JP2008087587A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire capable of enhancing the uniformity of the tire formed of a carcass material in which a carcass layer is composed of Lyocell fiber cords. <P>SOLUTION: In the pneumatic radial tire, a carcass material 10 obtained by joining ears 13 of a cord fabric 11 with a large number of Lyocell fiber cords 7 aligned in parallel in an overlapping manner is arranged so that the Lyocell fiber cords 7 are intersected with one another in the tire circumferential direction. Rayon fiber cords 8 are arranged at the ears 13 of the cord fabric 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire, and more particularly, to a pneumatic radial tire in which the uniformity of a tire in which a carcass layer is formed of a braided fabric made of lyocell fiber cord is improved.

  For the carcass layer of a pneumatic tire, a braided fabric in which cords made of nylon fiber or rayon fiber are arranged in parallel is used. Since rayon fiber has a larger elastic modulus than nylon fiber or the like, its steering stability can be further improved by using it in the carcass layer of a high-performance pneumatic radial tire. On the other hand, lyocell fiber, which is the same cellulose fiber, has higher elasticity and better dimensional stability than rayon fiber. By using lyocell fiber cord in the carcass layer instead of rayon fiber cord, steering stability is further improved. Has been proposed (see, for example, Patent Document 1).

  However, in the case where the carcass layer is made of a braided fabric made of lyocell fiber cord, there is a problem that a dent is generated in the tire side portion after vulcanization and the tire uniformity is deteriorated as described below.

That is, generally, as shown in FIG. 5 (A), the weave fabric 11 constituting the carcass layer is formed by arranging lyocell fiber cords in parallel as warp yarns, and fine wefts 9 are woven at a coarse pitch in a large number of cords 15. Is formed. This interwoven fabric 11 is rubberized and sequentially cut into a length Lw that is inserted in the tire width direction when the tire is formed in the arrangement direction of the cords to form a large number of short interdigital fabrics 11a, 11b,. Next, as shown in FIG. 5 (B), a large number of short weave fabrics 11a, 11b,... 11n are rearranged so that the ears 13, 13 ′ overlap each other, and are connected long in the direction of arrow E. It is formed in a continuous belt-like carcass material 10. The continuous strip of the carcass member 10 is cut to a length L _E of winding in the tire circumferential direction at the time of tire molding, the code is wound so as to be parallel to the axial direction of the forming drum, when it is unvulcanized tire It is molded so as to form an angle of approximately 90 ° in the tire circumferential direction.

As described above, since the joint portion between the ear portions 13 and 13 'of the carcass material 10 is twice as thick as the main body portion, the cord is increased twice in this portion. Therefore, since the lyocell fiber cord has a high elastic modulus and excellent dimensional stability, the carcass material 10 in which the lyocell fiber cord is arranged at a density twice that of the elongation of the main body 12 of the carcass material during vulcanization. The vicinity of the joint of the ear portion cannot follow the elongation, and a concave portion is generated in the side portion after vulcanization.
JP 2004-66930 A

  An object of the present invention is to provide a pneumatic radial tire in which the uniformity of a tire in which a carcass layer is formed of a braided fabric made of lyocell fiber cord is improved.

  The pneumatic radial tire of the present invention that achieves the above object is a carcass material in which the ears of a braided fabric in which a large number of lyocell fiber cords are arranged in parallel are joined together so that the lyocell fiber cords are arranged in the tire circumferential direction. In a pneumatic radial tire arranged so as to intersect, rayon fiber cords are arranged at the ears of the interwoven fabric.

  In the pneumatic radial tire of the present invention, the rayon fiber cord having a lower elastic modulus than that of the lyocell fiber cord is disposed in the ear part of the interwoven fabric made of lyocell fiber cord. By following the elongation of the main body, no concave portions are formed in the side portions, and the tire uniformity is improved.

