pneumatic tires

Abstract

We provide pneumatic tires that offer both improved bead separation resistance and low RRC (Resistant Retention Cost). [Solution] In the axial half-section of the tire 1, 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 25 is W3, and the tire thickness at an intermediate position between the belt end 31c and the maximum tire width position 25 in the radial direction of the tire is W2, then W1 > W2 and W3 > W2. At least a rubber layer 70 is placed between the bead filler 12 and the carcass ply 50 at a position corresponding to the outer bead filler end 12a, which is the outer end of the bead filler 12 in the radial direction of the tire, and if the thickness of the rubber layer 70 at the position corresponding to the outer bead filler end 12a is Wi3 and the thickness of the rubber layer 70 at the intermediate position is Wi2, then Wi3 > Wi2.

Description

Technical Field

[0001] The present disclosure 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 in the tread, a belt for reinforcing the tread is embedded. 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 the 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 cars, which have become increasingly popular, and low-aspect-ratio tires for large-inch wheels, tend to experience greater loads. Furthermore, there is a growing demand for a low rolling resistance coefficient (low RRC), and it is necessary to reduce weight and achieve a low RRC by thinning the rubber thickness. When the rubber thickness is reduced, the tire rigidity decreases, and the amount of deflection when the load on the tire increases increases, making it easier for strain to concentrate at the bead filler end. Therefore, when weight is reduced and RRC is lowered by thinning the rubber thickness, separation at the bead filler end becomes a concern. Thus, it is necessary to improve bead separation resistance, which is the resistance to separation at the bead filler end.

[0005] The insulation shown in Patent Document 1 above is arranged to protect the carcass ply from the inside, but it could not be expected to improve bead separation resistance.

[0006] The objective of this disclosure is to provide a pneumatic tire that can achieve both improved bead separation resistance and low RRC (Resistant Reinforced Concentration). [Means for solving the problem]

[0007] The pneumatic tire of the present disclosure comprises a pair of beads having a bead core and a bead filler extending radially outward from the bead core; a pair of sidewalls extending radially outward from each of the pair of beads; a tread disposed between the pair of sidewalls; and a carcass ply spanning across the pair of beads, wherein the tread includes a belt disposed on the outer surface side of the tire than the carcass ply, and the tire thickness in the axial half of the tire cross section is at a position corresponding to the belt end, which is the axial end of the belt. If W1 is the thickness of the bead filler, W3 is the thickness of the tire at the position corresponding to the maximum tire width, and W2 is the thickness of the tire at an intermediate position between the end of the belt and the maximum tire width in the tire radial direction, then W1 > W2 and W3 > W2. At least, if a rubber layer is disposed between the bead filler and the carcass ply at a position corresponding to the outer end of the bead filler, which is the outer end of the bead filler in the tire radial direction, and if Wi3 is the thickness of the rubber layer at the position corresponding to the outer end of the bead filler and Wi2 is the thickness of the rubber layer at the intermediate position, then Wi3 > Wi2. [Effects of the Invention]

[0008] This disclosure provides a pneumatic tire that can achieve both improved bead separation resistance and low RRC (Resistant Reinforced Consumption). [Brief explanation of the drawing]

[0009] [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] This is an enlarged view of area A, indicated by the dashed line in Figure 1, illustrating the thickness of tire 1. [Figure 3] This is an enlarged view of area A, indicated by the dashed line in Figure 1, illustrating the thickness of the rubber layer 70. [Modes for carrying out the invention]

[0010] The embodiments will be described below 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 axial direction of the tire. Tire 1 according to the embodiment is, for example, a pneumatic tire for a passenger car. The configuration of tire 1 in the embodiment can be used as a tire for various vehicles other than passenger cars, such as light trucks, trucks, and buses.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] The bead 10 includes a bead core 11 and a bead filler 12 extending radially outward from the bead core 11.

[0016] 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.

[0017] 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 radial direction to the outer end in the tire radial direction.

[0018] 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.

[0019] The tip of the inner end 21b of the sidewall rubber 21 in the tire radial direction and the tip of the outer end 13a of the rim strip rubber 13 in the tire radial direction abut against each other to form a rim line 15. The rim line 15 is an annular projection along the circumferential direction of the tire.

[0020] 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 sidewall rubber excluding the protruding portion of the rim line.

