JPH01156108A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve operational stability, trail wondering ability and durability of a bead portion by turning down at least one layer of plural carcass layers outside a bead wire and turning up the other carcass layers from the inside of a tire to the outside round the bead wire. CONSTITUTION:One carcass layer 5 comprising a textile cord is folded back from the inside 3 of a tire towards the outside 4 in the periphery of a bead wire 2 in a bead portion 1 to turn up. Another carcass layer 5' is turned down in the outside 4 of the bead wire 2. In this structure, the shortest distance B from 8 bead heal 10 to the reference line l of rotation of the bead portion with respect to the bead base width A is set to B/A>0.4. The outer periphery of the bead portion 1 is coated with a rubber layer 6 having JIS hardness of 65-85. Further, the turn-down edge 13 of one carcass layer 5' is kept at a distance from the reference line l of rotation on the bead base portion 11 below the bead wire 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pneumatic radial tire that has excellent actual vehicle characteristics (steering stability, rut wandering properties, etc.) and improved bead durability.

[Prior art]

Conventionally, pneumatic radial tires are shown in Figure 2 (A),
It has the bead structure shown in (B), (C) and (D). In FIG. 2(A), a two-layer carcass layer 5.5 made of textile cord is placed around the bead wire 2 in the bead portion 1 from the inner side 3 of the tire to the outer side 4 of the tire.
is folded back and turn-amplified (hereinafter referred to as 2-O
(referred to as PL structure). In FIG. 2 ('B), a three-layer carcass layer 5.5.5 made of textile cord is folded back and turned up around the bead wire 2 at the bead portion 1 from the inner side 3 of the tire to the outer side 4 of the tire. (
(hereinafter referred to as 3-OPL structure). FIG. 2C shows a structure in which one carcass layer 5 is turned up around the bead wire 2, and an IN carcass layer 5' is turned down outside the bead wire 2 (hereinafter referred to as 1). -I
2 (D) shows two carcass layers 5, 5 turned up around the bead wire 2, and one carcass layer 5' outside the bead wire 2. A turned down structure (hereinafter referred to as 2-IPL structure) is shown. In such conventional tires, the lower end is placed on the outside of the turn-up part of the carcass layer with a bead heel 1 to prevent the rim from shifting at the bead part.
around 0 and the upper end of the bead heel from 10 to about 35-40
A rim compression rubber made of a hard rubber layer 6 extending up to a position of about mm is arranged.

However, tires with 2-OPL structure or 3-OPL structure as shown in Fig. 2 (A), CB)
C), 1-1PL structure or 2-IPL shown in (D)
There is a problem that the steering stability and rut-wandering performance are inferior to that of structural tires;
In the tire with the 1-IPL structure or the 2-IPL structure shown in (D), the occurrence of cranks at the turndown edge of the carcass layer is unavoidable, and there is a drawback that the durability of the bead portion deteriorates. Purpose] An object of the present invention is to provide a pneumatic radial tire that has improved handling stability, rut-wandering performance, and bead durability by devising a bead structure. This tire is particularly useful as a flat radial tire for small trunks with an aspect ratio of 80 or less.

[Structure of the invention]

For this reason, the present invention consists of two or more carcass layers made of textile cord, at least one of the carcass layers is turned down to the outside of the bead wire, and the remaining carcass layers are turned down around the bead wire from the inside to the outside of the tire. The tire is turned up by turning it back, and the shortest distance B from the bead heel to the bead rotation reference line E with respect to the bead base width A is B/A>0.4, and the outer periphery of the bead is made with a hardness of J1S 65 to 85. This pneumatic radial tire is characterized in that it is covered with a rubber layer and that the turndown edge of the carcass layer is located away from the rotation reference line l on the bead base.

Hereinafter, the configuration of the present invention will be explained in detail with reference to the drawings.

Figures 1 (A), (B), and (C) are, respectively,
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory cross-sectional view showing an example of a bead structure of a pneumatic radial tire according to the present invention.

The tire of the present invention comprises two or more carcass layers made of textile cord, and at least I
N is turned down to the outside of the bead wire, and the remaining carcass layer is folded back around the bead wire from the inside to the outside of the tire to perform turn amplification.

That is, for example, as shown in FIG. 1(A) and FIG. 1(C), one carcass layer 5 made of textile cord is placed around the bead wire 2 in the bead portion 1 from the inner side 3 of the tire to the outer side 4 of the tire. is folded back and turned up, and one carcass layer 5' is turned down on the outside of the bead wire 2 (1-IPL structure)
, or as shown in FIG. 1(B), from the inner side 3 of the tire to the outer side 4 of the tire around the bead wire 2 in the bead portion 1.
, a two-layer carcass N5 made of textile cord,
5 is folded back and turned up, and one carcass layer 5° is turned down on the outside of the bead wire 2 (2-IPL structure). Here, the term "turndown" means that the edge of the carcass layer 5 degrees hangs down from the outside to the inside of the bead wire 2 without being folded back around the bead wire 2.

