Pneumatic tire

Abstract

Provided is a pneumatic tire that ensures a power supply path while improving the overall performance of low fuel consumption, durability, and steering stability during high-speed travel. A pneumatic tire characterized by having a tread portion, a pair of bead portions, a carcass, and a pair of lap portions, the carcass including at least one piece of carcass ply having a main portion extending from one side to the other of the bead portions and a pair of turn-back portions turned back and wound at the bead portions, the lap portions being disposed on the tire radial outer side of the turn-back portions of the carcass ply; the tire being provided with at least one electrically conductive wire extending from the lap portions to at least the tread portion.

Description

Technical Field

[0001] This invention relates to an inflatable tire. Background Technology

[0002] In recent years, pneumatic tires have tended to incorporate higher levels of silica in their tread and sidewall rubber. While silica offers advantages such as reduced rolling resistance and improved wet grip, its poor conductivity leads to increased tire resistance. In tires with higher resistance, static electricity accumulates, potentially causing radio noise and other forms of electromagnetic interference.

[0003] Patent document 1 discloses an inflatable tire, characterized in that when the tread is made of an insulating material or a poorly conductive material, a conductive component comprising a conductive layer made of a good conductive material is disposed on the radial inner side of the tire, and the conductive component is exposed on the tread surface of the tire at at least one location in the circumferential direction of the tire, thereby releasing static electricity generated by the vehicle body from the tread surface to the road surface.

[0004] [Existing Technical Documents]

[0005] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 09-071112 Summary of the Invention

[0007] [The problem the invention aims to solve]

[0008] However, even with tires like those in Patent Document 1, when a significant amount of silica is incorporated into the sidewalls, the conductive pathways become disconnected, leading to static electricity accumulation in the vehicle. Further improvements are needed to enhance the tire's discharge characteristics.

[0009] The purpose of this invention is to provide a pneumatic tire that, while ensuring the electrical path, improves the overall performance of low fuel consumption, durability, and handling stability at high speeds.

[0010] [Methods for solving the problem]

[0011] This invention relates to the following pneumatic tires.

[0012] A pneumatic tire having a tread portion, a pair of bead portions, a carcass and a pair of overlapping portions, the carcass comprising at least one carcass ply having a main body portion extending from one side of the bead portions to the other side and a pair of folded portions folded back around the bead portions, the overlapping portions being disposed radially outside the tire of the folded portions of the carcass ply.

[0013] The tire is provided with at least one conductive wire extending from the overlap portion to at least the tread portion.

[0014] [Invention Effects]

[0015] According to the present invention, a pneumatic tire can be provided that, while ensuring the electrical path, improves the overall performance of low fuel consumption, durability, and handling stability at high speeds. Attached Figure Description

[0016]

【 Figure 1 [Image 1] is a cross-sectional view of an inflatable tire according to an embodiment of the present invention, based on a plane passing through the tire's axis of rotation.

[0017]

Figure 2

[0018]

【 Figure 3 [Illustration] is a perspective view of a composite filament constituting a conductive filament in one embodiment.

[0019]

【 Figure 4 [Illustration] is a perspective view of a composite filament constituting a conductive filament in another embodiment.

[0020]

【 Figure 5 The diagram shows the shape of a conductive filament extending in a wavy pattern.

[0021]

【 Figure 6 The diagram above is a schematic cross-sectional view of a tire resistance measuring device.

[0022] [Explanation of Labels in the Attached Image]

[0023] 1: Pneumatic tires

[0024] 1A: The outermost radial surface of the tire

[0025] 1B: The surface on the radially inner side of the tire

[0026] 2: Fetal face

[0027] 3: Sidewall

[0028] 4: Bead area

[0029] 5: Tire bead core

[0030] 6: Fetus

[0031] 6A: Carcass ply

[0032] 6a: Main body

[0033] 6b: Turnaround section

[0034] 6c: Tire cord

[0035] 7A: Buffer layer

[0036] 7a, 7b: Buffer layer curtain fabric

[0037] 7B: Straps

[0038] 7C: Base tread

[0039] 7D: Tire tread surface

[0040] 8: Overlap section

[0041] 9: Conductive wire

[0042] 10: Composite yarn

[0043] 11: Conductive fibers

[0044] 12: Non-conductive fibers

[0045] W SW Sidewall thickness

[0046] W CC Tire thickness

[0047] L Y The length of the conductive wire from the end inside the overlap to the end of the folded-back section of the tire cord.

[0048] H: Height of the overlap

[0049] a1: Amplitude of the conductive wire

[0050] L1: Wavelength of the conductive wire

[0051] 41: Insulation board

[0052] 42: Metal plate

[0053] 43: Tire mounting shaft

[0054] 44: Resistance measuring instrument

[0055] T: Test tire

[0056] R: Wheel rim. Detailed Implementation

[0057] The pneumatic tire involved in this embodiment is as follows.

[0058] A pneumatic tire having a tread portion, a pair of bead portions, a carcass and a pair of overlapping portions, the carcass comprising at least one carcass ply having a main body portion extending from one side of the bead portions to the other side and a pair of folded portions folded back around the bead portions, the overlapping portions being disposed radially outside the tire of the folded portions of the carcass ply.

[0059] The tire is provided with at least one conductive wire extending from the overlap portion to at least the tread portion.

[0060] With the above configuration, (a) at least one conductive wire extends from the overlap portion in contact with the rim to the tread portion, thereby forming a conductive path from the rim to the tread portion, which helps to improve the discharge characteristics of the pneumatic tire.

[0061] Furthermore, it is believed that in a tire with such a configuration, (b) by positioning the end of the conductive wire within the overlap portion close to the end of the folded portion of the tire body, the end of the conductive wire is less likely to become a breakage point, thus improving tire durability; (c) by reducing the diameter of the conductive wire, the weight is reduced, thus improving fuel efficiency; and (d) by reducing the stress when the conductive wire is stretched, the restraining force in the tire width direction becomes more uniform in the circumferential direction, thus improving handling stability at high speeds.

[0062] Therefore, it is believed that, in addition to (a), (b), (c) and (d) can also play a synergistic role in ensuring the power supply path while improving the overall performance of low fuel consumption, durability and handling stability at high speeds.

[0063] The aforementioned at least one conductive wire is preferably disposed on the outer side of the folded portion of the tire carcass and on the outer side of the main body portion of the tire carcass.

[0064] With the above configuration, the process of configuring conductive wires becomes easier.

[0065] The length of the conductive wire from the end of the overlapping portion to the end of the folded portion of the tire cord is preferably 15 mm or less.

[0066] The shorter the length of the conductive filament, the more it can be suppressed from becoming a breakage point, thus improving the durability of the pneumatic tire.

[0067] In at least one of the above-mentioned carcass plies, the carcass adhesive rubber constituting the carcass plies closest to the outer surface of the tire contains a filler, the filler containing silica, and the content of the silica relative to 100% by mass of the filler is preferably greater than 50% by mass.

[0068] Even though the aforementioned tire carcass rubber is a silica-rich formula with silica as the main component, it is connected by conductive wires from the overlapping part in contact with the rim to the tread, forming a conductive path, thus improving the discharge characteristics of the pneumatic tire.

[0069] The pneumatic tire further has a sidewall, the sidewall rubber constituting the sidewall containing a filler containing silica, the silica content being preferably greater than 50% by mass relative to 100% by mass of the filler.

[0070] Even though the aforementioned sidewall rubber is a silica-rich formula with silica as the main component, it is connected by conductive wires from the overlap part in contact with the rim to the tread part, forming a conductive path, thus improving the discharge characteristics of the pneumatic tire.

