JPH07115567B2 - Pneumatic radial tires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention particularly relates to an improvement in a belt structure for improving high-speed durability of a flat pneumatic radial tire.

(Prior Art) In particular, with the recent increase in speed of pneumatic radial tires for passenger cars, the flatness of tires is becoming smaller and smaller, and at the same time, the belt structure is a conventional bias belt layer alone, especially on both sides or the entire belt. However, the high-speed durability of the belt tends to decrease due to the end effect of the belt that cannot be applied to the centrifugal effect.

Therefore, as shown in FIG. 1, an additional reinforcing layer composed of an organic fiber cord having a relatively large heat shrinkability is provided outside the original belt layer so that the cord is substantially parallel to the tire circumferential direction or one layer or Two layers are arranged and the method of forming the additional reinforcement layer is such that the entire width of the additional reinforcement layer is overlapped at one place on the circumference. Further, the additional reinforcement layer is used as a strip strip and the strip is wound in a spiral shape so that the joint width can be as wide as possible. There are techniques such as a method to reduce the number.

(Problems to be solved by the invention) Rather than overlapping and jointing the entire width of the additional reinforcing layer at one place on the circumference, the additional reinforcing layer is formed into a strip strip having a width of about 10 mm, and the strip is wound plural times in a spiral shape, The method of forming the additional reinforcing layer is preferable from the viewpoint of uniformity and high speed durability.

However, in recent years, there has been a trend toward ever-increasing speed, and there was no problem with the separation from the cord end that forms the additional reinforcing layer in the past, but ultra-flat tires called high-speed, high-performance tires (H / S
= 0.3 to 0.6), there is a possibility that the strip strip may be exposed to severe conditions such that separation occurs from the cord cut end of the unwinding end of the strip.

Therefore, the present invention is a tire in which the additional reinforcing layer is formed by winding a strip strip including a plurality of cords around the tire circumference a plurality of times, and a strip strip for improving separation from unwinding of the strip strip and cutting of the winding end. It is intended to provide the cut shape of the strip.

(Means for Solving Problems) As a result of various investigations by the present inventors, it was found that it is related to a change in the rigidity of the cut end, and specifically, it was achieved by the following method.

The flatness ratio H / S is 0.6 or less, the carcass layer extends substantially in parallel to the tire radial direction, and is located radially outward of the carcass layer and compared with the tire circumferential direction in the crown area. A belt layer composed of at least two layers of metal cords intersecting each other at a relatively small angle is arranged, and is in direct contact with the outermost layer of the belt layer, and surrounds at least both sides of the belt layer in the tire circumferential direction. In a pneumatic radial tire provided with an additional reinforcing layer made of a relatively large organic fiber having a relatively large heat shrinkage ratio arranged substantially in parallel, the additional reinforcing layer is a strip-shaped strip rubber-coated with a plurality of cords in the tire circumferential direction. Periphery length of the cut end at the winding end of the strip strip, which is rewound in a plurality of spirals, is at least twice the strip width. It was solved by having a constant inclination angle.

(Function) The belt layer is directly contacted with the outermost layer, and additional reinforcement for reinforcing at least both side areas of the belt layer is helically wound and shaped with a strip strip including a plurality of cords, and the strip strip is unwound and terminated. The reason why the peripheral edge of the cut end is cut obliquely with respect to the tire circumferential direction so that the peripheral length is at least 2 times or more, preferably 5 times or more of the strip width is that when the peripheral length is 2 times or less the strip width, A fault occurs, separation from that part occurs,
It reduces the high-speed durability.

It goes without saying that the additional reinforcing layer may be arranged so as to cover the entire belt layer. Particularly preferably, the additional reinforcing layer is two layers covering the entire width of the belt layer. In these cases, when the strip-shaped strip is wound and formed in a spiral shape, it is preferable that the unwinding and winding ends of the strip are substantially up to 1/4 of the tread width in view of the ground pressure during load rolling. High-speed durability can be improved.

(Example) Tire size: 255 / 40VR17 The tire carcass 1 has a structure in which two layers of rayon cord 1650d / 2 are arranged at 90 ° to the tire belt, and the bead core 2 is folded back from inside to outside, and the belt layer 3 is steel. A plurality of cords made of nylon cords arranged in parallel with each other in the tire circumferential direction are directly contacted with the outermost layer of the belt layer 3 having two layers in which the cords made of the cords intersect each other at 20 ° with respect to the tire circumferential direction. 1 shows a first embodiment in which a rubber strip S is spirally wound around a tire having a width of 10 mm, and the additional reinforcing layer 4 is arranged only on both sides of the belt layer.
In the second embodiment, the additional reinforcing layer 4 is formed in the same manner as the entire width of the belt layer, and in the third embodiment, the additional reinforcing layers of the first and second embodiments are arranged at the same time.

The cut end of the strip S, which is the point of the present invention, is cut at an angle of 5 ° with respect to the tire circumferential direction, and the peripheral length L is 11
It is 4 mm.

(Effects of the Invention) The conventional tire has substantially the same shape as the solid shapes in the first (A), second (B), and third (C) embodiments, except that the cut end of the strip strip S is different from the tire. 60 ° cutting in the circumferential direction (cutting edge peripheral length 11.5 mm and strip width 1.15
Double).

Table 1 shows the occurrence status (crack length) of the cord separation at the cut end of the strip of the tire of the present invention (Examples 2 and 3) when the conventional tires A, B, and C were set to 100 after constant running on the drum ( (300km / H, 5000km) Checked and indicated by an index, the smaller the index, the better the result.

The tire of the present invention shows a good result of about 20% as compared with the conventional tire.

[Brief description of drawings]

FIG. 1 is a partial sectional view in the circumferential direction of the pneumatic tire of the present invention. FIG. 2 is a partially developed view in the circumferential direction of the pneumatic tire of the present invention with the tread peeled off.

Claims (1)

[Claims] 1. A flatness H / S of 0.6 or less, at least one carcass layer extending substantially in parallel to a tire radial direction, and a radial outer side of the carcass layer, and a tire circumference in a crown area. A belt layer composed of at least two layers made of metal cords intersecting each other at a relatively small angle with respect to the direction is arranged, and is in direct contact with the outermost layer of the belt layer,
In a pneumatic radial tire provided with an additional reinforcing layer made of an organic fiber having a relatively large heat shrinkage ratio and arranged substantially parallel to the tire circumferential direction so as to surround at least both sides of the belt layer, the additional reinforcing layers are plural. A strip-shaped strip of the cord covered with rubber is spirally rewound a plurality of times in the tire circumferential direction, and the peripheral length of the cut end at the winding end of the strip-shaped strip is at least twice the strip-shaped width. As described above, a pneumatic radial tire having a constant inclination angle.