Tire

Abstract

To maintain electrical resistance reduction performance over the long term.SOLUTION: A tire includes: a pair of bead parts; a carcass layer bridged between the pair of bead parts; a belt layer provided on a tire radial direction outer side of the carcass layer; and a tread part provided on a radial direction outer side of the belt layer. The carcass layer includes a plurality of carcass cords, and a coat rubber which covers the plurality of carcass cords, and a conductive filament. The pair of bead parts has a pair of bead cores, and rubber parts which are provided around each of the pair of bead cores, and contacts a rim in the state of being mounted to the rim. At least 20[%] of an extension length of the conductive filament is covered with the coat rubber in a cross section in a direction perpendicular to an extension direction of the carcass layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to tires. [Background technology]

[0002] To improve the fuel economy of tires, the silica content of rubber compounds constituting the cap tread, undertread, sidewall rubber, etc. is sometimes increased. Because silica has high insulating properties, increasing the silica content of the cap tread increases the resistance of the cap tread, reducing the tire's anti-static performance. In the tire disclosed in Patent Document 1, conductive fibers with a thin metal layer applied to the surface of organic fibers, i.e., plated fibers, are exposed on the surface of the coating rubber of the carcass cord. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-112047 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when using plated conductive fibers or when providing them exposed on the surface of the coated rubber, the thin film may be damaged as the tire deforms, leaving room for improvement in maintaining the electrical resistance reduction performance over the long term.

[0005] The present disclosure has been made in view of the above, and an object of the present disclosure is to provide a tire that can maintain the performance of reducing electrical resistance for a long period of time. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, a tire according to one embodiment of the present disclosure includes a pair of bead portions, a carcass layer spanning between the pair of bead portions, a belt layer provided radially outside the carcass layer, and a tread portion provided radially outside the belt layer, wherein the carcass layer includes a plurality of carcass cords, a coating rubber covering the plurality of carcass cords, and a conductive linear body, and the pair of bead portions have a pair of bead cores and a rubber portion provided around each of the pair of bead cores and contacting the rim when mounted on the rim, and at least 20% of the extension length of the conductive linear body is covered by the coating rubber in a cross section perpendicular to the extension direction of the carcass layer. [Effects of the Invention]

[0007] A tire according to the present disclosure can maintain its electrical resistance reduction performance for a long period of time. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a tire according to a first embodiment taken along the tire meridian direction. [Figure 2] FIG. 2 is a diagram showing an example of a cross section in a direction perpendicular to the extending direction of the carcass layer. [Figure 3] FIG. 3 is a cross-sectional view showing an example of the arrangement of two carcass cords and conductive linear bodies provided between them. [Figure 4] FIG. 4 is a cross-sectional view showing an example of a splice portion of the carcass layer. [Figure 5] FIG. 5 is an enlarged view of a bead portion of the tire shown in FIG. [Figure 6] FIG. 6 is a diagram illustrating the diameter of the conductive linear body and the thickness of the coating rubber of the carcass layer at the location including the conductive linear body. [Figure 7] FIG. 7 is a diagram illustrating the periphery length of the portion of the carcass layer that comes into contact with the rubber portion. [Figure 8] FIG. 8 is a diagram showing a main part of a second embodiment, which is a modified example of the tire of the present disclosure. [Figure 9] FIG. 9 is a diagram showing a main portion of a third embodiment, which is another modified example of the tire of the present disclosure. [Figure 10A] FIG. 10A is a chart showing performance test results for tires of the present disclosure. [Figure 10B] FIG. 10B is a chart showing performance test results for tires of the present disclosure. [Figure 10C] FIG. 10C is a chart showing performance test results for tires of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

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

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

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

[0012] The tire 1 according to this embodiment has an annular structure centered on a rotation axis, and includes a tread portion 2, a pair of sidewall portions 3, 3, a pair of bead portions 10, 10, a carcass layer 13, a belt layer 14, and a tire inner surface rubber layer 20. Of these, the pair of sidewall portions 3, 3 and the pair of bead portions 10, 10 are each disposed on either side of the tire equatorial plane CL in the tire width direction.

[0013] The pair of bead portions 10, 10 are located radially inward of the pair of sidewall portions 3, 3, and each has a bead core 11, a bead filler 12, and a rubber portion 30 of the bead portion 10. That is, the pair of bead cores 11, 11, the pair of bead fillers 12, 12, and the pair of rubber portions 30 of the bead portions 10 are arranged on both sides of the tire equatorial plane CL in the tire width direction. Furthermore, the rubber portion 30 has a rim cushion rubber 31 and a chafer 32. Therefore, the pair of rim cushion rubbers 31, 31 and the pair of chafers 32, 32 are arranged on both sides of the tire equatorial plane CL in the tire width direction.

