JP6776529B2 - Golf ball - Google Patents

Description

The present invention relates to a golf ball. In particular, the present invention relates to improving the flight performance of a golf ball.

A golf ball has a large number of dimples on its surface. The dimples disturb the flow of air around the golf ball during flight, causing turbulent separation. This phenomenon is called "turbulence". The turbulence shifts the point of separation of air from the golf ball backwards, reducing drag. Due to the turbulence, the deviation between the upper peeling point and the lower peeling point of the golf ball due to the backspin is promoted, and the lift acting on the golf ball is enhanced. The reduction of drag and the improvement of lift are referred to as the "dimple effect". Good dimples better disrupt the flow of air. Excellent dimples produce a large flight distance.

Various proposals have been made regarding dimples. Japanese Unexamined Patent Publication No. 2009-172192 discloses a golf ball in which dimples are randomly arranged. The dimple pattern of this golf ball is called a random pattern. Random patterns can contribute to the flight performance of a golf ball. Japanese Patent Application Laid-Open No. 2012-10822 also discloses a golf ball having a random pattern.

Japanese Unexamined Patent Publication No. 2007-175267 discloses a dimple pattern in which the number of units in the high latitude region and the number of units in the low latitude region are different. Japanese Patent Application Laid-Open No. 2007-195591 discloses a dimple pattern in which the number of types of dimples in the low latitude region is larger than the number of types of dimples in the high latitude region. Japanese Unexamined Patent Publication No. 2013-153966 discloses a dimple pattern having a high dimple density and a small variation in dimple size.

Various improvements in the composition of golf balls have also been proposed for the purpose of improving flight performance. Japanese Unexamined Patent Publication No. 2008-212681 discloses a golf ball having a core formed from a rubber composition containing a copper salt. This core has excellent resilience performance on driver shots. Japanese Unexamined Patent Publication No. 2008-194471 discloses a golf ball having a core formed from a rubber composition containing an antiaging agent. This core contributes to flight performance on low head speed driver shots.

JP-A-2009-172192 JP2012-10822A JP-A-2007-175267 JP-A-2007-195591 JP 2013-153966 JP-A-2008-212681 Japanese Unexamined Patent Publication No. 2008-194471

A player's primary concern with a golf ball is flight performance. Players want a golf ball with excellent flight performance. From the point of view of flight performance, there is room for 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 is provided with a plurality of dimples on its surface. The ratio So of the total area of the dimples to the surface area of the virtual ball of the golf ball is 81.0% or more. The ratio Rs of the number of dimples whose diameter is 9.60% or more and 10.37% or less of the diameter of the golf ball to the total number of dimples is 50% or more. The hemispherical dimple pattern of the virtual sphere consists of three units that are rotationally symmetric with each other. The dimple pattern of each unit consists of two small units that are mirror-symmetrical to each other. This golf ball satisfies the following mathematical formula (1).
Rs ≧ −2.5 ・ So + 273 (1)

Preferably, the golf ball satisfies the following mathematical formula (2).
Rs ≧ −2.5 ・ So + 278 (2)
Preferably, the golf ball satisfies the following mathematical formula (3).
Rs ≧ −2.5 ・ So + 283 (3)

Preferably, the ratio Rs'of the number of dimples whose diameter is 10.10% or more and 10.37% or less of the diameter of the golf ball to the total number of dimples is 50% or more. Preferably, the golf ball satisfies the following mathematical formula (4).
Rs'≧ -2.2 ・ So + 245 (4)

Preferably, the golf ball satisfies the following mathematical formula (5).
Rs'≧ -2.2 ・ So + 252 (5)

Preferably, the depth of the deepest part of each dimple from the surface of the virtual sphere is 0.10 mm or more and 0.65 mm or less. Preferably, the total volume of the dimples is 450 mm ³ or more and 750 mm ³ or less.

The golf ball according to the present invention has a large dimple effect on driver shots. This golf ball has excellent flight performance.

