AIR TIRES AND METHOD FOR MAKING AN AIR TIRES

Abstract

Pneumatic tires (1), comprising: a running surface section (2); a belt layer (14) arranged in the tread section (2); and a belt cover layer (15) which is arranged on an outer side in a tire radial direction of the belt layer (14), wherein the belt cover layer (15) comprises the following: two layers with full coverage (40) arranged between shoulder areas (ash) on both sides in a tire width direction and layered in the tire radial direction; and a narrow cover (45) having a width in the tire width direction that is narrower than the widths of the full covers (40), wherein the narrow cover (45) is located at a position between the two layers of the full covers (40) and on an inside in the tire width direction with respect to the shoulder areas (ash), wherein the narrow cover (45) has a width in the tire width direction in a range of not less than 5 mm to not more than 40 mm.

Description

Technical area

[0001] The present invention relates to a pneumatic tire and a method for manufacturing a pneumatic tire. State of the art

[0002] Some prior art pneumatic tires have met performance expectations by designing a member disposed on an outer side in the tire radial direction of a belt layer. For example, a pneumatic tire described in Patent Document 1 improves protrusion resistance by disposing two belt protecting layers on an outer side in the tire radial direction of a belt layer, and the belt protecting layer on the outer side in the tire radial direction has a narrower width than the width of the belt protecting layer on an inner side in the tire radial direction. In a pneumatic tire described in Patent Document 2, a belt reinforcing layer is disposed between a tread portion and a belt layer, and the belt reinforcing layer is configured to be three layers on a tire equator portion to ensure fracture energy while suppressing weight gain.

[0003] A pneumatic tire described in Patent Document 3 includes a strip-shaped sound-absorbing member adhered to a tire inner surface in a tread portion, a full cover layer disposed on an outer peripheral side of a belt layer, and a middle cover layer disposed on an outer peripheral side of the full cover layer and locally covering a tire center width region. By defining the respective widths of the strip-shaped sound-absorbing member and the belt layer, the middle cover layer and the strip-shaped sound-absorbing member reduce the deterioration of high-speed durability due to heat buildup in the strip-shaped sound-absorbing member, while maintaining sufficient low noise by the strip-shaped sound-absorbing member.

[0004] In a pneumatic tire described in Patent Document 4, a belt cover layer consisting of an end-portion belt cover layer and a center-portion belt cover layer is disposed outside a belt layer, and a tensile strength of organic fiber cords constituting the end-portion belt cover layer and the center-portion belt cover layer, and a sum of the end-portion belt cover layer and the center-portion belt cover layer are defined to ensure a reduction in road noise in a high-frequency band and weight reduction. Furthermore, a pneumatic tire described in Patent Document 5 has a belt cover formed by spirally winding a strip material on an outer peripheral side of a belt layer.In the belt cover, overlapping the strip material at a position covering an end portion in a tire width direction in the belt layer and at a position covering a center portion in the tire width direction in the belt layer improves steering stability and durability. Literature listPatent literature Patent document 1: JP 4865259 B Patent Document 2: JP 2010-64644 A Patent Document 3: JP 2017-137032 A Patent document 4: JP 4635366 B Patent Document 5: JP 4687201 B

[0005] EP 3 539 795 A1 discloses a pneumatic tire comprising: a tread portion; a belt layer disposed in the tread portion; and a belt cover layer disposed on an outer side in a tire radial direction of the belt layer, the belt cover layer comprising: two full cover layers disposed between shoulder regions on both sides in a tire width direction and laminated in the tire radial direction; and a narrow cover formed with a width in the tire width direction narrower than widths of the full covers, the narrow cover being disposed at a position between the two full cover layers and on an inner side in the tire width direction with respect to the shoulder regions.

[0006] EP 3 064 374 A1 discloses a pneumatic tire in which above a narrow cover there are two half-layers which partially overlap; however, none of the half-layers constitutes a complete cover within the meaning of the present invention. Brief description of the inventionTechnical problem

[0007] For example, among pneumatic tires, there are pneumatic tires that can bear a high load, such as a pneumatic tire with ADDITIONAL LOAD standard. Such pneumatic tires can be used at relatively high air pressures to bear heavy loads. Meanwhile, as the air pressure of the pneumatic tire increases, the rigidity of a tread portion increases. As a result, the tread portion is less likely to deform when driving on a foreign material, and impact bursting caused by the tread of the foreign material is more likely to occur. In other words, using the pneumatic tire at high air pressure is likely to reduce the impact burst resistance performance, which is a resistance to impact bursting.

[0008] Impact bursting is likely to occur when a foreign material on a road surface is driven on a ground contact surface of the tread portion in an area at or near a tire equatorial plane. Accordingly, to improve impact bursting resistance performance, reinforcement near the tire equatorial plane in the tread portion is effective. However, when a reinforcement member near the tire equatorial plane is newly added, an edge portion, which is a portion that will become an end portion of the member, increases at a position at or near the tire equatorial plane, and thus, so-called edge separation, in which overlapped members separate from the edge portion, is likely to occur. Accordingly, it has become very difficult to improve impact bursting resistance performance without decreasing separation resistance performance, which is resistance to edge separation.

[0009] The present invention has been made in view of the foregoing, and an object of the present invention is to provide a pneumatic tire that enables improving impact burst resistance performance while suppressing separation resistance performance, and a method for manufacturing the pneumatic tire. Solution to the problem

[0010] To solve the above-described problems and achieve the object, a pneumatic tire according to an embodiment of the present invention includes: a tread portion, a belt layer, and a belt cap layer. A belt layer is disposed in the tread portion. A belt cap layer is disposed on an outer side in a tire radial direction of the belt layer. The belt cap layer includes: two full cap layers disposed between shoulder regions on both sides in a tire width direction and laminated in the tire radial direction; and a narrow cap formed with a width in the tire width direction narrower than the widths of the full caps. The narrow cap is disposed at a position between the two full cap layers and on an inner side in the tire width direction with respect to the shoulder regions.

[0011] In the pneumatic tire, the narrow cover has the width in the tire width direction in a range of not less than 5 mm to not more than 40 mm.

[0012] In the pneumatic tire, the narrow cover preferably has the width in the tire width direction in a range of not less than 5% to not more than 30% of a width of the belt cover layer in the tire width direction.

[0013] In the pneumatic tire, the full covers and the narrow cover are preferably formed by spirally winding each strip-shaped belt cover material around a tire rotation axis. The type of belt cover materials forming the full covers and each of the belt cover materials forming the narrow cover are preferably identical.

[0014] In the pneumatic tire, the narrow cover is preferably arranged above an equatorial plane of the tire in the tire width direction.

[0015] In the pneumatic tire, main grooves extending in a tire circumferential direction are preferably formed in the tread portion. A plurality of land portions are preferably defined by the main grooves. At least a part of the narrow cover is preferably arranged on an inner side in the tire radial direction of the land portion closest to an equatorial plane of the tire, among the plurality of land portions.

