JP2011084144A - Run flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a run flat tire improving run flat durability while suppressing the deterioration of cut resistance. <P>SOLUTION: The run flat tire 1 includes a bead portion 10, a carcass 12, and a reinforcing rubber layer 40 having a crescent cross section. The run flat tire 1 includes a protrusion 50 projecting out from an outer surface of a side wall portion 38 toward the outside in a tread width direction. When height in a tire diametrical direction TD from a tire diametrical direction inner end 14 of the bead portion 10 to a tire diametrical direction outer end 16 of the tread portion 34 is made to be cross section height H1, the thickness G of the side wall portion 38 in a run flat ground area A1 wherein height from the tire diametrical direction inner end 14 becomes not more than 75% of the cross section height H1 which is out of a ground end during normal traveling, and not less than 50% of the cross section height H1 which is in the ground end during run flat traveling, is from 1-4 mm. The protrusion 50 extends in the tire circumferential direction, and is provided in the run flat ground area A1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a run-flat tire including a reinforcing rubber layer provided from a tread portion to a sidewall portion and having a crescent-shaped cross section.

  Conventionally, in a run-flat tire in which the vehicle can travel a certain distance (run-flat running) even when the air pressure is greatly reduced or punctured, the cross section along the tread width direction is a crescent shape in the tire sidewall. A structure including a reinforced rubber layer is widely used.

  The reinforcing rubber layer suppresses deformation of the sidewall portion even when the air pressure is greatly reduced, and allows the vehicle to travel a certain distance.

  However, since the reinforcing rubber layer under the run-flat running receives a large stress, the reinforcing rubber layer is accompanied by heat generation inside. As a result, when the run flat running is continued, the temperature inside the reinforcing rubber layer exceeds the fracture limit of the reinforcing rubber layer and reaches 200 ° C. or more. Eventually, the reinforced rubber layer breaks and the run-flat tire fails.

  In order to lengthen the time until the failure of the run-flat tire under such a run-flat running, a method of increasing the elasticity of the composition of the reinforcing rubber layer and the carcass member is known (for example, Patent Documents). 1). Moreover, in order to reduce the temperature inside a reinforcement rubber layer, the method of changing the mixing | blending of the composition of a reinforcement rubber layer and suppressing self-heating is known (for example, patent document 2). Also, a method is known in which a turbulent flow generation projection is provided on the surface of the sidewall portion facing the outside of the vehicle (hereinafter abbreviated as the outer surface as appropriate) to promote cooling of the surface of the sidewall portion. (For example, Patent Document 3). In addition, a method is known in which the sidewall portions and the reinforcing rubber layer are thinned to suppress internal heat generation.

JP 2008-189911 A JP 2008-106148 A JP 2008-222006 A

  Such a run-flat tire with a reduced thickness of the sidewall portion and the reinforcing rubber layer can reduce the rolling resistance of the tire, and thus has the advantage of improving the fuel efficiency of the vehicle and reducing the cost by reducing the raw materials. However, the sidewall portion of the run flat tire in which the thickness of the sidewall portion and the reinforcing rubber layer is reduced is not grounded under traveling under normal internal pressure conditions, but is grounded under run flat traveling. Thereby, the damage (so-called side cut) of the sidewall portion due to stones or debris falling on the road surface easily reaches the carcass cord that is the skeleton member of the tire, and the possibility of tire failure increases. This is fatal as a run-flat tire intended to be able to travel safely over a certain distance even when the air pressure during a puncture is greatly reduced.

  Accordingly, an object of the present invention is to provide a run-flat tire with improved run-flat durability while suppressing a decrease in cut resistance in the sidewall portion when a reinforcing rubber layer is provided.

