JPH0285002A - Heavy duty pneumatic radial tire - Google Patents

Abstract

PURPOSE:To enhance the durability of a bead by installing metal cord reinforced layers over the outside of a carcass layer winding part and the inside of the unfolded carcass layer body at the bead part in such a way as independently each other with a bead core as boundary. CONSTITUTION:An outside metal cord reinforced layer 4a is installed over the outside of a winding part around a bead core 3 of a carcass layer 2, which an inside metal cord reinforced layer 4b arranged over the inside of the carcass layer body not folded back. These reinforcement layers 4a, 4b shall be arranged independently each other with the bead core 3 as boundary. The terminals 4m, 4n of reinforcement layers 4a, 4b on the bead core 3 side are situated at the side of the bead core 3, and the tensile strength of the cord of the inside metal cord reinforcement layer 4b is made greater than the tensile strength of the cord of the outside metal cord reinforcement layer 4a. Further two fiber cord reinforcement layers 10 are arranged around the bead core 3 over the extent from inside the tire to the outside so that the bottom terminals 4m, 4n of the reinforcement layers 4a, 4b are covered.

Description

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

[Conventional technology]

Conventionally, there is a bead structure of a pneumatic radial tire for heavy loads as shown in FIG. 5, for example. Fifth
In the figure, at the bead portion l, the end of the carcass layer 2 is folded and rolled up around the bead core 3 from the inside of the tire to the outside, and the rolled-up portion of the carcass layer 2 and the main body of the carcass layer 2 that is not folded back Reinforcement N4 is arranged so as to cover it.

However, when the reinforcement N4 is made of organic fiber cords such as nylon cords and polyester cords, the strength of the inner reinforcing layer 4 cords is insufficient because the organic fiber cords are highly flexible. During use, the tire bead section collapses toward the rim flange, a so-called "sagging" phenomenon, which reduces the durability of the bead section. In addition, when the reinforcing layer 4 is made of a metal cord such as a steel cord, there is a problem in the manufacturing process because the metal cord has high rigidity, so the reinforcing layer 4 is loosely wound around the bead core 3. carcass N2
There is a problem that the tightening becomes weaker. Similarly, as a problem in the manufacturing process, the carcass layer 2 changes the cord angle along the reinforcing layer 4 of the metal cord in the region sandwiched between the bead core 3 and the reinforcing layer 4 (between C and 0 in FIG. 5). (The carcass that should enter the radial direction is at an angle with respect to the radial direction.) As a result, the height of the end 2a of the rolled up portion of the carcass layer 2 is difficult to be uniform on the circumference of the tire. This results in non-uniform rigidity and reduced bead durability.

[Problem to be solved by the invention]

An object of the present invention is to provide a heavy-duty pneumatic radial tire that uses metal cords as the cords of the reinforcing layer in the bead portion, and has improved bead durability.

[Means to solve the problem]

The present invention has at least one carcass layer installed between a pair of left and right bead portions, the end of which is folded back and rolled up from the inside to the outside of the tire around a bead core, and the carcass layer and the tread are connected to each other. In a radial tire with two or more belt layers arranged between them, (a) an outer metal cord reinforcement layer and an inner metal cord reinforcement layer are provided on the outside of the carcass layer rolled-up portion and the inside of the carcass layer main body that is not folded back at the bead portion; arranging the layers independently with the bead core as a boundary; (b) positioning the ends of the metal cord reinforcing layers on the bead core side at the sides of the bead core;
(C) the tensile strength of the cords in the inner metal cord reinforcement layer is greater than the tensile strength of the cords in the outer metal cord reinforcement layer, and (d) at least one fiber cord reinforcement layer is provided around the bead core. A heavy-duty pneumatic radial tire, characterized in that the fiber cord reinforcing layer is arranged from the inside to the outside of the tire, and the fiber cord reinforcing layer covers the end of each of the outer metal cord reinforcing layer and the inner metal cord reinforcing layer on the bead core side. This is the summary.

This means will be explained in detail below with reference to the drawings. Note that the same parts and parts as in FIG. 5 are indicated by the same numbers.

