PNEUMATIC TIRE

Abstract

Provided is a pneumatic tire with which any change in steering stability between low-speed running and high-speed running is sufficiently minimized, and durability is also sufficiently improved. This pneumatic tire has a belt layer radially inward of the tread portion, wherein the ratio (tan δ/E*) of the loss tangent (tan δ) to the complex elastic modulus E*(MPa) of the rubber composition constituting the belt layer, as measured under the conditions of 70° C., frequency 10 Hz, initial distortion 5%, and dynamic distortion rate 1%, is 0.002 to 0.017 (inclusive), and the (formula 1) and (formula 2) are satisfied, where Wt (mm) is the cross-sectional width of the tire, Dt (mm) is the outside diameter, and the virtual volume V (mm.sup.3) is the volume of the space occupied by the tire, when the tire is installed on a standardized rim and the internal pressure is 250 kPa.

1700≤(Dt.sup.2×π/4)/Wt≤2827.4  (formula 1)

[(V+1.5×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 2)

Claims

1. A pneumatic tire having a belt layer radially inward of the tread portion, in which; the ratio of loss tangent (tan δ) to complex elastic modulus (E*: MPa), (tan δ/E*), of the rubber composition constituting the belt layer, measured under the conditions of 70° C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1%, is 0.002 or more and 0.017 or less; and the tire satisfies following (formula 1) and (formula 2),
1700≤(Dt.sup.2×π/4)/Wt≤2827.4  (formula 1)
[(V+1.5×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 2) , where the cross-sectional width of the tire is Wt (mm), the outer diameter is Dt (mm), and the volume of the space occupied by the tire is the virtual volume V (mm.sup.3), when the tire is installed on a standardized rim and the internal pressure is 250 kPa.

2. The pneumatic tire according to claim 1, wherein the following (formula 3) is satisfied.
[(V+2.0×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 3)

3. The pneumatic tire according to claim 2, wherein the following (formula 4) is satisfied.
[(V+2.5×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 4)

4. The pneumatic tire according to claim 1, wherein, when the outer diameter of the tire is Dt (mm) and the cross-sectional height of the tire is Ht (mm) when the tire is installed on a standardized rim and the internal pressure is 250 kPa, (Dt−2×Ht) is 470 (mm) or more.

5. The pneumatic tire according to claim 1, which has an aspect ratio of 40% or more.

6. The pneumatic tire according to claim 5, which has an aspect ratio of 45% or more.

7. The pneumatic tire according to claim 6, which has an aspect ratio of 47.5% or more.

8. The pneumatic tire according to claim 7, which has an aspect ratio of 50% or more.

9. The pneumatic tire according to claim 1, wherein the rubber composition constituting the belt layer has a ratio of loss tangent to complex elastic modulus (tan δ/E*) of 0.009 or less.

10. The pneumatic tire according to claim 1, characterized by satisfying the following (formula 5).
[(tan δ/E*)/Wt]×1000≤0.60  (formula 5)

11. The pneumatic tire according to claim 10, characterized by satisfying the following (formula 6).
[(tan δ/E*)/Wt]×1000≤0.55  (formula 6)

12. The pneumatic tire according to claim 1, characterized by satisfying the following (formula 7)
(tan δ/E*)×T≤1.00  (formula 7) , where the distance from the tread surface to the belt layer is T (mm).

13. The pneumatic tire according to claim 12, characterized by satisfying the following (formula 8).
(tan δ/E*)×T≤0.85  (formula 8)

14. The pneumatic tire according to claim 1, wherein the tread portion has circumferential grooves continuously extending in the tire circumferential direction, and the ratio of the groove width L.sub.80 at a depth of 80% of the maximum depth of the circumferential groove to the groove width L.sub.0 of the circumferential groove on the ground contact surface of the tread portion (L.sub.80/L.sub.0) is 0.3 to 0.7.

15. The pneumatic tire according to claim 1, wherein the tread portion has a plurality of circumferential grooves continuously extending in the tire circumferential direction, and the total cross-sectional area of the plurality of circumferential grooves is 10 to 30% of the cross-sectional area of the tread portion.

16. The pneumatic tire according to claim 1, wherein the tread portion has a plurality of lateral grooves extending in the tire axial direction, and the total volume of the plurality of lateral grooves is 2.0 to 5.0% of the volume of the tread portion.

17. The pneumatic tire according to claim 1, wherein Dt is less than 685 (mm), where Dt (mm) is the outer diameter of the tire when the tire is installed on a standardized rim and the internal pressure is 250 kPa.

