JP2005178668A - Run-flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance resistance against the slipping-off of a rim while the stability of uniformity is secured. <P>SOLUTION: A bead core 5 has approximately a rectangular section such that the intersecting angle of upper Y2 and lower long edges Y1 with short edges X1 and X2 on sides is 82-98°, and the ratio of the mean YO of lengths of the upper Y2 and lower long edges Y1 to the mean XO of the lengths of the short edges X1 and X2 is made 1.5-3.0, while the inclining angle α of the lower long edge Y1 relative to the tire axial direction is made 10±5°. The tire axial direction distance Lt between the apex P1 on the toe side and the toe side outside surface St is made 0.3-0.7 times as large as the mean YO, while the tire axial direction distance Lh between the apex P2 on the heel side and the heel side outside surface Sh is made 0.2-0.5 times as large as the mean YO. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a run-flat tire having improved rim detachment resistance.

  As a run-flat tire that can travel relatively long distances even when air in the tire is removed due to puncture or the like, for example, as schematically shown in FIG. A so-called side-reinforcing type having a side-reinforcing rubber layer b for supporting the surface is often used.

  In this type of tire, in order to obtain a necessary rim detachment resistance, a bead core having a rectangular cross section and a so-called tape bead structure in which the radially inner circumferential surface is parallel to the tire axial direction line is used. The inner diameter rc of c is reduced, or the width wc of the bead core c in the tire axial direction is increased to ensure the fitting force with the rim, and the bead toe portion d1 is provided with, for example, a hard reinforcing rubber e. The rubber volume and rigidity of the bead toe part d1 are increased, and the bead toe part d1 is prevented from getting over the rim hump when a lateral force is applied during puncture.

  However, in such a method, the rubber flow at the time of vulcanization molding becomes large due to the increase in the rubber volume in the bead toe part d1. As a result, there is a problem that the stability of the uniformity is impaired, such as excessive reinforcing rubber e and clinch rubber f flowing into the lower side of the core.

JP 2000-118210 A

  Therefore, the present invention is based on the use of a bead core having a substantially rectangular cross section whose inner circumferential surface in the radial direction is inclined at an angle α of 10 ± 5 ° with respect to the tire axial direction line. An object of the present invention is to provide a run-flat tire that can suppress the ride over the rim hump without increasing the rim hump, and can improve the rim removal resistance performance while ensuring uniformity stability.

In order to achieve the above object, the invention of claim 1 of the present application is a run flat tire including a carcass folded around a bead core of a bead portion through a sidewall portion from a tread portion,
In the bead core, in the tire meridian cross section, the long side on the rim seat side, the long side on the outer side in the radial direction, and the short side on the toe side and the heel side intersect with each other at an angle of 80 to 100 °. It has a substantially rectangular cross section,
The lower long side is inclined at an angle α of 10 ± 5 ° inward in the tire radial direction toward the inner side in the tire axial direction with respect to the tire axial line,
And while setting the ratio (long side average value / short side average value) of the long side average value which averages the length of the upper and lower long sides and the short side average value to 1.5 to 3.0,
The bead portion has a tire axial direction distance Lt between an apex at which the lower long side of the bead core intersects with a toe side short side and a toe side outer surface of the bead portion. 3 to 0.7 times, and the tire axial direction distance Lh between the apex at which the upper long side intersects with the short side on the heel side and the heel side outer surface of the bead portion is defined as 0 of the long side average value. 2 to 0.5 times and smaller than the tire axial distance Lt.

  According to a second aspect of the present invention, the bead portion has a core lower thickness Tb between the lower long side and the bottom surface in the radial direction of the bead portion on a radial line passing through the center of the cross section of the bead core. It is characterized by 4.0 mm.

  In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values specified when the bead part is held in accordance with the rim width defined by the tire size in a non-rim assembled state. .

  Since the present invention is configured as described above, it is possible to suppress the ride over the rim hump without increasing the rubber volume and rigidity in the bead toe portion, and to improve the rim removal resistance performance while ensuring the stability of the uniformity. It becomes possible to do.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, a run-flat tire 1 is disposed on a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, an inner side of the tread portion 2, and a radially outer side of the carcass 6. Belt layer 7 and a side reinforcing rubber layer 11 that is disposed on the side wall portion 3 and has a load supporting function when the tire escapes from the air.

