tire

Abstract

To provide a tire capable of establishing compatibility between steering stability performance and ride quality performance during high-speed traveling.SOLUTION: A tire comprises a belt layer 7. The belt layer 7 includes at least one belt ply 7A. The belt ply 7A includes a belt cord 7a that is made of a single steel line. In the belt cord 7a, a diameter d1 in a tire radius direction a is 0.2 mm or less. In the belt ply 7A, the 55-200 belt cords 7a per ply width of 5 cm are arranged.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tire having a belt layer. [Background technology]

[0002] Conventionally, tires having a belt layer on the radially inner side of the tread portion are known. For example, the following Patent Document 1 proposes a tire in which a belt made of two or more layers contains cords, and the gauge between the cords of two adjacent layers is specified, thereby achieving both noise performance and low fuel consumption performance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-177838 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in recent years, with improvements in vehicle performance and the development of infrastructure such as expressways, further improvements in steering stability and ride comfort during high-speed driving have been desired even for the tire of Patent Document 1.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire that can achieve both steering stability and ride comfort during high-speed driving. [Means for solving the problem]

[0006] The present invention is a tire having a belt layer, the belt layer including at least one belt ply, the belt ply including a belt cord made of a steel solid wire, the belt cord having a radial diameter of 0.2 mm or less, and the belt ply including 55 to 200 belt cords arranged per 5 cm of ply width.

[0007] In the tire of the present invention, the belt cord preferably contains, by mass %, 0.82 to 1.12% carbon.

[0008] In the tire of the present invention, in the belt ply, the product of the diameter (mm) of the belt cord and the number of the belt cords arranged per 5 cm of ply width is preferably 30 or less.

[0009] In the tire of the present invention, in the belt ply, the product of the diameter (mm) of the belt cord and the number of the belt cords arranged per 5 cm of ply width is preferably 10 or more.

[0010] In the tire of the present invention, in the belt ply, it is desirable that the product of the diameter (mm) of the belt cord and the number (pieces) of the belt cord arranged per 5 cm of ply width divided by the distance (mm) from the outer surface of the tread portion at the tire equator to the belt ply is 4.5 or less.

[0011] In the tire of the present invention, it is preferable that the belt cord has a circular cross section perpendicular to the longitudinal direction of the belt cord, and that the strength TS (MPa) of the belt cord satisfies the following formula (1). TS≧-1700d+4200 … (1) Where: d: Belt cord diameter (mm)

[0012] In the tire of the present invention, it is preferable that the belt cord has a flat cross section perpendicular to the longitudinal direction of the belt cord, and that the belt cord has an aspect ratio of 1.05 or more.

[0013] In the tire of the present invention, it is preferable that the belt layer includes two or more of the belt plies, and the distance between the belt cords of two adjacent belt plies in the tire radial direction is three times or less the diameter of the belt cord.

[0014] In the tire of the present invention, it is preferable that the tire has a band layer arranged radially outward of the belt layer, the band layer includes at least one band ply, and the band ply includes a band cord made of organic fiber and arranged at an angle of 5° or less with respect to the tire circumferential direction. Effect of the Invention

[0015] In the tire of the present invention, the belt layer includes at least one belt ply, the belt ply includes a belt cord made of a steel single wire, and the belt cord has a radial diameter of 0.2 mm or less. Such a belt ply can improve the ride comfort performance of the tire during high-speed running. This is because it is believed that the radial rigidity of the tire can be reduced because the radial diameter of the belt cord is small.

[0016] In addition, such a belt cord helps to achieve both steering stability and ride comfort of the tire during high-speed driving. This is because the belt cord is not twisted, so it is easy to generate stress in response to deformation, improving the ability of the tread portion to follow the road surface and generating excellent reaction force.

