JP5006629B2 - Run flat tire - Google Patents

Description

  The present invention relates to a run-flat tire that can be reduced in weight and can improve riding comfort.

  Conventionally, there has been known a run-flat tire that can continuously travel at a relatively high speed for a certain distance (hereinafter referred to as “run-flat travel”) even when the air from the tire is removed due to puncture or the like. (See Patent Documents 1 and 2 below). This type of run-flat tire is provided with side reinforcing rubber having a substantially crescent-shaped cross section in order to increase the bending rigidity of the sidewall portion. When tire air escapes, the longitudinal deflection of the tire is suppressed by the bending rigidity of the side reinforcing rubber.

  However, this type of run-flat tire has problems such as deterioration of fuel consumption performance due to an increase in tire mass and deterioration of riding comfort during normal driving when the internal pressure is properly filled due to the provision of side reinforcing rubber. Cheap.

  In order to solve such a problem, the present applicant has already proposed the following Patent Document 3. The run-flat tire has a plurality of groove-shaped depressions extending inward and outward in the tire radial direction and spaced in the tire circumferential direction on the inner surface of the side reinforcing rubber at an angle of 0 to 60 degrees with respect to the tire radial direction. Is provided. Such a run-flat tire can reduce the weight of the tire by reducing the volume of the side reinforcing rubber. However, there is room for further improvement in terms of improving ride comfort during normal driving.

JP 2002-301911 A Japanese Patent No. 2999489 JP 2005-67315 A

  The present invention has been devised in view of the above problems, and is based on limiting the maximum length, width, and spacing pitch of the concave grooves provided on the inner surface of the side reinforcing rubber. The main purpose is to provide a run-flat tire that can further reduce weight and improve riding comfort without impairing durability.

The invention according to claim 1 is a toroidal carcass that extends from the tread portion through the sidewall portion to the bead core of the bead portion, and is arranged inside the carcass and along the sidewall portion in the tire radial direction. A run-flat tire including a side reinforcing rubber extending on the inner surface facing the tire lumen side of a base having a substantially crescent-shaped cross section with a reduced thickness from the central portion to the inside and outside of the tire in the radial direction of the tire. A plurality of concave grooves each having a concave inner surface are provided in the circumferential direction of the tire, and each concave groove has two end portions provided without protruding from the inner surface of the side reinforcing rubber, and The maximum length between the end portions is 30 to 50 mm , the groove width is 10 to 20 mm, the separation pitch in the tire circumferential direction of the groove is 25 to 60 mm , and the groove has a groove width. large And a wide portion, characterized in that a substantially T-shape comprising a small narrow portion groove width than the width wide portion.

According to a second aspect of the present invention, the concave groove includes a first concave groove in which the wide portion faces the tread portion side, and a second concave groove in which the wide portion faces the bead portion side. The run-flat tire according to claim 1 , wherein the grooves and the second concave grooves are provided alternately in the tire circumferential direction .

The invention according to claim 3, wherein the groove is a run-flat tire according to claim 1, characterized in that disposed toward a wide portion in the tread portion side.

  The invention according to claim 4 is the run flat tire according to any one of claims 1 to 3, wherein the concave groove is inclined at 25 to 65 degrees with respect to a tire radial direction.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the concave grooves provided in the side reinforcing rubbers on both sides are inclined in the same rotational direction from the bead portion side toward the tread portion side. It is the run flat tire of description.

  According to a sixth aspect of the present invention, the concave groove provided in one side reinforcing rubber is inclined in the first rotation direction from the bead portion side toward the tread portion side and provided in the other side reinforcing rubber. The run-flat tire according to any one of claims 1 to 4, wherein the recessed groove formed is inclined in a second rotation direction opposite to the first rotation direction from the bead portion side toward the tread portion side. is there.

