pneumatic tires

Abstract

We provide pneumatic tires that offer both improved pinch-cut resistance and low RRC (Resistant Reduction Control). [Solution] In the tire 1, in the axial half-section of the tire, if the tire thickness at the position corresponding to the belt end 31c, which is the axial end of the belt 31, is W1, the tire thickness at the position corresponding to the maximum tire width position is W3, and the tire thickness at an intermediate position between the belt end and the maximum tire width position in the radial direction of the tire is W2, then W1 > W2 and W3 > W2, and at the high load maximum tire width position 250, which is the position where the tire width is maximum when loaded at 130% of the maximum load according to the tire standard ETRTO, three or more layers of carcass ply 50 are superimposed along the axial direction of the tire.

Description

Technical Field

[0001] The present invention relates to pneumatic tires.

Background Art

[0002] Generally, a pneumatic tire 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 in the tire axial direction, and a tread disposed between the pair of sidewalls and contacting the road surface in a tire axial cross-section view, also referred to as a tire meridian cross-section. Inside the tire, a carcass ply serving as the skeleton of the tire is spanned between a pair of beads, and a belt for reinforcing the tread is embedded in the tread. The inner surface of the tire facing the tire cavity is composed of an inner liner for holding air pressure. Patent Document 1 discloses a pneumatic tire in which a rubber layer called an insulation is disposed between the inner liner and the carcass ply in a region extending from near a position corresponding to the axial end of the tread to near the maximum width position of the tire.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, in recent years, tires for heavy vehicles such as EVs and hybrid vehicles, which have become increasingly popular, and low-aspect-ratio tires for large-inch wheels, tend to experience greater loads, so there is a particular need for improved durability against pinch cuts (cutting of the cords in the carcass ply), i.e., improved pinch-cut resistance. For example, increasing the tire thickness contributes to improved pinch-cut resistance, but the increase in tire weight leads to a higher RRC (rolling resistance coefficient). The insulation shown in Patent Document 1 above is arranged to protect the carcass ply from the inside, but it does not describe any function related to pinch-cut resistance.

[0005] The objective of this disclosure is to provide a pneumatic tire that can achieve both improved pinch-cut resistance and low RRC (Resistant Reduction Control). [Means for solving the problem]

[0006] The pneumatic tire of this disclosure comprises a pair of beads, a pair of sidewalls extending radially outward from each of the pair of beads, a tread positioned between the pair of sidewalls, and a carcass ply stretched across the pair of beads, wherein the tread includes a belt positioned on the outer surface side of the tire than the carcass ply, and in the axial half-section of the tire, if the tire thickness at a position corresponding to the belt end, which is the axial end of the belt, is W1, the tire thickness at a position corresponding to the maximum tire width position is W3, and the tire thickness at an intermediate position between the belt end and the maximum tire width position in the radial direction of the tire is W2, then W1 > W2 and W3 > W2, and at the high-load maximum tire width position, which is the position where the tire width is maximum when loaded at 130% of the maximum load according to the tire standard ETRTO, three or more layers of the carcass ply are superimposed along the axial direction of the tire. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a pneumatic tire that can achieve both improved pinch-cut resistance and low RRC (Resistant Reduction Control). [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the internal structure of a tire 1, which is a pneumatic tire according to an embodiment, and is a cross-sectional view showing a half-section in the axial direction of the tire. [Figure 2] Figure 1 shows an enlarged view of the area A indicated by the dashed line. [Modes for carrying out the invention]

[0009] The embodiments will now be described with reference to the drawings. Figure 1 is a diagram showing the internal structure of tire 1, which is a pneumatic tire according to the embodiment, and is a cross-sectional view showing a half-section in the tire axial direction. Figure 2 is an enlarged view of the area A shown by the dashed line in Figure 1. In Figure 2, hatching has been omitted except for the carcass ply 50 in order to clearly show the cross-sectional structure, boundary lines, dimension lines, etc. of the constituent members. Tire 1 according to the embodiment is, for example, a pneumatic tire for a passenger car. The configuration of tire 1 according to the embodiment can be used as a tire for various vehicles other than passenger cars, such as light trucks, trucks, and buses.

