Heavy-duty tires

Abstract

To provide a tire for heavy load that is superior in on-ice responsiveness (steering stability).SOLUTION: A tire for heavy load comprises a tread including: a rubber constituent containing styrene-butadiene rubber; carbon black; and silica. In the tire for heavy load, the tread has a plurality of sipes, and the formula (1) below is satisfied by a content A (mass%) of the styrene-butadiene rubber in the rubber constituent 100 mass%, and a component ratio B (mm-1) in a lateral direction of the sipe relative to a tread surface area. (1) A*B≥40.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In heavy-duty tires, for example, studless tires, a technology has been proposed to improve braking performance on ice by using a rubber composition primarily composed of natural rubber / butadiene rubber to soften the rubber surface at low temperatures and improve the rubber surface's conformity. However, this method is difficult to generate reaction force on smooth road surfaces, and the responsiveness on icy roads is not sufficient. Summary of the Invention [Problem to be solved by the invention]

[0003] The present invention aims to solve the above problems and provide a heavy-duty tire that has excellent responsiveness (steering stability) on ice. [Means for solving the problem]

[0004] The present invention provides a heavy-duty tire having a tread including a rubber component including styrene-butadiene rubber, carbon black, and silica, The tread has a plurality of sipes, The content A (mass%) of the styrene butadiene rubber in 100% by mass of the rubber component, the lateral direction component ratio B (mm -1 ) relates to a heavy-duty tire that satisfies the following formula (1): (1) A × B ≥ 40

[0005] In the tread, the content A (mass %) of styrene-butadiene rubber in 100% by mass of the rubber component is preferably 5 to 30% by mass.

[0006] The tread has a lateral direction component ratio B (mm -1 ) is 3.5mm-1 It is preferable that this is equal to or greater than this.

[0007] The tread preferably contains a terpene resin.

[0008] Preferably, the tread contains eggshell powder.

[0009] The eggshell powder preferably has an average particle size of 50 μm or more.

[0010] The carbon black preferably has an average particle size of 25 nm or less.

[0011] The tread preferably contains 20 to 60 parts by mass of the carbon black per 100 parts by mass of the rubber component.

[0012] The tread preferably contains 10 to 30 parts by mass of silica per 100 parts by mass of the rubber component. [Effects of the Invention]

[0013] According to the present invention, there is provided a heavy-duty tire having a tread including a rubber component containing styrene-butadiene rubber, carbon black, and silica, wherein the tread has a plurality of sipes, and the SBR content A (mass%) and the lateral component ratio B (mm -1 ) satisfies the above formula (1), a heavy-duty tire with excellent responsiveness (steering stability) on ice can be provided. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a drawing of a pattern of a tread portion of a tire according to one embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of the middle land area of ​​FIG. [Figure 3] FIG. 3 is an enlarged view of the first middle block of FIG. 2. [Figure 4] FIG. 4 is a cross-sectional view taken along line AA in FIG. [Figure 5] FIG. 2 is an enlarged view of the crown land portion of FIG. [Figure 6] FIG. 6 is an enlarged view of the first crown block of FIG. 5. [Figure 7] FIG. 2 is an enlarged view of the shoulder land portion of FIG. [Figure 8] FIG. 8 is a cross-sectional view taken along line BB in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention relates to a heavy-duty tire having a tread including a rubber component containing styrene butadiene rubber (SBR), carbon black, and silica, wherein the tread has a plurality of sipes, and the SBR content A (mass%) and the lateral direction component ratio B (mm -1 ) satisfies the formula (1). The heavy duty tire is excellent in responsiveness (steering stability) on ice.

[0016] The reason why such an effect is obtained is not clear, but is presumed to be as follows. The heavy-duty tire incorporates SBR in the rubber component, forming microscopically hard styrene domains within the rubber layer. This allows the rubber surface to achieve a gripping effect on smooth road surfaces, while also facilitating force transmission through the styrene domains within the rubber. Furthermore, the incorporation of silica improves tan δ at low temperatures while lowering tan δ at high temperatures. High tan δ at low temperatures is believed to facilitate energy loss due to deformation caused by tread domain catching on the styrene domains on the tread surface, improving grip on the surface. It is also believed that the difference between input and response (δ) within the rubber is reduced, resulting in faster force transmission. Furthermore, carbon black reinforces the SBR phase, thereby enhancing force generation within the SBR phase. Furthermore, increasing the lateral component ratio of the sipes facilitates deformation of the entire rubber. Furthermore, setting the product of the lateral component ratio of the sipes and the SBR content to 40 or more facilitates tread catching by the sipes and styrene phases on the tread surface, while deformation occurs throughout the rubber in the tread region, improving responsiveness. As a result of the above, greater deformation occurs on the tread surface, making it easier to obtain grip on the surface, while the interior, which is not in contact with the ground, also deforms more, making it easier to generate reaction force.As a result, it is thought that overall, a large reaction force can be transmitted instantly even on icy roads, improving responsiveness on ice.

[0017] In this way, the problem (objective) of improving responsiveness on ice is solved by configuring a heavy-duty tire with a tread containing a rubber component including styrene butadiene rubber (SBR), carbon black, and silica, in which the tread has a plurality of sipes and satisfies the formula (1) "A×B≧40." In other words, the parameter "A×B≧40" does not define the problem (objective); the object of the present application is to improve responsiveness on ice, and a configuration that satisfies the parameter is used as a means to achieve this.

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to this embodiment. FIG. 1 is a pattern drawing (contact surface) of a tread portion 2 of a tire 1 showing one embodiment of the present invention. The tire 1 can be used for various tires, such as a heavy-duty pneumatic tire and a non-pneumatic tire that is not filled with pressurized air inside the tire. The tire 1 is preferably a heavy-duty tire with a standard load of 1400 kg or more. In this specification, a heavy-duty tire refers to a tire with a standard load of 1400 kg or more.

[0019] The tire 1 of this embodiment is, for example, a pneumatic tire, and is suitably used as a heavy-duty winter tire.

[0020] The tread portion 2 is made of a rubber composition for tread containing, for example, a rubber component containing SBR, carbon black, and silica.

[0021] The SBR is not particularly limited, and examples thereof include emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. These may be used alone or in combination of two or more.

[0022] The styrene content of SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. Within the above range, the effect tends to be more favorable. In this specification, the styrene content of SBR is 1 It is calculated by H-NMR measurement.

[0023] The vinyl content of the SBR is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. The vinyl content is preferably 75% by mass or less, and more preferably 70% by mass or less. Within the above range, the effect tends to be more favorable. The vinyl content (amount of 1,2-bonded butadiene units) can be measured by infrared absorption spectroscopy.

[0024] The SBR may be unmodified or modified. The modified diene rubber may be any SBR having a functional group that interacts with a filler such as silica. Examples include terminal-modified SBR in which at least one terminal of SBR has been modified with a compound (modifier) ​​having the above functional group (terminal-modified SBR having the above functional group at the terminal), main-chain-modified SBR in which the main chain has the above functional group, main-chain-terminal-modified SBR in which the main chain and the terminals have the above functional group (for example, main-chain-terminal-modified SBR in which the main chain has the above functional group and at least one terminal has been modified with the above modifier), and terminal-modified SBR in which SBR has been modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and in which a hydroxyl group or epoxy group has been introduced.

