JPH082209A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To provide a twin tread tire that is able to check the occurrence of any buckling being liable to occur in a central part in the cross direction of a split crown without sacrificing any other performance. CONSTITUTION:A belt 3 turning to a cross-lamination layer consisting of a cord rubber coated layer and a tread part 4 reinforced with this belt 3 are installed on the circumference of a crown part of a toroidal radial carcass 2. Therefore this tread part 4 comes to have a toroidal recess 5 integrally hollowed along tread circumference at the tire radial inside together with the radial carcass 2 and the belt 3, whereby it is formed into two split crowns 6 and 7 in consequence, and each of narrow belt reinforced layers 11 consisting of the rubber coated layer of the cord obliquely arranged in a sense to be crossed in the tire circumferential detection is installed in an interval between the radial carcass 2 and the belt 3, and at a position corresponding to a cross direction central part 8 of the split crowns 6 and 7.

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 a tread portion having a plurality of divided crown configurations,
In particular, the present invention relates to a pneumatic tire (hereinafter, referred to as “twin tread tire”) including two tread portions having a split crown configuration in which an annular recess is provided in a center portion in the width direction of the tread portion, and specifically, A pneumatic radial tire that suppresses the occurrence of so-called buckling, in which the lateral force at the time of cornering mainly acts on the shoulder part and the center part in the width direction is suddenly depressed due to the relative weakness of the concave part of the center part It is a thing.

[0002]

2. Description of the Related Art Twin tread tires have been flattened in recent years due to higher performance of the vehicle and the tread contact width has been widened. This is a tire that has been developed because the hydroplaning phenomenon tends to occur in the.

[0003]

In the twin tread tire, when the sectional profile of the split crown is made flat, both side portions of the split crown tend to have a higher ground contact pressure than the central portion in the width direction. Therefore, the buckling may occur due to the lateral force during cornering of the tire. When this buckling occurs, the ground pressure in the width direction of the split crown is greatly reduced in the widthwise central part, so the grounding pressure on both sides is considerably larger than the ground pressure in the widthwise central part, and is uneven. Became. This not only deteriorates the running sensation but also induces uneven wear.

Further, even when the central portion in the width direction of the divided crown receives a local input to the inner side in the radial direction of the tire, the occurrence of buckling in the central portion in the width direction of the divided crown is suppressed as much as possible, and in the divided crown. , It was necessary to maintain the ground pressure in the width direction uniform.

Therefore, the present invention suppresses the occurrence of the above-mentioned buckling without sacrificing other performances in a pneumatic radial tire having a tread portion having a plurality of divided crown configurations, particularly in a twin tread tire. The purpose is to do.

[0006]

To achieve the above object, the present invention provides a belt in which cord rubberized layers are cross-laminated on the outer periphery of the crown portion of a toroidal radial carcass, and a tread reinforced by this belt. And a tread portion, having a radial carcass and a belt together with a radial carcass and an annular recess that is integrally recessed along the tire tread circumference along the tire radial direction, thereby forming a plurality of divided crown configurations, and the radial carcass and the belt. A narrow belt reinforcing layer made of rubberized layers of cords arranged in a slanting arrangement in a direction intersecting with the tire circumferential direction is disposed between and at a position corresponding to the center portion in the width direction of the divided crown. It is a pneumatic radial tire that does. Further, it is more preferable that the tread portion has a structure of two divided crowns. here,
The central portion in the width direction of the divided crown refers to a central portion when the two end portions of the divided crown are divided into three equal parts along the width direction, and both side portions of the central portion in the width direction are lateral portions.
When the side wall-side end of the divided crown has a curvature, this end position is set as an intersection point position between a line obtained by extending the sectional outline of the divided crown and a line obtained by extending the sectional outline of the sidewall, and When the end of the split crown on the side of the annular recess has a curvature, this end position is defined as the intersection point between the line extending the sectional profile of the split crown and the line extending the sectional profile of the annular recess.

