PNEUMATIC TIRE

Abstract

The present invention provides a pneumatic tire which is sufficiently reduced in the rolling resistance during high-speed travel, while having sufficiently improved chipping resistance. A pneumatic tire which has a tread part, wherein: at least one rubber layer that forms the tread part contains a rubber component that contains an isoprene rubber, a styrene butadiene rubber and a butadiene rubber, while containing more than 5 parts by mass but 25 parts by mass or less of carbon black relative to 100 parts by mass of the rubber component; and if Wt (mm) is the cross-sectional width of the tire, Dt (mm) is the outer diameter of the tire, and V (mm.sup.3) is the virtual volume that is the volume of the space occupied by the tire when this pneumatic tire is installed on a standardized rim and the internal pressure is 250 kPa, (formula 1) and (formula 2) are satisfied.

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 tread portion, wherein at least one of the rubber layers forming the tread portion contains a rubber component containing isoprene-based rubber, styrene-butadiene rubber and butadiene rubber, and more than parts by mass and 25 parts by mass or less of carbon black with respect to 100 parts by mass of the rubber component; and when 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, 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)

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

3. The pneumatic tire according to claim 2, wherein the tire satisfies the following (formula 4),
[(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, wherein the aspect ratio is 40% or more.

6. The pneumatic tire according to claim 5, wherein the aspect ratio is 45% or more.

7. The pneumatic tire according to claim 6, wherein the aspect ratio is 47.5% or more.

8. The pneumatic tire according to claim 7, wherein the aspect ratio is 50% or more.

9. The pneumatic tire according to claim 1, wherein the loss tangent (30° C.tan δ) of the rubber layer of the tread portion measured under the conditions of 30° C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1% is less than 0.15.

10. The pneumatic tire according to claim 1, wherein the amount of carbon black CB (parts by mass) and the cross-sectional width Wt (mm) of the tire satisfy the following (formula 5).
CB×Wt≥900  (formula 5)

11. The pneumatic tire according to claim 10, wherein following (formula 6) is satisfied.
CB×wt≥1500  (formula 6)

12. 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.

13. The pneumatic tire according to claim 1, wherein the tread portion has a plurality of circumferential grooves extending continuously 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.

14. 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.

15. The pneumatic tire according to claim 14, wherein at least one of the lateral grooves is a lateral groove in which groove width/groove depth is 0.50 to 0.80.

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

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

18. The pneumatic tire according to claim 17, wherein the cross-sectional width Wt (mm) is less than 200 mm.

19. The pneumatic tire according to claim 1, wherein, when the thickness of the rubber layer of the tread layer in the radial direction of the tire is Td (mm), and the loss tangent of the rubber layer measured under the conditions of 30° C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1% is 30° C.tan δ, following (formula 7) is satisfied
(30° C.tan δ/Td)×100≥2.00  (formula 7).

20. The pneumatic tire according to claim 19, wherein following (formula 8) is satisfied
(30° C.tan δ/Td)×100≥2.50  (formula 8).

21. The pneumatic tire according to claim 20, wherein following (formula 9) is satisfied
(30° C.tan δ/Td)×100≥3.00  (formula 9).

22. The pneumatic tire according to claim 1, wherein the tread portion is formed from a plurality of rubber layers, and the rubber composition is used in the cap rubber layer of the tread.

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

Description

EXAMPLES

[0178] Hereinafter, the present disclosure will be described in more specific with reference to Examples.

Experiment 1

[0179] In this experiment, 175 size tires were prepared and evaluated.

1. Manufacture of Rubber Compositions for Treads

[0180] First, a rubber composition for tread was produced.

(1) Compounding Material

[0181] First, each compounding material shown below was prepared.

(a) Rubber Component

[0182] (a-1) NR: TSR20 [0183] (a-2) SBR: Modified solution polymerization SBR produced according to the method described in the next paragraph. (Styrene content: 30% by mass, vinyl bond amount: 52% by mass, Mw: 250,000) [0184] (a-3) BR-1: UBEPOL-BR360B manufactured by Ube Kosan Co., Ltd. (cis content: 98% by mass) [0185] (a-4) BR-2: N103 manufactured by Asahi Kasei Chemicals Co., Ltd. (cis content: 35% by mass)

[0186] The abovementioned SBR was produced according to the procedure shown below. First, cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged into a nitrogen-substituted autoclave reactor. After adjusting the temperature of the contents of the reactor to 20° C., n-butyllithium was added to initiate polymerization. Polymerization was carried out under adiabatic conditions, and the maximum temperature reached 85° C. When the polymerization conversion reaches 99%, 1,3-butadiene was added, and then further polymerization was carried out for 5 minutes. Thereafter, N, N-bis (trimethylsilyl)-3-aminopropyltriethoxysilane was added as a modifying agent to carry out the reaction. After completion of the polymerization reaction, 2,6-di-tert-butyl-p-cresol was added. Then, the solvent was removed by steam stripping and dried by a heat roll adjusted to 110° C. to obtain the SBR.

