Pneumatic tires

Abstract

To provide a pneumatic tire that can improve rigidity of a bead and of a tread while suppressing weight increase and improve steering stability.SOLUTION: The pneumatic tire comprises: a pair of beads 10; 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 including a belt reinforcement layer cord 60g, arranged at outside in a tire radial direction of the belt 40; and at least one first carcass ply 51 including a plurality of carcass plies 51g, in which the pair of beads 10 is folded back. In the first carcass ply 51, each angle formed between each carcass plie 51g and a tire circumferential direction on an inside in a tire width direction of a bead filler 12 is different from that on an outside in the tire width direction of the bead filler, 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, a structure in which a carcass ply forming the framework of a tire is embedded in a pair of sidewalls and a tread between a pair of beads is known in pneumatic tires for vehicles. The bead is required to have high rigidity because it is the part where the tire is attached to the rim. For example, Patent Document 1 discloses a pneumatic tire in which reinforcing cords are embedded in the sidewalls and beads to improve the rigidity of the sidewalls and beads. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-93395 A Summary of the Invention [Problem to be solved by the invention]

[0004] In pneumatic tires, rolling resistance can be reduced by reducing the weight. However, providing reinforcing cords as separate members as disclosed in Patent Document 1 leads to an increase in weight due to an increase in the number of parts. In addition, Patent Document 1 does not mention how to effectively improve the rigidity of the tread, leaving 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 that can improve the rigidity of the beads and tread while suppressing an increase in weight, thereby achieving improved steering stability. [Means for solving the problem]

[0006] The pneumatic tire of the present invention comprises a pair of beads each having a bead core and a bead filler extending radially outward from the 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 including a belt reinforcing layer cord, and at least one carcass ply including a plurality of carcass cords and folded back on the pair of beads, wherein the at least one carcass ply has different angles between the carcass cord and the tire circumferential direction on the tire widthwise inner side and tire widthwise outer side of the bead filler, and the belt reinforcing layer cord includes aramid fiber. Effect of the Invention

[0007] According to the present invention, it is possible to provide a pneumatic tire that can improve the rigidity of both the beads and the tread while suppressing an increase in weight, thereby achieving improved steering 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 a schematic development view of a first carcass ply, a belt, and a cap ply (belt reinforcing layer) according to one embodiment. [Diagram 3] FIG. 2 is a schematic side view showing an arrangement of carcass cords in a first carcass ply according to one embodiment. [Figure 4] FIG. 4 is a schematic development view of a first carcass ply and a belt according to a first modified example of the embodiment. [Diagram 5] FIG. 11 is a schematic development view of a first carcass ply and a belt according to a second modified example of the embodiment. [Figure 6] FIG. 11 is a diagram showing a half cross section in the tire width direction of a pneumatic tire according to a third modified example of the embodiment. [Figure 7]FIG. 13 is a schematic side view showing the arrangement of carcass cords of the first and second carcass plies according to a third modified example. [Figure 8] FIG. 13 is a development view illustrating a schematic view of first and second carcass cords according to a third modified example. 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. The structure of the 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, the symbol S1 indicates 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 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, and 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, and 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. 6 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 which is a carcass ply 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 which constitutes 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] FIG. 2 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 II in FIG. 1. That is, FIG. 2 shows the belts 41, 42, a pair of ply pieces 51A of the first carcass ply 51, which will be described later, and the cap ply 60. 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. 2, the cap ply 60 is further broken in the circumferential direction to show the belts 41, 42. In FIG. 2, a part of the circumferential direction of the ply piece 51A in an expanded state is shown within a two-dot chain line frame. In FIG. 2, 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. As shown in FIG. 2, each of the belts 41 and 42 includes 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 made of steel cords or insulating organic fiber cords such as polyester and 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. Note that the belts to be laminated in the belt 40 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. 2, 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 is composed of a pair of ply pieces 51A that form the framework of the tire 1. The first carcass ply 51 has a cutout portion 50H that is discontinuous in the center in the tire width direction of the tread 30. The pair of ply pieces 51A are embedded in the tire 1 in such a manner that they are disposed on both sides in the tire width direction of the cutout portion 50H.