[0025] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imido group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, and an epoxy group. These functional groups may have a substituent. Among these, an amino group (preferably an amino group in which a hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), and an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

[0026] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0027] In the rubber composition for treads, the content of SBR (A (mass%)) in 100% by mass of the rubber component is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, particularly preferably 10% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, particularly preferably 20% by mass or less. Within the above range, micro styrene domains can be easily formed on the tread surface, and the effect tends to be more suitably obtained.

[0028] The rubber composition for tread may contain rubber components other than SBR. Examples of the other rubber components include other diene rubbers. Examples of the other diene rubbers include isoprene rubber, butadiene rubber (BR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR). Other examples include butyl rubber and fluororubber. Among these, isoprene rubber and BR are preferred from the viewpoint of more optimally achieving the desired effect. The other rubber component may be either a non-modified rubber or a modified rubber, and examples of the modified rubber include those having the above-mentioned functional groups.

[0029] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. Examples of NR include SIR20, RSS#3, and TSR20, which are commonly used in the tire industry. Examples of IR are not particularly limited, and examples of IR include IR2200, which are commonly used in the tire industry. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

[0030] In the rubber composition for treads, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, particularly preferably 60% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. Within the above ranges, the effects tend to be more suitably obtained.

[0031] The butadiene rubber (BR) is not particularly limited, and examples thereof include those commonly used in the tire industry, such as BR with a high cis content, BR containing 1,2-syndiotactic polybutadiene crystals (SPB-containing BR), butadiene rubber synthesized using a rare earth catalyst (rare earth BR), and tin-modified butadiene rubber modified with a tin compound (tin-modified BR). Commercially available BRs include those from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation. These may be used alone or in combination of two or more.

[0032] The cis content of the BR is preferably 90% by mass or more, and more preferably 95% by mass or more, from the viewpoint of good performance on snow and ice, abrasion resistance, and the like. In this specification, the cis content (amount of cis-1,4-bonds) is a value calculated from the signal intensity measured by infrared absorption spectrum analysis or NMR analysis.

[0033] In the rubber composition for treads, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, particularly preferably 20% by mass or more, and is preferably 60% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less, particularly preferably 30% by mass or less. Within the above ranges, the effects tend to be more suitably obtained.

[0034] The total styrene content in the rubber component is preferably 2.0% by mass or more, more preferably 3.0% by mass or more, even more preferably 4.0% by mass or more, particularly preferably 4.5% by mass or more, and is preferably 15.0% by mass or less, more preferably 10.0% by mass or less, even more preferably 8.0% by mass or less, particularly preferably 6.0% by mass or less. Within the above ranges, micro styrene domains can be easily formed on the tread surface, and the effect tends to be more suitably obtained.

[0035] Here, the total styrene amount in the rubber component is the total content of styrene moieties contained in the entire rubber component (unit: mass%) and can be calculated by Σ (content of each rubber component × styrene amount in each rubber component / 100). For example, if 100% by mass of the rubber component contains 85% by mass of SBR with a styrene content of 40% by mass, 5% by mass of SBR with a styrene content of 25% by mass, and 10% by mass of BR with a styrene content of 0% by mass, the total styrene amount in the rubber component is 35.25% by mass (= 85 × 40 / 100 + 5 × 25 / 100 + 10 × 0 / 100).

[0036] The amount of styrene in each rubber component can be measured by nuclear magnetic resonance (NMR) spectroscopy. In the examples of this specification, the total styrene amount in the rubber component is calculated according to the above-mentioned formula, but it may also be analyzed from the tire using, for example, a pyrolysis gas chromatograph mass spectrometer (Py-GC / MS) or the like.

[0037] The rubber composition for the tread contains carbon black. The carbon black is not particularly limited, and examples thereof include furnace blacks (furnace carbon blacks) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal blacks (thermal carbon blacks) such as FT and MT; channel blacks (channel carbon blacks) such as EPC, MPC, and CC; and graphite. These may be used alone or in combination of two or more.

[0038] The average particle size of the carbon black is preferably 25 nm or less, more preferably 23 nm or less, and even more preferably 20 nm or less. There is no particular lower limit, but it is preferably 15 nm or more. The average particle size of carbon black can be measured by using a TEM or the like to measure a sample cut out from the tread portion of a tire.

[0039] The carbon black preferably has a cetyltrimethylammonium bromide adsorption surface area (CTAB) of 130 m 2 / g or more, more preferably 140m 2 / g or more, more preferably 145m 2 / g or more, particularly preferably 150m 2 The upper limit is not particularly limited, but is preferably 250 m 2 / g or less, more preferably 200m 2 / g or less, more preferably 180m 2 Within the above range, the effect tends to be more favorably obtained. In this specification, the CTAB of carbon black is a value measured in accordance with JIS K6217-3:2001.

[0040] The nitrogen adsorption specific surface area (N2SA) of the carbon black is preferably 110 m 2 / g or more, more preferably 130m 2 / g or more, more preferably 140m 2 / g or more, particularly preferably 145m 2 The upper limit is not particularly limited, but is preferably 250 m 2 / g or less, more preferably 200m 2 / g or less, more preferably 180m 2 Within the above range, the effect tends to be more favorably obtained. The N2SA of carbon black is determined according to JIS K 6217-2:2001.

[0041] The iodine adsorption (IA) (mg / g) of carbon black is preferably 115 mg / g or more, more preferably 125 mg / g or more, even more preferably 130 mg / g or more, and particularly preferably 140 mg / g or more. There is no particular upper limit, but it is preferably 200 mg / g or less, more preferably 180 mg / g or less, and even more preferably 160 mg / g or less. Within the above range, the effect tends to be more favorably obtained. In this specification, the IA of carbon black is a value measured in accordance with JIS K6217-1:2001.

[0042] The ratio of the cetyltrimethylammonium bromide adsorption specific surface area (CTAB) to the iodine adsorption amount (IA) (mg / g) of carbon black (CTAB / IA) is preferably 0.85 m 2 / mg or more, more preferably 1.10m 2 / mg or more, more preferably 1.13m 2 The upper limit is not particularly limited, but is preferably 1.35 m 2 / mg or less, more preferably 1.30m 2 / mg or less, more preferably 1.25m 2 Within the above range, the effect tends to be more favorably obtained.

[0043] The dibutyl phthalate oil absorption (DBP) of the carbon black is preferably 100 cm 3 / 100g or more, preferably 110cm 3 / 100g or more, more preferably 115cm 3 The upper limit is not particularly limited, but is preferably 180 cm 3 / 100g or less, preferably 170cm 3 / 100g or less, more preferably 160cm 3 Within the above range, the effect tends to be more favorably obtained. The DBP of carbon black is measured in accordance with JIS K 6217-4:2001.

[0044] Among the carbon blacks mentioned above, CTAB is used at 140mJ in order to obtain the desired effect. 2 / g or more, CTAB / IA is 1.10m 2 It is particularly preferable to use a specific carbon black having a carbon black content of 1000 ppm or more.

[0045] The reason why such an effect is obtained when a specific carbon black is used is not clear, but is presumed to be as follows. The heavy-duty tire uses a specific carbon black, which makes it possible to strongly reinforce the SBR phase, thereby significantly increasing the force generated within the SBR phase. As a result, the inner part that is not in contact with the ground is more likely to deform and generate a reaction force, which is thought to enable a large reaction force to be transmitted instantly even on icy roads, improving responsiveness on ice.

