tire

Abstract

In a tire according to an embodiment of the present invention, a protrusion length L1 of a tie rubber layer extending along a carcass layer from a position A on a tire inner surface corresponding to a belt end to a position B on the tire inner surface corresponding to a bead toe is 0.2 times or more of a periphery length L2 of the tire inner surface between said position A and said position B. Regarding carbon black included in the tie rubber layer and a carcass coating rubber, the CTAB adsorption specific surface areas are 40-125 m2 / g and 25-40 m2 / g, the DBP absorption amounts are 100-130 mL / 100 g and 60-95 mL / 100 g, and the products of the DBP absorption amount and the volume fraction of the carbon black are 18.0-28.0 mL / 10000 g and 14.0-18.0 mL / 10000 g, respectively.

Description

tire

[0001] The present invention relates to a tire in which a tie rubber layer is disposed on the inner peripheral side of a carcass layer.

[0002] To reduce the environmental impact, there is a demand for improving the fuel efficiency of vehicles. To this end, tires are required to generate less heat during rolling and have low rolling resistance. To reduce heat generation in tires, it is effective to reduce the amount of carbon black compounded in the rubber composition used in each part of the tire. In order to further improve fuel efficiency, in recent years, studies have been conducted to suppress heat generation in rubber in each part of the tire, excluding the cap tread rubber that comes into contact with the road surface.

[0003] On the other hand, as the amount of carbon black compounded decreases in line with the trend toward lower heat generation in tires, the problem of higher tire electrical resistance arises. If the tire's electrical resistance is high and static electricity accumulated in the vehicle is difficult to discharge to the road surface, there is a risk of malfunctions occurring in the operation of the vehicle's electrical components (see, for example, Patent Document 1).

[0004] On the other hand, the tensile properties of the rubber composition may deteriorate due to a change in the composition of the rubber composition, which may result in a deterioration in tire durability. Tires used for passenger cars are required to have superior durability during high-speed driving compared to tires used for commercial vehicles such as taxis and buses, and therefore a rubber composition that deteriorates the tensile properties of the rubber composition is not preferable.

[0005] JP 2013-237337 A

[0006] An object of the present invention is to provide a tire that can improve the fuel economy performance of a vehicle, has low electrical resistance, and is excellent in durability during high-speed running.

[0007] The present disclosure includes the following aspects: Aspect [1] A tire comprising: a pair of annular bead cores, a carcass layer extending between the bead cores to form a toroidal shape and folded back around the bead cores, the carcass layer having a plurality of carcass cords and a carcass coat rubber covering the carcass cords, a belt layer disposed on the outer peripheral side of the carcass layer, and a tie rubber layer disposed on the inner peripheral side of the carcass layer, passing through a tire centerline and extending along the carcass layer on both sides of the tire centerline, wherein a protruding length L1 of the tie rubber layer extending along the carcass layer from a position A on the tire inner surface that passes through an outer belt end of the belt layer in the tire width direction and intersects with a perpendicular line perpendicular to the tire inner surface toward a position B on the tire inner surface corresponding to a bead toe that is an inner end in the tire width direction of a bead portion of the tire having the bead cores is a length that is 0.2 times or more a periphery length L2 of the tire inner surface between the position A and the position B, The tie rubber layer comprises 100 parts by mass of a rubber component containing 50 to 100% by mass of natural rubber and a rubber composition having a CTAB adsorption specific surface area of ​​40 to 125 m 2 and 30 to 75 parts by mass of carbon black having a DBP absorption of 100 to 130 mL / 100 g, wherein the product D1×(V1 / 100) of the DBP absorption of the carbon black and the volume fraction V1 [%] of the carbon black in the tie rubber layer is 18.0 to 28.0 mL / 10,000 g, and the carcass coat rubber comprises 100 parts by mass of a rubber component containing 50 to 100% by mass of natural rubber, and a CTAB adsorption specific surface area of ​​25 to 40 m 2 and 30 to 65 parts by mass of carbon black having a DBP absorption of 60 to 95 mL / 100 g, wherein the product D2 × (V2 / 100) of the DBP absorption of the carbon black D2 and the volume fraction V2 [%] of the carbon black in the carcass coat rubber is 14.0 to 18.0 mL / 10,000 g.

[0008] Aspect [2] The tire according to aspect [1], wherein the product TB1×EB1 of the tensile strength TB1 [MPa] and the elongation at break EB1 [%] of the rubber composition of the tie rubber layer, and the product TB2×EB2 of the tensile strength TB2 [MPa] and the elongation at break EB2 [%] of the rubber composition of the carcass coat rubber, satisfy TB1×EB1>TB2×EB2.

[0009] Aspect [3] The tire according to aspect [1] or [2], wherein the tensile stress M100 [MPa] at 100% elongation of the rubber composition of the carcass coat rubber is greater than the tensile stress M100 [MPa] at 100% elongation of the rubber composition of the tie rubber layer.

