tire

Abstract

To provide a tire which can achieve, while suppressing deterioration of RRC as much as possible, an electric resistance reduction in a long term.SOLUTION: A tire comprises: a pair of bead portions; a carcass layer which is bridged between the pair of bead portions; a belt layer which is arranged at an outer side of the carcass layer in a tire diameter direction; a tread portion which is arranged at an outer side of the belt layer in the diameter direction; and an inner liner layer which is arranged in a tire inner cavity side of the carcass layer. The carcass layer includes a carcass cord which is covered with a coat rubber whose volume resistivity is 1×10^8 [Ω cm] or more. The tread portion includes an earth tread rubber which is arranged at an outer side of the belt layer in a tire diameter direction and also includes a conductive linear body which extends from the bead portion to at least a belt end position of the belt layer. The conductive linear body is arranged at a splice part of the inner liner layer and volume resistivity of the conductive linear body is less than 1×10^8 [Ω cm].SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In recent years, there has been a trend toward increasing the silica content of rubber compounds that make up the cap tread, undertread, sidewall rubber, etc. in order to improve the fuel efficiency of tires. Because silica has high insulating properties, increasing the silica content of the cap tread increases the resistance of the cap tread, reducing the tire's anti-static performance. To solve this problem, Patent Document 1 proposes arranging linear conductive portions so that a portion of them is exposed on the innermost surface of the tire, thereby maintaining low electrical resistance even after driving. Patent Document 1 also suggests that it is preferable to provide a new cover rubber layer that covers a portion of the linear conductor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-77273 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the addition of a new rubber layer may worsen the rolling resistance coefficient (RRC). Therefore, there is room for improvement in the placement of the linear conductors to prevent the deterioration of RRC while achieving long-term reduction in electrical resistance.

[0005] The present disclosure has been made in view of the above, and an object thereof is to provide a tire that can achieve long-term reduction in electrical resistance while minimizing deterioration of RRC. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, a tire according to one aspect of the present disclosure includes a pair of bead portions, a carcass layer spanning between the pair of bead portions, a belt layer provided on the tire radially outer side of the carcass layer, a tread portion provided on the tire radially outer side of the belt layer, and an inner liner layer arranged on the tire cavity side of the carcass layer, wherein the carcass layer includes carcass cords coated with a coating rubber having a volume resistivity of 1×10^8 [Ω·cm] or more, the tread portion has earth tread rubber arranged on the tire radially outer side of the belt layer, and further includes conductive linear bodies extending at least from the bead portions to belt end positions of the belt layer, the conductive linear bodies being arranged at splice portions of the inner liner layer, and the volume resistivity of the conductive linear bodies being less than 1×10^8 [Ω·cm]. [Effects of the Invention]

[0007] According to the tire of the present disclosure, it is possible to achieve a long-term reduction in electrical resistance while minimizing deterioration of RRC. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a tire according to a first embodiment of the present disclosure in the tire meridian direction. [Figure 2] FIG. 2 is a diagram schematically illustrating an example of a cross section of the inner liner layer and the conductive linear body of the tire in FIG. [Figure 3] FIG. 3 is a diagram schematically illustrating an example of a cross section of the inner liner layer and the conductive linear body of the tire in FIG. [Figure 4] FIG. 4 is a diagram schematically illustrating an example of a cross section of the inner liner layer and the conductive linear body of the tire in FIG. [Figure 5] FIG. 5 is a diagram illustrating an example of a side surface of a tire according to the present disclosure as viewed from the rotation axis direction. [Figure 6] FIG. 6 is a diagram illustrating an example of a side surface of a tire according to the present disclosure as viewed from the rotation axis direction. [Figure 7]FIG. 7 is a diagram showing an example of a side surface of a tire according to the present disclosure as viewed from the direction of the rotation axis. [Figure 8] FIG. 8 is a diagram illustrating an example of a side surface of a tire according to the present disclosure as viewed from the rotation axis direction. [Figure 9] FIG. 9 is a diagram showing an example of the arrangement of conductive linear objects relative to a splice portion. [Figure 10] FIG. 10 is a diagram showing an example of the arrangement of conductive linear objects relative to a splice portion. [Figure 11] FIG. 11 is a diagram showing an example of the arrangement of conductive linear objects relative to a splice portion. [Figure 12] FIG. 12 is a diagram showing an example of the arrangement of conductive linear objects relative to a splice portion. [Figure 13] FIG. 13 is a diagram showing an example of the arrangement of conductive linear objects relative to a splice portion. [Figure 14] FIG. 14 is a diagram showing an example of the arrangement of conductive linear objects relative to a splice portion. [Figure 15A] FIG. 15A is a chart showing performance test results for tires of the present disclosure. [Figure 15B] FIG. 15B is a chart showing performance test results for tires of the present disclosure. [Figure 15C] FIG. 15C is a chart showing performance test results for tires of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description of each embodiment, components that are the same as or equivalent to those in other embodiments will be given the same reference numerals, and their description will be simplified or omitted. The present invention is not limited to each embodiment. Furthermore, the components of each embodiment include those that are easily replaceable by those skilled in the art, or those that are substantially the same. Note that the configurations described below can be combined as appropriate. Furthermore, the configurations can be omitted, replaced, or modified within the scope of the gist of the invention.

