tire

Abstract

To provide a tire that can maintain tire electrical resistance after travelling is finished.SOLUTION: A pneumatic tire 1 comprises a pair of bead parts 10, at least one carcass layer 13 laid across the pair of bead parts 10, a belt layer 14 arranged outside in a tire radial direction of the carcass layer 13, and a carcass inside rubber layer 20 arranged at a tire inner cavity side with respect to the carcass layer 13. The pneumatic tire further comprises a linear conductive part 50 extended continuously from at least the bead parts 10 up to the belt layer 14 and arranged in the carcass inside rubber layer 20. At least a portion of the linear conductive part 50 is arranged inside the carcass inside rubber layer 20 and volume resistivity thereof is less than 1×10^8 [Ω cm].SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] In recent years, there has been an increasing demand for fuel-efficient tires due to environmental issues and other factors. One method for improving tire fuel efficiency is to incorporate silica into the rubber used in the tread and sidewalls of tires to reduce their rolling resistance. However, because silica has high insulating properties, increasing the silica content of the tread rubber increases the tread rubber's electrical resistance, reducing the tire's static electricity suppression performance. A reduced tire's static electricity suppression performance increases the accumulation of static electricity generated while the vehicle is running, making it more likely to cause radio interference, such as radio noise.

[0003] For this reason, some conventional pneumatic tires are equipped with conductive members 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 to the road surface. For example, in Patent Document 1, the electrical resistance of the tire is reduced by arranging conductive threads with low electrical resistance that extend in a toroidal shape along the carcass ply between a pair of bead cores. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-133467 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when conductive fibers such as conductive yarns are arranged along the carcass ply, the electrical resistance of a new tire is low. However, due to deformation of the tire when a vehicle equipped with the tire is running, the conductive fibers are likely to rub against the carcass ply. In this case, there is a risk that the conductive fibers may break due to repeated rubbing against the carcass ply, and the conductive fibers may no longer be able to conduct electricity. If the conductive fibers are no longer able to conduct electricity due to breakage, the tire's electrical resistance is likely to increase, and the tire's anti-static performance is reduced. Therefore, there is room for improvement in terms of maintaining the tire's electrical resistance after running.

[0006] The present invention has been made in view of the above, and has an object to provide a tire that can maintain its tire electrical resistance after running. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the tire of the present invention is a tire comprising a pair of bead portions, at least one carcass layer spanning between the pair of bead portions, a belt layer disposed radially outward of the carcass layer, and a carcass inner rubber layer disposed on the tire cavity side of the carcass layer, and is characterized in that the tire comprises linear conductive portions extending continuously from at least the bead portions to the belt layer and disposed in the carcass inner rubber layer, at least a portion of the linear conductive portions being located within the carcass inner rubber layer, and having a volume resistivity of less than 1×10^8 [Ω·cm].

[0008] In the above tire, the belt layer has one or more belt plies extending in the tire width direction, and when perpendicular lines are drawn from both end portions in the tire width direction of the belt ply that is widest in the tire width direction to the tire inner surface, the periphery length between the intersections of the perpendicular lines and the tire inner surface is defined as Lbp, and the length in the periphery direction of the linear conductive portion of the portion located radially inward of the belt layer is defined as La, it is preferable that the linear conductive portion satisfies 0.01≦La / Lbp≦1.

[0009] In the above tire, it is preferable that, at least in a region radially outward of the bead portion, the linear conductive portion has a relationship between a thickness t of the carcass inner rubber layer and a distance t1 from the tire inner surface at a portion of the linear conductive portion where the distance from the tire inner surface is smallest, such that 0.2≦t1 / t≦0.8 is satisfied.

[0010] In addition, in the above tire, it is preferable that a bead portion rubber that abuts against a rim flange is arranged in the bead portion, the bead portion rubber has a volume resistivity of less than 1×10^8 [Ω·cm], and the linear conductive portion has a portion that overlaps with the bead portion rubber.

[0011] In the above tire, it is preferable that the linear conductive portion extends from the tire inner surface side beyond the bead toe of the bead portion to at least the bead base, and contacts the bead portion rubber at a position closer to the bead base than the bead toe.

[0012] In the tire, it is preferable that the linear conductive portions extend along the periphery direction at least in the region between the belt layer and the bead portion.

[0013] In addition, in the above tire, it is preferable that a portion of the linear conductive portion located on the radially inner side of the belt layer and a portion located on the bead portion each have a portion inclined at an inclination angle of 30° or less in the tire circumferential direction with respect to the periphery direction.

[0014] In addition, in the above tire, it is preferable that the carcass inner rubber layer is formed by laminating a first layer and a second layer, and that at least a portion of the linear conductive portion is disposed between the first layer and the second layer.

[0015] In the tire, it is preferable that the first layer is an inner liner and the second layer is a tie rubber.

[0016] In the tire, it is preferable that the linear conductive portion is sewn into the tie rubber.

[0017] In the tire, it is preferable that the linear conductive portion is sewn into the tie rubber while being exposed on the surface of the tie rubber with a length of 1 mm or more and 30 mm or less.

[0018] In the tire, the linear conductive portion is preferably formed by twisting together a plurality of linear members, including at least one conductive linear member having a volume resistivity of less than 1×10^8 [Ω·cm].

[0019] In the tire, the linear conductive portion is preferably formed by twisting together the conductive linear body and a non-conductive linear body having a volume resistivity of 1×10^8 [Ω·cm] or more.

[0020] In the tire, it is preferable that the conductive linear members are metal fibers and the non-conductive linear members are organic fibers.

[0021] In the tire, the conductive linear body is preferably formed by twisting together a plurality of carbon fibers.

[0022] In the tire, it is preferable that the conductive linear member is a single-wire cord made of carbon fiber.

[0023] In the tire, it is preferable that the total fineness of the linear conductive portions is 20 [dtex] or more and 1000 [dtex] or less.

[0024] In the tire, it is preferable that the linear conductive portions have an elongation percentage of 1.0% or more and 70.0% or less. [Effects of the Invention]

[0025] The tire according to the present invention has an effect of being able to maintain the tire electrical resistance after running. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a cross-sectional view of a pneumatic tire according to a first embodiment taken along the tire meridian direction. [Figure 2] FIG. 2 is a detailed view of a region on one side from the tire equatorial plane in the tire width direction in FIG. [Figure 3] FIG. 3 is an explanatory diagram of the wrap width of the linear conductive portions relative to the belt layer. [Figure 4] FIG. 4 is a detailed view of part A in FIG. [Figure 5] FIG. 5 is a detailed view of part B in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line CC in FIG. [Figure 7] FIG. 7 is a schematic diagram showing the arrangement of linear conductive portions when the pneumatic tire is viewed in the direction of the tire rotation axis. [Figure 8] FIG. 8 is an explanatory diagram of a linear conductive portion alone. [Figure 9] FIG. 9 is a cross-sectional view of a main part showing an arrangement of linear conductive portions in a pneumatic tire according to the second embodiment. [Figure 10] FIG. 10 is a cross-sectional view taken along line DD in FIG. [Figure 11] FIG. 11 is an explanatory diagram showing a modified example of the pneumatic tire according to the first embodiment, in which the carcass inner rubber layer and the linear conductive portions are positioned on the inner side of the bead portion rubber in the tire width direction. [Figure 12]FIG. 12 is an explanatory diagram showing a modified example of the pneumatic tire according to the first embodiment, in which linear conductive portions are also arranged on the bead base side. [Figure 13] FIG. 13 is an explanatory diagram showing a modified example of the pneumatic tire according to the first embodiment, in which conductive rubber is disposed in the bead rubber. [Figure 14] FIG. 14 is an explanatory diagram showing a modified example of the pneumatic tire according to the first embodiment, illustrating a state in which the linear conductive portions come into contact with the chafers of the bead portion rubber. [Figure 15] FIG. 15 is an explanatory diagram showing a modified example of the pneumatic tire according to the first embodiment, illustrating a state in which the linear conductive portions come into contact with the chafers of the bead portion rubber. [Figure 16] FIG. 16 is an explanatory diagram showing a modified example of the pneumatic tire according to the first embodiment, in which the linear conductive portions have portions that are inclined with respect to the periphery direction. [Figure 17] FIG. 17 is an explanatory diagram showing a modified example of the pneumatic tire according to the second embodiment, in which the linear conductive portions are sewn into the tie rubber while inclining in the tire circumferential direction. [Figure 18] FIG. 18 is an explanatory diagram showing a modified example of the pneumatic tire according to the second embodiment, in which linear conductive portions are woven into tie rubbers. [Figure 19] FIG. 19 is an explanatory diagram showing a modified example of the pneumatic tire according to the second embodiment, in which linear conductive portions are sewn into a tie rubber using linear non-conductive portions as well. [Figure 20] FIG. 20 is an explanatory diagram showing a modified example of the pneumatic tire according to the first embodiment, in which the carcass inner rubber layer has a cover rubber layer. [Figure 21] FIG. 21 is a view taken along the arrow EE in FIG. [Figure 22] FIG. 22 is an explanatory diagram showing a modified example of the pneumatic tire according to the first embodiment, in which linear conductive portions are arranged across both sides in the tire width direction. [Figure 23] FIG. 23 is an explanatory diagram showing a modified example of the pneumatic tire according to the first embodiment, in which linear conductive portions are arranged on both sides in the tire width direction. [Figure 24] FIG. 24 is an explanatory diagram showing a modified example of the pneumatic tire according to the first embodiment, in which an earth tread is arranged. [Figure 25A] FIG. 25A is a chart showing the results of a performance evaluation test of a pneumatic tire. [Figure 25B] FIG. 25B is a chart showing the results of a performance evaluation test of a pneumatic tire. DETAILED DESCRIPTION OF THE INVENTION

[0027] 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.

[0028] [Embodiment 1] [Pneumatic tires] In the following description, a pneumatic tire 1 will be used as an example of a tire according to the present invention. The pneumatic tire 1, which is an example of a tire, can be filled with air, an inert gas such as nitrogen, or other gases.

