Multi-piece golf ball
View Patent ↗An object of the present invention is to provide a golf ball showing a small ratio of a spin rate on driver shots to a spin rate on approach shots. The present invention provides a multi-piece golf ball comprising a spherical center, three or more envelope layers covering the spherical center, and a cover covering the envelope layers, wherein adjacent two envelope layers are formed so as to include a region composed of elements having a hitting deformation ratio of 30% or more, the hitting deformation ratio being obtained by analyzing a specified golf ball model by a finite element method; and the envelope layer which is radially outwardly positioned of the adjacent two envelope layers has a lowest hardness among all the envelope layers.
1. A multi-piece golf ball comprising a spherical center, three or more envelope layers covering the spherical center, and a cover covering the envelope layers, wherein
two adjacent envelope layers are formed so as to include a deformation region which is composed of elements having a hitting deformation ratio of 30% or more obtained by analyzing a golf ball model using a finite element method;
the envelope layer that is radially outwardly positioned of the two adjacent envelope layers formed to include the deformation region has a hardness (Hs) that is lowest among all the envelope layers;
the golf ball model comprises a twelve-layered spherical core, an intermediate layer covering the spherical core, and a cover covering the intermediate layer, and has a configuration described in Table 1 shown below; and
the elements are formed by dividing the golf ball model by radial lines, circumferential lines (longitudinal direction) and circumferential lines (latitudinal direction),
the hitting deformation ratio of each element is obtained by calculating the deformation ratio (von Mises strain) at the time when the golf ball model most deforms under the condition that a rigid plate (weight: 193.8 g, size: 30 mm×40 mm×0.2 mm) collides against the golf ball model at a speed of 40 m/s and a loft angle of 12 degrees,
the length of each element on a vertical cross section including the central point and the hitting point of the golf ball model in the radial direction is set at 0.5 mm in a distance range of 2 to 4 mm from the central point, is set at 1.0 mm in a distance range of 4 to 18 mm from the central point, is set at 0.85 mm in a distance range of 18 to 18.85 mm from the central point, is set at 0.5 mm in a distance range of 18.85 mm to 20.85 mm from the central point, and is set at 0.25 mm in a distance range of 20.85 to 21.35 mm from the central point,
the number of element divisions on the vertical cross section of the golf ball model in the circumferential direction is set at 80 in a distance range of 2 to 10 mm from the central point, is set at 160 in a distance range of 10 to 18.85 mm from the central point, and is set at 320 in a distance range of 18.85 to 21.35 mm from the central point,
the elements having a hitting deformation ratio of 30% or more are elements on the vertical cross section classified based on the hitting deformation ratio
TABLE 1
Distance (mm)
Distance (%)
Ten-
from
from
Hard-
sile
Den-
central
central
ness
modu-
Pois-
sity
point
point
(Sho-
lus
son's
(g/
of golf ball
of golf ball
re C)
(MPa)
ratio
cm 3 )
Core 1
0-2.00
mm
0%-9.4%
70
53
0.49
1.118
Core 2
2.00-4.00
mm
9.4%-18.7%
72
57
0.49
1.118
Core 3
4.00-6.00
mm
18.7%-28.1%
73
64
0.49
1.118
Core 4
6.00-8.00
mm
28.1%-37.5%
74
65
0.49
1.118
Core 5
8.00-10.00
mm
37.5%-46.8%
74
65
0.49
1.118
Core 6
10.00-12.00
mm
46.8%-56.2%
74
65
0.49
1.118
Core 7
12.00-14.00
mm
56.2%-65.6%
74
65
0.49
1.118
Core 8
14.00-16.00
mm
65.6%-74.9%
77
77
0.49
1.118
Core 9
16.00-18.00
mm
74.9%-84.3%
77
77
0.49
1.118
Core 10
18.00-18.85
mm
84.3%-88.3%
79
88
0.49
1.118
Core 11
18.85-19.35
mm
88.3%-90.6%
81
97
0.49
1.118
Core 12
19.35-19.85
mm
90.6%-93.0%
83
108
0.49
1.118
Inter-
19.85-20.85
mm
93.0%-97.7%
94
290
0.49
0.989
mediate
layer
Cover
20.85-21.35
mm
97.7%-100%
46
16
0.49
1.101.