[0010] (First embodiment) FIG. 1 is a cross-sectional view in the tire meridian direction of a tire 1 according to a first embodiment of the present disclosure. FIG. 1 is a cross-sectional view including a splice portion, which will be described later. FIG. 1 shows one side region in the tire diameter direction. FIG. 1 shows a radial tire for passenger cars as an example of the tire 1. The tire 1 according to this embodiment is preferably a pneumatic tire. As the gas to be filled into the tire 1, normal air or air with an adjusted oxygen partial pressure, as well as inert gases such as nitrogen, argon, and helium, can be used.

[0011] In the following description, the meridian section of the tire refers to a section of the tire cut by a plane including the tire's rotation axis (not shown). The tire diameter direction refers to a direction perpendicular to the rotation axis (not shown) of the tire 1, the tire diameter inner side refers to the side toward the rotation axis in the tire diameter direction, and the tire diameter outer side refers to the side away from the rotation axis in the tire diameter direction. The tire circumferential direction refers to a direction around the rotation axis as the central axis. The tire width direction refers to a direction parallel to the rotation 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 perpendicular to the rotation axis of the tire 1 and passing through the center of the tire width of the tire 1. The tire width is the width in the tire width direction between portions located on the outer sides in the tire width direction, that is, the distance between portions farthest from the tire equatorial plane CL in the tire width direction. 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 tire 1. In this embodiment, the tire equator line is given the same symbol "CL" as the tire equatorial plane.

[0012] The tire 1 according to this embodiment has an annular structure centered on a 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 an inner liner layer 17. Of these, the pair of sidewall portions 3, 3 and the pair of bead portions 10, 10 are arranged one on each side of the tire equatorial plane CL in the tire width direction.

[0013] 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 rubber portion 30 of the bead portion 10. That is, the pair of bead cores 11, 11, the pair of bead fillers 12, 12, and the pair of rubber portions 30 of the bead portions 10 are arranged on both sides of the tire equatorial plane CL in the tire width direction. Furthermore, the rubber portion 30 has a rim cushion rubber 31 and a chafer 32. Therefore, the pair of rim cushion rubbers 31, 31 and the pair of chafers 32, 32 are arranged on both sides of the tire equatorial plane CL in the tire width direction. Note that the chafer 32 may not be provided.

[0014] 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 diameter direction to reinforce the bead portion 10.

[0015] 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.

[0016] In this embodiment, a carcass layer 13 formed by laminating a plurality of carcass plies is continuously laid between the bead cores 11, 11 on both sides in the tire width direction. In addition, both end portions of the carcass layer 13 are wrapped back and secured to the outside in the tire width direction so as to enclose the bead cores 11 and the bead fillers 12. That is, the vicinity of both end portions of the carcass layer 13 in a cross section viewed in the tire meridian direction is wrapped back from the inside in the tire width direction of the bead cores 11 and the bead fillers 12 to the inside in the tire diameter direction and then to the outside in the tire width direction.

[0017] Furthermore, for the carcass ply of the carcass layer 13, the tan δ value at 60°C of the coating rubber of the carcass cord is preferably 0.20 or less. Furthermore, the volume resistivity of the coating rubber of the carcass cord is preferably 1×10^8 [Ω·cm] or more. This reduces the RRC of the tire 1. Coating rubber with such volume resistivity can be produced, for example, by using a low-heat-generating compound with a small amount of carbon. Furthermore, the coating rubber may be constructed without using silica, or may be reinforced by incorporating silica.

[0018] 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.

[0019] 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.

[0020] A pair of rubber portions 30, 30 of a pair of bead portions 10, 10 are respectively arranged on the tire diameter direction inner 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 rubber portion 30 of the bead portion 10 is the portion that abuts against the rim flange Ri of the rim when the tire 1 is mounted on the rim, and forms the contact surface of the bead portion 10 with the rim flange Ri. The volume resistivity of the rubber portion 30 is preferably less than 1×10^8 [Ω·cm]. The volume resistivity of the rubber portion 30 is more preferably 1×10^7 [Ω·cm] or less.

