JP4971671B2 - Run flat tire - Google Patents

Description

  The present invention relates to a run-flat tire that can continuously run for a relatively long distance even when punctured, and more particularly to a run-flat tire that can improve run-flat durability while minimizing deterioration in ride comfort during normal running.

  Conventionally, there has been known a run-flat tire that can travel a certain distance at a relatively high speed (hereinafter, referred to as “run-flat running”) even when the air from the tire is removed due to puncture or the like. Yes. In this type of run-flat tire, a side reinforcing rubber having a substantially crescent-shaped cross section is disposed on the sidewall portion. When the air from the tire escapes, the side reinforcing rubber supports the tire load, and the longitudinal deflection of the tire is suppressed.

  Therefore, in order to increase the run-flat travel distance, it is desirable to make the side reinforcing rubber larger and / or more elastic.

  However, increasing the size of the side reinforcement rubber further increases the longitudinal spring of the tire, so that there is a problem that the ride comfort is remarkably deteriorated during normal driving when the air pressure is properly filled.

  Related technologies include the following:

JP 2002-301911 A Japanese Patent No. 2999489

  The present invention has been devised in view of the above-described problems, and provides a bulging portion that protrudes outward from the tire on the outer side of the grounding end of the tread portion, and grounds the bulging portion during run-flat traveling. The main purpose is to provide a run-flat tire that can improve the run-flat durability while minimizing the deterioration of ride comfort during normal driving.

The invention according to claim 1 of the present invention includes a toroidal carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a side that is arranged on the inner side in the tire axial direction of the carcass and has a substantially crescent-shaped cross section. A run-flat tire having a reinforced rubber, in a normal load grounding state in which a normal rim is assembled with a rim and filled with a normal internal pressure, and a normal load is applied and grounded to a flat surface. A bulging portion that protrudes outward from the tire without contacting the flat surface is provided on the outer side in the tire axial direction, and the bulging portion is flat in the run-flat grounding state in which the internal pressure is zero from the normal load grounding state. And the bulging portion is connected to the grounding end and the tie in a normal no-load state in which a normal rim is assembled and a normal internal pressure is filled. Protruding height from buttress reference contour splicing smoothly and widest points 1.5 to 5.0 mm, and the width at the buttress reference contour is 5.0～15.0Mm, yet the Rise In order to increase the coefficient of friction between the road surface and the surface of the protruding portion, a plurality of hemispherical bulges are formed, and the average height of the tiny protrusions 11P included in the unit area is: It is 0.1 mm or more and 0.5 mm or less .

  The invention according to claim 2 is the run-flat tire according to claim 1, wherein the bulging portion is continuous in the tire circumferential direction.

  The invention according to claim 3 is the run flat tire according to claim 1 or 2, wherein the cross section including the tire rotation axis has end portions whose height decreases toward both ends in the width direction.

  According to a fourth aspect of the present invention, in the run-flat tire according to any one of the first to third aspects, the bulging portion is made of a rubber having the same composition as a tread rubber that is disposed between the ground contact ends and is in contact with the road surface. It is.

  According to a fifth aspect of the present invention, in the run flat tire according to any one of the first to third aspects, the bulging portion is made of a rubber having a different composition from the tread rubber disposed between the ground contact ends and contacting the road surface. It is.

According to a sixth aspect of the present invention, in the tire meridian section including the tire rotation axis in the normal no-load state, 45% of the tire maximum width (SW) from the intersection (CP) between the tire outer surface and the tire equator (C). When the point on the tire outer surface that separates the distance (SP) is defined as (P), the curvature radius (RC) of the tire outer surface gradually increases in the section from the intersection (CP) to the point (P) excluding the bulging portion. The run flat tire according to any one of claims 1 to 5, wherein the tire satisfies the following relationship.
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 of the maximum tire width (SW / 2) from the tire equator (C) to the tire axial direction. (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.)

