Pneumatic tire and method of manufacturing pneumatic tire

1. A pneumatic tire comprising:

a cylindrical annular structure having a plurality of through-holes;

a rubber layer that will become a tread portion provided along a circumferential direction of the annular structure on an outer side of the annular structure;

a plurality of main grooves provided on an outer side in a radial direction of the rubber layer, each main groove being parallel to the circumferential direction of the annular structure;

a land portion partitioned by the main grooves; and

a carcass portion including fibers covered by rubber, provided on at least both sides in a direction parallel to a center axis of a cylindrical structure including the annular structure and the rubber layer, wherein

an opening ratio of the through-holes in a region where each of the plurality of main grooves is provided is less than that in a region where the land portion is provided, and

spacing of the plurality of through-holes increases gradually from outer sides in the width direction toward a center in the width direction.

2. The pneumatic tire according to claim 1 , wherein a proportion of a total of an opening area of the through-holes to a surface area of the outer side in the radial direction in a case where the annular structure does not comprise the through-holes, is not less than 1% and not more than 30% in a region in a vicinity of a circumferential groove and not less than 0.5% and not more than 15% in a region where the circumferential groove is provided.

3. The pneumatic tire according to claim 1 , wherein a cross-sectional area of one of the through-holes is not less than 0.1 mm 2 and not more than 100 mm 2 .

4. The pneumatic tire according to claim 1 , wherein a sum of the area of the through-holes is not less than 0.5% and not more than 30% of the surface area of the outer side in the radial direction of the annular structure.

5. The pneumatic tire according to claim 1 , wherein the outer side of the rubber layer and the outer side of the annular structure, except a groove portion of the rubber layer, are parallel to the center axis.

6. The pneumatic tire according to claim 1 , wherein the annular structure is disposed farther outward in a radial direction of the structure than the carcass portion.

7. The pneumatic tire according to claim 1 , wherein the annular structure is a metal.

8. The pneumatic tire according to claim 1 , wherein a dimension in the direction parallel to the center axis of the annular structure is not less than 50% and not more than 95% of a total width in the direction parallel to the center axis of the pneumatic tire.

9. The pneumatic tire according to claim 1 , wherein a cross-sectional area of one of the through-holes is not less than 0.12 mm 2 and not more than 80 mm 2 .

10. The pneumatic tire according to claim 1 , wherein a cross-sectional area of one of the through-holes is not less than 0.15 mm 2 and not more than 70 mm 2 .

11. The pneumatic tire according to claim 1 , wherein a form of the through-holes is elliptical.

12. The pneumatic tire according to claim 1 , wherein an equivalent diameter 4×A/C of the through-holes, where C is a circumferential length of the through-holes and A is the opening area of the through-holes, is not less than 0.5 mm and not more than 10 mm.

13. The pneumatic tire according to claim 1 , wherein the through-holes have a circular form and a diameter of not less than 1.0 mm and not more than 8.0 mm, and wherein an equivalent diameter and the diameter of different of the through-holes are different, the equivalent diameter being defined by 4×A/C of the through-holes, where C is a circumferential length of the through-holes and A is the opening area of the through-holes.

14. The pneumatic tire according to claim 1 , wherein a sum of an area of the through-holes is not less than 1.0% and not more than 20% of a surface area of the outer side in the radial direction of the annular structure.

15. The pneumatic tire according to claim 1 , wherein the annular structure comprises recesses and protrusions which are unequally spaced.

16. The pneumatic tire according to claim 1 , wherein the annular structure comprises a welded portion, and a thickness at a region of the welded portion, except at a weld itself in the welded portion, is not less than 0.1 mm and not more than 0.8 mm.

17. The pneumatic tire according to claim 1 , wherein the annular structure comprises a welded portion, and a thickness at a region of the welded portion, except at a weld itself in the welded portion, is not less than 0.15 mm and not more than 0.7 mm.

18. The pneumatic tire according to claim 1 , wherein the annular structure comprises a welded portion, and a thickness of a portion of the welded portion that is greater than a thickness of surroundings thereof is not more than 1.2 times the thickness of the surroundings.

19. The pneumatic tire of claim 1 , wherein each of the main grooves has a corresponding continuous annular band having no through-holes.

20. The pneumatic tire of claim 1 , wherein

the land portion comprises a plurality of land portions;

the annular structure includes recesses and protrusions on both edges in the width direction with one of the plurality of through-holes present in each of the protrusions, and

the regions are circumferential regions extending along a circumference of the annular structure, the regions including a region extending between side of the plurality of main grooves as projected onto the annular structure and a region extending between sides of the plurality of land portions as projected onto the annular structure.

21. A pneumatic tire comprising:

a cylindrical annular structure having a plurality of through-holes, wherein a sum of an area of the through-holes is not less than 0.5% and not more than 20% of a surface area of an outer side in the radial direction of the annular structure;

a rubber layer that will become a tread portion provided along a circumferential direction of the annular structure on the outer side of the annular structure; and

a carcass portion including fibers covered by rubber, provided on at least both sides in a direction parallel to a center axis of the cylindrical structure including the annular structure and the rubber layer, wherein

a product of an elastic modulus of the annular structure and a thickness of the annular structure is not less than 10 GPa·mm and not more than 500 GPa·mm, and

a diameter or equivalent diameter of the plurality of through-holes decrease gradually from outer sides in the width direction toward a center in the width direction.