[0071] Of the at least one carcass ply fabric mentioned above, the thickness of the carcass ply fabric closest to the outer surface of the tire is preferably 0.5 mm or more.

[0072] Even though the thickness of the tire carcass cord is relatively thick, it is connected by conductive wires from the overlap part in contact with the rim to the tread area, forming a conductive path, which can improve the discharge characteristics of the pneumatic tire.

[0073] The thickness of the tire sidewall is preferably 1.0 mm or more.

[0074] Even though the sidewall thickness is relatively thick, the conductive wires connect the lap joint that contacts the rim to the tread area, forming a conductive path, which improves the discharge characteristics of the pneumatic tire.

[0075] The stress at 1% elongation of the conductive wire is preferably 13N or less.

[0076] This is because even when large deformations are applied locally to the tire, the breakage of the conductive wires can be suppressed.

[0077] The diameter of the conductive wire is preferably 0.03 mm or more and 1.00 mm or less.

[0078] This is because it can improve electrical conductivity without compromising the appearance of the tire.

[0079] The elongation at break of the aforementioned conductive wire is preferably 3% or more and 20% or less.

[0080] This is because even when large deformations are applied locally to the tire, the breakage of the conductive wires can be suppressed.

[0081] In this specification, as long as the spirit of the invention is not violated, the numerical values ​​accompanying "above," "greater than," "below," or "less than" the boundaries of a numerical range can be arbitrarily combined to form a numerical range. Furthermore, these numerical values ​​can also be combined with the values ​​in the embodiments as their upper or lower limits to form a numerical range. A numerical range thus formed, when represented as a range including boundary values, can be interpreted as simultaneously representing a numerical range that does not include its boundary values ​​in any alternative form, as long as the spirit of the invention is not violated. Therefore, for example, a numerical range represented as a range including boundary values ​​at both ends can be interpreted as a numerical range that does not include either boundary value or a numerical range that does not include both boundary values, as long as the spirit of the invention is not violated. Furthermore, a numerical range represented as a numerical range including only one boundary value and excluding the other boundary value can be interpreted as a numerical range that does not include both boundary values, as long as the spirit of the invention is not violated.

[0082] <Definition>

[0083] "Standard condition" refers to the tire being assembled on a standard rim and filled with air at the standard internal pressure under no load. Unless otherwise specified, tires in standard condition should be used.

[0084] Unless otherwise specified, "the dimensions of each part of the tire" are specific values ​​that appear on the outer surface of the tire in its normal state. On the other hand, "the dimensions of each part of the tire" that exist inside the tire, on the tire's cut surface, are specific values, for example, when the tire is cut in a plane containing the tire's axis of rotation, and the cut tire piece is held in the rim width of a normal rim.

[0085] "Standard rim" refers to the rim specified for each tire within a specification system that includes the tire's base specifications. For example, for JATMA (Japan Automobile Tire Association), it refers to the standard rim with the applicable dimensions listed in the "JATMA YEAR BOOK"; for ETRTO (The European Tyre and Rim Technical Organization), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL"; and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." The order of reference is JATMA, ETRTO, and TRA, and if an applicable dimension is available, that dimension is followed. Furthermore, in the case of tires not specified in the specifications, it refers to the narrowest rim among the smallest diameter rims that can be mounted on the tire rim and maintain internal pressure (i.e., prevent air leakage between the rim and tire).

[0086] "Standard tire pressure" refers to the air pressure specified for each tire in the specification system, including the tire's underlying specifications. For JATMA, it's the "maximum pressure"; for ETRTO, it's the "inflation pressure"; and for TRA, it's the maximum value recorded in the table "Tire Load Limits, ATVARIOUS, COLD Inflation Pressures." It is referenced in the same order as standard rims: JATMA, ETRTO, TRA. If an applicable size is available, its specification is followed. Furthermore, for tires not specified in the specifications, it refers to the standard tire pressure (of which 250 kPa or higher) for other tire sizes (specified in the specifications) listed using the aforementioned standard rims as the standard rim. Additionally, if multiple standard tire pressures of 250 kPa or higher are listed, the minimum value is used.

[0087] "Standard load capacity (kg)" refers to the load capacity specified for each tire within the specification system, including the tire's underlying specifications. For JATMA, it refers to the maximum load capacity; for ETRTO, it refers to "load capacity (LOADCAPACITY)"; and for TRA, it refers to the maximum value recorded in the table "Tire Load Limits at Various Cold Inflation Pressures (TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES)". Similar to "standard rim" and "standard internal pressure", it follows the order JATMA, ETRTO, TRA, and is subject to this specification. Furthermore, for tires not specified in the specification, the maximum load capacity W will be calculated separately. L Set to normal load capacity.

[0088] Maximum load capacity W L (kg) is calculated using the following formula. "V" is the virtual volume of the tire (mm). 3 In this context, "Dt" represents the tire's outer diameter (mm) under normal conditions, "Ht" represents the tire's cross-sectional height (mm) in the radial direction based on a plane containing the tire's axis of rotation, and "Wt" represents the tire's cross-sectional width (mm) under normal conditions. When the tire's rim diameter is set to R, Ht can be calculated using (Dt-R) / 2. If the tire sidewall has patterns or text, Wt is a value excluding these. Furthermore, the maximum load capacity has the same meaning as the normal load capacity described above.

[0089]

Number 1

[0090]

[0091] "Tread" refers to the portion of a tire that includes the tread surface that forms the contact patch with the tire. In a cross-section of the tire based on a plane containing the tire's axis of rotation, it refers to the radially outer portion of the tire carcass. Specifically, for example, it includes the buffer layer, belts, base tread, and tread running surface.

[0092] "Overlap" refers to one of the components that make up the outer surface of the tire, and is the part that contacts the rim.

[0093] "Height of the overlap" refers to the distance from the bead baseline to the outermost point of the overlap in the tire's width direction within a cross-section of the tire, based on a plane passing through the tire's axis of rotation. Figure 1 In Chinese, H represents the character.

[0094] "Thickness of the tire carcass cords" refers to the thickness of the rubber covering the tire carcass cords from the inner surface of the tire to the outer surface, measured at the tire's maximum width position. The tire's maximum width position refers to the position where the tire's width is greatest in the direction of the tire's rotation axis, based on a cross-section of the tire with a plane passing through the tire's axis of rotation (the same applies below).

[0095] "Sidewall thickness" refers to the thickness of the sidewall from the inner surface of the tire to the outer surface of the tire, measured at the maximum width of the tire.

[0096] "The length of the conductive wire from the end inside the overlap to the end of the folded-back section of the tire cord" refers to: Figure 1 L Y The length (mm) is indicated.

[0097] <Determination Method>

[0098] The diameter of the conductive filament is determined according to JIS L 1017:2002 concerning chemical fiber tire cords. The conductive filaments are grouped into sets of four, aligned without slack, and arranged parallel to each other. The width of this group is measured at five points and taken as its average value, accurate to 0.01 mm. Ideally, conductive filaments should be collected from new tires in a form where their physical properties remain unchanged (the same applies to the measurement methods for conductive filaments described below).

[0099] The "elongation at break of conductive filament (%)" is determined according to JIS L 1017 "Test method for chemical fiber tire cord", which involves a tensile test performed at a clamping interval of 250 mm and a tensile speed of 300 ± 20 mm / min. The result is the elongation (%) of the conductive filament when it is cut.