18. The pneumatic tire according to claim 1, wherein the cross-sectional width Wt (mm) is less than 205 mm.

19. The pneumatic tire according to claim 18, wherein the cross-sectional width Wt (mm) is less than 200 mm.

20. The pneumatic tire according to claim 1, wherein the steel cords in the belt layer extend at an angle of 15° or more and 50° or less with respect to the tire circumferential direction.

21. The pneumatic tire according to claim 1, which is a pneumatic tire for a passenger car.

Description

EXAMPLES

[0187] Hereinafter, the present disclosure will be described in more

Experiment 1

[0188] In this experiment, 175 size tires were prepared and evaluated.

1. Manufacture of Rubber Compositions for Belts

[0189] First, a rubber composition for belt was produced.

(1) Compounding Material

[0190] First, each compounding material shown below was prepared. [0191] (a) Rubber component [0192] NR: RSS3 [0193] (b) Compounding materials other than rubber components [0194] (b-1) Carbon Black-1: Show Black N326 manufactured by Cabot Japan Co., Ltd. (N.sub.2SA: 78m2/g) [0195] (b-2) Carbon Black-2: Show Black N550 manufactured by Cabot Japan Co., Ltd. (N.sub.2SA: 42m2/g) [0196] (b-3) Curable resin component-1: PR12686 manufactured by Sumitomo Bakelite Co., Ltd. (Cashew oil-modified phenolic resin) [0197] (b-4) Curable resin component-2: Sumikanol 620 manufactured by Taoka Chemical Co., Ltd. (Modified resorcinol resin) [0198] (b-5) Curing agent: Sumikanol 507 manufactured by Taoka Chemical Co., Ltd. (Methylene donor) [0199] (b-6) Cobalt organic acid: DICNATE NBC-2 manufactured by DIC Corporation (Boron cobalt neodecanoate, cobalt content 22.5% by mass) [0200] (b-7) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. [0201] (b-8) Anti-aging agent-1: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. [0202] (N-phenyl-N′(1,3-dimethylbutyl)-p-phenylenediamine) [0203] (b-9) Anti-aging agent-2: Antage RD manufactured by Kawaguchi Chemical Industry Co., Ltd. (2,2,4-trimethyl-1,2-dihydroquinoline) [0204] (b-10) Stearic acid: Stearic acid “Tsubaki” manufactured by NOF Corporation [0205] (b-11) Cross-linking agent, vulcanization accelerator, cross-linking aid [0206] Sulfur: powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. [0207] Vulcanization accelerator: Noxceler DZ manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd. (N,N-dicyclohexyl-2-benzothiazolylsulfenamide) [0208] Crosslinking aid: Duralink HTS manufactured by Flexis

(2) Production of Rubber Composition

[0209] In accordance with the formulation shown in Table 1 and Table 2, materials other than sulfur and the vulcanization accelerator were kneaded under the conditions of 150° C. for 5 minutes using a banbury mixer to obtain a kneaded product. Each compounding amount is a mass part.

[0210] Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded at 80° C. for 5 minutes using an open roll to obtain a rubber composition for belt.

2. Tire Manufacturing

[0211] Two-twisted steel cords with a filament diameter of 0.3 mm were pulled out and arranged so that 42 cords per 5 cm are arranged. The obtained rubber composition for belt was topped on the upper and lower sides of steel cords so that the total thickness becomes 0.95 mm. Then, after vulcanization, a belt member was obtained by cutting out so that the steel cord was at an angle of 24° to the tire circumferential direction.

[0212] After that, together with other tire members, two layers of the belt member were laminated so as to cross each other to form an unvulcanized tire, and press vulcanization was performed under the conditions of 170° C. for 10 minutes to produce each test tire having a size of 175 type (Example 1-1 to Example 1-5 and Comparative Example 1-1 to Comparative Example 1-5).

[0213] In each test tire, the above-mentioned (L.sub.80/L.sub.0) was set to 0.5, the total cross-sectional area of the circumferential groove was set to 22% of the cross-sectional area of the tread portion, and the total volume of the lateral grooves including the lateral grooves having the groove width/groove depth of 0.65 was set to 3.5% of the volume of the tread portion.