(b) Compounding Materials Other than Rubber Components [0187] (b-1) Carbon black: Show Black N134 manufactured by Cabot Japan Co., Ltd. (N.sub.2SA: 134 m.sup.2/g) [0188] (b-2) Silica: Ultrasil VN3 manufactured by Evonik (BET specific surface area: 165 m.sup.2/g) [0189] (b-3) Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl)disulfide) manufactured by Degussa [0190] (b-4) Oil: Process X-140 manufactured by Japan Energy Co., Ltd. [0191] (b-5) Resin: SYLVATRAXX 4401 (α-methylstyrene resin) manufactured by Arizona Chemical Co. [0192] (b-6) Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. [0193] (b-7) Anti-aging agent-1: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-phenyl-N′(1,3-dimethylbutyl)-p-phenylenediamine) [0194] (b-8) Anti-aging agent-2: Nocrac 224 manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (2,2,4-trimethyl-1,2-dihydroquinoline polymer) [0195] (b-9) Crosslinking agent and vulcanization accelerator [0196] Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. [0197] Vulcanization accelerator-1: Nocceler NS manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-tert-butyl-2-benzothiazolylsulfenamide) [0198] Vulcanization accelerator-2: Nocceler DPG manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (1,3-diphenylguanidine)

(2) Production of Rubber Composition

[0199] 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 part by mass.

2. Tire Manufacturing

[0200] 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 tread rubber composition. A tread is formed using the obtained tread rubber composition, bonded together with other tire members to form an unvulcanized tire, which is then press-vulcanized for 10 minutes under the condition of 170° C. 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 1-7).

3. Parameter Calculation

[0201] After that, for each test tire, the thickness Td (mm) of the rubber layer of the tread portion, the outer diameter Dt (mm) of the tire, the cross-sectional width Wt (mm), the cross-sectional height Ht (mm), and the aspect ratio (%) were obtained, and, in addition, a virtual volume V (mm.sup.3) was obtained.

[0202] At the same time, a rubber test piece for viscoelasticity measurement was produced by cutting out from the rubber layer of the tread portion of each test tire in a length 20 mm×width 4 mm×thickness 2 mm so that the tire circumferential direction was the long side. For each rubber test piece, tan δ (30° C.tan δ) was measured under the conditions of 30° C., frequency 10 Hz, initial strain 5%, and dynamic strain 1% using an Eplexor series manufactured by GABO Co., Ltd. Regarding the test tire having the same composition, the average of each measured value was used.

[0203] 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, CB×Wt, and (30° C.tan δ/Td)×100 were determined. The results are shown in Tables 1 and 2.

5. Performance Evaluation Test

(1) Evaluation of Rolling Resistance at High-Speed Running

[0204] Each test tire was installed on all wheels of the vehicle (domestic FF vehicle, displacement 2000 cc), filled with air so that the internal pressure became 250 kPa, and then driven on the test course on the dry road surface at a speed of 100 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 at high-speed running.

[0205] Next, the result in Comparative Example 1-5 was set to as 100, and the results were indexed based on the following formula to relatively evaluate the rolling resistance at high-speed running. The larger the value, the longer the distance from when the accelerator is turned off until the vehicle stops and the smaller the rolling resistance in the steady state, and showing excellent fuel efficiency.

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

(2) Evaluation of Chipping Resistance

[0206] Each test tire is mounted on all wheels of a vehicle (domestic FF vehicle, displacement 2000 cc), filled with air so that the internal pressure became 250 kPa, and then driven on the test course on the dry road surface at a speed of 100 km/h. After making a 10 km lap, it was made to lap the sand course as it was. After completing the lap, the number and size of chipped blocks on the tread portion of the tire were integrated, and the reciprocal number thereof was calculated.

