pneumatic tires

Abstract

To provide a pneumatic tire that can be improved in a steering performance, while maintaining straight-running stability during high-speed travelling.SOLUTION: A pneumatic tire comprises a tread part 2. In a grounding surface of the tread part 2, a center part in a tire axial direction protrudes to outside in a tire radial direction more than a tread end Te. A band layer 8 including band cords 10 is included inside the tread part 2. The band cords 10 are steel cords 11 including a plurality of steel filaments 12. Occupation ratios the filaments in the band 10 arranged closest to the tread end Te side in the band layer 8 are 0.15-0.50. Products of an average arrangement number Ea (number / 5 cm) per 5 cm in a tire width direction of the band cords 10 in the band layer 8 and total cross sectional areas ΣSf of the plurality of steel filaments 12 are five or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] For example, Patent Document 1 below proposes a motorcycle tire having a band layer inside the tread portion. The band layer is formed from a band ply having a steel band cord. The motorcycle tire is expected to improve steering stability and durability by specifying the compression rigidity, bending rigidity, etc. of the band cord. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-167716 Summary of the Invention [Problem to be solved by the invention]

[0004] Pneumatic tires with steel cords in the band layer, such as the above-mentioned motorcycle tires, experience little growth in outer diameter during running and are excellent in straight-line stability during high-speed running. Meanwhile, the band layer also suppresses moderate deformation of the tread portion near the tread edge. As a result, the above-mentioned pneumatic tires have a small contact area of ​​the tread portion during cornering, which leaves room for improvement in cornering performance.

[0005] The present disclosure has been devised in consideration of the above-mentioned problems, and its main object is to provide a pneumatic tire that can improve cornering performance while maintaining straight-line stability during high-speed driving. [Means for solving the problem]

[0006] The present disclosure relates to a pneumatic tire having a tread portion, wherein the contact surface of the tread portion has a central portion in the tire axial direction that protrudes radially outward from the tread end, and the inside of the tread portion includes a band layer including a band cord wound spirally in the tire circumferential direction, the band cord being a steel cord including a plurality of steel filaments, and the band cord arranged furthest to the tread end side of the band layer in a cross-sectional view of the tire including the tire rotation axis has an area Sv (mm ) of a virtual smallest circle that can completely surround the plurality of steel filaments. 2 ) and the total cross-sectional area of ​​the plurality of steel filaments ΣSf (mm 2 ) is 0.15 to 0.50, and the product of the average number Ea (pieces / 5 cm) of band cords arranged in the band layer per 5 cm in the tire width direction and the sum ΣSf of the cross-sectional areas of the plurality of steel filaments is 5 or more. [Effects of the Invention]

[0007] By having the above-described configuration, the pneumatic tire of the present disclosure can improve cornering performance while maintaining straight-line stability during high-speed driving. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a pneumatic tire according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is an enlarged perspective view of the band cord of FIG. [Figure 3] FIG. 2 is an enlarged cross-sectional view of a band cord. [Figure 4] FIG. 2 is a schematic diagram showing the measurement of bending rigidity. [Figure 5] (A) is a cord-containing sample used to measure compression stiffness, and (B) is a graph showing the compression load-compression amount curve of a band cord. [Figure 6] FIG. 10 is an enlarged cross-sectional view of a band cord according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 shows a cross-sectional view of a pneumatic tire 1 (hereinafter sometimes simply referred to as "tire") in a normal state, illustrating one embodiment of the present disclosure. The tire 1 of this embodiment is for a motorcycle, and is preferably used as a front tire for circuit racing. However, the present disclosure is not limited to this embodiment, and can be preferably used as a passenger car tire, a light truck tire, a truck / bus tire, etc.

[0010] "Normal condition" means, in the case of a tire for which various standards are established, a state in which the tire is mounted on a normal rim, inflated to a normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established, the normal condition means a standard use state according to the intended use of the tire, in which the tire is not mounted on a vehicle and no load is applied. Unless otherwise specified, in this specification, the dimensions of each part of the tire are values ​​measured in the normal condition. Furthermore, when measuring the physical properties of an inner member included in a finished tire based on this specification, the inner member is sampled in a manner that minimizes the impairment of its characteristics, and then the physical properties are measured.

[0011] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

[0012] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0013] As shown in Fig. 1, the axial center of the contact patch 2s of the tread portion 2 protrudes radially outward from the tread edge Te. In this embodiment, the contact patch 2s is curved in a convex arc shape radially outward. The tread edge Te corresponds to both axial ends of the contact patch 2s of the tread portion 2, and these may come into contact with the ground when cornering at the maximum camber angle, for example.

