JP4153253B2 - Pneumatic tire - Google Patents

Description

【００３６】
表の如く、実施例タイヤは、ロードノイズ性と操縦安定性とを両立して向上しているのが確認できる。
【００３７】
【発明の効果】
叙上の如く本発明は、キャップゴム部に高硬質のゴムを使用しトレッド部への拘束力を高めているため、半径方向の共振を抑えるとともに振動伝達率のピークをより高周波数側に移行させることができ、ロードノイズ性能と操縦安定性とを両立して向上させることができる。
【図面の簡単な説明】
【図１】本発明の一実施例のタイヤの断面図である。
【図２】その主要部を拡大して示す断面図である。
【図３】キャップゴム部のゴム硬度とロードノイズの関係を例示する線図である。
【符号の説明】
２ トレッド部
３ サイドウォール部
４ ビード部
５ ビードコア
６ カーカス
７ ベルト層
９ トレッド補強層
Ｇ トレッドゴム
Ｇ１ キャップゴム部
Ｇ２ ベースゴム部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire that improves both steering stability and road noise reduction.
[0002]
[Background Art and Problems to be Solved by the Invention]
Along with the higher grade and higher quality of vehicles, it is desired to reduce the so-called road noise that occurs when the running tire spreads the unevenness of the road surface and the vibration is transmitted to vibrate the air in the vehicle. . In order to reduce this road noise, conventionally, a soft rubber with a rubber hardness of about 60 to 65 degrees is used for the cap rubber portion of the tread rubber, and vibration is input by relaxing the impact force from the road surface. It is generally done to reduce.
[0003]
However, since the tread rigidity is reduced as the rubber hardness is reduced, the cornering power (CP) is inevitably lowered and the steering stability is lowered. Thus, road noise performance and steering stability have a trade-off relationship in the past, and it has been difficult to improve both of them.
[0004]
In view of such a situation, the present inventor has conducted various studies to achieve both road noise performance and steering stability. As a result, when the rubber hardness of the cap rubber part is increased contrary to the conventional case, as shown in FIG. 3, road noise performance deteriorates as the rubber hardness increases at a certain hardness. It has been found that the road noise performance is improved without exceeding, and both road noise performance and steering stability can be improved.
[0005]
This is because when the cap rubber part is hardened with a rubber hardness of 70 degrees or more, a tag-like restraining force is generated on the tread part, suppressing radial resonance, and changing the vibration transmission characteristics. This is presumed to cause a deviation from the peak of the vibration transmissibility of the vehicle, such as by shifting the peak to a higher frequency side.
[0006]
However, it has also been found that, in order to effectively exhibit such an effect, it is necessary to sufficiently secure the width of the cap rubber portion in the tire axial direction with respect to the width of the belt layer.
[0007]
That is, according to the present invention, the cap rubber portion is formed of a hard rubber having a rubber hardness of 70 ° or more, and the distance in the tire axial direction between the outer end of the cap rubber portion and the outer end of the belt layer is ensured to be 5 mm or more. The air that can improve both road noise performance and steering stability by increasing the restraint force on the tread, suppressing the resonance in the radial direction, and shifting the peak of vibration transmissibility to a higher frequency side. The purpose is to provide tires.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application includes a carcass extending from a tread portion through a sidewall portion to a bead core of the bead portion, and a belt layer disposed inside the tread portion and outside the carcass. A pneumatic tire comprising a tread reinforcing layer including
The tread rubber forming the tread portion is composed of the cap rubber portion and a base rubber portion disposed on the inner side in the radial direction and interposed between the tread reinforcing layer. Made of hard rubber with a rubber hardness (durometer A hardness) of 70-75 °,
The cap rubber portion is wider than the belt layer, and the tire axial distance between the outer end of the cap rubber portion in the tire axial direction and the outer end of the belt layer in the tire axial direction is 5 to 15 mm.
Moreover, the belt layer is characterized in that the complex elastic modulus E * of the topping rubber is 8 to 10 Mpa .