[0046] In the rubber composition for treads, the content of carbon black is preferably 5 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and particularly preferably 35 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 60 parts by mass or less, and particularly preferably 40 parts by mass or less. Within the above range, the effects tend to be more suitably obtained.

[0047] The rubber composition for a tread contains silica. Examples of silica include dry process silica (anhydrous silica) and wet process silica (hydrated silica). These may be used alone or in combination of two or more. Among these, wet process silica is preferred because it has a large number of silanol groups.

[0048] The nitrogen adsorption specific surface area (N2SA) of the silica is preferably 40 m 2 / g or more, more preferably 100m 2 / g or more, more preferably 130m 2 / g or more, particularly preferably 150m 2 / g or more. The N2SA of the silica is preferably 250m 2 / g or less, more preferably 220m 2 / g or less, more preferably 200m 2 Within the above range, the effect tends to be more favorably obtained. The N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0049] In the rubber composition for treads, the content of silica is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 45 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 25 parts by mass or less, and particularly preferably 20 parts by mass or less. Within the above range, the effect tends to be more suitably obtained.

[0050] As silica, for example, products from Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used.

[0051] The rubber composition for a tread preferably contains a silane coupling agent together with silica. The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocalcium nitrate, Examples include sulfide-based compounds such as bamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These compounds may be used alone or in combination of two or more. Among these, sulfide-based and mercapto-based compounds are preferred because they provide better effects.

[0052] As the silane coupling agent, for example, products from Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used.

[0053] In the rubber composition for treads, the content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, per 100 parts by mass of silica. The content is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less. Within the above range, the effect tends to be more favorably obtained.

[0054] The rubber composition for a tread may contain fillers other than silica and carbon black. Examples of other fillers that can be used include inorganic fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica; and poorly dispersible fillers, which are known in the rubber field.

[0055] In the rubber composition for treads, the total content of fillers (carbon black, silica, etc.) is, per 100 parts by mass of the rubber component, preferably 30 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 50 parts by mass or more, and particularly preferably 55 parts by mass or more, and is preferably 110 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 90 parts by mass or less. Within the above ranges, the effects tend to be more suitably obtained.

[0056] The rubber composition for a tread preferably contains a plasticizer. Here, the plasticizer is a material that imparts plasticity to the rubber component, and examples thereof include liquid plasticizers (plasticizers that are in a liquid state at room temperature (25°C)) and resins (resins that are in a solid state at room temperature (25°C)). Among these, it is preferable to contain the above-mentioned resins.

[0057] When the rubber composition for tread contains a plasticizer, the content of the plasticizer (total amount of plasticizer) is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less. Within the above range, better effects tend to be obtained.

[0058] Liquid plasticizers (plasticizers that are liquid at room temperature (25°C)) that can be used in the rubber composition for treads are not particularly limited, and examples include oils, liquid polymers (liquid resins, liquid diene-based polymers, liquid farnesene-based polymers, etc.), etc. These may be used alone or in combination of two or more.

[0059] The rubber composition for treads may or may not contain a liquid plasticizer, but the content of the liquid plasticizer is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 0 parts by mass, per 100 parts by mass of the rubber component. Within the above range, the effect tends to be more favorably obtained. The content of the liquid plasticizer also includes the amount of oil contained in the oil-extended rubber.

[0060] Examples of oils include process oils, vegetable oils, and mixtures thereof. Examples of process oils that can be used include paraffin-based process oils, aromatic process oils, and naphthenic process oils. Examples of vegetable oils that can be used include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. Commercially available products include those from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Corporation, Oriso Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and Nisshin Oillio Group, Ltd. Among these, process oils (paraffin-based process oils, aromatic process oils, naphthenic process oils, etc.) and vegetable oils are preferred.

[0061] Examples of liquid resins include terpene resins (including terpene phenol resins and aromatic modified terpene resins), rosin resins, styrene resins, C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene (DCPD) resins, coumarone-indene resins (including coumarone and indene simple resins), phenol resins, olefin resins, polyurethane resins, acrylic resins, etc. Hydrogenated products of these resins can also be used.

[0062] Examples of liquid diene polymers include liquid styrene butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), liquid styrene isoprene copolymers (liquid SIR), liquid styrene butadiene styrene block copolymers (liquid SBS block polymers), liquid styrene isoprene styrene block copolymers (liquid SIS block polymers), liquid farnesene polymers, and liquid farnesene butadiene copolymers, all of which are liquid at 25°C. The terminals or main chains of these polymers may be modified with polar groups. Hydrogenated versions of these polymers can also be used.

[0063] Examples of the resins (resins in a solid state at room temperature (25°C)) that can be used in the rubber composition for treads include aromatic vinyl polymers that are solid at room temperature (25°C), coumarone-indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, and acrylic resins. The resins may also be hydrogenated. These may be used alone or in combination of two or more. Among these, from the viewpoint of obtaining better effects, aromatic vinyl polymers, petroleum resins, and terpene resins are preferred, and terpene resins are more preferred.

[0064] The reason why such an effect is obtained when a terpene resin or the like is used is not clear, but is presumed to be as follows. By blending terpene resins and the like in the heavy-duty tires, the tan δ at low temperatures can be improved, which is thought to facilitate grip on the surface due to deformation caused by the styrene domains catching on the tread surface, and to reduce the difference between input and response (δ) inside the rubber, resulting in faster force transmission. Therefore, it is thought that the inside, which is not in contact with the ground, deforms significantly and is more likely to generate a reaction force, allowing a large reaction force to be transmitted instantly on icy roads, improving responsiveness on ice.

[0065] When the rubber composition for tread contains the above resin, the content of the above resin is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less. Within the above range, the effect tends to be more favorably obtained. Note that the content of the terpene resin is also preferably in the same range.

[0066] The softening point of the resin is preferably 50°C or higher, more preferably 55°C or higher, and even more preferably 60°C or higher. The upper limit is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 145°C or lower. Within the above range, the effect tends to be better obtained. The softening point of the resin is the temperature at which the ball drops when the softening point specified in JIS K6220-1:2001 is measured using a ring and ball softening point tester.

[0067] The aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a constituent unit. For example, it may be a resin obtained by polymerizing α-methylstyrene and / or styrene, and specifically may be a homopolymer of styrene (styrene resin), a homopolymer of α-methylstyrene (α-methylstyrene resin), a copolymer of α-methylstyrene and styrene, or a copolymer of styrene and another monomer.

[0068] The coumarone-indene resin is a resin containing coumarone and indene as the main monomer components constituting the resin skeleton (main chain). Other monomer components contained in the skeleton besides coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0069] The coumarone resin is a resin containing coumarone as a main monomer component constituting the skeleton (main chain) of the resin.

[0070] The indene resin is a resin containing indene as a main monomer component constituting the skeleton (main chain) of the resin.

[0071] The phenolic resin may be a known polymer obtained by reacting phenol with an aldehyde such as formaldehyde, acetaldehyde, or furfural in the presence of an acid or alkali catalyst. Of these, those obtained by reacting with an acid catalyst (such as novolac phenolic resin) are preferred.

[0072] Examples of the rosin resin include rosin-based resins such as natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0073] Examples of the petroleum resin include C5 resin, C9 resin, C5 / C9 resin, dicyclopentadiene (DCPD) resin, and hydrogenated versions of these resins. Of these, DCPD resin and hydrogenated DCPD resin are preferred.

