CN109107116B

CN109107116B - Golf ball

Info

Publication number: CN109107116B
Application number: CN201810636676.8A
Authority: CN
Inventors: 三村耕平; 佐嶌隆弘
Original assignee: Sumitomo Rubber Industries Ltd
Current assignee: Sumitomo Rubber Industries Ltd
Priority date: 2017-06-26
Filing date: 2018-06-20
Publication date: 2022-06-03
Anticipated expiration: 2038-06-20
Also published as: EP3421107A1; US20180369648A1; CN109107116A; EP3421107B1; KR20190001509A

Abstract

The purpose of the present invention is to provide a golf ball (2) having excellent flight performance. The solution is as follows: the golf ball (2) has a plurality of dimples (10) on its surface. The dimple pattern of the hemisphere of the virtual ball of the golf ball (2) is composed of 3 cells ((T1), (T2), and (T3)) that are rotationally symmetric to each other. The dimple pattern of each cell is composed of 2 small cells ((T1a), (T1b)) that are mirror-symmetrical to each other. The standard deviation Su of the areas of all the dents (10) is 1.7mm²The following. The standard deviation Pd of the distances L between all pairs of nearby dimples is less than 0.500 mm. The ratio So of the total area of the dimples (10) to the surface area of the virtual ball of the golf ball (2) is 78.0% or more.

Description

Golf ball

Technical Field

The present invention relates to golf balls. In particular, the present invention relates to a dimple pattern (double pattern) of a golf ball.

Background

The striking face of the golf club has a loft angle. If a golf ball is hit with the golf club, backspin due to a loft angle occurs in the golf ball. The golf ball flies with backspin.

The golf ball has a plurality of dimples on its surface. In flight, the dimples disturb the airflow around the golf ball, causing turbulent flow separation. This phenomenon is called "turbulent flow". Due to the turbulent flow, the separation point where the air is separated from the golf ball moves backward and the resistance decreases. Due to the turbulent flow, the offset between the upper and lower separation points of the golf ball caused by backspin is promoted, increasing the lift force acting on the golf ball. The reduction in drag and the increase in lift is referred to as the "dimple effect". The excellent dimples better disturb the air flow. Superior dimples produce greater flight distances.

Japanese patent laid-open publication No. 50-8630 discloses a golf ball comprising: a dimple pair having a plurality of dimples spaced from other dimples adjacent to the dimple by less than 0.065 inches. The golf ball is densely provided with a plurality of dimples.

Such a golf ball is disclosed in japanese patent laid-open publication 2008-389: there is a dimple pair having a sufficiently small spacing in comparison to the average diameter of the dimples. The golf ball has a plurality of dimples arranged densely.

Japanese patent laid-open publication No. 2013-153966 discloses a golf ball in which a plurality of dimples are densely arranged and the variation in the sizes of the dimples is small. The same golf ball is disclosed in Japanese patent laid-open publication No. 2015-24079.

[ Prior art documents ]

[ patent document ]

Patent document 1 Japanese patent laid-open No. Sho 50-8630

Patent document 2 Japanese patent laid-open No. 2008-389

Patent document 3 Japanese patent laid-open publication No. 2013-153966

Patent document 4 Japanese patent laid-open No. 2015-24079

Disclosure of Invention

Problems to be solved by the invention

The dense dimples are advantageous for the flight performance of the golf ball. However, the golfer desires further improvement in the flight distance. There is room for improvement in the dent from the viewpoint of flight performance.

The purpose of the present invention is to provide a golf ball having excellent flight performance.

Means for solving the problems

The golf ball according to the present invention has a plurality of dimples on the surface thereof. The standard deviation Su of all the dimple areas was 1.7mm²The following. The standard deviation Pd of the distances L between all pairs of nearby dimples is less than 0.500 mm.

Preferably, the standard deviation Pd is less than 0.400 mm.

Preferably, the dimple pattern of the hemisphere of the virtual ball of the golf ball is composed of 3 units that are rotationally symmetric to each other. The dimple pattern of each cell is composed of 2 small cells that are mirror-symmetrical to each other.

Preferably, the ratio So of the total dimple area to the surface area of the virtual ball of the golf ball is 78.0% or more.

Preferably, the total volume of all indentations is 450mm³Above 750mm³The following.

Preferably, the total number of dents is 300 to 390.

Effects of the invention

The golf ball has reasonable lift coefficient and drag coefficient during flying. The golf ball is excellent in flight performance.