  In order to solve the above-described problems, the present invention has the following features. First, the first feature of the present invention is that a pair of bead portions (bead portions 10) including at least a bead core (bead core 10a), and a carcass (carcass 12) provided from one bead portion to the other bead portion. And from the tread portion (tread portion 34) to the sidewall portion (sidewall portion 38) continuous with the tread portion, along the tread width direction (tread width direction TW) and the tire radial direction (tire radial direction TD). A run-flat tire (run-flat tire 1) including a reinforcing rubber layer (reinforcing rubber layer 40) having a crescent-shaped cross section, and protrudes outward in the tread width direction from the outer surface of the sidewall portion. A protruding portion (protruding portion 50), and the bead portion from the tire radial direction inner end (tire radial direction inner end 14) When the height along the tire radial direction to the tire radial outer end (tire radial outer end 16) of the red portion is defined as the cross-sectional height (cross-sectional height H1), the tire radial direction from the tire radial inner end A run along which the height along the line is 75% or less of the cross-sectional height outside the ground contact end during normal traveling and 50% or more of the cross-sectional height within the ground contact end during run-flat travel. The average value of the thickness (thickness G) of the sidewall portion in the flat ground contact region (run flat ground contact region A1) is 1 mm or more and 4 mm or less, and the projecting portion extends along the tire circumferential direction. The gist is to be provided in the run-flat grounding region.

  According to such a run-flat tire, a range of 75% or less of the cross-sectional height outside the ground contact end during normal traveling and 50% or more of the cross-sectional height within the ground contact end during run flat travel. The average value of the thickness of the sidewall portion in the run flat ground contact area is 1 mm or more and 4 mm or less. For this reason, it is excellent in heat dissipation compared with the conventional run flat tire, and run flat durability can be improved.

  Further, the protrusion extends along the tire circumferential direction TC and is provided in the run-flat contact area. For this reason, at the time of run flat running, such as when the run flat tire is punctured, the protrusions can suppress foreign matter from reaching the tire surface. Thereby, it can suppress that the cut resistance of a side wall part falls.

  Therefore, it is possible to provide a run-flat tire with improved run-flat durability during run-flat running while suppressing a reduction in cut resistance.

  A second feature of the present invention relates to the first feature of the present invention, wherein a ratio W / H, which is a ratio of the width W of the protrusion to the height H of the protrusion, is 0.8 or more, 1 .3 or less.

  A third feature of the present invention relates to the first or second feature of the present invention, and is a ratio B / W, which is a ratio of a distance B between the protrusion and the adjacent protrusion to the width W of the protrusion. Is summarized as 0.5 or more and 2.0 or less.

  A fourth feature of the present invention is according to any one of the first to third features of the present invention, wherein a ratio of the width W of the protrusion to the height H of the protrusion is a ratio W / H. In addition, when the ratio of the distance B between the protruding portion and the adjacent protruding portion to the width W of the protruding portion is a ratio B / W, the height along the tire radial direction from the tire radial direction inner end is The ratio W / H at a position of 75% of the cross-sectional height is 0.8 or more and 1.0 or less, the ratio B / W is 0.5 or more and 1.3 or less, and the tire diameter The ratio W / H at a position where the height along the tire radial direction from the inner end in the direction is 50% of the cross-sectional height is 1.0 or more and 1.3 or less, and the ratio B / W is 1. The gist is that it is 3 or more and 2.0 or less.

  A fifth feature of the present invention relates to any one of the first to fourth features of the present invention. In the side view of the tire, the protrusion is a straight line along the tire circumferential direction (tire circumferential direction TC). On the other hand, the gist is provided in a zigzag shape.

  A sixth feature of the present invention relates to any one of the first to fifth features of the present invention, and in the side view of the tire, the projection includes the first projection (first projection 52B), A second protrusion (second protrusion 54B) intersecting the first protrusion, and the first protrusion is inclined with respect to a straight line along the second protrusion, and the second protrusion Is summarized in that it is inclined to the opposite side to the first protrusion with respect to the straight line along the second protrusion.

  A seventh feature of the present invention relates to any one of the first to sixth features of the present invention, and the average value of the thickness of the sidewall portion in the run-flat ground region is 1.0 mm or more and 4.0 mm. The average value of the thickness of the sidewall portion at a position where the height along the tire radial direction from the inner end in the tire radial direction is 50% of the cross-sectional height is 1.0 mm or greater and 3.0 mm or less. The height H of the protrusion, which is the height from the outer surface, is 1.0 mm or more and 4.0 mm or less.

