JPH02296506A - Pneumatic radial-ply tire - Google Patents

Abstract

PURPOSE:To reduce the rolling resistance without hurting the riding comfortableness by setting up a cord of a belt layer at the outermost layer among a lot of belt layers set up at the upper part of a carcass ply orthogonal with the equator line of a tire, at a specified tilt angle to the equator line. CONSTITUTION:In a tire 10, a carcass ply 11 consisting of a steel cord is set up at a right angle with its equator line P. In addition, a lot of belt layers 5-8 are set up in an upper part of the carcass ply 11. In this case, a cord in a belt layer 8 at the outermost layer is set up at a tilt angle within a range of 3-10 deg. to the equator line P. The belt layer 8 at the outermost layer is of high extension cord withing a range of 4.0-8.0% in elongation percentage at time of rupture, and it is formed with a belt ply that embedded lang lay of an open cord into rubber. In addition, the belt layer 8 at the outermost layer is formed wider than a belt layer 7 so as to cover both sides of this belt layer 7 in the inner part of the belt layer 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic radial tire for heavy loads, and particularly to a pneumatic radial tire for heavy loads with improved rolling resistance and high-speed durability.

[Conventional technology]

Conventionally, pneumatic radial tires for heavy loads have four belt layers made of steel cords arranged at an angle with respect to the equator direction of the tire, arranged on the carcass in the tread part so as to intersect with each other. The outer belt layer is bonded at an angle close to the cord angle of the adjacent belt, with emphasis on trauma resistance.

That is, as shown in FIGS. 3 and 4, the tire 1
0, a carcass ply 11 extending substantially orthogonal to the equator line P is arranged, and four belt layers 1, 2, 3, 4 are arranged intersecting each other on the carcass ply 11 in this tread portion. ing. Each belt layer 1, 2, 3
, 4 are each made of steel cord, are arranged at an angle with respect to the equator line P, and have an outermost layer (fourth layer).
The belt layer 4 of the belt layer 4 has an adjacent belt layer (
The third layer) is formed at an approximate inclination angle to 3.

In the illustrated example, the first belt layer 1 has an inclination angle of 60° with respect to the equator line P, the second to fourth belt layers 2 to 4 are each set to 18'', and the second to third layer The cords have the same angle and are inclined in opposite directions.

[Problem to be solved by the invention]

For a long time, the issue has been how to reduce the rolling resistance of tires in order to make automobiles more fuel-efficient, and with the development of expressway networks, it is becoming increasingly important to improve rolling resistance, handling stability, and high-speed durability. Demands are increasing and this needs to be achieved without reducing the wear life of the tire. However, the conventional structures shown in FIGS. 3 and 4 have the drawbacks of high rolling resistance and poor high-speed durability.

[Means to solve the problem]

The present invention relates to a pneumatic radial tire in which a carcass ply extending substantially orthogonal to the equator of the tire is arranged, and a small number of belt layers are arranged on the carcass ply in a tread portion. The cords of the layer are arranged at an angle of inclination of 3 to 10 degrees with respect to the equator.

The outermost belt layer has an elongation rate of 4°0 to 8 at break.
．． The belt ply is a high tensile cord with 0% stretch and is made of open cord Langley strands embedded in rubber, and is made wider than the inner belt layer so as to cover both sides of the inner belt layer. It is preferable.

[Effect]

In the above configuration, the outermost belt layer, which transmits the fluctuations of the uneven road surface through the tread, has a high elongation rate and uses an open cord Langley twisted cord that allows the topping rubber to penetrate well. It is easy to absorb fluctuations from Furthermore, since the inner layer belt ends are all covered by such a belt layer, damage caused by interfacial peeling with the topping rubber, which conventionally occurs at these belt ends, can be effectively prevented. Furthermore, since the outermost belt layer is arranged at a small inclination angle within a predetermined range with respect to the tire's equator line, rolling resistance is reduced without impairing ride comfort, and the effect of the outermost belt layer is also added. It is possible to exhibit good heat generation durability.

(Example) In FIGS. 1 and 2, a carcass ply 1 made of steel cord is attached to the tire 10 at right angles to its equator line P.
1 is arranged on the carcass ply 11 in the tread portion 12 of this tire 10.
A pneumatic radial tie A7 is constructed by arranging belt layers 5°6.7.8 of the pneumatic radial tie A7. This belt [5,6
, 7 is a high elastic cord (initial elastic modulus 16
000 klJf/m12 or more).

The inclination of each belt layer with respect to the equator line P is 67° for the first belt layer 5, and the inclination angle of the second belt layer 6 in the same direction as the first belt layer 5, and the belt layer 7 has an inclination angle of 166gjI31.
The outermost belt layer 8 has an inclination angle of 16° in the opposite direction to that of the second belt layer 6, and the outermost belt layer 8 has an inclination angle of 4° in the same direction as the third belt layer 7. The cords of the outermost belt layer 8 may be arranged at an inclination angle of 3 to 10 degrees with respect to the equator line P. Further, the outermost belt layer 8 is formed to be wider than the first to third belt layers 5 to 7 on the inner side so as to cover both sides of the belt layers 5 to 7.

