JP2010163108A - Pneumatic run-flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve riding comfort and reduce weight of a tire without sacrificing run-flat durability in a side reinforced type pneumatic run-flat tire. <P>SOLUTION: When a gauge of a side reinforced rubber 26 on a first normal N1 passing an end in a tire width direction of a belt layer 20 and forming a right angle with respect to a tire contour line when seen from a cross section along a tire rotation axis is A, and a gauge of the side reinforced rubber 26 on a second normal N2 passing a tire maximum width position Wmax of a carcass 18 and orthogonal to an outer face of the carcass 18 is B, 0.2≤A/B≤0.4 is satisfied. The gauges of the side reinforced rubber 26 are optimized, run-flat durability is secured, the gauge of the side reinforced rubber 26 near an end of the belt layer 20 is made thinner and lighter in weight than conventionally, and riding comfort can be improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic run-flat tire, and more particularly to a vertical spring at normal internal pressure and a pneumatic run-flat tire capable of reducing tire weight without reducing run-flat durability.

  In the side reinforcing type run flat tire, run flat running is enabled by using a side reinforcing rubber having a crescent cross section (see, for example, Patent Document 1).

JP 2008-062716 A

However, the side-reinforcement type run-flat tire deteriorates in riding comfort due to an increase in the longitudinal spring constant of the tire as compared with a normal tire.
Further, by providing the side reinforcing rubber, the tire weight is increased as compared with a normal tire, and the unsprung load of the vehicle is increased, so that the steering stability is deteriorated. In addition, an increase in vehicle body input due to an increase in tire weight may affect the durability of the vehicle.

  In particular, when mounted on a real vehicle, a car with a large camber angle (for example, a camber angle of 1.5 degrees or more) and a camber angle that is relatively small (camber angle is 1 degree or less) due to alignment (giving a camber angle). Then, run-flat durability changes greatly, and durability is more severe when a large camber angle is attached.

  In view of the above facts, the present invention has an object to provide a pneumatic run-flat tire capable of improving riding comfort and reducing tire weight without sacrificing run-flat durability. .

  According to various experimental studies by the inventors, the side reinforcing rubber layer near the outer edge of the belt layer in the width direction has a large effect on the longitudinal spring of the tire, but has a very small effect on the run-flat durability. . Further, it has been found that the side reinforcing rubber layer at the tire maximum width position greatly contributes to run flat durability. For this reason, while ensuring the run-flat durability by making the gauge of the side reinforcement rubber layer near the width direction outer side end of the belt layer and the gauge of the side reinforcement layer at the tire maximum width position, It was found that the vertical spring can be reduced, that is, the riding comfort can be improved.

  The pneumatic run-flat tire according to claim 1 has a pair of bead portions, sidewall portions continuous to the bead portions, tread portions connected to the sidewall portions on both sides, and a toroidal shape between the pair of bead portions. A carcass disposed across, a belt layer disposed on the outer side in the tire radial direction of the carcass, and disposed along a tire width direction side portion of the carcass toward the outer side in the tire radial direction and the inner side in the tire radial direction. A side reinforcing rubber whose thickness gradually decreases according to the above, a belt cushion rubber disposed between a tire width direction end portion of the belt layer and the carcass, and passes through the tire width direction end portion of the belt layer, A gauge of the side reinforcing rubber on the first normal perpendicular to the tire contour when viewed in a cross section along the tire rotation axis is A, the carcass The side reinforcing rubber gauge in a second on the normal line which forms an outer surface at right angles with the carcass at Ya maximum width position when is B, satisfies 0.2 ≦ A / B ≦ 0.4.

Next, the operation of the pneumatic run flat tire according to claim 1 will be described.
In the pneumatic run-flat tire according to claim 1, a so-called crescent-shaped side reinforcing rubber whose thickness gradually decreases toward the outer side in the tire radial direction and the inner side in the tire radial direction is along the side in the tire width direction of the carcass. Therefore, when the internal pressure is zero, this side reinforcing rubber supports the load of the vehicle and enables run-flat running.

