阅读说明：本技术 充气轮胎 (Pneumatic tire ) 是由 甲田启 松田淳 丹野笃 长安政明 竹森谅平 笹谷雄贵 于 2018-12-04 设计创作，主要内容包括：提供一种如下充气轮胎：在胎侧部具备胎侧加强层的充气轮胎中,改善胎圈部的构造,并能够一边维持轮胎的耐久性一边减轻轮胎重量。胎圈芯(5)的最大宽度W0、轮胎径向最内侧的宽度W1以及轮胎径向最外侧的宽度W2满足W1>W2且W2≤0.5×W0的关系,将最大宽度W0的位置配置于比胎圈芯(5)的轮胎径向中心位置靠轮胎径向内侧处,使胎体层(4)一边沿着胎圈芯(5)的周缘弯折一边折回,使胎体层(4)的折回部(4B)一边与胎体层(4)的主体部(4A)接触一边朝向各胎侧部(2)侧延伸,在将在子午线截面中由胎圈钢丝(5A)的多个环绕部分的共同切线形成的多边形作为所述胎圈钢丝(5A)的轮廓形状时,使所述轮廓形状满足预定的关系。(A pneumatic tire having a side reinforcing layer at a side portion thereof, wherein the tire weight can be reduced while maintaining the durability of the tire by improving the structure of a bead portion and the tire weight can be reduced by improving the maximum width W0 of a bead core (5), the innermost width W1 in the tire radial direction, and the outermost width W2 in the tire radial direction, which satisfy the relationship of W1> W2 and W2 ≦ 0.5 × W0, arranging the position of the maximum width W0 at the inner side of the tire radial direction from the center position of the bead core (5) in the tire radial direction, folding back a carcass layer (4) while folding back the carcass layer (4) along the peripheral edge of the bead core (5), extending the folded back portion (4B) of the carcass layer (4) toward each side portion (2) while contacting a main portion (4A) of the carcass layer (4), and satisfying the predetermined relationship when a polygon formed by common tangents of a plurality of circumferential portions of the bead wire (5A) in a meridian cross section is taken as the contour shape of the bead wire (5A).)

1. A pneumatic tire comprising a tread portion extending in a tire circumferential direction and having a ring shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on inner sides of the sidewall portions in a tire radial direction, and having a bead core provided to each bead portion, a carcass layer laid between the pair of bead portions, and a side reinforcing layer having a crescent-shaped cross section provided on an inner side of the carcass layer in a tire width direction at the sidewall portion, the pneumatic tire characterized in that,

the bead core is composed of at least 1 bead wire wound in the tire circumferential direction, a plurality of wrapped-around portions of the bead wire form at least 1 row arranged in the tire width direction and a plurality of layers overlapping in the tire radial direction, a maximum width W0 of the bead core, a width W1 of an innermost layer in the tire radial direction, and a width W2 of an outermost layer in the tire radial direction satisfy a relationship of W1> W2 and W2 ≦ 0.5 × W0, a layer of the plurality of layers which is the maximum width W0 is located more inward in the tire radial direction than a tire radial direction center position of the bead core,

when a polygon formed by common tangents to a plurality of surrounded portions of the bead wire in a meridian section is taken as an outline shape of the bead wire, inner angles α, β of corner portions at both ends of a side located on the inner side in the tire radial direction of the outline shape satisfy the relationship of α >90 ° and β >90 °,

a circumferential length L0 of the contour, a length L1 of a side of the contour on the tire radial direction inner side, a length L2 of an inclined side of the contour on the toe side connected to the side on the tire radial direction inner side, and a length L3 of an inclined side of the contour on the heel side connected to the side on the tire radial direction inner side satisfy a relationship of 0.25 ≦ L1 + L2)/L0 ≦ 0.40 and 1.0 ≦ L1 + L2)/(2 ×L 3) ≦ 2.5,

the carcass layer includes a main body portion extending from the tread portion to each bead portion through each sidewall portion, and a folded portion folded back along a peripheral edge of the bead core at each bead portion and extending toward each sidewall portion while contacting the main body portion from a position of an outer end of the bead core in the tire radial direction.

2. A pneumatic tire according to claim 1,

in a meridian cross section, when an auxiliary line a0 perpendicular to the carcass layer through an intersection of a straight line extending parallel to the tire radial direction and 20mm away from a bead toe to the tire radial direction outer side and an outline of the outer surface of the sidewall portion, an auxiliary line a1 parallel to the auxiliary line a0 and 5mm away from the auxiliary line a0 to the tire radial direction inner side, and an auxiliary line a2 parallel to the auxiliary line a0 and 5mm away from the auxiliary line a0 to the tire radial direction outer side, a cross-sectional area SR of a portion of the sidewall reinforcing layer existing between the auxiliary line a1 and the auxiliary line a2 and an area SB of a closed region formed by the main body portion and the folded-back portion of the carcass layer satisfy a relationship of 0.4 SB/SR 2.5.

