tire

Abstract

Provided is a tire capable of having a reduced electric resistance while suppressing an increase in mass and an increase in fitting pressure. The length Lt between a tire central plane CL and an end 22a of a tie rubber 22 and the length Li between the tire central plane CL and an end 21a of an inner liner 21 satisfy the relationship Lt<Li. The end 21a of the inner liner 21 is located inward of an outermost part 11c of a bead core 11 in the tire width direction. The end 22a of the tie rubber 22 is located inward of a radially outermost part 11a of the bead core 11 in the tire radial direction. The distance Rtg of the end 22a of the tie rubber 22 and the distance Rrc of a rim cushion inside outermost part Rwi both from the tire rotation axis satisfy the relationship Rtg<Rrc. The relationship between a lap amount LAP [mm] between the tie rubber 22 and a rim cushion 30 and the thickness Gi [mm] of the inner liner 21 is in the range of 0.0075≤Gi / LAP≤1.5. The tie rubber 22 and the rim cushion 30 have a volume resistivity of less than 1×10^8 [Ω·cm].

Description

tire

[0001] The present invention relates to a tire.

[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, in Patent Document 1, a conductive layer with low electrical resistivity is disposed between the carcass layer and the inner liner and extends from the bead portion to the belt layer, thereby improving the static electricity suppression performance of the tire. Patent Document 1 also describes an example in which the conductive layer is made of a conductive rubber material and also serves as a tie rubber disposed around the entire circumference of the tire cavity.

[0004] JP 2015-40031 A

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

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

[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 spanned 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 length Li from the tire equatorial plane to the end of the inner liner along the periphery that satisfy the relationship Lt<Li, and the end of the inner liner is located more inward in the tire width direction than an outermost portion in the tire width direction of the bead core. The end of the tie rubber is located radially inward of the outermost diameter portion of the bead core in the tire radial direction, and when the distance in the tire radial direction of the end of the tie rubber from the tire rotational axis is Rtg and the distance in the tire radial direction from the tire rotational axis of the innermost rim cushion, 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, is Rrc, the end of the tie rubber and the innermost rim cushion satisfy the relationship Rtg<Rrc, and the innermost rim cushion and the front The relationship between the overlap amount LAP [mm] between the tie rubber and the rim cushion, which is indicated by the distance along the periphery to the end of the tie rubber, and the thickness Gi [mm] of the portion of the inner liner located within the overlap range, which is the range along the periphery between the innermost part of the rim cushion and the end of the tie rubber, is within the range of 0.0075≦Gi / LAP≦1.5, and 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] In the tire, it is preferable that the tie rubber has a thickness in the range of 0.1 mm to 1.5 mm.

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

[0010] In the tire, it is preferable that the inner liner has a thickness Gi of 0.1 mm or more and 1.5 mm or less at a portion located within the wrap range.

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

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

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

[0014] The tire preferably further comprises an earth tread having a volume resistivity of less than 1×10^8 [Ω·cm], penetrating the tread rubber to come into contact with the belt layer and exposed on the surface of the tread rubber.

[0015] 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 portion of the bead core and a position corresponding to the innermost diameter portion 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].

[0016] 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.

[0017] Moreover, the above tire further comprises a tread portion including the tread rubber, a rim cushion rubber that forms the rim fitting surface of the bead portion and is arranged from the inner side in the tire width direction to the outer side in the tire width direction of the bead core, and earth tread rubber that is a conductive rubber in the rib portion closest to the tire equatorial plane, and the carcass layer includes carcass cords and carcass coat rubber that wraps around the carcass cords, and it is preferable that the tie rubber has portions that are inserted between the carcass cords of the carcass layer at least in the arrangement range of the belt layer.

[0018] In addition, in the above tire, it is preferable that, in a cross section seen when the tire is cut in the tire circumferential direction for the rib portion of the tread portion closest to the tire equatorial plane, the tie rubber is inserted between the carcass cords of the carcass layer at at least one location along the tire circumferential direction within a range of 50 mm in the tire circumferential direction.

[0019] In the above tire, it is preferable that the relationship between the inter-cord cross-sectional area Sc(50Ave), calculated from the average center-to-center distance of the carcass cords and the average thickness of the carcass layer within a circumferentially long range of 50 mm along the tire circumferential direction in a cross section seen when the tire is cut in the tire circumferential direction at the rib portion of the tread portion closest to the tire equatorial plane, and the cross-sectional area St(50Ave) of the tie rubber embedded in the carcass coat rubber within the above range, is as follows: 0.02≦St(50Ave) / Sc(50Ave)≦0.5

[0020] In the tire, it is preferable that the thickness Tc of the carcass layer and the height Tt of the tie rubber embedded in the carcass coat rubber satisfy the following relationship: 0.014≦Tt / Tc≦0.8

[0021] In the tire, it is preferable that a cross-sectional area St of the tie rubber inserted between the carcass cords and a height Tt of the tie rubber inserted between the carcass cords satisfy the following relationship: 0.02 mm≦St / Tt≦2.0 mm

[0022] In the tire, it is preferable that a ratio Ht / Hc of a hardness Ht of the tie rubber to a hardness Hc of the carcass coat rubber is 0.5 or greater and 2.0 or less.

[0023] In the tire, when the tire is cut in the tire circumferential direction through the earth tread rubber, the earth tread rubber is arranged so that the ratio of a cross-sectional area Sea of ​​the earth tread rubber to a cross-sectional area Str of the tread portion satisfies the following relationship, and it is preferable that the tie rubber is inserted between the carcass cords of the carcass layer on the inner side in the tire radial direction of the arrangement range of the earth tread rubber: 0.8≦Sea / Str≦1

[0024] The tire according to the present invention has an effect of being able to reduce electrical resistance while suppressing an increase in mass and an increase in fitting pressure.

[0025] FIG. 1 is a cross-sectional view of a pneumatic tire according to an embodiment, taken in the tire meridian direction. FIG. 2 is a detailed view of a region on one side of the tire equatorial plane in the tire width direction of FIG. 1. FIG. 3 is a detailed view of a bead portion shown in FIG. 2. FIG. 4 is a detailed view of the bead portion shown in FIG. 2 and is an explanatory view of a rim cushion. FIG. 5 is a schematic view of a tread portion shown in FIG. 1. FIG. 6 is a detailed view of a bead portion of a modified example of a pneumatic tire according to an embodiment, showing a configuration in which a protrusion is disposed on the outer surface of the rim cushion. FIG. 7 is a view taken along the arrows B-B in FIG. 6 and is a schematic view showing an example of a protrusion. FIG. 8 is a view taken along the arrows B-B in FIG. 6 and is a schematic view showing an example of a protrusion. FIG. 9 is a schematic view of a modified example of a pneumatic tire according to an embodiment, showing a configuration in which the end of a tie rubber is located radially inward of a bead core. FIG. 10A is a diagram showing the results of a performance evaluation test of a pneumatic tire. FIG. 10B is a diagram showing the results of a performance evaluation test of a pneumatic tire. FIG. 11 is a diagram showing a portion of the tire meridian cross section shown in FIG. 1 . FIG. 12 is a diagram showing an example of a cross-sectional structure including two carcass layers. FIG. 13 is a diagram showing an example of a cross-sectional structure of a portion of the side rubber shown in FIG. 1 . FIG. 14 is a diagram showing a schematic external appearance of a tire. FIG. 15 is a diagram explaining the area of ​​a portion of the tie rubber that is inserted between the carcass cords of the carcass layer. FIG. 16 is a diagram explaining the variation in thickness of the carcass layer in the tire circumferential direction. FIG. 17 is a diagram explaining the height of the tie rubber that is inserted between the carcass cords. FIG. 18 is a diagram showing a modified example of the cross-sectional structure of a portion of the tread portion shown in FIG. 1 . FIG. 19 is a diagram explaining the cross-sectional area and height of the tie rubber that is inserted into the carcass coat rubber. FIG. 20 is a diagram showing a cross section when the tire is cut in the circumferential direction at the position of the earth tread rubber in FIG. 1 . FIG. 21 is a cross section in the tire meridian direction showing a pneumatic tire according to an embodiment in which a non-penetrating type earth tread rubber is adopted. FIG. 22 is a diagram showing a cross section when the tire is cut in the circumferential direction at the position of the earth tread rubber in FIG. 21 . 23A and 23B are tables showing the results of a performance evaluation test of a pneumatic tire.FIG. 23C is a chart showing the results of a performance evaluation test of a pneumatic tire.

[0026] 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.

[0027] [Embodiment] [Pneumatic Tire] 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.

[0028] In the following description, the tire radial direction refers to the direction perpendicular to the tire rotation axis (not shown), which is the rotation axis of the pneumatic tire 1. The tire radially inner side refers to the side toward the tire rotation axis in the tire radial direction, and the tire radially outer side refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotation axis as the central axis. The tire width direction refers to the direction parallel to the tire rotation axis. The tire widthwise inner side refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the tire widthwise 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 rotation axis and passes through the center of the tire width of the pneumatic tire 1. The tire equatorial plane CL coincides in position in the tire width direction with the tire widthwise 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 obtained by cutting the tire along a plane that includes the tire rotation axis.

