tire

Abstract

To provide a tire capable of reducing electrical resistance while suppressing deterioration of rolling resistance and increase in fitting pressure. [Solution] The length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 along the periphery and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 along the periphery satisfy the relationship Lt≧Li, the tie rubber 22 contacts the rim cushion 30, the end 22a of the tie rubber 22 is located within the range in the tire radial direction between the innermost rim cushion Rri and the outermost outer rim cushion Rwo, the distance Hout in the tire radial direction between the innermost rim cushion Rri and the outermost outer rim cushion Rwo is in the range 0.02SH≦Hout≦0.70SH relative to the tire cross-sectional height SH, the tie rubber 22 has a volume resistivity of less than 1×10^8 [Ω·cm], and the rim cushion 30 has a volume resistivity of less than 1×10^8 [Ω·cm].

Description

[Technical Field]

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

[0002] In recent years, there has been an increasing demand for fuel-efficient tires due to environmental issues and other factors. One method for improving tire fuel efficiency is to increase the silica content in the rubber compounds that make up the tire's cap tread, undertread, sidewall rubber, etc., thereby reducing the tire's rolling resistance. However, because silica has high insulating properties, increasing the silica content in the rubber compound used in the cap tread, etc., increases the electrical resistance of the cap tread, etc., and reduces the tire's anti-static performance. When the tire's anti-static performance decreases, static electricity generated during vehicle operation is more likely to accumulate, which can easily cause radio interference, such as radio noise.

[0003] For this reason, some conventional pneumatic tires are equipped with a conductive member with low electrical resistance to improve static electricity suppression performance and make it easier to release static electricity generated on a vehicle while the vehicle is running onto the road surface. For example, Patent Document 1 discloses that a conductive layer with low electrical resistivity is disposed between the carcass layer and the inner liner, extending from the bead portion to the belt layer, thereby improving the static electricity suppression performance of the tire. Patent Document 1 also discloses an example in which the conductive layer is made of a conductive rubber material and doubles as a tie rubber disposed around the entire circumference of the tire cavity. [Prior art documents] [Patent documents]

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

[0005] When using a tie rubber made of conductive rubber material to reduce electrical resistance, it is important to position the tie rubber in contact with the rim cushion. However, if the tie rubber overlaps the rim cushion for a long distance, rolling resistance may be adversely affected. Furthermore, because tie rubber made of conductive rubber material has a high carbon content and is relatively hard, if the tie rubber overlaps the rim cushion for a long distance, the mating pressure when mating the tire to the rim wheel may be increased. For these reasons, it is extremely difficult to reduce electrical resistance without adversely affecting rolling resistance or increasing mating pressure.

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

[0007] In order to solve the above-mentioned problems and achieve the object, a tire according to the present invention comprises a pair of bead portions arranged on both sides of a tire equatorial plane in the tire width direction, a bead core provided in each of the pair of bead portions, a rim cushion that constitutes a rim fitting surface of the bead portion and is arranged from the inner side in the tire width direction of the bead core to the outer side in the tire width direction, at least one carcass layer that is bridged between the pair of bead portions, a belt layer that is arranged on the outer side in the tire radial direction of the carcass layer, a tread rubber that is arranged on the outer side in the tire radial direction of the belt layer, an inner liner that is arranged on an inner surface of the tire along the carcass layer, and a tie rubber that is arranged between the carcass layer and the inner liner, wherein the inner liner and the tie rubber have a length Lt from the tire equatorial plane to an end of the tie rubber along the periphery and a width Lt from the tire equatorial plane to the periphery. the length Li along the fringe to the end of the inner liner satisfies the relationship Lt≧Li, the tie rubber contacts the rim cushion at at least one of the pair of bead portions, the end of the tie rubber is located within a range in the tire radial direction between the innermost rim cushion portion, which is the end of the rim cushion on the inner side in the tire radial direction, and the outermost rim cushion portion, which is the end of the rim cushion on the outer side in the tire width direction of the bead core, the distance Hout in the tire radial direction between the innermost rim cushion portion and the outermost rim cushion portion, where SH is the tire cross-sectional height, is within the range of 0.02SH≦Hout≦0.70SH, the tie rubber has a volume resistivity of less than 1×10^8 [Ω·cm], and the rim cushion has a volume resistivity of less than 1×10^8 [Ω·cm].

[0008] Furthermore, in the above tire, it is preferable that the distance Hin in the tire radial direction between the innermost rim cushion inner side, which is the outermost end of the rim cushion in the tire radial direction at a position on the inner side of the bead core in the tire width direction, and the innermost rim cushion inner side, is within the range of 0.02SH≦Hin≦0.70SH, relative to the tire cross-sectional height SH.

[0009] Also, in the above tire, when the lap amount LAPi between the inner liner and the rim cushion is indicated by the distance between the end of the inner liner and the outermost part inside the rim cushion, and the lap amount LAPi in the state where the inner liner and the rim cushion overlap is indicated as positive, and the lap amount LAPi in the state where the inner liner and the rim cushion do not overlap is indicated as negative, it is preferable that -5 [mm] < LAPi < +30 [mm].

[0010] Also, in the above tire, it is preferable that the lap amount LAPr between the part of the tie rubber that contacts the rim cushion and the rim cushion in the tie rubber is within the range of 0.1 [mm] ≤ LAPr ≤ 50.0 [mm].

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

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

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

[0014] Furthermore, in the above tire, the rim cushion outer surface, which is the face of the rim cushion on the outside in the tire width direction, has a convex portion that protrudes outward in the tire width direction, within a range between a position corresponding to the outermost diameter part of the bead core in the tire radial direction and a position corresponding to the innermost diameter part of the bead core in the tire radial direction, and when the electrical resistance of the convex portion is Rs [Ω] and the electrical resistance of the rim cushion is Rr [Ω], it is preferable that the relationship between the electrical resistance Rs [Ω] of the convex portion and the electrical resistance Rr [Ω] of the rim cushion satisfies Rs [Ω]≦Rr [Ω].

[0015] In addition, in the above tire, it is preferable that the length Ls [mm] of the convex portion in the tire circumferential direction, relative to the length L [mm] of one circumference in the tire circumferential direction at the position of the inner part of the convex portion in the tire radial direction, satisfies the relationship Ls / L≧0.1.

[0016] In addition, in the above tire, it is preferable that the tie rubber and the inner liner intersect at positions on the tire radial inside of the bead core with respect to an imaginary line that is tangent to the innermost portion of the bead core in the tire width direction and extends in the tire radial direction, and that the relationship between the thickness Gtt [mm] of the tie rubber and the thickness Git [mm] of the inner liner at the positions where they intersect with the imaginary line satisfies 0.1 Git ≦ Gtt ≦ 0.9 Git.

[0017] In addition, in the above tire, it is preferable that the tie rubber and the inner liner intersect with an imaginary line extending in the tire radial direction, tangent to the outermost portion of the bead core in the tire width direction, at a position on the tire radial inside of the bead core, and that the relationship between the thickness Gth [mm] of the tie rubber and the thickness Gih [mm] of the inner liner at the position where they intersect with the imaginary line satisfies 0.1 Gih≦Gth≦0.9 Gih.

[0018] In addition, it is preferable that the tire has an earth tread having a volume resistivity of less than 1×10^8 [Ω·cm], penetrating the tread rubber to contact the belt layer and exposed on the surface of the tread rubber. [Effects of the Invention]

[0019] The tire according to the present invention has an effect of being able to reduce electrical resistance while suppressing deterioration of rolling resistance and increase in fitting pressure. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment. [Figure 2] FIG. 2 is a detailed view of a region on one side from the tire equatorial plane in the tire width direction in FIG. [Figure 3] FIG. 3 is a detailed view of the bead portion shown in FIG. [Figure 4] FIG. 4 is a detailed view of the periphery of the bead core shown in FIG. 3, and is an explanatory view of the conductive path including the bead core. [Figure 5] FIG. 5 is a schematic diagram of the tread portion shown in FIG. [Figure 6] FIG. 6 is an explanatory diagram showing a state in which the inner liner overlaps the rim cushion. [Figure 7] FIG. 7 is an explanatory diagram showing a configuration in which the inner liner does not overlap the rim cushion. [Figure 8] FIG. 8 is a detailed view of a bead portion showing a modified example of the pneumatic tire according to the embodiment, in which a protrusion is arranged on the outer surface of the rim cushion. [Figure 9] FIG. 9 is a view taken along the arrow BB in FIG. 8, and is a schematic diagram showing an example of a convex portion. [Figure 10] FIG. 10 is a view taken along the arrow BB in FIG. 8, and is a schematic diagram showing an example of a convex portion. [Figure 11]FIG. 11 is a schematic diagram showing a modified example of the pneumatic tire according to the embodiment, in which an inner liner and a tie rubber are arranged from the inner side in the tire width direction to the outer side in the tire width direction at a position on the inner side in the tire radial direction of a bead core. [Figure 12] FIG. 12 is a schematic diagram showing a modified example of the pneumatic tire according to the embodiment, in which the bead core shown in FIG. 11 is substantially circular. [Figure 13A] FIG. 13A is a chart showing the results of a performance evaluation test of a pneumatic tire. [Figure 13B] FIG. 13B is a chart showing the results of a performance evaluation test of a pneumatic tire. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of a tire according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are replaceable and easily conceivable by a person skilled in the art, or those that are substantially the same.

[0022] [Embodiment] [Pneumatic tires] In the following description, a pneumatic tire 1 will be used as an example of a tire according to the present invention. The pneumatic tire 1, which is an example of a tire, can be filled with air, an inert gas such as nitrogen, or other gases.

[0023] In the following description, the tire radial direction refers to the direction perpendicular to the tire rotational axis (not shown), which is the rotational axis of the pneumatic tire 1, the tire radial inner side refers to the side toward the tire rotational axis in the tire radial direction, and the tire radial outer side refers to the side away from the tire rotational axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotational axis as the central axis. The tire width direction refers to the direction parallel to the tire rotational axis, the tire width inner side refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the tire width outer side 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 rotational axis and passes through the center of the tire width of the pneumatic tire 1, and the tire equatorial plane CL coincides in position in the tire width direction with the tire width centerline, which is the center position of the pneumatic tire 1 in the tire width direction. The tire width is the width in the tire width direction between the portions located outermost in the tire width direction, that is, the distance in the tire width direction between the portions farthest from the tire equatorial plane CL. The tire equator line refers to a line that is on the tire equatorial plane CL and extends along the tire circumferential direction of the pneumatic tire 1. In the following description, the tire meridian cross section refers to a cross section of the tire cut by a plane that includes the tire rotation axis.

[0024] 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire 1 according to an embodiment. The figure shows one side region in the tire radial direction. The figure also shows a radial tire for passenger cars as an example of a pneumatic tire.

