JP2006069290A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire suppressing separation from a carcass ply end portion, and improving the durability of a bead portion. <P>SOLUTION: In the pneumatic radial tire 100, a turn-back portion 10B of the carcass ply turned at a bead core 4 buried in the bead portion 1 is formed by cord with a corrugating habit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire, and more particularly to a pneumatic radial tire excellent in durability of a bead part and suitably used for heavy-duty vehicles such as trucks and buses.

  A carcass ply of a pneumatic radial tire has its end portion wound around a bead core and locked. The carcass ply is formed by arranging steel cords extending in the radial direction in parallel and covered with rubber, and the cords are arranged in a straight line along the tire circumferential direction.

  Conventionally, the main cause of a bead failure in a pneumatic radial tire is separation that occurs in the vicinity of the end of the cord of the carcass ply. When the pneumatic radial tire rolls, this separation causes the end of the cord to be rubbed with rubber, causing the end and surrounding rubber to peel off, and a crack centered on this peeling to occur from the adjacent end. Occurs when connected to a crack.

  In order to suppress such separation, reinforcement with an organic fiber cord layer can be considered.

In addition, a technology is disclosed in which the distance at the time of cracking is ensured and the separation is suppressed by controlling the end length when the adjacent steel cords are molded and the cords are cut (for example, Patent Documents). 1).
JP 63-166603 A

  However, reinforcement by the above-described organic fiber cord layer leads to an increase in tire weight and cost. Further, the organic fiber cord layer has a certain degree of effect on the separation, but also has a new demerit that separation is generated from the organic fiber cord layer.

  Moreover, with the technique disclosed in Patent Document 1, it is difficult to independently control the molding of the steel cord, which significantly impairs the productivity of the steel cord.

  In view of the above problems, an object of the present invention is to provide a pneumatic radial tire that suppresses separation from the end portion of the carcass ply and improves the durability of the bead portion.

In order to solve the above problems, a feature of the present invention is a pneumatic radial tire in which a folded portion of a carcass ply, which is folded by a bead core embedded in a bead portion, is formed by a cord brazed in a corrugated shape. It is a summary. According to this pneumatic radial tire, since the end portion of the cord is brazed in a wave shape, distortion of the cord end portion can be suppressed. Therefore, the separation from the end of the carcass ply is suppressed, and the durability of the bead portion is improved. In the above invention, the diameter of the cord brazed is D, the wave amplitude is H, the wave When the pitch width of the mold is L,
1.2 × D ≦ H ≦ 2.0 × D (1)
3 × D ≦ L ≦ 10 × D (2)
It is preferable to satisfy.

  If the amplitude H of the waveform is smaller than 1.2 × D, it is difficult to absorb the distortion generated at the end of the cord when rolling. On the other hand, when the amplitude H of the corrugation exceeds 2.0 × D, the stress tends to concentrate on the uneven portion of the cord that is brazed, and the cord tends to break.

  Further, if the corrugated pitch width L is smaller than 3 × D, it becomes difficult to process and manufacture the cord. On the other hand, when the corrugated pitch width L exceeds 10 × D, it is difficult to absorb distortion generated at the end of the cord when rolling.

  Moreover, in the said invention, it is preferable that a carcass ply is formed with the code | cord brazed in the waveform shape in the range from 10 mm to 25 mm from the edge part.

  If the distance from the end is less than 10 mm, it is difficult to absorb the distortion generated at the end of the cord when rolling. On the other hand, when the distance from the end exceeds 25 mm, the cord brazed in contact with the bead core may cause fretting and the cord may break.

  Moreover, in the said invention, it is preferable that the cord braided in the waveform is braided in the radial direction.

  When corrugated in the tire circumferential direction, the cord may break when the tire falls. Moreover, there is a possibility that the cords are broken when adjacent cords come into contact with each other.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic radial tire which suppresses the separation from a carcass ply edge part and improves the durability of a bead part can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Composition of pneumatic tire)
As shown in FIG. 1, a pneumatic radial tire 100 according to an embodiment of the present invention includes a pair of bead portions 1, a pair of sidewall portions 2, and a tread portion 3 that extends in a toroidal shape between the sidewall portions 2. With. The carcass 5 is a toroidal radial carcass that reinforces the bead part 1, the sidewall part 2, and the tread part 3 across a pair of bead cores 4 embedded in the bead part 1. The belt layer 6 of the layer or more is arranged, and the tread portion 3 is reinforced. In FIG. 1, two belt layers 6 are laminated.

  The carcass 5 includes a single carcass ply 10, and the carcass ply 10 is folded back from the tire inner side to the outer side in the bead core 4. The folded portion 10B of the carcass ply 10 folded inward is arranged along the main body portion 10A.

As shown in FIG. 2, the folded portion 10 </ b> B of the carcass ply 10 is formed by a cord (for example, a steel cord) brazed in a corrugated shape. When the diameter of the cord is D, the wave-shaped amplitude is H, and the wave-shaped pitch width is L,
1.2 × D ≦ H ≦ 2.0 × D (1)
3 × D ≦ L ≦ 10 × D (2)
It is brazed in a wave shape so as to satisfy.

  In addition, the carcass ply 10 is formed by a cord that is brazed in a wave shape in a range from 10 C to 25 mm (A in FIG. 1) from the end portion 10C. The cord is braided in a wave shape in the radial direction, not in the tire circumferential direction.

(Function and effect)
Conventionally, when the pneumatic radial tire rolls, the rubber between the end portions of the cord is distorted by pushing up the rubber from the rim and pulling the cord at the turn-up portion 10B of the carcass ply. This strain is a factor that causes the separation generated from the end of the cord to progress to a crack, and when this crack grows along the carcass ply connected to the crack that has progressed from the end of the adjacent cord, finally, Will lead to separation.

