GOLF BALL

Abstract

An object of the present disclosure is to provide a golf ball having an increased spin rate when being hit with an 8-iron while suppressing rise in a spin rate when being hit with a driver. The present disclosure provides a golf ball comprising a spherical core having an inner core and an outer core, and a cover positioned outside the spherical core, wherein A×a is 12,200 or less and B×b is 20,400 or more, where “a” represents an average hardness (Shore C) of a hardness (H2.5) at a point of 2.5 mm from a center of the spherical core and a hardness (H5) at a point of 5 mm from the center of the spherical core, “b” represents an average hardness (Shore C) of a hardness (H7.5) at a point of 7.5 mm from the center of the spherical core and a hardness (H9) at a point of 9 mm from the center of the spherical core, “A” represents an impulse difference (kN·µs) between a back spin impulse and a top spin impulse measured using a contact force tester under a condition corresponding to a condition when the golf ball is hit with a driver, and “B” represents an impulse difference (kN·µs) between a back spin impulse and a top spin impulse measured using a contact force tester under a condition corresponding to a condition when the golf ball is hit with an 8-iron.

Description

Claims

1. A golf ball comprising a spherical core having an inner core and an outer core, and a cover positioned outside the spherical core, wherein A×a is 12,200 or less, andB×b is 20,400 or more,where “a” represents an average hardness (Shore C) of a hardness (H2.5) at a point of 2.5 mm from a center of the spherical core and a hardness (H5) at a point of 5 mm from the center of the spherical core,“b” represents an average hardness (Shore C) of a hardness (H7.5) at a point of 7.5 mm from the center of the spherical core and a hardness (H9) at a point of 9 mm from the center of the spherical core,“A” represents an impulse difference (kN·µs) between a back spin impulse and a top spin impulse measured using a contact force tester under a condition corresponding to a condition when the golf ball is hit with a driver, and“B” represents an impulse difference (kN·µs) between a back spin impulse and a top spin impulse measured using a contact force tester under a condition corresponding to a condition when the golf ball is hit with an 8-iron.

2. The golf ball according to claim 1, wherein a ratio ((Bxb)/(Axa)) of the (B×b) to the (A×a) is 1.80 or more.

3. The golf ball according to claim 1, wherein a ratio (B/A) of the impulse difference “B” to the impulse difference “A” is 1.60 or more.

4. The golf ball according to claim 1, wherein the average hardness “a” is 70 or less in Shore C hardness, and the average hardness “b” is 70 or more in Shore C hardness.

5. The golf ball according to claim 1, wherein a hardness difference (Hs-H11) between a surface hardness (Hs) of the spherical core and a hardness (H11) at a point of 11 mm from the center of the spherical core is 0 or more in Shore C hardness.

6. The golf ball according to claim 1, wherein a hardness difference (H9-Ho) between the hardness (H9) at the point of 9 mm from the center of the spherical core and a center hardness (Ho) of the spherical core is 5 or more in Shore C hardness.

7. The golf ball according to claim 1, wherein the inner core is spherical and has a diameter ranging from 14 mm to 28 mm, and the outer core has a thickness ranging from 6 mm to 13 mm.

8. The golf ball according to claim 1, wherein the impulse difference “A” is 200 kN·µs or less.

9. The golf ball according to claim 1, wherein the impulse difference “B” is 230 kN·µs or more.

10. The golf ball according to claim 1, wherein a hardness difference (“b-a”) between the average hardness “b” and the average hardness “a” ranges from 5 to 40 in Shore C hardness.

11. The golf ball according to claim 1, wherein the hardness (H2.5) at the point of 2.5 mm from the center of the spherical core is 55 or more and 70 or less in Shore C hardness.

12. The golf ball according to claim 1, wherein the hardness (H5) at the point of 5 mm from the center of the spherical core is 60 or more and 75 or less in Shore C hardness.

13. The golf ball according to claim 1, wherein the hardness (H7.5) at the point of 7.5 mm from the center of the spherical core is 65 or more and 90 or less in Shore C hardness.

14. The golf ball according to claim 1, wherein the hardness (H9) at the point of 9 mm from the center of the spherical core is 70 or more and 95 or less in Shore C hardness.

15. The golf ball according to claim 1, wherein a hardness (H11) at a point of 11 mm from the center of the spherical core is 65 or more and 95 or less in Shore C hardness.

16. The golf ball according to claim 1, wherein a hardness (H12.5) at a point of 12.5 mm from the center of the spherical core is 65 or more and 95 or less in Shore C hardness.

17. The golf ball according to claim 1, wherein a hardness (H15) at a point of 15 mm from the center of the spherical core is 65 or more and 95 or less in Shore C hardness.

18. The golf ball according to claim 1, wherein a hardness difference (Hs-Ho) between a surface hardness (Hs) and a center hardness (Ho) of the spherical core is more than 10 in Shore C hardness.

19. The golf ball according to claim 1, wherein the cover comprises at least two layers.