GOLF BALL

Abstract

The present invention provides a golf ball in which a large number of dimples are formed on a ball surface, and when edge angles at points where depths are 10%, 20%, and 30% in a cross-section of one dimple are denoted by ED1, ED2, and ED3, respectively, dimples having a cross-sectional shape satisfying the following condition (1): ED1<ED2>ED3  (1) account for at least 10% of a total number of the dimples.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. § 119 (a) on Patent Application No. 2023-150041 filed in Japan on Sep. 15, 2023, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a golf ball having a large number of dimples formed on a ball surface, and more specifically, to a golf ball for stabilizing a trajectory by making a cross-sectional shape of the dimples formed on the ball surface unique.

BACKGROUND ART

In order to improve a distance of a golf ball, it is generally well known that air resistance during flight is reduced by dimples formed on a ball surface to improve aerodynamic properties. For example, a golf ball described in Patent Document 1 proposes that a shape of a wall surface close to a bottom portion in a dimple cross-section is optimized to optimize a trajectory of the ball when hit and increase the distance. Patent Document 2 discloses a golf ball in which dimples are formed by at least two different cross-sectional shapes, and the dimple shape is three-dimensionally optimized to dramatically improve aerodynamic properties. However, these golf balls are related to technologies focusing on improvement of the distance, and do not focus on the fact that the trajectory of the ball is stabilized and stable flight performance is obtained.

In addition, Patent Document 3 describes that a change amount ΔH of a depth every 20% of a distance from a dimple edge to a center of the dimple is optimized at a ratio of a depth in a dimple region of 20 to 100% of the above distance in order to reduce variation of the flight and improve aerodynamic performance. However, this technique does not focus on an edge angle with respect to the dimple depth, and although it is shown that the distance of the ball increases, it is not shown that the trajectory is stabilized.

CITATION LIST

• Patent Document 1: JP-A 2007-190382
• Patent Document 2: JP-A 2008-93481
• Patent Document 3: JP-A 2018-102483

SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a golf ball that stabilizes a trajectory by making a cross-sectional shape of a dimple formed on a ball surface unique.

As a result of intensive studies to achieve the above object, the present inventor has found that it is essential to improve stability of aerodynamic performance in order to secure stability of flight, and therefore focuses on specifying an optimum shape of an edge angle with respect to a dimple depth in a dimple cross-sectional shape. Specifically, when edge angles at points where depths are 10%, 20%, and 30% in a cross-section of one dimple are denoted by ED1, ED2, and ED3, respectively, dimples having a cross-sectional shape satisfying the following condition (1):

$\begin{array}{cc}\mathrm{ED}1<\mathrm{ED}2>\mathrm{ED}3& \left(1\right)\end{array}$

• • account for at least 10% of a total number of dimples formed on a ball surface, whereby a stable trajectory may be obtained and stability of flight may be improved, and thus the present invention has been completed.

Accordingly, the present invention provides a golf ball in which

• • a large number of dimples are formed on a ball surface, and when edge angles at points where depths are 10%, 20%, and 30% in a cross-section of one dimple are denoted by ED1, ED2, and ED3, respectively, dimples having a cross-sectional shape satisfying the following condition (1):

$\begin{array}{cc}\mathrm{ED}1<\mathrm{ED}2>\mathrm{ED}3& \left(1\right)\end{array}$

• • account for at least 10% of a total number of the dimples.

In a preferred embodiment of the golf ball according to the invention, the dimples satisfying the above condition (1) account for at least 50% of the total number of the dimples.

