JP7362956B1 - pneumatic tires - Google Patents

Abstract

[Object] To provide a pneumatic tire that can achieve both fuel efficiency and wet performance in a well-balanced manner. A pneumatic tire 1 according to the present invention is a pneumatic tire that includes a tread rubber provided on a tread 10 and has a specified mounting direction on a vehicle, and the tread rubber is attached along the circumferential direction of the tire. A plurality of extending main grooves 30, 31, 32, and a pair of shoulder blocks 60, 70 that are partitioned by the main grooves 30, 31, 32 and arranged on the outside in the tire axial direction, and between the pair of shoulder blocks 60, 70. The center blocks 40, 50 are rib-shaped blocks that are continuous in the circumferential direction of the tire, and the loss tangent (35°C tan δ) of the tread rubber at 35°C is The ratio of loss tangent (0°C tan δ) at 0°C (0°C tan δ/35°C tan δ) is 1.35 or more and 2.10 or less. [Selection diagram] Figure 4

Description

TECHNICAL FIELD The present invention relates to a pneumatic tire, and more particularly to a tire whose mounting direction on a vehicle is designated.

BACKGROUND ART Conventionally, pneumatic tires have been widely known that include a tread having a plurality of main grooves extending in the circumferential direction of the tire and blocks partitioned by the main grooves, and have a specified mounting direction on a vehicle. Tires that have a specified mounting direction on a vehicle generally have an asymmetrical tread pattern. For example, Patent Document 1 discloses that the tire has three main grooves extending in the circumferential direction and two center blocks partitioned by the three main grooves, and each center block has sipes formed in different patterns. A pneumatic tire is disclosed.

In addition, with the recent demand for lower fuel consumption of tires, various methods for improving the fuel efficiency of tires have been studied. The fuel efficiency of a tire can be evaluated by its rolling resistance, and it is known that the lower the rolling resistance, the better the tire's fuel efficiency. Patent Document 2 discloses a tire whose rolling resistance is reduced by devising a blend of the rubber composition constituting the tire tread.

Japanese Patent Application Publication No. 2016-150601 Patent No. 6835284

By the way, when the rolling resistance decreases, the grip force with the road surface decreases, and braking performance and grip performance on a wet road surface (hereinafter referred to as wet performance) tends to deteriorate. Therefore, it is not easy to improve wet performance while reducing rolling resistance.

An object of the present invention is to provide a pneumatic tire that can achieve both fuel efficiency and wet performance in a well-balanced manner.

A pneumatic tire according to the present invention is a pneumatic tire that includes tread rubber provided in the tread and has a specified mounting direction on a vehicle, and the tread rubber has a plurality of main grooves extending along the circumferential direction of the tire. , a pair of shoulder blocks partitioned by the main groove and arranged on the outside in the tire axial direction, and a center rib arranged between the pair of shoulder blocks, and the center rib has an interval in the tire circumferential direction. A plurality of sipes are formed with open spaces, and the sipe has a bent portion that crosses the center rib and protrudes to one side in the tire circumferential direction from the positions of both ends of the sipe in the tire circumferential direction when the center rib is viewed from above. and the ratio of the loss tangent at 0°C (0°C tan δ) to the loss tangent at 35°C (35°C tan δ) of the tread rubber (0°C tan δ/35°C tan δ) is 1.35 or more, 2. It is 10 or less.

According to the pneumatic tire according to the present invention, it is possible to achieve both fuel efficiency and wet performance in a well-balanced manner.

1 is a perspective view of a pneumatic tire that is an example of an embodiment. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of a pneumatic tire that is an example of an embodiment, showing a half cross section in the axial direction of the tire. FIG. 3 is a diagram schematically showing the shape of the ground contact surface of the tread. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a pneumatic tire that is an example of an embodiment, and is an enlarged view of a portion of a tread. It is a top view of the pneumatic tire which is another example of embodiment, Comprising: It is a figure which expands and shows a part of tread.

Hereinafter, an example of an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. The embodiments described below are merely examples, and the present invention is not limited to the following embodiments. Further, the present invention includes a form in which each component of the embodiments described below is selectively combined.

FIG. 1 is a perspective view of a pneumatic tire 1 that is an example of an embodiment. In FIG. 1, the internal structure of the pneumatic tire 1 is also illustrated. As shown in FIG. 1, the pneumatic tire 1 includes a tread 10, which is the part that contacts the road surface, a pair of sidewalls 12 placed on both sides of the tread 10, and a pair of sidewalls 12 placed on the inside of the sidewalls 12 in the tire radial direction. The tire includes a pair of beads 14, a carcass 15 spanning between the pair of beads 14, and an inner liner 16 disposed inside the carcass 15 in the tire radial direction.

The pneumatic tire 1 is a tire that has a specified mounting direction on a vehicle, and the mounting direction on the vehicle is opposite on the right side and the left side of the vehicle. The tread 10 has a tread pattern that is asymmetrical with respect to the tire equator CL (see FIG. 2). Note that the tire equator CL is an imaginary line along the tire circumferential direction that passes through the exact center of the tread 10 in the tire axial direction. In this specification, the term "left and right" is used for convenience of explanation, and the term "left and right" refers to the left and right when the pneumatic tire 1 is mounted on the vehicle in the direction of travel of the vehicle.

The tread 10 is composed of tread rubber 11. In this embodiment, the tread 10 has a main groove 30 (center main groove) formed on the tire equator CL and a pair of main grooves 31 and 32 (shoulder main grooves). The three main grooves 30, 31, and 32 are formed straight along the tire circumferential direction without being bent in the tire axial direction.

The tread 10 has a center rib 40 (first center rib ) defined by the main grooves 30 and 31, and a center rib 50 (second center rib ) defined by the main grooves 30 and 32. The tread 10 also includes a shoulder block 60 (first shoulder block) arranged to face the first center rib 40 in the tire axial direction with the shoulder main groove 31 in between, and a second center rib 50 with the shoulder main groove 32 in between. and a shoulder block 70 (second shoulder block) arranged to face each other in the tire axial direction. Each block is formed straight along the tire circumferential direction. Note that the block is a portion raised outward in the tire radial direction from a position corresponding to the bottom of the main groove, and is also called land.

The sidewall 12 is composed of sidewall rubber 13 of a different type from the tread rubber 11. The sidewalls 12 are arranged on both sides of the tread 10 and are formed in an annular shape along the tire circumferential direction. The sidewall 12 is the part of the pneumatic tire 1 that protrudes most outward in the axial direction of the tire, and is gently curved so as to be convex toward the outer side in the axial direction of the tire. The sidewall 12 has a function of preventing damage to the carcass 15. The sidewall 12 is the part that bends the most when the pneumatic tire 1 acts as a cushion, and is usually made of flexible rubber with fatigue resistance.

The bead 14 is a portion that is arranged inside the sidewall 12 in the tire radial direction and is fixed to the rim of the wheel. The bead 14 has a bead core 17 and a bead filler 18. The bead core 17 is an annular member made of a steel bead wire and extends all around the circumferential direction of the tire, and is embedded in the bead 14 . The bead filler 18 is an annular hard rubber member that has a tapered tip extending outward in the tire radial direction and extends over the entire circumference of the tire circumferential direction.

The carcass 15 is spanned between the pair of beads 14 and is locked by being folded back around the bead core 17. The carcass 15 includes a carcass cord made of organic fibers and topping rubber. The carcass cord is arranged substantially at right angles (eg, 80° to 90°) to the tire circumferential direction. Examples of organic fibers used in the carcass cord include polyester fibers, rayon fibers, aramid fibers, and nylon fibers.

