JP2009184512A - Run flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a run flat tire significantly improving an emergency running life, while keeping a simple tire structure, without using special equipment. <P>SOLUTION: The run flat tire includes: a pair of bead parts 1 in which a bead core 6 is buried; a pair of sidewall parts 2 extending from the bead parts 1 to the outside in a tire radial direction; a side reinforcement rubber layer 5 having a falcate cross section, and arranged in an internal sidewall part of a carcass 4 toroidally extending over each part of a tread part 3 extending between both of the sidewall parts. Rubber constituting the sidewall parts 2 contains a short fiber made of a metal fiber. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a run-flat tire (hereinafter, also simply referred to as “tire”), and more particularly, to a run-flat tire that can greatly improve the emergency running life.

  In recent years, run-flat tires in which side reinforcing rubber having a crescent-shaped cross section is disposed on the inner side wall portion of the carcass as a pneumatic tire that can run as soon as possible after the air pressure inside the tire has dropped has been widely used. ing.

  This run-flat tire enabled emergency running, but during emergency running, the temperature of the side-reinforced rubber layer with a crescent-shaped cross section of the side wall increased, and the elasticity of the side-reinforced rubber layer decreased, resulting in the emergency It has been difficult to improve the running life.

  With respect to this problem, in Patent Document 1, when using a run-flat tire having a reinforced sidewall portion, the tire shoulder portion and sidewall portion are cooled by a refrigerant every predetermined emergency traveling distance or every emergency traveling time. It has been proposed to do.

Further, in Patent Document 2, at least the high heat conduction gas such as helium gas is filled in the inner space of the tire, and an elastic ball is put in the inner space of the tire to promote stirring of the filled gas, or the wheel and the inner space of the tire A technique for quickly dissipating heat in the tire inner space by providing heat collecting fins on the contact surface is disclosed.
JP-A-5-8620 (Claims etc.) JP 2004-130855 A (Claims etc.)

However, the method of Patent Document 1 requires equipment for handling the cooling medium, which is expensive, and is sufficient because the thermal conductivity of the rubber constituting the sidewall portion is as low as 0.3 Wm ⁻¹ K ⁻¹ or less. A cooling effect cannot be obtained. In addition, the method of Patent Document 2 has a drawback that it is difficult to manufacture and attach a tire because helium gas or the like is used, or an elastic ball is enclosed inside a tire or a heat collecting fin is disposed. Therefore, today, there is a need for a technique that can greatly improve the emergency running life of a simple and inexpensive run-flat tire that eliminates these drawbacks.

  Accordingly, an object of the present invention is to provide a side wall portion-reinforced run-flat tire that can greatly improve the emergency running life while using a simple tire structure without using special equipment.

  As a result of intensive studies to solve such problems, the inventors have made the rubber constituting the sidewall portion of the run-flat tire contain short fibers made of metal fibers to improve the thermal conductivity of the sidewall portion. And the inventors have found that the object can be achieved by quickly dissipating heat, and have completed the present invention.

That is, the run-flat tire of the present invention includes a pair of bead portions in which a bead core is embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portion, and a tread portion extending between both sidewall portions. In the run flat tire formed by disposing a side reinforcing rubber layer having a crescent-shaped cross section on the inner sidewall portion of the carcass extending in a toroid shape,
The rubber constituting the sidewall portion contains short fibers made of metal fibers.

In the run flat tire of the present invention, as the short fiber made of the metal fiber contained in the sidewall portion, a metal fiber having a curved portion or a bent portion can be preferably used. An angle formed by connecting the midpoints, or one of the fiber ends and the inflection point of the fibers and the angle of the angle formed by connecting the midpoints is 20 to 160 ° or a bent or bent portion. Is more preferable. As the short fiber made of a metal fiber having a curved part or a bent part, a metal fiber obtained by cutting can be preferably mentioned. In the present invention, examples of the short fibers made of metal fibers include iron fibers, copper fibers, and aluminum fibers. Moreover, it is preferable that the short fiber which consists of the said metal fiber is a range whose aspect-ratio is 5-1000. Further, it is preferable that the content of the short fibers made of the metal fibers is in the range of 1 to 50 vol%, further, the thermal conductivity of the short fibers made of the metal fibers is 50Wm ^-1 K ^-1 or higher Furthermore, it is preferable that the rubber containing the short fiber made of the metal fiber has a thermal conductivity in the range of ^{1 to} 25 Wm ⁻¹ K ⁻¹ .

