Heavy-duty tires

Abstract

To provide a heavy-duty tire 2 that achieves improved wet performance and wear resistance while maintaining low rolling resistance. [Solution] The tire 2 comprises a tread 4 and a reinforcing layer 14. The rubber composition of the tread 4 includes a rubber component and a filler. The rubber component includes SBR and isoprene-based rubber. The filler includes carbon black and silica. The reinforcing layer 14 comprises a standard full band BF. The isoprene-based rubber content CNR, the carbon black content BCB, and the ratio of the axial width Wj of the standard full band BF to the axial width Wt of the tread 4 (Wj / Wt) satisfy the following relationship. (CNR+BCB)×(Wj / Wt)≧27.0

Description

Technical Field

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

Background Art

[0002] In tires, from the viewpoints of environmental consideration and safety, it is required to further improve low fuel consumption performance based on low rolling resistance and running performance on a wet road surface (hereinafter referred to as wet performance). In heavy-duty tires, not only improvement of these performances but also having good wear resistance performance is required.

[0003] In order to improve low fuel consumption performance, wet performance, and wear resistance performance, for example, in Patent Literature 1, it is proposed to set the ash content ratio of a tread composed of a rubber composition containing isoprene rubber and styrene-butadiene rubber as rubber components to a predetermined amount or more and form flask-shaped circumferential grooves in the tread.

Prior Art Documents

Patent Literature

[0004]

Patent Literature 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present invention is to provide a heavy-duty tire capable of achieving improvement in wet performance and wear resistance performance while maintaining low rolling resistance.

Means for Solving the Problems

[0006] The heavy-duty tire according to the present invention comprises a pair of beads, a carcass spanning between the pair of beads, a tread located radially outward of the carcass and in contact with the road surface, and a reinforcing layer located radially between the tread and the carcass. The tread is made of a rubber composition comprising a rubber component and a filler. The rubber component comprises styrene-butadiene rubber and isoprene-based rubber. The filler comprises carbon black and silica. The reinforcing layer comprises a belt comprising a number of parallel belt cords and a band comprising a helically wound band cord. The band comprises at least one full band formed by helically winding band strips. The full band having the widest axial width among the at least one full band is the reference full band. The material of the band cord of the reference full band is steel. The content of styrene-butadiene rubber (CSBR) in 100 parts by mass of the rubber component is 40 parts by mass or more. The content of isoprene-based rubber (CNR) in 100 parts by mass of the rubber component is 30 parts by mass or more. 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. The isoprene rubber content CNR, the carbon black content BCB, and the ratio (Wj / Wt) of the axial width Wj of the reference full band to the axial width Wt of the tread satisfy the following relationship. (CNR+BCB)×(Wj / Wt)≧27.0 [Effects of the Invention]

[0007] The present invention provides a heavy-duty tire that can achieve improved wet performance and wear resistance while maintaining low rolling resistance. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view showing a part of a heavy-duty tire according to one embodiment of the present invention. [Figure 2] This is a schematic diagram illustrating the structure of the reinforcement layer. [Figure 3]This is a perspective view showing a portion of the band strip. [Figure 4] This is a plan view showing the full band. [Figure 5] This is a side view showing the full band. [Figure 6] A portion of the cross-section shown in Figure 1 is visible. [Figure 7] This is a diagram showing a portion of the tread. [Figure 8] This is a cross-sectional view along the line VIII-VIII in Figure 7. [Figure 9] This is a cross-sectional view along the line IX-IX in Figure 7. [Figure 10] This is a cross-sectional view showing a modified example of a circumferential groove. [Figure 11] This is a cross-sectional view along the line XI-XI in Figure 7. [Figure 12] This is a diagram showing a modified example of a cross-sectional sipe. [Modes for carrying out the invention]

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

[0010] The tire of this invention is mounted on a rim. Air is filled inside the tire, and the internal pressure of the tire is regulated. A tire mounted on a rim is also called a tire-rim assembly. A tire-rim assembly comprises a rim and a tire mounted on this rim.

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

[0012] In this invention, unless otherwise specified, the dimensions and angles of each part of the tire are measured under normal conditions. The dimensions and angles of each part of the tire in the meridional cross-section, which cannot be measured when the tire is mounted on a standard rim, are measured at the tire's cross-section, obtained by cutting the tire along a plane containing the axis of rotation. In this measurement, the tire is set so that the distance between the left and right beads matches the distance between the beads in a tire mounted on a standard rim. The tire's structure, which cannot be confirmed when the tire is mounted on a standard rim, is confirmed at the aforementioned cross-section.

[0013] A genuine rim refers to a rim defined 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 considered genuine rims.

[0014] Regular tire pressure refers to the internal pressure specified in the tire's standard. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are all considered regular tire pressures.

[0015] The standard load refers to the load specified in the tire's specifications. The "maximum load capacity" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "LOAD CAPACITY" in the ETRTO standard are all considered standard loads.

[0016] In the present invention, crosslinked rubber is a crosslinked product of a rubber composition obtained by pressurizing and heating the rubber composition. The rubber composition is a material obtained by mixing rubber components with chemicals such as fillers in a kneading machine such as a Banbury mixer.

[0017] In this invention, "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 styrene content is "mass%".

[0018] In this 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 "styrene content" described above, 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 this invention, the number of cords contained per 50 mm width in a tire element containing parallel cords is expressed as cord ends (unit: ends / 50 mm). Unless otherwise specified, cord ends are obtained at the cross-section of the element obtained by cutting with a plane perpendicular to the length direction of the cord. For elements containing spirally wound cords, since multiple cords appear to be in parallel, the cord ends can be obtained in the same manner as for tire elements containing parallel cords.

[0020] In this invention, the tread portion of a tire is the part of the tire that comes into contact with the road surface. The bead portion is the part of the tire that is fitted onto the rim. The sidewall portion is the part of the tire that bridges the gap between the tread portion and the bead portion. The tire comprises the tread portion, a pair of bead portions, and a pair of sidewall portions. The tread portion includes the tread as a component of the tire. The sidewall portion includes the sidewall as a component of the tire. The bead portion includes the bead as a component of the tire. The central part of the tread is also called the crown. The edges of the tread are also called the shoulder.

[0021] [Practices that formed the basis of this invention] Increasing the proportion of styrene-butadiene rubber (SBR) in the rubber composition of the tread shifts the glass transition temperature (Tg) of the rubber component to a higher temperature, improving road surface tracking in the micro-deformation region. This allows the tire to improve wet performance. However, the SBR content affects the energy loss of the tread. There are concerns that increasing the SBR content will increase the energy loss of the tread and thus increase the rolling resistance of the tire. The rubber composition contains carbon black and silica as fillers. Adjusting the rubber composition to contain more silica than carbon black could potentially improve wet performance while maintaining low rolling resistance. However, there are concerns that increasing silica content would lead to a decrease in wear resistance. Therefore, the inventors diligently studied technologies that can improve wet performance and wear resistance while maintaining low rolling resistance, and have completed the present invention described below.

[0022] [Summary of Embodiments of the Invention] The present invention relates to a tire comprising a pair of beads, a carcass spanning the pair of beads, a tread located radially outward of the carcass and in contact with the road surface, and a reinforcing layer located radially between the tread and the carcass, wherein the tread is composed of a rubber composition comprising a rubber component and a filler, the rubber component comprising styrene-butadiene rubber and isoprene-based rubber, the filler comprising carbon black and silica, the reinforcing layer comprising a belt comprising a number of parallel belt cords and a band comprising a helically wound band cord, the band comprising at least one full band formed by helically winding band strips, and the widest axial direction of at least one full band A heavy-duty tire is provided in which a full band with a directional width is the reference full band, the material of the band cord of the reference full band is steel, the content of styrene-butadiene rubber (CSBR) in 100 parts by mass of the rubber component is 40 parts by mass or more, the content of isoprene-based rubber (CNR) in 100 parts by mass of the rubber component is 30 parts by mass or more, the content of carbon black (BCB) per 100 parts by mass of the rubber component is less than the content of silica (BSi) per 100 parts by mass of the rubber component, and the ratio of the isoprene-based rubber content (CNR), the carbon black content (BCB), and the axial width Wj of the reference full band to the axial width Wt of the tread (Wj / Wt) satisfies the following relationship. (CNR+BCB)×(Wj / Wt)≧27.0

[0023] The heavy-duty tire of the present invention can achieve improved wet performance and wear resistance while maintaining low rolling resistance. Although the mechanism by which the tire achieves these effects has not been fully elucidated, it is presumed to be as follows.

[0024] The rubber composition of the tread contains styrene-butadiene rubber (SBR). The SBR content (CSBR) is 40 parts by mass or more per 100 parts by mass of the rubber component. As the Tg of the rubber component increases, the road surface following ability in the micro-deformation region improves. This tire tread can contribute to improved wet performance. The rubber composition contains carbon black and silica as fillers. The carbon black content of BCB is lower than the silica content of BSi. BSi has a higher silica content, while BCB has a lower carbon black content. Silica can help suppress the increased energy loss caused by a high SBR content in the rubber component. This tire can improve wet performance while maintaining low rolling resistance.

[0025] A high silica content affects wear resistance. However, the tread rubber component includes isoprene-based rubber. The CNR (carbon density ratio) of isoprene-based rubber per 100 parts by mass of rubber component is 30 parts by mass or more. Isoprene-based rubber increases the strength of the tread. This suppresses wear caused by tread strength. The reinforcing layer includes a band, which includes a standard full band made of steel cords. The reinforcing layer can help suppress dimensional growth of the tire. Changes in the contact patch shape are suppressed. Wear caused by changes in the contact patch shape is also suppressed. In this tire, the isoprene rubber content (CNR), the carbon black content (BCB), and the ratio (Wj / Wt) are further set to satisfy the aforementioned relationship. This effectively enhances the tread strength and the restraining force provided by the reinforcing layer. Despite increasing the amount of silica, which negatively impacts wear resistance, this tire can achieve improved wear resistance. This tire achieves improved wet performance and wear resistance while maintaining low rolling resistance.

[0026] Preferably, the ratio of the axial width Wj of the reference full band to the axial width Wt of the tread (Wj / Wt) is 0.60 or greater. In this case, the band can contribute to suppressing the dimensional growth of the tire. This tire can further improve its wear resistance.

[0027] Preferably, the belt comprises at least one belt ply, the belt ply having the widest axial width among the at least one belt ply is the reference belt ply, the material of the belt cord of the reference belt ply is steel, and the ratio of the axial width Wb of the reference belt ply to the axial width Wt of the tread (Wb / Wt) is 0.70 or more. In this case, the belt can contribute to suppressing the dimensional growth of the tire. This tire can further improve its wear resistance.

[0028] Preferably, the ratio of the axial width Wj of the reference full band to the axial width Wb of the reference belt ply (Wj / Wb) is 0.60 or greater. In this case, the band can contribute to suppressing the dimensional growth of the tire. This tire can further improve its wear resistance.

[0029] Preferably, the reference full band and the reference belt ply are directly adjacent to each other in the radial direction. In this case, the reinforcing layer can contribute to suppressing dimensional growth of the tire. This tire can achieve improved wear resistance.

[0030] Preferably, the inclination angle Aj of the band cord of the reference full band and the inclination angle Ab of the belt cord of the reference belt ply satisfy the following relationship. Aj + Ab ≤ 25 In this case, the reinforcing layer can help suppress dimensional growth of the tire. This allows the tire to further improve its wear resistance.

[0031] Preferably, the code end Ej of the reference full band is 20 or greater. In this case, the band can contribute to suppressing the dimensional growth of the tire. This tire can further improve its wear resistance.

[0032] Preferably, the tread has a plurality of circumferential grooves arranged in the axial direction, at least one of the plurality of circumferential grooves is a circumferential narrow groove, the circumferential narrow groove comprises a body portion including the groove opening and a widened portion including the groove bottom, the body portion comprises the narrow groove portion, the maximum width of the widened portion is wider than the minimum width of the narrow groove portion, and when the tread contacts the road surface and deforms, a pair of wall surfaces of the circumferential narrow groove come into contact with each other in the narrow groove portion. In this case, in the initial stage of wear, the narrow groove portion of the circumferential narrow groove contributes to suppressing tread deformation. The circumferential narrow groove appears to increase the rigidity of the tread. The tire can further improve wear resistance while maintaining good wet performance. Furthermore, a widened portion is provided radially inward of the narrow groove portion of the circumferential narrow groove. After the narrow groove portion disappears, the widened portion is exposed. After the mid-stage of wear, when the narrow grooves disappear, the exposed widened section can help suppress the decline in wet performance. As wear occurs, the volume of the tread decreases. As the deformation allowance of the tread decreases, the rigidity of the tread appears to increase. Good wear resistance is maintained even after the mid-stage of wear.

[0033] Preferably, the tread comprises a plurality of land sections separated by circumferential grooves, at least one of the land sections having a transverse sipe that crosses the land section, and the transverse sipe extends in a zigzag pattern in the longitudinal or depth direction. In this case, the transverse sipe can function as an edge component that contributes to traction. The tire can further improve wet performance. When the tread deforms, the walls of the transverse sipes come into close contact with each other. The walls restrain each other, and the rigidity of the tread appears to increase. The tire can also further improve wear resistance.

[0034] Preferably, the filler contains silica with an average primary particle diameter of 16 nm or less. This is because such silica can contribute to improving wear resistance.

[0035] Preferably, the filler contains carbon black with an average primary particle diameter of 19 nm or less. This is because such carbon black can contribute to improved wear resistance.

[0036] Preferably, the rubber composition further comprises a silane coupling agent, and the silane coupling agent comprises a mercapto-silane coupling agent. This is because such a silane coupling agent can contribute to improving wear resistance.

[0037] Preferably, the styrene content (CSt) of the styrene-butadiene rubber is 25% by mass or less. In this case, the rigidity of the tread is adequately maintained. This tire can maintain good wear resistance.

[0038] Preferably, the rubber composition further includes a resin component. In this case, the resin component imparts flexibility to the tread. This improves road surface following ability in the micro-deformation region. The tread of this tire can contribute to improved wet performance.

