tire

Abstract

Provided is a tire with which it is possible to reduce electric resistance while suppressing an increase in mass and fitting pressure. This tire is characterised in that: a length Lt of a tie rubber 22 from a tire equatorial plane CL and a length Li of an inner liner 21 satisfy the relationship Lt < Li; an end part 21a of the inner liner 21 is positioned at a further inner side in a tire radial direction than a radially outermost part 11a of the bead core 11, at a further inner side in a tire width direction than the outermost side part 11b of a bead core 11; a distance Rtg of the end part 22a of the tie rubber 22, a distance Rf of a bead filler outer end part 14a, and a distance Rbc of the radially outermost part 11a of the bead core 11, from a tire rotation axis, satisfy the relationship Rbc < Rtg < Rf; a relationship between a lap amount LAP [mm] of the tie rubber 22 and the bead filler 14, and a maximum thickness Gp [mm] at a portion in contact with the tie rubber 22 in a lap range 500 in a carcass layer 15, is in the range of 0.02 ≤ Gp / LAP ≤ 4.0; and the tie rubber 22 has a volume resistivity of less than 1 × 10^8[Ω·cm].

Description

tire

[0001] This invention relates to tires.

[0002] In recent years, demand for fuel-efficient tires has increased due to environmental concerns. One method used to improve tire fuel efficiency is to increase the silica content in the rubber compound that makes up the tire's cap tread, under tread, and sidewall rubber, thereby reducing the tire's rolling resistance. However, because silica has high insulating properties, increasing the silica content in the rubber compound used in the cap tread, etc., increases the electrical resistance of the cap tread, etc., reducing the tire's static electricity suppression performance. When the tire's static electricity suppression performance decreases, static electricity generated when the vehicle is in motion accumulates more easily, making it more susceptible to radio interference such as radio noise.

[0003] For this reason, some conventional pneumatic tires are equipped with conductive materials with low electrical resistance to improve static electricity suppression performance and to facilitate the release of static electricity generated on the vehicle during driving onto the road surface. For example, Patent Document 1 describes how a conductive layer with low electrical resistivity is placed between the carcass layer and the inner liner and extends from the bead to the belt layer to improve the static electricity suppression performance of the tire. Patent Document 1 also describes an example in which the conductive layer is made of a conductive rubber material and also serves as a tie rubber that is placed around the entire circumference of the inner cavity of the tire.

[0004] Japanese Patent Publication No. 2015-40031

[0005] When reducing electrical resistance using a tie rubber made of conductive rubber material, it is important to position the tie rubber so that it overlaps the rim cushion. However, if the length of the tie rubber overlapping the rim cushion is long, there is a risk that the mass will increase due to the increased length of the tie rubber. In addition, because tie rubber made of conductive rubber material has a high carbon content and is therefore relatively hard, if the length of the tie rubber overlapping the rim cushion is long, there is a risk that the fitting pressure when fitting the tire onto the rim wheel will increase. For these reasons, it is extremely difficult to reduce electrical resistance without increasing mass or fitting pressure.

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

[0007] To solve the above-mentioned problems and achieve the objective, the tire according to the present invention comprises a pair of bead portions arranged on both sides of the tire equatorial plane in the tire width direction, a bead core provided on each of the pair of bead portions, a bead filler arranged on the radially outer side of the bead core, a rim cushion that constitutes the rim fitting surface of the bead portion and is arranged from the inner side in the tire width direction to the outer side of the bead core, at least one carcass layer spanning between the pair of bead portions, and arranged on the radially outer side of the carcass layer. The tire comprises a belt layer, a tread rubber disposed on the radially outer side of the belt layer, an inner liner disposed on the inner surface of the tire along the carcass layer, and a tie rubber disposed between the carcass layer and the inner liner, wherein the inner liner and the tie rubber satisfy the relationship Lt < Li, where Lt is the length from the tire equatorial plane to the end of the tie rubber along the periphery and Li is the length from the tire equatorial plane to the end of the inner liner along the periphery, and the end of the inner liner is in the tire width direction of the bead core. When the end of the tie rubber is located inward in the tire width direction from the outermost part of the bead core, and is located inward in the tire radial direction from the outermost diameter part of the bead core, and Rtg is the distance in the tire radial direction from the tire rotation axis of the end of the tie rubber, Rf is the distance in the tire radial direction from the tire rotation axis of the outer end of the bead filler, which is the outermost end of the bead filler, and Rbc is the distance in the tire radial direction from the tire rotation axis of the outermost diameter part of the bead core, then the end of the tie rubber, the outer end of the bead filler, and the outermost diameter part of the bead core are located inward in the tire width direction from the outermost diameter part of the bead core. The outer diameter satisfies the relationship Rbc < Rtg < Rf, and the relationship between the amount of overlap LAP [mm] between the tie rubber and the bead filler, which is the distance along the periphery between the end of the tie rubber and the outer end of the bead filler, and the maximum thickness Gp [mm] of the carcass layer in the overlap range, which is the range along the periphery between the end of the tie rubber and the outer end of the bead filler, is within the range of 0.02 ≤ Gp / LAP ≤ 4.0, and the tie rubber is characterized in that its volume resistivity is less than 1 × 10^8 [Ω・cm].

[0008] Furthermore, in the above-mentioned tire, it is preferable that the rim cushion has a volume resistivity of less than 1 × 10⁸ [Ω·cm].

[0009] Furthermore, in the above-mentioned tire, it is preferable that the relationship between the maximum thickness Gb [mm] of the bead filler in the lap range and the lap amount LAP [mm] is within the range of 0.01 ≤ Gb / LAP ≤ 3.5.

[0010] Furthermore, in the above-mentioned tire, it is preferable that the thickness of the tie rubber is within the range of 0.1 [mm] to 1.5 [mm].

[0011] Furthermore, in the above-mentioned tire, the overlap amount LAP [mm] between the tie rubber and the bead filler is preferably within the range of 3 [mm] to 40 [mm].

[0012] Furthermore, in the above-mentioned tire, it is preferable that the maximum thickness Gp [mm] of the carcass layer in the portion that contacts the tie rubber within the lap range is within the range of 0.5 [mm] to 4 [mm].

[0013] Furthermore, in the above-mentioned tire, it is preferable that the maximum thickness Gb [mm] of the bead filler in the lap range is within the range of 0.4 [mm] to 10 [mm].

[0014] Furthermore, in the above-mentioned tire, it is preferable that the bead filler has a volume resistivity of less than 1 × 10^10 [Ω・cm].

[0015] Furthermore, in the above-mentioned tire, when the electrical resistance of the carcass layer is Rpc [Ω] and the electrical resistance of the belt coating rubber of the belt layer is Rb [Ω], it is preferable that the electrical resistance Rpc [Ω] of the carcass layer satisfies Rpc [Ω] < 1 × 10^8 [Ω], and the electrical resistance Rb [Ω] of the belt coating rubber satisfies Rb [Ω] < 1 × 10^8 [Ω].

[0016] Furthermore, the above-mentioned tire comprises a tread portion including the tread rubber, a rim cushion rubber that constitutes the rim fitting surface in the bead portion and is arranged from the inside in the tire width direction to the outside in the tire width direction of the bead core, and conductive rubber Earthtread rubber in the rib portion of the tread portion closest to the tire equator, the carcass layer includes carcass cords and carcass coat rubber that surrounds the carcass cords, and preferably the tie rubber has a portion that is inserted between the carcass cords of the carcass layer, at least within the arrangement range of the belt layer.

[0017] Furthermore, in the above-mentioned tire, it is preferable that, in the cross-section of the rib portion of the tread portion closest to the tire's equatorial plane when the tire is cut in the circumferential direction, the tie rubber is inserted at least once between the carcass cords of the carcass layer along the circumferential direction of the tire, within a range of 50 mm in the circumferential direction of the tire.

[0018] Furthermore, in the above-mentioned tire, it is preferable that the relationship between the intercord cross-sectional area Sc(50Ave), calculated by the average distance between the centers of the carcass cords and the average thickness of the carcass layer in a cross-sectional area observed when the tire is cut in the circumferential direction of the rib portion of the tread closest to the tire's equatorial plane, along the circumferential direction of the tire, and the cross-sectional area St(50Ave) of the tie rubber that has entered the carcass coat rubber in the said range, is as follows: 0.02 ≤ St(50Ave) / Sc(50Ave) ≤ 0.5

[0019] Furthermore, in the above-mentioned tire, it is preferable that the thickness Tc of the carcass layer and the height Tt of the tie rubber embedded in the carcass coat rubber have the following relationship: 0.014 ≤ Tt / Tc ≤ 0.8

[0020] Furthermore, in the above-mentioned tire, it is preferable that the cross-sectional area St of the tie rubber inserted between the carcass cords and the height Tt of the tie rubber inserted between the carcass cords have the following relationship: 0.02 mm ≤ St / Tt ≤ 2.0 mm

[0021] Furthermore, in the above-mentioned tire, it is preferable that the ratio Ht / Hc of the hardness of the tire rubber to the hardness Hc of the carcass coat rubber is 0.5 or more and 2.0 or less.

[0022] Furthermore, in the above-mentioned tire, when the tire is cut in the circumferential direction passing through the Earthtread rubber, it is preferable that the Earthtread rubber is arranged such that the ratio of the cross-sectional area Sea of ​​the Earthtread rubber to the cross-sectional area Str of the tread portion has the following relationship: 0.8 ≤ Sea / Str ≤ 1

[0023] The tire according to the present invention has the effect of reducing electrical resistance while suppressing an increase in mass and fitting pressure.

[0024] Figure 1 is a meridional cross-sectional view of a pneumatic tire according to an embodiment. Figure 2 is a detailed view of the region on one side of the tire's equatorial plane in the tire width direction of Figure 1. Figure 3 is a detailed view of the bead portion shown in Figure 2. Figure 4 is a schematic diagram of the tread portion shown in Figure 1. Figure 5A is a chart showing the results of a performance evaluation test of a pneumatic tire. Figure 5B is a chart showing the results of a performance evaluation test of a pneumatic tire. Figure 6 is a diagram showing a portion of the meridional cross-section of the tire shown in Figure 1. Figure 7 is a diagram showing an example of a cross-sectional structure including a two-ply carcass layer. Figure 8 is a diagram showing an example of a cross-sectional structure of a portion of the side rubber shown in Figure 1. Figure 9 is a diagram showing a schematic of the tire's appearance. Figure 10 is a diagram illustrating the area of ​​the tie rubber portion that is inserted between the carcass cords of the carcass layer. Figure 11 is a diagram illustrating that the thickness of the carcass layer varies with respect to the tire's circumferential direction. Figure 12 is a diagram illustrating the height of the tie rubber that is inserted between the carcass cords. Figure 13 is a diagram showing a modified example of the cross-sectional structure of a portion of the tread portion shown in Figure 1. Figure 14 is a diagram illustrating the cross-sectional area and height of the tie rubber embedded in the carcass coat rubber. Figure 15 is a diagram showing a cross-section when the tire is cut circumferentially at the position of the Earthtread rubber in Figure 1. Figure 16 is a meridional cross-sectional view of a tire showing a pneumatic tire according to an embodiment in which a non-penetrating type of Earthtread rubber is used. Figure 17 is a diagram showing a cross-section when the tire is cut circumferentially at the position of the Earthtread rubber in Figure 16. Figure 18A is a chart showing the results of a performance evaluation test of a pneumatic tire. Figure 18B is a chart showing the results of a performance evaluation test of a pneumatic tire. Figure 18C is a chart showing the results of a performance evaluation test of a pneumatic tire.

[0025] Embodiments of the tire according to the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited by these embodiments. Furthermore, the components in the following embodiments include those that are substituted and readily conceivable by those skilled in the art, or that are substantially identical.

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

[0027] Furthermore, in the following explanation, the tire radial direction refers to the direction perpendicular to the tire rotation axis (not shown), which is the rotation axis of the pneumatic tire 1. The inner side of the tire radial direction refers to the side toward the tire rotation axis in the tire radial direction, and the outer side of the tire radial direction refers to the side away from the tire rotation axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotation axis as the central axis. The tire width direction refers to the direction parallel to the tire rotation axis. The inner side of the tire width direction refers to the side toward the tire equatorial plane (tire equator line) CL in the tire width direction, and the outer side of the tire width direction 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 tire rotation axis and passing through the center of the tire width of the pneumatic tire 1. The position of the tire equatorial plane CL in the tire width direction coincides with the center line in the tire width direction, which is the center position of the pneumatic tire 1 in the tire width direction. The tire width is the distance in the tire width direction between the outermost parts in that direction, that is, the distance between the parts furthest from the tire equatorial plane CL in that direction. The tire equatorial line is a line on the tire equatorial plane CL that runs along the circumferential direction of the pneumatic tire 1. In the following explanation, the tire meridional section refers to the cross-section obtained when the tire is cut by a plane containing the tire's axis of rotation.

[0028] Figure 1 is a cross-sectional view of a pneumatic tire 1 according to an embodiment, taken along the tire meridian. The figure shows one side of the tire in the radial direction. The figure also shows a passenger car radial tire as an example of a pneumatic tire.

