JP6718264B2 - Run flat tires - Google Patents

Description

The present invention relates to a run flat tire.

BACKGROUND ART Heretofore, as described in Patent Document 1, a technique for improving fuel economy by narrowing the width and increasing the diameter of a tire has been proposed, and for example, as a technique effective for use as a tire for an electric vehicle. Is expected.

International publication 2012/176476 pamphlet

In the above technology, it is also desired to have a run-flat running performance that allows running even in a state where the internal pressure is lowered due to, for example, a flat tire. However, a run-flat tire having a side-reinforcing rubber having a crescent-shaped cross section in the side wall portion may impair fuel economy due to an increase in weight due to the reinforcing rubber, and thus the tire having a narrow width and a large diameter as described above. In the above, it has been desired to achieve both the fuel efficiency and the run-flat durability that enables the vehicle to travel a predetermined distance with the internal pressure of the tire lowered.

Therefore, an object of the present invention is to provide a run-flat tire which has improved fuel economy and ensures run-flat durability.

The run-flat tire of the present invention has a tread portion, a pair of sidewall portions that are continuous with both sides of the tread portion, a bead portion that is continuous with each sidewall portion, and a crescent-shaped cross section disposed in the sidewall portion. A run-flat tire, which comprises a side reinforcing rubber and a carcass made of a ply of a radial array cord, which extends in a toroidal shape between the pair of bead portions,
When the tire is built into the rim and the internal pressure is set to 250 kPa or more,
When the sectional width SW (mm) of the tire is less than 165 (mm), the ratio SW/OD of the sectional width SW (mm) of the tire and the outer diameter OD (mm) is 0.26 or less. ,
When the sectional width SW (mm) of the tire is 165 (mm) or more, the sectional width SW (mm) and the outer diameter OD (mm) of the tire are expressed by a relational expression,
OD≧2.135×SW+282.3 (mm)
The filling,
Further comprising a belt composed of one or more belt layers on the outer side in the tire radial direction of the carcass,
The tread portion has one or more circumferential grooves extending in the tire circumferential direction,
In the tire width direction cross section at the time of the reference state in which the tire is incorporated in a rim, filled with a predetermined internal pressure, and made unloaded, among the one or more belt layers, the width of the belt layer in the tire width direction is the maximum. When the half width in the tire width direction is WB, the tread in which the tire width direction distance from the tire width direction end of the belt layer having the largest width in the tire width direction among the one or more belt layers is 0.2 WB. Among the one or more circumferential grooves, the outermost circumferential groove in the tire width direction is located in the outer region on the outer side in the tire width direction from the position of the portion in the tire width direction.
According to the run-flat tire of the present invention, run-flat durability can be ensured while improving fuel efficiency.

Here, in the present invention, the “rim” is an industrial standard that is effective in the region where tires are produced and used, and is JATMA YEAR BOOK of JATMA (Japan Automobile Tire Association) in Japan and ETRTO (Ther) in Europe. STANDARDS MANUAL of European Tire and Rim Technical Organization) and standard rim of applicable size (RT) of RT which is described in YEAR BOOK of TRA (The Tire and Rim Association, Inc.) in the United States, or in the future, is a standard ST for the applicable size of RT. It refers to Measuring Rim in MANUAL and Design Rim in TRA's YEAR BOOK (that is, the “rim” includes the current size and the size that may be included in the industry standard in the future. Examples of "sizes that can be used" include sizes described as "FUTURE DEVELOPMENTS" in the ETRTO 2013 edition.) However, in the case of sizes not listed in the above industrial standards, the bead width of the tire A rim of a corresponding width.
In addition, "predetermined internal pressure" refers to the state in which the air pressure (maximum air pressure) corresponds to the maximum load capacity of a single wheel in the applicable size and ply rating described in JATMA, etc., and is described in the above industry standards. In the case of no size, the “predetermined internal pressure” means the air pressure (maximum air pressure) corresponding to the maximum load capacity specified for each vehicle in which the tire is mounted. Further, the “maximum load capacity” described later means a load corresponding to the maximum load capacity. It should be noted that the air here may be replaced with an inert gas such as nitrogen gas or the like.

Further, in the present invention, "the circumferential groove is located in a predetermined area or a predetermined position such as an outer area" means that the tire width direction center position of the circumferential groove is included in the predetermined area or the like, Or, it means that the tire is located, and the "center position in the tire width direction" means the tire width at the midpoint of a line segment that connects between the boundary points of the circumferential groove and the tread surface in the tire width direction cross section. Refers to the directional position.
Further, "a half width in the tire width direction of a belt layer having the largest width in the tire width direction among one or more belt layers (WB)" means from the tire width direction end portion of the largest belt layer to the tire equatorial plane. Indicates the distance measured along the tire width direction. In addition, "the tire width direction distance from the tire width direction end portion of the maximum belt layer" refers to the distance measured along the tire width direction from the tire width direction end portion of the maximum belt layer.

Here, in the run flat tire of the present invention, the outermost circumferential groove in the tire width direction among the one or more circumferential grooves is a belt having the largest width in the tire width direction among the one or more belt layers. It is preferable that the layer is located on the tire width direction position of the tread portion where the tire width direction distance from the tire width direction end is 0.1 WB, or on the tire width direction inner side of the tire width direction position.
According to this configuration, it is possible to further improve fuel efficiency and sufficiently secure run flat durability.
The "distance in the tire width direction from the tire width direction end of the belt layer having the largest width in the tire width direction among the one or more belt layers" is measured along the tire width direction toward the inner side in the tire width direction. Refers to the measured length.

In the run-flat tire of the present invention, the circumferential groove located in the outer region and located on the outermost side in the tire width direction among the one or more circumferential grooves has a cross-sectional area of 10 in the reference state. It is preferably ˜50 mm ² .
According to this configuration, it is possible to further improve fuel efficiency, sufficiently secure run flat durability, and sufficiently secure cornering performance and drainage during normal traveling.
The “cross-sectional area” of the circumferential groove refers to the cross-sectional area in the direction orthogonal to the extending direction of the groove.