[0039] Thus, according to the present invention, a heavy-duty tire can be obtained that achieves improved wet performance and wear resistance while maintaining low rolling resistance. This will be explained in detail below.

[0040] [Details of the Embodiments of the Invention] [Rubber composition] The tread is made of a rubber composition. The tread is a crosslinked rubber composition, i.e., crosslinked rubber. The rubber composition for this tread is described below. The rubber composition comprises a rubber component and a filler.

[0041] [Rubber components] The rubber component includes styrene-butadiene rubber and isoprene-based rubber. The rubber component may include styrene-butadiene rubber and isoprene-based rubber, and may also include other rubber components, or it may consist only of styrene-butadiene rubber and isoprene-based rubber.

[0042] [SBR] There are no particular limitations on the styrene-butadiene rubber (hereinafter referred to as SBR), and examples 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 in which the ends and / or main chain are modified, and modified SBRs coupled with tin, silicon compounds, etc. (condensates, those with branched structures, etc.). Among these, it is preferable that the SBR contained in the rubber component be S-SBR and modified SBR. Furthermore, hydrogenated SBRs (hydrogenated SBRs) can also be used as SBR in this rubber composition. One type of SBR may be selected from these and used alone, or two or more types may be selected and used in combination.

[0043] SBR exhibits excellent viscoelastic properties in the region highly correlated with wet performance (specifically, grip performance on wet surfaces), and has excellent compatibility and responsiveness with silica, as described later. SBR is expected to contribute to improvements in wet performance and wear resistance.

[0044] From the viewpoint of improving wet performance, the styrene content CSt of SBR is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 9% by mass or more. From the viewpoint of improving wear resistance, the styrene content CSt of SBR is preferably 25% by mass or less, more preferably 18% by mass or less, and even more preferably 16% by mass or less.

[0045] The vinyl content CVi of SBR is 26 mol% or more. If the vinyl content CVi is less than 26 mol%, it is difficult to improve the wet performance and wear resistance to the extent necessary for tire performance. The vinyl content CVi is preferably 27 mol% or more, more preferably 28 mol% or more, even more preferably 29 mol% or more, and even more preferably 30 mol% or more. From the viewpoint of contributing to improved wet performance and wear resistance, the vinyl content CVi of SBR is preferably 45 mol% or less, more preferably 44 mol% or less, even more preferably 43 mol% or less, and even more preferably 42 mol% or less.

[0046] 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 -65°C or higher. From the viewpoint of reducing rolling resistance, the Tg of SBR is preferably -40°C or lower, more preferably -45°C or lower, even more preferably -50°C or lower, and even more preferably -55°C or lower. The Tg of SBR is determined by performing differential scanning calorimetry (DSC) in accordance with JIS K7121 on "pure SBR content" obtained by removing the spreading oil using acetone in accordance with JIS K6229.

[0047] 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 wear resistance. From the viewpoint of crosslinking uniformity, the Mw of SBR is preferably 2,500,000 or less, more preferably 2,000,000 or less, and even more preferably 1,000,000 or less. The Mw of SBR can be determined by converting the measured value by gel permeation chromatography (GPC) (for example, the GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation) to standard polystyrene equivalent.

[0048] The CSBR content of SBR in 100 parts by mass of rubber component is 40 parts by mass or more. This improves wet performance. From this viewpoint, the CSBR content of SBR in 100 parts by mass of rubber component is preferably 45 parts by mass or more, more preferably 50 parts by mass or more. From the viewpoint of improving wet performance and abrasion resistance, the CSBR content of SBR is preferably 70 parts by mass or less, more preferably 65 parts by mass or less, and even more preferably 60 parts by mass or less.

[0049] [Isoprene rubber] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. For NR, examples include SIR20, RSS#3, TSR20, etc., which are commonly used in the tire industry. For IR, there are no particular limitations, but examples include IR2200, which are commonly used in the tire industry. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity 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 individually or in combination of two or more. Among these, NR is preferred.

[0050] The CNR (Canal No. 9) of isoprene-based rubber in 100 parts by mass of rubber component is 30 parts by mass or more. This increases the strength of the tread and improves wear resistance. From this viewpoint, the CNR of isoprene-based rubber in 100 parts by mass of rubber component is preferably 35 parts by mass or more, more preferably 40 parts by mass or more. From the viewpoint of maintaining good wet performance, this CNR is preferably 70 parts by mass or less, more preferably 65 parts by mass or less, and even more preferably 60 parts by mass or less.

[0051] As mentioned above, the rubber component may include other rubber components besides SBR and isoprene-based rubber. Other rubber components besides SBR and isoprene-based rubber can be crosslinkable rubber components commonly used in the tire industry. Examples of such rubber components include butadiene rubber (BR), 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, polyethylene chloride 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.

[0052] The rubber component of the rubber composition for the tread may include BR as a rubber component other than SBR and isoprene-based rubber.

[0053] [Butadiene rubber] Butadiene rubber (BR) is not particularly limited, and common types used in the tire industry can be used, 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 synthesized using a rare-earth element catalyst (rare-earth BR), BR containing syndiotactic polybutadiene crystals (SPB-containing BR), and modified BR (high-cis modified BR, low-cis modified BR). These may be used individually or in combination of two or more types. The cis content of BR is calculated by infrared absorption spectroscopy.

[0054] When the rubber component contains BR, from the viewpoint of maintaining good wet performance and abrasion resistance, the BR content CBR per 100 parts by mass of the rubber component is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less. The BR content CBR may be 0 parts by mass.

[0055] [Filler] As mentioned above, the rubber composition for the tread includes a filler, and the filler includes carbon black and silica. In other words, the rubber composition includes carbon black and silica as fillers. The filler may also consist only of carbon black and silica. In other words, the rubber composition may include a filler consisting only of carbon black and silica.

[0056] [Carbon Black] The carbon black used is not particularly limited; for example, common types used in the tire industry such as GPF, FEF, HAF, ISAF, and SAF can be used. Furthermore, from the perspective of reducing environmental impact and suppressing heat generation by reducing friction between the carbon black surface and rubber molecular chains, this tire can also use recycled carbon black (rCB) obtained from the thermal decomposition of used tires. These carbon blacks may be used individually or in combination of two or more types. In this invention, to distinguish it from recycled carbon black (rCB), the aforementioned carbon black commonly used in the tire industry, such as GPF, FEF, HAF, ISAF, and SAF, is also called standard carbon black (sCB).

[0057] 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, cited in "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly on pp. 438, 440, and 442, describes that it can be obtained by the 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 usually lacks functional groups on its surface, as mentioned in

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

[0058] Recycled carbon black may lack functional groups on its surface, or it may be treated to contain functional groups on its surface. Treatment to contain functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3173251, carbon black containing hydroxyl and / or carboxyl groups on its surface is obtained by treating carbon black obtained from a thermal decomposition process with potassium permanganate under acidic conditions. In addition, in Japanese Patent No. 6856781, carbon black with an activated surface is obtained by treating carbon black obtained from a thermal decomposition process with an amino acid compound containing at least one thiol group or disulfide group. Recycled carbon black according to this embodiment also includes carbon black treated to contain functional groups on its surface. Recycled carbon black can be purchased from companies such as Strebl Green Carbon and LDCarbon.

[0059] From the viewpoint of improving wear resistance and durability, the average primary particle diameter of carbon black is preferably 25 nm or less, more preferably 22 nm or less, and even more preferably 19 nm or less. This average primary particle diameter is preferably 6 nm or more, more preferably 9 nm or more, and even more preferably 12 nm or more.

[0060] The average primary particle size of carbon black can be determined by observing the carbon black using a transmission or scanning electron microscope, measuring the outer diameter of 400 or more primary particles of carbon black observed within the field of view, and averaging these measurements.

[0061] From the perspective of improving wear resistance and durability, the nitrogen adsorption specific surface area (N2SA) of carbon black is 10 m². 2 Preferably 20m / g or more. 2 More preferably 30m 2 A value of 1 / g or more is even more preferable. The nitrogen adsorption specific surface area (N2SA) is 250 m².2 Preferably less than / g, 200m 2 More preferably less than / g, 150m 2 A value of less than / g is even more preferable. The nitrogen adsorption specific surface area (N2SA) of carbon black is measured in accordance with JIS K6217-2:2017.

[0062] The carbon black content (BCB) per 100 parts by mass of 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 exhibiting a reinforcing effect and preventing degradation by ultraviolet rays. From the viewpoint of reducing rolling resistance, it 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 even more preferably 30 parts by mass or less.

[0063] The amount of recycled carbon black in 100 parts by mass of carbon black is not particularly limited, but can 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 exhibiting the reinforcing effect of carbon black, it is preferable to have less than 95 parts by mass, more preferably less than 90 parts by mass, and even more preferably less than 85 parts by mass.

[0064] [silica] The silica used is not particularly limited; for example, silica prepared by the dry process (anhydrous silica) or silica prepared by the wet process (hydrated silica), which are common in the tire industry, can be used. Furthermore, from the viewpoint of environmental impact, silica made from biomass materials (for example, amorphous silica refined from rice husks) may also be used. Among these, hydrated silica prepared by the wet process is preferred because it contains a large number of silanol groups. These silicas may be used individually or in combination of two or more types.

[0065] Silica derived from biomass materials can be obtained, for example, by extracting silicates from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then using these silicates to react with sulfuric acid in the same way as conventional wet silica, the precipitate of silicon dioxide is filtered, washed with water, dried, and pulverized. When silica crystallizes, it becomes insoluble in water and the silicic acid that is its component cannot be utilized. By controlling the combustion temperature and combustion time, crystallization of silica in rice husk ash is suppressed (see Japanese Patent Laid-Open No. 2009-2594, Akita Prefectural University Web Journal B / 2019, vol. 6, p. 216-222, etc.). The amorphous silica extracted from rice husks may be commercially available from companies such as Wilmar.

[0066] From the viewpoint of improving abrasion resistance and durability, the average primary particle diameter of silica is preferably 22 nm or less, more preferably 19 nm or less, and even more preferably 16 nm or less. This average primary particle diameter is preferably 6 nm or more, more preferably 9 nm or more, and even more preferably 12 nm or more.

[0067] 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 particles of silica observed in the field of view, and calculating the average.

[0068] From the viewpoint of improving abrasion resistance and durability, the nitrogen adsorption specific surface area (N2SA) of silica is preferably 100 m 2 / g or more, more preferably 110 m 2 / g or more, and even more preferably 120 m 2 / g or more. This nitrogen adsorption specific surface area is preferably 500 m 2 / g or less, more preferably 350 m 2 / g or less, and even more preferably 250 m 2 / g or less. The nitrogen adsorption specific surface area (N2SA) of silica is measured by the BET method in accordance with ASTM D3037-93.

[0069] The silica content BSi per 100 parts by mass of rubber component is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more, from the viewpoint of improving abrasion resistance and durability. From the viewpoint of obtaining flexibility and relieving 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.

[0070] As mentioned above, the carbon black content BCB per 100 parts by mass of rubber component is less than the silica content BSi per 100 parts by mass of rubber component. From the viewpoint of enabling the tire to maintain low rolling resistance while balancing wet performance and wear resistance, the ratio BCB / BSi of carbon black content BCB to silica content BSi is preferably 0.50 or more, more preferably 0.55 or more, and even more preferably 0.60 or more. The ratio BCB / BSi is preferably 0.95 or less, more preferably 0.90 or less, and more preferably 0.85 or less.

[0071] [Other fillers] Other fillers besides silica and carbon black can be added, including aluminum hydroxide, calcium carbonate, alumina, clay, talc, and other materials commonly used in the tire industry.

[0072] From the viewpoint of enabling the tire to maintain low rolling resistance while balancing wet performance and wear resistance, the carbon black content (CCB) in 100 parts by mass of filler is preferably 30 parts by mass or more, more preferably 35 parts by mass or more. The carbon black content (CCB) is preferably 50 parts by mass or less, more preferably 45 parts by mass or less.

[0073] From the viewpoint of improving wear resistance and durability, the total content of filler per 100 parts by mass of rubber component is preferably 40 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 allowing the tread to gain flexibility and relieve stress, it 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.

[0074] [Silane coupling agent] As mentioned above, the rubber composition contains silica as a filler. Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, but any silane coupling agent that has conventionally been used in combination with silica in the tire industry can be used. Examples of silane coupling agents include mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 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 vinyltriethoxy Examples include vinyl silane coupling agents such as silanes and vinyltrimethoxysilane; amino silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, sulfide silane coupling agents and / or mercapto silane coupling agents are preferred, and mercapto silane coupling agents are more preferred. These silane coupling agents may be used individually or in combination of two or more.

[0075] A mercapto-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. A mercapto-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 shown in the following chemical formula (3) and a bonding unit B shown in the following chemical formula (4). Among these, at least one compound represented by the following chemical formula (1) and a compound containing a bonding unit A shown in the following chemical formula (3) and a bonding unit B shown in the following chemical formula (4) are preferred, and the compound represented by the following chemical formula (1) is more preferred, in order to better exhibit the effects of the present invention.

[0076] [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) selected from ) 1006 , R 1007 , and R 1008 These may be the same or different, and each is a hydrogen atom or a monovalent hydrocarbon group having 1 to 18 carbon atoms, with h having an average value of 1 to 4. 1002 R 1001 , hydrogen atom, or monovalent hydrocarbon group having 1 to 18 carbon atoms, R 1003 is -[O(R 1009 O) j ]-group(R 1009 is an alkylene group with 1 to 18 carbon atoms, and j is an integer from 1 to 4. ), R 1004R is a divalent hydrocarbon group having 1 to 18 carbon atoms. 1005 (where represents a monovalent hydrocarbon group with 1 to 18 carbon atoms, and x, y, and z are numbers that satisfy the relationships x + y + 2z = 3, 0 ≤ x ≤ 3, 0 ≤ y ≤ 2, and 0 ≤ z ≤ 1.)

[0077] [ka] (In the formula, R 101 , R 102 , and R 103 Each of these is independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or -O-(R 111 -O) z -R 112 (z R 111 Each of these independently represents a divalent hydrocarbon group having 1 to 30 carbon atoms; R 112 R represents a group represented by ) an alkyl group with 1 to 30 carbon atoms, an alkenyl group with 2 to 30 carbon atoms, an aryl group with 6 to 30 carbon atoms, or an aralkyl group with 7 to 30 carbon atoms; z represents an integer from 1 to 30. 104 (This represents alkylenes with 1 to 6 carbon atoms.)

