JP7128274B2 - run flat tires - Google Patents

Description

The present disclosure relates to runflat tires.

As a run-flat tire that allows running for a certain distance even when the internal pressure of the tire is low, there is a side-reinforced run-flat tire in which the tire side portion is reinforced with side-reinforcing rubber (see, for example, Japanese Patent Application Laid-Open No. 2012-116212). ).

As a run-flat tire, it is difficult to achieve both ride comfort performance during normal running and durability during run-flat running, so-called run-flat durability, and there is room for improvement.
For example, there is a method of lowering the vertical spring constant in order to improve ride comfort during normal driving, but if the side reinforcement rubber is made thinner or softer, the run-flat durability is reduced.
In addition, if the side reinforcement rubber is thickened in order to ensure run-flat durability, the vertical spring constant increases, the ride quality deteriorates during normal running, and the tire weight increases.

In consideration of the above facts, an object of the present disclosure is to provide a run-flat tire that achieves both ride comfort during normal driving and run-flat durability.

A run-flat tire according to the present disclosure includes a carcass including a pair of bead cores, a body portion spanning the pair of bead cores, and a folded portion for folding back the bead cores, and a belt provided outside the carcass in the tire radial direction. , a side reinforcing layer provided on the inner side of the carcass in the tire width direction and having a thickness gradually decreasing toward both sides in the tire radial direction; and a rim guard for restricting the bead portion from collapsing outward in the axial direction of the tire. The height dimension of the case line measured in the tire radial direction from a reference line parallel to the tire rotation axis passing through the tire radial direction outer end of the bead core when viewed in a cross section along the side height SH, The intersection of the case line and the first imaginary line passing through a position 10% of the side height SH outward from the reference line and parallel to the tire rotation axis is 0.1 SHp from the reference line. 0.3SHp from the reference line to the tire radial direction 0.8SHp from the reference line to the outside in the tire radial direction The total gauge from the inner surface of the tire to the outer surface of the tire excluding the rim guard is 0.9SHp at the intersection of the case line and the fourth imaginary line that passes through a position 90% away from the side height SH and is parallel to the tire rotation axis. is G, and the gauge from the inner surface of the tire to the case line is t, t / G between the intersection point 0.1Hp and the intersection point 0.3Hp is set within a range of 40 to 80%, t/G between the intersection point 0.8Hp and the intersection point 0.9Hp is set within a range of 30 to 60%, and the position of the top of the rim guard is the side height from the reference line to the outside in the tire radial direction. It is set within the range of 10 to 20% of SH.

In the run-flat tire according to the present disclosure, the t/G of the gauge is optimized as described above. You can improve your comfort.
In addition, since the rim guard is provided on the outer surface of the tire, it is possible to prevent the bead portion from excessively collapsing during run-flat running, thereby ensuring run-flat durability.
Accordingly, in the runflat tire according to the present disclosure, it is possible to achieve both ride comfort performance and runflat durability.

According to the run-flat tire of the present disclosure, it is possible to achieve both ride comfort during normal running and run-flat durability.

1 is a half cross-sectional view showing one side of a cut surface of a run-flat tire according to an embodiment of the present invention cut along the tire axial direction; 1 is a half cross-sectional view showing one side of a cut surface of a run-flat tire according to an embodiment of the present invention cut along the tire axial direction; It is an expanded sectional view which shows a tire side part. 1 is a half cross-sectional view showing one side of a cut surface of a run-flat tire according to an embodiment of the present invention cut along the tire axial direction;

(Construction of run-flat tires)
A run-flat tire 10 according to an embodiment of the present invention will be described below with reference to FIGS. 1 to 3. FIG. In addition, this embodiment demonstrates the run-flat tire 10 for passenger cars.

Here, the arrow TW in the drawing indicates the width direction of the run-flat tire 10 (tire width direction), and the arrow TR indicates the radial direction of the run-flat tire 10 (tire radial direction).

The term "tire width direction" as used herein refers to a direction parallel to the rotational axis of the run-flat tire 10, and is also referred to as the tire axial direction. Moreover, the tire radial direction refers to a direction perpendicular to the rotational axis of the run-flat tire 10 .

