JPH04271904A - Radial tire for light track - Google Patents

Abstract

PURPOSE:To lighten tire, and reduce the noise at the time of travelling. CONSTITUTION:Toroidal carcasses 5, which are formed by folding both ends of a code passing through a tread part 2 and side wall parts 3 and extending to the radial direction of a tire in parallel with each other around of bead cores 4A inside of bead parts 4, and a belt layer 6 made of steel code located inside of the described tread part and outside of the radial direction of the carcass are provided. As the described carcass, carcass ply obtained by locating twisted compound codes, which consists of a high elastic filament made of organic fiber and a low elastic filament made of organic fiber, in parallel 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 for light trucks, particularly a radial tire for light trucks that can reduce the weight of tires with 8 to 12 ply ratings and reduce noise during running.

0002

2. Description of the Related Art Tires for passenger cars and small commercial vehicles have been improved in durability by using steel or aramid cords for the belt cord of the belt layer to enhance the hoop effect. Furthermore, with the development of expressway networks in recent years, the demand for higher speeds for these vehicles has been increasing, and in order to satisfy the above-mentioned demands, a band layer is provided on the outside of the belt layer for tires. By providing the layer, the occurrence of so-called lifting reduction, in which the tread portion bulges outward in the radial direction and rises due to the centrifugal force generated in the tread portion as the tire rotates, is suppressed.

[0003] On the other hand, the global environment is deteriorating due to global warming and an increase in carbon dioxide, and attempts are being made to save fuel even in four-wheeled motor vehicles in order to prevent such environmental deterioration. .

[0004] In addition, the most effective way to reduce fuel consumption in vehicles is to reduce vehicle weight. For example, a 1% reduction in vehicle weight has the effect of improving fuel efficiency by 1%, and further weight reduction in tires is also effective. It has started to be requested.

[0005]

[Problems to be Solved by the Invention] In response to the above-mentioned request, there are belt cords in the belt layer that use aramid fibers, which have almost the same strength as steel, in place of steel; By using organic fibers, which have a lower specific gravity than steel, it is possible to reduce the weight of the tire, but compared to those using steel cords, there are problems with poor handling stability due to lack of rigidity, and high pattern noise due to decreased uniformity. There is. Especially 10-1
There is a significant increase in noise at 2KHZ.

[0006] The inventors have attempted to reduce the weight of such tires,
As a result of extensive research in order to balance the two problems of noise suppression, the carcass cord is twisted with a mixture of high-modulus filaments and low-modulus filaments, resulting in a carcass cord with low elasticity below the inflection point. They discovered that by making the carcass plies function as high elasticity in the upper part, the carcass ply could be made into a resply to reduce weight, and the generation of pattern noise could be suppressed by using steel cords.

[0007] The present invention is based on using a carcass ply made of a composite cord made by twisting high-elasticity filaments and low-elasticity filaments for the carcass, and using a belt ply made of steel cord for the belt layer, which increases pattern noise. You can reduce tire weight without
The aim is to provide radial tires for light trucks that can save energy.

[0008]

[Means for Solving the Problems] The present invention includes a tread portion, a sidewall portion extending radially inward from both ends of the tread portion, and bead portions located at both radial ends of the sidewall portion. and a toroidal carcass in which both ends of a cord extending substantially parallel to the radial direction of the tire through the tread portion and sidewall portion are folded around a bead core in the bead portion, and and a belt layer consisting of steel cords arranged on the outside, while the carcass is
This is a radial tire for light trucks that uses a carcass ply in which composite cords made by twisting high-modulus filaments made of organic fibers and low-modulus filaments made of organic fibers are arranged side by side.

[0009]

[Function] Since the carcass ply has a carcass cord consisting of a composite cord made by twisting high-modulus filaments and low-modulus filaments, the composite cord has a low elasticity region below the inflection point and a high elasticity region above the inflection point. Combined.

