Golf club head

Abstract

To provide a golf club head that is improved in head performance by making a boundary between a striking face and a crown surface or sole surface be a novel shape.SOLUTION: A head 4 includes a boundary between a striking face 10a and a crown surface 12a that has a curvature radius R and a boundary between the striking face 10a and the crown surface 12a that has a curvature radius S; on a toe side, the head 4 has a curvature radius Rt, a curvature radius St, a face height Ft and a head thickness Tt; in the center, the head 4 has a curvature radius Rc, a curvature radius Sc, a face height Fc and a head thickness Tc; and on a heel side, the head 4 has a curvature radius Rh, a curvature radius Sh, a face height Fh and a head thickness Th, where Ft / Tt is smaller than Fh / Th. The head 4 satisfies at least one of the relations (a)Rt>Rc≥Rh and (b)St>Sc≥Sh.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Golf club heads having a crown are known. For example, as disclosed in Japanese Patent Publication No. 2021-132995, in this head, a rounded shape is usually formed at the boundary between the crown surface and the striking face, and a rounded shape is also formed at the boundary between the sole surface and the striking face. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-132995 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The inventors have discovered that the rounded shape described above can produce new effects and benefits.

[0005] One of the objectives of the present invention is to provide a golf club head with improved head performance by creating a novel shape at the boundary between the striking face and the crown or sole surface. [Means for solving the problem]

[0006] In one embodiment, the golf club head of the present invention has a striking face including a face center, a crown surface, and a sole surface. The boundary between the striking face and the crown surface has a radius of curvature R. The boundary between the striking face and the sole surface has a radius of curvature S. The striking face has a face height F. The head has a head thickness T. At a position 15 mm toe-side from the face center, the radius of curvature R is Rt, the radius of curvature S is St, the face height F is Ft, and the head thickness T is Tt. At the position of the face center, the radius of curvature R is Rc, the radius of curvature S is Sc, the face height F is Fc, and the head thickness T is Tc. At a position 15 mm heel-side from the face center, the radius of curvature R is Rh, the radius of curvature S is Sh, the face height F is Fh, and the head thickness T is Th. Ft / Tt is less than Fh / Th. This head satisfies at least one of the following relationships (a) and (b). That is, this head satisfies only (a), or only (b), or satisfies both (a) and (b). (a) Rt > Rc ≥ Rh (b) St > Sc ≥ Sh [Effects of the Invention]

[0007] One aspect of this is that a novel shape at the boundary between the striking face and the crown or sole surface can improve head performance. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows a golf club with the head of the first embodiment attached. [Figure 2] Figure 2 is a plan view of the head of the first embodiment, as seen from the crown side. [Figure 3]Figure 3 is a front view of the head of the first embodiment, seen from the face side. Figure 3 shows the head in the standard state. [Figure 4] Figure 4(a) is the same front view as Figure 3, and Figure 4(b) is a cross-sectional view along line E1 in Figure 4(a). In Figure 4(b), only the cross-sectional lines of the outer surface of the head are shown. [Figure 5] Figure 5(a) shows the cross-sectional line of the outer surface of the head in the cross-sectional view along line aa in Figure 3, Figure 5(b) shows the cross-sectional line of the outer surface of the head in the cross-sectional view along line bb in Figure 3, and Figure 5(c) shows the cross-sectional line of the outer surface of the head in the cross-sectional view along line cc in Figure 3. [Figure 6] Figure 6 is an enlarged view of Figure 5(b). Figure 6 is an explanatory diagram of the definitions of radius of curvature R, radius of curvature S, face height F, and head thickness T. [Figure 7] Figure 7 is a plan view of the head of the second embodiment, as seen from the crown side. [Figure 8] Figure 8 is a front view of the head of the second embodiment, seen from the face side. Figure 8 shows the head in the standard state. [Figure 9] Figure 9(a) shows the cross-sectional line of the outer surface of the head in a cross-sectional view along line aa in Figure 8, Figure 9(b) shows the cross-sectional line of the outer surface of the head in a cross-sectional view along line bb in Figure 8, and Figure 9(c) shows the cross-sectional line of the outer surface of the head in a cross-sectional view along line cc in Figure 8. [Figure 10] Figure 10 is a plan view of the head of the third embodiment, as seen from the crown side. [Figure 11] Figure 11 is a front view of the head of the third embodiment, seen from the face side. Figure 11 shows the head in the standard state. [Figure 12] Figure 12(a) shows the cross-sectional line of the outer surface of the head in a cross-sectional view along line aa in Figure 11, Figure 12(b) shows the cross-sectional line of the outer surface of the head in a cross-sectional view along line bb in Figure 11, and Figure 12(c) shows the cross-sectional line of the outer surface of the head in a cross-sectional view along line cc in Figure 11. [Figure 13] Figure 13 is a plan view of the head of the fourth embodiment, as seen from the crown side. [Figure 14]FIG. 14 is a front view of the head according to the fourth embodiment viewed from the face side. FIG. 14 shows the head in a reference state. [Figure 15] FIG. 15(a) is a cross-sectional line of the outer surface of the head in a cross-sectional view taken along line a-a of FIG. 14, FIG. 15(b) is a cross-sectional line of the outer surface of the head in a cross-sectional view taken along line b-b of FIG. 14, and FIG. 15(c) is a cross-sectional line of the outer surface of the head in a cross-sectional view taken along line c-c of FIG. 14. [Figure 16] FIG. 16 is a front view of the head according to the fifth embodiment viewed from the face side. FIG. 16 shows the head in a reference state. [Figure 17] FIG. 17(a) is a cross-sectional view taken along line a-a of FIG. 3, FIG. 17(b) is a cross-sectional view taken along line b-b of FIG. 3, and FIG. 17(c) is a cross-sectional view taken along line c-c of FIG. 3. [Figure 18] FIG. 18 is a conceptual diagram for explaining the reference state. MODE FOR CARRYING OUT THE INVENTION

[0009] Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

[0010] In the present application, a reference state, a reference vertical plane, a toe-heel direction, a face-back direction, a up-down direction, a face center and a longitudinal cross-section are defined.

[0011] A state where the head is placed on a ground plane HP at a predetermined lie angle is defined as the reference state. As shown in FIG. 18, in this reference state, a shaft axis Z is included in a plane VP perpendicular to the ground plane HP. The shaft axis Z is the center line of the shaft. Normally, the shaft axis Z coincides with the center line of a hosel hole. Said plane VP is defined as the reference vertical plane. The predetermined lie angle is listed in, for example, a product catalog.

[0012] Furthermore, clubs equipped with a variable mechanism that allows adjustment of loft angle, lie angle, and face angle by the rotational position of a sleeve or similar component located at the tip of the shaft are known. In the head used in such a club, under the above-mentioned standard conditions, all adjustment items are set to neutral, and the shaft axis Z is determined. Neutral means the center of the adjustment range.

[0013] In this standard state, the face angle is considered to be 0 degrees. That is, in a plan view from above, the normal to the face center of the striking face is considered to be perpendicular to the toe-heel direction. The definitions of the face center and the toe-heel direction are described below.

[0014] In this application, the toe-heel direction is the direction of the intersection line NL between the reference vertical plane VP and the ground plane HP (see Figure 18).

[0015] In this application, the face-back direction is a direction that is perpendicular to the toe-heel direction and parallel to the ground plane HP.

