JP2019151301A - Pneumatic tire - Google Patents

Abstract

To provide a side reinforcement layer type run-flat tire capable of reducing a tire weight while maintaining steering stability and run-flat durability.SOLUTION: In a pneumatic run-flat tire, a carcass layer 4 is composed of a main body part 4A, and a folding part 4B which is folded along the peripheral border of a wedge-shaped bead core 5 in each bead part 3 to extend toward a sidewall part side while contacting a main body part from the outside end of the bead core in a tire radial direction, and plural fins 9 are provided on the external surface of the sidewall part. The distance WC along a tire width direction from a tire equatorial CL to the outermost side point of the carcass layer 4 in the tire width direction is made to be 1/2 time or less of a nominal tire sectional width. The protrusion height h of the fin in a position at which the fin protrudes at the outermost side in the tire width direction, and the maximum width A of a side reinforcement layer 8 satisfy the relation of h≥0.3×A. The position at which the fin protrudes at the outermost side in the tire width direction is disposed within 0.1 time of a height H of the tire maximum width position in the tire radial direction from the tire maximum width position.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire provided with a side reinforcing layer in a sidewall portion, and more specifically, while maintaining good steering stability and run rat durability, the structure of the bead portion is improved to reduce the tire weight. The present invention relates to a pneumatic tire.

  Generally, a bead core and a bead filler are embedded in a bead portion of a pneumatic tire. Furthermore, in the case of pneumatic tires (so-called run flat tires) that can travel safely over a certain distance even if puncture occurs, a side reinforcement layer (a cross-sectional shape is a crescent-shaped rigid body) that supports the load of the vehicle during puncture A rubber layer) 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 reducing the weight of tires, and weight reduction is also being considered for the above run-flat tires. For example, Patent Document 1 proposes to reduce the tire weight by eliminating the bead filler by devising the shape of the bead core in the pneumatic tire provided with a side reinforcing layer having a crescent-shaped cross section.

  However, in such a tire, even if it has a side reinforcing layer with a crescent-shaped cross section, the effect of eliminating the bead filler is significant, the rigidity of the sidewall portion is reduced, steering stability and run flat durability There was a risk of affecting. For this reason, 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.

JP 2002-301915 A

  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 provided with a side reinforcing layer in the sidewall portion. The object is to provide a pneumatic tire made possible.

  In order to achieve the above object, the pneumatic tire of the present invention includes a tread portion that extends in the tire circumferential direction and has an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and these sidewall portions. A pair of bead portions disposed on the inner side in the tire radial direction, 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 the 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 on the inner side in the tire width direction of the carcass layer in the sidewall portion, 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 in the meridian cross section in the tire width direction A plurality of layers overlapping the at least one row in the tire radial direction, and the width W0 of the layer having the maximum number of rows included in the plurality of layers and 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 satisfy the relationship of W1> W2 and W2 ≦ 0.5 × W0, and the layer having the maximum number of rows included in the plurality of layers is the bead core tire. When the outer shape of the bead wire is a polygon formed by a common tangent of a plurality of circumferential portions of the bead wire in the meridian cross section, which is located on the inner side in the tire radial direction from the radial center position, the tire radial direction of the outer shape Inner angles α and β of corners located at both ends of the inner side satisfy the relationship of α> 90 ° and β> 90 °, and the carcass layer reaches each bead portion from the tread portion through each sidewall portion. The main body, A folded portion that is folded while being bent along the periphery of the bead core in each bead portion and extends toward each sidewall portion while being in contact with the main body portion from the position of the outer end in the tire radial direction of the bead core. A plurality of fins protruding from the outer surface and extending along the tire radial direction on the outer surface of the sidewall portion are arranged at intervals in the tire circumferential direction over the entire tire circumference, from the tire equator The distance WC along the tire width direction to the outermost point in the tire width direction of the carcass layer is ½ times or less of the nominal tire cross-sectional width, and the fin is at the position where the fin protrudes most outward in the tire width direction. The protrusion height h of the fin and the maximum width A of the side reinforcing layer satisfy the relationship of h ≧ 0.3 × A, and the tire radial height at the tire maximum width position excluding the fin When the most protruding position the fins on the outer side in the tire width direction, characterized in that located within a range of 0.1H in the tire radial direction inside and outside the tire maximum width position excluding the fins.

