JP4681156B2 - Pneumatic tire - Google Patents

Description

【００４８】
【表２】

【００４９】
【発明の効果】
叙上の如く本発明は、短繊維補強ゴム層を、半径方向内外に区分されかつ短繊維の配合量を違えた複数のゴム領域によって形成しているため、カーカスの折返し高さおよびビードエーペックス高さを減じることにより転がり抵抗を改善したタイヤにおいて、操縦安定性、乗り心地性および耐久性を向上することが可能となる。
【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】ビード部を短繊維補強ゴム層とともに拡大して示す断面図である。
【図３】短繊維補強ゴム層の他の例を示す断面図である。
【図４】（Ａ）、（Ｂ）は、ゴム領域の間の境界線を例示する略断面図である。
【図５】従来技術を説明する線図である。
【符号の説明】
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
１０ 短繊維補強ゴム層
１１ ゴム領域[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire that can improve steering stability, ride comfort and durability in a tire in which rolling resistance is improved by reducing a carcass folding height and a bead apex height.
[0002]
[Prior art]
For example, as shown in FIG. 5, it is possible to reduce the rolling resistance by suppressing the height of the folded portion b1 of the carcass folded around the bead core a and the bead apex rubber c that rises radially outward from the bead core a. Therefore, it is conventionally known that it is effective.
[0003]
However, when such a structure is adopted, the tire rigidity is reduced, and the steering stability is particularly lowered. In addition, when such a sidewall portion of a tire is reinforced with a steel cord reinforcing layer, there are problems that the ride comfort is lowered and the effect of reducing rolling resistance is impaired.
[0004]
In view of this, the present applicant has proposed in Japanese Patent Application Laid-Open No. 8-175119 to use a short fiber reinforced rubber layer instead of the cord reinforcing layer. Such a short fiber reinforced rubber layer can appropriately increase the bending rigidity of the tire, and can improve both steering stability and ride comfort while maintaining excellent low rolling resistance.
[0005]
[Problems to be solved by the invention]
However, in the tire having such a structure, deformation is large and stress is concentrated in the bead portion. Therefore, the short fiber reinforced rubber layer g is likely to be damaged due to the contained short fibers, and the durability tends to be deteriorated. It becomes.
[0006]
Therefore, the present invention is based on the fact that the short fiber reinforced rubber layer is formed by a plurality of rubber regions that are divided inward and outward in the radial direction and have different blending amounts of short fibers. It is an object of the present invention to provide a pneumatic tire that can suppress damage to the tire and improve durability as well as steering stability and ride comfort while maintaining excellent low rolling resistance.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, in the invention of claim 1 of the present application, a ply turn-up portion that folds around the bead core is integrally provided in a ply body portion that extends from the tread portion to the bead core of the bead portion through the sidewall portion. A pneumatic tire comprising a carcass made of a single carcass ply and a bead apex rubber that extends between the ply main body and the ply turn-up portion and tapers outward from the bead core in the radial direction of the tire. And
The carcass ply has a height h1 from the bead base line of the radially outer end of the ply turn-up portion of 0.12 to 0.15 times the tire cross-section height H, and the bead apex rubber is radially outward. The height h2 from the end bead baseline is 0.20 to 0.25 times the tire cross-section height H,
In addition, a short fiber reinforced rubber layer extending along the outer surface of the bead apex rubber and extending along the outer surface of the ply main body portion along the outer surface of the bead apex rubber is disposed on the sidewall portion,
The short fiber reinforced rubber layer is formed by continuing a plurality of rubber regions that are divided inward and outward in the radial direction and have different blending amounts of short fibers ,
Moreover, the amount of short fibers in the radially outer rubber region is larger than the amount of short fibers in the adjacent rubber region on the radially inner side .
[0008]
According to a second aspect of the present invention, the short fiber reinforced rubber layer has a radial inner end starting from a position where the outer end of the ply folded portion extends radially outward, and the radial outer end has a maximum tire width. The outer end of the radially innermost rubber region is located in the vicinity of the point, and is characterized by being positioned radially outward from the outer end of the bead apex rubber.
[0009]
The invention of claim 3 is characterized in that a rubber thickness t of the short fiber reinforced rubber layer is 0.3 to 1.0 mm .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a meridional sectional view illustrating a case where the pneumatic tire 1 of the present invention is a radial tire for passenger cars. FIG. 2 is an enlarged cross-sectional view of the bead portion.
