JP2008012945A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively restrain permeation of air (oxygen) into a bead part 13 without lowering the performance of a rubber chafer 24. <P>SOLUTION: At least an inner surface of the ribber chafer 24 reaching a bead toe 38 from an inner end 37 in the radial direction of an inner liner 36 is covered by a covering layer 41 constituted of an air permeation preventive layer made of thermoplastic resin and a reinforcing layer made of elastomer, and consequently, it is possible to effectively restrain a state that air permeates toward a bead core 12 in the rubber chafer 24 as the inner surface of the rubber chafer 24 is blocked by the covering layer 41 from air in a tire inner chamber 17. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

    The present invention relates to a pneumatic tire in which an inner surface of a rubber chafer is covered with a coating layer.

    In general, an inner liner made of rubber having high air permeability is disposed on the inner surface of the pneumatic tire in order to prevent the air (internal pressure) filled in the pneumatic tire from leaking to the outside. However, such an inner liner does not extend to the bead toe for manufacturing reasons and the like, and its radially inner end ends slightly outside the bead toe.

  For this reason, the inner surface of the rubber chafer extending from the radially inner end of the inner liner to the bead toe is exposed to the tire inner chamber and is in direct contact with the air filled in the tire inner chamber. As a result, the air in the tire interior permeates through the rubber chafer toward the bead core, and oxygen in the air may deteriorate the rubber in the bead portion, particularly the carcass layer and the wire chafer coating rubber. there were.

In order to prevent such a situation, conventionally, for example, a pneumatic tire as described in Patent Document 1 below has been proposed.
JP 7-90125 A

  This is a rubber chafer with a total of 20 to 40% by weight of butyl rubber and / or halogenated butyl rubber, cis-1,4-polyisoprene rubber and epoxidized cis-1,4-polyisoprene rubber. A rubber composition consisting of ˜60% by weight is used, and thereby, the permeation of air (oxygen) toward the bead core is suppressed.

    However, in such a conventional pneumatic tire, since the ratio of butyl rubber and halogenated butyl rubber in the rubber composition constituting the rubber chafer is higher than before, the original role of the rubber chafer, for example, the bead portion There has been a problem that it is impossible to sufficiently prevent sagging, rim rubbing, rim sliding, and the like.

  An object of the present invention is to provide a pneumatic tire capable of effectively suppressing the permeation of air (oxygen) into the bead portion without deteriorating the performance of the rubber chafer.

    The purpose is to form a toroidal carcass layer between the bead cores, a rubber chafer disposed so as to wrap the bead core outside the carcass layer, and an inner end in the radial direction covering the inner surface of the carcass layer. In the pneumatic tire having an inner liner that overlaps the belt and a belt layer and a tread disposed radially outside the carcass layer, at least the inner surface of the rubber chafer extending from the radially inner end of the inner liner to the bead toe is heated. This can be achieved by a pneumatic tire covered with a coating layer having an air permeation preventive layer made of a plastic resin.

  In the present invention, at least the inner surface of the rubber chafer extending from the radially inner end of the inner liner to the bead toe is covered with a coating layer having an air permeation preventive layer made of a thermoplastic resin. The inner surface of the rubber chafer located between the two is blocked by the coating layer having an air permeation preventive layer from the air in the pneumatic tire, effectively preventing the air from passing through the rubber chafer toward the bead core. Can be suppressed. At this time, since it is not necessary to modify the composition of the rubber chafer, the rubber chafer can sufficiently fulfill its original role.

  Here, since the air permeation preventive layer is made of a thermoplastic resin having a high elastic modulus, it is inferior in crack resistance and bending fatigue resistance compared to rubber constituting the bead part, for example, rubber chafer, If the reinforcing layer made of an elastomer excellent in crack resistance and bending fatigue resistance is adhered and laminated to the air permeation preventive layer as described in claim 2, the crack resistance and bending fatigue resistance of the entire coating layer are improved. . Moreover, even when a crack occurs in the air permeation preventive layer, the permeation of air can be suppressed because the reinforcing layer has a certain degree of air permeation resistance.

  If the coating layer has the air permeation preventive layer and the reinforcing layer that are closely laminated as described above, the boundary between the air permeation preventive layer and the reinforcing layer is exposed at least at the radially outer end of the coating layer. From the exposed position of this boundary, air may enter between the air permeation preventive layer and the reinforcing layer, and wrinkles and blisters may occur. This can be prevented by covering the radially outer end with a cover layer and sealing the boundary between the air permeation preventive layer and the reinforcing layer.