  In the present specification, 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 and a “Design” for TRA. “Rim” or “Measuring Rim” for ETRTO.

  The “regular internal pressure” is the air pressure defined by each standard 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.

  Furthermore, the “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES "Maximum value for ETRTO is" LOAD CAPACITY ", but if the tire is for a passenger car, it will be 80% of each load considering the practical load capacity The corresponding load.

  Further, the “grounding end” is a position on the outermost side in the tire axial direction that makes contact with the plane in the normal load grounding state.

  Further, the “tire maximum width point” is determined from a tire cross-sectional contour shape excluding characters, trademarks, rim protectors, and the like provided on the sidewall portion in the normal no-load state. It is at the same height as the position of the maximum width.

  The run-flat tire according to the present invention has a rim assembled on a regular rim and filled with a regular internal pressure, and in a normal load grounding state in which a regular load is applied and grounded on a flat surface, the tread portion has an outer side in the tire axial direction on the grounding end. A bulging portion having a predetermined dimension that protrudes outward from the tire without contacting the flat surface is provided. Such a bulging part has few opportunities to make contact with the road surface during normal driving, and even if it makes contact with the road during turning, its protruding height and width are regulated within a certain range, so In addition, deterioration of steering stability can be suppressed.

  Further, in the run-flat grounding state in which the internal pressure is zero from the normal load grounding state, the bulging portion can be grounded to the plane, thereby suppressing the amount of deflection of the sidewall portion. In addition, this can reduce lifting where the central portion of the tread portion is lifted off the road surface. Therefore, these synergistic actions reduce the strain and heat generation acting on each part of the tire, and significantly increase the run-flat mileage.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a run-flat tire 1 of the present embodiment in a normal no-load state, and FIG. 2 is an enlarged view of a main part thereof. Here, the normal no-load state is a no-load state in which the rim is assembled to the normal rim J and the normal internal pressure is filled. Unless otherwise noted, the dimensions of the tire components are values in the normal unloaded state.

  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, a belt layer 7 disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2, And a bead apex 8 extending from the outer surface of the bead core 5 in the tire radial direction to the outer side in the tire radial direction; A side reinforcing rubber 9 formed and an inner liner rubber 10 made of rubber having a gas barrier property disposed on the inner side in the tire axial direction of the side reinforcing rubber 9 are shown in this example.

  The carcass 6 is formed of one or more carcass plies 6A in this example, in which carcass cords arranged at an angle of, for example, 70 to 90 ° with respect to the tire equator C are covered with a topping rubber. The carcass cord is preferably an organic fiber cord such as nylon, polyester, rayon or aromatic polyamide.

  The carcass ply 6A includes a toroid-like main body portion 6a extending across the bead cores 5 and 5 and a pair of folded portions that are provided on both sides of the bead core 5 and are folded from the inner side to the outer side in the tire axial direction. 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, for example, a relatively hard rubber having a rubber hardness of 65 to 95 degrees, more preferably 70 to 90 degrees, thereby increasing the bending rigidity of the bead portion 4 and improving the steering stability.

  The height ha in the tire radial direction from the bead base line BL to the outer end 8T of the bead apex rubber 8 is not particularly limited. However, if it is too small, the steering stability is likely to deteriorate, and conversely if it is too large, the riding comfort is deteriorated. May be incurred. From such a viewpoint, the height ha is preferably 20% or more, more preferably 25% or more of the tire cross-section height H, and the upper limit is preferably 50% or less, more preferably 45% or less. Is desirable.

  In the present embodiment, the folded portion 6b 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 sandwiched between the main body portion 6a and the belt layer 7. And terminate. Thereby, the side wall part 3 is effectively reinforced by the single carcass ply 6A.

