JP2010247698A - Run-flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a run-flat tire for reducing tire weight as compared with a conventional one without deteriorating run-flat durability, controllability, and stability. <P>SOLUTION: In the run-flat tire with a reinforcement rubber layer 5 having cross sections of crescent shapes at both sides along the inner surface of a carcass ply 4 extending from a crown to both beads through both sides, a reinforcement cord layer 10 is arranged adjacent to the carcass ply 4 in a portion containing at least a region from the end of a belt 8 to the maximum width of the side only at one of the sides on which an angle between a road surface and a tire equator surface is equal to or smaller than 90° with respect to a camber angle given to the tire when the tire is attached to a vehicle. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a run flat tire, and more specifically, a reinforcing rubber having a crescent cross section in a tire side portion, which can further reduce the tire weight without deteriorating run flat durability performance and steering stability. The present invention relates to a run-flat tire having a layer.

  In run-flat tires that enable emergency run-flat driving (RF driving) in punctures, etc., tires of various structures are provided to ensure the safety of drivers as the performance of vehicles equipped with these tires increases. Has been proposed.

  In order to extend the distance that can be traveled during the run-flat travel, the bulging deformation of the sidewall portion toward the outside in the tire width direction and the collapse deformation of the bead portion are suppressed with respect to the load received by the tire during the run-flat travel. By doing so, it is common to suppress the repeated deformation accompanying the rotation of the tire. Conventionally, for the purpose of suppressing each of these deformations, a reinforcing rubber layer having a crescent-shaped cross section has been provided inside the sidewall portion.

  Since the reinforcing rubber layer arranged in this way contributes to support of the vehicle body weight during the run-flat running, it is possible to advantageously prevent stress concentration on the sidewall portion and the carcass ply during the run-flat running.

  As a result, in the side-reinforced type run flat, crescent-shaped reinforcing rubber is provided to enable run flat running. However, the presence of this reinforcing rubber causes an increase in tire weight. The increase in the weight below will adversely affect the handling safety and durability of the vehicle's undercarriage. In addition, rolling resistance that has been attracting attention in recent years tends to be deteriorated due to the presence of reinforcing rubber in the side portion. Therefore, how to secure the necessary run-flat durability with a small weight increase is a major problem of the current side-reinforced run-flat tire. In order to solve this problem, it is easy to think of a thin reinforced rubber, but the sensitivity of the reinforced rubber gauge to the run flat durability is high. So far, effective weight reduction has not been possible.

  As a countermeasure against such problems, for example, in Patent Document 1, a high elastic modulus reinforcing layer (reinforcing cord layer) having a high elastic modulus cord inside the carcass and outside the reinforcing rubber layer (that is, between the carcass and the reinforcing rubber layer). It is proposed to improve the rigidity of the tire side portion.

Japanese Patent Laying-Open No. 2005-47441 (Claims etc.)

  However, in today's run-flat tire having a reinforcing rubber layer having a crescent-shaped cross section in the tire side portion, weight reduction (improvement in rolling resistance) has been demanded more than ever, and the tire described in Patent Document 1 However, it is still not a sufficient solution.

  Accordingly, an object of the present invention is to provide a run flat tire that can reduce the tire weight more than before without deteriorating the run flat durability performance and the steering stability.

  As a result of intensive investigations to enable reduction in tire weight and improvement in riding comfort performance without reducing the level of run-flat durability of run-flat tires, the present inventors have obtained the following knowledge. It was.

  First, when running on a flat run with tires attached to an actual vehicle, when the original camber angle is large, or when the camber angle is affected by a single wheel missing, the camber angle is relatively large. In many cases, it is driving.

  Therefore, the present inventor, in a sports vehicle equipped with a run-flat tire having a crescent-shaped reinforcing rubber layer on the tire side part, pulls out one rear wheel (drive wheel) and calculates a camber angle with a simple camber angle measuring machine. As a result of measurement, a camber angle of −2.5 ° was given, and when the run-flat running was finished in that state, the reinforcing rubber on the inner side was 31 ° C. to 39 ° C. higher than the reinforcing rubber on the outer side. Was found to be higher. From this result, it was confirmed that the influence of the camber angle change was significant. In addition, in the destruction of the reinforcing rubber, only the reinforcing rubber on the inner side of the mounting was broken, and the reinforcing rubber on the outer side of the mounting was not broken.