[0016] To solve the problems described above and achieve the object, a method for manufacturing a pneumatic tire according to an embodiment of the present invention spirally winds strip-shaped belt cover materials on an outer side in a tire radial direction of a belt layer around a tire rotation axis to arrange a belt cover layer. The belt cover layer is formed by laminating an inner full cover, a narrow cover, and an outer full cover from inside to outside in the tire radial direction. The method includes: spirally winding each of the belt cover materials on an outer side in the tire radial direction of the belt layer between shoulder regions on both sides in a tire width direction to form the inner full cover between the shoulder regions;spirally winding each of the belt cover materials at a position on the outer side in the tire radial direction of the inner full cover and on a region further inward in the tire width direction than the shoulder regions to form the narrow cover having a width in the tire width direction that is narrower than a width of the inner full cover in the tire width direction; and spirally winding each of the belt cover materials on the outer side in the tire radial direction of the narrow cover and the inner full cover between the shoulder regions on both sides in the tire width direction to form the outer full cover between the shoulder regions. The narrow cover has the width in the tire width direction in a range of not less than 5 mm to not more than 40 mm. Advantageous effects of the invention

[0017] The pneumatic tire and the method for manufacturing the pneumatic tire according to the embodiment of the present invention provide an effect of enabling improvement of the impact burst resistance performance while suppressing a decrease in the separation resistance performance. Brief description of the drawings Fig. 1 is a meridian cross-sectional view illustrating a main portion of a pneumatic tire according to an embodiment. Fig. 2 is a detailed view of a Fig. 1 illustrated tread section. Fig. 3 is a schematic graphic representation of a Fig. 2 illustrated belt cover layer. Fig. 4 is a detailed view of a Fig. 2 shown middle web section. Fig. 5 is a schematic representation of a belt cover material in a direction of arrow AA in Fig. 2. Fig. 6 is an explanatory diagram illustrating a state in which a protrusion on a road surface is traveled by the pneumatic tire according to an embodiment. Fig. 7 is a modified example of the pneumatic tire according to an embodiment, and is an explanatory diagram in a case where the belt cover material is overlap-wound. Description of embodiments

[0018] Below, a pneumatic tire and a method for manufacturing a pneumatic tire according to embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiment. Components of the following embodiment include elements that are substantially identical, or can be replaced or easily devised by a person skilled in the art. EmbodimentsPneumatic tires

[0019] Herein, "tire radial direction" refers to the direction perpendicular to the rotation axis (not illustrated) of a pneumatic tire 1. The "tire radial direction inner side" refers to the direction toward the rotation axis in the tire radial direction. The "tire radial direction outer side" refers to the direction away from the rotation axis in the tire radial direction. Furthermore, "tire circumferential direction" refers to the circumferential direction with the center axis as the rotation axis. Furthermore, "tire width direction" refers to a direction parallel to the rotation axis. "tire width direction inner side" refers to a side toward a tire equatorial plane (tire equator line) CL in the tire width direction. "tire width direction outer side" refers to a side away from the tire equatorial plane CL in the tire width direction."Tire equatorial plane CL" refers to a plane perpendicular to the tire rotation axis and passing through the tire width center of the pneumatic tire 1. The tire equatorial plane CL is a position in the tire width direction, and a center line in the tire width direction corresponds to the center position of the pneumatic tire 1 in the tire width direction. "Tire width" is the width in the tire width direction between portions located outermost in the tire width direction, or in other words, the distance between the portions farthest from the tire equatorial plane CL in the tire width direction. "Tire equator line" refers to the line in the tire circumferential direction of the pneumatic tire 1 that lies on the tire equatorial plane CL.

[0020] Fig.1 is a meridian cross-sectional view illustrating a main portion of the pneumatic tire 1 according to the embodiment. The pneumatic tire 1 according to the present embodiment is the pneumatic tire 1 capable of being used with high loads, for example, the pneumatic tire 1 of the ADDITIONAL LOAD standard. In the pneumatic tire 1 according to the present embodiment, a tread portion 2 is arranged on a portion on the outermost side in the tire radial direction when viewed in a meridian cross-section, and the tread portion 2 includes a tread rubber layer 4 made of a rubber composition.A surface of the tread portion 2, that is, a portion in contact with a road surface during travel of a vehicle (not illustrated) on which the pneumatic tires 1 are mounted, is formed as a ground contact surface 3, and the ground contact surface 3 forms a part of a contour of the pneumatic tire 1. A plurality of main grooves 30 extending in the tire circumferential direction are formed in the ground contact surface 3 in the tread portion 2, and a plurality of land portions 20 are defined by the plurality of main grooves 30 on the surface of the tread portion 2.

[0021] In this embodiment, four main grooves 30 are formed adjacent to each other in the tire width direction, and each two of the four main grooves 30 are arranged on both sides of the equatorial plane of the tire CL in the tire width direction. In other words, a total of four main grooves 30 are formed in the tread portion 2, including: two center main grooves 31 arranged on both sides of the equatorial plane of the tire CL; and two shoulder main grooves 32 arranged on an outer side in the tire width direction of each of the two center main grooves 31.

[0022] Note that "main groove 30" refers to a vertical groove in which at least a part of it extends in the tire circumferential direction. Generally, the main groove 30 has a groove width of not less than 3 mm and a groove depth of not more than 6 mm, and it has a treadwear indicator (slip sign) that indicates the final stages of wear. In the present embodiment, the main groove 30 has a groove width of not less than 6 mm to not more than 25 mm and a groove depth of not less than 6 mm to not more than 9 mm, and is substantially parallel to a tire equator line (center line) where the equatorial plane of the tire CL and the ground contact surface 3 intersect. The main grooves 30 may extend linearly in the tire circumferential direction, or may be provided in a wave shape or a zigzag shape.

[0023] Of the land portions 20 defined by the main grooves 30, the land portion 20 positioned between the two center main grooves 31 and positioned on the equatorial plane of the tire CL is a center land portion 21. Further, the land portions 20 positioned between the adjacent center main grooves 31 and shoulder main grooves 32 and arranged on the outer side in the tire width direction of the center land portion 21 are second land portions 22. Further, the land portions 20 positioned on the outer side in the tire width direction of the second land portions 22 and adjacent to the second land portions 22 with the shoulder main grooves 32 arranged therebetween are shoulder land portions 23.

[0024] Note that the land portions 20 may be formed in a rib shape around a circumference in the tire circumferential direction, and a plurality of lug grooves (not illustrated) extending in the tire width direction may be formed in the tread portion 2. Thus, the land portions 20 may be defined by the main grooves 30 and the lug grooves, and each of the land portions 20 may be formed in a block shape. In this embodiment, the land portion 20 is formed as a rib-like land portion 20 formed around a circumference of the tire in the circumferential direction.