[0017] The belt ply has an arrangement number of the belt cords per 5 cm of ply width of 55 to 200. Such a belt ply can improve the steering stability of the tire during high-speed running. This is because the density of the belt cords in the tire axial direction is high, so that the rigidity in the tire axial direction can be increased, and the reaction force from the belt cords is also considered to be large. As a result, the tire of the present invention can be considered to be able to increase the rigidity in the tire axial direction while decreasing the rigidity in the tire radial direction, and therefore can achieve both steering stability and ride comfort during high-speed running. [Brief description of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view showing one embodiment of a tire of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of a belt layer and a band layer of the present embodiment. [Diagram 3] FIG. 11 is a cross-sectional view of a belt layer and a band layer according to another embodiment. [Figure 4] FIG. 2 is a schematic diagram of a belt cord. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. 1 shows a tire meridian cross section including a rotation axis of a tire 1 of this embodiment in a normal state. Here, the "normal state" refers to a state in which, in the case of a pneumatic tire, the tire 1 is mounted on a normal rim, the tire pressure is adjusted to a normal internal pressure, and no load is applied. Unless otherwise specified below, the dimensions of each part of the tire 1 are values ​​measured in this normal state.

[0020] A "genuine rim" is a rim that is determined for each tire by a standard system that includes the standard on which tire 1 is based, for example, a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. If there is no standard system that includes the standard on which tire 1 is based, a "genuine rim" is a rim that can be assembled and does not leak air, and that has the smallest rim diameter and the smallest rim width among the rims.

[0021] "Normal internal pressure" is the air pressure set for each tire by a standard system that includes the standard on which tire 1 is based, such as "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. "Normal internal pressure" is the air pressure set for each tire by the manufacturer, etc., if there is no standard system that includes the standard on which tire 1 is based.

[0022] The tire 1 of this embodiment is suitable for use as a passenger car tire. In this specification, a passenger car tire refers to a rubber pneumatic tire that is intended to be mounted on a four-wheeled vehicle and has a normal load of 1000 kg or less. Although passenger car tires are not particularly limited as long as the normal load is 1000 kg or less, the normal load is preferably 900 kg, more preferably 750 kg, and even more preferably 700 kg. The normal internal pressure is 250 kPa for passenger car tires.

[0023] The "normal load" is the load that is determined for each tire by each standard in the standard system including the standard on which tire 1 is based, and is the "maximum load capacity" in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "LOAD CAPACITY" in the case of ETRTO.

[0024] The tire 1 is not limited to a passenger vehicle tire, and can be used as a heavy load tire, a motorcycle tire, a racing tire, etc. The tire 1 including the belt layer 6 described later can be used as various tires such as a resin tire using a thermoplastic elastomer and a non-pneumatic tire that is not filled with pressurized air.

[0025] 1, a tire 1 of this embodiment includes a tread portion 2 extending in an annular shape, a pair of sidewall portions 3 extending on both sides of the tread portion 2, and a pair of bead portions 4 extending continuous with the sidewall portions 3. The tire 1 of this embodiment has a toroidal carcass 6 extending across between bead cores 5 of the pair of bead portions 4, and a belt layer 7 disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2 in the tire radial direction a.

[0026] The tread portion 2 is desirably formed of at least one elastomer layer. The tread portion 2 may have, for example, two or more elastomer layers laminated in the tire radial direction a, or may have a plurality of elastomer layers in the tire axial direction. The elastomer layer of the tread portion 2 may be appropriately provided with, for example, circumferential grooves extending in the tire circumferential direction, lateral grooves extending in the tire axial direction, sipes with a groove width of 2 mm or less, and the like. Examples of the circumferential grooves include those that extend linearly and those that extend zigzag. The profile of the outer surface 2a of the tread portion 2 is, for example, a single arc or a combination of arcs with multiple curvatures.

[0027] Examples of the elastomer layer of the tread portion 2 include natural rubber, isoprene-based rubber such as isoprene rubber, butadiene rubber, styrene butadiene rubber, styrene isoprene butadiene rubber, chloroprene rubber, acrylonitrile butadiene rubber, and diene rubber such as butyl rubber.

