JP2910707B2 - Golf ball - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf ball having excellent symmetry properties, and more particularly, to a golf ball having the same trajectory as a pole hit and a seam hit, having excellent aerodynamic performance without variation in flight performance depending on a shot location. Related to golf balls.

[0002]

2. Description of the Related Art In a golf ball, the dimple arrangement and dimple shape (diameter, depth, cross-sectional shape, etc.) greatly affect the flight characteristics of the golf ball. Various methods of arranging many dimples evenly or densely have been proposed. Conventionally, as such a dimple arrangement method, a regular polyhedral arrangement and a hemisphere are positioned 1 to 1 from the center thereof.
A method of dividing into seven equal parts is known, and in particular, a method of dividing into three to six equal parts is common.

[0003] Further, the effective total volume of the dimples is substantially the same between the case where the dimple shape is adjusted and the golf ball is hit with the pole (the rotation axis is the equatorial plane) and the case where the golf ball is hit with the seam (the line where the rotation axis connects the pole). Attempts have been made to achieve the following (Japanese Patent Publication No. 6-7875).

[0004] However, golf balls have two
It is molded by a molding die that has a spherical cavity formed inside by joining the split molds that can be split in a separable manner. Roundness increases around the pole axis corresponding to the line connecting the, and conversely, roundness increases around the axis existing on the surface surrounded by the seam line corresponding to the mold split surface. Tends to be lower. For this reason, a conventional golf ball may have a difference in flight performance due to a difference in shot position due to a difference in roundness, and the ball cannot be moved except in a special case according to rules. In a golf game in which the ball must be hit with the ball as it is, the variation in the flying performance becomes a serious problem.

That is, when a golf ball is hit, a so-called backspin occurs regardless of the number of revolutions of the club depending on the club number. In this case, as shown in FIGS. Two points c and c facing each other on the seam line b of the ball a and a center point d
A so-called pole hit which hits the ball a so as to generate a backspin with the rotation axis being the straight line e connecting the three points (FIG. A)
And strikes the ball a so as to generate a backspin that is orthogonal to a circular plane g having a seam line b of the ball a as a circumferential line and having a rotation axis as a straight line h passing through the center d of the ball a.
However, as described above, in the case of the above-described pole hit (see FIG. A), since the circumference of the rotation axis e is not a perfect circle, it is easy to receive extra lift and drag.
On the other hand, in the case of seam striking (FIG. B), since the rotation around the rotation axis h is close to a perfect circle, there is almost no extra lift or drag on the golf ball. When designed to be equal to each other, the effect of dimples is greater in the case of pole hit due to disorder in roundness, and extra lift and drag is generated on the golf ball, and the flight performance is different from that in the case of seam hit As a result, the flight performance varies depending on the shot location.

Accordingly, in order to obtain a golf ball excellent in symmetry without variation in flight performance depending on the shot location, the dimple arrangement and the dimple shape are designed in consideration of the ball shape, that is, the roundness of the ball. Although it is desired to optimize the dimple effect, it has not yet sufficiently met the demand.

The present invention has been made in view of the above circumstances, and the same trajectory can be obtained by pole hitting and seam hitting.
An object of the present invention is to provide a golf ball excellent in symmetry without causing variation in flight performance depending on a shot location.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a pair of split molds having hemispherical cavities which are separably joined to form a spherical cavity therein. In the golf ball molded by the golf ball molding die to be formed, a portion of the ball surface corresponding to the dividing line of the die is assumed to be an equator, and both vertexes sandwiching the equator are poles, and formed on the ball surface. When the center point of each dimple is indicated by coordinate points (θ _j , φ _j ) represented by the ball's latitude (radian) and longitude, and the radius of the dimple is r _j and the volume is v _j , the following equation (1) ) To (4) each symmetry index Vi,
A golf ball characterized by satisfying one or more of the following conditions (A) to (D) for Si, Li, and Ni.

[0009]

(Equation 2) [Conditions] (A) Vi> 1, preferably 1.001 ≦ Vi ≦ 1.0
25 (B) Ni> 1 (C) Li> 1 (D) Si> 1

That is, in the golf ball of the present invention, in order to prevent a difference in the effect of the dimple between the case of hitting the pole and the case of hitting the seam, the golf ball according to the present invention has the following advantages. In consideration of the difference in the dimple effect between when and when the seam strikes, the dimple volume, area,
The dimple design itself consisting of the edge length and the arrangement makes the dimple effect different between when hitting a pole and when hitting a seam, and the effect of the dimple itself when hitting a pole is easier because the dimple effect is more likely to be exhibited due to low roundness Is low, and the effect of the dimple itself is high when the seam strikes where the dimple effect is unlikely to occur when hitting the pole.The difference in the effect of the dimple itself is offset by the increase and decrease in the dimple effect due to the difference in roundness described above. Thus, a uniform dimple effect can be obtained as a whole.

