Pneumatic tires

Abstract

To provide a pneumatic tire comprising a carcass ply including a pair of ply pieces divided at both sides in a tire width direction, which can improve rigidity and improve steering stability accompanying the improvement of rigidity.SOLUTION: The pneumatic tire comprises: a pair of beads 10 having bead cores 11 respectively; a pair of side walls 20; a tread 30; a belt 40 arranged in the tread 30; a cap ply 60 as a belt reinforcement layer arranged at an outside in a tire radial direction of the belt 40; and at least one pair of first carcass plies 51 arranged at an inside in the tire radial direction of the belt 40, one end 51a of each of which is arranged closer to inside in a tire width direction than each outer end in the tire width direction of the belt 40 and the other end 51b of each of which is folded back at each bead core 11. The cap ply 60 includes a belt reinforcement layer 60g and the belt reinforcement layer 60g includes aramid fiber.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[0002] Conventionally, in pneumatic tires for vehicles, an internal structure is known in which a carcass ply that forms the framework of the tire is stretched between a pair of beads. Patent Document 1 discloses a pneumatic tire in which a discontinuous hollow portion is provided in the center of the width direction of the tire tread in relation to such a carcass ply, thereby achieving weight reduction and a reduction in rolling resistance due to the weight reduction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-111004 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a pneumatic tire, when weight reduction and rolling resistance are attempted, there is a risk of a decrease in rigidity and an associated decrease in steering stability. However, the structure disclosed in Patent Document 1 does not mention in detail the rigidity and the associated steering stability, and there is room for improvement.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a pneumatic tire having a carcass ply including a pair of ply pieces split on both sides in the tire width direction, which can achieve improved rigidity and therefore improved handling stability. [Means for solving the problem]

[0006] The pneumatic tire of the present invention comprises a pair of beads each having a bead core, a pair of sidewalls extending radially outward from each of the pair of beads, a tread disposed between the pair of sidewalls, a belt disposed on the tread, a belt reinforcing layer disposed radially outward from the belt, and a first carcass ply disposed radially inward from the belt, the first carcass ply including a pair of ply pieces having one end disposed radially inward from the outer end of the belt and the other end folded back at the bead core, the belt reinforcing layer including a belt reinforcing layer cord, and the belt reinforcing layer cord including an aramid fiber. Effect of the Invention

[0007] According to the present invention, it is possible to provide a pneumatic tire having a carcass ply including a pair of ply pieces split on both sides in the tire width direction, which can achieve improved rigidity and therefore improved handling stability. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a half cross section in the tire width direction of a pneumatic tire according to one embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged view of part II in FIG. [Diagram 3] FIG. 2 is a schematic development view of a first carcass ply, a belt, and a cap ply (belt reinforcing layer) according to one embodiment. [Figure 4] FIG. 11 is a diagram showing a half cross section in the tire width direction of a pneumatic tire according to a modified example of an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing a half cross section in the tire width direction of a tire 1, which is a pneumatic tire according to one embodiment. Fig. 2 is an enlarged view of a portion indicated by II in Fig. 1. The structure of tire 1 is symmetrical in a cross section in the tire width direction, so Fig. 1 shows a cross section of the right half. In Fig. 1, reference symbol S1 denotes the tire equatorial plane. The tire equatorial plane S1 is a plane that is perpendicular to the tire rotation axis (tire meridian) and is located at the center in the tire width direction.

[0010] The cross-sectional view in Fig. 1 is a cross-sectional view in the tire width direction (cross-sectional view at the tire meridian) of a tire 1 mounted on a standard rim (not shown) and inflated to a specified internal pressure under no load. The specified internal pressure is, for example, 180 kPa when the tire is for a passenger car. The standard rim is a rim specified by JATMA according to the tire size.

[0011] Here, the tire width direction is a direction parallel to the tire rotation axis, and corresponds to the left-right direction on the paper surface in the cross-sectional view of Fig. 1. In Fig. 1, this direction is illustrated as tire width direction X. The inner side in the tire width direction is the direction approaching the tire equatorial plane S1, which is the left side on the paper in Fig. 1. The outer side in the tire width direction is the direction away from the tire equatorial plane S1, which is the right side on the paper in Fig. 1. The tire radial direction is a direction perpendicular to the tire rotation axis, and is the up-down direction on the paper surface in Fig. 1. In Fig. 1, this direction is illustrated as tire radial direction Y. The outer side in the tire radial direction is the direction away from the tire rotation axis, and is the upper side on the paper in Fig. 1. The inner side in the tire radial direction is the direction approaching the tire rotation axis, and is the lower side on the paper in Fig. 1. The same applies to FIG. 4 described later.