The inner liner 16 covers the inner surface of the tire between the pair of beads 14. The inner liner 16 is made of air-permeable rubber and has the function of maintaining the air pressure of the pneumatic tire 1.

The pneumatic tire 1 includes a belt 19 disposed on the outside of the carcass 15 in the tire radial direction, a cap ply 22 that covers the entire outside of the belt 19 in the tire radial direction, and a belt 19 disposed on the outside of the cap ply 22 in the tire radial direction. The tire further includes an edge ply 23 that covers both ends of the tire in the axial direction. The cap ply 22 and the edge ply 23 have the function of reinforcing the belt 19.

The belt 19 is disposed on the outer peripheral side of the top of the carcass 15, and is provided to overlap the outer peripheral surface of the carcass 15. The belt 19 is formed of a belt ply made of rubber-coated cords arranged in a direction oblique to the tire circumferential direction. The material of the cord of the belt 19 is not particularly limited, and examples thereof include organic fibers such as polyester, rayon, nylon, and aramid, and metals such as steel. In this embodiment, the belt 19 is composed of two belt plies 20 and 21 (see FIG. 2) including steel cords. Note that the number of belt plies is not particularly limited, and may be one or three or more.

Hereinafter, the internal structure of the pneumatic tire 1 will be explained in detail with reference to FIG. 2. FIG. 2 is a cross-sectional view of the pneumatic tire 1 of this embodiment perpendicular to the tire circumferential direction. Note that, except for the tread pattern, the pneumatic tire 1 is symmetrical with respect to the tire equator CL, so FIG. 2 shows only the vehicle outer half of the pneumatic tire 1.

As shown in FIG. 2, the pneumatic tire 1 includes a belt 19 disposed outside the carcass 15 in the tire radial direction. The belt 19 is composed of two belt plies 20 and 21. The belt ply 20 is arranged inside the belt ply 21 in the tire radial direction. The length of the belt ply 20 in the tire axial direction is greater than the length of the belt ply 21 in the tire axial direction. That is, the end portion 20A of the belt ply 20 is located on the outer side in the tire axial direction than the end portion 21A of the belt ply 21. Hereinafter, the end portion 20A of the belt ply 20 will be described as the end portion 19A of the belt 19.

A cap ply 22 and an edge ply 23 are arranged between the tread 10 and the belt 19. In this embodiment, the cap ply 22 and the edge ply 23 are configured as one continuous member. The cap ply 22 and the edge ply 23 are obtained by continuously winding organic fiber cords aligned in the length direction in a spiral shape in the tire circumferential direction. Examples of the organic fibers used for the cap ply 22 and the edge ply 23 include aramid fibers, polyester fibers, and nylon fibers.

The end portion 22A of the cap ply 22 is located further outward in the tire axial direction than the end portion 19A of the belt 19. That is, the cap ply 22 is arranged between the belt 19 and the tread rubber 11 so as to cover the entire outer side of the belt 19 in the tire radial direction.

The edge ply 23 is adjacent to the cap ply 22 on the outside in the tire radial direction, and is arranged so as to cover both ends of the belt 19 . In this embodiment, both ends of the cap ply 22 in the tire axial direction are folded back, and this folded back portion is the edge ply 23. The edge plies 23 arranged at both ends of the belt 19 are spaced apart from each other in the tire axial direction.

As described above, since the cap ply 22 is arranged to cover the entire outer side of the belt 19 in the tire radial direction, the restraining force in the tire radial direction that acts on the belt 19 from the cap ply 22 is limited to the entire tire axial direction. It is relatively uniform. On the other hand, since the edge ply 23 is arranged to cover both ends of the belt 19 in the tire axial direction, the restraining force in the tire radial direction acting on the belt 19 from the edge ply 23 is It acts concentratedly on both ends and the surrounding area.

In FIG. 2, a double-headed arrow LT represents the length in the tire axial direction from the tire equator CL to the end of the tread 10. Here, the end of the tread 10 means the end 11A of the tread rubber 11 in the tire axial direction. This length LT is half the length of the tread 10 in the tire axial direction. Moreover, the double-headed arrow LE represents the length in the tire axial direction from the outer end 23A of the edge ply 23 to the inner end 23B of the edge ply 23. This length LE is half the length of the edge ply 23 in the tire axial direction. Note that the length LT and the length LE mean the length in an unloaded state when the pneumatic tire 1 is assembled to a regular rim and the internal pressure is 0 kPa.

The length LE is 50% or more of the length LT, preferably 55% or more, and more preferably 60% or more. In this case, the restraining force acting on the outer side of the belt 19 in the axial direction of the tire increases, and the shape of the contact surface of the tread 10 can be curved. More specifically, as shown in FIG. 3, with respect to the length (contact length) of the contact patch along the tire circumferential direction on the tire equator CL, the contact distance near both ends (contact edges) in the tire axial direction of the contact patch The length is relatively short, and the shape of the ground contact surface of the tread 10 has a shape close to an ellipse. As a result, water on the road surface is effectively swept left and right along the contour of the contact surface of the tread 10, improving drainage performance and improving wet performance. Furthermore, by shortening the ground contact length near the ground contact end, the frequency of noise generated during running is dispersed, and pattern noise is reduced. Furthermore, since the restraining force acting on the belt 19 increases, vibrations in the tire axial direction during running are suppressed, and road noise is reduced. The upper limit of the length LE is, for example, 80% of the length LT.

It is preferable that the inner end 23B of the edge ply 23 is located inside the shoulder main groove 32 in the tire axial direction. As a result, the restraining force acting on the outer side of the belt 19 in the tire axial direction becomes larger, and it becomes easier to curve the shape of the contact surface of the tread 10.

The 2% modulus of the organic fiber cord used for the edge ply 23 is preferably 3000 N/mm ² or more, more preferably 5000 N/mm ² or more. In this case, wet performance is further improved and pattern noise and road noise can be further reduced. Further, the 2% modulus of the organic fiber cord used for the edge ply 23 is preferably 13,000 N/mm ² or less, more preferably 9,000 N/mm ² or less. In this case, the steering stability during driving is improved. Therefore, an example of a suitable range of the 2% modulus of the organic fiber cord used for the edge ply 23 is 3000 N/mm ² or more and 11000 N/mm ² or less. Note that the measurement of the 2% modulus of the organic fiber cord is performed in accordance with the regulations of "JIS L 1017."

In FIG. 2, a double-headed arrow LS indicates the tire distance from the tire equator CL to the part of the sidewall 12 that protrudes most outward in the tire axial direction when the pneumatic tire 1 is assembled on a regular rim and the internal pressure is 0 kPa under no load. It represents the length in the axial direction. This length LS is half of the tire's maximum cross-sectional width, that is, half of the nominal cross-sectional width. Here, the length LT is preferably 84% or more and 87% or less of the length LS. If the length LT is within this range, pattern noise and road noise can be easily reduced. In this specification, the "nominal cross-sectional width" is the "nominal cross-sectional width" included in the "tire designation" defined in JIS D4202 "Automotive Tires - Nomenclature and Specifications."

In this embodiment, as shown in FIG. 2, the reinforcing rubber layer 24 is placed between the two carcass 15 at a position between the end 19A of the belt 19 and the tip 18A of the bead filler 18. ing. The reinforcing rubber layer 24 extends annularly along the tire circumferential direction. The reinforcing rubber layer 24 has a function of improving the rigidity of the sidewall 12.

