JP2010172357A - Golf ball - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf ball having improved flight performance, in which the number of the units of the pole vicinity region is different from the number of the units of the equator vicinity region. <P>SOLUTION: The golf ball 14 has a northern hemisphere N above an equatorial line Eq and a southern hemisphere S below the equatorial line Eq. Each of the northern hemisphere N and the southern hemisphere S has the pole vicinity region 30, the equator vicinity region 32, and a mid region 34. Each of the pole vicinity region 30, the equator vicinity region 32, and the mid region 34 has numerous dimples 20. The dimple pattern of the pole vicinity region 30 includes the plurality of units that are rotationally symmetrical to each other about a pole P. The pole vicinity region 30 includes four units. The dimple pattern of the equator vicinity region 32 includes the plurality of units that are rotationally symmetrical to each other about the pole P. The equator vicinity region includes six units. The dimples 20 included in the mid region 34 are arranged along a mid latitude line 28. The number of the dimples 20 included in the mid region 34 is 24. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  The golf ball has a large number of dimples on its surface. The dimples disturb the air flow around the golf ball during flight and cause turbulent separation. Turbulent separation shifts the separation point of air from the golf ball backwards, reducing drag. Turbulent separation promotes the deviation between the upper separation point and the lower separation point of the golf ball due to backspin, and increases the lift acting on the golf ball. The reduction of drag and the improvement of lift are referred to as “dimple effect”. Excellent dimples better disturb the air flow. Excellent dimples produce a great flight distance.

  Various proposals regarding dimple patterns have been made. Japanese Patent Laid-Open No. 4-109968 discloses a golf ball in which a hemisphere is divided into six units. These units have dimple patterns equivalent to each other. Japanese Unexamined Patent Application Publication No. 2004-243124 discloses a dimple pattern in which an octahedron is used for a section in the pole vicinity region and an icosahedron is used in a section in the equator vicinity region.

  The present inventor has proposed a golf ball having an improved dimple pattern in Japanese Patent Application Laid-Open No. 2007-175267. This golf ball is shown in FIGS. The golf ball 2 includes a northern hemisphere N and a southern hemisphere S. Each hemisphere includes a pole vicinity region 4, an equator vicinity region 6, and an adjustment region 8. The number of units Up in the pole vicinity region 4 is different from the number of units Ue in the equator vicinity region 6. This difference disturbs the air flow. Differences between the characteristics of the pole vicinity region 4 and the characteristics of the equator vicinity region 6 are alleviated by the adjustment region 8.

JP-A-4-109968 JP-A-2004-243124 JP 2007-175267 A

  In the golf ball 2 disclosed in Japanese Patent Laid-Open No. 2007-175267, the difference between the characteristics of the pole vicinity region 4 and the characteristics of the equator vicinity region 6 is not sufficiently relaxed by the adjustment region 8. In the golf ball 2, the dimples 10 are unevenly distributed in the adjustment region 8. Due to this uneven distribution, a land having a large area is generated. This land impairs the dimple effect.

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

  The surface of the golf ball according to the present invention can be divided into a northern hemisphere and a southern hemisphere. Each of the northern hemisphere and the southern hemisphere includes a pole vicinity region, an equator vicinity region, and an intermediate region located between the pole vicinity region and the equator vicinity region. Each of the pole vicinity region, the equator vicinity region, and the intermediate region includes a large number of dimples. The dimple pattern in the pole vicinity region is composed of a plurality of units that are rotationally symmetric with respect to the pole point. The dimple pattern in the vicinity of the equator is composed of a plurality of units that are rotationally symmetric with respect to the pole. The number Np of units in the pole vicinity region is different from the number Ne of units in the equator vicinity region. The dimples included in the intermediate region are arranged substantially along one latitude line.

  Preferably, the latitude of the latitude line is 20 ° or more and 40 ° or less. Preferably, the latitude of the latitude line is substantially 30 °.

  Preferably, the number Np is 3 or more and 6 or less, and the number Ne is 3 or more and 6 or less.

Preferably, the number Nm of dimples in the intermediate region is 18 or more and 48 or less. Preferably, the number Nm is a common multiple of the number Np and the number Ne.

  Preferably, the dimples included in the intermediate region have the same diameter. These dimples are arranged at equal intervals along the latitude line.

  Preferably, the number of dimples adjacent to the boundary line between the pole vicinity region and the intermediate region and included in the pole vicinity region is the same as the number of dimples arranged along the intermediate latitude line. Preferably, the number of dimples adjacent to the boundary line between the equator vicinity region and the intermediate region and included in the equator vicinity region is the same as the number of dimples arranged along the intermediate latitude line.

