Golf ball

Abstract

A golf ball capable of reducing the moment of inertial while reducing spin in a driver shot will be provided. To that end, a golf ball of the disclosure is a golf ball having a cover and, provided that I b (g·cm 2 ) represents the moment of inertia of the golf ball, μ (mm) represents deflection hardness corresponding to a deformation amount (mm) of the golf ball in a load direction from when an initial load of 10 kgf is applied to the golf ball to when a final load of 130 kgf is applied to the golf ball, and D represents Shore D hardness of the cover, a spin change amount predictive index ΔS′ represented by the following formula: Δ   S ′ = ( μ D ) 2  82 - I b 82 2 · 10 6 is at least 2.0.

1 . A golf ball having a cover, wherein,
 provided that
 I b  (g·cm 2 ) represents a moment of inertia of the golf ball, 
 μ (mm) represents deflection hardness corresponding to a deformation amount (mm) of the golf ball in a load direction from when an initial load of 10 kgf is applied to the golf ball to when a final load of 130 kgf is applied to the golf ball, and 
 D represents Shore D hardness of the cover, 
   a spin change amount predictive index ΔS′ represented by the following formula:   
       
         
           
             
               Δ 
                
               
                   
               
                
               
                 
                   
                     S 
                     ′ 
                   
                    
                   
                     ( 
                     
                       μ 
                       D 
                     
                     ) 
                   
                 
                 2 
               
                
               
                 
                   
                     82 
                     - 
                     
                       I 
                       b 
                     
                   
                   
                     82 
                     2 
                   
                 
                 · 
                 
                   10 
                   6 
                 
               
             
           
         
       
       is at least 2.0. 
     
     
         2 . The golf ball according to  claim 1 , wherein the cover is made of urethane. 
     
     
         3 . The golf ball according to  claim 1 , wherein the spin change amount predictive index ΔS′ is at least 2.5. 
     
     
         4 . The golf ball according to  claim 1 , wherein the spin change amount predictive index ΔS′ is at least 3.0. 
     
     
         5 . The golf ball according to  claim 1 , wherein
 the cover is coated with a top coat, and   an elastic work recovery rate of the top coat is 30 to 98%.   
     
     
         6 . The golf ball according to  claim 1 , wherein
 an outer surface of the cover has a plurality of dimples, and   provided that
 PS7 represents an area of the golf ball in contact with a flat surface upon application of a load of 700 kgf to the golf ball against the flat surface, and 
 VS represents, assuming that the golf ball has no dimples on its surface, an area of a circle of a cross-section of the golf ball taken along a diameter of the golf ball, 
   the following formula:
   ( PS 7/ VS /μ)·100≧6.70(mm −1 )
 
   
       is satisfied.