JP4643817B2 - Pneumatic tire - Google Patents

Description

【００４４】
【発明の効果】
叙上の如く本発明は、ビードエーペックスゴムの高さを２０ｍｍ以下としその小型化を図る一方、カーカスの折返し部のタイヤ軸方向外側にサイズやゴム硬度などを規制した補強エーペックスを配しているため、カーカスの本体部に作用する引張力を低減せしめ、タイヤ固有振動数の上昇を抑制し低周波側のロードノイズ性能を向上させる一方、タイヤ剛性を充分に確保でき、優れた操縦安定性を発揮しうる。
【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】ビード部を拡大して示す断面図である。
【図３】補強エーペックスをさらに拡大して示す断面図である。
【図４】従来タイヤおよびその問題点を説明する線図である。
【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
６Ａ 本体部
６Ｂ 折返し部
８ ビードエーペックスゴム
１０ 凹部
１１ 補強エーペックスゴム
１２ クリンチゴム
１３ サイドウォールゴム
２０ 重なり部
ＢＬ ビードベースライン
Ｋ１ 下辺
Ｋ２ 内の斜辺
Ｋ３ 外の斜辺[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire that can reduce road noise while exhibiting excellent steering stability.
[0002]
[Prior art]
In a pneumatic tire, as shown in FIG. 4, a bead apex rubber e made of hard rubber extending radially outward from the bead core b is usually disposed between the main body portion c1 and the folded portion c2 of the carcass c, This reinforces from the bead portion to the sidewall portion to ensure the necessary tire rigidity.
[0003]
In recent years, the bead apex rubber e tends to be increased in size in order to increase tire rigidity and improve steering stability.
[0004]
[Problems to be solved by the invention]
However, when the tire is loaded, the bead apex rubber e is greatly bent and deformed outward in the tire axial direction above the rim flange, and a tensile force is applied to the main body portion c1 of the carcass c, and compression is applied to the folded portion c2. The force acts locally. And, as the height of the bead epex rubber e is higher, the distance from the bending neutral line N of the main body part c1 and the folded part c2 becomes larger, so the tensile force and compressive force become larger.
[0005]
The increase in the tensile force acting locally on the main body c1 causes an increase in the tire natural frequency and approaches the natural vibration on the vehicle side, so that, for example, an unpleasant low-frequency road noise performance of around 125 Hz is obtained. It will make it worse.
[0006]
Thus, the steering stability and the road noise performance on the low frequency side are in a trade-off relationship, and it has been a very difficult problem to achieve both at a high level.
[0007]
Therefore, the present invention is based on the fact that the bead apex rubber has a height of 20 mm or less and is intended to reduce its size, while the reinforcing apex that regulates the size, rubber hardness, etc. is arranged on the outer side in the tire axial direction of the folded portion of the carcass. While reducing the tensile force acting on the carcass body and suppressing the increase in tire natural frequency and improving road noise performance on the low frequency side, tire rigidity can be sufficiently secured and excellent steering stability is demonstrated. The purpose is to provide a pneumatic tire.
[0008]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, the invention of claim 1 of the present application provides a folded portion that is folded from the inner side to the outer side in the tire axial direction around the bead core to a main body portion that extends from the tread portion through the sidewall portion to the bead core of the bead portion. A pneumatic tire having a bead apex rubber disposed between a carcass provided in series and a main body portion and a folded portion of the carcass,
The bead apex rubber includes a lower side along the radial outer peripheral surface of the bead core in a cross section including the tire shaft, and an inner side extending along the main body portion radially outward from an inner end in the tire axial direction of the lower side. The hypotenuse and the outer hypotenuse connecting the outer end of the hypotenuse in the radial direction and the outer end of the lower side form a triangular section, and from the lower side to the outer end of the bead apex rubber The height h1 is 20 mm or less,
And the turning height h2 from the bead base line to the radially outer end of the turning portion is 0.4 times or more of the tire cross-section height h0,
The folded portion has a bead side region substantially in contact with the outer hypotenuse and a sidewall side region that is continuous with the bead side region and substantially in contact with the main body portion is recessed inward in the tire axial direction. Forming a recess,
In addition, between the outer end of the bead apex rubber and the outer end of the folded portion from the inner end located between the outer peripheral surface of the bead core and the outer end of the bead apex rubber in the recess. the reinforcing apex rubber extending along the turnup portion in the region up to the outer end located to provided,
The carcass forms a contact area extending in contact with the main body part and the folded part, the contact area includes a linear area extending linearly, and the linear area is in the vicinity of the outer end It is characterized by starting from .