[0025] A 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 a tie rubber 22. Of these, the pair of sidewall portions 4, 4 and the pair of bead portions 10, 10 are arranged one on each side of the tire equatorial plane CL in the tire width direction.

[0026] The pair of bead portions 10, 10 are located radially inward of the pair of sidewall portions 4, 4, and each has a bead core 11, a bead filler 14, and a rim cushion 30. That is, the pair of bead cores 11, 11, the pair of bead fillers 14, 14, and the pair of rim cushions 30, 30 are arranged on both sides of the tire equatorial plane CL in the tire width direction.

[0027] The pair of bead cores 11, 11 are annular members formed by bundling a plurality of bead wires and form the cores of the pair of bead portions 10, 10. The pair of bead fillers 14, 14 are respectively arranged on the outer sides of the pair of bead cores 11, 11 in the tire radial direction to reinforce the bead portion 10.

[0028] The carcass layer 15 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass plies stacked together, and is toroidally spanned between a pair of bead portions 10, 10 located on both sides in the tire width direction to form the tire framework. The carcass ply of the carcass layer 15 is formed by coating multiple carcass cords made of steel or organic fiber material such as aramid, nylon, polyester, or rayon with coating rubber and rolling them. The carcass ply of the carcass layer 15 has a carcass angle, defined as the inclination angle of the extension direction of the carcass cords with respect to the tire circumferential direction, in the range of 80 degrees to 95 degrees in absolute value.

[0029] In this embodiment, the carcass layer 15 has a single-layer structure and is continuously laid between the bead cores 11, 11 on both sides in the tire width direction. Both end portions of the carcass layer 15 are wound back and secured to the outer side in the tire width direction so as to enclose the bead cores 11 and the bead fillers 14. That is, the carcass layer 15 is wound back near both end portions in a tire meridian cross section from the inner side in the tire width direction of the bead cores 11 and the bead fillers 14 to the inner side in the tire radial direction, and then wound back to the outer side in the tire width direction.

[0030] For this reason, the carcass layer 15 has a carcass main body portion 15a disposed between the pair of bead portions 10, and a turnup portion 15b formed continuously from the carcass main body portion 15a and folded back from the inner side in the tire width direction of the bead core 11 to the outer side in the tire width direction. The carcass main body portion 15a here is a portion formed in the carcass layer 15 between the inner sides in the tire width direction of the pair of bead cores 11, and the turnup portion 15b is formed continuously from the carcass main body portion 15a on the inner side in the tire width direction of the bead core 11, and is a portion folded back through the inner side in the tire radial direction of the bead core 11 to the outer side in the tire width direction. The bead filler 14 is disposed on the inner side in the tire width direction of the turnup portion 15b, which is the portion folded back to the outer side in the tire width direction of the bead core 11, and on the outer side in the tire radial direction of the bead core 11.

[0031] In the carcass ply of the carcass layer 15 formed in this manner, the volume resistivity of the carcass coat rubber that coats the carcass cords is preferably less than 1×10^8 [Ω·cm].

[0032] The volume resistivity (volume specific resistance) is measured based on JIS K6271, "Vulcanized rubber and thermoplastic rubber - Determination of volume resistivity and surface resistivity." Generally, if the volume resistivity is less than 1 x 10^8 [Ω·cm] or the surface resistivity is less than 1 x 10^8 [Ω / cm], the material can be said to have conductivity that can suppress static electricity buildup.

[0033] The pair of rim cushions 30, 30 possessed by the pair of bead portions 10, 10 are respectively arranged on the tire radially inner side of the bead cores 11, 11 on both sides in the tire width direction and the turned-up portion of the carcass layer 15. More specifically, the rim cushions 30 are arranged at least from the tire widthwise inner side of the bead core 11 to the tire widthwise outer side. That is, the rim cushions 30 are arranged from the tire widthwise inner side of the bead core 11 of the bead portion 10, passing through the tire radially inner side of the bead core 11, to the tire widthwise outer side of the bead core 11.

[0034] The rim cushion 30 arranged in this manner is the part that comes into contact with the rim flange R of the rim wheel when the pneumatic tire 1 is mounted on the rim wheel, and constitutes the contact surface of the bead portion 10 that comes into contact with the rim flange R. Of the contact surface of the rim cushion 30 with the rim flange R, the part that forms the inner circumferential surface of the rim cushion 30 constitutes the rim fitting surface 32 of the bead portion 10 that fits into the rim wheel.

[0035] The rim cushion 30 is made up of a rubber member, rim cushion rubber 31. The rim cushion 30 has a volume resistivity of less than 1×10^8 [Ω·cm], that is, the rim cushion rubber 31 that makes up the rim cushion 30 has a volume resistivity of less than 1×10^8 [Ω·cm]. It is more preferable that the volume resistivity of the rim cushion 30 be less than 1×10^7 [Ω·cm].

[0036] The rim cushion rubber 31 has a tan δ value at 60° C. in the range of 0.085 to 0.35, and a rubber hardness Hs in the range of 35 to 111.

[0037] The tan δ value at 60°C is measured using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. under conditions of an initial strain of 10%, an amplitude of ±0.5%, and a frequency of 20 Hz. Rubber hardness Hs is measured at a temperature of 20°C in accordance with JIS K6253.

[0038] The rim cushion 30 may also have components other than the rim cushion rubber 31. For example, the rim cushion 30 may include a chafer, which is a component made of a fiber material or a rubber component, that prevents the carcass layer 15 from coming into contact with the rim flange R and being damaged when the pneumatic tire 1 is fitted onto a rim wheel.

[0039] The belt layer 18 has one or more belt plies extending in the tire width direction, and in this embodiment, multiple belt plies 181 to 183 are laminated. That is, in this embodiment, the belt layer 18 is configured by laminating a pair of cross belts 181, 182 and a belt cover 183 in the tire radial direction, and is disposed radially outward of the carcass layer 15 and wound around the outer periphery of the carcass layer 15. The pair of cross belts 181, 182 are configured by coating a plurality of belt cords made of steel or organic fiber material with coating rubber and rolling them, and the belt angle, which is the inclination angle of the extension direction of the belt cords with respect to the tire circumferential direction, is within the range of 20 degrees to 65 degrees in absolute value. Furthermore, the pair of cross belts 181, 182 have a so-called cross-ply structure in which the belt angles have opposite signs to each other and are laminated such that the extension directions of the belt cords cross each other. That is, the inclination directions of the belt cords of the pair of cross belts 181, 182 in the tire width direction relative to the tire circumferential direction are opposite to each other. The belt cover 183 is formed by rolling a plurality of cords made of steel or organic fiber material covered with coated rubber, and the belt angle is in the range of 0 degrees to 10 degrees in absolute value. The belt cover 183 is also arranged by being layered on the outer side of the cross belts 181, 182 in the tire radial direction.

[0040] The tread portion 2 is configured with tread rubber 3, which is a rubber composition, and is arranged radially outward of the carcass layer 15 and the belt layer 18, and is exposed at the outermost portion in the radial direction of the pneumatic tire 1. Therefore, the outer peripheral surface of the tread portion 2 forms part of the contour of the pneumatic tire 1, and a plurality of grooves, such as circumferential main grooves (not shown) and lug grooves (not shown), that extend in the circumferential direction of the tire are formed in the tread portion 2. In addition, the tread rubber 3 that configures the tread portion 2 has a cap tread 3a and an undertread 3b.

[0041] The cap tread 3a is a rubber member located at the outermost position of the tread portion 2 in the tire radial direction and constituting the tire contact patch 2a. It may have a single-layer structure (see FIG. 1) or a multi-layer structure (not shown). The tan δ value of the cap tread 3a at 60°C is preferably 0.25 or less. The volume resistivity of the cap tread 3a is preferably 1×10^8 Ω·cm or more, more preferably 1×10^10 Ω·cm or more, and even more preferably 1×10^12 Ω·cm or more. These properties reduce the rolling resistance of the pneumatic tire 1. A cap tread 3a with such a volume resistivity is produced by using a low-heat-generating compound with a low carbon content and reinforcing it with an increased silica content.

[0042] The undertread 3b is a member laminated on the inner side of the cap tread 3a in the tire radial direction. The volume resistivity of the undertread 3b is preferably lower than the volume resistivity of the cap tread 3a.

[0043] Each of the pair of sidewall portions 4, 4 includes a sidewall rubber 5, and the pair of sidewall rubbers 5, 5 of the pair of sidewall portions 4, 4 are disposed on the outer side of the carcass layer 15 in the tire width direction. The tan δ value of the sidewall rubber 5 at 60°C is preferably 0.20 or less. The volume resistivity of the sidewall rubber 5 is preferably 1×10^8 [Ω·cm] or more, more preferably 1×10^10 [Ω·cm] or more, and even more preferably 1×10^12 [Ω·cm] or more. This reduces the rolling resistance of the pneumatic tire 1. The sidewall rubber 5 with such a volume resistivity is produced by using a low-heat-generating compound with a low carbon content and reinforcing it with an increased silica content.

[0044] Although there are no particular limitations on the upper limit of the volume resistivity of the cap tread 3a, the lower limit of the volume resistivity of the undertread 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, they are subject to physical constraints since they are rubber members.

[0045] The inner liner 21 is disposed on the tire inner surface 25 along the carcass layer 15. That is, the inner liner 21 constitutes the tire inner surface 25, which is the inner surface of the pneumatic tire 1, and faces the tire cavity, which is the space inside the pneumatic tire 1. The inner liner 21 that constitutes the tire inner surface 25 is a rubber layer that is disposed on the tire cavity side with respect to the carcass layer 15, and covers the carcass layer 15 from the tire cavity side.

[0046] The tie rubber 22 is disposed between the carcass layer 15 and the inner liner 21. Like the inner liner 21, the tie rubber 22 is disposed along the carcass layer 15 on the tire cavity side of the carcass layer 15. That is, the inner liner 21 and the tie rubber 22 are laminated and disposed along the carcass layer 15 on the tire cavity side of the carcass layer 15.

[0047] The inner liner 21, which is disposed on the tire inner surface 25, is an air permeation prevention layer that is disposed to cover the carcass layer 15, thereby suppressing oxidation due to exposure of the carcass layer 15 and preventing leakage of the air filled in the tire. The inner liner 21 is composed of, for example, a rubber composition containing butyl rubber as a main component, 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 composed of a thermoplastic resin or a thermoplastic elastomer composition, the inner liner 21 can be made thinner than when it is composed of butyl rubber, thereby significantly reducing the tire weight.

[0048] In addition, the air permeability coefficient of the inner liner 21, when measured in accordance with JIS K7126-1 at a temperature of 30°C, is generally preferably 100×10^-12 [cc·cm / cm^2·sec·cmHg] or less, and more preferably 50×10^-12 [cc·cm / cm^2·sec·cmHg] or less.