[0014] The pair of bead cores 11, 11 are annular members formed by bundling a plurality of bead wires and form the cores of the pair of bead portions 10, 10. The pair of bead fillers 12, 12 are respectively arranged on the outer sides of the pair of bead cores 11, 11 in the tire radial direction to reinforce the bead portion 10.

[0015] The carcass layer 13 has a single-layer structure consisting of one carcass ply or a multi-layer structure consisting of multiple carcass plies stacked together, and is toroidally laid between the bead portions 10, 10 located on both sides in the tire width direction to form the tire framework. The carcass ply of the carcass layer 13 is formed by coating multiple carcass cords made of steel or organic fiber material such as aramid, nylon, polyester, or rayon with coating rubber and rolling them. The carcass ply of the carcass layer 13 has a carcass angle, defined as the inclination angle of the extension direction of the carcass cords with respect to the tire circumferential direction, in the range of 80 degrees to 95 degrees in absolute value.

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

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

[0018] The tan δ value at 60° C. is measured using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. under the conditions of an initial strain of 10%, an amplitude of ±0.5%, and a frequency of 20 Hz.

[0019] Volume resistivity (volume specific resistance) is measured based on JIS K6271, "Vulcanized rubber and thermoplastic rubber - Determination of volume resistivity and surface resistivity." Generally, if the volume resistivity is less than 1 x 10^8 [Ω·cm] or the surface resistivity is less than 1 x 10^8 [Ω / cm], the material can be said to have conductivity that can suppress static electricity buildup.

[0020] A pair of rubber portions 30, 30 of a pair of bead portions 10, 10 are respectively arranged on the tire radially inward side of the bead cores 11, 11 on both sides in the tire width direction and the turnup portion of the carcass layer 13. The rubber portion 30 of the bead portion 10 is the portion that abuts against the rim flange Ri of the rim when the tire 1 is mounted on the rim, and forms the contact surface of the bead portion 10 with the rim flange Ri. The volume resistivity of the rubber portion 30 is preferably less than 1×10^8 [Ω·cm]. The volume resistivity of the rubber portion 30 is more preferably 1×10^7 [Ω·cm] or less.

[0021] The belt layer 14 has one or more belt plies extending in the tire width direction, and in this embodiment, multiple belt plies are laminated. That is, in this embodiment, the belt layer 14 is configured by laminating a pair of cross belts 141, 142 and a belt cover 143 in the tire radial direction, and is disposed radially outward of the carcass layer 13 and wound around the carcass layer 13. The pair of cross belts 141, 142 are configured by coating a plurality of belt cords made of steel or organic fiber material with coating rubber and rolling them, and the belt angle, which is the inclination angle of the extension direction of the belt cords with respect to the tire circumferential direction, is within the range of 20 degrees to 65 degrees in absolute value. The pair of cross belts 141, 142 have a so-called cross-ply structure in which the belt angles have opposite signs and are laminated so that the extension directions of the belt cords cross each other. That is, the pair of cross belts 141, 142 have the inclination directions of the belt cords with respect to the tire circumferential direction in the tire width direction opposite to each other. The belt cover 143 is formed by rolling a plurality of cords made of steel or organic fiber material coated with coated rubber, and the belt angle is in the range of 0 to 10 degrees in absolute value. The belt cover 143 is also arranged by being layered on the outer side of the cross belts 141 and 142 in the tire radial direction.

[0022] The tread portion 2 is configured with tread rubber 15, which is a rubber composition, and is arranged radially outward of the carcass layer 13 and the belt layer 14, and is exposed at the outermost portion in the radial direction of the tire 1. Therefore, the outer peripheral surface of the tread portion 2 forms part of the contour of the tire 1, and a plurality of grooves, such as circumferential main grooves 6 and lug grooves (not shown), that extend in the circumferential direction of the tire are formed in the tread portion 2. In addition, the tread rubber 15 that configures the tread portion 2 has a cap tread 151 and an undertread 152.

[0023] The cap tread 151 is a rubber member located at the outermost position of the tread portion 2 in the tire radial direction and constituting the tire contact surface. It may have a single-layer structure (see FIG. 1) or a multi-layer structure (not shown). The tan δ value of the cap tread 151 at 60°C is preferably 0.25 or less. The volume resistivity of the cap tread 151 is preferably in the range of 1×10^8 [Ω·cm] or more, more preferably 1×10^10 [Ω·cm] or more, and even more preferably 1×10^12 [Ω·cm] or more. This reduces the rolling resistance of the tire 1. The cap tread 151 with such a volume resistivity is produced by using a low-heat-generating compound with a low carbon content and reinforcing it with an increased silica content.

[0024] The undertread 152 is a member laminated on the inner side in the tire radial direction of the cap tread 151. The volume resistivity of the undertread 152 is preferably lower than the volume resistivity of the cap tread 151.