[0078] [ka] [ka] (In the formula, x represents an integer greater than or equal to 0; y represents an integer greater than or equal to 1; R 201 R represents a hydrogen atom, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, or an alkynyl group having 2 to 30 carbon atoms (the alkyl group, alkenyl group, and alkynyl group may be substituted with a halogen atom, hydroxyl group, or carboxyl group); R 202 R represents alkylene with 1 to 30 carbon atoms, alkenylene with 2 to 30 carbon atoms, or alkynylene with 2 to 30 carbon atoms; here, R 201 and R 202 (They may form a ring structure.)

[0079] The compound represented by chemical formula (1) is R1005 , R 1006 , R 1007 , and R 1008 Preferably, each of these groups is independently selected from the group consisting of linear, cyclic, or branched alkyl, alkenyl, aryl, and aralkyl groups having 1 to 18 carbon atoms. 1002 If is a monovalent hydrocarbon group having 1 to 18 carbon atoms, it is preferably a group selected from the group consisting of linear, cyclic, or branched alkyl groups, alkenyl groups, aryl groups, and aralkyl groups. 1009 The alkylene group is preferably linear, cyclic, or branched, and is particularly preferred to be linear. 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 linear or branched, and the cycloalkylene groups, cycloalkylalkylene groups, arylene groups, and aralkylene groups may have functional groups such as lower alkyl groups on their rings. 1004 Preferably, the alkylene group has 1 to 6 carbon atoms, and in particular, linear alkylene groups such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene, and hexamethylene groups are preferred.

[0080] R in chemical formula (1) 1002 , R 1005 , R 1006 , R 1007 , and R 1008Specific examples include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group, cyclopentyl group, cyclohexyl group, vinyl group, propenyl group, allyl group, hexenyl group, octenyl group, cyclopentenyl group, cyclohexenyl group, phenyl group, tolyl group, xylyl group, naphthyl group, benzyl group, phenethyl group, naphthylmethyl group, and the like.

[0081] R in chemical formula (1) 1009 Examples of linear alkylene groups include methylene, ethylene, n-propylene, n-butylene, and hexylene groups, while examples of branched alkylene groups include isopropylene, isobutylene, and 2-methylpropylene groups.

[0082] Specific examples of silane coupling agents 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. Among these, 3-octanoylthiopropyltriethoxysilane is preferred.

[0083] The silane coupling agent represented by chemical formula (1) has a thioester structure (i.e., a protected mercapto group) within its molecule, exhibits low reactivity with rubber components up to high temperatures, can suppress the strong bonding between the rubber components, the silane coupling agent, and silica during mixing, and can appropriately disperse silica, thus tending to exhibit the effects of the present invention more effectively.

[0084] Examples of compounds 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). The compound represented by the following chemical formula (5) can be preferably used. These may be used individually or in combination of two or more. [ka]

[0085] Compounds containing the bonding unit A shown in chemical formula (3) and the bonding unit B shown in chemical formula (4) include, for example, those manufactured and sold by Momentive, Inc. These may be used individually or in combination of two or more types.

[0086] The content of the silane coupling agent relative to 100 parts by mass of silica (total amount when multiple silane coupling agents are used in combination) 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.

[0087] [Other compounding agents] In addition to the components mentioned above, the rubber composition according to this embodiment may also appropriately contain compounding agents commonly used in the tire industry, such as softeners, waxes, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0088] Examples of softening agents include resin components, oils, and liquid rubber.

[0089] The resin components that can be used in this embodiment are not particularly limited, but resins commonly used in the tire industry can be used, such as adhesive resins such as C9 resins, C5 resins, C5C9 resins, dicyclopentadiene resins, aromatic vinyl resins, coumarone resins, indene resins, terpene resins, rosin resins, and phenolic resins. These resin components may be used individually or in combination of two or more.

[0090] C9 resins refer to resins obtained by polymerizing a C9 fraction. These resins may be obtained by polymerizing the C9 fraction alone, or by copolymerizing the C9 fraction with other components. For example, a resin copolymerized with dicyclopentadiene (DCPD) and a C9 fraction is called a DCPD / C9 resin. These resins may also be hydrogenated or modified. Examples of C9 fractions include petroleum fractions with 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. These C9 resins may be used individually or in combination of two or more.

[0091] C5 resins refer to resins obtained by polymerizing C5 fractions, and may be hydrogenated or modified versions of these fractions. Examples of C5 fractions other than dicyclopentadiene include petroleum fractions with 4 to 5 carbon atoms, such as cyclopentadiene, isoprene, pentane, isopentane, neopentane, pentene, and pentadiene. These C5 resins may be used individually or in combination of two or more types.

[0092] C5C9 resins refer to resins obtained by copolymerizing the C5 fraction and the C9 fraction, and may be hydrogenated or modified versions of these resins. As C5C9 petroleum resins, for example, those commercially available from Tosoh Corporation, LUHUA, etc., can be used. These C5C9 resins may be used individually or in combination of two or more types.

[0093] A dicyclopentadiene resin refers to a resin containing cyclopentadiene (CPD) or dicyclopentadiene (DCPD) as a monomer component, and may be hydrogenated or modified. Examples of dicyclopentadiene resins include DCPD / C9 resins containing dicyclopentadiene and the C9 fraction as monomer components (the DCPD / C9 resin may be hydrogenated or modified), and 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 resins that can be used are those commercially available from ExxonMobil, ENEOS Corporation, Nippon Zeon Corporation, Maruzen Petrochemical Co., Ltd., etc. These dicyclopentadiene resins may be used individually or in combination of two or more types.

[0094] Aromatic vinyl resins refer to resins containing aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and p-chlorostyrene as the most abundant monomer component, and may also be hydrogenated or modified versions of these compounds. For aromatic vinyl resins, α-methylstyrene or a homopolymer of styrene, or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, due to their economical nature, ease of processing, and excellent heat generation properties. Aromatic vinyl resins that can be used are commercially available from companies such as Kraton, Eastman Chemical Company, and Mitsui Chemicals, Inc. These aromatic vinyl resins may be used individually or in combination of two or more types.

[0095] Coumarone-based resins refer to resins containing coumarone as a monomer component, and may be hydrogenated or modified resins. Examples of coumarone-based 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-based resins may be used individually or in combination of two or more types.

[0096] Indene resins refer to resins containing indene as a monomer component, and may be hydrogenated or modified resins. 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 individually or in combination of two or more types.

[0097] Terpene resins are resins that contain terpene compounds such as α-pinene, β-pinene, limonene, and dipentene as the most abundant monomer component, and may be hydrogenated or modified versions of these compounds. Specific examples of terpene resins include, for example, polyterpene resins containing only one or more of the aforementioned terpene compounds as monomer components; aromatically modified terpene resins containing the aforementioned terpene compounds and aromatic compounds as monomer components; and terpene-phenol resins containing the aforementioned terpene compounds and phenolic compounds as monomer components. Examples of aromatic compounds that serve as monomer components in aromatically modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds that serve as monomer components in terpene-phenol resins include phenol, bisphenol A, cresol, and xylenol. These terpene resins may be used individually or in combination of two or more types.

[0098] Rosin resins refer to resins containing rosin acid compounds such as abietic acid, neoabietic acid, palastic acid, and isopimal acid, and may be hydrogenated or modified versions of these compounds. Rosin resins are not particularly limited, but examples include natural resin rosin and rosin-modified resins obtained by hydrogenation, disproportionation, dimerization, esterification, etc. These rosin resins may be used individually or in combination of two or more types.

[0099] Phenolic resins refer to resins that contain phenol compounds such as phenol and cresol as the most abundant monomer component. Phenolic resins are not particularly limited, but examples include phenol-formaldehyde resins, alkylphenol-formaldehyde resins, alkylphenol-acetylene resins, and oil-modified phenol-formaldehyde resins. These phenolic resins may be used individually or in combination of two or more types.

[0100] From the viewpoint 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. Furthermore, from the viewpoint of processability and improved dispersibility between the rubber component and filler, it 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 determined by measuring the softening point specified in JIS K 6220-1:2015 7.7 using a ring-type softening point measuring device, and it is the temperature at which the sphere descends.

[0101] 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 viewpoint of ride comfort and wet performance. From the viewpoint of suppressing heat generation, 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 even more preferably 30 parts by mass or less.

[0102] Examples of oils include process oils, vegetable oils, and animal oils. Examples of process oils include paraffinic process oils, naphthenic process oils, and aromatic process oils. Process oils with a low content of polycyclic aromatic compounds (PCA), which are environmentally friendly, can also be used. Examples of low-PCA process oils include light extraction solvates (MES), processed distillate aromatic extracts (TDAEs), and heavy naphthenic oils.

[0103] If the rubber composition contains oil, the oil content per 100 parts by mass of 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 wear resistance, the oil content 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 even more preferably 30 parts by mass or less.

[0104] Liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at room temperature (25°C), but examples 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 individually or in combination of two or more types.

[0105] When the rubber composition contains liquid rubber, the liquid rubber content per 100 parts by mass 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. The liquid rubber content is 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.

[0106] The wax is not particularly limited and can be any petroleum-based wax such as paraffin wax or microcrystalline wax; or synthetic wax such as polymers of ethylene or propylene. Commercially available products from companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd. can be used. These may be used individually or in combination of two or more types.

[0107] When the rubber composition contains wax, the amount of wax per 100 parts by mass of 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. From the viewpoint of preventing whitening of the tire due to bloom, the amount of wax is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0108] While not particularly limited, examples of anti-aging agents include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, as well as metal carbamate salts. Phenylenediamine-based anti-aging agents 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 anti-aging agents such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline are preferred. These anti-aging agents may be used alone or in combination of two or more.

[0109] When a rubber composition contains an anti-aging agent, the amount of the anti-aging agent per 100 parts by mass of 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 the rubber's resistance to ozone cracking. From the viewpoint of wear resistance and wet grip performance, the amount of the anti-aging agent is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0110] Conventional known stearic acid can be used, and commercially available products from companies such as NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries Ltd., and Chiba Fatty Acid Co., Ltd. can be used. These may be used individually or in combination of two or more types.

[0111] When the rubber composition contains stearic acid, the stearic acid content 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. From the viewpoint of vulcanization rate, the stearic acid content is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0112] Conventional known zinc oxides can be used, and commercially available products from companies such as Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., and Sakai Chemical Industry Co., Ltd. can be used. These may be used individually or in combination of two or more types.

[0113] When the rubber composition contains zinc oxide, the zinc oxide content 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. From the viewpoint of wear resistance, the zinc oxide content is preferably 10 parts by mass or less, and more preferably 5.0 parts by mass or less.

[0114] Sulfur is preferably used as a vulcanizing agent. Suitable sulfur varieties include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0115] When a rubber composition contains sulfur as a vulcanizing agent, the sulfur content per 100 parts by mass of 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 part 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 by the amount of pure sulfur contained in the oil-containing sulfur.

[0116] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensates, 1,6-hexamethylenedithiosulfate sodium dihydrate, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane. These non-sulfur vulcanizing agents can be purchased commercially from companies such as Taoka Chemical Industries, Ltd., Lanxess Corporation, and Flexis.

[0117] Examples of vulcanization accelerators include sulfenamide, thiazole, thiuram, thiourea, guanidine, dithiocarbamate, aldehyde-amine or aldehyde-ammonia, imidazoline, or xanthate 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, guanidine, and thiazole vulcanization accelerators are preferred, with sulfenamide vulcanization accelerators being more preferred, as they more favorably yield the desired effect.

[0118] Examples of sulfenamide-based vulcanization accelerators include N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS), N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS), and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide (DCBS). Among these, N-tert-butyl-2-benzothiazolyl sulfenamide (TBBS) and N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS) are preferred.

[0119] Examples of guanidine-based vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salts of dicatecholborate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, and 1,3-di-o-cumenyl-2-propionylguanidine. Among these, 1,3-diphenylguanidine (DPG) is preferred.

[0120] Examples of thiazole-based vulcanization accelerators include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, and di-2-benzothiazolyl disulfide. Among these, 2-mercaptobenzothiazole is preferred.

[0121] When a 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 even more preferably 5.0 parts by mass or less. By keeping the content of the vulcanization accelerator within these ranges, it tends to be possible to ensure fracture strength and elongation.

[0122] The rubber composition is manufactured, for example, by kneading the aforementioned components using a rubber mixing device such as an open roll or Banbury mixer. Regarding the mixing conditions, in the base mixing step where additives other than the vulcanizing agent and vulcanization accelerator are mixed, the mixing temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finish mixing step where the vulcanizing agent and vulcanization accelerator are mixed, the mixing temperature is usually 120°C or lower, preferably 85 to 110°C.

[0123] The manufactured rubber composition is processed into a predetermined shape using an extruder or the like. In a molding machine, it 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 into a vulcanizing machine 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.

[0124] The rubber composition described above is used in the tire tread (specifically, the cap portion that comes into contact with the road surface when driving). Next, a tire having a tread formed using this rubber composition will be described.

[0125] [tire] Figure 1 shows an example of a tire 2 according to one embodiment of the present invention. This tire 2 is mounted on a vehicle such as a truck or bus. This tire 2 is a heavy-duty tire. The tire 2 comprises a tread section T, a pair of sidewall sections S, and a pair of bead sections B. The tire 2 shown in Figure 1 is mounted on a rim R (regular rim).

[0126] Figure 1 shows a portion of the cross-section of tire 2 (hereinafter referred to as the meridian cross-section) along a plane containing the rotation axis of tire 2 (not shown). The direction indicated by the double-headed arrow AD is the axial direction of tire 2. The axial direction of tire 2 means the direction parallel to the rotation axis of tire 2. The direction indicated by the double-headed arrow RD is the radial direction of tire 2. The direction perpendicular to the plane of paper in Figure 1 is the circumferential direction of tire 2. The dashed line EL extending radially represents the equatorial plane of tire 2.

