JPH09206407A - Golf ball - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a golf ball having excellent symmetricalness by forming a golf ball in such a manner that the symmetry indices relating to the volume, area, edge length and arrangement of dimples respectively satisfy specific conditions at the time of producing the golf ball by using a pair of split molds. SOLUTION: The central points of the respective dimples formed on the ball surface are indicated by the coordinate points (θj , ϕj ) expressed by the latitude and longitude of the ball when the part corresponding to the parting line of the metal molds for the ball surface is defined as the equator in a golf ball formed by metal molds for forming a golf ball. The dimples are so formed that the conditions of one or >=2 among the conditions Vi>1, (1.001<=Vi<=1.025), Ni>1, Li>1, Si>1 relating to the respective symmetry indices Vi, Si, Li, Ni obtd. from separate equations are satisfied when the radius of the dimples is defined as rj and the volume as vj . The surface occupying rate of the entire dimple to the ball surface is set at >=65%.

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, and in particular, the same trajectory can be obtained by striking with a pole and by striking with a seam. Regarding 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.) have a great influence on the flight characteristics of the golf ball. Various arrangement methods have been proposed in which a large number of dimples are evenly or densely arranged. 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).

However, golf balls have two
It is molded with a molding die that has a spherical cavity inside by joining the split molds that are divided into equal parts so that they can be axisymmetrically molded. The roundness is high around the pole axis corresponding to the line connecting the lines, and conversely, the roundness is around the axis existing on the surface surrounded by the seam line corresponding to the split surface of the mold. Tends to be lower. Therefore, in the conventional golf ball, due to the difference in the roundness, there may be a difference in the flight performance due to the difference in the shot position, and it is impossible to move the ball except in a special case according to the rule. In a golf game in which the player must hit the ball as it is, the variation in the flight performance becomes a serious problem.

That is, when hitting a golf ball, so-called backspin occurs in each of the clubs, although the number of rotations varies depending on the club number. In this case, as shown in FIGS. Two points c, c facing each other on the seam line b of the ball a, and a center point d
So-called pole striking f that strikes the ball a so as to generate backspin about the straight line e connecting the three points
And hitting the ball a so as to generate backspin which is orthogonal to a circular plane g having a seam line b of the ball a as a circumferential line and which has a straight line h passing through the center d of the ball a as a rotation axis.
It is roughly divided into so-called seam striking (Fig. B), but as described above, in the case of pole striking (Fig. A), since 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 the seam striking (Fig. B), since the circumference of the rotation axis h is close to a perfect circle, almost no extra lift or drag is generated on the golf ball. Therefore, the effect of the dimple is simply caused by the pole hit and the seam hit. If the golf balls are designed to be equal, the effect of dimples becomes larger when the ball is hit by the disorder of the roundness, and extra lift and drag force is generated on the golf ball, resulting in different flight performance from when hit by a seam. As a result, the flying performance varies depending on the shot location.

Therefore, in order to obtain a golf ball having excellent symmetry without variation in flight performance depending on shot locations, the dimple arrangement and 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 fully met the demand.

The present invention has been made in view of the above circumstances, and the same trajectory can be obtained by pole striking and seam striking.
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]

Means for Solving the Problems and Modes for Carrying Out the Invention In order to achieve the above-mentioned object, the present invention provides a spherical cavity inside by separably joining a pair of split molds each having a hemispherical cavity. In the golf ball molded by the mold for molding the golf ball to be formed, it is assumed that the portion of the ball surface that corresponds to the dividing line of the mold is the equator, and that both vertices sandwiching the equator are the poles, and the ball surface is formed. When the center point of each dimple is represented by coordinate points (θ _j , φ _j ) represented by the latitude (radian) and longitude of the ball, and the radius of the dimple is r _j and the volume is v _j , the following formula (1) )-(4) each symmetry index Vi,
Provided is a golf ball characterized by satisfying one or more of the following conditions (A) to (D) with respect to 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, there is no difference in the effect of the dimple between the case of hitting a pole and the case of hitting a seam. Considering that there is a difference in dimple effect between the seam striking and the seam striking, the dimple volume, area,
The dimple design itself consisting of edge length and arrangement makes the dimple effect different at the time of pole hitting and seam hitting, and the effect of the dimple itself at the time of pole hitting is easier to exert due to the low roundness It is designed so that the dimple effect is higher when the seam is hit and the dimple effect is less likely to occur than when hitting the pole, and the difference in the effect of the dimple itself is offset by the increase or decrease in the dimple effect due to the difference in roundness. As a whole, a uniform dimple effect can be obtained.

