JP2004306742A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable an operating stability to be realized while restricting a deterioration in road noise. <P>SOLUTION: A bead apex rubber 8 is formed by an apex main body part 8A extending from a bead core 5 to a point P in a form of fine extending shape and having a small triangular sectional shape and a sheet-like wing part 8B extending from the main body part. A rubber thickness Te is 0.8 to 1.5 mm. A height He of the bead apex rubber 8 occupies 30% to 40% of a tire sectional height H, and a height Hp at a point P occupies 25 to 35% of the height He. A clinch rubber 9 has a maximum rubber thickness Tc of about 4.0 to 5.0 mm at a position of the point P. A height Hc occupies 70 to 85% of the height He. Under a normal inner pressure state, a raising angle θ from a bead bottom surface S2 at a bead outer surface S1 occupies 80 to 90°. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００３９】
【発明の効果】
本発明は叙上の如く構成しているため、周方向共振周波数の上昇を抑えロードノイズの悪化を抑制しながら、操縦安定性を向上しうる。
【図面の簡単な説明】
【図１】本発明の空気入りタイヤの一実施例を示す断面図である。
【図２】５％内圧状態におけるビード部を拡大して示す断面図である。
【図３】正規内圧状態におけるビード部を拡大して示す断面図である。
【図４】（Ａ）、（Ｂ）は、従来技術が有する問題点を説明する断面図である。
【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 カーカスプライ
６ａ プライ本体部
６ｂ プライ折返し部
８ ビードエーペックスゴム
８Ａ エーペックス本体部
８Ｂ 翼部
９ クリンチゴム
Ｒ 正規リム
Ｒｆ フランジ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pneumatic tire capable of reducing road noise while ensuring steering stability.
[0002]
[Prior art]
The present invention relates to a pneumatic tire capable of improving steering stability while suppressing deterioration of road noise.
[0003]
2. Description of the Related Art
In a pneumatic tire, as shown in FIG. 4A, a bead apex rubber made of a hard rubber extending radially outward from a bead core b is provided between a ply body portion c1 and a ply turn-back portion c2 of a carcass c. e is thereby reinforced from the bead portion to the side wall portion to secure necessary tire rigidity. In recent years, the bead apex rubber e has been increasing in size in order to increase tire rigidity and improve steering stability.
[0004]
However, the enlargement of the bead apex rubber e increases the distance from the neutral bending line N when the tire is bent and deformed to the ply main body portion c1 and the ply turnover portion c2. And the compressive force acting on the ply turn-back portion c2 are increased. This causes the circumferential resonance frequency of the tire to rise, approaching the vehicle-side resonance frequency, thereby deteriorating road noise performance in a low frequency range (for example, around 125 Hz).
[0005]
As described above, the handling stability and the road noise performance on the low frequency side have conventionally been traded off, and it has been a very difficult problem to balance them. In Patent Document 1, the bead apex rubber e is reduced in size, and an auxiliary apex rubber g having a maximum thickness at the outer end of the bead apex rubber e is arranged between the ply folded portion c2 and the clinch rubber f. The technology is disclosed.