Further, the invention according to claim 7 is a tire meridian cross section including a tire rotation axis in a normal unloaded state in which a normal rim is assembled and a normal inner pressure is filled, and the tire outer surface profile is the tire outer surface. When the point on the outer surface of the tire separating the distance (SP) of 45% of the maximum tire width (SW) from the intersection (CP) between the tire and the tire equator (C) is (P), the point from the intersection (CP) The run-flat tire according to any one of claims 1 to 6, wherein the radius of curvature (RC) of the tire outer surface gradually decreases toward the outer side in the tire axial direction and satisfies the following relationship in a section up to (P): is there.
0.05 <Y60 / H ≦ 0.1
0.1 <Y75 / H ≦ 0.2
0.2 <Y90 / H ≦ 0.4
0.4 <Y100 / H ≦ 0.7
(Where Y60, Y75, Y90 and Y100 are the tire axial distances of 60%, 75%, 90% and 100% of the half width (SW / 2) of the maximum tire width in the tire axial direction from the intersection (CP). (The distances in the tire radial direction between the points P60, P75, P90 and P100 on the outer surface of the tire and the intersections (CP), and H is the tire cross-section height.)

  The run-flat tire of the present invention is further limited without impairing run-flat durability by limiting the maximum length, width and spacing pitch of the concave grooves provided on the inner surface of the side reinforcing rubber facing the tire lumen side. Weight reduction and ride comfort can be improved.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
1 is a cross-sectional view of the run-flat tire 1 of the present embodiment in a normal unloaded state, FIG. 2 is a cross-sectional view at a tire circumferential position different from FIG. 1, and FIG. 3 is a partially enlarged side wall portion of FIG. 4 and 4 are partial perspective views of the tire 1 as seen from the lumen side. Unless otherwise specified, the dimensions and the like of the tire are described as those in the normal no-load state.

  Here, the “regular no-load state” refers to a no-load state in which the run-flat tire 1 is assembled to the regular rim J and filled with the regular internal pressure.

  In addition, the “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, For ETRTO, use “Measuring Rim”.

  Furthermore, the “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA and the table “TIRE LOAD” is TRA. The maximum value described in “LIMITS AT VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 kPa for tires for passenger cars.

  The run-flat tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt layer 7 disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2. A bead apex 8 extending from the outer surface of the bead core 5 in the radial direction of the tire to the outer side in the radial direction of the tire, an inner liner rubber 10 made of rubber having a gas barrier property disposed inside the carcass 6, and the inner A side reinforcing rubber 9 disposed inside the liner rubber 10 and at least a part of the sidewall portion 3.

The carcass 6 is formed of at least one carcass ply 6A having a carcass cord arranged at an angle of, for example, 70 to 90 ° with respect to the tire equator C, in this embodiment, one carcass ply 6A. The carcass cord is preferably an organic fiber cord such as nylon, polyester, rayon or aromatic polyamide. The carcass ply 6A includes a toroidal main body portion 6a extending between the bead cores 5 and 5 and a pair of folded portions provided on both sides thereof and folded around the bead core 5 from the inner side to the outer side in the tire axial direction. and a part 6b.

  The bead apex rubber 8 is disposed between the main body portion 6a and the folded portion 6b of the carcass ply 6A. The bead apex rubber 8 is made of a relatively hard rubber, for example, having a rubber hardness of 65 to 95 degrees or more, more preferably 70 to 90 degrees, thereby increasing the bending rigidity of the bead portion 4 and thus improving the handling stability. To help.

  In the present embodiment, the folded portion 6b of the carcass ply 6A extends beyond the outer end 8t of the bead apex rubber 8 outward in the tire radial direction, and the outer end portion 6be is between the main body portion 6a and the belt layer 7. It is in the position between. Thereby, the side wall part 3 is effectively reinforced by one carcass ply 6A.

  The belt layer 7 is composed of two belt plies 7A and 7B having belt cords (steel cords in this embodiment) arranged at an angle of 10 to 35 ° with respect to the tire equator C, for example.

