JP2012020665A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire largely improving ride comfort on a vehicle, while securing excellent controllability and stability, by effectively preventing the occurrence of separation from the ply end of a carcass ply.SOLUTION: A side part of a carcass 1 composed of one carcass ply is formed as a rolled-up part 1b rolled up toward the outside from the inside in the tire width direction around a bead core 2. A folding-back part 1c folded back again to the bead core side is arranged in the rolled-up part 1b. The inner end in the radial direction of this folding-back part 1c is finished in response to an outside side surface in the tire width direction of the bead core 2. A height h1 in the radial direction of a folding-back place 1d of the carcass 1 is set as a separation point S or less from a rim flange FR of a tire outer surface under a tire attitude filled with normal air pressure by being installed in the normal rim.

Description

  The present invention relates to a pneumatic radial tire, and is particularly applied to a passenger car to prevent separation from the ply end of the carcass ply and to ensure excellent handling stability while ensuring excellent driving stability. It proposes a technique to improve.

  As a heavy-duty pneumatic radial tire that prevents the occurrence of separation from the ply end of the carcass ply to improve the durability of the bead portion and improves the steering stability, Patent Document 1 relating to the prior application of the applicant is disclosed in Patent Document 1. Some have been disclosed.

  This ensures that the carcass ply is resistant to pulling out from the bead core, and if the carcass ply is raised at a higher position in order to impart high lateral rigidity to the tire, Since a large strain is generated at the end of the ply that has not been applied and durability is lowered, at least one carcass ply is provided with a folded portion that wraps around the pair of bead cores from the inside to the outside of the tire. In a tire with a toroidal carcass that is folded back to the bead core side, the ply end of the carcass is attached to the regular rim outside the tire from the vertical line that stands on the tire rotation axis passing through the center of the bead core. In the state where the normal air pressure is filled, it passes through the separation point between the tire outer wall and the rim flange and is parallel to the tire rotation axis. Formed by arranging more be a straight line on the rim base side, it is an.

  According to this, the amount of distortion during load rolling of the tire decreases as it approaches the substantially rigid bead core, and the periphery of the bead core hardly deforms, so the carcass ply is wound up around the bead core. In addition, it is assumed that durability and lateral rigidity can be improved at the same time by bending the bead core again after winding up to some extent and disposing the carcass ply end near the bead core.

JP-A-1-297309

  However, in this prior art, the rim on the outer surface of the tire is mounted under the tire posture in which the normal height is filled with the radial height of the re-turned portion provided at the turn-back of the carcass ply and filled with the normal air pressure. Since it is positioned radially outward from the separation point from the flange, it is possible to achieve high steering stability by ensuring high lateral rigidity of the tire, but the radial height of the turn-up point again However, since it is higher than the above-mentioned separation point, the longitudinal rigidity of the tire inevitably becomes high, which causes a problem that the riding comfort on the vehicle is impaired.

  The present invention aims to solve such problems of the prior art, and its object is to effectively prevent the occurrence of separation from the ply end of the carcass ply, An object of the present invention is to provide a pneumatic radial tire that has improved driving comfort while ensuring excellent steering stability.

  In the pneumatic radial tire of the present invention, a side portion of a carcass made of at least one carcass ply is used as a winding portion wound around the bead core from the inner side to the outer side in the tire width direction. The part is provided with a folded part that is folded back to the bead core side, and the inner end in the radial direction of the folded part is terminated corresponding to the outer side surface of the bead core in the tire width direction. The height in the radial direction is equal to or less than the separation point of the outer surface of the tire from the rim flange under the tire posture in which the tire is mounted on the regular rim and filled with the regular air pressure.

Here, “the inner end in the radial direction of the folded portion is terminated corresponding to the outer side surface of the bead core in the tire width direction” means that the cross-sectional shape of the bead core in the cross section in the width direction of the tire Regardless, the ply end of the folded portion is positioned in the projection region of the bead core onto the plane orthogonal to the central axis of the tire.
Here, “applicable rim” refers to the rim specified in the following standards according to the tire size, and “regular air pressure” refers to the air pressure specified in accordance with the maximum load capacity in the following standards. The maximum load capacity refers to the maximum mass that is allowed to be applied to a tire according to the following standards.
Incidentally, it is possible to fill the tire with an inert gas such as nitrogen gas or the like.

  The standard is an industrial standard valid for the region where tires are produced or used. For example, “THE TIRE AND RIM ASSOCIATION INC. YEAR BOOK” in the United States, and “The European tire and Rim Technial Oranisation” in Europe. "STANDARDS MANUAL", and in Japan it is the "JATMA YEAR BOOK" of the Japan Automobile Tire Association.