[0025] Each of the pair of sidewall portions 3, 3 includes a sidewall rubber 16, and the pair of sidewall rubbers 16, 16 of the pair of sidewall portions 3, 3 are disposed on the outer side of the carcass layer 13 in the tire width direction. The tan δ value of the sidewall rubber 16 at 60°C is preferably 0.20 or less. The volume resistivity of the sidewall rubber 16 is preferably in the range of 1×10^8 [Ω·cm] or more, more preferably 1×10^10 [Ω·cm] or more, and even more preferably 1×10^12 [Ω·cm] or more. This reduces the rolling resistance of the tire 1. The sidewall rubber 16 with such a volume resistivity is produced by using a low-heat-generating compound with a low carbon content and reinforcing it with an increased silica content.

[0026] Although there are no particular limitations on the upper limit of the volume resistivity of the cap tread 151, the lower limit of the volume resistivity of the undertread 152, the upper limit of the volume resistivity of the sidewall rubber 16, and the lower limit of the volume resistivity of the rim cushion rubber 17, they are subject to physical constraints since they are rubber components.

[0027] The tire inner surface rubber layer 20 constitutes a tire inner surface 25, which is the inner surface of the tire 1, and faces the tire cavity, which is the space inside the tire 1. In this way, the tire inner surface rubber layer 20 constituting the tire inner surface 25 is disposed on the tire cavity side with respect to the carcass layer 13, and covers the carcass layer 13 from the tire cavity side.

[0028] In this embodiment, the bead portion 10 refers to the region from the measurement point of the rim diameter to 1 / 3 of the tire cross-sectional height SH. The tire cross-sectional height SH refers to 1 / 2 of the difference between the tire outer diameter and the rim diameter, and is measured with the tire 1 mounted on a specified rim, pressurized to a specified internal pressure, and in an unloaded state.

[0029] Here, the specified rim refers to the "applicable rim" specified by JATMA, the "design rim" specified by TRA, or the "measuring rim" specified by ETRTO. The specified internal pressure refers to the "maximum air pressure" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "inflation pressures" specified by ETRTO. The specified load refers to the "maximum load capacity" specified by JATMA, the maximum value of the "tire load limits at various cold inflation pressures" specified by TRA, or the "load capacity" specified by ETRTO. However, in JATMA, for passenger car tires, the specified internal pressure is 180 kPa, and the specified load is 88% of the maximum load capacity.

[0030] (Earth Rubber) As shown in FIG. 1, the tire 1 includes an earth rubber 7. The earth rubber 7 is made of a conductive rubber material having a volume resistivity lower than that of the tread rubber 15. Specifically, the volume resistivity of the earth rubber 7 is preferably less than 1×10^8 [Ω·cm], and more preferably 1×10^6 [Ω·cm] or less.

[0031] The earth rubber 7 is embedded in the tread rubber 15. A portion of the earth rubber 7 is exposed on the tread surface of the tread rubber 15. The earth rubber 7 penetrates the cap tread 151 and the undertread 152 and is in conductive contact with the belt layer 14 (belt cover 143). That is, in the tire meridian cross section, one end of the earth rubber 7 is in contact with the belt layer 14, and the other end of the earth rubber 7 is exposed on the tread surface of the tread portion 2. The earth rubber 7 is sometimes called an earth tread. The earth rubber 7 has an annular structure extending around the entire tire circumference, and extends continuously in the tire circumferential direction with a portion of it exposed on the tread surface. Therefore, as the tire rolls, the earth rubber 7 is always in contact with the road surface, thereby always ensuring a conductive path from the belt layer 14 to the road surface.

[0032] As described above, a conductive path is secured from the rubber portion 30 in contact with the rim flange Ri through the carcass layer 13 and the belt layer 14 in this order to the earth rubber 7. This allows static electricity on the vehicle to be released to the road surface. This prevents static electricity from building up on the vehicle on which the tire 1 is mounted. This allows the performance of reducing electrical resistance to be maintained over the long term.

[0033] (carcass layer) Fig. 2 is a diagram showing an example of a cross section perpendicular to the extending direction of the carcass layer 13. Fig. 3 is a cross section showing an example of the arrangement of two carcass cords 130a and 130b and a conductive linear body 131 provided between them.

[0034] 2, the carcass layer 13 includes carcass cords 130, conductive linear members 131, and coating rubber 132 that covers the carcass cords 130. The conductive linear members 131 are provided between the carcass cords 130. The volume resistivity of the conductive linear members 131 is preferably less than 1×10^8 [Ω·cm].

[0035] Here, attention is focused on the first carcass cord 130a and the second carcass cord 130b, which are adjacent to each other, among the carcass cords 130 of the carcass layer 13. The conductive linear body 131 is provided between the adjacent first carcass cord 130a and the adjacent second carcass cord 130b. The conductive linear body 131 and the carcass cords 130a and 130b are covered with a coating rubber 132.