  According to the characteristics of the present invention, when a reinforcing rubber layer is provided, it is possible to provide a run-flat tire with improved run-flat durability while suppressing a reduction in cut resistance.

1 is a partially exploded perspective view of a run flat tire according to an embodiment of the present invention. It is sectional drawing of the tread width direction and tire radial direction of the run flat tire which concerns on embodiment of this invention. It is a partial expanded sectional view of the tread width direction and tire radial direction of the run flat tire concerning the embodiment of the present invention. It is an expanded sectional view of the projection part of the run flat tire concerning the embodiment of the present invention. It is a partial exploded perspective view of a run flat tire concerning modification 1 of an embodiment of the present invention. It is a partially exploded perspective view of a run flat tire concerning modification 2 of an embodiment of the present invention. It is an expanded sectional view of a projection part of a run flat tire concerning modification 3 of an embodiment of the present invention. It is a figure which shows the curb used by cut resistance evaluation of this invention.

  Next, an embodiment of a run flat tire according to the present invention will be described with reference to the drawings. Specifically, (1) the configuration of the run-flat tire, (3) comparative evaluation, (4) action and effect, and (4) other embodiments will be described. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones.

  Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(1) Configuration of Run Flat Tire FIG. 1 is a partially exploded perspective view including a cross section in the tread width direction of the run flat tire 1 in the embodiment of the present invention. FIG. 2 is a cross-sectional view of the run flat tire 1 in the tread width direction and the tire radial direction. FIG. 3 is a partially enlarged cross-sectional view of the run flat tire 1 in the tread width direction and the tire radial direction.

  In FIGS. 1 and 2, hatching of a partial cross section is omitted in order to clarify the position of the carcass and the like. The run flat tire 1 shown in FIGS. 1 to 3 is a run flat tire excellent in durability at high speed traveling particularly when the air pressure is greatly reduced. Specifically, (1.1) bead portion, (1.2) carcass, (1.3) belt layer, (1.4) reinforcing rubber layer, and (1.5) protrusion 50 will be described.

(1.1) Bead part The run-flat tire 1 has a pair of bead parts 10 including at least a bead core 10a and a bead filler 10b. Specifically, a steel cord or the like is used for the bead core 10a constituting the bead unit 10.

(1.2) Carcass
The run-flat tire 1 includes a carcass 12 provided from one bead portion 10 to the other bead portion 10. The carcass 12 is folded back from the inner side in the tire radial direction to the outer side in the tire radial direction around the bead core 10a. The carcass 12 is made of a carcass cord and rubber, and forms a skeleton of the run-flat tire 1.

(1.3) Belt Layer The run-flat tire 1 includes a belt layer 24 having two cross belt layers (belt layer 20a and belt layer 20b) and at least one additional belt layer 22.

(1.4) Reinforced rubber layer
The run-flat tire 1 includes a reinforcing rubber layer 40 provided from the tread portion 34 to the sidewall portion 38 and having a crescent-shaped cross section along the tread width direction TW and the tire radial direction TD. An inner liner 18 that is a highly airtight rubber layer corresponding to a tube is provided inside the carcass 12 and the reinforcing rubber layer 40 in the tire radial direction.

  The reinforcing rubber layer 40 reinforces the sidewall portion 38. In the cross section along the tread width direction TW and the tire radial direction TD, the reinforcing rubber layer 40 becomes thicker as it goes from the tread portion 34 toward the sidewall portion 38, and becomes thicker as it goes from the bead core 10 a toward the sidewall portion 38.

  Moreover, in the cross section along the tread width direction TW and the tire radial direction TD, the average value of the thickness G of the sidewall portion 38 in the run-flat contact region A1 is 1 mm or more and 4 mm or less.

