JP5083041B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having flat spot resistance.

  The pneumatic tire includes a tread portion that forms a tread surface, shoulder portions on both sides of the tread portion, and a sidewall portion and a bead portion that are sequentially continuous from the shoulder portions. In addition, a carcass is bridged between the bead portions. The carcass is arranged in a toroidal shape in the tire circumferential direction to form a tire skeleton. A belt layer is disposed on the outer side in the tire radial direction of the carcass, and a belt reinforcing layer is disposed on the outer side in the tire radial direction of the belt layer.

  For example, such a pneumatic tire generates heat when a vehicle equipped with the pneumatic tire travels at a high speed. And when a vehicle stops in the state which generate | occur | produced heat | fever and a pneumatic tire has touched the road surface for a long time as it is, a flat spot may generate | occur | produce. That is, when the pneumatic tire is in contact with the road surface for a long time at a high temperature, the tread surface of the tread portion that contacts the road surface is deformed by the influence of a vertical load such as the weight of the vehicle. Thereafter, when the temperature of the pneumatic tire decreases, residual strain is generated while the rubber and organic fibers constituting the pneumatic tire remain deformed. A flat spot is a flat part formed by this residual strain. When a flat spot is generated, the vehicle starts to run and the deformation is maintained for a while. Therefore, the toroid shape becomes uneven with respect to the circumferential direction of the pneumatic tire, and vibration is generated to improve steering stability. May decrease.

  Conventionally, for example, a pneumatic tire described in Patent Document 1 has a reinforcing layer composed of a composite cord composed of low-rigidity fibers and high-rigidity fibers. The reinforcing layer is provided adjacent to the carcass so that the composite cord is parallel to the carcass cord, and preferably disposed in the region from the vicinity of the maximum tire width position to the bead core. The composite cord of the reinforcing layer has a low elastic region extending from the origin to the inflection point and a high elastic region exceeding the inflection point in the stress-elongation curve, and the elongation at the inflection point is 0.5. It is set in the range of [%] to 5.0 [%]. In addition, the stiffness index of the low elasticity region in the composite cord with respect to the stiffness index of the carcass is set to 50 [%] or less, and the stiffness index of the high elasticity region is set to 100 [%] or more.

JP 2006-298162 A

  According to the conventional pneumatic tire described above, the reinforcing layer is disposed adjacent to the carcass so that the composite cord is parallel to the carcass cord, so that the stress acting on the carcass from the inside of the tire can be reliably ensured by the reinforcing layer. Receiving to ensure tire rigidity. In addition, when the tire is stationary, the occurrence of a flat spot is suppressed by the rigidity of the high elastic region of the composite cord, while the riding comfort is prevented from being deteriorated by the rigidity of the low elastic region in the normal running state. As described above, in the conventional pneumatic tire, the generation of a flat spot is suppressed and the deterioration of riding comfort is prevented by the reinforcing layer including the element for increasing the rigidity and the element for decreasing the rigidity.

  However, even in a conventional pneumatic tire, there is a risk that unevenness in the circumference may occur due to a distortion difference of the carcass due to deformation of the sidewall portion between the ground contact area and the non-ground contact area when the vehicle is stopped. Further, due to the bending deformation of the tread portion between the grounding region and the non-grounding region, there is a risk that unevenness on the circumference may occur due to the strain difference of the belt reinforcing layer. For this reason, it is difficult to completely eliminate the occurrence of a flat spot, and durability is deteriorated due to unevenness on the circumference. For this reason, further improvement of a pneumatic tire is desired.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can suppress generation | occurrence | production of a flat spot, suppressing deterioration of durability.

In order to achieve the above object, in the pneumatic tire according to the present invention, each end is folded back by a pair of annular bead portions and arranged in a toroidal shape in the tire circumferential direction, and the tire circumference is aligned along the tire meridian direction. A pneumatic tire comprising at least one layer of a carcass having a plurality of carcass cords arranged in parallel in a direction and a belt layer having at least two belts arranged on an outer periphery of the carcass, wherein the carcass has at least one layer In the carcass cord, at least two types of cord portions having different carcass rigidity per unit circumferential length are arranged adjacent to each other in the tire circumferential direction, and an angle θ with respect to the tire equator line is disposed on the outer circumference of the carcass. Has a reinforcing cord arranged at 0 [degree] ≦ θ ≦ 3 [degree] and filled with the normal internal pressure. The reinforcing cord arrangement area H1 is set in a range of H1 ≦ (Ha × 0.9) or (Ha × 1.1) ≦ H1 with respect to the tire radial direction height Ha at the maximum width position in the tire width direction. A circumferential reinforcing layer, wherein the reinforcing cord of the circumferential reinforcing layer is composed of at least two kinds of composite cords made of high-rigidity fibers and low-rigidity fibers, and the composite cord has an origin at a stress-elongation curve. And a high elastic region exceeding the inflection point, and the elongation δ at the inflection point is 0.5 [%] ≦ δ ≦ 5.0 [%] It is set to a range .

According to this pneumatic tire, the number of ends of the carcass cord is substantially reduced in the range of the sidewall portion by the cord portion having a relatively low carcass rigidity, and a flexible region can be obtained. Accordingly, the rigidity of the carcass is reduced in the range of the sidewall portion, and the amount of deflection in the range is increased, so that the rigidity in the tire radial direction is reduced. In addition, by providing the circumferential reinforcing layer, the rigidity outside the range of the sidewall portion is increased, bending deformation of the tread portion, the shoulder portion or the bead portion is suppressed, and deformation at the sidewall portion is concentrated. As a result, nonuniform rigidity in the tire width direction and tire circumferential direction is suppressed, and tire durability is improved. Further, since vertical loads such as the weight of the vehicle are absorbed in the range of the sidewall portion, and deformation of the tread portion and the shoulder portion that are brought into contact with the road surface is suppressed, occurrence of a flat spot can be suppressed. Moreover, according to this pneumatic tire, when the tire is stationary, the occurrence of a flat spot can be suppressed by the rigidity of the high elastic region of the composite cord. On the other hand, in a normal running state, deterioration of riding comfort is prevented by the rigidity of the low elastic region. As a result, it is possible to prevent the deterioration of the riding comfort while suppressing the occurrence of flat spots by the reinforcing layer including the element for increasing the rigidity and the element for decreasing the rigidity.

  In the pneumatic tire according to the present invention, the circumferential reinforcing layer is disposed on the outer side in the tire radial direction from the maximum width position of the carcass in the tire width direction, and a part of the belt layer or the belt layer is provided. The belt reinforcing layer provided on the outer periphery is disposed on the inner side in the tire radial direction.

  According to this pneumatic tire, the bending deformation portion at the sidewall portion is displaced closer to the bead portion, so that bending deformation of the tread portion at the time of tire contact is suppressed. As a result, generation of flat spots can be further suppressed.

  In the pneumatic tire according to the present invention, the carcass rigidity per unit circumferential length of the cord portion having the highest carcass rigidity is RA, and the carcass per unit circumferential length of the cord portion having the lowest carcass rigidity. When the rigidity is RB, the carcass rigidity RB is set in a range of 0.4 ≦ RB / RA ≦ 0.9 with respect to the carcass rigidity RA.

