JP2003231405A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of preventing an air pressure from abruptly lowering by delaying a burst even if a carcass layer is broken by an impact when the tire rides on a small projection. <P>SOLUTION: In this pneumatic tire having at least the carcass layer 11 and a belt layer 12, a cord reinforcement layer 21 formed of reinforcement cords having an intermediate ductility larger than that of the carcass cord is disposed along the carcass body 11a of the carcass layer 11 starting near the end part of the belt layer 12 near to a bead core 13 so that the reinforcement cord 21 is positioned at ±20° or less relative to the carcass cord. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that prevents a shock burst when riding on a small projection or the like, and is particularly suitable for a tire having a low flatness. is there.

[0002]

2. Description of the Related Art In pneumatic tires, most tire breakage occurs in the sidewall portion. Therefore, measures to reinforce the sidewall portion have hitherto been disclosed in Japanese Patent Laid-Open Nos. 6-199113 and 2001-71715. Although it has been performed many times, it occurs when riding on a small projection (so-called cat's eye) that has a reflecting surface and a light emitting surface embedded in a road surface such as an intersection, which is increasing in recent years (cat's eye collision) The effective measures against the shock burst are mentioned as a subject.

In the shock burst due to the small projections, unlike the failure accompanied by the external damage that occurs when riding on a relatively large object such as a curb, the side rubber of the tire is not normally broken, and the carcass layer inside the tire is broken, In many cases, the side is bulged in appearance. When the carcass layer breaks, a burst accompanied by a rapid decrease in air pressure (rapid air loss) occurs, which may cause uncontrollable control and may cause a risk of falling. Also,
If the tire breakage due to the shock burst occurs before the end of its life due to tire wear, it is economically disadvantageous.

As a result of the failure investigation, the breakage of the carcass layer occurs near the shoulder, the center of the side, rarely near the bead, and the rubber is not cut due to elongation in the circumferential direction of the carcass layer. It is known that the carcass cord is cut in the direction.

It is presumed that when the side wall portion of the tire is relatively deformed, the carcass cord breaks because the carcass cord cannot absorb the deformation and the carcass cord is broken. Furthermore, near the edge of the belt layer, due to the influence of deformation suppression by the belt layer with high rigidity,
It is estimated that in the vicinity of the bead core, stress is concentrated on the carcass cord due to the influence of the tire being fixed by the rim flange having high rigidity, and the carcass cord is cut.

The above-mentioned phenomenon is such that the lower the tire flatness is, the more difficult it is for the carcass cord to absorb the deformation of the small protrusion when riding, so that the lower the flatness of the tire, the more easily the carcass cord is broken. Become. Further, the carcass layer formed by one ply is generated more frequently than the carcass layer formed by two plies.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire capable of delaying the burst even when the carcass layer is broken by an impact when riding on a small projection or the like and preventing a sudden decrease in air pressure. To provide.

[0008]

The pneumatic tire of the present invention for achieving the above object is a pneumatic tire having at least a carcass layer and a belt layer, and has an intermediate elongation greater than that of the carcass cord. A cord reinforcing layer including a reinforcing cord is provided along the carcass body of the carcass layer, and is arranged from the vicinity of the end portion of the belt layer to the vicinity of the bead core so that the reinforcing cord is ± 20 degrees or less with the carcass cord. Configured.

In the present invention, the intermediate elongation means cord 1.
The elongation rate (%) when a load of 66.7 N (6.8 kgf) is applied per wire.

Further, the carcass body means a portion excluding both folded-back portions when the carcass layer is laid over the bead cores on both sides.

According to the present invention, as described above, since the cord reinforcing layer made of the reinforcing cord having the intermediate elongation greater than the intermediate elongation of the carcass cord is arranged along the carcass body, the cat's eye or the like is not formed. Even if the carcass cord is broken without being able to absorb the deformation that occurs when the small protrusions are climbed up, the cord reinforcing layer having a high elongation absorbs the deformation and delays the burst, so that a sudden decrease in air pressure can be avoided.

The intermediate elongation of the reinforcing cord is preferably 1.05 to 1.3 times the intermediate elongation of the carcass cord. If it is less than 1.05 times, it becomes difficult to delay the burst after breaking the carcass cord. If it is more than 1.3 times, the load on the unbroken cord adjacent to the carcass broken cord becomes large, leading to tire destruction and no burst delay.

Further, the cord reinforcing layer is arranged so that the direction of the reinforcing cord is as close to the carcass cord of the carcass body as possible. That is, the reinforcing cords of the cord reinforcing layer are arranged so as to be within ± 20 degrees, preferably within ± 10 degrees, and most preferably 0 degrees with respect to the carcass cord of the carcass body. If it exceeds 20 degrees, the ability of the reinforcing cord to hold the deformation in the breaking direction of the carcass cord is lowered.