3. A pneumatic tire according to claim 1 or 2,

in a meridian section, a tire section width K on an auxiliary line A0 passing through an intersection of a straight line 20mm away from a bead toe toward the tire radial direction outer side and extending parallel to the tire radial direction and a contour line of an outer surface of the sidewall portion and perpendicular to the carcass layer satisfies a relationship of 1.2 ≦ L0/K ≦ 5.0 with a circumferential length L0 of the contour shape of the bead core.

4. A pneumatic tire according to any one of claims 1 to 3,

the ratio of the total area of the rubber present in the closed region formed by the main body portion and the folded-back portion of the carcass layer to the area of the closed region is 0.1% to 15%.

5. A pneumatic tire according to claim 4,

a sealant layer is provided on the outer side in the tire width direction of the main body portion and the folded-back portion of the carcass layer.

6. A pneumatic tire according to claim 5,

in a meridian cross section, when an auxiliary line a0 perpendicular to the carcass layer through an intersection of a straight line extending parallel to the tire radial direction and 20mm away from the bead toe to the tire radial direction outer side and an outline of the outer surface of the sidewall portion, an auxiliary line a1 parallel to the auxiliary line a0 and 5mm away from the auxiliary line a0 to the tire radial direction inner side, and an auxiliary line a2 parallel to the auxiliary line a0 and 5mm away from the auxiliary line a0 to the tire radial direction outer side, a cross-sectional area SF of a portion of the sealant layer existing between the auxiliary line a1 and the auxiliary line a2 and an area SB of a closed region formed by the main body portion and the folded back portion of the carcass layer satisfy a relationship of 0.6 < SB/SF < 2.4.

7. A pneumatic tire according to claim 5 or 6,

in a meridian section, when an auxiliary line a0 perpendicular to the carcass layer and passing through an intersection of a straight line extending parallel to the tire radial direction and 20mm away from the bead toe toward the tire radial direction outer side and the outer surface of the sidewall portion, an auxiliary line a1 parallel to the auxiliary line a0 and 5mm away from the auxiliary line a0 toward the tire radial direction inner side, and an auxiliary line a2 parallel to the auxiliary line a0 and 5mm away from the auxiliary line a0 toward the tire radial direction outer side are drawn, a cross-sectional area SR of a portion of the sidewall reinforcing layer existing between the auxiliary line a1 and the auxiliary line a2, a cross-sectional area SF of a portion of the caulk layer existing between the auxiliary line a1 and the auxiliary line a2, and an area SB of a closed region formed by the main body portion and the turnback portion of the carcass layer satisfy a relationship of 0.3 < SB/(SR + SF) < 2.0.

8. A pneumatic tire according to any one of claims 1 to 7,

the average diameter of the bead wire is 0.8 mm-1.8 mm.

9. A pneumatic tire according to any one of claims 1 to 8,

the total cross-sectional area of the bead wire is 10mm²～50mm²。

10. A pneumatic tire according to any one of claims 1 to 9,

the bead core has a length L2 of a toe-side inclined side connected to a tire radial direction inner side of the outline shape of the bead core of 1.5mm to 8 mm.

11. A pneumatic tire according to any one of claims 1 to 10,

the length L1 of the edge of the bead core on the inner side in the tire radial direction of the outline shape is 2mm to 10 mm.

Technical Field

The present invention relates to a pneumatic tire having a side reinforcing layer at a side portion, and more particularly, to a pneumatic tire having an improved bead structure, reduced tire weight while maintaining tire durability, and good rim drop resistance (japanese patent publication No. リム - れ resistance).

Background

In general, a bead core and a bead filler are embedded in a bead portion of a pneumatic tire. In a pneumatic tire (so-called run flat tire) capable of safely traveling a certain distance even when a puncture occurs, a side reinforcing layer (a layer made of a hard rubber having a crescent-shaped cross section) for supporting a load of a vehicle at the time of the puncture is provided in a side portion. In such a tire, the tire radial direction inner end portion of the side reinforcing layer may reach the vicinity of the bead portion, and the thickness near the bead portion tends to be thick, and the tire weight tends to increase. Further, if the vicinity of the portion where the rim flange abuts is highly rigid due to the presence of the side reinforcing layer, a force is generated to rotate the bead portion in the tire inner direction with the portion where the rim flange abuts as a fulcrum during run-flat running, and the rim tends to easily drop.