In another preferred embodiment of the inventive golf ball, in the dimples satisfying the above condition (1), when an edge angle at a point where the depth is 40% is further denoted by ED4, the following condition is satisfied:

$\mathrm{ED}3\ge \mathrm{ED}1\ge \mathrm{ED}4.$

In yet another preferred embodiment, in the dimples satisfying the above condition (1), when an edge angle at a point where the depth is 50% is further denoted by ED5, the following condition is satisfied:

$\mathrm{ED}1/\mathrm{ED}5\ge 1.2.$

In still another preferred embodiment, in the dimples satisfying the above condition (1), when an edge angle at a point where the depth is 50% is further denoted by ED5, the following condition is satisfied:

$\mathrm{ED}2/\mathrm{ED}5\ge 1.2.$

In a further preferred embodiment, in the dimples satisfying the above condition (1), when an edge angle at a point where the depth is 50% is further denoted by ED5, the following condition is satisfied:

$\mathrm{ED}3/\mathrm{ED}5\ge 1.2.$

In a yet further preferred embodiment, in the dimples satisfying the above condition (1), when an edge angle at a point where the depth is 60% is further denoted by ED6, the following condition is satisfied:

$\mathrm{ED}2/\mathrm{ED}6\ge 2..$

In a still further preferred embodiment, in the dimples satisfying the above condition (1), ED1, ED2, and ED3 are all not more than 90 degrees.

In another preferred embodiment, in the dimples satisfying the above condition (1), both ED5 and ED6 are not more than 90 degrees.

In yet another preferred embodiment, a total volume of the dimples satisfying the above condition (1) is 300 to 500 mm³.

In still another preferred embodiment, the number of types of the dimples satisfying the above condition (1) is at least three.

In a further preferred embodiment, the number of the dimples satisfying the above condition (1) is 250 to 500.

In a yet further preferred embodiment, a coverage ratio of the dimples satisfying the above condition (1) is 60 to 90%.

Advantageous Effects of the Invention

With the golf ball of the present invention, by defining a change in the edge angle of the dimple cross-section, a stable trajectory may be obtained and stability of flight may be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a dimple for explaining an edge angle at a point of a specific depth of the dimple.

FIG. 2 is a schematic view of a dimple for explaining ED1, ED2, and ED3.

FIG. 3 illustrates cross-sectional shape types A to D of dimples used in Examples and Comparative Examples.

FIG. 4 is a plan view of dimples used in each Example and Comparative Example.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention is described in more detail.

The golf ball of the present invention is characterized in that a large number of dimples are formed on a ball surface to define a change in an edge angle of a dimple cross-section, as described later.

The dimples are usually formed on the surface of a cover (outermost layer) of the ball simultaneously with molding such as injection molding of a resin material of the cover. Further, usually, a coating is applied to the surface of the above cover to complete the golf ball. The dimples in the present invention mean dimples formed on the surface of this completed golf ball. Therefore, numerical values such as a diameter and a depth of the dimples described later are numerical values of the dimples in the completed golf ball.

The number of the above dimples is not particularly limited, although the number of the dimples is preferably at least 250 and more preferably at least 300, and the upper limit is preferably not more than 500 and more preferably not more than 450.

As the shape of the dimples as viewed from a flat plane (shape in plan view), one type or a combination of at least two types such as a circular shape, various polygonal shapes, a dewdrop shape, an ellipse, and other non-circular shapes may be appropriately used.

The diameter of the dimples (diagonal length in a polygon) is not particularly limited, although the diameter may be preferably at least 2.0 mm, and more preferably at least 2.5 mm. The upper limit is also not particularly limited, although the upper limit may be preferably not more than 6.0 mm, and more preferably not more than 5.5 mm.

The depth at the deepest point of the dimples is not particularly limited, although the depth may be preferably from 0.05 to 0.5 mm, and more preferably from 0.09 to 0.4 mm.

A method of arranging the dimples is not particularly limited, although a method using a geometric arrangement pattern of regular polyhedrons such as a regular octahedron, a regular 12-hedron, and a regular 20-hedron, or a method of arranging the dimples so as to be rotationally symmetric about a pole point of the ball such as three-fold symmetry, four-fold symmetry, five-fold symmetry, and six-fold symmetry may be suitably employed.

A ratio (dimple surface coverage ratio) SR value (%) of a total area of a virtual spherical surface circumscribed by the edge portion of each dimple is usually at least 60% and preferably at least 80%, and the upper limit is preferably not more than 90%. If the SR value falls outside of the above range, an appropriate trajectory may be unattainable, and a distance may decrease.