[0100] "Stress at 1% elongation of conductive filament" refers to the stress measured when a conductive filament of a specified length (excluding the clamping end of the testing machine, e.g., 300-800 mm) suitable for tires is stretched to a straight position using a tensile testing machine, and this stress is measured as the stress when stretched by 1%. Here, "straight position" means the conductive filament is arranged vertically and stretched by its own weight or a small force. "Stress" refers to the force generated when the conductive filament is stretched with a specified deformation.

[0101] The electrical conductivity of the tire was determined by the method described in the examples described later.

[0102] The nitrogen adsorption specific surface area (N2SA) of carbon black was determined according to JIS K 6217-2:2017.

[0103] "Nitrogen adsorption specific surface area (N2SA) of silica" is determined by the BET method according to ASTM D3037-93.

[0104] The "average first-order particle size" is the value obtained by taking pictures of particles with a transmission or scanning electron microscope and calculating the arithmetic mean of the particle sizes of 400 particles. When the particle shape is spherical, the diameter of the sphere is set as the particle size; when the particle shape is not spherical, the diameter of the equivalent circle (the positive square root of {4 × (particle area) / π}) is calculated from the microscope image and set as the particle size.

[0105] <Pneumatic Tires>

[0106] like Figure 1 As shown, the pneumatic tire 1 of this embodiment has a pair of bead portions 4, a tire body 6, a pair of overlapping portions 8, and a conductive wire 9 extending from the overlapping portions 8 to the tread portion 2. The tire body 6 is composed of a body portion extending from one side of the bead portions 4 to the other side and a pair of folded portions that are folded back and wound around the bead portions. The pair of overlapping portions 8 are disposed on the radial outer side of the folded portions 6b of the tire body ply.

[0107] (Fetal cord fabric)

[0108] The carcass ply 6A is constructed by covering parallel carcass cords with adhesive rubber. The carcass ply can be obtained by known methods, and in this embodiment, the manufacturing method is not particularly limited. The rubber composition constituting the adhesive rubber of the carcass ply is described below.

[0109] Figure 1 The tire carcass 6 is composed of one tire carcass cord 6A, but it can also be composed of multiple tire carcass cords 6A. In addition, it goes without saying that the tire carcass cord 6A passes through the sidewall portion 3 between the bead portion 4 and the tread portion 2.

[0110] The carcass ply 6A comprises a main body portion 6a and a folded-back portion 6b. The main body portion 6a extends, for example, between two bead portions 4. Thus, the main body portion 6a extends from the bead core 5, through the sidewall portion 3, to the tread portion 2. On the other hand, the folded-back portion 6b, connected to the main body portion 6a, is a portion folded back from the inside to the outside in the tire axle direction around the bead core 5, wrapping around the bead core 5 and the bead filler therein, extending at least to the position where it connects with the main body portion 6a. The length at which the main body portion 6a connects with the folded-back portion 6b is not particularly limited. A longer length improves tire durability, while a shorter length reduces tire weight and improves fuel efficiency. Those skilled in the art can adjust the appropriate length for each tire.

[0111] In addition to steel cords, the carcass cords may also use conventionally known cords such as polyaramid and rayon. Preferably, the carcass cords are arranged at an angle of 70 to 90 degrees relative to the tire equator C.

[0112] (Fetal face)

[0113] As the preferred form for the tire face, Figure 1 In this tire, a tread portion 2 is provided on the radial outer side of the tire body 6, consisting of a buffer layer 7A, a belt 7B, a base tread 7C, and a tread running surface 7D. The buffer layer 7A is composed of two buffer layer cords 7a and 7b that overlap radially. The buffer layer cords of each buffer layer cord 7a and 7b are covered by buffer layer adhesive rubber, and they overlap radially inside and outside the tire in the direction in which the buffer layer cords intersect each other.

[0114] The cushioning layer fabric can be obtained by known methods, and in this embodiment, the manufacturing method is not particularly limited. The filler for the cushioning layer adhesive rubber can be mainly composed of silica, but preferably mainly composed of carbon black. Here, "main component" means that the content of this component relative to 100% by mass of the filler is greater than 50% by mass, preferably greater than 60% by mass, more preferably greater than 70% by mass, further preferably greater than 80% by mass, even more preferably greater than 90% by mass, and may also be 100% by mass. In addition, as the cushioning layer cord, for example, in addition to steel cord, conventionally known cords such as polyaramid, rayon, and other organic fiber cords can also be used.

[0115] The belt is composed of a belt fabric made by covering parallel belt cords with belt adhesive rubber. The belt fabric can be obtained by known methods, and in this embodiment, its manufacturing method is not particularly limited. The filler for the belt adhesive rubber can be mainly composed of silica, but preferably mainly composed of carbon black. Here, "main component" refers to a component whose content relative to the filler is greater than 50% by mass (100% by mass), preferably greater than 60% by mass, more preferably greater than 70% by mass, further preferably greater than 80% by mass, even more preferably greater than 90% by mass, and may also be 100% by mass. Furthermore, as the belt cords, for example, in addition to steel cords, conventionally known cords such as polyaramid, rayon, and other organic fiber cords can also be used.

[0116] The base tread is a component located radially outside the tire's buffer layer or belt and radially inside the tire's tread surface. The base tread can be obtained by known methods, and in this embodiment, its manufacturing method is not particularly limited. The filler in the rubber composition constituting the base tread can be primarily silica, but preferably primarily carbon black. Here, "primary component" refers to a component whose content relative to the filler is greater than 50% by mass (100% by mass), preferably greater than 60% by mass, more preferably greater than 70% by mass, further preferably greater than 80% by mass, even more preferably greater than 90% by mass, and may also be 100% by mass.

[0117] The tread is a component that constitutes the tread contact surface. In the case of a base tread, it is the component located radially outward of the tire on the base tread. The tread can be obtained by known methods, and in this embodiment, the manufacturing method is not particularly limited. The filler in the rubber composition constituting the tread can be mainly composed of silica, but preferably mainly composed of carbon black. Here, "main component" means that the content of this component relative to 100% by mass of the filler is greater than 50% by mass, preferably greater than 60% by mass, more preferably greater than 70% by mass, further preferably greater than 80% by mass, even more preferably greater than 90% by mass, and may also be 100% by mass.

[0118] When at least one component constituting the tread is made of a rubber composition primarily composed of silica, and there are concerns about excessive resistance in the tread, a conductive component, known as a base pen, can be incorporated into the tread to extend radially from the tread surface. The base pen is a component of the rubber composition whose filler is primarily composed of carbon black, a component with low resistance. By incorporating the base pen, a conductive path can be established connecting the tread to the ground contact surface.

[0119] (Conductive wire)

[0120] Figure 1 In the pneumatic tire 1 of this embodiment, at least one conductive wire 9 is disposed on the radially outer surface of the tire carcass ply 6A, extending from the overlap portion 8 on one side to the tread portion 2. Figure 1 Type, represented by dashed lines 9, conductive wires.

[0121] The conductive wire 9 is preferably disposed between the overlap portion and the tread portion, on the outer surface of the folded portion 6b of the carcass cord 6A and on the outer surface of the main body portion 6a of the carcass cord 6A. Figure 2 yes Figure 1The cross-sectional view of the AA line shows the configuration of the conductive filament 9 arranged along the outer surface of the main body 6a of the carcass ply 6A. The AA line coincides with the position of the maximum tire width. In the cross-section of the AA line, the radially outer surface of the tire is indicated by 1A, and the radially inner surface of the tire is indicated by 1B. The conductive filament 9 arranged along the outer surface of the carcass ply in this way also helps to prevent air from being trapped between the carcass ply 6A and other rubber components during tire manufacturing. This effect is sometimes referred to as "ventilation". Furthermore, "outer surface" refers to the surface of the carcass ply 6A on the tire's outer surface 1A side, indicating the outer surface of the rubber covering the carcass ply.