On the other hand, in recent years, reduction in tire weight has been strongly demanded, and reduction in weight has also been studied in the run-flat tires as described above. For example, patent document 1 proposes the following: in a pneumatic tire provided with a side reinforcing layer having a crescent-shaped cross section, bead fillers are excluded by devising the shape of a bead core. However, in such a tire, even if the weight of the tire can be reduced, the rigidity in the vicinity of the bead portion is reduced, and therefore, it cannot be said that sufficient tire durability is necessarily obtained, and further measures are required without considering the drop of the rim due to the rotational force with the portion where the rim flange abuts as the fulcrum.

Disclosure of Invention

Problems to be solved by the invention

The present invention aims to provide a pneumatic tire comprising: a pneumatic tire having a side reinforcing layer at the side portion thereof, wherein the structure of a bead portion is improved, the weight of the tire can be reduced while maintaining the durability of the tire, and the rim drop resistance is improved.

Means for solving the problems

The pneumatic tire for achieving the above object is characterized in that the bead core is composed of at least 1 bead wire (english: bead wire) wound in the tire circumferential direction, the bead cores are formed of at least 1 row of bead wires arranged in the tire width direction and a plurality of layers overlapped in the tire radial direction, the plurality of circumferential portions of the bead wires form a relationship of at least 1 row arranged in the tire width direction and a plurality of layers overlapped in the tire radial direction, the maximum width W0 of the bead core, the width W1 of the layer innermost in the tire radial direction, and the width W2 of the layer outermost in the tire radial direction satisfy W1 2 and W2 ≦ 0.5W 6, a relationship of a maximum width W2 and W2 ≦ 0.5W 6, a relationship of a toe-side profile of a bead wire which is a maximum width W0 and a toe-side curve of a bead wire profile of a bead wire which is formed by folding back the bead wire along a tangent line of a bead wire 2 and a bead wire 2 of a bead wire laid back side of the bead layer, a bead wire 2, a bead wire laid along a bead wire 2 of the bead wire, a tire radial direction, and a bead wire 2, the tire radial direction, and a tire side curve of a tire longitudinal direction, the tire longitudinal direction of the tire is formed by a toe-side curve of a tire longitudinal direction of a tire transverse angle of a tire transverse to a tire transverse angle of a tire transverse to a tire transverse angle of a.

ADVANTAGEOUS EFFECTS OF INVENTION

In the present invention, since the bead core has the above-described structure, the number of turns of the bead wires can be sufficiently secured at the inner side in the tire radial direction than the tire radial direction center position of the bead core while reducing the number of turns of the bead wires as a whole, and the amount of use of the bead wires can be reduced while maintaining sufficient performance as the bead core to secure the durability of the tire, thereby achieving reduction in the tire weight.

In the present invention, it is preferable that, in a meridian cross section, when an auxiliary line a0 perpendicular to the carcass layer through an intersection of a straight line extending parallel to the tire radial direction and 20mm away from the bead toe to the tire radial direction outer side and an outline of the outer surface of the sidewall portion, an auxiliary line a1 parallel to the auxiliary line a0 and 5mm away from the auxiliary line a0 to the tire radial direction inner side, and an auxiliary line a2 parallel to the auxiliary line a0 and 5mm away from the auxiliary line a0 to the tire radial direction outer side, a cross-sectional area SR of a portion of the sidewall reinforcing layer existing between the auxiliary line a1 and the auxiliary line a2 and an area SB of a closed region formed by the main body portion and the folded-back portion of the carcass layer satisfy a relationship of 0.4 SB/SR 2.5. This improves the cross-sectional structure in the vicinity of the portion where the rim flange abuts, and can suppress rim drop due to a rotational force about the portion where the rim flange abuts as a fulcrum, which is advantageous in improving the rim drop resistance.

In the present invention, it is preferable that in a meridian section, the relationship of 1.2. ltoreq. L0/K. ltoreq.5.0 is satisfied by the tire section width K on the auxiliary line A0 perpendicular to the carcass layer and the circumferential length L0 of the outline shape of the bead core at the intersection point of the straight line extending parallel to the tire radial direction and 20mm away from the bead toe toward the tire radial direction outer side, whereby the cross-sectional structure in the vicinity of the portion where the rim flange is in contact becomes good, the rim drop due to the rotational force with the portion where the rim flange is in contact as the fulcrum can be suppressed, and the rim drop resistance can be improved.

In the present invention, it is preferable that the ratio of the total area of the rubber present in the closed region formed by the main body portion and the folded-back portion of the carcass layer to the area of the closed region is 0.1% to 15%. Thereby, substantially only the bead core is present in the closed region formed by the main portion and the folded-back portion of the carcass layer, and hence it is advantageous to reduce the tire weight.

