tire

Abstract

To provide a tire that can reduce electrical resistance while suppressing increases in mass and fitting pressure. [Solution] The length Lt from the tire equatorial plane CL to the end 22a of the tire rubber 22 and the length Li from the end 21a of the inner liner 21 are equal to Lt

Description

[Technical Field]

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

[0002] In recent years, demand for fuel-efficient tires has increased due to environmental concerns. One method used to improve tire fuel efficiency is to increase the silica content in the rubber compound that makes up the tire's cap tread, under tread, and sidewall rubber, thereby reducing the tire's rolling resistance. However, because silica has high insulating properties, increasing the silica content in the rubber compound used in the cap tread, etc., increases the electrical resistance of the cap tread, etc., reducing the tire's static electricity suppression performance. When the tire's static electricity suppression performance decreases, static electricity generated when the vehicle is in motion accumulates more easily, making it more susceptible to radio interference such as radio noise.

[0003] For this reason, some conventional pneumatic tires are equipped with conductive materials with low electrical resistance to improve static electricity suppression performance and to facilitate the release of static electricity generated on the vehicle during driving onto the road surface. For example, Patent Document 1 describes how a conductive layer with low electrical resistivity is placed between the carcass layer and the inner liner and extends from the bead to the belt layer to improve the static electricity suppression performance of the tire. Patent Document 1 also describes an example in which the conductive layer is made of a conductive rubber material and also serves as a tie rubber that is placed around the entire circumference of the inner cavity of the tire. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-40031 Summary of the Invention [Problem to be solved by the invention]

[0005] When using tie rubber made of conductive rubber material to reduce electrical resistance, it is important to position the tie rubber so that it overlaps the rim cushion. However, if the tie rubber overlaps the rim cushion too long, the increased length of the tie rubber can easily increase mass. Furthermore, because tie rubber made of conductive rubber material is relatively hard due to its high carbon content, if the tie rubber overlaps the rim cushion too long, the mating pressure when mating the tire to the rim wheel can easily increase. For these reasons, it is extremely difficult to reduce electrical resistance without increasing mass or mating pressure.

[0006] The present invention has been made in view of the above, and has an object to provide a tire that can reduce electrical resistance while suppressing increases in mass and fitting pressure. [Means for solving the problem]

[0007] In order to solve the above-described problems and achieve the object, a tire according to the present invention includes a pair of bead portions disposed on both sides of the tire equatorial plane in the tire width direction, a bead core provided on each of the pair of bead portions, a rim cushion that constitutes a rim fitting surface in the bead portion and is disposed from the inner side to the outer side in the tire width direction of the bead core, at least one carcass layer bridged between the pair of bead portions, a belt layer disposed on the outer side in the tire radial direction of the carcass layer, a tread rubber disposed on the outer side in the tire radial direction of the belt layer, an inner liner disposed on the tire inner surface along the carcass layer, and tire rubber disposed between the carcass layer and the inner liner. The inner liner and the tire rubber satisfy the relationship Lt < Li, where Lt is the length from the tire equatorial plane along the periphery to the end of the tire rubber, and Li is the length from the tire equatorial plane along the periphery to the end of the inner liner. The end of the inner liner is located on the inner side in the tire width direction than the outermost portion in the tire width direction of the bead core, and the end of the tire rubber is located on the inner side in the tire radial direction than the outermost diameter portion in the tire radial direction of the bead core. When the distance in the tire radial direction from the tire rotation axis to the end of the tire rubber is Rtg, and the distance in the tire radial direction from the tire rotation axis to the outermost portion on the outer side in the tire radial direction at the position on the inner side in the tire width direction of the bead core in the rim cushion, which is the innermost outermost portion of the rim cushion, is Rrc, the end of the tire rubber and the innermost outermost portion of the rim cushion satisfy the relationship Rtg < Rrc. The lap amount LAP [mm] of the tire rubber and the rim cushion, which is indicated by the distance along the periphery between the innermost outermost portion of the rim cushion and the end of the tire rubber, and the thickness Gi [mm] of the portion located within the lap range, which is the range along the periphery between the innermost outermost portion of the rim cushion and the end of the tire rubber in the inner liner, satisfy the range of 0.0075 ≦ Gi / LAP ≦ 1.5. The tire rubber has a volume resistivity of less than 1 × 10^8 [Ω·cm], and the rim cushion has a volume resistivity of less than 1 × 10^8 [Ω·cm].

[0008] Furthermore, in the above-mentioned tire, it is preferable that the thickness of the tie rubber is within the range of 0.1 [mm] to 1.5 [mm].

[0009] Furthermore, in the above tire, it is preferable that the distance in the tire radial direction between the innermost rim cushion, which is the radially inner end of the rim cushion, and the innermost rim cushion end, is within the range of 10 mm to 40 mm, and the overlap amount LAP between the tie rubber and the rim cushion is within the range of 3 mm to 30 mm.

[0010] In the tire, it is preferable that the inner liner has a thickness Gi of a portion located within the wrap range in the range of 0.1 mm to 1.5 mm.

[0011] Furthermore, in the above-mentioned tire, it is preferable that the bead core has a volume resistivity of less than 1 × 10^8 [Ω·cm].

[0012] In the tire, it is preferable that the bead core has a bead wire and a bead insulation rubber surrounding the bead wire, and that the bead insulation rubber has a volume resistivity of less than 1×10^8 [Ω·cm].

[0013] In addition, in the above tire, when the electrical resistance of the carcass layer is Rpc [Ω] and the electrical resistance of the belt coat rubber of the belt layer is Rb [Ω], it is preferable that the electrical resistance Rpc [Ω] of the carcass layer satisfies Rpc [Ω] < 1 × 10^8 [Ω], and the electrical resistance Rb [Ω] of the belt coat rubber satisfies Rb [Ω] < 1 × 10^8 [Ω].

[0014] In addition, it is preferable that the tire has an earth tread having a volume resistivity of less than 1×10^8 [Ω·cm], penetrating the tread rubber to contact the belt layer and exposed on the surface of the tread rubber.

[0015] Furthermore, in the above-mentioned tire, a protrusion projecting outward in the tire width direction is arranged on the outer surface of the rim cushion, which is the outer surface of the rim cushion in the tire width direction, within the range between the position corresponding to the outermost diameter portion of the bead core and the position corresponding to the innermost diameter portion of the bead core in the tire diameter direction. When the electrical resistance of the protrusion is Rs[Ω] and the electrical resistance of the rim cushion is Rr[Ω], it is preferable that the relationship between the electrical resistance Rs[Ω] of the protrusion and the electrical resistance Rr[Ω] of the rim cushion satisfies Rs[Ω] ≤ Rr[Ω].

[0016] Furthermore, in the above-mentioned tire, it is preferable that the length Ls [mm] of the protrusion in the tire circumferential direction satisfies the relationship Ls / L ≥ 0.1 with respect to the length L [mm] of one circumference in the tire circumferential direction at the position of the inner portion of the protrusion in the tire radial direction. [Effects of the Invention]

[0017] The tire according to the present invention has an effect of being able to reduce electrical resistance while suppressing an increase in mass and an increase in fitting pressure. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment. [Figure 2] FIG. 2 is a detailed view of a region on one side from the tire equatorial plane in the tire width direction in FIG. [Figure 3] FIG. 3 is a detailed view of the bead portion shown in FIG. [Figure 4] FIG. 4 is a detailed view of the bead portion shown in FIG. 2, and is an explanatory view of the rim cushion. [Figure 5] FIG. 5 is a schematic diagram of the tread portion shown in FIG. [Figure 6] FIG. 6 is a detailed view of a bead portion showing a modified example of the pneumatic tire according to the embodiment, in which a protrusion is arranged on the outer surface of the rim cushion. [Figure 7]Figure 7 is a schematic diagram showing an example of a convex portion, viewed from the direction of arrow BB in Figure 6. [Figure 8] Figure 8 is a schematic diagram showing an example of a convex portion, viewed from the direction of arrow BB in Figure 6. [Figure 9] Figure 9 is a schematic diagram showing a modified example of the pneumatic tire according to the embodiment, in which the end of the tie rubber is located on the inside of the bead core in the tire radial direction. [Figure 10A] Figure 10A is a chart showing the results of performance evaluation tests for pneumatic tires. [Figure 10B] Figure 10B is a chart showing the results of performance evaluation tests for pneumatic tires. DETAILED DESCRIPTION OF THE INVENTION

[0019] Embodiments of the tire according to the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited by these embodiments. Furthermore, the components in the following embodiments include those that are substituted and readily conceivable by those skilled in the art, or that are substantially identical.

[0020] [Embodiment] [Pneumatic tires] In the following description, a pneumatic tire 1 will be used as an example of a tire according to the present invention. The pneumatic tire 1, which is an example of a tire, can be filled with air, an inert gas such as nitrogen, and other gases.

[0021] Furthermore, in the following explanation, the tire radial direction refers to the direction perpendicular to the tire rotation axis (not shown), which is the rotation axis of the pneumatic tire 1. The inner side of the tire radial direction refers to the side toward the tire rotation axis in the tire radial direction, and the outer side of the tire radial direction refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotation axis as the central axis. The tire width direction refers to the direction parallel to the tire rotation axis. The inner side of the tire width direction refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the outer side of the tire width direction refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane perpendicular to the tire rotation axis and passing through the center of the tire width of the pneumatic tire 1. The position of the tire equatorial plane CL in the tire width direction coincides with the center line in the tire width direction, which is the center position of the pneumatic tire 1 in the tire width direction. The tire width is the distance in the tire width direction between the outermost parts in that direction, that is, the distance between the parts furthest from the tire equatorial plane CL in that direction. The tire equatorial line is a line on the tire equatorial plane CL that runs along the circumferential direction of the pneumatic tire 1. In the following explanation, the tire meridional section refers to the cross-section obtained when the tire is cut by a plane containing the tire's axis of rotation.

[0022] Figure 1 is a cross-sectional view of a pneumatic tire 1 according to an embodiment, taken along the tire meridian. The figure shows one side of the tire in the radial direction. The figure also shows a passenger car radial tire as an example of a pneumatic tire.