[0021] Each of the pair of ply pieces 51A of the first carcass ply 51 has a ply main body portion 51c extending radially inward in the tire direction from one end 51a on the side of the cutout portion 50H arranged in the tread 30, a bent portion 51d folded back from the ply main body portion 51c at the bead core 11, and a folded-back portion 51e extending radially outward in the tire direction from the bent portion 51d. 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. 2, a pair of ply pieces 51A constituting the first carcass ply 51 includes a plurality of carcass cords 51g. The plurality of carcass cords 51g are arranged at an angle with respect to the tire width direction. The plurality of carcass cords 51g are arranged side by side at regular intervals 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 plurality of 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] Meanwhile, the other ends 51b of the pair of folded-back portions 51e are disposed radially outward of the tips 12b of the pair of bead fillers 12. Preferably, the other ends 51b are disposed radially outward of the tips of the bead fillers 12 by 10 mm or more (d1≧10 mm in FIG. 1). In this embodiment, the other ends 51b are disposed radially inward of the tire maximum width portion 20a (d2>0 in FIG. 1).

[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] 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.

[0030] 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.

[0031] 2, 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.

[0032] In this embodiment, the belt cord 41g is arranged at an inclination angle of, for example, 30° with respect to the tire circumferential direction (θ1=30°). Similarly, the belt cord 42g is arranged 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 arranged to intersect with each other, but have the same inclination angle of 30°.

[0033] 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.

[0034] As described above, the first carcass ply 51 is shown unfolded within the two-dot chain line frame in Fig. 2. The first carcass ply 51 is folded back at the fold back line W when assembled to the tire 1. In other words, the first carcass ply 51 is folded back around the bead core 11.

[0035] Fig. 3 is a diagram showing the tire 1 as viewed from the side in the direction of arrow III in Fig. 1, omitting the sidewall rubber portion 21 constituting the outer surface of the sidewall 20, and is a layout diagram of carcass cords 51g which are components of the ply piece 51A constituting the first carcass ply 51. In Fig. 3, the tire circumferential direction is indicated by an arrow S2.

[0036] As shown in Fig. 2 and Fig. 3, in this embodiment, the carcass cord 51g of the first carcass ply 51 is linear and arranged at an incline with respect to the tire width direction. By arranging in this manner, when the carcass cord 51g is folded back at the folding back line W, the extending direction of the carcass cord 51g before folding back and the extending direction of the carcass cord 51g after folding back are opposite to each other with respect to the tire radial direction. That is, in the first carcass ply 51, the angle of the carcass cord 51g with respect to the tire circumferential direction is different between the inner part in the tire width direction of the bead filler 12 before folding back and the outer part in the tire width direction of the bead filler 12 after folding back. The inclination angle of the carcass cord 51g in the extending direction on the inner side in the tire width direction of the bead filler 12 is the same as the inclination angle of the carcass cord 51g in the extending direction on the outer side in the tire width direction. 3, the carcass cord 51g is disposed so as to intersect with the inner side and the outer side in the tire width direction of the bead filler 12 in the tire side view. Preferably, the intersecting angle θ5 between the inner side and the outer side in the tire width direction of the bead filler 12 in the tire side view is 45° or more and 60° or less. If it is less than 45°, the hoop effect (effect of increasing rigidity) is insufficient, and if it is more than 60°, the weight increase is large.

[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 and a bead filler 12 extending radially outward from the bead core 11, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, a tread 30 disposed between the pair of sidewalls 20, a belt 40 disposed on the tread 30, a cap ply 60 as a belt reinforcing layer disposed radially outward from the belt 40 and including a belt reinforcing layer cord 60g, and at least one first carcass ply 51 including a plurality of carcass cords 51g and folded back on the pair of beads 10, wherein the first carcass ply 51 has different angles between the carcass cord 51g and the tire circumferential direction on the inner side and the outer side in the tire width direction of the bead filler 12, and the belt reinforcing layer cord 60g includes aramid fiber.

