Golf club head and manufacturing method thereof

Abstract

To adjust repulsion performance while suppressing changes in a trajectory of hit ball.SOLUTION: A golf club head 1 including a hollow part inside thereof includes: a face part 2; and a body part 3 including a crown part 4 extending backward of the head from the face part 2, and a sole part 5. The body part 3 is provided with at least one slit 10 penetrating the body part 3 and extending in a head longitudinal direction. The slit 10 includes: a pair of slit inner walls 11 extending in the head longitudinal direction; and at least one joint member 12 for connecting the pair of slit inner walls 11 to each other.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a golf club head having an internal hollow portion and a method for manufacturing the same. [Background technology]

[0002] The Rules of Golf established by the USGA (United States Golf Association) state that a golf club head must not have a spring effect that exceeds the upper limit set forth in the pendulum test protocol. More specifically, the CT (Characteristic time) value of a golf club head is restricted to a predetermined value or less. Patent Document 1 below proposes a technology for managing the CT value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-181007 Summary of the Invention [Problem to be solved by the invention]

[0004] During the mass production of golf club heads, various manufacturing errors can occur. To account for these manufacturing errors, golf club manufacturers typically manufacture golf club heads with CT values ​​significantly lower than the upper limit set by the Rules of Golf, and then adjust the CT values ​​to be closer to but below the upper limit set by the Rules of Golf. This adjustment can include, for example, polishing the striking surface.

[0005] However, the shape of the hitting surface of a golf club head has a significant effect on the trajectory of the ball, such as the launch angle and spin rate, so the conventional process of adjusting the CT value may result in changes to the trajectory of the golf club head.

[0006] The present disclosure has been devised in consideration of the above-described circumstances, and its main purpose is to provide a golf club head and a manufacturing method thereof that are capable of adjusting the repulsion performance while suppressing changes in the trajectory of the ball. [Means for solving the problem]

[0007] The present disclosure relates to a golf club head having a hollow portion therein, comprising a face portion and a main body portion including a crown portion and a sole portion extending from the face portion to the rear of the head, wherein the main body portion has at least one slit extending through the main body portion in the front-to-rear direction of the head, the slit having a pair of slit inner walls extending in the front-to-rear direction of the head, and at least one connecting member connecting the pair of slit inner walls to each other. [Effects of the Invention]

[0008] The golf club head and manufacturing method thereof disclosed herein can adjust the resilience performance while suppressing changes in the trajectory of the hit ball. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a golf club head according to a first embodiment. [Figure 2] FIG. 1 is a front view of a golf club head according to a first embodiment. [Figure 3] FIG. 1 is a plan view of a golf club head according to a first embodiment. [Figure 4] FIG. 2 is a bottom view of the golf club head of the first embodiment. [Figure 5] FIG. [Figure 6] FIG. [Figure 7] FIG. 10 is a perspective view of a slit with one connecting member removed. [Figure 8] FIG. 10 is a plan view of another example of a slit as viewed from the outer surface side of the head. [Figure 9] FIG. 10 is a plan view of another example of a slit as viewed from the inner surface side of the head. [Figure 10] 9 is a cross-sectional view taken along line XX in FIG. 8. [Figure 11] FIG. 10 is a perspective view of a golf club head according to a second embodiment. [Figure 12] FIG. [Figure 13] FIG. 10 is a perspective view of a groove with one connecting member removed. [Figure 14] 1 is a flowchart illustrating a manufacturing method according to an embodiment of the present invention. [Figure 15] 10(a) is a graph showing the distribution of CT values ​​of a first golf club head, (b) is a graph showing the distribution of CT values ​​of a second golf club head, and (c) is a graph showing the difference between the two. [Figure 16] 10 is a graph showing the difference in CT value between a second golf club head and a first golf club head in another example. [Figure 17] 10 is a graph showing the relationship between the number of slits removed and the increase in CT value at the face center. [Figure 18] 1A is a front view of a golf club head, and FIG. 1B is a cross-sectional view taken along line s1. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, several embodiments of the present disclosure will be described with reference to the drawings. Throughout all embodiments, the same components or parts are designated by the same reference numerals, and redundant description will be omitted.

[0011] [First embodiment] 1 to 4 show a perspective view, a front view, a plan view and a bottom view, respectively, of a golf club head (hereinafter sometimes simply referred to as a "head") 1 of a first embodiment.

[0012] [Standard conditions, etc.] 1 to 4, the head 1 is in a reference state. The reference state is a state in which the head 1 is placed on a horizontal plane HP while being maintained at a lie angle α (FIG. 2) and a loft angle (not shown) determined for the head 1. In addition, in the reference state, the shaft axis center line CL of the head 1 is disposed within a reference vertical plane VP (FIG. 3). The shaft axis center line CL is defined by the axial center line of the shaft insertion hole 7a formed in the hosel portion 7 of the head 1. Unless otherwise specified in this specification, the head 1 is assumed to be in this reference state.

[0013] Head Coordinate System In this specification, an xyz coordinate system is associated with the head 1. The x-axis is an axis perpendicular to the reference vertical plane VP and parallel to the horizontal plane HP. The y-axis is an axis parallel to both the reference vertical plane VP and the horizontal plane HP. The z-axis is an axis perpendicular to both the x-axis and the y-axis. With respect to the head 1, the direction along the x-axis is defined as the front-to-back direction of the head, the direction along the y-axis is defined as the toe-heel direction, and the direction along the z-axis is defined as the up-down direction of the head. With respect to the front-to-back direction of the head, the side of the face portion 2 is the front side, and the opposite side is the rear side.