[0016] In this application, the vertical direction is the direction perpendicular to the toe-heel direction and perpendicular to the face-back direction. In other words, in this application, the vertical direction is the direction perpendicular to the ground plane HP.

[0017] In this application, the face center is determined as follows: First, an arbitrary point Pr is selected near the approximate center of the striking face in the vertical and toe-heel directions. Next, a plane is determined that passes through this point Pr, extends along the normal direction of the striking face at point Pr, and is parallel to the toe-heel direction. A line is drawn between this plane and the striking face, and its midpoint Px is determined. Next, a plane is determined that passes through this midpoint Px, extends along the normal direction of the striking face at point Px, and is parallel to the vertical direction. A line is drawn between this plane and the striking face, and its midpoint Py is determined. Next, a plane is determined that passes through this midpoint Py, extends along the normal direction of the striking face at point Py, and is parallel to the toe-heel direction. A line is drawn between this plane and the striking face, 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 face at point Px, and is parallel to the vertical direction. A line is drawn at the intersection of this plane and the hitting face, and the midpoint Py is newly determined. This process is repeated to sequentially determine Px and Py. In the repetition of this process, the new position Py (the last position Py) at which the distance between the new midpoint Py and the immediately preceding midpoint Py becomes 0.5 mm or less is the face center.

[0018] In this application, a longitudinal section is a section defined by a plane perpendicular to the toe-heel direction. The longitudinal section is parallel to the face-back direction. The longitudinal section is perpendicular to the ground plane (HP). The cross-sectional line of the outer surface of the head in the longitudinal section is also called the longitudinal section line. The longitudinal section can be set at various positions in the toe-heel direction.

[0019] Figure 1 is an overall view of a golf club 2 including a head 4 according to a first embodiment of the present invention. As shown in Figure 1, the golf club 2 includes a golf club head 4, a shaft 6, and a grip 8. The shaft 6 has a tip end Tp and a butt end Bt. The head 4 is attached to the tip end of the shaft 6. The grip 8 is attached to the butt end of the shaft 6.

[0020] Golf club 2 is a driver (1-wood). Head 4 is a driver head. Typically, the club length of a driver is 43 inches or longer. Golf club 2 is a wood-type golf club.

[0021] The shaft 6 is tubular. The shaft 6 has a hollow structure. The material of the shaft 6 is carbon fiber reinforced resin. From the viewpoint of weight reduction, carbon fiber reinforced resin is preferred as the material of the shaft 6. The shaft 6 is a so-called carbon shaft. Preferably, the shaft 6 is made by curing a prepreg sheet. In this prepreg sheet, the fibers are substantially oriented in one direction. A prepreg in which the fibers are substantially oriented in one direction in this way is also called a UD prepreg. "UD" is an abbreviation for unidirection. Prepregs other than UD prepregs may be used. For example, the fibers contained in the prepreg sheet may be woven. The shaft 6 may contain metal wires. The material of the shaft 6 is not limited and may be, for example, metal.

[0022] Grip 8 is the part that is held by the golfer during the swing. Examples of materials for grip 8 include rubber compositions and resin compositions. The rubber composition of grip 8 may contain air bubbles.

[0023] Head 4 has a hollow structure. In this embodiment, head 4 is wood-shaped. Head 4 may also be hybrid. Preferred materials for head 4 include metal and fiber-reinforced plastic. Examples of metals include titanium alloy, pure titanium, stainless steel, maraging steel, and mild steel. An example of a fiber-reinforced plastic is carbon fiber reinforced plastic. Head 4 may also be a composite head having a metal portion and a fiber-reinforced plastic portion.

[0024] Figure 2 is a plan view of head 4 seen from above. Figure 3 is a front view of head 4. Figure 3 is a view of head 4 in the reference state seen from the face side. Figure 4(a) is the same front view as Figure 3. Figure 4(b) is a cross-sectional view along line E1 in Figure 4(a). Figure 4(b) shows only the cross-sectional lines of the outer surface of the head.

[0025] As shown in Figures 2 and 3, the head 4 has a face portion 10, a crown portion 12, a sole portion 14, and a hosel portion 16. The face portion 10 has a striking face 10a. The striking face 10a is made up of the outer surface of the face portion 10. The striking face 10a has a curved surface that is convex toward the outside of the head. The striking face 10a has a face bulge and a face roll. The striking face 10a is also simply called the face or face surface. The crown portion 12 forms the crown outer surface 12a. The crown outer surface 12a is also simply called the crown surface. The sole portion 14 forms the sole outer surface 14a. The sole outer surface 14a is also simply called the sole surface. The striking face 10a, the crown surface 12a, and the sole surface 14a are the outer surfaces of the head.

[0026] The striking face 10a has a face center C1 as defined above.

[0027] The striking face 10a has an outer edge k1. The outer edge k1 is the contour line of the striking face 10a. The outer edge k1 is the boundary line between the striking face 10a and other parts. The outer edge k1 of the striking face 10a can be defined as follows: As shown in Figures 4(a) and 4(b), there are a number of planes E1, E2, E3... that include a straight line connecting the center of gravity of the head 4 and the sweet spot SS. In the cross section of each of these planes E1, etc., a point P1 is determined where the radius of curvature r of the cross section line of the outer surface of the head is 200 mm for the first time when moving from the sweet spot SS side toward the outside of the striking face 10a. The set of these points P1 can be considered the outer edge k1 of the striking face 10a. The sweet spot SS is the intersection of the striking face 10a and a straight line that is perpendicular to the striking face 10a and passes through the center of gravity of the head 4.

[0028] As shown in Figure 2, the crown portion 12 has a crown protrusion 20. The crown protrusion 20 forms a convex shape on the crown surface 12a. In the front view of the head 4 as seen from the face side (Figure 3), the crown protrusion 20 is not visible. The entire crown protrusion 20 is located on the heel side of the face center C1.

[0029] Figure 5(a) is a cross-sectional view along line aa in Figure 3, Figure 5(b) is a cross-sectional view along line bb in Figure 3, and Figure 5(c) is a cross-sectional view along line cc in Figure 3. In Figures 5(a), 5(b), and 5(c), longitudinal section lines are shown. Figure 5(a) is a longitudinal section line at a position 15 mm toe-side from the face center C1. Figure 5(b) is a longitudinal section line at the face center C1. Figure 5(c) is a longitudinal section line at a position 15 mm heel-side from the face center C1.

[0030] Head 4 has a radius of curvature R at the boundary between the striking face 10a and the crown surface 12a. The radius of curvature R is measured along the longitudinal section line. The radius of curvature R is determined at each position in the toe-heel direction. As shown in Figure 5(a), the radius of curvature R at a position 15 mm toe-side from the face center C1 is the radius of curvature Rt. As shown in Figure 5(b), the radius of curvature R at the face center C1 is the radius of curvature Rc. As shown in Figure 5(c), 15 mm from the face center C1 heel The radius of curvature R at the side position is the radius of curvature Rh. For ease of understanding, in this application, "R," "Rt," "Rc," "Rh," etc., are symbols that specify the type of radius of curvature and are also used as reference numerals in drawings. The unit of these radii of curvature is mm.

