JPH10203109A - Pneumatic radial-ply tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make improvements in riding quality and high-speed durability as well as to aim at the promotion of lightweightiness by making up a reinforcing cord for a carcass ply consist of a acrylic fiber cord, and constituting at least one ply of the reinforcing cord out of belt plies with a strand cord consisting of an organic fiber. SOLUTION: A reinforcing cord of a carcass ply 4 is made up of a high strength acrylic fiber cord which is composed of a fiber containing a range of 40 to 100% of acrylonitrile at weight rate, and tensile strength is more than 5g/d, if possible, more than 7g/d, and further a degree of intermediate elongation in time of a load of 2.25g/d is 2.0 to 3.5%. Thus, since this fiber cord being high in tensile strength is able to reduce a cord diameter as securing the extent of necessary strength, the carcass ply 4 is reducible in thickness. Likewise, since a reinforcing cord in a No.2 belt ply 7B is composed of a strand cord consisting of an organic fiber, rigidity in a tread part is abatable, and further any impact from a road surface is hard to be transmitted to a vehicle.

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 excellent in high-speed durability, load durability, steering stability, and riding comfort of an actual vehicle, and particularly to a pneumatic radial tire for a passenger vehicle.

[0002]

2. Description of the Related Art Conventionally, in a pneumatic radial tire for a passenger car mounted on a high-performance vehicle, rayon fiber, which has a high elastic modulus and is excellent in steering stability, has been often used as a reinforcing cord of a carcass layer. . However, this rayon fiber has a problem in that it causes environmental pollution since it uses highly toxic carbon disulfide during production. Moreover,
Since the tensile strength is low, the cord diameter must be increased in order to secure the required strength. As a result, the gauge of the carcass layer becomes thicker, and the tire weight increases. Furthermore, since the fatigue resistance is low, when the carcass layer is made of rayon fiber cord, there is a problem that the load durability of the tire is reduced.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic air which is excellent in load durability, steering stability and riding comfort of a real vehicle, high speed durability and contributes to weight reduction. Provided is a radial tire including a tire.

[0004]

In order to achieve the above object, the present invention provides a carcass layer mounted between a pair of left and right bead portions, and both end portions of the carcass layer are turned around a bead core and a bead filler to form a tread portion. In the pneumatic radial tire in which a plurality of belt layers are arranged on the outer peripheral side of the carcass layer, the tensile strength of the reinforcing cord of the carcass layer is 5 g / d or more, and the intermediate elongation under load of 2.25 g / d is 2.0 to 3.0. 5%
And the reinforcing cord of at least one of the belt layers is a twisted cord made of organic fibers.

As described above, when the tensile strength is 5 g / d or more, 2.
A carcass layer is formed by arranging high-strength acrylic fiber cords having an intermediate elongation under a load of 25 g / d of 2.0 to 3.5%, a high elastic modulus and a high tensile strength, and also having excellent fatigue resistance. Therefore, excellent load durability, steering stability, and high-speed durability can be obtained. In addition, in the conventional tire, at least one reinforcing cord of the belt layer formed by arranging steel cords as the reinforcing cords is constituted by a twisted cord made of organic fibers, so that the elastic modulus is high and the strength is high. The rigidity of the tread portion, which is increased when the acrylic fiber cord is used, is canceled out and further reduced, so that it is possible to obtain good real-world riding comfort.

Further, since the high-strength acrylic fiber cord has a high tensile strength, the cord diameter can be reduced while securing the required strength. As a result, the gauge of the carcass layer becomes thinner and the weight of the tire can be reduced.

[0007]

FIG. 1 shows an example of a pneumatic radial tire according to the present invention, wherein 1 is a tread portion, 2 is a bead portion,
3 is a side wall part. Left and right sidewall portions 3 are connected to the right and left bead portions 2 and extend outward in the tire radial direction, and a tread portion 1 extending in the tire circumferential direction is provided between the left and right sidewall portions 3.