  In the pneumatic radial tire according to the present embodiment, the end portion 10C of the carcass ply is formed of a cord that is brazed in a wave shape in the folded portion 10B of the carcass ply, so that the rubber and the cord follow flexibly. As a result, the distortion between the cord ends is suppressed, and the occurrence of cracks at the cord ends is suppressed. Moreover, even if a crack occurs in the longitudinal direction of the cord, the surface is uneven, so that the suppression of the crack can be controlled in the corrugated concave portion or convex portion. That is, it is possible to sufficiently suppress the occurrence of separation that occurs when cracks are connected to each other, and the durability of the bead portion can be improved.

Further, in the pneumatic radial tire according to the present embodiment, the relationship between the diameter D of the cord brazed in the waveform, the amplitude H of the waveform, and the pitch width L of the waveform is
1.2 × D ≦ H ≦ 2.0 × D (1)
3 × D ≦ L ≦ 10 × D (2)
It is.

  If the amplitude H of the waveform is smaller than 1.2 × D, it is difficult to absorb the distortion generated at the end of the cord when rolling. On the other hand, when the amplitude H of the corrugation exceeds 2.0 × D, the stress tends to concentrate on the uneven portion of the cord that is brazed, and the cord tends to break.

  Further, if the corrugated pitch width L is smaller than 3 × D, it becomes difficult to process and manufacture the cord. On the other hand, when the corrugated pitch width L exceeds 10 × D, it is difficult to absorb distortion generated at the end of the cord when rolling.

  In addition, the carcass ply 10 of the pneumatic radial tire according to the present embodiment is formed by a cord brazed in a range from 10 C to 25 mm from the end 10C.

  If the distance from the end portion 10C is smaller than 10 mm, it becomes difficult to absorb the distortion generated at the end portion of the cord when rolling. On the other hand, if the distance from the end portion 10C exceeds 25 mm, the cord brazed in contact with the bead core may cause fretting and the cord may break.

  Further, the cord of the pneumatic radial tire according to the present embodiment is brazed in a wave shape in the radial direction.

  When corrugated in the tire circumferential direction, the cord may break when the tire falls. Moreover, there is a possibility that the cords are broken when adjacent cords come into contact with each other.

  Further, as described above, the pneumatic radial tire according to the present embodiment is excellent in durability of the bead portion, and therefore can be suitably used for heavy-duty vehicles such as trucks and buses.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples.

In order to confirm the effect of the present invention, one type of tire according to an example to which the present invention was applied, one type of conventional tire, and five types of comparative tires were manufactured, and the durability of the bead portion was examined. In both the example and the conventional example, the tire size was 11R22.5, and the internal pressure was 9.0 kg / cm ² .

  The durability of the bead portion was evaluated based on the distance traveled until each tire was subjected to an indoor drum tester, the separation occurred in the bead portion, and the tire broke down. The mileage was measured at a speed of 60 km / h with the load being increased every 6270 kgf for the first 144 hours and every 72 hours thereafter. The durability of the bead portion is expressed as an index with the conventional example being 100 with respect to the travel distance until failure, and the larger the value, the better the bead portion durability.

The conditions and results are shown in Table 1. In addition, the corrugated brazing at the end of the cord is performed by engaging the upper and lower gears with the end of the ply carcass treatment before molding the tire, and the treatment is pasted at the time of molding to obtain the tire of Example 1. .

(result)
In Example 1 and Comparative Examples 1 to 5, as compared with the conventional example, the bead durability was improved as a whole. Therefore, it was confirmed that the bead durability was improved in the pneumatic radial tire formed by the cord in which the folded portion of the carcass ply was brazed in a wave shape.

Further, the bead durability was improved in Example 1 as compared with Comparative Examples 1 and 2. Therefore, the diameter D of the cord and the amplitude H of the waveform are 1.2 × D ≦ H ≦ 2.0 × D (1)
As a result, it was confirmed that the bead durability was improved.

Further, in Example 1, the bead durability was improved as compared with Comparative Example 3. Therefore, the diameter D of the cord and the pitch width L of the corrugation are 3 × D ≦ L ≦ 10 × D (2)
As a result, it was confirmed that the bead durability was improved.

  Further, in Example 1, the bead durability was improved as compared with Comparative Examples 4 and 5. Therefore, it was confirmed that the bead durability was improved by forming the carcass ply with a corrugated cord in a range from 10 mm to 25 mm from the end.

1 is a cross-sectional view including a tire rotation axis of a pneumatic radial tire according to an embodiment. It is an enlarged view of a cord brazed into a corrugated shape according to the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Bead part 2 ... Side wall part 3 ... Tread part 4 ... Bead core 5 ... Carcass 6 ... Belt layer 10 ... Carcass ply 10A ... Main-body part 10B ... Turn-up part 10C ... End part 100 ... Pneumatic tire

Claims (4)

  A pneumatic radial tire characterized in that a folded portion of a carcass ply folded by a bead core embedded in a bead portion is formed by a cord brazed in a corrugated shape. When the diameter of the cord brazed into the corrugated shape is D, the amplitude of the corrugated shape is H, and the pitch width of the corrugated shape is L,
1.2 × D ≦ H ≦ 2.0 × D (1)
3 × D ≦ L ≦ 10 × D (2)
The pneumatic radial tire according to claim 1, wherein:   The pneumatic radial tire according to claim 1 or 2, wherein the carcass ply is formed by a cord that is brazed in the corrugated shape in a range from 10 mm to 25 mm from an end thereof. The pneumatic radial tire according to any one of claims 1 to 3, wherein the cord that is braided in a corrugated shape is braided in a corrugated shape in a radial direction.

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