JP5924958B2 - Golf ball - Google Patents

Description

  The present invention relates to a golf ball. More specifically, the present invention relates to an improvement in golf ball dimples.

  The golf ball has a large number of dimples on its surface. The dimples disturb the air flow around the golf ball during flight and cause turbulent separation. This phenomenon is called “turbulence”. Due to the turbulent flow, the separation point of air from the golf ball shifts backward, and drag is reduced. The turbulent flow promotes the deviation between the upper peeling point and the lower peeling point of the golf ball due to backspin, and the lift acting on the golf ball is enhanced. Excellent dimples better disturb the air flow. Excellent dimples produce a great flight distance.

  Various proposals regarding dimples have been made. Japanese Patent Application Laid-Open No. 2005-137692 discloses a golf ball having a standard deviation of the dimple diameter of 0.52 or less. Japanese Patent Application Laid-Open No. 2007-175267 discloses a golf ball in which the number of dimple pattern units near the pole is different from the number of dimple pattern units near the equator. Japanese Patent Application Laid-Open No. 2007-195591 discloses a golf ball in which the ratio of the number of dimples having a diameter of 3.40 mm or more to the total number of dimples is 90% or more. Japanese Patent Application Laid-Open No. 2008-389 discloses a golf ball having a small pitch between adjacent dimples.

  Japanese Patent Application Laid-Open No. 2009-95593 discloses a golf ball having dimples located on the equator. Similar golf balls are also disclosed in JP 2009-95589 A, JP 2010-57612 A, and JP 2010-57623 A.

  The ratio of the total area of all the dimples to the surface area of the phantom sphere of the golf ball is called the occupation ratio. This occupation rate affects the flight performance of the golf ball. It is known to those skilled in the art that a golf ball having a large occupation ratio has excellent flight performance.

  The standard deviation of the dimple diameter affects the flight performance of the golf ball. It is known to those skilled in the art that a golf ball having a small standard deviation has excellent flight performance.

Japanese Patent Laid-Open No. 2005-137692 JP 2007-175267 A JP 2007-195591 A JP 2008-389 JP 2009-95593 A JP 2009-95589 A JP 2010-57612 A JP 2010-57623 A

  By arranging small dimples in a narrow zone surrounded by a plurality of dimples, a dimple pattern having a high occupation ratio can be obtained. However, this small dimple is unlikely to contribute to turbulence. The golf ball having such small dimples has a large standard deviation. The occupation ratio and the standard deviation are contradictory.

  A golfer's greatest concern with golf balls is flight distance. From the viewpoint of flight performance, there is room for further improvement in the dimple pattern. An object of the present invention is to provide a golf ball having excellent flight performance.

The golf ball according to the present invention has a large number of dimples on the surface thereof. This golf ball satisfies the following mathematical formula (I).
Y ≦ 3.8 · X−2.894 (I)
In this formula, X represents the ratio of the total area of all the dimples to the surface area of the phantom sphere, and Y represents the standard deviation (mm) of the diameter of all the dimples.

  Preferably, the ratio X is 0.78 or more. Preferably, the standard deviation Y is 0.30 mm or less.

  Preferably, the number of dimples is 300 or more and 400 or less. Preferably, the outline of each dimple is a circle.

Preferably, the golf ball satisfies the following formula (II).
Y ≦ 3.8 · X−2.944 (II)
Preferably, the golf ball satisfies the following formula (III).
Y ≦ 3.8 · X−2.994 (III)

  In the golf ball according to the present invention, turbulence is promoted. This golf ball is excellent in flight performance.