[0122] From the perspective of preventing it from becoming a breakage point, the conductive thread 9 is preferably 15 mm or less in length from its end within the overlapping portion 8 to the end of the folded-back portion 6b of the tire cord fabric 6A. More preferably, this length is 12 mm or less, even more preferably 10 mm or less, and even more preferably 7 mm or less. On the other hand, from the viewpoint of ensuring a conductive path, this length is preferably 3 mm or more. More preferably, this length is 4 mm or more, and even more preferably 5 mm or more.

[0123] The resistance per unit length of conductive wire 9 is 10 Ω. 8 Below Ω / cm. Pneumatic tires equipped with such conductive wires 9 have low resistance, which can suppress the accumulation of static electricity in the vehicle.

[0124] Figure 3 An enlarged view of the conductive wire 9 in one embodiment is shown. The shape of the conductive wire 9 is not particularly limited as long as its resistance is below a specified value. For example, as... Figure 3 As shown, the conductive filament 9 can also be a composite filament 10 comprising conductive fibers 11 and non-conductive fibers 12. Alternatively, in other embodiments, the conductive filament 9 may be composed solely of conductive fibers 11. Furthermore, this specification... Figure 3 and Figure 4 In the figures other than those shown, the conductive filament 9 also includes the case of a composite filament, which is shown as a single filament material. The distinction between the conductive fiber 11 and the non-conductive fiber 12 is not shown.

[0125] For the conductive filament 9, the term "fiber" in the conductive fibers 11 and non-conductive fibers 12 constituting the composite filament 10 includes both relatively long filaments and relatively short staples. Preferably, the conductive fibers 11 and non-conductive fibers 12 are each composed of filaments. A single composite filament 10 is, for example, composed of down-twisted conductive fibers 11 and up-twisted non-conductive fibers 12. However, this configuration is not limited to this form; the composite filament 10 of this embodiment may include conductive fibers 11 and non-conductive fibers 12 in any configuration.

[0126] The conductive fiber 11 is a fiber that possesses conductivity at least to the extent necessary to prevent the generation of static electricity. Specifically, the conductive fiber 11 ideally has a resistance of 10 ohms per unit length. 5 Below Ω / cm, ideally the resistance mentioned above is 10. 2 Below Ω / cm. Furthermore, the resistance of the conductive filament 9 and the conductive fiber 11 can be adjusted by changing the ratio, type, etc. of the metal filaments, etc., as described later.

[0127] The conductive fiber 11 comprises, for example, metal filaments or carbon fibers. The conductive filament 9 may also be a blend of metal filaments and carbon fibers. Ideally, the metal filament is stainless steel. Carbon organic fibers are preferred as the carbon fiber. Such a conductive fiber 11 exhibits excellent corrosion resistance. In this specification, stainless steel refers to alloy steel as defined in JIS G 0203, containing less than 1.2% carbon and more than 10.5% chromium.

[0128] Ideally, stainless steels should be either ferrite-based or austenitic. These stainless steels exhibit excellent corrosion resistance and ductility, effectively preventing the breakage of conductive wires. Furthermore, ferrite-based stainless steels are those whose primary metallic texture is ferrite at room temperature. Austenitic stainless steels are those whose metallic texture is austenitic at room temperature.

[0129] In particular, austenitic stainless steel is non-magnetic, so the metal filaments will not become magnetized even after long-term use in tires. Therefore, it is possible to effectively suppress electromagnetic interference caused by tire rotation.

[0130] Ideally, the non-conductive fiber 12 is a material that exhibits superior adhesion to the rubber components of the tire compared to the conductive fiber 11. Furthermore, the non-conductive fiber 12 ideally possesses higher plasticity than the conductive fiber 11. The conductive filament 9 containing such a non-conductive fiber 12 readily adheres to the rubber components, thereby improving tire productivity and tire durability. From this perspective, the non-conductive fiber 12 may, for example, be made of a plastic material. More specifically, the non-conductive fiber 12 of this embodiment contains polyester or polyamide.

[0131] As a result of the materials described above, the non-conductive fiber 12 has conductivity that, compared to the conductive fiber 11, is only to a degree that cannot be expected to prevent static electricity. In this embodiment, the resistance per unit length of the non-conductive fiber 12 is not particularly limited; based on the above configuration, for example, the resistance per unit length is greater than 10 Ω. 8 Ω / cm.

[0132] Figure 4 In the diagram, an enlarged perspective view of the cross-section of a suitable composite wire 10 is shown, representing a conductive wire 9 as an alternative embodiment. Figure 4 As shown, the composite filament 10 of this embodiment, for example, has a conductive fiber 11 as the center, around which multiple non-conductive fibers 12 are twisted. Such a composite filament 10 has excellent adhesion to rubber, which helps to improve tire durability.

[0133] The conductive filament 9 in this embodiment is not limited to the above-described form. For example, it may also be a form in which conductive fibers 11 and non-conductive fibers 12 are respectively composed of short fibers and contained in the composite filament 10.

[0134] The conductive filament 9 preferably contains at least 50% non-conductive fiber 12 by weight, more preferably at least 60%, and even more preferably at 70%. On the other hand, from the viewpoint of ensuring conductivity, this weight ratio is preferably 90% or less. By keeping the weight ratio of non-conductive fiber 12 within the above range, the adhesion between the conductive filament 9 and the rubber components of the tire is improved, thereby increasing the tire's productivity and durability.

[0135] ≪Diameter≫

[0136] The diameter of the conductive filament 9 is preferably 0.03 to 1.00 mm. By making the diameter of the conductive filament 0.03 mm or more, durability is improved. On the other hand, by making the diameter of the conductive filament 1.00 mm or less, it helps to reduce tire weight and improve fuel efficiency. The diameter of the conductive filament 9 is more preferably 0.04 mm or more, and even more preferably 0.05 mm or more. Furthermore, the diameter of the conductive filament 9 is more preferably 0.50 mm or less, and even more preferably 0.30 mm.

[0137] ≪Elongation at break≫

[0138] The elongation at break (%) of the conductive wire 9 is preferably 3% to 20%, for example. Durability is improved by having an elongation at break of 3% or more. More preferably, the elongation at break of the conductive wire 9 is 4% or more, and even more preferably 5% or more. On the other hand, the diameter of the conductive wire 9 is more preferably 19% or less, even more preferably 18% or less, and even more preferably 17% or less.

[0139] Furthermore, the aforementioned elongation at break can be adjusted by the material and composition ratio of the fibers constituting the conductive filament 9, the number of twists of the conductive filament 9, and its thickness.

[0140] Stress during elongation

[0141] From the viewpoint of high-speed stability, the stress at 1% elongation of the conductive wire 9 is preferably 13N or less, more preferably 11N or less, and even more preferably 9N or less. On the other hand, the stress at 1% elongation of the conductive wire 9 is preferably 5N or more, more preferably 6N or more, and even more preferably 7N or more.

[0142] The stress at 1% elongation of the conductive filament 9 is preferably less than the stress at 1% elongation of the carcass cord 6c. Therefore, even during tire deformation, stress will not concentrate on the conductive filament 9, and the breakage of the conductive filament 9 is effectively suppressed.

[0143] Furthermore, the stress at 1% elongation can be adjusted by the material and composition ratio of the fibers constituting the conductive filament 9, the number of twists of the conductive filament 9, and its thickness. Specifically, it can be reduced by increasing the proportion of fibers with low elastic modulus, such as nylon and polyester, using short fibers instead of long fibers, increasing the number of twists, and reducing the wire diameter.