  In this golf ball, a large dimple effect is obtained because the number of units in the pole vicinity region is different from the number of units in the equator vicinity region. In this golf ball, the middle region suppresses uneven distribution of dimples. This golf ball is excellent in flight performance.

FIG. 1 is a schematic cross-sectional view showing a golf ball according to an embodiment of the present invention. FIG. 2 is an enlarged front view showing the golf ball of FIG. FIG. 3 is a plan view showing the golf ball of FIG. 4 is a plan view showing the golf ball of FIG. FIG. 5 is a plan view showing the golf ball of FIG. 6 is an enlarged cross-sectional view showing a part of the golf ball in FIG. 7 is a front view showing a golf ball according to Comparative Example 1. FIG. FIG. 8 is a plan view showing the golf ball of FIG. FIG. 9 is a front view showing a golf ball according to Comparative Example 2. FIG. FIG. 10 is a plan view showing the golf ball of FIG. FIG. 11 is a front view showing a golf ball according to Comparative Example 3. FIG. FIG. 12 is a plan view showing the golf ball of FIG. FIG. 13 is a plan view showing the golf ball of FIG. FIG. 13 is a plan view showing the golf ball of FIG.

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

  FIG. 1 is a schematic cross-sectional view showing a golf ball 14 according to an embodiment of the present invention. The golf ball 14 includes a spherical core 16 and a cover 18. A large number of dimples 20 are formed on the surface of the cover 18. A portion of the surface of the golf ball 14 other than the dimples 20 is a land 22. The golf ball 14 includes a paint layer and a mark layer outside the cover 18, but these layers are not shown. An intermediate layer may be provided between the core 16 and the cover 18.

  The golf ball 14 has a diameter of 40 mm or greater and 45 mm or less. From the viewpoint of satisfying the standards of the US Golf Association (USGA), the diameter is more preferably 42.67 mm or more. In light of suppression of air resistance, the diameter is more preferably equal to or less than 44 mm, and particularly preferably equal to or less than 42.80 mm. The golf ball 14 has a mass of 40 g or more and 50 g or less. In light of attainment of great inertia, the mass is more preferably equal to or greater than 44 g, and particularly preferably equal to or greater than 45.00 g. From the viewpoint that the USGA standard is satisfied, the mass is more preferably 45.93 g or less.

  The core 16 is formed by crosslinking a rubber composition. Examples of the base rubber of the rubber composition include polybutadiene, polyisoprene, styrene-butadiene copolymer, ethylene-propylene-diene copolymer, and natural rubber. Two or more kinds of rubbers may be used in combination. From the viewpoint of resilience performance, polybutadiene is preferred, and high cis polybutadiene is particularly preferred.

  For crosslinking of the core 16, a co-crosslinking agent is preferably used. From the viewpoint of resilience performance, preferred co-crosslinking agents are zinc acrylate, magnesium acrylate, zinc methacrylate and magnesium methacrylate. It is preferable that an organic peroxide is blended with the co-crosslinking agent in the rubber composition. Suitable organic peroxides include dicumyl peroxide, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di (t- Butyl peroxy) hexane and di-t-butyl peroxide.

  In the rubber composition of the core 16, various additives such as a filler, sulfur, a vulcanization accelerator, a sulfur compound, an anti-aging agent, a colorant, a plasticizer, and a dispersant are blended in an appropriate amount as necessary. Crosslinked rubber powder or synthetic resin powder may be blended with the rubber composition.

  The diameter of the core 16 is 30.0 mm or more, particularly 38.0 mm or more. The diameter of the core 16 is 42.0 mm or less, particularly 41.5 mm or less. The core 16 may be composed of two or more layers.

  A suitable polymer for the cover 18 is an ionomer resin. A preferable ionomer resin includes a binary copolymer of an α-olefin and an α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms. Other preferable ionomer resins include ternary α-olefin, α, β-unsaturated carboxylic acid having 3 to 8 carbon atoms and α, β-unsaturated carboxylic acid ester having 2 to 22 carbon atoms. A copolymer is mentioned. In this binary copolymer and ternary copolymer, preferred α-olefins are ethylene and propylene, and preferred α, β-unsaturated carboxylic acids are acrylic acid and methacrylic acid. In this binary copolymer and ternary copolymer, some of the carboxyl groups are neutralized with metal ions. Examples of the metal ions for neutralization include sodium ions, potassium ions, lithium ions, zinc ions, calcium ions, magnesium ions, aluminum ions, and neodymium ions.

