Pneumatic tire

Abstract

To provide a pneumatic tire that can make both improvement of pinch cut resistant performance and low RRC compatible and is suitable as tires such as a tire for a heavy vehicle and a tire with low flatness.SOLUTION: When a tire thickness at a position B1 corresponding to a belt end 31c of a belt 31 is defined as W1, a tire thickness at a position B3 corresponding to a tire maximum width position 25 is defined as W3, and a tire thickness at an intermediate position B2 between the belt end 31c and the tire maximum width position 25 in a tire radial direction is defined as W2, relational expressions of W1>W2 and W3>W2 are satisfied. A rubber layer 70 is arranged between an inner liner 60 and a carcass ply 50, in an area between the position B1 corresponding to the belt end 31c and the position corresponding to the tire maximum width position 25. When a thickness of the rubber layer 70 at the position B1 corresponding to the belt end 31c is defined as Wi1, a thickness of the rubber layer 70 at the intermediate position B2 is defined as Wi2, and a thickness of the rubber layer 70 at the position corresponding to the tire maximum width position is defined as Wi3, relational expressions of Wi1>Wi2 and Wi3>Wi2 are satisfied.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] In general, a pneumatic tire, when viewed in an axial cross section (also called a tire meridian cross section), has a structure including a pair of beads on both axial sides of the tire, a pair of sidewalls extending radially outward from each of the pair of beads, and a tread disposed between the pair of sidewalls and in contact with the road surface. A carcass ply, which forms the tire's framework, is placed between the pair of beads inside the tire, and a belt reinforcing the tread is embedded in the tread. The inner surface of the tire facing the tire cavity is composed of an inner liner that maintains air pressure. Patent Document 1 discloses a pneumatic tire in which a rubber layer called insulation is disposed between the inner liner and the carcass ply in a region extending from near the axial end of the tread to near the tire's maximum width position. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-147333 Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, tires for heavy vehicles such as electric vehicles (EVs) and hybrid vehicles, which have become increasingly popular in recent years, and tires with low aspect ratios compatible with high-inch wheels, tend to be subjected to greater loads, and therefore there is a particular need for improved durability against pinch cuts (cutting of the cords in the carcass ply), i.e., pinch cut resistance. For example, while increasing tire thickness contributes to improved pinch cut resistance, increasing tire weight increases the rolling resistance coefficient (RRC). The insulation shown in Patent Document 1 is positioned to protect the carcass ply from the inside, but does not describe its function related to pinch cut resistance.

[0005] The present invention has been made in view of the above circumstances, and aims to provide a pneumatic tire that achieves both improved pinch cut resistance and low RRC, thereby making it suitable for use as a tire for heavy vehicles, a tire with a low aspect ratio, etc. [Means for solving the problem]

[0006] The pneumatic tire of the present invention includes a pair of beads, a pair of sidewalls extending radially outward from each of the pair of beads, a tread disposed between the pair of sidewalls, a carcass ply stretched between the pair of beads, and an inner liner forming an inner surface of the tire, the tread including a belt disposed closer to the tire outer surface than the carcass ply, and in an axial half cross section of the tire, a tire thickness W1 at a position corresponding to a belt end that is an axial end of the belt, and a tire width W2 at a position corresponding to a maximum width position of the tire. If the tire thickness is W3 and the tire thickness at a midpoint between the belt end and the maximum tire width position in the tire radial direction is W2, then W1>W2 and W3>W2. A rubber layer is disposed between the inner liner and the carcass ply in the region between the position corresponding to the belt end and the position corresponding to the maximum tire width position. If the thickness of the rubber layer at the position corresponding to the belt end is Wi1, the thickness of the rubber layer at the midpoint is Wi2, and the thickness of the rubber layer at the position corresponding to the maximum tire width position is Wi3, then Wi1>Wi2 and Wi3>Wi2. [Effects of the Invention]