[0028] The sidewall portion 3 is desirably formed of at least one elastomer layer. The sidewall portion 3 may have, for example, two or more elastomer layers laminated in the tire axial direction, or may have a plurality of elastomer layers in the tire radial direction a. The elastomer layer of the sidewall portion 3 may be, for example, the same component as the elastomer layer of the tread portion 2, or may be a different component.

[0029] The boundary surface between the elastomer layer of the tread portion 2 and the elastomer layer of the sidewall portion 3 is, for example, located outside in the tire radial direction a from the inner end side at the outer end side in the tire axial direction. The boundary surface between the elastomer layer of the tread portion 2 and the elastomer layer of the sidewall portion 3 may be, for example, located inside in the tire radial direction a from the inner end side at the outer end side in the tire axial direction.

[0030] The carcass 6 includes at least one carcass ply 6A, one carcass ply 6A in this embodiment. The carcass ply 6A is formed of an elastomer layer including carcass cords (not shown) arranged at an angle of 75 to 90 degrees with respect to the tire circumferential direction, for example. As the carcass cords, for example, organic fiber cords such as aromatic polyamide (aramid), rayon, polyester, etc. can be used. Here, in this specification, "A to B" means "A or more and B or less."

[0031] The carcass ply 6A includes, for example, a main body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a turn-up portion 6b continuing to the main body portion 6a and turned up around the bead core 5 from the inner side to the outer side in the tire axial direction. The turn-up portion 6b may have an outer end in the tire radial direction extending to the belt layer 7, for example. Between the main body portion 6a and the turn-up portion 6b of the carcass ply 6A, for example, a bead apex 8 extending from the bead core 5 to the outer side in the tire radial direction is disposed. The bead apex 8 is formed of, for example, an elastomer layer.

[0032] The bead portion 4 may be provided with a bead reinforcing layer (not shown), for example, on the outer side in the tire axial direction of the turned-up portion 6b of the carcass 6. The bead reinforcing layer may be formed, for example, of an elastomer layer having the same component as that of the bead apex 8, or may be formed of an elastomer layer having a different component.

[0033] The bead portion 4 may be provided with a chafer (not shown), for example, on the axially outer side of the folded-up portion 6b of the carcass 6. When the bead reinforcing layer and the chafer are provided, it is preferable that the chafer be disposed axially outer than the bead reinforcing layer.

[0034] The tire 1 of this embodiment is provided with an inner liner 10 on the inside of the carcass 6. The inner liner 10 is desirably formed of an air-impermeable elastomer layer. Examples of the elastomer layer of the inner liner 10 include butyl rubber, halogenated butyl rubber, and the like. Such an inner liner 10 can maintain the air pressure filled in the tire 1.

[0035] The belt layer 7 includes at least one, preferably two or more, and in this embodiment, two belt plies 7A and 7B. The two belt plies 7A and 7B include, for example, a first belt ply 7A located on the inner side in the tire radial direction and a second belt ply 7B located on the outer side of the first belt ply 7A. Such a belt layer 7 can increase the rigidity of the tread portion 2 and improve the steering stability performance of the tire 1 during high-speed running.

[0036] Fig. 2 is a cross-sectional view of the belt layer 7 of this embodiment and a band layer 9 described later, and Fig. 3 is a cross-sectional view of the belt layer 7 and the band layer 9 of another embodiment. As shown in Fig. 2 and Fig. 3, the belt plies 7A and 7B of the belt layer 7 of this embodiment include a belt cord 7a made of a steel solid wire and an elastomer composition 7G that covers the belt cord 7a.

[0037] Such belt plies 7A, 7B are less likely to stretch than the stranded cords and can generate a large reaction force when subjected to deformation in the shear direction, thereby improving the steering stability of the tire 1 during high-speed driving.

[0038] The elastomer composition 7G of the belt plies 7A and 7B of this embodiment exhibits rubber elasticity. Examples of the elastomer composition 7G include a rubber composition and a thermoplastic elastomer composition. When the elastomer composition 7G is a rubber composition, examples of the rubber component include isoprene-based rubber, butadiene-based rubber, styrene-butadiene rubber, nitrile rubber, and butyl rubber. When the elastomer composition 7G is a thermoplastic elastomer composition, examples of the elastomer include block copolymers such as thermoplastic polyurethane, styrene-butadiene block copolymer, and styrene-ethylene-butylene-styrene block copolymer.