[0021] The tread 30 has an endless belt 31 and a cap ply 34 in the tire circumferential direction, and 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.

[0022] 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 belt cords such as a plurality of 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.

[0023] In addition, in the present embodiment, an auxiliary layer 313 is provided to cover the periphery of the outer end of the inner belt 311 in the tire axial direction. In the two-layer belt 31, by providing the auxiliary layer 313 between the inner belt 311 and the outer belt 312 and between the inner belt 311 and the carcass ply 50, the adhesion of each member can be improved and the belt separation resistance can be improved. The auxiliary layer 313 can be formed of, for example, a highly adhesive rubber.

[0024] The cap ply 34 is a member that reinforces the tread 30 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.

[0025] 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. Note that 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.

[0026] The tread rubber 36 is positioned radially outward of the cap ply 34. The tread rubber 36 is a component that makes up 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. This tread pattern includes, for example, a plurality of main grooves extending in the circumferential direction of the tire, sub-grooves between the main grooves, grooves and sipes extending in a direction intersecting the circumferential direction of the tire.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] The axially outer end 36a of the tread rubber 36 covers the axially outer end 34a of the cap ply 34. The radially outer end 21a of the sidewall rubber 21 is located axially outward of the axially outer end 36a of the tread rubber 36. A high-modulus rubber layer 41 is positioned 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.

[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 high modulus 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 folded 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, 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 folded 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 folded portion 50B. The ply body portion 50A and the folded 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 folded 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 folded portion 50B extends from the bent portion 50C, passing near the radial center of the sidewall 20 in the tire radial direction, to a position where it overlaps with the high modulus rubber layer 41 of the shoulder 40 in the tire axial direction. The rim strip rubber 13 described above is provided so as to surround the inner end of the carcass ply 50 in the tire radial direction, including the bent portion 50C.

[0036] Although the carcass ply 50 in this embodiment has a single-layer structure, the carcass ply 50 may have two or more layers. It is preferable that the carcass ply 50 be composed of two or more layers, as this sufficiently suppresses local deformation of the tire 1 near the rim mounting area.

[0037] 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.

[0038] Furthermore, within the tire of this embodiment, a rubber layer 70 is arranged from a position corresponding to the outer end 12a of the bead filler 12, which is the radially outer end of the bead filler 12, between the bead filler 12 and the carcass ply 50, to a position radially outward from the position corresponding to the maximum tire width position 25. Beyond the bead filler 12 in the radial direction, the rubber layer 70 is sandwiched between the ply body portion 50A and the folded portion 50B 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 desirable that the modulus of the rubber layer 70 be lower than the modulus of the bead filler 12. This allows for a stress-distributing effect. Also, if the modulus of the rubber layer 70 is higher than the modulus of the bead filler 12, not only will the rubber layer 70 have difficulty exhibiting its stress-distributing function, but the effect of improving separation resistance may also be weakened.

[0039] The inner liner 60 covers the inner surface of the ply body portion 50A of the carcass ply 50, except for the portion at the inner end in the tire radial direction. The portion at the inner end of the inner liner 60 in the tire radial direction covers the portion of the rim strip rubber 13 in the tire axial direction.

[0040] 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 durometer hardness according to JIS K6253-3:2012.

[0041] 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 extent, a balance between the flexibility of the tire and the rigidity around the bead 10 can be ensured.

[0042] Figure 2 is an enlarged view of area A indicated by the dashed line in Figure 1, illustrating the thickness of tire 1. Figure 3 is an enlarged view of area A indicated by the dashed line in Figure 1, illustrating the thickness of rubber layer 70. In Figures 2 and 3, hatching has been omitted except for rubber layer 70 in order to clearly show the cross-sectional structure, boundaries, and dimension lines of the constituent members.

[0043] In Figure 2, the thickness of the tire 1 at position B1 corresponding to the belt end 31c of the belt 31 is shown as W1, the thickness of the tire 1 at position B3 corresponding to the tire's maximum width position 25 is shown as W3, and the thickness of the 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 the tire 1 may be referred to as tire thickness W1, tire thickness W2, and tire thickness W3.

[0044] 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.

[0045] 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.