[0014] [Basic head shape] The head 1 is essentially made of a metal material and has a hollow portion i inside, as shown in Fig. 3. The hollow portion i may be, for example, an open space, or a gel or the like may be placed in part of it to adjust the weight.

[0015] Suitable metal materials for forming the head 1 include, for example, stainless steel, maraging steel, titanium, titanium alloy, magnesium alloy, aluminum alloy, etc. A fiber reinforced resin may be used for a portion of the head 1.

[0016] 1 to 4, the head 1 is, for example, a wood type. Wood type heads 1 include, for example, at least a driver, a fairway wood, a hybrid, etc. The head 1 of this embodiment is configured as a driver.

[0017] The head 1 includes a face portion 2 and a main body portion 3 extending from the face portion 2 toward the rear of the head. The main body portion 3 includes, for example, at least a crown portion 4, a sole portion 5, and a hosel portion 7. In Fig. 2, the symbol T indicates the toe of the head 1, and the symbol H indicates the heel of the head 1.

[0018] The face portion 2 is the portion that strikes the ball and is formed on the front side of the head 1. The face portion 2 includes a striking surface 2a that comes into direct contact with the ball. The face portion 2 has a relatively large thickness to prevent damage when striking the ball. In a preferred embodiment, the face portion 2 has a thickness greater than that of the crown portion 4 and the sole portion 5. The thickness of the face portion 2 is not particularly limited, but is, for example, 2.0 mm or more, preferably 2.2 mm or more. On the other hand, in order to allow the face portion 2 to be sufficiently flexed when striking the ball, the thickness of the face portion 2 is, for example, 4.0 mm or less, preferably 3.8 mm or less.

[0019] The face portion 2 has a periphery E that defines the boundary of the striking surface 2a. In this specification, the periphery E of the face portion 2 is a ridgeline that can be seen with the naked eye as a clear ridgeline. On the other hand, if such a ridgeline is not clearly formed, the periphery E of the face portion 2 is determined as follows. First, as shown in Figure 18(A), each cross section s1, s2, s3... including the normal line N connecting the head center of gravity G and the sweet spot SS is identified. Then, as shown in Figure 18(B), the position E in each cross section where the radius of curvature r of the face outer surface contour line Lf reaches 200 mm from the sweet spot SS side toward the outside of the face for the first time is determined to be the periphery of the face portion 2.

[0020] The crown portion 4 extends rearward from the periphery E of the face portion 2 to form the top surface of the head. A hosel portion 7 is provided on the heel side of the crown portion 4. A shaft insertion hole 7a for fixing a shaft (not shown) is formed in the hosel portion 7. The crown portion 4 is the portion excluding the face portion 2 and the hosel portion 7 in the plan view of the head shown in FIG. 3.

[0021] 1 and 4, the sole portion 5 extends rearward from the periphery E of the face portion 2 to form the bottom surface of the head. The sole portion 5 is the portion excluding the hosel portion 7 when viewed from the bottom of the head.

[0022] [slit] The main body portion 3 is provided with at least one slit 10 penetrating the main body portion 3. In a preferred embodiment, a plurality of slits 10 are formed in at least one of the crown portion 4 and the sole portion 5. The plurality of slits 10 are arranged at intervals in the toe-heel direction. In the example of FIGS. 1 to 4, a plurality of slits 10 are arranged at intervals in the toe-heel direction in each of the crown portion 4 and the sole portion 5.

[0023] Specifically, the crown portion 4 has two slits 10, which are arranged on the toe and heel sides of the head longitudinal line FCL that passes through the face center FC. The sole portion 5 has three slits 10, which are distributed in the toe-heel direction, on the toe and heel sides of the head longitudinal line FCL and on the head longitudinal line FCL. The face center FC is the center position of the striking surface 2a in the toe-heel direction and the upper limit direction. In other examples, the slits 10 may be provided only in the crown portion 4 or only in the face portion 2. Alternatively, the crown portion 4 may have only one slit 10, or the sole portion 5 may have only one slit 10.

[0024] FIG. 5 is a partially enlarged plan view of one slit 10, and FIG. 6 is a perspective view thereof. As shown in FIGS. 5 and 6, the slit 10 has a front end 10a, a rear end 10b, a pair of slit inner walls 11, a length L in the front-to-back direction of the head, and a width W in the toe-heel direction. The length L of the slit 10 is sufficiently greater than the width W of the slit 10. Therefore, the slit 10 is elongated in the front-to-back direction of the head. In this example, the slit 10 extends linearly in the front-to-back direction of the head. That is, the pair of slit inner walls 11 extend linearly along the front-to-back direction of the head.

[0025] When a ball is struck with the striking surface 2a of the face portion 2, the crown portion 4 and sole portion 5 connected to the face portion 2 undergo bending deformation in the front-to-rear direction of the head as well as tensile deformation in the toe-heel direction. Meanwhile, the slits 10 locally reduce the tensile rigidity of the main body portion 3 (e.g., the crown portion 4 or the sole portion 5) in the toe-heel direction. Therefore, the main body portion 3 provided with the slits 10 can bend (stretch) more significantly in the toe-heel direction starting from the slits 10, promoting bending of the face portion 2. This has the advantage of expanding the high-rebound region of the face portion 2 in the direction of the region where the slits are located.

[0026] In order to effectively promote the above-described deflection of the main body portion 3 in the toe-heel direction, the length L of the slit 10 is set to, for example, 10 mm or more, preferably 12 mm or more, and more preferably 15 mm or more. On the other hand, if the length L of the slit 10 is excessively large, the durability of the main body portion 3 may be reduced. From this perspective, the length L of the slit 10 is set to, for example, 40 mm or less, preferably 30 mm or less, and more preferably 25 mm or less.