[0010] The cross-sectional view in Figure 1 is a half-section view of the tire in the axial direction (tire meridian half-section view) under no-load conditions, with tire 1 mounted on a standard rim (not shown) and filled to the standard internal pressure. The standard rim is the rim specified for each tire in the standard system that includes the standard on which the tire is based. For example, it is the standard rim for JATMA, and the "Measuring Rim" for TRA and ETRTO. The standard internal pressure is the air pressure specified for each tire in the standard system that includes the standard on which the tire is based. For truck and bus tires and light truck tires, it is the maximum air pressure for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the "INFLATION PRESSURE" for ETRTO. For passenger car tires, it is usually 180 kPa, but for tires marked "Extra Load" or "Reinforced," it is 220 kPa.

[0011] In Figure 1, the symbol S1 represents the tire equatorial plane. The tire equatorial plane S1 is a plane perpendicular to the tire rotation axis (tire meridian) and located at the center of the tire axial direction. The basic internal structure of tire 1 is symmetrical in the cross-section along the tire axial direction with respect to the tire equatorial plane S1. Figure 1 shows a half-cross-section of the right half of tire 1, and the left half, which is not shown, has the same structure.

[0012] Here, the tire axis direction is the direction parallel to the tire rotation axis, and in the cross-sectional view of Figure 1, it is the left-right direction on the paper. In Figure 1, it is shown as the tire axis direction X. The inner direction in the tire axis direction is the direction approaching the tire equatorial plane S1, and in Figure 1, it is the left side of the paper. The outer direction in the tire axis direction is the direction away from the tire equatorial plane S1, and in Figure 1, it is the right side of the paper. The tire radial direction is the direction perpendicular to the tire rotation axis, and in Figure 1, it is the up-down direction on the paper. In Figure 1, it is shown as the tire radial direction Y. The outer direction in the tire radial direction is the direction away from the tire rotation axis, and in Figure 1, it is the upper side of the paper. The inner direction in the tire radial direction is the direction approaching the tire rotation axis, and in Figure 1, it is the lower side of the paper. Note that the tire radial direction is the same direction as the tire cross-sectional height direction.

[0013] As shown in Figure 1, the tire 1 according to this embodiment includes a pair of beads 10 provided on both sides of the tire axial direction, 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 pair of shoulders 40 which are the portions that transition from each of the pair of sidewalls 20 to the tread 30, a carcass ply 50 arranged across the pair of beads 10, and an inner liner 60 disposed on the inner side of the carcass ply 50.

[0014] The bead 10 includes a bead core 11 and a bead filler 12 extending radially outward from the bead core 11.

[0015] 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 fixes the air-filled tire 1 to the rim. The bead filler 12 has a tapered shape in which its thickness decreases as it extends from the inside in the radial direction of the tire to the outside in the radial direction of the tire. The bead filler 12 is provided to increase the rigidity of the peripheral part of the bead 10 and ensure high maneuverability and stability. The bead filler 12 is made of rubber that is harder than the surrounding rubber member, for example.

[0016] The bead 10 is surrounded by a rim strip rubber 13 with a carcass ply 50 in between. The rim strip rubber 13 is positioned at the inner end of the tire in the tire radial direction of the bead 10, wrapping around from the inner end in the tire axial direction to the outer end in the tire radial direction.

[0017] The sidewall 20 includes sidewall rubber 21 positioned on the axial side of the carcass ply 50. The sidewall rubber 21 constitutes the sidewall surface of the tire 1. The radially inner end 21b of the sidewall rubber 21 extends radially inward and covers the radially outer end 13a of the rim strip rubber 13. The sidewall rubber 21 is the part that flexes the most when the tire 1 is performing its cushioning action, and is usually made of a flexible rubber with fatigue resistance.

[0018] A rim line 15 is formed at the tip of the inner end 21b of the sidewall rubber 21 in the tire radial direction. The rim line 15 is an annular projection along the tire circumferential direction.

