tire

Abstract

The present invention ensures steering stability and reduces rolling resistance while suppressing any increase in electric resistance. The length Lt from a tire equatorial plane CL to an end part 22a of a tie rubber 22 along the periphery and the length Li from the tire equatorial plane CL to an end part 21a of an inner liner 21 satisfy the relationship Lt < Li. The distance Rtg of the end part 22a of the tie rubber 22 from the tire rotation axis, the distance Rf1 of a bead filler outside end part 14a, and the distance Rrc of a rim cushion outside outermost part Rwo satisfy the relationship Rf1 ≤ Rtg < Rrc. 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 using conductive rubber tie rubber to reduce electrical resistance, 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 rolling resistance will worsen due to the increased length of the tie rubber. On the other hand, if the length of the tie rubber is shortened to suppress the deterioration of rolling resistance, it becomes difficult to reduce electrical resistance. Also, shortening the length of the tie rubber tends to reduce the rigidity of the bead, which may reduce handling stability. For these reasons, it is extremely difficult to reduce rolling resistance while ensuring handling stability without increasing electrical resistance.

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

[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 carcass layer having a carcass body portion arranged between the pair of bead portions; a turn-up portion formed continuously from the carcass body portion and folded back from the inner side in the tire width direction to the outer side of the bead core; a conductive member arranged on the radially outer side of the carcass body portion and having a volume resistivity of less than 1 × 10^8 [Ω・cm]; 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 are connected from the tire equatorial plane to the end of the tie rubber along the periphery. The length Lt and the length Li from the tire equatorial plane to the end of the inner liner along the periphery satisfy the relationship Lt < Li, and Rtg is the distance in the tire radial direction from the tire rotation axis to the end of the tie rubber, Rf1 is the distance in the tire radial direction from the tire rotation axis to the outer end of the bead filler, which is the outermost end of the bead filler in the tire radial direction at the position of the bead core outside the tire width direction, and the distance from the tire rotation axis to the outermost outermost end of the conductive member, which is the outermost end of the conductive member in the tire radial direction at the position of the bead core outside the tire width direction When Rrc is the distance in the radial direction, the relationship Rf1 ≤ Rtg < Rrc is satisfied between the end of the tie rubber, the outer end of the bead filler, and the outermost outermost part of the conductive member, and the relationship between the overlap amount LAP [mm] between the tie rubber and the conductive member, which is indicated by the distance along the peripheral between the end of the tie rubber and the outermost outermost part of the conductive member, and the thickness Gp [mm] of the carcass layer is in the range of 0.02 ≤ Gp / LAP ≤ 4.00, and the tie rubber is characterized in that its volume resistivity is less than 1 × 10^8 [Ω・cm].

[0008] Furthermore, in the above-described tire, it is preferable that the conductive member constitutes the rim fitting surface in the bead portion and is a rim cushion positioned from the inner side in the tire width direction to the outer side in the tire width direction of the bead core.

[0009] 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].

[0010] Furthermore, in the above-described tire, the conductive member is a rim cushion 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 it is preferable that the distance Hrc in the tire radial direction between the innermost part of the rim cushion, which is the inner end of the rim cushion in the tire radial direction, and the outermost part outside the conductive member is within the range of 0.02 ≤ Hrc / SH ≤ 0.70 with respect to the tire cross-sectional height SH.

[0011] Furthermore, in the above-mentioned tire, it is preferable that the belt layer has a volume resistivity of less than 1 × 10⁸ [Ω·cm], and the carcass layer has a volume resistivity of less than 1 × 10⁸ [Ω·cm] in the area that overlaps with the belt layer in the tire radial direction.

[0012] Furthermore, the above-mentioned tire is provided with a pair of sidewall portions arranged on both sides of the tire equatorial plane in the tire width direction, and it is preferable that the thickness Gt of the tie rubber is within the range of 0.0033 ≤ Gt / Gs ≤ 0.3750 with respect to the thickness Gs of the sidewall portion at the outermost position on the outside of the conductive member in the tire radial direction.

[0013] Furthermore, in the above-mentioned tire, it is preferable that the end of the tie rubber is located radially outward from the rim flange of the specified rim.

[0014] Furthermore, in the above-mentioned tire, it is preferable that the distance Hrt in the tire radial direction between the outer end of the rim flange in the tire radial direction and the end of the tie rubber is within the range of 0.02 ≤ Hrt / SH ≤ 0.55 with respect to the tire cross-sectional height SH.

[0015] Furthermore, in the above-mentioned tire, it is preferable that the thickness of the bead filler in the tire width direction at the same position in the tire diameter direction as the outer end of the rim flange of the specified rim is within the range of 1.5 mm to 15 mm.

[0016] Furthermore, in the above-mentioned tire, it is preferable that the relationship between the cross-sectional area St [mm²] of the tie rubber and the cross-sectional area Sr [mm²] of the conductive member in the tire meridional cross-section within the lap range, which is the range along the periphery between the end of the tie rubber and the outermost part of the conductive member, is within the range of 0.1 ≤ Sr / St ≤ 200.

[0017] Furthermore, in the above-mentioned tire, it is preferable that the conductive member is a conductive reinforcing layer made of fibrous material and arranged on the outer side in the tire width direction of the carcass body.

[0018] 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.

[0019] 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.

[0020] 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

[0021] 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

[0022] 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

[0023] 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.

[0024] 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

[0025] The tire according to the present invention has the effect of suppressing an increase in electrical resistance while ensuring handling stability and reducing rolling resistance.

[0026] Figure 1 is a cross-sectional view of a pneumatic tire according to Embodiment 1, taken along the tire meridian. Figure 2 is a detailed view of the region on one side of the tire equatorial plane in the tire width direction of Figure 1. Figure 3 is a detailed view of the area near the bead shown in Figure 2. Figure 4 is a detailed view of the area near the bead shown in Figure 2, and is an explanatory diagram of the dimensions of the tie rubber and bead filler. Figure 5 is a detailed view of the area near the bead shown in Figure 2, and is an explanatory diagram of the cross-sectional area of ​​the tie rubber and rim cushion in the lap area. Figure 6 is a cross-sectional view taken along line A-A in Figure 3. Figure 7 is a schematic diagram of the tread shown in Figure 1. Figure 8 is a cross-sectional view of the main part around the bead in a pneumatic tire according to Embodiment 2. Figure 9 is a modified example of the pneumatic tire according to Embodiment 1, and is a cross-sectional view of the main part around the bead. Figure 10A is a chart showing the results of a performance evaluation test of a pneumatic tire. Figure 10B is a chart showing the results of a performance evaluation test of a pneumatic tire. Figure 10C is a chart showing the results of a performance evaluation test of a pneumatic tire. Figure 10D is a diagram showing the results of a performance evaluation test of a pneumatic tire. Figure 11 is a diagram showing a portion of the meridional cross-section of the tire shown in Figure 1. Figure 12 is a diagram showing an example of a cross-sectional structure including a two-ply carcass layer. Figure 13 is a diagram showing an example of a cross-sectional structure of a portion of the side rubber shown in Figure 1. Figure 14 is a diagram showing a schematic of the appearance of the tire. Figure 15 is a diagram illustrating the area of ​​the tie rubber portion that is inserted between the carcass cords of the carcass layer. Figure 16 is a diagram illustrating that the thickness of the carcass layer varies with respect to the circumferential direction of the tire. Figure 17 is a diagram illustrating the height of the tie rubber that is inserted between the carcass cords. Figure 18 is a diagram showing a modified example of the cross-sectional structure of a portion of the tread section shown in Figure 1. Figure 19 is a diagram illustrating the cross-sectional area and height of the tie rubber that is inserted into the carcass coat rubber. Figure 20 is a diagram showing a cross-section when the tire is cut circumferentially at the position of the Earthtread rubber in Figure 1. Figure 21 is a meridional cross-sectional view of a tire showing a pneumatic tire according to an embodiment in which a non-penetrating type Earthtread rubber is used. Figure 22 shows a cross-section of the tire when it is cut circumferentially at the position of the Earthtread rubber in Figure 21. Figure 23A is a chart showing the results of a performance evaluation test of a pneumatic tire.Figure 23B is a chart showing the results of the performance evaluation test of pneumatic tires. Figure 23C is a chart showing the results of the performance evaluation test of pneumatic tires.

[0027] 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.

[0028] [Embodiment 1] [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.

[0029] 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.

[0030] Figure 1 is a cross-sectional view of a pneumatic tire 1 according to Embodiment 1, 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.

[0031] The pneumatic tire 1 according to Embodiment 1 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] In this embodiment 1, 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.

[0036] 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.