Reference CL indicates the equatorial plane (tire equatorial plane) of the run-flat tire 10 . Furthermore, in the present embodiment, the rotational axis side of the run-flat tire 10 along the tire radial direction is defined as the "tire radial inner side", and the side opposite to the rotational axis of the run-flat tire 10 along the tire radial direction is defined as the "tire "radially outward".

On the other hand, the equatorial plane CL side of the run-flat tire 10 along the tire width direction is the "tire width direction inner side", and the side opposite to the equatorial plane CL of the run-flat tire 10 along the tire width direction is the "tire width direction outer side". and described.

In the following description, the rim means a standard rim (or "Approved Rim" or "Recommended Rim") in applicable sizes described in the following standards. The standards are set by industry standards in force in the region where the tire is produced or used. For example, in the United States, "The Tire and Rim Association Inc. Year Book", in Europe, "The European Tire and Rim Technical Organization Standards Manual", and in Japan, "JATMA Year Book" of the Japan Automobile Tire Manufacturers Association. It is

1 to 3 are cross-sectional views along the tire rotation axis of the run-flat tire 10 assembled on the standard rim 30 and not filled with internal pressure (at the same atmospheric pressure as the outside air).
As shown in FIG. 1, a runflat tire 10 according to the present embodiment includes a pair of bead portions 12, a carcass 14, a belt 16, a belt reinforcing layer 18, a tread portion 20, a tire side portion 22 , a side reinforcing rubber 24 as a side reinforcing layer, and an inner liner 32 .

A pair of left and right bead portions 12 are provided at intervals in the tire width direction (only the bead portion 12 on one side is illustrated in FIG. 1). A bead core 26 is embedded in each of the pair of bead portions 12 , and the carcass 14 straddles between the bead cores 26 .

(carcass)
The carcass 14 of the present embodiment is composed of one carcass ply 15, and the carcass ply 15 includes a plurality of cords (not shown. For example, organic fiber cords, metal cords, etc.) coated with a rubber coating. formed by The carcass 14 thus formed extends in a toroidal shape from one bead core 26 to the other bead core 26 to constitute the frame of the tire. Note that the run-flat tire 10 of the present embodiment is a tire having a radial structure, and the cords of the carcass ply 15 extend in the tire radial direction (radial direction) at the tire side portion, and extend at the tire equatorial plane at the tire outer peripheral portion. It extends in a direction crossing CL.

In the carcass 14, the portion extending from one bead core 26 to the other bead core 26 is called a body portion 14A, and the portion where the bead core 26 is folded back from the inside to the outside of the tire is called a folded portion 14B. In this embodiment, the end portion 14BE of the folded portion 14B is sandwiched between the belt 16 and the main body portion 14A of the carcass 14 in the vicinity of the tire width direction outermost end 16E of the belt 16, which will be described later.
Further, the end portion 14BE of the folded portion 14B is located outside the other end portion 24B of the side reinforcing rubber 24 described later in the tire width direction and inside the belt end of any of the belt plies 16A and 16B described later in the tire radial direction. is preferably arranged.

In the following description, “case line 14CL” refers to the center line of the thickness of the carcass 14 . For example, in the portion where the carcass ply 15 is one sheet, the center line of the thickness of the carcass ply 15 is set to "case line 14CL", and in the portion where the carcass ply 15 is overlapped, the carcass ply 15 is overlapped. Let the center line of thickness be "case line 14CL." In addition, in the portion where the main body portion 14A and the folded portion 14B of the carcass 14 are present (the portion where the bead filler 28 described later is disposed), the center line between the main body portion 14A and the folded portion 14B (a two-dot chain line in FIG. 1) ) is referred to as “case line 14CL”.

Further, in the present embodiment, in the run-flat tire 10 assembled to the standard rim 30 and not filled with internal pressure, the bead core 26 passes through the radially outer end of the tire and is parallel to the tire rotation axis (not shown). A maximum height SH of the case line 14CL measured from the reference line BL toward the outside in the tire radial direction is called a side height (see FIG. 1).

