JP4367914B2 - Tire bead core and pneumatic tire - Google Patents

Description

  The present invention relates to a bead core for a tire used for a pneumatic tire and a pneumatic tire using the same, and more specifically, a bead core for a tire and a pneumatic tire that suppresses torsion and deformation and improves steering stability. Regarding tires.

  A bead core is embedded in the bead portion of the pneumatic tire in order to ensure fitability to the rim. Such a bead core usually has a structure in which a rubber-coated circular or elliptical bead wire is wound in a circular or hexagonal cross section or twisted into a rectangular cross section.

  The above-mentioned bead core using a circular bead wire has a cross-sectional shape where adjacent bead wires are in point contact with each other via a covering rubber, so a large lateral force is applied during cornering during high-speed driving, and a large torsional force acts on the tire. Then, the bead core is twisted, and as a result, the bead portion attached to the rim is twisted, so that the steering stability is lowered.

  Therefore, conventionally, it has been proposed to use a rectangular bead wire having a rectangular cross section (see, for example, Patent Documents 1, 2, and 3). By constructing a bead core from a laminated body in which a plurality of annular parallel bodies each having a rectangular cross-sectional shape wound in parallel in the width direction are laminated in the radial direction, the contact area between the bead wires is increased, thereby It is possible to suppress the twist of the bead core and improve the handling stability.

However, all of the above-described bead cores have collapsed in the shape of the vulcanized tire. As a result, the tightening function as a bead core intended at the time of design has not been effectively exhibited, and the deformation of the shape is controlled. It contributed to the cause of inhibiting stability.
JP-A-9-66712 JP-A-10-95210 JP-A 49-119301

  An object of the present invention is to provide a bead core for a tire that can suppress twisting and deformation and improve steering stability, and a pneumatic tire using the same.

A tire bead core according to the present invention that achieves the above object is a tire bead core comprising a laminate in which a plurality of annular parallel bodies each having a rectangular cross-sectional shape wound in parallel in the width direction are laminated in the radial direction. The parallel body located on the outer side is arranged to be shifted from the parallel body located on the radially inner side to one side in the width direction which becomes the outer side of the tire when the tire is attached , and the laminated body is covered with a rubber layer. -A hardness is 71 to 75, 100% modulus at 100 ° C is 3.5 to 4.1 MPa, breaking strength at 100 ° C is 6.9 to 7.8 MPa, and breaking elongation at 100 ° C is 170 to 210%. and said that the content was.

  The pneumatic tire of the present invention is characterized in that the tire bead core is embedded in a bead portion.

  According to the present invention described above, the parallel body located radially outward is shifted to one side in the width direction so as to approach a stable cross-sectional shape that is not easily deformed during vulcanization, so that the intended bead core tightening It is possible to suppress the deformation of the tire bead core during vulcanization that greatly reduces the force.

  In addition, by using a bead wire having a square cross section for the tire bead core, the contact area between the bead wires laminated in parallel can be increased, so that the twist of the bead core for the tire against a large lateral force acting during cornering can be suppressed. Can do. Therefore, the twist and deformation of the bead core can be suppressed and the steering stability can be improved.

  Moreover, since the tightening function as the bead core can be effectively exhibited, it is possible to improve the rim detachment resistance during running.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of a tire bead core according to the present invention embedded in a bead portion of a pneumatic tire, wherein 1 is a tire bead core, 2 is a pneumatic tire showing essential parts, and 2A is a bead portion. Although not shown, the pneumatic tire 2 has an end portion of a carcass layer disposed inside the tire folded around the bead core 1 from the inside to the outside of the tire, The belt layer is provided.

  The tire bead core 1 includes a laminated body 5 in which a plurality of annular parallel bodies 4 in which bead wires 3 made of a hard steel wire having a rectangular cross section are wound in parallel in the width direction are laminated in a radial direction, and the laminated body 5 The rubber layer 6 which covers

  The laminated body 5 is configured by winding a single bead wire 3 having a rectangular cross section, and each parallel body 4 has a width that becomes the outer side of the tire when attached to the bead portion 2A by the parallel body 4 positioned radially outward. It is arranged so as to be shifted to one side of the direction (the right side of the figure) and has a substantially parallelogram shape.

