JPS616006A - Pneumatic radial tire for passenger's vehicle - Google Patents

Abstract

PURPOSE:To make a pneumatic radial tire lightweight and to enhance the durability thereof, by using carbon fiber cords for a lower belt reinforced layer and aromatic polyamide fiber cords for an upper belt reinforced layer. CONSTITUTION:A radial tire 1 is composed of a tread rubber 1, a side wall 2, a bead wire 3, a carcass layer 4, a bead filler 6 and an inner liner 7. In a belt reinforced layer, a lower belt reinforced layer 5d is made of carbon fiber cords, and an upper belt reinforced layer 5u is made of aromatic polyamide fiber cords. A belt cover 8 made of organic fiber cords is arranged over the entire range of spreaded width of the tread, between the upper belt reinforced layer 5u and the tread rubber 1. Further, the direction of cords of the belt cover 8 is coincident with the peripheral direction EE' of the tire.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pneumatic radial tire for use in passenger cars that require high-speed performance and vibration ride comfort performance.

[Prior art]

With the development of expressway networks, tires have come to be required to have higher handling performance than the 11th gear ratio of cars. Steel radial tires have been introduced to replace conventional bias tires in response to this demand.

Steel radial tires have various advantages such as durability and low rolling resistance because a carcass layer with cords in the radial direction is covered with a steel belt reinforcing layer in the tread surface. On the other hand, the strongness of this belt reinforcing layer is a negative factor in the vibration ride comfort of the car.

In terms of weight, tires have recently been reduced in weight to almost the same weight as a bias tire of equivalent size.
This too is becoming a limitation.

In addition, there is a growing demand for higher speeds, from the HR level to the VR level.

However, since steel radial tires use steel for the belt reinforcing layer, their mass is large, and the centrifugal force due to tire rotation (F = mv2/r, m: rt, amount of belt reinforcing layer, V: tire rotation speed, (r: Tire dynamic load pressure half time), a part of the shoulder rises up, and failures such as separation at the belt edge are likely to occur.

For this reason, various improvements have been made to the belt section, such as creating a folded structure and installing a nylon cover.
With the steel belt reinforcement layer, there is a limit to the reduction in belt mass, and at present no fundamental solution has been reached.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic radial tire for a passenger car that is lightweight, has excellent high-speed performance, and vibration riding comfort, and eliminates the above-mentioned conventional drawbacks.

[Structure of the invention]

Therefore, in the present invention, the lower belt reinforcing layer adjacent to the carcass layer of the tread portion is made of carbon fiber cord, and the upper belt reinforcing layer is made of aromatic polyamide fiber cord. A belt cover made of machine fiber cord is disposed between the reinforcing layer and the tread rubber so that the cord angle is substantially zero degrees with respect to the tire circumferential direction over the entire tread width. This article focuses on pneumatic radial tires for passenger cars.

Hereinafter, the configuration of the present invention will be explained in detail.

A pneumatic radial tire for a passenger car as used in the present invention is a tire that is used for a passenger car and has a pair of bead wires, a pair of sidewalls, and a belt reinforcing layer connected thereto between the tread rubber and the radial carcass layer. It is something. Organic chemical fibers such as nylon and polyester are generally used as the material for the carcass cord.

The belt reinforcing layer in the present invention consists of two layers, upper and lower, and the lower belt reinforcing layer is made of carbon fiber cord.

Here, carbon fiber cord has a tensile strength of 100 kgf/
lllll112 or more, tensile modulus 5000kgf/
mm2 or more, preferably tensile strength 200kgf/11
m2 or more, tensile modulus 15000 kgf/+mm
After applying 10 to 50% by weight of adhesive to carbon fibers having characteristics of 2 or more, twisting is added so that the twist coefficient expressed by the following formula falls within the range of 0≦ to ≦1800. be.

The twisting structure may be a so-called double-twisted structure in which several carbon fibers are first twisted individually, and then those several carbon fibers are combined and a final twist is added. A single-twist structure that simply adds twist may also be used.

K = TV'unevenness: twist coefficient, T: number of 1 chords (times/10cm)
, D: Total denier number of the cord.

This carbon fiber cord is made by impregnating untreated carbon fiber yarn with an adhesive mixture of resorcinol/formalin initial condensate and rubber latex (hereinafter abbreviated as RFL), drying and heat-treating it, and then Can be created by adding twists.