Explaining this point in more detail, each of the above symmetry indexes Vi, Si, Li, and Ni is a dimple on the seam line side of the golf ball and on both pole sides when the seam line is assumed to be the equator. This is a numerical representation of the symmetry compared to the dimple volume,
It shows symmetry with respect to area, edge length, and arrangement. In this case, when these symmetry indexes are 1, the dimple performances on the seam line side and the pole side are equal, and if each index is larger than 1, the dimple volume on the seam line side is 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, and the dimple effect at seam striking is higher than at pole striking by design, and conversely if each index is smaller than 1, seam The dimple volume is larger on the pole side than on the side, the area is large, the edge length is long, or the arrangement is biased to the pole side, and the dimple effect at the time of striking the pole is higher than that at the seam striking by design. Is. Further, in the present invention, by setting each of these symmetry indexes to be larger than 1, the dimple performance at the time of pole striking is more likely to be higher than the dimple performance at seam striking because the circularity is low and the dimple effect is likely to be high. By designing it low, the difference in dimple effect due to the dimple design offsets the increase or decrease in dimple effect due to the difference in roundness, and the same dimple effect can be achieved for both pole hits and seam hits. The symmetry property is obtained.

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 that corresponds to the mold dividing line 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 coordinate points (θ _j , φ _j ) represented by the latitude (radian) and longitude of the ball, and the radius of the dimple is r _j and the volume is v _j. Each symmetry index Vi, Si, Li, Ni
Among them, the dimples are designed so that at least one of them has a symmetry index of more than 1.

Here, the coordinate points (θ _j , φ _j ) of the respective dimples are, as described above, the portion corresponding to the parting line of the mold on the ball surface, that is, the seam line is the equator, and the two points sandwiching the equator are located. Assuming that the vertex is a pole, it is represented as latitude and longitude on the ball. In this case, θ _j shown as latitude on the ball connects the axis connecting the north pole-ball center-south pole, the dimple center position, and the ball center. The angle formed by the line is expressed in radians. Therefore, it indicates the polar coordinates that are generally used in the Northern Hemisphere. Since φ _j shown as longitude is not used in the calculation of each symmetry index, it may be expressed in a unit of ordinary degrees.

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, and particularly 2.4 to 4.1 mm. The depth is usually 0.05 to 0.3 mm, especially 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.
It is set to 25 mm ³ . Here, the golf ball of the present invention may have a plurality of types of dimples having different radii r _j , volume v _j, or both, but normally, the golf ball has 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 particularly 318.
It is preferable to set the number 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), and this volume symmetry index Vi is formed on the ball surface. It shows the symmetry between the equator (seamline) side and the both poles side of the ball with respect to the volume of the dimples, and the index Vi is 1
If so, it means that the dimple volume is evenly distributed over the entire ball, and if it is larger than 1, the dimple volume is relatively larger on the equator (seamline) side than on the both poles side and smaller than 1. If this is the case, on the contrary, the dimple volume is relatively larger on the bipolar side than on the equator (seamline) side.

[0016]

(Equation 3)

In the present invention, this volume symmetry index V
It is preferable to adjust i to a value exceeding 1, particularly 1.
Optimally, it should be 001 to 1.025. As a result, the dimple effect at the time of seam striking and at the time of pole striking becomes uniform, and the trajectory is stabilized. In this case, when the volume symmetry index Vi exceeds 1.030, the dimple effect at the time of seam striking becomes too high as compared with the dimple effect at the time of pole striking, depending on the conditions of other symmetry indices, but the dimple effect is increased. It may not be possible to make uniform.

The area symmetry index Si is obtained from the center point coordinates (θ _j , φ _j ) of each dimple and the radius r _j by the following equation (2). The area symmetry index Si is formed on the ball surface. It shows the symmetry between the equator (seamline) side and the both poles side of the ball in terms of the area of the dimples, and the index Si is 1
If so, it means that the dimple area is evenly distributed over the entire ball, and if it is larger than 1, the dimple area is relatively larger on the equator (seamline) side than on the both poles side and smaller than 1. If this is the case, on the contrary, the dimple area is relatively larger on the both poles side than on the equator (seam line) side. The dimple area means the plane area of the dimple projected onto a plane,
For example, when the plane shape of the dimple is circular, it is represented by πr ² when the radius of the dimple is r.

[0019]

(Equation 4)

In the present invention, this area symmetry index S
It is preferable to adjust i to a value exceeding 1, particularly 1.
Optimally, it should be 001 to 1.025. As a result, the dimple effect at the time of seam striking and at the time of pole striking becomes uniform, and the trajectory is stabilized. In this case, when the area symmetry index Si 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, depending on the conditions of other symmetry indices, and the dimple effect becomes greater. It may not be possible to make uniform.