[0127] In the axial direction, the direction away from the equatorial plane is the axial outward direction of tire 2, and the direction towards the equatorial plane is the axial inward direction of tire 2. The direction indicated by arrow RD1 is the radial outward direction of tire 2, and the direction indicated by arrow RD2 is the radial inward direction of tire 2.

[0128] The tire 2 comprises 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 cushioning layers 16, a pair of filler reinforcing layers 18, and an inner liner 20. Although the left side of the meridian cross-section relative to the equatorial plane is not shown in Figure 1, the internal structure of the tire 2 has a symmetrical structure with respect to the equatorial plane.

[0129] The tread 4 is located radially outward of the carcass 12. The tread 4 extends circumferentially. The tread 4 has a tread surface 22. The tread 4 contacts the road surface at the tread surface 22. Grooves 24 are cut into the tread 4.

[0130] The position indicated by the symbol Eq is the equator of tire 2. Equator Eq is the intersection of the tread surface 22 and the equatorial surface. In the case of tire 2, where there is a groove 24 on the equatorial surface, the equator is determined based on a virtual tread surface obtained by assuming that there is no groove 24.

[0131] The position indicated by the symbol TE is the edge of the tread surface 22. In the case of a tire where the edge of the tread surface is not identifiable by appearance, the position on the outer surface of the tire corresponding to the axial outer edge (i.e., the contact edge) of the contact surface obtained by applying a normal load to a tire in a normal state, setting the camber angle to 0°, and bringing the tire into contact with a plane is used as the edge of the tread surface.

[0132] In Figure 1, the length indicated by the arrow WT is the width of the tread surface 22. The width WT of the tread surface 22 is expressed as the axial distance from one end TE to the other end TE of the tread surface 22. The width WT of the tread surface 22 is measured along the tread surface 22. In this invention, the width WT of the tread surface 22 is used as the axial width Wt of the tread 4.

[0133] The tread 4 comprises a base portion 26 and a cap portion 28. The base portion 26 is made of cross-linked rubber. Although not described in detail, the base portion 26 of this tire 2 is made of cross-linked rubber, which is common as the cross-linked rubber that constitutes the base portion of heavy-duty tires. The base portion 26 covers the reinforcing layer 14. The cap portion 28 is located radially outward from the base portion 26. The cap portion 28 covers the base portion 26. The cap portion 28 has a tread surface 22. The cap portion 28 is made of cross-linked rubber. The cap portion 28 of this tire 2 is formed using the aforementioned rubber composition. In other words, the cross-linked rubber constituting the cap portion 28 is a cross-linked product of the aforementioned rubber composition.

[0134] Each sidewall 6 is connected to the tread 4. The sidewall 6 is located radially inward of the tread 4. The sidewall 6 is located axially outward of the carcass 12. The sidewall 6 is made of cross-linked rubber with cut resistance in mind.

[0135] The position indicated by the symbol PW is the axial outer end of tire 2 (hereinafter referred to as outer end PW). If there are decorations such as patterns or letters on the outer surface of tire 2, outer end PW is determined based on a hypothetical outer surface obtained assuming there are no decorations. Tire 2 exhibits its maximum width at outer end PW. Outer end PW is also called the maximum width position. The axial distance from one maximum width position PW to the other maximum width position PW obtained in a normal state tire 2 is the cross-sectional width of this tire 2 (see JATMA, etc.).

[0136] Each chafer 8 is located radially inward of the sidewall 6. The chafer 8 is in contact with the rim R. The chafer 8 is made of cross-linked rubber with wear resistance in mind.

[0137] Each bead 10 is located axially inward of the chafer 8. The bead 10 is located radially inward of the sidewall 6.

[0138] The bead 10 comprises a core 30 and an apex 32. The core 30 extends circumferentially. Although not shown, the core 30 contains wound steel wire. The core 30 has a substantially hexagonal cross-sectional shape. The apex 32 is located radially outward from the core 30. The apex 32 extends radially outward from the core 30. The apex 32 tapers outward. The radially outward end AG of the apex 32 is located radially inward from the maximum width position PW. Although not described in detail, the apex 32 comprises an inner apex and an outer apex. The inner apex is located radially outward from the core 30 and is made of rigid cross-linked rubber. The outer apex is located radially outward from the inner apex and is made of softer cross-linked rubber than the cross-linked rubber of the inner apex.

[0139] The carcass 12 is located inside the tread 4, a pair of sidewalls 6, and a pair of chafers 8. The carcass 12 spans between a pair of beads 10. The carcass 12 of this tire 2 has a radial structure.

[0140] The carcass 12 comprises at least one carcass ply 34. The carcass 12 of this tire 2 is composed of one carcass ply 34. The carcass ply 34 is folded over at each bead 10. The carcass ply 34 of this tire 2 is folded over at each bead 10 from the axially inward to the axially outward direction.

[0141] The carcass ply 34 comprises a ply body 36 and a pair of folded portions 38. The ply body 36 spans between a pair of beads 10. Each folded portion 38 is connected to the ply body 36 and is folded over at the bead 10.

[0142] Although not shown in the diagram, the carcass ply 34 contains numerous parallel carcass cords. These carcass cords are covered with topping rubber. Each carcass cord intersects the equatorial plane. The angle that the carcass cords make with respect to the equatorial plane is between 70° and 90°. The material of the carcass cords in this tire 2 is steel. The carcass cords are steel cords.

[0143] Each cushion layer 16 is located between the reinforcing layer 14 and the carcass 12 at the edge of the reinforcing layer 14. The cushion layer 16 is made of soft cross-linked rubber.

[0144] Each filler reinforcement layer 18 is located between the carcass 12 and the chafer 8 in the bead portion B. The filler reinforcement layer 18 is folded over at the bead 10. The filler reinforcement layer 18 is positioned to wrap around the radially inner portion of the bead 10 from the radially inner side of the carcass 12.

[0145] Although not shown in the illustration, the filler reinforcement layer 18 contains numerous parallel filler cords. These filler cords are covered with topping rubber. The material of the filler cords in this tire 2 is steel.

[0146] The inner liner 20 is located inside the carcass 12. The inner liner 20 is bonded to the inner surface of the carcass 12 via an insulation (not shown) made of cross-linked rubber. The inner liner 20 constitutes the inner surface of the tire 2. The inner liner 20 is made of cross-linked rubber with excellent air-shielding properties.

[0147] The reinforcing layer 14 is located radially between the tread 4 and the carcass 12. The reinforcing layer 14 is directly laminated to the carcass 12 on the radially inner side of the tread 4. Alternatively, the reinforcing layer 14 may be indirectly laminated to the carcass 12 via a rubber layer made of cross-linked rubber. The reinforcing layer 14 of this tire 2 comprises a belt 40 and a band 42.

[0148] Figure 2 shows the structure of the reinforcing layer 14. The direction indicated by the double arrows CD is the circumferential direction of the tire 2. The direction perpendicular to the plane of the paper in Figure 2 is the radial direction of the tire 2. The front side of the paper is the radially outward direction, and the back side is the radially inward direction.

[0149] The belt 40 of this tire 2 is provided with four belt plies 44. The four belt plies 44 are arranged radially, and from the radially inner side, they are the first belt ply 44A, the second belt ply 44B, the third belt ply 44C, and the fourth belt ply 44D. The first belt ply 44A is the belt ply 44 located radially inward. The fourth belt ply 44D is the belt ply 44 located radially outward.

[0150] The belt 40 only needs to have at least one belt ply 44. The number of layers of belt ply 44 constituting the belt 40 may be one, two, or three. The number of layers of belt ply 44 constituting the belt 40 may be five or more.

[0151] In Figure 1, the length indicated by the double arrow W1 is the axial width of the first belt ply 44A. The length indicated by the double arrow W2 is the axial width of the second belt ply 44B. The length indicated by the double arrow W3 is the axial width of the third belt ply 44C. The length indicated by the double arrow W4 is the axial width of the fourth belt ply 44D. The axial width of each belt ply 44 is expressed as the axial distance from one end of the belt ply 44 to the other end.

[0152] In this tire 2, the second belt ply 44B has the widest axial width W2. The axial width W2 of the second belt ply 44B is the axial width of the belt 40, and the end of the second belt ply 44B is the end of the belt 40. The end of the belt 40 in this tire 2 is also the end of the reinforcing layer 14 as described above. The fourth belt ply 44D has the narrowest axial width W4. The axial width W1 of the first belt ply 44A and the axial width W3 of the third belt ply 44C are the same, or the axial width W1 of the first belt ply 44A is slightly wider than the axial width W3 of the third belt ply 44C.

[0153] In this invention, the reference belt ply is the belt ply having the widest axial width among the at least one belt ply constituting the belt. As mentioned above, of the four belt plies 44 that make up the belt 40 of this tire 2, the belt ply 44 with the widest axial width is the second belt ply 44B. In this tire 2, the second belt ply 44B is the reference belt ply BP. The axial width W2 of the second belt ply 44B is the axial width Wb of the reference belt ply BP.

[0154] As shown in Figure 1, the ends of all four belt plies 44 are located axially outward of the shoulder circumferential groove, as will be described later. The end of the fourth belt ply 44D, which is located radially outward, may be positioned axially inward of the shoulder circumferential groove.

[0155] From the viewpoint of ensuring the rigidity of the tread portion T, the ratio of the axial width W1 of the first belt ply 44A to the axial width Wt of the tread 4 (W1 / Wt) is preferably 0.80 or more and 0.90 or less. The ratio of the axial width W2 of the second belt ply 44B to the axial width Wt of the tread 4 (W2 / Wt) is preferably 0.85 or more and 0.95 or less. The ratio of the axial width W3 of the third belt ply 44C to the axial width Wt of the tread 4 (W3 / Wt) is preferably 0.80 or more and 0.90 or less. The axial width W4 of the fourth belt ply 44D is set appropriately according to the specifications of the tire 2.

[0156] As shown in Figure 2, each belt ply 44 constituting the belt 40 contains a number of parallel belt cords 46. In Figure 2, for ease of explanation, the belt cords 46 are represented by solid lines, but the belt cords 46 are covered with belt topping rubber 48. The cord ends of the belt 40 are between 10 ends / 50 mm and 35 ends / 50 mm.

[0157] The material of the belt cord 46 is steel. In other words, the belt cord 46 of this tire 2 is a steel cord. As mentioned above, the second belt ply 44B of this tire 2 is the standard belt ply BP. The material of the belt cord 46 of the standard belt ply BP is steel.

[0158] As mentioned above, the belt 40 comprises at least one belt ply 44. If the belt 40 comprises two or more belt plies 44, the belt cords 46 of the belt plies 44 other than the reference belt ply BP may be made of organic fibers (hereinafter referred to as organic fiber cords). In this case, examples of 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 46 of all belt plies 44 constituting the belt 40 are steel cords, as in this tire 2.

[0159] The belt cords 46 of each belt ply 44 are inclined with respect to the circumferential direction. The direction of inclination of the belt cords 46 included in the first belt ply 44A (hereinafter, the inclination direction of the first belt cord 46A) is the same as the direction of inclination of the belt cords 46 included in the second belt ply 44B (hereinafter, the inclination direction of the second belt cord 46B). The inclination direction of the second belt cord 46B is opposite to the direction of inclination of the belt cords 46 included in the third belt ply 44C (hereinafter, the inclination direction of the third belt cord 46C). The inclination direction of the third belt cord 46C is the same as the direction of inclination of the belt cords 46 included in the fourth belt ply 44D (hereinafter, the inclination direction of the fourth belt cord 46D). The inclination direction of the first belt cord 46A may be opposite to the inclination direction of the second belt cord 46B. The inclination direction of the third belt cord 46C may be opposite to the inclination direction of the fourth belt cord 46D.

[0160] In Figure 2, angle θ1 is the angle that the first belt cord 46A makes with respect to the circumferential direction (hereinafter referred to as inclination angle θ1). Angle θ2 is the angle that the second belt cord 46B makes with respect to the circumferential direction (hereinafter referred to as inclination angle θ2). Angle θ3 is the angle that the third belt cord 46C makes with respect to the circumferential direction (hereinafter referred to as inclination angle θ3). Angle θ4 is the angle that the fourth belt cord 46D makes with respect to the circumferential direction (hereinafter referred to as inclination angle θ4). In this invention, unless otherwise specified, the inclination angle of each belt cord 46 is expressed as the angle that the belt cord 46 makes with respect to the equatorial plane. As mentioned above, the second belt ply 44B is the reference belt ply BP. The inclination angle θ2 of the second belt cord 46B is the same as the inclination angle Ab of the belt cord 46 of the reference belt ply BP.

[0161] The inclination angles θ1 of the first belt cord 46A, θ2 of the second belt cord 46B, θ3 of the third belt cord 46C, and θ4 of the fourth belt cord 46D are preferably 10 degrees or more and 60 degrees or less. From the viewpoint of effectively restraining the movement of the tread portion T and obtaining a stable contact surface with small shape changes, the inclination angle θ1 of the first belt cord 46A is more preferably 40 degrees or more and 60 degrees or less. The inclination angle θ2 of the second belt cord 46B is more preferably 15 degrees or more and 30 degrees or less, and even more preferably 15 degrees or more and 20 degrees or less. The inclination angle θ3 of the third belt cord 46C is more preferably 15 degrees or more and 30 degrees or less, and even more preferably 15 degrees or more and 20 degrees or less. The inclination angle θ4 of the fourth belt cord 46D is more preferably 15 degrees or more and 50 degrees or less.

[0162] From the viewpoint of effectively restricting the movement of the tread portion T and obtaining a stable contact surface with minimal shape change, it is preferable that the inclination direction of the third belt cord 46C is opposite to that of the second belt cord 46B, but the inclination angle θ3 of the third belt cord 46C is approximately the same as the inclination angle θ2 of the second belt cord 46B. The inclination angle θ3 of the third belt cord 46C being approximately the same as the inclination angle θ2 of the second belt cord 46B means that the absolute value of the difference between the inclination angle θ3 and the inclination angle θ2 is within 3 degrees.

[0163] Band 42 comprises at least one full band 50. The band 42 of this tire 2 is composed of one full band 50. The number of layers of the full band 50 constituting band 42 may be two, three or more. This band 42 may further comprise a pair of edge bands that are spaced apart in the axial direction with respect to the equatorial plane.