[0049] The volume resistivity of the inner liner 21 is 1×10^8 Ω·cm or more, and preferably 1×10^9 Ω·cm or more. The inner liner 21 also has a tan δ value at 60°C of 0.115 or more and 0.35 or less, and a rubber hardness Hs of 27 or more and 90 or less.

[0050] Examples of rubber compositions containing butyl rubber as a main component include butyl rubber (IIR), butyl-based rubber, etc. The butyl-based rubber is preferably a halogenated butyl rubber such as chlorinated butyl rubber (Cl-IIR) or brominated butyl rubber (Br-IIR).

[0051] 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, -based resins (e.g., aromatic polyesters such as 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, polyoxyalkylene diimide diacid / polybutylene terephthalate copolymer), polynitrile-based resins (e.g., polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), methacrylonitrile / styrene copolymer, methacrylonitrile / styrene / butadiene copolymer), poly(meth)acrylate-based resins (e.g., polymethyl methacrylate (PMMA), polyethyl methacrylate, ethylene-ethyl acrylate copolymer (EEA), ethylene-acrylic acid copolymer (EAA), ethylene-methyl acrylate resin (EMA)), polyvinyl-based resins (e.g., vinyl acetate (EVA), polyvinyl alcohol (PVA), vinyl alcohol / ethylene Examples of resins that can be used include: copolymers (EVOH), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymers, vinylidene chloride / methyl acrylate copolymers), cellulose-based resins (e.g., cellulose acetate, cellulose acetate butyrate), fluorine-based resins (e.g., polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymers (ETFE)), and imide-based resins (e.g., aromatic polyimides (PI)).

[0052] Examples of elastomers include diene rubbers and hydrogenated products thereof [e.g., NR, IR, epoxidized natural rubber, SBR, BR (high cis BR and low cis BR), NBR, hydrogenated NBR, hydrogenated SBR], olefin rubbers [e.g., ethylene propylene rubber (EPDM, EPM), maleic acid modified ethylene propylene rubber (M-EPM)], butyl rubber (IIR), copolymers of isobutylene and aromatic vinyl or diene monomers, acrylic rubber (ACM), ionomers, halogen-containing rubbers [e.g., Br-IIR, Cl-IIR, brominated isobutylene-paramethylstyrene copolymers (Br-IPMS)], chloroprene rubber (CR), hydrin rubber (CHC, CHR), chlorosulfur Examples of suitable materials include chlorinated polyethylene (CSM), chlorinated polyethylene (CM), maleic acid-modified chlorinated polyethylene (M-CM), silicone rubber (e.g., methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber), sulfur-containing rubber (e.g., polysulfide rubber), fluororubber (e.g., vinylidene fluoride-based rubber, fluorine-containing vinyl ether-based rubber, tetrafluoroethylene-propylene-based rubber, fluorine-containing silicone rubber, fluorine-containing phosphazene-based rubber), thermoplastic elastomer (e.g., styrene-based elastomer, olefin-based elastomer, polyester-based elastomer, urethane-based elastomer, polyamide-based elastomer), and the like.

[0053] Furthermore, the tie rubber 22 disposed between the inner liner 21 and the carcass layer 15 is a layer for preventing the carcass cords of the carcass layer 15 from digging into the inner liner 21 when the unvulcanized pneumatic tire 1 is inflated during tire manufacturing. Furthermore, the tie rubber 22 contributes to the air permeation prevention properties and steering stability on dry road surfaces in the manufactured pneumatic tire 1.

[0054] The tie rubber 22 is made of a rubber composition containing 30 to 100 parts by mass of carbon black having a CTAB adsorption specific surface area of ​​25 to 130 m / g per 100 parts by mass of diene rubber, and more preferably 40 to 70 parts by mass of carbon black. The carbon black-containing tie rubber 22 is a rubber composition containing 30 to 90 parts by mass of isoprene rubber and 20 to 70 parts by mass of styrene-butadiene rubber. By using this material blend, the electrical resistance of the tie rubber 22 can be reduced.

[0055] FIG. 2 is a detailed view of a region on one side of the tire equatorial plane CL in the tire width direction in FIG. 1. The pneumatic tire 1 according to this embodiment has an anti-static structure for dissipating static electricity generated on the vehicle while the vehicle is running to the road surface, and the anti-static structure uses a tie rubber 22. The tie rubber 22 is disposed between a pair of bead portions 10 along the carcass layer 15 and has a volume resistivity of less than 1×10^8 [Ω·cm]. The volume resistivity of the tie rubber 22 is more preferably less than 1×10^6 [Ω·cm]. Furthermore, the tie rubber 22 has a tan δ value at 60°C of 0.05 or more and 0.40 or less, and a rubber hardness Hs of 50 or more and 70 or less.

[0056] The inner liner 21 is disposed on the tire cavity side of the tie rubber 22 and extends between the pair of bead portions 10 .

[0057] In this embodiment, the bead portion 10 refers to the region from the measurement point of the rim diameter 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 with the pneumatic tire 1 mounted on a specified rim, pressurized to a specified internal pressure, and in an unloaded state.

[0058] Here, the specified rim refers to the "applicable rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. Also, the specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "inflation pressures" specified by ETRTO.

[0059] The inner liner 21 and tie rubber 22 arranged in a layered configuration have a length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 along the periphery and a length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 along the periphery satisfying the relationship Lt≧Li. That is, the length of the tie rubber 22 along the periphery in the tire meridian cross section is longer than the length of the inner liner 21 along the periphery in the tire meridian cross section.

[0060] As the tie rubber 22 has a longer length along the periphery than the inner liner 21, it comes into contact with the rim cushion 30 at at least one of the pair of bead portions 10. In this embodiment, the tie rubber 22 comes into contact with the rim cushion 30 at the bead portions 10 on both sides in the tire width direction.

[0061] In this embodiment, the length along the periphery refers to the length along the shape of each component at the same position in the tire circumferential direction. Specifically, the direction along the periphery is close to the tire width direction at the position of the tread portion 2, and close to the tire radial direction at the position of the sidewall portion 4.

[0062] In this embodiment, the rim cushion 30, which is arranged in the bead portion 10 and with which the tie rubber 22 comes into contact, is positioned such that on the tire widthwise inner side of the bead core 11, the tire radially outer end is located radially inward of the tire radially outer outer periphery of the bead core 11, and on the tire widthwise outer side of the bead core 11, the tire radially outer end is located radially outward of the tire radially outer periphery of the bead core 11.

[0063] Furthermore, the rim cushion 30 is arranged more inward in the tire width direction than the inner liner 21 and tie rubber 22 at the inner portion of the bead core 11 in the tire width direction, and more inward in the tire radial direction than the inner liner 21 and tie rubber 22 at the inner portion of the bead core 11 in the tire radial direction. Therefore, the rim cushion 30 covers the inner liner 21 and tie rubber 22 from the inner side in the tire width direction at the inner portion of the bead core 11 in the tire width direction, and covers the inner liner 21 and tie rubber 22 from the inner side in the tire radial direction at the inner portion of the bead core 11 in the tire radial direction.

[0064] In other words, the rim cushion 30, which is arranged in the bead portion 10 from the inner side in the tire width direction of the bead core 11 to the outer side in the tire width direction, is arranged to cover the bead core 11, carcass layer 15, inner liner 21, and tie rubber 22 in the bead portion 10. For this reason, in the bead portion 10, the surface of the inner liner 21 facing the tire cavity on the outer side in the tire radial direction of the position where the rim cushion 30 is arranged becomes the tire inner surface 25, and the surface of the rim cushion 30 facing the tire cavity on the position where the rim cushion 30 is arranged becomes the tire inner surface 25.

[0065] The rim cushion 30 disposed in the bead portion 10 in this manner forms a bead base 36, which is the inner peripheral surface of the bead portion 10, and a bead toe 35, which is the end of the bead base 36 on the inner side in the tire width direction. The bead base 36 is the part that comes into contact with the rim wheel when the pneumatic tire 1 is mounted on the rim wheel. The rim cushion 30 forms the bead base 36, which is the rim fitting surface 32 when the pneumatic tire 1 is mounted on the rim wheel.

[0066] Furthermore, the distance Hout in the tire radial direction between the rim cushion innermost part Rri and the rim cushion outermost part Rwo, relative to the tire cross-sectional height SH, is within the range of 0.02SH≦Hout≦0.70SH. In this case, the rim cushion innermost part Rri is the tire radially inner end of the rim cushion 30, and is located at the bead toe 35. The rim cushion outermost part Rwo is the tire radially outer end of the rim cushion 30 at a position outside the bead core 11 in the tire width direction.

[0067] The distance Hout in the tire radial direction between the innermost rim cushion Rri and the outermost rim cushion Rwo is preferably within the range of 0.05SH≦Hout≦0.65SH relative to the tire cross-sectional height SH.

[0068] An earth tread 50 is also disposed in the tread portion 2. The earth tread 50 is a conductive rubber member that is embedded in the tread rubber 3 and exposed to the tire contact surface. The earth tread 50 penetrates the tread rubber 3 to come into contact with the belt layer 18, and is disposed so as to be exposed to the tire contact surface 2a, which is the surface of the tread rubber 3. More specifically, the earth tread 50 is exposed to the tire contact surface 2a, and penetrates the cap tread 3a and under tread 3b of the tread rubber 3 to come into conductive contact with the belt layer 18. This ensures a conductive path from the belt layer 18 to the road surface by the earth tread 50.

[0069] The earth tread 50 has an annular structure extending around the entire circumference of the tire, and extends continuously in the tire circumferential direction with a portion of it exposed to the tire contact patch 2a. Therefore, when the pneumatic tire 1 rolls, the earth tread 50 can always be in contact with the road surface, and a conductive path from the belt layer 18 to the road surface can always be secured. The earth tread 50 is formed so that its width in the tire width direction is narrower than the groove width of, for example, circumferential main grooves (not shown) formed in the tread portion 2 and extending in the tire circumferential direction, and is disposed between adjacent circumferential main grooves in the tire width direction.

[0070] The earth tread 50 arranged in this manner is made of a conductive rubber material having a volume resistivity lower than that of the tread rubber 3, and the volume resistivity of the earth tread 50 is less than 1×10^8 [Ω·cm]. It is more preferable that the volume resistivity of the earth tread 50 is 1×10^6 [Ω·cm] or less.

[0071] Figure 3 is a detailed view of the bead portion 10 shown in Figure 2. The distance Hin in the tire radial direction between the rim cushion's innermost outermost portion Rwi and the rim cushion's innermost innermost portion Rri is within the range of 0.02SH≦Hin≦0.70SH, relative to the tire cross-sectional height SH. In this case, the rim cushion's innermost outermost portion Rwi is the outermost end of the rim cushion 30 in the tire radial direction, at a position on the inner side of the bead core 11 in the tire width direction.