[0009]
In the invention of claim 2, the base rubber portion is made of a low heat-generating rubber having a rubber hardness (durometer A hardness) of 50 to 60 ° and a loss tangent ( tan δ) of 0.05 to 0.1. It is characterized by that.
[0010]
The invention of claim 3 is characterized in that the cap rubber part G1 has a temperature of a secondary transition point (glass transition point) Tg of the rubber of -15 ° C. or lower .
[0011]
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 illustrating a case where the pneumatic tire of the present invention is a radial tire for passenger cars, and FIG. 2 is a cross-sectional view illustrating an enlarged main portion thereof.
[0012]
In FIG. 1, a pneumatic tire 1 is disposed on a carcass 6 extending from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, inside the tread portion 2, and radially outside the carcass 6. And a tread reinforcing layer 9 including a belt layer 7.
[0013]
The carcass 6 is formed from one or more carcass plies 6A in which the carcass cords are arranged at an angle of, for example, 75 to 90 ° with respect to the tire circumferential direction, in this example, one carcass ply 6A. An organic fiber cord such as polyester is preferably employed. The carcass ply 6A is integrally provided at both ends of a ply body portion 6a straddling the bead cores 5 and 5 with a ply turn-back portion 6b that folds around the bead core 5 from the inside to the outside. A bead apex rubber 8 for bead reinforcement is arranged between the folded portion 6b.
[0014]
The bead apex rubber 8 is made of a hard rubber having a triangular cross section extending in a tapered shape from the bead core 5 toward the outer side in the tire radial direction, and in this example, in order to ensure the tire rigidity necessary as a high performance tire, The height h1 from the bead base line BL is in the range of 0.25 to 0.5 times the tire cross-section height HT. The ply turn-up portion 6b has a so-called high turn-up structure that extends beyond the bead apex rubber 8 radially outward. In this example, the ply turn-up portion 6b is terminated in the vicinity of the tire maximum width position M. ing.
[0015]
Further, in this example, the tread reinforcing layer 9 is constituted by the belt layer 7 and a band layer 10 that is placed on the outer side of the belt layer 7 and improves the high-speed durability by suppressing lifting of the belt layer 7.
[0016]
The belt layer 7 is composed of two or more belt plies 7A and 7B in this example, in which highly elastic belt cords such as steel cords are arranged at an angle of, for example, 10 to 35 ° with respect to the tire circumferential direction. Is done. Of these, the ply width BW1 of the inner belt ply 7A is larger than the ply width of the outer belt ply 7B, and the belt width of the wide ply width BW1 is 105 to 120% of the tread grounding width TW. By doing so, substantially the entire width of the tread portion 2 is firmly reinforced. The belt plies 7A and 7B are placed with different inclination directions so that the belt cords cross each other between the plies, thereby increasing the belt rigidity.
[0017]
Here, the “tread grounding width TW” means the width in the tire axial direction of the tread grounding surface that is grounded when a normal load is applied to a tire in a normal internal pressure state in which a normal rim is assembled and filled with a normal internal pressure. . The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO means “Measuring Rim”. The “regular internal pressure” is the air pressure specified by the tire for each tire. The maximum air pressure in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, If it is ETRTO, it is “INFLATION PRESSURE”, but if the tire is for a passenger car, it is 180 kPa. The “regular load” is the load specified by the standard for each tire. The maximum load capacity shown in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” is the maximum load capacity for JATMA and TRA for TRA. If it is ETRTO, it is “LOAD CAPACITY”, but if the tire is for a passenger car, the load is 88%.
[0018]
The band layer 10 is composed of one or more band plies 10A in which a band cord is spirally wound at an angle of 5 ° or less with respect to the tire circumferential direction. As this band ply 10A, a full band ply covering almost the entire width of the belt layer 7 or a narrow edge band ply covering only the outer end portion can be used. In this example, the band layer 10 is the edge band ply 2. The thing which piled up the sheet | seat is illustrated.
