JP2004090766A

JP2004090766A - Pneumatic tire and method for measuring vibration transmission characteristic of wheel

Info

Publication number: JP2004090766A
Application number: JP2002254053A
Authority: JP
Inventors: Takanari Saguchi; 佐口　隆成; Yasuo Osawa; 大澤　靖雄; Takafumi Sawada; 澤田　貴文; Kazuto Fujita; 藤田　一人; Arata Tomita; 冨田　　新
Original assignee: Bridgestone Corp
Current assignee: Bridgestone Corp
Priority date: 2002-08-30
Filing date: 2002-08-30
Publication date: 2004-03-25
Anticipated expiration: 2022-08-30
Also published as: JP4275371B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for improving calmness in a cabin by taking countermeasures to reduce the solid-borne noise considering the vibration transmission characteristic for each kind of wheel. <P>SOLUTION: In the pneumatic tire fitted to a wheel in which the transmission ratio to an axle of the force in the radial direction to be input in one end part in the width direction of a rim is larger than that of the force in the radial direction to be input in the other end part in the width direction of the rim, at least two circumferential grooves 2 continuously extending in the circumferential direction are formed in the tread. The total groove volume over the total circumference of the tire per unit width in the tire width direction of transverse grooves formed in a land part array 3 on the end side in the width direction fitted to the wheel and located on the side of the larger transmission ratio out of the land part arrays to be demarcated by the circumferential grooves 2 is set to be smaller than that on the end side of the other width direction. The land part array 3 is divided into a land part array section 11 on the outer side in the width direction and a land part array section 12 on the inner side in the width direction by a narrow circumferential groove 10, and a plurality of holes 13 independent from the circumferential grooves and the transverse grooves are formed in the land part array section on the inner side in the width direction. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
この発明は、乗用車に用いて好適な空気入りタイヤに関するものであり、特に、ホイールとの関連のもとに車内の静粛性を向上させる技術を提案するものである。
【０００２】
【従来の技術】
乗用車の車内の静粛性を阻害する要因としては、タイヤから発生する直接音とタイヤの振動が車内へ伝達されて発生する固体伝播音とが挙げられる。このうち固体伝播音は、タイヤが路面の凹凸により強制入力を受けて全体的に振動し、その振動が車軸を介して車体に伝播し、車内において音になるロードノイズと、タイヤのトレッドパターン自体が有する幾何学的不連続によりタイヤが振動しそれが車軸を介して車体へ伝播し、車内において音となるパターンノイズに大別される。
【０００３】
【発明が解決しようとする課題】
これらの騒音のうち、固体伝播音の増加は、従来はタイヤの弾性振動の増大に原因をおくと考えられていたので、その低減のために、タイヤそれ自体に各種の対策が講じられてきたが、結果は必ずしも満足できるものではなかった。
これがため、本発明者らは固体伝播音についての種々の研究を行ったところ、その結果、ホイールの振動特性が固体伝播音を増大させる重要な要素であると言う知見を得た。また、タイヤの車両への振動伝達は、タイヤのトレッド部、左右のサイドウォール部、左右のビード部、ホイールリム、ホイールディスク、車軸の順番に行われ、タイヤトレッドの各ショルダー部から車軸に伝達される振動伝達特性はそれぞれ異なり、その態様はホイールディスクのホイールリムに対するオフセットの方向に起因するものではなく、ホイールそのものの寸法形状によるものであることも明らかになってきた。
【０００４】
そこで本発明は、ホイールの種類ごとの振動伝達特性を考慮した上で、固体伝播音の低減対策を施して、車内の静粛性を向上することができる空気入りタイヤを提供するものである。
【０００５】
【課題を解決するための手段】
