pneumatic tires

Abstract

To provide a pneumatic tire which can improve resistance to external damage to improve durability, while achieving reduction in weight due to a carcass ply in an inside hollow structure.SOLUTION: A carcass play 50 includes a pair of first ply pieces 51A and second ply pieces 52A divided in a tire width direction. The ply pieces 51A and 51B, arranged in a tread 30, have first tire width-directional inner ends 51a and second tire width-directional inner ends 52a separating from and opposing to each other in the tire width direction respectively. A reinforcement layer 70 is arranged at a tire inner cavity side between respective first tire width-directional inner ends 51a of the pair of first ply pieces 51A. Outer end parts 70B in the tire width direction of the reinforcement layer 70 and inner end parts 50B in the tire width direction of the ply pieces including the first tire width-directional inner ends 51 and the second tire width-directional inner ends 52a superpose on each other in a tire radial direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-101647 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if a damaging object such as a nail penetrates the outer surface of a tire in a portion corresponding to the cutout, the damaging object is likely to penetrate into the tire cavity and cause a puncture because there is no carcass ply, which makes the tire less resistant to external damage.

[0005] SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic tire that can achieve weight reduction by using a carcass ply with a hollowed-out structure, while also achieving improved durability through improved resistance to external damage. [Means for solving the problem]

[0006] The pneumatic tire of the present invention is a pneumatic tire including a pair of beads, a pair of sidewalls extending radially outward from each of the pair of beads, a tread arranged between the pair of sidewalls, a belt arranged on the tread, and a carcass ply spanning from the tread to the pair of beads, wherein the carcass ply includes a pair of ply pieces divided in the tire width direction, each of the pair of ply pieces being arranged on the tread and having tire width direction inner ends spaced apart from each other in the tire width direction and facing each other, a reinforcing layer being arranged on the tire cavity side between the tire width direction inner ends of each of the pair of ply pieces, and the tire width direction outer end of the reinforcing layer and the tire width direction inner end of the ply piece including the tire width direction inner end of the ply piece overlap in the tire radial direction. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a pneumatic tire that can achieve weight reduction by using a carcass ply with a hollowed-out structure, while also achieving improved durability through improved resistance to external damage. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view in the tire width direction of a pneumatic tire according to an embodiment. [Figure 2] FIG. 2 is an enlarged view of a portion of FIG. [Figure 3] FIG. 2 is a cross-sectional view in the tire width direction of a pneumatic tire according to a first modified example based on the embodiment. [Figure 4] FIG. 10 is a diagram schematically showing a tire circumferential cross section of a pneumatic tire according to a second modification based on the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment will be described with reference to the drawings. Fig. 1 shows a cross section in the tire width direction of a tire 1, which is a pneumatic tire according to an embodiment. Fig. 2 is an enlarged view of a part of Fig. 1, and is a cross section showing a portion from a tread 30 to a bead 10, which will be described later.

[0010] The tire 1 according to the embodiment is, for example, a pneumatic tire for a passenger car. The tire 1 according to the embodiment can be used for various vehicles such as a light truck, a truck, a bus, etc. in addition to passenger cars.

[0011] The structure of the tire 1 is symmetrical in a cross section in the tire width direction. In Fig. 1, the 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.

[0012] The cross-sectional view in Figure 1 shows the tire 1 mounted on a standard rim and inflated to a standard internal pressure under no load. The standard rim refers to a standard rim established by JATMA for a tire size. The standard internal pressure is, for example, 180 kPa when the tire 1 is for a passenger car.

[0013] Here, the tire width direction is a direction parallel to the tire rotation axis, and is the left-right direction on the paper in Fig. 1. In Fig. 1, this is illustrated as the tire width direction X. The inner side in the tire width direction is a direction approaching the tire equatorial plane S1, and is the center side on the paper in Fig. 1. The outer side in the tire width direction is a direction away from the tire equatorial plane S1, and is the left and right sides on the paper in Fig. 1.

[0014] The tire radial direction is a direction perpendicular to the tire rotation axis, and is the up-down direction on the paper in Fig. 1. In Fig. 1, this is illustrated as the tire radial direction Y. The tire radially outer side is a direction away from the tire rotation axis, and is the upper side on the paper in Fig. 1. The tire radially inner side is a direction approaching the tire rotation axis, and is the lower side on the paper in Fig. 1. The same applies to Fig. 2 and Fig. 3 described later.

