JP2015033958A - Run-flat tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a run-flat tire capable of achieving both a vehicle body input performance and a run-flat durability performance at high level.SOLUTION: A run-flat tire has a pair of bead parts 11, side wall parts 12 and a tread part 13 connecting between both side wall parts 12, has a carcass 1 straddling between the bead parts and extending in a toroidal shape as a skeleton, and comprises a side reinforcing rubber layer 5 in the side wall part. The tire has a recess 8 so that the contour of the side wall part in cross-section of a tire width direction becomes protrusion toward the inside of the tire width direction at the maximum width position of the tire.

Description

  The present invention relates to a run-flat tire (hereinafter, also simply referred to as “tire”), and more particularly, to a run-flat radial tire according to an improvement in the outer shape of a sidewall portion.

  Conventionally, new vehicle tires are required to have high vehicle body input performance, so-called riding comfort. In particular, for new car run-flat tires, it is important to have high run-flat durability performance in addition to high vehicle body input performance.

  It is known that the vehicle body input performance is generally greatly influenced by the thickness (gauge) of the side portion. In the case of so-called side reinforcement type run flat tires in which hard side reinforcement rubber is embedded in the sidewall part, the thickness of the side part tends to increase, so the balance between run flat durability performance and vehicle body input performance is balanced It becomes a problem.

  As a technique related to the improvement of the side portion of the tire, for example, in Patent Document 1, a lettering portion is formed on the outer surface of the sidewall portion, and the lettering portion is formed on the outer end portion in the tire radial direction of the sidewall portion. There has been disclosed a pneumatic tire in which concave grooves extending from the outer side in the tire radial direction and extending over the entire circumference in the tire circumferential direction are formed.

JP 2009-096212 A (Claims etc.)

  As described above, in new car tires, especially side-reinforced run-flat tires, there is a problem with the balance between the influence on the vehicle body input performance due to the thickness of the side part and the securing of the run-flat durability performance due to the embedded side reinforcing rubber. It becomes.

  Accordingly, an object of the present invention is to provide a run-flat tire capable of achieving both a vehicle body input performance and a run-flat durability performance at a high level.

  As a result of intensive studies, the present inventors have found the following. That is, when the thickness of the side portion is too thick, when running with the tire internal pressure being 0 kPa, heat is generated inside the tire and a large amount of heat is generated, which may not satisfy the requirement for high run-flat durability performance. Moreover, if the thickness of the side part that has a great influence on the vertical spring is made too thick, the riding comfort performance is deteriorated.

  On the other hand, in order to ensure run flat durability performance, it is also important to secure a certain amount of side reinforcement rubber thickness. Therefore, in order to achieve both vehicle body input performance and run flat durability performance, It is considered effective to reduce the thickness of the entire side portion while ensuring the thickness. From this viewpoint, as a result of further studies, the present inventor has found that the above problems can be solved by improving the outer shape of the sidewall portion of the tire, and has completed the present invention.

  That is, the present invention has a pair of bead portions and sidewall portions, and a tread portion continuous between both sidewall portions, and a carcass extending between the bead portions in a toroid shape as a skeleton, In the run flat tire having a side reinforcing rubber layer in the wall portion, the outer shape of the sidewall portion in the tire width direction cross section has a concave portion that protrudes inward in the tire width direction at the tire maximum width position. Is.

In the tire of the present invention, when the rim guard is provided, the outer shape of the sidewall portion in the tire width direction cross section is such that the mold split position A at the time of tire vulcanization on the sidewall portion surface and the vertex C of the rim guard. Between the convex portion protruding outward in the tire width direction and the concave portion protruding convex in the tire width direction, and the intersection of the convex portion and the concave portion is defined as B. When this is done, the tire radial height H _AB between _AB can be smaller than the tire radial height H _BC between _BC .

  According to the present invention, the configuration described above makes it possible to realize a run-flat tire capable of achieving both a vehicle body input performance and a run-flat durability performance at a high level.