[0074] The terpene resin is a polymer containing terpene as a structural unit. Examples include polyterpene resins obtained by polymerizing terpene compounds and aromatic-modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds. Examples of aromatic-modified terpene resins that can be used include terpene phenol resins made from terpene compounds and phenolic compounds, terpene styrene resins made from terpene compounds and styrene compounds, and terpene phenol styrene resins made from terpene compounds, phenolic compounds, and styrene compounds. Examples of terpene compounds include α-pinene and β-pinene, examples of phenolic compounds include phenol and bisphenol A, and examples of aromatic compounds include styrene compounds (styrene, α-methylstyrene, etc.).

[0075] The acrylic resin is a polymer containing an acrylic monomer as a constituent unit. For example, a styrene-acrylic resin having a carboxyl group and obtained by copolymerizing an aromatic vinyl monomer component with an acrylic monomer component can be used. Among them, a solvent-free carboxyl-containing styrene-acrylic resin can be preferably used.

[0076] Examples of plasticizers that can be used include products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Co., Ltd.

[0077] From the viewpoint of obtaining better effects, it is preferable that the rubber composition for a tread contains a surface roughening material. The surface roughening agent is not particularly limited, but examples thereof include eggshell powder, short fiber, zinc oxide whisker, shell powder, granular whitebait, crushed walnut, volcanic ash, and iron particles. Rubber powder such as recycled rubber and vulcanized rubber powder can also be used as the surface roughening agent. These may be used alone or in combination of two or more. Of these, eggshell powder is preferred. Eggshell powder is obtained by crushing eggshells, and its main component is calcium carbonate.

[0078] The reason why such an effect is obtained when eggshell powder is used is not clear, but is presumed as follows. In the heavy-duty tire, the eggshell powder causes deformation on the tread surface due to catching, making it easier to grip the surface. Therefore, it is presumed that the tread surface undergoes greater deformation, making it easier to obtain grip on the surface, which allows a large reaction force to be transmitted instantly even on icy roads, improving responsiveness on ice.

[0079] The average particle size of the surface roughening material (preferably eggshell powder) is preferably 50 μm or more, more preferably 70 μm or more, and even more preferably 90 μm or more. There is no particular upper limit, but it is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, and particularly preferably 120 μm or less. Within the above range, better effects tend to be obtained. The average particle size of the surface roughening material (eggshell powder) is measured using a particle size distribution measuring instrument.

[0080] As eggshell powder, for example, products from Green Techno 21 Co., Ltd., Kewpie Corporation, etc. can be used.

[0081] In the rubber composition for treads, the content of the surface roughening material is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 8 parts by mass or less. Within the above ranges, the effect tends to be more excellent. The content of eggshell powder is also preferably within the same range.

[0082] The rubber composition for a tread preferably contains an antioxidant from the viewpoint of crack resistance, ozone resistance, and the like.

[0083] The antioxidant is not particularly limited, but examples thereof include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and the like. Examples of suitable antioxidants include p-phenylenediamine antioxidants such as amines; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine antioxidants and quinoline antioxidants are preferred, with polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline being more preferred. Commercially available products include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and Flexis.

[0084] In the rubber composition for tread, the content of the antioxidant is preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, per 100 parts by mass of the rubber component, and is preferably 7.0 parts by mass or less, more preferably 4.0 parts by mass or less.

[0085] The rubber composition for a tread may contain stearic acid. The content of stearic acid in the rubber composition for a tread is preferably 0.5 to 10 parts by mass or more, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0086] As the stearic acid, conventionally known products can be used, for example, products available from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

[0087] The rubber composition for tread may contain zinc oxide. The content of zinc oxide in the rubber composition is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0088] As the zinc oxide, conventionally known products can be used, for example, products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0089] Wax may be blended into the rubber composition for tread. The content of wax in the rubber composition for tread is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the rubber component.

[0090] The wax is not particularly limited, and examples thereof include petroleum waxes, natural waxes, etc. Synthetic waxes obtained by refining or chemically treating multiple waxes can also be used. These waxes may be used alone or in combination of two or more types.

[0091] Examples of petroleum-based waxes include paraffin wax and microcrystalline wax. Natural waxes are not particularly limited as long as they are derived from non-petroleum resources, and include, for example, plant-based waxes such as candelilla wax, carnauba wax, Japan wax, rice wax, and jojoba wax; animal-based waxes such as beeswax, lanolin, and spermaceti; mineral-based waxes such as ozokerite, ceresin, and petrolactam; and refined products thereof. Commercially available products include those from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd.

[0092] The rubber composition for a tread may contain sulfur. In the rubber composition for treads, the sulfur content is preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, and even more preferably 0.7 part by mass or more, per 100 parts by mass of the rubber component, and is preferably 6.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less.

[0093] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. Commercially available products include those from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. These may be used alone or in combination of two or more.

[0094] The rubber composition for a tread may contain a vulcanization accelerator. In the rubber composition for tread, the content of the vulcanization accelerator is usually 0.3 to 10 parts by mass, and preferably 0.5 to 7 parts by mass, per 100 parts by mass of the rubber component.

[0095] The type of vulcanization accelerator is not particularly limited, and commonly used ones can be used. Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-orthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among these, sulfenamide vulcanization accelerators and guanidine vulcanization accelerators are preferred.

[0096] In the rubber composition for tread, the content of the vulcanization accelerator is preferably 0.3 to 4.0 parts by mass, more preferably 0.5 to 2.5 parts by mass, and further preferably 0.7 to 1.6 parts by mass, per 100 parts by mass of the rubber component.

[0097] As shown in Fig. 1, the tread portion 2 is provided with shoulder main grooves 4 that extend continuously in the tire circumferential direction on the tread edge Te side, and crown main grooves 3 that extend continuously in the tire circumferential direction on the tire equator C side of the shoulder main grooves 4. In the example of Fig. 1, the shoulder main grooves 4 and the crown main grooves 3 are formed in a zigzag pattern with their phases aligned with each other, but are not limited to such a zigzag formation.

[0098] The "tread edge Te" is the axially outermost contact point when the tire 1 is in a normal state, mounted on a normal rim, inflated to a normal internal pressure, and unloaded, and is placed on a flat surface with a normal load and a camber angle of 0 degrees. Unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal state.

[0099] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

[0100] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0101] "Normal load" is the load specified for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it is "maximum load capacity," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is "LOAD CAPACITY."

[0102] In the example shown in Fig. 1, the crown main grooves 3 include a first crown main groove 3A provided on one side of the tire equator C and a second crown main groove 3B provided on the other side of the tire equator C. In the example shown in Fig. 1, the first crown main groove 3A is provided on the left side of the tire equator C. The second crown main groove 3B is provided on the right side of the tire equator C.

[0103] The crown main groove 3 is preferably provided, for example, such that its groove centerline is 0.08 to 0.15 times the tread width TW from the tire equator C. The shoulder main groove 4 is preferably provided, for example, such that its groove centerline is 0.25 to 0.35 times the tread width TW from the tire equator C. However, the arrangement of the main grooves 3, 4 is not limited to these ranges. The tread width TW is the axial distance between the tread ends Te, Te in the normal state.

