tire

Abstract

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

Description

Technical Field

[0001] The present invention relates to a tire.

Background Art

[0002] In recent years, due to environmental problems and the like, the demand for low rolling resistance tires has been increasing. As a method for reducing the rolling resistance of tires, a method of suppressing the rolling resistance of tires by increasing the silica content of the rubber compound constituting the cap tread, under tread, sidewall rubber, etc. of the tire has been used. However, since silica has high insulating properties, when the silica content of the rubber compound used for the cap tread or the like increases, the electrical resistance value of the cap tread or the like increases, and the charge suppression performance of the tire deteriorates. When the charge suppression performance of the tire deteriorates, static electricity generated during vehicle running tends to accumulate, so that radio wave interference such as radio noise is likely to occur.

[0003] Therefore, among conventional pneumatic tires, there are some that are provided with a conductive member having a low electrical resistance value in order to improve the charge suppression performance and make it easier to discharge the static electricity generated in the vehicle to the road surface during vehicle running. For example, in Patent Document 1, a conductive layer having a low electrical resistivity is disposed between the carcass layer and the inner liner and extended from the bead portion to the belt layer, thereby improving the charge suppression performance of the tire. Further, Patent Document 1 describes an example in which the conductive layer is made of a conductive rubber material and also serves as a tie rubber disposed over the entire circumference of the tire inner cavity portion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When reducing electrical resistance using a tie rubber made of conductive rubber material, it is important to position the tie rubber so that it overlaps the rim cushion. However, if the length of the tie rubber overlapping the rim cushion is long, there is a risk that the mass will increase due to the increased length of the tie rubber. In addition, because tie rubber made of conductive rubber material has a high carbon content and is therefore relatively hard, if the length of the tie rubber overlapping the rim cushion is long, there is a risk that the fitting pressure when fitting the tire onto the rim wheel will increase. For these reasons, it is extremely difficult to reduce electrical resistance without increasing mass or fitting pressure.

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

[0007] In order to solve the above-described problems and achieve the object, the 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 in each of the pair of bead portions, a bead filler disposed outside the bead core in the tire radial direction, a rim cushion that constitutes a rim fitting surface of 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 outside the carcass layer in the tire radial direction, a tread rubber disposed outside the belt layer in the tire radial direction, an inner liner disposed on the inner surface of the tire along the carcass layer, and a tie rubber disposed between the carcass layer and the inner liner. 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 inside the tire width direction and inside the tire radial direction of the outermost diameter portion of the bead core in the tire width direction. Let the distance in the tire radial direction from the tire rotation axis to the end of the tie rubber be Rtg, the distance in the tire radial direction from the tire rotation axis to the outer end of the bead filler, which is the outer end of the bead filler in the tire radial direction, be Rf, and the distance in the tire radial direction from the tire rotation axis to the outermost diameter portion of the bead core be Rbc. Then, the end of the tie rubber, the outer end of the bead filler, and the outermost diameter portion of the bead core satisfy the relationship Rbc < Rtg < Rf. The lap amount LAP [mm] of the tie rubber and the bead filler, which is indicated by the distance along the periphery between the end of the tie rubber and the outer end of the bead filler, and the maximum thickness Gp [mm] of the portion in contact with the tie rubber in the lap range, which is the range along the periphery between the end of the tie rubber and the outer end of the bead filler in the carcass layer, satisfy the range of 0.02 ≦ Gp / LAP ≦ 4.0. The tie rubber is characterized in that its volume resistivity is less than 1 × 10^8 [Ω·cm].

[0008] Furthermore, in the above-mentioned tire, it is preferable that the rim cushion has a volume resistivity of less than 1 × 10^8 [Ω·cm].

[0009] Furthermore, in the above-mentioned tire, it is preferable that the relationship between the maximum thickness Gb [mm] of the bead filler in the lap range and the lap amount LAP [mm] is within the range of 0.01 ≤ Gb / LAP ≤ 3.5.

[0010] 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].

[0011] Furthermore, in the above-mentioned tire, the overlap amount LAP [mm] between the tie rubber and the bead filler is preferably within the range of 3 [mm] to 40 [mm].

[0012] Furthermore, in the above-mentioned tire, it is preferable that the maximum thickness Gp[mm] of the carcass layer in the portion in contact with the tie rubber within the lap range is within the range of 0.5[mm] to 4[mm].

[0013] Furthermore, in the above-mentioned tire, it is preferable that the maximum thickness Gb [mm] of the bead filler in the lap range is within the range of 0.4 [mm] to 10 [mm].

[0014] Furthermore, in the above-mentioned tire, it is preferable that the bead filler has a volume resistivity of less than 1 × 10^10 [Ω·cm].

[0015] Furthermore, in the above-mentioned tire, when the electrical resistance of the carcass layer is Rpc[Ω] and the electrical resistance of the belt coating 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 coating rubber satisfies Rb[Ω] < 1 × 10^8[Ω]. [Effects of the Invention]

[0016] The tire according to the present invention has an effect that it can reduce the electrical resistance while suppressing an increase in mass and fitting pressure. [Brief Description of the Drawings]

[0017] [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 of FIG. 1. [Figure 3] FIG. 3 is a detailed view of the bead portion shown in FIG. 2. [Figure 4] FIG. 4 is a schematic view of the tread portion shown in FIG. 1. [Figure 5A] FIG. 5A is a chart showing the results of a performance evaluation test of a pneumatic tire. [Figure 5B] FIG. 5B is a chart showing the results of a performance evaluation test of a pneumatic tire. [Modes for Carrying Out the Invention]

[0018] Hereinafter, embodiments of the tire according to the present invention will be described in detail based on the drawings. Note that the present invention is not limited by this embodiment. In addition, the components in the following embodiments include those that can be replaced by those skilled in the art and can be easily conceived, or those that are substantially the same.

[0019] [Embodiment] [Pneumatic Tire] In the following description, as an example of the tire according to the present invention, a pneumatic tire 1 will be used for explanation. 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.

[0020] In the following description, 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 in the tire radial direction refers to the side facing the tire rotation axis in the tire radial direction, and the outer side in the tire radial direction refers to the side away from the tire rotation axis in the tire radial direction. Further, the tire circumferential direction refers to the circumferential direction around the tire rotation axis as the central axis. Also, the tire width direction refers to the direction parallel to the tire rotation axis, the inner side in the tire width direction refers to the side facing the tire equatorial plane (tire equator line) CL in the tire width direction, and the outer side in 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 that is perpendicular to the tire rotation axis and passes through the center of the tire width of the pneumatic tire 1, and the tire equatorial plane CL coincides with the center line in the tire width direction which is the central position in the tire width direction of the pneumatic tire 1. The tire width is the width in the tire width direction between the outermost portions located in the tire width direction, that is, the distance between the portions that are farthest from the tire equatorial plane CL in the tire width direction. The tire equator line refers to a line on the tire equatorial plane CL along the tire circumferential direction of the pneumatic tire 1. Also, in the following description, the tire meridian cross-section refers to the cross-section when the tire is cut by a plane including the tire rotation axis.

[0021] FIG. 1 is a cross-sectional view in the tire meridian direction showing the pneumatic tire 1 according to the embodiment. The figure shows one-sided region in the tire radial direction. Also, as an example of the pneumatic tire, the figure shows a radial tire for a passenger car.

[0022] The pneumatic tire 1 according to the embodiment has an annular structure centered on the tire rotation axis, and includes 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 tie rubber 22. Among these, the pair of sidewall portions 4, 4 and the pair of bead portions 10, 10 are each arranged one by one on both sides of the tire equatorial plane CL in the tire width direction.

[0023] The pair of bead portions 10, 10 are located on the radially inner side 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.