[0029] 1 is a cross-sectional view of a pneumatic tire 1 according to an embodiment taken along the tire meridian. The figure shows one radial region of the tire. The figure also shows a radial tire for a passenger vehicle as an example of a pneumatic tire.

[0030] 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 each disposed on either side of the tire equatorial plane CL in the tire width direction.

[0031] 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.

[0032] The pair of bead cores 11, 11 are annular members formed by bundling a plurality of bead wires and constitute 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.

[0033] 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 an absolute value ranging from 80 degrees to 95 degrees.

[0034] 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.

[0035] 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 a 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.

[0036] 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].

[0037] The volume resistivity (volume specific resistance) is measured based on "Vulcanized rubber and thermoplastic rubber - Determination of volume resistivity and surface resistivity" as specified in JIS K6271. Generally, if the volume resistivity is less than 1×10^8 [Ω cm] or the surface resistivity is less than 1×10^8 [Ω / cm], it can be said that the member has conductivity capable of suppressing static electricity buildup.

[0038] 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 to the tire widthwise outer side of the bead core 11. That is, the rim cushions 30 are arranged from the tire widthwise inner side of the bead core 11 in 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.

[0039] 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 that comes into contact 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.

[0040] The rim cushion 30 is made of a rubber member, a 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 is less than 1×10^6 [Ω·cm].

[0041] 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.

[0042] The tan δ value at 60°C is measured using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho, Ltd. under conditions of an initial strain of 10%, an amplitude of ±0.5%, and a frequency of 20 Hz. The rubber hardness Hs is measured at a temperature of 20°C in accordance with JIS K6253.

[0043] The rim cushion 30 may also include a member other than the rim cushion rubber 31. For example, the rim cushion 30 may include a chafer, which is a member made of a fiber material or a rubber member, 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.

[0044] 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 belt angles with opposite signs and are laminated so that the extension directions of the belt cords cross each other, forming a so-called cross-ply structure. 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.

[0045] 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) extending in the circumferential direction of the tire are formed in the tread portion 2. In addition, the tread rubber 3 which configures the tread portion 2 has a cap tread 3a and an undertread 3b.

[0046] The cap tread 3a is a rubber member located at the outermost side of the tread portion 2 in the tire radial direction and constituting the tire contact surface 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. This reduces the rolling resistance of the pneumatic tire 1. The cap tread 3a having such a volume resistivity is produced by using a low-heat-generating compound with a low carbon content and reinforcing it with an increased silica content.

[0047] 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.

[0048] 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 having 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] The inner liner 21 disposed on the tire inner surface 25 is an air permeation prevention layer, and by being disposed to cover the carcass layer 15, it suppresses oxidation due to exposure of the carcass layer 15 and prevents leakage of 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.

[0053] In general, the air permeability coefficient of the inner liner 21, when measured at a temperature of 30°C in accordance with JIS K7126-1, is preferably 100 x 10-12 [cc cm / cm^2 sec cmHg] or less, and more preferably 50 x 10-12 [cc cm / cm^2 sec cmHg] or less.

[0054] The inner liner 21 has a volume resistivity of 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.

[0055] 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).

[0056] 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, and polyoxyalkylene diimide diacid / polybutylene terephthalate copolymer), polynitrile-based resins (e.g., polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), methacrylonitrile / styrene copolymer, and 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), and ethylene-methyl acrylate resin (EMA)), and polyvinyl-based resins (e.g., vinyl acetate (EVA), polyvinyl alcohol (PVA), and vinyl alcohol / ethylene copolymer (EVOH), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymer, vinylidene chloride / methyl acrylate copolymer), 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 copolymer (ETFE)), imide-based resins (e.g., aromatic polyimide (PI)), and the like can be used.

[0057] 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, and hydrogenated SBR], olefin rubbers [e.g., ethylene propylene rubber (EPDM, EPM), and 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, and brominated isobutylene-paramethylstyrene copolymers (Br-IPMS)], chloroprene rubber (CR), hydrin rubbers (CHC, CHR), and chlorosulfonyl ethers. chlorinated polyethylene (CSM), chlorinated polyethylene (CM), maleic acid modified chlorinated polyethylene (M-CM)], silicone rubber [for example, methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber], sulfur-containing rubber [for example, polysulfide rubber], fluororubber [for example, 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 [for example, styrene-based elastomer, olefin-based elastomer, polyester-based elastomer, urethane-based elastomer, polyamide-based elastomer], etc. may be used.

[0058] 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. The tie rubber 22 also contributes to the air permeation prevention properties and steering stability on dry road surfaces in the manufactured pneumatic tire 1.

[0059] 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 contains 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.

[0060] 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 traveling to the road surface. The anti-static structure uses a tie rubber 22. A single tie rubber 22 is disposed between a pair of bead portions 10 along the carcass layer 15, and has a volume resistivity of less than 1×10^8 [Ω-cm]. The volume resistivity of the tie rubber 22 is more preferably less than 1×10^6 [Ω-cm]. Furthermore, the tie rubber 22 has a tan δ value at 60°C in the range of 0.05 to 0.40, and a rubber hardness Hs in the range of 50 to 70.

[0061] 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 the bead wire 12. In this embodiment, the bead insulation rubber 13 has a volume resistivity of less than 1×10^8 [Ω-cm]. The volume resistivity of the bead core 11 is preferably less than 1×10^7 [Ω-cm].

[0062] 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 in the tire width direction of the removed bead core 11 to measure the electrical resistance of the removed bead core 11. The volume resistivity of the bead core 11 can be calculated based on the electrical resistance of the bead core 11 over the removed length measured in this way and the dimensions of the removed bead core 11.

[0063] A single inner liner 21 is disposed on the tire cavity side of the tie rubber 22, spanning between a pair of bead portions 10. Therefore, both an end portion 21 a of the inner liner 21 and an end portion 22 a of the tie rubber 22 are located in the bead portion 10.

[0064] In this embodiment, the bead portion 10 refers to the region from the measurement point of the rim diameter to one-third of the tire cross-sectional height SH. The tire cross-sectional height SH refers to one-half 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.

[0065] 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.

[0066] 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, which satisfies the relationship Lt<Li. In other words, the length of the tie rubber 22 along the periphery in the tire meridian cross section is shorter than the length of the inner liner 21 along the periphery in the tire meridian cross section.

[0067] It is preferable that the difference between the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 along the periphery and the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 along the periphery be within the range of 2≦Li−Lt≦12.

[0068] Since the tie rubber 22 has a shorter length along the periphery than the inner liner 21, the tie rubber 22 overlaps the rim cushion 30 at the bead portion 10, but is covered by the inner liner 21 without coming into contact with the rim cushion 30.

[0069] 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.

[0070] 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, its 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, its radially outer end is located radially outward of the tire radially outer periphery of the bead core 11.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] An earth tread (hereinafter sometimes referred to as earth tread rubber) 50 is 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.

[0075] The earth tread 50 has an annular structure extending around the entire tire circumference, 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 ensured. 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.

[0076] The earth tread 50 arranged in this manner is made of a conductive rubber material having a lower volume resistivity than the tread rubber 3, and the volume resistivity of the earth tread 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.

[0077] 3 is a detailed view of the bead portion 10 shown in FIG. 2. The end 22a of the tie rubber 22 located in the bead portion 10, i.e., the end 22a of the tie rubber 22 in the periphery direction, is located within a range in the tire radial direction in which the rim cushion 30 is disposed. The end 22a of the tie rubber 22 is also located radially inward of the outermost diameter portion 11a of the bead core 11 in the tire radial direction. In this embodiment, the end 22a of the tie rubber 22 is located radially inward of the bead core 11, and is positioned radially inward of the outermost diameter portion 11a of the bead core 11 in the tire radial direction and radially outward of the innermost diameter portion 11b of the bead core 11 in the tire radial direction.

[0078] Furthermore, the end 22a of the tie rubber 22 is located radially inward of the rim cushion innermost outermost part Rwi, which is the radially outer end of the rim cushion 30 at a position on the inner side of the bead core 11 in the tire width direction. In other words, if the distance in the tire radial direction of the end 22a of the tie rubber 22 from the tire rotational axis is Rtg, and the distance in the tire radial direction of the rim cushion innermost outermost part Rwi from the tire rotational axis is Rrc, the end 22a of the tie rubber 22 and the rim cushion innermost outermost part Rwi satisfy the relationship Rtg < Rrc. In this case, Rtg is the radius at the position of the end 22a of the tie rubber 22 centered on the tire rotational axis, and Rrc is the radius at the position of the rim cushion innermost outermost part Rwi centered on the tire rotational axis.

