JP2009137403A - Pneumatic radial-ply tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial-ply tire capable of further improving steering stability while maintaining high riding comfort and durability. <P>SOLUTION: This pneumatic radial-ply tire is equipped with a wing part. The wing part is formed of a rubber composition for a wing containing a rubber component and 2 pts.mass or more and 20 pts.mass or less of a fiber-like filler with respect to 100 pts.mass of the rubber component. In the wing part, a ratio E*a/E*b between a complex modulus E*a in the tire circumferential direction measured at 70°C, a frequency of 10 Hz, and ±2% dynamic strain and a complex modulus E*b in the tire radial direction is set to 1.5 or more. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire.

  In recent years, with improvement in durability performance of automobiles, improvement in durability performance (particularly wear resistance life) for tires is required. One attempt to meet this requirement is to design the tire groove depth deep. This makes it possible to prolong the wear resistance life of the tire to some extent, but as the grooves become deeper, the deformation strain of the tread block tends to increase, and uneven wear tends to occur.

  In order to solve this problem, it is conceivable to improve the rubber hardness of the tread part, but simply improving the rubber hardness of the tread part deteriorates the grip strength and riding comfort of the tire, resulting in the commercial value of the tire. Will decline.

Therefore, in order to improve these points, it has been proposed to define the complex elastic modulus of the tread portion of the tire (Patent Document 1), or to blend paper fibers into the tread rubber or sidewall rubber (Patent Document 2). However, with the recent improvement in the performance of automobiles, it is required to further improve ride comfort performance, durability performance, and steering stability.
JP 2006-213193 A JP 2006-306955 A

  The present invention has been made in view of the current situation as described above, and the object of the present invention is to provide a pneumatic system capable of further improving steering stability while maintaining high riding comfort performance and durability performance. It is to provide a radial tire.

  The pneumatic radial tire of the present invention is a pneumatic radial tire provided with a wing portion, and the wing portion is a rubber component and a fibrous form having a mass of 2 to 20 parts by mass with respect to 100 parts by mass of the rubber component. A rubber composition for a wing including a filler, and the wing portion has a complex elastic modulus E * a in the tire circumferential direction measured at a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 2%, and a tire radial. The ratio E * a / E * b to the complex elastic modulus E * b in the direction is set to 1.5 or more.

  The rubber component contained in the wing rubber composition preferably includes natural rubber and synthetic rubber, and the blending ratio of the synthetic rubber to the natural rubber is 0% by mass or more and 100% by mass or less. .

  Since the pneumatic radial tire of the present invention has the above-described configuration, the steering stability is further improved while maintaining high riding comfort performance and durability performance.

Hereinafter, the present invention will be described in more detail.
<Pneumatic radial tire>
The pneumatic radial tire of the present invention is provided with a wing portion. That is, the pneumatic radial tire of the present invention includes a pneumatic radial tire having any conventionally known structure as long as such a wing portion is provided.

  Here, the wing portion is a portion adjacent to the tread portion in contact with the road surface in the tire in the tire side surface direction, and is positioned between the tread portion and a sidewall portion forming a side surface extending inward in the tire radial direction. The part to do. A pneumatic radial tire having such a wing portion will be described with reference to FIG.

  That is, as illustrated in FIG. 1, such a pneumatic radial tire 1 includes a tread portion 2, a pair of wing portions 10 adjacent to the tread portion 2 in the tire side surface direction, and the wing portions thereof. In general, the structure includes a sidewall portion 3 that is in contact with the tire 10 and extends inward in the tire radial direction, and a bead portion 4 that is positioned at an inner end of each sidewall portion 3. A carcass 6 is bridged between the bead portions 4, and a belt layer 7 that reinforces the tread portion 2 with a tagging effect is disposed outside the carcass 6 and inside the tread portion 2. .

  The carcass 6 is formed of one or more carcass plies in which the carcass cord is arranged at an angle of, for example, 70 to 90 ° with respect to the tire equator CO. The carcass ply extends from the tread portion 2 to the sidewall portion 3. After that, the periphery of the bead core 5 of the bead portion 4 is folded back from the inner side in the tire axial direction to be locked.

  The belt layer 7 is composed of two or more belt plies in which the belt cords are arranged at an angle of, for example, 40 ° or less with respect to the tire equator CO. The belt layers 7 are stacked in different directions so that the belt cords cross each other. is doing.