[0036] 2 can be produced, for example, by providing reels of conductive linear bodies 131 between reels of carcass cords 130. Alternatively, the carcass layer 13 can be produced by placing the conductive linear bodies 131 on a pre-vulcanized carcass ply in which the carcass cords 130 are arranged, and then vulcanizing the carcass ply.

[0037] Here, the distance between the center P0 of the conductive linear body 131 and the center P1 of the first carcass cord 130a adjacent to the conductive linear body 131 is defined as Le1. The distance between the center P0 of the conductive linear body 131 and the center P2 of the second carcass cord 130b adjacent to the conductive linear body 131 is defined as Le2. The distance between the center P1 of the first carcass cord 130a and the center P2 of the second carcass cord 130b is defined as Lc. The relationship between these distances Le1, Le2, and Lc is as follows: 1.0≦(Le1+Le2) / Lc≦1.6 It is preferable that the following relationship is satisfied.

[0038] By setting the distances Le1, Le2, and Lc within the above ranges, sufficient coating rubber is interposed between adjacent carcass cords, and electrical conductivity can be maintained for a long period of time. Note that if 1.6<(Le1+Le2) / Lc, disconnection may occur when the tire deforms, which is not preferable. The relationship between the distances Le1, Le2, and Lc is as follows: 1.0≦(Le1+Le2) / Lc≦1.2 It is more preferable that:

[0039] The conductive linear body 131 has lower durability against impact, load, and air pressure than the carcass cord 130. Therefore, if the diameter of the conductive linear body 131 is too large, the durability of the entire tire 1 may decrease. Therefore, the ratio of the diameter of the conductive linear body 131 to the diameter of the carcass cord 130 is preferably 0.1 or more and 0.8 or less. If the diameter ratio is within the above range, the durability of the entire tire 1 can be maintained.

[0040] 3, the center P1 of the carcass cord 130a, the center P2 of the carcass cord 130b, and the center P0 of the conductive linear body 131 may be aligned along the same straight line (for example, the dashed line in FIG. 3), or may not be aligned along the same straight line like the center P0' of the conductive linear body 131' in FIG. 3. When they are not aligned along the same straight line, the relationship between the distance Le1' between the center P0' and the center P1, the distance Le2' between the center P0' and the center P2, and the distance Lc is as follows: 1.0≦(Le1'+Le2') / Lc≦1.9 It is preferable that the following relationship is satisfied.

[0041] It is preferable that the pitch between the carcass cords 130 is substantially constant. In Fig. 2, the distance Lc between the centers of the carcass cords 130a and 130b is the distance Lc1 between the centers of the carcass cords 130a and other carcass cords 130 adjacent to the carcass cord 130a. 0.95≦Lc1 / Lc≦1.05 In addition, with respect to the distance Lc between the carcass cord 130a and the carcass cord 130b, the distance Lc2 between the centers of the carcass cord 130b and another carcass cord 130 adjacent thereto is preferably 0.95≦Lc2 / Lc≦1.05 That is, it is preferable that the ratio Lc' / Lc of the distance Lc' between the centers of the other two carcass cords to the distance Lc between the centers of the first carcass cord 130a and the second carcass cord 130b is 0.95≦Lc' / Lc≦1.05 That is, by making the pitch between the carcass cords 130 substantially constant, the strength of the carcass layer 13 can be ensured.

[0042] 2 and 3 , the entire conductive linear body 131 is covered with the coating rubber 132. That is, 100% of the extension length of the conductive linear body 131 is covered with the coating rubber 132 in a cross section perpendicular to the extension direction of the carcass layer 13. To ensure the conductivity of the conductive linear body 131, it is not necessary for 100% of the extension length to be covered with the coating rubber 132; it is sufficient that only a portion of the extension length of the conductive linear body 131 is covered with the coating rubber 132. For example, it is sufficient that at least 20% of the extension length of the conductive linear body 131 is covered with the coating rubber 132 in a cross section perpendicular to the extension direction of the carcass layer 13. If at least 20% of the extension length of the conductive linear body 131 is covered with the coating rubber 132, the conductivity of the conductive linear body 131 and the durability of the conductive linear body 131 can be ensured.

[0043] The extension length of the conductive linear body 131 may be equal to or shorter than the extension length of the carcass layer 13. That is, the conductive linear body 131 may extend from one end of the carcass layer 13 to the other end, or may have a length shorter than that of the carcass layer 13. However, to ensure a conductive path, it is preferable that the conductive linear body 131 extend from the turn-up position of the carcass layer 13 in the bead portion 10 to at least a position radially inward of the belt layer 14 in the tire. In particular, it is preferable that the conductive linear body 131 extend to a position radially inward of the contact portion between the earth rubber 7 and the belt cover 143. Therefore, the conductive linear body 131 does not need to extend to the position of the tire equatorial plane CL.