[0011]
As shown in FIG. 1, a pneumatic tire 1 is arranged 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 outside the carcass 6. And a bead apex rubber 8 extending outward from the bead core 5 in the tire radial direction.
[0012]
The belt layer 7 is composed of two or more belt plies 7A and 7B in this example, in which high-elasticity belt cords are arranged at an angle of, for example, 10 to 35 ° with respect to the tire circumferential direction. The belt plies 7A and 7B are stacked with different inclination directions so that the belt cords cross each other between the plies. The belt triangle structure increases the rigidity of the belt so that the substantially full width of the tread portion 2 is reduced. Have and reinforce. As the belt cord, a steel cord or a high modulus organic fiber cord such as an aromatic polyamide fiber comparable to this is preferably used.
[0013]
Further, in this example, the case where the band layer 9 is disposed outside the belt layer 7 is illustrated for the purpose of increasing the restraining force on the belt layer 7 and improving the high speed durability performance. The band layer 9 has a band cord spirally wound at an angle of, for example, 5 degrees or less with respect to the tire circumferential direction, and extends at least covering the outer end portion of the belt layer 7 in the tire axial direction.
[0014]
The carcass 6 includes a single carcass ply 6A in which carcass cords are arranged at an angle of 75 to 90 degrees with respect to the tire circumferential direction. The carcass ply 6A is a ply main body that straddles between the bead cores 5 and 5. A ply turn-back portion 6b that folds from the inside to the outside around the bead core 5 is integrally provided at both ends of 6a. As the carcass cord, an organic fiber cord such as nylon, rayon, polyester, aromatic polyamide, or the like, or a steel cord can be used as appropriate, but an organic fiber cord is preferable from the viewpoint of weight reduction.
[0015]
The bead apex rubber 8 is made of a relatively hard rubber having a rubber hardness (durometer A hardness) of about 65 to 95 degrees, and passes between the ply body portion 6a and the ply folded portion 6b in the tire radial direction. Extends outwardly in a tapered shape.
[0016]
What is important here is that in the tire 1 of the present embodiment, in order to reduce rolling resistance,
(1) As the carcass 6, a height h1 (may be referred to as a turn-up height h1) of the radially outer end 6e (may be referred to as a turn-up end 6e) of the ply turn-up portion 6b from the bead base line BL Restricting to a range of 0.12 to 0.15 times the cross-sectional height H, and (2) As the bead apex rubber 8, from the bead base line BL of the outer end 8e (sometimes referred to as apex end 8e). The height h2 of the tire (which may be referred to as apex height h2) is restricted to a range of 0.20 to 0.25 times the tire cross-section height H.
[0017]
In this way, by restricting the apex height h2 to be small, energy loss due to heat generation of the bead apex rubber 8 is reduced in addition to weight reduction. Further, since the contour shape of the ply body portion 6a is linear from the bead portion 4 to the sidewall portion 3, the carcass cord path is shortened, and uniform and sufficient tension is applied to the entire carcass cord. Deflection is also suppressed as a whole. These synergistic effects reduce rolling resistance. Moreover, since the folding height h1 is also smaller than the apex height h2, further weight reduction can be achieved while suppressing damage at the folding end 6e, and the rolling resistance reduction effect can be further enhanced. .
[0018]
However, such a structure, on the other hand, tends to reduce tire rigidity and decrease steering stability.
[0019]
Therefore, in the tire 1 of the present embodiment, in order to improve the steering stability and the ride comfort while maintaining the above-described excellent low rolling resistance, and to ensure sufficient durability, the sidewall portion 3, the short fiber reinforced rubber layer 10 is disposed, and the short fiber reinforced rubber layer 10 is formed by a plurality of rubber regions 11 divided inward and outward in the radial direction.
[0020]
Specifically, as shown in FIG. 2, the short fiber reinforced rubber layer 10 is a thin rubber layer having a substantially constant rubber thickness t, and extends along the outer surface in the tire axial direction of the bead apex rubber 8. In addition to extending outward in the radial direction, after passing through the apex end 8e, the ply main body portion 6a extends along the outer surface in the tire axial direction.
[0021]
At this time, it is preferable that the short fiber reinforced rubber layer 10 has its radially inner end EL positioned radially outward beyond the folded end 6e so that it does not overlap with the ply folded portion 6b. The distance j between the inner end EL and the turned-back end 6e is preferably as small as possible within the range of 0 to 10 mm from the viewpoint of ensuring durability.