[0039] The belt cord 7a of the present embodiment is plated or ternary plated. Examples of the plating include zinc, copper, etc. Examples of the ternary plating include zinc, copper, cobalt, etc. Such a belt cord 7a has good adhesion to the elastomer composition 7G, and can generate a stress in cooperation with the belt cord 7a and the elastomer composition 7G even during high-speed running, thereby improving the steering stability of the tire 1 during high-speed running.

[0040] The belt cord 7a in Fig. 2 has a circular cross section, while the belt cord 7a in Fig. 3 has a flat cross section. In this specification, "circular" means that the ratio of the major axis to the minor axis of the cross section is less than 1.05, and "flat" means that the ratio of the major axis to the minor axis of the cross section is 1.05 or more.

[0041] The belt cords 7a are arranged at an angle of, for example, 10 to 30° with respect to the tire circumferential direction. The belt cords 7a of the first belt ply 7A and the belt cords 7a of the second belt ply 7B are desirably inclined in opposite directions with respect to the tire circumferential direction. Such a belt layer 7 can increase the rigidity of the tread portion 2 in a well-balanced manner and improve the steering stability performance of the tire 1 during high-speed running. Here, the angle of the belt cords 7a is the angle in the tire 1 in a normal state, and can be confirmed, for example, by partially peeling off the tread portion 2.

[0042] The belt cord 7a preferably has a diameter d1 in the tire radial direction a of 0.2 mm or less. Since the diameter d1 of the belt cord 7a in the tire radial direction a is small, the rigidity in the tire radial direction a of the belt cord 7a can be reduced, and the ride comfort performance of the tire 1 during high-speed running can be improved. From this viewpoint, the diameter d1 of the belt cord 7a in the tire radial direction a is more preferably 0.17 mm or less. The lower limit of the diameter d1 of the belt cord 7a is not particularly limited, but is preferably 0.1 mm or more, and more preferably 0.12 mm or more.

[0043] Here, the diameter d1 of the belt cord 7a in the tire radial direction a is the diameter of the cross section if the belt cord 7a has a circular cross section as shown in Fig. 2. Moreover, the diameter d1 of the belt cord 7a in the tire radial direction a is the diameter along the tire radial direction a if the belt cord 7a has a flat cross section as shown in Fig. 3.

[0044] Fig. 4 is a schematic diagram of a belt cord 7a. As shown in Fig. 4, when the belt cord 7a having a flat cross section is arranged at an angle with respect to the tire radial direction a, the minor axis Sd and major axis Ld of the belt cord 7a having a flat cross section, whichever has a smaller angle with respect to the tire radial direction a, is set as the diameter d1 in the tire radial direction a. In Fig. 4, the angle θ1 of the minor axis Sd direction with respect to the tire radial direction a is smaller than the angle θ2 of the major axis Ld direction, so the minor axis Sd is set as the diameter d1 in the tire radial direction a.

[0045] 2 and 3, the belt plies 7A and 7B preferably have 55 to 200 belt cords 7a arranged per 5 cm of ply width. Here, the number n1 of the belt cords 7a arranged per 5 cm of ply width is the number of the belt cords 7a arranged per 5 cm of ply width in a direction perpendicular to the longitudinal direction of the belt cords 7a. The number n1 of the belt cords 7a arranged can be determined, for example, from measurements of the belt plies 7A and 7B in an area including the tire equator C.

[0046] By setting the number n1 of the belt cords 7a per 5 cm of the ply width to 55 or more, it is possible to increase the rigidity of the tread portion 2 in the tire axial direction and improve the steering stability performance of the tire 1 during high-speed running. From this viewpoint, the number n1 of the belt cords 7a is more preferably 65 or more, and further preferably 75 or more.

