Multi-piece solid golf ball

Abstract

The present invention provides a multi-piece solid golf ball including a core, a surrounding layer, an intermediate layer, and a cover, in which a large number of dimples are formed on an outside surface of the cover, the core is formed of a single layer or a plurality of layers of a rubber composition, the surrounding layer is formed of a single layer or a plurality of layers of a resin composition, the intermediate layer and the cover are both formed of a single layer of a resin composition, and a relationship between an initial velocity of an intermediate layer-encased sphere and an initial velocity of the ball satisfies the following condition:(initial velocity of ball)<(initial velocity of intermediate layer-encased sphere).Further, a deflection of the ball under a predetermined load is optimized, and a lift coefficient and a drag coefficient at a predetermined Reynolds number and spin rate of the dimples are set within a predetermined range.

1 . A multi-piece solid golf ball comprising a core, a surrounding layer, an intermediate layer, and a cover, wherein a large number of dimples are formed on an outside surface of the cover, the core is formed of a single layer or a plurality of layers of a rubber composition, the surrounding layer is formed of a single layer or a plurality of layers of a resin composition, the intermediate layer and the cover are both formed of a single layer of a resin composition, and a relationship between an initial velocity of an intermediate layer-encased sphere and an initial velocity of the ball satisfies the following condition:
   (initial velocity of ball)<(initial velocity of intermediate layer-encased sphere), and   where a deflection when the ball is compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) is not more than 3.0 mm, a ratio CL1/CD1 of a lift coefficient CL1 at a Reynolds number of 218,000 and a spin rate of 2,800 rpm to a drag coefficient CD1 is denoted by A1, a ratio CL2/CD2 of a lift coefficient CL2 at a Reynolds number of 184,000 and a spin rate of 2,900 rpm to a drag coefficient CD2 is denoted by A2, and a ratio CL3/CD3 of a lift coefficient CL3 at a Reynolds number of 158,000 and a spin rate of 3,100 rpm to a drag coefficient CD3 is denoted by A3, the following two conditions are satisfied:
   0.590 ≤A 1≤0.640
 
   and   
       
         
           
             
               
                 
                   ( 
                   
                     
                       A 
                       ⁢ 
                       2 
                     
                     + 
                     
                       A 
                       ⁢ 
                       3 
                     
                   
                   ) 
                 
                 / 
                 2 
               
               ≥ 
               
                 0.67 
                 . 
               
             
           
         
       
     
     
         2 . The multi-piece solid golf ball according to  claim 1 , wherein the value of A1 is 0.590 to 0.613, the value of A2 is 0.635 to 0.668, and the value of A3 is 0.695 to 0.734. 
     
     
         3 . The multi-piece solid golf ball according to  claim 2 , wherein the value of A1 is 0.614 to 0.640, the value of A2 is 0.669 to 0.750, and the value of A3 is 0.735 to 0.815. 
     
     
         4 . The multi-piece solid golf ball according to  claim 1 , wherein the value of (A2+A3)/2 is 0.670 to 0.783. 
     
     
         5 . The multi-piece solid golf ball according to  claim 1 , wherein the following three conditions are satisfied:
   (initial velocity of intermediate layer-encased sphere)−(initial velocity of surrounding layer-encased sphere)≤0.70 (m/s)
     (initial velocity of surrounding layer-encased sphere)−(initial velocity of core)≥0.20 (m/s)
     1.00≤(initial velocity of intermediate layer-encased sphere)−(initial velocity of core)≤1.60 (m/s).
   
     
     
         6 . The multi-piece solid golf ball according to  claim 1 , wherein the following condition is satisfied:
   0.65≤(initial velocity of surrounding layer-encased sphere)−(initial velocity of core)≤1.00 (m/s).
   
     
     
         7 . The multi-piece solid golf ball according to  claim 1 , wherein the following condition is satisfied:
   ball surface hardness<surface hardness of intermediate layer-encased sphere>surface hardness of surrounding layer-encased sphere>core surface hardness   where the surface hardness of each sphere means Shore C hardness.   
     
     
         8 . The multi-piece solid golf ball according to  claim 1 , wherein the intermediate layer contains an inorganic particulate filler, and the resin material of the intermediate layer has a specific gravity of at least 1.05. 
     
     
         9 . The multi-piece solid golf ball according to  claim 1 , wherein a difference between the specific gravity of the cover and the specific gravity of the intermediate layer is not more than 0.15. 
     
     
         10 . The multi-piece solid golf ball according to  claim 1 , wherein the resin composition of the intermediate layer contains a high-acid ionomer resin having an acid content of at least 16 wt %. 
     
     
         11 . The multi-piece solid golf ball according to  claim 1 , wherein the following condition is satisfied:
   cover thickness<intermediate layer thickness≤surrounding layer thickness.
   
     
     
         12 . The multi-piece solid golf ball according to  claim 1 , wherein the core has a hardness profile in which, letting a Shore C hardness at a core center be Cc, a Shore C hardness at a midpoint M between the core center and the core surface be Cm, Shore C hardnesses at positions 2 mm, 4 mm, and 6 mm inward from the midpoint M be Cm−2, Cm−4, and Cm−6 respectively, Shore C hardnesses at positions 2 mm, 4 mm, and 6 mm outward from the midpoint M be Cm+2, Cm+4, and Cm+6 respectively, and a Shore C hardness at the core surface be Cs, and defining surface areas A to F as follows:
 surface area A: ½×2×(Cm−4−Cm−6) 
 surface area B: ½×2×(Cm−2−Cm−4) 
 surface area C: ½{grave over (×)}2×(Cm−Cm−2) 
 surface area D: ½×2×(Cm+2−Cm) 
 surface area E: ½×2×(Cm+4−Cm+2) 
 surface area F: ½×2×(Cm+6−Cm+4) 
 the following condition is satisfied:
   (surface area  E +surface area  F )−(surface area  A +surface area  B )≥1.0.
 
 
 
     
     
         13 . The multi-piece solid golf ball according to  claim 7 , wherein the following condition is satisfied:
   35≤(surface hardness of intermediate layer-encased sphere)−(core center hardness) where the hardnesses mean Shore  C  hardnesses.