2. The multi-piece golf ball according to claim 1 , wherein three adjacent envelope layers are formed so as to include the deformation region composed of the elements having the hitting deformation ratio of 30% or more; and the envelope layer among these three adjacent envelope layers that is positioned radially between the other two envelope layers has a hardness (Hs) that is lowest among all the envelope layers.
3. The multi-piece golf ball according to claim 2 , wherein all the envelope layers, including the deformation region composed of the elements having the hitting deformation ratio of 30% or more, have a slab hardness of 50 or less in Shore D hardness.
4. The multi-piece golf ball according to claim 1 , wherein the spherical center includes the deformation region composed of the elements having the hitting deformation ratio of 30% or more.
5. The multi-piece golf ball according to claim 1 , wherein the spherical center has a material hardness of 15 or more and 55 or less in Shore D hardness.
6. The multi-piece golf ball according to claim 1 , wherein the lowest hardness (Hs) is 40 or less in Shore D hardness.
7. The multi-piece golf ball according to claim 1 , wherein the outermost envelope layer is an envelope layer having a hardness (Hh) that is highest among all the envelope layers.
8. The multi-piece golf ball according to claim 7 , wherein the envelope layer having the highest hardness (Hh) among all the envelope layers has a material hardness of 30 or more and 85 or less in Shore D hardness.
9. The multi-piece golf ball according to claim 7 , wherein a hardness difference (highest hardness (Hh)−lowest hardness (Hs)) between the highest hardness (Hh) and the lowest hardness (Hs) is 30 or more and 80 or less in Shore D hardness.
10. The multi-piece golf ball according to claim 1 , wherein a material forming the envelope layer having the lowest hardness (Hs) among all the envelope layers has a tensile elastic modulus of 1 MPa or more and 20 MPa or less.
11. The multi-piece golf ball according to claim 7 , wherein a material forming the envelope layer having the highest hardness among all the envelope layers has a tensile elastic modulus of 150 MPa or more and 400 MPa or less.
12. The multi-piece golf ball according to claim 5 , wherein a hardness difference (material hardness (Ho) of spherical center−lowest hardness (Hs)) between the material hardness of the spherical center and the lowest hardness is 1 or more and 50 or less in Shore D hardness.
13. The multi-piece golf ball according to claim 7 , wherein a hardness difference (highest hardness (Hh)−material hardness (Ho) of spherical center) between the highest hardness (Hh) and the material hardness (Ho) of the spherical center is 1 or more and 70 or less in Shore D hardness.
14. The multi-piece golf ball according to claim 1 , wherein a material forming the spherical center has a tensile elastic modulus of 15 MPa or more and 80 MPa or less.
15. The multi-piece golf ball according to claim 1 , wherein the cover has a material hardness of 5 or more and 55 or less in Shore D hardness.
16. The multi-piece golf ball according to claim 1 , wherein a resin component constituting the envelope layer having the lowest hardness among all the envelope layers contains an ionomer resin and a thermoplastic styrene-based elastomer.
17. The multi-piece golf ball according to claim 16 , wherein a mass ratio of the ionomer resin to the thermoplastic styrene-based elastomer (ionomer resin/thermoplastic styrene-based elastomer) is 0.1 or more and 3.0 or less.
18. The multi-piece golf ball according to claim 7 , wherein a resin component constituting the envelope layer having the highest hardness among all the envelope layers contains an ionomer resin.
19. The multi-piece golf ball according to claim 18 , wherein a content of the ionomer resin in the resin component is 50 mass % or more.
20. The multi-piece golf ball according to claim 1 , wherein a material forming the cover contains a thermoplastic polyurethane resin in a resin component thereof.
21. The multi-piece golf ball according to claim 1 , wherein three adjacent envelope layers are formed so as to include the deformation region composed of the elements having the hitting deformation ratio of 30% or more,
all the envelope layers, including the deformation region composed of the elements having the hitting deformation ratio of 30% or more, have a slab hardness of 50 or less in Shore D,
the envelope layer from the three adjacent envelope layers forming the deformation region that is positioned radially between the other two envelope layers has a hardness (Hs) that is lowest among all the envelope layers,
the lowest hardness (Hs) is 40 or less in Shore D hardness,
the spherical center includes the region composed of the elements having the hitting deformation ratio of 30% or more,
the spherical center has a material hardness of 15 or more and 55 or less in Shore D hardness, and
the outermost envelope layer is an envelope layer having a hardness (Hh) that is highest among all the envelope layers.