Golf club head

Abstract

To provide a golf club head capable of improving a carry of a driven ball when the ball is hit at an ideal hitting point.SOLUTION: A golf club head is provided with a hollow part therein, and includes a face part 2 having a hitting surface 2a, a crown part, a sole part, a tow, and a heel. The hitting surface 2a includes a center part 10 including a face center FC and a transition part 20 formed outside the center part 10. The center part 10 has a certain thickness and has a surface area of equal to or greater than 100 mm2. The transition part 20 is formed so as to annularly surround the center part 10. The thickness of the transition part 20 increases from the center part 10 to each of the crown part, the sole part, the tow, and the heel. The maximum thickness of the transition part 20 is greater than the thickness of the center part 10.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a golf club head. [Background technology]

[0002] In recent years, various golf club heads have been proposed to improve repulsion performance, as shown in, for example, Patent Documents 1 to 3 listed below. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-132995 [Patent Document 2] Japanese Patent Publication No. 2022-108598 [Patent Document 3] Japanese Patent Publication No. 2022-120289 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0004] Golf club heads with high tolerance for mishits have been known up until now. These types of golf club heads have an improved face thickness distribution, etc., so that the loss of flight distance is small even when the ball is struck at a position that is off the ideal impact point on the face (for example, the face center, and so on).

[0005] On the other hand, golf club heads with high forgiveness do not offer much benefit in improving the distance of shots by professional and advanced golfers who can always hit the ball at the ideal impact point. Therefore, there is a demand for technology that can further improve the distance of shots for golfers who can hit the ball at the ideal impact point.

[0006] The present invention was devised in consideration of the above problems, and its main object is to provide a golf club head that can improve the flight distance of a ball when it is hit at an ideal impact point. [Means for solving the problem]

[0007] The present invention provides a golf club head having a hollow portion therein, a face portion having a striking surface, a crown portion, a sole portion, a toe portion, and a heel portion; the striking surface includes a central portion including a face center and a transition portion formed outside the central portion; the central portion has a constant thickness; The central part is 100 mm 2 having a surface area of ​​at least the transition portion is formed so as to be continuous with the central portion and to surround the central portion in an annular shape, the thickness of the transition portion increases from the central portion toward the crown portion, the sole portion, the toe portion, and the heel portion, respectively; The maximum thickness of the transition portion is greater than the thickness of the central portion. A golf club head. [Effects of the Invention]

[0008] By adopting the above-described configuration, the golf club head of the present invention can improve the flight distance of a ball when the ball is hit at an ideal impact point. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a golf club head according to an embodiment of the present invention; [Figure 2] FIG. 2 is a plan view of the golf club head of the present embodiment. [Figure 3] FIG. 2 is a front view of the golf club head of the present embodiment. [Figure 4] FIG. 2 is an enlarged front view of a face portion of the golf club head of the present embodiment. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV in FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 4. [Figure 7] (A) is a front view of the golf club head as seen from the sweet spot, and (B) is its s1 cross-sectional view. [Figure 8] FIG. 10 is a vertical cross-sectional view of a golf club head according to another embodiment. [Figure 9] FIG. 2 is a front view of a face showing the thickness distribution of a face portion of an embodiment. [Figure 10] FIG. 10 is a face front view showing the thickness distribution of the face portion of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will now be described with reference to the drawings. In each embodiment, the same or common elements are denoted by the same reference numerals, and redundant explanations will be omitted.

[0011] 1 to 3 are respectively a perspective view, a plan view, and a front view of a golf club head (hereinafter simply referred to as "head") 1 of this embodiment. In Figs. 1 to 3, the head 1 is placed in a standard state.

[0012] [Reference condition] In this specification, the "reference state" of the head 1 refers to a state in which the head 1 is placed on a horizontal plane HP at a lie angle α (FIG. 3) and a loft angle (not shown) set for the head 1. As shown in FIG. 2, in the reference state, the head 1 is maintained at the lie angle α and the loft angle with the shaft axis center line CL of the head 1 located within a reference vertical plane VP perpendicular to the horizontal plane HP. Unless otherwise specified in this specification, the head 1 is in the reference state. The "shaft axis center line CL" is defined by the axial center line of the shaft insertion hole 5a formed in the hosel portion 5 of the head 1.