  In the present invention, since the bead core has the above-described structure, the bead core as a whole can reduce the number of turns of the bead wire, and sufficiently secure the number of turns of the bead wire on the inner side in the tire radial direction from the center position in the tire radial direction of the bead core. Thus, while maintaining sufficient performance as a bead core and ensuring the durability of the tire, it is possible to reduce the tire weight by reducing the amount of bead wire used. In addition, since the carcass is folded while being bent along the bead core of this shape, only the bead core substantially exists 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 with the above-mentioned shape are provided on the outer surface of the sidewall portion, it is possible to suppress a reduction in the rigidity of the sidewall portion by this fin, and the steering stability and run flat durability are good. Can be maintained.

  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 within 40 mm. As a result, the shape of the carcass layer becomes good, the spring rigidity of the sidewall portion can be secured well, and this is advantageous for improving the run-flat durability.

  In the present invention, the distance BD along the tire width direction from the end point on the outer side 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 on the carcass layer is It is preferable that it is within 40 mm. As a result, the shape of the carcass layer becomes good, the spring rigidity of the sidewall portion can be secured well, and this is advantageous for improving the run-flat durability.

  In the present invention, it is preferable that the end point on the inner side in the tire radial direction of the side reinforcing layer is located on the inner side in the tire radial direction with respect to the outer end 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 on the inner side in the tire width direction from the end point on the outer side 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 to arrange in the range. In this way, the side reinforcing layer is sufficiently overlapped with the belt layer, which is advantageous for improving the run-flat durability.

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

  In this invention, it is preferable that the protrusion height h of a fin is 4 mm or more and 15 mm or less. Thereby, the shape of the fin is improved, which is advantageous for improving the steering stability and the run-flat durability.

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

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

  In the present invention, various dimensions are measured in a state where a tire is assembled on a regular rim and filled with a regular internal pressure. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO. Then, “Measuring Rim” is set. “Regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE ROAD LIMITS AT VARIOUS” is TRA. The maximum value described in “COLD INFRATION PRESURES”, “INFLATION PRESSURE” in the case of ETRTO, is 180 kPa when the tire is for passenger cars.

It is a meridian half section view of the pneumatic tire which consists of an embodiment of the present invention. It is explanatory drawing which extracts and shows 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 a prior art example and a 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 disposed on a tread portion 1, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and on the tire radial direction inner side of the sidewall portion 2. And a pair of bead portions 3. In FIG. 1, symbol CL indicates the tire equator. Although FIG. 1 is a meridian cross-sectional view and is not depicted, 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. The toroidal basic structure is constructed. Hereinafter, the structure of the present invention will be described with reference to a meridian cross-sectional view as shown in FIG. 1 (and FIG. 2 described later). Each tire constituent member in these meridian cross-sectional views is a tire circumference unless otherwise specified. 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 around the bead core 5 disposed in each bead portion 3 from the vehicle inner side to the outer side. In the following description, the portion from the tread portion 1 through each sidewall portion 2 to each bead portion 3 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 includes at least one bead wire 5A wound in the tire circumferential direction, and a plurality of circumferential portions of the bead wire 5A are arranged in the tire radial direction and at least one row arranged in the tire width direction. A plurality of overlapping layers are formed. In the present invention, as long as a plurality of bead wires 5A have a row and a layer as described above in a meridian cross section, a so-called single-winding structure in which a single bead wire 5A is continuously wound is used. A so-called layered winding structure in which a plurality of bead wires 5A are wound in an aligned state may be used. In the illustrated example, a layer including three rows of circumferential portions in order from the innermost side in the tire radial direction, a layer including four rows of circumferential portions, a layer including three rows of circumferential portions, a layer including two rows of circumferential portions, one row A total of five layers including the surrounding portion are stacked. 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 wires 5A is expressed in a similar format in which the number of rows included in each layer is connected by “+” in order from the innermost layer in the tire radial direction. Furthermore, in the bead core 5 in the illustrated example, the bead wires 5A are stacked in a stacking manner. Note that the “saddle stacking” is a stacking method in which the centers of the three surrounding portions that are in contact with each other form a substantially equilateral triangle, and is a stacked structure having a high filling rate, sometimes called a hexagonal packing arrangement.

