JP2024065522A - Golf ball - Google Patents

Abstract

[Solution] A dimple (12) formed on a golf ball (10) has a bottom surface (14), an opening periphery (16), and an inner wall portion (18) that tapers from the opening periphery toward the bottom surface. The bottom surface has a first bottom surface portion (20) that is the diametrically inner portion, and a second bottom surface portion (22) that is the diametrically outer portion. The intersection angle θ1 between a first imaginary horizontal line (M1) passing through the opening periphery and the inner wall portion is 3° to 62°. The shortest distance d2 between the shallowest part (DS) of the second bottom surface portion and the first imaginary horizontal line is 30% to 70% of the shortest distance d1 between the deepest part (DM) of the first bottom surface portion and the first imaginary horizontal line. [Selected Figure] Figure 2

Description

The present invention relates to a golf ball with dimples on its surface.

A number of dimples are formed on the surface of a golf ball to stabilize the flight trajectory when the ball is hit and to increase the flight distance. A typical dimple is shaped like a small notch carved out of the surface of a golf ball, but recently, various studies have been conducted on the shape of dimples in order to further increase the flight distance.

For example, Patent Document 1 proposes a dimple shape in which, in a cross section along the depth direction, a curved portion formed on the central side and an inclined straight portion formed on the peripheral side appear. Here, the straight portion has a first straight portion that continues to the curved portion, and a second straight portion that continues to the end of the first straight portion on the peripheral side. The inclination of the second straight portion with respect to the surface of the golf ball is greater than the inclination of the first straight portion with respect to the surface of the golf ball.

JP 2003-79763 A

In a shot using a driver club (driver shot), if the spin rate of the golf ball is too high, the trajectory will be what is called a "flying trajectory." In this case, the flight distance of the golf ball may decrease. Conversely, in a shot using a short iron or wedge club (approach shot), if the spin rate of the golf ball is too low, it is not easy to stop the golf ball at or near the target point.

Therefore, there is a demand for a golf ball that provides sufficient flight distance on driver shots and is easy to stop at or near the intended point on approach shots.

The present invention aims to solve the above-mentioned problems.

According to one embodiment of the present invention, in a golf ball having dimples on its surface, the dimples have a bottom surface having a first diameter, an opening periphery formed by the periphery of a circular opening and having a second diameter larger than the first diameter, and an inner wall portion extending from the opening periphery toward the bottom surface and inclining in a tapered manner when viewed along the depth direction of the dimple, and the bottom surface has a first bottom surface portion that forms a diametrically inner portion of the bottom surface and is curved in an arc shape when viewed along the depth direction of the dimple, and a second bottom surface portion that is located diametrically outward of the first bottom surface portion and forms a diametrically outer portion of the bottom surface and extends linearly when viewed along the depth direction of the dimple. The first diameter is 80% to 95% of the second diameter, and a first imaginary horizontal line passing through the periphery of the opening and a second imaginary horizontal line passing through the intersection of the first bottom surface portion and the second bottom surface portion and parallel to the first imaginary horizontal line are drawn, and the intersection angle between the inner wall portion and the first imaginary horizontal line is θ1 and the intersection angle between the second bottom surface portion and the second imaginary horizontal line is θ2, where θ1 is in the range of 3° to 62° and θ1>θ2, and where d1 is the shortest distance between the deepest part of the first bottom surface portion and the first imaginary horizontal line and d2 is the shortest distance between the shallowest part of the second bottom surface portion and the first imaginary horizontal line, d2 is 30% to 70% of d1.

A golf ball with the dimensions of the dimples set as described above provides sufficient distance for driver shots. This golf ball also rotates with a sufficient amount of spin for approach shots. Therefore, it is easy to stop the golf ball at or near the target point for approach shots.

FIG. 1 is a schematic overall plan view of a golf ball according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view taken along the depth direction of a dimple. FIG. 3 is a schematic cross-sectional view taken along the depth direction of a dimple having a peripheral wall portion. FIG. 4 is a chart showing the dimensions of the dimples on the golf ball of Example 1. FIG. 5 is a chart showing the dimensions of the dimples on the golf ball of Example 2. 6A and 6B are graphs showing the results obtained by the hitting test for the golf balls of Examples 1 and 2 and the Comparative Example.