  The run-flat ground contact area A1 is the air pressure of the run-flat tire 1 that is a prescribed air pressure such as JATMA. When the height along the tire radial direction TD to the tire radial outer end 16 is defined as the cross-sectional height H1, the height along the tire radial direction TD from the tire radial inner end 14 is the ground contact during normal driving. The range is 75% or less of the cross-sectional height H1 that is outside the end, and 50% or more of the cross-sectional height H1 that is inside the ground contact end during run-flat travel. That is, the run flat ground contact area A1 indicates an area where the height along the tire radial direction TD from the tire radial inner end 14 is in the range of H3 to H2.

  Note that the above-described normal traveling means a case where the air pressure of the run-flat tire 1 is set to a prescribed air pressure such as JATMA and the vehicle is traveling at a speed of 80 km / h in a vehicle in a maximum load state.

  The run-flat running means a case where the run-flat tire 1 runs at a speed of 80 km / h in a vehicle in a maximum load state when the air pressure is greatly reduced, such as when the run-flat tire 1 is punctured.

  Further, the thickness G of the sidewall portion 38 is perpendicular to the carcass 12 in a cross section along the tread width direction TW and the tire radial direction TD after setting the air pressure of the run flat tire 1 to a prescribed air pressure such as JATMA. The thickness from the carcass 12 in the appropriate direction to the outer surface of the side tread (that is, the outer surface of the sidewall portion 38) is shown.

  Specifically, the thickness G2 at the position of 75% of the cross-sectional height H1, that is, the height H2, is 1.0 mm or more and 4.0 mm or less, and is set to 2.5 mm, for example. The thickness G1 at the position of 50% of the cross-sectional height H1, that is, the height H3 is 1.0 mm or more and 3.0 mm or less, and is set to 1.5 mm, for example.

(1.5) Projection 50
Next, details of the protrusion 50 will be described with reference to FIGS. FIG. 4 shows an enlarged view of the cross section of the protrusion 50.

  As shown in FIG. 1, the run flat tire 1 includes a protrusion 50. The protrusion 50 protrudes outward in the tread width direction from the outer surface 56 (see FIG. 4) of the sidewall portion 38. The protrusion 50 extends along the tire circumferential direction TC, and is provided in a region where the height along the tire radial direction TD from the tire radial inner end 14 is 50% or more of the cross-sectional height H1.

  The protrusion 50 is provided in the run flat grounding area A1. The protrusion 50 is more preferably provided in a region where the height along the tire radial direction TD from the tire radial inner end 14 is 60% or more and 75% or less of the cross-sectional height H1.

  As shown in FIG. 4, in the cross section along the tread width direction TW and the tire radial direction TD, the protrusion 50 protrudes in a rectangular shape from the outer surface 56 of the sidewall portion 38 in the vertical direction. A length along the vertical direction from the outer surface 56 of the sidewall portion 38 is defined as a height H of the protrusion 50. Specifically, the height H of the protrusion 50 is set to 1.0 mm or more and 4.0 mm or less, for example, 3.0 mm. Further, in the cross section along the tread width direction TW and the tire radial direction TD, the length in the direction along the outer surface 56 of the sidewall portion 38 is defined as the width W of the protrusion 50. For example, the width W of the protrusion 50 is set to 3.0 mm. Further, the length in the direction along the outer surface 56 between the protrusion 50 and the adjacent protrusion 50 is defined as the interval B of the protrusion 50. For example, the interval B between the protrusions 50 is set to 0.8 mm or more and 9.0 mm or less. More preferably, the interval B between the protrusions 50 is set to 1.5 mm or more and 6.0 mm or less. The ratio W / H, which is the ratio of the width W of the protrusion 50 to the height H of the protrusion 50, is 0.8 or more and 1.3 or less. The ratio B / W, which is the ratio of the interval B to the width W of the protrusion 50, is 0.5 or more and 2.0 or less.