[0015] 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 carcass ply 50 extending from the tread 30 to the pair of beads 10, an inner liner 60 arranged on the tire cavity side of the carcass ply 50, and a reinforcing layer 70.

[0016] The bead 10 includes a bead core 11, a bead filler 12 extending from the bead core 11 outward in the tire radial direction, and a rim strip rubber 13.

[0017] The bead core 11 is an annular member in which a rubber-coated metal bead wire is wound multiple times in the circumferential direction of the tire. The bead core 11 is a member that serves to fix the tire 1 filled with air to the rim.

[0018] 2, the bead filler 12 has a tire radially outer end 12a that is the tip on the outer side in the tire radial direction. The bead filler 12 has a tapered shape as it extends from the tire radially inner side to the tire radially outer end 12a.

[0019] The bead filler 12 is 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.

[0020] As shown in Figure 1, the rim strip rubber 13 further surrounds the outside of the carcass ply 50, which is provided to surround the bead core 11 and bead filler 12. The rim strip rubber 13 comes into contact with the inside portion of the rim on which the tire 1 is mounted. A peak 13a is formed along the tire circumferential direction on the outer surface of the rim strip rubber 13 on the outer side in the tire width direction. The outer portion of the rim strip rubber 13 in the tire width direction, including the peak 13a, forms a rim protector 14 that protects the rim from external damage. The rim protector 14 is continuous in an annular shape in the tire circumferential direction.

[0021] The sidewall 20 includes a sidewall rubber 21 arranged on the outer side of the carcass ply 50 in the tire width direction. The sidewall rubber 21 forms the outer wall surface of the tire 1. The sidewall rubber 21 is the part that bends the most when the tire 1 performs its cushioning function, and typically, flexible rubber having fatigue resistance is used for the sidewall rubber 21. The inner end of the sidewall rubber 21 in the tire radial direction covers the outer end of the rim strip rubber 13 in the tire radial direction.

[0022] The tread 30 includes a tread rubber 31. An endless belt 40 and a cap ply 45 are arranged on the tread 30. The belt 40 is arranged on the outer side of the inner liner 60 in the tire radial direction. The cap ply 45 is arranged on the outer side of the belt 40 in the tire radial direction. The tread rubber 31 is arranged on the outer side of the cap ply 45 in the tire radial direction.

[0023] The belt 40 is a member that reinforces the tread 30. The belt 40 of this embodiment has a two-layer structure including an inner belt 41 arranged radially outward of the inner liner 60, and an outer belt 42 arranged radially outward of the inner belt 41. Both the inner belt 41 and the outer belt 42 have a structure in which a plurality of cords, such as steel cords, are covered with rubber. As shown in FIG. 2 , the belt 40 has an outer end 40B on the outer side in the tire width direction, where the inner belt 41 and the outer belt 42 overlap.

[0024] In the belt 40, the inner belt 41 is wider than the outer belt 42. Therefore, as shown in Fig. 2, an outer end 41A in the tire width direction, which is the outermost tip of the inner belt 41 in the tire width direction, is positioned further outward in the tire width direction than an outer end 42A in the tire width direction, which is the outermost tip of the outer belt 42 in the tire width direction. By providing the belt 40, the rigidity of the tire 1 is ensured and the contact of the tread 30 with the road surface is improved. Note that the belt 40 is not limited to a two-layer structure, and may have a one-layer structure or a three-layer or more structure.

[0025] The cap ply 45 is a member that reinforces the tread 30 together with the belt 40. The cap ply 45 has a structure in which a plurality of insulating organic fiber cords, such as polyamide fiber cords, are covered with rubber. As shown in FIG. 2, an outer end 45B of the cap ply 45 in the tire width direction is doubled by being folded from the outer side to the inner side in the tire radial direction. An outer end 45A in the tire width direction, which is the outer tip of the cap ply 45 in the tire width direction, is positioned further outward in the tire width direction than an outer end 41A in the tire width direction of the inner belt 41. The outer end 45B in the tire width direction of the cap ply 45 covers and is in close contact with the outer end 41B in the tire width direction of the inner belt 41. In other words, the cap ply 45 is a wide member that covers the entire belt 40 in one piece.