本発明に係る空気入りタイヤは、リムの幅方向の一方の端部分に入力される半径方向の力の、車軸への伝達率が、リムの幅方向の他方の端部分に入力される半径方向の力の同様の伝達率よりも大きいホイールに装着され、トレッドに、その周方向に連続して延びる少なくとも二本の周溝を設け、それらの周溝により区画される陸部列のうち、ホイールに装着されて伝達率が大きい側に位置することになる、幅方向端側の陸部列に設けられることのある横溝の、タイヤ幅方向の単位幅あたりの、タイヤの全周にわたるトータル溝容積を、他方の幅方向端側の陸部列に設けた横溝の同様のトータル溝容積よりも小さくするとともに、その陸部列を、細幅周溝により幅方向外側の陸部列部分と幅方向内側の陸部列部分とに分割し、幅方向内側の陸部列部分に、周溝および横溝から独立した複数の孔を設けてなる。
【０００６】
これによれば、ホイールに装着されて伝達率が大きい側に位置することになる、トレッドの幅方向端部側の陸部列の横溝のトータル溝容積を、他方の幅方向端部側の陸部列の横溝のトータル溝容積よりも小さくすることにより、伝達率が大きい側の陸部列の周方向の不連続成分を少なくすることができ、パターンノイズの発生を緩和、抑制することができる。また、ホイールに装着されて伝達率が大きい側に位置することになる、トレッドの幅方向端部側の陸部列を、細幅周溝により幅方向外側の陸部列部分と幅方向内側の陸部列部分とに分割し、幅方向内側の陸部列部分に、周溝および横溝から独立した複数の孔を設けて、その陸部列の圧縮剛性を低下させることにより、路面凹凸からタイヤへの入力を減少させて、車軸へ伝達される振動を抑制し、車室内に伝達されるロードノイズを低減することができる。また、細幅周溝および複数の孔は陸部列の周方向の不連続成分とはならないので、パターンノイズの発生を抑制することができる。
さらに、ホイールの振動伝達特性の小さい側に配置される陸部列には横溝を設けることにより、トレッドパターン全体での溝容積は確保でき、ウェット排水性能を確保することができる。
【０００７】
ここで好ましくは、細幅周溝の幅を、溝底からトレッド表面側にむかって漸次広くする。
【０００８】
これによれば、細幅周溝が路面上の小石等の異物をかみこんだ場合でも、その異物を外れやすくして、異物を抱き込んだまま走行することにより、偏摩耗核が幅方向内側の陸部列部分に発生することを防止することができる。
【０００９】
さらに好ましくは、幅方向内側の陸部列部分に設けた複数の孔の開口寸法を、タイヤ赤道線から遠ざかるにつれて大きくする。
【００１０】
これによれば、孔を設けた陸部列部分の圧縮剛性を、装着されるホイールの伝達率の大きい側の、接地端に近づくにつれて低下させることができ、より効果的に、路面凹凸からタイヤへの入力を減少させて、車軸へ伝達される振動を抑制し、車室内に伝達されるロードノイズを低減することができる。また、ロードノイズの低減に対し効果的な領域に孔を配置して、それ以外の部分になるべく配置しないようにする事により、それ以外の部分では操縦安定性やトレッド耐久性を良好に保つことが可能となる。
【００１１】
またここで、幅方向内側の陸部列部分に設けた複数の孔の相互の間隔を、タイヤ赤道線から遠ざかるにつれて小とすることが好ましい。
【００１２】
これによっても、孔を設けた陸部列部分の圧縮剛性を、接地端に近づくにつれて低下させることができ、より効果的に、車室内に伝達されるロードノイズを低減することができ、かつ、ロードノイズの低減に対して効果的な領域のみに孔を配置して、その他の部分の操縦安定性やトレッド耐久性を良好に保つことができる。
【００１３】
また好ましくは、幅方向内側の陸部列部分に設けた複数の孔の深さを、タイヤ赤道線から遠ざかるにつれて深くする。
【００１４】
これによっても、ロードノイズの低減効果を、接地端近傍で大きくすることができ、ロードノイズの低減に対して効果的な領域のみに孔を配置して、その他の部分の操縦安定性やトレッド耐久性を良好に保つことができる。
【００１５】
さらに、タイヤの最大負荷能力の７０％の負荷の作用下で、幅方向内側の陸部列部分の複数の孔を配置された領域の少なくとも一部が接地するようにトレッドを構成することが好ましい。
【００１６】
これによれば、例えばＦＦ車の制動時の後輪のように、前輪に比して後輪荷重が小さくなり接地幅が小さくなる場合でも、幅方向内側の陸部列部分の複数の孔を設けた領域を確実に接地させて、ロードノイズの低減効果を担保することができる。
ここで、最大負荷能力とは、ＪＡＴＭＡ、ＥＴＲＴＯ、ＴＲＡ等の規定の条件下でタイヤの負荷することが許される最大の荷重を言う。
【００１７】
さらに好ましくは、幅方向端側の陸部列部分の外側面の、タイヤ幅方向の断面内における外輪郭形状の曲率中心のうちの少なくとも一つを、その輪郭線の外側に位置させる一方、幅方向内側の陸部列部分の外輪郭形状の曲率中心を、その輪郭線の内側に位置させる。
【００１８】
これによれば、幅方向外側の陸部列部分の偏摩耗容積を減らし、外観を良好に保つことができる。
【００１９】
また、ホイールの振動伝達特性を測定するにあたっては、幅方向断面形状が赤道面に対して左右対称であるタイヤを装着したホイールを軸部材に取付け、タイヤトレッドの各ショルダー部を異なる複数の周波数にて半径方向に加振し、加振力に基づいて軸部材に生じる軸入力の、加振力に対する比率として表わされる伝達率をそれぞれ求め、各周波数ごとの伝達率の平均値を各ショルダー部ごとに求めて、それぞれの伝達率の平均値のいずれが大きいかを判定する。
【００２０】
これによれば、ホイールの伝達率の大きい側を正確に特定することができ、固体伝播音を抑制するための各種の解決手段を、効果的に適用することが可能となる。
【００２１】
さらに好ましくは、加振される周波数の帯域を３００〜１０００Ｈｚとする。
【００２２】
一般的にホイールの共振周波数は３００〜６００Ｈｚの帯域にあるため、これを含んで加振すると、さらに正確に、ホイールの伝達率の大きい側を特定することができる。
【００２３】
【発明の実施の形態】
以下に、この発明の実施の形態を図面に示すところに基づいて説明する。
図１は本発明の実施の形態を、ホイールに装着して空気圧を充填したタイヤを車両への組付姿勢としたときの正面視で示すトレッドパターンの展開図である。タイヤの内部構造は、一般的なラジアルタイヤのそれと同様であるので図示を省略する。
