JP7040139B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire having a side reinforcing layer on the sidewall portion, and more specifically, the structure of the bead portion is improved to reduce the tire weight while maintaining good steering stability and run rat durability. Regarding pneumatic tires that made it possible.

Generally, a bead core and a bead filler are embedded in the bead portion of a pneumatic tire. Furthermore, in pneumatic tires (so-called run-flat tires) that can safely travel a certain distance even if a flat tire occurs, a side reinforcing layer (a crescent-shaped rigid cross-sectional shape) to support the load of the vehicle during a flat tire. A layer made of rubber) is provided on the sidewall portion. In such a tire, the inner end portion in the tire radial direction of the side reinforcing layer may reach the vicinity of the bead portion, and the vicinity of the bead portion tends to be thick and the tire weight tends to increase. In recent years, there has been a strong demand for reduction in tire weight, and reduction in weight has also been studied for run-flat tires as described above. For example, Patent Document 1 proposes to eliminate bead fillers and reduce the weight of a tire by devising the shape of a bead core in a pneumatic tire provided with a side reinforcing layer having a crescent-shaped cross section.

However, even if such a tire has a side reinforcing layer having a crescent-shaped cross section, the effect of eliminating the bead filler is large, the rigidity of the sidewall portion is reduced, and the steering stability and run-flat durability are reduced. There was a risk of affecting. Therefore, there is a need for further measures that can reduce the tire weight while ensuring the rigidity of the sidewall portion and maintaining good steering stability and run-flat durability.

Japanese Unexamined Patent Publication No. 2002-301915

An object of the present invention is to improve the structure of the bead portion and reduce the tire weight while maintaining good steering stability and run rat durability in a pneumatic tire having a side reinforcing layer on the sidewall portion. It is to provide pneumatic tires that have made it possible.

The pneumatic tire of the present invention for achieving the above object has a tread portion extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and these sidewall portions. A pair of bead portions arranged inside in the radial direction of the tire, a bead core provided in each bead portion, a carcass layer mounted between the pair of bead portions, and the carcass layer in the tread portion. In a pneumatic tire having a plurality of belt layers provided on the outer peripheral side and a side reinforcing layer having a crescent-shaped cross section provided inside the carcass layer in the sidewall portion in the tire width direction, the bead core is a tire. It consists of at least one bead wire wound in the circumferential direction, and a plurality of circumferential portions of the bead wire form a plurality of layers overlapping in the tire radial direction with at least one row arranged in the tire width direction in the meridional cross section. The width W0 of the layer having the maximum number of rows included among the plurality of layers, the width W1 of the innermost layer in the tire radial direction, and the width W2 of the outermost layer in the tire radial direction are W1> W2 and W2 ≦ 0. The layer satisfying the relationship of .5 × W0 and having the maximum number of rows contained in the plurality of layers is located inside the tire radial center position of the bead core in the tire radial direction, and the bead wire is formed in the meridional cross section. When the polygon formed by the common tangents of the plurality of peripheral portions is the outer shape of the bead wire, the inner angles α and β of the corners located at both ends of the inner side in the tire radial direction of the outer shape are α> 90 °. Moreover, the relationship of β> 90 ° is satisfied, and the carcass layer is folded back while bending along the peripheral edge of the bead core at each bead portion and the main body portion from the tread portion to each bead portion via each sidewall portion. The bead core is composed of a folded portion extending from the position of the tire radial outer end toward the sidewall portion while in contact with the main body portion, and is raised from the outer surface on the outer surface of the sidewall portion. A plurality of fins extending along the tire radial direction are arranged at intervals in the tire circumferential direction over the entire circumference of the tire, and the tire width direction from the tire equatorial line to the outermost point in the tire width direction of the carcass layer. The distance WC along the tire is ½ or less of the nominal width of the tire cross section, and the protrusion height h of the fin and the maximum width A of the side reinforcing layer at the position where the fin protrudes most outward in the tire width direction. Satisfies the relationship of h ≧ 0.3 × A, and the height in the tire radial direction at the maximum width position of the tire excluding the fins. Assuming that the value is H, the position where the fins most protrude outward in the tire width direction is characterized by being located within 0.1H in and out of the tire radial direction with respect to the maximum tire width position excluding the fins. do.

In the present invention, since the bead core has the above-mentioned structure, the number of turns of the bead wire is reduced as a whole, and the number of turns of the bead wire is sufficiently secured inside the tire radial center position of the bead core in the tire radial direction. This makes it possible to reduce the amount of bead wire used and reduce the tire weight while maintaining sufficient performance as a bead core and ensuring the durability of the tire. Further, since the carcass is bent and folded along the bead core of this shape, substantially only the bead core is present in the closed region surrounded by the main body portion and the folded portion of the carcass layer. The tire weight can be reduced as compared with the tire having the bead filler. On the other hand, since the fins having the above-mentioned shape are provided on the outer surface of the sidewall portion, it is possible to suppress the decrease in the rigidity of the sidewall portion by these fins, and the steering stability and the run-flat durability are good. Can be maintained at.

In the present invention, the distance BT along the tire width direction from the outermost point in the tire width direction of the bead core to the outermost point in the tire width direction of the carcass layer is preferably 40 mm or less. As a result, the shape of the carcass layer becomes good, the spring rigidity of the sidewall portion can be satisfactorily secured, and it is advantageous to improve the run-flat durability.