Further, in the run-flat tire of the present invention, when the tire radial maximum length of the side reinforcing rubber in the tire width direction cross section in the reference state is H1, a relational expression,
10≦(SW/OD)×H1≦20
It is preferable to satisfy.
According to this configuration, it is possible to further improve run-flat durability while further improving fuel efficiency.
The "maximum length in the tire radial direction" refers to the maximum length of the side reinforcing rubber measured in the tire radial direction.

Further, in the run-flat tire of the present invention, the bead portion has a bead core, a bead filler is further provided on a tire radial outside of the bead core, and a tire in the tire width direction cross section in the reference state, the side reinforcing rubber tire. When the maximum radial length is H1 and the length of a line segment connecting the tire radial outermost point of the bead filler and the tire core radial outermost point of the bead core is H2,
1.8≦H1/H2≦3.5
It is preferable to satisfy.
According to this configuration, run flat durability can be secured while further improving fuel efficiency.
When there are a plurality of either or both of the “outermost point of the bead filler in the tire radial direction” and the “outermost point of the bead core in the tire radial direction”, the line segments are connected so that the above H2 is maximized. To do.

Further, in the run-flat tire of the present invention, the maximum thickness of the side reinforcing rubber measured along the direction perpendicular to the carcass is preferably 6 mm or less.
According to this configuration, fuel efficiency can be further improved.
In addition, when the carcass has a folded structure including a carcass body and a carcass folded portion, the maximum thickness measured along a direction perpendicular to the carcass body is referred to.

Further, in the run-flat tire of the present invention, the bead portion has a bead core, the carcass is a carcass body portion locked to the pair of bead cores, and extends from the carcass body portion, around the bead core. It is preferable that the carcass folded-back portion is folded back from the inner side in the tire width direction to the outer side, and the folded-back end of the carcass folded-back portion is located inward of the tire maximum width position in the tire radial direction.
According to this configuration, fuel efficiency can be further improved.

According to the present invention, it is possible to provide a run-flat tire in which run-flat durability is ensured while improving fuel economy.

It is a sectional view which shows the run flat tire concerning a 1st embodiment of the present invention along a tire width direction. FIG. 2 is a development view showing a tread pattern of the run flat tire shown in FIG. 1. It is sectional drawing which follows the tire width direction which expands a part and shows the run flat tire shown in FIG. FIG. 4(a) shows a narrow/large diameter runflat tire during runflat running (solid line) and during normal running (dashed line). The tire deformation that occurs inside is indicated by the degree of hatching (the darker the hatching, the greater the degree of deformation, and the area in which the line during hatching is from the upper right to the lower left, The area in which the line in the hatching is from the upper left to the lower right indicates that the inputs are in mutually opposite directions in the tire width direction). FIG. 4( b) shows a normal runflat tire (runflat tire that is not narrow or large in diameter) during runflat running (solid line) and during normal running (broken line). For, the tire deformation that occurs in the tire during the running is indicated by the shade of hatching. It is a development view showing a tread pattern of a run flat tire concerning a 2nd embodiment of the present invention.

Hereinafter, an embodiment of the present invention will be described as an example with reference to the drawings.
FIG. 1 is a cross-sectional view along a tire width direction showing a run flat tire (hereinafter, also simply referred to as a tire) according to a first embodiment of the present invention. The tire 1 of FIG. 1 is in a standard state in which it is mounted on a rim (not shown), filled with a predetermined internal pressure, and no load is applied.

Here, when the tire 1 has a tire 1 assembled on a rim and the internal pressure is 250 kPa or more, and the sectional width SW (mm) of the tire 1 is less than 165 (mm), the sectional width SW of the tire 1 is (Mm) and outer diameter OD (mm) ratio SW/OD is 0.26 or less, and when the sectional width SW of the tire 1 is 165 (mm) or more, the sectional width SW (mm of the tire 1 ) And the outer diameter OD (mm) satisfy the relational expression, OD≧2.135×SW+282.3 (mm).
The tire 1 of the present embodiment is not particularly limited, but for example, tire sizes of 145/60R19, 145/60R18, 145/60R17, 155/70R19, 155/55R19, 155/55R18, 165/60R19, 165/55R18. 175/60R19, 175/55R18, 175/55R20, 175/60R18, 185/60R20, 185/55R20, 185/60R19, 185/55R19, 195/50R20, 195/55R20, 205/50R21, etc. You can

As shown in FIG. 1, the tire 1 includes a tread portion 2, a pair of sidewall portions 3 (one side in the range shown in the drawing) connected to both sides of the tread portion 2, and a bead portion 4 connected to each sidewall portion 3. (One side in the illustrated range), a side reinforcing rubber 5 having a crescent-shaped cross section disposed in the sidewall portion 3, and a carcass 6 made of a ply of a radial arrangement cord that straddles between the pair of bead portions 4 in a toroidal shape. , Are provided. Further, the tire 1 further includes a belt 7 formed of one or more belt layers on the outer side of the carcass 6 in the tire radial direction.

Here, as shown in FIG. 1, the bead portion 4 has a bead core 4a. In the present invention, the bead core 4a can have various shapes such as a circular cross section and a polygonal cross section.
Further, in the present embodiment, a bead filler 4b having a substantially triangular cross section is arranged on the tire radial direction outer side of the bead core 4a. On the other hand, in the present invention, a structure having no bead filler may be used.
The bead portion 4 may be further provided with a reinforcing member such as a reinforcing rubber layer and a reinforcing cord layer. These reinforcing members can be provided at various positions in the bead portion 4, and for example, the reinforcing members can be provided on the outer side and/or the inner side in the tire width direction of the bead filler 4b.

Further, in the present embodiment, the carcass 6 includes a carcass body portion 6a that is locked to the pair of bead cores 4a, extends from the carcass body portion 6a, and is folded back around the bead core 4a from the inside in the tire width direction to the outside. And a carcass folded-back portion 6b.
On the other hand, in the present invention, the carcass 6 is not limited to the one having the folded structure as described above, and for example, the carcass is composed of a plurality of bead core members obtained by dividing the bead core 4a in the tire width direction or the radial direction. 6 may be sandwiched by a plurality of divided bead core members.

In the present invention, the carcass line may have various shapes. For example, the carcass maximum width position may be close to the bead portion 4 side or may be close to the tread portion 2 side.