[0023] The pneumatic tire 1 according to this embodiment has an annular structure centered on the tire rotation axis and comprises a tread portion 2, a pair of sidewall portions 4, 4, a pair of bead portions 10, 10, a carcass layer 15, a belt layer 18, an inner liner 21, and a tie rubber 22. Of these, the pair of sidewall portions 4, 4 and the pair of bead portions 10, 10 are each arranged one on each side of the tire equatorial plane CL in the tire width direction.

[0024] The pair of bead portions 10, 10 are located radially inward of the pair of sidewall portions 4, 4, and each has a bead core 11, a bead filler 14, and a rim cushion 30. That is, the pair of bead cores 11, 11, the pair of bead fillers 14, 14, and the pair of rim cushions 30, 30 are arranged on both sides of the tire equatorial plane CL in the tire width direction.

[0025] The pair of bead cores 11, 11 are annular members formed by bundling multiple bead wires, and constitute the core of the pair of bead portions 10, 10. The pair of bead fillers 14, 14 are positioned on the radially outer side of the pair of bead cores 11, 11 to reinforce the bead portion 10.

[0026] The carcass layer 15 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass plies stacked together, and is toroidally spanned between a pair of bead portions 10, 10 located on both sides in the tire width direction to form the tire framework. The carcass ply of the carcass layer 15 is formed by coating multiple carcass cords made of steel or organic fiber material such as aramid, nylon, polyester, or rayon with coating rubber and rolling them. The carcass ply of the carcass layer 15 has a carcass angle, defined as the inclination angle of the extension direction of the carcass cords with respect to the tire circumferential direction, in the range of 80 degrees to 95 degrees in absolute value.

[0027] In this embodiment, the carcass layer 15 has a single-layer structure and is continuously laid between the bead cores 11, 11 on both sides in the tire width direction. Both end portions of the carcass layer 15 are wound back and secured to the outer side in the tire width direction so as to enclose the bead cores 11 and the bead fillers 14. That is, the carcass layer 15 is wound back near both end portions in a tire meridian cross section from the inner side in the tire width direction of the bead cores 11 and the bead fillers 14 to the inner side in the tire radial direction, and then wound back to the outer side in the tire width direction.

[0028] Therefore, the carcass layer 15 has a carcass body portion 15a that is arranged between a pair of bead portions 10, and a turn-up portion 15b that is formed continuously from the carcass body portion 15a and is folded back from the inside in the tire width direction to the outside in the tire width direction of the bead core 11. The carcass body portion 15a is the portion of the carcass layer 15 that is formed between the inside in the tire width direction of a pair of bead cores 11, and the turn-up portion 15b is formed continuously from the carcass body portion 15a on the inside in the tire width direction of the bead core 11 and is folded back from the inside in the tire radial direction of the bead core 11 to the outside in the tire width direction. The bead filler 14 is arranged on the inside in the tire width direction of the turn-up portion 15b, which is the portion of the bead core 11 that is folded back to the outside in the tire width direction, and on the outside in the tire radial direction of the bead core 11.

[0029] Preferably, the carcass ply of the carcass layer 15 formed in this manner has a volume resistivity of less than 1 × 10^8 [Ω·cm] of the carcass coat rubber, which is the coating rubber of the carcass cord.

[0030] Volume resistivity (volume resistivity) is measured according to JIS K6271, "Vulcanized rubber and thermoplastic rubber - Method for determining volume resistivity and surface resistivity." Generally, if the volume resistivity is less than 1 × 10^8 [Ω·cm] or the surface resistivity is less than 1 × 10^8 [Ω / cm], the material can be said to have conductivity that can suppress the accumulation of static electricity.

[0031] The pair of rim cushions 30, 30 of the pair of bead portions 10, 10 are respectively located on the inner side in the tire radial direction of the bead cores 11, 11 and the reversal portion of the carcass layer 15 on both sides in the tire width direction. More specifically, the rim cushion 30 is located at least from the inner side in the tire width direction to the outer side in the tire width direction of the bead core 11. That is, the rim cushion 30 is located in the bead portion 10, passing from the inner side in the tire width direction of the bead core 11 through the inner side in the tire radial direction of the bead core 11 to the outer side in the tire width direction of the bead core 11.

[0032] The rim cushion 30 arranged in this manner is the part that comes into contact with the rim flange R of the rim wheel when the pneumatic tire 1 is mounted on the rim wheel, and constitutes the contact surface of the bead portion 10 that comes into contact with the rim flange R. Of the contact surface of the rim cushion 30 with the rim flange R, the part that forms the inner circumferential surface of the rim cushion 30 constitutes the rim fitting surface 32 of the bead portion 10 that fits into the rim wheel.

[0033] The rim cushion 30 is made up of a rubber member, rim cushion rubber 31. The rim cushion 30 has a volume resistivity of less than 1×10^8 [Ω·cm], that is, the rim cushion rubber 31 that makes up the rim cushion 30 has a volume resistivity of less than 1×10^8 [Ω·cm]. It is more preferable that the volume resistivity of the rim cushion 30 be less than 1×10^6 [Ω·cm].

[0034] The rim cushion rubber 31 has a tan δ value at 60° C. in the range of 0.085 to 0.35, and a rubber hardness Hs in the range of 35 to 111.

[0035] The tan δ value at 60°C is measured using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. under conditions of an initial strain of 10%, an amplitude of ±0.5%, and a frequency of 20 Hz. Rubber hardness Hs is measured at a temperature of 20°C in accordance with JIS K6253.

[0036] The rim cushion 30 may also have components other than the rim cushion rubber 31. For example, the rim cushion 30 may include a chafer, which is a component made of a fiber material or a rubber component, that prevents the carcass layer 15 from coming into contact with the rim flange R and being damaged when the pneumatic tire 1 is fitted onto a rim wheel.

[0037] The belt layer 18 has one or more belt plies extending in the tire width direction, and in this embodiment, a plurality of belt plies 181 to 183 are laminated. That is, in this embodiment, the belt layer 18 is constructed by laminating a pair of cross belts 181 and 182 and a belt cover 183 in the tire radial direction, and is positioned on the outside of the carcass layer 15 in the tire radial direction and wrapped around the outer circumference of the carcass layer 15. The pair of cross belts 181 and 182 are constructed by covering a plurality of belt cords made of steel or organic fiber material with coated rubber and rolling them, and the belt angle, which is the inclination angle of the direction of extension of the belt cords with respect to the tire circumferential direction, is within the range of 20 [deg] to 65 [deg] in absolute value. Furthermore, the pair of cross belts 181 and 182 have belt angles with opposite signs to each other and are laminated with the directions of extension of the belt cords intersecting each other, forming a so-called cross-ply structure. Specifically, the pair of cross belts 181 and 182 have belt cords inclined in opposite directions relative to the tire width direction with respect to the tire circumferential direction. The belt cover 183 is constructed by rolling multiple cords made of steel or organic fiber material covered with coated rubber, and the belt angle is within the range of 0 [deg] to 10 [deg] in absolute value. The belt cover 183 is also arranged stacked on the outer side of the cross belts 181 and 182 in the tire radial direction.

[0038] The tread portion 2 is composed of tread rubber 3, which is a rubber composition, and is located on the radially outer side of the carcass layer 15 and belt layer 18, and is exposed at the outermost radial point of the pneumatic tire 1. For this reason, the outer surface of the tread portion 2 constitutes part of the contour of the pneumatic tire 1, and the tread portion 2 has multiple grooves, such as circumferential main grooves (not shown) and lug grooves (not shown), that extend in the circumferential direction of the tire. Furthermore, the tread rubber 3 that constitutes the tread portion 2 has a cap tread 3a and an under tread 3b.

[0039] The cap tread 3a is a rubber member located at the outermost position of the tread portion 2 in the tire radial direction and constituting the tire contact patch 2a. It may have a single-layer structure (see FIG. 1) or a multi-layer structure (not shown). The tan δ value of the cap tread 3a at 60°C is preferably 0.25 or less. The volume resistivity of the cap tread 3a is preferably 1×10^8 Ω·cm or more, more preferably 1×10^10 Ω·cm or more, and even more preferably 1×10^12 Ω·cm or more. These properties reduce the rolling resistance of the pneumatic tire 1. A cap tread 3a with such a volume resistivity is produced by using a low-heat-generating compound with a low carbon content and reinforcing it with an increased silica content.

[0040] The undertread 3b is a member laminated on the inner side of the cap tread 3a in the tire radial direction. The volume resistivity of the undertread 3b is preferably lower than the volume resistivity of the cap tread 3a.

[0041] Each of the pair of sidewall portions 4, 4 includes a sidewall rubber 5, and the pair of sidewall rubbers 5, 5 of the pair of sidewall portions 4, 4 are disposed on the outer side of the carcass layer 15 in the tire width direction. The tan δ value of the sidewall rubber 5 at 60°C is preferably 0.20 or less. The volume resistivity of the sidewall rubber 5 is preferably 1×10^8 [Ω·cm] or more, more preferably 1×10^10 [Ω·cm] or more, and even more preferably 1×10^12 [Ω·cm] or more. This reduces the rolling resistance of the pneumatic tire 1. The sidewall rubber 5 with such a volume resistivity is produced by using a low-heat-generating compound with a low carbon content and reinforcing it with an increased silica content.

[0042] While there are no specific limitations on the upper limit of the volume resistivity of the cap tread 3a, the lower limit of the volume resistivity of the under tread 3b, the upper limit of the volume resistivity of the sidewall rubber 5, and the lower limit of the volume resistivity of the rim cushion rubber 31, these are subject to physical constraints because they are rubber components.

[0043] The inner liner 21 is positioned on the inner surface 25 of the tire along the carcass layer 15. That is, the inner liner 21 constitutes the inner surface 25 of the tire, which is the inner surface of the pneumatic tire 1, and faces the inner cavity of the tire, which is the inner space of the pneumatic tire 1. The inner liner 21 that constitutes the inner surface 25 of the tire is a rubber layer positioned on the inner cavity side of the carcass layer 15, and covers the carcass layer 15 from the inner cavity side.