[0079] It is preferable that the difference between the distance Rrc in the tire radial direction from the tire rotation axis to the inner outermost part Rwi of the rim cushion and the distance Rtg in the tire radial direction from the tire rotation axis to the end 22a of the tie rubber 22 is within the range of 3≦Rrc−Rtg≦20.

[0080] Furthermore, the end 21a of the inner liner 21 located in the bead portion 10, i.e., the end 21a of the inner liner 21 in the periphery direction, is also located within a range in the tire radial direction in which the rim cushion 30 is disposed, similar to the end 22a of the tie rubber 22. Furthermore, the end 21a of the inner liner 21 is located more inward in the tire width direction than the outermost portion 11c of the bead core 11 in the tire width direction. In this embodiment, the end 21a of the inner liner 21 is located inward in the tire radial direction of the bead core 11. In other words, the end 21a of the inner liner 21 is located inward in the tire radial direction of the bead core 11, and is located within a range in the tire width direction in which the bead core 11 is disposed.

[0081] In other words, the inner liner 21 is disposed so as to extend in the periphery direction outward in the tire width direction further than the tie rubber 22. As a result, the length Li (see FIG. 2) from the tire equatorial plane CL to the end 21 a of the inner liner 21 along the periphery is longer than the length Lt (see FIG. 2) from the tire equatorial plane CL to the end 22 a of the tie rubber 22 along the periphery.

[0082] Furthermore, 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.

[0083] Furthermore, the relationship between the overlap amount LAP [mm] in the tire meridian section between the tie rubber 22 and the rim cushion 30, which is indicated by the periphery distance between the innermost outermost part Rwi of the rim cushion and the end 22a of the tie rubber 22, and the thickness Gi [mm] of the portion of the inner liner 21 located within the overlap range where the tie rubber 22 and the rim cushion 30 overlap, is within the range of 0.0075≦Gi / LAP≦1.5.

[0084] In this case, the overlap amount LAP [mm] is the distance along the periphery of the tie rubber 22 between the radial position of the innermost part Rwi of the rim cushion of the tie rubber 22 and the end 22a of the tie rubber 22. The overlap range is the range along the periphery between the innermost part Rwi of the rim cushion and the end 22a of the tie rubber 22, and is the range in which the tie rubber 22 and the rim cushion 30 are overlapped in the bead portion 10 with the inner liner 21 interposed between them.

[0085] In this case, the thickness Gi [mm] of the inner liner 21 is the maximum thickness of the portion located within the overlap range of the inner liner 21. The thickness Gi of the portion located within the overlap range of the inner liner 21, i.e., the maximum thickness Gi of the inner liner 21 located within the overlap range, is in the range of 0.1 mm to 1.5 mm.

[0086] In addition, the thickness Gi of the portion of the inner liner 21 located within the overlap range between the tie rubber 22 and the rim cushion 30 is preferably in the range of 0.3 mm or more and 1.0 mm or less, and the relationship between the overlap amount LAP [mm] and the thickness Gi [mm] of the inner liner 21 is preferably in the range of 0.01≦Gi / LAP≦1.

[0087] The tie rubber 22 has a thickness Gt in the range of 0.1 mm to 1.5 mm. In this case, the thickness Gt [mm] of the tie rubber 22 is the maximum thickness of the tie rubber 22. The thickness Gt of the tie rubber 22 is preferably in the range of 0.3 mm to 1.0 mm.

[0088] Figure 4 is a detailed view of the bead portion 10 shown in Figure 2 and is an explanatory diagram of the rim cushion 30. The rim cushion 30 has a tire radial distance Hin between the rim cushion innermost portion Rri, which is the radially inner end of the rim cushion 30, and the rim cushion innermost portion Rwi, which is within a range of 10 mm to 40 mm. In this case, the rim cushion innermost portion Rri is the radially inner end of the rim cushion 30, and is located at the bead toe 35. The radial distance Hin between the rim cushion innermost portion Rri and the rim cushion innermost portion Rwi is the roll-up height of the rim cushion 30 at a position on the inner side of the bead core 11 in the tire width direction.

[0089] The distance Hin in the tire radial direction between the innermost rim cushion Rri and the innermost rim cushion Rwi is preferably within the range of 15 mm to 25 mm.

[0090] The overlap amount LAP between the tie rubber 22 and the rim cushion 30 is within the range of 3 mm to 30 mm. In other words, the overlap amount LAP, which is indicated by the distance along the periphery of the tie rubber 22 between the position in the tire radial direction of the inner outermost part Rwi of the rim cushion of the tie rubber 22 and the end 22a of the tie rubber 22, is within the range of 3 mm to 30 mm.

[0091] The overlap amount LAP between the tie rubber 22 and the rim cushion 30 is preferably within the range of 5 mm to 20 mm.

[0092] Fig. 5 is a schematic diagram of the tread portion 2 shown in Fig. 1. Note that Fig. 5 illustrates only the belt ply 18 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.

[0093] The belt layer 18 disposed in the tread portion 2 has belt cords 18a and belt coat rubber 18b wrapping the belt cords 18a. In the tread portion 2, the belt cords 18a and the belt coat rubber 18b form a conductive path in the tread portion 2. Note that the volume resistivity [Ω cm] of the belt coat rubber 18b is preferably less than 1×10^8 [Ω cm].

[0094] 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.

[0095] The carcass layer 15 also has carcass cords 16 and carcass coat rubber 17 wrapping the carcass cords 16, and the carcass layer 15 having the carcass cords 16 and the carcass coat rubber 17 also constitutes a conductive path in the tread portion 2. In the tread portion 2 where the carcass layer 15 is arranged, when the electrical resistance of the carcass layer 15 is Rpc [Ω] and the electrical resistance of the belt coat rubber 18b of the belt layer 18 is Rb [Ω], the electrical resistance Rpc [Ω] of the carcass layer 15 satisfies Rpc [Ω] < 1 × 10^8 [Ω]. In this case, the electrical resistance Rpc [Ω] of the carcass layer 15 is the electrical resistance Rpc [Ω] of the carcass layer 15 in the range in the tire width direction where the belt layer 18 is arranged.

[0096] [Actions and Effects] When the 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 is in contact with the road surface. The tire contact surface 2a, which is the surface of the tread portion 2, successively 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.

[0097] Furthermore, static electricity can be generated while the 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 each less than 10^8 [Ω·cm], making the tie rubber 22 and the rim cushion 30 relatively easy to conduct electricity through, and therefore allowing static electricity to be released onto the road surface.

[0098] In other words, because the tie rubber 22 and rim cushion 30 have low volume resistivities, it is possible to reduce 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 resistivities. At this time, the inner liner 21 is interposed between the rim cushion 30 and the tie rubber 22, but because the inner liner 21 is thin, static electricity that flows from the rim flange R to the rim cushion 30 can flow from the rim cushion 30 to the tie rubber 22 via the inner liner 21. Furthermore, between the rim cushion 30 and the tie rubber 22, static electricity can also flow via the carcass coat rubber 17 of the carcass layer 15, which is in contact with both the rim cushion 30 and the tie rubber 22.

[0099] The static electricity that has flowed to the tie rubber 22 further flows to the belt layer 18 and from the belt layer 18 to the tread rubber 3, and is thereby released to the road surface from the tread rubber 3. As a result, static electricity generated on the vehicle is released to the road surface, and charging of the vehicle by static electricity is suppressed.

[0100] 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 that satisfy the relationship Lt<Li. This allows the mass of the tie rubber 22 to be reduced, and therefore the mass of the pneumatic tire 1 to be reduced.

[0101] Furthermore, by making the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 satisfy the relationship Lt<Li, the length of the tie rubber 22 that overlaps the rim cushion 30 in the tire meridian cross section can be shortened. This makes it possible to prevent the fitting pressure when fitting the pneumatic tire 1 to a rim wheel from becoming too high, which would be caused by the length of the tie rubber 22 that overlaps the rim cushion 30 becoming too long.

[0102] In other words, the tie rubber 22 according to this embodiment is made of a conductive rubber material and therefore has a relatively hard rubber hardness, so the tie rubber 22 is less likely to elastically deform than the rim cushion 30. For this reason, if the length of the tie rubber 22 overlapping the rim cushion 30 is long, the proportion of the tie rubber 22 that is less likely to elastically deform increases, which may increase the fitting pressure when fitting the pneumatic tire 1 to the rim wheel.

[0103] In contrast, if the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 satisfy the relationship Lt<Li, it is possible to prevent the length by which the tie rubber 22 overlaps the rim cushion 30 from becoming too long. This makes it possible to reduce the ratio of the tie rubber 22 to the rim cushion 30, and when a conductive rubber material is used for the tie rubber 22, it is possible to prevent the fitting pressure when fitting the pneumatic tire 1 to the rim wheel from becoming too high.

