Heavy-duty tires

Abstract

To provide a heavy-duty tire (2) capable of improving ride comfort while suppressing the influence on durability due to the incorporation of an RFID tag (64). [Solution] The tread 4 of the tire 2 is made of a rubber composition containing a rubber component. The rubber component includes styrene-butadiene rubber. The RFID tag 64 is located radially between an end FE of a turned-up portion 62 of the carcass ply 58 and a maximum width position PW of the tire 2. The styrene content CSt and vinyl content CVi of the styrene-butadiene rubber, as well as the inclination angle Ab of the belt cord 78 of the reference belt ply BP and the inclination angle Aj of the band cord 84 of the reference full band BF, satisfy the following relational expressions (1) and (2). CSt+CVi≦80 (1) (Ab+Aj) / (CSt+CVi)≧0.20 (2)

Description

[Technical Field]

[0001] The present invention relates to a heavy duty tire. [Background technology]

[0002] It has been proposed to embed RFID (Radio Frequency Identification) tags in tires to manage data such as tire manufacturing control, customer information, and driving history.

[0003] Patent Document 1 discloses a tire in which an RFID tag is provided between the maximum width position and the bead core, and in order to ensure sufficient durability of the RFID tag, the tire employs a first belt layer having cords extending in the circumferential direction and a second belt layer having cords extending at an angle to the circumferential direction of the tire. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-6887 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a heavy-duty tire that can achieve improved ride comfort while suppressing the impact on durability caused by the incorporation of an RFID tag. [Means for solving the problem]

[0006] The heavy-duty tire according to the present invention comprises a pair of beads, a carcass spanning the pair of beads, a tread located outside the carcass and in contact with the road surface, a reinforcing layer located radially between the tread and the carcass, and a tag member including an RFID tag. The carcass comprises a carcass ply. The carcass ply comprises a ply body spanning the pair of beads and a pair of turn-up portions connected to the ply body and turned up at the beads. The tread is composed of a rubber composition including a rubber component. The rubber component includes styrene-butadiene rubber. The reinforcing layer comprises a belt including a plurality of parallel belt cords and a band including a spirally wound band cord. The belt comprises at least one belt ply. Of the at least one belt ply, the belt ply with the widest axial width is a reference belt ply. The belt cords of the reference belt ply are made of steel. The band comprises at least one full band formed by spirally winding a band strip. The full band having the widest axial width among the at least one full band layer is the reference full band. The band cord of the reference full band is made of steel. The RFID tag is located radially between the end of the turned-up portion and the maximum width position of the tire. The styrene content CSt and vinyl content CVi of the styrene-butadiene rubber, the inclination angle Ab of the belt cord of the reference belt ply, and the inclination angle Aj of the band cord of the reference full band satisfy the following relational expressions (1) and (2). CSt+CVi≦80 (1) (Ab+Aj) / (CSt+CVi)≧0.20 (2) [Effects of the Invention]

[0007] The present invention can provide a heavy-duty tire that can achieve improved ride comfort while suppressing the impact on durability caused by the incorporation of an RFID tag. [Brief explanation of the drawings]

[0008] [Figure 1]1 is a cross-sectional view showing a portion of a heavy-duty tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing a portion of the tire of FIG. [Figure 3] FIG. 2 is a cross-sectional view showing a portion of the tire of FIG. [Figure 4] FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 2 is a schematic diagram illustrating the configuration of a reinforcing layer. [Figure 7] FIG. 2 is a perspective view showing a part of the band strip. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] FIG. 4 is a cross-sectional view showing a circumferential narrow groove. [Figure 11] FIG. 10 is a cross-sectional view showing a modified example of the circumferential narrow groove. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the present invention will be described in detail based on preferred embodiments, with appropriate reference to the drawings.

[0010] The tire of the present invention is mounted on a rim. The inside of the tire is filled with air, and the internal pressure of the tire is adjusted. A tire mounted on a rim is also called a tire-rim assembly. A tire-rim assembly includes a rim and a tire mounted on the rim.

[0011] In the present invention, a state in which a tire is mounted on a standard rim, the internal pressure of the tire is adjusted to a standard internal pressure, and no load is applied to the tire is referred to as a standard state.

[0012] In the present invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured in a normal state. The dimensions and angles of each part of the tire's meridian cross section, which cannot be measured when the tire is mounted on a regular rim, are measured on a cut surface of the tire obtained by cutting the tire along a plane including the rotation axis. In this measurement, the tire is set so that the distance between the left and right beads matches the distance between the beads of the tire mounted on a regular rim. Note that the tire configuration, which cannot be confirmed when the tire is mounted on a regular rim, is confirmed on the cut surface.

[0013] A genuine rim is a rim specified in the standard on which the tire is based. The "standard rim" in the JATMA standard, the "design rim" in the TRA standard, and the "measuring rim" in the ETRTO standard are all genuine rims.

[0014] Normal tire pressure refers to the pressure specified in the standard on which the tire is based. The "maximum tire pressure" in the JATMA standard, the "maximum tire pressure" listed in the TRA standard's "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURE" and the "INFLATION PRESSURE" in the ETRTO standard are normal tire pressures.

[0015] Normal load refers to the load specified in the standard on which the tire is based. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are normal loads.

[0016] In the present invention, the crosslinked rubber refers to a crosslinked product of a rubber composition obtained by pressurizing and heating the rubber composition. The rubber composition is a material obtained by mixing a rubber component with chemicals such as a filler in a kneader such as a Banbury mixer.

[0017] In the present invention, the "styrene content" is a value calculated by NMR measurement, pyrolysis gas chromatography, infrared absorption spectroscopy, etc., and is applied to rubber components having repeating units derived from styrene, such as SBR. The unit of the styrene content is "% by mass."

[0018] In the present invention, the "vinyl content (amount of 1,2-bonded butadiene units)" is a value calculated by NMR measurement, pyrolysis gas chromatography, infrared absorption spectroscopy, etc., similar to the aforementioned "styrene content," and is applied to rubber components having repeating units derived from butadiene, such as SBR and BR. The unit of vinyl content is "mol %."

[0019] In the present invention, the number of cords contained in a tire element containing parallel cords per 50 mm width is expressed as cord ends (unit: ends / 50 mm). Unless otherwise specified, the cord ends are obtained on a cross section of the element obtained by cutting the element in a plane perpendicular to the longitudinal direction of the cord. In an element containing a spirally wound cord, multiple cords appear to be parallel, and therefore cord ends can be obtained in the same manner as in a tire element containing parallel cords.

[0020] In the present invention, the complex modulus of an element made of crosslinked rubber among elements constituting a tire is measured in accordance with the provisions of JIS K 6394. The measurement conditions are as follows. Initial strain = 10% Dynamic strain = ±1% Frequency = 10 Hz Mode = Decompression mode Temperature=70℃ In this measurement, a test piece (length 40 mm x width 4 mm x thickness 1 mm) is sampled from the tire. The longitudinal direction of the test piece is aligned with the circumferential direction of the tire. If it is not possible to sample a test piece from the tire, the test piece is sampled from a sheet of crosslinked rubber (hereinafter also referred to as a rubber sheet) obtained by pressing and heating the rubber composition used to form the element to be measured at a temperature of 170°C for 12 minutes. In the present invention, the complex modulus is expressed as the complex modulus at 70°C.

[0021] In the present invention, the tread portion of a tire is the portion of the tire that comes into contact with the road surface. The bead portion is the portion of the tire that fits onto the rim. The sidewall portion is the portion of the tire that bridges between the tread portion and the bead portion. A tire has the following portions: a tread portion, a pair of bead portions, and a pair of sidewall portions. The tread portion includes a tread as a tire component, the sidewall portion includes a sidewall as a tire component, and the bead portion includes a bead as a tire component. The center of the tread is also called the crown, and the edges of the tread are also called the shoulders.

[0022] [Findings that form the basis of the present invention] A load is applied to a tire, which causes the tire to deform. The tire undergoes repeated deformation and recovery. There is concern that incorporating an RFID tag into a tire may cause peculiar distortion in the tire. To minimize the impact of the RFID tag on durability, it is being considered to place the RFID tag in a location within the tire where movement is minimal. In the case of heavy-duty tires, the impact of the RFID tag on durability is taken into consideration, and RFID tags tend to be placed in the zone from the folded end of the carcass ply to the maximum width of the tire. When a tire deforms in such a way that its contour is crushed, large distortion occurs when the tire presses into the road surface and when it pushes off the road surface. However, by employing a band having cords extending in the circumferential direction, as in the first belt layer of the tire disclosed in the aforementioned Patent Document 1, the tire can deform while maintaining its circular shape. In this case, circumferential deformation is suppressed, and distortion that occurs when the tire presses into the road surface and when it pushes off the road surface can be reduced. The use of bands in tires is expected to further reduce the impact of RFID tags on tire durability, but as tire deformation is suppressed, tires face a new challenge: a reduction in ride comfort.

[0023] Therefore, the inventors conducted extensive research into technology that can improve the ride comfort of tires while suppressing the impact on durability caused by incorporating an RFID tag by using a band, and have completed the present invention, which is described below.

[0024] [Outline of the embodiment of the present invention] The present invention provides a tire comprising a pair of beads, a carcass spanning between the pair of beads, a tread located outside the carcass and in contact with a road surface, a reinforcing layer located radially between the tread and the carcass, and a tag member including an RFID tag, wherein the carcass comprises a carcass ply, and the carcass ply comprises a ply body spanning between the pair of beads and a pair of turned-up portions that are continuous with the ply body and are turned up at the beads, the tread is made of a rubber composition containing a rubber component, and the rubber component includes styrene-butadiene rubber, the reinforcing layer comprises a belt including a large number of belt cords arranged in parallel and a band including a spirally wound band cord, the belt comprises at least one belt ply, and the at least one belt ply the belt ply having the widest axial width among the at least one full band is the reference belt ply, the belt cords of the reference belt ply are made of steel, the band comprises at least one full band formed by spirally winding a band strip, the full band having the widest axial width among the at least one full band is the reference full band, the band cords of the reference full band are made of steel, the RFID tag is located radially between the end of the turned-up portion and the maximum width position of the tire, and the styrene content CSt and vinyl content CVi of the styrene-butadiene rubber, the inclination angle Ab of the belt cords of the reference belt ply, and the inclination angle Aj of the band cords of the reference full band satisfy the following relational expressions (1) and (2): CSt+CVi≦80 (1) (Ab+Aj) / (CSt+CVi)≧0.20 (2)

[0025] The heavy-duty tire of the present invention can achieve improved ride comfort while suppressing the impact on durability caused by the incorporation of an RFID tag. The mechanism by which the tire achieves this effect has not been clarified, but is presumed to be as follows.

[0026] The RFID tag of this tire is located radially between the end of the folded portion and the tire's widest point. The RFID tag is placed in a location within the tire where movement is minimal. This placement minimizes the impact of the RFID tag on tire durability.

[0027] The reinforcing layer includes a belt including many parallel belt cords and a band including a spirally wound band cord. The tire can deform while maintaining its circular shape. Circumferential deformation is effectively suppressed. This tire can reduce distortion that occurs when the tire presses into and pushes off the road surface. The reduced distortion suppresses the impact of RFID tags on durability.

[0028] This tire uses a reinforcing layer that includes a belt and band, which can reduce the impact on durability caused by incorporating an RFID tag. However, there are concerns that the tire's deformation will be suppressed, which could impair ride comfort.

[0029] However, the rubber composition constituting the tire tread contains styrene-butadiene rubber, and the styrene content CSt and vinyl content CVi of this styrene-butadiene rubber are set to satisfy the aforementioned relationship (1). This lowers the glass transition point of styrene-butadiene rubber, which is known to have a higher glass transition point than natural rubber and butadiene rubber. This styrene-butadiene rubber contributes to increasing the flexibility of the tread. Furthermore, the styrene content CSt and vinyl content CVi, as well as the inclination angle Ab of the belt cord of the reference belt ply and the inclination angle Aj of the band cord of the reference full band, are set to satisfy the aforementioned relationship (2). This tire achieves a balanced improvement in ride comfort while minimizing the impact of RFID tags on durability. This tire achieves improved ride comfort while minimizing the impact on durability caused by the incorporation of an RFID tag.

[0030] The smaller the angles Ab and Aj, the stronger the restraining force of the belt and band. Since tire deformation is suppressed, the impact of the RFID tag on durability is suppressed, but the tire may not be able to maintain a good ride quality. Also, if the tread has grooves, cracks may occur at the groove bottoms. On the other hand, the larger the angles Ab and Aj, the weaker the restraining force of the belt and band. Since tire deformation is promoted, ride quality is improved, but the tire may not be able to suppress the impact of the RFID tag on durability. Therefore, angles Ab and Aj are considered as follows.

[0031] It is preferable that the inclination angle Ab of the belt cord of the reference belt ply and the inclination angle Aj of the band cord of the reference full band satisfy the following relational expression (3). 15≦Ab+Aj≦30 (3) This allows the tire to improve ride comfort while suppressing the impact of RFID tags on durability. Furthermore, if the tire has grooves in the tread, the tire can also suppress the occurrence of cracks at the groove bottoms.

[0032] The band of this tire has a standard full band formed by spirally winding a band strip. If the circumferential positions of the start and end of the winding of the band strip are misaligned, the standard full band will have wide and narrow portions. In this case, the standard full band will have portions with high and low restraining force. Since the outer diameter growth is suppressed in the high-restraining force portions compared to the low-restraining force portions, there is a risk of the tire vibrating when traveling at high speeds. Therefore, the size of the zone where one end portion and the other end portion of the band strip that constitutes the standard full band overlap is considered as follows.

[0033] When the tire is viewed from the side in the axial direction, it is preferable that one end portion and the other end portion of the band strip constituting the standard full band overlap, and that the central angle of the zone where the one end portion and the other end portion overlap is 150 degrees or less. This effectively suppresses vibration during high-speed running. This tire can improve ride comfort.

[0034] The area where the RFID tag is installed is heavier than the area where it is not. Installing an RFID tag affects tire uniformity. The mass of the reference full band changes at the boundary of the edge of the band strip. The edge of the band strip also affects tire uniformity. If the circumferential position of the RFID tag and the circumferential position of the edge of the band strip coincide, there is a concern that uniformity will decrease. In addition, the edge of the band strip is more likely to peel off than other areas. Therefore, if the circumferential position of the RFID tag and the circumferential position of the edge of the band strip coincide, there is a concern that strain will concentrate at the edge of the band strip, causing belt edge looseness (hereinafter also referred to as BEL) starting from the edge of the band strip. Therefore, the circumferential position of the RFID tag and the circumferential position of the edge of the band strip are considered as follows.

[0035] It is preferable that the circumferential position of the RFID tag does not coincide with the circumferential position of one end of the band strip and the circumferential position of the other end of the band strip. This effectively suppresses vibration during high-speed driving. This tire can improve ride comfort. Since the concentration of strain at the end of the band strip is suppressed, this tire can also suppress the occurrence of BEL originating from the end of the band strip.

[0036] Preferably, each of the pair of beads includes a core and an apex, the apex including an inner apex located radially outward of the core and an outer apex located radially outward of the inner apex, and the RFID tag is located radially between the outer end of the outer apex and the end of the turned-up portion. This positions the RFID tag so that it overlaps with the outer apex in the axial direction. The outer apex suppresses deformation of the RFID tag due to the action of load. Since the RFID tag is positioned away from the end of the turned-up portion where strain is likely to concentrate, strain concentration on the RFID tag is also suppressed. This tire can suppress the impact of the RFID tag on durability.