[0010] Aspect [4] The tire according to any one of Aspects [1] to [3], wherein the rubber composition of the tie rubber layer and the rubber composition of the carcass coat rubber each further contain sulfur and a vulcanization accelerator, and the blending amounts of the sulfur and the vulcanization accelerator in the rubber composition of the carcass coat rubber per 100 parts by mass of the rubber component are greater than the blending amounts of the sulfur and the vulcanization accelerator in the rubber composition of the tie rubber layer per 100 parts by mass of the rubber component.

[0011] Aspect [5] A tire comprising: a pair of annular bead cores; a carcass layer extending between the bead cores to form a toroidal shape and folded back around the bead cores, the carcass layer having a plurality of carcass cords and a carcass coat rubber covering the carcass cords; a belt layer arranged on the outer peripheral side of the carcass layer; and a tie rubber layer arranged on the inner peripheral side of the carcass layer, passing through a tire centerline and extending along the carcass layer on both sides of the tire centerline, wherein a protruding length L1 of the tie rubber layer extending along the carcass layer from a position A on the tire inner surface that passes through an outer belt end of the belt layer in the tire width direction and intersects with a perpendicular line perpendicular to the tire inner surface toward a position B on the tire inner surface corresponding to a bead toe that is an inner end in the tire width direction of a bead portion of the tire having the bead cores is a length that is 0.2 times or more a periphery length L2 of the tire inner surface between the position A and the position B, The tie rubber layer includes carbon black (A) and carbon black (B) having different CTAB adsorption specific surface areas, and the tie rubber layer includes 100 parts by mass of a rubber component containing 50 to 100% by mass of natural rubber, and the carbon black (A) has a CTAB adsorption specific surface area of ​​40 to 125 m 2 30 to 75 parts by mass of carbon black having a CTAB adsorption specific surface area of ​​25 to 50 m / g and a DBP absorption of 100 to 130 mL / 100 g; 2 and 5 to 40 parts by mass of carbon black having a DBP absorption of 50 to 130 mL / 100 g, wherein the sum of the product D1a × (V1a / 100) of the DBP absorption of the carbon black (A) and the volume fraction V1a [%] of the carbon black (A) in the tie rubber layer and the product D1b × (V1b / 100) of the DBP absorption of the carbon black (B) and the volume fraction V1b [%] of the carbon black (B) in the tie rubber layer is 18.0 to 28.0 mL / 10,000 g; and the carcass coat rubber comprises 100 parts by mass of a rubber component containing 50 to 100% by mass of natural rubber, and a CTAB adsorption specific surface area of ​​25 to 40 m 2and 30 to 65 parts by mass of carbon black having a DBP absorption of 60 to 95 mL / 100 g, wherein the product D2 × (V2 / 100) of the DBP absorption of the carbon black D2 and the volume fraction V2 [%] of the carbon black in the carcass coat rubber is 14.0 to 18.0 mL / 10,000 g.

[0012] According to the tire of the above aspect, the fuel efficiency performance of the vehicle can be improved, the electrical resistance of the tire is low, and durability during high-speed running is excellent.

[0013] 1 is a diagram showing a meridian cross section of a tire according to an embodiment;

[0014] The tire of the embodiment will be described in detail below. The tire of the present invention is preferably an inflatable tire such as a pneumatic tire, and the tire of the present embodiment is a pneumatic tire. A cavity region surrounded by the inflatable tire and a rim on which the inflatable tire is mounted can be filled with air, an inert gas such as nitrogen, or other gases.

[0015] Fig. 1 is a diagram showing a tire meridian cross section (a cross section of a tire cut along a plane including the tire rotation axis) of this embodiment. As shown in Fig. 1, the tire of this embodiment includes a tread portion 1 extending in the tire circumferential direction to form an annular shape, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3 disposed on the tire radially inward side of the sidewall portions 2. In Fig. 1, CL indicates a tire centerline.

[0016] The bead portion 3 has an annular bead core 5 having a structure in which, for example, a rubber-coated steel wire is wound multiple times in the tire circumferential direction.

[0017] The carcass layer 4 extends between a pair of bead cores 5 to form a toroidal shape and is folded back around each bead core 5 from the inner side to the outer side in the tire width direction. The carcass layer 4 includes a plurality of parallel carcass cords extending in the tire radial direction and a carcass coat rubber covering the carcass cords. The carcass cords are reinforcing cords made of organic fibers such as PET fibers. The carcass coat rubber is a vulcanized rubber formed by sandwiching the parallel carcass cords between sheets of carcass coat rubber.

[0018] A bead filler 6 is disposed on the outer circumferential side of the bead core 5 , and the bead filler 6 is wrapped by the portion of the carcass layer 4 folded back around the bead core 5 .

[0019] Multiple belt layers 7 (two layers in the illustrated example) are embedded on the outer peripheral side (outside in the tire radial direction) of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes multiple reinforcing cords (e.g., steel cords) inclined with respect to the tire circumferential direction, and are arranged so that the inclination directions of the reinforcing cords intersect with each other between layers. In these belt layers 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set to a range of 10° to 40°, for example.