The amount of adhesive RFL applied to carbon fiber is 10~
50% is preferred. If it is less than 10%, not only will the adhesion with rubber be insufficient, but also the bending fatigue properties of carbon fibers cannot be improved, while if it exceeds 50%, the adhesive layer will be too thick when drying and heat-treating the adhesive. This not only results in poor drying, but also creates bubbles in the adhesive layer, making it impossible to obtain a uniform cord. More preferably, the amount of adhesive applied is 20 to 40
%.

When applying the adhesive, it is important to sufficiently impregnate the adhesive into the carbon fiber filament to improve bending fatigue, and for this purpose it is preferable to impregnate the adhesive with the carbon fiber filament in an open state. .

When twisting is applied to the bonded carbon fiber yarn, if there is too much twist, the strength and high modulus of the carbon fiber will be significantly impaired. Therefore, the twist coefficient K is 180
It is preferably 0 or less.

Since the adhesive is sufficiently attached to the adhesive-treated carbon fiber yarn, the cohesiveness of the yarn is maintained even if it is not twisted, but it is preferable to add some twist to it from the viewpoint of cohesiveness. Therefore, it is more preferable that the twisting coefficient K is 300≦1500.

Further, in the present invention, the upper belt reinforcing layer is composed of an aromatic polyamide fiber cord.

Here, the aromatic polyamide fiber cord refers to a tensile strength of 1
50kgf/ml12 or more, tensile modulus 3000k
An aromatic polyamide fiber having a property of gf/llll112 or more has a twist coefficient of 100 expressed by the following formula.
The cord was twisted in a range of 0≦ to ≦2800, and then subjected to adhesive heat treatment.

K-TV "Ni: twist coefficient, T: number of twists of cord (twists/10cm)
, D: Total denier number of the cord.

Furthermore, in the present invention, a belt cover made of organic fiber cords is placed between the belt reinforcing layer and the tread rubber so that the cords are oriented in the tire circumferential direction (that is, the cord angle is direction) so that it becomes essentially zero in the direction.

The fiber cord for the belt cover is selected from heat-shrinkable organic fibers such as nylon 6, nylon 66, and polyester, but considering the heat generated by the belt during running,
Nylon 66, which has good adhesion to rubber and high heat resistance, is preferred.

The shape of the tire of the present invention is not particularly limited, but preferably has an aspect ratio of 60 or less.

Generally speaking, when considering the equivalent size, as the aspect ratio decreases, the width of the belt reinforcing layer increases as well as the tread development width.

If a steel cord is included in a wide belt reinforcing layer, the total circumferential out-of-plane bending rigidity will increase and vibration ride comfort will deteriorate. Therefore, by using carbon fiber, which has approximately the same tensile rigidity but lower bending rigidity, as the belt reinforcement layer cord, it maintains the same durability, handling stability, and high-speed running performance as conventional steel radial tires. Vibration ride comfort can be improved.

From the above, the shape of the radial tire of the present invention having a belt reinforcing layer made of carbon fiber has a small aspect ratio;
It is preferably 60 or less.

Hereinafter, the tire structure of the present invention will be specifically explained with reference to the drawings.

FIG. 2 is a partially cutaway half-section perspective view of a conventional radial tie. In this figure, a tread rubber 1 is arranged on the tire tread surface, sidewalls 2 cover the whole on both sides, and a bead wire 3 is stretched in the tire circumferential direction EE' at the center of the bead portion. A carcass Wi4 is wound around the bead wire 3 and arranged in the radial direction.

There is a bead filler 6 above the bead wire 3, and the inside of the tire is covered with an inner liner 7. Between the carcass layer 4 of the tread portion and the tread rubber 1, two belt reinforcing layers 5 are laminated on a bias at an angle.

FIG. 1 is a partially cutaway half-sectional perspective view showing an example of the radial tire of the present invention, in which the tread rubber 1, sidewall 2, bead wire 3, carcass I'if 4, beat filler 6, and inner liner 7 are It is the same as the conventional product shown in the figure. However, the lower belt reinforcing layer 5d of the belt reinforcing layer is made of carbon fiber cord, and the upper belt reinforcing layer 5u is made of aromatic polyamide fiber cord. Further, between the upper belt reinforcing layer 5u and the tread rubber 1, a belt cover 8 made of organic fiber cord is disposed over the entire tread width. The cord direction of the belt cover 8 is oriented in the tire circumferential direction EE'.

Hereinafter, the effects of the present invention will be specifically explained with reference to Examples.

Example A tire of size 195/60R14 was prepared with the following specifications.