  The inner liner rubber 10 is disposed in a toroidal shape so as to straddle between the bead portions 4 and 4 along the inside of the carcass 6 in order to retain air in the tire lumen i. The inner liner rubber 10 is formed of a rubber composition having gas barrier properties such as butyl rubber, halogenated butyl rubber and / or brominated butyl rubber.

  As shown in FIGS. 1 and 2, the side reinforcing rubber 9 of the present embodiment is disposed inside the carcass 6 and the inner liner rubber 10, and from the center to the inner end 9 i and the outer end 9 o in the tire radial direction. Each of the base portions 9B includes a base portion 9B that gradually decreases in thickness toward the side wall portion 3 and smoothly curves and extends along the side wall portion 3. Further, the side reinforcing rubber 9 is provided continuously in an annular shape in the tire circumferential direction.

  The inner end 9 i of the side reinforcing rubber 9 is provided on the inner side in the tire radial direction with respect to the outer end 8 t of the bead apex 8 and on the outer side in the tire radial direction with respect to the bead core 5. Thereby, the bending rigidity from the side wall part 3 to the bead part 4 is improved with good balance. Further, the outer end 9o of the side reinforcing rubber 9 extends, for example, to the inside of the tread portion 2, and is provided at a position on the inner side in the tire axial direction from the outer end 7e of the belt layer 7 in this embodiment. Thereby, the rigidity of a buttress part etc. is improved effectively.

  The length L in the tire radial direction between the inner end 9i and the outer end 9o of the side reinforcing rubber 9 (that is, the length in the tire radial direction of the side reinforcing rubber 9) is not particularly limited. It is difficult to obtain the reinforcing effect, and on the other hand, even if it is too large, there is a tendency to deteriorate the ride comfort and rim assemblability during normal driving. From such a viewpoint, the length L is preferably 35 to 70%, more preferably about 40 to 65% of the tire cross-section height H, but it is preferably at least 60 mm or more. The tire cross-section height H is a distance from the bead base line BL to the outermost position in the tire radial direction.

  Further, the thickness t of the side reinforcing rubber 9 can be appropriately determined according to the load applied and the tire size. However, if the maximum thickness tc (shown in FIG. 2) is too small, the sidewall portion 3 It is difficult to obtain a reinforcing effect. From such a viewpoint, the maximum thickness tc is preferably 5 mm or more, more preferably 9 mm or more. On the other hand, if the maximum thickness tc is too large, tire mass may increase and excessive heat generation may occur. Therefore, the thickness tc is preferably 20 mm or less, more preferably 15 mm or less, and even more preferably 11 mm or less. desirable.

  Further, in order to suppress the longitudinal deflection of the tire during the run-flat running, the hardness of the side reinforcing rubber 9 is preferably 60 degrees or more, more preferably 65 degrees or more. On the other hand, if the hardness of the side reinforcing rubber 9 is too large, the vertical spring of the tire becomes remarkably large and the ride comfort during normal running tends to be remarkably deteriorated. Therefore, it is preferably 95 degrees or less, more preferably 85 degrees or less. Is desirable.

  In addition, in this specification, the hardness of rubber shall be the hardness by durometer type A based on JIS-K6253.

  Further, the side reinforcing rubber 9 has a plurality of concave grooves 11 in which the inner surface 9Bi is recessed in the tire circumferential direction on the inner surface 9Bi facing the tire lumen side of the base portion 9B. The concave grooves 11 of the present embodiment extend substantially parallel to the tire radial direction, and the same shape is provided at a constant tire circumferential pitch around the tire rotation axis.

  Further, as shown in FIGS. 4 and 5, each concave groove 11 includes a tire radial outer end portion 11 o and an inner end portion 11 i provided without protruding from the inner surface 9Bi of the side reinforcing rubber 9. Has two ends. Further, the concave groove 11 of the present embodiment extends across the tire maximum width position M, whereby the end portions 11i and 11o are provided on both sides of the tire maximum width position M, respectively.