The number of cords to be driven into the carcass 6 is not particularly limited, but may be 20 to 60 cords/50 mm, for example.

Further, in the present embodiment, the folding end 6c of the carcass folding portion 6b of the carcass 6 is located inside the tire radial direction from the tire maximum width position and inside the tire radial direction outside the tire radial outside end of the bead filler 4b. There is. The folding end 6c of the carcass folding portion 6b of the carcass 6 may be located outside the tire radial direction outer end of the bead filler 4b or the tire maximum width position in the tire radial direction outside.
Further, when the carcass 6 is composed of a plurality of carcass plies, the positions of the folded-back end portions 6c can be different between the plies.

Further, in the present embodiment, the carcass 6 extends completely continuously between the bead cores 4a, but in the present invention, the carcass 6 is not limited to the above example, and for example, one bead core 4a to a tread portion. It is also possible to form a pair of split carcasses extending to the outer side in the tire width direction of 2 (in this case, the carcass is in a state where the central portion is hollowed out in the tire width direction).

Here, in the present embodiment, as shown in FIG. 1, the tire 1 includes a belt 7 composed of one or more belt layers on the outer side of the carcass 6 in the tire radial direction. Specifically, the tire 1 is disposed on the tire radial direction outer side of the crown portion of the carcass 6, a belt 7 including two belt layers in the illustrated example, and further disposed on the tire radial direction outer side of the belt 7. In the illustrated example, one belt reinforcing layer 8 is provided.

The belt layer of the belt 7 may have its belt cord extending at an inclination angle of 20 to 75° with respect to the tire circumferential direction, and preferably 25 to 70° with respect to the tire circumferential direction. The inclination angle is more preferably 25 to 45° with respect to the tire circumferential direction.
When the belt 7 is composed of two layers or two or more belt layers as in the illustrated example, the belt cords can cross each other between the belt layers. The belt cord is not particularly limited, but, for example, a steel cord or an organic fiber cord can be used.

In the illustrated example, the tire width direction width of the tire radial direction inner belt layer is longer than the tire width direction width of the tire radial direction outer belt layer, but the tire width direction of the tire radial direction inner belt layer Can also be made shorter than the width of the belt layer on the outer side in the tire radial direction in the tire width direction.
Regarding the belt layer having the largest width in the tire width direction among the one or more belt layers (in the illustrated example, the belt layer on the tire radial inner side), the width in the tire width direction is 90% to 90% of the tread width. It is preferably 120%, and more preferably 100% to 110%. The "tread width" refers to a width measured along the tire width direction, which is filled with the above-mentioned predetermined internal pressure, and which comes into contact with the road surface when the maximum load is applied. ..

The belt reinforcing layer 8 can be configured by a spiral cord wound in a spiral shape substantially in the tire circumferential direction. The "substantially the tire circumferential direction" referred to here means, for example, an inclination angle of 5° or less with respect to the tire circumferential direction.

Further, in the illustrated example, the belt reinforcing layer 8 has a width measured along the tire width direction that is larger than that of the belt 7, and the belt 7 and the belt reinforcing layer 8 have the belt reinforcing layer 8 on the outer peripheral side. It is formed so as to cover from.
The width of the belt reinforcing layer 8 may be smaller than that of the belt 7 as measured along the tire width direction. Further, the belt reinforcing layer 8 is arranged on the tire radial direction outer side of the belt 7, but in the present invention, the belt reinforcing layer is not an essential constituent member and is arranged on the tire radial direction inner side of the belt 7. Good.

As a cord constituting the belt reinforcing layer 8, a high-rigidity cord (corresponding to a Young's modulus of 50 MPa or more, which is tested in accordance with JIS L1017(2002)8.5a and obtained according to JIS L1017(2002)8.8). ) Or a low rigidity cord (also a cord having a Young's modulus of less than 50 MPa), a high elongation cord, a high heat shrinkage cord (a cord having a heat shrinkage percentage of 1% or more under a load of 50 g at 170° C.) and the like. .. Further, as the cord constituting the belt reinforcing layer 8, a monofilament cord, a cord made of a plurality of filaments, or a cord made of filaments of different materials can be used.

The number of driving cords of the belt reinforcing layer 8 is not particularly limited, but may be, for example, 20 to 60/50 mm.
Further, the cords of the belt reinforcing layer 8 can be distributed by changing the rigidity, material, number of layers, driving number, etc. in the tire width direction, for example, increasing the number of layers only at the end portion in the tire width direction. Alternatively, the number of layers can be increased only in the central portion in the tire width direction.

Here, the tread portion 2 can be configured by one rubber layer, or can be configured by laminating a plurality of different rubber layers in the tire radial direction. When a plurality of different rubber layers are used, the loss tangent, the modulus, the hardness, the glass transition temperature, the material, etc. can be made different between the layers. In addition, the thickness of the plurality of rubber layers may vary in the tread width direction, and only the groove bottoms such as the grooves provided in the tread portion, for example, the circumferential grooves are different types of rubber layers from the periphery thereof. You can also
The tread portion 2 can also be configured by disposing a plurality of different rubber layers in the tire width direction, and in this case, loss tangent, modulus, hardness, glass transition temperature, material, etc. can be made different between the layers. it can. The ratio of the widths of the plurality of rubber layers in the tire width direction may change in the tread radial direction, or only the groove bottom provided in the tread portion, for example, the groove in the circumferential direction, only the vicinity of the tread end TE. It is also possible to make only some areas, such as only the outermost land portion in the tire width direction and only the land portion in the center in the tire width direction, a rubber layer of a type different from the surrounding area.
The term "tread edge" refers to a portion of the tire outer peripheral surface that comes into contact with the road surface when the tire 1 is mounted on the rim, the predetermined internal pressure is filled, and the maximum load is applied. , The outermost end in the tire width direction.

Further, in the tire width direction cross section in the above-mentioned reference state, in the tire width direction, passing through a point on the tread surface of the tire equatorial plane CL (in the case where the portion is a groove, a point on the virtual outer contour line of the tread). When the parallel straight line is m1, the straight line passing through the tread end TE and parallel to the tire width direction is m2, the distance in the tire radial direction between the straight line m1 and the straight line m2 is set to the high LCR, and the tread width is set to TW. LCR/TW is preferably 0.06 or less, and more preferably 0.02 or more and 0.05 or less. This is because the durability and wear resistance of the tire can be improved.