[0006]
[Patent Document 1]
JP 2002-160510 A
According to the present invention, a bead apex rubber is formed by an apex main body having a small triangular cross section and a thin plate-like wing extending therefrom, and the apex main body and the clinch rubber are regulated to a predetermined height, and the bead under an internal pressure state is formed. Based on the fact that the rising angle θ from the bead bottom surface on the outer side surface is set to 80 to 90 °, a pneumatic tire capable of improving steering stability while suppressing an increase in circumferential resonance frequency and suppressing deterioration of road noise. It is intended to be provided.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application is directed to a ply that is folded from the inner side in the tire axial direction to the outer side around the bead core in a ply main body part extending from the tread part to the bead core of the bead part through the sidewall part. A carcass composed of a carcass ply having a series of folded portions, a bead apex rubber extending radially outward from the bead core passing between the ply body and the ply folded portion, and a tire axial direction of the bead apex rubber. A pneumatic tire having a clinch rubber that is arranged outside and forms an outside surface of a bead portion,
The bead apex rubber is formed from an apex main body having a small triangular cross-section extending radially outward from the bead core to a point P, and a thin plate-shaped wing extending radially outward from the apex main body. ,
The bead apex rubber at the point P has a rubber thickness Te of 0.8 to 1.5 mm, and the clinch rubber has a maximum rubber thickness Tc of 4.0 to 5.0 mm at the position of the point P. Have
In a 5% internal pressure state where the rim is assembled to the regular rim and filled with 5% of the normal internal pressure,
The height He of the outer end of the bead apex rubber from the bead base line is 30% to 40% of the tire sectional height H, and the height Hp of the point P from the bead base line is the height He of the bead apex rubber. And the height Hc of the outer end of the clinch rubber from the bead baseline is 70 to 85% of the height He of the bead apex rubber;
In addition, in a normal internal pressure state where the rim is assembled to the normal rim and the normal internal pressure is filled, a rising angle θ of the outer surface of the bead portion facing the flange of the normal rim from the bead bottom surface is set to 80 to 90 °. And
[0009]
Further, in the invention of claim 2, the clinch rubber has a rubber hardness (durometer A hardness) Hs1 of 65 to 85 °, the bead apex rubber has a rubber hardness (durometer A hardness) Hs2 of 80 to 95 ° and the rubber hardness Hs1 It is characterized by being large.
[0010]
In the invention according to claim 3, the height h of the folded portion from the bead base line at the outer end thereof is larger than the height He of the bead apex rubber and 60% or less of the tire sectional height H. It is characterized by.
[0011]
In the present specification, the "regular rim" is a rim defined for each tire in a standard system including a standard on which the tire is based. For example, a standard rim for JATMA and a rim for TRA " Design Rim ”or“ Measurement Rim ”for ETRTO. The “regular internal pressure” is an air pressure defined for each tire according to the standard, and is the maximum air pressure for JATMA, and the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLASION PRESSURESRES” for TRA, In the case of ETRTO, it is "INFLATION PRESURE", but in the case of a tire for a passenger car, it is 180 KPa.
The "bead base line" means a line in the tire axial direction passing through a rim diameter position defined by the standard.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to illustrated examples.
FIG. 1 shows a meridian cross section in a 5% internal pressure state in which a pneumatic tire 1 of the present invention is formed as a passenger car tire, assembled with a regular rim R and filled with an internal pressure of 5% of the normal internal pressure.
[0014]
In FIG. 1, a pneumatic tire 1 includes a carcass 6 extending from a tread portion 2 to a bead core 5 of a bead portion 4 through a sidewall portion 3, and a belt disposed inside the tread portion 2 and outside the carcass 6. And a layer 7.
[0015]
The belt layer 7 is composed of two or more, in this example, two belt plies 7A and 7B in which high elastic belt cords are arranged at an angle of, for example, 10 to 35 ° with respect to the tire circumferential direction. Each of the belt plies 7A and 7B enhances belt rigidity by intersecting the belt cords between the plies, and strongly reinforces substantially the entire width of the tread portion 2 with a tag effect. As the belt cord, a steel cord or a high-modulus organic fiber cord comparable thereto, such as an aromatic polyamide fiber, can be suitably used.
[0016]
Further, a band layer 10 in which an organic fiber cord such as nylon is spirally wound at an angle of 5 degrees or less with respect to the circumferential direction of the tire is formed further outside the belt layer 7 to prevent lifting of the tread portion 2 due to high-speed running. Is preferred.
[0017]
The carcass 6 is composed of one or more carcass plies 6A in which 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. Organic fiber cords such as are preferred. The carcass ply 6A includes a series of ply folded portions 6b that are folded around the bead core 5 from the inside to the outside in the tire axial direction at both ends of the ply main body 6a extending between the bead cores 5 and 5.