In the present invention, the distance BD along the tire width direction from the outermost point in the tire width direction of the belt layer located on the innermost side in the tire radial direction among the plurality of belt layers to the outermost point in the tire width direction of the carcass layer is determined. It is preferably within 40 mm. As a result, the shape of the carcass layer becomes good, the spring rigidity of the sidewall portion can be satisfactorily secured, and it is advantageous to improve the run-flat durability.

In the present invention, it is preferable that the end point of the side reinforcing layer on the inner side in the tire radial direction is located on the inner side in the tire radial direction with respect to the outer end point in the tire radial direction of the bead core. As a result, when the conventional bead filler is not provided, the side reinforcing layer reaches the component (bead core) of the bead portion, and the run-flat durability can be effectively improved.

In the present invention, the end point on the outer side in the tire radial direction of the side reinforcing layer is 15 mm or more and 40 mm or less inward in the tire width direction from the outer end point in the tire width direction of the belt layer located on the innermost side in the tire radial direction among the plurality of belt layers. It is preferable that it is arranged in the range of. By sufficiently overlapping the side reinforcing layer with the belt layer in this way, it is advantageous to improve the run-flat durability.

In the present invention, the distance Q along the tire width direction from the tire equator to the inner end point of the side reinforcing layer in the tire radial direction and the tire of the belt layer located on the innermost side in the tire radial direction among the multiple belt layers from the tire equator. It is preferable that the difference from the distance P along the tire width direction to the outer end point in the width direction is within ± 20 mm. As a result, the end of the belt layer and the bead core are arranged on substantially the same straight line along the radial direction of the tire, which improves the structure of the entire tire and is advantageous for improving the run-flat durability. Become.

In the present invention, it is preferable that the protruding height h of the fin is 4 mm or more and 15 mm or less. This improves the shape of the fins, which is advantageous for improving steering stability and run-flat durability.

In the present invention, the circumference L0 of the outer shape of the bead wire, the length L1 of the inner side of the outer shape of the bead core in the tire radial direction, and the inclined side of the bead toe side connected to the inner side of the outer shape of the bead core in the tire radial direction. The length L2 of the bead core and the length L3 of the inclined side on the bead heel side connected to the inner side of the outer shape of the bead core in the tire radial direction are 0.25 ≦ (L1 + L2) / L0 ≦ 0.40 and 1.0 ≦ ( It is preferable to satisfy the relationship of L1 + L2) / (2 × L3) ≦ 2.5. By setting the shape of the bead core in this way, it is possible to efficiently reduce the tire weight while maintaining good basic performance (for example, rim detachment resistance) as the bead core.

In the present invention, the average diameter of the bead wire is preferably 0.8 mm to 1.8 mm. As a result, it is possible to efficiently reduce the tire weight while maintaining good basic performance as a bead core (for example, rim detachment resistance).

In the present invention, various dimensions are measured in a state where the tire is rim-assembled on a regular rim and the regular internal pressure is applied. A "regular rim" is a rim defined for each tire in a standard system including a standard on which a tire is based. For example, a standard rim for JATTA, "DesignRim" for TRA, or ETRTO. If so, it is set to "Measuring Rim". "Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATTA, the maximum air pressure, and for TRA, the table "TIRE ROAD LIMITED AT VARIOUS". The maximum value described in "COLD INFLATION PRESSURES" is "INFLATION PRESSURE" for ETRTO, but 180 kPa when the tires are for passenger cars.

It is a meridian semi-cross-sectional view of the pneumatic tire which comprises embodiment of this invention. It is explanatory drawing which shows by extracting the bead core of this invention. It is explanatory drawing which shows the sidewall part of FIG. It is a schematic diagram of the bead core which consists of another embodiment of this invention. It is explanatory drawing which shows typically the bead structure of the conventional example and the comparative example.

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

As shown in FIG. 1, the pneumatic tire of the present invention is arranged inside the tread portion 1, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and the sidewall portion 2 in the tire radial direction. It is provided with a pair of bead portions 3. In FIG. 1, the reference numeral CL indicates the tire equator. Although FIG. 1 is a cross-sectional view of the meridian, the tread portion 1, the sidewall portion 2, and the bead portion 3 each extend in the tire circumferential direction to form an annular shape, whereby the pneumatic tire is formed. The toroidal basic structure of is constructed. Hereinafter, the structure of the present invention will be described using a meridian cross-sectional view as shown in FIG. 1 (and FIG. 2 described later). Unless otherwise specified, all tire components in these meridian cross-sectional views are tire circumferences. It extends in the direction and forms a ring.

A carcass layer 4 is mounted between the 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 inside to the outside of the vehicle around the bead core 5 arranged in each bead portion 3. In the following description, the portion from the tread portion 1 to each bead portion 3 via each sidewall portion 2 is folded back around the bead core 5 in the main body portion 4A and each bead portion 3 toward each sidewall portion 2 side. The extending part is called 4B.