[0014] The tire 1 of this embodiment includes, for example, a carcass 6 and a band layer 8. The carcass 6 extends from the tread portion 2 through the sidewall portion 3 to the bead cores 5 of the bead portions 4. A known configuration may be appropriately adopted for the carcass 6. The band layer 8 is disposed inside the tread portion 2 and on the outer side of the carcass 6 in the tire radial direction. Although not included in this embodiment, another tread reinforcing layer may be disposed on the inner side of the band layer 8 in the tire radial direction.

[0015] The band layer 8 is configured as a so-called jointless band including a band cord 10 wound spirally in the tire circumferential direction. In a preferred embodiment, the band cord 10 is wound at an angle of 5° or less with respect to the tire circumferential direction.

[0016] Fig. 2 shows an enlarged perspective view of the band cord 10 of Fig. 1. As shown in Fig. 2, the band cord 10 is a steel cord in which a plurality of steel filaments 12 are covered with a topping rubber 11.

[0017] Conventionally, tires with steel cords in the band layer have little outer diameter growth during running and have excellent straight-line stability during high-speed running. However, the band layer also suppresses moderate deformation of the tread portion near the tread edge. Therefore, the tire tends to have a small contact area with the tread portion during cornering, leaving room for improvement in cornering performance.

[0018] In the present disclosure, in order to ensure appropriate deformation of the tread portion 2 near the tread end Te, a filament occupancy rate Fs is specified for the band cord 10e arranged closest to the tread end Te in the band layer 8 in a cross-sectional view of the tire including the tire rotation axis. The filament occupancy rate Fs is defined as follows.

[0019] 3 shows a cross-sectional view of a band cord 10e. As shown in FIG. 3, the filament occupancy rate is calculated by multiplying the area Sv of the smallest imaginary circle 15 (shown by a two-dot chain line in FIG. 3) that can completely surround all of the steel filaments 12 arranged in the band cord 10 in the cross section of one band cord 10 by the sum ΣSf (mm 2) The filament occupancy rate Fs is expressed as the ratio ΣSf / Sv of the filament occupancy rate Fs. A band cord 10 with a small filament occupancy rate Fs is more likely to stretch, while a band cord 10 with a large filament occupancy rate Fs is less likely to stretch. In the present disclosure, the filament occupancy rate Fs of the band cord 10e disposed closest to the tread end Te is set to 0.15 to 0.50. This allows the band cord 10e to stretch appropriately. Therefore, a large contact area can be secured near the tread end Te, thereby improving cornering performance.

[0020] On the other hand, if the total cross-sectional area ΣSf of the steel filaments 12 in the band cord 10 decreases, the binding force of the band cord 10 in the tread portion decreases, and the tread portion becomes more susceptible to deformation due to centrifugal force acting on the tread portion during high-speed driving, raising concerns about reduced straight-line stability. Therefore, the developers discovered that, as the total cross-sectional area ΣSf of the steel filaments 12 decreases, it is desirable to increase the average number Ea of band cords 10 arranged in the tire width direction in order to improve the binding force acting on the tread portion. Based on this finding, in this disclosure, the product of the average number Ea of band cords 10 arranged per 5 cm in the tire width direction (numbers / 5 cm) and the total cross-sectional area ΣSf of the steel filaments (hereinafter sometimes referred to as the "product Ea·ΣSf") is set to 5 or more. This ensures sufficient elongation of the band cord, improving cornering performance during high-speed driving while also providing binding force, which is believed to improve straight-line driving performance.

[0021] The above-described band cord 10 can be obtained, for example, by twisting together corrugated steel filaments 12. The filament occupancy rate Fs can be appropriately adjusted by changing the degree of corrugation of the steel filaments 12.

[0022] The following describes the configuration of this embodiment in more detail. Note that each configuration described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present disclosure can achieve the above-described effects even if it does not include the configurations described below. Furthermore, even if any one of the configurations described below is applied alone to a tire of the present disclosure having the above-described characteristics, performance improvement corresponding to each configuration can be expected. Furthermore, when several of the configurations described below are applied in combination, combined performance improvement corresponding to each configuration can be expected.

[0023] 1, the tire 1 of this embodiment is for a motorcycle, and has a tread aspect ratio Ta, which is expressed as the ratio h / W of the half contact width W, which is the distance in the tire axial direction from the tire equatorial plane C to the tread edge Te, to the contact height h, which is the height in the tire radial direction from the tread edge Te to the center of the contact surface 2s, of about 0.6 to 1.0. The developers have found that, in order to further enhance the above-mentioned effects, it is effective to specify the tread aspect ratio Ta in relation to the filament occupancy rate Fs.