3. Parameter Calculation

[0214] After that, the outer diameter Dt (mm), the cross-sectional width Wt (mm), the cross-sectional height Ht (mm), the aspect ratio (%), and the distance T (mm) from the tread surface to the belt layer of each test tire were obtained, and the virtual volume V (mm.sup.3) was obtained. At the same time, rubber was cut out from between the belt layers of each test tire to prepare a rubber test piece for viscoelasticity measurement with a length of 40 mm and a width of 4 mm. For each rubber test piece, using an Eplexor series manufactured by GABO Co., Ltd, tan δ and E* were measured under the conditions of 70° C., frequency of 10 Hz, initial strain of 5%, and dynamic strain of 1%, and (tan δ/E*) was calculated. The results are shown in Tables 1 and 2.

[0215] Then, (Dt−2×Ht), (Dt.sup.2×π/4)/Wt, (V+1.5×10.sup.7)/Wt, (V+2.0×10.sup.7)/Wt, (V+2.5×10.sup.7)/Wt, [(tan δ/E*)/Wt]×1000, and (tan δ/E*)×T were calculated. The results are shown in Tables 1 and 2.

4. Performance Evaluation Test

(1) Evaluation of Steering Stability

[0216] Each test tire is installed on all wheels of a vehicle (domestic FF vehicle, displacement 2000 cc). After filling air so that the internal pressure is 250 kPa, and running on a dry road test course at 40 km/h and 120 km/h, the change in handling performance due to changes in running speed was evaluated sensorily by the driver on a 5-point scale from 1 (feeling a significant change) to 5 (feeling almost no change). Then, the total points of the evaluations by the 20 drivers were calculated.

[0217] Then, taking the result in Comparative Example 1-4 as 100, the results of each test tire were indexed based on the following formula to evaluate steering stability. A larger value indicates better steering stability.

Steering stability=[(Result of test tire)/(Result of Comparative Example 1-4)]×100

(2) Evaluation of Durability Performance

[0218] After installing each test tire on all wheels of the vehicle (domestic FF vehicle, displacement 2000 cc) and filling it with air so that the internal pressure becomes 250 kPa, a driving 10 laps at a speed of 50 km/h, followed by climbing onto the unevenness provided on the road surface at a speed of 80 km/h was repeated on the test course on a dry road surface in an overloaded state. Thereafter, the lap was performed again at a speed of 50 km/h and then the speed was gradually increased to measure the speed at the time when the driver felt an abnormality.

[0219] Next, taking the result in Comparative Example 1-5 as 100, and the durability performance was relatively evaluated by indexing based on the following formula. The larger the value, the better the durability.

Durability performance=[(Result of test tire)/(Result of Comparative Example 1-5)]×100

(3) Comprehensive Evaluation

[0220] The evaluation results of (1) and (2) above were totaled to obtain a comprehensive evaluation.

(4) Evaluation Result

[0221] The results of each evaluation are shown in Tables 1 and 2.

TABLE-US-00001 TABLE 1 Example No. 1-1 1-2 1-3 1-4 1-5 SIZE 175/40R21 175/40R21 175/40R21 175/50R20 175/60R19 (Formulation) NR 100 100 100 100 100 Carbon black-1 55 55 55 55 Carbon black-2 55 Crosslinking aid 0.5 1.2 1.2 0.5 0.5 Curable resin component-1 3 3 3 Curable resin component-2 5 5 Cobalt organic acid 1.0 1.0 1.0 1.0 1.0 Zinc oxide 10 11 11 10 10 Anti-aging agent-1 1 1 1 1 1 Anti-aging agent-2 0.5 0.5 0.5 0.5 0.5 Stearic acid 1 1 1 1 1 Sulfur 7 7 7 7 7 Curing agent 1.5 3 3 1.5 1.5 Vulcanization accelerator 1.2 1.2 1.2 1.2 1.2 (Parameter) tan δ 0.13 0.1 0.08 0.13 0.13 E* (MPa) 9.4 10.5 8.7 9.4 9.4 Dt(mm) 671 673 675 685 691 V(mm.sup.3) 22706213 23338766 23576710 30495603 34138255 Wt(mm) 174 176 175 183 178 Ht(mm) 69 70 71 89 104 T (mm) 8.4 8.3 8.4 8.5 8.3 Dt-2 × Ht(mm) 533 533 533 507 483 tan δ/E* 0.01383 0.00952 0.00920 0.01383 0.01383 (Dt.sup.2 × π/4)/Wt 2032 2021 2045 2014 2107 (V + 1.5 × 10.sup.7)/Wt 216702 217834 220438 248610 276058 (V + 2.0 × 10.sup.7)/Wt 245438 246243 249010 275932 304147 (V + 2.5 × 10.sup.7)/Wt 274174 274652 277581 303255 332237 Aspect ratio (%) 40 40 41 49 58 [(tan δ/E*)/Wt] × 1000 0.079 0.054 0.053 0.076 0.078 (tan δ/E*) × T 0.116 0.079 0.077 0.118 0.115 (Evaluation result) Steering stability 115 118 120 110 118 Durability 117 122 135 115 112 Comprehensive evaluation 232 240 255 225 230