In the present invention, in this way, the 1-IPL structure or 2-IPL structure
In the tire having this structure, the shortest distance B from the bead heel 10 to the bead rotation reference line l with respect to the bead base width A is B/A>0.4. If B/A is 0.4 or less, the vicinity of the bead toe 14 will rise and deform in the direction of the arrow shown in Figure 1 (C) when the tire is filled with air pressure or when the tire is running, resulting in air pressure leakage and bead deformation. Due to the misalignment between the bead section and the rim (causing deterioration of the durability of the bead section, and in addition, the turndown edge 13 of the carcass layer will be located close to the rotation boundary line, This is because a rubber crank occurs at the edge part due to the movement of the rubber.
Although A is related to the size of the bead, etc., the upper limit is 0.
A value of about 7 is practical.

Here, the rotation reference line β refers to a perpendicular line drawn from the center of the bead wire 2 to the bead base portion 11.

In addition, in the present invention, the outer side of the bead part has a hardness of J1S 65 to
It is covered with a rubber layer 6 of 85. Here, the rim traction rubber consisting of the rubber layer 6 extends over the entire bead base portion 11 with one end extending beyond the bead heel 10 to the outside of the bead portion by approximately 35 mm.
The other end extends about 5 to 10 mm beyond the bead tow 14 and covers the outside of the bead. With this arrangement, it is possible to prevent the vicinity of the bead toe 14 from rising when the tire is filled with air pressure and during driving.

The reason why the hardness of the rubber layer 6 was set to J1S 65 to 85 was that of Jr.
If the S hardness is less than 65, the rubber will wear on the contact surface with the rim, resulting in poor bead durability. On the other hand, if the J1S hardness exceeds 85, the fracture strength characteristics of the rubber will deteriorate, leading to the occurrence of cranks on the rubber surface. This is because the durability of the repeat portion deteriorates. The gauge (thickness) G of this rubber layer 6 is 1.0 mm or more at any location near the bead base portion 11 and bead heel portion 12. This is because if it is less than 1.0 mm, it will be difficult to improve the durability of the bead portion. Note that this rubber layer 6 is made of natural rubber, styrene-
Carbon black, rubber such as butadiene copolymer rubber,
It is composed of a rubber composition containing additives such as sulfur.

Furthermore, in the present invention, the turndown edge 13 of the carcass layer 5' is located below the bead wire 2 and away from the rotational reference vAl on the bead base portion 11. Rotation standard vA7 with turndown edge 13! This is because by moving the rubber as far away as possible from the turndown edge 13, the movement of the rubber near the turndown edge 13 is reduced, thereby preventing cranking at the turndown edge 13.

Examples are shown below.

Example (1) Regarding tires with 1-IPL structure and tires with 2-OPL structure, tire size 205/60 R17,5
The handling stability and rut-wandering performance were evaluated using an evaluation vehicle, Dyna, with a 3-ton overload.

The results are shown in Table 1 below using indices. The higher the number, the better.

−j6 i・　law: Actual vehicle evaluation using 100 point system.

Sorting S poem ρF4 Kunami p1 monthly distribution method: Actual vehicle evaluation using 100 point system.

As can be seen from Table 1, tires with 1-IPL structure have 2-O
Both handling stability and rut wandering properties are superior to tires with PL structure. Therefore, in the present invention, as shown in FIG. 1(A) and FIG. 1(C), 1-IP
The L structure was adopted.

(2) A low-pressure, high-load drum durability test was conducted on various tires (tire a w e ) having the bead structure shown in FIG. 1(C). The results are shown in Table 2 below. In addition,
In Table 2, the traveling distance is the distance traveled until the bead part breaks.

Mr. ``Dome'' method: Air pressure: 50% of standard air pressure, Load: 150% of standard load, Speed: 50km/h.

(Margin below this page) From Table 2, when B/A>0.4 and the gauge G of the rubber layer 6 is 1.0 mm or more at both the bead base part 11 and the bead heel part 12 (tire C , tire e), the mileage is over 8,500 km, so it can be seen that the bead part durability is the best.

〔Effect of the invention〕

As explained above, according to the present invention, in addition to improving steering stability (especially roll characteristics when overloaded) and rut wandering properties, bead part durability (especially turndown edge part crank resistance under heavy loads) is improved. can be done.

[Brief explanation of the drawing]

Figures 1 (A), (B), and (C) are, respectively,
Cross-sectional explanatory diagrams showing an example of the bead structure of the pneumatic radial tire of the present invention, FIGS.
C) and (D) are cross-sectional explanatory views each showing an example of a bead structure of a conventional pneumatic radial tire. DESCRIPTION OF SYMBOLS 1... Bead part, 2... Bead wire, 3... Tire inside, 4... Tire outside, 5... Carcass layer,
5'...Carcass layer, 6...Rubber lN, 10...
・Bead heel, 11... Bead base part, 12...
・Bead heel part, 13... Turndown edge. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] The tire consists of two or more carcass layers made of textile cord, at least one of the carcass layers is turned down to the outside of the bead wire, and the remaining carcass layer is folded around the bead wire from the inside to the outside of the tire. The tire is a tire that has been turned up with a bead base width A, the shortest distance B from the bead heel to the bead rotation reference line l is B/A>0.4, and the outer periphery of the bead is covered with a rubber layer with a hardness of J1S65 to 85. A pneumatic radial tire characterized in that the turndown edge of the carcass layer is further away from the rotation reference line l on the bead base.