Further, in the present embodiment, the intersection of the case line 14CL and the imaginary line FL1, which passes through a position 10% of the side height SH outward from the reference line BL in the tire radial direction and is parallel to the tire rotation axis, is set to 0. 1SHp, 0.2SHp, the intersection of the case line 14CL and an imaginary line FL2 passing through a position 20% of the side height SH from the reference line BL to the outside in the tire radial direction and parallel to the tire rotation axis, and the reference line BL The intersection of the case line 14CL and the imaginary line FL4 passing through a position 40% of the side height SH to the outside in the tire radial direction and parallel to the tire rotation axis is 0.4SHp from the reference line BL to the outside in the tire radial direction. An intersection point between the case line 14CL and an imaginary line FL6 passing through a position 60% away from the side height SH and parallel to the tire rotation axis is called 0.6SHp.

The case line 14CL of the carcass 14 of the present embodiment is an arc projecting outward from the tire with the center of curvature on the inner side of the tire and the average radius of curvature R1 between the intersections 0.1SHp and 0.2SHp. A circular arc shape with a single radius of curvature between the intersection point 0.4SHp and the intersection point 0.6SHp that has the center of curvature on the inside of the tire and has a radius of curvature R2 that is convex to the outside of the tire. It is Incidentally, the case line 14CL between the intersection points 0.2SHp and 0.4SHp has a circular arc shape between the intersection points 0.1SHp and 0.2SHp and the case line 14CL between the intersection points 0.4SHp and 0.6SHp. It is an arc shape that is smoothly connected to the arc shape and convexes toward the outside of the tire.

In this embodiment, the curvature radius R1 is set larger than the curvature radius R2, and the ratio R2/R1 is set larger than 0.3. Moreover, it is preferable to set the ratio R2/R1 to be greater than 0.4. Note that the ratio R2/R1 is preferably set to be smaller than 1.3.
Furthermore, the radius of curvature R1 is preferably set within a range of 100 to 200% of the side height SH, and the radius of curvature R2 is preferably set within a range of 50 to 150% of the side height SH. preferable.

Here, the curvature radius R1 is an average value, and the case line 14CL between the intersection point 0.1SHp and the intersection point 0.2SHp may have an arc shape with a single curvature radius. It may be a circular arc shape with a constant curvature radius, or a substantially circular arc shape with a gradually changing radius of curvature. Also, the radius of curvature of the case line 14CL between the intersections 0.1SHp and 0.2SHp may be infinite in some cases. It may be in shape.

As shown in FIG. 2A, which shows the same run-flat tire 10 as in FIG. The intersection of the virtual line FLa and the case line 14CL is 0.1 SHp, and the virtual line FLb and the case are parallel along the tire rotation axis and pass through a position 30% of the side height SH from the reference line BL to the outside in the tire radial direction. The point of intersection with the line 14CL is 0.3SHp, and the point of intersection between the case line 14C and an imaginary line FLc passing through a position 55% of the side height SH outward in the tire radial direction from the reference line BL and parallel to the tire rotation axis. is 0.55SHp, and the intersection of the case line 14CL and an imaginary line FLd passing through a position 80% of the side height SH outward in the tire radial direction from the reference line BL and parallel to the tire rotation axis is 0.8SHp, The point of intersection with the case line 14CL, an imaginary line FLe passing through a position 90% of the side height SH from the reference line BL to the outside in the tire radial direction and parallel to the tire rotation axis, is 0.9SHp, as shown in FIG. 2B. , G is the total gauge from the inner surface of the tire to the outer surface of the tire excluding the rim guard 34 described later (measured in the direction perpendicular to the tangential line of the inner surface of the tire, in other words, in the direction of the normal line), and the gauge from the inner surface of the tire to the case line 14CL is set to t, t / G between the intersection point 0.1SHp and the intersection point 0.3SHp is set within the range of 40 to 80%, and t between the intersection point 0.8SHp and the intersection point 0.9SHp /G is set within the range of 30 to 60%.

Furthermore, as shown in FIG. 1, at a height position of 20% to 40% of the side height SH from the reference line BL to the outside in the tire radial direction (near the switching position between the arc with the radius of curvature R1 and the arc with the radius of curvature R2). It is preferable to set the t/G measured along the case line 14CL within the range of 50 to 80%, and the height position of 40 to 60% of the side height SH (rim guard 34 It is preferable to set t/G measured through the case line 14CL in the vicinity of the intermediate position between the buttress (shoulder) and the buttress (shoulder) within the range of 60 to 80%.