FIG. 1 is a cross-sectional view showing a golf ball according to an embodiment of the present invention. FIG. 2 is a plan view showing the golf ball of FIG. FIG. 3 is a front view showing the golf ball of FIG. FIG. 4 is an enlarged cross-sectional view showing a part of the golf ball of FIG. FIG. 5 is a graph showing the relationship between the ratio So and the ratio Rs. FIG. 6 is a graph showing the relationship between the ratio So and the ratio Rs'. FIG. 7 is a plan view showing a golf ball according to a second embodiment of the present invention. FIG. 8 is a front view showing the golf ball of FIG. 7. FIG. 9 is a plan view showing a golf ball according to a third embodiment of the present invention. FIG. 10 is a front view showing the golf ball of FIG. FIG. 11 is a plan view showing a golf ball according to a fourth embodiment of the present invention. FIG. 12 is a front view showing the golf ball of FIG. FIG. 13 is a plan view showing the golf ball according to Comparative Example 1. FIG. 14 is a front view showing the golf ball of FIG. FIG. 15 is a plan view showing a golf ball according to Comparative Example 2. FIG. 16 is a front view showing the golf ball of FIG. FIG. 17 is a plan view showing a golf ball according to Comparative Example 3. FIG. 18 is a front view showing the golf ball of FIG. FIG. 19 is a plan view showing a golf ball according to Comparative Example 4. FIG. 20 is a bottom view showing the golf ball of FIG. FIG. 21 is a right side view showing the golf ball of FIG. FIG. 22 is a front view showing the golf ball of FIG. FIG. 23 is a left side view showing the golf ball of FIG. FIG. 24 is a rear view showing the golf ball of FIG. FIG. 25 is a plan view showing the golf ball according to Comparative Example 5. FIG. 26 is a front view showing the golf ball of FIG. 25.

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

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. The golf ball 2 has a large number of dimples 10 on its surface. The portion of the surface of the golf ball 2 other than the dimples 10 is the land 12. The golf ball 2 has a paint layer and a mark layer on the outside of the cover 8, but the illustration of these layers is omitted.

The diameter of the golf ball 2 is preferably 40 mm or more and 45 mm or less. A diameter of 42.67 mm or more is particularly preferred from the perspective of meeting the standards of the United States Golf Association (USGA). From the viewpoint of suppressing air resistance, the diameter is more preferably 44 mm or less, and particularly preferably 42.80 mm or less. The diameter of the golf ball 2 according to the present embodiment is 42.70 mm. The 30 points above Land 12 are randomly selected. The diameter with each point as one end is measured. The diameter of the golf ball 2 is calculated by averaging these diameters.

The mass of the golf ball 2 is preferably 40 g or more and 50 g or less. From the viewpoint that a large inertia can be obtained, the mass is more preferably 44 g or more, and particularly preferably 45.00 g or more. From the viewpoint of satisfying the USGA standard, the mass is particularly preferably 45.93 g or less.

The core 4 is formed by cross-linking the 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 rubber may be used together. From the viewpoint of resilience performance, polybutadiene is preferable, and high cis polybutadiene is particularly preferable.

The rubber composition of the core 4 contains a co-crosslinking agent. Preferred co-crosslinking agents from the viewpoint of resilience performance 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-butylper). Oxy) hexane and di-t-butyl peroxide can be mentioned.

The rubber composition of the core 4 may contain additives such as fillers, sulfur, vulcanization accelerators, sulfur compounds, anti-aging agents, colorants, plasticizers and dispersants. The rubber composition may include a carboxylic acid or a carboxylic acid salt. The rubber composition may include synthetic resin powder or crosslinked rubber powder.

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 have two or more layers. The core 4 may have ribs on its surface. The core 4 may be hollow.

The intermediate layer 6 is made of a resin composition. A preferred base polymer for this resin composition is an ionomer resin. Preferred ionomer resins include binary copolymers of α-olefins and α, β-unsaturated carboxylic acids having 3 or more and 8 or less carbon atoms. As other preferable ionomer resins, a ternary copolymer of an α-olefin, an α, β-unsaturated carboxylic acid having 3 or more and 8 or less carbon atoms and an α, β-unsaturated carboxylic acid ester having 2 or more and 22 or less carbon atoms Examples include copolymers. In the binary copolymer and the ternary copolymer, preferable α-olefins are ethylene and propylene, and preferable α, β-unsaturated carboxylic acids are acrylic acid and methacrylic acid. In these binary copolymers and ternary copolymers, some of the carboxyl groups are neutralized with metal ions. Examples of the metal ion for neutralization include sodium ion, potassium ion, lithium ion, zinc ion, calcium ion, magnesium ion, aluminum ion and neodymium ion.

