JP2002254910A - Tire, and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the road holding of a tire by providing a bead part structure enabling deformation of a carcass ply around a bead core without degrading the torsional rigidity of the bead core. SOLUTION: In the tire comprising a carcass body in which at least one carcass ply is extended in a troidal manner from a tread part to a bead part via a side wall part, and a return part in which the ply is returned from the inside to the outside in the width direction of the tire around the bead core embedded in each bead part, the bead core is surrounded by a lined rubber layer disposed along the carcass ply between the carcass ply and the bead core in the bead part structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire exhibiting excellent running stability during turning of a vehicle, and more particularly to a tire suitable for use in a motorcycle.

[0002]

2. Description of the Related Art A motorcycle is a great feature different from a four-wheeled vehicle in that the vehicle turns at a large inclination when traveling in a corner or the like, and the tire applied to the motorcycle has excellent running stability when turning. Is essential. As a method for ensuring the running stability at the time of turning, it is effective to improve the contact property of the tire. For that purpose, it is preferable that the carcass inside the tire as well as the tread rubber of the tire be easily deformed.

As a means for easily deforming the carcass, it is effective to allow the carcass ply wound around the bead core to move to some extent in the axial direction.

[0004]

However, in order to allow the movement of the carcass ply, it is necessary to reduce the torsional rigidity of the bead portion, especially the bead core, which leads to a decrease in the breaking strength of the bead portion and also during running. In addition, it is difficult to increase the amount of deformation of the carcass since the tire and the rim are displaced in the tire circumferential direction or the width direction, resulting in rim displacement. Note that, among the rim shifts, a shift in the tire width direction leads to a worst case of a bead dropping off the bead portion from the rim and a bead drop.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bead portion structure capable of deforming a carcass ply around the bead core without lowering the torsional rigidity of the bead core, thereby improving the tire's contact property. It is in. Another object of the present invention is to propose a method for advantageously producing a tire having the above-described bead portion structure.

[0006]

That is, the gist of the present invention is as follows. (1) A carcass body in which at least one carcass ply is extended in a toroidal shape from a tread portion to a bead portion via a sidewall portion, and a bead core in which the ply is embedded in each bead portion, in a tire width direction. Tire having a folded portion folded from the inside to the outside of the tire,
An inner rubber layer arranged along the carcass ply between the carcass ply and the bead core surrounds the periphery of the bead core, and when the standard rim of the tire is mounted, the compression ratio of the bead core radially inner portion of the bead portion is 1.25. A tire characterized by being 1.33 to 1.33.

(2) The tire according to the above (1), wherein the tire is a two-wheeled automatic tire.

(3) The tire according to (1) or (2), wherein the thickness of the lining rubber layer is 0.5 mm or more.

(4) In any one of the above (1) to (3), the hardness of the lining rubber layer is 50 to 70 and the hardness of the highest hardness rubber in a region sandwiched between the carcass body and the folded portion is Tire characterized by being 50 to 80.

(5) In any one of the above (1) to (4), the distance of the lining rubber layer from the outermost bead base surface in the tire radial direction is 10 to 35% of the tire section height. Features tires.

(6) The tire according to any one of the above (1) to (5), wherein the bead core is a cable bead.

(7) After a squeegee rubber is stuck to the molded body to which the carcass ply is stuck, a bead ring is fitted to the width center of the squeegee rubber or in the vicinity thereof.
Next, after folding both sides of the carcass ply starting from the bead ring, a belt material and a tread material are pasted on the carcass ply to produce a raw tire, and the raw tire is subjected to a vulcanization step. Manufacturing method.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a tire according to the present invention will be described with reference to the drawings. FIG. 1 is a sectional view in the tire width direction showing an embodiment of the present invention for one bead portion. The tire includes a carcass body 1a including at least one carcass ply 1 extending from a tread portion (not shown) through a sidewall portion to a bead portion 2 in a toroidal manner, and a carcass body 1a.
a folded portion 1 that is wound from the inside in the tire width direction to the outside in the tire width direction around the bead core 3 in which the carcass ply 1 is embedded in the bead portion 2 from each side portion of FIG.
b).