[0024] 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 portions 10. The pair of bead fillers 14, 14 are formed so that their width in the tire width direction decreases as they move outward in the radial direction of the tire.

[0025] 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 stretched in a toroidal manner between a pair of bead portions 10, 10 located on both sides in the tire width direction to form the tire's skeleton. The carcass ply of the carcass layer 15 is constructed by covering multiple carcass cords made of steel or organic fiber materials such as aramid, nylon, polyester, or rayon with a coating rubber and then rolling them. The carcass angle of the carcass ply of this carcass layer 15, which is defined as the inclination angle of the direction in which the carcass cord extends with respect to the circumferential direction of the tire, is within the range of 80 degrees to 95 degrees in absolute value.

[0026] In this embodiment, the carcass layer 15 has a single-layer structure and is continuously stretched between the bead cores 11, 11 on both sides in the tire width direction. Furthermore, both ends of the carcass layer 15 are wrapped back outward in the tire width direction and secured so as to enclose the bead cores 11 and bead filler 14. In other words, the carcass layer 15, near both ends in the tire meridional section, is wrapped back outward in the tire width direction, passing from the inside in the tire width direction to the inside in the tire radial direction of the bead cores 11 and bead filler 14.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The rim cushion 30, arranged in this manner, is the part that contacts the rim flange R of the rim wheel when the pneumatic tire 1 is mounted onto the rim wheel, and constitutes the contact surface of the bead portion 10 with respect to the rim flange R. Of the contact surface of the rim cushion 30 with respect to the rim flange R, the portion that is the inner circumferential surface of the rim cushion 30 constitutes the rim fitting surface 32 of the bead portion 10, which is the surface that fits into the rim wheel.

[0032] The rim cushion 30 is composed of a rubber component, the 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 constituting 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 is less than 1 × 10^6 [Ω·cm].

[0033] Furthermore, the rim cushion rubber 31 has a tanδ value at 60°C that is in the range of 0.085 to 0.35, and a rubber hardness Hs that is in the range of 35 to 111.

[0034] The tanδ value at 60°C mentioned here is measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., under the conditions of initial strain of 10%, amplitude of ±0.5%, and frequency of 20Hz. The rubber hardness Hs is measured at a temperature of 20°C in accordance with JIS K6253.

[0035] Furthermore, the rim cushion 30 may have components other than the rim cushion rubber 31. For example, the rim cushion 30 may include a chafer, which is made of fibrous material or rubber, 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 the rim wheel.

[0036] 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.

[0037] 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.

[0038] The cap tread 3a is a rubber member located on the outermost side of the tread portion 2 in the tire radial direction and constitutes the tire contact surface 2a. It may have a single-layer structure (see Figure 1) or a multi-layer structure (not shown). The tanδ value of the cap tread 3a at 60°C is preferably 0.25 or less. Furthermore, 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 factors reduce the rolling resistance of the pneumatic tire 1. A cap tread 3a having such a volume resistivity is produced by using a low-heat-generating compound with a low carbon content and reinforcing it by increasing the silica content.

[0039] Furthermore, the undertread 3b is a component laminated on the inner side of the cap tread 3a in the tire radial direction. Preferably, the volume resistivity of the undertread 3b is lower than that of the cap tread 3a.

[0040] Each of the pair of sidewall sections 4, 4 is composed of sidewall rubber 5, and the pair of sidewall rubbers 5, 5 of the pair of sidewall sections 4, 4 are respectively arranged on the outer side in the tire width direction of the carcass layer 15. The tanδ value of the sidewall rubber 5 at 60 [℃] is preferably 0.20 or less. Furthermore, 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. These factors reduce the rolling resistance of the pneumatic tire 1. Sidewall rubber 5 having such volume resistivity is produced by using a low-heat generating compound with a low carbon content and reinforcing it by increasing the silica content.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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).

[0048] 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.

[0049] Examples of elastomers include diene rubbers and their hydrogenated versions [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), isobutylene and aromatic vinyl or diene monomer copolymers, acrylic rubber (ACM), ionomers, halogen-containing rubbers [e.g., Br-IIR, Cl-IIR, brominated isobutylene-paramethylstyrene copolymer (Br-IPMS), chloroprene rubber (CR), hydrin rubber (CHC, CHR), chlorosulfur Polyethylene chloride (CSM), chlorinated polyethylene (CM), maleic acid-modified chlorinated polyethylene (M-CM), silicone rubber (e.g., methyl vinyl silicone rubber, dimethyl silicone rubber, methylphenyl vinyl silicone rubber), sulfur-containing rubber (e.g., polysulfide rubber), fluororubber (e.g., vinylidene fluoride rubber, fluorovinyl ether rubber, tetrafluoroethylene-propylene rubber, fluorosilicone rubber, fluorophosphazene rubber), thermoplastic elastomers (e.g., styrene elastomers, olefin elastomers, polyester elastomers, urethane elastomers, polyamide elastomers), etc., can be used.

[0050] Furthermore, the tie rubber 22, positioned between the inner liner 21 and the carcass layer 15, is a layer designed to prevent the carcass cords of the carcass layer 15 from biting into the inner liner 21 when the unvulcanized pneumatic tire 1 is inflated during tire manufacturing. In addition, the tie rubber 22 contributes to air permeability prevention and handling stability on dry road surfaces in the pneumatic tire 1 after manufacturing.

[0051] 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.

[0052] Figure 2 is a detailed view of the region on one side of the tire equatorial plane CL in the tire width direction of Figure 1. The pneumatic tire 1 according to this embodiment has a charge suppression structure for releasing static electricity generated on the vehicle during vehicle operation to the road surface, and tie rubber 22 is used for the charge suppression structure. The tie rubber 22 is arranged in such a way that a single tie rubber 22 is placed along the carcass layer 15 between a pair of bead portions 10, and its volume resistivity is less than 1 × 10^8 [Ω·cm]. It is more preferable that the volume resistivity of the tie rubber 22 is less than 1 × 10^6 [Ω·cm]. In addition, the tie rubber 22 has a tanδ value at 60 [℃] in the range of 0.05 to 0.40, and a rubber hardness Hs in the range of 50 to 70.

[0053] 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.

[0054] 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.

[0055] Here, the specified rim refers to the "Applicable Rim" defined by JATMA, the "Design Rim" defined by TRA, or the "Measuring Rim" defined by ETRTO. Also, the specified internal pressure refers to the "Maximum Air Pressure" defined by JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" defined by TRA, or the "INFLATION PRESSURES" defined by ETRTO.

[0056] The inner liner 21 and the tread rubber 22 that are laminated and arranged satisfy the relationship Lt < Li, where Lt is the length from the tire equatorial plane CL to the end 22a of the tread 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 tread rubber 22 has a length along the periphery in the tire meridian cross-section that is shorter than the length of the inner liner 21 along the periphery in the tire meridian cross-section.

[0057] 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 tread rubber 22 along the periphery is within the range of 5 [mm] ≦ Li - Lt ≦ 70 [mm].

[0058] Since the tread rubber 22 has a shorter length along the periphery than the inner liner 21 in this way, the tread rubber 22 is covered by the inner liner 21 without contacting the rim cushion 30.

[0059] 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 a direction close to the tire width direction at the position of the tread portion 2 and a direction close to the tire diameter direction at the position of the sidewall portion 4.

[0060] In this embodiment, the rim cushion 30 placed on the bead portion 10 has a position in the tire radial direction where the outer end of the bead core 11 is located on the inner side in the tire width direction, and the outer end of the bead core 11 is located on the outer side in the tire radial direction, and the outer end of the bead core 11 is located on the outer side in the tire radial direction, and the outer end of the bead core 11 is located on the outer side in the tire radial direction, and the outer end of the bead core 11 is located on the outer side in the tire radial direction, and the outer side.