In the following explanation, the distance refers to the sum of the distance from the shot point to the landing point when the golf ball is hit (carry) and the distance from the landing point to the stopping point (run).

Figure 1 is a schematic overall plan view of a golf ball 10 according to this embodiment. The golf ball 10 has a number of dimples 12 on its surface. The dimples 12 are recesses recessed from the surface of the golf ball 10, and open in a circular shape on the surface of the golf ball 10. Each dimple 12 has a bottom surface 14, an opening periphery 16 formed by the periphery of the opening, and an inner wall portion 18. When a player views the golf ball 10 from above in the depth direction, the dimples 12 are visible. At this time, the bottom surface 14 and the opening periphery 16 are circular.

Figure 2 is a schematic cross-sectional view of the dimple 12 cut along the depth direction. As can be seen from Figure 2, the bottom surface 14 of the dimple 12 has a bottom diameter ΦB as a first diameter. The opening rim 16 of the dimple 12 has an opening diameter ΦA as a second diameter. The bottom diameter ΦB is smaller than the opening diameter ΦA. However, if the bottom diameter ΦB is excessively small compared to the opening diameter ΦA, the ball is likely to fly upwards on a driver shot, resulting in a reduced flight distance. Also, the amount of spin on the golf ball 10 may be insufficient on an approach shot. To avoid this, the bottom diameter ΦB is set to a length that is 80% to 95% of the opening diameter ΦA.

The opening diameter ΦA is preferably within the range of 3.0 mm to 5.5 mm. If the opening diameter ΦA is 5.0 mm, the bottom diameter ΦB is, for example, 4.6 mm.

The bottom diameter ΦB and opening diameter ΦA of all dimples 12 do not necessarily have to be the same. In this embodiment, the dimples 12 include a first dimple 12a to a fifth dimple 12e, each of which has a different opening diameter ΦA, as shown in FIG. 1. However, the first dimple 12a to the fifth dimple 12e all have the shape shown in FIG. 2.

The opening diameter ΦA decreases in the order of the first dimple 12a, the second dimple 12b, the third dimple 12c, the fourth dimple 12d, and the fifth dimple 12e. Examples of the opening diameters ΦA of the first dimple 12a to the fifth dimple 12e are 5.0 mm, 4.8 mm, 4.5 mm, 4.2 mm, and 3.5 mm, respectively. In this case, the ratio of each bottom diameter ΦB to each opening diameter ΦA of the first dimple 12a to the fifth dimple 12e is, for example, 92.0%, 91.7%, 91.1%, 90.5%, and 88.6%. Also, examples of the numbers of the first dimples 12a, the second dimples 12b, the third dimples 12c, the fourth dimples 12d, and the fifth dimples 12e are, for example, 80, 40, 130, 10, and 12, respectively.

The opening diameter ΦA and number of each of the first dimples 12a to the fifth dimples 12e are not particularly limited to the above values. In addition, the number of dimples 12 having an opening diameter ΦA different from that of the first dimples 12a to the fifth dimples 12e may be increased. Alternatively, one or more types of dimples from the first dimples 12a to the fifth dimples 12e may be omitted.

As shown in FIG. 2, the bottom surface 14 of the dimple 12 has a first bottom surface portion 20 and a second bottom surface portion 22. The first bottom surface portion 20 forms the diametrically inner portion of the bottom surface 14. The first bottom surface portion 20 is curved in an arc shape when viewed along the depth direction of the dimple 12. The first bottom surface portion 20 has a radius of curvature R. The radius of curvature R is set to be smaller in the order of the first dimple 12a to the fifth dimple 12e, for example. The deepest part DM is the most recessed part of the first bottom surface portion 20.

The opening diameter ΦA of the dimple 12 is preferably within the range of 18% to 50% of the radius of curvature R, and more preferably within the range of 25% to 45% of the radius of curvature R. In a typical example, the radii of curvature R of the first dimple 12a to the fifth dimple 12e are 17.4 mm, 16.0 mm, 14.1 mm, 12.2 mm, and 8.6 mm, respectively. When the opening diameter ΦA of the first dimple 12a to the fifth dimple 12e is the above-mentioned numerical value, the opening diameter ΦA of the first dimple 12a is 28.7% of the radius of curvature R. Also, the opening diameter ΦA of the second dimple 12b to the fifth dimple 12e is 29.9%, 32.0%, 34.4%, and 40.6% of the radius of curvature R, respectively.