[0029] In the following description, the tire radial direction refers to the direction perpendicular to the tire rotational axis (not shown), which is the rotational axis of the pneumatic tire 1, the tire radial inner side refers to the side toward the tire rotational axis in the tire radial direction, and the tire radial outer side refers to the side away from the tire rotational axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotational axis as the central axis. The tire width direction refers to the direction parallel to the tire rotational axis, the tire width inner side refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the tire width outer side refers to the side away from the tire equatorial plane CL in the tire width direction. The tire equatorial plane CL is a plane that is perpendicular to the tire rotational axis and passes through the center of the tire width of the pneumatic tire 1, and the tire equatorial plane CL coincides in position in the tire width direction with the tire width centerline, which is the center position of the pneumatic tire 1 in the tire width direction. The tire width is the width in the tire width direction between the portions located outermost in the tire width direction, that is, the distance in the tire width direction between the portions farthest from the tire equatorial plane CL. The tire equator line refers to a line that is on the tire equatorial plane CL and extends along the tire circumferential direction of the pneumatic tire 1. In the following description, the tire meridian cross section refers to a cross section of the tire cut by a plane that includes the tire rotation axis.

[0030] 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire 1 according to embodiment 1. The figure shows one side region in the tire radial direction. The figure also shows a radial tire for passenger cars as an example of a pneumatic tire.

[0031] A pneumatic tire 1 according to the first embodiment has an annular structure centered on the tire rotation axis, and includes a tread portion 2, a pair of sidewall portions 3, 3, a pair of bead portions 10, 10, a carcass layer 13, a belt layer 14, and a carcass inner rubber layer 20 (see FIG. 1). Of these, the pair of sidewall portions 3, 3 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.

[0032] The pair of bead portions 10, 10 are located radially inward of the pair of sidewall portions 3, 3, and each has a bead core 11, a bead filler 12, and a bead portion rubber 30. That is, on both sides of the tire equatorial plane CL in the tire width direction, a pair of bead cores 11, 11, a pair of bead fillers 12, 12, and a pair of bead portion rubbers 30, 30 are arranged. Furthermore, the bead portion rubber 30 has a rim cushion rubber 31 and a chafer 32. Therefore, a pair of rim cushion rubbers 31, 31 and a pair of chafers 32, 32 are arranged on both sides of the tire equatorial plane CL in the tire width direction.

[0033] The pair of bead cores 11, 11 are annular members formed by bundling a plurality of bead wires and form the cores of the pair of bead portions 10, 10. The pair of bead fillers 12, 12 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.

[0034] The carcass layer 13 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 laid between the 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 13 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 13 has a carcass angle, defined as the inclination angle of the extension direction of the carcass cords with respect to the tire circumferential direction, in the range of 80 degrees to 95 degrees in absolute value.

[0035] In the first embodiment, the carcass layer 13 has a single-layer structure and is continuously laid between the bead cores 11, 11 on both sides in the tire width direction. In addition, both end portions of the carcass layer 13 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 12. In other words, the carcass layer 13 is wound back near both end portions in a cross section viewed in the tire meridian direction from the inner side in the tire width direction of the bead cores 11 and the bead fillers 12 to the inner side in the tire radial direction, and then to the outer side in the tire width direction.

[0036] Furthermore, the carcass ply of the carcass layer 13 preferably has a tan δ value of 0.20 or less at 60°C of the coating rubber of the carcass cord, and a volume resistivity of 1×10^8 Ω·cm or more. This reduces the rolling resistance of the tire. Coating rubber with such a volume resistivity can be produced, for example, by using a low-heat-generating compound with a low carbon content. Furthermore, the coating rubber may be constructed without using silica, or may be reinforced by incorporating silica.

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

[0038] Volume resistivity (volume specific resistance) is measured based on JIS K6271, "Vulcanized rubber and thermoplastic rubber - Determination of volume resistivity and surface resistivity." Generally, if the volume resistivity is less than 1 x 10^8 [Ω·cm] or the surface resistivity is less than 1 x 10^8 [Ω / cm], the material can be said to have conductivity that can suppress static electricity buildup.

[0039] A pair of bead portion rubbers 30, 30 possessed by a pair of bead portions 10, 10 are respectively arranged on the tire radially inward side of the bead cores 11, 11 on both sides in the tire width direction and the turnup portion of the carcass layer 13. The bead portion rubber 30 is the portion that abuts against the rim flange R of the rim when the pneumatic tire 1 is mounted on the rim, and constitutes the contact surface of the bead portion 10 with the rim flange R. The bead portion rubber 30 has a volume resistivity of less than 1×10^8 [Ω·cm], and it is preferable that the volume resistivity of the bead portion rubber 30 be 1×10^7 [Ω·cm] or less.

[0040] The belt layer 14 has one or more belt plies extending in the tire width direction, and in the present embodiment 1, multiple belt plies 141 to 143 are laminated. That is, in the present embodiment 1, the belt layer 14 is configured by laminating a pair of cross belts 141, 142 and a belt cover 143 in the tire radial direction, and is disposed on the tire radial outer side of the carcass layer 13 and wound around the outer periphery of the carcass layer 13. The pair of cross belts 141, 142 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 or more and 65 degrees or less in absolute value. Moreover, the pair of cross belts 141, 142 have a so-called cross-ply structure in which the belt angles have opposite signs to each other and are laminated such that the extension directions of the belt cords cross each other. That is, the inclination directions of the belt cords of the pair of cross belts 141, 142 in the tire width direction relative to the tire circumferential direction are opposite to each other. The belt cover 143 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 143 is also arranged by being layered on the outer side of the cross belts 141, 142 in the tire radial direction.

[0041] The tread portion 2 is configured with tread rubber 15, which is a rubber composition, and is arranged radially outward of the carcass layer 13 and the belt layer 14, 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 6 and lug grooves (not shown), that extend in the circumferential direction of the tire are formed in the tread portion 2. In addition, the tread rubber 15 that configures the tread portion 2 has a cap tread 151 and an undertread 152.

[0042] The cap tread 151 is a rubber member located at the outermost position of the tread portion 2 in the tire radial direction and constituting the tire contact surface. 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 151 at 60°C is preferably 0.25 or less. The volume resistivity of the cap tread 151 is preferably in the range of 1×10^8 [Ω·cm] or more, more preferably in the range of 1×10^10 [Ω·cm] or more, and even more preferably in the range of 1×10^12 [Ω·cm] or more. This reduces the rolling resistance of the pneumatic tire 1. The cap tread 151 with such a volume resistivity is produced by using a low-heat-generating compound with a low carbon content and reinforcing it with an increased silica content.

[0043] The undertread 152 is a member laminated on the inner side in the tire radial direction of the cap tread 151. The volume resistivity of the undertread 152 is preferably lower than the volume resistivity of the cap tread 151.

[0044] Each of the pair of sidewall portions 3, 3 includes a sidewall rubber 16, and the pair of sidewall rubbers 16, 16 of the pair of sidewall portions 3, 3 are disposed on the outer side of the carcass layer 13 in the tire width direction. The tan δ value of the sidewall rubber 16 at 60°C is preferably 0.20 or less. The volume resistivity of the sidewall rubber 16 is preferably in the range of 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 16 with such a volume resistivity is produced by using a low-heat-generating compound with a low carbon content and reinforcing it with an increased silica content.

[0045] Although there are no particular limitations on the upper limit of the volume resistivity of the cap tread 151, the lower limit of the volume resistivity of the undertread 152, the upper limit of the volume resistivity of the sidewall rubber 16, and the lower limit of the volume resistivity of the rim cushion rubber 17, they are subject to physical constraints since they are rubber components.

[0046] The carcass inner rubber layer 20 constitutes a 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. In this way, the carcass inner rubber layer 20, which constitutes the tire inner surface 25, is a rubber layer that is placed on the tire cavity side with respect to the carcass layer 13, and covers the carcass layer 13 from the tire cavity side.

[0047] [Static charge suppression structure] 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 the first embodiment employs an anti-static structure to discharge static electricity generated on a vehicle while the vehicle is traveling to the road surface, and linear conductive portions 50 are used as the anti-static structure. The linear conductive portions 50 are linear members having a volume resistivity of less than 1×10^8 [Ω·cm], extend continuously at least from the bead portions 10 to the belt layer 14, and are disposed in the carcass inner rubber layer 20. At least a portion of the linear conductive portions 50 disposed in the carcass inner rubber layer 20 is located within the carcass inner rubber layer 20. In the first embodiment, the linear conductive portions 50 are disposed continuously from one of the bead portions 10 disposed on both sides of the tire equatorial plane CL in the tire width direction to a position on the tire radially inner side of the belt layer 14.

[0048] In the present embodiment 1, the bead portion 10 refers to the region from the measurement point of the rim diameter to 1 / 3 of the tire cross-sectional height SH. The tire cross-sectional height SH refers to 1 / 2 of the difference between the tire outer diameter and the rim diameter, and is measured with the pneumatic tire 1 mounted on a specified rim, a specified internal pressure applied, and no load applied.

[0049] 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. 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. The specified load refers to the "maximum load capacity" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "load capacity" specified by ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 kPa, and the specified load is 88% of the maximum load capacity.

[0050] At a position on the tire radially inner side of the belt layer 14, the linear conductive portions 50 are arranged within and along the carcass inner rubber layer 20 located on the tire radially inner side of the carcass layer 13, and the tire-direction outer end portions of the linear conductive portions 50 are located on the tire radially inner part of the belt layer 14. As a result, at a position on the tire radially inner side of the belt layer 14, the linear conductive portions 50 are arranged overlapping the belt layer 14 in the tire radial direction.

[0051] Furthermore, at the positions of the sidewall portion 3 and the bead portion 10, the linear conductive portions 50 are arranged within and along the carcass inner rubber layer 20, which is located on the inner side of the carcass layer 13 in the tire width direction. The inner end of the linear conductive portions 50 arranged in this manner is located on the inner side of the bead portion 10 in the tire width direction. Furthermore, the portion of the linear conductive portions 50 located at the bead portion 10 is arranged to overlap the bead portion rubber 30 in the tire width direction. This ensures a conductive path from the rim fitting surface to the linear conductive portions 50 via the bead portion rubber 30, and also ensures a conductive path from the position of the bead portion 10 to the position of the belt layer 14.

[0052] The linear conductive portions 50 arranged in this manner extend in a direction close to the tire width direction at positions where they overlap the belt layer 14 in the tire radial direction, and extend in a direction close to the tire radial direction at the positions of the sidewall portion 3 and the bead portion 10.