Further, in the tire 1, it is preferable that the sidewall portion 3 be thin. Specifically, the thickness of the sidewall portion 3 can be changed, for example, by changing the tire width direction cross-sectional area S1 of the bead filler 4b. More specifically, in the above reference state, the tire of the bead filler 4b can be changed. The cross-sectional area S1 in the width direction is preferably 1 to 4 times the cross-sectional area S2 in the tire width direction of the bead core 4a. This is because the ride comfort can be secured by setting S1 to 4 times or less of S2, and the steering stability can be secured by setting S1 to 1 or more times of S2.

Further, a side reinforcing rubber 5 having a crescent-shaped cross section is arranged on the side wall portion 3. Further, the side reinforcing rubber 5 can be arranged inside the carcass 6 in the tire width direction as shown in FIG. 1.

In the present embodiment, when the maximum tire radial direction length of the side reinforcing rubber 5 in the above standard state is H1 (mm), the sectional width SW (mm) of the tire 1, the outer diameter OD (mm), and the length thereof. The height H1 (mm) satisfies the relational expression, 10 (mm)≦(SW/OD)×H1≦20 (mm).
Further, in this embodiment, the maximum thickness of the side reinforcing rubber 5 measured in the direction perpendicular to the carcass 6 is 6 mm or less.
Further, in this embodiment, the length of a line segment connecting the outermost point in the tire radial direction of the bead filler 4b and the outermost point in the tire radial direction of the bead core 4a in the tire width direction cross section in the above-described reference state is H2( mm), 1.8≦H1/H2≦3.5 is satisfied.
The maximum tire radial direction length H1 of the side reinforcing rubber 5, the maximum thickness H2 of the side reinforcing rubber 5, and the length H2 may be different values in each half of the tire width direction. The above relationship may be satisfied by only one half of the tire width direction, but it is preferable that the above relationship be satisfied by both halves of the tire width direction.

The loss tangent tan δ of the side reinforcing rubber 5 is preferably 0.05 to 0.15. When the loss tangent tan δ is 0.05 or more, the damping property can be improved, while when the loss tangent tan δ is 0.15 or less, heat generation in the side reinforcing rubber 5 can be suppressed. Is.
Further, the 50% extension modulus of the side reinforcing rubber 5 is preferably set to 1.5 to 6.0 MPa. By setting the 50% extension modulus of the side reinforcing rubber 5 to 1.5 MPa or more, the steering stability can be further ensured, while the 50% extension modulus of the side reinforcing rubber 5 is set to 6.0 MPa or less. Thereby, the comfort and the riding comfort can be further secured.
The loss tangent tan δ and the 50% elongation modulus are measured with respect to a test piece having a thickness of 2 mm, a width of 5 mm and a length of 20 mm under the conditions of an initial strain of 1%, a dynamic strain frequency of 50 Hz and a temperature of 60°C. It means the value.

Here, in the tire 1, a porous member for reducing cavity resonance noise can be arranged on the inner surface of the tire. Further, for the same reason, electrostatic flocking can be applied to the inner surface of the tire.
Furthermore, an inner liner for holding the inner pressure of the tire can be arranged on the inner surface of the tire, and the inner liner may be formed by a rubber layer mainly containing butyl rubber and a film layer mainly containing resin. it can. Further, a sealant member for preventing air leakage at the time of puncture can be arranged on the inner surface of the tire.

Next, the tread pattern of the tire according to the first embodiment of the present invention will be described with reference to the development view shown in FIG.
As shown in FIG. 2, the tire 1 of the present embodiment has one or more circumferential grooves extending in the tire circumferential direction in the tread portion 2, and the tire width of the one or more circumferential grooves. The outermost circumferential groove is located in the outer region OR described later. Specifically, the tire 1 of the illustrated example has five circumferential grooves 9 to 13 continuously extending in the tire circumferential direction, and the circumferential grooves 11 and 13 located on both outer sides in the tire width direction. Are located in the outer regions OR on both sides in the tire width direction.
Further, in the present invention, the position of the circumferential groove can be set arbitrarily, but in the illustrated example, the three circumferential grooves 9 to 11 are the half on one side in the tire width direction with the tire equatorial plane CL as the boundary. And the two circumferential grooves 12 and 13 are located in the other half of the tire width direction.
Further, the tire 1 may be a tire in which the mounting direction in the vehicle is designated so that the half portion on one side in the tire width direction is located inside when the vehicle is mounted. Specifically, in the first embodiment shown in FIG. 2, a half portion on one side in the tread width direction having the tire equatorial plane CL as a boundary, in which the circumferential grooves 9 to 11 are located, is set to the vehicle mounting inner side, and the circumferential groove It is preferable that the other half of the tread width direction where the tires 12 and 13 are located with the tire equatorial plane CL as a boundary is outside the vehicle.
The phrase “extends in the tire circumferential direction” means that the inclination angle of the groove on the acute angle side with respect to the tire circumferential direction extends at 45° or less.

In the present embodiment, the circumferential grooves 9 to 13 and the widthwise grooves 14 to 16 and the narrow groove 17 described later can have any groove width and groove depth, but the groove width is 2 mm or more. And the groove depth can be 5 to 8.5 mm.

Further, as shown in FIG. 2, the tire 1 of the present embodiment has a plurality of width direction grooves 14 to 16 extending in the tire width direction on the tread surface 2a. Specifically, a plurality of widthwise grooves 14 and 15 are alternately provided in the tire circumferential direction in a half portion on one side in the tire width direction, extend from the tread end TE, and intersect the circumferential groove 11. After that, it terminates in the land portion outside the circumferential groove 10 in the tire width direction. A plurality of widthwise grooves 16 are provided in the tire circumferential direction on the other half of the tire widthwise direction, extend from the tread end TE, and intersect the circumferential grooves 12 and 13 before the tire equatorial plane. It ends in the land area before CL. Further, the widthwise groove 16 has an enlarged width portion 16a at the tire widthwise inner end that is wider than the groove width of the portion communicating with the circumferential groove 12.
Further, the circumferential groove 10 is formed with a narrow groove 17 extending inward in the tire width direction from the circumferential groove 10 and terminating in a land portion before the tire equatorial plane CL.
The phrase “extends in the tire width direction” means that the inclination angle of the groove on the acute side with respect to the tire circumferential direction extends beyond 45°.