[0022]
Further, in the short fiber reinforced rubber layer 10, it is preferable that the outer end EU in the radial direction is positioned in the vicinity Y of the tire maximum width point TM. If the position of the outer end EU is too low, the reinforcing effect is too small. Therefore, it becomes difficult to sufficiently improve the handling stability. On the contrary, if it is too high, low rolling resistance and riding comfort tend to be impaired. The “neighbor Y” means a range in which the distance in the radial direction from the tire maximum width point TM is 0.1 times or less of the tire cross-section height H.
[0023]
Next, the short fiber reinforced rubber layer 10 is made of a short fiber blended rubber in which short fibers are blended in a rubber base material, and in particular 90% or more of the short fibers are as small as ± 20 degrees or less with respect to the tire radial direction. It is preferable to align at an angle. Specifically, by the orientation of the short fibers, the complex elastic modulus E * a in the orientation direction (radial direction) of the short fibers and the complex elastic modulus E * b in the direction perpendicular to the orientation direction (circumferential direction) The ratio (E * a / E * b) ratio can be, for example, larger than 1.0, more preferably 5 or more, and still more preferably about 7 to 20. As a result, the compression and bending rigidity in the tire radial direction can be effectively compensated in the sidewall portion 3, and the steering stability and the ride comfort can be improved while maintaining excellent low rolling resistance. It becomes possible.
[0024]
The complex elastic modulus is measured using a viscoelastic spectrometer type VESF-III manufactured by Iwamoto Seisakusho Co., Ltd., and the measurement conditions are a temperature of 70 ° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of ± 1%. .
[0025]
Here, examples of the rubber base material of the short fiber reinforced rubber layer 10 include diene rubbers such as natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), and isoprene rubber (IR). One or a combination of a plurality of types can be suitably used.
[0026]
The short fibers are preferably organic fibers such as nylon, polyester, aramid, rayon, vinylon, cotton, cellulose resin, crystalline polybutadiene, etc., but other than these, for example, metal fibers, whiskers, boron, glass fibers, etc. Inorganic fibers such as these can be used, and these can be used alone or in combination of two or more. More preferably, the short fiber may be subjected to an appropriate surface treatment in order to improve the adhesion to the rubber substrate.
[0027]
The average diameter (D) of the short fibers is preferably 0.1 to 1.0 μm, for example. If the average diameter is smaller than 0.1 μm, the reinforcing effect tends to be relatively lowered, and conversely 1.0 μm If it is larger than that, the adhesive strength with the rubber tends to be relatively lowered, for example, cracks and cracks are likely to occur at the interface with the rubber. The short fibers are preferably those in which the ratio (L / D) of the average length (L) to the average diameter (D) is 5 or more, more preferably 50 or more, and still more preferably 50 to 2000. When this ratio (L / D) is less than 5, the reinforcing effect by the orientation of the short fibers cannot be sufficiently exhibited. The average length (L) of the short fibers is preferably 20 μm or more, and more preferably 50 to 1000 μm.
[0028]
In addition to the short fibers, the short fiber reinforced rubber layer 10 can be appropriately blended with rubber reinforcing agents such as carbon black and silica, and conventional additives for tire rubber such as sulfur and anti-aging agents.
[0029]
Further, the rubber thickness t of the short fiber reinforced rubber layer 10 is preferably in the range of 0.3 to 1.0 mm. When the rubber thickness t is less than 0.3 mm, the rigidity is insufficient and the steering stability is increased. Such an improvement effect is not sufficiently exhibited, and productivity is also deteriorated. On the contrary, if the rubber thickness t exceeds 1.0 mm, the orientation of the short fibers is lowered, and the reinforcing effect of the short fibers is reduced. On the other hand, the weight is unnecessarily increased and the low rolling resistance is impaired. Become.
[0030]
In the present embodiment, in order to suppress damage to the short fiber reinforced rubber layer 10 and increase the durability of the tire, the short fiber reinforced rubber layer 10 is divided into a plurality of rubber regions 11 that are divided inward and outward in the radial direction. In addition, each rubber region 11 is formed of different rubber compositions G with different blending amounts of the short fibers.