[0053] 3 is an explanatory diagram of the lap width La of the linear conductive portions 50 relative to the belt layer 14. The relationship between the width Lbp of the belt layer 14 in the periphery direction and the width of the linear conductive portions 50 in the periphery direction that overlaps with the belt layer 14 in the tire radial direction, i.e., the lap width La of the linear conductive portions 50 relative to the belt layer 14, satisfies 0.01≦La / Lbp≦1. In this case, the lap width La of the linear conductive portions 50 is the distance La in the periphery direction of the portions of the linear conductive portions 50 that are located inside the belt layer 14 in the tire radial direction. Note that in the present embodiment 1, the periphery direction refers to the direction along the surface of the pneumatic tire 1 at the same position in the tire circumferential direction.

[0054] In this case, the width Lbp of the belt layer 14 in the periphery direction is the periphery length between intersections P of perpendicular lines Q drawn from both end portions 144 in the tire width direction of the belt ply having the widest width in the tire width direction toward the tire inner surface 25 and the tire inner surface 25. The lap width La of the linear conductive portions 50 relative to the belt layer 14 is the length in the periphery of the portions of the linear conductive portions 50 located on the inner side in the tire radial direction of the belt layer 14, specifically, the length in the periphery of the portions of the linear conductive portions 50 located between the intersections P.

[0055] FIG. 4 is a detailed view of portion A in FIG. 2. The carcass inner rubber layer 20 is formed by laminating a first layer and a second layer, and at least a portion of the linear conductive portion 50 is disposed between the first layer and the second layer. In the first embodiment, the first layer of the carcass inner rubber layer 20 is an inner liner 21 that constitutes the tire inner surface 25, and the second layer is a tie rubber 22 that is disposed on the side of the inner liner 21 where the carcass layer 13 is located. Of these, the inner liner 21 is an air permeation prevention layer that is disposed to cover the carcass layer 13, thereby suppressing oxidation due to exposure of the carcass layer 13 and preventing leakage of air filled in the tire. The inner liner 21 is formed, for example, from a rubber composition primarily composed of butyl rubber, a thermoplastic resin, or a thermoplastic elastomer composition in which an elastomer component is blended into a thermoplastic resin. In particular, when the inner liner 21 is made of a thermoplastic resin or a thermoplastic elastomer composition, the inner liner 21 can be made thinner than when the inner liner 21 is made of butyl rubber, thereby significantly reducing the tire weight.

[0056] 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 100×10^-12 [cc·cm / cm^2·sec·cmHg] or less, and more preferably 50×10^-12 [cc·cm / cm^2·sec·cmHg] or less. The volume resistivity of the inner liner 21 is preferably 1×10^8 [Ω·cm] or more, and generally preferably 1×10^9 [Ω·cm] or more.

[0057] 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).

[0058] Examples of thermoplastic resins include polyamide resins (e.g., nylon 6 (N6), nylon 66 (N66), nylon 46 (N46), nylon 11 (N11), nylon 12 (N12), nylon 610 (N610), nylon 612 (N612), nylon 6 / 66 copolymer (N6 / 66), nylon 6 / 66 / 610 copolymer (N6 / 66 / 610), nylon MXD6, nylon 6T, nylon 9T, nylon 6 / 6T copolymer, nylon 66 / PP copolymer, nylon 66 / PPS copolymer), polyester, -based resins (e.g., aromatic polyesters such as polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), polybutylene terephthalate / tetramethylene glycol copolymer, PET / PEI copolymer, polyarylate (PAR), polybutylene naphthalate (PBN), liquid crystal polyester, polyoxyalkylene diimide diacid / polybutylene terephthalate copolymer), polynitrile-based resins (e.g., polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), methacrylonitrile / styrene copolymer, methacrylonitrile / styrene / butadiene copolymer), poly(meth)acrylate-based resins (e.g., polymethyl methacrylate (PMMA), polyethyl methacrylate, ethylene-ethyl acrylate copolymer (EEA), ethylene-acrylic acid copolymer (EAA), ethylene-methyl acrylate resin (EMA)), polyvinyl-based resins (e.g., vinyl acetate (EVA), polyvinyl alcohol (PVA), vinyl alcohol / ethylene Examples of resins that can be used include: copolymers (EVOH), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymers, vinylidene chloride / methyl acrylate copolymers), cellulose-based resins (e.g., cellulose acetate, cellulose acetate butyrate), fluorine-based resins (e.g., polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymers (ETFE)), and imide-based resins (e.g., aromatic polyimides (PI)).

[0059] Examples of elastomers include diene rubbers and hydrogenated products thereof [e.g., NR, IR, epoxidized natural rubber, SBR, BR (high cis BR and low cis BR), NBR, hydrogenated NBR, hydrogenated SBR], olefin rubbers [e.g., ethylene propylene rubber (EPDM, EPM), maleic acid modified ethylene propylene rubber (M-EPM)], butyl rubber (IIR), copolymers of isobutylene and aromatic vinyl or diene monomers, acrylic rubber (ACM), ionomers, halogen-containing rubbers [e.g., Br-IIR, Cl-IIR, brominated isobutylene-paramethylstyrene copolymers (Br-IPMS)], chloroprene rubber (CR), hydrin rubber (CHC, CHR), chlorosulfur Examples of suitable materials include chlorinated polyethylene (CSM), chlorinated polyethylene (CM), maleic acid-modified chlorinated polyethylene (M-CM), silicone rubber (e.g., methyl vinyl silicone rubber, dimethyl silicone rubber, methyl phenyl vinyl silicone rubber), sulfur-containing rubber (e.g., polysulfide rubber), fluororubber (e.g., vinylidene fluoride-based rubber, fluorine-containing vinyl ether-based rubber, tetrafluoroethylene-propylene-based rubber, fluorine-containing silicone rubber, fluorine-containing phosphazene-based rubber), thermoplastic elastomer (e.g., styrene-based elastomer, olefin-based elastomer, polyester-based elastomer, urethane-based elastomer, polyamide-based elastomer), and the like.

[0060] The tie rubber 22 disposed between the inner liner 21 and the carcass layer 13 is a layer for preventing the carcass cords of the carcass layer 13 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.

[0061] The bead portion rubber 30 disposed in the bead portion 10 is disposed from the inner side of the bead core 11 in the bead portion 10 in the tire width direction, passing through the inner side of the bead core 11 in the tire radial direction, and extending to the outer side of the bead core 11 in the tire width direction. At the position of the bead portion 10, the carcass inner rubber layer 20 is disposed from a position outer in the tire width direction of a portion of a chafer 32 of the bead portion rubber 30 positioned inner in the tire width direction of the bead core 11, to a position inner in the tire radial direction of the bead core 11. That is, at a position on the bead core 11 side relative to the chafer 32, the carcass inner rubber layer 20 extends beyond the position of a bead toe 35, which is the inner end in the tire width direction of a bead base 36 that is the inner circumferential surface of the bead portion 10, to the bead base 36 side.

[0062] Furthermore, the linear conductive portions 50 disposed in the carcass inner rubber layer 20 are located near the bead toe 35 on the outer side of the bead toe 35 in the tire radial direction at the bead portion 10. Therefore, the carcass inner rubber layer 20 and the linear conductive portions 50 overlap the bead portion rubber 30 at the bead portion 10.

[0063] Fig. 5 is a detailed view of part B in Fig. 4. Fig. 6 is a cross-sectional view taken along CC in Fig. 5. The carcass layer 13 has a plurality of carcass cords 131 and a coating rubber 132 that covers the carcass cords 131. The carcass cords 131 are inclined at an angle between 80 degrees and 95 degrees with respect to the tire circumferential direction. The linear conductive portions 50 arranged in the carcass inner rubber layer 20 are arranged between the inner liner 21 and the tie rubber 22 of the carcass inner rubber layer 20, and are arranged along the carcass inner rubber layer 20. The linear conductive portions 50 extend along the periphery direction at least in the region between the belt layer 14 and the bead portion 10. That is, the linear conductive portions 50 are arranged in a direction that is approximately parallel to the carcass cords 131 in the portion extending along the periphery direction.

[0064] 7 is a schematic diagram showing the arrangement of linear conductive portions 50 when the pneumatic tire 1 is viewed in the direction of the tire rotation axis. A plurality of linear conductive portions 50 are arranged in the pneumatic tire 1, and the plurality of linear conductive portions 50 are arranged without overlapping each other. For example, as shown in FIG. 7, the plurality of linear conductive portions 50 are arranged radially at predetermined intervals in the tire circumferential direction.

[0065] FIG. 8 is an explanatory diagram of a linear conductive portion 50 alone. FIG. 8 shows the twisted wire structure of the linear conductive portion 50. The linear conductive portion 50 has a linear structure including conductive linear bodies 51. The linear conductive portion 50 has a twisted wire structure formed by twisting together a plurality of linear bodies, each of which includes one or more conductive linear bodies 51 having a volume resistivity of less than 1×10^8 [Ω·cm]. The linear conductive portion 50 may also be a single-wire cord made of a conductive material (not shown).

[0066] The conductive linear body 51 is a linear body formed by shaping a conductive material into a linear shape. Therefore, the conductive linear body 51 refers to a single fiber, a thread, or a cord made of a conductive material. Therefore, for example, a single-wire cord made of metal or carbon fiber, or a metal fiber made by fiberizing a metal such as stainless steel, falls under the conductive linear body 51. Alternatively, the conductive linear body 51 may be a thread or cord whose surface is coated with a conductive material.

[0067] Examples of the twisted wire structure of the linear conductive portion 50 (see FIG. 8) include (1) a structure formed by twisting together multiple carbon fibers, and (2) a structure formed by twisting together conductive linear bodies 51 having a volume resistivity of less than 1×10^8 [Ω·cm] and non-conductive linear bodies 52 having a volume resistivity of 1×10^8 [Ω·cm] or more. There are no particular limitations on the twisted wire structure of the linear bodies, and any structure can be adopted.

[0068] The non-conductive linear body 52 in (2) above may be made of, for example, polyester fiber, nylon fiber, etc. In particular, it is preferable that the linear conductive portion 50 is a blended yarn formed by twisting together conductive linear body 51 made of metal fiber and non-conductive linear body 52 made of organic fiber such as polyester fiber.