[0013] [Head Direction] As shown in Figure 2, in the reference state of the head 1, the direction x perpendicular to the reference vertical plane VP is defined as the front-to-back direction of the head. With respect to the front-to-back direction of the head, the side of the striking surface 2a is defined as the front side, and the opposite side as the rear side. Furthermore, the direction y parallel to both the reference vertical plane VP and the horizontal plane HP is defined as the toe-heel direction. Furthermore, the direction z perpendicular to the horizontal plane HP is defined as the up-down direction of the head.

[0014] [Basic head structure] The head 1 of this embodiment is a golf club head having a hollow portion i (see FIGS. 5 and 6) provided therein. Examples of this type of head include a wood type and a hybrid type. In this embodiment, a wood type head 1 made of a metal material is exemplified.

[0015] As shown in FIGS. 1 to 3, a head 1 includes, for example, a face portion 2, a crown portion 3, a sole portion 4, a toe 7, and a heel 8.

[0016] FIG. 4 is an enlarged front view of the face portion 2 of the head 1. FIGS. 5 and 6 are partial cross-sectional views of the head 1 taken along lines VV and VI-VI in FIG. 4. The face portion 2 comprises a striking surface 2a, which is the surface for striking a ball, and an inner face surface 2i, which faces the hollow portion i of the head 1, as shown in FIGS. 5 and 6. The striking surface 2a may have, for example, a bulge and / or a roll. As is clear from FIGS. 5 and 6, the striking surface 2a of this embodiment is formed as a smooth, three-dimensional curved surface that is convex outward from the head. The striking surface 2a may also have multiple grooves extending in the toe-to-heel direction, known as face lines (not shown).

[0017] Furthermore, the striking surface 2a has a sweet spot SS, a face periphery E, and a face center FC.

[0018] In this specification, the "sweet spot SS" is the point of intersection of the striking surface 2a and a normal N extending from the center of gravity CG of the head to the striking surface 2a, as shown in FIG.

[0019] In this specification, the "face periphery E" defines the outline of the striking surface 2a and is defined as follows: First, as shown in Figure 7(A), each cross section s1, s2, s3... including the normal N connecting the center of gravity CG of the head and the sweet spot SS is identified. Then, as shown in Figure 7(B), the position Pe at each of the cross sections s1, s2, s3... where the radius of curvature r of the outline Lf on the outer surface of the head becomes 200 mm or less from the sweet spot SS toward the outside of the face is determined, and the connection of these positions Pe is defined as the face periphery E that defines the striking surface 2a.

[0020] In this specification, "radius of curvature" is measured on the curve of interest. The radius of curvature of any point on a curve is determined as the radius of a single circle passing through that point, a point 1 mm to one side of that point, and a point 1 mm to the other side of that point. These "1 mm" are the distance along the curve.

[0021] In this specification, the "face center" FC is determined as follows: First, an arbitrary point P (not shown) approximately near the center of the striking surface 2a in the up-down and toe-heel directions is selected. Next, a plane is determined that passes through this point P, extends along the normal to the striking surface 2a at point P, and extends in the toe-heel direction. A line of intersection between this plane and the striking surface 2a is drawn, and its midpoint Px is determined. Next, a plane is determined that passes through this midpoint Px, extends along the normal to the striking surface 2a at point Px, and extends in the up-down direction. A line of intersection between this plane and the face surface is drawn, and its midpoint Py is determined. Next, a plane is determined that passes through this midpoint Py, extends along the normal to the striking surface 2a at point Py, and extends in the toe-heel direction. A line of intersection between this plane and the striking surface 2a is drawn, and its midpoint Px is newly determined. Next, a plane is determined that passes through this new midpoint Px, extends along the normal direction of the striking surface 2a at this point Px, and is in the up-down direction. A line of intersection between this plane and the striking surface 2a is drawn, and its midpoint Py is newly determined. This process is repeated to sequentially determine Px and Py. During this process, the new position Py (last position Py) is determined as the face center when the distance between the new midpoint Py and the immediately preceding midpoint Py is first 0.5 mm or less.

[0022] The crown portion 3 extends rearward from the face portion 2 to form the top surface of the head. A hosel portion 5 is provided on the heel side of the crown portion 3. The hosel portion 5 has a shaft insertion hole 5a for fixing a club shaft (not shown).

[0023] The sole portion 4 extends rearward from the face portion 2 to form the bottom surface of the head. The sole portion 4 is, for example, the portion visible in a bottom view of the head.

