JPH0637583B2 - Tires with excellent bead durability - Google Patents

Description

TECHNICAL FIELD The present invention relates to a radial tire having excellent bead durability, which prevents separation near the tip of the carcass folded-back portion of the bead portion.

[Conventional technology]

On the radial surface including the grounded portion of the tire, the stress that tends to project outward acts in the lower region of the tire side. A carcass is folded along a bead assembly including a bead core and a bead filler of a tire, and a cord reinforcing layer made of an organic fiber cord or a steel cord is arranged outside the carcass. The folded portion of the carcass and the cord reinforcing layer, particularly the portion where the steel cord reinforcing layer is provided, have high rigidity and are difficult to deform, but the bead filler portion adjacent to the tip of this is easy to move. Therefore, the shear stress is concentrated in the vicinity of the carcass folded-back portion and the tip of the cord reinforcing layer, and separation is likely to occur.

Therefore, in order to prevent the separation of this part,
Conventionally, a method of arranging a hard rubber near the tip of the folded portion of the carcass to reduce stress concentration (Japanese Patent Laid-Open No. 53-11950).
No. 1, JP-A-55-106806), or a method of easing stress by arranging a soft rubber near the tip thereof (JP-A-57-182502, JP-A-58-403). Has been.

[Problems to be solved by the invention]

The organic fiber cord of the carcass or cord reinforcing layer is coated with an adhesive such as a resorcin / formalin reaction product and a latex to increase the adhesive force with rubber, and the steel cord is coated with copper by applying a copper alloy plating to the surface. Although the adhesive strength is enhanced, the cord cut surface at the folded portion of the carcass or the tip of the cord reinforcing layer does not have the above-mentioned surface treatment of the cord, so that the adhesive strength with rubber is weak.

For this reason, if stress concentrates near the tip of the carcass turn-back portion, the rubber will separate from the cut surface of the cord at the tip of the carcass turn-back portion and the cord reinforcing layer, and the rubber will move, and the rubber will be damaged at the cut end of the cord. The separation occurs.

Therefore, the present invention, the carcass folded portion of the tire, and the rubber that is in contact with both sides of the cord reinforcing layer on the outside thereof, has excellent adhesive force even to a cord cut surface that has not been surface-treated, and also has fracture resistance. Uses excellent rubber and aims to prevent separation of the bead.

[Means for solving problems]

As a result of repeated studies by the present inventors to achieve the above object,
A rubber composition containing a resorcin or a resorcin-aldehyde reaction product and a hexamethylenetramine or a melamine-aldehyde reaction product has a strong adhesive force with an organic fiber cord and a steel cord and, at the same time, has a large fracture resistance, and therefore, the carcass is folded by this rubber. The inventors have found that the separation of the bead portion can be prevented by constructing the tire so that the cord and the cord reinforcing layer on the outer side thereof are sandwiched from both the inner side and the outer side, and the present invention has been completed.

That is, according to the present invention, at least one end portion of the carcass ply in which cords are arranged substantially at right angles to the circumferential direction of the tire has a first triangular cross section adjacent to the outer peripheral surface of the bead core.
The cord reinforcing layer is folded back from the inside to the outside along a bead assembly including a bead filler composed of an element and a second element arranged on the outside thereof, and the carcass ply is folded along the outside of the folded portion. In the arranged tire having a radial structure, a layered rubber pad is disposed in contact with the outside of the cord reinforcing layer, and the bead inside is provided near the folded portion of the carcass ply and the tip of the cord reinforcing layer adjacent to the outside thereof. The filler is disposed so as to be sandwiched between the second element of the filler and the outer rubber pad, and the second element and the rubber pad are contained in an amount of 1 to 2 parts of resorcin or a condensate of resorcin and an aldehyde with respect to 100 parts by weight of a rubber component. Resorcinol-aldehyde reaction product 0.5-based on a mixture of bodies
A specific rubber composition containing 5 parts by weight, 0.1 to 5 parts by weight of a melamine-aldehyde reaction product whose main component is a mixture of hexamethylenetetramine or a condensate of a condensate of melamine and formaldehyde. The main feature is a tire with excellent bead durability.