[0007] According to the present invention, both improved pinch cut resistance and low RRC can be achieved, thereby providing a pneumatic tire suitable for use as a tire for heavy vehicles, a tire with a low aspect ratio, or the like. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a half cross-sectional view in the tire axial direction of a tire according to an embodiment. [Figure 2] 2 is an enlarged view of a portion indicated by II in FIG. 1, showing the change in tire thickness from the vicinity of the belt end to the vicinity of the maximum tire width position. FIG. [Figure 3] 2 is an enlarged view of a portion indicated by II in FIG. 1, showing a change in thickness from the vicinity of the belt end of the rubber layer according to the embodiment to the vicinity of the maximum width position of the tire. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described with reference to the drawings. Fig. 1 is a diagram showing the internal structure of a tire 1, which is a pneumatic tire according to an embodiment, and shows a half cross section in the tire axial direction. The tire 1 according to the embodiment is, for example, a pneumatic tire for passenger cars. Note that the configuration of the tire 1 according to the embodiment can be used as a tire for various vehicles such as light trucks, trucks, and buses in addition to passenger cars.

[0010] The cross-sectional view in FIG. 1 is a semi-sectional view in the axial direction of a tire (semi-sectional view of the tire meridian) in an unloaded state in which a tire 1 is mounted on a standard rim (not shown) and inflated to the standard internal pressure. The standard rim is a rim specified for each tire in a standard system including the standard on which the tire is based. For example, it is a standard rim for JATMA, and a "Measuring Rim" for TRA and ETRTO. The standard internal pressure is the air pressure specified for each tire in a standard system including the standard on which the tire is based. For truck / bus tires and light truck tires, it is the maximum air pressure for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE" table for TRA, and the "INFLATION PRESSURE" for ETRTO. For passenger car tires, the standard is usually 180 kPa, but for tires labeled "Extra Load" or "Reinforced," it is 220 kPa.

[0011] In FIG. 1, the symbol S1 denotes the tire equatorial plane. The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis (tire meridian) and located at the tire axial center. The basic internal structure of the tire 1 is symmetrical in an axial cross section with the tire equatorial plane S1 as the plane of symmetry. FIG. 1 shows a half cross section of the right half of the tire 1, and the left half (not shown) has the same structure.

[0012] Here, the tire axial direction is a direction parallel to the tire rotational axis, and is the left-right direction on the page in the cross-sectional view of FIG. 1. In FIG. 1, this is illustrated as the tire axial direction X. The tire axially inner side is the direction approaching the tire equatorial plane S1, and is the left side on the page in FIG. 1. The tire axially outer side is the direction away from the tire equatorial plane S1, and is the right side on the page in FIG. 1. The tire radial direction is the direction perpendicular to the tire rotational axis, and is the up-down direction on the page in FIG. 1. In FIG. 1, this is illustrated as the tire radial direction Y. The tire radially outer side is the direction away from the tire rotational axis, and is the upper side on the page in FIG. 1. The tire radially inner side is the direction approaching the tire rotational axis, and is the lower side on the page in FIG. 1. The tire radial direction is the same direction as the tire cross-section height direction.

[0013] As shown in FIG. 1, the tire 1 according to the embodiment includes a pair of beads 10 provided on both sides of the tire in the axial 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 pair of shoulders 40 that are portions where each of the pair of sidewalls 20 transitions to the tread 30, a carcass ply 50 arranged spanning between the pair of beads 10, and an inner liner 60 arranged on the tire cavity side of the carcass ply 50.

[0014] The bead 10 has a bead core 11 and a bead filler 12 extending outward from the bead core 11 in the tire radial direction.

[0015] The bead core 11 is an annular component in which a rubber-coated metal bead wire is wound multiple times around the tire circumferential direction. The bead core 11 is a component that serves to secure the tire 1 filled with air to the rim. The bead filler 12 has a tapered shape that reduces in thickness as it extends from the inner side in the tire radial direction to the outer side in the tire radial direction. 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 components.

[0016] The bead 10 is surrounded by a rim strip rubber 13 with the carcass ply 50 sandwiched therebetween. The rim strip rubber 13 is arranged at the radially inner end of the tire 1 in a manner that wraps around from the axially inner side of the bead 10, through the radially inner end of the tire, to the axially outer side of the tire.