  The rubber layer 6 is used to maintain the shape during molding and vulcanization and to ensure adhesion with the surrounding rubber in the bead portion 2A, and is conventionally made of a known rubber. For example, JIS A hardness is 71 to 75, 100% modulus at 100 ° C. is 3.5 to 4.1 MPa, breaking strength at 100 ° C. is 6.9 to 7.8 MPa, breaking elongation at 100 ° C. is 170 to 210% These rubbers can be preferably used.

  The present inventor has disassembled a large number of tires and examined the situation of the deformed shape of the bead core after vulcanization, and as a result of intensive studies, the inventors have found the following. That is, the pneumatic tire is usually vulcanized while being applied with an internal pressure after being set in a mold. In response to the force of the internal pressure at that time, the rolled bead wire is displaced, causing a collapse of the shape.

  Therefore, attention was paid to the cross-sectional shape of the bead core that was deformed in the tire after vulcanization. Although the deformed bead core may be displaced in the tire radial direction, all of the bead wires wound in the radially outward direction have been deformed into a substantially parallelogram shape shifted toward the tire outer side. This is a result of the bead core trying to be in a stable state during vulcanization, and if the cross-sectional shape is made stable from the beginning, the deformation during vulcanization can be suppressed.

  Based on such knowledge, in the present invention, the parallel bodies 4 positioned radially outward as described above are arranged so as to be shifted to one side in the width direction and have a stable cross-sectional shape from the beginning. Therefore, the tire bead core 1 can be prevented from being deformed during vulcanization, and as a result, the intended tightening function as the bead core can be effectively exhibited.

  Moreover, since the contact area of the bead wires 3 laminated in parallel can be increased by using the bead wire 3 having a rectangular cross section for the tire bead core 1, the bead core 1 for a tire when a large lateral force is applied during cornering. Torsion can be suppressed. Therefore, the twist and deformation of the tire bead core 1 are suppressed, and the steering stability can be improved.

  Furthermore, since the tightening function as the bead core can be effectively exhibited, it is possible to improve the rim detachment resistance during traveling.

  In the present invention, as the shift amount D, it is preferable to shift the radially outer parallel body 4 from 10% to 50% of the bead wire width W with respect to the inner parallel body 4 in each adjacent parallel body 4. That is, each bead wire 3 of the radially parallel parallel body 4 is shifted by 10% to 50% of the bead wire width W with respect to each corresponding bead wire 3 (in the same position) of the inner parallel body 4.

  When the deviation amount D is less than 10% of the bead wire width W, it becomes difficult to effectively suppress the deformation of the tire bead core 1 during vulcanization. On the other hand, if it exceeds 50%, the deviation becomes too large, and it becomes difficult to effectively exhibit the function as a bead core. More preferably, the bead wire width W should be shifted by 20% to 40%. By shifting 20% or more of the bead wire width W, it is possible to make it difficult to cause a shift in the tire radial direction when a force in the tire radial direction is applied during vulcanization.

  The bead wire 3 has a rectangular cross section in the above embodiment, but may instead be a square, a parallelogram, or a rhombus, and may be a quadrangle whose two opposite sides are parallel. These are collectively referred to as a square shape in the present invention. In addition, the rectangular shape of the present invention includes four sides that are formed by arcs having a large radius of curvature and two substantially opposite sides can be said to be parallel.

  The tire bead core 1 is constituted by covering the bead wire 3 with the rubber layer 6 as shown in FIG. 2 and using the rubber-coated bead wire 3 instead of the configuration in which the entire laminated body 5 is covered with the rubber layer 6. It may be.