  In the present invention, the maximum length L1 between the end portions 11i and 11o of the groove 11 is 30 to 50 mm, and the groove width W1 of the groove 11 is set to 10 to 20 mm. Here, as shown in FIG. 4, the maximum length L1 is the maximum length between the end portions 11i and 11o, and is measured along the inner surface 9Bi of the base portion 9B. The groove width of the concave groove 11 is an opening width, and is measured in a direction perpendicular to the maximum length direction.

  When the maximum length L1 of the concave groove 11 is less than 30 mm or the groove width W1 is less than 10 mm, the tire radial rigidity (longitudinal rigidity) of the side reinforcing rubber 9 cannot be alleviated sufficiently, thereby improving the ride comfort. Cannot be realized. On the contrary, when the maximum length L1 of the concave groove 11 is larger than 50 mm or the groove width W1 is larger than 20 mm, the rigidity in the tire radial direction of the side reinforcing rubber 9 is excessively decreased, and as a result, the run due to the decrease in the load supporting ability The flat durability deteriorates.

  FIG. 6 is a cross-sectional view taken along the line AA in FIG. The cross-sectional shape of the concave groove 11 may be rectangular as shown in FIG. 1A, but preferably as shown in FIG. 1B, the groove width 11b becomes smaller toward the groove bottom side. It is desirable that the groove walls 11w on both sides are inclined and the corner portion between the groove wall 11w and the groove bottom 11b is chamfered with an arc. The concave groove 11 having such a cross-sectional shape can suppress the occurrence of cracks or the like in the corner portion or the like over a long period of time due to strain during run flat running.

  Further, in the present invention, the concave grooves 11 are provided at an interval pitch P in the tire circumferential direction of 25 to 60 mm. Here, as shown in FIG. 5, the spacing pitch P is the center of gravity Gg, Gg of the adjacent grooves 11 and 11 (the center of gravity is the center of gravity of the opening area of the grooves). It is measured as an arcuate distance along the tire circumferential direction.

  When the spacing pitch P of the concave grooves 11 is less than 25 mm, in the side reinforcing rubber 9, the rigidity between the adjacent concave grooves 11 is remarkably lowered, and the durability is deteriorated by causing cracks or the like in the portions. Therefore, the spacing pitch P is particularly preferably 30 mm or more, and more preferably 35 mm or more. On the other hand, when the spacing pitch P is larger than 60 mm, the rigidity in the tire radial direction of the side reinforcing rubber 9 cannot be sufficiently relaxed, and thus the riding comfort cannot be improved. As a preferred embodiment, the spacing pitch P of the recessed grooves 11 is desirably determined in relation to the groove width W1 of the recessed grooves 11, and specifically, the spacing pitch P is determined as the groove width W1 of the recessed grooves 11. For example, about 2 to 4 times as large is desirable.

  Further, as shown in FIG. 3, in the present embodiment, the depth d1 of the concave groove 11 gradually decreases from the central portion in the length direction toward the inner end 11i and the outer end 11o in the tire radial direction. Things are shown. That is, the depth d1 of the concave groove 11 is also reduced based on the reduction of the thickness t of the side reinforcing rubber 9. As a result, strain concentration and the like are prevented at the end portions 11i and 11o of the groove 11.

  The depth d1 of the concave groove 11 (the maximum depth when the depth changes, the same shall apply hereinafter) is 2 mm or more, more preferably 3 mm or more. If the depth d1 is less than 2 mm, the rigidity in the tire radial direction of the side reinforcing rubber 9 cannot be sufficiently relaxed, and consequently the ride comfort cannot be improved. On the contrary, if the depth d2 of the concave groove 11 is too large, the difference in strain between the portion of the concave groove 11 and the portion of the base portion 9B increases, and cracks and the like are likely to occur. From such a viewpoint, the depth d1 of the groove 11 is preferably 8 mm or less, more preferably 6 mm or less. The relationship between the depth d1 of the concave groove 11 and the thickness t of the side reinforcing rubber will be described. The ratio (d1 / t) is preferably 0.05 or more, more preferably 0.10 or more, and still more preferably. Is preferably 0.20 or more, and the upper limit is preferably 0.70 or less, more preferably 0.60 or less, and still more preferably 0.50 or less.