[0024] From this perspective, the product Ta·Fs of the tread aspect ratio Ta and the filament occupancy rate Fs is preferably 0.40 or less, more preferably 0.38 or less, and even more preferably 0.35 or less. Since the larger the tread aspect ratio Ta, the greater the deformation near the tread end Te, it is considered desirable to reduce the filament occupancy rate Fs of the band cord 10e. Therefore, by setting the product Ta·Fs of the band cord 10e and the filament occupancy rate Fs to a certain value or less, the band cord 10e can be sufficiently elongated according to the tread aspect ratio Ta, thereby reliably improving cornering performance. Meanwhile, the lower limit of the product Ta·Fs is not particularly limited, but is preferably 0.15 or more, more preferably 0.20 or more, and even more preferably 0.22 or more. This optimizes the deformation of the contact patch near the tread end Te, further improving cornering performance.

[0025] The present disclosure is not limited to tires for motorcycles, but may also be applied to, for example, pneumatic tires for passenger cars. Such tires have a tread aspect ratio Ta of, for example, 0.30 or less. In this case, the product Ta·Fs is preferably 0.05 to 0.15.

[0026] 1, in the tire of the present embodiment 1, the band cords 10 are arranged in the tire width direction to form a band layer 8. The number of band cords 10 arranged per 5 cm in the tire width direction is preferably 40 cords / 5 cm or more, and more preferably 41 cords or more. On the other hand, the upper limit is preferably 80 cords / 5 cm or less, and more preferably 60 cords / cm or less. This optimizes the binding force acting on the tread portion, further improving straight-line stability and cornering performance.

[0027] The product of the average number of arranged filaments Ea and the total area of ​​the filaments ΣSf of the band cord 10 is preferably 5.5 or more, more preferably 5.8 or more. On the other hand, the upper limit is preferably 15.0 or less, more preferably 9 or less, and even more preferably 8 or less. This allows the band cord 10 to stretch moderately while maintaining the binding force applied to the tread portion, thereby further improving straight-line stability and cornering performance.

[0028] Furthermore, the difference (Ec - Ee) between the number Ec of the band cords 10 arranged per 5 cm in the tire width direction in the central portion of the contact patch (hereinafter sometimes referred to as the "tread central region") and the number Ee of the band cords 10 arranged in the width direction in the region on the tread edge Te side (hereinafter sometimes referred to as the "tread edge side region") is preferably 10 or less, and more preferably 9 or less. There is no particular restriction on the lower limit, but it is preferably 0 or more. This makes it possible to uniformize the binding force in the tread central region and the tread edge side region, making it easier to improve straight-line stability.

[0029] Note that Ea, Ec, and Ee, which represent the number of band cords 10 arranged in the tire width direction, all refer to the number of band cords 10 arranged in the tire width direction along the arrangement direction of the band cords 10, and in the case of the motorcycle tire shown in FIG. 1, refer to the number of band cords arranged in the direction along the arc of the band layer 8.

[0030] The average number of arranged band cords 10, Ea, is the average number of arranged band cords 10 per 5 cm across the entire band layer 8, and is calculated from the length of the band layer 8 along the arc and the number of band cords 10 included therein. The number of arranged cords in the tread central region, Ec, is the number of arranged band cords 10 within a range of ±2.5 cm from the tire equatorial plane. The number of arranged band cords 10 in the tread edge region, Ee, is the number of arranged band cords 10 within a range of 5 cm from the end point of the band layer 8 on the tread edge side toward the center. The number of arranged band cords 10 in the tread edge region, Ee, is the average number of arranged band cords 10 per 5 cm at both ends. These can be calculated by determining the number of band cords 10 in each region in a radial cross section of the tire including the tire rotation axis, with the distance between bead portions aligned to the normal rim width.

[0031] The average thickness of the band layer 8 in the tire radial direction is preferably 0.5 mm or more and 1.5 mm or less. The average thickness of the band layer here refers to the average thickness from one end of the band layer 8 to the other end.

[0032] As shown in Fig. 3, the band cord 10 of this embodiment has two to six steel filaments 12 twisted together. In a preferred embodiment, the band cord 10 has three to five steel filaments 12 twisted together. The steel filaments 12 are arranged so as to surround the center 16 of the band cord 10, and in a preferred embodiment, the steel filaments 12 are arranged at equal intervals around the periphery of the band cord 10 and are in contact with an imaginary minimum circle 15. However, the arrangement of the steel filaments 12 is not limited to this embodiment.