  Here, if the above-mentioned cover layer is constituted by a part of the reinforcing layer as described in claim 4, for example, compared with the case where another member is pasted as a cover layer, molding becomes easier and cost is reduced. It can also be made. Then, as described in claim 5, such a cover layer is cut by a cutter heated from the reinforcing layer side, and a part of the reinforcing layer is melt-flowed to the air permeation preventing layer side. If comprised by this, shaping | molding of a cover layer becomes easy and it can also reduce cost.

  According to the sixth aspect of the present invention, when the pneumatic tire is mounted on the rim, the radially inner end of the covering layer is sandwiched from both sides by the bead portion and the rim. Peeling from the rubber chafer is effectively suppressed. Furthermore, if comprised as described in Claims 7 and 8, the crack resistance and bending fatigue resistance of the coating layer can be improved.

Embodiment 1 of the present invention will be described below with reference to the drawings.
Reference numeral 11 denotes a heavy-duty pneumatic radial tire mounted on a truck, a bus, etc., and this pneumatic tire 11 has a pair of bead portions 13 which form a pair (in this case, a pair). The bead core 12 may be embedded. 14 is a rim on which the pneumatic tire 11 is mounted. When the pneumatic tire 11 is mounted on the rim 14 in this way, a bead base portion (inner circumference of the bead portion 13) 15 of the pneumatic tire 11 is A sealed tire inner chamber 17 seated on the bead seat portion 16 of the rim 14 and defined by the pneumatic tire 11 and the rim 14 is filled with a predetermined pressure of air (internal pressure).

  The pneumatic tire 11 includes a sidewall portion 18 extending from the bead portion 13 toward the outside in the substantially radial direction, and a substantially cylindrical tread portion 19 that connects the radially outer ends of the sidewall portions 18 to each other. Is further provided. The pneumatic tire 11 has a carcass layer 20 extending in a toroidal shape between the bead cores 12 to reinforce the sidewall portions 18 and the tread portions 19, and both end portions in the width direction of the carcass layer 20 are formed of the bead cores 12. It is folded around.

  The carcass layer 20 is composed of at least one carcass ply 21 in this case, and the carcass ply 21 intersects the tire equator S at a cord angle of 70 to 90 degrees, that is, substantially in a radial direction. It is composed of a large number of non-stretchable reinforcing cords extending in the meridian direction and a coating rubber that covers these reinforcing cords. Reference numeral 22 denotes a stiffener made of rubber for ensuring the rigidity of the bead portion 13, and these stiffeners 22 extend from the bead core 12 along the carcass layer 20 substantially outward in the radial direction.

  In addition, a cord chafer (here, a wire chafer) 23 reinforced by, for example, a steel cord, a nylon cord, or the like is disposed in the bead portion 13, and these cord chafers 23 are disposed outside the carcass layer 20 with a bead core. It is bent along the carcass layer 20 so as to wrap around 12. 24 is a rubber chafer arranged so as to wrap the bead core 12 outside the carcass layer 20 and the cord chafer 23. These rubber chafers 24 are mainly composed of a high-modulus elastic material such as diene rubber. Yes.

  27 is a belt layer arranged radially outside the carcass layer 20, and this belt layer 27 is constituted by laminating at least two (here, three) belt plies 28 in the radial direction. 28 is composed of non-stretchable parallel reinforcing cords made of, for example, steel or aromatic polyamide, and a coating rubber covering these reinforcing cords. Here, the reinforcing cord constituting the belt ply 28 is inclined at a predetermined angle of 10 to 70 degrees with respect to the tire equator S, or extends substantially parallel to the tire equator S. In the at least two belt plies 28, the inclination directions of the reinforcing cords are opposite to each other.

  31 is a top tread as a tread disposed radially outward of the carcass layer 20 and the belt layer 27. The outer surface of the top tread 31 has, for example, a plurality of main grooves 32 extending in the circumferential direction and the main tread 32. A lateral groove (not shown) that intersects the groove 32 is formed. Reference numeral 33 denotes side treads arranged on both outer sides in the axial direction of the carcass layer 20 and the stiffener 22 in the side wall portion 18, and the radial outer ends of these side treads 33 overlap the top tread 31, while the radius thereof The inner end in the direction overlaps the rubber stiffener 24 on the outer side in the axial direction from the bead core 12.