[0009]
According to a second aspect of the invention, the reinforcing apex rubber includes a rim slip preventing clinch rubber disposed in the bead portion, and a side wall rubber that is obliquely in contact with the clinch rubber at a radially outer portion and forms a sidewall portion. When the rubber hardness of the bead apex rubber is Hs1, the rubber hardness of the reinforcing apex rubber is Hs2, the rubber hardness of the clinch rubber is Hs3, and the rubber hardness of the sidewall rubber is Hs4, the following relationship is obtained: It is characterized by being satisfied.
Hs1 ≧ Hs2>Hs3> Hs4
[0010]
In the invention of claim 3, the reinforcing apex rubber has a maximum thickness position P in the vicinity of the outer end of the bead apex rubber, where the thickness in the tire axial direction is the maximum thickness tmax. The thickness is gradually reduced from the thickness position P toward the inside and outside in the radial direction, and the maximum thickness tmax is the thickness of the outer rubber from the folded portion to the tire outer surface on the tire axial line passing through the maximum thickness point P. It is characterized by being 0.25 to 0.50 times T.
[0011]
According to a fourth aspect of the present invention, the reinforcing apex rubber has a radial length L of 5 to 10 mm in the overlapping portion from the inner end to the outer end of the bead apex rubber. The sum of the thicknesses of the rubber and the bead apex rubber in the tire axial direction gradually decreases from the outer peripheral surface of the bead core toward the outer side in the radial direction. According to a fifth aspect of the invention, the reinforcing apex rubber is characterized in that the outer edge in the tire axial direction is formed in a linear shape or a convex arc shape protruding outward in the tire axial direction.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a meridian cross-sectional view in a 5% internal pressure state in which the pneumatic tire of the present invention is formed as a tire for a passenger car, assembled to a normal rim and filled with 5% of the 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 For ETRTO, use “Measuring Rim”. The “regular internal pressure” is the air pressure specified by the tire for each tire. The maximum air pressure for JATMA is the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for TRA. In the case of ETRTO, it is “INFLATION PRESSURE”, but in the case of a passenger car tire, it is 180 KPa.
[0013]
In FIG. 1, a pneumatic tire 1 includes a tread portion 2, a pair of sidewall portions 3 extending inward in the tire radial direction from both ends of the tread portion 2, and beads positioned at the inner ends of the sidewall portions 3. Part 4. A toroidal carcass 6 is bridged between the bead portions 4, 4, and a tough belt layer 7 is wound inside the tread portion 2 and radially outward of the carcass 6.
[0014]
The belt layer 7 includes two or more, for example, two inner and outer sheets in which highly elastic belt cords such as aromatic polyamide fiber cords and steel cords are arranged at an angle of 10 to 35 degrees with respect to the tire circumferential direction. It consists of belt plies 7A and 7B. The belt cords are arranged in different orientations so as to cross between the plies, thereby reinforcing the entire width of the tread portion 2 with a strong tagging effect and increasing the tread rigidity. . A band layer (not shown) in which an organic fiber cord such as nylon is spirally wound, for example, at an angle of 5 degrees or less with respect to the tire circumferential direction is formed on the outer side of the belt layer 7, and It is preferable to prevent lifting.
[0015]
The carcass 6 is formed of one or more radial structures, in this example, one carcass ply 6a in which carcass cords are arranged at an angle of 75 to 90 degrees with respect to the tire circumferential direction. As the carcass cord, an organic fiber cord selected from nylon, polyester, and rayon is suitably employed.