  According to the present invention, by including short fibers made of metal fibers in the rubber constituting the sidewall portion, the emergency running life can be greatly improved with a simple tire structure without using special equipment. A run-flat tire can be provided.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a partial cross-sectional view of a preferred example of a run-flat tire according to the present invention, which includes a pair of left and right bead portions 1 and a pair of sidewall portions 2, and a tread portion 3 connected to both side portions 2. A carcass ply 4 that extends in a toroidal manner between the bead parts 1 and reinforces each of the parts 1, 2, and 3, and a pair of crescents arranged inside the carcass ply 4 of the side part 2 And a side reinforcing rubber layer 5.

  In the illustrated tire, a bead filler 7 is disposed on the outer side in the tire radial direction of each of the ring-shaped bead cores 6 embedded in the bead portion 1, and the outer side in the tire radial direction of the tread portion of the carcass ply 4. A belt 8 composed of two belt layers is disposed in the belt. Furthermore, a belt reinforcing layer 9A is disposed so as to cover the entire belt 8 on the outer side in the tire radial direction of the belt 8, and a pair of belt reinforcing layers 9B are disposed so as to cover only both ends of the belt reinforcing layer 9A. Has been. Here, the belt layer is usually composed of a rubberized layer of a cord extending in an inclined manner with respect to the tire equatorial plane, preferably a rubberized layer of a steel cord, and the two belt layers constitute the belt layer. The belt 8 is formed by laminating the cords so as to cross each other with the equator plane interposed therebetween. The belt reinforcing layers 9A and 9B are usually made of rubberized layers of cords arranged substantially parallel to the tire circumferential direction.

  The carcass ply 4 in the illustrated example is composed of a single carcass ply formed by coating a plurality of reinforcing cords arranged in parallel with a coating rubber, and the carcass ply 4 is respectively disposed in the bead portion 1. The present invention comprises a main body portion extending in a toroidal shape between a pair of embedded bead cores 6 and a folded portion wound around each bead core 6 radially outward from the inner side to the outer side in the tire width direction. In the pneumatic tire, the number of plies and the structure of the carcass ply 4 are not limited thereto. As the reinforcing cord of the carcass ply, various types such as rayon, nylon, polyester, polyketone and the like can be suitably used. Furthermore, although the belt 8 in the illustrated example comprises two belt layers, the number of belt layers constituting the belt 8 is not limited to this in the pneumatic tire of the present invention. Furthermore, in the pneumatic tire of the present invention, it is not essential to dispose the belt reinforcing layers 9A and 9B, and a belt reinforcing layer having a different structure can be disposed.

  In this invention, the rubber which comprises the side wall part 2 contains the short fiber which consists of metal fibers, It is characterized by the above-mentioned. Thereby, the thermal conductivity of the sidewall portion 2 is increased, whereby the heat generated in the side reinforcing rubber layer 5 can be efficiently dissipated and the emergency running life can be improved.

  The short fibers made of metal fibers contained in the sidewall portion 2 preferably have a curved portion or a bent portion. Bending or bending is the angle (θ) between the fiber ends of the metal fiber and the midpoint thereof, or the angle between one of the fiber ends and the inflection point of the fiber and the midpoint thereof. Is more preferably in the range of 20 to 160 °. FIG. 2 and FIG. 3 show a metal fiber having a curved portion, and FIG. 4 shows a metal fiber having a bent portion. If the value of angle (theta) shown in each figure is in the said range, since the probability that fibers will contact will become high and heat can be conducted between fibers, heat conduction efficiency will improve favorably. On the other hand, if the value of θ is outside the above range, the short fibers are oriented during the extrusion process, and the heat conductivity in the extrusion thickness direction and the extrusion width direction cannot be obtained satisfactorily.