[0021] The belt layer 14 has one or more belt plies extending in the tire width direction, and in this embodiment, multiple belt plies 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 diameter direction, and is disposed on the tire diameter outer side of the carcass layer 13 and wound around 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 belt angles with opposite signs to each other, and are laminated with the extension directions of the belt cords crossing each other, forming a so-called cross-ply structure. That is, the pair of cross belts 141, 142 have belt cords with inclination directions in the tire width direction with respect to the tire circumferential direction opposite to each other. The belt cover 143 is formed by rolling a plurality of cords made of steel or organic fiber material coated with coated rubber, and the belt angle is in the range of 0 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 and 142 in the tire diameter direction.

[0022] 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 of the tire 1 in the radial direction. Therefore, the outer peripheral surface of the tread portion 2 forms part of the contour of the tire 1, and a plurality of grooves, such as circumferential main grooves 6 and lug grooves (not shown), extending in the circumferential direction of the tire are formed in the tread portion 2. The tread portion 2 has an earth tread rubber 7. The tread rubber 15 constituting the tread portion 2 has a cap tread 151 and an under tread 152.

[0023] The cap tread 151 is a rubber member located at the outermost position of the tread portion 2 in the tire diameter 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 1×10^10 [Ω·cm] or more, and even more preferably 1×10^12 [Ω·cm] or more. This reduces the RRC of the 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.

[0024] The undertread 152 is a member laminated on the inner side in the tire diameter 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.

[0025] 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 RRC of the tire 1. The sidewall rubber 16 with such volume resistivity is produced by using a low-heat-generating compound with a low carbon content and reinforcing it with an increased silica content.

[0026] 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 31, they are subject to physical constraints since they are rubber components.

[0027] The inner liner layer 17 is an air permeation prevention layer disposed on the inner circumferential surface of the carcass layer 13, and may or may not include a tie rubber, which will be described later. Here, conductive linear bodies 18 are provided at the splice portions of the inner liner layer 17. The splice portion refers to the circumferential joint portion of the material of the inner liner layer 17 and the joint portion formed during molding. The conductive linear bodies 18 only need to be provided at the splice portion, not around the entire circumference of the tire 1, making them easy to provide and minimizing deterioration of the RRC. The conductive linear bodies 18 are formed by forming a conductive material with a volume resistivity of less than 1×10^8 [Ω·cm] into a linear shape.

[0028] The conductive linear body 18 extends from the bead portion 10 to at least the end position of the belt layer 14. The conductive linear body 18 has a volume resistivity of less than 1×10^8 [Ω·cm]. The rim cushion rubber 31 has a volume resistivity of less than 1×10^8 [Ω·cm]. The sidewall rubber 16 has a volume resistivity of 1×10^8 [Ω·cm] or more.

[0029] One or more conductive linear members 18 are arranged at the splice portion of the inner liner layer 17. The number of conductive linear members 18 is preferably two or more and five or less. By providing a number of conductive linear members 18 within this range, the resistance value can be reduced. Providing more than five conductive linear members 18 is not preferred because it increases the RCC.

[0030] In this embodiment, the bead portion 10 refers to a range of height H from the measurement point of the rim diameter to 10% to 36% of the tire section height SH. That is, the ratio H / SH of the height H to the tire section height SH is 0.10≦H / SH≦0.35. The tire section height SH refers to half the difference between the tire outer diameter and the rim diameter, and is measured with the tire 1 mounted on a specified rim, pressurized to a specified internal pressure, and in an unloaded state.

[0031] 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.

[0032] Here, the ratio He / SH of the length He of the conductive linear body 18 in the tire diameter direction to the tire cross-sectional height SH is preferably 0.35 or more and 0.75 or less. If the ratio He / SH is 0.35 or more and 0.75 or less, deterioration of RRC due to the provision of the conductive linear body 18 can be minimized, and long-term reduction in electrical resistance can be achieved.

[0033] (Earth Red Rubber) As shown in FIG. 1, the tire 1 includes an earth tread rubber 7. The earth tread rubber 7 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 rubber 7 is preferably less than 1×10^8 [Ω·cm], and more preferably 1×10^6 [Ω·cm] or less.

