JP2004345432A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of securing driveability and riding comfortability, and reducing noise in the cabin such as road noise or the like. <P>SOLUTION: The tread part 4 is divided into five areas X, Y, Z in the tire width direction, and the rubber modulus of the base rubber layers 11x, 11y, 11z is set larger than the cap rubber layer 10 in respective areas. The modulus of the middle areas 10y, 11y is set to be the minimum, the modulus of the center areas 10x, 11x is set to be 1.5 to 2 times of the modulus of the middle areas 10y, 11y and shoulder areas 10z, 11x. Driveability and riding comfortability are secured, and road noise is reduced thereby. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００２２】
実施例１，２はキャップゴム層およびベースゴム層を夫々５領域に区分し、夫々のモジュラスを本発明の範囲に設定したラジアルタイヤの諸特性を示す。キャップゴム層１０およびベースゴム層１１を、センター領域Ｘ、中間領域Ｙおよびショルダー領域Ｚの５つの領域に区分し、赤道面Ａの位置を０としトレッド端部Ｂの位置を１００とするときに、第一境界線１５を５０、第二境界線１６を８０の位置にそれぞれ設定した。
【００２３】
比較例１は、キャップゴム層について特許文献１に示すように３分割構成とし、ベースゴム層は５分割構成としたものを示し、比較例２はキャップゴム層及びベースゴム層を共に３分割構成としたものを示す。比較例３はキャップゴム層及びベースゴム層を共に５分割構成としたものの、各部位のモジュラスが本発明の範囲外のものを示す。比較例４は、キャップゴム層及びベースゴム層がそれぞれ単一のゴムを使用したものを示し、これをコントロールとして、各タイヤのロードノイズ、操縦安定性、および乗り心地性の評価を行った。
【００２４】
供試タイヤは、タイヤサイズが２３５／４５ＺＲ１７のラジアルタイヤを使用し、テスト車両は３０００ｃｃのＦＲ車を使用した。操縦安定性および乗り心地性の評価はパネラーによる官能評価である。比較例４を１００とした場合の相対値で表しており、数値が高いほど操縦安定性および乗り心地性が優れていることを示す。
【００２５】
また、ロードノイズは、空気圧２２０ｋＰａを充填したタイヤ単体を回転ドラム上において行う単体台上試験により、ＪＡＳＯ Ｃ ６０６−８１に準拠したタイヤ騒音試験方法を採用した。ただし、騒音測定は、タイヤセンター部に鉛直下向きの荷重が入力したときのタイヤホイール鉛直下向きの伝達関数の２３５Ｈｚ〜２８０Ｈｚのパーシャル平均レベルを比較例４を「０」として、そのレベル差［ｄＢ］により評価した。レベルが低い（−）であるほど、ロードノイズが低減されていることを示す。
【００２６】
表１に示すように、キャップゴム層１０を５区域に区分した実施例１、２では、いずれも比較例４に比べてロードノイズが「−０．８」「−１．７」と低減されており、操縦安定性は維持あるいは向上しており、乗り心地性も良好になっている。
【００２７】
一方、３分割タイプの比較例１および比較例２においては、ロードノイズの低減はみられるものの、比較例１は、そのキャップゴム層１０において、センター領域１０Ｘのゴムモジュラスが、中間領域Ｙおよびショルダー領域Ｚのそれに比べて所定範囲（Ｘｃ／Ｙｃ≧１．５、Ｘｃ／Ｚｃ≧１．５）に設定されていないため、乗り心地性が比較例４に比べて低下している。また、比較例２は、そのベースゴム層１１において、センター領域１１Ｘのゴムモジュラスが、中間領域Ｙおよびショルダー領域Ｚのそれに比べて所定範囲（Ｘｂ／Ｙｂ≧１．５、Ｘｂ／Ｚｂ≧１．５）に設定されていないため、操縦安定性が比較例４に比べて低下している。比較例３は、そのキャップゴム層１０およびベースゴム層１１において、中間領域Ｙのゴムモジュラスをセンター領域Ｙおよびショルダー領域Ｚのそれに比べて高く設定した例であり、本発明の範囲外に設定されている。それ故、比較例３のタイヤでは、ロードノイズは比較例４に比べて高く（０．７）なり、また、乗り心地性も悪化している。
【００２８】
【発明の効果】
以上の説明から明らかなように、本発明によると、キャップゴム層およびベースゴム層を夫々５領域に区分し、各部位のゴムモジュラスを変化させることで、操縦安定性および乗り心地性の維持とロードノイズの低減が可能となる。
【図面の簡単な説明】
【図１】本発明の実施形態を示すラジアルタイヤの要部断面図
【符号の説明】
１ ラジアルタイヤ
２ ビード部
３ サイドウォール部
４ トレッド部
５ ビードコア
６ カーカス
７ ベルト層
１０ キャップゴム層
１１ ベースゴム層
１５ 第一境界線
１６ 第二境界線
Ａ タイヤ赤道面
Ｂ トレッド端部
Ｘ センター領域
Ｙ 中間領域
Ｚ ショルダー領域[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a pneumatic tire capable of ensuring steering stability and ride comfort and reducing vehicle noise such as road noise.