  Therefore, when running on a run-flat with an actual vehicle mounted, it is considered that the weight of the tire can be reduced without performing unnecessary reinforcement by considering the state in which the camber angle is given. The camber angle increases the reinforcement on the side of the side where the load increases (becomes severe), while the camber angle increases the load on the side where the load is reduced (becomes mild) First gained knowledge that it would be effective not to increase the reinforcement positively.

  By the way, when run-flat running is performed with the drive wheels removed, the run-flat performance is usually reduced by driving force compared to idle run-flat running. Therefore, when considering the camber angle, it is necessary to consider the camber angle of the drive wheel. In addition, when a camber angle is given by the driving wheel, the contact length on the side where the angle between the road surface and the tire equatorial plane becomes 90 ° or less becomes longer, and the driving force is transmitted mainly by the side part on the camber angle giving side. For this reason, it is necessary to consider that the conditions are more severe than the idle wheels.

  From the above, the present inventor has made the following three methods as means for enhancing the reinforcement of the necessary parts by making the reinforcement of the left and right side parts asymmetrical on the assumption that the camber angle is attached. Further study was conducted.

(1) Asymmetrical gauges for left and right reinforcement rubbers (thickening the reinforcement rubber with the camber angle attached)
(2) Modulus asymmetry of left and right reinforcement rubber (hardening the reinforcement rubber with camber angle)
(3) Asymmetrical left and right carcass structures (increase the number of plies with camber angles)
Among these three methods, the above methods (1) and (2) have a strong imbalance due to the difference in rigidity in the circumferential direction of the side part when expanding with the inner bladder at the time of manufacture. It turned out to be worse (especially lateral components) and not very effective.

  On the other hand, in the asymmetry of the carcass structure of (3), it was found that the circumferential rigidity is equal to the left and right, so that there is little adverse effect on uniformity and is effective. Therefore, in order to increase the number of plies with a camber angle, the same radial reinforcement layer as the carcass is applied to the side portion with the camber angle. It has been found that it is most effective to include at least the region from the belt end to the side maximum width portion so as to cover the portion. The present invention has been completed based on such a series of findings.

That is, the run flat tire of the present invention is a run flat tire having a crescent-shaped reinforcing rubber layer on both side portions along the inner surface of the carcass ply extending from the crown portion to both bead portions through both side portions,
Only the side part on the side where the angle between the road surface and the tire equatorial plane is 90 ° or less with respect to the camber angle given to the tire when the vehicle is mounted includes at least the region from the belt end to the side maximum width part. The reinforcing cord layer is disposed adjacent to the carcass ply at the site.

  In the run flat tire of the present invention, it is preferable that the reinforcing cord layer has a tensile rigidity equal to or higher than that of the carcass ply. The cord constituting the reinforcing cord layer is preferably a fiber cord selected from the group consisting of polyketone, rayon and aramid, and particularly preferably a polyketone fiber cord. Further, the inclination angle of the cord constituting the reinforcing cord layer is preferably within a range of ± 10 ° with respect to the tire radial direction.

  According to the run flat tire of the present invention, the tire weight can be further reduced without deteriorating the run flat durability performance and the steering stability.

It is sectional drawing of the run flat tire of an example (Example) of this invention. It is a tire side surface fragmentary sectional view which shows the inclination angle of the cord which comprises the reinforcement cord layer arrange | positioned at the run flat tire of this invention. It is a typical tire front view showing a camber angle. It is sectional drawing of the run flat tire of the prior art example 1. FIG. FIG. 6 is a cross-sectional view of a run flat tire of Conventional Example 2. 3 is a cross-sectional view of a run flat tire of Comparative Example 1. FIG. 5 is a cross-sectional view of a run flat tire of Comparative Example 2. FIG.

Hereinafter, embodiments of the present invention will be specifically described.
FIG. 1 is a partial cross-sectional view of a preferred example of the run-flat tire of the present invention, which has a pair of left and right bead portions 1 and a pair of side portions 2, and a tread portion 3 connected to both side portions 2. A carcass ply 4 that extends in a toroidal shape between the bead portions 1 and reinforces each of the portions 1, 2, and 3, and a pair of crescent-shaped cross sections disposed inside the carcass ply 4 of the side portion 2. The reinforcing rubber layer 5 is provided.

  In the present invention, in such a run-flat tire, the side portion on the side where the angle θ (see FIG. 3) between the road surface and the tire equatorial plane is 90 ° or less with respect to the camber angle CA given to the tire when the vehicle is mounted. However, it is important that the reinforcing cord layer 10 is disposed adjacent to the carcass ply 4 at least in a region including the region from the belt end to the side maximum width portion.