[0026] Although the cap ply 45 in the embodiment is a single layer, it may be a structure of two or more layers. By providing the cap ply 45, it is possible to improve durability and reduce road noise during driving.

[0027] As shown in FIG. 1, the tread rubber 31 is disposed on the outer side of the cap ply 45 in the tire radial direction. The tread rubber 31 is a member that forms a tread surface 31a that comes into contact with the road surface during driving. A tread pattern 32 consisting of, for example, a plurality of grooves is provided on the tread surface 31a of the tread rubber 31. As shown in FIG. 2, an outer end 31B of the tread rubber 31 in the tire width direction bends inward in the tire radial direction beyond an outer end 45A of the cap ply 45 in the tire width direction and comes into contact with the carcass ply 50. The outer end 31B of the tread rubber 31 in the tire width direction is covered by an outer end 21B of the sidewall rubber 21 in the tire radial direction.

[0028] The carcass ply 50 constitutes a ply that forms the framework of the tire 1. As shown in Fig. 1 , the carcass ply 50 of the embodiment includes a first carcass ply 51 and a second carcass ply 52. ​​The first carcass ply 51 is disposed on the tire outer surface side of the inner liner 60, and the second carcass ply 52 is disposed on the tire outer surface side of the first carcass ply 51. The first carcass ply 51 and the second carcass ply 52 each have a discontinuous cutout portion in the center of the tread 30 in the tire width direction, and are configured to be divided into two halves in the tire width direction with this cutout portion sandwiched between them.

[0029] The first carcass ply 51 includes a pair of first ply pieces 51A divided in the tire width direction. The first carcass ply 51 has a first cutout portion 51H that is discontinuous in a center portion of the tread 30 in the tire width direction. The pair of first ply pieces 51A are embedded in the tire 1 in a manner such that they are arranged on both sides in the tire width direction with the first cutout portion 51H sandwiched therebetween. The pair of first ply pieces 51A are an example of a pair of ply pieces divided in the tire width direction.

[0030] As shown in Fig. 2, the first ply piece 51A has a first tire widthwise inner end 51a at a tip on the first cutout portion 51H side, the first tire widthwise inner end 51a being opposed to and spaced apart from each other in the tire width direction. The first tire widthwise inner end 51a is an example of tire widthwise inner ends opposed to and spaced apart from each other in the tire width direction. The first tire widthwise inner end 51a is disposed at an outer end of the tread 30 in the tire width direction. The first ply piece 51A has a first tire widthwise inner end 51b on an inner side in the tire width direction, the first tire widthwise inner end 51b including the first tire widthwise inner end 51a.

[0031] As shown in FIG. 2, the first ply piece 51A has a first ply main body portion 51c extending from a first tire widthwise inner end 51a to the sidewall 20 and further extending to the tire widthwise inner side of the bead core 11, a first bent portion 51d wrapping around the bead core 11 from the first ply main body portion 51c and bending, a first folded-up portion 51e folded back from the first bent portion 51d toward the tire radially outer side, and a first folded-up end 51f which is the tire radially outer tip of the first folded-up portion 51e.

[0032] The first ply main body portion 51c, the first bent portion 51d, and the first turned-up portion 51e are continuous. An end portion on the inner side in the tire radial direction of the first ply main body portion 51c is disposed on the inner side in the tire width direction of the bead core 11 and the bead filler 12. The first turned-up portion 51e is disposed on the outer side in the tire width direction of the bead core 11 and the bead filler 12. The first bent portion 51d is disposed on the inner side in the tire radial direction of the bead core 11, and constitutes the innermost part in the tire radial direction of the first carcass ply 51. The first turned-up portion 51e extends radially outward beyond the tire maximum width position 20W. The first turned-up end 51f is disposed radially outward beyond the tire maximum width position 20W.

[0033] In the first carcass ply 51, a first hollow portion 51H is formed between first inner ends 51a in the tire width direction of the pair of first ply pieces 51A that face each other in the tire width direction.