The second bottom surface portion 22 forms the diametrically outer portion of the bottom surface 14. That is, the second bottom surface portion 22 surrounds the first bottom surface portion 20. The second bottom surface portion 22 extends linearly when viewed along the depth direction of the dimple 12. The bottom diameter ΦB is the diameter of a circle passing through the shallowest portion DS of the second bottom surface portion 22.

The first bottom surface portion 20 and the second bottom surface portion 22 intersect at an intersection point A. Here, a virtual horizontal line that passes through the intersection point A and is drawn parallel to the first virtual horizontal line M1 is defined as a second virtual horizontal line M2. Note that the first virtual horizontal line M1 is a virtual horizontal line that passes through the opening periphery 16.

The shortest distance between the deepest part DM of the first bottom surface portion 20 and the first virtual horizontal line M1 is defined as the first distance d1. In this embodiment, the first distance d1 is preferably within the range of 0.10 mm to 0.20 mm. In a typical example, the first distance d1 in the first dimple 12a to the fourth dimple 12d is 0.130 mm, and the first distance d1 in the fifth dimple 12e is 0.125 mm.

The shortest distance between the shallowest part DS of the second bottom surface part 22 and the first virtual horizontal line M1 is the second distance d2. If the second distance d2 is too small, it is not easy to prevent the golf ball 10 from flying up in a driver shot. Also, the amount of spin may be insufficient in an approach shot. For this reason, it is preferable to set the second distance d2 within a range of 30% to 70% of the first distance d1. In a typical example, the second distance d2 is set to 0.085 mm in the first dimple 12a to the fifth dimple 12e. As described above, when the first distance d1 in the first dimple 12a to the fourth dimple 12d is 0.130 mm and the first distance d1 in the fifth dimple 12e is 0.125 mm, the second distance d2 in the first dimple 12a to the fourth dimple 12d is 65.4% of the first distance d1. For the fifth dimple 12e, the second distance d2 is 68.0% of the first distance d1.

The inner wall portion 18 is the inner peripheral wall of the dimple 12 and extends from the opening periphery 16 toward the shallowest part DS of the second bottom surface portion 22. The inner wall portion 18 tapers from the opening periphery 16 toward the shallowest part DS of the second bottom surface portion 22. In other words, when the dimple 12 is viewed along the depth direction, the inner wall portion 18 is inclined in a tapered manner.

The intersection angle between the inner wall portion 18 and the first virtual horizontal line M1 is the first angle θ1. If the first angle θ1 is too small, the amount of spin of the golf ball 10 may be insufficient on an approach shot. If the first angle θ1 is too large, the trajectory of the golf ball 10 may be low, resulting in an insufficient flight distance. To avoid this, it is preferable that the first angle θ1 be within the range of 3° to 62°. A more preferable range for the first angle θ1 is 15° to 25°.

The intersection angle between the second bottom surface portion 22 and the second virtual horizontal line M2 is the second angle θ2. The relationship θ1>θ2 holds between the first angle θ1 and the second angle θ2. If the second angle θ2 is excessively large, it is not easy to improve the flight distance. Also, the amount of spin of the golf ball 10 may be insufficient on approach shots. To avoid this, it is preferable that the second angle θ2 is within the range of 0.2° to 6.0°. A more preferable range for the second angle θ2 is 0.5° to 2.0°.

A golf ball 10 having dimples 12 (first dimple 12a to fifth dimple 12e) with the opening diameter ΦA, bottom diameter ΦB, ΦB/ΦA, first distance d1, second distance d2, d2/d1, radius of curvature R of the first bottom surface portion 20, first angle θ1, and second angle θ2 set as described above provides a sufficient flight distance on driver shots. Furthermore, this golf ball 10 rotates with a sufficient amount of spin on approach shots. This makes it easy to stop the golf ball 10 at or near the target point.

As shown in FIG. 3, a peripheral wall portion 30 may be interposed between the second bottom surface portion 22 and the inner wall portion 18. The peripheral wall portion 30 in FIG. 3 is bent so as to intersect with the second bottom surface portion 22 and the inner wall portion 18 at a predetermined angle. However, the peripheral wall portion 30 is not particularly limited to this shape. For example, the peripheral wall portion 30 may be a curved portion with an extremely small radius of curvature. In either case, the peripheral wall portion 30 is bent and connected to the second bottom surface portion 22 and the inner wall portion 18.