[0031]
In this example, the short fiber reinforced rubber layer 10 is composed of three rubber regions 11 including a radially innermost rubber region 11A, a radially outer rubber region 11B, and a radially outermost rubber region 11C. Thus, each rubber region 11A, 11B, 11C is illustrated as being formed of rubber compositions GA, GB, GC having different fiber blending amounts.
[0032]
At this time, it is necessary for the damage suppression effect that the short fiber blending amounts ga, gb, and gc of the rubber compositions GA, GB, and GC have the following relationship.
ga <gb <gc
That is, it is necessary to increase the blending amount of the short fibers in the rubber region 11 on the radially outer side than the blending amount of the short fibers on the rubber region 11 adjacent on the radially inner side.
[0033]
This is because, in the tire 1 of the present embodiment having a low apex height h2, the deformation is large and the stress is concentrated in the bead portion 4, so that cracks and the like are easily generated in the rubber layer 10 due to the short fibers. Therefore, reducing the amount of short fibers and relatively improving the flex cracking performance of the rubber in the radially inner rubber region 11 having a higher degree of stress concentration is effective in suppressing damage. Conversely, as the rubber region 11 radially outward increases in rigidity, it becomes easier to balance steering stability and riding comfort, and further performance improvement can be expected.
[0034]
In order to suppress damage to the rubber layer 10, the innermost rubber region 11A preferably extends to a position where the radially outer end AU exceeds the apex end 8e radially outward. This is because stress is most easily concentrated in the vicinity of the apex end 8e. Therefore, it is preferable to dispose the innermost rubber region 11A at least in this portion in order to suppress damage. Note from the viewpoint of securing the rigidity, the outer end bead base line height from BL of AU h3 is better to keep more than 0.3 times the tire section height H.
[0035]
Here, in the rubber composition G, when the amount of the short fiber is less than 10 parts by weight, the effect of containing the short fiber is not exhibited, and conversely, when the amount exceeds 30 parts by weight, the rubber composition G is formed. Rubber kneading and extruding are difficult, and productivity is significantly deteriorated. Accordingly, the short fiber content of the rubber composition G is preferably in the range of 10 to 30 parts by weight. In particular, in order to maximize the effects of the division of the short fiber reinforced rubber layer 10, the rubber composition GA is used. The short fiber content ga in the rubber composition GC is 10 to 20 parts by weight with respect to 100 parts by weight of the rubber base material, the short fiber content gb in the rubber composition GB is 15 to 25 parts by weight, and the short fiber content in the rubber composition GC. The amount gc is preferably 20 to 30 parts by weight.
[0036]
Further, as shown in FIG. 3, the short fiber reinforced rubber layer 10 is divided into two parts, a radially innermost rubber region 11A made of the rubber composition GA and a radially outermost rubber region 11C made of the rubber composition GC. It can also be formed by two rubber regions 11. At this time, the short fiber blending amounts ga and gc of the rubber compositions GA and GC are
ga <gc
In addition, the short fiber blending amount ga is 10 to 20 parts by weight and the short fiber blending amount gc is 20 to 30 parts by weight in order to maximize the effect of the section of the short fiber reinforced rubber layer 10. Is preferable.
[0037]
When the number n of the rubber regions 11 is 4 or more, not only the effect due to the division cannot be expected, but also the forming work efficiency of the short fiber reinforced rubber layer 10 tends to be impaired. Therefore, as described above, the number n is 2 Or 3 is preferred.
[0038]
Each rubber region 11 is connected in series by abutting each end, and a boundary line N (corresponding to the abutting surface of the end) between the rubber regions 11 is shown in FIGS. 4 (A) and 4 (B). As described above, it may be parallel to the thickness direction, or may be inclined with respect to the thickness direction. It is preferable to incline the boundary line N from the viewpoint of durability because the butt area is large and the connection strength is increased.
[0039]
When the boundary line N is inclined, the length J in the radial direction along the rubber region 11 of the boundary line N is the width Wj of the narrow rubber region 11 in the inner and outer rubber regions 11 to be connected. Is preferably 0.5 times or less. When it exceeds 0.5 times, the effect of the division of the short fiber reinforced rubber layer 10 is not sufficiently achieved.
[0040]
Further, when the boundary line N is inclined, it is preferable for the damage suppression that the radially inner point of the boundary line N is radially outward from the apex end 8e, and from the viewpoint of securing rigidity, the boundary line N It is preferable that the height h3 from the bead base line BL at the radially outer point is set to 0.3 times or less of the tire cross-sectional height H.