Drawings

FIG. 1: fig. 1 is a schematic cross-sectional view showing a golf ball according to an embodiment of the present invention.

FIG. 2 is a schematic diagram: fig. 2 is an enlarged plan view showing the golf ball of fig. 1.

FIG. 3: fig. 3 is a front view showing the golf ball of fig. 2.

FIG. 4: fig. 4 is an enlarged sectional view showing a portion of the golf ball of fig. 1.

FIG. 5 is a schematic view of: fig. 5 is an enlarged view showing a portion of the golf ball of fig. 2 and 3.

FIG. 6: fig. 6 is an explanatory diagram of the definition of a neighborhood dimple used in the golf ball of fig. 2 and 3.

FIG. 7: fig. 7 is an explanatory diagram of the definition of a neighborhood dimple used in the golf ball of fig. 2 and 3.

FIG. 8: fig. 8 is an explanatory diagram of the definition of a neighborhood dimple used in the golf ball of fig. 2 and 3.

FIG. 9: fig. 9 is an explanatory diagram of the definition of a neighborhood dimple used in the golf ball of fig. 2 and 3.

FIG. 10: fig. 10 is a plan view showing a golf ball according to example 2 of the present invention.

FIG. 11: fig. 11 is a front view showing the golf ball of fig. 10.

FIG. 12: fig. 12 is a plan view showing a golf ball according to example 3 of the present invention.

FIG. 13: fig. 13 is a front view showing the golf ball of fig. 12.

FIG. 14: fig. 14 is a plan view showing a golf ball according to example 4 of the present invention.

FIG. 15: fig. 15 is a front view showing the golf ball of fig. 14.

FIG. 16: fig. 16 is a plan view showing a golf ball according to comparative example 1.

FIG. 17: fig. 17 is a front view showing the golf ball of fig. 16.

FIG. 18: fig. 18 is a plan view showing a golf ball according to comparative example 2.

FIG. 19: fig. 19 is a front view showing the golf ball of fig. 18.

FIG. 20: FIG. 20 is a plan view showing a golf ball according to example 5.

FIG. 21: fig. 21 is a front view showing the golf ball of fig. 20.

Description of the symbols

2. Golf ball

4. core

6. intermediate layer

8. coating layer

10. indent of

12. contact surface (land)

14. virtual ball

16. neighborhood dimple pair

Detailed Description

The present invention will be described in detail below based on preferred embodiments with reference to the accompanying 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 layer 8 located outside the intermediate layer 6. The golf ball 2 has a plurality of dimples 10 on its surface. The portion of the surface of the golf ball 2 other than the dimples 10 is the contact surface 12. The golf ball 2 includes a coating layer and a marker layer on the outer side of the cover layer 8, but these layers are not shown.

The diameter of the golf ball 2 is preferably 40mm to 45 mm. The diameter is particularly preferably 42.67mm or more from the viewpoint of satisfying the standards of the United States Golf Association (USGA). From the viewpoint of suppressing air resistance, the diameter is more preferably 44mm or less, and particularly preferably 42.80mm or less.

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

The core 4 is formed by crosslinking a rubber composition. Examples of the base rubber of the rubber composition include polybutadiene, polyisoprene, a styrene-butadiene copolymer, an ethylene-propylene-diene copolymer and natural rubber. More than 2 kinds of rubbers may be used in combination. From the viewpoint of the rebound property, 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 are zinc acrylate, magnesium acrylate, zinc methacrylate and magnesium methacrylate from the viewpoint of the rebound property. The rubber composition preferably contains both the co-crosslinking agent and the organic peroxide. Preferred organic peroxides include: dicumyl peroxide, 1-bis (t-butylperoxy) -3,3, 5-trimethylcyclohexane, 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexane and di-t-butyl peroxide.

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

The diameter of the core 4 is preferably 30.0mm or more, particularly preferably 38.0mm or more. The diameter of the core 4 is preferably 42.0mm or less, particularly preferably 41.5mm or less. The core 4 may have more than 2 layers. The core 4 may have ribs (rib) on its surface. The core 4 may be hollow.