The reinforcing rubber layer 24 is preferably arranged in a range of 20% or more and 60% or less of the tire cross-sectional height H based on the bead baseline BL, and 30% or more and 50% or less of the tire cross-sectional height H. It is more preferable to arrange it within the range of . When the reinforcing rubber layer 24 is arranged within this range, the rigidity of the sidewall 12 is improved, vibration transmission from the tread 10 to the bead 14 is suppressed, and road noise is further reduced. Here, the bead baseline BL is a virtual straight line in the tire axial direction that defines the rim diameter of the standard rim, and the tire cross-sectional height H is the unloaded state when the pneumatic tire 1 is assembled to the regular rim and the internal pressure is 0 kPa. is the distance in the tire radial direction from the bead baseline BL to the outer surface of the tread 10 at the tire equator CL position.

The thickness of the reinforcing rubber layer 24 is preferably 0.4 mm or more and 3.0 mm or less. If the thickness of the reinforcing rubber layer 24 is within this range, the effect of reducing road noise will be more pronounced. Although the thickness of the reinforcing rubber layer 24 may vary in the tire radial direction, in this embodiment, the reinforcing rubber layer 24 has a constant thickness across the tire radial direction.

The rubber hardness of the reinforcing rubber layer 24 is preferably higher than the rubber hardness of the sidewall 12 and lower than the rubber hardness of the bead filler 18. In this case, the effect of reducing road noise becomes more significant. For example, the bead filler 18 has a rubber hardness of 85 to 100, the reinforcing rubber layer 24 has a rubber hardness of 70 to 85, and the sidewall 12 has a rubber hardness of 45 to 70. In addition, the above-mentioned rubber hardness is a hardness measured by a method based on JIS K6253 described in Examples.

Hereinafter, the contact surface of the tread 10 of the pneumatic tire 1 will be explained in detail with reference to FIG. FIG. 3 is a diagram schematically showing the shape of the ground contact surface of the tread 10.

As mentioned above, by setting the length of the edge ply 23 in the tire axial direction to 50% or more of the length of the tread 10 in the tire axial direction, the restraining force acting on the outer side of the belt 19 in the tire axial direction increases, The shape of the ground contact surface of the tread 10 is curved. Therefore, as shown in FIG. 3, the contact surface of the tread 10 has a contact length (L2) near the contact edge that is relatively short compared to the contact length (L1) on the tire equator CL, and has a shape close to an ellipse. . Here, the ground contact length (L1) is a load equivalent to 70.4% of the regular load when an unused pneumatic tire is mounted on a regular rim and filled with air to the specified internal pressure. This is the length of the contact patch along the tire circumferential direction on the tire equator CL when . Further, the contact length (L2) is the length of the contact patch along the tire circumferential direction at a position 10 mm inside in the tire axial direction from both ends of the contact patch in the tire axial direction, which was determined under the above measurement conditions. Note that the predetermined internal pressure under the above measurement conditions is 200 kPa when the tire's aspect ratio is 60% or more, and is 220 kPa when the tire's aspect ratio is less than 60%. In addition, for tires described as Extra Load, the predetermined internal pressure under the above measurement conditions is 240 kPa when the aspect ratio is 60% or more, and 260 kPa when the aspect ratio is less than 60%. be.

In this specification, L2/L1 is defined as the rectangularity of the ground contact surface of the tread 10. In addition, in this embodiment, the ground contact length (L2) is substantially the same length on the left and right sides of the tread 10.

Here, the rectangularity of the ground contact surface of the tread 10 is preferably 0.85 or less, more preferably 0.83 or less. In this case, it becomes easy to improve wet performance and noise performance. Further, the rectangularity of the ground contact surface of the tread 10 is preferably 0.75 or more, and more preferably 0.77 or more. In this case, steering stability is improved. Therefore, an example of a suitable range of the rectangularity of the ground contact surface of the tread 10 is 0.75 or more and 0.85 or less, more preferably 0.77 or more and 0.83 or less.

Hereinafter, the tire tread rubber composition (hereinafter simply referred to as a rubber composition) constituting the tread rubber 11 will be explained in detail.

The rubber composition of the present invention has a ratio of loss tangent at 0°C (0°C tan δ) to loss tangent at 35°C (35°C tan δ) (0°C tan δ/35°C tan δ) of 1.35 or more, 2.10 or less. By applying the rubber composition to the tread rubber 11 having the tread pattern described below, it is possible to provide a pneumatic tire that achieves both fuel efficiency and wet performance in a well-balanced manner. In the present invention, 35°C tan δ is a value measured for the rubber composition after vulcanization under the conditions of temperature 35°C, initial strain 10%, dynamic strain 1%, and frequency 10Hz as described in the examples. , 0° C. tan δ is a value measured for the rubber composition after vulcanization under the conditions described in the examples at a temperature of 0° C., an initial strain of 10%, a dynamic strain of 1%, and a frequency of 10 Hz.

From the viewpoint of improving wet performance, the 0° C. tan δ/35° C. tan δ of the rubber composition is preferably 1.95 or less, more preferably 1.90 or less. Further, from the viewpoint of improving fuel efficiency, 0°C tan δ/35°C tan δ is preferably 1.50 or more, more preferably 1.45 or more, and even more preferably 1.50 or more. .

The 35°C tan δ of the rubber composition may satisfy 1.35≦0°C tan δ/35°C tan δ≦2.10, but from the viewpoint of further improving fuel efficiency, it is preferably 0.18 or less, and 0. More preferably, it is .17 or less. Further, the 35° C. tan δ is preferably 0.15 or more from the viewpoint of improving steering stability. Therefore, an example of a suitable range for the loss tangent tan δ is 0.15 or more and 0.18 or less.

The 0°C tan δ of the rubber composition may satisfy 1.35≦0°C tan δ/35°C tan δ≦2.10, but from the viewpoint of further improving wet performance, it is 0.24 or more and 0.31 or less. It is preferably 0.25 or more and 0.30 or less.

The rubber composition includes a rubber component containing styrene-butadiene-based rubber and isoprene-based rubber. By containing these two types of rubber, a rubber composition with improved processability can be obtained while exhibiting the effects of the present invention.

The styrene-butadiene rubber is not particularly limited as long as it has a styrene unit and a butadiene unit, and examples include emulsion polymerization styrene butadiene rubber (E-SBR) and solution polymerization styrene butadiene rubber (S-SBR). It will be done. In addition, in the styrene-butadiene rubber, the total content of styrene units and butadiene units in 100 parts by mass of rubber is, for example, 95 parts by mass or more, and may be 98 parts by mass or more, or 100 parts by mass. Although one type of these styrene-butadiene rubbers may be used alone, it is preferable to use two or more types in combination.

The styrene-butadiene rubber may be either unmodified SBR or modified SBR, but preferably contains modified SBR. Containing modified SBR tends to reduce rolling resistance and provide good fuel efficiency. In this specification, "modified" in the rubber component refers to a rubber component that has a functional group that is reactive with silica, and "unmodified" refers to a rubber component that has a functional group that is reactive with silica. Refers to something that does not. Examples of functional groups that are reactive with silica include hydroxyl groups, amino groups, carboxyl groups, alkoxy groups, alkoxysilyl groups, and epoxy groups. or may be introduced into the molecular chain.

As the styrene-butadiene rubber, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., ENEOS Materials Co., Ltd., Asahi Kasei Co., Ltd., Nippon Zeon Co., Ltd., etc. can be used.

