JP2006218988A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire having excellent durability which is capable of reducing the tire weight and maintaining high BES resistance even from the middle to the end of the belt separation trouble. <P>SOLUTION: The pneumatic radial tire comprises a carcass consisting of at least one radial carcass layer in a toroidal manner across a pair of right and left bead cores, a tread part which is arranged on the outer side in the tire radial direction of a crown area of the carcass to form a ground contact part, and a belt consisting of at least two belt layers which is arranged between the tread part and the crown area of the carcass to form a reinforcement part. At least one layer of the belt is reinforced by at least two kinds of steel monofilament cords of different wire diameter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire (hereinafter, also simply referred to as “tire”), and more particularly, to reduce the weight of the tire and sufficiently suppress the separation generated at the belt width end, so-called belt end separation. The present invention relates to a pneumatic radial tire with improved separation properties (hereinafter abbreviated as “BES resistance”).

  Pneumatic radial tires, particularly passenger car tires, are required to have low rolling resistance, good riding comfort, and low cost in order to improve the fuel efficiency of automobiles. In order to meet such demands, Patent Document 1 proposes to reduce the rolling resistance of the tire by using a steel monofilament cord instead of a cord for the belt reinforcing material.

Moreover, in patent document 2, the problem by using a steel monofilament cord as a belt reinforcing material, that is, the problem that the belt buckles and the steel monofilament cord breaks due to repeated sudden turning and causes uneven wear of the tread. In order to solve the problem and to avoid belt end separation, the belt is formed in the width direction of the belt without twisting 3 or 4 metal wires having a circular cross section and an elongation at break of 3.6% or more. It has been proposed that a bundle that is aligned and aligned is embedded in rubber with a driving number of 15 to 30 units per 50 mm width.
Japanese Utility Model Publication No. 63-19404 (claims, etc.) JP-A-11-208210 (Claims etc.)

  As described in Patent Document 2, the unit is a bundle in which steel monofilament cords as a belt reinforcing material are aligned and aligned in the width direction, and by increasing the rubber gauge between the bundles, the belt end separation failure in the initial stage Although the BES resistance can be improved, it was not sufficient from the middle to the end of the belt end separation failure. Here, belt end separation is caused by repeated input of the belt part during tire running, especially cornering, deformation of the belt part during lane change, and distortion at the belt end part causing cracks in the rubber. It is what happens. Therefore, in order to ensure the durability of the tire, it is important to maintain high BES resistance even from the middle to the end of the belt end separation failure.

  Accordingly, an object of the present invention is to provide a pneumatic radial tire that has a reduced tire weight and can maintain high BES resistance even from the middle to the end of a belt end separation failure, and as a result, has excellent durability. There is to do.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that the above object can be achieved by constituting the belt with a different diameter steel monofilament cord under predetermined conditions, and completes the present invention. It came to.

That is, the pneumatic radial tire of the present invention is arranged on the outer side in the tire radial direction of the carcass composed of at least one radial carcass layer straddling a pair of left and right bead cores in a toroidal shape and the crown region of the carcass. A pneumatic tread portion provided to form a grounding portion, and a belt composed of at least two belt layers disposed between the tread portion and the crown region of the carcass to form a reinforcing portion. In radial tires,
At least one layer of the belt is reinforced with two or more types of steel monofilament cords having different wire diameters.

  Preferably, two or more types of steel monofilament cords, each of which is arranged with a gap between the bundles, each bundle being a single bundle of steel monofilament cords without being twisted, each having a different wire diameter. Including. Moreover, the wire diameter difference of different wire diameter steel monofilament cords is preferably 0.01 mm or more, more preferably 0.02 mm or more.

  According to the present invention, the tire weight is reduced and high BES resistance can be maintained not only in the initial stage of the belt end separation failure but also in the middle to final stages. As a result, the pneumatic having excellent durability can be maintained. A radial tire can be provided.

FIG. 1 shows a pneumatic radial tire according to a preferred embodiment of the present invention.
The illustrated radial tire includes a tread portion 1, a pair of sidewall portions 2 extending inward in the tire radial direction continuously on both sides of the tread portion 1, and a bead continuous on the inner peripheral side of each sidewall portion 2. Part 3.

  The tread portion 1, the sidewall portion 2, and the bead portion 3 are reinforced by a carcass 4 including a single radial carcass layer extending in a toroidal shape from one bead portion 3 to the other bead portion 3. Further, the tread portion 1 is reinforced by two layers of a first belt layer 5a and a second belt layer 5b disposed on the outer peripheral side of the crown portion of the carcass 4, which will be described in detail below.

  Here, the radial carcass layer of the carcass 4 may be a plurality of layers, and an organic fiber cord extending in a direction substantially orthogonal to the tire circumferential direction, for example, an angle of 70 to 90 ° can be preferably used.