Here, the carcass ply 1 and the bead core 3
And a lining rubber layer 4 disposed along the carcass ply 1, and the bead core 3 is formed by the lining rubber layer 4.
It is important to surround the surrounding area. That is, as shown in FIG. 2, the carcass receives a force in the direction of arrow J due to the vehicle weight and the cornering force.
When the lining rubber layer 4 is disposed around the bead core 3, the distance I from the axis of the bead core 3 to the carcass body 1a increases as compared with the conventional structure in which the carcass ply is directly wound around the bead core 3, and the rotational moment around the bead core 3 Since J × I is increased, the amount of deformation of the carcass according to the force in the direction of arrow J can be increased as compared with the conventional structure. As a result, it is possible to provide a tire suitable for a motorcycle tire which is improved in contact with the tire and particularly excellent in turning performance.

In addition, when the tire is mounted on a standard rim,
It is also important to set the compression ratio of the bead core 2 in the radial direction inside the bead core 3 in the range of 1.25 to 1.33. That is, the compression rate is the bead core 3
Shows the change in the thickness of the rubber from the radially inner end to the bead base before and after the standard rim is mounted on the tire, and is defined as follows.

That is, in the tire before mounting the standard rim shown in FIG. 3A, 1/2 of the inner diameter of the bead core 3 is e, and the bead base portion 2a on the diameter of the bead core 3 passing through the axis of the bead core 3 is shown. In the tire after the standard rim 5 is mounted as shown in FIG. 3B, ｄ of the diameter is d, and similarly, の of the inner diameter of the bead core 3 is E, and the bead core 3 passing through the axis of the bead core 3 is similarly. A half of the diameter of the bead base portion 2a on the diameter is D, and the diameter of the cord or filament constituting the carcass ply is α, and the diameter of the cord or filament constituting the other bead reinforcing material, for example, chafer or the like. Where β is the sum of
The compression rate can be obtained by the following equation. (Compression rate) = {ed- (α + β)} /
{ED- (α + β)}

The compression rate is 1.25 to
It is important to be in the 1.33 range. This is because if the compression ratio is less than 1.25, rim misalignment is likely to occur, while if the compression ratio exceeds 1.33, the fitting pressure when filling the tire with gas increases, and the rim assemblability deteriorates.

Preferably, the thickness of the lining rubber layer 4 is 0.5 mm or more. That is, when the thickness of the lining rubber layer 4 is less than 0.5 mm, it is difficult to sufficiently increase the rotational moment around the bead core. It should be noted that securing the thickness of the lining rubber layer 4 is also effective in keeping the variation within a minimum range when the thickness of the coating rubber of the carcass ply and the coating rubber of the bead core vary during manufacturing.

In the illustrated example, since the number of carcass plies is one, the total thickness of the rubber portion occupying the area up to the carcass ply 1 is substantially the thickness of the lining rubber layer 4, and the carcass is composed of a plurality of layers. In this case, the total thickness of the rubber portion occupying the region up to the outermost carcass ply is a thickness obtained by subtracting the diameter of the cord or filament of the outermost carcass ply. In any case, it is needless to say that the diameters of the cords and the filaments constituting the bead portion reinforcing material, for example, the chafer or the like are removed.

Further, the hardness of the lining rubber layer 4 is preferably 50 to 70, and the hardness of the highest hardness rubber in a region sandwiched between the carcass body 1a and the folded portion 1b is advantageously 50 to 80. That is, if the hardness of the lining rubber layer 4 is less than 50, it is difficult to secure the rigidity required particularly at high speed running, while if the hardness exceeds 70, the riding comfort, the security at cornering and the rim assembly are improved. Sex is inhibited.

If the hardness of the maximum hardness rubber is less than 50, it is difficult to secure the required lateral rigidity particularly at high speed turning, while if the hardness exceeds 80, the riding comfort and the sense of security at cornering are increased. And rim assembly are impaired.