[0072] The distance Hin in the tire radial direction between the innermost outermost rim cushion part Rwi and the innermost innermost rim cushion part Rri is preferably within the range of 0.05SH≦Hin≦0.65SH relative to the tire cross-sectional height SH.

[0073] The end 22a of the tie rubber 22 that is located in the bead portion 10 and contacts the rim cushion 30, i.e., the end 22a of the tie rubber 22 in the periphery direction, is located within the range in the tire radial direction in which the rim cushion 30 is arranged. In other words, the end 22a of the tie rubber 22 is located within the range in the tire radial direction between the innermost rim cushion Rri and the outermost outer rim cushion Rwo, and the end 22a of the tie rubber 22 is covered by and contacts the rim cushion 30. In this embodiment, the end 22a of the tie rubber 22 is located on the inner side of the bead core 11 in the tire radial direction.

[0074] In this embodiment, the end 21a of the inner liner 21 in the periphery direction is also located within the range in the tire radial direction where the rim cushion 30 is arranged in the bead portion 10. In other words, since the inner liner 21 is arranged on the tire cavity side with respect to the tie rubber 22, the portion of the inner liner 21 located within the range where the rim cushion 30 is arranged is sandwiched between the rim cushion 30 and the tie rubber 22.

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

[0076] The inner liner 21 and tie rubber 22 are arranged overlapping each other in this manner, and the relationship between the thickness Gt [mm] of the tie rubber 22 at the bead portion 10 and the thickness Gi [mm] of the inner liner 21 at the bead portion 10 satisfies 0.1Gi≦Gt≦0.9Gi.

[0077] Furthermore, the length Lt of the tie rubber 22 from the tire equatorial plane CL to the end 22a of the tie rubber 22 is equal to or greater than the length Li of the inner liner 21 from the tire equatorial plane CL to the end 21a of the inner liner 21, and therefore the inner liner 21 is not disposed near the end 22a of the tie rubber 22. Therefore, in the portion near the end 22a of the tie rubber 22 where the inner liner 21 is not disposed, one of both surfaces in the thickness direction of the tie rubber 22, opposite to the side where the carcass layer 15 is located, is in contact with the rim cushion 30.

[0078] The tie rubber 22 that comes into contact with the rim cushion 30 at the bead portion 10 has an overlap amount LAPr between the portion of the tie rubber 22 that comes into contact with the rim cushion 30 and the rim cushion 30 in the tire meridian cross section that is within the range of 0.1 mm≦LAPr≦50.0 mm, and it is preferable that the overlap amount LAPr is within the range of 0.1 mm≦LAPr≦20.0 mm. In this case, the overlap amount LAPr between the portion of the tie rubber 22 that comes into contact with the rim cushion 30 and the rim cushion 30 is the length in the direction along the periphery of the tie rubber 22 in the tire meridian cross section.

[0079] In addition, the lap amount LAPr of the tie rubber 22 in this case does not include the length of the portion where the tie rubber 22 does not come into direct contact with the rim cushion 30 even if the tie rubber 22 overlaps the rim cushion 30 due to the presence of the inner liner 21. In other words, the lap amount LAPr of the tie rubber 22 is the length of the portion of the bead portion 10 where the tie rubber 22 is not covered by the inner liner 21, and therefore the lap amount LAPr of the tie rubber 22 is the length in the direction along the periphery of the tie rubber 22 from the end 21a of the inner liner 21 to the end 22a of the tie rubber 22.

[0080] FIG. 4 is a detailed view of the periphery of the bead core 11 shown in FIG. 3 and is an explanatory diagram of the conductive path including the bead core 11. The bead core 11 disposed in the bead portion 10 has a volume resistivity of less than 1×10^8 [Ω·cm]. As a result, the bead core 11 forms a conductive path in the bead portion 10. The bead core 11 has a bead wire 12 and a bead insulation rubber 13 that wraps around the bead wire 12. The bead insulation rubber 13 is made of a conductive rubber material and has a volume resistivity of less than 1×10^8 [Ω·cm]. As a result, the bead insulation rubber 13 forms a conductive path in the bead portion 10.

[0081] The volume resistivity of the bead core 11 is preferably less than 1×10^7 [Ω·cm]. The volume resistivity of the bead core 11 can be measured, for example, by cutting out the bead core 11 so that the length in the tire circumferential direction is relatively short, and then placing electrodes of a tester (not shown) on both sides of the cut-out bead core 11 in the tire width direction to measure the electrical resistance of the cut-out bead core 11. The volume resistivity of the bead core 11 can be calculated based on the electrical resistance of the cut-out length of the bead core 11 measured in this way and the dimensions of the cut-out bead core 11.

[0082] The carcass layer 15 has carcass cords 16 and carcass coat rubber 17 that wraps the carcass cords 16, and the carcass coat rubber 17 also forms a conductive path in the bead portion 10. The electrical resistance of the carcass coat rubber 17 that forms the conductive path is equal to or less than the electrical resistance of the bead insulation rubber 13 in the bead portion 10.

[0083] That is, the electrical resistance Rp [Ω] of the carcass coat rubber 17 in the bead portion 10 and the electrical resistance Rbi [Ω] of the bead insulation rubber 13 in the bead portion 10 satisfy the relationship Rp [Ω]≦Rbi [Ω]. In this case, the electrical resistance Rp of the carcass coat rubber 17 is the electrical resistance in the range of the carcass coat rubber 17 in the tire radial direction that is the same as the arrangement range of the bead cores 11 in the tire radial direction.

[0084] Furthermore, if the electrical resistance of the rim cushion 30 in the bead portion 10 is Rr [Ω], then the electrical resistance Rr [Ω] of the rim cushion 30 satisfies the relationships Rp [Ω]≦Rr [Ω] and Rbi [Ω]≦Rr [Ω] with respect to the electrical resistance Rp [Ω] of the carcass coat rubber 17 and the electrical resistance Rbi [Ω] of the bead insulation rubber 13. In this case, the electrical resistance Rr [Ω] of the rim cushion 30 is the electrical resistance within the range in the tire radial direction where the bead core 11 is located.

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

[0086] The belt layer 18 disposed in the tread portion 2 has belt cords 18a and belt coat rubber 18b wrapping the belt cords 18a. In the tread portion 2, the belt coat rubber 18b forms a conductive path in the tread portion 2. In the tread portion 2, the carcass coat rubber 17 of the carcass layer 15 also forms a conductive path in the tread portion 2. Note that the volume resistivity ρb [Ω·cm] of the belt coat rubber 18b is preferably less than 1×10^8 [Ω·cm].

[0087] The electrical resistances of the belt coat rubber 18b and the carcass coat rubber 17 that form the conductive path are both equal to or less than the electrical resistance of the tie rubber 22. In this case, the electrical resistances of the carcass coat rubber 17 and the tie rubber 22 are the electrical resistances of the carcass coat rubber 17 and the tie rubber 22 in the range where the belt layer 18 is arranged in the tire width direction.

[0088] In the tread portion 2 where the belt layer 18 is arranged, when the electrical resistance of the belt coat rubber 18b of the belt layer 18 is Rb [Ω], the electrical resistance Rb [Ω] of the belt coat rubber 18b satisfies Rb [Ω] < 1 × 10^8 [Ω]. In this case, the electrical resistance Rb [Ω] of the belt coat rubber 18b is the electrical resistance Rb [Ω] of the belt coat rubber 18b in the range where the belt layer 18 is arranged in the tire width direction.

[0089] In the tread portion 2, the carcass layer 15 having the carcass cords 16 and the carcass coat rubber 17 also constitutes a conductive path in the tread portion 2. In the tread portion 2 where the carcass layer 15 is arranged, when the electrical resistance of the carcass layer 15 is Rpc [Ω], the electrical resistance Rpc [Ω] of the carcass layer 15 satisfies Rpc [Ω] < 1 × 10^8 [Ω]. In this case, the electrical resistance Rpc [Ω] of the carcass layer 15 is the electrical resistance Rpc [Ω] of the carcass layer 15 in the range where the belt layer 18 is arranged in the tire width direction.

[0090] The electrical resistance Rb [Ω] of the belt coat rubber 18b and the electrical resistance Rt [Ω] of the tie rubber 22 in the range in the tire width direction where the belt layer 18 is disposed satisfy the relationship Rt [Ω] ≧ Rb [Ω]. Also, the electrical resistance Rpc [Ω] of the carcass coat rubber 17 and the electrical resistance Rt [Ω] of the tie rubber 22 in the range in the tire width direction where the belt layer 18 is disposed satisfy the relationship Rt [Ω] ≧ Rpc [Ω]. Furthermore, the electrical resistance Rb [Ω] of the belt coat rubber 18b, the electrical resistance Rpc [Ω] of the carcass coat rubber 17, and the electrical resistance Rt [Ω] of the tie rubber 22 satisfy the relationship Rt [Ω] ≧ Rpc [Ω] ≧ Rb [Ω].

[0091] [Actions and Effects] When a pneumatic tire 1 according to the embodiment is mounted on a vehicle and driven, the pneumatic tire 1 rotates while the lower portion of the surface of the tread portion 2 of the pneumatic tire 1 that faces the road surface comes into contact with the road surface. The tire contact surface 2a, which is the surface of the tread portion 2, sequentially comes into contact with the road surface in this manner, thereby generating frictional force between the pneumatic tire 1 and the road surface. This allows the vehicle to 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 the vehicle is able to drive using these driving force, braking force, and turning force.

[0092] Additionally, static electricity can be generated while a vehicle is running, and if static electricity builds up on the vehicle, it can easily cause radio interference, such as radio noise. In this embodiment, the volume resistivity of the tie rubber 22 and the volume resistivity of the rim cushion 30 are both less than 10^8 [Ω·cm], making the tie rubber 22 and the rim cushion 30 relatively easy to conduct electricity through, allowing static electricity to be released onto the road surface.

[0093] In other words, the low volume resistivity of the tie rubber 22 and rim cushion 30 reduces the tire electrical resistance, which is the electrical resistance of the pneumatic tire 1. As a result, static electricity generated while the vehicle is running can flow from the rim flange R through the rim cushion 30 and tie rubber 22, which have low volume resistivity, and then into the belt layer 18, and from the belt layer 18 into the tread rubber 3, thereby being released from the tread rubber 3 to the road surface. As a result, static electricity generated on the vehicle is released onto the road surface, suppressing charging of the vehicle due to static electricity.