[0044] The tie rubber 22 is positioned between the carcass layer 15 and the inner liner 21. The tie rubber 22 is positioned along the carcass layer 15, similar to the inner liner 21, on the inner side of the tire cavity relative to the carcass layer 15. That is, the inner liner 21 and the tie rubber 22 are laminated and positioned along the carcass layer 15, on the inner side of the tire cavity relative to the carcass layer 15.

[0045] The inner liner 21, positioned on the inner surface 25 of the tire, is an air permeability-preventing layer. By covering the carcass layer 15, it suppresses oxidation of the carcass layer 15 due to exposure and prevents air leakage from the tire. The inner liner 21 is composed of, for example, a rubber composition mainly composed of butyl rubber, a thermoplastic resin, or a thermoplastic elastomer composition in which an elastomer component is blended into a thermoplastic resin. In particular, when the inner liner 21 is made of a thermoplastic resin or a thermoplastic elastomer composition, the inner liner 21 can be made thinner compared to when the inner liner 21 is made of butyl rubber, thus significantly reducing the tire weight.

[0046] Furthermore, the air permeability coefficient of the inner liner 21 is generally preferably 100 × 10⁻¹² [cc·cm / cm²·sec·cmHg] or less, and more preferably 50 × 10⁻¹² [cc·cm / cm²·sec·cmHg] or less, when measured at a temperature of 30 [°C] in accordance with JIS K7126-1.

[0047] Furthermore, the volume resistivity of the inner liner 21 is 1 × 10^8 [Ω·cm] or greater, preferably 1 × 10^9 [Ω·cm] or greater. In addition, the inner liner 21 has a tanδ value at 60 [℃] in the range of 0.115 to 0.35, and a rubber hardness Hs in the range of 27 to 90.

[0048] As rubber compositions mainly composed of butyl rubber, for example, butyl rubber (IIR) and butyl-based rubbers can be used. The butyl-based rubber is preferably a halogenated butyl rubber such as chlorinated butyl rubber (Cl-IIR) or brominated butyl rubber (Br-IIR).

[0049] Examples of thermoplastic resins include polyamide resins [e.g., nylon 6 (N6), nylon 66 (N66), nylon 46 (N46), nylon 11 (N11), nylon 12 (N12), nylon 610 (N610), nylon 612 (N612), nylon 6 / 66 copolymer (N6 / 66), nylon 6 / 66 / 610 copolymer (N6 / 66 / 610), nylon MXD6, nylon 6T, nylon 9T, nylon 6 / 6T copolymer, nylon 66 / PP copolymer, nylon 66 / PPS copolymer], polyester Polyethylene resins [e.g., polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), polybutylene terephthalate / tetramethylene glycol copolymer, PET / PEI copolymer, polyarylate (PAR), polybutylene naphthalate (PBN), liquid crystal polyester, aromatic polyesters such as polyoxyalkylenediimidodic acid / polybutylene terephthalate copolymer], polynitrile resins [e.g., polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), methacrylonitrile / styrene copolymer, methacrylonitrile / styrene / butadiene copolymer], poly(meth)acrylate resins [e.g., polymethyl methacrylate (PMMA), polyethyl methacrylate, ethylene ethyl acrylate copolymer (EEA), ethylene acrylic acid copolymer (EAA), ethylene methyl acrylate resin (EMA)], polyvinyl resins [e.g., vinyl acetate (EVA), polyvinyl alcohol (PVA), vinyl alcohol / ethylene Copolymers (EVOH), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymer, vinylidene chloride / methyl acrylate copolymer, cellulose resins (e.g., cellulose acetate, cellulose acetate butyrate), fluororesins (e.g., polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETFE)), imide resins (e.g., aromatic polyimide (PI)), etc., can be used.

[0050] Examples of elastomers include diene rubbers and hydrogenated products thereof [e.g., NR, IR, epoxidized natural rubber, SBR, BR (high cis BR and low cis BR), NBR, hydrogenated NBR, hydrogenated SBR], olefin rubbers [e.g., ethylene propylene rubber (EPDM, EPM), maleic acid modified ethylene propylene rubber (M-EPM)], butyl rubber (IIR), copolymers of isobutylene and aromatic vinyl or diene monomers, acrylic rubber (ACM), ionomers, halogen-containing rubbers [e.g., Br-IIR, Cl-IIR, brominated isobutylene-paramethylstyrene copolymers (Br-IPMS)], chloroprene rubber (CR), hydrin rubber (CHC, CHR), chlorosulfur Examples of suitable materials include chlorinated polyethylene (CSM), chlorinated polyethylene (CM), maleic acid-modified chlorinated polyethylene (M-CM), silicone rubber (e.g., methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber), sulfur-containing rubber (e.g., polysulfide rubber), fluororubber (e.g., vinylidene fluoride-based rubber, fluorine-containing vinyl ether-based rubber, tetrafluoroethylene-propylene-based rubber, fluorine-containing silicone rubber, fluorine-containing phosphazene-based rubber), thermoplastic elastomer (e.g., styrene-based elastomer, olefin-based elastomer, polyester-based elastomer, urethane-based elastomer, polyamide-based elastomer), and the like.

[0051] Furthermore, the tie rubber 22 disposed between the inner liner 21 and the carcass layer 15 is a layer for preventing the carcass cords of the carcass layer 15 from digging into the inner liner 21 when the unvulcanized pneumatic tire 1 is inflated during tire manufacturing. Furthermore, the tie rubber 22 contributes to the air permeation prevention properties and steering stability on dry road surfaces in the manufactured pneumatic tire 1.

[0052] Thai Rubber 22 is a rubber composition containing 30 to 100 parts by mass of carbon black with a CTAB adsorption specific surface area of ​​25 [m2 / g] to 130 [m2 / g] per 100 parts by mass of diene rubber, with the carbon black being more preferably in the range of 40 to 70 parts by mass. Thai Rubber 22 containing carbon black is a rubber composition containing isoprene rubber in the range of 30 to 90 parts by mass and styrene-butadiene rubber in the range of 20 to 70 parts by mass. By having such a material composition, the electrical resistance of Thai Rubber 22 can be reduced.

[0053] FIG. 2 is a detailed view of a region on one side of the tire equatorial plane CL in the tire width direction in FIG. 1. The pneumatic tire 1 according to this embodiment has an anti-static structure for dissipating static electricity generated on the vehicle while the vehicle is running to the road surface. The anti-static structure uses a tie rubber 22. A single tie rubber 22 is disposed between a pair of bead portions 10 along the carcass layer 15, and has a volume resistivity of less than 1×10^8 [Ω·cm]. The volume resistivity of the tie rubber 22 is more preferably less than 1×10^6 [Ω·cm]. Furthermore, the tie rubber 22 has a tan δ value at 60°C of 0.05 or more and 0.40 or less, and a rubber hardness Hs of 50 or more and 70 or less.

[0054] The bead core 11 disposed in the bead portion 10 has a volume resistivity of less than 1×10^8 [Ω·cm]. As a result, the bead core 11 forms a conductive path in the bead portion 10. The bead core 11 has a bead wire 12 and a bead insulation rubber 13 that wraps around the bead wire 12, and in this embodiment, the bead insulation rubber 13 has a volume resistivity of less than 1×10^8 [Ω·cm]. The volume resistivity of the bead core 11 is preferably less than 1×10^7 [Ω·cm].

[0055] The volume resistivity of the bead core 11 can be calculated, for example, by cutting out a relatively short length of the bead core 11 in the tire circumferential direction, and measuring the electrical resistance of the extracted bead core 11 by applying the electrodes of a tester (not shown) to both sides of the extracted bead core 11 in the tire width direction. Based on the electrical resistance of the extracted length of the bead core 11 measured in this way and the dimensions of the extracted bead core 11, the volume resistivity of the bead core 11 can be calculated.

[0056] The inner liner 21 is positioned on the inner lumen side of the tie rubber 22, with a single inner liner 21 extending between the pair of bead portions 10. Therefore, both the end 21a of the inner liner 21 and the end 22a of the tie rubber 22 are located on the bead portion 10.

[0057] In this embodiment, the bead portion 10 refers to the area from the rim diameter measurement point to 1 / 3 of the tire cross-sectional height SH. The tire cross-sectional height SH refers to 1 / 2 of the difference between the tire outer diameter and the rim diameter, and is measured when the pneumatic tire 1 is mounted on a specified rim, a specified internal pressure is applied, and the measurement is taken under no-load conditions.

[0058] Here, "specified rim" refers to the "applicable rim" specified by JATMA, the "Design Rim" specified by TRA, or the "Measuring Rim" specified by ETRTO. Furthermore, "specified internal pressure" refers to the "maximum air pressure" specified by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "INFLATION PRESSURES" specified by ETRTO.

[0059] The inner liner 21 and the tie rubber 22 which are stacked and arranged satisfy the relationship Lt < Li, where Lt is the length from the tire equatorial plane CL to the end 22a of the tie rubber 22 along the periphery, and Li is the length from the tire equatorial plane CL to the end 21a of the inner liner 21 along the periphery. That is, the length of the tie rubber 22 along the periphery in the tire meridian cross-section is shorter than the length of the inner liner 21 along the periphery in the tire meridian cross-section.

[0060] Preferably, the difference between the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 along the periphery and the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 along the periphery is within the range of 2 ≤ Li - Lt ≤ 12.

[0061] Since the length of the tie rubber 22 along the periphery is shorter than that of the inner liner 21 in this way, the tie rubber 22 overlaps the rim cushion 30 at the bead portion 10 and is covered by the inner liner 21 without contacting the rim cushion 30.

[0062] In this embodiment, the length along the periphery refers to the length along the shape of each member at the same position in the tire circumferential direction. Specifically, the direction along the periphery is close to the tire width direction at the position of the tread portion 2 and close to the tire radial direction at the position of the sidewall portion 4.