  According to this pneumatic tire, when the ratio of the carcass rigidity RB to the carcass rigidity RA is less than 0.4, the difference in carcass rigidity between the cord portion having the highest carcass rigidity and the cord portion having the lowest carcass rigidity is large. The uniformity (UF: uniformity) of the pneumatic tire that causes the vibration of the steering wheel and the vehicle and the vehicle interior noise is deteriorated. On the other hand, when the ratio of the carcass rigidity RB to the carcass rigidity RA exceeds 0.9, the difference in the carcass rigidity between the cord portion having the highest carcass rigidity and the cord portion having the lowest carcass rigidity is small, and the rigidity of the carcass cannot be reduced. For this reason, it is preferable that the carcass rigidity RB is set in a range of 0.4 ≦ RB / RA ≦ 0.9 with respect to the carcass rigidity RA.

  Further, in the pneumatic tire according to the present invention, at least one portion is cut in a range from the outer end in the tire radial direction of the bead filler to the outermost end in the tire width direction of the belt layer. A cord portion having a different carcass rigidity per unit circumferential direction length is constituted by the cut cord portion provided with the cut portion.

  According to this pneumatic tire, the number of ends of the carcass cord is substantially reduced in the range of the sidewall portion by the cut portion of the cut cord portion, and a flexible region can be obtained. Accordingly, the rigidity of the carcass is reduced in the range of the sidewall portion, and the amount of deflection in the range is increased, so that the rigidity in the tire radial direction is reduced. In addition, by providing the circumferential reinforcing layer, the rigidity outside the range of the sidewall portion is increased, bending deformation of the tread portion, the shoulder portion or the bead portion is suppressed, and deformation at the sidewall portion is concentrated. As a result, nonuniform rigidity in the tire width direction and tire circumferential direction is suppressed, and tire durability is improved. Further, since vertical loads such as the weight of the vehicle are absorbed in the range of the sidewall portion, and deformation of the tread portion and the shoulder portion that are brought into contact with the road surface is suppressed, occurrence of a flat spot can be suppressed.

  In the pneumatic tire according to the present invention, in the carcass cord of the cutting cord portion, the cord end interval h of the cutting portion is set in a range of 0.5 [mm] ≦ h ≦ 10 [mm]. The number m1 of 50 carcass cords arranged side by side in the tire circumferential direction is set in a range of 5 [lines] ≦ m1 ≦ 25 [lines].

  According to this pneumatic tire, when the cord end interval h is less than 0.5 [mm], the effect on deformation is small, and it is difficult to obtain the effect of suppressing deformation of the tread portion and the shoulder portion. On the other hand, when the cord end interval h exceeds 10 [mm], the strength of the carcass is insufficient and the tire durability is deteriorated. For this reason, it is preferable that the cutting | disconnection cord part is set to the range of 0.5 [mm] <= h <= 10 [mm] in the code | symbol end space | interval h of a cutting part. In addition, when the number m1 of carcass cords in the cut cord portion per 50 carcass cords is less than 5 [pieces], the effect on deformation is small, and it is difficult to obtain the effect of suppressing the deformation of the tread portion and the shoulder portion. On the other hand, when the number m1 of the carcass cords in the cut cord portion per 50 carcass cords exceeds 25 [pieces], the strength of the carcass is insufficient and the tire durability is deteriorated. For this reason, it is preferable that the number m1 of 50 carcass cords in the cut cord portion is set in a range of 5 [lines] ≦ m1 ≦ 25 [lines].

  In the pneumatic tire according to the present invention, the cutting cord portion has a tire radial height H2 and a tire cross-sectional height at a maximum width position of the carcass in the tire radial direction. The height Ht is set in a range of (Ha−0.15 × Ht) ≦ H2 ≦ (Ha + 0.15 × Ht).

  According to this pneumatic tire, the number of ends of the carcass cord is substantially reduced within the range in which the amount of deformation can be increased with the maximum width in the tire width direction of the sidewall portion, and a flexible region can be obtained. For this reason, it is possible to further suppress the occurrence of flat spots by further absorbing the vertical load such as the weight of the vehicle and further suppressing the deformation of the tread portion and the shoulder portion that are in contact with the road surface.

  In the pneumatic tire according to the present invention, when the carcass is provided in two layers, the cutting cord portion is provided in any one of the two layers of the carcass.

  According to this pneumatic tire, when two layers of carcass are provided, if both carcass cords include a cut cord portion, the strength of the carcass is insufficient and tire durability is deteriorated. For this reason, when two layers of carcass are provided, the carcass cord in one of the carcass includes a cut cord portion, and the carcass cord in the other carcass does not include a cut cord portion. It is preferable that only a part is included.

  Further, in the pneumatic tire according to the present invention, when the carcass is provided with only one layer, the cutting cord portion is formed on the folded portion where the end portion of the carcass is folded outward at the bead portion. Is provided.

  According to this pneumatic tire, when only one layer of the carcass is provided, if the cutting portion is provided inside the bead portion before the end portion of the carcass is folded, the strength of the carcass is insufficient and the tire durability is reduced. Getting worse. For this reason, when only one layer of carcass is provided, it is preferable to provide a cutting portion at the outer folded portion that is folded.

  Further, in the pneumatic tire according to the present invention, in the folded portion where the end portion of the carcass is folded outward at the bead portion, the first cord portion in which the carcass cord is formed to a predetermined length, and the folded portion In the present invention, a cord portion having a different carcass rigidity per unit circumferential length is configured with the second cord portion formed so that the length of the carcass cord is shorter than that of the first cord portion. .

  According to this pneumatic tire, the number of ends of the carcass cord is substantially reduced in the range of the sidewall portion by the second cord portion formed with the length of the carcass cord shorter than that of the first cord portion. A region with the characteristics can be obtained. Accordingly, the rigidity of the carcass is reduced in the range of the sidewall portion, and the amount of deflection in the range is increased, so that the rigidity in the tire radial direction is reduced. In addition, by providing the circumferential reinforcing layer, the rigidity outside the range of the sidewall portion is increased, bending deformation of the tread portion, the shoulder portion or the bead portion is suppressed, and deformation at the sidewall portion is concentrated. As a result, nonuniform rigidity in the tire width direction and tire circumferential direction is suppressed, and tire durability is improved. Further, since vertical loads such as the weight of the vehicle are absorbed in the range of the sidewall portion, and deformation of the tread portion and the shoulder portion that are brought into contact with the road surface is suppressed, occurrence of a flat spot can be suppressed.

  In the pneumatic tire according to the present invention, the difference t in length between the carcass cord of the first cord portion and the carcass cord of the second cord portion at the folded portion is 10 [mm] ≦ t ≦ 50 [mm] and the ratio m2 of the total number of carcass cords in the second code portion to the total number of carcass cords in the first code portion is 0.1 ≦ m2 ≦ 0. It is set in the range of 5.

