JP2006282102A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of enhancing the driveability and riding comfort in good balance. <P>SOLUTION: The pneumatic tire is structured so that a bead core 5 is embedded in a bead part, wherein the bead core 5 consists of a winding 10 of a rubber-coated wire 9 formed by covering a bead wire 11 with coating rubber 12, and the coating rubber 12 is composed of an inner rubber part 12i arranged in contact with the bead wire 11 and an outer rubber part 12o arranged on the outside of the inner rubber part 12i and having a different level of hardness therefrom. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire that can improve steering stability and ride comfort in a well-balanced manner.

  An annular bead core is provided in the bead portion of the pneumatic tire in order to maintain the fitting property with the rim. The bead core is formed, for example, by winding a wire with rubber obtained by coating a metal bead wire with a coating rubber (see, for example, Patent Document 1 below).

JP 2000-318414 A

  By the way, the steering stability and riding comfort of the tire are greatly influenced by the rigidity of the bead portion. According to various experiments by the inventors, it has been found that the portion closer to the rim among the components of the bead portion has a greater influence on the handling stability and the ride comfort.

  The present invention has been devised in view of the above circumstances, and is operated with a simple configuration on the basis that the bead wire coating rubber constituting the bead core is formed of at least two types of rubbers having different hardnesses. It aims at providing the pneumatic tire which can improve stability and riding comfort.

  The invention according to claim 1 of the present invention is a pneumatic tire having a carcass including at least one carcass ply folded at a bead core of a bead portion through a sidewall portion from a tread portion, and the bead core is It consists of a wound body of wire with rubber coated with a bead wire with a coating rubber, and the coating rubber is disposed on the inner peripheral rubber portion in contact with the bead wire, and on the outer periphery and the inner peripheral rubber portion. Includes outer peripheral rubber portions having different hardnesses.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein the coating rubber has a hardness of the outer peripheral rubber portion larger than a hardness of the inner peripheral rubber portion.

  The invention according to claim 3 is the pneumatic tire according to claim 1, wherein the coating rubber has a hardness of the outer peripheral rubber portion smaller than a hardness of the inner peripheral rubber portion.

  The invention according to claim 4 is the pneumatic tire according to any one of claims 1 to 3, wherein a difference between the hardness of the outer peripheral rubber portion and the hardness of the inner peripheral rubber portion is 5 to 15 degrees.

  In the invention according to claim 5, in the wire with rubber, the total thickness of the coating rubber is 2.0 mm or less, and the thickness of the inner peripheral rubber portion and the outer peripheral rubber portion is 0.1 to 1.0 mm, respectively. The pneumatic tire according to any one of claims 1 to 4.

  In the pneumatic tire of the present invention, the coating rubber that covers the bead wire of the bead core has an inner peripheral rubber portion disposed in contact with the bead wire, and an outer peripheral rubber disposed on the outer side and having a hardness different from that of the inner peripheral rubber portion. Part. A rubber having a relatively high hardness contributes to an improvement in handling stability, and a rubber having a low hardness can improve the riding comfort. And since the said coating rubber can control the motion of a carcass ply in the position close | similar to a rim, the said steering stability and riding comfort can be improved with sufficient balance.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a cross-sectional view of a pneumatic tire 1 of the present embodiment. The pneumatic tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and inside the tread portion 2. In this example, a radial tire 1 for a passenger car is illustrated.

  The carcass 6 is composed of one or more radial structures in which carcass cords are arranged at an angle of, for example, 80 ° to 90 ° with respect to the tire equator C, in this example, one carcass ply 6A. As the carcass cord, for example, an organic fiber cord such as polyester, nylon, rayon, aramid, or a steel cord is used if necessary.

  The carcass ply 6A is folded from the inner side to the outer side in the tire axial direction around the bead core 5 extending from the main body part 6a and extending from the main body part 6a to the bead core 5 of the bead part 4 from the tread part 2 through the sidewall part 3. And the folded portion 6b. A bead apex 8 made of hard rubber extending from the bead core 5 to the outer side in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b of the carcass ply 6A, and the bead portion 4 is appropriately reinforced.

  FIG. 2 shows an enlarged sectional view of the bead core 5 before vulcanization, and FIG. 3 shows an enlarged sectional view of the wire 9 with rubber before winding. The bead core 5 is formed from a wound body 10 in which rubber wires 9 are wound.

  2 to 3, the wound body 10 of the present embodiment has a rubber wire 9 wound in four rows in the tire axial direction and three layers in the tire radial direction in the cross section. Moreover, in this embodiment, the wound body 10 is made by what is called a single wind system. Specifically, one rubber-equipped wire 9 is wound in a spiral manner in order from the inner layer in the tire radial direction to the outer layer in turn and while turning the winding direction in the axial direction at the end of each layer. Indicates Such a single-wind type bead core 5 has good productivity and can exert a large fitting force to the rim. However, the winding method of the wire 9 with rubber is not limited to the illustrated example, and can be implemented by various methods.