[0037] The carcass ply of the carcass layer 15 formed in this way preferably has a volume resistivity of the carcass coat rubber, which is the coat rubber of the carcass cord, of less than 1 × 10^8 [Ω·cm].

[0038] The volume resistivity (volume specific resistance) is measured based on "Vulcanized Rubber and Thermoplastic Rubber - Method for Measuring Volume Resistivity and Surface Resistivity" specified in JIS K6271. Generally, if the volume resistivity is less than 1 × 10^8 [Ω·cm] or the surface resistivity is less than 1 × 10^8 [Ω / cm], it can be said that the member has conductivity capable of suppressing electrostatic charging.

[0039] 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 diameter direction of the bead cores 11, 11 on both sides in the tire width direction and the turned-back part of the carcass layer 15. Specifically, the rim cushion 30 is arranged at least from the inner side in the tire width direction of the bead core 11 to the outer side in the tire width direction. 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, passing through the inner side in the tire diameter direction of the bead core 11, and extending across the outer side in the tire width direction of the bead core 11. For this reason, in the part on the outer side in the tire width direction of the bead core 11, the rim cushion 30 is arranged on the outer side in the tire width direction of the carcass main body part 15a and the turn-up part 15b with respect to the carcass layer 15.

[0040] The rim cushion 30 arranged in this way is the part that contacts the rim flange R of the rim wheel when mounting the pneumatic tire 1 on the rim wheel, and constitutes the contact surface of the bead part 10 with respect to the rim flange R. 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, which is the surface of the bead part 10 that fits into the rim wheel.

[0041] The rim cushion 30 is also provided as a conductive member in the first embodiment. The conductive member is a member having a volume resistivity of less than 1×10^8 [Ω·cm]. The rim cushion 30, which is a conductive member, is composed of a rim cushion rubber 31 that is a rubber member. Since the rim cushion 30 is provided as a conductive member, its volume resistivity is 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, which is a conductive member, is less than 1×10^6 [Ω·cm].

[0042] Further, 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.

[0043] Here, the tanδ value at 60 [°C] is measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. under the conditions of an initial strain of 10%, an amplitude of ±0.5%, and a frequency of 20 Hz. The rubber hardness Hs is measured under the temperature condition of 20 [°C] in accordance with JIS K6253.

[0044] Further, the rim cushion 30 may have a member other than the rim cushion rubber 31. The rim cushion 30 may include, for example, a chafing piece, 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 comes into contact with the rim flange R.

[0045] The belt layer 18 has one or more belt plies extending in the tire width direction, and in this embodiment 1, a plurality of belt plies 181 to 183 are laminated. That is, in this embodiment 1, the belt layer 18 is constructed by laminating a pair of cross belts 181 and 182 and a belt cover 183 in the tire radial direction, and is positioned on the outside of the carcass layer 15 in the tire radial direction and wrapped around the outer circumference of the carcass layer 15. The pair of cross belts 181 and 182 are constructed by covering a plurality of belt cords made of steel or organic fiber material with a coating rubber and rolling them, and the belt angle, which is the inclination angle of the direction of extension of the belt cords with respect to the tire circumferential direction, is within the range of 20 [deg] to 65 [deg] in absolute value. Furthermore, the pair of cross belts 181 and 182 have belt angles with opposite signs to each other and are laminated with the directions of extension of the belt cords intersecting each other, forming a so-called cross-ply structure. Specifically, the pair of cross belts 181 and 182 have belt cords inclined in opposite directions relative to the tire width direction with respect to the tire circumferential direction. The belt cover 183 is constructed by rolling multiple cords made of steel or organic fiber material covered with coated rubber, and the belt angle is within the range of 0 [deg] to 10 [deg] in absolute value. The belt cover 183 is also arranged stacked on the outer side of the cross belts 181 and 182 in the tire radial direction.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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).

[0057] Examples of thermoplastic resins include polyamide resins [e.g., nylon 6 (N6), nylon 66 (N66), nylon 46 (N46), nylon 11 (N11), nylon 12 (N12), nylon 610 (N610), nylon 612 (N612), nylon 6 / 66 copolymer (N6 / 66), nylon 6 / 66 / 610 copolymer (N6 / 66 / 610), nylon MXD6, nylon 6T, nylon 9T, nylon 6 / 6T copolymer, nylon 66 / PP copolymer, nylon 66 / PPS copolymer], polyester 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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 1 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 the volume resistivity is 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.

[0062] 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.

[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 30 [mm] ≤ Li - Lt ≤ 50 [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 1, the length along the periphery refers to the length along the shape of each component at the same position in the tire circumferential direction. Specifically, the direction along the periphery is close to the tire width direction at the tread portion 2 and close to the tire diameter direction at the sidewall portion 4.

[0067] In this embodiment 1, the rim cushion 30 placed on the bead portion 10 is positioned such that, on the inner side of the bead core 11 in the tire width direction, the position of the outer end in the tire radial direction is located radially outward from the outer circumference of the bead core 11 in the tire radial direction, and on the outer side of the bead core 11 in the tire width direction, the outer end in the tire radial direction is located radially outward from the outer circumference of the bead core 11 in the tire radial direction.

[0068] In this manner, the rim cushion 30 positioned on the bead portion 10 has an outermost end Rwo, which is the outermost end of the rim cushion 30 in the tire radial direction at a position outside the bead core 11 in the tire width direction, located inside the tire width direction of the end 18c of the belt layer 18 in the tire width direction. Since the rim cushion 30 is also provided as a conductive member, the outermost end Rwo of the rim cushion is the outermost end of the conductive member in the tire radial direction. More specifically, the distance Hrc in the tire radial direction between the innermost end Rri of the rim cushion 30 (the innermost end in the tire radial direction) and the outermost end Rwo of the rim cushion is within the range of 0.02 ≤ Hrc / SH ≤ 0.70 with respect to the tire cross-sectional height SH.

[0069] In this case, the tire section height SH is defined as half the difference between the tire outer diameter and the rim diameter, and is measured under no-load conditions with the pneumatic tire 1 mounted on a specified rim and with the specified internal pressure applied.

[0070] 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.

[0071] Furthermore, the distance Hrc in the tire radial direction between the innermost part Rri of the rim cushion and the outermost part Rwo of the rim cushion is preferably within the range of 0.05 ≤ Hrc / SH ≤ 0.65 with respect to the tire cross-sectional height SH.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] Figure 3 is a detailed view of the area near the bead portion 10 shown in Figure 2. The end 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. The end 22a of the tie rubber 22 is also located radially outward from the outer end 14a of the bead filler 14, which is the radially outward end of the bead filler 14. The end 22a of the tie rubber 22 is also located radially inward from the outermost outer rim cushion Rwo, which is the radially outward end of the rim cushion 30 at the position of the bead core 11 on the tire width side. The end 22a of the tie rubber 22 is also located radially outward from the inner outermost rim cushion Rwi, which is the radially outward end of the rim cushion at the position of the bead core 11 on the tire width side.

[0079] For these reasons, 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, Rf1 be the distance in the tire radial direction from the tire rotation axis to the outer end 14a of the bead filler, and Rrc be the distance in the tire radial direction from the tire rotation axis to the outermost part Rwo of the rim cushion, then the relationship Rf1 ≤ Rtg < Rrc is satisfied between the end 22a of the tie rubber 22, the outer end 14a of the bead filler, and the outermost part Rwo of the rim cushion.

[0080] 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 Rf1 from the tire rotation axis to the outer end 14a of the bead filler in the tire radial direction is within the range of 0 [mm] ≤ Rtg - Rf1 ≤ 60 [mm]. Also, it is preferable that the difference between the distance Rrc from the tire rotation axis to the outermost outer part Rwo of the rim cushion 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] ≤ Rrc - Rtg ≤ 60 [mm].

[0081] The end portion 22a of the tie rubber 22 is located inward in the tire radial direction from the outermost outermost part Rwo of the rim cushion 30. Therefore, the tie rubber 22 is arranged overlapping the rim cushion 30 in the tire width direction via the carcass layer 15. In this embodiment 1, the turn-up portion 15b of the carcass layer 15 is located inward in the tire radial direction from the end portion 22a of the tie rubber 22 at its outer end in the tire radial direction. Therefore, the tie rubber 22 does not overlap the turn-up portion 15b of the carcass layer 15, and the tie rubber 22 is arranged overlapping the rim cushion 30 in the tire width direction via the carcass body portion 15a of the carcass layer 15.

[0082] Thus, the tie rubber 22, which is arranged to overlap the rim cushion 30 in the tire width direction, and the carcass layer 15 interposed between the rim cushion 30 and the tie rubber 22, have a relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gp [mm] of the carcass layer 15 in contact with the tie rubber 22 in the overlap range 500 between the tie rubber 22 and the rim cushion 30, which is within the range of 0.02 ≤ Gp / LAP ≤ 4.00.