ここでは、トレッド１に、その周方向に連続して延びる少なくとも二本、ここでは三本の周溝２を設け、それらの周溝２により区画される陸部列のうち、ホイールに装着されて伝達率が大きい側に位置することになる、幅方向端側の陸部列３に設けられることのある横溝の（図に示すところでは横溝を設けていない）、タイヤ幅方向の単位幅あたりの、タイヤの全周にわたるトータル溝容積を、他方の幅方向端側の陸部列４に設けた横溝５の同様のトータル溝容積よりも小さくし、三本の周溝２により幅方向内側に区画される二列の陸部列６、７には、それぞれ傾斜溝８、９を設け、陸部列３に、トレッド周方向に連続して直線状に延びる細幅周溝１０を設け、この細幅周溝１０により陸部列３をトレッド幅方向に二分割する。ここでは細幅周溝１０よりトレッド幅方向端側に位置する陸部列部分１１狭幅リブとするとともに、細幅周溝１０よりトレッド幅方向内側に位置する陸部列部分１２に、周溝２、細幅周溝１０から独立した複数の孔１３を設ける。さらに陸部列部分１２にはタイヤ周方向に等間隔にてサイプ１４が設けられることもある。
【００２４】
これによれば、陸部列３の横溝のトータル溝容積を、陸部列４の横溝のトータル溝容積よりも小さくすることにより、振動伝達特性が大きい側の陸部列３の周方向の不連続成分となる横溝を相対的に少なくすることができ、横溝が接地する際に発生するパターンノイズの発生を防止することができる。また、陸部列３に、細幅周溝１０および複数の孔１３を設けることにより、陸部列３の圧縮剛性を低下させることで、路面凹凸からタイヤへの入力を減少させて、車軸へ伝達される振動を抑制し、車室内に伝達されるロードノイズを低減することができる。この際、細幅周溝１０および複数の孔１３は、横溝とは異なり、トレッド周方向に対しての不連続部分とはならないため、パターンノイズの発生をも抑制することができる。
また、陸部列４には横溝５を設けることにより、トレッドパターン全体での溝容積は確保でき、ウェット排水性能を確保することができる。
また陸部列部分１２に複数の孔を設けた上で、さらにサイプ１４を設けることで、陸部列部分１２の圧縮剛性をさらに下げることができ、これにより、ロードノイズをさらに低減することができる。
【００２５】
また、好ましくは、図２に示すところから明らかなように、細幅周溝１０の幅ｗ１０を、溝底からトレッド表面側にむかって漸次広くする。
【００２６】
これによれば、細幅周溝１０が路面上の小石等の異物をかみこんだ場合でも、その異物を外れやすくして、異物を抱き込んだまま走行することにより、偏摩耗核が細幅周溝１０の幅方向内側の陸部列部分１２に発生することを防止することができる。
【００２７】
また、好ましくは、図１に示すように、陸部列部分１２に設けた複数の孔１３の開口寸法ｄを、タイヤ赤道線から遠ざかるにつれて大きくし、複数の孔１３相互間の間隔ｗを、タイヤ赤道線Ｃから遠ざかるにつれて小とし、複数の孔１３の深さを、タイヤ赤道線から遠ざかるにつれて深くすることが好ましい。
【００２８】
これによれば、複数の孔１３を設けた陸部列部分１２のタイヤ半径方向の圧縮剛性を、装着されるホイールの伝達率の大きい側の、接地端に近づくにつれて低下させることができ、より効果的に、路面凹凸からタイヤへの入力を減少させて、車軸へ伝達される振動を抑制し、車室内に伝達されるロードノイズを低減することができる。また、ロードノイズの低減に対し効果的な領域に孔を配置して、トレッドのそれ以外の部分にはになるべく配置しないようにする事により、それ以外の部分では操縦安定性やトレッド耐久性を良好に保つことが可能となる。
【００２９】
さらに、図１に示すように、タイヤの最大負荷能力の７０％以上の負荷の作用下でのトレッドの接地幅Ｗ７０の幅方向内側に、陸部列部分１２の複数の孔１３を配置された領域を含めて、その領域の少なくとも一部が接地するようにトレッドを構成することが好ましい。
【００３０】
これによれば、例えばＦＦ車の制動時の後輪のように、前輪に比して後輪荷重が小さくなりトレッドの接地幅が小さくなる場合でも、陸部列部分１２に孔１３を設けた領域の少なくとも一部は確実に接地させて、ロードノイズの低減効果を担保することができる。
【００３１】
さらに好ましくは、図２に示すように陸部列部分１１の外側面の、タイヤ幅方向の断面内における外輪郭形状の曲率中心Ｃ１を、その輪郭線Ｓ１の外側に位置させる一方、幅方向内側の陸部列部分の外輪郭形状の曲率中心Ｃ２を、その輪郭線Ｓ２の内側に位置させる。
【００３２】
これによれば、陸部列部分１１の偏摩耗容積を減らし、外観を良好に保つことができる。
【００３３】
図３は、本発明の、ホイールの振動伝達特性を測定する方法を模式的に表わす図である。
幅方向断面形状が赤道面に対して左右対称であるタイヤ１５を装着したホイール１６をロードセル１７を装着した軸部材１８に取付け、タイヤトレッドの各ショルダー部１９、２０を異なる複数の周波数にて加振し、それらの加振力を入力Ｆ１、Ｆ２として、軸部材への入力Ｆ３を測定し、Ｆ３をＦ１、Ｆ２でそれぞれ除して求められる、伝達率α１、α２を各周波数ごとに求め、それらの伝達率α１、α２をそれぞれ平均して、伝達率α１、α２の平均値をそれぞれ求めて、それぞれの伝達率の平均値のいずれが大きいかを判定する。
【００３４】
これによれば、所定の周波数帯域における、タイヤトレッドの各ショルダー部１９、２０のどちらが、軸部材１８への入力に対して寄与が大きいかを正確に判定して、ホイールの振動伝達特性の大きい側を特定することができ、固体伝播音を抑制するためのタイヤ側の各種の解決手段を、ホイールに対し効果的に位置させて適用することが可能となる。
【００３５】
さらに好ましくは、所定の周波数帯域を３００〜１０００Ｈｚとする。
【００３６】
これによれば、さらに正確に、ホイールの伝達率の大きい側を特定することができる。
【００３７】
【実施例】
（実施例１）
本発明に係る、空気入りタイヤの、車室内騒音の低減効果を測定する目的で、サイズが２０５／６５Ｒ　１５の、図１に示すトレッドパターンを有する一種類の実施例タイヤと、図４、５に示すトレッドパターンを有する二種類の比較例タイヤとを、空気圧２００ｋＰａにて、サイズが１４×６ＪＪで裏側のほうが表側より伝達率の大きいアルミホイールに装着し、国産２０００ｃｃのＦＦ車に装着して、粗路面を６０ｋｍ／ｈで走行試験を行い、運転者の左耳の位置での３００〜８００Ｈｚの帯域値の騒音レベルを測定した。その結果を表１に示す。
【００３８】
比較例タイヤ１は、図４に示すように、トレッド５１に、その周方向に連続して延びる少なくとも二本、ここでは三本の周溝５２を設け、それらの周溝５２により区画される陸部列のうち、装着されてホイールの振動伝達特性の大きい側に配置される、幅方向端側の陸部列５３と、他方の幅方向端側の陸部列５４にそれぞれトータル溝容積が同じとなるように横溝５５、５６を設け、三本の周溝５２により幅方向内側に区画される二列の陸部列５７、５８には、それぞれ傾斜溝５９、６０を設けたものである。
【００３９】
比較例タイヤ２は、図５に示すように、実施例タイヤ１をホイールに対し表裏逆に装着したものである。
【表１】