  As shown in FIG. 3, the rubber-equipped wire 9 includes a bead wire 11 and a coating rubber 12 covering the bead wire 11.

  The bead wire 11 is made of a substantially non-stretchable wire, and is preferably a highly elastic organic fiber cord such as a metal cord or aromatic polyamide. The wire 11 includes not only a stranded wire obtained by twisting filaments but also a single wire that is not twisted such as a monofilament. The bead wire 11 of the present embodiment uses a monofilament made of a metal material and having a substantially circular cross section in accordance with the custom.

  The coating rubber 12 includes an inner peripheral rubber portion 12i disposed in contact with the bead wire 11, and an outer peripheral rubber portion 12o disposed on the outer side and having a hardness different from that of the inner peripheral rubber portion 12i. The

  In FIG. 3, the inner peripheral rubber portion 12 i is annularly arranged around the bead wire 11 with a substantially constant thickness ti. The outer peripheral rubber portion 12o is also disposed around the inner peripheral rubber portion 12i with a substantially constant thickness to. Accordingly, the coating rubber 12 of the present embodiment is composed of two layers of the inner peripheral rubber portion 12i and the outer peripheral rubber portion 12o that are concentrically arranged.

  In the pneumatic tire 1 of the present embodiment, in the coating rubber 12, rubber composition portions having different hardness are used for the inner peripheral rubber portion 12i and the outer peripheral rubber portion 12o. In one embodiment, the coating rubber 12 is configured such that the hardness of the outer peripheral rubber portion 12o is greater than the hardness of the inner peripheral rubber portion 12i.

  FIG. 4 shows an enlarged view of the vicinity of the bead core 5 of the pneumatic tire of FIG. When the wrapping body 10 of the wire 9 with rubber is vulcanized, the outer peripheral rubber portion 12o flows and flows into the gap between the inner peripheral rubber portions 12i of the adjacent bead wires 11. Thereby, the bead core 5 is shape | molded so that substantially the whole inner peripheral rubber part 12i of each bead wire 11 may be covered with the outer peripheral rubber part 12o. For this reason, the main body portion 6a and the folded portion 6b of the carcass ply 6A substantially come into contact with the outer peripheral rubber portion 12o.

  The outer peripheral rubber portion 12o having a high hardness comes into contact with the main body portion 6a and the folded portion 6b of the carcass ply 6A at a position close to the rim. Since the outer peripheral rubber portion 12o has high deformation resistance, the movement of the carcass ply 6A that is in contact with the outer rubber portion 12o is suppressed, and the steering stability is improved, particularly the steering response in the initial stage of steering is greatly improved. Further, an inner peripheral rubber portion 12i having a hardness smaller than that of the outer peripheral rubber portion 12o is disposed on the inner side of the outer peripheral rubber portion 12o so as to cover the individual bead wires 11. The inner peripheral rubber portion 12i can appropriately absorb vibration during traveling and suppress a significant deterioration in riding comfort.

  Although not particularly limited, the hardness Ho of the outer peripheral rubber portion 12o is preferably 65 degrees or more, more preferably 75 degrees or more, and still more preferably 80 degrees or more. When the hardness Ho is less than 65 degrees, the effect of suppressing the movement of the carcass cord may not be sufficiently obtained. On the other hand, if the hardness Ho of the outer peripheral rubber portion 12o is too large, the winding workability of the wire 9 with rubber may be deteriorated or the ride comfort may be deteriorated. From such a viewpoint, the hardness Ho of the outer peripheral rubber portion 12o is preferably 100 degrees or less, more preferably 95 degrees or less, and further preferably 90 degrees or less.

  Further, the hardness Hi of the inner peripheral rubber portion 12i is not particularly limited, but if it is too small, the hardness difference from the outer peripheral rubber portion 12o becomes remarkably large and peeling at the rubber interface is likely to occur. Tend to decrease, and on the contrary, if it is too large, the ride comfort may be deteriorated. From such a viewpoint, the hardness Hi of the inner peripheral rubber portion 12i is preferably 65 degrees or more, more preferably 75 degrees or more, further preferably 80 degrees or more, and the upper limit is preferably 100 degrees or less. More preferably, it is 95 degrees or less, and more preferably 90 degrees or less.

  In the present specification, the hardness of rubber is represented by the hardness according to durometer type A based on JIS-K6253.

  As a particularly preferred embodiment, the difference (Ho-Hi) between the hardness Ho of the outer peripheral rubber portion 12o and the hardness Hi of the inner peripheral rubber portion 12i is preferably 5 degrees or more, more preferably 10 degrees or more, and The upper limit is preferably 15 degrees or less.

