JPH0723046B2 - Pneumatic radial tires for passenger cars - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a pneumatic radial tire for passenger cars, and more specifically, to a structure of a belt layer for improving durability and steering stability. The present invention relates to a pneumatic radial tire for passenger cars.

[Conventional technology]

As the demand for low rolling resistance of tires has been increasing along with the weight reduction of vehicles to meet the needs of society to save energy, the tires have been largely shifted from bias tires to radial tires.

The radial tire, while arranging the carcass layer in the radial direction, has the belt layer in the tread portion for the purpose of imparting the hoop effect, so compared with the bias tire,
Good low rolling resistance, wear resistance, steering stability, high speed resistance, etc.

In particular, there is a strong demand for a reduction in rolling resistance as well as a reduction in the weight of tires that can contribute to a reduction in the weight of a vehicle even today.

In response to this strong demand for improvement in low rolling resistance, tire manufacturers have dealt with weight reduction of tires by lowering the hysteresis of rubber forming the tread portion. However,
It is a fact that the reduction in the hysteresis of the tread rubber is a factor that deteriorates the wet performance of the tire.

From such a background, as a reinforcing cord constituting a belt layer of a radial tire, a radial tire using a lightweight, high-elasticity and high-strength carbon fiber cord as a new material instead of a steel cord (Japanese Patent Publication No. 56-40043). Issue).

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

However, if all of the belt layers laminated in plural layers are made of carbon fiber cords, the durability is significantly inferior to that of the conventional radial tire under the present circumstances.

In other words, when the tire rotates on the ground, it transmits the driving force of the vehicle to the road surface and fulfills its role. However, in view of the life of the tire, it generally undergoes 10 ⁷ times of ground deformation.

At the time of this ground contact deformation, the tire is subjected to bending deformation, so-called bending deformation occurs, and therefore, a material having good bending fatigue resistance is required for the belt layer.

From this point of view, using the carbon fiber cord alone as a reinforcing cord for all belt layers is
The carbon fiber cord has a problem in bending fatigue and cannot be used as it is at present.

[Object of the Invention]

The present invention has been derived as a result of experiments and examinations for solving the above-mentioned problems.

Therefore, an object of the present invention is to improve the durability and steering stability while making it possible to use a carbon fiber cord as a reinforcing cord for a belt layer to reduce the weight and the rolling resistance of the tire. Another object of the present invention is to provide a pneumatic radial tire for passenger cars, which can also achieve the above.

[Structure of Invention]

The present invention, in a pneumatic radial tire for passenger cars,
Among the belt layers, a reinforcing cord made of carbon fiber cords is arranged on the carcass layer side, and a reinforcing cord made of steel cords is arranged on the tread portion side in proximity to the carcass layer side belt layer. , The carbon fiber cord has a tensile strength of 100 kg / mm ² or more and a tensile elastic modulus of 5000 k.
With carbon fiber of g / mm ² or more, with 10 to 50% by weight of adhesive per unit length The twist coefficient K value represented by (T: number of cord twists (number of turns / 10 cm), D: total number of denier of cord) is twisted in a range of 0 ≦ K ≦ 1800, and further, the carbon fiber cord The carcass layer side belt layer consisting of the two ends of the tread portion side belt layer consisting of the steel cord are superposed on both ends of the carcass layer side belt layer so as to extend to both outsides of the carcass layer side belt layer. The layer side belt layer and the tread portion side belt layer are arranged so that their cord angles intersect each other at 15 ° to 35 ° with respect to the tire circumferential direction.

In this way, by combining the steel cord belt layer and the carbon fiber cord belt layer, the bending fatigue resistance of the carbon fiber cord belt layer is supplemented, and the tread portion side steel cord belt layer is provided at both ends of the carcass side carbon fiber cord belt layer. By overlapping both ends so as to extend to both outsides, it prevents the carcass layer side carbon fiber cord belt layer end portion from rising due to the centrifugal force of the tire during high-speed running to prevent the occurrence of separation failure. Thereby, the durability of the tire can be improved. Further, by combining the steel cord belt layer and the carbon fiber cord belt layer, the rigidity of the entire belt layer can be increased and the steering stability can be improved.

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

1 (a) and 1 (b) show a pneumatic radial tire for a passenger vehicle according to an embodiment of the present invention, and FIG. 1 (a) is a perspective explanatory view in which a part of the first embodiment is cut away, FIG. (B) is an explanatory view showing a main part thereof, FIG. 2 is a view showing a result of a durability test, and FIG. 3 is a view showing a result of a steering stability test.

In the figure, E is a pneumatic radial tire for passenger cars comprising an embodiment of the present invention, a pair of left and right bead portions 1 and a pair of left and right side wall portions 2 connected to the bead portions 1,
A carcass layer 4 having a tread portion 3 located between the side wall portions 2 and 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 portions 1, and the tread is also provided. On the carcass layer 4 in the part 3, a plurality of belt layers 5 are arranged.