[0016]
The carcass is folded back on both sides of the toroidal main body portion 6A from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4 around the bead core 5 from the inner side to the outer side in the tire axial direction. Part 6B is provided in series.
[0017]
The bead core 5 has a ring shape formed by winding a bead wire (not shown). In this example, a long belt body in which a plurality of bead wires are aligned is arranged from the inner side to the outer side in the radial direction. The case of the tape bead type wound by the spiral shape is illustrated. Therefore, in this example, the bead core 5 has a rectangular cross section, and the radially outer circumferential surface S1 is arranged substantially parallel to the tire axial line. As the bead core 5, a single-wind type in which a single bead wire is continuously wound in a spiral shape can be used. At this time, it is formed into various cross-sectional shapes such as a hexagonal cross-section (including a flat hexagonal shape) and a circular cross-section. it can.
[0018]
The bead portion 4 is provided with a bead apex rubber 8 made of hard rubber that extends between the main body portion 6A and the folded portion 6B of the carcass 6 and extends outwardly in the tire radial direction from the bead core 5. Is done.
[0019]
As shown in an enlarged view in FIG. 2, the bead apex rubber 8 is formed on the main body 6 </ b> A radially outward from the lower end K <b> 1 along the outer peripheral surface S <b> 1 of the bead core 5 and the inner end in the tire axial direction of the lower side K <b> 1. An inner hypotenuse K2 extending along the outer hypotenuse that connects the outer end of the hypotenuse K2 in the radial direction (corresponding to the outer end 8E of the bead apex rubber 8) and the outer end of the lower side K1. The cross-sectional triangle shape which consists of K3 is made. In the bead apex rubber 8, the height h1 in the radial direction from the lower side K1 to the outer end 8E is greatly reduced to 20 mm or less.
[0020]
Further, the folded portion 6B of the carcass 6 is wound up radially outward while sequentially contacting the outer oblique side K2 and the main body portion 6A. That is, the folded portion 6B includes a bead side region B1 substantially in contact with the outer oblique side K2 and a sidewall side region B2 substantially in contact with the main body 6A, and the regions B1 and B2 A recess 10 that is recessed inward in the tire axial direction is formed. Here, “substantially contact” means, for example, a thin insulation rubber layer (thickness of 1.0 mm or less) between the outer hypotenuse K2 and the main body 6A for the purpose of improving adhesion. The insulation rubber layer is formed of rubber having substantially the same configuration as the topping rubber of the carcass ply.
[0021]
In this way, the bead apex rubber 8 is extremely miniaturized, and the main body portion 6A and the folded portion 6B of the carcass 6 extend substantially in contact with each other outward in the radial direction from the outer end 8E. Region Y is formed.
[0022]
As a result, in the main body portion 6A and the folded portion 6B, the distance from the bending neutral line N when a load is applied is reduced, and the tensile force acting locally on the main body portion 6A during bending deformation is reduced. Moreover, in the contact area Y, the main body portion 6A and the folded portion 6B are integrated and the rigidity thereof is increased, so that the bending neutral line N can be shifted to the inner side in the tire axial direction toward the main body portion 6A. The distortion itself at the time of bending deformation can also be reduced. Accordingly, it is possible to greatly reduce the tensile force acting on the main body 6A, suppress an increase in the tire natural frequency, and improve road noise performance on the low frequency side.
[0023]
At this time, in order to increase the rigidity, it is necessary to form the contact area Y within a certain range. For this reason, the folded height h2 from the bead base line BL of the outer end 6E of the folded portion 6B is set. The tire cross-section height h0 is 0.4 times or more. Here, the “bead base line BL” is defined as a tire axial direction line passing through a rim diameter defined by a standard such as JATMA.
[0024]
In the case where the carcass 6 is formed of a plurality of carcass plies, the folding height h2 of at least one carcass ply is within the above range. The upper limit of the folding height h2 is not particularly limited, but normally, the outer end 6E is generally terminated at a lower position than the outer end of the belt layer 7 in the tire axial direction.