[0025] Shoulder portions 5 are arranged at both ends on outer sides of the tread portion 2 in the tire width direction, and sidewall portions 8 are arranged on inner sides in the tire radial direction of the shoulder portions 5. In other words, the shoulder portions 8 are arranged on both sides in the tire width direction of the tread portion 2. In other words, the sidewall portions 8 are arranged at two regions on both sides in the tire width direction of the pneumatic tire 1 and form portions exposed to the outermost sides in the tire width direction of the pneumatic tire 1.

[0026] A bead portion 10 is located on an inner side in the tire radial direction of each of the sidewall portions 8 located on both sides in the tire width direction. Similar to the sidewall portions 8, the bead portions 10 are arranged on both sides of the equatorial plane of the tire CL. That is, a pair of the bead portions 10 are arranged on both sides in the tire width direction of the equatorial plane of the tire CL. Each bead portion 10 is provided with a bead core 11, and a bead filler 12 is provided on the outer side of the bead core 11 in the tire radial direction. The bead core 11 is an annular member formed by bundling tire bead wires, which are steel wires, into an annular shape, and the bead filler 12 is a rubber member arranged on the outer side of the bead core 11 in the tire radial direction.

[0027] A belt layer 14 is disposed in the tread portion 2. The belt layer 14 is formed by a multi-layer structure in which a plurality of belts 141, 142 are laminated, and the two layers of the belts 141, 142 are laminated in the present embodiment. The belts 141, 142 constituting the belt layer 14 are formed by rolling and covering a plurality of belt cords made of steel or an organic fiber material such as polyester, rayon, or nylon with coating rubber. A belt angle, defined as the inclination angle of the belt cords with respect to the tire circumferential direction, is within a predetermined range (for example, from not less than 20° to not more than 55°). Furthermore, the belt angles of the two layers of the belts 141, 142 are different from each other.Accordingly, the belt layer 14 is configured as a so-called cross-ply structure in which the two layers of belts 141 and 142 are layered with the inclination directions of the belt cords intersecting each other. In other words, the two layers of belts 141, 142 are provided as so-called cross belts in which the belt cords provided with the respective belts 141, 142 are arranged in intersecting orientations.

[0028] A belt cover layer 15 is disposed on an outer side of the belt layer 14 in the tire radial direction. The belt cover layer 15 is disposed on the outer side of the belt layer 14 in the tire radial direction, covers the belt layer 14 in the tire circumferential direction, and is provided as a reinforcing layer that reinforces the belt layer 14. The belt reinforcing layer 15 is formed by covering a plurality of cords (not illustrated) with coating rubber, which are arranged side by side in the tire transverse direction and substantially parallel to the tire circumferential direction. The cords provided with the belt cover layer 15 are made of, for example, steel or an organic fiber such as polyester, polyethylene terephthalate, rayon, nylon, and a hybrid of a polyamide composite + α, and a cord angle is in a range of ±5° with respect to the tire circumferential direction.Furthermore, in the cords provided with the belt cover layer 15, a wire diameter, which is a diameter of the cord, is within a range of not less than 0.5 mm to not more than 1.8 mm, and a cord number per 50 mm in an arrangement direction of the cords is within a range of not less than 30 to not more than 80. In the present embodiment, the belt cover layer 15 is arranged over the entire area of ​​the region in the tire width direction where the belt layer 14 is arranged, and covers end portions in the tire width direction of the belt layer 14. The tread rubber layer 4 provided with the tread portion 2 is arranged on the outer side of the belt cover layer 15 in the tread portion 2 in the tire radial direction.

[0029] A carcass layer 13 containing the cords of radial plies is continuously provided on the inner side in the tire radial direction of the belt layer 14 and on one side of the sidewall portion 8 near the equatorial plane of the tire CL. Accordingly, the pneumatic tire 1 according to this embodiment is configured as a so-called radial tire. The carcass layer 13 has a single-layer structure composed of one carcass ply or a multi-layer structure composed of a plurality of carcass plies and extends between the pair of bead portions 10 arranged on both sides in the tire transverse direction in a toroidal shape to form the frame structure of the tire.

[0030] Specifically, the carcass layer 13 is arranged to extend from one bead portion 10 to the other bead portion 10 in the pair of bead portions 10 located on both sides in the tire width direction, and bends back on the outer side in the tire width direction along the bead cores 11 at the bead portions 10, wrapping around the bead cores 11 and the bead fillers 12. The bead filler 12 is a rubber member arranged in a space formed on the outer side of the bead core 11 in the tire radial direction when the carcass layer 13 is bent back at the bead portion 10. Further, the belt layer 14 is arranged on the outer side in the tire radial direction of a portion located in the tread portion 2 of the carcass layer 13 extending between the pair of bead portions 10.Furthermore, the carcass ply of the carcass layer 13 is formed by rolling and covering a plurality of carcass cords made of steel or an organic fiber material such as aramid, nylon, polyester, or rayon with coating rubber. A plurality of carcass cords constituting the carcass plies are arranged side by side at an angle in the tire circumferential direction, the angle following a tire meridian direction with respect to the tire circumferential direction.

[0031] At the tire bead portion 10, a rim cushion rubber 17 is disposed on an inner side in the tire radial direction and an outer side in the tire width direction of the bead core 11 and a bent-back portion of the carcass layer 13. The rim cushion rubber 17 forms a contact surface of the tire bead portion 10 with the rim flange. Additionally, an inner liner 16 is formed along the carcass layer 13 on the inner side of the carcass layer 13 or on the inner side of the carcass layer 13 in the pneumatic tire 1. The inner liner 16 forms a tire inner surface 18, which is a surface on the inner side of the pneumatic tire 1.

[0032] Fig. 2 is a detailed view of the Fig. 1 illustrated tread section 2. Fig. 3 is a schematic graphic representation of the Fig.2. The belt cover layer 15, which is arranged on the outer side in the tire radial direction of the belt layer 14, includes two layers of full covers 40 laminated in the tire radial direction, and a narrow cover 45 disposed between the two layers of the full covers 40. Of these, the two layers of full covers 40 include an inner full cover 41 arranged on the outer side in the tire radial direction of the belt layer 14, and an outer full cover 42 arranged on the outer side in the tire radial direction of the inner full cover 41. In these inner full covers 41 and outer full cover 42, the inner full cover 41 has a width in the tire width direction that is wider than that of the outer full cover 42.The inner full cover 41 and the outer full cover 42 are both arranged between shoulder portions Ash on both sides in the tire width direction.

[0033] The narrow cover 45 is formed with a width in the tire width direction narrower than the width of the full cover 40, and is arranged at a position on the inner side in the tire width direction with respect to the shoulder regions Ash. The belt cover layer 15, including these inner full cover 41, outer full cover 42, and narrow cover 45, is formed by laminating the inner full cover 41, the narrow cover 45, and the outer full cover 42 in this order from the inner side to the outer side in the tire radial direction. Accordingly, the narrow cover 45, which has the narrowest width in the tire width direction, is completely covered with the outer full cover 42 in the tire width direction from the outer side in the tire radial direction.