[0019]
Next, the tread rubber G forming the tread portion 2 includes at least a cap rubber portion G1 forming the tread surface 2S. In this example, the tread rubber G is disposed on the cap rubber portion G1 and on the radially inner side thereof. An example of a two-layer structure with a base rubber portion G2 interposed between the tread reinforcing layer 9 is illustrated.
[0020]
In the present embodiment, as shown in an enlarged view in FIG. 2, a hard rubber having a rubber hardness Hs1 (durometer A hardness) of 70 to 75 ° is used for the cap rubber part G1, and this cap rubber part. A tire axial distance LA between the tire axial outer end Ge of G1 and the tire axial outer end 7e of the belt layer 7 is set to 5 to 15 mm.
[0021]
This is because, when a hard rubber having a rubber hardness Hs1 of 70 ° or more is used for the cap rubber part G1, the cap rubber part G1 has a function of restraining the tread part 2 in a tag-like shape, and suppresses resonance in the radial direction. At the same time, the vibration transmission characteristic is changed, and the effect of causing a deviation from the peak of the vibration transmission coefficient of the vehicle, such as shifting the peak of the vibration transmission coefficient to a higher frequency side, is produced.
[0022]
This effect overcomes the influence of vibration input from the road surface that rises due to the use of hard rubber, and as a result, road noise performance can be improved.
[0023]
At this time, in order for the cap rubber part G1 to exhibit the function effectively, the cap rubber part G1 is wider than the belt layer 7 and the distance LA between the outer ends Ge and 7e is secured to 5 mm or more. Is important. This is because when the distance LA is less than 5 mm, the restraining force on the tread portion 2 becomes too small, and the road noise performance cannot be improved, for example, the effect of suppressing the resonance in the radial direction is reduced. If the distance LA exceeds 15 mm, the distortion of the joint between the cap rubber part G1 and the side wall rubber 3G increases, which is disadvantageous in terms of durability. Therefore, the distance LA is preferably in the range of 5 to 10 mm.
[0024]
The outer end Ge of the cap rubber part G1 is on the outer side in the tire axial direction from the tread grounding end Te, and the tire axial distance LB between the outer end Ge and the tread grounding end Te is 7 mm or more. More preferable from the viewpoint of restraining force.
[0025]
If the rubber hardness Hs1 of the cap rubber part G1 is less than 70 °, the restraining force is too small to improve the road noise performance. The impact sound (striking sound) increases and the passing noise property tends to deteriorate. Therefore, the rubber hardness Hs1 is preferably in the range of 70 to 73 °. In consideration of low temperature embrittlement, the temperature of the secondary transition point (glass transition point) Tg of the rubber of the cap rubber part G1 is preferably −15 ° C. or lower, more preferably −20 ° C. or lower.
[0026]
Further, as a result of the inventor's research, increasing the complex elastic modulus E * of the topping rubber of the belt layer 7 to 8 Mpa or more also has an effect of restraining the vibration of the tread portion 2 and is used together with the cap rubber portion G1. As a result, it has been found that the effect of improving road noise performance can be further enhanced. In addition, the high elasticity of the topping rubber is advantageous in improving the steering stability because the cornering power of the tire is increased as in the case of the hardening of the cap rubber part G1.
[0027]
If the complex elastic modulus E * exceeds 10 Mpa, there is a disadvantage that it is difficult to make in the process. Therefore, the complex elastic modulus E * is preferably in the range of 8 to 9.5 Mpa. The complex elastic modulus is a value measured using a viscoelastic spectrometer at Iwamoto Seisakusho under the conditions of a measurement temperature of 70 ° C., an initial strain of 10%, a dynamic strain (amplitude) of ± 2.0%, and a frequency of 10 Hz.
[0028]
In the present embodiment, the so-called tread ring composed of the tread reinforcing layer 9 and the tread rubber G is sandwiched and packed between the high-rigidity belt layer 7 and the hard rubber cap rubber portion G1. This tread ring has a high rigidity.