【００４０】
表１において、比較例タイヤ１および２と実施例タイヤ１を比較すると、実施例タイヤ１は、ホイールの伝達率の大きい側に、横溝のトータル溝容積を小さくして細幅周溝と孔を設けた陸部列を位置させてホイールに装着することにより、その陸部列の圧縮剛性を低下させてロードノイズを低減し、陸部列の幾何学的不連続を少なくしてパターンノイズを低減し、固体伝播音を低減させて、車室内騒音を低減できることが分かる。
【００４１】
比較例タイヤ２は実施例タイヤ１を、ホイールの伝達率の小さい側に、横溝のトータル溝容積を小さくして細幅周溝と孔を設けた陸部列を位置させてホイールに装着させたものであるが、ホイールの伝達率の大きい側に配置される陸部列の横溝が多くなり、幾何学的不連続が増加することにより、パターンノイズが増加し、比較例タイヤ１と較べて車室内騒音がかえって悪化することが分かる。
【００４２】
（実施例２）
各種のホイールの伝達率の大きい側を特定する目的で、幅方向断面形状が赤道面に対して左右対称であるタイヤを装着した、サイズが１４×６ＪＪ、ピッチサークルディアメータが１００ｍｍで、リムに対するディスクのオフセット値が４５ｍｍである、図６に示す断面形状の、三種類のホイールＡ、Ｂ、Ｃを、ロードセルを内装した車軸部分に装着し、加振機によりタイヤトレッドの両ショルダー部をそれぞれ加振し、それらの加振力を入力とし、車軸部分で測定される力を出力として測定し、伝達率の周波数応答関数をホイールの表側と裏側とについてそれぞれ求め、各周波数ごとに伝達率の比（裏／表）を求め、３００〜１０００Ｈｚでの周波数帯域にて平均して、ホイールの振動伝達特性の大きい側を特定した。その結果を表２に示す。数値は１であれば表と裏の伝達率は同じであることを示し、１より大きければ、裏側のほうが伝達率が大きく、１より小さければ、表側のほうが伝達率が大きいことを示す。
【００４３】
【表２】