Golf balls 10 were produced having the first dimple 12a to the fifth dimple 12e shown in Figures 4 and 5, with the opening diameter ΦA, bottom diameter ΦB, ΦB/ΦA, shortest distance (first distance) d1 between the first bottom surface portion 20 and the first virtual horizontal line M1, shortest distance (second distance) d2, d2/d1 between the shallowest part DS of the second bottom surface portion 22 and the first virtual horizontal line M1, radius of curvature R, ΦA/R of the first bottom surface portion 20, intersection angle (first angle) θ1 between the inner wall portion 18 and the first virtual horizontal line M1, and intersection angle (second angle) θ2 between the second bottom surface portion 22 and the second virtual horizontal line M2. These golf balls 10 are referred to as Examples 1 and 2.

For comparative purposes, golf balls were produced that had the same opening diameter ΦA and first distance d1 as in Examples 1 and 2, and had five types of dimples, each consisting of a bottom surface that shows only one curved surface in a cross section along the depth direction, and an inner wall portion that is connected to the bottom surface and extends to the periphery of the opening.

The first tester hit each of the golf balls 10 of Examples 1 and 2 and the golf ball of the comparative example with a driver, and measured the maximum height of each ball, the distance from the shot point to the landing point (carry), and the flight distance from the shot point to the stopping point (the sum of the carry and run). The results of this driver shot are shown in Figure 6A.

Furthermore, the number of spins of each golf ball 10 of Examples 1 and 2 and the golf ball of the comparative example was determined when the first tester hit the ball with a wedge club. The results of this approach shot are also shown in Figure 6A.

The second tester hit each of the golf balls 10 of Examples 1 and 2 and the golf ball of the comparative example in the same manner as described above. The results for driver shots and approach shots are shown in Figure 6B.

From Figures 6A and 6B, it can be seen that the driver shot with the golf ball of the comparative example has a higher trajectory than the golf balls 10 of Examples 1 and 2. Therefore, the driver shot with the golf ball of the comparative example has a shorter flight distance than the golf balls 10 of Examples 1 and 2. In other words, by forming the dimples 12 as in Examples 1 and 2, the flight distance of the golf ball 10 can be increased.

6A and 6B also show that the golf balls 10 of Examples 1 and 2 achieve a greater amount of spin on approach shots than the golf ball of the comparative example. This indicates that the golf balls 10 of Examples 1 and 2 are easier to stop at or near the target point than the golf ball of the comparative example.

Next, ITR (Indoor Test Range) measurements were performed on the golf balls 10 of Examples 1 and 2 and the golf ball of the comparative example to measure the aerodynamic characteristics during flight. As a result, it was confirmed that the golf balls 10 of Examples 1 and 2 suppress excessive lift in the flight region where the amount of spin is large immediately after hitting, fly with low drag until they reach near the highest point, and maintain lift from near the highest point until they land. As a result, the flight distance of the golf balls 10 of Examples 1 and 2 is greater than the flight distance of the golf ball of the comparative example.

Furthermore, a structural analysis using the finite element method was used to analyze the stress distribution around the dimples 12 when a load was applied to a golf ball placed on a 3D model that imitates a golf club face. The numerical values of the material properties of the golf ball were used in this structural analysis. As a result, the analysis results showed that the golf balls 10 of Examples 1 and 2 were deformed while a greater stress was applied around the dimples 12 than the golf ball of the comparative example, and that the dimples 12 were in contact with the golf club face with a greater force.

