JP3477312B2 - Pneumatic radial tire - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire mainly used for passenger cars. 2. Description of the Related Art In pneumatic radial tires used for passenger cars, tires having small (low) rotational resistance R, ie, fuel-efficient tires, are required. If the weight of the tire is reduced (lightening), low fuel consumption and low cost can be expected. For this reason, the number of carcass used can be reduced, and the height of the carcass end around the bead core (usually the tire It has been studied to shorten the cross section height (about の), but it was technically difficult. [0003] If a single carcass is used and the winding height of the end portion is shortened, the durability of the bead portion is reduced, and the durability of the bead portion is not reduced. For this purpose, it is necessary to reinforce it with a piece of cloth (for example,
In addition, the rubber amount of the abrasion rubber is extremely increased, which is against the weight reduction of the tire. The inventor of the present invention has conducted various experiments, and as a result, by adjusting the winding height of the carcass end, the stretching height and thickness of the bead filler, and the stretching height and thickness of the abrasion rubber, The company succeeded in developing a pneumatic radial tire that can maintain the durability of the bead while reducing the weight of the tire. According to the present invention, a tire bead portion T is provided with an abrasion rubber 3 extending radially outward in a tire bead portion T, and a bead core 5 embedded in the tire bead portion T is provided in a tire radial direction. A pneumatic radial tire including a carcass 1 having a bead filler 2 extended outward and having a folded portion 7 having an end wound around the bead core 5 from the tire inside toward the tire outside, The following technical measures were taken: That is, according to the present invention, the carcass 1
And the winding height X of the folded portion 7 is 16
And the stretching height Y of the abrasion rubber 3 is equal to the stretching height Z of the bead filler 2.
And the ratio Y / X between Y and X is 1.5 to 2.
5, and the ratio Z / X between Z and X is 1.5.
In addition, the thickness a of the abrasion rubber 3 at the portion corresponding to the edge of the folded portion 7 in the carcass 1 is 3.5 mm or more, and the thickness a and the thickness b of the bead filler rubber 2 at the portion. Is set to 1.2 to 1.5, and the hoisting height X is 20
mm, the stretching height Y of the abrasion rubber 3 is 4
0 mm, and the stretch height Z of the bead filler 2 is 45
mm, the thickness a of the abrasion rubber 3 is 4.0
mm, the thickness b of the bead filler 2 is 3.0 mm
It is desirable to be before and after. By adopting the above configuration, it is possible to secure the durability of the bead portion without increasing the reinforcing layer and the amount of rubber separately, that is, without increasing the weight of the tire. This will be described with reference to examples. FIG. 1 shows one bead portion T of a pneumatic radial tire according to the present invention. The bead portion T has a tire rim 6 having a rim flange 6A having a height R. It is fitted to. The tire bead portion T is provided with an abrasion rubber (rim cushion rubber) 3 extending outward in the tire radial direction, and the bead filler 2 extended outward from the bead core 5 embedded in the tire bead portion T in the tire radial direction. The carcass 1 has a folded portion 7 whose end is wound up from the inside of the tire toward the outside of the tire around the bead core 5, and reference numeral 4 denotes an edge of the folded portion 7. In the radial tire T according to the present invention, the carcass 1 is one ply, the winding height X of the folded portion 7 is 16 to 24 mm, and the stretching height of the abrasion rubber 3 is further increased. Y is made smaller than the stretching height Z of the bead filler 2, and Y and X
Is set to 1.5 to 2.5, and the ratio Z / X between Z and X is set to 1.5 to 3.5. Further, the thickness a of the abrasion rubber 3 at a portion corresponding to the edge of the turn-back portion 7 in the carcass 1
Is 3.5 mm or more, and the ratio a / b of the thickness a to the thickness b of the bead filler rubber 2 at the site is 1.2 to 1.5. Specifically, the winding height X is 20
mm, the stretching height Y of the abrasion rubber 3 is 4
0 mm, and the stretch height Z of the bead filler 2 is 45
mm, the thickness a of the abrasion rubber 3 is 4.0
mm, the thickness b of the bead filler 2 is 3.0 mm
It is before and after. That is, the edge 4 of the folded portion 7 of the carcass 1 is located in the vicinity of the rim flange 6A. If the winding height X is too high, the distortion increases, and separation occurs from the edge 4 as a base point. On the other hand, if it is too low, the rigidity of the bead portion T is low, and the bead portion T becomes unstable, which may cause so-called bead slippage. The positional relationship between the stretch height Z and the thickness b of the bead filler 2, the stretch height Y and the thickness a of the abrasion rubber 3, and the edge 4 of the folded portion 7 is determined by the load of the edge 4 when the load is applied. The following test was conducted on the assumption that the distortion was as small as possible. The test tire is T / L185 / 70R14.
It is. The durability performance test is based on JIS-D4230. However, after 24 hours, the load was increased to 140% and the vehicle was run until it was damaged. Examples 1 and 2 of the present invention,
For Comparative Examples 1 to 8, the index is shown in Table 1 with the conventional example taken as 100. [Table 1] As described in detail above, according to the present invention, it is possible to provide a pneumatic tire that maintains the durability of the bead portion while reducing the weight, and does not require a reinforcing layer or the like. Is also advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a bead portion according to an embodiment of the present invention. [Description of Signs] T Bead portion 1 Carcass 2 Bead filler 3 Ablation rubber 5 Bead core 7 Turnback portion

Claims (1)

(1) An abrasion rubber (3) extending radially outward in a tire bead portion (T) and a bead core (3) embedded in the tire bead portion (T). 5) a bead filler (2) extending radially outward from the tire, and having a folded portion (7) whose end is wound up from the tire inside toward the tire outside around the bead core (5). In the pneumatic radial tire provided with the carcass (1), the carcass (1) is one ply, and the winding height (X) of the folded portion (7) is 16 to 24 mm. Stretch height (Y) of abrasion rubber (3)
Is smaller than the stretching height (Z) of the bead filler (2), and the ratio Y / X between (Y) and (X) is 1.5 to 2.
5, and the ratio Z / X of (Z) and (X).
Is 1.5 to 3.5, and the thickness (a) of the abrasion rubber (3) at a position corresponding to the edge of the folded portion (7) in the carcass (1) is 3.5 mm or more. A pneumatic radial tire, wherein the ratio a / b between (a) and the thickness (b) of the bead filler rubber (2) at the site is 1.2 to 1.5.