The intermediate layer 6 is formed of a resin composition. The preferred base polymer of the resin composition is an ionomer resin. Preferred ionomer resins include binary copolymers of α -olefins and α, β -unsaturated carboxylic acids having 3 to 8 carbon atoms. Preferred examples of the other ionomer resins include: a terpolymer of an alpha-olefin, an alpha, beta-unsaturated carboxylic acid having 3 to 8 carbon atoms and an alpha, beta-unsaturated carboxylic acid ester having 2 to 22 carbon atoms. In the binary copolymer and the ternary copolymer, preferred alpha-olefin is ethylene and propylene, and preferred alpha, beta-unsaturated carboxylic acid is acrylic acid and methacrylic acid. In the binary copolymer and the ternary copolymer, a part of the carboxyl groups is neutralized by metal ions. Examples of metal ions used for neutralization include: sodium ions, potassium ions, lithium ions, zinc ions, calcium ions, magnesium ions, aluminum ions, and neodymium ions.

The resin composition of the intermediate layer 6 may contain other polymers instead of the ionomer resin. Examples of other polymers include: polystyrene, polyamide, polyester, polyolefin, and polyurethane. The resin composition may contain 2 or more kinds of polymers.

The resin composition of the intermediate layer 6 may contain 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 brightener, and the like. The resin composition may contain powder of high specific gravity metal such as tungsten, molybdenum, etc. for the purpose of adjusting the specific gravity.

The thickness of the intermediate layer 6 is preferably 0.2mm or more, particularly preferably 0.3mm or more. The thickness of the intermediate layer 6 is preferably 2.5mm or less, and particularly preferably 2.2mm 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 2 or more layers.

The coating layer 8 is formed of a resin composition. The preferred base polymer of the resin composition is polyurethane. The resin composition may contain a thermoplastic polyurethane or a 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 polyether component as a soft segment.

The polyurethane has a urethane bond (urethane bond) in the molecule. The urethane bond may be formed by the reaction of a polyol and a polyisocyanate.

The polyol as a raw material of the urethane bond has a plurality of hydroxyl groups. Both low molecular weight polyols and high molecular weight polyols may be used.

Examples of the isocyanate of the polyurethane component include an alicyclic diisocyanate, an aromatic diisocyanate, and an aliphatic diisocyanate. Particularly preferred is an alicyclic diisocyanate. The alicyclic diisocyanate has no double bond in the main chain, and therefore can suppress yellowing of the coating layer 8. As the alicyclic diisocyanate, there can be mentioned: 4, 4' -dicyclohexylmethane diisocyanate (H)₁₂MDI), 1, 3-bis (isocyanatomethyl) cyclohexane (H)₆XDI), isophorone diisocyanate (IPDI) and trans-1, 4-cyclohexane diisocyanate (CHDI). From the viewpoint of versatility and processability, H is preferred₁₂MDI。

The resin composition of the coating layer 8 may contain other polymers instead of polyurethane. Examples of other polymers include: ionomer resins, polystyrene, polyamides, polyesters, and polyolefins. The resin composition may contain 2 or more kinds of polymers.

The resin composition of the coating layer 8 may contain a coloring agent 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 brightener, and the like.

The thickness of the coating layer 8 is preferably 0.2mm or more, particularly preferably 0.3mm or more. The thickness of the coating layer 8 is preferably 2.5mm or less, and particularly preferably 2.2mm or less. The specific gravity of the coating layer 8 is preferably 0.90 or more, and particularly preferably 0.95 or more. The specific gravity of the coating layer 8 is preferably 1.10 or less, and particularly preferably 1.05 or less. The clad layer 8 may have 2 or more layers.

The golf ball 2 may include a reinforcing layer between the intermediate layer 6 and the cover layer 8. The reinforcing layer is firmly attached to the intermediate layer 6 and also firmly attached to the coating layer 8. The reinforcing layer suppresses peeling of the coating layer 8 from the intermediate layer 6. The stiffening layer is formed from a polymer composition. Examples of the base polymer for the reinforcing layer include: two-pack curable epoxy resin and two-pack curable urethane resin.

As shown in fig. 2 and 3, each dimple 10 has a circular profile. The golf ball 2 includes a dimple a having a diameter of 4.40mm, a dimple B having a diameter of 4.30mm, a dimple C having a diameter of 4.15mm, a dimple D having a diameter of 3.90mm, and a dimple E having a diameter of 3.00 mm. The number of kinds of the dents 10 is 5.

The number of dimples a was 60, the number of dimples B was 158, the number of dimples C was 72, the number of dimples D was 36, and the number of dimples E was 12. The total number of the dents 10 is 338. By these dimples 10 and the contact surface 12, a dimple pattern is formed.