[0012] As shown in FIG. 1, the tire 1 includes a pair of beads 10 provided on both sides in the tire width direction, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, a tread 30 arranged between the pair of sidewalls 20, a belt 40 arranged on the tread 30, a first carcass ply 51 arranged between the pair of beads 10 on the radially inner side of the belt 40, a cap ply 60 arranged radially outward of the belt 40, an inner liner 70 arranged closest to the tire cavity, and an outer layer rubber 90 that forms the outer surfaces of the tread 30 and the pair of sidewalls 20.

[0013] The bead 10 includes a bead core 11, a bead filler 12 extending radially outward from the bead core 11, a chafer 13, and a rim strip rubber 14. The bead core 11 is an annular member formed by winding a rubber-coated metal bead wire multiple times, and serves to fix the tire 1 filled with air to the rim. The bead filler 12 is a rubber member with a tapered tip that extends outward in the tire radial direction from the bead core 11. The bead filler 12 is a member provided to increase the rigidity of the peripheral portion of the bead 10 and ensure high maneuverability and stability. The bead filler 12 is made of, for example, rubber that is harder than the surrounding rubber members. The chafer 13 and the rim strip rubber 14 will be described later.

[0014] The sidewall 20 includes a sidewall rubber portion 21 disposed on the outer side of the first carcass ply 51 in the tire width direction. The sidewall rubber portion 21 constitutes the outer wall surface of the tire 1. This sidewall rubber portion 21 is the portion that bends the most when the tire 1 performs its cushioning function, and flexible rubber having fatigue resistance is usually used for it.

[0015] The tread 30 includes an endless belt 40, a cap ply 60, and a tread rubber portion 31. The belt 40 is disposed on the outer side of the first carcass ply 51 in the tire radial direction. The cap ply 60 is disposed on the outer side of the belt 40 in the tire radial direction. The tread rubber portion 31 is disposed on the outer side of the cap ply 60 in the tire radial direction. The outer layer rubber 90 includes a tread rubber portion 31 and a pair of sidewall rubber portions 21 .

[0016] 3 is a development view showing a schematic view of a part of the circumferential direction of the tire 1 when the tread rubber portion 31 constituting the outer surface of the tread 30 is omitted from the direction of the arrow III in FIG. 1. That is, in FIG. 3, the belts 41, 42, a pair of ply pieces 51A of the first carcass ply 51 described later, and a cap ply 60 are shown. The belts 41, 42 are arranged in the center of the tire width direction and cover a part of the pair of ply pieces 51A arranged on both sides in the tire width direction. The cap ply 60 covers the belts 41, 42 and a part of the pair of ply pieces 51A in the center of the tire width direction. In FIG. 3, the cap ply 60 is further broken in the circumferential direction to show the belts 41, 42. In FIG. 3, the tire width direction X is shown as the left-right direction on the paper, and the tire circumferential direction is shown by an arrow S2.

[0017] The belt 40 of this embodiment has a two-layer structure including an inner belt 41 and an outer belt 42. In this embodiment, the end 41a of the inner belt 41 in the tire width direction is located outside the end 42a of the outer belt 42 in the tire width direction. As shown in FIG. 3, each of the belts 41 and 42 is a belt including a plurality of belt cords 41g and 42g. The belt 40 reinforces the tread 30 of the tire 1. The belt cords 41g and 42g are composed of a steel cord or an insulating organic fiber cord such as polyester or polyamide. The plurality of belt cords 41g and 42g are covered with rubber. By providing the belt 40, the rigidity of the tire 1 is ensured, and the contact state between the tread 30 and the road surface is improved. In the belt 40, the belts to be laminated are not limited to two layers.

