JP6239405B2 - Golf ball - Google Patents

Description

  The present invention relates to a golf ball, and more particularly, to a golf ball including a core and a cover covering the core.

  For example, Japanese Patent No. 4060601 (Patent Document 1) discloses a golf ball including a spherical core and a cover covering the spherical core. In this golf ball, a groove is formed on three great circles drawn on the surface of a spherical core and orthogonal to each other, and a protrusion that fits into the groove is formed on the inner surface of the cover.

Japanese Patent No. 4066001

  In the above golf ball, since the protrusion formed on the inner surface of the cover is fitted in the groove formed on the surface of the core, the adhesion between the cover and the core is improved, and the deviation between both at the time of hitting is improved. Less likely to occur. Thereby, since the loss of energy transmitted from the cover to the core at the time of impact can be reduced, the resilience performance can be improved.

  However, in the above golf ball, when the spherical core is molded with a mold, the groove is located on the split surface of the mold, so that a burr is formed in the groove. Since it is difficult to remove burrs formed in the groove, there is a problem that productivity is lowered.

  The present invention has been made in view of the above problems, and an object thereof is to provide a golf ball that can improve the coefficient of restitution and improve the productivity.

  The golf ball of the present invention includes a core and a single-layer or multi-layer cover that covers the core. The core includes a spherical surface portion and a groove portion recessed from the spherical surface portion. The groove portion is formed on each side of each side from the point where a line extending in the radial direction of the core through each vertex of the regular polyhedron intersects the surface of the groove portion on each side of the regular polyhedron when the spherical portion is simulated as a regular polyhedron. It is formed so that the depth dimension gradually decreases toward the point. Each midpoint is disposed on the spherical portion. The core has an equator that does not intersect the groove. The cover is disposed on the inner surface of the cover and includes a protrusion that fits into the groove.

  According to the golf ball of the present invention, the protrusion disposed on the inner surface of the cover is fitted into the groove portion of the core, so that the adhesion between the core and the cover is improved, and a deviation between the core and the cover at the time of hitting occurs. It becomes difficult to do. Thereby, the loss of energy transmitted from the cover to the core at the time of impact can be reduced, so that the resilience performance can be improved. Further, the groove is formed on each side of the regular polyhedron when the spherical part is assumed to be a regular polyhedron. For this reason, it can suppress that a hit feeling changes with the area | region of a golf ball at the time of a hit | damage. The groove is formed so that the depth dimension gradually decreases from the point where the line extending in the radial direction of the core through each vertex of the regular polyhedron intersects the surface of the groove toward each midpoint of each side of the regular polyhedron. Each midpoint is arranged on the spherical portion. For this reason, while being able to fit a core and a cover firmly in each vertex, it can make it easy to extract a metal mold | die at the time of shaping | molding. In addition, since the core has an equator that does not intersect the groove, it is prevented that burrs are formed in the groove by positioning the mold so that the equator is positioned on the split surface of the mold during molding. be able to. Thereby, since it is not necessary to remove the burr | flash formed in the groove part, productivity can be improved.

  In the above golf ball, at least two of the midpoints are arranged on the equator that does not intersect the groove. For this reason, the split surface of a metal mold | die can be formed in the linear form which passes each middle point. The formation of burrs can be suppressed by forming the split surface of the mold in a straight line.

  In the above golf ball, the core and the cover are formed of different materials. For this reason, a shift | offset | difference with a core and a cover generate | occur | produces at the time of a hit | damage. However, in the golf ball of the present invention, since the adhesion between the core and the cover is improved, it is difficult for the core and the cover to be displaced, and the loss of energy transmitted from the cover to the core at the time of hitting can be reduced. . For this reason, resilience performance can be improved.