It is a width direction one side sectional view showing an example of the run flat tire of the present invention. It is a width direction one side sectional view showing other examples of the run flat tire of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a cross-sectional side view of one example of the run-flat tire of the present invention in the width direction. The illustrated run-flat tire of the present invention has a pair of bead portions 11 and sidewall portions 12, and a tread portion 13 that is continuous between both sidewall portions 12. The extending carcass 1 is used as a skeleton, and the side reinforcing rubber layer 5 is provided on the sidewall portion 12. In the illustrated tire, a bead core 2 is embedded in the bead portion 11, and a bead filler 3 is disposed on the outer side in the tire radial direction.

  In the illustrated tire of the present invention, it is important that the outer shape of the sidewall portion 12 in the cross section in the tire width direction has a concave portion 8 that protrudes inward in the tire width direction at the tire maximum width position. That is, by providing the concave portion 8 at the tire maximum width position in the outer shape of the sidewall portion 12, the thickness of the side rubber is greatly reduced without changing the thickness of the side reinforcing rubber, and the thickness of the side portion is reduced. As a result, it is possible to promote the heat dissipation of the tire internal heat at the side portion during traveling in a state where the tire internal pressure is 0 kPa, and to suppress the occurrence of a failure due to the tire internal heat. It can be set as the tire which can satisfy the requirement of the high run flat durability performance in a tire. Further, by reducing the thickness of the side portion, it is possible to satisfy the demand for high vehicle body input performance in a new vehicle tire. On the other hand, since the thickness of the side reinforcing rubber is not changed, the run flat durability performance is not reduced due to the decrease in the thickness of the side reinforcing rubber.

  The concave portion 8 according to the present invention is present continuously in the entire tire circumferential direction, and preferably has a shape having a curvature center on the outer side in the tire width direction. Good. For example, the concave portion 8 may be provided by changing the curvature of the outer shape of the sidewall portion 12 two or more times, preferably 3 to 4 times in the vicinity of the tire maximum width portion P. Here, changing the curvature of the outer shape of the sidewall portion 12 two or more times in the vicinity of the tire maximum width portion P means that the outer shape of the sidewall portion 12 in the tire width direction cross section is convex toward the tire outer side. In addition to (R-shaped portion), it means that a portion (inverted R-shaped portion) that protrudes toward the inside of the tire is provided. The portion that protrudes toward the inner side of the tire (reverse R-shaped portion) may be provided so as to be smoothly connected to the portion that protrudes toward the outer side of the tire, or to a part of the portion that protrudes toward the outer side of the tire. You may provide so that a recessed part may be formed. In the present invention, in both cases where the rim guard is not provided or not provided, the irregularities due to the decorative portion such as the turbulent flow generating convex portion provided on the surface of the sidewall portion are the R-shaped portion and the inverse R. It is not included in the shape part.

  In general, the tire height direction position where the tire has the maximum width coincides with the tire height direction position corresponding to the maximum width of the carcass case line. Also in the present invention, the tire maximum width portion P means a position in the tire height direction corresponding to the maximum width of the carcass case line, and is preferably in the range of 70 to 40% of the tire cross-section height SH. Shall. The same applies to the case with a rim guard. Further, in the present invention, a tire maximum width SW described later means a tire width at a position in the tire height direction corresponding to the tire maximum width portion P. Here, the tire cross-section height SH is a tire cross-section height in a no-load state in which a tire is mounted on a standard rim and filled with a specified internal pressure. Standard rim and specified internal pressure are standard rims (or “Approved” in application sizes defined in industrial standards or standards effective in the area where tires are manufactured, sold or used, such as JATMA, TRA, ETRTO, etc. Rim "," Recommended Rim ") and the air pressure according to the maximum load capacity of the tire. The tire cross-section height SH means 1/2 of the difference between the outer diameter of the tire and the rim diameter of the applicable rim.