[0024] In the front view of the head shown in FIG. 3, the toe 7 of the head 1 is the position opposite to the hosel part 5 and means the position farthest from the hosel part 5 in the toe-heel direction. In addition, the "toe side" means the direction approaching the toe 7.

[0025] In the front view of the head shown in FIG. 3, the heel 8 of the head 1 is located on the hosel part 5 side and 0.875 inches above the horizontal plane HP. The "heel side" refers to the direction approaching the heel 8.

[0026] The main portion of the head 1 is made of, for example, a metal material. The metal material is not particularly limited, but examples thereof include pure titanium, titanium alloy, stainless steel, maraging steel, aluminum alloy, magnesium alloy, and tungsten-nickel alloy. A part of the head 1 (for example, the crown portion 3) may be made of a non-metallic material such as fiber-reinforced resin. The head 1 of this embodiment is made of, for example, a titanium alloy.

[0027] As shown in FIG. 4, the hitting surface 2 a of the face portion 2 includes a central portion 10 including a face center FC, and a transition portion 20 formed outside the central portion 10 .

[0028] The central portion 10 has a constant thickness tc. In this specification, the term "constant thickness" refers not only to a case where the central portion 10 has a completely uniform thickness along the striking surface 2a, but also to a case where the central portion 10 has variations due to unavoidable manufacturing and measurement errors. In the latter case, the thickness of the central portion 10 is determined based on the thickness of the face portion 2 at the face center FC, and any portion of the central portion 10 that varies within ±0.05 mm of this thickness is considered to have the same thickness as the thickness at the face center FC. If a face line is formed on the striking surface 2a, the thickness of each portion of the face portion 2 is measured with the face line buried.

[0029] The central part 10 is 100 mm 2 The central portion 10 has a surface area of ​​10. In Figure 4, the boundary position 10e of the central portion 10 is indicated by a dashed line. The surface area of ​​the central portion 10 is measured on the side of the striking surface 2a. Here, too, the surface area of ​​the central portion 10 is measured with the face line buried.

[0030] The transition portion 20 is formed so as to annularly surround the central portion 10. The thickness of the transition portion 20 increases from the central portion 10 toward the crown portion 3, the sole portion 4, the toe 7, and the heel 8, respectively. As a result, the maximum thickness of the transition portion 20 is formed to be greater than the thickness of the central portion 10.

[0031] In the head 1 of this embodiment formed as described above, the central portion 10 including the face center FC is relatively thinner than the transition portion 20. In addition, the thinned central portion 10 is 100 mm 2 or more. Therefore, with the head 1 of this embodiment, when a ball is hit at the face center FC, the face center FC, which is the impact point, is locally deformed significantly, and the restoring force of this deformation increases the initial velocity of the ball, thereby increasing the flight distance. Therefore, the head 1 of this embodiment can increase the flight distance of the ball when the ball is hit at the ideal impact point. In contrast, in conventional golf club heads with excellent tolerance, the thickness of the face center is usually relatively large and the peripheral portion is thinned, so the effect of directly deforming the impact point significantly, as with the head 1 of this embodiment, cannot be expected. Similarly, when the surface area of ​​the central portion 10 is 100 mm 2 If it is less than this, it becomes difficult to significantly deform the face center FC locally, and as a result, it becomes impossible to obtain a sufficient effect of increasing the flight distance of the ball when it is hit at an ideal impact point.

[0032] Preferred aspects of the head 1 of this embodiment will be described below.

[0033] [Central part] The surface area of ​​the central portion 10 is preferably 140 mm 2 More preferably, 150 mm 2 More than 250mm, preferably 2 This allows for greater local deformation in the vicinity of the face center FC, which in turn allows for a further increase in the flight distance of the ball.

[0034] On the other hand, from the viewpoint of ensuring durability at the face center FC, the surface area of ​​the thinned central portion 10 is preferably 400 mm 2 Less than 300mm, preferably 2 The following is said to be true.

[0035] From another perspective, it is desirable that the surface area of ​​the central portion 10 be 5% to 10% of the surface area of ​​the face portion 2. The surface area of ​​the face portion 2 is the area of ​​the striking surface 2a defined by the face periphery E, and is determined when the face line is filled in. In this way, when the surface area of ​​the central portion 10 is 5% or more of the surface area of ​​the face portion 2, local deformation near the face center FC when hitting the ball can be increased, further increasing the flight distance of the hit ball. Furthermore, when the surface area of ​​the central portion 10 is 10% or less of the surface area of ​​the face portion 2, deterioration of the durability of the face portion 2 can be prevented.