[0104] Furthermore, because the end 22a of the tie rubber 22 is located radially inward of the outermost diameter portion 11a of the bead core 11 in the tire radial direction, the inner liner 21 and the carcass layer 15 can be more reliably bonded by the tie rubber 22 when the pneumatic tire 1 is being molded, thereby preventing peeling between the inner liner 21 and the carcass layer 15. Furthermore, because the end 22a of the tie rubber 22 is located radially inward of the outermost diameter portion 11a of the bead core 11 in the tire radial direction, it is possible to prevent vulcanization failures such as air getting in between the inner liner 21 and the carcass layer 15 and creating air pockets when the pneumatic tire 1 is being vulcanized.

[0105] Furthermore, because the relationship between the distance Rtg from the tire rotational axis to the end 22a of the tie rubber 22 in the tire radial direction and the distance Rrc from the tire rotational axis to the innermost outermost part Rwi of the rim cushion in the tire radial direction satisfies Rtg < Rrc, it is possible to ensure an overlapping area between the tie rubber 22 and the rim cushion 30 in the bead portion 10. This ensures an overlapping area between the tie rubber 22 and the rim cushion 30, each of which has a volume resistivity of less than 1 x 10^8 [Ω cm], and therefore electrical resistance can be reduced by the tie rubber 22 and the rim cushion 30.

[0106] Furthermore, because the end 21a of the inner liner 21 is located more inward in the tire width direction than the outermost portions 11c of the bead cores 11 in the tire width direction, the length of the inner liner 21 in the tire meridian cross section can be shortened. This ensures the air permeation prevention properties of the inner liner 21 to suppress air leakage, while reducing the mass of the inner liner 21. This ensures the air pressure retention performance of the pneumatic tire 1 and suppresses an increase in the mass of the pneumatic tire 1.

[0107] Furthermore, because the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gi [mm] of the portion of the inner liner 21 located within the overlap range between the tie rubber 22 and the rim cushion 30 is within the range of 0.0075≦Gi / LAP≦1.5, electrical resistance can be reduced while maintaining the air pressure of the pneumatic tire 1. In other words, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gi [mm] of the inner liner 21 is Gi / LAP<0.0075, the thickness Gi [mm] of the inner liner 21 will be too thin, making it difficult to ensure the air permeation prevention properties of the inner liner 21 and potentially making it difficult to maintain air pressure. Furthermore, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gi [mm] of the inner liner 21 is Gi / LAP > 1.5, the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 is too small, making it difficult to secure a conductive path between the tie rubber 22 and the rim cushion 30 and potentially making it difficult to reduce electrical resistance.

[0108] In contrast, when the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gi [mm] of the inner liner 21 is within the range of 0.0075≦Gi / LAP≦1.5, the thickness Gi [mm] of the inner liner 21 can be ensured to ensure the air permeation prevention properties of the inner liner 21, while the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 can be ensured to ensure a conductive path between the tie rubber 22 and the rim cushion 30. This makes it possible to reduce electrical resistance while maintaining the air pressure of the pneumatic tire 1. As a result, electrical resistance can be reduced while suppressing increases in the mass of the pneumatic tire 1 and in the fitting pressure.

[0109] Furthermore, because the thickness Gt of the tie rubber 22 is within a range of 0.1 mm or more and 1.5 mm or less, it is possible to suppress an excessive increase in the mass of the tie rubber 22 while suppressing the occurrence of poor appearance due to the thickness Gt of the tie rubber 22 being too thin. In other words, if the thickness Gt of the tie rubber 22 is less than 0.1 mm, the thickness Gt of the tie rubber 22 is too thin, which may cause the inner liner 21 to be easily wedged between the carcass cords 16 of the carcass layer 15 during vulcanization molding of the pneumatic tire 1. In this case, there is a risk that the shape of the carcass cords 16 may be visible on the tire inner surface 25, resulting in poor appearance. Furthermore, if the thickness Gt of the tie rubber 22 is greater than 1.5 mm, the thickness Gt of the tie rubber 22 is too thick, which may increase the mass of the tie rubber 22 and thus the mass of the pneumatic tire 1.

[0110] In contrast, when the thickness Gt of the tie rubber 22 is within the range of 0.1 mm or more and 1.5 mm or less, it is possible to suppress an excessive increase in the mass of the tie rubber 22 while suppressing the occurrence of poor appearance due to the thickness Gt of the tie rubber 22 being too thin. As a result, it is possible to suppress an increase in mass while suppressing the occurrence of poor appearance of the pneumatic tire 1.

[0111] Furthermore, the rim cushion 30 has a tire radial distance Hin between the rim cushion innermost portion Rri and the rim cushion inner outermost portion Rwi that is within the range of 10 mm to 40 mm, which prevents air pockets and other appearance defects while minimizing an increase in the mass of the pneumatic tire 1. In other words, if the distance Hin between the rim cushion innermost portion Rri and the rim cushion inner outermost portion Rwi is less than 10 mm, the height of the rim cushion 30 in the tire radial direction at a position on the inner side of the bead core 11 in the tire width direction will be too low, which could result in insufficient adhesion between the rim cushion 30 and the inner liner 21. In this case, air could get between the rim cushion 30 and the inner liner 21 during vulcanization of the pneumatic tire 1, which could result in air pockets and other appearance defects. Furthermore, if the distance Hin between the rim cushion innermost part Rri and the rim cushion inner outermost part Rwi is greater than 40 mm, the height of the rim cushion 30 in the tire radial direction at the position on the inner side of the bead core 11 in the tire width direction will be too high, and there is a risk that the mass of the rim cushion 30 will become too large. In this case, there is a risk that the mass of the pneumatic tire 1 will easily increase as the mass of the rim cushion 30 increases.

[0112] In contrast, because the distance Hin between the innermost rim cushion Rri and the inner outermost rim cushion Rwi is within the range of 10 mm to 40 mm, it is possible to prevent the mass of the rim cushion 30 from becoming too large while ensuring an adhesive range between the rim cushion 30 and the inner liner 21. As a result, it is possible to prevent an increase in the mass of the pneumatic tire 1 while preventing air pockets and other appearance defects of the pneumatic tire 1.

[0113] Furthermore, because the overlap length LAP between the tie rubber 22 and the rim cushion 30 is within the range of 3 mm to 30 mm, it is possible to suppress an increase in the mass of the pneumatic tire 1 while suppressing the occurrence of appearance defects such as air trapping. In other words, if the overlap length LAP between the tie rubber 22 and the rim cushion 30 is less than 3 mm, the overlap length LAP is too small, making the length of the tie rubber 22 disposed in the bead portion 10 too short, which may result in air being more likely to enter between the inner liner 21 and the carcass layer 15 during vulcanization of the pneumatic tire 1. In this case, there is a risk that appearance defects such as air trapping may be more likely to occur. Furthermore, if the overlap length LAP between the tie rubber 22 and the rim cushion 30 is greater than 30 mm, the overlap length LAP is too large, which may result in the mass of the rim cushion 30 becoming too large. In this case, there is a risk that the mass of the pneumatic tire 1 may be more likely to increase as the mass of the rim cushion 30 increases.

[0114] In contrast, if the overlap amount LAP between the tie rubber 22 and the rim cushion 30 is within the range of 3 mm to 30 mm, the length of the tie rubber 22 placed in the bead portion 10 can be ensured and the mass of the rim cushion 30 can be prevented from becoming too large. As a result, the occurrence of appearance defects of the pneumatic tire 1 such as air pockets can be prevented, while an increase in the mass of the pneumatic tire 1 can be prevented.

[0115] Furthermore, the thickness Gi of the inner liner 21 at a portion located within the overlap area between the tie rubber 22 and the rim cushion 30 is within a range of 0.1 mm or more and 1.5 mm or less, thereby suppressing an increase in mass while suppressing air leakage from the pneumatic tire 1. In other words, if the thickness Gi of the inner liner 21 is less than 0.1 mm, the thickness Gi of the inner liner 21 is too thin, making it difficult to ensure the air pressure retention rate of the inner liner 21 and potentially making it difficult to retain air pressure. If the thickness Gi of the inner liner 21 is greater than 1.5 mm, the thickness Gi of the inner liner 21 is too thick, making it easy for the mass of the inner liner 21 to increase, and potentially making it easy for the mass of the pneumatic tire 1 to increase.

[0116] In contrast, when the thickness Gi of the inner liner 21 is within the range of 0.1 mm or more and 1.5 mm or less, it is possible to suppress an increase in the mass of the inner liner 21 while ensuring the air pressure retention rate of the inner liner 21. As a result, it is possible to suppress an increase in the mass of the pneumatic tire 1 while suppressing air leakage from the pneumatic tire 1.

[0117] 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 turn-up portion 15b of the carcass layer 15, from the turn-up portion 15b to the bead core 11, from the bead core 11 to the carcass main body 15a of the carcass layer 15, and from the carcass main body 15a to the tie rubber 22. 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. As a result, the electrical resistance of the pneumatic tire 1 can be more reliably reduced.

[0118] 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 having 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. As a result, the electrical resistance of the pneumatic tire 1 can be more reliably reduced while suppressing deterioration of rolling resistance.

[0119] 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.

[0120] 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 on the vehicle to the road surface, thereby more reliably reducing the electrical resistance of the pneumatic tire 1.