[0031] Head 4 has a radius of curvature S at the boundary between the striking face 10a and the sole surface 14a. The radius of curvature S is measured along the longitudinal section line. The radius of curvature S is measured at various positions in the toe-heel direction. As shown in Figure 5(a), the radius of curvature S at a position 15 mm toe-side from the face center C1 is the radius of curvature St. As shown in Figure 5(b), the radius of curvature S at the face center C1 is the radius of curvature Sc. As shown in Figure 5(c), 15 mm from the face center C1 heel The radius of curvature S at the side position is the radius of curvature Sh. For ease of understanding, in this application, "S," "St," "Sc," and "Sh" are symbols used to identify the type of radius of curvature, as well as reference numerals in drawings. The unit of these radii of curvature is mm.

[0032] The striking face 10a has a face height F. The face height F is measured along the longitudinal section line. The face height F is measured at each position in the toe-heel direction. As shown in Figure 5(a), the face height F at a position 15 mm toe-side from the face center C1 is the face height Ft. As shown in Figure 5(b), the face height F at the position of the face center C1 is the face height Fc. As shown in Figure 5(c), 15 mm from the face center C1 heel The face height F at the side position is the face height Fh. For ease of understanding, in this application, "F", "Ft", "Fc", "Fh", etc. are used as follows: Face height These symbols are used to identify the type of object, and are also used as reference symbols in drawings. The unit of measurement for these face heights is millimeters (mm).

[0033] Head 4The club has a head thickness T. The head thickness T is measured along the longitudinal section. The head thickness T is measured at various positions in the toe-heel direction. As shown in Figure 5(a), the head thickness T at a position 15 mm toe-side from the face center C1 is the head thickness Tt. As shown in Figure 5(b), the head thickness T at the position of the face center C1 is the head thickness Tc. As shown in Figure 5(c), 15 mm from the face center C1 heel The head thickness T at the side position is the head thickness Th. For ease of understanding, in this application, "T", "Tt", "Tc", "Th", etc. are used as follows: Head thickness These symbols are used to identify the type of head and are also used as reference symbols in drawings. The unit of measurement for these head thicknesses is mm.

[0034] The area from 15mm toe-side of face center C1 to 15mm heel-side of face center C1 has a high probability of being struck. This area is referred to as the primary striking area.

[0035] Figure 6 is an enlarged view of Figure 5(b). The definitions of radius of curvature R, radius of curvature S, face height F, and head thickness T are explained with reference to Figure 6.

[0036] The definition of the radius of curvature R may be as follows: In the longitudinal section, point P2 is determined where the radius of curvature is smallest between point P1, which constitutes the outer edge k1, and the crown portion 12. If the portion with the smallest radius of curvature is a range rather than a point, the midpoint of that range is defined as point P2. This midpoint is determined based on the distance along the longitudinal section. Furthermore, point P3 is determined on the crown side of point P2. Point P3 is determined such that point P2 is the midpoint between point P3 and point P1. This midpoint is determined based on the distance. That is, the distance between point P2 and point P3 (distance) is equal to the distance between point P1 and point P2 (distance). The radius of the circle passing through the three points P1, P2, and P3 may be defined as the radius of curvature R.

[0037] The definition of the radius of curvature S may be as follows: In the longitudinal section, point P4 is determined where the radius of curvature is smallest between point P1, which constitutes the outer edge k1, and the sole portion 14. If the portion with the smallest radius of curvature is a range rather than a point, the midpoint of that range is defined as point P4. This midpoint is determined based on the distance along the longitudinal section. Furthermore, point P5 is determined on the sole side of point P4. Point P5 is determined such that point P4 is the midpoint between point P5 and point P1. The distance between point P1 and point P4 (the distance along the path) is equal to the distance between point P4 and point P5 (the distance along the path). The radius of the circle passing through the three points P1, P4, and P5 may be defined as the radius of curvature S.

[0038] The definition of face height F can be as follows: upper point P1 and lower point P 1 The distance between two points (the straight-line distance between two points on the vertical section) can be defined as the face height F.

[0039] The definition of head thickness T may be as follows: A horizontal line L1 tangent to the upper side of the vertical section line and a horizontal line L2 tangent to the lower side of the vertical section line are determined. The distance between lines L1 and L2 may be defined as the head thickness T. Lines L1 and L2 are parallel to the ground plane HP. The direction of measurement for head thickness T is vertical.

[0040] Therefore, the head thickness T corresponds to the maximum thickness of the head at each position in the toe-heel direction. As shown in Figures 5(a) to (c), the face-back position of the highest point of the head Pm, which is tangent to the straight line L1, changes. The highest point of the head Pm1 (Figure 5(a)) at a position 15 mm toe-side from the face center C1 is further back than the highest point of the head Pm2 (Figure 5(b)) at the face center C1. The highest point of the head Pm2 (Figure 5(b)) at the face center C1 is further back than the highest point of the head Pm3 (Figure 5(c)) at a position 15 mm heel-side from the face center C1. In the main hitting area, the face-back position of the highest point of the head Pm moves towards the back as you move towards the toe.

[0041] In head 4, the radius of curvature R on the crown side is not constant. The radius of curvature R changes depending on the position in the toe-heel direction. This change is continuous. Head 4 satisfies the following relationship (a): (a) Rt > Rc ≥ Rh

[0042] In head 4, the radius of curvature R (radius of curvature Rt) at a position 15 mm toe-side from the face center C1 is greater than the radius of curvature R (radius of curvature Rc) at the face center C1. Also, the radius of curvature R (radius of curvature Rc) at the face center C1 is greater than or equal to the radius of curvature R (radius of curvature Rh) at a position 15 mm heel-side from the face center C1.

[0043] Furthermore, head 4 satisfies the following relationship (a1): (a1) Rt > Rc > Rh

[0044] In head 4, the radius of curvature R (radius of curvature Rc) at face center C1 is greater than the radius of curvature R (radius of curvature Rh) at a position 15 mm towards the heel from face center C1.

[0045] In head 4, the radius of curvature S on the sole side is not constant. The radius of curvature S changes depending on the position in the toe-heel direction. This change is continuous. Head 4 does not satisfy the following relationship (b). Head 4 does not satisfy the following relationship (b1). Head 4 satisfies the following relationship (b2). (b) St > Sc ≥ Sh (b1) St>Sc>Sh (b2) St <sc>Sh

[0046] In head 4, the radius of curvature S (radius of curvature St) at a position 15 mm toe-side from the face center C1 is smaller than the radius of curvature S (radius of curvature Sc) at the face center C1. Also, the radius of curvature S (radius of curvature Sc) at the face center C1 is larger than the radius of curvature S (radius of curvature Sh) at a position 15 mm heel-side from the face center C1.

[0047] With respect to the head thickness T, head 4 satisfies the following relationship (c): (c)Tt>Tc>Th

[0048] In head 4, the head thickness T (head thickness Tt) at a position 15 mm toe-side from the face center C1 is greater than the head thickness T (head thickness Tc) at the face center C1. In head 4, the head thickness T (head thickness Tc) at the face center C1 is greater than the head thickness T (head thickness Th) at a position 15 mm heel-side from the face center C1.

[0049] With respect to the face height F, head 4 satisfies the following relationship (d): (d)Ft <fc>Fh

[0050] In head 4, the face height F (face height Ft) at a position 15 mm toe-side from face center C1 is smaller than the face height F (face height Fc) at face center C1. In head 4, the face height F (face height Fc) at face center C1 is larger than the face height F (face height Fh) at a position 15 mm heel-side from face center C1.

