JP5134901B2

JP5134901B2 - Pneumatic tire

Info

Publication number: JP5134901B2
Application number: JP2007259764A
Authority: JP
Inventors: 秀永井
Original assignee: Bridgestone Corp
Current assignee: Bridgestone Corp
Priority date: 2007-10-03
Filing date: 2007-10-03
Publication date: 2013-01-30
Anticipated expiration: 2027-10-03
Also published as: JP2009083818A

Description

この発明は、トレッド部踏面に、タイヤ周方向に延びる少なくとも２本の周方向溝、及び、周方向溝により区画形成してなるリブ状陸部を具え、リブ状陸部は、周方向溝と路面とで形成される管内の共鳴により発生する騒音を低減するために路面接地域に開口した共鳴器を有し、共鳴器は、２本の周方向溝の夫々から分岐して延びる２本の枝溝部及び、枝溝部につながり、延在方向に直交する断面の面積が枝溝部のそれよりも大きい気室部を具える空気入りタイヤに関するものであり、かかる空気入りタイヤから発生する騒音を低減しつつも、石噛み防止性能の向上を図る。 The present invention comprises, on the tread portion tread, at least two circumferential grooves extending in the tire circumferential direction, and rib-like land portions formed by partitioning with the circumferential grooves. In order to reduce noise generated by resonance in the pipe formed by the road surface, the resonator has an opening opened in the road contact area, and the resonator extends from each of the two circumferential grooves. The present invention relates to a pneumatic tire including a branch groove portion and an air chamber portion having a cross-sectional area that is connected to the branch groove portion and orthogonal to the extending direction and is larger than that of the branch groove portion, and reduces noise generated from the pneumatic tire. In spite of this, the stone chewing prevention performance is improved.

近年、車両の静粛化に伴って、空気入りタイヤの負荷転動に起因した自動車騒音に対する寄与が大きくなり、その低減が求められている。中でも、高周波数、特に、１０００Ｈｚ周辺のタイヤノイズが車外騒音の主たる原因となっており、環境問題への対応からも、その低減対策が求められている。 In recent years, with the quietness of vehicles, the contribution to automobile noise resulting from load rolling of pneumatic tires has increased, and reduction thereof has been demanded. Among them, tire noise at a high frequency, particularly around 1000 Hz, is a main cause of noise outside the vehicle, and measures to reduce it are also required in response to environmental problems.

この１０００Ｈｚ周辺のタイヤノイズは、主に気柱共鳴音により発生する。気柱共鳴音とは、トレッド部踏面の周方向に連続して延びる周方向溝と、路面とによって囲曉される管内の空気の共鳴により発生する騒音であり、一般的な乗用車では８００〜１２００Ｈｚ程度に観測されることが多く、ピークの音圧レベルが高く、周波数帯域が広いことから、空気入りタイヤから発生する騒音の大部分を占めている。 The tire noise around 1000 Hz is mainly generated by air column resonance. The air column resonance sound is noise generated by resonance of air in a pipe surrounded by a circumferential groove continuously extending in the circumferential direction of the tread portion tread surface and a road surface, and is 800 to 1200 Hz in a general passenger car. It is often observed to a certain extent, and since the peak sound pressure level is high and the frequency band is wide, it accounts for most of the noise generated from pneumatic tires.

また、人間の聴覚は、１０００Ｈｚ周辺の周波数帯域（Ａ特性）で特に敏感であることから、走行時のフィーリング面での静粛性を向上させる上でも、このような気柱共鳴音の低減は有効である。 In addition, since human hearing is particularly sensitive in the frequency band (A characteristic) around 1000 Hz, the reduction of such air column resonance sound is also effective in improving the quietness of the feeling during running. It is valid.

そこで、かかる気柱共鳴音の低減を目的として、周方向溝の配設本数や容積を減じることが広く行われている他、特許文献１に開示されているように、一端だけが周方向溝に開口し、他端が陸部内で終端する長い横溝を設けて、その横溝内での反共振を用いて気柱共鳴音を低減させることが提案されている。しかし、周方向溝の溝容積を減少させた空気入りタイヤでは、周方向溝の溝容積が不足し、排水性能が低下する虞がある。また、特許文献１に記載の空気入りタイヤでは、長い横溝の配設が必須であることから、トレッドパターンのデザイン上の自由度が損なわれ、かつ、陸部の剛性が充分に確保されずに操縦安定性が低下する虞がある。 Therefore, in order to reduce the air column resonance noise, the number and the volume of the circumferential grooves are widely reduced, and as disclosed in Patent Document 1, only one circumferential groove is provided. It has been proposed to provide a long lateral groove that is open at the other end and terminates in the land portion at the other end, and to reduce air column resonance using anti-resonance in the lateral groove. However, in the pneumatic tire in which the groove volume of the circumferential groove is reduced, the groove volume of the circumferential groove is insufficient, and the drainage performance may be deteriorated. Further, in the pneumatic tire described in Patent Document 1, since it is essential to dispose long lateral grooves, the degree of freedom in designing the tread pattern is impaired, and the rigidity of the land portion is not sufficiently ensured. There is a possibility that the handling stability is lowered.

これら問題の解決策として、特許文献２又は３に記載されているように、ヘルムホルツタイプの共鳴器を配設することによって、反共振を用いて気柱共鳴音を低減する技術も提案されている。このことにより、周方向溝の溝容積を充分に確保して、排水性能を確保しつつも、特許文献１に記載の空気入りタイヤと比較して陸部の剛性を高くすることができる。 As a solution to these problems, as described in Patent Document 2 or 3, a technique for reducing air column resonance using anti-resonance by arranging a Helmholtz type resonator has been proposed. . Accordingly, the rigidity of the land portion can be increased as compared with the pneumatic tire described in Patent Document 1, while sufficiently securing the groove volume of the circumferential groove and ensuring the drainage performance.