In the above rubber composition, the content of styrene-butadiene rubber in 100 parts by mass of the rubber component is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and 50 parts by mass or more. is even more preferable. By setting the content of styrene-butadiene rubber to 30 parts by mass or more, good fuel efficiency tends to be obtained. Further, the content of the styrene-butadiene rubber is preferably 80 parts by mass or less. There is a concern that processability may deteriorate if a large amount of styrene-butadiene rubber is used, but by controlling the content of styrene-butadiene rubber to 80 parts by mass or less, deterioration in processability can be suppressed. Therefore, an example of a suitable range for the content of the styrene-butadiene rubber is 30 parts by mass or more and 80 parts by mass or less.

The glass transition temperature (Tg) of the styrene-butadiene rubber is preferably -70°C or more and -20°C or less from the viewpoint of obtaining the effects of the present invention satisfactorily. Here, the glass transition temperature of the styrene-butadiene rubber was determined by the differential scanning calorimetry (DSC) method in accordance with JIS K7121 at a heating temperature of 20°C/min (measurement temperature range: -150°C to 50°C). ) is measured.

As the isoprene rubber, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used, but from the viewpoint of improving wet performance, natural rubber is preferable. In addition to unmodified natural rubber (NR), natural rubber includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high purity natural rubber (UPNR), and grafted natural rubber. It also includes modified natural rubber such as synthetic natural rubber. These rubbers may be used alone or in combination of two or more.

In the above rubber composition, the content of isoprene rubber in 100 parts by mass of the rubber component is preferably 15 parts by mass or more, more preferably 20 parts by mass or more, and preferably 25 parts by mass or more. More preferred.

The rubber component may contain rubber components other than styrene-butadiene rubber and isoprene rubber. Examples of other rubber components include diene rubbers such as butadiene rubber (BR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and butyl rubber (IIR). These rubber components may be used alone or in combination of two or more.

The butadiene rubber (BR) is not particularly limited as long as it is a polymer whose main unit is a butadiene unit, and for example, BR with a high cis content, BR with a low cis content, etc. can be used. These may be used alone or in combination of two or more.

In this embodiment, carbon black and silica are used as reinforcing fillers.

The carbon black is not particularly limited, and various known types can be used. For example, it is preferable to use carbon black having a nitrogen adsorption specific surface area (N ₂ SA) (JIS K6217-2) of 70 to 150 m ² /g. Specifically, SAF class (N100 series), ISAF class (N200 series), and HAF class (N300 series) carbon black are exemplified. These grades of carbon black may be used alone or in combination of two or more.

The blending amount of carbon black is preferably less than 10 parts by mass, and preferably less than 8 parts by mass, based on 100 parts by mass of the rubber component. By reducing the amount of carbon black blended, the hardness of the rubber composition can be reduced and the noise performance can be improved. Further, the lower limit of the amount of carbon black added is, for example, more than 2 parts by mass. Therefore, an example of a suitable range for the amount of carbon black blended is more than 2 parts by mass and less than 10 parts by mass, and more preferably more than 2 parts by mass and less than 8 parts by mass.

The silica is not particularly limited, and, for example, wet silica such as wet precipitation silica or wet gel silica may be used. The BET specific surface area of silica (measured according to the BET method described in JIS K6430) is not particularly limited, and may be, for example, 90 to 250 m ² /g, or 150 to 220 m ² /g.

The amount of silica blended is preferably more than 60 parts by mass, more preferably 65 parts by mass or more, based on 100 parts by mass of the rubber component. Wet performance is improved by making the blending amount of silica more than 60 parts by mass. Further, the amount of silica blended is preferably less than 90 parts by mass, and more preferably 85 parts by mass or less. By setting the amount of silica to be less than 90 parts by mass, rolling resistance is reduced. Therefore, one example of a suitable range for the amount of silica is more than 60 parts by mass and less than 90 parts by mass.

In addition to the above-mentioned components, the rubber composition of this embodiment includes a silane coupling agent, stearic acid, zinc oxide, wax, anti-aging agent, oil, vulcanization accelerator, vulcanizing agent, etc. Various additives commonly used in products can be blended.

As the silane coupling agent, known silane coupling agents such as sulfide silane and mercaptosilane can be used. The amount of the silane coupling agent is not particularly limited, but it is preferably 2 parts by mass or more and 20 parts by mass or less, more preferably 5 parts by mass or more and 15 parts by mass or less of the silica content.

As the oil, various oils that are generally blended into rubber compositions can be used. For example, at least one mineral oil selected from the group consisting of paraffin oil, naphthenic oil, and aromatic oil may be used. The content of oil is not particularly limited, and may be, for example, 40 parts by mass or less, or 30 parts by mass or less with respect to 100 parts by mass of the rubber component.

Sulfur is preferably used as the vulcanizing agent. The amount of the vulcanizing agent is not particularly limited, and may be, for example, 0.1 parts by mass or more and 5 parts by mass or less, or 0.5 parts by mass or more and 3 parts by mass or less, based on 100 parts by mass of the rubber component. .

Examples of the vulcanization accelerator include various vulcanization accelerators such as sulfenamide type, thiuram type, thiazole type, and guanidine type. These vulcanization accelerators may be used alone or in combination of two or more. The amount of the vulcanization accelerator to be blended is not particularly limited, and may be, for example, 0.1 parts by mass or more and 5 parts by mass or less, or 0.5 parts by mass or more and 3 parts by mass or less, based on 100 parts by mass of the rubber component. good.

The rubber composition according to the present embodiment can be produced by kneading in accordance with a conventional method using a commonly used mixer such as a Banbury mixer, a kneader, or a roll. That is, for example, in the first mixing stage (non-professional kneading process), additives other than the vulcanizing agent and the vulcanization accelerator are added and mixed with the rubber component together with carbon black and silica, and then the resulting mixture is mixed with carbon black and silica. An unvulcanized rubber composition can be prepared by adding and mixing a vulcanizing agent and a vulcanization accelerator in the final mixing step (professional kneading step).

Note that the non-professional kneading step may be performed as a single mixing step, or may be divided into a plurality of mixing steps in which mixing and discharging are repeated. For example, the non-pro kneading process includes a first non-pro kneading process in which the entire amount of the rubber component and carbon black is mixed with a portion of silica and a silane coupling agent, and a mixture of silica and a silane coupling agent in the first non-pro kneading process. It may also include a second non-professional kneading step of mixing a portion of the zinc oxide and the entire amount of zinc oxide and the anti-aging agent. By carrying out the mixing process in multiple steps, it is possible to uniformly form a chemical bond between the filler and the polymer.

Hereinafter, the tread pattern of the pneumatic tire 1 will be explained in detail with reference to FIG. 4. FIG. 4 is a plan view of the pneumatic tire 1 (tread 10).

As shown in FIG. 4, the tread 10 has a tread pattern that is asymmetrical with respect to the tire equator CL. Hereinafter, the area closer to the ground contact edge E1 than the tire equator CL will be referred to as a first area 10A, and the area closer to the ground contact edge E2 than the tire equator CL will be referred to as a second area 10B. In this specification, "ground contact edges E1 and E2" refer to the points when an unused pneumatic tire 1 is mounted on a regular rim and filled with air to a regular internal pressure and a predetermined load is applied. , is defined as both axial ends of the tire's contact area (contact area) on a flat road surface. In the case of passenger car tires, the predetermined load is a load equivalent to 88% of the regular load. The tread pattern of the pneumatic tire 1 exhibits the effects of the present invention when the tire is mounted on a vehicle such that the first region 10A is located on the inside of the vehicle and the second region 10B is located on the outside of the vehicle. .

