JPH0725241B2 - 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 reduce the rolling resistance as well as the weight.

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 has a cord angle of 10 ° to 35 ° with respect to the tire circumferential direction.
In a pneumatic radial tire for passenger cars in which a plurality of belt layers having cords intersecting each other between plies are arranged on a tread, a belt layer made of carbon fiber cords is provided on the carcass layer side of the belt layers. With the arrangement, a belt layer made of steel cord is arranged on the tread portion side close to the carcass layer side belt layer, and the carbon fiber cord has a tensile strength of 100 kg / mm ² or more and a tensile elastic modulus of 5000 kg / mm.
^Two or more carbon fibers with 10 to 50% by weight of adhesive per unit length (T: the number of twists of the cord (times / 10cm), D: the total number of denier of the cord) The twist coefficient K value has a structure in which the twist is in the range of 0 ≦ K ≦ 1800. Bending at least one end portion of the tread portion side belt layer to the tread portion side, and both ends of the tread portion side belt layer from the both ends of the carcass layer side belt made of the carbon fiber cord to the left and right sides respectively 5 mm It is characterized in that it is projected above.

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 both ends of the carcass layer side carbon fiber cord belt layer are By protecting both ends of the steel cord layer on the tread side, which has excellent bending fatigue resistance, the carbon fiber cord belt layer side edge on the carcass side is prevented from rising due to the centrifugal force of the tire during high-speed running, thus preventing separation failure. It is possible to prevent the generation of the tire, and thereby improve the durability of the tire. 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) to 1 (d) show a pneumatic radial tire for a passenger vehicle according to each 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. Figure 1 (b) ~
(D) is an explanatory view in which a part of the essential parts of the second to fourth examples is cut away, FIG. 2 is a view showing a result of a durability test, and FIG. 3 is a result of a steering stability test. It is a figure.

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 with respect to the tire circumferential direction of 70 ° to 90 ° 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 portion 3, a plurality of belt layers 5 having cord angles with respect to the tire circumferential direction of 10 ° to 35 ° and cords intersecting each other between plies are arranged.

In the present invention, in particular, among the belt layers 5, the belt layer 5d made of the carbon fiber cord C is arranged on the carcass layer 4 side, and the belt layer 5u made of the steel cord S is arranged on the tread portion 3 side. Further, at least one end portion of the tread portion side belt layer 5u made of the steel cord S is bent to 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 portion side belt layer 5u, compared with the tire in which the belt layers are all made of carbon fiber cords as in the above-mentioned conventional, It is possible to significantly improve durability and steering stability.

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

Therefore, the impact force from the road surface of the tire can be absorbed by the belt layer 5u made of the 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, at least one end of the tread portion side belt layer 5u made of the steel cord S having excellent bending fatigue resistance is bent toward the tread portion side.

Therefore, the end portion of the tread portion side belt layer 5u can be double-layered, and the protection property of the carcass layer side belt layer 5d made of the carbon fiber cord C can be significantly improved, while
It is also possible to prevent the both edges of the belt layer from rising due to the centrifugal force of the tire during high-speed running, and to prevent the occurrence of separation failure.

In addition, in the present embodiment, as shown in FIGS. 1A to 1D, the left and right ends 5u ₁ of the tread portion side belt layer 5u made of the steel cord S are connected to the carcass layer made of the carbon fiber cord C. The left and right ends of the carcass layer side belt layer 5d are made to project from the left and right ends 5d _{1 of the} side belt layer 5d to the left and right
The 5d _1, are covered by the left and right end portions 5u ₁ of the tread portion side belt layer 5u.

That is, the left and right end portions 5d ₁ of the carcass layer side belt layer 5d made of the carbon fiber cord C are connected to the left and right end portions of the tread portion side belt layer 5u made of the steel cord S having a better bending fatigue resistance than the belt layer 5d. Covered by 5u ₁ .

Therefore, 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 largely protected, 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.

The left and right end portions 5u of the tread portion side belt layer 5u
The protruding width of ₁ from the left and right end portions 5d ₁ of the carcass layer side belt layer 5d is 5 mm or more. This is because when the protrusion width is less than 5 mm, the carcass layer side belt layer made of carbon fiber cord C is formed.
This is because the protection properties of the left and right ends 5d ₁ of 5d may be reduced, and the durability may not be improved.

The steel cord S constituting the reinforcing cord of the belt layer 5u on the tread portion side has a wire diameter of 0.2 mm or less, preferably 0.1 mm or less.
It is preferable to use a steel cord having a double twist structure made of a steel strand having a strand diameter of 75 mm or less.

The twist structure of this steel cord is n × m, and n
Is preferably 3 to 4 and m is 3 to 7, and further,
The strand pitch of this cord is preferably 8 mm or less, and the cord pitch is preferably 8 mm 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, tensile strength 100 kg / mm ² or more, tensile elastic modulus 5000 kg /
mm ² or more, preferably, a tensile rate 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: twist number of cords (times / 10 cm) D: total denier number of cords Further, the structure of each example shown in FIGS. 1 (a) to (d) will be described as follows. is there.

