JPH11139111A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance high speed durability and steering stability, and to improve uniformity. SOLUTION: A folded-back belt layer 8 which is formed by folding a beltlike body 7 rubber-coated to a reinforcing cord 7a back zigzag from the inside of a tire to its outside in belt width-directional both end parts while inclining the beltlike body 7 relating to a circumferential direction of the tire is provided in the outer peripheral side of a carcass layer 4 in a tread part 1, and a circumference-directional belt layer 9 wound spirally while arranging the beltlike body 7 rubber-coated to the reinforcing cord 7a substantially parallely to the circumferential direction of the tire is provided in the outer peripheral side of the belt layer 8.

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 having a belt layer formed of a belt made of a reinforcing cord, and more particularly to improving high-speed durability and steering stability and improving uniformity. The present invention relates to a pneumatic radial tire that has made it possible.

[0002]

2. Description of the Related Art Conventionally, in a pneumatic radial tire, two belt layers made of a steel cord are provided on the outer peripheral side of a carcass layer in a tread portion. These two belt layers are stacked so that the reinforcing cords are inclined with respect to the tire circumferential direction and cross each other between the layers.

However, in the belt layer laminated as described above, since the cut ends of the reinforcing cord are located at both ends in the tire width direction, stress concentrates on the cut ends during traveling,
As a result, there is a problem that separation easily occurs at the edge portion of the belt layer. Further, in the belt layer in which the reinforcing cords inclined in one direction intersect with each other as described above, since the twist is biased in one direction when the internal pressure is charged, the lateral force is generated during traveling due to the belt structure. Then, there is a problem that the lateral force adversely affects the steering stability during straight traveling.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic radial tire capable of improving high-speed durability and steering stability and improving uniformity.

[0005]

A pneumatic radial tire according to the present invention, which achieves the above object, has a belt-like body rubberized with a reinforcing cord inclined on the outer peripheral side of a carcass layer in a tread portion with respect to the tire circumferential direction. While providing a folded belt layer formed by folding in a zigzag shape from the inside to the outside of the tire at both ends in the belt width direction, a belt-like body rubberized with a reinforcing cord is provided on the outer peripheral side of the folded belt layer substantially parallel to the tire circumferential direction. And a circumferential belt layer wound spirally while being arranged in the above manner.

[0006] By providing a folded belt layer in which the belt-like body is folded in a zigzag manner from the inside to the outside of the tire at both ends in the belt width direction while being inclined with respect to the circumferential direction of the tire, both ends of the belt layer are provided. Since the cut ends of the reinforcing cords are not positioned, the occurrence of separation due to the concentration of stress on the edges can be prevented, and the high-speed durability can be improved.

Further, since the folded belt layers are repeatedly arranged in the tire circumferential direction so that the inclination direction of the reinforcing cords with respect to the tire circumferential direction is alternately opposite, the reinforcing cords which are inclined in one direction as in the prior art. Unlike a belt layer arranged so as to intersect between layers, a lateral force generated due to the belt structure can be suppressed, and steering stability can be improved.

Further, although the rigidity of the folded-back belt layer is periodically changed in the tire circumferential direction by alternately reversing the inclination direction of the reinforcing cord, a belt-like body is provided around the outer circumferential side of the folded-back belt layer. By providing a circumferential belt layer spirally wound while being arranged substantially parallel to the direction, the rigidity periodic characteristics of the folded belt layer are reduced,
The uniformity of the tire can be improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 illustrates a pneumatic radial tire according to an embodiment of the present invention, in which 1 is a tread portion, 2 is a bead portion, and 3 is a sidewall portion. The left and right sidewall portions 3 are connected to the left and right bead portions 2 and extend outward in the tire radial direction, and the tread portion 1 extending in the tire circumferential direction is provided between the left and right sidewall portions 3. I have.

[0010] Two carcass layers 4 are provided inside the tire. A bead core 5 is disposed on each of the left and right bead portions 2, and a bead filler 6 made of hard rubber is disposed on the outer periphery of the bead core 5. Carcass layer 4
Are bent from the inside of the tire to the outside around the bead core 5, and both ends 4 a of the inner carcass layer 4 </ b> A wrap the bead filler 6 so as to extend beyond the outer peripheral end 6 a of the bead filler 6 toward the tire radial outside. Extending.
Further, on the outer peripheral side of the carcass layer 4 in the tread portion 1, a folded belt layer 8 and a circumferential belt layer 9 made of a band-shaped body 7 are provided.

As shown in FIG. 3, the belt-shaped body 7 is obtained by aligning one or more reinforcing cords 7a and rubberizing them. As the reinforcing cord 7a of the strip 7, an organic fiber cord or a steel cord can be used. As organic fiber cord, aromatic polyamide fiber,
A twisted cord obtained by twisting at least one kind of fiber selected from nylon fiber, polyethylene terephthalate fiber, polyethylene 2,6-naphthalate fiber, polyvinyl alcohol fiber, polyparaphenylene benzobisoxazole fiber and the like can be used.