[0037] As mentioned above, the tread of this tire is flexible. Since a flexible tread is prone to rubber wear, adopting a flexible tread may result in reduced wear resistance. If the tread is made harder for wear resistance, the purpose of adopting a flexible tread would be lost. Typically, tire treads have grooves designed to accommodate wet conditions. These grooves affect the rigidity of the tread, so the tread structure is considered as follows:

[0038] Preferably, the tread has a plurality of circumferential grooves, at least one of which is a circumferential narrow groove, and the circumferential narrow groove has a body portion including the groove mouth of the circumferential narrow groove and a widened portion including the groove bottom of the circumferential narrow groove, the body portion having a narrow groove portion, the widened portion having a maximum width greater than the minimum width of the narrow groove portion, and when the tread comes into contact with the road surface and deforms, a pair of wall surfaces of the circumferential narrow groove contact each other at the narrow groove portion. This suppresses tread deformation. Despite employing a flexible tread, the tire can apparently increase tread rigidity. Because the occurrence of abrasion is suppressed, this tire can achieve improved wear resistance. However, even if a tread has good wear resistance, it will wear due to contact with the road surface. Because wear reduces groove volume, there is concern that driving performance on wet roads (hereinafter referred to as wet performance) will decline. However, wide widened portions are provided on the radially inner side of the narrow groove portions of the circumferential narrow grooves. After the narrow groove portions disappear, the widened portions become exposed. After the middle stage of wear, when the narrow groove portions disappear, the exposed widened portions can contribute to suppressing a decline in wet performance. This tire maintains good wear resistance while improving ride comfort, and can also suppress a decline in wet performance due to wear.

[0039] The larger the cord ends Ej of the standard full band, the greater the restraining force of the band. Since tire deformation is suppressed, the impact of RFID tags on durability is reduced, but the tire may not be able to maintain a good ride. If the band is too rigid, it may cause a large impact when the tire presses down on the road surface or make the steering more likely to be pulled when driving in ruts. The deformation that occurs when the tire presses down on the road surface may be concentrated in the tread, which may promote uneven wear. If a belt ply is located next to the standard full band, the distance between the band cord and the belt cord may decrease, which may cause separation due to contact between the two. A standard full band with a large cord ends Ej increases the tire mass. In this case, the tire's rolling resistance may also increase. Therefore, the cord ends Ej of the standard full band is considered as follows.

[0040] Preferably, the styrene content CSt and vinyl content CVi of the styrene-butadiene rubber, and the code ends Ej of the standard full band satisfy the following relational expression (4). (CSt+CVi)×Ej≦2400 (4) This allows the tire to improve ride comfort while minimizing the impact of RFID tags on durability. By maintaining the band's rigidity appropriately, the tire's impact when it steps on the road surface is mitigated, its wandering performance and uneven wear resistance are improved, and contact between the band cord and belt cord is prevented. Furthermore, by minimizing the impact of the standard full band on tire mass, the tire can maintain low rolling resistance.

[0041] Preferably, the styrene content CSt of the styrene-butadiene rubber is 27% by mass or less, which allows the styrene-butadiene rubber to contribute to increasing the flexibility of the tread, thereby improving the ride comfort of the tire.

[0042] Preferably, the vinyl content CVi of the styrene-butadiene rubber is 50 mol % or less, which allows the styrene-butadiene rubber to contribute to increasing the flexibility of the tread, thereby improving the ride comfort of the tire.

[0043] Preferably, the rubber composition further contains a filler, the filler contains silica and carbon black, and a content BSi of the silica per 100 parts by mass of the rubber component and a content BCB of the carbon black per 100 parts by mass of the rubber component satisfy the following relational formula (5): BSi≧BCB (5) This increases the flexibility of the tread, and the tread made of this rubber composition can contribute to improving the ride comfort of the tire.

[0044] The rubber composition preferably further contains a resin component, because the resin component can contribute to improving ride comfort.

[0045] It is preferable that the band strip is a cord arrangement in which a plurality of the band cords are arranged, and that the number of the band cords included in the band strip is five or less. This suppresses circumferential fluctuations in the axial width of the standard full band, thereby suppressing circumferential fluctuations in the restraining force and mass. Since vibration during high-speed driving is effectively suppressed, this tire can improve ride comfort. Since concentration of strain at the end of the band strip is suppressed, this tire can also suppress the occurrence of BEL originating from the end of the band strip.

[0046] As described above, the present invention provides a heavy-duty tire that can achieve improved ride comfort while minimizing the impact on durability caused by the incorporation of an RFID tag, as will be explained in detail below.

[0047] [Details of the embodiment of the present invention] [Rubber composition] The tread is made of a rubber composition. The tread is a cross-linked product of the rubber composition, i.e., a cross-linked rubber. The rubber composition for the tread will be described below. The rubber composition includes a rubber component and a filler.

[0048] [Rubber component] The rubber component contains styrene butadiene rubber (hereinafter referred to as SBR). The rubber component contains SBR and may further contain other rubber components, or may consist of only SBR.

[0049] [SBR] The SBR is not particularly limited, and examples thereof include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (modified S-SBR, modified E-SBR). Modified SBRs include SBRs whose terminals and / or main chains are modified, and modified SBRs (condensates, those having a branched structure, etc.) coupled with tin, silicon compounds, etc. Among these, S-SBR and modified SBR are preferred as the SBR contained in the rubber component. Furthermore, hydrogenated products of these SBRs (hydrogenated SBR) and the like can also be used as the SBR in this rubber composition. One of these SBRs may be selected and used alone, or two or more may be selected and used in combination.

[0050] SBR has excellent viscoelastic properties in the area highly correlated with wet performance (specifically, grip performance on wet roads), and it also has excellent compatibility and reactivity with silica, which will be described later. SBR is thought to contribute to improving wet performance and abrasion resistance. SBR is generally known as a rubber with a higher glass transition temperature than natural rubber or butadiene rubber. However, the SBR styrene content CSt and vinyl content CVi affect the glass transition temperature. The glass transition temperature of SBR with low amounts of these is lower than that of SBR with high amounts of these. The lower the glass transition temperature of the rubber composition that makes up the tread, the greater the flexibility of the tread. A flexible tread improves the ride comfort of a tire. SBR with a low glass transition temperature is thought to impart flexibility to the tread even at low temperatures, contributing to improved ride comfort of a tire.

[0051] From the viewpoint of contributing to an improvement in ride comfort, the styrene content CSt of the SBR is preferably 27% by mass or less, more preferably 25% by mass or less. From the viewpoint of contributing to an improvement in wet performance and abrasion resistance, the styrene content CSt of the SBR is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and particularly preferably 20% by mass or more.

[0052] From the viewpoint of contributing to an improvement in ride comfort, the vinyl content CVi of SBR is preferably 50 mol% or less, more preferably 42 mol% or less, even more preferably 30 mol% or less, and particularly preferably 20 mol% or less. From the viewpoint of contributing to an improvement in wet performance and abrasion resistance, the vinyl content CVi of SBR is preferably 5 mol% or more, more preferably 10 mol% or more.

[0053] From the viewpoint of improving wet performance, the glass transition temperature (Tg) of SBR is preferably -80°C or higher, more preferably -70°C or higher, and even more preferably -66°C or higher. From the viewpoint of reducing rolling resistance and improving ride comfort, the Tg of SBR is preferably -40°C or lower, more preferably -50°C or lower, even more preferably -61°C or lower, and particularly preferably -63°C or lower. The Tg of SBR is determined by performing differential scanning calorimetry (DSC) in accordance with JIS K7121 on a "pure SBR fraction" obtained by removing the extender oil with acetone in accordance with JIS K6229.

[0054] The weight-average molecular weight (Mw) of SBR is preferably 100,000 or more, more preferably 150,000 or more, and even more preferably 190,000 or more, from the viewpoint of improving abrasion resistance. From the viewpoint of crosslinking uniformity, etc., the Mw of SBR is preferably 2.5 million or less, more preferably 2 million or less, and even more preferably 1 million or less. The Mw of SBR can be determined in terms of standard polystyrene based on measurements obtained by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0055] The amount of SBR, CSBR, per 100 parts by mass of the rubber component is preferably 10 parts by mass or more. SBR can effectively contribute to improving ride comfort and wet performance. From this viewpoint, the amount of CSBR is preferably 15 parts by mass or more, more preferably 17 parts by mass or more, and even more preferably 19 parts by mass or more. From the viewpoint of maintaining good abrasion resistance, the amount of CSBR is preferably 60 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 25 parts by mass or less.

[0056] As mentioned above, the rubber component may contain rubber components other than SBR. Examples of rubber components other than BR include crosslinkable rubber components commonly used in the tire industry. Examples of such rubber components include isoprene rubber, styrene-butadiene rubber (SBR), styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. One of these other rubber components may be selected and used alone, or two or more may be selected and used in combination.

[0057] The rubber component of the rubber composition for the tread preferably contains an isoprene-based rubber and BR as rubber components other than SBR.

[0058] [Isoprene rubber] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. Examples of NR include SIR20, RSS#3, and TSR20, which are commonly used in the tire industry. Examples of IR include, but are not limited to, IR2200, which are commonly used in the tire industry. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more. Among these, NR is preferred.

[0059] When the rubber component contains NR, from the viewpoint of increasing the tread strength and improving the abrasion resistance, the content CNR of NR per 100 parts by mass of the rubber component is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 60 parts by mass or more. This content CNR is preferably 85 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 75 parts by mass or less.

[0060] [Butadiene rubber] The butadiene rubber (BR) is not particularly limited, and examples thereof include those commonly used in the tire industry, such as BR with a cis content of less than 50% by mass (low-cis BR), BR with a cis content of 90% by mass or more (high-cis BR), rare earth butadiene rubber (rare earth BR) synthesized using a rare earth catalyst, BR containing syndiotactic polybutadiene crystals (SPB-containing BR), and modified BR (high-cis modified BR, low-cis modified BR). These may be used alone or in combination of two or more. The cis content of BR is a value calculated by infrared absorption spectroscopy.

[0061] BR has excellent low-temperature properties. BR lowers the glass transition temperature of the rubber composition that makes up the tread. BR imparts flexibility to the tread even at low temperatures, which is thought to contribute to improving the ride comfort of tires.

[0062] When the rubber component contains BR, the BR content (CBR) per 100 parts by mass of the rubber component is preferably 10 parts by mass or more. This allows the BR to effectively contribute to improving ride comfort. From this perspective, the BR content (CBR) per 100 parts by mass of the rubber component is more preferably 15 parts by mass or more. From the perspective of maintaining good durability, the BR content (CBR) is preferably 30 parts by mass or less, more preferably 25 parts by mass or less.

[0063] When the rubber component further contains NR and BR in addition to SBR, the NR content (CNR) is preferably greater than the sum of the SBR content (CSBR) and the BR content (CBR). This is because the dispersibility of silica in the rubber composition is improved while maintaining the durability of the tread. In this case, the BR content (CBR) may be greater or less than the SBR content (CSBR). The BR content (CBR) may be the same as the SBR content (CSBR).

[0064] [Filler] As described above, the rubber composition for the tread preferably further contains a filler. In this case, the filler preferably contains carbon black and silica. In other words, the rubber composition contains carbon black and silica as fillers. The filler may contain only carbon black and silica. In other words, the rubber composition may contain a filler consisting only of carbon black and silica.

[0065] [Carbon black] The carbon black is not particularly limited, and can be, for example, GPF, FEF, HAF, ISAF, SAF, or other carbon black commonly used in the tire industry. Furthermore, from the viewpoint of reducing the environmental impact and reducing friction between the carbon black surface and rubber molecular chains, thereby suppressing heat buildup, recycled carbon black (rCB) obtained by pyrolysis of used tires can also be used in this tire. These carbon blacks can be used alone or in combination of two or more types. In the present invention, the aforementioned carbon blacks commonly used in the tire industry, such as GPF, FEF, HAF, ISAF, and SAF, are also called standard carbon blacks (sCB) to distinguish them from recycled carbon black (rCB).

[0066] As mentioned above, recycled carbon black can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes that recycled carbon black can be obtained by pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (

[0027] ). Carbon black obtained from such pyrolysis processes typically lacks functional groups on its surface, as mentioned in

[0004] of Japanese Patent No. 6856781 (Comparison of the Surface Morphology and Chemistry of Pyrolytic Carbon Black with Commercial Carbon Black, Powder Technology 160 (2005) pp. 190-193).

[0067] Recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. Treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, European Patent Application Publication No. 3,173,251 discloses that carbon black obtained from a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Japanese Patent No. 6,856,781 also discloses that carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. The recycled carbon black of this embodiment also includes carbon black treated to include functional groups on its surface. As the recycled carbon black, commercially available products from Strebl Green Carbon, LD Carbon, etc. can be used.

[0068] From the viewpoint of improving abrasion resistance and durability, the average primary particle size of carbon black is preferably 25 nm or less, more preferably 22 nm or less, and even more preferably 19 nm or less, and is preferably 6 nm or more, more preferably 9 nm or more, and even more preferably 12 nm or more.

[0069] The average primary particle diameter of carbon black can be determined by observing carbon black with a transmission or scanning electron microscope, measuring the outer diameters of 400 or more primary particles of carbon black observed within the field of view, and averaging the measured values.

[0070] From the viewpoint of improving wear resistance and durability, the nitrogen adsorption specific surface area (N2SA) of carbon black is 10m 2 / g or more is preferable, and 20m 2 / g or more is more preferable, and 30m 2 / g or more is more preferable. The nitrogen adsorption specific surface area (N2SA) is 250m 2 / g or less is preferable, and 200m 2 / g or less is more preferable, and 150m 2 The nitrogen adsorption specific surface area (N2SA) of carbon black is measured in accordance with JIS K6217-2:2017.

[0071] The carbon black content (BCB) per 100 parts by mass of the rubber component is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, from the viewpoint of exerting a reinforcing effect and preventing deterioration due to ultraviolet rays. From the viewpoint of imparting flexibility to the tread and alleviating stress, the content is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less.

[0072] The content of recycled carbon black in 100 parts by mass of carbon black is not particularly limited, but may be, for example, more than 1 part by mass, more than 5 parts by mass, more than 10 parts by mass, more than 20 parts by mass, more than 25 parts by mass, or more than 30 parts by mass. From the viewpoint of exerting the reinforcing effect of carbon black, the content is preferably less than 95 parts by mass, more preferably less than 90 parts by mass, and even more preferably less than 85 parts by mass.

[0073] [silica] The silica is not particularly limited, and can be, for example, silica prepared by a dry method (anhydrous silica) or silica prepared by a wet method (hydrated silica), which are commonly used in the tire industry. From the viewpoint of environmental impact, silica made from biomass materials (e.g., amorphous silica purified from rice husks) can also be used. Among these, hydrated silica prepared by a wet method is preferred because it contains a large number of silanol groups. These silicas can be used alone or in combination of two or more.

[0074] Silica made from biomass materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then reacting the silicate with sulfuric acid in the same manner as conventional wet-process silica to produce a silicon dioxide precipitate, which is then filtered, washed with water, dried, and pulverized. When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and duration, the crystallization of silica in rice husk ash can be suppressed (see, for example, JP 2009-2594 A and Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216-222). The amorphous silica extracted from rice husks may be commercially available from Wilmar Co., Ltd., etc.

[0075] From the viewpoint of improving abrasion resistance and durability, the average primary particle size of silica is preferably 22 nm or less, more preferably 19 nm or less, and even more preferably 16 nm or less, and the average primary particle size is preferably 6 nm or more, more preferably 9 nm or more, and even more preferably 12 nm or more.

[0076] The average primary particle diameter of silica can be determined by observing silica with a transmission or scanning electron microscope, measuring the outer diameters of 400 or more primary silica particles observed within the field of view, and averaging the measured values.

[0077] From the viewpoint of improving wear resistance and durability, the nitrogen adsorption specific surface area (N2SA) of silica is 100m 2 / g or more is preferable, and 110m 2 / g or more is more preferable, and 120m 2 / g or more is more preferable. 2 / g or less is preferable, and 350m 2 / g or less is more preferable, and 250m 2 / g or less is more preferable. The nitrogen adsorption specific surface area (N2SA) of silica is measured by the BET method in accordance with ASTM D3037-93.

[0078] The silica content BSi per 100 parts by mass of the rubber component is preferably 10 parts by mass or more. Silica can effectively reinforce the tread. The rigidity of the tread is increased, thereby improving abrasion resistance and durability. From this viewpoint, the silica content BSi is more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and particularly preferably 40 parts by mass or more. From the viewpoint of obtaining flexibility and relaxing stress, the silica content BSi is preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less.