[0017] The sidewall 20 includes a sidewall rubber 21 disposed axially outward of the carcass ply 50. The sidewall rubber 21 constitutes the sidewall surface of the tire 1. An end 21b on the inner side in the tire radial direction of the sidewall rubber 21 extends radially inward in the tire direction and covers an end 13a on the outer side in the tire radial direction of the rim strip rubber 13. The sidewall rubber 21 is the portion that bends the most when the tire 1 performs its cushioning function, and typically, flexible rubber having fatigue resistance is used for it.

[0018] The tip of the radially inner end 21b of the sidewall rubber 21 and the tip of the radially outer end 13a of the rim strip rubber 13 are butted together to form a rim line 15. The rim line 15 is an annular protrusion along the tire circumferential direction. A rim protector 16 is formed on the outer surface of the tire at the radially inner end 21b of the sidewall rubber 21 and the radially outer end 13a of the rim strip rubber 13. The rim protector 16 includes the rim line 15.

[0019] The outer surface of the sidewall 20 along the profile line has a tire maximum width position 25 that corresponds to the maximum width of the tire 1. The rim line 15 is located axially outward of the tire maximum width position 25. That is, the tire maximum width position 25 in the tire 1 of this embodiment is located on the outer surface of the sidewall 20 that is made up of the sidewall rubber 21 excluding the rim protector 16 portion.

[0020] The tread 30 has an endless belt 31, a cap ply 34, and a tread rubber 36. The belt 31 is disposed on the outer side of the carcass ply 50 in the tire radial direction. The cap ply 34 is disposed on the outer side of the belt 31 in the tire radial direction.

[0021] The belt 31 is a member that reinforces the tread 30. The belt 31 of this embodiment has a two-layer structure including an inner belt 32 arranged radially outward of the inner liner 60, and an outer belt 33 arranged radially outward of the inner belt 32. Both the inner belt 32 and the outer belt 33 have a structure in which a plurality of belt cords, such as steel cords, are covered with rubber. The inner belt 32 is wider than the outer belt 33. That is, the width of the inner belt 32 is the maximum width of the belt 31. The axially outer edge of the inner belt 32 constitutes the belt end 31c of the belt 31. The provision of the belt 31 ensures the rigidity of the tire 1 and improves the contact of the tread 30 with the road surface. The belt 31 is not limited to a two-layer structure, and may have a single-layer structure or a three- or more-layer structure.

[0022] The cap ply 34 is a member that reinforces the tread 30 together with the belt 31. The cap ply 34 has a structure in which a plurality of insulating organic fiber cords, such as polyamide fiber, are covered with rubber. The cap ply 34 covers the entire belt 31 from the tire outer surface side. By providing the cap ply 34, it is possible to improve durability and reduce road noise during driving. Note that although the cap ply 34 in the embodiment is a single layer, it may be a two-layer or more layer structure.

[0023] The tread rubber 36 is disposed radially outward of the cap ply 34. The tread rubber 36 is a member that constitutes a tread surface 37, which is the outer surface of the tread 30. A tread pattern (not shown) is formed on the tread surface 37. The tread pattern includes, for example, a plurality of main grooves extending in the tire circumferential direction, sub-grooves between the main grooves, and grooves and sipes that extend in a direction intersecting the tire circumferential direction.

[0024] The tread surface 37 includes a contact area 37A that comes into contact with the road surface. The contact area 37A is a region between contact edges 37b at both axial ends of the tire.

[0025] The contact area 37A is the area that comes into contact with the road surface when the tire 1, mounted on a standard rim and inflated to the standard internal pressure, comes into contact with the road surface and is subjected to a standard load. The standard load is the load determined for each tire by each standard, including the standard on which the tire is based. For JATMA, this is the "maximum load capacity," for TRA, this is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, this is the "LOAD CAPACITY." If the tire is for passenger cars, this is a load equivalent to 88% of the above load. If the tire is for racing karts, the standard load is 392 N. Both axial ends of the contact area 37A are contact edges 37b.

