a lug groove is disposed in the outermost rib row outside the vehicle from the tire equator line so as to stop in the middle of the rib.

It has four circumferential main grooves and two circumferential narrow grooves, and three block rows are formed by inclined lug grooves that intersect the circumferential main grooves inside the vehicle from the tire equator line, and at least the center The pneumatic tire according to any one of claims 8 to 10, wherein the acute angle portions of the blocks in the side two rows are chamfered.

The circumferential main grooves are in the range of 20 to 40% and 40 to 70% of the tread ground contact width from the tire equator line to the tire outer side inside the vehicle, and 5 to 5% of the tread ground contact width from the tire equator line to the tire outer side of the vehicle outside. The pneumatic tire according to claim 11, which is located in a range of 20% and 20 to 50%.

The circumferential narrow groove is in the range of 1 to 10% of the tread ground contact width from the tire equator line to the tire outer side of the vehicle, and in the range of 60 to 90% of the tread ground contact width from the tire equator line to the tire outer side of the vehicle. The pneumatic tire according to claim 11 or 12, which is located.