[0051] In head 4 (driver head), the face height Ft is suppressed. The face height Ft is greater than the face height Fh, but close to the face height Fh. The face height Ft may also be smaller than the face height Fh. The absolute value of the difference (Ft-Fh) may be 3 mm or less, further 2.5 mm or less, and further 2 mm or less.

[0052] Regarding the ratio of face height F to head thickness T, head 4 satisfies the following relationship (e): (e)Ft / Tt < Fh / Th

[0053] In head 4, the ratio of face height F to head thickness T (Ft / Tt) at a position 15 mm toe-side from face center C1 is smaller than the ratio of face height F to head thickness T (Fh / Th) at a position 15 mm heel-side from face center C1.

[0054] Furthermore, head 4 satisfies the following relationships (f) and (f1). (f)Ft / Tt < Fc / Tc ≤ Fh / Th (f1)Ft / Tt < Fc / Tc < Fh / Th

[0055] In head 4, the ratio of face height F to head thickness T (Ft / Tt) at a position 15 mm toe-side from face center C1 is smaller than the ratio of face height F to head thickness T (Fc / Tc) at face center C1. In head 4, the ratio of face height F to head thickness T (Fc / Tc) at face center C1 is smaller than the ratio of face height F to head thickness T (Fh / Th) at a position 15 mm heel-side from face center C1.

[0056] In head 4, the radius of curvature St is smaller than the radius of curvature Rt. That is, at a position 15 mm toe-side from the face center C1, the radius of curvature S (radius of curvature St) on the sole side is smaller than the radius of curvature R (radius of curvature Rt) on the crown side. In head 4, the radius of curvature Sc is smaller than the radius of curvature Rc. That is, at the position of the face center C1, the radius of curvature S (radius of curvature Sc) on the sole side is smaller than the radius of curvature R (radius of curvature Rc) on the crown side. In head 4, the radius of curvature Sh is larger than the radius of curvature Rh. That is, at a position 15 mm heel-side from the face center C1, the radius of curvature S (radius of curvature Sh) on the sole side is larger than the radius of curvature R (radius of curvature Rh) on the crown side.

[0057] In the first embodiment, which is an example of a driver head, the dimensions may be as follows: • Radius of curvature Rt on the crown side: 11.94 mm • Radius of curvature Rc on the crown side: 9.43 mm • Radius of curvature Rh on the crown side: 7.76 mm • Radius of curvature on the sole side: St: 9.01mm • Radius of curvature (Sc) on the sole side: 9.38mm • Radius of curvature on the sole side: 9.16mm Face height Ft: 38.06mm Face height Fc: 39.27mm Face height Fh: 37.25mm • Head thickness Tt: 58.84mm • Head thickness Tc: 58.01mm • Head thickness Th: 53.80mm

[0058] Figure 7 is a plan view of the head 24 of the second embodiment, viewed from above. Figure 8 is a front view of the head 24. Figure 8 is a view of the head 24 in the reference state, viewed from the face side. Figure 9(a) is a cross-sectional view along line aa in Figure 8, Figure 9(b) is a cross-sectional view along line bb in Figure 8, and Figure 9(c) is a cross-sectional view along line cc in Figure 8. Figures 9(a), 9(b), and 9(c) show longitudinal section lines. Figure 9(a) is a longitudinal section line at a position 15 mm toe-side from the face center C1. Figure 9(b) is a longitudinal section line at the position of the face center C1. Figure 9(c) is a longitudinal section line at a position 15 mm heel-side from the face center C1.

[0059] The head 24 has a face portion 30, a crown portion 32, a sole portion 34, and a hosel portion 36. The face portion 30 has a striking face 30a. The striking face 30a is formed by the outer surface of the face portion 30. The striking face 30a has a curved surface that is convex toward the outside of the head. The striking face 30a has a face bulge and a face roll. The crown portion 32 forms the crown surface 32a. The sole portion 34 forms the sole surface 34a. The striking face 30a, the crown surface 32a, and the sole surface 34a are the outer surfaces of the head. The head 24 has a hollow structure. The head 24 is a driver head.

[0060] As shown in Figure 7, the crown portion 32 has a crown protrusion 40. The crown protrusion 40 forms a convex shape on the crown surface 32a. In the front view of the head 24 as seen from the face side (Figure 8), the crown protrusion 40 is not visible. The entire crown protrusion 40 is located on the heel side of the face center C1.

[0061] In head 24, the radius of curvature R on the crown side is not constant. The radius of curvature R changes depending on the position in the toe-heel direction. This change in the radius of curvature R is continuous. Head 24 satisfies the following relationship (a). Furthermore, head 24 satisfies the following relationship (a1). (a) Rt > Rc ≥ Rh (a1) Rt > Rc > Rh

[0062] In head 24, the radius of curvature S on the sole side is not constant. The radius of curvature S changes depending on the toe-heel position. This change in the radius of curvature S is continuous. Head 24 does not satisfy the following relationship (b). Head 24 does not satisfy the following relationship (b1). Head 24 satisfies the following relationship (b2). Relationship (b2) can suppress the radius of curvature St. (b) St > Sc ≥ Sh (b1) St>Sc>Sh (b2) St <sc>Sh

[0063] With respect to the head thickness T, head 24 satisfies the following relationship (c): (c)Tt>Tc>Th

[0064] With respect to the face height F, the head 24 satisfies the following relationship (d): (d)Ft <fc>Fh

[0065] Regarding the ratio of face height F to head thickness T, head 24 satisfies the following relationship (e): (e)Ft / Tt < Fh / Th

[0066] Head 24 satisfies the following relationship (f). Head 24 does not satisfy the following relationship (f1). In Head 24, the ratio at the center (Fc / Tc) is equal to the ratio at the heel (Fh / Th). (f)Ft / Tt < Fc / Tc ≤ Fh / Th (f1)Ft / Tt < Fc / Tc < Fh / Th

[0067] In head 24, the radius of curvature St is smaller than the radius of curvature Rt. Also, the radius of curvature Sc is smaller than the radius of curvature Rc. Furthermore, the radius of curvature Sh is larger than the radius of curvature Rh.

[0068] In the second embodiment, which is another example of a driver head, the dimensions are as follows: • Crown side radius of curvature Rt: 11.40 mm • Radius of curvature Rc on the crown side: 9.43 mm • Radius of curvature Rh on the crown side: 7.99 mm • Radius of curvature on the sole side: St: 8.89mm • Radius of curvature (Sc) on the sole side: 9.30mm • Radius of curvature on the sole side: 9.08mm Face height Ft: 41.58mm Face height Fc: 42.41mm Face height Fh: 39.42mm • Head thickness Tt: 60.75mm • Head thickness Tc: 59.91mm • Head thickness Th: 55.69mm

[0069] Figure 10 is a plan view of the head 44 of the third embodiment, viewed from above. Figure 11 is a front view of the head 44. Figure 11 is a view of the head 44 in the reference state, viewed from the face side. Figure 12(a) is a cross-sectional view along line aa in Figure 11, Figure 12(b) is a cross-sectional view along line bb in Figure 11, and Figure 12(c) is a cross-sectional view along line cc in Figure 11. Figures 12(a), 12(b), and 12(c) show longitudinal section lines. Figure 12(a) is a longitudinal section line at a position 15 mm toe-side from the face center C1. Figure 12(b) is a longitudinal section line at the position of the face center C1. Figure 12(c) is a longitudinal section line at a position 15 mm heel-side from the face center C1.