It is preferable that at least one of the both ends of the cord reinforcing layer is arranged at a distance of 2 to 10 mm from the end on the belt layer side or at a position of 2 to 10 mm from the outer peripheral end of the bead core.

With this structure, the cord reinforcing layer is in a floating state without overlapping with the belt layer or the bead core, and at least one end side is free from being restrained. Therefore, even if the sidewall portion of the tire deforms so much that the carcass cord is broken, the cord reinforcing layer can absorb the deformation due to the slip of the end portion and the elongation of itself. Further, if the end portion is left free without being restricted, even if the cord is the same as the cord of the carcass layer, the intermediate elongation does not decrease due to heat shrinkage during vulcanization.

In the present invention described above, in particular, the pneumatic tire in which the carcass cord of the carcass layer is in the semi-radial direction within ± 30 degrees with respect to the radial direction or the tire radial direction, and the flatness ratio is 60% or less, preferably Is effective when applied to a pneumatic tire having a tire cross-section height of 50% or less, or 120 mm or less, preferably 100 mm or less, and the effect of preventing shock burst due to small protrusions becomes remarkable.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Pneumatic tires according to embodiments of the present invention will be described below with reference to the drawings.

A pneumatic tire 1 according to an embodiment of the present invention shown in FIG. 1 has a radial tire structure and is provided inside the tire across a tread portion 2, a shoulder portion 3, a sidewall portion 4, and a bead portion 5. Carcass layer 11 that has been
The belt layer 12 disposed on the tread portion 2 is formed. In the configuration of FIG. 1, the carcass layer 11
Is formed by one carcass ply, and the belt layer 12
Is formed of two outer belt layers 12a and an inner belt layer 12b.

The carcass layer 11 is formed by rubberizing an organic fiber cord or a steel cord as a carcass cord. When the carcass layer 11 has a one-ply structure,
Although it is a radial with the direction of the carcass cord in the tire radial direction, in the case of a two-ply structure, a structure including a semi-radial in which the direction of the carcass cord is 0 to 30 degrees with respect to the tire radial direction can be adopted.

Both ends of the carcass layer 11 are generally constructed by winding up a bead core 13 formed by bundling a plurality of steel wires so as to wrap the bead filler 14 from the inside of the tire to the outside thereof. In the case of the two-ply structure, the outer carcass layer may be wound from the tire outer side to the inner side. An inner liner 15 made of low air-permeable rubber is provided inside the carcass layer 11.

In the carcass layer 11, the carcass body 11a which is the bead portion excluding the folded portion
The cord reinforcing layer 21 is arranged outside the area along the carcass body 11a so as to cover from the vicinity of the end 12e of the belt layer 12 to the vicinity of the bead core 13. The cord reinforcing layer 21 may be arranged inside the carcass body 11a. 2 to 4, the cord reinforcing layers 21A to 21C are provided outside the carcass main body 11a, and
In the embodiment of FIG. 7, the cord reinforcing layers 21D to 21F are arranged inside the carcass body 11a. All of the cord reinforcing layers 21, 21A to 21F have at least one end of both end portions of the belt layer 12 and / or the bead core 1.
I try not to overlap with 3.

The reinforcing cord of the cord reinforcing layer 21 includes
1.05 to 1.3 times, preferably 1.1 to 1.2 times the intermediate elongation of the carcass cord forming the carcass layer 11.
A cord with a median elongation of 5 times greater is used.
The material of the reinforcing cord is not particularly limited, but preferably an organic fiber cord such as polyester fiber or nylon fiber. This cord may have substantially the same diameter, the same number of ends, and the same material as the carcass cord as long as it satisfies the above conditions as the intermediate elongation.

Since the reinforcing cord has the above structure,
Even if the carcass cords of the carcass layer 11 cannot be completely absorbed and deformed when the small protrusions are ridden, the cord reinforcing layer absorbs the deformations and delays the burst of the tire, so that the shock burst can be avoided.

The cord direction of the cord reinforcing layer 21 is
The angle is within ± 20 degrees, preferably within ± 10 degrees, and most preferably 0 degrees with respect to the cord direction of the carcass layer 11. In this way, by making them substantially in the same direction, the strength utilization rate of the cord reinforcing layer 21 can be effectively utilized for holding the carcass layer 11.

Further, the cord reinforcing layer 21 is not fixed to the bead core 13 or the belt layer 12 at both ends, and one end or both ends may be floating. That is, at least one end portion of the cord reinforcing layer 21 is preferably separated from the bead core 13 or the belt layer 12 by 2 to 10 mm. That is, the distance Sa along the carcass body 11a in FIGS. 1 and 2 and the distance Sb along the carcass body 11a in FIG. 3 are set to 2 to 10 mm.

In FIGS. 1, 2 and 7, the end 21a on the bead core 13 side is free, in FIGS. 3 and 6, the end 21b on the belt layer 12 side is free, and in FIGS. 4 and 7. Both the end 21a on the bead core 13 side and the end 21b on the belt layer 12 side are free.