FIG. 1 is an explanatory half-sectional view in the meridian direction of an example of the heavy-duty pneumatic radial tire of the present invention. In Fig. 1, a carcass layer 2 made of fiber cords such as nylon is installed between a pair of left and right bead portions 1.1, and the ends of the carcass layer 2 are folded around a bead core 3 from the inside of the tire to the outside and rolled up. There is. Between the carcass layer 2 and the trend 5, a belt layer 6 is arranged annularly in the tire circumferential direction. At least one carcass layer 2 is arranged, and two or more belt layers are arranged. 7 is the rim, and H3 is the height of the tire at its maximum width.

This height is based on the rim diameter corresponding to the nominal diameter R of the rim.

In the present invention, the following requirements (a) to (d) are defined for this pneumatic radial tire.

(al) An outer metal cord reinforcing layer and an inner metal cord reinforcing layer are independently arranged on the outside of the carcass layer rolled-up part and on the inside of the unfolded carcass layer main body at the bead part, with the bead core as the boundary.

In FIG. 2, an outer metal cord reinforcing layer 4a is arranged on the outside of the rolled-up portion of the carcass layer, and an inner metal cord reinforcing layer 4b is arranged on the inside of the carcass layer main body that is not folded back. In this way, the outer metal cord reinforcing layer 4a
The reason why the inner metal cord reinforcing layer 4b and the inner metal cord reinforcing layer 4b are arranged independently with the bead core 3 as a boundary (a so-called split structure) is to differentiate the functions of each and allow each to fully fulfill its role. Note that these metal cord reinforcing layers are made by embedding metal cords such as steel cords in covering rubber (coated rubber).

The inner metal cord reinforcing layer 4b is preferably arranged along the unfolded carcass layer main body, and its upper end is higher than the end 2a of the rolled up portion of the carcass layer 2. That is, the height h8 of the inner metal cord reinforcing layer 4b is greater than the height HC of the end 2a of the rolled up portion of the carcass layer 2 (
hi > HC). Further, the outer metal cord reinforcing layer 4a is
It is preferable that the bead core 3 is arranged so as to be gradually separated from the side surface of the bead core 3 toward the outside of the tire, and that its upper end is higher than the end 2a of the rolled-up portion of the carcass layer 2. That is, the height ho of the outer metal cord reinforcing layer 4a is greater than the height HC of the end 2a of the rolled up portion of the carcass layer 2 (ha > HC).
).

(bl) The ends of these metal cord reinforcing layers on the bead core side are located on the sides of the bead core.

In FIG. 2, the end of the outer metal cord reinforcement N4a on the bead core 3 side, that is, the upper end 4m, and the upper end 4n of the inner metal cord reinforcement 1'i4b are located on the side of the bead core. When the upper end 4m and the upper end 4n are located between the bottom surface of the bead core 3 and the rim sheet 8,
This is because cracks occur at the upper ends 4m and 4n due to the pressure between the bead core 3 and the rim sheet 8.

(C) The tensile strength of the cords in the inner metal cord reinforcing layer 4b is made greater than the tensile strength of the cords in the outer metal cord reinforcing layer 4a.

This is to prevent the tire bead from collapsing toward the rim flange during use of the tire.

In order to differentiate the tensile strength of the cords in this way, the tensile strength of the cord of the inner metal cord reinforcing layer 4b is set to 0.8 to 1.5 times the elastic modulus of the carcass layer, and the tensile strength of the cord of the outer metal cord reinforcing layer 4a is set to 0.8 to 1.5 times the elastic modulus of the carcass layer. It is preferable that the tensile strength of the cord is 0.5 to 1.0 times the elastic modulus of the carcass layer (to prevent separation from occurring at the end of the reinforcing layer). In addition, the inner metal cord reinforcing layer 4
By setting the cord arrangement angle to the tire circumferential direction of b to be 30' or less (preferably 00 to 20'), the shear rigidity with the carcass layer is increased due to the synergistic effect of increasing tensile strength,
In addition to increasing the resistance to "settling", the cord arrangement angle of the outer metal cord reinforcing layer 4a with respect to the tire circumferential direction is set to 20' to 45'' to increase cross-sectional bending rigidity and strengthen the reinforcing effect on the end of the carcass layer. It should be noted that the lower the cord arrangement angle of the inner metal cord reinforcing layer, the greater the reinforcing effect will be. On the other hand, if the cord arrangement angle is high, separation will occur at the upper end of the inner metal cord reinforcing layer 4b.

