Golf club head

Abstract

A golf club head with a cavity therein comprises a face portion having a club face for striking a ball, a crown portion, a sole portion, a toe and a heel. The club face comprises a central part including a face center, and a transitional part outside the central part. The central part has a constant thickness and a surface area of not less than 100 sq.mm. The transitional part annularly surrounds the central part. The thickness of the transitional part increases from the central part toward the crown portion, sole portion, toe and heel. The maximum thickness of the transitional part is larger than the thickness of the central part.

Description

Technical field

[0001] The present disclosure relates to a golf club head.Background art

[0002] In recent years, various golf club heads devised to be improved in coefficient of restitution have been proposed, for example, as shown in Patent Documents 1 to 3 listed below.Prior art document Patent Documents

[0003] Patent Document 1: Japanese Patent Application Publication No. 2021-132995 Patent Document 2: Japanese Patent Application Publication No. 2022-108598 Patent Document 3: Japanese Patent Application Publication No. 2022-120289 Summary of the Invention Problems to be solved by the Invention

[0004] Golf club heads having enhanced forgiveness on miss shots have been known. In such a golf club head, the thickness distribution of the face portion is improved in order that the drop in flight distance will become small even if the ball is hit at a position that deviates from an ideal impact position on the club face (for example, the face center, the same applies hereinafter).

[0005] On the other hand, in the case of professional golfers and advanced golfers who can always hit the ball at an ideal impact position, golf club heads having enhanced forgiveness on miss shots have little benefit in improving the flight distance. Therefore, for the golfers who can hit the ball at an ideal impact position, technology that can further increase the flight distance of the ball is required.

[0006] The present disclosure was devised in view of the problems as described above, and a primarily objective of the present disclosure is to provide a golf club head in which the flight distance of a ball when hit at an ideal impact position can be further improved.Means for solving the Problems

[0007] According to the present disclosure, a golf club head provided with a cavity therein, comprises a face portion having a club face for striking a ball, a crown portion, a sole portion, a toe and a heel, wherein the club face comprises a central part including a face center and a transitional part formed outside the central part, the thickness of the face portion 2 in the central part is constant, the surface area of the central part is not less than 100 sq.mm, the transitional part is continuous to the central part and is formed to annularly surround the central part, the thickness of the face portion 2 in the transitional part increases from the central part toward the crown portion, the sole portion, the toe and the heel, and the maximum thickness of the face portion 2 in the transitional part is larger than the thickness of the face portion 2 in the central part. Effects of the Invention

[0008] In the golf club head according to the present disclosure, as the above-described configuration is employed, it is possible to further improve the flight distance of a ball when hit at an ideal impact position.Brief description of the Drawings

[0009] FIG 1 is a perspective view of a golf club head as an embodiment of the present disclosure. FIG 2 is a top view thereof. FIG 3 is a front view thereof. FIG 4 is a front view of the face portion of the golf club head. FIG 5 is a cross-sectional view taken along line V-V in FIG 4. FIG 6 is a cross-sectional view taken along line VI-VI in FIG 4. FIGS. 7A and 7B are a front view and a s1-section view, respectively, of the face portion of a golf club head for explaining the peripheral edge of a club face for striking a ball. FIG 8 is a vertical cross-sectional view of as another example of the face portion of the golf club head. FIG 9 is a diagrammatic front view of the club face for explaining a thickness distribution of the face portion of the golf club head. FIG 10 is a diagrammatic front view of the club face of Comparative example showing the thickness distribution of the face portion thereof. Detailed description of the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described in detail in conjunction with accompanying drawings. Throughout all the embodiments, the same or common components are denoted by the same reference numerals, and redundant explanations are omitted.

[0011] FIGS. 1, 2 and 3 are a perspective view, a plan view, and a front view, respectively, of a golf club head 1 as an embodiment of the present disclosure (hereinafter simply referred to as the head 1) . In FIGS. 1-3, the head 1 is under its reference state.< Reference state >

[0012] In this application, the "reference state" of a golf club head is such a state that the head is placed on a horizontal plane HP at its lie angle α and loft angle (not shown) specified for the head, with a shaft axis CL of the head lying within a reference vertical plane VP (FIG 2) orthogonal to the horizontal plane HP at the lie angle α as shown in FIG 3.

[0013] In this application, descriptions are made assuming that the head is under the a reference state unless otherwise noted. In the case of the head alone, the "shaft axis CL" can be defined by the center line of the shaft insertion hole 5a formed in the hosel portion 5 of the head.< Directions related to the head >

[0014] As shown in FIG 2, a front-rear direction of the head 1 under the reference state is a direction x perpendicular to the above-mentioned reference vertical plane VP.

[0015] In the front-rear direction of the head, the side of the club face 2a is the front side, and the opposite side is the rear side.

[0016] Further, a toe-heel direction of the head 1 under the reference state is a direction parallel to both the above-mentioned horizontal plane HP and the reference vertical plane VP.

[0017] Furthermore, an up-down direction of the head 1 under the reference state is a direction perpendicular to the horizontal plane HP.< Basic structure of the head >

[0018] The head 1 in this embodiment is a golf club head provided with a cavity (i) therein (see FIGS. 5 and 6). Examples of this type of head include heads for wood-type golf clubs and hybrid-type golf clubs.

[0019] In this embodiment, the head 1 is designed as a wood-type head made of metal material or materials.