[0061] Furthermore, the rim cushion 30 is positioned further inward than the inner liner 21 in the tire width direction of the bead core 11, and further inward than the inner liner 21 in the tire diameter direction of the bead core 11. As a result, the rim cushion 30 covers the inner liner 21 from the inside in the tire width direction of the bead core 11, and covers the inner liner 21 from the inside in the tire diameter direction of the bead core 11.

[0062] In other words, the rim cushion 30, which is positioned in the bead portion 10 from the inside in the tire width direction to the outside in the tire width direction of the bead core 11, is positioned in the bead portion 10 so as to cover the bead core 11, the carcass layer 15, and the inner liner 21. Therefore, in the bead portion 10, the surface of the inner liner 21 on the inner cavity side of the tire becomes the inner surface 25 of the tire outside the position where the rim cushion 30 is positioned, and the surface of the rim cushion 30 on the inner cavity side of the tire becomes the inner surface 25 of the tire outside the position where the rim cushion 30 is positioned.

[0063] The rim cushion 30, positioned on the bead portion 10 in this manner, forms the bead base 36, which is the inner circumferential surface of the bead portion 10, and the bead toe 35, which is the inner end of the bead base 36 in the tire width direction. The bead base 36 is the part that contacts the rim wheel when the pneumatic tire 1 is mounted on the rim wheel. The rim cushion 30 thus forms the bead base 36, which is the rim fitting surface 32 when the pneumatic tire 1 is mounted on the rim wheel.

[0064] Furthermore, Earth Tread 40 is arranged in the tread portion 2. Earth Tread 40 is a conductive rubber member embedded in the tread rubber 3 and exposed on the tire contact surface. Earth Tread 40 penetrates the tread rubber 3 and contacts the belt layer 18, and is also exposed on the tire contact surface 2a, which is the surface of the tread rubber 3. Specifically, Earth Tread 40 is exposed on the tire contact surface 2a and penetrates the cap tread 3a and under tread 3b of the tread rubber 3 to make conductive contact with the belt layer 18. In this way, an conductive path from the belt layer 18 to the road surface is secured by Earth Tread 40.

[0065] Furthermore, the Earth Tread 40 has an annular structure that extends around the entire circumference of the tire, with a portion of it exposed to the tire contact surface 2a, and extends continuously in the circumferential direction of the tire. Therefore, when the pneumatic tire 1 rolls, the Earth Tread 40 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 ensured. The Earth Tread 40 is formed with a width in the tire width direction that is narrower than, for example, the groove width of the circumferential main groove (not shown) that extends in the circumferential direction of the tread portion 2, and is positioned between adjacent circumferential main grooves in the tire width direction.

[0066] The Earth Tread 40 arranged in this manner is made of a conductive rubber material having a lower volume resistivity than the tread rubber 3, and the volume resistivity of the Earth Tread 40 is less than 1 × 10^8 [Ω·cm]. It is more preferable that the volume resistivity of the Earth Tread 40 is 1 × 10^6 [Ω·cm] or less.

[0067] Figure 3 is a detailed view of the bead portion 10 shown in Figure 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 radially outward from the outermost diameter portion 11a of the bead core 11 in the tire radial direction. Furthermore, the end portion 22a of the tie rubber 22 is located radially inward from the outer end portion 14a of the bead filler 14, which is the radially outward end of the bead filler 14.

[0068] Therefore, when the distance in the tire radial direction from the tire rotation axis to the end portion 22a of the tie rubber 22 is defined as Rtg, the distance in the tire radial direction from the tire rotation axis to the outer end portion 14a of the bead filler is defined as Rf, and the distance in the tire radial direction from the tire rotation axis to the outermost diameter portion 11a of the bead core 11 is defined as Rbc, the end portion 22a of the tie rubber 22, the outer end portion 14a of the bead filler, and the outermost diameter portion 11a of the bead core 11 satisfy the relationship of Rbc < Rtg < Rf.

[0069] In addition, the difference between the distance Rf in the tire radial direction from the tire rotation axis to the outer end portion 14a of the bead filler and the distance Rtg in the tire radial direction from the tire rotation axis to the end portion 22a of the tie rubber 22 is preferably within the range of 0.5 [mm] ≦ Rf - Rtg ≦ 40 [mm]. Also, the difference between the distance Rtg in the tire radial direction from the tire rotation axis to the end portion 22a of the tie rubber 22 and the distance Rbc in the tire radial direction from the tire rotation axis to the outermost diameter portion 11a of the bead core 11 is preferably within the range of 0.5 [mm] ≦ Rtg - Rbc ≦ 40 [mm].

[0070] In addition, the end portion 22a of the tie rubber 22 is located outside in the tire radial direction than the innermost outermost portion Rwi of the rim cushion, which is the outer end portion in the tire radial direction at the position inside the tire width direction of the bead core 11 in the rim cushion 30. That is, when the distance in the tire radial direction from the tire rotation axis to the end portion 22a of the tie rubber 22 is defined as Rtg and the distance in the tire radial direction from the tire rotation axis to the innermost outermost portion Rwi of the rim cushion is defined as Rci, the end portion 22a of the tie rubber 22 and the innermost outermost portion Rwi of the rim cushion satisfy the relationship of Rci < Rtg. 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 Rci is the radius of the position of the innermost outermost portion Rwi of the rim cushion centered on the tire rotation axis.

[0071] Note that the difference 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 Rci in the tire radial direction of the innermost outermost Rwi of the rim cushion from the tire rotation axis is preferably within the range of 0.5 [mm] ≤ Rtg - Rci ≤ 70 [mm].

[0072] The rim cushion 30 has a distance Hin in the tire radial direction between the innermost part Rri of the rim cushion, which is the end on the tire radial inner side of the rim cushion 30, and the innermost outermost Rwi of the rim cushion within the range of 10 [mm] or more and 40 [mm] or less. In this case, the innermost part Rri of the rim cushion is the end on the tire radial inner side of the rim cushion 30 and is located at the bead toe 35. Also, the distance Hin in the tire radial direction between the innermost part Rri of the rim cushion and the innermost outermost Rwi of the rim cushion is the winding-up height at the position on the tire width inner side of the bead core 11 in the rim cushion 30.

[0073] Note that the distance Hin in the tire radial direction between the innermost part Rri of the rim cushion and the innermost outermost Rwi of the rim cushion is preferably within the range of 15 [mm] or more and 25 [mm] or less.

[0074] Also, the outer end 14a of the bead filler is located on the outer side in the tire radial direction with respect to the outermost outer Rwo of the rim cushion, which is the end on the outer side in the tire radial direction at the position on the outer side in the tire width direction of the bead core 11 in the rim cushion 30. That is, the distance Rf in the tire radial direction of the outer end 14a of the bead filler from the tire rotation axis and the distance Rco in the tire radial direction of the outermost outer Rwo of the rim cushion from the tire rotation axis satisfy the relationship Rco < Rf.

[0075] In addition, the distance Rco in the tire radial direction from the tire rotation axis to the outermost portion Rwo of the rim cushion on the outer side satisfies the relationship Rtg < Rco with respect to the distance Rtg in the tire radial direction from the tire rotation axis to the end portion 22a of the tie rubber 22. The difference between the distance Rco in the tire radial direction from the tire rotation axis to the outermost portion Rwo of the rim cushion on the outer side and the distance Rtg in the tire radial direction from the tire rotation axis to the end portion 22a of the tie rubber 22 is preferably within the range of 0.5 [mm] ≦ Rco - Rtg ≦ 40 [mm].