  In FIG. 2, the width direction one side sectional drawing of the other example of the run flat tire of this invention is shown. The illustrated run-flat tire of the present invention has a pair of bead portions 21 and sidewall portions 22, and a tread portion 23 that is continuous between both sidewall portions 22. The extended carcass 1 is used as a skeleton, and the side reinforcing rubber layer 5 is provided on the side wall portion in the same manner as the tire of FIG. 1 except that the rim guard 4 is provided. In the illustrated tire, reference numerals 2 and 3 denote a bead core and a bead filler, respectively, as in FIG.

In the tire of the present invention having the rim guard 4 shown in the figure, the outer shape of the sidewall portion 22 in the cross section in the tire width direction is such that the mold split position A and the vertex C of the rim guard 4 at the time of tire vulcanization on the surface of the sidewall portion 22. Between the tires in the tire radial direction and the convex part 9 that protrudes outward in the tire width direction and the concave part 8 that protrudes inward in the tire width direction. The tire radial height H _AB is preferably smaller than the tire radial height H _BC between _BCs .

  That is, in the case of a tire having the rim guard 4, by providing a convex portion toward the inner side of the tire so as to be smoothly connected to the rim guard 4 in the outer shape of the sidewall portion 22, the thickness of the side reinforcing rubber is not changed. In addition, the thickness of the side portion can be reduced. As in the case of the tire not having the rim guard in FIG. 1, it is possible to suppress the occurrence of a failure due to the tire internal heat generated at the side portion when traveling with the tire internal pressure being 0 kPa. It is possible to satisfy the requirements for high run-flat durability performance and high vehicle body input performance requirements for automobile tires at the same time.

In the present invention, the tire radial height H _AB between AB, are you less than the tire radial height H _BC between BC, by a large recess 8 between BC, Side This is because the thickness of the portion can be further reduced. Specifically, for example, the ratio H _AB : H _BC between the height H _AB and the height H _BC can be 1: 1.2 to 1: 1.65. Even in the case of a tire having the rim guard 4, the recess 8 is preferably provided at least in the tire maximum width position. However, the overall shape between the BCs may be convex toward the inside of the tire to form the recess 8, and is not particularly limited.

  The present invention is also applicable to general tires from the viewpoint that the effect of satisfying the requirements of high vehicle body input performance in new vehicle tires by reducing the thickness of the side portion is particularly high. This is useful in a run-flat tire having a side reinforcing rubber layer 5 on the side wall as shown in the figure because the effect of achieving both run-flat durability performance and high vehicle body input performance can be obtained.

  In the present invention, the ratio of the thickness of the side reinforcing rubber layer 5 to the total thickness of the sidewall portion measured in the tire width direction at a height of 60% of the tire cross-section height SH is 20 to 35%, particularly It is preferable that it is 25 to 30%. If the thickness ratio of the side reinforcing rubber layer 5 is too small, the side gauge is thinned by changing the curvature to make the concave portion, so that the side portion is not sufficiently reinforced and the run flat durability performance cannot be secured. For this reason, if it is too large, the rigidity in the tire radial direction of the side portion becomes too large, and the riding comfort performance deteriorates. In the present invention, the thickness of each part of the tire or the thickness measured in the tire width direction means the thickness when the rim guard is not provided even when the rim guard is provided.

  In the present invention, the ratio of the thickness of the bead filler 3 to the total thickness of the sidewall portion measured in the tire width direction at a height of 50% of the tire cross-section height SH is 0 to 10%, particularly It is preferable that it is 0 to 5%. Similarly, the ratio of the thickness of the bead filler 3 to the total thickness of the sidewall portion measured in the tire width direction at a height of 35% of the tire cross-section height SH is 20 to 30%, particularly 20 to 25%. It is also preferable. By reducing the height of the bead filler 3 to such an extent that the above range is satisfied, the thickness of the side portion can be further reduced, which is preferable.