More specifically, the above-mentioned symmetry indices Vi, Si, Li, and Ni are all dimples on the seam line side of the golf ball and on both pole sides when the seam line is assumed to be the equator. It is a numerical comparison of the symmetry, the volume of the dimple,
This shows the symmetry of the area, edge length, and arrangement. In this case, when these symmetry indices become 1, the dimple performances on the seam line side and the pole side become equal, and when each index is larger than 1, the dimple volume on the seam line side becomes larger than that on the pole side. , The area is large, the edge length is long, or the arrangement is biased toward the seam side. In design, the dimple effect at the time of seam strike is higher than at the time of pole strike, and conversely, if each index is smaller than 1, seam The dimple volume on the pole side is larger than the side, the area is large, the edge length is long, or the arrangement is biased to the pole side, so that the dimple effect at the time of hitting the pole is higher than that at the time of seam hitting by design It is. In the present invention, by setting each of these symmetry indices to be larger than 1, the dimple performance at the time of a pole hit, which tends to increase the dimple effect due to low roundness, is more than the dimple performance at the time of a seam hit. Also, by setting it low in the design, the difference in dimple effect in the dimple design offsets the increase and decrease in dimple effect due to the difference in roundness, and the same dimple effect is exerted on both pole hits and seam hits, resulting in good trajectory This is to achieve symmetry.

Hereinafter, the present invention will be described in more detail.
As described above, the golf ball of the present invention assumes that the portion of the ball surface corresponding to the dividing line of the mold is the equator, and that both vertices sandwiching the equator are poles, and the center point of each dimple formed on the ball surface is The coordinates are represented by the coordinates (θ _j , φ _j ) represented by the ball's latitude (radian) and longitude, and the radius of the dimple is r _j and the volume is v _j, and is obtained by the above equations (1) to (4). Each symmetry index Vi, Si, Li, Ni
Among them, the dimples are designed such that at least one of the symmetry indexes has a value exceeding 1.

As described above, the coordinate point (θ _j , φ _j ) of each dimple is defined as a portion corresponding to the dividing line of the mold on the ball surface, that is, the seam line is defined as the equator, and the two points sandwiching the equator are defined. Assuming that the vertex is a pole, it is expressed as latitude and longitude on the ball.In this case, θ _j indicated as latitude on the ball connects an axis connecting the north pole, the ball center and the south pole, the dimple center position, and the ball center. The angle formed by the line is expressed in radians. Therefore, in the Northern Hemisphere, it refers to commonly used polar coordinates. It should be noted that since φ _j shown as longitude is not used in the calculation of each of the above-mentioned symmetry indices, it may be expressed in a normal degree unit.

The dimple radius r _j is expressed in mm and is not particularly limited. Usually, the dimple diameter is 2.0 to 4.5 mm, particularly 2.4 to 4.1 mm. The depth is usually 0.05 to 0.3 mm, particularly 0.08 to 0.24 mm. Further, the dimple volume v _j is represented by mm ³ and is not particularly limited, but is usually 0.3 to 1.5 mm ³ , particularly 0.4 to 1.
25 mm ³ . Here, the golf ball of the present invention may have a plurality of types of dimples having different radii r _j , volumes v _j or both, but usually a golf ball having 1 to 6 types of dimples. It is possible,
The total number of dimples is not particularly limited and can be appropriately selected, but is usually 240 to 620, and especially 318.
Preferably, the number is up to 500.

The volume symmetry index Vi is obtained from the coordinates (θ _j , φ _j ) of the center point of each dimple and the volume v _j by the following equation (1). The volume symmetry index Vi is formed on the ball surface. The dimple volume indicates the symmetry between the ball's equator (seam line) side and both poles.
If it is, the dimple volume is uniformly distributed over the entire ball, and if it is larger than 1, the dimple volume is relatively larger on the equator (seam line) side than on both pole sides and smaller than 1. On the contrary, it indicates that the dimple volume is relatively larger on the both poles side than on the equator (seam line) side.

