JP2672966B2 - Flat radial tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to lifting of a belt during traveling of a radial tire (the belt shoulder is deformed and lifted by centrifugal force,
The present invention relates to a flat radial tire having a structure for preventing peeling damage between a metal cord of a belt and rubber. [Prior Art] Conventionally, in a method for manufacturing a radial tire, for example, a method for forming a belt reinforcing layer disclosed in Japanese Patent Laid-Open No. 61-51979, a cylindrical primary molding tire carcass is toroidal on a radial tire molding machine. In a radial tire molding method in which a belt and tread assembly, which has been endlessly laminated and integrated in advance, is attached to the outer surface by crimping, a predetermined number of belts are laminated on a belt ring. , Of the belt width on the outer peripheral surface of this belt
Over a range of 70% or more, one or a large number of synthetic fiber cords are continuously spirally wound in a circumferential direction at an equal pitch of 5 to 15 mm, and then a tread is wound on the spirally wound cord. The primary tire carcass is deformed into a toroidal shape to the extent that the outer surface of the tire carcass is pressure-bonded to almost the entire inner peripheral surface, and a green tire is molded. [Problems to be Solved by the Invention] In the above method, the cord winding pitch is 5 to 15 mm even if it is effective to prevent the undesired expansion of the equatorial diameter of the raw tire due to the shaping internal pressure during vulcanization. Since it is widely set, it is weak in terms of belt reinforcement when running tires. That is, the reinforcing effect against belt damage due to lifting during tire running is insufficient. Also, in the above method, there is no consideration for stretching the belt during running,
Since the belt is formed using a belt drum that has a surface with a flat cross-section through the shaft, the winding circumference of the cord during forming is the same at the belt shoulder and the center of the belt. The belt circumference is short at the belt shoulder part due to the shaping (expansion) process during vulcanization and becomes long at the belt center part, resulting in a large stretch at the belt center part and a small stretch at the belt shoulder part, resulting in heat shrinkage. There is a problem in that the force becomes low at the shoulder of the belt, the so-called hoop effect is reduced, and damage is caused by lifting while traveling. Also, when using a rubberized sheet that is made by arranging multiple synthetic fiber cords in a tape shape, the strength of the joint part changes suddenly, so that strain concentrates on the joint part at high speed running and durability deteriorates. Moreover, there is a drawback that uniformity is lowered in the tire manufacturing process. As a solution to such a drawback, it has been proposed to employ a so-called jointless band in which one to several nylon cords with rubber are wound in a spiral shape. However, this method has a problem that it takes a long time to wind the cord, resulting in poor productivity, and the wound cord becomes asymmetric in the tire cross section, resulting in poor uniformity such as conicity. The present invention has been made in order to eliminate such conventional drawbacks, reliably prevents the belt shoulder from being damaged by lifting during tire running, and has excellent tire uniformity and productivity. The present invention provides a flat radial tire. [Means for Solving the Problem] The present invention is directed to a pair of beads, at least one carcass formed of cords folded around the beads and locked and arranged in the radial direction, and a radial direction of the carcass. A pneumatic tire having an outer belt, which is composed of at least two metal cord layers, and a reinforcing layer, which is arranged radially outward of the belt and is composed of organic fiber cords wound substantially parallel to each other in the tire circumferential direction. In the above-mentioned reinforcing layer, two tapes formed by embedding a plurality of cords in a rubber layer at a pitch of 0.5 to 5.0 mm respectively form a spiral structure symmetrical with respect to the equatorial plane of the tire to form an entire belt layer. The tape is wound so as to cover it, and one end of each tape is located near the tire equatorial plane, and the other end is located between the belt layer side end and the equatorial plane. By both ends of the-loop are folded respectively more at the belt middle portion, and has a formed bilayer with shoulder structure. [Operation] In the above-mentioned configuration, the difference in stretch between the belt shoulder portion and the belt center portion of the vulcanized tire is reduced, and the heat shrinkage force of the belt shoulder portion is improved, so that there is an action of preventing lifting when the belt is running. It is exerted strongly, and therefore, peeling damage of the belt due to lifting during traveling can be reliably prevented. Moreover, since the cord has a spiral structure symmetrical with respect to the tire equatorial plane, the tire uniformity is excellent. [Example] FIG. 1 shows an example of a tape-shaped body 20 constituting a belt reinforcing layer of a radial tire of the present invention. As shown in this figure, the tape-like body 20 has a structure in which a plurality of cords 1, six cords in the illustrated example, are aligned and gathered together and integrated by a rubber coating 2. The cord 1 is a long cord 1 composed of a large number of spun yarns of organic fibers made of nylon 66, nylon 6, polyester, Kevlar, etc., monofilament yarns, single filaments of multifilament yarns or twisted yarns. ,
The coating rubber is the same as that used as the coating rubber of the conventional belt reinforcing layer (a nylon band having a joint in the width direction of the belt), for example, a rubber compound mainly composed of natural rubber or a natural rubber / SBR blend compound. Good adhesion with code 1. The diameter of the cord 1 is determined by the strength required for lifting prevention, for example, 0.5 to 1.5 mm, and the thickness of the rubber coating is determined by the required durability, for example, 0.05 to 0.8 m.
m. Each cord 1 has a pitch 1 between cords of 0.5 to 5.0 mm.