[0034] The earth tread rubber 7 is embedded in the tread rubber 15. A portion of the earth tread rubber 7 is exposed on the tread surface of the tread rubber 15. The earth tread rubber 7 penetrates the cap tread 151 and the under tread 152 and is in conductive contact with the belt layer 14 (belt cover 143). That is, in the tire meridian cross section, one end of the earth tread rubber 7 is in contact with the belt layer 14, and the other end of the earth tread rubber 7 is exposed on the tread surface of the tread portion 2. The earth tread rubber 7 is sometimes called earth rubber. The earth tread rubber 7 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, as the tire rolls, the earth tread rubber 7 is always in contact with the road surface, thereby always ensuring a conductive path from the belt layer 14 to the road surface.

[0035] As described above, a conductive path is secured from the rubber portion 30 in contact with the rim flange Ri through the carcass layer 13, the conductive linear body 18, and the belt layer 14 in this order to the earth tread rubber 7. This allows static electricity on the vehicle to be released to the road surface. This suppresses static electricity buildup on the vehicle on which the tire 1 is mounted. Therefore, deterioration of RRC due to the provision of the conductive linear body 18 can be minimized, and long-term reduction in electrical resistance can be achieved.

[0036] (Cross section of inner liner and conductive wire) 2 to 4 are diagrams that schematically show examples of cross sections of the inner liner layer 17 and the conductive linear body 18 of the tire 1 in FIG. 1. FIGS. 2 to 4 are diagrams that schematically show examples of cross sections of the splice portion SP of the inner liner layer 17 that contacts the carcass layer 13. In FIGS. 2 to 4, the left-right direction in the diagrams corresponds to the tire circumferential direction. In FIGS. 2 to 4, the up-down direction in the diagrams corresponds to the tire width direction, the up-down direction in the diagrams corresponds to the outer side in the tire width direction, and the down-down direction in the diagrams corresponds to the inner side in the tire width direction.

[0037] Fig. 2 schematically shows a first example of a cross section of the inner liner layer 17 and the conductive linear body 18. In Fig. 2, the inner liner layer 17 is in contact with the carcass layer 13. The inner liner layer 17 has a two-layer structure including a liner rubber 171 and a tie rubber 172. At the splice portion SP of the inner liner layer 17, the tie rubber 172 is in contact with the carcass layer 13. As shown in Fig. 2, the liner rubber 171, the tie rubber 172, and the liner rubber 171 are arranged in this order from the tie rubber 172 in contact with the carcass layer 13.

[0038] A conductive linear body 18 is provided at the splice portion SP. In Fig. 2, the conductive linear body 18 is provided at a position sandwiched between the liner rubber 171 and the tie rubber 172. By arranging the conductive linear body 18 at the splice portion SP of the inner liner layer 17, deterioration of the RRC can be minimized and long-term reduction in electrical resistance can be achieved.

[0039] Fig. 3 is a schematic diagram showing a second example of the cross section of the inner liner layer 17 and the conductive linear body 18. In Fig. 3, the inner liner layer 17 is arranged in the same order as in Fig. 2, from the tie rubber 172 in contact with the carcass layer 13, to the liner rubber 171, the tie rubber 172, and the liner rubber 171.

[0040] In Fig. 3, the conductive linear body 18 is provided at a position sandwiched between the carcass layer 13 and the tie rubber 172. By arranging the conductive linear body 18 at the splice portion SP of the inner liner layer 17, deterioration of the RRC can be minimized and long-term reduction in electrical resistance can be achieved.

[0041] Fig. 4 schematically shows a third example of the cross section of the inner liner layer 17 and the conductive linear body 18. In Fig. 4, the inner liner layer 17 is arranged in the same order as in Fig. 2, from the tie rubber 172 in contact with the carcass layer 13, to the liner rubber 171, the tie rubber 172, and the liner rubber 171.

[0042] In Fig. 4, the conductive linear body 18 is provided at a position in contact with the liner rubber 171 on the tire cavity side, away from the carcass layer 13. By arranging the conductive linear body 18 at the splice portion SP of the inner liner layer 17, deterioration of RRC can be minimized and long-term reduction in electrical resistance can be achieved.

[0043] When two or more conductive linear bodies 18 are provided at the splice portion SP, the conductive linear bodies 18 may be arranged in a combination of the arrangements shown in Figures 2 to 4. For example, the conductive linear bodies 18 may be provided at a position sandwiched between the liner rubber 171 and the tie rubber 172 shown in Figure 2, at a position sandwiched between the carcass layer 13 and the tie rubber 172 shown in Figure 3, and at a position in contact with the liner rubber 171 on the side farther from the carcass layer 13 shown in Figure 4.