  Further, a bead apex rubber 8 extending radially outward from the bead core 5 is disposed in the bead portion 4, and an inner liner rubber 9 forming a tire lumen surface is adjacent to the inside of the carcass 6. The outside of the carcass 6 is protected by clinch rubber 4G and sidewall rubber 3G.

  Such a pneumatic radial tire of the present invention can be applied to various uses such as for passenger cars, trucks and buses, and heavy machinery.

<Wing part>
The wing part of the present invention is formed of a rubber composition for a wing including a rubber component and a fibrous filler of 2 to 20 parts by mass with respect to 100 parts by mass of the rubber component, and the wing part Is a ratio E * a / E * b of the complex elastic modulus E * a in the tire circumferential direction and the complex elastic modulus E * b in the tire radial direction measured at a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 2%. It is set to 1.5 or more. The tire radial direction is a direction perpendicular to the tire circumferential direction.

  In general, it is effective to increase the rigidity of a tire in order to improve the steering stability of an automobile. However, simply increasing the rigidity may reduce the riding comfort performance. Therefore, the present invention increases the rigidity in the tire circumferential direction at the wing portion to ensure steering stability, and provides a relatively low rigidity in the tire radial direction compared to the tire circumferential direction, thereby improving ride comfort performance. It is intended to improve and improve the durability performance while maintaining these balances. And, improvement of such various characteristics is achieved not by merely controlling the complex elastic modulus, but by the synergistic action of both by selecting the composition of the rubber composition constituting the part. . As a result, vibrations due to road surface unevenness can be effectively absorbed and extremely good riding comfort performance can be ensured.Therefore, in the pneumatic radial tire of the present invention, steering stability is maintained while maintaining riding comfort performance. In addition to the improvement, the durability performance has also been improved.

  When the ratio E * a / E * b of the complex elastic modulus is 1.5 or more, the riding comfort performance and the steering stability are both good, and the performance balance is also good. This E * a / E * b is particularly preferably 1.6 or more, particularly preferably 10 or less, and further preferably 9 or less. If E * a / E * b is 10 or less, the tire circumferential direction and the tire radial direction do not become extremely rigid or low-rigidity, and it is possible to achieve both riding comfort performance and steering stability and wear resistance. Such an extreme decrease in durability performance is avoided.

  In the present invention, the complex elastic modulus E * a is preferably 10 MPa or more and 50 MPa or less. When E * a is 10 MPa or more, the wing part has sufficient rigidity and therefore steering stability is good, and when it is 50 MPa or less, there is little risk of impairing riding comfort performance and durability performance. In the present invention, the complex elastic modulus E * b is preferably 4 MPa or more and 11 MPa or less. When E * b is 4 MPa or more, steering stability is good, and when E * b is 11 MPa or less, there is little risk of impairing riding comfort performance and durability performance.

  Incidentally, the anisotropy of the complex elastic modulus in the tire circumferential direction and the tire radial direction in such a wing portion is, for example, the orientation of the fibrous filler in the wing rubber composition by adjusting the extrusion conditions of the wing rubber composition. It can be arbitrarily set by a method for controlling the state. Specifically, for example, by orienting the fibrous filler in the wing portion in the tire circumferential direction, the anisotropy can be controlled so that the tire circumferential direction is more rigid than the tire radial direction.

<Rubber composition for wing>
The rubber composition for a wing forming the wing part includes a rubber component and a fibrous filler of 2 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the rubber component. Such a rubber composition for wings may contain other components as long as it contains a rubber component and a fibrous filler.

<Rubber component>
The rubber component contained in the rubber composition for wings can contain natural rubber and synthetic rubber, either alone or in combination. And as for the compounding ratio of natural rubber and synthetic rubber, it is preferable that especially the compounding ratio of synthetic rubber with respect to natural rubber shall be 0 mass% or more and 100 mass% or less. By adopting such a blending ratio, it is possible to contribute extremely effectively to the development of the characteristics of the present invention, in which both steering stability and ride comfort performance are achieved and durability performance is also improved. When the blending ratio of the synthetic rubber exceeds 100% by mass, it may be difficult to develop such characteristics.

  The upper limit of the blending ratio of the synthetic rubber to the natural rubber is more preferably 90% by mass, still more preferably 80% by mass, and the lower limit is 10% by mass, further preferably 20% by mass.