[0076] Since the end portion 22a of the tie rubber 22 is located on the inner side in the tire radial direction with respect to the outer end portion 14a of the bead filler, the tie rubber 22 is arranged to overlap in the tire width direction with respect to the bead filler 14 through the carcass main body portion 15a of the carcass layer 15.

[0077] Thus, the tie rubber 22 arranged to overlap in the tire width direction with respect to the bead filler 14, and the carcass layer 15 interposed between the bead filler 14 and the tie rubber 22, the relationship between the lap amount LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] at the portion where the tie rubber 22 contacts in the lap range 50 between the tie rubber 22 and the bead filler 14 in the carcass layer 15 is within the range of 0.02 ≦ Gp / LAP ≦ 4.0.

[0078] In this case, the lap amount LAP [mm] between the tie rubber 22 and the bead filler 14 is the distance along the periphery of the tie rubber 22 between the end portion 22a of the tie rubber 22 and the outer end portion 14a of the bead filler. Also, the lap range 50 between the tie rubber 22 and the bead filler 14 is the range along the periphery between the end portion 22a of the tie rubber 22 and the outer end portion 14a of the bead filler, and is the range where the tie rubber 22 and the bead filler 14 are arranged to overlap through the carcass layer 15.

[0079] Furthermore, it is preferable that the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] in the overlap range 50 of the carcass layer 15 is within the range of 0.025 ≤ Gp / LAP ≤ 3.5.

[0080] The bead filler 14, which overlaps the tie rubber 22 in the tire width direction via the carcass layer 15, has a volume resistivity of less than 1 × 10^10 [Ω·cm]. Preferably, the volume resistivity of the bead filler 14 is less than 1 × 10^8 [Ω·cm].

[0081] Furthermore, the maximum thickness Gp [mm] of the carcass layer 15 in the portion that contacts the tie rubber 22 in the overlapping range 50, that is, the carcass body portion 15a in the carcass layer 15 that contacts the tie rubber 22 in the overlapping range 50, is within the range of 0.5 [mm] to 4 [mm]. Preferably, the maximum thickness Gp [mm] of the carcass layer 15 in the portion that contacts the tie rubber 22 in the overlapping range 50 is within the range of 1 [mm] to 3 [mm].

[0082] Furthermore, the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 is within the range of 3 [mm] to 40 [mm]. Preferably, the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 is within the range of 5 [mm] to 30 [mm].

[0083] Furthermore, the relationship between the maximum thickness Gb [mm] of the bead filler 14 in the wrap range 50 and the wrap amount LAP [mm] is within the range of 0.01 ≤ Gb / LAP ≤ 3.5. Preferably, the relationship between the maximum thickness Gb [mm] of the bead filler 14 in the wrap range 50 and the wrap amount LAP [mm] is within the range of 0.015 ≤ Gb / LAP ≤ 2.0.

[0084] Furthermore, the bead filler 14 has a maximum thickness Gb [mm] in the overlapping range 50 that is between 0.4 [mm] and 10 [mm]. Preferably, the maximum thickness Gb [mm] of the bead filler 14 in the overlapping range 50 is between 0.5 [mm] and 9 [mm].

[0085] Furthermore, the thickness Gbv [mm] of the bead filler 14 on a virtual line V that passes through the outermost outermost part Rwo of the rim cushion and is perpendicular to the tie rubber 22 in the meridional cross-section of the tire is within the range of 0.4 [mm] to 10 [mm].

[0086] The bead filler 14 is formed in a shape where its width in the tire width direction narrows as it moves outward in the tire radial direction. Therefore, the maximum thickness Gb of the bead filler 14 in the overlap area 50 and the thickness Gbv of the bead filler 14 on the imaginary line V are thinner than the thickness of the portion of the bead filler 14 located inward in the tire radial direction and near the bead core 11.

[0087] Furthermore, the end portion 21a of the inner liner 21 located in the bead portion 10, that is, the end portion 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. More specifically, the end portion 21a of the inner liner 21 is located inside the tire width direction of the outermost portion 11b of the bead core 11 in the tire width direction, and also inside the tire radial direction of the outermost diameter portion 11a of the bead core 11 in the tire radial direction. In this embodiment, the end portion 21a of the inner liner 21 is located inside the bead core 11 in the tire radial direction. That is, the end portion 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.

[0088] In other words, the inner liner 21 is positioned to extend inward in the tire radial 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. Thus, the inner liner 21 and the tie rubber 22, which have different lengths along the periphery, are positioned along the carcass layer 15, with the tie rubber 22 positioned between the carcass layer 15 and the inner liner 21.

[0089] The inner liner 21, arranged in this manner, has a thickness Gi within the range of 0.1 [mm] to 1.5 [mm]. In this case, the thickness Gi of the inner liner 21 is the maximum thickness of the portion of the inner liner 21 located within the overlap range 50. Preferably, the thickness Gi of the inner liner 21 is within the range of 0.3 [mm] to 1.0 [mm].

[0090] Furthermore, the tie rubber 22 has a thickness Gt within the range of 0.1 [mm] to 1.5 [mm]. In this case, the thickness Gt of the tie rubber 22 is the maximum thickness of the tie rubber 22. Preferably, the thickness Gt of the tie rubber 22 is within the range of 0.3 [mm] to 1.0 [mm].

[0091] The bead core 11, positioned in the bead portion 10, has a volume resistivity of less than 1 × 10^8 [Ω·cm]. Thus, the bead core 11 constitutes a conductive path in the bead portion 10. The bead core 11 includes a bead wire 12 and a bead insulation rubber 13 surrounding the bead wire 12. In this embodiment, the bead insulation rubber 13 has a volume resistivity of less than 1 × 10^8 [Ω·cm]. Preferably, the volume resistivity of the bead core 11 is less than 1 × 10^7 [Ω·cm].

[0092] 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.

[0093] Figure 4 is a schematic diagram of the tread section 2 shown in Figure 1. In Figure 4, the belt layer 18 is shown as only the belt ply with the widest width in the tire width direction among the multiple belt plies 181 to 183, and in the following explanation of Figure 4, the widest belt ply will be described as the belt layer 18.

[0094] The belt layer 18 arranged in the tread portion 2 has a belt cord 18a and a belt coat rubber 18b that surrounds the belt cord 18a. In the tread portion 2, the belt cord 18a and the belt coat rubber 18b constitute a conductive path in the tread portion 2. Preferably, the volume resistivity [Ω·cm] of the belt coat rubber 18b is less than 1 × 10^8 [Ω·cm].

[0095] In the tread portion 2 where the belt layer 18 is arranged, if the electrical resistance of the belt coat rubber 18b of the belt layer 18 is Rb[Ω], then 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 area where the belt layer 18 is arranged in the tire width direction.

[0096] Furthermore, the carcass layer 15 has carcass cords 16 and carcass coat rubber 17 that surrounds the carcass cords 16, and the carcass layer 15 having the carcass cords 16 and 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], then 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 area where the belt layer 18 is arranged in the tire width direction.

[0097] [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.

[0098] 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, since 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], the tie rubber 22 and the rim cushion 30 conduct electricity relatively easily, and since the tie rubber 22 is positioned overlapping with the bead filler 14, static electricity can be discharged to the road surface.

[0099] In other words, because the volume resistivity of 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 to the rim cushion 30, which has low volume resistivity. The rim cushion 30 is positioned so that the portion of the bead core 11 located on the inside in the tire width direction extends further outward in the tire diameter direction than the portion located on the outside in the tire width direction of the bead core 11. Therefore, static electricity that flows into the rim cushion 30 flows to the portion of the bead core 11 located on the outside in the tire width direction of the rim cushion 30.