[0104] The groove width W1 of the crown main groove 3 and the groove width W2 of the shoulder main groove 4 are preferably, for example, 3 to 7% of the tread width TW. In the heavy-duty tire of this embodiment, the groove depth of the crown main groove 3 and the shoulder main groove 4 is preferably, for example, 15 to 25 mm.

[0105] In the example of FIG. 1, the tread portion 2 is provided with a plurality of land portions separated by main grooves 3 and 4. The land portions in this embodiment include, for example, a crown land portion 10, a middle land portion 11, and a shoulder land portion 12. The crown land portion 10 is separated between the first crown main groove 3A and the second crown main groove 3B. The middle land portion 11 is separated, for example, between the crown main groove 3 and the shoulder main groove 4. The shoulder land portion 12 is separated, for example, between the shoulder main groove 4 and the tread edge Te.

[0106] Fig. 2 shows an enlarged view of the middle land portion 11. In Fig. 2, the grooves and sipes are lightly colored to facilitate understanding of the invention. In the example of Fig. 2, the middle land portion 11 is divided into shoulder main grooves 4 and crown main grooves 3, which are zigzag-shaped and aligned with each other.

[0107] The tread portion 2 has a plurality of sipes, and in the example of Fig. 2, the middle land portion 11 is provided with middle longitudinal sipes 30 extending in a zigzag pattern. In this specification, the term "sipe" means a groove width of 1.5 mm or less at the contact patch when a tire in a normal state is brought into contact with the ground under normal load and a camber angle of 0 degrees.

[0108] Here, the tire 1 has a tread portion 2 having a rubber content A (mass%) of SBR in 100 mass% of the rubber component, a lateral direction component ratio B (mm -1 ) satisfies the following formula (1). (1)A×B≧40 [mass% / mm] The lower limit of A×B is preferably 42 or more, more preferably 50 or more, even more preferably 55 or more, and particularly preferably 58 or more. There is no particular limitation on the upper limit, but it is preferably 100 or less, more preferably 80 or less, and even more preferably 70 or less. Within the above range, better effects tend to be obtained.

[0109] The tire 1 has a lateral direction component ratio B (mm -1 ) preferably satisfies the following formula: B≧3.5mm -1 The lower limit of B is 4.2 mm -1 More than 5.0mm is preferable. -1 More than 5.5mm is preferable. -1 More preferably, 5.8 mm or more -1 The upper limit is not particularly limited, but is preferably 10.0 mm. -1 Less than 8.0mm is preferable -1 Less than 7.0mm is preferable. -1 The following is more preferable: Within the above range, a greater effect tends to be obtained.

[0110] In this specification, the lateral direction component ratio B (mm -1 ) is a value calculated using the following method. <Lateral direction component ratio of sipe (B)> The linear distance in the lateral direction (axial direction of the tire) of the sipes in the tread portion is calculated. Here, the linear distance in the lateral direction of sipes that are oblique to the tire circumferential direction and tire axial direction is calculated only as the linear distance in the axial direction of the tire, and is a value different from the length of the sipe itself. Then, after calculating each linear distance in the lateral direction for each sipe in the tread portion, these are summed to calculate the total lateral length (mm) of the sipes. In addition, the tread surface area (mm 2 ) is found. Tread surface area = tire outer diameter (Dt) x tire cross-sectional width (Wt) x π (In the formula, the outer diameter (Dt) of the tire is the outer diameter of the tire when it is mounted on a standard rim, with the internal pressure set to 250 kPa and no load applied under normal conditions. The cross-sectional width (Wt) of the tire is the linear distance between the sidewalls, including all patterns and lettering on the sidewalls (total width of the tire), excluding any patterns and lettering on the sidewalls, when the tire is mounted on a standard rim, with the internal pressure set to 250 kPa and no load applied under normal conditions.) The lateral direction component ratio B of the sipe to the tread surface area (mm -1 ) is the total length of the lateral direction of the sipes (mm), the surface area of ​​the tread (mm 2 ) and calculated using the following formula: B(mm -1 ) = Total lateral length of sipes (mm) / Tread surface area (mm 2 )

[0111] In the example of Fig. 2, zigzag-extending middle longitudinal sipes 30 are provided in the middle land portion 11. When each middle longitudinal sipe 30 corresponds to the above definition of "sipe," the lateral length (linear distance) of each middle longitudinal sipe 30 in the example of Fig. 2 is indicated by Lm1, Lm2, etc., and the total lateral length of each middle longitudinal sipe 30 is calculated as Lm1 + Lm2 + (mm).

[0112] In the example of Figure 2, the middle longitudinal sipe 30 has a first apex 30a that is convex toward the shoulder main groove 4 and a second apex 30b that is convex toward the crown main groove 3, and these are arranged alternately in the circumferential direction of the tire.

[0113] The middle longitudinal sipes 30 preferably have a depth that is 0.55 to 0.65 times that of the shoulder main grooves 4, for example.

[0114] In the example of Fig. 2, the middle longitudinal sipes 30 extend in a zigzag pattern in the circumferential direction of the tire in the opposite phase to the shoulder main grooves 4 and the crown main grooves 3. Note that "extending in a zigzag pattern in the opposite phase" means that the peaks of one zigzag-extending main groove are aligned with the valleys of the other zigzag-extending main groove in the circumferential direction of the tire.

[0115] 2, the middle land portion 11 is provided with a plurality of middle lug grooves 32 extending from the shoulder main grooves 4 or the crown main grooves 3. The middle lug grooves 32 include, for example, a plurality of first middle lug grooves 32A and a plurality of second middle lug grooves 32B. In this embodiment, the first middle lug grooves 32A and the second middle lug grooves 32B are offset from each other in the tire circumferential direction.

[0116] 2, the first middle lug groove 32A extends from the shoulder main groove 4 toward the crown main groove 3 and terminates within the middle land portion 11. The second middle lug groove 32B extends from the crown main groove 3 toward the shoulder main groove 4 and terminates within the middle land portion 11. In this embodiment, the middle longitudinal sipe 30 extends from the first middle lug groove 32A to the second middle lug groove 32B.

[0117] The middle lug grooves 32 extend linearly with a constant groove width. The crown lug grooves 17 preferably have a groove width that is 0.7 to 0.8 times that of the shoulder main grooves 4. The middle lug grooves 32 preferably have a groove depth that is 0.70 to 0.80 times that of the shoulder main grooves 4.

[0118] In the example of Fig. 2, the middle land portion 11 includes middle blocks 33 separated by middle longitudinal sipes 30 and middle lug grooves 32. The middle blocks 33 include, for example, a first middle block 33A and a second middle block 33B. The first middle block 33A is separated by, for example, the middle longitudinal sipe 30 and a plurality of first middle lug grooves 32A. The second middle block 33B is separated by, for example, the middle longitudinal sipe 30 and a plurality of second middle lug grooves 32B.

[0119] FIG. 3 is an enlarged view of the first middle block 33A, illustrating the configuration of the middle block 33.

[0120] Preferably, the middle block 33 is provided with, for example, a plurality of middle lateral narrow groove pairs 35. Each middle lateral narrow groove pair 35 is composed of two middle lateral narrow grooves 36 that completely cross the entire width of the block. In this embodiment, three middle lateral narrow groove pairs 35 are provided in one middle block 33. As a result, the middle block 33 is divided into small block pieces 37 and large block pieces 38 that alternate in the tire circumferential direction.