[0079] As described above, it is preferable that the carbon black content BCB per 100 parts by mass of the rubber component and the silica content BSi per 100 parts by mass of the rubber component satisfy the above-mentioned relational expression (5). This is because the flexibility of the tread 4 is thereby effectively increased. In this case, it is presumed that the ride comfort of the tire 2 can be further improved. From this viewpoint, it is more preferable that the carbon black content BCB per 100 parts by mass of the rubber component is less than the silica content BSi per 100 parts by mass of the rubber component. In detail, the ratio BCB / BSi of the carbon black content BCB to the silica content BSi is preferably 5 / 6 or less, more preferably 2 / 3 or less, even more preferably 1 / 2 or less, and particularly preferably 1 / 3 or less. From the viewpoint of maintaining the durability of the tread, the ratio BCB / BSi is preferably 1 / 10 or more, more preferably 1 / 7 or more, and even more preferably 1 / 5 or more.

[0080] [Other fillers] Fillers other than silica and carbon black that have been generally used in the tire industry, such as aluminum hydroxide, calcium carbonate, alumina, clay, and talc, can be blended.

[0081] From the viewpoint of increasing the flexibility of the tread and improving the ride comfort of the tire, the carbon black content CCB in 100 parts by mass of the filler is preferably 45 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 35 parts by mass or less, and particularly preferably 30 parts by mass or less. From the viewpoint of maintaining the durability of the tread, the carbon black content CCB is preferably 10 parts by mass or more, more preferably 15 parts by mass or more.

[0082] From the viewpoint of improving abrasion resistance and durability, the total content of the filler per 100 parts by mass of the rubber component is preferably 45 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more. From the viewpoint of providing flexibility to the tread and alleviating stress, the content is preferably 75 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 65 parts by mass or less.

[0083] [Silane coupling agents] As described above, the rubber composition contains silica as a filler. It is preferable to use silica in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent conventionally used in combination with silica in the tire industry can be used. Examples of the silane coupling agent include mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane and Momentive's NXT-Z100, NXT-Z45, and NXT (3-octanoylthiopropyltriethoxysilane); sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl)disulfide and bis(3-triethoxysilylpropyl)tetrasulfide; thioester-based silane coupling agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane, and 3-octanoylthio-1-propyltrimethoxysilane; and vinyltriethoxysilane. Examples of suitable silane coupling agents include vinyl-based silane coupling agents such as silane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, sulfide-based silane coupling agents and / or mercapto-based silane coupling agents are preferred, and mercapto-based silane coupling agents are more preferred. These silane coupling agents may be used alone or in combination of two or more.

[0084] The mercapto-based silane coupling agent refers to a silane coupling agent having a mercapto group and a silane coupling agent in which the mercapto group is protected by a protecting group. The mercapto-based silane coupling agent is not particularly limited, and is, for example, at least one selected from the group consisting of a compound represented by the following chemical formula (1), a compound represented by the following chemical formula (2), and a compound containing a bonding unit A represented by the following chemical formula (3) and a bonding unit B represented by the following chemical formula (4). Among them, at least one of the compound represented by the following chemical formula (1) and a compound containing a bonding unit A represented by the following chemical formula (3) and a bonding unit B represented by the following chemical formula (4) is preferred, because it can better exhibit the effects of the present invention, and the compound represented by the following chemical formula (1) is more preferred.

[0085] [ka] (In the formula, R 1001 -Cl, -Br, -OR 1006 , -O(O=)CR 1006 , -ON=CR 1006 R 1007 , -ON=CR 1006 R 1007 , -NR 1006 R 1007 , and -(OSiR 1006 R 1007 ) h (OSiR 1006 R 1007 R 1008 a monovalent group (R 1006 , R 1007 , and R 1008 may be the same or different and each represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, and h has an average value of 1 to 4; 1002 is R 1001 , a hydrogen atom, or a monovalent hydrocarbon group having 1 to 18 carbon atoms, R 1003 is -[O(R 1009 O) j ]-group(R 1009 is an alkylene group having 1 to 18 carbon atoms, and j is an integer of 1 to 4. 1004is a divalent hydrocarbon group having 1 to 18 carbon atoms, R 1005 represents a monovalent hydrocarbon group having 1 to 18 carbon atoms, and x, y, and z are numbers that satisfy the relationship: x+y+2z=3, 0≦x≦3, 0≦y≦2, 0≦z≦1.

[0086] [ka] (In the formula, R 101 , R 102 , and R 103 are each independently an alkyl having 1 to 12 carbon atoms, an alkoxy having 1 to 12 carbon atoms, or -O-(R 111 -O) z -R 112 (z R 111 each independently represents a divalent hydrocarbon group having 1 to 30 carbon atoms; R 112 represents an alkyl having 1 to 30 carbon atoms, an alkenyl having 2 to 30 carbon atoms, an aryl having 6 to 30 carbon atoms, or an aralkyl having 7 to 30 carbon atoms; z represents an integer of 1 to 30; 104 represents an alkylene having 1 to 6 carbon atoms.

[0087] [ka] [ka] (wherein x represents an integer of 0 or more; y represents an integer of 1 or more; R 201 represents a hydrogen atom, an alkyl having 1 to 30 carbon atoms, an alkenyl having 2 to 30 carbon atoms, or an alkynyl having 2 to 30 carbon atoms (the alkyl, alkenyl, and alkynyl may be substituted with a halogen atom, a hydroxyl, or a carboxyl); R 202 represents an alkylene having 1 to 30 carbon atoms, an alkenylene having 2 to 30 carbon atoms, or an alkynylene having 2 to 30 carbon atoms; 201 and R 202 may form a ring structure with

[0088] The compound represented by chemical formula (1) is R1005 , R 1006 , R 1007 , and R 1008 are each independently a group selected from the group consisting of a linear, cyclic, or branched alkyl group, an alkenyl group, an aryl group, and an aralkyl group, each having from 1 to 18 carbon atoms. 1002 When R is a monovalent hydrocarbon group having 1 to 18 carbon atoms, it is preferably a group selected from the group consisting of a linear, cyclic, or branched alkyl group, an alkenyl group, an aryl group, and an aralkyl group. 1009 R is preferably a linear, cyclic, or branched alkylene group, and is particularly preferably a linear one. 1004 Examples of R include alkylene groups having 1 to 18 carbon atoms, alkenylene groups having 2 to 18 carbon atoms, cycloalkylene groups having 5 to 18 carbon atoms, cycloalkylalkylene groups having 6 to 18 carbon atoms, arylene groups having 6 to 18 carbon atoms, and aralkylene groups having 7 to 18 carbon atoms. The alkylene groups and alkenylene groups may be either linear or branched, and the cycloalkylene groups, cycloalkylalkylene groups, arylene groups, and aralkylene groups may have a functional group such as a lower alkyl group on the ring. This R 1004 As the alkylene group, an alkylene group having 1 to 6 carbon atoms is preferred, and a linear alkylene group such as a methylene group, ethylene group, trimethylene group, tetramethylene group, pentamethylene group, or hexamethylene group is particularly preferred.

[0089] R in chemical formula (1) 1002 , R 1005 , R 1006 , R 1007 , and R 1008Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, a cyclopentyl group, a cyclohexyl group, a vinyl group, a propenyl group, an allyl group, a hexenyl group, an octenyl group, a cyclopentenyl group, a cyclohexenyl group, a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a benzyl group, a phenethyl group, and a naphthylmethyl group.

[0090] R in chemical formula (1) 1009 Examples of the linear alkylene group include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, and a hexylene group, and examples of the branched alkylene group include an isopropylene group, an isobutylene group, and a 2-methylpropylene group.

[0091] Specific examples of the silane coupling agent represented by chemical formula (1) include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3-lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, and 2-lauroylthioethyltrimethoxysilane. Of these, 3-octanoylthiopropyltriethoxysilane is preferred.

[0092] The silane coupling agent represented by chemical formula (1) has a thioester structure (i.e., a protected mercapto group) in the molecule, and has low reactivity with rubber components up to high temperatures. This can suppress strong bonding between the rubber component, the silane coupling agent, and silica during kneading, and can disperse silica appropriately, so that the effects of the present invention tend to be more effectively exhibited.

[0093] Examples of the compound represented by chemical formula (2) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and the compound represented by the following chemical formula (5) (Si363 manufactured by Evonik Degussa GmbH), and the compound represented by the following chemical formula (5) can be preferably used. These may be used alone or in combination of two or more. [ka]

[0094] Examples of compounds containing a bonding unit A represented by chemical formula (3) and a bonding unit B represented by chemical formula (4) include those manufactured and sold by Momentive, Inc. These may be used alone or in combination of two or more.

[0095] The content of the silane coupling agent relative to 100 parts by mass of silica (when multiple silane coupling agents are used in combination, the total amount of all) is preferably more than 1 part by mass, more preferably more than 3 parts by mass, even more preferably more than 5 parts by mass, and even more preferably more than 7 parts by mass, from the viewpoint of improving the dispersibility of silica.Furthermore, from the viewpoint of preventing a decrease in wear resistance, the content is preferably less than 20 parts by mass, more preferably less than 15 parts by mass, and even more preferably less than 12 parts by mass.

[0096] [Other compounding agents] In addition to the above components, the rubber composition according to the present embodiment may appropriately contain compounding agents that are generally used in the tire industry, such as a softener, wax, stearic acid, zinc oxide, an antioxidant, a vulcanizing agent, and a vulcanization accelerator.

[0097] Examples of the softener include resin components, oils, and liquid rubbers.

[0098] The resin component usable in this embodiment is not particularly limited, but may be a resin commonly used in the tire industry, such as a C9 resin, a C5 resin, a C5C9 resin, a dicyclopentadiene resin, an aromatic vinyl resin, a coumarone resin, an indene resin, a terpene resin, a rosin resin, or a phenol resin. These resin components may be used alone or in combination of two or more.

[0099] C9 resin refers to a resin obtained by polymerizing a C9 fraction. It may be a C9 fraction polymerized alone or a copolymer obtained by copolymerizing a C9 fraction with other components. For example, a resin obtained by copolymerizing dicyclopentadiene (DCPD) with a C9 fraction is called a DCPD / C9 resin. These resins may also be hydrogenated or modified. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. These C9 resins may be used alone or in combination.

[0100] The C5 resin refers to a resin obtained by polymerizing a C5 fraction, and may be a hydrogenated or modified C5 resin. Examples of C5 fractions other than dicyclopentadiene include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, and pentadiene. These C5 resins may be used alone or in combination of two or more.

[0101] The C5C9 resin refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. As the C5C9 petroleum resin, for example, commercially available products from Tosoh Corporation, LUHUA, etc. can be used. These C5C9 resins may be used alone or in combination of two or more.

[0102] Dicyclopentadiene-based resins refer to resins containing cyclopentadiene (CPD) or dicyclopentadiene (DCPD) as monomer components, and may be hydrogenated or modified. Examples of dicyclopentadiene-based resins include DCPD / C9 resins containing dicyclopentadiene and the C9 fraction as monomer components (the DCPD / C9 resins may be hydrogenated or modified). DCPD / C9 resins containing dicyclopentadiene and styrene as monomer components are preferred, and DCPD / C9 resins containing dicyclopentadiene, styrene, and indene as monomer components are particularly preferred. Examples of dicyclopentadiene-based resins that can be used include those commercially available from ExxonMobil, ENEOS Corporation, Nippon Zeon Co., Ltd., Maruzen Petrochemical Co., Ltd., and the like. These dicyclopentadiene-based resins may be used alone or in combination.

[0103] The aromatic vinyl resin refers to a resin containing an aromatic vinyl compound such as styrene, α-methylstyrene, vinyltoluene, or p-chlorostyrene as the monomer component with the largest content, and may be a hydrogenated or modified version of such a compound. As the aromatic vinyl resin, a homopolymer of α-methylstyrene or styrene or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, because they are economical, easy to process, and have excellent heat generation properties. As the aromatic vinyl resin, for example, commercially available products from Kraton, Eastman Chemical Company, Mitsui Chemicals, Inc., etc. can be used. These aromatic vinyl resins may be used alone or in combination of two or more.

[0104] Coumarone resins refer to resins containing coumarone as a monomer component, and may be hydrogenated or modified. Examples of coumarone resins include coumarone-indene resins containing coumarone and indene as monomer components, and coumarone-indene-styrene resins containing coumarone, indene, and styrene as monomer components. These coumarone resins may be used alone or in combination of two or more.

[0105] Indene resins refer to resins containing indene as a monomer component, and may be hydrogenated or modified. Examples of indene resins include coumarone-indene resins containing coumarone and indene as monomer components, and coumarone-indene-styrene resins containing coumarone, indene, and styrene as monomer components. These indene resins may be used alone or in combination.

[0106] Terpene resins refer to resins containing terpene compounds such as α-pinene, β-pinene, limonene, and dipentene as the most abundant monomer component, and may be hydrogenated or modified. Specific examples of terpene resins include polyterpene resins containing only one or more of the terpene compounds as monomer components; aromatic-modified terpene resins containing the terpene compound and an aromatic compound as monomer components; and terpene phenolic resins containing the terpene compound and a phenolic compound as monomer components. Examples of aromatic compounds that serve as monomer components for aromatic-modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds that serve as monomer components for terpene phenolic resins include phenol, bisphenol A, cresol, and xylenol. These terpene resins may be used alone or in combination.

[0107] The rosin-based resin refers to a resin containing a rosin acid compound such as abietic acid, neoabietic acid, palustric acid, or isopimaric acid, and may be a hydrogenated or modified version of such a resin. The rosin-based resin is not particularly limited, but examples thereof include natural rosin resin and rosin-modified resins obtained by modifying rosin through hydrogenation, disproportionation, dimerization, esterification, or the like. These rosin-based resins may be used alone or in combination of two or more.

[0108] The phenolic resin refers to a resin that contains a phenolic compound such as phenol or cresol as the monomer component with the highest content. Examples of the phenolic resin include, but are not limited to, phenol formaldehyde resin, alkylphenol formaldehyde resin, alkylphenol acetylene resin, and oil-modified phenol formaldehyde resin. These phenolic resins may be used alone or in combination of two or more.

[0109] From the viewpoints of ride comfort and wet performance, the softening point of the resin component is preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher. From the viewpoints of processability and improving the dispersibility of the rubber component and the filler, the softening point is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. The softening point of the resin is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2015 7.7 is measured using a ring and ball softening point tester.

[0110] When the rubber composition contains a resin component, the content of the resin component per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, from the viewpoints of ride comfort and wet performance. From the viewpoint of suppressing heat buildup, the content of the resin component is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 30 parts by mass or less.

[0111] Examples of oils include process oil, vegetable oils and fats, and animal fats and oils. Examples of process oils include paraffinic process oil, naphthenic process oil, and aromatic process oil. In consideration of environmental impact, process oil with a low content of polycyclic aromatic compounds (PCA) can also be used. Examples of low-PCA process oils include mild extract solvates (MES), treated distillate aromatic extracts (TDAE), and heavy naphthenic oil.

[0112] When the rubber composition contains oil, the amount of oil per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, from the viewpoint of improving processability. From the viewpoint of improving abrasion resistance, the amount of oil is preferably 90 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 30 parts by mass or less.

[0113] The liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at room temperature (25°C), and examples thereof include liquid butadiene rubber (liquid BR), liquid styrene butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene isoprene rubber (liquid SIR), liquid farnesene rubber, etc. These liquid rubbers may be used alone or in combination of two or more.

[0114] When the rubber composition contains a liquid rubber, the content of the liquid rubber per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, and preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 20 parts by mass or less.

[0115] The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; and synthetic waxes such as polymers of ethylene, propylene, etc. Commercially available products that can be used include those from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. These may be used alone or in combination of two or more.

[0116] When the rubber composition contains wax, the content of the wax per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of weather resistance of the rubber. The content of the wax is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, from the viewpoint of preventing whitening of the tire due to bloom.

[0117] The antioxidant is not particularly limited, but examples thereof include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, as well as metal carbamates. Phenylenediamine-based antioxidants, such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine, and quinoline-based antioxidants, such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, are preferred. These antioxidants may be used alone or in combination.

[0118] When the rubber composition contains an antioxidant, the content of the antioxidant per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of ozone crack resistance of the rubber. The content of the antioxidant is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, from the viewpoint of abrasion resistance and wet grip performance.

[0119] As the stearic acid, conventionally known ones can be used, and commercially available products that can be used include products from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. These may be used alone or in combination of two or more kinds.