[0020] A belt reinforcing layer 8 (in the illustrated example, a pair of belt reinforcing layers 8 covering the ends of the belt layer 7 in the tire width direction) is provided on the outer peripheral side of the belt layer 7. The belt reinforcing layer 8 includes organic fiber cords oriented in the tire circumferential direction. In the belt reinforcing layer 8, the organic fiber cords are inclined at an angle of 0° to 5° with respect to the tire circumferential direction, for example.

[0021] An inner liner layer 9 is provided on the inner surface of the tire, which forms a cavity region between the tire and the rim. The inner liner layer 9 is made of a rubber composition mainly containing butyl rubber.

[0022] A tread rubber layer 10 is disposed on the outer peripheral side of the carcass layer 4 in the tread portion 1. The tread rubber layer 10 may have a structure in which two types of rubber layers with different physical properties (a cap tread rubber layer and an under tread rubber layer) are laminated in the tire radial direction.

[0023] In the sidewall portion 2, a side rubber layer 20 is disposed on the outer side of the carcass layer 4 in the tire width direction.

[0024] In the bead portion 3, a rim cushion rubber layer 30 is disposed around the carcass layer 4.

[0025] A tie rubber layer 40 is disposed between the inner liner layer 9 and the carcass layer 4. The tie rubber layer 40 is a rubber layer that passes through the tire centerline CL and extends along the carcass layer 4 on both sides of the tire centerline CL in the tire width direction. The tie rubber layer 40 extends in the tire circumferential direction and has an annular shape. By providing such a tie rubber layer 40 in a wide region in the tire width direction, including the center portion in the tire width direction, it is possible to improve the adhesion between the inner liner layer 9 and the carcass layer 4. The tie rubber layer 40 extends while maintaining a constant thickness, which is preferably 0.05 to 0.6 mm.

[0026] With respect to the tie rubber layer 40, the protruding length L1 of the tie rubber layer 40 extending along the carcass layer 4 from position A on the tire inner surface corresponding to the outer edge (belt end) of the belt layer 7 in the tire width direction toward position B on the tire inner surface corresponding to the bead toe, which is the inner edge of the bead portion 3 in the tire width direction, is 0.2 times or more the periphery length L2 of the tire inner surface between positions A and B. When the positions of the outer edges in the tire width direction differ among multiple belt layers 7 as in the illustrated example, the belt end refers to the edge of the belt layer 7 located outermost in the tire width direction. Position A on the tire inner surface corresponding to the position of the belt end refers to the position on the tire inner surface that intersects with a perpendicular line P that passes through the belt end and is perpendicular to the tire inner surface in the tire meridian cross section. The periphery length refers to the length of the tire inner surface measured in the tire meridian cross section. In the illustrated example, the tire inner surface is the surface of the inner liner layer 9 facing the cavity region. The protruding length L1 of the tie rubber layer 40 is preferably 0.5 times or more, and particularly preferably 1 time, the periphery length L2 of the tire inner surface, from the viewpoint of making it easier to secure a path for electricity to flow inside the tire from the rim side toward the road surface side.

[0027] The tie rubber layer 40 is made of 100 parts by mass of a rubber component containing 50 to 100% by mass of natural rubber (NR) and a rubber composition having a CTAB (n-hexadecyltrimethylammonium bromide) adsorption specific surface area of ​​40 to 125 m 2 and 30 to 75 parts by mass of carbon black having a DBP (dibutyl phthalate) absorption of 100 to 130 mL / 100 g.

[0028] A blending amount of natural rubber (NR) of 50 to 100% by mass in the tie rubber layer 40 improves the tensile strength and elongation at break of the tie rubber layer 40, contributing to improving the high-speed durability of the tire. The blending amount of natural rubber (NR) is preferably 60 to 95 parts by mass per 100 parts by mass of the rubber component of the tie rubber layer 40. It is also preferable that the rubber component of the tie rubber layer 40 further contains a diene rubber such as styrene-butadiene rubber (SBR) in addition to natural rubber (NR). This ensures the hardness of the tie rubber layer 40 and improves processability.

[0029] The CTAB adsorption specific surface area of ​​carbon black is 40 to 125 m 2 / g, and the larger the CTAB adsorption specific surface area, the smaller the particle size. The DBP absorption is preferably 100 to 130 mL / 100 g, and the larger the DBP absorption, the larger the particle chain structure. The DBP absorption of the carbon black in the tie rubber layer 40 is greater than that of the carbon black in the carcass coat rubber, which lengthens the carbon black particle connections and contributes to obtaining a larger structure. When the tie rubber layer 40 contains a large amount of such carbon black, i.e., 30 to 75 parts by mass per 100 parts by mass of the rubber component, the conductivity of the tie rubber layer 40 is likely to be improved and the electrical resistance of the tire is likely to be reduced. On the other hand, because the tie rubber layer 40 is a thin layer, even if the carbon black is contained in the above-mentioned amount, heat generation in the tie rubber layer 40 during tire rotation is likely to be suppressed, and the rolling resistance of the tire is unlikely to deteriorate. Furthermore, when the CTAB adsorption specific surface area is 40 to 125 m 2 / g of carbon black is contained in the above-mentioned blending amount, the tensile strength and breaking elongation of the tie rubber layer 40 are improved, and the high-speed durability of the tire is likely to be improved. The blending amount of carbon black in the tie rubber layer 40 is preferably 50 to 70 parts by mass per 100 parts by mass of the rubber component.