[0027] In order to effectively promote the bending of the main body portion 3 in the toe-heel direction, the width W of the slit 10 is set to, for example, 0.5 mm or more, preferably 1 mm or more, and more preferably 2 mm or more. On the other hand, if the width W of the slit 10 is large, the durability of the main body portion 3 may be reduced. From this perspective, the width W of the slit 10 is set to, for example, 10 mm or less, preferably 8 mm or less, and more preferably 6 mm or less. The width W of the slit 10 may be constant or may vary.

[0028] To effectively promote toe-heel deflection of the main body 3, the slit 10 is preferably positioned close to the face 2. As shown in FIG. 3, the shortest distance D between the front end 10a of the slit 10 (shown in FIG. 5) and the periphery E of the face 2 is, for example, 10 mm or less, preferably 3 mm or less, and more preferably 1 mm or less. The periphery E of the face 2 is a corner where the face 2 and the main body 3 are connected, and has high rigidity, so deformation upon impact with a ball is relatively small. Therefore, by positioning the front end 10a of the slit 10 close to the periphery E, there is also the advantage that an increase in stress near the front end 10a of the slit 10 is effectively suppressed.

[0029] [Connecting parts] As shown in Figures 5 and 6, the slit 10 has at least one joint member 12 connecting a pair of slit inner walls 11 to each other. In this example, one slit 10 has multiple joint members 12. The multiple joint members 12 are arranged at intervals in the front-to-rear direction of the head. As shown in Figure 6, the multiple joint members 12 include a front joint member 12a arranged at a distance from the front end 10a of the slit 10 in the front-to-rear direction of the head, a rear joint member 12b arranged at a distance from the rear end 10b of the slit 10 in the front-to-rear direction of the head, and at least one intermediate joint member 12c arranged at a distance from each of the front joint member 12a and the rear joint member 12b in the front-to-rear direction of the head.

[0030] The joint members 12 of this embodiment can be used as adjustment members to adjust the tensile rigidity of the main body portion 3 in the toe-heel direction. For example, after the head 1 is manufactured, at least one of the joint members 12 of any of the slits 10 may be at least partially removed as needed. The slits 10 from which the joint members 12 have been removed have a smaller tensile rigidity in the toe-heel direction without substantially changing the bending rigidity of the main body portion 3 in the front-to-back direction compared to other slits 10 from which the joint members 12 have not been removed. Such slits 10 provide greater deflection (elongation) of the main body portion 3 in the toe-heel direction when hitting a ball, thereby improving the resilience performance, i.e., the CT value, at the impact position corresponding to the slit 10. Furthermore, although the tensile rigidity of the main body portion 3 in the toe-heel direction changes depending on the presence and number of joint members 12, the change in bending rigidity in the front-to-back direction is very small. The present disclosure focuses on this point and changes the tensile rigidity in the toe-heel direction by the presence and number of joint members 12 without substantially changing the bending rigidity of the main body portion 3 in the front-to-back direction. This makes it possible to adjust the resilience performance without changing the spin or launch angle of the ball. However, a change (decrease) in the bending rigidity of the main body 3 in the front-to-rear direction of the head is undesirable because it changes (increases) the rotational deformation of the face when hitting the ball, which in turn changes the spin and launch angle of the ball.

[0031] For example, removing the joint member 12 from the toe-side slit 10 in the crown portion 4 and / or sole portion 5 can increase the CT value on the toe side of the striking surface 2a. Also, removing the joint member 12 from the heel-side slit 10 in the crown portion 4 and / or sole portion 5 can increase the CT value on the heel side of the striking surface 2a. Furthermore, removing the joint member 12 from the central slit 10 in the sole portion 5 can increase the CT value near the face center FC. Therefore, the CT value of the head 1 can be adjusted without polishing the face portion 2.

[0032] FIG. 7 is a perspective view showing an example in which one joint member 12 has been removed from the slit 10 of FIG. 6. In FIG. 7, the front joint member 12a has been removed. As a result, the portion where the front joint member 12a had been located becomes a new slit inner wall 11. Alternatively, the joint member 12 may be partially removed so that the connection between the pair of slit inner walls 11, 11 is released. For example, only the central portion of the joint member 12 in the toe-heel direction may be removed. In this manner, the tensile stiffness in the toe-heel direction around the slit 10 can be reduced.

[0033] When multiple joint members 12 are provided in one slit 10, one or more of the joint members 12 may be removed. Also, when multiple joint members 12 are provided in the front-to-rear direction of the head, the improvement in the CT value can be adjusted as desired by changing the number of joint members 12 to be removed.

[0034] The shape of the connecting members 12 is not particularly limited. The connecting members 12 may be, for example, rectangular or cylindrical extending in the toe-heel direction. The rectangular shape may be a square prism as in this embodiment, or various polygonal prisms such as a triangular prism. In the example shown in FIG. 6, each connecting member 12 has a wall thickness slightly smaller than that of the main body portion 3 (crown portion 4). The outer surface of each connecting member 12 may be recessed from the outer surface of the main body portion 3 in a stepped shape, as shown in the figure. In such an example, the removal position (removal position) of the connecting member 12 can be easily determined, thereby streamlining the removal process.

[0035] In this example, the joint member 12 extends in the toe-heel direction with a constant cross-sectional area. In another example, the joint member 12 may be formed with the same thickness as the main body portion 3. The cross-sectional area of ​​the joint member 12 may also vary, for example, by locally increasing or decreasing. Furthermore, the corner between the joint member 12 and the slit inner wall 11 may be smoothly connected by an arc in order to suppress stress concentration (not shown).