[0025]
Also in this embodiment, the contact area Y comprises a straight area portion Y1 extending linearly, the linear range portion Y1 is Ru begins from the vicinity of the outer end 8E. In such a case, the carcass cord path in the main body 6A is shortened, the amount of bending deformation at the time of loading is further reduced, and the tensile force of the carcass cord is made uniform, which is more advantageous for the road noise performance. .
[0026]
Next, a reinforcing apex 11 made of hard rubber is disposed in the recess 10 and reinforces from the bead portion 4 to the sidewall portion 3.
[0027]
The reinforcing apex 11 has an inner end 11a positioned between the outer peripheral surface S1 of the bead core 5 and the outer end 8E of the bead apex rubber 5, and the outer end 8E of the bead apex rubber 8 and the folded portion 6B. It extends along the folded portion 6B in a region up to the outer end 11b located between the outer end 6E and the outer end 6E. As a result, it is possible to moderately give rigidity to bending deformation, and particularly to improve the rigidity in the circumferential direction. This compensates for the decrease in rigidity due to the downsizing of the bead apex rubber 8, and the steering stability. Can be secured at a high level.
[0028]
The reinforcing apex 11 is covered on its outer surface by a clinching rubber 12 for preventing rim displacement and a side wall rubber 13 forming the side wall portion 3.
[0029]
The clinch rubber 12 is a hard rubber that forms the rubber skin of the bead portion 4, and includes at least a rising portion 12A that forms a bead outer surface from the heel portion. In this example, the clinch rubber 12 is connected to the rising portion 12A and below the core. The case where the base part 12B which forms a bead bottom face through is provided integrally is illustrated. The exposed surface of the clinch rubber 12 includes at least a rim contact area that contacts the rim, thereby preventing damage due to rim displacement.
[0030]
Further, a flexible side wall rubber 13 made of a soft rubber is connected to a radially outer portion of the clinch rubber 12 via a boundary line 15. The boundary line 15 is inclined radially outward from the outside in the tire axial direction toward the inside, and the radially outer end 15E intersects the outer surface of the reinforcing apex 11.
[0031]
Here, when the rubber hardness of the bead apex rubber 8 is Hs1, the rubber hardness of the reinforcing apex 11 is Hs2, the rubber hardness of the clinch rubber 12 is Hs3, and the rubber hardness of the sidewall rubber 13 is Hs4, the following relationship is established. Satisfy.
Hs1 ≧ Hs2>Hs3> Hs4
That is, the rubber hardness is gradually decreased from the inner side in the tire axial direction toward the outer side and from the inner side in the radial direction toward the outer side. Thereby, the road noise performance improving effect of the present invention based on the transition of the bending neutral line N can be exhibited without generating a rigid step.
[0032]
The rubber hardness of the bead apex rubber 8 is preferably 85 to 100 degrees so that the bead rigidity is sufficiently secured and the rim is securely engaged. The rubber hardness Hs2 of the reinforcing apex 11 is preferably 80 to 95 degrees in order to increase the circumferential rigidity and to obtain excellent steering stability. The rubber hardness Hs3 of the clinch rubber is preferably 65 to 85 degrees of hard rubber in order to prevent rim displacement and wear damage with the rim. In addition, the rubber hardness as used in this application means the durometer A hardness measured by durometer type A based on JIS-K6253.
[0033]
Further, as shown in FIG. 3, the reinforcing apex 11 has a maximum thickness position P in the vicinity of the outer end 8E of the bead apex rubber 8 where the thickness t in the tire axial direction becomes the maximum thickness tmax. The thickness is gradually decreased from the maximum thickness position P toward the inside and outside in the radial direction. Thereby, the reinforcing apex 11 and the bead apex rubber 8 are smoothly connected without causing a rigidity step. In particular, in this example, the sum t + j of the thickness t of the reinforcing apex rubber 11 in the tire axial direction and the thickness j of the bead apex rubber 8 in the tire axial direction at each height position is the outer peripheral surface S1 of the bead core 5. A preferable case of gradually decreasing from the outside toward the radial direction is illustrated. Thereby, the total rigidity of the reinforcing apex 11 and the bead apex rubber 8 changes more smoothly, and local strain concentration on the carcass 6, that is, local increase in tensile force can be suppressed.