【００４４】
これによれば、ホイールの振動伝達の大きい側を正確に特定することができ、固体伝播音を抑制するための各種の解決手段を、効果的に適用することが可能となる。
【００４５】
【発明の効果】
以上に述べたところから明らかなように、この発明によれば、ホイールに装着されて伝達率が大きい側に位置することになる、幅方向端側の陸部列に設けられることのある横溝の、タイヤ幅方向の単位幅あたりの、タイヤの全周にわたるトータル溝容積を、他方の幅方向端側の陸部列に設けた横溝の同様のトータル溝容積よりも小さくするとともに、その陸部列を、細幅周溝により幅方向外側の陸部列部分と幅方向内側の陸部列部分とに分割し、幅方向内側の陸部列部分に、周溝および横溝から独立した複数の孔を設けることにより、伝達率が大きい側の陸部列の周方向の不連続成分を小さくすることができ、パターンノイズの発生を防止することができ、陸部列の周方向の不連続成分を設けることなく、その陸部列の圧縮剛性を低下させて、路面凹凸からタイヤへの入力を減少させて、車軸へ伝達される振動を抑制し、車室内に伝達されるロードノイズを低減することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態を、ホイールに装着して空気圧を充填したタイヤを車両への組付姿勢としたときの正面視で示すトレッドパターンの展開図である。
【図２】本発明のトレッドパターンの一部を示す幅方向断面図である。
【図３】本発明のホイールの振動伝達特性を測定する方法を模式的に表わす図である。
【図４】比較例タイヤの形態を、ホイールに装着して空気圧を充填したタイヤを車両への組付姿勢としたときの正面視で示すトレッドパターンの展開図である。
【図５】比較例タイヤの他の形態を、ホイールに装着して空気圧を充填したタイヤを車両への組付姿勢としたときの正面視で示すトレッドパターンの展開図である。
【図６】ホイールの断面形状を模式的に表わした図である。
【符号の説明】
１　トレッド部
２　周溝
３　陸部列
４　陸部列
５　横溝
６　陸部列
７　陸部列
８　横溝
９　横溝
１０　細幅周溝
１１　陸部列部分（幅方向外側）
１２　陸部列部分（幅方向内側）
１３　孔
１４　サイプ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pneumatic tire suitable for use in a passenger car, and more particularly, to a technique for improving quietness in a car in relation to a wheel.
[0002]
[Prior art]
Factors that hinder the quietness of a passenger car include a direct sound generated from the tire and a solid-borne sound generated by transmitting the vibration of the tire into the vehicle. Among these, the solid-borne noise vibrates as a whole when the tire receives a forced input due to the unevenness of the road surface, the vibration propagates to the vehicle body via the axle, the road noise that becomes sound inside the vehicle, and the tread pattern itself of the tire The tires vibrate due to the geometric discontinuity of the vehicle, which propagates to the vehicle body via the axle, and is roughly classified into pattern noise which becomes sound in the vehicle.
[0003]
[Problems to be solved by the invention]
Of these noises, the increase in solid-borne noise was conventionally thought to be due to the increase in elastic vibration of the tire, and various measures have been taken on the tire itself to reduce it. However, the results were not always satisfactory.
For this reason, the present inventors conducted various studies on the sound propagating through the solid, and as a result, obtained the knowledge that the vibration characteristic of the wheel is an important factor for increasing the sound propagating through the solid. In addition, vibration transmission of the tire to the vehicle is performed in the order of the tire tread, left and right sidewall, left and right bead, wheel rim, wheel disc, and axle, and transmitted from each shoulder of the tire tread to the axle. It has also become clear that the vibration transmission characteristics to be performed differ from one another, and the aspect is not due to the direction of the offset of the wheel disc with respect to the wheel rim, but to the dimensions and shape of the wheel itself.
[0004]
Accordingly, the present invention provides a pneumatic tire capable of improving the quietness in a vehicle by taking measures to reduce solid-borne noise in consideration of the vibration transmission characteristics of each wheel type.
[0005]
[Means for Solving the Problems]
In the pneumatic tire according to the present invention, the transmission rate of a radial force input to one end portion in the width direction of the rim to the axle is changed in a radial direction input to the other end portion in the width direction of the rim. The tread is provided with at least two circumferential grooves extending continuously in the circumferential direction of the tread, and the tread is provided with at least two circumferential grooves which are larger than the same transmission rate of the force. The total groove volume per unit width in the tire width direction of the lateral groove that may be provided in the land portion row on the width direction end side that is mounted on Is made smaller than the similar total groove volume of the lateral groove provided in the land portion row on the other width direction end side, and the land portion row is formed with the land portion row portion outside in the width direction by the narrow width circumferential groove and the width direction. Divided into the inner row part and the inner part in the width direction A portion, formed by providing a plurality of holes that are independent of the circumferential grooves and lateral grooves.
[0006]
According to this, the total groove volume of the lateral grooves in the land portion row on the widthwise end side of the tread, which is mounted on the wheel and located on the side with the higher transmission rate, is reduced by the land width on the other widthwise end side. By making the total groove volume smaller than the total groove volume of the horizontal groove of the row, the discontinuous component in the circumferential direction of the land row on the side with the higher transmissibility can be reduced, and the occurrence of pattern noise can be reduced and suppressed. . In addition, the land portion row at the end portion in the width direction of the tread, which is mounted on the wheel and located on the side where the transmission rate is large, the land portion row portion in the width direction outside and the land portion row in the width direction inside by the narrow circumferential groove. It is divided into a land row section and a plurality of holes independent from the circumferential groove and the lateral groove are provided in the land row section inside in the width direction to reduce the compression rigidity of the land row, thereby reducing the tire from road surface unevenness. , The vibration transmitted to the axle can be suppressed, and the road noise transmitted to the vehicle interior can be reduced. Further, since the narrow circumferential groove and the plurality of holes do not become discontinuous components in the circumferential direction of the land portion row, the occurrence of pattern noise can be suppressed.
Further, by providing the lateral groove on the land portion row arranged on the side where the vibration transmission characteristic of the wheel is small, the groove volume of the entire tread pattern can be secured, and the wet drainage performance can be secured.
[0007]
Here, preferably, the width of the narrow circumferential groove is gradually increased from the groove bottom toward the tread surface side.
[0008]
According to this, even when the narrow circumferential groove has caught foreign matter such as pebbles on the road surface, the foreign matter is easily released, and traveling while holding the foreign matter causes the uneven wear nuclei to become inward in the width direction. This can be prevented from occurring in the land row portion of the vehicle.
[0009]
More preferably, the opening dimensions of the plurality of holes provided in the land portion row portion on the inner side in the width direction are increased as the distance from the tire equator line increases.
[0010]
According to this, the compression rigidity of the land row portion provided with the holes can be reduced as it approaches the ground contact end on the side where the transmission rate of the mounted wheel is large, and more effectively, the tire can be removed from the road surface unevenness. , The vibration transmitted to the axle can be suppressed, and the road noise transmitted to the vehicle interior can be reduced. In addition, by locating holes in areas that are effective in reducing road noise, and by arranging holes as little as possible in other areas, maintaining good handling stability and tread durability in other areas Becomes possible.
[0011]
Here, it is preferable that the distance between the plurality of holes provided in the land portion row portion on the inner side in the width direction is reduced as the distance from the tire equator line increases.
[0012]
With this, the compression stiffness of the land row portion provided with the holes can be reduced as approaching the grounding end, and the road noise transmitted to the vehicle interior can be reduced more effectively, and By arranging holes only in an area effective for reducing road noise, it is possible to maintain good steering stability and tread durability of other parts.
[0013]
Preferably, the depth of the plurality of holes provided in the land row portion on the inner side in the width direction is increased as the distance from the tire equator line increases.
[0014]
In this way, the effect of reducing road noise can be increased near the grounding end. Holes are placed only in areas that are effective in reducing road noise, and steering stability and tread durability in other areas are reduced. Properties can be kept good.
[0015]
Further, it is preferable that the tread is configured such that at least a part of a region where the plurality of holes of the land portion row portion in the width direction is arranged is in contact with the ground under a load of 70% of the maximum load capacity of the tire. .
[0016]
