JP4244118B2 - Pneumatic tire - Google Patents

Description

【００３３】
そのときの耐久性能評価結果を表２に示す。表中、「重量」とはタイヤ重量であり、従来品を１００としたときの指数値で示す。また、表中「耐久力」は、タイヤ故障が発生するまでの走行距離を従来品を１００としたときの指数評価で表したものである。
【００３４】
【表２】

【００３５】
表２に示すように、実施例１〜４のいずれもタイヤ重量及び耐久力が従来品に対して１１０〜１３０と向上しているのが判る。円弧径比４５％（実施例４）で耐久力が１１０であり、円弧径比３０％（実施例３）で耐久力が１１５、円弧径比１４％（実施例２）で耐久力が１３０と最高であり、円弧径比１０％（実施例１）で耐久力がやや下がって１２０となる。また、円弧径比が６０％の比較品の場合、従来品に比べてタイヤ重量が軽減されているが、耐久力については従来品と同等であった。従って、円弧径比がほぼ５０％を超える場合には、耐久性能向上の効果が小さいことが判明した。
【００３６】
このことから、タイヤ重量を増加することなく、耐久性能を向上させる円弧径比は１０〜５０％、好ましくは１０〜３０％、より好ましくは１０〜２０％といえる。
【００３７】
【発明の効果】
以上の説明から明らかな通り、本発明によると、サイドウオールの最大幅位置のカーカスライン形状を表わす円弧径が、カーカスラインを構成する全ての円弧径の中で最小となるサイド形状、特に、最大幅位置のカーカスラインを表わす円弧径を、カーカスラインにおけるベルト端部相当のカーカス位置、最大幅位置相当のカーカス位置、ビードコア位置相当のカーカス位置の３点を結ぶ円弧径に対して、その比率を１０〜５０％内に設定したので、タイヤ重量を増加することがなく耐久性能を向上させることができる。
【図面の簡単な説明】
【図１】本発明に係る空気入りタイヤの一実施形態である微小空気圧を充填したときのタイヤ幅方向断面図（右半分）である。
【図２】同じくその要部拡大断面図である。
【符号の説明】
１ 空気入りタイヤ
２ カーカス
３ ビードコア
４ ビードフィラー
５ トレッド
６ サイドウオール
７ リムストリップ
９ インナライナー
１０ ビードチェーファ
１１ フリッパー
１２ 接着ゴム層
１３ ベルト層
１４ ベルト補強層
ＲＬ リム径ライン
Ｄｍａｘ タイヤ最大幅位置ライン[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire that can solve a durability problem caused by separation between plies.
[0002]
[Prior art]
In a pneumatic tire having a small flatness ratio, a separation phenomenon occurs between the main carcass of the carcass layer and the winding ply, which causes a problem in durability.
[0003]
As a countermeasure,
i) An adhesive rubber layer is interposed between the main body carcass and the winding part.
ii) increase the thickness of the pre-tapping rubber,
iii) Change the winding ply position,
Therefore, it is conceivable to reduce the shear strain generated between the plies.
[0004]
[Problems to be solved by the invention]
By the way, when the improvement for the performance improvement is performed, if the adhesive rubber layer is interposed or the amount of the topping rubber is increased, the weight of the entire tire is increased.
[0005]
Further, if the position of the winding ply is changed, each member step becomes smaller as the flatness ratio becomes lower, so that the change is not easy. That is, generally, stress concentration occurs in the vicinity of the member end due to a difference in rigidity from the other member. Therefore, each member step becomes smaller as the flatness ratio becomes lower, and stress concentration points are adjacent to each other, and a failure is likely to occur. Therefore, it is not easy to change the position of the winding ply as the flatness ratio decreases.
[0006]
In view of the above problems, an object of the present invention is to provide a pneumatic tire capable of improving durability without accompanying an increase in weight.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors pay attention to a durability index such as strain energy, and in order to reduce it, by using an optimization method based on FEM (finite element method) analysis, the adhesion of the side portion is achieved. The tire cross-sectional shape of the optimal solution that can reduce the strain energy in the rubber layer was obtained, and this was replaced with the carcass line shape to define the tire cross-sectional shape.
[0008]
According to this, when the rim is assembled on a regular rim and filled with micro air pressure, the arc diameter representing the carcass line shape at the maximum width position of the side portion is the smallest of all the arc diameters constituting the carcass line. It has been found that the shape of the side portion can improve the durability without increasing the tire weight.
[0009]
That is, the present invention is characterized by a pneumatic tire having a side shape in which the arc diameter representing the carcass line at the maximum width position is the smallest among all the arc diameters constituting the carcass line.
[0010]
Specifically, when the rim is assembled on a normal rim and filled with micro air pressure, the arc diameter representing the carcass line at the maximum width position is the carcass position corresponding to the belt end in the carcass line, and the carcass position corresponding to the maximum width position. The side shape has a ratio within 10 to 50% with respect to the arc diameter connecting three points of the carcass position corresponding to the bead core position.
[0011]
According to the experiments by the present inventors, when the arc diameter is smaller than 10%, the manufacturing process is liable to occur, and when the arc diameter exceeds 50% and the arc diameter is large, the effect of improving the durability performance is small. It has been found.