Preferably, the carcass folding portion is sandwiched in the tire width direction by squeegee rubber and sidewall rubber, both softer than the chafer rubber and bead filler rubber.
In this case, the squeegee rubber can be disposed along the carcass ply winding portion, or can be disposed along the carcass ply main body portion other than the side portion forming the carcass ply winding portion. In any of these, the radially inner end portion of the squeegee rubber can be wound around the bead core to the inside in the tire width direction or to the outside in the width direction.

  Preferably, the bead is arranged adjacent to the outer peripheral side of the bead core between the side portion of the carcass and the carcass main body portion excluding the side portion, and gradually becomes thinner toward the outer side in the radial direction. The height of the radially outer end of the filler rubber is made lower than the radial height of the separation point from the rim flange on the outer surface of the tire.

And preferably, the maximum radial height of the bead filler rubber itself is made smaller than the radial height of the folded portion.
Here, “the maximum height of the bead filler rubber in the radial direction” may be that the outer peripheral surface of the bead core adjacent to the bead filler rubber is composed of a surface other than a plane parallel to the tire central axis. Is taken into account.

  In the pneumatic radial tire of the present invention, in particular, the radial height of the carcass folding portion is set to be not more than the separation point from the rim flange on the outer surface of the tire, and the rim flange extends radially outward from the rim flange. By removing the existing portion, it is possible to effectively reduce the longitudinal rigidity of the tire and improve the riding comfort of the vehicle.

Further, in this tire, the ply end of the carcass ply is formed by ending the inner end in the radial direction of the folded portion of the carcass corresponding to the side surface of the bead core in the vicinity of the bead core with a small amount of deformation accompanying the load rolling of the tire. It is possible to effectively prevent the separation and realize high bead durability.

  And here, since the three-layer reinforcement structure can be formed with a single carcass ply in the radially inward portion from the rim flange, sufficient rigidity of the bead portion can be secured, so that the tire has the required lateral rigidity. Excellent steering stability can be achieved.

  In such a tire, when the folded portion of the carcass is sandwiched between a relatively soft squeegee rubber and a sidewall rubber, by absorbing the deformation in each direction at the time of tire load rolling by the rubber, In the first place, coupled with the fact that the folded portion is located on the radially inward side from the separation point from the rim flange with a small amount of deformation, the concentration of stress at the folded portion is advantageously prevented, and the folded portion is prevented. Separation to a location can be prevented more effectively.

Here, when the height of the radially outer end of the bead filler rubber disposed adjacent to the outer peripheral surface of the bead core is lower than the radial height of the separation point from the rim flange on the outer surface of the tire, Effectively reducing the longitudinal rigidity of the tire, which can advantageously improve the riding comfort of the vehicle, and the tire cross-section thickness at the point of separation from the rim flange can be reduced, ensuring durability by reducing the surface distortion during loading can do.
On the other hand, when the height of the bead filler rubber in the radial direction is higher than the radial height of the separation point, the ride comfort on the vehicle is inevitably lowered due to an increase in the longitudinal rigidity of the tire. As the tire cross-sectional thickness increases, the surface strain increases and the durability decreases.

In addition, when the maximum radial height of the bead filler rubber itself is smaller than the radial height of the folded portion, the carcass main body portion and the winding portion are in contact with each other, so that durability against separation at the folded portion is achieved. Improves.
That is, when the maximum height of the bead filler rubber is equal to or greater than the height in the radial direction of the folded portion, the winding portion is adjacent to the bead filler rubber (hard rubber), so that separation at the folded portion is likely to occur. There is no denying the decline in durability.

It is a fragmentary sectional view of the tire width direction showing an embodiment of this invention about one bead part. It is a fragmentary sectional view similar to FIG. 1 which shows other embodiment. It is sectional drawing similar to FIG. 1 which shows the structure of the comparative example tire in an Example.

  In FIG. 1, reference numeral 1 in the figure indicates a radial carcass formed of at least one carcass ply in the figure, and 2 indicates a bead core embedded in each bead portion.

  Here, the main body portion 1a of the carcass 1 is extended toroidally between the bead cores 2 and the side portion of the carcass 1 is wound around the bead core 2 from the inner side to the outer side in the tire width direction. 1b, and a folded portion 1c that is folded back toward the bead core 2 and is directed inward in the tire radial direction is provided on the winding portion 1b. The folded portion 1c corresponds to the outside of the bead core 2 in the tire width direction. To finish.