  According to this pneumatic tire, when the difference in length t between the carcass cord of the first cord portion and the carcass cord of the second cord portion is less than 10 [mm], the effect on deformation is small, It is difficult to obtain an effect of suppressing deformation of the tread portion and the shoulder portion. On the other hand, when the difference in length t between the carcass cord of the first cord portion and the carcass cord of the second cord portion exceeds 50 [mm], the strength of the carcass is insufficient and the tire durability is deteriorated. To do. For this reason, the difference in length t between the carcass cord of the first cord portion and the carcass cord of the second cord portion is set in the range of 10 [mm] ≦ t ≦ 50 [mm]. preferable. Further, when the ratio m2 of the number of carcass cords in the second cord portion to the total number of carcass cords in the first cord portion is less than 0.1, the effect on the deformation is small, and the deformation of the tread portion and the shoulder portion is suppressed. It is difficult to obtain the effect. On the other hand, when the ratio m2 of the number of carcass cords in the second cord portion to the total number of carcass cords in the first cord portion exceeds 0.5, the strength of the carcass is insufficient and tire durability is deteriorated. For this reason, it is preferable that the ratio m2 of the number of carcass cords in the second code portion to the total number of carcass cords in the first cord portion is set in a range of 0.1 ≦ m2 ≦ 0.5.

  In the pneumatic tire according to the present invention, the tire radial height H3 of the folded portion end of the second cord portion is the tire radial height Ha and the tire cross-sectional height at the maximum width position of the carcass in the tire width direction. The height Ht is set in a range of (Ha−0.15 × Ht) ≦ H3 ≦ (Ha + 0.15 × Ht).

  According to this pneumatic tire, the number of ends of the carcass cord is substantially reduced within the range in which the amount of deformation can be increased with the maximum width in the tire width direction of the sidewall portion, and a flexible region can be obtained. For this reason, it is possible to further suppress the occurrence of flat spots by further absorbing the vertical load such as the weight of the vehicle and further suppressing the deformation of the tread portion and the shoulder portion that are in contact with the road surface.

  In the pneumatic tire according to the present invention, the total number n1 of the cord portions is set in a range of 20 ≦ n1 ≦ 200.

  According to this pneumatic tire, when the total number n1 of the cord portions is less than 20, the strength is insufficient due to a local decrease in the rigidity of the carcass, and the tire durability is deteriorated. On the other hand, when the total number n1 of the cord portions exceeds 200, the effect on deformation is small, and it is difficult to obtain the effect of suppressing the deformation (flat spot) of the tread portion and the shoulder portion. For this reason, it is preferable that the total number n1 of each code part is set in a range of 20 ≦ n1 ≦ 200.

  In the pneumatic tire according to the present invention, the composite cord forming the reinforcing cord of the circumferential reinforcing layer is characterized in that the high-rigidity fiber is aromatic polyamide and the low-rigidity fiber is 46 nylon. .

  According to the pneumatic tire, the flat spot resistance is improved by using the highly rigid fiber as an aromatic polyamide having high thermal dimensional stability and high elasticity. Furthermore, the flat spot resistance is improved by making the low-rigidity fiber 46 nylon having high thermal dimensional stability.

  In the pneumatic tire according to the present invention, the flatness is 55 [%] or less.

  According to this pneumatic tire, when applied to tires having a relatively long flatness ratio of 55 [%] or less in the tire width direction, the effect of improving the flat spot resistance is more remarkably exhibited.

  In the pneumatic tire according to the present invention, at least two types of cord portions having different carcass rigidity per unit circumferential length are arranged adjacent to each other in the tire circumferential direction, and a circumferential reinforcing layer is provided on the outer circumference of the carcass. Thereby, generation | occurrence | production of a flat spot can be suppressed, suppressing deterioration of durability.

  Embodiments of a pneumatic tire according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  FIG. 1 is a meridional sectional view of a pneumatic tire according to an embodiment of the present invention, FIG. 2 is a schematic side view showing a cord portion of a carcass in the pneumatic tire shown in FIG. 1, and FIGS. FIG. 6 is a graph showing a stress-elongation curve of the circumferential reinforcing layer, and FIG. 7 shows another cord portion of the carcass in the pneumatic tire shown in FIG. FIG. 8 is a schematic side view, FIG. 8 is a schematic view showing a cutting portion of the cutting cord portion shown in FIG. 7, and FIG. 9 is a schematic meridian in a form in which two layers of carcass are provided when the other cord portion shown in FIG. 7 is applied. FIG. 10 is a schematic meridional sectional view of a form in which one layer of carcass is provided when the other cord portion shown in FIG. 7 is applied, and FIG. 11 is still another example of the carcass in the pneumatic tire shown in FIG. Schematic side view showing the cord part, FIG. Is a table of results of performance tests of pneumatic tires according to the embodiment of the present invention.

  In the following description, the tire radial direction refers to a direction orthogonal to the rotation axis (not shown) of the pneumatic tire 1, and the tire radial direction inner side refers to the side toward the rotation axis in the tire radial direction, the tire radial direction outer side. Means the side away from the rotation axis in the tire radial direction. Further, the tire circumferential direction refers to a direction around the rotation axis as a central axis. Further, the tire width direction refers to a direction parallel to the rotation axis, the inner side in the tire width direction is the side toward the tire equator plane S in the tire width direction, and the outer side in the tire width direction is the tire equator plane S in the tire width direction. The side away from.

  The pneumatic tire described below is configured to be substantially symmetric about the tire equatorial plane S. The tire equator plane S is a plane that is orthogonal to the rotational axis of the pneumatic tire and passes through the center of the tire width of the pneumatic tire. The tire width is the width in the tire width direction between the portions located outside in the tire width direction, that is, the distance between the portions farthest from the tire equatorial plane in the tire width direction. The tire equator line is a line on the tire equator plane S along the circumferential direction of the pneumatic tire. Since the pneumatic tire described below is configured to be substantially symmetric about the tire equatorial plane S, the pneumatic tire is cut in a plane passing through the rotation axis of the pneumatic tire. In the meridional sectional view, only one side centered on the tire equatorial plane S is shown and only the one side is described, and description on the other side is omitted.

  As shown in FIG. 1, the pneumatic tire 1 according to the present embodiment includes a tread portion 2, shoulder portions 3 on both sides of the tread portion 2, and sidewall portions 4 and bead portions 5 successively from the shoulder portions 3. Have. The pneumatic tire 1 includes a carcass 6, a belt layer 7, and a belt reinforcing layer 8.

  The tread portion 2 is exposed to the outside of the pneumatic tire 1, and the surface thereof is the contour of the pneumatic tire 1. A tread surface 21 is formed on the outer peripheral surface of the tread portion 2, that is, on the tread surface that contacts the road surface during traveling. The tread surface 21 includes a plurality of (four in the present embodiment) circumferential main grooves 22 that extend in the tire circumferential direction, and a plurality of land that is defined by the circumferential main grooves 22. The rib 23 which makes a part is provided.

  The shoulder portion 3 is a portion on both outer sides in the tire width direction of the tread portion 2. Further, the sidewall portion 4 is exposed at the outermost side in the tire width direction of the pneumatic tire 1. The bead unit 5 includes a bead core 51 and a bead filler 52. The bead core 51 is formed by winding a bead wire, which is a steel wire, in a ring shape. The bead filler 52 is disposed in a space formed by folding the end of the carcass 6 outward in the tire width direction at the position of the bead core 51.