[0207] Then, with the calculation result in Comparative Examples 1-7 set to 100, the durability was evaluated relatively by indexing based on the following formula. The larger the numerical value, the smaller the number of chips in the block and smaller the size of chips, indicating that the chipping resistance is excellent.

Chipping resistance=[(calculation result of test tire)/(calculation result of Comparative Example 1-7)]×100

(3) Comprehensive Evaluation

[0208] The evaluation results of (1) and (2) above were totaled to obtain a comprehensive evaluation.

(4) Evaluation Result

[0209] 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 10 10 10 10 10 SBR 45 45 45 45 45 BR-1 35 35 35 35 35 BR-2 10 10 10 10 10 Carbon 6 15 25 6 6 Silica 49 47 47 49 49 Silane coupling agent 4.9 4.7 4.7 4.9 4.9 Oil 30 30 30 30 30 Resin 5 5 5 5 5 Wax 1.5 1.5 1.5 1.5 1.5 Anti-aging agent-1 2 2 2 2 2 Anti-aging agent-2 1 1 1 1 1 Sulfur 1.5 1.5 1.5 1.5 1.5 Vulcanization accelerator-1 2 2 2 2 2 Vulcanization accelerator-2 1 1 1 1 1 (Parameter) 30° C. tanδ 0.158 0.177 0.217 0.147 0.147 CB (part by mass) 6 15 25 6 6 Td(mm) 8.2 7.9 8.1 8.0 7.8 Dt(mm) 672 673 674 684 693 V(mm.sup.3) 23005355 23471373 23510297 30152956 34331262 Wt(mm) 176 177 177 183 177 Ht(mm) 69 70 70 88 105 Dt-2 × Ht(mm) 534 533 534 508 483 (Dt.sup.2 × Π/4)/Wt 2015 2010 2016 2008 2131 (V + 1.5 × 10.sup.7)/Wt 215940 217352 217572 246737 278708 (V + 2.0 × 10.sup.7)/Wt 244349 245601 245821 274060 306956 (V + 2.5 × 10.sup.7)/Wt 272758 273850 274069 301382 335205 Aspect ratio (%) 39.20 39.55 39.55 48.09 59.32 CB × Wt 1056 2655 4425 1098 1062 (30° C . tanδ/Td) × 100 1.93 2.24 2.68 1.84 1.88 (Evaluation result) Rolling resistance at high-speed running 110 108 106 112 115 Chipping resistance 118 126 135 115 108 Comprehensive evaluation 228 234 241 227 223

TABLE-US-00002 TABLE 2 Comparative example No. 1-1 1-2 1-3 1-4 1-5 1-6 1-7 SIZE 175/80R14 175/60R19 175/80R14 175/80R14 175/80R14 175/80R14 175/80R14 (Formulation) NR 10 55 10 10 SBR 55 55 55 45 45 45 BR-1 35 35 35 35 35 35 35 BR-2 10 10 10 10 10 10 10 Carbon 3 3 6 3 3 15 25 Silica 52 52 49 52 52 40 47 Silane coupling agent 5.2 5.2 4.9 5.2 5.2 4 4.7 Oil 30 30 30 30 30 30 30 Resin 5 5 5 5 5 5 5 Wax 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Anti-aging agent-1 2 2 2 2 2 2 2 Anti-aging agent-2 1 1 1 1 1 1 1 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Vulcanization 2 2 2 2 2 2 2 accelerator-1 Vulcanization 1 1 1 1 1 1 1 accelerator-2 (Parameter) 30° C.tanδ 0.156 0.156 0.164 0.158 0.153 0.165 0.217 CB (part by mass) 3 3 6 3 3 15 25 Td(mm) 7.8 8.1 7.9 8.1 8.2 7.7 7.8 Dt(mm) 636 692 693 694 636 635 637 V(mm.sup.3) 38394786 34466507 34331262 34854035 38612938 38099665 38669035 Wt(mm) 176 178 177 178 177 175 176 Ht(mm) 140 105 105 106 140 140 141 Dt-2 × Ht(mm) 356 482 483 482 356 355 355 (Dt.sup.2 × π/4)/Wt 1805 2113 2131 2125 1795 1810 1811 (V + 1.5 × 10.sup.7)/Wt 303379 277902 278708 280079 302898 303427 304938 (V + 2.0 × 10.sup.7)/Wt 331789 305992 306956 308169 331147 331998 333347 (V + 2.5 × 10.sup.7)/Wt 360198 334082 335205 336259 359395 360570 361756 Aspect ratio (%) 79.55 58.99 59.32 59.55 79.10 80.00 80.11 CB × Wt 528 534 1062 534 531 2625 4400 (30° C.tanδ/Td) × 100 2.00 1.93 2.08 1.95 1.87 2.14 2.78 (Evaluation result) Rolling resistance at 96 100 94 96 100 96 87 high-speed running Chipping resistance 92 88 95 96 88 95 100 Comprehensive 188 188 189 192 188 191 187 evaluation