[0069] Furthermore, the total fineness of the linear conductive portions 50 is preferably in the range of 20 dtex to 1000 dtex, and more preferably in the range of 150 dtex to 350 dtex. By setting the lower limit of the total fineness within the above range, breakage of the linear conductive portions 50 during tire manufacturing is suppressed. Furthermore, by setting the upper limit of the total fineness within the above range, breakage of the linear conductive portions 50 during tire rolling is suppressed.

[0070] The total fineness is measured in accordance with JIS L1017 (Test method for synthetic fiber tire cords 8.3 Correct fineness).

[0071] Furthermore, it is preferable that the elongation percentage of the linear conductive portions 50, i.e., the elongation of the linear conductive portions 50, is in the range of 1.0% to 70.0%. By setting the elongation to 1.0% or more, breakage of the linear conductive portions 50 during tire manufacturing is suppressed. Furthermore, by setting the elongation to 70.0% or less, breakage of the linear conductive portions 50 during tire rolling is suppressed.

[0072] The elongation of the linear body is measured in accordance with JIS L1017 (Test method for synthetic fiber tire cords 8.5 Tensile strength and elongation).

[0073] In the first embodiment, the linear conductive portions 50 are yarns, and are sandwiched between the carcass layer 13 and an adjacent member. As shown in Fig. 8, the linear conductive portions 50 have a twisted wire structure formed by twisting together conductive linear bodies 51 having a volume resistivity of less than 1 x 10^8 [Ω·cm] and non-conductive linear bodies 52 having a volume resistivity of 1 x 10^8 [Ω·cm] or more.

[0074] In the pneumatic tire 1 of this embodiment 1, the anti-static structure is configured as described above, so that the path from the rim R through the bead portion rubber 30 and the linear conductive portion 50 to the belt layer 14 can be used as a conductive path for dissipating static electricity from the vehicle to the road surface.

[0075] The bead portion rubber 30, the coating rubber of the carcass layer 13, and the coating rubber of the belt layer 14 serve as conductive paths from the rim R to the belt layer 14. For this reason, it is preferable that the volume resistivity of these rubbers be set low. This improves the conductive efficiency from the rim R to the belt layer 14.

[0076] [Actions and Effects] When the pneumatic tire 1 according to the first embodiment is mounted on a vehicle and the vehicle runs, the pneumatic tire 1 rotates while the lower portion of the surface of the tread portion 2 of the pneumatic tire 1 that faces the road surface comes into contact with the road surface. The pneumatic tire 1 can generate frictional forces with the road surface as the surface of the tread portion 2 successively comes into contact with the road surface in this manner. This allows the vehicle to transmit driving force, braking force, and turning force to the road surface due to the frictional forces between the pneumatic tire 1 and the road surface, and the vehicle can run using these driving force, braking force, and turning force.

[0077] Furthermore, static electricity may be generated while the vehicle is running, and this static electricity flows from the rim R through the bead portion rubber 30 and linear conductive portion 50 to the belt layer 14, from the belt layer 14 to the tread rubber 15, and is then released to the road surface from the tread rubber 15. This allows static electricity generated on the vehicle to be released to the road surface, suppressing charging of the vehicle due to static electricity.

[0078] That is, electricity flows relatively easily through linear conductive portions 50 having a volume resistivity of less than 1×10^8 [Ω·cm], which can reduce the tire electrical resistance, which is the electrical resistance of the pneumatic tire 1. As a result, the pneumatic tire 1 having the linear conductive portions 50 disposed therein can channel static electricity generated while the vehicle is traveling from the bead portion rubber 30 side to the belt layer 14 side via the linear conductive portions 50, thereby suppressing charging of the vehicle due to static electricity.

[0079] When the vehicle is running, the tread portion 2, sidewall portion 3, etc. rotate while deforming due to loads generated according to the running conditions of the vehicle. The linear conductive portions 50 are disposed on the tire cavity side relative to the carcass layer 13. Therefore, when the tread portion 2 or the sidewall portion 3 deforms, the carcass layer 13 also deforms in accordance with these deformations, which may cause the carcass layer 13 to rub against the linear conductive portions 50 and result in the disconnection of the linear conductive portions 50. For example, when the carcass layer 13 deforms, the carcass cords 131 of the carcass layer 13 rub against the linear conductive portions 50, which may result in the disconnection of the linear conductive portions 50.

[0080] If the linear conductive portions 50 break, the conductive path from the rim R to the belt layer 14 is cut off, making it difficult for static electricity generated in the vehicle to be released to the road surface. However, in the pneumatic tire 1 according to the first embodiment, at least a portion of the linear conductive portions 50 is located within the carcass inner rubber layer 20. Therefore, even if the tread portion 2 or the sidewall portion 3 is deformed, the carcass layer 13 is less likely to rub against the linear conductive portions 50. Therefore, the linear conductive portions 50 can ensure an electrical path between the bead portion rubber 30 and the belt layer 14 even after the pneumatic tire 1 has traveled a long distance. This makes it possible to prevent an increase in tire electrical resistance due to a break in the linear conductive portions 50 when the pneumatic tire 1 has traveled a long distance. As a result, the tire electrical resistance after travel can be maintained.

[0081] It is preferable that the linear conductive portions 50, at least a portion of which is located within the carcass inner rubber layer 20, are arranged without being exposed to the tire cavity side. That is, if the linear conductive portions 50 are exposed from within the carcass inner rubber layer 20 to the tire cavity side, inflated air may easily pass through the linear conductive portions 50 and escape from the tire cavity side to the carcass layer 13 side, which may result in air leakage. In this case, the air pressure decreases, which increases the amount of tire deformation during running, and the linear conductive portions 50 may be easily broken due to friction between the carcass inner rubber layer 20 and the linear conductive portions 50. If the linear conductive portions 50 break, the linear conductive portions 50 will no longer be able to ensure an electrical path, which will increase the tire electrical resistance. Therefore, it is preferable that the linear conductive portions 50 are arranged without being exposed to the tire cavity side.

[0082] Furthermore, the relationship between the width Lbp of the belt layer 14 in the periphery direction and the lap width La of the linear conductive portions 50 relative to the belt layer 14 satisfies 0.01≦La / Lbp≦1, so the linear conductive portions 50 can more reliably ensure an electrical path between the bead portion rubber 30 and the belt layer 14. In other words, if the relationship between the width Lbp of the belt layer 14 and the lap width La of the linear conductive portions 50 relative to the belt layer 14 is La / Lbp<0.01, the lap width La of the linear conductive portions 50 relative to the belt layer 14 is too small, which may make it difficult to ensure sufficient conductivity between the linear conductive portions 50 and the belt layer 14. In this case, even if the linear conductive portions 50 are provided, it may be difficult to ensure an electrical path between the bead portion rubber 30 and the belt layer 14, and this may make it difficult to effectively reduce the tire electrical resistance.

[0083] On the other hand, when the relationship between the width Lbp of the belt layer 14 and the lap width La of the linear conductive portions 50 relative to the belt layer 14 satisfies 0.01≦La / Lbp≦1, sufficient conductivity can be ensured between the linear conductive portions 50 and the belt layer 14, and the linear conductive portions 50 can ensure an electrical path between the bead portion rubber 30 and the belt layer 14. As a result, the linear conductive portions 50 can more reliably reduce the tire electrical resistance.

[0084] Furthermore, the bead rubber 30 has a volume resistivity of less than 1×10^8 [Ω·cm], and the linear conductive portions 50 are arranged to have portions that overlap with the bead rubber 30. This ensures sufficient conductivity between the linear conductive portions 50 and the bead rubber 30, and a conductive path can be established from the rim R to the linear conductive portions 50 via the bead rubber 30, making it easier to flow electricity more effectively. As a result, the electrical resistance of the pneumatic tire 1 when it is new can be reduced.

[0085] Furthermore, since the linear conductive portions 50 extend in the periphery direction at least in the region between the belt layer 14 and the bead portion 10, deformation of the sidewall portion 3 during running can be prevented from acting as a shear force on the linear conductive portions 50. This prevents the linear conductive portions 50 from being broken due to a shear force acting on the linear conductive portions 50 during running, and the linear conductive portions 50 can more reliably secure an electrical path between the bead portion rubber 30 and the belt layer 14 even after running. As a result, the tire electrical resistance after running can be more reliably maintained.

[0086] Furthermore, the carcass inner rubber layer 20 is formed by laminating an inner liner 21 as a first layer and a tie rubber 22 as a second layer, and at least a portion of the linear conductive portions 50 is disposed between the inner liner 21 and the tie rubber 22, so that the linear conductive portions 50 can be more reliably prevented from being rubbed by the carcass cords 131 when the tread portion 2 or the sidewall portion 3 is deformed. This makes it possible to more reliably ensure an electrical path between the bead portion rubber 30 and the belt layer 14 by the linear conductive portions 50 even after running. As a result, the tire electrical resistance after running can be more reliably maintained.

[0087] Furthermore, since the linear conductive portion 50 is formed by twisting together a plurality of linear bodies, including at least one conductive linear body 51 having a volume resistivity of less than 1×10^8 [Ω·cm], the strength of the linear conductive portion 50 can be ensured while ensuring the desired electrical resistivity. In other words, by making the linear conductive portion 50 a twisted wire structure of a plurality of linear bodies, strength against repeated fatigue and elongation can be improved compared to a linear conductive portion 50 configured as a single wire. As a result, tire electrical resistance can be reduced and the durability of the linear conductive portion 50 can be more reliably improved.

[0088] Furthermore, since the linear conductive portion 50 is formed by twisting together the conductive linear bodies 51 and the non-conductive linear bodies 52 having a volume resistivity of 1×10^8 [Ω·cm] or more, the desired electrical resistivity can be ensured while the weak points of the linear conductive portion 50 can be compensated for by the non-conductive linear bodies 52. As a result, the strength, heat resistance, and dimensional stability of the linear conductive portion 50 can be appropriately ensured, and the durability of the linear conductive portion 50 can be more reliably improved.

[0089] Furthermore, by using metal fiber for the conductive linear bodies 51 and organic fiber for the non-conductive linear bodies 52 of the linear conductive portion 50, it is possible to more reliably and appropriately ensure the strength, heat resistance, and dimensional stability of the linear conductive portion 50. As a result, it is possible to more reliably improve the durability of the linear conductive portion 50.