[0030] In this specification, the CTAB adsorption specific surface area of ​​carbon black is a value measured in accordance with JIS K6217-3. The CTAB adsorption specific surface area of ​​the carbon black in the tie rubber layer 40 is preferably 70 to 125 m 2 / g. Furthermore, 110 to 125 m 2 / g is preferred. In this specification, the DBP absorption of carbon black is a value measured in accordance with JIS K6217-4. The DBP absorption of the carbon black in the tie rubber layer 40 is preferably 110 to 130 mL / 100 g, more preferably 115 to 130 mL / 100 g. As the carbon black for the tie rubber layer 40, FEF, HAF, ISAF, or other grades are preferably used.

[0031] For the tie rubber layer 40, the product D1 × (V1 / 100) of the DBP absorption amount D1 of the carbon black and the volume fraction V1 [%] of the carbon black in the tie rubber layer 40 is 18.0 to 28.0 mL / 10,000 g. A large product of the DBP absorption amount and volume fraction of the carbon black in the rubber improves the conductivity of the rubber and tends to reduce the electrical resistance of the tire. The value of the product D1 × (V1 / 100) for the tie rubber layer 40 is relatively high, and the conductivity of the tie rubber layer 40 is better than that of the carcass coat rubber, contributing to reducing the electrical resistance of the tire. In this specification, the volume fraction of carbon black is calculated as the ratio of the volume of carbon black, obtained by dividing the mass of carbon black per unit part by mass of the rubber composition by its specific gravity, to the volume of the rubber composition, obtained by dividing the mass per unit part by mass of the rubber composition by its specific gravity.

[0032] The carcass coat rubber is a rubber composition containing 50 to 100 parts by mass of natural rubber and a CTAB adsorption specific surface area of ​​25 to 40 m per 100 parts by mass of the rubber component of the carcass coat rubber. 2and 30 to 65 parts by mass of carbon black having a DBP absorption of 60 to 95 mL / 100 g.

[0033] The amount of natural rubber (NR) in the carcass coat rubber of 50 to 100 parts by mass contributes to obtaining appropriate strength for the carcass layer 4. The amount of natural rubber (NR) is preferably 55 to 80 parts by mass per 100 parts by mass of the rubber component of the carcass coat rubber. It is also preferable that the rubber component of the tie rubber layer 40 further contains a diene rubber such as styrene-butadiene rubber (SBR) in addition to natural rubber (NR). This ensures appropriate hardness for the carcass coat rubber while improving processability.

[0034] CTAB adsorption specific surface area is 25-40m 2 The larger the CTAB adsorption specific surface area, the smaller the particle size. The DBP absorption is preferably in the range of 60 to 95 mL / 100 g, and by keeping it in this range, processability and productivity can be improved. The CTAB adsorption specific surface area of ​​the carbon black is preferably smaller than the CTAB adsorption specific surface area of ​​the carbon black in the tie rubber layer 40, more preferably 25 to 35 m 2 / g.

[0035] The DBP absorption of the carbon black in the carcass coat rubber is lower than that of the carbon black in the tie rubber layer 40, which suppresses heat generation in the carcass coat rubber and contributes to reducing the rolling resistance of the tire. In addition, the tensile strength and elongation at break of the carcass coat rubber are relatively smaller than those of the tie rubber layer 40, allowing the tire to achieve both good rolling resistance and high-speed durability. The DBP absorption of the carbon black is preferably 65 to 90 mL / 100 g. The carbon black in the carcass coat rubber is preferably GPF grade.

[0036] By limiting the amount of carbon black in the carcass coat rubber to 65 parts by mass or less per 100 parts by mass of the rubber component, heat generation in the carcass coat rubber during tire rolling is easily suppressed, and tire rolling resistance is easily reduced. Furthermore, the tensile strength and elongation at break of the carcass coat rubber tend to be moderate, contributing to improved high-speed durability of the tire. On the other hand, by limiting the amount of carbon black in the carcass coat rubber to 30 parts by mass or more per 100 parts by mass of the rubber component, necessary conductivity can be ensured even if the protruding length L1 of the tie rubber layer 40 is short. The amount of carbon black in the carcass coat rubber is preferably 40 to 60 parts by mass per 100 parts by mass of the rubber component. It is preferable that the rubber composition of the carcass coat rubber does not contain any carbon black other than the above-mentioned carbon black.