[0034] Note that the shoulder region Tsh in this case is a region between a position P corresponding to 85% of the width of the belt layer 14 in the tire width direction and an end portion 144 of the belt layer 14 in the tire width direction. Specifically, in a tire meridian cross section, the shoulder region Ash is a region positioned between two shoulder region boundary lines Lsh. The shoulder region boundary lines Lsh are respective lines extending perpendicularly from the position P at 85% of the width of a widest belt 143 in the tire width direction, which has the widest width in the tire width direction, of the plurality of belts 141, 142 provided with the belt layer 14, and the end portion 144 of the widest belt 143 to the tire inner surface 18.The shoulder areas Tsh thus defined as described above are defined on both sides of the equatorial plane of the tire CL in the tire width direction and are positioned on respective two sides of the equatorial plane of the tire CL in the tire width direction.

[0035] In this embodiment, of the two layers of belts 141 and 142 included in the belt layer 14, the width of the belt 141 in the tire width direction located on the inner side in the tire radial direction is wider than the width of the other belt 142 in the tire width direction, and the belt 141 located on the inner side in the tire radial direction is the widest belt 143.

[0036] In addition, the positions P at 85% of the width of the widest belt 143 in the tire width direction are positions of end portions of an 85% region when an area of ​​85% of the width of the widest belt 143 in the tire width direction is evenly distributed on both sides in the tire width direction, with the center of the widest belt 143 in the tire width direction or the position of the equatorial plane of the tire CL serving as the center. Accordingly, distances between the positions P at 85% of the width of the widest belt 143 in the tire width direction and the end portions 144 of the widest belt 143 are identical sizes between both sides of the equatorial plane of the tire CL in the tire width direction.

[0037] The shoulder area Ash defined in this way is defined by the shape in a state where the pneumatic tire 1 is mounted on a normal rim and inflated to the regular internal pressure. Here, "normal rim" refers to a "standard rim" as defined by JATMA, a "design rim" as defined by TRA, or a "measuring rim" as defined by ETRTO. Furthermore, a regular internal pressure refers to a "maximum air pressure" as defined by JATMA, the maximum value in "tire load limits at various cold inflation pressures" as defined by TRA, or "tire pressures" as defined by ETRTO.

[0038] Fig. 4 is a detailed view of the Fig.2. The narrow cover 45, which is sandwiched between the inner full cover 41 and the outer full cover 42 from both sides in the tire radial direction, has a width W in the tire width direction within a range of not less than 5 mm to not more than 40 mm. The width W of the narrow cover 45 in the tire width direction is within a range of not less than 5% to not more than 30% of a width CW (see Fig.2) the belt cover layer 15 in the tire width direction. Thus, the narrow cover 45 has end portions 45a on both sides in the tire width direction covered with the two layers of the full covers 40, that is, the end portions 45a on both sides of the narrow cover 45 in the tire width direction are covered with the outer full cover 42 with respect to the tread rubber layer 4. Since, in the present embodiment, the width of the inner full cover 41 in the tire width direction is wider than that of the outer full cover 42, the width CW of the belt cover layer 15 in the tire width direction is the width CW of the inner full cover 41 in the tire width direction.

[0039] Furthermore, the narrow cover 45 is arranged to extend across the equatorial plane of the tire CL in the tire width direction. Furthermore, at least a part of the narrow cover 45 is arranged on the inner side of the center land portion 21 in the tire radial direction.

[0040] Fig. 5 is a schematic representation of a belt cover material 50 in a direction of arrow AA in Fig. 2. The full cover 40 and the narrow cover 45 are formed by spirally winding the respective strip-shaped belt cover materials 50 around the tire rotation axis. Note that, to describe an aspect of arranging the belt cover material 50, Fig.5 representatively describes the belt cover material 50 forming the outer full cover 42 from the narrow cover 45 and the two layers of the full covers 40, the belt cover materials 50 forming the narrow cover 45 and the inner full cover 41 are also arranged in a similar aspect.

[0041] The belt cover material 50, which is a strip-shaped member, has a width ranging from not less than 5 mm to not more than 15 mm. The belt cover materials 50 are reinforcing layer components that form the belt cover layer 15, and a cord that forms the belt cover layer 15 is formed by coating with a coating rubber.

[0042] The inner full cover 41 is formed by spirally winding the thus formed belt cover materials 50 on the outer side of the belt layer 14 in the tire radial direction around the tire rotation axis. Furthermore, the narrow cover 45 is formed by spirally winding the belt cover material 50 on the outer side of the inner full cover 41 in the tire radial direction around the tire rotation axis. Furthermore, the outer full cover 42 is formed by spirally winding the belt cover material 50 on the outer side of the narrow cover 45 and the inner full cover 41 in the tire radial direction around the tire rotation axis.

[0043] The belt cover materials 50 that form the full covers 40, that is, the belt cover material 50 that forms the inner full cover 41, the belt cover material 50 that forms the outer full cover 42, and the belt cover material 50 that forms the narrow cover 45, are members of an identical type, and the respective belt cover materials 50 are formed by coating the cords that form the belt cover layer 15 with coating rubber. In other words, all of these belt cover materials 50 have a configuration in which, for example, widths and thicknesses, wire diameters of the cords and pitches of the cords, and materials of the cords and the coating rubbers can be considered identical. Method for producing a pneumatic tire

[0044] Next, a manufacturing method for the pneumatic tire 1 according to the embodiment will be described. To manufacture the pneumatic tire 1, first, each of the members constituting the pneumatic tire 1 is processed, and the processed members are joined together. That is, the rubber members such as the tread rubber layer 4 and the respective members such as the bead core 11, the carcass layer 13, the belt layer 14, and the belt cover layer 15 are each processed, and the processed members are joined together. Of these, the belt cover layer 15 is arranged on the outer side in the tire radial direction of the belt layer 14 by spirally winding the strip-shaped belt cover materials 50 on the outer side of the belt layer 14 in the tire radial direction around the tire rotation axis.

[0045] The belt cover layer 15 is formed by laminating the inner full cover 41, the narrow cover 45, and the outer full cover 42 from the inside to the outside in the tire radial direction. A step of forming the belt cover layer 15 includes a step of forming the inner full cover 41, a step of forming the narrow cover 45, and a step of forming the outer full cover 42, and the step of forming the inner full cover 41 is performed first. In the step of forming the inner full cover 41, the belt cover material 50 is spirally wound on the outer side of the belt layer 14 in the tire radial direction between the shoulder regions Ash on both sides in the tire width direction to form the inner full cover 41 between the shoulder regions Ash.

