JPS6092905A - Radial tire for heavy load - Google Patents

Abstract

PURPOSE:To check an expansional deformation as well as to relieve damage to a bead part in an effective manner, by disposing a lower end of an additionally reinforced layer in position between a carcass turnup part and a bead apex, while setting a cord angle in an optimum range. CONSTITUTION:A tire 1 is provided with a carcass 3 inclusive of a main body part 3a being bridged between a pair of symmetrical bead cores 2 and a bead core 2 and a steel cord having a turnup part 3b disposed in an end part of the main body part, turning up the circumference of the bead core 2 ranging from inside to outside, and substantially arranged in parallel in the tire radial direction. In addition, a bead apex 4 consisting of a belt layer disposed at the outside of a crown part of the carcass 3 and hard rubber disposed in a domain being sandwiched between the mainlbody part 3a of the carcass 3 and the turnup part 3b is installed. And, a main reinforced layer 5 disposed from inside to outside of a bead part and an additionally reinforced layer 7 disposed interposingly between the inside of the turnup part 3b of the carcass 3 and the bead apex 4 are installed as well.

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 an additional reinforcing layer 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 portion C of the carcass b, while an upper end d1 on the outside of the bead portion
is located below the upper end cl of the folded portion C of the carcass b, or is formed so as to exceed the upper end c1.

Furthermore, one or more organic fiber cord layers e such as nylon are attached to the outer side of the reinforcing layer d, and the cords are arranged so as to intersect with the cords of the reinforcing layer d, and the folded part C of the carcass b is Upper end c1 and upper end di of reinforcing lid
It alleviates the distortion in the area and prevents the glabella peeling that tends to occur in that area. Although this structure significantly reduces damage to the heat section, it is still insufficient for a heavy-duty radial tire that is used under high-load, high-speed conditions, and may be used several times with red correction. It is.

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 has a main body part 3a which is passed between the two, and a folded part 3b arranged at the end thereof and folded back around the bead core 2 from the inside to the outside.Tie-1 Steel cords arranged substantially parallel to the radial direction and a belt layer (
(not shown), a bead apex 4 made of hard rubber and arranged in a region sandwiched between the main body 3a of the carcass 3 and the folded part 3b of the carcass 3, and a bead apex 4 arranged from the inside to the outside of the bead part. It comprises a main reinforcing layer 5 and an additional reinforcing layer 7 inserted between the inside of the folded part 3b of the carcass 3 and the bead apex 4.

The additional reinforcement 1ii7 is inserted adjacently between the inside of the folded part 3b of the carcass 3 and the outside of the bead apex 4 with a small gap between them or in contact with each other.

By adopting such an arrangement, it is possible to suppress the repeated deformation of the tire during running, especially the expansion occurring on the outside of the bead portion due to deformation strain in the tire radial direction, that is, near the folded portion 3b of the carcass 3, and thereby reduce the damage. Therefore, the lower end 7A of the additional reinforcing layer 7 is inserted and fixed between the folded portion 3b and the bead apex 4. Conventionally, an organic fiber cord layer has been arranged outside the folded part 3b or the main reinforcing layer 5, but in such a case, the strain at the folded part 3b of the carcass 3 and the upper end 5A of the main reinforcement N5 is relaxed and absorbed. It's not enough to do that.

The cord angles of the reinforcement 7 and the main reinforcing layer 5 are arranged at an angle of 20 to 70 degrees with respect to the carcass cord. 20°
If it is smaller, the rigidity in the bending deformation direction of the bead portion will be high, and strain relaxation and absorption will be insufficient, and strain will likely occur at the upper end 7A of the additional reinforcing layer 7. On the other hand, if the angle exceeds 70°, the rigidity decreases and the strain alleviation effect decreases. In addition, when using a plurality of additional reinforcing layers 7, the plies are arranged so as to cross each other.