[0036] To effectively adjust the resilience performance, the total projected area of ​​the joint members 12 in a plan view of each slit 10 is preferably 0.8 times or less the projected area of ​​the slit 10 without the joint members 12. In the example of FIG. 6, the total projected area of ​​the joint members 12 is the sum of the projected areas of the front, rear, and middle joint members 12a, 12b, and 12c. The projected area of ​​the slit 10 without the joint members 12 is the total area enclosed by the outline of the slit 10 in FIGS. 5 and 6.

[0037] [Variations of slits] Fig. 8 is a plan view of another example of slit 10 as seen from the outer surface side of the head, and Fig. 9 is a plan view of another example of slit 10 as seen from the inner surface side of the head. Fig. 10 is a cross-sectional view taken along line XX in Fig. 8. As shown in Figs. 8 to 10, this slit 10 includes a first portion 101 extending from the front end 10a toward the rear of the head, and a second portion 102 connected to the first portion 101 and having a circular outline.

[0038] In this embodiment, the first portion 101 extends with a constant width. A plurality of joint members 12 are formed on the first portion 101.

[0039] The width of the second portion 102 is greater than the width of the first portion 101. Such a slit 10 helps to effectively suppress an increase in stress near the rear end 10b of the slit 10, where deformation of the main body 3 is likely to increase. In a preferred embodiment, the width of the second portion 102 is 1.5 times or more, or even 2.0 times or more, the width of the first portion 101.

[0040] Around the slit 10, a thickened portion 13 is formed by locally increasing the thickness of the main body 3. When hitting a ball, bending stress due to bending in the front-to-back direction of the head and tensile stress due to tensile deformation in the toe-heel direction act concentratedly around the slit 10 of the main body 3, making it prone to high stress. Strictly speaking, the slit 10 also slightly reduces the bending rigidity in the front-to-back direction of the head. However, when the thickened portion 13 is formed as described above, it is possible to suppress the reduction in bending rigidity in the front-to-back direction of the head while locally reducing the tensile rigidity in the toe-heel direction. Furthermore, the slit 10 with the thickened portion 13 distributes stress around the slit 10, thereby suppressing localized increases in stress.

[0041] The thick portion 13 is provided, for example, adjacent to the slit 10. As shown in Fig. 10, the thick portion 13 is formed by locally increasing the thickness of the main body 3. Outside the thick portion 13, a portion having a smaller thickness than the thick portion 13 is formed.

[0042] As shown in FIGS. 9 and 10, the thick portion 13 includes, for example, an inner thick portion 13a and an outer thick portion 13b.

[0043] The inner thick portion 13a protrudes, for example, toward the hollow portion i. The inner thick portion 13a is formed in a ring shape so as to surround the slit 10. Such an inner thick portion 13a is effective in alleviating stress in the periphery of the slit 10 of the main body portion 3. The inner thick portion 13a protrudes toward the hollow portion i from the inner surface 4i of the reference thickness portion 13c formed by the reference thickness tc of the main body portion 3 (in this example, the crown portion 4). The boundary in the thickness direction between the inner thick portion 13a and the reference thickness portion 13c is an imaginary boundary determined by smoothly extending the inner surface 4i of the reference thickness portion 13c to the slit 10.

[0044] The thickness ta of the inner thick portion 13a is not particularly limited, but is set to, for example, 0.5 mm or more, preferably 1.0 mm or more, and more preferably 1.5 mm or more in order to fully exert the stress reduction effect around the slit. Also, in order to suppress an increase in the weight of the head 1, the thickness ta of the inner thick portion 13a is set to, for example, 5.0 mm or less, preferably 4.0 mm or less, and more preferably 3.0 mm or less.

[0045] The outer thick portion 13b protrudes, for example, toward the outer surface of the head. The outer thick portion 13b may constitute the thick portion 13 together with or instead of the inner thick portion 13a. The outer thick portion 13b protrudes toward the outside of the head from the outer surface 4o of the reference thickness portion 13c formed by the reference thickness tc of the main body portion 3 (in this example, the crown portion 4). The boundary in the thickness direction between the outer thick portion 13b and the reference thickness portion 13c is a virtual boundary defined by smoothly extending the outer surface 4o of the reference thickness portion 13c to the slit 10.

[0046] As shown in FIG. 8, in this embodiment, the outer thick portion 13b is formed so as to be partially discontinued around the slit 10. Specifically, the outer thick portion 13b is not formed around the front portion including the front end 10a of the slit 10. Because the front end 10a of the slit 10 is located near the periphery E of the face portion 2, which has a relatively high rigidity, the increase in stress near the front end 10a of the slit 10 can be alleviated without providing the outer thick portion 13b in this portion. In addition, partially eliminating the outer thick portion 13b helps to reduce the weight of the main body portion 3 (especially the crown portion 4). Furthermore, as is clear from FIG. 8, the inner edge of the outer thick portion 13b matches the contour shape of the slit 10.

[0047] As shown in Figure 10, the thickness tb of the outer thick portion 13b is not particularly limited, but is set to, for example, 0.5 mm or more, preferably 1.0 mm or more, and more preferably 1.5 mm or more, in order to fully exert the effect of reducing tensile stress in the toe-heel direction around the slit. Furthermore, if the thickness tb is too thick, the bending rigidity in the front-to-back direction of the head increases, thereby increasing the bending stress in the front-to-back direction of the head. To fully exert the effect of reducing bending stress in the front-to-back direction around the slit and to suppress an increase in the weight of the head 1, the thickness tb of the outer thick portion 13b is set to, for example, 5.0 mm or less, preferably 4.0 mm or less, and more preferably 3.0 mm or less.