Instead of the ionomer resin, the resin composition of the intermediate layer 6 may contain other polymers. Examples of other polymers include polystyrene, polyamide, polyester, polyolefin and polyurethane. The resin composition may contain two or more polymers.

The resin composition of the intermediate layer 6 contains 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 whitening agent and the like. It may be. For the purpose of adjusting the specific gravity, this resin composition may contain powders of high specific gravity metals such as tungsten and molybdenum.

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

The cover 8 is made of a resin composition. A preferred substrate polymer for this resin composition is polyurethane. The resin composition may contain thermoplastic polyurethane or may contain thermosetting polyurethane. From the viewpoint of productivity, thermoplastic polyurethane is preferable. The thermoplastic polyurethane contains a polyurethane component as a hard segment and a polyester component or a polyether component as a soft segment.

Polyurethane has a urethane bond in the molecule. This urethane bond can be formed by the reaction of the polyol with the polyisocyanate.

The polyol, which is the raw material for urethane bonding, has a plurality of hydroxyl groups. Low molecular weight polyols and high molecular weight polyols can be used.

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

Instead of polyurethane, the resin composition of cover 8 may contain other polymers. Examples of other polymers include ionomer resins, polystyrenes, polyamides, polyesters and polyolefins. The resin composition may contain two or more polymers.

Even if the resin composition of the cover 8 contains 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 whitening agent and the like. Good.

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, and 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 have two or more layers.

The golf ball 2 may be provided with a reinforcing layer between the intermediate layer 6 and the cover 8. The reinforcing layer firmly adheres to the intermediate layer 6 and also firmly adheres to the cover 8. The reinforcing layer suppresses peeling of the cover 8 from the intermediate layer 6. The reinforcing layer consists of a polymer composition. Examples of the base polymer of the reinforcing layer include a two-component curable epoxy resin and a two-component curable urethane resin.

As shown in FIGS. 2 and 3, the contour of the dimple 10 is a circle. The golf ball 2 includes a dimple A having a diameter of 4.70 mm, a dimple B having a diameter of 4.60 mm, a dimple C having a diameter of 4.40 mm, and a dimple D having a diameter of 4.30 mm. It is equipped with dimples E having a diameter of 3.00 mm. The number of types of dimples 10 is 5. The golf ball 2 may have non-circular dimples in place of or with the circular dimples 10.

The number of dimples A is 30, the number of dimples B is 30, the number of dimples C is 150, the number of dimples D is 90, and the number of dimples E is 12. The total number of dimples 10 is 312. A dimple pattern is formed by these dimples 10 and lands 12.

FIG. 4 shows a cross section of the golf ball 2 along a plane passing through the center of the dimple 10 and the center of the golf ball 2. The vertical direction in FIG. 4 is the depth direction of the dimple 10. What is shown by the alternate long and short dash line 14 in FIG. 4 is a virtual sphere. The surface of the virtual sphere 14 is the surface of the golf ball 2 when the dimples 10 are assumed to be absent. The diameter of the virtual sphere 14 is the same as the diameter of the golf ball 2. The dimple 10 is recessed from the surface of the virtual sphere 14. The land 12 coincides with the surface of the virtual sphere 14. In the present embodiment, the cross-sectional shape of the dimple 10 is substantially an arc.

In FIG. 4, the arrow Dm indicates the diameter of the dimple 10. This diameter Dm is the distance between one contact Ed and the other contact Ed when a common tangent Tg is drawn on both sides of the dimple 10. The contact Ed is also the edge of the dimple 10. The edge Ed defines the contour of the dimple 10. In FIG. 4, the double-headed arrow Dp1 indicates the first depth of the dimple 10. This first depth Dp1 is the distance between the deepest part of the dimple 10 and the surface of the virtual sphere 14. In FIG. 4, the double-headed arrow Dp2 indicates the second depth of the dimple 10. This second depth Dp2 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 more and 6.0 mm or less. The dimples 10 having a diameter Dm of 2.0 mm or more contribute to turbulence. From this viewpoint, the diameter Dm is more preferably 2.5 mm or more, and particularly preferably 2.8 mm or more. The dimple 10 having a diameter Dm of 6.0 mm or less does not impair the essence of the golf ball 2 that it is substantially a sphere. From this viewpoint, the diameter Dm is more preferably 5.5 mm or less, and particularly preferably 5.0 mm or less.

