Multi-piece solid golf ball
The golf ball includes a core having an inner layer core and an outer layer core, a single-layered intermediate layer and cover, wherein the inner layer core is formed of a rubber composition, the intermediate layer and the cover are formed of a resin composition, and a relationship between an initial velocity of the inner layer core, an initial velocity of the entire core, an initial velocity of an intermediate layer-encased sphere, and an initial velocity of a ball satisfies the following conditions: (initial velocity of ball)<(initial velocity of intermediate layer-encased sphere) (initial velocity of intermediate layer-encased sphere)−(initial velocity of entire core)≤0.70 (m/s) (initial velocity of entire core)−(initial velocity of inner layer core)≥0.20 (m/s) and a specific gravity of the intermediate layer and a deflection of the golf ball when compressed under a predetermined load are set within specific ranges.
1. A multi-piece solid golf ball comprising a multi-layer core each having at least an inner layer core and an outer layer core, a single-layer intermediate layer, and a single-layer cover, wherein the inner layer core is formed of a rubber composition, the intermediate layer and the cover are both formed of a resin composition, and a relationship among an initial velocity of the inner layer core, an initial velocity of an entire core, an initial velocity of a sphere (intermediate layer-encased sphere) obtained by encasing core with the intermediate layer, and an initial velocity of a sphere (ball) obtained by encasing the intermediate layer-encased sphere with the cover satisfies the following three conditions:
(initial velocity of ball)<(initial velocity of intermediate layer-encased sphere)
(initial velocity of intermediate layer-encased sphere)−(initial velocity of entire core)≤0.70 (m/s)
(initial velocity of entire core)−(initial velocity of inner layer core)≥0.20 (m/s)
and a specific gravity of the intermediate layer is at least 1.05, and a deflection (mm) when the golf 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, and
wherein the following condition is satisfied:
1.00≤(initial velocity of intermediate layer-encased sphere)−(initial velocity of inner layer core)≤1.60 (m/s).
2. The multi-piece solid golf ball of claim 1 , wherein the following condition is satisfied:
0.50≤(initial velocity of entire core)−(initial velocity of inner layer core)≤1.00 (m/s).
3. The multi-piece solid golf ball of claim 1 , wherein the following condition is satisfied:
ball surface hardness<surface hardness of intermediate layer-encased sphere>outer layer core surface hardness>inner layer core surface hardness
(where the surface hardness of each sphere means Shore C hardness).
4. The multi-piece solid golf ball of claim 1 , wherein the intermediate layer contains an inorganic particulate filler.
5. The multi-piece solid golf ball of claim 1 , wherein a difference between a specific gravity of the cover and the specific gravity of the intermediate layer is not more than 0.15.
6. The multi-piece solid golf ball of 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 %.
7. The multi-piece solid golf ball of claim 1 , wherein the outer layer core is formed of a resin composition.
8. The multi-piece solid golf ball of claim 1 , wherein the following condition is satisfied:
cover thickness<intermediate layer thickness≤outer layer core thickness.
9. The multi-piece solid golf ball of claim 1 , wherein the core has a hardness profile in which, letting Cc be a Shore C hardness at the center of the core, C m be a Shore C hardness at a midpoint M between the center and the surface of the core, Cm−2, Cm−4, and Cm−6 be respective Shore C hardnesses at positions 2 mm, 4 mm, and 6 mm inward from the midpoint M, Cm+2, Cm+4, and Cm+6 be respective Shore C hardnesses at positions 2 mm, 4 mm, and 6 mm outward from the midpoint M, and Cs be a Shore C hardness at the surface of the core, the following surface areas A to F are defined:
½×2×( Cm− 4 −Cm− 6) surface area A:
½×2×( Cm− 2 −Cm− 4) surface area B:
½×2×( Cm−Cm− 2) surface area C:
½×2×( Cm+ 2 −Cm ) surface area D:
½×2×( Cm+ 4 −Cm+ 2) surface area E:
½×2×( Cm+ 6 −Cm+ 4) surface area F:
and the following condition is satisfied:
(surface area E +surface area F )−(surface area A +surface area B )≥1.0.
10. The multi-piece solid golf ball of claim 1 , wherein the following formula is satisfied:
[surface hardness of intermediate layer-encased sphere(Shore C )−center hardness of inner layer core(Shore C )]≥35.