[0083] In this case, the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 is the distance along the periphery of the tie rubber 22 from the end 22a of the tie rubber 22 to the outermost Rwo of the rim cushion. Furthermore, the overlap range 500 between the tie rubber 22 and the rim cushion 30 is the range along the periphery between the end 22a of the tie rubber 22 and the outermost Rwo of the rim cushion, and is the range in which the tie rubber 22 and the rim cushion 30 are arranged to overlap via the carcass layer 15.

[0084] Furthermore, it is preferable that the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gp [mm] in the overlap range 500 of the carcass layer 15 is within the range of 0.025 ≤ Gp / LAP ≤ 3.50.

[0085] Furthermore, the 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 thickness Gp [mm] of the carcass body portion 15a in 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 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].

[0086] Furthermore, the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 is within the range of 0.5 [mm] to 60 [mm]. Preferably, the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 is within the range of 1.0 [mm] to 50 [mm].

[0087] 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 1, 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.

[0088] 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.

[0089] The bead core 11, 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 surrounding the bead wire 12. In this embodiment 1, 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].

[0090] 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.

[0091] Figure 4 is a detailed view of the area around the bead portion 10 shown in Figure 2, and is an explanatory diagram of the dimensions of the tie rubber 22 and the bead filler 14. The thickness Gt of the tie rubber 22 that overlaps with the rim cushion 30 via the carcass layer 15 in the lap range 500 is within the range of 0.0033 ≤ Gt / Gs ≤ 0.3750 with respect to the thickness Gs of the sidewall portion 4 at the position of the outermost part Rwo on the outside of the rim cushion in the tire radial direction. In this case, the thickness Gs of the sidewall portion 4 at the position of the outermost part Rwo on the outside of the rim cushion in the tire radial direction is the thickness of the sidewall portion 4 on a virtual line passing through the outermost part Rwo on the outside of the rim cushion and perpendicular to the tie rubber 22 in the tire meridional cross-section. Furthermore, it is preferable that the thickness Gt of the tie rubber 22 that overlaps with the rim cushion 30 via the carcass layer 15 in the overlap range 500 is within the range of 0.0050 ≤ Gt / Gs ≤ 0.3000 with respect to the thickness Gs of the sidewall portion 4 at the outermost Rwo of the rim cushion in the tire radial direction.

[0092] The end 22a of the tie rubber 22, located between the outermost outermost part Rwo of the rim cushion and the outer end 14a of the bead filler in the tire radial direction, is located radially outward from the rim flange R of the specified rim. In other words, the end 22a of the tie rubber 22 is located radially outward from the rim flange R of the rim wheel that fits into the rim fitting surface 32 of the bead portion 10. More specifically, the distance Hrt in the tire radial direction between the outer end Ra of the rim flange R and the end 22a of the tie rubber 22 is within the range of 0.02 ≤ Hrt / SH ≤ 0.55 with respect to the tire cross section height SH. Preferably, the distance Hrt in the tire radial direction between the outer end Ra of the rim flange R and the end 22a of the tie rubber 22 is within the range of 0.04 ≤ Hrt / SH ≤ 0.50 with respect to the tire cross section height SH.

[0093] The tie rubber 22 arranged in this manner has a thickness Gt within the range of 0.1 [mm] to 1.5 [mm]. Preferably, the thickness Gt of the tie rubber 22 is within the range of 0.3 [mm] to 1.0 [mm].

[0094] Furthermore, the inner liner 21 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 thickness in the portion that overlaps with the tie rubber 22. Preferably, the thickness Gi of the inner liner 21 in the portion that overlaps with the tie rubber 22 is within the range of 0.3 [mm] to 1.0 [mm].

[0095] Furthermore, the bead filler 14 has a thickness Gbr in the tire width direction at the same position in the tire diameter direction as the outer end Ra of the rim flange R of the specified rim, which is between 1.5 mm and 15 mm. Preferably, the thickness Gbr in the tire width direction at the same position in the tire diameter direction as the outer end Ra of the rim flange R of the bead filler 14 is between 1.6 mm and 10 mm.

[0096] The bead filler 14 formed in this manner 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].

[0097] Figure 5 is a detailed view of the area around the bead portion 10 shown in Figure 2, and is an explanatory diagram of the cross-sectional areas of the tie rubber 22 and rim cushion 30 in the overlapping range 500. The relationship between the cross-sectional area St [mm²] of the tie rubber 22 and the cross-sectional area Sr [mm²] of the rim cushion 30 in the tire meridional section within the overlapping range 500 between the tie rubber 22 and the rim cushion 30 is within the range of 0.1 ≤ Sr / St ≤ 200. In this case, the cross-sectional area St [mm²] of the tie rubber 22 is the cross-sectional area in the tire meridional section of the portion of the tie rubber 22 located within the overlapping range 500. Similarly, the cross-sectional area Sr [mm²] of the rim cushion 30 is the cross-sectional area in the tire meridional section of the portion of the rim cushion 30 located within the overlapping range 500.

[0098] Furthermore, in the overlapping area 500 between the tie rubber 22 and the rim cushion 30, the relationship between the cross-sectional area St [mm²] of the tie rubber 22 and the cross-sectional area Sr [mm²] of the rim cushion 30 in the tire meridional section is preferably within the range of 0.3 ≤ Sr / St ≤ 150.

[0099] Figure 6 is a cross-sectional view taken along line A-A in Figure 3. The carcass layer 15 has a plurality of carcass cords 16 and a carcass coat rubber 17 that surrounds the carcass cords 16. The tie rubber 22 located between the carcass layer 15 and the inner liner 21 has an indentation portion 22b that fits between adjacent carcass cords 16 in the circumferential direction of the tire.

[0100] Specifically, the indentation portion 22b of the tie rubber 22 is formed by crossing a virtual line V, which is a virtual straight line that is in contact with the portion of the multiple carcass cords 16 of the carcass layer 15 that is on the inner surface 25 side of the tire, from the inside in the tire width direction to the outside in the tire width direction. As a result, the indentation portion 22b of the tie rubber 22 has a portion that is located outside the virtual line V in the tire width direction, and is formed by being indented between adjacent carcass cords 16 in the circumferential direction of the tire.

[0101] Figure 7 is a schematic diagram of the tread section 2 shown in Figure 1. In Figure 7, 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 7, the widest belt ply will be described as the belt layer 18.

[0102] 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. The volume resistivity [Ω・cm] of the belt layer 18 is less than 1 × 10^8 [Ω・cm]. Preferably, the volume resistivity [Ω・cm] of the belt layer 18 is less than 1 × 10^6 [Ω・cm].

[0103] 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.

[0104] 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. The volume resistivity of the carcass layer 15 in the area that overlaps with the belt layer 18 in the tire radial direction is less than 1 × 10^8 [Ω・cm]. Preferably, the volume resistivity of the area of ​​the carcass layer 15 that overlaps with the belt layer 18 is less than 1 × 10^6 [Ω・cm].

[0105] In the tread portion 2 where the carcass layer 15 is located, 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 same as the electrical resistance Rpc [Ω] of the carcass layer 15 in the area where the belt layer 18 is located in the tire width direction.

[0106] [Operation and Effects] When the pneumatic tire 1 according to Embodiment 1 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. In this way, 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, successively comes into contact with the road surface. 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.

[0107] 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 1, since the volume resistivity of the tie rubber 22 and the volume resistivity of the rim cushion 30 provided as a conductive member are both less than 10^8 [Ω・cm], the tie rubber 22 and the rim cushion 30 conduct electricity relatively easily. Also, since the tie rubber 22 is positioned overlapping with the bead filler 14, static electricity can be discharged to the road surface.

[0108] In other words, because the rim cushion 30, which is a conductive material, has a low volume resistivity, 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 a 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.

[0109] The outer portion of the bead core 11 in the rim cushion 30 in the tire width direction is in contact with the carcass body portion 15a of the carcass layer 15 at a position on the outer side of the bead filler 14 in the tire radial direction. Therefore, static electricity flowing through the rim cushion 30 flows to the carcass body portion 15a of the carcass layer 15 at a position on the outer side of the bead filler 14 in the tire radial direction.

[0110] The tie rubber 22 overlaps with the rim cushion 30 in the tire width direction via the carcass body portion 15a of the carcass layer 15 at a position on the radially outer side of the bead filler 14. Therefore, static electricity that flows from the rim cushion 30 to the carcass body portion 15a of the carcass layer 15 flows from the carcass body portion 15a to the tie rubber 22.

[0111] 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.

[0112] Here, the tie rubber 22 is positioned overlapping with the inner liner 21, 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.