[0018] The cap ply 60 is a belt reinforcing layer that reinforces the belt 40. As shown in FIG. 3, the cap ply 60 includes a plurality of belt reinforcing layer cords 60g. The material of the belt reinforcing layer cords 60g is preferably one that includes aramid fiber. In the present embodiment, the belt reinforcing layer cords 60g are more preferably hybrid cords having aramid fiber and nylon fiber. Such a hybrid cord can be formed by twisting aramid fiber and nylon fiber. The plurality of belt reinforcing layer cords 60g are covered with rubber. By providing the cap ply 60, it is possible to improve durability and reduce road noise during driving.

[0019] The tread rubber portion 31 is a member that constitutes the tread surface (contact surface with the road surface) 31a during normal running. The tread surface 31a of the tread rubber portion 31 is provided with a tread pattern 32 that is composed of, for example, a plurality of grooves. The tread pattern 32 has a plurality of main grooves 32A, 32B aligned in the tire width direction. Note that the main groove 32A shown in FIG. 1 is the outermost main groove 32A that is the main groove arranged on the outermost side in the tire width direction, and the main groove 32B is the innermost main groove 32B that is arranged at a position closest to the center in the tire width direction.

[0020] The first carcass ply 51 includes a pair of ply pieces 51A that form the framework of the tire 1. The first carcass ply 51 has a cut-out portion 50H that is discontinuous in the center in the tire width direction of the tread 30. The pair of ply pieces 51A are divided into two on either side in the tire width direction with the cut-out portion 50H in between, and are embedded in the tire 1 in such a manner that they are disposed on either side in the tire width direction of the cut-out portion 50H.

[0021] Each of the pair of ply pieces 51A of the first carcass ply 51 has a ply body portion 51c extending radially inward from one end 51a on the side of the cutout portion 50H disposed in the tread 30, a bent portion 51d folded back from the ply body portion 51c at the bead core 11, and a turned-up portion 51e extending radially outward from the bent portion 51d. The cutout portion 50H is formed between the opposing one ends 51a of the pair of ply pieces 51A. The ply body portion 51c, the bent portion 51d, and the turned-up portion 51e are continuous. The ply body portion 51c is disposed on the inner side in the tire radial direction of the bead core 11 and the bead filler 12 in the tire width direction, and the turned-up portion 51e is disposed on the outer side in the tire radial direction of the bead core 11 and the bead filler 12 in the tire width direction. In the portion other than the bead core 11 and the bead filler 12, the turned-up portion 51e is overlapped with the ply body portion 51c. The bent portion 51d constitutes the innermost portion in the tire radial direction of the first carcass ply 51.

[0022] As shown in Fig. 3, a pair of ply pieces 51A constituting the first carcass ply 51 includes a plurality of carcass cords 51g extending in the tire width direction. The plurality of carcass cords 51g are arranged side by side in the tire circumferential direction. The carcass cords 51g are made of steel cords or insulating organic fiber cords such as polyester or polyamide. The carcass cords 51g are covered with rubber.

[0023] 1, in a pair of ply pieces 51A constituting the first carcass ply 51, at least one of the pair of one ends 51a is located inward in the tire width direction from an inner wall 32c on the inner side in the tire width direction of the outermost main groove 32A of the tread 30. In addition, at least one of the pair of one ends 51a is located outward in the tire width direction from an outer wall 32d on the outer side in the tire width direction of the innermost main groove 32B of the tread 30.

[0024] On the other hand, the turned-up portion 51e extends to the tread 30, and the other end 51b, which is the end on the turned-up portion 51e side and is the turned-up end of the ply piece 51A, is arranged to overlap the belt 40 (belts 41, 42).

[0025] The bead 10 further has a chafer 13 and a rim strip rubber 14 . The chafer 13 is provided to surround an end portion on the inner side in the tire radial direction of the first carcass ply 51 including the bent portion 51d. That is, the chafer 13 covers, at the end portion on the inner side in the tire radial direction of the tire 1, from an outer surface on the inner side in the tire width direction of the ply main body portion 51c of the first carcass ply 51 to an outer surface on the inner side in the tire radial direction of the bent portion 51d, and covers an outer surface on the outer side in the tire width direction of the turned-up portion 51e.

[0026] The rim strip rubber 14 is disposed on the outer side in the tire width direction of the chafer 13 and the folded-up portion 51e of the first carcass ply 51. The rim strip rubber 14 is a member that comes into contact with the rim on which the tire 1 is mounted. The outer end of the rim strip rubber 14 in the tire radial direction is covered with the sidewall rubber portion 21.