  By arranging the reinforcing cord layer 10 only on the side portion on one predetermined side as described above, the tire weight can be further reduced without deteriorating the run-flat durability performance, the steering stability, and the rolling resistance. It becomes possible.

  With regard to the location of the reinforcing cord layer 10, in the run flat tire, the side portion 2 is bent during run flat running, but the tensile rigidity of the carcass ply 4 arranged outside the bend and the inside of the bend are bent. Considering that the compression rigidity of the reinforced rubber 5 that is arranged is combined to express the bending rigidity necessary for run-flat travel, it is most effective to arrange it “adjacent” to the carcass ply 4. It is possible to ensure a sufficient rigidity.

  The difference in rigidity between the case where the reinforcing cord layer 10 is adjacent to the inside of the carcass ply 4 and the case where the reinforcing cord layer 10 is adjacent to the outside is small and within a negligible range.

  The reinforcing cord layer 10 preferably has a tensile rigidity equal to or higher than that of the carcass ply in order to obtain the desired effect, and is most preferably a polyketone fiber cord having heat shrinkability at a high temperature. . In run-flat running, the temperature is usually higher than 100 ° C. However, when a polyketone fiber cord is applied, the progress of crushing can be delayed due to the heat shrinkage. Although not as good as polyketone, good effects can be obtained with rayon or aramid fiber cords.

  In the present invention, as shown in FIG. 2, the cords 11 constituting the reinforcing cord layer 10 are arranged to be inclined with respect to the tire radial direction (direction toward the tire center C). The inclination angle α of the cord 11 with respect to the direction toward the center C is preferably in the range of ± 10 °. By making it within such a range, it is possible to suppress the contribution to the vertical spring rise due to the arrangement of the reinforcing cord layer 10, and the riding comfort performance is not impaired.

  Further, in the illustrated tire, a bead filler 7 is arranged on the outer side in the tire radial direction of the ring-shaped bead core 6 embedded in the bead portion 1, and further, the outer side in the tire radial direction of the tread portion of the carcass ply 4. A belt 8 composed of two belt layers is disposed in the belt. Furthermore, a belt reinforcing layer 9A is disposed so as to cover the entire belt 8 on the outer side in the tire radial direction of the belt 8, and a pair of belt reinforcing layers 9B are disposed so as to cover only both ends of the belt reinforcing layer 9A. (So-called 1 cap + 1 layer). Here, the belt layer is usually composed of a rubberized layer of a cord extending in an inclined manner with respect to the tire equatorial plane, preferably a rubberized layer of a steel cord, and the two belt layers constitute the belt layer. The belt 8 is formed by laminating the cords so as to cross each other with the equator plane interposed therebetween. The belt reinforcing layers 9A and 9B are usually made of rubberized layers of cords arranged substantially parallel to the tire circumferential direction.

  The carcass ply 4 in the illustrated example is composed of a single carcass ply formed by coating a plurality of reinforcing cords arranged in parallel with a coating rubber, and the carcass ply 4 is respectively disposed in the bead portion 1. The present invention comprises a main body portion extending in a toroidal shape between a pair of embedded bead cores 6 and a folded portion wound around each bead core 6 radially outward from the inner side to the outer side in the tire width direction. In the pneumatic tire, the number of plies and the structure of the carcass ply 4 are not limited thereto.

  As the reinforcing cord of the carcass ply, various types such as rayon, nylon, polyester, polyketone and the like can be suitably used. Furthermore, although the belt 8 in the illustrated example comprises two belt layers, the number of belt layers constituting the belt 8 is not limited to this in the pneumatic tire of the present invention. Furthermore, in the pneumatic tire of the present invention, it is not essential to dispose the belt reinforcing layers 9A and 9B, and a belt reinforcing layer having a different structure can be disposed.

Hereinafter, the present invention will be described based on examples.
(Examples, conventional examples 1 and 2, comparative examples 1 and 2)
As test tires, tires having the following common configurations were respectively prototyped.
Tire size: 225/45 R17
Location of the crescent-shaped reinforcing rubber layer in the cross section: Between the carcass ply and the inner liner Belt layer: Two steel crossing belt layers, each inclined at ± 62 ° with respect to the tire axial direction Belt reinforcing layer: 1 cap + 1 layer carcass Ply: rayon fiber cord

  In Conventional Example 1, as shown in FIG. 4, the carcass ply 4H and the low carcass ply have a high turn-up portion that is wound radially outward from the inner side to the outer side in the tire width direction around each bead core 6, as shown in FIG. It is a known structure consisting of 4L (2P H / L).