  The carcass 6 is configured such that each tire width direction end portion is folded with respect to the pair of bead portions 5 and is wound around in a toroidal shape in the tire circumferential direction to constitute a tire skeleton. The carcass 6 is a carcass cord 61 (see FIG. 2) such as organic fiber (nylon, polyester, etc.) or steel covered with a rubber material. A plurality of carcass cords 61 are arranged in the tire circumferential direction while being along the tire meridian direction perpendicular to the tire equator line of the pneumatic tire 1. The carcass 6 shown in FIG. 1 is composed of one layer, but may have a multilayer structure in order to improve rigidity. That is, the carcass 6 in the present embodiment is provided with at least one layer according to the desired rigidity. Further, the carcass cord 61 is orthogonal to the tire equator line, but the angle with respect to the tire equator line (tire circumferential direction) is substantially 90 degrees, and is −5 with reference to 90 degrees with respect to the tire equator line. Includes angles in the range of [degrees] to +5 [degrees].

  The belt layer 7 has a multilayer structure in which at least two belts 71 and 72 are laminated, and is disposed on the outer side of the carcass 6 in the tire radial direction and covers the carcass 6 in the tire circumferential direction. The belts 71 and 72 are made of a cord made of organic fibers (nylon, polyester, etc.) or steel covered with a rubber material, and the cords have a predetermined angle with respect to the tire circumferential direction, that is, the tire equator line. Has been placed. The belts 71 and 72 are arranged with their cords inclined in opposite directions with respect to the tire equator line.

  The belt reinforcing layer 8 is disposed on the outer side in the tire radial direction which is the outer periphery of the belt layer 7 and covers the belt layer 7 in the tire circumferential direction. The belt reinforcing layer 8 is made of an organic fiber (nylon, polyester, etc.) or a steel cord covered with a rubber material, and the cord is substantially 0 degrees (tire) with respect to the tire circumferential direction, that is, the tire equator line. It arrange | positions so that the angle with respect to the circumferential direction may become an angle of 10 degrees or less.

  As shown in FIG. 2, the carcass cord 61 in at least one layer of the carcass 6 includes at least two types of cord portions 611 and 612 having different carcass rigidity per unit circumferential length. None, these cord portions 611 and 612 are arranged adjacent to each other in the tire circumferential direction. The carcass cord 61 in the present embodiment has two types of cord portions, a cord portion 611 having a relatively high carcass rigidity and a cord portion 612 having a relatively low carcass rigidity, but is not limited thereto. Three or more types of cord portions having different carcass rigidity per unit circumferential length may be formed.

  The cord portion 611 is configured as a high cord portion 611A having a relatively high carcass rigidity. As shown in FIG. 2, the high cord portion 611A has a close distance in the tire circumferential direction and has a predetermined size in the tire circumferential direction. The number of carcass cords 61 (number of ends [50/50 mm]) is relatively large. On the other hand, the cord portion 612 is configured as a low cord portion 612A having a relatively low carcass rigidity. As shown in FIG. 2, the low cord portion 612 </ b> A of the carcass 6 that is configured to have the same rigidity in the carcass 6 has a sparse distance adjacent to each other in the tire circumferential direction and a predetermined dimension in the tire circumferential direction. The number of carcass cords 61 (the number of ends [pieces / 50 mm]) is relatively small.

  The rigidity of one of the carcass cords 61 is defined by the force at the time of 2 [%] extension. This rigidity may be made the carcass rigidity by multiplying the number of cords per unit circumferential direction length of the carcass 6. Alternatively, the carcass 6 may be cut out together with the coat rubber by a width per unit circumferential length, and the force at the time of 2 [%] extension in the cord extending direction may be the carcass rigidity. In addition, although not clearly shown in the drawing, the high cord portion 611A and the low cord portion 612A change the cord material such as aramid fiber, rayon fiber, polyester fiber, or the cord diameter in addition to the above-described number of ends. The carcass rigidity can be adjusted by changing the initial tension or changing the number of turns. As described above, when the carcass rigidity is adjusted by the cord material, the cord diameter, the bending, the initial tension, and the number of twists, the high cord portion 611A and the low cord portion 612A are configured by one carcass cord 61. Can do.

  A circumferential reinforcing layer 9 is provided on the outer periphery of the carcass 6. The circumferential reinforcing layer 9 is formed by covering a reinforcing cord 91 (see FIG. 2) with a rubber material. The reinforcing cord 91 is made of a cord material such as nylon fiber, polyester fiber, rayon fiber, aramid fiber, polyester fiber, steel, and the like, and the cord materials of the same kind are brought together. The circumferential reinforcing layer 9 is wound around the outer circumference of the carcass 6 in the tire circumferential direction so that the reinforcing cord 91 is disposed at an angle θ with respect to the tire equator line of 0 [degree] ≦ θ ≦ 3 [degree]. . The circumferential reinforcing layer 9 is composed of, for example, a strip material having a width of 10 mm, in which reinforcing cords 91 are arranged along the longitudinal direction of the belt, and the strip material is spirally wound in the tire circumferential direction. There may be. When the circumferential reinforcing layer 9 is made of a strip material, the rigidity of the circumferential reinforcing layer 9 can be obtained by aligning the end portions of the strip materials, overlapping the end portions, or providing a gap between the end portions. Can be adjusted.

The circumferential reinforcing layer 9 has a tire radial height Ha at the maximum width position in the tire width direction of the carcass 6 as shown in FIG. 1 in a state in which the pneumatic tire 1 is filled with normal internal pressure (described later). On the other hand, the arrangement region H1 of the reinforcing cord 91 in the tire radial direction is provided in a range of H1 ≦ (Ha × 0.9) or (Ha × 1.1) ≦ H1. That is, the circumferential reinforcing layer 9 is -10 [% of the tire radial height Ha with respect to the tire radial height Ha at the outer periphery of the carcass 6 and at the maximum width position of the carcass 6 in the tire width direction. ] And less than +10 [%]. FIG. 1 shows a form in which the circumferential reinforcing layer 9 is provided in the vicinity of the shoulder portion 3 and in the range of (Ha × 1.1) ≦ H1. FIG. 3 shows a form in which the circumferential reinforcing layer 9 is provided in the vicinity of the bead portion 5 and in a range of H1 ≦ (Ha × 0.9).

  The tire radial direction height Ha is (outer diameter in the tire radial direction−rim diameter) / 2, and the carcass 6 from the tire radial inner end (that is, the position of the rim base 53) of the bead portion 5. This is the height in the tire radial direction up to the maximum width position in the tire width direction.