[0046] Next, the narrow cover forming step 45 is performed. In the narrow cover forming step 45, the belt cover material 50 is spirally wound at a position on the inner side in the tire width direction with respect to the shoulder regions Ash on the outer side of the inner full cover 41 in the tire radial direction, to form the narrow cover 45 with a width in the tire width direction that is narrower than the width of the inner full cover 41 in the tire width direction.

[0047] Next, the outer full cover 42 forming step is performed. In the outer full cover 42 forming step, the belt cover material 50 is spirally wound between the shoulder regions Ash on both sides in the tire width direction on the outer side of the narrow cover 45 and the inner full cover 41 in the tire radial direction to form the outer full cover 42 between the shoulder regions Ash.

[0048] As a result, the belt cover layer 15 is formed by layering the narrow cover 45 and the inner full cover 41 and the outer full cover 42, which are the full covers 40, from the inner side to the outer side in the tire radial direction on the outer side of the belt layer 14 in the tire radial direction in the order of the inner full cover 41, the narrow cover 45, and the outer full cover 42. In addition, by disposing the outer full cover 42 on the outer side of the narrow cover 45 in the tire radial direction between the shoulder regions Ash on both sides in the tire width direction, the narrow cover 45 is completely covered with the outer full cover 42 from the outer side in the tire radial direction of the narrow cover 45. Functions and effects

[0049] To mount the pneumatic tire 1 according to this embodiment on a vehicle, a rim wheel R (see Fig.6) attached to the bead portion 10 to mount the pneumatic tire 1 on the rim wheel R, then the inner portion is filled with air, and the rim wheel R with the pneumatic tire 1 in the inflated state is mounted on the vehicle. The pneumatic tire 1 according to the present embodiment is, for example, the pneumatic tire 1 that can be used at high loads, such as the pneumatic tire 1 of ADDITIONAL LOAD standard. In this respect, the pneumatic tire 1 can be used with an air pressure during inflation in a relatively high state. Thus, when the pneumatic tire 1 is used at a high load, the pneumatic tire 1 is used at an increased air pressure. When the vehicle runs with the pneumatic tires 1, the pneumatic tire 1 rotates with the ground contact surface 3 at a portion positioned on a lower side in the ground contact surface 3 in contact with the road surface.The vehicle travels by transmitting a driving force and a braking force to the road surface or generating a rotational force due to a frictional force between the ground contact surface 3 and the road surface.

[0050] For example, when the vehicle on which the pneumatic tires 1 are mounted travels on a dry road surface, the vehicle travels mainly by transmitting a driving force or a braking force to the road surface, or generating a turning force by a frictional force between the ground contact surface 3 and the road surface. When the vehicle travels on a wet road surface, the vehicle travels in such a way that water between the ground contact surface 3 and the road surface enters grooves such as the main grooves 30 and the lug grooves, and the water between the ground contact surface 3 and the road surface is discharged through these grooves. Accordingly, the ground contact surface 3 is easily grounded to the road surface, and the frictional force between the ground contact surface 3 and the road surface allows the vehicle to travel as desired.

[0051] Furthermore, during vehicle travel, the pneumatic tire 1 is subjected to a load associated with the weight of a vehicle body, acceleration / deceleration, and turning. Accordingly, a large load acts in the tire radial direction. This load is mainly absorbed by the air filled in the pneumatic tire 1, but is also absorbed by the tread portion 2 and the sidewall portion 8, as well as the air inside the pneumatic tire 1. That is, the sidewall portion 8 transmits a load between the bead portion 10 to which the rim wheel R is attached and the tread portion 2, and the tread portion 2 transmits the load between the sidewall portion 8 and the road surface.Therefore, the large load acts on the sidewall portion 8 and the tread portion 2 when the vehicle is running, and the sidewall portion 8 and the tread portion 2 receive this load by being deflected substantially in the tire radial direction.

[0052] Further, as the vehicle travels, the pneumatic tire 1 rotates, and therefore, the position of the ground contact surface 3 in contact with the road surface continuously moves in the tire circumferential direction. Accordingly, the positions of the sidewall portion 8 and the tread portion 2 that deflect due to the load during vehicle travel also move in the tire circumferential direction. Therefore, as the vehicle travels, the pneumatic tire 1 rotates, while the sequential deflection of the respective positions of the sidewall portion 8 and the tread portion 2 in the tire circumferential direction is repeated.

[0053] In addition, a protrusion protruding from a road surface, such as a stone, may be present on a road surface on which the vehicle is traveling, and the vehicle may travel over such a protrusion through the tread portion 2 of the pneumatic tire 1 during traveling. At this time, if the sidewall portion 8 and the tread portion 2 have a slight deflection due to the high air pressure with which the pneumatic tire 1 is inflated, the pneumatic tire 1 cannot absorb the shape change of the road surface caused by the protrusion, and the protrusion may penetrate into the tread portion 2 of the pneumatic tire 1.That is, in the pneumatic tire 1 with the increased internal pressure, when the protrusion is driven on the road surface, the slight deflection of the sidewall portion 8 and the tread portion 2 causes the protrusion to penetrate into the tread portion 2 and possibly cause an impact burst.

[0054] In contrast, in the pneumatic tire 1 according to the present embodiment, since the belt cover layer 15 includes the two layers of the full covers 40 laminated in the tire radial direction and the narrow cover 45 disposed between the two layers of the full covers 40, impact bursting at an increased internal pressure can be suppressed. Fig.6 is an explanatory diagram illustrating a state in which the pneumatic tire 1 according to the first embodiment travels on a protrusion 105 on a road surface 100. In the pneumatic tire 1 according to the present embodiment, the narrow cover 45 formed with the width in the tire width direction narrower than the width of the full cover 40 is arranged at the position on the inner side in the tire width direction with respect to the shoulder regions Ash at the position between the two layers of the full covers 40. This makes it possible to increase the number of layered belt cover materials 50 at the position where the narrow cover 45 is arranged. In other words, the number of belt cover materials 50 layered in the tire radial direction in the belt cover layer 15 can be increased at the position across the tire equatorial plane CL.Specifically, in the belt cover layer 15, while the two layers of the full covers 40, the inner full cover 41 and the outer full cover 42, are layered at the position other than the position where the narrow cover 45 is arranged, three layers in which the narrow cover 45 is added to the two layers of the full covers 40 can be layered at the position where the narrow cover 45 is arranged. This makes it possible to increase a breaking strength at or near the center in the tire width direction of the tread portion 2, where a ground contact pressure is likely to increase. Even when the protrusion 105 on the road surface 100 is driven on at or near the center land portion 21, the penetration of the protrusion 105 by the tread portion 2 can be suppressed.Accordingly, an impact burst caused by driving on the protrusion 105 during the running of the vehicle can be suppressed.