  Specifically, the ratio W / H when the height along the tire radial direction TD from the tire radial inner end 14 is 75% of the cross-sectional height H1 (that is, the height H2) is 0.8 or more. 1.0 or less, and the ratio B / W is preferably 0.5 or more and 1.3 or less. The ratio W / H at 75% of the cross-sectional height H1 (that is, the height H2) is more preferably 0.8 and the ratio B / W is more preferably 0.5. Further, the ratio W / H at 50% or more of the sectional height H1 (that is, the height H3) is 1.0 or more and 1.3 or less, and the ratio B / W is 1.3 or more and 2.0 or less. It is preferable that It is more preferable that the ratio W / H is 1.3 and the ratio B / W is 2.0 at 50% or more of the cross-sectional height H1 (that is, the height H3).

(2) Modified Example In the modified example, protrusions having different shapes along the tire circumferential direction TC will be described with reference to FIGS. FIG. 5 is a partially exploded perspective view of a run-flat tire according to Modification 1 of the embodiment of the present invention. FIG. 6 is a partially exploded perspective view of a run flat tire according to Modification 2 of the embodiment of the present invention. FIG. 7 is an enlarged cross-sectional view of a protrusion of the run flat tire according to the embodiment of the present invention. Note that, in the following modifications, differences from the embodiment will be mainly described, and redundant description will be omitted.

(2.1) Modification 1
As shown in FIG. 5, in a side view of the tire, the protrusion 50A is provided in a zigzag shape with respect to a straight line L1 along the tire circumferential direction TC. Specifically, the angle θ1 formed by the straight line L1 along the tire circumferential direction TC and the straight line passing through the center of the protrusion 50A is 0 degree or greater and 45 degrees or less.

(2.2) Modification 2
As illustrated in FIG. 6, the protrusion 50B includes a first protrusion 52B and a second protrusion 54B that intersects the first protrusion 52B. The first protrusion 52B is inclined with respect to the straight line L1 along the tire circumferential direction TC. The second protrusion 54B is inclined to the opposite side of the first protrusion 52B with respect to the straight line L1 along the tire circumferential direction TC. Specifically, the angles θ2 and θ3 formed by the straight line L1 along the tire circumferential direction TC and the straight line L1 passing through the centers of the first protrusion 52B and the second protrusion 54B are 22.5 degrees or more, 67. 5 degrees or less. More preferably, the angles θ2 and θ3 are set to 45 degrees. The second protrusion 54B is positioned symmetrically with respect to the first protrusion 52B with reference to the straight line L1 along the tire circumferential direction TC.

(2.3) Modification 3
As shown in FIG. 7, in the cross section along the tread width direction TW and the tire radial direction TD, the protruding portion 50C protrudes from the outer surface 56C of the sidewall portion 38C in a convex shape in the vertical direction. Specifically, the protrusion 50C is formed in a curved convex shape. Further, the outer side surface of the sidewall portion 38C is connected to the protruding portion 50C, and the outline of the protruding portion 50C and the outer side surface of the sidewall portion 38C is formed in a wave shape.

(3) Comparative Evaluation Next, in order to further clarify the effects of the present invention, comparative evaluation performed using pneumatic tires according to the following comparative examples and examples will be described. Specifically, (3.1) Evaluation method and (3.2) Evaluation result will be described. In addition, this invention is not limited at all by these examples.

(3.1) Evaluation Method Using three types of run flat tires, (3.1.1) tire internal temperature run flat running evaluation, (3.1.2) run flat durability evaluation, and (3.1) .3) The cut resistance was evaluated. Data on run-flat tires were measured under the following conditions.

・ Tire size: 245 / 45R19
・ Rim size: 8J-19
・ Air pressure condition: 0kPa
・ Test model: Automobile ・ Load condition: 585kgf
・ Camber angle: 0 degree ・ Slip angle: 0 degree Each run-flat tire has different sidewall thickness, presence / absence of protrusion, shape of protrusion, ratio W / H, ratio B / W The other configuration is the same as that of the run flat tire 1 of the present embodiment.