[0016]

(Equation 3)

In the present invention, the volume symmetry index V
It is preferable that i is adjusted to a value exceeding 1;
It is optimal to set 001 to 1.025. As a result, the dimple effect at the time of striking the seam and striking the pole is made uniform, and the trajectory is stabilized. In this case, if the volume symmetry index Vi exceeds 1.030, the dimple effect at the time of seam impact becomes too high as compared with the dimple effect at the time of pole impact, and the dimple effect is reduced, depending on other conditions of the symmetry index. In some cases, uniformity cannot be obtained.

The area symmetry index Si is obtained by the following equation (2) from the coordinates (θ _j , φ _j ) of the center point of each dimple and the radius r _j . The area symmetry index Si is formed on the ball surface. This indicates the symmetry between the equator (seamline) side of the ball and both poles, and the index Si is 1
If it is, the dimple area is uniformly distributed over the entire ball, and if it is larger than 1, the dimple area is relatively larger on the equator (seam line) side than on both pole sides and smaller than 1. On the contrary, it indicates that the dimple area is relatively larger on the both poles side than on the equator (seam line) side. In addition, the dimple area means the plane area when the dimple is projected on a plane,
For example, when the plane shape of the dimple is circular, the radius of the dimple is represented by r, which is represented by πr ² .

[0019]

(Equation 4)

In the present invention, the area symmetry index S
It is preferable that i is adjusted to a value exceeding 1;
It is optimal to set 001 to 1.025. As a result, the dimple effect at the time of striking the seam and striking the pole is made uniform, and the trajectory is stabilized. In this case, if the area symmetry index Si exceeds 1.030, the dimple effect at the time of seam impact becomes too high compared with the dimple effect at the time of pole impact, and the dimple effect is reduced, depending on other conditions of the symmetry index. In some cases, uniformity cannot be obtained.

The edge length symmetry index Li is given by
Center point coordinates of dimple (θ_j, Φ_j) And radius r_jFrom
This edge is obtained by the following equation (3).
The long symmetry index Li is the
For the edge length of the sample,
This shows the symmetry between the two sides.
If the index Li is 1, dimples over the entire ball
Edge lengths are uniformly distributed, so that
If it is large, the equator (seam line) side is better than the polar side
The edge length of the dimple is relatively long and smaller than 1.
Conversely, the polar side is more relative to the equator (seam line) side
This indicates that the edge length of the dimple is long. In addition,
The edge length of the dimple is the circumference of the dimple edge
Means, for example, when the dimple is a plane circular shape,
Assuming that the radius of the dimple is r, the edge length of the dimple is
2πr It is represented by

[0022]

(Equation 5)

In the present invention, it is preferable that the edge length symmetry index Li is adjusted to a value exceeding 1, and it is most preferable that the edge length symmetry index Li be 1.001 to 1.025. As a result, the dimple effect at the time of striking the seam and striking the pole is made uniform, and the trajectory is stabilized. In this case, the edge length symmetry index Li is 1.03.
If it exceeds 0, the dimple effect at the time of seam impact may be too high as compared with the dimple effect at the time of pole impact, and it may not be possible to equalize the dimple effect, although it depends on other conditions of the symmetry index.

The array symmetry index Ni is obtained from the coordinates (θ _j , φ _j ) of the center point of each dimple by the following equation (4).
i indicates the symmetry of the dimple array formed on the ball surface, that is, the dimple distribution state, between the equator (seam line) side and both pole sides of the ball. Are distributed uniformly, so that if it is larger than 1, the dimples are relatively biased on the equator (seam line) side than on both poles, and if it is smaller than 1, the dimples are reversed. Fig. 3 shows that dimples are distributed more deviated on both pole sides than on the equator (seam line) side.

[0025]

(Equation 6)

In the present invention, the sequence symmetry index N
It is preferable that i is adjusted to a value exceeding 1;
It is optimal to set 001 to 1.015. As a result, the dimple effect at the time of striking the seam and striking the pole is made uniform, and the trajectory is stabilized. In this case, when the array symmetry index Ni exceeds 1.020, the dimple effect at the time of seam impact becomes too high compared to the dimple effect at the time of pole impact, and the dimple effect is reduced, depending on other conditions of the symmetry index. In some cases, uniformity cannot be obtained.