[0120] When the rubber composition contains stearic acid, the content of stearic acid per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, from the viewpoint of vulcanization rate.

[0121] As the zinc oxide, conventionally known ones can be used, and commercially available products include those available from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more kinds.

[0122] When the rubber composition contains zinc oxide, the content of zinc oxide per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less from the viewpoint of abrasion resistance.

[0123] As the vulcanizing agent, sulfur is preferably used, and examples of sulfur that can be used include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0124] When the rubber composition contains sulfur as a vulcanizing agent, the sulfur content per 100 parts by mass of the rubber component is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1.0 parts by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction. From the viewpoint of preventing deterioration, the sulfur content is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.5 parts by mass or less. When oil-containing sulfur is used as the vulcanizing agent, the content of the vulcanizing agent is expressed as the amount of pure sulfur contained in the oil-containing sulfur.

[0125] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensates, sodium 1,6-hexamethylenedithiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. These vulcanizing agents other than sulfur can be commercially available from Taoka Chemical Co., Ltd., Lanxess K.K., Flexis, etc.

[0126] Examples of vulcanization accelerators include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, and xanthate-based vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. Among these, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based, guanidine-based, and thiazole-based vulcanization accelerators are preferred, and sulfenamide-based vulcanization accelerators are more preferred, in terms of more suitably achieving the desired effects.

[0127] Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), etc. Among these, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS) and N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) are preferred.

[0128] Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, etc. Among these, 1,3-diphenylguanidine (DPG) is preferred.

[0129] Examples of the thiazole vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, etc. Among these, 2-mercaptobenzothiazole is preferred.

[0130] When the rubber composition contains a vulcanization accelerator, the content of the vulcanization accelerator per 100 parts by mass of the rubber component is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2.0 parts by mass or more. The content of the vulcanization accelerator is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, even more preferably 6.0 parts by mass or less, and particularly preferably 5.0 parts by mass or less. By setting the content of the vulcanization accelerator within this range, it tends to be possible to ensure breaking strength and elongation.

[0131] The rubber composition is produced, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or a Banbury mixer. As for the kneading conditions, in the base kneading step in which additives other than the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finish kneading step in which the vulcanizing agent and vulcanization accelerator are kneaded, the kneading temperature is usually 120°C or lower, preferably 85 to 110°C.

[0132] The produced rubber composition is processed into a predetermined shape using an extruder or the like. In a molding machine, the rubber composition is combined with sidewalls and the like to prepare a green tire (a tire in an uncrosslinked state). The green tire is vulcanized in a mold incorporated in a vulcanizer to obtain a tire. The tire is a crosslinked product of the green tire. The vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C. The vulcanization time is usually 5 to 15 minutes.

[0133] The rubber composition described above is used in the tread of a tire (specifically, the cap portion that comes into contact with the road surface during driving). Next, a tire having a tread formed using this rubber composition will be described.

[0134] [tire] 1 shows a part of a tire 2 according to one embodiment of the present invention. This tire 2 is mounted on vehicles such as trucks and buses. This tire 2 is a heavy-duty tire.

[0135] FIG. 1 shows a portion of a cross section (hereinafter referred to as a meridian cross section) of the tire 2 taken along a plane including the rotation axis of the tire 2. The direction indicated by the double arrow AD is the axial direction of the tire 2. The axial direction of the tire 2 means a direction parallel to the rotation axis of the tire 2. The direction indicated by the double arrow RD is the radial direction of the tire 2. The direction perpendicular to the plane of the paper in FIG. 1 is the circumferential direction of the tire 2. The dashed dotted line EL extending in the radial direction represents the equatorial plane of the tire 2. FIG. 2 shows a portion of the cross section shown in FIG. 1. FIG. 2 shows a bead portion B of the tire 2.

[0136] In the axial direction, the direction away from the equatorial plane is the axially outer side of the tire 2, and the direction approaching the equatorial plane is the axially inner side of the tire 2. The direction indicated by arrow RD1 is the radially outer side of the tire 2, and the direction indicated by arrow RD2 is the radially inner side of the tire 2.

[0137] The tire 2 shown in Figure 1 is mounted on a rim R (regular rim). The solid line BBL extending in the axial direction is the bead base line. The bead base line is a line that defines the rim diameter of the rim R (see JATMA, etc.).

[0138] The tire 2 includes a tread 4, a pair of sidewalls 6, a pair of chafers 8, a pair of beads 10, a carcass 12, a reinforcing layer 14, a pair of cushion layers 16, a pair of filler reinforcing layers 18, a pair of interlayer strips 20, an inner liner 22, and a tag member 24. Although the left side of the equatorial plane in the meridian cross section is not shown in Fig. 1, the internal structure of the tire 2 excluding the tag member 24 has a symmetrical structure with respect to the equatorial plane.

[0139] The tread 4 is located radially outward of the carcass 12. The tread 4 extends in the circumferential direction. The tread 4 has a tread surface 26. The tire 2 comes into contact with the road surface at the tread surface 26. Grooves 28 are cut into the tread 4, thereby forming a tread pattern. The tread 4 has a tread pattern. The configuration of the grooves 28 of this tire 2 is symmetrical with respect to the equatorial plane.

[0140] The position indicated by the symbol Eq is the equator. The equator Eq is the intersection point between the tread surface 26 and the equatorial plane. If a groove 28 is present on the equatorial plane, the equator is identified based on a virtual tread surface obtained by assuming that the groove 28 does not exist. The radial distance from the bead base line to the equator Eq obtained for the tire 2 in a normal state is the cross-sectional height of the tire 2 (see JATMA, etc.).

[0141] The position indicated by the symbol TE is the edge of the tread surface 26. If the edge of the tread surface of a tire cannot be identified visually, the position on the outer surface of the tire corresponding to the axially outer edge of the contact patch obtained by applying a normal load to a normal tire in a normal state, setting the camber angle to 0°, and bringing the tire into contact with a flat surface is used as the edge of the tread surface. In this specification, the end TE of the tread surface 26 located on the left side of the equatorial plane (not shown) is also referred to as the first end TE1, and the end TE of the tread surface 26 located on the right side of the equatorial plane is also referred to as the second end TE2.

[0142] 1, the length indicated by the arrow WT is the width of the tread surface 26. The width WT of the tread surface 26 is the axial distance from one end TE to the other end TE of the tread surface 26. The width WT of the tread surface 26 is measured along the tread surface 26.

[0143] Figure 3 shows a cross section of the groove 28. The cross section of the groove 28 shown in Figure 3 is a cross section of the groove 28 along a plane perpendicular to the longitudinal direction of the groove 28. This cross section of the groove 28 is a cross section of a shoulder circumferential groove, which will be described later. The main configuration of the groove 28 will be explained using Figure 3.

[0144] Groove 28 has a pair of wall surfaces 28S including groove mouth 28M and a bottom surface 28B including groove bottom 28T. The groove width of groove 28 is represented by the shortest distance between first wall surface 28S and second wall surface 28S (hereinafter referred to as the wall-to-wall distance). The wall-to-wall distance is measured along a plane including a pair of edges 28E that form groove mouth 28M, or along a plane parallel to this plane.

[0145] In FIG. 3 , the length indicated by the double-headed arrow WG is the groove width of the groove 28 at the groove mouth 28M. The groove width WG is measured along a plane including a pair of edges 28E that form the groove mouth 28M. If the groove mouth 28M of the groove 28 is tapered, the groove width at the groove mouth 28M of the groove 28 is expressed based on a virtual edge obtained by assuming that the groove is not tapered. The length indicated by the double-headed arrow DG is the groove depth of the groove 28. The groove depth DG of the groove 28 is expressed as the shortest distance from a plane including the left and right edges 28E to the groove bottom 28T of the groove 28. The position, groove width WG, and groove depth DG of the groove 28 are determined appropriately according to the specifications of the tire 2.

[0146] Groove bottom 28T is the deepest position in the cross section of groove 28. The distance from a plane including left and right edges 28E that form groove mouth 28M to bottom surface 28B is measured along a normal to this plane. The position at which the distance from this plane to bottom surface 28B is greatest is groove bottom 28T. The direction of the normal to the plane including left and right edges 28E is the depth direction of groove 28. If a protrusion is provided on bottom surface 28B, groove bottom 28T is identified based on a virtual bottom surface obtained assuming that this protrusion does not exist.

[0147] A groove 28 having a groove width WG of less than 1.0 mm at its groove opening 28M is called a sipe. A groove 28 other than a sipe is called a normal groove, and has a groove width WG of 1.0 mm or more at its groove opening 28M. A normal groove having a narrow groove width, in which a pair of wall surfaces can come into contact with each other when the tread comes into contact with the road surface and deforms, is called a fine groove. A normal groove having a wide groove width, in which a pair of wall surfaces do not come into contact with each other when the tread comes into contact with the road surface and deforms, is called a main groove.

[0148] A plurality of circumferential grooves 30 aligned in the axial direction are formed in the tread 4 of this tire 2. Each of the circumferential grooves 30 extends continuously in the circumferential direction.

[0149] In the present invention, when the tread has a plurality of circumferential grooves aligned in the axial direction, the two circumferential grooves located on the outermost sides in the axial direction among these circumferential grooves are shoulder circumferential grooves. A circumferential groove located on the equatorial plane is a center circumferential groove. When no circumferential groove is provided on the equatorial plane, the circumferential groove located in the zone between the equatorial plane and the edge of the tread surface and closest to the equatorial plane is the center circumferential groove. When a circumferential groove is located between the center circumferential groove and the shoulder circumferential groove, the circumferential groove located between the center circumferential groove and the shoulder circumferential groove is the middle circumferential groove.

[0150] The tread 4 of this tire 2 has four circumferential grooves 30. Of the four circumferential grooves 30, two circumferential grooves 32 located on the axially outermost sides are shoulder circumferential grooves. Of the circumferential grooves 30 located in the zone between the equatorial plane and the edge TE of the tread surface 26, the circumferential groove 34 closest to the equatorial plane is a center circumferential groove. This tread 4 has a pair of center circumferential grooves 34 and a pair of shoulder circumferential grooves 32.

[0151] The length indicated by the double-headed arrow WGs in Fig. 3 is the groove width at the groove mouth 32M of the shoulder circumferential groove 32. From the viewpoint of contributing to drainage and traction performance, the groove width WGs of the shoulder circumferential groove 32 is preferably 2% to 10% of the width WT of the tread surface 26. The length indicated by the double-headed arrow DGs in Fig. 3 is the groove depth of the shoulder circumferential groove 32. The groove depth DGs of the shoulder circumferential groove 32 is, for example, 10 mm to 21 mm. From the viewpoint of enabling the tire 2 to exhibit good wet performance, the groove depth DGs is preferably 13 mm to 18 mm.

[0152] The shoulder circumferential groove 32 has a wide groove width, and a pair of wall surfaces 32S do not come into contact with each other even when the tread 4 comes into contact with the road surface and deforms, and is also called a circumferential main groove MG. The tread 4 of this tire 2 has a plurality of circumferential grooves 30, and the plurality of circumferential grooves 30 includes two circumferential main grooves MG located at the outermost positions in the axial direction. The pair of wall surfaces 32S of each of the two circumferential main grooves MG do not come into contact with each other even when the tread 4 comes into contact with the road surface and deforms.

[0153] As described above, the tread 4 has a plurality of circumferential grooves 30. The plurality of circumferential grooves 30 define a plurality of land portions 36 in the tread 4.

[0154] In the present invention, of the multiple land portions configured in the tread, the two land portions located outermost in the axial direction are shoulder land portions. A land portion located on the equatorial plane is a center land portion. When no land portion is provided on the equatorial plane, the land portion located in the zone between the equatorial plane and the edge of the tread surface that is closest to the equatorial plane is the center land portion. When a land portion is located between the center land portion and the shoulder land portion, the land portion located between the center land portion and the shoulder land portion is a middle land portion.

[0155] The tread 4 of this tire 2 has five land portions 36. Of the five land portions 36, two land portions 38 located at the axially outermost positions are shoulder land portions. The shoulder land portions 38 include the edge TE of the tread surface 26. The land portion 40 located on the equatorial plane is a center land portion. The land portion 42 located between the center land portion 40 and the shoulder land portions 38 is a middle land portion. This tread 4 comprises a center land portion 40, a pair of middle land portions 42, and a pair of shoulder land portions 38. Although not described in detail, the width of each land portion 36 is determined appropriately depending on the specifications of the tire 2.

[0156] The tread 4 comprises a base portion 44 and a cap portion 46. The base portion 44 is made of cross-linked rubber. Although not described in detail, the base portion 44 of this tire 2 is made of cross-linked rubber, which is a common cross-linked rubber that constitutes the base portion of a heavy-duty tire. The base portion 44 covers the reinforcing layer 14. The cap portion 46 is located radially outward of the base portion 44. The cap portion 46 covers the base portion 44. The cap portion 46 comprises the tread surface 26. The cap portion 46 is made of cross-linked rubber. The cap portion 46 of this tire 2 is formed using the rubber composition described above. The cross-linked rubber that constitutes the cap portion 46 is a cross-linked product of the rubber composition described above.

[0157] Each sidewall 6 is continuous with the edge of the tread 4. The sidewalls 6 are located axially outward of the carcass 12. The radially outer ends SG of the sidewalls 6 are located radially inward of the edge TE of the tread surface 26. The radially inner ends SU of the sidewalls 6 are located radially between the end of the turned-up portion of the carcass ply and the radially outer end FG of the rim R, which will be described later. The sidewalls 6 are made of crosslinked rubber. The complex modulus of elasticity of the sidewalls 6 is 2.0 MPa or more and 6.0 MPa or less.

[0158] The position indicated by the symbol PW is the axial outer end of the tire 2 (hereinafter referred to as the outer end PW). If the outer surface of the tire 2 has decorations such as patterns or letters, the outer end PW is determined based on a virtual outer surface obtained assuming that there is no decoration. The tire 2 shows its maximum width at the outer end PW. The outer end PW is also called the maximum width position. The axial distance from the first maximum width position PW (not shown) to the second maximum width position PW obtained in the tire 2 in a normal state is the cross-sectional width of the tire 2 (see JATMA, etc.).

[0159] 1, the length indicated by the double-headed arrow H is the radial distance from the bead base line to the maximum width position PW. The radial distance H is also referred to as the radial height of the maximum width position PW. In a tire 2 in a normal state, the ratio of the radial height H of the maximum width position PW to the cross-sectional height of the tire 2 is 0.40 or more and 0.60 or less.

[0160] Each chafer 8 is located radially inward of the sidewall 6. The chafers 8 contact the rim R. The position indicated by the symbol CG is the radially outer end of the chafer 8. The chafers 8 are made of crosslinked rubber in consideration of wear resistance. The complex modulus of elasticity of the chafers 8 is 10 MPa or more and 15 MPa or less.

[0161] The outer end CG of the chafer 8 is located radially outward of the inner end SU of the sidewall 6. The outer end CG of the chafer 8 is covered by the sidewall 6. The outer end CG of the chafer 8 contacts the bead 10 (more specifically, the outer apex, which will be described later). The length indicated by the double arrow C in Figure 2 is the radial distance from the bead base line to the outer end CG of the chafer 8. The radial distance C is also called the radial height of the chafer 8.

[0162] Each bead 10 is located axially inward of the chafer 8. The beads 10 are located radially inward of the sidewall 6.

[0163] The bead 10 includes a core 48 and an apex 50. The core 48 extends in the circumferential direction. Although not shown, the core 48 includes a wound steel wire. The core 48 has a generally hexagonal cross-sectional shape. The apex 50 is located radially outside the core 48. The apex 50 extends radially outward from the core 48. The apex 50 tapers outward. The radially outer end AG of the apex 50 is located radially outward from the outer end CG of the chafer 8. The outer end AG of the apex 50 is located radially inward from the maximum width position PW.

[0164] 2, the length indicated by the double-headed arrow L is the radial distance from the bead base line to the outer end AG of the apex 50. The radial distance L is also referred to as the radial height of the apex 50. In this tire 2, from the viewpoint of achieving a good balance between the rigidity of the bead portion B and the deflection of the tire 2, the ratio (L / H) of the radial height L of the apex 50 to the radial height H of the maximum width position PW is preferably 0.55 or more and 0.95 or less. From the same viewpoint, the ratio (L / C) of the radial height L of the apex 50 to the radial height C of the chafer 8 is preferably 1.08 or more and 1.54 or less.