[0044] Here, the fineness of the carcass cord 130 is Tc, and the fineness of the conductive linear body 131 is Te. The fineness is the weight per unit length. The ratio Te / Tc of the fineness Te to the fineness Tc is given by 0.0050≦Te / Tc<1 It is preferable that the ratio Te / Tc is within the above range, thereby maintaining good conductivity. If Te / Tc<0.0050, the conductive linear body 131 is too thin and does not have sufficient conductivity, which is not preferable. Furthermore, if 1≦Te / Tc, the conductive linear body 131 heats up, which reduces durability, which is also not preferable. It is more preferable that the ratio Te / Tc is 0.010≦Te / Tc≦0.40.

[0045] The fineness is measured in accordance with JIS L1017 (Test method for synthetic fiber tire cords 8.3 Correct fineness).

[0046] FIG. 4 is a cross-sectional view showing an example of a splice portion of the carcass layer 13. As shown in FIG. 4, the splice portion is a portion where the first carcass 13a and the second carcass 13b constituting the carcass layer 13 overlap when the carcass layer 13 is molded. As shown in FIG. 4, the conductive linear body 131 is preferably included in the splice portion of the carcass layer 13. By including the conductive linear body 131 in the molded splice portion of the carcass layer 13, breakage of the conductive linear body 131 can be prevented. In FIG. 4, the conductive linear body 131 is included in the first carcass 13a on the lower side in the figure, but the conductive linear body 131 may also be included in the second carcass 13b on the upper side in the figure.

[0047] Here, the elongation percentage of the conductive linear body 131 is preferably 1.0% or more and 70.0% or less. When the elongation percentage of the conductive linear body 131 is within the above range, breakage of the conductive linear body 131 during manufacturing and tire deformation can be suppressed, and conductivity can be maintained.

[0048] The elongation of the linear body is measured in accordance with JIS L1017 (Test method for synthetic fiber tire cords 8.5 Tensile strength and elongation).

[0049] It is preferable that the conductive linear body 131 contains metal fibers, which provide good conductivity. Metal fibers include stainless steel, steel, aluminum, copper, etc., and oxides of these materials.

[0050] The conductive linear body 131 is preferably a blended yarn containing conductive fiber with a volume resistivity of less than 1.0×10^8 [Ω·cm] and non-conductive fiber with a volume resistivity of 1.0×10^8 [Ω·cm] or more. The blended yarn of conductive fiber and non-conductive fiber ensures durability.

[0051] (Bead part) Fig. 5 is an enlarged view of the bead portion 10 of the tire 1 shown in Fig. 1. As shown in Fig. 5, in the bead portion 10, the carcass layer 13 extends from the outer side to the inner side in the tire radial direction, passes from the inner side in the tire width direction of the bead core 11 and the bead filler 12 to the inner side in the tire radial direction, and is wound back to the outer side in the tire width direction. The conductive linear body 131 in the carcass layer 13 is located on the outer side in the tire radial direction of the bead toe 35. The conductive linear body 131 in the carcass layer 13 may extend from the tire inner surface 25 side, past the bead toe 35, to the bead base 36. The tire inner surface rubber layer 20 has a structure in which an inner liner 21 and a tie rubber 22 are laminated.

[0052] The rubber portion 30 of the bead portion 10 includes a chafer 32 and a rim cushion rubber 31 that contact the rim flange Ri (see FIG. 1). The chafer 32 may not be provided. The periphery length of the portion of the rubber portion 30 that contacts the rim flange Ri and the carcass layer 13 that includes the conductive linear members is defined as L [cm]. That is, the periphery length of the portion of the carcass layer 13 that includes the conductive linear members that contacts the rubber portion 30 is defined as L [cm].

[0053] Fig. 6 is a diagram illustrating the diameter R of the conductive linear body 131 and the thickness T of the coating rubber of the carcass layer 13 at a portion including the conductive linear body 131. Fig. 7 is a diagram illustrating the periphery length L of the portion of the carcass layer 13 that contacts the rubber portion 30. Fig. 7 is a diagram schematically illustrating a cross section of the AA portion in Fig. 6.

[0054] In FIG. 6, the thickness of the coating rubber of the carcass layer 13 at the location including the conductive linear body 131 is T [cm]. The volume resistivity of the coating rubber of the carcass layer 13 is ρ [Ω·cm]. The diameter of the conductive linear body 131 is R [cm]. In FIG. 7, the periphery length of the portion of the carcass layer 13 including the conductive linear body that contacts the rubber portion 30 is L [cm]. These relationships are expressed as follows: ρ×T / (R×L)<1.0×10^8[Ω] It is preferable to satisfy the above relationship. By satisfying the above relationship, good conductivity can be obtained. It is more preferable that these relationships satisfy 2.0×10^6[Ω]<ρ[Ω·cm]×T[cm] / (R[cm]×L[cm])<5.0×10^6[Ω].