[0113] 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 volume of the components constituting the pneumatic tire 1 can be reduced. This reduces the amount of components constituting the pneumatic tire 1, and thus reduces the amount of components that undergo elastic deformation when the pneumatic tire 1 rotates, thereby reducing rolling resistance.

[0114] 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 Rf1, the distance Rf1 in the tire radial direction from the tire rotation axis to the outer end 14a of the bead filler, satisfies Rf1 ≤ 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 the mass of the tie rubber 22, and also reduces rolling resistance by reducing the amount of components that make up the pneumatic tire 1.

[0115] Furthermore, 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 Rrc, the distance Rwo from the tire rotation axis to the outermost part of the rim cushion in the tire radial direction, satisfies the relationship Rtg < Rrc, thus ensuring the amount of overlap LAP between the tie rubber 22 and the rim cushion 30. This ensures the width of the transmission path when static electricity from the rim cushion 30 is transmitted through the carcass layer 15 to the tie rubber 22, which has a volume resistivity of less than 1 × 10^8 [Ω・cm], thereby reducing electrical resistance by making it easier for static electricity to flow from the rim cushion 30 to the tie rubber 22.

[0116] Furthermore, 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 Rrc, the distance Rwo, the outermost part of the rim cushion in the tire radial direction from the tire rotation axis, satisfies the relationship Rtg < Rrc, and by ensuring the overlap amount LAP between the tie rubber 22 and the rim cushion 30, it is possible to shorten the length of the tie rubber 22 while ensuring rigidity at the position of the bead filler 14 on the outer side in the tire radial direction. In other words, by arranging the tie rubber 22 and the rim cushion 30, which are relatively rigid members, in overlapping directions in the tire width direction, rigidity can be ensured by the overlapping tie rubber 22 and rim cushion 30, and rigidity near the bead portion 10 can be ensured when shortening the length of the tie rubber 22. This ensures steering stability.

[0117] Furthermore, since the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the conductive material rim cushion 30 and the thickness Gp [mm] of the carcass layer 15 is within the range of 0.02 ≤ Gp / LAP ≤ 4.00, it is possible to reduce electrical resistance while suppressing an increase in rolling resistance. In other words, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness 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 rim cushion 30 will become too large. In this case, the length of the tie rubber 22 will become too long, which may make it difficult to reduce rolling resistance. Also, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gp [mm] of the carcass layer 15 is Gp / LAP > 4.00, there is a risk that the overlap amount LAP between the tie rubber 22 and the rim cushion 30 will become too small. In this case, the length of the tie rubber 22 becomes too short, making it difficult to secure a path for static electricity between the rim cushion 30 and the tie rubber 22, which may make it difficult to reduce electrical resistance.

[0118] In contrast, if the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gp [mm] of the carcass layer 15 is within the range of 0.02 ≤ Gp / LAP ≤ 4.00, the length of the tie rubber 22 can be kept appropriate by preventing it from becoming too long or too short. This reduces electrical resistance by ensuring a path for static electricity between the rim cushion 30 and the tie rubber 22 while suppressing an increase in rolling resistance. As a result, it is possible to reduce rolling resistance while ensuring steering stability while suppressing an increase in electrical resistance.

[0119] Furthermore, since the rim cushion 30 is used as a conductive member, static electricity can be passed from the rim flange R to the tie rubber 22 without the need to newly arrange a conductive member. Therefore, electrical resistance can be reduced while keeping the amount of components constituting the pneumatic tire 1 down. As a result, electrical resistance can be reduced while suppressing an increase in rolling resistance.

[0120] 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 volume 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 caught 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 volume of the tie rubber 22 will increase, making it difficult to reduce rolling resistance.

[0121] 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 volume of the tie rubber 22. As a result, it is possible to reduce rolling resistance while suppressing the occurrence of appearance defects in the pneumatic tire 1.

[0122] Furthermore, the conductive rim cushion 30 has a distance Hrc in the tire radial direction between the innermost Rri and outermost Rwo of the rim cushion, which is within the range of 0.02 ≤ Hrc / SH ≤ 0.70 relative to the tire cross-sectional height SH. Therefore, it is possible to reduce electrical resistance while suppressing an increase in rolling resistance. In other words, if the distance Hrc in the tire radial direction between the innermost Rri and outermost Rwo of the rim cushion is Hrc / SH < 0.02 relative to the tire cross-sectional height SH, there is a risk that the distance Hrc in the tire radial direction between the innermost Rri and outermost Rwo of the rim cushion is too small. In this case, it becomes difficult to secure the overlap amount LAP with the tie rubber 22, making it difficult to secure a path for static electricity between the rim cushion 30 and the tie rubber 22, and thus there is a risk that it will be difficult to reduce electrical resistance. Furthermore, if the distance Hrc in the tire radial direction between the innermost part Rri and the outermost part Rwo of the rim cushion is Hrc / SH > 0.70 with respect to the tire cross-sectional height SH, there is a risk that the distance Hrc in the tire radial direction between the innermost part Rri and the outermost part Rwo of the rim cushion may be too large. In this case, the volume of the rim cushion 30 may become too large, making it difficult to reduce rolling resistance.

[0123] In contrast, if the distance Hrc in the tire radial direction between the innermost part Rri of the rim cushion and the outermost part Rwo of the rim cushion is within the range of 0.02 ≤ Hrc / SH ≤ 0.70 with respect to the tire cross-sectional height SH, it is possible to ensure the overlap amount LAP with the tie rubber 22 while suppressing the volume of the rim cushion 30 from becoming too large. This makes it possible to reduce electrical resistance by ensuring a path for static electricity between the rim cushion 30 and the tie rubber 22 while suppressing the increase in rolling resistance. As a result, rolling resistance can be reduced while suppressing the increase in electrical resistance.

[0124] Furthermore, since the belt layer 18 has a volume resistivity [Ω・cm] of less than 1 × 10⁸ [Ω・cm], and the carcass layer 15 has a volume resistivity of less than 1 × 10⁸ [Ω・cm] in the area overlapping with the belt layer 18, the electrical resistance from the tie rubber 22 to the tread rubber 3 can be reduced by the carcass layer 15 and the belt layer 18. 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 layer 18, 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.

[0125] Furthermore, the thickness Gt of the tie rubber 22 is within the range of 0.0033 ≤ Gt / Gs ≤ 0.3750 relative to the thickness Gs of the sidewall portion 4 at the outermost Rwo of the rim cushion in the tire radial direction, so that steering stability can be ensured while suppressing an increase in rolling resistance. In other words, if the thickness Gt of the tie rubber 22 is Gt / Gs < 0.0033 relative to the thickness Gs of the sidewall portion 4 at the outermost Rwo of the rim cushion in the tire radial direction, there is a risk that the thickness Gt of the tie rubber 22 is too thin relative to the thickness Gs of the sidewall portion 4. In this case, even if the tie rubber 22 and the rim cushion 30 are stacked, it becomes difficult to effectively ensure rigidity, and there is a risk that steering stability will be difficult to ensure. Furthermore, if the thickness Gt of the tie rubber 22 is Gt / Gs > 0.3750 relative to the thickness Gs of the sidewall portion 4 at the outermost Rwo of the rim cushion in the tire radial direction, there is a risk that the thickness Gt of the tie rubber 22 is too thick relative to the thickness Gs of the sidewall portion 4. In this case, the volume of the tie rubber 22 becomes too large, which may make it difficult to reduce rolling resistance.

[0126] In contrast, if the thickness Gt of the tie rubber 22 is within the range of 0.0033 ≤ Gt / Gs ≤ 0.3750 relative to the thickness Gs of the sidewall portion 4 at the outermost Rwo of the rim cushion in the tire radial direction, then rigidity can be ensured by overlapping the tie rubber 22 and the rim cushion 30 while suppressing the volume of the tie rubber 22 from becoming too large. As a result, steering stability can be ensured by the rigidity of the overlapping tie rubber 22 and rim cushion 30 while suppressing an increase in rolling resistance. Consequently, steering stability can be ensured while reducing rolling resistance.

[0127] Furthermore, since the end portion 22a of the tie rubber 22 is located radially outward from the rim flange R, the length of the tie rubber 22 can be more reliably shortened, and the volume of the tie rubber 22 can be reduced. As a result, rolling resistance can be reduced more reliably.