As shown in FIG. 2, the bead core 5 is composed of at least one bead wire 5A wound in the tire circumferential direction, and a plurality of peripheral portions of the bead wire 5A are arranged in the tire width direction and at least one row in the tire radial direction. It forms multiple overlapping layers. In the present invention, as long as a plurality of peripheral portions of the bead wire 5A form a row and a layer in the meridian cross section as described above, even if it is a so-called single winding structure in which a single bead wire 5A is continuously wound. , A so-called layer winding structure may be used in which a plurality of bead wires 5A are wound in a aligned state. In the illustrated example, a layer including three rows of orbital portions in order from the innermost side in the tire radial direction, a layer including four rows of orbital portions, a layer including three rows of orbital portions, a layer including two rows of orbital portions, and one row. It has a structure in which a total of 5 layers including the peripheral portion of the tire are laminated. In the following description, this structure is referred to as "3 + 4 + 3 + 2 + 1 structure". Similarly, in the following description, the laminated structure of the bead wire 5A is expressed in the same form in which the number of rows included in each layer is connected by "+" in order from the innermost layer in the tire radial direction. Further, in the bead core 5 of the illustrated example, the bead wires 5A are laminated in a bale-like manner. In addition, "bale stacking" is a stacking method in which the centers of three peripheral portions in contact with each other form a substantially equilateral triangle, and is a laminated structure having a high filling rate, which is sometimes called a hexagonal filling arrangement.

At this time, for 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 are W1> W2 and W2. The relationship of ≦ 0.5 × W0 is satisfied. Further, among the plurality of layers constituting the bead core 5, the layer having the maximum width W0 is located inside the tire radial direction of the bead core 5 with respect to the tire radial center position. That is, in each bead core 5, the width of the bead core 5 is smaller than the width on the innermost diameter side of the tire toward the outer diameter side of the tire from the portion having the maximum width located inside the tire radial direction from the center position in the tire radial direction. It has a tapered shape (hereinafter, this shape may be referred to as "outer diameter side wedge shape"). As shown in the figure, the widths W0 to W2 are lengths along the tire width direction between the outer ends in the tire width direction of the peripheral portions on both outer sides in the tire width direction of each layer.

Further, when each bead core 5 has a polygon formed by a common tangent line (broken line in the figure) of a plurality of peripheral portions of the bead wire 5A in the meridian cross section as the outer shape of the bead wire 5A, the outer shape is inside the tire radial direction. The internal angles α and β of the corners located at both ends of the side satisfy the relationship of α> 90 ° and β> 90 °, preferably 100 ° ≦ α ≦ 150 ° and 100 ° ≦ β ≦ 150 °.

The carcass layer 4 is folded 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 a bead core. Bend along the periphery of 5. For example, in the illustrated example, as a result of the bead core 5 satisfying the above settings, the cross-sectional shape is substantially pentagonal, so that the carcass layer 4 extending along the peripheral edge thereof is also bent into a substantially pentagonal shape. Further, the portion outside the tire radial direction of the bead core 5 of the folded portion 4B of the carcass layer 4 is in contact with the main body portion 4A of the carcass layer 4 along the main body portion 4A of the carcass layer 4. It extends toward the sidewall 2 side. As a result, the main body portion 4A and the folded portion 4B of the carcass layer 4 form a closed region surrounding the bead core 5.

In addition to this, in the carcass layer 4 of the present invention, the distance WC along the tire width direction from the tire equatorial CL to the outermost point in the tire width direction of the carcass layer 4 is 1/2 times or less of the nominal tire cross-sectional width. It is configured to be.

A plurality of layers (two layers in the illustrated example) of the belt layer 6 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Each belt layer 6 includes a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction. The reinforcing cords are arranged so that the reinforcing cords intersect each other between the layers. In these belt layers 6, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set to, for example, in the range of 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, two layers are provided, a full cover layer covering the entire width of the belt layer 6 and an edge cover layer covering only both ends of the belt reinforcing layer 7. The belt reinforcing layer 7 contains an organic fiber cord 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 arranged inside the carcass layer 4 in the sidewall portion 2 in the tire width direction. The side reinforcing layer 8 is made of rubber that is 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 of 100% elongation, for example, 9.0 MPa to 10.0 MPa. The side reinforcing layer 8 having such physical characteristics supports a load at the time of a puncture based on its rigidity and enables run-flat running.

On the other hand, on the outer surface of the sidewall portion 2, as illustrated in FIG. 3, a plurality of fins 9 that rise from the outer surface and extend along the tire radial direction are provided. These plurality of fins 9 are arranged at intervals in the tire circumferential direction over the entire circumference of the tire. For each fin 9, the protruding height h of the fin 9 at the position where the fin 9 protrudes most outward in the tire width direction satisfies the relationship of h ≧ 0.3 × A with respect to the maximum width A of the side reinforcing layer. There is. Further, assuming that the height in the tire radial direction of the tire maximum width position excluding the fins 9 is H, the position where the fins 9 protrude most outward in the tire width direction is the tire diameter with respect to the tire maximum width position excluding the fins 9. It is located within 0.1H inside and outside the direction. In other words, the difference ΔH between the tire radial height H at the maximum tire width position excluding the fin 9 and the tire radial height H ′ at the position where the fin 9 protrudes most outward in the tire width direction is within 0.1H. be.

