Golf ball

Abstract

A golf ball 2 includes a core 4 , a mid layer 6 , and a cover 8 . A difference DH in hardness between a surface and a central point of the core 4 ; a thickness Tm (mm), a hardness Hm, and a volume Vm (mm 3 ) of the mid layer 6 ; and a thickness Tc (mm), a hardness Hc, and a virtual volume Vc (mm 3 ) of the cover 8 meet the following mathematical formulas. ( DH*Hm )/( Hc*Tc )>63 3.0<(( Vm*Hm )/( Vc*Hc ))<7.5 A dimple pattern of each hemisphere of the golf ball 2 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.

What is claimed is: 
     
         1 . A golf ball comprising a core, a mid layer positioned outside the 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 difference DH in Shore C hardness between a surface and a central point of the core; a Shore D hardness Hm of the mid layer; and a thickness Tc (mm), and a Shore D hardness Hc of the cover meet the following mathematical formula (1.1):
   ( DH*Hm )/( Hc*Tc )>63  (1.1).
   
     
     
         3 . The golf ball according to  claim 1 , wherein a Shore D hardness Hm, and a volume Vm (mm 3 ) of the mid layer; and a Shore D hardness Hc, and a virtual volume Vc (mm 3 ) of the cover meet the following mathematical formula (1.2):
   3.0<(( Vm*Hm )/( Vc*Hc ))<7.5  (1.2).
   
     
     
         4 . The golf ball according to  claim 1 , wherein a Shore D hardness Hc of the cover is equal to or less than 40. 
     
     
         5 . The golf ball according to  claim 1 , wherein a Shore D hardness Hm of the mid layer is equal to or greater than 55. 
     
     
         6 . 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).
   
     
     
         7 . The golf ball according to  claim 6 , wherein the golf ball meets the following mathematical formula (2.3):
     Rs≧− 2.5* So+ 283  (2.3).
   
     
     
         8 . 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).
 
   
     
     
         9 . The golf ball according to  claim 8 , wherein the golf ball meets the following mathematical formula (2.5):
     Rs′≧− 2.2* So+ 252  (2.5).
   
     
     
         10 . 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. 
     
     
         11 . 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 . 
     
     
         12 . The golf ball according to  claim 1 , wherein a ratio of a number of the dimples each having a diameter exceeding 10.37% of the diameter of the golf ball, relative to the total number of the dimples, is less than 50%.