A bead filler 28 extending outward in the tire radial direction from a bead core 26 is embedded in a region of the bead portion 12 sandwiched between the main body portion 14A and the folded portion 14B of the carcass 14 . Also, the bead filler 28 has a thickness that decreases toward the outside in the tire radial direction. The bead filler 28 is made of rubber harder than the side rubber 23 . The shape and material of the bead filler 28 are not limited to those of this embodiment.

Further, the main body portion 14A of the carcass 14 preferably has a curved shape (substantially circular arc shape) in which the portion adjacent to the bead filler 28 on the outer side of the bead core 26 in the tire radial direction is convex toward the inner side of the tire.

When Abf is the cross-sectional area of the bead filler 28 and Arr is the cross-sectional area of the side reinforcing rubber 24 when the run-flat tire 10 is sectioned along the tire rotation axis, the ratio Abf/Arr is from 0.04 to 0.04. It is preferably within the range of 0.17, more preferably within the range of 0.08 to 0.15, and even more preferably within the range of 0.09 to 0.13.

When the cross-sectional area of the side reinforcing rubber 24 radially inward of the phantom line FLW is Arri, and the cross-sectional area of the side reinforcing rubber 24 radially outward of the phantom line FLW is Arro, the ratio Arri/Arro is 0.0. It is preferably within the range of 3 to 1.5, more preferably within the range of 0.3 to 1.0, and even more preferably within the range of 0.5 to 0.6.

When the cross-sectional area of the bead core 26 is Ac, the ratio Ac/Abf is preferably within the range of 0.7 to 1.1, more preferably within the range of 0.8 to 1.8. , more preferably in the range of 0.90 to 0.95.

The ratio ta/G between the total gauge G and the thickness ta is preferably within the range of 0.6 to 1.0, more preferably within the range of 0.6 to 0.8, and 0.7. It is more preferable to be in the range of ~0.8.

The aspect ratio of the run-flat tire 10 is preferably 65% or less, more preferably 50% or less, and even more preferably 35% or less.

As shown in FIG. 3 , the point of intersection where an imaginary line FLH passing through the rim end of the standard rim 30 and parallel to the tire radial direction intersects the main body portion 14A of the carcass 14 on the inner side of the tire maximum width portion Wmax in the tire radial direction is denoted by Pa. When the angle between the intersection point Pa and the tire width direction inner end 26P of the bead core 26 formed by the imaginary line FLα with respect to the tire width direction is α, 30°<α<70° is preferable, and 35°< α<60° is more preferable, and 35°<α<45° is even more preferable.

Pb is the intersection point where the virtual line FLH intersects the main body portion 14A of the carcass 14 on the tire radial direction outer side of the tire maximum width portion Wmax, and the virtual line FLβ connecting the intersection point Pb and the tire width direction inner end 26P of the bead core 26 is When the angle formed with respect to the tire width direction is β, it is preferably 50°<β<80°, more preferably 55°<β<70°, and 55°<β<65°. It is even more preferable to

As shown in FIG. 1, the other end portion 24B side of the side reinforcing rubber 24 on the tire radial direction outer side is arranged on the tire width direction inner side of the belt end of the first belt ply 16A and the belt end of the second belt ply 16B. It is preferable that

It is preferable that the apex 34T of the rim guard 34 be arranged on the outside in the tire width direction of the tire width direction outer end 14max of the main body portion 14A of the carcass 14 .

(belt)
A belt 16 is arranged outside the carcass 14 in the tire radial direction. The belt 16 of this embodiment is composed of one or more belt plies. As an example, the belt 16 of the present embodiment includes a first belt ply 16A on the inner side in the tire radial direction, and a second belt arranged on the outer side in the tire radial direction of the first belt ply 16A and narrower than the first belt ply 16A. ply 16B.

