JPS61222803A - Pneumatic radial-ply tire for passenger car - Google Patents

Abstract

PURPOSE:To make improvements in durability and steering stability, by setting up a belt layer using a carbon fiber cord at the carcass side while a belt layer using a steel cord at the side of a tread part, respectively, and bending an end part of the belt layer at the tread side to the side of the tread part, consti tuting the belt layer. CONSTITUTION:Belt layers 5d composed of a carbon fiber cord C is set up at the carcass side,while belt layers 5u composed of a steel cord S is set up at the side of a tread part 3. And, an end part of at least one layer of these belt layers 5u is bent to the side of the tread part 3, constituting a belt layer 5. With this constitution, durability and steering stability both are improvable.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a pneumatic radial tire for passenger cars, and more specifically, the present invention relates to a pneumatic radial tire for passenger cars, and more specifically, the present invention relates to a pneumatic radial tire for passenger cars. This invention relates to pneumatic radial tires for passenger cars.

[Conventional technology]

In response to society's need for energy conservation, there has been a growing demand for lighter vehicles and tires with lower rolling resistance, and there has been a significant shift from bias tires to radial tires.

Radial tires have a carcass layer in the radial direction and a belt layer in the tread to give a hoop effect, so compared to bias tires,
Good low rolling resistance, wear resistance, handling stability, high speed resistance, etc.

In particular, even today there is a strong demand for lower rolling resistance, as well as lighter tires that can contribute to reducing the weight of vehicles.

Tire manufacturers have responded to this strong demand for lower rolling resistance by reducing the weight of tires and reducing the hysteresis of the rubber that makes up the tread. However, it is a fact that reducing the hysteresis of the tread rubber is a factor that reduces the wet performance of the tire.

Against this background, we have developed a new material that is lightweight and has high elasticity to replace steel cord as a reinforcing cord that makes up the belt layer of radial tires.

A radial tire using a high-strength carbon fiber cord (Japanese Patent Publication No. 56-40043) has been proposed.

It is true that if such a new material is used as a reinforcing cord for the belt layer, it is possible to reduce the weight and reduce the rolling resistance.

However, if all of the belt layers, which are laminated in multiple layers, are made of carbon fiber cord, the current situation is that the durability is significantly inferior to that of conventional radial tires.

In other words, tires transmit the driving force of a vehicle to the road surface by rotating when they touch the ground, and fulfill this role, but in general, when considering the lifespan of a tire, it deforms as many as 107 times when it touches the ground.

During this ground contact deformation, the tire undergoes bending deformation, so-called bending deformation, and therefore the belt layer is required to be made of a material with good bending fatigue resistance.

Considering this point of view, using carbon fiber cords alone as reinforcing cords for all belt layers has a problem with the bending fatigue properties of the carbon fiber cords, and cannot be used as is at present.

[Purpose of the invention]

The present invention was developed as a result of experiments and studies to solve the above-mentioned problems.

Accordingly, an object of the present invention is to provide an excellent pneumatic radial tire for passenger cars that can improve durability and handling stability by devising the structure of the belt layer.

[Structure of the invention]

That is, the present invention provides a pneumatic radial tire for passenger cars, in which a belt layer made of carbon fiber cords is disposed on the carcass layer side of the belt layer, and a steel cord is disposed on the tread portion side close to the belt layer on the carcass layer side. The gist of the tire is a pneumatic radial tire for a passenger car, characterized in that a belt layer made of steel cord is arranged, and an end of at least one layer of the tread side belt layer made of the steel cord is bent toward the tread side. It is something.

Hereinafter, the present invention will be specifically described by way of examples with reference to the drawings.

FIGS. 1(a) to (dl) show pneumatic radial tires for passenger cars according to embodiments of the present invention; FIG. 1(a) is a partially cutaway perspective explanatory view of the first embodiment; Figure (b) ~
(dl is a partially cutaway explanatory diagram showing the main parts of Examples 2 to 4, Figure 2 is a diagram showing the results of the durability test, and Figure 3 is a diagram showing the results of the handling stability test. .

In the figure, E denotes a pneumatic radial tire for a passenger car according to an embodiment of the present invention, which includes a pair of left and right bead portions 1, a pair of left and right sidewall portions 2 connected to the bead portions 1,
It consists of a tread part 3 located between each sidewall part 2, and a carcass layer 4 having a cord angle of 70° to 90° with respect to the tire circumferential direction is mounted between the pair of left and right bead parts 1, and the tread Carcass layer 4 in section 3
Above, the cord angle to the tire circumferential direction is 10° to 35°.
It is constructed by arranging a plurality of belt layers 5 that intersect with each other at .degree.

In the present invention, in particular, a belt layer 5d made of carbon fiber cord C is arranged on the carcass layer 4 side of the belt layer 5, and a belt layer 5u made of steel cord S is arranged on the tread portion 3 side. Furthermore, the end portion of at least one layer of the tread portion side belt layer 5u made of the steel cord S is bent toward the tread portion side.