In this case, it is preferable that the body portion and the folded-back portion of the carcass layer have the respective cushion layers (japanese character: フィラー body regions) on the outer sides in the tire width direction. Thus, even when the conventional bead filler layer is not substantially present between the main body portion and the folded-back portion of the carcass layer, the cross-sectional structure of the tire (particularly, the rubber thickness from the bead portion to the sidewall portion) can be improved, which is advantageous in improving the durability and rim drop resistance of the tire. Further, since the filler layer is provided instead of the conventional bead filler layer, the weight of the tire is not increased as compared with the conventional tire having a bead filler layer even if the filler layer is provided.

Further, it is preferable that, in a meridian cross section, when an auxiliary line a0 passing through an intersection of a straight line extending 20mm away from the bead toe toward the tire radial direction outer side and parallel to the tire radial direction and the outline of the outer surface of the sidewall portion and perpendicular to the carcass layer, an auxiliary line a1 spaced 5mm away from the auxiliary line a0 toward the tire radial direction inner side and parallel to the auxiliary line a0, and an auxiliary line a2 spaced 5mm away from the auxiliary line a0 toward the tire radial direction outer side and parallel to the auxiliary line a0 are drawn, a cross-sectional area SF of a portion of the caulk layer existing between the auxiliary line a1 and the auxiliary line a2 and an area SB of a closed region formed by the main body portion and the folded portion of the carcass layer satisfy a relationship of 0.6 ≦ SB/SF ≦ 2.4. Thus, even when substantially only the bead core is present in the closed region formed by the main body portion and the folded-back portion of the carcass layer, the cross-sectional structure in the vicinity of the portion where the rim flange abuts is improved, and the rim drop due to the rotational force about the portion where the rim flange abuts is suppressed, which is advantageous in improving the rim drop resistance.

Further, in a meridian cross section, when an auxiliary line a0 passing through an intersection of a straight line extending 20mm away from the bead toe toward the tire radial direction outer side and parallel to the tire radial direction and the outline of the outer surface of the sidewall portion and perpendicular to the carcass layer, an auxiliary line a 15mm away from the auxiliary line a0 toward the tire radial direction inner side and parallel to the auxiliary line a0, and an auxiliary line a2 spaced 5mm away from the auxiliary line a0 toward the tire radial direction outer side and parallel to the auxiliary line a0 are drawn, it is preferable that a cross-sectional area SR of a portion of the sidewall reinforcing layer existing between the auxiliary line a1 and the auxiliary line a2, a cross-sectional area SF of a portion of the rubber layer existing between the auxiliary line a1 and the auxiliary line a2, and an area SB of the closed region formed by the main body portion and the folded-back portion of the carcass layer satisfy a relationship of 0.3 < SB/(SR + SF) < 2.0. Thus, even when substantially only the bead core is present in the closed region formed by the main body portion and the folded-back portion of the carcass layer, the cross-sectional structure in the vicinity of the portion where the rim flange abuts is improved, and the rim drop due to the rotational force about the portion where the rim flange abuts is suppressed, which is advantageous in improving the rim drop resistance.

In the present invention, it is preferable that the bead wire has an average diameter of 0.8mm to 1.8 mm. By setting the average diameter of the bead wire in an appropriate range in this way, it is advantageous to achieve both reduction in tire weight and improvement in rim drop resistance.

In the present invention, it is preferable that the total cross-sectional area of the bead wire is 10mm²～50mm². By setting the total cross-sectional area of the bead wire in an appropriate range in this way, it is advantageous to achieve both reduction in tire weight and improvement in rim drop resistance.

In the present invention, it is preferable that the length L2 of the inclined side on the toe side, which is continuous with the side on the inner side in the tire radial direction, of the outline shape of the bead core is 1.5mm to 8 mm.

In the present invention, it is preferable that the length L1 of the side of the bead core on the inner side in the tire radial direction in the outline shape is 2mm to 10mm, and thus the shape of the bead core becomes more favorable, which is advantageous in achieving both the reduction in the tire weight and the improvement in the rim drop resistance.

In the present invention, "regular Rim" means a Rim that is specified for each TIRE in a standard system including a standard on which TIREs are based, in a standard system in which TIRE rims are assembled to the regular Rim (japanese: size リム) and filled with a regular internal PRESSURE (japanese: size internal PRESSURE), "regular Rim" means, for example, a standard Rim (japanese: publication リム) in case of JATMA, "Design Rim" in case of TRA, or "measurement Rim" in case of ETRTO, and "regular internal PRESSURE" means an air PRESSURE that is specified for each TIRE in a standard system including a standard on which TIREs are based, a maximum air PRESSURE in case of JATMA, and a maximum air PRESSURE in case of TRA, a TIRE load under various cold inflation PRESSURES in case of TRA, and "TIRE load limit under inflation PRESSURE in case of" inner wheel L imit variousoushouse L D INF L press "(L kPa)" in case of ETRTO indicate a maximum value of TIRE load for a vehicle.