[0037] For the carcass coat rubber, the product D2 × (V2 / 100) of the DBP absorption amount D2 of the carbon black and the volume fraction V2 [%] of the carbon black in the carcass coat rubber is 14.0 to 18.0 mL / 10,000 g. The value of the product D2 × (V2 / 100) of the carcass coat rubber is relatively small, which suppresses heat generation in the carcass coat rubber and contributes to reducing the rolling resistance of the tire.

[0038] The thickness of each of the carcass coat rubber sheets sandwiching the paralleled carcass cords from both sides is preferably 0.1 to 0.8 mm.

[0039] The rubber compositions of the tie rubber layer 40 and the carcass coat rubber preferably contain, in addition to natural rubber (NR) and carbon black, an alkylphenol resin and an amine-based antioxidant. The amount of alkylphenol resin is preferably 0.1 to 5 parts by mass per 100 parts by mass of the rubber component of the tie rubber layer 40 or the carcass coat rubber. The inclusion of this amount of alkylphenol resin in the tie rubber layer 40 improves adhesion and facilitates tire moldability. Paraoctylphenol resin or the like is preferably used as the alkylphenol resin. The amount of amine-based antioxidant is preferably 0.1 to 5 parts by mass per 100 parts by mass of the rubber component of the tie rubber layer 40 or the carcass coat rubber. The inclusion of the amine-based antioxidant in this amount tends to improve the high-speed durability of the tire. The tie rubber layer 40 preferably uses an aromatic secondary amine-based antioxidant such as N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine (6PPD) as the amine-based antioxidant. For the carcass coating rubber, an amine-based antioxidant such as 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ) is preferably used.

[0040] The rubber compositions of the tie rubber layer 40 and the carcass coat rubber preferably further contain compounding ingredients such as oil, stearic acid, zinc oxide, sulfur, and a vulcanization accelerator. The compounding amount of sulfur and vulcanization accelerator in the rubber composition of the carcass coat rubber per 100 parts by mass of the rubber component is preferably greater than the compounding amount of sulfur and vulcanization accelerator in the rubber composition of the tie rubber layer 40 per 100 parts by mass of the rubber component. This tends to reduce rolling resistance and improve high-speed durability.

[0041] The rubber compositions constituting the rim cushion rubber layer 30, the bead filler 6, the side rubber layer 20, the inner liner layer 9, and the tread rubber layer 10 are not particularly limited as long as they are generally used as rubber compositions for each component of a tire.

[0042] The tire described above can improve the fuel economy of a vehicle, has low electrical resistance, and is excellent in durability during high-speed driving. Such a tire is suitable for use as a passenger car tire.

[0043] With respect to the product TB1×EB1 of the tensile strength TB1 [MPa] and the elongation at break EB1 [%] of the rubber composition of the tie rubber layer 40, and the product TB2×EB2 of the tensile strength TB2 [MPa] and the elongation at break EB2 [%] of the rubber composition of the carcass coat rubber, it is preferable that TB1×EB1 > TB2×EB2. When the tie rubber layer 40 and the carcass coat rubber satisfy the above relationship, the high-speed durability of the tire is likely to be improved. The tensile strength TB is a value [MPa] measured in accordance with JIS K6251 at a temperature of 23°C. The elongation at break EB is a value [%] measured in accordance with JIS K6251 at a temperature of 23°C. The value of TB1×EB1 is preferably 7500 to 9500 [MPa·%]. The value of TB2×EB2 is preferably 7000 to 8000 [MPa·%].

[0044] The tensile stress M100 [MPa] at 100% elongation of the rubber composition of the carcass coat rubber is preferably greater than the tensile stress M100 [MPa] at 100% elongation of the rubber composition of the tie rubber layer 40. When the tie rubber layer 40 and the carcass coat rubber satisfy the above relationship, the high-speed durability of the tire is likely to be improved. The tensile stress M100 is a value measured using a No. 3 dumbbell test piece in accordance with JIS K6251 under conditions of a tensile speed of 500 mm / min and a temperature of 23°C. The tensile stress M100 value of the rubber composition of the carcass coat rubber is preferably 3.0 to 4.5 [MPa]. The tensile stress M100 value of the rubber composition of the tie rubber layer is preferably 3.0 to 4.2 [MPa].

[0045] According to another embodiment (hereinafter also referred to as a second embodiment) different from the embodiment described above (hereinafter also referred to as a first embodiment), the rubber composition of the tie rubber layer 40 contains carbon black (A) and carbon black (B) having different CTAB adsorption specific surface areas.

[0046] In the second embodiment, the rubber composition of the tie rubber layer 40 comprises 100 parts by mass of a rubber component containing 50 to 100% by mass of natural rubber, and carbon black (A) having a CTAB adsorption specific surface area of ​​40 to 125 m 2 / g and DBP absorption of 100 to 130 mL / 100 g, and 30 to 75 parts by mass of carbon black (B) having a CTAB adsorption specific surface area of ​​25 to 50 m 2 and 5 to 40 parts by mass of carbon black having a DBP absorption of 50 to 130 mL / 100 g.