A total dimple space volume formed downward from a flat plane circumscribed by the edge of the dimple is preferably from 300 to 500 mm³. In addition, a ratio (volume occupancy ratio) VR of the total dimple space volume to a volume of a virtual sphere assuming that no dimple exists on the ball surface is not particularly limited, although the ratio may be usually at least 0.7%, preferably at least 0.75%, and more preferably at least 0.8%. The upper limit is also not particularly limited, although the upper limit may be not more than 1.5%, preferably not more than 1.45%, and more preferably not more than 1.4%. By setting the volume occupancy ratio VR within the above range, it is possible to prevent the ball from being blown up too much when the ball is struck with a club such as a driver that gains distance, and to prevent the ball from dropping without rising.

In the present invention, when the edge angles at points where the depths are 10%, 20%, and 30% in the cross-section of one dimple are denoted by ED1, ED2, and ED3, respectively, dimples having a cross-sectional shape satisfying the following condition (1):

$\begin{array}{cc}\mathrm{ED}1<\mathrm{ED}2>\mathrm{ED}3& \left(1\right)\end{array}$

• • are included. As described above, in the present invention, a stable trajectory may be obtained by specifying optimum shapes of the edge angles with respect to the dimple depth.

Here, the above-described “cross-section of a dimple” means a cross-section when the dimple is vertically cut so as to pass through the deepest portion (bottom central portion) of the dimple.

The above-described edge angles are defined as follows. That is, as illustrated in FIG. 1, a spherical surface (spherical surface of the golf ball in a state without dimples) Q of the golf ball before a dimple is formed is assumed on a dimple D. In addition, in a case where a depth DP of the dimple D is 100%, a tangent T is drawn at a wall portion P of the dimple D where the depth is n %. A point at which the tangent T intersects the above virtual spherical surface Q is denoted by Q1. An angle θ formed by a horizontal straight line (in the figure, a line segment connecting points Q1 and Q1) of Q1 and the above tangent T is denoted as an edge angle. In FIG. 1, points E and E are outer peripheral edge portions of the dimple, a distance therebetween is a diameter DM of the dimple D, and the depth DP of the dimple D is a distance between the bottom central portion thereof and the above line segment EE.

Specifically, FIG. 2 is an explanatory diagram of ED1, ED2, and ED3.

In a measurement method of ED1, first, a tangent (T1) at a point P1 having a dimple depth of 10% is drawn, an intersection between the tangent and the virtual spherical surface Q is obtained, and a line is drawn in a horizontal direction from the intersection (straight line E1). ED1 is an angle formed by the tangent line T1 and the straight line E1.

In a measurement method of ED2, first, a tangent (T2) at a point P2 having a dimple depth of 20% is drawn, an intersection between the tangent and the virtual spherical surface Q is obtained, and a line is drawn in the horizontal direction from the intersection (straight line E2). ED2 is an angle formed by the tangent line T2 and the straight line E2.

In a measurement method of ED3, first, a tangent (T3) at a point P2 having a dimple depth of 30% is drawn, an intersection between the tangent and the virtual spherical surface Q is obtained, and a line is drawn in the horizontal direction from the intersection (straight line E3). ED3 is an angle formed by the tangent line T3 and the straight line E3.

A ratio of the dimples having a cross-sectional shape satisfying the above condition (1) is at least 10%, preferably at least 30%, more preferably at least 50%, and even more preferably at least 80% with respect to 100% of a total number of the dimples formed on the ball surface.

The number of types of dimples having a cross-sectional shape satisfying the above condition (1) is preferably at least three. Even if the cross-sectional shapes are the same, if those having different diameters and depths are included, they are treated as different types of dimples.

As shown in the above condition (1), the edge angle ED2 at the point where the dimple depth is 20% is larger than the edge angles ED1 and ED3 at the points where the dimple depths are 10% and 30%. It is estimated that, in the dimple cross-sectional shape, an effect of the dimple is easily exhibited stably by an action of smoothing a flow of air entering the inside of the dimple, variation in the ball trajectory is reduced, and a more stable trajectory is obtained.

The edge angle ED3 at the point where the dimple depth is 30% is preferably larger than the edge angle ED1 at the point where the dimple depth is 10% in order to further stabilize the trajectory. In addition, each of the above edge angles ED1, ED2, and ED3 is preferably not more than 90 degrees.