The folded belt layer 8 is formed by folding the belt-like body 7 in a zigzag manner from the inside to the outside of the tire at both ends in the belt width direction while inclining the belt-like body 7 with respect to the tire circumferential direction E as shown in FIG. By shifting the phase of the band-like body 7 every time the turn is repeated while repeating the turn in the tire circumferential direction, the turn-up belt layer 8 is arranged to extend in the tire circumferential direction E as shown in FIG.

On the other hand, on the outer peripheral side of the folded belt layer 8,
A circumferential belt layer 9 is provided in which the belt-shaped body 7 is spirally wound while being arranged substantially parallel to the tire circumferential direction E. It is sufficient that at least one circumferential belt layer 9 is provided, and a plurality of circumferential belt layers 9 may be stacked as necessary.
The circumferential belt layer 9 is preferably disposed so as to cover the entire surface of the folded belt layer 8, but it is sufficient that the circumferential belt layer 9 covers at least 50% or more of the folded belt layer 8 in the tire width direction.

As described above, the belt layer 8 is formed by folding the belt-like body 7 in a zigzag manner from the inside to the outside of the tire at both ends in the belt width direction while inclining the belt-like body 7 with respect to the tire circumferential direction E. Since the cut ends of the reinforcing cords 7a are not located at both ends in the tire width direction of the tire No. 8, separation due to concentration of stress on the edges can be prevented, and high-speed durability can be improved.

Further, as shown in FIG. 2, the folded belt layers 8 are repeatedly arranged in the tire circumferential direction E such that the inclination direction of the reinforcing cords 7a with respect to the tire circumferential direction E is alternately opposite. Unlike the belt layer in which the reinforcing cords inclined in one direction intersect with each other, the lateral force generated due to the belt structure can be suppressed, and the steering stability can be improved. .

If the direction of inclination of the reinforcing cords 7a of the folded belt layer 8 is alternately reversed as described above, the rigidity of the folded belt layer 8 changes periodically along the tire circumferential direction E. However, in the present invention, by providing the circumferential belt layer 9 in which the belt-shaped member 7 is spirally wound while being disposed substantially parallel to the tire circumferential direction E on the outer peripheral side of the folded belt layer 8, Since the rigidity periodic characteristics are reduced, the uniformity of the tire can be improved.

The effect of improving the uniformity can be effectively obtained by a combination of the folded belt layer 8 and the circumferential belt layer 9. For example, when the belt 7 is meandering in the tire circumferential direction instead of the folded belt layer 8, the same periodic characteristics as those of the folded belt layer 8 are generated. In this case, the inside of the turn is processed in the same plane. Therefore, if the belt 7 is spirally wound around its outer periphery, air is entangled in the turn and vulcanization failure is likely to occur. In addition, the arrangement of the edges is irregular, so that the effect of improving the uniformity is almost lost. I can't get it. Therefore, in the present invention, it is necessary to provide the folded belt layer 8 having the above configuration.

In the present invention, it is possible to use a twisted cord obtained by twisting polyethylene 2,6-naphthalate fiber as the reinforcing cord 7a of the folded belt layer 8. This polyethylene 2,6-naphthalate fiber has been considered unsuitable for belt applications because it has a lower modulus and strength than aromatic polyamide fibers generally used as a tire belt material.
With the use of the belt and the circumferential belt layer 9, sufficient rigidity can be obtained.

The twisted cord of polyethylene 2,6-naphthalate fiber as described above has a modulus of 2000 to 3500 kg / mm ² and a twist coefficient K represented by the following formula of 8:
It is preferable to use one in the range of 00 to 1800. K = T√D where T represents the number of twists (twice / 10 cm), and D represents the total denier of the cord.

The reinforcing cords 7a of the folded belt layer 8 and the circumferential belt layer 9 may be different from each other.
It is preferable that these are composed of the same reinforcing cord 7a. By configuring the folded belt layer 8 and the circumferential belt layer 9 from the same reinforcing cord 7a in this manner,
Since the belt layers 8 and 9 can be formed from the same belt-like body 7, the productivity of the tire can be improved.

Preferably, the width of the band 7 is 5 to 50 mm. If the width of the strip 7 is less than 5 mm, the productivity will be reduced, and if it is more than 50 mm, the splice portion will be large and the uniformity will be reduced. In addition, the band 7
Preferably, the number of reinforcing cords 7a per 50 mm width is 20 to 65. Width 50 of strip 7
If the number of reinforcing cords 7a per mm is less than 20, the reinforcing effect becomes insufficient, and if it is more than 65, it becomes difficult to fold the band-shaped material 7.