  During run-flat running, the tire reinforcement in the tire radial direction center directly supports the load with the compression rigidity of the rubber, effectively contributing to the load support at zero internal pressure. At the end of the direction, the rigidity of the tire is secured by making it difficult to bend the whole with shear rigidity.

It has been found that the rigidity of the end portion in the tire radial direction of the side reinforcing rubber is relatively weak in supporting the load when the internal pressure is zero. Therefore, in the vicinity of the crescent-shaped side reinforcing rubber, there is a strong tendency to contribute to the deterioration of the riding comfort at the normal internal pressure than the load support at the zero internal pressure.
In particular, the side reinforcing rubber layer adjacent to the tread portion that actually contacts the road surface is more likely to receive an impact from the contact surface, and thus contributes to the ride comfort more.

  In the pneumatic run flat tire according to claim 1, on the first normal line that passes through the end of the belt layer in the tire width direction and is perpendicular to the tire contour when viewed in a section along the tire rotation axis. The ratio A / B between the gauge A of the side reinforcing rubber and the gauge B of the side reinforcing rubber on the second normal perpendicular to the outer surface of the carcass at the maximum tire width position of the carcass is 0.2 ≦ A / The side-reinforced rubber gauge is optimized to satisfy B ≦ 0.4, ensuring run-flat durability, and the side-reinforced rubber gauge near the belt layer end is thinner and lighter than before. The ride comfort was also improved.

  In addition, a camber angle is given to a tire for actual vehicle mounting. In vehicles with a large camber angle (for example, a camber angle of 1.5 degrees or more) and a relatively small camber angle (a camber angle of 1 degree or less), the run-flat durability changes greatly and a large camber angle is added. In the case of the pneumatic run flat tire according to claim 1, the gauge of the side reinforcing rubber near the end of the belt layer is optimized, so that it is durable even at a large camber angle. Sex is sufficiently secured.

  When A / B <0.2, the side reinforcing rubber near the end of the belt layer becomes too thin, and sufficient run-flat durability cannot be ensured. On the other hand, when A / B> 0.4, the side reinforcing rubber in the vicinity of the belt layer end is thick, and the tire weight cannot be reduced.

  According to a second aspect of the present invention, in the pneumatic run-flat tire according to the first aspect, L is a distance from the tread side end portion of the side reinforcing rubber to the tire equatorial plane measured along the carcass, along the carcass. When the width of the belt layer to be measured is W, 0.3 <L / W <0.45 is satisfied.

Next, the operation of the pneumatic run-flat tire according to claim 2 will be described.
When L / W ≦ 0.3, the side reinforcing rubber penetrates deeply into the tread portion with respect to the tire width direction, so that the vertical springs cannot be reduced and the riding comfort cannot be sufficiently improved.

On the other hand, if L / W ≧ <0.45, the distortion at the belt end increases during run-flat travel, which leads to premature failure caused by this, which is not preferable.
Therefore, it is preferable that 0.3 <L / W <0.45 is satisfied.

  According to a third aspect of the present invention, in the pneumatic run flat tire according to the first or second aspect, a cushion rubber is disposed between the outer end portion in the tire width direction of the belt layer and the carcass. .

Next, the operation of the pneumatic run flat tire according to claim 3 will be described.
If the side reinforcement rubber near the outer edge of the belt layer in the tire width direction becomes thinner and the influence of distortion on the side reinforcement rubber becomes larger, the belt layer is positioned between the outer edge of the belt layer in the tire width direction and the carcass. By disposing the cushion rubber on, the influence of the distortion can be reduced.

  As described above, since the pneumatic run flat tire of the present invention has the above-described configuration, it is possible to improve riding comfort and reduce tire weight without sacrificing run flat durability. Has an excellent effect.

It is sectional drawing along the tire rotating shaft of the pneumatic run-flat tire which concerns on embodiment with which this invention was applied.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the pneumatic run-flat tire 10 according to the present embodiment includes a bead portion 12, a sidewall portion 14, a tread portion 16, a carcass 18, a belt layer 20, a belt reinforcing layer 22, a layer layer 24, And a side reinforcing rubber 26.

