JPH0350003A - Heavy duty pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve durability of a tire by piling up plural reinforced layers, which have a required cord angle so as to cross each other, along carcass plies in an inside and outside of a bead portion, and by arranging a lower end of the crossing zone round a bead base, and an upper end of the crossing zone between a folding-back portion and a widest portion. CONSTITUTION:Along a carcass ply 3 in an inside of a bead 1, doubled reinforced layers 9, 9' having a cord angle of 10 deg. to 30 deg. with respect to the circumferential direction of a tire are piled up crosswise mutually. Along a folding back portion of the carcass ply 3, doubled reinforced layers 10, 10' having a cord angle of 45 deg. to 60 deg. with respect to the circumferential direction of the tire are piled up crosswise mutually. Lower ends of a crossing portion of these reinforced layers 9, 9' and 10, 10' are located at a bead toe portion of a bead base portion and heights of upper ends h1, h2 from the bead base are set within the range from an end 3e of a folded back portion of the carcass ply 3 to the position corresponding to a maximum width of a tire section. By this constitution, durability of a bead portion of a tire can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heavy-duty pneumatic radial tire with improved bead durability.

[Conventional technology]

Conventionally, the bead part of heavy-duty pneumatic radial tires was
For example, it is configured as shown in FIG. In FIG. 4, along the carcass ply 3 that is folded back and rolled up from the inside of the tire to the outside around the bead wire 4,
Two fiber cord reinforcing layers 9°1 intersecting each other at almost the same cord angle of 20” to 7° with respect to the tire circumferential direction
Further, a fiber cord reinforcing layer 11 is arranged on the outer side of the tire above this reinforcing layer 9.10. However, even if such a reinforcing layer as described above is provided, the problem of strain being concentrated at the winding end 3e of the carcass ply 3 and separation occurring from the winding end 3e has not been sufficiently solved.

By the way, when the tire 20 built into the rim 2 is loaded with a load and runs on the road surface M, as shown in FIG.
, shear deformation occurs in the tire circumferential direction as indicated by the arrow. Further, as shown in FIG. 6, when a load is applied to the bead portion, a bending deformation l occurs in the cross-sectional direction (tire width direction) of the ground contact center portion. The present inventors believe that in order to prevent the above-mentioned separation from occurring and improve the bead durability, these shear deformations in the tire circumferential direction and bending deformations in the cross-sectional direction should be avoided. We have found that it is effective to reduce the internal strain generated in the bead by reducing the , and have conducted extensive research to arrive at the present invention.

[Problem to be solved by the invention]

An object of the present invention is to reduce internal strain in the blade portion,
To provide a heavy-duty pneumatic radial tire that prevents the occurrence of separation at the folded end of a carcass ply and improves the durability of a bead part.

[Means for Solving the Problem] The above object of the present invention is to provide at least one layer of carcass ply consisting of a metal cord or a fiber cord having at least the same modulus of elasticity as the metal cord, around a pair of left and right bead cores. In a radial tire having a bead portion that is folded back from the inside of the tire to the outside and rolled up so that the folded end is at a position lower than the height of the tire cross-sectional maximum width position, 10' in the tire circumferential direction
At least two reinforcing layers having a cord angle of ~30° are laminated to cross each other, and along the outside of the folded part of the carcass ply, a reinforcement layer of 40° is formed in the tire circumferential direction.
At least two reinforcing layers having a cord angle of 5° to 60° are arranged in a stacked manner so as to cross each other, and the lower ends of the intersecting regions of both the reinforcing layers inside and outside the bead portion are respectively distributed around the bead base. This can be achieved by arranging the upper end of the intersection area at a height from the end of the folded portion of the carcass ply to the tire cross-sectional maximum width position.

A detailed description will be given below with reference to the drawings.