  The belt layer 7 is composed of a total of two cross belt plies 7A and 7B inside and outside of the tire in which a belt cord arranged at an angle of 10 to 35 ° with respect to the tire equator C is covered with a topping rubber, for example. Is done. The width of the belt layer 7 (in this example, the width of the wide belt ply 7A) BW is preferably 0.70 to 0.95 times the tire maximum width SW. Thereby, a tagging effect is imparted over almost the entire area of the tread portion 2, and the profile of the tire outer surface described later is maintained. The tire maximum width SW is a tire axial distance between the tire maximum width points M and M.

  The inner liner rubber 10 is disposed in a toroid shape so as to include the inner side of the side reinforcing rubber 9 and substantially straddle between the bead portions 4 and 4 in order to retain air in the tire lumen. The inner liner rubber 10 desirably contains butyl rubber, halogenated butyl rubber and / or brominated butyl rubber having gas barrier properties.

  The side reinforcing rubber 9 is formed in a substantially crescent shape in which the thickness is gradually reduced from the thick central portion toward the inner end 9i and the outer end 9o in the tire radial direction.

  It is desirable that the inner end 9 i of the side reinforcing rubber 9 is located on the inner side in the tire radial direction than the outer end 8 T of the bead apex 8 and on the outer side in the tire radial direction than the bead core 5. Thereby, the bending rigidity from the side wall part 3 to the bead part 4 can be improved with good balance. From such a viewpoint, the length Wi in the tire radial direction of the overlapping portion between the side reinforcing rubber 9 and the bead apex rubber 8 is preferably about 5 to 50 mm.

  The outer end 9o of the side reinforcing rubber 9 extends to the inside of the tread portion 2, and specifically, it is preferably terminated at a position on the inner side in the tire axial direction from the outer end 7e of the belt layer 7. Thereby, a location with remarkably low rigidity in the buttress portion or the like can be eliminated. The length Wo in the tire axial direction of the overlapping portion between the side reinforcing rubber 9 and the belt layer 7 is preferably about 5 to 50 mm.

  The length L in the tire radial direction between the inner end 9i and the outer end 9o of the side reinforcing rubber 9 is not particularly limited, but if it is too small, the reinforcing effect of the sidewall portion 3 is likely to be reduced, and conversely if too large, There is a tendency to deteriorate the riding comfort and rim assemblability during normal driving. From such a viewpoint, the length L of the side reinforcing rubber 9 is preferably set to 35 to 70%, more preferably about 40 to 65% of the tire cross-section height H.

  The maximum thickness t of the side reinforcing rubber 9 can be appropriately determined according to the tire size and the like. However, if it is too small, the effect of reinforcing the sidewall portion 3 is difficult to obtain. May increase and cause excessive heat generation. From such a viewpoint, the maximum thickness t is preferably 5 mm or more, more preferably 8 mm or more, and the upper limit is preferably 20 mm or less, more preferably 15 mm or less.

  In order to limit the amount of vertical deflection of the tire 1 during run-flat running, and thus enable longer run-flat running, the side reinforcing rubber 9 has, for example, a hardness of 60 degrees or more, more preferably 70 degrees or more, More preferably, it is formed from rubber of 75 degrees or more. On the other hand, even if the side reinforcing rubber 9 is too hard, the ride comfort during normal running may be significantly deteriorated. Therefore, it is preferably 95 degrees or less, more preferably 90 degrees or less. In addition, the hardness of rubber | gum is defined as the hardness by the durometer type A based on JIS-K6253.

  FIG. 3 shows a tire rotation in a normal load grounding state in which the run-flat tire 1 is assembled to a normal rim J and filled with a normal internal pressure, and a normal load is applied and grounded to the plane HP (camber angle is 0 degree). A cross-sectional view including an axis is shown. FIG. 4 is a cross-sectional view including the tire rotation shaft in the run-flat contact state in which the internal pressure is zero from the normal load contact state in FIG.