(dl At least one fiber cord reinforcing layer is arranged around the bead core 3 from the inside to the outside of the tire,
This fiber cord reinforcing layer covered the ends of each of the outer metal cord reinforcing layer 4a and the inner metal cord reinforcing layer 4b on the bead core side.

In FIG. 2, two fiber cord reinforcing layers 10 are arranged around the bead core 3 from the inside of the tire to the outside, an upper end 4m of the outer metal cord reinforcing layer 4a and an upper end 4n of the inner metal cord reinforcing layer 4b. is covered. The fiber cord reinforcing layer 10 is made by embedding fiber cords such as nylon in a covering rubber.

If the outer metal cord reinforcing layer 4a and the inner metal cord reinforcing layer 4b are arranged independently with the bead core 3 as a boundary, the positions of these metal cord reinforcing layers will easily move during the steps from molding to vulcanization during tire manufacturing. This is because the carcass layer 2 is likely to be damaged due to the pressure between the bead core 3 and the rim sheet 8.

Therefore, by arranging the fiber cord reinforcing layer 10 in this manner, it becomes possible to manufacture a tire by stabilizing the positions of the outer metal cord reinforcing layer 4a and the inner metal cord reinforcing layer ji4b.

Next, FIG. 3 shows the separate bead structure of the pneumatic radial tire of the present invention. In FIG. 3, the height of the upper end of the fiber cord reinforcing layer 10 is lower than the height of the end 2a of the rolled up portion of the carcass layer 2 and the height of the upper end of the outer metal cord reinforcing layer 4a. This is the same as in Figure 2. Moreover, FIG. 4 shows a bead part structure for comparison, and is the same as that in FIG. 3 except that the fiber cord reinforcing layer 10 is not arranged.

Examples are shown below.

〔Example〕

Regarding the following tires (inventive tires, comparative tires 1 to 3) with tire size 11/70 R22,514PR,
The durability of the bead portion was evaluated by conducting an indoor rotating drum durability test. The results are shown in Table 1. In these tires, the carcass layer, belt layer, and bead core had the following specifications.

Steel cord layer consisting of one layer, 3+9+15(0,1
75)”, tensile strength per unit width 816 kg/cra
The average number of strokes from the bead core unwinding part (inside) to the unwinding end (outside) is 25 and 150 am.

Hillside 1: 4 layers. The steel cords in the second and third layers counting from the carcass layer intersect with each other between the plies.

Danjieyue: A single-wound bead with a rubber coating on steel wire with a diameter of 1.60 arm and a number of turns of 72, with the bottom surface of the bead core having an angle of inclination that is almost the same as the bead seat on the rim.

■ Tire of the present invention.

Bead part structure; Fig. 3, inner metal cord reinforcing layer 4 b
; 3 + 9 + 15 (0,175)'', steel cord, number of cords is 25, 150 mm, tensile strength (f) of cord is 850 kg/cm, cord arrangement angle (α) with respect to tire circumferential direction is 20゜Outer metal cord reinforcement layer 4aH steel cord, 7 x 3 (0,15
)''', the number of cords is 24, 150Il111, and the tensile strength (f) of the cord is 456 kg/cs+.

The cord arrangement angle (α) with respect to the tire circumferential direction is 35°.The fiber cord reinforcing layer 10 has a width of 10 mm upward from each upper end of the upper end 4m of the outer metal cord reinforcing layer 4a and the inner metal cord reinforcing layer 4b. Upper terminal 4n
Covered with nylon cord, 1260 D/2, number of cords is 40, 750 mm, and two layers are crossed at an angle of 75 degrees with respect to the tire circumferential direction.

■ Comparative tire 1° bead structure; Figure 3, inner metal cord reinforcement layer 4 b
; 3 + 9 + 15 (0,175)", steel cord, number of cords is 25 150 mm +, tensile strength of cord (f) 850 kg/c + a, cord arrangement angle (α) with respect to the tire circumferential direction is 35 ``Outer metal cord reinforcement layer 4a; steel cord, ? X 3 (
0,15)'', the number of cords is 24 750 wm, the tensile strength (f) of the cord is 456 kg7cm, the cord arrangement angle (α) with respect to the tire circumferential direction is 35'', fiber cord reinforcement layer lO; Covering the upper end 4m of the outer metal cord reinforcing layer 4a and the upper end 4n of the inner metal cord reinforcing layer 4b over a width of 10 m upward from the upper end, nylon cord, 1260 D/2, cord driving. The number is 40 x 150, and the cord arrangement angle with respect to the tire circumferential direction is 75'' and 75', with two layers intersecting.