  36 is an inner liner that is affixed to the carcass layer 20 and covers almost the entire inner surface of the carcass layer 20, and this inner liner 36 is made of a highly air-permeable rubber such as butyl rubber or halogenated butyl rubber. It is configured. Further, the radially inner end portion of the inner liner 36 overlaps with the radially outer end portion of the rubber chafer 24 located on the inner side in the axial direction from the bead core 12 on the tire inner chamber 17 side, and the radially inner end portion thereof. 37 is a predetermined distance from the bead toe 38, usually 2.0% or more of the nominal diameter of the rim 14.

  As a result, the inner surface of the rubber chafer 24 extending from the radially inner end 37 of the inner liner 36 to the bead toe 38 is exposed to the tire inner chamber 17 and directly contacts the air filled in the tire inner chamber 17. Become. As a result, the air in the tire inner chamber 17 permeates through the bead portion 13 from the exposed portion of the rubber chafer 24 toward the bead core 12, and the oxygen in the air causes the rubber in the bead portion 13, particularly the carcass layer 20, cord The coating rubber of the chafer 24 will deteriorate.

  In order to prevent such a situation, in this embodiment, at least the inner surface of the rubber chafer 24 extending from the radially inner end 37 of the inner liner 36 to the bead toe 38 is covered with a coating layer 41 having high air permeability. ing. As a result, the inner surface of the rubber chafer 24 located between the inner liner 36 and the bead toe 38 is shielded from the air in the pneumatic tire 11 (tire inner chamber 17) by the coating layer 41, and the air is rubber chafer. The situation of passing through the inside 24 toward the bead core 12 is effectively suppressed. At this time, since it is not necessary to modify the composition of the rubber chafer 24, the rubber chafer 24 can sufficiently fulfill its original role, for example, prevention of bead portion 13 sag, rim rubbing, rim sliding, and the like. .

  Here, it is sufficient that the radially outer end 42 of the covering layer 41 overlaps with the radially inner end 37 of the inner liner 36 at least in order to shield the inner surface of the rubber chafer 24 from the air. However, if the amount of overlap between the outer radial end of the coating layer 41 and the inner radial end of the inner liner 36 is 5 mm or more, the above-described air shutoff can be ensured. It is preferable to match. However, if the overlap amount exceeds 30 mm, the air blocking effect is saturated and only the adverse effect of weight increase occurs. Therefore, the overlap amount is preferably 30 mm or less.

  On the other hand, as for the inner end in the radial direction of the coating layer 41, it is sufficient to overlap at least the bead toe 38. However, the coating layer 41 is extended so that the inner end in the radial direction extends along the rubber chafer 24. It is preferable to extend the bead base portion 15 between the bead toe 38 and the bead heel 44. The reason is that in this way, when the pneumatic tire 11 is mounted on the rim 14, the radially inner end portion of the covering layer 41 is sandwiched from both sides by the bead portion 13 and the rim 14, and thereby the covering layer This is because peeling of 41 from the rubber chafer 24 can be effectively suppressed.

  The covering layer 41 has at least an air permeation preventing layer 47 made of a thermoplastic resin having high air permeation resistance. In this embodiment, as shown in FIG. In addition to the prevention layer 47, the air permeation prevention layer 47 includes first and second reinforcing layers 48 and 49 made of elastomer which are closely laminated on the rubber chafer 24 side rear surface and the tire inner chamber 17 side surface, respectively. Yes.

  This is because the air permeation preventive layer 47 is made of a thermoplastic resin having a high elastic modulus, so that it is inferior in crack resistance and bending fatigue resistance as compared with rubber constituting the bead portion 13, for example, rubber chafer 24. However, as described above, if at least one reinforcing layer 48, 49 made of an elastomer excellent in crack resistance and bending fatigue resistance is adhered and laminated on the air permeation prevention layer 47, the crack resistance of the entire coating layer 41, This is because the bending fatigue resistance is improved.