In the case of non-circular dimples, circular dimples 10 having the same area as the area of the non-circular dimples are virtualized. The diameter of this virtual dimple 10 is considered to be the diameter of the non-circular dimple.

The ratio Pd of the diameter Dm of the dimple 10 to the diameter of the golf ball 2 is preferably 9.60% or more and 10.37% or less. Dimples 10 having this ratio of 9.60% or more contribute to turbulence. From this viewpoint, the ratio Pd is more preferably 9.90% or more, and particularly preferably 10.10% or more. The dimple 10 having this ratio Pd of 10.37% or less does not impair the essence of the golf ball 2 that it is substantially a ball. From this viewpoint, the ratio Pd is more preferably 10.32% or less, and particularly preferably 10.27% or less.

The ratio Rs of the number of dimples 10 having a ratio Pd of 9.60% or more and 10.37% or less to the total number of dimples 10 is preferably 50% or more. A dimple pattern having a ratio Rs of 50% or more contributes to turbulence. From this viewpoint, the ratio Rs is more preferably 60% or more, and particularly preferably 70% or more. The ratio Rs may be 100%.

The ratio Rs'of the number of dimples 10 having a ratio Pd of 10.10% or more and 10.37% or less to the total number of dimples 10 is preferably 50% or more. A dimple pattern having a ratio Rs'of 50% or more contributes to turbulence. From this viewpoint, the ratio Rs'is more preferably 60% or more, and particularly preferably 70% or more. The ratio Rs'may be 100%.

The ratio of the number of dimples 10 having a ratio Pd of more than 10.37% to the total number of dimples 10 is preferably less than 50%. In the dimple pattern in which this ratio is less than 50%, the degree of freedom in designing the dimple pattern is high, and therefore the width of the land 12 is unlikely to be excessive. From this point of view, this ratio is more preferably 30% or less, and particularly preferably 10% or less. This ratio may be zero.

From the viewpoint of suppressing the hops of the golf ball 2, the first depth Dp1 of the dimple 10 is preferably 0.10 mm or more, more preferably 0.13 mm or more, and particularly preferably 0.15 mm or more. From the viewpoint of suppressing the drop of the golf ball 2, the first depth Dp1 is preferably 0.65 mm or less, more preferably 0.60 mm or less, and particularly preferably 0.55 mm or less.

The area s of the dimple 10 is the area of the area surrounded by the contour of the dimple 10 when the center of the golf ball 2 is viewed from infinity. In the case of the circular dimple 10, the area S is calculated by the following formula.
S = (Dm / 2) ² * π

In the golf ball 2 shown in FIGS. 2 and 3, the area of the dimple A is 17.35 mm ² , the area of the dimple B is 16.62 mm ² , the area of the dimple C is 15.20 mm ² , and the dimple. The area of D is 14.52 mm ² , and the area of dimple E is 7.07 mm ² .

In the present invention, the ratio of the total area S of all dimples 10 to the surface area of the virtual sphere 14 is referred to as the occupancy rate So. From the viewpoint that sufficient turbulence can be obtained, the occupancy rate So is preferably 81.0% or more, more preferably 82.0% or more, and particularly preferably 83.0% or more. The occupancy rate is preferably 95% or less. In the golf ball 2 shown in FIGS. 2 and 3, the total area of the dimples 10 is 4691.5 mm ² . Since the surface area of the virtual ball 14 of the golf ball 2 is 5278.0 mm ² , the occupancy rate is 81.9%.

From the viewpoint that a sufficient occupancy rate is achieved, the total number N of the dimples 10 is preferably 250 or more, more preferably 280 or more, and particularly preferably 300 or more. From the viewpoint that each dimple 10 can contribute to turbulence, the total number N is preferably 450 or less, more preferably 400 or less, and particularly preferably 380 or less.