Drawings

Fig. 1 is a meridian half sectional view of a pneumatic tire constituted by an embodiment of the present invention.

Fig. 2 is an explanatory view schematically showing a layered structure of a bead wire of the present invention.

Fig. 3(a) to 3(d) are explanatory views schematically showing a layered structure of a bead wire according to the present invention.

Fig. 4 is an enlarged explanatory view of the vicinity of the bead portion of fig. 1.

Fig. 5(a) to 5(c) are explanatory views schematically showing bead structures of a conventional example and a comparative example.

Detailed Description

Hereinafter, the structure of the present invention will be described in detail with reference to the drawings.

As shown in fig. 1, the pneumatic tire of the present invention includes a tread portion 1 extending in a tire circumferential direction and having a ring shape, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3 disposed on the inner side of the sidewall portions 2 in the tire radial direction, and in fig. 1, C L represents a tire equator.

A carcass layer 4 is provided between a pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the vehicle inner side to the vehicle outer side around bead cores 5 disposed in the respective bead portions 3. In the following description, a portion from the tread portion 1 to each bead portion 3 through each sidewall portion 2 is referred to as a body portion 4A, and a portion where each bead portion 3 is folded around a bead core 5 and extends toward each sidewall portion 2 side is referred to as a portion 4B.

As shown in fig. 2 in an enlarged scale, the bead core 5 is constituted by at least 1 bead wire 5A wound in the tire circumferential direction, and a plurality of wrapped portions of the bead wire 5A are formed into a plurality of rows aligned in the tire width direction and a plurality of layers overlapping in the tire radial direction. In the present invention, when a plurality of rows and a plurality of layers are formed in the plurality of circumferential portions of the bead wire 5A in the meridian cross section as described above, a so-called one-ply wound structure in which a single bead wire 5A is continuously wound or a so-called layer wound structure in which a plurality of bead wires 5A are wound in a state of being aligned may be employed. In the illustrated example, the tire has a structure in which a total of 6 layers including 4 rows of circumferential portions, 5 rows of circumferential portions, 4 rows of circumferential portions, 3 rows of circumferential portions, 2 rows of circumferential portions, and 1 row of circumferential portions are laminated in this order from the innermost side in the tire radial direction. In the following description, this structure will be referred to as a "4 +5+4+3+2+1 structure". Similarly, in the following description, the layered structure of the bead wires 5A is represented in the same manner in which the number of rows included in each layer is connected to "+" in order from the innermost layer in the tire radial direction. Also, in the bead core 5 of the illustrated example, the bead cores 5A are stacked up in a bale stack (Japanese: Biao み). The term "straw-bale packing" refers to a packing system in which the centers of 3 surrounding portions in contact with each other form a substantially regular triangle, and refers to a laminated structure having a high packing rate, which is also referred to as a hexagonal packing arrangement.

At this time, regarding each bead core 5, if the maximum width of the bead core 5 is W0, the width of the innermost layer in the tire radial direction is W1, and the width of the outermost layer in the tire radial direction is W2, these widths satisfy the relationship of W1> W2 and W2 ≦ 0.5 × W0. in addition, the layer that is the maximum width W0 among the plurality of layers constituting the bead core 5 is located on the tire radial direction inner side than the tire radial direction center position of the bead core 5. that is, each bead core 5 has a shape that becomes thinner toward the tip end so that the width of the bead core 5 becomes smaller toward the tire outer diameter side than the width of the tire innermost side from the portion of the maximum width located on the tire radial direction inner side than the tire radial direction center position (hereinafter, there is a case where this shape is referred to as "outer diameter side wedge shape" to point out), further, as shown in the drawings, the widths W0 to W2 are lengths along the tire width direction between the outer ends of the tire width direction surrounding portions on both outer sides in the tire width direction of the respective.

Further, each bead core 5 satisfies, when a polygon formed by common tangents (broken lines in the drawing) to a plurality of circumferential portions of the bead wire 5A in a meridian section is taken as the contour shape of the bead wire 5A, inner angles α, β of corner portions at both ends of a side on the inner side in the tire radial direction of the contour shape in a relationship of α >90 ° and β >90 °, preferably in a relationship of 100 ° ≦ α ≦ 150 ° and 100 ° ≦ β ≦ 150 °, and if the circumference of the contour shape (sum of lengths of all sides of the polygon formed by the common tangents to the plurality of circumferential portions of the bead wire 5A) is β, the length of the side on the inner side in the tire radial direction of the contour shape is β, the length of the inclined side on the toe side connected to the side in the tire radial direction of the contour shape is β, the length of the inclined side connected to the side in the contour shape is β, and the heel side)/(the length of the bead wire is 3533, these satisfy the relationship of 350.7.7)/(the relationship of β, 3527 + 460.7)/(368, preferably, 360.7.7.7)/(368, 3613, and β + 460.7.7.4.4 and 360.7.4 + 368).