[0047] The sum of the product D1a × (V1a / 100) of the DBP absorption amount D1a of the carbon black (A) and the volume fraction V1a [%] of the carbon black (A) in the tie rubber layer 40 and the product D1b × (V1b / 100) of the DBP absorption amount D1b of the carbon black (B) and the volume fraction V1b [%] of the carbon black (B) in the tie rubber layer 40 is 18.0 to 28.0 mL / 10,000 g.

[0048] Except for the above-described configuration, the tire of the second embodiment is configured similarly to the tire of the first embodiment. The carbon black (A) is configured similarly to the carbon black contained in the tie rubber layer 40 of the tire of the first embodiment.

[0049] The fact that the sum of the above-mentioned product D1a × (V1a / 100) and product D1b × (V1b / 100) is 18.0 to 28.0 mL / 10,000 g reduces the electrical resistance of the tie rubber layer 40, contributing to reducing the electrical resistance of the tire, as in the first embodiment. The volume fractions V1a and V1b of carbon black (A) and (B) are calculated in the same manner as the volume fraction of carbon black described in the first embodiment. The sum of the product D1a × (V1a / 100) and product D1b × (V1b / 100) is calculated, for example, according to the following formula: D1a × (V1a / 100) + D1b × (V1b / 100) = {D1a × (amount of carbon black (A) in the tie rubber layer 40 [parts by mass] / specific gravity of carbon black (A)) + D1b × (amount of carbon black (B) in the tie rubber layer 40 [parts by mass] / specific gravity of carbon black (B))} / (total amount of components contained in the tie rubber layer 40 [parts by mass] / specific gravity of the tie rubber layer 40)

[0050] The tire of the second embodiment, like the tire of the first embodiment, can improve the fuel economy of a vehicle, has low tire electrical resistance, and is excellent in durability during high-speed driving. Such a tire is suitable as a passenger car tire. In particular, the tire of the second embodiment contains carbon black (A) with a small particle size in the tie rubber layer 40 in addition to carbon black (B) with a large particle size, thereby improving the balance between the hardness, tensile strength, and elongation at break of the tie rubber layer 40, improving high-speed durability, reducing rolling resistance, and lowering the tire's electrical resistance. Furthermore, the presence of carbon black (A) and carbon black (B) in the tie rubber layer 40 in the above-described blending amounts improves the balance between the tire's handling stability and high-speed durability.

[0051] The CTAB adsorption specific surface area of ​​the carbon black (B) is preferably 27 to 40 m 2 / g, more preferably 27 to 38 m 2The DBP absorption of the carbon black (B) is preferably 70 to 130 mL / 100 g. The blending amount of the carbon black (B) in the tie rubber layer 40 is preferably 10 to 35 parts by mass, and more preferably 15 to 30 parts by mass, per 100 parts by mass of the rubber component of the tie rubber layer 40.

[0052] It is preferable that carbon black (A) and carbon black (B) have different CTAB adsorption specific surface areas and also different DBP absorption amounts.

[0053] (Examples, Comparative Examples, Reference Examples) In order to confirm the effects of the tire of this embodiment, tires having a tire size of 235 / 45R18 and the basic structure shown in FIG. 1 were produced by changing the specifications of the tie rubber layer and the carcass coat rubber in various ways (Reference Examples, Comparative Examples, Examples), and evaluated for electrical resistance, rolling resistance, and high-speed durability.

[0054] The specifications of the tie rubber layer and the carcass coat rubber are as follows: Carbon blacks CB1 to CB5 shown in Tables 4 to 6 are as follows:

[0055]

[0056] The rubber composition of the tie rubber layer, which is common to the reference examples, comparative examples, and examples, has the composition of raw materials as shown in Table 2 below. The values ​​in the table represent parts by mass relative to 100 parts by mass of the rubber component.

[0057]

[0058] The blending of raw materials for the rubber compositions of carcass coat rubbers A to F shown in Tables 4 to 6 is as shown in the following Table 3. The values ​​in the table represent parts by mass relative to 100 parts by mass of the rubber component.

[0059]

[0060] Other raw materials shown in the table are as follows: NR: TSR20 SBR: SBR1502, Zeon Corporation Aroma oil: Diana Process NH-70S, Idemitsu Kosan Co., Ltd. Stearic acid: Stearic acid 50S, Nissin Rika Co., Ltd. Zinc oxide: Three types of zinc oxide, manufactured by Seido Chemical Industry Co., Ltd. Antiaging agent 1: Nocrac 6C, manufactured by Ouchi Shinko Chemical Co., Ltd. Antiaging agent 2: PILNOX TMQ, manufactured by NOCIL LIMITED Alkylphenol resin: Hitanol 1502Z, Hitachi Chemical Co., Ltd. Insoluble sulfur: Myucron OT-20, manufactured by Shikoku Chemical Industry Co., Ltd. Vulcanization accelerator: Suncerer NS-G, manufactured by Sanshin Chemical Industry Co., Ltd.

