JPH08175122A - Pneumatic radial tire for automobile - Google Patents

Abstract

PURPOSE: To reduce the material cost without reducing the rigidity in the longitudinal and transverse direction and damaging the stability and controllability by increasing the number of driving in the cord per unit width of the second ply toward a bead part along the outer side of a first ply fold-back part of a carcass by the prescribed times of that of a first ply. CONSTITUTION: A carcass is provided with a first ply 8 having a fold-back part 10 which extends across bead cores 6 in the troydal manner, and extends and folds back from the inner side in the axial direction of a tire around the bead cores 6 to the outer side. The carcass is provided with a second ply 9 which extends toward a bead heel 7 of a bead part 2 along the outer side in the axial direction of the tire of the fold-back part 10, and the number of driving in the cord per unit width of the second ply 9 is >=1.05 times that of the first ply. The rigidity in the vertical and right-to-left direction of the tire is secured, and the material cost can be reduced without damaging the stability and controllability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reduces the manufacturing cost by making a pneumatic radial tire, especially a pneumatic radial tire for passenger cars, simple, and accordingly, the rigidity in the vertical (vertical) direction of the tire or the right and left ( The present invention relates to a radial tire structure that suppresses a decrease in rigidity in the lateral direction and a decrease in steering stability.

[0002]

2. Description of the Related Art A radial tire for a passenger vehicle having a carcass composed of two or more layers of plies generally comprises a radial array ply of rubber-coated organic fiber cords straddling in a toroidal shape between a pair of bead cores. Each of the plies has a structure in which the plurality of plies are folded around each bead core and extend from the inside to the outside of the tire (tire A in FIG. 1), or at least one of the plies has a bead core. Is a carcass structure (tire B in FIG. 2 or tire C in FIG. 3) that is not folded back around and is arranged as a second ply extending toward the bead heel along the tire axial direction outer side.

[0003]

In the prior art, even a tire having the same carcass structure having a plurality of plies has a structure in which each of the plurality of plies is folded back from the inside of the tire around the bead core like the tire A. In comparison with the tire B or the tire C, the structure in which at least one ply is not folded back around the bead core uses less ply material, and thus the tire material cost is lower. However, on the other hand, plies that do not fold back around the bead core bear a low ply tension, so such tires have lower rigidity in the vertical (longitudinal) direction and lateral (horizontal) direction, which results in stable steering of the tire. However, there is a problem in that Therefore, the problem to be solved by the present invention is a tire having a carcass structure in which at least one ply of a plurality of plies such as the tire B or the tire C is not wound around the bead core, and the tire is vertically (longitudinal). Direction, left and right (side)
It is an object of the present invention to provide a tire structure in which the directional rigidity does not decrease, that is, the steering stability of the tire is not impaired, and the material cost is reduced.

[0004]

When a plurality of plies are applied to a radial tire for passenger cars, it is common to use the same cord / rubber composite for each of the plurality of plies. Further, in a tire such as the tire B or the tire C in which at least one layer of a plurality of plies is not folded back from the inside to the outside of the bead core, the tire is not folded back around the bead core, so the tension load of that portion is reduced, This leads to a reduction in tire rigidity and steering stability. As a result of diligent research focusing on such points, as compared to a ply folded around the bead core, by increasing the number of cords to be driven per unit width of the ply that is not folded, the tire B or the tire C is It has been found that even radial tires for passenger cars can suppress the deterioration of the rigidity in the longitudinal or lateral direction as a tire and the deterioration of the maneuverability, and have reached the present invention.

That is, the pneumatic radial tire for passenger cars according to the first aspect of the invention is a carcass comprising at least one layer of plies of radial arrangement cords extending in a toroidal shape between a pair of bead portions, and a non-carcass arranged in the crown portion of the carcass. The carcass has a belt layer made of an extensible cord, and the carcass has at least one first layer having a folded portion of the ply which is wound around the bead core embedded in each bead portion and extends from the inner side toward the outer side in the axial direction of the tire. In a pneumatic radial tire for passenger cars consisting of a ply and at least one second ply extending toward the bead portion along the axially outer side of the tire of the folded portion, the number of cords to be driven per unit width of the second ply is , Characterized in that it is larger than the number of cords driven in per unit width of the first ply

A pneumatic radial tire for passenger cars according to a second aspect is the pneumatic radial tire for passenger cars according to the first aspect, wherein the number of cords to be driven per unit width of the second ply is equal to that of the first ply. It is characterized in that it is 1.05 times to 1.30 times the number of entered cords.

A pneumatic radial tire for a passenger vehicle according to a third aspect is the pneumatic radial tire for a passenger vehicle according to the first or second aspect, wherein the first ply and the second ply are composed of one layer. There is.