  The run flat tires according to Comparative Examples 1 and 2 are not provided with a protrusion. Further, the sidewall portion of the run flat tire according to Comparative Example 1 is thicker than the sidewall portion of the run flat tire 1 of the present embodiment. The run flat tires according to Examples 1 to 8 are the same as the run flat tire 1 according to this embodiment except for the shape of the protrusions.

(3.1.1) Tire internal temperature run-flat running evaluation Evaluation method: Each run-flat tire is mounted on a test drum, the speed is set to 80 km / h, and after running for 30 minutes, the inside of the reinforcing rubber layer of the run-flat tire The temperature of was measured.

(3.1.2) Run flat durability evaluation Evaluation method: Each run flat tire was mounted on a test drum, the speed was set to 80 km / h, and the running distance when a failure occurred was measured. In addition, the measurement result of each run flat tire was shown as an index with the run flat durability of the run flat tire according to Comparative Example 1 as 100. The larger the index value, the better the run flat durability.

(3.1.3) Cut Resistance Evaluation Method: Cut resistance was evaluated using the curbstone 200 shown in FIG. FIG. 8A shows a front view of the curbstone 200. FIG. 8B shows a side view of the curbstone 200. FIG. 8 (c) shows a plan view of the curbstone 200. As shown in FIG. 8, the curb stone 200 has a height of 5 mm and a width of 500 mm, and the tip angle is 45 degrees.

  Specifically, each run flat tire is mounted on a vehicle, passes over the curb 200 at an angle of 30 degrees with respect to the curb 200 shown in FIG. On the outer surface, the carcass cord was checked for breakage. The evaluation starts at a speed of 20 km / h and increases at a speed of every 2.5 km / h, and a fracture that occurs in a part of the outer side surface of the sidewall portion (excluding the protruding portion) reaches the carcass. The speed when this was confirmed visually was recorded. In addition, the measurement result of each run flat tire was indicated as an index with the cut resistance of the run flat tire according to Comparative Example 1 as 100. The larger the index value, the better the cut resistance.

(3.2) Evaluation Results The evaluation results of each run flat tire will be described with reference to Table 1.

  The run flat tire according to Comparative Example 2 showed durability superior to the run flat tire according to Comparative Example 1, but the cut resistance was reduced. The run-flat tires according to Examples 1 to 8 have cut resistance equivalent to that of Comparative Example 1, but have durability equivalent to that of Comparative Example 1 and Comparative Example 2, or superior to Comparative Example 1 and Comparative Example 2. Indicated. In particular, the run flat tires according to Examples 2, 3, 6, and 7 were able to achieve both cut resistance and durability at a high level.

(4) Actions / Effects As described above, according to the run flat tire 1 according to the present embodiment, 75% or less of the cross-sectional height H1 that is outside the ground contact end during normal running, and during run flat running. The average value of the thickness G of the sidewall portion 38 in the run-flat contact region A1 that is 50% or more of the cross-sectional height H1 in the contact end is 1 mm or more and 4 mm or less.

  For this reason, it is excellent in heat dissipation compared with the conventional run flat tire, and run flat durability can be improved.

  Further, the protrusion 50 extends along the tire circumferential direction TC and is provided in the run-flat contact area A1. For this reason, during run flat running such as when the run flat tire 1 is punctured, the protrusion 50 can suppress foreign matter from reaching the tire surface. Thereby, generation | occurrence | production of a side cut can be suppressed, ie, it can suppress that the cut resistance of the reinforcement rubber layer 40 falls.

  Therefore, it is possible to provide a run-flat tire with improved run-flat durability during run-flat running while suppressing a reduction in cut resistance.

  According to the present embodiment, the ratio W / H, which is the ratio of the width W of the protrusion 50 to the height H of the protrusion 50, is 0.8 or more and 1.3 or less. When the ratio W / H is 0.8 or more, the protrusion 50 can be prevented from falling down. Moreover, the ratio W / H is 1.3 or less, so that heat dissipation from the outer surface 56 where the protrusions 50 are not provided can be promoted.