[0019] The outer surface along the profile line of the sidewall 20 has a tire maximum width position 25 corresponding to the maximum width of the tire 1. In the pneumatic tire 1 of the present embodiment, the rim line 15 is located on the inner side in the tire axial direction from the tire maximum width position 25. Therefore, the tire maximum width position 25 coincides with the position of the maximum width in the pneumatic tire 1. However, there are also tires in which the rim line is located on the outer side in the tire axial direction from the maximum width position near the middle in the tire radial direction of the sidewall 20. The tire maximum width position 25 in such a tire is defined as the maximum width position located on the outer surface of the sidewall 20 composed of the sidewall rubber 21 excluding the protruding portion of the rim line 15.

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

[0021] The belt 31 is a member for reinforcing the tread 30. The belt 31 of the embodiment has a two-layer structure including an inner belt 311 disposed on the outer side in the tire radial direction of the inner liner 60, and an outer belt 312 disposed on the outer side in the tire radial direction of the inner belt 311. Both the inner belt 311 and the outer belt 312 have a structure in which a plurality of belt cords such as steel cords are covered with rubber. The inner belt 311 is wider than the outer belt 312. That is, the width of the inner belt 311 is the maximum width of the belt 31. The outer end in the tire axial direction of the inner belt 311 constitutes the belt end 31c of the belt 31. By providing the belt 31, the rigidity of the tire 1 is ensured and the grounding property of the tread 30 with respect to the road surface is improved. Note that the belt 31 is not limited to a two-layer structure and may have a single-layer or three-layer or more structure.

[0022] In addition, in the present embodiment, an auxiliary layer 313 is provided between the inner belt 311 and the outer belt 312. In the two-layer belt 31, by providing the auxiliary layer 313 between the inner belt 311 and the outer belt 312, the adhesiveness of each member can be improved and the belt separation resistance can be improved. The auxiliary layer 313 can be formed of, for example, rubber with high adhesiveness.

[0023] The cap ply 34 is a member that reinforces the tread ۳۰ together with the belt 31. The cap ply 34 of the embodiment has an inner cap ply 341 and an outer cap ply 342 laminated on the tire outer surface side of the inner cap ply 341. Each of the cap plies 341 and 342 has a structure in which a plurality of insulating organic fiber cords such as polyamide fibers are covered with rubber.

[0024] The outer end 34a of the cap ply 34 in the tire axial direction is disposed in the region of the shoulder 40. At the end 34a, the outer ends of the inner cap ply 341 and the outer cap ply 342 in the tire axial direction are aligned in the thickness direction of the shoulder 40. The cap ply 34 covers the entire belt 31 from the tire outer surface side. That is, the outer end 34a of the cap ply 34 in the tire axial direction is located slightly outside the belt end 31c of the belt 31 in the tire axial direction. By providing the cap ply 34, the durability can be improved and the road noise during driving can be reduced. The cap ply 34 of the embodiment has a two-layer structure in which the inner cap ply 341 and the outer cap ply 342 are laminated, but it may be a single layer or a structure of three or more layers.

[0025] The tread rubber 36 is disposed outside the cap ply 34 in the tire radial direction. The tread rubber 36 is a member that forms the 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 and sub-grooves between the main grooves, grooves and sipes extending in a direction intersecting the tire circumferential direction, etc.

[0026] The tread surface 37 includes a contact area 37A that contacts the road surface. The contact area 37A is the region between the contact ends 37b at both ends of the tire in the axial direction.

[0027] The contact area 37A is the area that contacts the road surface when tire 1, mounted on a standard rim and filled with standard internal pressure, is in contact with the road surface and a standard load is applied. The standard load is the load specified for each tire in the standards system, including the standard on which the tire is based. For JATMA, it is the "maximum load capacity," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "LOAD CAPACITY." If the tire is for a passenger car, the standard load is equivalent to 88% of the above load. If the tire is for a racing kart, the standard load is 392N. The axial ends of the contact area 37A of the tire become the contact ends 37b.

