JP2005297876A - Pneumatic radial-ply tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial-ply tire capable of enhancing its running durability at the time of run-flat running without impairing the vibratory comfortableness of the vehicle while the tire is in the normal condition. <P>SOLUTION: The pneumatic radial-ply tire is equipped with a tread part 1, a pair of side walls 2 extending inward in the radial direction from the sides of the tread part 1, bead parts 3 continued to the inside surfaces of the side walls 2, and at least one carcass ply 5 extended toroidally between the bead cores 4 provided in the respective bead parts 3 in such a way that the side is turned up to the outside in the radial direction round the bead cores, in which reinforcing rubber 10 having a crescent section across the tire width is laid chiefly in the inside part of each side wall, wherein at least one side part reinforcing layer 11 consisting of reinforcing cords extending at an angle of ±10° with respect to the tire radial direction is laid stretching along the turned-up part 6 of the carcass ply 5, and the modulus of elasticity in the region where the elongation of the reinforcing cords is no less than 0.1% and below 1.5% is made smaller than that in the region where the elongation of the cords is 1.5% or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic radial tire suitable for use in a passenger car, and the tire internal pressure is reduced or completely lost without impairing the vibration ride performance of the vehicle in a normal state of the tire. The present invention proposes a technology that realizes excellent running durability during load rolling of tires (hereinafter referred to as run-flat running).

When the filled air inside the tire leaks due to tire puncture or the like, the tire loses its load bearing ability and the stability of the movement of the vehicle is impaired. On the other hand, when running in this state, extremely large bending deformation occurs in the sidewall portion of the tire, and local destruction may occur in the sidewall portion due to the concentration of strain on the tire portion and an increase in temperature. There is.
In order to avoid such an event, the sidewall portion of the pneumatic radial tire has a relatively high elastic modulus as described in JP-A-7-31516 and JP-A-9-58229. Reinforced with rubber with a crescent-shaped cross-sectional shape in the width direction of the thick wall, and a reinforcing layer made of rubberized steel cord is arranged on the outer side in the tire width direction of the carcass from the sidewall part to the bead part to fill the inside of the tire A so-called run-flat tire has been proposed in which even when air leaks, the bending deformation of the sidewall portion is suppressed, and the load bearing ability of the tire is ensured to prevent the behavior of the vehicle from becoming unstable.
Here, the reason why the reinforcing layer is provided adjacent to the outer side in the tire width direction of the carcass is that when only the crescent-shaped reinforcing rubber is provided, the thickness of the reinforcing rubber is excessively increased in order to obtain the required load bearing capacity. In order to reduce the weight of the reinforcing rubber, a part of the load is applied to the reinforcing layer and the thickness of the reinforcing rubber is reduced.
Japanese Patent Laid-Open No. 7-315016 JP-A-9-58229

  However, in the run-flat tire having such a configuration, it is possible to suppress the bending deformation of the sidewall portion and improve the excellent running durability under a high load bearing ability at the time of run-flat running. The vibration ride comfort performance in the state has a problem that the bending deformation of the sidewall portion is suppressed particularly by the reinforcing layer, and therefore, it deteriorates.

  An object of the present invention is to solve such problems of the prior art, and the tire travels during run-flat travel without impairing the vibration ride performance of the vehicle in a normal state of the tire. A pneumatic radial tire with improved durability is provided.

  The pneumatic radial tire according to the present invention includes a tread portion, a pair of sidewall portions extending radially inward from both side portions of the tread portion, and each bead portion continuing to the inner peripheral side of each sidewall portion. And at least one carcass ply in which the side portion is extended radially outward around the bead core between the bead cores arranged in each bead portion, and the cross-sectional shape in the tire width direction is crescent The reinforcing rubber is mainly disposed on the inner side portion of the sidewall portion, and along the winding portion of the carcass ply at an angle of ± 10 degrees with respect to the radial direction of the tire. Elasticity modulus in a region where at least one side portion reinforcing layer composed of extending reinforcing cords is disposed, and the elongation of the reinforcing cords is 0.1% or more and less than 1.5% , Elongation of the cord is made smaller than the elastic modulus of 1.5% or more regions.