Here, FIG. 3 is a cross-sectional view of the tire according to the first embodiment taken along a tire width direction in which a part thereof is enlarged. The illustrated tire 1 is mounted on a rim and filled with a predetermined internal pressure, It is in a standard condition with no load.
In the tire 1 of the present embodiment, when the half width in the tire width direction of the belt layer having the largest width in the tire width direction among the one or more belt layers is WB, the tire width of the one or more belt layers The outer region OR (outer region OR is defined as the outer region OR from the tire width direction position of the tread portion 2 where the tire width direction distance from the tire width direction end of the belt layer having the maximum width in the tire width direction is 0.2 WB. Is included in the tire width direction position of the tread portion 2 where the tire width direction distance is 0.2 WB) (hereinafter, "the belt layer having the largest width in the tire width direction among the one or more belt layers" is Also referred to as the "largest belt layer."
Then, in the tire 1 of the present embodiment, in the outer region OR, the outermost circumferential groove in the tire width direction among the one or more circumferential grooves (hereinafter, “the tire width direction most out of one or more circumferential grooves”). The "outer circumferential groove" is also referred to as the outermost circumferential groove). Specifically, in the illustrated example, the circumferential grooves 11 and 13 of the five circumferential grooves 9 to 13 are located in the outer region OR.
In the present embodiment, the circumferential grooves other than the circumferential grooves 11 and 13 can be located in the outer region OR, and the outermost circumferential groove is located only in the outer region OR on one side in the tire width direction. You can also

Further, in the tire 1 of the present embodiment, the circumferential groove can have any cross-sectional area, groove width, and groove depth as long as the groove width is 2 mm or more as described above, but the outer region The outermost circumferential grooves 11 and 13 located at OR have a cross-sectional area of 10 to 50 mm ² in the standard state. The outermost circumferential grooves 11 and 13 have a groove width of 2 to 5 mm and a groove depth of 5 to 8.5 mm in the standard state.
The groove width of a groove refers to the length of a line segment that connects two boundary points between the groove and the tread surface in a cross section in a direction orthogonal to the extending direction of the groove. The depth refers to the length measured along the tire radial direction from the line segment to the groove bottom.

The operational effects of the runflat tire of the first embodiment will be described below.
The present inventor has earnestly studied to solve the problem of ensuring run-flat durability while improving fuel efficiency. As a result, as shown in FIGS. 4(a) and 4(b), in the narrow width/large diameter tire satisfying the relational expression between the sectional width SW and the outer diameter OD as described above, as shown in FIGS. There is a tendency for buckling (a phenomenon in which the center part of the tread tread in the tire width direction rises significantly from the road surface) to occur on the road, but there is a tendency for the input in the tire width direction from the shoulder to the buttress to become relatively large. It was found that the deformation increased from the shoulder portion to the buttress portion as shown in FIG. 4A (note that in FIG. 4A and FIG. 4B, the greater the degree of deformation, the more the deformation was described in the tire). In the normal run-flat tire of FIG. 4(b), the deformation in the vicinity of the bead portion is relatively large when the run-flat running is performed, while the hatching is illustrated in the narrow range of FIG. 4(a). With wide-width and large-diameter runflat tires, the deformation from the shoulder to the buttresses is relatively large during runflat running.)
Therefore, in the run-flat tire of the present embodiment, the outermost circumferential groove in the tire width direction among the one or more circumferential grooves is positioned in the outer region OR. Therefore, since the rigidity in the tire width direction of the tread portion of the outer region OR is reduced, it is possible to disperse and relax the input in the tire width direction that occurs when the shoulder portion of the tread tread comes into contact with the ground during runflat running. Then, as a result of the input being relaxed, the deformation portion of the tire due to the input can be made wider and the deformation can be made gentle, and the ground contact property of the shoulder portion can be improved (concentration of ground pressure can be reduced). Can be reduced), and run flat durability can be secured. Further, since the buckling can be further suppressed and the heat generated by the buckling can be reduced by making the deformed portion wider, the rolling resistance can be reduced and the fuel economy can be improved.
As described above, according to the tire of the present embodiment, run flat durability can be ensured while improving fuel efficiency.
In the run-flat tire of the present embodiment, the belt layer is used as a reference for defining the outer region OR because the belt layer mainly bears the overall tire width direction rigidity of the tread portion. ..

Here, in order to further alleviate the input of the shoulder portion or the like during run-flat traveling, the outermost circumferential grooves 11 and 13 are not located too outside in the tire width direction, and the tire surface is in contact with the road surface during run-flat traveling. It is preferably located within. Therefore, preferably, the outermost circumferential grooves 11 and 13 are provided on the tire width direction position of the tread portion 2 where the tire width direction distance WG from the tire width direction end of the largest belt layer is 0.1 WB, or It is located inside the tire width direction with respect to the tire width direction position.

Further, in the present embodiment, it is preferable that the outermost circumferential grooves 11 and 13 located in the outer region OR have a cross-sectional area of 10 to 50 mm ² in the reference state.
According to this configuration, by setting the cross-sectional area to 10 mm ² or more, it is possible to effectively mitigate the input of the shoulder portion and the like during run-flat traveling. Further, by setting the cross-sectional area to 50 mm ² or less, cornering performance during normal running (during running when the tire has a normal internal pressure) can be secured. Further, for example, when the circumferential groove is provided in the inner region IR inside the tread portion 2 with respect to the outer region OR, or from the tread end TE toward the center in the tire width direction to the vicinity of the center. When the extending widthwise groove (lug groove) is provided, drainage of the tire can be ensured even if the cross-sectional area is 50 mm ² or less.
From the same viewpoint, it is more preferable that the outermost circumferential grooves 11 and 13 located in the outer region OR have a cross-sectional area of 10 to 30 mm ² in the reference state.

