JPH05294117A - Pneumatic radial tire for rally - Google Patents

Abstract

PURPOSE:To provide a pneumatic tire for a rally which is superior in cutting resistance, prevents exfoliation of a filler and breakage of rubber for a tire main body, and improve durability. CONSTITUTION:In a pneumatic radial tire for a rally is employed a composite cord comprising high elastic filament composed of aromatic polyamide film and low elastic filament twisted together as a cord for a filler 9 for reinforcing a side wall part 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire for a rally, which is capable of preventing peeling of a filler and enhancing durability without impairing cut resistance and riding comfort.

[0002]

2. Description of the Related Art In a tire running on rough terrain, particularly a pneumatic tire for a rally, cracks are generated when a crushed stone hits a sidewall during running.
The growth of this crack often cuts the sidewall portion. Conventionally, in order to prevent such a cut, for example, as disclosed in Japanese Patent Application Laid-Open No. 3-82611, the outer skin of the sidewall portion is formed of hard rubber.

However, although the structure described above can prevent the generation of cracks due to the collision of crushed stones, as a result of the repeated bending stress acting on the sidewall portion by running, the outer surface of the sidewall portion is exposed. There is a problem that the tensile stress is applied and the sidewall portion is broken.

In order to solve one of the above problems, a filler is provided to reinforce from the bead portion to the sidewall portion, and the filler is formed of a ply in which steel cords are arranged in order to further improve the cut resistance.

[0005]

However, as described above, the sidewall portion is subjected to repetitive compressive stress on the inner side in the axial direction of the tire and tensile stress on the outer side. Since it is formed by using steel cord, it is not possible to absorb the elongation and shrinkage corresponding to the bending inside the steel cord, and the filler causes peeling starting from its end, reducing the durability etc. The problem has not been solved yet.

In addition, under severe operating conditions such as a rally, the end of the filler may break through the carcass and project into the tire due to impact on the sidewall, causing tube damage or tire damage. There were many. This is because the cord strength of the filler is too strong for the carcass cord.

Therefore, it is conceivable to use an aromatic polyamide fiber which is an organic fiber and has a cut resistance substantially equal to that of steel as the filler cord, but when the aromatic polyamide fiber is used as a filler cord. ,
There is a problem that the adhesiveness to rubber is poor and the cord and rubber are easily separated.

As a result of intensive studies, the inventors have found that the above problems can be solved by using a composite cord composed of two kinds of filaments having different elastic values for the filler cord, and thus the present invention is completed. I made it.

The present invention is based on the use of a composite cord obtained by twisting a high-elasticity filament and a low-elasticity filament as a filler cord, and has excellent cut resistance and improved durability, which is suitable for a rally tire. The purpose is to provide pneumatic radial tires for rallies that can be adopted.

[0010]

SUMMARY OF THE INVENTION According to the present invention, a folded-back portion that is folded back around the bead core from the inner side in the tire axial direction to the outer side is integrally formed on a main body portion extending from a tread portion to a sidewall portion to a bead portion. A carcass provided with cords of a radial arrangement, a bead apex extending radially outward from the bead core between the carcass main body portion and a folded portion, and a belt layer arranged inside the tread portion and outside the carcass. And a rally pneumatic radial tire including a filler arranged on the tire axial direction outer side of the folded portion of the carcass, wherein the filler is at least a part of the folded portion of the carcass inside and outside from the tire maximum width point. It covers and extends a high elastic filament made of aromatic polyamide fiber and a low elastic filament made of organic fiber. Allowed was a pneumatic radial tire for rally, characterized in that it consists of plies having an array of complex code.

[0011]

Since the filler which extends inward and outward in the radial direction from the tire maximum width point to cover at least a part of the folded portion of the carcass is provided, the sidewall portion has increased rigidity and cut resistance.