[0121] The small block pieces 37 are defined between the two middle lateral narrow grooves 36. The large block pieces 38 are defined between the middle lug grooves 32 and the middle lateral narrow groove pairs 35, or between the middle lateral narrow groove pairs 35 adjacent in the tire circumferential direction. The large block pieces 38 have a larger width in the tire circumferential direction than the small block pieces 37.

[0122] In the example shown in Figure 2, in a preferred embodiment, the small block pieces 37 include a first small block piece 37a provided in the circumferential center of the first middle block 33A or the second middle block 33B, and a second small block piece 37b that is axially longer than the first small block piece 37a. The first small block piece 37a formed on the first middle block 33A is preferably adjacent to the second small block piece 37b formed on the second middle block 33B with the middle longitudinal sipe 30 interposed therebetween. Similarly, the first small block piece 37a formed on the second middle block 33B is preferably adjacent to the second small block piece 37b formed on the first middle block 33A with the middle longitudinal sipe 30 interposed therebetween.

[0123] The middle horizontal narrow groove pair 35 is made up of, for example, two middle horizontal narrow grooves 36 extending in the same direction, and in a more desirable embodiment, is made up of two middle horizontal narrow grooves 36 extending parallel to each other.

[0124] In the example of Figure 3, the middle horizontal narrow groove pair 35 includes, for example, a first middle horizontal narrow groove pair 35A in which two middle horizontal narrow grooves 36 are parallel to each other and extend in a straight line, and a second middle horizontal narrow groove pair 35B in which two middle horizontal narrow grooves 36 are bent while remaining parallel to each other.

[0125] Each middle lateral narrow groove 36 of the second middle lateral narrow groove pair 35B of this embodiment includes, for example, a first portion 36a inclined with respect to the tire axial direction and a second portion 36b bent and continuing to both sides of the first portion 36a. The second portion 36b is, for example, disposed at a smaller angle with respect to the tire axial direction than the first portion 36a. As a result, each middle lateral narrow groove 36 of the second middle lateral narrow groove pair 35B is bent in a substantially S-shape.

[0126] It is desirable that at least one of the middle lateral narrow groove pairs 35 communicate with both circumferential sides of the first crest 30a or the second crest 30b of the middle longitudinal sipe 30. More specifically, one middle lateral narrow groove 36 of one middle lateral narrow groove pair 35 communicates with one circumferential side of the apex of the first crest 30a or the second crest 30b, and the other middle lateral narrow groove 36 of one middle lateral narrow groove pair 35 communicates with the other circumferential side of the apex.

[0127] It is desirable that at least one of the middle lateral narrow grooves 36 provided in the first middle block 33A smoothly connects with the middle lateral narrow groove 36 provided in the second middle block 33B via the middle longitudinal sipe 30.

[0128] In this embodiment, more than half of the multiple middle lateral narrow grooves 36 provided in one first middle block 33A smoothly connect to the middle lateral narrow grooves 36 provided in the second middle block 33B. It is desirable that at least one of the middle lateral narrow grooves 36 communicates with the middle lug groove 32.

[0129] The middle lateral narrow groove 36 has an opening width of, for example, 3 mm or less, preferably 2.5 mm or less. As shown in the cross-sectional view of the middle lateral narrow groove pair 35 taken along line AA in Fig. 4, the middle lateral narrow groove 36 has an outer portion 24 and an inner portion 25, and when the width at a position 40% of the groove depth from the tread surface (a position 40% of the depth from the tread surface out of the entire groove depth of 100%) is 1.5 mm or less, it meets the definition of "sipe" above and is configured as a sipe.

[0130] In the example of Fig. 3, the first middle block 33A is provided with a first middle lateral narrow groove pair 35A in which two middle lateral narrow grooves 36 extend linearly and parallel to each other, and a second middle lateral narrow groove pair 35B in which two middle lateral narrow grooves 36 bend while remaining parallel to each other. When each middle lateral narrow groove 36 meets the definition of a "sipe" above, the lateral length (linear distance) of each middle lateral narrow groove 36 in the example of Fig. 3 is indicated by Lm3, Lm4, etc., and the total lateral length of each middle lateral narrow groove 36 is calculated as Lm3 + Lm4 + (mm).

[0131] Fig. 4 shows a cross-sectional view of the middle lateral narrow groove pair 35 taken along line AA. As shown in Fig. 4, the middle lateral narrow groove 36 includes, in cross section, an outer portion 24 on the tread side and an inner portion 25 provided radially inward of the outer portion 24.

[0132] The outer portion 24 has an opening width W11 of, for example, 1.5 to 2.5 mm. The depth d1 of the outer portion 24 is, for example, 0.5 to 1.5 mm. It is desirable that the inner portion 25 extend with a constant width of, for example, 1.5 mm or less.

[0133] The middle lateral narrow groove 36 of this embodiment has, for example, a first wall surface 26 and a second wall surface 27. In a cross section, the first wall surface 26 extends linearly from the bottom to the tread surface. In a cross section, the second wall surface 27 includes a first portion 27a that extends linearly in the tire radial direction and constitutes the inner portion 25, and a second portion 27b that is connected to the tire radially outward of the first portion 27a and bends in a direction that widens the groove width and constitutes the outer portion 24.

[0134] In a preferred embodiment, in one pair of middle horizontal narrow grooves 35, the first wall surfaces 26 of the middle horizontal narrow grooves 36 on both sides are arranged on the side of the small block piece 37 therebetween.

[0135] The middle lateral narrow groove 36 preferably has a depth d2 that is, for example, 0.55 to 0.65 times that of the shoulder main groove 4. In a more preferred embodiment, the middle lateral narrow groove 36 has the same depth as the middle longitudinal sipe 30.

[0136] 5 shows an enlarged view of the crown land portion 10. In FIG. 5, the grooves and sipes are lightly colored to make the invention easier to understand.

[0137] In the example of Fig. 5, crown longitudinal sipes 15 extending in a zigzag pattern are provided in the crown land portion 10. When each crown longitudinal sipe 15 corresponds to the above definition of "sipe," the lateral length (linear distance) of each crown longitudinal sipe 15 in the example of Fig. 5 is indicated by Lc1, Lc2, etc., and the total lateral length of each crown longitudinal sipe 15 is calculated as Lc1 + Lc2 + (mm).

[0138] In the example of Figure 5, the crown longitudinal sipe 15 has a first apex 15a that is convex toward the first crown main groove 3A side and a second apex 15b that is convex toward the second crown main groove 3B side, and these are arranged alternately in the circumferential direction of the tire.

[0139] The crown longitudinal sipes 15 preferably have a depth greater than, for example, the middle longitudinal sipes 30. Specifically, the crown longitudinal sipes 15 preferably have a depth 1.05 to 1.10 times that of the middle longitudinal sipes 30.

[0140] The crown longitudinal sipes 15 preferably extend in a zigzag pattern in the tire circumferential direction, for example, in the opposite phase to the first crown main groove 3A and the second crown main groove 3B.

[0141] 5, the crown land portion 10 is provided with, for example, a plurality of crown lug grooves 17 extending from the crown main groove 3. The crown lug grooves 17 include, for example, a plurality of first crown lug grooves 17A and a plurality of second crown lug grooves 17B. The first crown lug grooves 17A and the second crown lug grooves 17B are, for example, misaligned in the tire circumferential direction.