[0044] (Arrangement of conductive linear elements as seen from the side of the tire) Figures 5 to 8 are diagrams showing examples of the side of the tire 1 of the present disclosure as viewed from the rotational axis direction. Figures 5 to 8 are schematic diagrams showing the appearance of the tire 1 as viewed from the direction of arrow Y1 in Figure 1. Figure 5 is a diagram showing the arrangement of the conductive linear members 18 as viewed from the side of the tire.

[0045] FIG. 5 is a diagram showing a side view of a tire 1, which is an example of a tire according to the present disclosure. As shown in FIG. 5, the entire conductive linear member 18 is provided at the splice portion SP. The conductive linear member 18 shown in FIG. 5 extends linearly in the tire diameter direction. In FIG. 5, the length He is the length of the conductive linear member 18 in the tire diameter direction within the range of the splice portion SP, and corresponds to the length He in FIG. 1. By arranging the conductive linear member 18 at the splice portion of the inner liner layer 17, it is possible to minimize deterioration of RRC due to the provision of the conductive linear member 18, thereby achieving long-term reduction in electrical resistance.

[0046] The conductive linear body 18 may extend in a curved shape rather than a straight shape. FIG. 6 is a diagram showing a side view of a tire 1a, which is another example of a tire according to the present disclosure. As shown in FIG. 6, a conductive linear body 18a is provided at a splice portion SP. The outer end of the conductive linear body 18a in the tire diameter direction is disposed within the range of the splice portion SP. The inner end of the conductive linear body 18a in the tire diameter direction is disposed outside the range of the splice portion SP. In FIG. 6, the length He is the length of the conductive linear body 18a in the tire diameter direction within the range of the splice portion SP, and corresponds to the length He in FIG. 1. In this manner, a portion of the conductive linear body 18a may be provided within the range of the splice portion SP, and another portion of the conductive linear body 18a may be provided outside the range of the splice portion SP. Even in this case, by disposing the conductive linear body 18a at the splice portion of the inner liner layer 17, deterioration of RRC due to the provision of the conductive linear body 18a can be minimized, thereby achieving long-term reduction in electrical resistance.

[0047] FIG. 7 is a diagram showing a side view of a tire 1b, which is another example of a tire according to the present disclosure. As shown in FIG. 7, both the radially outer end and the radially inner end of the conductive linear body 18b are disposed outside the range of the splice portion SP. In FIG. 7, the length He is the length of the conductive linear body 18b in the radial direction of the tire within the range of the splice portion SP, and corresponds to the length He in FIG. 1. In this manner, a portion of the conductive linear body 18a (i.e., both ends) may be disposed within the range of the splice portion SP, and another portion of the conductive linear body 18a (i.e., a portion other than the both ends) may be disposed outside the range of the splice portion SP. Even in this case, by disposing the conductive linear body 18b at the splice portion of the inner liner layer 17, deterioration of the RRC due to the provision of the conductive linear body 18b can be minimized, thereby achieving long-term reduction in electrical resistance.

[0048] FIG. 8 is a diagram showing a side view of a tire 1c, another example of a tire according to the present disclosure. As shown in FIG. 8, the entire conductive linear body 18c is provided at the splice portion SP. The conductive linear body 18c shown in FIG. 8 is not linear but extends in a wavy line shape, i.e., extends in the tire radial direction while changing its position in the tire circumferential direction. In FIG. 8, the length He is the length of the conductive linear body 18c in the tire radial direction within the splice portion SP, and corresponds to the length He in FIG. 1. In this way, the conductive linear body 18c may extend in the tire radial direction in a wavy line shape within the splice portion SP. Even in this case, by arranging the conductive linear body 18c at the splice portion of the inner liner layer 17, deterioration of RRC due to the provision of the conductive linear body 18c can be minimized, and long-term reduction in electrical resistance can be achieved.

[0049] (Example of arrangement of conductive linear bodies relative to the splice) 9 to 14 are diagrams showing examples of the arrangement of conductive linear bodies relative to the splice portion SP. In the following description, the conductive linear bodies 18, 18a, 18b, and 18c may be collectively referred to as "conductive linear body 18." Similar to FIGS. 2 to 4, FIGS. 9 to 14 are diagrams showing examples of cross sections of the inner liner layer 17 and the conductive linear body 18. FIGS. 9 to 14 are diagrams showing examples of cross sections of the splice portion SP of the inner liner layer 17 that contacts the carcass layer 13. In FIGS. 9 to 14, the left-right direction in the diagrams corresponds to the tire circumferential direction. In FIGS. 9 to 14, the up-down direction in the diagrams corresponds to the tire width direction, the up-down direction in the diagrams corresponds to the outer side in the tire width direction, and the down-down direction in the diagrams corresponds to the inner side in the tire width direction.