Further, in the present embodiment, as shown in FIG. 2, it is preferable that at least one circumferential groove extending continuously in the tire circumferential direction is located in the inner region IR that is inside the outer region OR in the tire width direction. .. With this configuration, it is possible to sufficiently secure the drainage property of the tire. It is more preferable to provide two or more circumferential grooves continuously extending in the tire circumferential direction in the inner region IR. In this case, it is preferable that the groove width of the circumferential groove located in the inner region IR is 5 mm or more.

The circumferential groove may extend linearly in the tire circumferential direction as shown in FIG. 2, or may extend in a zigzag shape or while curving. Further, the circumferential groove may be provided as a plurality of groove portions extending in the tire circumferential direction so as to be spaced apart from each other in the tire circumferential direction (in such a case, a gap between adjacent groove portions may be different from that of the groove portion). 3 times or less of the extension length). Further, the circumferential groove (including the groove portion) is preferably a groove extending at an acute angle of 30° or less with respect to the tire circumferential direction.

By the way, in the present embodiment, when the maximum tire radial direction length of the side reinforcing rubber 5 is H1 (mm) as in the illustrated example, a relational expression,
10 (mm) ≤ (SW/OD) x H1 ≤ 20 (mm)
It is preferable to satisfy.
By setting (SW/OD)×H1 to 10 (mm) or more, the volume of the side reinforcing rubber 5 can be secured, and run flat durability can be further secured, while (SW/OD)× By setting H1 to 20 (mm) or less, the weight of the side reinforcing rubber 5 can be reduced and the fuel economy can be further improved.

Further, in the present embodiment, as in the illustrated example, a line segment that connects the tire radial outermost point of the bead filler 4b and the tire radial outermost point of the bead core 4a in the tire width direction cross section in the above reference state. When the length of H is H2 (mm), it is preferable that 1.8≦H1/H2≦3.5 is satisfied.
Fuel economy can be further improved by setting the ratio H1/H2 to 1.8 or more, while run flat durability can be further secured by setting the ratio H1/H2 to 3.5 or less. You can

Further, in the present embodiment, as in the illustrated example, the maximum thickness of the side reinforcing rubber 5 measured along the direction perpendicular to the carcass 6 is preferably 6 mm or less. Fuel economy can be further improved.

Further, in the present embodiment, as in the illustrated example, the folded end 6c of the carcass folded-back portion 6b may be located on the tire radial direction inner side of the tire maximum width position in the tire width direction cross section in the reference state. preferable. Fuel economy can be further improved.
For the same reason, in the tire width direction cross section in the above-described reference state, the height in the tire radial direction from the innermost position in the tire radial direction of the carcass 6 of the folding end 6c of the carcass folding portion 6b is 30 mm or less. It is preferable.

In this embodiment, the negative ratio (ratio of the groove area to the area of the entire tread surface) is preferably 25% or less. This is because the steering stability can be improved. For the same reason, the negative rate is more preferably 15% or less.
Furthermore, in this embodiment, when the tire inner diameter, which is the diameter of the portion that contacts the rim when the tire is assembled to the rim, is RD, it is preferable that OD/RD is 1.4 or less. By setting the negative ratio of such a tire to 25% or less (more preferably 15% or less), it is possible to achieve a high level of both steering stability and fuel economy.
Furthermore, in the present embodiment, when a plurality of circumferential grooves are formed, the circumferential width on the outer side in the tire width direction can be increased. This is because the drainage property can be improved. In this embodiment, the width of the widthwise groove is smaller than the width of the circumferential groove, and the widthwise groove is formed in the circumferential land portion defined by the plurality of circumferential grooves. Is preferably formed from the circumferential groove toward the inner side of the circumferential land portion and terminates at the end portion in the circumferential land portion. This is because the driving force and the braking force can be increased. Further, in the present embodiment, the circumferential groove is formed with a narrow groove that communicates with the circumferential groove and ends in the land portion, and the angle formed by the narrow groove with respect to the tire width direction is 20° or less. Is preferred. This is because it is possible to secure lateral force and riding comfort. Further, in the present embodiment, the widthwise groove formed in the circumferential land portion has a widened portion having a groove width wider than the groove width of the communicating portion with the circumferential groove, and the widthwise groove is widened from the widened portion. It is preferable that the width becomes narrower toward the terminal end. This is because the drainage property can be improved. Furthermore, in the present embodiment, in the state where the tire is mounted on the vehicle, the negative rate (ratio of the groove area of the circumferential groove to the area of the tread tread surface) on the vehicle inner side than the tire equatorial plane CL is the vehicle outer side. Is preferably larger than the negative ratio (ratio of the groove area of the circumferential groove to the tread surface area). This is because the cornering performance can be improved. Alternatively, the negative ratio inside the vehicle mounting side of the tire equatorial plane CL (ratio of the groove area of all the grooves to the area of the tread tread) is the negative ratio outside the vehicle mounting (groove of all the grooves to the area of the tread tread surface). It is preferably smaller than the area ratio). This is because the drainage property can be improved.
In addition, in the present embodiment, the small land portion divided into the circumferential groove and the widthwise groove is arranged side by side in the tire circumferential direction, and the small land portion is the land surface corresponding to the tread surface that abuts the road surface. , A land side surface forming the groove wall surface of the widthwise groove, and a land surface and a land slope connected to the land side, the land slope from the tire width direction outer side to the inner side, the tire circumferential direction And, the height of the land portion side surface, which is the height from the groove bottom surface of the width direction groove, that is inclined toward the tire width direction and has a convex curved surface toward the tire center side in the tire radial direction is the land portion. The connecting portion that decreases in accordance with the slope of the slope and connects the land slope and the surface of the land has a round shape in which a convex curved portion is formed toward the tire radial outer side. It is preferable that the connecting portions extend substantially in the tire circumferential direction, and the adjacent connecting portions match in the tire circumferential direction.

Further, in the present embodiment, it is preferable that the groove area (total sum) of the widthwise grooves is larger than the groove area (total sum) of the circumferential grooves. This is because the drainage property can be improved. Also in this case, it is preferable that the OD/RD is 1.4 or less, so that the fuel efficiency and the driving stability student can be particularly compatible with each other.