[0002]
[Prior art]
When a vehicle travels on a relatively rough road surface, noise called road noise is generated in the vehicle interior. This road noise is one of the noises related to the tire, and the unevenness of the road surface is input to the tire tread and the tire vibrates, and this vibration follows the propagation path with the axle, suspension, and vehicle body, and finally the vehicle Appears as room noise.
[0003]
As a method of reducing the road noise, mainly, to increase the rubber thickness of the tire tread portion for the purpose of attenuating tire vibration, lower the rigidity of the tire side portion, and the like, but if the rubber thickness of the tread rubber is increased, The tire mass increases, and fuel efficiency and the like deteriorate. If a method of reducing the hardness of the tread rubber or a method of reducing the rigidity of the tire side portion is used to reduce the input from the road surface, the pattern rigidity of the tread is reduced, and the steering stability is reduced. Therefore, it has been difficult to achieve both a reduction in road noise and steering stability by changing the rubber composition and hardness of a single tread.
[0004]
In order to solve this problem, as shown in Patent Document 1, a method has been proposed in which a tread portion is divided into three in the tire axial direction, and rubbers having different hardnesses are used in a central region of the tread portion and shoulder regions on both sides. ing. In this method, a low-hardness rubber is used for a part of the tread portion, so that road noise and the like are reduced, and a decrease in steering stability is suppressed.
[0005]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2001-10308 (see paragraph 0006)
[0006]
[Problems to be solved by the invention]
However, the method disclosed in Japanese Patent Application Laid-Open No. H11-157556 only maintains the steering stability, does not sufficiently reduce the road noise and the riding comfort, and the appearance of a pneumatic tire that can satisfy these performances is expected. It is rare.
[0007]
The present invention has been made in view of the above circumstances, and has as its object to provide a pneumatic tire that can ensure steering stability and ride comfort and reduce vehicle interior noise such as road noise.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present inventor first made various studies with a focus on reduction of road noise. High-frequency road noise (250 Hz to 300 Hz) transmitted as vehicle interior noise has a portion that overlaps with cavity resonance of a tire, and this causes vehicle interior noise. Tire cavity resonance can be avoided by shifting or reducing the vibration mode frequency. As a method for this, it is only necessary to change the modulus of the tread rubber in various ways, but in this case, a sufficient effect cannot be expected with the three-division method described in Patent Document 1.
[0009]
Therefore, the present inventor divided the tread portion into five regions in the tire width direction using FEM analysis, set the rubber modulus in each region to a predetermined range, and set the rigidity in the longitudinal, lateral, front and rear directions at this time. It was found that a pneumatic tire capable of sufficiently reducing road noise and also having sufficiently satisfactory steering stability and ride comfort could be provided.
[0010]
That is, the pneumatic tire according to the present invention has a tread portion having a two-layer structure of a cap rubber layer on the tread surface side and a base rubber layer disposed inside the cap rubber layer, and has a tire equator in the tire width direction. The center region through which the surface passes, an intermediate region formed on both sides of the center region, and a shoulder region formed further outside the intermediate region are divided into five regions,
A) In each area, the rubber modulus of the base rubber layer is set larger than that of the cap rubber layer,
B) In each of the cap rubber layer and the base rubber layer, the modulus in the middle region is the smallest, and the modulus in the center region is set to 1.5 to 2 times the modulus in the middle region and the shoulder region. And
[0011]
When the relations of the above (a) and (a) are mathematically expressed, the respective rubber moduli of the center region X, the intermediate region Y and the shoulder region Z in the cap rubber layer are Xc, Yc and Zc, and the center region X and the intermediate region in the base rubber layer. Assuming that the rubber modulus of each of the region Y and the shoulder region Z is Xb, Yb, Zb,
A) Xc <Xb, Yc <Yb, Zc <Zb
B) Yc ≦ Zc, 1.5 * Yc ≦ Xc ≦ 2 * Yc,
1.5 * Zc ≦ Xc ≦ 2 * Zc
C) Yb ≦ Zb, 1.5 * Yb ≦ Xb ≦ 2 * Yb,
1.5 * Zb ≦ Xb ≦ 2 * Zb
The rubber modulus of each region is set so that the relationship of
[0012]
According to the above configuration, it is possible to maintain steering stability and ride comfort and reduce road noise by changing the rubber modulus in each region. This is because the rate of increase in tire stiffness and road noise with respect to the change in rubber modulus in each region, that is, the sensitivity is different. In the present invention, by utilizing these differences in sensitivity, maintenance of steering stability and ride comfort and reduction of road noise and the like are compatible. In particular, by keeping the rubber modulus in the intermediate region less than that in the shoulder region, these characteristics can be maintained and improved.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a principal part of a pneumatic tire according to an embodiment of the present invention in the axial (width) direction of a radial tire, and shows from a tire equatorial plane A to a tread end B on one side. .