  As shown in FIG. 3, the run-flat tire 1 of the present embodiment protrudes outward of the tire without coming in contact with the plane HP on the outer side in the tire axial direction of the grounding end 2 e of the tread portion 2 in the normal load grounding state. The bulging portion 11 is provided. Further, as shown in FIG. 4, the bulging portion 11 can be grounded to the plane HP in the run-flat grounding state.

  Such a bulging portion 11 effectively increases the bending rigidity of the buttress portion 12 which is a region between the ground contact end 2e and the tire maximum width point M, and a large load is applied as in run-flat running. Even when acting, the amount of bending deformation of the buttress portion 12 can be reduced. Further, when the tire is run flat, as shown by an arrow A in FIG. 5, the shoulder portion is deformed toward the tire equator C side, and if this deformation is large, the longitudinal deflection of the tire increases, and as a result, the tire equator C The amount of lifting (lifting amount) Lf of the tread from the plane HP at the position also increases.

  In the run flat tire 1 of the present embodiment, when the bulging portion 11 is brought into contact with the road surface during run flat running, the bulging portion 11 becomes resistance to the road surface, and deformation of the shoulder portion toward the tire equator C side is suppressed. Is done. Thereby, not only the vertical deflection of the tire can be suppressed, but also the lifting amount Lf can be suppressed small. Since the lifting amount Lf is the amount of deflection to the inside of the tread portion 2, if it increases, the tread rubber 2G will be excessively heated and easily damaged. However, as in the run-flat tire 1 of the present embodiment, the bulging portion 11 is grounded on a flat surface in the run-flat contact state, thereby reducing the lifting amount Lf and reducing the strain generated in the tire. In FIG. 5, the contour line 1S of the tire 1 having the bulging portion 11 in the run-flat contact state is indicated by a solid line, and the contour line 20S of the tire not having the bulging portion 11 is indicated by a virtual line.

  And since the distortion and heat generation acting on each part of the run-flat tire 1 are greatly reduced by these synergistic actions, it is possible to delay the occurrence of damage, in particular, the occurrence of damage to the side reinforcing rubber 9 that easily stores heat. The run-flat mileage can be significantly increased.

  Here, as shown in FIG. 1 and FIG. 2 which is a partially enlarged view thereof, the bulging portion 11 is a buttress reference that smoothly connects the ground contact end 2e and the tire maximum width point M in a normal no-load state. The protrusion height PT from the contour line 14 is set to 1.5 to 5.0 mm, and the width PW on the buttress reference contour line 14 is set to 5.0 to 15.0 mm. In the present embodiment, the buttress reference contour line 14 is formed by a curve formed of a smooth continuous arc whose radius of curvature continuously decreases from the ground contact edge 2e toward the tire maximum width point M. This will be described later.

  When the protruding height PT of the bulging portion 11 is less than 1.5 mm or when the width PW is less than 5.0 mm, the effect of reducing the amount of vertical deflection during the run-flat running and the lifting amount Lf of the tread portion 2 described above. Is not enough. On the other hand, when the protruding height PT of the bulging portion 11 is greater than 5.0 mm or when the width PW is greater than 15.0 mm, the tire weight increases, turning during normal driving, and slight load fluctuations. As a result, the bulging portion 11 is likely to come into contact with the road surface, which may impair ride comfort and handling stability.

  From the above viewpoint, the protruding height PT of the bulging portion 11 is preferably 2.0 mm or more, more preferably 2.5 mm or more, and the upper limit is preferably 4.5 mm or less, more preferably Is preferably 4.0 mm or less. Similarly, the width PW of the bulging portion 11 is preferably 6.0 mm or more, more preferably 7.0 mm or more, and the upper limit is preferably 12.0 mm or less, more preferably 10.0 mm or less. desirable.

  Moreover, the bulging part 11 may be spaced apart in the tire circumferential direction. However, in such an aspect, there is a possibility of causing periodic vibrations or the like during tire weight imbalance or run-flat running. From such a viewpoint, it is desirable that the bulging portion 11 is annularly and continuously extending in the tire circumferential direction. In particular, those having the same cross-sectional shape and continuously extending in the tire circumferential direction are desirable.