FIG. 1 shows a width cross section of a typical pneumatic tire of the present invention, in which 1 is a pneumatic radial tire and 2 is a radial tire.
Is a radial carcass, 3 is a belt, 4 is a tread portion, 5
Is an annular recessed portion, 6 and 7 are divided crowns, 8 is a central portion in the width direction of the divided crowns, and 9 and 10 are lateral portions. A pneumatic radial tire 1 shown in FIG. 1 includes a belt 3 which is a cross-laminated cord rubberized layer and a tread portion 4 reinforced by the belt 3 on the outer circumference of a crown portion of a toroidal radial carcass 2. The tread portion 4 has an annular recess 5 that is integrally recessed along the circumference of the tread on the inner side in the tire radial direction together with the radial carcass 2 and the belt 3, thereby forming two divided crowns 6 and 7.
It should be noted that in this figure, the annular concave portion 5 is defined by the divided crowns 6 and 7.
Are arranged in the tire widthwise central position so as to be symmetrical, but the annular recessed portion 5 is displaced from the tire widthwise central position in the widthwise direction as long as the water that has entered the tire ground contact center area can be drained. You may. In this figure, the number of divided crowns forming the tread portion 4 is two.

Further, between the radial carcass 2 and the belt 3 and at a position corresponding to the center portion 8 in the width direction of the divided crown, a narrow rubber layer of cords arranged in a slanting direction in a direction intersecting with the tire circumferential direction. A belt reinforcing layer 11 having a width is arranged. By disposing the belt reinforcing layer 11, the belt 4 is arranged at the central portion 8 in the width direction on the outer side in the tire radial direction as compared with the side portions 9 and 10.

The cord of the belt reinforcing layer 11 is, in particular,
In order to suppress an increase in weight, it is preferable to use an organic fiber cord, for example, a non-stretchable cord such as rayon or polyester, but a metal cord such as steel may be used.
This cord may be tilted in a direction intersecting with the tire circumferential direction, but it is preferably tilted at an angle of 45 ° or more, and most preferably at an angle of 90 ° with respect to a plane including the tire circumference. .

The width of the belt reinforcing layer 11 is 10 to 50 mm.
And the belt reinforcing layer 11 is preferable.
As for the disposition position in the tire width direction, it is preferable that the widthwise bisector position of the belt reinforcing layer 11 is within a range of 10 mm from the center circumferential line 12 position of the divided crown. The rubber thickness of the belt reinforcing layer 11 is preferably in the range of 0.5 to 1.5 mm, and the number of sheets is preferably 1 to 2. The belt reinforcing layer 11 does not have to be provided for each divided crown, but may be provided only for the divided crown where buckling is likely to occur.

The tire shown in FIG. 1 further includes two rubberized layers of cords arranged substantially along the tire circumferential direction.
A cap layer 1 made of a single sheet and substantially covering the entire surface of the belt.
3 and a pair of narrow layer layers 14 covering both ends of the cap layer 13, which are arranged from the viewpoint of high-speed durability and the like, and are essential constituent members of the present invention. Instead, they can be arranged as needed.

[0012]

According to the present invention, the belt reinforcing layer 11 is disposed between the radial carcass 2 and the belt 3 and at a position corresponding to the widthwise central portion 8 of the divided crowns 6 or 7, and 4 in the divided crown 6 or 7 in the widthwise central portion 8 as compared to the lateral portions 9 and 10 and more outwardly in the tire radial direction, by lateral force during cornering of the tire, Even when the central portion 8 in the width direction of the split crowns 6 and 7 receives a local input inward in the tire radial direction, the belt 3 located in the central portion 8 in the width direction.
However, since the limit displacement inward in the tire radial direction until the buckling occurs becomes large, it is possible to suppress a sudden decrease in the ground contact pressure at the widthwise central portion 8 due to the buckling.

When a central input in the width direction central portion 8 of the divided crowns 6 and 7 is locally received inward in the tire radial direction, a pull is applied to the central portion 8 in the width direction of the divided crowns 6 and 7 recessed by this input. Although the stress acts, the belt reinforcing layer 11 is formed by the rubberized layer of the cords that are arranged so as to be inclined in the direction intersecting with the tire circumferential direction, so that the tensile stress can be counteracted. It effectively acts to suppress the generation of rings.