The tread 10 includes a center main groove 30 formed on the tire equator CL, a shoulder main groove 31 formed between the tire equator CL and a ground contact edge E1 on the inside of the vehicle, and a center main groove 31 formed on the tire equator CL and a ground contact edge on the outside of the vehicle. It has a shoulder main groove 32 formed between E2 and a plurality of blocks partitioned by the three main grooves 30, 31, and 32. Note that the number of main grooves is not limited to three, and may be two or four or more.

The shoulder main grooves 31 and 32 are preferably formed at positions equidistant from the tire equator CL (center main groove 30). Thereby, the rigidity balance in the left and right regions with the tire equator CL as a boundary becomes good, and the effects of the present invention are more clearly exhibited.

The total width of the three main grooves 30, 31, and 32 is 3% or more of the length along the tire axial direction from the ground contact edge E1 to the ground contact edge E2 (hereinafter referred to as "tire ground contact width"). It is preferably 5% or more, more preferably 8% or more. In this case, drainage performance is improved and wet performance is significantly improved. Further, the total width of the three main grooves 30, 31, and 32 is preferably 30% or less, more preferably 28% or less, and even more preferably 25% or less of the tire ground contact width. . In this case, excellent steering stability can be ensured. Therefore, an example of a suitable range for the total width of the three main grooves 30, 31, and 32 is 5% or more and 30% or less of the tire ground contact width. Further, when more emphasis is placed on improving wet performance, the total width of the three main grooves 30, 31, and 32 may be 10% or more and 30% or less of the tire ground contact width. In this specification, the width of the groove means the width in the profile plane along the ground contact surface of the tread 10, unless otherwise specified.

The width of the shoulder main grooves 31 and 32 is preferably larger than the width of the center main groove 30 formed on the tire equator CL. In this case, drainage performance is improved and wet performance is significantly improved. The width of the center main groove 30 is, for example, 8 mm or more and 14 mm or less, and the width of the shoulder main grooves 31 and 32 is, for example, 9 mm or more and 15 mm or less. The depth of the three main grooves 30, 31, and 32 is not particularly limited, and is, for example, 7 mm or more and 15 mm or less.

At least one of the three main grooves 30, 31, 32 is generally provided with a wear indicator (not shown). The wear indicator is a protrusion placed at the bottom of the groove, and serves as an index for checking the wear level of the tread rubber.

The walls of the three main grooves 30, 31, and 32 are inclined so that the groove width gradually becomes narrower toward the groove bottom. The walls of the main groove constitute the side walls of the block, so in other words, the side walls of the block are inclined such that the width of the block increases as it moves away from the ground plane.

The tread 10 has a first center rib 40 defined by main grooves 30 and 31 and a second center rib 50 defined by main grooves 30 and 32. The tread 10 also includes a first shoulder block 60 that is arranged to face the first center rib 40 in the axial direction of the tire with the shoulder main groove 31 in between, and a second center rib 50 that is arranged to face the first center rib 40 in the axial direction of the tire with the shoulder main groove 32 in between. and a second shoulder block 70 disposed opposite to the second shoulder block 70 .

The first center rib 40 and the second center rib 50 are rib-shaped blocks that are continuous in the tire circumferential direction. In addition, in this specification, a "rib-shaped block" means a block in which a groove with a width of more than 2 mm is not formed. By making the first center rib 40 and the second center rib 50 continuous rib-shaped blocks in the tire circumferential direction, the rigidity of the tread 10 is improved. As a result, the amount of deformation of the tread rubber 11 when the vehicle is running is reduced, thereby reducing the amount of energy loss and reducing rolling resistance.

When wide grooves are present in the first center rib 40 and the second center rib 50, the rigidity of the tread 10 tends to decrease. As a result, when a rubber composition with low rolling resistance is applied to the tread rubber 11, steering stability may deteriorate. According to the pneumatic tire 1 of the present embodiment, since wide grooves are not formed in the first center rib 40 and the second center rib 50, even when a rubber composition with low rolling resistance is applied to the tread rubber 11, Even if there is, steering stability can be ensured. In other words, it is possible to improve fuel efficiency while ensuring steering stability.

The first center rib 40 and the second center rib 50 are separated by the center main groove 30. Further, the first center rib 40 is separated from the first shoulder block 60 by the shoulder main groove 31, and the second center rib 50 is separated from the second shoulder block 70 by the shoulder main groove 32. In this embodiment, the first center rib 40 and the second center rib 50 have the same width. Further, the first shoulder block 60 and the second shoulder block 70 are formed wider than the first center rib 40 and the second center rib 50, and have the same width. The pneumatic tire 1 has excellent performance not only on dry roads but also on wet roads, snowy and icy roads, and is suitable as an all-season tire.

Hereinafter, the center ribs 40, 50 and the shoulder blocks 60, 70 that constitute the tread 10 will be explained in further detail with reference to FIG. 4.

[First center rib 40]
The first center rib 40 is formed straight along the tire circumferential direction and has a constant width over its entire length. The width of the contact surface of the first center rib 40 has a width corresponding to, for example, 12 to 25% of the tire contact width. If the width of the first center rib 40 is within this range, steering stability will be improved. An example of the width of the first center rib 40 is 15 mm or more and 35 mm or less.

A plurality of sipes 41 are formed on the first center rib 40 at intervals in the tire circumferential direction. In this specification, a narrow groove with a groove width of 2.0 mm or less is defined as a sipe. The width of the sipe is, for example, 0.5 mm or more and 1.5 mm or less, or 0.5 mm or more and 1.0 mm or less. The sipes 41 contribute to improving steering stability and wet performance. Although another sipe having a different shape from the sipe 41 may be formed on the first center rib 40, only the sipe 41 is formed in this embodiment. Each sipe 41 has substantially the same shape. As will be described in detail later, the number of sipes that cross the first center rib 40 is greater than the number of sipes that cross the second center rib 50.

For example, the sipes 41 may be formed at a variable pitch in which the spacing between the sipes is slightly changed in units of a predetermined number in the tire circumferential direction, or may be formed at the same spacing. The interval between the sipes 41 adjacent to each other in the tire circumferential direction is, for example, smaller than the width of the center main groove 30, and is 5 mm or more and 30 mm or less. Further, the distance between the sipes 41 is smaller than the distance between the sipes formed on the second center rib 50.

The sipe 41 has a bent portion 42 that is bent so as to protrude toward one side in the tire circumferential direction from both longitudinal ends of the sipe in a plan view of the first center rib 40 . By having the bent portion 42, even when a rubber composition with low rolling resistance is applied to the tread rubber 11, excellent braking performance is exhibited due to the edge effect of the sipes 41. When braking the vehicle, the ground contact area becomes large in the first region 10A on the inside of the vehicle, so forming many sipes 41 on the first center rib 40 increases the edge effect and greatly improves braking performance on wet road surfaces. Further, the greatly bent sipes 41 increase the edge component in the lateral direction, and improve the steering stability when the vehicle turns.

The sipe 41 is a sipe that crosses the first center rib 40. Since the sipes 41 cross the first center rib 40 and communicate with the main grooves 30 and 31, the number of channels through which air flows increases in the axial center of the tread 10. As a result, the frequency of air columnar resonance that occurs during running is dispersed, and pattern noise is reduced.

