JP2006168420A - Code ply for tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve joint dent caused by an uneven distance between code centers at a joint part of a zipper joint. <P>SOLUTION: End faces Es of respective side edges 14E of a base cloth ply 14 obtained by cutting a raw ply 13 are abutted and jointed to each other, so as to form a cord ply 10. A code sequence 12 in the base cloth ply 13 comprises 2-8 side codes 11e arranged on a side edge 14E, and central codes 11c arranged between them. The respective codes 11e, 11c are arranged at the same intervals, and elongation Le of the side code 11e from an initial condition where an initial load of 2N is applied to a loaded condition where a load of 50N is applied is made 1.4 to 2.0 times the elongation Lc of the code of the central code 11c. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a tire cord ply of a zipper joint in which end surfaces of respective base fabric plies are butted against each other.

  As shown in FIG. 6, a cord ply a for tires, for example, a carcass, is formed by using an unvulcanized original ply d with rubber tops on both sides of a cord array c in which steel cords b are arranged in parallel. The

  Specifically, the base ply f is first cut by cutting the original ply d at a desired angle θ (about 90 ° in the radial carcass) and length in a direction intersecting the steel cord b. The base ply f is sequentially joined between the side edge portions fe and fe parallel to the steel cord b, whereby the cord ply in which the steel cord b is inclined at the angle θ with respect to the length direction. a was formed. The cord ply a is cut to a predetermined size in the green tire forming step and wound once on a forming drum, thereby forming a cylindrical carcass ply before shaping.

  At this time, the bonding between the base fabric plies f and f has been conventionally performed by a so-called overlap joint that overlaps and press-bonds the side edge portions fe and fe as shown in FIG. . However, in the joint portion J of such an overlap joint, since the cord b overlaps vertically, the elongation of the cord b when filling the tire internal pressure is reduced unevenly, and the joint portion J is recessed in a band shape. There is a problem that joint dents occur and the tire appearance is remarkably impaired.

  Therefore, in recent years, in order to suppress the joint dent, as shown in FIG. 7B, a zipper joint has been proposed in which the end surfaces of the side edge portions fe are brought into contact with each other (see Patent Documents 1 and 2).

JP-A-9-70902 JP 2001-105508 A

  However, in this zipper joint, the urging force F in the abutting direction acts strongly in order to ensure the necessary bonding strength. As a result, the cord peculiar to this zipper joint such as the cord center distance pe of the two to eight side cords be arranged at the side edge portion fe is smaller than the cord center distance pc of the other cords bc. Non-uniform center distance occurs. Therefore, although the joint dent is improved as compared with the overlap joint, a satisfactory improvement effect has not been obtained.

  Therefore, the present invention is based on the fact that the elongation of the cords arranged on the side edge portions is set to be larger than the elongation of the remaining cords, so that the joint dent in the zipper joint can be further improved and the appearance performance of the tire can be improved. It aims at providing the cord ply for tires which can be improved more.

In order to achieve the above object, the invention of claim 1 of the present application is directed so that an unvulcanized raw ply in which a cord array in which steel cords are arranged in parallel with each other and covered with a topping rubber is crossed with the steel cord. Cutting and forming a base fabric ply, and joining the base fabric ply with the end faces of the side edges parallel to the steel cord butting each other,
The code array is composed of a side region composed of 2 to 8 side cords arranged on each side edge portion, and a central region consisting of a central cord arranged therebetween, and the side code and the center. Each cord and the cord are both arranged at the same interval,
In the side cord, the cord elongation Le from the initial state with an initial load of 2N to the loaded state with a load of 50N is 1.4 to 2.0 times the elongation Lc of the cord of the central cord. It is characterized by that.

  In the invention of claim 2, the base fabric ply is characterized in that each side edge portion is joined by a zipper joint using two top bodies having cone surfaces around the rotation axis.

  According to a third aspect of the present invention, the central cord has an elongation Lc of 0.05 to 0.10%.

  According to a fourth aspect of the present invention, the zipper joint approaches the maximum diameter portion of the cone surface of the piece body, and the rotation at an angle at which one bus bar of each of the two piece bodies is parallel to the surface of the cord ply. It is characterized by being joined using a joining means that is arranged with the shaft centers crossed and that is positioned between the side edges of the cord plies to be joined between the two pieces.

