JPH0616005A - Radial tire - Google Patents

Abstract

PURPOSE:To reduce the weight of a tire, reduce noise generated while a vehicle runs and increase riding comfort. CONSTITUTION:A radial tire has a toroidal carcass 5 formed of cords extending almost parallel with the radius of the tire through the tread part 2 and the side wall parts 3, and having both ends folded around bead cores 4A of the bead parts 4, and belt layers 6 formed of aromatic polyamide fiber cords, which are set inside the tread part 2 and radially outside of the carcass 5. In the carcass 5, a carcass ply having parallel arranged composite cords comprising high elastic filaments formed of organic fibers and low elastic filaments formed of organic fibers, stranded with each other, is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial tire, and more particularly to a radial tire having a weight reduction of 8 to 12 plies and a reduced rolling resistance as well as improved durability and riding comfort.

[0002]

2. Description of the Related Art Conventionally, as a light truck tire, a carcass in which two or three plies of polyester fiber cords are superposed, and a steel cord as a belt cord of a belt layer are made of cut ply. The durability was improved by using a belt layer made of. On the other hand, global warming and deterioration of the global environment are becoming serious problems year by year, and the development and popularization of electric vehicles, represented by solar cars, has been greatly highlighted to prevent such environmental pollution. .

Further, as drivers age, the demand for comfortable cars even for light trucks is increasing.

On the other hand, the global environment is deteriorating due to global warming and an increase in carbon dioxide. In order to prevent such environmental deterioration, even automobiles are attempted to save fuel. .

Further, the most effective way to reduce fuel consumption in a vehicle is to reduce the vehicle weight. For example, reducing the vehicle weight by 1% has the effect of improving the fuel consumption by 1%. I was requested.

[0006]

In response to the above demand, there is a market in which the belt cord of the belt layer is replaced with steel and an aramid fiber having a strength substantially equal to that of steel is used. Although it is possible to reduce the tire weight by using organic fiber having a smaller specific gravity than steel, there is a problem that the steering stability deteriorates due to insufficient rigidity compared to steel cord and pattern noise is high due to deterioration of uniformity. . In particular 10~12KH _Z
The increase of noise in is remarkable.

The inventors of the present invention reduce the weight of such a tire,
As a result of intensive studies to achieve both of the two problems of noise suppression, as a carcass cord, by mixing and twisting a high elastic filament and a low elastic filament, the carcass cord is changed in its load-elongation curve. By functioning as low elasticity below the bending point and as high elasticity above the inflection point, the number of constituent carcass plies is reduced and weight is reduced, and pattern noise is caused by the ply made of aromatic polyamide fiber. It was found that it can be reduced by stacking two or more sheets.

According to the present invention, a carcass ply composed of a composite cord in which a high elastic filament and a low elastic filament are twisted together is used, and a plurality of plies using aromatic polyamide fibers are superposed on the belt layer. Based on the above, it is an object of the present invention to provide a radial tire which can reduce the weight of the tire without increasing the pattern noise and can save energy.

[0009]

DISCLOSURE OF THE INVENTION The present invention comprises a tread portion, side wall portions extending radially inward from both ends thereof, and bead portions located at both radial end portions of the side wall portion. A troid carcass in which both ends of a carcass ply in which carcass cords extending through the tread portion and the side wall portion and extending substantially parallel to the tire radial direction are arranged are folded back around the bead core in the bead portion, and the tread. A belt layer formed by stacking two or more plies made of cords of aromatic polyamide fibers disposed inside the portion and radially outside the carcass is provided, and the carcass cords are made of a highly elastic filament made of organic fibers and an organic fiber. A radial tire comprising a composite cord in which a low elastic filament made of fibers is twisted together.

[0010]

Since the carcass ply comprises a carcass cord composed of a composite cord in which a high elastic filament and a low elastic filament are twisted together, the composite cord has a low elastic region below the inflection point in its load-elongation curve. Also, it has a high elastic region above the inflection point.

Therefore, the elasticity corresponding to the elongation of the carcass cord (about 3%) occurring during the tire vulcanization step is in the low elasticity region, and this elasticity is the inside of the raw tire during vulcanization in the tire vulcanization mold. The outer peripheral surface of the tire can be pressed against the inner surface of the vulcanization mold by the internal pressure of 1. together with the elongation of the composite cord, so that the vulcanization molding of the tire is facilitated and the accuracy of the tire is improved despite having the highly elastic filament. Therefore, noise can be reduced by improving the finishing accuracy of the tire.

