JPH1044711A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten edge separation resistance of a belt layer so as to improve belt durability by arranging rubber, containing short fiber at specified weight percent, between an edge part of a belt layer and a belt cover layer. SOLUTION: Lateral side wall parts are extended on the radial outer side of a tire being connected to lateral bead parts. A tread part 1 extended in the circumferential direction of the tire is provided between the side wall parts 3. Annular bead cores 5 are respectively embedded in the lateral bead parts 2, and a bead filler 6 is provided at the outer periphery of each bead core 5. An end part 4A of a carcass layer 4 holds the bead filler 6 in and is folded around the bead core 5. A rubber layer 9 containing short fiber at 20-50wt% is provided between an edge part 7x of a belt layer 7 and a belt cover layer 8. The rubber layer 9 reinforced by the short fiber is laminated on the outer peripheral side of the edge parts of belt layers 7A, 7B while covering a stepped part 7y.

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 having a belt cover layer provided on an edge portion of a belt layer to enhance edge separation resistance of the belt layer. .

[0002]

2. Description of the Related Art In a belt layer in which cut ends of a reinforcing cord are located at both ends in the width direction of a tire, stress concentrates on the cut end during running, and the tension of the reinforcing cord is reduced at the end. Is easy to occur. Therefore, as a countermeasure, there is a proposal of a pneumatic tire in which a belt cover layer in which organic fiber cords are arranged in the tire circumferential direction is provided on the outer peripheral side of the belt layer so as to cover an edge portion of the belt layer. By covering the edge of the belt layer in this way,
A reduction in the tension of the reinforcing cord at the end is suppressed, the edge separation resistance of the belt layer is increased, and the belt durability is improved.

[0003] By the way, a plurality of such belt layers are provided on the outer peripheral side of the carcass layer in the tread portion. A step occurs at the edge of the belt layer due to the difference in belt width, and the belt cover layer is provided so as to cover the step. In particular, in pneumatic tires used for heavy-duty vehicles such as light trucks, buses, and ordinary trucks,
The step is large.

In such a pneumatic tire having a large step at the edge portion of the belt layer, there is a risk that air remains between the belt cover layer and the edge portion of the belt layer after the tire is formed.
If the air remains in this manner, the adhesion between the belt cover layer and the edge portion of the belt layer is reduced, and thus the binding force of the belt layer edge portion by the belt cover layer is reduced. For this reason, due to a decrease in the tension of the reinforcing cord of the belt layer, edge separation resistance is reduced, and belt durability is deteriorated.

Therefore, as a countermeasure, there is a proposal to insert a rubber layer between the belt cover layer and the edge portion of the belt layer. By filling the space between the belt cover layer and the belt layer edge where the air remains in this manner with the rubber layer,
An air pool is suppressed from occurring. But,
When the rubber layer is interposed in this way, the rubber layer acts as a cushion, so that the reinforcing cord of the belt cover layer cannot sufficiently exert the hoop effect of restraining the edge of the belt layer, resulting in sufficient belt durability. There is a problem that the effect of improving the properties cannot be obtained.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire in which a belt cover layer is provided at an edge portion of a belt layer, even if a step at the edge portion of the belt layer is large, the edge separation resistance of the belt layer. It is an object of the present invention to provide a pneumatic tire capable of improving the durability and belt durability.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method of laminating a plurality of belt layers having different belt widths on the outer peripheral side of a carcass layer of a tread portion, and facing the tread portion surface side due to a difference in belt width. In a pneumatic tire provided with a belt cover layer in which reinforcing cords are arranged on an outer peripheral side of the belt layer edge portion so as to cover a step portion generated at an edge portion of the belt layer, a gap between the belt layer edge portion and the belt cover layer is provided. And a rubber layer containing 20 to 40% by weight of short fibers.

As described above, since the rubber layer is provided between the belt layer edge portion and the belt cover layer, even if the step at the belt layer edge portion is large, the belt cover layer is formed in the same manner as when the conventional rubber layer is disposed. The space between the belt layer and the edge of the belt layer where there is a danger of air remaining can be filled with the rubber layer, so that the adhesion between the belt cover layer and the belt layer edge due to the occurrence of air pockets may be reduced. Absent.

