JPH0624206A - Radial tire for light truck - Google Patents

Abstract

PURPOSE:To construct a tire light in weight and enhance the amenity in car cabin by forming a carcass from thick threads having more than 4500 denier, and forming a belt layer from composite cords prepared by twining together high resilient filament consisting of organic fiber material and low resilient filament consisting of organic fiber material. CONSTITUTION:A belt carcass 5 consists of one carcass ply prepared by lining a woven fabric with rubber, wherein the fabric is made in the form of a rattan screen from thick threads whose degree of fiber of organic fiber cords is more than 4500 denier. A belt layer is formed as a cloth belt from three or four belt plies 6A-6C overlapped inside and outside in the radial direction where composite cords 12 are laid in line consisting of twining together of high resilient filaments 10 of organic fiber material and low resilient filaments 11 of organic fiber material. The composite cord has a low resilience region whose stress-elongation curve leads from the point of origin to the point of inflection and a high resilience region lying beyond the point of inflection, wherein the point of inflection is within the range 7-11%, and the ratio of the modulus of elasiticity in the high range to that in the low range should be between 8-20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light truck tire, particularly a tire having a strength formed by stacking 3 to 4 ordinary carcass plies on a carcass,
The present invention relates to a so-called 8 to 12 ply rating tire, which is a radial tire for a light truck which is lightweight and has reduced rolling resistance and improved durability and riding comfort.

[0002]

2. Description of the Related Art As a light truck tire for tires having a maximum tire width of 165 mm or more and a rim diameter of 380 mm or more, and a tire strength of 8 to 12 ply rating as described above, a polyester fiber cord is conventionally used as a light truck tire. The durability was improved by using a carcass in which two to three plies used were superposed and a belt layer formed of a cut ply using a steel cord as a belt cord. The tire formed in this manner has a large weight and a large rolling resistance, and therefore has a high fuel consumption during traveling. On the other hand, global warming,
The deterioration of the global environment is becoming a serious problem year after year, and the development and popularization of electric vehicles typified by solar cars is being greatly highlighted in order to prevent such environmental pollution.

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

Further, in recent years, in order to prevent environmental deterioration such as global warming and increase of carbon dioxide, it is attempted to save fuel even in a four-wheeled motor vehicle. On the other hand, 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%, and even tires are required to be further lightweight. It became so.

[0005]

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 lack of rigidity compared to steel cord, and pattern noise is high due to deterioration of uniformity. . Especially 10-12KH
The noise increase in _Z is significant.

The inventors of the present invention reduce the weight of such a tire,
As a result of intensive research to solve the three problems of suppressing noise in addition to reducing rolling resistance, as a carcass cord, rubber fiber is applied to the blind fabric of thick organic fiber cord with a fineness of 4500 denier or more. The carcass ply is made into a toroidal carcass by winding it around a pair of left and right bead cores to reduce the weight of the carcass, and as a belt cord, a high elastic filament and a low elastic filament are mixed and twisted. The belt cord is made to function as a low elasticity below the inflection point in the load-elongation curve and a high elasticity above the inflection point to adjust the tightening effect of the belt according to the rotation speed of the tire. It was found that it is possible to improve the durability and reduce the pattern noise.

According to the present invention, the carcass is formed by one carcass ply using a thick cord of 4500 denier or more, and the belt layer is formed by adjusting the elastic modulus ratio between the high elastic filament and the low elastic filament. It is possible to reduce tire weight without increasing pattern noise and reduce rolling resistance to save fuel consumption based on the fact that 3 to 4 belt plies using twisted composite cords are stacked. The purpose is to provide radial tires for light trucks.

[0008]

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. And a toroidal carcass in which both ends of a cord that extends substantially parallel to the radial direction of the tire passing through the tread portion and the side wall 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. In a light truck tire having a belt layer arranged on the outside and having a maximum width in the meridional direction of 165 mm or more and a rim diameter of 380 mm or more and having a tire strength equivalent to 8 to 12 ply rating, the carcass comprises: An organic fiber cord, the cord of which has a fineness of 4500 denier or more, is rubberized on a woven fabric made of thick yarn. It consists of one carcass ply,
The belt layer is formed by arranging three to four belt plies in which a composite cord in which a high-elasticity filament made of an organic fiber and a low-elasticity filament made of an organic fiber are twisted and arranged is arranged side by side in the radial direction. The composite cord is formed as a cross belt intersecting with each other, and the composite cord has a low elastic region where the stress-elongation curve extends from the origin to the inflection point and a high elastic region that exceeds the inflection point. And the inflection point is 7 ~
A radial tire for a light truck, characterized in that the 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 20 in the range of 11%.