  As another embodiment, the coating rubber 12 is configured such that the hardness Ho of the outer peripheral rubber portion 12o is smaller than the hardness Hi of the inner peripheral rubber portion 12i. In this embodiment, contrary to the above, as a result of the outer peripheral rubber portion 12o being able to deform relatively easily, the movement of the carcass ply 6A extending in contact therewith is allowed relatively large. Therefore, the outer peripheral rubber portion 12o of this embodiment is excellent in performance of absorbing vibrations or shocks of the carcass ply 6A, and can particularly effectively enhance the ride comfort. In addition, an inner peripheral rubber portion 12 i having a hardness higher than that of the outer peripheral rubber portion 12 o is disposed inside the outer peripheral rubber portion 12 o so as to cover the individual bead wires 11. The inner peripheral rubber portion 12i can maintain the rigidity of the bead core to be moderately hard, and can suppress a significant deterioration in steering stability.

  As a particularly preferred embodiment, the difference (Hi-Ho) between the hardness Ho of the outer peripheral rubber portion 12o and the hardness Hi of the inner peripheral rubber portion 12i is preferably 5 degrees or more, more preferably 10 degrees or more, and The upper limit is preferably 15 degrees or less.

  In the state before winding, the total thickness T (= to + ti) of the coating rubber 12 of the wire 9 with rubber is preferably 0.2 mm or more, more preferably 0.4 mm or more, and the upper limit is Preferably, it is 2.0 mm or less, more preferably 1.8 mm or less. If the thickness T is too small, there is a tendency that the improvement of the steering stability or the ride comfort cannot be expected sufficiently. On the contrary, if the thickness T is too large, the gap between the bead wires 11 becomes large and the bead core 5 as a whole is fitted to the rigidity or rim. The resultant force tends to decrease.

  Furthermore, the thicknesses ti and to of the inner rubber portion 12i and the outer rubber portion 12o are each 0.1 mm or more, more preferably 0.2 mm or more, and the upper limit is preferably 1.0 mm or less, more preferably Is preferably 0.9 mm or less. When the thickness ti or to is less than 0.1 mm, the above-described outer peripheral rubber portion 12o and inner peripheral rubber portion 12i tend not to be expected to improve steering stability and riding comfort. On the other hand, when the thickness ti or to exceeds 1.0 mm, the rigidity and durability of the bead core 5 tend to decrease, which is not preferable.

  In the coating rubber 12, the thickness ratio (to / ti) between the outer peripheral rubber portion 12o and the inner peripheral rubber portion 12i is not particularly limited, but the movement of the carcass ply 6A is more influenced by the outer peripheral rubber portion 12o. In order to receive strongly, it is desirable to improve the desired performance by relatively increasing the thickness of the outer peripheral rubber portion 12o. In particular, the ratio (to / ti) is preferably greater than 1.0, more preferably 1.5 or more, and even more preferably 2.0 or more. The upper limit of the ratio (to / ti) is preferably 5.0 or less.

  The rubber-coated wire 9 in which the coating rubber 12 includes two types of rubber compositions as in the present embodiment is a first coating apparatus that coats the inner peripheral rubber portion 12i on the bead wire 9 as schematically shown in FIG. It can be manufactured using M1 and the second coating apparatus M2 that can coat the outer peripheral rubber portion 12o on the outer side of the inner peripheral rubber portion 12i.

  Each of the coating apparatuses M1 and M2 includes, for example, an extrusion part b on which a screw shaft or the like is arranged and can knead the rubber compositions R1 and R2, and a coating head h arranged on the extrusion side. The coating head h includes a storage part g in which the rubbers R1 and R2 extruded from the extrusion part b are stored at a predetermined pressure, and an inlet I and an outlet O for allowing the bead wire 9 to pass through the storage part g. . By passing the bead wire 9 through the storage portion g, the coating rubber can be attached to the surface of the bead wire 9. Further, by adjusting the die diameter of the outlet O, the coating thickness of each rubber part 12i, 12o can be adjusted.

  In the two coating apparatuses M1 and M2, the respective inlets I and outlets O are substantially arranged in a straight line. Thereby, the bead wire 9 can be continuously passed through the two coating apparatuses M1 and M2 without bending. This helps to improve the coating accuracy.

  Then, the step of coating the bead wire 9 with the inner peripheral rubber portion 12i by passing the bead wire 9 through the storage portion g of the first coating apparatus M1, and the second step of applying the bead wire 9 coated with the inner peripheral rubber portion 12i to the second. The wire 11 with rubber is manufactured including the step of coating the outer peripheral rubber portion 12o on the outer side of the inner peripheral rubber portion 12i by passing the storage portion g of the coating apparatus M2.

