JPS624614A - Pneumatic radial tire for passenger car - Google Patents

Abstract

PURPOSE:To diminish the cutting of cords by configurating a device in such a way that the turned-up section of a cord is allowed to go along a carcass layer main body, and a bead filler having the specified hardness is arranged on the outside of the said turned-up section in a tire having a carcass cord made of carbon fibers as referred to the titled. CONSTITUTION:A turned-up section TU of a cord 4 of a carcass layer main body 4A made of carbon fibers is allowed to go along the carcass layer main body 4A in such a way that it wraps a lower bead filler F2. And an upper bead filler F1 having the JIS hardness value of 75-95 deg. is provided on the outside of the turned-up section. A bending neutral axis of the bead section 3 with fulcrum at the edge of a rim 8 approaches close to the carcass layer main body 4 while being out of the turned-up section TU. This configuration is capable of preventing a compressive force from additionally acting on the carcass cord 4 of the turned-up section TU when a tire is deformed while contacting on ground. Accordingly, the carcass cord can be prevented from being cut.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pneumatic radial tire for passenger cars that can significantly reduce carcass cord breakage occurring at the carcass turn-up portion of carbon fiber cords.

[Prior art]

Radial tires for passenger cars generally use organic fibers such as nylon, polyester, and rayon for the carcass cord.
The belt layer has steel belt layers that intersect with each other, and compared to conventional bias tires, the insertion of the steel belt layer improves wear resistance, high speed performance, steering stability, etc., and reduces rolling resistance.

Furthermore, in order to improve productivity and reduce weight, the carcass cord was changed from 2 ply to 1 ply.
In large-sized pneumatic radial tires such as 05/70HR14 and above, it is very difficult to use the organic fiber cord as a single-ply carcass cord due to strength problems.

Therefore, in recent years, it has been proposed to use carbon fiber as the carcass cord of pneumatic radial tires. However, by using carbon fiber as the carcass cord as described above, it is certain that the strength problem is eliminated, but in this case, a new problem arises in that the carcass cord is easy to break at the carbon fiber carcass turn-up part. occured.

This is because carbon fiber has a high crystallinity due to its molecular structure, and the compressive force generated as the tire deforms on the ground tends to cause compressive fatigue failure in the carcass cord in the carcass turn-up portion.

[Purpose of the invention]

This invention was devised by focusing on the conventional problems, and its purpose is to improve the durability of the carcass turn-up part of a pneumatic radial tire for passenger cars that uses carbon fiber in the carcass layer. To provide a pneumatic radial tire for a passenger car.

[Structure of the invention]

In order to achieve the above object, the present invention provides a pneumatic radial tire for a passenger car that uses carbon fiber for the carcass cord, in which the turn-up part of the 8 yen carcass cord is aligned with the carcass layer main body, and the outer side thereof has a JIS hardness of 75.
The gist is that the upper bead filler is provided at an angle of 95 degrees to 95 degrees.

The present invention will be explained below based on the accompanying drawings.

FIG. 1 shows a front sectional view of essential parts of a pneumatic radial tire for a passenger car in which the present invention is implemented, and this pneumatic radial tire for a passenger car includes a pair of bead wires 3, a pair of sidewalls 2, A belt layer 5 consisting of an upper belt reinforcing layer 5A and a lower belt reinforcing layer 5B is arranged between the tread 1 connected to the sidewall 2 and the carcass cord 4 made of carbon fiber cord. has been done.

Further, the turn-up portion Tu of the carcass cord 4 is arranged so as to wrap around the lower bead filler F2.
along with JIS hardness of 75 degrees to 9 on the outside.
An upper bead filler F1 with a range of 5 degrees is provided.

In the present invention, a steel cord is used as the cord for the belt layer 5, but aramid or the like can also be used. A device has also been proposed in which a nylon cover is inserted along the circumferential direction to improve high speed.

The carbon fiber cord used as the material of the carcass cord 4 of the carcass layer has a tensile strength of 100 kg/mm.
2 or more, tensile modulus of 5000 kg/mff12 or more, preferably tensile strength of 200 kg/mm2 or more, tensile modulus of 15. 10% to 50% of the weight per unit length of the carbon fiber is added to the carbon fiber having a property of OOOkg/mm2 or more.
After applying % adhesive, twist is added to the twist coefficient expressed by the formula k=lower (〒-) so that the value is in the range of 0≦≦1800.The twist structure is A so-called twisted structure may be used, in which several carbon fibers are first twisted individually, and then several carbon fibers are combined and further twisted, or a structure in which only one carbon fiber thread is twisted is used. A single-stranded structure may also be used.

