Golf ball

Abstract

A golf ball includes a core, one or more mid layers, a cover, and dimples. A central hardness Ho and a surface hardness Hs of the core, a hardness Hm(min) of a layer having a lowest hardness among the mid layers, and a hardness Hc of the cover satisfy the following mathematical formulas (i) to (iv). Hs−Ho >15  (i) Hc−Hm (min)>20  (ii) −10< Hm (min)− Ho <15  (iii) 5< Hc−Hs <20  (iv)

What is claimed is: 
     
         1 . A golf ball comprising a core, one or more mid layers positioned outside the core, and a cover positioned outside the mid layers, wherein
 a Shore C hardness Ho at a central point of the core, a Shore C hardness Hs at a surface of the core, a Shore C hardness Hm(min) of a layer having a lowest hardness among the mid layers, and a Shore C hardness Hc of the cover satisfy the following mathematical formulas (i) to (iv),
     Hs−Ho> 15  (i),
 
     Hc−Hm (min)>20  (ii),
 
   −10< Hm (min)− Ho< 15  (iii), and
 
   5< Hc−Hs< 20  (iv),
 
   the hardness Hc of the cover is higher than a Shore C hardness Hm(max) of a layer having a highest hardness among the mid layers,   the golf ball further comprises a plurality of dimples on a surface thereof,   a minimum value of 15 peak values obtained by executing steps (a) to (h) for each of 15 axes Ax is not less than 95 mm, when spherical polar coordinates of a point that is located on a surface of a phantom sphere of the golf ball and has a latitude of θ (degrees) and a longitude of ϕ (degrees) are represented by (θ, ϕ), the 15 axes Ax being   (1) a first axis Ax 1  passing through a point Pn 1  coordinates of which are (75, 270) and a point Ps 1  coordinates of which are (−75, 90),   (2) a second axis Ax 2  passing through a point Pn 2  coordinates of which are (60, 270) and a point Ps 2  coordinates of which are (−60, 90)   (3) a third axis Ax 3  passing through a point Pn 3  coordinates of which are (45, 270) and a point Ps 3  coordinates of which are (−45, 90),   (4) a fourth axis Ax 4  passing through a point Pn 4  coordinates of which are (30, 270) and a point Ps 4  coordinates of which are (−30, 90),   (5) a fifth axis Ax 5  passing through a point Pn 5  coordinates of which are (15, 270) and a point Ps 5  coordinates of which are (−15, 90),   (6) a sixth axis Ax 6  passing through a point Pn 6  coordinates of which are (75, 0) and a point Ps 6  coordinates of which are (−75, 180),   (7) a seventh axis Ax 1  passing through a point Pn 7  coordinates of which are (60, 0) and a point Ps 7  coordinates of which are (−60, 180),   (8) an eighth axis Ax 8  passing through a point Pn 8  coordinates of which are (45, 0) and a point Ps 8  coordinates of which are (−45, 180),   (9) a ninth axis Ax 9  passing through a point Pn 9  coordinates of which are (30, 0) and a point Ps 9  coordinates of which are (−30, 180),   (10) a tenth axis Ax 10  passing through a point Pn 10  coordinates of which are (15, 0) and a point Ps 10  coordinates of which are (−15, 180),   (11) an eleventh axis Ax 11  passing through a point Pn 11  coordinates of which are (75, 90) and a point Ps 11  coordinates of which are (−75, 270),   (12) a twelfth axis Ax 12  passing through a point Pn 12  coordinates of which are (60, 90) and a point Ps 12  coordinates of which are (−60, 270),   (13) a thirteenth axis Ax 13  passing through a point Pn 13  coordinates of which are (45, 90) and a point Ps 13  coordinates of which are (−45, 270),   (14) a fourteenth axis Ax 14  passing through a point Pn 14  coordinates of which are (30, 90) and a point Ps 14  coordinates of which are (−30, 270), and   (15) a fifteenth axis Ax 15  passing through a point Pn 15  coordinates of which are (15, 90) and a point Ps 15  coordinates of which are (−15, 270), the steps (a) to (h) being the steps of   (a) assuming a great circle that is present on the surface of the phantom sphere and is orthogonal to the axis Ax,   (b) assuming two small circles that are present on the surface of the phantom sphere, that are orthogonal to the axis Ax, and of which absolute values of central angles with the great circle are each 30°,   (c) defining a region, of the surface of the golf ball, which is obtained by dividing the surface of the golf ball at these small circles and which is sandwiched between these small circles,   (d) determining 30240 points, on the region, arranged at intervals of a central angle of 3° in a direction of the axis Ax and at intervals of a central angle of 0.25° in a direction of rotation about the axis Ax,   (e) calculating a length L 1  of a perpendicular line that extends from each point to the axis Ax,   (f) calculating a total length L 2  by summing 21 lengths L 1  calculated on the basis of 21 perpendicular lines arranged in the direction of the axis Ax,   (g) obtaining a transformed data constellation by performing Fourier transformation on a data constellation of 1440 total lengths L 2  calculated along the direction of rotation about the axis Ax, and   (h) calculating a peak value and an order of a maximum peak of the transformed data constellation,   a minimum value of 15 orders obtained by executing the steps (a) to (h) is not less than 27,   a maximum value of the 15 orders obtained by executing the steps (a) to (h) is not greater than 37, and   an average of the 15 orders obtained by executing the steps (a) to (h) is not less than 30 and not greater than 34.   
     
     
         2 . The golf ball according to  claim 1 , wherein a total thickness of the cover and the mid layer is not greater than 2.8 mm. 
     
     
         3 . The golf ball according to  claim 1 , wherein an average of the 15 peak values obtained by executing the steps (a) to (h) is not less than 200 mm. 
     
     
         4 . The golf ball according to  claim 1 , wherein a total volume of the dimples is not less than 450 mm 3  and not greater than 750 mm 3 .