[0034] As shown in Fig. 1, the second carcass ply 52 includes a pair of second ply pieces 52A divided in the tire width direction. The second carcass ply 52 has a second cutout portion 52H that is discontinuous in a center portion of the tread 30 in the tire width direction. The pair of second ply pieces 52A are embedded in the tire 1 in a manner such that they are disposed on both sides in the tire width direction with the second cutout portion 52H sandwiched therebetween. The pair of second ply pieces 52A is an example of a pair of ply pieces divided in the tire width direction.

[0035] As shown in FIG. 2 , the second ply piece 52A has a second tire widthwise inner end 52a at a tip end on the second cutout portion 52H side, the second tire widthwise inner end 52a being opposed to and spaced apart from each other in the tire width direction. The second tire widthwise inner end 52a is an example of tire widthwise inner ends opposed to and spaced apart from each other in the tire width direction. The second tire widthwise inner end 52a is disposed at an outer end of the tread 30 in the tire width direction. The second ply piece 52A has a second tire widthwise inner end 52b including the second tire widthwise inner end 52a on an inner side in the tire width direction. The second tire widthwise inner end 52b is disposed in a state sandwiched between the tire widthwise outer end 40B of the belt 40 and the first ply piece 51A in the tire radial direction.

[0036] A second inner end 52a in the tire width direction of the second ply piece 52A is disposed outward in the tire width direction from a first inner end 51a in the tire width direction of the first ply piece 51A.

[0037] As shown in FIG. 2, the second ply piece 52A has a second ply main body portion 52c extending from a second tire widthwise inner end 52a to the sidewall 20 and further extending to the tire widthwise inner side of the bead core 11, a second bent portion 52d wrapping around the bead core 11 from the second ply main body portion 52c and bending, a second folded portion 52e folded back from the second bent portion 52d toward the tire radially outer side, and a second folded end 52f which is the tire radially outer tip of the second folded portion 52e.

[0038] The second ply body portion 52c, the second bent portion 52d, and the second turned-up portion 52e are continuous. The second ply body portion 52c is in close contact with the tire outer surface of the first ply body portion 51c of the first ply piece 51A. The radially inner end of the second ply body portion 52c is sandwiched between the bead core 11 and the bead filler 12 and the first ply body portion 51c. The second bent portion 52d is sandwiched between the bead core 11 and the first bent portion 51d of the first ply piece 51A. The second bent portion 52d constitutes the radially innermost portion of the second carcass ply 52. ​​The second turned-up portion 52e is sandwiched between the bead core 11 and the bead filler 12 and the first turned-up portion 51e of the first ply piece 51A. The second folded portion 52e extends partway along the bead filler 12. The second folded end 52f is disposed on the outer side of the bead filler 12 in the tire width direction.

[0039] In the tire radial direction, a second tire width direction inner end portion 52b of the second ply piece 52A is disposed in a sandwiched state between the belt 40 and the first ply piece 51A.

[0040] The folded portion 51e of the first ply piece 51A is in close contact with the outer surface of the second folded portion 52e of the second ply piece 52A from the inner end in the tire radial direction to the folded end 51f, then in close contact with the outer surface of the bead filler 12, and then through the tire radial outer end 12a of the bead filler 12 to be in close contact with the outer surface of the second ply main body portion 52c.

[0041] The rim strip rubber 13 of the bead 10 described above covers the periphery of the portion of the first ply body portion 51c that corresponds to the bead 10.

[0042] In the second carcass ply 52, a second hollow portion 52H is formed between second inner ends 52a in the tire width direction of the pair of second ply pieces 52A that face each other in the tire width direction.

[0043] Here, the first tire width direction inner end portion 51b of the first ply piece 51A and the second tire width direction inner end portion 52b of the second ply piece 52A constitute the tire width direction inner end portion 50B of the carcass ply 50 as a whole.

[0044] Both the first ply piece 51A and the second ply piece 52A include a plurality of carcass cords (not shown) that form the framework of the tire 1. The plurality of carcass cords extend, for example, along a plane along the tire width direction and are arranged side by side in the tire circumferential direction. These carcass cords are made of insulating organic fiber cords such as polyester or polyamide. The first ply piece 51A and the second ply piece 52A are made by covering the plurality of carcass cords with rubber.