Further, in the embodiment as the reference example , the groove 11 extends with a constant groove width W1. However, in the present invention, as shown in FIG. 7, the groove 11 has a substantially T shape including a wide portion 12 having a large groove width W1a and a narrow portion 13 having a groove width W1b smaller than the wide portion 12. that make up the. Such a groove 11 reduces the rigidity of the side reinforcing rubber 9 in the radial direction of the tire by the wide portion 12 while reducing the rigidity of the side reinforcing rubber 9 by the narrow portion 13. it can. Therefore, the handling stability and the ride comfort can be improved in a balanced manner.

  In particular, in order to further improve the ride comfort, such a substantially T-shaped concave groove 11 extends in the tire radial direction, the wide portion 12 is on the tread portion 2 side, and the narrow portion 13 is a bead. It is desirable to be arranged on the part 4 side. Thereby, while the impact input to the tread portion 2 is effectively absorbed by the wide portion 12, the decrease in the longitudinal rigidity of the side reinforcing rubber 9 is suppressed on the bead portion 4 side, and consequently the steering stability is deteriorated. It can be effectively prevented.

In order to improve the above-described riding comfort and steering stability in a more balanced manner, in the substantially T-shaped groove 11, the width W1a of the wide portion 12 is 15 to 20 mm, and the width W1b of the narrow portion 13 (< W1a) is preferably 10 to 15 mm. Further, if the length L2 of the wide portion is too small, improvement in riding comfort cannot be expected sufficiently, so 5 to 10 mm is preferable.

In addition, as FIG. 8 shows, you may include the 1st ditch | groove 11A in which the wide part 12 faces the tread part side, and the 2nd ditch | groove 11B in which the wide part 12 faces the bead part side. In this case, it is desirable to provide the first concave grooves 11A and the second concave grooves 11B alternately in the tire circumferential direction. During run-flat running, the wide portion 12 of the concave groove 11 tends to be a starting point of bending of the sidewall portion 3, and the deflection amount of that portion tends to increase. In the aspect of FIG. 7, since the wide portions 12 are arranged at the same position in the tire radial direction on the tread portion side, distortion is likely to be concentrated at a certain position in the tire radial direction, and as a result, the amount of vertical deflection during run flat running Tend to be larger.

  On the other hand, in the embodiment of FIG. 8, since the wide portions 12 appear alternately on the tread portion side and the bead portion side, the longitudinal strain of the tire during run-flat running can be dispersed in and out of the tire radial direction. . Therefore, it is possible to exert an advantageous effect in terms of durability, such as reducing the amount of vertical deflection of the tire during run-flat running and suppressing heat generation.

  Further, as shown in FIG. 9, the recessed groove 11 may be inclined with respect to the tire radial direction. The concave groove 11 inclined with respect to the tire radial direction can adjust the riding comfort and the handling stability in relation to the rotation direction R1 or R2 of the tire. The direction is displayed with an arrow etc.).

10 and 11 are sectional views of the ground contact portion cut at the tire equator C position of the run-flat tire 1. For example, when importance is attached to steering stability, as shown in FIG. 10, it is desirable that the concave groove 11 is inclined toward the rotational direction first arrival side from the bead portion 4 side toward the tread portion 2 side. In such an embodiment, the base portion 9B between the concave grooves 11 and 11 of the side reinforcing rubber 9 is inclined to resist the shearing force F that the tire receives during driving. Accordingly, the rigidity in the tire circumferential direction of the side reinforcing rubber 9 is increased at the time of ground contact, and as a result, the traction performance and the steering stability are improved.

On the other hand, when emphasizing the ride comfort, as shown in FIG. 11, it is desirable that the concave groove 11 be inclined toward the rear arrival side in the rotational direction from the bead portion 4 side toward the tread portion 2 side. In such an embodiment, the base portion 9B between the concave grooves 11 and 11 of the side reinforcing rubber 9 is inclined in the same direction as the direction of the shearing force F. Therefore, at the time of ground contact, the deformation of the side reinforcing rubber 9 in the tire radial direction can be promoted, the impact mitigating ability can be enhanced, and the riding comfort can be improved.