[0164] In Figure 1, the length indicated by the double arrow WF is the axial width of the full band 50. The axial width WF of the full band 50 is represented by the axial distance from one end of the full band 50 to the other end. As mentioned above, the band 42 of this tire 2 is composed of a single layer of full band 50. The axial width WF of the full band 50 is also the axial width of the band 42 of this tire 2. As shown in Figure 1, the full band 50 of this tire 2 is wider than the fourth belt ply 44D but narrower than the first belt ply 44A, the second belt ply 44B, and the third belt ply 44C. The band 42 of this tire 2 is narrower than the belt 40. The end of the band 42 is located axially inward of the end of the belt 40.

[0165] As shown in Figure 2, the full band 50 constituting band 42 includes the band code 52. In Figure 2, for ease of explanation, the band code 52 is represented by a solid line, but the band code 52 is covered with band topping rubber 54. The code ends of band 42 are between 15 ends / 50 mm and 40 ends / 50 mm.

[0166] Although not described in detail, this tire 2 is manufactured by a known method. A band strip 56, shown in Figure 3, is used to form the band 42. The band strip 56 is strip-shaped. The band strip 56 contains one or more band cords 52. The band strip 56 shown in Figure 3 contains five band cords 52. These band cords 52 are aligned in the width direction of the band strip 56 and extend in the length direction of the band strip 56. The band strip 56 is a cord array, consisting of one or more band cords 52 arranged in a sequence. The number of band codes 52 included in the band strip 56 is preferably 5 or less, more preferably 3 or less. The number of band codes 52 is preferably 2 or more.

[0167] As will be described later, the band 42 is formed by spirally winding the band strip 56. The band 42 includes a spirally wound band cord 52. The band cord 52 is slightly inclined with respect to the circumferential direction. In Figure 2, angle θd is the angle that the band cord 52 makes with respect to the circumferential direction (hereinafter referred to as the inclination angle θd). The inclination angle θd of the band cord 52 is preferably 5 degrees or less. The band cord 52 extends substantially in the circumferential direction. The band 42 has a jointless structure. In this invention, unless otherwise specified, the inclination angle θd of the band code 52 is expressed as the angle that the band code 52 makes with respect to the equatorial plane.

[0168] Figure 4 shows the full band 50 that constitutes band 42. The full band 50 is formed by spirally winding a band strip 56 from one end in its axial direction (hereinafter referred to as the first end FE1) to the other end (hereinafter referred to as the second end FE2). When the longitudinal tip BS1 of the band strip 56 is set to a position corresponding to the first end FE1 of the full band 50, the formation of the full band 50 begins. When the longitudinal rear end BS2 of the band strip 56 reaches a position corresponding to the second end FE2 of the full band 50, the formation of the full band 50 is completed. The full band 50 is a crosslinked product of a band molded body formed by spirally winding a band strip 56. The full band 50 includes the tip BS1 and the rear end BS2 of the band strip 56.

[0169] As shown in Figure 4, the band strip 56 is wound such that the leading end portion BS1 and the trailing end portion BS2 overlap in the axial direction. The circumferential position of the leading end BS1 and the circumferential position of the trailing end BS2 do not coincide. The band strip 56 may be wound such that the circumferential position of the leading end BS1 and the circumferential position of the trailing end BS2 coincide.

[0170] In Figure 4, in the zone indicated by the symbol LZ, from the leading edge BS1 to the trailing edge BS2 of the band strip 56, the leading edge BS1 portion and the trailing edge BS2 portion of the band strip 56 overlap. This overlapping zone LZ of the band strip 56 is called the overlapping zone of the band strip 56. The full band 50 of this tire 2 includes the overlapping zone LZ of the band strip 56.

[0171] Figure 5 shows the full band 50 shown in Figure 4, viewed from the side of the second end FE2. The direction perpendicular to the plane of the paper in Figure 5 is the axial direction of the tire 2. The position indicated by the symbol RA is the rotation axis of the tire 2. In Figure 5, the outline of the tire 2 is shown by a dashed line.

[0172] In the full band 50, the size of the overlap zone LZ of the band strip 56 is represented by the angle between the line segment connecting the tip BS1 of the band strip 56 and the axis of rotation RA and the line segment connecting the rear end BS2 of the band strip 56 and the axis of rotation RA, i.e., the central angle. The angle θp in Figure 5 is the central angle of the overlap zone LZ of the band strip 56. When the circumferential position of the tip BS1 of the band strip 56 and the circumferential position of the rear end BS2 coincide, the central angle θp is 0 degrees. In the present invention, the axial width WF of the full band 50, as described above, is represented by the axial width of the full band 50 in zones other than the overlap zone LZ.

[0173] As mentioned above, the band 42 of this tire 2 comprises at least one full band 50. The full band 50 is a component of the tire 2 formed by spirally winding a band strip 56. This band 42 comprises at least one full band 50 formed by spirally winding a band strip 56.

[0174] In this invention, the reference full band is the full band having the widest axial width among at least one full band that constitutes the band. As mentioned above, the band 42 of this tire 2 is composed of a single full band 50. This full band 50 is the reference full band BF, which has the widest axial width among the at least single full bands 50 that make up the band 42. The inclination angle θd of the band code 52 of the full band 50 is the inclination angle Aj of the band code 52 of the reference full band BF. The axial width WF of the full band 50 is the axial width Wj of the reference full band BF of this tire 2.

[0175] The material of the band code 52 for the full band 50 of this tire 2 is steel. The material of the band code 52 for the standard full band BF is steel.

[0176] As mentioned above, the band 42 comprises at least one full band 50. If the band 42 comprises two or more full bands 50, the band cords 52 of the full bands 50 other than the reference full band BF may be organic fiber cords. In this case, examples of 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 band cords 52 of all full bands 50 constituting the band 42 are steel cords.

[0177] As mentioned above, the rubber component of the rubber composition constituting the tread 4 (specifically, the cap portion 28) contains styrene-butadiene rubber (SBR), and the SBR content (CSBR) in 100 parts by mass of the rubber component is 40 parts by mass or more. As the Tg of the rubber component increases, the road surface following ability in the micro-deformation region improves. The tread 4 of this tire 2 can contribute to improved wet performance.

[0178] As mentioned above, the rubber composition for tread 4 contains carbon black and silica as fillers, with BCB having a lower carbon black content than BSi having a lower silica content. BSi has a higher silica content, while BCB has a lower carbon black content. Silica can help suppress the increased energy loss caused by a high SBR content in the rubber component. This tire 2 can improve wet performance while maintaining low rolling resistance.

[0179] A high silica content affects wear resistance. However, as mentioned above, the rubber component of tread 4 contains isoprene-based rubber, and the CNR of isoprene-based rubber content per 100 parts by mass of rubber component is 30 parts by mass or more. Isoprene-based rubber increases the strength of tread 4. This suppresses wear caused by the strength of tread 4.

[0180] As described above, the reinforcing layer 14 is equipped with a band 42, and the band 42 includes a standard full band BF with steel cords as band cords 52. The reinforcing layer 14 can contribute to suppressing the dimensional growth of the tire 2. Changes in the contact patch shape are suppressed. The occurrence of wear caused by changes in the contact patch shape is also suppressed.

[0181] In this tire 2, the isoprene rubber content CNR, the carbon black content BCB, and the ratio (Wj / Wt) are further set to satisfy the following relationship, as described above. (CNR+BCB)×(Wj / Wt)≧27.0 This effectively enhances the strength of the tread 4 and the restraining force provided by the reinforcing layer 14. Despite increasing the amount of silica, which negatively impacts wear resistance, this tire 2 can achieve improved wear resistance.

[0182] This tire 2 achieves improved wet performance and wear resistance while maintaining low rolling resistance.

[0183] From the viewpoint of improving wet performance and wear resistance, it is preferable that the CNR content, BCB content, and ratio (Wj / Wt) satisfy the following relationship. (CNR+BCB)×(Wj / Wt)≧30.0 From a similar viewpoint, the product of the sum of the isoprene rubber content CNR and the carbon black content BCB (CNR+BCB) and the ratio (Wj / Wt), (CNR+BCB)×(Wj / Wt), is more preferably 35.0 or more, even more preferably 40.0 or more, even more preferably 45.0 or more, even more preferably 50.0 or more, even more preferably 55.0 or more, and even more preferably 60.0 or more.

[0184] From the viewpoint of maintaining low rolling resistance and good wet performance, it is preferable that the CNR content, BCB content, and ratio (Wj / Wt) satisfy the following relationship. (CNR+BCB)×(Wj / Wt)≦120.0 From a similar viewpoint, the product (CNR+BCB)×(Wj / Wt) is more preferably 110.0 or less, even more preferably 100.0 or less, even more preferably 90.0 or less, even more preferably 80.0 or less, and even more preferably 70.0 or less.

[0185] The ratio (Wj / Wt) of the axial width Wj of the reference full band BF to the axial width Wt of the tread 4 is preferably 0.60 or higher. This allows the band 42 to contribute to suppressing the dimensional growth of the tire 2. This allows the tire 2 to have improved wear resistance. From this viewpoint, a ratio (Wj / Wt) of 0.70 or higher is more preferable. From the viewpoint of suppressing damage caused by the concentration of strain at the edge of the reference full band BF, a ratio (Wj / Wt) of 0.90 or lower is preferable, and 0.80 or lower is more preferable.

[0186] The ratio (Wb / Wt) of the axial width Wb of the reference belt ply BP to the axial width Wt of the tread 4 is preferably 0.70 or higher. This allows the belt 40 to contribute to suppressing the dimensional growth of the tire 2. This allows the tire 2 to have improved wear resistance. From this viewpoint, a ratio (Wb / Wt) of 0.80 or higher is more preferable. From the viewpoint of suppressing damage caused by strain concentration at the edge of the reference belt ply BP, a ratio (Wb / Wt) of 0.95 or lower is preferable, and 0.90 or lower is more preferable.

[0187] The ratio (Wj / Wb) of the axial width Wj of the reference full band BF to the axial width Wb of the reference belt ply BP is preferably 0.60 or higher. This allows the band 42 to contribute to suppressing the dimensional growth of the tire 2. This allows the tire 2 to have improved wear resistance. From this viewpoint, a ratio (Wj / Wb) of 0.70 or higher is more preferable. From the viewpoint of suppressing damage caused by strain concentration at the end of the reference full band BF, a ratio (Wj / Wb) of 0.90 or lower is preferable, and 0.80 or lower is more preferable.

[0188] The inclination angle Aj of band code 52 of the reference full band BF and the inclination angle Ab of belt code 46 of the reference belt ply BP preferably satisfy the following relationship. Aj + Ab ≤ 25 This allows the reinforcing layer 14 to contribute to suppressing the dimensional growth of the tire 2. This allows the tire 2 to have improved wear resistance. From this viewpoint, it is more preferable that the sum of the inclination angle Aj and the inclination angle Ab (Aj+Ab) is 20 degrees or less. From the viewpoint of reducing the strain generated between the carcass 12 and the reinforcing layer 14, it is preferable that the sum of the inclination angle Aj and the inclination angle Ab (Aj+Ab) is 15 degrees or more.

[0189] The inclination angle Aj of the band code 52 of the standard full band BF is preferably between 0 degrees and 5 degrees. This allows the band 42 to contribute to suppressing the dimensional growth of the tire 2. This allows the tire 2 to have improved wear resistance. From this viewpoint, it is more preferable that the inclination angle Aj is between 0 degrees and 3 degrees.

[0190] The inclination angle Ab of the belt cord 46 of the reference belt ply BP is preferably 30 degrees or less. This allows the belt 40 to contribute to suppressing the dimensional growth of the tire 2. This allows the tire 2 to have improved wear resistance. From this viewpoint, an inclination angle Ab of 20 degrees or less is more preferable. As mentioned above, the carcass 12 has a radial structure. From the viewpoint of reducing strain based on the angle difference with the carcass cords contained in the carcass 12, it is preferable that the inclination angle Ab is 15 degrees or more.

[0191] The code ends Ej of the standard full band BF is preferably 20 ends / 50 mm or more. This allows the band 42 to contribute to suppressing the dimensional growth of the tire 2. This allows the tire 2 to have improved wear resistance. From this viewpoint, the code ends Ej is more preferably 23 ends / 50 mm or more. The code ends Ej of the reference full band BF is preferably 35 ends / 50 mm or less. This suppresses the influence of the reference full band BF on the mass of tire 2. This tire 2 can maintain low rolling resistance. From this viewpoint, the code ends Ej is more preferably 32 ends / 50 mm or less.

[0192] The code ends Eb of the standard belt ply BP is preferably 15 ends / 50 mm or more. This allows the belt 40 to contribute to suppressing the dimensional growth of the tire 2. This allows the tire 2 to have improved wear resistance. From this viewpoint, the code ends Eb is more preferably 19 ends / 50 mm or more. The code ends Eb of the reference belt ply BP is preferably 30 ends / 50 mm or less. This suppresses the influence of the reference belt ply BP on the mass of tire 2. This tire 2 can maintain low rolling resistance. From this viewpoint, the code ends Eb is more preferably 28 ends / 50 mm or less, and even more preferably 26 ends / 50 mm or less.

[0193] The code end Ej of the reference full band BF is preferably greater than the code end Eb of the reference belt ply BP. This allows the band 42 to contribute to suppressing the dimensional growth of the tire 2. This tire 2 can have improved wear resistance. From this viewpoint, the ratio (Ej / Eb) of the code end Ej of the reference full band BF to the code end Eb of the reference belt ply BP is preferably 1.05 or greater, and more preferably 1.10 or greater. The ratio (Ej / Eb) is preferably 1.45 or less. This suppresses the influence of the reference full band BF on the mass of tire 2. This tire 2 can maintain low rolling resistance. From this viewpoint, the ratio (Ej / Eb) is more preferably 1.30 or less.