[0048] The width TW (shown in FIG. 9) of the inner thick portion 13a and the outer thick portion 13b is not particularly limited, but is set to, for example, 1.0 mm or more, preferably 2.0 mm or more, and more preferably 3.0 mm or more, in order to fully exert the stress reduction effect around the slit. Furthermore, in order to suppress an increase in the weight of the head 1, the width TW of the inner thick portion 13a and the outer thick portion 13b is set to, for example, 15.0 mm or less, preferably 12.0 mm or less, and more preferably 10.0 mm or less. The width TW is measured in a direction perpendicular to the edge of the slit 10, as illustrated in FIG. 9.

[0049] [Second embodiment] Next, a head 1 according to a second embodiment of the present disclosure will be described with reference to FIGS. Fig. 11 is a perspective view of a head 1 of the second embodiment, and Fig. 12 is an enlarged view of a main portion of the crown portion 4. The head 1 of the second embodiment differs from the first embodiment in that the main body portion 3 is provided with at least one groove 20 (in this example, multiple grooves) extending in the front-to-rear direction of the head instead of the slit 10. In Fig. 11, the groove 20 is provided in the same position as the slit 10 shown in Figs. 1 to 4.

[0050] 12, each of the plurality of grooves 20 includes a pair of groove walls 21, 21 extending in the front-to-rear direction of the head, a groove bottom 22, and at least one joint member 23 that locally protrudes from the groove bottom 22 and connects the pair of groove walls 21, 21. In this example, three joint members 23 are formed in one groove 20.

[0051] The grooves 20 provide the same advantages as the slits 10 of the first embodiment. That is, the grooves 20 locally reduce the rigidity of the main body portion 3 (e.g., the crown portion 4 and the sole portion 5) in the toe-heel direction without substantially changing the bending rigidity in the front-to-rear direction of the head. Therefore, the main body portion 3 provided with the grooves 20 can bend more greatly in the toe-heel direction, starting from the grooves 20, when hitting a ball. This expands the high-rebound region of the face portion 2 in the direction of the region where the slits are located.

[0052] As in the first embodiment, the joint members 23 provided in the grooves 20 can be used as adjustment members to adjust the tensile stiffness of the head body in the toe-heel direction. For example, after the head 1 is manufactured, at least one of the joint members 23 of any of the grooves 20 may be at least partially removed as needed. The grooves 20 from which the joint members 23 have been removed have a lower tensile stiffness of the main body portion 3 in the toe-heel direction compared to other grooves 20 from which the joint members 23 have not been removed. Such grooves 20 provide greater deflection of the main body portion 3 in the toe-heel direction when hitting a ball, thereby expanding the high-resilience region in the direction in which the groove 20 is located (increasing the CT value). Therefore, the head 1 of this example also allows adjustment of the resilience performance (CT value) without polishing the face portion 2. In other words, the head 1 allows adjustment of the resilience performance while suppressing changes in the trajectory of the hit ball.

[0053] FIG. 13 is a perspective view showing an example in which one joint member 23 has been removed from the groove 20 of FIG. 12. In FIG. 13, the frontmost joint member 23 has been removed. The joint member 23 may be completely removed, for example, so that it is a flat surface continuous with the groove bottom 22. In another example, the joint member 23 may be partially removed. In this case, the protruding height of the partially removed joint member 23 is reduced compared to its previous state, but it may still protrude from the groove bottom 22. Such partial removal of the joint member 23 may also reduce the tensile stiffness in the vicinity of the groove 20.

[0054] When multiple joint members 23 are provided in one groove 20, one or more of the joint members 23 may be removed. Also, when multiple joint members 23 are provided in the front-to-rear direction of the head, the improvement in the CT value can be adjusted as desired by changing the number of joint members 23 to be removed. In addition, the length L, width W, and formation position of the slit 10 described in the first embodiment can be applied to the length, width, and formation position of the groove 20 in the second embodiment, respectively.

[0055] [Slit and groove cover] In the head 1 of the first and second embodiments, a cover (not shown) made of an elastic material such as rubber, resin, elastomer, etc. may be provided in the gap of the slit 10 and / or groove 20. Such a cover can prevent foreign matter from entering the slit 10 or groove 20 without interfering with the deformation of the main body 3.

[0056] [Manufacturing method of golf club head] Next, a method for manufacturing the golf club head of this embodiment will be described. The procedure of this manufacturing method is shown in FIG.

[0057] [1st step] As shown in Fig. 14, the manufacturing method of this embodiment includes a first step of preparing a first golf club head (step S1). The first golf club head has the same configuration as the head 1 of the first embodiment described with reference to Figs. 1 to 6, for example. That is, the head 1 includes a face portion 2 and a main body portion 3 including a crown portion 4 and a sole portion 5 extending from the face portion 2 toward the rear of the head. The main body portion 3 is provided with at least one slit 10 extending through the main body portion 3 in the front-to-rear direction of the head. As shown in Figs. 5 and 6, the slit 10 includes a pair of slit inner walls 11 extending in the front-to-rear direction of the head, and at least one joint member 12 connecting the pair of slit inner walls 11 to each other.

[0058] [Second process] Next, the manufacturing method of this embodiment includes a second step of measuring the CT value of the first golf club head (step S2).

[0059] It is desirable to measure the CT value at multiple positions in the toe-heel direction and the head up-down direction on the striking surface 2a of the head 1 in Figure 2. For example, with the face center FC of the striking surface 2a as the origin, a range of 25 mm on the toe and heel sides and 15 mm on the top and bottom sides of the head is divided into grids at 5 mm intervals, and the CT value is measured at several of these grid positions. The CT value of a golf club head often tends to be highest at the face center. In this example, the CT value is measured at multiple positions including the face center FC.