As described above, in this embodiment, in a golf ball (10) having a dimple (12) on its surface, the dimple has a bottom surface (14) having a first diameter (ΦB), an opening periphery (16) formed by the periphery of a circular opening and having a second diameter (ΦA) larger than the first diameter, and an inner wall portion (18) extending from the opening periphery toward the bottom surface and inclining in a tapered manner when viewed along the depth direction of the dimple, and the bottom surface has a first bottom surface portion (20) that forms a diametrically inner portion of the bottom surface and is curved in an arc shape when viewed along the depth direction of the dimple, and a second bottom surface portion (21) that is located diametrically outside the first bottom surface portion and forms a diametrically outer portion of the bottom surface and extends linearly when viewed along the depth direction of the dimple. and a bottom surface portion (22), the first diameter is 80% to 95% of the second diameter, a first imaginary horizontal line (M1) passing through the periphery of the opening, and a second imaginary horizontal line (M2) passing through an intersection point (A) between the first bottom surface portion and the second bottom surface portion and parallel to the first imaginary horizontal line are drawn, and the intersection angle between the inner wall portion and the first imaginary horizontal line is θ1 and the intersection angle between the second bottom surface portion and the second imaginary horizontal line is θ2, where θ1 is within a range of 3° to 62° and θ1>θ2, and where d1 is the shortest distance between the deepest part (DM) of the first bottom surface portion and the first imaginary horizontal line, and d2 is the shortest distance between the shallowest part (DS) of the second bottom surface portion and the first imaginary horizontal line, d2 is 30% to 70% of d1.

A golf ball with the dimple dimensions set as described above provides sufficient distance on driver shots. This golf ball also rotates with a sufficient amount of spin on approach shots. Therefore, it is easy to stop the golf ball at or near the target point on approach shots.

This embodiment discloses a golf ball in which the second diameter is 18% to 50% of the radius of curvature (R) of the first bottom surface portion and is within the range of 3.0 mm to 5.5 mm, and the shortest distance d1 is within the range of 0.10 mm to 0.20 mm.

This embodiment discloses a golf ball in which the intersection angle θ2 is within the range of 0.2° to 6.0°.

In either case, the golf ball is prevented from flying upwards, particularly on driver shots. Also, the amount of spin on approach shots is more sufficient. In other words, a golf ball is obtained that has a more sufficient flight distance on driver shots and is easier to stop at or near the target point on approach shots.

This embodiment discloses a golf ball in which a peripheral wall portion (30) is interposed between the inner wall portion and the second bottom surface portion and is bent and connected to the inner wall portion and the second bottom surface portion.

With this configuration, as with the above, a golf ball can be obtained that provides sufficient distance on driver shots and is easy to stop at or near the target point on approach shots.

The present invention is not limited to the above disclosure, and various configurations may be adopted without departing from the gist of the present invention.

10... Golf ball 12, 12a to 12e... Dimple 14... Bottom surface 16... Opening periphery 18... Inner wall portion 20... First bottom surface portion 22... Second bottom surface portion 30... Peripheral wall portion DM... Deepest portion of first bottom surface portion DS... Shallowest portion of second bottom surface portion M1... First imaginary horizontal line M2... Second imaginary horizontal line

FIG. 1 is a schematic overall plan view of a golf ball according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view taken along the depth direction of a dimple. FIG. 3 is a schematic cross-sectional view taken along the depth direction of a dimple having a peripheral wall portion. FIG. 4 is a table showing the dimensions of the dimples on the golf ball of Reference Example 1. FIG. 5 is a chart showing the dimensions of the dimples on the golf ball of Example 2. 6A and 6B are graphs showing the results obtained by the hitting test for the golf balls of Reference Example 1, Example 2 and Comparative Example.

Golf balls 10 were fabricated having first dimples 12a to fifth dimples 12e as shown in Figures 4 and 5, with opening diameter ΦA, bottom diameter ΦB, ΦB/ΦA, shortest distance (first distance) d1 between first bottom surface portion 20 and first virtual horizontal line M1, shortest distance (second distance) d2, d2/d1 between shallowest part DS of second bottom surface portion 22 and first virtual horizontal line M1, radius of curvature R, ΦA/R of first bottom surface portion 20, intersection angle (first angle) θ1 between inner wall portion 18 and first virtual horizontal line M1, and intersection angle (second angle) θ2 between second bottom surface portion 22 and second virtual horizontal line M2.

For the purpose of comparison, golf balls were produced that had the same opening diameter ΦA and first distance d1 as in Reference Example 1 and Example 2, and had five types of dimples each consisting of a bottom surface that shows only one curved surface in a cross section along the depth direction, and an inner wall portion that is connected to the bottom surface and extends to the periphery of the opening.

A first tester hit each of the golf balls 10 of Reference Example 1 and Example 2 and the golf ball of the Comparative Example with a driver, and measured the maximum height of each ball, the distance from the shot point to the landing point (carry), and the flight distance from the shot point to the stopping point (total value of carry and run). The results of this driver shot are shown in Figure 6A.