[0045] The inner liner 60 is disposed on the inner surface of the tire between a pair of beads 10. The inner liner 60 covers the inner surfaces of the belt 40 and the first ply piece 51A in the tread 30 region. The inner liner 60 also covers the inner surface of the first ply piece 51A in the sidewall 20 region. Furthermore, the inner liner 60 covers the inner surface of the first ply piece 51A in the region on the outer side of the bead 10 in the tire radial direction, and covers the rim strip rubber 13 in the region on the inner side of the bead 10 in the tire radial direction.

[0046] The inner liner 60 is made of air-permeable rubber and prevents air from leaking out of the tire cavity.

[0047] The rubber used for the bead filler 12 has a hardness higher than that of at least the sidewall rubber 21 and the inner liner 60. The hardness of the rubber is a value (durometer hardness) measured with a type A durometer in an atmosphere of 23°C in accordance with JIS K6253.

[0048] For example, when the hardness of the sidewall rubber 21 is used as a reference, it is preferable that the hardness of the bead filler 12 be about 1.2 to 2.3 times that of the sidewall rubber 21. It is more preferable that the hardness of the rim strip rubber 13 be about 1 to 1.6 times that of the sidewall rubber 21. By using such hardness, it is possible to ensure a balance between the flexibility of the tire and the rigidity in the vicinity of the bead 10.

[0049] 1, the reinforcing layer 70 is disposed on the tire cavity side of the tread 30. The reinforcing layer 70 has an annular shape that extends around the entire circumference of the tire inner surface. The reinforcing layer 70 also has a symmetrical shape in a cross section in the tire width direction.

[0050] The reinforcing layer 70 is disposed on the tire cavity side so as to cover from the inside the cutout portions 51H and 52H of the pair of first ply pieces 51A and the pair of second ply pieces 52A. That is, the reinforcing layer 70 is disposed on the tire cavity side between a pair of first tire width direction inner ends 51a of the first ply pieces 51A that face each other and are spaced apart from each other in the tire width direction, and between a pair of tire width direction inner ends 52a of the second ply pieces 52A that face each other and are spaced apart from each other in the tire width direction.

[0051] The reinforcing layer 70 is adhered to the inner liner 60 by an adhesive layer 80. The adhesive layer 80 is a cured layer of adhesive applied to the inner liner 60. The reinforcing layer 70 is adhered to the inner liner 60 by attaching the outer peripheral surface 73 to the adhesive applied to the inner liner 60. The adhesive layer 80 is disposed in the regions of the cutout portions 51H and 52H, and extends from these regions outward in the tire width direction to cover the first inner end portion 51b of the first ply piece 51A and the second inner end portion 52b of the second ply piece 52A.

[0052] The cross-sectional shape of the reinforcing layer 70 in the tire width direction has a flattened trapezoidal shape as shown in FIG. 1. The reinforcing layer 70 has tire width direction outer end portions 70B at both ends in the tire width direction. End inner surfaces 72 of these tire width direction outer end portions 70B are inclined surfaces that extend outward in the tire radial direction as they move outward in the tire width direction. The reinforcing layer 70 has tire width direction outer end portions 70A at the outer tips in the tire width direction of the inclined end inner surfaces 72. The reinforcing layer 70 has a central inner surface 71 between the end inner surfaces 72 on both sides in the tire width direction. This central inner surface 71 is approximately parallel to the tire width direction.

[0053] The reinforcing layer 70 has the function of protecting the tread 30, which has the cutout portions 51H and 52H, from external damage. To ensure the external damage resistance of the tread 30, the reinforcing layer 70 is formed of a solid material that is difficult to penetrate by damaging objects such as nails. Examples of such materials include, but are not limited to, solid resins such as polyurethane. However, lightweight resins such as polyurethane are preferable to reduce rolling resistance by reducing weight. The reinforcing layer 70 is also preferably formed of a resin that is flexible enough to follow the deflection of the tread 30. The reinforcing layer 70, which is formed into an annular shape from resin, is adhered to the inner liner 60 via an adhesive layer 80.

[0054] The reinforcing layer 70 preferably has a length in the tire width direction such that its outer end 70B in the tire width direction overlaps with the inner end 50B in the tire width direction of the carcass ply 50 and sufficiently blocks the cutout portions 51H and 52H from the tire cavity side. The thickness, i.e., the distance between the outer peripheral surface 73 and the central inner surface 71, is preferably a dimension such that a damaging object such as a nail that has penetrated the tread rubber 31, cap ply 45, belt 40, and inner liner 60 is unlikely to reach the tire cavity from the central inner surface 71, and is, for example, about 5 mm to 10 mm.