In the golf ball of the present invention, at least one of the volume symmetry index Vi, the area symmetry index Si, the edge length symmetry index Li, and the array symmetry index Ni has the above-mentioned preferable value. By designing the dimple so that at least one of the symmetry indices becomes a value exceeding 1, the dimple effect is adjusted so that there is no difference between the seam strike and the pole strike, and stable. It is intended to obtain a good trajectory. In this case, among the dimple conditions including the volume, the area, the edge length, and the arrangement, particularly, a change in the dimple volume has a large effect on the dimple effect. Therefore, at least the value of the volume symmetry index Vi is a value exceeding 1. It is particularly preferable to design the dimple so that the value of the volume symmetry index Vi is 1.001 to 1.025.

As described above, in the present invention, it is preferable that the volume symmetry index Vi be at least a value exceeding 1 and particularly set to 1.001 to 1.025, but the present invention is not necessarily limited to this. Even if the symmetry index Vi is 1 or less, other conditions, that is, at least one condition of the area symmetry index Si, the edge length symmetry index Li, and the array symmetry index Ni are set to 1
By adjusting to a value exceeding, especially the above-mentioned optimum value, the same dimple effect can be exerted in both seam hitting and pole hitting, and the object of the present invention is achieved by improving ballistic symmetry. Is possible. In the most preferred embodiment of the golf ball of the present invention, each of the symmetry indices Vi, Si, Li, and Ni is 1
, Particularly adjusted to the above-mentioned preferable value.

As described above, the golf ball of the present invention has the volume symmetry index Vi and the area symmetry index S
i, the edge length symmetry index Li, and the array symmetry index Ni are used as indices to adjust the dimple effect in consideration of the distortion of the roundness of the ball. The dimple effect is not particularly limited. It is preferable to design the dimples so that the surface occupation ratio with respect to the surface is 65% or more, particularly 65 to 75%, whereby the adjustment of the dimple effect by each of the above-mentioned symmetry indices is more effectively performed, and the ballistic symmetry is improved. A good golf ball can be obtained more reliably, and the flight distance can be increased. Here, the area of the dimple is the plane area of the dimple as described above. The volume occupancy of the total dimple volume with respect to the ball volume is not particularly limited and can be set as appropriate.
It can be about 1.3%, especially about 0.7 to 1.0%.

The dimples may be arranged in a known manner such as an octahedral array, a dodecahedral array, a icosahedral array, or a symmetrical array in which a hemisphere is equally divided by 1 to 7 from its center. Further, the pattern formed on the ball surface by the arrangement of the dimples can be various patterns such as a square shape, a hexagon shape, a pentagon shape, and a triangle shape.

Further, the kind of dimples formed on the surface of one ball may be one kind or a mixture of two or more kinds of dimples. In particular, one kind or two to six kinds of dimples are arranged. The shape of the dimple is not particularly limited, and may be various shapes. Usually, a circular dimple is preferable.

The golf ball of the present invention may be any one in which the design of the dimple is adjusted as described above using the above-mentioned respective symmetry indices as an index, and the structure of the ball is not particularly limited. One-piece golf balls, two-piece golf balls It may be a solid golf ball such as a multi-piece golf ball having a three-layer structure or a thread-wound golf ball. In this case, the golf ball of the present invention is capable of separating a pair of split molds having hemispherical cavities. Solid golf ball or thread-wound golf ball of two or more pieces having a cover layer formed by an injection molding method or a compression molding method using a molding die for forming a spherical cavity therein, or a similar injection molding method or a compression molding method Around the pole axis, such as one-piece solid golf balls The difference in roundness between about the axis on surrounded by emission surface is applied to a golf ball occurs.

When the golf ball of the present invention is manufactured, it can be manufactured by a known method using a known material according to the ball structure such as a solid golf ball and a thread wound golf ball. Further, the ball properties such as the diameter and weight of the ball can be appropriately set in accordance with the Rules of Golf.

[0034]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples 1 to 5 and Comparative Example 1] Seven types of two-piece solid golf balls (Examples 1 to 5) were the same except that the design of the dimple was as shown in Table 1 below.
5, Comparative Example 1) was produced by a known method. In Table 1, Vi is a volume symmetry index, Si is an area symmetry index, Li is an edge length symmetry index, Ni is an array symmetry index, and the dimple arrangement of each golf ball is as shown in FIGS.

[0036]

[Table 1]

Next, for each golf ball shown in Table 1, a golf ball was hit with a swing robot using a driver (# W1) as a club at a head speed of 45 m / sec (FIG. 6).
The hitting direction (A) and the seam hitting (the hitting direction in FIG. 6B) were repeated to measure carry, run, and total flight distance, and to compare the trajectories. Table 2 shows the results. All units are meters (m).