[0028] As shown in Figure 1, in the tire 1 according to this embodiment, if 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 (width of the contact area 37A) is CW, then it is preferable that 1.00 ≤ BW1 / CW ≤ 1.15.

[0029] The axial outer end 36a of the tread rubber 36 covers the axial outer end 34a of the cap ply 34. The radial outer end 21a of the sidewall rubber 21 is located axially outward of the axial outer end 36a of the tread rubber 36.

[0030] A rubber layer 41 is positioned between the carcass ply 50 and the outer axial end 36a of the tread rubber 36. In the inner portion of the rubber layer 41 in the tire width direction, a belt 31 and a cap ply 34 are positioned on the outer side of the rubber layer 41 in the tire radial direction. In the region where the rubber layer 41 is positioned, the stress applied to the belt end 31c can be distributed, and separation at the belt end 31c can be suppressed.

[0031] The shoulder 40 includes the axial outer end 36a of the tread rubber 36, the radial outer end 21a of the sidewall rubber 21, and the rubber layer 41.

[0032] The carcass ply 50 is stretched between a pair of beads 10. The carcass ply 50 has a structure in which multiple parallel ply cords are covered with rubber. The ply cords are made of steel cords or insulating organic fiber cords such as polyester or polyamide, and function as the skeleton of the tire 1. The carcass ply 50 is embedded in the tire 1 in such a manner that it passes between the pair of beads 10, through a pair of sidewalls 20, a pair of shoulders 40, and the inner side of the tread 30. In the tread 30, a belt 31 is positioned on the radially outer side of the carcass ply 50.

[0033] The carcass ply 50 has a ply body portion 50A, a winding portion 50B, and a bent portion 50C. The ply body portion 50A is the portion that extends from the inner side of one bead core 11 in the tire axial direction, through one sidewall 20, one shoulder 40, the tread 30, the other shoulder 40, and the other sidewall 20, to the inner side of the other bead core 11 in the tire axial direction. The winding portion 50B is the portion that extends radially outward on the outer side of the bead filler 12 in the tire axial direction, by being folded back around the bead core 11 from the inner end of the ply body portion 50A in the tire radial direction. The bent portion 50C is the portion that bends in a U-shape in cross-section from the ply body portion 50A around the bead core 11 and connects to the winding portion 50B. The ply body portion 50A and the winding portion 50B are continuous via the bent portion 50C.

[0034] The ply body portion 50A is positioned radially inward of the tire and axially inward of the bead core 11 and bead filler 12. The winding portion 50B is positioned axially outward of the bead core 11 and bead filler 12. The bent portion 50C includes the innermost part of the carcass ply 50 radially in the tire.

[0035] The carcass ply 50 of this embodiment has a two-layer structure in which a first carcass ply 51 and a second carcass ply 52 are stacked on top of each other. In the ply body portion 50A, the first carcass ply 51 is positioned on the inner side of the tire cavity of the second carcass ply 52.

[0036] In the winding section 50B, the first carcass ply 51 is positioned on the tire axial side of the second carcass ply 52. ​​The first carcass ply 51 of the winding section 50B extends radially outward from the bending section 50C beyond the tire's maximum width position 25 of the sidewall 20, and extends radially outward beyond the high-load tire's maximum width position 250.

[0037] Here, the maximum tire width position 250 under heavy load is the position where the tire width is at its maximum when the tire is loaded at 130% of the maximum load specified in the ETRTO tire standard. In this embodiment, the maximum tire width position 250 under heavy load when the tire is loaded at 130% of the maximum load specified in the ETRTO tire standard is located 4% radially outward from the tire section height at 100% load compared to the maximum tire width position 25 under 100% load. For example, if the tire size is 275 / 50R22, the tire section height is 137.5 mm, so the maximum tire width position 250 under heavy load when the tire is loaded at 130% of the maximum load specified in the ETRTO tire standard is located approximately 5.5 mm radially outward from the maximum tire width position under 100% load.