[0060] [Step 3, Part 1] Next, the manufacturing method of this embodiment includes a step of determining whether the measured CT value is smaller than a predetermined threshold value (step S3). For example, if the maximum CT value (hereinafter referred to as "CTmax") of the first golf club head is to be further improved, CTmax is compared with the threshold value. The threshold value can be determined based on, for example, the upper limit of the CT value (239 μs) set forth in the Rules of Golf. For example, the threshold value may be the upper limit of the CT value. In another example, the threshold value may be set to a value slightly smaller than the upper limit, taking into account measurement error, etc.

[0061] [Step 2 of 3] Next, if the measured CT value is smaller than a predetermined threshold (Yes in step S3), the manufacturing method of this embodiment includes a step of at least partially removing at least one of the joint members 12 of the first golf club head to obtain a second golf club head (step S4). The second golf club head has a slit 10 where the joint member 12 was removed, as shown in Figure 7. The removal can be performed by various methods such as cutting, cutting, grinding, etc.

[0062] For example, if the CTmax of the first golf club head is smaller than a threshold value, one or more of the joint members 12 at a predetermined position are removed. The number of joint members 12 to be removed is determined appropriately according to the difference between CTmax and the threshold value. For example, the larger the difference, the more desirable it is to remove the number of joint members 12. Furthermore, it is desirable to select the joint members 12 that are closest to the position of CTmax in the toe-heel direction as the joint members 12 to be removed.

[0063] In order to increase CTmax more effectively, it is advisable to determine in advance by experiment or simulation the relationship between the number and positions of the connecting members 12 to be removed and the amount of improvement in the CT value and the positions at which the CT is improved. In a preferred embodiment, the dimensions of the connecting members 12 may be designed so that removing one of them improves the CT value in the range of 2 to 4 μs.

[0064] If necessary, the CT value of the second golf club head may be measured after the joint member 12 is removed. In this case, if the difference between the CTmax of the second golf club head and the threshold value is greater than a predetermined value, the third step may be repeated again.

[0065] While the above example describes a case where CTmax is further increased, the manufacturing method of this embodiment can also be used to adjust the distribution of CT values. For example, in many cases, the CT value of a golf club head tends to be low at impact positions shifted to the toe and heel from the face center FC. Therefore, if the CT value at the position shifted to the toe is smaller than a predetermined threshold, removing some of the connecting members 12 provided in the toe-side slits 10 can effectively increase the CT value at the toe-side impact position while suppressing an excessive increase in CTmax. Similarly, if the CT value at the position shifted to the heel is smaller than a predetermined threshold, removing some of the connecting members 12 provided in the heel-side slits 10 can effectively increase the CT value at the heel-side impact position while suppressing an excessive increase in CTmax.

[0066] In the above example, the first golf club head is the head 1 of the first embodiment, but in another example, the first golf club head may be the head 1 of the second embodiment. That is, the first golf club head may include a face portion 2 and a main body portion 3 extending from the face portion 2 toward the rear of the head, the main body portion 3 being provided with at least one groove 20 extending in the front-to-rear direction of the head, and the groove 20 may include a pair of groove walls 21 extending in the front-to-rear direction of the head, a groove bottom 22, and at least one joint member 23 that locally protrudes from the groove bottom 22 and connects the pair of groove walls 21.

[0067] Although the embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above specific disclosure, and can be implemented with various modifications within the scope of the technical idea described in the claims. [Example]

[0068] A wood type golf club head was prepared as shown in Figures 1 to 4. The specifications of this head are as follows. Head material: Titanium alloy Head volume: 460cc Head weight: 172g Face thickness: The thickness is 3.7 mm in the center and 2.1 mm at the periphery, with a smooth change in thickness between the center and periphery. Slit length L: 22mm Slit width W: 2mm Number of connecting pieces in one slit: 3 Joint material: All have a square cross section, with a thickness of 1.8 mm in the vertical direction and a length of 1.8 mm in the front-to-back direction of the head Slits in the crown: Located 24mm apart from the face center on the toe and heel sides, parallel to the front and back of the head Shortest distance D between the slit in the crown and the periphery of the face: 1.0 mm Slits in the sole: Located parallel to the front-to-back direction of the head, in the center area and at positions 26 mm apart from the face center on the toe and heel sides

[0069] First, the CT value of the first golf club head with all joints remaining was measured. The CT values ​​at the main impact positions were as shown in Figure 15(a). In each table in Figure 15, the horizontal axis represents the toe-heel direction, the vertical axis represents the head up-down direction, the origin is the face center, and the unit of each coordinate is the distance (millimeters) from the origin. As is clear from Figure 15(a), CTmax occurs at the face center, and its value is 234 (unit: μs), which is smaller than the upper limit (threshold) of 239 μs set by the Rules of Golf.

[0070] Next, all three connecting members in the center slit of the sole of the first golf club head were removed by cutting to obtain a second golf club head. The main CT value of the striking surface of the second golf club head was as shown in Figure 15(b). The CTmax of the second golf club head occurred at the face center, and this value was equal to 239 μs, the upper limit set by the Rules of Golf. In this example, removing all three connecting members in one slit resulted in an increase in the CT value of 5 μs at the face center.

[0071] Figure 15(c) shows the difference obtained by subtracting the CT value of the first golf club head from the CT value of the second golf club head. As is clear from Figure 15(c), in the second golf club head, a significant increase in CT value (12 μs) was observed at a position 15 mm from the face center on the sole, corresponding to the removed joint member.

[0072] Next, another example of a manufacturing method will be described. For the first golf club head described above, all three connecting members of the slits on the toe side of the sole portion were removed by cutting to obtain a second golf club head. FIG. 16 shows the difference obtained by subtracting the CT value of the first golf club head from the CT value of the second golf club head. As is clear from FIG. 16, in the second golf club head, a significant increase in CT value (13 μs) was observed at the impact position closest to the toe and sole, corresponding to the removed connecting members. The CT value at the face center remained at 2 μs.