[0046] The rubber layer 70 described above is positioned in a region at least between the position corresponding to the outer end 12a of the bead filler 12, which is the radially outer end of the bead filler 12, and the position corresponding to the maximum tire width position 25, i.e., the position corresponding to the tire thickness W3. In the region where the rubber layer 70 is positioned, the stress applied to the tire 1 can be distributed, and local deformation of the tire 1 can be suppressed. Therefore, separation of the bead filler 12 can be suppressed.

[0047] In Figure 3, the thickness of the rubber layer 70 at position B5, which corresponds to the outer end 12a of the bead filler, is shown as Wi3; the thickness of the rubber layer 70 at position B2, which is an intermediate position between the belt end 31c and the tire's maximum width position 25 in the tire's radial direction, is shown as Wi2; and the thickness of the rubber layer 70 at position B4, which corresponds to the high-load tire's maximum width position at 130% of the maximum load according to the tire standard ETRTO, is shown as Wi1.

[0048] In this embodiment, the position of the maximum tire width under heavy load at 130% of the maximum load according to the ETRTO tire standard is 4% radially outward from the tire section height at 100% load, compared to the position 25 at 100% load. For example, if the tire size is 275 / 50R22, the tire section height is 137.5 mm, so the position of the maximum tire width under heavy load at 130% of the maximum load according to the ETRTO tire standard is approximately 5.5 mm radially outward from the position of the maximum tire width at 100% load.

[0049] In the tire 1 according to this embodiment, the thicknesses Wi1, Wi2, and Wi3 of the rubber layer 70 described above are not uniform, and Wi3 > Wi2 and Wi1 > Wi2. That is, the thickness of the rubber layer 70 is greater near position B5 corresponding to the outer end 12a of the bead filler and near position B4, the maximum width position of the high-load tire, than the thickness at the intermediate position B2. Wi1 > Wi2 and Wi3 > Wi2. That is, the thickness of the rubber layer 70 is greater near the belt end 31c and near position 25, the maximum width position of the tire, than the thickness at the intermediate position B2. Note that the thicknesses Wi1 and Wi3 of the rubber layer 70 may be the same or different.

[0050] The rubber layer 70 is expected to have the effect of distributing stress during the deformation of the tire 1 and suppressing the concentration of deformation. Therefore, by increasing the thickness of the rubber layer 70 near position B5, which corresponds to the outer end 12a of the bead filler, the resistance to bead separation can be improved. In addition, by increasing the thickness of the rubber layer 70 near position B4, which is the maximum width position of the high-load tire, the resistance to pinch cuts can be improved. On the other hand, if the rubber layer 70 is made thick throughout the entire tire, it will lead to an increase in tire weight, which is disadvantageous for reducing RRC. Therefore, as described above, by setting Wi3 > Wi2 and Wi1 > Wi2, it is possible to improve bead separation resistance and pinch cut resistance while simultaneously reducing RRC.

[0051] The rubber layer 70, from near the belt end 31c towards the tread 30, has a tapered cross-section as it approaches the tread 30. The rubber layer 70, from near the maximum tire width position 25 towards the bead 10, has a tapered cross-section as it approaches the bead 10. The rubber layer 70, near the outer end in the tire axial direction, has a tapered cross-section as it approaches the outer end in the tire radial direction. Also, the rubber layer 70, near the inner end in the tire axial direction, has a tapered cross-section as it approaches the inner end in the tire radial direction.

[0052] The inner end 70a of the rubber layer 70, which is the inner end in the tire radial direction, is preferably located at a position of 10 mm or more inward in the tire radial direction from the outer end 12a of the bead filler. This ensures a sufficient overlapping area between the rubber layer 70 and the bead filler 12 in the tire axial direction. As described above, in the area where the rubber layer 70 is located, the stress applied to the tire 1 can be distributed, and local deformation of the tire 1 can be suppressed. Therefore, by having the inner end 70a of the rubber layer located at a position of 10 mm or more inward in the tire radial direction from the outer end 12a of the bead filler, the effect of suppressing separation of the bead filler 12 can be enhanced.

[0053] The outer end of the rubber layer 70, which is the outermost end of the rubber layer 70 in the tire's radial direction, should preferably be located at a position of 10 mm or more radially outward from the tire's maximum width position 25. This ensures that the rubber layer 70 is positioned in the area where the deformation is expected to be greatest, thereby suppressing stress concentration near the outer end of the rubber layer 70b.