Next, the tread pattern of the tire according to the second embodiment of the present invention will be described with reference to the development view shown in FIG.
The tire 1 shown in FIG. 5 is in a standard state in which it is mounted on a rim (not shown), filled with a predetermined internal pressure, and unloaded. The internal structure of the tire according to the second embodiment of the present invention (other than the tread pattern) can be the same as the internal structure of the tire according to the first embodiment described above. Further, of the constituent elements of the tire according to the second embodiment of the present invention, the description of the same or equivalent constituent elements as those of the first embodiment will be appropriately omitted.

The tire 1 of the second embodiment shown in FIG. 5 has five circumferential grooves 18 to 22 continuously extending in the tire circumferential direction in the tread portion 2, and is located on both outer sides in the tire width direction. The circumferential grooves (outermost circumferential grooves) 18 and 22 are located in the outer regions OR on both sides in the tire width direction. In the illustrated example, two circumferential grooves 18 and 19 are provided in a half portion on one side in the tire width direction with the tire equatorial plane CL as a boundary, and two circumferential grooves 21 and 22 are provided in a half portion on the other side in the tire width direction. However, one circumferential groove 20 is formed on the tire equatorial plane CL.

In the second embodiment, the circumferential grooves (outermost circumferential grooves) 18 and 22 located on both outer sides in the tire width direction have a groove width of 2 to 5 mm, and the circumferential grooves 19 to 21 are grooves. The width can be 5 mm or more. Further, the tire 1 of the present embodiment has a plurality of auxiliary grooves 23 having a groove width of less than 2 mm in the tread portion 2.

Further, in the present embodiment, as described above, the plurality of circumferential grooves 18 to 22 and the tread end TE define a plurality of land portions, and each land portion has a rib shape. In addition, the rib-shaped land portion is not provided with a groove (having a groove width of 2 mm or more) such that both ends thereof are opened in the circumferential grooves 18 to 22 or the tread end TE, in other words, in the land portion. , Each land portion refers to a land portion that extends in the tire circumferential direction without being divided by the groove. The rib-shaped land portion includes those having a groove that terminates in the rib-shaped land portion and those that are divided by sipes (groove width is less than 2 mm).

In addition, in the present embodiment, for example, the half portion on one side in the tire width direction may be the outside when the vehicle is mounted (that is, the tire in which the mounting direction is designated may be used). In the present embodiment, the tire in which the circumferential grooves 21, 22 are located with the half of the circumferential grooves 18, 19 on one side in the tread width direction with the tire equatorial plane CL as the boundary being the vehicle mounting inner side, It is preferable that the other half of the tread width direction, which has the equatorial plane CL as a boundary, is on the outside of the vehicle.

The operational effects of the runflat tire of the second embodiment shown in FIG. 5 will be described below.
In the tire according to the second embodiment shown in FIG. 5, like the tire according to the first embodiment, in the outer region OR, among the one or more circumferential grooves, the outermost circumferential grooves 18, 22 in the tire width direction are provided. Since it is located, run flat durability can be secured while improving fuel efficiency.
Further, the tire according to the second embodiment has circumferential grooves (outermost circumferential grooves) 18, 22 located on both outer sides in the tire width direction and a tread end TE, as compared with the tire according to the first embodiment. Since the land portion (the outermost land portion in the tire width direction) defined by the above is rib-shaped, the steering stability can be improved.

In the second embodiment, the tread surface has only at least one circumferential groove extending in the tire circumferential direction as the groove, or the circumferential groove and at least one other than the circumferential groove as the groove. The auxiliary groove of the book, the auxiliary groove having a groove width of less than 2 mm in a tread width direction region of 80% of the tread width centered on the tire equatorial plane CL of the tread tread, and a circumferential groove The negative rate of is preferably 12% or more and 20% or less. This is because it is possible to achieve both drainage and running performance on dry road surfaces. Further, in the second embodiment, the auxiliary groove (including a hole-shaped recess having a diameter of less than ² mm) preferably has a total extension per unit area of the tread surface of 0.05 (mm/mm ² ) or less. .. This is because it is possible to further secure running performance on a dry road surface. The "total extension" is defined as the extension length (length along the extension direction) of all the auxiliary grooves arranged in the tread tread, divided by the area of the tread tread. Further, in the second embodiment, the tread tread has at least two circumferential grooves extending in the tire circumferential direction, and the tire width is defined by the tread end TE and the circumferential groove closest to the tread end TE. Direction outermost land portion and at least one tire width direction inner land portion partitioned between the circumferential grooves on the tire width direction innermost side of the tire width direction outermost land portion, and the tread width direction outermost portion. The width of the outer land portion in the tire width direction is preferably 1/5 or more of the tread width. This is because the steering stability can be improved. Furthermore, in the second embodiment, when at least two circumferential grooves that extend in the tire circumferential direction are provided and at least one tire width direction inner land portion that is partitioned between the circumferential grooves is provided, the tread width is The width in the tire width direction of the inward land portion is preferably 23 mm or more. This is because the steering stability can be improved. In addition, the tire width direction inner land portion partitioned between the circumferential grooves, and the circumferential groove closest to the tread end TE and the tread width of 80% of the tread width centered on the tire equatorial plane CL on the tread tread surface. The projection length of the auxiliary groove in the tire width direction is W1 (mm) in at least one land portion among the land portions defined by the boundary line that defines the directional region, and the tire width direction of the at least one land portion Where W2 (mm) is the width of the auxiliary groove and ΣW1 (mm) is the total of the projected lengths of the auxiliary grooves within one pitch in the tire circumferential direction, two relational expressions, 1/4≦W1/W2≦ It is preferable that both 3/4 and ΣW1≧W2 are satisfied. This is because the running performance on a dry road surface can be further improved.

Furthermore, in the tire 1 according to any of the above-described embodiments, the internal pressure thereof is preferably 250 kPa or more, more preferably 280 kPa or more, and further preferably 300 kPa or more.
Further, this tire preferably has an air volume of 15000 cm ³ or more in order to cope with a load that can be used on public roads.

Although the first and second embodiments of the present invention have been described above with reference to the drawings, the run-flat tire of the present invention is not limited to the above example, and can be appropriately modified.