In the present invention, the "volume of dimples" means the volume of a portion surrounded by the surface of the virtual sphere 14 and the surface of the dimples 10. From the viewpoint of rising of the golf ball 2 is suppressed, the total volume is 450 mm ³ or more preferably a dimple 10, and more preferably 480 mm ³ or more, 500 mm ³ or more is particularly preferable. In view of dropping of the golf ball 2 is suppressed, the total volume is preferably 750 mm ³ or less, more preferably 730 mm ³ or less, 710 mm ³ or less is particularly preferred.

In the graph shown in FIG. 5, the horizontal axis is the dimple occupancy rate So. In this graph, the vertical axis is the ratio Rs of the number of dimples 10 having a ratio Pd of 9.60% or more and 10.37% or less to the total number of dimples 10. The straight line represented by the symbol L1 in this graph is represented by the following mathematical formula.
Rs = -2.5 ・ So + 273
In this graph, the golf ball 2 plotted in the zone above the straight line L1 satisfies the following mathematical formula (1).
Rs ≧ −2.5 ・ So + 273 (1)
In the golf ball 2 satisfying the above mathematical formula (1), turbulence is promoted. This golf ball 2 is excellent in flight performance on driver shots.

The straight line represented by the reference numeral L2 in the graph of FIG. 5 is represented by the following mathematical formula.
Rs = -2.5 ・ So + 278
In this graph, the golf ball 2 plotted in the zone above the straight line L2 satisfies the following mathematical formula (2).
Rs ≧ −2.5 ・ So + 278 (2)
In the golf ball 2 satisfying the above mathematical formula (2), turbulence is promoted. This golf ball 2 is excellent in flight performance on driver shots.

The straight line represented by the reference numeral L3 in the graph of FIG. 5 is represented by the following mathematical formula.
Rs = -2.5 ・ So + 283
In this graph, the golf ball 2 plotted in the zone above the straight line L3 satisfies the following mathematical formula (3).
Rs ≧ −2.5 ・ So + 283 (3)
In the golf ball 2 satisfying the above mathematical formula (3), turbulence is promoted. This golf ball 2 is excellent in flight performance on driver shots.

In the graph shown in FIG. 6, the horizontal axis is the dimple occupancy rate So. In this graph, the vertical axis is the ratio Rs'of the number of dimples 10 having a ratio Pd of 10.10% or more and 10.37% or less to the total number of dimples 10. The straight line represented by the symbol L4 in this graph is represented by the following mathematical formula.
Rs'= -2.2 ・ So + 245
In this graph, the golf ball 2 plotted in the zone above the straight line L4 satisfies the following mathematical formula (4).
Rs'≧ -2.2 ・ So + 245 (4)
In the golf ball 2 satisfying the above mathematical formula (4), turbulence is promoted. This golf ball 2 is excellent in flight performance on driver shots.

The straight line represented by the reference numeral L5 in the graph of FIG. 6 is represented by the following mathematical formula.
Rs'= -2.2 ・ So + 252
In this graph, the golf ball 2 plotted in the zone above the straight line L5 satisfies the following mathematical formula (5).
Rs'≧ -2.2 ・ So + 252 (5)
In the golf ball 2 satisfying the above mathematical formula (5), turbulence is promoted. This golf ball 2 is excellent in flight performance on driver shots.

As shown in FIG. 3, the surface of the golf ball 2 (or virtual sphere 14) can be partitioned into two hemispherical HEs by the equator Eq. Specifically, the surface can be partitioned into the Northern Hemisphere NH and the Southern Hemisphere SH. Each hemispherical HE has a pole P. The pole P corresponds to the deepest point of the molding for the golf ball 2.

FIG. 2 shows the Northern Hemisphere. The Southern Hemisphere has a pattern in which the dimple pattern of FIG. 2 is rotated around a pole P. Each of the line segments S1, S2 and S3 shown in FIG. 2 extends from the pole P. The angle between the line segment S1 and the line segment S2 at the pole P is 120 °. The angle between the line segment S2 and the line segment S3 at the pole P is 120 °. The angle between the line segment S3 and the line segment S1 at the pole P is 120 °.