Next, the contents of the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view of an example of a bead portion of a tire of the present invention.
(1) is a bead core, a bead filler (2) made of rubber having a wedge-shaped cross section is arranged in contact with the bead core, and an organic fiber cord is provided along the circumference of the bead assembly composed of the bead core (1) and the bead filler (2). Alternatively, the end region of the carcass ply (3) made of steel cord is folded back from the inside of the tire toward the outside, and the cord reinforcing layer (4) is arranged in contact with the outside. The cord reinforcing layer (4) is composed of a steel cord reinforcing layer (5) and an organic cord reinforcing layer (6) outside the steel cord reinforcing layer, and the steel cord reinforcing layer is only a portion outside the bead core (1) and in contact with the carcass folded portion (7). It is located in. The cord reinforcing layer (4) does not include the steel cord layer (5) and may be composed of only the organic cord layer (6). Bead filler (2)
Is the first element (8) with a triangular cross section that contacts the bead core (1)
And a second element (9) arranged on the outside of the carcass and contacting the inside of the carcass folding part (7) and the cord reinforcing layer (4), the outside of the carcass folding part (7) and the cord reinforcing layer (4). In contact with each other, a bead pad (10) made of a rubber layer is provided.

The second element (9) of the bead filler (2) and the bead pad
(10) is a resorcinol-aldehyde reaction product containing a mixture of a condensate of resorcinol and an aldehyde as a main component and a dimer,
And a specific rubber composition containing a melamine-aldehyde reaction product containing, as a main component, a mixture of a dimer of a condensate of melamine and formaldehyde, which has a strong adhesive force with a steel cord and an organic cord and at the same time has excellent fracture resistance. Composed of things.

The compounding amount of the resorcin or the resorcin-aldehyde reactant in the specific rubber composition is 100 parts by weight of the rubber.
0.5 to 5 parts by weight is preferable. Below 0.5 parts by weight,
Even if the specific rubber composition is used, the effect of improving the durability of the bead portion is small, and even if it is compounded in an amount of more than 5 parts by weight, the effect does not increase.

The amount of the hexamethylenetetramine or melamine-aldehyde reaction product in the specific rubber composition is appropriately 0.1 to 5 parts by weight per 100 parts by weight of the rubber component. If it is less than 0.1 part by weight, the effect of improving the resorcin or resorcin-aldehyde reaction product is not produced, and if it exceeds 5 parts by weight, the effect of improving the resorcin or resorcinaldehyde reaction product is not increased.

In the specific rubber composition, silica is used as a rubber component in order to accelerate the reaction between resorcin and hexamethylenetetramine.
It is preferable to add 5 to 20 parts by weight with respect to parts by weight.

It is desirable that the first element (8) of the bead filler (2) be made of a rubber having high hardness, which is more rigid than the second element (9), but the first element (8) and the second element (9) are You may comprise with the same specific rubber composition.

The desirable hardness range of the first element is 60 to 90,
The element hardness is preferably in the range of 55-85.

It is preferable that the thickness of the second element (9) in the end portion of the carcass folded-back portion (7) and the cord reinforcing layer (4) is 2 mm or more, and the thickness of the bead pad (10) is 1.5 mm or more. Even if the specific rubber composition is damaged at the tip of the cord, the growth of the damage is slow. Therefore, by increasing the thickness to some extent, it is possible to prevent the damage from growing and reaching the separation.

The tip of the carcass turnup part (7) and the steel cord reinforcement layer
The positional relationship between the upper end of (5) and the upper end of the organic cord reinforcing layer (6) is not limited to the arrangement illustrated in FIG. The upper end of the layer (5) may protrude upward.

The rubber chain (11) is arranged outside the organic cord reinforcing layer (6), and the upper part thereof is in contact with the side wall (12).

[Action]

According to the tire having excellent bead durability of the present invention, the end portion of the carcass folded-back portion and the steel cord reinforcing layer adjacent to the outer side thereof, the vicinity of the tip portion of the organic cord reinforcing layer are both inside and outside, and have excellent adhesive force with the cord. Since it is arranged so as to be sandwiched by the specific rubber composition, even if a large stress is concentrated on the carcass folded portion, the adhesive force between the cord cut portion and the cord surface and the rubber is strong, and the cord and the rubber do not peel off, and further, Even if the specific rubber is damaged at the tip of the cord, the growth of the scratch is slow,
It is possible to prevent the occurrence of separation.

Further, it is desirable to increase the rigidity of the bead filler to avoid stress concentration, but since the specific rubber composition used in the present invention has a property of easily scorching, it is not recommended to blend a large amount of carbon black to obtain high hardness. Have difficulty. Accordingly, the bead filler is divided into a first element that contacts the bead core and a second element that contacts the carcass folded-back portion, and the first element is made of a rubber composition having a hardness higher than that of the specific rubber composition of the second element. It is possible to achieve both the rigidity of the part and the adhesiveness.