Further, since the rubber layer for suppressing the generation of air pockets is made of rubber containing 20 to 40% by weight of short fibers, it is possible to greatly increase the hardness as compared with the conventional rubber layer consisting only of rubber. it can. Therefore, the amount of crushing of the rubber layer reinforced with short fibers is suppressed as much as possible, and the belt cover layer in which the reinforcing cords are arranged via such a rubber layer has a high tagging effect of restraining the belt layer edge. Can be demonstrated.

Therefore, in a pneumatic tire provided with a belt cover layer at the edge of the belt layer, even if the step at the edge of the belt layer is large, the belt cover layer enhances the edge separation resistance of the belt layer, Durability can be improved.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows an example of the pneumatic tire of the present invention, wherein 1 is a tread portion, 2 is a bead portion, and 3 is a sidewall portion. Left and right sidewalls 3 are extended outwardly in the tire radial direction in connection with the left and right bead portions 2, and a tread portion 1 extending in the tire circumferential direction is provided between the left and right sidewall portions 3. One carcass layer 4 is provided inside the tire. An annular beat core 5 is embedded in each of the left and right bead portions 2, and a bead filler 6 is provided on the outer periphery of the beat core 5. Both ends 4 </ b> A of the carcass layer 4 are folded around the beat core 5 from the inside to the outside of the tire so as to sandwich the bead filler 6.

On the outer peripheral side of the carcass layer 4 of the tread portion 1,
The reinforcing cords are arranged obliquely with respect to the tire circumferential direction, and two layers of belt layers 7 intersecting with each other are embedded. The two belt layers 7 are configured to have different belt widths. The belt width of the inner first belt layer 7A adjacent to the carcass layer 4 is the same as that of the second belt layer 7
It is formed wider than the belt width of B. Due to the difference between the belt widths of the two belt layers 7A and 7B, step portions 7y are formed at both edge portions 7x of the two belt layers 7 facing the surface 1A side of the tread portion 1, respectively. I have.

An annular belt cover layer 8 formed by embedding a reinforcing cord made of nylon fibers or the like in the tire circumferential direction in rubber is provided on the outer peripheral side of both edge portions 7x of the belt layer 7. I have. This belt cover layer 8
Extends from the edge 7a of the first belt layer 7A having a wide belt width to the inside in the tire width direction so as to cover the stepped portion 7y, and covers the edge portions of both belt layers 7A and 7B from the outer peripheral side thereof. Has become.

In the present invention, in the pneumatic tire configured as described above, a rubber layer 9 containing 20 to 40% by weight of short fibers is provided between the edge portion 7x of the belt layer 7 and the belt cover layer 8. Have been. The rubber layer 9 reinforced with the short fibers is laminated on the outer peripheral side of the edge portions of the belt layers 7A and 7B so as to almost overlap the belt cover layer 8 in plan view while covering the step portion 7y of the belt layer 7. Have been.

By providing the rubber layer 9 between the belt layer edge 7x and the belt cover layer 8 as described above, even if the step at the belt layer edge 7x is large, the rubber layer 9 can be used as the belt cover layer. Since air is buried in the space between the belt member 8 and the belt layer edge portion 7x where air may remain, it is possible to suppress the occurrence of air accumulation. In addition, since the rubber layer 9 is configured to contain 20 to 40% by weight of short fibers, the hardness can be greatly increased as compared with the conventional rubber layer composed of only rubber. By means of the belt cover layer 8 on which reinforcing cords are arranged via 9, the hoop effect of restraining the belt layer edge portion 7x can be sufficiently exerted. Therefore, the edge separation resistance of the belt layer 7 can be improved, and the belt durability can be improved.

If the content of the short fibers in the rubber layer 9 is less than 20% by weight, the hardness of the rubber layer 9 is reduced, so that the belt cover layer 8 has an insufficient rebound effect. On the other hand, if it exceeds 40% by weight, there arises a problem that the step at the belt edge cannot be sufficiently filled. The rubber layer 9 is
JIS hardness of 55 or more, and 20 showing viscoelasticity
It can be composed of a rubber having a tan δ of 0.38 or less. When the JIS hardness is less than 55 or the tan δ at 20 ° C. is more than 0.38, the rubber layer 9 reinforced with short fibers is used.
The hardness of the belt cover layer becomes insufficient, so that it is difficult to sufficiently exert the hoop effect by the belt cover layer 8. From the viewpoint of sufficient filling effect and adhesiveness, the upper limit of JIS hardness is 65,
The lower limit of 20 ° C. tan δ can be 0.06.