FIG. 1 is a cross-sectional view illustrating a golf ball according to an embodiment of the present invention. FIG. 2 is an enlarged plan view showing the golf ball of FIG. FIG. 3 is a bottom view showing the golf ball of FIG. FIG. 4 is a right side view showing the golf ball of FIG. FIG. 5 is a front view showing the golf ball of FIG. FIG. 6 is a left side view showing the golf ball of FIG. FIG. 7 is a rear view showing the golf ball of FIG. FIG. 8 is a graph showing the relationship between the occupation ratio X and the standard deviation Y. FIG. 9 is an enlarged cross-sectional view showing a part of the golf ball of FIG. FIG. 10 is a plan view showing the golf ball according to the first embodiment of the present invention. FIG. 11 is a bottom view showing the golf ball of FIG. FIG. 12 is a right side view showing the golf ball of FIG. 13 is a front view showing the golf ball of FIG. FIG. 14 is a left side view showing the golf ball of FIG. 15 is a rear view showing the golf ball of FIG. FIG. 16 is a plan view showing a golf ball according to Example 3 of the present invention. FIG. 17 is a bottom view showing the golf ball of FIG. FIG. 18 is a right side view showing the golf ball of FIG. FIG. 19 is a front view showing the golf ball of FIG. FIG. 20 is a left side view showing the golf ball of FIG. FIG. 21 is a rear view showing the golf ball of FIG. FIG. 22 is a plan view showing a golf ball according to Example 4 of the present invention. 23 is a bottom view showing the golf ball of FIG. FIG. 24 is a right side view showing the golf ball of FIG. 25 is a front view showing the golf ball of FIG. FIG. 26 is a left side view showing the golf ball of FIG. 27 is a rear view showing the golf ball of FIG. FIG. 28 is a plan view showing a golf ball according to Embodiment 5 of the present invention. FIG. 29 is a bottom view showing the golf ball of FIG. FIG. 30 is a right side view showing the golf ball of FIG. FIG. 31 is a front view showing the golf ball of FIG. FIG. 32 is a left side view showing the golf ball of FIG. FIG. 33 is a rear view showing the golf ball of FIG. FIG. 34 is a plan view showing a golf ball according to Example 6 of the present invention. FIG. 35 is a bottom view showing the golf ball of FIG. FIG. 36 is a right side view showing the golf ball of FIG. FIG. 37 is a front view showing the golf ball of FIG. FIG. 38 is a left side view showing the golf ball of FIG. FIG. 39 is a rear view showing the golf ball of FIG. FIG. 40 is a plan view showing a golf ball according to Example 7 of the present invention. FIG. 41 is a bottom view showing the golf ball of FIG. FIG. 42 is a right side view showing the golf ball of FIG. FIG. 43 is a front view showing the golf ball of FIG. FIG. 44 is a left side view showing the golf ball of FIG. 45 is a rear view showing the golf ball of FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  The golf ball 2 shown in FIG. 1 includes a spherical core 4, an intermediate layer 6 located outside the core 4, and a cover 8 located outside the intermediate layer 6. A large number of dimples 10 are formed on the surface of the cover 8. A portion of the surface of the golf ball 2 other than the dimples 10 is a land 12. The golf ball 2 includes a paint layer and a mark layer on the outside of the cover 8, but these layers are not shown.

  The golf ball 2 preferably has a diameter of 40 mm to 45 mm. The diameter is particularly preferably equal to or greater than 42.67 mm from the viewpoint that US Golf Association (USGA) standards are satisfied. In light of suppression of air resistance, the diameter is more preferably equal to or less than 44 mm, and particularly preferably equal to or less than 42.80 mm. The golf ball 2 preferably has a mass of 40 g or more and 50 g or less. In light of attainment of great inertia, the mass is more preferably equal to or greater than 44 g, and particularly preferably equal to or greater than 45.00 g. In light of satisfying the USGA standard, the mass is particularly preferably equal to or less than 45.93 g.

  The core 4 is formed by crosslinking a rubber composition. Examples of the base rubber of the rubber composition include polybutadiene, polyisoprene, styrene-butadiene copolymer, ethylene-propylene-diene copolymer, and natural rubber. Two or more kinds of rubbers may be used in combination. From the viewpoint of resilience performance, polybutadiene is preferred, and high cis polybutadiene is particularly preferred.

  For crosslinking of the core 4, a co-crosslinking agent is preferably used. From the viewpoint of resilience performance, preferred co-crosslinking agents are zinc acrylate, magnesium acrylate, zinc methacrylate and magnesium methacrylate. It is preferable that the rubber composition contains an organic peroxide together with a co-crosslinking agent. Preferred organic peroxides include dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t-butyl). Peroxy) hexane and di-t-butyl peroxide.

  In the rubber composition of the core 4, various additives such as a filler, sulfur, a vulcanization accelerator, a sulfur compound, an anti-aging agent, a colorant, a plasticizer, and a dispersant are blended in appropriate amounts as necessary. Synthetic resin powder or crosslinked rubber powder may be blended with the rubber composition.