  In Conventional Example 2, as shown in FIG. 5, the ply structure is formed from a single carcass ply 4 </ b> H having a high turn-up portion that is wound radially outward from the inner side to the outer side in the tire width direction around each bead core 6. (1P H).

  In the embodiment, as shown in FIG. 1, the ply structure is composed of one carcass ply having a high turn-up portion wound radially outward from the inner side to the outer side in the tire width direction around each bead core (1P H) and the side from the belt end only to the side part on the side where the angle between the road surface and the tire equatorial plane is 90 ° or less (CA inside) with respect to the camber angle given to the tire when the vehicle is mounted. A reinforcing cord layer having a width of 90 mm is disposed adjacent to the carcass ply at a portion including the region up to the maximum width portion. As a result of using a polyketone fiber cord having a higher tensile rigidity than the rayon fiber cord, the reinforcing cord layer has a higher tensile rigidity than the carcass ply. The twisted structure of the cord, the number of driving and the covering rubber are the same as those of the carcass ply. In addition, the inclination angle of the cords constituting the reinforcing cord layer was in a range of ± 10 ° with respect to the tire radial direction.

  In Comparative Example 1, as shown in FIG. 6, everything is the same as that of the example except that the same reinforcing cord layers as those of the example are arranged on both sides (CA inner side and CA outer side) of the side portion.

  In Comparative Example 2, as shown in FIG. 7, everything is the same as that of the example except that the same reinforcing cord layer as that of the example is disposed only on the side portion opposite to the example (CA outer side).

  In the evaluation, a test tire was attached to the right rear of the BMW 3 series vehicle. Under the condition of a regular load determined by JATMA and a speed of 80 km / h, the vehicle was run flat on a test course and evaluated for ride comfort and run flat durability performance. Riding comfort was evaluated based on the vertical spring value at normal internal pressure, assuming normal use. The run flat durability performance was evaluated by the run flat durability distance. The tire weight was also evaluated.

  For this evaluation, the evaluation index for the tire of Conventional Example 1 was set to 100, and an evaluation index for relative evaluation was calculated. The evaluation results are also shown in Table 1 below. The evaluation results in Table 1 indicate that the performance is higher as the evaluation index is larger for the run flat (RF) durability distance, and the performance is higher as the evaluation index is lower for other performances.

  From the evaluation results shown in Table 1, it can be seen that the tires of the examples have improved run comfort performance while maintaining run-flat durability as compared with the tires of the conventional example 1, while the tire weight can be reduced. . Moreover, although the tire weight of the tire of the example is slightly increased as compared with the tire of the conventional example 2, it can be seen that the run-flat durability can be significantly increased while suppressing the deterioration of the riding comfort performance. Further, from the comparison between the tire of the example and the tires of Comparative Examples 1 and 2, it is possible to maintain the run-flat durability, improve the riding comfort performance, and the tire by arranging the reinforcing cord layer only on the CA inner side portion. It can be seen that it is important in realizing weight reduction.

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side part 3 Tread part 4 Carcass ply 5 Reinforcement rubber layer 6 Bead core 7 Bead filler 8 Belt 9A, 9B Belt reinforcement layer 10 Reinforcement cord layer 11 Cord

Claims (5)

In a run flat tire having a crescent-shaped reinforcing rubber layer on both side portions along the inner surface of the carcass ply extending from the crown portion to both bead portions through both side portions,
Only the side part on the side where the angle between the road surface and the tire equatorial plane is 90 ° or less with respect to the camber angle given to the tire when the vehicle is mounted includes at least the region from the belt end to the side maximum width part. A run-flat tire characterized in that a reinforcing cord layer is disposed adjacent to the carcass ply at a site.   The run-flat tire according to claim 1, wherein the reinforcing cord layer has a tensile rigidity equal to or greater than that of the carcass ply.   The run flat tire according to claim 1 or 2, wherein the cord constituting the reinforcing cord layer is a fiber cord selected from the group consisting of polyketone, rayon and aramid.   The run flat tire according to claim 3, wherein the cord constituting the reinforcing cord layer is a polyketone fiber cord.   The run flat tire according to any one of claims 1 to 4, wherein an inclination angle of a cord constituting the reinforcing cord layer is in a range of ± 10 ° with respect to a tire radial direction.

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