  In the present invention, it is important that at least one layer of the belt is reinforced with two or more types of steel monofilament cords having different wire diameters. The tire weight can be reduced by using a steel monofilament cord as a belt reinforcement. In addition, by using two or more types of steel monofilament cords with different wire diameters as the steel monofilament cords, the BES resistance is enhanced by the irregularities formed by the different wire diameter steel monofilament cords at the initial stage of belt end separation failure. In addition, since the crack propagation distance can be extended from the middle to the last stage of the belt end separation failure, high BES resistance can be maintained.

  Specific examples of cross sections of the steel monofilament cords of the belt reinforced with two or more types of steel monofilament cords having different wire diameters are shown in FIGS. 2 to 12, but the arrangement of the steel monofilament cords is not limited to these, Also, the steel monofilament cords do not need to be strictly aligned, and a somewhat disturbed arrangement is allowed.

  In FIG. 2, two types of steel monofilament cords with different wire diameters are alternately arranged in the tire axial direction at almost equal intervals, and the centers of all steel monofilament cord cross sections are set at approximately the same height from the outer surface in the tire radial direction of the carcass. Has been.

  In FIG. 3, two types of steel monofilament cords having different wire diameters are alternately arranged in the tire axial direction at almost equal intervals, and the tire axial tangents on the inner side in the tire radial direction of all the steel monofilament cords are outside the tire radial direction of the carcass. It is set to approximately the same height from the side.

  In FIG. 4, two types of steel monofilament cords having different wire diameters are arranged in the tire axial direction alternately at a ratio of one small-diameter cord per two large-diameter cords at almost equal intervals. Are set at substantially the same height from the outer surface of the carcass in the tire radial direction.

  In FIG. 5, two types of steel monofilament cords having different wire diameters are arranged as one bundle of two large-diameter cords, and this bundle and one of the small-diameter cords are alternately arranged at substantially equal intervals in the tire axial direction. The center of the cross section of the steel monofilament cord is set at substantially the same height from the outer surface in the tire radial direction of the carcass.

  In FIG. 6, two types of steel monofilament cords with different wire diameters, one with two large diameters and one with a small diameter next to each other, are arranged as a bundle, and they are arranged at almost equal intervals in the tire axial direction. The center of all steel monofilament cord cross sections is set at substantially the same height from the outer surface in the tire radial direction of the carcass.

  In FIG. 7, two types of steel monofilament cords having different wire diameters, one having two large diameters and one having a small diameter in between, are arranged as a bundle and are arranged at almost equal intervals in the tire axial direction. The centers of all the steel monofilament cord cross sections are set at substantially the same height from the outer surface in the tire radial direction of the carcass.

  In FIG. 8, two types of steel monofilament cords having different wire diameters, one having two small diameters and one having a large diameter in between, are bundled and arranged in a tire axial direction at substantially equal intervals. The centers of all the steel monofilament cord cross sections are set at substantially the same height from the outer surface in the tire radial direction of the carcass.

  In FIG. 9, the bundle shown in FIG. 7 and the bundle shown in FIG. 8 are arranged at substantially equal intervals in the tire axial direction, and the centers of all steel monofilament cord cross sections are set at substantially the same height from the outer surface in the tire radial direction of the carcass. Has been.

  In FIG. 10, two types of steel monofilament cords with different wire diameters, each having four large diameter cords and three small diameter cords juxtaposed between them, are bundled together, and are arranged at approximately equal intervals in the tire axial direction. The center of all the steel monofilament cord cross sections is set at substantially the same height from the outer surface in the tire radial direction of the carcass.

  In FIG. 11, two types of steel monofilament cords having different wire diameters, each having four large diameter cords and three small diameter cords arranged side by side as one bundle, are arranged at approximately equal intervals in the tire axial direction. The center of the large-diameter steel monofilament cord cross section is set to approximately the same height from the outer surface in the tire radial direction of the carcass, and the center of the small-diameter steel monofilament cord cross section is at a random height from the outer surface in the tire radial direction of the carcass Is set to

  In FIG. 12, two types of steel monofilament cords having different wire diameters are arranged in the order of large diameter, large diameter, small diameter, small diameter, large diameter, small diameter, and large diameter as one bundle, which is almost equal in the tire axial direction. The centers of all steel monofilament cord cross sections are set at substantially the same height from the outer surface in the tire radial direction of the carcass.

  In the present invention, from the viewpoint that the BES resistance can be enhanced by the unevenness formed by the different-diameter steel monofilament cords and the crack propagation distance can be increased, preferably steel as shown in FIGS. It is preferable to arrange two or more kinds of steel monofilament cords having different bundle diameters, with the bundles of monofilament cords arranged as a unit without being twisted being arranged as a unit and spaced apart from each other. From the same viewpoint, the wire diameter difference of different diameter steel monofilament cords is preferably 0.01 mm or more, more preferably 0.02 mm or more.