Further, when the edge angle at the point where the dimple depth is 40% is denoted by ED4, the following condition is preferably satisfied:

$\mathrm{ED}1\ge \mathrm{ED}4.$

Furthermore, in order to further stabilize the trajectory, when an edge angle at a point where the dimple depth is 50% is denoted by ED5, the above edge angle ED5 is preferably not more than 90 degrees, and at least one of the following three conditions is preferably satisfied.

$\mathrm{ED}1/\mathrm{ED}5\ge 1.2$ $\mathrm{ED}2/\mathrm{ED}5\ge 1.2$ $\mathrm{ED}3/\mathrm{ED}5\ge 1.2$

Further, when an edge angle at a point where the dimple depth is 60% is denoted by ED6, the above edge angle ED6 is preferably not more than 90 degrees, and the following condition is preferably satisfied.

$\mathrm{ED}2/\mathrm{ED}6\ge 2.$

As described above, the present invention focuses on the change in the dimple edge angle within a range where the dimple depth is from 10 to 60%, and in particular, the optimum shapes of the dimple edge angles of 10%, 20%, and 30% in a range relatively close to the edge of the dimple are achieved, whereby aerodynamic performance is stabilized by an action of the dimple, and eventually the trajectory is stabilized.

For preparation of a mold for forming the above dimple, a method of directly three-dimensionally cutting out an entire surface shape in a reversing master mold using 3DCAD/CAM, a method of directly three-dimensionally cutting out a cavity portion (inner wall surface) of the mold for molding, or the like may be adopted.

Similarly to a normal golf ball, the ball surface may be subjected to various types of coating, such as white enamel coating, epoxy coating, and clear coating. In this case, it is desirable to perform coating uniformly without unevenness so that the cross-sectional shape of the above dimple is not impaired.

The golf ball of the present invention is not particularly limited in terms of its internal structure, and may be a solid golf ball such as a one-piece golf ball, a two-piece golf ball, or a multi-piece golf ball having a structure of at least three layers, or may be a wound golf ball, and may be applied to any type of golf ball.

Ball specifications such as the weight and the diameter of the golf ball may be appropriately set according to the Rules of Golf.

EXAMPLES

Hereinafter, the present invention is specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Examples 1 and 2 and Comparative Examples 1 to 4

A core having a diameter of 38.6 mm is prepared. The compounding of the cores is common to all Examples and Comparative Examples. As a base rubber, 20 parts by weight of polybutadiene A (trade name “BR51” manufactured by ENEOS Materials Corporation), 80 parts by weight of polybutadiene B (trade name “BR730” manufactured by ENEOS Materials Corporation), 29.5 parts by weight of zinc acrylate (manufactured by Wako Pure Chemical Corporation), 0.6 parts by weight of dicumyl peroxide (trade name “Percumyl D” manufactured by NOF Corporation) as an organic peroxide, 0.1 parts by weight of 2,2-methylenebis(4-methyl-6-butylphenol) (trade name “Nocrac NS-6” manufactured by Ouchi Shinko Chemical Industrial Co., Ltd.) as an antioxidant, 19.3 parts by weight of zinc oxide (trade name “Grade 3 Zinc Oxide” manufactured by Sakai Chemical Industry Co., Ltd.), and 0.3 parts by weight of pentachlorothiophenol zinc salt (manufactured by Wako Pure Chemical Corporation) as an organosulfur compound are blended. A rubber composition is vulcanized at a temperature of 155° C. for a time of 15 minutes. The specific gravity of the blend is 1.138.

[Formation of Intermediate Layer]

Next, a resin material for an intermediate layer is injection molded around the core having a diameter of 38.6 mm to prepare an intermediate layer-encased sphere having an intermediate layer having a thickness of 1.25 mm. The resin material of the intermediate layer is common to all Examples and Comparative Examples, and trade names “Himilan 1605”, “Himilan 1557”, and “Himilan 1706” (ionomer resins manufactured by Dow-Mitsui Polychemicals Co., Ltd.) are blended at 50:12:38 (weight ratio) respectively, and 1.1 parts by weight of trimethylolpropane (manufactured by Tokyo Chemical Industry Co., Ltd.) is blended per 100 parts by weight of a total of the ionomer resins.