  Further, here, the radial height h1 of the turning portion 1d that contributes to the formation of the turning portion 1c of the carcass 1 is set on the outer surface of the tire T under the tire posture in which the normal rim R is mounted and filled with the normal air pressure. The radial height h2 or less of the separation point S from the rim flange RF ensures high bead portion rigidity in the vicinity of the bead core 2 and separation from the end of the carcass ply that is the end of the folded portion 1C of the carcass 1. Thoroughly eliminate the risk of occurrence.

  Preferably, the folded portion 1d of the carcass 1 is sandwiched between the squeegee rubber 3 and the side wall rubber 4 made of soft rubber in the tire width direction, and the outer side of the tire at the tire bead portion at the time of tire load rolling. By absorbing the falling-down deformation, the circumferential shear deformation, etc. with the deformation of these rubbers 3 and 4, it is possible to effectively prevent the concentration of stress on the folded portion 1d and to prevent the separation at the folded portion 1d. Prevent more effectively.

  Further, preferably, it is arranged adjacent to the outer peripheral surface of the bead core 2 between the side portion of the carcass and the carcass main body portion 1a excluding the side portion, and gradually becomes thinner outward in the radial direction. By making the height h3 of the radially outer end of the bead filler rubber 5 lower than the radial height h2 of the separation point S from the rim flange RF on the outer surface of the tire, the ride comfort to the vehicle is secured. In addition, the tire cross-section gauge at the rim flange separation point S is thinned to ensure excellent durability under reduced surface strain.

Also preferably, the maximum height h4 in the radial direction of the bead filler rubber 5 is made smaller than the radial height h5 of the turned-up portion 1c of the wound-up portion 1b to improve the riding comfort of the vehicle.
Further, by providing an overlapping portion (1c) between the carcass main body portion 1a and the winding portion 1b, durability against ply separation can be ensured.

  By the way, as shown in FIG. 2A, the squeegee rubber 3 is arranged in the radial direction between the bead filler rubber 5 and the bead core 2 and the winding portion 1b and wound around the bead core 2. 2B, the bead filler rubber 5 and the bead core 2 extend inward in the radial direction between the carcass main body 1a and wrap around the bead core 2, as shown in FIG. In any of these cases, the squeegee rubber 3 and the side wall rubber 4 can bring the same effect as described above by sandwiching the folded portion 1d of the carcass 1. it can.

  In FIGS. 1 and 2, reference numeral 6 denotes a chafer rubber having a relatively high rubber hardness.

Table 1 shows a comparative example tire in which carcass winding portions and bead fillers are arranged as shown in FIG. 3 and a configuration shown in FIG. 1 as a basic structure in a passenger car pneumatic radial tire of size PSR 155 / 65R13. Example tires 1 and 2 having various dimensional specifications were evaluated for bead portion durability, steering stability and riding comfort performance, and the results shown in Table 2 were obtained.
Here, the bead portion durability is an index evaluation by measuring the load rolling distance until the ply end separation occurs,
Steering stability is evaluated by indexing the steering stability when driving a real vehicle,
Riding comfort was evaluated with an index based on the feeling of riding during actual driving.
In all of the evaluations, a larger index value indicates a better result.

  As shown in Table 2, it can be seen that the example tire 2 can greatly improve the ride comfort while ensuring high bead durability.

DESCRIPTION OF SYMBOLS 1 Carcass 1a Body part 1b Winding part 1c Folding part 1d Folding part 2 Bead core 3 Squeegee rubber 4 Side wall rubber 5 Bead filler rubber 6 Chafer rubber T Tire R Rim RF Rim flange S Separation point h1, h2, h5 Radial height h3 Radial direction Height of outer end h4 Maximum height in the radial direction

Claims (4)

The side portion of the carcass composed of at least one carcass ply is a winding portion wound around the bead core from the inner side to the outer side in the tire width direction, and the folded portion is turned back to the bead core side at the winding portion. A radial radial tire in which a radially inner end of the folded portion is provided corresponding to the outer side surface of the bead core in the tire width direction,
A pneumatic radial tire having a radial height at a carcass turn-up point that is below the separation point from the rim flange on the outer surface of the tire under a tire posture that is mounted on a normal rim and filled with normal air pressure. The pneumatic radial tire according to claim 1, wherein the folded portion of the carcass is sandwiched between the squeegee rubber and the sidewall rubber in the tire width direction. Radial direction of the bead filler rubber that is disposed adjacent to the outer peripheral surface of the bead core between the side portion of the carcass and the carcass main body portion excluding the side portion, and gradually becomes thinner radially outward. The pneumatic radial tire according to claim 1 or 2, wherein the height of the outer end is made lower than the height in the radial direction of the separation point from the rim flange on the outer surface of the tire. The pneumatic radial tire according to any one of claims 1 to 3, wherein a maximum radial height of the bead filler rubber is smaller than a radial height of the folded portion.

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