In the present invention, since the bead core 5 has a special shape (outer diameter side wedge shape) as described above, the bead core 5 as a whole reduces the number of turns of the bead wire 5A and is more than the center position in the tire radial direction of the bead core 5. A sufficient number of turns of the bead wire 5A can be secured on the inner side in the radial direction of the tire, and the amount of the bead wire 5 used is reduced to reduce the tire weight while maintaining sufficient performance as the bead core 5 and ensuring the durability of the tire. It can be reduced. Further, when the outer shape of the bead core 5 (particularly the relationship between the peripheral length L0 and the lengths L1 to L3) is set as described above, the lengths L1 and L2 having a large contribution to the rim detachment during run-flat running are sufficient. It can be secured and the rim detachment resistance can be further improved.

On the other hand, since the fin 9 having the above-mentioned shape is provided on the outer surface of the sidewall portion 2, the sidewall portion 2 is reinforced by the fin 9 and the decrease in rigidity can be suppressed, so that the steering stability can be suppressed. And run-flat durability can be maintained well. In particular, since the fin 9 has the above-mentioned shape and is provided at the above-mentioned position, it surely prevents the carcass layer 4 from easily buckling in the vicinity of the tire maximum width position, and efficiently provides run-flat durability. Can be enhanced. Further, by providing the fins 9 on the outer surface of the sidewall portion 2, the heat dissipation effect of the fins 9 can be expected, and the durability can be further improved.

In the above structure, if the widths W0, W1 and W2 do not satisfy the above relationship, the shape of the bead core 5 becomes inappropriate and the shape of the bead portion 3 cannot be stabilized. In particular, when the relationship is W1 ≦ W2 or W2> 0.5 × W0, the width of the upper end of the bead core 5 becomes large, so that the rigidity in the vicinity of the portion where the rim flange abuts increases and the portion where the rim flange abuts increases. It becomes difficult to suppress the rim detachment caused by the rotational force used as the fulcrum, and the rim detachment resistance is lowered. If the internal angles α and 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 reduced. Further, when the internal angles α and β are 90 ° or less, the bead wires 5A located at both ends of the inner side in the tire radial direction of the outer shape are easily affected by the rubber flow during vulcanization, and the bead core 5 after vulcanization It becomes difficult to maintain a good shape.

Further, in the above-mentioned structure, if the shape and arrangement of the fins 9 are out of the above-mentioned range, the sidewall portion 2 cannot be properly reinforced by the fins 9, and the steering stability and the run-flat durability are good. Will be difficult to maintain. In particular, when the protruding height h of the fin 9 has a relationship of h <0.3 × A with respect to the maximum width A of the side reinforcing layer 8, the fin 9 does not sufficiently rise and a reinforcing effect is obtained. I can't. From the viewpoint of the balance between the structure of the entire tire and the fins 9, the protruding height h of the fins 9 is preferably 4 mm or more and 15 mm or less. Further, if the position where the fin 9 protrudes most outward in the tire width direction is out of the above range, the region where the carcass layer 4 is most likely to buckle cannot be appropriately reinforced in the sidewall portion 2, and the steering is stable. The effect of maintaining sex and run-flat durability cannot be expected.

The shape of each fin 9 is not particularly limited, but the width Wf of the fin 9 (width of the fin 9 measured along the tire circumferential direction) is preferably 3 mm to 10 mm, and the length Lf of the fin 9 (longitudinal direction of the fin 9). The length measured along the above) is preferably 15 mm to 70 mm. As the front view shape of the fin 9, in addition to the substantially rectangular shape shown in the figure, there are various shapes such as an arc shape curved toward one side in the tire circumferential direction, an S shape, a hook shape, and a shape having a plurality of bent portions. Can be adopted.

As described above, regarding the bead core 5, if the polygon formed by the common tangents (broken lines in the figure) of the plurality of peripheral portions of the bead wire 5A in the meridional cross section is the outer shape of the bead wire 5A, the peripheral length (bead wire) of this outer shape is taken as the outer shape. L0 is the sum of the lengths of all the sides of the polygon formed by the common tangents of the multiple perimeters of 5A, L1 is the length of the inner side of the outer shape in the tire radial direction, and the inner side of the outer shape is the inner side in the tire radial direction. Assuming that the length of the bead toe side inclined side connected to the side is L2 and the length of the bead heel side inclined side connected to the inner side of the outer shape in the tire radial direction is L3, these lengths are preferably 0. 25 ≦ (L1 + L2) / L0 ≦ 0.40 and 1.0 ≦ (L1 + L2) / (2 × L3) ≦ 2.5, more preferably 0.28 ≦ (L1 + L2) / L0 ≦ 0.36 and 1.1 It is preferable that the relationship of ≦ (L1 + L2) / (2 × L3) ≦ 2.0 is satisfied. By defining the shape of the bead core in this way, it is possible to achieve both reduction of tire weight and improvement of rim detachment resistance in a well-balanced manner. At this time, if the circumference L0 and the lengths L1 to L3 do not satisfy the above-mentioned relationship, it is not possible to reduce the tire weight and improve the rim disengagement resistance at the same time. In particular, if the relationship is 0.25> (L1 + L2) / L0 or 1.0> (L1 + L2) / (2 × L3), the rim detachment resistance deteriorates, and (L1 + L2) /L0> 0.40 or (L1 + L2). ) / (2 × L3)> 2.5, the tire weight cannot be reduced.