Further, even when a crack occurs in the air permeation preventive layer 47, the reinforcing layers 48 and 49 have a certain degree of air permeation resistance. it can. As described above, the air permeation preventive layer 47 has a high air permeation resistance. Here, the high air permeation resistance means that the air permeation coefficient is 1.5 × 10 ⁻⁹ cm ³ · cm / cm ^2. -The thing of sec * kPa or less is said, and in order to suppress air permeation | transmission strongly, it is preferable to use that whose air permeability coefficient is 3 * 10 < ^-15 > cm < ³ > cm / cm < ² > * sec * kPa or less.

  Examples of such a highly air-permeable thermoplastic resin include polyester resins (for example, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate), nylon (polyamide) resins (for example, nylon 6, nylon 66). , Polyvinyl resins (for example, polyvinyl chloride, polyvinylidene chloride), polyolefin resins (for example, polyethylene, polypropylene), and the like, but an epoxy compound is reacted as a resin of an ethylene-vinyl alcohol copolymer system. Since the modified ethylene-vinyl alcohol copolymer has a considerably high air permeation resistance and is excellent in crack resistance and bending fatigue resistance, it is preferably used for the air permeation prevention layer 47.

  Other thermoplastic resins such as polyamide resins (for example, nylon 46, nylon 11, nylon 12, nylon 610, nylon 612, nylon 6/66 copolymer, nylon 6/66/610 copolymer, nylon MXD6) , Nylon 6T, nylon 6 / 6T copolymer, nylon 66 / PP copolymer, nylon 66 / PPS copolymer), polyester resin (for example, polyethylene isophthalate, polyarylate, liquid crystal polyester, polyoxyalkylene diimide acid) / Aromatic polyesters such as polybutyrate terephthalate copolymer), polynitrile resins (for example, polyacrylonitrile, polymethacrylonitrile, acrylonitrile / styrene copolymer, methacrylonitrile / styrene copolymer, methacrylonitrile / styrene) / Butadiene copolymer), polymethacrylate resin (eg, polymethyl methacrylate, polyethyl methacrylate), polyvinyl resin (eg, vinyl acetate, polyvinyl alcohol, vinyl chloride / vinylidene chloride copolymer, vinylidene chloride / Methyl acrylate copolymer, vinylidene chloride / acrylonitrile copolymer), cellulose resin (eg, cellulose acetate, cellulose acetate butyrate), fluorine resin (eg, polyvinylidene fluoride, polyvinyl fluoride, polychlorofluoroethylene (PCTFE)) , Tetrafluoroethylene / ethylene copolymer), imide resins (for example, aromatic polyimide), and the like can also be used.

  On the other hand, examples of the elastomer constituting the first and second reinforcing layers 48 and 49 include diene rubber and hydrogenated products thereof (for example, natural rubber, isoprene rubber, epoxidized natural rubber, styrene-butadiene rubber, butadiene rubber, (Acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber), olefin rubber (eg ethylene propylene rubber, maleic acid-modified ethylene propylene rubber, isobutylene-isoprene rubber, isobutylene and aromatic vinyl or diene monomer copolymer, acrylic rubber) Halogen-containing rubber (for example, chloroprene rubber, hydrin rubber, chlorosulfonated polyethylene, chlorinated polyethylene, maleic acid-modified chlorinated polyethylene), silicone rubber (for example, methyl vinyl silicone rubber, dimethyl silicone rubber, Tilphenyl vinyl silicon rubber), fluorine rubber (for example, vinylidene fluoride rubber, fluorine-containing vinyl ether rubber, tetrafluoroethylene-propylene rubber, fluorine-containing silicon rubber, fluorine-containing phosphazene rubber), thermoplastic elastomer (for example, Styrene elastomer, olefin elastomer, ester elastomer, urethane elastomer, polyamide elastomer). Among the elastomers, the thermoplastic urethane-based elastomer can greatly improve the crack resistance and the bending fatigue resistance of the coating layer 41, and has excellent adhesiveness. Therefore, the reinforcing layers 48 and 49 It is preferable to use this as

  Here, the covering layer material formed by laminating the air permeation preventive layer 47 and the first and second reinforcing layers 48 and 49 as described above is formed by, for example, a method of melt-extruding an elastomer into a thermoplastic resin film or sheet. , Conversely, a method of melt-extruding a thermoplastic resin on an elastomer substrate, a method of co-extrusion of a thermoplastic resin, an elastomer, a method of laminating an elastomer film, a sheet, etc. on a thermoplastic resin film, a sheet, Or it can carry out by the method of sticking an elastomer film on a thermoplastic resin film on a drum at the time of tire fabrication.