[0165] The apex 50 includes an inner apex 52 and an outer apex 54. The inner apex 52 is located radially outward of the core 48. The outer apex 54 is located radially outward of the inner apex 52.

[0166] The inner apex 52 tapers outward. A radially outer end UAG of the inner apex 52 is located radially inside the outer end CG of the chafer 8. The inner apex 52 is made of hard crosslinked rubber. The complex elastic modulus of the inner apex 52 is 60 MPa or more and 90 MPa or less.

[0167] The outer apex 54 is thick near the outer end UAG of the inner apex 52. The outer apex 54 tapers inward from this thick portion and then outward. The radially inner end SAU of the outer apex 54 is located radially inside the inner end SU of the sidewall 6. The outer end SAG of the outer apex 54 is the outer end AG of the apex 50. The outer apex 54 is softer than the inner apex 52. The outer apex 54 is made of a soft crosslinked rubber. The complex modulus of elasticity of the outer apex 54 is 3.0 MPa or more and 6.0 MPa or less.

[0168] The apex 50 of the tire 2 further includes an edge strip 56. The edge strip 56 is located axially outward of the outer apex 54 and constitutes a part of the outer surface of the apex 50. The edge strip 56 is located radially between the outer end CG of the chafer 8 and the inner end SAU of the outer apex 54. The edge strip 56 is made of crosslinked rubber. The edge strip 56 is softer than the chafer 8 and harder than the outer apex 54. The complex elastic modulus of the edge strip 56 is 7.0 MPa or more and 12 MPa or less.

[0169] The carcass 12 is located inside the tread 4, the pair of sidewalls 6, and the pair of chafers 8. The carcass 12 bridges between the pair of beads 10. The carcass 12 of the tire 2 has a radial structure.

[0170] The carcass 12 includes at least one carcass ply 58. The carcass 12 of the tire 2 is configured with one carcass ply 58. The carcass ply 58 is turned up at each bead 10.

[0171] The carcass ply 58 includes a ply body 60 and a pair of turned-up portions 62. The ply body 60 spans between a pair of beads 10, i.e., between a first bead 10 and a second bead 10 (not shown). Each turned-up portion 62 is continuous with the ply body 60 and turned up at the bead 10. The turned-up portions 62 of this tire 2 are turned up at the bead 10 from the axially inner side to the axially outer side. An end FE of the turned-up portion 62 is located radially inward of the outer end UAG of the inner apex 52. The end FE of the turned-up portion 62 is in contact with the edge strip 56. The inner end SU of the sidewall 6 described above is located radially inward of the end FE of the turned-up portion 62.

[0172] Although not shown, the carcass ply 58 includes a large number of carcass cords arranged in parallel. These carcass cords are covered with a topping rubber. Each carcass cord intersects with the equatorial plane. The angle that the carcass cord makes with the equatorial plane is between 70° and 90°. The material of the carcass cords of this tire 2 is steel. The carcass cords are steel cords.

[0173] 2, the length indicated by the double-headed arrow N is the radial distance from the bead base line to the end FE of the turned-up portion 62. The radial distance N is also referred to as the radial height of the turned-up portion 62. In this tire 2, the ratio (N / H) of the radial height N of the turned-up portion 62 to the radial height H of the maximum width position PW is set in the range of 0.25 to 0.45.

[0174] Each cushion layer 16 is located between the reinforcing layer 14 and the carcass 12 at an end 14e of the reinforcing layer 14. The cushion layer 16 is made of a soft crosslinked rubber.

[0175] Each filler reinforcing layer 18 is positioned between the carcass 12 and the chafer 8. The filler reinforcing layer 18 is positioned outside the carcass 12 and turned up at the bead 10. The filler reinforcing layer 18 is arranged so as to wrap around the radially inner portion of the bead 10 from the radially inner side of the carcass 12. The inner end RN of the filler reinforcing layer 18 is positioned between the ply body 60 and the inner liner 22 in the axial direction. The inner end RN of the filler reinforcing layer 18 is positioned between the outer end UAG of the inner apex 52 and the core 48 in the radial direction. The outer end RG of the filler reinforcing layer 18 is positioned between the turned-up portion 62 and the chafer 8 in the axial direction. The outer end RG of the filler reinforcing layer 18 is positioned between the end FE of the turned-up portion 62 and the core 48 in the radial direction.

[0176] Although not shown, the filler reinforcing layer 18 includes a large number of filler cords arranged in parallel. These filler cords are covered with a topping rubber. The filler cords of this tire 2 are made of steel.

[0177] Each interlayer strip 20 is positioned axially between the chafer 8 and the apex 50 (more specifically, the outer apex 54). The radially outer end IG of the interlayer strip 20 is positioned radially inside the outer end CG of the chafer 8. The interlayer strip 20 and the edge strip 56 cover the end FE of the turned-up portion 62, and the interlayer strip 20 and the chafer 8 cover the outer end RG of the filler reinforcement layer 18 axially outside the turned-up portion 62. The interlayer strip 20 is made of cross-linked rubber. The interlayer strip 20 has a rigidity similar to that of the edge strip 56. The complex modulus of the interlayer strip 20 is 7.0 MPa or more and 12 MPa or less. "The interlayer strip 20 has a rigidity similar to that of the edge strip 56" means that the ratio of the complex modulus of the interlayer strip 20 to the complex modulus of the edge strip 56 is in the range of 0.8 to 1.2.

[0178] The inner liner 22 is positioned inside the carcass 12. The inner liner 22 is joined to the inner surface of the carcass 12 via insulation (not shown) made of crosslinked rubber. The inner liner 22 forms the inner surface of the tire 2. The inner liner 22 is made of crosslinked rubber that has excellent air barrier properties.

[0179] The tag member 24 is embedded in the boundary between the sidewall portion S and the bead portion B of the tire 2. The tag member 24 may be embedded in the sidewall portion S or the bead portion B.

[0180] The tire 2 has a pair of sidewalls 6, and the tag member 24 of this tire 2 is provided on one of the pair of sidewalls 6. This tire 2 may have a pair of tag members 24, with one tag member 24 provided on one of the sidewalls 6 and the other tag member 24 provided on the other sidewall 6. From the viewpoint of preventing a decrease in durability, it is preferable that the tag member 24 be provided on only one of the pair of sidewalls 6. Although multiple tag members 24 may be provided at intervals in the circumferential direction, it is more preferable that one tag member 24 be provided on only one of the sidewalls 6, from the viewpoint of preventing a decrease in durability.

[0181] 2, the tag member 24 is located axially between the bead 10 and the sidewall 6. The tag member 24 is located radially between the end FE of the turned-up portion 62 and the maximum width position PW of the tire 2.

[0182] FIG. 4 is a plan view of the tag member 24. FIG. 5 is a cross-sectional view taken along line VV in FIG. 4. The tag member 24 is plate-shaped. The tag member 24 is long in the lengthwise direction and short in the widthwise direction. As shown in FIG. 2, the tag member 24 is disposed in the tire 2 such that a first end 24s in the widthwise direction thereof is located on the radially outer side of the tire 2 and a second end 24u is located on the radially inner side. In the tire 2, the first end 24s of the tag member 24 is also called the outer end, and the second end 24u is also called the inner end.

[0183] The tag member 24 includes an RFID tag 64. In FIG. 4 , the RFID tag 64 is shown with a solid line for ease of explanation, and is entirely covered with a protective body 66. The tag member 24 includes the RFID tag 64 and the protective body 66 that covers the entire RFID tag 64. The RFID tag 64 is located at the center of the tag member 24. The protective body 66 is made of cross-linked rubber. In this tire 2, the formation of a good communication environment is taken into consideration, and the protective body 66 is made of cross-linked rubber having high electrical resistance. The protective body 66 of this tire 2 has rigidity approximately equal to that of the outer apex 54. The complex elastic modulus of the protective body 66 is 3.0 MPa or more and 6.0 MPa or less. "The protective body 66 has rigidity approximately equal to that of the outer apex 54" means that the ratio of the complex elastic modulus of the protective body 66 to the complex elastic modulus of the outer apex 54 is in the range of 0.8 or more and 1.2 or less.

[0184] The RFID tag 64 is a small, lightweight electronic component. Although not described in detail, the RFID tag 64 is a small, lightweight electronic component consisting of a semiconductor chip 68 that integrates a transmitter / receiver circuit, a control circuit, a memory, and other components, and an antenna 70. When the RFID tag 64 receives an interrogation radio wave, it uses the received signal as electrical energy and transmits the data stored in the memory as a response radio wave. This RFID tag 64 is a type of passive radio frequency identification transponder.

[0185] The RFID tag 64 of this tire 2 includes a semiconductor chip 68 and a pair of antennas 70. The semiconductor chip 68 is located between the pair of antennas 70. Each antenna 70 extends from the semiconductor chip 68 in the length direction of the tag member 24.

[0186] The tag member 24 is a plate-shaped member in which an RFID tag 64 is covered with crosslinked rubber. In the tag member 24, the RFID tag 64 is arranged so that its length direction coincides with the length direction of the tag member 24. The length TL of the tag member 24 before being embedded in the tire 2 is 60 mm or more and 80 mm or less. The width TW is 10 mm or more and 20 mm or less. The length GL of the RFID tag 64 is 30 mm or more and 50 mm or less.

[0187] 2, the position indicated by the symbol TU is the radially inner end of the RFID tag 64 (specifically, the semiconductor chip 68). The position indicated by the symbol TS is the radially outer end of the semiconductor chip 68, i.e., the radially outer end of the RFID tag 64. In the present invention, when the inner end TU of the RFID tag 64 in the tire 2 is located radially outward from a reference position (hereinafter referred to as the reference position), the RFID tag 64 is located radially outward from the reference position. When the outer end TS of the RFID tag 64 in the tire 2 is located radially inward from the reference position, the RFID tag 64 is located radially inward from the reference position.

[0188] The reinforcing layer 14 is located radially outside the carcass 12. The reinforcing layer 14 is located radially inside the tread 4. The reinforcing layer 14 is located radially between the tread 4 and the carcass 12. The reinforcing layer 14 includes a belt 72 and a band 74. The end 14e of the reinforcing layer 14 located on the second end TE2 side of the tread surface 26 is called the second end 14e2 of the reinforcing layer 14. Although not shown, the end 14e of the reinforcing layer 14 located on the first end TE1 side of the tread surface 26 is called the first end 14e1 of the reinforcing layer 14.

[0189] Fig. 6 shows the configuration of the reinforcing layer 14. The direction indicated by the double arrow CD is the circumferential direction of the tire 2. The direction perpendicular to the paper surface of Fig. 6 is the radial direction of the tire 2. The front side of the paper surface is the radially outer side, and the back side is the radially inner side.

[0190] The belt 72 of the tire 2 includes four belt plies 76. The four belt plies 76 are arranged in the radial direction and, from the inside in the radial direction, are a first belt ply 76A, a second belt ply 76B, a third belt ply 76C, and a fourth belt ply 76D. The first belt ply 76A is the belt ply 76 located at the innermost position in the radial direction. The fourth belt ply 76D is the belt ply 76 located at the outermost position in the radial direction.

[0191] The belt 72 may have at least one belt ply 76. The number of layers of the belt ply 76 constituting the belt 72 may be one, two, or three. The number of layers of the belt ply 76 constituting the belt 72 may be five or more.

[0192] In FIG. 1, the length indicated by the double arrow W1 is the axial width of the first belt ply 76A. The length indicated by the double arrow W2 is the axial width of the second belt ply 76B. The length indicated by the double arrow W3 is the axial width of the third belt ply 76C. The length indicated by the double arrow W4 is the axial width of the fourth belt ply 76D. The axial width of each belt ply 76 is represented by the axial distance from one end 76e of the belt ply 76 to the other end 76e.

[0193] In the tire 2, the second belt ply 76B has the widest axial width W2. The axial width W2 of the second belt ply 76B is the axial width of the belt 72, and the end 76Be of the second belt ply 76B is the end 72e of the belt 72. The end 72e of the belt 72 in the tire 2 is also the end 14e of the reinforcing layer 14. The fourth belt ply 76D has the narrowest axial width W4. The axial width W1 of the first belt ply 76A and the axial width W3 of the third belt ply 76C are the same, or the axial width W1 of the first belt ply 76A is slightly wider than the axial width W3 of the third belt ply 76C.

[0194] In the present invention, the belt ply having the widest axial width among at least one belt ply constituting the belt is the reference belt ply. As described above, the second belt ply 76B is the belt ply 76 having the widest axial width among the four belt plies 76 constituting the belt 72 of the tire 2. In the tire 2, the second belt ply 76B is the reference belt ply BP.

[0195] 1, all of the ends 76e of the four belt plies 76 are located axially outward of the shoulder circumferential groove 32, in other words, the circumferential main groove MG located axially outward. An end 76De of the fourth belt ply 76D located radially outward may be located axially inward of the circumferential main groove MG.

[0196] From the viewpoint of ensuring the rigidity of the tread portion T, the ratio (W1 / WT) of the axial width W1 of the first belt ply 76A to the width WT of the tread surface 26 is preferably 0.80 or more and 0.90 or less. The ratio (W2 / WT) of the axial width W2 of the second belt ply 76B to the width WT of the tread surface 26 is preferably 0.85 or more and 0.95 or less. The ratio (W3 / WT) of the axial width W3 of the third belt ply 76C to the width WT of the tread surface 26 is preferably 0.80 or more and 0.90 or less. The axial width W4 of the fourth belt ply 76D is set appropriately depending on the specifications of the tire 2.

[0197] As shown in Fig. 6, each belt ply 76 constituting the belt 72 includes a large number of parallel belt cords 78. For ease of explanation, the belt cords 78 are represented by solid lines in Fig. 6, but the belt cords 78 are covered with belt topping rubber 80. The cord ends of each belt ply 76 are 15 ends / 50 mm or more and 30 ends / 50 mm or less.

[0198] The material of the belt cords 78 is steel. As described above, the second belt ply 76B of the tire 2 is the standard belt ply BP. The material of the belt cords 78 of the standard belt ply BP is steel.

[0199] As described above, the belt 72 includes at least one belt ply 76. When the belt 72 includes two or more belt plies 76, the belt cords 78 of the belt plies 76 other than the reference belt ply BP may be cords made of organic fibers (hereinafter referred to as organic fiber cords). In this case, examples of the organic fibers include nylon fibers, rayon fibers, polyester fibers, and aramid fibers. From the viewpoint of ensuring the rigidity of the tread portion T, it is preferable that the belt cords 78 of all the belt plies 76 constituting the belt 72 are steel cords.

[0200] The belt cords 78 of each belt ply 76 are inclined with respect to the circumferential direction. The inclination direction of the belt cords 78 included in the first belt ply 76A (hereinafter referred to as the inclination direction of the first belt cords 78A) is the same as the inclination direction of the belt cords 78 included in the second belt ply 76B (hereinafter referred to as the inclination direction of the second belt cords 78B). The inclination direction of the second belt cords 78B is opposite to the inclination direction of the belt cords 78 included in the third belt ply 76C (hereinafter referred to as the inclination direction of the third belt cords 78C). The inclination direction of the third belt cords 78C is the same as the inclination direction of the belt cords 78 included in the fourth belt ply 76D (hereinafter referred to as the inclination direction of the fourth belt cords 78D). The inclination direction of the first belt cords 78A may be opposite to the inclination direction of the second belt cords 78B. The inclination direction of the third belt cords 78C may be opposite to the inclination direction of the fourth belt cords 78D.

[0201] In Fig. 6, angle θ1 is the angle that the first belt cord 78A makes with respect to the circumferential direction (hereinafter referred to as inclination angle θ1). Angle θ2 is the angle that the second belt cord 78B makes with respect to the circumferential direction (hereinafter referred to as inclination angle θ2). Angle θ3 is the angle that the third belt cord 78C makes with respect to the circumferential direction (hereinafter referred to as inclination angle θ3). Angle θ4 is the angle that the fourth belt cord 78D makes with respect to the circumferential direction (hereinafter referred to as inclination angle θ4). In the present invention, unless otherwise specified, the inclination angle of each belt cord 78 is represented by the angle that the belt cord 78 makes with respect to the equator plane. As described above, the second belt ply 76B is the reference belt ply BP. The inclination angle θ2 of the second belt cord 78B is the inclination angle Ab of the belt cord 78 of the reference belt ply BP.