国際公開第０４／１０３７３７号パンフレットInternational Publication No. 04/103737 Pamphlet 特開平５−３３８４１１号公報Japanese Patent Laid-Open No. 5-338411 特開２０００−１１８２０７号公報JP 2000-118207 A

しかし、特許文献２に記載の空気入りタイヤは、負荷転動時に路面に散在する石や砂利の上を通過した場合に、石や砂利がトレッド部の共鳴器内に噛み込まれて石噛みし、共鳴器の気室部が埋まることで、共鳴器としての機能が損なわれ、気柱共鳴音を低減することができなくなる虞がある。また、このとき、気柱共鳴音を低減できないばかりか、気室部に噛み込まれた石が、タイヤの回転に伴い路面に接触する度に接地音を発生させて、より大きな騒音を発生させる可能性がある。また、特許文献３に記載の空気入りタイヤは、タイヤ負荷転動時に、ヘルムホルツタイプの共鳴器が路面と接地しないように配設されていることから、共鳴器の路面との衝突によるピッチノイズの発生及び石や砂利の噛み込みを有効に防止することができ、かつ、配設可能な共鳴器の体積が小さく制限されていることから、トレッド部の陸部剛性が高く、操縦安定性を充分に確保することができるが、その反面、共鳴器の形状・寸法が限定されることから、設定可能な共鳴周波数の周波数帯域も限定されることとなり、気柱共鳴音が充分に低減されない可能性があり、それら性能が二律背反の関係にあることから、その両立が困難であった。 However, when the pneumatic tire described in Patent Document 2 passes over stones and gravel scattered on the road surface during load rolling, the stones and gravel are bitten in the resonator of the tread portion, and the stone is bitten. If the air chamber portion of the resonator is filled, the function as the resonator is impaired, and there is a possibility that the air column resonance noise cannot be reduced. In addition, at this time, not only the air column resonance noise can be reduced, but also the stone caught in the air chamber part generates a grounding sound every time it contacts the road surface with the rotation of the tire, thereby generating a larger noise. there is a possibility. Further, the pneumatic tire described in Patent Document 3 is arranged so that the Helmholtz type resonator does not come into contact with the road surface at the time of tire load rolling, so that the pitch noise caused by the collision with the road surface of the resonator is reduced. Generation and rock and gravel biting can be effectively prevented, and the volume of the resonator that can be installed is limited to a small size. However, since the shape and dimensions of the resonator are limited, the frequency band of the settable resonance frequency is also limited, and the air column resonance may not be sufficiently reduced. Since the performance is in a trade-off relationship, it is difficult to achieve both.

したがって、この発明の目的は、共鳴器の形状の適正化を図ることにより、走行時の気柱共鳴音を低減しつつも、石噛み防止性能が向上した空気入りタイヤを提供することにある。 Accordingly, an object of the present invention is to provide a pneumatic tire with improved stone biting prevention performance while reducing air column resonance noise during traveling by optimizing the shape of the resonator.

前記目的を達成するため、この発明の空気入りタイヤは、トレッド部踏面に、タイヤ周方向に延びる少なくとも２本の周方向溝、及び、周方向溝により区画形成してなるリブ状陸部を具え、リブ状陸部は、周方向溝と路面とで形成される管内の共鳴により発生する騒音を低減するために路面接地域に開口した共鳴器を有し、共鳴器は、２本の周方向溝の夫々から分岐して延びる２本の枝溝部及び、枝溝部につながり、延在方向に直交する断面の面積が枝溝部のそれよりも大きい気室部を具えており、かかる２本の枝溝部は、タイヤ周方向に対し同一方向に傾斜し、かつタイヤ赤道面に投影した形状が相互に離間してなり、枝溝部の傾斜角度は、タイヤ周方向に対し３０〜６０°の範囲内にあることを特徴とする。２本の枝溝部が夫々別の周方向溝に連通した共鳴器を配設していることから、共鳴器を配設したリブ状陸部を区画形成する２本の周方向溝にて発生する気柱共鳴音を低減することができる。また、共鳴器の気室部内に石又は砂利が噛み込んでしまった場合であっても、２本の枝溝部が、タイヤ周方向に対し同一方向に傾斜していることから、タイヤ負荷転動時にトレッド部踏面が駆動力あるいはコーナリング力によって変形する際、２本の枝溝部が同時に開き、気室部のトレッド部踏面における開口面積が大きくなるように共鳴器が変形するので、石又は砂利がトレッド部踏面から外れ易くなり、石噛み防止性能を有効に向上することが可能となる。更に、２本の枝溝部のタイヤ赤道面に投影した形状が相互に離間して配設されていることから、２本の枝溝部により気室部が全体にバランスよく開き、気室部内に噛み込まれた位置によらず石又は砂利がトレッド部踏面から外れ易くなるので、石噛み防止性能を有効に向上することが可能となる。また、石噛み防止性能の向上により、気室部に噛み込まれた石又は砂利がその近傍のゴムへとタイヤ負荷転動により繰返し押し込まれにくくなり、かかるゴム領域の亀裂の発生が抑制されるので、タイヤの耐久性を向上させることが可能となる。ここでいう「２本の枝溝部は、タイヤ周方向に対し同一方向に傾斜」とは、枝溝部が、タイヤ周方向をＹ軸、タイヤ幅方向をＸ軸とした直交座標を仮定したとき、タイヤ周方向と枝溝とのなす角のうち鋭角が、第１象限及び第３象限にある関係、または第２象限及び第４象限にある関係をいうものとする。また、タイヤ幅方向に直交する傾斜角度も含むものとする。更に、ここでいう「枝溝部の傾斜角度」とは、枝溝部が、タイヤ周方向をＹ軸、タイヤ幅方向をＸ軸とした直交座標を仮定したとき、タイヤ周方向と枝溝とのなす角のうち鋭角をいうものであり、タイヤ幅方向に直交する傾斜角度も含むものとする。 In order to achieve the above object, a pneumatic tire according to the present invention is provided with at least two circumferential grooves extending in the tire circumferential direction on a tread portion tread surface, and a rib-like land portion formed by a circumferential groove. The rib-like land portion has a resonator opened in the road contact area in order to reduce noise generated by resonance in the pipe formed by the circumferential groove and the road surface, and the resonator has two circumferential directions. Two branch grooves extending from each of the grooves, and an air chamber part connected to the branch groove part and having a cross-sectional area perpendicular to the extending direction larger than that of the branch groove part. groove is inclined in the same direction with respect to the tire circumferential direction, and Ri shape projected on the tire equatorial plane greens apart from each other, the inclination angle of the branch groove, with respect to the tire circumferential direction within a range of 30 to 60 ° It is characterized by that. Since the two branch grooves are provided with resonators that communicate with different circumferential grooves, they are generated in the two circumferential grooves that define the rib-like land where the resonators are provided. Air column resonance can be reduced. Further, even when stones or gravel is caught in the air chamber portion of the resonator, the two branch grooves are inclined in the same direction with respect to the tire circumferential direction. Sometimes when the tread surface is deformed by driving force or cornering force, the two branch grooves open at the same time, and the resonator is deformed so that the opening area of the tread surface of the air chamber is increased. It becomes easy to come off from the tread surface, and it becomes possible to effectively improve the stone biting prevention performance. In addition, since the shapes projected on the tire equatorial plane of the two branch grooves are arranged away from each other, the air chamber is opened in a balanced manner by the two branch grooves, and the air chamber is bitten in the air chamber. Since stones or gravel can easily be removed from the tread surface, regardless of the inserted position, it is possible to effectively improve the stone biting prevention performance. In addition, the improvement in stone biting prevention performance makes it difficult for stones or gravel bitten into the air chamber portion to be repeatedly pushed into the nearby rubber by tire load rolling, and the occurrence of cracks in the rubber region is suppressed. As a result, the durability of the tire can be improved. Here, “the two branch groove portions are inclined in the same direction with respect to the tire circumferential direction” means that the branch groove portions assume orthogonal coordinates with the tire circumferential direction as the Y axis and the tire width direction as the X axis. Of the angles formed by the tire circumferential direction and the branch grooves, the acute angle is in the first quadrant and the third quadrant, or in the second quadrant and the fourth quadrant. Moreover, the inclination angle orthogonal to the tire width direction is also included. Further, the “inclination angle of the branch groove portion” as used herein refers to the relationship between the tire circumferential direction and the branch groove when the branch groove portion assumes orthogonal coordinates with the tire circumferential direction as the Y axis and the tire width direction as the X axis. It means an acute angle among the angles, and includes an inclination angle orthogonal to the tire width direction.