In order to confirm the effect of the present invention, tires of Examples 1 and 2 and Comparative Examples 1 and 2 as described below were prototyped, and a test for evaluating the fuel economy and run flat durability of the tire was conducted.

The tire of Example 1 is a tire as shown in FIGS. 1 and 2, and the tire of Example 1 has a sectional width SW of the tire and an outside of the tire when the tire is incorporated into a rim and the internal pressure is set to 250 kPa or more. Diameters OD are 155 mm and 653 mm, respectively, and the outermost circumferential groove is located in the outer region OR, and the tire width direction end portion of the belt layer having the largest width in the tire width direction among the plurality of belt layers. Is provided at a position where the distance in the tire width direction is 0.1 WB.
Example 2 Example 2 is the same as the tire of Example 1, except that the specifications were changed as shown in Table 1.
The tires of Comparative Examples 1 and 2 are the same as the tires of Example 1 except that the outermost circumferential groove is not located in the outer region OR and the specifications are changed as shown in Table 1.

<Fuel efficiency>
A test was conducted by running in JC08 mode. The evaluation result is represented by an index with the evaluation result of the tire according to Comparative Example 1 as 100, and the larger the index, the better the fuel consumption.
<Run flat durability>
The drum tester applies a load that is 65% of the maximum load according to the LI (Load Index) and runs at a speed of 80 km/h, and the distance until the tire cannot run due to tire failure with 160 km as a complete condition for 2 hours Was measured. Table 1 shows the results of index evaluation with the run flat durability of the tire of Comparative Example 1 as 100. The larger the value, the better the run flat durability of the tire.
The results of these evaluations are shown in Table 1 below along with the specifications of the tire.

＊１：最外側周方向溝の、タイヤ幅方向の幅が最大のベルト層のタイヤ幅方向端部からのタイヤ幅方向距離を示す。

*1: Indicates the tire width direction distance from the tire width direction end of the belt layer having the largest width in the tire width direction of the outermost circumferential groove.

As shown in Table 1, it can be seen that the tires according to Inventive Examples 1 and 2 were able to achieve both fuel efficiency and run flat durability in comparison with the tires according to Comparative Examples 1 and 2. ..

According to the present invention, it is possible to provide a run-flat tire in which run-flat durability is ensured while improving fuel economy.

1 Run-flat tire (tire)
2 tread portion 2a tread tread surface 3 sidewall portion 4 bead portion 4a bead core 4b bead filler 5 side reinforcing rubber 6 carcass 6a carcass body portion 6b carcass folding portion 6c folding end 7 belt 8 belt reinforcing layers 9, 10, 12 circumferential groove 11, 13 circumferential groove (outermost circumferential groove)
14, 15, 16 Width direction groove 16a Widened portion 17 Narrow groove 19, 20, 21 Circumferential groove 18, 22 Circumferential groove (outermost circumferential groove)
23 auxiliary groove CL tire equatorial plane TE tread edge OR outer area IR inner area

Claims (7)

A tread portion, a pair of sidewall portions connected to both sides of the tread portion, a bead portion connected to each of the sidewall portions, a side reinforcing rubber having a crescent-shaped cross section disposed in the sidewall portion, and a pair of the A run-flat tire comprising a carcass made of a ply of a radial arrangement cord, which extends in a toroidal shape between the bead portions,
When the tire is built into the rim and the internal pressure is set to 250 kPa or more,
When the sectional width SW (mm) of the tire is less than 165 (mm), the ratio SW/OD of the sectional width SW (mm) of the tire and the outer diameter OD (mm) is 0.26 or less. ,
When the sectional width SW (mm) of the tire is 165 (mm) or more, the sectional width SW (mm) and the outer diameter OD (mm) of the tire are expressed by a relational expression,
OD≧2.135×SW+282.3 (mm)
The filling,
Further comprising a belt composed of one or more belt layers on the outer side in the tire radial direction of the carcass,
The tread surface of the tread portion has one or more circumferential grooves extending in the tire circumferential direction,
In the tire width direction cross section at the time of the reference state in which the tire is incorporated in a rim, filled with a predetermined internal pressure, and made unloaded, among the one or more belt layers, the width of the belt layer in the tire width direction is the maximum. When the half width in the tire width direction is WB, the tread in which the tire width direction distance from the tire width direction end of the belt layer having the largest width in the tire width direction among the one or more belt layers is 0.2 WB. A run-flat tire, in which the outermost circumferential groove of the one or more circumferential grooves is located in an outer region on the outer side in the tire width direction from a position in the tire width direction of the portion. The outermost circumferential groove in the tire width direction among the one or more circumferential grooves is a tire width from a tire width direction end of a belt layer having the largest width in the tire width direction among the one or more belt layers. The run flat tire according to claim 1, which is located on the tire width direction position of the tread portion having a directional distance of 0.1 WB or on the tire width direction inner side of the tire width direction position. The circumferential groove located in the outer region and located at the outermost side in the tire width direction among the one or more circumferential grooves has a cross-sectional area in the reference state of 10 to 50 mm ^2. The run flat tire according to 2. When the tire radial maximum length of the side reinforcing rubber in the tire width direction cross section in the reference state is H1, a relational expression,
10≦(SW/OD)×H1≦20
The run flat tire according to any one of claims 1 to 3, which satisfies the above condition. Having a bead core in the bead portion, further having a bead filler on the tire radial outside of the bead core,
In the tire width direction cross section in the reference state, the maximum tire radial length of the side reinforcing rubber is H1, and a line connecting the tire radial outermost point of the bead filler and the tire radial outermost point of the bead core. When the length of the minute is H2,
1.8≦H1/H2≦3.5
The run flat tire according to any one of claims 1 to 4, which satisfies the above condition. The run-flat tire according to any one of claims 1 to 5, wherein a maximum thickness of the side reinforcing rubber measured along a direction perpendicular to the carcass is 6 mm or less. The bead portion has a bead core,
The carcass includes a carcass body portion that is locked to the pair of bead cores, and a carcass folded-back portion that extends from the carcass body portion and is folded around the bead core from the tire width direction inner side to the outer side. ,
The run-flat tire according to any one of claims 1 to 6, wherein a folded-back end of the carcass-folded-back portion is located inside a tire maximum width position in a tire radial direction.

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