[0036] The thickness tc of the central portion 10 at the face center is preferably 2.5 mm or more, and more preferably 2.6 mm or more. This effectively prevents deterioration of the durability of the face portion 2. On the other hand, the thickness tc of the central portion 10 at the face center is preferably 3.0 mm or less, more preferably 2.9 mm or less, and even more preferably 2.8 mm or less. This increases the local deformation near the face center FC when hitting the ball, further increasing the flight distance of the hit ball. In this embodiment, the thickness tc of the central portion 10 at the face center is 2.75 mm.

[0037] As shown in FIG. 4 , the contour of the central portion 10 (the contour identified by the boundary position 10e of the central portion 10) has an elliptical or oval shape that is longer in the toe-heel direction than in the vertical direction. Since the striking surface 2a of the face portion 2 also has a contour shape that is longer in the toe-heel direction than in the vertical direction, by matching the contour shape of the central portion 10 to that of the striking surface 2a, it is possible to effectively cause large local deformation at or near the face center FC when striking a ball. While not particularly limited, the maximum length of the central portion 10 in the toe-heel direction is preferably 10 mm or more, more preferably 15 mm or more, and even more preferably 20 mm or more. Similarly, although not particularly limited, the maximum length of the central portion 10 in the vertical direction is preferably 10 mm or more, more preferably 15 mm or more.

[0038] [First Transition Section] The transition portion 20 may include, for example, a first transition portion 21. The first transition portion 21 annularly surrounds the central portion 10. The first transition portion 21 has a thickness that continuously changes from the central portion 10 toward the face periphery E. More specifically, the first transition portion 21 of this embodiment has a thickness tt that continuously increases from the central portion 10 toward the crown portion 3, the sole portion 4, the toe 7, and the heel 8, respectively, until it reaches a maximum thickness. The first transition portion 21 serves to alleviate stress concentration near the boundary between the central portion 10 and the transition portion 20 during ball impact, further improving the durability of the face portion 2. In a preferred embodiment, the maximum thickness tt of the first transition portion 21 is greater than the thickness tc (2.75 mm in this embodiment) at the face center FC of the central portion 10 + 0.05 mm (i.e., 2.80 mm). The first transition portion 21 of this embodiment has a thickness tt that continuously increases to 3.10 mm.

[0039] [Second transition section and / or third transition section] The transition portion 20 may include, for example, a second transition portion 22 that continues from the toe 7 side of the first transition portion 21. The second transition portion 22 extends in the toe-heel direction with a constant thickness. In addition to or instead of the second transition portion 22, the transition portion 20 may include, for example, a third transition portion 23 that continues from the heel 8 side of the first transition portion 21. The third transition portion 23 extends in the toe-heel direction with a constant thickness.

[0040] 4, the face portion 2 of this embodiment includes both a second transition portion 22 and a third transition portion 23. The second transition portion 22 and the third transition portion 23 each extend in the toe-heel direction, for example, at the maximum value (e.g., 3.10 mm) of the thickness tt of the first transition portion 21. That is, the thicknesses of the second transition portion 22 and the third transition portion 23 are greater than the thickness tc of the central portion 10.

[0041] The second transition portion 22 is curved in an arc shape having its center on the face center FC side (i.e., convex toward the toe 7 side), and has an upper end 22a on the crown portion 3 side and a lower end 22b on the sole portion 4 side. The width of the second transition portion 22 in the toe-heel direction continuously decreases toward the upper end 22a and the lower end 22b.

[0042] The third transitional portion 23 is also curved in an arc shape having its center on the face center FC side (i.e., convex toward the heel 8 side), and has an upper end 23a on the crown portion 3 side and a lower end 23b on the sole portion 4 side. The width of the third transitional portion 23 in the toe-heel direction continuously decreases toward the upper end 23a and the lower end 23b. The third transitional portion 23 is disposed at an interval from the second transitional portion 22 in the toe-heel direction.