[0194] The central angle θp of the overlapping zone LZ of the band strip 56 in the reference full band BF is preferably 150 degrees or less. This effectively suppresses vibrations during high-speed driving that occur due to the reference full band BF, which is formed by winding the band strip 56, having both wide and narrow sections. Since changes in the contact shape are suppressed, the occurrence of wear caused by changes in the contact shape is also suppressed. From this viewpoint, 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. The central angle θp may also be 0 degrees.

[0195] As shown in Figure 1, the reference full band BF is located radially between the second belt ply 44B and the third belt ply 44C. As previously mentioned, the inclination direction of the third belt cord 46C is opposite to that of the second belt cord 46B. The reference full band BF of this tire 2 is located between the second belt ply 44B and the third belt ply 44C, where the inclination directions of the belt cords 46 are opposite to each other.

[0196] In this invention, when a reference full band BF is located between two belt plies whose belt cord inclination directions are opposite to each other, the belt ply located radially inside the reference full band BF is called the inner belt ply, and the belt ply located radially outside the reference full band BF is called the outer belt ply. In the case of this tire 2, the second belt ply 44B is the inner belt ply, and the third belt ply 44C is the outer belt ply.

[0197] Furthermore, in this invention, when the inner belt ply is a reference belt ply BP, the outer belt ply is called a sub-reference belt ply BPs, and when the outer belt ply is a reference belt ply BP, the inner belt ply is called a sub-reference belt ply BPs. A sub-reference belt ply BPs is a belt ply located radially next to the reference belt ply BP, and the direction of the inclination of the belt cord is opposite to the direction of the inclination of the belt cord of the reference belt ply BP. In the case of this tire 2, the inner belt ply, the second belt ply 44B, is the standard belt ply BP, so the outer belt ply, the third belt ply 44C, is the sub-standard belt ply BPs.

[0198] The reference full band BF of this tire 2 is located between the reference belt ply BP and the sub-reference belt ply BPs, where the inclination direction of the belt cords 46 is opposite to that of the reference belt ply BP. The reinforcing layer 14, including the reference belt ply BP, the sub-reference belt ply BPs, and the reference full band BF, can effectively contribute to suppressing the dimensional growth of the tire 2. Since the band cords 52 included in the reference full band BF extend substantially in the circumferential direction, and the belt cords 46 included in the sub-reference belt plies BPs are arranged to intersect with the belt cords 46 included in the reference belt plies BP, the shear strain generated in the rubber located between the band cords 52 and the belt cords 46 is reduced. The reference full band BF can continue to stably exhibit its dimensional growth suppression function. This tire 2 can improve wear resistance. From this viewpoint, it is preferable that the belt ply 44 having the widest axial width among the at least one belt ply 44 constituting the belt 40 is the reference belt ply BP, the belt plies 44 located radially next to this reference belt ply BP, and whose inclination direction of the belt cords 46 is opposite to that of the belt cords 46 of the reference belt ply BP are the sub-reference belt plies BPs, and the reference full band BF is located radially between the reference belt ply BP and the sub-reference belt plies 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 plies BPs are located radially outside the reference full band BF.

[0199] The full band 50, or reference full band BF, shown in Figure 4, is formed by spirally winding a band strip 56 from the first end FE1 to the second end FE2, counterclockwise when viewed from the side of the second end FE2. Therefore, the band cord 52 of the reference full band BF is slightly inclined with respect to the circumferential direction. In the reinforcing layer 14 shown in Figure 2, the direction of inclination of the band cord 52 included in the reference full band BF is opposite to the direction of inclination of the belt cord 46 included in the reference belt ply BP. The direction of inclination of the band cord 52 included in the reference full band BF may be the same as the direction of inclination of the belt cord 46 included in the reference belt ply BP.

[0200] In this tire 2, the reinforcing layer 14 is configured such that the direction of inclination of the band cords 52 included in the standard full band BF is opposite to the direction of inclination of the belt cords 46 included in the standard belt ply BP. This effectively reduces the shear strain generated in the rubber located between the band cords 52 and the belt cords 46. As a result, the reinforcing layer 14 can stably continue to perform its function of suppressing the dimensional growth of the tire 2. This tire 2 can improve wear resistance. From this viewpoint, it is preferable that the direction of inclination of the band cords 52 included in the standard full band BF is opposite to the direction of inclination of the belt cords 46 included in the standard belt ply BP.

[0201] As shown in Figure 1, the reference full band BF and the reference belt ply BP are directly adjacent to each other in the radial direction. In Figure 1, the reference belt ply BP is located radially inside the reference full band BF. If the reference full band BF and the reference belt ply BP are directly adjacent to each other in the radial direction, the reference belt ply BP may be located radially outside the reference full band BF. In this tire 2, the reference full band BF and the reference belt ply BP are directly adjacent to each other in the radial direction, allowing the reinforcing layer 14 to contribute to suppressing dimensional growth of the tire 2. This allows for improved wear resistance of the tire 2. From this viewpoint, it is preferable that the reference full band BF and the reference belt ply BP are directly adjacent to each other in the radial direction.

[0202] As shown in Figure 1, not only the reference full band BF and the reference belt ply BP, but also the reference full band BF and the sub-reference belt ply BPs are directly adjacent to each other in the radial direction. This allows the reinforcing layer 14 to effectively contribute to suppressing the dimensional growth of the tire 2. This tire 2 can achieve improved wear resistance. From this viewpoint, when the reference full band BF and the reference belt ply BP are directly adjacent to each other in the radial direction, it is more preferable that the reference full band BF and the sub-reference belt ply BP are also directly adjacent to each other in the radial direction. 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 BP is located radially outside the reference full band BF.

[0203] Figure 6 shows a portion of the cross-section of Figure 1. Figure 6 shows a cross-section of the reinforcement layer 14 in the equatorial plane. In Figure 6, the length indicated by the double arrow DBC represents the inter-code distance between the band code 52 of the reference full-band BF and the belt code 46 of the reference belt ply BP. The inter-code distance DBC represents the thickness of the rubber component located between the band code 52 of the reference full-band BF and the belt code 46 of the reference belt ply BP. In Figure 6, the lengths indicated by the double-headed arrows DBCs represent the inter-code distance between the band code 52 of the reference full-band BF and the belt code 46 of the sub-reference belt ply BPs. The inter-code distance DBCs represents the thickness of the rubber component located between the band code 52 of the reference full-band BF and the belt code 46 of the sub-reference belt ply BPs.

[0204] In this tire 2, from the viewpoint that the reinforcing layer 14 can effectively contribute to improving wear resistance, the cord-to-cord distance DBC is preferably 0.36 mm or more and 1.25 mm or less, and more preferably 0.38 mm or more and 1.20 mm or less. From a similar viewpoint, the code interval DBCs is preferably 0.36 mm or more and 1.25 mm or less, and more preferably 0.38 mm or more and 1.20 mm or less.

[0205] As mentioned above, grooves 24 are cut into the tread 4 of this tire 2. This forms the tread pattern. The tread 4 has a tread pattern.

[0206] Figure 7 is a plan view of a portion of the tread 4 unfolded. Figure 7 shows an example of a tread pattern. The tread pattern shown in Figure 7 is that of a new, unworn tire 2. The portion of the tread surface 22 other than the grooves 24 is also called the land surface 58.

[0207] Figure 8 shows a cross-section of the groove 24. The cross-section of the groove 24 shown in Figure 8 is a cross-section of the groove 24 along a plane perpendicular to the longitudinal direction of the groove 24. This cross-section of the groove 24 is the cross-section of the shoulder circumferential groove, which will be described later. The main components of the groove 24 will be explained using Figure 8.

[0208] The groove 24 comprises a pair of wall surfaces 24S including a groove opening 24M and a bottom surface 24B including a groove bottom 24T. The groove opening 24M is composed of a pair of edges 24E. In other words, the groove opening 24M comprises a pair of edges 24E. Each edge 24E is the boundary between the land surface 58 and the groove 24. Each of the pair of wall surfaces 24S spans between the edges 24E and the bottom surface 24B. Unless otherwise specified, the groove bottom 24T is represented by the position where the distance from the reference plane RP to the bottom surface 24B is maximized, measured along the normal to the reference plane RP, which is the plane containing the groove opening 24M. If the bottom surface 24B is a plane, the groove bottom 24T is represented by the width center of the bottom surface 24B. If the bottom surface 24B has a projection, the groove bottom 24T is identified based on a virtual bottom surface obtained by assuming the absence of the projection. The normal to the reference plane RP, which connects the reference plane RP and the groove bottom 24T, is the reference normal RN, and the direction of this reference normal RN is in the depth direction of the groove 24. The width of the groove 24 is expressed as the distance between one wall surface 24S and the other wall surface 24S (hereinafter referred to as the inter-wall distance). Unless otherwise specified, the inter-wall distance is measured along a line perpendicular to the reference normal RN. If the profile of the tread surface 22 can be confirmed, the profile of the tread surface 22 may be used as the reference surface RP to determine the groove bottom 24T and width of the groove 24.

[0209] In Figure 8, the length indicated by the double arrow WG is the width of the groove 24 at the groove opening 24M. If the groove opening 24M portion of the groove 24 is machined in a tapered manner, the width of the groove 24 at the groove opening 24M is expressed based on a virtual edge obtained assuming that it is not machined in a tapered manner. The length indicated by the double arrow DG is the depth of the groove 24. Unless otherwise specified, the depth DG of the groove 24 is expressed as the distance from the reference surface RP to the groove bottom 24T of the groove 24, measured along the reference normal RN. The position, width WG, and depth DG of the groove 24 are determined as appropriate according to the specifications of the tire 2.

[0210] In groove 24M, grooves 24 with a width WG of less than 1.0 mm are called sipes. Grooves 24 other than sipes are called ordinary grooves. Ordinary grooves have a width WG of 1.0 mm or more in their groove 24M. When a tire presses against the road surface, the tread deforms. Even among ordinary grooves, those with a wide width and a pair of walls that do not come into contact with each other even when the tread deforms are also called main grooves. Ordinary grooves with a narrow width and a pair of walls that can come into contact with each other when the tread deforms are also called narrow grooves.

[0211] The tread 4 of this tire 2 is provided with multiple circumferential grooves 60. The multiple circumferential grooves 60 are aligned in the axial direction. The multiple circumferential grooves are arranged symmetrically with respect to the equatorial plane. Each circumferential groove 60 is continuous in the circumferential direction. The circumferential grooves 60 of this tire 2 extend in a straight line in the circumferential direction. The circumferential grooves 60 may also be configured to extend in a zigzag pattern in the circumferential direction.

[0212] As shown in Figure 7, the tread 4 of this tire 2 has five circumferential grooves 60. Of the five circumferential grooves 60, the two circumferential grooves 60 located on the outermost axial side are the shoulder circumferential grooves 62. The circumferential groove 60 located on the equatorial plane is the center circumferential groove 64. The circumferential groove 60 located between the center circumferential groove 64 and the shoulder circumferential grooves 62 is the middle circumferential groove 66. The tread 4 of this tire 2 has a center circumferential groove 64, a pair of middle circumferential grooves 66, and a pair of shoulder circumferential grooves 62. If there are no circumferential grooves 60 on the equatorial plane, the circumferential groove 60 closest to the equatorial plane among the circumferential grooves 60 located in the zone between the equatorial plane and the edge TE of the tread surface 22 is called the center circumferential groove.

[0213] The tread 4 of this tire 2 comprises multiple land sections 68 separated by circumferential grooves 60. As shown in Figure 7, the tread 4 of this tire 2 comprises six land sections 68. Of the six land sections 68, the two land sections 68 located on the outermost axial side are the shoulder land sections 70. The shoulder land sections 70 include the edge TE of the tread surface 22. Among the land sections 68 located in the zone between the equatorial plane and the edge TE of the tread surface 22, the land section 68 closest to the equatorial plane is the center land section 72. The land section 68 located between the center land section 72 and the shoulder land sections 70 is the middle land section 74. The tread 4 of this tire 2 comprises a pair of center land sections 72, a pair of middle land sections 74, and a pair of shoulder land sections 70. When a land section 68 is located on the equatorial plane, the land section 68 located on the equatorial plane is called the center land section.

[0214] Figure 8 shows a cross-section of the shoulder circumferential groove 62. Figure 9 shows a cross-section of the middle circumferential groove 66. Although not shown, the center circumferential groove 64 has a shape similar to that of the shoulder circumferential groove 62. The circumferential grooves 60 provided in the tread 4 of this tire 2 consist of two types of circumferential grooves 60 with different shapes, namely circumferential main grooves 76 and circumferential narrow grooves 78.

[0215] Figure 8 shows a cross-section of the circumferential main groove 76. The circumferential main groove 76 is the main groove described above. The pair of wall surfaces 76S of the circumferential main groove 76 do not come into contact with each other even when the tread 4 is in contact with the road surface and deforms. The width WGm of the groove opening 76M of the circumferential main groove 76 is preferably 2% to 10% of the axial width Wt of the tread 4, from the viewpoint of contributing to drainage and traction performance. The depth DGm of the circumferential main groove 76 is, for example, 10 mm to 21 mm. From the viewpoint of enabling the tire 2 to exhibit good wet performance, the depth DGm is preferably 13 mm to 18 mm.

[0216] Figure 9 shows a cross-section of a circumferential groove 78. The circumferential groove 78 comprises a pair of wall surfaces 78S including a groove opening 78M and a bottom surface 78B including a groove bottom 78T. The dashed line LC is the center line of the circumferential groove 78. The circumferential groove 78 of this tire 2 has a cross-sectional shape symmetrical with respect to the center line LC. The center line LC extends in the depth direction of the circumferential groove 78 and passes through the groove bottom 78T. The circumferential groove 78 may have a cross-sectional shape asymmetrical with respect to the center line LC.

[0217] The circumferential groove 78 comprises a body portion 80 and a widened portion 82. The body portion 80 includes the groove opening 78M of the circumferential groove 78. The widened portion 82 includes the groove bottom 78T of the circumferential groove 78. When the tread 4 wears down and the body portion 80 disappears, the widened portion 82 is exposed. In Figure 9, the length indicated by the double arrow WC1 is the minimum width of the circumferential groove 78, and the length indicated by the double arrow WC2 is the maximum width of the circumferential groove 78. The circumferential groove 78 shows the minimum width WC1 in the body portion 80 and the maximum width WC2 in the widened portion 82.