  At this time, for each bead core 5, assuming that 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. ≦ 0.5 × W0 is satisfied. The layer having the maximum width W0 among the plurality of layers constituting the bead core 5 is located on the inner side in the tire radial direction of the bead core 5 in the tire radial direction center. That is, each bead core 5 is configured such that the width of the bead core 5 is smaller than the width on the tire innermost diameter side toward the tire outer diameter side from the maximum width portion located on the inner side in 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 all lengths along the tire width direction between the outer ends in the tire width direction of the circumferential portions on both outer sides in the tire width direction of each layer.

  Further, each bead core 5 has an inner shape in the tire radial direction of the outer shape of the bead wire 5A when a polygon formed by a common tangent (broken line in the drawing) of a plurality of circumferential portions of the bead wire 5A in the meridian section is used as the outer shape of the bead wire 5A. The inner angles α and β of the corners located at both ends of the side of the side satisfy 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. However, 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 has 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 setting, the cross-sectional shape is substantially pentagonal, and thus the carcass layer 4 extending along the periphery thereof is also bent into a substantially pentagonal shape. Furthermore, the portion of the folded portion 4B of the carcass layer 4 on the outer side in the tire radial direction from the outer end in the tire radial direction of the bead core 5 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 side wall 2 side. As a result, a closed region surrounding the bead core 5 is formed by the main body portion 4A and the folded portion 4B of the carcass layer 4.

  In addition, in the carcass layer 4 of the present invention, the distance WC along the tire width direction from the tire equator CL to the outermost point in the tire width direction of the carcass layer 4 is ½ 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 belt layers 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 inclined with respect to the tire circumferential direction. The reinforcing cords are arranged so that the reinforcing cords cross 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 in a range of 10 ° to 40 °, for example. 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 of a full cover layer that covers the entire width of the belt layer 6 and an edge cover layer that covers only both end portions of the belt reinforcing layer 7 are provided. The belt reinforcing layer 7 includes an organic fiber cord oriented in the tire circumferential direction. In the belt reinforcing layer 7, the organic fiber cord has an angle with respect to the tire circumferential direction set to, for example, 0 ° to 5 °.

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

  On the other hand, as illustrated in FIG. 3, a plurality of fins 9 that protrude from the outer surface and extend along the tire radial direction are provided on the outer surface of the sidewall portion 2. The 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 protrusion 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. Yes. Further, assuming that the height in the tire radial direction of the tire maximum width position excluding the fin 9 is H, the position where the fin 9 protrudes most outward in the tire width direction is the tire diameter with respect to the tire maximum width position excluding the fin 9. It is located within 0.1H within 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. is there.

  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 is less than the center position in the tire radial direction of the bead core 5 while reducing the number of turns of the bead wire 5A. On the inner side in the tire radial direction, a sufficient number of turns of the bead wire 5A can be secured, and while maintaining sufficient performance as the bead core 5 and ensuring the durability of the tire, the use amount of the bead wire 5 is reduced to reduce the tire weight. Mitigation can be achieved. Further, when the outer 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, the lengths L1 and L2 that have a large contribution to rim disengagement during run-flat running are sufficient. The rim detachment resistance can be further improved.

  On the other hand, since the fin 9 having the above-described shape is provided on the outer surface of the sidewall portion 2, the sidewall portion 2 can be reinforced by the fin 9 to suppress a reduction in rigidity. And run flat durability can be maintained well. In particular, since the fin 9 has the above-described shape and is provided at the above-described position, the carcass layer 4 is surely prevented from buckling in the vicinity of the maximum tire width position, and the run-flat durability is efficiently achieved. Can be increased. In addition, by providing the fins 9 on the outer surface of the sidewall portion 2, a heat dissipation effect by the fins 9 can be expected, and further durability can be 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 W1 ≦ W2 or W2> 0.5 × W0, the width of the upper end of the bead core 5 is increased, so that the rigidity in the vicinity of the portion where the rim flange comes into contact increases and the portion where the rim flange comes into contact is increased. It becomes difficult to suppress rim detachment due to the rotational force as a fulcrum, and the rim detachment resistance decreases. If the inner 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 inner angles α and β are 90 ° or less, the bead wires 5A positioned at both ends of the outer side of the outer shape of the tire in the tire radial direction 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 structure, if the shape and arrangement of the fins 9 are out of the above range, the sidewalls 2 cannot be properly reinforced by the fins 9, and the steering stability and run flat durability are good. To be difficult to maintain. In particular, when the protrusion height h of the fin 9 is in 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 protrusion height h of the fins 9 is preferably 4 mm or more and 15 mm or less. Moreover, 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 properly reinforced in the sidewall portion 2, and steering stability is improved. The effect of maintaining the durability and run-flat durability is not expected.