[0014]

EXAMPLES Specific examples of the pneumatic tire according to the present invention will be described with reference to the drawings. -Examples The invention tires used in the examples are twin tread tires having a width-direction cross section shown in FIG. 1 and a tire size of 235 / 45R17 (tread width: 200 mm).
On the outer circumference of the radial carcass 2 consisting of two plies of 1500d / 2 polyester cord, 1x5 steel cords are provided with two rubberized layers so that they are arranged at an angle of 24 ° with respect to the tire circumference. It comprises a belt 3 formed by stacking and a tread portion 4 reinforced by the belt 3,
The tread portion 4 has an annular recess 5 that is integrally recessed along the circumference of the tread on the inner side in the tire radial direction together with the radial carcass 2 and the belt 3, thereby forming two divided crowns 6 and 7. The annular recess 5 is arranged at the center in the width direction of the tire, and has a width of 32 mm and a groove depth of 2 mm.
It was set to 0 mm. Each of the divided crowns 6 or 7 has one narrow belt made of a rubberized layer of rayon cords in a radial arrangement at a position between the radial carcass 2 and the belt 3 and at a position corresponding to the widthwise central portion 8. Reinforcing layers 11 are provided respectively. This belt reinforcing layer 11 has a width of 20 m.
m, its rubber thickness is 0.9 mm, and the position of the bisector of the belt reinforcing layer 11 in the width direction is shifted from the position of the central circumferential line 12 of the divided crown by 5 mm inward in the tire width direction. 11 is arranged. Nylon cords were used as the cords of the cap layer and were arranged along the circumference of the tire.

Comparative Example The conventional tire used in the comparative example has substantially the same structure as the tire used in the example except that it does not have the belt reinforcing layer 11.

Test Method In the test, each of the above-mentioned test tires was assembled on a rim of size 8J × 17 to form a tire wheel, and the tire wheel had an internal tire pressure of 2.1 kgf / cm ² and a tire load of 450
Under a condition of kgf and a slip angle of 4 °, a ground pressure measuring device measures a ground pressure index with respect to a widthwise position of the tire grounding surface at an arbitrary position, thereby calculating a widthwise central portion of the divided crown. It was evaluated from the difference of the ground contact pressure of the above with respect to the ground contact pressure of both sides. Fig. 2 (a) shows the ground contact shape of the tire, and Fig. 2 (b) shows the result of measuring the ground contact pressure of the tire.

From the results shown in FIG. 2 (b), the difference in the ground pressure in the example was smaller than that in the comparative example.

[0018]

According to the present invention, it is possible to prevent a sudden decrease in the ground contact pressure at the widthwise central portion 8 due to the buckling. Therefore, a good running feeling is maintained and uneven wear is suppressed.

[Brief description of drawings]

FIG. 1 is a width sectional view of a typical pneumatic radial tire according to the present invention.

FIG. 2A is a view showing a ground contact shape of a tire, and FIG. 2B is a view showing a result of measuring a ground contact pressure of the tire in a width direction of the tire.

[Explanation of symbols]

 1 Pneumatic radial tire 2 Radial carcass 3 Belt 4 Tread part 5 Annular recess 6,7 Divided crown 8 Center of width direction of divided crown 9,10 Side of divided crown 11 Belt reinforcement layer 12 Center line of divided crown 13 Cap layer 14 layer layer

Claims (2)

[Claims] 1. A tire having a toroidal radial carcass, which has a belt formed by cross-laminating cord rubberized layers and a tread portion reinforced by the belt, on the outer periphery of the crown portion of the radial carcass, the tread portion together with the radial carcass and the belt. By having an annular recess that is integrally depressed along the circumference of the tread on the inside in the radial direction, a plurality of divided crown configurations are provided, which corresponds between the radial carcass and the belt and corresponds to the central portion in the width direction of the divided crown. A pneumatic radial tire characterized in that a narrow belt reinforcing layer made of a rubberized layer of cords arranged obliquely in a direction intersecting the tire circumferential direction is disposed at a position. 2. The pneumatic radial tire according to claim 1, wherein the tread portion has a two-piece crown construction.