[0038]

[Table 2]

As shown in Table 2, the results of the impact test were as follows. (1) In Comparative Example 1, the ball hit was higher in the case of the pole hit than in the case of the seam hit, and the carry and the total flight distance were different. Also, the ball trajectory was clearly different between the pole hit and the seam hit. (2) In the balls of Example 1 and Example 2, the volume symmetry index Vi was adjusted to a value exceeding 1 by increasing the dimple volume around the pole portion and the seam portion. The ball striking the pole hit slightly higher than the seam striking, but the flight distance was almost the same, indicating good symmetry. (3) The balls of Example 3 had respective symmetry indices (N
i, Li, Si, and Vi) were all adjusted to suitable values exceeding 1, and the ball showed no trajectory difference between pole hit and seam hit, and showed excellent symmetry. (4) The ball of Example 1 and the ball of Comparative Example 1 are almost the same except for the volume symmetry index Vi, but the ball trajectory of Comparative Example 1 is obviously different depending on the hitting direction. In the ball of Example 1, there was almost no difference in trajectory, and there was no difference in flight distance. Therefore, it was recognized that the volume symmetry index Vi is an important factor for improving the symmetry property. (5) In the balls of Example 4 and Example 5, two conditions including the volume symmetry index Vi among the respective symmetry indices (Ni, Li, Si, Vi) were adjusted to optimal values, and both were good. It had symmetry properties. (6) Since the ball of Example 2 had a surface occupancy of 65% or less, the flight distance was slightly inferior.

From the above results, the golf ball of the present invention can provide the same trajectory for the ball hitting and the seam hitting, and has excellent symmetry without causing variation in flying performance depending on the shot location. It was confirmed that there was.

[0041]

As described above, according to the present invention,
Correcting the difference in trajectory at the hit location due to the difference in the roundness of the ball, and reliably obtaining a golf ball with excellent symmetry without causing inconvenience such as a difference in flight characteristics depending on the hit location. Can be done.

[Brief description of the drawings]

FIG. 1 is a diagram showing dimple arrangement patterns of golf balls of Example 1 and Comparative Example 1.

FIG. 2 is a dimple arrangement pattern diagram of the golf ball of Example 2.

FIG. 3 is a diagram showing a dimple arrangement pattern of the golf ball of Example 3;

FIG. 4 is a diagram showing a dimple arrangement pattern of the golf ball of Example 4;

FIG. 5 is a diagram showing a dimple arrangement pattern of the golf ball of Example 5;

FIGS. 6A and 6B are explanatory diagrams illustrating a hitting direction when a golf ball is shot, wherein FIG. 6A shows a pole hit and FIG. 6B shows a seam hit;

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Michio Inoue 20th Ohnohara, Chichibu City, Saitama Prefecture Inside Bridgestone Sports Co., Ltd. (72) Inventor Hiroshi Masutani 20th Onohara, Chichibu City, Saitama Prefecture 20th Bridgestone Sports Corporation (58) Field surveyed (Int. Cl. ⁶ , DB name) A63B 37/00

Claims (6)

(57) [Claims] 1. A golf ball formed by a golf ball molding die in which a pair of split molds having hemispherical cavities are separably joined to form a spherical cavity therein, wherein the metal on the surface of the ball is formed. Assuming that the portion corresponding to the dividing line of the mold is the equator and the vertices sandwiching the equator are the poles, the center point of each dimple formed on the ball surface is represented by the coordinate point (θ) represented by the ball's latitude (radian) and longitude.
_j , φ _j ) and the radius of the dimple is r _j ,
Assuming that the volume is v _j , for each symmetry index Vi, Si, Li, Ni obtained from the following equations (1) to (4), one or two or more of the following conditions (A) to (D) are used. A golf ball characterized by satisfying. (Equation 1) [Conditions] (A) Vi> 1 (B) Ni> 1 (C) Li> 1 (D) Si> 1 2. The golf ball according to claim 1, wherein at least one of the conditions (A) to (D) is satisfied. 3. The golf ball according to claim 2, wherein the condition (A) is satisfied and at least one of the conditions (B) to (D) is satisfied. 4. The golf ball according to claim 3, wherein all of the conditions (A) to (D) are satisfied. 5. The golf ball according to claim 1, wherein the value of Vi is in a range of 1.001 to 1.025. 6. The method according to claim 1, wherein a surface occupation ratio of all dimples to the ball surface is 65% or more.
A golf ball according to the item.