[0090] Furthermore, by forming the conductive linear body 51 of the linear conductive portion 50 by twisting together a plurality of carbon fibers, it is possible to ensure the desired electrical resistivity while also ensuring the strength of the linear conductive portion 50. As a result, it is possible to reduce the tire electrical resistance and more reliably improve the durability of the linear conductive portion 50.

[0091] Furthermore, by forming the conductive linear body 51 of the linear conductive portion 50 from a single-wire cord made of carbon fiber, it is possible to easily ensure a desired electrical resistivity, which makes it easier to reduce the tire electrical resistance.

[0092] Furthermore, since the linear conductive portions 50 have a total fineness of 20 dtex or more and 1000 dtex or less, it is possible to optimize the total fineness of the linear conductive portions 50. That is, by having the total fineness of the linear conductive portions 50 be 20 dtex or more, it is possible to suppress breakage of the linear conductive portions 50 during tire manufacturing. Furthermore, by having the total fineness of the linear conductive portions 50 be 1000 dtex or less, it is possible to suppress breakage of the linear conductive portions 50 during tire rolling.

[0093] Furthermore, since the elongation rate of the linear conductive portions 50 is 1.0% or more and 70.0% or less, it is possible to optimize the elongation rate of the linear conductive portions 50. That is, by making the elongation rate of the linear conductive portions 50 1.0% or more, it is possible to prevent breakage of the linear conductive portions 50 during tire manufacturing. Furthermore, by making the elongation rate 70.0% or less, it is possible to prevent breakage of the linear conductive portions 50 during tire rolling.

[0094] [Embodiment 2] The pneumatic tire 1 according to the second embodiment has substantially the same configuration as the pneumatic tire 1 according to the first embodiment, but is characterized in that the linear conductive portions 50 are sewn into the tie rubber 22. Since the other configurations are the same as those of the first embodiment, the description thereof will be omitted and the same reference numerals will be used.

[0095] Fig. 9 is a cross-sectional view of a main part showing an arrangement of the linear conductive portions 50 in a pneumatic tire 1 according to the second embodiment. Fig. 9 is a detailed cross-sectional view of the positions where the linear conductive portions 50 are arranged when viewed in the tire circumferential direction, and is, for example, a detailed cross-sectional view of a position corresponding to part B in Fig. 4 in the first embodiment. In the pneumatic tire 1 according to the second embodiment, similar to the pneumatic tire 1 according to the first embodiment, the linear conductive portions 50 extending continuously at least from the bead portions 10 to the belt layer 14 are arranged in the carcass inner rubber layer 20. Furthermore, in the second embodiment, unlike the first embodiment, the linear conductive portions 50 are sewn into the tie rubber 22 of the carcass inner rubber layer 20.

[0096] Specifically, the linear conductive portions 50 are sewn into the tie rubber 22 by repeatedly moving back and forth between the surface of the tie rubber 22 facing the carcass layer 13 and the surface of the tie rubber 22 facing the inner liner 21 in the thickness direction while extending in the periphery. That is, the linear conductive portions 50 are exposed from the tie rubber 22 on the surfaces of the tie rubber 22 facing the carcass layer 13 and the inner liner 21 in the thickness direction of the tie rubber 22.

[0097] Furthermore, at least in a region of the linear conductive portions 50 that is radially outward of the bead portions 10, the relationship between the thickness t of the carcass inner rubber layer 20 and the distance t1 from the tire inner surface 25 at the portion of the linear conductive portions 50 where the distance from the tire inner surface 25 is smallest satisfies 0.2≦t1 / t≦0.8. In the second embodiment, the linear conductive portions 50 are exposed on the surface of the tie rubber 22 on the inner liner 21 side, and therefore the distance t1 from the tire inner surface 25 of the linear conductive portions 50 is substantially the same as the thickness of the inner liner 21.

[0098] Fig. 10 is a DD cross-sectional view of Fig. 9. In Fig. 10, the portions of the linear conductive portions 50 exposed on the surface 22a of the tie rubber 22 are indicated by solid lines, and the portions of the linear conductive portions 50 not exposed on the surface 22a of the tie rubber 22 are indicated by dashed lines. The linear conductive portions 50 exposed on the surface 22a of the tie rubber 22 have an exposed length Le on the surface 22a of the tie rubber 22 in the range of 1 mm to 30 mm. In this way, the linear conductive portions 50 arranged in the carcass inner rubber layer 20 are sewn into the tie rubber 22 while being exposed on the surface 22a of the tie rubber 22 by a length Le of 1 mm to 30 mm.

[0099] In the second embodiment, the linear conductive portions 50 are sewn into the tie rubber 22, and therefore the linear conductive portions 50 can suppress movement of the tie rubber 22 when the pneumatic tire 1 deforms as the vehicle equipped with the pneumatic tire 1 runs. This minimizes friction between the linear conductive portions 50 and the tie rubber 22, even when the carcass inner rubber layer 20, in which the linear conductive portions 50 are arranged, deforms in conjunction with deformation of the pneumatic tire 1. This prevents breakage of the linear conductive portions 50 due to friction between the linear conductive portions 50 and the tie rubber 22, and ensures that the linear conductive portions 50 maintain an electrical path between the bead portion rubber 30 and the belt layer 14 even after running. As a result, the tire's electrical resistance can be more reliably maintained after running.

[0100] Furthermore, the relationship between the thickness t of the carcass inner rubber layer 20 and the distance t1 of the linear conductive portions 50 from the tire inner surface 25 satisfies 0.2≦t1 / t≦0.8, so that the electrical path between the bead portion rubber 30 and the belt layer 14 can be more reliably secured even after running. In other words, if the relationship between the thickness t of the carcass inner rubber layer 20 and the distance t1 of the linear conductive portions 50 from the tire inner surface 25 is t1 / t<0.2, the linear conductive portions 50 are too close to the tire inner surface 25, and there is a risk that air on the tire cavity side may easily escape to the carcass layer 13 side from areas where the rubber is thin between the linear conductive portions 50 and the tire inner surface 25. In this case, a decrease in the air pressure of the pneumatic tire 1 increases the amount of tire deformation during running, and friction between the carcass inner rubber layer 20 and the linear conductive portions 50 makes the linear conductive portions 50 more likely to break, which may make it difficult to secure an electrical path through the linear conductive portions 50. Furthermore, when the relationship between the thickness t of the carcass inner rubber layer 20 and the distance t1 of the linear conductive portions 50 from the tire inner surface 25 is t1 / t>0.8, the distance between the linear conductive portions 50 and the carcass cords 131 is too close, and the linear conductive portions 50 may be easily rubbed by the carcass cords 131 due to deformation of the carcass cords 131 accompanying tire deformation during running. In this case, the linear conductive portions 50 may be easily broken, making it difficult to ensure an electrical path through the linear conductive portions 50.

[0101] In contrast, when the relationship between the thickness t of the carcass inner rubber layer 20 and the distance t1 of the linear conductive portions 50 from the tire inner surface 25 satisfies 0.2≦t1 / t≦0.8, the linear conductive portions 50 are prevented from being easily rubbed by the carcass cords 131, and the carcass inner rubber layer 20 and the linear conductive portions 50 are prevented from being easily rubbed due to an increase in tire deformation caused by air escaping from the tire cavity side. This makes it possible to prevent breakage of the linear conductive portions 50, and the linear conductive portions 50 can more reliably secure an electrical path between the bead portion rubber 30 and the belt layer 14 even after running. As a result, the tire electrical resistance after running can be more reliably maintained.

[0102] Furthermore, since the linear conductive portions 50 are sewn into the tie rubber 22 while being exposed on the surface 22a of the tie rubber 22 for a length of 1 mm to 30 mm, an electrical path through the linear conductive portions 50 can be more reliably secured even after running. In other words, if the length Le of the linear conductive portions 50 exposed on the surface 22a of the tie rubber 22 is shorter than 1 mm, the sewing intervals of the linear conductive portions 50 are too short, which may make it difficult to sew the linear conductive portions 50 to the tie rubber 22. Furthermore, if the length Le of the linear conductive portions 50 exposed on the surface 22a of the tie rubber 22 is longer than 30 mm, the sewing intervals of the linear conductive portions 50 are too long, which may make it difficult to effectively suppress the movement of the tie rubber 22 even if the linear conductive portions 50 are sewn to the tie rubber 22. In this case, it becomes difficult to prevent the linear conductive portions 50 from rubbing against the tie rubber 22 when the tire deforms, and it may become difficult to prevent breakage of the linear conductive portions 50 due to rubbing between the linear conductive portions 50 and the tie rubber 22. Furthermore, if the length Le of the linear conductive portions 50 exposed on the surface 22a of the tie rubber 22 is longer than 30 mm, the stitching interval of the linear conductive portions 50 is too long, and therefore the portion of the linear conductive portions 50 exposed on the surface 22a of the tie rubber 22 may rub against the carcass cord 131, making the linear conductive portions 50 more susceptible to breakage.

[0103] In contrast, when the length Le of the linear conductive portions 50 exposed on the surface 22a of the tie rubber 22 is set to 1 mm or more and 30 mm or less and the linear conductive portions 50 are sewn to the tie rubber 22, sewing the linear conductive portions 50 to the tie rubber 22 is facilitated, and the linear conductive portions 50 can effectively suppress movement of the tie rubber 22 and suppress friction between the linear conductive portions 50 and the carcass cords 131. Therefore, it is possible to suppress breakage of the linear conductive portions 50 due to friction between the tie rubber 22 caused by movement of the tie rubber 22 during running, or breakage of the linear conductive portions 50 due to friction between the linear conductive portions 50 and the carcass cords 131, and the linear conductive portions 50 can be more reliably secured by the linear conductive portions 50 to ensure an electrical path between the bead portion rubber 30 and the belt layer 14 even after running. As a result, the tire electrical resistance after running can be more reliably maintained.

[0104] [Variations] In the above-described embodiment 1, the carcass inner rubber layer 20 and the linear conductive portion 50 are arranged between the bead portion rubber 30 and the bead core 11 at the position of the bead portion 10, but the carcass inner rubber layer 20 and the linear conductive portion 50 may be arranged at a position other than this at the position of the bead portion 10.