  Here, any natural rubber may be used as the natural rubber, and the place of origin is not limited. Such natural rubber mainly contains cis 1,4 polyisoprene, but may also contain trans 1,4 polyisoprene. Therefore, the natural rubber includes natural rubber mainly containing trans 1,4 isoprene, such as balata which is a kind of rubber of the South American Acatecaceae, in addition to natural rubber mainly containing cis 1,4 polyisoprene. It is. One or more of such natural rubbers can be included.

  Such natural rubber also includes modified natural rubber obtained by modifying or purifying the above natural rubber. For example, epoxidized natural rubber (ENR), deproteinized natural rubber (DPNR) and the like are included.

  On the other hand, examples of the synthetic rubber include styrene butadiene rubber (SBR), butadiene rubber (BR), styrene isoprene copolymer rubber, isoprene rubber (IR), ethylene-propylene-diene rubber (EPDM), butyl rubber (IIR), and chloroprene. Examples thereof include rubber (CR), acrylonitrile butadiene rubber (NBR), halogenated butyl rubber (X-IIR), and a halide of a copolymer of isobutylene and p-methylstyrene. One or more of such synthetic rubbers can be included.

  The ethylene-propylene-diene rubber (EPDM) is an ethylene-propylene rubber (EPM) containing a third diene component. Examples of the third diene component include non-conjugated dienes having 5 to 20 carbon atoms such as 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, and 2,5-dimethyl-1,5. -Hexadiene and 1,4-octadiene, cyclic dienes such as 1,4-cyclohexadiene, cyclooctadiene, dicyclopentadiene, 5-ethylidene-2-norbornene, 5-butylidene-2-norbornene, 2-methallyl-5 Preferred examples include alkenyl norbornene such as -norbornene and 2-isopropenyl-5-norbornene. In particular, dicyclopentadiene, 5-ethylidene-2-norbornene and the like can be preferably used.

<Fibrous filler>
The fibrous filler contained in the rubber composition for wings of the present invention is contained at a compounding ratio of 2 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the rubber component. If the blending ratio of the fibrous filler is 2 parts by mass or more, the wing part has a sufficient reinforcing effect, and if it is 20 parts by mass or less, the ride performance deteriorates due to the wing part becoming too hard, and the tension It is possible to prevent a decrease in durability due to a decrease in strength or the like. The blending ratio of the fibrous filler is more preferably 3 parts by mass or more, further preferably 4 parts by mass or more, and is preferably 15 parts by mass or less, more preferably 10 parts by mass or less.

  By including the fibrous filler in the wing portion in this way, the above-mentioned characteristics are achieved mainly by effectively improving the rigidity in the tire circumferential direction of the wing portion (in particular, improving the uneven wear resistance performance of the tire shoulder portion). Can contribute to the expression of. And the rigidity of the tire peripheral direction of such a wing part can be controlled simply and arbitrarily by setting the kind and compounding quantity of a fibrous filler suitably.

  Here, the fibrous filler used in the present invention refers to short fibers, and preferably has the following shape, for example. That is, short fibers having an average length L of 5 μm or more and a ratio L / D of the average length L to the average diameter D of 10 or more are preferable.

  Further, the average length L is preferably in the range of 10 to 1000 μm. When this average length L is 5 micrometers or more, it can contribute to expression of the above outstanding various characteristics. Moreover, when this average length L is 1000 micrometers or less, the dispersion | distribution defect of the fibrous filler in a rubber composition and the nonuniformity of the physical property of a rubber composition are prevented favorably.

  Moreover, it is preferable that the average diameter D of a fibrous filler shall be in the range of 0.05-800 micrometers, for example, further in the range of 1-400 micrometers, and also in the range of 10-200 micrometers. When the average diameter D is 0.05 μm or more, it can contribute to the development of the excellent properties as described above, and when it is 800 μm or less, poor dispersion of the fibrous filler in the rubber composition or rubber Nonuniformity in the physical properties of the composition is well prevented.

  And in this invention, it is preferable that ratio L / D of this average length L and this average diameter D is 10 or more, and also exists in the range of 20-2000. When the ratio L / D is 10 or more, it can contribute to the development of the excellent properties as described above. When the ratio L / D is 2000 or less, poor dispersion of the fibrous filler in the rubber composition or the rubber composition. Unevenness of physical properties of the material can be prevented well.