[0027] In the bead 10, the sidewall 20, and the tread 30, an inner liner 70 is provided as a rubber layer constituting the inner wall surface of the tire 1 on the tire cavity side of the first carcass ply 51. In the tread 30, the inner liner 70 covers the inner surface of the first carcass ply 51 and the inner surface of the belt 40 in the hollowed-out portion 50H. In addition, the inner liner 70 covers the inner surface of the first carcass ply 51 in the sidewall 20. Furthermore, in the bead 10, the inner liner 70 covers the inner surfaces of the first carcass ply 51 and the chafer 13. The inner liner 70 is made of air-resistant rubber and prevents air within the tire cavity from leaking to the outside.

[0028] In this embodiment, as described above, the belt 40 of the tread 30 has a two-layer structure including the inner belt 41 and the outer belt 42. The inner belt 41 is disposed adjacent to the first carcass ply 51 on the outer side in the tire radial direction, and the outer belt 42 is disposed adjacent to the outer side in the tire radial direction of the inner belt 41. In this embodiment, the dimension of the inner belt 41 in the tire width direction is larger than the dimension of the outer belt 42 in the tire width direction. The end 41a in the tire width direction of the inner belt 41 is located outside in the tire width direction of the end 42a in the tire width direction of the outer belt 42.

[0029] As described above, in this embodiment, the other ends 51b of the pair of ply pieces 51A on the side of each turned-up portion 51e are arranged to overlap with the belt 40. That is, the other ends 51b of the ply pieces 51A overlap with at least a part of the belt 40 in the member lamination direction from the tire cavity side toward the tire outer surface side. This overlapping arrangement allows the first carcass ply 51 to be held by the belt 40.

[0030] In detail, in the belt 40 (41, 42) of this embodiment, the end 42a of the outer belt 42 is located inside the end 41a of the inner belt 41 in the tire width direction, and the other end 51b of the ply piece 51A is located inside the end 42a of the outer belt 42 in the tire width direction. Therefore, the other end 51b of the ply piece 51A overlaps with both of the belts 41 and 42. Also, the other end 51b of the ply piece 51A is located outside the tire width direction of one end 51a of the ply piece 51A on the cutout portion 50H side. Furthermore, the other end 51b of the ply piece 51A is located inside the tire width direction of the end 60a of the cap ply 60 in the tire width direction.

[0031] In order to hold the first carcass ply 51 by the belt 40, it is sufficient that the other end 51b of the ply piece 51A overlaps with either one of the two belts 41, 42 constituting the belt 40. In other words, the other end 51b is located between the end 41a of the belt 41 and the end 42a of the belt 42 in the tire width direction, so that it overlaps with the inner belt 41 and does not have to overlap with the outer belt 42.

[0032] The cap ply 60 is a wide member that covers the entire belts 41, 42 including the end portions 41a, 42a. Although the cap ply 60 in this embodiment is a single layer, two or more layers may be disposed.

[0033] As shown in Fig. 2, in this embodiment, an endless rubber pad 80 is disposed between both ends of the belt 40 on the outer side in the tire width direction and the folded-up portion 51e of the first carcass ply 51. The cross-sectional shape of the pad 80 is a flat triangular shape. The tire radial direction ends 41a, 42a of the belts 41, 42 and the tire width direction end 60a of the cap ply 60 are located in the tire width direction between the tire width direction outer end 80a and the tire width direction inner end 80b of the pad 80, that is, in the area where the pad 80 is present. The pad 80 may be omitted.

[0034] 3, the inclination angle θ1 of the belt cords 41g, which are components of the belt 41, with respect to the tire circumferential direction is preferably 26° or more and 33° or less (26°≦θ1≦33°). Similarly, the inclination angle θ2 of the belt cords 42g, which are components of the belt 42, with respect to the tire circumferential direction is preferably 26° or more and 33° or less (26°≦θ2≦33°). In other words, the belt cords 41g, 42g of each of the belts 41, 42 are preferably arranged at an inclination angle of 26° or more and 33° or less with respect to the tire circumferential direction.