[0128] Furthermore, the distance Hrt between the outer end Ra of the rim flange R in the tire radial direction and the end 22a of the tie rubber 22 is within the range of 0.02 ≤ Hrt / SH ≤ 0.55 with respect to the tire cross-sectional height SH. This allows for reduced rolling resistance while maintaining steering stability and suppressing an increase in electrical resistance. In other words, if Hrt / SH < 0.02, the distance Hrt between the outer end Ra of the rim flange R and the end 22a of the tie rubber 22 is too small, which may cause the length of the tie rubber 22 to become too long. In this case, the volume of the tie rubber 22 increases, which may make it difficult to reduce rolling resistance. Also, if Hrt / SH > 0.55, the distance Hrt between the outer end Ra of the rim flange R and the end 22a of the tie rubber 22 is too large, which may cause the length of the tie rubber 22 to become too short. In this case, it becomes difficult to secure the amount of overlap (LAP) between the tie rubber 22 and the rim cushion 30, which may make it difficult to secure a path for static electricity between the rim cushion 30 and the tie rubber 22, or make it difficult to secure rigidity in the part where the tie rubber 22 and the rim cushion 30 overlap.

[0129] In contrast, if the distance Hrt in the tire radial direction between the outer end Ra of the rim flange R and the end 22a of the tie rubber 22 is within the range of 0.02 ≤ Hrt / SH ≤ 0.55 with respect to the tire cross-sectional height SH, the length of the tie rubber 22 can be set to an appropriate length. This prevents the volume of the tie rubber 22 from becoming too large, ensures a path for static electricity between the rim cushion 30 and the tie rubber 22, and further ensures rigidity in the overlapping portion of the tie rubber 22 and the rim cushion 30. As a result, it is possible to reduce rolling resistance while ensuring steering stability while suppressing an increase in electrical resistance.

[0130] Furthermore, the bead filler 14 has a thickness Gbr in the tire width direction at the same position as the outer end Ra of the rim flange R in the tire radial direction, which is within the range of 1.5 mm to 15 mm. This allows for reduced rolling resistance while ensuring handling stability. In other words, if the thickness Gbr of the bead filler 14 in the tire width direction at the same position as the outer end Ra of the rim flange R in the tire radial direction is less than 1.5 mm, there is a risk that the thickness Gbr of the bead filler 14 is too small. In this case, it may become difficult to ensure the rigidity of the bead filler 14, and thus difficult to ensure handling stability. Also, there is a risk that the thickness Gbr of the bead filler 14 in the tire width direction at the same position as the outer end Ra of the rim flange R in the tire radial direction may be too large than 15 mm. In this case, the volume of the bead filler 14 may become too large, making it difficult to reduce rolling resistance.

[0131] In contrast, if the thickness Gbr of the bead filler 14 in the tire width direction at the same position as the outer end Ra of the rim flange R in the tire radial direction is within the range of 1.5 [mm] to 15 [mm], then the rigidity of the bead filler 14 can be ensured while suppressing the volume of the bead filler 14 from becoming too large. As a result, the rigidity of the bead portion 10 can be ensured by the bead filler 14 while suppressing an increase in rolling resistance, thereby ensuring handling stability. Consequently, handling stability can be ensured while reducing rolling resistance.

[0132] Furthermore, regarding the tie rubber 22 and the rim cushion 30, the relationship between the cross-sectional area St [mm²] of the tie rubber 22 and the cross-sectional area Sr [mm²] of the rim cushion 30 in the tire meridional section within the overlap range 500 of the tie rubber 22 and the rim cushion 30 is within the range of 0.1 ≤ Sr / St ≤ 200. Therefore, it is possible to suppress the increase in electrical resistance while ensuring handling stability and reducing rolling resistance. In other words, if the relationship between the cross-sectional area St [mm²] of the tie rubber 22 and the cross-sectional area Sr [mm²] of the rim cushion 30 in the overlap range 500 of the tie rubber 22 and the rim cushion 30 is Sr / St < 0.1, there is a risk that the cross-sectional area Sr of the rim cushion 30 in the overlap range 500 will become too small. In this case, it may become difficult to secure a path for static electricity between the rim cushion 30 and the tie rubber 22, making it difficult to reduce electrical resistance. Furthermore, the cross-sectional area of ​​the portion of the rim cushion 30 that overlaps with the tie rubber 22 becomes smaller, which may make it difficult to secure rigidity near the bead portion 10.

[0133] Furthermore, if the relationship between the cross-sectional area St [mm²] of the tie rubber 22 and the cross-sectional area Sr [mm²] of the rim cushion 30 in the overlapping range 500 between the tie rubber 22 and the rim cushion 30 is Sr / St > 200, there is a risk that the cross-sectional area Sr of the rim cushion 30 in the overlapping range 500 will become too large. In this case, the volume of the rim cushion 30 will become too large, which may make it difficult to reduce rolling resistance.

[0134] In contrast, if the relationship between the cross-sectional area St [mm²] of the tie rubber 22 and the cross-sectional area Sr [mm²] of the rim cushion 30 in the overlapping range 500 between the tie rubber 22 and the rim cushion 30 is within the range of 0.1 ≤ Sr / St ≤ 200, then it is possible to ensure rigidity near the bead portion 10 while suppressing the volume of the rim cushion 30 from becoming too large, and to appropriately ensure the path of static electricity between the rim cushion 30 and the tie rubber 22. As a result, it is possible to ensure steering stability and reduce rolling resistance while suppressing the increase in electrical resistance.

[0135] [Embodiment 2] The pneumatic tire 1 according to Embodiment 2 has substantially the same configuration as the pneumatic tire 1 according to Embodiment 1, but is characterized in that a conductive reinforcing layer 60 is used for the conductive member. The other configurations are the same as in Embodiment 1, so their description is omitted and the same reference numerals are used.

[0136] Figure 8 is a cross-sectional view of the main part around the bead portion 10 in the pneumatic tire 1 according to Embodiment 2. In the pneumatic tire 1 according to Embodiment 2, a conductive member is used, which is a conductive reinforcing layer 60 made of fibrous material. The conductive reinforcing layer 60 is a sheet-like member that reinforces the bead portion 10. The conductive reinforcing layer 60 contains conductive fibers such as metal fibers, and has a volume resistivity of less than 1 × 10^8 [Ω・cm]. Preferably, the volume resistivity of the conductive reinforcing layer 60 is less than 1 × 10^6 [Ω・cm].

[0137] The sheet-like conductive reinforcing layer 60 is positioned between the carcass body portion 15a and the turn-up portion 15b in the carcass layer 15, extending outward in the tire radial direction of the turn-up portion 15b. The portion of the conductive reinforcing layer 60 located between the carcass body portion 15a and the turn-up portion 15b is positioned on the radially outer side of the bead core 11 and between the bead filler 14 and the turn-up portion 15b.

[0138] Furthermore, the portion of the conductive reinforcing layer 60 that is positioned on the outer side in the tire radial direction of the turn-up portion 15b is positioned along the carcass body portion 15a on the outer side in the tire width direction of the carcass body portion 15a. Also, the portion of the conductive reinforcing layer 60 that is positioned on the outer side in the tire radial direction of the turn-up portion 15b is located inward in the tire width direction from the rim cushion 30. For this reason, in the area on the outer side in the tire radial direction of the turn-up portion 15b of the carcass layer 15, and in the area where the rim cushion 30 is positioned in the tire radial direction, the conductive reinforcing layer 60 is positioned between the carcass body portion 15a of the carcass layer 15 and the rim cushion 30.

[0139] The outermost end Rso of the conductive reinforcing layer 60, which is the outermost end in the tire radial direction, is located inward in the tire width direction from the end 18c (see Figure 2) of the belt layer 18 in the tire width direction. Since the conductive reinforcing layer 60 is provided as a conductive member in Embodiment 2, the outermost end Rso of the reinforcing layer is the outermost end of the conductive member, which is the outermost end in the tire radial direction of the conductive member.

[0140] The outermost outermost part of the reinforcement layer, Rso, which is the outermost outermost part of the conductive member, is located radially outward from the end 22a of the tie rubber 22 in the tire direction. Therefore, if Rtg is the distance from the tire rotation axis to the end 22a of the tie rubber 22 in the tire direction, Rf1 is the distance from the tire rotation axis to the outer end 14a of the bead filler in the tire direction, and Rrc is the distance from the tire rotation axis to the outermost outermost part of the reinforcement layer, Rf1 ≤ Rtg < Rrc is satisfied between the end 22a of the tie rubber 22, the outer end 14a of the bead filler, and the outermost outermost part of the reinforcement layer, Rso.

[0141] Furthermore, in Embodiment 2, the outermost Rwo of the rim cushion 30 is located radially inward of the outermost Rso of the reinforcing layer. Also, the outermost Rwo of the rim cushion is located radially outward of the turn-up portion 15b and radially inward of the end portion 22a of the tie rubber 22. For this reason, in Embodiment 2, the rim cushion 30 does not overlap the tie rubber 22 in the tire width direction, and the conductive reinforcing layer 60 overlaps the tie rubber 22 in the tire width direction via the carcass body portion 15a of the carcass layer 15.