[0041]
Further, in each rubber region 11, it is preferable that the types of the short fibers to be blended are the same, but the types of the short fibers may be different depending on requirements. In addition, that the kind of short fiber is different means that any one of the fiber material, the average diameter, and the average length is different.
[0042]
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.
[0043]
【Example】
A tire having a tire size of 205 / 65R15 and having the structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and each sample tire was tested for rolling resistance, handling stability, riding comfort, and durability. The structure other than the short fiber reinforced rubber layer is the same for each tire as shown in Table 2.
The test method is as follows.
[0044]
(1) Rolling resistance:
Using a rolling resistance tester, the measured rolling resistance value of each tire was measured under the conditions of rim (15 × 6.5JJ), internal pressure (200 kPa), speed (80 km / h), and load (4.5 kN). The index is displayed as an index with the conventional example as 100. The smaller the index, the better the resistance.
[0045]
(2) Steering stability and ride comfort;
Steering stability and riding when the tire is mounted on four wheels of a passenger vehicle (2000cc, FF vehicle) under the conditions of rim (15 × 6.5JJ) and internal pressure (200 kPa) and traveling on a dry asphalt road test course The comfort is displayed as an index with the conventional example being 100 based on the sensory evaluation of the driver. A larger index is better.
[0046]
(3) Durability;
Using a drum tester, a step speed method was performed in accordance with a load / speed performance test defined by ECE30 under the conditions of a rim (15 × 6.5 JJ) and an internal pressure (200 kPa). In the test, the running speed is sequentially increased, and the speed when the tire breaks is displayed as an index with the conventional example being 100. A larger index is better.
[0047]
[Table 1]

[0048]
[Table 2]

[0049]
【The invention's effect】
As described above, in the present invention, the short fiber reinforced rubber layer is formed by a plurality of rubber regions which are divided inward and outward in the radial direction and have different blending amounts of the short fibers, so that the folded height of the carcass and the height of the bead apex are increased. In the tire having improved rolling resistance by reducing the height, it is possible to improve the handling stability, the ride comfort and the durability.
[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 together with a short fiber reinforced rubber layer.
FIG. 3 is a cross-sectional view showing another example of a short fiber reinforced rubber layer.
4A and 4B are schematic cross-sectional views illustrating a boundary line between rubber regions. FIG.
FIG. 5 is a diagram for explaining the prior art.
[Explanation of symbols]
3 Sidewall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 6a Ply body part 6b Ply turn-up part 8 Bead apex rubber 10 Short fiber reinforced rubber layer 11 Rubber region

Claims (3)

A carcass composed of a single carcass ply in which a ply turn-up portion that folds around the bead core is integrally provided on a ply main body portion that extends from the tread portion through the sidewall portion to the bead core of the bead portion, and the ply main body portion and the ply A pneumatic tire comprising a bead apex rubber that extends in a tapered manner from the bead core toward the outside in the radial direction of the tire through the folded portion,
The carcass ply has a height h1 from the bead base line of the radially outer end of the ply turn-up portion of 0.12 to 0.15 times the tire cross-section height H, and the bead apex rubber is radially outward. The height h2 from the end bead baseline is 0.20 to 0.25 times the tire cross-section height H,
In addition, a short fiber reinforced rubber layer extending along the outer surface of the bead apex rubber and extending along the outer surface of the ply main body portion along the outer surface of the bead apex rubber is disposed on the sidewall portion,
The short fiber reinforced rubber layer is formed by continuing a plurality of rubber regions that are divided inward and outward in the radial direction and have different blending amounts of short fibers ,
In addition , the pneumatic tire is characterized in that the blending amount of the short fibers in the radially outer rubber region is larger than the blending amount of the short fibers in the adjacent rubber region on the radially inner side .   The short fiber reinforced rubber layer starts from a position where its radially inner end exceeds the outer end of the ply folded portion radially outward, and the radially outer end is located in the vicinity of the tire maximum width point, 2. The pneumatic tire according to claim 1, wherein an outer end of the radially innermost rubber region is located radially outward from the outer end of the bead apex rubber. The pneumatic tire according to claim 1 or 2, wherein a rubber thickness t of the short fiber reinforced rubber layer is 0.3 to 1.0 mm .

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