[0202] The inclination angle θ1 of the first belt cord 78A, the inclination angle θ2 of the second belt cord 78B, the inclination angle θ3 of the third belt cord 78C, and the inclination angle θ4 of the fourth belt cord 78D are preferably 10 degrees or greater and 60 degrees or less. From the viewpoint of effectively restricting the movement of the tread portion T and obtaining a ground contact patch with a stable shape with minimal shape change, the inclination angle θ1 of the first belt cord 78A is more preferably 40 degrees or greater and 60 degrees or less. The inclination angle θ2 of the second belt cord 78B is more preferably 15 degrees or greater and 30 degrees or less, and even more preferably 15 degrees or greater and 20 degrees or less. The inclination angle θ3 of the third belt cord 78C is more preferably 15 degrees or greater and 30 degrees or less, and even more preferably 15 degrees or greater and 20 degrees or less. The inclination angle θ4 of the fourth belt cord 78D is more preferably 15 degrees or greater and 50 degrees or less.

[0203] From the viewpoint of effectively restricting the movement of the tread portion T and obtaining a ground contact patch with a stable shape with little change in shape, it is preferable that the inclination direction of the third belt cord 78C is opposite to the inclination direction of the second belt cord 78B, but the inclination angle θ3 of the third belt cord 78C is approximately the same as the inclination angle θ2 of the second belt cord 78B. The inclination angle θ3 of the third belt cord 78C being approximately the same as the inclination angle θ2 of the second belt cord 78B means that the absolute value of the difference between the inclination angle θ3 and the inclination angle θ2 is within 3 degrees.

[0204] The band 74 of the tire 2 includes one full band 82. The band 74 is configured with one layer of the full band 82. The number of layers of the full band 82 that configures the band 74 may be two layers, or may be three or more layers. The band 74 includes at least one layer of the full band 82. The band 74 may further include a pair of edge bands that are arranged axially spaced apart from each other across the equatorial plane.

[0205] 1, the end 82e of the full band 82 is located axially outward of the shoulder circumferential groove 32, in other words, the circumferential main groove MG located axially outermost. The length indicated by the double arrow WF is the axial width of the full band 82. The axial width WF of the full band 82 is the axial distance from one end 82e (not shown) of the full band 82 to the other end 82e. From the viewpoint of ensuring the rigidity of the tread portion T, the ratio (WF / WT) of the axial width WF of the full band 82 to the width WT of the tread surface 26 is preferably 0.60 or more and 0.90 or less.

[0206] An end 82e of the full band 82 of the tire 2 is located axially between an end 76De of the fourth belt ply 76D and an end 76Ce of the third belt ply 76C. The end 82e of the full band 82 is located axially inward of an end 76Be of the second belt ply 76B, which serves as the end 72e of the belt 72. The full band 82 is narrower than the first belt ply 76A, the second belt ply 76B, and the third belt ply 76C. The band 74 of the tire 2 is constituted by a single full band 82. An end 74e of the band 74 is located axially inward of the end 72e of the belt 72.

[0207] As shown in Fig. 6, a full band 82 constituting the band 74 includes a spirally wound band cord 84. The full band 82 has a jointless structure. For ease of explanation, the band cord 84 is shown by a solid line in Fig. 6, but the band cord 84 is covered with a band topping rubber 86.

[0208] As will be described later, the full band 82 is formed by spirally winding a band strip including a band cord 84. The band cord 84 is slightly inclined with respect to the circumferential direction. In FIG. 6, angle θd is the angle that the band cord 84 makes with respect to the circumferential direction (hereinafter referred to as the inclination angle θd). The inclination angle θd of the band cord 84 is preferably 5 degrees or less. The band cord 84 extends substantially in the circumferential direction. In the present invention, unless otherwise specified, the inclination angle θd of the band cord 84 is represented by the angle that the band cord 84 forms with respect to the equator plane.

[0209] 1 is manufactured by a known manufacturing method. An unvulcanized tire 2, i.e., a green tire (not shown), is prepared by combining components such as a tread 4 and a sidewall 6. The green tire is then pressurized and heated in a mold to obtain the tire 2.

[0210] As described above, the band 74 of the tire 2 includes a full band 82. The full band 82 is formed using the band strip 88 shown in FIG. 7. The band strip 88 is strip-shaped. The band strip 88 includes one or more band cords 84. The band strip 88 shown in FIG. 7 includes five band cords 84. These band cords 84 are aligned in the width direction of the band strip 88 and extend in the length direction of the band strip 88. The band strip 88 is a cord arrangement in which a plurality of band cords 84 are arranged.

[0211] 7, the length indicated by the double-headed arrow Dj is the outer diameter (hereinafter referred to as the cord diameter Dj) of the band cord 84. The cord diameter Dj of the band cord 84 is set in the range of 1.0 mm or more and 2.0 mm or less.

[0212] The full band 82 shown in FIG. 6 is formed by spirally winding a band strip 88 from one end 82e (hereinafter referred to as the first end 82e1) of the full band 82 to the other end 82e (hereinafter referred to as the second end 82e2) of the full band 82, as shown in FIG. 8. When forming the full band 82, one end 88e (hereinafter referred to as the first end BS1) of the band strip 88 is set at a position corresponding to the first end 82e1 of the full band 82, and the other end 88e (hereinafter referred to as the second end BS2) of the band strip 88 is set at a position corresponding to the second end 82e2 of the full band 82. The full band 82 is a crosslinked band molding formed by spirally winding the band strip 88. The full band 82 includes a first end BS1 and a second end BS2 of the band strip 88.

[0213] 8, the band strip 88 is wound so that a first end BS1 portion and a second end BS2 portion of the band strip 88 overlap in the axial direction. The circumferential position of the first end BS1 does not coincide with the circumferential position of the second end BS2. The band strip 88 may also be wound so that the circumferential position of the first end BS1 coincides with the circumferential position of the second end BS2.

[0214] In a zone from the first end BS1 to the second end BS2 of the band strip 88, indicated by the symbol LZ in Fig. 8, a portion at the first end BS1 and a portion at the second end BS2 of the band strip 88 overlap. This zone LZ, in which the portion at the first end BS1 and the portion at the second end BS2 of the band strip 88 overlap, is called an overlap zone of the band strip 88. The full band 82 of the tire 2 includes the overlap zone LZ of the band strip 88. The position indicated by the solid line LM in Fig. 8 is the circumferential center of the overlap zone LZ.

[0215] Fig. 9 shows the full band 82 shown in Fig. 8 as viewed from the second end 82e2 side. The direction perpendicular to the paper surface of Fig. 9 is the axial direction of the tire 2. The position indicated by the symbol RA is the axis of the rotational shaft of the tire 2. In Fig. 9, the outline of the tire 2 and the tag member 24 are indicated by dotted lines.

[0216] The size of the overlap zone LZ of the band strip 88 in the full band 82 is expressed by the angle, i.e., the central angle, formed by the line segment connecting the first end BS1 of the band strip 88 to the axis RA of the rotating shaft and the line segment connecting the second end BS2 of the band strip 88 to the axis RA of the rotating shaft. The angle θp in Figure 9 is the central angle of the overlap zone LZ of the band strip 88. When the circumferential position of the first end BS1 of the band strip 88 and the circumferential position of the second end BS2 of the band strip 88 are the same, the central angle θp is 0 degrees.

[0217] In Figure 9, the zone indicated by the symbol CZ is the zone 180 degrees opposite the overlap zone LZ. The position indicated by the symbol CM is the position corresponding to the position 180 degrees opposite the circumferential center LM of the overlap zone LZ. The axial width WF of the full band 82 described above is expressed as the axial width of the full band 82 in a zone other than the overlap zone LZ.

[0218] As described above, the band 74 of the tire 2 includes at least one layer of the full band 82. The full band 82 is a component of the tire 2 formed by spirally winding the band strip 88. The band 74 includes at least one layer of the full band 82 formed by spirally winding the band strip 88.

[0219] In the present invention, the full band having the widest axial width among at least one layer of full bands constituting the band is the reference full band. As described above, the band 74 of the tire 2 is composed of a single layer of full band 82. This full band 82 is the reference full band BF having the widest axial width among the at least one layer of full bands that constitute the band 74. The inclination angle θd of the band cord 84 of the full band 82 described above is the inclination angle Aj of the band cord 84 of the reference full band BF.

[0220] The material of the band cord 84 of the full band 82 of this tire 2 is steel. The material of the band cord 84 of the standard full band BF is steel.

[0221] As described above, the band 74 includes at least one layer of full band 82. When the band 74 includes two or more layers of full bands 82, the band cords 84 of the full bands 82 other than the standard full band BF may be organic fiber cords. In this case, examples of the organic fiber include nylon fiber, rayon fiber, polyester fiber, and aramid fiber. From the viewpoint of ensuring the rigidity of the tread portion T, it is preferable that the band cords 84 of all of the full bands 82 constituting the band 74 are steel cords.

[0222] 2, the RFID tag 64 of this tire 2 is located in the radial direction between the end FE of the folded-back portion 62 and the maximum width position PW of the tire 2. The RFID tag 64 is placed in a location of the tire 2 that is less prone to movement. This placement suppresses the impact of the RFID tag 64 on durability.

[0223] The reinforcing layer 14 includes the belt 72 including a large number of parallel belt cords 78 and the band 74 including the spirally wound band cord 84, so that the tire 2 can deform while maintaining its annular shape. Since circumferential deformation is effectively suppressed, the tire 2 can reduce distortion that occurs when the tire presses onto and pushes off the road surface. The reduced distortion suppresses the impact of the RFID tag 64 on durability.

[0224] The tire 2 employs a reinforcing layer including the belt 72 and the band 74, thereby making it possible to suppress the influence on durability caused by incorporating the RFID tag 64.

[0225] The rubber composition constituting the tread 4 of this tire 2 contains styrene-butadiene rubber, and the styrene content CSt and vinyl content CVi of this styrene-butadiene rubber are set to satisfy the aforementioned relationship (1). Styrene-butadiene rubber is known to have a higher glass transition temperature than natural rubber and butadiene rubber, and this can lower that glass transition temperature. Styrene-butadiene rubber with a low total amount of styrene content CSt and vinyl content CVi can contribute to increasing the flexibility of the tread 4. Furthermore, the styrene content CSt and vinyl content CVi, as well as the inclination angle Ab of the belt cord 78 of the standard belt ply BP and the inclination angle Aj of the band cord 84 of the standard full band BF, are set to satisfy the aforementioned relationship (2). This tire 2 can achieve a balanced improvement in ride comfort while suppressing the impact of RFID tags on durability.

[0226] This tire 2 can achieve improved ride comfort while suppressing the impact on durability caused by the incorporation of the RFID tag 64.

[0227] As described above, the styrene content CSt and vinyl content CVi of the styrene-butadiene rubber satisfy the above-mentioned relational expression (1), in other words, the sum of the styrene content CSt and the vinyl content CVi is not more than 80. From the viewpoint of improving ride comfort, the sum of the styrene content CSt and the vinyl content CVi (CSt + CVi) is preferably not more than 50, and more preferably not more than 40. From the viewpoint of improving wet performance and wear resistance, the sum (CSt + CVi) is preferably not less than 10, more preferably not less than 20, and even more preferably not less than 30.

[0228] As described above, the styrene content CSt and vinyl content CVi, as well as the inclination angle Ab of the belt cord 78 of the standard belt ply BP and the inclination angle Aj of the band cord 84 of the standard full band BF, satisfy the above-described relational expression (2). In other words, the ratio (Ab + Aj) / (CSt + CVi) of the sum (Ab + Aj) of the inclination angle Ab and the inclination angle Aj to the sum (CSt + CVi) of the styrene content CSt and the vinyl content CVi is 0.20 or greater. From the viewpoint of improving ride comfort, the ratio (Ab + Aj) / (CSt + CVi) is preferably 0.30 or greater, and more preferably 0.40 or greater. From the viewpoint of improving wet performance and abrasion resistance, the ratio (Ab + Aj) / (CSt + CVi) is preferably 3.0 or less, more preferably 2.0 or less, even more preferably 1.5 or less, and particularly preferably 1.0 or less.

[0229] The inclination angle Ab of the belt cord 78 of the standard belt ply BP and the inclination angle Aj of the band cord 84 of the standard full band BF satisfy the above-mentioned relational expression (3). In other words, it is preferable that the sum of the inclination angle Ab and the inclination angle Aj (Ab + Aj) is 15 degrees or more and 30 degrees or less. By setting the sum (Ab+Aj) of the inclination angle Ab and the inclination angle Aj to 15 degrees or more, the restraining force of the belt 72 and the band 74 is appropriately maintained. Since the tire 2 can deform effectively, the ride comfort of the tire 2 is improved. The tire 2 can also suppress the occurrence of cracks at the groove bottoms of the circumferential grooves 30. From this viewpoint, it is more preferable that the sum (Ab+Aj) be 17 degrees or more. By setting the sum (Ab+Aj) of the inclination angle Ab and the inclination angle Aj to 30 degrees or less, the belt 72 and the band 74 can contribute to suppressing deformation of the tire 2. The tire 2 can effectively suppress the influence of the RFID tag 64 on durability. From this viewpoint, it is more preferable that the sum (Ab+Aj) be 25 degrees or less.

[0230] The central angle θp of the overlap zone LZ of the band strip 88 in the reference full band BF is preferably 150 degrees or less. This effectively suppresses vibrations during high-speed running that occur because the reference full band BF formed by wrapping the band strip 88 has wide and narrow portions. This tire 2 can improve ride comfort. From this perspective, the central angle θp is more preferably 120 degrees or less, even more preferably 90 degrees or less, and particularly preferably 45 degrees or less.

[0231] As shown in FIG. 9 , for example, the tag member 24 is disposed such that a position CM corresponding to a position 180 degrees opposite the circumferential center LM of the overlap zone LZ of the band strip 88 coincides with the position of the RFID tag 64 in the circumferential direction. The circumferential position of the RFID tag 64 does not coincide with the circumferential position of the first end BS1 or the circumferential position of the second end BS2 of the band strip 88. The mass of the reference full band BF is prevented from suddenly changing at the end 88e of the band strip 88. The influence of the built-in RFID tag 64 on uniformity is effectively suppressed. Since vibration during high-speed running is effectively suppressed, the tire 2 can improve ride comfort. Since concentration of strain at the end 88e of the band strip 88 is suppressed, the tire 2 can also suppress the occurrence of BEL originating from the end 88e of the band strip 88. From this viewpoint, it is preferable that the circumferential position of the RFID tag 64 does not coincide with the circumferential positions of the first end BS1 and the second end BS2 of the band strip 88. From the viewpoint of improving the uniformity of the tire 2, it is more preferable that the RFID tag 64 be located in a zone other than the overlap zone LZ, and it is even more preferable that the RFID tag 64 be located in a zone CZ that is 180 degrees opposite the overlap zone LZ. It is particularly preferable that the tag member 24 be arranged so that the position CM corresponding to the 180 degrees opposite side of the circumferential center LM of the overlap zone LZ and the position of the RFID tag 64 coincide in the circumferential direction.

[0232] As described above, the band strip 88 is a cord arrangement in which a plurality of band cords 84 are arranged. The number of band cords 84 included in this band strip 88 is preferably five or less. This suppresses circumferential fluctuations in the axial width of the reference full band BF, thereby suppressing circumferential fluctuations in the binding force and mass. Since vibrations during high-speed driving are effectively suppressed, the tire 2 can improve ride comfort. Since concentration of strain at the end 88e of the band strip 88 is suppressed, the tire 2 can also suppress the occurrence of BEL originating from the end 88e of the band strip 88. From this perspective, it is more preferable that the number of band cords 84 included in the band strip 88 is three or less.

