JPH07323703A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To restrain deformation of a belt breadth end part at the time of loading and unify ground pressure distribution of a tread and improve sterring stability by arranging a belt reinforcing layer with a cord arranged in a direction actaully crossing the tire peripheral direction buried in it between the belt breadth end parts and a carcass. CONSTITUTION:A belt reinforcing layer 5 with a cord arranged in a direction actually crossing the tire peripheral direction buried in it is arranged between a belt breadth end part and a carcass 3. This belt reinforcing layer 5 is rubberized by way of arranging a large number of steel cords crossing the tire peripheral direction actually at 90 deg. in parallel Consequently, it is possible to unify tread ground pressure distribution and to improve steering stability by restraining deformation of the belt breadth end part at the time of loading.

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, and more particularly to a passenger car tire.

[0002]

2. Description of the Related Art It is preferable to make the contact pressure distribution in the tread of a pneumatic radial tire uniform, from the viewpoint of steering stability and uneven wear control. From the past, the outer contour shape in the width direction of the tread, especially the crown radius is set. The shape of the shoulder and the shape of the shoulder have been considered. However, the present invention is still not sufficient, and the inventor has reached the present invention by paying attention to the reinforcing structure in the tread portion and repeating the examination.

Generally, when a pneumatic radial tire is filled with air, the tire is deformed so as to approach a single circle. The belt arranged as a reinforcing layer in the crown portion of the carcass is arranged to bend the tire, that is, to suppress the deformation into the single circle,
Due to the air filling, the cross-sectional shape in the width direction forms an arc having a center of curvature inside the tire or is deformed so that the curvature of the arc becomes large. Along with this, the outer contour shape in the width direction of the tread portion is also deformed so that the curvature becomes large.

[0004]

When a load is applied to this tire, the side wall portion is bent and deformed and falls down, so that the belt width end portion is pressed against the road surface. That is, the belt width end portion is deformed to the road surface side, and accordingly, the ground contact pressure at the tread width end portion increases. This point becomes even more noticeable during cornering, which is a cause of reducing steering stability by suppressing the maximum cornering force.

Therefore, an object of the present invention is to improve the steering stability by suppressing the deformation of the belt width end portion under load to make the ground pressure distribution of the tread uniform.

[0006]

The present invention relates to a pneumatic radial tire having a carcass extending in a toroidal shape across the left and right bead cores, and a belt arranged at the crown portion of the carcass, in a tire circumferential direction. The pneumatic radial tire is characterized in that a belt reinforcing layer in which cords arranged in a direction substantially intersecting is embedded is arranged between a belt width end and a carcass.

Here, the larger the angle formed by the cord embedded in the belt reinforcing layer and the tire circumferential direction, the better. Specifically, it is preferably 45 ° or more, and most preferably around 90 °. Further, it is preferable that the cord is a non-stretchable cord such as steel or aromatic polyamide fiber, and that the width of the belt reinforcing layer is 20 to 30% of the belt width.

Here, for convenience sake, the belt width end portion means a portion located at the outermost portion when the belt width is divided into five equal parts. In the present invention, the belt reinforcing layer is arranged in the area between this portion and the carcass, but it is not always necessary to arrange the belt reinforcing layer in the entire area, and at least a part of the belt reinforcing layer is located in the area. Should be placed in.

[0009]

As described above, in the conventional tire,
When the side wall falls under load, the belt width end is deformed so as to approach the road surface. In particular, this deformation occurs on the outer side in the tire width direction from the outermost groove in the tire width direction when there are a plurality of grooves extending substantially along the tire circumferential direction in the tread. At this time, the tensile stress acts on the belt from the carcass. In the present invention, since the cords embedded in the belt reinforcing layer disposed between the belt width end portion and the carcass are arranged in the direction substantially intersecting the tire circumferential direction, the tensile stress It becomes possible to have a large tension rigidity, and it is possible to suppress the deformation of the belt width end portion.

In order to increase the deformation suppressing effect, it is preferable that the angle formed by the cord embedded in the belt reinforcing layer and the tire circumferential direction is large, and the cord is preferably a non-extensible cord. It is necessary for the belt reinforcing layer to have a certain width in order to achieve the above-mentioned action, and it is preferable that the belt reinforcing layer has a width of 20% or more of the belt width. However, there is no point in arranging it in the central portion of the belt width, and rather, the rolling resistance increases as the weight increases, so it is preferably 30% or less.