  Further, the coating layer 41 as described above, for example, after pasting a belt-like coating layer material on the drum, the inner liner 36, the rubber chafer 24, and the carcass layer 20 are sequentially pasted on the drum, and thereafter The raw tire may be formed by a known method, and the raw tire may be vulcanized to be provided on the pneumatic tire 11, and a belt-shaped coating layer material may be provided on the bead portion 13 of the raw tire via an adhesive. After pasting, it may be provided on the pneumatic tire 11 by vulcanization, and further, by sticking a belt-like coating layer material to the bead portion 13 of the vulcanized pneumatic tire 11 via an adhesive, The pneumatic tire 11 may be provided.

  Furthermore, when the sheet of the covering layer material formed as described above is wide and long, the strip-shaped covering layer material having a predetermined width is cut out from the sheet one after another by the cutter, and the strip-shaped covering layer material is described above. However, after such a belt-like covering layer material is attached to the pneumatic tire 11, the cutting end by the cutter is the radially outer end 42 of the covering layer 41 and the bead base portion. The extended end 53 is in close contact with 15.

  Here, at least at the radially outer end 42 of the covering layer 41 (only when the radially inner end of the covering layer 41 overlaps the bead toe 38, even at the radially inner end), the air permeation preventing layer 47 and the first, Since the boundary between the second reinforcing layers 48 and 49 is exposed in the tire inner chamber 17, the air in the tire inner chamber 17 is exposed to the air permeation preventing layer 47 and the first and second reinforcing layers 48 and 49 from the exposed position of the boundary. After intruding, the cord chafer 23 may stay near the radially outer end of the inner side in the axial direction and develop into wrinkles and blisters.

  For this reason, in this embodiment, at least the radially outer end 42 of the covering layer 41 (and the radially inner end when the radially inner end is also exposed) is covered with the thin cover layer 55, and the air The boundary between the permeation preventive layer 47 and the first and second reinforcing layers 48 and 49 is sealed. In this way, the intrusion of air between the air permeation preventive layer 47 and the first and second reinforcing layers 48 and 49 is prevented, and the generation of wrinkles and blisters described above can be prevented.

  Here, when the first and second reinforcing layers 48 and 49 are made of a thermoplastic elastomer, the cover layer 55 described above can be easily molded and the cost can be reduced by molding as follows. That is, as shown in FIG. 3, after placing a wide and long coating layer material on the anvil 57, the cutter 58 is used to cut the coating layer material and cut the strip-shaped coating layer material. While heating, the coating layer material is cut from one of the reinforcing layers, here the second reinforcing layer 49 side, by the heated cutter 58, whereby a part of the second reinforcing layer 49 is air-blocking layer. On the 47th side, in this case, the first reinforcing layer 48 is melt-flowed to be molded.

  And when cutting a coating layer raw material with the cutter 58 as mentioned above, it is preferable to make the temperature of this cutter 58 into the range of 150-400 degreeC. The reason for this is that if the temperature of the cutter 58 is less than 150 degrees, the melt flow of the reinforcing layer may be insufficient, and sealing of the boundary by the cover layer 55 may be uncertain, whereas if it exceeds 400 degrees This is because the melt flow of the reinforcing layer becomes excessive, and the shape of the cut end may become unstable or burnt.

  In addition, a liquid elastomer is applied to the cut end of the belt-shaped covering layer material, or a sheet-like elastomer is attached with an adhesive to cover the cut end (at least radially outside the covering layer 41 with a cover layer separate from the band-shaped covering layer material). Although it is conceivable to cover the end 42), in this case, the molding is troublesome and the cost is increased. On the other hand, if the cover layer 55 is constituted by a part of the first or second reinforcing layer 48 or 49, the molding becomes easy and the cost can be reduced.

    FIG. 4 is a diagram showing a second embodiment of the present invention. In this embodiment, the covering layer 61 is made of an air permeation preventive layer 62 made of a thermoplastic resin having high air permeation resistance, and an elastomer laminated tightly on the surface of the air permeation preventive layer 62 on the tire inner chamber 17 side. The air permeation preventive layer 62 is affixed directly to the inner surface of the rubber chafer 24 extending from at least the radially inner end 37 of the inner liner 36 to the bead toe 38 with, for example, an adhesive. . Other configurations and operations are the same as those of the first embodiment.