[0018]
The bead portion 4 has a bead apex rubber 8 that passes between the ply body portion 6a and the ply turn-up portion 6b and rises radially outward from the bead core 5, and a tire axial outside of the bead apex rubber. And a clinch rubber 9 forming an outer surface S1 of the bead portion 4 (sometimes referred to as a bead outer surface S1 for convenience).
[0019]
Of these, the bead apex rubber 8 is made of hard rubber having a rubber hardness (durometer A hardness) Hs2 of 80 to 95 °, and as shown in an enlarged view in FIG. It is composed of an apex main body 8A having a small triangular cross section and extending to P, and a wing 8B extending radially outward from the apex main body 8A.
[0020]
Here, the apex main body 8A has a rubber thickness Te at the point P of 0.8 to 1.5 mm. The wing portion 8B is formed in a thin plate shape having a substantially constant thickness from the point P. Therefore, the wing portion 8B extends with a thickness substantially equal to the rubber thickness Te. Note that the “substantially constant thickness” means that variations in thickness due to vulcanization pressure and the like at the time of tire molding and taper at the tip end can be tolerated.
[0021]
In the 5% internal pressure state, the bead apex rubber 8 has a height He (which may be referred to as an apex height He for convenience) from an outer end of the bead base line BL, which is 30% of a tire sectional height H. The height Hp of the point P from the bead base line (sometimes referred to as a P point height Hp for convenience) is set to 25% to 35% of the Apex height He. That is, the P point height Hp is set to be very low, in the range of 7.5 to 14% of the tire section height H.
[0022]
Note that the ply turn-up portion 6b of the carcass 6 extends along the outer surface of the bead apex rubber 8 in the tire axial direction, and in this example, extends along the ply body portion 6a after passing over the bead apex rubber 8. I do. At this time, the height h of the outer end of the ply folded portion 6b from the bead base line BL (may be referred to as a folded height h for convenience) is set to be 60% or less of the tire cross-sectional height H in this example. are doing.
[0023]
Next, the clinch rubber 9 is a rubber member for preventing rim displacement in which a rubber hardness (durometer A hardness) Hs1 is 65 to 85 ° and smaller than a rubber hardness Hs2 of the bead apex rubber 8. And rises radially outward from the bead heel portion 4h along the ply turn-up portion 6b and is joined to the sidewall rubber 3G. At this time, the clinch rubber 9 is exposed in a region facing the flange Rf of the regular rim R, and forms at least a part of the bead outer surface S1.
[0024]
Here, the clinch rubber 9 has a maximum rubber thickness Tc of 4.0 to 5.0 mm at the position of the point P, and gradually decreases the rubber thickness inward and outward in the radial direction. . In the 5% internal pressure state, the clinch rubber 9 has a height Hc (referred to as a clinch height Hc for convenience) of the outer end of the clinch rubber 9 set to 70 to 85% of the apex height He. ing.
[0025]
By employing such a structure, it is possible to improve steering stability while exhibiting an effect of improving road noise performance.
[0026]
Explaining the mechanism, the tire 1 reduces the size of the apex main body 8A and places the ply main body 6a and the turn-back portion 6b of the carcass 6 close to each other radially outward from the point P which is the outer end point. Let it be arranged. As a result, in the ply body 6a and the ply turnup 6b, the distance from the bending neutral line when the tire is bent is reduced, and the tensile force acting on the ply body 6a and the compression acting on the ply turnup 6b are reduced. The force is reduced. As a result, it is possible to suppress a rise in the circumferential resonance frequency of the tire, and to improve road noise performance in a low frequency range. For that purpose, it is necessary to set the rubber hardness Hs2 of the bead apex rubber 8 to be larger than the rubber hardness Hs1 of the clinch rubber 9 (Hs2> Hs1). If Hs2 ≦ Hs1, the bending neutral line is required. Is shifted to the clinch rubber 9 side, so that the above effect cannot be sufficiently achieved. Therefore, the difference Hs2−Hs1 in rubber hardness is preferably set to 3 ° or more, more preferably 8 ° or more.