[0010] Therefore, the elasticity corresponding to the elongation of the carcass cord (nearly 3%) during the tire vulcanization process is in a low elasticity range, so during vulcanization in the tire vulcanization mold, the internal pressure inside the green tire The outer circumferential surface of the tire can be pressed against the inner surface of the vulcanization mold along with the elongation of the composite cord, making it easier to vulcanize the tire while using high-elastic filaments, and improving tire accuracy. Therefore, noise can be reduced by increasing the accuracy of tire finishing.

[0011] Also, when the tire rotates at high speed with high deformation,
The composite cord of the carcass ply exhibits high elasticity and improves the hoop effect of the belt layer made of steel cord, thereby preventing so-called lifting of the belt layer.
By suppressing the generation of standing waves, the tire's high-speed durability is improved and vibrations are suppressed.

Furthermore, since a highly strong composite cord is used for the carcass cord, the number of carcass plies can be reduced compared to when conventional polyester or nylon cords are used. In other words, the weight can be reduced by forming a resply.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a light truck radial tire T has a sidewall portion 3 extending radially inward from both ends of a tread portion 2, and a bead portion 4 located at the radially inner end of the sidewall portion 3. Furthermore, a toroidal carcass 5 is formed of a cord extending substantially parallel to the radial direction of the tire, and both ends are folded back around the bead core 4A, and a toroidal carcass 5 is provided inside the tread portion 2 and on the outside of the carcass 5 in the radial direction. A belt layer 6 is arranged. In this example, a band layer 7 is disposed on the radially outer side of the belt layer 6 over the entire width of the belt layer 6.

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

The belt layer 6 is made up of upper and lower belt plies 6B and 6A, and the lower belt ply 6A is wider than the upper belt ply 6B. The example has a cut end structure in which the side ends are cut.

The belt plies 6A and 6B of the belt layer 6 may have the same width or different widths, and the upper belt ply 6B may have a wider width.

As shown in FIG. 2(A), the ply of the carcass 5 uses a composite cord 12 in which high elastic filaments 10 and low elastic filaments 11 are twisted together.

The angle of inclination of the carcass cords is 70° to 90° with respect to the circumferential direction of the tire, and when a plurality of plies are used, 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, and has a strength of 15 g/d.
The polyvinyl alcohol fibers or carbon fibers mentioned above are used, and the elastic modulus exceeds 1000 kg/mm 2 , preferably 1500 kg/mm 2 . Moreover, a relatively thin diameter of about 1000 to 3000 deniers is used.

Furthermore, as the low elasticity filament 11,
Nylon fiber, polyester fiber, vinylon fiber, etc., with an elastic modulus of 1000 kg/mm2 or less, preferably 7
00 kg/mm2 or less is used.

One or more of such high modulus filaments 10 are pre-twisted at the same time, and one or more low modulus filaments 1 are pre-twisted in the same direction.
The composite cord 12 is formed by twisting the cords 1 and 1 in opposite directions. In addition, when using a plurality of high-elasticity filaments 10 and low-elasticity filaments 11, each filament may be twisted individually, or a plurality of filaments may be twisted together. Further, the composite cord 12 may be made by twisting one each of the high elasticity filament 10 and the low elasticity filament 11, as shown in FIG. The composite cord 12 can also be formed by twisting a plurality of cords together.

When a tensile force is applied to such a composite cord 12, as shown in FIG. 2(B), the composite cord 12 is untwisted and elongated. Also, due to the elongation, the initial twist pitch P1 of the composite cord 12 increases to the pitch P2 due to the elongation. This elongation is shown in FIGS. 3(A) and (B) for the high elastic filament 10.
As schematically shown in , the highly elastic filament 10A, which had a coiled shape in its initial state, becomes a straight filament 10B by a predetermined elongation. Therefore, from this state, the high modulus of elasticity of the high elastic filament 10 is exhibited. In this way, by winding the high elastic filament 10 in a spiral shape in advance, the spiral state shown in FIG.
There is a low elasticity region where the elongation is relatively large between the state of A) and the straight state shown in Fig. 3(B), and a high elasticity region where the elongation is small due to the further load applied from the state of Fig. 3(B). It is clear that the elastic region can be provided, and the straight state shown in FIG. 3(B) forms an inflection point of the elongation-stress curve.