[0035] In this embodiment, the belt cord 41g is disposed at an inclination angle of, for example, 30° with respect to the tire circumferential direction (θ1=30°). Similarly, the belt cord 42g is disposed at an inclination angle of, for example, 30° with respect to the tire circumferential direction (θ2=30°). Here, the inclination angles θ1 and θ2 are shown in absolute values. Therefore, in the illustrated example, the belt cords 41g and 42g are disposed so as to intersect with each other, but the inclination angles are the same, 30°.

[0036] The belt reinforcing layer cord 60g of the cap ply 60 is aligned along the tire circumferential direction. That is, the inclination angle of the reinforcing layer cord 60g with respect to the tire circumferential direction is 0°. In this manner, the inclination angle of the reinforcing layer cord 60g with respect to the tire circumferential direction is preferably smaller than the inclination angles θ1, θ2 (=30°) of the belt cords 41g, 42g with respect to the tire circumferential direction. The angle θ3 between the inclination angle (0°) of the belt reinforcing layer cord 60g with respect to the tire circumferential direction and the inclination angle θ1 of the belt cord 41g with respect to the tire circumferential direction, and the angle θ4 between the inclination angle (0°) of the belt reinforcing layer cord 60g with respect to the tire circumferential direction and the inclination angle θ2 of the belt cord 42g with respect to the tire circumferential direction are preferably all 20° or more.

[0037] The tire 1 of the present embodiment described above provides the following advantages.

[0038] (1) The tire 1 according to this embodiment includes a pair of beads 10 each having a bead core 11, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, a tread 30 arranged between the pair of sidewalls 20, a belt 40 arranged on the tread 30, a cap ply 60 as a belt reinforcing layer arranged radially outward of the belt 40, and a first carcass ply 51 arranged radially inward of the belt 40, the first carcass ply 51 including a pair of ply pieces 51A having one end 51a arranged radially inward of the outer end of the belt 40 and the other end 51b folded back at the bead core 11, the cap ply 60 including a belt reinforcing layer cord 60g, and the belt reinforcing layer cord 60g including aramid fiber.

[0039] This achieves both weight reduction and the associated reduction in rolling resistance, as well as improved steering stability during high-speed driving due to the increased rigidity achieved by the belt reinforcing layer cords 60g of the cap ply 60 containing aramid fibers.

[0040] (2) In the tire 1 according to the present embodiment, it is preferable that the other ends 51b of the pair of ply pieces 51A constituting the first carcass ply 51, which are folded back at the bead cores 11, overlap with the belt .

[0041] As a result, the first carcass ply 51 is firmly held by the belt 40, and the steering stability can be improved as the rigidity is improved. Moreover, the other end 51b on the turned-up portion 51e side can be attached to the ply piece 51A itself, so that the first carcass ply 51 can be disposed in a stable position.

[0042] (3) In the tire 1 according to this embodiment, each of the belts 41, 42 constituting the belt 40 includes belt cords 41g, 42g, respectively, and it is preferable that the belt cords 41g, 42g are arranged at an inclination angle of 26° or more and 33° or less with respect to the tire circumferential direction.

[0043] When the belt cords 41g, 42g are arranged along the tire circumferential direction (at an inclination angle of 0° relative to the tire circumferential direction), the rigidity is highest, and the rigidity decreases as the inclination angle increases. In this embodiment, by setting the inclination angle of the belt cords 41g, 42g to a range of 26° to 33° relative to the tire circumferential direction, a good balance can be obtained between the steering stability associated with moderate rigidity and the good ride comfort due to flexibility.

[0044] (4) In the tire 1 according to this embodiment, the inclination angle of the belt reinforcing layer cord 60g of the cap ply 60 with respect to the tire circumferential direction is smaller than the inclination angle of the belt cords 41g, 42g of the belts 41, 42 with respect to the tire circumferential direction, and it is preferable that the angle between the inclination angle of the belt reinforcing layer cord 60g with respect to the tire circumferential direction and the inclination angle of the belt cords 41g, 42g with respect to the tire circumferential direction is 20° or more.

[0045] This makes it possible to obtain a good balance between the steering stability provided by the appropriate rigidity and the comfortable ride provided by flexibility.