FIG. 1 shows a half cross-sectional view of the pneumatic radial tire of the present invention in the meridian direction.
In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 5 is mounted between a pair of left and right bead cores 4 embedded in the bead portion 3, and ends in the tire width direction are folded around the bead core 4 from the tire inner side to the outer side. In the tread portion 1, a pair of upper and lower belt layers 6 are disposed outside the carcass layer 5 over the circumference of the tire.

  As shown in FIG. 2, the carcass material 10 constituting the carcass layer 5 is configured by overlapping a plurality of short weave fabrics 11 a, 11 b,. A large number of lyocell fiber cords 7 are arranged in parallel so as to be substantially orthogonal to the longitudinal direction E of the carcass material 10 on the main body 12 of the short weave fabrics 11a, 11b,. Are arranged in parallel so that the lyocell fiber cord 7 and the rayon fiber cord 8 are mixed.

  FIG. 3 is a plan view of one short weave fabric 11a, 11b,... 11n, and the arrow E is the length direction of the carcass material 10 which becomes the tire circumferential direction after the tire is formed.

  The short weave fabrics 11a, 11b,... 11n are woven so that the main body portion 12 has a large number of lyocell fiber cords 7 and the ear portions 13, 13 ′ at both ends are mixed with the rayon fiber cords 8. After the RFB liquid is dip-treated and coated with unvulcanized rubber, the braided fabric (see FIG. 5A) has a predetermined length so as to be substantially orthogonal to the lyocell fiber cord 7 and the rayon fiber cord 8. It is formed by cutting into Lw. As shown in FIG. 2, a large number of short weave fabrics 11 a, 11 b,... 11 n cut in this way are continuous in the direction of arrow E while overlapping the ears 13 and 13 ′ and repeating joining. The belt-shaped carcass material 10 is connected to the belt-shaped carcass material 10.

  The continuous belt-like carcass material 10 is cut to a length that is wound in the tire circumferential direction when the tire is molded, and the cord is wound so as to be parallel to the axial direction of the molding drum. It is formed so as to form an angle of approximately 90 ° with respect to the direction.

  In the present invention, the rayon fiber cord 8 is disposed at least partially on the ear portion 13 of the carcass material 10 formed as described above. Since the rayon fiber cord has a lower elastic modulus than the lyocell fiber cord, the lift of the body portion 12 of the carcass material allows the extension of the carcass material ear portion 13 during lift-up by a bladder during tire vulcanization. . For this reason, a dent is not generated in the side part.

  The arrangement of the rayon fiber cords in the ear portions 13 and 13 ′ of the carcass material 10 is not particularly limited, but preferably, as shown in FIGS. 4 (a) to 4 (c), the rayon fiber cords and lyocells are used. It is preferable to arrange the fiber cords one by one alternately. Further, as shown in FIG. 4D, the carcass material ears 13 and 13 'may be all made of rayon fiber cords.

  When the lyocell fiber cord and the rayon fiber cord are alternately arranged, as shown in FIG. 4A, the odd number from the end 14 of the ear portion 13 of the carcass material may be a rayon fiber cord. The even number may be a rayon fiber cord as shown in (b), but preferably the odd number is used as shown in FIG. Further, as shown in FIG. 4 (c), the arrangement order of the rayon fiber cords may be different at both end portions 14 and 14 '. These arrangements may be selected according to the difference in characteristics between the lyocell fiber cord and the rayon fiber cord and the type and size of the tire.

  On the other hand, rayon fibers are easier to absorb moisture than lyocell fibers and have the property of shrinking due to moisture absorption. For this reason, as a rayon fiber cord used for the carcass layer of the present invention, before weaving the interwoven fabric, a rewinding treatment is performed under a tension of 100 g or less to give a shrinkage allowance to the rayon fiber cord. It is preferable. By this rewinding treatment, the ears of the interlaced fabric at both ends are eliminated and the flatness of the interlaced fabric is improved, so that the unvulcanized rubber coating process can be made smooth.