[0014]
The radial tire 1 has a pair of bead portions 2 and a sidewall portion 3 extending radially outward from the bead portion, a tread portion 4 connecting the upper ends thereof, and both ends thereof being folded back by a bead core 5 along the inner periphery thereof. And a carcass 6 that is supported. Since a belt layer 7 is provided between the tread portion 4 and the carcass 6, and its reinforcing structure is the same as that of a general radial tire, a detailed description is omitted.
[0015]
The tread portion 4 has a cap-base structure including a cap rubber layer 10 and a base rubber layer 11 located inside the cap rubber layer 10. A plurality of main grooves 12 extending linearly or zigzag in the circumferential direction of the tire are formed on the outer peripheral surface of the cap rubber layer 10, and are not shown in the sectional views of the drawings. A lateral groove in the direction intersecting with the main groove 12, and an auxiliary groove connecting the auxiliary groove and the lateral groove which are narrower than the main groove in the tire circumferential direction are formed, and a predetermined tread pattern is formed.
[0016]
The cap rubber layer 10 and the base rubber layer 11 are respectively formed with a center region X formed with the equatorial plane A as a center, an intermediate region Y formed on both sides of the center region X, and a middle region Y. Are divided into a total of five regions of shoulder regions Z formed on both sides thereof. The five regions are divided by the upper and lower cap rubber layers 10 and the base rubber layer 11 so as to substantially coincide with each other. In the figure, each part of the center region X, the intermediate region Y, and the shoulder region Z in the cap rubber layer 10 is indicated by 10x, 10y, and 10z. In addition, respective portions of the center region X, the intermediate region Y, and the shoulder region Z in the base rubber layer 11 are indicated by 10x, 10y, and 10z.
[0017]
The rubber modulus (JIS K6251 M100, the same applies hereinafter) of each of the center region X, the intermediate region Y, and the shoulder region Z in the cap rubber layer 10 is Xc, Yc, Zc, and the base rubber layer 11 In the case where the rubber moduli of the respective portions 11x, 11y, 11z of the center region X, the intermediate region Y and the shoulder region Z are Xb, Yb, Zb,
A) Xc <Xb, Yc <Yb, Zc <Zb
B) Yc ≦ Zc, 1.5 * Yc ≦ Xc ≦ 2 * Yc,
1.5 * Zc ≦ Xc ≦ 2 * Zc
C) Yb ≦ Zb, 1.5 * Yb ≦ Xb ≦ 2 * Yb,
1.5 * Zb ≦ Xb ≦ 2 * Zb
Is set so that the following relationship holds.
[0018]
Further, the first boundary line 15 that separates the center region X and the intermediate region Y is formed along the bottom surface of the main groove 12. The second boundary line 16 that separates the intermediate region Y and the shoulder region Z is set near the belt layer end. The first boundary line 15 and the second boundary line 16 are respectively formed in pairs symmetrically with respect to the equatorial plane A. Note that the first boundary line 15 and the second boundary line 16 may be formed on the land surface of the tread portion 4.
[0019]
According to FEM analysis, the first boundary 15 and the second boundary 16 are arranged such that when the equator plane is 0 and the position of the tread edge is 100, the first boundary 15 is within the range of 5 to 60. It has been found that it is preferable to position the second boundary line within the range of 30 to 90. Further, when the first boundary 15 was positioned within the range of 30 to 60 and the second boundary 16 was positioned within the range of 70 to 90, more preferable results were obtained.
[0020]
An example of the pneumatic tire having the above configuration will be described. Table 1 shows the results of evaluation tests performed on road noise, steering stability, and riding comfort performance by producing six types of radial tires.
[0021]
[Table 1]

[0022]
Examples 1 and 2 show various characteristics of the radial tire in which the cap rubber layer and the base rubber layer are each divided into five regions, and each modulus is set within the range of the present invention. When the cap rubber layer 10 and the base rubber layer 11 are divided into five regions of a center region X, a middle region Y and a shoulder region Z, and the position of the equatorial plane A is 0 and the position of the tread end B is 100 , The first boundary line 15 was set at 50, and the second boundary line 16 was set at 80.