[0063] In this embodiment, the rim cushion 30 with which the tie rubber 22 contacts and is arranged at the bead portion 10 has, on the inner side in the tire width direction of the bead core 11, the outer end in the tire radial direction located more radially inward than the outer peripheral portion on the outer side in the tire radial direction of the bead core 11, and on the outer side in the tire width direction of the bead core 11, the outer end in the tire radial direction located more radially outward than the outer peripheral portion on the outer side in the tire radial direction of the bead core 11.

[0064] Furthermore, the rim cushion 30 is arranged more inward in the tire width direction than the inner liner 21 and tie rubber 22 at the inner portion of the bead core 11 in the tire width direction, and more inward in the tire radial direction than the inner liner 21 and tie rubber 22 at the inner portion of the bead core 11 in the tire radial direction. Therefore, the rim cushion 30 covers the inner liner 21 and tie rubber 22 from the inner side in the tire width direction at the inner portion of the bead core 11 in the tire width direction, and covers the inner liner 21 and tie rubber 22 from the inner side in the tire radial direction at the inner portion of the bead core 11 in the tire radial direction.

[0065] In other words, the rim cushion 30, which is arranged in the bead portion 10 from the inner side in the tire width direction of the bead core 11 to the outer side in the tire width direction, is arranged to cover the bead core 11, carcass layer 15, inner liner 21, and tie rubber 22 in the bead portion 10. For this reason, in the bead portion 10, the surface of the inner liner 21 facing the tire cavity on the outer side in the tire radial direction of the position where the rim cushion 30 is arranged becomes the tire inner surface 25, and the surface of the rim cushion 30 facing the tire cavity on the position where the rim cushion 30 is arranged becomes the tire inner surface 25.

[0066] The rim cushion 30 disposed in the bead portion 10 in this manner forms a bead base 36, which is the inner peripheral surface of the bead portion 10, and a bead toe 35, which is the end of the bead base 36 on the inner side in the tire width direction. The bead base 36 is the part that comes into contact with the rim wheel when the pneumatic tire 1 is mounted on the rim wheel. The rim cushion 30 forms the bead base 36, which is the rim fitting surface 32 when the pneumatic tire 1 is mounted on the rim wheel.

[0067] An earth tread 50 is also disposed in the tread portion 2. The earth tread 50 is a conductive rubber member that is embedded in the tread rubber 3 and exposed to the tire contact surface. The earth tread 50 penetrates the tread rubber 3 to come into contact with the belt layer 18, and is disposed so as to be exposed to the tire contact surface 2a, which is the surface of the tread rubber 3. More specifically, the earth tread 50 is exposed to the tire contact surface 2a, and penetrates the cap tread 3a and under tread 3b of the tread rubber 3 to come into conductive contact with the belt layer 18. This ensures a conductive path from the belt layer 18 to the road surface by the earth tread 50.

[0068] The earth tread 50 has an annular structure extending around the entire circumference of the tire, and extends continuously in the tire circumferential direction with a portion of it exposed to the tire contact patch 2a. Therefore, when the pneumatic tire 1 rolls, the earth tread 50 can always be in contact with the road surface, and a conductive path from the belt layer 18 to the road surface can always be secured. The earth tread 50 is formed so that its width in the tire width direction is narrower than the groove width of, for example, circumferential main grooves (not shown) formed in the tread portion 2 and extending in the tire circumferential direction, and is disposed between adjacent circumferential main grooves in the tire width direction.

[0069] The earth tread 50 arranged in this manner is made of a conductive rubber material having a volume resistivity lower than that of the tread rubber 3, and the volume resistivity of the earth tread 50 is less than 1×10^8 [Ω·cm]. It is more preferable that the volume resistivity of the earth tread 50 is 1×10^6 [Ω·cm] or less.

[0070] FIG. 3 is a detailed view of the bead portion 10 shown in FIG. 2. The end portion 22a of the tie rubber 22 located in the bead portion 10, that is, the end portion 22a of the tie rubber 22 in the peripheral direction, is located within the range in the tire radial direction where the rim cushion 30 is disposed. Further, the end portion 22a of the tie rubber 22 is located radially inward of the tire with respect to the outermost diameter portion 11a of the bead core 11 in the tire radial direction. In the present embodiment, the end portion 22a of the tie rubber 22 is located inward of the tire width direction with respect to the bead core 11, and the position in the tire radial direction is radially inward of the outermost diameter portion 11a of the bead core 11 in the tire radial direction and radially outward of the innermost diameter portion 11b of the bead core 11 in the tire radial direction.

[0071] Further, the end portion 22a of the tie rubber 22 is located radially inward with respect to the radially outer end portion of the rim cushion 30 at the position inward of the tire width direction of the bead core 11, that is, the radially outer end portion Rwi of the rim cushion 30. That is, when the distance in the tire radial direction of the end portion 22a of the tie rubber 22 from the tire rotation axis is Rtg and the distance in the tire radial direction of the radially outer end portion Rwi of the rim cushion 30 from the tire rotation axis is Rrc, the end portion 22a of the tie rubber 22 and the radially outer end portion Rwi of the rim cushion 30 satisfy the relationship of Rtg < Rrc. In this case, Rtg is the radius of the position of the end portion 22a of the tie rubber 22 centered on the tire rotation axis, and Rrc is the radius of the position of the radially outer end portion Rwi of the rim cushion 30 centered on the tire rotation axis.

[0072] Note that the difference between the distance Rrc in the tire radial direction of the radially outer end portion Rwi of the rim cushion 30 from the tire rotation axis and the distance Rtg in the tire radial direction of the end portion 22a of the tie rubber 22 from the tire rotation axis is preferably within the range of 3 ≦ Rrc - Rtg ≦ 20.

[0073] Furthermore, the end 21a of the inner liner 21 located in the bead portion 10, that is, the end 21a of the inner liner 21 in the peripheral direction, is located within the range in the tire radial direction where the rim cushion 30 is positioned, similar to the end 22a of the tie rubber 22. Also, the end 21a of the inner liner 21 is located inward in the tire width direction from the outermost part 11c of the bead core 11 in the tire width direction. In this embodiment, the end 21a of the inner liner 21 is located inside the bead core 11 in the tire radial direction. That is, the end 21a of the inner liner 21 is located inside the bead core 11 in the tire radial direction, and its position in the tire width direction is located within the range in the tire width direction where the bead core 11 is positioned.

[0074] In other words, the inner liner 21 is positioned to extend outward in the tire width direction compared to the tie rubber 22 in the peripheral direction. As a result, the length Li (see Figure 2) from the tire equatorial plane CL to the end 21a of the inner liner 21 along the periphery is longer than the length Lt (see Figure 2) from the tire equatorial plane CL to the end 22a of the tie rubber 22 along the periphery.

[0075] Furthermore, the inner liner 21 and the tie rubber 22 are each positioned along the carcass layer 15, and the tie rubber 22 is positioned between the carcass layer 15 and the inner liner 21. Therefore, even in the area where the rim cushion 30 is positioned, the tie rubber 22 is positioned along the carcass layer 15 on the side of the inner liner 21 where the carcass layer 15 is located.

[0076] Furthermore, the relationship between the inner liner 21, the amount of overlap LAP [mm] in the tire meridional section between the tie rubber 22 and the rim cushion 30, which is indicated by the distance along the periphery between the outermost inner part Rwi of the rim cushion and the end 22a of the tie rubber 22, and the thickness Gi [mm] of the portion of the inner liner 21 located within the overlap area, which is the range where the tie rubber 22 and the rim cushion 30 overlap, is within the range of 0.0075 ≤ Gi / LAP ≤ 1.5.

[0077] In this case, the lap amount LAP [mm] is the distance along the periphery of the tie rubber 22 between the position of the outermost inner part Rwi of the rim cushion in the tire radial direction and the end 22a of the tie rubber 22. The lap range is the range along the periphery between the outermost inner part Rwi of the rim cushion and the end 22a of the tie rubber 22, and is the range in which the tie rubber 22 and the rim cushion 30 overlap via the inner liner 21 in the bead portion 10.

[0078] Furthermore, in this case, the thickness Gi [mm] of the inner liner 21 is the maximum thickness of the portion of the inner liner 21 located within the overlapping range. Also, the thickness Gi of the portion of the inner liner 21 located within the overlapping range, i.e., the maximum thickness Gi of the inner liner 21 located within the overlapping range, is within the range of 0.1 [mm] to 1.5 [mm].

[0079] In addition, the thickness Gi of the portion of the inner liner 21 located within the overlap range between the tie rubber 22 and the rim cushion 30 is preferably within the range of 0.3 mm or more and 1.0 mm or less, and the relationship between the overlap amount LAP [mm] and the thickness Gi [mm] of the inner liner 21 is preferably within the range of 0.01≦Gi / LAP≦1.

[0080] The tie rubber 22 has a thickness Gt in the range of 0.1 mm to 1.5 mm. In this case, the thickness Gt [mm] of the tie rubber 22 is the maximum thickness of the tie rubber 22. The thickness Gt of the tie rubber 22 is preferably in the range of 0.3 mm to 1.0 mm.

[0081] Figure 4 is a detailed view of the bead portion 10 shown in Figure 2 and is an explanatory diagram of the rim cushion 30. The rim cushion 30 has a tire radial distance Hin between the rim cushion innermost part Rri, which is the radially inner end of the rim cushion 30, and the rim cushion innermost part Rwi, which is within a range of 10 mm to 40 mm. In this case, the rim cushion innermost part Rri is the radially inner end of the rim cushion 30, and is located at the bead toe 35. Furthermore, the radial distance Hin between the rim cushion innermost part Rri and the rim cushion innermost part Rwi is the roll-up height of the rim cushion 30 at a position on the inner side of the bead core 11 in the tire width direction.

[0082] The distance Hin in the tire radial direction between the innermost rim cushion Rri and the inner outermost rim cushion Rwi is preferably within the range of 15 mm to 25 mm.