[0050] In FIG. 9, the width of the splice portion SP of the inner liner layer 17 along the tire circumferential direction is defined as length W. The length W refers to the width of the splice portion of the inner liner layer 17, regardless of whether a tie rubber is used. The conductive linear body 18 is provided within a range of 0.3W to the right and 0.3W to the left of the center position Wc of the length W in the figure, i.e., a total range of 0.6W. In FIG. 9, similar to the case of FIG. 2, the conductive linear body 18 is provided between the liner rubber 171 and the tie rubber 172. Placing the conductive linear body 18 within the above range, including the center position Wc of the splice portion SP, reduces friction caused by movement of the components during transportation or running. This holds the conductive linear body 18 in place, thereby maintaining low electrical resistance. It is more preferable to provide the conductive linear body 18 within a range of 0.2W to the right and 0.2W to the left of the center position Wc of the splice portion SP, i.e., a total range of 0.4W. When the tire 1 is a PC (Passenger Car) tire, the length W is preferably about 5 mm in actual dimension.

[0051] FIG. 10 is a diagram showing the relationship between the diameter of the carcass cords of the carcass layer 13 and the diameter of the conductive linear body 18. In FIG. 10, as in FIG. 2, the inner liner layer 17 is in contact with the carcass layer 13. The carcass layer 13 has a plurality of carcass cords 131. Here, the diameter of the carcass cords 131 of the carcass layer 13 is Φc, and the diameter of the conductive linear body 18 is Φe. The relationship between the diameter Φc and the diameter Φe preferably satisfies (Φe + 0.4) x 5 ≤ W when Φc ≤ Φe. If the diameter Φe of the conductive linear body 18 is within this range, friction due to movement of the components during transportation or running is suppressed. This holds the conductive linear body 18 in place, thereby maintaining low electrical resistance.

[0052] In FIG. 11, similar to the case of FIG. 3, the conductive linear body 18 is provided at a position sandwiched between the carcass layer 13 and the tie rubber 172. In FIG. 12, similar to the case of FIG. 4, the conductive linear body 18 is provided at a position away from the carcass layer 13 and in contact with the liner rubber 171 on the tire cavity side. In FIGS. 11 and 12 as well, the relationship between the diameter Φc and the diameter Φe preferably satisfies (Φe + 0.4) x 5 ≦ W when Φc ≦ Φe. If the diameter Φe of the conductive linear body 18 is within this range, friction due to movement of the components during transportation or running is suppressed. This holds the conductive linear body 18 in place, thereby maintaining low electrical resistance.

[0053] FIG. 13 is a diagram showing an example of the arrangement of the conductive linear body 18 when the diameter Φe of the conductive linear body 18 is smaller than the diameter Φc of the carcass cord 131 of the carcass layer 13. In FIG. 13, the gauge (i.e., thickness) of the splice portion SP of the inner liner layer 17 is T. The center of the conductive linear body 18 is P. When the relationship between the diameter Φc and the diameter Φe is Φc > Φe, the center P of the conductive linear body 18 is preferably set in the range of 0.1 times (i.e., 0.1T or more) to 0.9 times (i.e., 0.9T or less) the gauge T of the splice portion SP of the inner liner layer 17. Note that the ratio Φe / Ti of the diameter Φe of the conductive linear body 18 to the gauge Ti of the inner liner layer 17 is preferably 0.7 to 1.8. A ratio Φe / Ti of less than 0.7 is not preferable because it is not possible to maintain low electrical resistance of the conductive linear body 18. If the ratio Φe / Ti exceeds 1.8, the RRC deteriorates, which is not preferable.

[0054] 14 is a diagram showing an example of the arrangement of the conductive linear body 18 when the diameter Φe of the conductive linear body 18 is equal to or larger than the diameter Φc of the carcass cord 131 of the carcass layer 13. When the relationship between the diameter Φc and the diameter Φe is Φc≦Φe, the center P of the conductive linear body 18 is preferably set in the range of 0.3 times or more (i.e., 0.3T or more) and 0.7 times or less (i.e., 0.7T or less) the gauge thickness T of the splice portion SP of the inner liner layer 17.