[0047] By setting the number n1 of the belt cords 7a arranged per 5 cm of the ply width to 200 or less, it is possible to prevent the rigidity of the tread portion 2 from becoming excessively high, and to improve the ride comfort performance of the tire 1 during high-speed running. From this viewpoint, the number n1 of the belt cords 7a arranged is more preferably 190 or less, and further preferably 180 or less.

[0048] In such belt plies 7A, 7B, the density of the belt cords 7a in the tire axial direction is high, so that the rigidity in the tire axial direction can be increased, and the steering stability performance of the tire 1 during high-speed running can be improved. Therefore, the tire 1 of the present embodiment can achieve both steering stability performance and ride comfort performance during high-speed running.

[0049] In the belt plies 7A and 7B, the product (d1×n1) of the diameter d1 (mm) of the belt cord 7a and the number n1 (pieces) of the belt cord 7a arranged per 5 cm of the ply width is preferably equal to or less than 30. Such a product (d1×n1) is the ratio of the belt cord 7a to the width direction of the belt plies 7A and 7B, and is an index related to the interval between adjacent belt cords 7a.

[0050] By making the product (d1×n1) 30 or less, it is possible to suppress an excessive increase in rigidity of the tread portion 2 and improve the ride comfort performance of the tire 1 during high-speed running. From this viewpoint, the product (d1×n1) is more preferably 25 or less, and further preferably 20 or less.

[0051] In the belt plies 7A and 7B, the product (d1×n1) of the diameter d1 (mm) of the belt cord 7a and the number n1 (pieces) of the belt cord 7a arranged per 5 cm of the ply width is preferably 10 or more. When the product (d1×n1) is 10 or more, the restraint of the tread portion 2 is improved, and the tire 1 can achieve both low fuel consumption performance and ride comfort performance. From this viewpoint, the product (d1×n1) is more preferably 13 or more, and further preferably 15 or more.

[0052] As shown in Figures 1 to 3, in the belt plies 7A and 7B, it is preferable that the value (d1 x n1 / L1) obtained by dividing the above-mentioned product (d1 x n1) by the distance L1 (mm) from the outer surface 2a of the tread portion 2 at the tire equator C to the belt plies 7A and 7B is 4.5 or less.

[0053] Here, the distance L1 is the straight-line distance from the outer surface 2a of the tread portion 2 at the tire equator C to the second belt ply 7B, which is the outermost in the tire radial direction in this embodiment, and is the straight-line distance from an imaginary line filling the groove when a groove is present on the tire equator C. Such a value (d1×n1 / L1) is an index showing the relationship between the deformation of the tread portion 2 radially outer than the belt layer 7 and the product (d1×n1).

[0054] The tire 1 can achieve both steering stability and ride comfort during high-speed driving by specifying the product (d1×n1) and the distance L1 so that the value (d1×n1 / L1) is 4.5 or less. That is, when the product (d1×n1) is large, the distance L1 can be increased to absorb vibrations transmitted to the belt plies 7A and 7B and maintain the rigidity of the belt layer 7 at a high level, thereby achieving both steering stability and ride comfort of the tire 1 during high-speed driving. Also, when the product (d1×n1) is small, the distance L1 can be decreased to make the belt plies 7A and 7B more likely to generate a reaction force and improve the ability to follow the road surface, thereby achieving both steering stability and ride comfort of the tire 1 during high-speed driving.

[0055] The belt cord 7a preferably contains, by mass %, 0.82 to 1.12% carbon. Such belt cord 7a has an excellent balance between strength TS and toughness, and therefore can increase the rigidity of the tread portion 2 and improve the steering stability of the tire 1 during high-speed running.

[0056] In addition to the above-mentioned carbon, the elements contained in the belt cord 7a include, for example, silicon, manganese, phosphorus, sulfur, etc. The belt cord 7a may contain, for example, by mass %, 0.15 to 0.35% silicon, 0.30 to 0.60% manganese, 0.30% or less phosphorus, and 0.30% or less sulfur.