[0094] Here, the tie rubber 22 is arranged overlapping the inner liner 21 and extending to the position of the rim cushion 30, and the inner liner 21 and the tie rubber 22 have a length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 and a length Li from the tire equatorial plane CL to the end 21a of the inner liner 21, such that Lt≧Li. Therefore, the tie rubber 22 can be arranged so that at least one of the pair of bead portions 10 contacts the rim cushion 30, allowing static electricity generated on the vehicle to more reliably flow from the rim cushion 30 to the tie rubber 22. As a result, static electricity generated on the vehicle can be more reliably channeled by the tie rubber 22 from the rim cushion 30 side to the belt layer 18 side, and can be released from the tread rubber 3 to the road surface.

[0095] Furthermore, the rim cushion 30 has a radial distance Hout between the innermost rim cushion part Rri and the outermost rim cushion part Rwo, which is within the range of 0.02SH≦Hout≦0.70SH relative to the tire cross-sectional height SH, which prevents the rubber volume of the rim cushion 30 from becoming too large while ensuring a sufficient contact area between the rim cushion 30 and the tie rubber 22. In other words, if the radial distance Hout between the innermost rim cushion part Rri and the outermost rim cushion part Rwo, relative to the tire cross-sectional height SH, is Hout<0.02SH, the size of the rim cushion 30 in the radial direction of the tire will be too small, making it difficult to ensure a sufficient contact area between the rim cushion 30 and the tie rubber 22. In this case, it may be difficult to conduct static electricity from the rim cushion 30 to the tie rubber 22. Furthermore, if the distance Hout in the tire radial direction between the innermost rim cushion Rri and the outermost outer rim cushion Rwo is Hout > 0.70SH relative to the tire cross-sectional height SH, the size of the rim cushion 30 in the tire radial direction will be too large, and there is a risk that the rubber volume of the rim cushion 30 will be too large. In this case, there is a risk that the rolling resistance of the pneumatic tire 1 will deteriorate due to the rim cushion 30 having too much rubber volume.

[0096] In contrast, if the distance Hout in the tire radial direction between the rim cushion innermost part Rri and the rim cushion outermost part Rwo is within the range of 0.02SH≦Hout≦0.70SH relative to the tire cross-sectional height SH, it is possible to ensure a sufficient contact area between the rim cushion 30 and the tie rubber 22 while preventing the rubber volume of the rim cushion 30 from becoming too large. This ensures that static electricity can easily flow from the rim cushion 30 to the tie rubber 22 while preventing a deterioration in the rolling resistance of the pneumatic tire 1, and reduces the electrical resistance of the pneumatic tire 1.

[0097] Furthermore, since the end 22a of the tie rubber 22 is located within the range in the tire radial direction between the innermost rim cushion Rri and the outermost outer rim cushion Rwo, it is possible to prevent the fitting pressure from becoming too high when fitting the pneumatic tire 1 to the rim wheel, while ensuring the ease of flow of static electricity from the rim cushion 30 to the tie rubber 22.

[0098] In other words, if the end 22a of the tie rubber 22 is located radially outward of the outermost part Rwo of the rim cushion, there is a risk that the length over which the tie rubber 22 overlaps the rim cushion 30 will be too long. The tie rubber 22 according to this embodiment is made of a conductive rubber material and therefore has a relatively hard rubber hardness, making the tie rubber 22 less susceptible to elastic deformation than the rim cushion 30. For this reason, if the length over which the tie rubber 22 overlaps the rim cushion 30 is long, the proportion of the tie rubber 22 that is less susceptible to elastic deformation will increase, which may increase the fitting pressure when fitting the pneumatic tire 1 to the rim wheel.

[0099] In contrast, when the end 22a of the tie rubber 22 is located within the range in the tire radial direction between the innermost rim cushion Rri and the outermost outer rim cushion Rwo, the length by which the tie rubber 22 overlaps the rim cushion 30 can be prevented from becoming too long. This makes it possible to reduce the ratio of the tie rubber 22 to the rim cushion 30, and prevents the fitting pressure when fitting the pneumatic tire 1 to the rim wheel from becoming too high when a conductive rubber material is used for the tie rubber 22. As a result, the pneumatic tire 1 according to this embodiment can reduce electrical resistance while suppressing an increase in rolling resistance and an increase in fitting pressure.

[0100] Furthermore, the rim cushion 30 has a tire radial distance Hin between the innermost rim cushion side Rwi and the innermost rim cushion side Rri that is within the range of 0.02SH≦Hin≦0.70SH relative to the tire cross-sectional height SH, which prevents the rubber volume of the rim cushion 30 from becoming too large while ensuring a sufficient contact area between the rim cushion 30 and the tie rubber 22. In other words, if the tire radial distance Hin between the innermost rim cushion side Rwi and the innermost rim cushion side Rri is Hin<0.02SH relative to the tire cross-sectional height SH, the size of the rim cushion 30 in the tire radial direction will be too small, making it difficult to ensure a sufficient contact area between the rim cushion 30 and the tie rubber 22. In this case, it may be difficult to conduct static electricity from the rim cushion 30 to the tie rubber 22. Furthermore, if the distance Hin in the tire radial direction between the outermost inner rim cushion part Rwi and the innermost inner rim cushion part Rri is Hin > 0.70SH relative to the tire cross-sectional height SH, the size of the rim cushion 30 in the tire radial direction will be too large, and there is a risk that the rubber volume of the rim cushion 30 will be too large. In this case, there is a risk that the rolling resistance of the pneumatic tire 1 will deteriorate due to the rim cushion 30 having too much rubber volume.

[0101] In contrast, if the distance Hin in the tire radial direction between the rim cushion innermost outermost part Rwi and the rim cushion innermost innermost part Rri is within the range of 0.02SH≦Hin≦0.70SH relative to the tire cross-sectional height SH, it is possible to ensure a sufficient contact area between the rim cushion 30 and the tie rubber 22 while preventing the rubber volume of the rim cushion 30 from becoming too large. This ensures that static electricity can easily flow from the rim cushion 30 to the tie rubber 22 while preventing a deterioration in the rolling resistance of the pneumatic tire 1, and reduces the electrical resistance of the pneumatic tire 1.

[0102] Furthermore, because the overlap amount LAPr between the portion of the tie rubber 22 that contacts the rim cushion 30 and the rim cushion 30 is within the range of 0.1 mm≦LAPr≦50.0 mm, the overlap length of the tie rubber 22 with the rim cushion 30 is prevented from becoming too long, while ensuring the ease of flow of static electricity from the rim cushion 30 to the tie rubber 22. In other words, if the overlap amount LAPr between the portion of the tie rubber 22 that contacts the rim cushion 30 and the rim cushion 30 is LAPr<0.1 mm, the length of the portion of the tie rubber 22 that contacts the rim cushion 30 is too short, which may make it difficult for static electricity to flow from the rim cushion 30 to the tie rubber 22. In this case, it may be difficult to reduce the electrical resistance of the pneumatic tire 1. Furthermore, if the overlap amount LAPr between the portion of the tie rubber 22 that comes into contact with the rim cushion 30 and the rim cushion 30 is LAPr > 50.0 mm, the length of the portion of the tie rubber 22 that comes into contact with the rim cushion 30 will be too long, and there is a risk that the length over which the tie rubber 22 overlaps the rim cushion 30 will be too long. In this case, there is a risk that the rolling resistance of the pneumatic tire 1 will be easily deteriorated, and there is also a risk that the fitting pressure when fitting the pneumatic tire 1 to the rim wheel will be easily increased.

[0103] In contrast, when the overlap amount LAPr between the portion of the tie rubber 22 that contacts the rim cushion 30 and the rim cushion 30 is within the range of 0.1 mm≦LAPr≦50.0 mm, it is possible to prevent the length of overlap of the tie rubber 22 with the rim cushion 30 from becoming too long, while ensuring the ease of flow of static electricity from the rim cushion 30 to the tie rubber 22. Therefore, by preventing the length of overlap of the tie rubber 22 with the rim cushion 30 from becoming too long, it is possible to prevent a deterioration in rolling resistance and an increase in fitting pressure, and by ensuring the ease of flow of static electricity from the rim cushion 30 to the tie rubber 22, it is possible to reduce the electrical resistance of the pneumatic tire 1. As a result, it is possible to reduce electrical resistance while preventing a deterioration in rolling resistance and an increase in fitting pressure.

[0104] Furthermore, because the bead core 11 has a volume resistivity of less than 1×10^8 [Ω·cm], the bead core 11 can be used as a conductive path for flowing static electricity. Therefore, the following paths can be used as conductive paths for static electricity flowing from the rim wheel to the rim cushion 30: from the rim cushion 30 to the carcass coat rubber 17 of the turnup portion 15b of the carcass layer 15, from the carcass coat rubber 17 of the turnup portion 15b to the bead core 11, from the bead core 11 to the carcass coat rubber 17 of the carcass main body portion 15a of the carcass layer 15, and from the carcass coat rubber 17 of the carcass main body portion 15a to the tie rubber 22. This allows static electricity flowing from the rim wheel to the rim cushion 30 to be more reliably flow to the tie rubber 22, further reducing electrical resistance.

[0105] Furthermore, because the bead insulation rubber 13 of the bead core 11 has a volume resistivity of less than 1×10^8 [Ω·cm], the electrical resistance of the bead core 11 can be more reliably reduced. This allows static electricity flowing from the rim wheel to the rim cushion 30 to be more reliably channeled to the tie rubber 22, further reducing electrical resistance. Furthermore, because the bead core 11 with the bead insulation rubber 13 undergoes less deformation when a load is applied, deterioration of rolling resistance can be suppressed even when a highly conductive rubber material is used for the bead insulation rubber 13. Therefore, by ensuring conductivity by using a rubber material with a volume resistivity of less than 1×10^8 [Ω·cm] for the bead insulation rubber 13, electrical resistance can be reduced while suppressing deterioration of rolling resistance.

[0106] Furthermore, the electrical resistance Rpc [Ω] of the carcass layer 15 satisfies Rpc [Ω] < 1 × 10^8 [Ω], and the electrical resistance Rb [Ω] of the belt coat rubber 18b satisfies Rb [Ω] < 1 × 10^8 [Ω], so the carcass layer 15 and the belt coat rubber 18b can reduce the electrical resistance from the tie rubber 22 to the tread rubber 3. As a result, static electricity that flows from the rim cushion 30 side to the belt layer 18 side by the tie rubber 22 can be channeled to the tread rubber 3 by the carcass layer 15 and the belt coat rubber 18b, and can be released from the tread rubber 3 to the road surface. As a result, electrical resistance can be more reliably reduced, and static electricity buildup on the vehicle can be suppressed.