  In the above embodiment, the inclination angle θ (shown in FIG. 9) of the concave groove 11 with respect to the tire radial direction is preferably 25 to 65 degrees. When the angle θ is less than 25 °, there is no great difference from the case along the tire radial direction. Conversely, when the angle θ exceeds 65 degrees, the rigidity of the side reinforcing rubber 9 is greatly reduced, and the run-flat durability may be deteriorated. There is. From such a viewpoint, the angle θ is preferably 30 degrees or more, more preferably 35 degrees or more, and the upper limit is preferably 55 degrees or less, more preferably 50 degrees or less.

  Moreover, in the run flat tire 1 in which the rotational direction is determined as described above, the concave grooves 11 provided in the side reinforcing rubbers 9 on both sides are the same rotational direction from the bead portion 4 side to the tread portion 2 side. It is desirable to incline (that is, one of the first arrival side or the rear arrival side in the rotation direction). At this time, the angles θ of the concave grooves 11 on both sides are preferably the same.

  On the other hand, a run flat tire having a substantially point-symmetric tread pattern in which the rotation direction is not defined may be used in both rotation directions. Accordingly, it is desirable to configure the tire so that there is no significant difference in the tire characteristics regardless of the direction of rotation. In such a case, the concave groove 11 provided in one side reinforcing rubber 9 is inclined in the first rotation direction R1 from the bead portion 4 side toward the tread portion 2 side, and the other side reinforcing rubber is provided. It is desirable that the concave groove 11 provided in 9 is inclined in a second rotation direction R2 opposite to the first rotation direction from the bead portion side toward the tread portion side. At this time, the angles θ of the concave grooves 11 on both sides are preferably the same.

  The run flat tire 1 as described above can be easily manufactured, for example, by cutting the groove 11 on the inner surface of the base portion 9B of the side reinforcing rubber 9 after being normally vulcanized. Moreover, in order to improve productivity, it is also preferable to form the said recessed groove 11 simultaneously with the vulcanization molding of a tire.

  For example, a convex portion is provided in advance at a position in contact with the side reinforcing rubber 9 of a rubber balloon-like bladder that molds the inner surface of the tire, whereby the inner surface of the side reinforcing rubber 9 is recessed to provide the concave groove 11. .

  Further, as shown in FIG. 12, the inner surface of the side reinforcing rubber 9 of the unvulcanized tire raw cover 1a has a heat-resistant block piece (for example, a heat-resistant resin, metal, or the like) that is not substantially deformed by heat during vulcanization. 15 (consisting of vulcanized rubber pieces, etc.) is attached using heat-resistant adhesive tape 16 or the like, and as shown in FIG. 13, a normal mold MD and a bladder having a smooth surface V and B are vulcanized and molded. The side reinforcing rubber 9 is plasticized by heat during vulcanization, and the heat-resistant block piece 15 pressed by the bladder B is embedded therein. And as FIG. 14 shows, the said recessed part 11 is easily formed by removing the heat-resistant block 15 from the side reinforcement rubber 9 after vulcanization.

Further, the run-flat tire 1 of the present embodiment has a tire outer surface profile (contour line) TL as shown in FIG. 15 (regular unloaded state). The profile TL is specified in a state where the groove of the tread portion 2 is filled. In the normal no-load state, the profile TL is determined from the intersection point CP, where P is a point on the tire outer surface that is separated by a distance SP of 45% of the maximum tire width SW from the intersection point CP between the tire outer surface and the tire equator C. In the section up to the point P, the radius of curvature RC of the tire outer surface is gradually decreased toward the outer side in the tire axial direction, and the following relationship is satisfied.
0.05 <Y60 / H ≦ 0.1
0.1 <Y75 / H ≦ 0.2
0.2 <Y90 / H ≦ 0.4
0.4 <Y100 / H ≦ 0.7
Here, Y60, Y75, Y90, and Y100 separate the tire axial distances of 60%, 75%, 90%, and 100% of the half width (SW / 2) of the maximum tire width in the tire axial direction from the tire equator C, respectively. The distances in the tire radial direction between the points P60, P75, P90 and P100 on the tire outer surface and the intersection point CP. The “H” is a tire cross-sectional height.