[Formation of Cover (Outermost Layer)]

Next, an ether-type thermoplastic polyurethane (trade name “PANDEX” manufactured by DIC Covestro Polymer Ltd., Shore D hardness 43, and rebound resilience 61%) is used as a resin material of the cover (outermost layer). Using another mold for injection molding, the above-described resin material is injection-molded around the above-described intermediate layer-encased sphere to prepare a three-piece golf ball having a diameter of 42.7 mm and an outermost layer having a thickness of 0.8 mm. At this time, a predetermined large number of dimples described below are formed on the surface of the cover.

[Formation of Coating Layer (Coating Film)]

Next, a golf ball of each Example in which a coating layer (coating film) having a thickness of 15 μm is formed is prepared by applying a coating composition containing a polyester polyol (main component) and an isocyanate curing agent to the surface of the outermost layer on which a large number of dimples are formed in a coating formulation listed in Table 1 below using an air spray gun.

[Dimples]

As for details of the dimples of the Examples and Comparative Examples, as shown in FIG. 3, the dimples of Examples 1 and 2 and Comparative Examples 1 to 4 listed in Tables 1 to 6 are obtained by using four types of cross-section types of type A, type B, type C, and type D as bases and appropriately changing the diameters and depths. Contents (data) of the dimples in each of these tables are to analyze a golf ball with a coating applied to the surface of the cover with a laser device (“LT-8010” manufactured by Keyence Corporation) to calculate the diameters, depths, edge angles, and the like of the dimples. In addition, all dimple arrangement modes (patterns) of these Examples are common, and dimples having a circular shape in plan view are combined in a plurality of types, and a plan view thereof is illustrated in FIG. 4.

TABLE 1
			Total volume: 350.82 mm3
Dimple mode in Example 1			Total surface area: 4844.1 mm2
Cross-	Edge angle (Degrees)	Edge angle ratio		Surface		n ×
section		Diameter	Depth	ED1	ED2	ED3	ED4	ED5	ED6	ED1/	ED2/	ED3/	ED2/	Volume	area	n ×	surface
type	Number	(mm)	(mm)	10%	20%	30%	40%	50%	60%	ED5	ED5	ED5	ED6	(mm3)	(mm2)	volume	area
Type A	12	4.6	0.150	8.72	9.11	8.75	7.76	6.13	3.65	1.42	1.49	1.43	2.50	1.28	16.6	15.4	199.4
Type A	234	4.5	0.140	8.33	8.69	8.35	7.41	5.85	3.48	1.42	1.49	1.43	2.50	1.14	15.9	266.8	3721.6
Type A	60	3.95	0.150	10.13	10.57	10.16	9.02	7.13	4.25	1.42	1.48	1.42	2.49	0.94	12.3	56.4	735.3
Type A	12	2.95	0.110	9.95	10.39	9.98	8.86	7	4.17	1.42	1.48	1.43	2.49	0.39	6.8	4.7	82.0
Type A	6	3.4	0.140	10.96	11.44	11	9.77	7.72	4.6	1.42	1.48	1.42	2.49	0.65	9.1	3.9	54.5
Type A	6	3.3	0.140	11.29	11.78	11.32	10.06	7.95	4.74	1.42	1.48	1.42	2.49	0.62	8.6	3.7	51.3

