Patent Description:
For example, <CIT> proposes a tire, for a motorcycle, including a band layer inside a tread portion. The band layer is formed from a band ply having a steel band cord. The tire for a motorcycle is expected to have improved steering stability and durability by specifying the compressive stiffness or the bending stiffness of the band cord.

Other relevant prior art is known from <CIT>, <CIT> and <CIT>.

A pneumatic tire having a steel cord provided in a band layer as in the above-described tire for a motorcycle has less outer diameter growth during running, and has excellent straight running stability during high speed running. On the other hand, the band layer also suppresses appropriate deformation of the tread portion near each tread end. Therefore, the tread portion of the pneumatic tire has a small ground-contact area during cornering, and there is room for improvement in cornering performance.

The present invention has been made in view of the above-described problem, and a main object of the present invention is to provide a pneumatic tire that can have improved cornering performance while maintaining straight running stability during high speed running.

The present invention is directed to a pneumatic tire according to claim <NUM>.

By having the above-described configuration, the pneumatic tire of the present invention can have improved cornering performance while maintaining straight running stability during high speed running.

<FIG> shows a transverse cross-sectional view of a pneumatic tire (hereinafter, sometimes simply referred to as "tire") <NUM> showing an embodiment of the present invention, in a normal state. The tire <NUM> of the present embodiment is for a motorcycle, and is suitably used as a front wheel tire for circuit running. However, the present invention is not limited to such a mode, and is suitable for use for a tire for a passenger car, a tire for a light truck, a tire for a truck or a bus, etc..

In the case of a tire for which various standards are defined, the "normal state" is a state where the tire is fitted on a normal rim and inflated to a normal internal pressure and no load is applied to the tire. In the case of a tire for which various standards are not defined, the normal state means a standard use state, corresponding to the purpose of use of the tire, where the tire is not mounted on a vehicle and no load is applied to the tire. In the present specification, unless otherwise specified, dimensions and the like of components of the tire are values measured in the normal state. Moreover, when measuring the physical properties of an inner member included in a tire as a product on the basis of the present specification, the inner member is taken in a manner that does not impair the characteristics thereof as much as possible, and then the physical properties are measured.

The "normal rim" is a rim that is defined, in a standard system including a standard on which the tire is based, by the standard for each tire, and is, for example, the "standard rim" in the JATMA standard, the "Design Rim" in the TRA standard, or the "Measuring Rim" in the ETRTO standard.

The "normal internal pressure" is an air pressure that is defined, in a standard system including a standard on which the tire is based, by the standard for each tire, and is the "maximum air pressure" in the JATMA standard, the maximum value indicated in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, or the "INFLATION PRESSURE" in the ETRTO standard.

As shown in <FIG>, in a ground-contact surface <NUM> of a tread portion <NUM>, a center portion in the tire axial direction projects outward in the tire radial direction with respect to each tread end Te. In the present embodiment, the ground-contact surface <NUM> is curved in an arc shape so as to be convex outward in the tire radial direction. The tread ends Te correspond to both ends in the tire axial direction of the ground-contact surface <NUM> of the tread portion <NUM>, and can be brought into contact with the ground at a maximum camber angle during cornering.

The tire <NUM> of the present embodiment includes, for example, a carcass <NUM> and a band layer <NUM>. The carcass <NUM> extends from the tread portion <NUM> through sidewall portions <NUM> to bead cores <NUM> of bead portions <NUM>. A known configuration is used as appropriate for the carcass <NUM>. The band layer <NUM> is disposed inside the tread portion <NUM> and disposed outward of the carcass <NUM> in the tire radial direction. Although not included in the present embodiment, another tread reinforcing layer may be disposed inward of the band layer <NUM> in the tire radial direction.

The band layer <NUM> is formed as a so-called jointless band including a band cord <NUM> helically wound in the tire circumferential direction. In a preferable mode, the band cord <NUM> is wound at an angle of not greater than <NUM>° with respect to the tire circumferential direction.

<FIG> show an enlarged perspective view of the band cord <NUM> in <FIG>. As shown in <FIG>, the band cord <NUM> is a steel cord in which a plurality of steel filaments <NUM> are covered with a topping rubber <NUM>.