なお、共鳴器の種類は限定されないが、例えばヘルムホルツタイプの共鳴器とすることができる。この場合、その共鳴周波数ｆ_０は、一般に図１に示すような形状として表され、枝溝部２の半径をｒ、長さをｌ_０、枝溝部の断面積をＳとし、気室部３の容積をＶ、音速をｃとしたとき、

として表すことができる。ここで、上記式中における枝溝部２端の補正は、通常は、実験によって求められるものであり、その値は、文献によって相違することになるも、ここでは、１．３ｒを用いるものとする。この場合、枝溝部２の断面が円形でないときは、枝溝部２の断面積から円形を仮定したｒを算出して使用するものとする。従って、共鳴器１の共鳴周波数ｆ_０は、枝溝部２の断面積Ｓ、気室部３の容積Ｖ等を選択することで、所要に応じて変化させることができる。 In addition, although the kind of resonator is not limited, For example, it can be set as a Helmholtz type resonator. In this case, the resonance frequency f ₀ is generally expressed as a shape as shown in FIG. 1. The radius of the branch groove 2 is r, the length is l ₀ , the cross-sectional area of the branch groove is S, and the air chamber 3 When the volume is V and the sound velocity is c,

Can be expressed as Here, the correction of the end of the branch groove portion 2 in the above formula is usually obtained by experiment, and the value thereof varies depending on the literature, but 1.3r is used here. . In this case, when the cross section of the branch groove portion 2 is not circular, r assuming the circular shape from the cross sectional area of the branch groove portion 2 is used. Therefore, the resonance frequency f ₀ of the resonator 1, by selecting the branch groove 2 cross-sectional area S, volume V and the like of the air chamber portion 3, can be changed if desired.

また、図２に示すように、共鳴器１の気室部３及び枝溝部２をそれぞれ第１管路４、第２管路５とみなして、それらを相互に連結した連結管路からなる段付きタイプの共鳴器とすることもでき、この場合の共鳴周波数ｆ_０は、以下のようにして求めることができる。 Further, as shown in FIG. 2, the air chamber portion 3 and the branch groove portion 2 of the resonator 1 are regarded as the first conduit 4 and the second conduit 5, respectively, and are connected to each other. It is also possible to use an attached type resonator, and the resonance frequency f _{0 in} this case can be obtained as follows.