A single carcass layer 4 in which reinforcing cords are arranged in the tire radial direction between right and left bead portions 2 is mounted inside the tire. An annular bead core 5 is disposed in each of the left and right bead portions 2.
An annular bead filler 6 is continuously provided on the outer periphery of. Both ends 4 a of the carcass layer 4 are folded around the bead core 5 from the inside of the tire to the outside so as to wrap the bead filler 6.

On the outer peripheral side of the carcass layer 4 of the tread portion 1, there are buried two belt layers 7 in which reinforcing cords are arranged so that the inclined directions with respect to the tire circumferential direction are opposite to each other and cross each other. . Note that CL is a tire center line passing through the tire equatorial plane. In the present invention, in the pneumatic radial tire having the above configuration, the carcass layer 4
Is made of a high-strength acrylic fiber cord. The high-strength acrylic fiber cord used here is
It consists of fibers containing 40 to 100% of acrylonitrile by weight, and has a tensile strength of 5 g / d or more, preferably 7 g / d.
d or more, and the intermediate elongation under 2.25 g / d load is 2.
0 to 3.5%.

The use of the high-strength acrylic fiber cord having high strength and elastic modulus and high resistance to fatigue as the reinforcing cord of the carcass layer 4 provides the rayon fiber cord with load durability, handling stability and high-speed durability. Can be increased more than conventional tires using the same. Moreover, the high-strength acrylic fiber cord having a high tensile strength can reduce the cord diameter while securing the required strength, so that the carcass layer 4 can be made thinner, and thus the weight can be reduced.
In addition, there is no problem of causing environmental pollution during production.

The above-mentioned fibers are obtained, for example, by spinning an acrylonitrile polymer spinning stock solution while maintaining a discharge linear speed ratio (= spinning stock solution discharge linear speed / spun gel yarn winding speed) at 4 or more. After the washed spun gel yarn is washed with water and stretched, it is subjected to a tension dry heat treatment to an effective total draw ratio of 15 times or more,
Alternatively, it can be obtained by dry stretching. If the tensile strength of the acrylic fiber cord is less than 5 g / d, the acrylic fiber cord is not suitable as a reinforcing material in terms of strength, and the weight of the tire cannot be reduced. If the intermediate elongation under a load of 2.25 g / d is less than 2.0%, the load durability deteriorates,
If it exceeds 3.5%, the high-speed durability deteriorates. Acrylic fiber cords are preferably as large as their tensile strength. However, in order to increase the tensile strength, it is necessary to avoid applying a hot stretching treatment of 1.0 g / d or more after impregnating the adhesive from the viewpoint of fatigue resistance. No.

However, when the carcass layer 4 is made of such a high-strength acrylic fiber cord as a tire,
Since the cord has a high elastic modulus, the impact from the road surface is easily transmitted to the vehicle, and the riding comfort (harshness) of the actual vehicle tends to be reduced. Therefore, in the present invention, of the two belt layers 7, the reinforcing cord of the inner first belt layer 7A is made of steel cord, whereas the reinforcing cord of the outer second belt layer 7B is made of steel cord. It consists of a twisted cord made of organic fibers. By using the organic fiber cord for one of the belt layers as described above, the rigidity of the tread portion can be reduced, so that it is difficult for the impact from the road surface to be transmitted to the vehicle, and good ride comfort of the actual vehicle is secured. be able to.

In the present invention, preferred examples of the organic fiber used for the reinforcing cord of the second belt layer 7B include aramid fiber and PBO (polyparaphenylene benzobisoxazole) fiber. Also, when using the steel cord reinforcing cords of the belt layer 7A as described above, to set the belt stiffness coefficient K represented by the following formula in the tread center portion to 5.8 to 10.6 mm ^2/50 mm Good.