With the construction in which at least one end of the cord reinforcing layer 21 is not restrained in this way, even if the sidewall portion 4 of the tire is largely deformed by riding on a small protrusion, the cord reinforcing layer 21 has a free end portion. Since it slips to release the deformation load, it absorbs impact energy and
The occurrence of code breaks can be suppressed.

According to the above-mentioned tire structure of the present invention, even if the carcass cord is broken due to a large deformation such as a cat's-eye impact when a small protrusion rides,
Since the cord reinforcing layer 21 can absorb and delay the shock burst, it is possible to avoid a fall accident due to inability to control.

[0029]

EXAMPLES In a tire structure having a tire size of 215 / 45R17 and a single carcass layer in FIG. 1, the intermediate elongation of the cord of the cord reinforcing layer is 1.1 times the intermediate elongation of the carcass cord of the carcass layer, And a pneumatic tire (Example) in which the reinforcing cord is set to 0 degrees with respect to the carcass cord,
Two types of pneumatic tires, comparative tires without the cord reinforcing layer, were manufactured.

When the breaking energy of these two types of pneumatic tires was measured, the breaking energy of the comparative tire was 0.111 kN · m (index 100), but a sudden drop in air pressure was observed. On the other hand, in the example tire, 0.156 kN · m (index 141),
No sudden decrease in air pressure was observed.

[0031]

As described above, according to the pneumatic tire of the present invention, the cord reinforcing layer is arranged from the vicinity of the end of the belt layer to the vicinity of the bead core along the inside or outside of the carcass body, Since the reinforcing cord used has a larger intermediate elongation than the carcass cord, even if the carcass cord breaks due to deformation such as when riding on a small protrusion, the cord reinforcing layer absorbs the deformation and bursts. Can be delayed.

Therefore, steerability of the tire does not occur due to a sudden decrease in air pressure, and the safety of the tire can be improved.

[Brief description of drawings]

FIG. 1 is a half cross-sectional view showing the configuration of a pneumatic tire according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing a positional relationship among a cord reinforcing layer, a carcass layer, and a belt layer of the pneumatic tire of the first embodiment.

FIG. 3 is a cross-sectional view schematically showing a positional relationship among a cord reinforcing layer, a carcass layer, and a belt layer of the pneumatic tire of the second embodiment.

FIG. 4 is a sectional view schematically showing a positional relationship among a cord reinforcing layer, a carcass layer, and a belt layer of a pneumatic tire according to a third embodiment.

FIG. 5 is a cross-sectional view schematically showing a positional relationship among a cord reinforcing layer, a carcass layer and a belt layer of a pneumatic tire according to a fourth embodiment.

FIG. 6 is a sectional view schematically showing a positional relationship among a cord reinforcing layer, a carcass layer and a belt layer of a pneumatic tire according to a fifth embodiment.

FIG. 7 is a cross-sectional view that schematically shows the positional relationship among a cord reinforcing layer, a carcass layer, and a belt layer of a pneumatic tire according to a sixth embodiment.

[Explanation of symbols]

1 pneumatic tire 11 carcass layers 11a Carcass body 12, 12a, 12b Belt layer 12e Edge of belt layer 13 bead core 14 bead filler 21,21A-21F Cord reinforcement layer 21a End of the cord reinforcing layer on the bead wire side 21b Belt-side end of the cord reinforcing layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shinichi Itagaki             2-1, Oiwake, Hiratsuka-shi, Kanagawa Yokohama Rubber Co., Ltd.             Ceremony Company Hiratsuka Factory

Claims (6)

[Claims] 1. In a pneumatic tire having at least a carcass layer and a belt layer, a cord reinforcing layer made of a reinforcing cord having an intermediate elongation greater than that of the carcass cord is provided along a carcass body of the carcass layer. And a pneumatic tire arranged from the vicinity of the end of the belt layer to the vicinity of the bead core so that the reinforcing cord is within ± 20 degrees from the carcass cord. 2. The pneumatic tire according to claim 1, wherein the intermediate elongation of the reinforcing cord is 1.05 to 1.3 times larger than the intermediate elongation of the carcass cord. 3. The pneumatic tire according to claim 1, wherein at least one end of the cord reinforcing layer is floated at a distance of 2 to 10 mm from the end of the belt layer or the outer peripheral end of the bead core. 4. The pneumatic tire according to claim 1, 2 or 3, wherein the reinforcing cord is made of the same material and has the same diameter as the carcass cord. 5. The pneumatic tire according to claim 1, wherein the carcass cord of the carcass layer is in a radial direction or a semi-radial direction within ± 30 degrees with respect to a tire radial direction. 6. An aspect ratio of 60% or less, or a tire cross-sectional height of 120 mm or less.
The pneumatic tire according to item.