JP2011255804A - Pneumatic tire and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having improved durability in a bead part by securing adhesiveness between a bead filler and a carcass, and to provide a method for manufacturing the tire.SOLUTION: The pneumatic tire includes a carcass as a skeleton toroidally structured between a pair of beads having a bead core and a bead filler, wherein the bead filler includes a core rubber and a coating rubber layer disposed in at least a part in contact with the carcass, and the coating rubber layer is softer than the core rubber and has a thickness of 0.1-0.7 mm.

Description

  The present invention relates to a pneumatic tire in which the adhesion between a bead filler and a carcass is ensured and the durability of a bead portion is improved, and a manufacturing method thereof.

In order to improve the performance of a tire, it is generally necessary to improve the handling stability and the ride comfort, and these performances are greatly influenced by the side rigidity of the tire. Therefore, a bead filler is used as one of side reinforcing materials for increasing the side rigidity.
The bead filler is disposed on the outer side in the tire radial direction of the bead core and is disposed between the main body portion and the folded portion of the carcass, and is often made of a relatively hard rubber. Therefore, the bead filler has poor adhesion to a soft carcass coating rubber, and conventionally, rubber cement has been used as an adhesive (for example, Patent Document 1).

JP-A-6-270616

However, rubber cement is an environmentally reduced material. Moreover, when using the rubber cement mentioned above, the process of apply | coating rubber cement to a bead filler was needed, and the working efficiency fell.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic tire and a method for manufacturing the same that ensure the adhesion between the bead filler and the carcass without using rubber cement and improve the durability of the bead portion. .

The gist of the present invention is as follows.
(1) In a pneumatic tire having a skeleton of a carcass straddling a toroidal shape between a pair of bead portions having a bead core and a bead filler,
The bead filler comprises a core rubber and a covering rubber layer provided at least in a portion in contact with the carcass,
The covering rubber layer softer than the core rubber has a thickness of 0.1 mm to 0.7 mm.
A pneumatic tire characterized by that.

(2) The pneumatic tire according to (1), wherein the coated rubber layer is provided on a portion of the bead filler that is in contact with the bead core.

(3) The pneumatic tire according to (1) or (2), wherein the covering rubber layer is provided over the entire circumference of the core rubber.

(4) The pneumatic tire according to any one of (1) to (3), wherein the covering rubber layer is the same rubber as the coating rubber of the carcass.

(5) The pneumatic tire according to any one of (1) to (3), wherein the covering rubber layer is a softer rubber than the coating rubber of the carcass.

(6) The method for manufacturing a pneumatic tire according to any one of (1) to (5), wherein the core rubber and the covering rubber layer are formed by integral extrusion.

  According to the present invention, it is possible to provide a pneumatic tire in which the adhesion between the bead filler and the carcass is secured and the durability of the bead portion is improved without using rubber cement which is refrained from an environmental viewpoint. Can do.

It is width direction sectional drawing of the half part of the pneumatic tire of this invention. It is an enlarged view of the bead part of the pneumatic tire of the present invention. It is a figure which shows the modification of the bead part of the pneumatic tire of this invention. It is a figure which shows the modification of the bead part of the pneumatic tire of this invention. It is a figure which shows the modification of the bead part of the pneumatic tire of this invention.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view in the width direction of a half portion of the pneumatic tire of the present invention. The pneumatic tire 10 of the present invention has a tire equatorial plane CL on the outer side in the tire radial direction of the crown portion of the carcass 2 with a carcass 2 straddling a toroidal shape between a pair of bead portions having a bead core 1 and a bead filler 5. A plurality of cords disposed obliquely with respect to the rubber, and a belt 3 comprising inclined belt layers 3a and 3b in which the cords cross each other between the laminated layers, and a tread 4 on the outer side in the tire radial direction of the belt 3 Is arranged. The bead filler 5 is disposed on the outer side in the tire radial direction of the bead core 1 and between the main body portion 2a and the folded portion 2b of the carcass 2.
The bead core 1, the carcass 2, the belt 3, the tread 4, and the like are not limited to the illustrated example. For example, the carcass 2 may be formed of two layers of carcass plies, or may be further provided with a circumferential belt layer. .

FIG. 2 is an enlarged view of a bead portion of the pneumatic tire of the present invention. The bead filler 5 has a configuration in which a coating rubber layer 5b softer than the core rubber 5a is provided around a relatively hard core rubber 5a.
The core rubber 5a is a relatively hard rubber, for example, a rubber having a JIS hardness of 85 or more. The hard core rubber 5a is formed by increasing the blending amount of carbon black and sulfur and blending a resin. Therefore, if the entire bead filler 5 is made of the material of the core rubber 5a, the tackiness at the time of unvulcanization is lowered, and the adhesive strength with the carcass 2 after vulcanization is lowered. As a result, there arises a problem that peeling is likely to occur between the bead filler 5 and the carcass 2. Therefore, rubber cement has been conventionally used as an adhesive, but recently there has been a demand for reducing the use of rubber cement for environmental reasons.
The rubber cement is composed of natural rubber, carbon black, sulfur and toluene, and among these, toluene is a substance that is refrained from environmental and work use.
Therefore, in the present invention, a covering rubber layer 5b that is softer than the core rubber 5a is provided around the core rubber 5a to improve the adhesion to the carcass 2. This eliminates the problem of peeling and improves the durability of the bead portion. Furthermore, it is possible to suppress the problem of manufacturing defects in which air enters between the bead filler 5 and the carcass 2 and between the bead filler 5 and the bead core 1.
The covering rubber layer 5b is preferably the same as the coating rubber of the carcass 2 or is softer than the coating rubber of the carcass 2. The covering rubber layer 5b is preferably a rubber having a JIS hardness of 50 to 70, for example.