  The carcass 6 includes one or more carcass plies 6A in which carcass cords are arranged at an angle of 70 to 90 ° with respect to the tire circumferential direction. In this example, the carcass ply 6A includes the bead cores 5, 5 On both sides of the ply main body portion 6a, the ply turn-up portions 6b that are turned back from the inner side in the tire axial direction around the bead core 5 are provided in series. A bead apex rubber 8 for bead reinforcement that extends in a tapered manner from the bead core 5 to the outer side in the tire radial direction is disposed between the ply main body portion 6a and the folded portion 6b. An inner liner rubber layer 12 made of an air permeable rubber such as butyl rubber is attached to the inner surface of the ply body 6a.

  In this example, the case where the ply turn-up portion 6b is wound high outward in the radial direction of the tire and its outer end is sandwiched between the belt layer 7 and the ply main body portion 6a and ends. Yes. As a result, the bending rigidity from the bead portion 4 to the sidewall portion 3 is increased, and the outer end of the ply turn-up portion 6b does not appear in the sidewall portion 3 that is greatly bent during puncture travel. A cord looseness etc. can be controlled suitably. The overlapping width Wj in the tire axial direction between the ply turn part 6b and the belt layer 7 is preferably in the range of 5 to 25 mm.

  The belt layer 7 is formed by two or more belt plies 7A and 7B in which high-strength belt cords such as steel cords are arranged at, for example, about 10 to 35 ° with respect to the tire circumferential direction. The belt cords cross each other between the plies to increase the belt rigidity, and substantially reinforce the substantially entire width of the tread portion 2 with a tagging effect.

  Next, in the run flat tire 1 of the present embodiment, the side reinforcing rubber layer 11 is provided on the side wall portion 3 and the tire lumen side to increase the bending rigidity of the side wall portion 3 and to support the load load at the time of puncture. This ensures run-flat performance.

  The side reinforcing rubber layer 11 has a substantially crescent-shaped cross section extending gradually from the central portion having the maximum thickness T inward and outward in the radial direction of the tire, and the radially outer end thereof is connected to the belt layer 7 and the tire radius. It ends with an overlapping portion Ku inside and outside in the direction, and its inner end in the radial direction ends with an overlapping portion Kl inside and outside the bead apex rubber 8 in the tire axial direction. At this time, in order to ensure run-flat performance, it is preferable that the maximum thickness T is in the range of 5.0 to 20.0 mm, and the rigidity step at the inner and outer ends of the side reinforcing rubber layer 11 is alleviated and In order to perform reinforcement in a well-balanced manner, it is preferable that the overlapping widths Wu and Wl of the overlapping portions Ku and Kl be 5 mm or more, further 10 mm or more, respectively.

  When the carcass 6 is formed of a single carcass ply 6A as in this example, the side reinforcing rubber layer 11 is the tire lumen side (FIG. 1) from the ply main body 6a or the ply main body. It can arrange | position between 6a and the ply folding | turning part 6b. When the carcass 6 is formed of a plurality of carcass plies 6A, the ply main body portions 6a, 6a, or the innermost ply main body portion 6a, the tire lumen side, or the outermost ply main body portion 6a It can arrange | position between ply folding | turning parts 6b. As the rubber used for the side reinforcing rubber layer 11, a low heat-generating rubber having a complex elastic modulus E * of 8 to 15 Mpa and a loss tangent tan δ of 0.03 to 0.08 is preferable from the viewpoint of durability during run-flat running. . The complex elastic modulus is a value measured using a viscoelastic spectrometer under conditions of a temperature of 70 ° C., an initial strain of 10%, a frequency of 10 Hz, and an amplitude of 2%.

  And in the run-flat tire 1 of this embodiment, in order to improve the rim detachment resistance performance, as shown in an enlarged view in FIG.

  First, in the tire meridian cross section, the bead core 5 is composed of a lower long side Y1 on the rim seat side, an upper long side Y2 on the radially outer side, and a short side on the toe side and heel side. X1 and X2 are each formed in a substantially oblong cross-sectional shape with a horizontally long flat crossing at an intersecting angle of 80 to 100 °, preferably 83 to 97, respectively.