[0038] In this embodiment, the end 51a of the first carcass ply 51 of the winding section 50B is located 10 mm radially outward from the bending section 50C beyond the maximum tire width position 250 under heavy load. The second carcass ply 52 of the winding section 50B extends from the bending section 50C to a position radially inward from the maximum tire width position 25 at 100% load. In this embodiment, the end 52a of the second carcass ply 52 of the winding section 50B is located 20 mm radially inward from the maximum tire width position 25. The portion of the first carcass ply 51 of the winding section 50B that is radially outward from the end 52a of the second carcass ply 52 overlaps with the second carcass ply 52 of the ply body section 50A. The rim strip rubber 13 described above is provided to surround the radially inward end of the carcass ply 50 including the bending section 50C.

[0039] In this embodiment, as described above, the first carcass ply 51 of the winding section 50B extends radially outward from the maximum width position 250 of the high-load tire. Therefore, in the tire 1 of this embodiment, at the maximum width position 250 of the high-load tire when loaded at 130% of the maximum load according to the tire standard ETRTO, three layers of carcass ply are stacked along the tire axis. Specifically, from the inside in the tire axis direction, the first carcass ply 51 of the ply body section 50A, the second carcass ply 52 of the ply body section 50A, and the first carcass ply 51 of the winding section 50B are stacked in that order.

[0040] The maximum width position 250 of the high-load tire approximately coincides with the position in the sidewall 20 that flexes the most when a higher-than-normal load is applied. Therefore, this is a position where there is a high risk of pinch cuts (cutting of the carcass ply cords) occurring under high loads. In the tire 1 of this embodiment, since the carcass ply is arranged in three layers in a superimposed arrangement along the tire axial direction at the maximum width position 250 of the high-load tire, the load can be distributed to each carcass ply, effectively suppressing pinch cuts. In other words, pinch cut resistance can be improved.

[0041] To more effectively improve the pinch-cut resistance described above, it is desirable that at least one end of the winding portion 50B of the first carcass ply 51 and the winding portion 50B of the second carcass ply 52 be located at a position of 10 mm or more radially outward from the maximum width position 250 of the high-load tire. In the tire 1 of this embodiment, the end 51a of the winding portion 50B of the first carcass ply 51 is located at a position of 10 mm or more radially outward from the maximum width position 250 of the high-load tire. Alternatively, the end 52a of the winding portion 50B of the second carcass ply 52 may be located at a position of 10 mm or more radially outward from the maximum width position 250 of the high-load tire. Furthermore, the end portion 51a of the winding portion 50B of the first carcass ply 51 and the end portion 52a of the winding portion 50B of the second carcass ply 52 may both be located at a position of 10 mm or more outward in the tire radial direction from the maximum width position 250 of the high-load tire.

[0042] In the tire 1 of this embodiment, at the maximum width position 250 of the high-load tire, three layers of carcass ply are arranged in a superimposed arrangement along the tire axial direction, but for example, four or more layers may be arranged in a superimposed arrangement. Increasing the number of superimposed carcass ply layers can enhance the effect of suppressing pinch cuts.

[0043] Although the carcass ply 50 in this embodiment has a two-layer structure, the carcass ply 50 may have three or more layers. It is preferable that the carcass ply 50 is composed of two or more layers, as this sufficiently suppresses local deformation of the tire 1 near the maximum width position 250 of the high-load tire, thereby further enhancing the effect of suppressing the pinch cut described above.

[0044] The inner liner 60 forms the inner surface 1c of the tire between the pair of beads 10. The inner liner 60 is made of air-permeable rubber to prevent air inside the tire cavity from leaking to the outside.

[0045] Furthermore, inside the tire 1 of this embodiment, a rubber layer 70 is arranged from near the tire's maximum width position 25 to near the midpoint between the tire's axial end of the tread 30 and the tire's equatorial plane S1. This rubber layer 70 is arranged 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 constitute the tire 1, but it is preferable that it 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.

[0046] In the tire 1 of this embodiment, the rubber layer 70 extends to the maximum width position 250 of the high-load tire at 130% of the maximum load specified in the ETRTO tire standard. Therefore, the rubber layer 70 can reinforce the area where the tire flexes the most under high load, further enhancing the effect of suppressing pinch cuts.