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

  As described above, regarding the bead core 5, when the polygon formed by the common tangents (broken lines in the drawing) of a plurality of circumferential portions of the bead wire 5 </ b> A in the meridian cross section is the outer shape of the bead wire 5 </ b> A, 5A is the sum of the lengths of all sides of the polygon formed by the common tangent line of the plurality of circumferential portions), L1 is the length of the outer side of the outer shape of the tire in the radial direction of the tire, When the length of the inclined side on the bead toe side continuous with the side of the bead heel is L2, and the length of the inclined side of the bead heel side continuous with the inner side in the tire radial direction of the outer shape 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 ≦ (L1 + L2) / (2 × L3) may satisfy the relation of ≦ 2.0. By defining the shape of the bead core in this way, it is possible to achieve both a reduction in tire weight and an improvement in rim removal resistance in a balanced manner. At this time, if the circumferential length L0 and the lengths L1 to L3 do not satisfy the above-described relationship, it is impossible to achieve both reduction in tire weight and improvement in rim detachment resistance. In particular, when 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 circumferential length L0 and the lengths L1 to L3 only have to satisfy the above-mentioned relationship. Among these lengths, the length L1 of the outer side of the outer shape of the bead core in the tire radial direction and the outer diameter of the outer shape of the bead core The length L2 of the inclined side of the bead toe that is continuous with the inner side greatly contributes to rim removal 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 2 mm to 10 mm, more preferably 2.5 mm to 7 mm. When the length L2 is smaller than 1.5 mm, the effect of improving the rim detachment resistance is limited, and when the length L2 is larger than 8 mm, the effect of reducing the tire weight is limited. When the length L1 is smaller than 2 mm, the effect of improving the rim detachment resistance is limited, and when 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 in view of achieving both reduction in tire weight and improvement in rim detachment resistance, the average diameter is preferably 0.8 mm to 1.8 mm, more preferably 1.0 mm to The thickness may be 1.6 mm, more preferably 1.1 mm to 1.5 mm. The total cross-sectional area preferably 10mm ² ~50mm ² a (sum of the cross-sectional area of the winding portion of the bead wire 5A contained in meridian cross-section of each bead core 5) of the bead wire 5A, more preferably 15mm ² ~48mm ^2, more preferably better to 20mm ² ~45mm ^2. When 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 when 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 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 constituent member (disposed 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 is The member that increases the rigidity over the wall portion 2) is basically not arranged and only the bead core 5 exists. In other words, even if there is an insulation rubber that covers the bead wire 5A or a rubber that fills a slight gap formed between the bead core 5 and the carcass layer 4, the bead has a large volume as in a conventional pneumatic tire. No filler is used. Therefore, in the present invention, the tire weight can be effectively reduced. In particular, the rubber occupation rate of the closed region, that is, the ratio of the total area a of the rubber existing in the closed region to the area A of the closed region in the meridian section (a / A × 100%) is 0.1% to 15%. It is preferable to make it. When the rubber occupation rate 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 is difficult to further increase the effect of reducing the tire weight. In addition, since there is always an insulation rubber or the like covering the bead wire 5A in the tire structure, the rubber occupation rate in the closed region is not basically less than 0.1%.

  Thus, since only the bead core 5 is substantially present in the closed region, even if another reinforcing member is added to the bead portion 3 in the present invention, the tire weight is increased as compared with the tire having the conventional bead filler layer. Will not do. For example, a filler layer can be 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. 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 side reinforcing layer 8 to form the sidewall portion 2. The rigidity of this is ensured moderately. 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, the structure of the filler layer and the like may be associated 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 hardness H2 satisfy the relationship of 0.15 ≦ (S2 × H2) / (S1 × H1) ≦ 0.60. Accordingly, it is possible to appropriately obtain the reinforcing effect by the filler layer while suppressing the use amount of the filler layer 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, and W2 and the lengths L0 to L3 satisfy the above relationship. For example, the shape shown in FIG. 4 can be adopted. In the example of FIG. 4, all of the widths W0, W1, and W2 satisfy the above-described relationship, and therefore correspond to the “outer diameter wedge shape” of the present invention, and the lengths L0 to L3 satisfy the above-described relationship. . More specifically, FIG. 4 (a) has a 4 + 5 + 4 + 3 + 2 + 1 structure of piling, FIG. 4 (b) has a 3 + 4 + 3 + 2 structure of piling, and FIG. 4 (c) has a 3 + 4 + 4 + 3 + 2 + 1 structure of piling. 4 (d) shows that 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, but are stacked in series (the circumferential portions adjacent in the tire radial direction are stacked vertically in the tire width direction). 3 + 4 + 4 + 3 + 2 + 1 structure.