The depth of the sipe 41 is, for example, 60 to 90% of the depth of the center main groove 30 at its deepest portion. The depth of the sipe 41 may be shallower in a predetermined length range from both lengthwise ends than in other parts. In this case, a decrease in the rigidity of the first center rib 40 due to the formation of the sipes 41 can be suppressed, and steering stability is improved. The predetermined length range is, for example, a length range corresponding to 3 to 10% of the width of the first center rib 40.

[Second center rib 50]
As described above, the second center rib 50 is arranged to face the first center rib 40 in the tire axial direction with the center main groove 30 in between, and is formed straight along the tire circumferential direction. The width of the contact surface of the second center rib 50 is, for example, 12 to 25% of the tire contact width. If the width of the second center rib 50 is within this range, steering stability will be improved. In this embodiment, the second center rib 50 has the same width as the first center rib 40, and is formed with a constant width over the entire length.

A plurality of first sipes 51 are formed on the second center rib 50 at intervals in the tire circumferential direction. For example, the plurality of first sipes 51 may be formed at a variable pitch in which the spacing between the sipes is slightly changed in units of a predetermined number in the tire circumferential direction, or may be formed at the same spacing. Although only the first sipe 51 may be formed on the second center rib 50, in this embodiment, in addition to the first sipe 51, three types of sipes (second sipe 52, third sipe 53, and a fourth sipe 54) are formed.

The first sipe 51 is a sipe that crosses the second center rib 50 and is connected to the main grooves 30 and 32. It is preferable that the first sipe 51 has a substantially S-shape when the second center rib 50 is viewed from above. In this case, even if a rubber composition with low rolling resistance is applied to the tread rubber 11, the steering stability when the vehicle turns is further improved.

In the second center rib 50, a second sipe group consisting of a plurality of second sipes 52 and a third sipe group consisting of a plurality of third sipes 53 are arranged in a region overlapping with each of the first sipes 51 in the tire axial direction. is formed. The second sipe 52 extends from the center main groove 30 and terminates within the block, and the third sipe 53 extends from the shoulder main groove 32 and terminates within the block. The second sipe 52 and the third sipe 53 are short sipes formed at a predetermined distance from the first sipe 51. Further, each sipe is inclined at a predetermined angle with respect to the tire axial direction and the circumferential direction.

In this embodiment, the second sipe group that overlaps one first sipe 51 in the tire axial direction is composed of three second sipes 52. The three second sipes 52 are, for example, formed parallel to each other at equal intervals. Similarly, the third sipe group is composed of three third sipes 53 formed in parallel with each other at equal intervals. The plurality of second sipes 52 constituting each second sipe group have different lengths, and the longer they get closer to the first sipe 51. Further, the plurality of third sipes 53 constituting each third sipe group have different lengths, and the closer they are to the first sipe 51, the longer the third sipes 53 are.

That is, each of the second sipes 52 extending from the center main groove 30 is longer in the region where the first sipe 51 is convex in the direction of the shoulder main groove 32, and shorter in the region where the first sipe 51 is convex in the direction of the center main groove 30. ing. The third sipe 53 extending from the shoulder main groove 32 is long in the region where the first sipe 51 is convex in the direction of the center main groove 30, and short in the region where the first sipe 51 is convex in the direction of the shoulder main groove 32. In this case, the rigidity balance of the second center rib 50 is improved, and more reliable tire performance can be achieved.

A substantially linear fourth sipe 54 that crosses the second center rib 50 is formed in a region between the first sipes 51 of the second center rib 50 . That is, in the second center rib 50, the first sipes 51 and the fourth sipes 54 are arranged alternately in the tire circumferential direction. The fourth sipe 54 is formed parallel to the second sipe 52 and the third sipe 53, and extends straight without bending in the middle.

The fourth sipe 54 plays an important role in noise reduction. Specifically, the fourth sipe 54 communicates with the main grooves 30 and 32, thereby increasing the number of channels through which air flows. As a result, the frequency of air columnar resonance that occurs during running is dispersed, and pattern noise is reduced.

The depth of each sipe formed in the second center rib 50 may be the same. The depth of each sipe is, for example, 60 to 90% of the depth of the center main groove 30 at the deepest part. In this embodiment, the second sipe 52 and the third sipe 53, which are shorter in length, have a constant depth over their entire length. On the other hand, the first sipe 51 and the fourth sipe 54 are shallower in a predetermined length range from both longitudinal ends than in other parts. In this case, it is possible to suppress a decrease in the rigidity of the second center rib 50 due to the formation of sipes. The predetermined length range is, for example, a length range corresponding to 3 to 10% of the width of the second center rib 50.

It is preferable that the number of sipes crossing the second center rib 50 is smaller than the number of sipes crossing the first center rib 40. In the first center rib 40, all the sipes cross the block, but in the second center rib 50, the second sipe 52 and the third sipe 53 terminate within the block, and the first sipe 51 and the fourth sipe 54 crosses the block. Moreover, the interval in the tire circumferential direction between the sipes formed in each block is larger in the second center rib 50 than in the first center rib 40. Therefore, when comparing the center ribs 40 and 50, the number of sipes crossing the block is significantly reduced in the second center rib 50.

Furthermore, when the second sipe 52 and the third sipe 53 arranged on the same straight line are counted as one, the number of sipes on the first center rib 40 is greater than the number of sipes on the second center rib 50. Good too. In this case, the number of sipes of the first center rib 40 is, for example, 1.1 to 1.5 times the number of sipes of the second center rib 50. Alternatively, when each of the second sipe 52 and the third sipe 53 is counted as one, the number of sipes of the first center rib 40 may be greater than the number of sipes of the second center rib 50. By setting the number of sipes of the first center rib 40>the number of sipes of the second center rib 50, the frequency of air columnar resonance generated during running is dispersed, and pattern noise is reduced. Furthermore, it becomes easier to achieve both braking performance and handling stability at a higher level.

[First shoulder block 60]
The first shoulder block 60 is arranged to face the first center rib 40 in the tire axial direction with the shoulder main groove 31 in between, and is formed straight along the tire circumferential direction. The width of the contact surface of the first shoulder block 60 is, for example, 15 to 35% of the tire contact width, and is larger than the width of the contact surface of the first center rib 40. In this embodiment, the first shoulder block 60 has the same width as the second shoulder block 70, and is formed with a constant width over the entire length.

Two types of lateral grooves 61 and 62 having different lengths are formed in the first shoulder block 60 as lateral grooves extending in the tire axial direction and connected to the shoulder main groove 31. Each of the lateral grooves has a length extending from the shoulder main groove 31 to the ground contact end E1, and crosses the ground contact surface of the first shoulder block 60. The lateral grooves 61 and 62 have a width of more than 2 mm and are distinguished from sipes, which are thin linear grooves. As described above, the first shoulder block 60 has a ground contact surface divided in the tire circumferential direction by the lateral grooves 61 and 62.

In this specification, the expression "the lateral grooves extend in the axial direction of the tire" refers to a form in which the lateral grooves extend along the axial direction of the tire, and a form in which the lateral grooves extend at an inclination angle of 45 degrees or less, preferably 30 degrees or less with respect to the tire axial direction. Both are intended. The same applies to the main groove extending in the tire circumferential direction, and the main groove may be formed in a zigzag shape while being bent at an inclination angle of 45° or less with respect to the tire circumferential direction.