Furthermore, the number of spins of each of the golf balls 10 of Reference Example 1 and Example 2 and the golf ball of the Comparative Example was determined when a first tester hit the golf balls 10 with a wedge club. The results of the approach shots are also shown in FIG. 6A.

A second tester hit each of the golf balls 10 of Reference Example 1 and Example 2, and the golf ball of the Comparative Example in the same manner as above. The results for driver shots and approach shots are shown in FIG. 6B.

6A and 6B show that the driver shot with the golf ball of the Comparative Example has a higher trajectory than the golf balls 10 of Reference Example 1 and Example 2. Therefore, the driver shot with the golf ball of the Comparative Example has a shorter flight distance than the golf balls 10 of Reference Example 1 and Example 2. In other words, by forming the dimples 12 as in Reference Example 1 and Example 2, the flight distance of the golf ball 10 can be increased.

6A and 6B, it can be seen that a greater amount of spin is obtained on approach shots with the golf balls 10 of Reference Example 1 and Example 2 than with the golf ball of the Comparative Example. This indicates that the golf balls 10 of Reference Example 1 and Example 2 can be more easily stopped at or near the target point than the golf ball of the Comparative Example.

Next, ITR (Indoor Test Range) measurements were carried out on the golf balls 10 of Reference Example 1 and Example 2 and the golf ball of the Comparative Example to measure the aerodynamic characteristics during flight. As a result, it was confirmed that the golf balls 10 of Reference Example 1 and Example 2 suppress excessive lift in the flight region where the spin rate is large immediately after hitting, fly with low drag until they reach the vicinity of the highest point, and maintain lift from the vicinity of the highest point until they land. As a result, the flight distance of the golf balls 10 of Reference Example 1 and Example 2 is greater than the flight distance of the golf ball of the Comparative Example.

Furthermore, a structural analysis using the finite element method was used to analyze the stress distribution around the dimples 12 when a load was applied to a golf ball placed on a 3D model simulating a golf club face. The numerical values of the material properties of the golf ball were used in this structural analysis. As a result, the analysis results showed that the golf balls 10 of Reference Example 1 and Example 2 were deformed while a greater stress was applied around the dimples 12 than the golf ball of the Comparative Example, and the dimples 12 were in contact with the golf club face with a greater force.

Claims (4)

In a golf ball having dimples on its surface,
The dimple has a base having a first diameter;
an aperture periphery defined by a periphery of a circular aperture and having a second diameter greater than the first diameter;
an inner wall portion that extends from the periphery of the opening toward the bottom surface and is tapered when viewed along the depth direction of the dimple;
having
the bottom surface has a first bottom surface portion which forms a diametrically inner portion of the bottom surface and which is curved in an arc shape when viewed along the depth direction of the dimple, and a second bottom surface portion which is located diametrically outward of the first bottom surface portion and forms a diametrically outer portion of the bottom surface and which extends linearly when viewed along the depth direction of the dimple,
the first diameter is between 80% and 95% of the length of the second diameter;
a first imaginary horizontal line passing through the periphery of the opening and a second imaginary horizontal line passing through an intersection point between the first bottom surface portion and the second bottom surface portion and parallel to the first imaginary horizontal line are drawn; an intersection angle between the inner wall portion and the first imaginary horizontal line is θ1; and an intersection angle between the second bottom surface portion and the second imaginary horizontal line is θ2; θ1 is within a range of 3° to 62° and θ1>θ2;
a golf ball, wherein d1 is the shortest distance between the deepest part of the first bottom surface portion and the first imaginary horizontal line, and d2 is the shortest distance between the shallowest part of the second bottom surface portion and the first imaginary horizontal line, and d2 is 30% to 70% of d1. 2. The golf ball of claim 1, wherein the second diameter is 18% to 50% of the radius of curvature of the first base portion and is within a range of 3.0 mm to 5.5 mm;
A golf ball, wherein the shortest distance d1 is within a range of 0.10 mm to 0.20 mm. The golf ball according to claim 1 or 2, wherein the crossing angle θ2 is within the range of 0.2° to 6.0°. The golf ball according to claim 1 or 2, wherein a peripheral wall portion is interposed between the inner wall portion and the second bottom surface portion, the peripheral wall portion being bent and connected to the inner wall portion and the second bottom surface portion.