In addition, T in the above formula is the number of twists of the cord (twists/10Cff
i), and D is the total denier of the cord.

In addition, as a manufacturing method for the above-mentioned carbon fiber cord used in this tire, untreated carbon fiber yarn is mixed with a mixture of an adhesive, a resorcin formalin initial condensate, and rubber latex (hereinafter abbreviated as RFL). After impregnation and dry heat treatment, a predetermined twist is added to create the fabric.

The amount of RFL, which is the adhesive, attached to carbon fiber is 10
If it is less than 50%, not only will the adhesion with rubber be insufficient, but the bending fatigue properties of carbon fibers cannot be improved. On the other hand, if it exceeds 50%, the adhesive layer will be The thickness of the adhesive layer not only results in insufficient drying, but also creates bubbles in the adhesive layer, making it difficult to obtain a uniform cord, so the amount of adhesive applied is preferably 20 to 40%.

In addition, when applying adhesive, it is important to sufficiently impregnate the carbon fiber filament with the adhesive to improve bending fatigue, and for this reason, it is necessary to impregnate the carbon fiber filament with the adhesive while it is open. is preferred.

When twisting the carbon fiber yarn that has been bonded above,
Too much twist will significantly impair the high strength and high elastic modulus properties of carbon fibers, so twisting should be done when the twist coefficient k is 180.
It is preferable that it is 0 or less.

The adhesive-treated carbon fiber yarn has sufficient adhesive adhesion, so the yarn maintains its cohesiveness even without twisting. Therefore, the twist is preferably 300≦ to 1≦1.
500 is more preferred.

As mentioned above, in this example, by using carbon fiber carcass cord 4 in the carcass layer, the number of carcass cords 4 is changed from 2 plies to 1 ply, thereby improving productivity and reducing weight. In this case, as mentioned above, there was a problem that the carcass cord at the turn-up part was easily cut at the turn-up part Tu of the carcass cord 4.
The lower bead filler F2, which is obtained by dividing the turn-up portion Tu of the carbon fiber carcass cord 4, is placed along the carcass layer main body 4A so as to enclose it.

Next, the reason why the turn-up portion Tu of the carbon fiber carcass cord 4 is aligned with the carcass layer as described above will be explained in the second section.
A description will be given while comparing the conventional tire shown in FIGS. (a) to 2(tc), the tire of the present invention, and a comparative tire.

First, when the tire is deformed in contact with the ground via the tread 1, the bead portion of the tire is bent in the direction of the arrow B shown in FIGS. 2(al) to 2(C) using the edge of the rim 8 as a fulcrum.

Therefore, when a bead structure using an integral bead filler F is adopted as shown in FIGS. 2(a) and 2fc), the neutral axis N of bending This is near the center of the bead filler F between the turn-up portion Tu of the carcass cord 4, and a compressive force is applied to the turn-up portion Tu.

For this reason, when the carcass cord 4 made of carbon fiber with low compression fatigue resistance is used for the carcass layer, compression fatigue fracture occurs in the carcass cord 4 of the turn-up part Tu due to the compressive force generated due to the tire's contact deformation. I end up.

On the other hand, in the case of the tire of this invention (Fig. 2(b))
adopts a bead structure in which the bead filler F is divided into an upper bead filler Fl and a lower bead filler F2, so the neutral axis N of bending is close to the carcass layer main body 4A, but the turn-up part of the carcass cord 4 No compressive force is substantially applied to the Tu carcass cord 4.

Therefore, when using carbon fiber as the carcass cord 4, which has lower compression fatigue resistance than conventional polyester, nylon, rayon, etc., the carcass cord 4 can be This means that cord breakage at the turn-up portion Tu can be effectively prevented.

However, if the turn-up portion Tu of the carcass cord 4 is simply placed along the carcass layer main body, the turn-up portion T
If the compressive rigidity of the upper bead filler F1 located on the outside of u is low, durability cannot be effectively improved, and the filler height b of the lower bead filler F2 is lower than the rim flange height a of the rim 8. 10mm or more high (bmm>am
m+10 mm), the durability cannot be effectively improved.

Therefore, in the embodiment of the present invention, the turn-up portion Tu of the carcass cord 4 is aligned with the carcass layer main body, and
An upper bead filler F1 having a JIS hardness of 75 to 95 degrees is provided on the outside thereof.