[0083] Additionally, the overlap amount LAP between the tie rubber 22 and the rim cushion 30 is within the range of 3 mm to 30 mm. In other words, the overlap amount LAP, which is indicated by the distance along the periphery of the tie rubber 22 between the position in the tire radial direction of the inner outermost part Rwi of the rim cushion of the tie rubber 22 and the end 22a of the tie rubber 22, is within the range of 3 mm to 30 mm.

[0084] The overlap amount LAP between the tie rubber 22 and the rim cushion 30 is preferably within the range of 5 mm to 20 mm.

[0085] Fig. 5 is a schematic diagram of the tread portion 2 shown in Fig. 1. In Fig. 5, the belt layer 18 is illustrated as only the belt ply that is widest in the tire width direction among the multiple belt plies 181 to 183, and in the following description of Fig. 5, the widest belt ply will be described as the belt layer 18.

[0086] The belt layer 18 disposed in the tread portion 2 has belt cords 18a and belt coat rubber 18b wrapping the belt cords 18a. In the tread portion 2, the belt cords 18a and the belt coat rubber 18b form a conductive path in the tread portion 2. The volume resistivity [Ω·cm] of the belt coat rubber 18b is preferably less than 1×10^8 [Ω·cm].

[0087] In the tread portion 2 where the belt layer 18 is arranged, when the electrical resistance of the belt coat rubber 18b of the belt layer 18 is Rb [Ω], the electrical resistance Rb [Ω] of the belt coat rubber 18b satisfies Rb [Ω] < 1 × 10^8 [Ω]. In this case, the electrical resistance Rb [Ω] of the belt coat rubber 18b is the electrical resistance Rb [Ω] of the belt coat rubber 18b in the range where the belt layer 18 is arranged in the tire width direction.

[0088] The carcass layer 15 also has carcass cords 16 and carcass coat rubber 17 wrapping the carcass cords 16, and the carcass layer 15 having the carcass cords 16 and the carcass coat rubber 17 also constitutes a conductive path in the tread portion 2. In the tread portion 2 where the carcass layer 15 is arranged, if the electrical resistance of the carcass layer 15 is Rpc [Ω] and the electrical resistance of the belt coat rubber 18b of the belt layer 18 is Rb [Ω], the electrical resistance Rpc [Ω] of the carcass layer 15 satisfies Rpc [Ω] < 1 × 10^8 [Ω]. In this case, the electrical resistance Rpc [Ω] of the carcass layer 15 is the electrical resistance Rpc [Ω] of the carcass layer 15 in the range where the belt layer 18 is arranged in the tire width direction.

[0089] [Effects / Effects] When the pneumatic tire 1 according to this embodiment is mounted on a vehicle and driven, the pneumatic tire 1 rotates while the lower part of the surface of the tread portion 2 of the pneumatic tire 1 that is facing the road surface comes into contact with the road surface. The pneumatic tire 1 can generate frictional force with the road surface as the tire contact surface 2a, which is the surface of the tread portion 2, successively comes into contact with the road surface. As a result, the vehicle can transmit driving force, braking force, and turning force to the road surface through the frictional force between the pneumatic tire 1 and the road surface, and can drive using these driving force, braking force, and turning force.

[0090] Furthermore, static electricity can be generated while a vehicle is in motion, and if static electricity builds up on the vehicle, it can easily cause radio interference such as radio noise. In this embodiment, the volume resistivity of the tie rubber 22 and the volume resistivity of the rim cushion 30 are both less than 10^8 [Ω·cm], and since the tie rubber 22 and the rim cushion 30 conduct electricity relatively easily, static electricity can be discharged to the road surface.

[0091] In other words, because the volume resistivity of the tie rubber 22 and the rim cushion 30 is low, the tire electrical resistance, which is the electrical resistance of the pneumatic tire 1, can be reduced. Therefore, static electricity generated while the vehicle is running can flow from the rim flange R through the rim cushion 30 and tie rubber 22, which have low volume resistivity. At this time, an inner liner 21 is interposed between the rim cushion 30 and the tie rubber 22, but because the inner liner 21 is thin, static electricity that flows from the rim flange R to the rim cushion 30 can flow from the rim cushion 30 to the tie rubber 22 via the inner liner 21. In addition, static electricity can also flow between the rim cushion 30 and the tie rubber 22 via the carcass coat rubber 17 of the carcass layer 15, which is in contact with both the rim cushion 30 and the tie rubber 22.

[0092] The static electricity flowing into the tie rubber 22 further flows into the belt layer 18 and then from the belt layer 18 into the tread rubber 3, and can be discharged from the tread rubber 3 to the road surface. As a result, the static electricity generated in the vehicle is discharged to the road surface, suppressing the charging of the vehicle due to static electricity.

[0093] Here, the tie rubber 22 overlaps with the inner liner 21 and is arranged to extend to the position of the rim cushion 30. However, between the inner liner 21 and the tie rubber 22, the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 satisfy the relationship Lt < Li. Thereby, the mass of the tie rubber 22 can be reduced, and thus the mass of the pneumatic tire 1 can be reduced.

[0094] Further, since the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 satisfy the relationship Lt < Li, the length of the tie rubber 22 overlapping the rim cushion 30 in the tire meridian cross-section can be shortened. Thereby, it is possible to suppress the fitting pressure from becoming too large when fitting the pneumatic tire 1 onto the rim wheel due to the length of the tie rubber 22 overlapping the rim cushion 30 becoming too long.

[0095] That is, since the tie rubber 22 according to the present embodiment is made of a rubber material having conductivity and thus has a relatively hard rubber hardness, the tie rubber 22 is less likely to elastically deform compared to the rim cushion 30. For this reason, when the length of the tie rubber 22 overlapping the rim cushion 30 is long, the proportion of the tie rubber 22 that is less likely to elastically deform increases, and thus there is a risk that the fitting pressure when fitting the pneumatic tire 1 onto the rim wheel may increase.

[0096] On the other hand, when the length Lt from the tire equatorial plane CL to the end 22a of the tire rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 satisfy the relationship Lt < Li, it is possible to suppress the length of the tire rubber 22 overlapping the rim cushion 30 from becoming too long. Thereby, the ratio of the tire rubber 22 to the rim cushion 30 can be suppressed, and when a rubber material having conductivity is used for the tire rubber 22, it is possible to suppress the fitting pressure from becoming too high when the pneumatic tire 1 is fitted to the rim wheel.

[0097] Further, since the end 22a of the tire rubber 22 is located radially inward of the tire in the tire radial direction of the bead core 11, when the pneumatic tire 1 is molded, the inner liner 21 and the carcass layer 15 can be more reliably adhered by the tire rubber 22, and peeling between the inner liner 21 and the carcass layer 15 can be suppressed. Further, since the end 22a of the tire rubber 22 is located radially inward of the tire in the tire radial direction of the bead core 11, air enters between the inner liner 21 and the carcass layer 15 during vulcanization molding of the pneumatic tire 1, and the occurrence of vulcanization failures such as air pockets can be suppressed.

[0098] Further, since the relationship between the distance Rtg in the tire radial direction of the end 22a of the tire rubber 22 from the tire rotation axis and the distance Rrc in the tire radial direction of the innermost outer part Rwi of the rim cushion from the tire rotation axis satisfies Rtg < Rrc, a range where the tire rubber 22 and the rim cushion 30 overlap can be ensured in the bead portion 10. Thereby, since a range where the tire rubber 22 and the rim cushion 30, each having a volume resistivity of less than 1 × 10^8 [Ω·cm], overlap can be ensured, the electrical resistance can be reduced by the tire rubber 22 and the rim cushion 30.

[0099] Furthermore, because the end 21a of the inner liner 21 is located more inward in the tire width direction than the outermost portions 11c of the bead cores 11 in the tire width direction, the length of the inner liner 21 in the tire meridian cross section can be shortened. This ensures the air permeation prevention properties of the inner liner 21 to suppress air leakage, while also reducing the mass of the inner liner 21. This ensures the air pressure retention performance of the pneumatic tire 1, and also prevents an increase in the mass of the pneumatic tire 1.

[0100] Furthermore, the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gi [mm] of the portion of the inner liner 21 located within the overlap range between the tie rubber 22 and the rim cushion 30 is within the range of 0.0075≦Gi / LAP≦1.5, so electrical resistance can be reduced while maintaining the air pressure of the pneumatic tire 1. In other words, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gi [mm] of the inner liner 21 is Gi / LAP<0.0075, the thickness Gi [mm] of the inner liner 21 will be too thin, making it difficult to ensure the air permeation prevention properties of the inner liner 21 and potentially making it difficult to maintain air pressure. Furthermore, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gi [mm] of the inner liner 21 is Gi / LAP > 1.5, the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 is too small, making it difficult to secure a conductive path between the tie rubber 22 and the rim cushion 30 and potentially making it difficult to reduce electrical resistance.

[0101] In contrast, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gi [mm] of the inner liner 21 is within the range of 0.0075 ≤ Gi / LAP ≤ 1.5, then the thickness Gi [mm] of the inner liner 21 can be ensured to maintain air permeability prevention by the inner liner 21, while the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 can be ensured to maintain electrical conductivity between the tie rubber 22 and the rim cushion 30. This makes it possible to reduce electrical resistance while maintaining the air pressure of the pneumatic tire 1. As a result, it is possible to reduce electrical resistance while suppressing the increase in mass and fitting pressure of the pneumatic tire 1.

[0102] Furthermore, since the thickness Gt of the tie rubber 22 is within the range of 0.1 [mm] to 1.5 [mm], it is possible to suppress the occurrence of appearance defects caused by the tie rubber 22 being too thin, while also suppressing an excessive increase in the mass of the tie rubber 22. In other words, if the thickness Gt of the tie rubber 22 is less than 0.1 [mm], the thickness Gt of the tie rubber 22 is too thin, which may cause the inner liner 21 to easily get stuck between the carcass cords 16 of the carcass layer 15 during the vulcanization molding of the pneumatic tire 1. In this case, there is a risk that appearance defects will occur in which the shape of the carcass cords 16 will be visible on the inner surface 25 of the tire. Also, if the thickness Gt of the tie rubber 22 is thicker than 1.5 [mm], the thickness Gt of the tie rubber 22 is too thick, which may increase the mass of the tie rubber 22 and thus increase the mass of the pneumatic tire 1.