Further, as shown in FIG. 1, the outermost bead core base surface 2 of the lining rubber layer 4 in the tire radial direction is provided.
It is preferable that the distance h from a is 10 to 35% of the tire section height. Because the distance h is 10 times the tire section height
When the distance h is less than 35%, it is difficult to secure the necessary lateral rigidity when turning, and furthermore, to secure the stability when turning. On the other hand, when the distance h exceeds 35%, the riding comfort, cornering security, and rim assembling properties are improved. This is because such is hindered.

It is recommended to use a cable bead for the bead core. In other words, since the cable bead is formed by winding a wire around a spiral and forming it into a ring shape, in comparison with a bead core having a square or hexagonal cross section, the movement of the carcass around the bead core axis is smooth. Is possible.

Next, the method for producing the tire of the present invention will be described in detail. First, when one carcass ply is provided, as shown in FIG. 4A, a squeegee rubber 11 serving as the lining rubber layer 4 is placed at a predetermined position on a molded body 10 obtained by laminating the carcass ply 1 on a drum. Then, a bead ring 12 is fitted to the center of the width of the squeegee rubber 11 or in the vicinity thereof, and then, as shown in FIG. Then bead ring 12 squeegee rubber
A structure that forms a bead portion that surrounds 11 in a substantially triangular cross section is formed. Thereafter, a belt material and a tread material are sequentially pasted on the carcass ply of the molded body 10 to produce a raw tire, and the raw tire may be subjected to a vulcanization step.

When there are a plurality of carcass plies,
As shown in FIG. 5A, the first carcass ply 10a
After the squeegee rubber 11 serving as a lining rubber layer is attached to a predetermined position, the second carcass ply 10b is attached thereto.
As shown in (b), manufacturing is performed in the same procedure as above.

Alternatively, as shown in FIG. 6A, after the two carcass plies 10a and 10b are bonded on a drum, a squeegee rubber 11 serving as a lining rubber layer is bonded at a predetermined position. As shown in FIG. 6B, manufacturing is performed in the same procedure as above.

In the tire manufacturing method described above, in particular, the region R (FIG. 1) surrounded by the carcass body 1a and the folded portion 1b.
), It is advantageous to secure the rigidity indispensable for the tire. That is,
A region R surrounded by the carcass body 1a and the folded portion 1b
In general, a relatively hard rubber called a so-called bead filler is disposed, but the cross-sectional area of the bead filler in the tire width direction is determined by a lateral rigidity and a riding property required during high-speed running. Since this has a very large effect on comfort, it is necessary to keep this cross-sectional area constant at all times, and high precision has been required during tire manufacturing.

That is, conventionally, in order to form a bead filler having a predetermined cross-sectional area, a rubber sheet having a predetermined shape is produced by extrusion molding at a high temperature using a die, and the obtained rubber sheet is attached to the outside of a bead core. However, it was extremely difficult to precisely maintain the cross-sectional area of the rubber sheet.

In the method of manufacturing by extrusion using a die, the shape of the opening of the die and the cross-sectional shape of the rubber extruded at a high temperature after being cooled and stabilized in many cases are often different. Because it is greatly affected and difficult to predict, it is difficult to keep the molding accuracy high especially when a bead filler having a small cross-sectional area is required.

On the other hand, in the manufacturing method of the present invention, since the squeegee rubber having a predetermined thickness is turned back in advance and the region R is partitioned by the squeegee rubber, the bead filler can be formed by the squeegee rubber. Become. Furthermore, compared to the method of manufacturing a rubber sheet having a predetermined shape by extrusion molding with a die, the area R can be filled with an appropriate amount of rubber with squeegee rubber having a fixed width and thickness. The quantity can be kept constant with high precision. Because, during vulcanization, the region R
By the carcass body 1a and the folded portion 1b surrounding the
This is because the flow of the squeegee rubber is prevented, and the squeegee rubber is prevented from flowing out of the region R. Like,
Since the variation in the amount of rubber in the region R during manufacturing can be suppressed,
It is possible to stably impart excellent steering stability and ride comfort to the obtained tire.

When the entire area R is formed of the above-mentioned lining rubber layer 4, if the thickness of the squeegee rubber forming the lining rubber layer 4 is increased, a bead structure as shown in FIG. 7 is realized. . Here, reference numeral 6 denotes a chafer for reinforcing the bead portion.