[0100] The outer portion of the bead core 11 in the rim cushion 30 in the tire width direction is in contact with the outer portion of the turn-up portion 15b in the carcass layer 15 in the tire width direction. Therefore, static electricity flowing to the rim cushion 30 flows to the turn-up portion 15b in the carcass layer 15. The carcass layer 15 has the turn-up portion 15b located on the outer side of the bead filler 14 in the tire width direction, and the carcass body portion 15a located on the inner side of the bead filler 14 in the tire width direction, sandwiching the bead filler 14 from both sides in the tire width direction between the turn-up portion 15b and the carcass body portion 15a. For this reason, static electricity flowing to the turn-up portion 15b of the carcass layer 15 flows towards the carcass body portion 15a side via the bead filler 14.

[0101] In this process, the bead filler 14 narrows in width in the tire direction as it moves outward in the tire radial direction. Static electricity flowing between the turn-up portion 15b and the carcass body portion 15a of the carcass layer 15 via the bead filler 14 flows more easily in the portion of the bead filler 14 that is closer to the outer side in the tire radial direction. Therefore, static electricity that flows from the rim cushion 30 to the turn-up portion 15b of the carcass layer 15 flows mainly from the turn-up portion 15b of the carcass layer 15 to the carcass body portion 15a side via the portion of the bead filler 14 that is closer to the outer side in the tire radial direction.

[0102] Since the tie gum 22 is disposed so as to overlap with a portion of the bead filler 14 closer to the outer side in the tire radial direction through the carcass main body portion 15a of the carcass layer 15 in the tire width direction, the static electricity flowing from the turn-up portion 15b of the carcass layer 15 to the carcass main body portion 15a side through the bead filler 14 flows from the carcass main body portion 15a to the tie gum 22.

[0103] The static electricity flowing into the tie gum 22 further flows into the belt layer 18 and from the belt layer 18 into the tread rubber 3, so that it can be discharged from the tread rubber 3 to the road surface. Thereby, the static electricity generated in the vehicle is discharged to the road surface, and the charging of the vehicle due to static electricity is suppressed.

[0104] Here, the tie gum 22 overlaps with the inner liner 21 and extends to the bead portion 10. The length Lt from the tire equatorial plane CL to the end portion 22a of the tie gum 22 and the length Li from the tire equatorial plane CL to the end portion 21a of the inner liner 21 satisfy the relationship Lt < Li. Thereby, the mass of the tie gum 22 can be reduced, and thus the mass of the pneumatic tire 1 can be reduced.

[0105] Also, since the length Lt from the tire equatorial plane CL to the end portion 22a of the tie gum 22 and the length Li from the tire equatorial plane CL to the end portion 21a of the inner liner 21 satisfy the relationship Lt < Li, it is possible to make it difficult for the tie gum 22 to overlap with the rim cushion 30 in the tire meridian cross section, and the number of members overlapping with the rim cushion 30 can be reduced. Thereby, it is possible to suppress the fitting pressure from becoming too large when fitting the pneumatic tire 1 to the rim wheel due to a large amount of the tie gum 22 overlapping with the rim cushion 30.

[0106] That is, since the tie gum 22 according to the present embodiment is made of a rubber material having conductivity and thus has a relatively high rubber hardness, the tie gum 22 is less likely to elastically deform compared to the rim cushion 30. Therefore, when the tie gum 22 overlaps the rim cushion 30 with a long length, the relatively non-elastic tie gum 22 overlaps the rim cushion 30 more, which may increase the fitting pressure when the pneumatic tire 1 is fitted to the rim wheel.

[0107] On the other hand, when the length Lt from the tire equatorial plane CL to the end 22a of the tie gum 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 tie gum 22 can be made less likely to overlap the rim cushion 30. Therefore, it is possible to suppress the tie gum 22 from overlapping the rim cushion 30, or to suppress the tie gum 22 from overlapping the rim cushion 30 with a long length even when they overlap. Thereby, it is possible to suppress the fitting pressure from becoming too high when the pneumatic tire 1 is fitted to the rim wheel when a rubber material having conductivity is used for the tie gum 22.

[0108] Further, since the end 21a of the inner liner 21 is located on the inner side in the tire width direction with respect to the outermost side portion 11b of the bead core 11 in the tire width direction, the length of the inner liner 21 in the tire meridian cross-section can be shortened. Thereby, the mass of the inner liner 21 can be suppressed. Further, since the end 21a of the inner liner 21 is located on the inner side in the tire radial direction with respect to the outermost diameter portion 11a of the bead core 11 in the tire radial direction, the air pressure holding performance of the pneumatic tire 1 by the inner liner 21 can be ensured while shortening the length of the inner liner 21. Therefore, while ensuring the air permeation prevention property by the inner liner 21 and suppressing air leakage, the mass of the inner liner 21 can be suppressed. Thereby, the air pressure holding performance of the pneumatic tire 1 can be ensured and an increase in the mass of the pneumatic tire 1 can be suppressed.

[0109] In addition, since the relationship between the distance Rtg in the tire radial direction of the end portion 22a of the tie rubber 22 from the tire rotation axis and the distance Rbc in the tire radial direction of the outermost diameter portion 11a of the bead core 11 from the tire rotation axis satisfies Rbc < Rtg, the length of the tie rubber 22 can be shortened. Thereby, by suppressing the length of the tie rubber 22 and suppressing the mass of the tie rubber 22, the mass of the pneumatic tire 1 is reduced, and the overlapping of the tie rubber 22 on the rim cushion 30 is suppressed to reduce the fitting pressure when the pneumatic tire 1 is fitted to the rim wheel.

[0110] In addition, since the relationship between the distance Rtg in the tire radial direction of the end portion 22a of the tie rubber 22 from the tire rotation axis and the distance Rf in the tire radial direction of the outer end portion 14a of the bead filler from the tire rotation axis satisfies Rtg < Rf, the lap amount LAP between the tie rubber 22 and the bead filler 14 can be ensured. Thereby, when static electricity from the rim cushion 30 is transmitted to the tie rubber 22 having a volume resistivity of less than 1×10^8 [Ω·cm] through the carcass layer 15 and the bead filler 14, the width of the transmission path can be ensured, and the static electricity can flow easily from the rim cushion 30 to the tie rubber 22, thereby reducing the electrical resistance.

[0111] In addition, since the relationship between the distance Rtg in the tire radial direction of the end portion 22a of the tie rubber 22 from the tire rotation axis and the distance Rf in the tire radial direction of the outer end portion 14a of the bead filler from the tire rotation axis satisfies Rtg < Rf, and the lap amount LAP between the tie rubber 22 and the bead filler 14 is ensured, the rigidity of the bead portion 10 can be ensured. That is, by arranging the tie rubber 22 and the bead filler 14, which are relatively high-rigidity members, to overlap in the tire width direction, the high-rigidity members can be arranged in the bead portion 10 without interruption in the tire radial direction, so that the rigidity of the bead portion 10 can be ensured. Thereby, the handling stability can be ensured.

[0112] Furthermore, the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] of the carcass layer 15 in contact with the tie rubber 22 within the overlap range 50 is within the range of 0.02 ≤ Gp / LAP ≤ 4.0, which allows for a reduction in electrical resistance while suppressing an increase in the mass of the pneumatic tire 1. In other words, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] of the carcass layer 15 is Gp / LAP < 0.02, there is a risk that the overlap amount LAP between the tie rubber 22 and the bead filler 14 will become too large. In this case, the length of the tie rubber 22 will become too long, increasing the mass of the tie rubber 22 and making it difficult to reduce the mass of the pneumatic tire 1. Furthermore, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] of the carcass layer 15 is Gp / LAP > 4.0, there is a risk that the overlap amount LAP between the tie rubber 22 and the bead filler 14 will become too small. In this case, the tie rubber 22 will become too short, making it difficult to secure an electrostatic path from the rim cushion 30 to the tie rubber 22 via the bead filler 14, which may make it difficult to reduce electrical resistance.