  As described above, the pneumatic tire 1 includes the cord portion 611 (high cord portion 611A) and the cord portion 612 (low cord portion 612A) having different carcass rigidity, so that the side wall is formed by the low cord portion 612A. In the range of the portion 4, the number of ends of the carcass cord 61 is substantially reduced, and a flexible region is obtained. Thereby, the rigidity of the carcass 6 is reduced in the range of the sidewall portion 4 and the amount of deflection in the range is increased, so that the rigidity in the tire radial direction is reduced. Moreover, the provision of the circumferential reinforcing layer 9 increases the rigidity outside the range of the sidewall portion 4, and the bending deformation of the tread portion 2, the shoulder portion 3 or the bead portion 5 is suppressed, and the deformation at the sidewall portion 4 is suppressed. Concentrate. For this reason, the nonuniformity of rigidity in the tire width direction and the tire circumferential direction is suppressed, and the tire durability is improved. As a result, the vertical load such as the weight of the vehicle is absorbed in the range of the sidewall portion 4, and the deformation of the tread portion 2 and the shoulder portion 3 that are in contact with the road surface is suppressed, so that the occurrence of a flat spot can be suppressed. .

  Further, in the pneumatic tire 1 according to the present embodiment, as shown in FIGS. 4 and 5, the circumferential reinforcing layer 9 is outside in the tire radial direction from the maximum width position of the carcass 6 in the tire width direction (that is, ( Ha × 1.1) ≦ H1) and a part of the belts 71 and 72 of the belt layer 7 or the inner side of the belt reinforcing layer 8 in the tire radial direction.

  According to such a configuration, the bending deformation portion in the sidewall portion 4 is displaced closer to the bead portion 5, so that the bending deformation of the tread portion 2 at the time of tire contact is suppressed. As a result, generation of flat spots can be further suppressed.

  In the pneumatic tire 1 according to the present embodiment, the reinforcing cord 91 of the circumferential reinforcing layer 9 is configured as at least two types of composite cords composed of high-rigid fibers and low-rigid fibers. As shown in the graph of FIG. 6, the composite cord has a low elastic region from the origin 0 to the inflection point C and a high elastic region beyond the inflection point C in the stress-elongation curve R. Yes. In this case, the inflection point C is the intersection of the curve R and the perpendicular passing through the intersection X of the tangent T1 that is in contact with the curve in the state of zero elongation and the tangent T2 that is in contact with the curve at the breaking point. The elongation δ at the inflection point C in the composite cord is set to be in the range of 0.5 [%] ≦ δ ≦ 5.0 [%].

  This composite cord is a twisted combination of high-rigidity fibers and low-rigidity fibers. The filament yarn of high-rigidity fibers and the filament yarn of low-rigidity fibers that are each given a lower twist are combined and twisted together. Twist while giving. The lower twist yarn may be one filament yarn of high-rigidity fiber and one filament yarn of low-elasticity fiber, a plurality of filament yarns, or a combination of different numbers of both. . In the lower twisting, it is preferable that both the high-rigid fiber filament yarn and the low-rigid fiber filament yarn are twisted in the same direction. Moreover, it is preferable that the direction of an upper twist is a direction opposite to a lower twist. Alternatively, a high-stiffness fiber filament yarn and a low-rigidity fiber filament yarn may be pre-twisted in the lower twist, and a plurality of the obtained composite lower twist yarns may be twisted together and twisted. In any case, the twisting direction and twisting form are not limited to these, and it is important to set the range of the elongation δ described above as a composite cord. The high-rigidity fiber preferably has an elastic modulus of 25 to 250 GPa, and examples thereof include wholly aromatic polyester fibers such as aromatic polyamide fibers and polyethylene naphthalate fibers, and poly-p-phenylenebenzoxazole fibers. The low-rigidity fibers preferably have an elastic modulus of 2 to 15 GPa, and examples thereof include organic fibers such as nylon fibers, polyester fibers, and polyvinyl alcohol fibers.

  According to such a configuration, when the tire is stationary, the occurrence of a flat spot can be suppressed by the rigidity of the high elastic range of the composite cord. On the other hand, in a normal running state, deterioration of riding comfort is prevented by the rigidity of the low elastic region. As a result, it is possible to prevent the deterioration of the riding comfort while suppressing the occurrence of flat spots by the reinforcing layer including the element for increasing the rigidity and the element for decreasing the rigidity.

  In the pneumatic tire 1 according to the present embodiment, the composite cord (reinforcing cord 91) of the circumferential reinforcing layer 9 has high-rigid fibers made of aromatic polyamide (aramid) and low-rigid fibers made of 46 nylon.

  According to such a configuration, the flat spot resistance is improved by using the highly rigid fiber as an aromatic polyamide having high thermal dimensional stability and high elasticity. Furthermore, the flat spot resistance is improved by making the low-rigidity fiber 46 nylon having high thermal dimensional stability.

  Further, in the pneumatic tire 1 according to the present embodiment, the carcass stiffness per unit circumferential direction length of the high cord portion 611A having the highest carcass rigidity is RA, and the unit circumferential direction of the low cord portion 612A having the lowest carcass stiffness is shown. When the carcass rigidity per length is RB, the carcass rigidity RB is set in a range of 0.4 ≦ RB / RA ≦ 0.9 with respect to the carcass rigidity RA. That is, the ratio of the carcass rigidity RB per unit circumferential direction length of the low cord part 612A to the carcass rigidity RB per unit circumferential direction length of the high cord part 611A is 40 [%] or more and 90 [%] or less. Set to range.

  If the ratio of the carcass rigidity RB to the carcass rigidity RA is less than 40 [%], the difference in the carcass rigidity between the high cord portion 611A and the low cord portion 612A is large, which causes the vibration of the steering wheel and the vehicle and the occurrence of the vehicle interior noise The uniformity (UF: uniformity) of the pneumatic tire becomes worse. On the other hand, if the ratio of the carcass rigidity RB to the carcass rigidity RA exceeds 90 [%], the difference in carcass rigidity between the high cord portion 611A and the low cord portion 612A is small, and the rigidity of the carcass 6 cannot be reduced. For this reason, it is preferable that the ratio of the carcass rigidity RB to the carcass rigidity RA is set in a range of 40 [%] to 90 [%].

  When the carcass stiffness is set by changing the number of ends of the carcass cord 61, in order to set the range of the carcass stiffness ratio RB / RA, for example, the high cord portion 611A is 48 [lines / 50 mm], and the low cord It is preferable that the part 612A be 24 to 38 [lines / 50 mm]. Further, when the ratio of the carcass rigidity RB to the carcass rigidity RA is set in the range of 50 [%] to 80 [%] (0.5 ≦ RB / RA ≦ 0.8), the uniformity is deteriorated. Since it can prevent and the rigidity of the carcass 6 can be reduced, it is more preferable.

  In the pneumatic tire 1 according to the present embodiment, the total number n1 of the cord portions 611 and 612 is set in a range of 20 ≦ n1 ≦ 200.

  When the total number n1 of the cord portions 611 and 612 is less than 20, the strength is insufficient due to a local decrease in the rigidity of the carcass 6 and tire durability is deteriorated. On the other hand, when the total number n1 of the cord portions 611 and 612 exceeds 200, the effect on deformation is small, and it is difficult to obtain the effect of suppressing the deformation (flat spot) of the tread portion 2 and the shoulder portion 3. For this reason, it is preferable that the total number n1 of the code portions 611 and 612 is set in a range of 20 ≦ n1 ≦ 200.

  In addition, the pneumatic tire 1 according to the present embodiment is applied to a tire having a relatively long flatness ratio of 55 [%] or less in particular in the tire width direction, thereby significantly improving flat spot resistance. There is an effect. The flatness ratio is a ratio of the tire height Ht to the tire width W, as shown in FIG.