[0026] As shown in FIG. 1, in the tire 1 according to the embodiment, when the maximum width of the belt 31 is BW1 and the width between the contact ends 37b on both sides of the tire axial direction in the tread 30 (the width of the contact area 37A) is CW, it is preferable that 1.00≦BW1 / CW≦1.15.

[0027] An axially outer end 36a of the tread rubber 36 covers an axially outer end 34a of the cap ply 34. An axially outer end 21a of the sidewall rubber 21 is disposed axially outward of the axially outer end 36a of the tread rubber 36. A high modulus rubber layer 41 is disposed between the radially outer end 21a of the sidewall rubber 21 and the axially outer end 36a of the tread rubber 36. The high modulus rubber layer 41 has a higher modulus than the sidewall rubber 21 and the tread rubber 36.

[0028] The shoulder 40 includes an axially outer end 36 a of the tread rubber 36 , a radially outer end 21 a of the sidewall rubber 21 , and a high modulus rubber layer 41 .

[0029] The carcass ply 50 is laid between a pair of beads 10. The carcass ply 50 has a configuration in which a plurality of parallel ply cords are coated with rubber. The ply cords are made of steel cords or insulating organic fiber cords such as polyester or polyamide cords, and function as the framework of the tire 1. The carcass ply 50 is embedded in the tire 1 in a manner that it passes between the pair of beads 10, through the pair of sidewalls 20, the pair of shoulders 40, and the tire cavity side of the tread 30. In the tread 30, a belt 31 is arranged on the outer side of the carcass ply 50 in the tire radial direction.

[0030] The carcass ply 50 has a ply main body portion 50A, a turned-up portion 50B, and a bent portion 50C. The ply main body portion 50A extends from the axially inner side of one bead core 11, through one sidewall 20, one shoulder 40, the tread 30, the other shoulder 40, and the other sidewall 20, to the axially inner side of the other bead core 11. The turned-up portion 50B is folded back from the radially inner end of the ply main body portion 50A around the bead core 11, thereby extending radially outward on the axially outer side of the bead filler 12. The bent portion 50C is bent from the ply main body portion 50A around the bead core 11 into a U-shaped cross section and connected to the turned-up portion 50B. The ply main body portion 50A and the turned-up portion 50B are continuous via the bent portion 50C.

[0031] The ply body portion 50A is disposed radially inward of the tire, axially inward of the bead core 11 and the bead filler 12. The turned-up portion 50B is disposed axially outward of the bead core 11 and the bead filler 12. The bent portion 50C includes the radially innermost portion of the carcass ply 50.

[0032] The carcass ply 50 of the embodiment has a two-layer structure in which a first carcass ply 51 and a second carcass ply 52 are overlapped. In the ply main body portion 50A, the first carcass ply 51 is disposed on the tire cavity side of the second carcass ply 52.

[0033] In the turnup portion 50B, the first carcass ply 51 is disposed axially outward of the second carcass ply 52. ​​The first carcass ply 51 in the turnup portion 50B extends from the bend 50C in the tire radial direction to near the tire radial center of the sidewall 20 and near the tire maximum width position 25. The second carcass ply 52 in the turnup portion 50B extends from the bend 50C to partway through the bead filler 12. A portion of the first carcass ply 51 in the turnup portion 50B that is radially outward of the bead filler 12 overlaps the second carcass ply 52 of the ply body portion 50A. The above-mentioned rim strip rubber 13 is provided so as to surround the radially inner end of the carcass ply 50 including the bend 50C.

[0034] Although the carcass ply 50 in the embodiment has a two-layer structure, the carcass ply 50 may have a single layer, or three or more layers. When the carcass ply 50 is configured with a ply having a two-layer or more layer structure, local deformation of the tire 1 near the mounting portion of the rim is preferably suppressed.

[0035] The inner liner 60 forms the tire inner surface 1c between the pair of beads 10. The inner liner 60 is made of air-permeable rubber and prevents air within the tire cavity from leaking to the outside.

