GOLF BALL
A golf ball 2 includes an inner core 4 , an outer core 6 , a mid layer 8 , a cover 10 , and dimples 12 . A diameter D1, a volume V1, a hardness H1o at a central point, a boundary inside hardness H1in, and a hardness difference De1 of the inner core 4 ; a volume V2 (mm 3 ) and a hardness difference De2 of the outer core 6 ; a thickness Tm and a hardness Hm of the mid layer 8 ; and a thickness Tc and a hardness Hc of the cover 10 meet the following mathematical formulas. 1.0< V 2/ V 1<7.0 De 2− De 1<0 600<( H 1 o*H 1in)*( D 1/2)/2<1000 620< Tc*Hc*Hm/Tm <900 A dimple pattern of each hemisphere of the golf ball 2 includes three units rotationally symmetrical to each other.
1 . A golf ball comprising an inner core, an outer core positioned outside the inner core, a mid layer positioned outside the outer core, and a cover positioned outside the mid layer, wherein
the golf ball has a plurality of dimples on a surface thereof,
a ratio So of a sum of areas of the dimples relative to a surface area of a phantom sphere of the golf ball is equal to or greater than 81.0%,
a ratio Rs of a number of the dimples each having a diameter of equal to or greater than 9.60% but equal to or less than 10.37%, of a diameter of the golf ball, relative to a total number of the dimples, is equal to or greater than 50%,
a dimple pattern of each hemisphere of the golf ball includes three units that are rotationally symmetrical to each other,
a dimple pattern of each unit includes two small units that are mirror-symmetrical to each other, and
the golf ball meets the following mathematical formula (2.1):
Rs≧− 2.5* So+ 273 (2.1).
2 . The golf ball according to claim 1 , wherein
a volume V1 (mm 3 ) of the inner core and a volume V2 (mm 3 ) of the outer core meets the following mathematical formula (1.1):
1.0< V 2/ V 1<7.0 (1.1).
3 . The golf ball according to claim 2 , wherein the golf ball meets the following mathematical formula:
2.0< V 2/ V 1<6.0.
4 . The golf ball according to claim 1 , wherein
a difference De1 between a boundary inside hardness H1in (Shore C) and a hardness H1o (Shore C) at a central point of the inner core; and a difference De2 between a surface hardness H2s (Shore C) and a boundary outside hardness H2out (Shore C) of the outer core meets the following mathematical formula (1.2):
De 2− De 1<0 (1.2).
5 . The golf ball according to claim 1 , wherein
a diameter D1 (mm), a hardness H1o (Shore C) at a central point, and a boundary inside hardness H1in (Shore C) of the inner core meets the following mathematical formula (1.3):
600<( H 1 o+H 1in)*( D 1/2)/2<1000 (1.3).
6 . The golf ball according to claim 5 , wherein the golf ball meets the following mathematical formula:
700<( H 1 o+H 1in)*( D 1/2)/2<900.
7 . The golf ball according to claim 1 , wherein
a thickness Tm (mm) and a hardness Hm (Shore D) of the mid layer; and a thickness Tc (mm) and a hardness Hc (Shore D) of the cover meets the following mathematical formula (1.4):
620< Tc*Hc*Hm/Tm< 900 (1.4).
8 . The golf ball according to claim 7 , wherein the golf ball meets the following mathematical formula:
640< Tc*Hc*Hm/Tm< 800.
9 . The golf ball according to claim 1 , wherein the golf ball meets the following mathematical formula (2.2):
Rs≧− 2.5* So+ 278 (2.2).
10 . The golf ball according to claim 9 , wherein the golf ball meets the following mathematical formula (2.3):
Rs≧− 2.5* So+ 283 (2.3).
11 . The golf ball according to claim 1 , wherein
a ratio Rs' of a number of the dimples each having a diameter of equal to or greater than 10.10% but equal to or less than 10.37%, of the diameter of the golf ball, relative to the total number of the dimples, is equal to or greater than 50%, and
the golf ball meets the following mathematical formula (2.4):
Rs′≧− 2.2 *So+ 245 (2.4).
12 . The golf ball according to claim 11 , wherein the golf ball meets the following mathematical formula (2.5):
Rs′≧− 2.2* So+ 252 (2.5).
13 . The golf ball according to claim 1 , wherein a depth of a deepest part of each dimple from a surface of the phantom sphere is equal to or greater than 0.10 mm but equal to or less than 0.65 mm.
14 . The golf ball according to claim 1 , wherein a total volume of the dimples is equal to or greater than 450 mm 3 but equal to or less than 750 mm 3 .