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. In fig. 4, a two-dot chain line 14 shows a virtual ball. The surface of the virtual ball 14 is the surface of the golf ball 2 assuming that the dimple 10 is not present. The diameter of the virtual ball 14 is the same as the diameter of the golf ball 2. The dimple 10 is recessed from the surface of the virtual ball 14. The contact surface 12 conforms to the surface of the virtual ball 14. In the present embodiment, the cross-sectional shape of the dimple 10 is substantially a circular arc. In fig. 4, the radius of curvature of the arc is denoted by symbol CR.

In fig. 4, an arrow Dm indicates the diameter of the dimple 10. The diameter Dm is a distance between one tangent point Ed and the other tangent point Ed when the tangent line Tg common to both sides of the dimple 10 is drawn. The tangent point Ed is also the edge of the dimple 10. The edge Ed defines the contour of the dimple 10.

The diameter Dm of each dimple 10 is preferably 2.0mm to 6.0 mm. Indentations 10 with a diameter Dm of 2.0mm or more are beneficial for turbulent flow. From this viewpoint, the diameter Dm is more preferably 2.5mm or more, and particularly preferably 2.8mm or more. Dimples 10 having a diameter Dm of 6.0mm or less do not detract from the nature of the substantially spherical golf ball 2. From this viewpoint, the diameter Dm is more preferably 5.5mm or less, and particularly preferably 5.0mm or less.

In fig. 4, a double arrow Dp1 indicates the first depth of the dimple 10. The first depth Dp1 is the distance between the deepest part of the dimple 10 and the surface of the virtual ball 14. In fig. 4, a double arrow Dp2 indicates the second depth of the dimple 10. The second depth Dp2 is the distance between the deepest part of the dimple 10 and the tangent Tg.

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

The area S of the dimple 10 is an area of a region 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 dents 10, the area S is calculated by the following mathematical formula.

S＝(Dm/2)²×π

In the golf ball 2 shown in FIGS. 2 and 3, the area of the dimples A is 15.21mm²The area of the dimple B is 14.52mm²The area of the dimple C was 13.53mm²The area of the dimple D is 11.95mm²The area of the dimple E is 7.07mm²。

In the present invention, the ratio of the total of the areas S of all the dimples 10 to the surface area of the virtual ball 14 is referred to as an occupancy So. From the viewpoint of obtaining sufficient turbulent flow, the occupancy So is preferably 78% or more, more preferably 80% or more, and particularly preferably 82% or more. The occupancy So is preferably 95% or less. In the golf ball 2 shown in FIGS. 2 and 3, the total area of the dimples 10 is 4695.6mm². The surface area of the virtual ball 14 of the golf ball 2 is 5728mm²Therefore, the occupancy So is 82.0%.

The standard deviation Su of the areas of all the dimples 10 is preferably 1.7mm²The following. Su of 1.7mm²The following golf ball 2 is excellent in flight performance. From this viewpoint, the standard deviation Su is more preferably 1.61mm²Hereinafter, 1.44mm is particularly preferable²The following. The standard deviation Su is preferably 1.2mm²The above. In the present embodiment, the average of the areas of all the dimples 10 is 13.89mm². Therefore, the standard deviation Su of these areas is calculated by the following mathematical formula.

Su＝(((15.20-13.89)²×60+(14.52-13.89)²×158+(13.53-13.89)²×72+(11.95-13.89)²×36+(7.07-13.89)²×12)/338)^1/2

＝1.61

From the viewpoint of achieving a sufficient occupancy So, the total number of dimples 10 is preferably 250 or more, more preferably 280 or more, and particularly preferably 300 or more. From the viewpoint that the respective indentations 10 may contribute to the turbulent flow, the total number is preferably 450 or less, more preferably 410 or less, and particularly preferably 390 or less.

In the present invention, the "volume V of the dimple" refers to the volume of a portion surrounded by the surface of the virtual ball 14 and the surface of the dimple 10. The total volume TV of the dimple 10 is preferably 450mm³Above 750mm³The following. The total volume TV is 450mm³The above golf ball 2 can suppress the bounce in flight. From this point of view, the total volume TV is more preferably 480mm³Above, particularly preferably 500mm³The above. Total volume TV 750mm³The following golf ball 2 can suppress falling in flight. From this viewpoint, the total volume TV is more preferably 730mm³Hereinafter, 710mm is particularly preferable³The following.