[0036] A rubber layer 70 is disposed inside the tire, extending from near the radially outer end of the bead 10 to near the axially outer end of the tread 30. This rubber layer 70 is disposed inside the tire, sandwiched between the inner liner 60 and the first carcass ply 51 of the carcass ply 50. The rubber layer 70 may be formed from any rubber material that can be used to form the tire 1, but it is preferable that the rubber layer 70 be made of rubber with a higher modulus than the inner liner 60. In other words, it is preferable that the rubber layer 70 has a higher modulus than the inner liner 60.

[0037] The inner liner 60 covers the inner surface of the ply main body portion 50A of the carcass ply 50 except for its end portion on the inner side in the tire radial direction. In the region where the rubber layer 70 is present, the inner liner 60 covers the inner surface of the ply main body portion 50A of the carcass ply 50 via the rubber layer 70. The end portion on the inner side in the tire radial direction of the inner liner 60 covers the axially inner portion of the rim strip rubber 13.

[0038] 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 durometer hardness type A according to JIS K6253-3:2012.

[0039] For example, when the hardness of the sidewall rubber 21 is used as a reference, the hardness of the bead filler 12 is preferably about 1.2 to 2.3 times the hardness of the sidewall rubber 21. By setting the hardness at such a level, it is possible to ensure a balance between the flexibility of the tire and the rigidity in the vicinity of the bead 10.

[0040] Figures 2 and 3 are both enlarged views of the part indicated by II in Figure 1. In Figures 2 and 3, hatching is omitted except for the rubber layer 70 in order to clearly show the cross-sectional structures, boundary lines, dimension lines, etc. of the constituent members.

[0041] 2, the thickness of the tire 1 at position B1 corresponding to belt end 31c of belt 31 is shown as W1, the thickness of the tire 1 at position B3 corresponding to tire maximum width position 25 is shown as W3, and the thickness of the tire 1 at intermediate position B2 in the tire radial direction between belt end 31c and tire maximum width position 25 is shown as W2. Hereinafter, the thicknesses W1, W2, and W3 of the tire 1 may be referred to as tire thickness W1, tire thickness W2, and tire thickness W3.

[0042] The tire thickness here is the distance between the tire inner surface 1c and the tire outer surface 1b, and the direction of the tire thickness is based on the direction of a normal line substantially perpendicular to the tangent line of the tire inner surface 1c in the tire axial half cross section. That is, the tire thickness W1 is the tire thickness in the direction of a normal line to the tire inner surface 1c that passes through the belt end 31c. The intersection of the line indicating the tire thickness W1 and the tire inner surface 1c is position B1 corresponding to the belt end 31c. The tire thickness W3 is the tire thickness in the direction of a normal line to the tire inner surface 1c that passes through the tire maximum width position 25. The intersection of the line indicating the tire thickness W3 and the tire inner surface 1c is position B3 corresponding to the tire maximum width position 25. The intermediate position B2 is the intersection of the tire inner surface 1c and a line L3 that runs along the tire axial direction and passes through the midpoint between position B1 corresponding to the belt end 31c and position B3 corresponding to the tire maximum width position 25. The tire thickness W2 is the tire thickness in the direction of a normal line to the tire inner surface 1c that passes through intermediate position B2.

[0043] In the tire 1 according to the embodiment, the tire thicknesses W1, W2, and W3 are not uniform, but rather W1>W2 and W3>W2. Note that the tire thickness W1 and the tire thickness W3 may be the same or different.

[0044] The above-mentioned rubber layer 70 is arranged at least in the region between the position corresponding to the belt end 31c, i.e., the position corresponding to the tire thickness W1, and the position corresponding to the tire maximum width position 25, i.e., the position corresponding to the tire thickness W3.

[0045] In Figure 3, the thickness of the rubber layer 70 at position B1 corresponding to belt end 31c is shown as Wi1, the thickness of the rubber layer 70 at position B3 corresponding to the tire maximum width position 25 is shown as Wi3, and the thickness of the rubber layer 70 at intermediate position B2 between belt end 31c and the tire maximum width position 25 in the tire radial direction is shown as Wi2.

