JPS60135312A - Radial tyre for heavy load - Google Patents

Abstract

PURPOSE:To prevent the occurrence of compression deformation and to effectively reduce damage of a bead part, by a method wherein a reinforcing layer is located between carcass and bead apex, and a height thereof and a cord angle, are set to 20-70 deg.. CONSTITUTION:A tyre 1 has a pair of bead cores 2 on both sides, a carcass 3 being radially aligned in parallel, and a reinforcing layer 5 for a bead apex 4. The reinforcing layer 5 is inserted between the inside of a main body part 3a of the carcass 3 and a fold-back part 3b and the outside of the bead apex 4. The reinforcing layer 5 is inclined at a cord angle of 20-70 deg. with the carcass cord for alignment. A height Ha of the inside of the bead part of the reinforcing layer 5 is set to a value higher than a height Hd of the outside of the bead part and a height Hc of an upper end 3bA of the fold-back part 3b of the carcass 3, and elongation strain is relieved to relieve a risk of the bead part being damaged.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heavy-duty radial tire in which strain at the upper end of the folded portion of the carcass is alleviated by inserting a reinforcing layer in a specific arrangement between the folded portion of the carcass and the bead apex.

In a heavy-duty radial tire used for heavy vehicles such as buses and trucks, the bead portion usually has a carcass b made of steel cord folded around a bead core a from the inside to the outside, as shown in FIG. A reinforcing layer d using a steel cord is arranged on the outside of the folded part C of the carcass b, while the upper fid on the outside of the bead part
1 is positioned toward the upper end 01 of the folded portion C of the carcass b, or is formed so as to exceed the upper end C1.

This structure increases the rigidity of the bead,
Although the shear strain is reduced, there is a drawback that rubber peeling tends to occur at the upper end d1 due to severe compressive strain near the upper fidl on the outside of the reinforcing layer.

-Additionally, one or more organic fiber cord layers e such as nylon are added to the outer side of the reinforcement Nd, and the cords are arranged so as to intersect with the cords of the reinforcement jWd, and the folded portion C of the carcass b is Upper end C1 and upper end d of reinforcement Nd
1, and prevents the glabella peeling that tends to occur in that area. Although this structure considerably reduces damage to the bead, it is still insufficient for N-load radial tires that are used under high-load, high-speed conditions, and whose tread may be re-used several times. be.

An object of the present invention is to provide a heavy-duty radial tire (hereinafter referred to as a tire) with excellent bead durability.

An embodiment of the present invention will be described below based on the drawings.

In FIG. 2, which shows only one bead portion enlarged, the tire 1 includes a pair of left and right bead cores 2, and the bead cores 2.
．． The frame is a carcass that includes a main body part 3a that is passed between the two parts, and a folded part 3b that is arranged at the end of the main part 3a and is folded back around the bead core 2 from the inside to the outside, and that includes steel cords that are arranged substantially parallel to the tire radial direction. 3, a belt layer (not shown) disposed on the outside of the crown portion of the carcass 3, and a relatively hard rubber disposed in a region sandwiched between the main body portion 3a of the carcass 3 and the folded portion 3b of the carcass 3. The bead apex 4 comprises a bead apex 4, and a reinforcing layer 5 disposed from the inside to the outside of the bead portion between the bead apex and the carcass.

The reinforcing layer 5 has the main body part 3a of the scrap 3 and the folded part 3.
The inner side of the bead apex 4 and the outer side of the bead apex 4 are placed adjacent to each other with a small gap between them or in contact with each other. By adopting such an arrangement, compressive strain occurring on the outside of the bead portion, that is, near the folded portion 3b of the carcass 3′ due to repeated deformation during tire running, especially due to deformation strain in the tire radial direction, is suppressed and damage thereof is reduced. can.

The cord angle of reinforcement Iw5 is 2 with respect to the carcass cord.
Tsukuda are arranged at 0 to 70 degrees. If the angle is smaller than 20°, the bead portion will have high rigidity in the direction of bending deformation, and strain relaxation and absorption will be insufficient, and strain will likely occur in the upper parts #5A and 5B of the reinforcing layer 5. On the other hand, if the angle exceeds 70°, the rigidity decreases and the effect of alleviating strain decreases. Note that when a plurality of reinforcing layers 5 are used, the plies are arranged so as to cross each other.