Experiment 2

[0210] In this experiment, 195 size tires were prepared and evaluated.

[0211] After producing the test tires of Examples 2-1 to 2-5 and Comparative Examples 2-1 to 2-7 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. In this experiment, the result in Comparative Example 2-5 was set as 100, when evaluating rolling resistance during high-speed running, and the result in Comparative Example 2-7 was set as 100, when evaluating chipping resistance. 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 10 10 10 10 10 SBR 45 45 45 45 45 BR-1 35 35 35 35 35 BR-2 10 10 10 10 10 Carbon 6 15 25 6 6 Silica 69 67 67 69 69 Silane coupling agent 6.9 6.7 6.7 6.9 6.9 Oil 30 30 30 30 30 Resin 5 5 5 5 5 Wax 1.5 1.5 1.5 1.5 1.5 Anti-aging agent-1 2 2 2 2 2 Anti-aging agent-2 1 1 1 1 1 Sulfur 1.5 1.5 1.5 1.5 1.5 Vulcanization accelerator-1 2 2 2 2 2 Vulcanization accelerator-2 1 1 1 1 1 (Parameter) 30° C. tanδ 0.205 0.243 0.288 0.205 0.205 CB (part by mass) 6 15 25 6 6 Td(mm) 8.3 7.7 7.7 8.2 8.1 Dt(mm) 665 663 664 680 691 V(mm.sup.3) 29087378 28526824 28431992 35417448 42618582 Wt(mm) 200 199 198 196 202 Ht(mm) 79 78 78 99 117 Dt-2 × Ht(mm) 507 507 508 482 457 (Dt.sup.2 × Π/4)/Wt 1737 1735 1749 1853 1856 (V + 1.5 × 10.sup.7)/Wt 220437 218728 219353 257232 285241 (V + 2.0 × 10.sup.7)/Wt 245437 243853 244606 282742 309993 (V + 2.5 × 10.sup.7)/Wt 270437 268979 269859 308252 334745 Aspect ratio (%) 39.50 39.20 39.39 50.51 57.92 CB × Wt 1200 2985 4950 1176 1212 (30° C . tanδ/Td) × 100 2.47 3.16 3.74 2.50 2.53 (Evaluation result) Rolling resistance at high-speed running 108 104 100 112 116 Chipping resistance 120 128 138 115 110 Comprehensive evaluation 228 232 238 227 226

TABLE-US-00004 TABLE 4 Comparative example No. 2-1 2-2 2-3 2-4 2-5 2-6 2-7 SIZE 195/65R17 195/40R20 195/65R17 195/65R17 195/65R17 195/65R17 195/65R17 (Formulation) NR 10 55 10 10 SBR 55 55 55 45 45 45 BR-1 35 35 35 35 35 35 35 BR-2 10 10 10 10 10 10 10 Carbon 3 3 6 3 3 15 25 Silica 72 72 69 72 72 60 67 Silane coupling agent 7.2 7.2 6.9 7.2 7.2 6 6.7 Oil 30 30 30 30 30 30 30 Resin 5 5 5 5 5 5 5 Wax 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Anti-aging agent-1 2 2 2 2 2 2 2 Anti-aging agent-2 1 1 1 1 1 1 1 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Vulcanization 2 2 2 2 2 2 2 accelerator-1 Vulcanization 1 1 1 1 1 1 1 accelerator-2 (Parameter) 30° C.tanδ 0.187 0.187 0.195 0.198 0.210 0.210 0.288 CB (part by mass) 3 3 6 3 3 15 25 Td(mm) 7.9 7.8 8.2 8.1 8.0 8.1 8.2 Dt(mm) 686 664 664 664 686 686 686 V(mm.sup.3) 44829249 28719183 28131992 28575587 43937124 43714093 43937124 Wt(mm) 201 200 198 199 197 196 197 Ht(mm) 127 78 78 78 127 127 127 Dt-2 × Ht(mm) 432 508 508 508 432 432 432 (Dt.sup.2 × π/4)/Wt 1839 1731 1749 1740 1876 1886 1876 (V + 1.5 × 10.sup.7)/Wt 297658 218596 219353 218973 299173 299562 299173 (V + 2.0 × 10.sup.7)/Wt 322534 243596 244606 244098 324554 325072 324554 (V + 2.5 × 10.sup.7)/Wt 347409 268596 269859 269224 349935 350582 349935 Aspect ratio (%) 63.18 39.00 39.39 39.20 64.47 64.80 64.47 CB × Wt 603 600 1188 597 591 2940 4925 (30° C.tanδ/Td) × 100 2.37 2.40 2.38 2.44 2.63 2.59 3.51 (Evaluation result) Rolling resistance at 98 100 92 96 100 96 86 high-speed running Chipping resistance 90 88 94 96 88 94 100 Comprehensive 188 188 186 192 188 190 186 evaluation

