JPH05338404A - Radial tire - Google Patents

Abstract

PURPOSE:To uniform uniformity and lighten a tire without lowering various performance of the tire and to reduce fuel consumption and noise by forming a carcass of a composite cord made by twisting a high elastic filament made of organic fiber and a low elastic filament made of organic fiber. CONSTITUTION:A carcass 5 uses a carcass ply placing a composite cord 12 made by twisting a high elastic filament 10 made of organic fiber and a low elastic filament 11 made of organic fiber in parallel. Additionally, the composite cord 12 has a low elastic region where its stress-extensional curve starts from its original point and reaches its inflection point and a high elastic region where the stress-extensional curve exceeds the inflection point, the inflection point is within a range of extension 1-11%, and a ratio EH/EL of an elastic modulus EH of the high elastic region and an elastic modulus EL of the low elastic region is specified as 8-20. Consequently, it is possible to lighten a tire and to reduce noise at the time of traveling.

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 tire for a light truck, a carcass in which two or three plies using polyester fiber cords are stacked and a belt cord of a belt layer using steel cords are cut plies made of steel cords. 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 is being greatly highlighted in order to prevent such environmental pollution. ..

Further, as drivers become older, there is an increasing demand for comfortable cars even for light trucks.

On the other hand, the global environment is deteriorating such as global warming and an increase in carbon dioxide. In order to prevent such environmental deterioration, even a four-wheeled vehicle is attempted to save fuel. ..

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

[0006]

In response to the above-mentioned demand, there is a market in which a belt cord of a 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 in noise is remarkable.

The inventors of the present invention reduce the weight of such a tire,
As a result of intensive studies to achieve two problems of suppressing noise, 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 is formed by using a carcass ply composed of a composite cord in which a high elastic filament and a low elastic filament are regulated and twisted in elastic modulus ratio thereof, and aromatic polyamide fiber is formed in a belt layer. It is an object of the present invention to provide a radial tire capable of reducing the tire weight without increasing the pattern noise and conserving energy, based on the fact that a plurality of plies using the above are laminated and formed.

[0009]

SUMMARY OF THE INVENTION The present invention comprises a tread portion, side wall portions extending inward from both ends thereof in a radial direction, and bead portions located at both radial end portions of the side wall portion. And a toroidal carcass in which both ends of a cord that extends substantially parallel to the tire radial direction through the tread portion and the sidewall portion are folded back around the bead core in the bead portion, and the inside of the tread portion and the radial direction of the carcass. The carcass comprises a high elastic filament made of organic fibers and a low elastic filament made of organic fibers, while a belt layer formed by polymerizing two or more plies made of cords of aromatic polyamide fibers arranged outside is provided. Using a carcass ply in which twisted composite cords are juxtaposed, the composite cord has a stress-elongation curve. Has a low elastic region from the origin to the inflection point and a high elastic region beyond the inflection point, and the inflection point is in the range of 7 to 11% in elongation, and the elastic modulus EH in the high elastic region is low. The ratio EH / EL with the elastic modulus EL in the elastic region is 8 to 2
It is a radial tire characterized by being set to 0.

[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 inner peripheral pressure of the tire allows the outer peripheral surface of the tire to be pressed against the inner surface of the vulcanization mold along with the elongation of the composite cord, which facilitates the vulcanization molding of the tire and improves the tire accuracy despite having the highly elastic filaments. Therefore, noise can be reduced by improving the finish 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 uses a cord made of an 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.

Since the inflection point exists in the range of elongation of 7 to 11%, when the raw tire is mounted on the vulcanization mold and the raw tire is filled with the internal pressure during tire production, the internal pressure is increased. Thus, the belt layer swells due to the extension of the composite cord, and the outer peripheral surface is pressed against the inner surface of the mold, so that the tread portion 2 can be provided with a groove formed in the mold. In addition, the swelling due to the internal pressure filling of the raw tire,
This is performed by stretching the composite cord in the low elasticity region. Therefore, the inflection point is set in the range of 7 to 11% of elongation.
As a result, inflation of the molded tire and expansion of the tire due to centrifugal force acting at 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 8 to 20. When it is 8 or less, the suppressing effect is poor, and when it exceeds 20, it is unnecessary from the viewpoint of tire balance.

In this way, the inflection point is extended from the composite cord 7 to
By setting the range to 11%, the molding accuracy of the raw tire is increased, and by setting the elastic ratio EH / EL to 8 to 20, the expansion of the tire during high-speed rotation is effectively suppressed, and durability and riding comfort are improved. The comfort can be further improved.

[0016]

DETAILED 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 radially outside the carcass 5.
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 upper, middle and lower belt plies 6C, 6B, 6A which are sequentially arranged from the tread surface side inward in the radial direction, and each of the belt plies 6A, 6B, 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. 2 (A), 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 adjacent plies are inclined in opposite directions.