It is arranged to be. By arranging and integrating a plurality of cords 1 in this manner, the pitch l between the cords 1 is
Can be accurately set and can be easily formed by an extruder or a calendar ball. Although the drawing shows an example in which the tape-shaped body 20 is composed of six cords 1, this number may be selected within a range of 5 to 10. In this case, from the viewpoint of tire uniformity, it is desirable that the number of windings is such that the angle with respect to the circumferential direction does not greatly exceed 0 °. FIG. 2 shows a tape-shaped body 20 on the outer peripheral surface of a belt 4 having a two-layer structure wound around a belt drum or a belt ring 5.
An example in which the belt reinforcing layer is formed by continuously winding the tape in a spiral shape over the entire width of the belt in a circumferential direction, and further winding the tape-shaped body 20 on both shoulders BS of the belt 4 so as to overlap the two. Shows. In the figure, only the convenience code 1 is shown and the rubber coating 2 is omitted. The tape-shaped body 20 is wound in a symmetrical structure with respect to the tire equatorial plane. That is, FIG. 2 (B)
As shown in FIG. 2, the two tape-shaped bodies 20a and 20b are spirally wound from the central position 30 toward both outer sides in a symmetrical structure with each other, and are folded at both ends to be wound into a two-layer structure only in the BS part. Alternatively, as shown in FIG. 2 (C), first, winding may be started from the BS portion, folded back at the end portion, and wound up to the central position 30. Also, the winding tension of the tape-shaped body 20 is the same as that of the cord 1 above.
The winding tension may be set so as to be uniform in the width direction of the belt 4, but the tension of the cord 1 after vulcanization of the tire is uniform over the entire belt width, or the tension of the cord 1 Wrap the cord so that the constant load elongation is small at the shoulder of the belt 4 and large at the center of the belt 4, and the winding tension of the cord is maximum at the belt shoulder and minimum at the belt center. Is preferred. The winding tension of the tape-shaped body 20 may be appropriately selected depending on the size and structure of the tire. For example, when 1260d / 2 of nylon 66 is used for the cord 1, the tension of the cord 1 is set to a minimum of 20 g at the center of the belt. At the same time, the tape-like body 20 may be wound so that the belt shoulder has a maximum of 40 g, and the cord tension of the belt-reinforcing layer of the belt after vulcanization can be increased. 50g evenly over the entire width. 3 and 4 show a belt reinforcing layer forming device, in which the winding device 7 is provided with a pair of feeding means for feeding the tape-shaped body 20, whereby the two tape-shaped bodies 20 are arranged at the center of the belt. The belts are symmetrically wound from the position toward the shoulders at the same time. That is, screwed onto the screw shafts 71a and 71b in the same direction, and slidably mounted on rails 71e and 71f provided on the frame 70c in parallel with the screw shafts 71a and 71b, respectively.