Conventionally, a tire having a steel cord provided in a band layer has less outer diameter growth during running, and has excellent straight running stability during high speed running. However, the band layer also suppresses appropriate deformation of a tread portion near each tread end. Therefore, the ground-contact area of the tread portion of the tire during cornering tends to be smaller, and there is room for improvement in cornering performance.

In the present invention, in order to ensure appropriate deformation of the tread portion <NUM> near each tread end Te, in a tire cross-sectional view including the tire rotation axis, a filament occupancy ratio Fs is specified for a band cord 10e disposed closest to the tread end Te in the band layer <NUM>. The filament occupancy ratio Fs is defined as described below.

<FIG> shows a transverse cross-sectional view of the band cord 10e. As shown in <FIG>, the filament occupancy ratio is represented by the ratio ΣSf/Sv of a total ΣSf(mm<NUM>) of the cross-sectional areas of the plurality of steel filaments <NUM> to an area Sv of a smallest virtual circle <NUM> (shown by an alternate long and two short dashes line in <FIG>) that can completely enclose all of the plurality of steel filaments <NUM> arranged in one band cord <NUM> in a transverse cross-section of this band cord <NUM>. A band cord <NUM> having a small filament occupancy ratio Fs is easily stretched, and a band cord <NUM> having a large filament occupancy ratio Fs is difficult to stretch. In the present invention, the filament occupancy ratio Fs of the band cord 10e disposed closest to the tread end Te is <NUM> to <NUM>. Accordingly, it is easier for the band cord 10e to appropriately stretch. Therefore, a large ground-contact surface can be ensured near each tread end Te, and cornering performance can be improved.

On the other hand, if the total ΣSf of the cross-sectional areas of the steel filaments <NUM> in the band cord <NUM> decreases, the holding force of the tread portion by the band cord <NUM> decreases, so that the tread portion easily becomes deformed by the centrifugal force acting on the tread portion during high speed running, causing a concern that straight running stability may decrease. Therefore, the developers have found that, as the total ΣSf of the cross-sectional areas of the steel filaments <NUM> decreases, in order to improve the holding force acting on the tread portion, it is preferable to increase an average number Ea of the band cords <NUM> arranged in the tire width direction. On the basis of such finding, in the present invention, the product of the average number Ea of the band cords <NUM> arranged per <NUM> in the tire width direction (cords/<NUM>) and the total ΣSf of the cross-sectional areas of the steel filaments <NUM> (hereinafter, sometimes referred to as "product Ea*ΣSf") is not less than <NUM>. Accordingly, sufficient stretch is ensured by the band cord, and a sufficient holding force is also obtained while cornering performance during high speed running is improved, so that it is considered that it is also possible to improve straight running performance.

The above-described band cord <NUM> can be obtained, for example, by twisting together corrugated steel filaments <NUM>. In addition, the filament occupancy ratio Fs can be adjusted as appropriate by changing the degree of corrugation of the steel filaments <NUM>.

Hereinafter, more detailed configurations of the present embodiment will be described. The configurations described below show a specific mode of the present embodiment. Therefore, it is needless to say that the present invention can achieve the above-described effect even when the configurations described below are not provided. In addition, even when any one of the configurations described below is independently applied to the tire according to the present invention having the above-described characteristics, performance improvement corresponding to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, complex performance improvement corresponding to each configuration can be expected.

As shown in <FIG>, the tire <NUM> of the present embodiment is for a motorcycle, and a tread aspect ratio Ta represented by the ratio h/W of a ground-contact height h, which is the height in the tire radial direction from the tread end Te to the center portion of the ground-contact surface <NUM>, to a ground-contact half width W, which is the distance in the tire axial direction from a tire equator plane C to the tread end Te, is, for example, about <NUM> to <NUM>. The developers have found that in order to further enhance the above-described effect, it is effective to specify the tread aspect ratio Ta and the filament occupancy ratio Fs in relation to each other.