As shown in fig. 3, the surface of the golf ball 2 (or the virtual ball 14) may be divided into 2 hemispheres HE by the equator Eq. Specifically, the surface may be divided into a northern hemisphere NH and a southern hemisphere SH. Each hemisphere HE has a pole P. The pole point P corresponds to the deepest point of the forming mold for the golf ball 2.

The plan view of fig. 2 shows the northern hemisphere. The southern hemisphere (corresponding to the bottom view) has the dimple pattern of fig. 2 rotated about the pole P. The respective line segments S1, S2, and S3 shown in fig. 2 extend from pole P. The angle of the line segment S1 and the line segment S2 in the pole P is 120 °. The angle of the line segment S2 and the line segment S3 in the pole P is 120 °. The angle in the pole P of the segment S3 and the segment S1 is 120 °.

In the surface of the golf ball 2 (or the virtual ball 14), an area surrounded by the line segment S1, the line segment S2, and the equator Eq (see fig. 2) is a first spherical triangle T1. In the surface of the golf ball 2 (or the virtual ball 14), an area surrounded by the line segment S2, the line segment S3, and the equator Eq is a second spherical triangle T2. In the surface of the golf ball 2 (or the virtual ball 14), an area surrounded by the line segment S3, the line segment S1, and the equator Eq is a third spherical triangle T3. Each spherical triangle is a unit. The hemisphere HE may be divided into 3 units.

If the dimple pattern of the first spherical triangle T1 is rotated by 120 ° with the straight line connecting the 2 poles P as an axis, it substantially coincides with the dimple pattern of the second spherical triangle T2. If the dimple pattern of the second spherical triangle T2 is rotated by 120 ° with the straight line connecting the 2 poles P as an axis, it substantially coincides with the dimple pattern of the third spherical triangle T3. If the dimple pattern of the third spherical triangle T3 is rotated by 120 ° with the straight line connecting the 2 poles P as an axis, it substantially coincides with the dimple pattern of the first spherical triangle T1. In other words, the dimple pattern of the hemisphere of the virtual sphere is composed of 3 cells that are rotationally symmetric to each other.

The dimple pattern of the hemisphere HE is rotated by 120 ° about a straight line connecting 2 poles, and substantially overlaps with the dimple pattern before rotation. The dimple pattern of the hemisphere HE is 120 ° rotationally symmetric.

The line segment S4 shown in fig. 2 extends from the pole P. The angle of the line segment S4 and the line segment S1 in the pole P is 60 °. The angle of the line segment S4 and the line segment S2 in the pole P is 60 °. The first spherical triangle T1 (cell) may be divided into a small spherical triangle T1a and other small spherical triangles T1b by a line segment S4. The spherical triangle T1a and the spherical triangle T1b are small units.

The pattern of the dimples of the spherical triangle T1a flipped relative to the plane containing the line connecting the two poles P and the line segment S4 substantially coincides with the dimple pattern of the spherical triangle T1 b. In other words, the dimple pattern of the first spherical triangle T1 (cell) is composed of 2 small cells that are mirror-symmetrical to each other.

Although not shown, the dimple pattern of the second spherical triangle T2 is also composed of 2 small cells that are mirror-symmetrical to each other, as in the first spherical triangle T1. The dimple pattern of the third spherical triangle T3 is also composed of 2 small cells that are mirror-symmetrical to each other. The dimple pattern of the hemisphere HE is composed of 6 small cells.

From the knowledge obtained by the present inventors, it is known that the dimple pattern of the hemisphere of the virtual ball is composed of 3 cells that are rotationally symmetric with each other by 120 °, and the golf ball 2 in which the dimple pattern of each cell is composed of 2 small cells that are mirror-symmetric with each other can promote turbulence. The golf ball 2 is excellent in flight performance.

The golf ball may have a dimple pattern in which the cells are not divided into 2 small cells that are mirror-symmetrical to each other. The golf ball may have a dimple pattern in which the hemisphere is not divided into 3 cells that are rotationally symmetric with respect to each other by 120 °.

Fig. 5 is an enlarged view showing a part of the golf ball 2 of fig. 2. The first dimple 10a and the second dimple 10b are shown in fig. 5. For the first dimple 10a, the second dimple 10b is a neighborhood dimple. For the second dimple 10b, the first dimple 10a is a neighborhood dimple. The first dimple 10a and the second dimple 10b form 1 nearby dimple pair 16.