[0034]
The maximum thickness tmax is preferably 0.25 to 0.50 times the outer rubber thickness T from the folded portion 6B to the tire outer surface on the tire axial line passing through the maximum thickness point P. As a result, the rigidity can be improved without greatly changing the position of the bending neutral line N from that before the reinforcement apex 11 is formed. That is, rigidity can be imparted without impairing the road noise performance improvement effect of the present invention based on the transition of the bending neutral line N, and compatibility with steering stability can be achieved. If it is less than 0.25 times, the steering stability tends to be reduced due to insufficient rigidity, and if it exceeds 0.50 times, the bending neutral line N shifts outward in the tire axial direction, improving road noise performance. Inhibits.
[0035]
In addition, in order to reduce the influence on the bending neutral line N, it is preferable that the thickness t at each height position is 0.5 times or less of the outer rubber thickness T at the height position.
[0036]
Further, in this example, the radial length L of the overlapping portion 20 between the reinforcing apex rubber 11 and the bead apex rubber 8 is set to 5 to 10 mm, so that a reduction in rigidity is further suppressed. This is because when the bead apex rubber 8 is reduced in size, its outer end 8E is positioned in the vicinity of the flange height of the rim. Therefore, by optimizing the length L, the filling internal pressure and the flange can be reduced. This is because the overlapping portion 20 is pressed so as to be integrated by the restraint caused by the above, and the rigidity is prevented from being lowered at this portion. If the length L is less than 5 mm, the bend in the vicinity of the outer end 8E becomes abrupt, and there is a possibility of incurring problems such as a decrease in durability, such as causing air accumulation in this portion during manufacturing.
[0037]
In order to secure the steering stability at a higher level, the outer end 11b of the reinforcing apex 11 is connected from the outer end 8E of the bead apex 8 to the outer end 6E of the folded portion 6 as in this example. The outer end 11b is preferably provided on the linear region Y1 in order to perform reinforcement in a well-balanced manner. At this time, the tire axial direction inner edge of the reinforcing apex rubber 11 is formed in a straight line from the maximum thickness point P to the outer end 11b. Incidentally, axially outer side edge is preferably formed in a linear shape or axially outwardly Totsuru convex arcuate.
[0038]
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.
[0039]
【Example】
A tire for a passenger car having a tire size of 175 / 65R14 was prototyped based on the specifications in Table 1 and tested for longitudinal rigidity, lateral rigidity, tire natural frequency, low-frequency road noise performance, and steering stability. The results are shown in Table 1.
[0040]
(1) Longitudinal rigidity, lateral rigidity, tire natural frequency,
Conventional samples were measured for longitudinal stiffness, lateral stiffness, and tire natural frequency under the conditions of rim (5.5J × 14), internal pressure (200kPa), longitudinal load (3.53kN) on a sample tire. The index was evaluated with an index of 100. The greater the value, the higher the stiffness and the tire natural frequency.
[0041]
(2) Low-frequency road noise performance Trial tires are mounted on all wheels of a vehicle (1500cc, FF vehicle) under conditions of rim (5.5J x 14) and internal pressure (200kPa), and the speed of paved rough roads The vehicle was run at 50 km / h, the in-vehicle noise was measured with the right ear of the driver's seat, and the noise level at 125 Hz was displayed as an index with the conventional example being 100. The larger the value, the smaller the noise level and the better.
[0042]
(3) Steering stability Using the vehicle, the vehicle was run on a dry test course, and was displayed as an index with a conventional example of 100 by sensory evaluation of the driver. The test was performed by five drivers, and the average value of the evaluation evaluation of five people was adopted. The larger the value, the better the steering stability.