The belt plies 16A and 16B are formed by covering a plurality of cords (steel cords in this embodiment) arranged in parallel with each other with a covering rubber. The cords forming the belt plies 16A and 16B are arranged at an angle to the tire circumferential direction (for example, they are inclined at an angle of 15 to 30 degrees to the tire circumferential direction). The cords of the belt ply 16A and the cords of the belt ply 16B are inclined in opposite directions with respect to the tire equatorial plane CL. That is, the belt 16 of this embodiment is a so-called cross belt.

A belt reinforcing layer 18 is arranged outside the belt 16 in the tire radial direction. The belt reinforcing layer 18 includes, for example, cords extending along the tire circumferential direction, and is arranged so as to cover the entire belt 16 .

A tread rubber 21 forming a tread portion 20 is arranged outside the belt 16 and the belt reinforcing layer 18 in the tire radial direction. The tread portion 20 is a portion that contacts the road surface during running, and a circumferential groove 20A extending in the tire circumferential direction is formed on the surface of the tread portion 20 . Further, the tread portion 20 is formed with widthwise grooves (not shown) extending in the tire width direction. The shape and number of the circumferential grooves 20</b>A and widthwise grooves are appropriately set according to the performance required for the run-flat tire 10 , such as drainage performance and steering stability.

A tire side portion 22 is provided between the bead portion 12 and the tread portion 20 . The tire side portion 22 extends in the tire radial direction and connects the bead portion 12 and the tread portion 20 . A side rubber 23 is arranged outside the carcass 14 in the tire width direction in the tire side portion 22 and the bead portion 12 .

(side reinforcement rubber)
The tire side portion 22 is configured as described below so as to bear the load acting on the runflat tire 10 during runflat running.
The tire side portion 22 is provided with a side reinforcing rubber 24 made of a single rubber material for reinforcing the tire side portion 22 inside the carcass 14 in the tire width direction. The side reinforcing rubber 24 is a reinforcing rubber for running a predetermined distance while supporting the weight of the vehicle and the occupant when the internal pressure of the runflat tire 10 is reduced due to puncture or the like. In this embodiment, the side reinforcing rubbers 24 mainly composed of rubber are provided as an example, but the present invention is not limited to this, and the side reinforcing rubbers 24 may be formed of other materials. , a thermoplastic resin or the like as a main component.

In the present embodiment, the side reinforcing rubbers 24 are made of one type of rubber member, but are not limited to this, and may be made of a plurality of rubber members having different hardnesses, for example. In addition, the side reinforcing rubber 24 may contain other materials such as fillers, short fibers, resins, etc., as long as the rubber member is the main component. Furthermore, in order to increase durability during run-flat running, the rubber member constituting the side reinforcing rubber 24 may include a rubber member having a JIS hardness of 70 to 85 measured at 20° C. using a durometer hardness tester. . Furthermore, a loss factor tan δ measured using a viscoelastic spectrometer (for example, a spectrometer manufactured by Toyo Seiki Seisakusho) under the conditions of a frequency of 20 Hz, an initial strain of 10%, a dynamic strain of ±2%, and a temperature of 60 ° C. is 0.10 or less. A rubber member having physical properties may be included.

The side reinforcing rubber 24 extends in the tire radial direction along the inner surface of the main body portion 14A of the carcass 14, and has a shape whose thickness decreases toward the bead core 26 side and the tread portion 20 side, for example, a substantially crescent shape in cross section. ing. The thickness here refers to the length of the side reinforcing rubber 24 measured vertically from the inner surface of the tire when the runflat tire 10 is mounted on the standard rim 30 and the internal pressure is zero.

One end portion 24</b>A side of the side reinforcing rubber 24 on the inner side in the tire radial direction overlaps with the bead filler 28 with the carcass 14 interposed therebetween. That is, the one end portion 24A side of the side reinforcing rubber 24 is arranged so as to overlap the bead filler 28 in the tire radial direction.
On the other hand, the other end portion 24</b>B side of the side reinforcing rubber 24 on the tire radial direction outer side overlaps the belt 16 with the carcass 14 interposed therebetween. That is, the other end portion 24B side of the side reinforcing rubber 24 is arranged so as to overlap the belt 16 in the tire width direction.