[0103] In contrast, if the thickness Gt of the tie rubber 22 is within the range of 0.1 [mm] to 1.5 [mm], it is possible to suppress the occurrence of appearance defects caused by the tie rubber 22 being too thin, while also suppressing an excessive increase in the mass of the tie rubber 22. As a result, it is possible to suppress the occurrence of appearance defects in the pneumatic tire 1 while also suppressing an increase in mass.

[0104] Furthermore, the rim cushion 30 has a tire radial distance Hin between the rim cushion innermost part Rri and the rim cushion inner outermost part Rwi that is within the range of 10 mm to 40 mm, which prevents air pockets and other appearance defects while minimizing an increase in the mass of the pneumatic tire 1. In other words, if the distance Hin between the rim cushion innermost part Rri and the rim cushion inner outermost part Rwi is less than 10 mm, the height of the rim cushion 30 in the tire radial direction at a position on the inner side of the bead core 11 in the tire width direction will be too low, which could result in insufficient adhesion between the rim cushion 30 and the inner liner 21. In this case, air may get trapped between the rim cushion 30 and the inner liner 21 during vulcanization of the pneumatic tire 1, which could result in air pockets and other appearance defects. Furthermore, if the distance Hin between the rim cushion innermost part Rri and the rim cushion inner outermost part Rwi is greater than 40 mm, the height of the rim cushion 30 in the tire radial direction at the position on the inner side of the bead core 11 in the tire width direction will be too high, and there is a risk that the mass of the rim cushion 30 will become too large. In this case, there is a risk that the mass of the pneumatic tire 1 will easily increase as the mass of the rim cushion 30 increases.

[0105] In contrast, because the distance Hin between the rim cushion innermost part Rri and the rim cushion inner outermost part Rwi is within the range of 10 mm to 40 mm, it is possible to prevent the mass of the rim cushion 30 from becoming too large while ensuring an adhesive range between the rim cushion 30 and the inner liner 21. As a result, it is possible to prevent an increase in the mass of the pneumatic tire 1 while suppressing the occurrence of poor appearance of the pneumatic tire 1, such as air pockets.

[0106] Furthermore, because the overlap amount LAP between the tie rubber 22 and the rim cushion 30 is within a range of 3 mm to 30 mm, it is possible to suppress an increase in the mass of the pneumatic tire 1 while suppressing the occurrence of poor appearance such as air pockets. In other words, if the overlap amount LAP between the tie rubber 22 and the rim cushion 30 is less than 3 mm, the overlap amount LAP is too small, making the length of the tie rubber 22 disposed in the bead portion 10 too short. This may result in air being more likely to get trapped between the inner liner 21 and the carcass layer 15 during vulcanization of the pneumatic tire 1. In this case, there is a risk that poor appearance such as air pockets may occur. Furthermore, if the overlap amount LAP between the tie rubber 22 and the rim cushion 30 is greater than 30 mm, the overlap amount LAP is too large, which may result in the mass of the rim cushion 30 becoming too large. In this case, there is a risk that the mass of the pneumatic tire 1 may easily increase as the mass of the rim cushion 30 increases.

[0107] In contrast, if the overlap amount LAP between the tie rubber 22 and the rim cushion 30 is within the range of 3 mm to 30 mm, the length of the tie rubber 22 placed in the bead portion 10 can be ensured and the mass of the rim cushion 30 can be prevented from becoming too large. As a result, the occurrence of appearance defects of the pneumatic tire 1 such as air pockets can be prevented, while an increase in the mass of the pneumatic tire 1 can be suppressed.

[0108] Furthermore, the thickness Gi of the inner liner 21 at a portion located within the overlap area between the tie rubber 22 and the rim cushion 30 is within a range of 0.1 mm to 1.5 mm, which makes it possible to suppress air leakage from the pneumatic tire 1 while suppressing an increase in mass. In other words, if the thickness Gi of the inner liner 21 is less than 0.1 mm, the thickness Gi of the inner liner 21 is too thin, making it difficult to ensure the air pressure retention rate of the inner liner 21 and potentially making it difficult to retain air pressure. If the thickness Gi of the inner liner 21 is greater than 1.5 mm, the thickness Gi of the inner liner 21 is too thick, making it easy for the mass of the inner liner 21 to increase, which may potentially increase the mass of the pneumatic tire 1.

[0109] In contrast, if the thickness Gi of the inner liner 21 is within the range of 0.1 [mm] to 1.5 [mm], the increase in the mass of the inner liner 21 can be suppressed while ensuring the air pressure retention rate of the inner liner 21. As a result, air leakage from the pneumatic tire 1 can be suppressed while suppressing the increase in the mass of the pneumatic tire 1.

[0110] Furthermore, since the bead core 11 has a volume resistivity of less than 1 × 10^8 [Ω·cm], the bead core 11 can be used as a conductive path for conducting static electricity. For this reason, the path from the rim cushion 30 to the turn-up portion 15b of the carcass layer 15, from the turn-up portion 15b to the bead core 11, from the bead core 11 to the carcass body portion 15a of the carcass layer 15, and from the carcass body portion 15a to the tie rubber 22 can be used as a conductive path for the static electricity that has flowed from the rim wheel to the rim cushion 30. This makes it possible to more reliably conduct the static electricity that has flowed from the rim wheel to the rim cushion 30 to the tie rubber 22, and to further reduce electrical resistance. As a result, the electrical resistance of the pneumatic tire 1 can be reduced more reliably.

[0111] Furthermore, the bead insulation rubber 13 of the bead core 11 has a volume resistivity of less than 1×10^8 [Ω·cm], which more reliably reduces the electrical resistance of the bead core 11. This allows static electricity flowing from the rim wheel to the rim cushion 30 to be more reliably channeled to the tie rubber 22, further reducing electrical resistance. Furthermore, the bead core 11 with the bead insulation rubber 13 undergoes less deformation when a load is applied, so even if a highly conductive rubber material is used for the bead insulation rubber 13, a deterioration in rolling resistance can be suppressed. Therefore, by ensuring conductivity by using a rubber material with a volume resistivity of less than 1×10^8 [Ω·cm] for the bead insulation rubber 13, electrical resistance can be reduced while suppressing a deterioration in rolling resistance. As a result, the electrical resistance of the pneumatic tire 1 can be more reliably reduced while suppressing a deterioration in rolling resistance.

[0112] Furthermore, the electrical resistance Rpc [Ω] of the carcass layer 15 satisfies Rpc [Ω] < 1 × 10^8 [Ω], and the electrical resistance Rb [Ω] of the belt coat rubber 18b satisfies Rb [Ω] < 1 × 10^8 [Ω], so the carcass layer 15 and the belt coat rubber 18b can reduce the electrical resistance from the tie rubber 22 to the tread rubber 3. As a result, static electricity that flows from the rim cushion 30 side to the belt layer 18 side by the tie rubber 22 can be channeled to the tread rubber 3 by the carcass layer 15 and the belt coat rubber 18b, and can be released from the tread rubber 3 to the road surface. As a result, electrical resistance can be more reliably reduced, and static electricity buildup on the vehicle can be suppressed.

[0113] Furthermore, the tread portion 2 is provided with an earth tread 50 having a volume resistivity of less than 1×10^8 [Ω·cm], which penetrates the tread rubber 3 to contact the belt layer 18 and is exposed to the tire contact surface 2a, thereby ensuring a conductive path from the belt layer 18 to the road surface by the earth tread 50. This makes it possible to more reliably reduce the electrical resistance between the rim wheel and the road surface and more reliably release static electricity generated in the vehicle to the road surface, thereby more reliably reducing the electrical resistance of the pneumatic tire 1.

[0114] Furthermore, by providing the earth tread 50, it is possible to suppress a decrease in anti-static performance when the silica content of the rubber compound constituting the cap tread 3a, under tread 3b, sidewall rubber 5, etc. is increased in order to reduce the rolling resistance of the pneumatic tire 1 and improve fuel economy. In other words, because silica has high insulating properties, an increase in the silica content of the cap tread 3a increases the volume resistivity of the cap tread 3a and reduces anti-static performance, but by providing the earth tread 50, a conductive path between the belt layer 18 and the road surface can be secured. As a result, it is possible to reduce the electrical resistance of the pneumatic tire 1 while reducing rolling resistance.

[0115] [Variations] In the above-described embodiment, the tie rubber 22, the rim cushion 30, and the bead core 11 are described as conductive members in the bead portion 10, but other members may also be used as conductive members in the bead portion 10.

[0116] Figure 6 is a detailed view of a bead portion 10 showing a modified example of a pneumatic tire 1 according to the embodiment, in which protrusions 40 are arranged on the rim cushion outer surface 33. In the bead portion 10, protrusions 40 that protrude outward in the tire width direction may be arranged on the rim cushion outer surface 33, which is the surface of the rim cushion 30 on the outside in the tire width direction, as shown in Figure 6, and the protrusions 40 may be used as conductive members. In this case, the protrusions 40 are arranged on the rim cushion outer surface 33 within a range between a position corresponding to the outermost diameter portion 11a of the bead core 11 in the tire radial direction and a position corresponding to the innermost diameter portion 11b of the bead core 11 in the tire radial direction.

[0117] The protrusion 40, which is positioned to protrude from the outer surface 33 of the rim cushion, preferably has a height Hs [mm] in the tire width direction of the protrusion 40 within the range of 0.1 [mm] ≤ Hs ≤ 2.0 [mm]. Furthermore, the width Ws [mm] of the protrusion 40 in the tire diameter direction of the protrusion 40 is preferably within the range of 0.1 [mm] ≤ Ws ≤ 2.0 [mm].