The circumference L0 and the lengths L1 to L3 may satisfy the above-mentioned relationship. Among these lengths, the length L1 of the inner side of the outer shape of the bead core in the tire radial direction and the length L1 of the outer side of the bead core in the tire radial direction. The length L2 of the inclined side on the bead toe side connected to the inner side greatly contributes to the rim coming off during run-flat running. Therefore, the length L2 is preferably set to 1.5 mm to 8 mm, more preferably 2 mm to 5 mm, and the length L1 is preferably set to preferably 2 mm to 10 mm, more preferably 2.5 mm to 7 mm. If the length L2 is smaller than 1.5 mm, the effect of improving the rim detachment resistance is limited, and if the length L2 is larger than 8 mm, the effect of reducing the tire weight is limited. If the length L1 is smaller than 2 mm, the effect of improving the rim detachment resistance is limited, and if the length L1 is larger than 10 mm, the effect of reducing the tire weight is limited.

The structure of the bead wire 5A itself is not particularly limited, but the average diameter is preferably 0.8 mm to 1.8 mm, more preferably 1.0 mm or more, in view of achieving both reduction in tire weight and improvement in rim detachment resistance. It is preferably 1.6 mm, more preferably 1.1 mm to 1.5 mm. Further, the total cross-sectional area of the bead wire 5A (the total cross-sectional area of the circumferential portion of the bead wire 5A included in the meridian cross section of each bead core 5) is preferably 10 mm ² to 50 mm ² , more preferably 15 mm ² to 48 mm ² , still more preferably. It is preferable to set it to 20 mm ² to 45 mm ² . If the average diameter of the bead wire 5A is smaller than 0.8 mm, the effect of improving the rim detachment resistance is limited, and if the average diameter of the bead wire 5A is larger than 1.8 mm, the effect of reducing the tire weight is limited. Become. If the total cross-sectional area of the bead wire 5A is smaller than 10 mm ² , the effect of improving the rim detachment resistance is limited, and if the total cross-sectional area of the bead wire 5A is larger than 50 mm ² , the effect of reducing the tire weight is limited. Become.

As described above, the closed region is formed by the main body portion 4A and the folded portion 4B of the carcass layer 4. In this closed region, a conventional bead filler or a similar tire component (arranged on the outer side in the tire radial direction of the bead core 5 and wrapped by the main body portion 4A and the folded portion 4B of the carcass layer 4 from the bead portion 3 to the side. A member that increases the rigidity of the wall portion 2) is basically not arranged, and only the bead core 5 exists. That is, even if there is an insulation rubber that covers the bead wire 5A and a rubber that fills a slight gap formed between the bead core 5 and the carcass layer 4, the bead has a large volume like a conventional pneumatic tire. No filler is used. Therefore, in the present invention, the tire weight can be effectively reduced. In particular, the rubber occupancy rate of this closed region, that is, the ratio of the total area a of rubber existing in the closed region (a / A × 100%) to the area A of the closed region in the meridian cross section is 0.1% to 15%. Is preferable. When the rubber occupancy of the closed region is larger than 15%, it becomes substantially the same as the case where the bead filler of the conventional pneumatic tire is present, and it becomes difficult to further enhance the effect of reducing the tire weight. Since the insulation rubber or the like that covers the bead wire 5A is always present due to the tire structure, the rubber occupancy rate in the closed region is basically never less than 0.1%.

Since only the bead core 5 is substantially present in the closed region as described above, in the present invention, even if another reinforcing member is added to the bead portion 3, the tire weight is increased as compared with the tire provided with the conventional bead filler layer. It will not be done. For example, a filler layer may be provided on the outer side of the carcass layer 4 (main body portion 4A and folded portion 4B) in the sidewall portion 2 in the tire width direction. This filler layer is different from the bead filler provided between the main body portion 4A and the folded portion 4B of the carcass layer 4 in the conventional pneumatic tire, and cooperates with the above-mentioned side reinforcing layer 8 to form the sidewall portion 2. The rigidity of the tire is appropriately secured. Even if such a filler layer is provided, the filler layer is merely a member provided in place of the conventional bead filler layer, so that the tire weight does not increase as compared with the tire provided with the conventional bead filler layer. In order to reduce the tire weight more effectively, it is preferable to associate the structure of the filler layer with the side reinforcing layer 8, for example, the cross-sectional area of the filler layer with respect to the cross-sectional area S1 and the hardness H1 of the side reinforcing layer 8. It is preferable that S2 and the hardness H2 satisfy the relationship of 0.15 ≦ (S2 × H2) / (S1 × H1) ≦ 0.60. This makes it possible to appropriately obtain the reinforcing effect of the filler layer while suppressing the amount of the filler layer used and suppressing the influence on the tire weight.

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-mentioned relationship. For example, the shape shown in FIG. 4 can be adopted. In the example of FIG. 4, since the widths W0, W1 and W2 satisfy the above-mentioned relationship, they correspond to the "outer diameter wedge shape" of the present invention, and the lengths L0 to L3 satisfy the above-mentioned relationship. .. More specifically, FIG. 4 (a) has a 4 + 5 + 4 + 3 + 2 + 1 structure for bale stacking, FIG. 4 (b) has a 3 + 4 + 3 + 2 structure for bale stacking, and FIG. 4 (c) has a 3 + 4 + 4 + 3 + 2 + 1 structure for bale stacking. In 4 (d), the second layer from the inner side in the tire radial direction and the layer adjacent to the inner side in the tire radial direction are not stacked in bales but in series (the peripheral portions adjacent to each other in the tire radial direction are laminated vertically in the tire width direction). It has a 3 + 4 + 4 + 3 + 2 + 1 structure.