The carcass layer 4 is folded back around the bead core 5 as described above, but since the bead core 5 of the present invention has a special shape (outer diameter side wedge shape) as described above, the carcass layer 4 is folded along the periphery of the bead core 5. For example, in the illustrated example, as a result of the bead core 5 satisfying the above-described setting, the cross-sectional shape is substantially pentagonal, and therefore the carcass layer 4 extending along the peripheral edge thereof is also bent substantially pentagonal. The portion of the folded portion 4B of the carcass layer 4 that is located further toward the tire radial direction outer side than the tire radial direction outer end of the bead core 5 extends toward each sidewall portion 2 side along the body portion 4A of the carcass layer 4 while contacting the body portion 4A of the carcass layer 4. As a result, a closed region surrounding the bead core 5 is formed by the main portion 4A and the folded portion 4B of the carcass layer 4.

A plurality of (2 in the illustrated example) belt layers 6 are embedded in the tread portion 1 on the outer circumferential side of the carcass layer 4. Each belt layer 6 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction. The reinforcing cords are arranged between the layers in such a manner that the reinforcing cords cross each other. In these belt layers 6, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in the range of, for example, 10 ° to 40 °. Further, a belt reinforcing layer 7 is provided on the outer peripheral side of the belt layer 6. In particular, in the illustrated example, 2 layers of a full cover layer covering the entire width of the belt layer 6 and an edge cover layer covering only both end portions of the belt reinforcing layer 7 are provided. The belt reinforcing layer 7 contains organic fiber cords oriented in the tire circumferential direction. In the belt reinforcing layer 7, the angle of the organic fiber cord with respect to the tire circumferential direction is set to, for example, 0 ° to 5 °.

A side reinforcing layer 8 having a crescent-shaped cross section is disposed on the inner side of the carcass layer 4 in the tire width direction in the side portion 2. The side reinforcing layer 8 is made of rubber harder than the other rubbers constituting the sidewall portion 2. Specifically, the rubber constituting the side reinforcing layer 8 has A JIS-A hardness of, for example, 70 to 80 and A modulus at 100% elongation of, for example, 9.0 to 10.0 MPA. The side reinforcing layer 8 having such physical properties can support a load at the time of air leakage based on the rigidity thereof, thereby enabling run-flat running.

In the illustrated example, the rubber layer 9 is provided on the outer side in the tire width direction of the carcass layer 4 (the main body portion 4A and the folded portion 4B) in the sidewall portion 2. As shown in the drawing, the bead filler layer 9 is a layer that can be arbitrarily provided as described below when only the bead core 5 is provided (the conventional bead filler is not present) in the closed region formed by the main body portion 4A and the folded portion 4B of the carcass layer 4.

In the present invention, since the bead core 5 has a special shape (outer diameter side wedge shape) as described above, it is possible to sufficiently secure the number of turns of the bead wire 5A at the inner side in the tire radial direction than the tire radial direction center position of the bead core 5 while reducing the number of turns of the bead wire 5A as the entire bead core 5, and to reduce the tire weight while maintaining sufficient performance as the bead core 5 and securing durability of the tire, in this case, the contour shape of the bead core 5 (particularly, the relationship between the circumferential length L0 and the lengths L1 to L3) is set as described above, and therefore, the lengths L1 and L2 that contribute greatly to the rim drop during run-flat can be sufficiently secured, and the rim drop resistance can be improved.

In the above-described structure, if the widths W0, W1, W2 do not satisfy the above-described relationship, the shape of the bead core 5 becomes inappropriate and the shape of the bead portion 3 cannot be stabilized, in particular, if the relationships W1 ≦ W2, W2>0.5 × W0 are such that the width of the upper end of the bead core 5 becomes large, so the rigidity in the vicinity of the portion with which the rim flange is in contact is increased and it is difficult to suppress the drop-off of the rim due to the rotational force with the portion with which the rim flange is in contact as a fulcrum, and the drop-off resistance is decreased, in particular, if the inner angles α, β are 90 ° or less, the number of turns of the bead wire 5A cannot be sufficiently reduced and the effect of reducing the tire weight is decreased, and in addition, if the inner angles α, 862 are 90 ° or less, the bead wires 5A positioned at both ends of the side on the inner side in the tire radial direction of the profile shape are easily affected by the rubber flow at the time of vulcanization, and it is difficult to maintain the good balance between the relationship α and the length)/(α to 8623)/(α, and the relationship α, and α > α, and the drop-off resistance is increased (α >) (α > + α) and α is not satisfied by α and α (α).