[0057] 2, the belt cord 7a of this embodiment has a circular cross section perpendicular to the longitudinal direction of the belt cord 7a. It is desirable that the strength TS of the belt cord 7a satisfies the following formula (1). Such a belt cord 7a can have a strength TS (MPa) suitable for improving the steering stability performance of the tire 1 during high-speed running. Here, the strength TS (MPa) of the belt cord 7a is the breaking strength at 25°C in accordance with JIS Z2241. TS≧-1700d+4200 … (1) Where: d: diameter d1 of belt cord 7a (mm)

[0058] From this viewpoint, it is more preferable that the strength TS (MPa) of the belt cord 7a satisfies the following formula (2). TS≧-1700d+4500 … (2) Where: d: diameter d1 of belt cord 7a (mm)

[0059] As shown in Fig. 3, the belt cord 7a of another embodiment has a flat cross section perpendicular to the longitudinal direction of the belt cord 7a. The aspect ratio of the belt cord 7a is preferably 1.05 or more. Such a belt cord 7a can easily have different rigidity in the tire axial direction and in the tire radial direction a, which helps to achieve both the steering stability and ride comfort of the tire 1 during high-speed running. From this viewpoint, the aspect ratio of the belt cord 7a is more preferably 1.10 or more, and even more preferably 1.20 or more.

[0060] As shown in Figs. 1 to 3, the distance L3 between the belt cords 7a of two belt plies 7A, 7B adjacent in the tire radial direction a is preferably three times or less the diameter d1 of the belt cord 7a in the tire radial direction a.

[0061] In the present embodiment, a band layer 9 is disposed on the inner side of the tread portion 2 in the tire radial direction a, and on the outer side of the belt layer 7 in the tire radial direction a. The band layer 9 includes at least one band ply 9A, in the present embodiment, one band ply 9A. Such a band layer 9 enhances the restraint of the tread portion 2 even during high-speed running, and can achieve both ride comfort and low fuel consumption performance of the tire 1.

[0062] The band ply 9A of this embodiment includes a band cord 9a arranged at an angle of 5° or less with respect to the tire circumferential direction, and an elastomer composition 9G that covers the band cord 9a. The elastomer composition 9G of the band ply 9A preferably exhibits rubber elasticity, similar to the elastomer composition 7G of the belt plies 7A and 7B. The elastomer composition 9G may be, for example, the same as the elastomer composition 7G.

[0063] The band cord 9a in Fig. 2 has a circular cross section, while the band cord 9a in Fig. 3 has a flat cross section. The band cord 9a is made of, for example, organic fibers. The band cord 9a preferably has a diameter d2 in the tire radial direction a of 0.40 to 0.70 mm.

[0064] Here, the diameter d2 of the band cord 9a in the tire radial direction a is the diameter of the cross section if the band cord 9a has a circular cross section as shown in Fig. 2. Moreover, the diameter d2 of the band cord 9a in the tire radial direction a is the diameter along the tire radial direction a if the band cord 9a has a flat cross section as shown in Fig. 3.

[0065] Although not shown in the figure, when the band cord 9a with a flat cross section is arranged at an angle with respect to the tire radial direction a, of the minor diameter and major diameter of the band cord 9a with a flat cross section, the one having the smaller angle with respect to the tire radial direction a is set to the diameter d2 in the tire radial direction a (see FIG. 4).

[0066] By setting the diameter d2 of the band cord 9a in the tire radial direction a to 0.40 mm or more, the restraint of the tread portion 2 can be reliably improved, and both fuel economy and ride comfort can be achieved. From this viewpoint, the diameter d2 of the band cord 9a is more preferably 0.50 mm or more, and further preferably 0.55 mm or more.

[0067] By setting the diameter d2 of the band cord 9a in the tire radial direction a to 0.70 mm or less, it is possible to suppress an increase in the thickness of the tread portion 2 and reliably reduce the rolling resistance of the tire 1. From this viewpoint, the diameter d2 of the band cord 9a is more preferably 0.65 mm or less.