■ Comparative tire 2° bead structure; Figure 4, inner metal cord reinforcement layer 4 b
i 3 + 9 + 15 (0,175)", 5--
) Lt code, number of code inputs is 25 150 m+++
, the tensile strength (f) of the cord is 850 kg/cm, the cord arrangement angle (α) with respect to the tire circumferential direction is 20°.Outer metal cord reinforcement layer 4a; steel cord, 7 x 3
(0,15) IW, number of cords is 24 750 m
The tensile strength (f) of the 111% cord is 456 kg/c Tsuru, and the cord arrangement angle (α) with respect to the tire circumferential direction is 35°.
.

■ Comparative tire 3° bead structure; Figure 5. Metal cord reinforcement layer 4; 3
+9 +15(0,175)+1'I, steel cord, number of cords is 25, 150 mm, tensile strength (f) of cord is 850 kg/cm, cord arrangement angle (α) with respect to tire circumferential direction is 20 ''.The metal cord reinforcing layer 4 is folded back and rolled up around the bead core 3 from the inside of the tire to the outside.

Low dome: Rim 22.5 x 7.50, air pressure 9.6 kgf/
cJ (120% of the standard), a load of 5200 kg (190% of the standard), and a speed of 45 km/h, and the distance traveled until the bead failed was expressed as an index to evaluate the durability of the bead. The larger the number, the better.

As is clear from Table 1, it can be seen that the tire of the present invention has excellent bead durability. In addition, in the comparison tire 1, separation occurred from the upper end of the inner metal cord reinforcing layer 4b.

This is because the cord arrangement angle (α) of the inner metal cord reinforcing layer 4b with respect to the tire circumferential direction is too large. In comparison tire 2, the bead portion durability fluctuated because the placement positions of the outer metal cord reinforcing layer 4a and the inner metal cord reinforcing layer 4b were not determined. Comparative tire 3 has carcass layer 2
Since the winding of the carcass layer 2 onto the bead core 3 was not tight enough, separation occurred from the end 2a of the rolled-up portion of the carcass layer 2.

4. [Effects of the Invention] As explained above, according to the present invention, since the bead structure is defined in the pneumatic radial tire, the bead durability can be improved. This bead structure is particularly suitable for tires that have a bead portion with different lengths on each side of the cross section of the bead core facing the carcass layer turn-up section, such as a tubeless tire built into a rim with a bead seat tilted at 15 degrees. suitable.

[Brief explanation of drawings]

FIG. 1 is an explanatory half-sectional view in the meridian direction of an example of the pneumatic radial tire for heavy loads of the present invention, FIG. 2 is an explanatory cross-sectional view showing the bead structure, and FIG. FIG. 4 is a cross-sectional explanatory diagram showing the bead structure for comparison. FIG. 5 is a cross-sectional diagram showing the bead structure of an example of a conventional heavy-duty pneumatic radial tire. It is an explanatory diagram. DESCRIPTION OF SYMBOLS 1... Bead part, 2... Carcass layer, 3... Bead core, 4... Reinforcement layer, 4a... Outer metal cord reinforcement layer, 4b... Inner metal cord reinforcement layer, 5... - Tread, 6... Belt layer, 7... Rim, 10... Fiber cord reinforcement layer.

Claims (1)

[Scope of Claims] At least one carcass layer is installed between a pair of left and right bead portions, and the end portion is folded and rolled up from the inside of the tire to the outside around the bead core, and the carcass layer and the tread In a radial tire with two or more belt layers arranged between (a) an outer metal cord reinforcing layer and an inner metal The cord reinforcing layers are arranged independently with the bead core as a boundary, (b) the terminals of these metal cord reinforcing layers on the bead core side are respectively located on the sides of the bead core, and (c) the cords of the inner metal cord reinforcing layer are arranged independently. (d) at least one fiber cord reinforcing layer is arranged around the bead core from the inside of the tire to the outside of the tire; 1. A pneumatic radial tire for heavy loads, characterized in that a reinforcing layer covers the ends of each of the outer metal cord reinforcing layer and the inner metal cord reinforcing layer on the bead core side.