Since at least a part of each of the structures shown in FIG. 4 is laminated in a bale-like manner, the bead wires 5A are arranged more densely than the bead wires having a structure in which the whole is laminated in series to fill the bead wires 5A. The rate can be increased. As a result, the tire weight can be reduced and these performances can be exhibited in a well-balanced manner while maintaining the running performance by satisfactorily ensuring the rigidity and the pressure resistance performance of the bead portion 3. Focusing on the filling factor of the bead wire 5A, it is preferable that all the bead wires 5A are stacked in a bale shape as shown in FIGS. 4A to 4C.

Further, regarding the shape of the bead core 5, in order to improve the 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 point of view, the shapes shown in FIGS. 4A, 4B, and 4D are preferable.

The shapes of these various bead cores 5 can be appropriately selected based on the above-mentioned various viewpoints in consideration of the structure of the entire pneumatic tire, the characteristics to be emphasized, and the like.

In the present invention, not only the distance WC along the tire width direction from the tire equatorial CL to the outermost point in the tire width direction of the carcass layer 4 is set in the above range, but also the outermost point in the tire width direction of the bead core 5 is set. The distance BT along the tire width direction from the carcass layer 4 to the outermost point in the tire width direction is preferably within 40 mm, more preferably 15 mm or more and 30 mm or less. As a result, the shape of the carcass layer 4 becomes good, the spring rigidity of the sidewall portion 2 can be satisfactorily secured, and it is advantageous to improve the run-flat durability. At this time, if the distance BT exceeds 40 mm, the curvature of the sidewall portion 2 becomes large, it becomes difficult to sufficiently secure the spring rigidity, and the effect of improving the run-flat durability cannot be sufficiently expected.

Further, a distance BD along the tire width direction from the outermost end point in the tire width direction of the belt layer 6 located on the innermost side in the tire radial direction of the plurality of belt layers 6 to the outermost point in the tire width direction of the carcass layer 4. Is preferably 40 mm or less, more preferably 15 mm or more and 30 mm or less. As a result, the shape of the carcass layer 4 becomes good, the spring rigidity of the sidewall portion 2 can be satisfactorily secured, and it is advantageous to improve the run-flat durability. At this time, if the distance BD exceeds 40 mm, the curvature of the sidewall portion 2 becomes large, it becomes difficult to sufficiently secure the spring rigidity, and the effect of improving the run-flat durability cannot be sufficiently expected.

As described above, in the present invention, since the conventional bead filler is not provided, it is preferable that the end portion of the side reinforcing layer 8 on the inner side in the tire radial direction reaches the bead portion 3 to secure the rigidity of the sidewall portion 2. .. Specifically, the end points of the side reinforcing layer 8 on the inner side in the tire radial direction may be arranged on the inner side in the tire radial direction from the outer end in the tire radial direction of the bead core 5. For example, the overlap amount D1 between the inner end portion of the side reinforcing layer 8 in the tire radial direction and the bead core 5 along the tire radial direction may be 15 mm or more and 30 mm or less. As a result, when the tire is attached to the rim, the side reinforcing layer 8 reaches the bead portion 3 (bead core 5) fixed by the rim, and the run-flat durability can be effectively improved.

On the other hand, it is preferable that the end points of the side reinforcing layer 8 on the outer side in the tire radial direction are appropriately overlapped with the belt layer 6. Specifically, the end points of the side reinforcing layer 8 on the outer side in the tire width direction are set from the outer end points in the tire width direction of the belt layer 6 located on the innermost side in the tire radial direction of the plurality of belt layers 6 to the inner side in the tire width direction. It is preferable to arrange it in a range of 15 mm or more and 40 mm or less. In other words, the overlap amount D2 between the belt layer 6 located on the innermost side in the tire radial direction and the side reinforcing layer 8 may be 15 mm or more and 40 mm or less. By sufficiently overlapping the end portion of the side reinforcing layer 8 with the belt layer 6 in this way, it is advantageous to improve the run-flat durability. At this time, if the overlapping amount D2 is less than 15 mm, the effect of increasing the rigidity of the sidewall portion 2 becomes limited. If the overlapping amount D2 exceeds 40 mm, the spring rigidity of the sidewall portion 2 becomes excessive, and the riding comfort is lowered. Further, since the volume of the side reinforcing layer 8 becomes large, the effect of reducing the tire weight may be affected.

In setting the position of the end point of the side reinforcing layer 8 in this way, further, the distance Q along the tire width direction from the tire equatorial CL to the inner end point of the side reinforcing layer 8 in the tire radial direction and a plurality of layers from the tire equatorial CL. The difference from the distance P along the tire width direction to the outermost end point in the tire width direction of the belt layer 6 located on the innermost side in the tire radial direction of the belt layer 6 is preferably within ± 20 mm, more preferably ± 10 mm. It should be set within. As a result, the end portion of the belt layer 6 and the end portion of the side reinforcing layer 8 and the bead core 5 are arranged on substantially the same straight line along the tire radial direction, and the structure of the entire tire is improved and the run It is advantageous to improve flat durability. At this time, if the difference between the distance P and the distance Q exceeds 20 mm, the deviation between the end of the belt layer 6 and the end of the side reinforcing layer 8 and the bead core 5 becomes large, which has the effect of further improving the run-flat durability. Is not fully expected.