[0073] Figure 17 shows the relationship between the number of slits removed from the center of the sole in the toe-heel direction and the increase in the CT value at the face center for the first golf club head. As is clear from Figure 17, the CT value increases as the number of connecting members removed increases.

[0074] Furthermore, Table 1 shows the results of a hitting test using a swing robot. In the hitting test, the first golf club head and the second golf club head were used, and the same golf ball was hit under the same conditions. The backspin amount and launch angle of each hit ball were then measured.

[0075] [Table 1]

[0076] As a result of the test, the second golf club head had a CT value increased by 13 μs compared to the first golf club head, but no substantial difference in trajectory was observed compared to that of the first golf club head.

[0077] [Note] The present disclosure includes the following aspects.

[0078] [Disclosure 1] A golf club head having a hollow portion therein, a face portion; and a main body portion including a crown portion and a sole portion extending from the face portion toward the rear of the head, The main body portion is provided with at least one slit that penetrates the main body portion and extends in the front-rear direction of the head, The slit includes a pair of slit inner walls extending in the front-rear direction of the head, and at least one joint member connecting the pair of slit inner walls to each other. Golf club head. [Disclosure 2] The golf club head according to Disclosure 1, wherein a plurality of the slits are arranged at intervals in the toe-heel direction in at least one of the crown portion and the sole portion. [Disclosure 3] The golf club head according to Disclosure 1 or 2, wherein the slit is provided with a plurality of the joint members. [Disclosure 4] The golf club head according to any one of Disclosures 1 to 3, wherein the joint member is cylindrical or prismatic and extends in the toe-heel direction. [Disclosure 5] the slit includes a front end and a rear end in the front-rear direction of the head, The golf club head according to any one of Disclosures 1 to 4, wherein the joint member is disposed at a distance from the front end and the rear end of the slit in the front-to-rear direction of the head. [Disclosure 6] A golf club head according to any one of Disclosures 1 to 5, wherein, in a plan view of the slits, the total projected area of ​​the joint members is 0.8 times or less the projected area of ​​the slits assuming that the joint members are not present. [Disclosure 7] The golf club head according to any one of Disclosures 1 to 6, wherein a thick portion is formed around the slit by locally increasing the thickness of the main body portion. [Disclosure 8] A golf club head having a hollow portion therein, a face portion; and a main body portion including a crown portion and a sole portion extending from the face portion toward the rear of the head, The main body portion is provided with at least one groove extending in the front-rear direction of the head, The groove includes a pair of groove walls extending in the front-rear direction of the head, a groove bottom, and at least one joint member that locally protrudes from the groove bottom and connects the pair of groove walls. Golf club head. [Disclosure 9] The golf club head according to Disclosure 8, wherein the groove is provided with a plurality of the joint members. [Disclosure 10] 10. The golf club head according to Disclosure 8 or 9, wherein a plurality of the grooves are arranged at intervals in the toe-heel direction in at least one of the crown portion and the sole portion. [Disclosure 11] A method for manufacturing a golf club head, comprising: a first step of preparing a first golf club head, the first golf club head including a face portion and a main body portion including a crown portion and a sole portion extending from the face portion toward the rear of the head, the main body portion being provided with at least one slit extending through the main body portion in a front-to-rear direction of the head, the slit having a pair of slit inner walls extending in the front-to-rear direction of the head and at least one joint member connecting the pair of slit inner walls to each other; a second step of measuring the CT value of the first golf club head; and a third step of at least partially removing at least one of the joint members of the first golf club head to obtain a second golf club head when the CT value is smaller than a predetermined threshold value. A method for manufacturing a golf club head. [Disclosure 12] A method for manufacturing a golf club head, comprising: a first step of preparing a first golf club head, the first golf club head including a face portion, and a main body portion including a crown portion and a sole portion extending from the face portion toward the rear of the head, the main body portion being provided with at least one groove extending in a front-to-rear direction of the head, the groove including a pair of groove walls extending in the front-to-rear direction of the head, a groove bottom, and at least one joint member locally protruding from the groove bottom to connect the pair of groove walls; a second step of measuring the CT value of the first golf club head; and a third step of at least partially removing at least one of the joint members of the first golf club head to obtain a second golf club head when the CT value is smaller than a predetermined threshold value. A method for manufacturing a golf club head. [Explanation of symbols]

[0079] 1 head 2 Face section 3 Main body 4 Crown part 5 Sole 10 slits 10a Front edge of slit 10b Rear end of slit 11 Slit inner wall 12 Joint members 13 Thick wall part 20 grooves 21 Groove Wall 22 Groove bottom 23 Joint material

Claims

1. A golf club head having a hollow portion therein, a face portion; and a main body portion including a crown portion and a sole portion extending from the face portion toward the rear of the head, The main body portion is provided with at least one slit that penetrates the crown portion or the sole portion and extends in the front-rear direction of the head, The slit includes a pair of slit inner walls extending in the front-rear direction of the head, and at least one joint member connecting the pair of slit inner walls to each other, A plurality of the slits are arranged at intervals in a toe-heel direction in at least one of the crown portion and the sole portion. Golf club head.

2. A golf club head having a hollow portion therein, a face portion; and a main body portion including a crown portion and a sole portion extending from the face portion toward the rear of the head, the main body portion is provided with at least one slit extending in the front-to-rear direction of the head, penetrating at least one of the crown portion and the sole portion; The slit includes a pair of slit inner walls extending in the front-rear direction of the head, and at least one joint member connecting the pair of slit inner walls to each other, A plurality of the joint members are provided in the slit. Golf club head.