Further, the inclination angle of the belt-like body 7 constituting the folded belt layer 8 with respect to the tire circumferential direction E is 15 to 45 °.
Is preferable. If the inclination angle of the belt-shaped body 7 constituting the folded belt layer 8 with respect to the tire circumferential direction E is less than 15 °, the steering stability decreases, and if it exceeds 45 °, the high-speed durability decreases. The reinforcing cord 7a of the circumferential belt layer 9 has a cutting elongation at a temperature of 20 ° C. of 6 to 12%.
It is preferred that If the cutting elongation of the reinforcing cord 7a of the circumferential belt layer 9 is less than 6%, it becomes difficult to carry out vulcanization molding while applying a lift tension from the inside of the tire. 9, the high-speed durability becomes insufficient due to the reduction of the hoop effect.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Tires 1 to 3 according to the present invention in which the tire size is common to 185 / 60R14 and the folded belt layer and the circumferential belt layer are arranged on the outer peripheral side of the carcass layer in the tread portion as shown in FIG. A comparative tire in which only a belt layer was arranged and a conventional tire in which two step belt layers having cut ends at both ends in the belt width direction were arranged so that cords crossed each other were manufactured.

The inclination angle of the reinforcing cord in each test tire was 21 °. Further, the width of the belt-like body constituting the folded belt layer and the circumferential belt layer was 15 mm, and the number of reinforcing cords per 50 mm width was 50. As the reinforcing cord, aromatic polyamide fiber (Kevlar), polyethylene 2,6-naphthalate fiber (PE
N), a twisted cord of nylon fiber was used.

The test tires were evaluated for steering stability, high-speed durability and uniformity according to the following test methods. The results are shown in Table 1. Driving stability: A test tire was mounted on a passenger car at an air pressure of 200 kPa, and a feeling test was performed by five test drivers to evaluate driving stability. The evaluation results were obtained by calculating an average evaluation value for each test tire, and expressed as an index with the conventional tire being 100. The larger the index value, the better the steering stability.

High-speed durability: Test tires are pneumatically operated at 240k
Installed on a drum tester as Pa, JIS D4230
A high-speed durability test was performed in accordance with the above standards, and the running distance until a failure occurred at the belt edge was measured. The evaluation results were indicated by an index with the conventional tire being 100. The higher the index value, the better the high-speed durability.

Uniformity: Radial force variation (RFV) was measured in accordance with the uniformity test method for automobile tires of JASO C607. The evaluation results were indicated by an index with the conventional tire being 100. The smaller the index value, the better the uniformity.

[0028]

As is clear from Table 1, all of the inventive tires 1 to 3 have improved steering stability and high-speed durability as compared with the conventional tire and the comparative tire, and have improved uniformity. .

[0030]

As described above, according to the present invention, the belt-shaped body rubberized to the reinforcing cord is inclined on the outer circumferential side of the carcass layer in the tread portion with respect to the tire circumferential direction at both ends in the belt width direction. A zigzag folded belt layer is provided from the inside to the outside of the tire, and a belt-like body rubberized with a reinforcing cord is arranged on the outer peripheral side of the folded belt layer in a spiral shape while being substantially parallel to the tire circumferential direction. By providing the wound circumferential belt layer, high-speed durability and steering stability can be improved as compared with the related art, and uniformity can be improved by using the folded belt layer and the circumferential belt layer together. .

[Brief description of the drawings]

FIG. 1 is a meridional sectional view illustrating a pneumatic radial tire according to an embodiment of the present invention.

FIG. 2 is a plan view showing a folded belt layer in FIG.

FIG. 3 is a plan view showing the belt-like body in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tread part 4 Carcass layer 7 Belt 7a Reinforcement cord 8 Folded belt layer 9 Circumferential belt layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B60C 9/22 B60C 9/22 C

Claims (8)

[Claims] 1. A belt formed by rubberizing a reinforcing cord at an outer peripheral side of a carcass layer in a tread portion is folded in a zigzag shape from the tire inner side to the outer side at both ends in the belt width direction while being inclined with respect to the tire circumferential direction. A pneumatic pump provided with a folded back belt layer, and a circumferential belt layer formed by helically winding a belt-like body rubberized on a reinforcing cord while being arranged substantially parallel to the tire circumferential direction on the outer peripheral side of the folded belt layer. Radial tire. 2. The pneumatic radial tire according to claim 1, wherein the reinforcing cord of the folded belt layer is a twisted cord obtained by twisting polyethylene 2,6-naphthalate fiber. 3. The twisted cord is 2000-3500k.
g / mm ² and twist factor K is 800
The pneumatic radial tire according to claim 2, which is in the range of ~ 1800. 4. The folded belt layer and the circumferential belt layer are formed of the same reinforcing cord.
The pneumatic radial tire according to any one of the above items. 5. The pneumatic radial tire according to claim 1, wherein the width of the band is 5 to 50 mm. 6. The pneumatic radial tire according to claim 1, wherein the number of the reinforcing cords per 50 mm width of the strip is 20 to 65. 7. The pneumatic radial tire according to claim 1, wherein an inclination angle of the belt-shaped body constituting the folded belt layer with respect to a tire circumferential direction is 15 to 45 °. 8. The pneumatic radial tire according to claim 1, wherein the reinforcing cord of the circumferential belt layer has a cutting elongation at a temperature of 20 ° C. of 6 to 12%.