[0043] [Periphery] The face portion 2 may include a peripheral portion 30 outside the transition portion 20. The peripheral portion 30 is formed to continuously or partially surround the transition portion 20, and the thickness tp of the peripheral portion 30 is smaller than the thickness tc of the central portion 10. In this embodiment, the peripheral portion 30 is formed in an annular shape and continuously surrounds the transition portion 20 (in this embodiment, the first, second, and third transition portions). The peripheral portion 30 helps to make the face portion 2 more flexible when hitting a ball, thereby further increasing the flight distance. From this perspective, the thickness of the peripheral portion 30 is, for example, 2.9 mm or less, preferably 2.8 mm or less, and more preferably 2.7 mm or less. On the other hand, if the thickness tp of the peripheral portion 30 is excessively small, the durability of the face portion 2 may be deteriorated and the flexibility of the central portion 10 may be reduced. From this perspective, the thickness tp of the peripheral portion 30 is set to, for example, 2.1 mm or more, preferably 2.2 mm or more, and more preferably 2.3 mm or more.

[0044] The peripheral portion 30 may include, for example, a crown-side peripheral portion 31 that is continuous with the crown portion 3 side of the transition portion 20 , and a sole-side peripheral portion 32 that is continuous with the sole portion 4 side of the transition portion 20 .

[0045] The crown-side peripheral portion 31 extends in the toe-heel direction on the crown portion 3 side (upper side) of the face center FC and across a vertical line passing through the face center FC. The sole-side peripheral portion 32 extends in the toe-heel direction on the sole portion 4 side (lower side) of the face center FC and across a vertical line passing through the face center FC.

[0046] The peripheral portion 30 may further include a toe side peripheral portion 33 that is contiguous with the toe 7 side of the transition portion 20 and a heel side peripheral portion 34 that is contiguous with the heel 8 side of the transition portion 20 .

[0047] The toe-side peripheral portion 33 extends vertically on the toe 7 side of the face center FC and across a horizontal line passing through the face center FC. The heel-side peripheral portion 34 extends vertically on the heel 8 side of the face center FC and across a horizontal line passing through the face center FC.

[0048] In this embodiment, the crown-side peripheral portion 31 has a constant thickness. Similarly, in this embodiment, the sole-side peripheral portion 32 has a constant thickness. The thickness of the crown-side peripheral portion 31 and the thickness of the sole-side peripheral portion 32 may be the same, but in this embodiment, they are different. More specifically, the thickness of the sole-side peripheral portion 32 is formed to be smaller than the thickness of the crown-side peripheral portion 31. Generally, the sole portion 4 has higher bending rigidity than the crown portion 3, so the sole-side peripheral portion 4 side of the face portion 2 tends to be less likely to flex when hitting a ball. On the other hand, by forming the thickness of the sole-side peripheral portion 32 to be smaller than the thickness of the crown-side peripheral portion 31, the sole-side peripheral portion 4 side of the face portion 2 becomes more likely to flex, which in turn makes it possible to further increase the flight distance of the ball.

[0049] The thicknesses of the toe-side peripheral portion 33 and the heel-side peripheral portion 34 are also formed to be smaller than the thickness of the crown-side peripheral portion 31. The thicknesses of the upper end sides of the toe-side peripheral portion 33 and the heel-side peripheral portion 34 increase continuously and are connected to the crown-side peripheral portion 31.

[0050] The head 1 of this embodiment can be implemented in various ways. For example, the face portion 2 may be formed by pressing or forging. In this case, the face portion 2 may be formed as a cup face type having a return portion that partially extends from the face periphery E toward the rear of the head. Alternatively, the face portion 2 may be formed as a face plate having a contour 40 (see FIG. 3) inside the face periphery E, and this may be formed by fixing it to a head main body having a face opening.

[0051] Another embodiment is shown in FIG. 8. FIG. 8 is a longitudinal cross-sectional view of the head taken along a vertical plane passing through the face center FC. As shown in FIG. 8, in this embodiment, the radius of curvature R1 at a first boundary point B1, which is the boundary between the face inner surface 2i and the inner surface 3i of the crown portion 3 in the longitudinal cross-sectional view of the head, is preferably 4.0 to 10.0 mm. Here, the first boundary point B1 is the point near the boundary between the face inner surface 2i and the inner surface 3i of the crown portion 3 where the radius of curvature of the contour line of the head inner surface is minimum. If the part with the minimum radius of curvature is a curve (arc) rather than a point, the midpoint of the curve is set as the first boundary point B1. Furthermore, the thickness t1 of the head at the first boundary point B1 is preferably set to 1.5 mm or more.