[0029]
As a result, a low heat-generating rubber having a rubber hardness Hs2 of 50 to 60 ° and a loss tangent (tan δ) of 0.05 to 0.1 can be adopted for the base rubber part G2, and the road noise characteristics and steering can be improved. While maintaining the improvement effect with stability, it is possible to improve the ride comfort and fuel efficiency. At this time, the ratio t1 / t2 of the thickness t1 of the cap rubber part G1 and the thickness t2 of the base rubber part G2 is preferably in the range of 1.0 to 3.0.
[0030]
When the rubber hardness Hs2 is less than 50 ° and the loss tangent (tan δ) is less than 0.05, the improvement effect of road noise and steering stability cannot be exhibited. On the other hand, when the rubber hardness Hs2 is larger than 60 ° and the loss tangent (tan δ) is larger than 0.1, the effect of improving the riding comfort and the low fuel consumption becomes insufficient.
[0031]
The tire according to the present embodiment can be suitably used for a super flat tire having a tire flatness ratio of less than 65%, which is particularly important in handling stability. As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.
[0032]
【Example】
A tire having the structure shown in FIG. 1 and having a tire size of 205 / 65R15 was made on the basis of the specifications shown in Table 1, and road noise characteristics and steering stability of each sample tire were tested. The results are shown in Table 1 . .
[0033]
(1) Road noise characteristics;
(A) The replica test tire is coasted at a speed of 60 km / H to 30 km / H on the replica road surface under the conditions of rim (6JJ × 15), internal pressure (220 kPa), and load (3.5 kN). The axial force at this time was measured, and the peak frequencies of vertical resonance were compared. The higher the peak frequency, the better the road noise.
(B) Measured test sample tires are mounted on four wheels of a vehicle (2000 cc / FF vehicle) under the conditions of rim (6JJ × 15) and internal pressure (220 kPa), and the speed of the rough asphalt road for noise evaluation The vehicle was run at 50 km / h, and evaluated by a five-point method with Comparative Example 1 as three points by sensory evaluation of the driver. A larger value is better.
[0034]
(2) Steering stability;
The cornering power was determined from the cornering force measured using an indoor tester, and the results were compared using an index with Example 3 as 100. The larger the value, the higher the cornering power and the better the steering stability.
[0035]
[Table 1]

[0036]
As shown in the table, it can be confirmed that the example tires improve both road noise performance and steering stability.
[0037]
【The invention's effect】
As described above, the present invention uses a hard rubber for the cap rubber part to increase the restraint force on the tread part, so that the resonance in the radial direction is suppressed and the peak of vibration transmissibility is shifted to the higher frequency side. It is possible to improve both road noise performance and steering stability.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a tire according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view showing the main part.
FIG. 3 is a diagram illustrating the relationship between the rubber hardness of a cap rubber part and road noise.
[Explanation of symbols]
2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 9 Tread reinforcement layer G Tread rubber G1 Cap rubber part G2 Base rubber part

Claims (3)

A pneumatic tire comprising a carcass extending from a tread portion through a sidewall portion to a bead core of a bead portion, and a tread reinforcing layer including a belt layer disposed inside the tread portion and outside the carcass,
The tread rubber forming the tread portion is composed of the cap rubber portion and a base rubber portion disposed on the inner side in the radial direction and interposed between the tread reinforcing layer. Made of hard rubber with a rubber hardness (durometer A hardness) of 70-75 °,
The cap rubber portion is wider than the belt layer, and the tire axial distance between the outer end of the cap rubber portion in the tire axial direction and the outer end of the belt layer in the tire axial direction is 5 to 15 mm.
Moreover , the pneumatic tire is characterized in that the belt layer has a complex elastic modulus E * of the topping rubber of 8 to 10 Mpa . The base rubber portion is made of a low heat-generating rubber having a rubber hardness (durometer A hardness) of 50 to 60 ° and a loss tangent ( tan δ) of 0.05 to 0.1. The described pneumatic tire.   The pneumatic tire according to claim 1 or 2, wherein the cap rubber part G1 has a rubber secondary transition point (glass transition point) Tg of -15 ° C or lower.

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