[0144] Configuration Form

[0145] Figure 5 The image shows an enlarged view of the conductive wire 9 extending in a wavy shape. (See image below.) Figure 5 As shown, since the conductive wire 9 in this embodiment is arranged in a wavy shape, it can be appropriately extended according to the deformation of the tire, thus suppressing its breakage and maintaining the discharge characteristics.

[0146] The conductive wire 9 extends in a wavy shape, for example, with an amplitude a1 (peak-to-peak amplitude) of 2.0 mm or less. Ideally, the amplitude a1 is 0.5 to 1.5 mm. This suppresses breakage of the conductive wire 9 and reduces the increase in tire weight caused by the conductive wire 9. From the same point of view, the wavelength L1 of the conductive wire 9 is preferably 100 mm or less, for example. Specifically, the wavelength L1 is preferably 30 to 80 mm.

[0147] like Figure 1As shown, the tread portion 2 and sidewall portion 3 deform more during driving than the bead portion 4. Therefore, the conductive wires 9 tend to be stretched more in the tread portion 2 and sidewall portion 3. From this perspective, the amplitude of the conductive wires 9 in the tread portion 2 is ideally greater than the amplitude of the conductive wires 9 in the bead portion 4. Furthermore, the amplitude of the conductive wires 9 in the sidewall portion 3 is ideally greater than the amplitude of the conductive wires 9 in the bead portion 4. Thus, the increase in tire weight caused by the conductive wires 9 can be suppressed while effectively preventing the breakage of the conductive wires 9 in the more deformed portions.

[0148] In the aforementioned wavy conductive wire 9, the center of its amplitude does not extend in a straight line along the radial direction. Ideally, the center of the amplitude is arranged from the overlap on one side to the tread portion 2, with an amplitude of about 50 to 150 mm in the tire circumference and a larger wave shape (about 0.25 to 0.75 cycles from the overlap on one side to the tread portion). That is, the conductive wire 9 of this embodiment preferably extends in a wavy shape with the aforementioned smaller amplitude a1, while forming the aforementioned larger wave shape from the overlap on one side to the tread portion. As a result, the breakage of the conductive wire 9 is suppressed, and thus the maintenance of discharge characteristics can be expected.

[0149] ≪Number of roots≫

[0150] At least one conductive wire 9 is required in a pneumatic tire; ideally, multiple wires are arranged circumferentially around the tire. This substantially improves the conductivity of the pneumatic tire 1. From the viewpoint of improved conductivity and air permeability, the number of conductive wires 9 in the tire side view is preferably two or more, more preferably three or more. Furthermore, from the same viewpoint, the number of conductive wires is preferably twelve or less. However, the number of conductive wires is not limited to this configuration.

[0151] (Overlap section)

[0152] The overlap portion 8 is a component located radially outside the folded portion 6b of the tire carcass ply 6A, and it is the component that contacts the rim. The overlap portion can be obtained by known methods, and in this embodiment, its manufacturing method is not particularly limited. The filler in the rubber composition constituting the overlap portion is primarily carbon black. Here, "primary component" refers to a component whose content relative to the filler is greater than 50% by mass (100% by mass), preferably greater than 60% by mass, more preferably greater than 70% by mass, further preferably greater than 80% by mass, even more preferably greater than 90% by mass, and may also be 100% by mass.

[0153] (Tire sidewall)

[0154] The sidewall is the component that makes up the side of the tire, for example, such as... Figure 1The sidewall is connected to the overlap, tire carcass, and base tread, as shown. The sidewall can be obtained by known methods, and in this embodiment, there is no particular limitation on its manufacturing method. From the viewpoint of conductivity, the filler in the rubber composition constituting the sidewall is generally preferably carbon black as the main component, but in this embodiment, silica can also be the main component. This is because even when the filler in the sidewall rubber is silica as the main component, the conductivity of the tire can be ensured by using conductive filament 9. Here, "main component" refers to a component whose content relative to the filler is 100% by mass, greater than 50% by mass, preferably greater than 60% by mass, more preferably greater than 70% by mass, further preferably greater than 80% by mass, even more preferably greater than 90% by mass, and may also be 100% by mass. The case where the rubber composition constituting the sidewall is silica as the main component will be described below.

[0155] Sidewall of tire with silica as the main filler

[0156] A rubber composition constituting the tire sidewall rubber with silica as the main filler can be obtained, for example, by mixing fillers such as silica, carbon black, clay, mica, and aluminum hydroxide into a rubber component containing at least one selected from the group consisting of isoprene rubbers such as natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR); plasticizers such as oils, resins, and liquid rubbers; processing aids such as fatty acid metal salts; waxes; antioxidants; vulcanization accelerators such as stearic acid and zinc oxide; vulcanizing agents such as sulfur; and various additives such as vulcanization accelerators.

[0157] The filler described above contains silica as its main component, and may contain fillers other than silica as desired. Carbon black is preferred as a filler other than silica. The filler preferably contains both silica and carbon black, but may also consist solely of silica and carbon black. The silica content in the filler is greater than 50% by mass relative to 100% by mass of the filler, but this silica content can be greater than 60% by mass, greater than 70% by mass, greater than 80% by mass, or greater than 90% by mass.

[0158] From a reinforcing perspective, the nitrogen adsorption specific surface area (N2SA) of silica is preferably greater than 185 m². 2 / g, more preferably greater than 200m 2 / g, more preferably greater than 220m 2 / g, preferably 230m 2 / g or more. Furthermore, from the viewpoint of heat generation and processability, a value of less than 350m is preferred. 2 / g, more preferably less than 300m 2 / g, more preferably less than 250m2 / g. Furthermore, the N2SA content of silica was determined using the method described above.

[0159] From the viewpoints of heat generation and processability, the average primary particle size of silica is preferably greater than 10 nm, more preferably greater than 12 nm, and even more preferably greater than 14 nm. Furthermore, from the viewpoint of reinforcement, this average primary particle size is preferably less than 18 nm, more preferably less than 17 nm, and even more preferably less than 16 nm. The average primary particle size of silica is determined by the aforementioned measurement method.

[0160] From a reinforcing perspective, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably greater than 30 m². 2 / g, more preferably greater than 35m 2 / g, more preferably greater than 40m 2 / g. Furthermore, from the viewpoint of exothermic properties and processability, a value of less than 60m is preferred. 2 / g, more preferably less than 55m 2 / g, more preferably less than 50m 2 / g. Furthermore, the N2SA of carbon black was determined using the method described above.

[0161] From the viewpoints of exothermic properties and processability, the average primary particle size of the carbon black is preferably greater than 40 nm, more preferably greater than 43 nm, and even more preferably greater than 46 nm. Furthermore, from the viewpoint of reinforcing properties, this average primary particle size is preferably less than 54 nm, more preferably less than 52 nm, and even more preferably less than 50 nm. The average primary particle size of the carbon black is determined by the aforementioned measurement method.

[0162] As a rubber component, it is preferable to contain isoprene-based rubber, SBR, and BR, but it may also consist solely of isoprene-based rubber, SBR, and BR. Of 100 parts by weight of the rubber component, the content of isoprene-based rubber is preferably 30% by weight or more, more preferably 35% by weight or more, and even more preferably 40% by weight or more. On the other hand, this content is preferably 60% by weight or less, more preferably 55% by weight or less, and even more preferably 50% by weight or less. Of 100 parts by weight of the rubber component, the content of SBR is preferably 15% by weight or more, more preferably 20% by weight or more, and even more preferably 25% by weight or more. On the other hand, this content is preferably 45% by weight or less, more preferably 40% by weight or less, and even more preferably 35% by weight or less. Of 100 parts by weight of the rubber component, the content of BR is preferably 10% by weight or more, more preferably 15% by weight or more, and even more preferably 20% by weight or more. On the other hand, this content is preferably 40% by weight or less, more preferably 35% by weight or less, and even more preferably 30% by weight or less.