  According to the present embodiment, the ratio B / W, which is the ratio of the distance B between the protrusion 50 and the adjacent protrusion 50 to the width W of the protrusion 50, is 0.5 or more and 2.0 or less. . When the ratio B / W is 0.5 or more, heat dissipation from the outer surface 56 where the protrusions 50 are not provided can be promoted. When the ratio B / W is 2.0 or less, the protection effect of the sidewall portion 38 (that is, the side portion) by the protrusion 50 can be obtained.

  According to this embodiment, the ratio W / H at a position where the height along the tire radial direction TD from the tire radial inner end 14 is 75% of the cross-sectional height H1 is 0.8 or more and 1.0. Hereinafter, the ratio B / W is 0.5 or more and 1.3 or less. For this reason, at the position of 75% of the cross-sectional height H1, it is possible to efficiently achieve both the protection effect of the sidewall portion 38 and the improvement of heat dissipation.

  Further, the ratio W / H at a position where the height along the tire radial direction TD from the tire radial direction inner end 14 is 50% of the cross-sectional height H1 is 1.0 or more and 1.3 or less, and the ratio B / W is 1.3 or more and 2.0 or less. For this reason, at the position of 50% of the cross-sectional height H1, heat radiation from the outer surface 56 of the sidewall portion 38 can be further promoted while ensuring the necessary minimum protection effect of the sidewall portion 38.

  According to the first modification of the present embodiment, the protrusion 50A is inclined with respect to the straight line L1 along the tire circumferential direction TC in a side view of the tire. For this reason, the protrusion 50 </ b> A generates turbulent flow on the outer surface 56 of the sidewall portion 38 as the tire rolls. Thereby, the heat radiation from the outer surface 56 of the sidewall portion 38 can be further promoted.

  According to the second modification of the present embodiment, in the side view of the tire, the protrusion 50B includes the first protrusion 52B and the second protrusion 54B, and the first protrusion 52B and the second protrusion 54B. Is inclined with respect to a straight line L1 along the tire circumferential direction TC. For this reason, the protrusion 50 </ b> B generates turbulent flow on the outer surface 56 of the sidewall portion 38 as the tire rolls. Thereby, the heat radiation from the outer surface 56 of the sidewall portion 38 can be further promoted.

  Further, the second protrusion 54B is inclined to the opposite side to the first protrusion 52B with respect to the straight line L1 along the tire circumferential direction TC. That is, the first protrusion 52B and the second protrusion 54B intersect each other and support each other in a side view of the tire, so that the rigidity of the first protrusion 52B and the second protrusion 54B can be further increased. Thereby, the fall of the 1st projection part 52B and the 2nd projection part 54B at the time of grounding can be suppressed.

  Note that the angles θ2 and θ3 of the first protrusion 52B and the second protrusion 54B are set to 45 degrees, so that the first protrusion 52B and the second protrusion 54B support each other most effectively. The rigidity of the first protrusion 52B and the second protrusion 54B can be effectively increased.

(4) Other Embodiments As described above, the contents of the present invention have been disclosed through the embodiments of the present invention. However, it is understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. Should not. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, the embodiment of the present invention can be modified as follows. In the embodiment described above, in the cross section along the tread width direction TW and the tire radial direction TD, the shape of the adjacent protrusions 50 is substantially the same shape, but is not limited to this, and gradually the ratio W / H, The shape may change the ratio B / W.

In the above-described embodiment, in the cross section along the tread width direction TW and the tire radial direction TD, the protrusion 50 protrudes from the outer surface 56 of the sidewall 38 in a rectangular shape in the vertical direction. However, the present invention is not limited to this. For example, in the cross section along the tread width direction TW and the tire radial direction TD, the protrusion 50 protrudes in a triangular shape from the outer surface 56 of the sidewall 38 in the vertical direction. Also good. Further, in the cross section along the tread width direction TW and the tire radial direction TD, the outer side surface 56 of the sidewall portion 38 is connected to the protruding portion 50, and the contour line between the protruding portion 50 and the outer side surface 56 of the sidewall portion 38. May be formed in a zigzag shape.
As described above, the present invention naturally includes various embodiments that are not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