  The cross-sectional shape and the like of the bulging portion 11 can be determined as appropriate, but in the present embodiment, the width direction central portion 11a at which the protrusion height PT is maximum and the width from the central portion 11a toward both ends e in the width direction. And the end portions 11b and 11b whose projecting height PT gradually decreases. The bulging portion 11 having such a cross-sectional shape can alleviate the concentration of strain on both ends e of the bulging portion 11 during the ground contact during run-flat travel. Therefore, damage such as rubber chipping and cracking in the vicinity of the bulging portion 11 can be effectively prevented. Further, it is desirable that the cross-sectional shape of the bulging portion 11 is formed with a smoothly continuous curve without having a distinct edge.

  Moreover, although the bulging part 11 of this embodiment is formed in one smooth hump shape, as shown to Fig.6 (a), as shown in Fig.6 (a), it is two hump shape, Furthermore, although not shown, it is three or more hump shapes. May be formed. Such a cross-sectional shape having a plurality of bumps is excellent in heat dissipation because its surface area is increased. Furthermore, as shown in FIGS. 6B to 6C, the bulging portion 11 may have a projecting height PT that changes stepwise. Although these examples show what the protrusion height PT changes in two steps, it goes without saying that the protrusion height PT may change stepwise in three or more steps.

  Further, the bulging portion 11 can be formed of rubber having the same composition as the tread rubber 2G that is disposed between the grounding ends 2e and 2e of the tread portion 2 and is grounded to the road surface. In such an embodiment, the tread rubber 2G is preliminarily provided with a bulge approximating the bulge portion 11 and subjected to extrusion molding, and the bulge portion 11 is easily molded by vulcanization molding.

  Further, as shown in FIG. 7A, the bulging portion 11 may be formed of a rubber 11G having a different composition from the tread rubber 2G. That is, during the run-flat running, a large ground pressure acts on the bulging portion 11 locally compared to other portions. For this reason, rubber 11G having a rubber hardness and / or a complex elastic modulus larger than that of the tread rubber 2G is suitable for the bulging portion 11 so as to meet such a large contact pressure. Regarding the hardness, when the hardness of the tread rubber 2G is Hd1, and the hardness of the rubber 11G of the bulging portion 11 is Hd2, (Hd2-Hd1) is more preferably 2 degrees or more, and further preferably 4 degrees. The above is desirable. As a result, the amount of deformation of the bulging portion 11 can be prevented from locally increasing during run-flat travel, and early wear and the like can be suppressed. The upper limit of the difference in hardness (Hd2−Hd1) is not particularly limited, but if it is excessively large, strain tends to concentrate on the interface between the two rubbers, and therefore preferably 8 degrees or less, more preferably 6 degrees or less. desirable.

  Further, as shown in FIG. 7B, in order to further improve the durability of the bulging portion 11, the bulging portion 11 is formed of rubber 11Ga containing short fibers in which short fibers f are blended. It is desirable. A large compressive stress acts in the width direction on the bulging portion 11 that contacts the road surface. Therefore, as shown in FIG. 7B, for example, by orienting the longitudinal direction of the short fibers f along the width direction (tire axis direction) of the bulging portion 11, the compression rigidity in the width direction is effectively increased. As a result, the durability of the bulging portion 11 can be improved. However, it goes without saying that the orientation direction of the short fibers f can be changed as appropriate.

  Further, the bulging portion 11 may be made of a rubber composition having a loss tangent tan δ larger than that of the tread rubber 2G. In this case, for example, it is desirable in that it has an excellent envelope effect (impact absorption capability) when overcoming unevenness on a rough road surface or a protrusion on a smooth road.

