JP2010274769A - Run-flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a run-flat radial tire disposed with a reinforcing rubber layer having a substantially crescent-shape in cross section to make durability performance during a run-flat traveling time and riding comfort during a normal internal pressure traveling time compatible. <P>SOLUTION: When a region from a straight line L1 passing a belt end 4a of straight lines orthogonal to a tire center axis in a cross section passing the tire center axis to the tire width direction inside is called a first region X and a region held by a straight line L3 away from the tire center axis by (RB+0.65H) when a tire cross-sectional height is H and a straight line L4 away from the tire center axis by (RB+0.45H) is called a second region Y in this run-flat tire 10, a ratio A(S1/S2) of area S1 of a reinforcing rubber part 21 included in the first region X to area S2 of the reinforcing rubber part 22 included in the second region Y is constituted to be 10% or below. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a run-flat radial tire in which a reinforcing rubber layer having a substantially crescent-shaped cross section is disposed on the inner peripheral side of the radial carcass at least in a portion corresponding to the sidewall portion, in particular, durability performance during run-flat running, The present invention relates to a vehicle that can achieve both a comfortable ride during normal pressure traveling.

  Conventionally, as shown in a cross-sectional view in FIG. 1, each side portion around a tread rubber 1 disposed on a tread portion 11 and constituting a ground contact surface, and a pair of bead cores 2 disposed on each bead portion 12. A radial carcass 3 made of one or more carcass plies wound back outward in the radial direction, a belt 4 made of one or more belt plies disposed between the radial carcass 3 and the tread rubber 1, and at least a sidewall A run-flat radial tire 10 is known that includes a reinforcing rubber layer 5 having a substantially crescent-shaped cross section disposed on the inner side in the tire width direction of the radial carcass 3 at a portion corresponding to the portion 13 (see, for example, Patent Document 1). ).

  Such a run-flat radial tire 10 includes the reinforcing rubber layer 5 disposed on the sidewall portion 13 even in a so-called run-flat state where the air pressure in the tire is reduced or even zero. By maintaining this shape, the vehicle can travel with sufficient durability.

Japanese Patent No. 4104825

  However, since the reinforcing rubber layer 5 needs to have the above-described functions, it is possible to use a highly rigid rubber material, increase the thickness of the layer, or add a fiber reinforcing layer. Along with this, there has been a problem that the spring constant during normal internal pressure running increases and the ride comfort deteriorates.

  The present invention has been made in view of such problems, and has a substantially crescent-shaped reinforcing rubber that can achieve both durability performance during run-flat traveling and riding comfort during normal internal pressure traveling. An object of the present invention is to provide a run-flat radial tire provided with a layer.

The present invention includes a tread portion, a pair of sidewall portions extending radially inward from both side portions of the tread portion, and a bead portion continuous on the inner peripheral side of each sidewall portion, and is disposed in each bead portion. A radial carcass composed of one or more carcass plies each having a side portion rolled back radially outward around the pair of bead cores, and one or more belts disposed radially outward of the radial carcass in the tread portion In a run-flat radial tire comprising a belt made of ply and a reinforcing rubber layer having a substantially crescent-shaped cross section disposed at the inner side in the tire width direction of the radial carcass at a portion corresponding to at least the sidewall portion,
Of the straight lines orthogonal to the tire center axis C in the cross section passing through the tire center axis C when the tire is mounted on a predetermined rim and the internal pressure is atmospheric pressure, the inner side in the tire width direction of the straight line L1 corresponding to the end face of the belt This region is called the first region X, and the tire cross-section height is H, half of the rim diameter is RB, and the straight line L3 that is (RB + 0.65H) away from the tire center axis is separated by (RB + 0.45H) When the region sandwiched between the straight lines L4 is called the second region Y, the ratio of the area S1 of the reinforcing rubber included in the first region X to the area S2 of the reinforcing rubber included in the second region Y is 10%. A run-flat radial tire having the following characteristics.

  The present invention provides the entire reinforcing rubber layer having an area S2 of the reinforcing rubber layer included in the second region Y in a cross section passing through the tire central axis when the tire is mounted on a predetermined rim and the internal pressure is atmospheric pressure. The ratio S2 / S3 to the area S3 is preferably 50 to 65%.