  6A and 6B show an example of another embodiment of the present invention. In these embodiments, the rubber wire 11 has a non-circular cross section, specifically, a polygonal (preferably regular polygonal) cross-sectional shape.

  6A shows a rubber-equipped wire 9 having a substantially square cross-sectional shape, and FIG. 6B shows a rubber-attached wire 9 having a substantially regular hexagonal cross-sectional shape. As shown in FIGS. 7A and 7B, these rubber-equipped wires 9 increase the contact area of each outer peripheral surface between the adjacent rubber-equipped wires 9, and between the bead wires 11, 11. The coating rubber 12 is infiltrated more reliably. This helps to form a bead core 5 having no durability between the wires 11 and 11 and having excellent durability.

  The rubber-equipped wire 9 having a polygonal cross section as shown in FIG. 6 can achieve the above-described effects as long as at least the outer peripheral surface is polygonal. Accordingly, the outer peripheral surface of the outer peripheral rubber portion 12o and the outer peripheral surfaces of the cross sections of the bead wire 9 and the inner peripheral rubber portion 12i can have various arbitrary cross-sectional shapes (in this embodiment, all are circular).

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be modified and implemented in various embodiments. For example, the bead wire 11 may have a non-circular cross section such as a horizontally oblong, substantially elliptical shape. In each of the above embodiments, the coating rubber is composed of two layers, but may be three or more layers.

  In order to confirm the effect of the present invention, a pneumatic tire for passenger cars (size: 195 / 60R15) was prototyped based on the specifications of FIG. 1 and Table 1. Then, the handling stability and riding comfort of each pneumatic tire were tested. The configuration other than the bead core coating rubber was the same. The test method is as follows.

<Steering stability>
Each test tire is mounted on a rim (15 x 6.5 JJ) and filled with an internal pressure of 200 kPa, and a four-wheel test tire is mounted on a domestic FF passenger car with a displacement of 2000 cm ³ for a dry asphalt road test course. I drove with one driver. The driver's sensory evaluation comprehensively evaluated the handle response, rigidity, grip and other characteristics. The results were expressed as an index with the conventional example being 100. The larger the value, the better.

<Ride comfort>
Using a test vehicle similar to the above, sensory evaluation was performed on ruggedness, push-up and dumping on stepped roads on dry asphalt roads, Belgian roads (cobblestone roads), Bitzmann roads (roads covered with pebbles), etc. Is expressed as an index with 100 being 100. The larger the value, the better.
Table 1 shows the test results.

  As a result of the test, it was confirmed that the tire of the example improved the steering stability and the ride comfort in a well-balanced manner as compared with the conventional example. In particular, it has been confirmed that the steering stability or the ride comfort can be remarkably improved by making the thickness of the outer peripheral rubber portion relatively larger than that of the inner peripheral rubber portion.

It is sectional drawing of the pneumatic tire which shows one Embodiment of this invention. It is an expanded sectional view of a bead core. It is an expanded sectional view of a wire with rubber. It is an expanded sectional view of the bead core which shows other embodiments of the present invention. It is sectional drawing explaining the manufacturing method and manufacturing apparatus of a wire with rubber | gum. (A), (B) is sectional drawing which shows other embodiment of the wire with a rubber | gum. (A), (B) is sectional drawing which shows other embodiment of a bead core.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6A Carcass ply 7 Belt layer 9 Wire with rubber 10 Rolled body 11 Bead wire 12 Coating rubber 12i Inner peripheral rubber part 12o Outer peripheral rubber part

Claims (5)

A pneumatic tire having a carcass including at least one carcass ply folded at a bead core of a bead portion from a tread portion through a sidewall portion,
The bead core is composed of a rolled body of wire with rubber in which a bead wire is coated with a coating rubber, and
The coating rubber includes an inner peripheral rubber portion disposed in contact with the bead wire and an outer peripheral rubber portion disposed on the outer side and having a hardness different from that of the inner peripheral rubber portion. .   The pneumatic tire according to claim 1, wherein the coating rubber has a hardness of the outer peripheral rubber portion larger than a hardness of the inner peripheral rubber portion.   The pneumatic tire according to claim 1, wherein the coating rubber has a hardness of the outer peripheral rubber portion smaller than a hardness of the inner peripheral rubber portion.   The pneumatic tire according to any one of claims 1 to 3, wherein a difference between the hardness of the outer peripheral rubber portion and the hardness of the inner peripheral rubber portion is 5 to 15 degrees.   5. The rubber-equipped wire has a total thickness of the coating rubber of 2.0 mm or less, and the inner rubber part and the outer rubber part each have a thickness of 0.1 to 1.0 mm. 6. The pneumatic tire according to Crab.

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