  In the above golf ball, the core includes first and second hemispheres sandwiching the equator. The entire groove formed in the first hemisphere is exposed when viewed from the first hemisphere side in a direction perpendicular to the radial direction of the equator. The entire groove formed in the second hemisphere is exposed when viewed from the second hemisphere side in a direction orthogonal to the radial direction of the equator. For this reason, when the 1st and 2nd hemispheres are extracted from a metal mold | die, generation | occurrence | production of an undercut can be prevented. Thereby, since the structure of a metal mold | die can be simplified, productivity can be improved and production cost can be suppressed.

  In the above golf ball, the groove has a V-shaped cross-sectional shape that opens to the spherical surface. For this reason, the occurrence of undercut can be suppressed when the groove is removed from the mold.

  In the above golf ball, the groove part may have a bottom part that curves outwardly in the radial direction of the core along the direction in which the groove part extends. Thereby, it can be made to extend to each middle point vicinity without making a groove part excessively deep, and generation | occurrence | production of the undercut in a bottom part can be suppressed.

  As described above, according to the golf ball of the present invention, the coefficient of restitution can be improved and the productivity can be improved.

1 is a schematic cross-sectional view of a golf ball according to an embodiment of the present invention. 1 is a schematic front view of a golf ball core according to an embodiment of the present invention. It is an enlarged front view of the P1 part of FIG. FIG. 3 is a perspective view of a cut-through base shape that forms a groove in a P2 portion of FIG. 2. It is a schematic sectional drawing in alignment with the VV line of FIG. It is a figure which shows the structure which has the bottom part which the groove part of the golf ball core in one embodiment of this invention curves, Comprising: It is a schematic sectional drawing corresponding to FIG. It is a schematic front view of the modification 1 of the golf ball core in one embodiment of the present invention. It is a schematic front view of the modification 2 of the golf ball core in one embodiment of the present invention. It is a schematic front view of the modification 3 of the golf ball core in one embodiment of the present invention. It is a schematic front view of the modification 4 of the golf ball core in one embodiment of the present invention. It is a schematic front view of Modification 5 of the golf ball core in one embodiment of the present invention. It is a schematic front view of Modification 6 of the golf ball core in one embodiment of the present invention. It is a schematic front view of Modification 7 of the golf ball core in one embodiment of the present invention. It is a schematic front view of Modification 8 of the golf ball core in one embodiment of the present invention. It is a schematic front view of Modification 9 of the golf ball core in one embodiment of the present invention. It is a figure which shows the relationship between the maximum depth of a sample and an area occupation rate in an Example. It is a figure which shows the relationship between the energy loss and the maximum displacement by the hysteresis of the comparative examples 1-3 in an Example, and Examples 1-3. It is a figure for demonstrating a hysteresis. It is a figure which shows the relationship between the resilience coefficient and the degree of compression of Comparative Examples 1-3 in Examples and Examples 1-3.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, the structure of the golf ball in the present embodiment will be described.

  Referring to FIG. 1, the golf ball of the present embodiment has a core 1 and a cover 2 that covers core 1. The core 1 and the cover 2 are formed of different materials. The golf ball of the present embodiment is a so-called two-piece golf ball. The diameter of the golf ball composed of the core 1 and the cover 2 covering the core 1 is required to be 42.67 mm or more according to rules (see R & A and USGA). However, in consideration of aerodynamic characteristics and the like, it is preferable to make the ball diameter as small as possible, for example, 42.7 mm. The present invention is not limited to the two-piece ball, and the same effect can be obtained even with a structure of three-piece or more. For example, the cover 2 may be provided with a plurality of layers.

  1 and 2, the core 1 is formed in a spherical shape. The core 1 includes a spherical portion 11 and a groove portion 12 that is recessed from the spherical portion 11. The spherical portion 11 constitutes the spherical surface of the core 1 and includes both a region surrounded by the groove portion 12 and a region above the groove portion 12. The groove portion 12 is a point where a line extending in the radial direction of the core 1 through each vertex AP of the regular polyhedron intersects the surface of the groove portion 12 on each side SI of the regular polyhedron when the spherical surface portion 11 is assumed to be a regular polyhedron. The depth dimension gradually decreases from SP toward each midpoint CP of each side SI. FIG. 2 shows a configuration when the spherical portion 11 of the core 1 is simulated as a regular dodecahedron.