TABLE-US-00002 TABLE 2 Comparative example No. 1-1 1-2 1-3 1-4 1-5 SIZE 175/80R14 175/60R19 175/80R14 175/80R14 175/80R14 (Formulation) NR 100 100 100 100 100 Carbon black-1 65 65 55 55 Carbon black-2 55 Crosslinking aid 0.5 1.2 1.2 Curable resin component-1 3 Curable resin component-2 5 5 Cobalt organic acid 1.0 1.0 1.0 1.0 1.0 Zinc oxide 10 10 10 11 11 Anti-aging agent-1 1 1 1 1 1 Anti-aging agent-2 0.5 0.5 0.5 0.5 0.5 Stearic acid 1 1 1 1 1 Sulfur 6.5 6.5 7 7 7 Curing agent 1.5 3 3 Vulcanization accelerator 1.2 1.2 1.2 1.2 1.2 (Parameter) tan δ 0.13 0.13 0.13 0.1 0.08 E* (MPa) 6.5 6.5 9.4 10.5 8.7 Dt(mm) 635 693 636 637 634 V(mm.sup.3) 38535090 34331262 38831091 38669035 37827524 Wt(mm) 177 177 178 176 175 Ht(mm) 140 105 140 141 139 T (mm) 8.5 8.3 8.4 8.5 8.3 Dt-2 × Ht(mm) 355 483 356 355 356 tan δ/E* 0.02000 0.02000 0.01383 0.00952 0.00920 (Dt.sup.2 × π/4)/Wt 1789 2131 1785 1811 1804 (V + 1.5 × 10.sup.7)/Wt 302458 278708 302422 304938 301872 (V + 2.0 × 10.sup.7)/Wt 330707 306956 330512 333347 330443 (V + 2.5 × 10.sup.7)/Wt 358955 335205 358602 361756 359014 Aspect ratio (%) 79 59 79 80 79 [(tan δ/E*)/Wt] × 1000 0.113 0.113 0.078 0.054 0.053 (tan δ/E*) × T 0.170 0.166 0.116 0.081 0.076 (Evaluation result) Steering stability 93 92 95 100 92 Durability 85 90 91 94 100 Comprehensive evaluation 178 182 186 194 192

Experiment 2

[0222] In this experiment, 195 size tires were prepared and evaluated.

[0223] After producing the test tires of Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-5 shown in Tables 3 and 4 in the same manner as in Experiment 1, each parameter was calculated by performing the same procedure. Then, in the same manner, a performance evaluation test was conducted and evaluated. The steering stability was evaluated with the result of Comparative Example 2-4 being set as 100, and the durability performance was evaluated with the result of Comparative Example 2-5 being set as 100. The results of each evaluation are shown in Tables 3 and 4.

TABLE-US-00003 TABLE 3 Example No. 2-1 2-2 2-3 2-4 2-5 SIZE 195/40R20 195/40R20 195/40R20 195/50R19 195/60R18 (Formulation) NR 100 100 100 100 100 Carbon black-1 55 55 55 55 Carbon black-2 55 Crosslinking aid 0.5 1.2 1.2 0.5 0.5 Curable resin component-1 3 3 3 Curable resin component-2 5 5 Cobalt organic acid 1.0 1.0 1.0 1.0 1.0 Zinc oxide 10 11 11 10 10 Anti-aging agent-1 1 1 1 1 1 Anti-aging agent-2 0.5 0.5 0.5 0.5 0.5 Stearic acid 1 1 1 1 1 Sulfur 7 7 7 7 7 Curing agent 1.5 3 3 1.5 1.5 Vulcanization accelerator 1.2 1.2 1.2 1.2 1.2 (Parameter) tan δ 0.13 0.1 0.08 0.13 0.13 E* (MPa) 9.4 10.5 8.7 9.4 9.4 Dt(mm) 664 662 665 680 690 V(mm.sup.3) 28719183 28585634 29087378 36682357 41835961 Wt(mm) 200 202 200 203 200 Ht(mm) 78 77 79 99 116 T (mm) 9.1 9.0 9.2 9.1 9.1 Dt-2 × Ht(mm) 508 508 507 482 458 tan δ/E* 0.01383 0.00952 0.00920 0.01383 0.01383 (Dt.sup.2 × π/4)/Wt 1731 1704 1737 1789 1870 (V + 1.5 × 10.sup.7)/Wt 218596 215770 220437 254593 284180 (V + 2.0 × 10.sup.7)/Wt 243596 240523 245437 279223 309180 (V + 2.5 × 10.sup.7)/Wt 268596 265275 270437 303854 334180 Aspect ratio (%) 39 38 40 49 58 [(tan δ/E*)/Wt] × 1000 0.069 0.047 0.046 0.068 0.069 (tan δ/E*) × T 0.126 0.086 0.085 0.126 0.126 (Evaluation result) Steering stability 116 123 126 1 115 119 Durability 110 115 126 114 110 Comprehensive evaluation 226 238 252 229 229