[0142] Furthermore, since the outermost outermost part Rwo of the rim cushion 30 is located radially outward relative to the turn-up portion 15b, at a position radially outward from the turn-up portion 15b, the rim cushion 30 is in contact with the conductive reinforcing layer 60 from the outside in the tire width direction of the conductive reinforcing layer 60.

[0143] The overlap amount LAP [mm] between the tie rubber 22 and the conductive reinforcing layer 60 overlapping via the carcass layer 15 in the overlap range 500 is within the range of 0.5 [mm] to 60 [mm], similar to the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 in Embodiment 1. Preferably, the overlap amount LAP [mm] between the tie rubber 22 and the conductive reinforcing layer 60 is within the range of 1.0 [mm] to 50 [mm].

[0144] In this case, the overlap amount LAP [mm] between the tie rubber 22 and the conductive reinforcing layer 60 is the distance along the periphery of the tie rubber 22 from the end 22a of the tie rubber 22 to the outermost Rso outside the reinforcing layer. Furthermore, the overlap range 500 between the tie rubber 22 and the conductive reinforcing layer 60 is the range along the periphery between the end 22a of the tie rubber 22 and the outermost Rso outside the reinforcing layer, and is the range in which the tie rubber 22 and the conductive reinforcing layer 60 are arranged to overlap via the carcass layer 15.

[0145] Since the conductive reinforcing layer 60 is a member that can reinforce the bead portion 10, the rigidity of the bead portion 10 can be increased by the conductive reinforcing layer 60. This improves the handling stability when the vehicle is in motion. Furthermore, in Embodiment 2, since the conductive reinforcing layer 60 is also used as a conductive member, a conductive member can be placed that allows static electricity to flow from the rim flange R to the tie rubber 22 while ensuring the rigidity of the bead portion 10. As a result, handling stability can be improved and electrical resistance can be reduced.

[0146] [Modifications] In the embodiments 1 and 2 described above, the outer end of the turn-up portion 15b of the carcass layer 15 in the tire radial direction and the outer end 14a of the bead filler are located at approximately the same position in the tire radial direction. However, the outer end of the turn-up portion 15b in the tire radial direction and the outer end 14a of the bead filler may be offset in the tire radial direction. In other words, the outer end of the turn-up portion 15b of the carcass layer 15 in the tire radial direction may be located outside the outer end 14a of the bead filler in the tire radial direction, or inside the outer end 14a of the bead filler in the tire radial direction. Furthermore, the outer end of the turn-up portion 15b of the carcass layer 15 in the tire radial direction may be located outside the outermost Rwo of the rim cushion 30 in the tire radial direction.

[0147] Furthermore, in embodiments 1 and 2 described above, a bead filler 14 is arranged in the bead portion 10, but the bead filler 14 does not have to be arranged in the bead portion 10. Figure 9 is a modified example of the pneumatic tire 1 according to embodiment 1, and is a cross-sectional view of the main part around the bead portion 10. The bead portion 10 may have a structure in which the bead filler 14 is omitted for purposes such as weight reduction, as shown in Figure 9. The bead core 11 arranged in the bead portion 10 shown in Figure 9 has a contour shape in the meridional cross-section of the tire that is approximately pentagonal, with the outer portion in the radial direction of the tire being a corner that points outward in the radial direction of the tire. That is, the bead wire 12 that constitutes the bead core 11 is wound around the bead core 11 so that the contour shape of the bead core 11 in the meridional cross-section of the tire is approximately pentagonal.

[0148] Since no bead filler 14 is placed on the radially outer side of the bead core 11, the carcass layer 15 that folds around the bead core 11 bends along the periphery of the bead core 11. In other words, since the bead core 11 has a roughly pentagonal shape in the meridional cross-section of the tire, the carcass layer 15 extending along the periphery of the bead core 11 is also bent in a roughly pentagonal shape. Furthermore, the portion of the turn-up portion 15b of the carcass layer 15 that is radially outer of the outer end of the bead core 11 in the tire direction contacts the carcass body portion 15a of the carcass layer 15 and extends along the carcass body portion 15a toward the side where the sidewall portion 4 is located. As a result, a closed region surrounding the bead core 11 is formed in the bead portion 10 by the carcass body portion 15a and the turn-up portion 15b of the carcass layer 15.

[0149] In the closed region formed by the carcass body portion 15a and the turn-up portion 15b of the carcass layer 15, substantially only the bead core 11 exists. For this reason, in the modified example shown in Figure 9, a bead filler 14 or a similar tire component (a component that is positioned on the radially outer side of the bead core 11 and is enclosed by the carcass body portion 15a and the turn-up portion 15b of the carcass layer 15 to increase the rigidity from the bead portion 10 to the sidewall portion 4) is not provided. That is, in the pneumatic tire 1 of the modified example shown in Figure 9, bead insulation rubber 13 that covers the bead wire 12 and rubber that fills the small gap formed between the bead core 11 and the carcass layer 15 are present in the closed region, but a bead filler 14 with a large volume is not used. In the modified pneumatic tire 1 shown in Figure 9, if the ratio of the total area a of rubber present in the closed region to the area A of the closed region in the meridional cross-section of the tire (a / A × 100%) is defined as the rubber occupancy rate of the closed region, then the rubber occupancy rate is within the range of 0.1% to 15%.

[0150] Thus, even in a pneumatic tire 1 in which a bead filler 14 is not placed in the bead portion 10, the outermost outermost part Rwo of the rim cushion 30 is located radially outward from the end 22a of the tie rubber 22, so that the rim cushion 30 overlaps with the tie rubber 22 via the carcass layer 15 in the lap area 500. For this reason, in the modified example shown in Figure 9, by omitting the bead filler 14, the mass of the pneumatic tire 1 is reduced, thereby reducing rolling resistance, while securing a path for static electricity to flow from the rim cushion 30 to the tie rubber 22. As a result, rolling resistance can be reduced while suppressing an increase in electrical resistance.

[0151] 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.

[0152] [Examples] Figures 10A to 10D 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 rolling resistance of the pneumatic tire, and the handling stability when driving a vehicle equipped with the pneumatic tire.

[0153] 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.

[0154] Furthermore, the evaluation test for the rolling resistance of pneumatic tires was conducted by mounting the test tire onto a rim wheel with a rim size of 18 x 7.0J, and performing an indoor drum test on the test tire using a drum testing machine with a drum diameter of 1707 [mm]. The rolling resistance of the test tire was measured under the conditions of an air pressure of 230 [kPa], a load of 6.86 [kN], and a speed of 80 [km / h]. The evaluation of the rolling resistance of pneumatic tires was performed using an index evaluation, where the reciprocal of the measured rolling resistance was set to 100, as described later in Conventional Example 1. A higher index evaluation value indicates lower rolling resistance and superior rolling resistance performance.

[0155] 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 from 10 km / h to 180 km / h, and a test driver performed a subjective evaluation of steering performance during lane changes and cornering, and 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 at 100. A higher index evaluation value indicates better handling stability on dry surfaces. If the index is 99 or higher, it is considered that the handling stability is maintained at a level comparable to Conventional Example 1, and that performance is comparable to Conventional Example 1 in terms of handling stability.

[0156] Performance evaluation tests were conducted on 36 types of pneumatic tires, including Conventional Example 1, which is an example of a conventional pneumatic tire; Examples 1 to 32, which are pneumatic tires 1 according to the present invention; and Comparative Examples 1 to 3, which are pneumatic tires compared to pneumatic tire 1 according to the present invention. Of these, in Conventional Example 1, the distance Rf1 from the tire rotation axis to the outer end of the bead filler is greater than the distance Rtg from the tire rotation axis to the end of the tie rubber. In Comparative Example 1, the distance Rtg from the tire rotation axis to the end of the tie rubber is greater than the distance Rrc, which is the outermost point outside the conductive member. For these reasons, neither Conventional Example 1 nor Comparative Example 1 satisfy the relationship Rf1 ≤ Rtg < Rrc for the distance Rtg from the tire rotation axis to the end of the tie rubber, the distance Rf1 from the outer end of the bead filler, and the distance Rrc, which is the outermost point outside the conductive member. Furthermore, in the pneumatic tires of Comparative Examples 2 and 3, the relationship between the overlap amount LAP [mm] between the tie rubber and the conductive member and the carcass layer thickness Gp [mm] does not satisfy 0.02 ≤ Gp / LAP ≤ 4.00.