In the composite cord 12, the inflection point V is thus set to be located within the range of 2 to 7% of the elongation. The composite cord 12 is a twisted body of a high modulus filament 10 and a low modulus filament 11. Therefore, as shown in FIG. 2(B), the high modulus filament 10 and the low modulus filament 11 do not twist even when a load is applied. Therefore, its inflection point V is shown in Figs. 3(A) and (B
) is not as noticeable as in the typical case. The stress-elongation curve of the composite cord 12 is illustrated in FIG. In the figure, curve a shows the elongation curve of a low modulus filament 11 made of nylon 1260d, and curve b shows the elongation curve of a high modulus filament 10 made of aromatic polyamide of 1500d. Further, the case of a composite cord 12 in which two of these high elastic filaments 10 and one low elastic filament 11 are twisted together is shown by curve c. Curve c is located between curve a and curve b, and the inflection point V is elongated from 2 to 7.
It can be seen that it is in the range of %. In addition, in the composite code 12, the inflection point V is the intersection point of the vertical line passing through the intersection X of the tangent S1 that is in contact with the curve in the state of zero elongation and the tangent S2 drawn to the curve C at the breaking point. Defined.

Further, the composite cord 12 has a high elasticity region from the inflection point V to the breaking point, and a high elasticity region from the origin where the elongation is 0 to the inflection point V.
The ratio EH/EL of the elastic modulus EH in the high elasticity range to the elastic modulus EL in the low elasticity range is 2 to 2.
The range is 10. Such a composite code 12 is
By appropriately selecting the thickness, number, elastic modulus, etc. of the high-elastic filament, and the thickness, number, elastic modulus, etc. of the low-elastic filament, and adjusting the twisting conditions such as the filament angle, the above range can be satisfied as shown in Figure 4. It is possible to form a composite cord 12 that is transparent. It can also be adjusted by selecting the stretching treatment applied to the composite cord 12, the high elastic filament 10, and the low elastic filament 11.

[0025] Since the inflection point V exists in the range of 2 to 7% elongation, when the green tire is mounted in a vulcanization mold and the green tire is filled with internal pressure during tire production, the Due to the internal pressure, the belt layer 7 is compressed by the composite cord 12
By expanding and pressing the outer circumferential surface against the inner surface of the mold, the groove shape formed in the mold can be carved in the tread portion 2. Note that the expansion caused by filling the green tire with internal pressure is performed by elongating the composite cord 12 in a low elasticity region. For this reason, the inflection point V is set in the range of elongation of 2 to 7%. Note that it is preferable that the required elongation of the composite cord 12 in the mold due to internal pressure filling be located near the inflection point V. As a result, inflation of the molded tire and expansion of the tire due to centrifugal force acting during high-speed rotation can be suppressed by the high elasticity region as shown in FIG. 4. For this reason, the ratio EH/EL of the elastic modulus EH in the high elasticity region to the elastic modulus EL in the low elasticity region is set to 2 to 10. When it is less than 2, the above-mentioned suppressing effect is poor, and when it exceeds 10, it is unnecessary from the viewpoint of tire balance.

The band layer 7 is composed of one or more band plies 7A, 7A, and the band ply 7A is formed by winding a long and narrow strip ply 20 around the outside of the belt layer 6. .

The band-shaped ply 20 is made up of one band cord 21 or a plurality of band cords 21 arranged in parallel, two in this embodiment, embedded in a coating rubber 22 as shown in FIG. Organic fiber cords such as nylon, Teflon, and aromatic polyaramid polyester are used. Note that nylon fibers have a higher elastic elongation than other organic fibers, and by wrapping 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 is moved. can be efficiently prevented.