[0029] The pneumatic tire 1 according to this embodiment has an annular structure centered on the tire rotation axis and comprises a tread portion 2, a pair of sidewall portions 4, 4, a pair of bead portions 10, 10, a carcass layer 15, a belt layer 18, an inner liner 21, and a tie rubber 22. Of these, the pair of sidewall portions 4, 4 and the pair of bead portions 10, 10 are each arranged one on each side of the tire equatorial plane CL in the tire width direction.

[0030] The pair of bead portions 10, 10 are located on the radially inner side of the pair of sidewall portions 4, 4, and each has a bead core 11, a bead filler 14, and a rim cushion 30. That is, the pair of bead cores 11, 11, the pair of bead fillers 14, 14, and the pair of rim cushions 30, 30 are arranged on both sides of the tire equatorial plane CL in the tire width direction.

[0031] The pair of bead cores 11, 11 are annular members formed by bundling multiple bead wires, and constitute the core of the pair of bead portions 10, 10. The pair of bead fillers 14, 14 are positioned on the radially outer side of the pair of bead cores 11, 11 to reinforce the bead portions 10. The pair of bead fillers 14, 14 are formed so that their width in the tire width direction decreases as they move outward in the radial direction of the tire.

[0032] The carcass layer 15 has a single-layer structure consisting of one carcass ply, or a multi-layer structure consisting of multiple carcass plies stacked together, and is stretched in a toroidal manner between a pair of bead portions 10, 10 located on both sides in the tire width direction to form the tire's skeleton. The carcass ply of the carcass layer 15 is constructed by coating multiple carcass cords made of steel or organic fiber materials such as aramid, nylon, polyester, or rayon with coating rubber and then rolling them. The carcass angle of the carcass ply of this carcass layer 15, which is defined as the inclination angle of the direction in which the carcass cord extends with respect to the circumferential direction of the tire, is within the range of 80 [deg] to 95 [deg] in absolute value.

[0033] In this embodiment, the carcass layer 15 has a single-layer structure and is continuously stretched between the bead cores 11, 11 on both sides in the tire width direction. Furthermore, both ends of the carcass layer 15 are wrapped back outward in the tire width direction and secured so as to enclose the bead cores 11 and bead filler 14. In other words, the carcass layer 15, near both ends in the tire meridional section, is wrapped back outward in the tire width direction, passing from the inside in the tire width direction to the inside in the tire radial direction of the bead cores 11 and bead filler 14.

[0034] Therefore, the carcass layer 15 has a carcass body portion 15a that is arranged between a pair of bead portions 10, and a turn-up portion 15b that is formed continuously from the carcass body portion 15a and is folded back from the inside in the tire width direction to the outside in the tire width direction of the bead core 11. The carcass body portion 15a is the portion of the carcass layer 15 that is formed between the inside in the tire width direction of a pair of bead cores 11, and the turn-up portion 15b is formed continuously from the carcass body portion 15a on the inside in the tire width direction of the bead core 11 and is folded back from the inside in the tire radial direction of the bead core 11 to the outside in the tire width direction. The bead filler 14 is arranged on the inside in the tire width direction of the turn-up portion 15b, which is the portion of the bead core 11 that is folded back to the outside in the tire width direction, and on the outside in the tire radial direction of the bead core 11.

[0035] Preferably, the carcass ply of the carcass layer 15 formed in this manner has a volume resistivity of less than 1 × 10⁸ [Ω·cm] of the carcass coat rubber, which is the coating rubber of the carcass cord.

[0036] Volume resistivity (volume resistivity) is measured according to JIS K6271, "Vulcanized rubber and thermoplastic rubber - Method for determining volume resistivity and surface resistivity." Generally, if the volume resistivity is less than 1 × 10⁸ [Ω・cm] or the surface resistivity is less than 1 × 10⁸ [Ω / cm], the material can be said to have conductivity that can suppress the accumulation of static electricity.

[0037] The pair of rim cushions 30, 30 of the pair of bead parts 10, 10 are respectively arranged on the inner side in the tire radial direction of the bead cores 11, 11 on both sides in the tire width direction and the turned-back parts of the carcass layer 15. Specifically, the rim cushion 30 is arranged at least from the inner side in the tire width direction to the outer side in the tire width direction of the bead core 11. That is, the rim cushion 30 is arranged from the inner side in the tire width direction of the bead core 11 in the bead part 10, passes through the inner side in the tire radial direction of the bead core 11, and extends across the outer side in the tire width direction of the bead core 11.

[0038] The rim cushion 30 arranged in this way is the part that abuts against the rim flange R of the rim wheel when the pneumatic tire 1 is mounted on the rim wheel, and constitutes the contact surface with respect to the rim flange R in the bead part 10. Among the contact surfaces of the rim cushion 30 with respect to the rim flange R, the part that becomes the inner peripheral surface of the rim cushion 30 constitutes the rim fitting surface 32 that is the surface of the bead part 10 that fits into the rim wheel.

[0039] The rim cushion 30 is composed of a rim cushion rubber 31 which is a rubber member. The rim cushion 30 has a volume resistivity of less than 1×10^8 [Ω·cm]. That is, the rim cushion rubber 31 that constitutes the rim cushion 30 has a volume resistivity of less than 1×10^8 [Ω·cm]. More preferably, the volume resistivity of the rim cushion 30 is less than 1×10^6 [Ω·cm].

[0040] In addition, the rim cushion rubber 31 has a tanδ value at 60 [°C] within the range of 0.085 or more and 0.35 or less, and a rubber hardness Hs within the range of 35 or more and 111 or less.

[0041] Here, the tanδ value at 60 [°C] is measured under the conditions of an initial strain of 10%, an amplitude of ±0.5%, and a frequency of 20 Hz using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. The rubber hardness Hs is measured under the temperature condition of 20 [°C] in accordance with JIS K6253.

[0042] Further, the rim cushion 30 may have members other than the rim cushion rubber 31. The rim cushion 30 may include, for example, a chafer which is a member made of a fiber material or a rubber member that suppresses damage to the carcass layer 15 when the pneumatic tire 1 is fitted to the rim wheel and the carcass layer 15 contacts the rim flange R.

[0043] The belt layer 18 has one or more belt plies extending in the tire width direction. In the present embodiment, a plurality of belt plies 181 to 183 are laminated. That is, in the present embodiment, the belt layer 18 is configured by laminating a pair of crossed belts 181 and 182 and a belt cover 183 in the tire radial direction, and is disposed outside the carcass layer 15 in the tire radial direction and wound around the outer periphery of the carcass layer 15. The pair of crossed belts 181 and 182 are configured by covering a plurality of belt cords made of steel or an organic fiber material with a coating rubber and performing rolling processing, and the belt angle, which is the inclination angle of the extending direction of the belt cords with respect to the tire circumferential direction, is within a range of 20 [deg] or more and 65 [deg] or less in absolute value. Further, the pair of crossed belts 181 and 182 have belt angles with opposite signs and are laminated with the extending directions of the belt cords crossing each other, having a so-called cross ply structure. That is, in the pair of crossed belts 181 and 182, the inclination directions of the belt cords in the tire width direction with respect to the tire circumferential direction are opposite to each other. The belt cover 183 is configured by performing rolling processing on a plurality of cords made of steel or an organic fiber material covered with a coating rubber, and the belt angle is within a range of 0 [deg] or more and 10 [deg] or less in absolute value. Further, the belt cover 183 is laminated and disposed outside the crossed belts 181 and 182 in the tire radial direction.

[0044] The tread portion 2 is composed of tread rubber 3, which is a rubber composition, and is located on the radially outer side of the carcass layer 15 and belt layer 18, and is exposed at the outermost radial point of the pneumatic tire 1. For this reason, the outer surface of the tread portion 2 constitutes part of the contour of the pneumatic tire 1, and the tread portion 2 has multiple grooves, such as circumferential main grooves (not shown) and lug grooves (not shown), that extend in the circumferential direction of the tire. Furthermore, the tread rubber 3 that constitutes the tread portion 2 has a cap tread 3a and an under tread 3b.

[0045] The cap tread 3a is a rubber member located on the outermost side of the tread portion 2 in the tire radial direction and constitutes the tire contact surface 2a. It may have a single-layer structure (see Figure 1) or a multi-layer structure (not shown). The tanδ value of the cap tread 3a at 60°C is preferably 0.25 or less. Furthermore, the volume resistivity of the cap tread 3a is preferably 1 × 10^8 [Ω・cm] or more, more preferably 1 × 10^10 [Ω・cm] or more, and even more preferably 1 × 10^12 [Ω・cm] or more. These factors reduce the rolling resistance of the pneumatic tire 1. A cap tread 3a having such a volume resistivity is produced by using a low-heat-generating compound with a low carbon content and reinforcing it by increasing the silica content.

[0046] Furthermore, the undertread 3b is a component laminated on the inner side of the cap tread 3a in the tire radial direction. Preferably, the volume resistivity of the undertread 3b is lower than that of the cap tread 3a.

[0047] Each of the pair of sidewall sections 4, 4 is composed of sidewall rubber 5, and the pair of sidewall rubbers 5, 5 of the pair of sidewall sections 4, 4 are respectively arranged on the outer side in the tire width direction of the carcass layer 15. The tanδ value of the sidewall rubber 5 at 60 [°C] is preferably 0.20 or less. Furthermore, the volume resistivity of the sidewall rubber 5 is preferably 1 × 10^8 [Ω・cm] or more, more preferably 1 × 10^10 [Ω・cm] or more, and even more preferably 1 × 10^12 [Ω・cm] or more. These factors reduce the rolling resistance of the pneumatic tire 1. Sidewall rubber 5 having such volume resistivity is produced by using a low-heat-generating compound with a low carbon content and reinforcing it by increasing the silica content.

[0048] While there are no specific limitations on the upper limit of the volume resistivity of the cap tread 3a, the lower limit of the volume resistivity of the under tread 3b, the upper limit of the volume resistivity of the sidewall rubber 5, and the lower limit of the volume resistivity of the rim cushion rubber 31, these are subject to physical constraints because they are rubber components.

[0049] The inner liner 21 is positioned on the inner surface 25 of the tire along the carcass layer 15. That is, the inner liner 21 constitutes the inner surface 25 of the tire, which is the inner surface of the pneumatic tire 1, and faces the inner cavity of the tire, which is the inner space of the pneumatic tire 1. The inner liner 21 that constitutes the inner surface 25 of the tire is a rubber layer positioned on the inner cavity side of the carcass layer 15, and covers the carcass layer 15 from the inner cavity side.

[0050] The tie rubber 22 is positioned between the carcass layer 15 and the inner liner 21. The tie rubber 22 is positioned along the carcass layer 15, similar to the inner liner 21, on the inner side of the tire cavity relative to the carcass layer 15. That is, the inner liner 21 and the tie rubber 22 are laminated and positioned along the carcass layer 15, on the inner side of the tire cavity relative to the carcass layer 15.

[0051] The inner liner 21, positioned on the inner surface 25 of the tire, is an air permeability-preventing layer. By covering the carcass layer 15, it suppresses oxidation of the carcass layer 15 due to exposure and prevents air leakage from the tire. The inner liner 21 is composed of, for example, a rubber composition mainly composed of butyl rubber, a thermoplastic resin, or a thermoplastic elastomer composition in which an elastomer component is blended into a thermoplastic resin. In particular, when the inner liner 21 is made of a thermoplastic resin or a thermoplastic elastomer composition, the inner liner 21 can be made thinner compared to when the inner liner 21 is made of butyl rubber, thus significantly reducing the tire weight.

[0052] Furthermore, the air permeability coefficient of the inner liner 21 is generally preferably 100 × 10⁻¹² [cc・cm / cm²・sec・cmHg] or less, and more preferably 50 × 10⁻¹² [cc・cm / cm²・sec・cmHg] or less, when measured at a temperature of 30 [°C] in accordance with JIS K7126-1.

[0053] Furthermore, the volume resistivity of the inner liner 21 is 1 × 10⁸ [Ω·cm] or more, preferably 1 × 10⁹ [Ω·cm] or more. In addition, the inner liner 21 has a tanδ value at 60 [°C] in the range of 0.115 to 0.35, and a rubber hardness Hs in the range of 27 to 90.

[0054] As rubber compositions mainly composed of butyl rubber, for example, butyl rubber (IIR) and butyl-based rubbers can be used. The butyl-based rubber is preferably a halogenated butyl rubber such as chlorinated butyl rubber (Cl-IIR) or brominated butyl rubber (Br-IIR).

[0055] 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 Polynitrile resins [e.g., 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, aromatic polyesters such as polyoxyalkylenediimidodic acid / polybutylene terephthalate copolymer], polynitrile resins [e.g., polyacrylonitrile (PAN), polymethacrylonitrile, acrylonitrile / styrene copolymer (AS), methacrylonitrile / styrene copolymer, methacrylonitrile / styrene / butadiene copolymer], poly(meth)acrylate resins [e.g., polymethyl methacrylate (PMMA), polyethyl methacrylate, ethylene ethyl acrylate copolymer (EEA), ethylene acrylic acid copolymer (EAA), ethylene methyl acrylate resin (EMA)], polyvinyl resins [e.g., vinyl acetate (EVA), polyvinyl alcohol (PVA), vinyl alcohol / ethylene Copolymers (EVOH), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC), vinyl chloride / vinylidene chloride copolymer, vinylidene chloride / methyl acrylate copolymer, cellulose resins (e.g., cellulose acetate, cellulose acetate butyrate), fluororesins (e.g., polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), polychlorofluoroethylene (PCTFE), tetrafluoroethylene / ethylene copolymer (ETFE)), imide resins (e.g., aromatic polyimide (PI)), etc., can be used.