段付きタイプの共鳴器につき、第１管路の延在方向に直交する断面積をＳ_１、第２管路の延在方向に直交する断面積をＳ_２、境界における第１管路４側の音響インピーダンスをＺ_１２、境界における第２管路５側の音響インピーダンスをＺ_２１とすると、連続の条件から次式が導かれる。
Ｚ_２１＝（Ｓ_２／Ｓ_１）・Ｚ_１２
第２管路５の第２管路の周方向溝に開口している部分からの距離ｘの点における音圧Ｐ_２は、境界条件を、ｘ＝０でＶ_２＝Ｖ_０ｅ^ｊｗｔとし、ｘ＝ｌ_２でＰ_２／Ｖ_２＝Ｚ_２としたとき、次式により導かれる。
Ｐ_２＝Ｚ_ｓ・{Ｚ_２１ｃｏｓ（ｋ（ｌ_２−ｘ））＋ｊＺ_ｃｓｉｎ（ｋ（ｌ_２−ｘ））／Ｚ_ｃｃｏｓ（ｋｌ_２）+ ｊＺ_２１ｓｉｎ（ｋｌ_２）}・Ｖ₀ｅ^ｊｗｔ、（ただし、ｋ＝２πｆ_０／ｃ）
このとき、Ｖ_２は第２管路５の粒子速度分布を、Ｖ₀は入力点の粒子速度を、ｊは虚数単位を、Ｚｃはρｃ（ρ：空気の密度、ｃ：音速）を夫々示している。
第１管路４の音圧Ｐ_１は、境界条件を、ｘ＝ｌ₁でＶ₁＝０とし、ｘ＝ｌ_２でＰ_２／Ｖ_２＝Ｚ_２１としたとき、次式により導かれる。
Ｐ_１＝Ｚ_ｓ・[Ｚ_２１ｃｏｓ（ｋ（ｌ_２−ｘ））／ｃｏｓ（ｋｌ₁）・｛Ｚ_ｃｃｏ（ｋｌ_２）＋ｊＺ_２１ｓｉｎ（ｋｌ_２）｝]・Ｖ_０ｅ^ｊｗｔ For the stepped resonator, the cross-sectional area perpendicular to the extending direction of the first pipe is S ₁ , the cross-sectional area perpendicular to the extending direction of the second pipe is S ₂ , and the first pipe 4 side at the boundary If the acoustic impedance of the second pipe 5 at the boundary is Z ₁₂ and the acoustic impedance of the boundary is Z ₂₁ , the following expression is derived from the continuous condition.
Z ₂₁ = (S ₂ / S ₁ ) · Z ₁₂
The sound pressure _{P 2} at a point a distance x from an opening portion in the circumferential groove of the second conduit of the second conduit 5, the boundary conditions, and _V 2 ₌ _V ^{0 e jwt} at x = 0, When x = l ₂ and P ₂ / V ₂ = Z ₂ , the following equation is derived.
_{_{_{P 2 = Z s · {Z}}} 21 cos (k (l 2 -x)) + jZ c sin (k (l 2 -x)) / Z c cos (kl 2) + jZ 21 sin (kl 2)} · V ₀ e ^jwt , where k = 2πf ₀ / c
At this time, V ₂ represents the particle velocity distribution of the second pipe 5, V ₀ represents the particle velocity at the input point, j represents the imaginary unit, and Zc represents ρc (ρ: density of air, c: sound velocity). ing.
The sound pressure _{P 1} of the first conduit 4, the boundary condition, and V ₁ = 0 at x = l _1, when the _P 2 _/ V 2 _{= Z 21} in x = _{l 2,} is guided by the following equation.
_{_{_{P 1 = Z s · [Z}}} 21 cos (k (l 2 -x)) / cos (kl 1) · {Z c co (kl 2) + jZ 21 sin (kl 2)}] · V 0 e jwt

よって、共鳴周波数ｆ_０の条件式は、共鳴の条件をｘ＝０でＰ₂＝０とした場合に、次式として導かれる。この共鳴の条件式に基づいてｋ、ｌ_１、ｌ_２、Ｓ_２、Ｓ_１、ｃを決定して共鳴周波数ｆ_０を求めることができる。
ｔａｎ（ｋｌ₁）ｔａｎ（ｋｌ₂）−（Ｓ₂／Ｓ₁）＝０ Therefore, the conditional expression of the resonance frequency f ₀ is derived as the following expression when the resonance condition is x = 0 and P ₂ = 0. Based on this resonance conditional expression, k, l ₁ , l ₂ , S ₂ , S ₁ , and c can be determined to obtain the resonance frequency f ₀ .
tan (kl ₁ ) tan (kl ₂ ) − (S ₂ / S ₁ ) = 0

また、枝溝部の傾斜角度は、より好ましくはタイヤ周方向に対し４０〜５０°の範囲内にある。 The inclination angle of the branch groove portion is more preferably in the range of 40 to 50 ° with respect to the tire circumferential direction .

更に、枝溝部が離間している離間距離が、気室部のタイヤ周方向長さの少なくとも５０％以上であることが好ましい。 Furthermore, it is preferable that the separation distance in which the branch groove portions are separated is at least 50% or more of the length in the tire circumferential direction of the air chamber portion.

更にまた、気室部は、トレッド部踏面における開口形状が略矩形状であることが好ましい。ここでいう「略矩形状」とは、４辺から構成され、全体として矩形状をなした形状をいい、例えば角部が曲率半径を有するものや、夫々の辺が湾曲しているものを含むものとする。 Furthermore, it is preferable that the air chamber portion has a substantially rectangular opening shape on the tread surface. The “substantially rectangular shape” as used herein refers to a shape that is composed of four sides and has a rectangular shape as a whole, and includes, for example, a corner portion having a radius of curvature and a curved portion on each side. Shall be.

加えて、気室部に連通する枝溝部の開口部は、気室部の対向する一対の角部に配設してなることが好ましい。なお、ここでいう「対向する一対の角部」とは、略矩形状の気室部の対角線上にある角部をいうものであり、かかる角部に曲率半径を有するものも含む。
また、気室部は、タイヤ幅方向長さよりもタイヤ周方向長さが大きい形状であることが好ましい。 In addition, it is preferable that the opening portion of the branch groove portion communicating with the air chamber portion is disposed at a pair of corner portions opposed to the air chamber portion. Here, the “pair of opposite corners” means corners on the diagonal of the substantially rectangular air chamber, and includes those having a radius of curvature at the corner.
Moreover, it is preferable that an air chamber part is a shape where a tire circumferential direction length is larger than a tire width direction length.

この発明によれば、トレッドパターンの適正化を図ることにより、走行時の気柱共鳴音を低減しつつも、石噛み防止性能を向上した空気入りタイヤを提供することが可能となる。 According to the present invention, by optimizing the tread pattern, it is possible to provide a pneumatic tire with improved stone biting prevention performance while reducing air column resonance noise during traveling.