  In addition, the average length L and the average diameter D of the fibrous filler in the present invention are evaluated by a method of calculating from values measured by image analysis from an image taken using, for example, a scanning electron microscope.

  Examples of such fibrous filler include fibrous fillers such as carbon fiber, paper fiber, and organic fiber. Here, as the carbon fiber, for example, a single-walled carbon nanotube, a multi-walled carbon nanotube, a carbon fiber, or the like can be used.

  Paper fibers include pulp obtained by pulping methods such as kraft pulp, semi-chemical pulp, mechanical pulp, non-wood pulp derived from kenaf, bagasse, bamboo, cotton, seaweed, used copy paper, old paper Examples thereof include those prepared by using one kind or a mixture of two or more kinds of raw paper obtained from waste paper pulp obtained by deinking waste paper such as newspaper and old corrugated cardboard. For example, paper fibers having a relatively large physical strength such as pulverized kraft paper are preferably used. Kraft paper refers to all paper obtained by making kraft pulp (KP), and includes unbleached kraft paper and bleached kraft paper. Kraft pulp is the mainstream of those classified as chemical pulp, and since it has a relatively long fiber length, kraft paper is widely used for packaging applications and the like as paper having excellent strength. As the kraft pulp, either softwood kraft pulp or hardwood kraft pulp can be used, but softwood kraft pulp is preferable because of its relatively long fiber length.

  Such kraft pulp is generally produced by the following method. First, impurities of the chip as a raw material are removed, and the thickness, length, etc. are made uniform within a certain range. Next, the chips are steamed with chemicals such as caustic soda and sodium sulfide at a high temperature of, for example, about 150 to 160 ° C. to elute mainly lignin in the chips and pulp. After passing through a washing step for separating the eluted lignin and chemicals from the pulp, the pulp is further treated with oxygen and alkali to further elute residual lignin in the pulp. Finally, foreign matter is removed and washed to obtain unbleached kraft pulp. Unbleached kraft pulp can be made bleached kraft pulp through a bleaching process. By making unbleached kraft pulp, unbleached kraft paper and by making bleached kraft pulp can be produced.

  On the other hand, examples of the organic fiber include vinylon fiber, nylon fiber, polyester fiber, and acrylic fiber.

<Other ingredients>
The rubber composition for a wing of the present invention may contain other components in addition to the above components. Examples of such other components include carbon black, white filler, silane coupling agent, vulcanizing agent (sulfur), vulcanization accelerator, vulcanization aid, cross-linking agent, cross-linking accelerator, anti-aging agent, A range in which the above-mentioned effects of the present invention are exhibited by using various conventionally known compounding agents or additives blended for tires or general rubber compositions such as fillers, waxes, oils, softeners, plasticizers and coupling agents It can mix | blend by the arbitrary compounding quantity of these.

  In the present invention, it is preferable to blend a silane coupling agent among the above-mentioned various blending agents. Such a silane coupling agent is preferably blended in an amount of 0.1 to 5 parts by mass with respect to 100 parts by mass of the rubber component. As a result, the fibrous filler (particularly the hydroxyl group contained in the polysaccharide such as paper fiber) and the silane coupling agent react with each other, thereby providing a good reinforcing effect to the rubber composition. Therefore, when a silane coupling agent is blended in the rubber composition for a wing of the present invention, the wear resistance (that is, durability performance) and steering stability of the tire can be remarkably improved. When the compounding amount of the silane coupling agent is 0.1 parts by mass or more with respect to 100 parts by mass of the rubber component, the effect of improving the wear resistance and the steering stability can be favorably obtained. Moreover, when the compounding quantity of a silane coupling agent is 5 mass parts or less, there is little danger that the rubber | gum kneading | mixing and the burning (scorch) in an extrusion process will arise. As the silane coupling agent, a sulfur-containing silane coupling agent is particularly preferably used in terms of reaction efficiency, dispersibility during processing, and the like. Preferred sulfur-containing silane coupling agents include 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, trimethoxysilylpropyl-mercaptobenzothiazole tetrasulfide, triethoxysilylpropyl-methacrylate-monosulfide, dimethoxy Examples include methylsilylpropyl-N, N-dimethylthiocarbamoyl-tetrasulfide, bis- [3- (triethoxysilyl) -propyl] tetrasulfide, 3-mercaptopropyltrimethoxysilane and the like.

