Golf ball

Abstract

A golf ball 2 includes a core 4 , a mid layer 6 , a cover 8 , and dimples 10 . A difference DH in hardness between a surface and a central point of the core 4 , a thickness Tm and a hardness Hm of the mid layer 6 , a thickness Tc and a hardness Hc of the cover 8 , and an amount of compressive deformation Sb meet the following mathematical formulas. ( DH*Hm )/( Hc*Tc )>80 (( Sb*Tc )/( Hc* Hm*Tm ))*1000>0.75 An area ratio So of dimples 10 and a ratio Rs of a number of the dimples 10 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 2 meet the following mathematical formula (3). Rs ≧−2.5 *So +273   ( 3 )

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
 a thickness Tm (mm) and a Shore D hardness Hm of the mid layer, a thickness Tc (mm) and a Shore D hardness Hc of the cover, and an amount of compressive deformation Sb (mm) of the golf ball meet the following mathematical formula (2),
   (( Sb*Tc )/( Hc*Hm*Tm ))*1000>0.75   (2),
 
   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 phantom sphere 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 (3) :
     Rs ≧−2.5 *So +273   (3).
 
   
     
     
         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 meets the following mathematical formula (1). 
     
     
         3 . The golf ball according to  claim 1 , wherein the hardness Hc of the cover is equal to or less than 40. 
     
     
         4 . The golf ball according to  claim 1 , wherein the hardness Hm of the mid layer is equal to or greater than 55. 
     
     
         5 . The golf ball according to  claim 1 , wherein the golf ball meets the following mathematical formula (4):
     Rs ≧−2.5 *So +278   (4).
   
     
     
         6 . The golf ball according to  claim 3 , wherein the golf ball meets the following mathematical formula (5):
     Rs ≧−2.5 *So +283   (5).
   
     
     
         7 . 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 (6):
     Rs ′≧−2.2 *So +245   (6).
 
   
     
     
         8 . The golf ball according to  claim 5 , wherein the golf ball meets the following mathematical formula (7):
     Rs ′≧−2.2 *So +252   (7).
   
     
     
         9 . 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. 
     
     
         10 . 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 .