[0070] The head 44 has a face portion 50, a crown portion 52, a sole portion 54, and a hosel portion 56. The face portion 50 has a striking face 50a. The striking face 50a is formed by the outer surface of the face portion 50. The striking face 50a forms a curved surface that is convex toward the outside of the head. The striking face 50a has a face bulge and a face roll. The crown portion 52 forms the crown surface 52a. The sole portion 54 forms the sole surface 54a. The striking face 50a, the crown surface 52a, and the sole surface 54a are the outer surfaces of the head. The head 44 has a hollow structure. The head 44 is a fairway wood type head. The head 44 is a 5-wood.

[0071] As shown in Figure 10, the crown portion 52 has a crown step 60. The crown step 60 forms a step on the crown surface 52a. As shown in Figure 12(a), at a position 15 mm toe-side from the face center C1, the crown step 60 forms a step such that its face side is higher than its back side. As shown in Figure 12(b), at the position of the face center C1, the crown step 60 forms a step such that its face side is higher than its back side. As shown in Figure 12(c), at a position 15 mm heel-side from the face center C1, the crown step 60 forms a step such that its face side is higher than its back side. Throughout the entire main hitting area, the crown step 60 forms a step such that its face side is higher than its back side. This crown step 60 makes the crown portion 52 more flexible in the face-back direction. This crown step 60 can contribute to improving rebound performance.

[0072] In head 44, the radius of curvature R on the crown side is not constant. The radius of curvature R changes depending on the position in the toe-heel direction. This change in the radius of curvature R is continuous. Head 44 satisfies the following relationship (a). Furthermore, head 44 satisfies the following relationship (a1). (a) Rt > Rc ≥ Rh (a1) Rt > Rc > Rh

[0073] In head 44, the radius of curvature S on the sole side is not constant. The radius of curvature S changes depending on the toe-heel position. This change in the radius of curvature S is continuous. Head 44 does not satisfy the following relationship (b). Head 44 does not satisfy the following relationship (b1). Head 44 does not satisfy the following relationship (b2). Head 44 satisfies the following relationship (b3). In head 44, the radius of curvature St is smaller than the radius of curvature Sc. In head 44, the radius of curvature Sc is smaller than the radius of curvature Sh. Relationship (b3) can suppress the radius of curvature St. (b) St > Sc ≥ Sh (b1) St>Sc>Sh (b2) St <sc>Sh (b3) St <Sc<Sh

[0074] Regarding the head thickness T, head 44 does not satisfy the following relationship (c). Head 44 satisfies the following relationship (c1). In head 44, the head thickness Tt is smaller than the head thickness Tc. In head 44, the head thickness Tc is larger than the head thickness Th. (c)Tt>Tc>Th (c1)Tt <tc>Th

[0075] In the Head 44 (fairway wood type head), the difference between the head thickness Tt and the head thickness Th can be smaller compared to the driver head. The difference (Tt-Th) can be 5.0 mm or less, even 4.5 mm or less, and even 4.0 mm or less. The difference (Tt-Th) can be 1.0 mm or more, even 1.5 mm or more, and even 2.0 mm or more.

[0076] With respect to the face height F, head 44 satisfies the following relationship (d): (d)Ft <fc>Fh

[0077] In head 44 (fairway wood type head), the face height Ft is suppressed and close to the face height Fh. The face height Ft is smaller than the face height Fc. The face height Ft is larger than the face height Fh. However, the face height Ft is approximately equal to the face height Fh. The face height Ft may be smaller than the face height Fh. The absolute value of the difference (Ft-Fh) may be 1.5 mm or less, further 1.0 mm or less, and further 0.5 mm or less.

[0078] Regarding the ratio of face height F to head thickness T, head 44 satisfies the following relationship (e): (e)Ft / Tt < Fh / Th

[0079] Furthermore, head 44 satisfies the following relationships (f) and (f1). (f)Ft / Tt < Fc / Tc ≤ Fh / Th (f1)Ft / Tt < Fc / Tc < Fh / Th

[0080] In head 44, the radius of curvature St is smaller than the radius of curvature Rt. In head 44, the radius of curvature Sc is smaller than the radius of curvature Rc. In head 44, the radius of curvature Sh is smaller than the radius of curvature Rh.

[0081] In the third embodiment, which is an example of a fairway wood-type head, the dimensions may be as follows: • Crown side radius of curvature Rt: 12.33 mm • Crown side radius of curvature Rc: 10.11 mm • Radius of curvature Rh on the crown side: 7.72 mm • Radius of curvature on the sole side: St: 3.25mm • Radius of curvature (Sc) on the sole side: 3.47mm • Radius of curvature on the sole side: 3.63mm Face height Ft: 22.81mm Face height Fc: 24.46mm Face height Fh: 22.72mm • Head thickness Tt: 36.37mm • Head thickness Tc: 36.39mm • Head thickness Th: 33.45mm

[0082] Figure 13 is a plan view of the head 64 of the fourth embodiment, viewed from above. Figure 14 is a front view of the head 64. Figure 14 is a view of the head 64 in the reference state, viewed from the face side. Figure 15(a) is a cross-sectional view along line aa in Figure 14, Figure 15(b) is a cross-sectional view along line bb in Figure 14, and Figure 15(c) is a cross-sectional view along line cc in Figure 14. Figures 15(a), 15(b), and 15(c) show longitudinal section lines. Figure 15(a) is a longitudinal section line at a position 15 mm toe-side from the face center C1. Figure 15(b) is a longitudinal section line at the position of the face center C1. Figure 15(c) is a longitudinal section line at a position 15 mm heel-side from the face center C1.

[0083] The head 64 has a face portion 70, a crown portion 72, a sole portion 74, and a hosel portion 76. The face portion 70 has a striking face 70a. The striking face 70a is formed by the outer surface of the face portion 70. The striking face 70a has a curved surface that is convex toward the outside of the head. The striking face 70a has a face bulge and a face roll. The crown portion 72 forms the crown surface 72a. The sole portion 74 forms the sole surface 74a. The striking face 70a, the crown surface 72a, and the sole surface 74a are the outer surfaces of the head. The head 64 has a hollow structure. The head 64 is a hybrid type head.

[0084] As shown in Figure 13, the crown portion 72 has a crown step 80. The crown step 80 forms a step on the crown surface 72a. As shown in Figure 15(a), at a position 15 mm toe-side from the face center C1, the crown step 80 forms a step such that the face side is higher than the back side. As shown in Figure 15(b), at the position of the face center C1, the crown step 80 forms a step such that the face side is higher than the back side. As shown in Figure 15(c), at a position 15 mm heel-side from the face center C1, the crown step 80 forms a step such that the face side is higher than the back side.