[0009]

The carcass is composed of one carcass ply using a thick carcass cord of 4500 denier or more, so it is 5% to 15% compared to the conventional structure in which two to three plies are stacked. The weight can be reduced, the rolling resistance of the tire is reduced accordingly, and the fuel efficiency of the vehicle is improved. Further, since the carcass is formed by one carcass ply as described above, the productivity is greatly increased.

Further, since the belt layer comprises a belt 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. Moreover, a high elastic region is also present above the inflection point.

Therefore, the elasticity corresponding to the elongation of the belt cord (about 3%) occurring in the tire vulcanizing step is in the low elastic region, and this elasticity is the inside of the raw tire when vulcanizing in the tire vulcanizing 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. Further, when the tire is rotated at a high speed with high deformation, the composite cord in the ply of the belt layer exhibits high elasticity.

Since the inflection point of the composite cord as the belt cord exists in the range of elongation of 7 to 11%, the raw tire is mounted on the vulcanization mold and the internal pressure is applied to the raw tire during tire production. When the belt layer is filled, the belt layer bulges due to the extension of the composite cord due to the internal pressure, and the outer peripheral surface is pressed against the inner surface of the mold, so that the groove formed in the mold is formed in the tread portion 2 of the belt layer. it can. The swelling of the green tire due to the filling with the internal pressure is performed by the expansion of the composite cord in the low elastic region. Therefore, the inflection point is set in the range of 7 to 11% of elongation. 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 are caused by the high elasticity region.
It can be suppressed as shown in. 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 8 to 2
It is set to 0. 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 set at 7 to 7
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.

The elastic modulus is 600 kg on the outside of the belt layer.
When a band layer formed by spirally winding a band cord of / mm ² or more, for example, a cord made of an aromatic polyamide fiber, is wound substantially parallel to the equator, the hoop effect is improved and so-called belt layer lifting can be prevented. By suppressing the generation of standing waves, the high-speed durability of the tire is further improved and the generation of vibration is suppressed. Furthermore, the ruggedness is reduced when riding on rough roads such as gravel roads and step roads, and riding comfort is improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a radial tire T for a light truck
Has a maximum tire width of 160 mm when normal internal pressure is applied.
A tire for use in a light truck having a rim diameter of 380 mm or more, a sidewall portion 3 extending inward in the radial direction from both ends of the tread portion 2, and a bead located at the radially inner end of the sidewall portion 3. The radial tire T has 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 axial direction. A toroidal carcass 5 made of one carcass ply and a belt layer 6 are arranged inside the tread portion 2 and outside the carcass 5 in the radial direction.
Here, that the carcass cord extends substantially parallel to the axial direction means that the carcass cord is inclined at an angle of 5 ° or less with respect to the tire axis, which is a so-called radial structure.

The carcass ply is formed by rubber-coating a so-called interwoven cloth, which is made by weaving the thick carcass cord made of organic fiber such as polyester, nylon, aromatic polyamide fiber or the like having a denier of 4500 or more with a thin weft. Fabric is used.

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 as each other, and the belt ply 6C above the width may be wider than the other belt plies 6A and 6B.

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

Further, the inclination angle of the belt cords is 10 ° to 30 ° with respect to the tire circumferential direction, and when a plurality of plies are overlapped as in this embodiment, the belt cords of the adjacent plies are inclined in opposite directions. The so-called cross belt structure.

The highly elastic filament 10 is made of aromatic polyamide fiber, wholly aromatic polyester fiber, and 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 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. 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 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 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 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 breaking 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.

As described above, the inflection point V is extended by 7 to 11%.
Is set to the range. 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 8 to 20.