TABLE-US-00004 TABLE 4 Comparative example No. 2-1 2-2 2-3 2-4 2-5 SIZE 195/65R17 195/40R20 195/65R17 195/65R17 195/65R17 (Formulation) NR 100 100 100 100 100 Carbon black-1 65 65 55 55 Carbon black-2 55 Crosslinking aid 0.5 1.2 1.2 Curable resin component-1 3 Curable resin component-2 5 5 Cobalt organic acid 1.0 1.0 1.0 1.0 1.0 Zinc oxide 10 10 10 11 11 Anti-aging agent-1 1 1 1 1 1 Anti-aging agent-2 0.5 0.5 0.5 0.5 0.5 Stearic acid 1 1 1 1 1 Sulfur 6.5 6.5 7 7 7 Curing agent 1.5 3 3 Vulcanization accelerator 1.2 1.2 1.2 1.2 1.2 (Parameter) tan δ 0.13 0.13 0.13 0.1 0.08 E* (MPa) 6.5 6.5 9.4 10.5 8.7 Dt(mm) 685 663 687 686 684 V(mm.sup.3) 44971685 28813525 45631809 44829249 44175819 Wt(mm) 202 201 203 201 200 Ht(mm) 127 78 128 127 126 T (mm) 9.0 9.2 9.1 9.1 9.3 Dt-2 × Ht(mm) 431 507 431 432 432 tan δ/E* 0.02000 0.02000 0.01383 0.00952 0.00920 (Dt.sup.2 × π/4)/Wt 1824 1718 1826 1839 1837 (V + 1.5 × 10.sup.7)/Wt 296890 217978 298679 297658 295879 (V + 2.0 × 10.sup.7)/Wt 321642 242853 323309 322534 320879 (V + 2.5 × 10.sup.7)/Wt 346394 267729 347940 347409 345879 Aspect ratio (%) 63 39 63 63 63 [(tan δ/E*)/Wt] × 1000 0.099 0.100 0.068 0.047 0.046 (tan δ/E*) × T 0.180 0.184 0.126 0.087 0.086 (Evaluation result) Steering stability 88 95 93 100 90 Durability 86 91 92 96 100 Comprehensive evaluation 174 186 185 196 190

Experiment 3

[0224] In this experiment, 225 size tires were prepared and evaluated.

[0225] After producing the test tires of Examples 3-1 to 3-5 and Comparative Examples 3-1 to 3-5 shown in Tables 5 and 6 in the same manner as in Experiment 1, each parameter was calculated by performing the same procedure. Then, in the same manner, a performance evaluation test was conducted and evaluated. The result in Comparative Example 3-4 was set as 100 for evaluation of changes in steering stability (handling performance), and the result in Comparative Example 3-5 was set as 100 for evaluation of durability performance. The results of each evaluation are shown in Tables 5 and 6.