[0218] The body 80 is provided with a grooved section 84. The grooved section 84 of this tire 2 extends from the groove opening 78M of the circumferential groove 78 in the depth direction of the circumferential groove 78. This grooved section 84 includes the groove opening 78M of the circumferential groove 78. The body 80 exhibits a minimum width WC1 in the grooved section 84. The minimum width WC1 is set so that when the tread 4 contacts the road surface and deforms, a pair of wall surfaces 78S of the circumferential groove 78 contact each other in the grooved section 84.

[0219] The narrow groove section 84 has a portion that extends straight in the depth direction (hereinafter also referred to as the straight section 86). The straight section 86 is the portion of the narrow groove section 84 that has a uniform width WC1 in the depth direction. The narrow groove section 84 includes the straight section 86 that has a uniform width WC1 in the depth direction. Although not shown, the narrow groove section 84 may be configured such that its width gradually widens from, for example, the position showing the minimum width WC1 toward the groove opening 78M and the widening section 82, respectively.

[0220] The widened portion 82 is located radially inward of the body portion 80. The width of the widened portion 82 is wider than the width of the body portion 80. The position indicated by the symbol PX is the position where the widened portion 82 exhibits its maximum width WC2 (hereinafter, maximum width position PX). The widened portion 82 tapers outward from the maximum width position PX and then tapers inward from the maximum width position PX.

[0221] In Figure 9, the position indicated by the solid line LPE is the boundary between the body portion 80 (specifically the narrow groove portion 84) and the widened portion 82. This boundary LPE is represented by the position where the circumferential narrow groove 78 shows a width Wc that is 1.1 times the minimum width WC1 of the narrow groove portion 84. If the portion showing a width Wc that is 1.1 times the minimum width WC1 has a certain length, the radial outer end of that portion is the boundary LPE.

[0222] The widened portion 82 of this tire 2 comprises a curved portion 88 and a bottom portion 90. The widened portion 82 exhibits its maximum width WC2 at the bottom portion 90. In Figure 9, the position indicated by reference numeral H4 is the boundary between the curved portion 88 and the bottom portion 90. The inflection section 88 connects the narrow groove section 84 and the bottom section 90. The width of the inflection section 88 gradually increases from the boundary LPE with the narrow groove section 84 towards the boundary H4 with the bottom section 90. The inflection section 88 curves inward from its outside. Specifically, in the cross-section of the circumferential narrow groove 78, the contour of the inflection section 88 is represented by a circular arc. In Figure 9, arrow RC1 is the radius of the circular arc representing the contour of the inflection section 88. The circular arc representing the contour of the inflection section 88 is tangent to the straight line representing the contour of the straight section 86 at the boundary H3 between the inflection section 88 and the straight section 86.

[0223] The bottom portion 90 is located radially inward of the inflection portion 88. The bottom portion 90 includes the groove bottom 78T of the circumferential groove 78. The contour of the bottom portion 90 of this tire 2 is represented by a single circular arc with radius Rw in the cross-section of the circumferential groove 78 shown in Figure 9. The center of the circular arc representing the contour of the bottom portion 90 lies on the centerline LC of the circumferential groove 78. The radius Rw of the circular arc representing the contour of the bottom portion 90 is equal to half the length of the maximum width WC2 of the widening portion 82. The circular arc representing the contour of the bottom portion 90 is tangent to the circular arc representing the contour of the inflection portion 88 at boundary H4.

[0224] In Figure 9, the length indicated by the double arrow D1 is the depth of the circumferential groove 78. The length indicated by the double arrow D2 is the depth of the body portion 80 of the circumferential groove 78. The groove depth D2 represents the distance in the depth direction from the groove opening 78M of the circumferential groove 78 to the boundary LPE. The length indicated by the double arrow D3 is the depth from the groove opening 78M of the circumferential groove 78 to the position PX where the widened portion 82 shows its maximum width WC2.

[0225] The depth D1 of the circumferential groove 78 of this tire 2 is the same as the depth DGm of the circumferential main groove 76, or the circumferential groove 78 is shallower than the circumferential main groove 76. Specifically, the ratio D1 / DGm of the depth D1 of the circumferential groove 78 to the groove depth DGm of the circumferential main groove 76 is between 0.75 and 1.00.

[0226] In this tire 2, when the tread 4 contacts the road surface and deforms, the pair of wall surfaces 78S of the circumferential groove 78 come into contact with each other in the groove portion 84. The land portions 68 located on both sides of the circumferential groove 78 support each other, thus suppressing deformation of the tread 4. In the initial stages of wear, the groove portion 84 of the circumferential groove 78 contributes to suppressing deformation of the tread 4. The circumferential groove 78 appears to increase the rigidity of the tread 4. Tire 2 can further improve wear resistance while maintaining good wet performance. In this tire 2, the maximum width WC2 of the widened section 82 is wider than the minimum width WC1 of the narrow groove section 84. A wide widened section 82 is provided radially inward of the narrow groove section 84 of the circumferential narrow groove 78. After the narrow groove section 84 disappears, the widened section 82 is exposed. From the mid-stage of wear, when the narrow groove section 84 disappears, the exposed widened section 82 can contribute to suppressing the deterioration of wet performance. The volume of the tread 4 decreases with wear. As the deformation allowance of the tread 4 decreases, the rigidity of the tread 4 appears to increase. Good wear resistance is maintained even from the mid-stage of wear onward. This tire 2 can achieve both wet performance and wear resistance while maintaining low rolling resistance from the time of initial use until replacement with a new tire 2 is necessary. From this viewpoint, it is preferable that at least one of the multiple circumferential grooves 60 provided in the tread 4 is a circumferential narrow groove 78. In this case, it is preferable that the circumferential narrow groove 78 comprises a narrow groove portion 84 and a widened portion 82, with the maximum width WC2 of the widened portion 82 being wider than the minimum width WC1 of the narrow groove portion 84, and that when the tread 4 contacts the road surface and deforms, the pair of wall surfaces 78S of the circumferential narrow groove 78 contact each other in the narrow groove portion 84.

[0227] If at least one of the multiple circumferential grooves 60 provided in the tread 4 is a circumferential narrow groove 78, then the circumferential grooves 60 other than the circumferential narrow groove 78 are circumferential main grooves 76. In this tire 2, the center circumferential groove 64 and the shoulder circumferential groove 62 are the main circumferential grooves 76, and the middle circumferential groove 66 is the fine circumferential groove 78. Although not shown in the figures, the center circumferential groove 64 may be a circumferential narrow groove 78, and the shoulder circumferential groove 62 may be a circumferential narrow groove 78. If the center circumferential groove 64 or the shoulder circumferential groove 62 is a circumferential narrow groove 78, then the middle circumferential groove 66 may be a circumferential main groove 76. From the viewpoint of maintaining good wet performance, it is preferable that at least the shoulder circumferential groove 62 located on the outermost axial side is a circumferential main groove 76, as in this tire 2. In this case, from the viewpoint of reducing rolling resistance and improving wear resistance, it is preferable that at least one of the one or more circumferential grooves 60 located between the two circumferential main grooves 76 is a circumferential narrow groove 78. When this tire 2 is mounted on the steering shaft of a vehicle, it is preferable that at least three circumferential grooves 60 are provided between two circumferential main grooves 76, and of the at least three circumferential grooves 60, the central circumferential groove 60 is the circumferential main groove 76, and the circumferential grooves 60 located on both sides of this circumferential main groove 76 are circumferential narrow grooves 78. When this tire 2 is mounted on the drive shaft of a vehicle, it is preferable that at least two circumferential grooves 60 are provided between two circumferential main grooves 76, and that at least two of the circumferential grooves 60 are all circumferential narrow grooves 78.

[0228] As mentioned above, the maximum width WC2 of the widened section 82 is wider than the minimum width WC1 of the narrow groove section 84. From the viewpoint of maintaining good wet performance, it is preferable that the maximum width WC2 of the widened section 82 is at least twice the minimum width WC1 of the narrow groove section 84, and more preferably three times or more. From the viewpoint of minimizing the impact on the rigidity of the crown portion of the tread 4 and enabling the tire 2 to maintain good resistance to uneven wear, it is preferable that the maximum width WC2 of the widened section 82 is eight times or less the minimum width WC1 of the narrow groove section 84, and more preferably seven times or less.

[0229] The minimum width WC1 of the groove portion 84 is preferably 2.5 mm or less. Thereby, when the tread 4 contacts and deforms with the road surface, in the groove portion 84, the pair of wall surfaces 78S of the circumferential groove 78 can effectively contact. The deformation of the tread 4 is suppressed, and this tire 2 can further improve the wear resistance performance. From this viewpoint, the minimum width WC1 is more preferably 2.0 mm or less. From the viewpoint that water existing between the tread 4 and the wet road surface is effectively drained through the circumferential groove 78, the minimum width WC1 is preferably 1.0 mm or more.

[0230] In this tire 2, the radius RC1 of the arc representing the contour of the bending portion 88 is preferably larger than the radius Rw of the arc representing the contour of the bottom portion 90. Thereby, the circumferential groove 78 can fully exhibit its function. From this viewpoint, the ratio RC1 / Rw of the radius RC1 to the radius Rw is preferably 1.5 or more and 20 or less. From the viewpoint of improving the wear resistance performance, the ratio RC1 / Rw is more preferably 2.0 or more. From the viewpoint of maintaining good wet performance, the ratio RC1 / Rw is more preferably 15 or less.

[0231] The ratio D2 / D1 of the depth D2 of the carcass portion 80 to the depth DI of the circumferential groove 78 is preferably 0.25 or more and 0.70 or less. By setting the ratio D2 / D1 to 0.25 or more, the groove depth D2 of the carcass portion 80 is appropriately maintained. When the tread 4 contacts and deforms with the road surface, the pair of wall surfaces 78S of the circumferential groove 78 can sufficiently contact in the groove portion 84. This tire 2 can further improve the wear resistance performance. From this viewpoint, the ratio D2 / D1 is more preferably 0.30 or more. By setting the ratio D2 / D1 to 0.70 or less, this tire 2 can form the widened portion 82 having a necessary groove volume. The exposed widened portion 82 can effectively contribute to suppressing the deterioration of wet performance. From this viewpoint, the ratio D2 / D1 is more preferably 0.65 or less.

[0232] From the viewpoint of effectively contributing to suppressing a decrease in wet performance, it is preferable that the ratio D3 / D1 of the groove depth D3 from the groove opening 78M of the circumferential narrow groove 78 to the groove depth D1 of the circumferential narrow groove 78, with respect to the groove depth D1 of the circumferential narrow groove 78, be 0.75 or more and 0.95 or less.

[0233] As shown in Figure 10, the groove opening 78M of the circumferential groove 78 may be machined to be tapered. In this case, the body 80 of the circumferential groove 78 is provided with a funnel portion 92 on the radially outer side of the groove portion 84. The funnel portion 92 can contribute to increasing the groove volume of the circumferential groove 78 and can effectively suppress the concentration of strain on the edges 78E of the land portions 68 located on both sides of the circumferential groove 78. From this viewpoint, it is preferable that the body portion 80 of the circumferential groove 78 is provided with a funnel portion 92 including the groove opening 78M of the circumferential groove 78 on the radially outer side of the groove portion 84. In this case, the boundary LTP between the funnel portion 92 and the groove portion 84 is represented by the position at the boundary portion between the funnel portion 92 and the groove portion 84 where the circumferential groove 78 exhibits a width Wd that is 1.1 times the minimum width WC1 of the groove portion 84. The width WA of the funnel portion 92 is preferably 0.15 times or more and 0.45 times or less the groove width WGm of the circumferential main groove 76. The ratio D4 / D1 of the depth D4 of the funnel portion 92 to the groove depth D1 of the circumferential narrow groove 78 is preferably 0.12 or more and 0.14 or less.

[0234] As mentioned above, the tread 4 of this tire 2 has multiple land sections 68 separated by circumferential grooves 60. In this tire 2, at least one of the multiple land sections 68 is provided with a transverse sipe 102 that crosses this land section 68. The transverse sipe 102 spans between the circumferential grooves 60 located on both sides of the land section 68. The transverse sipe 102 is the aforementioned sipe. The transverse sipe 102 has a width of less than 1.0 mm at its groove opening 102M. The transverse sipe 102 has a groove width that is uniform in the depth direction.

[0235] Figure 11 shows a cross-section of a transverse sipe 102. As shown in Figure 11, the transverse sipe 102 extends in a zigzag pattern in the depth direction. The transverse sipe 102 shown in Figure 7 extends in a straight line in the length direction, but the transverse sipe 102 may be configured to extend in a zigzag pattern in its length direction, as shown in Figure 12. This tire 2 can use a sipe that extends straight in the length direction and in a zigzag pattern in the depth direction (first sipe), a sipe that extends in a zigzag pattern in the length direction and in a straight line in the depth direction (second sipe), and a sipe that extends in a zigzag pattern in both the length and depth directions (third sipe) as the transverse sipe 102. In other words, this tire 2 can use a sipe that extends in a zigzag pattern in either the length or depth direction as the transverse sipe 102.

[0236] The transverse sipes 102 can function as edge components that contribute to traction. The tire 2 can further improve its wet performance. When the tread 4 deforms, the wall surfaces 102S of the transverse sipes 102 come into close contact with each other. The wall surfaces 102S restrain each other, and the rigidity of the tread 4 appears to increase. The tire 2 can also further improve its wear resistance. From this viewpoint, it is preferable that at least one of the multiple land portions 68 provided on the tread 4 has a transverse sipe 102 that crosses the land portion 68, and that the transverse sipe 102 extends in a zigzag pattern in the length direction or depth direction. In this case, it is preferable that the amplitude of the zigzag is 0.5 mm or more and 3.0 mm or more.

[0237] In Figure 11, the length indicated by the double-headed arrow DGs represents the depth of the transverse sipe 102. The transverse sipes 102 are preferably shallower than the circumferential grooves 78. This suppresses the influence of the transverse sipes 102 on the rigidity of the land portion 68. This tire 2 can maintain good wear resistance while maintaining low rolling resistance. From this viewpoint, the ratio of the depth DGs of the transverse sipes 102 to the depth D1 of the circumferential grooves 78 (DGs / D1) is preferably 0.85 or less. From the viewpoint that the transverse sipes 102 can effectively contribute to suppressing the decrease in wet performance due to wear, the ratio (DGs / D1) is preferably 0.30 or more, and more preferably 0.50 or more.