From such a viewpoint, the product Ta*Fs of the tread aspect ratio Ta and the filament occupancy ratio Fs is preferably not greater than <NUM>, more preferably not greater than <NUM>, and further preferably not greater than <NUM>. As the tread aspect ratio Ta increases, the deformation near each tread end Te becomes larger, so that it is considered that it is preferable to make the filament occupancy ratio Fs of the band cord 10e smaller. Therefore, by setting the product Ta*Fs of the tread aspect ratio Ta and the filament occupancy ratio Fs of the band cord 10e to be not greater than a certain value, sufficient stretch of the band cord 10e can be ensured according to the tread aspect ratio Ta, and cornering performance can be reliably improved. On the other hand, the lower limit of the product Ta*Fs is not particularly limited, but the product Ta*Fs is preferably not less than <NUM>, more preferably not less than <NUM>, and further preferably not less than <NUM>. Accordingly, the deformation of the ground-contact surface near each tread end Te is made appropriate, and cornering performance is further improved.

The present invention is not limited to the tire for a motorcycle, and may be applied, for example, to a pneumatic tire for a passenger car. The tread aspect ratio Ta of such a tire is, for example, not greater than <NUM>. In this case, the product Ta*Fs is preferably <NUM> to <NUM>.

Moreover, as shown in <FIG>, in the tire <NUM> of the present embodiment, the band cord <NUM> is arranged in the tire width direction to form the band layer <NUM>. The number of the band cords <NUM> arranged per <NUM> in the tire width direction is preferably not less than <NUM> (cords/<NUM>) and more preferably not less than <NUM>. On the other hand, as for the upper limit of this number, this number is preferably not greater than <NUM> (cords/<NUM>) and more preferably not greater than <NUM> (cords/<NUM>). Accordingly, the holding force acting on the tread portion is made appropriate, and straight running stability and cornering performance are further improved.

The product of the average number Ea of the band cords <NUM> arranged and the total ΣSf of the areas of the filaments <NUM> is preferably not less than <NUM> and more preferably not less than <NUM>. On the other hand, as for the upper limit of the product, the product is preferably not greater than <NUM>, more preferably not greater than <NUM>, and further preferably not greater than <NUM>. Accordingly, appropriate stretch of the band cord <NUM> occurs while the holding force acting on the tread portion is maintained, so that straight running stability and cornering performance are even further improved.

Moreover, the difference (Ec-Ee) between a number Ec of the band cords <NUM> arranged per <NUM> in the tire width direction in the center portion (hereinafter, sometimes referred to as "tread center region") of the ground-contact surface and a number Ee of the band cords <NUM> arranged in the width direction in a region on the tread end Te side (hereinafter, sometimes referred to as "tread end side region") is preferably not greater than <NUM> and more preferably not greater than <NUM>. The lower limit of the difference (Ec-Ee) is not particularly limited, but the difference (Ec-Ee) is preferably not less than <NUM>. Accordingly, the holding force in the tread center region and the tread end side region can be made uniform, and it is easier to improve straight running stability.

Ea, Ec, and Ee, each of which represents the number of the band cords <NUM> arranged in the tire width direction, are each the number of the band cords <NUM> arranged in the tire width direction along the arrangement direction of the band cord <NUM>, and refers to the number of the band cords <NUM> arranged in a direction along the arc of the band layer <NUM> in the case of the tire for a motorcycle shown in <FIG>.

The average number Ea of the band cords <NUM> arranged is the average number of the band cords <NUM> arranged per <NUM> over the entirety of the band layer <NUM>, and is calculated from the length along the arc of the band layer <NUM> and the number of the band cords <NUM> included therein. The number Ec of the band cords <NUM> arranged in the tread center region is the number of the band cords <NUM> arranged in a range of ±<NUM> centered on the tire equator plane. In addition, the number Ee of the band cords <NUM> arranged in the tread end side region is the number of the band cords <NUM> in a range of <NUM> from the end point on the tread end portion side of the band layer <NUM> toward the center portion thereof. The number Ee of the band cords <NUM> arranged in the tread end side region is the average of the numbers of the band cords <NUM> arranged per <NUM> at end portions on both sides. These numbers can be calculated by obtaining the number of the band cords <NUM> in each region in a state where the distance between the bead portions is adjusted to a normal rim width in a cross-section in the tire radial direction including the tire rotation axis.

Moreover, the average thickness in the tire radial direction of the band layer <NUM> is preferably not less than <NUM> and not greater than <NUM>. As used herein, the average thickness of the band layer refers to the average thickness from one end of the band layer <NUM> to the other end of the band layer <NUM>.