[0121] Furthermore, by providing the earth tread 50, it is possible to suppress a decrease in charge-suppressing 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 charge-suppressing performance, but by providing the earth tread 50, it is possible to ensure a conductive path between the belt layer 18 and the road surface. As a result, it is possible to reduce the electrical resistance of the pneumatic tire 1 while reducing rolling resistance.

[0122] [Modifications] In the above-described embodiment, the tie rubber 22, the rim cushion 30, and the bead core 11 are described as conductive members in the bead portion 10, but other members may also be used as conductive members in the bead portion 10.

[0123] Figure 6 is a detailed view of a bead portion 10 of a modified example of the pneumatic tire 1 according to the embodiment, showing a configuration in which protrusions 40 are arranged on the rim cushion outer surface 33. In the bead portion 10, protrusions 40 that protrude outward in the tire width direction may be arranged on the rim cushion outer surface 33, which is the surface of the rim cushion 30 on the outside in the tire width direction, as shown in Figure 6, and the protrusions 40 may be used as conductive members. In this case, the protrusions 40 are arranged on the rim cushion outer surface 33 within a range between a position corresponding to the outermost diameter portion 11a of the bead core 11 in the tire radial direction and a position corresponding to the innermost diameter portion 11b of the bead core 11 in the tire radial direction.

[0124] The protrusions 40 thus arranged to protrude from the rim cushion outer surface 33 preferably have a height Hs (mm) of the protrusions 40 in the tire width direction within the range of 0.1 mm≦Hs≦2.0 mm. Also, the protrusions 40 preferably have a width Ws (mm) of the protrusions 40 in the tire radial direction within the range of 0.1 mm≦Ws≦2.0 mm.

[0125] 7 and 8 are diagrams taken along the arrows B-B in FIG. 6 , and are schematic diagrams showing an example of a protrusion 40. The protrusion 40 arranged on the rim cushion outer surface 33 may be arranged continuously around the tire circumferential direction as shown in FIG. 7 , or may be divided into multiple protrusions 40 in the tire circumferential direction, with the multiple protrusions 40 arranged intermittently around the tire circumferential direction as shown in FIG. 8 . In this way, it is preferable that the protrusions 40 arranged along the tire circumferential direction satisfy the relationship Ls [mm] of the length Ls [mm] of the protrusion 40 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 protrusion 40 in the tire radial direction, such that Ls / L≧0.1.

[0126] 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 protrusions 40 arranged on the rim cushion outer surface 33 have an electrical resistance that is equal to or less than the electrical resistance of the rim cushion 30.

[0127] 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.

[0128] 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.

[0129] 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 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.

[0130] 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 due to static electricity can be suppressed.

[0131] Furthermore, the length Ls [mm] of the protrusion 40 in the tire circumferential direction satisfies the relationship Ls / L≧0.1 with respect to the length L [mm] of one circumference of the protrusion 40 in the tire radial direction, so that the area of ​​the protrusion 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 protrusion 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.

[0132] Furthermore, in the above-described embodiment, the end 22 a of the tie rubber 22 is located on the inside of the bead core 11 in the tire width direction, but the end 22 a of the tie rubber 22 may be positioned in a position other than this.

[0133] 9 is a schematic diagram illustrating a modified example of the pneumatic tire 1 according to the embodiment, in which the end 22 a of the tie rubber 22 is located radially inward of the bead core 11. As shown in FIG. 9 , the end 22 a of the tie rubber 22 may be located radially inward of the bead core 11. The position of the end 22 a of the tie rubber 22 may be a position other than that in the above-described embodiment, as long as the length Lt (see FIG. 2 ) from the tire equatorial plane CL to the end 22 a of the tie rubber 22 along the periphery and the length Li (see FIG. 2 ) from the tire equatorial plane CL to the end 21 a of the inner liner 21 along the periphery satisfy the relationship Lt < Li, the end 22 a of the tie rubber 22 is located radially inward of the outermost diameter portion 11 a of the bead core 11 in the tire radial direction, and the end 22 a is disposed in the bead portion 10 so as to overlap with the rim cushion 30 via the inner liner 21.

[0134] The above-described embodiments and modified examples 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.

[0135] 10A and 10B are tables showing the results of performance evaluation tests of pneumatic tires. Performance evaluation tests conducted on the pneumatic tire 1 of Conventional Example 1, the pneumatic tire 1 according to the present invention, and a comparative pneumatic tire compared to 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 tire mass (which is the mass of the pneumatic tire), the fitting pressure when fitting the pneumatic tire to a rim wheel, and the appearance performance of the pneumatic tire.

[0136] 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 by measuring the electrical resistance [Ω] of the test tire using an R8340A Ultra High Resistance Meter manufactured by Advantest Corporation, based on the measurement conditions specified by JATMA.

[0137] The tire mass evaluation test was conducted by measuring the mass of each test tire and calculating the reciprocal of the measured mass as an index, with Conventional Example 1, described below, being set at 100. The larger the index value for the tire mass, the lighter the tire mass and the better the evaluation of the tire mass.

[0138] In addition, an evaluation test for fitting pressure when fitting a pneumatic tire to a rim wheel was performed by fitting a test tire to a rim wheel with a rim size of 18 x 7.0J, inflating the test tire with air at a supply pressure of 500 kPa, and assembling the test tire to the rim wheel. While assembling the test tire to the rim wheel in this manner, the air filling was temporarily stopped the moment the bead portion of the test tire passed 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 number calculated by taking the reciprocal of the air pressure measured as the fitting pressure and setting Conventional Example 1, described below, as 100. The higher the index number 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.

[0139] Furthermore, the appearance performance was evaluated by vulcanizing and molding 1,000 or more test tires, visually inspecting the vulcanized and molded test tires and counting the number of test tires that had appearance defects such as air pockets or the shape of the carcass cords showing on the inner surface of the tire, to calculate the incidence of appearance defects, and then using the reciprocal of the calculated incidence of appearance defects as an index rating, with Conventional Example 1, described below, being set at 100. A larger index rating indicates a lower incidence of appearance defects and better performance in terms of appearance defects.

[0140] The performance evaluation tests were conducted on 24 types of pneumatic tires: Conventional Example 1, which is an example of a conventional pneumatic tire; Examples 1 to 21, which are pneumatic tire 1 according to the present invention; and Comparative Examples 1 and 2, which are pneumatic tires compared to pneumatic tire 1 according to the present invention. Of these, Conventional Example 1 has a relationship of Lt > Li between the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21. Furthermore, in the pneumatic tires of Comparative Examples 1 and 2, the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gi [mm] of the portion of the inner liner 21 located within the overlap range does not satisfy 0.0075≦Gi / LAP≦1.5.

[0141] In contrast, in all of Examples 1 to 21, which are examples of the pneumatic tire 1 of the present invention, the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 satisfy the relationship Lt < Li, and the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gi [mm] of the portion of the inner liner 21 located within the overlap range is within the range of 0.0075≦Gi / LAP≦1.5. Furthermore, the pneumatic tires 1 of Examples 1 to 21 differ from one another in the thickness Gt [mm] of the tie rubber 22, the wrap height Hin [mm] of the rim cushion 30 at the inner position of the bead core 11 in the tire width direction, the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30, the thickness Gi [mm] of the inner liner 21, the volume resistivity [Ω cm] of the bead core 11, the electrical resistance Rpc [Ω] of the carcass layer 15, the electrical resistance Rb [Ω] of the belt coat rubber 18b, and the presence or absence of convex portions 40 on the rim cushion outer surface 33.

[0142] 10A and 10B , 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 were able to reduce electrical resistance without increasing the tire mass or fitting pressure compared to Conventional Example 1 and Comparative Examples 1 and 2. In other words, the pneumatic tires 1 according to Examples 1 to 21 were able to reduce electrical resistance while suppressing increases in mass and fitting pressure.

[0143] [Other Modifications] Fig. 11 is a diagram showing a portion of the meridian cross section of the tire shown in Fig. 1. Fig. 11 shows an example of the cross-sectional structure of a portion of the tread portion 2 shown in Fig. 1. Fig. 11 shows a cross section cut along the tire circumferential direction. Referring to Fig. 11, a belt layer 18, a carcass layer 15, a tie rubber 22, and an inner liner 21 are provided in this order on the inner side in the tire radial direction of the tread rubber 3. The tie rubber 22 is arranged between the carcass layer 15 and the inner liner 21.

[0144] The carcass layer 15 includes carcass cords 16 and a carcass coat rubber 17 that wraps around the carcass cords 16. Focusing on the tie rubber 22, a portion 221 of the tie rubber 22 extends radially outward and is embedded between the carcass cords 16. Specifically, if the portion 221 of the tie rubber 22 crosses an imaginary line L1 that passes through the radially inner side of each carcass cord 16, the portion 221 can be considered to be embedded between the carcass cords 16. That is, the tie rubber 22 has a portion 221 that is embedded between the carcass cords 16 of the carcass layer 15, at least within the range of the belt layer 18. The inclusion of the tie rubber 22 between the carcass cords 16 reduces the thickness of the carcass coat rubber 17, shortening the conductive distance and improving conductivity. Furthermore, the inclusion of the tie rubber 22 in the carcass coat rubber 17 increases the adhesion area between the tie rubber 22 and the carcass layer 15. This improves the adhesion between the tie rubber 22 and the carcass layer 15, making it possible to maintain low electrical resistance even after running.