[0054] While the rubber layer 70 can improve bead separation resistance, increasing the area covered by the rubber layer 70 leads to an increase in the weight of the tire 1, which is detrimental to reducing RRC (Rated Ratio Concentration). Therefore, it is desirable to provide the rubber layer 70 only in an appropriate area.

[0055] Therefore, for the sake of reducing RRC, it is desirable that the inner end 70a of the rubber layer be located within 15 mm from the outer end 12a of the bead filler in the radial direction of the tire.

[0056] Furthermore, for the sake of reducing RRC, it is desirable that the outer edge 70b of the rubber layer be located within 35 mm of the outer edge 12a of the bead filler in the radial direction outward.

[0057] In this embodiment, the inner end 70a of the rubber layer is positioned 11 mm inward in the tire radial direction from the outer end 12a of the bead filler. Also in this embodiment, the outer end 70b of the rubber layer is positioned 18 mm outward in the tire radial direction from the tire's maximum width position 25.

[0058] 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.

[0059] In the embodiment, the tire 1 has a rubber layer 70 positioned at least between the bead filler 12 and the carcass ply 50, at a position corresponding to the outer end 12a of the bead filler 12, which is the radially outer end of the bead filler 12, and extending to a position corresponding to the maximum tire width position 25, i.e., the position corresponding to the tire thickness W3. As a result, even when the tire 1 flexes significantly when driving over a bump, and an impact is applied from the rim that engages with the bead 10 to the vicinity of the belt end 31c, the impact is cushioned by the rubber layer 70. This cushioning function is easily obtained because the modulus of the rubber layer 70 is higher than the modulus of the bead filler 12. Therefore, the outer end 12a of the bead filler is protected by the rubber layer 70, and bead separation is suppressed. In other words, an improvement in bead separation resistance is expected, reducing the need to increase the tire thickness to improve bead separation resistance, and thus suppressing an increase in tire weight and achieving a low RRC.

[0060] Furthermore, in the rubber layer 70 of the tire 1 according to this embodiment, Wi3 > Wi2 and Wi1 > Wi2 are set, thereby improving bead separation resistance and pinch cut resistance when the tire 1 flexes significantly when going over a bump, etc., and an impact is applied from the rim to the belt end 31c where it fits onto the bead 10, while also achieving a low RRC (Resistant Reduction Control).

[0061] The phenomenon described above, where the tire 1 flexes significantly when driving over a protrusion, causing an impact from the rim where it engages with the bead 10 to the vicinity of the belt end 31c, 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.

[0062] 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.

[0063] 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 in the tire axial direction in the tread 30, is CW, it is preferable that 1.00 ≦ BW1 / CW ≦ 1.15. Thereby, the width of the belt 31 becomes 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. For this reason, the contact property of the tread 30 is ensured even at the tire axial direction end portion 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.

[0064] According to the tire 1 according to the above-described embodiment, the following effects can be obtained.

[0065] (1) The tire 1 according to this embodiment comprises a pair of beads 10 having a bead core 11 and a bead filler 12 extending radially outward from the bead core 11, a pair of sidewalls 20 extending radially outward from each of the pair of beads 10, a tread 30 disposed between the pair of sidewalls 20, 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, a position corresponding to the belt end 31c which is the axial end of the belt 31 If the tire thickness at the base is W1, the tire thickness at the position corresponding to the maximum tire width is W3, and the tire thickness at an intermediate position between the belt end 31c and the maximum tire width in the tire radial direction is W2, then W1 > W2 and W3 > W2. At least a rubber layer 70 is placed between the bead filler 12 and the carcass ply 50 at a position corresponding to the outer bead filler end 12a, which is the outer end of the bead filler 12 in the tire radial direction, and the thickness of the rubber layer 70 at the position corresponding to the outer bead filler end 12a is Wi3, and the thickness of the rubber layer 70 at the intermediate position is Wi2, then Wi3 > Wi2.

[0066] This makes it possible to achieve both improved bead separation resistance and low RRC (Reduced Ratio Concentration).