In the carcass layer, 40 pieces of 1500 d/2 polyester were arranged per 5 cm on the tire's equatorial plane. The lower helt reinforcement layer is made of carbon fiber cord, RFL coating weight is 20% and 18
00d /2, twisted structure 10z X 10s (T
/ 10cm), the 100% modulus is 45kgf
/cal rubber and 40 pieces per 5 cm were arranged at an angle of 25° to the circumferential direction of the tire. The upper belt reinforcing layer has an aromatic polyamide fiber cord of 1500 d/2 and a twist structure of 30
zX 30s (T / 10cm) in rubber with a 100% modulus of 45kgf/cat 5 cm + 5
0 tires are arranged at 120° to the circumferential direction (intersecting with the lower side). The organic fiber cord reinforcing layer contains Na.
100% modulus of Ron 66 cord 840d/2 is 3
60 pieces per 5 cm were arranged substantially in the circumferential direction of the tire in 0 kg/- of rubber.

As a comparative example, tires of the same size were manufactured with the following specifications.

For the belt reinforcing layer, 44 pieces of 1×5 steel cord (0°25) per 5CI11 were arranged in rubber having a 100% modulus of 45 kgf/cal so as to cross each other at 20° with respect to the tire circumferential direction. The parts other than this belt reinforcing layer are the same as above.

A photographic ride comfort test and a high-speed performance test were conducted using the two types of tires (Example and Comparative Example) described above as follows.

fil Vibration ride comfort test: As a vibration ride comfort test, a test was conducted using an indoor protrusion testing machine.

The indoor projection tester is a drum with a diameter of 2500IIIm and a hemispherical projection with a diameter of 20IIIB and a height of 10mm attached at one location on the circumference. By detecting the axial force in the longitudinal direction when the test tire passes over this protrusion, the magnitude of the axial force is used as a representative value of vibration ride comfort.

The test conditions were: air pressure P = 1.9 kgf/cd, load - = 445 kgf, speed v = 60.80.100.1
The speed was set at 20km/hr.

Figure 3 shows the results of this test. In FIG. 3, the value of the comparative example is set as 100 and expressed as an index.

From FIG. 3, it can be seen that the vibration riding comfort of the tire of the present invention is improved by about 15% compared to the comparative example (conventional product).

(2) High-speed performance test: As a high-speed performance test, an indoor drum testing machine (diameter 1707
mm).

The test conditions were: air pressure P = 30 kgf/cut, load - = 454 kgf, and speed V = 170 k.
m/hr, the vehicle was accelerated by 10 km/hr every 10 minutes until it broke.

The results are shown in FIG. From FIG. 4, it can be seen that the high-speed performance of the tire of the present invention is superior to that of the comparative example (conventional product) by about lθ%.

〔Effect of the invention〕

The radial tire of the present invention has the following effects.

(11) By using carbon fiber cord for the lower belt reinforcing layer, it is lighter than the conventional steel coat, and the durability of the belt reinforcing layer can be improved.

(2) Since the aromatic polyamide fiber cord is used for the upper belt reinforcing layer, it is lighter than the conventional steel cord, and it is possible to prevent the bending fatigue resistance of carbon fiber from decreasing against impact force from the road surface.

(3) 18r between the belt reinforcement layer and tread rubber
Since the machine fiber cord belt cover is provided, it can maintain the same durability and handling stability as steel cord.

(4) By employing the structures (1) to (4) above, vibration ride comfort and high-speed performance can be improved.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway half-section perspective view of an example of a radial tire of the present invention, and FIG. 2 is a partially cutaway half-section perspective view of an example of a conventional radial tire. ! FIG. 83 is an explanatory diagram showing vibration ride comfort in a graph, and FIG. 4 is an explanatory diagram showing high-speed performance in a graph. l...Tread rubber, 2...Side wall, 3
... Bead wire, 4... Carcass layer, 5... Belt reinforcing layer, 5d... Lower belt reinforcing layer, 5u...
Upper belt reinforcing layer, 6... Bead filler, 7...
Inner liner, 8...Belt cover. Agent Patent Attorney Shin Ogawa − Kenshosai Noguchi Shimo Kazuhiko Figure 2F' Figure 3 Figure 4

Claims (1)

[Claims] The lower belt reinforcing layer adjacent to the carcass layer of the tread portion is made of carbon fiber cord, and the upper belt reinforcing layer is made of aromatic polyamide fiber cord. A pneumatic radial tire for a passenger car, characterized in that a belt cover made of fiber cord is arranged over the entire tread width so that the cord angle is substantially zero degrees with respect to the tire circumferential direction.