  Each midpoint CP is disposed on the spherical portion 11. The core 1 has an equator EL that does not intersect the groove 12. That is, this equator EL is not formed in the groove 12. At least two of the midpoints are disposed on the equator EL that does not intersect the groove 12. The equator EL of the core 1 is a great circle of the core 1.

  The core 1 includes first and second hemispheres HE1 and HE2 that sandwich the equator EL. Groove portion 12 formed in first hemisphere HE1 is exposed as a whole when viewed from first hemisphere HE1 side in a direction perpendicular to the radial direction of equator EL (in the direction of center line CL of core 1). Further, the entire groove portion 12 formed in the second hemisphere HE2 is exposed when viewed from the second hemisphere HE2 side in a direction (center line CL direction) orthogonal to the radial direction of the equator EL.

  Referring to FIGS. 2 and 3, groove 12 has a V-shaped cross-sectional shape. Referring to FIG. 3, the groove 12 extends in three directions at an equal angle around the apex AP. The groove portion 12 has a shape in which the triangular prism shown in FIG. 4 is in contact with the surface of the core 1 from the point SP side and the apex AP is located on the spherical surface portion 11. That is, the triangular prism has a hollow base shape that forms the groove 12. Since the spherical portion 11 of the core 1 is formed in a spherical shape, the groove portion 12 is formed so as to be pointed from the point SP toward the tip. Note that each reference numeral in FIG. 4 will be described in an embodiment described later.

  Referring to FIG. 5, the maximum depth of groove 12 is, for example, 0.58 mm. The maximum depth of the groove 12 is the length in the radial direction of the core 1 from the vertex AP to the point SP. That is, the length in the radial direction from the spherical surface portion 11 of the core 1 to the deepest portion of the bottom portion BP of the groove portion 12. The bottom part BP of the groove part 12 is formed linearly from the point SP toward the tip. In FIG. 5, the ratio of the depth to the length of the groove portion 12 is shown larger than the actual size for easy viewing.

  In addition, referring to FIG. 6, groove 12 may have a bottom BP that is curved. The groove part 12 may have a bottom part BP that curves outwardly in the radial direction of the core 1 along the direction in which the groove part 12 extends. For this reason, the bottom portion BP has a small depth at the curved portion.

  The core 1 is formed in a spherical shape and is composed of a rubber composition. The diameter of the core 1 is preferably 37.5 to 40.7 mm, more preferably 38.1 to 39.5 mm. This is because if the diameter is smaller than 37.5 mm, the layer thickness of the cover 2 is increased and the feel at impact is deteriorated. On the other hand, if the diameter of the core 1 is larger than 40.7 mm, it is necessary to make the cover 3 thin, so that the durability is lowered. The core 1 preferably has a Shore D hardness of 40 or more and 55 or less. The hardness of the core 1 is the hardness of the core surface.

  The core 1 can be manufactured from a known rubber composition containing a base rubber, a cross-linking material, a metal salt of an unsaturated carboxylic acid, a filler, and the like. As the base rubber, natural rubber, polyisobrene rubber, styrene butadiene rubber, EPDM and the like can be used, but high cis polybutadiene having at least 40% or more, preferably 80% or more of cis 1,4 bonds should be used. Is particularly preferred.

  As the crosslinking agent, for example, organic peroxides such as dicumyl peroxide and t-butyl peroxide can be used, but it is particularly preferable to use dicumyl peroxide. A compounding quantity is 0.3-5 weight part with respect to 100 weight part of base rubbers, Preferably it is 0.5-2 weight part.

