JP2009143277A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent drawing, and to maximally extract the durability of a tire by surely preventing the displacement of a tip of a carcass folding part in a pneumatic tire having a wind bead structure. <P>SOLUTION: A ply formed by coating a plurality of cords with rubber is folded from the inside to the outside around a pair of bead cores molded by winding one bead wire coated with rubber a plurality of times. This pneumatic tire has a carcass around which the folding part of the ply is wound. A bending part when sifted to a next winding side of the bead wire is dispersed in a circumferential direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire mainly used for trucks and buses, and in particular, reliably prevents the tip portion of the carcass ply turn-up portion from being displaced from a predetermined position along with the improvement of the durability of the tire. is there.

  In the pneumatic tire used for trucks and buses, the carcass ply may be pulled out during tire load rolling. When such pull-out occurs, the durability of the bead portion deteriorates, and as a result, the durability of the tire deteriorates. Therefore, in order to suppress the occurrence of such pull-out, the carcass ply is folded around the bead core from the inside of the tire to the outside, and the tip of the folded portion is embedded and fixed in rubber.

  However, in such a structure, the stress is concentrated on the tip portion and the vicinity thereof due to repeated deformation from the bead portion to the sidewall portion at the time of tire load rolling, so that the tip portion is separated from the rubber. There is a problem that so-called separation occurs.

In order to solve such a problem, Patent Document 1 discloses that the folding portion of the carcass ply has a structure in which the tip of the carcass ply is wound around the bead core (called a wind bead structure) to effectively prevent separation. Technology has been proposed.
JP 2000-309210 A

  However, in the above technique, the tip portion of the folded portion may deviate from a predetermined winding position due to deformation (cross-sectional shape) of the bead core. If such a deviation occurs, the carcass may be pulled out after a long period of tire use, and there is a concern about deterioration of the durability of the tire.

  The present invention advantageously solves the above-described problem, and in the pneumatic tire having the above-described wind bead structure, the occurrence of pull-out is prevented by reliably preventing the positional deviation of the tip portion of the carcass folded portion. Therefore, the object is to maximize the durability of the tire.

  That is, the present invention folds a ply covered with a plurality of cords around a pair of bead cores formed by winding a plurality of bead wires coated with rubber a plurality of times, and wraps the ply A pneumatic tire having a carcass around which a folded portion is wound, wherein the bead core has a bent portion at a dislocation portion of the winding, and the bent portion is distributed in the circumferential direction of the bead core. It is a pneumatic tire.

  According to the present invention, the displacement of the tip portion of the carcass ply folded portion can be reliably prevented, so that the occurrence of pull-out can be prevented. As a result, the durability of the tire can be maximized.

The elucidation process of the present invention will be described below.
Now, the inventors have investigated in detail the cause of the displacement of the tip portion. The results of this investigation will be described with reference to the drawings.

  First, FIG. 1 shows a tire width direction cross section of a bead portion and a sidewall portion of a tire. In FIG. 1, reference numeral 1 denotes a bead core, 2 denotes a carcass, 3 denotes a bead portion, 4 denotes a sidewall portion, and 5 denotes a rim.

  Next, the figure which expanded the cross section of the width direction of the bead part 3 at FIG. 2 is shown. In FIG. 2, reference numeral 1a denotes a bead wire, 2a denotes a carcass ply, 2b denotes a folded portion of the carcass ply 2a, and 2c denotes a tip portion of the folded portion 2b of the carcass ply. The bead portion 3 is formed by folding the carcass ply 2a around the bead core 1 from the inside to the outside of the tire and winding the turned portion 2b. Here, the tip portion 2 c is directly disposed on the peripheral surface of the bead core 1.

  The bead core 1 is formed by winding a single rubber-coated wire, and the structure thereof will be described below. First, the first stage of winding of the bead core 1 is shown in FIG. In FIG. 3, symbol A is a bent portion, S is a step, and M is the starting end of winding of the bead wire 1a. In the first stage, after winding the wire 1a covered with rubber on one wire in a ring shape, the wire 1a is bent when the wire 1a is moved to the next winding side, thereby winding the wire 1a. The stage S is formed by shifting in the traveling direction (in the direction of arrow B) and repeating this operation a predetermined number of times.

  Then, the wire 1a after winding at the end of the first stage is stacked on the wire 1a wound at the end of the first stage while being shifted by a half pitch of the wire width in the direction of winding, and wound in a ring shape. After turning, the wire 1a is bent and shifted in the direction of winding reverse to the first stage, and this operation is repeated a predetermined number of times to form the second stage.

  Further, in the third and subsequent stages, the bead core 1 is formed as a result of stacking a plurality of stages S by repeating the same operation as the first and second stages a plurality of times.

  Here, the bent portion A is formed to include the start end M of the bead wire 1a in the first roll. And the bending part A will closely_contact | adhere so that it may overlap in the advancing direction of winding.