  Since any structure shown in FIG. 4 is at least partially laminated in a stack, the bead wires 5A are more densely arranged than the bead wires having a structure in which the whole is stacked in series, and the bead wires 5A are filled. The rate can be increased. As a result, while ensuring the rigidity and pressure resistance performance of the bead part 3 and maintaining the running performance, the tire weight can be reduced and these performances can be exhibited in a well-balanced manner. When paying attention to the filling rate of the bead wires 5A, it is preferable that all the bead wires 5A are stacked in a stacked manner as shown in FIGS.

  Further, with respect to the shape of the bead core 5, in order to increase the stability of the shape of the entire bead core 5, the shape of the entire bead core 5 is preferably axisymmetric with respect to the center of the bead core 5 in the tire width direction. From this point of view, the shapes as shown in FIGS. 4A, 4B, and 4D 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 based on the various viewpoints described above.

  In the present invention, not only the distance WC along the tire width direction from the tire equator 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. The distance BT along the tire width direction from the outermost point of 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. Thereby, the shape of the carcass layer 4 becomes favorable, the spring rigidity of the sidewall portion 2 can be secured well, and it is advantageous for improving the run-flat durability. At this time, if the distance BT exceeds 40 mm, the side wall 2 is greatly curved, and it becomes difficult to sufficiently secure the spring rigidity, and the effect of improving the run-flat durability cannot be fully expected.

  Furthermore, the distance BD along the tire width direction from the end point on the outer side 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 on the carcass layer 4 Is preferably within 40 mm, more preferably 15 mm to 30 mm. Thereby, the shape of the carcass layer 4 becomes favorable, the spring rigidity of the sidewall portion 2 can be secured well, and it is advantageous for improving the run-flat durability. At this time, if the distance BD exceeds 40 mm, the curvature of the sidewall portion 2 increases, and it becomes difficult to sufficiently secure the spring rigidity, and the effect of improving the run-flat durability cannot be sufficiently expected.

  In the present invention, as described above, since the conventional bead filler is not provided, it is preferable to ensure the rigidity of the sidewall portion 2 by causing the end portion on the inner side in the tire radial direction of the side reinforcing layer 8 to reach the bead portion 3. . Specifically, the end point on the inner side in the tire radial direction of the side reinforcing layer 8 may be arranged on the inner side in the tire radial direction with respect to the outer end in the tire radial direction of the bead core 5. For example, the overlap amount D1 along the tire radial direction between the end portion of the side reinforcing layer 8 on the inner side in the tire radial direction and the bead core 5 may be 15 mm or more and 30 mm or less. Thereby, when it mounts | wears with a rim | limb, the side reinforcement layer 8 will reach | attain to the bead part 3 (bead core 5) fixed with the rim | limb, and run flat durability can be improved effectively.

  On the other hand, it is preferable that the end point on the outer side in the tire radial direction of the side reinforcing layer 8 is appropriately overlapped with the belt layer 6. Specifically, the end point on the outer side in the tire radial direction of the side reinforcing layer 8 is set to the inner side in the tire width direction from the end point on the outer side in the tire width direction of the belt layer 6 located on the innermost side in the tire radial direction among the plurality of belt layers 6. Preferably it is good to arrange in the 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 is preferably 15 mm or more and 40 mm or less. Thus, by sufficiently overlapping the end portion of the side reinforcing layer 8 with the belt layer 6, it is advantageous for improving the run-flat durability. At this time, if the overlap amount D2 is less than 15 mm, the effect of increasing the rigidity of the sidewall portion 2 is limited. When the overlap amount D2 exceeds 40 mm, the spring rigidity of the sidewall portion 2 becomes excessive, and riding comfort is reduced. Further, since the volume of the side reinforcing layer 8 is increased, there is a possibility that the effect of reducing the tire weight is affected.