Further, the surface of the bulging portion 11, a surface treatment for increasing the friction coefficient between the road surface that has been subjected. For example, as shown in FIGS. 10A and 10B, a plurality of recesses D are provided in the reference profile plane PL by performing shot blasting or shot peening on a substantially smooth reference profile plane PL. The bulging portion 11 can be molded with a tire vulcanization mold MD having a roughened molding surface. Thereby, on the surface of the bulging portion 11, for example, a plurality of minute convex portions 11p protruding in a hemispherical shape can be formed. Such a small convex portion 11p can be physically caught by fine irregularities on the road surface during run flat traveling, and can more effectively suppress deformation of the shoulder portion toward the tire equator. In order to realize such an effect, the height of the minute projections 11P included in the unit area (this is preferably an average value of Rd corresponding to the amount of depression from the reference profile plane PL is 0.1 mm or more although, more preferably not less than 0.2 mm, also with respect to the upper limit, but it is 0.5mm or less, more preferably at most 0.4 mm. Note that Ru is shown in FIG. 10 (c) Rise The minute convex portion 11p of the protruding portion 11 includes a plurality of first convex portions 11p1 extending in the tire circumferential direction and a plurality of second convex portions 11p2 extending between them and extending in the tire axial direction. It is formed like a shape .

Next, a profile (contour line) of a preferred embodiment of a tire outer surface that may come into contact with the road surface including the tread portion 2 will be described. FIG. 8 shows a profile TL of the tire outer surface in a normal no-load state. The profile TL is specified excluding the groove of the tread portion 2 and the bulging portion 11. When the point on the tire outer surface that separates the distance SP of 45% of the maximum tire width SW from the intersection CP of the tire outer surface and the tire equator C in the normal no-load state is P, the distance from the intersection CP to the point P It is desirable to gradually decrease the radius of curvature RC of the tire outer surface in the section and satisfy the following relationship.
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 relationship is shown as a graph in FIG. As apparent from FIGS. 8 and 9, the profile TL of the tire outer surface that satisfies the above relationship is very round. For this reason, the contact shape of a tire having such a profile TL has a small contact width and a large contact length. This helps to improve noise performance and hydroplaning performance.

  Moreover, such a profile increases the area of the tread that is easily bent, but has a feature that the area of the sidewall portion 3 is shortened. For this reason, the run flat tire 1 having the profile is excellent in ride comfort with reduced longitudinal springs, and can reduce the length and the rubber volume of the side reinforcing rubber 9, thereby achieving a reduction in mass in the run flat tire. Is particularly preferable. The curvature radius RC may be reduced stepwise, but it is preferable that the curvature radius RC is continuously reduced as in the present embodiment. In the present embodiment, the buttress reference contour line 14 is drawn by this profile TL.

  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 basic structure of the tire is as shown in FIG. 1, and the change in performance was examined by changing the profile of the bulging portion and the outer surface of the tire. The common specifications of the side reinforcement rubber are as follows.

Tire axial length Wo that overlaps with the belt layer Wo: 15mm
Tire radial length Wi which overlaps with bead apex rubber Wi: 10mm
Tire radial length L: 30mm
Maximum thickness t: 7mm

Also, For Example, the bulging portion is formed using a tire vulcanizing mold having a roughened bulge portion forming surface. Thereby, on the surface of the bulging portion, a substantially hemispherical minute convex portion having an average height of 0.2 mm was provided in almost the entire region. In another example, the bulging portion was formed with a tire vulcanization mold having a substantially smooth bulging portion forming surface. The test method is as follows.

<Ride comfort>
Each test tire is mounted on a rim of 18 x 8.5 JJ, filled with 230 kPa of internal pressure, mounted with 4 wheels of 4300 cm ³ domestic FR vehicle, stepped on dry asphalt road surface, Belgian road (stone-paved road surface) ), Bitzmann road (road surface covered with pebbles), etc., sensory evaluation was performed with respect to ruggedness, push-up, and damping, and Comparative Example 1 was displayed as an index of 100. The larger the value, the better.