[0056] Examples of elastomers include diene rubbers and their hydrogenated derivatives [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), isobutylene and aromatic vinyl or diene monomer copolymers, acrylic rubber (ACM), ionomers, halogen-containing rubbers [e.g., Br-IIR, Cl-IIR, brominated isobutylene-paramethylstyrene copolymer (Br-IPMS), chloroprene rubber (CR), hydrin rubber (CHC, CHR), chlorosulfur Materials such as chlorinated polyethylene (CSM), chlorinated polyethylene (CM), maleic acid-modified chlorinated polyethylene (M-CM), silicone rubber (e.g., methyl vinyl silicone rubber, dimethyl silicone rubber, methylphenyl vinyl silicone rubber), sulfur-containing rubber (e.g., polysulfide rubber), fluororubber (e.g., vinylidene fluoride rubber, fluorovinyl ether rubber, tetrafluoroethylene-propylene rubber, fluorosilicone rubber, fluorophosphazene rubber), and thermoplastic elastomers (e.g., styrene elastomers, olefin elastomers, polyester elastomers, urethane elastomers, polyamide elastomers) can be used.

[0057] Furthermore, the tie rubber 22, which is positioned between the inner liner 21 and the carcass layer 15, is a layer that prevents the carcass cords of the carcass layer 15 from biting into the inner liner 21 when the unvulcanized pneumatic tire 1 is inflated during tire manufacturing. In addition, the tie rubber 22 contributes to air permeability prevention and handling stability on dry road surfaces in the pneumatic tire 1 after manufacturing.

[0058] Thai rubber 22 is a rubber composition containing 30 to 100 parts by mass of carbon black with a CTAB adsorption specific surface area of ​​25 [m² / g] to 130 [m² / g] per 100 parts by mass of diene rubber, and more preferably the amount of carbon black is in the range of 40 to 70 parts by mass. Thai rubber 22 containing carbon black is a rubber composition containing isoprene rubber in the range of 30 to 90 parts by mass and styrene-butadiene rubber in the range of 20 to 70 parts by mass. By having such a material composition, the electrical resistance of Thai rubber 22 can be reduced.

[0059] Figure 2 is a detailed view of the region on one side of the tire equatorial plane CL in the tire width direction of Figure 1. The pneumatic tire 1 according to this embodiment has a charge suppression structure for releasing static electricity generated on the vehicle during vehicle operation to the road surface, and tie rubber 22 is used for the charge suppression structure. The tie rubber 22 is arranged in such a way that a single tie rubber 22 is placed along the carcass layer 15 between a pair of bead portions 10, and has a volume resistivity of less than 1 × 10^8 [Ω・cm]. It is more preferable that the volume resistivity of the tie rubber 22 is less than 1 × 10^6 [Ω・cm]. In addition, the tie rubber 22 has a tanδ value at 60 [℃] in the range of 0.05 to 0.40, and a rubber hardness Hs in the range of 50 to 70.

[0060] The inner liner 21 is positioned on the inner lumen side of the tie rubber 22, with a single inner liner 21 extending between the pair of bead portions 10. Therefore, both the end 21a of the inner liner 21 and the end 22a of the tie rubber 22 are located on the bead portion 10.

[0061] In this embodiment, the bead portion 10 refers to the area from the rim diameter measurement point to one-third of the tire cross-sectional height SH. The tire cross-sectional height SH refers to half the difference between the tire outer diameter and the rim diameter, and is measured when the pneumatic tire 1 is mounted on a specified rim, a specified internal pressure is applied, and the measurement is taken under no-load conditions.

[0062] Here, "specified rim" refers to the "applicable rim" specified in JATMA, the "Design Rim" specified in TRA, or the "Measuring Rim" specified in ETRTO. Furthermore, "specified internal pressure" refers to the "maximum air pressure" specified in JATMA, the maximum value of "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified in TRA, or the "INFLATION PRESSURES" specified in ETRTO.

[0063] The inner liner 21 and tie rubber 22, which are stacked and arranged, satisfy the relationship Lt < Li between the length Lt of the tie rubber 22 from the tire equatorial plane CL to the end 22a of the tie rubber 22 along the periphery and the length Li of the inner liner 21 from the tire equatorial plane CL to the end 21a of the inner liner 21 along the periphery. In other words, the length of the tie rubber 22 along the periphery in the tire meridional cross-section is shorter than the length of the inner liner 21 along the periphery in the tire meridional cross-section.

[0064] Furthermore, it is preferable that the difference between the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 along the periphery and the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 along the periphery is within the range of 5 [mm] ≤ Li - Lt ≤ 70 [mm].

[0065] Because the tie rubber 22 is shorter in length along the periphery than the inner liner 21, the tie rubber 22 is covered by the inner liner 21 without coming into contact with the rim cushion 30.

[0066] In this embodiment, the length along the periphery refers to the length along the shape of each component at the same position in the circumferential direction of the tire. Specifically, the direction along the periphery is close to the tire width direction at the position of the tread portion 2, and close to the tire diameter direction at the position of the sidewall portion 4.

[0067] In this embodiment, the rim cushion 30 placed on the bead portion 10 has a position in the tire radial direction where the outer end of the bead core 11 is located on the inner side in the tire width direction, and the outer end of the bead core 11 is located on the outer side in the tire radial side of the bead core 11 is located on the outer side in the tire radial direction.

[0068] Furthermore, the rim cushion 30 is positioned further inward than the inner liner 21 in the tire width direction on the inner portion of the bead core 11 in the tire width direction, and further inward than the inner liner 21 in the tire diameter direction on the inner portion of the bead core 11 in the tire diameter direction. As a result, the rim cushion 30 covers the inner liner 21 from the inside in the tire width direction on the inner portion of the bead core 11 in the tire width direction, and covers the inner liner 21 from the inside in the tire diameter direction on the inner portion of the bead core 11 in the tire diameter direction.

[0069] In other words, the rim cushion 30, which is positioned in the bead portion 10 from the inside to the outside in the tire width direction of the bead core 11, is positioned in the bead portion 10 so as to cover the bead core 11, the carcass layer 15, and the inner liner 21. For this reason, in the bead portion 10, the surface of the inner liner 21 on the inner cavity side of the tire becomes the inner surface 25 of the tire outside the position where the rim cushion 30 is positioned, and the surface of the rim cushion 30 on the inner cavity side of the tire becomes the inner surface 25 of the tire outside the position where the rim cushion 30 is positioned.

[0070] The rim cushion 30, positioned on the bead portion 10 in this manner, forms the bead base 36, which is the inner circumferential surface of the bead portion 10, and the bead toe 35, which is the inner end of the bead base 36 in the tire width direction. The bead base 36 is the part that comes into contact with the rim wheel when the pneumatic tire 1 is mounted on the rim wheel. The rim cushion 30 thus forms the bead base 36, which is the rim fitting surface 32 when the pneumatic tire 1 is mounted on the rim wheel.

[0071] Furthermore, Earth Tread (hereinafter sometimes referred to as Earth Tread rubber) 50 is arranged in the tread portion 2. Earth Tread 50 is a conductive rubber member embedded in the tread rubber 3 and exposed on the tire contact surface. Earth Tread 50 penetrates the tread rubber 3 and contacts the belt layer 18, and is also exposed on the tire contact surface 2a, which is the surface of the tread rubber 3. Specifically, Earth Tread 50 is exposed on the tire contact surface 2a and penetrates the cap tread 3a and under tread 3b of the tread rubber 3 to make conductive contact with the belt layer 18. As a result, an conductive path from the belt layer 18 to the road surface is secured by Earth Tread 50.

[0072] Furthermore, the Earth Tread 50 has an annular structure that extends around the entire circumference of the tire, and extends continuously in the circumferential direction of the tire, with a portion of it exposed to the tire contact surface 2a. Therefore, when the pneumatic tire 1 rolls, the Earth Tread 50 can always be in contact with the road surface, and a conductive path from the belt layer 18 to the road surface can always be ensured. The Earth Tread 50 is formed with a width in the tire width direction that is narrower than, for example, the groove width of the circumferential main groove (not shown) that extends in the circumferential direction of the tire in the tread portion 2, and is arranged between adjacent circumferential main grooves in the tire width direction.

[0073] The Earth Tread 50 arranged in this manner is made of a conductive rubber material having a lower volume resistivity than the tread rubber 3, and the volume resistivity of the Earth Tread 50 is less than 1 × 10⁸ [Ω·cm]. It is more preferable that the volume resistivity of the Earth Tread 50 is 1 × 10⁶ [Ω·cm] or less.

[0074] Figure 3 is a detailed view of the bead portion 10 shown in Figure 2. The end portion 22a of the tie rubber 22 located in the bead portion 10, that is, the end portion 22a of the tie rubber 22 in the peripheral direction, is located radially outward from the outermost diameter portion 11a of the bead core 11 in the tire radial direction. Furthermore, the end portion 22a of the tie rubber 22 is located radially inward from the outer end portion 14a of the bead filler 14, which is the radially outward end of the bead filler 14.

[0075] Therefore, if we let Rtg be the distance in the tire radial direction from the tire rotation axis to the end 22a of the tie rubber 22, Rf be the distance in the tire radial direction from the tire rotation axis to the outer end 14a of the bead filler, and Rbc be the distance in the tire radial direction from the tire rotation axis to the outermost diameter portion 11a of the bead core 11, then the relationship Rbc < Rtg < Rf is satisfied for the end 22a of the tie rubber 22, the outer end 14a of the bead filler, and the outermost diameter portion 11a of the bead core 11.

[0076] Furthermore, it is preferable that the difference between the distance Rf from the tire rotation axis to the outer end 14a of the bead filler in the tire radial direction and the distance Rtg from the tire rotation axis to the end 22a of the tie rubber 22 in the tire radial direction is within the range of 0.5 [mm] ≤ Rf - Rtg ≤ 40 [mm]. Also, it is preferable that the difference between the distance Rtg from the tire rotation axis to the end 22a of the tie rubber 22 in the tire radial direction and the distance Rbc from the tire rotation axis to the outermost diameter portion 11a of the bead core 11 in the tire radial direction is within the range of 0.5 [mm] ≤ Rtg - Rbc ≤ 40 [mm].

[0077] Furthermore, the end portion 22a of the tie rubber 22 is located further outward in the tire radial direction than the outermost inner portion Rwi of the rim cushion, which is the outermost portion in the tire radial direction at the inner side of the bead core 11 in the tire width direction within the rim cushion 30. In other words, if Rtg is the distance in the tire radial direction from the tire rotation axis of the end portion 22a of the tie rubber 22, and Rci is the distance in the tire radial direction from the tire rotation axis of the outermost inner portion Rwi of the rim cushion, then the relationship Rci < Rtg is satisfied between the end portion 22a of the tie rubber 22 and the outermost inner portion Rwi of the rim cushion. In this case, Rtg is the radius of the position of the end portion 22a of the tie rubber 22 with respect to the tire rotation axis, and Rci is the radius of the position of the outermost inner portion Rwi of the rim cushion with respect to the tire rotation axis.

[0078] Furthermore, it is preferable that the difference between the distance Rtg from the tire rotation axis to the end 22a of the tie rubber 22 in the tire radial direction and the distance Rci from the tire rotation axis to the outermost inner part Rwi of the rim cushion in the tire radial direction is within the range of 0.5 [mm] ≤ Rtg - Rci ≤ 70 [mm].

[0079] The rim cushion 30 has a distance Hin in the tire radial direction between the innermost part Rri and the outermost part Rwi, which are the inner ends of the rim cushion 30 in the tire radial direction, that is between 10 mm and 40 mm. In this case, the innermost part Rri is the inner end of the rim cushion 30 in the tire radial direction and is located at the bead toe 35. Furthermore, the distance Hin in the tire radial direction between the innermost part Rri and the outermost part Rwi is the height of the bead core 11 in the rim cushion 30 at the inner position in the tire width direction.

[0080] Furthermore, the distance Hin in the tire radial direction between the innermost part Rri of the rim cushion and the outermost part Rwi of the inner rim cushion is preferably within the range of 15 mm to 25 mm.

[0081] Furthermore, the outer end portion 14a of the bead filler is located radially outward from the outermost end portion Rwo of the rim cushion, which is the outermost end portion in the tire radial direction at the outermost position of the bead core 11 in the tire width direction within the rim cushion 30. In other words, the distance Rf from the tire rotation axis to the outer end portion 14a of the bead filler in the tire radial direction and the distance Rco from the tire rotation axis to the outermost end portion Rwo of the rim cushion in the tire radial direction satisfy the relationship Rco < Rf.

[0082] Furthermore, the distance Rco in the tire radial direction from the tire rotation axis to the outermost outermost part Rwo of the rim cushion satisfies the relationship Rtg < Rco with respect to the distance Rtg in the tire radial direction from the tire rotation axis to the end 22a of the tie rubber 22. Preferably, the difference between the distance Rco in the tire radial direction from the tire rotation axis to the outermost outermost part Rwo of the rim cushion and the distance Rtg in the tire radial direction from the tire rotation axis to the end 22a of the tie rubber 22 is within the range of 0.5 [mm] ≤ Rco - Rtg ≤ 40 [mm].