[0113] In contrast, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] of the carcass layer 15 is within the range of 0.02 ≤ Gp / LAP ≤ 4.0, the length of the tie rubber 22 can be kept from becoming too long or too short, and an appropriate length can be achieved. This reduces the mass of the pneumatic tire 1 by suppressing the mass of the tie rubber 22, while also reducing electrical resistance by ensuring a path for static electricity to the tie rubber 22 via the bead filler 14. As a result, electrical resistance can be reduced while suppressing increases in mass and fitting pressure.

[0114] Furthermore, since the rim cushion 30 has a volume resistivity of less than 1 × 10^8 [Ω·cm], it can more reliably receive static electricity from the rim flange R and pass it from the rim cushion 30 to other components such as the carcass layer 15. As a result, electrical resistance can be reduced.

[0115] Furthermore, the relationship between the maximum thickness Gb [mm] of the bead filler 14 in the lap range 50 and the lap amount LAP [mm] is within the range of 0.01 ≤ Gb / LAP ≤ 3.5, which allows for a reduction in electrical resistance while suppressing a decrease in handling stability. In other words, if the relationship between the maximum thickness Gb [mm] of the bead filler 14 in the lap range 50 and the lap amount LAP [mm] is Gb / LAP < 0.01, the maximum thickness Gb of the bead filler 14 is too thin, which may make it difficult to ensure the rigidity of the bead filler 14. In this case, it may become difficult to ensure the rigidity of the bead portion 10, which may easily lead to a decrease in handling stability. Furthermore, if the relationship between the maximum thickness Gb [mm] of the bead filler 14 and the amount of lap LAP [mm] in the lap range 50 is Gb / LAP > 3.5, the maximum thickness Gb of the bead filler 14 is too thick, which may cause the distance between the portion of the bead core 11 located on the outer side in the tire width direction in the rim cushion 30 and the tie rubber 22 to become too large. In this case, static electricity will not flow easily between the rim cushion 30 and the tie rubber 22 via the bead filler 14, which may make it difficult to reduce electrical resistance.

[0116] In contrast, if the relationship between the maximum thickness Gb [mm] of the bead filler 14 and the amount of wrap LAP [mm] in the wrap range 50 is within the range of 0.01 ≤ Gb / LAP ≤ 3.5, it is possible to suppress the maximum thickness Gb of the bead filler 14 from becoming too thin or too thick, thereby making the maximum thickness Gb of the bead filler 14 an appropriate thickness. This makes it possible to suppress the decrease in handling stability caused by the maximum thickness Gb of the bead filler 14 becoming too thin, while also suppressing the maximum thickness Gb of the bead filler 14 from becoming too thick, thereby ensuring good electrostatic flow and reducing electrical resistance. As a result, it is possible to reduce electrical resistance while suppressing the decrease in handling stability.

[0117] Furthermore, since the thickness 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 thickness Gt of 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, and there is a risk that the inner liner 21 will 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 revealed 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, and there is a risk that the mass of the tie rubber 22 will increase, and the mass of the pneumatic tire 1 will easily increase.

[0118] 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.

[0119] Furthermore, since the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 is within the range of 3 [mm] to 40 [mm], it is possible to suppress the increase in mass of the pneumatic tire 1 while suppressing the occurrence of appearance defects such as air pockets. In other words, if the overlap amount LAP between the tie rubber 22 and the bead filler 14 is less than 3 [mm], the overlap amount LAP is too small, and there is a risk that the distance between the end 22a of the tie rubber 22 and the outer end 14a of the bead filler will become too small. In this case, because the end 22a of the tie rubber 22 and the outer end 14a of the bead filler are placed close together, it is easy for parts with large changes in rigidity to occur, and air is more likely to enter between the inner liner 21 and the carcass layer 15 during the vulcanization molding of the pneumatic tire 1, which may cause appearance defects such as air pockets. Furthermore, if the overlap amount LAP between the tie rubber 22 and the bead filler 14 is greater than 40 [mm], the overlap amount LAP is too large, which may cause the length of the tie rubber 22 to become too long. In this case, as the mass of the tie rubber 22 increases, the mass of the pneumatic tire 1 is likely to increase as well.

[0120] In contrast, if the overlap amount LAP between the tie rubber 22 and the bead filler 14 is within the range of 3 [mm] to 40 [mm], it is possible to ensure the distance between the end 22a of the tie rubber 22 and the outer end 14a of the bead filler, while also preventing the length of the tie rubber 22 from becoming too long. As a result, it is possible to suppress the occurrence of cosmetic defects in the pneumatic tire 1, such as air pockets, while also suppressing an increase in the mass of the pneumatic tire 1.

[0121] Furthermore, since the maximum thickness Gp [mm] of the carcass layer 15 in contact with the tie rubber 22 in the lap range 50 is within the range of 0.5 [mm] to 4 [mm], it is possible to suppress the increase in mass while suppressing the decrease in handling stability. In other words, if the maximum thickness Gp of the carcass layer 15 in contact with the tie rubber 22 in the lap range 50 is less than 0.5 [mm], the maximum thickness Gp of the carcass layer 15 is too thin, which may make it difficult to ensure the rigidity of the carcass layer 15. In this case, the rigidity of the pneumatic tire 1 is likely to decrease, which may lead to a decrease in handling stability. Also, if the maximum thickness Gp of the carcass layer 15 in contact with the tie rubber 22 in the lap range 50 is greater than 4 [mm], the maximum thickness Gp of the carcass layer 15 is too thick, which may lead to an increase in the mass of the carcass layer 15. In this case, as the mass of the carcass layer 15 increases, the mass of the pneumatic tire 1 may also increase.

[0122] In contrast, if the maximum thickness Gp of the carcass layer 15 in the portion in contact with the tire rubber 22 within the lap range 50 is within the range of 0.5 [mm] to 4 [mm], it is possible to suppress the maximum thickness Gp of the carcass layer 15 from becoming too thin or too thick, thereby making the maximum thickness Gp of the carcass layer 15 an appropriate thickness. This makes it possible to suppress the decrease in handling stability caused by a decrease in the rigidity of the carcass layer 15 due to the maximum thickness Gp of the carcass layer 15 becoming too thin, while also suppressing the increase in mass caused by the maximum thickness Gp of the carcass layer 15 becoming too thick. As a result, it is possible to suppress the increase in mass of the pneumatic tire 1 while suppressing the decrease in handling stability.

[0123] Furthermore, since the maximum thickness Gb [mm] of the bead filler 14 in the lap range 50 is within the range of 0.4 [mm] to 10 [mm], it is possible to suppress the increase in mass while suppressing the decrease in handling stability. In other words, if the maximum thickness Gb of the bead filler 14 in the lap range 50 is less than 0.4 [mm], the maximum thickness Gb of the bead filler 14 is too thin, which may make it difficult to ensure the rigidity of the bead filler 14. In this case, it may become difficult to ensure the rigidity of the bead section 10, which may easily lead to a decrease in handling stability. Also, if the maximum thickness Gb of the bead filler 14 in the lap range 50 is greater than 10 [mm], the maximum thickness Gb of the bead filler 14 is too thick, which may easily lead to an increase in the mass of the bead filler 14. In this case, as the mass of the bead filler 14 increases, the mass of the pneumatic tire 1 may easily increase.