[0033] The outer diameter D1 of the imaginary minimum circle 15 is, for example, 0.50 to 1.50 mm in the tread end region, preferably 0.55 to 1.00 mm, and more preferably 0.60 to 0.80 mm. On the other hand, in the tread central region, it is, for example, 0.50 to 1.00 mm, preferably 0.55 to 0.90 mm, and more preferably 0.60 to 0.80 mm. This increases the binding force in the tread portion, and makes it easier for the band cord 10 to elongate during cornering, thereby optimizing the ground contact shape and making it easier to improve straight-line stability and cornering performance.

[0034] By determining the outer diameter D1, the area Sv of the virtual minimum circle 15 can be determined. In the tread central region, the outer diameter D1 can be calculated from the virtual minimum circle of the band cord 10 that is closest to the equatorial plane in the band layer 8, and in the tread edge region, the outer diameter D1 can be calculated from the virtual minimum circle of the band cord 10 at the end point of the band layer 8. The outer diameter D1 and area Sv of the virtual minimum circle in the tread edge region are the average values ​​of both ends.

[0035] The outer diameter d1 of the steel filament 12 is, for example, 0.15 to 0.27 mm, and preferably 0.18 to 0.24 mm, although the outer diameter d1 is not limited to this range.

[0036] If the filament occupancy rate Fs in the band cord 10e is excessively small, the effect of reducing rigidity in the vicinity of the tread end Te spreads, making the central portion of the tread portion 2 more susceptible to deformation, which may result in a decrease in straight-line stability during high-speed running. Therefore, the filament occupancy rate Fs in the band cord 10e is desirably 0.20 or more, more desirably 0.25 or more, and desirably 0.40 or less, more desirably 0.35 or less. This improves straight-line stability and cornering performance during high-speed running in a well-balanced manner.

[0037] Furthermore, the band cord 10e having the filament occupancy rate Fs specified within the above range has appropriate elasticity, thereby exhibiting the above-mentioned effects and making it difficult for the band cord 10e to meander when the tread rubber contracts after the tire is vulcanized. Therefore, minute wavy deformation of the tread portion 2 caused by meandering of the band cord 10e around the tread edge Te (hereinafter, such a defect may be referred to as "tread waviness") is suppressed, and the rate of molding defects during tire manufacturing is reduced.

[0038] From the same viewpoint, the absolute value of the difference between the tread aspect ratio Ta and the filament occupancy rate Fs of the band cord 10 is preferably 1.0 or less, more preferably 0.1 to 0.9, and even more preferably 0.2 to 0.8.

[0039] The bending rigidity of the band cord 10 is, for example, 35.0 g·cm or less, and preferably 5.0 to 15.0 g·cm, which makes it possible to suppress tread waviness while maintaining a sense of rigidity of the tire during cornering.

[0040] The bending rigidity is measured as follows. Fig. 4 shows a schematic diagram of the bending rigidity measurement. As shown in Fig. 4, the bending rigidity is measured using, for example, a stiffness tester (e.g., Model 150-D) manufactured by Taber (USA). The bending rigidity corresponds to the average value of the bending moment at +15 degrees and the bending moment at -15 degrees when both ends of a 145 mm long band cord 10 are attached to clamps and the band cord 10 is bent at angles of +15 degrees and -15 degrees.

[0041] The compression stiffness CS of the band cord 10 is, for example, 500 N / mm or less, preferably 200 to 500 N / mm, and more preferably 300 to 400 N / mm, thereby improving the compression fatigue resistance of the band cord 10.

[0042] The compression stiffness CS is measured as follows: As shown in Fig. 5(A), a cord-containing sample K1 is prepared in which a single 25 mm long band cord 10 is embedded in the height direction at the center of a cylindrical rubber g having a diameter of 25 mm and a height of 25 mm, and a cord-free sample K2 (not shown) for correction is prepared in which the band cord 10 is not embedded. Each sample K1 and K2 is vulcanized under the same vulcanization conditions (for example, a temperature of 165°C for 18 minutes) and has substantially the same physical properties except for the presence or absence of the band cord 10.