[0163] The above-mentioned rubber composition can be manufactured by known methods. For example, it can be manufactured by mixing the above-mentioned components using rubber mixing equipment such as open rolling mills or closed mixing mills (Banbury mixers, kneaders, etc.). The mixing process includes, for example, the following steps: a basic kneading step in which compounding agents and additives other than vulcanizing agents and vulcanization accelerators are mixed; and a final kneading (F-kneading) step in which vulcanizing agents and vulcanization accelerators are added to the mixture obtained in the basic kneading step and mixed. Furthermore, the above-mentioned basic kneading step can also be divided into multiple steps as desired. There are no particular limitations on the mixing conditions, but examples include: mixing at a discharge temperature of 130~170°C for 1~10 minutes in the basic kneading step and mixing at 50~110°C for 1~5 minutes in the final kneading step.

[0164] The rubber composition obtained above is extruded in an unvulcanized state into the shape of a tire sidewall, and then bonded to other tire components on a tire forming machine to form an unvulcanized tire. This unvulcanized tire is then heated and pressurized in a vulcanizing machine, thereby becoming the sidewall constituting the tire. There are no particular limitations on the vulcanization conditions; for example, crosslinking at 150-200°C for 5-40 minutes can be cited.

[0165] The thickness of the sidewall thus obtained is typically, for example, preferably 1.0 to 3.0 mm. More preferably, the sidewall thickness is 1.1 mm, even more preferably 1.2 mm, even more preferably 1.3 mm, even more preferably 1.4 mm, and even more preferably 1.5 mm. Furthermore, the sidewall thickness is more preferably 2.8 mm, even more preferably 2.6 mm, even more preferably 2.4 mm, even more preferably 2.2 mm, and even more preferably 2.0 mm. On the other hand, in this embodiment, the sidewall is made of a silica-rich formula with silica as the main component, and conductive wires connect the lap joint from the rim contact area to the tread portion to form a conductive path. Therefore, the sidewall thickness can be greater than 2.5 mm or greater than 3.0 mm.

[0166] (Rubber adhesive on tire cords)

[0167] Tire carcass cord adhesive rubber is the rubber that covers the tire carcass cords, for example, such as... Figure 1As shown, it is in contact with the overlap portion, tire sidewall, buffer layer, etc. The tire carcass cord adhesive rubber can be obtained by known methods, and in this embodiment, there is no particular limitation on its manufacturing method. From the viewpoint of conductivity, the filler constituting the tire carcass cord adhesive rubber is generally preferably a filler with carbon black as the main component, but in this embodiment, a filler with silica as the main component may also be used. This is because even if the filler of the tire carcass cord adhesive rubber is a filler with silica as the main component, the conductivity of the tire can be ensured by using conductive filament 9. Here, "main component" refers to a component whose content relative to the filler is 100% by mass, greater than 50% by mass, preferably greater than 60% by mass, more preferably greater than 70% by mass, further preferably greater than 80% by mass, even more preferably greater than 90% by mass, and may also be 100% by mass. The following describes the case where the rubber composition constituting the tire carcass cord adhesive rubber is mainly composed of silica.

[0168] ≪Carcass Cord Rubber with Silica as the Main Filler≫

[0169] A rubber composition comprising tire cord adhesive rubber with silica as the main filler can be obtained, for example, by mixing fillers such as silica, carbon black, clay, mica, and aluminum hydroxide into a rubber component containing at least one selected from the group consisting of isoprene rubbers such as natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR); plasticizers such as oils, resins, and liquid rubbers; processing aids such as fatty acid metal salts; waxes; antioxidants; vulcanization accelerators such as stearic acid and zinc oxide; vulcanizing agents such as sulfur; and various additives such as vulcanization accelerators.

[0170] The filler described above contains silica as its main component, and may contain fillers other than silica as desired. Carbon black is preferred as a filler other than silica. The filler preferably contains both silica and carbon black, but may also consist of only silica and carbon black. The silica content in the filler is greater than 50% by mass relative to 100% by mass, but may also be greater than 60%, 70%, 80%, or 90% by mass.

[0171] From a reinforcing perspective, the nitrogen adsorption specific surface area (N2SA) of silica is preferably greater than 160 m². 2 / g, more preferably greater than 165m 2 / g, more preferably greater than 170m 2 / g. Furthermore, from the viewpoint of exothermic properties and processability, a value of less than 200m is preferred. 2 / g, more preferably less than 190m 2 / g, more preferably less than 180m 2 / g. Furthermore, the N2SA content of silica was determined using the method described above.

[0172] From the viewpoints of heat generation and processability, the average primary particle size of silica is preferably greater than 16 nm, more preferably greater than 17 nm, and even more preferably greater than 18 nm. Furthermore, from the viewpoint of reinforcement, this average primary particle size is preferably less than 22 nm, more preferably less than 21 nm, and even more preferably less than 20 nm. The average primary particle size of silica is determined by the aforementioned measurement method.

[0173] From a reinforcing perspective, the nitrogen adsorption specific surface area (N2SA) of carbon black is preferably greater than 60 m². 2 / g, more preferably greater than 65m 2 / g, more preferably greater than 70m 2 / g. Furthermore, from the viewpoint of exothermic properties and processability, a value of less than 120m is preferred. 2 / g, more preferably less than 100m 2 / g, more preferably less than 80m 2 / g. Furthermore, the N2SA of carbon black was determined using the method described above.

[0174] From the viewpoints of exothermic properties and processability, the average primary particle size of the carbon black is preferably greater than 20 nm, more preferably greater than 24 nm, and even more preferably greater than 28 nm. Furthermore, from the viewpoint of reinforcing properties, this average primary particle size is preferably less than 40 nm, more preferably less than 36 nm, and even more preferably less than 32 nm. The average primary particle size of the carbon black is determined by the aforementioned measurement method.

[0175] As a rubber component, it is preferred to contain isoprene-based rubber, but it can also be composed of only isoprene-based rubber.

[0176] ≪Carcass cord fabric with silica as the main filler≫

[0177] The aforementioned rubber composition can be used to cover the tire carcass cords in an unvulcanized state to form a cord-rubber composite. This composite is then bonded to other tire components on a tire forming machine to form an unvulcanized tire. By heating and pressurizing this unvulcanized tire in a vulcanizing machine, it is transformed into the tire carcass cords. There are no particular limitations on the mixing and vulcanization conditions of the rubber composition, and they are the same as those for the sidewall rubber described above.

[0178] In the resulting carcass ply, the thickness of the ply closest to the outer surface of the tire is typically, for example, preferably 0.5 to 2.0 mm. More preferably, the thickness is 0.6 mm or more, further preferably 0.7 mm or more, and even more preferably 0.8 mm or more. Furthermore, more preferably, the thickness is 1.9 mm or less, further preferably 1.8 mm or less, further preferably 1.7 mm or less, further preferably 1.6 mm or less, and even more preferably 1.5 mm or less. On the other hand, in this embodiment, even if the carcass ply is a silica-rich formulation with silica as the main component, and conductive wires connect the ply from the overlap portion in contact with the rim to the tread portion to form a conductive path, the thickness of the carcass ply can be greater than 1.5 mm or greater than 2.0 mm.