  Since the present invention is configured as described above, the joint dent can be improved to a sufficiently satisfactory level even when the distance between the cord centers peculiar to the zipper joint occurs.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an example of a tire using a tire cord ply of the present invention as a carcass ply.

  In FIG. 1, a tire 1 is a heavy duty radial tire, and includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, an inner side of the tread portion 2, and the carcass 6. It comprises at least a belt layer 7 arranged on the outer side in the radial direction.

  The belt layer 7 is formed of two or more belt plies (three or more in the case of heavy duty tires) using a steel cord as a belt cord. In this example, the belt layer 7 includes a first belt ply 7A on the innermost side in the radial direction in which belt cords are arranged at an angle of, for example, 60 ± 15 ° with respect to the tire circumferential direction, and 10 to 10 with respect to the tire circumferential direction. A case of a four-sheet structure with second to fourth belt plies 7B to 7D arranged at a small angle of 35 ° is illustrated. The belt plies 7 </ b> A to 7 </ b> D are provided with one or more places where the belt cords cross each other between the plies, and are superposed to enhance belt rigidity and reinforce the tread portion 2 with a tagging effect.

  Further, the carcass 6 is formed of one or more carcass plies 6A, in this example, one carcass ply 6A in which carcass cords made of steel cord are arranged at an angle of 70 to 90 ° with respect to the tire circumferential direction. The carcass ply 6A is provided with a series of ply turn-up portions 6b that are turned back from the inside in the tire axial direction around the bead core 5 on both sides of the ply main body portion 6a straddling the bead cores 5 and 5. A bead apex rubber 8 for bead reinforcement extending radially outward from the bead core 5 is disposed between the main body portion 6a and the folded portion 6b.

  The carcass ply 6A is formed using the cord ply 10 of the present invention.

  As shown in FIG. 2, the cord ply 10 includes an unvulcanized original ply 13 in which a steel cord 11 (carcass cord) is arranged in parallel with each other and both surfaces of a cord array body 12 covered with a topping rubber G. The base ply 13 is cut in a direction crossing the steel cord 11 to form a base fabric ply 14, and among the base fabric plies 14, the side edge portion 14 </ b> E parallel to the steel cord 11 is formed. As shown in FIG. 3, the end surfaces Es and Es are formed by abutting and joining each other by a zipper joint.

  Here, as shown in the cross section of FIG. 4, the code array 12 is arranged between the side area Ye composed of 2 to 8 side codes 11 e arranged on each side edge portion 14 </ b> E, and between them. Each of the cords 11 including the central cord 11c and the side cord 11e and the central cord 11c are arranged at the same interval in the state before the joining.

  Further, as schematically shown in FIG. 3, the zipper joint is performed by using a well-known joining means 21 including two pieces 20 having a cone surface 20S around the rotation axis N in this example. Each piece 20 intersects the rotation axis N at an angle at which the maximum diameter portion 22 of the cone surface 20S is brought close to each other and one bus bar X forming each cone surface 20S is parallel to the surface of the base fabric ply 14. Distributed. Then, each piece 20 is rotated by positioning the middle of the two pieces 20 in the center between the side edges 14E and 14E of the base fabric ply 14 to be joined. Thereby, the side edge part 14E can be urged | biased in the abutting direction, between the end surfaces Es and Es can be strongly pressed and it can join firmly.

  However, in this zipper joint, as shown in FIG. 5, the cord center distance pe of the side cord 11e is reduced by the strong biasing force F in the butting direction, and becomes smaller than the cord center distance pc of the center cord 11c. The uneven distance between the cord centers makes the joint dent improvement effect insufficient.

  Therefore, in the present invention, in the cord array 12, the extension Le of the cord in the low load region from the initial state of the side cord 11e to which a load of 2N is applied to the load state to which a load of 50N is applied is expressed as the center cord 11e. It is set to 1.4 to 2.0 times the cord elongation Lc of the cord 11c.

  Thus, since the extension Le of the side cord 11e is set to be large, the extension at the joint portion J, that is, the side edge portion 14E (side region Ye) due to the reduction of the cord center distance pe. It is possible to make up for the shortage of joints and suppress the occurrence of joint dents.