  Further, the tire bead core 1 is preferably arranged so as to be shifted to the one side in the width direction as the parallel body 4 positioned on the radially outer side as described above, but as shown in an example in FIG. The parallel body 4A located on the outer peripheral side is shifted to one side in the width direction, and the parallel body 4D located on the outermost radial side on the outer peripheral side is further shifted to the parallel body 4B. The parallel body 4 positioned on the radially outer side is shifted to the one side in the width direction from the parallel body 4 positioned on the radially inner side, such as by shifting with respect to 4C, so as to approach a stable cross-sectional shape that is not easily deformed during vulcanization. It may be as described above.

  The bead core 1 for tires of the present invention can be suitably used for any pneumatic tire.

  The tire of the present invention manufactured using the tire bead core shown in FIG. 1 with a tire size of 195 / 65R15, the tire bead core of the present invention, and the comparative tire 1 using a bead wire having an elliptical cross section, are displaced in the comparative tire 1. The comparative tire 2 in which the amount D was set to 0 and the conventional tire in which the shift amount D was set to 0 in the present invention were prepared. The deviation D in the tire of the present invention and the comparative tire 1 is 20% of the bead wire width W.

  Each test tire has a configuration in which both end portions of one carcass layer are folded around the bead core from the inside to the outside of the tire, and two belt layers are arranged on the outer periphery side of the carcass layer in the tread portion.

When each of these test tires was subjected to a steering stability evaluation test by the measurement method shown below, the results shown in Table 1 were obtained.
Steering stability Each test tire is mounted on a rim with a rim size of 15 x 6 JJ, mounted on a vehicle with a displacement of 2000 cc with an air pressure of 200 kPa, and a feeling test is conducted by a test driver on a dry road test course. The conventional tire is indicated by an index value of 100. The larger this value, the better the steering stability.

表１から、本発明タイヤは、操縦安定性を改善できることがわかる。

From Table 1, it can be seen that the tire of the present invention can improve steering stability.

1 is a cross-sectional view showing an embodiment of a tire bead core according to the present invention in a state where the bead core is embedded and attached to a bead portion of a pneumatic tire. FIG. 6 is a cross-sectional view showing another embodiment of a tire bead core according to the present invention in a state where it is embedded in and attached to a bead portion of a pneumatic tire. FIG. 6 is a cross-sectional view showing still another embodiment of a tire bead core according to the present invention in a state where it is buried in and attached to a bead portion of a pneumatic tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead core for tires 2 Pneumatic tire 2A Bead part 3 Bead wire 4 Parallel body 5 Laminated body 6 Rubber layer

Claims (7)

In a tire bead core composed of a laminated body in which a plurality of annular parallel bodies each having a rectangular cross-section wound in parallel in the width direction are laminated in the radial direction, the parallel body located on the radially outer side is located on the radially inner side. The laminated body is shifted from the parallel body to one side in the width direction which is the outer side of the tire when the tire is attached , and the laminated body is covered with a rubber layer. The rubber layer has a JIS-A hardness of 71 to 75 and 100 ° C. at 100 ° C. A tire bead core having a% modulus of 3.5 to 4.1 MPa, a breaking strength at 100 ° C. of 6.9 to 7.8 MPa, and a breaking elongation at 100 ° C. of 170 to 210% .   The tire bead core according to claim 1, wherein the parallel body positioned radially outward is shifted to one side in the width direction.   The bead core for a tire according to claim 2, wherein in each adjacent parallel body, the radially outer parallel body is shifted by 10% to 50% of the bead wire width with respect to the inner parallel body.   The tire bead core according to claim 3, wherein in each adjacent parallel body, the radially outer parallel body is shifted by 20% to 40% of the bead wire width with respect to the inner parallel body.   The bead core for tire according to claim 1, 2, 3 or 4, wherein the laminated body is configured by winding one bead wire. The tire bead core according to claim 1, 2, 3, 4 or 5, wherein the bead wire is covered with the rubber layer . A pneumatic tire in which the tire bead core according to claim 1, 2, 3, 4, 5, or 6 is embedded in a bead portion.

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