  Other silane coupling agents include vinyltrichlorosilane, vinyltris (2-methoxyethoxy) silane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and γ- (2-aminoethyl) amino. Propyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and the like can be used.

  In the present invention, other coupling agents such as aluminate coupling agents and titanium coupling agents can be used alone or in combination with a silane coupling agent depending on the application.

<Manufacturing method>
The pneumatic radial tire of the present invention is manufactured with extremely good processability by a conventionally known method using the above-described rubber composition for a wing. That is, the rubber composition for a wing having the above-described structure is kneaded, extruded in accordance with the shape of the wing portion of the tire at an unvulcanized stage, and a normal method on a tire molding machine together with other members of the tire. An unvulcanized tire is formed by molding with. By heating and pressurizing this unvulcanized tire in a vulcanizer, the pneumatic tire of the present invention can be obtained with extremely good workability.

  As described above, the anisotropy of the complex elastic modulus in the tire circumferential direction and the tire radial direction in such a wing portion is, for example, in the wing rubber composition by adjusting the extrusion conditions of the wing rubber composition. It can be arbitrarily set by a method for controlling the orientation state of the fibrous filler. Specifically, for example, by orienting the fibrous filler in the wing portion in the tire circumferential direction, the anisotropy can be controlled so that the tire circumferential direction is more rigid than the tire radial direction.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Examples 1-6 and Comparative Examples 1-2>
<Preparation of rubber composition for wing>
In accordance with the formulation shown in Table 1, using a 1.7L Banbury mixer manufactured by Kobe Steel, the components other than sulfur and vulcanization accelerator were filled so that the filling rate was 58%, and the rotation speed was 80 rpm. And kneading at 150 ° C. for 5 minutes. Subsequently, sulfur and a vulcanization accelerator were added to the obtained kneaded material in the amounts shown in Table 1, and then kneaded for 5 minutes at 90 ° C. using a biaxial open roll. Examples 1 to 6 and comparison The kneaded rubber composition for wings of Examples 1 and 2 was obtained.

In Table 1, the details of various blending components used in Examples and Comparative Examples are as follows.
(1) NR: Natural rubber (“RSS # 3” made in Thailand).
(2) BR: Butadiene rubber ("BR150" manufactured by Ube Industries). These NR and BR are rubber components.
(3) Fibrous filler A: carbon fiber. “MLD-300” manufactured by Toray Industries, Inc. (average length L: 130 μm, L / D: 18.6).
(4) Fibrous filler B: paper fiber (craft paper pulverized product). “Mill Five 100” manufactured by Sankyo Seimitsu Co., Ltd. (average length L: 10 μm, L / D: 100).
(5) Fibrous filler C: Organic fiber (vinylon fiber). A product obtained by freeze-kneading “Kuraray Vinylon” manufactured by Kuraray Co., Ltd. (average length L: 200 μm, L / D: 10).
(6) Carbon black: “N220” manufactured by Mitsubishi Chemical Corporation.
(7) Silane coupling agent: “Si266” manufactured by Degussa.
(8) Aroma oil: “Diana Process AH40” manufactured by Idemitsu Kosan Co., Ltd. as process oil.
(9) Wax: “Sannok N” manufactured by Ouchi Shinsei Chemical Co., Ltd.
(10) Anti-aging agent A: “Ozonon 6C” manufactured by Seiko Chemical Co., Ltd.
(11) Anti-aging agent B: “NOCRACK 224” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.
(12) Stearic acid: manufactured by NOF Corporation. Acts as a vulcanization aid.
(13) Zinc oxide: “Ginbae R” manufactured by Toho Zinc Co., Ltd. Acts as a vulcanization aid.
(14) Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Co., Ltd.
(15) Vulcanization accelerator: “Noxeller NS” (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.

<Production of pneumatic radial tire>
Each rubber sheet (with the cross-sectional shape shown in FIG. 2 and having a length of 1880 mm) is prepared using the rubber composition for each wing obtained above, and then bonded together with other members. Pneumatic radial tires (size: 195 / 65R15) of Examples 1 to 6 and Comparative Examples 1 to 2 were produced by press vulcanization at 25 kgf at 150 ° C. for 35 minutes.

  Such a pneumatic radial tire has a structure as shown in FIG. 1, and the details thereof are as follows.