  According to the present invention, the ratio of the area S2 of the reinforcing rubber included in the first region to the area S1 of the reinforcing rubber included in the second region Y is 10% or less. It is possible to achieve both durability performance during run-flat travel and ride comfort during normal internal pressure travel.

  Further, by setting the ratio S2 / S3 of the area S2 of the reinforcing rubber layer included in the second region Y to the area S3 of the entire reinforcing rubber layer to be 50 to 65%, the durability performance during run flat running The riding comfort during normal internal pressure traveling can be further improved while maintaining the above.

It is sectional drawing which shows the conventional run flat tire. 1 is a cross-sectional view showing a run flat tire according to the present invention.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a cross-sectional view showing the run-flat tire of this embodiment, FIG. 3 is an enlarged cross-sectional view showing a portion near the belt end of the run-flat radial tire, and the run-flat radial tire 10 is One or more carcasses having a tread rubber 1 disposed on the tread portion 11 and constituting a ground contact surface, and a pair of bead cores 2 disposed on each bead portion 12, each side portion being rolled back radially outward. The radial carcass 3 made of ply, the belt 4 made of one or more belt plies disposed between the radial carcass 3 and the tread rubber 1, and the tire of the radial carcass 3 at least at a portion corresponding to the sidewall portion 13. A reinforcing rubber layer 5 having a substantially crescent-shaped cross section disposed on the inner side in the width direction is provided.

  The run-flat radial tire 10 is characterized in that the end surface of the belt 4 (of the straight line orthogonal to the tire center axis in a cross section passing through the tire center axis when the tire is mounted on a predetermined rim and filled with a predetermined internal pressure) (Hereinafter also referred to as “belt end”) A region inside the tire width direction from the straight line L1 passing through 4a is referred to as a first region X, a tire cross-section height H, a half of the rim diameter as RB, and (RB + 0.65H) When the region sandwiched between the straight line L3 separated by (RB + 0.45H) and the straight line L4 separated by (RB + 0.45H) is called a second region Y, the reinforcing rubber portion 22 included in the second region Y The ratio A (S1 / S2) of the area S1 of the reinforcing rubber portion 21 included in the first region X with respect to the area S2 is configured to be 10% or less.

  In the case where the belt 4 has a belt reinforcing layer, the belt 4 also includes this belt reinforcing layer. For example, the belt 4 is a cross belt layer in which two belt plies 41 and 42 whose inclination angles with respect to the equator plane are opposite to each other are bonded together. 40 and the belt reinforcing layer 43 disposed on the outer side in the radial direction of the crossing belt layer 40, the belt end 4 a becomes the outer end of the belt reinforcing layer 43.

  In the run flat tire 10 of the present invention, the ratio B (S2 / S3) of the area S2 of the reinforcing rubber layer included in the second region Y to the area S3 of the entire reinforcing rubber layer is 50 to 65%. Is preferred.

  In the present specification, the predetermined internal pressure (described later) is an air pressure corresponding to the maximum load (maximum load capacity) of a single wheel in an applicable size described in a predetermined industrial standard, Is the standard rim (or “Approved Rim”, “Recommended Rim”) at the applicable size described in the standard. For such industrial standards, there are standards that are valid in each region where tires are produced or used. For example, in the United States, “The Tire and Rim Association Inc. Year Book” (including design guides) ) In Europe according to “The European Tire and Rim Technical Organization Standards Manual” and in Japan according to “JATMA YEAR BOOK” of the Japan Automobile Tire Association. The tire cross-sectional height is half of the difference between the tire maximum diameter and the rim diameter, and the rim diameter is the rim diameter of the standard rim in the applicable size described in the same standard.

  The inventors came up with the above-mentioned configuration because the inventors divided the tire into finite elements, and the stress of each element was at a normal internal pressure simulating normal internal pressure running. As a result of comparison between the normal internal pressure state where 75% load of the predetermined load is applied and the zero internal pressure state where the internal pressure simulating run-flat running is zero and 75% of the predetermined load is applied, in the first region X, Based on this finding, we obtained the knowledge that higher stress is generated in the normal internal pressure state than in the zero internal pressure state, and in this region, the contribution to the load support in the zero internal pressure state is small. Since the contribution to the load support during driving is too great, reducing the stiffness in this area minimizes the impact on durability at zero internal pressure and reduces the spring constant under normal internal pressure. In This is because the thought that.