FIG. 5 shows another embodiment of the present invention. In this example, as described above, the carcass 5 is formed by one carcass ply using the interwoven fabric made of the carcass cord having a denier of 4500 or more. The carcass 5 has the carcass 5 on the outer side in the radial direction. A belt layer 6 including four belt plies 6A, 6B, 6C, and 6D using the cord 12 is provided. On the outer side of the belt layer 6 in the radial direction, a band layer 7 having band cords 21 arranged substantially parallel to the tire equator C is provided. In the present embodiment, the band layer 7 is substantially the same as the belt layer 6. It is formed as a full band covering the width, so that the band layer 7 covers both side edges 6a, 6a of the belt layer 6. As the band layer 7, end bands arranged only on the both side edge portions 6a, 6a of the belt layer 6 can be appropriately adopted.

The band layer 7 is composed of one or more band plies 7A, 7A in this example. 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. In this embodiment, two band cords 21 are embedded in a coating rubber 22. The band cords 21 are elastic. For example, an organic fiber cord of 300 kg / mm ² or more such as nylon, Teflon, aromatic polyaramid, polyester or the like is 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 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 so as to prevent the wound belt-shaped ply 20 from loosening.

Since the belt-shaped ply 20 is formed by spirally winding it 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 improved. The noise can be further reduced.

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.

[0034]

SPECIFIC EXAMPLE A tire having a tire size of 700R16 12PR and having the configuration shown in FIGS. 1 and 5 was prototyped according to the specifications shown in Table 1 (Examples 1 to 4), and a conventional tire (Comparative Examples 1 and 2) was used. The tire weight, riding comfort, and running noise were compared.

The tire weight is shown as an index with the comparative example 1 being 100 by measuring the net weight not including the tube and the rim. The smaller the number, the lighter it is. For the riding comfort, we attached the trial tires to the actual vehicle and traveled on the general road,
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 shown as an index with Comparative Example 1 set to 100 by mounting a test tire on a vehicle and measuring the overall noise level at a position 1 m away from the tire. The smaller the number, the smaller the noise.

[0036]

[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.

[0038]

As described above, in the radial tire for a light truck of the present invention, the carcass is made of thick yarn of 4500 denier or more, and the belt layer is made of a high elastic filament made of an organic fiber and a low elastic filament made of an organic fiber. Since the main point is to have a composite cord that matches the above, it is possible to make the uniformity of the tire uniform and reduce the weight of the tire without deteriorating various performances of the tire and increasing noise, reducing fuel consumption and improving riding comfort. It can be suitably used as a commercial 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 sectional view showing another embodiment.

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

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 12 composite cord

Claims (5)

[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. A toroidal carcass obtained by folding both ends of a cord that extends substantially parallel to the radial direction of the tire through the portion around the bead core in the bead portion, and a belt layer disposed inside the tread portion and radially outside the carcass. Provided and maximum width in meridian direction is 1
65mm or more and rim diameter of 380mm or more and 8
In a light truck tire having a tire strength equivalent to -12 plies, the carcass is an organic fiber cord, and one of the carcasses is rubberized to a woven fabric made of thick yarn having a fineness of 4500 denier or more. The belt layer is composed of plies, and a belt ply in which a composite cord in which a high elastic filament made of an organic fiber and a low elastic filament made of an organic fiber are twisted and arranged is arranged side by side is laminated 3 to 4 in a radial direction. The composite cords of adjacent belt plies are formed as a cross belt that intersects with each other, and the composite cords have a low elasticity region in which the stress-elongation curve extends from the origin to the inflection point and a high elasticity exceeding the inflection point. And the inflection point is in the range of 7 to 11% elongation, and the elastic modulus EH in the high elastic region is low. The ratio EH / EL of the elastic modulus EL of sexual zone
A radial tire for a light truck, characterized in that 2. The high elasticity filament is aromatic polyamide fiber, wholly aromatic polyester fiber or strength 15 g /
The radial tire for a light truck according to claim 1, wherein the radial tire is an organic fiber made of a polyvinyl alcohol fiber having a length of d or more. 3. The radial tire for a light truck 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 under-twisted high-elasticity filaments and one or more under-twisted low-elasticity filaments in the same direction in opposite directions. The radial tire for a light truck according to claim 1, wherein 5. The outer side of the belt layer in the radial direction is 300 kg.
^2. The light truck according to claim 1, wherein a band layer formed by spirally winding a band cord having an elastic modulus of / mm ² or more substantially parallel to the tire equator is arranged at a position covering at least both side edges of the belt layer. For radial tires.