[0043] Furthermore, a compression load-compression curve, which is a graph showing the relationship between the compression load CL and the compression amount CA, is obtained for each of the samples K1 and K2. This compression load-compression curve is obtained by compressing each of the samples K1 and K2 at a speed of 2.0 mm / min using a tensile tester and measuring the compression load CL and the compression amount CA. Then, the measurement data for the cord-containing sample K1 is corrected with the measurement data for the cord-free sample K2 (i.e., the influence of the rubber portion of the sample is removed and data that can be assumed to represent only the cord is extracted), thereby obtaining the compression load-compression curve for the band cord 10 as shown in Figure 5(B). The slope in the middle region of this curve is defined as the compression stiffness CS (N / mm).

[0044] 1, in a cross-sectional view of the tire, the band layer 8 includes a plurality of band cords 10 aligned in the tire axial direction. The filament occupancy rate Fs of the plurality of band cords 10 preferably decreases as they are closer to the tread end Te. This improves straight-line stability and cornering performance during high-speed driving in a well-balanced manner.

[0045] More specifically, when viewed in cross section of the tire, the contact surface of the tread portion 2 from the tire equatorial plane C to the tread edge Te is divided into three equal parts, and the region on the tread edge Te side is defined as the shoulder region 21, the region on the tire equatorial plane C side is defined as the crown region 23, and the region between the shoulder region 21 and the crown region 23 is defined as the middle region 22. It is desirable to specify a filament occupancy rate Fs for each band cord 10 included in each region.

[0046] In this embodiment, at least the band cord 10s included in the shoulder region 21 has substantially the same characteristics as the above-described band cord 10e. That is, any of the configurations of the above-described band cord 10e can be applied to the band cord 10s arranged in the shoulder region 21. This reliably improves cornering performance.

[0047] The average value Am of the filament occupancy rates Fs of the band cords 10m included in the middle region 22 is preferably larger than the average value As of the filament occupancy rates Fs of the band cords 10s included in the shoulder regions 21. Specifically, the average value Am is preferably 1.30 to 1.50 times the average value As. Furthermore, the average value Ac of the filament occupancy rates Fs of the band cords 10c included in the crown region 23 is preferably larger than both the average values ​​As and Am. Specifically, the average value Ac is preferably 1.70 to 1.90 times the average value As. This improves straight-line stability and cornering performance at high speeds in a well-balanced manner. The boundaries between the shoulder regions 21 and the middle region 22 and the boundaries between the middle region 22 and the crown region 20 extend in the tire normal direction, perpendicular to the contact patch 2s, in a cross-sectional view of the tire.

[0048] Fig. 6 shows an enlarged cross-sectional view of a band cord 10e according to another embodiment. As shown in Fig. 6, the band cord 10e may be, for example, one in which the steel filaments 12 are arranged in a row in one direction within an imaginary minimum circle 15. In this embodiment, the steel filaments 12 are arranged so that an imaginary line 30 connecting the centers 12c of adjacent steel filaments 12 forms a convex shape in one direction. This band cord 10 has a small filament occupancy rate Fs and can ensure a larger contact surface near the tread edge Te. The embodiment shown in Fig. 6 may also be applied to band cords 10 arranged in other positions.

[0049] 1, the band layer 8 of the tire 1 according to the present embodiment of the present disclosure is preferably formed by covering a band cord 10 with a band cord covering layer. Examples of the band cord covering layer include a rubber composition using a diene rubber and a thermoplastic elastomer composition using a thermoplastic elastomer.

[0050] When the band cord covering layer is a rubber composition, rubber components that are known in the tire field can be used. Examples include diene rubbers such as isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These may be used alone or in combination of two or more. Among these, isoprene rubber is preferred from the viewpoint of obtaining good adhesion to the band cord 10.

[0051] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. NRs such as SIR20, RSS#3, and TSR20 are commonly used in the tire industry. IRs are not particularly limited, and examples of IRs such as IR2200 are commonly used in the tire industry. Modified NRs include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Modified NRs include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Modified IRs include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more. NR is preferred.

[0052] The content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 65% ​​by mass or more, more preferably 80% by mass or more, and even more preferably 100% by mass.

[0053] The rubber composition preferably contains a filler. Examples of fillers include carbon black, silica, clay, alumina, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, and titanium oxide. These may be used alone or in combination of two or more. These fillers may be derived not only from petroleum or minerals, but also from biomass materials.

[0054] The filler is preferably contained in an amount of 40 to 150 parts by mass per 100 parts by mass of the rubber component, which is believed to provide sufficient strength and improve straight-line stability and cornering performance.

[0055] The rubber composition may contain a plasticizer. The content of the plasticizer is preferably 3 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the rubber component.