  At this time, the lower long side Y1 is inclined at an angle α of 10 ± 5 ° inward in the tire radial direction toward the inner side in the tire axial direction with respect to the tire axial direction line, and the upper and lower long sides Y1. The ratio of the long side average value Y0 that averages the lengths of Y2 and the short side average value X0 of the short sides X1 and X2 (long side average value Y0 / short side average value X0) is 1.5 to 3.0. Is set. For convenience, the direction of inclination of the long side Y1 may be referred to as downward inclination for convenience. Such a bead core 5 can be formed by a so-called single wind method in which one bead wire is spirally wound in multiple rows and multiple stages.

  Second, in the bead portion 4, the tire axial distance Lt between the apex P <b> 1 where the lower long side Y <b> 1 of the bead core 5 intersects the toe side short side X <b> 1 and the toe side outer surface St of the bead portion 4. Is 0.3 to 0.7 times the long side average value Y0, the apex P2 where the upper long side Y2 and the short side X2 on the heel side intersect, and the heel side outer surface Sh of the bead part 4 Is set to be 0.2 to 0.5 times the long side average value Y0 and smaller than the tire axial distance Lt.

  Here, the rim R to be mounted on the run flat tire 1 is a so-called 5 ° deep rim whose rim seat Rs is inclined downward at an angle β of 5 ° with respect to the tire axial direction line. Rim, TRA “Design Rim”, ETRTO “Measuring Rim”, and other regular rims defined by the standard on which the tire is based are suitably employed. The bottom surface Sb of the bead portion 4 seated on the rim seat Rs is an inclined surface having an angle γ larger than the angle β of the rim seat Rs. In this example, the heel side is inclined substantially the same as the lower long side Y1. This example shows a two-step inclination of a gentle inclined surface Sb1 and a toe-side steeply inclined surface Sb2 inclined at an angle larger by about 3 to 15 °, for example. The bottom surface Sb, the gently inclined surface Sb1, or the steeply inclined surface Sb2 alone may be used. Further, the bead diameter Db of the bead portion 4 is set to 99.5 to 99.9% of the rim diameter Dr of the rim R and slightly smaller than the rim diameter Dr, as in the conventional tire.

Next, the function and effect of the bead structure will be described.
As described above, in the present invention, the bead core 5 is formed in a horizontally long and flat rectangular section with the ratio (Y0 / X0) in the range of 1.5 to 3.0. Therefore, the rim sheet Rs can be fitted with a relatively wide width, and the crimping effect with the rim can be improved without impairing the rim assembly performance. If the ratio (Y0 / X0) is less than 1.5, the fitting width is insufficient, and the improvement of the crimping effect cannot be expected. Conversely, if it exceeds 3.0, the rigidity of the bead core 5 is reduced and the steering is reduced. In addition to incurring a decrease in stability, the fracture strength of the bead core tends to be impaired. From such a viewpoint, the lower limit of the ratio (Y0 / X0) is preferably 1.8 or more, and the upper limit is preferably 2.8 or less.

  Further, in the bead core 5, the lower long side Y1 is inclined downward at an angle α of 10 ± 5 ° which is equal to or larger than the angle β of the rim sheet Rs. Thus, as conceptually shown in FIG. 3, when the bead contour shape is the same as in the case of the conventional bead core (indicated by a one-dot chain line), the bead toe portion 5e is the same. As the rubber volume at is reduced, the rigidity at the bead toe portion 5 e is substantially increased by the approach of the bead core 5. As a result, when a lateral force is applied during puncture, the bead toe portion 5e can be prevented from getting over the rim hump Rh, and the rim detachment resistance can be greatly increased.

  Further, the conventional reinforcing rubber e (FIG. 4) for increasing the rigidity of the bead toe portion is not necessary, and the rubber volume in the bead toe portion 5e is reduced. Therefore, other rubbers such as the reinforcing rubber e and the clinch rubber f are provided below the bead core. This can solve the problem of non-uniform flow, stabilize the rubber distribution under the bead core, and improve the tire uniformity.