The reinforcing layer 5 is made of inorganic fiber cords such as steel cords and glass fiber cords, or organic fiber cords such as nylon, polyester, rayon, and aromatic polyamide fiber cords in relatively hard rubber, for example, rubber with a JIs hardness of 60 to 95 degrees. It is formed using ply embedded in the Particularly preferably, as the cord of the reinforcing layer 5, a fiber cord having a high elastic modulus such as a steel cord or an aromatic polyamide fiber cord is particularly preferably used.

The bead inner side height Ha from the inner upper end 5B of the reinforcing layer 5 to the bead bottom is set higher than the outer height Hd of the bead and the height He of the upper end 3bA of the folded part 3b of the carcass 3. The main body portion 3a in the bead portion is subjected to tensile strain, but by raising the reinforcing layer 5 inward to the height Ha, the tensile strain can be alleviated and the risk of damage to the bead portion is reduced.

Furthermore, the height Hc of the upper end 5A on the outside of the bead portion of the reinforcing layer is:
By arranging it so as to exceed the height Hc of the upper end 3bA of the folded portion, stress concentration at the upper end 3bA of the folded portion is alleviated. Moreover, since the upper end 5A of the reinforcing layer on the outside of the bead part is arranged inside the bead part of the folded part, it is located even closer to the center of the bead part. Distortion can be reduced because it is close to the neutral zone of distortion. Note that Hd is in the range of 110 to 180% of Hc.

Next, bead apex 4 is a rubber with high hardness, such as J
A material having an IS hardness of 58° to 90°, preferably 60° to 80° is used, and together with the reinforcement N5, it reinforces the bead portion and effectively achieves strain absorption and relaxation. In addition, the height He of the bead apex 4 to #4A is 20 to 20 times the cross-sectional height of the tire from the top surface of the tread part to the bottom of the bead
40%, and the upper end 5B of the reinforcing layer 5 inside the bead portion is near the upper end 4A of the bead apex 4,
Preferably, it is located slightly below the upper end 4A of the bead apex 4.

Furthermore, the reinforcing layer 5 may be constructed by dividing the inner and outer parts of the bead part into two layers.Also, an additional reinforcing layer made of steel cords or organic fiber cords may be arranged on the outside of the folded part 3b of the carcass 3. It's okay. The additional reinforcing layers are arranged at an angle of 20° to 70° with respect to the carcass cords, and when two or more layers are used, they are arranged so that the cords intersect with each other.

As mentioned above, the tire of the present invention is based on the fact that the reinforcing layer is inserted between the carcass and the bead apex, and the height and cord angle of the reinforcing layer are set within the optimum range. Damage can be effectively reduced.

EXAMPLE A steel radial tire with a tire size of 1QQQR20 using steel cord for the carcass and belt layer was manufactured according to the specifications shown in Table 1, and the durability of the bead portion of the tire was evaluated by a drum test.

The drum test was carried out at a speed of 80 km and a load of 3000 kg/piece, and the distance traveled until damage occurred to the bead portion was measured. The results are also shown in Table 1. All of the products of this example have improved bead part durability compared to the comparative example products. Note that the bead portion durability is expressed as a ratio of running distance, with the comparison example product being 100.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view illustrating a bead portion of a conventional tire, and FIG. 2 is a cross-sectional view of a bead portion illustrating an embodiment of the present invention. 2-・-bead core, 3-・-carcass, 3a-・-
Living body part, 3b-folding part, 4--bead apex, 5--reinforcing layer, 7--additional reinforcing layer. Patent applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent attorney Tadashi Naemura

Claims (3)

[Claims] (1) A pair of left and right bead cores, and the frame has a main body section that extends over these bead cores, and a folded section that is folded around the bead cores arranged on both sides from the inside to the outside, and is substantially parallel to the tire radial direction. A carcass containing arranged steel cords, a belt layer arranged on the outside of the crown part of this carcass, a bead apex arranged in the area sandwiched between the main part of the carcass and the folded part, and the inside of the bead part from the inside to the outside of the bead part. The cords are inserted between the carcass, the inside of its folded part, and the bead apex so that the height Ha exceeds the bead outside height Hd, and the cords are arranged at an angle of 20 to 70 degrees with respect to the carcass cord. l! Radial tie for heavy loads with layers - 1.
. (2) The heavy-duty radial tire according to claim 1, wherein the reinforcing layer has a height (Hd) at the outside of the bead portion that is higher than a height (Hc) at the folded portion of the carcass. (3) The heavy-duty radial tire according to claim 1, wherein the cord of the reinforcing layer is a steel cord or a fiber cord.