[0020] As shown in FIGS. 1 to 3, the head 1 comprises a face portion 2, a crown portion 3, a sole portion 4, a toe 7 and a heel 8.

[0021] FIG 4 is a front view of the head 1 showing the face portion 2. FIG 5 is a cross-sectional view of the face portion of the head 1 taken along line V-V in FIG 4. FIG 6 is a cross-sectional view of the face portion of the head 1 taken along line VI-VI in FIG 4.

[0022] As shown in FIGS. 5 and 6, the face portion 2 has an outer surface defining a club face 2a for hitting a ball, and an inner surface 2i facing the cavity (i) of the head 1, The club face 2a may be provided with a bulge and / or a roll, for example.

[0023] As is clear from FIGS. 5 and 6, the club face 2a in this embodiment is a smoothly three-dimensionally curved surface which is convex toward the outside of the head.

[0024] The club face 2a may be provided with narrow grooves called face lines (not shown) extending in the toe-heel direction.

[0025] The club face 2a has a sweet spot SS, a face peripherally edge E and a face center FC.

[0026] In this application, the "sweet spot SS" of the club face 2a is a point of intersection of a normal line N with the club face 2a, wherein the normal line N is a straight line drawn from the gravity center CG of the head to the club face 2a normally to the club face 2a.

[0027] In this application, the peripherally edge E of the club face defines the contour of the club face 2a, and is defined as follows.

[0028] For each cross section (s1, s2, s3 ----) including the normal line N as shown in FIG 7A, firstly, obtain positions Pe on the outer contour line Lf of the head at which the curvature radius (r) is decreased and first becomes 200 mm in a course from the sweet spot SS toward the periphery of the club face as shown in FIG 7B, and then, obtain a curve passing through the obtained positions Pe, and define it as the peripheral edge E.

[0029] In this application, the radius of curvature at any position on a curved line may be determined as the radius of a circle passing through three points: a first point at said any position, a second point on the curved line at 1 mm toward one side of the first point along the curved line, and a third point on the curved line at 1 mm toward the other side of the first point along the curved line.

[0030] In this application, the face center FC is determined as follows. (step 1) arbitrary-select a point P (not shown) on the club face 2a which is regarded as being approximately center in the up-down direction and also approximately center in the toe-heel direction of the head 1. (step 2) determine a plane parallel with the toe-heel direction which passes through the point P and extends along the normal direction to the club face 2a at the point P. (step 3) obtain a midpoint Px of a line of intersection between the plane determined in step 2 and the club face 2a. (step 4) determine a plane parallel with the up-down direction which passes through the midpoint Px obtained in step 3 and extends along the normal direction to the club face 2a at this midpoint Px. (step 5) obtain a midpoint Py of a line of intersection between the plane determined in step 4 and the club face 2a. (step 6) determine a plane parallel with the toe-heel direction which passes through the midpoint Py obtained in step 5 and extends along the normal direction to the club face 2a at this midpoint Py. (step 7) obtain a new midpoint Px of a line of intersection between the plane determined in step 6 and the club face 2a. (step 8) determine a plane parallel with the up-down direction which passes through the new midpoint Px obtained in step 7 and extends along the normal direction to the club face 2a at this midpoint Px. (step 9) obtain a new midpoint Py of a line of intersection between the plane determined in step 8 and the club face 2a.

[0031] As described above, by repeating the steps such as step 1-step 9, midpoints Px and midpoints Py are sequentially obtained. And, during sequentially obtaining midpoints Py, when the distance between the newly obtained midpoint Py and the last obtained midpoint Py first becomes 0.5 mm or less, the position of the newly obtained midpoint Py is determined as the face center FC.

[0032] The crown portion 3 extends from the face portion 2 toward the rear of the head so as to form the upper surface of the head.

[0033] On the heel side of the crown portion 3, a hosel portion 5 is formed.

[0034] The hosel portion 5 is provided with a shaft insertion hole 5a into which a tip end of a club shaft (not shown) is inserted and fixed.

[0035] The sole portion 4 extends from the face portion 2 toward the rear of the head so as to form the bottom surface of the head. The sole portion 4 is, for example, defined as a portion visible in a bottom view of the head.

[0036] In the front view of the head, as shown in FIG 3, the toe 7 of the head 1 means a position which is opposite to the hosel portion 5 and farthest from the hosel portion 5 in the toe-heel direction. The term "toe side" means a direction approaching the toe 7.

[0037] In the front view of the head, as shown in FIG 3, the heel 8 of the head 1 means a position which is located on the hosel portion 5 side and 0.875 inches above the horizontal plane HP. The term "heel side" means a direction approaching the heel 8.

[0038] The head 1 in this example comprises a main portion made of a metal material or materials. As to the metal materials, for example, pure titanium, titanium alloys, stainless steels, maraging steels, aluminum alloys, magnesium alloys, tungsten-nickel alloys, etc. can be used although not particularly limited. Further, 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. In this embodiment, the head 1 is made of a titanium alloy.

[0039] As shown in FIG 4, the club face 2a of the face portion 2 comprises a central part 10 in which a face center FC is located, and a transitional part 20 formed outside the central part 10.

[0040] The central part 10 is a region in which the face portion has a constant thickness tc.

[0041] In this application, the constant thickness tc in the central part 10 means not only a case where the thickness is completely the same continuously along the club face 2a, but also a case where the thickness varies within a range of manufacturing errors and a range of measurement errors which may inevitably occur.

