JP4256720B2 - Pneumatic tire - Google Patents

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]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire capable of ensuring steering stability and ride comfort and reducing vehicle interior noise such as road noise.
[0002]
[Prior art]
When the vehicle travels on a relatively rough road surface, noise called road noise is generated in the passenger compartment. This road noise is one of the noises related to tires. Road irregularities are input to the tire tread, causing the tires to vibrate, and this vibration follows the axle, suspension, vehicle body and propagation path, and finally the vehicle. Appears as room noise.
[0003]
As a method for reducing this road noise, there are mainly the purpose of increasing the rubber thickness of the tire tread part for the purpose of attenuating the tire vibration, reducing the rigidity of the tire side part, etc.When the rubber thickness of the tread rubber is increased, Tire mass will increase and fuel economy will deteriorate. If a technique for lowering the hardness of the tread rubber or a technique for lowering the rigidity of the tire side portion in order to ease the input from the road surface, the pattern rigidity of the tread is lowered, and the steering stability is lowered. Therefore, it has been difficult to achieve both road noise reduction 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 the tread portion is divided into three in the tire axial direction and rubbers having different hardness are used in the central region of the tread portion and the shoulder portions on both sides. ing. In this method, rubber having low hardness 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]
JP 2001-10308 A (see paragraph 0006)
[0006]
[Problems to be solved by the invention]
However, the method shown in Patent Document 1 is not limited to maintaining steering stability, and is not sufficiently satisfactory in reducing road noise and riding comfort, and it is hoped that a pneumatic tire capable of satisfying these performances will appear. It is rare.
[0007]
The present invention has been made in view of the above problems, and an object of the present invention is to provide a pneumatic tire that can ensure steering stability and ride comfort and can reduce in-vehicle sound such as road noise.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present inventor first made various studies focusing on reducing road noise. High-frequency road noise (250 Hz to 300 Hz) propagated as vehicle interior noise has a portion overlapping with tire cavity resonance, which causes vehicle interior noise. Tire cavity resonance can be avoided by shifting the vibration mode frequency or lowering the level. As the method, the modulus of the tread rubber may be changed variously, but in this case, the three-split method described in Patent Document 1 cannot be expected to provide a sufficient effect.
[0009]
Accordingly, the present inventor used FEM analysis to divide the tread portion into five regions in the tire width direction, set the rubber modulus of each region within a predetermined range, and then the longitudinal, lateral, and longitudinal rigidity at this time As a result, it was found that it is possible to provide a pneumatic tire that can sufficiently reduce road noise and sufficiently satisfy driving stability and ride comfort.
[0010]
That is, in the pneumatic tire according to the present invention, 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 tread portion. It is divided into five regions from a 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,
A) In each region, the base rubber layer has a larger rubber modulus than the cap rubber layer,
B) The cap rubber layer and the base rubber layer each have the smallest modulus in the middle region, and the modulus of the center region is set to 1.5 to 2 times the modulus of the middle region and the shoulder region. It is said.
[0011]
When the relations (a) and (a) above are mathematically expressed, the 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 intermediate in the base rubber layer are When the rubber moduli of the region Y and the shoulder region Z are Xb, Yb, Zb,
A) Xc <Xb, Yc <Yb, Zc <Zb
A) 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 above relationship is established.
[0012]
According to the above configuration, it is possible to maintain steering stability and riding comfort and reduce road noise by changing the rubber modulus of each region. This is because the tire rigidity and road noise increase rate 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, it is possible to achieve both maintenance of driving stability and riding comfort and reduction of road noise and the like. In particular, these characteristics can be maintained and improved by setting the rubber modulus in the middle region to be lower than that in the shoulder region.
[0013]
DETAILED DESCRIPTION OF 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 an essential part in the axial (width) direction of a radial tire among pneumatic tires showing an embodiment of the present invention, and illustrates 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 sidewall portions 3 extending radially outward from the bead portions, a tread portion 4 connecting the upper ends thereof, and both ends thereof are folded back by bead cores 5 along the inner periphery thereof. And a carcass 6 supported. Since the belt layer 7 is provided between the tread portion 4 and the carcass 6 and the reinforcing structure thereof is the same as that of a general radial tire, a detailed description thereof is omitted.
[0015]
The tread portion 4 has a cap-base structure composed of two layers of a cap rubber layer 10 and a base rubber layer 11 located inside thereof. A plurality of main grooves 12 extending linearly or zigzag in the tire circumferential direction are formed on the outer peripheral surface of the cap rubber layer 10 and are not shown in the cross-sectional view of the figure. A lateral groove in a direction intersecting with the main groove 12 and an auxiliary groove connecting the sub-groove and the lateral groove narrower than the main groove in the tire circumferential direction are formed to form a predetermined tread pattern.
[0016]
The cap rubber layer 10 and the base rubber layer 11 each have a center region X formed with the equator plane A sandwiched therebetween, an intermediate region Y formed on both sides of the center region X, and the intermediate region Y sandwiched therebetween. Are divided into a total of five regions, 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, the center region X, the intermediate region Y, and the shoulder region Z in the cap rubber layer 10 are indicated by 10x, 10y, and 10z. Moreover, each part of the center area | region X in the base rubber layer 11, the intermediate | middle area | region Y, and the shoulder area | region Z is shown by 10x, 10y, 10z.
[0017]
The rubber moduli (JIS K6251 M100, hereinafter the same) of the portions 10x, 10y, and 10z of the center region X, the intermediate region Y, and the shoulder region Z in the cap rubber layer 10 are defined as Xc, Yc, Zc, and the base rubber layer 11 When the rubber moduli of the respective portions 11x, 11y, and 11z of the center region X, the intermediate region Y, and the shoulder region Z are Xb, Yb, and Zb,
A) Xc <Xb, Yc <Yb, Zc <Zb
A) 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 relationship is established.
[0018]
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 divides the intermediate region Y and the shoulder region Z is set in the vicinity of the belt layer end portion. The first boundary line 15 and the second boundary line 16 are formed in pairs at symmetrical positions with the equator plane A interposed therebetween. The first boundary line 15 and the second boundary line 16 may be formed on the land portion surface of the tread portion 4.
[0019]
According to the FEM analysis, the first boundary line 15 and the second boundary line 16 are arranged within a range of 5 to 60 when the equatorial plane is 0 and the position of the tread edge is 100. It has been found that it is preferable to position the second boundary line within the range of 30-90. Furthermore, when the 1st boundary line 15 was located in the range of 30-60, and the 2nd boundary line 16 was located in the range of 70-90, the more preferable result was obtained.
[0020]
Examples of the pneumatic tire having the above-described configuration will be described. Table 1 shows the results of producing six types of radial tires and conducting evaluation tests on road noise, steering stability, and riding comfort performance.
[0021]
[Table 1]