  As the metal salt of the unsaturated carboxylic acid, it is preferable to use a metal salt of a monovalent or divalent unsaturated carboxylic acid having 3 to 8 carbon atoms such as acrylic acid or methacrylic acid, but zinc acrylate is used. Then, the resilience performance of the ball can be improved, which is particularly preferable. The blending amount is preferably 10 to 40 parts by weight with respect to 100 parts by weight of the base rubber.

  What is normally mix | blended with a core can be used for a filler, for example, a zinc oxide, barium sulfate, a calcium carbonate etc. can be used. The blending amount is preferably 2 to 50 parts by weight with respect to 100 parts by weight of the base rubber. Moreover, you may mix | blend an anti-aging agent or a peptizer as needed.

  In addition, the material which comprises the core 1 can use a well-known elastomer other than the said rubber composition.

  The cover 2 is made of an elastomer and is coated on the surface of the core 1 as shown in FIG. A predetermined dimple (not shown) is formed on the surface of the cover 2. A protrusion 21 is disposed on the inner surface of the cover 2. The protrusion 21 is provided so as to fit into the groove 12. The protrusion 21 has the same cross-sectional shape as the groove 12, and extends along each side SI of the regular polyhedron so as to fill the entire groove 12.

  The cover 2 preferably has a Shore D hardness (based on JIS K 7215) of 55 to 70. The layer thickness of the cover 2 is preferably 1.0 to 2.6 mm, and more preferably 1.6 to 2.3 mm. This is because if the layer thickness of the cover 2 is smaller than 1.0 mm, the durability of the cover 2 is remarkably lowered and molding becomes difficult, while if it exceeds 2.6 mm, it becomes hard and the shot feeling becomes worse. is there. Note that the layer thickness of the cover 2 is a distance from an arbitrary point on the outermost side in the radial direction where no dimples are formed to an arbitrary point where the protrusion 21 is not formed and is in contact with the core 1. It is the value measured along.

  As the elastomer constituting the cover 2, the following can be used. For example, styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), etc. Styrenic thermoplastic elastomers: Olefin-based thermoplastic elastomers with polyethylene or polypropylene as hard segments and butadiene rubber or ethylene / propylene rubber as soft segments; Crystalline polyvinyl chloride as hard segments with amorphous polyvinyl chloride or acrylonitrile Polyvinyl chloride plastic elastomer with butadiene rubber as soft segment; Polyurethane as hard segment and polyether Urethane plastic elastomer with polyester urethane as soft segment; Polyester plastic elastomer with polyester as hard segment and polyether or polyester as soft segment; Amide with polyamide as hard segment and polyether or polyester as soft segment It is possible to use a plastic elastomer; an ionomer resin; a balata rubber.

Next, a method for manufacturing the golf ball of the present embodiment will be described.
First, a first mold (not shown) having an inner wall surface corresponding to the outer peripheral surface of the core 1 is prepared. The first mold (mold) can be divided into a plurality of parts so that the core 1 can be removed without the groove 12 being caught. The first mold (mold) is set so that the split surface of the first mold (mold) is positioned at the equator EL of the core 1. Subsequently, the mold material is filled with the above-described core material and compression molded at about 130 to 170 ° C. for 5 to 30 minutes. At this time, in addition to compression molding, the core 1 can also be molded by injection molding. Following this, the core 1 molded as described above is placed in the second mold, and the cover 3 is covered by a known injection molding method. At this time, the core 1 can be wrapped with a pair of cover materials previously formed in a hemispherical shell shape, and the cover 2 can be formed by compression molding.

Next, each modification of the present embodiment will be described.
Referring to FIG. 7, in golf ball modification 1 of the present embodiment, the maximum depth of groove 12 is different from that of the golf ball of the present embodiment. In the first modification, the maximum depth of the groove 12 is, for example, 0.29 mm.

  Referring to FIG. 8, also in the golf ball modification 2 of the present embodiment, the maximum depth of the groove 12 is different from that of the golf ball of the present embodiment. In the second modification, the maximum depth of the groove 12 is, for example, 0.97 mm.