[0028] The band ply 7A is formed by spirally winding the band layer 7 from one end line, across the tire equator CL, toward the other broken line, and approximately parallel to the tire equator CL. Ru. In this embodiment, when winding the belt-shaped ply 20, as shown in FIG. 6, the opposite side edges 20a, 20a of the belt-shaped ply 20 are wrapped so as to be wrapped. Therefore, loosening of the belt-shaped ply 20 is prevented.

Furthermore, since the band-shaped ply 20 is spirally wound in the tire circumferential direction, there is no seam in the direction crossing the tire circumferential direction, so running stability and riding comfort during running can be further improved, and noise can be further reduced. It is possible to reduce the

Note that while the band layer 7 is formed of a monoply band ply, the belt layer 6 may be formed of a belt ply 6A formed of a spirally wound band-like ply having the above structure.

[0031]

[Specific example] Tire size is 700R16 12PR1
4 and having the configuration shown in FIG. 1, the tire weight and the noise during running were compared with those of prototypes (Examples 1 and 2) with the specifications shown in Table 1.

[0032] The tire weight was determined by measuring the net weight excluding the tube and rim, and expressed as an index with Comparative Example 1 being 100. The smaller the number, the lighter the weight. In addition, the noise level was determined by measuring the overall noise level at a position 1 m away from the sample tire while installing the sample tire on the vehicle, and expressed as an index with Comparative Example 1 being 100. The smaller the number, the smaller the noise.

[0033] The weight of the example was able to be reduced compared to that of Comparative Example 1 without a significant increase in noise, and the noise was reduced compared to that of Comparative Example 2, but this could not be confirmed. Ta.

[0034]

[Effects of the Invention] As described above, the radial tire for light trucks of the present invention has a carcass having a composite cord made by twisting high elastic filaments made of organic fibers and low elastic filaments made of organic fibers. The tire uniformity can be made uniform and the tire weight can be reduced without deteriorating various performances of the tire, and fuel consumption and noise can be reduced, so that it can be suitably adopted as a commercial tire.

[Brief explanation of the drawing]

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

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

FIGS. 3A and 3B are front views schematically showing the initial and stretched states of the high elastic filament.

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

FIG. 5 is a perspective view showing an example of a narrow ply forming a belt ply.

FIG. 6 is a sectional view showing the 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 Belt ply 10 High elastic filament 11 Low elastic filament

[Table 1]

Claims (5)

[Claims] 1. A tread comprising: a tread portion, a sidewall portion extending radially inward from both ends of the tread portion, and bead portions located at both radial ends of the sidewall portion; A toroidal carcass in which both ends of a cord extending substantially parallel to the radial direction of the tire through the tread portion are folded around a bead core in the bead portion, and a steel cord arranged inside the tread portion and outside the carcass in the radial direction. The radial tire for light trucks is provided with a belt layer, and the carcass uses a carcass ply in which composite cords made by twisting high elastic filaments made of organic fibers and low elastic filaments made of organic fibers are arranged side by side. 2. The high modulus filament is an aromatic polyamide fiber, a wholly aromatic polyester fiber, or a fiber having a strength of 15 g/
The radial tire for light trucks according to claim 1, characterized in that the organic fiber is made of polyvinyl alcohol fiber having a molecular weight of d or more. 3. The radial tire for light trucks according to claim 1, wherein the low modulus filament is nylon fiber, polyester fiber or vinylon fiber. 4. The composite cord is formed by twisting one or more pre-twisted high-elasticity filaments and one or more low-elasticity filaments pre-twisted in the same direction in opposite directions. The radial tire for light trucks according to claim 1, characterized in that: 5. The composite cord has a stress-elongation curve having a low elasticity region extending from the origin to an inflection point and a high elasticity region exceeding the inflection point, and the inflection point has an elongation of 2 to 7. % range, and the elastic modulus EH in the high elastic range and the elastic modulus EL in the low elastic range
The radial tire for light trucks according to claim 1, wherein the ratio EH/EL is 2 to 10.