[0008]

In the tire structure in which at least one ply is not folded back around the bead core like the tire B or the tire C, the ply tension that the second ply bears is low, so that the steering stability of the tire is deteriorated. Therefore, by increasing the number of cords to be driven per unit width of the second ply in comparison with the first ply, the load of the ply tension of the second ply is increased, so that ) And left / right (lateral) direction stiffness reductions can be compensated for, and tire steering stability degradation can also be suppressed. Therefore, the steering stability of the tire can be sufficiently ensured while enjoying the cost reduction effect associated with the material cost reduction peculiar to the tire structure such as the tire B or C.

[0009]

EXAMPLE FIG. 1 shows an example of a pneumatic radial tire for a passenger car as a conventional example, a tire A, showing only the left half of the tire. From the description in the drawings, the names of the tire constituent members such as the crown portion 1, the bead portion 2, the crown center 3, the carcass 4, the belt 5, the bead core 6, the bead heel 7, the first ply 8, and the folded portion 10 are self-explanatory. .

Further, in the structure of the tire B of the conventional example shown in FIG. 2, the first ply 8 constituting the carcass 4 is made of a rubber-coated ply of radially arranged organic fiber cords in a toroidal shape between a pair of bead cores 6. It has a folded-back portion 10 of the above-mentioned ply which extends across and extends around the bead core 6 from the inner side in the axial direction of the tire to the outer side. The second ply 9 also straddles between the pair of bead cores 6 in a toroidal shape. Thus, the first ply 8 and the second ply 9 have the same number of cords to be struck per unit width, although they extend toward the bead heel 7 of the bead portion 2 along the tire axial direction outer side of the folded-back portion 10.

In the structure of the conventional tire C shown in FIG. 3, the first ply 8 constituting the carcass 4 is the same as the tire A, but the second ply 9 straddles between the pair of bead cores 6 in a toroidal shape. Not extending, it extends from the shoulder portion of the tire toward the bead portion 2 along the tire axial direction outer side of the folded portion 10, but the unit width of the first ply 8 and the second ply 9 is the same as in FIG. The number of hits per cord is the same.

Here, the definitions of the first ply and the second ply are as follows. That is, the first ply extends in a toroidal shape across a pair of bead cores in a ply of rubber-covered radial-aligned organic fiber cords, and extends at least one layer around the bead cores by folding back from the inner side to the outer side in the axial direction of the tire. It is the ply of. The second ply is at least one ply in which the ply is not folded back around the pair of beads.

FIG. 4 shows an embodiment of a pneumatic radial tire for a passenger car according to the invention, again only for the left half of the tire. In the structure of the tire D shown here, the carcass 4 has a ply of rubber-coated radial organic fiber cords that extends in a toroidal shape across a pair of bead cores 6 and extends around the bead wires 6 along the axis of the tire. A first ply 8 having a folded-back portion 10 of the ply that extends back from the inner side in the direction, and a bead portion along the tire axial direction outer side of the folded-back portion 10 that straddles a toroidal shape between a pair of bead cores 6 in the same manner. The second ply 9 extends toward the second bead heel 7. In addition, in FIG. 4, the first ply and the second ply each show an example of one layer, but may have a plurality of layers,
When the carcass has an odd number of layers of 3 or more, the number of the first plies is often one more than that of the second plies. If it is not necessary to consider the manufacturing cost of the tire, it is possible to greatly improve the maneuverability by greatly increasing the number of plies that are not folded around the bead core. Therefore, it is possible to increase the number of cords per unit width of the second ply 9 that is driven in, in comparison with the number of cords per unit width of the first ply 8 that is driven.

Here, the number of cords of a plurality of plies to be imprinted is the number of cords of a plurality of plies to be imprinted per unit width, as in the case of a single ply.

On the other hand, when a balance between tire manufacturing cost and maneuverability is required, the number of cords per unit width of the second ply 9 is compared with the number of cords per unit width of the first ply 8, It is necessary to be 1.05 times to 1.30 times. The basis is shown in FIG. In the tire structure of the tire B, the horizontal axis of FIG. 7 shows the number of cords to be imprinted per unit width of the second ply in the tire structure by changing the multiple, and the left vertical axis shows The left / right (horizontal) rigidity of the tire A is shown as an index when the left / right (horizontal) rigidity of the tire A is set to 100, and the right vertical axis corresponds to the left / right (horizontal) rigidity of the tire and the tire of the tire B. In the structure, the material cost of the ply material when changing the number of the second plies driven per unit width in comparison with the first ply
It is displayed as a contrast index. That is, FIG. 7 shows a relationship in which the left-right rigidity of the tire increases as the number of second plies driven increases, and the cost also increases. Here, considering the range where the cost is lower than that of the tire A and the steering stability is also acceptable, it is an area of 90 or more in the index of left and right (lateral) rigidity of the tire in comparison with the tire A. It can be seen that the number of cords imprinted in the second ply belonging to such an area is in the range of 1.05 times to 1.30 times that of the first ply.

In the structure of the tire E shown in FIG. 5, the first ply 8 constituting the carcass 4 is the same as the tire A, but the second ply 9 extends in a toroidal shape between the pair of bead cores 6. The bead portion 2 along the tire axial direction outer side of the folded portion 10 from the shoulder portion of the tire.
Extending towards. Further, the number of cords to be imprinted in the second ply is increased as compared with the number of cords to be imprinted per unit width in the first ply.