The diameter of the steel monofilament cord that can be used in the present invention is preferably 0.17 to 0.35 mm, more preferably 0.19 to 0.27 mm. If the diameter is less than 0.17 mm, it is difficult to ensure the rigidity of the belt. On the other hand, if it exceeds 0.35 mm, the rigidity becomes too large and the ride comfort deteriorates. The tensile strength of the steel monofilament cord is preferably 2700 N / mm ² or more. The steel monofilament cord having a high tensile strength is desirably one containing at least 0.7% by mass, preferably at least 0.8% by mass of carbon.

  The radial tire of the present invention relates to an improvement in the belt structure, and other structures and materials are not particularly limited, and known structures and materials can be adopted.

Hereinafter, the present invention will be specifically described with reference to examples.
A pneumatic radial tire having a structure including the two-layer steel belt shown in FIG. 1 was produced under the conditions shown in Table 1 below. The tire size was 185 / 70R14, and the steel monofilament cord driving angles of the first belt layer 5a and the second belt layer 5b were + 22 ° and −22 °, respectively, with respect to the tire circumferential direction. The tires of the obtained Examples and Comparative Examples were evaluated for the degree of weight increase based on Comparative Example 1 and the belt end separation resistance (hereinafter referred to as BES resistance) as follows. The results are also shown in Table 1 below and FIG.

(weight)
The weight difference (g) when Comparative Example 1 is zero is shown.

(Evaluation of BES resistance)
Each test tire is mounted on a regular rim specified by JATMA, filled with 220 kPa of internal pressure and mounted on a test passenger car. After running on the BES drum with a constant force of SF, the tire is dissected. Then, the length of the crack generated at the end of the belt layer was measured. The crack length of each test tire was indicated by an index with the crack length of the tire of Comparative Example 1 as 100. The smaller the index value, the better the BES resistance.

  From Table 1 and FIG. 13, in the tires of Examples 1 to 3, the BES resistance is improved while reducing the weight as compared with the tires of Comparative Example 1 and Comparative Example 2. I understand that.

1 is a cross-sectional view of a pneumatic radial tire according to a preferred example of the present invention. It is an expanded partial sectional view of the steel monofilament cord of the belt layer concerning one suitable example of the present invention. It is an expanded partial sectional view of the steel monofilament cord of the belt layer concerning other suitable examples of the present invention. It is an expanded partial sectional view of the steel monofilament cord of the belt layer concerning other suitable examples of the present invention. It is an expanded partial sectional view of the steel monofilament cord of the belt layer concerning other suitable examples of the present invention. It is an expanded partial sectional view of the steel monofilament cord of the belt layer concerning other suitable examples of the present invention. It is an expanded partial sectional view of the steel monofilament cord of the belt layer concerning other suitable examples of the present invention. It is an expanded partial sectional view of the steel monofilament cord of the belt layer concerning other suitable examples of the present invention. It is an expanded partial sectional view of the steel monofilament cord of the belt layer concerning other suitable examples of the present invention. It is an expanded partial sectional view of the steel monofilament cord of the belt layer concerning other suitable examples of the present invention. It is an expanded partial sectional view of the steel monofilament cord of the belt layer concerning other suitable examples of the present invention. It is an expanded partial sectional view of the steel monofilament cord of the belt layer concerning other suitable examples of the present invention. It is a graph which shows the relationship between the weight difference in an Example, and BES resistance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass 5a 1st belt layer 5b 2nd belt layer

Claims (4)

A carcass composed of at least one radial carcass layer straddling a pair of left and right bead cores in a toroidal shape, and a tread portion disposed on the outer side in the tire radial direction of the crown region of the carcass to form a ground contact portion A pneumatic radial tire comprising: a belt composed of at least two belt layers disposed between the tread portion and the crown region of the carcass to form a reinforcing portion;
A pneumatic radial tire characterized in that at least one layer of the belt is reinforced with two or more types of steel monofilament cords having different wire diameters.   The bundle comprising two or more types of steel monofilament cords, each of which is arranged with an interval between the bundles, with a bundle of the steel monofilament cords arranged without being twisted as a unit, and each bundle having a different wire diameter. The pneumatic radial tire according to 1.   The pneumatic radial tire according to claim 1 or 2, wherein the wire diameter difference between the different diameter steel monofilament cords is 0.01 mm or more.   The pneumatic radial tire according to claim 3, wherein the difference in wire diameter of the different wire diameter steel monofilament cords is 0.02 mm or more.

Images