TABLE-US-00005 TABLE 5 Example No. 3-1 3-2 3-3 3-4 3-5 SIZE 225/35R22 225/35R22 225/35R22 225/50R20 225/40R21 (Formulation) NR 100 100 100 100 100 Carbon black-1 55 55 55 55 Carbon black-2 50 Crosslinking aid 0.5 1.2 0.5 0.5 Curable resin component-1 3 3 3 Curable resin component-2 5 5 Cobalt organic acid 1.0 1.0 1.0 1.0 1.0 Zinc oxide 10 11 11 10 10 Anti-aging agent-1 1 1 1 1 1 Anti-aging agent-2 0.5 0.5 0.5 0.5 0.5 Stearic acid 1 1 1 1 1 Sulfur 7 7 7 7 7 Curing agent 1.5 3 3 1.5 1.5 Vulcanization accelerator 1.2 1.2 1.2 1.2 1.2 (Parameter) tan δ 0.13 0.1 0.07 0.13 0.13 E* (MPa) 9.4 10.5 8.7 9.4 9.4 Dt(mm) 716 719 717 735 714 V(mm.sup.3) 36203610 36616393 36418787 52265389 40755756 Wt(mm) 229 228 230 235 231 Ht(mm) 79 80 79 114 90 T (mm) 9.6 9.7 9.6 9.5 9.6 Dt-2 × Ht(mm) 558 559 559 507 534 tan δ/E* 0.01383 0.00952 0.00805 0.01383 0.01383 (Dt.sup.2 × π/4)/Wt 1758 1781 1755 1805 1733 (V + 1.5 × 10.sup.7)/Wt 223597 226388 223560 286236 241367 (V + 2.0 × 10.sup.7)/Wt 245431 248318 245299 307512 263012 (V + 2.5 × 10.sup.7)/Wt 267265 270247 267038 328789 284657 Aspect ratio (%) 34 35 34 49 39 [(tan δ/E*)/Wt] × 1000 0.060 0.042 0.035 0.059 0.060 (tan δ/E*) × T 0.133 0.092 0.077 0.131 0.133 (Evaluation result) Steering stability 125 130 140 126 122 Durability 116 115 123 108 113 Comprehensive evaluation 241 245 263 234 235

TABLE-US-00006 TABLE 6 Comparative example No. 3-1 3-2 3-3 3-4 3-5 SIZE 225/60R20 225/50R20 225/60R20 225/60R20 225/60R20 (Formulation) NR 100 100 100 100 100 Carbon black-1 65 65 55 55 Carbon black-2 55 Crosslinking aid 0.5 1.2 1.2 Curable resin component-1 3 Curable resin component-2 5 5 Cobalt organic acid 1.0 1.0 1.0 1.0 1.0 Zinc oxide 10 10 10 11 11 Anti-aging agent-1 1 1 1 1 1 Anti-aging agent-2 0.5 0.5 0.5 0.5 0.5 Stearic acid 1 1 1 1 1 Sulfur 6.5 6.5 7 7 7 Curing agent 1.5 3 3 Vulcanization accelerator 1.2 1.2 1.2 1.2 1.2 (Parameter) tan δ 0.13 0.13 0.13 0.1 0.08 E* (MPa) 6.5 6.5 9.4 10.5 8.7 Dt(mm) 776 733 777 778 780 V(mm.sup.3) 61890670 51503396 62080258 61904251 62184635 Wt(mm) 229 234 228 227 226 Ht(mm) 134 113 135 135 136 T (mm) 9.6 9.6 9.7 9.5 9.6 Dt-2 × Ht(mm) 508 507 507 508 508 tan δ/E* 0.02000 0.02000 0.01383 0.00952 0.00920 (Dt.sup.2 × π/4)/Wt 2065 1803 2080 2094 2114 (V + 1.5 × 10.sup.7)/Wt 335767 284203 338071 338785 341525 (V + 2.0 × 10.sup.7)/Wt 357601 305570 360001 360812 363649 (V + 2.5 × 10.sup.7)/Wt 379435 326938 381931 382838 385773 Aspect ratio (%) 59 48 59 59 60 [(tan δ/E*)/Wt] × 1000 0.087 0.085 0.061 0.042 0.041 (tan δ/E*) × T 0.192 0.192 0.134 0.090 0.088 (Evaluation result) Steering stability 86 92 88 100 84 Durability 84 86 88 91 100 Comprehensive evaluation 170 178 176 191 184

Summary of Experiments 1 to 3

[0226] From the results of Experiments 1 to 3 (Tables 1 to 6), for tires of any size, 175 size, 195 size, 225 size, it turns out that it is possible to provide a pneumatic tire in which the steering stability is sufficiently improved and also the durability is sufficiently improved, when (tan δ/E*) is 0.002 or more and 0.017 or less and the above (formula 1) and (formula 2) are satisfied.

[0227] Then, it turns out that, by satisfying each of the requirements defined in the present disclosure, it is possible to provide a tire with further improved changes in steering stability and durability performance.

[0228] On the other hand, when (tan δ/E*) does not satisfy 0.002 or more and 0.017 or less, or when either of (formula 1) or (formula 2) is not satisfied, it was found that the change in the handling performance between low-speed and high-speed could not be sufficiently reduced, and the durability could not be sufficiently improved.