  The diameter of the core 4 is preferably 30.0 mm or more, and particularly preferably 38.0 mm or more. The diameter of the core 4 is preferably 42.0 mm or less, and particularly preferably 41.5 mm or less. The core 4 may be composed of two or more layers. The core 4 may include a rib on the surface thereof. The core 4 may be hollow.

  A suitable polymer for the mid layer 6 is an ionomer resin. A preferable ionomer resin includes a binary copolymer of an α-olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms. Other preferable ionomer resins include ternary α-olefin, α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and α, β-unsaturated carboxylic acid ester having 2 to 22 carbon atoms. A copolymer is mentioned. In this binary copolymer and ternary copolymer, preferred α-olefins are ethylene and propylene, and preferred α, β-unsaturated carboxylic acids are acrylic acid and methacrylic acid. In this binary copolymer and ternary copolymer, some of the carboxyl groups are neutralized with metal ions. Examples of the metal ions for neutralization include sodium ions, potassium ions, lithium ions, zinc ions, calcium ions, magnesium ions, aluminum ions, and neodymium ions.

  Other polymers may be used for the mid layer 6 instead of the ionomer resin. Examples of other polymers include polystyrene, polyamide, polyester, polyolefin, and polyurethane. Two or more kinds of polymers may be used in combination.

  The intermediate layer 6 includes a colorant such as titanium dioxide, a filler such as barium sulfate, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent agent, a fluorescent brightening agent, and the like as necessary. Appropriate amount is blended. For the purpose of adjusting the specific gravity, the intermediate layer 6 may be mixed with a powder of a high specific gravity metal such as tungsten or molybdenum.

  The thickness of the mid layer 6 is preferably 0.2 mm or more, and particularly preferably 0.3 mm or more. The thickness of the mid layer 6 is preferably 2.5 mm or less, and particularly preferably 2.2 mm or less. The specific gravity of the mid layer 6 is preferably 0.90 or more, particularly preferably 0.95 or more. The specific gravity of the mid layer 6 is preferably 1.10 or less, particularly preferably 1.05 or less. The intermediate layer 6 may be composed of two or more layers.

  The cover 8 is made of a resin composition. The base polymer of this resin composition is polyurethane. Thermoplastic polyurethanes and thermosetting polyurethanes can be used. From the viewpoint of productivity, thermoplastic polyurethane is preferred. The thermoplastic polyurethane includes a polyurethane component as a hard segment and a polyester component or a polyether component as a soft segment.

Examples of the curing agent for the polyurethane component include alicyclic diisocyanate, aromatic diisocyanate and aliphatic diisocyanate. In particular, alicyclic diisocyanates are preferred. Since the alicyclic diisocyanate does not have a double bond in the main chain, yellowing of the cover 8 is suppressed. Examples of alicyclic diisocyanates include 4,4′-dicyclohexylmethane diisocyanate (H ₁₂ MDI), 1,3-bis (isocyanatomethyl) cyclohexane (H ₆ XDI), isophorone diisocyanate (IPDI), and trans-1,4- Examples are cyclohexane diisocyanate (CHDI). From the viewpoint of versatility and workability, H ₁₂ MDI is preferable.

  Instead of polyurethane, another polymer may be used for the cover 8. Examples of other polymers include ionomer resin, polystyrene, polyamide, polyester, and polyolefin. Two or more kinds of polymers may be used in combination.

  If necessary, the cover 8 may contain an appropriate amount of a colorant such as titanium dioxide, a filler such as barium sulfate, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent agent, and a fluorescent brightening agent. Blended.

  The thickness of the cover 8 is preferably 0.2 mm or more, and particularly preferably 0.3 mm or more. The thickness of the cover 8 is preferably 2.5 mm or less, and particularly preferably 2.2 mm or less. The specific gravity of the cover 8 is preferably 0.90 or more, particularly preferably 0.95 or more. The specific gravity of the cover 8 is preferably 1.10 or less, and particularly preferably 1.05 or less. The cover 8 may be composed of two or more layers.

  The golf ball 2 may include a reinforcing layer between the mid layer 6 and the cover 8. The reinforcing layer is firmly attached to the intermediate layer 6 and is also firmly attached to the cover 8. The reinforcing layer suppresses peeling of the cover 8 from the intermediate layer 6. Examples of the base polymer of the reinforcing layer include two-component curable epoxy resins and two-component curable urethane resins.