Furthermore, since the first to third belt layers 5, 6, and 7 have a high elastic modulus, strain concentrates at the interface with the tread rubber at these side edges, which tends to cause peeling. 4
It is covered with a belt layer 8 to prevent peeling.

The outermost belt layer 8 is made of HE cord (Ilight
longation code). This consists of open cords or Langley cords with an elongation rate of 4 to 8% at break (compared to 2 to 3% for conventional cords), and these cords are used because the movement and deformation of the tread is directly transmitted. This is because the outermost layer is required to have characteristics that allow it to easily follow the movement of the rubber, and it is also preferable for strengthening the adhesiveness with the rubber.

In order to confirm the effects of this invention, tests as shown in the table on the next page were conducted in comparison with a conventional structure and a comparative example.

In the table above, A is 3/0.20 + 6/0.
35 cord, B indicates a 4X 410.22 cord (Langley twist of open cord), and belt width (%) indicates the ratio (%) of each belt width WB/tread width WT.

In addition, the heat generation durability test was conducted using a drum running test machine with a smooth surface at a speed of 1801v/h, a JIS Ja heavy load, and a maximum internal pressure of 10km/h every 24 hours.
The speed is increased by h, the distance traveled until failure is determined, and the value of the comparative example is set as 100, and an index is displayed.The larger the index, the better the durability.

The rolling resistance test is calculated by pressing the tire against a drum running test machine with a smooth surface and a diameter of 1.6 m, accelerating it to a speed of 80 km/h, and measuring the tangential force acting on the ground surface during rotational disturbance. The value of Comparative Example 1 in the table is expressed as an index as 100, and the larger the index, the smaller the rolling resistance and the better.

The ride comfort test is based on a 5-point evaluation based on a real-life feeling test conducted by three experienced test drivers, and the average value of the three is expressed as an index, with the higher the value, the better the ride comfort.

The passing standard as a test result is that the rolling resistance is 105.
As described above, the heat generation durability is 110 or more, and the ride comfort is 95 or more.

In the above table, the rolling resistance of the conventional product is the acceptance standard value (
105) Below, there are 95 cases whose heat generation durability is below the standard m(110), whereas Examples 1.2.3 of this invention all have values above the acceptance standard value. Unlike conventional products, the bottom layer cord angle is large (16°)
It can be seen that the rolling resistance and heat generation durability are poor. Regarding the ride comfort, each of the examples 1.2°3 exceeded the acceptance standard value (95).

Further, in Comparative Example 2 in which the arrangement angle of the outermost layer was set to 26 degrees, the ride comfort was lower than the acceptance standard value, and in Comparative Example 1 in which the arrangement angle was 12 degrees, the light and heat durability was lower than the acceptance standard value.

From this, it can be seen that the arrangement angle of the outermost layer needs to be set within the range of 3 to 10''.

〔Effect of the invention〕

As explained above, according to the present invention, since the outermost belt layer is arranged at a small inclination angle within a predetermined range with respect to the equator line of the tire, rolling resistance can be reduced without impairing riding comfort. It is also possible to exhibit good heat generation durability. In addition, the outermost belt layer, which transmits fluctuations from the uneven road surface through the tread, has a high elongation rate and uses open cord Langley twisted cord, which allows the topping rubber to penetrate well. It is easy to absorb and the local occurrence of shear hands is alleviated. Furthermore, since the inner layer belt ends are all covered by such a belt layer, damage caused by interfacial peeling with the topping rubber, which conventionally occurred at these belt ends, can be effectively prevented.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the cord arrangement of a belt layer in a tread portion of a tire showing an embodiment of the present invention. 5... First belt layer, 6... Second belt layer, 7... Third belt layer, 8... Outermost layer (fourth layer) belt layer, 10. ...Tire, 11...Carcass ply, 12...Tread section.

Claims (1)

[Claims] 1. A carcass ply extending substantially perpendicular to the equator of the tire, and a plurality of belt layers intersecting each other on the carcass ply inside the tread portion. A pneumatic radial tire characterized in that the cords of the outermost belt layer are arranged at an inclination angle of 3 to 10 degrees with respect to the equator line. 2. The outermost belt layer has an elongation rate of 4.0 at break.
It is a high tensile cord of ~8.0% and is composed of a belt ply made of open cord Langley strands embedded in rubber, and is wider than the inner belt layer so as to cover both sides of the inner belt layer. 2. The pneumatic radial tire according to claim 1, wherein the pneumatic radial tire is formed as follows.