The main reinforcing layer 5 and the additional reinforcing layer 7 are made of relatively hard rubber such as inorganic fiber cord such as steel cord or glass fiber cord or organic fiber cord such as nylon, polyester, rayon, or aromatic polyamide fiber cord, for example, JIS hardness of 60. Formed using plies embedded in ~95' rubber. Particularly preferably, the additional reinforcing layer 7 is an organic fiber cord or a steel cord having a lower modulus of elasticity than the main reinforcing layer 5, and as the cord for the main reinforcing layer 5, a steel cord or an aromatic polyamide fiber cord is particularly preferably used. be done.

The inner height Ha of the bead part from the inner upper end 5B of the main reinforcing layer 5 to the bead bottom is the height H of the upper end 7A of the additional reinforcing layer 7.
b and the upper end 3 of the folded part 3b of the carcass 3
The height of bA is set higher than the height Hc. The main body portion 3a in the bead portion is subjected to compressive strain, but by raising the main reinforcing layer 5 inward to the height Ha, the compressive strain can be alleviated and the risk of damage to the bead portion can be reduced.

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 main reinforcing layer 5 and the additional reinforcing layer 7, it reinforces the bead portion and effectively achieves strain absorption and relaxation. Further, the height Ha of the bead apex 4 to its upper end 4A is set in a range of 20 to 40% of the tire cross-sectional height from the top surface of the tread part to the bead bottom, and the upper end 7A of the additional reinforcing layer 7 is set to the height Ha of the bead apex 4. upper end 4A
, preferably slightly below the upper end 4A of the bead apex 4.

Further, the main reinforcing layer 5 may be constructed by dividing the inner side and the outer side of the bead part into two pieces, and the height Hc of the folded part 3b of the carcass 3 shown in FIG. Height H
Unlike when setting the height Hc higher than d, the height Hc is set higher than the outer height H
It can also be formed lower than d. At this time, it is preferable that the inner height Ha of the bead portion of the main reinforcement N5 is configured to be an intermediate height between the outer height Hd of the main reinforcement layer 5 and the height Hb of the additional reinforcement N7.

As stated on paper, the tire of the present invention is based on the fact that the lower end of the additional reinforcing layer is inserted between the carcass folded part and the bead apex, and the cord angle is set within the optimum range, thereby suppressing elongation strain and improving the strength of the bead part. Table 1 Note 1) The relationship between the outer height Hd) and the folded height Hc) of the main reinforcing layer 5 in Figure 2 is reversed.

Damage can be effectively reduced.

EXAMPLE A steel radial tire having a tire size of 1000R20 and 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 products. Note that the bead portion durability is expressed as a ratio of mileage, with the comparative 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-main body part,
3b - folded part, 4 - bead apex, 5 - main reinforcement layer, 7 - additional reinforcement layer. Patent applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent attorney Tadashi Naemura

Claims (1)

[Scope of Claims] 1) A pair of left and right bead cores, the frame has a main body part that extends over these bead cores, and a folded part that is folded back from the inside to the outside around the bead cores arranged on both sides of the body part, and has a structure that extends in the tire radial direction. A carcass including steel cords arranged substantially in parallel, a belt layer arranged on the outside of the crown part of this carcass, a bead apex made of hard rubber arranged in an area sandwiched between the main part of the carcass and the folded part, and a bead. A main reinforcing layer in which the cords are arranged in a direction intersecting the carcass cord at an angle of 20 to 70 degrees from the inside to the outside of the carcass, and a main reinforcing layer that is inserted between the inside of the folded part of the carcass and the bead apex and crosses the carcass cord. A heavy-duty radial tire comprising an additional reinforcing layer in which the cords are arranged at an angle of 20 to 70 degrees. (2) A patent claim characterized in that the height Ha) of the main reinforcing layer inside the bead portion is lower than the height Hb) of the additional reinforcing layer, and is higher than the height He) of the folded portion of the carcass. A radial tire for heavy loads according to item 1. (3) The heavy-duty radial tire according to claim 1, wherein the cord of the main reinforcing layer is a steel cord or a fiber cord. (4) The heavy-duty radial tire according to claim 1, wherein the cord of the additional reinforcing layer is a steel cord or an organic fiber cord.