[0067] (2) In the tire 1 described in (1) above, it is preferable that the inner end of the rubber layer 70a, which is the inner end of the rubber layer 70 in the tire radial direction, is located at a position of 10 mm or more inward in the tire radial direction from the outer end of the bead filler 12a, and the outer end of the rubber layer 70b, which is the outer end of the rubber layer 70 in the tire radial direction, is located at a position of 10 mm or more outward in the tire radial direction from the maximum width position of the tire.

[0068] This further enhances resistance to bead separation.

[0069] (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.

[0070] This suppresses the amount of deflection of tire 1, further improving bead separation resistance and pinch cut resistance.

[0071] (4) In the tire 1 described in (1) to (3) above, it is preferable that the inner end of the rubber layer 70a, which is the inner end of the rubber layer 70 in the tire radial direction, is located within 15 mm in the tire radial direction from the outer end of the bead filler 12a, and the outer end of the rubber layer 70b, which is the outer end of the rubber layer 70 in the tire radial direction, is located within 35 mm in the tire radial direction from the outer end of the bead filler 12a.

[0072] This allows for improved bead separation resistance while maintaining a low RRC (Rapid Reduction Cost).

[0073] (5) In the pneumatic tire described in (1) to (4) above, if Wi1 is the thickness of the rubber layer 70 at the position corresponding to the maximum width of the high-load tire when it is loaded at 130% of the maximum load in the tire standard ETRTO, then it is preferable that Wi1 > Wi2.

[0074] This makes it possible to achieve both improved bead separation resistance and low RRC (Reduced Ratio Concentration).

[0075] (6) In the pneumatic tire described in (1) to (5) above, it is preferable that the modulus of the rubber layer 70 is lower than the modulus of the bead filler 12.

[0076] This enhances the stress-distributing effect of the rubber layer 70.

[0077] (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.

[0078] (Modified form 1) In the implementation form, an example in which one rubber layer 70 is arranged was given for explanation. However, the explanation is not limited to this, and for example, additional layers that have the effect of distributing stress, such as a second rubber layer or a third rubber layer, may be provided.

[0079] This disclosure is not limited to the embodiments described above. [Explanation of Symbols]

[0080] 1 tire 1b Outer surface of tire 1c inner surface of tire 10 beads 11 Bead core 12 Bead Fillers 12a Bead filler outer end 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 312a Outer belt end 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 High Modulus Rubber Layer 50 Carcass Ply 50A Ply Body 50B Folded section 50C bent part 60 Inner Liner 70 Rubber layer 70a Inner edge of rubber layer 70b Outer edge of the rubber layer

Claims

1. A pneumatic tire comprising: a pair of beads having a bead core and a bead filler extending radially outward from the bead core; a pair of sidewalls extending radially outward from each of the pair of beads; a tread positioned between the pair of sidewalls; and a carcass ply spanning 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 rubber layer is disposed between the bead filler and the carcass ply at a position corresponding to the outer end of the bead filler, which is the radially outer end of the bead filler, A pneumatic tire in which, if the thickness of the rubber layer at the position corresponding to the outer end of the bead filler is Wi3 and the thickness of the rubber layer at the intermediate position is Wi2, then Wi3 > Wi2.

2. In the pneumatic tire described in claim 1, The inner end of the rubber layer, which is the inner end of the rubber layer in the tire radial direction, is located at a position of 10 mm or more inward in the tire radial direction from the outer end of the bead filler, and A pneumatic tire in which the outer end of the rubber layer, which is the outer end of the rubber layer in the radial direction of the tire, is located at a position of 10 mm or more outward in the radial direction of the tire from the position of the tire's maximum width.

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.

4. In the pneumatic tire according to claim 1 or claim 2, The inner end of the rubber layer, which is the inner end of the rubber layer in the tire radial direction, is located within 15 mm from the outer end of the bead filler in the tire radial direction, and A pneumatic tire in which the outer end of the rubber layer, which is the outer end of the rubber layer in the radial direction of the tire, is located within 35 mm in the radial direction outward from the outer end of the bead filler.

5. In the pneumatic tire according to claim 1 or claim 2, A pneumatic tire in which, if Wi1 is the thickness of the rubber layer at the position corresponding to the maximum width of the high-load tire when loaded at 130% of the maximum load according to the tire standard ETRTO, then Wi1 > Wi2.

6. In the pneumatic tire according to claim 1 or claim 2, A pneumatic tire in which the modulus of the rubber layer is lower than the modulus of the bead filler.

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