[0052] As described above, by forming the first boundary point B1, which is the boundary between the face inner surface 2i and the inner surface 3i of the crown portion 3, with a specific radius of curvature R1 and thickness t1, the vicinity of the first boundary point B1 is prevented from becoming the starting point of bending when hitting a ball. Therefore, the impact force received by the hitting surface 2a is effectively transmitted to the crown portion 3, increasing the deflection of the crown portion 3 and, ultimately, further improving the flight distance of the ball.

[0053] Similarly, in the head longitudinal section shown in Figure 8, the radius of curvature R2 at the second boundary point B2, which is the boundary between the face inner surface 2i and the inner surface 4i of the sole portion 4, is preferably 3.0 to 10.0 mm. Here, the second boundary point B2 is the point near the boundary between the face inner surface 2i and the inner surface 4i of the sole portion 4 where the radius of curvature of the contour line of the head inner surface is minimum. If the part where the radius of curvature is minimum is a curve (arc) rather than a point, the midpoint of that curve is taken as the second boundary point B2. Furthermore, the thickness t2 at the second boundary point B2 is preferably set to 1.5 mm or more.

[0054] In this way, by forming the second boundary point B2, which is the boundary between the face inner surface 2i and the inner surface 4i of the sole portion 4, with a specific radius of curvature R2 and thickness t2, the vicinity of the second boundary point B2 is prevented from becoming the starting point of bending when hitting a ball. Therefore, the impact force received by the hitting surface 2a is effectively transmitted to the sole portion 4, increasing the deflection of the sole portion 4 and, ultimately, further improving the flight distance of the ball.

[0055] To allow the crown portion 3 to flex more when hitting a ball, the crown portion 3 has the smallest thickness at first point P1 in a first region A1 extending from first boundary point B1 to first point P1, which is 10 mm toward the crown (backward of the head). This further suppresses bending at first boundary point B1 when hitting a ball, while increasing bending of the crown portion 3 further back of the head. Here, the "10 mm" refers to the distance along the contour of the inner surface of the head.

[0056] It is desirable that the thickness of the crown portion 3 decreases without increasing from the first boundary point B1 to the first point P1. In other words, in the first region A1, the thickness of the crown portion 3 may decrease continuously toward the first point P1, or may have a constant thickness portion, but it is desirable that the thickness does not increase toward the first point P1. This further suppresses bending at the first boundary point B1 when hitting the ball, and further enhances the effect of increasing the deflection of the crown portion 3.

[0057] At the first point P1, the thickness t10 of the crown portion 3 is preferably 1.0 mm or less. By thinning the first point P1 in this manner, the deflection of the crown portion 3 when hitting the ball is shifted closer to the first point P1 than the first boundary point B1, and bending at the first boundary point B1 can be more reliably suppressed. From the perspective of maintaining the durability of the crown portion 3, the thickness t10 is set to, for example, 0.4 mm or more, preferably 0.6 mm or more.

[0058] Additionally, in order to allow the sole portion 4 to flex more when hitting a ball, in the second region A2 from the second boundary point B2 to a second point P2, which is 15 mm toward the rear of the head, the sole portion 4 has the smallest thickness at the second boundary point P2. This further suppresses bending at the second boundary point B2 when hitting a ball, while increasing the flexure of the sole portion 4 further behind the head. Here, the "15 mm" refers to the distance along the contour line of the inner surface of the head.

[0059] It is desirable that the thickness of the sole portion 4 decreases without increasing from the second boundary point B2 to the second point P2. In other words, in the second region A2, the sole portion 4 may have a thickness that decreases continuously toward the second point P2 or may have a constant thickness portion, but it is desirable that the thickness does not increase toward the second point P2. This further suppresses bending at the second boundary point B2 when hitting the ball, and further enhances the effect of increasing the flexure of the sole portion 4.

[0060] At the second point P2, the thickness t20 of the sole portion 4 is desirably 1.0 mm or less. By thinning the second point P2 in this manner, the deflection of the sole portion 4 when hitting the ball can be shifted closer to the second point P2 than the second boundary point B2, and bending at the second boundary point B2 can be more reliably suppressed. From the perspective of maintaining the durability of the sole portion 4, the thickness t20 is set to, for example, 0.4 mm or more, preferably 0.6 mm or more.