In the present invention, in particular, of the belt layer 5, a belt layer 5d having a reinforcing cord made of carbon fiber cord C is arranged on the carcass layer 4 side, and the tread is provided close to the carcass layer side belt layer 5d. A belt layer 5u having reinforcing cords made of steel cords S is arranged on the side of the portion 3 and further a carcass layer side belt layer made of the carbon fiber cords C.
The left and right ends 5d ₁ of the tread portion side belt layer 5u made of steel cord S are superposed on the left and right ends 5d ₁ of the 5d so as to extend to the outside of the left and right ends 5d ₁ of the carcass layer side belt layer 5d. ing. The carcass layer side belt layer 5d and the tread portion side belt layer 5u are arranged such that the cord angles thereof are 15 ° to 35 ° with respect to the tire circumferential direction and the cords intersect between the plies.

In the present invention, as described above, the reinforcing cord is the carbon fiber cord C on the carcass layer 4 side of the belt layer 5.
The carbon fiber cord C is formed by arranging the belt layer 5d made of C and the belt layer 5u made of the steel cord S as the reinforcing cord on the tread portion 3 side in the vicinity of the carcass layer side belt layer 5d. Since it is possible to supplement the bending fatigue resistance of the belt layer 5d with the belt layer 5u made of the steel cord S which is more excellent in bending fatigue resistance than the above, as described above, all the belt layers are made of carbon fiber cords. Compared with the tire described above, durability and steering stability can be significantly improved.

Further, in the present invention, as described above, the left and right ends 5d of the carcass layer side belt layer 5d made of the carbon fiber cord C are formed.
₁ , the left and right end portions 5u ₁ of the tread portion side belt layer 5u made of the steel cord S which is more excellent in bending fatigue resistance than the belt layer 5d are overlapped so as to extend to both outsides.

Therefore, the protection properties of the left and right end portions 5d ₁ of the carcass layer side belt layer 5d made of the carbon fiber cord C can be significantly improved, and the edge of the belt layer due to the centrifugal force of the tire during high speed running can be raised. Therefore, it is possible to prevent the occurrence of the separation failure and improve the durability of the tire.

Further, the carcass layer side belt layer 5d and the tread portion side belt layer 5u are arranged such that the cord angles thereof are 15 ° to 35 ° with respect to the tire circumferential direction, and the cords intersect between the plies. is there.

This is because the crossing angle of each cord with respect to the tire circumferential direction is 15
If it is less than 0, it is difficult to cut the belt layer during tire production, and if it exceeds 35, the rigidity in the tire circumferential direction decreases, which is not preferable.

As the steel cord S constituting the reinforcing cord of the belt layer 5u on the tread portion side, it is preferable to use a steel cord composed of a steel wire material having a carbon content of 0.62 to 0.87% and a tensile strength of 250 kg / mm ² or more.

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

That is, tensile strength 100 kg / mm ² or more, tensile elastic modulus 5000 kg /
mm ² or more, preferably, a tensile strength of 200 kg / mm ² or more, the carbon fiber having a tensile modulus 15,000 kg / mm ² or more characteristics, coated with 10-50% of the adhesive weight per unit length of the carbon fibers After that, the twist coefficient K value represented by the following formula is 0 ≦ K ≦ 1800
The twist is added so that the range becomes.

The twisted structure may be a so-called moist twisted structure in which first a lower twist is added to each of several carbon fibers, and then a plurality of them are combined and an upper twist is added, or a twist is added to one carbon fiber yarn. A single twist structure may be used.

K: twist coefficient T: number of twists of cord (times / 10 cm) D: total number of denier of cord [Experimental Example] A durability test and a steering stability performance test were conducted to confirm the effect of the present invention. (Specifications of tires used for each test) <Invention tire> Tire size: 175 / 70R13.

Carcass layer: A polyester cord with 1500d / 2 and 40 ends was used as the reinforcing cord, and was further arranged so that the cord angle would be 90 ° to the tire circumferential direction.

Carcass layer Belt side layer ... 1800d / 2 as reinforcement cord, end number 50,
Further, a carbon fiber cord having a coefficient K = 600 (10 twists / 10 cm of entangled structure) was further arranged so that the cord angle would be 20 ° with respect to the tire circumferential direction.

The width was 125 mm.

Belt layer on the tread side: Steel cords with 1 × 5 (0.25) and 44 ends are used as reinforcement cords, and the cord angle is set to 24 ° with respect to the tire circumferential direction. The parts were made to protrude by 5 mm from both ends of the carcass layer side belt layer, and were superposed on the left and right ends of the carcass layer side belt layer.

The total width is 150 mm.

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

Carcass layer: A polyester cord with 1500d / 2 and 40 ends was used as the reinforcing cord, and was further arranged so that the cord angle would be 90 ° to the tire circumferential direction.