  In setting the position of the end point of the side reinforcing layer 8 in this way, a plurality of layers are further formed from the distance Q along the tire width direction from the tire equator CL to the end point on the inner side in the tire radial direction of the side reinforcing layer 8 and the tire equator CL. The difference between the belt layer 6 and the distance P along the tire width direction to the outer end in the tire width direction of the belt layer 6 located on the innermost side in the tire radial direction is preferably within ± 20 mm, more preferably ± 10 mm. It is good to set within. As a result, the end portion of the belt layer 6, 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, the structure of the entire tire is improved, and the run This is advantageous for improving flat durability. At this time, if the difference between the distance P and the distance Q exceeds 20 mm, the gap between the end portion of the belt layer 6 and the end portion of the side reinforcing layer 8 and the bead core 5 increases, and the effect of further improving the run-flat durability. Can not be fully expected.

  The structure of each part described above can be used in appropriate combination. In any case, in the pneumatic tire having the above-described structure, the structure of the bead portion 3 is improved. Therefore, the tire weight is reduced while maintaining the durability of the tire, and the rim detachment resistance is improved. Can do.

  The tire size is 205 / 55R16, has the basic structure shown in FIG. 1, has a bead core structure, the presence or absence of a 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 bead core tire. Width W2 of outermost layer in radial direction, inner angles α and β of corners located at both ends of outer side of tire radial direction of outer shape of bead wire, outer circumferential length L0, outer side of outer shape of tire in radial direction of tire Length L1, the length L2 of the bead toe side inclined to the inner side in the tire radial direction of the outer shape, the length L3 of the inclined side of the bead heel side continuous to the inner side of the outer shape in the tire radial direction, (L1 + L2) / L0, Formula (L1 + L2) / (2 × L3), Presence / absence of fins on the outer surface of the sidewall portion, fin protrusion height h, maximum width A of side reinforcing layer, tire excluding fins The difference ΔH between the tire radial height H at the large position and the tire radial height H ′ at the position where the fin 9 protrudes most outward in the tire width direction, from the tire equator to the outermost point in the tire width direction of the carcass layer Distance WC along the tire 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, and the belt layer located on the innermost side in the tire radial direction The distance BD along the tire width direction from the end point on the outer side in the tire width direction to the outermost point in the tire width direction on the carcass layer, the tire radial direction along the tire radial direction end of the side reinforcing layer and the bead core The overlap amount D1, the overlap amount D2 between the belt layer located on the innermost side in the tire radial direction and the side reinforcing layer, the distance Q along the tire width direction from the tire equator to the end point on the inner side in the tire radial direction of the side reinforcing layer And the distance P along the tire width direction from the tire equator to the outermost end in the tire width direction 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. Thus, 32 types of pneumatic tires of Conventional Example 1, 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. The conventional example 1 and the comparative examples 1 and 2 are examples using a conventional general bead core, and the bead core has a 5 + 5 + 5 structure stacked in series as shown in FIG. The bead core of Comparative Example 3 has a 5 + 5 + 4 + 3 + 2 + 1 structure stacked in series as shown in FIG.

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

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

Tire mass Five masses were measured for each test tire, and the average value was obtained. The evaluation results are shown as an index with the value of Conventional Example 1 being 100. A smaller index value means a smaller tire mass.

Run-flat durability Test tire is assembled to a wheel with a rim size of 18 × 7.5J and run on a drum testing machine under the drum durability test condition for run-flat tire described in ECE30. The mileage was measured. The evaluation results are shown as an index with the value of Conventional Example 1 being 100. A larger index value means better run flat durability.

Steering stability Each test tire is assembled on a wheel with a rim size of 18 x 7.5 J, the air pressure is 230 kPa, and the test vehicle is installed on a test vehicle with a displacement of 2000 cc. Went. The evaluation results are shown as an index with the value of Conventional Example 1 being 100. A larger index value means better steering stability.

  As is clear from Tables 1 to 3, all of Examples 1 to 25 reduced the tire mass while maintaining or improving the run flat durability better than Conventional Example 1. Further, the rim removal resistance was also maintained or improved well. On the other hand, Comparative Example 1 eliminates the bead filler while using the conventional quadrangular bead core, and has no fins on the outer surface of the side wall portion. It got worse. In Comparative Example 2, since the bead filler was removed while the conventional square bead core was used, the run-flat durability and the rim detachment resistance were deteriorated. In Comparative Example 3, the shape of the bead core was inappropriate, and the run-flat durability and rim detachment resistance deteriorated. In Comparative Example 4, since the distance WC was too large, run-flat durability and rim detachment resistance were deteriorated. In Comparative Example 5, the run-flat durability and rim detachment resistance deteriorated because the protrusion height of the fins was too small. In Comparative Example 6, since the tire maximum width position excluding the fins and the position where the fins protruded most outward in the tire width direction are greatly separated, run-flat durability and rim detachment resistance deteriorated.