  The ratio A of the area S1 of the reinforcing rubber portion 21 included in the first region X to the area S2 of the reinforcing rubber portion 22 included in the second region Y of the reinforcing rubber layer 5 and the above-mentioned included in the second region Y Prototype tires in which the ratio B of the area S2 of the reinforcing rubber layer to the area S3 of the entire reinforcing rubber layer was changed, and for each tire, the spring constant was measured for the normal internal pressure state and the zero internal pressure state. The results are shown in Table 1. The size of the prototype tire was 245 / 45R19.

  Here, as described above, the normal internal pressure state refers to a state in which the tire is mounted on a predetermined rim, is filled with the predetermined internal pressure, and is loaded with 75% of the predetermined load, and the zero internal pressure state is the tire on the predetermined rim. A state where the internal pressure is set to zero (atmospheric pressure) and 75% of the specified load is applied. Therefore, the spring constant in the normal internal pressure state is a parameter that simulates the spring constant during normal internal pressure travel, and the spring constant in the zero internal pressure state can be considered as a parameter that represents durability during run-flat travel. The spring constant was measured by applying a load passing through the central axis in a plane perpendicular to the axial direction of the tire and measuring the deflection in the load direction. The results were expressed as an index with the tire having the ratio A of 12% and the ratio B of 45% as Comparative Example 1, and the spring constant of the tire of Comparative Example 1 as 100. A smaller index means a smaller spring constant. Here, in Table 1, the normal internal pressure state spring constant spring constant was determined to be 97 or less as acceptable.

(Note 1) The ratio S1 / S2 of the area S1 of the reinforcing rubber portion 21 included in the first region X to the area S2 of the reinforcing rubber portion 22 included in the second region Y.
(Note 2) The ratio S2 / S3 of the area S2 of the reinforcing rubber layer included in the second region Y to the area S3 of the entire reinforcing rubber layer.

DESCRIPTION OF SYMBOLS 1 Tread rubber 2 Bead core 3 Radial carcass 4 Belt 4a Belt end 5 Reinforcement rubber layer 5a Reinforcement rubber layer inner end in the tire width direction 10 Run flat tire 11 Tread portion 12 Bead portion 13 Side wall portion 21 Reinforcement rubber included in the first region Layer 22 Reinforcing rubber layer included in second region 40 Crossing belt layer 41, 42 Belt ply belt ply constituting crossing belt layer 43 Belt reinforcing layer X First region Y Second region

Claims (2)

A tread portion, a pair of side wall portions extending radially inward from both side portions of the tread portion, and a pair of bead cores arranged on each bead portion, the bead portion being continuous on the inner peripheral side of each side wall portion. A radial carcass made up of one or more carcass plies, each side part of which is wound outward in the radial direction, and a belt made up of one or more belt plies arranged radially outward of the radial carcass in the tread part In a run-flat radial tire provided with a reinforcing rubber layer having a substantially crescent-shaped cross section disposed at the inner side in the tire width direction of the radial carcass at a portion corresponding to at least the sidewall portion,
Of the straight lines orthogonal to the tire center axis C in the cross section passing through the tire center axis C when the tire is mounted on a predetermined rim and the internal pressure is atmospheric pressure, the inner side in the tire width direction of the straight line L1 corresponding to the end face of the belt This region is called the first region X, and the tire cross-section height is H, half of the rim diameter is RB, and the straight line L3 that is (RB + 0.65H) away from the tire center axis is separated by (RB + 0.45H) When the region sandwiched between the straight lines L4 is called the second region Y, the ratio of the area S1 of the reinforcing rubber included in the first region X to the area S2 of the reinforcing rubber included in the second region Y is 10%. A run-flat radial tire characterized by:   When the tire is mounted on a predetermined rim and the internal pressure is atmospheric pressure, the area S2 of the reinforcing rubber layer included in the second region Y in the cross section passing through the tire central axis is relative to the area S3 of the entire reinforcing rubber layer. The run-flat radial tire according to claim 1, wherein the ratio S2 / S3 is 50 to 65%.