[0083] Since the end portion 22a of the tie rubber 22 is located radially inward of the outer end portion 14a of the bead filler, the tie rubber 22 is positioned overlapping the bead filler 14 in the tire width direction via the carcass body portion 15a of the carcass layer 15.

[0084] Thus, the tie rubber 22, which is arranged to overlap the bead filler 14 in the tire width direction, and the carcass layer 15 interposed between the bead filler 14 and the tie rubber 22, have a relationship between the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] of the carcass layer 15 in the portion that contacts the tie rubber 22 within the overlap range 500 between the tie rubber 22 and the bead filler 14, which is within the range of 0.02 ≤ Gp / LAP ≤ 4.0.

[0085] In this case, the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 is the distance along the periphery of the tie rubber 22 between the end 22a of the tie rubber 22 and the outer end 14a of the bead filler. Furthermore, the overlap range 500 between the tie rubber 22 and the bead filler 14 is the range along the periphery between the end 22a of the tie rubber 22 and the outer end 14a of the bead filler, and is the range in which the tie rubber 22 and the bead filler 14 are arranged overlapping via the carcass layer 15.

[0086] Furthermore, it is preferable that the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] in the overlap range 500 of the carcass layer 15 is within the range of 0.025 ≤ Gp / LAP ≤ 3.5.

[0087] The bead filler 14, which overlaps the tie rubber 22 in the tire width direction via the carcass layer 15, has a volume resistivity of less than 1 × 10^10 [Ω・cm]. Preferably, the volume resistivity of the bead filler 14 is less than 1 × 10^8 [Ω・cm].

[0088] Furthermore, the maximum thickness Gp [mm] of the carcass layer 15 in the portion that contacts the tie rubber 22 in the overlapping range 500, that is, the carcass body portion 15a of the carcass layer 15 that contacts the tie rubber 22 in the overlapping range 500, is within the range of 0.5 [mm] to 4 [mm]. Preferably, the maximum thickness Gp [mm] of the carcass layer 15 in the portion that contacts the tie rubber 22 in the overlapping range 500 is within the range of 1 [mm] to 3 [mm].

[0089] Furthermore, the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 is within the range of 3 [mm] to 40 [mm]. Preferably, the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 is within the range of 5 [mm] to 30 [mm].

[0090] Furthermore, the relationship between the maximum thickness Gb [mm] of the bead filler 14 in the wrap range 500 and the wrap amount LAP [mm] is within the range of 0.01 ≤ Gb / LAP ≤ 3.5. Preferably, the relationship between the maximum thickness Gb [mm] of the bead filler 14 in the wrap range 500 and the wrap amount LAP [mm] is within the range of 0.015 ≤ Gb / LAP ≤ 2.0.

[0091] Furthermore, the bead filler 14 has a maximum thickness Gb [mm] in the overlapping range 500 that is within the range of 0.4 [mm] to 10 [mm]. Preferably, the maximum thickness Gb [mm] of the bead filler 14 in the overlapping range 500 is within the range of 0.5 [mm] to 9 [mm].

[0092] Furthermore, the thickness Gbv [mm] of the bead filler 14 on a virtual line V that passes through the outermost outermost part Rwo of the rim cushion and is perpendicular to the tie rubber 22 in the meridional cross-section of the tire is within the range of 0.4 [mm] to 10 [mm].

[0093] The bead filler 14 is formed in a shape where its width in the tire width direction narrows as it moves outward in the tire radial direction. Therefore, the maximum thickness Gb of the bead filler 14 in the overlap area 500 and the thickness Gbv of the bead filler 14 on the imaginary line V are thinner than the thickness of the portion of the bead filler 14 located inward in the tire radial direction and near the bead core 11.

[0094] Furthermore, the end portion 21a of the inner liner 21 located in the bead portion 10, that is, the end portion 21a of the inner liner 21 in the peripheral direction, is located within the range in the tire radial direction where the rim cushion 30 is positioned. More specifically, the end portion 21a of the inner liner 21 is located inward in the tire width direction from the outermost portion 11b of the bead core 11 in the tire width direction, and also inward in the tire radial direction from the outermost diameter portion 11a of the bead core 11 in the tire radial direction. In this embodiment, the end portion 21a of the inner liner 21 is located inside the bead core 11 in the tire radial direction. That is, the end portion 21a of the inner liner 21 is located inside the bead core 11 in the tire radial direction, and its position in the tire width direction is located within the range in the tire width direction where the bead core 11 is positioned.

[0095] In other words, the inner liner 21 is positioned to extend inward in the tire radial direction compared to the tie rubber 22 in the peripheral direction. As a result, the length Li (see Figure 2) from the tire equatorial plane CL to the end 21a of the inner liner 21 along the periphery is longer than the length Lt (see Figure 2) from the tire equatorial plane CL to the end 22a of the tie rubber 22 along the periphery. Thus, the inner liner 21 and the tie rubber 22, which have different lengths along the periphery, are positioned along the carcass layer 15, with the tie rubber 22 positioned between the carcass layer 15 and the inner liner 21.

[0096] The inner liner 21, arranged in this manner, has a thickness Gi within the range of 0.1 [mm] to 1.5 [mm]. In this case, the thickness Gi of the inner liner 21 is the maximum thickness of the portion of the inner liner 21 located in the overlap range 500. Preferably, the thickness Gi of the inner liner 21 is within the range of 0.3 [mm] to 1.0 [mm].

[0097] Furthermore, the tie rubber 22 has a thickness Gt within the range of 0.1 [mm] to 1.5 [mm]. In this case, the thickness Gt of the tie rubber 22 is the maximum thickness of the tie rubber 22. Preferably, the thickness Gt of the tie rubber 22 is within the range of 0.3 [mm] to 1.0 [mm].

[0098] The bead core 11, which is positioned in the bead portion 10, has a volume resistivity of less than 1 × 10⁸ [Ω·cm]. Thus, the bead core 11 constitutes a conductive path in the bead portion 10. The bead core 11 includes a bead wire 12 and a bead insulation rubber 13 that surrounds the bead wire 12. In this embodiment, the bead insulation rubber 13 has a volume resistivity of less than 1 × 10⁸ [Ω·cm]. Preferably, the volume resistivity of the bead core 11 is less than 1 × 10⁷ [Ω·cm].

[0099] The volume resistivity of the bead core 11 can be calculated, for example, by cutting out a piece of the bead core 11 so that its length in the tire circumferential direction is relatively short, and then measuring the electrical resistance of the extracted bead core 11 by applying the electrodes of a tester (not shown) to both sides of the extracted bead core 11 in the tire width direction. Based on the electrical resistance of the extracted length of the bead core 11 measured in this way, and the dimensions of the extracted bead core 11, the volume resistivity of the bead core 11 can be calculated.

[0100] Figure 4 is a schematic diagram of the tread section 2 shown in Figure 1. In Figure 4, the belt layer 18 is shown as only the belt ply with the widest width in the tire width direction among the multiple belt plies 181 to 183, and in the following explanation of Figure 4, the widest belt ply will be described as the belt layer 18.

[0101] The belt layer 18 arranged in the tread portion 2 has a belt cord 18a and a belt coat rubber 18b that surrounds the belt cord 18a. In the tread portion 2, the belt cord 18a and the belt coat rubber 18b constitute a conductive path in the tread portion 2. Preferably, the volume resistivity [Ω・cm] of the belt coat rubber 18b is less than 1 × 10^8 [Ω・cm].

[0102] In the tread portion 2 where the belt layer 18 is arranged, if the electrical resistance of the belt coat rubber 18b of the belt layer 18 is Rb [Ω], then the electrical resistance Rb [Ω] of the belt coat rubber 18b satisfies Rb [Ω] < 1 × 10^8 [Ω]. In this case, the electrical resistance Rb [Ω] of the belt coat rubber 18b is the electrical resistance Rb [Ω] of the belt coat rubber 18b in the area where the belt layer 18 is arranged in the tire width direction.

[0103] Furthermore, the carcass layer 15 has carcass cords 16 and carcass coat rubber 17 that surrounds the carcass cords 16, and the carcass layer 15 having the carcass cords 16 and carcass coat rubber 17 also constitutes a conductive path in the tread portion 2. In the tread portion 2 where the carcass layer 15 is arranged, if the electrical resistance of the carcass layer 15 is Rpc [Ω], then the electrical resistance Rpc [Ω] of the carcass layer 15 satisfies Rpc [Ω] < 1 × 10^8 [Ω]. In this case, the electrical resistance Rpc [Ω] of the carcass layer 15 is the electrical resistance Rpc [Ω] of the carcass layer 15 in the area where the belt layer 18 is arranged in the tire width direction.

[0104] [Operation and Effects] When the pneumatic tire 1 according to this embodiment is mounted on a vehicle and driven, the pneumatic tire 1 rotates while the lower part of the surface of the tread portion 2 of the pneumatic tire 1 that is facing the road surface comes into contact with the road surface. The pneumatic tire 1 can generate frictional force with the road surface as the tire contact surface 2a, which is the surface of the tread portion 2, comes into contact with the road surface in this manner. As a result, the vehicle can 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 can drive using these driving force, braking force, and turning force.

[0105] Furthermore, static electricity can be generated while a vehicle is in motion, and if static electricity builds up on the vehicle, it can easily cause radio interference such as radio noise. In this embodiment, since the volume resistivity of the tie rubber 22 and the volume resistivity of the rim cushion 30 are both less than 10^8 [Ω・cm], the tie rubber 22 and the rim cushion 30 conduct electricity relatively easily, and since the tie rubber 22 is positioned overlapping with the bead filler 14, static electricity can be discharged to the road surface.

[0106] In other words, because the volume resistivity of the rim cushion 30 is low, the tire electrical resistance, which is the electrical resistance of the pneumatic tire 1, can be reduced. Therefore, static electricity generated while the vehicle is running can flow from the rim flange R to the rim cushion 30, which has low volume resistivity. The rim cushion 30 is positioned so that the portion of the bead core 11 located on the inside in the tire width direction extends further outward in the tire diameter direction than the portion located on the outside in the tire width direction of the bead core 11. Therefore, static electricity that flows into the rim cushion 30 flows to the portion of the bead core 11 located on the outside in the tire width direction of the rim cushion 30.

[0107] The outer portion of the bead core 11 in the rim cushion 30 in the tire width direction is in contact with the outer portion of the turn-up portion 15b in the carcass layer 15 in the tire width direction. Therefore, static electricity flowing to the rim cushion 30 flows to the turn-up portion 15b in the carcass layer 15. The carcass layer 15 has the turn-up portion 15b located on the outer side of the bead filler 14 in the tire width direction, and the carcass body portion 15a located on the inner side of the bead filler 14 in the tire width direction, sandwiching the bead filler 14 from both sides in the tire width direction between the turn-up portion 15b and the carcass body portion 15a. For this reason, static electricity flowing to the turn-up portion 15b of the carcass layer 15 flows towards the carcass body portion 15a side via the bead filler 14.

[0108] In this process, the bead filler 14 narrows in width in the tire direction as it moves outward in the tire radial direction. Static electricity flowing between the turn-up portion 15b and the carcass body portion 15a of the carcass layer 15 via the bead filler 14 flows more easily in the portion of the bead filler 14 that is closer to the outer side in the tire radial direction. Therefore, static electricity that flows from the rim cushion 30 to the turn-up portion 15b of the carcass layer 15 flows mainly from the turn-up portion 15b of the carcass layer 15 to the carcass body portion 15a side via the portion of the bead filler 14 that is closer to the outer side in the tire radial direction.

[0109] Since the tie rubber 22 is positioned to overlap in the tire width direction with the portion of the bead filler 14 that is closer to the outer side in the tire radial direction, via the carcass body portion 15a of the carcass layer 15, static electricity that flows from the turn-up portion 15b of the carcass layer 15 to the carcass body portion 15a side via the bead filler 14 flows from the carcass body portion 15a to the tie rubber 22.

[0110] The static electricity that flows through the tie rubber 22 then flows to the belt layer 18 and from the belt layer 18 to the tread rubber 3, allowing it to be released from the tread rubber 3 onto the road surface. As a result, the static electricity generated in the vehicle is released onto the road surface, and the static charge buildup of the vehicle is suppressed.

[0111] Here, the tie rubber 22 is positioned overlapping the inner liner 21 and extending to the bead portion 10, but the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 satisfy the relationship Lt < Li. This reduces the mass of the tie rubber 22, and therefore reduces the mass of the pneumatic tire 1.

[0112] Furthermore, by ensuring that the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 satisfy the relationship Lt < Li, the tie rubber 22 can be made less likely to overlap with the rim cushion 30 in the tire meridional cross-section, thereby reducing the amount of material that overlaps with the rim cushion 30. This prevents the fitting pressure from becoming too high when fitting the pneumatic tire 1 onto the rim wheel, which can be caused by a large amount of tie rubber 22 overlapping the rim cushion 30.