According to this, the reinforcing cords of the side portion reinforcing layers can be arranged in a range of ± 10 degrees with respect to the radial direction, and the load burden due to the reinforcing cords can be made more effective.
If the angle of the reinforcing cord of the side portion reinforcing layer with respect to the tire circumferential direction is less than −10 degrees or greater than +10 degrees, the effect of suppressing the bending deformation generated in the sidewall portion during the run-flat running becomes too small.
In addition, the elastic cord has an elastic modulus in the region where the elongation is 0.1% or more and less than 1.5% smaller than the elastic modulus in the region where the elongation is 1.5% or more. The large bending deformation caused by the crushing deformation of the sidewall portion is suppressed by the tensile strength in the region where the elastic modulus of the reinforcing cord has a large elastic modulus of 1.5% or more, and the sidewall portion is expanded in the width direction. Preventing deformation and improving running durability, and small bending deformation that occurs in the sidewall portion in the normal state of the tire reduces the elastic modulus in the region where the elongation is 0.1% or more and less than 1.5%. The vibration ride comfort performance can be enhanced by allowing it.

Here, it is preferable that the side portion reinforcing layer be disposed along the outer side in the width direction of the winding portion of the carcass ply.
According to this, since the side portion reinforcing layer can be positioned on the outer side in the tire width direction from the center of the bending deformation of the sidewall portion, the large bending deformation caused by the crushing deformation of the sidewall portion during the run flat running Is suppressed by the tensile strength in the region where the elastic modulus of the reinforcing cord has a large elastic modulus of 1.5% or more, and the sidewall portion is prevented from bulging and deforming in the width direction, thereby improving the running durability. Can be further increased.

Here, preferably, the side portion reinforcing layer is provided in a range of 20% to 70% of the tire cross-sectional height with the tire maximum width position as the center. According to this, by arranging the side portion reinforcing layer in a region where the bending deformation of the sidewall portion is particularly large, it is possible to more effectively suppress the bending deformation generated in the sidewall portion during run flat running. Therefore, the running durability of the tire during run flat running can be improved.
When the arrangement range of the side portion reinforcing layer is made smaller than 20%, the effect of suppressing the bending deformation of the side wall portion at the time of run flat running becomes too small, and when the arrangement range of the side portion reinforcing layer is made larger than 70%, The rigidity of the side portion becomes too high, and the vibration riding comfort performance of the tire in the normal state is deteriorated, and the weight of the tire is increased, which is not preferable.

Here, the maximum width position of the tire is, as shown in FIG. 1, the tire equator plane in the tire width direction cross section in which the tire is mounted on the applied rim and filled with the prescribed air pressure to be in a no-load state. A tangent L drawn parallel to EX refers to a position M in contact with the outer contour excluding patterns, characters and rim guards on the side of the tire.
Moreover, the tire cross-sectional height means 1/2 of the difference between the outer diameter of the tire and the rim diameter, and the outer diameter of the tire means that the tire is attached to the applicable rim and is filled with a prescribed air pressure. It shall mean the outer diameter of a tire that has been unloaded. Here, the applicable rim refers to the rim specified in the following standards, the specified air pressure refers to the air pressure specified in accordance with the maximum load capacity in the following standards, and the maximum load capacity refers to the following The maximum mass allowed to be applied to a tire by standard.
The standard is determined by an industrial standard effective in the region where the tire is produced or used. For example, “THE TIRE and RIM ASSOCIATION INC. YEAR BOOK” in the United States, “The European Tire and Rim Technical Organization STANDARDS MANUAL” in Europe, and “JATMA YEAR BOOK” from the Japan Automobile Tire Association in Japan. .