The structures of the above-mentioned parts can be appropriately combined and adopted. In any case, in the pneumatic tire having the above-mentioned structure, the structure of the bead portion 3 is improved, so that the tire weight is reduced while maintaining the durability of the tire, and the rim detachment resistance is improved. Can be done.

The tire size is 205 / 55R16 and has the basic structure shown in FIG. 1, the structure of the bead core, the presence or absence of the bead filler, the maximum width W0 of the bead core, the width W1 of the innermost layer in the tire radial direction of the bead core, and the tire of the bead core. The width W2 of the outermost layer in the radial direction, the inner angles α and β of the corners located at both ends of the tire radial inner side of the bead wire outer shape, the circumference length L0 of the outer shape, and the tire radial inner side of the outer shape. Length L1, length L2 of the bead toe side inclined side connected to the tire radial inner side of the outer shell shape, length L3 of the bead heel side inclined side connected to the outer tire radial inner side of the outer shell shape, formula (L1 + L2) / L0, formula (L1 + L2) / (2 × L3), presence / absence of fins on the outer surface of the sidewall, protrusion height h of fins, maximum width A of side reinforcing layer, maximum tire width excluding fins Difference ΔH between the tire radial height H at the position and the tire radial height H ′ at the position where the fin 9 protrudes most outward in the tire width direction, the tire from the tire equatorial line to the outermost point in the tire width direction of the carcass layer. Distance WC along the width direction, distance BT along the tire width direction from the outermost point in the tire width direction of the bead core to the outermost point in the tire width direction of the carcass layer, the innermost belt layer in the tire radial direction Distance BD along the tire width direction from the outer end point in the tire width direction to the outermost point in the tire width direction of the carcass layer, overlap along the tire radial direction between the inner end portion of the side reinforcing layer in the tire radial direction and the bead core. Amount D1, overlap amount D2 between the innermost belt layer and the side reinforcement layer in the tire radial direction, the distance Q along the tire width direction from the tire equatorial line to the inner end point of the side reinforcement layer in the tire radial direction, and from the tire equatorial line. Conventional examples in which the difference from the distance P along the tire width direction to the outer end point of the belt layer located on the innermost side in the tire radial direction and the average diameter of the bead wire are set as shown in Tables 1 to 3, respectively. 1. 32 types of pneumatic tires of Comparative Examples 1 to 6 and Examples 1 to 25 were produced.

In the column of "bead core structure" in Tables 1 to 3, the corresponding drawing numbers are shown. In addition, Conventional Example 1 and Comparative Examples 1 and 2 are examples using conventional general bead cores, and the bead cores have a 5 + 5 + 5 structure laminated in series as shown in FIG. 5 (a). The bead core of Comparative Example 3 has a 5 + 5 + 4 + 3 + 2 + 1 structure laminated in series as shown in FIG. 5 (b).

In the example in which the fins are provided, as shown in FIG. 3, rectangular fins having a fin width Wf of 2 mm and a fin length Lf of 50 mm are adopted, and the distance between the fins adjacent to each other in the tire circumferential direction is adopted. Was set to 100 mm. When the overlap amount D1 of Example 14 in Table 2 is "0 mm", the end portion of the side reinforcing layer on the inner side in the tire radial direction is located on the outer side in the tire radial direction with respect to the outer end portion in the tire radial direction of the bead core. It means that the reinforcing layer and the bead core are separated from each other.

The tire mass, run-flat durability, and steering stability were evaluated for these pneumatic tires by the following evaluation methods, and the results are also shown in Tables 1 to 3.

Tire mass The mass of 5 tires was measured for each test tire, and the average value was calculated. The evaluation result is shown by an index with the value of Conventional Example 1 as 100. The smaller this index value is, the smaller the tire mass is.

Run-flat durability test tires are attached to wheels with a rim size of 18 x 7.5J and run on a drum tester under the run-flat tire drum durability test conditions described in ECE30 until the tire breaks down. The mileage was measured. The evaluation result is shown by an index with the value of Conventional Example 1 as 100. The larger this index value is, the better the run-flat durability is.

Steering stability Each test tire is attached to a wheel with a rim size of 18 x 7.5J, the air pressure is 230kPa, and it is mounted on a test vehicle with a displacement of 2000cc. Sensitivity evaluation by a test driver on a test course consisting of a flat asphalt road surface. Was done. The evaluation result is shown by an index with the value of Conventional Example 1 as 100. The larger this index value is, the better the steering stability is.

As is clear from Tables 1 to 3, in each of Examples 1 to 25, the tire mass was reduced while maintaining or improving the run-flat durability better than that of the conventional example 1. In addition, the rim detachment resistance was also maintained or improved satisfactorily. On the other hand, in Comparative Example 1, since the bead filler is removed while the conventional square bead core is used and the outer surface of the sidewall portion is not provided with fins, the run-flat durability and the rim detachment resistance are improved. It got worse. In Comparative Example 2, since the bead filler was discharged while using the conventional square bead core, the run-flat durability and the rim detachment resistance were deteriorated. In Comparative Example 3, since the shape of the bead core was inappropriate, the run-flat durability and the rim detachment resistance were deteriorated. In Comparative Example 4, the run-flat durability and the rim detachment resistance deteriorated because the distance WC was too large. In Comparative Example 5, the protrusion height of the fins was too small, so that the run-flat durability and the rim detachment resistance were deteriorated. In Comparative Example 6, since the maximum tire width position excluding the fins and the position where the fins most protrude outward in the tire width direction are largely separated from each other, the run-flat durability and the rim detachment resistance are deteriorated.