[0012]
The tire cross-sectional shape according to the present invention can be applied regardless of the flatness of the tire, but is preferably applied to a tire with a flatness of 45 or less, in which the position of the winding ply cannot be easily changed. .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of a pneumatic tire according to the present invention, and shows a cross-sectional view in the tire width direction of a tire with a small flatness ratio when a rim is assembled on a regular rim and filled with micro air pressure (internal pressure of 20 kPa). Yes. Since the tire cross-sectional shape is symmetrical, only the right half is shown. FIG. 2 is an enlarged cross-sectional view of the main part.
[0014]
In the figure, 1 is a pneumatic tire, 2 is a carcass, 3 is a bead core, 4 is a bead filler, 5 is a tread, 6 is a side wall, 7 is a rim strip, 9 is an inner liner, 10 is a bead chafer, and 11 is a flipper. , 12 is an adhesive rubber layer, 13 is a belt layer, and 14 is a belt reinforcing layer. In FIG. 1, RL indicates a rim diameter line, and Dmax indicates a tire maximum width position line.
[0015]
The pneumatic tire 1 according to the present embodiment includes a pair of left and right bead portions that serve to fix a tire filled with air pressure to a rim, a tread portion that contacts the road surface, and a side portion between the tread portion and the bead portion. The cross section is formed in a substantially arc shape.
[0016]
The main components of the pneumatic tire 1 are a bead core 3 constituting a pair of left and right bead portions, and a bead portion that extends from the tread portion to both bead portions through both side portions and is wound around the bead core 3 from the inside of the tire to the outside. A substantially arc-shaped carcass 2 that is moored to hold a large internal pressure, a belt layer 13 that is disposed outside the carcass 2 in the tread portion in the radial direction and suppresses dimensional growth of the tire in use, and a radial direction of the belt layer 13 A tread 5 made of a rubber layer arranged on the outside and in contact with the road surface to transmit the force directly, and a rubber layer protecting the side part that is susceptible to trauma during running disposed on the outer side in the tire axial direction of the carcass 2 at the side part And side wall 6.
[0017]
The carcass 2 is composed of at least one ply carcass ply. The carcass ply is formed by weaving a cord with a structure in which a plurality of heat-shrinkable organic fibers, such as nylon and polyester, are twisted together and rubber-coating the cord. The cord direction is the radial direction. ing. An inner liner 9 for holding the tire internal pressure instead of the tube is attached to the inside of the carcass 2 to the bead portion.
[0018]
In the bead portion, a bead core 3 formed by coating a plurality of metal core wires with rubber, and a bead filler 4 having a substantially triangular cross section made of hard rubber extending from the bead core 3 to the side wall side are provided. The flipper 11 is wound, and a bead portion 2b continuous to the carcass main body 2a of the carcass 2 is wound outside the flipper 11 from the inside of the tire to the outside, and the end portion of the winding portion 2c is the tire maximum width position Dmax. It has reached the vicinity.
[0019]
Further, in the bead portion, the outer side of the folded portion (bead portion 2b) of the carcass 2 is covered by the chafer 10, and the bead portion is reinforced. The inner side in the tire axial direction of the chafer 10 is covered with an inner liner 9, and a rim strip 7 made of rubber having a substantially inverted triangular cross section is joined to the outer side in the tire axial direction.
[0020]
In the side portion, an adhesive rubber layer 12 is interposed between the carcass main body 2a on the tire inner side and the winding portion 2c on the tire outer side, and the adhesive rubber layer 12 is more tire-shaped than the end portion in the width direction of the belt layer 13. It reaches to the equator side. A side wall 6 is disposed on the outer side in the tire axial direction of the adhesive rubber layer 12 so as to continue to the rim strip 7 and to the end in the tire width direction of the tread rubber 5.
[0021]
In the tread portion, the two belt layers 13 are arranged on the outer side in the radial direction of the carcass 2, the two belt reinforcing layers 14 are arranged on the outer side in the radial direction, and the tread rubber 5 is arranged on the outer side. .
