JPH10244816A - Pneumatic radial tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire with improved wandering performance resisting a rut without deteriorating durability. SOLUTION: This pneumatic radial tire has at least two carcass layers 1, 2 and at lest two belt layers 4a, 4b, or 4c arranged outside the carcass layer 2 at the tread part T. At least one reinforcing layer 5 made of an organic fiber code is extended between the carcass layers 1, 2 from the outermost position in the direction of width of the tire to the end of the belt layer 4b having the maximum width in the direction of width thereof and an angle formed by the code of the reinforcing layer 5 and the code of the carcass layers 1, 2 is 5 to 60 degrees.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire having improved rudder wandering resistance without impairing durability, and more particularly to a pneumatic radial tire used as a tire for a small truck.

[0002]

2. Description of the Related Art Conventionally, a pneumatic radial tire has a problem that its rut wandering resistance is inferior to that of a bias tire. The rut wandering referred to here refers to the inner side of the tire that is received from the rut edge when trying to escape from the rut while the tire mounted on the vehicle runs along the rut formed in the road surface. It is a phenomenon in which the vehicle is pushed back into the rut by the reaction force in the direction and the vehicle fluctuates and cannot escape. Therefore, the rut wandering resistance refers to the tire performance that enables the escape from the rut without any wobbling.

Conventionally, in pneumatic radial tires,
As a countermeasure to improve the rut wandering resistance, the rubber thickness from the shoulder to the side of the tire is increased to increase the rigidity in this region.
However, when the rubber thickness is increased in this manner, although the rut wandering resistance is improved, the heat generation is deteriorated due to the large rubber thickness (that is, high heat is generated), and particularly, the flattening rate is reduced. In the case of a tire of 80% or less, there is a problem that the stepping pressure of the shoulder portion becomes larger than that of the central portion in the width direction of the tread, so that the tire is more likely to generate heat and the durability is reduced.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic radial tire having improved rut wandering resistance without impairing durability.

[0005]

SUMMARY OF THE INVENTION The present invention provides at least two
In a pneumatic radial tire having a plurality of carcass layers and at least two belt layers disposed on the outer periphery of a tread portion of the carcass layer, between the carcass layers between the vicinity of the end of the belt layer and the vicinity of the tire maximum width , At least one reinforcing layer made of an organic fiber cord is interposed, and the intersection angle between the cord of the reinforcing layer and the cord of the carcass layer is 5 ° to 60 °.

Since the reinforcing layer of the organic fiber cord is interposed between the layers of the carcass layer from the vicinity of the end of the belt layer to the vicinity of the maximum width of the tire as described above, the reinforcement from the shoulder portion to the side portion without increasing the rubber thickness. , The rigidity can be increased, thereby improving the rut wandering resistance. Further, since the rubber thickness is not increased, the heat build-up does not deteriorate, and the durability can be maintained even in the case of a tire having an aspect ratio of 80% or less.

[0007]

FIG. 1 is a half sectional view in the tire meridian direction showing an example of a pneumatic radial tire according to the present invention.
In FIG. 1, two carcass layers 1 and 2 are mounted between a pair of left and right bead cores 3 and one of the carcass layers 1 is wound around the end of the bead core 3 from the inside of the tire to the outside. And the other carcass layer 2 is
The end covers the outside of the winding end 1 a of the carcass layer 1 and terminates near the bead core 3. Each of the two carcass layers 1 and 2 has a carcass cord made of an organic fiber cord such as a nylon fiber cord, a polyester fiber cord, or an aromatic polyamide fiber cord. Two or more carcass layers are provided as light truck tires. Usually, two or three sheets are provided.

In the tread portion T, three belt layers 4a, 4b, 4c are arranged outside the carcass layer 2. These belt layers are made of organic fiber cords such as steel cords or aromatic polyamide fiber cords. It is sufficient that at least two belt layers are provided, and two or three belt layers are preferable for a light truck tire.

A reinforcing layer 5 made of an organic fiber cord is provided between the two carcass layers 1 and 2 so as to extend from the vicinity of the maximum width of the tire to the end of the belt layer 4b having the maximum width. . The end of the reinforcing layer 5 on the side of the belt layer 4b does not overlap with any of the belt layers. When the tires overlap, the reinforcement layer 5 is moved by the movement of the carcass layers 1 and 2 during running of the tire, and this movement causes separation at the edge of the belt layer, thereby impairing the durability of the belt layer. Because it becomes.