[0055] Furthermore, the narrow cover 45 is arranged to be sandwiched in the tire radial direction between the two layers of the full covers 40 arranged between the shoulder regions Ash on both sides in the tire width direction. Accordingly, separation at or near the end portions 45a in the tire width direction of the narrow cover 45 from the tread rubber layer 4 can be suppressed. In other words, since physical properties of the belt cover materials 50 constituting the belt cover layer 15 are different from the tread rubber layer 4, when the tread portion 2 is deflected, the belt cover layer 15 and the tread rubber layer 4 are deflected in a state of different elasticity.Therefore, when the narrow cover 45 is disposed adjacent to the tread rubber layer 4, stress is likely to concentrate at or near the tire width-direction end portion 45a of the narrow cover 45, which is a boundary portion between the belt cover layer 15 and the tread rubber layer 4 having different elasticities. In this case, repeated variation of a load acting on the narrow cover 45, along with vehicle running, may cause the narrow cover 45 and the tread rubber layer 4 to separate at or near the end portion 45a of the narrow cover 45.

[0056] On the other hand, when the narrow cover 45 is arranged to be sandwiched between the two layers of the full covers 40 in the tire radial direction, the narrow cover 45 can be arranged without the end portions 45a of the narrow cover 45 being in direct contact with the tread rubber layer 4. As a result, contact between the end portion 45a of the narrow cover 45 and the tread rubber layer 4 can be suppressed at the position at or near the center of the tread portion 2 in the tire width direction where a variation in load is large. This makes it possible to suppress the boundary portion between the belt cover layer 15 and the tread rubber layer 4 with the different elasticities from being positioned at or near the center of the tread portion 2 in the tire width direction.As a result, so-called edge separation, which is a separation between the narrow cover 45 and the tread rubber layer 4 from or near the end portion 45a of the narrow cover 45, can be suppressed, and the separation resistance performance can be ensured. As a result, it is possible to improve the impact burst resistance performance while suppressing the decrease in the separation resistance performance.

[0057] In addition, since the width W of the narrow cover 45 in the tire width direction is within a range of not less than 5 mm to not more than 40 mm, it is possible to more reliably improve the fracture strength at or near the center of the tread portion 2 in the tire width direction while suppressing excessive weight gain of the belt cover layer 15. In other words, when the width W of the narrow cover 45 in the tire width direction is less than 5 mm, the width W of the narrow cover 45 is excessively small, which may make it difficult to effectively ensure the strength at or near the position where the narrow cover 45 is arranged.In this case, even if the narrow cover 45 is arranged, it is difficult to effectively improve the fracture strength at or near the center of the tread portion 2 in the tire width direction, and this may make it difficult to effectively suppress the penetration of the protrusion 105 traveled by the tread portion 2 by the tread portion 2. If the width W of the narrow cover 45 in the tire width direction is greater than 40 mm, the width W of the narrow cover 45 is excessively large, so there is a possibility that the belt cover material 50 used becomes excessively large. In this case, the weight of the belt cover layer 15 may increase excessively, and the weight of the pneumatic tire 1 may increase excessively, which is caused by the provision of the narrow cover 45.

[0058] On the other hand, when the width W of the narrow cover 45 in the tire width direction is within a range of not less than 5 mm to not more than 40 mm, while suppressing the excessive weight increase of the belt cover layer 15, the strength at or near the position where the narrow cover 45 is arranged can be more reliably ensured, and the fracture strength at or near the center of the tread portion 2 in the tire width direction, where a ground contact pressure is likely to increase, can be more reliably improved. As a result, while suppressing the weight increase of the pneumatic tire 1, the impact burst resistance performance can be improved.

[0059] In addition, the width W of the narrow cover 45 in the tire width direction is within a range of not less than 5% to not more than 30% of the width CW of the belt cover layer 15 in the tire width direction, thus it is possible to reliably improve the fracture strength at or near the center of the tread portion 2 in the tire width direction while suppressing the excessive weight increase of the belt cover layer 15. In other words, if the width W of the narrow cover 45 in the tire width direction is less than 5% of the width CW of the belt cover layer 15, the width W of the narrow cover 45 in the tire width direction is excessively narrow, and thus, effectively ensuring the strength at or near the position where the narrow cover 45 is arranged may be difficult.In this case, even if the narrow cover 45 is arranged, it is difficult to effectively improve the fracture strength at or near the center of the tread portion 2 in the tire width direction, and this may make it difficult to effectively suppress the penetration of the protrusion 105 traveled by the tread portion 2 by the tread portion 2. If the width W of the narrow cover 45 in the tire width direction is greater than 30% of the width CW of the belt cover layer 15, the width W of the narrow cover 45 in the tire width direction is excessively large, which may cause the excessive increase in weight of the belt cover layer 15. In this case, the weight of the pneumatic tire 1 may be excessively increased, which is caused by the provision of the narrow cover 45.

[0060] On the other hand, when the width W of the narrow cover 45 in the tire width direction is within a range of not less than 5% to not more than 30% of the width CW of the belt cover layer 15, the strength at or near the position where the narrow cover 45 is arranged can be more reliably ensured while suppressing the excessive weight increase of the belt cover layer 15. As a result, while suppressing the weight increase of the pneumatic tire 1, the impact burst resistance performance can be improved.

[0061] Furthermore, in the full cover 40 and the narrow cover 45, the belt cover material 50 forming the full cover 40 and the belt cover material 50 forming the narrow cover 45 are of the same type. Thus, the full cover 40 and the narrow cover 45 can be formed without separately preparing the belt cover material 50 for the full cover 40 or the belt cover material 50 for the narrow cover 45. As a result, a decrease in productivity can be suppressed when the full cover 40 and the narrow cover 45 are formed using the belt cover materials 50.Furthermore, since the belt cover material 50 forming the full cover 40 and the belt cover material 50 forming the narrow cover 45 are of the same type, the strength at or near the position where the narrow cover 45 is disposed can be appropriately improved according to the arrangement range of the narrow cover 45 disposed between the two layers of the full covers 40. As a result, the impact burst resistance performance and the like can be more reliably improved.

[0062] Furthermore, since the narrow cover 45 is arranged above the equatorial plane of the tire CL in the tire width direction, the fracture strength can be more reliably increased at the position in the tread portion 2 where the ground contact pressure is likely to increase during vehicle travel. As a result, the impact bursting when the protrusion 105 on the road surface 100 is driven on can be more reliably suppressed. As a result, it is possible to more reliably improve the impact bursting resistance performance.

[0063] Furthermore, since at least a part of the narrow cover 45 is arranged on the inner side in the tire radial direction of the center land portion 21, the fracture strength can be more reliably increased at the position at or near the center of the center land portion 21 in the tread portion 2, where a ground contact pressure is likely to increase during vehicle travel. As a result, impact bursting can be more reliably suppressed when the protrusion 105 on the road surface 100 is driven on by the center land portion 21. As a result, it is possible to more reliably improve the impact bursting resistance performance.