[0107] Furthermore, in the tread portion 2, within the range in the tire width direction where the belt layer 18 is disposed, the electrical resistance Rb [Ω] of the belt coat rubber 18b of the belt layer 18, the electrical resistance Rpc [Ω] of the carcass coat rubber 17 of the carcass layer 15, and the electrical resistance Rt [Ω] of the tie rubber 22 satisfy the relationship Rt [Ω] ≥ Rpc [Ω] ≥ Rb [Ω]. This allows the carcass coat rubber 17 and the belt coat rubber 18b to reduce the electrical resistance from the tie rubber 22 to the tread rubber 3. 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 channeled to the tread rubber 3 by the carcass coat rubber 17 and the belt coat rubber 18b, and released from the tread rubber 3 to the road surface. As a result, electrical resistance can be more reliably reduced, and static electricity buildup on the vehicle can be suppressed.

[0108] Furthermore, the tread portion 2 is provided with an earth tread 50 having a volume resistivity of less than 1×10^8 [Ω·cm], which penetrates the tread rubber 3 to contact the belt layer 18 and is exposed to the tire contact surface 2a, thereby ensuring a conductive path from the belt layer 18 to the road surface by the earth tread 50. This makes it possible to more reliably reduce the electrical resistance between the rim wheel and the road surface and more reliably release static electricity generated in the vehicle to the road surface, thereby more reliably reducing the electrical resistance of the pneumatic tire 1.

[0109] Furthermore, by providing the earth tread 50, it is possible to suppress a decrease in anti-static performance when the silica content of the rubber compound constituting the cap tread 3a, under tread 3b, sidewall rubber 5, etc. is increased in order to reduce the rolling resistance of the pneumatic tire 1 and improve fuel economy. In other words, because silica has high insulating properties, an increase in the silica content of the cap tread 3a increases the volume resistivity of the cap tread 3a and reduces anti-static performance, but by providing the earth tread 50, a conductive path between the belt layer 18 and the road surface can be secured. As a result, it is possible to reduce the electrical resistance of the pneumatic tire 1 while more reliably reducing rolling resistance.

[0110] [Variations] In the above-described embodiment, the inner liner 21 is arranged in a form in which the vicinity of the end portion 21 a overlaps the rim cushion 30 , but the inner liner 21 does not necessarily have to overlap the rim cushion 30 .

[0111] Fig. 6 is an explanatory diagram showing a configuration in which the inner liner 21 overlaps the rim cushion 30. Fig. 7 is an explanatory diagram showing a configuration in which the inner liner 21 does not overlap the rim cushion 30. The end 21a of the inner liner 21 may be located radially inward of the rim cushion's inner outermost part Rwi in the tire direction, as shown in Fig. 6, or the end 21a of the inner liner 21 may be located radially outward of the rim cushion's inner outermost part Rwi in the tire direction, as shown in Fig. 7. In other words, the inner liner 21 may overlap the rim cushion 30 near the end 21a as shown in Fig. 6, or the end 21a may not overlap the rim cushion 30 and be spaced radially outward from the rim cushion 30 as shown in Fig. 7.

[0112] The lap amount LAPi between the inner liner 21 and the rim cushion 30, which is indicated by the distance between the end 21a of the inner liner 21 and the outermost part Rwi on the inner side of the rim cushion, is preferably within the range of -5 [mm] < LAPi < +30 [mm] when the lap amount LAPi in the state where the inner liner 21 and the rim cushion 30 overlap (see Fig. 6) is indicated as positive (+), and the lap amount LAPi in the state where the inner liner 21 and the rim cushion 30 do not overlap (see Fig. 7) is indicated as negative (-).

[0113] That is, when the lap amount LAPi between the inner liner 21 and the rim cushion 30 is LAPi < -5 [mm], since the length of the inner liner 21 is too short, there is a risk that the arrangement range of the inner liner 21 arranged on the inner surface 25 of the tire becomes too small. In this case, there is a risk that the function of preventing the leakage of the air filled in the tire by the inner liner 21 is likely to deteriorate. Further, when the lap amount LAPi between the inner liner 21 and the rim cushion is LAPi > +30 [mm], there is a risk that the length of the inner liner 21 overlapping the rim cushion 30 becomes too long. In this case, there is a risk that the rolling resistance of the pneumatic tire 1 is likely to deteriorate.

[0114] On the other hand, when the lap amount LAPi between the inner liner 21 and the rim cushion 30 is within the range of -5 [mm] < LAPi < +30 [mm], while ensuring the function of preventing air leakage by the inner liner 21, it is possible to suppress the length of the inner liner 21 overlapping the rim cushion 30 from becoming too long. For this reason, by ensuring the function of preventing air leakage by the inner liner 21, it is possible to suppress the leakage of the air filled in the tire, and by suppressing the length of the inner liner 21 overlapping the rim cushion 30 from becoming too long, it is possible to suppress the deterioration of the rolling resistance. As a result, it is possible to suppress the deterioration of the rolling resistance while suppressing the leakage of the air filled in the tire.

[0115] Note that the lap amount LAPi between the inner liner 21 and the rim cushion 30 is more preferably within the range of 0 [mm] < LAPi < +10 [mm]. By setting the lap amount LAPi between the inner liner 21 and the rim cushion 30 within this range, it is possible to more reliably suppress air leakage and suppress deterioration of the rolling resistance.

[0116] In addition, in the above-described embodiment, the conductive members in the bead portion 10 have been described by way of example as the tie rubber 22, the rim cushion 30, the bead insulation rubber 13, and the carcass coat rubber 17. However, other members may also be used as the conductive members in the bead portion 10.

[0117] FIG. 8 is a detailed view of the bead portion 10 showing a modified example of the pneumatic tire 1 according to the embodiment, in which a convex portion 40 is arranged on the outer surface 33 of the rim cushion. In the bead portion 10, a convex portion 40 protruding outward in the tire width direction is arranged on the outer surface 33 of the rim cushion, which is the outer surface in the tire width direction of the rim cushion 30, as shown in FIG. 8, and the convex portion 40 may be used as a conductive member. In this case, the convex portion 40 is arranged within the range between the position corresponding to the outermost diameter portion 11a in the tire radial direction of the bead core 11 and the position corresponding to the innermost diameter portion 11b in the tire radial direction of the bead core 11 on the outer surface 33 of the rim cushion.

[0118] The convex portion 40 arranged to protrude from the outer surface 33 of the rim cushion in this way preferably has a height Hs [mm] of the convex portion 40 in the tire width direction within the range of 0.1 [mm] ≤ Hs ≤ 2.0 [mm]. Further, the convex portion 40 preferably has a width Ws [mm] of the convex portion 40 in the tire radial direction within the range of 0.1 [mm] ≤ Ws ≤ 2.0 [mm].

[0119] 9 and 10 are views taken in the direction of the arrow BB in FIG. 8, and are schematic diagrams showing an example of a protrusion 40. The protrusions 40 arranged on the rim cushion outer surface 33 may be arranged continuously around one circumference in the tire circumferential direction as shown in FIG. 9, or may be divided into multiple protrusions 40 in the tire circumferential direction, with the multiple protrusions 40 arranged intermittently in the tire circumferential direction as shown in FIG. 10. In this way, it is preferable that the protrusions 40 arranged along the tire circumferential direction have a tire circumferential length Ls [mm] of the protrusion 40 with respect to the tire circumferential length L [mm] of one circumference in the tire radial direction at the position of the inner part of the protrusion 40, satisfy the relationship Ls / L≧0.1.

[0120] The protrusions 40 may be made of the same material as the rim cushion rubber 31 that constitutes the rim cushion 30, or may be made of a different material from the rim cushion rubber 31. Furthermore, it is preferable that the protrusions 40 have a volume resistivity of less than 1×10^8 [Ω·cm]. In this way, the electrical resistance of the protrusions 40 arranged on the rim cushion outer surface 33 is equal to or less than the electrical resistance of the rim cushion 30.

[0121] In other words, if the electrical resistance of the protrusions 40 is Rs [Ω] and the electrical resistance of the rim cushion 30 is Rr [Ω], the relationship between the electrical resistance Rs [Ω] of the protrusions 40 and the electrical resistance Rr [Ω] of the rim cushion 30 satisfies Rs [Ω]≦Rr [Ω]. In this case, the electrical resistance Rr [Ω] of the rim cushion 30 is the electrical resistance over a range of the rim cushion 30 in the tire radial direction that is the same as the range in which the protrusions 40 are arranged in the tire radial direction.

[0122] By arranging the convex portions 40 that protrude outward in the tire width direction on the rim cushion outer surface 33 of the bead portion 10 as described above, it is possible to increase the contact area between the bead portion 10 and the rim wheel. In other words, when the pneumatic tire 1 is fitted to the rim wheel, the rim cushion outer surface 33 is separated from the rim flange R, and the pneumatic tire 1 is fitted with a gap between the rim cushion outer surface 33 and the rim flange R.

[0123] In contrast, if protrusions 40 that protrude outward in the tire width direction are arranged on the rim cushion outer surface 33, the protrusions 40 can come into contact with the rim flange R when the pneumatic tire 1 is fitted to the rim wheel, increasing the contact area between the bead portion 10 and the rim wheel. As a result, when the protrusions 40 are arranged on the rim cushion outer surface 33, the protrusions 40 can be used as a conductive path between the pneumatic tire 1 and the rim wheel, further reducing electrical resistance.

[0124] Furthermore, because the electrical resistance Rs [Ω] of the protrusions 40 and the electrical resistance Rr [Ω] of the rim cushion 30 satisfy the relationship Rs [Ω]≦Rr [Ω], the electrical resistance between the rim wheel and the rim cushion 30 can be reduced by the protrusions 40. This makes it easier for static electricity flowing from the rim wheel to the rim cushion 30 to flow through the protrusions 40, making it easier for static electricity generated on the vehicle to be released to the road surface via the pneumatic tire 1. As a result, electrical resistance can be reduced more reliably, and charging of the vehicle by static electricity can be suppressed.

[0125] Furthermore, the length Ls [mm] of the protrusions 40 in the tire circumferential direction satisfies the relationship Ls / L≧0.1 with respect to the length L [mm] of one circumference of the protrusions 40 in the tire radial direction, so that the area of ​​the protrusions 40 as viewed in the tire width direction can be secured. This makes it possible to more reliably increase the contact area between the bead portion 10 and the rim wheel by the protrusions 40, and reduce the electrical resistance between the rim wheel and the rim cushion 30. As a result, static electricity buildup on the vehicle can be more reliably suppressed.

[0126] In addition, in the above-described embodiment, the end 22a of the tie rubber 22 is located on the radially inner side of the bead core 11 in the tire direction, but the end 22a of the tie rubber 22 may be located in a position other than this.

[0127] Fig. 11 is a schematic diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which an inner liner 21 and a tie rubber 22 are arranged from the inner side in the tire width direction to the outer side in the tire width direction at a position on the inner side in the tire radial direction of the bead core 11. Fig. 12 is a schematic diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the bead core 11 shown in Fig. 11 is substantially circular. As shown in Figs. 11 and 12, the inner liner 21 and the tie rubber 22 may each be arranged from the inner side in the tire width direction to the outer side in the tire width direction at a position on the inner side in the tire radial direction of the bead core 11.