The circumferential length L0 and the lengths L1 to L03 may satisfy the above-described relationship, but of these lengths, the length L1 of the side on the inner side in the tire radial direction, which is the outline shape of the bead core, and the length L2 of the inclined side on the bead toe side, which is connected to the side on the inner side in the tire radial direction, which is the outline shape of the bead core, contribute greatly to rim drop during run-flat traveling, and therefore, the length L2 may be set to preferably 1.5mm to 8mm, more preferably 2mm to 5mm, and the length L1 may be set to preferably 2mm to 10mm, more preferably 2.5mm to 7mm, the effect of improving rim drop resistance may be limited if the length L2 is less than 1.5mm, the effect of improving rim drop resistance may be limited if the length L2 is greater than 8mm, the effect of improving rim drop resistance may be limited if the length L1 is less than 2mm, and the effect of reducing the tire weight may be limited if the length L1 is greater than 10 mm.

The structure of the bead wire 5A itself is not particularly limited, but in view of satisfying both reduction in tire weight and improvement in rim drop resistance, the average diameter may be preferably 0.8mm to 1.8mm, more preferably 1.0mm to 1.6mm, and further preferably 1.1mm to 1.5 mm. In addition, the total cross-sectional area of the bead wire 5A (the portion of the bead wire 5A surrounding the meridian cross section of each bead core 5) may be setSum of sectional areas of) is preferably 10mm²～50mm²More preferably 15mm²～48mm²More preferably 20mm²～45mm². If the average diameter of the bead wire 5A is less than 0.8mm, the effect of improving the rim drop resistance is limited, and if the average diameter of the bead wire 5A is more than 1.8mm, the effect of reducing the weight of the tire is limited. If the total cross-sectional area of the bead wire 5A is less than 10mm²The effect of improving the rim drop resistance is limited, and if the total cross-sectional area of the bead wire 5A is larger than 50mm²The effect of reducing the weight of the tire is limited.

As described above, the closed region is formed by the main body portion 4A and the folded-back portion 4B of the carcass layer 4, in this closed region, a conventional bead filler or a tire constituent member similar thereto (a member which is disposed outside the bead core 5 in the tire radial direction and is enclosed by the main body portion 4A and the folded-back portion 4B of the carcass layer 4 to improve the rigidity from the bead portion 3 to the sidewall portion 2) can be disposed, but in order to effectively reduce the tire weight, as shown in the drawing, only the bead core 5 may be substantially present in the closed region, that is, even if there is an insulating rubber covering the bead wire 5A and a rubber embedding a minute gap formed between the bead core 5 and the carcass layer 4, it is preferable not to use a bead filler having a large volume as in the conventional pneumatic tire, and in particular, it is preferable that the rubber occupancy of this closed region, that is, the ratio of the total area a of the rubber existing in the closed region in the radial cross section to the area a of the closed region (a/a × 100%) is 0.1% to 15%, that is substantially equal to the closed region, and that the rubber covering the closed region is not necessary to be covered by the conventional pneumatic tire, that the rubber, and that the closed region is further increased by the tire.

In the case where only the bead core 5 is substantially present in the closed region as described above, the filler layer 9 can be provided as described above, and the filler layer 9 can appropriately ensure the rigidity of the side wall portion 2 in cooperation with the side reinforcing layer 8 described above, unlike the bead filler provided between the main body portion 4A and the folded-back portion 4B of the carcass layer 4 in the conventional pneumatic tire, even if such a filler layer 9 is provided, the filler layer 9 is merely a member provided in place of the conventional bead filler layer, and therefore the tire weight is not increased as compared with the conventional tire provided with the bead filler layer, and further, in order to more effectively reduce the tire weight, the structure of the filler layer 9 and the like can be associated with the side reinforcing layer 8, and for example, the cross-sectional area S2 and the hardness H2 of the filler layer 9 can satisfy the relationship of 0.15 ≦ to (S2 × H2)/(S1 × H1) ≦ 0.60) with respect to the cross-sectional area S1 and the hardness H1 of the side reinforcing layer 8, and thereby, the amount of use of the filler layer 9 can be suppressed, and the effect of the tire weight can be appropriately obtained by the.

The specific shape of the bead core 5 is not particularly limited as long as the widths W0, W1, W2, and the lengths L0 to L3 satisfy the above-described relationship, and for example, the shape shown in fig. 3 can be adopted, in the example of fig. 3, since the widths W0, W1, and W2 all satisfy the above-described relationship, it corresponds to the "outer diameter wedge shape" of the present invention, and the lengths L0 to L3 satisfy the above-described relationship, in detail, fig. 3(a) has a 3+4+3+2+1 structure of a bale pile, fig. 3(b) has a 3+4+3+2 structure of a bale pile, fig. 3(c) has a 3+4+3+2+1 structure of a bale pile, and fig. 3(d) has a2 nd layer from the tire radial inner side and a layer adjacent thereto in the tire radial inner side which are not a bale pile but a straight pile (japanese: み) (a structure of a pile of a width +3+ 4+3 in the tire radial direction of the circumferential portions adjacent to each other in the tire radial direction).