[0043]
[Table 1]

[0044]
【The invention's effect】
As described above, in the present invention, the height of the bead apex rubber is set to 20 mm or less to reduce the size thereof, while the reinforcing apex with the size, the rubber hardness, and the like regulated on the outer side in the tire axial direction of the folded portion of the carcass. Therefore, the tensile force acting on the carcass body is reduced, the increase in the natural frequency of the tire is suppressed and the road noise performance on the low frequency side is improved, while the tire rigidity can be sufficiently secured and the excellent steering stability is achieved. Can be demonstrated.
[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 of a bead portion.
FIG. 3 is a cross-sectional view showing a reinforcing apex further enlarged.
FIG. 4 is a diagram illustrating a conventional tire and its problems.
[Explanation of symbols]
2 Tread portion 3 Side wall portion 4 Bead portion 5 Bead core 6 Carcass 6A Main body portion 6B Folded portion 8 Bead apex rubber 10 Recessed portion 11 Reinforced apex rubber 12 Clinch rubber 13 Side wall rubber 20 Overlapping portion BL Bead base line K1 Oblique side K3 in lower side K2 Outer hypotenuse

Claims (5)

A carcass having a series of folded portions that are folded from the inner side to the outer side in the tire axial direction around the bead core on the main body portion extending from the tread portion to the bead core through the sidewall portion, and the main body portion and the folded portion of the carcass A pneumatic tire with a bead apex rubber arranged between
The bead apex rubber includes a lower side along the radial outer peripheral surface of the bead core in a cross section including the tire shaft, and an inner side extending along the main body portion radially outward from an inner end in the tire axial direction of the lower side. The hypotenuse and the outer hypotenuse connecting the outer end of the hypotenuse in the radial direction and the outer end of the lower side form a triangular section, and from the lower side to the outer end of the bead apex rubber The height h1 is 20 mm or less,
And the folding height h2 from the bead base line to the radially outer end of the folding portion is 0.4 times or more of the tire cross-section height h0,
The folded portion has a bead side region substantially in contact with the outer hypotenuse and a sidewall side region that is continuous with the bead side region and substantially in contact with the main body portion is recessed inward in the tire axial direction. Forming a recess,
In addition, between the outer end of the bead apex rubber and the outer end of the folded portion from the inner end located between the outer peripheral surface of the bead core and the outer end of the bead apex rubber in the recess. the reinforcing apex rubber extending along the turnup portion in the region up to the outer end located to provided,
The carcass forms a contact area extending in contact with the main body part and the folded part, the contact area includes a linear area extending linearly, and the linear area is in the vicinity of the outer end Pneumatic tire characterized by starting from . The reinforcing apex rubber is covered with clinching rubber for preventing rim displacement disposed in the bead part, and side wall rubber that is obliquely in contact with the clinch rubber at a radially outer portion and forms a side wall part,
When the bead apex rubber is Hs1, the reinforcing apex rubber is Hs2, the clinch rubber is Hs3, and the side wall rubber is Hs4, the following relationship is satisfied: The pneumatic tire according to claim 1.
Hs1 ≧ Hs2>Hs3> Hs4   The reinforcing apex rubber has a maximum thickness position P in the vicinity of the outer end of the bead apex rubber, where the thickness in the tire axial direction is the maximum thickness tmax. The maximum thickness tmax is 0.25 to 0. 0 of the outer rubber thickness T from the folded portion to the tire outer surface on the tire axial line passing through the maximum thickness point P. The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire is 50 times. In the reinforcing apex rubber, a length L in the radial direction of the overlapping portion from the inner end to the outer end of the bead apex rubber is set to 5 to 10 mm, and the tire of the reinforcing apex rubber and the bead apex rubber The pneumatic tire according to any one of claims 1 to 3, wherein the sum of the axial thicknesses gradually decreases from the outer peripheral surface of the bead core toward the radially outer side. The pneumatic tire according to any one of claims 1 to 4, wherein the reinforcing apex rubber has a tire axially outer edge formed linearly.

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