  As shown in FIGS. 2 to 7, the outline of the dimple 10 is a circle. The dimple 10 whose contour is a circle is excellent in aerodynamic symmetry. The golf ball 2 includes a dimple A having a diameter of 4.50 mm, a dimple B having a diameter of 4.40 mm, a dimple C having a diameter of 4.30 mm, and a dimple D having a diameter of 4.15 mm. ing. The number of types of dimples 10 is four.

  The number of dimples A is 28, the number of dimples B is 122, the number of dimples C is 100, and the number of dimples D is 74. The total number N of the dimples 10 is 324. The average value of the diameters of all the dimples 10 is 4.321 mm.

The area s of the dimple 10 is an area of a region surrounded by a contour line when the center of the golf ball 2 is seen from infinity. In the case of the circular dimple 10, the area s is calculated by the following mathematical formula.
s = (Dm / 2) ²・ π
In this equation, Dm represents the diameter of the dimple 10. In the golf ball 2 shown in FIGS. 2 to 7, the dimple A has an area of 15.90 mm ² , the dimple B has an area of 15.21 mm ² , and the dimple C has an area of 14.52 mm ^2. The area of D is 13.53 mm ² .

The ratio of the total area s of all the dimples 10 to the surface area of the phantom sphere is referred to as an occupation ratio X. From the viewpoint of turbulence, the occupation ratio X is preferably 0.78 or more, more preferably 0.79 or more, and particularly preferably 0.80 or more. The occupation ratio X is preferably 0.95 or less. In the golf ball 2 shown in FIGS. 2 to 7, the total area of the dimples 10 is 4753.5 mm ² . Since the surface area of the phantom sphere of this golf ball 2 is 5728.0 mm ² , the occupation ratio X is 0.830.

The standard deviation Y of the diameters of all the dimples 10 is preferably 0.30 or less. In the golf ball 2 having the standard deviation Y of 0.30 or less, turbulence is promoted. In this respect, the standard deviation Y is more preferably equal to or less than 0.29, and particularly preferably equal to or less than 0.28. The standard deviation Y may be zero. The standard deviation Y of the golf ball 2 shown in FIGS. 2 to 7 is calculated by the following mathematical formula.
Y = (((4.500 - 4.321 ) 2 · 28 + (4.400 - 4.321) 2 · 122 +
(4.300 - ^{4.321) 2} 100 + (4.150 - ^{4.321) 2} 74) / ^{324) 1/2}
The standard deviation Y of this golf ball 2 is 0.109.

In the graph of FIG. 8, the horizontal axis represents the occupation ratio, and the vertical axis represents the standard deviation Y. The straight line indicated by the symbol L1 in FIG. 8 is represented by the following mathematical formula.
Y = 3.8 · X-2.894
According to the knowledge obtained by the present inventor, the golf ball 2 whose coordinates (X, Y) are above or below the straight line L1 is excellent in flight performance. In other words, the golf ball 2 satisfying the following formula (I) is excellent in flight performance. The reason is presumed that turbulence is promoted.
Y ≦ 3.8 · X−2.894 (I)

The straight line indicated by the symbol L2 in the graph of FIG. 8 is represented by the following mathematical formula.
Y = 3.8 · X-2.944
According to the knowledge obtained by the present inventor, the golf ball 2 whose coordinates (X, Y) are above or below the straight line L2 is superior in flight performance. In other words, the golf ball 2 satisfying the following formula (II) is excellent in flight performance. The reason is presumed that turbulence is promoted.
Y ≦ 3.8 · X−2.944 (II)

A straight line indicated by a symbol L3 in the graph of FIG. 8 is represented by the following mathematical formula.
Y = 3.8 · X-2.994
According to the knowledge obtained by the present inventor, the golf ball 2 whose coordinates (X, Y) are above or below the straight line L3 is particularly excellent in flight performance. In other words, the golf ball 2 satisfying the following formula (III) is excellent in flight performance. The reason is presumed that turbulence is promoted.
Y ≦ 3.8 · X−2.994 (III)

  When arranging the dimples 10, the designer first designs the basic arrangement of the dimples 10, and then places the small dimples 10 in a narrow zone surrounded by a plurality of dimples 10 in order to further increase the occupation ratio. Often measures are taken. However, this small dimple 10 contributes to the effect of increasing the occupation ratio, but inhibits the effect of reducing the standard deviation. The arrangement of the small dimples 10 is not consistent with the spirit of the present invention. In designing the dimple pattern according to the present embodiment, the designer pays attention to the distance between the centers of the adjacent dimples 10 from the stage of designing the basic dimple 10. The designer designs the pattern while considering that the distance between the centers of the adjacent dimples 10 is as small as possible. Therefore, even if the small dimples 10 are not arranged, the occupation ratio can be increased.