以下、図面を参照しつつ、この発明の実施の形態を説明する。図３はこの発明に従う空気入りタイヤ（以下「タイヤ」という。）のトレッド部の一部の展開図であり、図４は、この発明に従うその他のタイヤのトレッド部の一部の展開図である。 Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a development view of a part of a tread portion of a pneumatic tire (hereinafter referred to as “tire”) according to the present invention, and FIG. 4 is a development view of a part of the tread portion of another tire according to the present invention. .

この発明のタイヤは、図３に示すように、トレッド部踏面６に、タイヤ周方向に延びる２本の周方向溝７、及び、周方向溝７により区画形成してなるリブ状陸部８を具え、かかるリブ状陸部８は、周方向溝７と路面とで形成される管内の共鳴により発生する騒音を低減するために路面接地域に開口した枝溝部２及びトレッド部踏面６における開口形状が楕円状である気室部３からなる共鳴器１を具える。また、枝溝部２は、２本の周方向溝７の夫々から分岐して延びている。かかる構成により、共鳴器１を配設したリブ状陸部８を区画形成する２本の周方向溝７にて発生する気柱共鳴音は、共鳴器１を用いて、有効に低減することができる。また、２本の枝溝部２は、タイヤ周方向に対し同一方向に傾斜しており、具体的には、タイヤ周方向と枝溝部とのなす角のうち鋭角が、第１象限及び第３象限にある。かかる構成により、共鳴器１の気室部３内に石又は砂利が噛み込んでしまった場合であっても、タイヤ負荷転動時にトレッド部踏面６が駆動力、あるいはコーナリング力によって変形する際、２本の枝溝部２が同時に開き、枝溝部２が１本である共鳴器１を配設する場合に比べ、気室部３のトレッド部踏面６における開口面積が大きくなるように変形するので、石又は砂利がトレッド部踏面６から外れ易くなり、石噛み防止性能を有効に向上することが可能となる。更に、２本の枝溝部２のタイヤ赤道面ＣＬに投影した形状が相互に離間して配設されている。２本の枝溝部２のタイヤ赤道面ＣＬに投影した形状がオーバーラップしている場合には、気室部３が２本の枝溝部２近傍にて局所的に大きく開くが、気室部を囲む陸部の剛性が位置によって大きく異なるので、石噛み防止性能も気室部３のどの位置に噛み込まれたかにより大きく異なる。それに対し、この発明のタイヤのように、枝溝部２が離間していることにより、気室部３を囲む陸部における陸部剛性の差も小さくなり、また、タイヤ負荷転動時には枝溝部２が離間した位置で開口することから、気室部３が全体にバランスよく開き、気室部３内に噛み込まれた位置に関係なく石又は砂利がトレッド部踏面６から外れ易くなるので、石噛み防止性能を有効に向上することが可能となる。また、石噛み防止性能の向上により、気室部３に噛み込まれた石又は砂利が外れ易くなるので、タイヤ負荷転動により石又は砂利がゴムに向かって繰返し押し込まれる回数が少なくなり、かかるゴム領域における亀裂の発生を抑制することができるので、タイヤの耐久性を向上させることが可能となる。 As shown in FIG. 3, the tire according to the present invention has two circumferential grooves 7 extending in the tire circumferential direction on the tread portion tread surface 6, and rib-shaped land portions 8 that are partitioned by the circumferential grooves 7. The rib-like land portion 8 has an opening shape in the branch groove portion 2 and the tread portion tread surface 6 opened in the road contact area in order to reduce noise generated by resonance in the pipe formed by the circumferential groove 7 and the road surface. Is provided with a resonator 1 composed of an air chamber portion 3 having an elliptical shape. Further, the branch groove portion 2 branches and extends from each of the two circumferential grooves 7. With this configuration, the air column resonance generated in the two circumferential grooves 7 defining the rib-like land portion 8 provided with the resonator 1 can be effectively reduced using the resonator 1. it can. Further, the two branch groove portions 2 are inclined in the same direction with respect to the tire circumferential direction, and specifically, the acute angle among the angles formed by the tire circumferential direction and the branch groove portion is the first quadrant and the third quadrant. It is in. With this configuration, even when stones or gravel is caught in the air chamber portion 3 of the resonator 1, when the tread portion tread 6 is deformed by driving force or cornering force at the time of tire load rolling, Since the two branch groove portions 2 open simultaneously and the resonator 1 having one branch groove portion 2 is disposed, the opening area in the tread portion tread surface 6 of the air chamber portion 3 is deformed so as to increase. Stone or gravel can easily come off from the tread portion tread 6, and the stone biting prevention performance can be effectively improved. Further, the shapes projected on the tire equatorial plane CL of the two branch groove portions 2 are arranged apart from each other. When the shape projected on the tire equatorial plane CL of the two branch groove portions 2 overlaps, the air chamber portion 3 opens widely in the vicinity of the two branch groove portions 2. Since the rigidity of the surrounding land portion varies greatly depending on the position, the stone biting prevention performance also varies greatly depending on where the air chamber portion 3 is bitten. On the other hand, as the tire of the present invention is separated from the branch groove portion 2, the difference in land portion rigidity in the land portion surrounding the air chamber portion 3 is also reduced, and the branch groove portion 2 during tire load rolling. Since the air chamber portion 3 opens in a well-balanced manner and the stone or gravel is easily removed from the tread portion tread surface 6 regardless of the position where the air chamber portion 3 is bitten in the air chamber portion 3. It is possible to effectively improve the biting prevention performance. Moreover, since the stone or gravel bitten into the air chamber part 3 is easily removed due to the improvement of the stone biting prevention performance, the number of times the stone or gravel is repeatedly pushed toward the rubber by the tire load rolling is reduced, and this is required. Since the occurrence of cracks in the rubber region can be suppressed, the durability of the tire can be improved.