[0046] (5) In the tire 1 according to the present embodiment, the belt reinforcing layer cord 60g of the cap ply 60 is preferably a hybrid cord having an aramid fiber and a nylon fiber.

[0047] This improves the reinforcing effect and durability of the belt 40 by the cap ply 60, and improves steering stability during high-speed driving due to the improved rigidity even in the tire 1 that has been made lighter by providing the hollowed-out portion 50H. In addition, the hybrid cord having aramid fiber and nylon fiber has excellent adhesion to rubber, and separation of the belt reinforcing layer cord 60g from the tread rubber portion 31 is suppressed.

[0048] (6) In the tire 1 according to this embodiment, the tread 30 has a tread pattern 32 including a plurality of main grooves 32A, 32B arranged side by side in the tire width direction, and it is preferable that one end 51a of at least one of a pair of ply pieces 51A of the first carcass ply 51 is positioned on the inner side in the tire width direction of the inner inner wall 32c in the tire width direction of the outermost main groove 32A arranged on the outermost side in the tire width direction in the tread pattern 32.

[0049] This ensures high rigidity. That is, since the main groove 32A of the tread 30 has a concave shape, it is formed by being pressed from a mold during vulcanization molding of the tire 1, and therefore, by arranging one end 51a of the ply piece 51A on the inner side in the tire width direction from the inner wall 32c of the outermost main groove 32A, the ply piece 51A can be firmly held by receiving the pressing force from the mold during vulcanization molding. As a result, it is possible to improve rigidity and, accordingly, improve steering stability.

[0050] (7) In the tire 1 according to this embodiment, the tread 30 has a tread pattern 32 including a plurality of main grooves 32A, 32B arranged side by side in the tire width direction, and it is preferable that one end 51a of at least one of a pair of ply pieces 51A of the first carcass ply 51 is positioned on the outer side in the tire width direction of the outer wall 32d on the outer side in the tire width direction of the innermost main groove 32B that is located at a position closest to the center of the tire width direction in the tread pattern 32.

[0051] As a result, one end 51a of the ply piece 51A is located between the main grooves 32A and 32B aligned in the tire width direction, and the ply piece 51A is firmly held during the vulcanization molding described above. As a result, it is possible to improve rigidity and, therefore, improve steering stability.

[0052] Next, a modified example of the present invention will be described with reference to Fig. 4. In the following description, the same components as those in the above embodiment are denoted by the same reference numerals, and the description thereof will be omitted, and only the differences from the above embodiment will be described.

[0053] 4, the carcass ply further includes a second carcass ply 52 in addition to the first carcass ply 51. The second carcass ply 52 does not have a hollow portion 50H like the first carcass ply 51, and is bridged between a pair of beads 10.

[0054] The second carcass ply 52 is disposed on the tire radial inner side of the first carcass ply 51 in the tread 30, and has a center portion 52a disposed in the hollow portion 50H. The second carcass ply 52 has a ply body portion 52c extending from the center portion 52a toward the tire radial inner side along the sidewall 20, a bent portion 52d folded back around the bead core 11, and a turned-up portion 52e extending from the bent portion 52d toward the tire radial outer side. The turned-up portion 52e extends to a position closer to the tire radial inner side than the end portion 12a on the tire radial outer side of the bead filler 12. That is, the other end 52b in the tire width direction of the second carcass ply 52 is located within the tire radial region of the bead 10. The second carcass ply 52 may be disposed outside the first carcass ply 51 .

[0055] (8) In the tire 1 according to this modified example, as a carcass ply other than the first carcass ply 51, at least one second carcass ply 52 is further provided, which is arranged radially inward of the first carcass ply 51 and folded back around each of a pair of bead cores 11.

[0056] As a result, compared to the above embodiment in which the carcass ply is composed of only the first carcass ply 51, the rigidity is improved due to the increased number of carcass plies, and therefore the steering stability can be further improved.

[0057] (9) Furthermore, of the pair of ply pieces 51A of the first carcass ply 51 and the second carcass ply 52, the other end 51b of the ply piece 51A of the first carcass ply 51 overlaps with the belt 40, and the other end 52b of the second carcass ply 52 on the folded-back portion 52e side is located within the tire radial area of ​​the bead 10.

[0058] As a result, the beads 10 are reinforced by the second carcass ply 52, while the first carcass ply 51 is firmly held by the belt 40, and the improved rigidity leads to improved steering stability.