As shown in <FIG>, in the band cord <NUM> of the present embodiment, two to six steel filaments <NUM> are twisted together. In a preferable mode, in the band cord <NUM>, three to five steel filaments <NUM> are twisted together. In addition, the respective steel filaments <NUM> are arranged so as to surround a center <NUM> of the band cord <NUM>, and in a preferable mode, the respective steel filaments <NUM> are arranged at an equal interval in the outer circumferential direction of the band cord <NUM> and are tangent to the smallest virtual circle <NUM>. However, the arrangement of the steel filament <NUM> is not limited to such a mode.

An outer diameter D1 of the smallest virtual circle <NUM> is, for example, <NUM> to <NUM>, preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM> in the tread end side region. On the other hand, in the tread center region, the outer diameter D1 is, for example, <NUM> to <NUM>, preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>. Accordingly, while the holding force at the tread portion is increased, the band cord <NUM> can be easily stretched during cornering, whereby the ground-contact shape can be made appropriate, and it can be easier to improve straight running stability and cornering performance.

The area Sv of the smallest virtual circle <NUM> can be obtained by obtaining the above-described outer diameter D1. In the tread center region, the outer diameter D1 can be calculated from the smallest virtual circle of the band cord <NUM> closest to the equator plane in the band layer <NUM>, and in the tread end side region, the outer diameter D1 can be calculated from the smallest virtual circle of the band cord <NUM> at the end point of the band layer <NUM>. The outer diameter D1 and the area Sv of the smallest virtual circle in the tread end side region are each an average of the values at both end portions.

An outer diameter d1 of the steel filament <NUM> is, for example, <NUM> to <NUM> and preferably <NUM> to <NUM>. However, the outer diameter d1 is not limited to such a range.

If the filament occupancy ratio Fs in the band cord 10e is excessively small, the stiffness reduction effect near each tread end Te spreads to the center portion of the tread portion <NUM>, the center portion of the tread portion <NUM> also easily becomes deformed, and a decrease in straight running stability during high speed running may be caused. Therefore, the filament occupancy ratio Fs in the band cord 10e is preferably not less than <NUM> and more preferably not less than <NUM>, and is preferably not greater than <NUM> and more preferably not greater than <NUM>. Accordingly, cornering performance and straight running stability during high speed running are improved in a well-balanced manner.

Moreover, the band cord 10e for which the filament occupancy ratio Fs is specified in the above-described range has appropriate elasticity, and thus exhibits the above-described effect and is less likely to meander during tread rubber shrinkage after tire vulcanization molding. Therefore, fine wavy deformation of the tread portion <NUM> caused by meandering of the band cord 10e around each tread end Te (hereinafter, such a defect is sometimes referred to as "tread waviness") is suppressed, so that the molding defect rate during tire production is reduced.

From the same viewpoint, the absolute value of the difference between the tread aspect ratio Ta and the filament occupancy ratio Fs of the band cord <NUM> is preferably not greater than <NUM>, more preferably <NUM> to <NUM>, and further preferably <NUM> to <NUM>.

The bending stiffness of the band cord <NUM> is, for example, not greater than <NUM>·cm and preferably <NUM> to <NUM>·cm. Accordingly, tread waviness can be suppressed while a tire stiffness feeling during cornering is maintained.

The bending stiffness is measured as follows. <FIG> shows a schematic diagram when measuring the bending stiffness. As shown in <FIG>, the bending stiffness is measured, for example, by using a stiffness tester (for example, <NUM>-D type) manufactured by TABER INDUSTRIES (USA). The bending stiffness corresponds to the average of a bending moment at +<NUM> degrees and a bending moment at -<NUM> degrees when both ends of a band cord <NUM> having a length of <NUM> are attached to clamps and bending angles of +<NUM> degrees and -<NUM> degrees are given to the band cord <NUM>.

A compressive stiffness CS of the band cord <NUM> is, for example, not greater than <NUM> N/mm, preferably <NUM> to <NUM> N/mm, and more preferably <NUM> to <NUM> N/mm. Accordingly, the compression fatigue resistance of the band cord <NUM> is improved.

The compressive stiffness CS is measured as follows. As shown in <FIG>, a cord-included sample K1 in which one band cord <NUM> having a length of <NUM> is embedded at the center of a cylindrical rubber g having a diameter of <NUM> and a height of <NUM> in the height direction, and a correction cord-free sample K2 (not shown) having no band cord <NUM> embedded therein are prepared. Each sample K1, K2 is vulcanized under the same vulcanization conditions (for example, temperature: <NUM>, <NUM> minutes), and has substantially the same physical properties except for the presence or absence of the band cord <NUM>.