By the way, as the reinforcing cord, a wavy or zigzag detour cord or a high elongation cord is used.
Each of these cords has a small elastic modulus in a region where the elongation is 0.1% or more and less than 1.5%, and has a high elastic modulus in a region of 1.5% or more. By any of these, it is possible to improve the vibration ride comfort performance in the normal state of the tire and to improve the running durability during run-flat running.
Here, the detour cord is a cord in which the cord is plastically deformed into a wave shape or a zigzag shape, and the elongation satisfies the above conditions, and is characterized by easy control of the elastic modulus. Further, the high elongation cord is a straight cord, but is a cord whose elongation meets the above conditions, and has excellent tire moldability.

  As is apparent from the above description, according to the present invention, the bending deformation generated in the sidewall portion during the run-flat running is suppressed by the tension of the reinforcing cord, and the running durability is improved. In the normal state, the elastic modulus in the region where the elongation of the reinforcing cord is 0.1% or more and less than 1.5% is made smaller than the elastic modulus of the region where the elongation is 1.5% or more. The vibration riding comfort performance can be enhanced without hindering the bending deformation generated in the wall portion.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a cross-sectional view in the tire width direction, showing an embodiment of the present invention, with a tire mounted on an applied rim and filled with a prescribed air pressure, in an unloaded state. In the figure, 1 indicates a tread portion, 2 indicates a pair of sidewall portions extending radially inward from both side portions of the tread portion, and 3 indicates each of the sidewall portions 2 continuous to the inner peripheral side of each sidewall portion 2. The bead part 3 is shown.

  Here, the bead portion 3, the sidewall portion 2, and the tread portion 1 are reinforced with the carcass ply 5 extending between the bead cores 4 disposed in the respective bead portions 3, and the side portions of the carcass ply 5 are also provided. Is wound up radially outward around the bead core 4 to form a wound-up portion 6, and a belt 7 comprising one or more belt layers that reinforce the tread portion 1 is formed on the outer peripheral side of the crown portion of the carcass ply 5. Further, a protective layer 8 is disposed on the outer peripheral side thereof. An inner liner 9 is disposed on the inner peripheral side of the carcass ply 5, and the reinforcing rubber 10 is mainly formed between the carcass ply 5 and the inner liner 9 in the sidewall portion so as to have a crescent shape in the cross section in the tire width direction. Arrange. Further, a side portion reinforcing layer 11 made of a rubberized reinforcing cord is disposed adjacent to the outer side in the tire width direction of the carcass winding portion 6. The reinforcement cord 12 of the side portion reinforcement layer 11 is inclined by ± 10 degrees with respect to the radial direction R as shown in FIG. 2 through the reinforcement cord 12 in a side view of the tire. Arrange. Such a side portion reinforcing layer 11 is provided in the range of 20 to 70% of the tire cross-sectional height H, centered on the tire maximum width position M, in this case 40%, and the elongation of the reinforcing cord is 0.1% or more and The elastic modulus in the region of less than 1.5% is made smaller than the elastic modulus in the region of 1.5% or more.

FIG. 3 is a schematic diagram showing the form of the reinforcing cord.
The reinforcing cord 12 can be the above-described high elongation cord as shown in FIG. 3A, or can be a wave-like detour cord as shown in FIG. As shown in (c), a zigzag detouring cord can be used.
FIG. 4 is a load-elongation diagram showing the characteristics of the high elongation cord.
As shown in FIG. 4, the high elongation cord used in the present invention has an elongation range with a small elastic modulus of 0.1% or more and less than 1.5%. Therefore, the side wall portion can be bent and deformed, and the vibration ride performance can be improved. Further, during run-flat running, bending durability of the sidewall portion can be suppressed and running durability can be improved with a high elastic modulus in a region where the elongation is 1.5% or more.