[0061] In the above embodiment, it is sufficient that the above-mentioned characteristics are satisfied in the longitudinal section of the head passing through the face center FC, but it is preferable that the above-mentioned characteristics are satisfied within a range of 10 mm or more in the toe-heel direction centered on the face center FC, preferably a range of 15 mm or more, and even more preferably a range of 20 mm or more.

[0062] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above specific disclosure, and can be implemented in various modified forms within the scope of the technical idea described in the claims. [Example]

[0063] More specific examples of the present invention will be described below, but the present invention is not limited to these specific examples. [Examples 1 to 4] Several types of wood-type golf club heads having the basic structure shown in Figures 1 to 6 were prepared based on the specifications in Table 1, and their flight distance performance and durability were tested. The thickness distribution shape of the face portion of the example is shown in Figure 9. For comparison, the same test was also conducted on Comparative Example 1.

[0064] [Comparative Example 1] Comparative Example 1 is a wood-type golf club head outside the scope of the present invention, and differs only in the thickness distribution of the face portion from the heads of the Examples. Specifically, as shown in Figure 10, the head of Comparative Example 1 includes a thick portion in the center of the face portion with a thickness of 3.3 mm, a transition portion formed around the thick portion and having a thickness that continuously decreases from 3.3 mm to 2.5 mm toward the periphery of the face, a toe side portion formed on the toe side of the transition portion and having a thickness that continuously decreases from 2.5 mm to 2.1 mm toward the toe side, a toe side portion formed on the heel side of the transition portion and having a thickness that continuously decreases from 2.5 mm to 2.1 mm toward the heel side, and a peripheral portion extending annularly along the periphery of the face. The peripheral portion has a constant thickness of 2.5 mm on the crown side and 2.3 mm on the sole side.

[0065] For the distance performance test, the same club shaft was attached to each golf club head to prepare the golf clubs, which were then attached to a swing robot and the distance measured when hitting the ball at the face center 10 times, and the average value was calculated. The results are expressed as an index with the average distance of Comparative Example 1 set to 100, and the higher the value, the better the distance performance.

[0066] For the durability performance test, a club was attached to a swing robot and a two-piece ball was hit at a head speed of 54 m / s. The impact point was set to the face center FC. The face surface was inspected in detail every 50 hits to check for cracks or other damage. Hitting was stopped when damage was found. If no damage occurred after 5,000 hits, hitting was stopped at 5,000. The number of hits at which the hitting was stopped was the evaluation result of the durability performance test.

[0067] [Table 1]

[0068] As a result of the test, it was confirmed that each head of the example had improved distance performance compared to the first comparative example.

[0069] The present invention includes the following aspects. [Invention 1] A golf club head having a hollow portion therein, a face portion having a striking surface, a crown portion, a sole portion, a toe portion, and a heel portion; the striking surface includes a central portion including a face center and a transition portion formed outside the central portion; the central portion has a constant thickness; The central part is 100 mm 2 having a surface area of ​​at least the transition portion is formed so as to be continuous with the central portion and to surround the central portion in an annular shape, the thickness of the transition portion increases from the central portion toward the crown portion, the sole portion, the toe portion, and the heel portion, respectively; The maximum thickness of the transition portion is greater than the thickness of the central portion. Golf club head. [Invention 2] The face portion further includes a peripheral portion on the outside of the transition portion, the peripheral portion continuously or partially surrounds the transition portion; The golf club head according to the first aspect of the present invention, wherein the thickness of the peripheral portion is smaller than the thickness of the central portion. [Invention 3] 3. The golf club head according to claim 2, wherein the peripheral portion continuously surrounds the transition portion. [Invention 4] 4. The golf club head according to any one of claims 1 to 3, wherein the thickness of the central portion is 2.5 to 3.0 mm. [Invention 5] 5. The golf club head according to any one of claims 1 to 4, wherein the surface area of ​​the central portion is 5% to 10% of the surface area of ​​the face portion. [Invention 6] 6. The golf club head according to any one of claims 1 to 5, wherein the central portion has an elliptical or oblong contour that is longer in the toe-heel direction than in the vertical direction. [Invention 7] the transition portion includes a first transition portion; the first transition portion annularly surrounds the central portion, A golf club head according to any one of the first to sixth aspects of the present invention, wherein the thickness of the first transition portion increases continuously from the central portion toward the crown portion, the sole portion, the toe and the heel, respectively. [Invention 8] The transition portion includes a second transition portion connected to a toe side of the first transition portion, 8. The golf club head according to claim 7, wherein the second transition portion extends in the toe-to-heel direction with a constant thickness. [Invention 9] the transition portion includes a third transition portion connected to a heel side of the first transition portion, 9. The golf club head according to claim 7 or 8, wherein the third transition portion extends in the toe-to-heel direction with a constant thickness. [Invention 10] The golf club head according to the second aspect of the present invention, wherein the thickness of the peripheral portion is 2.1 to 2.9 mm. [Invention 11] the peripheral portion includes a crown-side peripheral portion that is continuous with the transition portion on the crown portion side, and a sole-side peripheral portion that is continuous with the transition portion on the sole side, The golf club head according to invention 2 or 10, wherein the thickness of the sole-side peripheral portion is smaller than the thickness of the crown-side peripheral portion. [Invention 12] the peripheral portion includes a toe-side peripheral portion that is continuous with the toe side of the transition portion and a heel-side peripheral portion that is continuous with the heel side of the transition portion, 12. The golf club head according to claim 11, wherein the thickness of the toe side peripheral portion and the heel side peripheral portion is smaller than the thickness of the crown side peripheral portion. [Explanation of symbols]