[0046] In the tire 1 according to the embodiment, the thicknesses Wi1, Wi2, and Wi3 of the rubber layer 70 are not uniform, but rather Wi1>Wi2 and Wi3>Wi2. That is, the thickness of the rubber layer 70 near the belt end 31c and near the tire maximum width position 25 is greater than the thickness at the intermediate position B2. The cross section of the rubber layer 70 from near the belt end 31c toward the tread 30 tapers toward the tread 30. The cross section of the rubber layer 70 from near the tire maximum width position 25 toward the bead 10 tapers toward the bead 10. The thickness Wi1 of the rubber layer 70 and the thickness Wi3 of the rubber layer 70 may be the same or different.

[0047] The tire 1 according to the embodiment has been described above.

[0048] In the tire 1 according to the embodiment, when the tire thicknesses W1, W2, and W3 are considered, W1>W2 and W3>W2. This allows the tire 1 to be lightweight while ensuring the overall tire thickness, and makes it easier to achieve reduced rolling resistance, i.e., a low RRC.

[0049] In the tire 1 according to the embodiment, a rubber layer 70 is disposed between the inner liner 60 and the carcass ply 50 at least in the region between the position B1 corresponding to the belt end 31c and the intermediate position B2. This allows the rubber layer 70 to cushion the impact even when the tire 1 bends significantly, such as when going over a protrusion, and the rim engaging with the bead 10 applies an impact to the vicinity of the belt end 31c. This cushioning function is easily achieved when the modulus of the rubber layer 70 is higher than that of the inner liner 60. Therefore, the carcass ply 50 near the belt end 31c is protected by the rubber layer 70, and the cords of the carcass ply 50 are prevented from being cut. In other words, pinch cut resistance is improved. This expected improvement in pinch cut resistance reduces the need to increase the tire thickness to improve pinch cut resistance, thereby preventing an increase in tire weight and achieving a low RRC.

[0050] In the tire 1 according to the embodiment, when the thicknesses Wi1 and Wi2 of the rubber layer 70 are considered, Wi1 > Wi2. Since the thickness Wi1 of the rubber layer 70 at the position B1 corresponding to the belt end 31c is greater than the thickness Wi2 of the rubber layer 70 at the intermediate position B2, the function of the rubber layer 70 to protect the carcass ply 50 near the belt end 31c is ensured or enhanced. Therefore, pinch cut resistance is further improved. Meanwhile, since the thickness Wi2 of the rubber layer 70 near the intermediate position B2 is smaller than the thickness Wi1 of the rubber layer 70 near the position B1 corresponding to the belt end 31c, the weight of the rubber layer 70 can be reduced, enabling a low RRC.

[0051] In the tire 1 according to the embodiment, a rubber layer 70 is disposed between the inner liner 60 and the carcass ply 50 in a region between position B1 corresponding to the belt end 31c and position B3 corresponding to the tire maximum width position 25. This allows the rubber layer 70 to cushion the impact even when the tire 1 bends significantly, such as when driving over a protrusion, and the rim engaging with the bead 10 applies an impact near the belt end 31c. This cushioning function is easily achieved when the modulus of the rubber layer 70 is higher than that of the inner liner 60. In this case, a portion of the rubber layer 70 near position B1 corresponding to the belt end 31c may collide with a portion of the rubber layer 70 near position B3 corresponding to the tire maximum width position 25. However, the cushioning function is enhanced by the rubber layer 70 overlapping twice with the inner liner 60 interposed therebetween. Therefore, the carcass ply 50 near the belt end 31c is protected by the rubber layer 70, suppressing cord breakage in the carcass ply 50. This improves pinch cut resistance. Such an expected improvement in pinch cut resistance reduces the need to increase the tire thickness to improve pinch cut resistance, thereby suppressing an increase in tire weight and achieving a low RRC.