[0042] Regarding the latter case, based on the thickness of the face portion 2 at the face center FC, if the difference from this thickness is within + / - 0.05 mm, then a portion having such difference is considered to be a portion having the same thickness, namely, the central part 10.

[0043] Incidentally, when face lines or face grooves are formed on the club face 2a, the thickness of such grooved part of the face portion 2 is determined assuming that the face groove is filled up, in other words, assuming that there is no face groove.

[0044] The central part 10 has a surface area of not less than 100 sq.mm.

[0045] In FIG 4, the boundary position 10e of the central part 10 is indicated by a short-dashes line. The surface area of the central part 10 is measured on the club face 2a.

[0046] If the above-mentioned face lines or face grooves are formed on the club face 2a, then the surface area of the central part 10 is determined assuming that the face grooves are filled up.

[0047] The transitional part 20 is formed to annularly surround the central part 10.

[0048] The thickness of the transitional part 20, which is the thickness of the face portion measured in the transitional part 20, increases from the central part 10 towards the crown portion 3, sole portion 4, toe 7 and heel 8.

[0049] Therefore, the maximum of the thickness of the face portion 2 in the transitional part 20 is larger than the thickness of the central part 10.

[0050] In the head 1 in this embodiment formed as described above, the thickness of the face portion is smaller in the central part 10 including the face center FC than in the transitional part 20, and the thin central part 10 has a surface area of not less than 100 sq.mm. Therefore, in the head 1 in the present embodiment, when a ball is hit at the face center FC, the central part 10 is locally significantly deformed at the face center FC and a larger restoring force is obtained. As a result, the initial velocity of the ball is increased, and the flight distance is increased.

[0051] In this way, the head 1 in this embodiment can increase the flight distance of a ball when hit at an ideal impact position or the face center FC.

[0052] On the other hand, in conventional golf club heads having excellent forgiveness on miss shots, generally, the thickness of the face portion is relatively large at the face center and relatively small in its surrounding portion, so it cannot be expected to directly significantly deform the impact position as in the head 1 in the present embodiment.

[0053] If the surface area of the central part 10 of the head 1 in this embodiment is less than 100 sq.mm, then it becomes difficult to locally significantly deform the central part 10 at the face center FC, and as a result, it is not possible to obtain a sufficient effect of increasing the flight distance of a ball when hit at an ideal impact position.

[0054] Hereinafter, features preferred for the head 1 in this embodiment will be described.< Central part >

[0055] The surface area of the central part 10 is preferably not less than 140 sq.mm, more preferably not less than 150 sq.mm, still more preferably not less than 250 sq.mm. Thereby, the local deformation around the face center FC can be made larger, and the flight distance of the ball can be further increased.

[0056] On the other hand, from the viewpoint of ensuring the durability at the face center FC, the surface area of the thin central part 10 is preferably not more than 400 sq.mm, more preferably not more than 300 sq.mm.

[0057] From another point of view, it is desirable that the surface area of the central part 10 is in a range from 5% to 10% of the surface area of the face portion 2.

[0058] Incidentally, the surface area of the face portion 2 is the area of the club face 2a defined by the above-described peripherally edge E, by filling up the face grooves if provided.

[0059] In this way, as the surface area of the central part 10 is not less than 5% of the surface area of the face portion 2, the local deformation around the face center FC at impact can be made larger, thereby further increasing the flight distance of the hit ball.

[0060] Further, as the surface area of the central part 10 is not more than 10% of the surface area of the face portion 2, deterioration of the durability of the face portion 2 can be prevented.

[0061] The thickness tc in the central part 10 at the face center is preferably not less than 2.5 mm, more preferably not less than 2.6 mm. Thereby, deterioration of the durability of the face portion 2 can be effectively prevented.

[0062] On the other hand, the thickness tc of the face portion 2 in the central part 10 at the face center is preferably not more than 3.0 mm, more preferably not more than 2.9 mm, still more preferably not more than 2.8 mm.

[0063] Thereby, it is possible to further increase the local deformation around the face center FC at impact to further increase the flight distance of the ball.

[0064] In this embodiment, the thickness tc of the face portion 2 in the central part 10 at the face center is 2.75 mm.

[0065] The central part 10 has a contour (the contour defined by the boundary position 10e of the central part 10) which is generally an elliptical or oval shape being longer in the toe-heel direction than in the up-down direction as shown in FIG 4.

[0066] Since the club face 2a of the face portion 2 also has a contour shape being longer in the toe-heel direction than in the up-down direction, by making the contour shape of the central part 10 correspond to that of the club face 2a, it becomes possible to effectively locally largely deform the face center FC or its vicinity when hit by a ball.

[0067] The maximum length in the toe-heel direction of the central part 10 is not less than 10 mm, preferably not less than 15 mm, more preferably not less than 20 mm although not particularly limited.

[0068] The maximum dimension in the up-down direction of the central part 10 is not less than 10 mm, preferably not less than 15 mm although not particularly limited.< First transitional part >

[0069] The transitional part 20 may include a first transitional part 21 as in the present embodiment.

[0070] The first transitional part 21 annularly surrounds the central part 10.

[0071] In the first transitional part 21, the thickness tt of the face portion continuously changes from the central part 10 toward the face peripheral edge E.