[0022]
The belt layer 13 is composed of two belt plies, and each belt ply has a plurality of cords that are inclined with respect to the tire circumferential direction and that intersects each other in adjacent belt plies. Yes. The belt reinforcement layer 14 is formed by rubberizing nylon cords or the like arranged substantially parallel to the tire circumferential direction into a ribbon shape.
[0023]
The cross-sectional shape of the tire 1 is a convex shape on the outer side in the tire axial direction at the side portion, when the rim is assembled on a regular rim (not shown) and filled with micro air pressure (20 kPa in this embodiment). An arc diameter R1 representing a carcass line at a large position (a line passing through the center in the thickness direction of the carcass) is set to be the smallest among all the arc diameters R2 constituting the carcass line.
[0024]
Here, 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 is used for JATMA, “Design Rim” is used for TRA, and ETRTO is used. Then “Measuring Rim”.
[0025]
As a specific aspect of the arc diameter, as shown in FIG. 2, the arc diameter R1 representing the carcass line at the maximum width position is a carcass position A corresponding to the belt end, a carcass position B corresponding to the maximum width position, and a bead core position. The ratio is set to an arc diameter within 10 to 50% with respect to the arc diameter R2 connecting the three points of the corresponding carcass position C. Further, the preferable arc diameter ratio is 10 to 30%, more preferably 10 to 20%.
[0026]
Here, as shown in FIG. 2, the carcass position A corresponding to the belt end portion is the intersection of the perpendicular line from the belt end portion 13a and the carcass line, and the carcass position B corresponding to the maximum width position is the maximum width position. The intersection of the straight line parallel to the rim diameter line RL and the carcass line, and the carcass position C corresponding to the bead core position are the intersection of the straight line passing through the upper end of the bead core 3 and parallel to the rim diameter line RL and the carcass line.
[0027]
These three points are designated because the arc connecting the three designated points is approximately similar to the shape of the conventional tire side portion, and the conventional tire cross-sectional shape is compared with the tire cross-sectional shape according to the present invention. This is because it was considered suitable for clearly showing the difference between the two.
[0028]
FIG. 2 shows the cross-sectional shape of a 205 / 40ZR17 tire. In this example, the arc diameter R1 representing the carcass line at the maximum width position has a radius of 3.5 mm, whereas the three points A and B specified above are used. , C is shown as a tire whose arc diameter R2 is set to approximately 24 mm (arc diameter ratio 14%).
[0029]
Such a tire shape is an optimal solution tire cross-sectional shape that can reduce the strain energy of the adhesive rubber layer of the sidewall by using an optimization method based on FEM (finite element method) analysis. Although not shown, according to the FEM analysis, as an optimal solution, there is a tire shape that is partially convex inside the tire, but vulcanization molding cannot be easily performed with such a tire shape that is partially convex. There are drawbacks. Considering the ease of vulcanization molding, a tire shape that is convex only on the tire outer side without projecting on the tire inner side is suitable.
[0030]
【Example】
The present inventors performed a durability test on the cross-sectional shape of the tire according to the present invention under the following conditions. Test tires are conventional products (arc diameter ratio 88%), Example 1 (10%), Example 2 (14%), Example 3 (30%), Example 4 (45%), and Comparative product (60 %), And tires of 205 / 40ZR17 were used in all cases. Note that when the arc diameter is smaller than 10%, a manufacturing process defect is likely to occur, and thus test evaluation was not performed.
[0031]
The test item is an indoor durability performance test shown in Table 1. The indoor durability performance test was conducted under the test load extension conditions in which the load was increased step by step under the test conditions defined in JIS D4230 in order to promote early failure after test stage 3.
[0032]
[Table 1]