[0056] Plasticizers are materials that impart plasticity to rubber components, and include, for example, fats and oils (oils) such as process oil, extender oil, vegetable oil, and animal oil; resins such as liquid polymers and liquid resins; and waxes. Specifically, they are components that are extracted from rubber compositions using acetone. Furthermore, liquid low-molecular-weight hydrocarbons obtained by thermal decomposition of rubber compositions other than the above-mentioned petroleum- and naturally-derived plasticizers, as well as refined used lubricating oils and edible oils, may also be used as plasticizers.

[0057] In addition to the above materials, from the viewpoint of adhesion to the band cord covering layer, it is preferable to include an organic acid metal salt in an amount of 0.1 part by mass or more and 2 parts by mass or less per 100 parts by mass of the rubber component. This makes it possible to improve adhesion between the band cord 10 and the band cord covering layer. Examples of metal elements in the organic acid metal salt include chromium, iron, cobalt, nickel, tin, antimony, and bismuth.

[0058] In addition to the materials mentioned above, it is possible to appropriately select and use materials that are generally used in rubber compositions, such as antioxidants, wax, zinc oxide, processing aids, sulfur, and vulcanization accelerators.

[0059] When the band cord covering layer is made of a thermoplastic elastomer composition, the procedure is the same except that the rubber component is replaced with a thermoplastic elastomer. A thermoplastic elastomer is an elastomer that has hard and soft segments and forms a network through the van der Waals forces of the hard segments.

[0060] Examples of thermoplastic elastomers include styrene-butadiene-styrene block copolymers (SBS), styrene-ethylene-butadiene-styrene block copolymers (SEBS), and styrene-isoprene-styrene block copolymers (SIS).

[0061] In addition, from the viewpoint of adhesion to the coating layer, it is preferable that the surface of the band cord 10 in the present disclosure is plated. As the type of plating layer, two-component plating using copper and zinc, as well as three-component plating using copper, zinc, and cobalt, etc. can be used.

[0062] As shown in FIG. 1, the tread rubber arranged on the outside of the band layer 8 may comprise a plurality of rubber compositions or thermoplastic elastomer compositions in the axial direction of the tire, or may comprise a plurality of rubber composition or thermoplastic elastomer layers in the axial direction of the tire.

[0063] The material used for the tread rubber is the same as that for the band cord covering layer described above, but in the case of a rubber composition, it is preferable to use isoprene-based rubber, butadiene rubber, or styrene-butadiene rubber as the rubber component, and two or more of these may be used in combination. Of these, it is preferable to use styrene-butadiene rubber.

[0064] The thickness of the tread rubber is preferably 5 mm or more and 12 mm or less. The thickness of the tread rubber refers to the thickness of the tread rubber at the center of the tread portion, and when grooves are provided in the tread center portion, it refers to the thickness from the intersection of a line connecting the outermost ends of the grooves and the tire equatorial plane in the tread cross section to the outermost part of the band layer 8.

[0065] Although a pneumatic tire according to one embodiment of the present disclosure has been described in detail above, the present disclosure is not limited to the specific embodiment described above and can be modified and implemented in various aspects. [Example]

[0066] A front motorcycle tire with a size of 120 / 70R17 and the basic structure shown in FIG. 1 was prototyped based on the specifications in Tables 1 and 2. Furthermore, tires were prototyped as Comparative Examples 1 to 4, in which the filament occupancy rate Fs and / or the product Ea·ΣSf were outside the ranges of the present disclosure. Except for the above points, the tires of Comparative Examples 1 to 4 were substantially the same as the tires of the Examples. Each tire was tested for straight-line stability and cornering performance during high-speed driving. The common specifications and test methods for each tire are as follows: Test vehicle: 1000cc motorcycle Rim size: MT3.50 x 17 Internal pressure: 290kPa The test method is as follows:

[0067] <Straight-line stability at high speeds> The test vehicle was driven on a circuit, and the straight-line stability during high-speed driving was evaluated by the driver. The results were evaluated as a score based on Comparative Example 1 being 100, with a higher score indicating better straight-line stability.

[0068] <Turning performance> The test vehicle was driven on a circuit, and the cornering performance when the tread edge was in contact with the ground was evaluated by the driver. The results were evaluated as a score based on Comparative Example 1 being 100, with a higher score indicating better cornering performance. The test results are shown in Tables 1-2.