  Referring to FIG. 9, also in the golf ball modification 3 of the present embodiment, the maximum depth of the groove 12 is different from that of the golf ball of the present embodiment. In the third modification, the maximum depth of the groove 12 is, for example, 1.35 mm.

  Referring to FIG. 10, also in the golf ball modification 4 of the present embodiment, the maximum depth of the groove 12 is different from that of the golf ball of the present embodiment. In the fourth modification, the maximum depth of the groove 12 is, for example, 1.93 mm.

  Referring to FIG. 11, in the golf ball modification 5 of the present embodiment, the shape of the groove 12 is different from that of the golf ball of the present embodiment. In the fifth modification, the groove portion 12 has a shape in which the outer peripheral surface of the cylinder is in contact with the spherical portion 11 of the core 1.

  With reference to FIG. 12, in the modified example 6 of the golf ball of the present embodiment, the shape of the groove 12 is different from that of the golf ball of the present embodiment. In the sixth modification, the groove portion 12 has a shape in which the outer peripheral surface of the quadrangular prism is in contact with the spherical portion 11 of the core 1.

  With reference to FIG. 13, in the modified example 7 of the golf ball of the present embodiment, the shape of the groove 12 is different from that of the golf ball of the present embodiment. In the modified example 7, the groove portion 12 is formed on each side of the regular hexahedron when the spherical surface portion 11 is assumed to be a regular hexahedron.

  Referring to FIG. 14, in the golf ball modification 8 of the present embodiment, the shape of the groove 12 is different from that of the golf ball of the present embodiment. In the modified example 8, the groove 12 is formed on each side of the regular octahedron when the spherical surface 11 is assumed to be a regular octahedron.

  Referring to FIG. 15, in the modified example 9 of the golf ball of the present embodiment, the shape of the groove 12 is different from that of the golf ball of the present embodiment. In this modified example 9, the groove 12 is formed on each side of the regular icosahedron when the spherical surface 11 is assumed to be a regular icosahedron.

Next, the function and effect of the golf ball of the present embodiment will be described.
As shown in FIG. 1, according to the golf ball of the present embodiment, the protrusion 21 disposed on the inner surface of the cover 2 fits into the groove 12 of the core 1, and thus the adhesion between the core 1 and the cover 2. And the shift between the core 1 and the cover 2 at the time of impact is less likely to occur. Thereby, the loss of energy transmitted from the cover 2 to the core 1 at the time of impact can be reduced, so that the resilience performance can be improved. In addition, as shown in FIG. 2, the groove 12 is formed on each side SI of the regular polyhedron when the spherical surface 11 is simulated as a regular polyhedron. For this reason, it can suppress that a hit feeling changes with the area | region of a golf ball at the time of a hit | damage. Further, the groove 12 has a depth from a point SP where a line extending in the radial direction of the core 1 through each vertex AP of the regular polyhedron intersects the surface of the groove 12 toward each midpoint CP of each side SI of the regular polyhedron. The midpoint CP is arranged on the spherical surface portion 11 so that the dimensions are gradually reduced. For this reason, the core 1 and the cover 2 can be firmly fitted at each apex AP, and the mold can be easily pulled out during molding. Further, since the core 1 has an equator EL that does not intersect the groove portion 12, burrs are formed in the groove portion 12 by positioning the mold so that the equator EL is positioned on the split surface of the mold during molding. Can be prevented. Thereby, since it is not necessary to remove the burr | flash formed in the groove part 12, productivity can be improved.

  In the golf ball of the present embodiment, at least two of the midpoints CP are disposed on the equator EL that does not intersect the groove 12. For this reason, the split surface of a metal mold | die can be formed in the linear form which passes along each midpoint CP. The formation of burrs can be suppressed by forming the split surface of the mold in a straight line.

