JP3306414B2 - Pneumatic radial tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having improved structural durability at a bead portion.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 5, a carcass ply A of a pneumatic radial tire is wound up from the inside in the axial direction of a bead core B to the outside. For heavy duty radial tires used in trucks, buses, etc.,
In this carcass ply A, a steel cord is generally used, and a winding end A1, which is the upper end of the winding portion, is located below the sidewall portion in the axial direction outside of the tire beyond the bead portion so that the bead portion is formed. Increases rigidity.

[0003] On the other hand, the steel cord adheres to the rubber by bonding of brass or the like adhered by plating on the surface with sulfur compounded in the rubber, but the steel cord is cut at the winding end A1, and the cut surface is cut. Has no adhesion to rubber because of no plating.

In addition, a heavy load radial tire has a large acting load, and this large load exerts a compressive and tensile force on a bead portion as the tire rotates. In particular, at the winding end A1, compressive strain is generated due to the deformation indicated by the arrow C shown in FIG. 5, so that adhesive breakage starting from the winding end A1 is likely to occur. In some cases, a reinforcing layer D made of a steel cord is arranged to increase the bending rigidity of the bead portion. This can reduce the bead portion from falling down to some extent, but the distortion generated at the winding end A1 is large. Therefore, damage from the winding end A1 cannot be effectively prevented.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic radial tire capable of preventing bead damage without sacrificing other performances and improving the structural durability of a bead portion.

[0006]

SUMMARY OF THE INVENTION The present invention provides a carcass,
A belt layer made of a highly elastic cord disposed outside the inner carcass of the tread portion, and the carcass layer extends from the tread portion to the sidewall portion and extends outside the bead core of the bead portion in the tire axial direction. A carcass ply having a winding portion that is turned up inward in the tire axial direction by folding back inward in the radial direction of the bead core, and further, the bead portion includes a carcass ply between a main body portion and a winding portion of the carcass ply. A bead apex having a tapered cross-sectional shape extending outward from the bead core in the tire radial direction is arranged, the main body extends radially inward along the bead apex, and the winding part rises along the bead apex, Moreover, between the winding portion and the bead apex, a buffer layer made of an organic fiber cord layer or a rubber layer is provided, Serial is winding unit, in the rim sets the state to 5 ° Teparimu tire, the height h1 winding from the bead base less and 1.6 times 0.7 times the flange height H of the rim, or 2.0 It is a pneumatic radial tire that is at least twice and at most 2.6 times.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIGS. 1 and 2 show a case where the pneumatic radial tire of the present invention is a tube-type radial tire. The bead portion 4 is provided with a bead core 5 in a toroidal shape.

The tire 1 is mounted on a regular rim or a compatible rim 7 defined according to the tire according to a tire standard such as JATMA, TRA, or ETRTO. In this example, the rim 7 employs a 5 ° tapered rim in which the rim seat surface 7S is inclined at an angle of 5 ° with respect to the tire axial direction, and the tire bore formed by the tire 1 and the rim 7 A tube T indicated by a dashed line is arranged. A flat base rim seat surface 7S whose rim seat surface is parallel to the tire axial direction line can also be employed.

Further, the tire 1 has a carcass layer 6 and a belt layer 8 that is disposed inside the tread portion 2 and radially outside the carcass layer 6 and uses a plurality of plies, for example, four plies made of a highly elastic cord. The bead portion 4 is provided with a bead apex 9 that extends radially outward from the bead core 5 and a tapered reinforcing layer 10. The carcass layer 6 is composed of one or more (one steel cord ply in this example) carcass ply 6a using a high elasticity cord such as steel cord or aramid, or a cord such as polyamide or polyester. As the carcass ply, another carcass ply (not shown) that turns the bead core 5 from the inside to the outside of the tire can be used together.

The carcass ply 6a has a main body 6A.
And a winding portion 6B folded back at the bead portion 5. The main body portion 6A extends radially inward along the outer surface of the bead apex 9 through the tread portion 2 and the sidewall portion 3 and has a bead portion. 4 reaches the outside of the bead core 5 in the tire axial direction. The winding portion 6B is continuous with the main body portion 6A, and turns back inward in the radial direction of the bead core 5 from the outside in the tire axial direction to the inside, and stands inside the tire axial direction along the inner surface in the tire axial direction of the bead apex 9. Go up. In addition, the winding part 6B
The bead apex 9 is composed of an organic fiber cord layer or a rubber layer, and the winding part 6B and the bead apex 9
And along the inner surface thereof via a buffer layer 9A for buffering between them.