[0055] (Actions and Effects) When a tire 1 according to the embodiment is mounted on a vehicle and driven, the tire 1 rotates while the lower portion of the surface of the tread portion 2 of the tire 1 that faces the road surface comes into contact with the road surface. As the surface of the tread portion 2 of the tire 1 comes into contact with the road surface in this manner, a frictional force can be generated between the tire 1 and the road surface. This allows the vehicle to transmit driving force, braking force, and turning force to the road surface through the frictional force between the tire 1 and the road surface, and the vehicle can drive using these driving force, braking force, and turning force.

[0056] Furthermore, static electricity may be generated while the vehicle is running, and this static electricity flows from the rim flange Ri through the rubber part 30 of the bead part 10, through the conductive linear body 131, to the belt layer 14, and is then released from the belt layer 14 to the road surface via the earth rubber 7. This allows static electricity generated on the vehicle to be released onto the road surface, suppressing charging of the vehicle due to static electricity.

[0057] That is, the conductive linear members 131 having a volume resistivity of less than 1×10^8 [Ω·cm] allow electricity to flow relatively easily, thereby reducing the electrical resistance of the tire 1. As a result, the tire 1 can channel static electricity generated while the vehicle is running from the rubber portion 30 of the bead portion 10 to the belt layer 14 via the conductive linear members 131 of the carcass layer 13, thereby suppressing charging of the vehicle due to static electricity.

[0058] When the vehicle is running, the tread 2, sidewall 3, etc. rotate while deforming due to loads generated according to the running conditions of the vehicle. Because the tread 2 and sidewall 3 are made by laminating different members, when the tread 2 or sidewall 3 deforms, shear forces tend to occur in directions that cause the members that make up these parts to shift relative to each other.

[0059] If the conductive linear member 131 breaks due to the shear force, the conductive path from the rim flange Ri to the belt layer 14 is severed, making it difficult for static electricity generated in the vehicle to be released onto the road surface. However, in the tire 1 according to this embodiment, the conductive linear member 131 is disposed within the carcass layer 13. Therefore, even if the tread portion 2 or the sidewall portion 3 is deformed, the conductive linear member 131 is not squeezed by other members. Therefore, even after the tire 1 has traveled a long distance, an electrical path between the rubber portion 30 and the belt layer 14 can be secured. This makes it possible to prevent the electrical resistance of the tire 1 from increasing due to the conductive linear member 131 breaking when the tire 1 has traveled a long distance. As a result, the tire's electrical resistance after travel can be maintained.

[0060] (Variation) FIG. 8 is a diagram illustrating a main portion of a second embodiment, which is a modified example of a tire according to the present disclosure. As shown in FIG. 8, in the second embodiment, the structure of the bead portion 10a is different from the structure of the bead portion 10 (see FIG. 5) of the first embodiment. In the bead portion 10a, the carcass layer 13 includes a carcass 13b and a carcass 13c. As in the case of FIG. 5, the carcass 13b extends from the outer side to the inner side in the tire radial direction, passes from the inner side in the tire width direction of the bead core 11 and the bead filler 12 to the inner side in the tire radial direction, and is wound back to the outer side in the tire width direction. In contrast, the carcass 13c extends from the outer side to the inner side in the tire radial direction, passes from the outer side in the tire width direction of the bead core 11 and the bead filler 12 to the inner side in the tire radial direction, and terminates at the inner side in the tire radial direction of the bead core 11. Even in the case of the carcass layer 13 shown in FIG. 8, a conductive path can be ensured if the carcass 13b includes a conductive linear body 131 (see FIG. 2).

[0061] FIG. 9 is a diagram showing a main portion of a third embodiment, which is another modified example of a tire according to the present disclosure. As shown in FIG. 9, in the third embodiment, the structure of the bead portion 10b is different from the structure of the bead portion 10 (see FIG. 5) of the first embodiment. In the bead portion 10b, the carcass layer 13 includes a carcass 13b and a carcass 13d. As in the case of FIG. 5, the carcass 13b extends from the outer side to the inner side in the tire radial direction, passes from the inner side of the bead core 11 and the bead filler 12 in the tire width direction to the inner side in the tire radial direction, and is wound back to the outer side in the tire width direction. In contrast, the carcass 13d extends from the outer side to the inner side in the tire radial direction and terminates on the outer side of the bead core 11 and the bead filler 12 in the tire width direction. Even in the case of the carcass layer 13 shown in FIG. 9, a conductive path can be ensured if the carcass 13b includes a conductive linear body 131 (see FIG. 2).