[0142] For example, the first crown lug groove 17A extends from the first crown main groove 3A toward the second crown main groove 3B and terminates within the crown land portion 10. For example, the second crown lug groove 17B extends from the second crown main groove 3B toward the first crown main groove 3A and terminates within the crown land portion 10. In this embodiment, the crown longitudinal sipe 15 extends from the first crown lug groove 17A to the second crown lug groove 17B.

[0143] The crown lug grooves 17 extend linearly with a constant groove width. The crown lug grooves 17 preferably have a groove width greater than that of the middle lug grooves 32 (shown in FIG. 2). The crown lug grooves 17 preferably have a groove depth greater than that of the middle lug grooves 32.

[0144] In the example of Fig. 5, the crown land portion 10 includes crown blocks 18 divided by crown longitudinal sipes 15 and crown lug grooves 17. The crown blocks 18 include, for example, a first crown block 18A and a second crown block 18B. The first crown block 18A is divided by, for example, the crown longitudinal sipes 15 and a plurality of first crown lug grooves 17A. The second crown block 18B is divided by, for example, the crown longitudinal sipes 15 and a plurality of second crown lug grooves 17B.

[0145] FIG. 6 shows an enlarged view of the first crown block 18A to illustrate the configuration of the crown block 18. Preferably, the crown block 18 is provided with, for example, a plurality of crown lateral narrow groove pairs 20. Each crown lateral narrow groove pair 20 is composed of two crown lateral narrow grooves 21 that completely cross the entire width of the block. The crown lateral narrow groove 21 has substantially the same configuration as the middle lateral narrow groove 36 (shown in FIG. 4) in cross section, and therefore, a description thereof will be omitted here. In this embodiment, three crown lateral narrow groove pairs 20 are provided in one crown block 18. As a result, the crown block 18 is divided into small block pieces 22 and large block pieces 23 that alternate in the tire circumferential direction.

[0146] The small block piece 22 is defined between two crown lateral narrow grooves 21. The large block piece 38 is defined between the crown lug groove 17 and the crown lateral narrow groove pair 20, or between adjacent crown lateral narrow groove pairs 20 in the tire circumferential direction. The large block piece 23 has a larger width in the tire circumferential direction than the small block piece 22.

[0147] 5, it is desirable that at least one of the crown lateral narrow groove pairs 20 communicate with both sides in the tire circumferential direction of the first crest 15a or the second crest 15b of the crown longitudinal sipe 15. More specifically, one crown lateral narrow groove 21 of one crown lateral narrow groove pair 20 communicates with one side in the tire circumferential direction of the apex of the first crest 15a or the second crest 15b, and the other crown lateral narrow groove 21 of one crown lateral narrow groove pair 20 communicates with the other side in the tire circumferential direction of the apex.

[0148] It is desirable that at least one of the crown lateral narrow grooves 21 provided in the first crown block 18A smoothly connects with the crown lateral narrow groove 21 provided in the second crown block 18B via the crown longitudinal sipe 15.

[0149] In this embodiment, more than half of the multiple crown lateral narrow grooves 21 provided in one first crown block 18A are smoothly continuous with the crown lateral narrow grooves 21 provided in the second crown block 18B. It is desirable that at least one of the crown lateral narrow grooves 21 communicates with the crown lug groove 17.

[0150] In the example of Fig. 6, the first crown block 18A is provided with a plurality of lateral crown narrow grooves 21. When each lateral crown narrow groove 21 corresponds to the definition of a "sipe" as described above, the lateral length (linear distance) of each lateral crown narrow groove 21 in the example of Fig. 6 is indicated by Lc3, Lc4, etc., and the total lateral length of each lateral crown narrow groove 21 is calculated as Lc3 + Lc4 + (mm).

[0151] Fig. 7 shows an enlarged view of the shoulder land portion 12. In Fig. 7, the grooves and sipes are lightly colored to facilitate understanding of the invention. In the example of Fig. 7, the shoulder land portion 12 is provided with, for example, a shoulder longitudinal sipe 40 extending linearly. Note that in this specification, the lateral length of the longitudinal sipe extending linearly in the tire circumferential direction is set to 0 (zero) mm.

[0152] 7, the shoulder land portion 12 is provided with, for example, a plurality of shoulder lug grooves 42 extending from the shoulder main groove 4 or the tread edge Te. The shoulder lug grooves 42 include, for example, a plurality of first shoulder lug grooves 42A and a plurality of second shoulder lug grooves 42B. It is desirable that the first shoulder lug grooves 42A and the second shoulder lug grooves 42B are misaligned in the tire circumferential direction, for example.

[0153] For example, the first shoulder lug groove 42A extends from the tread edge Te toward the shoulder main groove 4 and terminates within the shoulder land portion 12. For example, the second shoulder lug groove 42B extends from the shoulder main groove 4 toward the tread edge Te and terminates within the shoulder land portion 12. In this embodiment, the shoulder longitudinal sipe 40 extends from the first shoulder lug groove 42A to the second shoulder lug groove 42B.

[0154] The first shoulder lug grooves 42A preferably have a groove width that gradually increases toward the tread end Te side, and a groove depth that gradually increases toward the tread end Te side.

[0155] The second shoulder lug grooves 42B preferably extend with a constant groove width. The second shoulder lug grooves 42B preferably have a groove width that is 0.75 to 0.85 times that of the middle lug grooves 32. The second shoulder lug grooves 42B preferably have a groove depth that is 0.85 to 0.95 times that of the middle lug grooves 32.

[0156] The shoulder land portion 12 includes, for example, shoulder blocks 43 separated by shoulder longitudinal sipes 40 and shoulder lug grooves 42. The shoulder blocks 43 include, for example, a first shoulder block 43A and a second shoulder block 43B. The first shoulder block 43A is separated by, for example, the shoulder longitudinal sipe 40 and a plurality of first shoulder lug grooves 42A. The second shoulder block 43B is separated by, for example, the shoulder longitudinal sipe 40 and a plurality of second shoulder lug grooves 42B.

[0157] In the example of Figure 7, the shoulder block 43 is preferably provided with, for example, a plurality of shoulder lateral groove pairs 45. Each shoulder lateral groove pair 45 is composed of two shoulder lateral grooves 46 that completely cross the entire width of the block. The shoulder lateral grooves 46 have substantially the same configuration in cross section as the crown lateral groove 21, and therefore, a description thereof will be omitted here.

[0158] In this embodiment, two shoulder lateral narrow groove pairs 45 are provided in one shoulder block 43. As a result, the shoulder block 43 is divided into a small block piece 47 separated between the two shoulder lateral narrow grooves 46 and a large block piece 48 having a larger width in the tire circumferential direction.

[0159] In the example of Fig. 7, one shoulder block 43 is provided with multiple shoulder lateral narrow grooves 46. When each shoulder lateral narrow groove 46 meets the definition of a "sipe" above, the lateral length (linear distance) of each shoulder lateral narrow groove 46 in the example of Fig. 6 is indicated by Ls1, etc., and the total lateral length of each shoulder lateral narrow groove 46 is Ls1 + (mm).

[0160] The first shoulder block 43A is provided with a wide lateral narrow groove 49 between the two pairs of shoulder lateral narrow grooves 45, the wide lateral narrow groove 49 having a larger opening width at the tread surface than the shoulder lateral narrow groove 46.