[0145] [Modifications of Carcass Layer] The carcass layer 15 described with reference to Fig. 11 preferably has a one-ply structure, but is not limited to this. Fig. 12 is a diagram showing an example of a cross-sectional structure including a two-ply carcass layer 150. The carcass layer 150 has a two-ply structure, including a ply made of carcass cords 161 and carcass coat rubber 171 wrapping the same, and another ply made of carcass cords 162 and carcass coat rubber 172 wrapping the same.

[0146] 12 , the portion 221 of the tie rubber 22 also extends radially outward in the tire direction and enters between the carcass cords 161. In the case of a two-ply structure, an imaginary line L12 is drawn between the ply consisting of the carcass cords 161 and the carcass coat rubber 171 and the ply consisting of the carcass cords 162 and the carcass coat rubber 172. If the portion 221 of the tie rubber 22 crosses the imaginary line L1 that passes through the ply on the inner side in the tire radial direction of the imaginary line L12, i.e., the ply closest to the tie rubber 22 in the tire radial direction, it can be considered that the portion 221 of the tie rubber 22 enters between the carcass cords 161.

[0147] By inserting the tie rubber 22 between the carcass cords 161, the thickness of the carcass coat rubber 171 is reduced, shortening the conductive distance and improving conductivity. In addition, by inserting the tie rubber 22 into the carcass coat rubber 171, the adhesive area between the tie rubber 22 and the carcass layer 150 is increased. This improves the adhesiveness between the tie rubber 22 and the carcass layer 150, making it possible to maintain low electrical resistance even after running.

[0148] Also, the vicinity of the side rubber may have the same configuration as that shown in Fig. 11. Fig. 13 is a diagram showing an example of a cross-sectional structure of a portion of the sidewall rubber 5 shown in Fig. 1. Referring to Fig. 13, a carcass layer 15, a tie rubber 22, and an inner liner 21 are provided in this order from the tread rubber 3 toward the tire cavity side.

[0149] Focusing on the tie rubber 22 in FIG. 13 , a portion 221 of the tie rubber 22 extends radially outward and enters between the carcass cords 16. That is, the tie rubber 22 has a portion 221 that enters between the carcass cords 16 of the carcass layer 15, even within the arrangement range of the sidewall rubber 5. By having the tie rubber 22 enter between the carcass cords 16, the thickness of the carcass coat rubber 17 is reduced, shortening the conductive distance and improving conductivity. Furthermore, by entering the carcass coat rubber 17, the adhesive area between the tie rubber 22 and the carcass layer 15 is increased. This improves the adhesion between the tie rubber 22 and the carcass layer 15, allowing low electrical resistance to be maintained even after driving.

[0150] [Number of Locations Where Tie Rubber Inserts] FIG. 14 is a diagram showing a schematic external view of a tire 1. As shown in FIG. 14 , in the tire 1 of this example, four measurement locations in the tire circumferential direction are designated as measurement locations S1, S2, S3, and S4. These four measurement locations are, for example, one location every 90 degrees in the tire circumferential direction. Here, within a 50 mm circumferential length of measurement location S1, it is preferable that there is at least one portion 221 in which the tie rubber 22 inserts between the carcass cords 16 of the carcass layer 15. In other words, it is preferable that the tie rubber 22 inserts between the carcass cords 16 at at least one location per 50 mm circumferential length of the tire. The greater the number of locations where the tie rubber 22 inserts, the greater the adhesion area between the tie rubber 22 and the carcass layer 15. This improves adhesion between the tie rubber 22 and the carcass layer 15, allowing low electrical resistance to be maintained even after running.

[0151] Similarly, it is preferable that at least one portion of each of the other measurement portions S2, S3, and S4 of the tire 1 is embedded. Note that the four measurement portions S1, S2, S3, and S4 in Fig. 14 are examples, and more portions may be used as measurement portions.

[0152] 15 is a diagram illustrating the area of ​​a portion 221 of the tie rubber 22 that is inserted between the carcass cords 16 of the carcass layer 15. The average value Sc(50Ave) of the inter-cord cross-sectional area Sc calculated from the average center-to-center distance of the carcass cords 16 and the average thickness of the carcass layer 15 within a range of 50 mm in the tire circumferential length at measurement points S1, S2, S3, and S4, and the cross-sectional area St [mm ２ ] and the average value St(50Ave) preferably satisfy the following formula (1): 0.02≦St(50Ave) / Sc(50Ave)≦0.5 (1)

[0153] In the above formula (1), St(50Ave) is the cross-sectional area St [mm ２ ]. Sc(50Ave) is the average value of area Sc. Area Sc [mm ２ ] is the cross-sectional area of ​​the carcass layer 15 with the thickness Tc and the center-to-center distance Lc of the carcass cords 16. That is, the area Sc = Tc × Lc [mm ２ The thickness Tc [mm] is the length between a point P18 where a perpendicular line drawn from the center of the carcass cord 16 toward the belt layer 18 intersects with the interface of the belt layer 18 outward in the tire radial direction, and a point P22 where a perpendicular line drawn toward the inner side in the tire radial direction intersects with the interface of the tie rubber 22.

[0154] By satisfying the above condition (1), the conductivity can be improved and the electrical resistivity can be reduced while maintaining the durability of the tire. If the St(50Ave) / Sc(50Ave) is less than 0.02, the improvement in conductivity is small and the electrical resistance does not decrease. On the other hand, if the St(50Ave) / Sc(50Ave) is more than 0.5, the durability deteriorates due to the openings that widen the spaces between the carcass cords 16, and it is not possible to maintain low electrical resistance after running. Note that the cross-sectional area St [mm ２ It is more preferable that the relationship between the average value St(50Ave) of the area Sc and the average value Sc(50Ave) of the area Sc satisfies 0.1≦St(50Ave) / Sc(50Ave)≦0.35.

[0155] Here, the thickness Tc [mm] of the carcass layer 15 is not constant in the tire circumferential direction but varies. This will be explained with reference to Fig. 16. Fig. 16 is a diagram illustrating that the thickness of the carcass layer 15 varies in the tire circumferential direction.

[0156] In Fig. 16, a perpendicular line S16 is drawn from the center of the carcass cord 16 toward the tire radially inward. The distance along the tire radial direction from a point P16 where this perpendicular line S16 intersects with the boundary surface between the tie rubber 22 and the carcass coat rubber 17 to the boundary surface between the carcass coat rubber 17 and the belt layer 18 is not constant, but varies depending on the height to which the portion 221 of the tie rubber 22 penetrates. For example, in Fig. 16, the thickness Tcmax is the maximum value, the thickness Tcmin is the minimum value, and the thickness Tcave is the average value. The above area Sc [mm ２ ] is calculated by multiplying the average thickness Tcave by the center-to-center distance Lc of the carcass cords 16.

[0157] [Height of the Tie Rubber] Figure 17 is a diagram illustrating the height of the tie rubber that has entered between the carcass cords 16. In Figure 17, the thickness of the carcass layer 15 is Tc, and the height of the tie rubber that has entered into the carcass coat rubber is Tt. It is preferable that the relationship between the thickness Tc and the height Tt satisfy the following formula (2): 0.014 ≤ Tt / Tc ≤ 0.8 (2)

[0158] In formula (2), the thickness Tc is the thickness [mm] of the carcass layer 15. The thickness Tc is the distance from the interface between the tie rubber 22 and the carcass layer 15 to the interface between the belt layer 18 and the carcass layer 15. In formula (2), the height Tt is the height [mm] of the portion 221 of the tie rubber 22 that is sandwiched between the carcass cords 16. The height Tt is the distance from the interface between the tie rubber 22 and the carcass layer 15 to the outermost portion of the portion 221 of the tie rubber 22 in the tire radial direction. If Tt / Tc in formula (2) is less than 0.014, the improvement in conductivity is small and electrical resistance is not reduced. Furthermore, if Tt / Tc is greater than 0.8, durability deteriorates due to the opening of the carcass cords, making it impossible to maintain low electrical resistance after running. It is more preferable that the relationship between the thickness Tc and the height Tt be 0.2≦Tt / Tc≦0.6.