[0233] The styrene content CSt and vinyl content CVi of the styrene-butadiene rubber, and the number of band cords 84 per 50 mm width of the standard full band BF (specifically, the number of cross sections of the band cords 84 per 50 mm width of the standard full band BF) satisfy the aforementioned relational expression (4). In other words, the product of the sum of the styrene content CSt and the vinyl content CVi and the cord ends Ej of the standard full band BF is preferably 2400 or less. This allows the tire 2 to improve ride comfort while suppressing the impact of the RFID tag 64 on durability. Since the rigidity of the band 74 is appropriately maintained, impact when the tire 2 steps on the road surface is mitigated, wandering performance and uneven wear resistance are improved, and contact between the band cords 84 and the belt cord 78 is prevented. Furthermore, since the impact of the standard full band BF on tire mass is suppressed, the tire 2 can maintain low rolling resistance. From this viewpoint, the product of the sum of the styrene content CSt and the vinyl content CVi and the cord ends Ej of the standard full band BF is more preferably equal to or less than 1500, further preferably equal to or less than 1200, and particularly preferably equal to or less than 1000. From the viewpoint of enabling the tire 2 to maintain good durability, the product of the sum of the styrene content CSt and the vinyl content CVi and the cord ends Ej of the standard full band BF is preferably equal to or greater than 600.

[0234] The chord ends Ej of the reference full band BF are preferably 20 ends / 50 mm or more and 30 ends / 50 mm or less. By setting the cord ends Ej of the reference full band BF to 20 ends / 50 mm or more, the band 74 can contribute to suppressing deformation of the tire 2. The tire 2 can effectively suppress the impact of the RFID tag 64 on durability. From this viewpoint, it is more preferable that the cord ends Ej be 22 ends / 50 mm or more. By setting the cord ends Ej of the standard full band BF to 30 ends / 50 mm or less, the restraining force of the band 74 is appropriately maintained. The tire 2 can deform effectively, thereby improving the ride comfort of the tire 2. The end 82e of the standard full band BF is positioned away from the interface between the tread 4 and the sidewall 6, thereby suppressing the concentration of strain at the end 82e of the standard full band BF. This tire 2 can maintain good durability. Furthermore, the impact of the standard full band BF on the tire mass is also suppressed, so this tire 2 can maintain low rolling resistance. From this perspective, it is more preferable that the cord ends Ej be 28 ends / 50 mm or less.

[0235] In the tire 2, the RFID tag 64 is preferably located between the outer end SAG of the outer apex 54 and the end FE of the turned-up portion 62 in the radial direction. This allows the RFID tag 64 to be positioned so as to overlap with the outer apex 54 in the axial direction. The outer apex 54 suppresses deformation of the RFID tag 64 due to the action of a load. Since the RFID tag 64 is located away from the end FE of the turned-up portion 62 where strain is likely to concentrate, strain concentration on the RFID tag 64 is also suppressed. In the tire 2, the impact of the RFID tag 64 on durability can be suppressed. From this viewpoint, it is more preferable that the RFID tag 64 be located between the outer end SAG of the outer apex 54 and the outer end CG of the chafer 8 in the radial direction, and it is even more preferable that the entire tag member 24 be located between the outer end SAG of the outer apex 54 and the outer end CG of the chafer 8 in the radial direction.

[0236] As described above, the outer apex 54 can contribute to suppressing deformation of the RFID tag 64 due to the action of a load. From the viewpoint that the outer apex 54 can effectively suppress deformation of the RFID tag 64 due to the action of a load, when the RFID tag 64 is arranged so as to overlap with the outer apex 54 in the axial direction, it is preferable that the outer apex 54 has a rigidity higher than that of the sidewall 6. More specifically, it is more preferable that the complex elastic modulus of the outer apex 54 is 1.1 to 3.0 times the complex elastic modulus of the sidewall 6.

[0237] 1, the reference full band BF is located between the second belt ply 76B and the third belt ply 76C in the radial direction. As described above, the inclination direction of the third belt cord 78C is opposite to the inclination direction of the second belt cord 78B. The reference full band BF of the tire 2 is located between the second belt ply 76B and the third belt ply 76C, whose belt cords 78 have inclination directions opposite to each other.

[0238] In the present invention, when a standard full band BF is located between two belt plies whose belt cords have inclination directions opposite to each other, the belt ply located radially inside this standard full band BF is called an inner belt ply, and the belt ply located radially outside this standard full band BF is called an outer belt ply. In the case of the tire 2, the second belt ply 76B is the inner belt ply, and the third belt ply 76C is the outer belt ply. Furthermore, in the present invention, when the inner belt ply is the reference belt ply BP, the outer belt ply is called a sub-reference belt ply BPs, and when the outer belt ply is the reference belt ply BP, the inner belt ply is called a sub-reference belt ply BPs. The sub-reference belt ply BPs is a belt ply that is located adjacent to the reference belt ply BP in the radial direction and has belt cords with an inclination direction opposite to that of the belt cords of the reference belt ply BP. In the case of the tire 2, the second belt ply 76B, which is the inner belt ply, is the reference belt ply BP, and therefore the third belt ply 76C, which is the outer belt ply, is the sub-reference belt ply BPs.

[0239] The reference full band BF of this tire 2 is located between the reference belt ply BP and the sub-reference belt ply BPs, whose belt cords 78 have inclination directions opposite to each other. The reinforcing layer 14, which includes the reference belt ply BP, the sub-reference belt ply BPs, and the reference full band BF, can effectively contribute to suppressing growth in outer diameter due to running. Since the band cords 84 included in the standard full band BF extend substantially in the circumferential direction and the belt cords 78 included in the sub-standard belt ply BPs are arranged to intersect with the belt cords 78 included in the standard belt ply BP, shear strain occurring in the rubber located between the band cords 84 and the belt cords 78 is reduced. The standard full band BF can continue to stably exert its function of suppressing outer diameter growth. The tire 2 can improve ride comfort while suppressing the impact of the built-in RFID tag 64 on durability. From this perspective, it is preferable that the belt ply 76 having the widest axial width among the at least one belt ply 76 constituting the belt 72 is the standard belt ply BP, the belt ply 76 located radially adjacent to the standard belt ply BP and having belt cords 78 with an inclination direction opposite to that of the belt cords 78 of the standard belt ply BP is the sub-standard belt ply BPs, and the standard full band BF is located radially between the standard belt ply BP and the sub-standard belt ply BPs. In this case, it is more preferable that the reference belt ply BP is located radially inside the reference full band BF, and the sub-reference belt ply BPs is located radially outside the reference full band BF.

[0240] The standard full band BF shown in FIG. 6 is formed by spirally winding the band strip 88 counterclockwise from the first end 82e1 to the second end 82e2 as viewed from the second end 82e2. Therefore, the band cords 84 of the standard full band BF are slightly inclined with respect to the circumferential direction. In the reinforcing layer 14 shown in FIG. 6, the direction of inclination of the band cords 84 included in the standard full band BF is opposite to the direction of inclination of the belt cords 78 included in the standard belt ply BP. The direction of inclination of the band cords 84 included in this standard full band BF may be the same as the direction of inclination of the belt cords 78 included in the standard belt ply BP. From the viewpoint of effectively reducing shear strain generated in the rubber located between the band cords 84 and the belt cords 78, it is preferable that the direction of inclination of the band cords 84 included in the standard full band BF be opposite to the direction of inclination of the belt cords 78 included in the standard belt ply BP.

[0241] 10 shows a cross section of the center circumferential groove 34. The cross section of the center circumferential groove 34 shown in FIG. 10 is a cross section of the center circumferential groove 34 taken along a plane perpendicular to the length direction of the center circumferential groove 34.

[0242] The central circumferential groove 34 has a pair of wall surfaces 34S including a groove mouth 34M and a bottom surface 34B including a groove bottom 34T. A dashed dotted line LC is the center line of the central circumferential groove 34. The central circumferential groove 34 has a cross-sectional shape that is symmetrical with respect to the center line LC. The center line LC extends in the depth direction of the central circumferential groove 34 and passes through the groove bottom 34T.

[0243] The central circumferential groove 34 of this tire 2 has a narrow groove width, and is a groove (hereinafter referred to as a circumferential narrow groove HG) in which a pair of wall surfaces 34S can come into contact with each other when the tread 4 comes into contact with the road surface and deforms. At least one of the plurality of circumferential grooves 30 formed in the tread 4 of this tire 2 is a circumferential narrow groove HG.

[0244] The circumferential narrow groove HG has a body portion 90 and a widened portion 92. The body portion 90 includes a groove mouth 34M of the circumferential narrow groove HG. The widened portion 92 includes a groove bottom 34T of the circumferential narrow groove HG. When the tread 4 wears and the narrow groove portion 94 disappears, the widened portion 92 is exposed. In FIG. 10 , the length indicated by the double arrow WC1 is the minimum groove width of the circumferential narrow groove HG, and the length indicated by the double arrow WC2 is the maximum groove width of the circumferential narrow groove HG. The circumferential narrow groove HG has the minimum groove width WC1 at the body portion 90 and the maximum groove width WC2 at the widened portion 92.

[0245] The body portion 90 has narrow groove portions 94. The narrow groove portions 94 of this tire 2 extend from the groove openings 34M of the circumferential narrow grooves HG in the depth direction of the circumferential narrow grooves HG. The narrow groove portions 94 include the groove openings 34M of the circumferential narrow grooves HG. The body portion 90 exhibits a minimum groove width WC1 at the narrow groove portions 94. The minimum groove width WC1 is set so that a pair of wall surfaces 34S of the circumferential narrow grooves HG come into contact with each other at the narrow groove portions 94 when the tread 4 comes into contact with the road surface and deforms.

[0246] The narrow groove portion 94 has a portion (hereinafter also referred to as a straight portion 96) that extends straight in the depth direction. The straight portion 96 is a portion of the narrow groove portion 94 that has a uniform groove width WC1 in the depth direction. The narrow groove portion 94 includes the straight portion 96 that has a uniform groove width WC1 in the depth direction. Although not shown, the narrow groove portion 94 may be configured so that the groove width gradually increases from the position showing the minimum groove width WC1 toward the groove opening 34M and the widened portion 92, for example.

[0247] The widened portion 92 is located radially inward of the body portion 90. The groove width of the widened portion 92 is wider than the groove width of the body portion 90. The position indicated by the symbol PX is the position where the widened portion 92 exhibits the maximum groove width WC2 (hereinafter referred to as the maximum groove width position). The widened portion 92 tapers outward from the maximum groove width position PX and tapers inward from the maximum groove width position PX.

[0248] 10, the position indicated by the solid line LPE is the boundary between the body portion 90 (specifically, the narrow groove portion 94) and the widened portion 92. This boundary LPE is represented by the position where the circumferential narrow groove HG exhibits a width Wb that is 1.1 times the minimum groove width WC1 of the narrow groove portion 94. When the portion exhibiting the width Wb that is 1.1 times the minimum groove width WC1 has a certain length, the radially outer end of that portion is the boundary LPE.

[0249] The widened portion 92 of this tire 2 has an inflection portion 98 and a bottom portion 100. The widened portion 92 has a maximum groove width WC2 at the bottom portion 100. The position indicated by reference symbol H4 in FIG. The inflection portion 98 connects the narrow groove portion 94 and the bottom portion 100. The groove width of the inflection portion 98 gradually increases from the boundary LPE with the narrow groove portion 94 toward the boundary H4 with the bottom portion 100. The inflection portion 98 curves so as to recess inward from its outer side. Specifically, in the cross section of the circumferential narrow groove HG, the outline of the inflection portion 98 is represented by an arc. In FIG. 10, arrow RC1 indicates the radius of the arc representing the outline of the inflection portion 98. The arc representing the outline of the inflection portion 98 is tangent to the straight line representing the outline of the straight portion 96 at the boundary H3 between the inflection portion 98 and the straight portion 96.

[0250] The bottom portion 100 is located radially inward of the inflection portion 98. The bottom portion 100 includes the groove bottom 34T of the circumferential narrow groove HG. The outline of the bottom portion 100 of the tire 2 is represented by a single arc having a radius Rw in the cross section of the circumferential narrow groove HG shown in FIG. 10. The center of the arc representing the outline of the bottom portion 100 is located on the center line LC of the circumferential narrow groove HG. The radius Rw of the arc representing the outline of the bottom portion 100 is equal to half the length of the maximum groove width WC2 of the widened portion 92. The arc representing the outline of the bottom portion 100 is tangent to the arc representing the outline of the inflection portion 98 at a boundary H4.

[0251] 10, the length indicated by the double-headed arrow D1 is the groove depth of the circumferential narrow groove HG. The length indicated by the double-headed arrow D2 is the groove depth of the body portion 90 of the circumferential narrow groove HG. The groove depth D2 is expressed as the distance in the depth direction from the groove opening 34M of the circumferential narrow groove HG to the boundary LPE. The length indicated by the double-headed arrow D3 is the groove depth from the groove opening 34M of the circumferential narrow groove HG to the position PX where the widened portion 92 shows the maximum groove width WC2.

[0252] The groove depth D1 of the circumferential narrow groove HG of this tire 2 is the same as the groove depth DGs of the shoulder circumferential groove 32, in other words, the circumferential main groove MG, or the circumferential narrow groove HG is shallower than the circumferential main groove MG. Specifically, the ratio D1 / DGs of the groove depth D1 of the circumferential narrow groove HG to the groove depth DGs of the circumferential main groove MG is 0.75 or more and 1.00 or less.

[0253] As described above, the center circumferential groove 34 of this tire 2 is a circumferential narrow groove HG. When the tread 4 comes into contact with the road surface and deforms, a pair of wall surfaces 34S of the circumferential narrow groove HG come into contact with each other at the narrow groove portion 94. The land portions 36 located on both sides of the circumferential narrow groove HG support each other, thereby suppressing deformation of the tread 4. Despite employing a flexible tread 4 (specifically, a flexible cap portion 46), the tire 2 can apparently increase the rigidity of the tread 4. Because the occurrence of abrasion is suppressed, this tire 2 can achieve improved wear resistance.

[0254] As the tread 4 wears, the circumferential narrow grooves HG gradually disappear. After the narrow groove portions 94 disappear, the widened portions 92 are exposed. In the circumferential narrow grooves HG, the maximum groove width WC2 of the widened portions 92 is wider than the minimum groove width WC1 of the narrow groove portions 94. After the middle stage of wear, when the narrow groove portions 94 disappear due to wear of the tread 4, the exposed widened portions 92 can contribute to suppressing deterioration of wet performance. This tire 2 can maintain good wear resistance while improving ride comfort, and can also suppress deterioration of wet performance due to wear. From this perspective, it is preferable that at least one circumferential groove 30 of the multiple circumferential grooves 30 provided in the tread 4 is a circumferential narrow groove HG. In this case, it is preferable that the circumferential narrow groove HG has a narrow groove portion 94 and a widened portion 92, the maximum groove width WC2 of the widened portion 92 is wider than the minimum groove width WC1 of the narrow groove portion 94, and when the tread 4 comes into contact with the road surface and deforms, the pair of wall surfaces 34S of the circumferential narrow groove HG come into contact with each other at the narrow groove portion 94.

[0255] As described above, in the tire 2, of the multiple circumferential grooves 30 in the tread 4, the two circumferential grooves 30 located at the outermost positions in the axial direction are shoulder circumferential grooves 32, and these shoulder circumferential grooves 32 are circumferential main grooves MG. The two center circumferential grooves 34 located between the two circumferential main grooves MG are circumferential narrow grooves HG. In the tire 2, from the viewpoint of effectively increasing the rigidity of the crown portion, when multiple circumferential grooves 30 are located between two circumferential main grooves MG, it is preferable that at least one of the multiple circumferential grooves 30 is a circumferential narrow groove. In other words, it is preferable that, of the multiple circumferential grooves 30 in the tread 4, the two circumferential grooves 30 located at the outermost positions in the axial direction are circumferential main grooves MG, and at least one of the multiple circumferential grooves 30 located between the two circumferential main grooves MG is a circumferential narrow groove HG. From the same viewpoint, it is more preferable that all of the multiple circumferential grooves 30 located between the two circumferential main grooves MG are circumferential narrow grooves HG.