[0033]
The durability performance evaluation results at that time are shown in Table 2. In the table, “weight” is the weight of the tire, and is indicated by an index value when the conventional product is taken as 100. Further, “durability” in the table is an index evaluation with the conventional product as 100 as the running distance until a tire failure occurs.
[0034]
[Table 2]

[0035]
As shown in Table 2, it can be seen that in all of Examples 1 to 4, the tire weight and durability are improved to 110 to 130 with respect to the conventional product. The durability is 110 when the arc diameter ratio is 45% (Example 4), the durability is 115 when the arc diameter ratio is 30% (Example 3), and the durability is 130 when the arc diameter ratio is 14% (Example 2). It is the highest, and the durability is slightly reduced to 120 at an arc diameter ratio of 10% (Example 1). Further, in the case of a comparative product having an arc diameter ratio of 60%, the tire weight is reduced as compared with the conventional product, but the durability is equivalent to that of the conventional product. Accordingly, it has been found that when the arc diameter ratio exceeds approximately 50%, the effect of improving the durability performance is small.
[0036]
From this, it can be said that the arc diameter ratio for improving the durability performance without increasing the tire weight is 10 to 50%, preferably 10 to 30%, more preferably 10 to 20%.
[0037]
【The invention's effect】
As is apparent from the above description, according to the present invention, the arc shape representing the carcass line shape at the maximum width position of the side wall has the smallest side shape among all the arc diameters constituting the carcass line, particularly the most The ratio of the arc diameter representing the carcass line at the large position to the arc diameter connecting three points of the carcass position corresponding to the belt end, the carcass position corresponding to the maximum width position, and the carcass position corresponding to the bead core position in the carcass line. Since it is set within the range of 10 to 50%, the durability performance can be improved without increasing the tire weight.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view (right half) in the tire width direction when filled with micro air pressure, which is an embodiment of a pneumatic tire according to the present invention.
FIG. 2 is an enlarged cross-sectional view of the main part of the same.
[Explanation of symbols]
1 Pneumatic tire 2 Carcass 3 Bead core 4 Bead filler 5 Tread 6 Side wall 7 Rim strip 9 Inner liner 10 Bead chafer 11 Flipper 12 Adhesive rubber layer 13 Belt layer 14 Belt reinforcement layer RL Rim diameter line Dmax Tire maximum width position line

Claims (2)

The flatness is 45 or less, the bead portion continuous to the carcass main body of the carcass is folded back and wound from the inside of the tire to the outside, the end of the rolled-up portion reaches the vicinity of the tire maximum width position, and the shape of the side portion When the rim is assembled on a regular rim and filled with air pressure of 20 kPa, the arc diameter representing the carcass line at the maximum width position has a side portion that is the smallest of all the arc diameters constituting the carcass line. Pneumatic tire characterized by.   The arc diameter representing the carcass line at the maximum width position is the intersection of the perpendicular from the belt end and the carcass line, the intersection of a straight line passing through the maximum width position and parallel to the rim diameter line, and the carcass line, and the upper end of the bead core 2. The air according to claim 1, wherein the ratio is set in a range of 10 to 50% with respect to an arc diameter connecting three points of intersection of a straight line parallel to the rim diameter line and the carcass line. Enter tire.

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