  Furthermore, in the present invention, the maximum width CW of the case line of the carcass 1 in the cross section in the tire width direction is preferably 105 to 115%, particularly 108 to 112% of the tread contact width TW, and the tire maximum width SW It is also preferable that it is 90 to 99%, particularly 95 to 99%. Thereby, the gauge of the side rubber | gum of the outer part of a case line can be made thin. Here, the case line of the carcass 1 refers to a line passing through the center of the carcass 1 in the cross section in the tire width direction. Further, the tread contact width TW refers to the distance along the tire width direction from one contact end to the other contact end in the tire tread portion.

  In the tire according to the present invention, only the point that satisfies the condition relating to the outer shape of the sidewall portion is important, and thereby the desired effect of the present invention can be obtained. In the present invention, the details of the tire structure other than that and the material of each member are not particularly limited, and can be appropriately selected from conventionally known ones.

  For example, the carcass 1 is composed of one or more carcass plies formed by covering a plurality of carcass ply cords arranged in parallel with rubber, and in the illustrated example, around the bead core 2 from the inside to the outside in the tire width direction. And is wound up and locked outward in the radial direction of the tire.

  Further, one or more, usually two or more belt layers 6 are disposed on the outer side of the carcass 1 in the tire radial direction. The belt layer 6 is composed of a rubberized layer of a reinforcing cord that extends at an angle of 10 ° to 40 ° with respect to the tire equatorial plane, preferably a rubberized layer of a steel cord, and usually constitutes a belt layer. The cords are stacked so that they cross each other across the equator plane. Further, one or more, usually two or more belt reinforcing layers 7 that cover the entire belt layer 6 are disposed outside the belt layer 6 in the tire radial direction. The belt reinforcing layer 7 is usually composed of a rubberized layer of reinforcing cords arranged substantially parallel to the tire circumferential direction, and is not limited to the illustrated example, and is provided in a pair so as to cover only both ends of the belt layer 6. May be.

  Furthermore, in the tire of the present invention, a tread pattern is appropriately formed on the surface of the tread portion, and an inner liner (not shown) is formed in the innermost layer. Furthermore, in the tire of the present invention, as the gas filled in the tire, normal or air having a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.

  The present invention is particularly useful in a super flat tire having a flat rate of about 40% or less. This is because when the tire flatness is low, that is, when the height is low relative to the width of the tire, the vulcanizing bladder is pressed to press the raw tire against the mold by pressing the raw tire from the inside during tire vulcanization. Since the pressure tends to be low, the thickness of the sidewall portion is likely to increase, but this problem can be solved by changing the mold shape by improving the outer shape of the sidewall portion according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to examples.
<Example>
With a tire size of 255 / 30R20, a run-flat tire having a side reinforcement rubber layer on the sidewall and having a rim guard as shown in FIG. 2 was produced. As shown in the drawing, the outer shape of the sidewall portion in the tire width direction cross section of the tire is such that the intersection B is sandwiched between the split position A of the mold during tire vulcanization on the surface of the sidewall portion and the vertex C of the rim guard. Thus, a convex portion that protrudes outward in the tire width direction and a concave portion that protrudes inward in the tire width direction were formed in order from the outer side in the tire radial direction. Further, the ratio H _AB : H _BC between the tire radial height H _AB between _AB and the tire radial height H _BC between _BC was 1.35.

  The tire maximum width portion is located at a position of 50% of the tire cross-section height SH, and the side reinforcement occupies the total thickness of the sidewall portion measured in the tire width direction at a height of 60% of the tire cross-section height SH. The ratio of the thickness of the rubber layer was 28%. Furthermore, the ratio of the thickness of the bead filler to the total thickness of the sidewall portion measured in the tire width direction is 0% at a height of 50% of the tire cross-section height SH, and is 35% of the tire cross-section height SH. It was 22% in height. Furthermore, the maximum width CW of the carcass case line in the cross section in the tire width direction is 110% of the tread contact width TW and 90% of the tire maximum width SW.