When the tire is rotated at a high speed with high deformation, the composite cord in the ply of the carcass exhibits high elasticity, and the belt layer is made of a cord made of aromatic polyamide fiber and two plies are stacked. Since they are formed together, the hoop effect is improved, so-called lifting of the belt layer can be prevented, the occurrence of standing waves is suppressed, the high speed durability of the tire is improved, and the occurrence of vibration is suppressed. . In addition, the ruggedness is reduced when traveling on rough roads such as gravel roads and step roads,
The riding comfort is improved.

In addition, since a high-strength composite cord is used as the carcass cord, the number of carcass plies can be reduced as compared with the case where a conventional polyester or nylon cord is used. That is, the weight of the tire can be reduced by making the resply.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the radial tire T has a sidewall portion 3 extending inward in the radial direction from both ends of the tread portion 2, and a bead portion 4 located at an inner end in the radial direction of the sidewall portion 3, and The radial tire T includes a carcass ply having a carcass cord extending from the tread portion 2 to the sidewall portion 3 around the bead core 4A of the bead portion 4 and extending substantially parallel to the tire radial direction. -Shaped carcass 5 and a belt layer 6 inside the tread 2 and outside the carcass 5 in the radial direction.
And are arranged.

Here, the fact that the carcass 5 extends substantially parallel to the radial direction means that the carcass 5 is inclined at an angle within 30 ° with respect to the tire axis, and includes radial tires and semi-radial tires.

The belt layer 6 is composed of three belt plies 6C, 6B and 6A, which are the upper, middle and lower belt plies 6A, 6B, which are sequentially arranged from the tread surface side inward in the radial direction. In the present embodiment, 6C has a cut end structure in which the side ends are cut, and is formed as a cross belt in which the belt cords of each ply cross each other. In this embodiment, the lower belt ply 6A is replaced with the inner belt ply 6B.
The upper belt ply 6C is narrower than the inner belt ply 6B.

The belt plies 6A and 6B in the lower and inner portions of the belt layer 6 may have the same width, and the belt ply 6C on the upper width may be wider than the other belt plies 6A and 6B.

As shown in FIG. 2A, the carcass cord uses a composite cord 12 in which high elastic filaments 10 ... And low elastic filaments 11 ... Are twisted together.

The inclination angle of the carcass cord is 60 ° to 90 ° with respect to the tire circumferential direction, and when a plurality of plies are superposed as in the present embodiment, the cords of the adjacent plies are inclined opposite to each other.

The highly elastic filament 10 is made of aromatic polyamide fiber, wholly aromatic polyester fiber, strength of 15 g / d.
Polyvinyl alcohol fiber or carbon fiber as described above, having an elastic modulus of 1000 kg / mm ² , preferably 150
Fibers exceeding 0 kg / mm ² are used. Also, its thickness is
A relatively thin diameter of about 1000 to 3000 denier is used.

Further, as the low elastic filament 11,
Nylon fibers, polyester fibers, vinylon fibers, etc., having an elastic modulus of 1000 kg / mm ² or less, preferably 700
Those of less than kg / mm ² are used.

One or a plurality of such high-elasticity filaments 10 are simultaneously ply-twisted, and one or a plurality of low-elasticity filaments 1 ply-twisted in the same direction.
The composite cord 12 is formed by twisting 1 and 1 in opposite directions. When a plurality of high-elasticity filaments 10 and a plurality of low-elasticity filaments 11 are used, each one may be pretwisted, or a plurality of them may be combined and pretwisted. The composite code 12 is
As shown in FIG. 2A, one of each of the high-elasticity filament 10 and the low-elasticity filament 11 may be twisted together, or one may be one and the other may be plural.
It is also possible to form the composite cord 12 by twisting together a plurality of pieces.

When a tensile force is applied to such a composite cord 12, as shown in FIG. 2 (B), the composite cord 12 is stretched while untwisting. Further, the elongation increases the initial twist pitch P1 of the composite cord 12 to the pitch P2 due to the elongation. This extension is shown in FIG.
As schematically shown in (B), the high-elasticity filament 10A, which has a coil shape in the initial state, becomes a straight filament 10B by a predetermined elongation. Therefore, from such a state, the original high elastic modulus of the high elastic filament 10 is exhibited. By thus preliminarily winding the high-elasticity filament 10 in a spiral shape, the elongation is relatively large from the spiral state of FIG. 3A to the straight state of FIG. 3B. It is clear that a low elasticity region and a high elasticity region in which the load is further applied from the state of FIG.
The straightened state shown in (B) forms an inflection point of the elongation-stress curve.