  By the way, in the pneumatic tire 1 according to the present embodiment, as shown in FIG. 7, the carcass cord 61 in the carcass 6 of at least one layer is a continuous cord portion 611B as other cord portions 611 and 612 having different carcass rigidity. And a cutting cord portion 612B.

  The cutting cord portion 612B constitutes a cord portion 612 having a relatively low carcass rigidity. The cut cord portion 612B is a tire of the belt layer 7 (the belt 71 having the maximum width in the tire width direction) from the position of the normal line A (see FIG. 1) of the carcass 6 that passes through the tire radial direction outer end of the bead filler 52. A cut portion 612Ba cut at least at one place is provided in the range up to the position of the normal line B (see FIG. 1) of the carcass 6 passing through the outermost end in the width direction, that is, the range of the sidewall portion 4. The cutting part 612Ba is provided by cutting or dividing the carcass cord 61 along the tire meridian direction.

  The continuous cord portion 611B constitutes a cord portion 611 having a relatively high carcass rigidity. The continuous cord portion 611B is formed by continuously forming the carcass cord 61 along the tire meridian direction and does not have the cutting portion 612Ba.

  As shown in FIG. 7, the continuous cord portion 611B not having the cutting portion 612Ba and the cutting cord portion 612B having the cutting portion 612Ba are configured by a plurality of carcass cords 61 arranged in parallel in the tire circumferential direction. It may be the one made up of one carcass cord 61.

  Thus, in the pneumatic tire 1 including the cord portion 611 (continuous cord portion 611B) and the cord portion 612 (cut cord portion 612B) having different carcass rigidity, the side wall is formed by the cut portion 612Ba of the cut cord portion 612B. In the range of the portion 4, the number of ends of the carcass cord 61 is substantially reduced, and a flexible region is obtained. As a result, the rigidity of the carcass 6 is reduced in the range of the sidewall portion 4 and the amount of deflection in the range is increased, so that the rigidity in the tire radial direction is reduced, and bending deformation of the tread portion 2 and the shoulder portion 3 is suppressed. Is done. For this reason, deterioration of the rigidity in the tire width direction and the tire circumferential direction is suppressed, and the tire durability is improved. Moreover, the provision of the circumferential reinforcing layer 9 increases the rigidity outside the range of the sidewall portion 4, and the bending deformation of the tread portion 2, the shoulder portion 3 or the bead portion 5 is suppressed, and the deformation at the sidewall portion 4 is suppressed. Concentrate. For this reason, the nonuniformity of rigidity in the tire width direction and the tire circumferential direction is suppressed, and the tire durability is improved. As a result, the vertical load such as the weight of the vehicle is absorbed in the range of the sidewall portion 4, and the deformation of the tread portion 2 and the shoulder portion 3 that are in contact with the road surface is suppressed, so that the occurrence of a flat spot can be suppressed. .

  In the pneumatic tire 1 shown in FIG. 7, as shown in FIG. 8, in the cut cord portion 612 </ b> B, the cord end interval h of the cut portion 612 Ba is in the range of 0.5 [mm] ≦ h ≦ 10 [mm]. Is set to Further, in the cut cord portion 612B, the number m1 of 50 carcass cords 61 arranged in parallel in the tire circumferential direction is set in a range of 5 [pieces] ≦ m1 ≦ 25 [pieces].

  When the cord end interval h is less than 0.5 [mm], the effect on deformation is small, and it is difficult to obtain the effect of suppressing deformation of the tread portion 2 and the shoulder portion 3. On the other hand, when the cord end interval h exceeds 10 [mm], the strength of the carcass 6 is insufficient and the tire durability is deteriorated. For this reason, in the cut cord portion 612B, the cord end interval h of the cut portion 612Ba is preferably set in a range of 0.5 [mm] ≦ h ≦ 10 [mm]. Moreover, when the number m1 per 50 is less than 5 [pieces], the effect on deformation is small, and the effect of suppressing the deformation of the tread portion 2 and the shoulder portion 3 is difficult to be obtained. On the other hand, when the number m1 per 50 exceeds 25 [pieces], the strength of the carcass 6 is insufficient and the tire durability is deteriorated. For this reason, in the cut cord portion 612B, the number m1 of 50 carcass cords 61 is preferably set in a range of 5 [lines] ≦ m1 ≦ 25 [lines].

  In the pneumatic tire 1 shown in FIG. 7, as shown in FIG. 1, the height H2 of the center position in the tire radial direction of the cutting portion 612Ba of the cutting cord portion 612B is the maximum width position of the carcass 6 in the tire width direction. Is set to a range of (Ha−0.15 × Ht) ≦ H2 ≦ (Ha + 0.15 × Ht).

  The tire cross-section height Ht is (outer diameter in the tire radial direction−rim diameter) / 2, and the tire equatorial plane from the inner radial side end of the bead portion 5 (that is, the position of the rim base 53). This is the height in the tire radial direction to the center crown CL, which is the intersection of S and the tread surface 21. Further, the height H2 of the center position in the tire radial direction of the cut portion 612Ba is the height in the tire radial direction from the rim base 53 of the bead portion 5 in the same manner as the tire cross-sectional height Ht.

  According to such a configuration, the number of ends of the carcass cord 61 is substantially reduced within a range in which the deformation amount can be increased at the maximum width position of the sidewall portion 4 in the tire width direction, and a flexible region can be obtained. For this reason, it is possible to further suppress the occurrence of flat spots by further absorbing the vertical load such as the weight of the vehicle and further suppressing the deformation of the tread portion 2 and the shoulder portion 3 that contact the road surface.

  In the pneumatic tire 1 shown in FIG. 7, when two layers of carcass 6 are provided as shown in FIG. 9, a cut cord portion 612B is provided in one of the two layers of carcass 6. The other carcass 6 is provided with only the continuous cord portion 611B.

  When the carcass 6 is provided in two layers, if the carcass cord 61 in both carcass 6 includes the cut cord portion 612B, the strength of the carcass 6 is insufficient due to the cut portion 612Ba and tire durability deteriorates. For this reason, when the carcass 6 is provided in two layers, the carcass cord 61 in one of the carcass 6 includes the cutting cord portion 612B, and the carcass cord 61 in the other carcass 6 includes the cutting cord. It is preferable that only the continuous code portion 611B is included without including the portion 612B.

  In the pneumatic tire 1 shown in FIG. 7, as shown in FIG. 10, the cutting portion 612Ba of the cutting cord portion 612B has a bead portion 5 in the carcass 6 when only one layer of the carcass 6 is provided. Thus, the end portion of the carcass 6 is provided in a folded portion 6a that is folded outward.

  When only one layer of the carcass 6 is provided, if the cut portion 612Ba is provided inside the bead portion 5 before the end portion of the carcass 6 is folded back, the strength of the carcass 6 is insufficient and the tire durability is deteriorated. For this reason, when only one layer of the carcass 6 is provided, it is preferable to provide the cutting part 612Ba in the folded-back outer part 6a.