On the surface of the golf ball 2 (or the virtual sphere 14), the zone surrounded by the line segment S1, the line segment S2, and the equator Eq is the first spherical triangle T1. On the surface of the golf ball 2 (or the virtual sphere 14), the zone surrounded by the line segment S2, the line segment S3, and the equator Eq is the second spherical triangle T2. On the surface of the golf ball 2 (or the virtual sphere 14), the zone surrounded by the line segment S3, the line segment S1 and the equator Eq is the third spherical triangle T3. Each spherical triangle is a unit. This hemispherical HE can be divided into three units.

When the dimple pattern of the first spherical triangle T1 is rotated by 120 ° about the straight line connecting the two poles P, it substantially overlaps with the dimple pattern of the second spherical triangle T2. When the dimple pattern of the second spherical triangle T2 is rotated by 120 ° about the straight line connecting the two poles P, it substantially overlaps with the dimple pattern of the third spherical triangle T3. When the dimple pattern of the third spherical triangle T3 is rotated by 120 ° about the straight line connecting the two poles P, it substantially overlaps with the dimple pattern of the first spherical triangle T1. In other words, the hemispherical dimple pattern consists of three units that are rotationally symmetric with each other.

The pattern in which the dimple pattern of the hemispherical HE is rotated by 120 ° about the straight line connecting the two poles P substantially overlaps with the dimple pattern before the rotation. The dimple pattern of the hemispherical HE is 120 ° rotationally symmetric.

The line segment S4 shown in FIG. 2 extends from the pole P. The angle between the line segment S4 and the line segment S1 at the pole P is 60 °. The angle between the line segment S4 and the line segment S2 at the pole P is 60 °. The line segment S4 may partition the first spherical triangle T1 (unit) into a small spherical triangle T1a and a small spherical triangle T1b. The spherical triangle T1a and the spherical triangle T1b are small units.

The pattern in which the dimple pattern of the spherical triangle T1a is inverted with respect to the plane including the straight line connecting the two poles P and the line segment S4 substantially overlaps with the dimple pattern of the spherical triangle T1b. In other words, the dimple pattern of each unit consists of two small units that are mirror-symmetrical to each other.

Similarly, the dimple pattern of the second spherical triangle T2 consists of two small units that are mirror-symmetrical to each other. The dimple pattern of the third spherical triangle T3 also consists of two small units that are mirror-symmetrical to each other. The dimple pattern of this hemispherical HE consists of 6 small units.

According to the findings obtained by the present inventor, the golf ball 2 consists of three units whose hemispherical dimple patterns are 120 ° rotationally symmetric with each other, and two small units whose dimple patterns of each unit are mirror-symmetrical with each other. Then, turbulence is promoted. This golf ball 2 is excellent in flight performance on driver shots.

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

[Example 1]
100 parts by mass of high cis polybutadiene (trade name "BR-730" of JSR Corporation), 22.5 parts by mass of zinc acrylate, 5 parts by mass of zinc oxide, 5 parts by mass of barium sulfate, 0.5 parts by mass Diphenyl disulfide and 0.6 parts by mass of dicumyl peroxide were kneaded to obtain a rubber composition. This rubber composition was put into a mold consisting of an upper mold and a lower mold both having a hemispherical cavity, and heated at 170 ° C. for 18 minutes to obtain a core having a diameter of 38.5 mm.

50 parts by mass of ionomer resin (trade name "Himilan 1605" by Mitsui DuPont Polychemical), 50 parts by mass of other ionomer resin (trade name "Himilan AM7329" by Mitsui DuPont Polychemical) and 4 parts by mass titanium dioxide 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 1.6 mm.

A coating composition (trade name "Porin 750LE" of Shinto Paint Co., Ltd.) using a two-component curable epoxy resin as a base polymer was prepared. The main component solution of this coating composition is 30 parts by mass of bisphenol A solid epoxy resin. And 70 parts by mass of the solvent. The curing agent solution of this coating composition is composed of 40 parts by mass of the modified polyamide amine, 55 parts by mass of the solvent, and 5 parts by mass of titanium dioxide as the main agent solution. The mass ratio with the curing agent solution is 1/1. 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.