[0039] In this embodiment, the carcass cord 51g of the first carcass ply 51 forms different angles with the tire circumferential direction on the inner side and the outer side of the bead filler 12 in the tire width direction, so that a hoop effect is generated and the rigidity of the bead 10 is improved. Since the rigidity of the bead 10 is improved without providing other members such as a reinforcing layer, an increase in weight is suppressed. In addition, the belt reinforcing layer cord 60g of the cap ply 60 contains aramid fiber, so that the rigidity of the tread 30 including the cap ply 60 is improved. As a result, the steering stability is improved.

[0040] (2) In the tire 1 according to this embodiment, the first carcass ply 51 includes a pair of ply pieces 51A, one end 51a of which is positioned inward in the tire width direction from the outer end of the belt 40 in the tire width direction, and the other end 51b of which is folded back around the bead 10.

[0041] This achieves both weight reduction and the associated reduction in rolling resistance, as well as improved steering stability due to increased rigidity.

[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 the steering stability during running can be improved 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 at least one of the ends 51a of a pair of ply pieces 51A of the first carcass ply 51 on the side of a pair of cutout portions 50H is preferably positioned more inward in the tire width direction than the inner wall 32c on the inner side in the tire width direction of the outermost main groove 32A located 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, it is preferable that at least one of a pair of ends 51a of the pair of ply pieces 51A of the first carcass ply 51 on the side of the cutout portion 50H is positioned on the outer side in the tire width direction of the outer wall 32d of the innermost main groove 32B located at a position closest to the tire width direction center in the tread pattern 32.

[0051] As a result, one end of the ply piece 51A is positioned 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. (8) In the tire 1 according to this embodiment, it is preferable that the carcass cord 51g of the first carcass ply 51 has an intersection angle between the inner side in the tire width direction and the outer side in the tire width direction of the bead filler 12 of 45° or more and 60° or less in side view of the tire.

[0052] As a result, the rigidity of the bead 10 and the sidewall 20 is improved by the carcass cord 51g of the first carcass ply 51, and the improved rigidity leads to improved steering stability.

[0053] In addition, in this embodiment, one end 51a of the ply piece 51A on the side of the cutout portion 50H is located more inward in the tire width direction than the other end 51b on the side of the folded-back portion 51e, so that the other end 51b can be attached to the ply piece 51A itself, thereby achieving a stable arrangement of the carcass ply 11.

[0054] In this embodiment, the other end 51b of the ply piece 51A is disposed radially outward of the tip 12b of the bead filler 12. Specifically, the other end 51b of the ply piece 51A is disposed radially outward of the tip 12b of the bead filler 12 by 10 mm or more. Therefore, in a side view of the tire, a region in which the extending direction of the carcass cord 51g differs from the tip 12b of the bead filler 12 in the tire radial direction can be secured to a certain extent or more. As a result, a certain degree or more of a hoop effect can be generated, and the rigidity due to the hoop effect and the associated improvement in steering stability can be realized. In addition, the other end 51b of the ply piece 51A is disposed radially inward of the tire maximum width portion 20a. Therefore, the length of the folded-up portion 51e of the first carcass ply 51 can be kept below a certain level, and therefore the size of the first carcass ply 51 can be kept below a certain level, thereby achieving weight reduction.

[0055] Next, first to third modified examples of the tire 1 according to the above embodiment will be described. 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.

[0056] (First Modification) A first modified example of the pneumatic tire 1 will be described with reference to FIG. 2, Fig. 4 is a development view showing a schematic view of a part of the circumferential direction of the tire 1 when the tire 1 is viewed from the outer surface side with the tread rubber portion 31 omitted, and here, the cap ply 60 is omitted. In Fig. 4 as well, the first carcass ply 51, which is folded back at the fold-back line W along the bead core 11, is shown in an unfolded state within a two-dot chain line frame. In FIG. 4, 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. The same applies to FIG.