  Therefore, the ratio Lt / Y0 between the distance Lt on the toe side and the long side average value Y0 is 0.3 to 0.7, and the ratio Lh / Y0 between the distance Lh on the heel side and the long side average value Y0 is It is regulated to 0.2 to 0.5. When the ratio Lt / Y0 is greater than 0.7 and the ratio Lh / Y0 is greater than 0.5, the rubber flow becomes large, which tends to destabilize the rubber distribution under the bead core. On the other hand, if the ratio Lt / Y0 is less than 0.3 and the ratio Lh / Y0 is less than 0.2, there is a problem that the bead portion 4 is scratched due to insufficient rubber volume of the bead portion 4.

  Also, if the inclination angle α of the lower long side Y1 exceeds 15 ° and becomes too large, the compression force acting on the bead bottom surface Sb becomes non-uniform, and a sufficient fitting force with the rim cannot be secured. If it exceeds 5 ° and becomes too small, the effect of suppressing the ride over the rim hump becomes too small, and the rim detachment resistance cannot be increased. Therefore, the inclination angle α is preferably 10 ° ± 4 °, more preferably 10 ° ± 3 °.

  In this example, in order to ensure the fitting force with the rim, the core lower thickness between the lower long side Y1 and the bead bottom surface Sb on the radial line passing through the center (centroid) of the cross section of the bead core 5 is ensured. The thickness Tb is regulated within a range of 2.0 to 4.0 mm. If the thickness Tb under the core is less than 2.0 mm, damage such as cracks is likely to occur in the lower portion of the core due to the fitting force, and if it exceeds 4.0 mm, the fitting force tends to decrease.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A run-flat tire having a tire size of 225 / 50R17 having the structure shown in FIG. 1 was prototyped according to the specifications shown in Table 1, and the anti-rim removal performance of the sample tire was tested. The specifications other than those shown in Table 1 were the same.

(1) Rim detachment resistance (rim detachment resistance):
In accordance with the bead unseat test specified in Section 5.2 of JIS D4230, after assembling the rim without a lubricant on the standard rim, the internal pressure is released and lateral force is applied to the bead portion of the tire to cause the bead portion to come off the rim. The value of the lateral force when it occurred was measured.

  As shown in the table, it can be confirmed that the tires of the examples can greatly improve the rim detachment resistance. In addition, when the conventional tire shown in FIG. 4 is produced, the occurrence rate of tires with poor FV whose FV (force variation) is less than the in-house standard is about 15%, but in the case of Example 1, it is suppressed to 1% or less. I was able to.

It is sectional drawing which shows one Example of the run flat tire of this invention. It is sectional drawing which expands and shows the bead part. It is a diagram explaining the effect of this invention. It is sectional drawing explaining the problem of a prior art.

Explanation of symbols

2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 9 Reinforcement cord layer M Tire maximum width point

Claims (2)

A run-flat tire having a carcass that is turned around the bead core of the bead portion from the tread portion to the sidewall portion,
In the bead core, in the tire meridian cross section, the long side on the rim seat side, the long side on the outer side in the radial direction, and the short side on the toe side and the heel side intersect with each other at an angle of 80 to 100 °. It has a substantially rectangular cross section,
The lower long side is inclined at an angle α of 10 ± 5 ° inward in the tire radial direction toward the inner side in the tire axial direction with respect to the tire axial line,
And while setting the ratio (long side average value / short side average value) of the long side average value which averages the length of the upper and lower long sides and the short side average value to 1.5 to 3.0,
The bead portion has a tire axial direction distance Lt between an apex at which the lower long side of the bead core intersects with a toe side short side and a toe side outer surface of the bead portion. 3 to 0.7 times, and the tire axial direction distance Lh between the apex at which the upper long side intersects with the short side on the heel side and the heel side outer surface of the bead portion is defined as 0 of the long side average value. A run flat tire characterized by being 2 to 0.5 times smaller than the tire axial distance Lt.   In the bead portion, a core under-thickness Tb between the lower long side and a radial bottom surface of the bead portion on a radial line passing through the cross-sectional center of the bead core is 2.0 to 4.0 mm. The run flat tire according to claim 1.

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