また、枝溝部２の傾斜角度は、タイヤ周方向に対し３０〜６０°の範囲内にあることが好ましく、より好ましくは４０〜５０°の範囲内にある。枝溝部２の傾斜角度がタイヤ周方向に対し３０°未満の場合には、コーナリング走行する際に、トレッド部がタイヤ幅方向に引っ張られて、枝溝部２がタイヤ幅方向に充分に開口するので、気室部３のトレッド部踏面６における開口面積を充分に大きくして、石噛み防止性能を向上することができる。しかし、直進走行する際には、トレッド部がタイヤ周方向に引っ張られても、枝溝部２がタイヤ周方向に充分に開口せずに、気室部３のトレッド部踏面６における開口面積が充分に大きくならないので、石噛み防止性能が充分に確保されない可能性がある。一方、枝溝部２の傾斜角度がタイヤ周方向に対し６０°を超える場合には、直進走行する際に、トレッド部がタイヤ周方向に引っ張られて、枝溝部２がタイヤ周方向に充分に開口するので、気室部３のトレッド部踏面６における開口面積を充分に大きくして、石噛み防止性能を向上することができる。しかし、コーナリング走行する際には、トレッド部がタイヤ幅方向に引っ張られても、枝溝部２がタイヤ幅方向に充分に開口せずに、気室部３のトレッド部踏面６における開口面積が充分に大きくならないので、石噛み防止性能が充分に確保されない可能性がある。 Moreover, it is preferable that the inclination angle of the branch groove part 2 exists in the range of 30-60 degrees with respect to a tire circumferential direction, More preferably, it exists in the range of 40-50 degrees. When the inclination angle of the branch groove portion 2 is less than 30 ° with respect to the tire circumferential direction, the tread portion is pulled in the tire width direction and the branch groove portion 2 is sufficiently opened in the tire width direction when cornering. The opening area in the tread portion tread 6 of the air chamber portion 3 can be made sufficiently large to improve the stone biting prevention performance. However, when traveling straight, even if the tread portion is pulled in the tire circumferential direction, the branch groove portion 2 does not sufficiently open in the tire circumferential direction, and the opening area in the tread portion tread 6 of the air chamber portion 3 is sufficient. Therefore, there is a possibility that the stone biting prevention performance is not sufficiently ensured. On the other hand, when the inclination angle of the branch groove portion 2 exceeds 60 ° with respect to the tire circumferential direction, the tread portion is pulled in the tire circumferential direction when traveling straight, and the branch groove portion 2 is sufficiently opened in the tire circumferential direction. Therefore, the opening area in the tread part tread surface 6 of the air chamber part 3 can be made sufficiently large to improve the stone biting prevention performance. However, when cornering, even if the tread portion is pulled in the tire width direction, the branch groove portion 2 does not sufficiently open in the tire width direction, and the opening area in the tread portion tread 6 of the air chamber portion 3 is sufficient. Therefore, there is a possibility that the stone biting prevention performance is not sufficiently ensured.

一般に共鳴器１をトレッド部に配設する場合には、周方向溝により区画形成されたリブ状陸部内に納まる形状及び寸法とする必要がある。一般的な周方向溝の共鳴周波数である１０００Ｈｚ前後の周波数に効果を奏する共鳴器とするためには、気室部をタイヤ幅方向長さよりもタイヤ周方向長さが大きい形状とすることがパターン構成上避けがたい。かかる形状の気室部３に石又は砂利が噛み込まれると、石又は砂利がタイヤ負荷転動により路面の凹凸と引っかかることで、タイヤの進行方向に石が移動して、石又は砂利が気室部のタイヤ周方向端側に集まることとなる。また、気室部のタイヤ周方向端近傍の陸部の剛性が他の部分における陸部剛性に比べ高いことから、タイヤ負荷転動時にトレッド部踏面と路面との摩擦によるタイヤ周方向端近傍における変形量が小さく、噛み込まれた石又は砂利が外れ難くなり、気柱共鳴音を有効に低減することができなくなる虞がある。その対策として、枝溝部２が離間している離間距離Ｗ１が、気室部３のタイヤ周方向長さＷ２の少なくとも５０％以上であることが好ましい。かかる構成により、気室部３のタイヤ周方向端近傍に枝溝部２が配置されることとなり、気室部３のタイヤ周方向端近傍における陸部剛性が有意に小さくなる。また、タイヤ負荷転動時に気室部３のタイヤ周方向端近傍にて枝溝部２が開くこととなるので、気室部３のタイヤ周方向端側に集まった石又は砂利が外れ易くなり、石がみ防止性能をより向上することが可能となる。 In general, when the resonator 1 is disposed in the tread portion, it is necessary to have a shape and size that can be accommodated in a rib-like land portion defined by a circumferential groove. In order to make a resonator effective for a frequency around 1000 Hz that is a resonance frequency of a general circumferential groove, the pattern is that the air chamber portion has a shape having a tire circumferential length larger than the tire width length. Inevitable in configuration. When stone or gravel is caught in the air chamber portion 3 having such a shape, the stone or gravel is caught by road surface irregularities by rolling the tire load, so that the stone moves in the traveling direction of the tire and the stone or gravel is noticed. It will gather at the tire circumferential direction end side of the chamber. In addition, since the rigidity of the land portion in the vicinity of the tire circumferential direction end of the air chamber portion is higher than the land portion rigidity in other portions, it is near the tire circumferential direction end due to friction between the tread portion tread surface and the road surface at the time of tire load rolling. There is a possibility that the amount of deformation is small, and the bite stones or gravel are difficult to come off, and the air column resonance noise cannot be effectively reduced. As a countermeasure, it is preferable that the separation distance W1 at which the branch groove portions 2 are separated is at least 50% or more of the tire circumferential direction length W2 of the air chamber portion 3. With this configuration, the branch groove portion 2 is disposed in the vicinity of the end of the air chamber portion 3 in the tire circumferential direction, and the land portion rigidity in the vicinity of the end of the air chamber portion 3 in the tire circumferential direction is significantly reduced. Further, since the branch groove portion 2 is opened in the vicinity of the tire circumferential direction end of the air chamber portion 3 at the time of tire load rolling, stones or gravel collected on the tire circumferential direction end side of the air chamber portion 3 are easily detached, It becomes possible to further improve the anti-stone-breaking performance.