[0085] In head 64, the radius of curvature R on the crown side is not constant. The radius of curvature R changes depending on the position in the toe-heel direction. This change in the radius of curvature R is continuous. Head 64 satisfies the following relationship (a). Furthermore, head 64 satisfies the following relationship (a1). (a) Rt > Rc ≥ Rh (a1) Rt > Rc > Rh

[0086] In head 64, the radius of curvature S on the sole side is not constant. The radius of curvature S changes depending on the position in the toe-heel direction. This change in the radius of curvature S is continuous. Head 64 does not satisfy the following relationship (b). Head 64 does not satisfy the following relationship (b1). Head 64 does not satisfy the following relationship (b3). Head 64 satisfies the following relationship (b2). (b) St > Sc ≥ Sh (b1) St>Sc>Sh (b2) St <sc>Sh (b3) St <Sc<Sh

[0087] Regarding the head thickness T, head 64 does not satisfy the following relationship (c). Head 64 satisfies the following relationship (c1). (c)Tt>Tc>Th (c1)Tt <tc>Th

[0088] The head thickness Tt is greater than the head thickness Th. In the Head 64 (hybrid type head), the difference between the head thickness Tt and the head thickness Th can be smaller compared to the driver head. The difference (Tt-Th) can be 4.0 mm or less, even 3.5 mm or less, and even 3.0 mm or less. The difference (Tt-Th) can be 0.5 mm or more, even 1.0 mm or more, and even 1.5 mm or more.

[0089] With respect to the face height F, head 64 satisfies the following relationship (d): (d)Ft <fc>Fh

[0090] In head 64 (hybrid type head), the face height Ft is suppressed and close to the face height Fh. The face height Ft is smaller than the face height Fc. The face height Ft is smaller than the face height Fh. The face height Ft is approximately equal to the face height Fh. The face height Ft may be larger than the face height Fh. The absolute value of the difference (Ft-Fh) may be 2.0 mm or less, further 1.5 mm or less, and further 1.0 mm or less.

[0091] Regarding the ratio of face height F to head thickness T, head 64 satisfies the following relationship (e): (e)Ft / Tt < Fh / Th

[0092] Furthermore, head 64 satisfies the following relationships (f) and (f1). (f)Ft / Tt < Fc / Tc ≤ Fh / Th (f1)Ft / Tt < Fc / Tc < Fh / Th

[0093] In head 64, the radius of curvature St is smaller than the radius of curvature Rt. Also, the radius of curvature Sc is smaller than the radius of curvature Rc. Furthermore, the radius of curvature Sh is smaller than the radius of curvature Rh.

[0094] In the fourth embodiment, which is an example of a hybrid head, the dimensions may be as follows: • Radius of curvature Rt on the crown side: 9.50 mm • Radius of curvature Rc on the crown side: 8.02 mm • Radius of curvature Rh on the crown side: 6.50 mm • Radius of curvature on the sole side: St: 3.49mm • Radius of curvature (Sc) on the sole side: 3.50mm • Radius of curvature on the sole side: 3.49mm Face height Ft: 25.85mm Face height Fc: 27.14mm Face height Fh: 25.87mm • Head thickness Tt: 35.57mm • Head thickness Tc: 35.83mm • Head thickness Th: 33.49mm

[0095] Figure 16 is a front view of the head 84 of the fifth embodiment. The head 84 has a face portion 90, a crown portion 92, a sole portion 94, and a hosel portion 96. The face portion 90 has a striking face 90a. The crown portion 92 forms a crown surface 92a. The sole portion 94 forms a sole surface 94a. The head 84 has a hollow structure. The head 84 is a fairway wood type head.

[0096] In head 84, the radius of curvature R on the crown side is slightly variable or constant. In the main striking area, the change in the radius of curvature R may be 1.0 mm or less, more preferably 0.8 mm or less, more preferably 0.6 mm or less, or more preferably 0.4 mm or less. Head 84 does not satisfy the following relationships (a) and (a1). Head 84 may satisfy relationships (a) and / or (a1). (a) Rt > Rc ≥ Rh (a1) Rt > Rc > Rh

[0097] In head 84, the radius of curvature S on the sole side is not constant. The radius of curvature S changes depending on the position in the toe-heel direction. This change in the radius of curvature S is continuous. Head 84 satisfies the following relationship (b). Head 84 satisfies the following relationship (b1). (b) St > Sc ≥ Sh (b1) St>Sc>Sh

[0098] Except for the radii of curvature R and S, the head 84 is the same as the head 44 of the third embodiment. In the head 44, the change in the radius of curvature R is greater than the change in the radius of curvature S, but in the head 84, the change in the radius of curvature S is greater than the change in the radius of curvature R.

[0099] Regarding the face height F, head 84 does not satisfy the following relationship (d). Head 84 satisfies the following (d1). (d)Ft <fc>Fh (d1)Ft <Fc<Fh

[0100] In the Head 84 (fairway wood type head), the radius of curvature St is increased, and the face height Ft is decreased. Face height Ft is smaller than face height Fh.

[0101] Regarding the ratio of face height F to head thickness T, head 84 satisfies the following relationship (e): (e)Ft / Tt < Fh / Th

[0102] Furthermore, head 84 satisfies the following relationships (f) and (f1). (f)Ft / Tt < Fc / Tc ≤ Fh / Th (f1)Ft / Tt < Fc / Tc < Fh / Th

[0103] In head 84, the radius of curvature St is smaller than the radius of curvature Rt. Also, the radius of curvature Sc is smaller than the radius of curvature Rc. Furthermore, the radius of curvature Sh is smaller than the radius of curvature Rh.

[0104] Each of the embodiments described above has the following effects.

[0105] By satisfying at least one of the following relationships (a) and (b), and increasing at least one of the radius of curvature Rt and St on the toe side, the face height Ft can be suppressed, and the following relationship (e) may hold. In this case, when hitting on the toe side, the boundary area with a large radius of curvature (the part with radius of curvature Rt and / or radius of curvature St) flexes, and because the face height Ft is small, the load on the face is reduced. Therefore, the durability of the head is improved (toe durability improvement effect). When the face height Ft is suppressed, the flexing of the face becomes smaller, which may cause a decrease in rebound performance. However, because the boundary area with a large radius of curvature Rt and / or St flexes, the overall amount of flexing on the toe side can be maintained. Therefore, rebound performance can be maintained (toe rebound maintenance effect). On the other hand, on the heel side, the face height Fh is basically small due to the structure of the head, which is advantageous in terms of durability. By reducing the radius of curvature Rh and / or the radius of curvature Sh, the face height Fh can be secured. By securing the face height Fh, the flex of the face portion 10 is ensured on the heel side, thereby improving rebound performance (heel rebound improvement effect). In addition, by maintaining the face height Fh on the heel side, the visible hitting face does not become narrower, providing a sense of security at address. From these viewpoints, it is more preferable to satisfy at least one of the following (a1) and (b1). (a) Rt > Rc ≥ Rh (b) St > Sc ≥ Sh (a1) Rt > Rc > Rh (b1) St>Sc>Sh (e)Ft / Tt < Fh / Th

[0106] The above relationship in the main striking area enhances the effects described above in actual striking.

[0107] The first, second, third, and fourth embodiments described above satisfy relationship (a) or (a1) above, and relationship (e) above is established. Therefore, when striking on the toe side, the crown-side boundary portion having a large radius of curvature Rt flexes, and the face height Ft on the toe side is suppressed. Thus, the load on the face portion on the toe side is reduced, and the durability of the head is improved (toe durability improvement effect). When the face height Ft is suppressed, the flexing of the face portion becomes smaller and the rebound performance may decrease, but since the portion with radius of curvature Rt flexes, the overall amount of flexing can be maintained. Thus, the rebound performance on the toe side can be maintained (toe rebound maintenance effect). On the other hand, on the heel side, the face height Fh is basically small, which is advantageous in terms of durability. By reducing the radius of curvature Rh, the face height Fh can be secured. By securing the face height Fh, the flexing of the face portion on the heel side can be secured, and the rebound performance can be improved (heel rebound improvement effect). These effects improve the rebound performance and durability of the entire face. Furthermore, maintaining the face height Fh on the heel side prevents the visible impact face from becoming smaller, providing a sense of confidence at address.