Experiment 3

[0212] In this experiment, 225 size tires were prepared and evaluated.

[0213] After producing the test tires of Examples 3-1 to 3-5 and Comparative Examples 3-1 to 3-7 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. In this experiment, the result in Comparative Example 3-5 was set as 100, when evaluating rolling resistance during high-speed running, and the result in Comparative Example 3-7 was set as 100, when evaluating chipping resistance. 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 10 10 10 10 10 SBR 45 45 45 45 45 BR-1 35 35 35 35 35 BR-2 10 10 10 10 10 Carbon 6 15 25 6 6 Silica 84 82 82 84 84 Silane coupling agent 8.4 8.2 8.2 8.4 8.4 Oil 30 30 30 30 30 Resin 5 5 5 5 5 Wax 1.5 1.5 1.5 1.5 1.5 Anti-aging agent-1 2 2 2 2 2 Anti-aging agent-2 1 1 1 1 1 Sulfur 1.5 1.5 1.5 1.5 1.5 Vulcanization accelerator-1 2 2 2 2 2 Vulcanization accelerator-2 1 1 1 1 1 (Parameter) 30° C. tanδ 0.255 0.296 0.344 0.255 0.255 CB (part by mass) 6 15 25 6 6 Td(mm) 7.8 7.9 8.0 8.2 8.1 Dt(mm) 716 718 717 734 713 V(mm.sup.3) 36203610 37040131 35785417 50043281 40161995 Wt(mm) 229 231 226 227 228 Ht(mm) 79 80 79 113 90 Dt-2 × Ht(mm) 558 558 559 508 533 (Dt.sup.2 × Π/4)/Wt 1758 1753 1787 1864 1751 (V + 1.5 × 10.sup.7)/Wt 223597 225282 224714 286534 241939 (V + 2.0 × 10.sup.7)/Wt 245431 246927 246838 308561 263868 (V + 2.5 × 10.sup.7)/Wt 267265 268572 268962 330587 285798 Aspect ratio (%) 34.50 34.63 34.96 49.78 39.47 CB × Wt 1374 3465 5650 1362 1368 (30° C . tanδ/Td) × 100 3.27 3.75 4.30 3.11 3.15 (Evaluation result) Rolling resistance at high-speed running 110 104 102 112 116 Chipping resistance 118 124 130 113 106 Comprehensive evaluation 228 228 232 225 222