3. A golf club head having a hollow portion therein, a face portion; and a main body portion including a crown portion and a sole portion extending from the face portion toward the rear of the head, the main body portion is provided with at least one slit extending in the front-to-rear direction of the head, penetrating at least one of the crown portion and the sole portion; The slit includes a pair of slit inner walls extending in the front-rear direction of the head, and at least one joint member connecting the pair of slit inner walls to each other, The joint member is cylindrical or prismatic and extends in the toe-heel direction. Golf club head.

4. A golf club head having a hollow portion therein, a face portion; and a main body portion including a crown portion and a sole portion extending from the face portion toward the rear of the head, the main body portion is provided with at least one slit extending in the front-to-rear direction of the head, penetrating at least one of the crown portion and the sole portion; The slit includes a pair of slit inner walls extending in the front-rear direction of the head, and at least one joint member connecting the pair of slit inner walls to each other, the slit includes a front end and a rear end in the front-rear direction of the head, The joint members are disposed at distances from the front end and the rear end of the slit in the front-rear direction of the head. Golf club head.

5. A golf club head having a hollow portion therein, a face portion; and a main body portion including a crown portion and a sole portion extending from the face portion toward the rear of the head, the main body portion is provided with at least one slit extending in the front-to-rear direction of the head, penetrating at least one of the crown portion and the sole portion; The slit includes a pair of slit inner walls extending in the front-rear direction of the head, and at least one joint member connecting the pair of slit inner walls to each other, In a plan view of the slit, the total projected area of ​​the joint members is 0.8 times or less of the projected area of ​​the slit assuming that the joint members are not present. Golf club head.

6. A golf club head having a hollow portion therein, a face portion; and a main body portion including a crown portion and a sole portion extending from the face portion toward the rear of the head, the main body portion is provided with at least one slit extending in the front-to-rear direction of the head, penetrating at least one of the crown portion and the sole portion; The slit includes a pair of slit inner walls extending in the front-rear direction of the head, and at least one joint member connecting the pair of slit inner walls to each other, A thick portion is formed around the slit by locally increasing the thickness of the main body portion. Golf club head.

7. A golf club head as described in any one of claims 2 to 6, wherein a plurality of the slits are arranged at intervals in the toe-heel direction in at least one of the crown portion and the sole portion.

8. A golf club head as described in any one of claims 1, 3, 4, 5 and 6, wherein the slit is provided with a plurality of the connecting members.

9. A golf club head as described in any one of claims 1, 2, 4, 5 and 6, wherein the connecting member is cylindrical or rectangular extending in the toe-heel direction.

10. The slit includes a front end and a rear end in the head front-rear direction, 7. The golf club head according to claim 1, wherein the joint members are disposed at a distance from the front end and the rear end of the slit in the front-to-rear direction of the head.

11. A golf club head as described in any one of claims 1, 2, 3, 4 and 6, wherein, in a planar view of the slit, the total projected area of ​​the connecting members is 0.8 times or less the projected area of ​​the slit assuming that the connecting members are not present.

12. A golf club head as described in any one of claims 1 to 5, wherein a thick portion is formed around the slit, by locally increasing the thickness of the main body portion.

13. A golf club head having a hollow portion therein, a face portion; and a main body portion including a crown portion and a sole portion extending from the face portion toward the rear of the head, The main body portion is provided with at least one groove extending in the front-rear direction of the head, the groove includes a pair of groove walls extending in the front-rear direction of the head, a groove bottom, and at least one joint member that locally protrudes from the groove bottom and connects the pair of groove walls, A plurality of the joint members are provided in the groove. Golf club head.

14. A golf club head having a hollow portion therein, a face portion; and a main body portion including a crown portion and a sole portion extending from the face portion toward the rear of the head, The main body portion is provided with at least one groove extending in the front-rear direction of the head, the groove includes a pair of groove walls extending in the front-rear direction of the head, a groove bottom, and at least one joint member that locally protrudes from the groove bottom and connects the pair of groove walls, A plurality of the grooves are arranged at intervals in a toe-heel direction in at least one of the crown portion and the sole portion. Golf club head.

15. A golf club head as described in claim 14, wherein the groove is provided with a plurality of the joining members.

16. A golf club head as described in claim 13, wherein a plurality of the grooves are arranged at intervals in the toe-heel direction in at least one of the crown portion and the sole portion.

17. A method for manufacturing a golf club head, comprising: a first step of preparing a first golf club head, the first golf club head including a face portion, and a main body portion including a crown portion and a sole portion extending from the face portion to the rear of the head, the main body portion being provided with at least one slit extending in a front-to-rear direction of the head through the crown portion or the sole portion, the slit having a pair of slit inner walls extending in the front-to-rear direction of the head and at least one joint member connecting the pair of slit inner walls to each other; a second step of measuring a CT value of the first golf club head; and a third step of at least partially removing at least one of the joint members of the first golf club head to obtain a second golf club head when the CT value is smaller than a predetermined threshold value. A method for manufacturing a golf club head.

18. A method for manufacturing a golf club head, comprising: a first step of preparing a first golf club head, the first golf club head including a face portion, and a main body portion including a crown portion and a sole portion extending from the face portion toward the rear of the head, the main body portion being provided with at least one groove extending in a front-to-rear direction of the head, the groove including a pair of groove walls extending in the front-to-rear direction of the head, a groove bottom, and at least one joint member locally protruding from the groove bottom to connect the pair of groove walls; a second step of measuring a CT value of the first golf club head; and a third step of at least partially removing at least one of the joint members of the first golf club head to obtain a second golf club head when the CT value is smaller than a predetermined threshold value. A method for manufacturing a golf club head.

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