In fig. 5, symbol CL denotes a line segment connecting the center of the first dimple 10a and the center of the second dimple 10 b. In fig. 5, symbol L indicates the distance between the pair of nearby dimples 16. The distance L is measured along the line CL.

Although the surface of the golf ball 2 is a curved surface, the size of the dimple 10 is sufficiently small compared to the size of the golf ball 2, and therefore, in fig. 5, the curved surface is approximated to a plane, and the line segment CL is drawn to measure the distance L. In fig. 6 to 9 below, the curved surface is similarly approximated to be a plane.

The definition of the nearby dimple is explained below. The first dimple 10a and the second dimple 10b are shown in fig. 6. A line segment CL connecting the center of the first dimple 10a and the center of the second dimple 10b does not intersect the dimples 10 other than the first dimple 10a and the second dimple 10 b.

In fig. 6, the symbol Tg1 denotes the first internal common tangent of the first dimple 10a and the second dimple 10 b. One end of the first internal common tangent Tg1 is located on the circumference of the first dimple 10a, and the other end is located on the circumference of the second dimple 10 b. The first internal common tangent Tg1 does not intersect any dimple 10.

In fig. 6, the symbol Tg2 denotes the second internal common tangent of the first dimple 10a and the second dimple 10 b. One end of the second internal common tangent Tg2 is located on the circumference of the first dimple 10a, and the other end is located on the circumference of the second dimple 10 b. The second internal common tangent Tg2 does not intersect any of the dimples 10.

In the present invention, when 2 dimples 10 satisfy both of the following conditions (1) and (2), these dimples 10 are referred to as "nearby dimple pairs".

(1) The straight line connecting the centers of these dents does not intersect with other dents.

(2) The 2 internal common tangents of these dimples each did not intersect any dimple.

When the pair of nearby dimples 16 is present, one dimple 10 of the pair of nearby dimples 16 is a nearby dimple with respect to the other dimple 10, and the other dimple 10 is a nearby dimple with respect to the one dimple 10.

The first dimple 10a and the second dimple 10b shown in fig. 6 form a neighborhood dimple pair 16. The first dimple 10a is a neighborhood dimple with respect to the second dimple 10b, and the second dimple 10b is a neighborhood dimple with respect to the first dimple 10 a.

The first dimple 10a, the second dimple 10b, and the third dimple 10c are shown in fig. 7. A line segment CL connecting the center of the first dimple 10a and the center of the second dimple 10b crosses the third dimple 10 c. Therefore, the pair of the first dimple 10a and the second dimple 10b is not the neighborhood dimple pair 16. The first dimple 10a is not a neighborhood dimple relative to the second dimple 10b, and the second dimple 10b is not a neighborhood dimple relative to the first dimple 10 a.

The first dimple 10a, the second dimple 10b, and the third dimple 10c are shown in fig. 8. A line segment CL connecting the center of the first dimple 10a and the center of the second dimple 10b does not intersect the dimples 10 other than the first dimple 10a and the second dimple 10 b. The first internal common tangent Tg1 does not intersect any of the dimples 10. However, the second internal common tangent Tg2 intersects the third dimple 10 c. Therefore, the pair of the first dimple 10a and the second dimple 10b is not the neighborhood dimple pair 16. The first dimple 10a is not a neighborhood dimple relative to the second dimple 10b, and the second dimple 10b is not a neighborhood dimple relative to the first dimple 10 a.

The first dimple 10a, the second dimple 10b, the third dimple 10c, the fourth dimple 10d, and the fifth dimple 10e are shown in fig. 9.

A line segment connecting the center of the first dimple 10a and the center of the second dimple 10b does not intersect the dimples 10 other than the first dimple 10a and the second dimple 10 b. Further, the 2 internal common tangents of the first dimple 10a and the second dimple 10b, respectively, do not intersect any dimple 10. The first dimple 10a and the second dimple 10b form a neighborhood dimple pair 16.

A line segment connecting the center of the first dimple 10a and the center of the third dimple 10c does not intersect the dimples 10 other than the first dimple 10a and the third dimple 10 c. Further, the 2 internal common tangents of the first dimple 10a and the third dimple 10c, respectively, do not intersect any dimple 10. The first dimple 10a and the third dimple 10c form a neighborhood dimple pair 16.

1 of the 2 internal common tangents of the first dimple 10a and the fourth dimple 10d intersect the second dimple 10 b. Therefore, the first dimple 10a and the fourth dimple 10d do not form the neighborhood dimple pair 16.