[0027]
Further, since the tensile force and the compressive force applied to the carcass 6 are reduced, the bead portion 4 is given flexibility, and when the regular internal pressure is filled (shown in FIG. 3), the amount of bulging outward in the tire axial direction increases. I do. Thereby, the contact pressure with the upper part of the flange Rf increases, and the movement of the bead portion 4 is strongly restrained, so that the steering stability can be improved. The pressure contact with the upper portion of the flange Rf exerts a force for strongly pressing the bead bottom surface S2 and the bead heel portion 4h against the rim sheet R1 and the heel portion R2, so that the restraint on the bead portion 4 is ensured and the seating is stabilized. Let it.
[0028]
For this purpose, in the normal internal pressure state, the rising angle θ of the bead outer surface S1 from the bead bottom surface S2 needs to be set to 80 to 90 °. The rising angle θ means an angle between the root S1a of the bead outer surface S1 and the bead bottom surface S2. In the non-rim assembled state, the bead outer surface S1 has a straight root portion S1a extending substantially perpendicularly to the tire axial direction from the bead heel portion 4h and a concave arc shape having a center outside the tire. It is formed of a curved portion S1b that joins the root portion S1a and the side wall portion 3, and in the 5% internal pressure state, extends from the root portion S1a to the curved portion S1b and is in close contact with the flange Rf. However, in the normal internal pressure state, the root portion S1a is separated from the flange Rf between the press-contact portion J1 and the bead heel portion 4h due to the pressure contact with the upper portion of the flange Rf, whereby the rising angle θ is reduced. Reduced to 80-90 °.
[0029]
Here, if the rising angle θ is larger than 90 °, the pressure contact with the flange Rf becomes insufficient, and the effect of improving the steering stability cannot be obtained. Conversely, if the rising angle θ is smaller than 80 °, the portion separated from the flange Rf is separated. The remaining air in the air becomes excessive and adversely affects the force variation (FV).
[0030]
Further, in order to effectively exert the effect of improving the steering stability, it is necessary that the bead portion 4 has appropriate elasticity and rigidity. Therefore, as described above, the height of the apex in the bead apex rubber 8 is required. The He, P point height Hp, the rubber thickness Te of the wing portion 8B, the clinch height Hc of the clinch rubber 9, the maximum rubber thickness Tc at the point P, and the like are regulated within the above ranges.
[0031]
That is, in the bead apex rubber 8,
The apex height He is less than 30% of the tire section height H;
The P point height Hp is less than 25% of the Apex height He,
When the rubber thickness Te is less than 0.8 mm and in the clinch rubber 9,
The clinch height Hc is less than 70% of the Apex height He,
When the maximum rubber thickness Tc at the point P is less than 4.0 mm,
In each case, the elasticity and rigidity of the bead portion 4 become too small, so that the effect of improving the steering stability cannot be exhibited and the durability is disadvantageous. When the maximum rubber thickness Tc of the clinch rubber 9 is larger than 5.0 mm, the rigidity is increased and the contact pressure with the flange Rf is reduced, so that the effect of improving the steering stability cannot be obtained.
[0032]
In the bead apex rubber 8,
The apex height He is greater than 40% of the tire section height H;
The P point height Hp is greater than 35% of the Apex height He;
When the rubber thickness Te is larger than 1.5 mm and in the clinch rubber 9,
When the clinch height Hc is greater than 85% of the Apex height He,
In each case, the circumferential resonance frequency of the tire increases, and the effect of improving road noise performance cannot be achieved.
[0033]
As described above, particularly preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to the illustrated embodiments, and can be implemented in various forms.