  By the way, in the pneumatic tire 1 according to the present embodiment, as shown in FIG. 11, the carcass cord 61 in the carcass 6 of at least one layer is a long cord portion ( It may have a first code portion) 611C and a short code portion (second code portion) 612C.

  The long cord portion 611C constitutes a cord portion 611 having a relatively high carcass rigidity. In the long cord portion 611C, the cord length of the carcass cord 61 is formed to a predetermined length in the folded portion 6a in which the end portion of at least one layer of the carcass 6 is folded outward.

  The short cord portion 612C constitutes a cord portion 612 having relatively low carcass rigidity. The short cord portion 612C is formed such that the cord length of the carcass cord 61 is shorter than the long cord portion 611C in the folded portion 6a.

  As shown in FIG. 11, the long cord portion 611 </ b> C and the short cord portion 612 </ b> C may be configured by a plurality of carcass cords 61 arranged in parallel in the tire circumferential direction, or from one carcass cord 61. It may be configured.

  As described above, in the pneumatic tire 1 including the cord portion 611 (long cord portion 611C) and the cord portion 612 (short cord portion 612C) having different carcass rigidity, the range of the sidewall portion 4 is defined by the short cord portion 612C. , The number of ends of the carcass cord 61 is substantially reduced, and a flexible region can be obtained. As a result, the rigidity of the carcass 6 is reduced in the range of the sidewall portion 4 and the amount of deflection in the range is increased, so that the rigidity in the tire radial direction is reduced, and bending deformation of the tread portion 2 and the shoulder portion 3 is suppressed. Is done. For this reason, deterioration of the rigidity in the tire width direction and the tire circumferential direction is suppressed, and the tire durability is improved. Moreover, the provision of the circumferential reinforcing layer 9 increases the rigidity outside the range of the sidewall portion 4, and the bending deformation of the tread portion 2, the shoulder portion 3 or the bead portion 5 is suppressed, and the deformation at the sidewall portion 4 is suppressed. Concentrate. For this reason, the nonuniformity of rigidity in the tire width direction and the tire circumferential direction is suppressed, and the tire durability is improved. As a result, the vertical load such as the weight of the vehicle is absorbed in the range of the sidewall portion 4, and the deformation of the tread portion 2 and the shoulder portion 3 that are in contact with the road surface is suppressed, so that the occurrence of a flat spot can be suppressed. .

  In the pneumatic tire 1 shown in FIG. 11, the difference in length t between the carcass cord 61 of the long cord portion 611C and the folded portion 6a between the carcass cord 61 of the short cord portion 612C is 10 [mm] ≦ t ≦ 50 [mm] is set. Further, the ratio m2 of the number of carcass cords 61 in the short cord portion 612C to the total number of carcass cords 61 in the long cord portion 611C is set in a range of 0.1 ≦ m2 ≦ 0.5.

  When the length difference t is less than 10 [mm], the effect on deformation is small, and it is difficult to obtain the effect of suppressing deformation of the tread portion 2 and the shoulder portion 3. On the other hand, when the length difference t exceeds 50 [mm], the strength of the carcass 6 is insufficient and the tire durability is deteriorated. For this reason, it is preferable that the difference t in the length of the carcass cord 61 at the folded portion 6a between the long cord portion 611C and the short cord portion 612C is set in a range of 10 [mm] ≦ t ≦ 50 [mm]. . Further, when the ratio m2 of the number is less than 0.1, the effect on deformation is small, and it is difficult to obtain the effect of suppressing the deformation of the tread portion 2 and the shoulder portion 3. On the other hand, when the ratio m2 of the number exceeds 0.5, the strength of the carcass 6 is insufficient and the tire durability is deteriorated. For this reason, it is preferable that the ratio m2 of the number of carcass cords 61 in the short cord portion 612C to the total number of carcass cords 61 in the long cord portion 611C is set in a range of 0.1 ≦ m2 ≦ 0.5. .

  Further, in the pneumatic tire 1 shown in FIG. 11, the height H2 of the folded portion 6a end of the short cord portion 612C is higher than the height Ha and the tire cross-section height Ht at the maximum width position of the carcass 6 in the tire width direction. It is set in the range of (Ha−0.15 × Ht) ≦ H2 ≦ (Ha + 0.15 × Ht).

  According to such a configuration, the number of ends of the carcass cord 61 is substantially reduced within a range in which the deformation amount can be increased at the maximum width position of the sidewall portion 4 in the tire width direction, and a flexible region can be obtained. For this reason, it is possible to further suppress the occurrence of flat spots by further absorbing the vertical load such as the weight of the vehicle and further suppressing the deformation of the tread portion 2 and the shoulder portion 3 that contact the road surface.

  In the present embodiment, performance tests regarding tire durability and flat spot resistance were performed on a plurality of types of pneumatic tires having different conditions (see FIG. 12).

  In this performance test, a pneumatic tire having a tire size of 225 / 45ZR17 was assembled to a regular rim, filled with a regular internal pressure, and a regular load was applied. The regular rim here refers to an “applied rim” defined in JATMA, a “Design Rim” defined in TRA, or a “Measuring Rim” defined in ETRTO. The normal internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load means “maximum load capacity” defined in JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “LOAD CAPACITY” defined in ETRTO.

  In the tire durability performance test, after completion of the JATMA high-speed durability test with a drum diameter of 1707 mm, the test was continued at a speed of 10 km / h every 30 minutes until the tire was destroyed. Based on this result, index evaluation using the comparative example as a reference (100) is performed. This evaluation is preferable as the numerical value increases. In the uniformity performance test and flat spot resistance performance test, the uniformity was measured in accordance with JASO C607 “Testing method for uniformity of automobile tires” and spared for 30 minutes at 150 km / h. After running, the drum is stopped for 1 hour with a load applied. Thereafter, the tire uniformity is measured again, and the difference ΔRFV before and after the preliminary running of the radial force variation is evaluated. The smaller this difference ΔRFV, the better the flat spot resistance. Based on this result, index evaluation using the comparative example as a reference (100) is performed. This evaluation is preferable as the numerical value increases.

  The pneumatic tire of the comparative example does not change the carcass rigidity in the tire circumferential direction and does not have a circumferential reinforcing layer. On the other hand, the pneumatic tires of Examples 1 to 6 change the carcass rigidity in the tire circumferential direction and are provided with a circumferential reinforcing layer. In the pneumatic tires of Examples 7 to 11, the cord portion is composed of the continuous cord portion and the cut cord portion, the regulation of the cut cord portion is optimized, and the circumferential reinforcing layer is provided. . In the pneumatic tires of Examples 12 to 14, the cord portion is composed of the long cord portion and the short cord portion, the definition of the short cord portion is optimized, and the circumferential reinforcing layer is provided. .

  As shown in the test results of FIG. 12, it can be seen that the pneumatic tires of Examples 1 to 14 each have durability maintained within an allowable range and are excellent in flat spot resistance.

  As described above, the pneumatic tire according to the present invention is suitable for suppressing the occurrence of flat spots while suppressing deterioration in durability.