1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Belt layer 7 Belt reinforcement layer 8 Side reinforcement layer 9 Fin CL Tire equator

Claims (9)

A tread portion extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged inside the tire radial direction of these sidewall portions. A bead core provided in each bead portion, a carcass layer mounted between the pair of bead portions, a plurality of belt layers provided on the outer peripheral side of the carcass layer in the tread portion, and the side surface. In a pneumatic tire having a crescent-shaped side reinforcing layer with a cross section provided inside the carcass layer in the tire width direction in the wall portion.
The bead core is composed of at least one bead wire wound in the tire circumferential direction, and has a plurality of layers overlapping in the tire radial direction with at least one row in which a plurality of peripheral portions of the bead wire are arranged in the tire width direction in a meridian cross section. Forming and
The width W0 of the layer having the maximum number of rows included among the plurality of layers, the width W1 of the innermost layer in the tire radial direction, and the width W2 of the outermost layer in the tire radial direction are W1> W2 and W2 ≦ 0. The layer satisfying the relationship of .5 × W0 and having the maximum number of rows included in the plurality of layers is located inside the tire radial center position of the bead core in the tire radial direction.
When the polygon formed by the common tangents of the plurality of peripheral portions of the bead wire in the meridian cross section is the outer shape of the bead wire, the internal angles α of the corners located at both ends of the inner side in the tire radial direction of the outer shape, β satisfies the relationship of α> 90 ° and β> 90 °,
The carcass layer is folded back while bending along the peripheral edge of the bead core at each bead portion and the main body portion extending from the tread portion through each sidewall portion to each bead portion, and the tire radial outer end of the bead core. It consists of a folded part that extends toward each sidewall part while contacting the main body part from the position.
A plurality of fins rising from the outer surface and extending along the tire radial direction are arranged on the outer surface of the sidewall portion at intervals in the tire circumferential direction over the entire circumference of the tire.
The distance WC along the tire width direction from the tire equator to the outermost point in the tire width direction of the carcass layer is ½ or less of the nominal tire cross-sectional width.
The protruding height h of the fin and the maximum width A of the side reinforcing layer at the position where the fin protrudes most outward in the tire width direction satisfy the relationship of h ≧ 0.3 × A.
Assuming that the height of the tire maximum width position excluding the fins in the tire radial direction is H, the position where the fins most protrude outward in the tire width direction is inside and outside the tire radial direction with respect to the tire maximum width position excluding the fins. Pneumatic tires characterized by being located within the range of 0.1H. The pneumatic according to claim 1, wherein the distance BT along the tire width direction from the outermost point in the tire width direction of the bead core to the outermost point in the tire width direction of the carcass layer is within 40 mm. tire. The distance BD along the tire width direction from the outermost end point in the tire width direction of the belt layer located on the innermost side in the tire radial direction among the plurality of belt layers to the outermost point in the tire width direction of the carcass layer is within 40 mm. The pneumatic tire according to claim 1 or 2, wherein the tire is. The pneumatic tire according to any one of claims 1 to 3, wherein the end point of the side reinforcing layer on the inner side in the tire radial direction is located on the inner side in the tire radial direction with respect to the outer end on the tire radial direction of the bead core. The end point of the side reinforcing layer on the outer side in the tire radial direction is within a range of 15 mm or more and 40 mm or less inward in the tire width direction from the outer end point of the belt layer located on the innermost side in the tire radial direction of the plurality of belt layers in the tire width direction. The pneumatic tire according to any one of claims 1 to 4, wherein the tire is arranged in a tire. The distance Q along the tire width direction from the tire equatorial line to the inner end point of the side reinforcing layer in the tire radial direction and the tire width direction of the belt layer located on the innermost side in the tire radial direction from the tire equatorial line. The pneumatic tire according to any one of claims 1 to 5, wherein the difference from the distance P along the tire width direction to the outer end point is within ± 20 mm. The pneumatic tire according to any one of claims 1 to 6, wherein the protruding height h of the fin is 4 mm or more and 15 mm or less. The circumference L0 of the outer shape of the bead wire, the length L1 of the inner side of the outer shape of the bead core in the tire radial direction, and the inclined side of the bead toe side connected to the inner side of the outer shape of the bead core in the tire radial direction. The length L2 and the length L3 of the inclined side on the bead heel side connected to the inner side of the outer shape of the bead core in the tire radial direction are 0.25 ≦ (L1 + L2) / L0 ≦ 0.40 and 1.0 ≦ ( The pneumatic tire according to any one of claims 1 to 7, wherein the relationship of L1 + L2) / (2 × L3) ≦ 2.5 is satisfied. The pneumatic tire according to any one of claims 1 to 8, wherein the bead wire has an average diameter of 0.8 mm to 1.8 mm.

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