[0062] The tire of the present disclosure does not need to include the earth rubber 7 shown in Fig. 1. In other words, if the volume resistivity of the cap tread 151 and the under tread 152, which are located radially outward of the belt cover 143, is sufficiently low, the earth rubber 7 does not need to be included. This is because if the volume resistivity of the cap tread 151 and the under tread 152 is sufficiently low, a conductive path can be secured from the rubber portion 30 in contact with the rim to the road surface, passing through the carcass layer 13 and the belt layer 14 in this order.

[0063] (Example) 10A to 10C are tables showing the results of performance tests on the tire 1 according to the present disclosure. Performance evaluation tests conducted on the tire 1 according to the present disclosure and a conventional tire will be described below. Performance evaluation tests were conducted on the electrical resistance of the new tire and the tire after running. The conductive linear members of the tire 1 according to the present disclosure include metal fibers.

[0064] Performance evaluation tests were conducted using pneumatic tires with a nominal tire size of 195 / 65R15 91H as specified by JATMA as test tires. Evaluation tests for new electrical resistance were conducted using an R8340A Ultra High Resistance Meter manufactured by Advantest Corporation, measuring the electrical resistance [Ω] of the test tires according to the measurement conditions specified by JATMA.

[0065] In addition, an indoor drum-type tire rolling resistance tester with a drum diameter of 1707 mm was used to evaluate electrical resistance after driving. The test tire was mounted on a rim specified by JATMA, and an air pressure of 200 kPa and 80% of the maximum load specified by JATMA were applied to the test tire. After driving for 60 minutes at a speed of 81 km / h, the test tire's electrical resistance (Ω) was measured using an Advantest R8340A Ultra High Resistance Meter in accordance with the measurement conditions specified by JATMA. The lower the measured value for tire electrical resistance when new and after driving, the lower the electrical resistance and the better the tire's performance in terms of electrical resistance.

[0066] The performance evaluation test was conducted on 23 types of tires, including a conventional tire and tire 1 according to the present disclosure, from Example 1 to Example 22. Of these, the conventional tire is a tire in which conductive fibers formed by plating the surface of organic fibers are exposed on the surface of the coated rubber of the carcass cord. As shown in Figures 10A to 10C, the tires of Example 1 to Example 22 showed better results in maintaining electrical resistance reduction performance over the long term than the conventional tire.

[0067] The present disclosure encompasses the following inventions. <1> a pair of bead portions; a carcass layer laid between the pair of bead portions; a belt layer provided on the tire radially outer side of the carcass layer; and a tread portion provided on the tire radially outer side of the belt layer; Including, The carcass layer A plurality of carcass cords, a coating rubber covering the plurality of carcass cords, and a conductive linear body; Including, The pair of bead portions are a pair of bead cores; and rubber portions provided around the pair of bead cores, each of which comes into contact with the rim when the tire is attached to the rim; and At least 20% of the extension length of the conductive linear body is covered by the coating rubber in a cross section perpendicular to the extension direction of the carcass layer. tire. <2> The tire further includes an earth rubber provided in the tread portion, In the tire meridian section, one end of the earth rubber is in contact with the belt layer, and the other end of the earth rubber is exposed to the tread surface of the tread portion. <1> A tire as described in <3> The volume resistivity of the carcass layer is 1×10^8 [Ω·cm] or more, The volume resistivity of the rubber portion is less than 1×10^8 [Ω·cm], The volume resistivity of the conductive linear body is less than 1×10^8 [Ω·cm] <1> or <2> A tire as described in <4> In a cross section in a direction perpendicular to the extending direction of the carcass layer, a distance Le1 between the center of the conductive linear body and the center of a first carcass cord adjacent to the conductive linear body; a distance Le2 between the center of the conductive linear body and the center of a second carcass cord adjacent to the conductive linear body; The relationship between the distance Lc between the center of the first carcass cord and the center of the second carcass cord is 1.0≦(Le1+Le2) / Lc≦1.6 is <1> from <3> 1. A tire according to any one of the preceding items. <5> A ratio Lc' / Lc of a distance Lc' between the centers of the other two carcass cords to a distance Lc between the centers of the first carcass cord and the second carcass cord is 0.95≦Lc' / Lc≦1.05 is <4> A tire as described in <6> The fineness Te of the conductive linear body relative to the fineness Tc of the carcass cord is 0.0050≦Te / Tc<1 is <1> from <5> 1. A tire according to any one of the preceding items. <7> The conductive wire is included in the splice portion of the carcass layer. <1> from <6> 1. A tire according to any one of the preceding items. <8> The conductive linear body has an elongation rate of 1.0% or more and 70.0% or less. <1> from <7> 1. A tire according to any one of the preceding items. <9> The conductive linear body includes a metal fiber <1> from <8> 1. A tire according to any one of the preceding items. <10> The conductive linear body is a blended yarn containing conductive fibers with a volume resistivity of less than 10^8 [Ω·cm] and non-conductive fibers with a volume resistivity of 10^8 [Ω·cm] or more. <1> from <9> 1. A tire according to any one of the preceding items. <11> The relationship between the periphery length L [cm] of the portion of the carcass layer including the conductive linear body that contacts the rubber portion, the thickness T [cm] of the coating rubber of the carcass layer at the portion including the conductive linear body, the volume resistivity ρ [Ω cm] of the coating rubber, and the diameter R of the conductive linear body is as follows: ρ×T / (R×L)<1.0×10^8[Ω] is <1> from <10> 1. A tire according to any one of the preceding items. <12> The ratio of the diameter of the conductive linear body to the diameter of the carcass cord is 0.1 or more and 0.8 or less. <1> from <11> 1. A tire according to any one of the preceding items. [Explanation of symbols]