[0161] Fig. 8 shows a BB line cross section of the wide lateral narrow groove 49. As shown in Fig. 8, the wide lateral narrow groove 49 includes an outer portion 50 that opens on the tread side with an opening width W12 of, for example, 2.0 to 3.0 mm, and an inner portion 51 that is provided radially inward of the outer portion 50 and extends with a constant width of 1.5 mm or less. As shown in the BB line cross section of the wide lateral narrow groove 49 in Fig. 7, the wide lateral narrow groove 49 has the outer portion 50 and the inner portion 51, and when the width at a position 40% of the groove depth from the tread surface (a position 40% of the depth from the tread surface out of a total groove depth of 100%) is 1.5 mm or less, it meets the definition of a "sipe" above and is configured as a sipe.

[0162] In the example of Fig. 7, the first shoulder block 43A is provided with wide lateral narrow grooves 49. When each wide lateral narrow groove 49 corresponds to the definition of "sipe" above, the lateral length (linear distance) of each wide lateral narrow groove 49 in the example of Fig. 7 is indicated by Ls2 or the like, and the total lateral length of each wide lateral narrow groove 49 is calculated as Ls2 + (mm).

[0163] 7, the second shoulder block 43B is provided with a shoulder sipe 52 that completely traverses the entire width of the block, for example, between the second shoulder lug groove 42B and the shoulder lateral narrow groove 46. The shoulder sipe 52 of this embodiment includes, for example, a first portion 52a that is inclined with respect to the tire axial direction, and second portions 52b that are disposed on both sides of the first portion 52a and extend in the tire axial direction.

[0164] In the example of Fig. 7, shoulder sipes 52 are provided in the second shoulder block 43B. When each shoulder sipe 52 meets the definition of "sipe" above, the lateral length (linear distance) of each shoulder sipe 52 in the example of Fig. 7 is indicated by Ls3 or the like, and the total lateral length of each shoulder sipe 52 is calculated as Ls3 + (mm).

[0165] In the example of tire 1 shown in Figures 1 to 9, the total lateral length of the sipes is the total lateral length (straight-line distance) of the above-mentioned "sipes", such as each middle longitudinal sipe 30, each middle lateral narrow groove 36, each crown longitudinal sipe 15, each crown lateral narrow groove 21, each shoulder lateral narrow groove 46, each wide lateral narrow groove 49, and each shoulder sipe 52.

[0166] The heavy-duty tire is manufactured by a conventional method using the rubber composition for tread. That is, the rubber composition, to which various additives are optionally blended, is extruded in an unvulcanized state to match the shape of the tire tread, molded in a conventional method on a tire building machine, and laminated together with other tire components to form an unvulcanized tire, which is then heated and pressurized in a vulcanizer to manufacture the tire.

[0167] The tread of the heavy duty tire may be at least partially made of the rubber composition for tread, or may be entirely made of the rubber composition for tread.

[0168] In the above-mentioned heavy duty tires, all-steel tires are generally used in which the cords used in the case and breaker are both steel cords.

[0169] The heavy duty tires have good performance on ice and can therefore be suitably used as heavy duty winter tires (heavy duty studless tires, heavy duty snow tires, heavy duty studded tires, etc.).

[0170] Although a tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be modified and practiced in various aspects. [Example]

[0171] The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

[0172] The various chemicals used in the examples and comparative examples will be explained below. NR:TSR20 SBR: SBR1502 (styrene content 23.5% by mass) manufactured by Sumitomo Chemical Co., Ltd. BR: BR150B (cis content 98% by mass) manufactured by Ube Industries, Ltd. Eggshell powder: Eggshell powder (average particle size 130 μm) manufactured by Green Techno 21 Co., Ltd. Carbon black: N110 (N2SA142m) manufactured by Mitsubishi Chemical 2 / g, DBP oil absorption 116cm 3 / 100g, average particle size 19nm) Silica: Uratosil VN3 (N2SA175m) manufactured by Evonik Degussa 2 / g) Silane coupling agent: Si-266 manufactured by Evonik Degussa Terpene resin: YS Resin PX1150N (β-pinene resin, softening point: 115°C, Tg: 65°C) manufactured by Yasuhara Chemical Co., Ltd. Wax: Ozoace wax manufactured by Nippon Seiro Co., Ltd. Anti-aging agent: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Paulownia wood from NOF Corporation Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Oil: Idemitsu Kosan Co., Ltd. Diana Process NH-70S (aromatic process oil) 5% oil sulfur: HK200-5 (5% oil-containing powder sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela NS (N-tert-butyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0173] Examples and Comparative Examples According to the formulation shown in Table 1, chemicals other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded product. Next, sulfur and vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded for 5 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into the shape of a cap tread, and was laminated together with other tire components to produce an unvulcanized tire. The tire was then press-vulcanized at 170°C for 10 minutes to obtain a test tire (heavy-duty winter tire, size: 275 / 80R22.5, normal load: 3450 kg).

[0174] The test tires obtained were evaluated as follows, and the results are shown in Table 1.

[0175] <Response on ice (steering stability)> Each test tire was used to evaluate actual vehicle performance on ice. Each test vehicle was fitted with each test tire on all wheels and driven on an icy road surface, and the responsiveness (handling stability) during the drive was evaluated on a 10-point scale based on the feeling of 10 drivers. The total score was calculated as a rating, and the reference comparative example was assigned a score of 100, which was then converted into an index. The higher the index, the better the responsiveness (handling stability) on ice. Tire size 11R22.5 Rim: 7.50 x 22.5 Tire pressure: 800kPa Test vehicle: 10-ton truck (2-D vehicle) with a 5-ton load Tire mounting position: All wheels

[0176] [Table 1]

[0177] From Table 1, it can be seen that in heavy-duty tires having a tread containing a rubber component containing SBR, carbon black, and silica, the tires of the examples in which the tread had a plurality of sipes and satisfied the above formula (1) had excellent responsiveness (steering stability) on ice. [Explanation of symbols]

[0178] 2 Tread section 3 Crown main groove 4 Shoulder main groove 11 Middle Track 30 Middle vertical sipe Te tread edge

Claims

1. A heavy-duty tire having a tread including a rubber component including styrene-butadiene rubber, carbon black, and silica, The tread has a plurality of sipes, The content A (mass%) of the styrene-butadiene rubber in 100% by mass of the rubber component, the lateral direction component ratio B (mm －１ ) satisfies the following formula (1): A heavy-duty tire in which the lateral direction component ratio B (mm −1 ) of the sipes to the tread surface area is 3.5 mm −1 or more. (1) 40≦A×B≦100

2. 2. The heavy duty tire according to claim 1, wherein the tread has a content A (mass %) of styrene-butadiene rubber in 100% by mass of the rubber component of 5 to 30% by mass.

3. The heavy duty tire according to claim 1 or 2, wherein the tread contains a terpene resin.

4. The heavy duty tire according to any one of claims 1 to 3, wherein the tread contains eggshell powder.

5. 5. The heavy duty tire according to claim 4, wherein the eggshell powder has an average particle size of 50 [mu]m or more.

6. 6. The heavy duty tire according to claim 1, wherein the carbon black has an average particle size of 25 nm or less.

7. 7. The heavy duty tire according to claim 1, wherein the tread contains 20 to 60 parts by mass of the carbon black per 100 parts by mass of the rubber component.

8. 8. The heavy duty tire according to claim 1, wherein the tread contains 10 to 30 parts by mass of silica per 100 parts by mass of a rubber component.

Images