A resin composition was obtained by kneading 100 parts by mass of a thermoplastic polyurethane elastomer (trade name "Elastran XNY85A" manufactured by BASF Japan Ltd.) and 4 parts by mass of titanium dioxide with a twin-screw extruder. From this resin composition, a half shell was obtained by a compression molding method. Two half shells covered a sphere consisting of a core, an intermediate layer and a reinforcing layer. These half shells and spheres were put into a final mold consisting of an upper mold and a lower mold both 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 thickness of the cover was 0.5 mm. The cover was formed with dimples having an inverted shape of the pimples. 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 42.70 mm and a mass of about 45.6 g. The amount of compression deformation of this golf ball when the load was 98N-1274N was 2.45 mm. The specifications of the dimples of this golf ball are shown in Table 1 below.

[Examples 2-4 and Comparative Examples 1-3]
Golf balls of Example 2-4 and Comparative Example 1-3 were obtained in the same manner as in Example 1 except that the dimple specifications were as shown in Table 1-2 below. In each golf ball, the hemispherical dimple pattern consists of three units that are rotationally symmetric with each other. The dimple pattern of each unit consists of two small units that are mirror-symmetrical to each other. The number of small units in the hemisphere is six. The hemispherical dimple pattern of the golf ball according to the fourth embodiment is 60 ° rotational symmetry, 120 ° rotational symmetry, and 180 ° rotational symmetry.

[Comparative Example 4-5]
The golf balls of Comparative Example 4-5 were obtained in the same manner as in Example 1 except that the dimple specifications were as shown in Table 2 below. The golf ball dimple pattern according to Comparative Example 4 is the same as the golf ball dimple pattern according to Example 1 of JP2013-153966A. The hemispherical dimple pattern of the golf ball according to Comparative Example 4 is not rotationally symmetric. The golf ball dimple pattern according to Comparative Example 5 is the same as the golf ball dimple pattern according to Comparative Example 1 of JP2013-153966A. The hemispherical dimple pattern of the golf ball according to Comparative Example 5 is not rotationally symmetric.

[Flight test]
A driver equipped with a titanium alloy head (Dunlop Sports' brand name "SRIXON Z-TX", shaft hardness: X, loft angle: 8.5 °) was attached to the swing machine of Golf Laboratory. The distance from the launch point to the rest point was measured by hitting the golf ball under the conditions that the head speed was 50 m / sec, the launch angle was about 10 °, and the backspin speed was about 2500 rpm. At the time of the test, there was almost no wind. The average value of the data obtained in 20 measurements is shown in Table 3-4 below.

As shown in Table 3-4, the golf balls of each embodiment are excellent in flight performance. From this evaluation result, the superiority of the present invention is clear.

The above-mentioned dimple pattern is applied not only to three-piece golf balls but also to golf balls having various structures such as one-piece golf balls, two-piece golf balls, four-piece golf balls, five-piece golf balls, six-piece golf balls, and thread-wound golf balls. Can be done.

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

Claims (5)

A golf ball with multiple dimples on its surface
The ratio So of the total area of the dimples to the surface area of the virtual ball of the golf ball is 81.0% or more.
In the case of circular dimples, the diameter of this circle, and in the case of non-circular dimples, the diameter of the dimples , which is the diameter of the circle of circular dimples having the same area as the area of the non-circular dimples, is the diameter of the golf ball. The ratio Rs of the number of dimples of 9.60% or more and 10.37% or less to the total number of dimples is 50% or more.
The hemispherical dimple pattern of the above virtual sphere consists of three units that are rotationally symmetric with each other.
The dimple pattern of each unit consists of two small units that are mirror-symmetrical to each other.
Satisfy the following formula (1)
The ratio Rs'of the number of dimples whose diameter is 10.10% or more and 10.37% or less of the diameter of the golf ball to the total number of dimples is 50% or more.
A golf ball that satisfies the following formula (5).
Rs ≧ −2.5 ・ So + 273 (1)
Rs'≧ -2.2 ・ So + 252 (5) The golf ball according to claim 1, which satisfies the following mathematical formula (2).
Rs ≧ −2.5 ・ So + 278 (2) The golf ball according to claim 2, which satisfies the following mathematical formula (3).
Rs ≧ −2.5 ・ So + 283 (3) The golf ball according to any one of claims 1 to 3, wherein the deepest portion of each dimple has a depth of 0.10 mm or more and 0.65 mm or less from the surface of the virtual sphere. The golf ball according to any one of claims 1 to 4, wherein the total volume of the dimples is 450 mm ³ or more and 750 mm ³ or less.

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