As described above, by providing the entangled portion 6B on the inner side in the tire axial direction, which is a region where a tensile force acts when a load is applied, the compressive strain generated at the upper end 6b of the entangled portion 6B can be reduced, and Peeling can be suppressed.

Further, as shown in FIG. 2, the carcass ply is wound around the bead base line F passing through the intersection of the rim seat surface 7S of the rim 7 and the extension of the inner surface of the rim flange 7F and parallel to the tire axis. The winding height h of the part 6B
1 and the rim flange height H, in the case of a tube-type heavy-load radial tire mounted on a 5 ° taper rim, the carcass hoisting height h1 is first set to the flange height when the rim is assembled. 0.7-1.
Six times, or 2.0 to 2.6 times.

If h1 / H is less than 0.7, the carcass ply 6a cannot withstand the tensile force due to the internal pressure, so that the carcass ply tends to blow through during traveling. , Carcass ply winding end 6E
Is located in an area where deformation is large, cracks are likely to occur from the ply end, and if it exceeds 2.6 times, manufacturing becomes difficult.

Further, the reinforcing layer 10 includes a main body 10A along the tire-direction outer surface of the main body 6A of the carcass ply 6a passing through the bead apex 9 in the tire axial direction.
In addition, an inner portion 10B that is folded below the bead core 5 and rises up on the inner surface in the tire axial direction of the winding portion 6B is integrally provided to increase the bending rigidity of the entire bead portion.

The reinforcing layer 10 is employed for the purpose of improving the durability at high internal pressure and large deflection. The reinforcing layer 10 has a steel cord having an angle of 20 to 45 ° with respect to the tire circumferential tangent. Although it is composed of plies, if it is larger than 45 °, the reinforcing effect is small due to a decrease in rigidity in the circumferential direction. If the angle is less than 20 °, the cord density at the tip end in the tire radial direction is increased, and damage from the end of the reinforcing layer is likely to occur. The reinforcing layer 10 can employ not only a steel cord but also an organic fiber such as aramid. The reinforced layer 10 may be a single ply or a plurality of plies, in which case the cords of each ply cross each other. At this time, the angle of each cord with respect to the tire circumferential direction may be different.

The height h2 of the main portion 10A of the reinforcing layer 10 from the bead base line F and the height h3 of the inner portion 10B.
Is set smaller than the winding height h1 of the winding portion of the carcass ply. Each end 10 of the reinforcing layer 10 extends radially outward of the tire beyond the winding height h1 of the carcass ply.
This is because if a and 10b are located, damage starting from them is likely to occur. Either the height h2 or h3 of the main body 10A or the inner part 10B may be increased. However, if the heights are the same, the bending rigidity of the bead greatly changes at that position, which is not preferable.

The bead apex 9 is made of a hard rubber having a JISA hardness of 80 to 95 ° and increases the rigidity of the bead portion 4. Hard rubber (JISA hardness 80-95 °)
And a soft rubber (J) which is softer than the hard rubber and is disposed outside both in the radial direction and the axial direction of the hard rubber.
(ISA hardness: 57 to 65 °), and the strain may be dispersed by soft rubber. The bead core 5 is a ring body around which a metal wire is wound. In this example, the cross section is hexagonal and the fastening force with the rim 7 is strong. A circular or rectangular cross section may be used. The bead core 5 covers the wire wound body with hard rubber, cloth, or the like.

The height h4 of the bead apex 9 from the bead base line B is larger than the winding height h1 of the winding portion of the carcass ply, thereby increasing the rigidity of the bead portion and separating the main body 6A from the winding portion 6B. Add.

Further, the rim sheet 7S,
Extending to a height h5 of about 1.2 to 2.8 times the height H of the rim flange, including the portion that comes into contact with the rim flange 7F;
A chafer 11 made of rubber that is hard to wear is provided.

The radially outer end of the tire enters the sidewall rubber 12 and terminates. This serves to prevent rim displacement and increase the rigidity of the bead portion, and prevents the rubber from peeling off by making the tip end enter. The height h5 is within the above range, and is a height between the height h4 of the tip end portion of the bead apex and the winding height h1 of the carcass.

The shortest distance Lk from the height h6, which is 1.5 times the height H of the flange 7F at the winding portion 6B of the carcass 6, to the main body 6A of the carcass ply 6a, and therefore at the height K The thickness of the bead apex 9 ranges from 0.35 to 0.9 times the maximum width W of the bead core 5 in the axial direction. From the height position K, the bead apex 9 has a shape whose thickness gradually decreases outward in the tire radial direction.