[0057] In the first modified example, the arrangement of the carcass cords 51g of the first carcass ply 51 is different from that of the above embodiment. In the first modified example, each carcass cord 51g has a first portion 51g1 extending in the tire width direction and a second portion 51g2 extending at an angle with respect to the tire width direction. The first portion 51g1 and the second portion 51g2 are both straight and are arranged to cross the turn-back line W.

[0058] In the first modified example, by folding back at the folding line W, the first portion 51g1 positioned on the inner side of the bead filler 12 in the tire width direction and the second portion 51g2 positioned on the outer side of the bead filler 12 in the tire width direction have different angles with the tire circumferential direction and are positioned so as to intersect with each other in a side view of the tire.

[0059] As in the first modified example, the arrangement angle of the carcass cord 51g does not necessarily have to be constant. That is, the carcass cord 51g may be separated into two or more cords, which may be arranged at different angles.

[0060] (Second Modification) A second modified example of the pneumatic tire 1 will be described with reference to FIG.

[0061] In the second modified example, the arrangement of the carcass cords 51g of the carcass ply 51 is different from that of the above embodiment and the first modified example. In the second modified example, the carcass cords 51g are not completely straight, but have a curved third portion 51g3. Specifically, each carcass cord 51g has a first portion 51g1 extending in the tire width direction similar to the first modified example, a second portion 51g2 extending at an angle from the tire width direction similar to the first modified example, and a curved third portion 51g3 connecting the first portion 51g1 and the second portion 51g2.

[0062] In the second modified example, by folding back at the folding line W, the first portion 51g1 positioned on the inner side of the bead filler 12 in the tire width direction and the second portion 51g2 positioned on the outer side of the bead filler 12 in the tire width direction form different angles with the tire circumferential direction and are positioned so as to intersect with each other in a side view of the tire.

[0063] As in the second modified example, the shape of one continuous carcass cord 51g does not necessarily have to be straight, that is, the carcass cord 51g may have a curved portion.

[0064] (Third Modification) A third modified example of the pneumatic tire 1 will be described with reference to FIGS.

[0065] 6 includes a first carcass ply 51 and a second carcass ply 52. ​​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.

[0066] 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 has substantially the same length as the first carcass ply 51 (the turned-up portion 51e of the ply piece 51A). Therefore, the end portion 52b of the turned-up portion 52e is located at substantially the same position in the tire radial direction as the other end 51b of the first carcass ply 51. It should be noted that the length of the turned-up portion 52e of the second carcass ply 52 is not limited to this.

[0067] 7 is a diagram of the tire 1 as seen from the side with the sidewall rubber portion 21 omitted, similar to Fig. 3, and shows a plurality of carcass cords 51g which are components of the ply piece 51A constituting the first carcass ply 51, and a plurality of carcass cords 52g which are components of the second carcass ply 52. ​​In Fig. 7, the tire circumferential direction is indicated by an arrow S2.

[0068] Fig. 8 partially illustrates the first carcass ply 51 and the second carcass ply 52 within the double-dashed line frames, similar to Fig. 2. As illustrated in Fig. 8, the multiple carcass cords 51g and the multiple carcass cords 52g are each arranged at regular intervals in the circumferential direction.

[0069] 7 and 8, in the third modified example, the multiple carcass cords 51g of the first carcass ply 51 (ply piece 51A) which is a hollow ply extend linearly in parallel to the tire width direction over the entire length, while the multiple carcass cords 52g of the second carcass ply 52 extend linearly at an angle to the tire width direction over the entire length.

