JPS61129305A - Pneumatic radial tire for passenger car - Google Patents

Abstract

PURPOSE:To improve the durability of a folded-back portion of a pneumatic radial tire in which a carcass layer using aromatic polyamide fiber cord is disposed, by disposing a predetermined hardness upper side bead filler on the outside of a turn-up portion of the carcass layer. CONSTITUTION:An end of a carcass layer 4 is raised from the inside of a tire to the outside around a bead wire 3 and an under side bead filler 6 to form a turn-up portion 4a along a carcass layer body 4b. And outside the turn-up portion 4a is disposed an upper side bead filler 7 having JIS hardness of 75-95. By this constitution, is located the neutral shaft for tire bending near the inside surface of tire in the upper side bead filler 7 so that a compressive force of the turn-up portion 4a to a code can be avoided to prevent breakage of the cord and improve the durability.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a turn amplifier section (folded section) of a carcass layer.
This invention relates to a pneumatic radial tire for passenger cars that has improved durability.

[Prior art]

Pneumatic radial tires for passenger cars generally use organic fiber cords such as nylon fibers, polyester fibers, and rayon fibers for the cords of the carcass layer, and have a belt layer consisting of mutually crossed steel cords as the belt layer. Compared to conventional bias tires, the presence of this belt layer improves abrasion resistance, high-speed durability, handling stability, etc., and reduces rolling resistance.

In addition, in order to improve productivity and reduce weight, the carcass layer is arranged as 1 ply instead of 2 ply! There is a direction.

However, in a pneumatic radial tire of a large size larger than 195/70 SR14, it is difficult to make the carcass layer into a single ply with the above-mentioned seeded fiber cord due to strength problems.

Therefore, recently, as shown in Japanese Patent Application Laid-Open No. 49-120303, it has been proposed to use aromatic polyamide fiber cords as cords for the carcass layer of pneumatic radial tires.

Aromatic polyamide fibers have significantly higher strength than conventional organic fiber cord materials, so when aromatic polyamide fiber cords are used, the carcass layer, which conventionally requires two plies, can be replaced with one ply, increasing productivity. There are advantages to improving. However, on the other hand, aromatic polyamide fibers have a high crystallinity due to their molecular structure and have poor adhesion to coating rubber. Therefore, when aromatic polyamide fiber cords are used, separation (between the cord and rubber) is created in the turn-up part of the carcass layer. There is a drawback that peeling phenomenon) is likely to occur.

[Purpose of the invention]

An object of the present invention is to provide a pneumatic radial tire for a passenger car in which the durability of a carcass layer using an aromatic polyamide fiber cord, particularly the durability of a turn-up portion of the carcass layer, is improved.

[Structure of the invention]

Therefore, the present invention provides a pneumatic radial tire in which aromatic polyamide fiber cords are arranged in the carcass layer.
The end of the carcass layer is rolled up around a circular bead wire from the inside of the tire to the outside to form a turn-up part, and this turn-up part is made to run along the main body of the carcass layer, and the outside of the turn-up part is coated with a JIS hardness of 75 to 75. The gist of the present invention is a pneumatic radial tire for a passenger car, which is characterized in that a No. 95 upper bead filler is provided.

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

FIG. 1 is an explanatory diagram of a calf half cross section of an example of a pneumatic radial tire for a passenger car according to the present invention. In this Figure 1,
2 is a tread, 2 is a pair of left and right sidewalls, 4 is a carcass layer installed between a pair of left and right annular bead wires 3.3, and in the tread 1, this carcass layer 4
A belt layer consisting of two layers, an upper belt layer 5u and a lower belt layer 5d, is arranged so as to surround the outer periphery of the belt.

Steel cords are mainly used as cords for the belt layer, but any other cords may be used, for example, aromatic polyamide fiber cords may also be used.

Further, a single layer of belt cover may be disposed in a ring shape in the tire circumferential direction on the outside of this belt layer, thereby further improving high-speed running performance.

The carcass layer 4 is provided with aromatic polyamide fiber cords. The aromatic polyamide fiber cord used here is an aromatic polyamide fiber having a tensile strength of 150 kg/1I11 or more, a tensile modulus of 3000 kg/- or more, and a value of 1 for the coefficient 1 expressed by the following formula.
The cord was twisted in a range of 000≦3500, and then subjected to adhesive heat treatment.

K=T'f: twist coefficient, T: number of twists of cord (twists/10am)
, D: Total denier number of the cord.

In the present invention, the end of the carcass layer 4 is rolled up inside the tire (outward from the rule) around the annular bead wire 3 and the lower bead filler 6 disposed thereon to form a turn-up section 4a. The turn-up portion 4a is aligned with the carcass layer main body 4b, and the turn-up portion 4a is
Upper bead filler 7 with JIS hardness of 75 to 95 on the outside of
. In FIG. 1, a represents the rim flange height, and b represents the height of the lower bead filler 6.

The reason why the structure of the bead portion 8 is defined in this way is as follows.

FIGS. 2A, 2B, and 2C are enlarged views of the main parts of the tire bead. Figure 2 (A) shows a tire with a conventional bead structure in which organic fiber cords such as polyester fibers, nylon fibers, and rayon fibers are used for the cords of the carcass layer 4. Figure 2 (C) shows a tire with a bead structure according to the present invention in which aromatic polyamide fiber cords are used in the cords of the carcass layer 4. This is a case where one piece of polyamide fiber cord is used.