  FIG. 9 shows a cross section along a plane passing through the center of the dimple 10 and the center of the golf ball 2. The vertical direction in FIG. 9 is the depth direction of the dimple 10. In FIG. 9, what is indicated by a two-dot chain line 14 is a virtual sphere. The surface of the phantom sphere is the surface of the golf ball 2 when it is assumed that the dimple 10 does not exist. The dimple 10 is recessed from the surface of the phantom sphere. The land 12 coincides with the surface of the phantom sphere. In the present embodiment, the cross-sectional shape of the dimple 10 is substantially an arc.

  In FIG. 9, what is indicated by a double-headed arrow Dm is the diameter of the dimple 10. The diameter Dm is a distance between one contact Ed and the other contact Ed when a common tangent line Tg is drawn on both sides of the dimple 10. The contact point Ed is also an edge of the dimple 10. The edge Ed defines the contour of the dimple 10. In FIG. 9, what is indicated by a double-headed arrow Dp is the depth of the dimple 10. This depth Dp is the distance between the deepest part of the dimple 10 and the tangent Tg.

  The diameter Dm of each dimple 10 is preferably 2.0 mm or greater and 6.0 mm or less. The dimple 10 having a diameter Dm of 2.0 mm or more contributes to turbulence. In this respect, the diameter Dm is more preferably equal to or greater than 2.2 mm, and particularly preferably equal to or greater than 2.4 mm. The dimple 10 having a diameter Dm of 6.0 mm or less does not impair the essence of the golf ball 2 that is substantially a sphere. In this respect, the diameter Dm is more preferably 5.8 mm or less, and particularly preferably 5.6 mm or less.

In FIG. 9, what is indicated by an arrow CR is the radius of curvature of the dimple 10. The curvature radius CR is calculated by the following mathematical formula (1).
^{CR = (Dp 2 + Dm 2} /4) / (2 * Dp) (1)
Even in the case of the dimple 10 whose cross-sectional shape is not an arc, the curvature radius CR is approximately calculated based on the above formula (1).

  In light of achieving a sufficient occupation ratio X, the total number N of the dimples 10 is preferably 300 or more, more preferably 310 or more, and particularly preferably 320 or more. From the viewpoint that each dimple 10 can contribute to turbulence, the total number N is preferably 400 or less, more preferably 390 or less, and particularly preferably 380 or less.

In the present invention, the “volume of the dimple 10” means the volume of the portion surrounded by the plane including the outline of the dimple 10 and the surface of the dimple 10. From the viewpoint of rising of the golf ball 2 is suppressed, the total volume of the dimples 10 is preferably 250 mm ³ or more, more preferably 260 mm ³ or more, 270 mm ³ or more is particularly preferable. In view of dropping of the golf ball 2 is suppressed, the total volume is preferably 400 mm ³ or less, more preferably 390 mm ³ or less, 380 mm ³ or less is particularly preferred.

  From the viewpoint that hops of the golf ball 2 are suppressed, the depth Dp of the dimple 10 is preferably 0.05 mm or more, more preferably 0.08 mm or more, and particularly preferably 0.10 mm or more. In light of suppression of dropping of the golf ball 2, the depth Dp is preferably equal to or less than 0.60 mm, more preferably equal to or less than 0.45 mm, and particularly preferably equal to or less than 0.40 mm.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
100 parts by weight of high-cis polybutadiene (trade name “BR-730” from JSR), 35 parts by weight of zinc acrylate, 5 parts by weight of zinc oxide, an appropriate amount of barium sulfate, 0.5 parts by weight of diphenyl disulfide and 0 parts 9 parts by mass of dicumyl peroxide was kneaded to obtain a rubber composition. This rubber composition was put into a mold composed of an upper mold and a lower mold each having a hemispherical cavity and heated at 170 ° C. for 18 minutes to obtain a core having a diameter of 39.7 m. The amount of barium sulfate was adjusted to obtain a golf ball having a mass of 45.6 g.