[0070] 1 golf club head 2 Face section 3 Crown 4 Sole 7 Tou 8 Heels 10 Central part 20 Transition 21 First Transitional Section 22 Second Transitional Section 23 Third Transitional Section 30 Periphery 31 Crown side periphery 32 Sole side periphery 33 Toe side periphery 34 Heel side periphery FC Face Center

Claims

1. A golf club head having a hollow portion therein, a face portion having a striking surface, a crown portion, a sole portion, a toe portion, and a heel portion; the striking surface includes a central portion including a face center and a transition portion formed outside the central portion; the central portion has a constant thickness; The central part is 100 mm ２ having a surface area of ​​at least the transition portion is formed so as to be continuous with the central portion and to surround the central portion in an annular shape, the thickness of the transition portion increases from the central portion toward the crown portion, the sole portion, the toe portion, and the heel portion, respectively; The maximum thickness of the transition portion is greater than the thickness of the central portion. Golf club head.

2. The face portion further includes a peripheral portion on the outside of the transition portion, the peripheral portion continuously or partially surrounds the transition portion; The golf club head of claim 1 , wherein the thickness of the peripheral portion is less than the thickness of the central portion.

3. The golf club head of claim 2 , wherein the periphery continuously surrounds the transition portion.

4. 2. The golf club head according to claim 1, wherein the thickness of the central portion is 2.5 to 3.0 mm.

5. 2. The golf club head according to claim 1, wherein the surface area of ​​the central portion is 5% to 10% of the surface area of ​​the face portion.

6. 2. The golf club head according to claim 1, wherein the central portion has an elliptical or oval contour that is longer in the toe-heel direction than in the vertical direction.

7. the transition portion includes a first transition portion; the first transition portion annularly surrounds the central portion, The golf club head of claim 1 , wherein the thickness of the first transition portion increases continuously from the central portion toward the crown portion, the sole portion, the toe portion, and the heel portion, respectively.

8. The transition portion includes a second transition portion connected to a toe side of the first transition portion, The golf club head according to claim 7 , wherein the second transition portion extends in the toe-heel direction with a constant thickness.

9. the transition portion includes a third transition portion connected to a heel side of the first transition portion, 9. The golf club head according to claim 7, wherein the third transition portion extends in the toe-heel direction with a constant thickness.

10. 3. The golf club head according to claim 2, wherein the thickness of the peripheral portion is 2.1 to 2.9 mm.

11. the peripheral portion includes a crown-side peripheral portion that is continuous with the transition portion on the crown portion side, and a sole-side peripheral portion that is continuous with the transition portion on the sole side, The golf club head according to claim 2 , wherein the thickness of the sole-side peripheral portion is smaller than the thickness of the crown-side peripheral portion.

12. the peripheral portion includes a toe-side peripheral portion that is continuous with the toe side of the transition portion and a heel-side peripheral portion that is continuous with the heel side of the transition portion, The golf club head according to claim 11 , wherein the thickness of the toe-side periphery and the heel-side periphery is less than the thickness of the crown-side periphery.

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