[0023]
Comparative Example 1 shows a configuration in which the cap rubber layer has a three-part configuration as shown in Patent Document 1, and a base rubber layer has a five-part configuration. Comparative Example 2 has a three-part configuration in which both the cap rubber layer and the base rubber layer are configured. Are shown. Comparative Example 3 shows the case where the cap rubber layer and the base rubber layer were both divided into five parts, but the modulus of each part was out of the range of the present invention. Comparative Example 4 shows a case in which the cap rubber layer and the base rubber layer each used a single rubber, and using this as a control, the road noise, steering stability, and riding comfort of each tire were evaluated.
[0024]
The test tire used was a radial tire having a tire size of 235 / 45ZR17, and the test vehicle was a 3000 cc FR vehicle. Evaluation of steering stability and ride comfort is a sensory evaluation by panelists. The values are shown as relative values when Comparative Example 4 is set to 100, and the higher the numerical value, the more excellent the steering stability and ride comfort.
[0025]
For the road noise, a tire noise test method based on JASO C 606-81 was adopted by a single unit test in which a single tire filled with an air pressure of 220 kPa was performed on a rotating drum. However, in the noise measurement, the partial average level of 235 Hz to 280 Hz of the transfer function of the tire wheel vertically downward when a vertically downward load was input to the tire center portion was set to “0” in Comparative Example 4, and the level difference [dB] Was evaluated. The lower the level (-), the more the road noise is reduced.
[0026]
As shown in Table 1, in Examples 1 and 2 in which the cap rubber layer 10 was divided into five sections, the road noise was reduced to “−0.8” and “−1.7” as compared with Comparative Example 4. The steering stability has been maintained or improved, and the riding comfort has also been improved.
[0027]
On the other hand, in Comparative Examples 1 and 2 of the three-split type, although the road noise is reduced, in Comparative Example 1, the rubber modulus of the center region 10X in the cap rubber layer 10 is reduced by the middle region Y and the shoulder. Since the predetermined range (Xc / Yc ≧ 1.5, Xc / Zc ≧ 1.5) is not set as compared with that of the region Z, the riding comfort is lower than that of the comparative example 4. In Comparative Example 2, in the base rubber layer 11, the rubber modulus of the center region 11X is in a predetermined range (Xb / Yb ≧ 1.5, Xb / Zb ≧ 1. Since it is not set to 5), the steering stability is lower than that of Comparative Example 4. Comparative Example 3 is an example in which the rubber modulus of the intermediate region Y is set higher in the cap rubber layer 10 and the base rubber layer 11 than those of the center region Y and the shoulder region Z, and is set outside the scope of the present invention. ing. Therefore, in the tire of Comparative Example 3, the road noise is higher (0.7) than that of Comparative Example 4, and the riding comfort is deteriorated.
[0028]
【The invention's effect】
As apparent from the above description, according to the present invention, the cap rubber layer and the base rubber layer are each divided into five regions, and the rubber modulus of each part is changed to maintain the steering stability and the riding comfort. Road noise can be reduced.
[Brief description of the drawings]
FIG. 1 is a sectional view of an essential part of a radial tire showing an embodiment of the present invention.
REFERENCE SIGNS LIST 1 radial tire 2 bead portion 3 sidewall portion 4 tread portion 5 bead core 6 carcass 7 belt layer 10 cap rubber layer 11 base rubber layer 15 first boundary line 16 second boundary line A tire equatorial plane B tread edge X center area Y Intermediate area Z Shoulder area

Claims (2)

The tread portion has a two-layer structure including a cap rubber layer on the tread surface side and a base rubber layer disposed inside the cap rubber layer, and sandwiches the center region through which the tire equatorial plane passes in the tire width direction. And divided into five regions from an intermediate region formed on both sides thereof and a shoulder region formed further outside the intermediate region,
A) In each area, the rubber modulus of the base rubber layer is set larger than that of the cap rubber layer,
B) In each of the cap rubber layer and the base rubber layer, the modulus in the middle region is the smallest, and the modulus in the center region is set to 1.5 to 2 times the modulus in the middle region and the shoulder region. And pneumatic tires. The tread portion has a two-layer structure of a cap rubber layer C on the tread surface side and a base rubber layer B disposed inside the cap rubber layer C, and a center region X through which the tire equatorial plane passes in the tire width direction; The center region X, the middle region Y and the shoulder region in the cap rubber layer are divided into five regions from an intermediate region Y formed on both sides of the region and a shoulder region Z formed further outside the intermediate region. Assuming that the respective rubber moduli of Z are Xc, Yc and Zc, and the respective rubber moduli of the center region X, the intermediate region Y and the shoulder region Z in the base rubber layer are Xb, Yb and Zb.

The pneumatic tire is characterized in that the rubber modulus of each region is set so that the following relationship is satisfied.

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