TABLE 2
			Total volume: 349.92 mm3
Dimple mode in Example 2			Total surface area: 4844.1 mm2
Cross-	Edge angle (Degrees)	Edge angle ratio		Surface		n ×
section		Diameter	Depth	ED1	ED2	ED3	ED4	ED5	ED6	ED1/	ED2/	ED2/	ED3/	Volume	area	n ×	surface
type	Number	(mm)	(mm)	10%	20%	30%	40%	50%	60%	ED5	ED5	ED5	ED6	(mm3)	(mm2)	volume	area
Type A	12	4.6	0.150	8.72	9.11	8.75	7.76	6.13	3.65	1.42	1.49	1.43	2.50	1.28	16.6	15.4	199.4
Type A	234	4.5	0.140	8.33	8.69	8.35	7.41	5.85	3.48	1.42	1.49	1.43	2.50	1.14	15.9	266.8	3721.6
Type B	60	3.95	0.150	8.12	9.33	9.45	8.85	7.64	5.88	1.06	1.22	1.24	1.59	0.93	12.3	55.8	735.3
Type B	12	2.95	0.110	7.97	9.17	9.18	8.69	7.51	5.78	1.06	1.22	1.22	1.59	0.38	6.8	4.6	82.0
Type B	6	3.4	0.140	8.79	10.1	10.23	9.58	8.28	6.38	1.06	1.22	1.24	1.58	0.64	9.1	3.8	54.5
Type B	6	3.3	0.140	9.05	10.4	10.54	9.86	8.52	6.57	1.06	1.22	1.24	1.58	0.60	8.6	3.6	51.3

TABLE 3
Dimple mode in			Total volume: 345.0 mm3
Comparative Example 1			Total surface area: 4844.1 mm2
Cross-	Edge angle (Degrees)	Edge angle ratio		Surface		n ×
section		Diameter	Depth	ED1	ED2	ED3	ED4	ED5	ED6	ED1/	ED2/	ED3/	ED2/	Volume	area	n ×	surface
type	Number	(mm)	(mm)	10%	20%	30%	40%	50%	60%	ED5	ED5	ED5	ED6	(mm3)	(mm2)	volume	area
Type B	12	4.6	0.150	6.98	8.03	8.14	7.61	6.57	5.06	1.06	1.22	1.24	1.59	1.26	16.6	15.1	199.4
Type B	234	4.5	0.140	6.66	7.66	7.77	7.27	6.27	4.83	1.06	1.22	1.24	1.59	1.12	15.9	262.1	3721.6
Type B	60	3.95	0.150	8.12	9.33	9.45	8.85	7.64	5.88	1.06	1.22	1.24	1.59	0.93	12.3	55.8	735.3
Type B	12	2.95	0.110	7.97	9.17	9.18	8.69	7.51	5.78	1.06	1.22	1.22	1.59	0.38	6.8	4.6	82.0
Type B	6	3.4	0.140	8.79	10.1	10.23	9.58	8.28	6.38	1.06	1.22	1.24	1.58	0.64	9.1	3.8	54.5
Type B	6	3.3	0.140	9.05	10.4	10.54	9.86	8.52	6.57	1.06	1.22	1.24	1.58	0.60	8.6	3.6	51.3

TABLE 4
Dimple mode in			Total volume: 344.9 mm3
Comparative Example 2			Total surface area: 4844.1 mm2
Cross-	Edge angle (Degrees)	Edge angle ratio		Surface		n ×
section		Diameter	Depth	ED1	ED2	ED3	ED4	ED5	ED6	ED1/	ED2/	ED3/	ED2/	Volume	area	n ×	surface
type	Number	(mm)	(mm)	10%	20%	30%	40%	50%	60%	ED5	ED5	ED5	ED6	(mm3)	(mm2)	volume	area
Type C	12	4.6	0.150	7.37	6.7	6.11	5.61	5.14	4.68	1.43	1.30	1.19	1.43	1.25	16.6	15.0	199.4
Type C	234	4.5	0.140	7.03	6.4	5.84	5.35	4.91	4.46	1.43	1.30	1.19	1.43	1.12	15.9	262.1	3721.6
Type C	60	3.95	0.150	8.56	7.79	7.11	6.52	5.99	5.44	1.43	1.30	1.19	1.43	0.93	12.3	55.8	735.3
Type C	12	2.95	0.110	8.41	7.65	6.98	6.4	5.88	5.35	1.43	1.30	1.19	1.43	0.38	6.8	4.6	82.0
Type C	6	3.4	0.140	9.27	8.44	7.7	7.07	6.49	5.9	1.43	1.30	1.19	1.43	0.64	9.1	3.8	54.5
Type C	6	3.3	0.140	9.55	8.69	7.93	7.28	6.68	6.08	1.43	1.30	1.19	1.43	0.60	8.6	3.6	51.3