[0124] In contrast, if the maximum thickness Gb of the bead filler 14 in the lap range 50 is within the range of 0.4 [mm] to 10 [mm], it is possible to suppress the maximum thickness Gb of the bead filler 14 from becoming too thin or too thick, thereby making the maximum thickness Gb of the bead filler 14 an appropriate thickness. This suppresses the decrease in handling stability caused by a decrease in the rigidity of the bead filler 14 due to the maximum thickness Gb of the bead filler 14 becoming too thin, while also suppressing the increase in mass caused by the maximum thickness Gb of the bead filler 14 becoming too thick. As a result, it is possible to suppress the increase in mass of the pneumatic tire 1 while suppressing the decrease in handling stability.

[0125] Furthermore, since the bead filler 14 has a volume resistivity of less than 1 × 10^10 [Ω·cm], it can facilitate the flow of static electricity from the rim cushion 30 to the turn-up portion 15b of the carcass layer 15 towards the carcass body portion 15a, and thus facilitate the flow of static electricity towards the tie rubber 22. As a result, a reduction in electrical resistance can be achieved more reliably.

[0126] 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]. Therefore, the electrical resistance from the tie rubber 22 to the tread rubber 3 can be reduced by the carcass layer 15 and the belt coat rubber 18b. As a result, static electricity flowing from the rim cushion 30 side to the belt layer 18 side by the tie rubber 22 can be directed to the tread rubber 3 by the carcass layer 15 and the belt coat rubber 18b, and then released from the tread rubber 3 to the road surface. As a result, electrical resistance can be reduced more reliably, and static electricity buildup on the vehicle can be suppressed.

[0127] [Differentiation] In the above-described embodiment, the end 22a of the tie rubber 22 is located radially outward of the outermost inner part Rwi of the rim cushion 30. However, the end 22a of the tie rubber 22 may be located radially inward of the outermost inner part Rwi of the rim cushion 30. For example, if the outermost inner part Rwi of the rim cushion is located radially outward of the outermost diameter portion 11a of the bead core 11, the end 22a of the tie rubber 22 may be located radially outward of the outermost diameter portion 11a of the bead core 11 and radially inward of the outermost inner part Rwi of the rim cushion. Regardless of the relative positional relationship between the end 22a of the tie rubber 22 and the outermost inner part Rwi of the rim cushion, by positioning the tie rubber 22 radially outward of the outermost diameter portion 11a of the bead core 11, the length of the tie rubber 22 can be shortened, thereby reducing its mass.

[0128] Furthermore, in the above-described embodiment, the outermost part Rwo of the rim cushion is located radially outward from the end 22a of the tie rubber 22, but the outermost part Rwo of the rim cushion may be located radially inward from the end 22a of the tie rubber 22. Even if the outermost part Rwo of the rim cushion is located radially inward from the end 22a of the tie rubber 22, if the volume resistivity of the bead filler 14 is low or the bead filler 14 is thin in the tire width direction, it is possible to facilitate the flow of static electricity from the turn-up portion 15b side of the carcass layer 15 to the carcass body portion 15a side via the bead filler 14. This ensures a path for static electricity from the rim cushion 30 to the tie rubber 22, thereby reducing electrical resistance.

[0129] Furthermore, the embodiments and modifications described above may be combined as appropriate. In addition, although the embodiments described above used pneumatic tire 1 as an example of a tire according to the present invention, the tire according to the present invention may be other than 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 with gas.

[0130] [Examples] Figures 5A and 5B are charts showing the results of performance evaluation tests of pneumatic tires. Below, we will describe the performance evaluation tests conducted on the above-mentioned pneumatic tire 1, comparing it with a conventional pneumatic tire, the pneumatic tire 1 according to the present invention, and a comparative example pneumatic tire used for comparison with the pneumatic tire 1 according to the present invention. The performance evaluation tests included the electrical resistance of the pneumatic tire, the tire mass (the mass of the pneumatic tire), the fitting pressure when fitting the pneumatic tire to the rim wheel, the appearance performance of the pneumatic tire, and the handling stability when driving a vehicle equipped with the pneumatic tire.

[0131] The performance evaluation tests were conducted using pneumatic tires with a nominal tire size of 235 / 60R18 as specified by JATMA. For the evaluation of the electrical resistance of the pneumatic tires, the electrical resistance [Ω] of the test tires was measured using an R8340A ultra-high resistance meter manufactured by Advantest Corporation, based on the measurement conditions specified by JATMA.

[0132] Furthermore, the tire mass evaluation test involved measuring the mass of each test tire and using an index evaluation method where the reciprocal of the measured mass was set to 100, as described later in the conventional example. A higher index evaluation value indicates a lighter tire mass and a better evaluation of the tire mass.

[0133] Furthermore, the evaluation test of the fitting pressure when fitting a pneumatic tire to a rim wheel was conducted by fitting the test tire to a rim wheel with a rim size of 18 x 7.0J, inflating the test tire with air at a supply pressure of 500 [kPa], and then assembling the test tire into the rim wheel. During the process of assembling the test tire into the rim wheel, the air inflation was temporarily stopped at the moment the bead of the test tire crossed 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, where the reciprocal of the measured air pressure was set to 100, as described later for the conventional example. A higher index value indicates that the air pressure when fitting the pneumatic tire to the rim wheel is lower, and that the performance in terms of fitting pressure is superior.

[0134] Furthermore, for appearance performance, more than 1000 test tires were vulcanized and molded. The number of test tires exhibiting appearance defects, such as air pockets or the shape of the carcass cords appearing on the inner surface of the tire, was counted during visual inspection of the vulcanized test tires to calculate the appearance defect rate. The reciprocal of the calculated appearance defect rate was then used as an index evaluation, with the conventional example described later set to 100. A higher index evaluation value indicates a lower appearance defect rate and superior performance in terms of appearance defects.

[0135] Furthermore, the handling stability evaluation test was conducted by mounting test tires, which were mounted on rim wheels with a rim size of 18 x 7.0J, onto a test vehicle. The test vehicle was driven on a test course with a flat, dry surface at speeds ranging from 10 km / h to 180 km / h, and a test driver performed a subjective evaluation of steering performance during lane changes and cornering, as well as stability during straight-line driving. The handling stability evaluation was performed using an index evaluation based on the test driver's subjective evaluation, with the conventional example described later set at 100. A higher index evaluation value indicates better handling stability on dry surfaces.

[0136] Performance evaluation tests were conducted on 23 types of pneumatic tires, including a conventional pneumatic tire (an example of a conventional pneumatic tire), Examples 1 to 20 (pneumatic tire 1 according to the present invention), and Comparative Examples 1 and 2 (pneumatic tires compared to pneumatic tire 1 according to the present invention). Of these, in the conventional 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 are in the relationship Lt > Li. In addition, 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 bead filler 14 and the maximum thickness Gp [mm] in the overlap range 50 of the carcass layer 15 in contact with the tie rubber 22 does not satisfy 0.02 ≤ Gp / LAP ≤ 4.0.

[0137] On the other hand, in all of Examples 1 to 20 which are examples of the pneumatic tire 1 according to the present invention, 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 lap amount LAP [mm] between the tread rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] of the portion in the lap range 50 of the carcass layer 15 that contacts the tread rubber 22 are within the range of 0.02 ≦ Gp / LAP ≦ 4.0. Further, the pneumatic tire 1 according to Examples 1 to 20 has the relationship (Gb / LAP) between the maximum thickness Gb [mm] of the bead filler 14 in the lap range 50 and the lap amount LAP [mm], the thickness Gt [mm] of the tread rubber 22, the lap amount LAP [mm] between the tread rubber 22 and the bead filler 14, the maximum thickness Gp [mm] of the portion in the lap range 50 of the carcass layer 15 that contacts the tread rubber 22, the maximum thickness Gb [mm] of the bead filler 14 in the lap range 50, the volume resistivity [Ω·cm] of the bead filler 14, the electrical resistance Rb [Ω] of the belt coat rubber 18b, and the electrical resistance Rpc [Ω] of the carcass layer 15 are all different.