[0052] In the tire 1 according to the embodiment, when considering the thicknesses Wi1, Wi2, and W3 of the rubber layer 70 described above, Wi1 > Wi2 and Wi3 > Wi2. In this way, the thickness Wi1 of the rubber layer 70 at the position B1 corresponding to the belt end 31c is larger than the thickness Wi2 of the rubber layer 70 at the intermediate position B2, and the thickness Wi3 of the rubber layer 70 at the position B3 corresponding to the maximum tire width position 25 is larger than the thickness Wi2 of the rubber layer 70 at the intermediate position B2. Thus, the function of protecting the carcass ply 50 by the rubber layer 70 is ensured or increased. This is because when the rubber layer 70 described above is double - overlapped, the buffering function increases. Therefore, the pinch - cut resistance near the belt end 31c is further improved. On the other hand, since the thickness Wi2 of the rubber layer 70 near the intermediate position B2 is smaller than the thickness Wi1 of the rubber layer 70 near the position B1 corresponding to the belt end 31c and the thickness Wi3 of the rubber layer 70 near the position B3 corresponding to the maximum tire width position 25, the weight of the rubber layer 70 is reduced, and the reduction of RRC becomes possible.

[0053] The phenomenon that when the tire 1 greatly deflects when crossing the above - mentioned protrusions and an impact is applied to the vicinity of the belt end 31c from the rim fitted to the bead 10 easily occurs in tires for high - weight vehicles such as EVs and hybrid vehicles, and tires such as low - profile tires corresponding to high - inch wheels. Therefore, the tire 1 of the embodiment is preferably used for such tires for high - weight vehicles or low - profile tires. For example, the tire 1 of the embodiment is preferably a low - profile tire with a tire aspect ratio (the ratio of the tire section height to the tire section width) of, for example, 50% or less. Also, for the same reason, it is preferably a tire of the HLC (High Load Capacity) standard with a high load - carrying capacity.

[0054] In the tire 1 according to the embodiment, as described above, the tire thickness W1 and the tire thickness W3 may be the same or different. Here, when the tire thickness W1 and the tire thickness W3 are different and W1 > W3, the cushioning property of the tire 1 is improved, so the riding comfort is improved. On the other hand, when W1 < W3, the tire rigidity is improved, so the pinch - cut resistance is improved.

[0055] In the tire 1 according to the embodiment, as described above, when the maximum width of the belt 31 is BW1 and the contact width, which is the width between the contact ends 37b on both sides of the tread 30 in the tire axial direction, is CW, it is preferable that 1.00≦BW1 / CW≦1.15. As a result, the width of the belt 31 is equal to or greater than the contact width of the tread 30, and the contact width of the tread 30 is covered by the belt 31. This ensures the contact properties of the tread 30 even at the tire axial end portions near the belt ends 31c, and also improves tire rigidity. As a result, the amount of deflection of the tire 1 is suppressed, which also improves pinch cut resistance.

[0056] In the embodiment, the radially outer end of the rubber layer 70 on the tread 30 side overlaps in the tire radial direction with the axially outer end of the tread 30 at the contact width CW. That is, the contact edge 37b of the tread 30 is disposed axially outward of the axially inner end of the rubber layer 70. This allows the cushioning properties of the rubber layer 70 to act on the contact edge 37b, improving the cushioning properties of the tire 1 and enabling an improved ride comfort.

[0057] The tire 1 of the above embodiment provides the following effects.

[0058] (1) A tire 1 according to an embodiment includes 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 carcass ply 50 stretched between the pair of beads 10, and an inner liner 60 forming an inner surface of the tire. The tread 30 is a pneumatic tire including a belt 31 disposed closer to the tire outer surface than the carcass ply 50, and in an axial half cross section of the tire, at a position B1 corresponding to a belt end 31c which is an axial end of the belt 31, is defined as W1, the tire thickness at position B3 corresponding to the tire maximum width position 25 is defined as W3, and the tire thickness at intermediate position B2 between belt end 31c and tire maximum width position 25 in the tire radial direction is defined as W2, then W1>W2 and W3>W2. A rubber layer 70 is disposed between the inner liner 60 and the carcass ply 50 in at least the region between the position corresponding to belt end 31c and intermediate position B2, and if the thickness of the rubber layer 70 at position B1 corresponding to belt end 31c is defined as Wi1 and the thickness of the rubber layer 70 at intermediate position B2 is defined as Wi2, then Wi1>Wi2.