In the composite cord 12, the inflection point V is thus set so as to be located within the range of 2 to 7% of the elongation. The composite cord 12 is a twisted body of the high-elasticity filament 10 and the low-elasticity filament 11. Therefore, as shown in FIG. 2B, the high-elasticity filament 10 and the low-elasticity filament 11 are twisted even when a load is applied. , And therefore its inflection point V is shown in FIG.
It is not remarkable as compared with the schematic case of (B). The stress-elongation curve of the composite cord 12 is illustrated in FIG.
In the figure, a curve a shows an elongation curve of the low elastic filament 11 of nylon 1260d, and a curve b shows an elongation curve of the high elastic filament 10 made of aromatic polyamide of 1500d. In addition, these high elastic filaments 10
A curve c shows the case of the composite cord 12 in which one piece and one low-elasticity filament 11 are twisted together. The curve c is located between the curve a and the curve b, and the inflection point V extends from 2 to 2.
It can be seen that it is in the range of 7%. In the composite cord 12, the inflection point V is an intersection point of a vertical line passing through an intersection point X where the tangent line S1 tangent to the curve in the state of zero elongation and the tangent line S2 drawn to the curve c at the break point intersect. It is defined.

The composite cord 12 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.
The elastic modulus EH in the high elastic region and the elastic modulus EL in the low elastic region are set to a ratio EH / EL of 2 to
The range is 10. Such a composite code 12 is
The thickness, number, and elastic modulus of the high-elasticity filament, the thickness, the number, and the elastic modulus of the low-elasticity filament are appropriately selected, and the filament angle and other twisting conditions are adjusted to satisfy the above range as shown in FIG. The composite cord 12 can be formed. It can also be adjusted by selecting the stretching process applied to the composite cord 12, the high elastic filament 10 and the low elastic filament 11.

Since the inflection point V exists in the range of elongation of 2 to 7%, when a green tire is mounted on a vulcanization mold and an internal pressure is filled in the green tire during tire production, Due to the internal pressure, the belt layer 7 becomes the composite cord 12
By swelling due to the expansion of and the outer peripheral surface is pressed against the inner surface of the mold, the groove shape formed in the mold can be engraved on the tread portion 2. The swelling of the green tire due to the filling with the internal pressure is performed by the expansion of the composite cord 12 in the low elasticity region. Therefore, the inflection point V is set in the range of 2 to 7% of elongation. The required elongation of the composite cord 12 in the mold due to internal pressure filling is preferably located near the inflection point V. As a result, the inflation of the molded tire and the expansion of the tire due to the centrifugal force acting at the time of high speed rotation can be suppressed by the high elasticity region as shown in FIG. Therefore, the ratio EH / EL of the elastic modulus EH in the high elastic region and the elastic modulus EL in the low elastic region is set to 2 to 10. When it is 2 or less, the above-mentioned suppression effect is poor, and when it exceeds 10, it is unnecessary from the viewpoint of tire balance.

FIG. 5 shows another embodiment of the present invention. In this example, the composite cord 12 having the above-mentioned configuration is used, and two pieces are provided on the outer side in the radial direction of the carcass 5 formed of one carcass ply.
A belt layer 6 including a plurality of belt plies 6A and 6B is provided, and a band layer 7 in which a band cord 21 is arranged substantially parallel to the tire equator C is provided on the outer side in the radial direction of the belt layer 6. Layer 7 covers substantially the entire width of belt layer 6.

The band layer 7 comprises one or more band plies 7A, 7A in FIG. 5, and the band ply 7A is obtained by winding a long and narrow band ply 20 around the belt layer 6. It is formed.

As shown in FIG. 6, the band-shaped ply 20 comprises one band cord 21 or two band cords 21 arranged in parallel, and in this embodiment, two band cords 21 are embedded in a coating rubber 22. Organic fiber cords such as nylon, Teflon, and aromatic polyaramid polyester are used. Nylon fibers have a greater elastic elongation than other organic fibers, and by winding a belt-shaped ply of the nylon fibers around the outside of the belt layer 6, the belt layer 6 is pressed inward in the radial direction of the tire to move the belt layer 6. Can be efficiently blocked.