  Specific examples of the metal fiber having a curved portion or a bent portion include short fibers obtained by cutting. Since the fiber obtained by cutting has a curved portion, for example, a crimped fiber shape, it is difficult to align in one direction by orientation, and it exhibits sufficient thermal conductivity in the rubber extrusion thickness direction and extrusion width direction. Can do. On the other hand, the fiber obtained by spinning has a straight shape, and when dispersed in rubber, the fiber direction is aligned by orientation, so that the distance between the fibers becomes long, and good thermal conductivity cannot be obtained.

  Examples of short fibers made of metal fibers contained in the rubber constituting the sidewall portion 2 can include iron fibers, copper fibers, aluminum fibers, and the like having high thermal conductivity, and these are preferably used. Can do.

  In the present invention, the short fibers made of metal fibers preferably have an aspect ratio in the range of 5 to 1000. When the aspect ratio is less than 5, the distance between the fibers when dispersed in the rubber becomes long, and sufficient thermal conductivity cannot be obtained, and the effects of the present invention cannot be obtained satisfactorily. On the other hand, when the aspect ratio exceeds 1000, the dispersion in the rubber is deteriorated and uniform thermal conductivity cannot be obtained, and the effect of the present invention cannot be obtained satisfactorily. The aspect ratio indicates the ratio (L / D) between the major axis L and the minor axis D of the fiber. Moreover, it is preferable that the fiber diameter of a short fiber is the range of 50-500 micrometers, when obtaining the desired effect of this invention.

  Furthermore, it is preferable that the content rate of the short fiber which consists of a metal fiber contained in the rubber which comprises the side wall part 2 is in the range of 1 to 50% by volume. If it is less than 1%, sufficient thermal conductivity cannot be obtained, and the effects of the present invention cannot be obtained satisfactorily. On the other hand, if it exceeds 50%, the moldability of the rubber is deteriorated and it is difficult to use it practically.

Furthermore, the thermal conductivity of the short fibers made of metal fibers contained in the rubber constituting the sidewall portion 2 is preferably 50 Wm ⁻¹ K ⁻¹ or more. If the short fibers made of metal fibers have a thermal conductivity of less than 50 Wm ⁻¹ K ⁻¹ , sufficient thermal conductivity cannot be obtained even if they are contained in the rubber constituting the sidewall portion 2, and the effects of the present invention are improved. Can't get.

Furthermore, it is preferable that the thermal conductivity of the short fiber-containing rubber made of metal fibers constituting the sidewall portion 2 is in the range of ^{1 to} 25 Wm ⁻¹ K ⁻¹ . If it is less than ¹ Wm ⁻¹ K ⁻¹ , sufficient and efficient heat dissipation cannot be performed, so that the effect of the present invention cannot be obtained satisfactorily. On the other hand, when short fibers made of metal fibers are contained so as to exceed 25 Wm ⁻¹ K ⁻¹ , rubber moldability deteriorates and it becomes difficult to use them practically.

Hereinafter, the present invention will be specifically described based on examples.
(Examples 1-9, Comparative Examples 1-3)
Using short metal fibers having aspect ratios and thermal conductivities shown in Tables 1 to 3 below, run flat tires having predetermined short metal fiber contents and side walls having thermal conductivities shown in Tables 1 to 3 below. Produced. The run flat durability of the obtained run flat tire was evaluated by the following method, and the results are shown in Tables 1 to 3 below.

(Run flat durability)
Run-flat durability was evaluated by conducting a drum test without filling the test tire with internal pressure. The run-flat durability was measured by measuring the distance traveled until the tire failed, and the index was displayed with the distance traveled until the tire failure of the comparative example was taken as 100. The larger the index value, the longer the distance traveled until failure, and the better the run flatness. Tire size and drum test conditions are shown below each table.