K = d ² × n × E d: diameter of steel wire constituting steel cord (mm) n: number of steel wires per steel cord (wire) E: number of ends (steel per unit width) the code end count (the / 50 mm)) belt rigidity coefficient K of less than 5.8 mm ^2/50 mm, the stiffness reduction of the tread portion is increased, steering stability, load durability, high-speed durability is lowered. Conversely, the belt stiffness coefficient K is 1
If it exceeds 0.6 mm ² / 50mm, the rigidity of the tread is too high. Preferably, the belt stiffness coefficient K is 7.5 to 9.
5 mm ^2/50 mm to the well, whereby it is possible to balance better the steering stability and the actual vehicle ride comfort property. When the belt stiffness coefficient K less than 7.5 mm ^2/50 mm, it is preferable to reinforce the belt layer 7 on the outer peripheral side by arranging the belt cover layer of the belt layer 7.

The belt rigidity coefficient K is 5.8 to 10.6 mm ²
As a specific method for setting the / 50mm, for example,
(a) 1 × 2 or 1 steel cord with conventional 2 + 2 structure
A method of reducing the number of strands of the steel cord by using a steel cord having a × 3 structure or using a single-wire spiral cord, (b) a method of reducing the number of wires (ends) per unit width of the steel cord, (c) A preferred example is a method of reducing the wire diameter of the steel cord.

In the above embodiment, the reinforcing cord of the first belt layer 7A is made of a steel cord.
The reinforcing cords of all the belt layers 7A and 7B may be formed of twisted cords made of organic fibers, and the reinforcing cords of at least one belt layer may be twisted cords made of organic fibers. The belt layer 7A using the steel cord and the organic fiber cord as described above,
When 7B is used, as described above, it is preferable to employ a steel cord as the reinforcing cord of the first belt layer 7A and an organic fiber cord as the reinforcing cord of the second belt layer 7B in terms of facilitating the production. It does not matter.

In the present invention, the height H of the bead filler 6 is preferably 20 to 40% of the tire section height SH. As a result, the bead filler height H can be made lower than before (about 50% in the past), the rigidity of the side wall 3 on the bead portion 2 side can be made lower than in the past, and it is difficult to transmit the impact from the road surface. it can. Bead filler height H is 20 of tire section height SH.
%, The steering stability is lowered because the height is too low. Desirably, the ratio is set to 25 to 35%, whereby the riding comfort and the driving stability can be better balanced.

In the present invention, it is preferable that the turnover height TUH of the carcass layer 4 is set to 20 to 50% of the tire section height SH. In this way, by making the folded height TUH lower than before (about 60% in the past),
The rigidity of the sidewall portion 3 on the bead portion side can be reduced as compared with the related art, and the impact from the road surface can be hardly transmitted. If the turnover height TUH is less than 20%, the steering stability is reduced because it is too low. Desirably, the content is set to 25 to 45% in order to better balance the real-world riding comfort and the steering stability. It is more preferable to use the carcass layer 4 having a reduced turn height TUH in combination with the bead filler 6 having a reduced bead filler height H.

In addition, the bead filler height H mentioned here,
The folded height TUH of the carcass layer 4 and the tire cross-section height SH are heights (lengths in the tire radial direction) from the rim diameter equivalent position R, respectively. Also, the tire section height SH
Is the length in the tire radial direction from the rim diameter equivalent position R to the surface 1a of the tread portion 1 on the center line CL.

Although the present invention has been described with reference to the embodiment in which one carcass layer 4 is provided, the present invention is not limited to this.
A plurality of layers may be arranged. Further, the belt layer 7 is not limited to two layers, but may be provided with more layers. In this case, the reinforcement cord of one belt layer is made of steel cord, and the reinforcement cord of the remaining belt layer is made of organic cord. It is preferable to use a twisted cord made of fiber.

The present invention can be suitably used particularly for high performance pneumatic radial tires for passenger cars.

[0022]

【Example】

(1) Tire size 225 / 50VR16, carcass layer 2
Pneumatic radial tire having a carcass structure and a belt structure of the contents shown in Tables 1 to 7 in a pneumatic radial tire having a layer, a belt layer, two layers, a nylon belt cover layer, and a nylon belt edge cover layer. Example 1
35), a comparative tire (Comparative Examples 1 to 3), and a conventional tire (conventional example) were produced.