  50 parts by weight of ionomer resin (DuPont's trade name “Surlin 8945”), 50 parts by weight of other ionomer resin (Mitsui DuPont Polychemicals trade name “Himiran AM7329”), 4 parts by weight of titanium dioxide and 0 parts by weight .04 parts by mass of ultramarine blue was kneaded with a twin-screw kneading extruder to obtain a resin composition. This resin composition was coated around the core by an injection molding method to form an intermediate layer. The thickness of this intermediate layer was 1.0 mm.

  A coating composition (trade name “Porin 750LE”, manufactured by Shinto Paint Co., Ltd.) using a two-component curable epoxy resin as a base polymer was prepared. The main component liquid of this coating composition was 30 parts by mass of bisphenol A type solid epoxy resin The curing agent liquid of this coating composition is composed of 40 parts by mass of modified polyamidoamine, 55 parts by mass of solvent, and 5 parts by mass of titanium oxide. The mass ratio with respect to the curing agent liquid was 1/1, and this coating composition was applied to the surface of the intermediate layer with a spray gun and held at 23 ° C. for 6 hours to obtain a reinforcing layer. The thickness of the reinforcing layer was 10 μm.

  100 parts by mass of a thermoplastic polyurethane elastomer (BASF Japan trade name “Elastolan XNY85A”) and 4 parts by mass of titanium dioxide were kneaded with a twin screw extruder to obtain a resin composition. A half shell was obtained from this resin composition by compression molding. A sphere composed of a core, an intermediate layer and a reinforcing layer was covered with two half shells. The half shell and the sphere were both put into a final mold including an upper mold and a lower mold having a hemispherical cavity and a large number of pimples on the cavity surface, and a cover was obtained by a compression molding method. The cover thickness was 0.5 mm. A large number of dimples having a shape obtained by inverting the shape of the pimples were formed on the cover. A clear paint based on a two-component curable polyurethane was applied around the cover to obtain a golf ball of Example 1 having a diameter of about 42.7 mm and a mass of about 45.6 g. The specifications of this golf ball dimple are shown in Table 1 below.

[Example 2-7 and Comparative Example 1-5]
Golf balls of Example 2-7 and Comparative Example 1-5 were obtained in the same manner as Example 1 except that the dimple specifications were as shown in Table 1-3 below. The golf ball according to Comparative Example 1 has a dimple pattern equivalent to the dimple pattern of the golf ball according to Example 1 described in Japanese Unexamined Patent Application Publication No. 2009-95593. The golf ball according to Comparative Example 2 has a dimple pattern equivalent to the dimple pattern of the golf ball according to Comparative Example 2 described in JP-A-2008-389. The golf ball according to Comparative Example 3 has a dimple pattern equivalent to the dimple pattern of the golf ball according to Comparative Example 2 described in JP2011-30909A.

[Flight distance test]
A driver equipped with a titanium alloy head (trade name “SRIXON Z-TX”, manufactured by SRI Sports, shaft hardness: X, loft angle: 8.5 °) was mounted on a golf laboratory swing machine. A golf ball was hit with a head speed of 50 m / sec, a launch angle of about 10 °, and a backspin speed of about 2500 rpm, and the distance from the launch point to the rest point was measured. During the test, there was almost no wind. The average value of the data obtained by 20 measurements is shown in Table 4-6 below.

  As shown in Table 4-6, the golf balls of the examples are excellent in flight performance. From this evaluation result, the superiority of the present invention is clear.

  The aforementioned dimples can be applied not only to a three-piece golf ball but also to a one-piece golf ball, a two-piece golf ball, a four-piece golf ball, a five-piece golf ball, a six-piece golf ball, and a thread-wound golf ball.

2 ... Golf ball 4 ... Core 6 ... Intermediate layer 8 ... Cover 10 ... Dimple 12 ... Land 14 ... Virtual sphere

Claims (3)

A golf ball having a large number of dimples on its surface and satisfying the following formula (III) .
Y ≦ 3.8 · X−2.994 (III)
(In this equation, X represents the ratio of the total area of all the dimples to the surface area of the phantom sphere, and Y represents the standard deviation (mm) of the diameter of all the dimples. The ratio X is 0.805 or more. The standard deviation Y is 0.223 mm or less. The golf ball according to claim 1 , wherein the number of the dimples is 300 or more and 400 or less. The golf ball according to claim 1 , wherein the contour of each dimple is a circle.

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