Further, since the filler uses a composite cord composed of a high-elasticity filament and a low-elasticity filament, the cord functions as a low-elasticity cord at the time of normal traveling, which provides steering stability and riding comfort. The cords function as a highly elastic cord when they are subjected to an impact load such as crushed stones hitting the sidewalls while holding the However, the generation of cracks and their growth can be prevented, and the durability can be further enhanced.

Further, since the high elastic filament of the cord is made of aromatic polyamide fiber, it retains strength substantially equal to that of steel to protect the sidewall portion from impact and is an organic fiber. The risk of breaking through the carcass due to the peeling of the filler end such as steel cord can be eliminated, and the cut resistance is enhanced and tire damage is prevented.

In addition, the high-elasticity filament made of the aromatic polyamide fiber forms a composite cord in cooperation with the low-elasticity filament made of the organic fiber. The poor adhesiveness of (1) is compensated by the low elasticity filament, the peeling of the cord is prevented, and the durability is improved.

As described above, the above-mentioned constitutions are organic and integrated so that cut resistance and riding comfort are maintained.
Prevents peeling of the filler and damage of the rubber layer to improve durability,
It can be suitably used for rally.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In Figure 1, pneumatic radial tire for rally 1
Is a body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a folded-back portion 6b for folding back around the bead core 5 from the inner side to the outer side in the tire axial direction is integrally provided. One or more, in this example, two carcass plies 6A, 6A, a carcass 6, and the bead core 5 to the main body 6a of the carcass 6 and the folded portion 6b.
A bead apex 8 that extends radially outward between and
And a belt layer 7 disposed inside the tread portion 2 and outside the carcass 6 in the radial direction. In this embodiment, the tip of the folded portion 6b of the carcass 6 has a so-called low turn-up structure in which the tip of the folded portion 6b is located inside the tip P of the bead apex 8 which is located outside in the radial direction.

Further, a pneumatic radial tire for rally 1
Is the maximum width point B of the tire located at the maximum width W of the tire
By extending radially upward and downward from
In the present embodiment, a filler 9 is provided to cover a part of b, and an outer carcass 11 is provided to cover the filler 9 and extend from the tread portion 2 to the sidewall portion 3 along the bead bottom surface 4a of the bead portion 4. There is.

The carcass ply 6A of the carcass 6 is
In this example, a carcass cord made of organic fibers such as nylon, polyester, aromatic polyamide, aromatic polyester, rayon, etc., carbon fibers and steel cords is tilted 70 to 90 degrees with respect to the tire equator C in this example to provide a radial or semi-radial arrangement. Make up. The outer carcass 11 is also formed by a single carcass ply in which carcass cords are arranged in substantially the same manner as the carcass 6 described above.

The belt layer 7 is composed of four belt plies 7A ... As described above, and the belt ply 7A is a belt cord composed of an organic fiber such as aromatic polyamide, aromatic polyester, nylon, polyester or rayon, and a steel cord. Are arranged in a direction crossing each other to reinforce the tread portion 2 with a hoop effect.

The bead apex 8 is made of hard rubber, and by raising the outer end P to the vicinity of the maximum width point B of the tire as in this embodiment, the sidewall portion 3 is formed.
It is possible to increase the rigidity of the lower part of the.

The filler 9 is a sheet body formed by rubber-coating a composite cord in which a high elastic filament 30 made of an aromatic polyamide fiber and a low elastic filament 31 made of an organic fiber are twisted together. Further, the composite cord 21 is 60 to 90 with respect to the tire equator C.
The carcass 6 is arranged at an angle of ° and inclined in a direction intersecting with the carcass cord in the folded portion 6b of the carcass 6.

The high elastic filament 30 is an aromatic polyamide fiber and has a high elastic modulus exceeding 1000 kg / mm ² , preferably 1500 kg / mm ^2, and its thickness is about 1000 to 3000 denier. I am trying.

Further, as the low elastic filament 31, nylon fiber, polyester fiber or vinylon fiber,
Elastic modulus is 1000 kg / mm ² or less, preferably 700 kg /
mm ² or less is used.