Furthermore, the total gauge from the tire inner surface to the tire outer surface when measured on the imaginary line FLW passing through the tire maximum width portion Wmax of the run-flat tire 10 and parallel to the tire rotation axis is G, and from the tire inner surface to the case line 14CL. is measured in a direction perpendicular to the inner surface of the tire, the distance t between the virtual line FL1 and the virtual line FL6 is within the range of 30 to 70% of the total gauge G. preferably set.

Further, the side reinforcing rubber maximum width position 24P where the side reinforcing rubber 24 has the maximum width (tmax) is preferably in the range of 20 to 60% of the side height SH, and preferably in the range of 30 to 50% of the side height SH. More preferably, it is in the range of 30 to 40% of the side height SH.

(inner liner)
In this embodiment, an inner liner 32 is provided on the inner surfaces of the carcass 14 and the side reinforcing rubber 24 on the inner side of the tread portion 20 in the tire radial direction. The inner liner 32 is made of rubber containing butyl rubber as a main component, for example. The rubber forming the inner liner 32 has a higher gas permeability and a larger loss (loss coefficient tan δ) than other rubbers forming the runflat tire 10 (eg, the tread rubber 21, the side rubber 23, etc.). is used.

In the inner liner 32 of the present embodiment, the tire width direction end 32E extends outward in the tire width direction from the imaginary line FLE passing through the outermost end 16E in the tire width direction of the belt 16 (the end in the width direction of the first belt ply 16A). They are arranged so that they cannot be crossed.

The tire side portion 22 and part of the bead portion 12 have a separation point SP from the rim flange 30A (the bead portion 12 and the rim flange when the run-flat tire 10 is mounted on the standard rim 30 and the internal pressure is zero). A rim guard 34 is integrally provided on the outer surface outside in the tire radial direction of the point where the rim 30A starts to separate.

(rim guard)
As shown in FIG. 1, the rim guard 34 has a substantially triangular shape projecting outward from the imaginary contour line 22FL of the tire side portion 22 when viewed in cross section along the tire rotation axis, and has a vertex 34T (virtual contour line). An inclined surface 34A radially outward from the line 22FL (the point furthest to the outside of the tire) is smoothly connected to the outer surface of the tire side portion 22, and an inclined surface 34B radially inward from the vertex 34T is normal. , and the rim flange 30A with a gap S therebetween.

A vertex 34T of the rim guard 34 is provided within a range of 10 to 20% of the side height SH outward from the reference line BL in the tire radial direction.

A distance La in the tire radial direction between the vertex 34T of the rim guard 34 and the virtual line FL2 is preferably set within a range of 4 to 10% of the side height SH.
A distance Lb in the tire radial direction between the apex 34T of the rim guard 34 and an imaginary line FLa parallel to the tire rotation axis passing through the radially outermost end of the rim flange 30A is 3 to 10% of the side height SH. It is preferable to set within the range.
It is preferable that the apex 34T of the rim guard 34 be provided within a range of 10 to 20% of the side height SH from the reference line BL toward the outside in the tire radial direction.
Also, the thickness ta from the vertex 34T of the rim guard 34 to the case line 14CL should be set within a range of 140 to 300% of the thickness tb of the bead portion 12 at the separation point SP (measured perpendicular to the case line 14CL). is preferred.

(action, effect)
Next, the operation of the run-flat tire 10 of this embodiment will be described.
In the run-flat tire 10 of this embodiment, the value of the ratio t/G is optimized as described above from the bead portion 12 to the tread portion 20. It is possible to reduce the spring constant and improve the ride comfort during normal driving.
In addition, since the rim guard 34 is provided, it is possible to prevent the bead portion 12 from excessively collapsing during run-flat running, thereby ensuring run-flat durability.
Therefore, the run-flat tire 10 of this embodiment can achieve both ride comfort performance and run-flat durability.

In the run-flat tire 10 of the present embodiment, the height position of 20 to 40% of the side height SH from the reference line BL to the outside in the tire radial direction (the switching position between the arc with the curvature radius R1 and the arc with the curvature radius R2 By setting the t/G measured through the case line 14CL in the vicinity of the spring 14CL within the range of 50 to 80%, the effect of lowering the longitudinal spring constant can be enhanced.