[0064] The method for manufacturing the pneumatic tire 1 according to the embodiment includes the step of spirally winding the belt cover material 50 on the outer side in the tire radial direction of the belt layer 14 to form the inner full cover 41; and the step of spirally winding the belt cover material 50 on the outer side in the tire radial direction of the inner full cover 41 to form the narrow cover 45. Accordingly, the fracture strength can be increased at or near the center of the tread portion 2 in the tire width direction, where ground contact pressure is likely to increase.As a result, even if the protrusion 105 on the road surface 100 is driven over from the vicinity of the center land portion 21, the penetration of the protrusion 105 by the tread portion 2 can be suppressed, and an impact burst caused by driving over the protrusion 105 during the running of the vehicle can be suppressed.

[0065] Furthermore, since the step of spirally winding the belt covering material 50 on the outer side in the tire radial direction of the narrow cover 45 and the inner full cover 41 to form the outer full cover 42 is included, the narrow cover 45 can be completely covered from the outer side in the tire radial direction of the narrow cover 45 with the outer full cover 42. This makes it possible to suppress the direct contact between the end portion 45a of the narrow cover 45 and the tread rubber layer 4 at the position at or near the center of the tread portion 2 in the tire width direction where a variation in load is large, and makes it possible to suppress the boundary portion between the belt cover layer 15 and the tread rubber layer 4 with the different elasticities from being positioned at or near the center of the tread portion 2 in the tire width direction.As a result, so-called edge separation, which is a separation between the narrow cover 45 and the tread rubber layer 4 from or near the end portion 45a of the narrow cover 45, can be suppressed, and the separation resistance performance can be ensured. As a result, it is possible to improve the impact burst resistance performance while suppressing a decrease in the separation resistance performance. Modified examples

[0066] Note that in the above-described embodiments, the belt cover materials 50 forming the full covers 40 and the narrow cover 45 are spirally wound with adjacent portions in the tire width direction aligned in the tire width direction, without overlapping the adjacent portions in the tire width direction in one belt cover material 50 in the tire radial direction. However, the winding may be performed with the belt cover material 50 overlapped. Fig. Fig. 7 is a modified example of the pneumatic tire 1 according to the embodiment, and is an explanatory diagram in a case where the belt cover material 50 is wound overlappingly. As in Fig.As illustrated in Figure 7, the respective belt cover materials 50 that are spirally wound may be spirally wound while the adjacent portions in the tire width direction in one belt cover material 50 overlap in the tire radial direction by a width within a predetermined range. Thus, in an adjacent winding portion 55 as a portion in one belt cover material 50 where the adjacent portions in the tire width direction overlap in the tire radial direction, a width Wb in the width direction of the belt cover material 50 is preferably within a range of not less than 20% to not more than 70% of a width Wa of the belt cover material 50.

[0067] The belt cover material 50 is spirally wound while overlapping the adjacent portions in the tire width direction, and is spirally wound while forming the adjacent winding portion 55. Thus, the belt cover layer 15 can be arranged with further high strength. As a result, the fracture strength of the tread portion 2 can be increased to a wider range by the belt cover layer 15, and impact bursting can be more reliably suppressed.

[0068] In the above-described embodiment, four main grooves 30 are formed, but the number of main grooves 30 may be different from four. In the above-described embodiments, although the center land portion 21 is positioned on the equatorial plane of the tire CL, the land portion 20 does not need to be positioned on the equatorial plane of the tire CL. For example, the main groove 30 may be positioned on the equatorial plane of the tire CL. When the main groove 30 is positioned on the equatorial plane of the tire CL, at least a part of the narrow cover 45 is preferably positioned on the inner side in the tire radial direction of the land portion 20 closest to an equatorial plane of the tire CL among the plurality of land portions 20.

[0069] In the above-described embodiments, in the two layers of full covers 40, the inner full cover 41 has a width in the tire width direction that is wider than that of the outer full cover 42, but the ratio between the widths of the two layers of full covers 40 may be different. For example, the outer full cover 42 may have a width in the tire width direction that is wider than that of the inner full cover 41, and the widths in the tire width direction of the inner full cover 41 and the outer full cover 42 may be the same width. As long as each of the two layers of full covers 40 is arranged between the shoulder regions Ash on both sides in the tire width direction, any relative ratio between the widths in the tire width direction is used.

[0070] Furthermore, the above-described embodiments and modified examples can be combined as appropriate. In the pneumatic tire 1, at least the narrow cover 45, whose width in the tire width direction is formed narrower than the widths of the full covers 40, is arranged between the two layers of the full covers 40 at the position on the inner side in the tire width direction with respect to the shoulder regions Ash. This enables an improvement in the impact burst resistance performance while suppressing the decrease in the separation resistance performance. Examples

[0071] Tables 8A-I, 8A-II, 8B-I, and 8B-II are tables showing the results of performance evaluation tests of pneumatic tires. The following describes performance evaluation tests of the above-described pneumatic tire 1, which were conducted on pneumatic tires of prior art examples and the pneumatic tires 1 according to embodiments of the present invention. The performance evaluation tests conducted a piston test, which is an evaluation test for impact burst resistance performance, and a separation resistance performance test, which is the performance of the improbability of edge separation.

[0072] The performance evaluation tests were conducted using pneumatic tire 1 with the nominal size of 275 / 45ZR19 105Y of the tire defined by JATMA and mounted on a standard JATMA rim wheel with a rim size of 19 × 9.5 J. The evaluation method for each of the test items was evaluated for the piston test by inflating the test tire to an air pressure of a regular internal pressure, conducting a piston burst test according to JIS K6302 with a piston diameter of 19 mm and an insertion speed of 50 mm / minute, and measuring a tire burst energy J. The evaluation results of the piston test show that the larger the measured tire burst energy J, the higher a tire strength and the higher the impact burst resistance performance.

[0073] In addition, the separation resistance performance was evaluated through a high-speed durability test. For high-speed durability performance, the test tires were inflated to an internal pressure of 120% of the regular internal pressure and subjected to drying degradation at a temperature of 80°C for five days. After that, the test tires were inflated to the regular internal pressure and mounted on a tire testing drum with a drum diameter of 1707 mm, applying a camber. The test began at a speed of 120 km / h with a load of 5 kN applied to the test tire. While the speed was increased by 10 km / h every 24 hours, the test was conducted until the tire failed, and a driving distance to failure was measured.The separation resistance performance is expressed as index ratings of the travel distance measured in the high-speed durability test, with the prior art example 2 described below being rated as 100. Larger index values ​​indicate a longer travel distance until the tire fails and superior separation resistance performance.

[0074] The performance evaluation test was conducted on 13 types of pneumatic tires, including pneumatic tires of Prior Art Examples 1 and 2 as examples of the prior art pneumatic tires, and Examples 1 to 11 as the pneumatic tires 1 according to the embodiment of the present invention. Of these, the pneumatic tire of Prior Art Example 1 does not include the narrow cover 45 in the belt cover layer 15. In the pneumatic tire of Prior Art Example 2, the belt cover layer 15 includes the narrow cover 45 but does not include the two layers of full covers 40 sandwiching the narrow cover 45, and the narrow cover 45 is in direct contact with the tread rubber layer 4.