Moreover, for each sample K1, K2, a compression load-compression amount curve which is a graph showing the relationship between a compression load CL and a compression amount CA is obtained. The compression load-compression amount curve is obtained by compressing each sample K1, K2 at a speed of <NUM>/min using a tensile tester, and measuring the compression load CL and the compression amount CA. Then, the measurement data of the cord-included sample K1 is corrected with the measurement data of the cord-free sample K2 (that is, the effect of the rubber part of the sample is removed, and data that can be simulated as the cord only is extracted), thereby obtaining a compression load-compression amount curve of the band cord <NUM> as shown in <FIG>. The gradient in a middle region of this curve is defined as the compressive stiffness CS (N/mm).

As shown in <FIG>, in the tire cross-sectional view, the band layer <NUM> includes a plurality of the band cords <NUM> arranged in the tire axial direction. As for these band cords <NUM>, the filament occupancy ratio Fs of the band cord <NUM> closer to the tread end Te is smaller. Accordingly, cornering performance and straight running stability during high speed running are improved in a well-balanced manner.

More specifically, in the tire cross-sectional view, when the ground-contact surface of the tread portion <NUM> from the tire equator plane C to the tread end Te is divided into three equal regions, the region on the tread end Te side is referred to as a shoulder region <NUM>, the region on the tire equator plane C side is referred to as a crown region <NUM>, and the region between the shoulder region <NUM> and the crown region <NUM> is referred to as a middle region <NUM>, the filament occupancy ratio Fs is preferably specified for each of the band cords <NUM> included in the respective regions.

In the present embodiment, at least band cords <NUM> included in the shoulder region <NUM> have substantially the same characteristics as the above-described band cord 10e. That is, the configuration of the above-described band cord 10e can all be applied to the band cords <NUM> disposed in the shoulder region <NUM>. Accordingly, cornering performance is reliably improved.

An average Am of the filament occupancy ratios Fs of band cords <NUM> included in the middle region <NUM> is preferably larger than an average As of the filament occupancy ratios Fs of the band cords <NUM> included in the shoulder region <NUM>. Specifically, the average Am is preferably <NUM> to <NUM> times the average As. In addition, an average Ac of the filament occupancy ratios Fs of band cords 10c included in the crown region <NUM> is preferably larger than the average As and the average Am. Specifically, the average Ac is preferably <NUM> to <NUM> times the average As. Accordingly, cornering performance and straight running stability at high speed are improved in a well-balanced manner. The boundary between the shoulder region <NUM> and the middle region <NUM> and the boundary between the middle region <NUM> and the crown region <NUM> extend in a tire normal direction orthogonal to the ground-contact surface <NUM>, in the tire cross-sectional view.

<FIG> shows an enlarged cross-sectional view of a band cord 10e of another embodiment. As shown in <FIG>, the band cord 10e may be, for example, a band cord in which steel filaments <NUM> are arranged in a row in one direction inside a smallest virtual circle <NUM>. In this embodiment, the steel filaments <NUM> are arranged such that a virtual line <NUM> connecting centers 12c of the adjacent steel filaments <NUM> extends in the one direction so as to have a convex shape. Such a band cord <NUM> has a small filament occupancy ratio Fs, and a larger ground-contact surface can be ensured near each tread end Te. The embodiment shown in <FIG> may be applied to the band cord <NUM> disposed at another position.

As shown in <FIG>, the band layer <NUM> of the tire <NUM> of the present embodiment of the present invention is preferably formed by covering the band cord <NUM> with a band cord coating layer. Examples of the band cord coating layer include a thermoplastic elastomer composition using a thermoplastic elastomer as well as a rubber composition using a diene-based rubber.

In the case where the band cord coating layer is a rubber composition, as a rubber component, one known in the tire field can be used. Examples of the rubber component include isoprene-based rubbers, and diene-based rubbers such as butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), isobutylene-isoprene-rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). One of these rubbers may be used alone, or two or more of these rubbers may be used in combination. Among them, from the viewpoint of obtaining good adhesion to the band cord <NUM>, an isoprene-based rubber is preferably used.