When it is desired to arrange a rubber type different from the lining rubber layer 4 in the region R, a rubber having a desired cross-sectional shape produced by extrusion molding with a die, for example, is placed on the squeegee rubber to be the lining rubber layer 4. By arranging the sheets and manufacturing the tire according to the above-described manufacturing method, a bead portion structure having a small bead filler 7 inside the lining rubber layer 4 as shown in FIG. 8 is realized.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the bead structure shown in FIG.
A 120 / 70R17 radial tire for motorcycles was prototyped. In addition, as a comparison, a conventional tire having no rubber liner was prototyped in the same size. The turning performance of each tire thus obtained was investigated. The results are shown in Table 1 together with the specifications of the rubber lining.

The turning performance was adjusted by adjusting the tire pressure to 200 kPa after assembling the test tire on the rim of MT3.5 × 17.
The motorcycle was mounted on the rear wheel of a 125 cc motorcycle with a displacement of 125 cc, and the feeling of safety and stability during cornering was evaluated. That is, under the condition that all the front tires are mounted on the same tire, four types of tires shown in Table 1 are mounted on the rear wheels, and
In cornering at a speed of km / h, various performances were evaluated. First, the driver's score was set to 100 on the tire of Invention Example 1, with the sense of security during cornering as the index of the slide controllability on slippery road surfaces, and the stability at the time of cornering as the index of the steadiness of the sense of rigidity. It was shown by the index of time.

[0035]

[Table 1]

[0036]

According to the present invention, it is possible to provide a bead portion structure capable of deforming the carcass ply around the bead core without reducing the torsional rigidity of the bead core, thereby improving the tire's contact with the ground. In particular, it is possible to provide a tire excellent in turning performance, particularly suitable for a motorcycle tire.

[Brief description of the drawings]

FIG. 1 is a sectional view in the tire width direction showing a bead portion of a tire according to the present invention.

FIG. 2 is a diagram showing a movement of a carcass around a bead core.

FIG. 3 is a diagram illustrating a compression rate.

FIG. 4 is a diagram illustrating a method of forming a bead portion according to the present invention.

FIG. 5 is a diagram illustrating a method of forming a bead portion according to the present invention.

FIG. 6 is a diagram illustrating a method of forming a bead portion according to the present invention.

FIG. 7 is a diagram showing a bead portion structure according to the present invention.

FIG. 8 is a diagram showing a bead portion structure according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carcass ply 1a Carcass main body 1b Folded part 2 Bead part 3 Bead core 4 Lining rubber layer 5 Rim

Claims (7)

[Claims] 1. A tire comprising: a carcass body in which at least one carcass ply extends in a toroidal form from a tread portion to a bead portion via a sidewall portion; and a bead core in which the ply is embedded in each bead portion. A tire having a folded portion folded back from the inside to the outside in the width direction, wherein the tire has a rubber liner arranged along the carcass ply between the carcass ply and the bead core, surrounding the bead core, and A tire having a compression ratio of 1.25 to 1.33 in a radially inner portion of a bead core when a standard rim is mounted. 2. The tire according to claim 1, wherein the tire is a two-wheeled automatic tire. 3. The tire according to claim 1, wherein the thickness of the lining rubber layer is 0.5 mm or more. 4. The method according to claim 1, wherein
The hardness of the lining rubber layer is 50 to 70 and the hardness of the highest hardness rubber in the area sandwiched between the carcass body and the folded part is
Tire characterized by being 50 to 80. 5. The method according to claim 1, wherein
A tire characterized in that the distance from the outermost bead base surface in the tire radial direction of the lining rubber layer is 10 to 35% of the tire section height. 6. The method according to claim 1, wherein
A tire wherein the bead core is a cable bead. 7. A squeegee rubber is stuck to the molded body to which the carcass ply is stuck, and then a bead ring is fitted to the width center of the squeegee rubber or in the vicinity thereof. A method of manufacturing a tire, comprising: folding a carcass ply, attaching a belt material and a tread material to the carcass ply, producing a green tire, and subjecting the green tire to a vulcanization step.