The high elastic filament 10 is made of aromatic polyamide fiber, wholly aromatic polyester fiber, strength 15 g / d.
The above-mentioned polyvinyl alcohol fiber or carbon fiber 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 fiber, polyester fiber, vinylon fiber, 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 the plural twisted filaments 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 cord 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. As described above, by winding the high-elasticity filament 10 in a spiral shape in advance, the elongation is relatively large from the spiral state of FIG. 3A to the straight state of FIG. 3B. It is obvious that a low elastic region and a high elastic region in which elongation is small by further applying a load from the state of FIG. 3 (B) can be provided, and 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 in the range of 7 to 11% of the elongation. The composite cord 12 is a twisted body of the high-elasticity filament 10 and the low-elasticity filament 11, and therefore, as shown in FIG.
The low-elasticity filament 11 has a twist even when a load is applied, and therefore the inflection point V thereof is as 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 the elongation curve of the low elastic filament 11 of nylon 1260d, and a curve b shows the 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 a composite cord 12 in which one filament and one low-elasticity filament 11 are twisted together. The curve c is located between the curves a and b, and the inflection point V extends from 7 to 7.
It can be seen that it is in the range of 11%. Composite code 12
In the above, the inflection point V is defined as an intersection of a vertical line passing through an intersection X where a tangent line S1 tangent to the curve in the state of zero elongation and a tangent line S2 drawn to the curve c at the break point intersect. .

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 have a ratio EH / EL of 2 to
The range is 10. Such a composite code 12 is
By appropriately selecting the thickness, number and elastic modulus of the high elastic filaments, the thickness, the number and elastic modulus of the low elastic filaments, and adjusting the twisting conditions such as the filament angle, the above range is satisfied 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.

As described above, the inflection point V is extended by 7 to 11%.
Is set to the range. It is preferable that the required expansion of the composite cord 12 in the mold due to the internal pressure filling is located near the inflection point V. As a result, inflation of the molded tire and expansion of the tire due to centrifugal force acting at 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 8 to 20.

FIG. 5 shows another embodiment of the present invention. In this example, the composite cord 12 having the above-described configuration is used, and two pieces are provided on the outer side in the radial direction of the carcass 5 including 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 the belt layer 6.

The band layer 7 is composed of one or more band plies 7A, 7A in FIG. 5, and the band ply 7A is formed 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 larger elastic elongation than other organic fibers, and by winding a belt-shaped ply made of the nylon fibers around the outside of the belt layer 6, the belt layer 6 is pressed inward in the tire radial direction and the belt layer 6 moves. 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 belt-shaped 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 of the above structure.

[0035]

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

The tire weight is shown as an index with the net weight not including the tube and the rim being measured and Comparative Example 1 being 100. The smaller the number, the lighter it is. Ride comfort is that the trial tires are attached to the actual vehicle, and the vehicle travels on general roads.
Judgment was made according to the feeling of the test driver, and the result was displayed as an index with Comparative Example 1 being 100. The larger the value, the better. 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.

[0037]

[Table 1]

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

[0039]

As described above, the radial tire of the present invention is characterized by comprising a composite cord in which a carcass is twisted with a high elastic filament made of an organic fiber and a low elastic filament made of an organic fiber. Therefore, the tire can be preferably used as a commercial tire, for example, with uniform uniformity, weight reduction of the tire, reduction of fuel consumption and noise, and improvement of riding comfort without deteriorating various performances of the tire.

[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 cross-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 a strip 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 (5)

[Claims] 1. A tread portion, a side wall 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 in which both ends of a cord extending substantially parallel to the radial direction of the tire passing through a portion are folded back around a bead core in a bead portion, and an aromatic polyamide fiber arranged inside the tread portion and radially outside the carcass. While providing a belt layer formed by polymerizing two or more plies made of cords, the carcass is provided with juxtaposed composite cords in which high elastic filaments made of organic fibers and low elastic filaments made of organic fibers are twisted together. In addition to using a carcass ply, the composite cord has a low-elasticity curve whose stress-elongation curve extends from the origin to the inflection point. The elastic modulus EH in the high elastic region and the elastic modulus EL in the low elastic region. Radial tire characterized by EH / EL of 8 to 20. 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 an organic fiber composed of a polyvinyl alcohol fiber having a length of d or more. 3. The radial tire according to claim 1, wherein the low-elasticity filament is a nylon fiber, a polyester fiber or a vinylon fiber. 4. The composite cord is formed by twisting one or more high-elasticity filaments twisted in the lower direction and one or more low-elasticity filaments twisted in the same direction in the opposite direction. The radial tire according to claim 1, wherein: 5. 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.