The edge length symmetry index Li is
Center point coordinates of dimple (θ_j, Φ_j) And radius r_jFrom
This edge is calculated by the following equation (3).
The long symmetry index Li is the dimensional index formed on the ball surface.
The edge length of the sample is
This shows the symmetry property between the (
If the index Li is 1, dimples are made over the entire ball
The edge lengths of are evenly distributed, and
If it is large, the equator (seam line) side is more
The dimple edge length is relatively long and less than 1.
On the contrary, the opposite side is more relative than the equator (seam line) side.
It means that the edge length of the dimple is long. In addition,
The edge length of the sample is the circumference of the dimple edge.
Means, for example, when the dimple has a circular plane shape,
If 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 to adjust the edge length symmetry index Li to a value exceeding 1, and it is most preferable to set it to 1.001 to 1.025. As a result, the dimple effect at the time of seam striking and at the time of pole striking becomes 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 striking becomes too high as compared with the dimple effect at the time of pole striking, but it may not be possible to make the dimple effect uniform, although it depends on other conditions of the symmetry index.

The array symmetry index Ni is obtained by the following equation (4) from the center point coordinates (θ _j , φ _j ) of each dimple, and this array symmetry index N
i indicates the dimple arrangement formed on the surface of the ball, that is, the dimple distribution state, indicating the symmetry between the equator (seamline) side and the pole side of the ball. If this index Ni is 1, the dimples are distributed over the entire ball. Are evenly distributed, and if it is larger than 1, the dimples are distributed more disproportionately on the equator (seamline) side than on the both poles side, and if it is smaller than 1, it is the opposite. It is shown that the dimples are relatively unevenly distributed on the both pole sides than on the equator (seamline) side.

[0025]

(Equation 6)

In the present invention, this sequence symmetry index N
It is preferable to adjust i to a value exceeding 1, particularly 1.
Optimally, it should be 001 to 1.015. As a result, the dimple effect at the time of seam striking and at the time of pole striking becomes 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 striking becomes too high as compared with the dimple effect at the time of pole striking, depending on the conditions of other symmetry indices. It may not be possible to make uniform.

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, that is, By designing dimples so that at least one of each symmetry index exceeds 1, a dimple effect is adjusted so that there is no difference between seam impact and pole impact, and stable It is designed to obtain a unique trajectory. In this case, even among the dimple conditions including the volume, the area, the edge length, and the arrangement, the change in the dimple volume has a great influence on the dimple effect, and therefore at least the value of the volume symmetry index Vi is more than 1. Is preferable, and it is particularly preferable to perform the dimple design 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 at least the volume symmetry index Vi is set to a value exceeding 1, particularly 1.001 to 1.025. Even if the symmetry index Vi is 1 or less, the other condition, that is, at least one of the area symmetry index Si, the edge length symmetry index Li, and the array symmetry index Ni is set to 1
By adjusting to a value exceeding the above value, particularly the above optimum value, it is possible to exhibit the same dimple effect in both seam striking and pole striking, and to improve the ballistic symmetry and achieve the object of the present invention. Is possible enough. In the most preferred embodiment of the golf ball of the present invention, each of the above symmetry indexes Vi, Si, Li and Ni is 1
The value is adjusted to a value of more than 1, particularly the above-mentioned preferable value.

The golf ball of the present invention has the volume symmetry index Vi and the area symmetry index S as described above.
i, the edge length symmetry index Li, and the array symmetry index Ni are used as indexes to adjust the dimple effect in consideration of the distortion of the roundness of the ball, and it is not particularly limited, but balls of all dimples are further adjusted. It is preferable to design the dimples so that the surface occupancy ratio to the surface is 65% or more, particularly 65 to 75%, whereby the dimple effect is adjusted more effectively by the above symmetry indexes, and the ballistic symmetry property 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 ratio of the total dimple volume to the ball volume is not particularly limited and can be set appropriately, and is usually 0.6 to
It can be about 1.3%, particularly about 0.7 to 1.0%.

The dimples may be arranged in any known manner such as regular octahedron arrangement, regular dodecahedron arrangement, regular icosahedron arrangement, and symmetrical arrangement in which the hemisphere is divided into 1 to 7 parts 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 type, a hexagon type, a pentagon type and a triangle type.

Furthermore, the type of dimples formed on one ball surface may be one type or a mixture of two or more types of dimples. In particular, one type or 2 to 6 types of dimples should be arranged. The planar shape of the dimples is not particularly limited and may be various shapes, but it is usually preferable to use circular dimples.