[0108] The first, second, third, and fourth embodiments described above satisfy the following relationship (f). Furthermore, the first, third, and fourth embodiments described above satisfy the following relationship (f1). Therefore, the effect based on the above relationship (e) is further enhanced. (f)Ft / Tt < Fc / Tc ≤ Fh / Th (f1)Ft / Tt < Fc / Tc < Fh / Th

[0109] The first, second, third, and fourth embodiments described above do not satisfy relationships (b) and (b1). The head may satisfy relationship (b) instead of relationship (a). Also, the head may satisfy relationship (b1) instead of relationship (a1). The head may satisfy relationships (a) and (b). Also, the head may satisfy relationships (a1) and (b1). If the face height Ft is too small, the hitting face may appear narrow, which can reduce confidence at address. From this viewpoint, if relationship (a) is satisfied, it is preferable that relationship (b) is not satisfied, and it is more preferable that relationship (b2) or (b3) is satisfied. If relationship (a1) is satisfied, it is preferable that relationship (b1) is not satisfied, and it is more preferable that relationship (b2) or (b3) is satisfied.

[0110] The fifth embodiment described above satisfies relationships (b) and (b1). When relationships (b) and (b1) are satisfied, the change in the radius of curvature S on the sole side is large, which tends to increase the influence on the shape of the sole surface. The shape of the sole surface affects the ground contact resistance of the head. From the viewpoint of design freedom for the shape of the sole surface, a head that does not satisfy relationships (b) and (b1) is preferable. On the other hand, when relationship (b) or (b1) is satisfied, relationship (e) can be achieved without changing the radius of curvature R. When the radius of curvature R is changed, it tends to affect how the head looks at address. If it is desired that the appearance of the head at address be the same as that of a conventional head, relationship (b) or (b1) can be satisfied.

[0111] The fifth embodiment described above satisfies relationships (b) and (b1). The distribution of impact points on the face has a high density of impact points in the region from below the heel to above the toe. By satisfying relationship (b) or (b1), it becomes possible to form the impact face in a region with a high density of impact points.

[0112] The position 15 mm toe-side from the face center C1 is also called the toe reference position. The position of the face center C1 is also called the center position. The position 15 mm heel-side from the face center C1 is also called the heel reference position. The main hitting area is the area from the heel reference position to the toe reference position.

[0113] In the first embodiment described above, the radius of curvature R changes continuously in the main striking region. In this main striking region, the radius of curvature R increases as you move towards the toe. These points are the same in the second, third, and fourth embodiments described above. In the fifth embodiment described above, the radius of curvature S changes continuously in the main striking region. In this main striking region, the radius of curvature S increases as you move towards the toe.

[0114] In the first embodiment described above, the radius of curvature R also changes on the toe side of the main striking area (see Figure 3). The radius of curvature R at 5 mm toe-side from the toe reference position is the radius of curvature Rt1. The radius of curvature Rt1 is greater than the radius of curvature Rt. The radius of curvature R at 15 mm toe-side from the toe reference position is the radius of curvature Rt2. The radius of curvature Rt2 is greater than the radius of curvature Rt. The radius of curvature Rt2 is greater than the radius of curvature Rt1. These points are the same in the second, third, and fourth embodiments described above.

[0115] In the third embodiment (fairway wood type head) and the fourth embodiment (hybrid type head), the radius of curvature S on the sole side is smaller than the radius of curvature R on the crown side. That is, the radius of curvature St is smaller than the radius of curvature Rt, the radius of curvature Sc is smaller than the radius of curvature Rc, and the radius of curvature Sh is smaller than the radius of curvature Rh. With fairway wood type heads and hybrid type heads, there are many occasions when hitting a ball placed directly on the grass without teeing it up. If the radius of curvature S is large, the vertical distance from the contact surface to the leading edge tends to be large. In this case, when hitting a ball placed directly on the grass, mis-shots (so-called tops, or thin shots in English) are more likely to occur. In the third and fourth embodiments, these mis-shots are suppressed.

[0116] From the viewpoint of suppressing the above mis-shots, the following is preferable for fairway wood type heads and hybrid type heads: The radius of curvature St is preferably 7.0 mm or less, more preferably 6.0 mm or less, more preferably 5.0 mm or less, and more preferably 4.0 mm or less. From the viewpoint of suppressing face height Ft, the radius of curvature St is preferably 1.5 mm or more, more preferably 2.0 mm or more, and more preferably 2.5 mm or more.

[0117] From the viewpoint of suppressing the above mis-shots, the following is preferable for fairway wood type heads and hybrid type heads: The radius of curvature Sc is preferably 7.0 mm or less, more preferably 6.0 mm or less, more preferably 5.0 mm or less, and more preferably 4.0 mm or less. From the viewpoint of ground resistance, the radius of curvature Sc is preferably 1.5 mm or more, more preferably 2.0 mm or more, and more preferably 2.5 mm or more.

[0118] From the viewpoint of suppressing the above-mentioned mis-shots and maintaining the face height Fh, the following are preferred for fairway wood type heads and hybrid type heads. The radius of curvature Sh is preferably 7.0 mm or less, more preferably 6.0 mm or less, more preferably 5.0 mm or less, and more preferably 4.0 mm or less. From the viewpoint of ground resistance, the radius of curvature Sh is preferably 1.5 mm or more, more preferably 2.0 mm or more, and more preferably 2.5 mm or more.

[0119] In driver heads, the radius of curvature S can be set larger compared to fairway wood and hybrid heads. Because driver heads strike a teed-up ball, the aforementioned mis-shots are less likely to occur. Furthermore, driver heads have a relatively large face height F, allowing for greater room to reduce the face height F. From these perspectives, it is desirable to increase the radius of curvature S in driver heads to increase the flex at the sole boundary and improve rebound performance. In driver heads, the radii of curvature St, Sc, and Sh can be 7.5 mm or more, even 8.0 mm or more, and even 8.5 mm or more. (Undersized) Na Fu From the perspective of preventing face height Ft, the radius of curvature St, radius of curvature Sc, and radius of curvature Sh of the driver head may be 12.0 mm or less, further 11.0 mm or less, and further 10.0 mm or less.

[0120] From the viewpoint of suppressing the above mis-shots, Rt / St is preferably 1.5 or higher, more preferably 2.0 or higher, and most preferably 2.5 or higher. Considering the preferred values ​​of the radius of curvature St and face height Ft, Rt / St is preferably 5.0 or lower, more preferably 4.5 or lower, and most preferably 4.0 or lower.

[0121] From the viewpoint of suppressing the above mis-shots, Rc / Sc is preferably 1.5 or higher, more preferably 2.0 or higher, and most preferably 2.5 or higher. Considering the preferred values ​​of radius of curvature Sc and face height Fc, Rc / Sc is preferably 5.0 or lower, more preferably 4.5 or lower, and most preferably 4.0 or lower.