[0011]

EXAMPLES Tire 1 shown in FIG. 1 is a pneumatic radial tire for passenger cars of size 205 / 60R15 according to the present invention. This tire 1 has a pair of left and right bead cores.
2, a carcass 3 that extends in a toroidal shape and extends between them, and a belt 4 that is arranged at the crown portion of the carcass. Here, the carcass 3 is composed of a carcass layer 1 made of rubberized polyester cords arranged in a direction substantially orthogonal to the tire circumferential direction, and the belt 4 is made of steel arranged at an angle of 24 ° with respect to the tire circumferential direction. A cord is formed by laminating two belt layers 4-1 and 4-2, which are rubberized, so that the cords intersect each other with the tire circumferential direction sandwiched therebetween.

Further, the tire 1 is provided with a belt reinforcing layer 5 in which cords arranged in a direction substantially intersecting the tire circumferential direction are embedded between a belt width end portion and a carcass. The belt reinforcing layer 5 is made by rubber-lining a number of steel cords that are arranged in parallel at substantially 90 ° with respect to the tire circumferential direction and are rubberized.
Equivalent to%. Here, the belt width means the width of the narrower belt layer when the widths of the belt layers laminated so that the cords intersect each other are different. Tire 1 in Figure 1
In the case of, since the width of the belt layer 4-2 is narrow, this is taken as the belt width, and the width of the belt reinforcing layer 5 is 25% of the width of the belt layer 4-2.
Is equivalent to.

The position of the belt reinforcing layer 5 is set so that the width end (outer side) of the belt reinforcing layer 5 comes to a position 5 mm away from the width end of the belt layer 4-1 inward in the tire width direction. . Although FIG. 1 shows only the right side of the tire equatorial plane M, the left side is omitted because this tire is bilaterally symmetrical.

As a comparison between the tire of the present invention and this tire, a conventional tire having no belt reinforcing layer 5 arranged therein and cords embedded in the belt reinforcing layer 5 were arranged in parallel at a minute angle with respect to the tire circumferential direction. A comparative tire was prototyped. These test tires were mounted on a rim of size 6JJ, and the following measurements were performed in a state where the internal pressure was filled with 1.85 kgf / cm ² .

FIG. 2 shows a load of 600 kgf on these tires.
Fig. 4 shows a ground contact shape when a load is applied, (a) is an invention tire, (b) is a comparative tire, and (c) is a conventional tire. Further, FIG. 3 shows the contact pressure distribution of the test tire, but it is clear that the contact pressure distribution of the invention tire is most uniform.

Further, the load is set to 300 by an indoor tester.
The maximum value of cornering force when changing to kgf, 500 kgf, and 700 kgf was obtained. Table 1 shows the conventional tires in index notation of 100.

[0017]

[Table 1]

As is clear from Table 1, as the load increases, the maximum cornering force of the inventive tire becomes larger than that of the conventional tire. That is, the effect of the present invention increases in a load-dependent manner. Therefore,
Among passenger car tires, high-performance tires (tires with a low aspect ratio can be considered to correspond to this, specifically, tires with an aspect ratio of 0.6 or less correspond to this) and large passenger cars. It is effective when the present invention is applied to tires of various sizes.

[0019]

According to the present invention, by suppressing the deformation of the belt width end portion under load, it is possible to make the contact pressure distribution of the tread uniform and improve the steering stability.

[Brief description of drawings]

FIG. 1 is a widthwise sectional view of a tire according to the present invention.
Only the right side of the equatorial plane of the tire is shown, but the left side is omitted because this tire is symmetrical.

FIG. 2 shows a ground contact shape of a test tire, where (a) is an invention tire, (b) is a comparative tire, and (c) is a conventional tire.

FIG. 3 shows a contact pressure distribution of a test tire.

[Explanation of symbols]

 1 Pneumatic radial tire 2 Bead core 3 Carcass 4 Belt 4-1,4-2 Belt layer 5 Belt reinforcement layer M Tire equatorial plane

Claims (1)

[Claims] 1. A pneumatic radial tire having a carcass extending in a toroidal shape across the left and right bead cores, and a belt arranged at the crown portion of the carcass, in a direction substantially intersecting the tire circumferential direction. A pneumatic radial tire characterized in that a belt reinforcing layer in which arranged cords are embedded is arranged between a belt width end and a carcass.