Table 1 shows that the intermediate elongation of the acrylic fiber cord of the carcass layer is sequentially changed in the above-mentioned range (2.0 to 3.5%), and the bead filler height H and the turnover height THU are each preferable. This is an embodiment with a range.
Tables 2 and 3 show examples in which the conditions of the reinforcing cords of the carcass layer were the same and the structure of the belt layer was changed.

Table 4 shows an embodiment in which the conditions of the reinforcing cord of the carcass layer are the same, the structure of the belt layer is changed, and the height H of the bead filler is set to 20 to 40% of the height SH of the tire section. Table 5 is an example in which the conditions of the reinforcing cords of the carcass layer were made the same, the structure of the belt layer was changed, and the turning height THU was set to 20 to 50% of the tire section height SH.

Table 6 shows an embodiment in which the conditions of the reinforcing cord of the carcass layer were made the same, the structure of the belt layer was changed, and the height H of the bead filler and the turning height THU were each changed within a preferable range. Table 7 shows a comparative example in which the structure of the belt layer was the same, and the tensile strength or the intermediate elongation of the acrylic fiber cord of the carcass layer was out of the range described above.
This is a conventional example in which a rayon fiber cord is used as a reinforcing cord for a carcass layer.

The test tires were evaluated for high-speed durability, load durability, steering stability, actual vehicle riding comfort, and tire weight under the following measurement conditions. The results shown in Tables 1 to 7 were obtained. I got High-speed durability Using a drum tester with a smooth drum surface made of steel and having a diameter of 1707 mm, the ambient temperature is controlled to 38 ± 3 ° C., the rim size is 7.5JJ-16, and the test internal pressure is 220 kP.
a, Under a speed of 81 km / h, run for 120 minutes at 88% of the load corresponding to the pneumatic condition specified by JATMA, then allow it to cool for 3 hours or more, readjust it to the test air pressure, and then complete the run To start.

The actual running starts at a speed of 121 km / h, and the speed is gradually increased by 8 km / h every 30 minutes of running, and the vehicle runs until a failure occurs. The distance until a failure occurred in each test tire was evaluated by an index value with the failure occurrence distance of the conventional tire being 100. The larger the value,
Excellent high-speed durability. Load durability Using a drum tester with a smooth drum surface made of steel and having a diameter of 1707 mm, the ambient temperature is controlled to 38 ± 3 ° C., the rim size is 7.5 JJ-16, the test internal pressure is 180 kPa, and the speed is 81 km / h. At 85% of the maximum load specified by JATMA for 4 hours, and then 6% at 90% of the maximum load.
Run for 24 hours, then at maximum load for 24 hours. Here, the driving is temporarily stopped, and if there is no abnormality in the appearance, the vehicle is further driven at 115% of the maximum load for 4 hours and then at 130% of the maximum load for 2 hours. At this time, if an abnormality occurs in the external appearance or the inside, it is rejected (x), and if not, it is passed (o).

If the test passes, the vehicle is further run for 2 hours at 130% of the maximum load, then for 4 hours at 145% of the maximum load, and then for 4 hours at 160% of the maximum load. Passed if there is no failure in appearance or inside at this time (◎)
And Driving stability Each test tire assembled into a 7.5 JJ x 16 rim with an internal pressure of 210 kPa was mounted on a 3.0-liter FR passenger car, and the trained five drivers traveled on the test course to feel. evaluate. The results were scored by the five-point method based on the following criteria, and represented by the average score of three persons excluding the highest point and the lowest point.

Criterion 5: Excellent, 4: Excellent, 3.5: Somewhat excellent,
3: Equivalent to standard, 2.5: slightly inferior (lower limit of practical use), 2: inferior, 1: greatly inferior. Real vehicle ride comfort Each test tire assembled into a 7.5 JJ x 16 rim at an internal pressure of 210 kPa was mounted on a 3.0-liter FR passenger car, and a trained five drivers drove a test course to drive the tires. Evaluate the ring. The results were scored by the five-point method based on the following criteria, and represented by the average score of three persons excluding the highest point and the lowest point.