[0256] As described above, the maximum groove width WC2 of the widened portion 92 is wider than the minimum groove width WC1 of the narrow groove portion 94. From the viewpoint of maintaining good wet performance, the maximum groove width WC2 of the widened portion 92 is preferably at least two times, and more preferably at least three times, the minimum groove width WC1 of the narrow groove portion 94. From the viewpoint of suppressing the effect on the rigidity of the crown portion of the tread 4 and enabling the tire 2 to maintain good uneven wear resistance, the maximum groove width WC2 of the widened portion 92 is preferably no more than eight times, and more preferably no more than seven times, the minimum groove width WC1 of the narrow groove portion 94.

[0257] The minimum groove width WC1 of the narrow groove portion 94 is preferably 2.5 mm or less. This allows the pair of wall surfaces 34S of the circumferential narrow groove HG to come into effective contact with each other in the narrow groove portion 94 when the tread 4 comes into contact with the road surface and deforms. This suppresses deformation of the tread 4, and improves the wear resistance of the tire 2. From this perspective, the minimum groove width WC1 is more preferably 2.0 mm or less. From the perspective of effectively draining water present between the tread 4 and a wet road surface through the circumferential narrow groove HG, the minimum groove width WC1 is preferably 1.0 mm or more.

[0258] In the tire 2, the radius RC1 of the arc that defines the contour of the inflection portion 98 is larger than the radius Rw of the arc that defines the contour of the bottom portion 100. This allows the circumferential narrow groove HG to fully exhibit its function. From this viewpoint, the ratio RC1 / Rw of the radius RC1 to the radius Rw is preferably 1.5 or greater and 20 or less. Setting the ratio RC1 / Rw to be 1.5 or greater can suppress the occurrence of uneven wear due to a sudden change in rigidity of the tire 2. From this viewpoint, the ratio RC1 / Rw is more preferably 2.0 or greater. Setting the ratio RC1 / Rw to be equal to or less than 20 makes it possible to suppress deterioration in wet performance of the tire 2. From this viewpoint, the ratio RC1 / Rw is more preferably equal to or less than 15.

[0259] The ratio D2 / D1 of the groove depth D2 of the body portion 90 to the groove depth D1 of the circumferential narrow grooves HG is preferably 0.25 or more and 0.70 or less. By setting the ratio D2 / D1 to 0.25 or greater, the groove depth D2 of the trunk portion 90 is appropriately maintained. When the tread 4 comes into contact with the road surface and deforms, the pair of wall surfaces 34S of the circumferential narrow groove HG can come into sufficient contact at the narrow groove portion 94. This tire 2 can have improved wear resistance. From this viewpoint, it is more preferable that the ratio D2 / D1 be 0.30 or greater. By setting the ratio D2 / D1 to 0.70 or less, the tire 2 can have the widened portion 92 with the required groove volume. The exposed widened portion 92 can effectively contribute to suppressing a decrease in wet performance. From this viewpoint, it is more preferable that the ratio D2 / D1 be 0.65 or less.

[0260] From the viewpoint that the widened portion 92 can effectively contribute to suppressing a deterioration in wet performance, it is preferable that the ratio D3 / D1 of the groove depth D3 from the groove mouth 34M of the circumferential narrow groove HG to the position PX where the widened portion 92 has the maximum groove width WC2 to the groove depth D1 of the circumferential narrow groove HG be 0.75 or more and 0.95 or less.

[0261] 11, the groove opening 34M of the circumferential narrow groove HG may be tapered. In this case, the body 90 of the circumferential narrow groove HG has a funnel portion 102 radially outward of the narrow groove portion 94. The funnel portion 102 can contribute to increasing the groove volume of the circumferential narrow groove HG and can effectively suppress the concentration of strain on the edges of the land portions 36 located on both sides of the circumferential narrow groove HG. From this viewpoint, it is preferable that the body portion 90 of the circumferential narrow groove HG is provided with the funnel portion 102 including the groove mouth 34M of the circumferential narrow groove HG radially outward from the narrow groove portion 94. In this case, the boundary LTP between the funnel portion 102 and the narrow groove portion 94 is represented by the position at the boundary portion between the funnel portion 102 and the narrow groove portion 94 where the circumferential narrow groove HG exhibits a width Wa that is 1.1 times the minimum groove width WC1 of the narrow groove portion 94. The groove width WA of the funnel portion 102 is preferably 0.15 to 0.45 times the groove width WGs of the circumferential main groove MG. The ratio D4 / D1 of the groove depth D4 of the funnel portion 102 to the groove depth D1 of the circumferential narrow groove HG is preferably 0.12 or more and 0.14 or less.

[0262] As is clear from the above description, the present invention provides a heavy-duty tire 2 that can achieve improved ride comfort while suppressing the impact on durability caused by incorporating an RFID tag. [Example]

[0263] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0264] Various chemicals used in the examples and comparative examples are explained. NR:TSR20 SBR1: HPR840 (S-SBR, Tg: -60°C, styrene content: 10% by mass, vinyl content: 42% by mole) manufactured by JSR Corporation SBR2: SLR3402 (S-SBR, Tg: -62°C, styrene content: 15% by mass, vinyl content: 30% by mole) manufactured by TRINSEO SBR3: Tufuden 2000R (T2000R) manufactured by Asahi Kasei Corporation (S-SBR, Tg: -66°C, styrene content: 25% by mass, vinyl content: 10% by mole) SBR4: HPR850 (S-SBR, Tg: -24°C, styrene content: 28% by mass, vinyl content: 59% by mole) manufactured by JSR Corporation BR: UBEPOL BR (registered trademark) 150B (cis content: 97 mol%) manufactured by Ube Industries, Ltd. Carbon black: Mitsubishi Chemical Corporation's Diablack N134 (N2SA:148m 2 / g) Silica: Ultrasil 9100GR (N2SA: 230 ml) manufactured by Evonik Degussa 2 / g, average primary particle diameter: 15nm) Silane coupling agent: NXT (3-octanoylthiopropyltriethoxysilane) manufactured by Momentive Resin component: Exxon Mobil's Oppera PR-383 (hydrogenated DCPD / C9 resin, containing dicyclopentadiene, styrene, and indene as monomer components, softening point: 103°C) Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant 1: Nocrac 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 2: Nocrac RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Camellia stearic acid beads manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: HK-200-5 (powdered sulfur containing 5% oil) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela NS (Nt-butyl-2-benzothiazole sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0265] [Examples and Comparative Examples] According to the formulation shown in Table 1, materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded mixture. Next, sulfur and vulcanization accelerator were added to the obtained kneaded mixture, and the mixture was kneaded for 5 minutes at 80°C using an open roll to obtain a rubber composition (uncrosslinked rubber composition). The obtained rubber composition was molded into a tread and then bonded together with other parts such as sidewalls to form an unvulcanized tire. The unvulcanized tire was press-vulcanized for 12 minutes at 150°C to produce a test tire (size: 315 / 70R22.5, truck and bus tire) having the basic configuration shown in Figure 1. The presence of an RFID tag in the "RFID tag" column of Table 1 below is indicated by a "Y." The fact that the test tire had a standard full band and that the band cord of the standard full band was made of steel is indicated by a "Y" in the "S-JLB" column of Table 1 below.

[0266] [Ride comfort] The test tires, with rims (8.25 x 22.5) and internal pressure (900 kPa), are mounted on all wheels of a 2-D test vehicle with a fixed load capacity of 10 tons. The ride comfort when traveling on the tire test course is evaluated by the driver's sensory evaluation using an index where Comparative Example 1 is set to 100. The results are shown in the "Ride Comfort" column in Table 1 below. The higher the value, the better the ride comfort.

[0267] [Table 1] [Industrial Applicability]

[0268] The technology described above, which can improve ride comfort while suppressing the impact on durability caused by incorporating an RFID tag, can be applied to various types of tires.

[0269] [Note] The present invention includes the following aspects.

[0270] [1] A tire comprising a pair of beads, a carcass spanning the pair of beads, a tread located outside the carcass and in contact with the road surface, a reinforcing layer located radially between the tread and the carcass, and a tag member including an RFID tag, wherein the carcass comprises a carcass ply, and the carcass ply comprises a ply body spanning the pair of beads and a pair of folded-up portions connected to the ply body and folded up at the beads, the tread is made of a rubber composition including a rubber component, and the rubber component includes styrene-butadiene rubber, the reinforcing layer comprises a belt including a number of parallel belt cords and a band including a spirally wound band cord, the belt comprises at least one belt ply, and the at least one belt ply a belt ply having the widest axial width among the at least one full band layer is a reference belt ply, belt cords of the reference belt ply are made of steel, the bands include at least one full band layer formed by spirally winding a band strip, the full band having the widest axial width among the at least one full band layer is the reference full band, band cords of the reference full band are made of steel, the RFID tag is located radially between an end of the turned-up portion and a maximum width position of the tire, and the styrene content CSt and vinyl content CVi of the styrene-butadiene rubber, the inclination angle Ab of the belt cords of the reference belt ply, and the inclination angle Aj of the band cords of the reference full band satisfy the following relational expressions (1) and (2): CSt+CVi≦80 (1) (Ab+Aj) / (CSt+CVi)≧0.20 (2) [2] The heavy-duty tire according to the above-mentioned [1], wherein the inclination angle Ab of the belt cord of the reference belt ply and the inclination angle Aj of the band cord of the reference full band satisfy the following relational expression (3): 15≦Ab+Aj≦30 (3) [3] When the tire is viewed from the side in the axial direction, one end portion and the other end portion of the band strip constituting the reference full band overlap, The heavy-duty tire according to the above-mentioned [1] or [2], wherein a central angle of a zone where the one end portion and the other end portion overlap is 150 degrees or less. [4] A heavy-duty tire according to any one of [1] to [3] above, wherein the circumferential position of the RFID tag does not coincide with the circumferential position of one end of the band strip and the circumferential position of the other end of the band strip. [5] A heavy-duty tire according to any one of [1] to [4] above, wherein each of the pair of beads comprises a core and an apex, the apex comprising an inner apex located radially outward of the core and an outer apex located radially outward of the inner apex, and the RFID tag is located radially between the outer end of the outer apex and the end of the folded-up portion. [6] A heavy-duty tire according to any one of the above [1] to [5], wherein the tread has a plurality of circumferential grooves, at least one of the plurality of circumferential grooves is a circumferential narrow groove, the circumferential narrow groove has a body portion including a groove mouth of the circumferential narrow groove and a widened portion including a groove bottom of the circumferential narrow groove, the body portion has a narrow groove portion, the widened portion has a maximum width greater than the minimum width of the narrow groove portion, and when the tread comes into contact with a road surface and deforms, a pair of wall surfaces of the circumferential narrow groove come into contact with each other at the narrow groove portion. [7] A heavy-duty tire according to any one of the above [1] to [6], wherein the styrene content CSt and vinyl content CVi of the styrene-butadiene rubber, and the code ends Ej of the standard full band satisfy the following relational expression (4): (CSt+CVi)×Ej≦2400 (4) [8] The heavy-duty tire according to any one of [1] to [7] above, wherein the styrene butadiene rubber has a styrene content CSt of 27% by mass or less. [9] The heavy-duty tire according to any one of the above [1] to [8], wherein the vinyl content CVi of the styrene-butadiene rubber is 50 mol% or less.

[10] The heavy-duty tire according to any one of the above [1] to [9], wherein the rubber composition further contains a filler, the filler contains silica and carbon black, and a content BSi of the silica per 100 parts by mass of the rubber component and a content BCB of the carbon black per 100 parts by mass of the rubber component satisfy the following relational expression (5): BSi≧BCB (5)

[11] The heavy-duty tire according to any one of [1] to

[10] above, wherein the rubber composition further contains a resin component.

[12] A heavy-duty tire according to any one of [1] to

[11] above, wherein the band strip is a cord arrangement in which a plurality of the band cords are arranged, and the number of the band cords included in the band strip is five or less. [Explanation of symbols]

[0271] 2. Tires 4. Tread 6. Sidewall 10 Bead 12. Carcass 14. Reinforcement layer 24 Tag member 26 Tread surface 30, HG, MG...Circumferential groove 36... Rikubu 44 Base 46 Cap part 48 cores 50···Apex 52 Inner apex 54 Outer apex 58···Carcass ply 60-ply body 62... Folded part 64... RFID tags 66 Protective body 72 Belt 74···Band 76, 76A, 76B, 76C, 76D, BP... Belt ply 78···Belt cord 82, BF... Full Band 84...Band cord 88···Band Strip 90... Torso 92 Widened section 94...Narrow groove part

Claims

1. A tire comprising: a pair of beads; a carcass spanning the pair of beads; a tread located on the outside of the carcass and in contact with a road surface; a reinforcing layer located between the tread and the carcass in a radial direction; and a tag member including an RFID tag, the carcass comprises a carcass ply; The carcass ply includes a ply body that spans between the pair of beads, and a pair of turn-up portions that are connected to the ply body and turned up at the beads, the tread is made of a rubber composition containing a rubber component, the rubber component contains styrene-butadiene rubber, The reinforcing layer includes a belt including a large number of parallel belt cords and a band including a spirally wound band cord, The belt includes at least one belt ply, Among the at least one belt ply, a belt ply having the widest axial width is a reference belt ply, The belt cord of the reference belt ply is made of steel, The band includes at least one full band layer formed by spirally winding a band strip, A full band having the widest axial width among the full bands of at least one layer is a reference full band, The material of the band cord of the standard full band is steel, the RFID tag is located between an end of the folded-up portion and a maximum width position of the tire in a radial direction, a styrene content CSt and a vinyl content CVi of the styrene-butadiene rubber, an inclination angle Ab of the belt cord of the reference belt ply, and an inclination angle Aj of the band cord of the reference full band satisfy the following relational expressions (1) and (2): Heavy duty tires. CSt+CVi≦80 (1) (Ab+Aj) / (CSt+CVi)≧0.20 (2)

2. an inclination angle Ab of the belt cord of the reference belt ply and an inclination angle Aj of the band cord of the reference full band satisfy the following relational expression (3), 2. The heavy duty tire according to claim 1. 15≦Ab+Aj≦30 (3)

3. When the tire is viewed from the side in the axial direction, one end portion and the other end portion of the band strip constituting the reference full band overlap, a central angle of a zone where the one end portion and the other end portion overlap is 150 degrees or less; 2. The heavy duty tire according to claim 1.

4. The circumferential position of the RFID tag does not match the circumferential position of one end of the band strip and the circumferential position of the other end of the band strip.

2. The heavy duty tire according to claim 1.

5. Each of the pair of beads includes a core and an apex, the apex includes an inner apex located radially outward of the core, and an outer apex located radially outward of the inner apex, the RFID tag is located between the outer end of the outer apex and the end of the folded-back portion in the radial direction; 2. The heavy duty tire according to claim 1.

6. the tread having a plurality of circumferential grooves; At least one of the plurality of circumferential grooves is a circumferential narrow groove, The circumferential narrow groove has a body portion including a groove mouth of the circumferential narrow groove and a widened portion including a groove bottom of the circumferential narrow groove, The body portion has a narrow groove portion, and the maximum width of the widened portion is wider than the minimum width of the narrow groove portion, When the tread comes into contact with a road surface and deforms, a pair of wall surfaces of the circumferential narrow groove come into contact with each other at the narrow groove portion.

2. The heavy duty tire according to claim 1.

7. The styrene content CSt and vinyl content CVi of the styrene-butadiene rubber, and the code ends Ej of the reference full band satisfy the following relational expression (4):

2. The heavy duty tire according to claim 1. (CSt+CVi)×Ej≦2400 (4)

8. The styrene butadiene rubber has a styrene content CSt of 27% by mass or less.

2. The heavy duty tire according to claim 1.

9. The vinyl content CVi of the styrene-butadiene rubber is 50 mol% or less.

2. The heavy duty tire according to claim 1.

10. The rubber composition further comprises a filler, the filler comprises silica and carbon black; a content BSi of the silica per 100 parts by mass of the rubber component and a content BCB of the carbon black per 100 parts by mass of the rubber component satisfy the following relational expression (5):

2. The heavy duty tire according to claim 1. BSi≧BCB (5)

11. The rubber composition further contains a resin component.

2. The heavy duty tire according to claim 1.

12. The band strip is a cord arrangement in which a plurality of the band cords are arranged, The number of the band cords included in the band strip is 5 or less. A heavy duty tire according to any one of claims 1 to 10.

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