The short fibers mixed into the rubber layer 9 may be either inorganic or organic fibers, and preferably organic fibers. As this organic fiber, for example, a nylon fiber can be preferably exemplified. The length of the short fiber can be 20 to 40 μm, and the diameter thereof can be 0.15 to 0.45 μm. Preferably, the short fibers have a length of about 30 μm and a diameter of about 0.3 μm.
m is good.

In the above embodiment, the case where the belt cover layer 8 is provided on the outer peripheral side only at the edge portion of the belt layer 7 has been described. However, the belt cover layer 8 is provided on the outer peripheral side of the belt layer 7 so as to cover the entire belt layer. The belt cover layer 8 may be a belt cover layer, as long as the belt cover layer 8 covers at least an edge portion of the belt layer.

Further, in the present invention, an example in which two belt layers are provided in the above-described embodiment has been described. However, the present invention is not limited to this, and a step is formed at the belt layer edge portion facing the tread surface side. Needless to say, two or more belt layers may be provided. INDUSTRIAL APPLICABILITY The present invention can be particularly suitably applied to a pneumatic tire used in a heavy-duty vehicle such as a light truck, a bus, or a normal truck, in which a step at a belt layer edge portion is large and air is likely to remain.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a tire according to the present invention in which the tire size is common to 195 / 85R16 and a rubber layer containing short fibers is disposed between a belt cover layer and an edge portion of a belt layer. A conventional tire 1 without a rubber layer reinforced with short fibers and a conventional tire 2 with a rubber layer made of only rubber instead of the rubber layer reinforced with short fibers in FIG. 1 were produced.

The short fiber content of the rubber layer of the tire of the present invention is 3
0% by weight, and the rubber layer has a JIS hardness of 5
7, 20 ° C. It is composed of rubber having a tan δ of 0.35. 6 nylon is used for the short fiber, and its diameter is about 0.3 μm and its length is about 30 μm. Each of the test tires was subjected to a belt durability evaluation test under the following measurement conditions, and the results shown in Table 1 were obtained. Belt durability Each test tire was mounted on a JATMA standard rim and the air pressure was 4
At 50 kPa, an indoor drum test was performed to measure the durability until the tire (edge portion of the belt layer) was broken,
The result was evaluated by an index value with the conventional tire 1 being 100. The greater the value, the better the belt durability.

[0022]

[Table 1] As is clear from Table 1, it is understood that the tire of the present invention can obtain high belt durability.

[0023]

As described above, the present invention relates to a pneumatic tire in which a belt cover layer is provided at an edge of a belt layer, wherein a short fiber is present at 20 to 40% by weight between the belt layer edge and the belt cover layer. Since the rubber layer is contained, even if the step at the edge of the belt layer is large, the edge separation resistance of the belt layer can be improved, and the belt durability can be increased.

[Brief description of the drawings]

FIG. 1 is a sectional view of an essential part of a tire meridian showing an example of a pneumatic tire of the present invention.

[Explanation of symbols]

Reference Signs List 1 tread portion 1A tread portion surface 4 carcass layer 7 belt layer 7A first belt layer 7B second belt layer 7x edge portion 7y step portion 8 belt cover layer 9 rubber layer

Claims (3)

[Claims] A plurality of belt layers having different belt widths are laminated on an outer peripheral side of a carcass layer of a tread portion so as to face a tread portion surface side due to a difference in belt width so as to cover a step portion generated at an edge portion of the belt layer. In a pneumatic tire provided with a belt cover layer in which reinforcing cords are arranged on the outer peripheral side of the belt layer edge portion, between the belt layer edge portion and the belt cover layer,
A pneumatic tire having a rubber layer containing short fibers of 20 to 40% by weight. 2. The pneumatic tire according to claim 1, wherein the rubber constituting the rubber layer has a JIS hardness of 55 or more and a tan δ at 20 ° C. of 0.38 or less. 3. The staple fiber having a diameter of 0.15 to 0.45 μm.
3. The pneumatic tire according to claim 1, wherein the pneumatic tire is made of organic fibers having a length of 20 to 40 [mu] m.