  The bead portions 12 are portions each having an annular bead core 28, and a pair of bead portions 12 are provided in the tire width direction. Further, the bead portion 12 is provided with a bead filler 29 which is made of rubber harder than the rubber constituting the sidewall portion 14 and extends outward from the bead core 28 in the tire radial direction.

The sidewall portion 14 is a portion that continues to the bead portion 12, and constitutes a side surface of the pneumatic run-flat tire 10 together with the carcass 18 and other rubber layers.
The tread portion 16 is a rubber layer continuous with the sidewall portions 14 on both sides, and has circumferential main grooves 30 and 32 formed on the surface thereof, and is a portion that contacts the road surface during traveling.

The carcass 18 is disposed between the pair of bead portions 12 in a toroidal shape, and is formed by covering a plurality of cords arranged in the radial direction with rubber (in this embodiment, 2 Sheet) carcass ply.
The belt layer 20 is disposed on the outer periphery of the crown portion of the carcass 18, and is configured by laminating a plurality of belt plies, two in this embodiment, and tightening the crown portion of the carcass 18. The taga effect is demonstrated.
A cushion rubber 34 having a substantially triangular cross section is disposed between the carcass 18 and the outer end of the belt layer 20 in the tire width direction. The cushion rubber 34 is made of a softer rubber than the side reinforcing rubber layer 26.

The belt reinforcing layer 22 is formed by winding around the outer periphery of the belt layer 20, for example, a belt-shaped strip formed by covering a plurality of cords with rubber so as to cover the belt layer 20. is there. In the present embodiment, the belt reinforcing layer 22 has a two-layer structure.
The layer layer 24 is disposed so as to cover the side edges of the belt reinforcing layer 22 in the tire axial direction, and a plurality of cords parallel to each other are inclined with respect to the tire circumferential direction. And configured as a rubber-coated ply.

  The side reinforcing rubber 26 is a rubber having a substantially crescent-shaped cross section disposed on the inner surface side of the carcass 18 of the sidewall portion 14 and having a thickness that gradually decreases toward the inner side and the outer side in the tire radial direction. Rubber that is harder than the rubber that constitutes the sidewall portion 14 is used so as to be disposed between the inner liner 36 and the carcass 18 and to support a load during run-flat travel.

The side reinforcing rubber 26 of the present embodiment is formed thickest in the vicinity of the maximum tire width position of the carcass 18. The outer side portion in the tire radial direction of the side reinforcing rubber 26 extends beyond the end portion in the tire width direction of the belt layer 20 toward the tire equatorial plane CL. Further, the inner side portion of the side reinforcing rubber 26 in the tire radial direction extends to the bead core side so as to partially overlap the bead filler 29.
In the pneumatic run-flat tire 10 of the present embodiment, a first normal line that passes through the end of the belt layer 20 in the tire width direction and is perpendicular to the tire contour when viewed in a section along the tire rotation axis. When the gauge of the side reinforcing rubber 26 on N1 is A, and the gauge of the side reinforcing rubber 26 on the second normal N2 perpendicular to the outer surface of the carcass 18 at the maximum tire width position Wmax of the carcass 18 is B. 0.2 ≦ A / B ≦ 0.4 must be satisfied.

  When the distance from the tread side end of the side reinforcing rubber 26 to the tire equatorial plane CL measured along the carcass 18 is L, and the width of the belt layer 20 measured along the carcass 18 is W, 0. It is preferable to satisfy 3 <L / W <0.45.

(Function)
In the pneumatic run flat tire 10 of the present embodiment, the gauge of the side reinforcing rubber 26 is optimized, so the run flat durability is ensured, and the gauge of the side reinforcing rubber near the belt layer end is thinner than before. The weight has been reduced and the ride comfort has been improved.
Further, since the cushion rubber 34 is disposed between the outer end portion in the tire width direction of the belt layer 20 and the carcass 18, the side reinforcement rubber 26 in the vicinity of the outer end portion in the tire width direction of the belt layer 20 is thinned. The influence of distortion on the rubber 26 can be reduced.