TABLE-US-00006 TABLE 6 Comparative example No. 3-1 3-2 3-3 3-4 3-5 3-6 3-7 SIZE 225/60R20 225/50R20 225/60R20 225/60R20 225/60R20 225/60R20 225/60R20 (Formulation) NR 10 55 10 10 SBR 55 55 55 45 45 45 BR-1 35 35 35 35 35 35 35 BR-2 10 10 10 10 10 10 10 Carbon 3 3 6 3 3 15 25 Silica 87 87 84 87 87 75 82 Silane coupling agent 8.7 8.7 8.4 8.7 8.7 7.5 8.2 Oil 30 30 30 30 30 30 30 Resin 5 5 5 5 5 5 5 Wax 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Anti-aging agent-1 2 2 2 2 2 2 2 Anti-aging agent-2 1 1 1 1 1 1 1 Sulfur 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Vulcanization 2 2 2 2 2 2 2 accelerator-1 Vulcanization 1 1 1 1 1 1 1 accelerator-2 (Parameter) 30° C.tanδ 0.236 0.236 0.254 0.255 0.272 0.270 0.344 CB (part by mass) 3 3 6 3 3 15 25 Td(mm) 7.7 8.2 8.1 7.9 8.2 8.1 8.0 Dt(mm) 778 736 732 735 777 776 778 V(mm.sup.3) 62176957 51904024 50611309 51375765 62080258 61350140 61631545 Wt(mm) 228 233 232 231 228 227 226 Ht(mm) 135 114 112 114 135 134 135 Dt-2 × Ht(mm) 508 508 508 507 507 508 508 (Dt.sup.2 × π/4)/Wt 2085 1826 1814 1837 2080 2083 2103 (V + 1.5 × 10.sup.7)/Wt 338495 287142 282807 287341 338071 336344 339078 (V + 2.0 × 10.sup.7)/Wt 360425 308601 304359 308986 360001 358371 361202 (V + 2.5 × 10.sup.7)/Wt 382355 330060 325911 330631 381931 380397 383325 Aspect ratio (%) 59.21 48.93 48.28 49.35 59.21 59.03 59.73 CB × Wt 684 699 1392 693 684 3405 5650 (30° C.tanδ/Td) × 100 3.06 2.88 3.14 3.23 3.32 3.33 4.30 (Evaluation result) Rolling resistance at 96 100 96 96 100 96 88 high-speed running Chipping resistance 94 90 96 96 86 96 100 Comprehensive 190 190 192 192 186 192 188 evaluation

Summary of Experiments 1 to 3

[0214] 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 rolling resistance at high-speed running is sufficiently reduced and the chipping resistance is improved, when the above (formula 1) and (formula 2) are satisfied.

[0215] Then, it turns out that, by satisfying each of the requirements specified in claim 2 and thereafter, it is possible to provide a tire with further improved rolling resistance and chipping resistance at high-speed running.

[0216] On the other hand, when either (formula 1) or (formula 2) is not satisfied, the rolling resistance at high-speed running cannot be sufficiently reduced, and the chipping resistance cannot be sufficiently improved.

Experiment 4

[0217] 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, in addition to the evaluation of rolling resistance and chipping resistance at high-speed running, the ride comfort was also evaluated.

[0218] Specifically, each test tire was mounted on all wheels of a vehicle (domestic FF vehicle, displacement 2000 cc), filled with air so that the internal pressure became 250 kPa, and then driven on a dry road test course. The driver sensory-tested the ride comfort when driving 10 laps at a speed of 100 km/h on a 5-point scale. After summing up the evaluations by 20 drivers, the evaluation was indexed based on the following formula, with the total score in Example 4-3 being 100, and the riding comfort was relatively evaluated. A larger value indicates better riding comfort.

Ride comfort=[(Total evaluation score of test tire)/(Total evaluation score of Example 4-3)]×100

[0219] Then, as in Experiments 1 to 3, each evaluation result was totaled to obtain a comprehensive evaluation. The results of each evaluation are shown in Table 7.

TABLE-US-00007 TABLE 7 Example No. 4-1 4-2 4-3 SIZE 175/ 195/ 225/ 55R18 50R19 45R20 (Formulation) NR 10 10 10 SBR 45 45 45 BR-1 35 35 35 BR-2 10 10 10 Carbon 8 8 8 Silica 67 67 67 Silane coupling agent 6.7 6.7 6.7 Oil 30 30 30 Resin 5 5 5 Wax 1.5 1.5 1.5 Anti-aging agent-1 2 2 2 Anti-aging agent-2 1 1 1 Sulfur 1.5 1.5 1.5 Vulcanization 2 2 2 accelerator-1 Vulcanization 1 1 1 accelerator-2 (Parameter) 30° C. tanδ 0.200 0.200 0.200 CB (part by mass) 8 8 8 Td(mm) 7.6 8.1 8.3 Dt(mm) 649 679 710 V(mm.sup.3) 30354118 36015050 43478150 Wt(mm) 182 201 225 Ht(mm) 96 98 101 Dt-2 × Ht(mm) 457 483 508 (Dt.sup.2 × Π/4)/Wt 1818 1801 1760 (V + 1.5 × 10.sup.7)/Wt 249198 253806 259903 (V + 2.0 × 10.sup.7)/Wt 276671 278682 282125 (V + 2.5 × 10.sup.7)/Wt 304144 303557 304347 Aspect ratio (%) 52.75 48.76 44.89 CB × Wt 1456 1608 1800 (30° C . tanδ/ 2.63 2.47 2.41 Td) × 100 (Evaluation result) Rolling resistance at 117 106 100 high-speed running Chipping resistance 106 104 100 Ride comfort 116 108 100 Comprehensive 339 318 300 evaluation