[0070] In a side view of the tire, the crossing angle between the side of the carcass cord 51g in the first carcass ply 51 arranged on the inner side of the bead filler 12 in the tire width direction and the side of the carcass cord 51g arranged on the outer side of the bead filler 12 in the tire width direction is preferably 0° or more and 5° or less. Here, the carcass cord 51g is parallel to the tire width direction, so the crossing angle is 0°. On the other hand, in a side view of the tire, the crossing angle between the side of the carcass cord 52g in the second carcass ply 52 arranged on the inner side of the bead filler 12 in the tire width direction and the side of the carcass cord 52g arranged on the outer side of the bead filler 12 in the tire width direction is preferably 45° or more and 60° or less. Therefore, the crossing angle (θ6 in FIG. 7) between the carcass cord 51g and the carcass cord 52g in this embodiment is 22.5° or more and 30° or less (22.5°≦θ6≦30°).

[0071] (9) The tire 1 according to the third modification further includes a second carcass ply 52 that is continuously laid between the pair of beads 10 .

[0072] 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.

[0073] In addition, in a configuration having two or more carcass plies, such as the third modified example, the second carcass ply 52 only needs to have angles that differ from each other with respect to the tire circumferential direction, at least in the regions on the inner side and the outer side in the tire width direction of the bead filler 12, as shown in the second and third modified examples. The carcass cords 51g of the first carcass ply 51 may be arranged at an incline with respect to the tire width direction, and the carcass cords 52g of the second carcass ply 52 may be arranged along the tire width direction. Alternatively, both the carcass cords 51g of the first carcass ply 51 and the carcass cords 52g of the second carcass ply 52 may be arranged at an incline with respect to the tire width direction.

[0074] In the third modified example, the second carcass ply 52, like the first carcass ply 51, may have a hollow portion.

[0075] 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 includes a pair of ply pieces having one end positioned in the tire width direction more inward than the outer end of the belt 40 in the tire width direction and the other end folded back around the bead 10 (having a cutout portion), and at least one of which may be continuously spanned between a pair of beads 10 (having no cutout portion). [Explanation of symbols]

[0076] 1. Tires (pneumatic tires) 10 Beads 11 Bead core 12 Bead filler 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 (carcass ply) 51A Ply Piece 51a One end of a ply piece 51g carcass cord 52 Second carcass ply 60 Cap ply (belt reinforcement layer) 60g belt reinforcement cord

Claims

1. A pair of beads each having a bead core and a bead filler extending radially outward from the 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 an outer side of the belt in the tire radial direction and including a belt reinforcing layer cord; At least one carcass ply including a plurality of carcass cords and folded back around the pair of beads; The carcass cord in the at least one carcass ply has a first portion disposed on an inner side of the bead filler in a tire width direction and a second portion disposed on an outer side of the bead filler in a tire width direction, When developed in a planar state, the first portion extends in a tire width direction, and the second portion extends at an angle with respect to the tire width direction, The pneumatic tire, wherein the belt reinforcing layer cord contains aramid fiber.

2. The pneumatic tire according to claim 1 , wherein the at least one carcass ply includes a pair of ply pieces, one end of which is disposed on the inner side in the tire width direction relative to an outer end of the belt in the tire width direction, and the other end of which is folded back around the bead.

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

4. 4. The pneumatic tire according to claim 3, 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.

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

6. The tread has a tread pattern including a plurality of main grooves arranged side by side in a tire width direction, 3. The pneumatic tire according to claim 2, wherein at least one of the one ends 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.

7. 7. The pneumatic tire according to claim 6, wherein at least one of the one ends of the pair of ply pieces is located outboard in the tire width direction relative to 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.

8. The pneumatic tire according to claim 7 , wherein the carcass cord of the at least one carcass ply has an intersection angle between an inner side in the tire width direction and an outer side in the tire width direction of the bead filler of 45° or more and 60° or less in a tire side view.

9. The pneumatic tire according to any one of claims 1 to 8, further comprising a second carcass ply that is continuously laid between the pair of beads.

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