Criterion 5: Excellent, 4: Excellent, 3.5: Somewhat excellent,
3: Equivalent to standard, 2.5: slightly inferior (lower limit of practical use), 2: inferior, 1: greatly inferior. Tire Weight The weight of each test tire was measured with a measuring instrument.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

[0035]

[Table 5]

[0036]

[Table 6]

[0037]

[Table 7]

As can be seen from Tables 1 to 7, the tire of the present invention in which the reinforcing cord of the carcass layer is constituted by the above-mentioned high-strength acrylic fiber cord and the reinforcing cord of at least one belt layer is constituted by the organic fiber cord, It can be seen that the tire has excellent durability, load durability, steering stability, and real-world riding comfort, and also has reduced tire weight. (2) In a pneumatic radial tire having the same tire size and tire configuration as described above, test tires 1 and 2 in which the belt stiffness coefficient K was changed as shown in Table 8, bead filler height H and carcass layer folded height Test tires 3 and 4 in which the TUH was smaller than 20% of the tire section height SH were produced.

The test tires were evaluated for high-speed durability, load durability, steering stability, actual vehicle riding comfort, and tire weight under the same measurement conditions as described above. The results shown in Table 8 were obtained. Was.

[0040]

[Table 8]

It can be seen from Table 8 that if the belt stiffness coefficient K is too high, ride comfort deteriorates, and if it is too low, steering stability decreases. Further, it can be seen that the steering stability is deteriorated even if the bead filler height H and the turnback height TUH of the carcass layer become too low.

[0042]

As described above, the present invention has a tensile strength of 5%.
Intermediate elongation under load of 2.25 g / d at 2.0 g / d or more is 2.0
Up to 3.5% high-strength acrylic fiber cord is used for the reinforcing cord of the carcass layer, while at least one reinforcing cord of the belt layer is composed of a twisted cord made of organic fibers, so that load durability and steering stability are maintained. In addition, the tires can be excellent in performance, riding comfort, and high-speed durability, and can reduce the weight of tires.

[Brief description of the drawings]

FIG. 1 is a tire meridian half sectional view showing an example of a pneumatic radial tire of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Tread part 2 Bead part 3 Side wall part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 7A 1st belt layer 7B 2nd belt layer CL Tire center line

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B60C 9/20 B60C 9/20 F D

Claims (5)

[Claims] 1. A carcass layer is mounted between a pair of left and right bead portions, and both end portions of the carcass layer are turned around a bead core and a bead filler, and a plurality of belt layers are arranged on the outer side of the carcass layer in a tread portion. In the pneumatic radial tire, the reinforcing cord of the carcass layer has a tensile strength of 5 g / d or more,
2.25 g / d of an acrylic fiber cord having an intermediate elongation of 2.0 to 3.5% under a load, and at least one of the belt layers, a reinforcing cord of a belt layer, made of an organic fiber. Pneumatic radial tire made of cord. 2. The reinforcing cord of one belt layer of the belt layers is made of a steel cord, while the reinforcing cord of the remaining belt layer is made of a twisted cord made of an organic fiber. ^2. The pneumatic radial tire according to claim 1, wherein a belt stiffness coefficient K in a tread center portion of the belt layer having the following formula is set to 5.8 to 10.6 mm 2/50 mm. K = d ² × n × E d: diameter of steel wire constituting steel cord (mm) n: number of steel wires per steel cord (wires) E: number of ends (number of steel cords inserted per unit width) (Book / 50mm) 3. The pneumatic radial tire according to claim 1, wherein the reinforcing cords of the plurality of belt layers are all formed of twisted cords made of organic fibers. 4. The tire according to claim 1, wherein the height H of the bead filler is 20 to 40% of the tire sectional height SH.
The described pneumatic radial tire. 5. The method according to claim 1, wherein the carcass layer has a folded height TUH of 20 to 50% of the tire cross-section height SH.
The pneumatic radial tire according to 2, 3, or 4.