[0179] <Tire Manufacturing Method>

[0180] As described in the section on tire sidewalls and tire carcass cords above, the pneumatic tire of this embodiment is manufactured by bonding necessary components together in an uncured state to form an uncured tire, and then heating the uncured tire. The conditions for heat curing are as described above.

[0181] The above description describes an inflatable tire according to one embodiment of the present invention. However, the present invention is not limited to the specific embodiment described above and can be implemented in various forms.

[0182]

Example

[0183] The following are examples (embodiments) that are considered preferred in practice, but the scope of the invention is not limited to these embodiments.

[0184] <Various Chemicals>

[0185] The following is a summary of various chemicals.

[0186] IR-based rubber: NR (TSR20)

[0187] SBR: Styrene-butadiene rubber (SLR6430, S-SBR manufactured by Dow Chemical, styrene content: 40% by mass, vinyl content: 20% by mol%, Tg -36℃, containing 37.5 parts by mass of oil-extended oil per 100 parts by mass of rubber composition)

[0188] BR: Butadiene rubber (UBEPOL BR (registered trademark) 150B manufactured by UBE Corporation, cis content: 97 mol%)

[0189] Carbon Black 1: SHOBLACK N550 (N2SA: 42m) manufactured by Cabot Japan Co., Ltd. 2 / g, average primary particle size: 48nm)

[0190] Carbon Black 2: SHOBLACK N330 (N2SA: 75m) manufactured by Cabot Japan Co., Ltd. 2 / g, average primary particle size: 30nm)

[0191] Silica 1: Evonik ULTRASIL 9100GR (N2SA: 230m) 2 / g, average primary particle size: 15nm)

[0192] Silica 2: ULTRASIL VN3 (N2SA: 175m) manufactured by Evonik Industries, Inc. 2 / g, average primary particle size: 18nm)

[0193] Coupling agent 1: Silane coupling agent (NXT manufactured by Momentive, 3-octanoylthiopropyltriethoxysilane)

[0194] Coupling agent 2: Silane coupling agent (Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Industries)

[0195] Oil: VivaTec500 (TDAE oil) manufactured by H&R Corporation

[0196] Resin: ExxonMobil Oppera PR383 (hydrogenated DCPD / C9 resin; resin containing dicyclopentadiene, styrene, and indene as monomers; softening point: 103℃)

[0197] Thermosetting resin: SUMIKANOL 620 (modified resorcinol resin) manufactured by Taoka Chemical Industry Co., Ltd.

[0198] Curing agent: SUMIKANOL 507AP (modified etherified hydroxymethyl melamine resin) manufactured by Taoka Chemical Industry Co., Ltd.

[0199] Wax: OZOACE 0355 (paraffin wax) manufactured by Nippon Seiwa Co., Ltd.

[0200] Antioxidant 1: NOCRAC 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0201] Antioxidant 2: NOCRAC RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0202] Zinc oxide: Zinc No. 1 manufactured by Mitsui Metals Mining Co., Ltd.

[0203] Stearic acid: TSUBAKI stearic acid beads manufactured by Nippon Oil Co., Ltd.

[0204] Sulfur: HK-200-5 (powdered sulfur containing 5% oil) manufactured by Hosoi Chemical Industry Co., Ltd.

[0205] Vulcanization accelerator 1: NOCCELLER CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS)) manufactured by Ouchi Shinshin Chemical Co., Ltd.

[0206] Vulcanization accelerator 2: NOCCELLER D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0207] Manufacturing of Uncured Tire Sidewall Rubber

[0208] According to the compounding formulation shown in Table 1, using a 1.7L closed-type Banbury mixer, the chemicals other than sulfur and vulcanization accelerator are mixed for 1-10 minutes until the discharge temperature reaches 150-160°C to obtain a compound. Then, using a twin-screw open roll mill, sulfur and vulcanization accelerator are added to the obtained compound, and kneaded for 4 minutes until 105°C is reached to obtain an unvulcanized rubber composition for tire sidewalls. Using the above unvulcanized rubber composition, the tire sidewall is extruded into shape using an extruder with a die of a specified shape to obtain unvulcanized tire sidewall rubber.

[0209] <Manufacturing of Unvulcanized Cord-Rubber Composites>

[0210] According to the compounding formula shown in Table 2, using a 1.7L closed-type Banbury mixer, the chemicals other than sulfur and vulcanization accelerator were mixed for 1-10 minutes until the discharge temperature reached 150-160°C to obtain a compound. Then, using a bi-spindle open-roll mill, sulfur and vulcanization accelerator were added to the obtained compound, and kneaded for 4 minutes until 105°C was reached to obtain an unvulcanized rubber composition for tire carcass bonding. Using the above unvulcanized rubber composition, steel cord (composition: 1×2×0.295) was covered to obtain an unvulcanized cord-rubber composite. This cord-rubber composite was used as the tire carcass ply.

[0211] <Tire Manufacturing>

[0212] Using the uncured sidewall rubber (SW formulation in Table 1) and the uncured cord-rubber composite (CT formulation in Table 2) obtained in this way as tire components, other tire components are bonded together with these tire components to form an uncured tire, conforming to the tire structure specified in Table 3. During this process, after the carcass cord is wound, conductive filaments are arranged along the outer surface of the folded portion and the outer surface of the main body of the carcass cord, extending from one side of the overlap portion through the tread portion to the other side of the overlap portion. Three of these conductive filaments are arranged at approximately equal intervals around the tire circumference. Furthermore, the conductive filaments are composite filaments formed by twisting down-twisted conductive fibers and up-twisted non-conductive fibers. The conductive fibers are metal filaments (stainless steel) or carbon organic fibers, and the non-conductive fibers are polyester, polyamide, or cotton yarn. The mass ratio of the non-conductive fibers to 100% of the conductive filaments is 80% by mass.

[0213] The uncured tires obtained in this way were pressurized at 150°C for 35 minutes to produce test tires (size: 195 / 70R15, overlap height H: 15mm, for passenger cars).

[0214] <Tire conductivity>

[0215] For each test tire, the tire's resistance was measured according to the following method to evaluate its conductivity. If the resistance value is less than 10... 10 Ω represents a sufficiently low resistance value; in this embodiment, the tire has a sufficiently low resistance value.

[0216] The method for measuring resistance is as follows. That is, as... Figure 6 As shown, a device comprising a resistor 10 ohms is used in an insulating plate 41. 12 A measuring device consisting of a metal plate 42 (with a resistance value of 10Ω or less) with a surface ground to a value of 1Ω or higher, a tire mounting shaft 43 maintaining the conductivity of the tire-rim assembly, and a resistance measuring device 44, is used to measure the resistance value of the assembly of the test tire T and the rim R, according to JATMA specifications. Furthermore, each test tire T is a tire that has been thoroughly dried beforehand, with all surface release agent and dirt removed. Other conditions are described below.

[0217] Wheel rim material: Aluminum alloy

[0218] Wheel rim size: 15×6.0J

[0219] Internal pressure: 230 kPa

[0220] Load capacity: 4.8kN

[0221] Test ambient temperature (laboratory temperature): 24℃

[0222] Humidity: 24%

[0223] The resistance measuring instrument's measuring range is 1.0 × 10⁻⁶. 3 ~1.6×10 16 Ω

[0224] Test voltage (applied voltage): 1000V

[0225] The key points of the experiment are as follows.

[0226] (1) Install the test tire T onto the rim to prepare the tire-rim assembly. At this time, use soapy water as a lubricant at the contact point between the two.