  Now, in the bent part A, since there is one bead wire, it becomes sparse compared with the most dense part (parts other than the bent part A), so that the shape of the bead core in the region near the bent part A is deformed.

  For example, as shown in a cross-sectional view in the width direction of the bead core in FIG. 4, the middle stage of the bead core 1 is biased outward in the width direction of the bead core 1, so The tip portion 2c is displaced from a predetermined position. As a result, the position of the folded portion 2b becomes unstable on the circumference of the bead core 1, and pulling out easily occurs, so that the durability of the tire cannot be maximized.

Therefore, the present invention solves this problem by adopting the following structure.
FIG. 5 shows a cross section in the width direction of the bead core and the carcass of the pneumatic tire according to the present invention. In FIG. 5, symbol E indicates a gap between adjacent bead wires 1a, and the other symbols are the same as those shown in FIG.

  FIG. 5 shows that a ply 2a covered with rubber on a plurality of cords is folded from the inside of the tire to the outside around a bead core 1 formed by winding a single bead wire 1a covered with rubber a plurality of times. A carcass 2 in which a folded portion 2b is wound around a bead core 1 is shown.

  Next, the first stage of the bead core 1 is shown in FIG. In FIG. 6, the first step is to wind the bead wire 1a coated with rubber on one wire in a ring shape and then bend the wire 1a at the dislocation portion of the winding when the wire 1a is transferred to the next winding side. To shift the wire 1a in the direction of winding (in the direction of arrow B) and repeat this operation a predetermined number of times to form a step.

  Then, the wire 1a after winding at the end of the first stage is shifted by a half pitch of the wire width in the winding direction, laminated on the wire 1a wound at the end of the first stage, and wound in a ring shape. After that, the wire 1a is bent and shifted in the direction of winding reverse to the first step, and this operation is repeated a predetermined number of times to form the second step. Further, the third and subsequent stages are formed by repeating the same operation as the first and second stages described above a plurality of times.

  Here, it is important that the bead core 1 has a bent portion at the dislocation portion of the winding, and the bent portion A is distributed in the circumferential direction of the bead core.

  That is, the bent portion A is distributed in the circumferential direction of the bead core, and in the illustrated example, the bend core is uniformly distributed, so that the shape of only a part of the bead core on the circumference of the bead core 1 does not change, but the circumference is uniform. Will be transformed.

  Therefore, since the shape of the bead core 1 is substantially the same on any of the circumferences of the bead core 1, it is possible to reliably prevent the positional deviation of the tip portion 2c of the folded portion 2b. Therefore, the position of the folded portion 2b is stabilized on the circumference of the bead core 1, and the withdrawal can be more reliably prevented. As a result, the durability of the tire can be maximized.

  A pneumatic tire of size 495 / 45R22.5 having a bead core and a carcass shown in FIG. 5 was prototyped. And the product defect rate about the tire and the durability of the tire were investigated. The results are shown in Table 1. The conventional example is a pneumatic tire to which the bead core and carcass shown in FIG. 2 are applied.

  The defect rate of the product is the position of the tip of the folded portion of the carcass ply on the peripheral surface of the bead core in the bent portion of the conventional pneumatic tire and the pneumatic tire of the invention example and the portion other than the bent portion (normal portion). CT scan is used to take a picture of 36 bead parts on the circumference per tire, measure the position of the tip 2c of the ply turn-up part 2b in the cross section, and deviate the position from the target. Each of the conventional tires and the tires of the present invention was prototyped and investigated and evaluated.

  In addition, the durability of the bead portion was evaluated by an indoor drum test to determine whether the durability of the tire could be maximized. It was run with a bead durable drum and the running distance until failure occurred was measured. Then, the measurement results were indexed and compared.

  From the results shown in Table 1, in the conventional example, there is a pneumatic tire in which the tip portion of the folded portion is displaced from the position on the peripheral surface of the bead core in the bent portion, whereas in the invention example, the tip portion of the folded portion is the bead core. Since there is no pneumatic tire deviated from the position on the peripheral surface, the carcass is not pulled out. As a result, the durability of the tire can be maximized.

It is a figure which shows the 1st step | paragraph of the conventional bead core. It is a figure which shows the width direction cross section of the conventional bead core and a carcass. It is a figure which shows the conventional bead part and side wall part. It is a figure which shows the modification of a bead core. It is a figure which shows the width direction cross section of the bead core of this invention, and a carcass. It is a figure which shows the 1st step | paragraph of the bead core of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Bead wire 1 Bead core 2a Carcass ply 2b Folding part 2c Tip part 2 Carcass 3 Bead part 4 Side wall 5 Rim

Claims (1)

  Around a pair of bead cores formed by winding one rubber-coated bead wire a plurality of times, a ply covered with rubber on a plurality of cords was folded from the inside to the outside of the tire, and the folded portion of the ply was wound A pneumatic tire having a carcass, wherein the bead core has a bent portion at a winding dislocation portion, and the bent portion is dispersedly arranged in a circumferential direction of the bead core.

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