  Another polymer may be used for the cover 18 instead of the ionomer resin. Examples of other polymers include polyurethane, polystyrene, polyamide, polyester, and polyolefin. From the viewpoint of spin performance and scratch resistance, polyurethane is preferred. Two or more kinds of polymers may be used in combination.

  If necessary, the cover 18 may contain an appropriate amount of a colorant such as titanium dioxide, a filler such as barium sulfate, a dispersant, an antioxidant, an ultraviolet absorber, a light stabilizer, a fluorescent agent, and a fluorescent brightening agent. Blended. For the purpose of adjusting the specific gravity, the cover 18 may be mixed with powder of a high specific gravity metal such as tungsten or molybdenum.

  The cover 18 has a thickness of 0.2 mm or more, particularly 0.3 mm or more. The cover 18 has a thickness of 2.5 mm or less, particularly 2.2 mm or less. The specific gravity of the cover 18 is 0.90 or more, particularly 0.95 or more. The specific gravity of the cover 18 is 1.10 or less, particularly 1.05 or less. The cover 18 may be composed of two or more layers.

  FIG. 2 is an enlarged front view showing the golf ball 14 of FIG. In FIG. 2, two pole points P, two first latitude lines 24, two second latitude lines 26, two intermediate latitude lines 28, and an equator Eq are depicted. The latitude of the pole P is 90 °, and the latitude of the equator Eq is 0 °. The latitude of the first latitude line 24 is greater than the latitude of the second latitude line 26. The latitude of the intermediate latitude line 28 is smaller than the latitude of the first latitude line 24 and larger than the latitude of the second latitude line 26.

  This golf ball 14 includes a northern hemisphere N above the equator Eq and a southern hemisphere S below the equator Eq. Each of the northern hemisphere N and the southern hemisphere S includes a pole vicinity region 30, an equator vicinity region 32, and an intermediate region 34. The first latitude line 24 is a boundary line between the pole vicinity region 30 and the intermediate region 34. The second latitude line 26 is a boundary line between the equator vicinity region 32 and the intermediate region 34. The pole vicinity region 30 is located between the pole point P and the first latitude line 24. The equator vicinity region 32 is located between the second latitude line 26 and the equator Eq. The intermediate region 34 is located between the first latitude line 24 and the second latitude line 26. In other words, the intermediate region 34 is located between the pole vicinity region 30 and the equator vicinity region 32.

  Each of the pole vicinity region 30, the equator vicinity region 32, and the intermediate region 34 includes a large number of dimples 20. As is apparent from FIG. 2, the planar shape of all the dimples 20 is a circle. In the dimple 20 that intersects the first latitude line 24 or the second latitude line 26, the region to which the dimple 20 belongs is determined based on the center position of the dimple 20. The dimple 20 that intersects the first latitude line 24 and whose center is located in the pole vicinity region 30 belongs to the pole vicinity region 30. The dimple 20 that intersects the second latitude line 26 and whose center is located in the equator vicinity region 32 belongs to the equator vicinity region 32. The center of the dimple 20 is a point where a straight line connecting the deepest part of the dimple 20 and the center of the golf ball 14 intersects the surface of the phantom sphere. The surface of the phantom sphere is the surface of the golf ball 14 when it is assumed that the dimple 20 does not exist.

  3, 4 and 5 are plan views showing the golf ball 14 of FIG. In FIG. 3, four first meridians 36 are shown along with the first latitude line 24 and the second latitude line 26. In FIG. 3, the pole vicinity region 30 is surrounded by the first latitude line 24. The pole vicinity region 30 can be divided into four units Up. The unit Up is a spherical triangle. The outline of the unit Up is composed of a first latitude line 24 and two first meridians 36. In FIG. 3, the type of the dimple 20 is indicated by reference signs A, B, D, E, F, and G for one unit Up. The pole vicinity region 30 includes a dimple A having a diameter of 5.00 mm, a dimple B having a diameter of 4.80 mm, a dimple D having a diameter of 4.40 m, a dimple E having a diameter of 4.00 m, A dimple F having a diameter of 3.60 mm and a dimple G having a diameter of 3.00 mm are provided.