In the present invention, as described above, since the steel cord S is used as the reinforcing cord of the tread side belt layer 5u, compared to the conventional tire in which the belt layer is entirely made of carbon fiber cord as described above, Durability and handling stability can be significantly improved.

That is, the belt layer 5d made of carbon fiber cord C is covered with the belt layer 5u made of steel cord S which has better bending fatigue resistance than this belt layer 5d.

Therefore, the impact force from the tire tread surface can be absorbed by the belt layer 5u made of steel cord S having excellent bending fatigue resistance, and the durability and steering stability of the belt layer 5 can be improved.

Furthermore, as described above, the end of at least one layer of the tread side belt layer 5u made of steel cord S having excellent bending fatigue resistance is bent toward the tread side.

Therefore, the end of the tread side belt layer 5u can be made into two layers, and the protection of the carcass layer side belt layer 5d made of carbon fiber cord C can be greatly improved. It is also possible to prevent both ends of the belt layer from rising due to centrifugal force, thereby preventing separation failure from occurring.

In addition, in this embodiment, as shown in FIGS. The belt layer 5d protrudes left and right from both left and right ends 5d+ of the belt layer 5d, and the left and right ends 5dl of the carcass side belt layer 5d are covered by the left and right ends 5u+ of the tread side belt layer 5u.

In other words, both left and right ends 5di of the carcass side belt layer 5d made of carbon fiber cord C are replaced with right and left ends 5u+ of the tread part side belt layer 5u made of steel cord S which has better bending fatigue resistance than this belt layer 5d. It is covered by

Therefore, the protection of both left and right ends 5d+ of the carcass side belt layer 5d made of carbon fiber cord C can be greatly improved, and the belt layer ends are prevented from rising due to the centrifugal force of the tire during high-speed running. This makes it possible to prevent separation failure and improve tire durability.

Note that both left and right ends 5u of the tread side belt layer 5u
It is preferable that the protrusion width of No. 1 from the left and right ends 5a+ of the carcass layer side belt layer 5d is 5f1 or more. This is because if the protrusion width is less than 5 cranes, the protection of both left and right ends 5d+ of the carcass layer side belt layer 5d made of carbon fiber cord C will be reduced, and there is a possibility that durability cannot be improved.

The steel cord S constituting the reinforcing cord of the tread side belt layer 5u has a double-stranded structure made of steel wire having a wire diameter of 0.2 m or less, preferably 0.175 m or less. Preferably, steel cord is used.

In addition, the twist structure of this steel cord is nxm, and n
is preferably 3 to 4, m is preferably 3 to 7, and further,
The strand pinch of this cord is preferably 8u or less, and the cord pitch is preferably 8m1 or less.

Further, the carbon fiber cord C constituting the reinforcing cord of the carcass layer side belt layer 5d is as follows.

That is, the tensile strength is 100+r/fi2 or more, the tensile modulus is 5000 kg/wm2 or more, preferably the tensile strength is 200 kgA1 or more, and the tensile modulus is 150.
After applying an adhesive in an amount of 10 to 50% of the weight per unit length of carbon fiber to carbon fiber having a property of 00kgZdragging2 or more, the twist coefficient expressed by the following formula has a value of 0≦≦1.
Add twist so that it becomes a range of 800.

The twisted structure may be a so-called twisted structure in which each of several carbon fibers is first twisted, and then the several carbon fibers are combined and subjected to pre-twisting, or a single carbon fiber thread is twisted. A single-strand structure may also be used.

K=T (Correct: Twist coefficient T: Number of twists of the cord (twists/10cna) D: Total denier number of the cord Further, the structure of each of the embodiments shown in FIG. 1 (al to (d)) will be explained as follows. It is as follows.

In the first embodiment of the present invention shown in FIG. 1+a), a belt layer 5d made of carbon fiber cord C is arranged on the carcass layer 4 side, and a belt layer 5u made of steel cord S is placed on the tread portion 3 side. This is an example of a one-layer arrangement.

The left and right ends of the tread side belt layer 5u made of the steel cord S are bent toward the tread side.

A second embodiment of the present invention shown in FIG. 1(b) has two belt layers 5d made of carbon fiber cords C on the carcass layer 4 side, and a belt layer made of steel cords S on the tread portion 3 side. This is an example in which 5u are arranged in one layer.

The left and right ends of the tread side belt layer 5u made of the steel cord S are bent toward the tread side.

In the third embodiment of the present invention shown in FIG. 1(C), a belt layer 5d made of carbon fiber cords C is arranged on the carcass layer 4 side, and a belt layer 5u made of steel cords S is placed on the tread portion 3 side. This is an example of a two-layer arrangement.

Note that one end of each tread side belt layer 5u made of the steel cord S is bent toward the tread side while facing each other.