[0068] In the band ply 9A, preferably, 35 to 65 band cords 9a are arranged per 5 cm of ply width. Here, the number n2 of arranged band cords 9a per 5 cm of ply width is the number arranged per 5 cm of ply width in the direction perpendicular to the longitudinal direction of the band cords 9a.

[0069] By setting the number n2 of the band cords 9a per 5 cm of the ply width to 35 or more, the restraint of the tread portion 2 can be reliably improved, and both fuel efficiency and ride comfort of the tire 1 can be achieved. From this viewpoint, the number n2 of the band cords 9a is more preferably 40 or more, and further preferably 45 or more.

[0070] By setting the number n2 of the band cords 9a per 5 cm of the ply width to 65 or less, it is possible to prevent the rigidity of the tread portion 2 from becoming excessively high, and to improve the ride comfort performance of the tire 1. From this viewpoint, the number n2 of the band cords 9a is more preferably 60 or less, and further preferably 55 or less.

[0071] In the band ply 9A, the product (d2×n2) of the diameter d2 (mm) of the band cord 9a in the tire radial direction a and the number n2 (pieces) of the band cord 9a arranged per 5 cm of the ply width is preferably 15 to 45. Such a product (d2×n2) is the ratio of the band cord 9a to the width direction of the band ply 9A, and is an index related to the interval between adjacent band cords 9a.

[0072] By making the product (d2×n2) 15 or more, it is possible to reliably improve the restraining ability of the tread portion 2 and achieve both low fuel consumption performance and ride comfort performance of the tire 1. From this viewpoint, the product (d2×n2) is more preferably 20 or more.

[0073] The product (d2×n2) of 45 or less can suppress peeling caused by small intervals between the band cords 9a, thereby improving the durability of the tire 1. From this viewpoint, the product (d2×n2) is more preferably 40 or less.

[0074] The product (d2×n2×L2) of the above product (d2×n2) and the distance L2 (mm) from the outer surface 2a of the tread portion 2 at the tire equator C to the band ply 9A is preferably 90 or more. Such a product (d2×n2×L2) is an index showing the restraint of the tread portion 2. The distance L2 is also called the gauge of the tread portion 2, and is an index showing the rubber thickness of the tread portion 2.

[0075] By having the product (d2×n2×L2) of 90 or more, even when the gauge (distance L2) of the tread portion 2 is small, the tread portion 2 exhibits sufficient restraint during high-speed driving, enabling the tire 1 to achieve both ride comfort and low fuel consumption performance.

[0076] The elongation of the band cord 9a under a load of 66 N is preferably 2.5% or more. When the elongation of the band cord 9a under a load of 66 N is 2.5% or more, the band cord 9a can stretch even when the tire 1 is expanded during vulcanization molding, thereby suppressing contact with the belt cord 7a. From this viewpoint, the elongation of the band cord 9a under a load of 66 N is more preferably 3.0% or more, and even more preferably 3.5% or more.

[0077] The band cord 9a preferably has an elongation of 7.0% or less when loaded with 198 N. By making the band cord 9a have an elongation of 7.0% or less when loaded with 198 N, the band cord 9a exhibits sufficient restraint on the tread portion 2 during high-speed running, and can achieve both ride comfort and fuel economy of the tire 1. From this viewpoint, the elongation at a load of 198 N is more preferably 6.5% or less, and even more preferably 6.0% or less.

[0078] Although a particularly preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment and can be modified in various ways. EXAMPLES

[0079] A tire having the basic structure shown in Figure 1 was prototyped based on the specifications in Tables 1 and 2. Using the prototype tires, the handling stability and ride comfort performance during high-speed driving were tested. The common specifications and test methods are as follows:

[0080] <Common specifications> Tire size: 205 / 55R16 Air pressure: 220kPa Test vehicle: Front-wheel drive mid-size passenger car

[0081] <Handling stability at high speeds> The prototype tires were fitted to all wheels of a test vehicle, and the vehicle was driven around a test course at high speed in a zigzag manner. The test drivers evaluated the vehicle's handling stability on a scale of 1 to 5. Similar tests were conducted by 20 test drivers, and the total score was calculated. The results were expressed as an index, with the total score of Comparative Example 1 being 100, and the higher the index value, the better the handling stability during high-speed driving.