Such a high-elasticity filament 30 is one or more simultaneously twisted, and one or more low-elasticity filaments 1 twisted in the same direction.
The composite cord 21 is formed by twisting 1 and 1 in the opposite directions. When a plurality of high-elasticity filaments 30 and a plurality of low-elasticity filaments 31 are used, each one may be pretwisted, or a plurality of them may be combined and pretwisted. The composite code 21 is
As shown in FIG. 2, one of each of the high-elasticity filament 30 and the low-elasticity filament 31 may be twisted together, or one may be made into one and the other may be made into a plurality, and both may be twisted together. Combined code 21
Can also be formed.

When a tensile force is applied to the composite cord 21 as described above, as shown in FIG. Also, due to the extension, the initial twist pitch P1 of the composite cord 21
Increases to the pitch P2 due to extension. This extension, as schematically shown in FIGS. 7 and 8 for the high-elasticity filament 30, the high-elasticity filament 30A, which has a coil shape in the initial state, becomes a straight filament 30B by a predetermined extension. Therefore, from such a state, the original high elastic modulus of the high elastic filament 30 is exhibited. As described above, by winding the high-elasticity filament 30 in a spiral shape in advance, a low-elasticity region in which the elongation is relatively large between the spiral state of FIG. 4 and the straight state of FIG. From the state of 5, it is obvious that it is equipped with a high elasticity region where the elongation is small by further applying a load,
The straight state shown in FIG. 5 forms an inflection point of the elongation-stress curve.

In the composite cord 21, the inflection point V is thus set so as to be located in the range of 7 to 11% of the elongation. The composite cord 21 is a twisted body of the high-elasticity filament 30 and the low-elasticity filament 31. Therefore, as shown in FIG. 3, the high-elasticity filament 30 and the low-elasticity filament 31 have a twist even when a load is applied. Therefore, the inflection point V is not remarkable as compared with the schematic cases of FIGS. The stress-elongation curve of the composite cord 21 is illustrated in FIG. In the figure, the curve a is of the low-elasticity filament 31 of nylon 840d,
The curve b shows the elongation curve of the highly elastic filament 30 made of aromatic polyamide of 1000d. Further, the case of the composite cord 21 in which one of these high elastic filaments 30 and two of the low elastic filaments 31 are twisted together is shown by a curve c. It can be seen that the curve c is located between the curve a and the curve b, and the inflection point V is in the range of elongation 7 to 11%. In the composite cord 21, the inflection point V
Is a tangent line S1 tangent to the curve in the state of zero elongation,
It is defined as an intersection with a vertical line passing through an intersection X where the tangent line S2 drawn to the curve c intersects at the break point.

The composite cord 21 has a high elasticity region from the inflection point V to the break point and an inflection point V from the origin at which the elongation is zero.
And a ratio EH / EL of the elastic modulus EH in the high elastic region to the elastic modulus EL in the low elastic region is 8 to 2
The range is 0. In such a composite cord 21, the thickness, the number, the elastic modulus, the thickness, the number, the elastic modulus, etc. of the high elastic filaments 30 are appropriately selected, and the composite angle is adjusted by adjusting the twisting conditions such as the filament angle. As shown in FIG. 6, the composite cord 21 that can satisfy the above range can be formed. It can also be adjusted by selecting the stretching process applied to the composite cord 21, the high elastic filament 30, and the low elastic filament 31.

Since the inflection point exists in the range of elongation of 7 to 11%, the expansion due to the internal pressure filling of the raw tire and the expansion at the time of inflation are performed by the expansion of the composite cord 21 in the low elasticity. .. On the other hand, when an impact load is applied to the sidewall portion 3, the composite cord 21
The high elasticity eliminates the risk of cuts.