  The dimple pattern of the four units Up is 90 ° rotationally symmetric. In other words, when the dimple pattern of a certain unit Up rotates 90 degrees in the longitude direction around the pole P, it substantially overlaps with the dimple pattern of the adjacent unit Up. The “substantially overlap” state includes a state where one dimple 20 is slightly displaced from the other dimple 20. The “slightly shifted state” includes a state in which the center of one dimple 20 is slightly separated from the center of the other dimple 20. The distance between the center of one dimple 20 and the center of the other dimple 20 is preferably 1.0 mm or less, and more preferably 0.5 mm or less. Here, the “slightly shifted state” includes a state in which the size of one dimple 20 is slightly different from the size of the other dimple 20. The dimensional difference is preferably 0.5 mm or less, and more preferably 0.3 mm or less. The dimension means the length of the longest line segment that can be drawn on the outline of the dimple 20. In the case of the circular dimple 20, its dimension matches the diameter.

  The dimple pattern in the pole vicinity region 30 can be partitioned into two units. In this case, the dimple pattern of each unit is 180 ° rotationally symmetric. The dimple pattern in the pole vicinity region 30 has two rotational symmetry angles (that is, 90 ° and 180 °). In a region having a plurality of rotational symmetry angles, the unit Up is partitioned based on the smallest rotational symmetry angle (90 ° in this example).

  In FIG. 4, six second meridians 38 are shown along with the first latitude line 24 and the second latitude line 26. In FIG. 4, the outside of the second latitude line 26 is the equator vicinity region 32. The equator vicinity region 32 can be partitioned into six units Ue. The unit Ue is a spherical trapezoid. The outline of the unit Ue includes a second latitude line 26, two second meridians 38, and an equator Eq (see FIG. 2). In FIG. 4, the types of the dimples 20 are indicated by symbols A, B, and D for one unit Ue. The equator vicinity region 32 includes a dimple A having a diameter of 5.00 mm, a dimple B having a diameter of 4.80 mm, and a dimple D having a diameter of 4.40 mm.

  The dimple pattern of the six units Ue is 60 ° rotationally symmetric. In other words, when the dimple pattern of a certain unit Ue rotates 60 ° in the longitude direction around the pole P, it substantially overlaps with the dimple pattern of the adjacent unit Ue. The dimple pattern in the equator vicinity region 32 can be divided into three units. In this case, the dimple pattern of each unit is 120 ° rotationally symmetric. The dimple pattern in the equator vicinity region 32 can be divided into two units. In this case, the dimple pattern of each unit is 180 ° rotationally symmetric. The dimple pattern in the equator vicinity region 32 has three rotational symmetry angles (ie, 60 °, 120 °, and 180 °). In a region having a plurality of rotational symmetry angles, the unit Ue is partitioned based on the smallest rotational symmetry angle (60 ° in this example).

  FIG. 5 shows the first latitude line 24 and the second latitude line 26. In FIG. 5, an intermediate region 34 is surrounded by the first latitude line 24 and the second latitude line 26. The intermediate region 34 includes 24 dimples 20. As shown in FIG. 5, the intermediate region 34 includes only dimples C. In other words, the dimples 20 included in the intermediate region 34 have the same diameter. The diameter of the dimple C is 4.70 mm.

  As shown in FIG. 2, all the dimples 20 included in the intermediate region 34 are arranged along the intermediate latitude line 28. In other words, the latitude of the dimple 20 included in the intermediate region 34 is the same as the latitude of the intermediate latitude line 28. The intermediate region 34 may include dimples 20 whose latitude is slightly different from the latitude of the intermediate latitude line 28. The difference between the latitude of the dimple 20 and the latitude of the intermediate latitude line 28 is preferably 5 ° or less, and more preferably 2 ° or less.

  In this golf ball 14, the number Np of units Up in the pole vicinity region 30 is 4, and the number Ne of units Ue in the equator vicinity region 32 is 6. They are different. The dimple pattern in which the number Np and the number Ne are different is rich in change. In the golf ball 14, the air flow during flight is well disturbed. This golf ball 14 is excellent in flight performance. As combinations (Np, Ne) of the numbers Np and Ne, (2, 3), (2, 4), (2, 5), (2, 6), (3, 2), (3, 3) 4), (3,5), (3,6), (4,2), (4,3), (4,5), (4,6), (5,2), (5,3) , (5,4), (5,6), (6,2), (6,3), (6,4) and (6,5).

  From the viewpoint of the dimple effect, it is preferable that the pole vicinity region 30 has a sufficient area and the equator vicinity region 32 has a sufficient area. From the viewpoint of the area of the equator vicinity region 32, the latitudes of the first latitude line 24 and the second latitude line 26 are preferably 20 ° or more, and more preferably 25 ° or more. From the viewpoint of the area of the pole vicinity region 30, the latitude of the first latitude line 24 and the second latitude line 26 is preferably 40 ° or less, and more preferably 35 ° or less. The first latitude line 24 can be arbitrarily selected from an infinite number of latitude lines. The second latitude line 26 can be arbitrarily selected from an infinite number of latitude lines. The intermediate latitude line 28 can also be arbitrarily selected from an infinite number of latitude lines.