[0072] More specifically, in the first transitional part 21 of this embodiment, the thickness tt increases continuously from the central part 10 toward the crown portion 3, sole portion 4, toe 7, and heel 8, and reaches the maximum thickness.

[0073] Such first transitional part 21 helps to mitigate stress concentration occurring near the boundary between the central part 10 and the transitional part 20 at impact, thereby further improving the durability of the face portion 2.

[0074] Preferably, the maximum value of the thickness tt of the first transitional part 21 is larger than the thickness tc of the face portion 2 in the central part 10 at the face center FC.

[0075] In this embodiment, the maximum value of the thickness tt is larger than the thickness tc(=2.75 mm) + 0.05 mm = 2.80 mm.

[0076] In the first transitional part 21 in this embodiment, the thickness tt continuously increases to 3.10 mm.< Second transitional part and / or third transitional part >

[0077] The transitional part 20 may include a second transitional part 22 as in the present embodiment. The second transitional part 22 is connected to the first transitional part 21 on the toe 7 side thereof.

[0078] The second transitional part 22 extends in the toe-heel direction while keeping a constant thickness.

[0079] Further, the transitional part 20 may include a third transitional part 23 instead of the second transitional part 22 or in combination with the second transitional part 22 as in the present embodiment.

[0080] The third transitional part 23 is connected to the first transitional part 21 on the heel 8 side thereof.

[0081] The third transitional part 23 extends in the toe-heel direction while keeping a constant thickness.

[0082] In this embodiment, as shown in FIG 4, the face portion 2 includes both the second transitional part 22 and the third transitional part 23. The second transitional part 22 and the third transitional part 23 each extend in the toe-heel direction while keeping a constant thickness which is, for example, corresponds to the maximum value (in this example, 3.10 mm) of the thickness tt of the first transitional part 21.

[0083] That is, the thicknesses in the second transitional part 22 and the third transitional part 23 are larger than the thickness tc of the face portion 2 in the central part 10.

[0084] The second transitional part 22 is curved in an arc-like shape having a center or centers on the face center FC side (that is, convex toward the toe 7), and has an upper end 22a on the crown portion 3 side and a lower end 22b on the sole portion 4 side.

[0085] And, toward both the upper end 22a and the lower end 22b, the second transitional part 22 is tapered, and the width of the second transitional part 22 measured in the toe-heel direction is continuously decreased.

[0086] In this example, the second transitional part 22 has generally a crescent shape.

[0087] The third transitional part 23 is also curved in an arc-like shape having a center or centers on the face center FC side (that is, convex toward the heel 8), and has an upper end 23a on the crown portion 3 side and a lower end 23b on the sole portion 4 side.

[0088] And, toward both the upper end 23a and the lower end 23b, the third transitional part 23 is tapered, and the width of the third transitional part 23 measured in the toe-heel direction is continuously decreased.

[0089] In this example, the third transitional part 23 has generally a crescent shape.

[0090] The third transitional part 23 and the second transitional part 22 are spaced apart from each other in the toe-heel direction.< Peripheral part >

[0091] The face portion 2 may include a peripheral part 30 outside the transitional part 20 as in the present embodiment as shown in FIG 4.

[0092] The peripheral part 30 may be formed so as to continuously or intermittently surround the transitional part 20.

[0093] The thickness tp of the face portion 2 in the peripheral part 30 is smaller than the thickness tc of the face portion 2 in the central part 10.

[0094] In this embodiment, the peripheral part 30 is formed in an annular shape and continuously surrounds the transitional part 20 (namely, all the first, second, and third transitional parts in this embodiment).

[0095] The peripheral part 30 makes the face portion 2 more flexible when hit by a ball, and helps to further increase the flight distance of the ball. From this point of view, the thickness of the face portion 2 in the peripheral part 30 is, for example, not more than 2.9 mm, preferably not more than 2.8 mm, more preferably not more than 2.7 mm.

[0096] On the other hand, if the thickness tp of the face portion 2 in the peripheral part 30 becomes too small, the durability of the face portion 2 will deteriorate and there is a possibility that the deflection of the central part 10 will decrease. From this point of view, the thickness tp of the face portion 2 in the peripheral part 30 is, for example, set to be not less than 2.1 mm, preferably not less than 2.2 mm, more preferably not less than 2.3 mm.

[0097] The peripheral part 30 may include a crown-side peripheral part 31 and a sole side peripheral part 32 as in the present embodiment.

[0098] The crown-side peripheral part 31 is connected to the transitional part 20 on the crown portion 3 side thereof.

[0099] The sole side peripheral part 32 is connected to the transitional part 20 on the sole portion 4 side thereof.

[0100] The crown-side peripheral part 31 extends in the toe-heel direction on the crown portion 3 side (upper side) than the face center FC and crosses a vertical line passing through the face center FC in the front view.

[0101] The sole side peripheral part 32 extends in the toe-heel direction on the sole portion 4 side (lower side) than the face center FC and crosses the vertical line passing through the face center FC in the front view.

[0102] The peripheral part 30 may further include a toe-side peripheral part 33 and a heel-side peripheral part 34 as in the present embodiment.

[0103] The toe-side peripheral part 33 is connected to the transitional part 20 on the toe 7 side thereof.

[0104] The heel-side peripheral part 34 is connected to the transitional part 20 on the heel 8 side thereof.