[0227] (2) After placing the tire and rim assembly in the test chamber for 2 hours, it is installed on the tire mounting shaft 43.

[0228] (3) Apply the above load to the tire and rim assembly for 0.5 minutes, remove the load and apply it for another 0.5 minutes, and then apply it for another 2 minutes.

[0229] (4) Apply a test voltage and, after 5 minutes, measure the resistance between the tire mounting shaft 43 and the metal plate 42 using a resistance measuring device 44. The above measurements are performed at 16 equal intervals along the tire circumference, and the average value of these measurements is taken as the resistance value (measured value) of the tire T.

[0230] Low fuel consumption performance

[0231] Each test tire was assembled onto a standard rim, inflated to the standard internal pressure, and subjected to a standard load. The rolling resistance coefficient (RRC) was measured on the drum of a rolling resistance testing machine at a speed of 80 km / h. The results were expressed as an index with the baseline set to 100. The higher the index, the lower the rolling resistance of the tire and the better its fuel efficiency.

[0232] <Durability>

[0233] All test tires were installed on all wheels of the vehicle (a Japanese-made FF car with a 2000cc engine). After inflating to an internal pressure of 250 kPa, the vehicle was driven for 10 laps at 50 km / h on a dry test track under overload conditions. This was followed by repeated driving at 80 km / h on a surface with uneven surfaces. Then, the vehicle was driven in laps again at 50 km / h, and the speed was gradually increased, measuring the speed at which the driver felt the abnormality. The average speed of the five drivers during this test was calculated and expressed exponentially with a baseline of 100. A higher exponent indicates better durability performance.

[0234] Handling stability at high speeds

[0235] Test tires, assembled on standard rims and inflated to the correct pressure, were installed on the vehicle. Drivers evaluated the vehicle's high-speed stability using their senses. Specifically, after acclimatizing to a test track on dry roads, the vehicle was driven at approximately 120 km / h, undergoing lane changes. Each driver evaluated the presence of swaying on a five-point scale (1 point: significant swaying felt) to 5 points (5 points: no swaying felt). The total score from 20 drivers was calculated, and a baseline of 100 was used to represent the index. A higher index indicates better handling stability at high speeds.

[0236] Table 1

[0237]

[0238] Table 2

[0239]

[0240] Table 3

[0241]

[0242] <Implementation Method>

[0243] Examples of embodiments of the present invention are shown below.

[0244] <1> A pneumatic tire, characterized in that it is a pneumatic tire having a tread portion, a pair of bead portions, a carcass and a pair of overlapping portions, the carcass comprising at least one carcass ply having a main body portion extending from one side of the bead portions to the other side and a pair of folded portions folded back around the bead portions, the overlapping portions being disposed on the tire radially outer side of the folded portions of the carcass ply.

[0245] The tire is provided with at least one conductive wire extending from the overlap portion to at least the tread portion.

[0246] <2> According to the above <1> The pneumatic tire wherein at least one conductive wire is disposed on the outer side of the folded portion of the tire carcass and on the outer side of the main body portion of the tire carcass.

[0247] <3> According to the above <1> or <2> In the pneumatic tire, the length of the conductive wire from its end in the overlapping portion to the end of the folded portion of the tire carcass is 15 mm or less, preferably 12 mm or less, more preferably 10 mm or less, and even more preferably 7 mm or less.

[0248] <4> According to the above <1> ~ <3> In any one of the pneumatic tires, wherein the carcass rubber constituting the carcass cord closest to the outer surface of the tire contains a filler.

[0249] The filler contains silicon dioxide.

[0250] The content of silica relative to 100% by mass of the filler is greater than 50% by mass, preferably greater than 60% by mass, more preferably greater than 70% by mass, even more preferably greater than 80% by mass, and even more preferably greater than 90% by mass.

[0251] <5> According to the above <1> ~ <4> The pneumatic tire described in any one of the following examples, wherein it is a pneumatic tire further having a sidewall.

[0252] The sidewall rubber constituting the tire sidewall contains fillers.

[0253] The filler contains silicon dioxide.

[0254] The content of silica relative to 100% by mass of the filler is greater than 50% by mass, preferably greater than 60% by mass, more preferably greater than 70% by mass, even more preferably greater than 80% by mass, and even more preferably greater than 90% by mass.

[0255] <6> According to the above <1> ~ <5> In any one of the pneumatic tires, the thickness of the carcass ply closest to the outer surface of the tire is 0.5 mm or more, preferably 0.6 mm or more, more preferably 0.7 mm or more, and even more preferably 0.8 mm or more.

[0256] <7> According to the above <5> The pneumatic tire wherein the sidewall thickness is 1.0 mm or more, preferably 1.1 mm, more preferably 1.2 mm, even more preferably 1.3 mm, even more preferably 1.4 mm, and even more preferably 1.5 mm.

[0257] <8> According to the above <1> ~ <7> In any one of the pneumatic tires, the stress at 1% elongation of the conductive filament is 13N or less, preferably 11N or less, and more preferably 9N or less.

[0258] <9> According to the above <1> ~ <8> In any one of the pneumatic tires, the diameter of the conductive wire is 0.03 mm or more and 1.00 mm or less, preferably 0.04 mm or more and 0.50 mm or less, and more preferably 0.05 mm or more and 0.30 mm or less.

[0259] <10> According to the above <1> ~ <9> In any one of the pneumatic tires, the breaking elongation of the conductive filament is 3% or more and 20% or less, preferably 4% or more and 19% or less, more preferably 5% or more and 18% or less, and even more preferably 5% or more and 17% or less.

Claims

1. A pneumatic tire, characterized in that, It is an inflatable tire having a tread, a pair of bead portions, a carcass and a pair of overlapping portions, wherein the carcass includes at least one carcass ply having a main body portion extending from one side of the bead portions to the other side and a pair of folded portions folded back around the bead portions, and the overlapping portions are disposed on the radially outer side of the folded portions of the carcass ply. The tire is provided with at least one conductive wire extending from the overlap portion to at least the tread portion.

2. The pneumatic tire according to claim 1, wherein, The at least one conductive wire is disposed on the outer side of the folded portion of the tire carcass and on the outer side of the main body portion of the tire carcass.

3. The pneumatic tire according to claim 1 or 2, wherein, The length of the conductive wire from its end within the overlap portion to the end of the folded portion of the tire cord is 3 mm or more and 15 mm or less.

4. The pneumatic tire according to claim 1 or 2, wherein, In the at least one carcass ply, the carcass adhesive rubber constituting the carcass ply closest to the outer surface of the tire contains a filler. The filler contains silicon dioxide. The content of silica is greater than 50% by mass relative to 100% of the filler.

5. The pneumatic tire according to claim 1 or 2, further comprising a sidewall. The sidewall rubber constituting the tire sidewall contains fillers. The filler contains silicon dioxide. The content of silica is greater than 50% by mass relative to 100% of the filler.

6. The pneumatic tire according to claim 1 or 2, wherein, Of the at least one carcass ply, the carcass ply closest to the outer surface of the tire has a thickness of 0.5 mm or more.

7. The pneumatic tire according to claim 5, wherein, The thickness of the tire sidewall is 1.0 mm or more.

8. The pneumatic tire according to claim 1 or 2, wherein, The stress of the conductive wire is less than 13N when it is 1% elongated.

9. The pneumatic tire according to claim 1 or 2, wherein, The diameter of the conductive wire is greater than 0.03 mm and less than 1.00 mm.

10. The pneumatic tire according to claim 1 or 2, wherein, The breaking elongation of the conductive wire is above 3% and below 20%.

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