[0128] In this way, when the inner liner 21 and the tie rubber 22 are each positioned at a position radially inward of the bead core 11 in the tire radial direction, it is preferable that the relationship between the thickness Gtt [mm] of the tie rubber 22 and the thickness Git [mm] of the inner liner 21 at a position in the tire direction that is the same as the innermost part of the bead core 11 in the tire width direction satisfies 0.1Git≦Gtt≦0.9Git.

[0129] In this case, the thickness Gtt [mm] of the tie rubber 22 and the thickness Git [mm] of the inner liner 21 are the thickness of the tie rubber 22 that intersects with an imaginary line Bi that extends in the tire radial direction and is in contact with the innermost portion of the bead core 11 in the tire width direction, at a position on the tire radially inner side of the bead core 11, and the thickness of the inner liner 21 that intersects with the imaginary line Bi that is in contact with the innermost portion of the bead core 11 in the tire width direction, and the thickness of the inner liner 21 that intersects with the imaginary line Bi at a position on the tire radially inner side of the bead core 11. It is more preferable that the thickness Gtt [mm] of the tie rubber 22 and the thickness Git [mm] of the inner liner 21 thus defined satisfy the relationship 0.2Git≦Gtt≦0.8Git.

[0130] Furthermore, when the inner liner 21 and the tie rubber 22 are each positioned at a position radially inward of the bead core 11 in the tire radial direction, it is preferable that the relationship between the thickness Gth [mm] of the tie rubber 22 and the thickness Gih [mm] of the inner liner 21 at a position in the tire direction that is the same as the outermost part of the bead core 11 in the tire width direction satisfies 0.1Gih≦Gth≦0.9Gih.

[0131] In this case, the thickness Gth [mm] of the tie rubber 22 and the thickness Gih [mm] of the inner liner 21 are the thickness of the tie rubber 22 that intersects with an imaginary line Bo that extends in the tire radial direction and is in contact with the outermost portion of the bead core 11 in the tire width direction, at a position on the tire radially inner side of the bead core 11, and the thickness of the inner liner 21 that intersects with the imaginary line Bo that is in contact with the outermost portion of the bead core 11 in the tire width direction, and the thickness of the inner liner 21 that intersects with the imaginary line Bo that is in contact with the tire radially inner side of the bead core 11. It is more preferable that the thickness Gth [mm] of the tie rubber 22 and the thickness Gih [mm] of the inner liner 21 thus defined satisfy the relationship 0.2Gih≦Gth≦0.8Gih.

[0132] Furthermore, when the thickness of the tie rubber 22 and the thickness of the inner liner 21 are defined at the positions where they intersect with the imaginary line Bi or the imaginary line Bo that are in contact with the bead core 11, the bead core 11 may have a substantially rectangular shape in the tire meridian cross section as shown in FIG. 11 or a substantially circular shape in the tire meridian cross section as shown in FIG. 12.

[0133] In this way, the thickness Gtt [mm] of the tie rubber 22 at the position where it intersects with the imaginary line Bi and the thickness Git [mm] of the inner liner 21 satisfy the relationship 0.1Git≦Gtt≦0.9Git, and the thickness Gth [mm] of the tie rubber 22 at the position where it intersects with the imaginary line Bo and the thickness Gih [mm] of the inner liner 21 satisfy 0.1Gih≦Gth≦0.9Gih, thereby preventing the thickness of the tie rubber 22 from becoming too thick while ensuring the ease of flow of static electricity from the rim cushion 30 to the tie rubber 22.

[0134] In other words, if the relationship between the thickness Gtt [mm] of the tie rubber 22 and the thickness Git [mm] of the inner liner 21 is Gtt<0.1 Git, or if the relationship between the thickness Gth [mm] of the tie rubber 22 and the thickness Gih [mm] of the inner liner 21 is Gth<0.1 Gih, the thicknesses Gtt [mm] and Gth [mm] of the tie rubber 22 may be too thin. In this case, static electricity may not easily flow from the rim cushion 30 to the tie rubber 22, making it difficult to reduce the electrical resistance of the pneumatic tire 1. Furthermore, if the relationship between the thickness Gtt [mm] of the tie rubber 22 and the thickness Git [mm] of the inner liner 21 is Gtt>0.9 Git, or if the relationship between the thickness Gth [mm] of the tie rubber 22 and the thickness Gih [mm] of the inner liner 21 is Gth>0.9 Gih, the thicknesses Gtt [mm] and Gth [mm] of the tie rubber 22 may be too thick. In this case, there is a risk that the rolling resistance of the pneumatic tire 1 may be easily deteriorated, and there is also a risk that the fitting pressure when fitting the pneumatic tire 1 to a rim wheel may be easily increased.

[0135] In contrast, if the thickness Gtt [mm] of the tie rubber 22 and the thickness Git [mm] of the inner liner 21 satisfy the relationship 0.1 Git≦Gtt≦0.9 Git, or if the thickness Gth [mm] of the tie rubber 22 and the thickness Gih [mm] of the inner liner 21 satisfy the relationship 0.1 Gih≦Gth≦0.9 Gih, the ease of flow of static electricity from the rim cushion 30 to the tie rubber 22 can be ensured while preventing the tie rubber 22 from becoming too thick. Therefore, by preventing the tie rubber 22 from becoming too thick, it is possible to prevent a deterioration in rolling resistance and an increase in fitting pressure, and by ensuring a ease of flow of static electricity from the rim cushion 30 to the tie rubber 22, it is possible to reduce the electrical resistance of the pneumatic tire 1. As a result, it is possible to reduce electrical resistance while preventing a deterioration in rolling resistance and an increase in fitting pressure.

[0136] The above-described embodiments and variations may be combined as appropriate. In the above-described embodiments, the pneumatic tire 1 has been used as an example of a tire according to the present invention, but the tire according to the present invention may be a tire other than the pneumatic tire 1. The tire according to the present invention may be, for example, a so-called airless tire that can be used without being filled with gas.

[0137] [Example] 13A and 13B are tables showing the results of performance evaluation tests of pneumatic tires. Performance evaluation tests conducted on the above-described pneumatic tire 1 for a conventional pneumatic tire, the pneumatic tire 1 according to the present invention, and a comparative pneumatic tire for comparison with the pneumatic tire 1 according to the present invention will be described below. The performance evaluation tests included tests on the electrical resistance of the pneumatic tire, the rolling resistance of the pneumatic tire, and the fitting pressure when fitting the pneumatic tire to a rim wheel.

[0138] The performance evaluation test was carried out using a pneumatic tire with a nominal tire size of 235 / 60R18 as specified by JATMA as the test tire. The evaluation test for the electrical resistance of the pneumatic tire was carried out based on the measurement conditions specified by JATMA, using an R8340A Ultra High Resistance Meter manufactured by Advantest Corporation to measure the electrical resistance [Ω] of the test tire.

[0139] In addition, evaluation tests for the rolling resistance of pneumatic tires were conducted by mounting the test tire on a rim wheel with a rim size of 18 x 7.0J and conducting an indoor drum test on the test tire using a drum testing machine with a drum diameter of 1707 mm. The rolling resistance of the test tire was measured under conditions of an air pressure of 210 kPa, a load of 4.82 kN, and a speed of 80 km / h. The rolling resistance of the pneumatic tire was evaluated using an index based on the reciprocal of the measured rolling resistance, with the conventional tire described below being assigned an index of 100. The higher the index value for the rolling resistance of the pneumatic tire, the lower the rolling resistance and the better the rolling resistance performance. Note that a rolling resistance index of 98 or higher is considered to maintain a similar level to that of the conventional tire and to ensure performance comparable to that of the conventional tire in terms of rolling resistance.

[0140] In addition, to evaluate the fitting pressure when fitting a pneumatic tire to a rim wheel, the test tire was fitted to a rim wheel with a rim size of 18 x 7.0J, inflated with air at a supply pressure of 600 kPa, and then assembled to the rim wheel. While fitting the test tire to the rim wheel, the air filling was stopped the moment the bead of the test tire climbed over the hump of the rim wheel, and the air pressure at that time was measured as the fitting pressure. The fitting pressure when fitting a pneumatic tire to a rim wheel was evaluated using an index value calculated by taking the reciprocal of the air pressure measured as the fitting pressure and setting the conventional example described below as 100. The higher the index value for the fitting pressure when fitting a pneumatic tire to a rim wheel, the lower the air pressure when fitting the pneumatic tire to the rim wheel, indicating better fitting pressure performance. In addition, if the mating pressure index is 98 or higher, it is considered that the same level as the conventional example is maintained, and performance with respect to mating pressure is comparable to that of the conventional example.

[0141] The performance evaluation tests were conducted on 23 types of pneumatic tires: a conventional pneumatic tire, which is an example of a conventional pneumatic tire; Examples 1 to 21, which are pneumatic tire 1 according to the present invention; and a comparative example, which is a pneumatic tire compared to pneumatic tire 1 according to the present invention. Of these, the conventional pneumatic tire has a tie rubber volume resistivity of 1×10^8 [Ω·cm] or more. Furthermore, the comparative example pneumatic tire has a tie rubber volume resistivity of less than 1×10^8 [Ω·cm], but the end of the tie rubber is located radially outward of the outermost rim cushion Rwo, and the rim cushion volume resistivity is 1×10^8 [Ω·cm] or more.

[0142] In contrast, in all of Examples 1 to 21, which are examples of the pneumatic tire 1 according to the present invention, the volume resistivity of the tie rubber 22 and the volume resistivity of the rim cushion 30 are each less than 1×10^8 [Ω·cm], and the end 22a of the tie rubber 22 is located within a range in the tire radial direction between the rim cushion innermost portion Rri and the rim cushion outermost portion Rwo. Furthermore, in the pneumatic tires 1 according to Examples 1 to 21, the ratio of the distance Hin in the tire radial direction between the rim cushion innermost portion Rwi and the rim cushion innermost portion Rri to the tire cross-sectional height SH, the overlap amount LAPi [mm] between the inner liner 21 and the rim cushion 30, the overlap amount LAPr [mm] between the portion of the tie rubber 22 that contacts the rim cushion 30 and the rim cushion 30, whether the volume resistivity of the bead core 11 is less than 1×10^8 [Ω·cm], whether the electrical resistance Rpc of the carcass layer 15 and the electrical resistance Rb [Ω] of the belt coat rubber 18b are Each of these differs in whether it is less than 1 x 10^8 [Ω], whether or not there is a protrusion 40 arranged on the rim cushion outer surface 33, the ratio of the thickness Gtt [mm] of the tie rubber 22 to the thickness Git [mm] of the inner liner 21 at a position where it intersects with the imaginary line Bi that is in contact with the part of the bead core 11 that is located most inward in the tire width direction, and the ratio of the thickness Gth [mm] of the tie rubber 22 to the thickness Gih [mm] of the inner liner 21 at a position where it intersects with the imaginary line Bo that is in contact with the part of the bead core 11 that is located most outward in the tire width direction.