[0055] When the diameter Φc of the carcass cord 131 is large, the carcass layer 13 becomes thicker, which is thought to prevent the conductive linear body 18 from biting into the tire. By arranging the conductive linear body 18 within the above range, the conductive linear body is held in place without rubbing after running, thereby maintaining low electrical resistance. When Φc≦Φe, if the position of the center P of the conductive linear body 18 is less than 0.3 T, the conductive linear body 18 is exposed to the tire cavity side and breaks after running, making it impossible to maintain low electrical resistance. Furthermore, if the position is greater than 0.7 T, distortion occurs in the carcass layer 13, deteriorating the RRC. The position of the conductive linear body 18 is preferably Φc>Φe, and the center P is preferably in the range of 0.3 T to 0.6 T. By arranging the conductive linear body 18 within the above range, the conductive linear body is held in place without rubbing after running, thereby further maintaining low electrical resistance.

[0056] (Material of conductive wire) The conductive linear body 18 preferably contains carbon fiber or metal fiber. That is, the conductive linear body 18 preferably contains at least one of carbon fiber and metal fiber. The use of carbon fiber or metal fiber improves durability after running, thereby maintaining the effect of reducing electrical resistance. Metal fibers include stainless steel, steel, aluminum, copper, etc., and oxides of these materials.

[0057] (Physical properties of conductive wires) A blended yarn made of conductive and non-conductive fibers may be used for the conductive linear body 18. For example, a blended yarn made of conductive fibers with a volume resistivity of less than 1×10^8 [Ω·cm] and non-conductive fibers with a volume resistivity of 1×10^8 [Ω·cm] or more may be used for the conductive linear body 18. When the conductive linear body 18 is made of a blended yarn of conductive and non-conductive fibers, durability is ensured and the effect of reducing electrical resistance after running can be maintained.

[0058] The elongation of the conductive linear member 18 is preferably 1.0% or more and 70.0% or less. By making the elongation of the conductive linear member 18 1.0% or more, breakage of the linear conductor during tire manufacturing is suppressed. Furthermore, by making the elongation of the conductive linear member 18 70.0% or less, breakage of the linear conductor during tire rolling is suppressed. The elongation of the conductive linear member 18 is more preferably 10% or more and 50% or less. The elongation of the conductive linear member 18 is measured in accordance with JIS L1017 (Test Method for Chemical Fiber Tire Cords 8.5 Tensile Strength and Elongation).

[0059] (Example) 15A to 15C are tables showing the results of performance tests on tires according to the present disclosure. Performance evaluation tests conducted on a conventional tire and a tire according to the present disclosure are described below. Performance evaluation tests were conducted on the electrical resistance of a new tire and a tire after running. The conventional tire is a tire that does not have conductive linear members 18 arranged thereon.

[0060] (Evaluation method) 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 the electrical resistance of new tires were conducted based on the measurement conditions specified in JIS K6271, using an R8340A Ultra High Resistance Meter manufactured by Advantest Corporation to measure the electrical resistance [Ω] of the test tires.

[0061] In addition, the evaluation test for electrical resistance after driving was performed using an indoor drum-type tire rolling resistance tester with a drum diameter of 1707 mm. The test tire was mounted on a rim specified by JATMA, and the test tire was inflated to 200 kPa and subjected to 80% of the maximum load specified by JATMA. After driving for 60 minutes at a speed of 81 km / h, the tire was measured using the same method as for a new tire. The lower the measured value for electrical resistance of a new tire and after driving, the lower the electrical resistance and the better the tire's performance in terms of electrical resistance.

[0062] Regarding RRC, in accordance with ISO standards, each test tire was mounted on a wheel with a rim size of 15 x 6J, and rolling resistance was measured using an indoor drum-type tire rolling resistance tester when the tire was driven under conditions of an air pressure of 210 kPa, a load of 4.82 kN, and a speed of 80 km / h.

[0063] Performance evaluation tests were conducted on a conventional tire and on tires of each example according to the present disclosure. Of these, the conventional tire is a tire that does not have conductive linear members 18 arranged therein. This conventional tire was set as the reference value (100), and the tires of each example were evaluated. A higher value indicates better performance. Note that by providing a conductor in the tires of each example, the RRC is reduced below the reference value. Even if the RRC is reduced below the reference value, an evaluation value of around "98" can be evaluated as minimizing the reduction in RRC, and is considered to pose no problem in terms of tire performance.

[0064] As can be seen from Figures 15A to 15C, with the tire of the present disclosure, a conductive path is secured from the rim cushion rubber 31 to the earth tread rubber 7 via the conductive linear member 18. This allows static electricity on the vehicle to be released to the road surface. This prevents static electricity from building up on the vehicle on which the tire of the present disclosure is mounted. This allows the effect of reducing electrical resistance to be maintained over the long term.