[0113] In other words, the tie rubber 22 according to this embodiment is made of a conductive rubber material and is therefore harder, so the tie rubber 22 is less elastically deformable compared to the rim cushion 30. For this reason, if the tie rubber 22 overlaps the rim cushion 30 over a long length, the tie rubber 22, which is less elastically deformable, overlaps the rim cushion 30 more, which may increase the fitting pressure when fitting the pneumatic tire 1 to the rim wheel.

[0114] In contrast, if the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 satisfy the relationship Lt < Li, the tie rubber 22 can be made less likely to overlap with the rim cushion 30. Therefore, it is possible to suppress the tie rubber 22 from overlapping with the rim cushion 30, or even if the tie rubber 22 overlaps with the rim cushion 30, it is possible to suppress the overlapping over a long length. As a result, when a conductive rubber material is used for the tie rubber 22, it is possible to suppress the fitting pressure when fitting the pneumatic tire 1 to the rim wheel from becoming too high.

[0115] Furthermore, since the end portion 21a of the inner liner 21 is located inward in the tire width direction from the outermost portion 11b of the bead core 11 in the tire width direction, the length of the inner liner 21 in the tire meridional cross-section can be shortened. This reduces the mass of the inner liner 21. Also, since the end portion 21a of the inner liner 21 is located inward in the tire radial direction from the outermost diameter portion 11a of the bead core 11 in the tire radial direction, the performance of the inner liner 21 in maintaining the air pressure of the pneumatic tire 1 can be ensured while shortening the length of the inner liner 21. Therefore, the mass of the inner liner 21 can be reduced while ensuring air permeability prevention by the inner liner 21 and suppressing air leakage. This ensures the performance of the pneumatic tire 1 in maintaining the air pressure and suppresses an increase in the mass of the pneumatic tire 1.

[0116] Furthermore, since the relationship between Rtg, the distance Rtg in the tire radial direction from the tire rotation axis to the end 22a of the tie rubber 22, and Rbc, the distance Rbc in the tire radial direction from the tire rotation axis to the outermost diameter portion 11a of the bead core 11, satisfies Rbc < Rtg, the length of the tie rubber 22 can be shortened. This reduces the mass of the pneumatic tire 1 by reducing the length of the tie rubber 22 and thus the mass of the tie rubber 22, and also reduces the fitting pressure when fitting the pneumatic tire 1 to the rim wheel by preventing the tie rubber 22 from overlapping the rim cushion 30.

[0117] Furthermore, since the relationship between Rtg, the distance Rtg from the tire rotation axis to the end 22a of the tie rubber 22 in the tire radial direction, and Rf, the distance Rf from the tire rotation axis to the outer end 14a of the bead filler in the tire radial direction, satisfies Rtg < Rf, it is possible to secure the amount of overlap LAP between the tie rubber 22 and the bead filler 14. This ensures that the width of the transmission path is secured when static electricity from the rim cushion 30 is transmitted to the tie rubber 22, which has a volume resistivity of less than 1 × 10^8 [Ω・cm], via the carcass layer 15 and the bead filler 14, and by making it easier for static electricity to flow from the rim cushion 30 to the tie rubber 22, electrical resistance can be reduced.

[0118] Furthermore, by ensuring that the relationship between Rtg, the distance Rtg from the tire rotation axis to the end 22a of the tie rubber 22 in the tire radial direction, and Rf, the distance Rf from the tire rotation axis to the outer end 14a of the bead filler in the tire radial direction, satisfies Rtg < Rf, thereby securing the overlap amount LAP between the tie rubber 22 and the bead filler 14, the rigidity of the bead portion 10 can be secured. In other words, by arranging the tie rubber 22 and the bead filler 14, which are relatively rigid members, in overlapping positions in the tire width direction, the rigid members can be arranged in the bead portion 10 without interruption in the tire radial direction, thus securing the rigidity of the bead portion 10. This ensures handling stability.

[0119] Furthermore, the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] of the carcass layer 15 in contact with the tie rubber 22 in the overlap range 500 is within the range of 0.02 ≤ Gp / LAP ≤ 4.0, which makes it possible to reduce electrical resistance while suppressing an increase in the mass of the pneumatic tire 1. In other words, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] of the carcass layer 15 is Gp / LAP < 0.02, there is a risk that the overlap amount LAP between the tie rubber 22 and the bead filler 14 will become too large. In this case, the length of the tie rubber 22 will become too long, which may increase the mass of the tie rubber 22 and make it difficult to reduce the mass of the pneumatic tire 1. Furthermore, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] of the carcass layer 15 is Gp / LAP > 4.0, there is a risk that the overlap amount LAP between the tie rubber 22 and the bead filler 14 will become too small. In this case, the tie rubber 22 will become too short, making it difficult to secure a path for static electricity from the rim cushion 30 to the tie rubber 22 via the bead filler 14, which may make it difficult to reduce electrical resistance.

[0120] In contrast, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] of the carcass layer 15 is within the range of 0.02 ≤ Gp / LAP ≤ 4.0, the length of the tie rubber 22 can be kept from becoming too long or too short, and an appropriate length can be achieved. This reduces the mass of the pneumatic tire 1 by suppressing the mass of the tie rubber 22, while also reducing electrical resistance by ensuring a path for static electricity to the tie rubber 22 via the bead filler 14. As a result, electrical resistance can be reduced while suppressing increases in mass and fitting pressure.

[0121] Furthermore, since the rim cushion 30 has a volume resistivity of less than 1 × 10⁸ [Ω·cm], it can more reliably receive static electricity from the rim flange R and pass it from the rim cushion 30 to other components such as the carcass layer 15. As a result, electrical resistance can be reduced.

[0122] Furthermore, the relationship between the maximum thickness Gb [mm] of the bead filler 14 in the lap range 500 and the lap amount LAP [mm] is within the range of 0.01 ≤ Gb / LAP ≤ 3.5, which allows for a reduction in electrical resistance while suppressing a decrease in handling stability. In other words, if the relationship between the maximum thickness Gb [mm] of the bead filler 14 in the lap range 500 and the lap amount LAP [mm] is Gb / LAP < 0.01, the maximum thickness Gb of the bead filler 14 is too thin, which may make it difficult to ensure the rigidity of the bead filler 14. In this case, it may become difficult to ensure the rigidity of the bead portion 10, which may easily lead to a decrease in handling stability. Furthermore, if the relationship between the maximum thickness Gb [mm] of the bead filler 14 in the lap range 500 and the lap amount LAP [mm] is Gb / LAP > 3.5, the maximum thickness Gb of the bead filler 14 is too thick, which may cause the distance between the portion of the bead core 11 located on the outer side in the tire width direction in the rim cushion 30 and the tie rubber 22 to become too large. In this case, static electricity will not flow easily between the rim cushion 30 and the tie rubber 22 via the bead filler 14, which may make it difficult to reduce electrical resistance.

[0123] In contrast, if the relationship between the maximum thickness Gb [mm] of the bead filler 14 in the lap range 500 and the lap amount LAP [mm] is within the range of 0.01 ≤ Gb / LAP ≤ 3.5, it is possible to suppress the maximum thickness Gb of the bead filler 14 from becoming too thin or too thick, thereby making the maximum thickness Gb of the bead filler 14 an appropriate thickness. As a result, it is possible to suppress the decrease in handling stability caused by the maximum thickness Gb of the bead filler 14 becoming too thin, while also suppressing the maximum thickness Gb of the bead filler 14 from becoming too thick, thereby ensuring the ease of static electricity flow and reducing electrical resistance. Consequently, it is possible to reduce electrical resistance while suppressing the decrease in handling stability.

[0124] Furthermore, since the thickness of the tie rubber 22 is within the range of 0.1 [mm] to 1.5 [mm], it is possible to suppress the occurrence of appearance defects caused by the tie rubber 22 being too thin, while also suppressing an excessive increase in the mass of the tie rubber 22. In other words, if the thickness Gt of the tie rubber 22 is less than 0.1 [mm], the tie rubber 22 is too thin, and there is a risk that the inner liner 21 will easily get stuck between the carcass cords 16 of the carcass layer 15 during the vulcanization molding of the pneumatic tire 1. In this case, there is a risk that appearance defects will occur in which the shape of the carcass cords 16 will be visible on the inner surface 25 of the tire. Also, if the thickness Gt of the tie rubber 22 is thicker than 1.5 [mm], the tie rubber 22 is too thick, and there is a risk that the mass of the tie rubber 22 will increase, and the mass of the pneumatic tire 1 will easily increase.

[0125] In contrast, when the thickness Gt of the tie rubber 22 is within the range of 0.1 [mm] to 1.5 [mm], it is possible to suppress the occurrence of appearance defects caused by the tie rubber 22 being too thin, while also suppressing an excessive increase in the mass of the tie rubber 22. As a result, it is possible to suppress the occurrence of appearance defects in the pneumatic tire 1 while also suppressing an increase in mass.

[0126] Furthermore, since the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 is within the range of 3 [mm] to 40 [mm], it is possible to suppress the increase in mass of the pneumatic tire 1 while suppressing the occurrence of appearance defects such as air pockets. In other words, if the overlap amount LAP between the tie rubber 22 and the bead filler 14 is less than 3 [mm], the overlap amount LAP is too small, and there is a risk that the distance between the end 22a of the tie rubber 22 and the outer end 14a of the bead filler will become too small. In this case, since the end 22a of the tie rubber 22 and the outer end 14a of the bead filler are positioned close together, it is easy for parts with large changes in rigidity to occur, and air is more likely to enter between the inner liner 21 and the carcass layer 15 during the vulcanization molding of the pneumatic tire 1, and there is a risk that appearance defects such as air pockets will occur. Furthermore, if the overlap amount LAP between the tie rubber 22 and the bead filler 14 is greater than 40 [mm], the overlap amount LAP is too large, which may cause the length of the tie rubber 22 to become too long. In this case, as the mass of the tie rubber 22 increases, the mass of the pneumatic tire 1 is likely to increase as well.

[0127] In contrast, when the overlap amount (LAP) between the tie rubber 22 and the bead filler 14 is within the range of 3 mm to 40 mm, it is possible to ensure the distance between the end 22a of the tie rubber 22 and the outer end 14a of the bead filler, while also preventing the tie rubber 22 from becoming too long. As a result, it is possible to suppress the occurrence of cosmetic defects in the pneumatic tire 1, such as air pockets, while also suppressing an increase in the mass of the pneumatic tire 1.

[0128] Furthermore, since the maximum thickness Gp [mm] of the carcass layer 15 in the portion that contacts the tie rubber 22 in the lap range 500 is within the range of 0.5 [mm] to 4 [mm], it is possible to suppress the increase in mass while suppressing the decrease in handling stability. In other words, if the maximum thickness Gp of the carcass layer 15 in the portion that contacts the tie rubber 22 in the lap range 500 is less than 0.5 [mm], the maximum thickness Gp of the carcass layer 15 is too thin, which may make it difficult to ensure the rigidity of the carcass layer 15. In this case, the rigidity of the pneumatic tire 1 is likely to decrease, which may lead to a decrease in handling stability. Also, if the maximum thickness Gp of the carcass layer 15 in the portion that contacts the tie rubber 22 in the lap range 500 is greater than 4 [mm], the maximum thickness Gp of the carcass layer 15 is too thick, which may lead to an increase in the mass of the carcass layer 15. In this case, as the mass of the carcass layer 15 increases, the mass of the pneumatic tire 1 may also increase.

[0129] In contrast, if the maximum thickness Gp of the carcass layer 15 in the portion in contact with the tire rubber 22 within the lap range 500 is within the range of 0.5 [mm] to 4 [mm], it is possible to suppress the maximum thickness Gp of the carcass layer 15 from becoming too thin or too thick, thereby making the maximum thickness Gp of the carcass layer 15 an appropriate thickness. This makes it possible to suppress the decrease in handling stability caused by a decrease in the rigidity of the carcass layer 15 due to the maximum thickness Gp of the carcass layer 15 becoming too thin, while also suppressing the increase in mass caused by the maximum thickness Gp of the carcass layer 15 becoming too thick. As a result, it is possible to suppress the increase in mass of the pneumatic tire 1 while suppressing the decrease in handling stability.

[0130] Furthermore, since the maximum thickness Gb [mm] of the bead filler 14 in the lap range 500 is within the range of 0.4 [mm] to 10 [mm], it is possible to suppress the increase in mass while suppressing the decrease in handling stability. In other words, if the maximum thickness Gb of the bead filler 14 in the lap range 500 is less than 0.4 [mm], the maximum thickness Gb of the bead filler 14 is too thin, which may make it difficult to ensure the rigidity of the bead filler 14. In this case, it may become difficult to ensure the rigidity of the bead portion 10, which may easily lead to a decrease in handling stability. Also, if the maximum thickness Gb of the bead filler 14 in the lap range 500 is greater than 10 [mm], the maximum thickness Gb of the bead filler 14 is too thick, which may easily lead to an increase in the mass of the bead filler 14. In this case, as the mass of the bead filler 14 increases, the mass of the pneumatic tire 1 may easily increase.