For the purpose of evaluating the running durability of a pneumatic radial tire according to an embodiment of the present invention during run-flat running and the vibration ride performance of the vehicle in a normal state of the tire, the size is 215/45 ZR17. Example tire 1 in which the region where the side portion reinforcing layer is disposed is 30% of the tire cross-sectional height H around the tire maximum width position M, and the reinforcing cord of the side portion reinforcing layer is a wavy detour cord. Example tire 2 as a detour cord, Example tire 3 as a high elongation cord, Comparative tire 1 without a side portion reinforcing layer, and the reinforcing cord of the side portion reinforcing layer have an initial elongation region region having a low elastic modulus. About the comparative example tire 2 which did not use the usual steel cord,
Attached to a rim with a nominal size of 7.5JJ-17, the valve core is removed to completely leak the filled air pressure into the tire, load the mass corresponding to the maximum load capacity, and rotate the drum at a speed of 90km / h. A test was conducted, and the distance until the failure occurred in the tire, that is, the run-flat running distance was measured.

Furthermore, it is mounted on a rim with a nominal size of 7.5JJ-17, the tire filling air pressure is 230 kPa, a mass of 425kgf corresponding to the maximum load capacity is loaded, and the distance from the tread tread to the rim diameter line is measured. The vertical section of the tire was measured by pulling the tire cross-section height, measuring the deflection, and dividing the mass by the deflection.
Table 1 shows the results of index evaluation of the respective measurement results using the comparative example tire 1 as a control tire. As for the run-flat travel distance, the larger the index, the better the performance. The smaller the index, the smaller the longitudinal spring constant, and the better the vibration ride performance.

In Table 1, when the comparative example tire 1 and the example tires 1 to 3 are compared, the example tires 1 to 3 can increase the run-flat running distance and increase the running durability of the tire during run-flat running. You can see that
Comparing Example tires 1 to 3 and Comparative example tire 2 reveals that the example tire has a small longitudinal spring constant and can improve the vibration ride comfort performance of the vehicle in the normal state of the tire.

  The present invention is effective when applied to a pneumatic radial tire or the like in which the running durability of the tire during run-flat running is enhanced and the vibration riding comfort performance of the vehicle in a normal state of the tire is enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. It is a tire axial direction partial arrow directional view which shows the extension aspect of the reinforcement cord of the side part reinforcement layer of the tire shown in FIG. FIG. 2 is a development view showing various forms of reinforcing cords of the tire shown in FIG. 1. FIG. 3 is a load-elongation diagram showing characteristics of a high elongation cord.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Carcass ply 6 Winding part 7 Belt 8 Protective layer 9 Inner liner 10 Reinforcement rubber 11 Side part reinforcement layer 12 Reinforcement cord

Claims (5)

A tread portion, a pair of sidewall portions extending radially inward from both side portions of the tread portion, each bead portion continuing to the inner peripheral side of each sidewall portion, and a bead core disposed on each bead portion It is provided with at least one carcass ply that extends in a toroidal shape and winds a side portion around the bead core radially outward, and a reinforcing rubber having a crescent-shaped cross section in the tire width direction, A pneumatic radial tire disposed on an inner portion of the sidewall portion,
At least one side portion reinforcing layer made of a reinforcing cord extending at an angle of ± 10 degrees with respect to the radial direction of the tire is disposed along the rolled-up portion of the carcass ply. A pneumatic radial tire in which an elastic modulus in a region of 1% or more and less than 1.5% is made smaller than an elastic modulus of a region in which the elongation of the cord is 1.5% or more. 2. The pneumatic radial tire according to claim 1, wherein the side portion reinforcing layer is arranged along an outer side in a width direction of a winding portion of the carcass ply. The pneumatic radial tire according to claim 1 or 2, wherein the side portion reinforcing layer is provided in a range of 20% to 70% of a tire cross-sectional height with the tire maximum width position as a center. The pneumatic radial tire according to any one of claims 1 to 3, wherein the reinforcing cord is a detour cord extending in a wave shape or a zigzag shape. The pneumatic radial tire according to any one of claims 1 to 3, wherein the reinforcing cord is a high elongation cord.

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