[0118] 7 and 8 are views taken in the direction of the arrow BB in FIG. 6, and are schematic diagrams showing examples of the protrusions 40. The protrusions 40 arranged on the rim cushion outer surface 33 may be arranged continuously around one circumference in the tire circumferential direction as shown in FIG. 7, or may be divided into multiple protrusions 40 in the tire circumferential direction, with the multiple protrusions 40 arranged intermittently in the tire circumferential direction as shown in FIG. 8. In this way, it is preferable that the protrusions 40 arranged along the tire circumferential direction satisfy the relationship Ls / L≧0.1, where Ls [mm] is the length L of the protrusions 40 in the tire circumferential direction and L [mm] is the length L of one circumference in the tire circumferential direction at the position of the inner part of the protrusion 40 in the tire radial direction.

[0119] The protrusions 40 may be made of the same material as the rim cushion rubber 31 that constitutes the rim cushion 30, or may be made of a different material from the rim cushion rubber 31. Furthermore, it is preferable that the protrusions 40 have a volume resistivity of less than 1×10^8 [Ω·cm]. In this way, the electrical resistance of the protrusions 40 arranged on the rim cushion outer surface 33 is equal to or less than the electrical resistance of the rim cushion 30.

[0120] In other words, if the electrical resistance of the protrusion 40 is Rs[Ω] and the electrical resistance of the rim cushion 30 is Rr[Ω], then the relationship between the electrical resistance Rs[Ω] of the protrusion 40 and the electrical resistance Rr[Ω] of the rim cushion 30 satisfies Rs[Ω]≦Rr[Ω]. In this case, the electrical resistance Rr[Ω] of the rim cushion 30 corresponds to the electrical resistance in the rim cushion 30 over a range in the tire radial direction that is the same range as the arrangement range of the protrusion 40 in the tire radial direction.

[0121] By arranging the protrusion 40 that projects outward in the tire width direction, as described above, on the outer surface 33 of the rim cushion of the bead portion 10, the contact area between the bead portion 10 and the rim wheel can be increased. In other words, when the pneumatic tire 1 is fitted onto the rim wheel, the outer surface 33 of the rim cushion is separated from the rim flange R, and the pneumatic tire 1 is fitted with a gap between the outer surface 33 of the rim cushion and the rim flange R.

[0122] In contrast, if a protrusion 40 that projects outward in the tire width direction is placed on the outer surface 33 of the rim cushion, the protrusion 40 can be brought into contact with the rim flange R when the pneumatic tire 1 is fitted onto the rim wheel, thereby increasing the contact area between the bead portion 10 and the rim wheel. As a result, if a protrusion 40 is placed on the outer surface 33 of the rim cushion, the protrusion 40 can be used as a conductive path between the pneumatic tire 1 and the rim wheel, thereby further reducing electrical resistance.

[0123] Furthermore, since the electrical resistance Rs[Ω] of the protrusion 40 and the electrical resistance Rr[Ω] of the rim cushion 30 satisfy the relationship Rs[Ω]≦Rr[Ω], the electrical resistance between the rim wheel and the rim cushion 30 can be reduced by the protrusion 40. This makes it easier for static electricity flowing from the rim wheel to the rim cushion 30 to flow through the protrusion 40, and makes it easier for static electricity generated in the vehicle to be released to the road surface via the pneumatic tire 1. As a result, electrical resistance can be reduced more reliably, and the charging of the vehicle due to static electricity can be suppressed.

[0124] Furthermore, the length Ls [mm] of the protrusion 40 in the tire circumferential direction satisfies the relationship Ls / L ≥ 0.1 with respect to the length L [mm] of one turn of the tire circumferential direction at the position of the protrusion 40 in the tire radial direction, thus ensuring a sufficient area of ​​the protrusion 40 in the tire width direction. This allows the contact area between the bead portion 10 and the rim wheel to be increased more reliably by the protrusion 40, and reduces the electrical resistance between the rim wheel and the rim cushion 30. As a result, static electricity buildup on the vehicle can be suppressed more reliably.

[0125] Furthermore, in the embodiment described above, the end portion 22a of the tie rubber 22 is located on the inside of the bead core 11 in the tire width direction, but the end portion 22a of the tie rubber 22 may be located in a different portion.

[0126] FIG. 9 is a schematic view showing a modified example of the pneumatic tire 1 according to the embodiment, in which the end portion 22a of the tie rubber 22 is located on the inner side in the tire radial direction of the bead core 11. As shown in FIG. 9, the end portion 22a of the tie rubber 22 may be located on the inner side in the tire radial direction of the bead core 11. The tie rubber 22 satisfies the relationship Lt < Li, where Lt is the length from the tire equatorial plane CL to the end portion 22a of the tie rubber 22 along the periphery (see FIG. 2), and Li is the length from the tire equatorial plane CL to the end portion 21a of the inner liner 21 along the periphery (see FIG. 2). If the end portion 22a of the tie rubber 22 is located on the inner side in the tire radial direction of the outermost diameter portion 11a of the bead core 11 in the tire radial direction and overlaps with the rim cushion 30 via the inner liner 21 in the bead portion 10, the position of the end portion 22a may be a position other than the position in the above-described embodiment.

[0127] In addition, the above-described embodiments and modified examples may be combined as appropriate. In the above-described embodiment, the pneumatic tire 1 has been described as an example of the tire according to the present invention. However, the tire according to the present invention may be other than the pneumatic tire 1. The tire according to the present invention may be, for example, a so-called airless tire that can be used without filling a gas.

[0128] [Examples] FIGS. 10A and 10B are charts showing the results of a performance evaluation test of a pneumatic tire. Hereinafter, a performance evaluation test conducted on the above-described pneumatic tire 1, a conventional pneumatic tire, the pneumatic tire 1 according to the present invention, and a pneumatic tire of a comparative example compared with the pneumatic tire 1 according to the present invention will be described. The performance evaluation test was conducted on the electrical resistance of the pneumatic tire, the tire mass which is the mass of the pneumatic tire, the fitting pressure when fitting the pneumatic tire to the rim wheel, and the appearance performance of the pneumatic tire.

[0129] The performance evaluation test was carried out using a pneumatic tire with a nominal tire size of 235 / 60R18 as specified by JATMA as the test tire. The evaluation test for the electrical resistance of the pneumatic tire was carried out based on the measurement conditions specified by JATMA, using an R8340A Ultra High Resistance Meter manufactured by Advantest Corporation to measure the electrical resistance [Ω] of the test tire.

[0130] The tire mass evaluation test was conducted by measuring the mass of each test tire and calculating the reciprocal of the measured mass as an index, with the conventional example described below being set at 100. The larger the index value for tire mass, the lighter the tire mass and the better the evaluation of the tire mass.

[0131] In addition, to evaluate the fitting pressure when fitting a pneumatic tire to a rim wheel, the test tire was fitted to a rim wheel with a rim size of 18 x 7.0J, inflated with air at a supply pressure of 500 kPa, and then assembled to the rim wheel. While fitting the test tire to the rim wheel, the air filling was stopped the moment the bead of the test tire climbed over the hump of the rim wheel, and the air pressure at that time was measured as the fitting pressure. The fitting pressure when fitting a pneumatic tire to a rim wheel was evaluated using an index value calculated by taking the reciprocal of the air pressure measured as the fitting pressure and setting the conventional example described below as 100. The higher the index value for the fitting pressure when fitting a pneumatic tire to a rim wheel, the lower the air pressure when fitting the pneumatic tire to the rim wheel, indicating better fitting pressure performance.

[0132] Furthermore, the appearance performance was evaluated by vulcanizing and molding 1,000 or more test tires, visually inspecting the vulcanized test tires and counting the number of test tires that had appearance defects such as air pockets or the shape of the carcass cords showing on the inner surface of the tire, to calculate the incidence of appearance defects, and then using the reciprocal of the calculated incidence of appearance defects as an index rating, with the Conventional Example described below being set at 100. The larger the index rating for appearance defects, the lower the incidence of appearance defects and the better the performance in terms of appearance defects.

[0133] The performance evaluation tests were conducted on 24 types of pneumatic tires, including a Conventional Example pneumatic tire, which is an example of a conventional pneumatic tire, Examples 1 to 21 which are pneumatic tire 1 according to the present invention, and Comparative Examples 1 and 2 which are pneumatic tires compared to pneumatic tire 1 according to the present invention. Of these, in the Conventional Example pneumatic tire, the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 have the relationship Lt > Li. Furthermore, in the pneumatic tires of Comparative Examples 1 and 2, the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gi [mm] of the portion of the inner liner 21 located within the overlap range does not satisfy 0.0075≦Gi / LAP≦1.5.

[0134] In contrast, in Examples 1 to 21 which are examples of the pneumatic tire 1 according to the present invention, in all of them, the length Lt from the tire equatorial plane CL to the end 22a of the tread rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 satisfy the relationship Lt < Li, and the relationship between the lap amount LAP [mm] between the tread rubber 22 and the rim cushion 30 and the thickness Gi [mm] of the portion located within the lap range in the inner liner 21 is within the range of 0.0075 ≦ Gi / LAP ≦ 1.5. Further, for the pneumatic tires 1 according to Examples 1 to 20, the thickness Gt [mm] of the tread rubber 22, the winding-up height Hin [mm] at the position on the inner side in the tire width direction of the bead core 11 of the rim cushion 30, the lap amount LAP [mm] between the tread rubber 22 and the rim cushion 30, the thickness Gi [mm] of the inner liner 21, the volume resistivity [Ω·cm] of the bead core 11, the electrical resistance Rpc [Ω] of the carcass layer 15, the electrical resistance Rb [Ω] of the belt coat rubber 18b, and the presence or absence of the convex portion 40 on the outer surface 33 of the rim cushion are all different.

[0135] As a result of conducting an evaluation test using these pneumatic tires 1, as shown in FIGS. 10A and 10B, it was found that the pneumatic tires 1 according to Examples 1 to 21 can reduce the electrical resistance without increasing the tire mass or the fitting pressure as compared with the conventional example and Comparative Examples 1 and 2. That is, the pneumatic tires 1 according to Examples 1 to 21 can reduce the electrical resistance while suppressing an increase in mass and an increase in fitting pressure.