In any of the structures shown in fig. 3, since at least a part of the bead wires are stacked in a straw-wrapped stack, the bead wires 5A can be arranged closer to each other and the filling ratio of the bead wires 5A can be increased as compared with the bead wires having a structure in which the entire structure is stacked in series. As a result, while maintaining the traveling performance while ensuring the rigidity and the pressure resistance of the bead portion 3 satisfactorily, the tire weight can be reduced and these performances can be exhibited in a well-balanced manner. When the filling rate of the bead wires 5A is taken into consideration, it is preferable that all the bead wires 5A are stacked in a straw-wrapped stack as shown in fig. 3(a) to 3 (c).

In addition, regarding the shape of the bead core 5, in order to improve stability of the shape of the entire bead core 5, it is preferable that the shape of the entire bead core 5 is line-symmetrical with respect to the center of the bead core 5 in the tire width direction. From this viewpoint, the shapes as shown in fig. 3(a), 3(b), and 3(d) are preferable.

The shape of these various bead cores 5 can be appropriately selected in consideration of the structure of the entire pneumatic tire, important characteristics, and the like from the various viewpoints described above.

As described above, in the pneumatic tire including the side reinforcing layer 8, when the rigidity is high in the vicinity of the portion where the rim flange abuts, a force may be generated to rotate the bead portion in the tire inner direction with the portion where the rim flange abuts as a fulcrum during run-flat running, and the rim may be dropped. Therefore, it is effective to optimize the structure in the vicinity of the portion where the rim flange abuts to improve the rim drop resistance. That is, in the meridian cross section, as shown enlarged in fig. 4, the structure of the region between the auxiliary line a1 and the auxiliary line a2 (hatched portion in the figure: hereinafter referred to as rim flange contact region) when the auxiliary line a0 is drawn perpendicular to the carcass layer through the intersection of the straight line extending parallel to the outer surface of the sidewall portion and 20mm away from the bead toe toward the tire radial direction outer side, the straight line being separated from the bead toe toward the tire radial direction inner side, the auxiliary line a1 being separated from the auxiliary line a0 toward the tire radial direction inner side and being parallel to the auxiliary line a0, and the auxiliary line a2 being separated 5mm toward the tire radial direction outer side from the auxiliary line a0 and being parallel to the auxiliary line a0 can be optimized.

Specifically, the cross-sectional area SR of the portion of the sidewall reinforcing layer 8 included in the rim flange contact region and the area SB of the closed region formed by the body portion 4A and the folded-back portion 4B of the carcass layer 4 may preferably satisfy the relationship of 0.4 ≦ SB/SR ≦ 2.5, and more preferably satisfy the relationship of 0.7 ≦ SB/SR ≦ 2.0, and the tire cross-sectional width K on the auxiliary line a0 and the circumferential length L0 of the contour shape of the bead core 5 may preferably satisfy the relationship of 1.2 ≦ L0/K ≦ 5.0, and more preferably satisfy the relationship of 1.4 ≦ L/K ≦ 4.5.

Similarly, the case of providing the bead filler layer 9 as shown in the figure may be such that the cross-sectional area SF of the bead filler layer 9 included in the rim flange contact region and the area SB of the closed region formed by the body portion and the folded-back portion of the carcass layer preferably satisfy the relationship of 0.6 < SB/SF < 2.4, and more preferably satisfy the relationship of 0.7< SB/SF < 2.1. Further, the cross-sectional area SR of the portion of the side reinforcing layer 8 included in the rim flange contact region, the cross-sectional area SF of the portion of the bead filler layer 9 included in the rim flange contact region, and the area SB of the closed region formed by the main body portion 5A and the turnback portion 5B of the carcass layer 5 may preferably satisfy the relationship of 0.3 < SB/(SR + SF) < 2.0, and more preferably satisfy the relationship of 0.4 < SB/(SR + SF) < 1.7. This improves the cross-sectional structure of the rim flange contact region, and can suppress rim drop due to a rotational force about the portion where the rim flange contacts as a fulcrum, which is advantageous in improving the rim drop resistance. The larger the cross-sectional areas SF and SR, the greater the rigidity of the rim flange contact region, and the more likely a rotational force is generated with the portion where the rim flange contacts as a fulcrum, and the larger the area SB, the larger the bead core 5 and the more limited the effect of reducing the tire weight.

The structures of the above-described respective portions may be appropriately combined and employed. In any case, in the pneumatic tire having the above-described structure, the structure of the bead portion 3 is improved, so that the tire weight can be reduced while maintaining the durability of the tire, and the rim drop resistance can be improved.