[0105] The toe-side peripheral part 33 extends in the up-down direction on the toe 7 side of the face center FC so as to cross a horizontal line passing through the face center FC in the front view.

[0106] The heel-side peripheral part 34 extends in the up-down direction on the heel 8 side of the face center FC so as to cross the horizontal line passing through the face center FC in the front view.

[0107] In this embodiment, the thickness of the face portion 2 in the crown-side peripheral part 31 has a constant value.

[0108] In this embodiment, the thickness of the face portion 2 in the sole side peripheral part 32 also has a constant value.

[0109] Although, the thickness of the face portion 2 in the crown-side peripheral part 31 and the thickness of the face portion 2 in the sole side peripheral part 32 may be the same thickness value, these thicknesses in this embodiment are different from each other.

[0110] More specifically, the thickness of the face portion 2 in the sole side peripheral part 32 is smaller than the thickness of the face portion 2 in the crown-side peripheral part 31.

[0111] In general, the sole portion 4 has higher bending rigidity than the crown portion 3, so the sole portion 4 side of the face portion 2 tends to be difficult to bend when hit by a ball.

[0112] In the present embodiment, however, as the thickness of the face portion 2 in the sole side peripheral part 32 is smaller than the thickness of the face portion 2 in the crown-side peripheral part 31, the sole portion 4 side of the face portion 2 becomes relatively easy to be bent, and as a result, it becomes possible to further increase the flight distance of the ball.

[0113] The thickness of the face portion 2 in the toe-side peripheral part 33 and the thickness of the face portion 2 in the heel-side peripheral part 34 are, for example, set to be smaller than the thickness of the face portion 2 in the crown-side peripheral part 31.

[0114] An upper end part of the toe-side peripheral part 33 and an upper end part of the heel-side peripheral part 34 are each continuously increased in the thickness of the face portion 2 toward the crown-side peripheral part 31, and are each connected to the crown-side peripheral part 31.

[0115] The head 1 in this embodiment can be manufactured in various modes. For example, the face portion 2 may be formed by pressing or forging. In such cases, the face portion 2 may be formed as a cup face type which includes a turnback partially extending toward the rear of the head from the face peripheral edge E. Further, the face portion 2 may be formed as a face plate (without turnback) which has, as shown in FIG 3, a contour 40 positioned inside the face peripheral edge E and which is fitted and fixed to a front opening of a main body of the head.

[0116] FIG 8 shows features preferred for the head 1 in the present embodiment. FIG 8 is a vertical cross-sectional view of the head 1 taken along a vertical plane which passes through the face center FC and is orthogonal to both the above-mentioned horizontal plane HP and reference vertical plane VP.

[0117] As shown in FIG 8, in this embodiment, a radius of curvature R1 at a first boundary point B1 is preferably set in a range from 4.0 to 10.0 mm in the vertical cross-sectional view of the head.

[0118] Here, the first boundary point B1 is a point on the inner surface of the head 1 facing the cavity (i), which point is located around the boundary between the inner surface 2i of the face portion 2 and the inner surface 3i of the crown portion 3, and at which the radius of curvature of the outline of the inner surface of the head 1 becomes a minimum in the vertical cross-sectional view of the head.

[0119] If the minimum occurs along a curved line (circular arc), not at a point, then the first boundary point B1 is defined by the midpoint of the length of the curved line.

[0120] Further, at the first boundary point B1, the thickness t1 of the head 1 (wall thickness shown in FIG.8) is preferably set to be not less than 1.5 mm.

[0121] As described above, by configuring the head structure around the first boundary point B1 so as to have the specific curvature radius R1 and thickness t1, this portion around the first boundary point B1 can be prevented from becoming the starting point of bending when hit by a ball.

[0122] Therefore, the impact force received by the club face 2a is effectively transmitted to the crown portion 3, which makes it possible to increase the deflection of the crown portion 3, and as a result, the flight distance of the ball can be further improved.

[0123] Similarly, a radius of curvature R2 at a second boundary point B2 is preferably set in a range from 3.0 to 10.0 mm in the vertical cross-section of the head shown in FIG 8. Here, the second boundary point B2 is a point on the inner surface of the head 1 facing the cavity (i), which point is located around the boundary between the inner surface 2i of the face portion 2 and the inner surface 4i of the sole portion 4, and at which the radius of curvature of the outline of the inner surface of the head becomes a minimum in the vertical cross-sectional view of the head.

[0124] If the minimum occurs along a curved line (circular arc), not at a point, then the second boundary point B2 is defined by the midpoint of the length of the curved line.

[0125] Further, at the second boundary point B2, the thickness t2 of the head 1 (wall thickness shown in FIG 8) is preferably set to be not less than 1.5 mm.

[0126] As described above, by configuring the head structure around the second boundary point B2 so as to have the specific curvature radius R2 and thickness t2, the portion around the second boundary point B2 can be prevented from becoming the starting point of bending when hit by a ball.

[0127] Therefore, the impact force received by the club face 2a is effectively transmitted to the sole portion 4, which makes it possible to increase the deflection of the sole portion 4, and as a result, the flight distance of the ball can be further improved.

[0128] In order to make the crown portion 3 to be deflected more in a position away from the first boundary point B1 when hit by a ball,

[0129] in a first area A1 defined as extending from the first boundary point B1 to a first point P1, the crown portion 3 has a smallest thickness at the first point P1, wherein the first point P1 is away from the first boundary point B1 toward the crown portion side (or, back side of the head) by 10 mm along the contour line of the inner surface of the head.