According to this, even when the rear wheel load is smaller and the contact width is smaller than the front wheel, for example, as in the case of the rear wheel during braking of an FF vehicle, a plurality of holes in the land portion row portion on the width direction inside are reduced. The provided area can be reliably grounded, and the effect of reducing road noise can be ensured.
Here, the maximum load capacity refers to a maximum load allowed to be applied to the tire under prescribed conditions such as JATMA, ETRTO, and TRA.
[0017]
More preferably, the outer surface of the land portion row portion on the width direction end side, at least one of the centers of curvature of the outer contour shape in the cross section in the tire width direction is located outside the contour line, The center of curvature of the outer contour shape of the land row portion on the inner side in the direction is located inside the contour line.
[0018]
According to this, the uneven wear volume of the land portion row portion on the outer side in the width direction can be reduced, and the appearance can be kept good.
[0019]
Also, when measuring the vibration transmission characteristics of the wheel, a wheel equipped with a tire whose cross-sectional shape in the width direction is symmetrical to the equatorial plane is attached to the shaft member, and each shoulder of the tire tread is set to different frequencies. Vibration is applied in the radial direction, and the transmissivity expressed as a ratio of the vibrating force to the shaft input generated on the shaft member based on the vibrating force is calculated, and the average value of the transmissivity for each frequency is calculated for each shoulder. , It is determined which of the average values of the respective transmissivities is larger.
[0020]
According to this, it is possible to accurately specify the side of the wheel where the transmissibility is large, and it is possible to effectively apply various solutions for suppressing the sound propagating through the body.
[0021]
More preferably, the frequency band to be excited is 300 to 1000 Hz.
[0022]
Generally, since the resonance frequency of the wheel is in the band of 300 to 600 Hz, when the vibration including the resonance frequency is included, it is possible to more accurately specify the side of the wheel having the higher transmissivity.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a development view of a tread pattern shown in a front view when the tire according to the embodiment of the present invention mounted on a wheel and filled with pneumatic pressure is set in a mounting posture to a vehicle. Since the internal structure of the tire is the same as that of a general radial tire, the illustration is omitted.
Here, the tread 1 is provided with at least two, here three, circumferential grooves 2 extending continuously in the circumferential direction thereof, and the tread 1 is mounted on a wheel in a land portion row defined by the circumferential grooves 2. The lateral groove (which is not provided in the figure) which may be provided in the land portion row 3 on the width direction end side, which is located on the side where the transmissibility is large, has a per unit width in the tire width direction. The total groove volume over the entire circumference of the tire is made smaller than the similar total groove volume of the lateral groove 5 provided in the land portion row 4 on the other width direction end side, and is divided inward in the width direction by three circumferential grooves 2. The two land sections 6 and 7 are provided with inclined grooves 8 and 9, respectively, and the land section 3 is provided with narrow circumferential grooves 10 extending linearly continuously in the tread circumferential direction. The land row 3 is divided into two in the tread width direction by the width circumferential groove 10. Here, the land portion row portion 11 located on the end side in the tread width direction from the narrow circumferential groove 10 is a narrow rib, and the land portion row portion 12 located on the inner side in the tread width direction from the narrow circumferential groove 10 is provided with a circumferential groove. 2. A plurality of holes 13 independent of the narrow circumferential groove 10 are provided. Further, sipe 14 may be provided on land row portion 12 at equal intervals in the tire circumferential direction.
[0024]
According to this, by making the total groove volume of the horizontal grooves of the land portion row 3 smaller than the total groove volume of the horizontal grooves of the land portion row 4, the circumferential direction of the land portion row 3 on the side where the vibration transmission characteristics are large is improved. The number of horizontal grooves that are continuous components can be relatively reduced, and the generation of pattern noise that occurs when the horizontal grooves are grounded can be prevented. Also, by providing the narrow circumferential groove 10 and the plurality of holes 13 in the land portion row 3, the compression rigidity of the land portion row 3 is reduced, so that the input to the tire from the unevenness of the road surface is reduced and the land portion row 3 is connected to the axle. The transmitted vibration can be suppressed, and the road noise transmitted to the vehicle interior can be reduced. At this time, unlike the lateral groove, the narrow circumferential groove 10 and the plurality of holes 13 do not become discontinuous portions in the tread circumferential direction, so that generation of pattern noise can be suppressed.
Further, by providing the lateral grooves 5 in the land row 4, the groove volume of the entire tread pattern can be secured, and the wet drainage performance can be secured.
Further, by providing a plurality of holes in the land row portion 12 and further providing the sipes 14, the compression rigidity of the land row portion 12 can be further reduced, thereby further reducing road noise. it can.
[0025]
Preferably, the width w10 of the narrow circumferential groove 10 is gradually increased from the groove bottom toward the tread surface, as is apparent from FIG.
[0026]
According to this, even when the narrow peripheral groove 10 has caught foreign matter such as pebbles on the road surface, the foreign matter is easily released, and the uneven wear nuclei are narrowed by running while holding the foreign matter. This can be prevented from occurring in the land row portion 12 inside the circumferential groove 10 in the width direction.
[0027]
Also, preferably, as shown in FIG. 1, the opening dimension d of the plurality of holes 13 provided in the land row portion 12 increases as the distance from the tire equator increases, and the interval w between the plurality of holes 13 increases. It is preferable that the depth decreases as the distance from the tire equator C increases, and the depth of the plurality of holes 13 increases as the distance from the tire equator C increases.
[0028]
According to this, the compression rigidity in the tire radial direction of the land portion row portion 12 provided with the plurality of holes 13 can be reduced as it approaches the ground contact end on the side where the transmission rate of the mounted wheel is higher. Effectively, the input to the tire from the unevenness of the road surface is reduced, the vibration transmitted to the axle is suppressed, and the road noise transmitted to the vehicle interior can be reduced. In addition, by placing holes in the area that is effective for reducing road noise and keeping it as little as possible in other parts of the tread, steering stability and tread durability in other parts are reduced. It is possible to keep good.
[0029]
Further, as shown in FIG. 1, a plurality of holes 13 of the land portion row portion 12 are arranged on the inner side in the width direction of the tread contact width W70 under the action of a load of 70% or more of the maximum load capacity of the tire. It is preferable to configure the tread so that at least a part of the region including the region is grounded.
[0030]
According to this, the hole 13 is provided in the land row portion 12 even when the rear wheel load is smaller than the front wheel and the tread contact width is smaller than the front wheel, such as the rear wheel at the time of braking of an FF vehicle. At least a part of the region can be reliably grounded to ensure the effect of reducing road noise.
[0031]
More preferably, as shown in FIG. 2, the center of curvature C1 of the outer contour of the outer surface of the land portion row portion 11 in the cross section in the tire width direction is located outside the contour S1, while the inner side in the width direction is located. The center of curvature C2 of the outer contour of the land row portion is located inside the contour S2.
[0032]
According to this, the uneven wear volume of the land portion row portion 11 can be reduced, and the appearance can be kept good.
[0033]
FIG. 3 is a diagram schematically illustrating a method of measuring the vibration transmission characteristics of a wheel according to the present invention.
A wheel 16 on which a tire 15 having a cross section in the width direction is symmetrical with respect to the equatorial plane is mounted on a shaft member 18 on which a load cell 17 is mounted, and