In the first embodiment of the present invention shown in FIG. 1 (a), a belt layer 5d made of carbon fiber cord C is disposed 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 in which is further arranged.

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

In the second embodiment of the present invention shown in FIG. 1 (b), two belt layers 5d made of carbon fiber cords C are arranged 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 of further arranging 5u.

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

In the third embodiment of the present invention shown in FIG. 1 (c), a belt layer 5d made of carbon fiber cord C is disposed 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 in which two layers are arranged.

It should be noted that one end portion of each tread portion side belt layer 5u made of the steel cord S is made to face each other and is bent to the tread portion side.

In the fourth embodiment of the present invention shown in FIG. 1 (d), a belt layer 5d made of carbon fiber cord C is disposed 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 in which two layers are arranged.

Each tread portion side belt layer 5u made of the steel cord S has its left and right ends bent to the tread portion side, as shown in the figure, only the belt layer located on the upper side.

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

〔Example〕

To confirm the effect of the present invention, a durability test and a steering stability performance test were conducted.

(Specifications of tires used for each test) <Invention tire> Tire size: 185 / 70R13.

Carcass layer: A polyester cord with 1000d / 2 and 35 ends was used as a reinforcing cord, and two layers were arranged so that the cord angle would be 90 ° with respect to the tire circumferential direction.

Carcass layer Belt side layer ... 1800d / 2 as reinforcement cord, end number 50,
A carbon fiber cord with a twisting coefficient K = 600 (10 twists / 10 cm of entangled twist structure) was further arranged so that the cord angle would be 24 ° with respect to the tire circumferential direction.

A width of 130 mm was used.

Belt layer on the tread side: Steel cords with 3 × 7 (0.15) and 35 ends are used as reinforcement cords, and the cord angle is 24 ° with respect to the tire circumferential direction.
Use a 220 mm one, and put the left and right ends on the tread side 4
Bent by 0 mm.

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

Carcass layer: A polyester cord with 1000d / 2 and 35 ends was used as a reinforcing cord, and two layers were arranged so that the cord angle would be 90 ° with respect 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 with a twist coefficient of 0 and a twist coefficient of K = 600 (10 twists / 10 cm of woven structure) 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 km / hr, and the load was increased from 450 kg by 68 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 apparent from FIG. 2, it is understood that the tire of the present invention has improved durability performance by about 28% 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 250 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… 1.9kg / cm ² Loading… 450kg Speed… 20km / hr 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 15% as compared with the conventional tire.

〔The invention's effect〕

As described above, according to the present invention, a pneumatic radial tire for a passenger vehicle, which has a cord angle with respect to the tire circumferential direction of 10 ° to 35 ° and is arranged on a tread of a plurality of belt layers in which cords intersect each other between plies. In the belt layer, a belt layer made of carbon fiber cords is arranged on the carcass layer side, and a belt layer made of steel cords is arranged on the tread portion side in proximity to the carcass layer side belt layer. Tensile strength of fiber cord 100kg / mm ²
Carbon fiber with tensile modulus of 5000 kg / mm ² or more and 10 to 50% by weight of adhesive per unit length (T: the number of twists of the cord (times / 10cm), D: the total number of denier of the cord) The twist coefficient K value has a structure in which the twist is in the range of 0 ≦ K ≦ 1800. Bending at least one end portion of the tread portion side belt layer to the tread portion side, and both ends of the tread portion side belt layer from the both end portions of the carcass layer side belt made of the carbon fiber cord to the left and right sides respectively 5 mm Because of the above-mentioned protrusion, it is possible to use a carbon fiber cord as a reinforcing cord for the belt layer, thereby improving the durability and the steering stability while reducing the weight and the rolling resistance of the tire. Is possible.

[Brief description of drawings]

1 (a) to 1 (d) show a pneumatic radial tire for a passenger vehicle according to each 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. Figure 1 (b) ~
(D) is a partially cutaway explanatory view showing an essential part of the second to fourth embodiments, 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. is there. 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) References JP-A-59-29503 (JP, A) JP-A-50-101686 (JP, A) JP-B-56-40043 (JP, B2)

Claims (1)

[Claims] 1. A cord angle with respect to a tire circumferential direction is 10 ° to
In a pneumatic radial tire for passenger cars, in which a plurality of belt layers of 35 ° and cords intersecting between plies are arranged on a tread, a belt layer made of carbon fiber cords is arranged on the carcass layer side of the belt layers. Along with the carcass layer side belt layer, a belt layer made of steel cord is arranged on the tread portion side, and the carbon fiber cord has a tensile strength of 100 kg / mm ² or more and a tensile elastic modulus of 500.
Carbon fiber of 0kg / mm ² or more, 10 to 50% by weight per unit length
With glue (T: the number of twists of the cord (times / 10cm), D: the total number of denier of the cord) The twist coefficient K value has a structure in which the twist is in the range of 0 ≦ K ≦ 1800. Bending at least one end portion of the tread portion side belt layer to the tread portion side, and both ends of the tread portion side belt layer from the both end portions of the carcass layer side belt made of the carbon fiber cord to the left and right sides respectively 5 mm A pneumatic radial tire for passenger cars, which is characterized by being projected as described above.