[0130] Thereby, the bending at the first boundary point B1 when hit by a ball is further suppressed, while the bending of the crown portion 3 in the rear of the first point P1 can be increased.

[0131] It is preferable that, from the first boundary point B1 to the first point P1, the thickness of the crown portion 3 decreases without increasing. That is, in the first region A1, the thickness of the crown portion 3 is continuously decreased from the first boundary point B1 to the first point P1, or the crown portion 3 does not have a part where the thickness increases toward the first point P1, but may have a part where the thickness is constant.

[0132] Thereby, bending occurring around the first boundary point B1 when hit by a ball can be further suppressed, and the effect of increasing the deflection of the crown portion 3 can be further enhanced.

[0133] It is preferable that, at the first point P1, the thickness t10 of the crown portion 3 is set to be not more than 1.0 mm, for example.

[0134] By making the thickness at the first point P1 smaller in this way, the position where the crown portion 3 is deflected when hit by a ball can be shifted toward the first point P1 from the first boundary point B1, and bending occurring around the first boundary point B1 can be suppressed more reliably.

[0135] From the viewpoint of securing the durability of the crown portion 3, the thickness t10 is preferably set to be not less than 0.4 mm, more preferably not less than 0.6 mm.

[0136] Further, in order to make the sole portion 4 to be deflected more in a position away from the second boundary point B2 when hit by a ball, in a second region A2 defined as extending from the second boundary point B2 to a second point P2, the sole portion 4 has a smallest thickness at the second point P2, wherein the second point P2 is away from the second boundary point B2 toward the back side of the head by 15 mm along the contour line of the inner surface of the head.

[0137] Thereby, the bending at the second boundary point B2 when hit by a ball is further suppressed, while the bending of the sole portion 4 in the rear of the second point P2 can be increased.

[0138] It is preferable that, from the second boundary point B2 to the second point P2, the thickness of the sole portion 4 decreases without increasing. That is, in the second region A2, the thickness of the sole portion 4 is continuously decreased from the second boundary point B2 to the second point P2, or the sole portion 4 does not have a part where the thickness increases toward the second point P2, but may have a part where the thickness is constant.

[0139] Thereby, bending occurring around the second boundary point B2 when hit by a ball can be further suppressed, and the effect of increasing the deflection of the sole portion 4 can be further enhanced.

[0140] It is preferable that, at the second point P2, the thickness t20 of the sole portion 4 is set to be not more than 1.0 mm.

[0141] By making the thickness at the second point P2 smaller in this way, the position where the sole portion 4 is deflected when hit by a ball can be shifted toward the second point P2 from the second boundary point B2, and bending occurring around the second boundary point B2 can be suppressed more reliably.

[0142] From the viewpoint of securing the durability of the sole portion 4, the thickness t20 is preferably set to be not less than 0.4 mm, more preferably not less than 0.6 mm.

[0143] In this embodiment, the above-described features are satisfied at least in the vertical cross-section of the head passing through a position of the face center FC.

[0144] It is more desirable that the above-described features are satisfied in a vertical cross-section of the head passing through at any position within a range of 10 mm or more, preferably 15 mm or more, more preferably 20 mm or more, in the toe-heel direction toward each side of the face center FC.

[0145] While detailed description has been made of preferable embodiments of the present disclosure, the present disclosure can be embodied in various forms without being limited to the illustrated embodiments.Examples

[0146] More specific examples of the present disclosure will be described below. The present disclosure is not limited to such specific examples.< Examples 1 to 4 >

[0147] Based on the structure shown in FIGS. 1 to 6, wood-type golf club heads having specifications shown in Table 1, were prepared as Examples 1 to 4 and tested for the flying distance performance and durability performance.

[0148] The face portions of the Examples 1 to 4 had the thickness distribution pattern shown in FIG 9.< Comparative example 1 >

[0149] For comparison, a Comparative Example 1 was prepared and tested in the same way as the Examples.

[0150] The Comparative Example 1 was a wood-type golf club head not included in the scope of the present disclosure, and differs from the Examples only in the distribution of the wall thickness of the face portion.

[0151] Specifically, as shown in FIG 10, the Comparative Example 1 had a face portion including: a thick portion having a thickness of 3.3 mm and formed in the center of the face portion; a transitional portion formed around the thick portion and having a thickness decreasing continuously from 3.3 mm to 2.5 mm toward the periphery of the club face; a toe side portion formed on the toe side of the transitional portion and having a thickness continuously decreasing from 2.5 mm to 2.1 mm towards the toe; a heel side portion formed on the heel side of the transitional portion and having a thickness continuously decreasing from 2.5 mm to 2.1 mm towards the heel; and a peripheral portion extending annularly along peripheral edge of the club face.

[0152] The peripheral portion included a crown side peripheral portion having a constant thickness of 2.5 mm, and a sole side peripheral portion having a constant thickness of 2.3 mm.< Flight distance test >

[0153] In the flight distance performance test, the test golf club heads were attached to identical golf club shafts and golf clubs were prepared.

[0154] For each of the test golf club heads, the golf club was attached to a swing robot, and the flight distance of a ball when hit at the face center under the same conditions, was measured. The measurements were performed 10 times, and the average of the flight distance values was calculated.