shoulder portions

19 and 20 of the tire tread are applied at a plurality of different frequencies. With the vibrating forces as inputs F1 and F2, the input F3 to the shaft member is measured, and the transmissivities α1 and α2 obtained by dividing F3 by F1 and F2 are obtained for each frequency, The transmissivities α1 and α2 are respectively averaged to determine the average values of the transmissivities α1 and α2, and it is determined which of the average values of the transmissivities is larger.
[0034]
According to this, it is accurately determined which of the

shoulder portions

19 and 20 of the tire tread in the predetermined frequency band has a large contribution to the input to the shaft member 18, and the vibration transmission characteristic of the wheel is large. The tire side can be specified, and various solution means on the tire side for suppressing the solid-borne noise can be effectively positioned and applied to the wheel.
[0035]
More preferably, the predetermined frequency band is 300 to 1000 Hz.
[0036]
According to this, it is possible to more accurately specify the side with the higher transmission rate of the wheel.
[0037]
【Example】
(Example 1)
One example tire having a tread pattern shown in FIG. 1 having a size of 205 / 65R15 and having the tread pattern shown in FIG. Attach the two types of comparative tires having the tread pattern shown in Fig. 1 to an aluminum wheel with a size of 14 x 6JJ and a higher transmission rate on the back side than the front side at an air pressure of 200 kPa. A running test was performed on a rough road surface at a speed of 60 km / h, and a noise level of a band value of 300 to 800 Hz at the position of the driver's left ear was measured. Table 1 shows the results.
[0038]
As shown in FIG. 4, the comparative example tire 1 is provided with at least two, here three, circumferential grooves 52 extending continuously in the circumferential direction on a tread 51, and a land defined by the circumferential grooves 52. Among the rows, the total groove volume is equal to the land section row 53 on the width direction end side and the land section row 54 on the other width direction end which are mounted and arranged on the side where the vibration transmission characteristic of the wheel is large. The

horizontal grooves

55 and 56 are provided so that the two

land sections

57 and 58 defined on the inner side in the width direction by the three peripheral grooves 52 are provided with

inclined grooves

59 and 60, respectively.
[0039]
As shown in FIG. 5, the comparative example tire 2 was obtained by mounting the example tire 1 upside down on the wheel.
[Table 1]

[0040]
In Table 1, when the comparative example tires 1 and 2 are compared with the example tire 1, the example tire 1 has a smaller total groove volume of the lateral groove and a narrower circumferential groove and a hole on the side where the transmission rate of the wheel is larger. By positioning the land rows provided and mounting them on the wheels, the compression rigidity of the land rows is reduced to reduce road noise, and geometric discontinuities in the land rows are reduced to reduce pattern noise. However, it can be seen that the vehicle interior noise can be reduced by reducing the solid-borne noise.
[0041]
In Comparative Example Tire 2, the Example Tire 1 was mounted on the wheel with the total groove volume of the lateral grooves reduced and the land portion row provided with narrow circumferential grooves and holes positioned on the side with the lower transmission rate of the wheel. However, the number of lateral grooves in the land row arranged on the side where the transmissibility of the wheel is large increases, and the geometric discontinuity increases, so that the pattern noise increases. It turns out that the room noise worsens.
[0042]
(Example 2)
For the purpose of specifying the side with the higher transmission rate of various wheels, tires whose widthwise cross-sectional shape is symmetrical with respect to the equatorial plane are mounted, the size is 14 × 6JJ, the pitch circle diameter is 100 mm, and the Three types of wheels A, B, and C having a disk offset value of 45 mm and having the cross-sectional shape shown in FIG. 6 were mounted on the axle portion containing the load cell, and the two tread portions of the tire tread were respectively moved by a vibrator. Excitation, input those excitation forces, measure the force measured at the axle part as output, determine the frequency response function of transmissivity for the front and back sides of the wheel, respectively. The ratio (back / front) was determined and averaged in a frequency band of 300 to 1000 Hz to identify a side of the wheel having a large vibration transmission characteristic. Table 2 shows the results. A numerical value of 1 indicates that the transmissivity of the front and the back is the same, and a value greater than 1 indicates that the transmissivity of the back side is higher and a value of less than 1 indicates that the transmissivity of the front side is higher.
[0043]
[Table 2]