[0105] FIG. 11 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the first embodiment, in which the carcass inner rubber layer 20 and the linear conductive portions 50 are located on the inner side of the bead portion rubber 30 in the tire width direction. For example, as shown in FIG. 11, the carcass inner rubber layer 20 may be located on the inner side of the bead portion rubber 30 in the tire width direction at the position of the bead portion 10. In the modified example shown in FIG. 11, the end portion on the inner side in the tire radial direction of the carcass inner rubber layer 20 is located near the bead toe 35. Therefore, the linear conductive portions 50 arranged in the carcass inner rubber layer 20 are also located near the bead toe 35 on the outer side in the tire radial direction of the bead portion 10. As a result, the linear conductive portions 50 and the carcass inner rubber layer 20 both overlap the bead portion rubber 30 at the position of the bead portion 10.

[0106] Fig. 12 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the first embodiment, in which the linear conductive portions 50 are also arranged on the bead base 36 side. Furthermore, as shown in Fig. 12, the linear conductive portions 50 arranged in the carcass inner rubber layer 20 may extend from the tire inner surface 25 side, past the bead toe 35 of the bead portion 10, to the bead base 36, at a position on the bead core 11 side with respect to the chafer 32 arranged in the bead portion 10. That is, in the modified example shown in Fig. 12, as in the above-described first embodiment, at the position of the bead portion 10, the carcass inner rubber layer 20 is arranged from a position on the outer side in the tire width direction of a portion of the chafer 32 of the bead portion rubber 30 located on the inner side in the tire width direction of the bead core 11, to a position on the inner side in the tire radial direction of the bead core 11.

[0107] 12, the linear conductive portions 50 are also arranged, like the carcass inner rubber layer 20, from a position outside in the tire width direction of a portion of the chafer 32 of the bead portion rubber 30 that is located inside in the tire width direction of the bead core 11 to a position inside in the tire radial direction of the bead core 11. As a result, in the modified example shown in Fig. 12, the linear conductive portions 50 of the carcass inner rubber layer 20 all extend beyond the bead toe 35 to the bead base 36 side at a position on the bead core 11 side relative to the chafer 32, and overlap the bead portion rubber 30.

[0108] In the first embodiment described above, the bead portion rubber 30 includes a rim cushion rubber 31 and a chafer 32. However, the bead portion rubber 30 may also include a member having a volume resistivity of less than 1×10^8 [Ω·cm]. FIG. 13 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the first embodiment, in which a conductive rubber 33 is disposed in the bead portion rubber 30. For example, as shown in FIG. 13, the bead portion rubber 30 may include a conductive rubber 33, which is a rubber member having a volume resistivity of less than 1×10^8 [Ω·cm], disposed in the chafer 32. The conductive rubber 33 shown in FIG. 13 is disposed in communication from the inner side to the outer side in the tire radial direction in the portion of the chafer 32 that forms the bead base 36. This allows the conductive rubber 33 to come into contact with the rim R when the pneumatic tire 1 is mounted on the rim. In this way, when conductive rubber 33 with a volume resistivity of less than 1×10^8 [Ω·cm] is placed in the bead portion rubber 30, the rim cushion rubber 31 and the chafer 32 do not need to have a volume resistivity of less than 1×10^8 [Ω·cm].

[0109] When the conductive rubber 33 is disposed on the chafer 32 in this manner, the linear conductive portion 50 of the carcass inner rubber layer 20 is disposed at a position on the bead core 11 side of the chafer 32, extending beyond the bead toe 35 to the bead base 36 side, as in the modified example shown in Fig. 12. As a result, the linear conductive portion 50 is disposed overlapping the conductive rubber 33 in the bead portion rubber 30, which has a volume resistivity of less than 1 x 10^8 [Ω cm], and the conductive rubber 33 can ensure conductivity between the rim R and the linear conductive portion 50. Therefore, a conductive path can be connected from the rim R to the linear conductive portion 50 via the conductive rubber 33, making it easier for electricity to flow more effectively and reducing the electrical resistance of the new pneumatic tire 1.

[0110] Furthermore, in the above-described first embodiment, the linear conductive portions 50 are arranged only to overlap the bead portion rubber 30, but the linear conductive portions 50 may also be in contact with the bead portion rubber 30. FIG. 14 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the first embodiment, illustrating a state in which the linear conductive portions 50 are in contact with the chafer 32 of the bead portion rubber 30. For example, similar to the modified example shown in FIG. 12 , the linear conductive portions 50 may extend from the tire inner surface 25 side to at least the bead base 36 beyond the bead toe 35 of the bead portion 10 at a position on the bead core 11 side relative to the chafer 32, and further contact the bead portion rubber 30 at a position closer to the bead base 36 than the bead toe 35, as shown in FIG. 14 . That is, the linear conductive portions 50 may have contact portions 50a that are in contact with the bead portion rubber 30. Specifically, in the modified example shown in Figure 14, the linear conductive portion 50 arranged in the carcass inner rubber layer 20 comes out from the carcass inner rubber layer 20 at a position overlapping the portion of the chafer 32 that forms the bead base 36, and comes into contact with the chafer 32 that the bead portion rubber 30 has, thereby forming a contact portion 50a.

[0111] 15 is a modified example of the pneumatic tire 1 according to the first embodiment, and is an explanatory diagram showing a state in which the linear conductive portions 50 contact the chafers 32 of the bead portion rubber 30. Alternatively, as shown in FIG. 15, the linear conductive portions 50 may be positioned in the carcass inner rubber layer 20 partially toward the chafer 32 at a position in the carcass inner rubber layer 20 that overlaps with a portion of the chafer 32 that forms the bead base 36, thereby forming contact portions 50a that contact the bead portion rubber 30.

[0112] As described above, the linear conductive portions 50 have contact portions 50a that contact the bead rubber 30, thereby ensuring a conductive path between the linear conductive portions 50 and the bead rubber 30, thereby ensuring a conductive path from the rim R through the bead rubber 30 to the linear conductive portions 50. This allows electricity to pass more effectively, further reducing the tire's electrical resistance when new. Furthermore, the linear conductive portions 50 have contact portions 50a that contact the bead rubber 30 in a region that extends beyond the bead toe 35 to the bead base 36, allowing the linear conductive portions 50 to contact the bead rubber 30 while reducing the possibility of air leakage. As a result, the tire's electrical resistance can be more reliably maintained after driving.

[0113] Furthermore, in the first embodiment described above, the linear conductive portions 50 extend in a direction along the periphery direction, but the linear conductive portions 50 may extend in a direction other than the periphery direction. Fig. 16 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the first embodiment, in which the linear conductive portions 50 have portions inclined with respect to the periphery direction. A portion of the linear conductive portions 50 located on the tire radially inner side of the belt layer 14 and a portion located in the bead portion 10 may each have a portion inclined in the tire circumferential direction at an inclination angle θ of 30° or less with respect to the periphery direction. In other words, the linear conductive portions 50 extend substantially along the periphery direction in a portion located between the tire radially inner side of the belt layer 14 and the bead portion 10, and a portion of the linear conductive portions 50 located on the tire radially inner side of the belt layer 14 and the bead portion 10 may each have a portion inclined in the tire circumferential direction with respect to the periphery direction.

[0114] For example, as shown in Fig. 16, the linear conductive portions 50 may be formed in a wave shape that extends in the periphery direction and curves in the tire circumferential direction at a position on the inner side of the belt layer 14 in the tire radial direction and at the position of the bead portion 10. In this case, the linear conductive portions 50 formed in a wave shape preferably have an inclination angle θ of 30° or less in the tire circumferential direction with respect to the periphery direction. This allows the tire electrical resistance of the pneumatic tire 1 to be reduced when it is new.

[0115] In other words, tire deformation during running is reduced in both the portions of the pneumatic tire 1 where the belt layers 14 are arranged and in the bead portions 10, and the linear conductive portions 50 are less likely to rub against other components even during running. Therefore, by making the linear conductive portions 50 extend in the periphery and inclined in the tire circumferential direction between the radially inner position of the belt layer 14 and the position of the bead portions 10, it is possible to increase the overlapping length of the linear conductive portions 50 with the belt layer 14 and the bead portion rubber 30 while suppressing breakage of the linear conductive portions 50 due to rubbing against other components. As a result, it is possible to reduce the tire electrical resistance of the pneumatic tire 1 when it is new while ensuring durability.

[0116] Furthermore, in the above-described second embodiment, the linear conductive portions 50 are sewn into the tie rubber 22 while extending in the periphery direction. However, the linear conductive portions 50 may be sewn into the tie rubber 22 while inclined relative to the periphery direction. FIG. 17 is a modified example of the pneumatic tire 1 according to the second embodiment, and is an explanatory diagram showing a state in which the linear conductive portions 50 are sewn into the tie rubber 22 while inclining toward the tire circumferential direction. Note that FIG. 17 is an explanatory diagram showing the carcass inner rubber layer 20 as viewed from the surface 22a on the tie rubber 22 side, i.e., as viewed in the same direction as the DD cross section in FIG. 9. The linear conductive portions 50 are sewn into the tie rubber 22 of the carcass inner rubber layer 20 while repeatedly inclining toward the tire circumferential direction relative to the periphery direction, so that the portions of the linear conductive portions 50 exposed on the surface 22a of the tie rubber 22 may be inclined relative to the tire circumferential direction, as shown in FIG.

[0117] That is, the linear conductive portions 50 may be sewn into the tie rubber 22 while oscillating in the tire circumferential direction with respect to the periphery direction, so that the portions exposed on the surface 22a of the tie rubber 22 are inclined with respect to both the periphery direction and the tire circumferential direction, as shown in Example 1 of Fig. 17. Alternatively, the linear conductive portions 50 may be sewn into the tie rubber 22 while oscillating in the tire circumferential direction with respect to the periphery direction, so that the portions exposed on the surface 22a of the tie rubber 22 are inclined at about 90° with respect to the periphery direction and extend in the tire circumferential direction, as shown in Example 2 of Fig. 17. When the linear conductive portions 50 are sewn into the tie rubber 22 of the carcass inner rubber layer 20, it is preferable that the linear conductive portions 50 are sewn so that they are exposed on the surface 22a of the tie rubber 22 by a length Le of 1 mm or more and 30 mm or less, regardless of the angle of the portions exposed on the surface 22a of the tie rubber 22.