A line segment connecting the center of the first dimple 10a and the center of the fifth dimple 10e crosses the third dimple 10 c. Therefore, the first dimple 10a and the fifth dimple 10e do not form the neighborhood dimple pair 16.

As described above, the first dimple 10a and the second dimple 10b form the neighborhood dimple pair 16, and the first dimple 10a and the third dimple 10c also form the neighborhood dimple pair 16. In fig. 9, there are at least 2 nearby dimple pairs 16.

As described above, for the first dimple 10a, the second dimple 10b is a neighborhood dimple, and the third dimple 10c is also a neighborhood dimple. The first dimple 10a has at least 2 neighboring dimples. Therefore, the first dimple 10a has at least 2 distances L (see fig. 5). The first dimple 10a may have another nearby dimple. In the entirety of the golf ball 2, each dimple 10 may have a nearby dimple. In the golf ball 2, there are a plurality of pairs of nearby dimples 16.

The standard deviation Pd of the distances L between all pairs of nearby dimples 16 is preferably less than 0.500 mm. In other words, a small standard deviation Pd is preferred. As described above, in the golf ball 2, the standard deviation Su of the area of the dimples 10 is small. In the golf ball 2 having a small standard deviation Su and a small standard deviation Pd, dimples 10 having small dimensional deviations are uniformly arranged. The golf ball 2 is excellent in flight performance. From the viewpoint of flight performance, the standard deviation Pd is more preferably 0.458mm or less, and particularly preferably 0.317mm or less.

The average value of the distances L between all the pairs of nearby dimples 16 is preferably 1.0mm or less, more preferably 0.7mm or less, and particularly preferably 0.5mm or less. The average value is preferably 0.0mm or more.

[ examples ] A

The effects of the present invention will be illustrated by the following examples, but the present invention is not to be construed as being limited to the contents disclosed in these examples.

[ example 1]

100 parts by mass of high cis polybutadiene (trade name "BR-730" from JSR company), 22.5 parts by mass of zinc acrylate, 5 parts by mass of acidified zinc, 5 parts by mass of barium sulfate, 0.5 part by mass of diphenyl disulfide and 0.6 part by mass of dicumyl peroxide were kneaded to obtain a rubber composition. The rubber composition was charged into a mold comprising an upper mold and a lower mold having a hemispherical cavity, and heated at 170 ℃ for 18 minutes to obtain a core having a diameter of 38.5 mm.

50 parts by mass of an ionomer resin (trade name "HIMILAN 1605" of Tri-Du Pont-Mitsui Polychemical Co., Ltd.), 50 parts by mass of another ionomer resin (trade name "HIMILAN AM 7329" of Tri-Du Pont Polychemical Co., Ltd.), and 4 parts by mass of titanium dioxide were kneaded by a biaxial kneading extruder to obtain a resin composition. The resin composition is coated around the core by injection molding to form the intermediate layer. The thickness of the intermediate layer was 1.6 mm.

A coating composition (trade name "POLIN 750 LE" from Shendong paint Co., Ltd.) was prepared in which a two-component curable epoxy resin was used as a base polymer. The main agent liquid of the coating composition was composed of 30 parts by mass of a bisphenol a type solid epoxy resin and 70 parts by mass of a solvent. The curing agent liquid of the coating composition was composed of 40 parts by mass of a modified polyamidoamine, 55 parts by mass of a solvent, and 5 parts by mass of titanium dioxide. The mass ratio of the main agent liquid to the curing agent liquid is 1/1. The coating composition was applied to the surface of the intermediate layer with a spray gun and kept at 23 ℃ 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 (trade name "ELASTOLLAN XNY 85A" from BASF Japan) and 4 parts by mass of titanium dioxide were kneaded by a biaxial kneading extruder to obtain a resin composition. A half shell was obtained from the resin composition by compression molding. The sphere consisting of the core, the intermediate layer and the reinforcing layer is covered with 2 half shells. These half shells and spheres are put into a final mold comprising an upper mold and a lower mold having a hemispherical cavity and a plurality of small protrusions (pimples) on the cavity surface, and the coating layer is obtained by a compression molding method. The thickness of the coating layer is 0.5 mm. An indentation having a shape obtained by inverting the small protrusion is formed on the clad layer. A clear coat paint containing a two-part curable polyurethane as a base material was applied to the periphery of the cover layer to obtain a golf ball of example 1 having a diameter of about 42.7mm and a mass of about 45.6 g. The dimple pattern of the golf ball is shown in fig. 2 and 3. The dimple specifications of the golf ball are shown in table 1 below. The dimple pattern of the hemisphere of the virtual ball of the golf ball is composed of 3 units that are rotationally symmetric to each other. The dimple pattern of each cell is composed of 2 small cells that are mirror-symmetrical to each other.