  From the viewpoint of contribution of the pole vicinity region 30 to the dimple effect, the ratio of the number of the dimples 20 existing in the pole vicinity region 30 to the number of the dimples 20 existing in the hemisphere is preferably 20% or more, and more preferably 30% or more. This ratio is preferably 70% or less.

  From the viewpoint of contribution of the equator vicinity region 32 to the dimple effect, the ratio of the number of dimples 20 existing in the equator vicinity region 32 to the number of dimples 20 existing in the hemisphere is preferably 20% or more, and more preferably 30% or more. This ratio is preferably 70% or less.

  If the pole vicinity region 30 is adjacent to the equator vicinity region 32 across the boundary line, the dimples 20 cannot be densely arranged near the boundary line due to the difference in the number of units. In this case, there is a wide land 22 in the vicinity of the boundary line. The wide land 22 inhibits the dimple effect. In the golf ball 14 according to the present invention, an intermediate region 34 exists between the pole vicinity region 30 and the equator vicinity region 32. This intermediate region 34 alleviates the difference between the characteristics of the pole vicinity region 30 and the characteristics of the equator vicinity region 32. The intermediate region 34 suppresses the uneven distribution of the dimples 20 in the vicinity of the first latitude line 24, and also suppresses the uneven distribution of the dimples 20 in the vicinity of the second latitude line 26. In the golf ball 14 having the intermediate region 34, a dimple pattern without the large land 22 can be achieved. With this golf ball 14, a large dimple effect is obtained. This golf ball 14 is excellent in flight performance.

  As described above, the number Nm of the dimples 20 included in the intermediate region 34 is 24. On the other hand, the number Np of units Up in the pole vicinity region 30 is four. The number Nm is a multiple of the number Np. In the golf ball 14, the uneven distribution of the dimples 20 can be suppressed in the vicinity of the first latitude line 24. The number Ne of the units Ue in the equator vicinity region 32 is 6. The number Nm is a multiple of the number Ne. In the golf ball 14, the uneven distribution of the dimples 20 can be suppressed in the vicinity of the second latitude line 26.

  Preferably, the number Nm is a common multiple of the number Np and the number Ne. In the golf ball 14 in which the number Nm is this common multiple, the intermediate region 34 is partitioned into units of several Np and can be partitioned into units of several Ne.

  The number Np of units Up in the pole vicinity region 30 is preferably 3 or more. In the golf ball 14 in which the number Np is 3 or more, the area of each unit Up is not excessive. This golf ball 14 is excellent in aerodynamic symmetry. The number Np is preferably 6 or less. In the golf ball 14 having the number Np of 6 or less, a large dimple effect can be obtained.

  The number Ne of the units Ue in the equator vicinity region 32 is preferably 3 or more. In the golf ball 14 in which the number Ne is 3 or more, the area of each unit Ue is not excessive. This golf ball 14 is excellent in aerodynamic symmetry. The number Ne is preferably 6 or less. In the golf ball 14 having the number Ne of 6 or less, a large dimple effect can be obtained.

  Preferred combinations of number Np, number Ne and number Nm are shown in Table 1 below.

  The number of dimples 20 adjacent to the first latitude line 24 and included in the pole vicinity region 30 preferably matches the number of dimples 20 arranged along the intermediate latitude line 28. Due to this coincidence, the dimples 20 existing in the pole vicinity region 30 and the dimples 20 existing in the intermediate region 34 can be alternately arranged across the first latitude line 24. Due to the alternate arrangement, uneven distribution of the dimples 20 is suppressed. In the dimple pattern shown in FIGS. 2 to 5, the number of dimples 20 adjacent to the first latitude line 24 and included in the pole vicinity region 30 is 24. In this pattern, the number of dimples 20 arranged along the intermediate latitude line 28 is 24. Both are in agreement.

  It is preferable that the number of dimples 20 adjacent to the second latitude line 26 and included in the equator vicinity region 32 matches the number of dimples 20 arranged along the intermediate latitude line 28. Due to this coincidence, the dimples 20 existing in the equator vicinity region 32 and the dimples 20 existing in the intermediate region 34 can be alternately arranged across the second latitude line 26. Due to the alternate arrangement, uneven distribution of the dimples 20 is suppressed. In the dimple pattern shown in FIGS. 2 to 5, the number of dimples 20 adjacent to the second latitude line 26 and included in the equator vicinity region 32 is 24. In this pattern, the number of dimples 20 arranged along the intermediate latitude line 28 is 24. Both are in agreement.