The band ply 7A is formed by spirally winding from one end line of the band layer 7 as a starting point, over the tire equator CL, toward the other broken line and substantially parallel to the tire equator C. It In this embodiment, the belt-shaped ply 2
When winding 0, as shown in FIG.
The side edges 20a, 20a facing each other of 0 are wrapped and wound. Therefore, the looseness of the strip ply 20 is prevented.

Since the belt-shaped ply 20 is spirally wound in the tire circumferential direction, a seam in a direction intersecting with the tire circumferential direction does not occur, so that running stability and riding comfort during running can be further enhanced and noise can be further reduced. It can be lowered.

The band layer 7 may be formed by a monoply band ply, while at least one of the belt plies forming the belt layer 6 may be formed by spirally winding the band-shaped ply having the above structure.

[0033]

SPECIFIC EXAMPLE For a tire having a tire size of 700R16 12PR and having the configuration shown in FIG. 1, the tire weight and running noise were compared with the prototypes (Examples 1 and 2) according to the specifications shown in Table 1.

The tire weight is shown by an index in which the net weight not including the tube and rim is measured and Comparative Example 1 is 100. The smaller the number, the lighter it is. Further, the noise level was measured by mounting the test tire on the vehicle and measuring the overall noise level at a position 1 m away from the tire. The smaller the number, the smaller the noise.

[0035]

[Table 1]

As a result of the test, it was confirmed that the weight of each of the examples was able to be reduced as compared with that of the comparative example 1 without significantly increasing noise.

[0037]

As described above, the radial tire of the present invention is provided with a composite cord in which a carcass is twisted with a highly elastic filament made of organic fiber and a low elastic filament made of organic fiber. Therefore, the tires can be preferably used as a commercial tire without reducing various performances of the tire, uniformizing the uniformity, reducing the weight of the tire, reducing fuel consumption and noise, and improving riding comfort.

[Brief description of drawings]

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

FIG. 2A is a front view illustrating a composite cord.
(B) is a front view showing the extended state.

3 (A) and 3 (B) are front views schematically showing an initial state and a stretched state of a high-elasticity filament.

FIG. 4 is a diagram showing an example of an elongation curve of a cord.

FIG. 5 is a sectional view showing another embodiment.

FIG. 6 is a perspective view showing an example of a band-shaped ply forming a band ply.

FIG. 7 is a cross-sectional view showing winding of the band-shaped ply.

[Explanation of symbols]

 2 tread part 3 sidewall part 4 bead part 4A bead core 5 carcass 6 belt layer 6A, 6B, 6C belt ply 7 band layer 10 high elastic filament 11 low elastic filament

Claims (6)

[Claims] 1. A tread portion, a side wall portion extending radially inward from both ends of the tread portion, and a bead portion located at both radial end portions of the side wall portion. Carcass ply arranged carcass cords extending substantially parallel to the radial direction of the tire passing through the portion of the carcass ply folded back around the bead core in the bead portion, and the inside of the tread portion and the outer side in the radial direction of the carcass. And a belt layer formed by stacking two or more plies made of cords of aromatic polyamide fibers arranged on the carcass cord, and the carcass cord is made of a highly elastic filament made of organic fibers,
A radial tire made of a composite cord in which a low elastic filament made of organic fiber is twisted together. 2. The high elasticity filament is aromatic polyamide fiber, wholly aromatic polyester fiber or strength 15 g /
The radial tire according to claim 1, wherein the radial tire is formed by using any one of d or more polyvinyl alcohol fibers. 3. The radial tire according to claim 1, wherein the low-elasticity filament is formed by using any one of nylon fiber, polyester fiber and vinylon fiber. 4. 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. The radial tire according to claim 1, wherein: 5. The composite cord has a low elasticity region whose stress-elongation curve extends from the origin to the inflection point and a high elasticity region exceeding the inflection point, and the inflection point extends from 2 to 7 % Elastic modulus EH in the high elastic range and elastic modulus EL in the low elastic range
The radial tire according to claim 1, wherein the ratio EH / EL is 2 to 10. 6. The radial tire according to claim 1, wherein the tread portion has a band cord made of an aromatic polyamide fiber spirally wound substantially parallel to the equator on the radially outer side of the belt layer.