Moreover, the thickness D of the covering rubber layer 5b is 0.1 mm to 0.7 mm. If the thickness D is less than 0.1 mm, the function of adhering the covering rubber layer 5b and the coating rubber of the carcass 2 cannot be sufficiently achieved. On the other hand, if the thickness D is greater than 0.7 mm, the proportion of the soft rubber in the bead filler 5 increases, which may reduce the steering stability.
Furthermore, the core rubber 5a and the covering rubber layer 5b are molded by integral extrusion. By performing the integral extrusion, there is no need for a process of attaching the covering rubber layer 5b around the core rubber 5a, and the working efficiency can be improved.

Hereinafter, although the modification of the bead part of the pneumatic tire of this invention is shown in FIGS. 3-5, this invention is not limited to these examples.
In FIG. 3, the covering rubber layer 5 b is disposed between the core rubber 5 a and the main body 2 a of the carcass 2 and between the core rubber 5 a and the folded portion 2 b of the carcass 2. Since the covering rubber layer 5b is not disposed between the core rubber 5a and the bead core 1, the core rubber 5a and the bead core 1 are in contact with each other, but the covering rubber layer 5b and the carcass 2 are bonded to each other. The problem of peeling can be prevented.
In FIG. 4, the folded portion 2 b of the carcass 2 does not extend to the outer end 5 </ b> E in the tire radial direction of the bead filler 5, but terminates at a position at an intermediate height of the bead filler 5. In this case, by providing the covering rubber layer 5b2 in contact with the main body portion 2a and the covering rubber layer 5b1 in contact with the folded portion 2b, the above-described peeling problem can be prevented. That is, it is only necessary to provide the covering rubber layers 5b1 and 5b2 only on the portions of the carcass 2 that are in contact with the main body 2a and the folded portion 2b.
In FIG. 5, the folded portion 2 b of the carcass 2 is wound around the bead core 1 and is not wound around the bead filler 5. In this case, the above-described peeling problem can be prevented by providing the covering rubber layer 5b on the portion in contact with the main body 2a and the portion in contact with the folded portion 2b.

Examples of the present invention will be described below, but the present invention is not limited thereto.
Invention tires and conventional tires having a tire size of 215 / 55R17 were produced as prototypes, and the adhesion between the carcass and the bead filler was evaluated.
The inventive tire has the tire structure shown in FIGS. 1 and 2, and the conventional tire is coated with rubber cement instead of the coated rubber layer 5b of the inventive tire.
Each test tire was mounted on a standard rim, and was run on a rotating drum tester at a speed of 20 km / h for 600 hours under conditions of an internal pressure of 800 kPa and a load of 58.5 kN. The adhesion state with the bead filler was examined. In any of the test tires, no separation between the carcass and the bead filler was observed.
According to the present invention, it has been confirmed that a pneumatic tire with improved durability of the bead portion can be provided without using a rubber cement that causes environmental problems, without causing a problem of peeling between the carcass and the bead filler. .

DESCRIPTION OF SYMBOLS 1 Bead core 2 Carcass 2a Main body part 2b Folding part 3 Belt 4 Tread 5 Bead filler 5a Core rubber 5b Covering rubber layer 10 Tire

Claims (6)

In a pneumatic tire having a skeleton of a carcass straddling a toroidal shape between a pair of bead portions having a bead core and a bead filler,
The bead filler comprises a core rubber and a covering rubber layer provided at least in a portion in contact with the carcass,
The covering rubber layer softer than the core rubber has a thickness of 0.1 mm to 0.7 mm.
A pneumatic tire characterized by that.   The pneumatic tire according to claim 1, wherein the covering rubber layer is provided on a portion of the bead filler that is in contact with the bead core.   The pneumatic tire according to claim 1, wherein the covering rubber layer is provided over the entire circumference of the core rubber.   The pneumatic tire according to claim 1, wherein the covering rubber layer is the same rubber as the coating rubber of the carcass.   The pneumatic tire according to any one of claims 1 to 3, wherein the covering rubber layer is a softer rubber than the carcass coating rubber. The method for manufacturing a pneumatic tire according to any one of claims 1 to 5, wherein the core rubber and the covering rubber layer are formed by integral extrusion.

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