The golf ball of the present invention may be any golf ball as long as the dimple design is adjusted as described above using each symmetry index as an index, and the structure of the ball is not particularly limited. One-piece golf balls and two-piece golf balls The golf ball of the present invention may be a solid golf ball such as a multi-piece golf ball having a three-layer structure or more, or a thread-wound golf ball. In this case, the golf ball of the present invention has a pair of split dies having hemispherical cavities that are separably joined. A solid golf ball or wound golf ball having two or more pieces with a cover layer formed by an injection molding method or a compression molding method using a molding die that forms a spherical cavity inside, or a similar injection molding method or compression molding method. One piece solid golf ball molded by 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 depending on 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 according to the golf rules.

[0034]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Examples 1 to 5 and Comparative Example 1] Seven kinds of two-piece solid golf balls (Examples 1 to 1) except that dimples were designed as shown in Table 1 below (Examples 1 to 5)
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, and Ni is an array symmetry index, and the dimple array of each golf ball is as shown in FIGS.

[0036]

[Table 1]

Next, for each golf ball shown in Table 1, a swing robot used a driver (# W1) as a club and a pole hit at a head speed of 45 m / sec (see FIG. 6).
By repeating the (A) striking direction) and the seam striking (the striking direction of FIG. 6B), the carry, run, and total flight distance were measured, and the trajectory was compared. Table 2 shows the results. All units are meters (m).

[0038]

[Table 2]

As shown in Table 2, the results of the batting test were as follows: (1) In Comparative Example 1, the ball hit was higher in the pole hit than in the seam hit, and the carry and the total flight distance were different. Also, apparently, the ball trajectory was different between a pole hit and a seam hit. (2) In the balls of Examples 1 and 2, the volume symmetry index Vi was adjusted to a value exceeding 1 by increasing the dimple volume of the pole portion and the peripheral portion of the seam portion. The ball hit of the pole hit was slightly higher than that of the seam hit, but the flight distance was almost the same and good symmetry was shown. (3) The ball of Example 3 has each symmetry index (N
All of i, Li, Si, and Vi) are adjusted to a suitable value exceeding 1, and the ball has no difference in trajectory between pole hits and seam hits and exhibits excellent symmetry. (4) The ball of Example 1 and the ball of Comparative Example 1 are substantially the same except that the volume symmetry index Vi is different. However, the ball of Comparative Example 1 has a clearly different ball trajectory depending on the hitting direction. Although there was a difference in flight distance, the ball of Example 1 had almost no difference in trajectory and no difference in flight distance. Therefore, it was confirmed that the volume symmetry index Vi is an important factor for improving the symmetry property. (5) The balls of Example 4 and Example 5 were prepared by adjusting two conditions including the volume symmetry index Vi among the respective symmetry indexes (Ni, Li, Si, Vi) to optimum values, and both of them were excellent. It had a symmetry property. (6) The ball of Example 2 was slightly inferior in flight distance because the surface occupancy rate was 65% or less.

From the above results, the golf ball of the present invention is a golf ball excellent in symmetry, in which the same trajectory can be obtained by pole hitting and seam hitting, and the flying performance does not vary depending on the shot location. It was confirmed that there is.

[0041]

As described above, according to the present invention,
Correcting the difference in the trajectory depending on the hit location due to the difference in the roundness of the ball, and surely obtaining a golf ball with excellent symmetry that does not cause the inconvenience that the flight characteristics differ depending on the hit location. Is something that can be done.

[Brief description of drawings]

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

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

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

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

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

6A and 6B are explanatory views for explaining a hitting direction when a golf ball is shot, in which FIG. 6A shows a pole hit and FIG. 6B shows a seam hit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Michio Inoue 20 Onohara, Chichibu City, Saitama Prefecture, within Bridgestone Sports Co., Ltd. (72) Inventor Hiroshi Masutani 20, Onohara, Chichibu City, Saitama Prefecture, within Bridgestone Sports Co., Ltd.

Claims (6)

[Claims] 1. A golf ball molded by a mold for molding a golf ball, wherein a pair of split molds having hemispherical cavities are separably joined to each other to form a spherical cavity therein. Assuming that the part corresponding to the parting line of the mold is the equator and both vertices sandwiching the equator are poles, the center point of each dimple formed on the surface of the ball is the coordinate point (θ) representing the latitude (radian) and longitude of the ball.
_j , φ _j ) and the radius of the dimple is r _j ,
When the volume is v _j , one or more of the following conditions (A) to (D) are satisfied for each symmetry index Vi, Si, Li, Ni obtained from the following formulas (1) to (4). 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, which satisfies at least the condition (A) among the above conditions (A) to (D). 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, which satisfies all the above conditions (A) to (D). 5. The golf ball according to claim 1, wherein the value of Vi is in the range of 1.001 to 1.025. 6. The surface occupancy ratio of all the dimples to the ball surface is 65% or more, according to any one of claims 1 to 5.
A golf ball according to the item.