When the ratio Lk / W is less than 0.35,
It is difficult to secure the bending rigidity, and if it exceeds 0.9 times, the distortion at the winding part 6B and the end 6b of the winding part 6B becomes too large. Further, by arranging the thickness L from the height position K so as to gradually decrease, the bending rigidity of the bead portion decreases as going outward in the tire radial direction, and there is no place where the rigidity changes greatly, and the sidewall is smoothly changed. Can be connected to

The distance Lb in the shortest direction from the end 6b of the winding portion 6B of the carcass ply 6a to the main body 6A is 2.
5 mm or more is required. When the diameter is less than 2.5 mm, it has been found that the effect of the present invention in which the winding portion 6B of the carcass ply is disposed axially inward of the main body 6A is hardly exhibited. The normal distance Lb is about 2.5 to 12 mm, preferably about 5 to 8 mm, and more preferably about 6.5 mm.

Further, the main body 6A of the carcass 6 has a height h1 / H of 0.7 to 1.6 times.
As shown in FIG. 3, it is possible to extend along a carcass imaginary line Y extending near the center line of the thickness of the bead portion 4 through the center of the bead core 5. At this time, the thickness of the bead apex 9 gradually decreases outward in the radial direction, and the ratio Lb / W of the thickness Lb at the upper end b of the winding portion 6B to the maximum width W of the bead core is 0.4 to 0.4. It can be in the range of 0.1.

FIG. 4 shows a case where the pneumatic radial tire of the present invention is a tubeless type radial tire. In the tire 1, the rim sheet surface 7S defined according to the tire standard in the tire standard is aligned with the tire axial direction. 15 for
The example is simply illustrated with reference to the case where it is mounted on a regular rim having a taper of 15 ° inclined at an angle of 15 ° or a compatible rim 7 (parts corresponding to the embodiment in FIGS. 1 and 2 are denoted by the same reference numerals).
You . The bead portion 4 is provided with a carcass layer 6 that is turned inward from the outside in the tire axial direction by the bead core 5, a bead apex 9 that extends outward in the radial direction from the bead core 5, and a reinforcing layer 10. An inner liner layer 13 is provided on the surface facing the tire cavity to maintain airtightness. The carcass layer 6 is made of a single steel cord carcass ply 6a.

The carcass ply 6a has a main body 6A and a winding part 6 folded back at a bead part 5 as in the above embodiment.
B, the main body portion 6A extends radially inward along the outer surface of the bead apex 9 through the tread portion 2 and the sidewall portion 3 and reaches the outside of the bead core 5 in the tire axial direction. Further, the winding portion 6B is continuous with the main body 6A, and turns inward in the radial direction of the bead portion 5 from the outside in the tire axial direction to turn inward. Get up. Further, the carcass ply winding portion 6B based on the bead base line B
The winding height h1 of the rim with respect to the rim flange height H,
It is 1.1 times to 5.2 times. If h1 / H is less than 1.1, the carcass ply 6a is liable to cause a blow-through phenomenon of the carcass ply during traveling due to internal pressure, and if it exceeds 5.2 times, manufacturing becomes difficult.

Further, similarly to the above-described embodiment, the reinforcing layer 10 is provided on the main body 10A along the tire-direction outer surface of the carcass ply main body 6A on the inner side of the winding part 6B which rises on the inner side in the tire axial direction. Part 10B is provided integrally,
The height h2 of the main portion 10A and the height h3 of the inner portion 10B of the reinforcing layer 10 are set smaller than the winding height h1 of the winding portion of the carcass ply.
a, 10b to prevent the occurrence of damage. The heights h2 and h3 of the main portion 10A and the inner portion 10B may be increased. However, if the heights are the same, the bending stiffness of the bead portion greatly changes at that position, which is not preferable.

The height h4 of the bead apex 9 from the bead base line B is larger than the winding height h1 of the winding portion of the carcass ply, and the chafer 11 is arranged in the bead portion 4 as in the above embodiment. The height h5 is set to the height h4 of the tip of the bead apex.
And the winding height h1 of the carcass.

Further, in this example, the height h of the flange 7F is
6, the shortest distance Lk from the position K at a height h6 that is 3.2 times the height H to the main body 6A of the carcass ply 6a, and thus the thickness of the bead apex 9 at the position K at the height h6 is 0.32 times to 0.6 times the maximum width W in the axial direction of
The range is eight times. From the height position K, the bead apex 9 has a shape whose thickness gradually decreases outward in the tire radial direction. Further, the winding portion 6 of the carcass ply 6a
Even when the B height h1 is maximum, the distance Lb in the shortest direction from the end 6b to the main body 6A needs to be 2.5 mm or more. By selecting the range of each value in this manner, the same operation and effect as in the above embodiment can be obtained.