[0034]
【Example】
A tire for a passenger car having a tire size of 175 / 65R14 having the structure shown in FIG. 1 was prototyped based on the specifications in Table 1, and the steering stability, ride comfort, and road noise performance of each test tire were measured and compared. Except for the specifications in Table 1, the specifications were the same.
[0035]
(1) Steering stability and riding comfort;
The test tires were mounted on four wheels of a vehicle (1000 cc, front-wheel drive) with a rim (5.5 J × 14) and an internal pressure (220 kPa), and the steering stability (rigidity) when running on a tire test course on dry asphalt road surface Sensation and handle response) and ride comfort performance were evaluated by a 10-point method with the conventional example being 6 points by sensory evaluation of the driver. The higher the value, the better.
[0036]
(2) Road noise performance;
Using the vehicle, a rough asphalt road for noise evaluation was run at a speed of 50 km / h, and the overall noise level was measured at the left ear of the driver's seat. The higher the value, the better.
[0037]
(3) vertical spring;
The reciprocal of the difference in the amount of longitudinal deflection when the load was changed by ± (0.5 kN) with respect to the load state of the load (3.53 kN) was evaluated by an index with the conventional example being 100. . The larger the value, the less the tire deformation.
[0038]
[Table 1]

[0039]
【The invention's effect】
Since the present invention is configured as described above, it is possible to improve the steering stability while suppressing the increase in the circumferential resonance frequency and the deterioration of the road noise.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an embodiment of a pneumatic tire according to the present invention.
FIG. 2 is an enlarged sectional view showing a bead portion in a 5% internal pressure state.
FIG. 3 is an enlarged sectional view showing a bead portion in a normal internal pressure state.
FIGS. 4A and 4B are cross-sectional views for explaining problems of the related art.
[Explanation of symbols]
2 Tread 3 Sidewall 4 Bead 5 Bead core 6 Carcass 6A Carcass ply 6a Ply body 6b Ply turnback 8 Bead apex rubber 8A Apex body 8B Wing 9 Clinch rubber R Regular rim Rf Flange

Claims (3)

A carcass consisting of a carcass ply having a series of ply turn-up portions that are turned around from the tread portion to the bead core of the bead portion in the ply body portion around the bead core from the inside to the outside in the tire axial direction; A bead apex rubber extending radially outward from the bead core passing between the main body portion and the ply turn-up portion; and a clinch rubber disposed outside the bead apex rubber in the tire axial direction and forming an outer surface of the bead portion. A pneumatic tire,
The bead apex rubber is formed from an apex main body having a small triangular cross-section extending radially outward from the bead core to a point P, and a thin plate-shaped wing extending radially outward from the apex main body. ,
The bead apex rubber at the point P has a rubber thickness Te of 0.8 to 1.5 mm, and the clinch rubber has a maximum rubber thickness Tc of 4.0 to 5.0 mm at the position of the point P. Have
In a 5% internal pressure state where the rim is assembled to the regular rim and filled with 5% of the normal internal pressure,
The height He of the outer end of the bead apex rubber from the bead base line is 30% to 40% of the tire sectional height H, and the height Hp of the point P from the bead base line is the height He of the bead apex rubber. And the height Hc of the outer end of the clinch rubber from the bead baseline is 70 to 85% of the height He of the bead apex rubber;
In addition, in a normal internal pressure state where the rim is assembled to the normal rim and the normal internal pressure is filled, a rising angle θ of the outer surface of the bead portion facing the flange of the normal rim from the bead bottom surface is set to 80 to 90 °. And pneumatic tires. The clinch rubber has a rubber hardness (durometer A hardness) Hs1 of 65 to 85 °, and the bead apex rubber has a rubber hardness (durometer A hardness) Hs2 of 80 to 95 ° and larger than the rubber hardness Hs1. The pneumatic tire according to claim 1. The height of the folded portion from the bead base line at the outer end thereof is set to be larger than the height He of the bead apex rubber and equal to or less than 60% of the tire sectional height H. 2. The pneumatic tire according to 2.

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