[0068] 1 tire 2 Tread section 3 Sidewall 6 Circumferential main groove 7 Earth Rubber 10, 10a, 10b Bead part 11 Bead core 12 Bead filler 13 Carcass layer 13a, 13b, 13c, 13d Carcass 14 Belt Layer 15 Tread rubber 16 Sidewall rubber 17 Rim cushion rubber 21 Inner liner 22 Thai Rubber 25 Tire inner surface 30 Rubber part 31 Rim cushion rubber 32 Chafer 35 Bead Toe 36 Bead base 130, 130a, 130b carcass cord 131 Conductive wire 132 Coated Rubber 141, 142 Belt 143 Belt cover 151 Cap Tread CL Tire equatorial plane Ri rim flange

Claims

1. a pair of bead portions; a carcass layer laid between the pair of bead portions; a belt layer provided on the tire radially outer side of the carcass layer; and a tread portion provided on the tire radially outer side of the belt layer; Including, The carcass layer A plurality of carcass cords, a coating rubber covering the plurality of carcass cords, and a conductive linear body; Including, The pair of bead portions are a pair of bead cores; and rubber portions provided around the pair of bead cores, each of which comes into contact with the rim when the tire is attached to the rim; and At least 20% of the extension length of the conductive linear body is covered by the coating rubber in a cross section perpendicular to the extension direction of the carcass layer. tire.

2. The tire further includes an earth rubber provided in the tread portion, In the tire meridian section, one end of the earth rubber is in contact with the belt layer, and the other end of the earth rubber is exposed to the tread surface of the tread portion.

2. The tire of claim 1.

3. The volume resistivity of the carcass layer is 1×10^8 [Ω cm] or more, The volume resistivity of the rubber portion is less than 1×10^8 [Ω cm], The conductive linear body has a volume resistivity of less than 1×10^8 [Ω·cm]. The tire according to claim 1 or claim 2.

4. In a cross section in a direction perpendicular to the extending direction of the carcass layer, a distance Le1 between the center of the conductive linear body and the center of a first carcass cord adjacent to the conductive linear body; a distance Le2 between the center of the conductive linear body and the center of a second carcass cord adjacent to the conductive linear body; The relationship between the distance Lc between the center of the first carcass cord and the center of the second carcass cord is as follows: 1.0≦(Le1+Le2) / Lc≦1.6 is The tire according to claim 1 or claim 2.

5. A ratio Lc' / Lc of a distance Lc' between the centers of the other two carcass cords to a distance Lc between the centers of the first carcass cord and the second carcass cord is 0.95≦Lc′ / Lc≦1.05 is 5. The tire of claim 4.

6. The fineness Te of the conductive linear body relative to the fineness Tc of the carcass cord is 0.0050≦Te / Tc<1 is The tire according to claim 1 or claim 2.

7. The conductive wire is included in the splice portion of the carcass layer. The tire according to claim 1 or claim 2.

8. The conductive linear body has an elongation rate of 1.0% or more and 70.0% or less. The tire according to claim 1 or claim 2.

9. The conductive linear body includes a metal fiber The tire according to claim 1 or claim 2.

10. The conductive linear body is a blended yarn containing conductive fibers having a volume resistance of less than 10^8 [Ω·cm] and non-conductive fibers having a volume resistance of 10^8 [Ω·cm] or more. The tire according to claim 1 or claim 2.

11. The relationship between the periphery length L [cm] of the portion of the carcass layer including the conductive linear body that contacts the rubber portion, the thickness T [cm] of the coating rubber of the carcass layer at the portion including the conductive linear body, the volume resistivity ρ [Ω cm] of the coating rubber, and the diameter R of the conductive linear body is as follows: ρ×T / (R×L)<1.0×10^8[Ω] is The tire according to claim 1 or claim 2.

12. The ratio of the diameter of the conductive linear body to the diameter of the carcass cord is 0.1 or more and 0.8 or less. The tire according to claim 1 or claim 2.

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