[0075] In contrast, in Examples 1 to 11, which are examples of the pneumatic tires 1 according to the embodiments of the present invention, all the belt cover layers 15 include the narrow covers 45, and the narrow covers 45 are sandwiched in the tire radial direction between the two layers of the full covers 40. Furthermore, in the pneumatic tires 1 according to Examples 1 to 11, the respective width W of the narrow cover 45 and the width W of the narrow cover 45 are different from the width CW of the belt cover layer 15.

[0076] Tables 8A-I and 8A-II show the results of performance evaluation tests of pneumatic tires. Tables 8B-I and 8B-II show the results of performance evaluation tests of pneumatic tires. As a result of the performance evaluation tests using these pneumatic tires 1 shown in Tables 8A-I, 8A-II, 8B-I, and 8B-II, it was found that the pneumatic tires 1 according to Examples 2 to 6 and 8 to 11 can improve the impact burst resistance performance evaluated by the piston test compared to those of Prior Art Examples 1 and 2, without deteriorating the separation resistance performance compared to those of Prior Art Examples 1 and 2. In other words, the pneumatic tires 1 according to Examples 2 to 6 and 8 to 11 and the manufacturing method for the pneumatic tires 1 according to Examples 2 to 6 and 8 to 11 can improve the impact burst resistance performance while suppressing a decrease in the separation resistance performance. [Table 8A-I] Example of the prior art 1 Example of the state of the art 2 Comparison example 1 Example 2 Presence of narrow coverage No Yes Yes Yes Presence of two layers with full covers, between which a narrow cover is sandwiched - No Yes Yes Width of the narrow cover - 24 mm 4 mm 5 mm Width of the narrow cover to the width of the belt cover layer - 15 % 15 % 15 % Piston test (J) 580 598 611 624 Separation resistance performance 95 100 102 104 [Table 8A-II] Example 3 Example 4 Example 5 Presence of narrow coverage Yes Yes Yes Presence of two layers with full covers, between which a narrow cover is sandwiched Yes Yes Yes Width of the narrow cover 10 mm 24 mm 30 mm Width of the narrow cover to the width of the belt cover layer 15 % 15 % 15 % Piston test (J) 630 636 639 Separation resistance performance 108 112 113 [Table 8B-I] Example 6 Comparison example 7 Example 8 Example 9 Presence of narrow coverage Yes Yes Yes Yes Presence of two layers with full covers, between which a narrow cover is sandwiched Yes Yes Yes Yes Width of the narrow cover 40 mm 41 mm 24 mm 24 mm Width of the narrow cover to the width of the belt cover layer 15 % 15 % 4 % 5 % Piston test (J) 648 660 660 660 Separation resistance performance 114 115 113 113 [Table 8B-II] Example 10 Example 11 Presence of narrow coverage Yes Yes Presence of two layers with full covers, between which a narrow cover is sandwiched Yes Yes Width of the narrow cover 24 mm 24 mm Width of the narrow cover to the width of the belt cover layer 30 % 31 % Piston test (J) 660 660 Separation resistance performance 113 113 List of reference symbols 1 pneumatic tire 2 Tread section 3 Ground contact surface 4 Tread rubber layer 5 shoulder section 8 Side wall section 10 bead section 13 carcass layer 14 Belt layer 141, 142 Belts 143 widest belt 144 final section 15 Belt cover layer 16 Inner core 18 Tire inner surface 20 bridge section 21 middle bridge section 22 second bridge section 23 shoulder bar section 30 main groove 31 middle main groove 32 shoulder main groove 40 Full Coverage 41 Inner full cover 42 Outer full coverage 45 Narrow cover 45a final section 50 belt cover material 55 Adjacent changing section 100 road surface 105 lead

Claims

[1] Pneumatic tyre (1), comprising: a tread section (2); a belt layer (14) arranged in the tread portion (2); and a belt cover layer (15) arranged on an outer side in a tire radial direction of the belt layer (14), wherein the belt cover layer (15) comprises: two full cover layers (40) disposed between shoulder regions (Ash) on both sides in a tire width direction and layered in the tire radial direction; and a narrow cover (45) formed with a width in the tire width direction that is narrower than widths of the full covers (40), the narrow cover (45) being provided at a position between the two layers of the full covers (40) and is arranged on an inner side in the tire width direction with respect to the shoulder regions (Ash), wherein the narrow cover (45) has the width in the tire width direction in a range of not less than 5 mm to not more than 40 mm. [2] The pneumatic tire (1) according to claim 1, wherein the narrow cover (45) has the width in the tire width direction in a range of not less than 5% to not more than 30% of a width of the belt cover layer (15) in the tire width direction. [3] Pneumatic tire (1) according to one of claims 1 to 2, wherein the full covers (40) and the narrow cover (45) are formed by spirally winding each of the strip-shaped belt cover materials (50) around a tire rotation axis, and the belt cover materials (50) forming the full covers (40) and each of the belt cover materials (50) forming the narrow cover (45) are of an identical type. [4] A pneumatic tire (1) according to any one of claims 1 to 3, wherein the narrow cover (45) is arranged across an equatorial plane (CL) of the tire in the tire width direction. [5] Pneumatic tire (1) according to one of claims 1 to 4, wherein a plurality of main grooves (30) extending in a tire circumferential direction are formed in the tread portion (2), and a plurality of land portions (20) are defined by the main grooves (30), and at least a part of the narrow cover (45) is arranged on an inner side in the tire radial direction of the land portion (20) closest to an equatorial plane (CL) of the tire (1) among the plurality of land portions (20). [6] A method of manufacturing a pneumatic tire (1) which spirally winds strip-shaped belt cover materials (50) on an outer side in a tire radial direction of a belt layer (14) around a tire rotation axis to arrange a belt cover layer (15), the belt cover layer (15) being formed by laminating an inner full cover (40), a narrow cover (45) and an outer full cover (40) from inside to outside in the tire radial direction, the method comprising: spirally winding each of the belt cover materials (50) on an outer side in the tire radial direction of the belt layer (14) between shoulder regions (Ash) on both sides in a tire width direction, to form the inner full cover (40) between the shoulder areas (Ash); spirally winding each of the belt cover materials (50) at a position on the outer side in the tire radial direction of the inner full cover (40) and on an inner side in the tire width direction with respect to the shoulder regions (Ash) to form the narrow cover (45) having a width in the tire width direction that is narrower than a width of the inner full cover (40) in the tire width direction; and spirally winding each of the belt cover materials (50) on the outer side in the tire radial direction of the narrow cover (45) and the inner full cover (40) between the shoulder regions (Ash) on both sides in the tire width direction to form the outer full cover (40) between the shoulder regions (Ash), wherein the narrow cover (45) has the width in the tire width direction in a range of not less than 5 mm to not more than 40 mm.

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