[0157] In contrast, in all of the examples 1 to 32, 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, the distance Rtg of the end 22a of the tie rubber 22 from the tire rotation axis, the distance Rf1 of the outer end 14a of the bead filler and the distance Rrc of the outermost outermost conductive member satisfy the relationship Rf1 ≤ Rtg < Rrc, and the relationship between the overlap amount LAP [mm] between the tie rubber 22 and the rim cushion 30 and the thickness Gp [mm] of the carcass layer 15 is within the range of 0.02 ≤ Gp / LAP ≤ 4.00. Furthermore, the pneumatic tire 1 according to Examples 1 to 32 has limitations such as whether the conductive member is a rim cushion 30, the thickness Gt [mm] of the tie rubber 22, the distance Hrc (Hrc / SH) in the tire radial direction between the innermost Rri and outermost Rwo of the rim cushion relative to the tire cross-sectional height SH, the electrical resistance Rpc [Ω] of the carcass layer 15, the electrical resistance Rb [Ω] of the belt coat rubber 18b, the thickness Gt (Gt / Gs) of the tie rubber 22 relative to the thickness Gs of the sidewall portion 4 at the position of the outermost Rwo of the rim cushion in the tire radial direction, and the end 22a of the tie rubber 22 being further from the rim flange R. The differences include whether or not it is located on the outer side in the tire radial direction, the relationship between the distance Hrt [mm] between the outer end Ra of the rim flange R and the end 22a of the tie rubber 22 in the tire radial direction and the tire cross section height SH (Hrt / SH), the thickness [mm] of the bead filler 14 in the tire width direction at the same position as the outer end Ra of the rim flange R in the tire radial direction, the relationship between the cross-sectional area St of the tie rubber 22 and the cross-sectional area Sr of the rim cushion 30 in the overlap range 500 between the tie rubber 22 and the rim cushion 30 (Sr / St), and whether or not the conductive member is a conductive reinforcing layer 60.

[0158] As a result of evaluation tests conducted using these pneumatic tires 1, as shown in Figures 10A to 10D, it was found that the pneumatic tires 1 according to Examples 1 to 32 can ensure handling stability equivalent to or better than that of Conventional Example 1 without increasing electrical resistance, and can also reduce rolling resistance. In other words, the pneumatic tires 1 according to Examples 1 to 32 can ensure handling stability and reduce rolling resistance while suppressing an increase in electrical resistance.

[0159] [Other Modifications] Figure 11 shows a portion of the meridional cross-section of the tire shown in Figure 1. Figure 11 shows an example of the cross-sectional structure of a portion of the tread portion 2 shown in Figure 1. Figure 11 shows a cross-section cut along the circumferential direction of the tire. Referring to Figure 11, a belt layer 18, a carcass layer 15, tie rubber 22, and an inner liner 21 are provided 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.

[0160] 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.

[0161] [Modified Carcass Layers] A one-ply structure is preferred for the carcass layer 15 described with reference to Figure 11, but it is not limited thereto. Figure 12 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.

[0162] In the case shown in Figure 12, 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.

[0163] 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.

[0164] Furthermore, the area around the side rubber may have the same configuration as in Figure 11. Figure 13 shows an example of the cross-sectional structure of a part of the sidewall rubber 5 shown in Figure 1. Referring to Figure 13, 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.

[0165] In Figure 13, focusing on the tie rubber 22, a 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 increases. 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.

[0166] [Number of locations where the tie rubber is inserted] Figure 14 is a schematic diagram of the appearance of tire 1. As shown in Figure 14, 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.

[0167] 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 14 are examples, and more locations may be used as measurement points.

[0168] [Cross-sectional area of ​​tie rubber] Figure 15 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)

[0169] 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] ２ The 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.

[0170] 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.

[0171] 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 16. Figure 16 is a diagram illustrating that the thickness of the carcass layer 15 varies in the circumferential direction of the tire.

[0172] In Figure 16, 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 16, thickness Tcmax is the maximum value, thickness Tcmin is the minimum value, and thickness Tcave is the average value. The above area Sc [mm] 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.

[0173] [Height of the inserted tie rubber] Figure 17 illustrates the height of the tie rubber inserted between the carcass cords 16. In Figure 17, the thickness of the carcass layer 15 is denoted as Tc, and the height of the tie rubber inserted into the carcass coat rubber is denoted as 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)

[0174] 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.

[0175] [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 18 shows a modified cross-sectional structure of the tread portion 2 shown in Figure 1. As shown in Figure 18, 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].

[0176] [Cross-sectional area and height of the inserted tie rubber] Figure 19 illustrates the cross-sectional area and height of the tie rubber inserted into the carcass coat rubber. In Figure 19, the cross-sectional area of ​​the tie rubber inserted between the carcass cords is given by St [mm²]. ２Let 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.

[0177] 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.

[0178] [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.

[0179] 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.

[0180] 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.

[0181] 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.

[0182] [Arrangement of Earth Red Rubber] The arrangement of the Earth Red Rubber 50 will be explained with reference to Figures 20 to 22. Figure 20 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 20 is a cross-section when the Earth Red Rubber 50 is a through-type Earth rubber.

[0183] In Figure 20, 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 20, a small portion of the cap tread 3a may remain on the outermost edge of the tread rubber 3 in the tire radial direction.

[0184] On the other hand, Figure 21 is a meridional cross-sectional view of a tire showing a pneumatic tire according to an embodiment in which a non-penetrating type earth tread rubber is used. Figure 22 is a cross-sectional view of the tire when it is cut circumferentially at the position of the earth tread rubber in Figure 21. In Figures 21 and 22, the earth tread rubber 50a is a non-penetrating type earth tread rubber. Therefore, the earth tread rubber 50a does not penetrate the tread rubber 3 but terminates by contacting the under tread 3b. Although the earth tread rubber 50a does not contact the belt layer 18, conductivity can be maintained if the volume resistivity of the under tread 3b is sufficiently low. Note that, as shown in Figure 22, a small amount of the cap tread 3a may remain on the outermost part of the tread rubber 3 in the radial direction of the tire.

[0185] In each of the cross-sections shown in FIGS. 20 and 22, the cross-sectional area of the tread portion is defined as Str [mm ２ . The cross-sectional area Str is the total area of the cross-sectional area of the cap tread 3a, the cross-sectional area of the earth tread rubber 50 or 50a, and the cross-sectional area of the undertread 3b. Also, the cross-sectional area of the earth tread rubber is defined as 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. 20 and 22, 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. Note that the ratio Sea / Str is more preferably 0.9 or more and 1 or less.

[0186] The earth tread rubber 50 is made of a conductive rubber material having a lower volume resistivity than the tread rubber 3, and the volume resistivity of the earth tread rubber 50 is less than 1×10^8 [Ω·cm]. The volume resistivity of the earth tread rubber 50 is more preferably not more than 1×10^6 [Ω·cm].

[0187] [Example] FIGS. 23A to 23C are charts showing the results of a performance evaluation test of a pneumatic tire. Hereinafter, a performance evaluation test performed on the above pneumatic tire 1 will be described in comparison with the pneumatic tire of Comparative Example 2 and the pneumatic tire 1 according to the present disclosure. In the performance evaluation test, the electrical resistance of the pneumatic tire was measured before and after running with the pneumatic tire.

[0188] Regarding the electrical resistance of the tire, based on the measurement conditions specified by JATMA, the electrical resistance [Ω] of the test tire was measured using an R8340A ultra-high resistance meter manufactured by Advantest Corporation. For running with the pneumatic tire, an indoor drum-type tire rolling resistance tester with a drum diameter of 1707 [mm] was used. The test tire was assembled to an application rim specified by JATMA, and an air pressure of 200 [kPa] and 80% of the maximum load specified by JATMA were applied to the test tire. After running for 60 minutes at a speed of 81 [km / h], the electrical resistance of the tire was measured by the above method.

[0189] In Figure 23A, 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 23A, 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 23A to 23C, it can be seen that the tires of each embodiment of this disclosure maintain their electrical resistance value even after running.