[0159] [Modification of Coat Rubber of Belt Layer] The tie rubber 22 may penetrate into the carcass coat rubber 17, and the coat rubber of the belt layer 18 may penetrate into the carcass coat rubber 17. FIG. 18 is a diagram showing a modification of the cross-sectional structure of a portion of the tread portion 2 shown in FIG. 1. As shown in FIG. 18, a portion 221 of the tie rubber 22 extends toward the tire radially outward in the carcass coat rubber 17. That is, the portion 221 of the tie rubber 22 crosses the imaginary line L1, and the portion 221 penetrates between the carcass cords 16. Furthermore, a portion of the coat rubber 18b of the belt layer 18 crosses the imaginary line L2 passing through the tire radially outer side of the carcass cords 16, and the coat rubber 18b penetrates between the carcass cords 16. Note that the volume resistivity of the coat rubber 18b of the belt layer 18 is preferably less than 1×10^8 [Ω cm].

[0160] [Cross-sectional area and height of the intruded tie rubber] Fig. 19 is a diagram for explaining the cross-sectional area and height of the tie rubber intruded into the carcass coat rubber. In Fig. 19, the cross-sectional area of ​​the tie rubber intruded between the carcass cords is expressed as St [mm ２]. The height of the tie rubber inserted between the carcass cords is defined as Tt. In this case, it is preferable that the relationship between the cross-sectional area St and the height Tt satisfies the following formula (3). That is, it is preferable that the following formula be satisfied: 0.02 mm≦St / Tt≦2.0 mm (3).

[0161] It is more preferable that the relationship between the cross-sectional area St and the height Tt satisfies the following: 0.2 mm≦St / Tt≦0.6 mm. ２ ] and height Tt [mm] are both average values ​​in a range of 50 mm in the circumferential direction of the tire, along the circumferential direction of the tire, at a cross section seen when the tire is cut in the circumferential direction of the tire.

[0162] [Rubber Hardness] When the hardness of the carcass coat rubber 17 is Hc and the hardness of the tie rubber 22 is Ht, the ratio Ht / Hc of the hardness Ht to the hardness Hc is preferably 0.5 or more and 2.0 or less. The ratio Ht / Hc is more preferably 0.7 or more and 1.5 or less, and even more preferably 0.9 or more and 1.3 or less.

[0163] If the ratio Ht / Hc of the tie rubber hardness to the carcass coat rubber hardness is within the above range, the hardness difference is small, and small peeling that occurs in the tire after running can be suppressed. This ensures electrical conductivity, and suppresses deterioration of electrical resistance before and after running.

[0164] The hardness Hc of the carcass coat rubber 17 is, for example, 55 points or more and 75 points or less. The hardness Ht of the tie rubber 22 is, for example, 50 points or more and 65 points or less. Here, hardness refers to durometer hardness measured at a temperature of 23°C using a type A durometer (rubber hardness tester) in accordance with JIS-K6253, and is also called JIS-A hardness. The hardness of the rubber is the average value measured at four or more points using the durometer on a cut sample tire.

[0165] In the land portion of the tread portion 2 closest to the tire equatorial plane CL, it is preferable that there is at least one location where the tie rubber 22 is inserted between the carcass cords 16 of the carcass layer 15 within a tire circumferential length of 50 mm along the tire circumferential direction in a cross section seen when the pneumatic tire 1 is cut in the tire circumferential direction. By having at least one location where the tie rubber 22 is inserted, it is possible to maintain low electrical resistance while maintaining the durability of the tire.

[0166] [Arrangement of Earth Tread Rubber] The arrangement of the earth tread rubber 50 will be described with reference to Fig. 20 to Fig. 22. Fig. 20 is a diagram showing a cross section of the tire cut in the circumferential direction at the position of the earth tread rubber 50 in Fig. 1. Fig. 20 is a diagram showing a cross section when the earth tread rubber 50 is a through-type earth rubber.

[0167] In Figure 20, the earth tread rubber 50 is a penetrating type earth rubber. Therefore, the earth tread rubber 50 penetrates the tread rubber 3 and comes into contact with the belt layer 18. Therefore, the earth tread rubber 50 comes into contact with the road surface, improving electrical conductivity. Note that, as shown in Figure 20, a small amount of cap tread 3a may remain on the outermost side of the tread rubber 3 in the tire radial direction.

[0168] On the other hand, Figure 21 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment in which a non-penetrating type earth tread rubber is used. Figure 22 is a diagram showing a cross section of the tire cut in the circumferential direction at the position of the earth tread rubber in Figure 21. In Figures 21 and 22, the earth tread rubber 50a is a non-penetrating type earth rubber. Therefore, the earth tread rubber 50a does not penetrate the tread rubber 3, but terminates in contact with the undertread 3b. Although the earth tread rubber 50a does not contact the belt layer 18, electrical conductivity can be maintained as long as the volume resistivity of the undertread 3b is sufficiently low. Note that, as shown in Figure 22, a small amount of cap tread 3a may remain on the outermost side of the tread rubber 3 in the tire radial direction.

[0169] In each cross section shown in FIG. 20 and FIG. 22, the cross-sectional area of ​​the tread portion is expressed as Str [mm ２ The cross-sectional area Str is the total area of ​​the cross-sectional area of ​​the cap tread 3a, the cross-sectional area of ​​the earth tread rubber 50 or 50a, and the cross-sectional area of ​​the under tread 3b. The cross-sectional area of ​​the earth tread rubber is expressed as Sea [mm ２ In this case, it is preferable that the ratio Sea / Str of the cross-sectional area Sea to the cross-sectional area Str is 0.8 or more and 1 or less. When the cross-sectional area ratio is in the above range and the portion 221 of the tie rubber 22 penetrates into the carcass coat rubber 17 of the carcass layer 15 as shown in Figures 20 and 22, the electrical conductivity is further improved. It is more preferable that the ratio Sea / Str is 0.9 or more and 1 or less.

[0170] The earth tread rubber 50 is made of a conductive rubber material having a lower volume resistivity than the tread rubber 3, and the volume resistivity of the earth tread rubber 50 is less than 1×10^8 [Ω·cm]. The volume resistivity of the earth tread rubber 50 is more preferably 1×10^6 [Ω·cm] or less.

[0171] 23A to 23C are tables showing the results of performance evaluation tests of pneumatic tires. Performance evaluation tests conducted on the pneumatic tire of Conventional Example 2 and the pneumatic tire 1 according to the present disclosure will be described below for the pneumatic tire 1. In the performance evaluation tests, the electrical resistance of the pneumatic tire was measured before and after driving with the pneumatic tire.

[0172] Regarding the electrical resistance of the tire, the electrical resistance [Ω] of the test tire was measured based on the measurement conditions specified by JATMA using an R8340A Ultra High Resistance Meter manufactured by Advantest Corporation. For running with pneumatic tires, an indoor drum-type tire rolling resistance tester with a drum diameter of 1707 mm was used, and the test tire was mounted on a rim that conforms to the JATMA standard, and an air pressure of 200 kPa and 80% of the maximum load specified by JATMA were applied to the test tire. After running for 60 minutes at a speed of 81 km / h, the electrical resistance of the tire was measured using the above method.

[0173] In FIG. 23A , a tire without tie rubber embedded in the carcass coat rubber is designated "Conventional Example 2." It is believed that the tie rubber embedded between the carcass cords peels off slightly as the tire runs, resulting in an increase in resistance compared to before the tire runs. Note that an increase in electrical resistance of 1.5×10^7 [Ω·cm] or less is considered acceptable. In FIG. 23A , the tire of Conventional Example 2 exhibits an increase in resistance of 1.9×10^7 [Ω·cm] after running compared to before running. In contrast, FIGS. 23A to 23C show that the tires of each example of the present disclosure maintain their electrical resistance even after running.