As the organic fiber cord constituting the reinforcing layer 5, a nylon fiber cord, a polyester fiber cord, an aromatic polyamide fiber cord and the like are preferably used.
When the reinforcing layer 5 is made of a steel cord, the weight of the tire increases and separation at the end of the reinforcing layer 5 easily occurs, which is not preferable. This reinforcing layer 5
May be arranged at least one between the carcass layers. Therefore, when N carcass layers are arranged, N-1 carcass layers can be arranged one by one between each carcass layer.

The reinforcing layer 5 must be arranged so that the direction of the cords intersects the respective cords of the carcass layers 1 and 2, and the angle of intersection is in the range of 5 ° to 60 °. If the crossing angle is less than 5 °, the effect of improving the rudder wandering resistance is small, and if it exceeds 60 °, it becomes difficult to manufacture a tire. By simply arranging the reinforcing layer 5 in this manner, the rigidity from the shoulder portion S to the side portion W can be increased without increasing the rubber thickness, so that the rudder wandering resistance can be improved. Since the heat generation at this location does not deteriorate, the durability is not impaired. Further, since the heat generation does not deteriorate, not only the rolling resistance of the tire can be reduced, but also the amount of rubber used can be reduced, so that the weight and cost can be reduced.

The pneumatic radial tire of the present invention is suitable for small truck tires and passenger car tires having a flatness of 80% or less, but is particularly suitable for small truck tires.

[0013]

EXAMPLE For a pneumatic radial tire having a tire structure shown in FIG. 1 and having a tire size of 195 / 60R17.5, the carcass angle (cord angle of the carcass cord with respect to the tire circumferential direction) and the reinforcing layer angle are shown in Table 1. (Cord angle of reinforcing layer cord with respect to tire circumferential direction),
Six types of tires having different cord intersection angles (intersection angles between the cord of the reinforcing layer and the cord of the carcass layer) and the thickness of the shoulder portion were manufactured (conventional tire, comparative tire 1).
2, the present invention tires 1 to 3). Here, a steel cord is used for the belt layer, a nylon fiber cord is used for the carcass layer, and a polyester fiber cord is used for the reinforcement layer.Each of these layers is buried in a coat rubber to form a sheet. Configured.

The tires were evaluated for rut wandering resistance, heat generation, and rolling resistance as follows.
The results are shown in Table 1. Rudder wandering resistance : Conventional tires show the rudder wandering resistance when traveling on a test course with a rut under the conditions of working air pressure 600 kPa, load 9.81 kN, and speed 100 Km / h by a protest driver. Was evaluated as a reference (6 points) (the larger the score, the better the result).

Heat generation : After running continuously for 2 hours on a drum having a drum diameter of 1707 mm under the conditions of an air pressure of 600 kPa, a load of 9.81 kN and a speed of 100 km / h, the internal temperature of the shoulder was measured. 1
The index was evaluated as 00 (meaning that the index is better).

Rolling resistance : Working air pressure: 600 kPa
Under the conditions of a load of 9.81 kN and a speed of 80 Km / h, the result of measuring the rolling resistance during running was evaluated as an index with the conventional tire set as 100 (the larger the index, the better the index).

[0017]

[Table 1]

As is clear from Table 1, the tire 1 of the present invention
No. 3 to No. 3 are superior in heat generation (do not impair durability) and have improved rut wandering resistance as compared with the conventional tires and Comparative tires 1 and 2.

[0019]

As described above, in the pneumatic radial tire according to the present invention, at least one reinforcing layer made of an organic fiber cord is provided between at least two carcass layers between the vicinity of the tire maximum width and the belt layer. Since it is extended to the vicinity of the end and the intersection angle between the cord of the reinforcing layer and the cord of the carcass layer is set to 5 ° to 60 °, the rigidity is increased without increasing the rubber thickness and the rudder wandering resistance is improved. In addition, since the thickness of the rubber is not increased, the heat generation does not increase and the durability is maintained. Further, not only the rolling resistance of the tire can be reduced, but also the weight and cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a half sectional view in the tire meridian direction showing an example of a pneumatic radial tire of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carcass layer 2 Carcass layer 3 Bead core 4a, 4b, 4c Belt layer 5 Reinforcement layer

Claims (3)

[Claims] 1. A pneumatic radial tire having at least two carcass layers and having at least two belt layers disposed on an outer periphery of a tread portion of the carcass layer, wherein an end of the belt layer is located between layers of the carcass layer. At least one reinforcing layer made of an organic fiber cord is interposed from the vicinity of the portion to the vicinity of the tire maximum width, and the intersection angle between the cord of the reinforcing layer and the cord of the carcass layer is 5 °.
A pneumatic radial tire having an angle of up to 60 °. 2. The pneumatic radial tire according to claim 1, wherein the flatness is 80% or less. 3. The pneumatic radial tire according to claim 1, which is used as a light truck tire.