[0238] When the transverse sipe 102 is shallower than the circumferential groove 78, it is preferable that the groove bottom 102T of the transverse sipe 102 is located radially inward from the boundary LPE between the narrow groove portion 84 and the widened portion 82 of the circumferential groove 78, and radially outward from the maximum width position PX of the widened portion 82. In other words, it is preferable that the groove bottom 102T of the transverse sipe 102 is located radially between the boundary LPE between the narrow groove portion 84 and the widened portion 82 and the maximum width position PX of the widened portion 82. This allows the tire 2 to minimize the impact on wear resistance and wet performance due to the transition from the transverse sipe 102 to the widened portion 82 of the circumferential groove 78. This tire 2 can further improve wet performance while maintaining good wear resistance even in the mid-to-late stages of wear when the narrow groove portion 84 disappears. This tire 2 can achieve a balance between wet performance and wear resistance while maintaining low rolling resistance from the time of initial use until the next new tire 2 needs to be replaced.

[0239] In this tire 2, the center land section 72 and the middle land section 74, located between the two circumferential main grooves 76, each have multiple transverse sipes 102 arranged in the circumferential direction. Transverse sipes 102 may be provided only on the center land section 72, or only on the middle land section 74. From the viewpoint of enabling the tire 2 to effectively achieve both wet performance and wear resistance while maintaining low rolling resistance, it is preferable that all of the multiple land sections 68 located between the two circumferential main grooves 76 have multiple transverse sipes 102 arranged in the circumferential direction.

[0240] The shoulder land portion 70 is provided with transverse grooves 104 that bridge the gap between the shoulder circumferential grooves 62 and the edge TE of the tread surface 22. The transverse grooves 104 are the conventional grooves described above. Transverse sipes 102 may be cut into this shoulder land portion 70.

[0241] As is clear from the above description, the present invention provides a heavy-duty tire 2 that can achieve improved wet performance and wear resistance while maintaining low rolling resistance. [Examples]

[0242] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0243] The various chemicals used in the examples and comparative examples are described. NR:TSR20 SBR: HPR840 (S-SBR, Tg: -60℃, Styrene content: 10% by mass, Vinyl content: 42 mol%) 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 Dia Black N134 (N2SA: 148ml) 2 / g, average primary particle diameter: 18nm) Silica: Evonik Degussa's UltraSil 9100GR (N2SA: 230m 2 / g, average primary particle diameter: 15nm) Silane coupling agent: NXT (3-octanoylthiopropyltriethoxysilane) manufactured by Momentive Resin components: 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. Anti-aging agent 1: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Anti-aging agent 2: Nocrack RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Beads of stearic acid manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: HK-200-5 (5% oil-containing powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator: Nocceler NS (N-t-butyl-2-benzothiazolesulfenamide) manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0244] [Examples and Comparative Examples] According to the formulation shown in Table 1, using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd., materials other than sulfur and the vulcanization accelerator are kneaded at 150 °C for 5 minutes to obtain a kneaded product. Next, sulfur and the vulcanization accelerator are added to the obtained kneaded product, and it is kneaded at 80 °C for 5 minutes using an open roll to obtain a rubber composition (unvulcanized product of the rubber composition). The obtained rubber composition is formed into a tread and bonded together with other parts such as the sidewall to form an unvulcanized tire. The unvulcanized tire is press-vulcanized at 150 °C for 12 minutes to manufacture a test tire (size: 315 / 70R22.5, for trucks and buses) having the basic configuration shown in FIG. 1. It is indicated by "Y" in the column of "S-JLB" in Table 1 below that the test tire has a reference full band and the material of the band code of the reference full band is steel. "N" in the column of "S-JLB" indicates that the reference full band is not provided, in other words, the reinforcing layer does not have a band.

[0245] [Wet Performance (WET)] Using the following test vehicle, a test of wet performance (wet braking performance) is conducted in accordance with R117-02 (ECE Regulation No. 117 Revision 2). The test tires are mounted on all wheels of the test vehicle. In this wet performance, on a water-sprinkled road surface, the braking distance from the specified initial speed to the stop is measured. Test vehicle: 10-ton truck (2-D vehicle) Load: 75% of the standard loading capacity Wet road surface: Water depth 0.5 - 2 mm Speed: 65 km / h The measured values of Examples 1-3 and Comparative Examples 1-3 are expressed as an index with Comparative Example 1 as 100 by the following formula. (Wet performance index) = (Braking distance of the tire of Comparative Example 1) / (Braking distance of each test tire) × 100 The results are shown in the "WET" column of Table 1 below. A higher number indicates better wet performance.

[0246] [Wear resistance] Test tires will be mounted on all wheels of a 10-ton fixed-load test vehicle (2-D) with rims (9.00 x 22.5) and internal pressure (900 kPa). The groove depth of the circumferential main grooves will be measured after 8000 km of driving on the tire test course, and the distance traveled when the groove depth decreases by 1 mm (hereinafter referred to as the wear index value) will be calculated. The wear index values ​​for Examples 1-3 and Comparative Examples 1-3 are expressed as an index with Comparative Example 1 set to 100 using the following formula. (Wear resistance index) = (Wear index value of each test tire) / (Wear index value of the tire in comparative example 1) × 100 The results are shown in the "Abrasion Resistance" column of Table 1 below. A higher number indicates better abrasion resistance.

[0247] [Overall performance] The sum of the wet performance index and the wear resistance index is calculated. The result is shown in the "Overall Performance" column of Table 1 below. A higher number indicates better wet performance and wear resistance.

[0248] [Table 1] [Industrial applicability]

[0249] The technologies described above, which achieve improved wet performance and wear resistance while maintaining low rolling resistance, can be applied to various types of tires.

[0250] [Note] The present invention includes the following embodiments.

[0251] [1] A tire comprising a pair of beads, a carcass spanning the pair of beads, a tread located radially outward of the carcass and in contact with the road surface, and a reinforcing layer located radially between the tread and the carcass, wherein the tread is composed of a rubber composition comprising a rubber component and a filler, the rubber component comprising styrene-butadiene rubber and isoprene rubber, the filler comprising carbon black and silica, the reinforcing layer comprising a belt comprising a number of parallel belt cords and a band comprising a helically wound band cord, the band comprising at least one full band formed by helically winding band strips, the widest of the at least one full band A full band having a certain axial width is the reference full band, the material of the band cord of the reference full band is steel, the content of styrene-butadiene rubber (CSBR) in 100 parts by mass of the rubber component is 40 parts by mass or more, the content of isoprene-based rubber (CNR) in 100 parts by mass of the rubber component is 30 parts by mass or more, the content of carbon black (BCB) per 100 parts by mass of the rubber component is less than the content of silica (BSi) per 100 parts by mass of the rubber component, and the ratio of the isoprene-based rubber content (CNR), the carbon black content (BCB), and the axial width Wj of the reference full band to the axial width Wt of the tread (Wj / Wt) satisfies the following relationship: Heavy-duty tires. (CNR+BCB)×(Wj / Wt)≧27.0 [2] The heavy-duty tire described in [1] above, wherein the ratio of the axial width Wj of the reference full band to the axial width Wt of the tread (Wj / Wt) is 0.60 or more. [3] The heavy-duty tire according to [1] or [2] above, wherein the belt comprises at least one belt ply, the belt ply having the widest axial width among the at least one belt ply is the reference belt ply, the material of the belt cord of the reference belt ply is steel, and the ratio of the axial width Wb of the reference belt ply to the axial width Wt of the tread (Wb / Wt) is 0.70 or more. [4] The heavy-duty tire described in [3] above, wherein the ratio (Wj / Wb) of the axial width Wj of the reference full band to the axial width Wb of the reference belt ply is 0.60 or more. [5] The heavy-duty tire according to [3] or [4] above, wherein the reference full band and the reference belt ply are directly adjacent to each other in the radial direction. [6] A heavy-duty tire according to any of the above [3] to [5], wherein the inclination angle Aj of the band cord of the reference full band and the inclination angle Ab of the belt cord of the reference belt ply satisfy the following relationship. Aj + Ab ≤ 25 [7] A heavy-duty tire as described in any of [1] to [6] above, wherein the code end Ej of the standard full band is 20 or greater. [8] The heavy-duty tire according to any one of [1] to [7] above, wherein the tread has a plurality of circumferential grooves arranged in the axial direction, at least one of the plurality of circumferential grooves is a circumferential narrow groove, the circumferential narrow groove comprises a body portion including the groove opening of the circumferential narrow groove and a widened portion including the groove bottom of the circumferential narrow groove, the body portion comprises the narrow groove portion, the maximum width of the widened portion is wider 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 come into contact with each other in the narrow groove portion. [9] The heavy-duty tire according to any one of [1] to [8] above, wherein the tread comprises a plurality of land portions separated by circumferential grooves, at least one of the land portions comprises a transverse sipe that crosses the land portion, and the transverse sipe extends in a zigzag pattern in the longitudinal or depth direction.

[10] The heavy-duty tire according to any one of the above [1] to [9], wherein the filler contains silica with an average primary particle diameter of 16 nm or less.

[11] A heavy-duty tire according to any one of the above [1] to

[10] , wherein the filler contains carbon black having an average primary particle diameter of 19 nm or less.

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

[11] above, wherein the rubber composition further comprises a silane coupling agent, and the silane coupling agent comprises a mercapto-silane coupling agent.

[13] The heavy-duty tire according to any one of the above [1] to

[12] , wherein the styrene content CSt of the styrene-butadiene rubber is 25% by mass or less.

[14] The heavy-duty tire according to any one of the above [1] to

[13] , wherein the rubber composition further comprises a resin component. [Explanation of Symbols]

[0252] 2 tires 4. Tread 6. Sidewall 10...bead 12...Carcass 14. Reinforcement layer 22...Tread surface 26...Base section 28... Cap section 34.. Carcass ply 40... belt 42...band 44, 44A, 44B, 44C, 44D... Belt ply 46, 46A, 46B, 46C, 46D... Belt cord 50...Full Band 52... Band Code 56... Band strip 60...Circumferential groove 68... Rikubu 76...Circumferential main groove 78... Circumferential narrow groove 80... Torso 82... Widening section 84...Narrow groove part 102...Transverse sipes

Claims

1. A tire comprising a pair of beads, a carcass spanning the pair of beads, a tread located radially outward of the carcass and in contact with the road surface, and a reinforcing layer located radially between the tread and the carcass, The tread is composed of a rubber composition containing a rubber component and a filler. The rubber component includes styrene-butadiene rubber and isoprene-based rubber. The filler comprises carbon black and silica. The reinforcing layer comprises a belt including a number of parallel belt cords and a band including a spirally wound band cord. The band comprises at least one full band formed by spirally winding a band strip, The reference full band is the full band having the widest axial width among at least one of the full bands. The material of the band cord of the aforementioned standard full band is steel. The CSBR content of styrene-butadiene rubber in 100 parts by mass of the rubber component is 40 parts by mass or more. The CNR content of the isoprene-based rubber in 100 parts by mass of the rubber component is 30 parts by mass or more. 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. The CNR content of the isoprene-based rubber, the BCB content of the carbon black, and the ratio (Wj / Wt) of the axial width Wj of the reference full band to the axial width Wt of the tread satisfy the following relationship: Heavy-duty tires. (CNR+BCB)×(Wj / Wt)≧27.0

2. The ratio of the axial width Wj of the reference full band to the axial width Wt of the tread (Wj / Wt) is 0.60 or more. A heavy-duty tire according to claim 1.

3. The belt comprises at least one belt ply, The reference belt ply is the belt ply having the widest axial width among at least one of the belt plies. The material of the belt cord of the aforementioned reference belt ply is steel. The ratio of the axial width Wb of the reference belt ply to the axial width Wt of the tread (Wb / Wt) is 0.70 or greater. A heavy-duty tire according to claim 1.

4. The ratio (Wj / Wb) of the axial width Wj of the reference full band to the axial width Wb of the reference belt ply is 0.60 or greater. A heavy-duty tire according to claim 3.

5. In the radial direction, the reference full band and the reference belt ply are directly adjacent to each other. A heavy-duty tire according to claim 3.

6. The inclination angle Aj of the band cord of the reference full band and the inclination angle Ab of the belt cord of the reference belt ply satisfy the following relationship: A heavy-duty tire according to claim 3. Aj + Ab ≤ 25

7. The code end Ej of the aforementioned reference full band is 20 or greater. A heavy-duty tire according to claim 1.

8. The tread comprises a plurality of circumferential grooves arranged in the axial direction, Of the multiple circumferential grooves, at least one circumferential groove is a circumferential narrow groove. The circumferential groove comprises a body portion including the groove opening of the circumferential groove and a widened portion including the groove bottom of the circumferential groove, The body portion is provided with a narrow groove, and the maximum width of the widened portion is wider than the minimum width of the narrow groove, When the tread comes into contact with the road surface and deforms, the pair of wall surfaces of the circumferential grooves come into contact with each other in the groove portion. A heavy-duty tire according to claim 1.

9. The tread comprises a plurality of land portions separated by circumferential grooves, At least one of the multiple land sections is provided with a transverse sipe that crosses the land section, The transverse sipe extends in a zigzag pattern in the length or depth direction. A heavy-duty tire according to claim 1.

10. The aforementioned filler contains silica with an average primary particle diameter of 16 nm or less. A heavy-duty tire according to claim 1.

11. The aforementioned filler contains carbon black with an average primary particle size of 19 nm or less. A heavy-duty tire according to claim 1.

12. The rubber composition further comprises a silane coupling agent, The silane coupling agent includes a mercapto-silane coupling agent. A heavy-duty tire according to claim 1.

13. The styrene content (CSt) of the styrene-butadiene rubber is 25% by mass or less. A heavy-duty tire according to claim 1.

14. The rubber composition further comprises a resin component. A heavy-duty tire according to claim 1.

Images