更にまた、図４に示すように、気室部３は、トレッド部踏面６における開口形状が略矩形状であり、気室部３に連通する枝溝部２の開口部は、気室部３の対向する一対の角部に配設してなることが好ましい。なぜなら、気室部３のトレッド部踏面６における開口形状が略矩形状である場合には、気室部３の対向する一対の角部に枝溝部２を配設すると、タイヤ負荷転動時に枝溝部２が大きく開き、気室部３のトレッド部踏面６における開口面積も最も大きくなるので、石噛み防止性を有効に向上することができるからである。 Furthermore, as shown in FIG. 4, the air chamber portion 3 has a substantially rectangular opening shape in the tread portion tread surface 6, and the opening portion of the branch groove portion 2 that communicates with the air chamber portion 3 corresponds to the air chamber portion 3. It is preferable to arrange at a pair of opposing corners. This is because, when the opening shape of the tread portion tread surface 6 of the air chamber portion 3 is substantially rectangular, if the branch groove portions 2 are disposed at a pair of opposing corner portions of the air chamber portion 3, branching occurs at the time of tire load rolling. This is because the groove portion 2 opens widely and the opening area of the tread portion tread surface 6 of the air chamber portion 3 becomes the largest, so that the stone biting prevention property can be effectively improved.

なお、上述したところはこの発明の実施形態の一部を示したに過ぎず、この発明の趣旨を逸脱しない限り、これらの構成を交互に組み合わせたり、種々の変更を加えたりすることができる。 The above description shows only a part of the embodiment of the present invention, and these configurations can be combined alternately or various changes can be made without departing from the gist of the present invention.

次に、１本の枝溝部を有する共鳴器を具える従来のタイヤ（従来例タイヤ）、２本の枝溝部を有する共鳴器を具える比較例のタイヤ（比較例タイヤ１〜３）及びこの発明の共鳴器を具えるタイヤ（実施例タイヤ２〜５、参考例タイヤ１，６〜８）を、タイヤサイズ２２５／５５Ｒ１７の乗用車用ラジアルタイヤとして、夫々試作し、性能評価を行ったので、以下に説明する。 Next, a conventional tire including a resonator having one branch groove (conventional tire), a comparative tire (comparative tires 1 to 3) including a resonator having two branch grooves, and this Tires having the resonator of the invention (Example tires 2 to 5, Reference example tires 1 and 6 to 8 ) were respectively prototyped as radial tires for passenger cars having a tire size of 225 / 55R17, and performance evaluation was performed. This will be described below.

従来例タイヤは、図５に示すように、矩形状の気室部及び１本の枝溝部を有する共鳴器を具えており、表１に示す諸元を有する。また、比較例タイヤ１は、図６に示すように、矩形状の気室部、及び、異なる周方向溝に同一直線上にて延在し、タイヤ幅方向に平行な２本の枝溝部を有する共鳴器を具えており、表1に示す諸元を有する。比較例タイヤ２は、図７に示すように、矩形状の気室部、及び、異なる周方向溝に延在し、タイヤ赤道面に投影した形状がオーバーラップしており、タイヤ周方向に対し同一傾斜角度にて傾斜する２本の枝溝部を有する共鳴器を具えており、表1に示す諸元を有する。比較例タイヤ３は、図８に示すように、矩形状の気室部、及び、周方向溝に平行な気室部の一辺にある角部から、同一の周方向溝に延びる２本の枝溝部を有する共鳴器を具え、表1に示す諸元を有する。実施例タイヤ２〜５及び参考例タイヤ１，６〜８は、矩形状の気室部、及び、気室部の対向する角部から、異なる周方向溝に延在し、夫々タイヤ周方向に対し２０〜９０°の範囲内で傾斜して延在している枝溝部を有する共鳴器を具えており、表１に示す諸元を有する。 As shown in FIG. 5, the conventional example tire includes a resonator having a rectangular air chamber portion and one branch groove portion, and has specifications shown in Table 1. In addition, as shown in FIG. 6, the comparative tire 1 has rectangular air chambers and two branch grooves extending on the same straight line in different circumferential grooves and parallel to the tire width direction. It has a resonator and has the specifications shown in Table 1. As shown in FIG. 7, the comparative example tire 2 extends in a rectangular air chamber portion and different circumferential grooves, and the shape projected on the tire equatorial plane overlaps with the tire circumferential direction. It has a resonator having two branch grooves inclined at the same inclination angle, and has the specifications shown in Table 1. As shown in FIG. 8, the comparative example tire 3 has two branches extending from the corner portion on one side of the rectangular air chamber portion and the air chamber portion parallel to the circumferential groove to the same circumferential groove. It has a resonator having a groove and has the specifications shown in Table 1. The example tires 2 to 5 and the reference example tires 1 and 6 to 8 extend from the rectangular air chamber portion and the opposite corner portions of the air chamber portion to different circumferential grooves, respectively in the tire circumferential direction. On the other hand, it has a resonator having a branch groove portion that is inclined and extends within a range of 20 to 90 °, and has the specifications shown in Table 1.

これら各供試タイヤをサイズ７．５Ｊ×１７．０のリムに取付けてタイヤ車輪とし、空気圧：２２０ｋＰａ（相対圧）、二名乗車相当の負荷荷重を適用し、テスト用車両に装着した状態で各種試験に供し、その性能を評価した。 Each of these test tires is attached to a rim of size 7.5J × 17.0 to make a tire wheel, air pressure: 220 kPa (relative pressure), a load load equivalent to two passengers is applied, and various types of tires are mounted on a test vehicle. It used for the test and evaluated the performance.