[0059] In the above modified example, the second carcass ply 52 may have a hollow portion, similar to the first carcass ply 51. Similarly to the first carcass ply 51, the second carcass ply 52 may have a folded-up portion 52e extending to the tread 30 and the other end 52b overlapping with the belt 40. The second carcass ply 52 may be disposed on the outer side in the tire radial direction of the first carcass ply 51, or at least one may be disposed on each of the inner and outer sides in the tire radial direction.

[0060] The above describes specific embodiments of the present invention and variations thereof. However, the present invention is not limited to the above embodiments, and even if modifications and improvements are made within the scope of the present invention, they will still be included in the scope of the present invention. For example, the tire may have three or more carcass plies, at least one of which has a hollow portion, i.e., the center portion in the tire width direction is open, and the tire may include a pair of ply pieces divided into two on both sides in the tire width direction. Also, the folded portion of at least one of the three or more carcass plies may extend to the tread 30, and its end portion (corresponding to the other end 51b in the above embodiment) may overlap the belt 40. [Explanation of symbols]

[0061] 1. Tires (pneumatic tires) 10 Beads 11 Bead core 20 Sidewall 30 Tread 32 Tread pattern 32A Outermost main groove (main groove) 32B Innermost main groove (main groove) 32c inner wall 32d Exterior wall 40, 41, 42 Belt 41g, 42g belt cord 51 First carcass ply 51A Ply Piece 51a One end of a ply piece 51b Other end of ply piece 52 Second carcass ply 52b the other end of the second carcass ply 60 Cap ply (belt reinforcement layer) 60g belt reinforcement cord

Claims

1. A pair of beads each having a bead core; a pair of sidewalls extending radially outward from each of the pair of beads; a tread disposed between the pair of sidewalls; A belt disposed on the tread; A belt reinforcing layer disposed on the outer side of the belt in the tire radial direction; a first carcass ply including a pair of ply pieces arranged on the inner side of the belt in the tire radial direction, one end of which is arranged on the inner side of an outer end of the belt in the tire width direction, and the other end of which is folded back at the bead core; The belt reinforcing layer includes a belt reinforcing layer cord, and the belt reinforcing layer cord includes an aramid fiber. the other end of each of the pair of ply pieces folded back at the bead core overlaps with the belt, The tread has a tread pattern including a plurality of main grooves arranged side by side in a tire width direction, The one end of at least one of the pair of ply pieces is located on the inner side in the tire width direction of an inner wall on the inner side in the tire width direction of an outermost main groove that is the main groove arranged on the outermost side in the tire width direction in the tread pattern, the other end of each of the pair of ply pieces is located outboard in the tire width direction relative to an outer wall of the outermost main groove in the tire width direction.

2. The pneumatic tire according to claim 1 , wherein the belt includes a belt cord, and the belt cord is disposed at an inclination angle of 26° to 33° with respect to a circumferential direction of the tire.

3. 3. The pneumatic tire according to claim 2, wherein an inclination angle of the belt reinforcing layer cord with respect to the tire circumferential direction is smaller than an inclination angle of the belt cord with respect to the tire circumferential direction, and an angle between the inclination angle of the belt reinforcing layer cord with respect to the tire circumferential direction and an inclination angle of the belt cord with respect to the tire circumferential direction is 20° or more.

4. The pneumatic tire according to any one of claims 1 to 3, wherein the belt reinforcing layer cord is a hybrid cord having an aramid fiber and a nylon fiber.

5. 5. The pneumatic tire according to claim 1, wherein the one end of at least one of the pair of ply pieces is located on the outer side in the tire width direction of an outer wall on the outer side in the tire width direction of an innermost main groove, which is the main groove arranged at a position closest to a center in the tire width direction in the tread pattern.

6. The pneumatic tire according to any one of claims 1 to 5, further comprising at least one second carcass ply arranged on the inner or outer side of the first carcass ply in the tire radial direction and having the other end folded back on each of the pair of bead cores.

7. 7. The pneumatic tire according to claim 6, wherein one of the other ends of the pair of ply pieces of the first carcass ply and the other end of the second carcass ply overlaps with the belt, and the other end is located in the bead region in the tire radial direction.

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