  From the viewpoint of suppressing the uneven distribution of the dimples 20, it is preferable that the dimples 20 included in the intermediate region 34 have the same diameter. From the viewpoint of suppressing the uneven distribution of the dimples 20, it is preferable that these dimples 20 are arranged at equal intervals along the intermediate latitude line 28.

  The number Nm of the dimples 20 in the intermediate region 34 is preferably 18 or more. In the golf ball 14 having a number Nm of 18 or more, the individual dimples 20 are not excessive. In the golf ball 14, the area of the land 22 can be suppressed. In this respect, the number Nm is more preferably equal to or greater than 20, and particularly preferably equal to or greater than 24. When the dimples 20 included in the intermediate region 34 have the same diameter and are arranged at equal intervals, the center angle between two adjacent dimples 20 is preferably 20 ° or less, more preferably 18 ° or less, and 15 °. The following are particularly preferred:

  The number Nm of the dimples 20 in the intermediate region 34 is preferably 48 or less. In the golf ball 14 having a number Nm of 48 or more, each dimple 20 is sufficiently large. Due to the dimple 20, a large dimple effect can be obtained. In this respect, the number Nm is more preferably equal to or less than 45, and particularly preferably equal to or less than 42. When the dimples 20 included in the intermediate region 34 have the same diameter and are arranged at equal intervals, the center angle between two adjacent dimples 20 is preferably 7.5 ° or more, more preferably 8.0 ° or more. The angle is preferably 8.5 ° or more.

  The latitude of the intermediate latitude line 28 is preferably 20 ° or more and 40 ° or less. By setting the latitude to 20 ° or more, the equator vicinity region 32 has a sufficient area. By setting this latitude to 40 ° or less, the pole vicinity region 30 has a sufficient area. In the golf ball 14 whose latitude is 20 ° or more and 40 ° or less, the air flow is sufficiently disturbed. In this respect, the latitude is particularly preferably 25 ° or more. The latitude is particularly preferably 35 ° or less. Ideally this latitude is 30 °. In the golf ball 14 whose latitude is 30 °, the area of the surface of the phantom sphere between the intermediate latitude line 28 and the equator Eq is the surface of the phantom sphere, the intermediate latitude line 28 and the pole P. This corresponds to the area of the region existing between the two.

  From the viewpoint of aerodynamic symmetry, it is preferable that the dimple pattern of the northern hemisphere N and the dimple pattern of the southern hemisphere S are equivalent. When a pattern that is symmetrical with the dimple pattern of the northern hemisphere N with respect to the plane including the equator Eq substantially overlaps with the dimple pattern of the southern hemisphere S, the two patterns are equivalent. Both patterns are equivalent when a pattern that is symmetrical to the dimple pattern of the northern hemisphere N with respect to the plane including the equator Eq substantially overlaps with the dimple pattern of the southern hemisphere S when rotated about the pole P. .

  The dimple 20 may intersect with the equator Eq. The dimple 20 whose center is in the northern hemisphere N belongs to the northern hemisphere N. The dimple 20 whose center is in the southern hemisphere S belongs to the southern hemisphere S. The dimple 20 whose latitude is zero belongs to the northern hemisphere N and also belongs to the southern hemisphere S.

  From the viewpoint of obtaining a sufficient dimple effect, the total number of the dimples 20 is preferably 200 or more, particularly preferably 260 or more. From the viewpoint that each dimple 20 can have a sufficient diameter, the total number is preferably 600 or less, more preferably 500 or less, and particularly preferably 400 or less.

  FIG. 6 is an enlarged cross-sectional view showing a part of the golf ball 14 of FIG. FIG. 6 shows a cross section along a plane passing through the deepest part of the dimple 20 and the center of the golf ball 14. The vertical direction in FIG. 6 is the depth direction of the dimple 20. In FIG. 6, what is indicated by a two-dot chain line 40 is the surface of the phantom sphere 40. The dimple 20 is recessed from the surface of the phantom sphere 40. The land 22 coincides with the surface of the phantom sphere 40.