[0155] The results are shown in Table 1 by an index based on the average flight distance of Comparative Example 1 being 100, wherein the larger the value, the better the flight distance performance.< Durability test >

[0156] In the durability test, using the swing robot, for each of the test golf club heads, a two-piece ball was repeatedly hit at the face center FC at a head speed of 54 m / s, and, after every 50 hits, the club face was inspected for cracks or other damage. When some damage was found on the club face, the hitting test was ended.

[0157] If no damage occurred until the number of hits reached 5,000, the hitting test was ended at 5,000 hits.

[0158] If some damage occurred before the number of hits reached 5,000, the number of hits at the time of damage was found is used as the durability evaluation value.

[0159] The test results are shown in Table 1. Table 1 (continues)HeadComparative Example 1Example 1Thickness of Central part tc (mm)Thin peripheral structure shown in Fig. 103.302.75Surface area of Face portion(sq.mm)3520.23520.2Surface area of Center portion(sq.mm)280280Center portion surface area / Face portion surface area (%)7.95%7.95%Thickness of First transitional part tt1 (mm)Decreased from 3.35 to 2.10Increased from 2.75 to 3.10Thickness of Second transitional part tt2 (mm)2.103.10Thickness of Third transitional part tt3 (mm)2.103.10Crown side peripheral part thickness tpc (mm)2.502.50Sole side peripheral part thickness tps (mm)2.302.30Toe side peripheral part thickness tpt (mm)2.302.30heel side peripheral part thickness tph (mm)2.302.30Peripheral portion thickness tp1 (mm)changed from 2.30 to 2.50changed from 2.30 to 2.50Peripheral portion thickness tp2 (mm)changed from 2.30 to 2.50changed from 2.30 to 2.50Configurations of Connection part between Face portion and Crown portion and Connection part between Face portion and Sole portion shown in FIG. 8 (rebound frame)Not applicableNot applicableFlying distance performance (index)100110Durability performance (number of hitting times to crack)5000 (no crack)5000 (no crack) Table 1 (continued) HeadExample 2Example 3Example 4Thickness of Central part tc (mm)2.752.75Surface area of Face portion(sq.mm)3520.23520.23520.2Surface area of Center portion(sq.mm)280140420Center portion surface area / Face portion surface area (%)7.95%3.98%11.93%Thickness of First transitional part tt1 (mm)Increased from 2.75 to 3.10Increased from 2.75 to 3.10Increased from 2.75 to 3.10Thickness of Second transitional part tt2 (mm)3.103.103.10Thickness of Third transitional part tt3 (mm)3.103.103.10Crown side peripheral part thickness tpc (mm)2.502.502.50Sole side peripheral part thickness tps (mm)2.302.302.30Toe side peripheral part thickness tpt (mm)2.302.302.30heel side peripheral part thickness tph (mm)2.302.302.30Peripheral portion thickness tp1 (mm)changed from 2.30 to 2.50changed from 2.30 to 2.50changed from 2.30 to 2.50Peripheral portion thickness tp2 (mm)changed from 2.30 to 2.50changed from 2.30 to 2.50changed from 2.30 to 2.50Configurations of Connection part between Face portion and Crown portion and Connection part between Face portion and Sole portion shown in FIG. 8 (rebound frame)ApplicableNot applicableNot applicableFlying distance performance (index)120103115Durability performance (number of hitting times to crack)5000 (no crack)5000 (no crack)4000 (crack)

[0160] From the test results, it was confirmed that each of the Examples had improved flight distance performance as compared to Comparative Example 1.Statement of the present disclosure

[0161] The present disclosure is as follows.< Present Disclosure 1 >

[0162] A golf club head with a cavity therein, comprising a face portion having a club face for striking a ball, a crown portion, a sole portion, a toe and a heel, wherein the club face comprises a central part including a face center, and a transitional part formed outside the central part, the thickness of the face portion 2 in the central part is constant, the surface area of the central part is not less than 100 sq.mm, the transitional part is continuous to the central part and is formed to annularly surround the central part, the thickness of the face portion 2 in the transitional part increases from the central part toward the crown portion, the sole portion, the toe and the heel, and the maximum thickness of the face portion 2 in the transitional part is larger than the thickness of the face portion 2 in the central part. < Present Disclosure 2>

[0163] The golf club head according to Present Disclosure 1, wherein the club face further includes a peripheral part outside the transitional part, the peripheral part continuously or intermittently surrounds the transitional part, and the thickness of the face portion 2 in the peripheral part is smaller than the thickness of the face portion 2 in the central part. < Present Disclosure 3>

[0164] The golf club head according to Present Disclosure 2, wherein the peripheral part continuously surrounds the transitional part.< Present Disclosure 4>

[0165] The golf club head according to any one of Present Disclosures 1 to 3, wherein the thickness of the face portion 2 in the central part is in a range from 2.5 to 3.0 mm.< Present Disclosure 5>

[0166] The golf club head according to any one of Present Disclosures 1 to 4, wherein the surface area of the central part is a range from 5% to 10% of the surface area of the face portion.< Present Disclosure 6>

[0167] The golf club head according to any one of Present Disclosures 1 to 5, wherein the central part has an elliptical or oblong contour line which is longer in the toe-heel direction than in an up-down direction.< Present Disclosure 7>