[0118] Furthermore, in the above-described second embodiment, the linear conductive portions 50 are sewn into the tie rubber 22 by extending in the periphery direction and repeatedly moving back and forth between both surfaces of the tie rubber 22 in the thickness direction. However, the linear conductive portions 50 may be sewn into the tie rubber 22 in other ways. FIG. 18 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the second embodiment, illustrating a state in which the linear conductive portions 50 are woven into the tie rubber 22. For example, as shown in FIG. 18 , the linear conductive portions 50 may extend in the periphery direction and repeatedly move back and forth between both surfaces of the tie rubber 22 in the thickness direction, and also repeatedly move back and forth in the periphery direction, so that the linear conductive portions 50 intertwine with each other and are woven into the tie rubber 22. By weaving the linear conductive portions 50 into the tie rubber 22, the linear conductive portions 50 can more reliably suppress movement of the tie rubber 22 when the pneumatic tire 1 is deformed due to the running of a vehicle equipped with the pneumatic tire 1.

[0119] Furthermore, the linear conductive portions 50 may be sewn into the tie rubber 22 using other members as well. FIG. 19 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the second embodiment, in which the linear conductive portions 50 are sewn into the tie rubber 22 using linear non-conductive portions 55 as well. In FIG. 19, the linear non-conductive portions 55 are indicated by dashed lines to distinguish between the linear conductive portions 50 and the linear non-conductive portions 55. For example, as shown in FIG. 19, the linear conductive portions 50 may be sewn into the tie rubber 22 using linear non-conductive portions 55 as well. In this case, the linear non-conductive portions 55 are linear members having a volume resistivity of 1×10^8 [Ω·cm] or more. In the modified example shown in Figure 19, the linear conductive portions 50 are sewn into the tie rubber 22 from the surface side facing the inner liner 21, and the linear non-conductive portions 55 are sewn into the tie rubber 22 from the surface side facing the carcass layer 13.The linear conductive portions 50 and the linear non-conductive portions 55 engage with each other within the tie rubber 22, whereby the linear conductive portions 50 are sewn into the tie rubber 22.

[0120] By sewing the linear conductive portions 50 into the tie rubber 22 by engaging them with the linear non-conductive portions 55 sewn into the tie rubber 22 from the surface of the tie rubber 22 facing the carcass layer 13, the linear conductive portions 50 can be sewn into the tie rubber 22 while increasing the distance between the linear conductive portions 50 and the carcass cords 131. This allows the linear conductive portions 50 to suppress movement of the tie rubber 22 during deformation of the pneumatic tire 1, thereby suppressing friction between the linear conductive portions 50 and the tie rubber 22 and suppressing friction of the linear conductive portions 50 against the carcass cords 131. Therefore, breakage of the linear conductive portions 50 caused by friction between the linear conductive portions 50 and the tie rubber 22 or the carcass cords 131 during deformation of the pneumatic tire 1 can be suppressed, and the linear conductive portions 50 can be secured by the linear conductive portions 50 to maintain an electrical path between the bead portion rubber 30 and the belt layer 14 even after running. As a result, the tire's electrical resistance can be more reliably maintained after running.

[0121] Furthermore, in the above-described first embodiment, the linear conductive portions 50 are disposed inside the carcass inner rubber layer 20 without being exposed to the tire inner surface 25, but the linear conductive portions 50 may be partially exposed to the tire inner surface 25. It is preferable that 60% or more of the length of the linear conductive portions 50 in the extension direction be disposed within the carcass inner rubber layer 20 without being exposed to the tire inner surface 25.

[0122]

[0063] In the first embodiment described above, the carcass inner rubber layer 20 in which the linear conductive portions 50 are arranged is formed by laminating the inner liner 21 and the tie rubber 22, but the carcass inner rubber layer 20 may be made of a material other than the inner liner 21 and the tie rubber 22. Fig. 20 is a modified example of the pneumatic tire 1 according to the first embodiment, and is an explanatory diagram of a case in which the carcass inner rubber layer 20 has a cover rubber layer 23. Fig. 21 is a view taken along the arrow E-E in Fig. 20. For example, as shown in Figs. 20 and 21, the carcass inner rubber layer 20 may have the cover rubber layer 23 in addition to the inner liner 21 and the tie rubber 22. In this case, the linear conductive portions 50 are arranged on the surface of the inner liner 21 facing the tire cavity, i.e., the surface of the inner liner 21 opposite to the surface facing the tie rubber 22, and the cover rubber layer 23 is arranged to cover the linear conductive portions 50 from the tire cavity side. The cover rubber layer 23, which is a component of the carcass inner rubber layer 20 and is disposed to cover the linear conductive portions 50, is a strip-shaped member made of a rubber material.

[0123] The band-shaped cover rubber layer 23 extends substantially in the periphery along the linear conductive portions 50, and covers the linear conductive portions 50 over the entire longitudinal area of ​​the linear conductive portions 50 arranged in the inner liner 21. In other words, in the modified example shown in Figures 20 and 21, the carcass inner side rubber layer 20 has the cover rubber layer 23 as the first layer and the inner liner 21 as the second layer, and the linear conductive portions 50 are arranged between the cover rubber layer 23, which is the first layer, and the inner liner 21, which is the second layer. As a result, the linear conductive portions 50 are located and arranged within the carcass inner side rubber layer 20.

[0124] By arranging the linear conductive portions 50 in the carcass inner rubber layer 20 as described above, they are less likely to rub against the carcass layer 13 when the pneumatic tire 1 deforms, which makes it possible to prevent breakage of the linear conductive portions 50. Therefore, the linear conductive portions 50 can ensure an electrical path between the bead portion rubber 30 and the belt layer 14 even after the pneumatic tire 1 has traveled a long distance, and the tire electrical resistance after travel can be maintained.

[0125] Furthermore, in the above-described first embodiment, the linear conductive portions 50 are arranged on one side of the tire equatorial plane CL in the tire width direction, but the linear conductive portions 50 may be arranged on both sides of the tire equatorial plane CL in the tire width direction. Fig. 22 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the first embodiment, in which the linear conductive portions 50 are arranged on both sides in the tire width direction. For example, as shown in Fig. 22, the linear conductive portions 50 may be arranged on both sides in the tire width direction. That is, the linear conductive portions 50 may be arranged continuously from one bead portion 10 side to the other bead portion 10 side of the bead portions 10 located on both sides in the tire width direction.

[0126] Fig. 23 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the first embodiment, in which the linear conductive portions 50 are arranged on both sides in the tire width direction. Furthermore, as shown in Fig. 23, the linear conductive portions 50 may be arranged such that mutually independent linear conductive portions 50 extend from the position of the bead portion 10 to the position of the belt layer 14 in regions on both sides of the tire equatorial plane CL in the tire width direction. In this case, the lap width La of the linear conductive portions 50 with respect to the belt layer 14 (see Fig. 3) may be the same size for the linear conductive portions 50 arranged on both sides in the tire width direction, or may be different sizes.

[0127] Furthermore, in the above-described first embodiment, the linear conductive portions 50 are used as a charge-reducing structure for discharging static electricity generated on the vehicle while the vehicle is traveling to the road surface. However, the charge-reducing structure may also use other components than the linear conductive portions 50. FIG. 24 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the first embodiment, in which an earth tread 60 is arranged. For example, as shown in FIG. 24, an earth tread 60 may be used as a charge-reducing structure for discharging static electricity generated on the vehicle to the road surface. In this case, the earth tread 60 is a conductive rubber embedded in the tread rubber 15 and exposed to the tire contact surface. In a charge-reducing structure having the linear conductive portions 50 and the earth tread 60, static electricity from the vehicle, which is caused to flow into the belt layer 14 by the linear conductive portions 50, is discharged from the belt layer 14 via the earth tread 60 to the road surface, thereby suppressing charging of the vehicle.

[0128] More specifically, the earth tread 60 is exposed on the tread surface of the tread rubber 15, and penetrates the cap tread 151 and the under tread 152 to be in conductive contact with the belt layer 14. That is, the earth tread 60 penetrates at least the cap tread 151 to be exposed on the tire contact surface. In the modified example shown in Fig. 24, the earth tread 60 penetrates the cap tread 151 and the under tread 152, and its inner end in the tire radial direction is in conductive contact with the belt cover 143. This ensures a conductive path from the belt layer 14 to the road surface.

[0129] The earth tread 60 has an annular structure extending around the entire tire circumference, and extends continuously in the tire circumferential direction with a portion of it exposed on the tread surface. Therefore, when the pneumatic tire 1 rolls, the earth tread 60 is always in contact with the road surface, thereby always ensuring a conductive path from the belt layer 14 to the road surface. In the modified example shown in Fig. 24, the width of the earth tread 60 in the tire width direction is narrower than the groove width of the circumferential main grooves 6 formed in the tread portion 2 and extending in the tire circumferential direction, and the earth tread 60 is formed between circumferential main grooves 6 adjacent in the tire width direction.

[0130] The earth tread 60 is made of a conductive rubber material having a volume resistivity lower than that of the tread rubber 15. Specifically, the volume resistivity of the earth tread 60 is preferably less than 1×10^8 [Ω·cm], and more preferably 1×10^6 [Ω·cm] or less.

[0131] By using the earth tread 60 in addition to the linear conductive portions 50 to form a static charge suppression structure, the path from the rim R through the bead rubber 30, the linear conductive portions 50, and the belt layer 14 to the earth tread 60 can be used as a conductive path for dissipating static electricity from the vehicle to the road surface. In other words, the earth tread 60 has a volume resistivity of less than 1×10^8 [Ω·cm] and penetrates at least the cap tread 151 to be exposed to the tire contact surface, thereby ensuring a conductive path from the belt layer 14 to the road surface. This ensures a conductive path from the linear conductive portions 50 to the road surface, and more reliably ensures a conductive path from the rim R to the earth tread 60. This more reliably reduces electrical resistance between the rim R and the road surface, allowing static electricity generated on the vehicle to be more reliably discharged to the road surface. As a result, static charge suppression performance is more reliably ensured.

[0132] Furthermore, by providing the earth tread 60, it is possible to suppress a decrease in anti-static performance when the silica content of the rubber compound constituting the cap tread 151, under tread 152, sidewall rubber 16, 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, when the silica content of the cap tread 151 increases, the volume resistivity of the cap tread 151 increases and the anti-static performance decreases, but by providing the earth tread 60, a conductive path between the belt layer 14 and the road surface can be secured. As a result, it is possible to secure anti-static performance when reducing rolling resistance.

[0133] In the first embodiment described above, the carcass inner rubber layer 20 has the inner liner 21 and the tie rubber 22 arranged over the same range in the periphery direction. However, the carcass inner rubber layer 20 may have different arrangement ranges for the inner liner 21 and the tie rubber 22. For example, the tie rubber 22 may be arranged within a portion of the range in which the inner liner 21 is arranged. In this case, the tie rubber 22 is preferably arranged in a portion of the carcass inner rubber layer 20 that is subject to large deformation when the pneumatic tire 1 deforms, and the linear conductive portions 50 are preferably arranged between the inner liner 21 and the tie rubber 22 or sewn into the tie rubber 22 in the portion of the carcass inner rubber layer 20 where the tie rubber 22 is arranged. In this way, by arranging the tie rubber 22 in a portion of the carcass inner rubber layer 20 that is subject to large deformation and by arranging the linear conductive portions 50 within the carcass inner rubber layer 20, it is possible to prevent the carcass cords 131 from rubbing against the linear conductive portions 50, and to prevent breakage of the linear conductive portions 50.

[0134] Furthermore, the method of manufacturing the pneumatic tire 1 in which the linear conductive portions 50 are disposed in the carcass inner rubber layer 20 as described above may be carried out using a member in which the linear conductive portions 50 are disposed between the multiple rubber layers that constitute the carcass inner rubber layer 20, as in the first embodiment, or may be carried out using a member in which the linear conductive portions 50 are sewn to one of the multiple rubber layers that constitute the carcass inner rubber layer 20, as in the second embodiment. Alternatively, as in the modified examples shown in Figures 20 and 21 , the pneumatic tire 1 may be manufactured by attaching the linear conductive portions 50 to the tire inner surface 25 of the carcass inner rubber layer 20 using an adhesive or the like after tire formation, and then attaching the cover rubber layer 23 to the tire inner surface 25 while covering the linear conductive portions 50. The method of manufacturing the pneumatic tire 1 is not limited as long as at least a portion of the linear conductive portions 50 is disposed in the carcass inner rubber layer 20.

[0135] [Example] 25A and 25B are tables showing the results of performance evaluation tests of pneumatic tires. Performance evaluation tests conducted on the conventional pneumatic tire and the pneumatic tire 1 according to the present invention for the above-described pneumatic tire 1 will be described below. The performance evaluation tests were conducted on the electrical resistance of the pneumatic tire 1 when it was new and after it had been driven.

[0136] Performance evaluation tests were conducted using pneumatic tires with a nominal tire size of 195 / 65R15 91H as specified by JATMA as test tires. Evaluation tests for new electrical resistance were conducted using an R8340A Ultra High Resistance Meter manufactured by Advantest Corporation, measuring the electrical resistance [Ω] of the test tires according to the measurement conditions specified by JATMA.

[0137] In addition, an indoor drum-type tire rolling resistance tester with a drum diameter of 1707 mm was used to evaluate electrical resistance after driving. The test tire was mounted on a rim specified by JATMA, and an air pressure of 200 kPa and 80% of the maximum load specified by JATMA were applied to the test tire. After driving for 60 minutes at a speed of 81 km / h, the test tire's electrical resistance (Ω) was measured using an Advantest R8340A Ultra High Resistance Meter in accordance with the measurement conditions specified by JATMA. The lower the measured value for tire electrical resistance when new and after driving, the lower the electrical resistance and the better the tire's performance in terms of electrical resistance.

[0138] The performance evaluation test was carried out using a conventional pneumatic tire, which is an example of a conventional pneumatic tire, and an example of the pneumatic tire 1 according to the present invention. 5 ~13 and , Reference Examples 1 to 4 The test was carried out on 14 types of pneumatic tires. Of these, the conventional pneumatic tire had linear conductive portions arranged on the surface of the carcass.

[0139] In contrast to this, an embodiment of the pneumatic tire 1 according to the present invention is 5 In Examples 1 to 13, all of the linear conductive portions are disposed within the carcass inner rubber layer.5 ~13 And Reference Examples 1 to 4 The pneumatic tires 1 according to the present invention are different in the relationship (La / Lbp) between the width Lbp of the belt layer 14 in the periphery direction and the lap width La of the linear conductive portions 50 relative to the belt layer 14, the relationship (t1 / t) between the thickness t of the carcass inner rubber layer 20 and the distance t1 of the linear conductive portions 50 from the tire inner surface 25, the presence or absence of contact portions 50a of the linear conductive portions 50, the angle of the linear conductive portions 50, the presence or absence of the linear conductive portions 50 being sewn into the tie rubber 22, the exposed length of the linear conductive portions 50 on the surface 22a of the tie rubber 22, the total fineness of the linear conductive portions 50, and the elongation rate of the linear conductive portions 50.

[0140] As a result of carrying out an evaluation test using these pneumatic tires 1, as shown in FIGS. 25A and 25B, 5 It was found that the pneumatic tires 1 according to the examples 1 to 13 can reduce the tire electrical resistance after running compared to the conventional example. 5 It was found that the pneumatic tires 1 according to the embodiments 1 to 13 can prevent a significant increase in the tire electrical resistance after running compared to the tire electrical resistance when new, and can prevent a significant change in the tire electrical resistance between when new and after running, compared to the conventional example. 5 The pneumatic tire 1 according to any one of claims 1 to 3 can maintain the tire electrical resistance after running. [Explanation of symbols]

[0141] 1 pneumatic tire 2 Tread section 3 Sidewall 6 Circumferential main groove 10 Bead section 11 Bead core 12 Bead filler 13 Carcass layer 131 Carcass Cord 132 Coated Rubber 14 Belt Layer 15 Tread rubber 151 Cap Tread 152 Undertread 16 Sidewall rubber 20 Carcass inner rubber layer 21 Inner liner 22 Thai Rubber 22a surface 23 Cover rubber layer 25 Tire inner surface 30 Bead rubber 31 Rim cushion rubber 32 Chafer 33 Conductive rubber 35 Bead Toe 36 Bead base 50 Linear conductive part 50a Contact part 51 Conductive wire 52 Non-conductive linear object 55 Linear non-conductive part 60 Earth Red

Claims

1. A tire comprising a pair of bead portions, at least one carcass layer spanning the pair of bead portions, a belt layer disposed radially outward of the carcass layer, and an inner carcass rubber layer disposed on the tire cavity side of the carcass layer, a linear conductive portion that extends continuously from at least the bead portion to the belt layer and is disposed in the carcass inner rubber layer; At least a portion of the linear conductive portion is located in the carcass inner rubber layer, and has a volume resistivity of less than 1×10^8 [Ω cm], the linear conductive portion, at least in a region radially outward of the bead portion, has a relationship between a thickness t of the carcass inner rubber layer and a distance t1 from the tire inner surface at a portion of the linear conductive portion where the distance from the tire inner surface is smallest, which satisfies 0.2≦t1 / t≦0.

8.

2. The belt layer has one or more belt plies extending in the tire width direction, When perpendicular lines are drawn from both end portions in the tire width direction of the belt ply having the widest width in the tire width direction to the tire inner surface, a periphery length between the intersections of the perpendicular lines and the tire inner surface is defined as Lbp, and a length in the periphery direction of a portion of the linear conductive portion located on the tire radially inner side of the belt layer is defined as La, The tire according to claim 1 , wherein the linear conductive portion satisfies 0.01≦La / Lbp≦1.

3. A bead portion rubber is disposed in the bead portion and contacts the rim flange, The bead portion rubber has a volume resistivity of less than 1×10^8 [Ω cm], The tire according to claim 1 or 2, wherein the linear conductive portion has a portion overlapping with the bead portion rubber.

4. The tire according to claim 3 , wherein the linear conductive portion extends from the tire inner surface side beyond the bead toe of the bead portion at least to the bead base, and contacts the bead portion rubber at a position closer to the bead base than the bead toe.

5. The tire according to any one of claims 1 to 4, wherein the linear conductive portions extend along the periphery direction at least in a region between the belt layer and the bead portion.

6. The tire according to any one of claims 1 to 5, wherein a portion of the linear conductive portion located on the tire radial inner side of the belt layer and a portion located on the bead portion each have a portion inclined at an inclination angle of 30° or less in the tire circumferential direction with respect to the periphery direction.

7. The carcass inner rubber layer is formed by laminating a first layer and a second layer, The tire according to any one of claims 1 to 6, wherein at least a portion of the linear conductive portion is disposed between the first layer and the second layer.

8. 8. The tire of claim 7, wherein said first layer is an inner liner and said second layer is a tie rubber.

9. The tire according to claim 8 , wherein the linear conductive portion is sewn into the tie rubber.

10. The tire according to claim 9 , wherein the linear conductive portion is sewn into the tie rubber while being exposed on the surface of the tie rubber with a length of 1 mm to 30 mm.

11. The tire according to any one of claims 1 to 10, wherein the linear conductive portion is formed by twisting together a plurality of linear bodies, including one or more conductive linear bodies having a volume resistivity of less than 1 x 10^8 [Ω cm].

12. The tire according to claim 11, wherein the linear conductive portion is formed by twisting together the conductive linear body and a non-conductive linear body having a volume resistivity of 1×10^8 [Ω·cm] or more.

13. The tire according to claim 12, wherein the conductive linear members are metal fibers and the non-conductive linear members are organic fibers.

14. The tire according to claim 11 or 12, wherein the conductive linear member is formed by twisting together a plurality of carbon fibers.

15. The tire according to claim 11 or 12, wherein the conductive linear member is a single-wire cord made of carbon fiber.

16. The tire according to any one of claims 1 to 15, wherein the linear conductive portions have a total fineness of 20 dtex or more and 1000 dtex or less.

17. The tire according to claim 16, wherein the linear conductive portion has an elongation percentage of 1.0% or more and 70.0% or less.

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