Experiment 4

[0229] Next, three types of tires (Examples 4-1 to 4-3) in which the relationship between the virtual volume V and the cross-sectional width Wt did not differ significantly were produced with the same formulation and evaluated in the same manner. Here, the result in Example 4-1 was set as 100 for the change in steering stability (handling performance), and the result in Example 4-3 was set as 100 for the durability performance.

[0230] Further, in this experiment, in addition to the above-described evaluations of steering stability and durability performance, fuel efficiency was also evaluated.

[0231] Specifically, each test tire was installed on all wheels of a vehicle (domestic FF vehicle, displacement 2000 cc), and after filling air so that the internal pressure was 250 kPa, the tire was run on a dry road test course on the dry road surface at a speed of 80 km/h. After making a 10 km lap, the accelerator was released, and the distance from when the accelerator was turned off until the vehicle stopped was measured as the rolling resistance of each test tire.

[0232] Next, the result in Example 4-3 was set as 100, the result for each test tire was indexed based on the following formula, and the rolling resistance during high-speed running was relatively evaluated to evaluate fuel efficiency. The larger the value, the longer the distance from when the accelerator is released until the vehicle stops, the smaller the rolling resistance in a steady state, and the better the fuel efficiency.

Fuel efficiency=[(Result of test tire)/(Result of Example 4-3)]×100

(Comprehensive Evaluation)

[0233] As in Experiments 1 to 3, each evaluation result was totaled to obtain a comprehensive evaluation. Table 7 shows the results of each evaluation.

TABLE-US-00007 TABLE 7 Example No. 4-1 4-2 4-3 SIZE 175/55R18 195/50R19 225/45R20 (Formulation) NR 100 100 100 Carbon black-1 55 55 55 Carbon black-2 Crosslinking aid 1.2 1.2 1.2 Curable resin component-1 Curable resin component-2 5 5 5 Cobalt organic acid 1.0 1.0 1.0 Zinc oxide 11 11 11 Anti-aging agent-1 1 1 1 Anti-aging agent-2 0.5 0.5 0.5 Stearic acid 1 1 1 Sulfur 7 7 7 Curing agent 3 3 3 Vulcanization accelerator 1.2 1.2 1.2 (Parameter) tan δ 0.1 0.1 0.1 E* (MPa) 10.5 10.5 10.5 Dt(mm) 648 680 711 V(mm.sup.3) 30132749 35836776 43355989 Wt(mm) 181 200 224 Ht(mm) 96 98 101 T (mm) 8.5 9.1 9.4 Dt-2 × Ht(mm) 456 484 509 tan δ/E* 0.00952 0.00952 0.00952 (Dt.sup.2 × π/4)/Wt 1822 1816 1772 (V + 1.5 × 10.sup.7)/Wt 249352 254184 260518 (V + 2.0 × 10.sup.7)/Wt 276977 279184 282839 (V + 2.5 × 10.sup.7)/Wt 304601 304184 305161 Aspect ratio (%) 53 49 45 [(tan δ/E*)/Wt] × 1000 0.053 0.048 0.043 (tan δ/E*) × T 0.081 0.087 0.090 (Evaluation result) Steering stability 100 106 110 Durability 115 105 100 110 105 100 Comprehensive evaluation 325 316 310

[0234] Table 7 shows that, when there is no large difference in the relationship between the virtual volume V and the cross-sectional width Wt, all of steering stability, durability performance and fuel efficiency are improved as the cross-sectional width Wt becomes smaller as from less than 205 mm to less than 200 mm, and as the aspect ratio increases. That is, it can be seen a remarkable effect is exhibited.

[0235] Although the present disclosure has been described above based on the embodiments, the present disclosure is not limited to the above embodiments. Various modifications can be made to the above embodiments within the same and equal range as the present disclosure.

[0236] The present disclosure (1) is; [0237] a pneumatic tire having a belt layer radially inward of the tread portion, in which; [0238] the ratio of loss tangent (tan δ) to complex elastic modulus (E*: MPa), (tan δ/E*), of the rubber composition constituting the belt layer, measured under the conditions of 70° C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1%, is 0.002 or more and 0.017 or less; and [0239] the tire satisfies following (formula 1) and (formula 2),

1700≤(Dt.sup.2×π/4)/Wt≤2827.4  (formula 1)

[(V+1.5×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 2)

, where the cross-sectional width of the tire is Wt (mm), the outer diameter is Dt (mm), and the volume of the space occupied by the tire is the virtual volume V (mm.sup.3), when the tire is installed on a standardized rim and the internal pressure is 250 kPa.