タイヤサイズ：１８５／４５ＺＲ１５
ドラム試験条件：ドラム径１．７０７ｍ，荷重２．９６ｋＮ，速度８９ｋｍ，温度３８℃

Tire size: 185 / 45ZR15
Drum test conditions: Drum diameter 1.707m, load 2.96kN, speed 89km, temperature 38 ° C

タイヤサイズ：２２５／４５ＺＲ１７
ドラム試験条件：ドラム径１．７０７ｍ，荷重４．５９ｋＮ，速度８９ｋｍ，温度３８℃

Tire size: 225 / 45ZR17
Drum test conditions: Drum diameter 1.707m, load 4.59kN, speed 89km, temperature 38 ° C

タイヤサイズ：２０５／４５ＺＲ１７
ドラム試験条件：ドラム径１．７０７ｍ，荷重４．１７ｋＮ，速度８９ｋｍ，温度３８℃

Tire size: 205 / 45ZR17
Drum test conditions: Drum diameter 1.707m, load 4.17kN, speed 89km, temperature 38 ° C

  From the results of Examples 1 to 9 and Comparative Examples 1 to 3, it can be seen that run-flat durability is improved by including short fibers made of metal fibers in the rubber constituting the sidewall portion. In addition, when using short fibers obtained by cutting as short fibers made of metal fibers, run flat durability is significantly improved compared to using metal fibers obtained by spinning. confirmed.

It is sectional drawing of the right half surface of an example of the run flat tire of this invention. It is explanatory drawing which shows angle (theta) of the metal short fiber which has a curved part. It is explanatory drawing which shows angle (theta) of the metal short fiber which has a curved part and has an inflection point. It is explanatory drawing which shows angle (theta) of the short metal fiber which has a bending part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Carcass 5 Side reinforcement rubber layer 6 Bead core 7 Bead filler 8 Belt 9A, 9B Belt reinforcement layer 10 Metal short fiber 11 Metal short fiber end 12 Midpoint 13 Inflection point

Claims (9)

A pair of bead portions in which bead cores are embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portions, and an inner side of the carcass extending in a toroid shape across each portion of the tread portion extending between both sidewall portions. In the run flat tire formed by arranging a side reinforcing rubber layer having a crescent cross section in the wall portion,
A run-flat tire characterized by containing short fibers made of metal fibers in the rubber constituting the sidewall portion.   The run-flat tire according to claim 1, wherein the short fiber made of the metal fiber has a curved portion or a bent portion.   A curve in which the angle between the fiber ends of the metal fiber and the midpoint thereof, or the angle between one of the fiber ends and the inflection point of the fiber and the midpoint of the fiber is 20 to 160 °. The run flat tire according to claim 2, which has a bent portion or a bent portion.   The run-flat tire according to any one of claims 1 to 3, wherein the short fibers made of the metal fibers are made of fibers obtained by cutting.   The run-flat tire according to any one of claims 1 to 4, wherein the short fibers made of metal fibers are at least one metal fiber selected from the group consisting of iron fibers, copper fibers, and aluminum fibers.   The run flat tire according to any one of claims 1 to 5, wherein an aspect ratio of the short fibers made of the metal fibers is in a range of 5 to 1000.   The run flat tire according to any one of claims 1 to 6, wherein a content ratio of the short fibers made of the metal fibers contained in the sidewall portion is in a range of 1 to 50% by volume. The run flat tire according to any one of claims 1 to 7, wherein the short fibers made of the metal fibers contained in the sidewall portion have a thermal conductivity of 50 Wm ^-1 K ^-1 or more. The run flat according to any one of claims 1 to 8, wherein a thermal conductivity of rubber containing short fibers made of the metal fibers constituting the sidewall portion is in a range of ¹ to 25 Wm ^-1 K ^-1. tire.

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