A golf ball ( 1 ) comprises a large number of dimples ( 4 ) and a land portion ( 5 ) on a surface thereof. The dimple ( 4 ) is concaved from the surface of a phantom sphere shown in a two-dotted chain line. The dimple ( 4 ) includes an edge (E). The dimple ( 4 ) includes an outer region ( 6 ) on an outside of the edge (E). A mean value of a width (W) of the outer region ( 6 ) is 0.03 mm to 0.20 mm. A mean value of a ratio (W/d) of the width (W) of the outer region ( 6 ) to a maximum dimension (d) of the dimple ( 4 ) is 0.015 to 0.040. A mean value of an angle (α) formed by the outer region ( 6 ) and a maximum dimension line (T) is 1.0 degree to 15.0 degrees. The separation of air flowing into the dimple ( 4 ) can be suppressed by the outer region ( 6 ).
1. A golf ball comprising a cover and a core, wherein the cover has a large number of dimples on a surface thereof, and wherein the dimples include dimples having an edge, a boundary defining the outer perimeter of the outer region, and an outer region positioned on an outside of the edge
wherein the boundary is defined by the intersection of a surface of a phantom sphere and a land portion of the over from which the phantom sphere surface extends; wherein the edge is defined by a common tangential line extending across an outer periphery of the dimple; wherein the outer region is defined between the boundary and the edge so as to be below the phantom sphere surface;
and wherein a mean value of a width W of the outer region is 0.03 mm to 0.20 mm.
2. The golf ball according to claim 1 , wherein a mean value of a ratio (W/d) of the width W of the outer region to a maximum dimension d of the dimple is 0.01 to 0.040, wherein the maximum dimension d is the longest segment that can be drawn within a plane defined by the edge, and wherein the width W is defined by a line extending from the edge to the boundary.
3. The golf ball according to claim 1 , wherein a mean value of an angle a formed by α line extending from the edge to the boundary within the outer region and a maximum dimension line T is 1.0 degree to 15.0 degrees, wherein the maximum dimension line T is the longest tangential segment that can be drawn between two points within the edge of the dimple.
4. The golf ball according to claim 2 , wherein a mean value of an angle α formed by a line extending from the edge to the boundary within the outer region and a maximum dimension line T is 1.0 degree to 15.0 degrees, wherein the maximum dimension line T is the longest tangential segment that can be drawn between two points within the edge of the dimple.
5. The golf ball according to claim 1 , wherein the mean value of the width W of the outer region is 0.05 to 0.18 mm.
6. The golf ball according to claim 1 , wherein the mean value of the width W of the outer region is 0.07 mm to 0.15 mm.
7. The golf ball according to claim 1 , wherein the proportion of dimples on the golf ball which have the defined outer region width mean value is 90% or greater.
8. The golf ball according to claim 2 , wherein the mean value of a ratio (W/d) of the width W of the outer region to a maximum dimension d of the dimple is 0.018 to 0.037.
9. The golf ball according to claim 2 , wherein the mean value of a ratio CW/d) of the width W of the outer region to a maximum dimension d of the dimple is 0.020 to 0.035.
10. The golf ball according to claim 2 , wherein the proportion of the number of dimples having the mean value ratio (W/d) is 50% or more.
11. The golf ball according to claim 2 , wherein the proportion of the number of dimples having the mean value ratio (W/d) is 65% or more.
12. The golf ball according to claim 2 , wherein the proportion of the number of dimples having the mean value ratio (W/d) is 80% or more.
13. The golf ball according to claim 3 , wherein the mean value of the angle α formed by the outer region an a maximum dimension line T is 3.0 degrees to 12.0 degrees.
14. The golf ball according to claim 3 , wherein the mean value of the angle α formed by the outer region an a maximum dimension line T is 5.0 degrees to 10.0 degrees.
15. The golf ball according to claim 3 , wherein the proportion of the number of dimples having the angle α is 50% or more.
16. The golf ball according to claim 3 , wherein the proportion of the number of dimples having the angle α is 65% or more.
17. The golf ball according to claim 3 , wherein the proportion of the number of dimples having the angle α is 80% or more.