[0055] 2, the tire width direction outer end 70B of the reinforcing layer 70 and the tire width direction inner end 50B of the carcass ply 50 overlap in the tire radial direction. Specifically, the first tire width direction inner end 51b of the first ply piece 51A overlaps in the tire radial direction with the tire width direction outer end 70B of the reinforcing layer 70. Furthermore, the second tire width direction inner end 52b of the second ply piece 52A overlaps in the tire radial direction with the tire width direction outer end 70B of the reinforcing layer 70.

[0056] 2, the length in the tire width direction of the tire radial overlap between the tire width direction outer end 70B of the reinforcing layer 70 and the tire width direction inner end 50B of the carcass ply 50, i.e., the overlap length, is indicated by distance L2. This distance L2 is the distance in the tire width direction between the first tire width direction inner end 51a of the first ply piece 51A and the tire width direction outer end 70A of the reinforcing layer 70 arranged further outward in the tire width direction than the first tire width direction inner end 51a. In an embodiment, this distance L2 is preferably 10 mm or more.

[0057] 2, the tire width direction outer end of the belt 40, i.e., the tire width direction outer end 41A of the inner belt 41, is disposed further outward in the tire width direction than the tire width direction outer end 70A of the reinforcing layer 70. In the embodiment, the distance L1 in the tire width direction between the tire width direction outer end 41A of the inner belt 41 and the tire width direction outer end 70A of the reinforcing layer 70 is preferably 5 mm or more.

[0058] In addition, in the tire radial direction, the first tire width direction inner end 51b of the first ply piece 51A and the second tire width direction inner end 52b of the second ply piece 52A, which constitute the tire width direction inner end 50B of the carcass ply 50, are arranged between the tire width direction outer end 40B of the belt 40 and the tire width direction outer end 70B of the reinforcing layer 70.

[0059] The tire 1 of the embodiment described above has two carcass plies, the first carcass ply 51 and the second carcass ply 52, which provide rigidity to withstand the loads and impacts that the tire 1 receives during driving, as well as the inflated air pressure, and also provide appropriate road contact properties and ride comfort.

[0060] In the tire 1 according to the embodiment, the first carcass ply 51 and the second carcass ply 52 constituting the carcass ply 50 have the cutout portion 51H and the cutout portion 52H, respectively. Therefore, the tire 1 is lightweight despite having two carcass plies.

[0061] In the tire 1 of the embodiment, the cutout portions 51H and 52H are blocked by a reinforcing layer 70 disposed on the tire cavity side. A tread 30 without a carcass ply cannot be expected to provide the external damage resistance provided by the carcass ply. However, the tire 1 of the embodiment has the reinforcing layer 70 disposed in the cutout portions 51H and 52H, thereby improving external damage resistance compared to tires with a simple cutout structure. That is, if a damaging object such as a nail penetrates the tread surface 31a of the tread 30 in the portions corresponding to the cutout portions 51H and 52H, the damaging object penetrates the reinforcing layer 70, thereby preventing penetration. This reduces the occurrence of punctures. To prevent punctures in this way, the reinforcing layer 70 is solid rather than porous and is formed of a material with appropriate hardness.

[0062] The hardness of such a reinforcing layer 70 is preferably 50 or more and 100 or less on the Shore hardness scale.

[0063] Furthermore, the reinforcing layer 70 is expected to absorb cavity resonance within the tire 1. This suppresses cavity resonance, thereby reducing interior vehicle noise caused by cavity resonance.

[0064] The tire 1 of the embodiment described above provides the following effects.

[0065] (1) A tire 1 according to an embodiment is a pneumatic tire including a pair of beads 10, 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, and a carcass ply 50 extending from the tread 30 to the pair of beads 10. The carcass ply 50 includes a first ply piece 51A and a second ply piece 52A as a pair of ply pieces separated in the tire width direction, and each pair of the first ply piece 51A and the second ply piece 52A is disposed on the tread 30 and separated in the tire width direction. Each pair of first ply pieces 51A and second ply pieces 52A has a first tire width direction inner end 51a and a second tire width direction inner end 52a as tire width direction inner ends facing each other at a distance from each other, a reinforcing layer 70 is arranged on the tire cavity side between the first tire width direction inner end 51a and the second tire width direction inner end 52a of each pair of first ply pieces 51A and second ply pieces 52A, and a tire width direction outer end 70B of this reinforcing layer 70 and tire width direction inner end parts 50B of the first ply piece 51A and second ply piece 52A including the tire width direction inner end 51a of the first ply piece 51A and the second tire width direction inner end 52a of the second ply piece 52A overlap in the tire radial direction.

