Golf ball

Abstract

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.

What is claimed is: 
     
         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 .