[0047] The inner liner 60 covers the inner surface of the ply body 50A of the carcass ply 50, except for the portion at the inner edge 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 body 50A of the carcass ply 50 via the rubber layer 70. The portion at the inner edge of the inner liner 60 in the tire radial direction covers the portion of the rim strip rubber 13 in the tire axial direction.

[0048] Here, the rubber used for the bead filler 12 is one that is at least harder than the sidewall rubber 21 and the inner liner 60. The hardness of the rubber is Type A of the durometer hardness according to JIS K6253-3:2012.

[0049] For example, when using the hardness of the sidewall rubber 21 as a reference, the hardness of the bead filler 12 is preferably between 1.2 and 2.3 times the hardness of the sidewall rubber 21. By setting the hardness to this level, it is possible to ensure a balance between the flexibility of the tire and the rigidity around the bead 10.

[0050] In Figure 2, the thickness of tire 1 at position B1 corresponding to the belt end 31c of belt 31 is shown as W1, the thickness of tire 1 at position B3 corresponding to the tire's maximum width position 25 is shown as W3, and the thickness of tire 1 at intermediate position B2 between the belt end 31c and the tire's maximum width position 25 in the tire's radial direction is shown as W2. Hereafter, the respective thicknesses W1, W2, and W3 of tire 1 may be referred to as tire thickness W1, tire thickness W2, and tire thickness W3.

[0051] Here, tire thickness is the distance between the inner surface 1c and the outer surface 1b of the tire, and the direction of tire thickness is based on the direction of the normal that is approximately perpendicular to the tangent to the inner surface 1c in the axial half-section of the tire. That is, tire thickness W1 is the tire thickness in the direction of the normal to the inner surface 1c passing through the belt end 31c, and the intersection of the line representing this tire thickness W1 and the inner surface 1c is the position B1 corresponding to the belt end 31c. Tire thickness W3 is the tire thickness in the direction of the normal to the inner surface 1c passing through the maximum tire width position 25, and the intersection of the line representing this tire thickness W3 and the inner surface 1c is the position B3 corresponding to the maximum tire width position 25. Intermediate position B2 is the intersection of the inner surface 1c and the line L3 along the tire axis that passes through the midpoint between position B1 corresponding to the belt end 31c and position B3 corresponding to the maximum tire width position 25 in the radial direction of the tire. Tire thickness W2 is the tire thickness in the direction of the normal to the inner surface 1c passing through intermediate position B2.

[0052] In the tire 1 according to this embodiment, the tire thicknesses W1, W2, and W3 are not uniform, with W1 > W2 and W3 > W2. Note that the tire thicknesses W1 and W3 may be the same or different.

[0053] Furthermore, it is desirable that the aforementioned rubber layer 70 extends from the position 250, which is the maximum width of the high-load tire at at least 130% of the maximum load specified in the ETRTO tire standard, to the position corresponding to the belt end 31c. This suppresses the cutting of the cords in the carcass ply 50, thereby improving pinch-cut resistance.

[0054] The rubber layer 70 has a tapered cross-section near its inner end in the tire radial direction, as it moves inward in the tire radial direction. Similarly, the rubber layer 70 has a tapered cross-section near its inner end in the tire axial direction, as it moves inward in the tire axial direction. In the axial half-section of the tire, the thickness of the rubber layer 70 is approximately constant, except for the tapered portions near both ends. However, the thickness of the rubber layer 70 excluding the portions near both ends is not necessarily constant and may vary depending on its position in the tire radial direction.

[0055] In the tire 1 according to this embodiment, when considering the tire thicknesses W1, W2, and W3 described above, W1 > W2 and W3 > W2. This allows for weight reduction while maintaining the overall tire thickness of the tire 1, making it easier to reduce rolling resistance, i.e., achieve low RRC.