In the pneumatic radial tire shown in Fig. 3, the rim 2
A carcass ply 3, which is folded back from the inside of the tire to the outside around a bead core 4, is mounted between a pair of left and right bead portions 1 of a tire mounted on the tire. This carcass ply 3 is made of a metal cord such as a steel cord or an aromatic polyamide fiber having an elastic modulus equal to or higher than the metal cord.
Made of fiber cords such as glass fiber, carbon fiber, etc.
At least one layer is arranged. On the carcass ply 3 of the tread T of this tire, a belt layer B consisting of at least two layers of steel cords is arranged annularly in the tire circumferential direction.

The steel cords constituting this belt layer B are arranged so that at least two layers cross each other between the plies.

As shown in FIG. 1, the tire of the present invention has a carcass ply 3 that is folded back and rolled up from the inside of the tire to the outside around the bead core 4 at the bead portion, that is, along the carcass ply 3 inside the bead portion. Two reinforcing layers 9°9° are laminated. Additionally, two tire outer reinforcing layers 10, 10 are provided along the folded portion of the carcass ply 3, that is, along the carcass ply 3 on the outside of the corner portion.
A bead filler 7.7'' is filled above the bead core 4 so as to be sandwiched between the main body of the carcass ply 3 and its folded portion, and further includes a carcass ply folded end 3e and a reinforcing layer 10.10. A cushion rubber layer 8e is provided so as to be sandwiched between the reinforcing layers 10 and 10''.A rim cushion rubber layer 8 is also provided along the rim base side outside the reinforcing layer 10.10''.

The reinforcing layers 9,9' are formed so as to intersect with each other at cord angles in the range of 10° to 30° with respect to the tire circumferential direction. On the other hand, the reinforcing layer 10. to'' are formed so that they intersect with each other at cord angles in the range of 45° to 60° with respect to the tire circumferential direction.

The lower ends of the reinforcing layer 9.9'' and the reinforcing layer 10.10' in the area where the cords intersect with each other are located at the bead toe portion of the bead base portion.

On the other hand, the upper terminals of these intersection areas have a height from the bead base m, and h! are located between the height hc of the folded end 3e of the carcass ply 3 and the maximum tire cross-sectional width position height SH.

The reinforcing layer 9.9 degrees on the inside of the bead portion has the effect of increasing the tensile rigidity in the tire circumferential direction by making the cord angle relative to the tire circumferential direction relatively small, 10' to 30 degrees. Therefore, the most effective action is performed to suppress the deformation of the bead portion due to the internal pressure P caused by the filled air, and the concentration of strain on the carcass ply folded end 3e is reduced. In addition, it acts to make it difficult for the cord spacing of the carcass ply 3 to open due to shear deformation in the tire circumferential direction at the portion corresponding to the ground contact end as shown in Fig. 5. Concentration of distortion on the return terminal 3e is also suppressed. If the cord angular force of the reinforcing layer 9.9" exceeds 30 degrees, the tensile rigidity in the circumferential direction will not increase sufficiently, and the strain concentration on the folded end 3e of the carcass ply cannot be reduced. In this case, although the effect of suppressing the strain concentration described above is sufficient, a new problem arises: a peeling phenomenon between the reinforcing layer and the carcass ply.

Furthermore, by setting the cord angle of the reinforcing layer 10.10' on the outside of the bead within a range of 45° to 60° with respect to the tire circumferential direction, it becomes possible to improve the cross-sectional bending rigidity of the bead. . If the cord angle is 45°, the tensile stress in the cross-sectional radial direction when the bead bends cannot be effectively shared, so the carcass ply 3
The bending deformation in the vicinity of the folded terminal 3e increases, and the concentration of strain caused by this increases the tendency for separation to occur at the terminal 3e.・Also, since the tensile stress due to bending deformation in the cross-sectional direction of the tire becomes effective as the square of the distance from the bending neutral line, arranging the reinforcing layer 10.10'' on the outside of the bead portion has the above effect. This will make it work most efficiently.

On the other hand, if the cord angle exceeds 60°, the effect of suppressing shear deformation in the circumferential direction of the tire decreases, and distortion at the folded end of the carcass ply increases, making separation at that end more likely.