[0240] The present disclosure (2) is the pneumatic tire according to the present disclosure (1), wherein the following (formula 3) is satisfied.

[(V+2.0×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 3)

[0241] The present disclosure (3) is the pneumatic tire according to the present disclosure (2), wherein the following (formula 4) is satisfied.

[(V+2.5×10.sup.7)/Wt]≤2.88×10.sup.5  (formula 4)

[0242] The present disclosure (4) is the pneumatic tire of any combination of the present disclosures (1) to (3), wherein, when the outer diameter of the tire is Dt (mm) and the cross-sectional height of the tire is Ht (mm) when the tire is installed on a standardized rim and the internal pressure is 250 kPa, (Dt−2×Ht) is 470 (mm) or more.

[0243] The present disclosure (5) is the pneumatic tire of any combination of the present disclosures (1) to (4), which has an aspect ratio of 40% or more.

[0244] The present disclosure (6) is the pneumatic tire according to the present disclosure (5), which has an aspect ratio of 45% or more.

[0245] The present disclosure (7) is the pneumatic tire according to the present disclosure (6), which has an aspect ratio of 47.5% or more.

[0246] The present disclosure (8) is the pneumatic tire according to the present disclosure (7), which has an aspect ratio of 50% or more. [0204]

[0247] The present disclosure (9) is the pneumatic tire of any combination of the present disclosures (1) to (8), wherein the rubber composition constituting the belt layer has a ratio of loss tangent to complex elastic modulus (tan δ/E*) of 0.009 or less.

[0248] The present disclosure (10) is the pneumatic tire of any combination of the present disclosures (1) to (9), characterized by satisfying the following (formula 5).

[(tan δ/E*)/Wt]×1000≤0.60  (formula 5)

[0249] The present disclosure (11) is the pneumatic tire according to the present disclosure (10), characterized by satisfying the following (formula 6).

[(tan δ/E*)/Wt]×1000≤0.55  (formula 6)

[0250] The present disclosure (12) is the pneumatic tire of any combination of the present disclosures (1) to (11), characterized by satisfying the following (formula 7)

(tan δ/E*)×T≤1.00  (formula 7)

, where the distance from the tread surface to the belt layer is T (mm).

[0251] The present disclosure (13) is the pneumatic tire according to the present disclosure (12), characterized by satisfying the following (formula 8).

(tan δ/E*)×T≤0.85  (formula 8)

[0252] The present disclosure (14) is the pneumatic tire of any combination of the present disclosures (1) to (13), wherein the tread portion has circumferential grooves continuously extending in the tire circumferential direction, and the ratio of the groove width L.sub.80 at a depth of 80% of the maximum depth of the circumferential groove to the groove width L.sub.0 of the circumferential groove on the ground contact surface of the tread portion (L.sub.80/L.sub.0) is 0.3 to 0.7.

[0253] The present disclosure (15) is the pneumatic tire of any combination of the present disclosures (1) to (14), wherein the tread portion has a plurality of circumferential grooves continuously extending in the tire circumferential direction, and the total cross-sectional area of the plurality of circumferential grooves is 10 to 30% of the cross-sectional area of the tread portion.

[0254] The present disclosure (16) is the pneumatic tire of any combination of the present disclosures (1) to (15), wherein the tread portion has a plurality of lateral grooves extending in the tire axial direction, and the total volume of the plurality of lateral grooves is 2.0 to 5.0% of the volume of the tread portion

[0255] The present disclosure (17) is the pneumatic tire of any combination of the present disclosures (1) to (16), wherein Dt is less than 685 (mm), where Dt (mm) is the outer diameter of the tire when the tire is installed on a standardized rim and the internal pressure is 250 kPa.

[0256] The present disclosure (18) is the pneumatic tire of any combination of the present disclosures (1) to (17), wherein the cross-sectional width Wt (mm) is less than 205 mm.

[0257] The present disclosure (19) is the pneumatic tire according to the present disclosure (18), wherein the cross-sectional width Wt (mm) is less than 200 mm.

[0258] The present disclosure (20) is the pneumatic tire of any combination of the present disclosures (1) to (19), wherein the steel cords in the belt layer extend at an angle of 15° or more and 50° or less with respect to the tire circumferential direction.

[0259] The present disclosure (21) is the pneumatic tire of any combination of the present disclosures (1) to (20), which is a pneumatic tire for a passenger car.