A pair of feeding means 73b, 73c, which traverse in a direction away from the central position (arrow direction), are juxtaposed in the width direction of the belt drum 6, and the gears thereof rotate in opposite directions by the rotation of the motor 71c. , 71b are rotated in opposite directions, and the pair of feeding means 73b, 73c are moved in opposite directions at the same speed. Further, the feeding means 73b and 73c have arms 77a,
Each arm 77a, 77b has a plurality of guide pulleys 75 attached thereto. This arm independently biases in the drum direction slidably on the rail 71g by the spring 85,
The roll 78a comes into contact with the follower plate 79, and each feeding means is configured to be movable in the belt width direction with a desired distance from the surface of the belt drum. The two screw shafts 71a, 71b may be formed with screws in mutually opposite directions, and these two shafts may be rotated in the same direction. The lower end of the frame 70c of the winding device 7 is placed on the guide rail 70a, and the movement of the frame 70c along the guide rail 70a causes the distal ends of the arms 77a and 77b and the belt drum 6 to move. The spacing is finely adjusted. Further, a tension detecting device (differential transformer type) 80 is provided on the frame 70c, and the tape-shaped body 20 which is applied with a predetermined winding tension through the brake pulley 74 and the guide pulley 75a is the tension detecting device 80. The tension is detected through the guide roll 80a and the detection roll 80b, the deviation from the set value is fed back to the brake pulley 74, and the brake amount is adjusted. A pressing roll 74a is urged toward the brake pulley 74 by a spring 84 via a link. Rings 81a and 81b are connected to the guide pulley 75a, the proximity switch 82 faces the link 81a, and the spring 83 urges the guide pulley 75a in the arrow direction with the shaft 83a as a fulcrum. When excessive tension acts on the tape-shaped body 20 for some reason, the link 81a operates the proximity switch 82 to stop the feeding of the tape-shaped body 20. It is also possible to employ a system in which the pair of feeding means are moved so as to be separated from each other in the left-right direction from the center of the drum by using only one screw shaft having left and right reverse screws. In the above-mentioned apparatus, first, the winding start position, the winding end position, the winding pitch, the winding tension set value, etc. of the belt drum 6 in the width direction are set by the control means (not shown). Then, the belt drum 6 is rotated, and the tape-shaped body 20 is fed while a predetermined tension is applied by the brake pulley 74. And screw shafts 71a, 71b
By rotating the two in opposite directions, the feeding means 73b,
Traverse 73c from the winding start end position. As a result, the respective tape-shaped bodies 20 have a symmetrical structure, and are continuously spirally wound at a predetermined pitch. It should be noted that the winding start position (winding start end) and the winding end position (winding end end) of each tape-shaped body are preferably offset from each other in the circumferential direction. That is, the tape-shaped body 20
This is because the strength at the longitudinal end of the abruptly changes, and it is necessary to disperse the influence of this end as much as possible. Further, since stress tends to concentrate at the widthwise end of the belt 4, the longitudinal end of the tape-shaped body 20 should be as close to the belt 4 as possible.
It is preferable to locate it at the center portion in the width direction. Thus, by simultaneously operating the pair of feeding means 73b and 73c in mutually opposite directions, the time required for winding the cord 1 can be reduced to half of the time required when winding the cord 1 by a normal single winding means. Productivity can be doubled.
In particular, since the tape-shaped body 20 is used, the winding efficiency is further improved. If the cords 1 are not wound in a symmetrical structure, the tire cross-sectional shape will be distorted. However, the symmetrical structure as described above solves this problem. (Effects of the Invention) As described above, according to the present invention, two tapes each having a plurality of cords embedded in a rubber layer at a pitch of 0.5 to 5.0 mm are symmetrical with respect to the tire equatorial plane. The tape is wound so as to form a spiral structure so as to cover the entire belt layer, and one end of each tape is located near the tire equatorial plane, and the other end is located between the belt layer side end and the equatorial plane. By folding both side ends of each tape in this way, one layer was formed at the center of the belt and two layers were formed at the shoulders.
The difference in stretch between the belt shoulder and the center of the vulcanized tire is reduced, and the heat contraction force of the belt shoulder is improved, so the effect of preventing lifting of the belt during running is strongly demonstrated, and therefore during running. The peeling damage of the belt due to the lifting can be reliably prevented. Moreover, in the present invention, since the cord has a spiral structure symmetrical with respect to the equatorial plane of the tire, the tire uniformity is excellent, and since two tapes are wound at the same time, the productivity is also excellent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional explanatory view of an organic fiber cord applied to the present invention, and FIG. 2 (A) is a cross-sectional explanatory view of a belt reinforcing layer showing an embodiment of the present invention. 2 (B) and 2 (C) are explanatory views showing the winding loci of the cord of the present invention, respectively.
FIG. 4 is a front view showing an embodiment of an apparatus for carrying out the present invention, and FIG. 4 is a left side view of FIG. 1 ... Organic fiber cord, 2 ... Rubber coating, 4 ...
… Belt, 6 …… Belt drum, 7 …… Winding device, 20
...... A tape-shaped body with an integrated cord.

Claims (1)

(57) [Claims] At least one carcass consisting of a pair of beads and cords folded around this bead and locked and arranged in the radial direction, and at least two metal cord layers arranged radially outside of this carcass. And a pneumatic tire having a reinforcing layer arranged on the outer side in the radial direction of the belt, the reinforcing layer consisting of organic fiber cords wound substantially parallel to each other in the tire circumferential direction, wherein the reinforcing layer has a plurality of cords of 0.5. Two tapes embedded in the rubber layer with a pitch of ~ 5.0 mm are wound so as to form a spiral structure symmetrical with respect to the tire equatorial plane to cover the entire belt layer and one end of each tape. Is located near the equatorial plane of the tire, and both ends of each tape are folded back so that the other end is located between the belt layer side end and the equatorial plane. More belt central portion more, flat radial tire characterized by having formed on the two layers at the shoulder structure.