[0138] As a result of conducting an evaluation test using these pneumatic tires 1, as shown in FIGS. 5A and 5B, it was found that the pneumatic tires 1 according to Examples 1 to 20 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 20 can reduce the electrical resistance while suppressing an increase in the mass and the fitting pressure.

[0139] 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 in each of the pair of bead portions, A bead filler disposed radially outside of the bead core in the tire diameter direction, 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 spanning between the pair of bead portions, A belt layer disposed on the outer side in the tire radial direction of the carcass layer, 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, Tire rubber disposed between the carcass layer and the inner liner, Comprising, 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 inside the tire width direction from the outermost side in the tire width direction of the bead core and inside the tire radial direction from 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 tire rubber is Rtg, the distance in the tire radial direction from the tire rotation axis to the outer end of the bead filler, which is the outer end of the bead filler on the outer side in the tire radial direction, is Rf, and the distance in the tire radial direction from the tire rotation axis to the outermost diameter part of the bead core is Rbc, the end of the tire rubber, the outer end of the bead filler, and the outermost diameter part of the bead core satisfy the relationship Rbc < Rtg < Rf, The wrap amount LAP [mm] of the tire rubber and the bead filler, indicated by the distance along the periphery between the end of the tire rubber and the outer end of the bead filler, and the maximum thickness Gp [mm] of the portion in contact with the tire rubber in the wrap range, which is the range along the periphery between the end of the tire rubber and the outer end of the bead filler in the carcass layer, satisfy the range of 0.02 ≦ Gp / LAP ≦ 4.0, The tire rubber is characterized in that the volume resistivity is less than 1 × 10^8 [Ω·cm]. Invention [2] The tire according to the invention [1], wherein the rim cushion has a volume resistivity of less than 1 × 10^8 [Ω·cm]. Invention [3] The tire according to Invention [1] or Invention [2], wherein the relationship between the maximum thickness Gb [mm] of the bead filler in the lap range and the lap amount LAP [mm] is within the range of 0.01 ≤ Gb / LAP ≤ 3.5. invention [4] The tire according to any one of inventions [1] to [3], wherein the rubber tie has a thickness in the range of 0.1 [mm] to 1.5 [mm]. invention [5] The tire according to any one of inventions [1] to [4], wherein the lap amount LAP [mm] between the tie rubber and the bead filler is in the range of 3 [mm] or more and 40 [mm] or less. invention [6] The tire according to any one of Inventions [1] to [5], wherein the carcass layer has a maximum thickness Gp [mm] in the portion in contact with the tie rubber within the wrap range that is in the range of 0.5 [mm] to 4 [mm]. invention [7] The tire according to any one of inventions [1] to [6], wherein the bead filler has a maximum thickness Gb [mm] in the lap range that is in the range of 0.4 [mm] to 10 [mm]. invention [8] The tire according to any one of inventions [1] to [7], wherein the bead filler has a volume resistivity of less than 1 × 10^10 [Ω·cm]. invention[9] When the electrical resistance of the carcass layer is Rpc [Ω] and the electrical resistance of the belt coating 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 inventions [1] to [8], wherein the electrical resistance Rb[Ω] of the belt coating rubber satisfies Rb[Ω] < 1 × 10^8[Ω]. [Explanation of Symbols]

[0140] 1. Pneumatic tire 2 Tread section 2a Tire contact surface 3 Tread Rubber 3a Cap Tread 3b Undertread 4. Sidewall section 5 Sidewall rubber 10 Bead section 11 Bead core 11a Outermost diameter part 11b Outermost part 12 bead wires 13 Bead Insulation Rubber 14 Bead Filler 14a Bead filler outer end 15. Carcass layer 15a Carcass main body 15b Turn-up section 16 Carcass Chord 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 Inner surface of tire 30 Rim Cushion 31 Rim cushion rubber 32 Rim fitting surface 35 Bead Toe 36 Bead Base 40 Earth Red 50 Wrap range

Claims

1. A pair of bead portions are arranged on both sides of the tire's equatorial plane in the tire width direction, A bead core provided in each of the pair of bead portions, A bead filler is positioned on the radially outer side of the bead core, The rim fitting surface in the bead portion is formed and is arranged from the inner side in the tire width direction to the outer side in the tire width direction of the bead core, and is a rim cushion. At least one carcass layer is stretched between the pair of bead portions, A belt layer is disposed on the outer side of the carcass layer in the radial direction of the tire, The tread rubber arranged on the radially outer side of the belt layer, An inner liner arranged on the inner surface of the tire along the carcass layer, A tie rubber is disposed between the carcass layer and the inner liner, Equipped with, The inner liner and the tie rubber satisfy the relationship Lt < Li between the length Lt from the tire's equatorial plane to the end of the tie rubber along the periphery and the length Li from the tire's equatorial plane to the end of the inner liner along the periphery. The end of the inner liner is located inward in the tire width direction from the outermost part of the bead core in the tire width direction, and inward in the tire diameter direction from the outermost diameter part of the bead core in the tire diameter direction. Let Rtg be the distance in the tire radial direction from the tire rotation axis to the end of the tie rubber, let Rf be the distance in the tire radial direction from the tire rotation axis to the outer end of the bead filler, which is the outermost end of the bead filler in the tire radial direction, and let Rbc be the distance in the tire radial direction from the tire rotation axis to the outermost diameter portion of the bead core. Then the relationship Rbc < Rtg < Rf is satisfied between the end of the tie rubber, the outer end of the bead filler, and the outermost diameter portion of the bead core. The relationship between the overlap amount LAP [mm] between the tie rubber and the bead filler, which is the distance along the periphery between the end of the tie rubber and the outer end of the bead filler, and the maximum thickness Gp [mm] of the carcass layer in the overlap range, which is the range along the periphery between the end of the tie rubber and the outer end of the bead filler, is within the range of 0.02 ≤ Gp / LAP ≤ 4.

0. The aforementioned tire rubber is characterized in that its volume resistivity is less than 1 × 10⁸ [Ω·cm].

2. The tire according to claim 1, wherein the rim cushion has a volume resistivity of less than 1 × 10⁸ [Ω·cm].

3. The tire according to claim 1, wherein the relationship between the maximum thickness Gb [mm] of the bead filler in the lap range and the lap amount LAP [mm] is within the range of 0.01 ≤ Gb / LAP ≤ 3.

5.

4. The tire according to claim 1, wherein the tie rubber has a thickness within the range of 0.1 [mm] to 1.5 [mm].

5. The tire according to claim 1, wherein the overlap amount LAP [mm] between the tie rubber and the bead filler is within the range of 3 [mm] or more and 40 [mm] or less.

6. The tire according to claim 1, wherein the carcass layer has a maximum thickness Gp [mm] in the portion in contact with the tie rubber within the wrap range that is between 0.5 [mm] and 4 [mm].

7. The tire according to claim 1, wherein the bead filler has a maximum thickness Gb [mm] in the lap range that is between 0.4 [mm] and 10 [mm].

8. The tire according to claim 1, wherein the bead filler has a volume resistivity of less than 1 × 10¹⁰ [Ω·cm].

9. When the electrical resistance of the carcass layer is Rpc [Ω] and the electrical resistance of the belt coating 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 electrical resistance Rb [Ω] of the belt coating rubber satisfies Rb [Ω] < 1 × 10^8 [Ω].

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