RY60 = Y60 / H
RY75 = Y75 / H
RY90 = Y90 / H
RY100 = Y100 / H
Then, the range satisfying the above relationship is shown as a graph in FIG. As is clear from these, the profile TL of the tire outer surface that satisfies the above relationship becomes very round. For this reason, the ground contact shape of the tire having this profile TL has a small ground contact width and a large ground contact length. This helps to reduce tire noise while driving and improve hydroplaning performance.

  Further, the profile TL increases the area where the tread portion 2 is easily bent, but shortens the area of the sidewall portion 3. For this reason, the run flat tire 1 having the profile can significantly reduce the weight of the tire due to a synergistic effect with the weight reduction of the side reinforcing rubber 9. The radius of curvature RC is preferably decreased continuously as in the present embodiment, but can be decreased step by step. Furthermore, since the profile TL reduces the vertical spring of the tire, the riding comfort during normal driving is excellent.

  The present invention is particularly suitable for a passenger car, but it is needless to say that the present invention is not limited to the illustrated embodiment and can be implemented in various forms.

  In order to confirm the effects of the present invention, a plurality of run-flat tires having a tire size of “245 / 40ZR18” were prototyped based on the specifications in Table 1, and the following performance was tested. The maximum thickness tc of the side reinforcing rubber was unified to 10 mm, and the length in the tire radial direction along the inner surface of the base was unified to 70 mm.

Moreover, Examples 1-3 show the aspect of FIG. 7 , Example 4 shows the aspect of FIG. In these examples, the width W1a of the wide portion is 15 mm and the length is 10 mm, and the width W1b of the narrow portion is 10 mm and the length is 30 mm.

  Furthermore, two types of profiles A and B were tested as the specifications of the tire outer surface are described in Table 1. The test method is as follows.

<Runflat durability>
Each test tire was assembled on the rim described below, filled with an internal pressure of 230 kPa, and allowed to stand at a temperature of 38 ° C. for 34 hours, and then the valve core of the rim was removed to allow the tire lumen to communicate freely with the atmosphere. And in this state, it was made to run on the drum test machine which has a drum with a radius of 1.7 m on the following conditions, and the running distance until a tire broke was measured. The results were expressed as an index with Comparative Example 1 as 100. The larger the value, the better.
Rims: 18 x 8.5 JJ
Speed: 80km / h
Longitudinal load: 4.14kN

<Tire mass>
The mass of each test tire was measured. The results are shown as an index with Comparative Example 1 as 100. A smaller number indicates a lighter weight.

<Ride comfort and handling stability>
The driver's sensation gives the driver stability in response to turning on dry asphalt road surface and grip feeling under the condition of the above rim and internal pressure of 230 kPa while mounting four test tires on a domestic FR car with a displacement of 4300 cm ³ It was evaluated by. Similarly, on asphalt step roads, Belgian roads (cobblestone roads), and Bitzmann roads (roads covered with pebbles), sensory evaluations related to riding comfort such as ruggedness, push-up and damping were performed. In each case, the evaluation was made with a score of Comparative Example 1 as 100 points. The larger the value, the better.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the tires of the examples were reduced in weight without impairing the run-flat durability, and an improvement in riding comfort could be expected.