[0044]
According to this, it is possible to accurately specify the side of the wheel where the vibration transmission is large, and it is possible to effectively apply various solutions for suppressing the solid-borne sound.
[0045]
【The invention's effect】
As is apparent from the above description, according to the present invention, the lateral grooves which are mounted on the wheel and located on the side where the transmissibility is large and which may be provided on the land portion row on the width direction end side are described. The total groove volume per unit width in the tire width direction over the entire circumference of the tire is made smaller than the similar total groove volume of the lateral groove provided in the land portion row on the other width direction end side, and the land row Is divided into a land portion row portion on the outside in the width direction and a land portion row portion on the inside in the width direction by the narrow width circumferential groove, and a plurality of holes independent of the circumferential groove and the lateral groove are formed on the land portion row portion on the inside in the width direction. By providing, it is possible to reduce the discontinuous component in the circumferential direction of the land row on the side where the transmissibility is large, to prevent the occurrence of pattern noise, and to provide the discontinuous component in the circumferential direction of the land row. Without reducing the compression stiffness of the land row From the road surface asperities reduce the input to the tire to suppress the vibration transmitted to the axle, it is possible to reduce the road noise transmitted to the passenger compartment.
[Brief description of the drawings]
FIG. 1 is a development view of a tread pattern shown in a front view when an embodiment of the present invention is mounted on a wheel and a tire filled with air pressure is placed in a mounting posture to a vehicle.
FIG. 2 is a cross-sectional view in the width direction showing a part of the tread pattern of the present invention.
FIG. 3 is a diagram schematically illustrating a method of measuring a vibration transmission characteristic of a wheel according to the present invention.
FIG. 4 is a developed view of a tread pattern shown in a front view when the tire of the comparative example is mounted on a wheel and filled with air pressure in a mounting posture to a vehicle.
FIG. 5 is a development view of a tread pattern shown in a front view when another form of the comparative example tire is mounted on a wheel and filled with air pressure in a mounting posture to a vehicle.
FIG. 6 is a diagram schematically illustrating a cross-sectional shape of a wheel.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tread part 2 Circumferential groove 3 Land part row 4 Land part row 5 Horizontal groove 6 Land part row 7 Land part row 8 Horizontal groove 9 Horizontal groove 10 Narrow peripheral groove 11 Land part row part (width direction outside)
12 Land row part (width direction inside)
13 holes 14 sipes

Claims

The transmissibility of the radial force input to one end of the rim in the width direction to the axle is greater than the similar transmission of the radial force input to the other end of the rim in the width direction. A pneumatic tire mounted on a large wheel,
The tread is provided with at least two circumferential grooves extending continuously in the circumferential direction, and is located on the side of the land portion row defined by those circumferential grooves which is mounted on the wheel and has a high transmission rate. The total groove volume over the entire circumference of the tire per unit width in the width direction of the lateral groove that may be provided in the land portion row on the width direction end side is provided in the land portion row on the other width direction end side. While making the total groove volume smaller than the similar total groove volume of the lateral groove, the land row is divided into a land part row part on the outside in the width direction and a land part row part on the inside in the width direction by the narrow circumferential groove, and A pneumatic tire in which a plurality of holes independent of a circumferential groove and a lateral groove are provided in a land row portion.

The pneumatic tire according to claim 1, wherein the width of the narrow circumferential groove is gradually increased from the groove bottom toward the tread surface side.

The pneumatic tire according to claim 1 or 2, wherein the opening dimensions of the plurality of holes provided in the land portion row portion on the inner side in the width direction are increased as the distance from the tire equator line increases.

The pneumatic tire according to any one of claims 1 to 3, wherein a distance between the plurality of holes provided in the land row portion on the inner side in the width direction decreases as the distance from the tire equator increases.

The pneumatic tire according to any one of claims 1 to 4, wherein the depth of the plurality of holes provided in the land portion row portion on the inner side in the width direction increases as the distance from the tire equator increases.

2. The tread according to claim 1, wherein at least a part of a region where the plurality of holes of the land row portion on the width direction inner side are grounded under a load of 70% of the maximum load capacity of the tire. A pneumatic tire according to any one of claims 1 to 5.

At least one of the centers of curvature of the outer contour shape in the cross section in the tire width direction of the outer surface of the width direction outer land portion row portion is located outside the contour line, while the width direction inner land portion. The pneumatic tire according to any one of claims 1 to 6, wherein the center of curvature of the outer contour shape of the row portion is located inside the contour line.

A wheel equipped with a tire whose width direction cross section is symmetrical to the equatorial plane is attached to the shaft member, and each shoulder portion of the tire tread is excited in the radial direction at a plurality of different frequencies, based on the exciting force The transmission rate expressed as a ratio of the shaft input generated in the shaft member to the excitation force is obtained, and the average value of the transmission rate for each frequency is obtained for each shoulder portion. A method for measuring the vibration transmission characteristics of a wheel, which determines whether the wheel is large.

9. The method for measuring vibration transmission characteristics of a wheel according to claim 8, wherein a frequency band to be excited is 300 to 1000 Hz.