[0069] [Table 1]

[0070] [Table 2]

[0071] A 190 / 55R17 size motorcycle rear tire (mounted rim: MT6.00×17, internal pressure: 290 kPa) having the basic structure of FIG. 1 was prototyped based on the specifications in Tables 3 and 4. Furthermore, tires were prototyped as Comparative Examples 5 to 8, in which the filament occupancy rate Fs and / or the product Ea·ΣSf were outside the ranges of the present disclosure. Except for the above points, the tires of Comparative Examples 5 to 8 were substantially the same as the tires of the Examples. Similar tests were conducted on these tires. The ratings for straight-line stability and cornering performance during high-speed driving of the Examples in Tables 3 and 4 shown below are based on the rating of Comparative Example 5 as 100. The test results are shown in Tables 3-4.

[0072] [Table 3]

[0073] [Table 4]

[0074] As a result of the test, it was confirmed that the tire of the example had improved cornering performance while maintaining straight running stability during high speed driving.

[0075] [Note] The present disclosure includes the following aspects.

[0076] [Disclosure 1] A pneumatic tire having a tread portion, The contact surface of the tread portion has a center portion in the tire axial direction that protrudes outward in the tire radial direction beyond the tread end, The inside of the tread portion includes a band layer including a band cord wound spirally in the tire circumferential direction, the band cord is a steel cord including a plurality of steel filaments, In a tire cross-sectional view including the tire rotation axis, the band cord arranged closest to the tread end of the band layer has an area Sv (mm 2 ) and the total cross-sectional area of ​​the plurality of steel filaments ΣSf (mm 2 ) the filament occupancy rate, expressed as the ratio ΣSf / Sv, is 0.15 to 0.50, The product of the average number Ea (number / 5 cm) of the band cords arranged in the band layer per 5 cm in the tire width direction and the sum ΣSf of the cross-sectional areas of the plurality of steel filaments is 5 or more. Pneumatic tires. [Disclosure 2] The pneumatic tire according to Disclosure 1, wherein the band cord has 2 to 6 steel filaments twisted together. [Disclosure 3] 3. The pneumatic tire according to Disclosure 1 or 2, which is for a motorcycle. [Disclosure 4] The pneumatic tire according to any one of Disclosures 1 to 3, wherein the average number Ea of arranged cords of the band cord per 5 cm in the tire width direction is 40 to 80. [Disclosure 5] 5. The pneumatic tire according to any one of Disclosures 1 to 4, wherein, in a cross-sectional view of the tire, the product of the tread aspect ratio, which is expressed as the ratio h / W of a contact radius W (mm), which is the distance in the axial direction of the tire from the tire equatorial plane to the tread edge, and a contact height h (mm), which is the height in the radial direction of the tire from the tread edge to the center of the contact surface, and the filament occupancy rate, is 0.40 or less. [Disclosure 6] The pneumatic tire according to Disclosure 5, wherein the absolute value of the difference between the tread aspect ratio and the filament occupancy rate is 1.0 or less. [Disclosure 7] The pneumatic tire according to any one of Disclosures 1 to 6, wherein the filament occupancy is 0.20 to 0.40. [Disclosure 8] A pneumatic tire described in any one of Disclosures 1 to 7, wherein the difference (Ec - Ee) between the average number of band cords arranged per 5 cm in the tire width direction in the central portion of the contact patch, Ec, and the average number of band cords arranged on the tread end side, Ee, is 10 or less. [Disclosure 9] The pneumatic tire according to any one of Disclosures 1 to 8, wherein the bending rigidity of the band cord is 35.0 g·cm or less. [Disclosure 10] 10. The pneumatic tire according to any one of Disclosures 1 to 9, wherein the band cord has a compression rigidity of 100 N / mm or less. [Disclosure 11] The pneumatic tire according to any one of Disclosures 1 to 10, wherein the steel filaments have an outer diameter of 0.15 to 0.27 mm. [Disclosure 12] the tread portion includes a crown region on the tire equatorial plane side, shoulder regions on the tread end sides, and a middle region between the crown region and the shoulder region, In the tire cross-sectional view, the band layer includes a plurality of band cords arranged in the crown region, the middle region, and the shoulder region, 12. The pneumatic tire according to any one of Disclosures 1 to 11, wherein the filament occupancy rate of the band cord arranged in the crown region is greater than the filament occupancy rate of the band cord arranged in the shoulder region. [Explanation of symbols]

[0077] 2 Tread section 8 Band Layer 10 Band cord 11 Steel cord 12 Steel Filaments C Tire equatorial plane Te tread edge Fs filament occupancy Ea Average number of band cords arranged per 5cm in the tire width direction in the band layer