<Structure of pneumatic radial tire>
Carcass: Material Polyester (1500 denier)
Composition 1500 denier / 2 (1670 dtex / 2)
Ends 50 code / 50mm
Belt layer: Material Steel cord,
Structure 1 × 4 × 0.27, Ends 40 code / 50mm
Angle 22 ° × 22 °
<Performance evaluation>
The following performance evaluation was performed. The results are shown in Table 1.

<Complex modulus>
A strip-shaped sample (width 4 mm × length 30 mm × thickness 1.5 mm) is prepared from the wing portion of the pneumatic radial tire obtained above, and the temperature is set to 70 with a viscoelastic spectrometer manufactured by Iwamoto Seisakusho using this sample. The complex elastic modulus E * a in the tire circumferential direction and the complex elastic modulus E * b in the tire radial direction are measured under the conditions of ° C, frequency 10 Hz, and dynamic strain ± 2%, and the ratio E * a / E * b is Asked. The results are shown in Table 1.

<Tensile strength>
In accordance with JIS-K6251, the rubber composition for wings obtained in the above is pressed under pressure at 160 ° C. for 30 minutes to prepare a sheet (length 100 mm × width 100 mm × thickness 2 mm). A sample was punched out and a tensile test was performed using this sample. The results are shown in Table 1.

<Hardness>
A block-like sample (length 30 mm × width 50 mm × height 15 mm) was prepared by press-pressing the kneaded rubber composition for wing obtained above at 160 ° C. for 30 minutes, and using this sample, JIS was used. The hardness (Hs) was measured according to -K6253. The results are shown in Table 1.

<Tensile breaking elongation (EB)>
The test was conducted according to JIS-K6251. The results are shown in Table 1.

<Steering stability and ride comfort>
The pneumatic radial tire obtained above is installed in the car, and it runs at 40-120km / h on the test course. Steering stability (handle responsiveness, rigidity, grip) and riding comfort performance depend on the test driver. A feeling test was carried out. The evaluation of the test was performed by a ten-point scale method, and the average value of the three drivers was represented by an index with the pneumatic radial tire of Comparative Example 1 being “6”. The larger the numerical value, the better the steering stability and ride comfort performance. The results are shown in Table 1.

<Durability>
The pneumatic radial tire obtained above is mounted on an automobile (Toyota "Corolla") with a tire internal pressure of 230 kPa, and the rain rate is 30% or less when traveling on a regular road / highway at a ratio of 50/50 for 8000 km. The MIX road wear test was performed under the conditions, and the durability performance was evaluated by observing the presence or absence of uneven wear on the tire shoulder. In the evaluation, “A” indicates that there is no uneven wear, “B” indicates that there is uneven wear, and “C” indicates that there is significant uneven wear. Is excellent). The results are shown in Table 1.

<Evaluation results>
As is clear from Table 1, the pneumatic radial tires of the examples showed excellent handling stability while maintaining high ride comfort and durability performance compared to the pneumatic radial tires of the comparative examples. Therefore, the complex elastic modulus E * a in the tire circumferential direction and the tire radial direction, which are formed of the specific rubber composition for wings defined in the present invention and measured at a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 2%. Pneumatic radial tires with wings that have a ratio E * a / E * b to 1.5 or higher of the complex elastic modulus E * b are excellent while maintaining high ride comfort and durability. It was confirmed that the steering stability was improved.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic sectional drawing which shows an example of the pneumatic radial tire of this invention. It is the figure which showed the cross-sectional shape of the rubber sheet.

Explanation of symbols

  1 Pneumatic radial tire, 2 tread part, 3 side wall part, 4 bead part, 5 bead core, 6 carcass, 7 belt layer, 8 bead apex rubber, 9 inner liner rubber, 10 wing part.

Claims (2)

A pneumatic radial tire having a wing portion,
The wing part is formed of a rubber composition for a wing that includes a rubber component and a fibrous filler of 2 to 20 parts by mass with respect to 100 parts by mass of the rubber component, and
The wing portion has a ratio E * a / E of a complex elastic modulus E * a in the tire circumferential direction and a complex elastic modulus E * b in the tire radial direction measured at a temperature of 70 ° C., a frequency of 10 Hz, and a dynamic strain of ± 2%. * Pneumatic radial tire with b set to 1.5 or higher.   The pneumatic radial according to claim 1, wherein the rubber component contained in the rubber composition for wing includes natural rubber and synthetic rubber, and a blending ratio of the synthetic rubber to the natural rubber is 0% by mass or more and 100% by mass or less. tire.

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