Patent Application
20200031175
The present invention relates to a heavy load tire and a method for manufacturing a heavy tire, in particular, a heavy load tire having superior separation resistance around a bead core and a method for manufacturing the heavy load tire.
In a bead core formed by a bead wire wound in a ring shape, a technique to suppress jumping of the bead wire is known. In the invention disclosed in Patent Literature 1, the jumping of the bead wire is suppressed by winding an organic fiber tape on an end portion of the bead wire.
[PTL 1] Japanese Unexamined Patent Application Publication No. 2016-088259
A use condition of a tire such as a heavy load tire used in a severe environment under a high speed and a heavy load might become further severe, and therefore high durability and high degradation resistance of the tire are required. Specifically, improvement of separation resistance around a bead core is expected.
Accordingly, an object of the present invention is, in consideration of the problem described above, to provide a heavy load tire capable of improving separation resistance around a bead core and a method for manufacturing the heavy load tire.
The inventors conducted a study and recognized that the separation resistance around the bead core has been improved by using a rubber sheet described below instead of a conventional organic fiber tape, so that the present invention was completed.
A heavy load tire according to a first aspect includes a bead core formed by a bead wire wound plural times in a ring shape, and a rubber sheet formed of a rubber material. The rubber sheet is wound on a region including one end portion and another end portion of the bead wire. The one end portion is served as an end portion closest to the another end portion in a tire circumferential direction.
In the first aspect, a tensile stress M50 at 50% elongation of the rubber sheet, which is measured based on JIS K6251 under a condition of a measurement temperature of 25° C. after vulcanization, is 1.0 MPa or more.
A method for manufacturing the heavy load tire according to the first aspect includes winding a rubber sheet formed of a rubber material on a region including one end portion and another end portion of the bead wire, and vulcanizing after winding the rubber sheet. The one end portion is served as an end portion closest to the another end portion in the tire circumferential direction.
According to the present invention, the separation resistance around the bead core in the heavy load tire is improved.
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The same reference signs are assigned to the same parts in the drawings and the description thereof is therefore omitted.
A configuration of a heavy load tire 1 according to the present embodiment is described with reference to
As shown in
The bead portion 2 has a bead core 5 and a bead filler 6. The carcass layer 3 is extended between the bead cores 5 in a troidal manner.
At least two bead cores 5 are arranged to be separated to each other in a tread width direction. Further, the bead core 5 is formed by one bead wire 8 wound plural times in a ring shape. The bead core 5 is formed to support cord tension of the carcass layer 3 generated due to inner pressure of the heavy load tire 1. The bead wire 8 is coated with a rubber material.
The bead filler 6 is a rubber element for reinforcing the bead core 5. The bead filler 6 is arranged in a space formed by folding both end portions of the carcass layer 3 at positions corresponding to the bead cores 5, toward respective outer side in a tire width direction.
A belt layer 7 is arranged between the carcass layer 3 and the tread portion 4. A plurality of the belt layers 7 is extended along a tire circumferential direction so as to be laminated to each other.
As shown in
The rubber sheet 10 used in the present embodiment is mainly formed of natural rubber, however it is not limited to this. A tensile stress M50 at 50% elongation of the rubber sheet 10, which is measured based on JIS K6251 under a condition of a measurement temperature of 25° C. after vulcanization, is 1.0 MPa or more. Here, the rubber sheet 10 used in the present embodiment has a width of 45 mm, a thickness of 1 mm, and a length of 400 mm, however the dimensions thereof is not limited to those.
As shown in
A method for manufacturing the heavy load tire 1 according to the present embodiment is described with reference to a flow chart shown in
In the bead core forming step S10, one bead wire 8 is wound plural times in a ring shape so as to form the bead core 5.
In the rubber sheet winding step S20, the rubber sheet 10 is wound on the region including the winding start end portion 8a and the winding finish end portion 8b of the bead wire 8.
In the vulcanizing step S30, a green tire having the bead core 5 on which the rubber sheet 10 is wound is vulcanized so as to form the heavy load tire 1.
Next, a compared result is described with reference to
A horizontal axis in
As shown in
As described above, according to the present embodiment, the heavy load tire 1 includes the rubber sheet 10, and the rubber sheet 10 is wound on the region including the winding start end portion 8a and the winding finish end portion 8b of the bead wire 8. With this, the separation resistance around the bead core 5 in the heavy load tire 1 is improved, compared to the configuration in which the conventional organic fiber tape is wound.
The entire contents of Japanese Patent Application No. 2016-238233 (filed on Dec. 8, 2016) are incorporated in the present specification by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-238233 | Dec 2016 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2017/042324 | 11/27/2017 | WO | 00 |