In the fourth embodiment of the present invention shown in FIG. 1 (dl), a belt layer 5d made of carbon fiber cord C is arranged on the carcass layer 4 side, and a belt layer 5u made of steel cord S is placed on the tread part 3 side. This is an example of a two-layer arrangement.

In addition, in each tread section side belt layer 5u made of this steel cord S, only the upper belt layer is bent at both left and right ends toward the tread section side, as shown in the figure.

As described above, in the present invention, 1. A plurality of belt layers 5d made of carbon fiber cords C located on the carcass layer 4 side may be arranged, and a belt layer 5d made of steel cords S located on the tread portion 3 side may be arranged. Of course, a plurality of belt layers 5u may be arranged.

[Experiment example]

In order to confirm the effects of the present invention, a durability performance test and a steering stability performance test were conducted.

(Specifications of tires used in each test) <Tire of the present invention> Tire size: 185/70R13° Carcass layer: 1000 d/2 as reinforcement cord
.

Polyester coat with 35 ends Cord angle is at 90° to the tire circumferential direction. I arranged it in two layers so that it would look like this.

Carcass layer side belt layer...1800 d as reinforcement cord
/2.

Number of ends: 50. 6 carbon fiber cords with a twist coefficient of =600 (frivolous twist structure: 10 turns/10 cm) were arranged in one layer so that the cord angle was 24° with respect to the tire circumferential direction.

The width is 130**. did.

Tread side belt layer: 3 x 7 as reinforcement cord
(0,15) End number 35. The steel cords were arranged in one layer so that the cord angle was 24° with respect to the tire circumferential direction, and the width was 220 mm, and both left and right ends were bent by 4011 I toward the tread portion.

<Conventional tires> Tire size: Same as the tire of the present invention.

Carcass layer: 1000 d as reinforcement cord
/2.

En)’ number 35. polyester co code angle The degree is 90゛ relative to the tire circumferential direction. It was arranged in two layers so that

Belt layer: Both the carcass side belt layer and the tread side belt layer have a reinforcing cord of 1800 d/2 and 50 ends.
Twist coefficient = 600 (More twist structure 10 times/Loa
The carbon fiber cord of m) was arranged so that the cord angle was 24° with respect to the tire circumferential direction.

Naori - of the belt layer on the waste layer side The width is 130 dragons, and the tread side The width of the belt layer was 140 mm.

[Experimental example 1] Durability performance test As the main durability performance test, an indoor drum testing machine (diameter 1707
Dragon) was used.

<Test conditions> Air pressure is 2.3 kg/cot, speed is 81 km/hr
The load was increased from 450 kg to 68 kg every 4 hours, and the vehicle was run until it broke.

The test results are shown in Figure 2. In addition, in FIG. 2, the test results of conventional tires are expressed as an index, with the test results set as 100.

As is clear from FIG. 2, it can be seen that the tire of the present invention has improved durability performance by about 28% compared to the conventional tire.

[Experiment Example 2] Maneuvering stability performance test As a maneuvering stability performance test, an indoor cornering test machine (
The tires had a diameter of 2500 m) and had a slip angle of 2 degrees, and the lateral force at this time was multiplied by 2 to obtain CP (cornering power), which was used as a representative value.

Test conditions> Air pressure: 1.9 kg/cal Load: 450 kg Speed: 20 to 11/hr The test results are shown in Figure 3. In addition, FIG. 3 is shown as an index with the test result of the conventional tire set as 100.

As is clear from FIG. 3, it can be seen that the tire of the present invention has improved steering stability by about 15% compared to the conventional tire.

〔Effect of the invention〕

As described above, the present invention particularly provides a belt layer made of carbon fiber cords on the carcass layer side of the belt layer, and a belt made of steel cords on the tread portion side close to the belt layer on the carcass layer side. Since the end portion of at least one layer of the tread side belt layer made of steel cord is bent toward the tread side, durability can be greatly improved compared to conventional tires. It is also possible to improve steering stability.

[Brief explanation of drawings]

FIGS. 1(a) to 1(d) show pneumatic radial tires for passenger cars according to embodiments of the present invention, and FIG. Figure (b) ~
(dl is a partially cutaway explanatory diagram showing the main parts of Examples 2 to 4, Figure 2 is a diagram showing the results of the durability test, and Figure 3 is a diagram showing the results of the handling stability test. 1...Bead part, 2...Side wall part, 3...
- Tread part, 4... Carcass layer, 5... Belt layer, 5d... Carcass layer side belt layer, 5u... Tread part side belt layer, C... Carbon fiber cord, S... Steel cord.

Claims (1)

[Claims] In a pneumatic radial tire for a passenger car, a belt layer made of carbon fiber cord is arranged on the carcass layer side of the belt layer, and a belt layer made of steel cord is placed on the tread side close to the belt layer on the carcass layer side. A pneumatic radial tire for a passenger car, characterized in that the end portion of at least one layer of the tread side belt layer made of the steel cord is bent toward the tread side.