  In FIG. 6, what is indicated by a double-pointed arrow Di is the diameter of the dimple 20. The diameter Di is a distance between one contact point Ed and the other contact point Ed when a common tangent line T is drawn on both sides of the dimple 20. The contact point Ed is also the edge of the dimple 20. The edge Ed defines the outline of the dimple 20. The diameter Di is preferably 2.00 mm or greater and 6.00 mm or less. By setting the diameter Di to be 2.00 mm or more, a large dimple effect can be obtained. In this respect, the diameter Di is more preferably 2.20 mm or more, and particularly preferably 2.40 mm or more. By setting the diameter Di to 6.00 mm or less, the original characteristic of the golf ball 14 that is substantially a sphere is maintained. In this respect, the diameter Di is more preferably equal to or less than 5.80 mm, and particularly preferably equal to or less than 5.60 mm.

The area s of the dimple 20 is an area of a region surrounded by a contour line when the center of the golf ball 14 is viewed from infinity. In the case of the circular dimple 20, the area s is calculated by the following mathematical formula.
s = (Di / 2) ²・ π
In the golf ball 14 shown in FIGS. 1 to 6, the area of the dimple A is 19.63 mm ² , the area of the dimple B is 18.10 mm ² , and the area of the dimple C is 17.35 mm ² , The area of the dimple D is 15.20 mm ² , the area of the dimple E is 12.57 mm ² , the area of the dimple F is 10.18 mm ² , and the area of the dimple G is 7.07 mm ² .

In the present invention, the ratio of the total area s of all the dimples 20 to the surface area of the phantom sphere 40 is referred to as an occupation ratio. From the viewpoint of obtaining a sufficient dimple effect, the occupation ratio is preferably 60% or more, more preferably 65% or more, and particularly preferably 70% or more. The occupation ratio is preferably 88% or less. In the golf ball 14 shown in FIGS. 2 to 6, the total area of the dimples 20 is 4442.8 mm ² . Since the surface area of the phantom sphere 40 of this golf ball 14 is 5728.0 mm ² , the occupation ratio is 77.6%.

In the present invention, “dimple volume” means the volume of a portion surrounded by a plane including the outline of the dimple 20 and the surface of the dimple 20. From the viewpoint of rising of the golf ball 14 is suppressed, the total volume of the dimples 20 is preferably 250 mm ³ or more, more preferably 260 mm ³ or more, 270 mm ³ or more is particularly preferable. In view of dropping of the golf ball 14 is suppressed, the total volume is preferably 400 mm ³ or less, more preferably 390 mm ³ or less, 380 mm ³ or less is particularly preferred.

  In light of suppression of hops in the golf ball 14, the depth of the dimple 20 is preferably 0.05 mm or more, more preferably 0.08 mm or more, and particularly preferably 0.10 mm or more. In light of suppression of dropping of the golf ball 14, the depth is preferably 0.60 mm or less, more preferably 0.45 mm or less, and particularly preferably 0.40 mm or less. The depth is a distance between the tangent line T and the deepest part of the dimple 20.

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

[Example 1]
100 parts by weight of polybutadiene (trade name “BR-730” from JSR), 30 parts by weight of zinc acrylate, 6 parts by weight of zinc oxide, 10 parts by weight of barium sulfate, 0.5 parts by weight of diphenyl disulfide and 0.5 parts by mass of dicumyl peroxide was kneaded to obtain a rubber composition. This rubber composition was put into a mold composed of an upper mold and a lower mold each having a hemispherical cavity and heated at 170 ° C. for 18 minutes to obtain a core having a diameter of 39.7 mm. On the other hand, 50 parts by mass of ionomer resin (trade name “HIMILAN 1605” from Mitsui DuPont Polychemical Co.), 50 parts by mass of other ionomer resins (trade name “HIMILAN 1706” from Mitsui DuPont Polychemical Co., Ltd.) and 3 parts by mass Part of titanium dioxide was kneaded to obtain a resin composition. The core was put into a final mold having a large number of pimples on the inner peripheral surface, and the resin composition was injected around the sphere by an injection molding method to form a cover having a thickness of 1.5 mm. A large number of dimples having a reversed pimple shape were formed on the cover. A clear paint based on a two-component curable polyurethane was applied to this cover to obtain a golf ball of an example having a diameter of 42.7 mm and a mass of about 45.4 g. The golf ball has a PGA compression of about 85. This golf ball has the dimple pattern shown in FIGS. Details of the dimple specifications are shown in Table 2 below.