Claims

1. A pneumatic tire having a tread portion, The contact surface of the tread portion has a center portion in the tire axial direction that protrudes outward in the tire radial direction beyond the tread end, The inside of the tread portion includes a band layer including a band cord wound spirally in the tire circumferential direction, the band cord is a steel cord including a plurality of steel filaments, In a tire cross-sectional view including the tire rotation axis, the band cord arranged closest to the tread end among the band layers has an area Sv (mm ２ ) and the total cross-sectional area of ​​the plurality of steel filaments ΣSf (mm ２ ) the filament occupancy rate represented by the ratio ΣSf / Sv of the filament occupancy rate to the filament occupancy rate is 0.15 to 0.50, the product of the average number Ea (number / 5 cm) of the band cords arranged in the band layer per 5 cm in the tire width direction and the sum ΣSf of the cross-sectional areas of the plurality of steel filaments is 5 or more, the tread portion includes a crown region on the tire equatorial plane side, shoulder regions on the tread end sides, and a middle region between the crown region and the shoulder region, In the tire cross-sectional view, the band layer includes a plurality of band cords arranged in the crown region, the middle region, and the shoulder region, the filament occupancy rate of the band cord arranged in the crown region is greater than the filament occupancy rate of the band cord arranged in the shoulder region; Pneumatic tires.

2. A pneumatic tire having a tread portion, The contact surface of the tread portion has a center portion in the tire axial direction that protrudes outward in the tire radial direction beyond the tread end, The inside of the tread portion includes a band layer including a band cord wound spirally in the tire circumferential direction, the band cord is a steel cord including a plurality of steel filaments, In a tire cross-sectional view including the tire rotation axis, the band cord arranged closest to the tread end among the band layers has an area Sv (mm ２ ) and the total cross-sectional area of ​​the plurality of steel filaments ΣSf (mm ２ ) the filament occupancy rate represented by the ratio ΣSf / Sv of the filament occupancy rate to the filament occupancy rate is 0.15 to 0.50, the product of the average number Ea (number / 5 cm) of the band cords arranged in the band layer per 5 cm in the tire width direction and the sum ΣSf of the cross-sectional areas of the plurality of steel filaments is 5 or more, the tread portion includes a crown region on the tire equatorial plane side, shoulder regions on the tread end sides, and a middle region between the crown region and the shoulder region, In the tire cross-sectional view, the band layer includes a plurality of band cords arranged in the crown region, the middle region, and the shoulder region, the filament occupancy rate of the band cord arranged in the middle region is greater than the filament occupancy rate of the band cord arranged in the shoulder region; Pneumatic tires.

3. A pneumatic tire as described in claim 1 or 2, wherein the band cord arranged furthest from the band layer toward the tread end has the plurality of steel filaments arranged in a row in one direction within the virtual minimum circle.

4. The pneumatic tire according to claim 1 or 2, wherein the band cord has 2 to 6 steel filaments twisted together.

5. The pneumatic tire according to any one of claims 1 to 4, which is for a motorcycle.

6. The pneumatic tire according to any one of claims 1 to 5, wherein an average number Ea of the band cords arranged per 5 cm in the tire width direction is 40 to 80.

7. 7. The pneumatic tire according to claim 1, wherein, in a cross-sectional view of the tire, a product of a tread aspect ratio, expressed as a ratio h / W of a contact radius W (mm) that is a distance in the tire axial direction from the tire equatorial plane to the tread edge to a contact height h (mm) that is a height in the tire radial direction from the tread edge to the center of the contact surface, and the filament occupancy rate is 0.40 or less.

8. The pneumatic tire according to claim 7 , wherein an absolute value of a difference between the tread aspect ratio and the filament occupancy rate is 1.0 or less.

9. The pneumatic tire according to any one of claims 1 to 8, wherein the filament occupancy ratio is 0.20 to 0.

40.

10. 10. The pneumatic tire according to claim 1, wherein a difference (Ec - Ee) between an average number of arranged band cords per 5 cm in the tire width direction in the central portion of the contact patch, Ec, and an average number of arranged band cords per 5 cm in the tire width direction in the tread end side, Ee, is 10 or less.

11. The pneumatic tire according to claim 1 , wherein the band cord has a bending rigidity of 35.0 g·cm or less.

12. The pneumatic tire according to claim 1 , wherein the band cord has a compression rigidity of 100 N / mm or less.

13. 13. The pneumatic tire according to claim 1, wherein the steel filaments have an outer diameter of 0.15 to 0.27 mm.

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