[0131] In contrast, if the maximum thickness Gb of the bead filler 14 in the lap range 500 is within the range of 0.4 [mm] to 10 [mm], it is possible to suppress the maximum thickness Gb of the bead filler 14 from becoming too thin or too thick, thereby making the maximum thickness Gb of the bead filler 14 an appropriate thickness. This makes it possible to suppress the decrease in handling stability caused by a decrease in the rigidity of the bead filler 14 due to the maximum thickness Gb of the bead filler 14 becoming too thin, while also suppressing the increase in mass caused by the maximum thickness Gb of the bead filler 14 becoming too thick. As a result, it is possible to suppress the increase in mass of the pneumatic tire 1 while suppressing the decrease in handling stability.

[0132] Furthermore, since the bead filler 14 has a volume resistivity of less than 1 × 10¹⁰ [Ω·cm], the static electricity that flows from the rim cushion 30 to the turn-up portion 15b of the carcass layer 15 can be easily directed towards the carcass body portion 15a by the bead filler 14, and thus easily directed towards the tie rubber 22. As a result, electrical resistance can be reduced more reliably.

[0133] Furthermore, the electrical resistance Rpc [Ω] of the carcass layer 15 satisfies Rpc [Ω] < 1 × 10⁸ [Ω], and the electrical resistance Rb [Ω] of the belt coat rubber 18b satisfies Rb [Ω] < 1 × 10⁸ [Ω]. Therefore, the electrical resistance from the tie rubber 22 to the tread rubber 3 can be reduced by the carcass layer 15 and the belt coat rubber 18b. As a result, static electricity flowing from the rim cushion 30 side to the belt layer 18 side by the tie rubber 22 can be directed to the tread rubber 3 by the carcass layer 15 and the belt coat rubber 18b, and then released from the tread rubber 3 to the road surface. As a result, electrical resistance can be reduced more reliably, and static electricity buildup on the vehicle can be suppressed.

[0134] [Modification] In the above-described embodiment, the end portion 22a of the tie rubber 22 is located radially outward from the outermost inner portion Rwi of the rim cushion 30. However, the end portion 22a of the tie rubber 22 may be located radially inward from the outermost inner portion Rwi of the rim cushion 30. For example, if the outermost inner portion Rwi of the rim cushion is located radially outward from the outermost diameter portion 11a of the bead core 11, the end portion 22a of the tie rubber 22 may be located radially outward from the outermost diameter portion 11a of the bead core 11 and radially inward from the outermost inner portion Rwi of the rim cushion. Regardless of the relative positional relationship between the end portion 22a of the tie rubber 22 and the outermost inner portion Rwi of the rim cushion, by positioning the tie rubber 22 radially outward from the outermost diameter portion 11a of the bead core 11, the length of the tie rubber 22 can be shortened, thereby reducing its mass.

[0135] Furthermore, in the above-described embodiment, the outermost part Rwo of the rim cushion is located radially outward from the end 22a of the tie rubber 22, but the outermost part Rwo of the rim cushion may be located radially inward from the end 22a of the tie rubber 22. Even if the outermost part Rwo of the rim cushion is located radially inward from the end 22a of the tie rubber 22, if the volume resistivity of the bead filler 14 is low or the bead filler 14 is thin in the tire width direction, it is possible to facilitate the flow of static electricity from the turn-up portion 15b side of the carcass layer 15 to the carcass body portion 15a side via the bead filler 14. This ensures a path for static electricity from the rim cushion 30 to the tie rubber 22, thereby reducing electrical resistance.

[0136] Furthermore, the embodiments and modifications described above may be combined as appropriate. In addition, although the embodiments described above used pneumatic tire 1 as an example of a tire according to the present invention, the tire according to the present invention may be other than pneumatic tire 1. The tire according to the present invention may be, for example, a so-called airless tire that can be used without filling with gas.

[0137] [Examples] Figures 5A and 5B are charts showing the results of performance evaluation tests of pneumatic tires. Below, we will describe the performance evaluation tests conducted on the above-mentioned pneumatic tire 1, the pneumatic tire of Conventional Example 1, the pneumatic tire 1 according to the present invention, and a comparative example pneumatic tire for comparison with the pneumatic tire 1 according to the present invention. The performance evaluation tests included tests on the electrical resistance of the pneumatic tire, the tire mass which is the mass of the pneumatic tire, the fitting pressure when fitting the pneumatic tire to the rim wheel, the appearance performance of the pneumatic tire, and the handling stability when driving a vehicle equipped with the pneumatic tire.

[0138] The performance evaluation tests were conducted using pneumatic tires with a nominal tire size of 235 / 60R18 as specified by JATMA as the test tires. For the evaluation tests of the electrical resistance of the pneumatic tires, the electrical resistance [Ω] of the test tires was measured using an R8340A ultra-high resistance meter manufactured by Advantest Corporation, based on the measurement conditions specified by JATMA.

[0139] Furthermore, the tire mass evaluation test involved measuring the mass of each test tire and using an index evaluation method where the reciprocal of the measured mass was set to 100, as described later in Conventional Example 1. A higher index evaluation value indicates a lighter tire mass and a better evaluation of the tire mass.

[0140] Furthermore, in the evaluation test of the fitting pressure when fitting a pneumatic tire to a rim wheel, the test tire was fitted to a rim wheel with a rim size of 18 x 7.0J, and air was supplied to the test tire at a supply pressure of 500 [kPa] before the test tire was assembled to the rim wheel. During the process of assembling the test tire to the rim wheel, the air filling was temporarily stopped at the moment the bead of the test tire crossed the hump of the rim wheel, and the air pressure at that time was measured as the fitting pressure. The fitting pressure when fitting a pneumatic tire to a rim wheel was evaluated using an index, where the reciprocal of the measured air pressure as the fitting pressure was set to 100, as described later in Conventional Example 1. The larger the index value of the fitting pressure when fitting a pneumatic tire to a rim wheel, the lower the air pressure when the pneumatic tire is fitted to the rim wheel, indicating superior performance in terms of fitting pressure.

[0141] Furthermore, for appearance performance, more than 1,000 test tires were vulcanized and the number of test tires exhibiting appearance defects, such as air pockets or the shape of the carcass cords appearing on the inner surface of the tire, was counted during visual inspection of the vulcanized test tires to calculate the appearance defect rate. The reciprocal of the calculated appearance defect rate was then used as an index evaluation, with Conventional Example 1 (described later) set to 100. A higher index evaluation value indicates a lower appearance defect rate and superior performance in terms of appearance defects.

[0142] Furthermore, the evaluation test for handling stability was conducted by mounting test tires, which were mounted on rim wheels with a rim size of 18 x 7.0J, onto a test vehicle. The test vehicle was driven on a test course with a flat, dry surface at speeds ranging from 10 km / h to 180 km / h, and a test driver performed a subjective evaluation of steering performance during lane changes and cornering, as well as stability during straight-line driving. The evaluation of handling stability was performed using an index evaluation based on the subjective evaluation of the test driver, with Conventional Example 1, described later, set to 100. A higher index evaluation value indicates better handling stability on dry surfaces.

[0143] Performance evaluation tests were conducted on 23 types of pneumatic tires, including Conventional Example 1, which is an example of a conventional pneumatic tire; Examples 1 to 20, which are pneumatic tires 1 according to the present invention; and Comparative Examples 1 and 2, which are pneumatic tires compared to pneumatic tire 1 according to the present invention. Of these, in Conventional Example 1, the relationship between the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 is Lt > Li. In addition, in Comparative Examples 1 and 2, the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] in the overlap range 500 of the carcass layer 15 in contact with the tie rubber 22 does not satisfy 0.02 ≤ Gp / LAP ≤ 4.0.

[0144] In contrast, in all of the Examples 1 to 20, which are examples of the pneumatic tire 1 according to the present invention, the length Lt from the tire equatorial plane CL to the end 22a of the tie rubber 22 and the length Li from the tire equatorial plane CL to the end 21a of the inner liner 21 satisfy the relationship Lt < Li, and the relationship between the amount of overlap LAP [mm] between the tie rubber 22 and the bead filler 14 and the maximum thickness Gp [mm] of the carcass layer 15 in contact with the tie rubber 22 in the overlap range 500 is within the range of 0.02 ≤ Gp / LAP ≤ 4.0. Furthermore, the pneumatic tire 1 according to Examples 1 to 20 differs in the relationship between the maximum thickness Gb [mm] of the bead filler 14 in the lap range 500 and the lap amount LAP [mm] (Gb / LAP), the thickness Gt [mm] of the tie rubber 22, the lap amount LAP [mm] between the tie rubber 22 and the bead filler 14, the maximum thickness Gp [mm] of the carcass layer 15 in the portion in contact with the tie rubber 22 in the lap range 500, the maximum thickness Gb [mm] of the bead filler 14 in the lap range 500, the volume resistivity [Ω・cm] of the bead filler 14, the electrical resistance Rb [Ω] of the belt coat rubber 18b, and the electrical resistance Rpc [Ω] of the carcass layer 15.

[0145] As a result of evaluation tests conducted using these pneumatic tires 1, as shown in Figures 5A and 5B, it was found that the pneumatic tires 1 according to Examples 1 to 20 can reduce electrical resistance without increasing tire mass or fitting pressure compared to Conventional Example 1 and Comparative Examples 1 and 2. In other words, the pneumatic tires 1 according to Examples 1 to 20 can reduce electrical resistance while suppressing increases in mass and fitting pressure.

[0146] [Other Modifications] Figure 6 shows a portion of the meridional cross-section of the tire shown in Figure 1. Figure 6 shows an example of the cross-sectional structure of a portion of the tread portion 2 shown in Figure 1. Figure 6 shows a cross-section cut along the circumferential direction of the tire. Referring to Figure 6, the belt layer 18, carcass layer 15, tie rubber 22, and inner liner 21 are arranged in order on the radially inner side of the tread rubber 3. The tie rubber 22 is positioned between the carcass layer 15 and the inner liner 21.

[0147] The carcass layer 15 has carcass cords 16 and carcass coat rubber 17 that surrounds the carcass cords 16. Focusing on the tie rubber 22, a portion 221 of the tie rubber 22 extends outward in the tire radial direction and fits between the carcass cords 16. Specifically, if a portion 221 of the tie rubber 22 crosses a virtual line L1 that passes through the inside of each carcass cord 16 in the tire radial direction, it can be considered that the tie rubber 22 fits between the carcass cords 16. That is, the tie rubber 22 has a portion 221 that fits between the carcass cords 16 of the carcass layer 15, at least within the arrangement range of the belt layer 18. By the tie rubber 22 fitting between the carcass cords 16, the thickness of the carcass coat rubber 17 is reduced, the conductive distance is shortened, and thus conductivity is improved. In addition, by fitting into the carcass coat rubber 17, the adhesive area between the tie rubber 22 and the carcass layer 15 is increased. This improves the adhesion between the tie rubber 22 and the carcass layer 15, allowing low electrical resistance to be maintained even after driving.

[0148] [Modified Carcass Layers] A one-ply structure is preferred for the carcass layer 15 described with reference to Figure 6, but it is not limited thereto. Figure 7 shows an example of a cross-sectional structure including a two-ply carcass layer 150. The carcass layer 150 includes a ply made of carcass cord 161 and carcass coat rubber 171 surrounding it, and another ply made of carcass cord 162 and carcass coat rubber 172 surrounding it, thus having a two-ply structure.

[0149] In the case shown in Figure 7, portion 221 of the tie rubber 22 extends outward in the tire radial direction and is inserted between the carcass cords 161. In the case of a two-ply structure, a virtual line L12 is drawn between the ply consisting of carcass cords 161 and carcass coat rubber 171 and the ply consisting of carcass cords 162 and carcass coat rubber 172. If portion 221 of the tie rubber 22 crosses the virtual line L12, which passes through the inside of the carcass cords 161 in the tire radial direction of the inner ply in the tire radial direction, i.e., the ply closer to the tie rubber 22 in the tire radial direction, then it can be considered that it is inserted between the carcass cords 161.

[0150] As the tie rubber 22 penetrates between the carcass cords 161, the thickness of the carcass coat rubber 171 is reduced, shortening the conductive distance and thus improving conductivity. Furthermore, by penetrating into the carcass coat rubber 171, the adhesive area between the tie rubber 22 and the carcass layer 150 increases. This improves the adhesion between the tie rubber 22 and the carcass layer 150, allowing low electrical resistance to be maintained even after driving.

[0151] Furthermore, the area around the side rubber may have the same configuration as in Figure 6. Figure 8 shows an example of the cross-sectional structure of a part of the sidewall rubber 5 shown in Figure 1. Referring to Figure 8, the carcass layer 15, tie rubber 22, and inner liner 21 are arranged in order from the tread rubber 3 toward the inner cavity of the tire.

[0152] In Figure 8, focusing on the tie rubber 22, portion 221 of the tie rubber 22 extends outward in the radial direction of the tire and is inserted between the carcass cords 16. That is, even within the area where the sidewall rubber 5 is placed, the tie rubber 22 has a portion 221 that is inserted between the carcass cords 16 of the carcass layer 15. By the tie rubber 22 being inserted between the carcass cords 16, the thickness of the carcass coat rubber 17 is reduced, and the conductive distance is shortened, thus improving conductivity. In addition, by being inserted into the carcass coat rubber 17, the adhesive area between the tie rubber 22 and the carcass layer 15 is increased. As a result, the adhesion between the tie rubber 22 and the carcass layer 15 is improved, and low electrical resistance can be maintained even after driving.