Examples 2 to 4 and comparative examples 1 and 2

Golf balls of examples 2 to 4 and comparative examples 1 and 2 were obtained in the same manner as in example 1 except that the final mold was changed and the specifications of dimples were as shown in tables 1 and 2 below. The dimple specifications of the respective golf balls are shown in tables 1 and 2 below. The dimple pattern of the hemisphere of the virtual ball of the golf ball is composed of 3 units that are rotationally symmetric to each other. The dimple pattern of each cell is composed of 2 small cells that are mirror-symmetrical to each other.

[ example 5]

The golf ball of example 5 was obtained in the same manner as in example 1 except that the final mold was changed and the specifications of the dimples were as shown in table 2 below. The dimple specifications of the golf ball are shown in table 2 below. The dimple pattern of the hemisphere of the virtual ball of the golf ball cannot be divided into 3 units that are rotationally symmetric with each other.

[ flight test #1]

A driver (trade name "XXIO 10", shaft hardness: R, and loft angle: 10.5 °) having a head made of a titanium alloy was attached to a swing training machine (swing machine) of Golf Laboratory Inc (gold Laboratory Inc.). The golf ball was hit at a head speed of 40 m/sec, a launch angle of about 12 °, and a backspin speed of about 2300rpm, and the distance from the launch point to the rest point was measured. Almost no wind was present during the test. The average values of the data obtained by 20 measurements are shown in tables 3 to 4 below.

[ flight test #2]

A driver having a head made of titanium alloy (trade name "SRIXON Z-TX", shaft hardness: X, and loft angle: 8.5, manufactured by Sumitomo rubber industries Co., Ltd.) was attached to a swing training device of Golf laboratory Co. The golf ball was hit under the conditions of a head speed of 50 m/sec, a launch angle of about 10 °, and a backspin speed of about 2500rpm, and the distance from the launch point to the rest point was measured. Almost no wind was present during the test. The average values of the data obtained by 20 measurements are shown in tables 3 to 4 below.

[ TABLE 1]

TABLE 1 dimple Specifications

[ TABLE 2]

TABLE 2 evaluation results

[ TABLE 3 ]

Table 3 evaluation results

[ TABLE 4 ]

Table 4 evaluation results

As shown in tables 3 to 4, the golf balls of the examples were excellent in flight performance under the condition that the head speed was 40 m/sec. In other words, the golf balls of the embodiments are suitable for golfers having an average head speed. Further, the golf balls according to examples 1 to 4 were also excellent in flight performance at a head speed of 50 m/sec. From these evaluation results, the superiority of the present invention is apparent.

Industrial applicability of the invention

The dimple pattern described above can be applied not only to a three-layer golf ball but also to golf balls having various structures such as a single-layer golf ball, a double-layer golf ball, a four-layer golf ball, a five-layer golf ball, a six-layer golf ball, and a wire-wound golf ball.

Claims

1. A golf ball having a plurality of dimples on a surface thereof,

the standard deviation of the area of all the indentations was 1.7mm²In the following, the following description is given,

the standard deviation Pd of the distances L between all nearby dimple pairs is less than 0.500mm,

the contour of each dimple is circular, and the ratio So of the total area of the dimples to the surface area of the virtual ball is 80.0% to 95%.

2. A golf ball as in claim 1, wherein said standard deviation Pd is less than 0.400 mm.

3. The golf ball according to claim 1 or 2,

the dimple pattern of the hemisphere of the virtual ball of the golf ball is composed of 3 units that are rotationally symmetric with each other,

the dimple pattern of each cell is composed of 2 small cells that are mirror-symmetrical to each other.

4. The golf ball according to claim 1 or 2, wherein a ratio So of a total of areas of the dimples to a surface area of the virtual ball is 82.0% or more and 95% or less.

5. A golf ball as claimed in claim 1 or 2, wherein the total volume of all dimples is 450mm³Above 750mm³The following.

6. The golf ball according to claim 1 or 2, wherein the total number of dimples is 300 or more and 390 or less.