Examples of the isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), reformed NR, modified NR, and modified IR. As the NR, for example, NRs that are generally used in the tire industry, such as SIR20, RSS#<NUM>, and TSR20, can be used. The IR is not particularly limited, and, as the IR, for example, IRs that are generally used in the tire industry, such as IR2200, can be used. Examples of the reformed NR include deproteinized natural rubber (DPNR) and ultra-pure natural rubber (UPNR), examples of the modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber, and examples of the modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These rubbers may be used individually, or two or more of these rubbers may be used in combination. Among them, NR is preferable.

The amount of the isoprene-based rubber in <NUM>% by mass of the rubber component is preferably not less than <NUM>% by mass, more preferably not less than <NUM>% by mass, and further preferably <NUM>% by mass.

Moreover, the rubber composition preferably contains a filler. Examples of the filler include carbon black, silica, clay, alumina, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, magnesium hydroxide, magnesium oxide, and titanium oxide. These fillers may be used individually, or two or more of these fillers may be used in combination. In addition, as these fillers, fillers made from biomass materials as well as fillers derived from petroleum and minerals may be used.

The filler is preferably contained in a range of not less than <NUM> parts by mass and not greater than <NUM> parts by mass per <NUM> parts by mass of the rubber component. By setting the amount of the filler to be in this range, sufficient strength is exhibited, so that it is considered that it is possible to improve straight running stability and cornering performance.

Moreover, the rubber composition may contain a plasticizer. The amount of the plasticizer per <NUM> parts by mass of the rubber component is preferably not less than <NUM> parts by mass and not greater than <NUM> parts by mass.

The plasticizer is a material that imparts plasticity to the rubber component, and examples of the plasticizer include: fats and oils (oils) such as process oils, extender oils, vegetable oils, and animal oils; resins such as liquid polymers and liquid resins; and waxes. Specifically, the plasticizer is a component that can be extracted from the rubber composition using acetone. In addition to the above-described petroleum-derived and naturally derived plasticizers, liquid low molecular hydrocarbons obtained by pyrolysis of the rubber composition, and oils obtained by refining used lubricating oils and edible oils may be used as the plasticizer.

In addition to the above-described materials, from the viewpoint of adhesion to the band cord coating layer, an organic acid metal salt is preferably contained in a range of not less than <NUM> parts by mass and not greater than <NUM> parts by mass per <NUM> parts by mass of the rubber component. Accordingly, it is possible to improve the adhesion between the band cord <NUM> and the band cord coating layer. Examples of the metal element of the organic acid metal salt include chromium, iron, cobalt, nickel, tin, antimony, and bismuth.

Moreover, in addition to the above-described materials, it is possible to appropriately select and use materials that are generally used for the rubber composition, such as an antioxidant, a wax, zinc oxide, a processing aid, sulfur, and a vulcanization accelerator.

Moreover, in the case where the band cord coating layer is a thermoplastic elastomer composition, the band cord coating layer is the same except that the above-described rubber component is replaced with a thermoplastic elastomer. The thermoplastic elastomer is an elastomer having hard segments and soft segments and forming a network by the van der Waals forces of the hard segments.

Examples of the thermoplastic elastomer include styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butadiene-styrene block copolymer (SEBS), and styrene-isoprene-styrene block copolymer (SIS).

Moreover, from the viewpoint of adhesion to the coating layer, the surface of the band cord <NUM> in the present invention is preferably plated. As the type of the plating layer, in addition to plating of two elements using copper and zinc, it is possible to use plating of three elements using copper, zinc, and cobalt, etc..

As shown in <FIG>, a tread rubber disposed outward of the band layer <NUM> may include a plurality of rubber compositions or thermoplastic elastomer compositions in the tire axial direction, or may include a plurality of rubber compositions or thermoplastic elastomer layers in the tire axial direction.

The materials used for the tread rubber are the same as for the above-described band cord coating layer. In the case of a rubber composition, isoprene-based rubber, butadiene rubber, or styrene-butadiene rubber is preferably used as a rubber component, and two or more of these rubbers may be used in combination. Among them, styrene-butadiene rubber is preferably used.