[0153] [Number of locations where the tie rubber is inserted] Figure 9 is a schematic diagram of the appearance of tire 1. As shown in Figure 9, in tire 1 of this example, four locations in the tire circumferential direction are designated as measurement locations S1, S2, S3, and S4. These four locations in the tire circumferential direction are, for example, one location every 90 degrees in the tire circumferential direction. Here, within a circumferential length of 50 mm at measurement location S1, it is preferable that there is at least one portion 221 in which the tie rubber 22 is inserted between the carcass cords 16 of the carcass layer 15. In other words, it is preferable that there is at least one location in which the tie rubber 22 is inserted between the carcass cords 16 for every 50 mm of circumferential length of the tire. The more locations in which the tie rubber 22 is inserted, the greater the adhesive area between the tie rubber 22 and the carcass layer 15. This improves the adhesion between the tie rubber 22 and the carcass layer 15, and allows low electrical resistance to be maintained even after driving.

[0154] Similarly, it is preferable that at least one measurement point is included in each of the other measurement points S2, S3, and S4 of tire 1. Note that the four measurement points S1, S2, S3, and S4 in Figure 9 are examples, and more locations may be used as measurement points.

[0155] [Cross-sectional area of ​​tie rubber] Figure 10 illustrates the area of ​​portion 221 of the tie rubber 22 that is inserted between the carcass cords 16 of the carcass layer 15. Within a tire circumferential length of 50 mm at measurement points S1, S2, S3, and S4, the average value of the inter-cord cross-sectional area Sc (50Ave), calculated from the average distance between the centers of the carcass cords 16 and the average thickness of the carcass layer 15, and the cross-sectional area St [mm²] of the tie rubber that is inserted into the carcass coat rubber within that range are shown. ２ It is preferable that the relationship between the mean value St(50Ave) and Sc(50Ave) satisfies the following equation (1): 0.02 ≤ St(50Ave) / Sc(50Ave) ≤ 0.5 …(1)

[0156] In the above equation (1), St(50Ave) is the cross-sectional area St [mm²] of the tie rubber that has entered between the carcass cords. ２ This is the average value of Sc(50Ave). Area Sc [mm²] ２The area Sc = Tc × Lc [mm²] is the cross-sectional area determined by the thickness Tc of the carcass layer 15 and the distance Lc between the centers of the carcass cords 16. That is, Area Sc = Tc × Lc [mm²] ２ The thickness Tc [mm] is the length between point P18, where a perpendicular line drawn radially outward from the center of the carcass cord 16 toward the belt layer 18 intersects with the interface of the belt layer 18, and point P22, where a perpendicular line drawn radially inward intersects with the interface of the tie rubber 22.

[0157] By satisfying the conditions in (1) above, the conductivity can be improved while maintaining the durability of the tire, and the electrical resistivity can be reduced. If the above St(50Ave) / Sc(50Ave) is less than 0.02, the improvement in conductivity is small, and the electrical resistance does not decrease. Also, if the above St(50Ave) / Sc(50Ave) is greater than 0.5, the durability deteriorates due to the widening of the gaps between the carcass cords 16, and it is not possible to maintain low electrical resistance after driving. Note that the cross-sectional area St [mm ２ It is more preferable that the relationship between the average value St(50Ave) of ] and the average value Sc(50Ave) of area Sc is 0.1 ≤ St(50Ave) / Sc(50Ave) ≤ 0.35.

[0158] Here, the thickness Tc [mm] of the carcass layer 15 is not constant in the circumferential direction of the tire, but varies. This will be explained with reference to Figure 11. Figure 11 is a diagram illustrating that the thickness of the carcass layer 15 varies in the circumferential direction of the tire.

[0159] In Figure 11, a perpendicular line S16 is drawn from the center of the carcass cord 16 toward the radially inward direction of the tire. The distance along the tire radial direction from point P16, where this perpendicular line S16 intersects the interface between the tie rubber 22 and the carcass coat rubber 17, to the interface between the carcass coat rubber 17 and the belt layer 18, is not constant and varies depending on the height to which the portion 221 of the tie rubber 22 intrudes. For example, in Figure 11, thickness Tcmax is the maximum value, thickness Tcmin is the minimum value, and thickness Tcave is the average value. The above area Sc [mm²] ２ This is calculated as the product of the average value thickness Tcave and the center-to-center distance Lc of the carcass code 16.

[0160] [Height of the inserted tie rubber] Figure 12 illustrates the height of the tie rubber inserted between the carcass cords 16. In Figure 12, the thickness of the carcass layer 15 is Tc, and the height of the tie rubber inserted into the carcass coat rubber is Tt. It is preferable that the relationship between the thickness Tc and the height Tt satisfies the following equation (2): 0.014 ≤ Tt / Tc ≤ 0.8 …(2)

[0161] In equation (2), thickness Tc is the thickness [mm] of the carcass layer 15. Thickness Tc is the distance from the interface between the tie rubber 22 and the carcass layer 15 to the interface between the belt layer 18 and the carcass layer 15. In equation (2), height Tt is the height [mm] of the portion 221 of the tie rubber 22 that is inserted between the carcass cords 16. Height Tt is the distance from the interface between the tie rubber 22 and the carcass layer 15 to the outermost part of the portion 221 of the tie rubber 22 in the tire radial direction. If Tt / Tc in equation (2) is less than 0.014, the improvement in conductivity is small and the electrical resistance is not reduced. Also, if Tt / Tc is greater than 0.8, the durability deteriorates due to the opening of the carcass cords, and it is not possible to maintain low electrical resistance after driving. It is more preferable that the relationship between thickness Tc and height Tt is 0.2 ≤ Tt / Tc ≤ 0.6.

[0162] [Modified Belt Layer Coating Rubber] The tie rubber 22 may penetrate into the carcass coating rubber 17, and the coating rubber of the belt layer 18 may also penetrate into the carcass coating rubber 17. Figure 13 shows a modified cross-sectional structure of the tread portion 2 shown in Figure 1. As shown in Figure 13, the portion 221 of the tie rubber 22 extends outward in the tire radial direction within the carcass coating rubber 17. That is, the portion 221 of the tie rubber 22 crosses the imaginary line L1, and the portion 221 penetrates between the carcass cords 16. Furthermore, a portion of the coating rubber 18b of the belt layer 18 crosses the imaginary line L2 passing on the outer side of the carcass cords 16 in the tire radial direction, and the coating rubber 18b penetrates between the carcass cords 16. It is preferable that the volume resistivity of the coating rubber 18b of the belt layer 18 is less than 1 × 10^8 [Ω・cm].

[0163] [Cross-sectional area and height of the inserted tie rubber] Figure 14 illustrates the cross-sectional area and height of the tie rubber inserted into the carcass coat rubber. In Figure 14, the cross-sectional area of ​​the tie rubber inserted between the carcass cords is given by St [mm²]. ２ Let the following be the case. Also, let Tt be the height of the tie rubber that is inserted between the carcass cords. In this case, it is preferable that the relationship between the cross-sectional area St and the height Tt satisfies the following equation (3). That is, it is preferable that 0.02 mm ≤ St / Tt ≤ 2.0 mm …(3) is satisfied.

[0164] Furthermore, it is more preferable that the relationship between the cross-sectional area St and the height Tt satisfies the following: that is, it is more preferable that 0.2 mm ≤ St / Tt ≤ 0.6 mm. Note that the cross-sectional area St [mm ２ The height Tt [mm] is the average value of the cross-section observed when the tire is cut in the circumferential direction, along the circumferential direction of the tire, within a range of 50 mm in length.

[0165] [Rubber Hardness] When the hardness of the carcass coat rubber 17 is Hc and the hardness of the tie rubber 22 is Ht, the ratio of hardness Ht to hardness Hc, Ht / Hc, is preferably 0.5 or more and 2.0 or less. Furthermore, the ratio Ht / Hc is more preferably 0.7 or more and 1.5 or less, and even more preferably 0.9 or more and 1.3 or less.

[0166] If the ratio of the hardness of the tie rubber to the hardness of the carcass coat rubber (Ht / Hc) is within the above range, the hardness difference will be reduced, suppressing the small delaminations that occurred in the tires after driving. This ensures conductivity, thus suppressing the deterioration of electrical resistance before and after driving.

[0167] The hardness Hc of the carcass coat rubber 17 is, for example, between 55 and 75 points. The hardness Ht of the tie rubber 22 is, for example, between 50 and 65 points. Here, hardness refers to the durometer hardness measured at a temperature of 23°C using a Type A durometer (rubber hardness tester) in accordance with JIS-K6253, and is also called JIS-A hardness. The hardness of the rubber is the average value measured at four or more locations using the above durometer on a cut sample tire.

[0168] Regarding the land portion of the tread section 2 closest to the tire equatorial plane CL, it is preferable that in the cross-section seen when the pneumatic tire 1 is cut in the circumferential direction, there is at least one location along the circumferential direction of the tire, within a circumferential length of 50 mm, where the tie rubber 22 is inserted between the carcass cords 16 of the carcass layer 15. Having at least one location where the tie rubber 22 is inserted helps maintain low electrical resistance while maintaining tire durability.

[0169] [Arrangement of Earth Red Rubber] The arrangement of the Earth Red Rubber 50 will be explained with reference to Figures 15 to 17. Figure 15 is a cross-section of the tire when it is cut circumferentially at the position of the Earth Red Rubber 50 in Figure 1. Figure 15 is a cross-section when the Earth Red Rubber 50 is a through-type Earth Rubber.

[0170] In Figure 15, the Earthtread rubber 50 is a through-type Earthtread rubber. Therefore, the Earthtread rubber 50 penetrates the tread rubber 3 and contacts the belt layer 18. Consequently, the conductivity is improved by the Earthtread rubber 50 contacting the road surface. As shown in Figure 15, a small portion of the cap tread 3a may remain on the outermost edge of the tread rubber 3 in the tire radial direction.

[0171] On the other hand, FIG. 16 is a cross-sectional view in the tire meridian direction showing a pneumatic tire according to an embodiment when a non-penetrating type ground tread rubber is adopted. FIG. 17 is a view showing a cross-section when the tire is cut in the circumferential direction at the position of the ground tread rubber in FIG. 16. In FIGS. 16 and 17, the ground tread rubber 50a is a non-penetrating type ground rubber. Therefore, the ground tread rubber 50a does not penetrate the tread rubber 3 and contacts the under-tread 3b and terminates. Although the ground tread rubber 50a does not contact the belt layer 18, if the volume resistivity of the under-tread 3b is sufficiently low, the electrical conductivity can be maintained. As shown in FIG. 17, a small amount of cap tread 3a may remain on the outermost side in the tire radial direction of the tread rubber 3.

[0172] In each of the cross-sections shown in FIGS. 15 and 17, let the cross-sectional area of the tread portion be Str [mm ２ . The cross-sectional area Str is the total area of the cross-sectional area of the cap tread 3a, the cross-sectional area of the ground tread rubber 50 or 50a, and the cross-sectional area of the under-tread 3b. Also, let the cross-sectional area of the ground tread rubber be Sea [mm ２ . At this time, it is preferable that the ratio Sea / Str of the cross-sectional area Sea to the cross-sectional area Str is 0.8 or more and 1 or less. When the ratio of the cross-sectional areas is within the above range and, as shown in FIGS. 15 and 17, the portion 221 of the tire rubber 22 enters the carcass coat rubber 17 of the carcass layer 15, the electrical conductivity is further improved. More preferably, the ratio Sea / Str is 0.9 or more and 1 or less.

[0173] The ground tread rubber 50 is made of a conductive rubber material having a lower volume resistivity than the tread rubber 3, and the volume resistivity of the ground tread rubber 50 is less than 1×10^8 [Ω·cm]. More preferably, the volume resistivity of the ground tread rubber 50 is 1×10^6 [Ω·cm] or less.

[0174] [Examples] Figures 18A to 18C are charts showing the results of performance evaluation tests of pneumatic tires. Below, we will describe the performance evaluation tests performed on the pneumatic tire 1 described above, comparing it to the pneumatic tire of Conventional Example 2 and the pneumatic tire 1 according to this disclosure. In the performance evaluation tests, the electrical resistance of the pneumatic tire was measured before and after driving with the pneumatic tire.

[0175] Regarding the electrical resistance of the tires, the electrical resistance [Ω] of the test tires was measured using an R8340A ultra-high resistance meter manufactured by Advantest Corporation, based on the measurement conditions specified by JATMA. For running with pneumatic tires, an indoor drum-type tire rolling resistance tester with a drum diameter of 1707 [mm] was used. The test tires were mounted on rims conforming to the JATMA specifications, and the test tires were subjected to an air pressure of 200 [kPa] and 80% of the maximum load specified by JATMA. After running at a speed of 81 [km / h] for 60 minutes, the electrical resistance of the tires was measured using the method described above.

[0176] In Figure 18A, a tire in which the tie rubber is not embedded in the carcass coat rubber is designated as "Conventional Example 2". It is thought that the tie rubber embedded between the carcass cords peels off slightly as the tire runs, so the resistance value increases compared to before running. However, an increase in electrical resistance of 1.5 × 10^7 [Ω・cm] or less is considered to be within an acceptable range. In Figure 18A, for the tire of Conventional Example 2, an increase in resistance value of 1.9 × 10^7 [Ω・cm] is observed after running compared to before running. In contrast, in Figures 18A to 18C, it can be seen that the tires of each embodiment of this disclosure maintain their electrical resistance value even after running.