[0066] This improves durability by improving resistance to external damage while realizing weight reduction with the hollowed-out carcass ply 50. In addition, the reinforcing layer 70 absorbs cavity resonance within the tire 1, thereby reducing interior noise caused by cavity resonance.

[0067] (2) In the tire 1 according to the embodiment, it is preferable that the tire width direction distance L2 between the tire width direction inner end 51a of the first ply piece 51A and the tire width direction outer end 70A of the reinforcing layer 70, which is arranged on the tire width direction outer side of the tire width direction inner end 51a of the first ply piece 51A, is 10 mm or more.

[0068] This ensures that the overlap length between the tire width direction inner end 50B of the carcass ply 50, including the first tire width direction inner end 51b of the first ply piece 51A, and the tire width direction outer end 70B of the reinforcing layer 70 is 10 mm or more. Therefore, the cutout portions 51H and 52H are reliably filled with the reinforcing layer 70, further improving external damage resistance.

[0069] (3) In the tire 1 according to the embodiment, the outer end 41A in the tire width direction of the inner belt 41 of the belt 40 is disposed further outward in the tire width direction than the outer end 70A in the tire width direction of the reinforcing layer 70.

[0070] As a result, the tire width direction outer end 41A of the inner belt 41, which is the outer end in the tire width direction of the entire belt 40, and the tire width direction outer end 70A of the reinforcing layer 70 are misaligned in the tire width direction. As a result, the thickness of the tire width direction inner end of the carcass ply 50 changes in stages. This suppresses stress concentration on the tread 30, improving the durability of the tire.

[0071] (4) In the tire 1 according to the embodiment, the distance L1 in the tire width direction between the outer end 41A of the belt 40 in the tire width direction and the outer end 70A of the reinforcing layer 70 in the tire width direction is preferably 5 mm or more.

[0072] This makes it possible to obtain an even greater effect of suppressing stress concentration.

[0073] (5) In the tire 1 according to the embodiment, the tire width direction inner end 50B of the carcass ply 50 formed by the first ply piece 51A and the second ply piece 52A is arranged in the tire radial direction between the tire width direction outer end 40B of the belt 40 and the tire width direction outer end 70B of the reinforcing layer 70.

[0074] As a result, the tire width direction inner end portions 50B of the first ply piece 51A and the second ply piece 52A are held by the belt 40 and the reinforcing layer 70, increasing the restraining force. Therefore, when the tire 1 is subjected to a lateral force, tension increases in the first ply body portion 51c of the first ply piece 51A and the second ply body portion 52c of the second ply piece 52A, increasing resistance to the lateral force. As a result, the tire has high lateral rigidity.

[0075] (6) In the tire 1 according to the embodiment, the reinforcing layer 70 is preferably made of resin.

[0076] This allows the reinforcing layer 70 to be made lighter, while maintaining the function of reducing the tire weight achieved by the carcass ply 50 having a hollow structure.

[0077] Next, Modifications 1 and 2, which are partial modifications of the above embodiment, will be described with reference to Figures 3 and 4. These modifications are the same as the above embodiment except for a partial change in the shape of the reinforcing layer 70. Therefore, the same components as those in the above embodiment are denoted by the same reference numerals, and their description will be omitted.

[0078] (Variation 1) 3, in Modification 1, the shape of a central inner surface 71 on the tire cavity side of the reinforcing layer 70 has a wave shape in a cross section in the tire width direction. That is, a plurality of ridges 71a and grooves 71b extending in the tire circumferential direction are formed on the central inner surface 71. The wave-shaped portion formed by the plurality of ridges 71a and grooves 71b may be formed over the entire circumference, or may be formed partially dispersed in the circumferential direction.