[0220] Table 7 shows that, when there is no large difference in the relationship between the virtual volume V and the cross-sectional width Wt, the rolling resistance at high-speed running and durability are both 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.

[0221] 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.

[0222] The present disclosure (1) is; [0223] a pneumatic tire having a tread portion, wherein [0224] at least one of the rubber layers forming the tread portion contains a rubber component containing isoprene-based rubber, styrene-butadiene rubber and butadiene rubber, and more than 5 parts by mass and 25 parts by mass or less of carbon black with respect to 100 parts by mass of the rubber component; and [0225] , when 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, 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)

[0226] 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)

[0227] 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)

[0228] 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.

[0229] 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.

[0230] The present disclosure (6) is the pneumatic tire according to the present disclosure (5), which has an aspect ratio of 45% or more.

[0231] The present disclosure (7) is the pneumatic tire according to the present disclosure (6), which has an aspect ratio of 47.5% or more.

[0232] The present disclosure (8) is the pneumatic tire according to the present disclosure (7), which has an aspect ratio of 50% or more.

[0233] The present disclosure (9) is the pneumatic tire of any combination of the present disclosures (1) to (8), wherein the loss tangent (30° C.tan δ) of the rubber layer of the tread portion measured under the conditions of 30° C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1% is less than 0.15.

[0234] The present disclosure (10) is the pneumatic tire of any combination of the present disclosures (1) to (9), wherein the amount of carbon black CB (parts by mass) and the cross-sectional width Wt (mm) of the tire satisfy the following (formula 5).

CB×Wt≥900  (formula 5)

[0235] This disclosure (11) is the pneumatic tire according to the present disclosure (10), wherein following (formula 6) is satisfied.

CB×Wt≥1500  (formula 6)

[0236] The present disclosure (12) is the pneumatic tire of any combination of the present disclosures (1) to (11), 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.

[0237] The present disclosure (13) is the pneumatic tire of any combination of the present disclosures (1) to (12), 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.

[0238] The present disclosure (14) is the pneumatic tire of any combination of the present disclosures (1) to (13), 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

[0239] The present disclosure (15) is the pneumatic tire according to the present disclosure (14), wherein at least one of the lateral grooves is a lateral groove in which groove width/groove depth is 0.50 to 0.80.

[0240] The present disclosure (16) is the pneumatic tire of any combination of the present disclosures (1) to (15), 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.

[0241] The present disclosure (17) is the pneumatic tire of any combination of the present disclosures (1) to (16), wherein the cross-sectional width Wt (mm) is less than 205 mm.

[0242] The present disclosure (18) is the pneumatic tire according to the present disclosure (17), wherein the cross-sectional width Wt (mm) is less than 200 mm.

[0243] The present disclosure (19) is the pneumatic tire according to the present disclosure (18), wherein, when the thickness of the rubber layer of the tread layer in the radial direction of the tire is Td (mm), and the loss tangent of the rubber layer measured under the conditions of 30° C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1% is 30° C.tan δ, following (formula 7) is satisfied.

(30° C.tan δ/Td)×100≥2.00  (formula 7)

[0244] The present disclosure (20) is the pneumatic tire according to the present disclosure (19), wherein following (formula 8) is satisfied.

(30° C.tan δ/Td)×100≥2.50  (formula 8)

[0245] The present disclosure (21) is the pneumatic tire according to the present disclosure (20), wherein following (formula 9) is satisfied.

(30° C.tan δ/Td)×100≥3.00  (formula 9)

[0246] The present disclosure (22) is the pneumatic tire of any combination of the present disclosures (1) to (21), wherein the tread portion is formed from a plurality of rubber layers, and the rubber composition is used in the cap rubber layer of the tread.

[0247] The present disclosure (23) is the pneumatic tire of any combination of the present disclosures (1) to (22), which is a pneumatic tire for a passenger car.