[0168] The golf club head according to any of Present Disclosures 1-6, wherein the transitional part includes a first transitional part annularly surrounding the central part, and the thickness of the face portion 2 in the first transitional part increases continuously from the central part toward the crown portion, the sole portion, the toe and the heel.< Present Disclosure 8>

[0169] The golf club head according to Present Disclosure 7, wherein the transitional part includes a second transitional part continuous to the first transitional part on the toe side thereof, and the second transitional part extends in a toe-heel direction with a constant thickness of the face portion.< Present Disclosure 9>

[0170] The golf club head according to Present Disclosure 7 or 8, wherein the transitional part includes a third transitional part continuous to the first transitional part on the heel side thereof, and the third transitional part extends in the toe-heel direction with a constant thickness of the face portion.< Present Disclosure 10>

[0171] The golf club head according to Present Disclosure 2, wherein the thickness of the face portion 2 in the peripheral part is in a range from 2.1 to 2.9 mm.< Present Disclosure 11>

[0172] The golf club head according to Present Disclosure 2 or 10, wherein the peripheral part includes a crown side peripheral part continuous to the transitional part on the crown side thereof, and a sole side peripheral part continuous to the transitional part on the sole side thereof, and the thickness of the face portion 2 in the sole side peripheral part is smaller than the thickness of the face portion 2 in the crown-side peripheral part. < Present Disclosure 12>

[0173] The golf club head according to the present disclosure 11, wherein the peripheral part includes a toe side peripheral part continuous to the transitional part on the toe side thereof, and a heel side peripheral part continuous to the transitional part on the heel side thereof, and the thickness of the face portion 2 in the toe-side peripheral part and the thickness of the face portion 2 in the heel-side peripheral part are smaller than the thickness of the face portion 2 in the crown-side peripheral part. Description of the reference signs

[0174] 1golf club head 2face portion 3crown portion 4sole portion 7toe 8heel 10central part 20transitional part 21first transitional part 22second transitional part 23third transitional part 30peripheral part 31crown side peripheral part 32sole side peripheral part 33toe side peripheral part 34heel side peripheral part FCface center

Claims

1. A golf club head provided with a cavity therein, comprising: a face portion having a club face for striking a ball, a crown portion, a sole portion, a toe and a heel, wherein the club face comprises a central part including a face center, and a transitional part formed outside the central part, the thickness of the face portion (2) in the central part is constant, the surface area of the central part is not less than 100 sq.mm, the transitional part is continuous to the central part and is formed to annularly surround the central part, the thickness of the face portion (2) in the transitional part increases from the central part toward the crown portion, the sole portion, the toe and the heel, and the maximum thickness of the face portion (2) in the transitional part is larger than the thickness of the face portion (2) in the central part.

2. The golf club head according to claim 1, wherein the club face further includes a peripheral part outside the transitional part, the peripheral part continuously or intermittently surrounds the transitional part, and the thickness of the face portion (2) in the peripheral part is smaller than the thickness of the face portion (2) in the central part.

3. The golf club head according to claim 2, wherein the peripheral part continuously surrounds the transitional part.

4. The golf club head according to any one of claim 1 to 3, wherein the thickness of the face portion (2) in the central part is in a range from 2.5 to 3.0 mm.

5. The golf club head according to any one of claim 1 to 4, wherein the surface area of the central part is a range from 5% to 10% of the surface area of the face portion.

6. The golf club head according to any one of claim 1 to 5, wherein the central part has an elliptical or oblong contour line which is longer in the toe-heel direction than in an up-down direction.

7. The golf club head according to any one of claim 1 to 6, wherein the transitional part includes a first transitional part annularly surrounding the central part, and the thickness of the face portion in the first transitional part increases continuously from the central part toward the crown portion, the sole portion, the toe and the heel.

8. The golf club head according to claim 7, wherein the transitional part includes a second transitional part continuous to the first transitional part on the toe side thereof, and the second transitional part extends in a toe-heel direction with a constant thickness of the face portion.

9. The golf club head according to claim 7 or 8, wherein the transitional part includes a third transitional part continuous to the first transitional part on the heel side thereof, and the third transitional part extends in the toe-heel direction with a constant thickness of the face portion.

10. The golf club head according to claim 2, wherein the thickness of the face portion 2 in the peripheral part is in a range from 2.1 to 2.9 mm.

11. The golf club head according to claim 2 or 10, wherein the peripheral part includes a crown side peripheral part continuous to the transitional part on the crown side thereof, and a sole side peripheral part continuous to the transitional part on the sole side thereof, and the thickness of the face portion (2) in the sole side peripheral part is smaller than the thickness of the face portion (2) in the crown-side peripheral part.

12. The golf club head according to claim 11, wherein the peripheral part includes a crown side peripheral part continuous to the transitional part on the crown side thereof, and a sole side peripheral part continuous to the transitional part on the sole side thereof, and the thickness of the face portion (2) in the sole side peripheral part is smaller than the thickness of the face portion (2) in the crown-side peripheral part.

13. The golf club head according to claim 11 or claim 12, wherein the peripheral part includes a toe side peripheral part continuous to the transitional part on the toe side thereof, and a heel side peripheral part continuous to the transitional part on the heel side thereof, and the thickness of the face portion (2) in the toe-side peripheral part and the thickness of the face portion (2) in the heel-side peripheral part are smaller than the thickness of the face portion (2) in the crown-side peripheral part.

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