[0065] The present disclosure includes the following inventions. <1> a pair of bead portions, a carcass layer laid between the pair of bead portions, a belt layer provided on the outer side of the carcass layer in the tire diameter direction, a tread portion provided on the outer side of the belt layer in the tire diameter direction, and an inner liner layer arranged on the tire cavity side of the carcass layer; Including, The carcass layer includes carcass cords coated with a coating rubber having a volume resistivity of 1×10^8 [Ω·cm] or more, the tread portion has earth tread rubber disposed on the outer side of the belt layer in the tire diameter direction, The belt further includes a conductive linear body extending at least from the bead portion to a belt end position of the belt layer, the conductive linear body is disposed at a splice portion of the inner liner layer, A tire in which the volume resistivity of the conductive linear body is less than 1×10^8 [Ω·cm]. <2> The conductive linear body is disposed within the inner liner layer within a range of 0.3W from the center of the splice portion, where W is the width of the splice portion of the inner liner layer. <1> A tire as described in <3> When a diameter Φc of the carcass cord is larger than a diameter Φe of the conductive linear body, a center of the conductive linear body is disposed within a range of 0.1 to 0.9 from the tire cavity side of the gauge of the splice portion, When the diameter Φc of the carcass cord is equal to or smaller than the diameter Φe of the conductive linear body, the center of the conductive linear body is disposed within a range of 0.3 to 0.7 times the gauge of the splice portion from the tire cavity side. <1> or <2> A tire as described in <4> The conductive linear body includes at least one of carbon fiber and metal fiber. <1> or <2> A tire as described in <5> The conductive linear body is a blended yarn made of conductive fibers with a volume resistivity of less than 1×10^8 [Ω·cm] and non-conductive fibers with a volume resistivity of 1×10^8 [Ω·cm] or more. <1> or <2> A tire as described in <6> The conductive linear body has an elongation of 1.0% or more and 70.0% or less. <1> or <2> A tire as described in [Explanation of symbols]

[0066] 1, 1a, 1b, 1c tires 2 Tread section 3 Sidewall 6 Circumferential main groove 7 Earth Tread Rubber 10 Bead section 11 Bead core 12 Bead filler 13 Carcass layer 14 Belt Layer 15 Tread rubber 16 Sidewall rubber 17 Inner liner layer 18, 18a, 18b, 18c conductive wire body 30 Rubber part 31 Rim cushion rubber 32 Chafer 131 Carcass Cord 141, 142 Cross Belt 143 Belt cover 151 Cap Tread 152 Undertread 171 Liner rubber 172 Thai Rubber CL Tire equatorial plane P center Ri rim flange SP splice part

Claims

1. a pair of bead portions, a carcass layer laid between the pair of bead portions, a belt layer provided on the outer side of the carcass layer in the tire diameter direction, a tread portion provided on the outer side of the belt layer in the tire diameter direction, and an inner liner layer arranged on the tire cavity side of the carcass layer; Including, The carcass layer includes carcass cords coated with a coating rubber having a volume resistivity of 1×10^8 [Ω cm] or more, the tread portion has earth tread rubber disposed on the outer side of the belt layer in the tire diameter direction, The belt further includes a conductive linear body extending at least from the bead portion to a belt end position of the belt layer, the conductive linear body is disposed at a splice portion of the inner liner layer, The tire, wherein the conductive linear body has a volume resistivity of less than 1×10^8 [Ω·cm].

2. The conductive linear body is disposed within the inner liner layer within a range of 0.3W from the center of the splice portion, where W is the width of the splice portion of the inner liner layer.

2. The tire of claim 1.

3. when a diameter Φc of the carcass cord is larger than a diameter Φe of the conductive linear body, a center of the conductive linear body is disposed within a range of 0.1 to 0.9 from a tire cavity side of a gauge of the splice portion, 3. The tire according to claim 1, wherein when a diameter Φc of the carcass cord is equal to or smaller than a diameter Φe of the conductive linear body, a center of the conductive linear body is disposed within a range of 0.3 to 0.7 times the gauge of the splice portion from the tire cavity side.

4. The tire according to claim 1 , wherein the conductive linear members include at least one of carbon fibers and metal fibers.

5. 5. The tire according to claim 1, wherein the conductive linear body is a blended yarn made of a conductive fiber having a volume resistivity of less than 1×10^8 [Ω·cm] and a non-conductive fiber having a volume resistivity of 1×10^8 [Ω·cm] or more.

6. 6. The tire according to claim 1, wherein the conductive linear body has an elongation percentage of 1.0% or more and 70.0% or less.

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