<Conventional example>
A run-flat tire of a conventional example was produced in the same manner as in the example except that the concave portion and the convex portion were not provided on the outer shape of the sidewall portion in the cross section in the tire width direction.

<Run flat durability drum test>
Each of the test tires was assembled on a rim having a rim width of 8.5 J, and a run flat durability drum test was performed under the conditions of an internal pressure of 0 kPa and a load of 510 kgf. The distance traveled until the tire failed was measured and indicated by an index with the conventional example being 100. The higher the number, the better the result. The evaluation results are shown in the following table.

<Body input performance (EP drum) test>
Each of the above test tires was assembled on a rim having a rim width of 8.5 J, and an EP drum test was performed under conditions of an internal pressure of 330 kPa and a load of 610 kgf. The vertical force input to the axle attached to the tire was measured and indicated by an index with the conventional example being 100. The smaller the number, the better the result. The evaluation results are shown in the following table.

＊１）タイヤ断面高さＳＨの５０％の高さにおけるタイヤ幅方向に測ったサイドゴムおよびサイド補強ゴムの厚みである。

* 1) The thickness of the side rubber and the side reinforcing rubber measured in the tire width direction at a height of 50% of the tire cross-section height SH.

  From the results in the above table, by providing the concave region BC and the convex region AB in the outer shape of the sidewall portion in the cross section in the tire width direction, the vehicle body input performance and the run-flat durability performance are compared with the case where it is not provided. It has been confirmed that it is possible to achieve both at a high level required for a new vehicle.

1: carcass, 2: bead core, 3: bead filler, 4: rim guard, 5: side reinforcing rubber layer, 6: belt layer, 7: belt reinforcing layer, 8: concave, 9: convex, 11, 21: bead , 12, 22: Side wall part, 13, 23: Tread part

Claims (7)

It has a pair of bead portions and sidewall portions, and a tread portion continuous between both sidewall portions, and a carcass extending in a toroid shape across the bead portions is used as a skeleton, and side reinforcing rubber is provided on the sidewall portions. In run flat tires with layers,
A run-flat tire characterized in that an outer shape of the sidewall portion in a tire width direction cross section has a concave portion that protrudes inward in the tire width direction at a tire maximum width position. A rim guard is provided, and an outer shape of the sidewall portion in the tire width direction cross section is between the split position A of the mold at the time of tire vulcanization on the sidewall portion surface and the apex C of the rim guard from the outer side in the tire radial direction. Sequentially, having a convex portion that protrudes outward in the tire width direction and the concave portion that protrudes inward in the tire width direction, where B is the intersection of the convex portion and the concave portion, the tire radial direction between AB The run-flat tire according to claim 1, wherein the height H _AB is smaller than the height H _BC in the tire radial direction between _BC .   The ratio of the thickness of the side reinforcing rubber layer to the total thickness of the sidewall portion measured in the tire width direction at a height of 60% of the tire cross-section height SH is 20 to 35%. The described run-flat tire.   The sidewall portion measured in the tire width direction at a height of 50% of the tire cross-section height SH, comprising a bead core embedded in the bead portion and a bead filler disposed on the outer side in the tire radial direction of the bead core. The run-flat tire according to any one of claims 1 to 3, wherein a ratio of the thickness of the bead filler to the total thickness is 0 to 10%.   The sidewall portion measured in the tire width direction at a height of 35% of the tire cross-section height SH, comprising a bead core embedded in the bead portion and a bead filler disposed on the outer side in the tire radial direction of the bead core. The run flat tire according to any one of claims 1 to 4, wherein a ratio of the thickness of the bead filler to the total thickness of the tire is 20 to 30%.   The run-flat tire according to any one of claims 1 to 5, wherein a maximum width CW of the carcass case line in a tire width direction cross section is 105 to 115% of a tread contact width TW.   The run-flat tire according to any one of claims 1 to 6, wherein a maximum width CW of the carcass case line in a tire width direction cross section is 90 to 99% of a maximum tire width SW.

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