[0056] In the embodiment of the tire 1, the first carcass ply 51 of the winding portion 50B extends radially outward from the bending portion 50C beyond the tire's maximum width position 25 on the sidewall 20, and extends radially outward beyond the high-load tire's maximum width position 250. Therefore, in the tire 1 of this embodiment, at the high-load tire's maximum width position 250 when the tire is loaded at 130% of the maximum load according to the tire standard ETRTO, three layers of carcass ply are superimposed along the tire axis. This effectively suppresses pinch cuts even when a high load is applied that causes the tire 1 to bend significantly and the sidewall 20 to deform significantly, such as when driving over a bump. In other words, an improvement in pinch cut resistance is expected, reducing the need to increase the tire thickness to improve pinch cut resistance, and thus suppressing an increase in tire weight and achieving a low RRC.

[0057] Furthermore, in the embodiment, the tire 1 has a rubber layer 70 positioned between the inner liner 60 and the carcass ply 50 at the maximum tire width position 250, at least when loaded at 130% of the maximum load according to the tire standard ETRTO. This suppresses deformation of the sidewall 20 and effectively prevents pinch cuts even when a high load is applied that causes the tire 1 to flex significantly, such as when driving over a bump. In addition, since the rubber layer 70 is also positioned near the belt end 31c, the impact is cushioned by the rubber layer 70 when an impact occurs near the belt end 31c. This cushioning function is easily obtained because the modulus of the rubber layer 70 is higher than that of the inner liner 60. As a result, the carcass ply 50 near the belt end 31c is protected by the rubber layer 70, and the cutting of the cords in the carcass ply 50 is suppressed. In other words, pinch cut resistance is improved. As a result of this expected improvement in pinch-cut resistance, the need to increase tire thickness to improve pinch-cut resistance is reduced, and therefore the increase in tire weight is suppressed, leading to a lower RRC (Rapid Cost Contribution).

[0058] The phenomenon described above, where the tire 1 flexes significantly when driving over a protrusion, causing an impact to be applied from the rim that engages with the bead 10 to the vicinity of the belt end 31c, and the sidewall 20 flexes significantly, is more likely to occur in tires for heavy vehicles such as EVs and hybrid vehicles, or low-aspect-ratio tires compatible with large-inch wheels. Therefore, the tire 1 of this embodiment is suitably used in such heavy-duty vehicles or low-aspect-ratio tires. For example, the tire 1 of this embodiment is preferably a low-aspect-ratio tire with a tire aspect ratio (ratio of tire section height to tire section width) of, for example, 50% or less. Also, for the same reason, it is preferable that it be an HLC (High Load Capacity) standard tire with high load capacity.

[0059] 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 bead separation resistance and pinch cut resistance are improved.

[0060] 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 CW is the width between the contact ends 37b on both sides in the tire axial direction of the tread 30, it is preferable that 1.00 ≦ BW1 / CW ≦ 1.15. Thereby, the width of the belt 31 becomes not less than the contact width of the tread 30, and the contact width of the tread 30 is covered by the belt 31. For this reason, the contact property of the tread 30 is ensured even at the tire axial end near the belt end 31c, and the tire rigidity is also improved. As a result, the deflection amount of the tire 1 is suppressed, and thereby the bead separation resistance and pinch cut resistance are also improved.

[0061] According to the tire 1 according to the above-described embodiment, the following effects are obtained.

[0062] (1) The tire 1 according to this embodiment comprises 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, and a carcass ply 50 stretched across the pair of beads 10, wherein the tread 30 is a pneumatic tire including a belt 31 disposed on the outer surface side of the tire than the carcass ply 50, and in the axial half cross section of the tire, the belt is the axial end of the belt 31 If W1 is the tire thickness at the position corresponding to the end 31c, W3 is the tire thickness at the position corresponding to the maximum tire width position 25, and W2 is the tire thickness at an intermediate position between the belt end 31c and the maximum tire width position 25 in the tire radial direction, then W1 > W2 and W3 > W2, and the carcass ply 50 is arranged in three or more layers in a superimposed arrangement along the tire axial direction at the high load maximum tire width position 250, which is the position where the tire width is maximum when loaded at 130% of the maximum load according to the tire standard ETRTO.