TABLE 5
Dimple mode in			Total volume: 464.6 mm3
Comparative Example 3			Total surface area: 4844.1 mm2
Cross-	Edge angle (Degrees)	Edge angle ratio		Surface		n ×
section		Diameter	Depth	ED1	ED2	ED3	ED4	ED5	ED6	ED1/	ED2/	ED3/	ED2/	Volume	area	n ×	surface
type	Number	(mm)	(mm)	10%	20%	30%	40%	50%	60%	ED5	ED5	ED5	ED6	(mm3)	(mm2)	volume	area
Type D	12	4.6	0.150	12.48	12.35	11.96	11.3	10.37	9.15	1.20	1.19	1.15	1.35	1.68	16.6	20.2	199.4
Type D	234	4.5	0.140	11.92	11.8	11.42	10.79	9.91	8.74	1.20	1.19	1.15	1.35	1.51	15.9	353.3	3721.6
Type D	60	3.95	0.150	14.45	14.31	13.85	13.1	12.03	10.62	1.20	1.19	1.15	1.35	1.25	12.3	75.0	735.3
Type D	12	2.95	0.110	14.2	14.06	13.61	12.87	11.82	10.44	1.20	1.19	1.15	1.35	0.51	6.8	6.1	82.0
Type D	6	3.4	0.140	15.61	15.46	14.97	14.16	13.01	11.5	1.20	1.19	1.15	1.34	0.86	9.1	5.2	54.5
Type D	6	3.3	0.140	16.06	15.9	15.4	14.57	13.39	11.83	1.20	1.19	1.15	1.34	0.81	8.6	4.9	51.3

TABLE 6
Dimple mode in			Total volume: 348.4 mm3
Comparative Example 4			Total surface area: 4844.1 mm2
Cross-	Edge angle (Degrees)	Edge angle ratio		Surface		n ×
section		Diameter	Depth	ED1	ED2	ED3	ED4	ED5	ED6	ED1/	ED2/	ED3/	ED2/	Volume	area	n ×	surface
type	Number	(mm)	(mm)	10%	20%	30%	40%	50%	60%	ED5	ED5	ED5	ED6	(mm3)	(mm2)	volume	area
Type D	12	4.6	0.110	9.22	9.12	8.83	8.34	7.65	6.74	1.21	1.19	1.15	1.35	1.24	16.6	14.9	199.4
Type D	234	4.5	0.105	9	8.91	8.62	8.14	7.46	6.57	1.21	1.19	1.16	1.36	1.13	15.9	264.4	3721.6
Type D	60	3.95	0.115	11.17	11.06	10.71	10.11	9.28	8.18	1.20	1.19	1.15	1.35	0.95	12.3	57.0	735.3
Type D	12	2.95	0.090	11.7	11.58	11.21	10.59	9.72	8.57	1.20	1.19	1.15	1.35	0.41	6.8	4.9	82.0
Type D	6	3.4	0.100	11.29	11.17	10.81	10.22	9.37	8.26	1.20	1.19	1.15	1.35	0.62	9.1	3.7	54.5
Type D	6	3.3	0.100	11.62	11.5	11.13	10.52	9.65	8.51	1.20	1.19	1.15	1.35	0.58	8.6	3.5	51.3

[Definition of Dimples]

• • Edge: Highest point in a cross-section passing through the center of the dimple
  • Diameter: Diameter of the flat plane circumscribed by the edge of the dimple
  • Depth: Maximum depth of the dimple from the flat plane circumscribed by the edge of the dimple
  • Edge angle: As illustrated in FIG. 1, the tangent T at a point P having a specific dimple depth is drawn, an intersection between the tangent and the virtual spherical surface Q is obtained, and a line is drawn in the horizontal direction from the intersection (straight line E1 as illustrated in FIG. 2). The edge angle is an angle formed by the tangent T and a straight line E.
  • SR: Ratio of the sum of individual dimple surface areas, each defined by the flat plane circumscribed by the edge of the dimple, to the ball spherical surface area on the assumption that the ball has no dimples
  • Dimple volume: Volume of the dimple under the flat plane circumscribed by the edge of the dimple

For each of the above-described golf balls, a driver is mounted on a golf swing robot, and the distance traveled (carry and total) when the golf ball is struck at a head speed (HS) of 45 m/s is measured. The club used is a driver manufactured by Bridgestone Sports Co., Ltd. with a drive angle of 10°, and the spin rate of the ball immediately after striking is adjusted to 2,800 rpm.