石噛み防止性能を評価する試験では、テスト用車両を、直径１〜１０ｍｍ程度の石及び砂利を敷き詰めた一周約３００ｍの未舗装路を６００ｍ走行させ、次いで、石及び砂利が路上に散在しておらず、直進路及びコーナリング路を含む舗装路を２０００ｍ走行させた後に、前後輪の４輪全ての気室部内に噛み込まれた石及び砂利の個数を数え、比較例タイヤ１の気室部内の石及び砂利の４輪の平均残留個数を基準値として、指数化した。なお、数値が小さいほど、石噛み防止性能に優れていることを示している。石噛み防止性能の評価結果は、表２に示す。 In the test to evaluate the stone biting prevention performance, the test vehicle is run on a non-paved road of about 300 m in a circle with stones and gravel having a diameter of about 1 to 10 mm, and then stones and gravel are scattered on the road. After traveling 2000 m on a paved road including a straight road and a cornering road, the number of stones and gravel caught in the air chambers of all four front and rear wheels was counted, and the inside of the air chamber of the comparative example tire 1 was counted. The average remaining number of stone and gravel wheels was indexed. In addition, it has shown that it is excellent in the stone biting prevention performance, so that a numerical value is small. The evaluation results of the stone biting prevention performance are shown in Table 2.

静粛性を評価する試験では、テスト用車両を長い直線部分を含む周回路及び緩やかなカーブの多いハンドリング評価路等からなるテストコース内を、低速から時速１００ｋｍ／ｈまでの範囲の速度で走行させて、気柱共鳴音の聞こえ易さ及び気になり易さをプロのドライバーがフィーリングにより評価した。 In a test to evaluate quietness, a test vehicle is run at a speed ranging from a low speed to 100 km / h on a test course consisting of a circumference circuit including a long straight portion and a handling evaluation road with many gentle curves. The professional driver evaluated the ease of hearing the air column resonance sound and the ease of concern.

表２の結果から明らかなように、実施例タイヤ２〜５及び参考例タイヤ１，６〜８は、従来例タイヤよりも石噛み防止性能が向上している。なお、実施例タイヤ３及び４における石噛み防止性能が顕著に向上していた。また、実施例タイヤ２〜５及び参考例タイヤ１，６〜８は、従来例タイヤ及び比較例タイヤ１〜３と同程度に気柱共鳴音が低減していた。 As is apparent from the results in Table 2, the example tires 2 to 5 and the reference example tires 1 and 6 to 8 have improved stone biting prevention performance than the conventional tires. In addition, the stone biting prevention performance in the Example tires 3 and 4 was remarkably improved. Moreover, in Example tires 2 to 5 and Reference example tires 1 and 6 to 8, the air column resonance sound was reduced to the same extent as that of the conventional example tires and the comparative example tires 1 to 3.

以上のことから明らかなように、共鳴器の形状の適正化を図ることにより、走行時の気柱共鳴音を低減しつつも、石噛み防止性能を向上した空気入りタイヤを提供することが可能となる。 As is clear from the above, by optimizing the shape of the resonator, it is possible to provide a pneumatic tire with improved stone biting prevention performance while reducing air column resonance noise during traveling It becomes.

ヘルムホルツタイプの共鳴器を模式的に示す図である。It is a figure which shows typically a Helmholtz type resonator. 段付きタイプの共鳴器を模式的に示す図である。It is a figure which shows a stepped type resonator typically. この発明に従うタイヤのトレッド部の一部の平面図である。It is a top view of a part of tread part of a tire according to this invention. この発明に従うその他のタイヤのトレッド部の一部の平面図である。FIG. 6 is a plan view of a part of a tread portion of another tire according to the present invention. 従来例タイヤのトレッド部の一部の平面図である。It is a top view of a part of tread part of a conventional example tire. 比較例タイヤ１のトレッド部の一部の平面図である。3 is a plan view of a part of a tread portion of a comparative tire 1. FIG. 比較例タイヤ２のトレッド部の一部の平面図である。3 is a plan view of a part of a tread portion of a comparative example tire 2. FIG. 比較例タイヤ３のトレッド部の一部の平面図である。3 is a plan view of a part of a tread portion of a comparative example tire 3. FIG.

Explanation of symbols

１共鳴器
２枝溝部
３気室部
４第１管路
５第２管路
６トレッド部踏面
７周方向溝
８リブ状陸部
ＣＬタイヤ赤道面
Ｗ１枝溝部の離間距離
Ｗ２気室部のタイヤ周方向長さ DESCRIPTION OF SYMBOLS 1 Resonator 2 Branch groove part 3 Air chamber part 4 1st pipe line 5 2nd pipe line 6 Tread part tread 7 Circumferential groove 8 Rib-like land part CL Tire equatorial plane W1 Spacing distance W2 Branch part tire circumference Direction length

Claims

The tread portion tread includes at least two circumferential grooves extending in the tire circumferential direction, and rib-shaped land portions formed by partitioning the circumferential grooves. The rib-shaped land portions include the circumferential grooves and the road surface. In order to reduce noise generated by resonance in the pipe formed by the two, the resonator has an opening in the road surface contact area, and the two resonators extend from each of the two circumferential grooves. In a pneumatic tire having a branch groove portion and an air chamber portion connected to the branch groove portion and having a cross-sectional area perpendicular to the extending direction larger than that of the branch groove portion,
Two the branches grooves are inclined in the same direction with respect to the tire circumferential direction, and Ri projected shape to the tire equatorial plane greens apart from each other,
The pneumatic tire according to claim 1, wherein an inclination angle of the branch groove portion is in a range of 30 to 60 ° with respect to a tire circumferential direction .

The pneumatic tire according to claim 1 , wherein a separation distance in which the branch groove portions are separated is at least 50% or more of a length in the tire circumferential direction of the air chamber portion.

The pneumatic tire according to claim 1 or 2 , wherein the air chamber portion has a substantially rectangular opening shape on a tread portion tread surface.

The pneumatic tire according to claim 3 , wherein the opening portion of the branch groove portion communicating with the air chamber portion is disposed at a pair of corner portions opposed to the air chamber portion.

The pneumatic tire according to any one of claims 1 to 4 , wherein the air chamber portion has a shape having a tire circumferential direction length larger than a tire width direction length .