[0174] The present disclosure includes the following inventions: Invention [1] A tire comprising a pair of bead portions arranged 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 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 spanning between the pair of bead portions, a belt layer arranged on the outer side in the tire radial direction of the carcass layer, a tread rubber arranged on the outer side in the tire radial direction of the belt layer, an inner liner arranged on the inner surface of the tire along the carcass layer, and a tie rubber 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 length Li from the tire equatorial plane to the end of the inner liner along the periphery that satisfy the relationship Lt<Li, and the end of the inner liner is located on the inner side in the tire width direction of the outermost part of the bead core, the end of the tie rubber is located radially inward of the outermost diameter portion of the bead core in the tire radial direction, and where Rtg is the distance in the tire radial direction of the end of the tie rubber from the tire rotational axis and Rrc is the distance in the tire radial direction from the tire rotational axis of the innermost rim cushion, which is the outermost end of the rim cushion in the tire radial direction at a position inward in the tire width direction of the bead core, the end of the tie rubber and the innermost rim cushion satisfy the relationship Rtg<Rrc, the relationship between the overlap amount LAP [mm] between the tie rubber and the rim cushion, which is the distance along the periphery between the innermost rim cushion outermost portion and the end of the tie rubber, and the thickness Gi [mm] of the portion of the inner liner located within the overlap range, which is the range along the periphery between the innermost rim cushion outermost portion and the end of the tie rubber, is within the range of 0.0075≦Gi / LAP≦1.5, and 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].Invention [2] The tire according to Invention [1], wherein the tie rubber has a thickness in the range of 0.1 mm to 1.5 mm. Invention [3] The tire according to Invention [1] or Invention [2], wherein the rim cushion has a tire radial distance between the innermost rim cushion end, which is the radially innermost end of the rim cushion, and the innermost rim cushion end, in the range of 10 mm to 40 mm, and the overlap amount LAP between the tie rubber and the rim cushion is in the range of 3 mm to 30 mm. Invention [4] The tire according to any one of Inventions [1] to [3], wherein the inner liner has a thickness Gi of 0.1 mm to 1.5 mm at a portion located within the overlap area. Invention [5] The tire according to any one of Inventions [1] to [4], wherein the bead core has a volume resistivity of less than 1 x 10^8 Ω-cm. Invention [6] The tire according to Invention [5], wherein the bead core has a bead wire and a bead insulation rubber wrapping the bead wire, and the bead insulation rubber has a volume resistivity of less than 1×10^8 [Ω cm]. Invention [7] The tire according to any one of Inventions [1] to [6], wherein, 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], and the electrical resistance Rb [Ω] of the belt coat rubber satisfies Rb [Ω] < 1×10^8 [Ω]. Invention [8] A tire according to any one of inventions [1] to [7], which has a volume resistivity of less than 1 x 10^8 [Ω cm], penetrates the tread rubber, contacts the belt layer, and is exposed on the surface of the tread rubber.Invention [9] A tire according to any one of Inventions [1] to [8], wherein the rim cushion outer surface, which is the surface of the rim cushion on the outside in the tire width direction, has protrusions that protrude outward in the tire width direction, within a range between a position corresponding to the outermost diameter part of the bead core and a position corresponding to the innermost diameter part of the bead core in the tire radial direction, and wherein, where the electrical resistance of the protrusions is Rs [Ω] and the electrical resistance of the rim cushion is Rr [Ω], the relationship between the electrical resistance Rs [Ω] of the protrusions and the electrical resistance Rr [Ω] of the rim cushion satisfies Rs [Ω] ≦ Rr [Ω]. Invention

[10] The tire according to Invention [9], wherein the length Ls [mm] of the protrusions in the tire circumferential direction, with respect to the length L [mm] of one circumference in the tire circumferential direction at the position of the innermost part of the protrusion in the tire radial direction, satisfies the relationship Ls / L ≧ 0.1. Invention

[11] A tire according to invention [1], further comprising: a tread portion including the tread rubber, a rim cushion rubber that forms 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, and earth tread rubber that is a conductive rubber in a rib portion closest to the tire equatorial plane, wherein the carcass layer includes carcass cords and carcass coat rubber that wraps around the carcass cords, and the tie rubber has a portion that enters between the carcass cords of the carcass layer at least in an arrangement range of the belt layer. Invention

[12] A tire according to invention [1 ...Invention

[13] A tire according to invention

[11] or invention

[12] , wherein the relationship between an inter-cord cross-sectional area Sc(50Ave), calculated from the average center-to-center distances of carcass cords and the average thickness of carcass layers in a 50 mm circumferential length range along the tire circumferential direction in a cross section seen when the tire is cut in the tire circumferential direction at a rib portion of the tread portion closest to the tire equatorial plane, and a cross-sectional area St(50Ave) of tie rubber embedded in the carcass coat rubber within said range, is as follows: 0.02≦St(50Ave) / Sc(50Ave)≦0.5 Invention

[14] A tire according to any one of inventions

[11] to

[13] , wherein the relationship between the carcass layer thickness Tc and the height Tt of the tie rubber embedded in the carcass coat rubber is as follows: Invention

[15] The tire according to any one of Inventions

[11] to

[14] , wherein a cross-sectional area St of the tie rubber inserted between the carcass cords and a height Tt of the tie rubber inserted between the carcass cords have the following relationship: 0.02 mm≦St / Tt≦2.0 mm Invention

[16] The tire according to any one of Inventions

[11] to

[15] , wherein a ratio Ht / Hc of a hardness Ht of the tie rubber to a hardness Hc of the carcass coat rubber is 0.5 or more and 2.0 or less. Invention

[17] A tire according to any one of inventions

[11] to

[16] , wherein, when the tire is cut in the tire circumferential direction through the earth tread rubber, the earth tread rubber is arranged so that the ratio of a cross-sectional area Sea of ​​the earth tread rubber to a cross-sectional area Str of the tread portion has the following relationship, and the tie rubber is inserted between the carcass cords of the carcass layer on the tire radially inner side of the arrangement range of the earth tread rubber: 0.8≦Sea / Str≦1.

[0175] REFERENCE SIGNS LIST 1 pneumatic tire 2 tread portion 2a tire contact surface 3 tread rubber 3a cap tread 3b under tread 4 sidewall portion 5 sidewall rubber 10 bead portion 11 bead core 11a outermost diameter portion 11b innermost diameter portion 11c outermost portion 12 bead wire 13 bead insulation rubber 14 bead filler 15 carcass layer 15a carcass main body portion 15b turnup portion 16 carcass cord 17 carcass coat rubber 18 belt layer 18a belt cord 18b belt coat rubber 21 inner liner 21a end portion 22 tie rubber 22a end portion 25 tire inner surface 30 rim cushion 31 rim cushion rubber 32 rim fitting surface 33 rim cushion outer surface 35 bead toe 36 Bead base 40 Convex part 50 Earth tread

Claims

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

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

3. A tire as described in claim 1, wherein the distance in the tire radial direction between the innermost part of the rim cushion, which is the innermost end of the rim cushion in the tire radial direction, and the outermost inner part of the rim cushion is within the range of 10 mm to 40 mm, and the overlap amount LAP between the tie rubber and the rim cushion is within the range of 3 mm to 30 mm.

4. The tire according to claim 1, wherein the thickness Gi of the inner liner at the portion located within the wrap range is within the range of 0.1 mm to 1.5 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. A tire according to claim 5, wherein the bead core has a bead wire and bead insulation rubber surrounding the bead wire, and the bead insulation rubber has a volume resistivity of less than 1 x 10^8 [Ω·cm].

7. A tire as set forth in claim 1, wherein, 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 x 10^8 [Ω], and the electrical resistance Rb [Ω] of the belt coat rubber satisfies Rb [Ω] < 1 x 10^8 [Ω].

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

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

10. A tire as described in claim 9, wherein the length Ls [mm] of the protrusion in the tire circumferential direction satisfies the relationship Ls / L≧0.1, where L [mm] is the length of one circumference in the tire circumferential direction at the position of the inner part of the protrusion in the tire radial direction.

11. A tire as claimed in claim 1, further comprising: a tread portion including said tread rubber; rim cushion rubber that forms the rim fitting surface of said bead portion and is arranged from the inner side in the tire width direction of said bead core to the outer side in the tire width direction; and earth tread rubber that is a conductive rubber in the rib portion closest to the tire equatorial plane; wherein said carcass layer includes carcass cords and carcass coat rubber that wraps around said carcass cords; and said tie rubber has portions that are inserted between said carcass cords of said carcass layer at least in the arrangement range of said belt layer.

12. A tire as described in claim 11, wherein the tie rubber is inserted between the carcass cords of the carcass layer at least in one location within a circumferential length of 50 mm along the tire circumferential direction in a cross section seen when the tire is cut in the tire circumferential direction at the rib portion of the tread portion closest to the tire equatorial plane.

13. A tire according to claim 11 or 12, wherein the relationship between the inter-cord cross-sectional area Sc(50Ave), calculated from the average center-to-center distance of the carcass cords and the average thickness of the carcass layer within a circumferentially long range of 50 mm along the tire circumferential direction in a cross section seen when the tire is cut in the tire circumferential direction at the rib portion of the tread portion closest to the tire equatorial plane, and the cross-sectional area St(50Ave) of the tie rubber embedded in the carcass coat rubber within said range, is as follows: 0.02≦St(50Ave) / Sc(50Ave)≦0.5 14. A tire according to claim 11 or 12, wherein the thickness Tc of the carcass layer and the height Tt of the tie rubber embedded in the carcass coat rubber satisfy the following relationship: 0.014≦Tt / Tc≦0.8 15. A tire according to claim 11 or 12, wherein a cross-sectional area St of the tie rubber inserted between the carcass cords and a height Tt of the tie rubber inserted between the carcass cords satisfy the following relationship: 0.02 mm≦St / Tt≦2.0 mm 16. A tire according to claim 11 or 12, wherein the ratio Ht / Hc of the hardness Ht of the tie rubber to the hardness Hc of the carcass coat rubber is 0.5 or more and 2.0 or less.

17. A tire according to claim 11 or 12, wherein the earth tread rubber is arranged so that, when the tire is cut in the circumferential direction through the earth tread rubber, the ratio of the cross-sectional area Sea of ​​the earth tread rubber to the cross-sectional area Str of the tread portion satisfies the following relationship, and the tie rubber is inserted between the carcass cords of the carcass layer on the inner side in the tire radial direction of the range in which the earth tread rubber is arranged: 0.8≦Sea / Str≦1

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