In the structure of the tire F shown in FIG. 6, the first ply 8 constituting the carcass 4 is the same as the tire A, but the second ply 9 extends in a toroidal shape across the pair of bead cores 6. Not, belt 5 and first ply 8
Although it extends along the tire axial direction outer side of the folding | returning part 10 from between, it has not reached even the bead heel 7, and the end of the 2nd ply 9 is stopped by the bead part 2. In addition, comparing with the number of cords per unit width of the first ply,
This is a structure in which the number of cords for the second ply is increased.

Here, tires A to F having the structures shown in FIGS. 1 to 6 were prototyped as radial tires for passenger cars, tire size 205 / 55R16, and the tire performance was measured at the same time as the cost.

The results are shown in Tables 1 and 2. here,
Vertical (longitudinal) direction rigidity and lateral (horizontal) direction rigidity are substitute characteristics of the steering stability of the tire. Generally, the higher the rigidity of the tire, the better the steering stability of the tire.
These stiffnesses were measured by the following measuring methods.

The vertical (longitudinal) rigidity was calculated by the Amsler tester from the change in the vertical deflection of the tire with respect to the normal internal pressure defined in the JATMA standard, and the vertical spring constant was calculated and displayed as an index. The left and right (lateral) direction rigidity is also the same,
From the change in the lateral displacement of the tire, calculate the lateral spring constant,
Displayed as an index.

[0021]

[Table 1]

As can be seen from Table 1, when the structure of the tire A is changed to the structure of the tire B, the vertical direction of the tire,
Although the rigidity in the left-right direction is reduced, if the number of driven cords of the second ply is made larger than that of the first ply as in the case of the tire D, the rigidity of the tire D in the up-down direction and the left-right direction is almost the same as that of the tire A. It has been improved to a certain degree, and the material cost has been reduced at the same time.

[0023]

[Table 2]

Table 2 compares tire C with tire C,
The material cost is shown as an index together with the rigidity of the tire E and the tire F in the vertical direction and the lateral direction. As is clear from Table 2,
When the tire structure is changed from the tire B to the tire C, the rigidity of the tire is deteriorated. However, when the tire structure in which the number of second plies of the cords of the second ply is increased is used like the tires E and F, the steering stability substitute characteristic is obtained. The rigidity in the vertical direction and the rigidity in the left-right direction have been improved to a level close to that of the tire B, and the material cost has been reduced.

[0025]

As described above, when the pneumatic radial tire for passenger cars adopts a tire structure in which at least one ply is not folded back around the bead core like the tire D, the tire E or the tire F. By increasing the number of cords per unit width of the second ply to be larger than that of the first ply, particularly preferably 1.05 times to 1.30 times, the vertical direction of the tire and Lateral rigidity is ensured, and without impairing steering stability,
It has been possible to provide a tire structure capable of achieving a reduction in material cost during tire manufacturing.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a tire A having a conventional structure having a carcass structure including two plies.

FIG. 2 is a cross-sectional view of a tire B having a conventional structure having a carcass structure including two plies.

FIG. 3 is a cross-sectional view of a tire C having a conventional structure having a carcass structure including two plies.

FIG. 4 is a sectional view of a tire D that is an embodiment of the present invention having a carcass structure composed of two plies.

FIG. 5 is a sectional view of a tire E that is an embodiment of the present invention having a carcass structure composed of two plies.

FIG. 6 is a cross-sectional view of a tire F that is an embodiment of the present invention having a carcass structure composed of two plies.

FIG. 7 is a graph showing a relationship between the number of driven cords of the second ply, which is compared with the first ply, on the rigidity of the tire and the material cost of the tire.

[Explanation of symbols]

 1 crown part 2 bead part 3 crown center 4 carcass 5 belt 6 bead core 7 bead heel 8 first ply 9 second ply 10 folded part

Claims (3)

[Claims] 1. A carcass comprising a carcass consisting of at least one layer of plies of radial arrangement cord extending in a toroidal shape between a pair of bead portions, and a belt layer consisting of a non-extensible cord arranged in the crown portion of the carcass. Is
At least one first ply having a folded portion of the ply extending around the bead core embedded in each bead portion from the inner side to the outer side in the axial direction of the tire, and along the outer side of the folded portion in the axial direction of the tire. In a pneumatic radial tire for passenger cars comprising at least one second ply extending toward the bead portion, the number of cords per unit width of the second ply is equal to the number of cords per unit width of the first ply. A pneumatic radial tire for passenger cars, which is 1.05 times or more. 2. The number of driven cords per unit width of the second ply is 1.05 to 1.30 times the number of driven cords per unit width of the first ply. 1. A pneumatic radial tire for passenger cars according to 1. 3. The pneumatic radial tire for passenger cars according to claim 1, wherein the first ply and the second ply are composed of one layer.