Belt layer: Both the carcass layer side belt layer and the tread side belt layer are 1800d / 2 as reinforcing cords and the number of ends is 5
A carbon fiber cord having a twist coefficient K of 600 and a twist coefficient of K = 600 (10 twists / 10 cm) was arranged so that the cord angle was 24 ° with respect to the tire circumferential direction.

The width of the carcass layer side belt layer was 130 mm and the width of the tread portion side belt layer was 140 mm.

[Experimental Example 1] Durability performance test As an endurance performance test, an indoor drum tester (diameter 1707 mm)
Was used.

<Test conditions> The air pressure was 2.3 kg / cm ² , the speed was 81 kg / hr, and the load was increased from 405 kg by 61 kg every 4 hours until the vehicle broke.

The test results are shown in FIG. Note that FIG. 2 is shown as an index with the conventional tire test result as 100.

As is clear from FIG. 2, it is understood that the tire of the present invention has an improved durability performance of about 10% as compared with the conventional tire.

[Experimental Example 2] Steering stability performance test As a steering stability performance test, a slip angle of 2 ° was attached to the tire with an indoor cornering tester (diameter 2500 mm), and the lateral force at this time was divided by 2 to obtain CP (cornering power). Was determined and used as a representative value.

<Test conditions> Air pressure: 1.9 kg / cm ² Load: 405 kg Speed: 20 km / hr The test results are shown in FIG. Note that FIG. 3 is shown as an index with the conventional tire test result being 100.

As is apparent from FIG. 3, it is understood that the tire of the present invention has improved steering stability by about 10% as compared with the conventional tire.

〔The invention's effect〕

As described above, according to the present invention, in the pneumatic radial tire for passenger cars, among the belt layers, the reinforcing cords are arranged on the carcass layer side, and the belt layer made of carbon fiber cords is arranged, and on the carcass layer side belt layer. A belt layer consisting of steel cords as reinforcement cords is placed in close proximity to the tread side, and the carbon fiber cords have a tensile strength of 100 kg / mm.
² or more and a tensile elastic modulus of 5000 kg / mm ² or more on carbon fiber with 10 to 50% by weight of adhesive per unit length (T: the number of twists of the cord (times / 10 cm), D: the total number of denier of the cord) The twist coefficient K value is in the range of 0 ≦ K ≦ 1800, and the carbon fiber cord is further twisted. Carcass layer side belt layer consisting of both ends of the tread portion side belt layer consisting of the steel cord is overlapped so as to extend to both outer sides than both ends of the carcass layer side belt layer, and the carcass Since the layer side belt layer and the tread portion side belt layer are arranged such that the cord angles thereof intersect each other at 15 ° to 35 ° with respect to the tire circumferential direction, it is possible to use carbon fiber cords as reinforcing cords for the belt layer. While making it possible to reduce the weight and lower rolling resistance of the tire, while improving durability,
It is also possible to improve steering stability.

[Brief description of drawings]

1 (a) and 1 (b) show a pneumatic radial tire for a passenger car according to an embodiment of the present invention, and FIG. 1 (a) is a perspective explanatory view in which a part of the embodiment is cut away, FIG. 1 (b). ) An explanatory view showing the main part thereof, FIG. 2 is a view showing the results of the durability test, and FIG.
The figure shows the results of the steering stability test. 1 ... Bead part, 2 ... Sidewall 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.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-53-104906 (JP, A) JP-A-50-101686 (JP, A) JP-A-57-15004 (JP, A) JP-B-58- 47364 (JP, B2) JP-B 56-40043 (JP, B2) JP-B 58-53603 (JP, B2) JP-B 47-32321 (JP, Y2)

Claims (1)

[Claims] 1. In a pneumatic radial tire for passenger cars, a belt layer having carbon fiber cords as reinforcing cords is arranged on the carcass layer side of the belt layer, and the tread portion side is close to the carcass layer side belt layer. A belt layer made of steel cords as reinforcement cords is arranged on the carbon fiber cords and the tensile strength is 100 kg / mm ² or more and the tensile elastic modulus is 5
Carbon fiber of 000kg / mm ² or more with 10 to 50% by weight of adhesive per unit length The twist coefficient K value represented by (T: number of cord twists (number of turns / 10 cm), D: total number of denier of cord) is twisted in a range of 0 ≦ K ≦ 1800, and further, the carbon fiber cord Carcass layer side belt layer consisting of both ends of the tread portion side belt layer consisting of the steel cord is overlapped so as to extend to both outer sides than both ends of the carcass layer side belt layer, and the carcass A pneumatic radial tire for passenger cars, wherein the layer side belt layer and the tread portion side belt layer are arranged such that their cord angles intersect each other at 15 ° to 35 ° with respect to the tire circumferential direction.