[0029]

SPECIFIC EXAMPLE Tires (Examples 1 and 2) each having a tire size of 7.00R16 and having the structure shown in FIG. 1 were prototyped and their performances were tested. A conventional tire without a filler (Comparative Example 1) and a tire (Comparative Examples 2 to 5) not having the constitution of the present invention were also tested to compare their performances.

The test conditions are as follows. (1) High-speed durability With the test tire assembled on a standard rim and 4.5 kgf /
While filling the inner pressure of cm ² with the tire having a diameter of 1.5
The traverse test machine of m was run at a speed of 65 km / H while applying a load 1.5 times the maximum load defined by JIS, and the total running distance until cracks were generated on the tire surface was set to 1 in Comparative Example 4.
It is indicated by an index of 00. The larger the value, the better.

(2) Cut-destruction resistance performance An actual vehicle equipped with a trial tire is made to enter at an angle of 15 ° with respect to an iron protrusion having a height of 230 mm, a width of 100 mm and a length of 1500 mm provided on the side of a test road. In order to raise the protrusion, the approach speed is successively increased in steps of 10 km / H to 5 km / H, and the speed when punctured is set to 1 in Comparative Example 4.
It is indicated by an index of 00. The larger the value, the better.

(3) Riding comfort A protrusion having a width of 50 mm and a height of 10 mm is fixed on a steel drum having a diameter of 3 m, and a test tire is brought into contact with the steel drum and then the drum is rotated. The vertical vibration when the tire passed over the protrusion was measured by an accelerometer as a force acting on the tire mounting shaft, and the magnitude of the swing was measured from the waveform recorded at this time.
It is displayed with the index. The higher the value, the better the riding comfort. The test results are shown in Table 1.

[0033]

[Table 1]

[0034]

As described above, the pneumatic radial tire for a rally of the present invention is a composite in which a high elastic filament made of an aromatic polyamide fiber and a low elastic filament are twisted as a cord of a filler for reinforcing the sidewall portion. Because it uses a cord as the gist, it has excellent cut resistance and riding comfort, and prevents peeling of the filler end, prevents damage to the carcass and rubber of the tire body, and enhances durability, making it suitable for rallying. Can be adopted.

[Brief description of drawings]

FIG. 1 is a sectional view of a left half of a tire showing an embodiment of the present invention.

FIG. 2 is a front view illustrating a composite cord.

FIG. 3 is a front view illustrating a composite cord.

FIG. 4 is a front view illustrating the elongation of the high elasticity cord.

FIG. 5 is a front view illustrating the extension of the high elasticity cord.

FIG. 6 is a diagram illustrating the elongation characteristics of a composite cord.

[Explanation of symbols]

 2 tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 7 belt layer 8 bead apex 9 filler 21 composite cord 30 high elastic filament 31 low elastic filament B tire maximum width point W tire maximum width point

Claims (3)

[Claims] 1. A body part extending from a tread part to a bead part through a side wall part is integrally provided with a turn-back part that turns back around the bead core from the inner side to the outer side in the tire axial direction, and has a cord of radial arrangement. A carcass, a bead apex extending outward in the radial direction from the bead core to the carcass main body portion and a folded portion, a belt layer arranged inside the tread portion and outside the carcass, and a tire of the folded portion of the carcass. A pneumatic radial tire for a rally including a filler arranged axially outside,
The filler extends inward and outward from the tire maximum width point to cover at least a part of the folded portion of the carcass, and further, a composite cord in which a high elastic filament made of an aromatic polyamide fiber and a low elastic filament made of an organic fiber are twisted together. A pneumatic radial tire for a rally, which is composed of plies in which are arranged. 2. The pneumatic radial tire for a rally according to claim 1, wherein the low elastic filaments are nylon fibers, polyester fibers or vinylon fibers. 3. The composite cord is formed by twisting one or more under-twisted high-elasticity filaments and one or more under-twisted low-elasticity filaments in the same direction in opposite directions. A pneumatic radial tire for a rally according to claim 1.