[0079] (Variation 2) As shown in Fig. 4, in Modification 2, the shape of the central inner surface 71 on the tire cavity side of the reinforcing layer 70 has a wave-shaped shape in a cross section in the tire circumferential direction. That is, on the central inner surface 71, a plurality of ridges 71c and grooves 71d extending in the tire width direction are formed adjacent to each other in the tire circumferential direction and continuously. Note that the wave-shaped portion formed by the plurality of ridges 71c and grooves 71d may be formed around the entire circumference, or may be formed partially dispersed in the circumferential direction. Furthermore, the ridges 71c and grooves 71d may also be formed on the end inner surfaces 72.

[0080] (7) In the tires 1 of Modifications 1 and 2, at least the central inner surface 71 of the reinforcing layer 70 on the tire cavity side has a waveform shape. This improves the effect of reducing cavity resonance noise within the tire 1.

[0081] Although specific embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and modifications and improvements made within the scope of the present invention are also included in the scope of the present invention.

[0082] For example, in the above embodiment, both the first carcass ply 51 and the second carcass ply 52 are hollow lies having the hollowed portions 51H and 52H, respectively, but either one may not be a hollow ply but may be a ply that continues between a pair of beads 10. Also, the carcass ply 50 may include three or more carcass plies, at least one of which may be a hollow ply.

[0083] The reinforcing layer 70 may be a molded body made of resin only, or may be a resin in which auxiliary reinforcing members such as reinforcing fibers or reinforcing particles are dispersed and embedded inside the resin. [Explanation of symbols]

[0084] 1. Tires (pneumatic tires) 10 beads 11 Bead core 12 Bead filler 20 Sidewall 30 tread 40 Belt 41A Outer edge of belt in tire width direction 50 carcass ply 50B Inner end of ply piece in tire width direction 51 First carcass ply 51A First ply piece (ply piece) 51a: First inner end of first ply piece in the tire width direction (inner end of ply piece in the tire width direction) 52 Second carcass ply 52A Second ply piece (ply piece) 52a: Second inner end in the tire width direction of the second ply piece (inner end in the tire width direction of the ply piece) 70 Reinforcement layer 70A Outer end of reinforcing layer in tire width direction 70B Outer end portion of reinforcing layer in the tire width direction 71 Inner surface of reinforcing layer

Claims

1. a pair of beads; a pair of sidewalls extending radially outward from the pair of beads, respectively; a tread disposed between the pair of sidewalls; a belt disposed on the tread; A pneumatic tire comprising: a carcass ply extending from the tread to the pair of beads; The carcass ply includes a pair of ply pieces divided in the tire width direction, Each of the pair of ply pieces is disposed in the tread and has inner ends in the tire width direction that are spaced apart from each other and opposed to each other in the tire width direction, a reinforcing layer is disposed on the tire cavity side between inner ends of the pair of ply pieces in the tire width direction, the reinforcing layer is disposed on the tire cavity side of an inner liner disposed on the inner surface of the tread, a tire width direction outer end portion of the reinforcing layer and a tire width direction inner end portion of the ply piece including the tire width direction inner end portion of the ply piece overlap in the tire radial direction.

2. 2. The pneumatic tire according to claim 1, wherein a distance L2 in the tire width direction between an inner end in the tire width direction of the ply piece and an outer end in the tire width direction of the reinforcing layer arranged further outward in the tire width direction than the inner end is 10 mm or more.

3. The pneumatic tire according to claim 1 or 2, wherein an outer end in the tire width direction of the belt is disposed more outward in the tire width direction than an outer end in the tire width direction of the reinforcing layer.

4. The pneumatic tire according to any one of claims 1 to 3, wherein a distance in the tire width direction between an outer end of the belt in the tire width direction and an outer end of the reinforcing layer in the tire width direction is 5 mm or more.

5. 5. The pneumatic tire according to claim 1, wherein an inner end portion in the tire width direction of the ply piece is disposed between an outer end portion in the tire width direction of the belt and an outer end portion in the tire width direction of the reinforcing layer in the tire radial direction.

6. The pneumatic tire according to any one of claims 1 to 5, wherein the reinforcing layer is formed of a resin.

7. The pneumatic tire according to any one of claims 1 to 6, wherein the inner surface of the reinforcing layer on the tire cavity side has a wave-shaped shape.

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