The lateral grooves 61 and 62 have, for example, a constant width from the shoulder main groove 31 to the ground contact end E1. By forming the lateral grooves 61 and 62 connected to the shoulder main groove 31, drainage performance is improved and wet performance is significantly improved. If the lateral grooves 61, 62 are communicated with the shoulder main groove 31, air will flow from the shoulder main groove 31 into the lateral grooves 61, 62, which is expected to increase noise and air resistance. Since they are arranged inside the vehicle, the influence of the lateral grooves 61 and 62 is small. Note that the lateral groove 62 is formed linearly over the entire length. The lateral groove 61 is formed in a straight line up to a position beyond the ground contact edge E1, and curved to one side in the tire circumferential direction at or near the boundary with the sidewall 12.

In the first shoulder block 60, two types of sipes (a first sipe 63 and a second sipe 64) having different lengths are formed in a region located between the lateral grooves 61 and 62. Each of the sipes has a length extending from the shoulder main groove 31 to the ground contact end E1, and is connected to each other at the shoulder of the pneumatic tire 1. The second sipe 64 is longer than the first sipe 63 and has the same length as the lateral groove 62. Grooves and sipes are repeatedly formed in the first shoulder block 60 in the order of a lateral groove 61, a first sipe 63, a second sipe 64, and a lateral groove 62 in the tire circumferential direction. Note that the plurality of grooves and sipes are formed, for example, at a variable pitch.

The lateral grooves 61 and 62, the first sipe 63, and the second sipe 64 are formed substantially parallel to each other and are inclined with respect to the tire axial direction. The angle of inclination of the lateral grooves and the sipes is smaller than the angle of inclination of the sipes of the center ribs 40 and 50, for example.

[Second shoulder block 70]
The second shoulder block 70 is arranged to face the second center rib 50 in the tire axial direction with the shoulder main groove 32 in between, and is formed straight along the tire circumferential direction. The width of the contact surface of the second shoulder block 70 is, for example, 20 to 35% of the tire contact width, and is larger than the second center rib 50. The second shoulder block 70 does not have a groove that crosses the ground contact surface of the block, but is continuous in the tire circumferential direction.

The second shoulder block 70 is common to the first shoulder block 60 in that it has lateral grooves 71 and 72, a first sipe 73, and a second sipe 74 that extend in the tire axial direction. Note that the lateral groove 71, which is the longer groove, is curved in the opposite direction to the lateral groove 61 of the first shoulder block 60 at or near the boundary with the sidewall 12. Grooves and sipes are repeatedly formed in the second shoulder block 70 in the order of a lateral groove 71, a second sipe 74, a first sipe 73, and a lateral groove 72 in the tire circumferential direction. On the other hand, the second shoulder block 70 differs from the first shoulder block 60 in that the lateral grooves 71 and 72 are not directly connected to the shoulder main groove 32.

In this embodiment, the lateral grooves 71 and 72 are connected to the shoulder main groove 32 via the third sipe 75. In this case, it is possible to suppress air from flowing into the lateral grooves 71 and 72 from the shoulder main groove 32 and being released to the outside of the vehicle, so that the noise suppression effect becomes more pronounced. Moreover, the air resistance of the pneumatic tire 1 is also effectively reduced. Noise and air resistance are more influenced by the groove configuration of the second shoulder block 70 located on the outside of the vehicle than the first shoulder block 60 located on the inside of the vehicle. Although the length of the third sipe 75 is not particularly limited, a preferred example is 5 to 40% or 10 to 30% of the width of the ground contact surface of the second shoulder block 70. For example, each of the third sipes 65 has the same length.

Further, as illustrated in FIG. 5, the lateral grooves 61 and 62 formed in the first shoulder block 60 are connected to the shoulder main groove 3 through the third sipe 65, similarly to the lateral grooves 71 and 72 of the second shoulder block 70. It may be connected to That is, in the tread pattern illustrated in FIG. 4, the connection forms of the lateral grooves and the main grooves are different in the left and right shoulder blocks 60, 70, but in the tread pattern illustrated in FIG. The connection form of the grooves is the same. The length, width, depth, etc. of the third sipe 65 may be substantially the same as the third sipe 75 of the second shoulder block 70.

Examples will be shown below, but the present invention is not limited to these Examples.

Using a Banbury mixer, in the first mixing stage, other compounding ingredients except sulfur and vulcanization accelerator were added to the rubber component and kneaded (discharged) according to the compounding amounts (parts by mass) shown in Table 1 below. Then, in the final mixing stage, sulfur and a vulcanization accelerator were added to the resulting kneaded product and kneaded (discharge temperature = 90°C) to prepare a rubber composition. Details of each component in Table 1 are as follows.

・SBR1: "HPR355" manufactured by ENEOS Materials Co., Ltd. (modified solution polymerization SBR with Tg = -21°C)
・SBR2: "HPR850" manufactured by ENEOS Materials Co., Ltd. (modified solution polymerization SBR at Tg = -24°C)
・SBR3: "HPR350" manufactured by ENEOS Materials Co., Ltd. (modified solution polymerization SBR with Tg = -32°C)
・SBR4: "HPR840" manufactured by ENEOS Materials Co., Ltd. (modified solution polymerization SBR with Tg = -60°C)
・SBR5: "Tuf1834" manufactured by Asahi Kasei Corporation (solution polymerization SBR with Tg = -68°C)
・SBR6: “SBR0122” manufactured by ENEOS Materials Co., Ltd. (unmodified ESBR with Tg = -40°C)
・BR: “BR150B” manufactured by Ube Industries, Ltd.
・NR:RSS#3
・Carbon black 1: “Seest 6” manufactured by Tokai Carbon Co., Ltd.
・Carbon black 2: "Seest KH" manufactured by Tokai Carbon Co., Ltd.
・Silica: "Ultrasil VN3" manufactured by Evonik Industries
・Silane coupling agent: “Si75” manufactured by Evonik Industries
・Oil 1: Aroma oil, “Process NC140” manufactured by JX Nippon Oil & Energy Corporation
・Oil 2: Aroma oil, “Process P200” manufactured by JX Nippon Oil & Energy Corporation
・Resin: C5/C9 aliphatic/aromatic copolymer hydrocarbon resin, “Petrotac 90” manufactured by Tosoh Corporation (glass transition temperature: 65°C, softening point: 95°C)
・Stearic acid: "Lunac S-20" manufactured by Kao Corporation
・Zinc oxide: “Zinc oxide type 3” manufactured by Mitsui Mining & Smelting Co., Ltd.
・Wax: “OZOACE0355” manufactured by Nippon Seizu Co., Ltd.
・Anti-aging agent 1: “Nocrac 6C” manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
・Anti-aging agent 2: “Antage RD” manufactured by Kawaguchi Chemical Industry Co., Ltd.
・Vulcanization accelerator 1: “Noxeler D” manufactured by Ouchi Shinko Chemical Industry Co., Ltd.
・Vulcanization accelerator 2: "Soccinol CZ" manufactured by Sumitomo Chemical Co., Ltd.
・Sulfur: “Powdered sulfur” manufactured by Tsurumi Chemical Industry Co., Ltd.

Each of the unvulcanized rubber compositions of Examples 1 to 8 and Comparative Examples 1 and 2 obtained in Table 1 was vulcanized at 160°C for 30 minutes to prepare a test piece of a predetermined shape, and the hardness and viscoelastic properties were evaluated. did. Each evaluation method is as follows.

<Hardness measurement>
In accordance with JIS K6253, the hardness Hs of each rubber test piece at a temperature of 23° C. was measured using a durometer type A (model: GS-719N, manufactured by Techlock Co., Ltd.).