Further, in the run-flat tire 10 of the present embodiment, the case line at a height position (around the middle position between the rim guard 34 and the buttress (shoulder)) of 40% to 60% of the side height SH outward in the tire radial direction from the reference line BL. By setting t/G measured through 14CL within the range of 60 to 80%, the effect of lowering the longitudinal spring constant can be enhanced.

Further, in the runflat tire 10 of the present embodiment, the position of the apex 34T of the rim guard 34 is provided within a range of 10 to 20% of the side height SH from the reference line BL to the outside in the tire radial direction. Excessive collapse of the bead portion 12 during running is suppressed, and durability of the run-flat tire is ensured.

[Other embodiments]
An embodiment of the present invention has been described above, but the present invention is not limited to the above, and can of course be implemented in various modifications without departing from the gist of the present invention. is.

Although the carcass 14 of the above embodiment is composed of one carcass ply 15 , the present invention is not limited to this, and the carcass 14 may be composed of a plurality of carcass plies 15 .

Although the belt 16 in the above embodiment is a so-called intersecting belt made up of two belt plies, it may be a spiral belt. Also, the belt 16 may have a structure in which a cord is embedded in a resin layer.

In the above embodiments, run-flat tires for passenger cars have been described, but the present invention can also be applied to run-flat tires for vehicles other than passenger cars.

The disclosure of Japanese Patent Application No. 2018-120304 filed on June 25, 2018 is referred to in its entirety.
All publications, patent applications and technical standards mentioned in this specification are hereby expressly incorporated herein by reference to the same extent as if each individual publication, patent application or technical standard were specifically and individually noted to be referred to. Referenced throughout the specification.

Claims (4)

a pair of bead cores;
a carcass comprising a body portion straddling the pair of bead cores and a folded portion for folding back the bead cores;
a belt provided outside the carcass in the tire radial direction;
A side reinforcing layer provided inside the carcass in the tire width direction and having a thickness gradually decreasing toward both sides in the tire radial direction;
a rim guard that is provided on the outer surface of the tire and contacts the rim flange during run-flat running to restrict the bead portion in which the bead core is embedded from tilting outward in the axial direction of the tire;
with
A case line is a center line passing through the center of the thickness of the carcass,
Measured in the tire radial direction from a reference line parallel to the tire rotation axis passing through the tire radial outer end of the bead core when viewed in a cross section along the tire rotation axis when mounted on a standard rim and in a state of zero internal pressure. side height SH,
0.1SHp is the intersection of the case line and a first imaginary line that passes through a position 10% of the side height SH outward from the reference line and is parallel to the tire rotation axis;
0.3SHp, the intersection of the case line and a second imaginary line passing through a position 30% of the side height SH outward from the reference line and parallel to the tire rotation axis;
0.8SHp is the intersection of the case line and a third imaginary line that passes through a position 80% of the side height SH from the reference line to the outside in the tire radial direction and is parallel to the tire rotation axis;
The intersection of the case line and a fourth imaginary line passing through a position 90% of the side height SH from the reference line outward in the tire radial direction and parallel to the tire rotation axis is 0.9SHp,
The total gauge from the inner surface of the tire to the outer surface of the tire excluding the rim guard is G,
The gauge from the inner surface of the tire to the case line is t,
and when
t/G between the intersection point 0.1Hp and the intersection point 0.3Hp is set within a range of 40 to 80%,
t/G between the intersection point 0.8Hp and the intersection point 0.9Hp is set within a range of 30 to 60%,
The position of the apex of the rim guard is set within a range of 10 to 20% of the side height SH from the reference line to the outside in the tire radial direction.
run-flat tires. t/G measured through the case line at a height position of 20% to 40% of the side height SH from the reference line outward in the tire radial direction is set within a range of 50% to 80%. 1. The run-flat tire according to 1. t/G measured through the case line at a height position of 40% to 60% of the side height SH from the reference line to the outside in the tire radial direction is set within a range of 60% to 80%. A runflat tire according to claim 1 or claim 2. The runflat according to any one of claims 1 to 3, wherein the apex of the rim guard is provided within a range of 10 to 20% of the side height SH from the reference line to the outside in the tire radial direction. tire.

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