  When the elongation Le is less than 1.4 times the elongation Lc, the joint dent suppressing effect cannot be expected. When the elongation Le exceeds 2.0 times, the joint Le is excessively stretched, and conversely, a bulge in which the joint J protrudes in a band shape occurs. It becomes a trend. Similarly, if the number of the side cords 11e is less than 2, the width for suppressing the joint dent is too small and the effect becomes insufficient. If the number of the side cords 11e exceeds 8, the strip bulges are newly added on both sides of the joint portion J. Tend to occur. Therefore, it is more preferable that the lower limit value of the elongation Le is 1.6 times or more of the elongation Lc and the upper limit value is 1.8 times or less of the elongation Lc. The number of the side cords 11e is more preferably 4 or more and the upper limit is 6 or less.

  In the central cord 11c, the elongation Lc is preferably in the range of 0.05 to 0.10%, as in the case of a conventional carcass cord, from the viewpoint of moldability and durability.

As a means for changing the elongation Le and Lc,
(1) The number of cord twists is different between the side cord 11e and the central cord 11c;
(2) Use a filament containing a corrugated filament for the side cord 11e;
(3) A filament including a corrugated filament is used for both the side cord 11e and the central cord 11c, and the corrugated height of the corrugated filament is different between the side cord 11e and the central cord 11c;
(4) Different tension balance when twisting filaments;
At least one of the above can be adopted.

  The elongation Le and Lc can be made different by changing at least one of the filament material, the thickness, and the twisted structure of the cord, but in such a case, the elongation is greatly different even in a high load region. This may adversely affect the running performance of the tire.

  As described above, the particularly preferred embodiment of the present invention has been described in detail. However, the present invention is not limited to the illustrated embodiment. For example, the tire cord ply can be used for forming a belt ply. It can be implemented by modifying to the embodiment.

  A tire for heavy load (10.00R20 14PR) using the cord ply having the specifications shown in Table 1 as a carcass ply was made as a prototype, and the appearance performance on the sidewall surface of the prototype tire was compared with that of a conventional tire. Both the side cord and the central cord have a 3 + 8 × 0.21 cord structure in which the filament material, the thickness, and the cord twist structure are the same. , Lc is wrong. Further, the elongations Le and Lc of the cord mean the elongation from an initial state where a 2N initial load is applied to a load state where a 50N load is applied.

<Appearance performance>
When the tire is mounted on a 7.50 × 20 rim and an internal pressure of 725 kPa is applied, the side wall surface is observed, the depth of the dent (concave) generated at the position of the joint portion of the cord ply, or the bulge The height of (convex) was measured at 10 positions, and the average value was described.

  As shown in the table, it can be confirmed that the tires of the examples can reduce the generation of dents and bulges and can improve the appearance performance.

It is sectional drawing which shows one Example of the tire which used the cord ply of this invention for the carcass ply. It is a diagram explaining the formation method of a cord ply. It is a diagram which shows the joining means of a zipper joint schematically. It is sectional drawing which shows a code arrangement | sequence body. It is sectional drawing which expands and shows the joint part by a zipper joint. It is a diagram explaining the formation method of the carcass ply of the conventional tire. (A), (B) is sectional drawing of the joint part explaining the problem of a prior art.

Explanation of symbols

11 Steel cord 11e Side cord 11c Center cord 12 Cord array 13 Original ply 14 Base fabric ply 14E Side edge 20 Top body 20S Cone surface Es End surface G Topping rubber Ye Side region Yc Center region

Claims (4)

A base fabric ply is formed by cutting an unvulcanized raw ply in which steel cords are arranged parallel to each other and covered with a topping rubber so as to cross the steel cord. While joining the end faces of each side edge parallel to the steel cord butting each other,
The code array is composed of a side region composed of 2 to 8 side cords arranged on each side edge portion, and a central region consisting of a central cord arranged therebetween, and the side code and the center. Each cord and the cord are both arranged at the same interval,
In the side cord, the cord elongation Le from the initial state with an initial load of 2N to the loaded state with a load of 50N is 1.4 to 2.0 times the elongation Lc of the cord of the central cord. A cord ply for tires.   The tire cord ply according to claim 1, wherein each side edge of the base fabric ply is joined by a zipper joint using two pieces having a cone surface around a rotation axis.   The tire cord ply according to claim 1 or 2, wherein the central cord has an elongation Lc of 0.05 to 0.10%.   The zipper joint is arranged so that the maximum diameter portion of the cone surface of the piece body is brought close to each other and the rotation axis is intersected at an angle at which one bus bar of each of the two piece bodies is parallel to the surface of the cord ply. 3. The tire cord ply according to claim 2, wherein the tire cord ply is joined using a joining means positioned between the side edges of the cord plies to be joined.

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