[0143] 13A and 13B, evaluation tests were conducted using these pneumatic tires 1. As a result, it was found that the pneumatic tires 1 according to Examples 1 to 21 could reduce electrical resistance compared to the conventional example while minimizing the deterioration in rolling resistance and fitting pressure performance. In other words, the pneumatic tires 1 according to Examples 1 to 21 could reduce electrical resistance while suppressing the deterioration in rolling resistance and the increase in fitting pressure.

[0144] The present disclosure encompasses 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 rim cushion that constitutes a rim fitting surface of the bead portion and is disposed from the inner side in the tire width direction to the outer side in the tire width direction of the bead core; at least one carcass layer bridged between the pair of bead portions; a belt layer disposed on the outer side of the carcass layer in the tire radial direction; a tread rubber disposed on the outer side of the belt layer in the tire radial direction; an inner liner disposed on the tire inner surface along the carcass layer; a tie rubber disposed between the carcass layer and the inner liner; Equipped with the inner liner and the tie rubber satisfy a relationship of Lt≧Li, where Lt is a length from the tire equatorial plane to an end of the tie rubber along the periphery, and Li is a length from the tire equatorial plane to the end of the inner liner along the periphery, the tie rubber contacts the rim cushion at at least one of the pair of bead portions, The end of the tie rubber is located within the range in the tire radial direction between the innermost part of the rim cushion, which is the inner end in the tire radial direction of the rim cushion, and the outermost part of the rim cushion outside, which is the outer end in the tire radial direction of the rim cushion at the position outside the bead core in the tire width direction. In the rim cushion, the distance Hout in the tire radial direction between the innermost part of the rim cushion and the outermost part of the rim cushion outside is within the range of 0.02SH ≦ Hout ≦ 0.70SH with respect to the tire section height SH. The tie rubber has a volume resistivity of less than 1×10^8 [Ω·cm]. The rim cushion is characterized in that the volume resistivity is less than 1×10^8 [Ω·cm]. Invention [2] The tire according to Invention [1], wherein in the rim cushion, the distance Hin in the tire radial direction between the outermost part of the rim cushion inside, which is the outer end in the tire radial direction of the rim cushion at the position inside the bead core in the tire width direction, and the innermost part of the rim cushion is within the range of 0.02SH ≦ Hin ≦ 0.70SH with respect to the tire section height SH. Invention [3] For the tire according to Invention [2], when the lap amount LAPi between the inner liner and the rim cushion, which is indicated by the distance between the end of the inner liner and the outermost part of the rim cushion inside, shows the lap amount LAPi in the overlapping state of the inner liner and the rim cushion as positive and the lap amount LAPi in the non - overlapping state of the inner liner and the rim cushion as negative, it is within the range of - 5 [mm] < LAPi < +30 [mm]. Invention [4] The tire according to any one of Invention [1] to Invention [3], wherein the lap amount LAPr between the part of the tie rubber contacting the rim cushion in the tie rubber and the rim cushion is within the range of 0.1 [mm] ≦ LAPr ≦ 50.0 [mm]. Invention [5] The tire according to any one of the inventions [1] to [4], wherein the bead core has a volume resistivity of less than 1×10^8 [Ω·cm]. Invention[6] The bead core has a bead wire and a bead insulation rubber that wraps the bead wire, The tire according to the invention [5], wherein the bead insulation rubber has a volume resistivity of less than 1×10^8 [Ω·cm]. Invention[7] When the electrical resistance of the carcass layer is Rpc [Ω] and the electrical resistance of the belt coat rubber of the belt layer is Rb [Ω], The electrical resistance Rpc [Ω] of the carcass layer satisfies Rpc [Ω] < 1 × 10^8 [Ω], The tire according to any one of the inventions [1] to [6], wherein the electrical resistance Rb [Ω] of the belt coat rubber satisfies Rb [Ω] < 1 × 10^8 [Ω]. Invention[8] a rim cushion outer surface, which is the outer surface of the rim cushion in the tire width direction, has a protrusion that protrudes outward in the tire width direction, within a range between a position corresponding to an outermost diameter portion of the bead core in the tire radial direction and a position corresponding to an innermost diameter portion of the bead core in the tire radial direction; A tire according to any one of inventions [1] to [7], wherein when the electrical resistance of the convex portion is Rs [Ω] and the electrical resistance of the rim cushion is Rr [Ω], the relationship between the electrical resistance Rs [Ω] of the convex portion and the electrical resistance Rr [Ω] of the rim cushion satisfies Rs [Ω] ≦ Rr [Ω]. Invention[9] The tire according to invention [8], wherein the length Ls [mm] of the convex portion in the tire circumferential direction satisfies the relationship Ls / L≧0.1 with respect to the length L [mm] of one circumference in the tire circumferential direction at the position of the inner part of the convex portion in the tire radial direction. Invention

[10] A tire according to any one of inventions [1] to [9], wherein the tie rubber and the inner liner intersect with an imaginary line that is tangent to the innermost part of the bead core in the tire width direction and extends in the tire radial direction, at positions on the tire radial inner side of the bead core, and the relationship between the thickness Gtt [mm] of the tie rubber and the thickness Git [mm] of the inner liner at the positions where they intersect with the imaginary line satisfies 0.1 Git ≦ Gtt ≦ 0.9 Git. Invention

[11] A tire according to any one of inventions [1] to

[10] , wherein the tie rubber and the inner liner intersect with an imaginary line that is tangent to the outermost portion of the bead core in the tire width direction and extends in the tire radial direction, at positions on the tire radial inside of the bead core, and the relationship between the thickness Gth [mm] of the tie rubber and the thickness Gih [mm] of the inner liner at the positions where they intersect with the imaginary line satisfies 0.1 Gih≦Gth≦0.9 Gih. Invention

[12] A tire according to any one of inventions [1] to

[11] , having a volume resistivity of less than 1 x 10^8 [Ω·cm], and comprising an earth tread that penetrates the tread rubber, contacts the belt layer, and is exposed on the surface of the tread rubber. [Explanation of symbols]

[0145] 1 pneumatic tire 2 Tread section 3 Tread rubber 4 Sidewall 5 Sidewall rubber 10 Bead section 11 Bead core 12 Bead wire 13 Bead insulation rubber 14 Bead filler 15 Carcass layer 16 Carcass cord 17 Carcass coat rubber 18 Belt Layer 18a belt cord 18b Belt Coat Rubber 21 Inner liner 21a, 22a end 22 Thai Rubber 25 Tire inner surface 30 Rim Cushion 31 Rim cushion rubber 32 Rim mating surface 33 Rim cushion outer surface 40 Convex part 50 Earth Red

Claims

1. a pair of bead portions disposed on both sides of the tire equatorial plane in the tire width direction; a bead core provided in each of the pair of bead portions; a rim cushion that constitutes a rim fitting surface of the bead portion and is disposed from the inner side in the tire width direction to the outer side in the tire width direction of the bead core; at least one carcass layer disposed between the pair of bead portions; a belt layer disposed on the outer side of the carcass layer in the tire radial direction; a tread rubber disposed on the outer side of the belt layer in the tire radial direction; an inner liner disposed on the tire inner surface along the carcass layer; a tie rubber disposed between the carcass layer and the inner liner; Equipped with the inner liner and the tie rubber satisfy a relationship of Lt≧Li, where Lt is a length from the tire equatorial plane to an end of the tie rubber along the periphery, and Li is a length from the tire equatorial plane to the end of the inner liner along the periphery, the tie rubber contacts the rim cushion at at least one of the pair of bead portions, an end of the tie rubber is located within a range in the tire radial direction between an innermost rim cushion end portion on the inner side of the rim cushion in the tire radial direction and an outermost rim cushion end portion on the outer side of the rim cushion in the tire radial direction at a position on the outer side of the bead core in the tire width direction, the rim cushion has a distance Hout in the tire radial direction between the innermost part of the rim cushion and the outermost part of the rim cushion, the distance Hout being within a range of 0.02SH≦Hout≦0.70SH relative to a tire cross-sectional height SH, The tie rubber has a volume resistivity of less than 1×10^8 [Ω cm], The tire is characterized in that the rim cushion has a volume resistivity of less than 1×10^8 [Ω·cm].

2. 2. The tire according to claim 1, wherein the distance Hin in the tire radial direction between the innermost rim cushion inner side, which is the outermost end of the rim cushion in the tire radial direction at a position on the inner side of the bead core in the tire width direction, and the innermost rim cushion inner side, is within the range of 0.02SH≦Hin≦0.70SH, where SH is the tire cross-sectional height.

3. 3. The tire of claim 2, wherein an overlap amount LAPi between the inner liner and the rim cushion, expressed as the distance between an end of the inner liner and the outermost inner edge of the rim cushion, is within the range of -5 mm < LAPi < +30 mm, where the overlap amount LAPi when the inner liner and the rim cushion overlap is expressed as a positive value and the overlap amount LAPi when the inner liner and the rim cushion do not overlap is expressed as a negative value.

4. 2. The tire according to claim 1, wherein an overlap amount LAPr between the portion of the tie rubber that contacts the rim cushion and the rim cushion is within a range of 0.1 mm≦LAPr≦50.0 mm.

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

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

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

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

9. 9. The tire according to claim 8, wherein the protrusions have a circumferential length Ls [mm] of the protrusions in the tire circumferential direction, and a circumferential length L [mm] of one circumference of the protrusions in the tire radial direction at a position of an inner portion of the protrusions in the tire radial direction, such that Ls / L≧0.

1.

10. 2. The tire according to claim 1, wherein the tie rubber and the inner liner intersect with an imaginary line extending in the tire radial direction and tangent to the innermost portion of the bead core in the tire width direction at a position on the tire radial inner side of the bead core, and the relationship between the thickness Gtt [mm] of the tie rubber and the thickness Git [mm] of the inner liner at the position where they intersect with the imaginary line satisfies 0.1 Git≦Gtt≦0.9 Git.

11. 2. The tire according to claim 1, wherein the tie rubber and the inner liner intersect with an imaginary line extending in the tire radial direction and tangent to the outermost portion of the bead core in the tire width direction at a position on the tire radially inner side of the bead core, and the relationship between the thickness Gth [mm] of the tie rubber and the thickness Gih [mm] of the inner liner at the position where they intersect with the imaginary line satisfies 0.1 Gih≦Gth≦0.9 Gih.

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

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