  Further, in a general golf ball, the core 1 and the cover 2 are formed of different materials, so that the core 1 and the cover 2 are displaced at the time of hitting. However, in the golf ball according to the present embodiment, the adhesion between the core 1 and the cover 2 is improved to make it difficult for the core 1 and the cover 2 to be displaced. Energy loss can be reduced. For this reason, resilience performance can be improved.

  Further, in the golf ball of the present embodiment, the grooves 12 formed in the first and second hemispheres HE1 and HE2 are first and second in a direction (centerline CL direction) perpendicular to the radial direction of the equator EL. The whole is exposed when viewed from the two hemispheres HE1 and HE2. For this reason, when the 1st and 2nd hemisphere HE1 and HE2 are extracted from a metal mold | die, generation | occurrence | production of an undercut can be prevented. Thereby, since the structure of a metal mold | die can be simplified, productivity can be improved and production cost can be suppressed.

  Further, in the golf ball of the present embodiment, the groove portion 12 has a V-shaped cross-sectional shape that opens to the spherical surface portion 11. For this reason, generation | occurrence | production of an undercut can be suppressed when extracting the groove part 12 from a metal mold | die.

  As shown in FIG. 6, in the golf ball of the present embodiment, the groove 12 has a bottom BP that curves outwardly in the radial direction of the core 1 along the direction in which the groove 12 extends. have. For this reason, generation | occurrence | production of the undercut in bottom part BP can be suppressed.

  Examples of the present invention will be described below.

  First, referring to Table 1, the inventors create samples 1 to 20 having the same configuration as the golf ball of the embodiment, and the ratio of the maximum depth of the groove and the area of the groove to the surface area of the core We examined the relationship with the area occupancy. Each code | symbol of Table 1 respond | corresponds to the code | symbol of FIG. D1 in Table 1 is the depth (maximum depth) of the center of the groove, H is the length of the bottom of the triangular prism, and D2 is the depth of the tip of the groove. L of FIG. 4 is the length of a triangular prism, and it is all 8 mm in the samples 1-20. In Samples 1 to 20, the core diameter is 39.3 mm.

  Referring to Table 1 and FIG. 16, it was found that undercutting occurs when the maximum depth is large and the area occupation ratio is small. It was also found that when the maximum depth was small and the area occupation ratio was large, the angle of the groove was too shallow and the cover did not bite into the core.

  Next, the inventors prepared Comparative Examples 1 to 3 and Examples 1 to 3 having the configurations shown in Tables 2 and 3.

  In Comparative Examples 1 to 3, no groove is formed in the core, while in Examples 1 to 3, the groove is formed in the core. The cores of Examples 1 to 3 have the shape shown in FIG. Comparative Examples 1 to 3 and Examples 1 to 3 have different core surface JIS-C hardnesses.

  With reference to Table 4, FIG. 17, and FIG. 18, about the comparative examples 1-3 and Examples 1-3, inventors examined the relationship between the shape of a core and a hysteresis. An autograph AG5000D manufactured by Shimadzu Corporation was used as a testing machine. A steel plate having a sufficient thickness was attached in parallel to the testing machine, and the golf ball placed between them was compressed and deformed. The relationship between the load and the displacement when the compressive load is from 0 kN to 3 kN was graphed. The compression speed was 0.2 mm / sec. After being deformed by applying a load, it was similarly unloaded at a speed of 0.2 mm / sec. As shown in FIG. 18, the hysteresis was measured by determining the area of the difference between the load displacement curves when compressing and unloading. The maximum displacement (mm) is the maximum displacement amount of the golf ball diameter when a load of up to 3 kN is applied.

  As shown in FIG. 17, the loss due to hysteresis was smaller in Examples 1 to 3 than in Comparative Examples 1 to 3. For this reason, in Examples 1-3, it turned out that the loss of energy between the time of compressing and the time of unloading becomes small. Thereby, in Examples 1-3, it turned out that resilience performance can be improved.