  Further, in the pneumatic run flat tire 10 of the present embodiment, the gauge of the side reinforcing rubber 26 in the vicinity of the belt layer end is optimized, so that a large camber angle is given when the vehicle is mounted (1.5 degrees). Also in the above, failure from the belt end is suppressed, and sufficient durability is ensured.

  When A / B <0.2, the side reinforcing rubber 26 in the vicinity of the end of the belt layer 20 in the tire width direction becomes too thin, and sufficient run-flat durability cannot be ensured. On the other hand, when A / B> 0.4, the side reinforcing rubber 26 in the vicinity of the end of the belt layer 20 in the tire width direction is thick, and the tire weight cannot be reduced.

Further, when L / W ≦ 0.3, the side reinforcing rubber 26 penetrates deeply into the tread portion side with respect to the tire width direction, so that the vertical springs can be reduced and the riding comfort cannot be sufficiently improved.
On the other hand, if L / W ≧ <0.45, the distortion at the end of the belt layer 20 increases during run-flat travel, and this causes an early failure due to this, which is not preferable.

(Test example)
First, in order to confirm the effect of the present invention, two types of tires of comparative examples and two types of tires of examples to which the present invention was applied were prototyped, and run-flat durability and longitudinal spring constant were compared.
The tires of the comparative examples and examples, and the tires, the same constituent members as those of the above-described embodiment are used, and the values of A / B and L / W are respectively changed as described in Table 1 below. ing.
The tire sizes are the same and are 225/50 R17. The carcass consists of two carcass plies including a rayon cord. The belt layer is composed of two belt plies including a steel cord, and the inclination angle of the steel cord with respect to the tire width direction is 64 degrees.

Drum tests were conducted for run-flat durability, and evaluation was performed under the following conditions.
After the tire is mounted on the rim, the valve core is pulled out, the air pressure is set to 0 kPa, and a radial load of 525 kgf is applied to the rotating drum of the test machine to press it, and the drum speed is 89 km / h. Drum travel distance was measured until failure occurred.
The measurement result is an index with the travel distance of Comparative Example 1 as 100, and the larger the value, the better the run-flat durability.
Longitudinal spring constant: It was determined using a testing machine (at an internal pressure of 230 kPa).

試験の結果、本発明の適用された実施例１，２のタイヤは、ランフラット耐久性を犠牲にすることなく、通常内圧時の縦バネ定数を低下できていることが分かる。

As a result of the test, it can be seen that the tires of Examples 1 and 2 to which the present invention was applied were able to reduce the vertical spring constant during normal internal pressure without sacrificing run-flat durability.

  Note that a decrease in the longitudinal spring constant during normal internal pressure improves riding comfort.

DESCRIPTION OF SYMBOLS 10 Pneumatic run flat tire 12 Bead part 14 Side wall part 16 Tread part 18 Carcass 20 Belt layer 26 Side reinforcement rubber

Claims (3)

With carcass,
A belt layer disposed on the outer side in the tire radial direction of the carcass;
A side reinforcing rubber that is disposed along the side portion of the carcass and gradually decreases in thickness as it goes toward the outer side in the tire radial direction and the inner side in the tire radial direction;
A belt cushion rubber disposed between a tire width direction end of the belt layer and the carcass;
With
A gauge of the side reinforcing rubber on the first normal that is perpendicular to the tire contour when viewed in a cross section along the tire rotation axis through the tire width direction end of the belt layer, A,
When the gauge of the side reinforcing rubber on the second normal line perpendicular to the outer surface of the carcass at the maximum tire width position of the carcass is B,
A pneumatic run-flat tire satisfying 0.2 ≦ A / B ≦ 0.4. When the distance from the tread side end of the side reinforcing rubber to the tire equatorial plane measured along the carcass is L, and the width of the belt layer measured along the carcass is W,
The pneumatic run-flat tire according to claim 1, wherein 0.3 <L / W <0.45 is satisfied.   The pneumatic run-flat tire according to claim 1 or 2, wherein a cushion rubber is disposed between an outer end portion in the tire width direction of the belt layer and the carcass.

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