1 is a meridional sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a schematic side view showing a carcass cord portion in the pneumatic tire shown in FIG. 1. It is a schematic meridional sectional view showing an arrangement example of the circumferential reinforcing layer. It is a schematic meridional sectional view showing an arrangement example of the circumferential reinforcing layer. It is a schematic meridional sectional view showing an arrangement example of the circumferential reinforcing layer. It is a graph showing the stress-elongation curve of a circumferential direction reinforcement layer. It is a schematic side view showing the other code | cord | chord part of the carcass in the pneumatic tire shown in FIG. It is the schematic showing the cutting part of the cutting code part shown in FIG. FIG. 8 is a schematic meridional sectional view of a form in which two layers of carcass are provided when the other cord portion shown in FIG. 7 is applied. FIG. 8 is a schematic meridional sectional view of a form in which one layer of carcass is provided when the other cord portion shown in FIG. 7 is applied. FIG. 6 is a schematic side view showing still another cord portion of the carcass in the pneumatic tire shown in FIG. 1. It is a graph which shows the result of the performance test of the pneumatic tire concerning embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Shoulder part 4 Side wall part 5 Bead part 51 Bead core 52 Bead filler 53 Rim base 6 Carcass 6a Folding part 61 Carcass cord 611 Cord part 611A High cord part 611B Continuous cord part 611C Long cord part (1st Code part)
612 code part 612A low code part 612B cut code part 612Ba cut part 612C short code part (second code part)
7 Belt layer 71, 72 Belt 8 Belt reinforcement layer 9 Circumferential reinforcement layer 91 Reinforcement cord CL Center crown h Cord end interval H1 Area of reinforcement cord in the tire radial direction H2 Tire radial height of the cut portion in the cut cord portion H3 Height in the radial direction of the end of the folded portion at the second cord portion m1 Number of cut cords per 50 carcass cords m2 Ratio of the number of short cords to the total number of long cords n1 Total number of cut cord portions and continuous cord portions RA Carcass rigidity of the cord part with the highest carcass rigidity RB Carcass rigidity of the cord part with the lowest carcass rigidity S Tire equatorial plane t Difference in the length of the folded part between the short cord part and the long cord part θ Angle with respect to the tire equator line

Claims (14)

At least one layer having a plurality of carcass cords in which each end portion is folded at a pair of annular bead portions and arranged in a toroidal shape in the tire circumferential direction, and arranged in parallel in the tire circumferential direction along the tire meridian direction In a pneumatic tire comprising a carcass and a belt layer having at least two belts arranged on the outer periphery of the carcass,
The carcass cord in the carcass of at least one layer is provided with at least two types of cord portions having different carcass rigidity per unit circumferential direction length adjacent to the tire circumferential direction,
On the outer periphery of the carcass, there is a reinforcing cord disposed at an angle θ with respect to the tire equator line of 0 [degree] ≦ θ ≦ 3 [degree], and the carcass is filled with a normal internal pressure in the tire width direction of the carcass The circumferential direction in which the reinforcing cord arrangement area H1 is set in the range of H1 ≦ (Ha × 0.9) or (Ha × 1.1) ≦ H1 with respect to the tire radial direction height Ha at the maximum width position. With a reinforcing layer ,
The reinforcing cord of the circumferential reinforcing layer is composed of at least two kinds of composite cords composed of high-rigid fibers and low-rigid fibers,
The composite cord has a low elastic region extending from the origin to the inflection point and a high elastic region exceeding the inflection point in the stress-elongation curve, and the elongation δ at the inflection point is 0.5. A pneumatic tire characterized by being set in a range of [%] ≦ δ ≦ 5.0 [%] .   The circumferential reinforcing layer is disposed on the outer side in the tire radial direction from the maximum width position in the tire width direction of the carcass, and a part of the tire diameter of the belt reinforcing layer provided on the outer periphery of the belt layer or the belt layer. The pneumatic tire according to claim 1, wherein the pneumatic tire is disposed on an inner side in the direction. RA is the carcass rigidity per unit circumferential length of the cord portion having the highest carcass rigidity.
When the carcass rigidity per unit circumferential length of the cord portion having the lowest carcass rigidity is RB,
3. The pneumatic tire according to claim 1, wherein the carcass rigidity RB is set in a range of 0.4 ≦ RB / RA ≦ 0.9 with respect to the carcass rigidity RA. A continuous cord portion that is continuous in the tire meridian direction, and a cut cord portion that is provided with a cut portion in which at least one portion is cut in a range from the tire radial direction outer end of the bead filler to the tire width direction outermost end of the belt layer. and, the pneumatic tire according to claim 1 or 2 encoding unit carcass rigidity per unit circumferential length are different, characterized in that it is configured. The carcass cords of the cutting cord portions are arranged in parallel in the tire circumferential direction, with a cord end interval h of the cutting portions set in a range of 0.5 [mm] ≦ h ≦ 10 [mm]. 5. The pneumatic tire according to claim 4 , wherein the number m1 of 50 carcass cords is set in a range of 5 [lines] ≦ m1 ≦ 25 [lines]. In the cutting cord portion, the tire radial height H2 of the cutting portion is (Ha-0.15) relative to the tire radial height Ha and the tire cross-sectional height Ht at the maximum width position of the carcass in the tire width direction. 6. The pneumatic tire according to claim 4 , wherein the pneumatic tire is set in a range of xHt) ≦ H2 ≦ (Ha + 0.15 × Ht). The cutting cord portion, when the carcass is provided two layers, according to any one of claims 4-6, characterized in that provided on one of the carcass of the two layers Pneumatic tires. The cutting cord portion may include the cutting portion provided in a folded portion where an end portion of the carcass is folded outward at the bead portion when only one layer of the carcass is provided. The pneumatic tire according to any one of Items 4 to 7 . In the folded portion where the end portion of the carcass is folded outward at the bead portion, the carcass cord is formed to have a predetermined length, and the folded portion further includes the carcass than the first cord portion. The pneumatic tire according to claim 1 or 2 , wherein a cord portion having a different carcass rigidity per unit circumferential length is configured with the second cord portion formed with a short cord length. . The difference in length t at the folded portion between the carcass cord of the first cord portion and the carcass cord of the second cord portion is set in a range of 10 [mm] ≦ t ≦ 50 [mm], The ratio m2 of the total number of carcass cords in the second code portion to the total number of carcass cords in the first cord portion is set in a range of 0.1 ≦ m2 ≦ 0.5. The pneumatic tire according to claim 9 . The tire radial direction height H3 of the folded portion end of the second cord portion is (Ha-0.15) with respect to the tire radial height Ha and the tire cross-sectional height Ht at the maximum width position of the carcass in the tire width direction. The pneumatic tire according to claim 9 or 10 , wherein the pneumatic tire is set in a range of xHt) ≤H3≤ (Ha + 0.15xHt). The total number n1 of each said code | cord | chord part is set to the range of 20 <= n1 <= 200, The pneumatic tire as described in any one of Claims 1-11 characterized by the above-mentioned. Composite cord constituting the reinforcing cord of the circumferential reinforcing layer, said high-rigidity fibers and aromatic polyamide, wherein any one of claims 1 to 12, characterized in that a low-rigidity fiber nylon 46 The described pneumatic tire. The flat tire according to any one of claims 1 to 13 , wherein the flatness is 55% or less.

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