[0061] The thickness of the tie rubber layer at a portion where the thickness was maintained constant was 0.5 mm. The reinforcing cord of the carcass layer was a PET fiber cord, and the thickness of the carcass layer was 1.0 mm. The rubber compositions of each portion of the tire except for the carcass coat rubber and the tie rubber layer were compositions generally used in, for example, fuel-efficient tires.

[0062] In the table, L1 / L2 means the ratio of the protrusion length L1 to the periphery length L2 between positions A and B.

[0063] Electrical resistance, rolling resistance, and high-speed durability were evaluated as follows.

[0064] (Electrical Resistance) In an environment with a temperature of 23°C and humidity of 50%, a test tire was mounted on a wheel with a rim size of 18x7J, and a voltage of 1000V was applied to the wheel under conditions of an air pressure of 200kPa and a load of 5.26kN. Five minutes later, the electrical resistance value [Ω] between the tread surface and the rim was measured. Measurements were taken at three locations around the circumference of the tire, and the average value was calculated. The value of this average value, expressed as 10 to the power of n (n is a natural number) (indicated as "10^n" in the table), is shown in the table. The smaller the value, the lower the electrical resistance of the tire, and the better its discharge and charge-suppressing performance.

[0065] (Rolling Resistance) The test tire was mounted on a wheel with a rim size of 18x7J, and the rolling resistance was measured using an indoor drum testing machine (drum diameter: 1707.6 mm) in accordance with ISO 28580 under conditions of an air pressure of 210 kPa, a load of 4.82 kN, and a speed of 80 km / h, and the measured values ​​were expressed as an index, with the reference example being set at 100. The smaller the index value, the lower the rolling resistance, meaning that the vehicle's fuel economy performance is excellent.

[0066] (High-Speed ​​Durability) Test tires were mounted on wheels with a rim size of 18x7J and stored for 7 days at a temperature of 70°C under an internal pressure of 350 kPa and oxygen-sealed conditions. The test tires thus pretreated were inflated to a pressure of 230 kPa and mounted on an indoor drum testing machine (drum diameter: 1707.6 mm). A test was conducted in which the tire was loaded with a load of 88% of the maximum load capacity specified by JATMA, starting at a speed of 120 km / h, and the speed was increased by 8 km / h every 30 minutes until tire failure occurred. The running distance was expressed as an index, with the running distance of the reference example being 100. A higher index value indicates better high-speed durability.

[0067]

[0068]

[0069]

[0070] A comparison between Example 1 and Comparative Examples 7 to 14 shows that the protruding length L1 of the tie rubber layer is 0.2 times or more the periphery length L2 between positions A and B, and the rubber compositions of the tie rubber layer and the carcass coat rubber contain natural rubber (NR) and carbon black whose CTAB adsorption specific surface area, DBP absorption amount, and product of DBP absorption amount and volume fraction are within the above ranges, respectively, in the above-mentioned compounding amounts, thereby making it possible to obtain a tire that has low rolling resistance, excellent durability at high speeds, and low electrical resistance.

[0071] A comparison of Examples 1 to 3 reveals that the larger the particle size of the carbon black in the tie rubber layer, the lower the rolling resistance. A comparison of Examples 3, 5, and 6 reveals that the longer the protrusion length L1 of the tie rubber layer, the better the high-speed durability. A comparison of Examples 4 and 7 reveals that a high blending amount of sulfur and vulcanization accelerator in the carcass coat rubber makes it easier to satisfy the relationship TB1 x EB1 > TB2 x EB2 and the relationship tensile stress M100 of the carcass coat rubber > tensile stress M100 of the tie rubber layer, thereby improving high-speed durability.

[0072] Although the tire of the present invention has been described in detail above, the tire of the present invention is not limited to the above-described embodiments or examples, and various improvements and modifications may be made without departing from the spirit and scope of the present invention.

[0073] REFERENCE SIGNS LIST 1 tread portion 2 sidewall portion 3 bead portion 4 carcass layer 5 bead core 6 bead filler 7 belt layer 8 belt reinforcing layer 9 inner liner layer 10 tread rubber layer 20 side rubber layer 30 rim cushion rubber layer 40 tie rubber layer CL tire equator