[0082] <Ride comfort when driving at high speeds> The prototype tires were fitted to all wheels of a test vehicle, and the vehicle was driven around a test course at a speed of 100km / h. The test driver evaluated the ride comfort performance on a scale of 1 to 5 using his senses. Similar tests were conducted by 20 test drivers, and the total score was calculated. The results were expressed as an index, with the total score of Comparative Example 1 being 100, and the higher the value, the better the ride comfort performance during high-speed driving.

[0083] The test results are shown in Tables 1 and 2. [Table 1] [Table 2]

[0084] As a result of the tests, the tires of the examples were superior to the comparative examples in terms of handling stability and ride comfort during high-speed driving, and the overall performance determined by the sum of each performance was also good, confirming that it is possible to achieve both handling stability and ride comfort during high-speed driving. [Explanation of symbols]

[0085] 1 Tire 7 Belt layer 7A Belt ply 7a Belt cord

Claims

1. A tire having a belt layer, The belt layer includes at least one belt ply, The belt ply includes a belt cord made of a steel single wire, The belt cord has a radial diameter of 0.17 mm or less and a cross section perpendicular to the longitudinal direction of the belt cord is flat, The aspect ratio of the belt cord is 1.05 or more, The belt ply has 55 to 200 belt cords arranged per 5 cm of ply width. tire.

2. A tire having a belt layer, The belt layer includes at least one belt ply, The belt ply includes a belt cord made of a steel single wire, The belt cord has a radial diameter of 0.17 mm or less and contains, by mass%, 0.82 to 1.12% carbon, The belt ply has 55 to 200 belt cords arranged per 5 cm of ply width. tire.

3. A band layer is arranged radially outward of the belt layer, The band layer includes at least one band ply, The band ply includes a band cord made of organic fiber and arranged at an angle of 5° or less with respect to the tire circumferential direction, The tire according to claim 1 or 2, wherein the band cord has an elongation of 7.0% or less under a load of 198 N.

4. A tire having a belt layer, The belt layer includes at least one belt ply, The belt ply includes a belt cord made of a steel single wire, The belt cord has a radial diameter of 0.2 mm or less in the tire radial direction, The belt ply has 55 to 200 belt cords arranged per 5 cm of ply width, A band layer is disposed on the outer side of the belt layer in the tire radial direction, The band layer includes at least one band ply, The band ply includes a band cord made of organic fiber and arranged at an angle of 5° or less with respect to the tire circumferential direction, The band cord has an elongation of 7.0% or less under a load of 198 N. tire.

5. The tire as described in claim 4, wherein the belt cord has a radial diameter of 0.17 mm or less.

6. A tire as described in any one of claims 1 to 5, wherein in the belt ply, the product of the diameter (mm) of the belt cord and the number of the belt cords arranged (pieces) per 5 cm of ply width is 30 or less.

7. A tire as described in any one of claims 1 to 6, wherein in the belt ply, the product of the diameter (mm) of the belt cord and the number of the belt cords arranged (pieces) per 5 cm of ply width is 10 or more.

8. A tire as described in any one of claims 1 to 7, wherein in the belt ply, the product of the diameter (mm) of the belt cord and the number (pieces) of the belt cord arranged per 5 cm of ply width divided by the distance (mm) from the outer surface of the tread portion at the tire equator to the belt ply is 4.5 or less.

9. The belt cord has a circular cross section perpendicular to the longitudinal direction of the belt cord, The tire according to claim 1 , wherein a strength TS (MPa) of the belt cord satisfies the following formula (1): TS≧-1700d+4200… (1) Where: d: Belt cord diameter (mm)

10. The belt layer includes two or more of the belt plies, The tire according to claim 1 , wherein a distance between the belt cords of two belt plies adjacent to each other in a radial direction of the tire is equal to or less than three times the diameter of the belt cord.

Images