[0063] This makes it possible to achieve both improved pinch-cut resistance and low RRC (Reduced Ratio Concentration).

[0064] (2) In the tire 1 described in (1) above, the carcass ply 50 has a ply body portion 50A and a pair of winding portions 50B that are wound around each of the pair of beads 10 from the ply body portion 50A, are folded outward in the radial direction of the tire and extend along the sidewall, and it is preferable that the end portion 51a of at least one of the carcass ply 50s that are superimposed at the maximum width position 250 of the high load tire is located at a position of 10 mm or more outward in the radial direction of the tire from the maximum width position 250 of the high load tire.

[0065] This allows for a more effective improvement in pinch-cut resistance.

[0066] (3) In the tire 1 described in (1) or (2) above, if the maximum width of the belt 31 is BW1 and the contact width between the contact ends on both sides of the tire axial direction in the tread 30 is CW, then it is preferable that 1.00 ≤ BW1 / CW ≤ 1.15.

[0067] This suppresses the amount of deflection of tire 1, further improving bead separation resistance and pinch cut resistance.

[0068] (Transformed form) The embodiments described above are not limited to those described above, and various modifications and changes are possible, which are also within the scope of this disclosure.

[0069] (Modified form 1) In the implementation form, an example in which one rubber layer 70 is provided was given for explanation. However, the explanation is not limited to this, and for example, additional layers having a reinforcing effect like the rubber layer 70 (for example, a second rubber layer, a third rubber layer, etc.) may be provided. [Explanation of symbols]

[0070] 1 tire 1b Outer surface of tire 1c inner surface of tire 10 beads 11 Bead core 12 Bead Fillers 13 Rim strip rubber 13a Rim strip rubber outer edge in the tire radial direction 15 Rimline 20 Sidewall 21 Sidewall rubber 21a The outer edge of the tire in the radial direction of the sidewall rubber 21b Sidewall rubber, inner edge in the tire's radial direction 25 Maximum tire width position 30 tread 31 belt 31c belt end 311 Inner belt 312 Outer belt 313 Auxiliary layer 34 Cap Ply 34a Cap ply, outer end of tire axial direction 341 Inner cap ply 342 Outer cap ply 36 Tread Rubber 36a Tread rubber tire axial outer edge 37 Tread surface 37A ground area 37b Ground end 40 Shoulder 41 Rubber layer 50 Carcass Ply 50A Ply Body 50B Winding section 50C bent part 51 First Carcass Spry 51a End of the first carcass ply 52. Second Carcass Spry 52a End of the second carcass ply 60 Inner Liner 70 Rubber layer 250 Maximum width position of heavy load tires

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 positioned between the pair of sidewalls, and a carcass ply stretched across the pair of beads, wherein the tread includes a belt positioned on the outer surface side of the tire than the carcass ply, In the axial half-section of the tire, If W1 is the tire thickness at the position corresponding to the belt end, which is the axial end of the belt, W3 is the tire thickness at the position corresponding to the maximum tire width, and W2 is the tire thickness at an intermediate position between the belt end and the maximum tire width in the tire radial direction, then W1 > W2 and W3 > W2. A pneumatic tire in which three or more carcass plies are arranged in a superposition along the tire axial direction at the high-load tire maximum width position, which is the position where the tire width is at its maximum when loaded with 130% of the maximum load according to the tire standard ETRTO.

2. In the pneumatic tire described in claim 1, The carcass ply has a ply body and a pair of winding portions that are wound around each of the pair of beads from the ply body, are folded back outward in the radial direction of the tire, and extend along the sidewall. A pneumatic tire in which the end of the winding portion of at least one of the carcass plies, which are superimposed at the maximum width position of the heavy-load tire, is located at a position of 10 mm or more radially outward from the maximum width position of the heavy-load tire.

3. In the pneumatic tire according to claim 1 or claim 2, A pneumatic tire in which, if the maximum width of the belt is BW1 and the contact width between the contact ends on both sides of the tire axial direction in the tread is CW, then 1.00 ≤ BW1 / CW ≤ 1.15.

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