[0059] This allows for both improved pinch cut resistance and low RRC.

[0060] (2) A tire 1 according to an embodiment includes 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 carcass ply 50 spanning between the pair of beads 10, and an inner liner 60 forming an inner surface of the tire. The tread 30 is a pneumatic tire including a belt 31 disposed closer to the tire outer surface than the carcass ply 50, and in an axial half cross section of the tire, a tire thickness W1 at a position B1 corresponding to a belt end 31c that is an axial end of the belt 31, and a position 25 corresponding to a tire maximum width position 25. If the tire thickness at B3 is W3 and the tire thickness at intermediate position B2 in the tire radial direction between belt end 31c and maximum tire width position 25 is W2, then W1>W2 and W3>W2. A rubber layer 70 is arranged between the inner liner 60 and the carcass ply 50 in the region between position B1 corresponding to belt end 31c and position B3 corresponding to maximum tire width position 25, and if the thickness of the rubber layer 70 at position B1 corresponding to belt end 31c is Wi1, the thickness of the rubber layer 70 at intermediate position B2 is Wi2, and the thickness of the rubber layer 70 at position B3 corresponding to maximum tire width position 25 is Wi3, then Wi1>Wi2 and Wi3>Wi2.

[0061] This allows for both improved pinch cut resistance and low RRC.

[0062] (3) In the tire 1 according to the above embodiments (1) and (2), when the maximum width of the belt 31 is BW1 and the contact width between the contact ends 37b on both sides of the tire axial direction of the tread 30 is CW, it is preferable that 1.00≦BW1 / CW≦1.15.

[0063] This ensures the contact of the tread 30 with the ground and also improves the tire rigidity, which in turn improves pinch cut resistance.

[0064] (4) In the tire 1 according to the embodiment described above in (1) to (3), the tire aspect ratio is preferably 50% or less.

[0065] Tires with an aspect ratio of 50% or less are prone to pinch cuts, but by providing the above configuration (1) or (2), the tire has low RRC and improved pinch cut resistance.

[0066] The present invention is not limited to the above-described embodiment, and any modifications and improvements made within the scope of the present invention are included within the scope of the present invention. [Explanation of symbols]

[0067] 1... tire (pneumatic tire), 1b... tire outer surface, 1c... tire inner surface, 10... bead, 20... sidewall, 25... tire maximum width position, 30... tread, 31... belt, 31c... belt end, 37b... ground contact edge, 50... carcass ply, 60... inner liner, 70... rubber layer, B1... position corresponding to belt end, B2... intermediate position, B3... position corresponding to tire maximum width position.

Claims

1. A pneumatic tire comprising: a pair of beads; a pair of sidewalls extending radially outward from each of the pair of beads; a tread disposed between the pair of sidewalls; a carcass ply stretched across the pair of beads; and an inner liner forming an inner surface of the tire, wherein the tread includes a belt disposed closer to the tire outer surface than the carcass ply, In the tire axial half section, When the tire thickness at a position corresponding to the belt end, which is the end of the belt in the tire axial direction, is W1, the tire thickness at a position corresponding to the tire maximum width position is W3, and the tire thickness at an intermediate position between the belt end and the tire maximum width position in the tire radial direction is W2, W1 > W2 and W3 > W2, a rubber layer is disposed between the inner liner and the carcass ply in a region between a position corresponding to the belt end and a position corresponding to the tire maximum width position; A pneumatic tire in which, when the thickness of the rubber layer at a position corresponding to the belt end is Wi1, the thickness of the rubber layer at the intermediate position is Wi2, and the thickness of the rubber layer at a position corresponding to the tire maximum width position is Wi3, Wi1>Wi2 and Wi3>Wi2.

2. 2. The pneumatic tire according to claim 1, wherein BW1 is the maximum width of the belt, and CW is the contact width between the contact ends of the tread on both sides in the tire axial direction, and 1.00≦BW1 / CW≦1.

15.

3. The pneumatic tire according to claim 1 or 2, wherein the tire aspect ratio is 50% or less.

Images