θ1, θ2 ... angle, A1 ... ground contact area, A2 ... non-ground contact area, B ... spacing, B / W ... ratio, L1 ... straight line, TC ... tire circumferential direction, TD ... tire radial direction, TW ... tread width direction, W / H ... ratio, 1 ... run flat tire, 10 ... bead portion, 10a ... bead core, 10b ... bead filler, 12 ... carcass, 14 ... tire radial inner end, 16 ... tire radial outer end, 18 ... inner liner, 20a, 20b ... belt layer, 22 ... additional belt layer, 24 ... belt layer, 34 ... tread portion, 38, 38C ... sidewall portion, 40 ... reinforcing rubber layer, 50, 50A, 50B, 50C ... projection, 52B ... 1st protrusion part, 54B ... 2nd protrusion part, 200 ... curbstone

Claims (7)

A pair of bead portions including at least a bead core;
A carcass provided from one bead part to the other bead part;
A reinforcing rubber layer provided from the tread portion to a sidewall portion connected to the tread portion and having a crescent-shaped cross-sectional shape along the tread width direction and the tire radial direction,
A run-flat tire comprising:
Protruding portions that protrude from the outer surface of the sidewall portion toward the outer side in the tread width direction,
When the height along the tire radial direction from the tire radial direction inner end of the bead portion to the tire radial direction outer end of the tread portion is the cross-sectional height,
The height along the tire radial direction from the inner end in the tire radial direction is 75% or less of the cross sectional height outside the ground contact end during normal running, and the cross sectional height within the ground contact end during run flat running The average value of the thickness of the sidewall portion in the run flat ground contact area that is 50% or more of the thickness is 1 mm or more and 4 mm or less,
The protrusion is a run-flat tire that extends along a tire circumferential direction and is provided in the run-flat contact area.   2. The run-flat tire according to claim 1, wherein a ratio W / H, which is a ratio of the width W of the protrusion to the height H of the protrusion, is 0.8 or more and 1.3 or less.   The ratio B / W, which is the ratio of the interval B between the protrusion and the adjacent protrusion, to the width W of the protrusion is 0.5 or more and 2.0 or less. Run flat tire. The ratio of the width W of the protrusion to the height H of the protrusion is a ratio W / H, and the ratio of the interval B between the protrusion and the adjacent protrusion to the width W of the protrusion Is the ratio B / W,
The ratio W / H at a position where the height along the tire radial direction from the tire radial direction inner end is 75% of the cross-sectional height is 0.8 or more and 1.0 or less, and the ratio B / W is 0.5 or more and 1.3 or less,
The ratio W / H at a position where the height along the tire radial direction from the tire radial direction inner end is 50% of the cross-sectional height is 1.0 or more and 1.3 or less, and the ratio B / W is The run flat tire according to any one of claims 1 to 3, wherein the run flat tire is 1.3 or more and 2.0 or less. In the side view of the tire,
The run-flat tire according to any one of claims 1 to 4, wherein the protrusion is provided in a zigzag shape with respect to a straight line along the tire circumferential direction. In the side view of the tire,
The protrusion is composed of a first protrusion and a second protrusion that intersects the first protrusion.
The first protrusion is inclined with respect to a straight line along the tire circumferential direction,
The run-flat tire according to any one of claims 1 to 5, wherein the second protrusion is inclined to the opposite side of the first protrusion with respect to a straight line along the tire circumferential direction. The average value of the thickness of the sidewall portion at a position where the height along the tire radial direction from the tire radial direction inner end is 75% of the cross-sectional height is 1.0 mm or more and 4.0 mm or less,
The average value of the thickness of the sidewall portion at a position where the height along the tire radial direction from the tire radial direction inner end is 50% of the cross-sectional height is 1.0 mm or more and 3.0 mm or less,
The run-flat tire according to any one of claims 1 to 6, wherein a height H of the protrusion, which is a height from the outer surface, is 1.0 mm or greater and 4.0 mm or less.

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