[0022]
Examples 1 and 2 show the characteristics of a radial tire in which the cap rubber layer and the base rubber layer are divided into five regions, and the respective moduli are set within the scope of the present invention. When the cap rubber layer 10 and the base rubber layer 11 are divided into five regions of the center region X, the intermediate region Y, and the shoulder region Z, 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 cap rubber layer having a three-part structure as shown in Patent Document 1, and a base rubber layer having a five-part structure. Comparative Example 2 has a cap rubber layer and a base rubber layer having a three-part structure. Is shown. In Comparative Example 3, the cap rubber layer and the base rubber layer are both divided into five parts, but the modulus of each part is outside the scope of the present invention. In Comparative Example 4, 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 3000cc FR vehicle. Steering stability and ride comfort are evaluated by panelists. It represents with the relative value at the time of setting the comparative example 4 as 100, and it shows that steering stability and riding comfort are excellent, so that a numerical value is high.
[0025]
For road noise, a tire noise test method based on JASO C 606-81 was adopted by a stand-alone table test in which a tire alone filled with an air pressure of 220 kPa was placed 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 vertical downward when the vertical downward load is input to the tire center portion is set to 0 as Comparative Example 4, and the level difference [dB] It was evaluated by. It shows that road noise is reduced, so that a level is low (-).
[0026]
As shown in Table 1, in Examples 1 and 2 in which the cap rubber layer 10 is divided into five areas, the road noise is reduced to “−0.8” and “−1.7” in comparison with Comparative Example 4. The steering stability is maintained or improved, and the ride comfort is also good.
[0027]
On the other hand, in the comparative example 1 and the comparative example 2 of the three split type, road noise is reduced, but in the comparative example 1, the rubber modulus of the center region 10X in the cap rubber layer 10 is the middle region Y and the shoulder. Since it is not set to a predetermined range (Xc / Yc ≧ 1.5, Xc / Zc ≧ 1.5) compared to that of the region Z, the riding comfort is lower than that of the comparative example 4. Further, in Comparative Example 2, in the base rubber layer 11, the rubber modulus of the center region 11X is 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 than that of the center region Y and the shoulder region Z in the cap rubber layer 10 and the base rubber layer 11, 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 also deteriorated.
[0028]
【The invention's effect】
As is clear 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 handling stability and the riding comfort. Road noise can be reduced.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an essential part of a radial tire showing an embodiment of the present invention.
DESCRIPTION OF SYMBOLS 1 Radial tire 2 Bead part 3 Side wall part 4 Tread part 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 part X Center area Y Middle area Z Shoulder area

Claims (2)

The tread portion has a two-layer structure of a cap rubber layer on the tread surface side and a base rubber layer disposed inside the tread portion, and in the tire width direction, a center region through which the tire equatorial surface passes and a center region sandwiched And is 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 region, the base rubber layer has a larger rubber modulus than the cap rubber layer,
B) The cap rubber layer and the base rubber layer each have the smallest modulus in the middle region, and the modulus of the center region is set to 1.5 to 2 times the modulus of 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 on the inside thereof, and a center region X through which the tire equatorial plane passes in the tire width direction, and a center It is 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, and the center region X, intermediate region Y and shoulder region in the cap rubber layer If the rubber moduli of Z are Xc, Yc, Zc, and the rubber moduli of the center region X, intermediate region Y and shoulder region Z in the base rubber layer are Xb, Yb, Zb,
A) Xc <Xb, Yc <Yb, Zc <Zb
A) 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
A pneumatic tire characterized in that the rubber modulus of each region is set so that

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