FIG. 6 shows an example of a method of manufacturing a tire according to the present invention in the case of a tubeless tire having an inner liner. The molding former 14 is provided on both sides of a base 16 having an outer diameter Df larger than the inner diameter Db of the bead core 5,
A shoulder 17 having a sticking surface extending radially inward and inward in the tire axial direction via the arc portion is provided. The base 1
6, the inner liner 13 is wound around the
The bead apex 9 is placed on the. At this time, an integrated product in which the bead apex 9 and the inner liner 13 have been assembled in advance can be placed on the forming former 14.
The bead apex 9 is bent along the shoulder 17, and the bead core 5 is disposed in contact with the inner end of the bead apex 9. Note that the bead core 5 can also be integrated with the bead apex 9.

On the outward faces of the inner liner 13 and the bead apex 9, a carcass ply 6a, a reinforcing layer 10,
Chafer 11, sidewall rubber not shown, etc.
Other components such as rubber are wound and integrated. In addition, the winding portions 6B at both edges of the carcass ply 6a
Hang down from the bead core 5.

Thereafter, the forming former 14 is reduced in diameter and width, and the inner liner 13, the bead apex 9, the bead core 5, the carcass ply 6a, and the reinforcing layer 1 are formed.
0 is integrated with the primary molding 20
4, the outer peripheral surface is gripped, and the winding portion 6 </ b> B of the carcass ply is beaded together with the reinforcing layer 10 and the like.
The tire base is formed by folding the lower portion inward in the tire axial direction and along the inner surface of the bead apex 9 in the tire axial direction.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is applied to a size 10.00R20 14PR.
And 11R22.5 14PR were compared with those of the conventional structure in two sizes. Table 1 shows the results.

[0034]

[Table 1]

[0035]

In the test using the indoor bench tester, the load was 180% of the normal maximum load, the internal pressure was 7.5 kgf / cm ² , and the speed was 2
The vehicle was driven at 0 km / h. And 550hrs running the Examples 1 and 2 was checked for abnormalities of the bead structure was disassembled with three.

Comparative Examples 1 and 2 of the conventional structure were 480 hrs,
While the bead crack occurred at 430 hrs, the tires of the present invention all exhibited high durability.

In Example 3, peeling (separation) between the steel cord and the rubber was observed at the end of the carcass ply, but in Examples 1 and 2, no damage was observed.

[0039]

According to the pneumatic radial tire of the present invention, the carcass ply is wound up from the outside in the axial direction of the tire to the inside, and the distortion at the winding end is reduced, and no new reinforcing element is added. The structural durability of the bead portion was improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing details of a bead portion.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a sectional view showing another example of a bead portion.

FIG. 5 is a diagram showing a conventional structure.

FIG. 6 is a diagram illustrating a method for forming a bead structure according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 tire 2 tread portion 3 sidewall portion 4 bead portion 5 bead core 6 carcass 7 rim 8 belt layer 9 bead apex 10 reinforcing layer 11 chafer 13 inner liner 14 molding former

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-315013 (JP, A) JP-A-6-1222 (JP, A) JP-A-6-143947 (JP, A) 41242 (JP, B1) (58) Fields studied (Int. Cl. ⁷ , DB name) B60C 15/00-15/02 B60C 15/06 B60C 9/02 B60C 9/08

Claims (1)

(57) [Claims] 1. A carcass, comprising: a belt layer made of a highly elastic cord disposed outside of an inner carcass of a tread portion; and the carcass layer is formed of a bead core of a bead portion from a tread portion to a sidewall portion. The carcass ply includes a carcass ply having a winding portion that is turned up through the inside of the bead core in the radial direction and is turned up inside the tire in the tire axial direction, and the bead portion includes a carcass ply main body and a carcass ply. A bead apex having a tapered cross-section extending from the bead core radially outward from the bead core is disposed between the bead core and the bead apex, and the main body extends radially inward along the bead apex, and the bend part Rises along the bead apex, and furthermore, an organic fiber cord layer or rubber is provided between the winding portion and the bead apex. In the rim assembly state of the tire on the 5 ° taper rim, the winding height h1 from the bead base is 0.7 times or more the flange height H of the rim and 1.6. double below, also
Is a pneumatic radial tire that is 2.0 times or more and 2.6 times or less.