Claims

1. A tire comprising: a pair of annular bead cores; a carcass layer extending between the bead cores to form a toroidal shape and folded back around the bead cores, the carcass layer having a plurality of carcass cords and a carcass coat rubber covering the carcass cords; a belt layer disposed on the outer circumferential side of the carcass layer; and a tie rubber layer disposed on the inner circumferential side of the carcass layer, passing through a tire centerline and extending along the carcass layer on both sides of the tire centerline, wherein a protruding length L1 of the tie rubber layer extending along the carcass layer from a position A on the tire inner surface that passes through an outer belt end of the belt layer in the tire width direction and intersects with a perpendicular line perpendicular to the tire inner surface toward a position B on the tire inner surface corresponding to a bead toe that is an inner end in the tire width direction of a bead portion of the tire having the bead cores is a length that is 0.2 times or more a periphery length L2 of the tire inner surface between the positions A and B, The tie rubber layer is made of 100 parts by mass of a rubber component containing 50 to 100% by mass of natural rubber and a rubber composition having a CTAB adsorption specific surface area of ​​40 to 125 m 2 and 30 to 75 parts by mass of carbon black having a DBP absorption of 100 to 130 mL / 100 g, wherein the product D1×(V1 / 100) of the DBP absorption of the carbon black and the volume fraction V1 [%] of the carbon black in the tie rubber layer is 18.0 to 28.0 mL / 10,000 g. The carcass coat rubber comprises 100 parts by mass of a rubber component containing 50 to 100 mass % of natural rubber, and a CTAB adsorption specific surface area of ​​25 to 40 m. 2 and 30 to 65 parts by mass of carbon black having a DBP absorption of 60 to 95 mL / 100 g, wherein the product D2×(V2 / 100) of the DBP absorption of the carbon black D2 and the volume fraction V2 [%] of the carbon black in the carcass coat rubber is 14.0 to 18.0 mL / 10,000 g.

2. The tire according to claim 1, wherein the product TB1×EB1 of the tensile strength TB1 [MPa] and the breaking elongation EB1 [%] of the rubber composition of the tie rubber layer, and the product TB2×EB2 of the tensile strength TB2 [MPa] and the breaking elongation EB2 [%] of the rubber composition of the carcass coat rubber, satisfy TB1×EB1>TB2×EB2.

3. A tire according to claim 1 or 2, wherein the tensile stress M100 [MPa] of the rubber composition of the carcass coat rubber at 100% elongation is greater than the tensile stress M100 [MPa] of the rubber composition of the tie rubber layer at 100% elongation.

4. The tire according to claim 1 or 2, wherein the rubber composition of the tie rubber layer and the rubber composition of the carcass coat rubber each further contain sulfur and a vulcanization accelerator, and the amount of the sulfur and the vulcanization accelerator in the rubber composition of the carcass coat rubber per 100 parts by mass of the rubber component is greater than the amount of the sulfur and the vulcanization accelerator in the rubber composition of the tie rubber layer per 100 parts by mass of the rubber component.

5. A tire comprising: a pair of annular bead cores; a carcass layer extending between the bead cores to form a toroidal shape and folded back around the bead cores, the carcass layer having a plurality of carcass cords and a carcass coat rubber covering the carcass cords; a belt layer disposed on the outer circumferential side of the carcass layer; and a tie rubber layer disposed on the inner circumferential side of the carcass layer, passing through a tire centerline and extending along the carcass layer on both sides of the tire centerline, wherein a protruding length L1 of the tie rubber layer extending along the carcass layer from a position A on the tire inner surface that passes through an outer belt end of the belt layer in the tire width direction and intersects with a perpendicular line perpendicular to the tire inner surface toward a position B on the tire inner surface corresponding to a bead toe that is an inner end in the tire width direction of a bead portion of the tire having the bead cores is 0.2 times or more the periphery length L2 of the tire inner surface between the positions A and B, The tie rubber layer is made of a rubber composition containing carbon black (A) and carbon black (B) having different CTAB adsorption specific surface areas. The rubber composition of the tie rubber layer includes 100 parts by mass of a rubber component containing 50 to 100 mass% of natural rubber, and the carbon black (A) having a CTAB adsorption specific surface area of ​​40 to 125 m. 2 30 to 75 parts by mass of carbon black having a CTAB adsorption specific surface area of ​​25 to 50 m / g and a DBP absorption of 100 to 130 mL / 100 g; 2 and 5 to 40 parts by mass of carbon black having a DBP absorption of 50 to 130 mL / 100g, wherein a sum of a product D1a×(V1a / 100) of a DBP absorption amount D1a of the carbon black (A) and a volume fraction V1a [%] of the carbon black (A) in the tie rubber layer and a product D1b×(V1b / 100) of a DBP absorption amount D1b of the carbon black (B) and a volume fraction V1b [%] of the carbon black (B) in the tie rubber layer is 18.0 to 28.0 mL / 10,000 g, and the carcass coat rubber comprises 100 parts by mass of a rubber component containing 50 to 100 mass% of natural rubber, and a CTAB adsorption specific surface area of ​​25 to 40 m 2 and 30 to 65 parts by mass of carbon black having a DBP absorption of 60 to 95 mL / 100 g, wherein the product D2×(V2 / 100) of the DBP absorption of the carbon black D2 and the volume fraction V2 [%] of the carbon black in the carcass coat rubber is 14.0 to 18.0 mL / 10,000 g.

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