[0190] This disclosure encompasses the following inventions: Invention [1] A carcass layer 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 tire radially outward side of the bead core; a carcass body portion arranged between the pair of bead portions; a turn-up portion formed continuously from the carcass body portion and folded back from the tire width direction inner side of the bead core to the tire width direction outer side; a conductive member arranged on the tire width direction outer side of the carcass body portion and having a volume resistivity of less than 1 × 10^8 [Ω・cm]; a belt layer arranged on the tire radially outward side of the carcass layer; a tread rubber arranged on the tire radially outward side of the belt layer; an inner liner arranged on the tire inner surface along the carcass layer; and a tie rubber arranged between the carcass layer and the inner liner. 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, and when Rtg is the distance in the tire radial direction from the tire rotation axis to the end of the tie rubber, Rf1 is the distance in the tire radial direction from the tire rotation axis to the outer end of the bead filler, which is the outermost end of the bead filler in the tire radial direction, and Rrc is the distance in the tire radial direction from the tire rotation axis to the outermost outermost part of the conductive member, which is the outermost end of the conductive member in the tire radial direction at a position outside the tire width direction of the bead core, then the end of the tie rubber, the outer end of the bead filler, and the outermost outermost part of the conductive member satisfy the relationship Rf1 ≤ Rtg < Rrc. A tire characterized in that the relationship between the overlap amount LAP [mm] between the tie rubber and the conductive member, which is indicated by the distance along the peripheral from the end of the tie rubber to the outermost outer part of the conductive member, and the thickness Gp [mm] of the carcass layer is within the range of 0.02 ≤ Gp / LAP ≤ 4.00, 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 conductive member constitutes the rim fitting surface in the bead portion and is a rim cushion positioned from the inside in the tire width direction to the outside in the tire width direction of the bead core. Invention [3] The tire according to Invention [1] or Invention [2], wherein the tie rubber has a thickness in the range of 0.1 [mm] or more and 1.5 [mm] or less. Invention [4] The tire according to any one of Inventions [1] to [3], wherein the conductive member constitutes the rim fitting surface in the bead portion and is a rim cushion positioned from the inside in the tire width direction to the outside in the tire width direction of the bead core, and the distance Hrc in the tire radial direction between the innermost part of the rim cushion, which is the inner end of the rim cushion in the tire radial direction, and the outermost part outside of the conductive member is in the range of 0.02 ≤ Hrc / SH ≤ 0.70 with respect to the tire cross-sectional height SH. Invention [5] A tire according to any one of Inventions [1] to [4], wherein the belt layer has a volume resistivity of less than 1 × 10⁸ [Ω·cm], and the carcass layer has a volume resistivity of less than 1 × 10⁸ [Ω·cm] in the area overlapping with the belt layer in the tire radial direction. Invention [6] A tire according to any one of Inventions [1] to [5], comprising a pair of sidewall portions arranged on both sides of the tire equatorial plane in the tire width direction, wherein the thickness Gt of the tie rubber is within the range of 0.0033 ≤ Gt / Gs ≤ 0.3750 with respect to the thickness Gs of the sidewall portion at the outermost position of the conductive member in the tire radial direction. Invention [7] A tire according to any one of Inventions [1] to [6], wherein the end of the tie rubber is located radially outward from the rim flange of the specified rim. Invention [8] The tire according to Invention [7], wherein the tie rubber is such that the distance Hrt in the tire radial direction between the outer end of the rim flange in the tire radial direction and the end of the tie rubber is within the range of 0.02 ≤ Hrt / SH ≤ 0.55 with respect to the tire cross-sectional height SH.Invention [9] The tire according to any one of Inventions [1] to [8], wherein the bead filler has a thickness in the tire width direction at the same position as the outer end of the rim flange of the specified rim in the tire radial direction, which is 1.5 [mm] or more and 15 [mm] or less. Invention

[10] The tire according to any one of Inventions [1] to [9], wherein the relationship between the cross-sectional area St [mm^2] of the tie rubber and the cross-sectional area Sr [mm^2] of the conductive member in the tire meridional cross section in the lap range, which is the range along the periphery between the end of the tie rubber and the outermost outer part of the conductive member, is within the range of 0.1 ≤ Sr / St ≤ 200. Invention

[11] The tire according to Invention [1], wherein the conductive member is a conductive reinforcing layer made of fibrous material and arranged on the outside of the carcass body in the tire width direction. Invention

[12] 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 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 a 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

[13] A tire according to Invention

[12] , 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

[14] A tire according to Invention

[12] or Invention

[13] , wherein, in the cross section seen when the tire is cut in the circumferential direction of the rib portion of the tread portion closest to the tire equator, 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

[15] A tire according to any one of Inventions

[12] to

[14] , 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

[16] A tire according to any one of Inventions

[12] to

[15] , 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 Invention

[17] A tire according to any one of Inventions

[12] to

[16] , 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

[18] A tire according to any one of Inventions

[12] to

[17] , 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.

[0191] 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 12. Bead wire 13. Bead insulation rubber 14. Bead filler 14a. Outer end of bead filler 15. Carcass layer 15a. Carcass main body 15b. Turn-up section 16. Carcass cord 17. Carcass coat rubber 18. Belt layer 21. Inner liner 21a. End 22. Tie rubber 22a. End 22b. Indentation 25. Inner surface of tire 30. Rim cushion 31. Rim cushion rubber 32. Rim fitting surface 35. Bead toe 36. Bead base 50. Earth tread 60. Conductive reinforcement layer 500. Wrap area

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 carcass layer having a carcass body portion arranged between the pair of bead portions; a turn-up portion formed continuously from the carcass body portion and folded back from the inner side in the tire width direction to the outer side in the tire width direction of the bead core; a conductive member arranged on the radially outer side of the carcass body portion and having a volume resistivity of less than 1 × 10^8 [Ω・cm]; 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 tie rubber arranged between the carcass layer and the inner liner. 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, and when Rtg is the distance in the tire radial direction from the tire rotation axis to the end of the tie rubber, Rf1 is the distance in the tire radial direction from the tire rotation axis to the outer end of the bead filler, which is the outermost end of the bead filler in the tire radial direction, and Rrc is the distance in the tire radial direction from the tire rotation axis to the outermost outermost part of the conductive member, which is the outermost end of the conductive member in the tire radial direction at a position outside the tire width direction of the bead core, then the end of the tie rubber, the outer end of the bead filler, and the outermost outermost part of the conductive member satisfy the relationship Rf1 ≤ Rtg < Rrc. A tire characterized in that the relationship between the overlap amount LAP [mm] between the tie rubber and the conductive member, which is indicated by the distance along the peripheral from the end of the tie rubber to the outermost outer part of the conductive member, and the thickness Gp [mm] of the carcass layer is within the range of 0.02 ≤ Gp / LAP ≤ 4.00, 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 conductive member constitutes the rim fitting surface in the bead portion and is a rim cushion positioned from the inside in the tire width direction to the outside in the tire width direction of the bead core.

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

4. The tire according to claim 1, wherein the conductive member is a rim cushion 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 the distance Hrc in the tire radial direction between the innermost part of the rim cushion, which is the inner end of the rim cushion in the tire radial direction, and the outermost part of the conductive member is within the range of 0.02 ≤ Hrc / SH ≤ 0.70 with respect to the tire cross-sectional height SH.

5. The tire according to claim 1, wherein the belt layer has a volume resistivity of less than 1 × 10⁸ [Ω·cm], and the carcass layer has a volume resistivity of less than 1 × 10⁸ [Ω·cm] in the region that overlaps with the belt layer in the tire radial direction.

6. The tire according to claim 1, comprising a pair of sidewall portions arranged on both sides of the tire equatorial plane in the tire width direction, wherein the thickness Gt of the tie rubber is within the range of 0.0033 ≤ Gt / Gs ≤ 0.3750 with respect to the thickness Gs of the sidewall portion at the outermost position of the conductive member in the tire radial direction.

7. The tire according to claim 1, wherein the end of the tie rubber is located radially outward from the rim flange of the specified rim.

8. The tire according to claim 7, wherein the distance Hrt in the tire radial direction between the outer end of the rim flange in the tire radial direction and the end of the tie rubber is within the range of 0.02 ≤ Hrt / SH ≤ 0.55 with respect to the tire cross-sectional height SH.

9. The tire according to claim 1, wherein the bead filler has a thickness in the tire width direction at the same position in the tire radial direction as the outer end of the rim flange of the specified rim, which is in the tire radial direction, and the thickness in the tire width direction is within the range of 1.5 mm to 15 mm.

10. The tire according to claim 1, wherein the relationship between the cross-sectional area St [mm²] of the tie rubber and the cross-sectional area Sr [mm²] of the conductive member in the tire meridional cross-section in the wrap range, which is the range along the periphery between the end of the tie rubber and the outermost outer part of the conductive member, is within the range of 0.1 ≤ Sr / St ≤ 200.

11. The tire according to claim 1, wherein the conductive member is a conductive reinforcing layer made of a fibrous material and arranged on the outer side of the carcass body in the tire width direction.

12. 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.

13. The tire according to claim 12, 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.

14. The tire according to claim 12 or 13, 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 15. The tire according to claim 12 or claim 13, 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 16. The tire according to claim 12 or claim 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 have the following relationship: 0.02 mm ≤ St / Tt ≤ 2.0 mm 17. The tire according to claim 12 or claim 13, 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.

18. The tire according to claim 12 or 13, 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

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