Results of flight performance of the balls are listed in Table 7.

	TABLE 7
	Example	Comparative Example
	1	2	1	2	3	4
Dimples	Number	330	330	330	330	330	330
	Coverage ratio	84.6	84.6	84.6	84.6	84.6	84.6
	SR (%)
	Total	345.0	349.9	345.0	344.9	464.6	348.4
	volume (mm3)
	ED1 < ED2 >	100	75	0	0	0	0
	ED3 ratio
Evalu-	Carry (m)	217.1	216.8	215.6	214.8	213.2	212.1
ation	Standard	2.1	2.15	2.4	2.3	2.3	2.5
result	deviation
	Total (m)	229.4	228.5	226.6	225.7	223.3	221.8
	Standard	3.1	3.1	3.3	3.5	3.4	3.6
	deviation

As listed in Table 7, with the golf balls of Examples 1 and 2, a standard deviation of the distances of the golf balls after striking may be made lower than that with each of the Comparative Examples, and the flight may be stabilized.

Japanese Patent Application No. 2023-150041 is incorporated herein by reference. Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims.

Claims

1. A golf ball in which a large number of dimples are formed on a ball surface, wherein when edge angles at points where depths are 10%, 20%, and 30% in a cross-section of one dimple are denoted by ED1, ED2, and ED3, respectively, dimples having a cross-sectional shape satisfying the following condition (1): ED ⁢ 1 < ED ⁢ 2 > ED ⁢ 3 ( 1 ) account for at least 10% of a total number of the dimples.

2. The golf ball according to claim 1, wherein the dimples satisfying the above condition (1) account for at least 50% of the total number of the dimples.

3. The golf ball according to claim 1, wherein in the dimples satisfying the above condition (1), when an edge angle at a point where the depth is 40% is further denoted by ED4, the following condition is satisfied: ED ⁢ 3 ≥ ED ⁢ 1 ≥ ED 4.

4. The golf ball according to claim 1, wherein in the dimples satisfying the above condition (1), when an edge angle at a point where the depth is 50% is further denoted by ED5, the following condition is satisfied: ED ⁢ 1 / ED ⁢ 5 ≥ 1.2.

5. The golf ball according to claim 1, wherein in the dimples satisfying the above condition (1), when an edge angle at a point where the depth is 50% is further denoted by ED5, the following condition is satisfied: ED ⁢ 2 / ED ⁢ 5 ≥ 1.2.

6. The golf ball according to claim 1, wherein in the dimples satisfying the above condition (1), when an edge angle at a point where the depth is 50% is further denoted by ED5, the following condition is satisfied: ED ⁢ 3 / ED ⁢ 5 ≥ 1.2.

7. The golf ball according to claim 1, wherein in the dimples satisfying the above condition (1), when an edge angle at a point where the depth is 60% is further denoted by ED6, the following condition is satisfied: ED ⁢ 2 / ED ⁢ 6 ≥ 2..

8. The golf ball according to claim 1, wherein in the dimples satisfying the above condition (1), ED1, ED2, and ED3 are all not more than 90 degrees.

9. The golf ball according to claim 1, wherein in the dimples satisfying the above condition (1), both ED5 and ED6 are not more than 90 degrees.

10. The golf ball according to claim 1, wherein a total volume of the dimples satisfying the above condition (1) is from 300 to 500 mm3.

11. The golf ball according to claim 1, wherein number of types of the dimples satisfying the above condition (1) is at least three.

12. The golf ball according to claim 1, wherein number of the dimples satisfying the above condition (1) is from 250 to 500.

13. The golf ball according to claim 1, wherein an occupancy ratio of the dimples satisfying the above condition (1) is 60 to 90%.