DESCRIPTION OF SYMBOLS 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)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. A bead core provided in each bead part; a carcass layer mounted between the pair of bead parts; a plurality of belt layers provided on an outer peripheral side of the carcass layer in the tread part; and the side In the pneumatic tire having a crescent-shaped side reinforcing layer provided on the inner side in the tire width direction of the carcass layer in the wall portion,
The bead core is composed of at least one bead wire wound in a tire circumferential direction, and a plurality of layers in which a plurality of circumferential portions of the bead wire overlap in the tire radial direction overlap with at least one row in the meridian cross section. Formed,
Of the plurality of layers, the width W0 of the layer having the maximum number of rows, 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. A layer satisfying the relationship of 5 × W0 and having the largest number of rows included among the plurality of layers is located on the inner side in the tire radial direction of the bead core in the tire radial direction center;
When a polygon formed by a common tangent of a plurality of circumferential portions of the bead wire in the meridian cross section is an outer shape of the bead wire, an inner angle α of corner portions positioned at both ends of the outer side of the outer shape in the tire radial direction β satisfies the relationship of α> 90 ° and β> 90 °,
The carcass layer is folded back while being bent along the periphery of the bead core at each bead portion from the tread portion through each sidewall portion to each bead portion, and at the tire radial outer end of the bead core. A folded portion extending toward each sidewall portion while contacting the main body portion from the position,
A plurality of fins protruding from the outer surface and extending along the tire radial direction on the outer surface of the sidewall portion are arranged at intervals in the tire circumferential direction over the entire tire circumference,
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 times or less the nominal tire cross-sectional width,
The protrusion height h of the fin at the position where the fin protrudes most outward in the tire width direction and the maximum width A of the side reinforcing layer satisfy a relationship of h ≧ 0.3 × A.
When the height in the tire radial direction of the tire maximum width position excluding the fin is H, the position where the fin protrudes most outward in the tire width direction is the inside and outside of the tire radial direction with respect to the tire maximum width position excluding the fin. The pneumatic tire is located within a range of 0.1H or less.   2. The pneumatic according to claim 1, wherein a 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 end point on the outer side in the tire width direction of the belt layer located on the innermost side in the tire radial direction of the plurality of belt layers to the outermost point in the tire width direction on the carcass layer is within 40 mm. The pneumatic tire according to claim 1, wherein the pneumatic tire is a tire.   The pneumatic tire according to any one of claims 1 to 3, wherein an end point on the inner side in the tire radial direction of the side reinforcing layer is located on an inner side in the tire radial direction with respect to an outer end in the tire radial direction of the bead core.   The end point of the side reinforcing layer on the tire radial direction outer side is a range of 15 mm or more and 40 mm or less from the end point on the tire width direction outer side of the belt layer located on the innermost side in the tire radial direction of the plurality of belt layers to the inner side in the tire width direction. The pneumatic tire according to any one of claims 1 to 4, wherein   The distance Q along the tire width direction from the tire equator to the end point on the inner side in the tire radial direction of the side reinforcing layer and the tire width direction of the belt layer located on the innermost side in the tire radial direction among the plurality of belt layers from the tire equator The pneumatic tire according to any one of claims 1 to 5, wherein a difference from the distance P along the tire width direction to the outer end point is within ± 20 mm.   The pneumatic tire according to claim 1, wherein a protrusion height h of the fin is 4 mm or more and 15 mm or less.   The outer circumference L0 of the outer shape of the bead wire, the length L1 of the outer side of the outer shape of the bead core in the tire radial direction, and the inclined side of the bead toe side that is continuous with the inner radial side of the outer shape of the bead core. The length L2 and the length L3 of the inclined side of the bead heel side continuous with the outer 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 claim 1, wherein a relationship of L1 + L2) / (2 × L3) ≦ 2.5 is satisfied.   The pneumatic tire according to claim 1, wherein an average diameter of the bead wire is 0.8 mm to 1.8 mm.

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