[0177] This disclosure encompasses the following inventions:Invention [1] A tire comprising: a pair of bead portions arranged on both sides of the tire equatorial plane in the tire width direction; a bead core provided on each of the pair of bead portions; a bead filler arranged on the radially outer side of the bead core; a rim cushion which constitutes the rim fitting surface of the bead portion and is arranged from the inner side in the tire width direction to the outer side of the bead core; at least one carcass layer spanning between the pair of bead portions; a belt layer arranged on the radially outer side of the carcass layer; tread rubber arranged on the radially outer side of the belt layer; an inner liner arranged on the inner surface of the tire along the carcass layer; and a tie rubber arranged between the carcass layer and the inner liner, wherein the inner liner and the tie rubber satisfy the relationship Lt < Li between the length Lt from the tire equatorial plane to the end of the tie rubber along the periphery and the length Li from the tire equatorial plane to the end of the inner liner along the periphery, The end of the inner liner is located inward in the tire width direction from the outermost part of the bead core in the tire width direction, and inward in the tire radial direction from the outermost diameter part of the bead core in the tire radial direction, and when Rtg is the distance in the tire radial direction from the tire rotation axis of the end of the tie rubber, Rf is the distance in the tire radial direction from the tire rotation axis of the outer end of the bead filler, which is the outermost end of the bead filler in the tire radial direction, and Rbc is the distance in the tire radial direction from the tire rotation axis of the outermost diameter part of the bead core, the relationship Rbc < Rtg < Rf is satisfied between the end of the tie rubber, the outer end of the bead filler, and the outermost diameter part of the bead core. A tire characterized in that the relationship between the amount of overlap LAP [mm] between the tie rubber and the bead filler, which is the distance along the periphery between the end of the tie rubber and the outer end of the bead filler, and the maximum thickness Gp [mm] of the carcass layer in the overlap range, which is the range along the periphery between the end of the tie rubber and the outer end of the bead filler, is within the range of 0.02 ≤ Gp / LAP ≤ 4.0, and the tie rubber has a volume resistivity of less than 1 × 10^8 [Ω・cm].Invention [2] The tire according to Invention [1], wherein the rim cushion has a volume resistivity of less than 1 × 10^8 [Ω・cm]. Invention [3] The tire according to Invention [1] or Invention [2], wherein the relationship between the maximum thickness Gb [mm] of the bead filler in the lap range and the lap amount LAP [mm] is within the range of 0.01 ≤ Gb / LAP ≤ 3.5. Invention [4] The tire according to any one of Inventions [1] to [3], wherein the tie rubber has a thickness within the range of 0.1 [mm] or more and 1.5 [mm] or less. Invention [5] The tire according to any one of Inventions [1] to [4], wherein the lap amount LAP [mm] between the tie rubber and the bead filler is within the range of 3 [mm] or more and 40 [mm] or less. Invention [6] The tire according to any one of Inventions [1] to [5], wherein the maximum thickness Gp [mm] of the carcass layer in the portion in contact with the tie rubber in the lap range is within the range of 0.5 [mm] to 4 [mm]. Invention [7] The tire according to any one of Inventions [1] to [6], wherein the maximum thickness Gb [mm] of the bead filler in the lap range is within the range of 0.4 [mm] to 10 [mm]. Invention [8] The tire according to any one of Inventions [1] to [7], wherein the volume resistivity of the bead filler is less than 1 × 10^10 [Ω・cm]. Invention [9] A tire according to any one of Inventions [1] to [8], where the electrical resistance of the carcass layer is Rpc [Ω] and the electrical resistance of the belt coat rubber of the belt layer is Rb [Ω], the electrical resistance of the carcass layer Rpc [Ω] satisfies Rpc [Ω] < 1 × 10^8 [Ω], and the electrical resistance of the belt coat rubber Rb [Ω] satisfies Rb [Ω] < 1 × 10^8 [Ω].Invention

[10] A tire according to Invention [1], comprising a tread portion including the tread rubber, a rim cushion rubber that constitutes the rim fitting surface in the bead portion and is arranged from the inside in the tire width direction to the outside in the tire width direction of the bead core, and Earthtread rubber which is conductive rubber in the rib portion of the tread portion closest to the tire equator, wherein the carcass layer comprises carcass cords and carcass coat rubber that surrounds the carcass cords, and the tie rubber has a portion that is inserted between the carcass cords of the carcass layer, at least in the arrangement range of the belt layer. Invention

[11] A tire according to Invention

[10] , wherein in the cross section seen when the tire is cut in the tire circumferential direction with respect to the rib portion of the tread portion closest to the tire equator, the tie rubber is inserted at least in one place between the carcass cords of the carcass layer in a range of 50 mm in the tire circumferential direction along the tire circumferential direction. Invention

[12] A tire according to Invention

[10] or Invention

[11] , wherein, in the cross section of the tread portion closest to the tire equator, when the tire is cut in the circumferential direction, the relationship between the intercord cross-sectional area Sc(50Ave), calculated by the average distance between the centers of the carcass cords and the average thickness of the carcass layer in a range of 50 mm in the circumferential direction of the tire, and the relationship between the intercord cross-sectional area St(50Ave) of the tie rubber embedded in the carcass coat rubber in the range is as follows: 0.02 ≤ St(50Ave) / Sc(50Ave) ≤ 0.5 Invention

[13] A tire according to any one of Inventions

[10] to

[12] , wherein the thickness Tc of the carcass layer and the height Tt of the tie rubber embedded in the carcass coat rubber have the following relationship. 0.014 ≤ Tt / Tc ≤ 0.8 Invention

[14] A tire according to any one of Inventions

[10] to

[13] , wherein the cross-sectional area St of the tie rubber inserted between the carcass cords and the height Tt of the tie rubber inserted between the carcass cords are in the following relationship: 0.02 mm ≤ St / Tt ≤ 2.0 mm Invention

[15] A tire according to any one of Inventions

[10] to

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

[16] A tire according to any one of Inventions

[10] to

[15] , wherein when the tire is cut in the circumferential direction through the Earthtread rubber, the Earthtread rubber is arranged such that the ratio of the cross-sectional area Sea of ​​the Earthtread rubber to the cross-sectional area Str of the tread portion is as follows, and the tie rubber is inserted between the carcass cords of the carcass layer on the inner side of the Earthtread rubber arrangement range in the radial direction of the tire: 0.8 ≤ Sea / Str ≤ 1.

[0178] 1. Pneumatic tire 2. Tread section 2a. Tire contact surface 3. Tread rubber 3a. Cap tread 3b. Under tread 4. Sidewall section 5. Sidewall rubber 10. Bead section 11. Bead core 11a. Outermost diameter section 11b. Outermost section 12. Bead wire 13. Bead insulation rubber 14. Bead filler 14a. Outer end of bead filler 15. Carcass layer 15a. Carcass body section 15b. Turn-up section 16. Carcass cord 17. Carcass coat rubber 18. Belt layer 18a. Belt cord 18b. Belt coat rubber 21. Inner liner 21a. End section 22. Tie rubber 22a. End section 25. Inner surface of tire 30. Rim cushion 31. Rim cushion rubber 32. Rim fitting surface 35. Bead toe 36. Bead base 50 Earth Red 500 lap range

Claims

1. A tire comprising: a pair of bead portions arranged on both sides of the tire equatorial plane in the tire width direction; a bead core provided on each of the pair of bead portions; a bead filler arranged on the radially outer side of the bead core; a rim cushion forming the rim fitting surface of the bead portion and arranged from the inner side to the outer side of the bead core in the tire width direction; at least one carcass layer spanning between the pair of bead portions; a belt layer arranged on the radially outer side of the carcass layer; tread rubber arranged on the radially outer side of the belt layer; an inner liner arranged on the inner surface of the tire along the carcass layer; and a tie rubber arranged between the carcass layer and the inner liner, wherein the inner liner and the tie rubber satisfy the relationship Lt < Li between the length Lt from the tire equatorial plane to the end of the tie rubber along the periphery and the length Li from the tire equatorial plane to the end of the inner liner along the periphery. The end of the inner liner is located inward in the tire width direction from the outermost part of the bead core in the tire width direction, and inward in the tire radial direction from the outermost diameter part of the bead core in the tire radial direction, and when Rtg is the distance in the tire radial direction from the tire rotation axis of the end of the tie rubber, Rf is the distance in the tire radial direction from the tire rotation axis of the outer end of the bead filler, which is the outermost end of the bead filler in the tire radial direction, and Rbc is the distance in the tire radial direction from the tire rotation axis of the outermost diameter part of the bead core, the relationship Rbc < Rtg < Rf is satisfied between the end of the tie rubber, the outer end of the bead filler, and the outermost diameter part of the bead core. A tire characterized in that the relationship between the amount of overlap LAP [mm] between the tie rubber and the bead filler, which is the distance along the periphery between the end of the tie rubber and the outer end of the bead filler, and the maximum thickness Gp [mm] of the carcass layer in the overlap range, which is the range along the periphery between the end of the tie rubber and the outer end of the bead filler, is within the range of 0.02 ≤ Gp / LAP ≤ 4.0, and the tie rubber has a volume resistivity of less than 1 × 10^8 [Ω・cm].

2. The tire according to claim 1, wherein the rim cushion has a volume resistivity of less than 1 × 10⁸ [Ω·cm].

3. The tire according to claim 1, wherein the relationship between the maximum thickness Gb [mm] of the bead filler in the lap range and the lap amount LAP [mm] is within the range of 0.01 ≤ Gb / LAP ≤ 3.

5.

4. The tire according to claim 1, wherein the tie rubber has a thickness within the range of 0.1 [mm] to 1.5 [mm].

5. The tire according to claim 1, wherein the overlap amount LAP [mm] between the tie rubber and the bead filler is within the range of 3 [mm] or more and 40 [mm] or less.

6. The tire according to claim 1, wherein the maximum thickness Gp [mm] of the carcass layer in the portion in contact with the tie rubber within the wrap range is within the range of 0.5 [mm] to 4 [mm].

7. The tire according to claim 1, wherein the bead filler has a maximum thickness Gb [mm] in the lap range that is between 0.4 [mm] and 10 [mm].

8. The tire according to claim 1, wherein the bead filler has a volume resistivity of less than 1 × 10¹⁰ [Ω·cm].

9. The tire according to claim 1, where the electrical resistance of the carcass layer is Rpc [Ω] and the electrical resistance of the belt coat rubber of the belt layer is Rb [Ω], the electrical resistance of the carcass layer Rpc [Ω] satisfies Rpc [Ω] < 1 × 10⁸ [Ω], and the electrical resistance of the belt coat rubber Rb [Ω] satisfies Rb [Ω] < 1 × 10⁸ [Ω].

10. The tire according to claim 1, comprising: a tread portion including the tread rubber; a rim cushion rubber that constitutes the rim fitting surface in the bead portion and is arranged from the inside in the tire width direction to the outside in the tire width direction of the bead core; and an earth tread rubber which is conductive rubber in the rib portion of the tread portion closest to the tire equator, wherein the carcass layer comprises carcass cords and carcass coat rubber that encloses the carcass cords, and the tie rubber has a portion that is inserted between the carcass cords of the carcass layer, at least within the arrangement range of the belt layer.

11. The tire according to claim 10, wherein, in the cross-section of the tread portion closest to the tire equator, when the tire is cut in the circumferential direction, the tie rubber is inserted at least once between the carcass cords of the carcass layer in a range of 50 mm in the circumferential direction of the tire.

12. The tire according to claim 10 or claim 11, wherein the relationship between the intercord cross-sectional area Sc(50Ave), calculated by the average distance between the centers of the carcass cords and the average thickness of the carcass layer in a cross-sectional area of ​​the rib portion of the tread closest to the tire equator when the tire is cut in the circumferential direction, and the cross-sectional area St(50Ave) of the tie rubber that has entered the carcass coat rubber in the said range, is as follows: 0.02 ≤ St(50Ave) / Sc(50Ave) ≤ 0.5 13. The tire according to claim 10 or claim 11, wherein the thickness Tc of the carcass layer and the height Tt of the tie rubber embedded in the carcass coat rubber have the following relationship: 0.014 ≤ Tt / Tc ≤ 0.8 14. The tire according to claim 10 or claim 11, wherein the cross-sectional area St of the tie rubber inserted between the carcass cords and the height Tt of the tie rubber inserted between the carcass cords have the following relationship: 0.02 mm ≤ St / Tt ≤ 2.0 mm 15. The tire according to claim 10 or claim 11, wherein the ratio Ht / Hc of the hardness of the tie rubber to the hardness Hc of the carcass coat rubber is 0.5 or more and 2.0 or less.

16. The tire according to claim 10 or 11, wherein, when the tire is cut in the circumferential direction through the Earthtread rubber, the Earthtread rubber is arranged such that the ratio of the cross-sectional area Sea of ​​the Earthtread rubber to the cross-sectional area Str of the tread portion is as follows, and the tie rubber is inserted between the carcass cords of the carcass layer on the inner side of the Earthtread rubber arrangement range in the radial direction of the tire: 0.8 ≤ Sea / Str ≤ 1

Images