<Dynamic viscoelasticity measurement>
In accordance with JIS K6394, the 0°C tan δ and 35°C tan δ of each rubber test piece were measured using a viscoelasticity tester manufactured by Toyo Seiki Co., Ltd. The measurement conditions for each are as follows.
0℃ tan δ: measurement temperature 0℃, initial strain 10%, dynamic strain 1%, frequency 10Hz
35℃ tan δ: measurement temperature 35℃, initial strain 10%, dynamic strain 1%, frequency 10Hz

The unvulcanized rubber compositions of Examples 1 to 8 and Comparative Examples 1 and 2 obtained in Table 1 were used as tread rubber, and the tread pattern shown in FIG. 4 was obtained by vulcanization molding according to a conventional method. A pneumatic tire (tire size: 195/60R17 90H) was produced. The obtained test pneumatic tire was evaluated as follows.

<Rolling resistance>
Using a rolling resistance measurement drum testing machine, the rolling resistance of each tire was measured under the conditions of an air pressure of 230 kPa, a load of 450 kgf, a temperature of 23° C., and 80 km/h, and the value of Comparative Example 1 was set as 100 and expressed as an index evaluation. The smaller the index, the better the fuel efficiency.

<Wet performance>
Each test tire was attached to a FF vehicle with a displacement of 2000cc, and the ABS was activated at a speed of 90km/h on a wet road surface, and the braking distance when decelerating to 20km/h was measured (average value of n = 10), and a comparison example It is expressed as an index with 1 as 100. The larger the value, the shorter the braking distance and the better the braking performance.

The results are shown in Table 1. As shown in Table 1, pneumatic tires with 0° C. tan δ/35° C. tan δ of 1.35 or more and 2.10 or less have a good balance of fuel efficiency and wet performance. Compared to the pneumatic tire of Comparative Example 1, the pneumatic tire of the example has similar wet performance, while the rolling resistance is greatly reduced and the fuel efficiency is greatly improved.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments, their omissions, substitutions, changes, etc. are included within the scope and gist of the invention as well as within the scope of the invention described in the claims and its equivalents.

1 pneumatic tire, 10 tread, 11 tread rubber, 11A end, 12 sidewall, 13 sidewall rubber, 14 bead, 15 carcass, 16 inner liner, 17 bead core, 18 bead filler, 18A tip, 19 belt, 19A, 20A, 21A, 22A end, 20, 21 belt ply, 22 cap ply, 23 edge ply, 23A outer end, 23B inner end, 24 reinforcing rubber layer, 30 main groove (center main groove), 31, 32 main groove ( shoulder main groove), 40 center rib (first center rib ), 41 sipe, 42 bent part, 50 center rib (second center rib ), 51, 63, 73 first sipe, 52, 64, 74 second sipe, 53, 65, 75 3rd sipe, 54 4th sipe, 60 shoulder block (first shoulder block), 61, 62, 71, 72 horizontal groove, 70 shoulder block (second shoulder block)

Claims (10)

A pneumatic tire that has tread rubber provided on the tread and has a specified mounting direction on a vehicle,
The tread rubber is
A plurality of main grooves extending along the circumferential direction of the tire;
a pair of shoulder blocks partitioned by the main groove and arranged on the outer side in the tire axial direction;
a center rib arranged between the pair of shoulder blocks;
has
A plurality of sipes are formed on the center rib at intervals in the tire circumferential direction,
The sipe has a bent portion that crosses the center rib and is bent so as to protrude to one side in the tire circumferential direction from the positions of both ends of the sipe in the tire circumferential direction, when the center rib is viewed from above,
The ratio of the loss tangent at 0°C (0°C tanδ) to the loss tangent at 35°C (35°C tanδ) of the tread rubber (0°C tanδ/35°C tanδ) is 1.35 or more and 2.10 or less. A pneumatic tire. A pneumatic tire that has tread rubber provided on the tread and has a specified mounting direction on a vehicle,
The tread rubber is
A plurality of main grooves extending along the circumferential direction of the tire;
a pair of shoulder blocks partitioned by the main groove and arranged on the outer side in the tire axial direction;
a center rib arranged between the pair of shoulder blocks;
has
A plurality of sipes are formed on the center rib at intervals in the tire circumferential direction,
The sipe has a substantially S-shape in a plan view of the center rib,
The ratio of the loss tangent at 0°C (0°C tanδ) to the loss tangent at 35°C (35°C tanδ) of the tread rubber (0°C tanδ/35°C tanδ) is 1.35 or more and 2.10 or less. A pneumatic tire. A pneumatic tire that has tread rubber provided on the tread and has a specified mounting direction on a vehicle,
The tread rubber is
A plurality of main grooves extending along the circumferential direction of the tire;
a pair of shoulder blocks partitioned by the main groove and arranged on the outer side in the tire axial direction;
a center rib arranged between the pair of shoulder blocks;
has
The main groove is
A pair of shoulder main grooves located on the outside in the tire axial direction;
a center main groove disposed between the pair of shoulder blocks;
has
The center rib is
a first center rib defined by the shoulder main groove and the center main groove and arranged on the inside of the vehicle from the tire equator;
a second center rib defined by the shoulder main groove and the center main groove and arranged on the outer side of the vehicle than the tire equator;
has
The number of sipes crossing the second center rib is smaller than the number of sipes crossing the first center rib,
The ratio of the loss tangent at 0°C (0°C tanδ) to the loss tangent at 35°C (35°C tanδ) of the tread rubber (0°C tanδ/35°C tanδ) is 1.35 or more and 2.10 or less. A pneumatic tire. A pneumatic tire that has tread rubber provided on the tread and has a specified mounting direction on a vehicle,
The tread rubber is
A plurality of main grooves extending along the circumferential direction of the tire;
a pair of shoulder blocks partitioned by the main groove and arranged on the outer side in the tire axial direction;
a center rib arranged between the pair of shoulder blocks;
has
The shoulder block is
a first shoulder block located on the inside of the vehicle relative to the tire equator;
a second shoulder block located on the outer side of the vehicle than the tire equator;
has
A lateral groove extending in the axial direction of the tire is formed in the second shoulder block,
The lateral groove is connected to the shoulder main groove via a sipe,
The ratio of the loss tangent at 0°C (0°C tanδ) to the loss tangent at 35°C (35°C tanδ) of the tread rubber (0°C tanδ/35°C tanδ) is 1.35 or more and 2.10 or less. A pneumatic tire. The pneumatic tire according to any one of claims 1 to 4 , wherein the 35°C tan δ is 0.15 or more and 0.18 or less. The pneumatic tire according to any one of claims 1 to 4, wherein the total width of the main grooves is 3% or more and 30% or less of the tire ground contact width. carcass and
a belt disposed on the outer side of the carcass in the tire radial direction;
an edge ply arranged on the outside of the belt in the tire radial direction and covering both ends of the belt in the tire axial direction;
Furthermore,
The edge plies are spaced apart from each other in the tire axial direction,
The pneumatic tire according to any one of claims 1 to 4 , wherein the total length of the edge ply in the tire axial direction is 50% or more of the length of the tread in the tire axial direction. The pneumatic tire according to claim 7 , further comprising a cap ply disposed between the belt and the edge ply and covering the outside of the belt in the tire radial direction. The pneumatic tire according to claim 7 , wherein the rectangularity of the contact surface of the tread is 0.75 or more and 0.85 or less. The pneumatic tire according to claim 7 , wherein the length of the tread in the tire axial direction is 84% or more and 87% or less of a nominal cross-sectional width.

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