It is sectional drawing of the run flat tire which shows embodiment of a reference example . It is sectional drawing in the tire circumferential direction position different from FIG. It is the elements on larger scale of the side wall part of FIG. It is the fragmentary perspective view of the sidewall part seen from the tire lumen. It is the side view which looked at the side reinforcement rubber of this embodiment from the tire lumen side. (A), (b) is AA sectional drawing of FIG. It is a side view of a side reinforcing rubber showing a implementation form of the present invention. It is a side view of a side reinforcing rubber showing a implementation form of the present invention. It is a side view of the side reinforcement rubber which shows other embodiment. It is a fragmentary sectional view along the tire equator which shows the contact state of a tire. It is a fragmentary sectional view along the tire equator which shows the contact state of a tire. It is sectional drawing of the raw cover which shows an example of the manufacturing method of a run flat tire. It is sectional drawing explaining the vulcanization | cure. It is sectional drawing after vulcanization which shows an example of the manufacturing method of the run flat tire of this embodiment. It is a diagram which shows the profile of a tire outer surface. It is a diagram which shows the range of RYi in each position of a tire outer surface.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Run flat tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 9 Side reinforcement rubber 9B Side reinforcement rubber base 9Bi Side reinforcement rubber inner surface 11 Groove 11i Part 11o tire radial direction outside edge part of ditch

Claims (7)

A run-flat tire comprising a toroidal carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a side reinforcing rubber disposed inside the carcass and extending inward and outward in the tire radial direction along the sidewall portion Because
The side reinforcing rubber has an inner surface facing the tire lumen side of a base portion having a substantially crescent shape with a reduced thickness from the central portion to the inside and outside of the tire in the tire radial direction. Separated by
Each of the concave grooves has two ends provided without protruding from the inner surface of the side reinforcing rubber, and the maximum length between the ends is 30 to 50 mm and the groove width is 10 to 20 mm. ,
The spacing pitch in the tire circumferential direction of the groove is 25 to 60 mm, and the groove includes a wide portion having a large groove width and a narrow portion having a groove width smaller than the wide portion. A run-flat tire characterized by its shape .
The concave groove includes a first concave groove with the wide portion facing the tread portion side and a second concave groove with the wide portion facing the bead portion side, and the first concave groove and the second concave groove are The run-flat tire according to claim 1, wherein the run-flat tire is provided alternately in a tire circumferential direction .
The groove extends in the tire radial direction, the run-flat tire according to claim 1, wherein the wide portion is arranged toward the tread portion side.
  The run-flat tire according to any one of claims 1 to 3, wherein the concave groove is inclined at 25 to 65 degrees with respect to a tire radial direction.   The run-flat tire according to any one of claims 1 to 4, wherein the concave grooves provided in the side reinforcing rubbers on both sides are inclined in the same rotational direction from the bead portion side toward the tread portion side. The concave groove provided in one side reinforcing rubber is inclined in the first rotation direction from the bead portion side toward the tread portion side, and
The concave groove provided in the other side reinforcing rubber is inclined in a second rotation direction opposite to the first rotation direction from the bead portion side toward the tread portion side. The run-flat tire described in 1. In the tire meridian cross section including the tire rotation shaft in the normal unloaded state in which the rim is assembled to the regular rim and filled with the regular internal pressure,
The profile of the tire outer surface is defined as a point on the tire outer surface (P) that is separated from the intersection (CP) of the tire outer surface and the tire equator (C) by a distance (SP) of 45% of the maximum tire width (SW). The curvature radius (RC) of the tire outer surface gradually decreases toward the outer side in the tire axial direction in the section from the intersection (CP) to the point (P), and satisfies the following relationship: The run flat tire according to any one of the above.
0.05 <Y60 / H ≦ 0.1
0.1 <Y75 / H ≦ 0.2
0.2 <Y90 / H ≦ 0.4
0.4 <Y100 / H ≦ 0.7
(Where Y60, Y75, Y90 and Y100 are the tire axial distances of 60%, 75%, 90% and 100% of the half width (SW / 2) of the maximum tire width in the tire axial direction from the intersection (CP). (The distances in the tire radial direction between the points P60, P75, P90 and P100 on the outer surface of the tire and the intersections (CP), and H is the tire cross-section height.)

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