    In the above-described embodiment, the present invention is applied to the pneumatic tire 11 for trucks and buses. However, the present invention can also be applied to tires for passenger cars, large tires for construction machines, and aircraft tires. . In the above-described embodiment, the inner liner 36 is made of rubber. However, in the present invention, the inner liner 36 may be made of the same material as the coating layer.

    Next, test examples will be described. In this test, the conventional tire in which the bead portion is not provided with the coating layer, the implementation tire 1 in which the bead portion is provided with the coating layer having the three-layer structure as shown in FIGS. 1 and 2, and the bead portion in FIG. Example tire 2 provided with a coating layer having a two-layer structure as shown was prepared. Here, the size of each tire was 275 / 70R22.5, and the applicable rim was 8.25 × 22.5.

  In the tires 1 and 2, the air permeation preventive layer is made of a modified ethylene-vinyl alcohol copolymer, while the reinforcing layer is made of a thermoplastic urethane elastomer, and the thicknesses thereof are 60 μm and 60 μm, respectively. It was. Furthermore, the amount of overlap between the radially outer end of the coating layer and the radially inner end of the inner liner is 20 mm, and the coating layer material is cut with a 300 ° C. A cover layer was provided.

  Next, after mounting each of these tires on an applicable rim, the vehicle was filled with 900 kPa and traveled on a drum at 100,000 km at a speed of 60 km / h while applying a load of 30.9 kN. Thereafter, the coating rubber of the carcass layer around the bead core was taken out, and the elongation until breaking was measured. As a result, when the conventional tire is represented by an index of 100, it is 125 for the implementation tire 1 and 123 for the implementation tire 2, and it can be understood that the deterioration of the rubber inside the bead portion is effectively suppressed in the implementation tire.

  The present invention can be applied to the industrial field of pneumatic tires in which the inner surface of a rubber chafer is covered with a coating layer.

It is meridian sectional drawing which shows Embodiment 1 of this invention. It is meridian sectional drawing of the radial direction outer end vicinity of a coating layer. It is sectional drawing explaining the cutting state of a coating layer raw material. It is meridian sectional drawing similar to FIG. 2 which shows Embodiment 2 of this invention.

Explanation of symbols

11 ... Pneumatic tire 12 ... Bead core
15 ... Bead base 20 ... Carcass layer
24 ... Rubber chafer 27 ... Belt layer
31 ... Tread 36 ... Inner liner
37 ... Radial inner end 38 ... Bead toe
41… Coating layer 44… Bead heel
47… Air permeation prevention layer 48, 49… Reinforcement layer
55 ... Cover layer 58 ... Cutter

Claims (8)

    A carcass layer extending in a toroidal manner between the bead cores, a rubber chafer arranged to wrap the bead core outside the carcass layer, an inner liner covering the inner surface of the carcass layer and having a radially inner end overlapping the rubber chafer, In a pneumatic tire provided with a belt layer and a tread disposed radially outside the carcass layer, at least the inner surface of the rubber chafer from the inner end in the radial direction of the inner liner to the bead toe is air permeable made of thermoplastic resin. A pneumatic tire characterized by being covered with a covering layer having a prevention layer.     The pneumatic tire according to claim 1, wherein the coating layer further includes a reinforcing layer made of an elastomer closely adhered to the air permeation preventive layer.     The pneumatic tire according to claim 2, wherein at least a radially outer end of the covering layer is covered with a cover layer to seal a boundary between the air permeation preventive layer and the reinforcing layer.     The pneumatic tire according to claim 3, wherein the cover layer comprises a part of a reinforcing layer.     When the reinforcing layer is made of a thermoplastic elastomer, the cover layer is cut with a cutter heated from the reinforcing layer side to melt and flow a part of the reinforcing layer to the air permeation preventive layer side to constitute a cover layer. The pneumatic tire according to claim 4.     The pneumatic tire according to any one of claims 1 to 5, wherein an inner end portion in a radial direction of the covering layer extends to a bead base portion between a bead toe and a bead heel.     The pneumatic tire according to any one of claims 1 to 6, wherein the air permeation preventive layer is made of a modified ethylene-vinyl alcohol copolymer.     The pneumatic tire according to claim 1, wherein the reinforcing layer is made of a thermoplastic urethane-based elastomer.

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