As the tire deforms while contacting the ground, the bead portion of the tire is bent from the inside of the tire to the outside in the direction indicated by arrow A in FIGS. 2(A), 2(B), and 2(C). Therefore, a tensile force acts on the inside of the tire, and a compressive force acts on the outside. Therefore, when the conventional bead structure shown in FIGS. 2(A) and 2(B) is adopted, the neutral axis T of bending is located midway between the carcass layer main body 4b and the turn-up portion 4a as shown in the figure. As a result, compressive force is applied to the turn amplifier section 4a. As a result, when an aromatic polyamide fiber cord with low compression fatigue resistance is used for the carcass layer (Fig. 2 (B)), the cord in the turn-up section 4a suffers compression fatigue due to the compressive force generated due to the tire's contact deformation. It will destroy it.

On the other hand, when the one-piece structure of the present invention as shown in FIG. Therefore, compressive force is not substantially applied to the cord of the turn-up portion 4a. Therefore, it is possible to prevent cord breakage in the turn-up portion 4a of the carcass layer.

However, as shown in FIG. 2(C), simply aligning the turn-up portion 4a along the carcass layer main body 4b and disposing the upper bead filler 7 outside the turn-up portion 4a does not allow the outer side of the turn-up portion 4a to If the compressive stiffness of the material is low, the durability cannot be effectively improved. Also,
The lower bead filler 6 is 10 mm higher than the rim flange height a.
If it is higher than 11I11 (a IIIm> b mm+
10 mm), durability cannot be similarly improved.

Therefore, the JIS hardness of the upper bead filler 7 disposed outside the turn-up portion 4a is set to 75 to 95. If this JIS hardness is less than 75, the durability cannot be improved as described above, while if it exceeds 95, it will not only be difficult to mold but also impair riding comfort, so this hardness should be within the above range. It is necessary that the In addition, it is preferable that the JIS hardness of the lower bead filler 6 is equal to or higher than that of the upper bead filler 7 from the viewpoint of steering stability.

〔Effect of the invention〕

As explained above, according to the present invention, in a pneumatic radial tire in which aromatic polyamide fiber cords are arranged in the carcass layer, the turn-up part is arranged along the carcass layer main body, and the outer side of the turn-up part has a JIS hardness of 75 to 75.
Since the upper bead filler 95 is provided, the durability of the tire, especially the durability of the turn-up portion of the carcass layer, can be improved.

The effects of the present invention will be specifically explained below using experimental examples.

EXPERIMENTAL EXAMPLE Inventive tire 1, comparative tire 1, comparative tire 2, and conventional tire 1 were trial-manufactured with tire size 195/70 HR14 and the following specifications.

fll Invention tire 1 Belt layer Nisteel cord l x 5 (0,25) 5
40 pieces per 0mm are laminated on a bias at 20° to the tire circumferential direction.

Carcass layer: aromatic polyamide fiber 10000/2 per 5On+m 37 tires in the circumferential direction and placed at essentially 90°.

Bead structure: As shown in Figure 2 (C).

JIS hardness of upper bead filler: 9o0 Value of aromatic polyamide fiber cord: 3000° (2) Comparative tire 1 The same belt layer and carcass layer as inventive tire 1, but the bead structure is as shown in Figure 2 (B) street.

(3) Comparison Tire 2 Same material and structure as Invention Tire 4.1, but with JIS hardness of 65 for the upper bead filler.

(4) Conventional tire 1 Belt layer 2 Same as inventive tire 1.

Carcass layer: 2 layers of polyester fiber cord 10000/2, 55 pieces per 50++ uw, laminated at substantially 90° to the tire circumferential direction.

Bead structure: As shown in Figure 2 (A).

Regarding these prototype tires, the drum tl17 of the testing machine
An indoor durability test was conducted as 07mn+. This test is based on Rim: 5 AJJX 14. Air pressure: 1.9kg
/-2 Speed: 80km/hr, Initial load: 52
Under the condition of 5 kg, the weight was increased by 50 kg every 2 hours until destruction.

By running it all the way to the end. The results are expressed as an index in FIG. 3, with the conventional tire set as 100.

From FIG. 3, it can be seen that the tire 1 of the present invention, which uses aromatic polyamide fiber cords as the cords of the carcass layer and has the bead structure shown in FIG. 2(C), has a durability of 15% compared to the conventional tire 1. It can be seen that it is improving. Furthermore, it can be seen that the durability is superior to Comparative Tire 1 and Comparative Tire 2.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a calf half cross section of an example of the pneumatic radial tire for passenger cars of the present invention, and FIG. 2 (A), (B), (C)
3 is an enlarged explanatory view of the main part of the tire bead portion, and FIG. 3 is an explanatory view showing the durability of various tires in graphs. 1...Tread, 2...Sidewall, 3...
Bead wire, 4... Carcass layer, 5u... Upper belt layer, 5d... Lower belt layer, 6... Lower bead filler, 7... Upper bead filler, 8... Bead portion. Agent Patent Attorney Shin Ogawa - Kenshosai Noguchi Kazuhiko Shimo Figure 1 Figure 2 (A) Figure 2 (B) Figure 2 (C)

Claims (1)

[Claims] In a pneumatic radial tire in which an aromatic polyamide fiber cord is arranged in the carcass layer, the end of the carcass layer is wound up around an annular bead wire from the inside of the tire to the outside to form a turn-up part, and this turn-up part is connected to the carcass layer. A pneumatic radial tire for a passenger car, characterized in that an upper bead filler having a JIS hardness of 75 to 95 is disposed along the layer body and on the outside of the turn-up portion.