[0136] The present disclosure includes the following inventions. Invention [1] A pair of bead portions disposed on both sides of the tire equatorial plane in the tire width direction, A bead core provided on each of the pair of bead portions, A rim cushion that constitutes the rim fitting surface in the bead portion and is disposed from the inner side to the outer side in the tire width direction of the bead core, At least one carcass layer spanned between the pair of bead portions, A belt layer disposed on the outer side in the tire radial direction of the carcass layer A tread rubber disposed on the outer side in the tire radial direction of the belt layer, An inner liner disposed on the inner surface of the tire along the carcass layer, A tie rubber disposed between the carcass layer and the inner liner, and comprising The inner liner and the tie rubber satisfy the relationship Lt < Li, where Lt is the length from the tire equatorial plane to the end of the tie rubber along the periphery, and Li is the length from the tire equatorial plane to the end of the inner liner along the periphery. The end of the inner liner is located on the inner side in the tire width direction than the outermost side in the tire width direction of the bead core. The end of the tie rubber is located on the inner side in the tire radial direction than the outermost diameter part in the tire radial direction of the bead core. When the distance in the tire radial direction from the tire rotation axis to the end of the tie rubber is Rtg, and the distance in the tire radial direction from the tire rotation axis to the outermost part on the inner side of the rim cushion, which is the end on the outer side in the tire radial direction at the position on the inner side in the tire width direction of the bead core in the rim cushion, is Rrc, the end of the tie rubber and the outermost part on the inner side of the rim cushion satisfy the relationship Rtg < Rrc. The relationship between the lap amount LAP [mm] of the tie rubber and the rim cushion, which is indicated by the distance along the periphery between the outermost part on the inner side of the rim cushion and the end of the tie rubber, and the thickness Gi [mm] of the part located within the lap range, which is the range along the periphery between the outermost part on the inner side of the rim cushion and the end of the tie rubber in the inner liner, is within the range of 0.0075 ≦ Gi / LAP ≦ 1.5. The tie rubber has a volume resistivity of less than 1 × 10^8 [Ω·cm]. The rim cushion has a volume resistivity of less than 1 × 10^8 [Ω·cm], and a tire characterized by this. Invention [2] [[ID=​​​​The rim cushion has a tire radial distance between an innermost rim cushion end, which is the innermost end of the rim cushion in the tire radial direction, and an innermost rim cushion end, which is the outermost end of the rim cushion in the tire radial direction, within a range of 10 mm to 40 mm, The tire according to the invention [1] or [2], wherein the overlap amount LAP between the tie rubber and the rim cushion is within the range of 3 mm or more and 30 mm or less. Invention[4] The tire according to any one of Inventions [1] to [3], wherein the thickness Gi of the inner liner at the portion located within the wrap range is in the range of 0.1 [mm] or more and 1.5 [mm] or less. Invention[5] The tire according to any one of the inventions [1] to [4], wherein the bead core has a volume resistivity of less than 1×10^8 [Ω·cm]. Invention[6] The bead core has a bead wire and a bead insulation rubber that wraps the bead wire, The tire according to the invention [5], wherein the bead insulation rubber has a volume resistivity of less than 1×10^8 [Ω·cm]. Invention[7] When the electrical resistance of the carcass layer is Rpc [Ω] and the electrical resistance of the belt coat rubber of the belt layer is Rb [Ω], The electrical resistance Rpc [Ω] of the carcass layer satisfies Rpc [Ω] < 1 × 10^8 [Ω], The tire according to any one of the inventions [1] to [6], wherein the electrical resistance Rb [Ω] of the belt coat rubber satisfies Rb [Ω] < 1 × 10^8 [Ω]. Invention[8] A tire according to any one of inventions [1] to [7], having a volume resistivity of less than 1×10^8 [Ω·cm], and comprising an earth tread that penetrates the tread rubber, contacts the belt layer, and is exposed on the surface of the tread rubber. Invention[9] a rim cushion outer surface, which is the surface of the rim cushion on the outside in the tire width direction, has a protrusion that protrudes outward in the tire width direction, within a range between a position corresponding to the outermost diameter portion of the bead core and a position corresponding to the innermost diameter portion of the bead core in the tire radial direction; A tire according to any one of inventions [1] to [8], wherein when the electrical resistance of the convex portion is Rs [Ω] and the electrical resistance of the rim cushion is Rr [Ω], the relationship between the electrical resistance Rs [Ω] of the convex portion and the electrical resistance Rr [Ω] of the rim cushion satisfies Rs [Ω] ≦ Rr [Ω]. Invention

[10] The tire according to invention [9], wherein the length Ls [mm] of the convex portion in the tire circumferential direction satisfies the relationship Ls / L≧0.1 with respect to the length L [mm] of one circumference in the tire circumferential direction at the position of the inner part of the convex portion in the tire radial direction. [Explanation of symbols]

[0137] 1 pneumatic tire 2 Tread section 2a Tire contact surface 3 Tread rubber 3a Cap Tread 3b Undertread 4 Sidewall 5 Sidewall rubber 10 Bead section 11 Bead core 11a Outermost diameter part 11b Innermost diameter part 11c outermost part 12 Bead wire 13 Bead insulation rubber 14 Bead filler 15 Carcass layer 15a Carcass main body 15b Turn-up section 16 Carcass cord 17 Carcass coat rubber 18 Belt Layer 18a belt cord 18b Belt Coat Rubber 21 Inner liner 21a End 22 Thai Rubber 22a end 25 Tire inner surface 30 Rim Cushion 31 Rim cushion rubber 32 Rim mating surface 33 Rim cushion outer surface 35 Bead Toe 36 Bead base 40 Convex part 50 Earth Red

Claims

1. a pair of bead portions disposed on both sides of the tire equatorial plane in the tire width direction; a bead core provided in each of the pair of bead portions; a rim cushion that constitutes a rim fitting surface of the bead portion and is disposed from the inner side in the tire width direction to the outer side in the tire width direction of the bead core; at least one carcass layer disposed between the pair of bead portions; a belt layer disposed on the outer side of the carcass layer in the tire radial direction; a tread rubber disposed on the outer side of the belt layer in the tire radial direction; an inner liner disposed on the tire inner surface along the carcass layer; a tie rubber disposed between the carcass layer and the inner liner; Equipped with the inner liner and the tie rubber satisfy a relationship of Lt<Li, where Lt is a length from the tire equatorial plane to an end of the tie rubber along the periphery, and Li is a length from the tire equatorial plane to the end of the inner liner along the periphery, an end portion of the inner liner is located more inward in the tire width direction than an outermost portion of the bead core in the tire width direction; an end portion of the tie rubber is located radially inward of an outermost diameter portion of the bead core in the tire radial direction, where Rtg is the distance in the tire radial direction from the tire rotational axis of the end of the tie rubber, and Rrc is the distance in the tire radial direction from the tire rotational axis to the innermost part of the rim cushion, which is the outermost part of the rim cushion in the tire radial direction at a position on the inner side of the bead core in the tire width direction, and the relationship between an overlap amount LAP [mm] between the tie rubber and the rim cushion, which is indicated by the distance along the periphery between the innermost outermost part of the rim cushion and the end of the tie rubber, and a thickness Gi [mm] of a portion of the inner liner located within an overlap range, which is the range along the periphery between the innermost outermost part of the rim cushion and the end of the tie rubber, is within the range of 0.0075≦Gi / LAP≦1.5, The tie rubber has a volume resistivity of less than 1×10^8 [Ω cm], The tire is characterized in that the rim cushion has a volume resistivity of less than 1×10^8 [Ω·cm].

2. The tire according to claim 1, wherein the tie rubber has a thickness in the range of 0.1 mm to 1.5 mm.

3. the rim cushion has a tire radial direction distance between an innermost rim cushion end, which is the innermost end of the rim cushion in the tire radial direction, and an innermost rim cushion end, which is the innermost end of the rim cushion in the tire radial direction, within a range of 10 mm to 40 mm; The tire according to claim 1, wherein the overlap amount LAP between the tie rubber and the rim cushion is within a range of 3 mm to 30 mm.

4. The tire according to claim 1, wherein the inner liner has a thickness Gi of 0.1 mm or more and 1.5 mm or less at a portion located within the wrap area.

5. The tire according to claim 1, wherein the bead core has a volume resistivity of less than 1×10^8 [Ω·cm].

6. The bead core has a bead wire and a bead insulation rubber that wraps the bead wire, The tire according to claim 5, wherein the bead insulation rubber has a volume resistivity of less than 1×10^8 [Ω·cm].

7. When the electrical resistance of the carcass layer is Rpc [Ω] and the electrical resistance of the belt coat rubber of the belt layer is Rb [Ω], The electrical resistance Rpc [Ω] of the carcass layer satisfies Rpc [Ω] < 1 × 10^8 [Ω], The tire according to claim 1, wherein the belt coat rubber has an electrical resistance Rb [Ω] that satisfies Rb [Ω] < 1×10^8 [Ω].

8. 2. The tire according to claim 1, further comprising an earth tread having a volume resistivity of less than 1×10^8 [Ω·cm], penetrating the tread rubber to contact the belt layer and exposed on a surface of the tread rubber.

9. a rim cushion outer surface, which is the surface of the rim cushion on the outside in the tire width direction, has a protrusion that protrudes outward in the tire width direction, within a range between a position corresponding to the outermost diameter portion of the bead core and a position corresponding to the innermost diameter portion of the bead core in the tire radial direction; The tire according to claim 1, wherein when the electrical resistance of the convex portion is Rs [Ω] and the electrical resistance of the rim cushion is Rr [Ω], the relationship between the electrical resistance Rs [Ω] of the convex portion and the electrical resistance Rr [Ω] of the rim cushion satisfies Rs [Ω] ≦ Rr [Ω].

10. 10. The tire according to claim 9, wherein the protrusions have a length Ls [mm] in the tire circumferential direction, where L [mm] is the length of one circumference in the tire circumferential direction at a position of an inner portion of the protrusion in the tire radial direction, and the length L [mm] satisfies the relationship Ls / L≧0.1.

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