The lyocell fiber cord and rayon fiber cord used for the carcass layer of the present invention preferably have a twist coefficient α represented by the following formula (I) of 2000 to 3200, more preferably 2300 to 2900. Good.
α = N × (T / 1.111) ^1/2 (I)
(In the formula, N is the number of twists [times / 10 cm], and T is the total fineness [dtex] of the fiber cord.)

  By setting the twist coefficient α to 2000 or more, the convergence of the cord is maintained, the process passability is improved, and the durability is improved. Moreover, by setting it as 3200 or less, the high elastic modulus of a lyocell fiber cord and a rayon fiber cord can be maintained, and the outstanding steering stability can be ensured.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further, the scope of the present invention is not limited to these Examples.

Examples 1-3
The tire size is 195 / 60R14, the tire structure is that shown in FIG. 1, and the carcass material forming the carcass layer is composed of the interwoven fabric made of lyocell fiber cords. Four types of pneumatic radial tires (Examples 1 to 3, conventional examples) having different arrangements as shown in Table 1 were manufactured.

  The steering stability and the yield of the side dents of the obtained tire were evaluated by the following methods, and the results obtained are shown in Table 1.

Steering stability A test tire is mounted on a rim with a rim size of 14 x 6 JJ, mounted on a passenger car with an air pressure of 220 kPa, and the average of the feelings when five trained test drivers go around the test course is scored. The value was evaluated. The obtained results were expressed as an index with the conventional example as 100. The higher this value, the better the steering stability.

Side Recess Yield The reciprocal of the result obtained by measuring the depth of the dent in the side portion of the test tire was expressed as an index with the conventional example being 100. It shows that the yield of a side part dent is excellent, so that this figure is high.

  In the types of cords in Table 1, “Lyocell” represents a lyocell fiber cord having a twist coefficient α of 2705 and a moisture content of 12% by weight, and “Rayon” has a twist coefficient α of 2705 and a moisture content of 14.5. This represents a 7% by weight rayon fiber cord.

It is a half sectional view of the meridional direction of the pneumatic radial tire of the present invention. It is a fragmentary sectional view of the longitudinal section of the carcass material used for the pneumatic radial tire of the present invention. FIG. 3 is a development view of a short weave fabric constituting the carcass material of FIG. 2. (A)-(d) is explanatory drawing which illustrates the tinting fabric ear | edge part used for the carcass material of the pneumatic radial tire of this invention, respectively. (A) is a development view of the weave fabric used for the carcass material, and (B) is a development view of the carcass material obtained by continuously joining the weave fabric of (A) in a short shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 Carcass layer 7 Lyocell fiber cord 8 Rayon fiber cord 10 Carcass material 11 Weave fabric 11a, 11b, ... 11n Short shape weave fabric 12 Body part 13 Ear part

Claims (6)

In a pneumatic radial tire in which a carcass material joined in such a manner that ears of a braid fabric in which a large number of lyocell fiber cords are arranged in parallel is overlapped with each other, the lyocell fiber cords are arranged so as to intersect in the tire circumferential direction.
A pneumatic radial tire in which rayon fiber cords are arranged at the ears of the interwoven fabric.   2. The pneumatic radial tire according to claim 1, wherein the lyocell fiber cord and the rayon fiber cord are alternately arranged at an ear portion of the interwoven fabric.   The pneumatic radial tire according to claim 1 or 2, wherein the rayon fiber cords are arranged oddly from the end of the ear part of the interwoven fabric.   The pneumatic radial tire according to claim 1 or 2, wherein the rayon fiber cords are arranged evenly from an end of the ear part of the interwoven fabric.   The pneumatic radial tire according to any one of claims 1 to 4, wherein the rayon fiber cord before weaving the interwoven fabric is subjected to rewinding treatment with a tension of 100 g or less. The pneumatic radial tire according to any one of claims 1 to 5, wherein a twist coefficient α represented by the following formula (I) of the lyocell fiber cord and the rayon fiber cord is 2000 to 3200.
α = N × (T / 1.111) ^1/2 (I)
(In the formula, N is the number of twists [times / 10 cm], and T is the total fineness [dtex] of the fiber cord.)

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