The thickness of the tread rubber is preferably not less than <NUM> and not greater than <NUM>. The thickness of the tread rubber is the thickness of the tread rubber at the center of the tread portion. In the case where the tread center portion has a groove, the thickness of the tread rubber is the thickness from the point of intersection of the tire equator plane and a straight line connecting end portions of the outermost portion of the groove to the outermost portion of the band layer <NUM> in a tread cross-section.

Although the tire of the embodiment of the present invention has been described in detail above, the present invention is not limited to the above specific embodiment but only by the appended claims.

Front wheel tires for a motorcycle having a size of <NUM>/70R17 and having the basic structure in <FIG> were produced as test tires on the basis of specifications in Tables <NUM> and <NUM>. In addition, as Comparative Examples <NUM> to <NUM>, tires in which the filament occupancy ratio Fs and/or the product Ea*ΣSf was outside the range of the present invention were produced as test tires. The tires of Comparative Examples <NUM> to <NUM> are substantially the same as the tires of Examples except for the above point. Each tire was tested for straight running stability during high speed running and cornering performance. The common specifications and the test methods for the respective tires are as follows.

The above test vehicle was caused to run on a circuit, and sensory evaluation was made by a driver for straight running stability during high speed running. The results are indicated as scores with the result of Comparative Example <NUM> being regarded as <NUM>. A higher value indicates that the straight running stability is better.

The above test vehicle was caused to run on a circuit, and sensory evaluation was made by a driver for cornering performance during cornering in which a tread end was brought into contact with the ground. The results are indicated as scores with the result of Comparative Example <NUM> being regarded as <NUM>. A higher value indicates that the cornering performance is better.

The test results are shown in Tables <NUM> and <NUM>.

Rear wheel tires for a motorcycle having a size of <NUM>/55R17 and having the basic structure in <FIG> (mount rim: MT6. <NUM>×<NUM>, internal pressure: <NUM> kPa) were produced as test tires on the basis of specifications in Tables <NUM> and <NUM>. In addition, as Comparative Examples <NUM> to <NUM>, tires in which the filament occupancy ratio Fs and/or the product Ea*ΣSf was outside the range of the present invention were produced as test tires. The tires of Comparative Examples <NUM> to <NUM> are substantially the same as the tires of Examples except for the above point. The same tests were performed for these tires. The scores of straight running stability during high speed running and cornering performance of Examples in Tables <NUM> and <NUM> shown below are based on the results of Comparative Example <NUM> being regarded as <NUM>.

Claim 1:
A pneumatic tire (<NUM>) comprising a tread portion (<NUM>), wherein
the tread portion (<NUM>) has a ground-contact surface (<NUM>) in which a center portion in a tire axial direction projects outward in a tire radial direction with respect to each tread end (Te),
a band layer (<NUM>) including a band cord (<NUM>) helically wound in a tire circumferential direction is included inside the tread portion (<NUM>),
the band cord (<NUM>) is a steel cord including a plurality of steel filaments (<NUM>),
a filament occupancy ratio (Fs) of the band cord (10e) disposed closest to the tread end (Te) in a tire cross-sectional view including a tire rotation axis is represented by a ratio ΣSf/Sv of a total ΣSf (mm<NUM>) of cross-sectional areas of the plurality of steel filaments (<NUM>) and an area Sv (mm<NUM>) of a smallest virtual circle (<NUM>) that can completely enclose the plurality of steel filaments (<NUM>), and is <NUM> to <NUM>, and
a product (Ea*ΣSf) of an average number Ea of the band cords (<NUM>) arranged in the band layer (<NUM>) per <NUM> in a tire width direction (cords/<NUM>) and the total ΣSf of the cross-sectional areas of the plurality of steel filaments (<NUM>) is not less than <NUM>;
wherein the tread portion (<NUM>) includes a crown region (<NUM>) on the tire equator plane (C) side, a shoulder region (<NUM>) on the tread end (Te) side, and a middle region (<NUM>) between the crown region (<NUM>) and the shoulder region (<NUM>),
in the tire cross-sectional view, the band layer (<NUM>) includes a plurality of band cords (10c, <NUM>, <NUM>) disposed in the crown region (<NUM>), the middle region (<NUM>), and the shoulder region (<NUM>), and
the filament occupancy ratio (Fs) of the band cord (10c) disposed in the crown region (<NUM>) is larger than the filament occupancy ratio (Fs) of the band cord (<NUM>) disposed in the shoulder region (<NUM>).