<Run flat durability performance>
Each test tire is assembled on a rim of 18 x 8.5 JJ, filled with 230 kPa of internal pressure and left at a temperature of 38 ° C for 34 hours. It was. In this state, the vehicle was run on a drum tester having a drum having a radius of 1.7 m under the conditions of a speed of 80 km / h and a longitudinal load of 4.14 kN, and the running distance until the tire broke was measured. The results were displayed as an index with Comparative Example 1 as 100. The larger the value, the better.
Table 1 shows the test results.

  As a result of the test, it was confirmed that the tire of the example improved the run flat durability performance without impairing the riding comfort as compared with the comparative example.

It is sectional drawing in the regular no-load state of the run flat tire which shows embodiment of this invention. It is the principal part enlarged view. It is sectional drawing in the regular load grounding state of the run flat tire of this embodiment. It is sectional drawing in the run flat grounding state. It is an outline figure of a tire in a run flat grounding state. (A)-(c) is sectional drawing which shows other embodiment of a bulging part. (A) And (b) is sectional drawing which shows other embodiment of a bulging part. It is a diagram which shows the profile of the tread surface of this embodiment. It is a diagram which shows the range of RYi in each position of a tire outer surface. (A) is a fragmentary sectional view which shows other embodiment of a bulging part, (b) is the perspective view, (c) is a perspective view which shows other embodiment of a bulging part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Run flat tire 2 Tread part 2e Grounding end 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 9 Side reinforcement rubber 11 Bulging part 14 Buttress reference outline

Claims (6)

A run-flat tire comprising a toroidal carcass extending from a tread portion through a sidewall portion to a bead core of the bead portion, and a side reinforcing rubber disposed on the inner side in the tire axial direction of the carcass and having a substantially crescent cross section. ,
In a normal load grounding state in which a normal rim is assembled and a normal internal pressure is filled and a normal load is applied and grounded to a plane, the tire is not grounded to the plane on the outer side in the tire axial direction of the grounding end of the tread portion. A bulging portion protruding outward is provided, and the bulging portion is in contact with the plane in the run-flat grounding state in which the internal pressure is zero from the normal load grounding state, and
The bulging portion has a protruding height from a buttress reference contour line that smoothly connects the ground contact edge and the tire maximum width point in a normal no-load state in which a normal rim is assembled and a normal inner pressure is filled. 1.5 to 5.0 mm, and the width on the buttress reference contour line is 5.0 to 15.0 mm ,
Moreover, in order to increase the coefficient of friction with the road surface, a plurality of hemispherical bulges are formed on the surface of the bulging portion, and the average height of the tiny protrusions 11P included in the unit area is formed. A run flat tire having a value of 0.1 mm to 0.5 mm .
  The run-flat tire according to claim 1, wherein the bulging portion extends continuously in the tire circumferential direction.   The run-flat tire according to claim 1, wherein the bulging portion has an end portion whose height decreases toward both ends in the width direction in a cross section including the tire rotation axis.   The run-flat tire according to any one of claims 1 to 3, wherein the bulging portion is made of a rubber having the same composition as a tread rubber that is disposed between the ground contact ends and contacts the road surface.   The run-flat tire according to any one of claims 1 to 3, wherein the bulging portion is made of a rubber having a different composition from a tread rubber disposed between the ground contact ends and contacting the road surface. In the tire meridian section including the tire rotation axis in the normal no-load state, on the tire outer surface 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 tire maximum width (SW). (P), the radius of curvature (RC) of the tire outer surface gradually decreases in the section from the intersection (CP) to the point (P) excluding the bulging portion,
The run-flat tire according to any one of claims 1 to 5, which satisfies the following relationship.
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 of the maximum tire width (SW / 2) from the tire equator (C) to the tire axial direction. (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.)

Images