In addition, the hardness of the upper bead filler F1 (JIS hardness) is 7.
The reason for setting the angle between 5 degrees and 95 degrees is that J
If the IS hardness is less than 75 degrees, the turn-up part Tu
The outer rigidity of the material decreases, reducing its durability. Also JIS
If the hardness exceeds 95 degrees, a problem arises in that the bead portion becomes more rigid than necessary, resulting in poor riding comfort.

Therefore, it is preferable to provide the upper bead filler F1 having a JIS hardness of 75 degrees to 95 degrees.

Further, it is preferable that the JIS hardness of the lower bead filler F2 is equal to or higher than the JIS hardness of the above-mentioned upper bead filler F1 in terms of handling stability.

〔Effect of the invention〕

This invention provides a pneumatic radial tire for passenger cars using carbon fiber for the carcass cord as described above, in which the turn-up part of the carcass cord is aligned with the carcass layer main body, and the outer side thereof has a JIS hardness of 75 degrees to 95 degrees. By providing the upper bead filler in the range of 2.0 to 3.0, it is possible to effectively prevent failures occurring at the turn-up portion of the carcass cord, that is, cord breakage, and therefore, the durability can be improved accordingly.

[Embodiments of the invention]

Next, radial tires were prototyped based on the embodiment of the present invention, and the tire of the present invention, the conventional tire, and the comparative tire
The results of a comparative evaluation test with the comparative tire ■ are shown in the third
This will be explained with reference to the figures.

The specifications of the types of tires that were subjected to the comparative evaluation test are as follows.

(1), Conventional tire layer carcass cord: polyester, 1000d/2
, number of ends 35. Number of twists: 50 x 50, integrated filler rubber: JIS hardness 65 degrees (2), tire single layer carcass cord of this invention: carbon fiber carcass 1800d/2
, Number of twists: 10
2, Number of twists: 10xlO, number of ends 35, split type upper filler rubber: JIS hardness 65 degrees, (4), comparison tire■ Single layer car force cord: carbon fiber carcass, 1800d/
2. Number of twists: 1OXIO, number of ends: 35, integrated filler rubber: JIS hardness 90 degrees, upper bead filler F
The height of l is all 1. of the cross-sectional height of the tire. /2.

For the purpose of evaluating the durability of the tire, an indoor durability test was conducted on the above prototype tire under the test conditions shown below.

(a) Prototype tire: A radial tire of 205/'1OHR14 size, mounted on a 51/2JX14 rim.

(b), Rim flange height: 17.5 mm.

(C), Air pressure: 2. Okg/c+a.

(d) 0 rotational speed: An indoor durability test was conducted using a testing machine with a drum diameter of 1707 mm at 8Q km/hr.

The initial load is 585 kg, and the load value is increased to 50 kg every 2 hours.
Figure 3 shows the results of an experiment in which the load was increased in increments of kg and the vehicle was run until failure.

In FIG. 3, the durability of the conventional tire is set at 100.

As is clear from the graph in FIG. 3, the radial tire of the present invention, which has the structure of the carbon fiber carcass cord 4 and the second turn-up part Tu, has a 10% improvement in durability compared to the conventional tire. I can see that it is being done.

That is, the durability of the comparison tire (2) is 97 compared to 100 of the durability of the conventional tire, and the durability of the comparison tire I is 93, which is inferior to the durability of the conventional tire. are conventional tires, comparative tires I
, the durability is improved compared to the comparison tire (■).

[Brief explanation of drawings]

FIG. 1 is a front sectional view of main parts of a pneumatic radial tire for a passenger car according to an embodiment of the present invention, and FIGS.
Figure (C) is an enlarged explanatory view of the bead portion of a radial tire to explain the comparison between the tire of the present invention, a conventional tire, and a comparative tire, and Figure 3 is a graph showing the results of an evaluation test of the radial tire. It is an explanatory diagram. 3... Bead wire, 4A... Carcass layer body,
4...Carcass cord, F2...Lower bead filler, Fl...Upper bead filler, K...Carcass layer,
Tu...Carcass turn-up part. Figure 1

Claims (1)

[Claims] In a pneumatic radial tire for passenger cars that uses carbon fiber for the carcass cord, the turn-up portion of the carcass cord is aligned with the carcass layer main body, and an upper bead filler with a JIS hardness of 75 degrees to 95 degrees is provided on the outside thereof. A pneumatic radial tire for passenger cars that is characterized by: