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 tire inner surface rubber layer 20 constituting a tire inner surface 25. 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 tire inner surface rubber layer 20. At least a portion of the linear conductive part 50 is exposed to a tire inner cavity side 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 onto the road surface.For example, in Patent Document 1, conductive yarns with low electrical resistance are arranged on at least one surface of a carcass ply to reduce the electrical resistance of the tire. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-43122 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when conductive fibers such as conductive yarns are arranged along the surface of the carcass ply, the electrical resistance of the tire when new 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 broken and no longer able to conduct electricity, the tire's electrical resistance is likely to increase, and the tire's anti-static performance will be 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 according to 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 tire inner surface rubber layer constituting the tire inner surface, and is characterized in that the tire comprises linear conductive portions that extend continuously from at least the bead portions to the belt layer and are disposed in the tire inner surface rubber layer, at least a portion of the linear conductive portions being exposed to the tire cavity side, and having a volume resistivity of less than 1×10^8 [Ω·cm].

[0008] Further, in the above tire, the belt layer has one or more belt plies extending in the tire width direction. When perpendicular lines are drawn from both ends of the belt ply having the widest width in the tire width direction toward the inner surface of the tire, and the peripheral length between the intersections of the perpendicular lines and the inner surface of the tire is defined as Lbp, and the length in the peripheral direction of the portion of the linear conductive part located radially inside the belt layer in the tire diameter direction is defined as La, it is preferable that the linear conductive part satisfies 0.01 ≦ La / Lbp ≦ 1.

[0009] Further, in the above tire, bead rubber that abuts against the rim flange is disposed in the bead portion. The bead rubber has a volume resistivity of less than 1 × 10^8 [Ω·cm]. It is preferable that the relationship between the surface length Lbg of the bead rubber in the peripheral direction and the length Lbc of the portion of the linear conductive part overlapping with the bead rubber satisfies 0.01 ≦ Lbc / Lbg ≦ 1.00.

[0010] Further, in the above tire, it is preferable that the linear conductive part extends from the inner surface side of the tire beyond the bead toe of the bead portion and at least to the bead base.

[0011] Further, in the above tire, when the embedding amount of the linear conductive part into the inner surface rubber layer of the tire from the inner surface side of the tire is defined as f, and the thickness of the inner surface rubber layer of the tire is defined as t, it is preferable that the embedding amount f in the region where the embedding amount f of the linear conductive part into the inner surface rubber layer of the tire is the largest satisfies f / t < 0.5.

[0012] Further, in the above tire, it is preferable that the relationship between the length L1 of the linear conductive part in the peripheral direction and the total length L2 of the linear conductive part satisfies 1 < L2 / L1 < 5.

[0013] Also, in the above tire, for the linear conductive part, the relationship between the circumferential distance Lc of the part located between the position on the inner side in the tire radial direction of the belt layer in the linear conductive part and the bead part, and the actual length Lrc of the part located between the position on the inner side in the tire radial direction of the belt layer in the linear conductive part and the bead part satisfies 1.0 < Lrc / Lc < 3.0; the relationship between the circumferential distance La of the part located on the inner side in the tire radial direction of the belt layer in the linear conductive part and the length Lra of the part located on the inner side in the tire radial direction of the belt layer in the linear conductive part satisfies Lrc / Lc < Lra / La < 8.0; and the relationship between the circumferential distance Lb of the part located at the bead part in the linear conductive part and the length Lrb of the part located at the bead part in the linear conductive part preferably satisfies Lrc / Lc < Lrb / Lb < 8.0.

[0014] Also, in the above tire, it is preferable that a plurality of the linear conductive parts are arranged and the plurality of linear conductive parts are arranged without overlapping each other.

[0015] Also, in the above tire, the linear conductive part preferably comprises a plurality of linear bodies formed by twisting one or more conductive linear bodies having a volume resistivity of less than 1×10^8 [Ω·cm].

[0016] Also, in the above tire, the linear conductive part preferably comprises a twisted combination of the conductive linear body and a non-conductive linear body having a volume resistivity of 1×10^8 [Ω·cm] or more.

[0017] Also, in the above tire, it is preferable that the conductive linear body is a metal fiber and the non-conductive linear body is an organic fiber.

[0018] Also, in the above tire, it is preferable that the conductive linear body is formed by twisting a plurality of carbon fibers.

[0019] Also, in the above tire, it is preferable that the conductive linear body is a single-wire cord made of carbon fiber.

[0020] 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.

[0021] 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.

[0022] Preferably, the tire further comprises a cover rubber layer provided on the tire cavity side of the linear conductive portions and covering a portion of the linear conductive portions. [Effects of the Invention]

[0023] 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]

[0024] [Figure 1] FIG. 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment. [Figure 2] FIG. 2 is a detailed view of a region on one side from the tire equatorial plane in the tire width direction in FIG. [Figure 3] FIG. 3 is an explanatory diagram of the wrap width of the linear conductive portions relative to the belt layer. [Figure 4] FIG. 4 is an explanatory diagram of the length of the portion of the linear conductive portion that is disposed at the position of the belt layer and the bead portion. [Figure 5] FIG. 5 is a detailed view of part A in FIG. [Figure 6] FIG. 6 is a detailed view of the tire inner surface rubber layer and the linear conductive portions in the cross section direction BB of 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 an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which the linear conductive portions are positioned on the outer side of the bead portion rubber in the tire width direction. [Figure 10] FIG. 10 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which the linear conductive portions extend beyond the bead toe to the bead base. [Figure 11] FIG. 11 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which the linear conductive portions extend beyond the bead toe to the outer side of the bead core in the tire width direction. [Figure 12] FIG. 12 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which a portion of the linear conductive portion at a predetermined position is embedded in the tire inner surface rubber layer. [Figure 13] FIG. 13 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which the linear conductive portions are entirely embedded in the tire inner surface rubber layer at predetermined positions. [Figure 14] FIG. 14 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which the actual length of the linear conductive portions is longer than the length in the periphery direction. [Figure 15] FIG. 15 is a diagram illustrating a modified example of the pneumatic tire according to the embodiment, in which the rate at which the actual length of the linear conductive portions is increased varies depending on the position on the pneumatic tire. [Figure 16] FIG. 16 is an explanatory diagram showing an example of an arrangement of linear conductive portions. [Figure 17] FIG. 17 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which a cover rubber layer is disposed. [Figure 18] FIG. 18 is a view taken along the arrow CC in FIG. [Figure 19] FIG. 19 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which linear conductive portions are arranged across the tire equatorial plane in the tire width direction. [Figure 20]FIG. 20 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which linear conductive portions are arranged across the tire equatorial plane in the tire width direction. [Figure 21] FIG. 21 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which linear conductive portions are arranged on both sides in the tire width direction. [Figure 22] FIG. 22 is an explanatory diagram showing a modified example of the pneumatic tire according to the embodiment, in which linear conductive portions are arranged on 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 embodiment, in which the linear conductive portions have portions that are disposed away from the tire inner surface. [Figure 24] FIG. 24 is an explanatory diagram showing a modified example of the pneumatic tire according to the 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

[0025] 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.

[0026] [Embodiment] [Pneumatic tires] In the following description, a pneumatic tire 1 will be used as an example of a tire according to the present invention. The pneumatic tire 1, which is an example of a tire, can be filled with air, an inert gas such as nitrogen, or other gases.

[0027] 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.

[0028] 1 is a cross-sectional view in the tire meridian direction showing a pneumatic tire 1 according to an embodiment. The figure shows one side region in the tire radial direction. The figure also shows a radial tire for passenger cars as an example of a pneumatic tire.

[0029] A pneumatic tire 1 according to the embodiment has an annular structure centered on the tire rotation axis, and includes a tread portion 2, a pair of sidewall portions 3, 3, a pair of bead portions 10, 10, a carcass layer 13, a belt layer 14, and a tire inner surface 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] In this 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. 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 encase the bead cores 11 and the bead fillers 12. That is, 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 wound back to the outer side in the tire width direction.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] The belt layer 14 has one or more belt plies extending in the tire width direction, and in this embodiment, multiple belt plies 141 to 143 are laminated. That is, in this embodiment, 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 radially outward 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 to 65 degrees in absolute value. Furthermore, 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] The tire inner surface 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 tire inner surface rubber layer 20, which constitutes the tire inner surface 25, is disposed on the tire cavity side with respect to the carcass layer 13, and covers the carcass layer 13 from the tire cavity side.

[0045] [Static charge suppression structure] FIG. 2 is a detailed view of a region on one side of the tire equatorial plane CL in the tire width direction in FIG. 1 . The pneumatic tire 1 according to this embodiment employs an anti-static structure to discharge static electricity generated on a vehicle while the vehicle is traveling to the road surface. The anti-static structure uses linear conductive portions 50. The linear conductive portions 50 are linear members with a volume resistivity of less than 1×10^8 [Ω·cm], extend continuously at least from the bead portion 10 to the belt layer 14, and are disposed in the tire inner surface rubber layer 20. The linear conductive portions 50 disposed in the tire inner surface rubber layer 20 are disposed on the tire inner surface 25 of the tire inner surface rubber layer 20 and are disposed exposed to the tire cavity side. That is, the linear conductive portions 50 are disposed on the tire inner surface 25 of the tire inner surface rubber layer 20, continuously from a position on the inner side of the bead portion 10 in the tire width direction to a position on the inner side of the belt layer 14 in the tire radial direction. In this embodiment, the linear conductive portion 50 is continuously arranged from a position on the inner side in the tire width direction of one of the bead portions 10 arranged on both sides of the tire equatorial plane CL in the tire width direction to a position on the inner side in the tire radial direction of the belt layer 14.

[0046] In this embodiment, the bead portion 10 refers to the region from the measurement point of the rim diameter to 1 / 3 of the tire cross-sectional height SH. The tire cross-sectional height SH refers to 1 / 2 of the difference between the tire outer diameter and the rim diameter, and is measured with the pneumatic tire 1 mounted on a specified rim, pressurized to a specified internal pressure, and in an unloaded state.

[0047] 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.

[0048] At a position on the inner side in the tire radial direction of the belt layer 14, the linear conductive portions 50 are arranged along the tire inner surface 25 on the inner side in the tire radial direction of the tire inner surface rubber layer 20, and the outer end portions in the tire direction of the linear conductive portions 50 are located on the inner part in the tire radial direction of the belt layer 14. As a result, at a position on the inner side in the tire radial direction of the belt layer 14, the linear conductive portions 50 are arranged overlapping the belt layer 14 in the tire radial direction.

[0049] Furthermore, at the positions of the sidewall portion 3 and the bead portion 10, the linear conductive portions 50 are arranged along the tire inner surface 25 on the inner side in the tire width direction of the tire inner surface rubber layer 20 or the bead portion rubber 30. The inner end of the linear conductive portions 50 arranged in this manner on the tire width direction is located on the inner side in the bead portion 10 of the tire width direction. Furthermore, the portion of the linear conductive portions 50 located at the bead portion 10 is arranged overlapping the bead portion rubber 30 in the tire width direction and is in contact with the bead portion rubber 30. 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.

[0050] 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.

[0051] 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. In this embodiment, the periphery direction refers to the direction along the surface of the pneumatic tire 1 at the same position in the tire circumferential direction.

[0052] 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.

[0053] 4 is an explanatory diagram of the lengths of the portions of the linear conductive portions 50 that are located at the positions of the belt layer 14 and the bead portion 10. FIG. 4 is a developed view in which the periphery direction of the pneumatic tire 1 is oriented horizontally in the drawing. The belt layer 14 is disposed on both sides of the tire equatorial plane CL in the tire width direction, straddling the tire equatorial plane CL, and therefore the width Lbp of the belt layer 14 in the periphery direction is a width that straddles the tire equatorial plane CL, as shown in FIG. 4. The linear conductive portions 50 extend continuously from the belt layer 14 to the bead portion 10, and the lap width La of the linear conductive portions 50 with respect to the belt layer 14 is the length of the portions of the linear conductive portions 50 that are located within the range of the width Lbp of the belt layer 14 in the periphery direction, as shown in FIG. 4.

[0054] FIG. 5 is a detailed view of portion A in FIG. 2. The tire inner surface rubber layer 20 is formed by laminating an inner liner 21 that constitutes the tire inner surface 25 and a tie rubber 22 that is disposed on the side of the inner liner 21 where the carcass layer 13 is located. The inner liner 21 is an air permeation-preventing 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 formed from a thermoplastic resin or a thermoplastic elastomer composition, the inner liner 21 can be made thinner than when the inner liner 21 is formed from butyl rubber, thereby significantly reducing the tire weight.

[0055] 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.

[0056] 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).

[0057] 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)).

[0058] 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.

[0059] 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.

[0060] 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 tire inner surface rubber layer 20 is located on the inner side of the bead portion rubber 30 in the tire width direction, and is located near the bead toe 35, which is the inner end in the tire width direction of the bead base 36, which is the inner circumferential surface of the bead portion 10. Furthermore, the linear conductive portions 50 disposed in the tire inner surface rubber layer 20 are located on the outer side of the bead toe 35 in the tire radial direction, and near the bead toe 35, at the position of the bead portion 10. Therefore, both the linear conductive portions 50 and the tire inner surface rubber layer 20 overlap the bead portion rubber 30 at the position of the bead portion 10.

[0061] The linear conductive portions 50 arranged overlapping the bead portion rubber 30 have a surface length Lbg of the bead portion rubber 30 in the periphery direction and a length Lbc of the portion of the linear conductive portions 50 overlapping with the bead portion rubber 30, and the relationship between these lengths satisfies 0.01≦Lbc / Lbg≦1.00. The bead portion rubber 30 has a rim cushion rubber 31 and a chafer 32, and in this embodiment, the surface length Lbg of the bead portion rubber 30 is the surface length Lbg of the chafer 32 of the bead portion rubber 30 in the periphery direction.

[0062] Furthermore, the length Lbc of the portion of the linear conductive portion 50 overlapping with the bead portion rubber 30 is the length in the periphery direction of the portion of the linear conductive portion 50 overlapping with the chafer 32 of the bead portion rubber 30. In other words, the length Lbc of the portion of the linear conductive portion 50 overlapping with the bead portion rubber 30 is the length of the portion of the linear conductive portion 50 located within the surface length Lbg of the chafer 32 of the bead portion rubber 30 in the periphery direction (see FIG. 4).

[0063] The surface length Lbg of the bead rubber 30 may be the length in the periphery of the rim cushion rubber 31 of the bead rubber 30, or the length in the periphery of the entire bead rubber 30, which is the combination of the rim cushion rubber 31 and the chafer 32 of the bead rubber 30. In other words, the length Lbc of the portion of the linear conductive portion 50 overlapping with the bead rubber 30 may be the length in the periphery of the portion of the bead rubber 30 overlapping with the rim cushion rubber 31, or the length in the periphery of the portion of the bead rubber 30 overlapping with the entire bead rubber 30, which is the combination of the rim cushion rubber 31 and the chafer 32. The surface length Lbg of the bead rubber 30 is preferably the length in the periphery of a portion of the bead rubber 30 having a volume resistivity of less than 1×10^8 [Ω cm].

[0064] Fig. 6 is a detailed view of the tire inner surface rubber layer 20 and the linear conductive portions 50 in the BB cross section direction of Fig. 5. The linear conductive portions 50 are arranged on the tire inner surface 25 of the tire inner surface rubber layer 20, and are arranged on the tire inner surface 25 side of the tire inner surface rubber layer 20 by using an adhesive, for example. In other words, the linear conductive portions 50 are arranged on the tire inner surface 25 of the inner liner 21 in the tire inner surface rubber layer 20 where the inner liner 21 and tie rubber 22 are laminated.

[0065] 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.

[0066] 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).

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] The total fineness is measured in accordance with JIS L1017 (Test method for synthetic fiber tire cords 8.3 Correct fineness).

[0072] 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.

[0073] 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).

[0074] In this 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.

[0075] In the pneumatic tire 1 according to this embodiment, 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.

[0076] 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.

[0077] [Actions and Effects] When a pneumatic tire 1 according to the embodiment is mounted on a vehicle and driven, the pneumatic tire 1 rotates while the lower portion of the surface of the tread portion 2 of the pneumatic tire 1 that faces the road surface comes into contact with the road surface. As the surface of the tread portion 2 of the pneumatic tire 1 comes into contact with the road surface in this manner, a frictional force can be generated between the pneumatic tire 1 and the road surface. This allows the vehicle to transmit driving force, braking force, and turning force to the road surface through the frictional force between the pneumatic tire 1 and the road surface, and the vehicle can drive using these driving force, braking force, and turning force.

[0078] 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.

[0079] 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.

[0080] When the vehicle is running, the tread 2, sidewall 3, etc. rotate while deforming due to loads generated according to the running conditions of the vehicle. Because the tread 2 and sidewall 3 are made by laminating different members, when the tread 2 or sidewall 3 deforms, shear forces tend to occur in directions that cause the members that make up these parts to shift relative to each other.

[0081] For this reason, if the linear conductive portions 50, which play a role in dissipating static electricity generated while the vehicle is traveling to the road surface, are arranged, for example, between the carcass layer 13 and the tire inner surface rubber layer 20, there is a risk that the linear conductive portions 50 will be broken by a shear force in a direction that causes the carcass layer 13 and the tire inner surface rubber layer 20 to shift. In other words, if a shear force is generated in a direction that causes the carcass layer 13 and the tire inner surface rubber layer 20 to shift, the linear conductive portions 50 arranged therebetween will be squeezed by the carcass layer 13 and the tire inner surface rubber layer 20, and therefore, if a shear force is repeatedly generated in a direction that causes the carcass layer 13 and the tire inner surface rubber layer 20 to shift, there is a risk that the linear conductive portions 50 will be repeatedly squeezed and broken.

[0082] 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 this embodiment, the linear conductive portions 50 are exposed to the tire cavity side and disposed in the tire inner surface rubber layer 20. Therefore, even if the tread portion 2 or the sidewall portion 3 deforms, the linear conductive portions 50 are not squeezed by other components, so the linear conductive portions 50 can ensure the 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.

[0083] 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.

[0084] 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.

[0085] Furthermore, the bead portion rubber 30 has a volume resistivity of less than 1×10^8 [Ω·cm], and the relationship between the surface length Lbg of the bead portion rubber 30 and the length Lbc of the linear conductive portion 50 that overlaps with the bead portion rubber 30 satisfies 0.01≦Lbc / Lbg≦1.00, so the linear conductive portion 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 surface length Lbg of the bead portion rubber 30 and the length Lbc of the linear conductive portion 50 that overlaps with the bead portion rubber 30 is Lbc / Lbg<0.01, it may be difficult to ensure sufficient conductivity between the linear conductive portion 50 and the bead portion rubber 30 because the length Lbc of the linear conductive portion 50 that overlaps with the bead portion rubber 30 is too short. 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 it may be difficult to effectively reduce the tire electrical resistance.

[0086] In contrast, when the relationship between the surface length Lbg of the bead portion rubber 30 and the length Lbc of the linear conductive portions 50 overlapping with the bead portion rubber 30 satisfies 0.01≦Lbc / Lbg≦1.00, sufficient conductivity can be ensured between the linear conductive portions 50 and the bead portion rubber 30, 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.

[0087] Furthermore, because multiple linear conductive portions 50 are arranged, multiple electrical paths can be secured between the bead portion rubber 30 and the belt layer 14, further reducing the tire electrical resistance. Furthermore, because the multiple linear conductive portions 50 are arranged without overlapping each other, the linear conductive portions 50 can secure an electrical conductive path from the rim R to the belt layer 14 even after long-distance driving. In other words, if the linear conductive portions 50 are arranged so that they overlap each other, the linear conductive portions 50 may rub against each other due to tire deformation during driving, and the linear conductive portions 50 may be broken due to the rubbing between the linear conductive portions 50. If the linear conductive portions 50 are broken, it becomes difficult for the linear conductive portions 50 to secure an electrical conductive path from the rim R to the belt layer 14. Therefore, there is a risk that the tire electrical resistance of the pneumatic tire 1 after the linear conductive portions 50 are broken will increase compared to the pneumatic tire 1 before the linear conductive portions 50 are broken.

[0088] In contrast, in the pneumatic tire 1 according to the embodiment, the multiple linear conductive portions 50 are arranged without overlapping each other, which prevents the linear conductive portions 50 from rubbing against each other and prevents disconnection of the linear conductive portions 50 due to the linear conductive portions 50 rubbing against each other. This allows the linear conductive portions 50 to ensure a conductive path from the rim R to the belt layer 14 even after long-distance driving. As a result, an increase in tire electrical resistance after driving can be suppressed.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] [Variations] In the above-described embodiment, the linear conductive portions 50 are located on the inner side in the tire width direction of the bead portion rubber 30 at the position of the bead portion 10, but the linear conductive portions 50 may be located on the outer side in the tire width direction of the bead portion rubber 30 at the position of the bead portion 10. Fig. 9 is a modified example of the pneumatic tire 1 according to the embodiment, and is an explanatory diagram of a case where the linear conductive portions 50 are located on the outer side in the tire width direction of the bead portion rubber 30. For example, as shown in Fig. 9, the linear conductive portions 50 are located on the outer side in the tire width direction of a portion of a chafer 32 of the bead portion rubber 30 that is located on the inner side in the tire width direction of the bead core 11.

[0097] That is, when the portion of the tire inner surface rubber layer 20 located in the bead portion 10 is located inward in the tire width direction from the bead core 11 and outward in the tire width direction from the chafer 32 of the bead portion rubber 30, as shown in Fig. 9, the linear conductive portion 50 arranged along the tire inner surface rubber layer 20 may be arranged sandwiched between the tire inner surface rubber layer 20 and the chafer 32. Note that Fig. 9 is a cross section at the position of the linear conductive portion 50, and therefore the portion of the chafer 32 located inward in the tire width direction from the bead core 11 covers the linear conductive portion 50, but the chafer 32 covers the tire inner surface rubber layer 20 in parts other than the part where the linear conductive portion 50 is located in the tire circumferential direction.

[0098] As described above, the linear conductive portions 50 are disposed on the outer side in the tire width direction of the chafer 32 of the bead portion rubber 30, and are disposed sandwiched between the tire inner surface rubber layer 20 and the chafer 32, thereby enabling direct contact with the chafer 32. This makes it possible to more reliably ensure an electrical path between the linear conductive portions 50 and the bead portion rubber 30, and the linear conductive portions 50 can more reliably reduce the tire electrical resistance.

[0099] Furthermore, in the above-described embodiment, the linear conductive portions 50 are located on the outer side of the bead toe 35 in the tire radial direction at the position of the bead portion 10, but the linear conductive portions 50 may extend from the tire inner surface 25 side beyond the bead toe 35 of the bead portion 10 to the bead base 36. Fig. 10 is a modified example of the pneumatic tire 1 according to the embodiment, and is an explanatory diagram of a case where the linear conductive portions 50 extend beyond the bead toe 35 to the bead base 36. Fig. 11 is a modified example of the pneumatic tire 1 according to the embodiment, and is an explanatory diagram of a case where the linear conductive portions 50 extend beyond the bead toe 35 to the outer side of the bead core 11 in the tire width direction. For example, as shown in FIG. 10 , when the tire inner surface rubber layer 20 and the linear conductive portion 50 are located more inward in the tire width direction than the portion of the chafer 32 of the bead portion rubber 30 that is located more inward in the tire width direction than the bead core 11, the linear conductive portion 50 may extend from the tire inner surface 25 side, past the bead toe 35, to the bead base 36.

[0100] 11 , for example, in a case where the tire inner surface rubber layer 20 and the linear conductive portions 50 are positioned outward in the tire width direction than a portion of a chafer 32 of the bead portion rubber 30 that is positioned inward in the tire width direction from the bead core 11, the linear conductive portions 50 may extend from the tire inner surface 25 side, past the bead toe 35, to the bead base 36, and further extend to the outer side in the tire width direction of the bead core 11. By extending the linear conductive portions 50 from the tire inner surface 25 side, past the bead toe 35, to at least the bead base 36 in this manner, the overlapping distance between the linear conductive portions 50 and the bead portion rubber 30 can be increased.

[0101] That is, by extending from the tire inner surface 25 side, past the bead toe 35, to at least the bead base 36, the linear conductive portions 50 can increase Lbc / Lbg, which is the relationship between the surface length Lbg of the bead portion rubber 30 in the periphery direction and the length Lbc of the portion of the linear conductive portions 50 that overlaps with the bead portion rubber 30. This makes it easier for electricity to flow between the linear conductive portions 50 and the bead portion rubber 30, making it easier for static electricity from the vehicle to pass more effectively from the rim R to the linear conductive portions 50, and reducing the tire electrical resistance.

[0102] Furthermore, in the above-described embodiment, the linear conductive portions 50 are disposed on the tire inner surface 25 of the tire inner surface rubber layer 20, but the linear conductive portions 50 may be embedded in the tire inner surface rubber layer 20. FIG. 12 is a modified example of the pneumatic tire 1 according to the embodiment, and is an explanatory diagram showing a state in which a portion of the linear conductive portions 50 at a predetermined position is embedded in the tire inner surface rubber layer 20. FIG. 13 is a modified example of the pneumatic tire 1 according to the embodiment, and is an explanatory diagram showing a state in which the entire linear conductive portions 50 at a predetermined position is embedded in the tire inner surface rubber layer 20. The linear conductive portions 50 may be partially embedded in the tire inner surface rubber layer 20 from the tire inner surface 25 side at a partial position in the extension direction of the linear conductive portions 50, for example, as shown in FIG. 12. Alternatively, the linear conductive portions 50 may be entirely embedded in the tire inner surface rubber layer 20 from the tire inner surface 25 side at a partial position in the extension direction of the linear conductive portions 50, for example, as shown in FIG. 13. In other words, it is sufficient that at least a portion of the linear conductive portion 50 is exposed to the tire cavity side, and it may be arranged with a portion buried in the tire inner surface rubber layer 20, as shown in Figures 12 and 13.

[0103] When the linear conductive portions 50 are embedded in the tire inner surface rubber layer 20 as described above, where f is the embedment depth of the linear conductive portions 50 into the tire inner surface rubber layer 20 from the tire inner surface 25 side and t is the thickness of the tire inner surface rubber layer 20, it is preferable that the embedment depth f of the linear conductive portions 50 in the region where the embedment depth f in the tire inner surface rubber layer 20 is greatest satisfies f / t<0.5. In this case, the embedment depth f of the linear conductive portions 50 is measured by the distance between the tire inner surface 25 and the portion of the linear conductive portions 50 that is farthest from the tire inner surface 25 of the tire inner surface rubber layer 20 to the outside of the tire.

[0104] In other words, when the relationship between the embedding amount f of the linear conductive portions 50 in the tire inner surface rubber layer 20 and the thickness t of the tire inner surface rubber layer 20 is f / t≧0.5, the linear conductive portions 50 are likely to be squeezed by the surrounding tire inner surface rubber layer 20 during running, and there is a risk that the linear conductive portions 50 will break after repeated running. In this case, it becomes difficult to ensure an electrical path through the linear conductive portions 50, and there is a risk that it will be difficult to reduce the tire electrical resistance using the linear conductive portions 50.

[0105] In contrast, when the relationship between the embedding amount f of the linear conductive portions 50 in the tire inner surface rubber layer 20 and the thickness t of the tire inner surface rubber layer 20 satisfies f / t<0.5, the proportion of the linear conductive portions 50 exposed from the tire inner surface rubber layer 20 can be increased. This makes the linear conductive portions 50 less likely to be squeezed by the tire inner surface rubber layer 20 during running and less likely to break even after repeated running, making it possible to continuously 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 tire electrical resistance.

[0106] The linear conductive portions 50 are preferably arranged so that 60% or more of the length in the extension direction of the linear conductive portions 50 is exposed to the tire cavity side. As long as 60% or more of the length of the linear conductive portions 50 is exposed to the tire cavity side, the linear conductive portions 50 may be partially embedded in the tire inner surface rubber layer 20.

[0107] Further, the linear conductive part 50 may be arranged by attaching it to the inner surface 25 of the tire using an adhesive after tire molding, or may be arranged by embedding it in the inner surface rubber layer 20 of the tire during tire molding.

[0108] Also, in the above-described embodiment, the linear conductive part 50 is arranged along the circumferential direction. However, the linear conductive part 50 does not necessarily have to be along the circumferential direction. FIG. 14 is a modified example of the pneumatic tire 1 according to the embodiment, and is an explanatory diagram showing a state where the actual length L2 of the linear conductive part 50 is longer than the length L1 in the circumferential direction. FIG. 14 is a developed view of the pneumatic tire 1 with the circumferential direction of the pneumatic tire 1 being the horizontal direction in the figure. The linear conductive part 50 is arranged, for example, as shown in FIG. 14, while being curved in the tire circumferential direction with respect to the circumferential direction, so that the total length L2, which is the actual length of the linear conductive part 50, may be longer than the length L1 of the linear conductive part 50 in the circumferential direction. By making the total length L2 of the linear conductive part 50 longer than the length L1 in the circumferential direction, the tension of the linear conductive part 50 can be reduced, and disconnection of the linear conductive part 50 due to repeated bending deformation caused by the rolling of the pneumatic tire 1 can be suppressed. As a result, even when driving is repeated, the linear conductive part 50 is less likely to be disconnected, so that an electrical path between the bead rubber 30 and the belt layer 14 can be continuously ensured, and an increase in tire electrical resistance after driving can be suppressed.

[0109] Also, when making the total length L2 of the linear conductive part 50 longer than the length L1 of the linear conductive part 50 in the circumferential direction, it is preferable that the relationship between the length L1 of the linear conductive part 50 in the circumferential direction and the total length L2 of the linear conductive part 50 satisfies 1 < L2 / L1 < 5. That is, when the relationship between the length L1 of the linear conductive part 50 in the circumferential direction and the total length L2 of the linear conductive part 50 is L2 / L1 ≧ 5, the total length L2 of the linear conductive part 50 becomes too long, and there is a risk that the electrical resistance of the linear conductive part 50 itself increases. In this case, even if the linear conductive part 50 is arranged, there is a risk that it becomes difficult to effectively reduce the electrical resistance between the bead rubber 30 and the belt layer 14.

[0110] On the other hand, when the relationship between the length L1 of the linear conductive part 50 in the circumferential direction and the total length L2 of the linear conductive part 50 satisfies 1 < L2 / L1 < 5, without increasing the electrical resistance of the linear conductive part 50 itself, the electrical resistance between the bead part rubber 30 and the belt layer 14 can be effectively reduced by the linear conductive part 50. As a result, the tire electrical resistance can be more reliably reduced by the linear conductive part 50.

[0111] Further, when making the actual length of the linear conductive part 50 longer than the length of the linear conductive part 50 in the circumferential direction, the ratio of increasing the actual length of the linear conductive part 50 may be varied for each position in the pneumatic tire 1. FIG. 15 is a modified example of the pneumatic tire 1 according to the embodiment, and is an explanatory diagram when the ratio of increasing the actual length of the linear conductive part 50 is varied for each position in the pneumatic tire 1. FIG. 15 is a developed view in which the circumferential direction of the pneumatic tire 1 is taken as the horizontal direction of the figure. The linear conductive part 50 is, for example, the distance Lc in the circumferential direction of the part located between the position inside the tire diameter of the belt layer 14 in the linear conductive part 50 and the bead part 10, that is, the part located in the sidewall part 3, and the actual length Lrc of the part located in the sidewall part 3 in the linear conductive part 50. It is preferable that the relationship satisfies 1.0 < Lrc / Lc < 3.0. Thereby, the linear conductive part 50 can be arranged at an appropriate length without being too long in the actual length Lrc with respect to the distance Lc in the circumferential direction in the sidewall part 3, and the electrical resistance can be effectively reduced by the linear conductive part 50.

[0112] Further, it is preferable that the relationship between the circumferential direction distance La of the portion of the linear conductive part 50 located on the inner side in the tire diameter direction of the belt layer 14 in the linear conductive part 50 and the length Lra of the portion of the linear conductive part 50 located on the inner side in the tire diameter direction of the belt layer 14 satisfies Lrc / Lc < Lra / La < 8.0. Thereby, in the portion of the linear conductive part 50 located on the inner side in the tire diameter direction of the belt layer 14, the linear conductive part 50 can be more surely arranged to overlap with the belt layer 14 with a longer length, and the electrical resistance between the belt layer 14 and the linear conductive part 50 can be more surely reduced.

[0113] Also, it is preferable that the relationship between the circumferential direction distance Lb of the portion of the linear conductive part 50 located in the bead part 10 in the linear conductive part 50 and the length Lrb of the portion of the linear conductive part 50 located in the bead part 10 in the linear conductive part 50 satisfies Lrc / Lc < Lrb / Lb < 8.0. Thereby, in the portion of the linear conductive part 50 located in the bead part 10, the linear conductive part 50 can be more surely arranged to overlap with the bead rubber 30 with a longer length, and the electrical resistance between the bead rubber 30 and the linear conductive part 50 can be more surely reduced. As a result, the linear conductive part 50 can more surely reduce the tire electrical resistance by effectively reducing the electrical resistance between the bead rubber 30 and the belt layer 14, and by being arranged with a length that is actually long with respect to the length in the circumferential direction, the disconnection of the linear conductive part 50 can be suppressed and the durability of the linear conductive part 50 can be ensured.

[0114] As described above, when the length of the linear conductive portions 50 is to be increased at a position on the inner side of the belt layer 14 in the tire radial direction or at the position of the bead portion 10, the length may be increased by arranging the linear conductive portions 50 in various ways. FIG. 16 is an explanatory diagram showing an example of an arrangement of the linear conductive portions 50. FIG. 16 is a developed view in which the periphery direction of the pneumatic tire 1 is set to the horizontal direction in the drawing. At a position on the inner side of the belt layer 14 in the tire radial direction, the linear conductive portions 50 may be arranged, for example, so as to extend in the periphery direction and oscillate in the tire circumferential direction as in Examples 1 to 3 of FIG. 16, or so as to be arranged so as to reciprocate in the periphery direction as in Example 4, or so as to be wound around as in Example 5.

[0115] 16, or may be arranged so as to extend in the periphery direction while oscillating in the tire circumferential direction as in Example 2, or may be arranged in a spiral shape as in Example 3, or may be arranged so as to reciprocate in the periphery direction as in Example 4. The linear conductive portions 50 may be arranged in any manner to make the actual length longer than the length in the periphery direction at the position on the inner side of the belt layer 14 in the tire radial direction or at the position of the bead portion 10, as long as the arrangement can prevent the electrical resistance of the linear conductive portions 50 themselves from becoming too long.

[0116] Furthermore, in the above-described embodiment, the linear conductive portions 50 are disposed on the tire inner surface 25 of the tire inner surface rubber layer 20, but the linear conductive portions 50 may be partially covered by another member. FIG. 17 is a modified example of the pneumatic tire 1 according to the embodiment, and is an explanatory diagram showing a state in which the cover rubber layer 23 is disposed. FIG. 18 is a view taken along arrow CC in FIG. 17. For example, as shown in FIGS. 17 and 18, the linear conductive portions 50 may be partially covered by the cover rubber layer 23. That is, the pneumatic tire 1 may further include a cover rubber layer 23 that is provided on the tire cavity side of the linear conductive portions 50 and covers part of the linear conductive portions 50. In this case, the cover rubber layer 23 is a strip-shaped member made of a rubber material.

[0117] For example, when the linear conductive portions 50 are arranged exposed in the bead portion 10 without being covered by the bead portion rubber 30, the strip-shaped cover rubber layer 23 is arranged to cover the portions of the linear conductive portions 50 that are exposed by the bead portion rubber 30. In other words, when the linear conductive portions 50 are exposed on the tire cavity side or the bead base 36 side, the cover rubber layer 23 is preferably arranged to cover the linear conductive portions 50 from the tire cavity side to the bead base 36 side in the bead portion 10.

[0118] In this way, by disposing the cover rubber layer 23 in the bead portion 10 and covering the linear conductive portions 50 with the cover rubber layer 23, it is possible to prevent damage to the linear conductive portions 50 due to contact with a tire lever when assembling the tire to the rim. This makes it possible to prevent the linear conductive portions 50 from being cut while the tire is running, thereby more reliably reducing the tire electrical resistance even after the tire has been running.

[0119] When the cover rubber layer 23 is disposed to cover the linear conductive portions 50 in this manner, the thickness of the cover rubber layer 23 is preferably less than 1 mm. If the thickness of the cover rubber layer 23 is 1 mm or more, this leads to a deterioration in the rolling resistance of the pneumatic tire 1, so the thickness of the cover rubber layer 23 covering the linear conductive portions 50 is preferably less than 1 mm.

[0120] Furthermore, the range in which the cover rubber layer 23 is disposed is preferably within a range of 1 / 3 or less of the tire cross-sectional height SH (see FIG. 2) radially outward from the rim diameter measurement point. That is, in an area that exceeds 1 / 3 of the tire cross-sectional height SH radially outward from the rim diameter measurement point, tire deformation is large, and disposing the cover rubber layer 23 in this area leads to a deterioration in the rolling resistance of the pneumatic tire 1. For this reason, the cover rubber layer 23 is preferably disposed within a range of 1 / 3 or less of the tire cross-sectional height SH radially outward from the rim diameter measurement point.

[0121] Furthermore, in the above-described embodiment, the linear conductive portions 50 are arranged without straddling the tire equatorial plane CL in the tire width direction, but the linear conductive portions 50 may be arranged straddling the tire equatorial plane CL in the tire width direction. FIGS. 19 and 20 are explanatory diagrams showing modified examples of the pneumatic tire 1 according to the embodiment, in which the linear conductive portions 50 are arranged straddling the tire equatorial plane CL in the tire width direction. For example, as shown in FIGS. 19 and 20 , the linear conductive portions 50 may be arranged straddling the tire equatorial plane CL in the tire width direction. In this case, the outer end of the linear conductive portions 50 in the tire radial direction may be located on the inner side of the belt layer 14 in the tire radial direction, as shown in FIG. 19 . Alternatively, the linear conductive portions 50 arranged straddling the tire equatorial plane CL in the tire width direction may extend beyond the range in which the belt layer 14 is arranged in the tire width direction, to the sidewall portion 3 opposite the sidewall portion 3 on which the linear conductive portions 50 are arranged, as shown in FIG. 20 .

[0122] Furthermore, in the above-described 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. 21 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the linear conductive portions 50 are arranged on both sides in the tire width direction. For example, as shown in FIG. 21 , 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.

[0123] Fig. 22 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the linear conductive portions 50 are arranged on both sides in the tire width direction. Alternatively, as shown in Fig. 22, the linear conductive portions 50 may be arranged such that the linear conductive portions 50 are independent of each other and 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.

[0124] Furthermore, in the above-described embodiment, the linear conductive portions 50 are arranged in the tire inner surface rubber layer 20 along the tire inner surface 25, but the linear conductive portions 50 may have portions that are not arranged in the tire inner surface rubber layer 20. FIG. 23 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, in which the linear conductive portions 50 have portions that are arranged away from the tire inner surface 25. For example, as shown in FIG. 23 , a portion of the linear conductive portions 50 arranged in the tire inner surface rubber layer 20 may be arranged away from the tire inner surface 25 toward the tire cavity. The entire linear conductive portion 50 does not have to be arranged in contact with the tire inner surface rubber layer 20 or the bead portion rubber 30, and may be arranged partly away from the tire inner surface 25 toward the tire cavity.

[0125] Furthermore, in the above-described embodiment, the linear conductive portions 50 are used as the charge-suppressing structure for discharging static electricity generated on the vehicle while the vehicle is traveling to the road surface. However, the charge-suppressing structure may also include components other than the linear conductive portions 50. FIG. 24 is an explanatory diagram showing a modified example of the pneumatic tire 1 according to the embodiment, illustrating a state in which an earth tread 60 is disposed. For example, as shown in FIG. 24, the charge-suppressing structure for discharging static electricity generated on the vehicle to the road surface may include an earth tread 60. 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 the charge-suppressing 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] [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.

[0132] 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.

[0133] 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.

[0134] 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. 10 ~14 and , Reference Examples 1 to 9 The test was carried out on 15 types of pneumatic tires. Of these, the conventional pneumatic tire had linear conductive portions arranged on the surface of the carcass.

[0135] In contrast to this, an embodiment of the pneumatic tire 1 according to the present invention is 10 In Examples 1 to 14, all of the linear conductive portions are disposed on the inner surface of the tire. 10~14 and Reference Examples 1 to 9 The pneumatic tire 1 according to the present invention is characterized in that 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 volume resistivity of the bead portion rubber 30, the relationship (Lbc / Lbg) between the surface length Lbg of the bead portion rubber 30 in the periphery direction and the length Lbc of the overlapping portion of the linear conductive portions 50 with the bead portion rubber 30, the embedding amount f of the linear conductive portions 50 in the tire inner surface rubber layer 20 and the The relationship between the thickness t of the layer 20 (f / t), the relationship between the length L1 of the linear conductive portions 50 in the periphery direction and the total length L2 of the linear conductive portions 50 (L2 / L1), the relationship between the distance in the periphery direction and the actual length for each position in the linear conductive portions 50 (Lra / La, Lrb / Lb, Lrc / Lc), whether or not the linear conductive portions 50 overlap, the total fineness of the linear conductive portions 50, the elongation of the linear conductive portions 50, and the presence or absence of a cover rubber layer 23 are different for each group.

[0136] As a result of carrying out an evaluation test using these pneumatic tires 1, as shown in FIGS. 25A and 25B, 10 It was found that the pneumatic tires 1 according to the examples 1 to 14 can reduce the tire electrical resistance after running compared to the conventional example. 10 It was found that the pneumatic tires 1 according to the embodiments 1 to 14 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. 10 The pneumatic tire 1 according to any one of claims 1 to 14 can maintain the tire electrical resistance after running. [Explanation of symbols]

[0137] 1 pneumatic tire 2 Tread section 3 Sidewall 6 Circumferential main groove 10 Bead section 11 Bead core 12 Bead filler 13 Carcass layer 14 Belt Layer 15 Tread rubber 151 Cap Tread 152 Undertread 16 Sidewall rubber 20 Tire inner surface rubber layer 21 Inner liner 22 Thai Rubber 23 Cover rubber layer 25 Tire inner surface 30 Bead rubber 31 Rim cushion rubber 32 Chafer 35 Bead Toe 36 Bead base 50 Linear conductive part 51 Conductive wire 52 Non-conductive linear object 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 a tire inner surface rubber layer constituting an inner surface of the tire, a linear conductive portion that extends continuously from at least the bead portion to the belt layer and is disposed in the tire inner surface rubber layer, At least a portion of the linear conductive portion is exposed to the tire cavity side, and has a volume resistivity of less than 1×10^8 [Ω cm], The linear conductive portion is a relationship between a distance Lc in the periphery direction of a portion of the linear conductive portion located between a position on the inner side in the tire radial direction of the belt layer and the bead portion and an actual length Lrc of the portion of the linear conductive portion located between the position on the inner side in the tire radial direction of the belt layer and the bead portion satisfies 1.0<Lrc / Lc<3.0, a relationship between a distance La in the periphery direction of a portion of the linear conductive portion located on the inner side in the tire radial direction of the belt layer and a length Lra of the portion of the linear conductive portion located on the inner side in the tire radial direction of the belt layer satisfies Lrc / Lc<Lra / La<8.0, a relationship between a distance Lb in the periphery direction of a portion of the linear conductive portion located in the bead portion and a length Lrb of the portion of the linear conductive portion located in the bead portion satisfies Lrc / Lc<Lrb / Lb<8.

0.

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 inner side of the belt layer in the tire radial direction 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], 3. The tire according to claim 1, wherein a relationship between a surface length Lbg of the bead portion rubber in the periphery direction and a length Lbc of the linear conductive portion that overlaps with the bead portion rubber satisfies 0.01≦Lbc / Lbg≦1.

00.

4. The tire according to any one of claims 1 to 3, wherein the linear conductive portion extends from the tire inner surface side beyond a bead toe of the bead portion to at least a bead base.

5. When the embedding amount of the linear conductive portion from the tire inner surface side into the tire inner surface rubber layer is denoted by f and the thickness of the tire inner surface rubber layer is denoted by t, The tire according to any one of claims 1 to 4, wherein the embedded amount f of the linear conductive portion in the tire inner surface rubber layer in a region where the embedded amount f is greatest satisfies f / t<0.

5.

6. The tire according to any one of claims 1 to 5, wherein a relationship between a length L1 of the linear conductive portion in the periphery direction and a total length L2 of the linear conductive portion satisfies 1 < L2 / L1 < 5.

7. a plurality of the linear conductive portions are arranged; The tire according to any one of claims 1 to 6, wherein the plurality of linear conductive portions are arranged without overlapping with each other.

8. The tire according to any one of claims 1 to 7, 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].

9. 9. The tire according to claim 8, 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.

10. The tire according to claim 9, wherein the conductive linear members are metal fibers and the non-conductive linear members are organic fibers.

11. The tire according to claim 8 or 9, wherein the conductive linear member is formed by twisting together a plurality of carbon fibers.

12. 10. The tire according to claim 8, wherein the conductive linear member is a single-wire cord made of carbon fiber.

13. The tire according to any one of claims 1 to 12, wherein the linear conductive portions have a total fineness of 20 dtex or more and 1000 dtex or less.

14. The tire according to claim 13, wherein the linear conductive portion has an elongation percentage of 1.0% or more and 70.0% or less.

15. The tire according to any one of claims 1 to 14, further comprising a cover rubber layer provided on the tire cavity side of the linear conductive portions and covering a portion of the linear conductive portions.

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