In the area where the cords of the reinforcing layer 9.9° inside the bead portion and the reinforcing layer 10.10′ outside the bead portion intersect with each other, the lower end is located near the bead portion, and the upper end height is It is necessary that h2 and hl be located between the height hc of the folded end 3e of the carcass ply 3 and the height SR of the tire maximum width position. By protecting the folded end 3e of the carcass ply between the upper and lower ends of the cord crossing area of the reinforcing layers 9 and 9° and the reinforcing layer 10 and 10' in this way, the folded end 3e of the carcass ply is protected.
separation can be prevented.

Note that the height hc of the folded end 3e of the carcass ply 3 and the height hs of the tire maximum width position are both heights based on the rim reference line m in FIG. This corresponds to the name R of the rim when it is assembled into a regular rim and filled with the regular internal pressure.

Further, a regular rim refers to a standard rim specified by JATMA, and "filled with a regular internal pressure" means that air is filled into the tire so that the regular internal pressure is achieved.

In the tire of the present invention, as shown in FIG.
A reinforcing layer 9 is laminated on the inside of the bead portion of the reinforcing layer 11, and two reinforcing layers 10 are laminated on the outside of the bead portion. It is also possible to stack lO'. However, even in the tire shown in FIG. 2, the reinforcing layers 9 and 11 on the inner side of the tread portion have cords that cross each other, and the upper end of the area where the cords intersect is the folded end of the carcass ply 3. It is located above the height hc of 3e, and the lower end is located at the bead heel. On the other hand, the lower end h1 of the intersection area of the reinforcing layer 10.10'' outside the bead portion
is similarly located at the bead heel portion, and the upper end is located above the height hc of the folded side end bundle 3e of the carcass ply 3.

As the cords constituting the reinforcing layer of the tire of the present invention, steel cords and organic or inorganic fiber cords are used. Alternatively, a combination of different types of cords, such as steel cords and nylon cords, may be used.

Further, in the tire of the present invention, the carcass ply 3 folded back by the beat core 4 and the reinforcing layer 10 on the outside of the bead portion
．． 10', it is desirable to fill the extrusion rubber 8e so as to gradually separate it from the side surface of the beat core 4 toward the sidewall. The hardness of this extrusion rubber 88 is
It is preferable that the hardness is 1.2 times or more the hardness of the coat rubber (covering rubber) and less than or equal to the hardness of the upper bead filler rubber 7. In addition, this extrusion rubber 8e is
It is preferable that the cobalt metal salt is contained in an amount of 0.1 to 0.4 parts by weight in terms of the amount of cobalt element per 100 parts by weight of rubber.

〔Example〕

Example 1 A tire I of the present invention having the bead structure shown in FIG. 1 and having the constituent materials and specifications shown below was prepared.

Tire size: IIR22,514PR Carcass ply: 3 + 9 + 15 (0,175) 1″ steel cord bead core; The angle of inclination of the bottom surface is approximately the same as the rim bead seat, and the number of turns is 63 turns made of steel wire with a diameter of 1.60 m + a.
Height of main bead carcass ply folding terminal 3e hC: 38II
III+ Bead filler: A hard rubber filler is used as the lower bead filler 7°, and a soft rubber filler is arranged as the upper bead filler 7 in a triangular shape. Reinforcement layer 9.9° inside the bead part and reinforcement layer 10.10" outside the bead part. : Reinforcement layer made of 12600/2 nylon cord with 35 strands and 75 mm.Outer reinforcement?J@eyebrow angle αI: 50° Inner reinforcement layer angle α2: 20° Reinforcement layer outside the bead part 10.10 'Height of upper terminal h
:65mm Height of upper end of reinforcing layer 9,9゛ inside bead part h2:6
01° On the other hand, in the tire (2) of the present invention, α1. Conventional tires in which α2゜hl and h2 are different as shown in the table,
Three types of tires, Comparative Tires 1 and H, were created.

The following indoor rotating drum durability test was conducted on the four types of tires described above, and the results shown in the table were obtained.

Ro − ゛ −mu − ′
: Rim 22.5X7.50, air pressure 8.4 kg
f/cm” (Regulation 4δ(7) 120ri, load 520
0Kg (Standard (7) 190%), speed 45++
/hr, each tire was rotated on a drum several times, and the distance until the bead part failed was measured and expressed as an index, with the durability of the conventional tire being 100.