[Comparative Example 1]
The golf ball of Comparative Example 1 was obtained in the same manner as the Example. FIG. 7 is a front view showing the golf ball, and FIG. 8 is a plan view thereof. The golf ball's northern and southern hemispheres each have a pole vicinity region, an equator vicinity region, and an intermediate region. The pole vicinity region is composed of four units Up that are rotationally symmetric with respect to the pole P. The equator vicinity region is composed of four units Ue that are rotationally symmetric with respect to the pole P. The intermediate region has 24 dimples. These dimples are arranged along a latitude line having a latitude of 30 °.

[Comparative Example 2]
The golf ball of Comparative Example 1 was obtained in the same manner as the Example. FIG. 9 is a front view showing the golf ball, and FIG. 10 is a plan view thereof. The golf ball's northern and southern hemispheres each have a pole vicinity region, an equator vicinity region, and an intermediate region. The pole vicinity region is composed of six units Up that are rotationally symmetric with respect to the pole P. The equator vicinity region is composed of six units Ue that are rotationally symmetric with respect to the pole P. The intermediate region has 24 dimples. These dimples are arranged along a latitude line having a latitude of 30 °.

[Comparative Example 3]
A golf ball of Comparative Example 3 was obtained in the same manner as in Example except that the final mold was changed and the dimples whose specifications were shown in Table 3 below were formed. FIG. 11 is a front view showing the golf ball, and FIGS. 12 to 14 are plan views thereof. The golf ball's northern and southern hemispheres each have a pole vicinity region, an equator vicinity region, and an adjustment region. The pole vicinity region includes five units Up that are rotationally symmetric with respect to the pole P. The equator vicinity region is composed of six units Ue that are rotationally symmetric with respect to the pole P. This golf ball is disclosed in Japanese Patent Application Laid-Open No. 2007-175267.

[Flight distance test]
A driver with a titanium head (trade name “XXIO”, Sumitomo Rubber Industries, Ltd., shaft hardness: X, loft angle: 9 °) equipped with a titanium head was attached to a swing machine manufactured by Tsurutemper. A golf ball was hit under the conditions that the head speed was 49 m / sec, the launch angle was about 11 °, and the spin rate of backspin was about 3000 rpm, and the distance from the launch point to the rest point was measured. During the test, there was almost no wind. The average value of 20 measurements is shown in Table 4 below.

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

  The dimple pattern according to the present invention can be applied not only to a two-piece golf ball but also to a one-piece golf ball, a multi-piece golf ball and a thread wound golf ball.

14 ... Golf ball 16 ... Core 18 ... Cover 20 ... Dimple 22 ... Land 24 ... First latitude line 26 ... Second latitude line 28 ... Intermediate latitude line 30 ... Near pole region 32 ... Near equator region 34 ... Intermediate region 36 ... First meridian 38 ... Second meridian 40 ... Virtual sphere AG ... Dimple N ... Northern hemisphere P. ..Pole S ... Southern Hemisphere Up, Us ... Unit

Claims (9)

Each of the northern hemisphere and the southern hemisphere on the surface includes a pole vicinity region, an equator vicinity region, and an intermediate region located between the pole vicinity region and the equator vicinity region,
The pole vicinity region, the equator vicinity region, and the intermediate region each have a large number of dimples,
The dimple pattern in the pole vicinity region is composed of a plurality of units that are rotationally symmetric with respect to the pole point,
The dimple pattern in the region near the equator consists of a plurality of units that are rotationally symmetric with respect to each other around the pole,
The number Np of units in the pole vicinity region is different from the number Ne of units in the equator vicinity region,
A golf ball in which dimples included in an intermediate region are arranged substantially along one latitude line.   The golf ball according to claim 1, wherein the latitude of the latitude line is 20 ° or more and 40 ° or less.   The golf ball according to claim 2, wherein the latitude of the latitude line is substantially 30 °.   4. The golf ball according to claim 1, wherein the number Np is 3 or more and 6 or less, and the number Ne is 3 or more and 6 or less.   The golf ball according to claim 1, wherein the number Nm of dimples in the intermediate region is 18 or more and 48 or less.   The golf ball according to claim 1, wherein the number Nm of dimples in the intermediate region is a common multiple of the number Np and the number Ne.   The golf ball according to claim 1, wherein the dimples included in the intermediate region have the same diameter, and the dimples are arranged at equal intervals along the latitude line.   The number of dimples adjacent to the boundary line between the pole vicinity region and the intermediate region and included in the pole vicinity region is the same as the number of dimples arranged along the intermediate latitude line. Golf ball.   9. The number of dimples adjacent to the boundary line between the equator vicinity region and the intermediate region and included in the equator vicinity region is the same as the number of dimples arranged along the intermediate latitude line. Golf balls.

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