〔Example〕

Compounding examples of the specific rubber composition used in the present invention in which natural rubber is compounded with resorcin or a resorcin condensate and hexamethylenetetramine or a melamine derivative are shown in Table 1A.
~ C. An example of a rubber composition used for a conventional tire bead filler is shown in Tables D and E of Table 1.

In Table 1, the fracture resistance test is 100 mm long, 10 mm wide,
60mm long at the center of thickness of 4mm thick rubber sheet
40 pieces of steel cords are embedded at intervals of 1.95 mm with one end aligned with the edge of the rubber sheet to make test pieces, and a hammer with a radius of curvature of 55 cm and a weight of 30 kg is 10 cm from the height of 10 cm. 1 at the center of the test piece at a rate of 60 times per minute
After free-falling 800 times, the test piece was disassembled and the length of the crack generated in the rubber adjacent to the steel cord end was measured, and the average length was used as an index with the E-blended rubber as the standard (100). Indicated.

The rubbers of Formulations D and E containing no resorcin or a condensate of resorcin and Formulation F containing a small amount of compound have a large crack length. The higher the amount of resorcin or the resorcin condensate compounded, the better the fracture resistance.

Using the rubber compositions shown in Table 1 as the rubber of the first element, the second element and the bead pad of the bead filler,
Tire size 10 having the bead structure shown in FIG.
A tire of the present invention of 00R20S was manufactured and a drum durability test was conducted. The results are shown in Examples 1 to 5 in Table 2. Further, using the rubber compositions of D, E and F in Table 1, tires having the same structure having bead fillers and bead pads were manufactured, and the test results are similarly shown in Table 2 as Comparative Examples 1 to 3. .

In Table 2, the drum durability is the tire inflated to an internal pressure of 7.25 kg / cm ² and pressed against the drum with a load of 5400 kg. The drum was rotated at a speed of 40 km / h, and the tire was broken until it broke. The case of Comparative Example 3 was set as 100 and displayed as an index.

〔The invention's effect〕

According to the tire having excellent bead durability of the present invention, while maintaining the rigidity of the bead portion relatively large, the adhesive strength between the carcass folded-back portion and the reinforcing layer on the outside thereof and the rubber is improved, and the separation of the bead portion is improved. It can prevent and improve the durability of the tire.

[Brief description of drawings]

FIG. 1 is a sectional view of an example of a bead portion of a tire of the present invention. (1) …… bead core, (2) …… bead filler, (3) …… carcass ply, (4) …… cord reinforcement layer, (5) …… steel cord reinforcement layer, (6) …… organic cord reinforcement layer , (7) …… Carcass turn-up part, (8) …… First element, (9) …… Second element, (10) …… Bead pad, (11) …… Rubber chain, (12) …… Sidewall.

Claims (3)

[Claims] 1. A carcass ply in which cords are arranged substantially at right angles to a circumferential direction of a tire, is provided with a bead core, a first element having a triangular cross section adjacent to an outer peripheral surface of the bead core, and an outer side thereof. A radial structure in which a cord reinforcing layer is disposed along the outer side of the folded portion of the carcass ply by folding back from the inside along a bead assembly including a bead filler composed of the second element arranged in In a tire having a structure, a layered rubber pad is arranged in contact with the outside of the cord reinforcing layer, and the vicinity of the folded portion of the carcass ply and the tip of the cord reinforcing layer adjacent to the outer side of the carcass ply is the innermost bead filler. The second element and the rubber pad are arranged so as to be sandwiched between the two elements and the rubber pad on the outer side, and the second element and the rubber pad are resorcin or a resin with respect to 100 parts by weight of the rubber component. 1-2 of the condensation product of Shin and aldehyde
0.5 to 5 parts by weight of resorcin-aldehyde reaction product containing a mixture of monomers as a main component, and melamine-aldehyde reaction product containing a mixture of hexamethylenetetramine or a condensate of melamine and formaldehyde as a main component A tire having excellent bead durability, which is characterized by comprising a specific rubber composition containing 0.1 to 5 parts by weight. 2. A tire having excellent bead durability according to claim 1, wherein the first element is composed of a rubber composition having a hardness higher than that of the specific rubber composition of the second element. 3. The bead durability according to claim 2, wherein the first element is made of a rubber composition having a hardness of 60 to 90, and the second element is made of the specific rubber composition having a hardness of 55 to 85. Excellent tire.