  Subsequently, with reference to Table 5 and FIG. 19, the inventors examined the relationship between the core shape and the coefficient of restitution (COR) in Comparative Examples 1 to 3 and Examples 1 to 3. The coefficient of restitution was calculated by measuring the speed of incidence and reflection when a golf ball launched from an air gun hits an iron plate (rigid body) with sufficient thickness and weight and bounces back. The ball speed was obtained by measuring the time for the ball to pass between the infrared sensors installed at two locations. The two infrared sensors were arranged at such a distance that they were not affected by the deceleration of the ball when the ball passed between the two points. After the golf ball was left in a constant temperature bath at 24 ° C. for 24 hours or longer, a coefficient of restitution measurement test was conducted. As the restitution coefficient, a value at an incident speed of 43.5 m / s was adopted. This is because the value of the coefficient of restitution changes when the speed changes. In the experiment, measurements were made five times each at an incident velocity of 35 m / s, 40 m / s, and 45 m / s, and a coefficient of restitution equivalent to 43.5 m / s was calculated using an approximate line. The degree of compression is a load (kgf) required to compress and deform the diameter of the golf ball by 2.54 mm.

  As shown in FIG. 19, Examples 1 to 3 had a larger coefficient of restitution than Comparative Examples 1 to 3. For this reason, in Examples 1-3, it turned out that resilience performance can be improved.

  Then, with reference to Table 6, the inventors examined the flight distance of the golf ball in Comparative Examples 1 to 3 and Examples 1 to 3. A golf swing robot manufactured by Miyamae Co., Ltd. was used as a testing machine. A Mitsuno driver (JPX800: 10.5 degrees loft) was attached to the swing robot, and the head speed just before hitting was adjusted to 42 m / s. The ball was hit at the face center, and was launched into a flat field under conditions of a wind speed of 0 to 1 m / s and an air temperature of 28 degrees. The launch conditions (ball speed, launch angle, spin amount) were measured by Trackman made by Trackman, and the total flight distance was measured by actual distance.

  As shown in Table 6, the ball initial speed was higher in Examples 1 to 3 than in Comparative Examples 1 to 3. From this, it was found that the resilience performance can be improved in Examples 1 to 3.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The present invention can be applied particularly advantageously to a golf ball having a core and a cover covering the core.

  1 core, 2 cover, 11 spherical surface part, 12 groove part, 21 protrusion part, AP apex, BP bottom part, CP midpoint, EL equator, HE1 first hemisphere, HE2 second hemisphere, SI side, SP point.

Claims (6)

The core,
A single layer or a plurality of layers covering the core,
The core includes a spherical portion and a groove portion recessed from the spherical portion,
The groove part is a point where a line extending in the radial direction of the core through each vertex of the regular polyhedron intersects the surface of the groove part on each side of the regular polyhedron when the spherical part is simulated as a regular polyhedron. To be formed so that the depth dimension gradually decreases from each side toward each midpoint of each side.
Each of the midpoints is disposed on the spherical portion,
The core has an equator that does not intersect the groove,
The cover is a golf ball that is disposed on an inner surface of the cover and includes a protrusion that fits into the groove.   The golf ball according to claim 1, wherein at least two of the midpoints are arranged on the equator that does not intersect the groove.   The golf ball according to claim 1, wherein the core and the cover are formed of different materials. The core includes first and second hemispheres sandwiching the equator,
The groove formed in the first hemisphere is entirely exposed when viewed from the first hemisphere side in a direction perpendicular to the radial direction of the equator,
The groove portion formed in the second hemisphere is entirely exposed when viewed from the second hemisphere side in a direction orthogonal to the radial direction of the equator. The golf ball described in the item.   The golf ball according to claim 1, wherein the groove portion has a V-shaped cross-sectional shape that opens to the spherical portion.   6. The golf ball according to claim 1, wherein the groove part has a bottom part that curves outwardly in a radial direction of the core along a direction in which the groove part extends.

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