(Margins below this page) As is clear from the table, α1 of the present invention. α2゜h,,h
It can be seen that the tire I of the present invention, which satisfies the provisions of , has extremely excellent durability of its bead portion.

Example 2 A tire size is 10.0OR2014P, which has the bead structure shown in Fig. 2 and has the following constituent materials and specifications.
A tire (2) of the present invention of R was prepared.

Reinforcement layer 11: 3 + 9 (0,22) Made of metal cord with a 20” cord structure, the number of implants is 2.
7 reinforcing layers of 150 mm inner and outer reinforcing layers 9, 10, 10' of the bead part:
Made of 12600/2 6 nylon, 3 stitches
5 reinforcement layers of 150s+a+ Cord angle of reinforcement layer inside bead part: Nylon cord reinforcement layer (9) 20°X metal cord reinforcement layer (11) 20°Cord angle of reinforcement layer outside bead part: Nylon cord reinforcement Layer (10) 50° x Nylon cord reinforcement layer (10') 50° hc = 63 + am, ht = 82 mm + h
t=75aus.

Similar to the inventive tire (■) of Example 1, the bead part durability of the inventive tire (2) was evaluated, and it was found that the separation gin resistance of the carcass ply winding terminal was improved by 20χ compared to the conventional tire having the reinforcing layer cord angle shown below. It also had excellent bead durability.

Conventional tire; Reinforcement layer on the outside of the bead Cord angle: Nylon cord reinforcement layer (10) 35' X Nylon cord reinforcement layer (10°)
35', reinforcing layer cord angle inside bead part: nylon cord reinforcing layer (9) 35° x metal cord reinforcing layer (11) 35''.

〔Effect of the invention〕

As explained above, according to the present invention, the tire inner carcass ply and the tire outer carcass ply, which are folded around the bead core from the inside of the tire to the outside, each have a specific cord angle with respect to the tire circumferential direction. By stacking more than one reinforcing layer so that the cords intersect with each other and by specifying the placement position, deformation of the bead part due to internal filling pressure can be reduced. This reduces shearing deformation in the circumferential direction and bending deformation in the cross-sectional direction (tire width direction) that occurs at the ground-contacting end of the sidewall when the tire is driven on the road surface, thereby preventing separation at the folded end of the carcass ply.
Tire durability can be improved.

[Brief explanation of drawings]

FIGS. 1 and 2 are enlarged sectional views showing an example of the bead structure of a heavy-duty radial tire of the present invention, and FIG. 3 is a meridian showing the general structure of a heavy-duty radial tire of the present invention. 4 is a cross-sectional explanatory view showing an example of the bead structure of a conventional heavy-duty radial tire, and FIGS. 5 and 6 respectively show how the radial tire deforms when running under load. FIG. l... Bead portion, 2... Rim, 3... Carcass ply, 4... Bead core, 8... Rim compression rubber, 9.9'', to, to'... Reinforcement layer. Section C)

Claims (1)

[Claims] At least one layer of carcass ply made of a metal cord or a fiber cord having an elastic modulus at least equivalent to the metal cord is folded around a pair of left and right bead cores from the inside of the tire to the outside, and the folded ends are placed at the outermost edge of the tire cross section. In a radial tire that has a bead part that is rolled up so that it is at a position lower than the height of the wide position,
At least two reinforcing layers having cord angles of 10° to 30° with respect to the tire circumferential direction are laminated so as to cross each other along the carcass ply located inside the bead portion, and the carcass ply is folded back. At least two reinforcing layers having cord angles of 45° to 60° with respect to the tire circumferential direction are stacked and arranged to cross each other along the outside of the bead part, and the intersection area of both the reinforcing layers inside and outside the bead part is A pneumatic radial tire for heavy loads, wherein the lower ends are arranged around the bead base, and the upper end of the intersection area is arranged at a height from the end of the folded part of the carcass ply to the maximum width position of the tire cross section.