[0122] From the viewpoint of suppressing the above mis-shots, Rh / Sh is preferably 1.0 or higher, more preferably 1.5 or higher, and even more preferably 2.0 or higher. Considering the preferred values ​​of radius of curvature Sh and face height Fh, Rh / Sh is preferably 4.5 or lower, more preferably 4.0 or lower, and even more preferably 3.5 or lower.

[0123] Rt / Rh is the ratio of the radius of curvature Rt on the toe side to the radius of curvature Rh on the heel side. From the viewpoint of improving toe durability, maintaining toe rebound, and improving heel rebound, Rt / Rh is preferably 1.20 or higher, more preferably 1.25 or higher, more preferably 1.30 or higher, more preferably 1.35 or higher, and more preferably 1.40 or higher. If the radius of curvature Rt is too large, the face height Ft will be too small, which may reduce the sense of security at address. From this viewpoint, Rt / Rh is preferably 1.80 or lower, more preferably 1.75 or lower, and more preferably 1.70 or lower.

[0124] When the above relationship (a) or (a1) is satisfied and Rt / Rh is large, it is preferable that St / Sh be small. If Rt / Rh and St / Sh are large, the face height Ft may be too small. If the face height Ft is too small, the sense of security at address may decrease. From this viewpoint, when Rt / Rh is in the above preferred range of 1.20 or more, St / Sh is preferably 1.15 or less, more preferably 1.10 or less, and more preferably 1.05 or less. If the radius of curvature St is too small, the face height Ft increases, and the above effect of improving toe durability may decrease. From this viewpoint, St / Sh is preferably 0.80 or more, more preferably 0.85 or more, and more preferably 0.90 or more.

[0125] Ft / Fh is the ratio of the face height Ft on the toe side to the face height Fh on the heel side. From the viewpoint of improving toe durability, maintaining toe rebound, and improving heel rebound, Ft / Fh is preferably 1.15 or less, more preferably 1.12 or less, more preferably 1.09 or less, and more preferably 1.06 or less. If the radius of curvature Rt or radius of curvature St is too large and the face height Ft is too small, the sense of security at address may decrease. From this viewpoint, Ft / Fh is preferably 0.85 or more, more preferably 0.90 or more, and more preferably 0.95 or more.

[0126] As shown in Figure 3, the radius of curvature R at a position 5 mm toe-side from the toe reference position is the radius of curvature Rt1. The radius of curvature Rt1 is greater than the radius of curvature Rt. The face height F at this position is the face height Ft1. The face height Ft1 is less than the face height Ft.

[0127] As shown in Figure 3, the face height F at a position 15 mm toe-side from the toe reference position is the face height Ft2. Face height Ft2 is smaller than face height Ft. The radius of curvature R at this position is the radius of curvature Rt2, and the radius of curvature S at this position is the radius of curvature St2. As mentioned above, the radius of curvature Rt2 is larger than the radius of curvature Rt. Due to the large radius of curvature Rt2, the face height Ft2 is small.

[0128] From the viewpoint of extending the above effect to the toe side beyond the main hitting area, Ft2 / Fh is preferably 0.97 or less, more preferably 0.94 or less, and more preferably 0.91 or less. If the radius of curvature Rt2 or radius of curvature St2 is too large and the face height Ft2 is too small, the sense of security at address may decrease. From this viewpoint, Ft2 / Fh is preferably 0.55 or more, more preferably 0.60 or more, and more preferably 0.65 or more.

[0129] In order to satisfy the above relationship (a) or (a1) and relationship (e), enhance the above-mentioned effects based on these relationships, and conform to the specifications of each head type, the radius of curvature R may be within the following range. In the following description, (x) is a preferred range, (y) is a more preferred range, and (z) is an even more preferred range.

[0130] [Driver head radius of curvature Rt] (x)9.5mm or more and 13.5mm or less (y) 10.0 mm or more and 13.0 mm or less (z)10.5mm or more and 12.5mm or less

[0131] [Driver head radius of curvature Rc] (x)7.5mm or more and 11.5mm or less (y) 8.0 mm to 11.0 mm (z)8.5mm or more and 10.5mm or less

[0132] [Driver head radius of curvature Rh] (x)6.0mm or more and 10.0mm or less (y)6.5mm or more and 9.5mm or less (z)7.0mm or more and 9.0mm or less

[0133] [Rt - radius of curvature of fairway wood head] (x)10.0mm or more and 14.0mm or less (y) 10.5mm or more and 13.5mm or less (z) 11.0mm or more and 13.0mm or less

[0134] [Rc radius of curvature of fairway wood head] (x)8.0mm or more and 12.0mm or less (y)8.5mm or more and 11.5mm or less (z)9.0mm or more and 11.0mm or less

[0135] [Rh - radius of curvature of fairway wood head] (x)6.0mm or more and 10.0mm or less (y)6.5mm or more and 9.5mm or less (z)7.0mm or more and 9.0mm or less

[0136] [Hybrid head radius Rt] (x)7.5mm or more and 11.5mm or less (y) 8.0 mm to 11.0 mm (z)8.5mm or more and 10.5mm or less

[0137] [Hybrid head radius Rc] (x)6.0mm or more and 10.0mm or less (y)6.5mm or more and 9.5mm or less (z)7.0mm or more and 9.0mm or less

[0138] [Hybrid head radius of curvature Rh] (x)4.5mm or more and 8.5mm or less (y) 5.0 mm or more and 8.0 mm or less (z)5.5mm or more and 7.5mm or less

[0139] From the viewpoint of satisfying the above relationships (e), (f), or (f1), enhancing the above effects resulting from these relationships, and conforming to the specifications of each head type, the ratio (F / T) may be within the following range. In the following description, (x) is a preferred range, (y) is a more preferred range, and (z) is an even more preferred range.

[0140] [Driver head Ft / Tt] (x) 0.61 or more and 0.71 or less (y) 0.62 or more and 0.70 or less (z) 0.63 or more and 0.69 or less

[0141] [Driver head Fc / Tc] (x) 0.62 or more and 0.72 or less (y) 0.63 or more and 0.71 or less (z) 0.64 or more and 0.70 or less

[0142] [Driver head Fh / Th] (x) 0.64 or more and 0.74 or less (y) 0.65 or more and 0.73 or less (z) 0.66 or more and 0.72 or less

[0143] [Ft / Tt of fairway wood-type heads] (x)0.58 or more and 0.68 or less (y) 0.59 or more and 0.67 or less (z) 0.60 or more and 0.66 or less

[0144] [Fairway wood type head Fc / Tc] (x) 0.62 or more and 0.72 or less (y) 0.63 or more and 0.71 or less (z) 0.64 or more and 0.70 or less

[0145] [Fh / Th of fairway wood-type heads] (x) 0.63 or more and 0.73 or less (y) 0.64 or more and 0.72 or less (z) 0.65 or more and 0.71 or less

[0146] [Ft / Tt of hybrid head] (x)0.68 or more and 0.78 or less (y) 0.69 or more and 0.77 or less (z)0.70 or more and 0.76 or less

[0147] [Fc / Tc of hybrid heads] (x)0.71 or more and 0.81 or less (y) 0.72 or more and 0.80 or less (z) 0.73 or more and 0.79 or less

[0148] [Fh / Th of hybrid heads] (x) 0.72 or more and 0.82 or less (y) 0.73 or more and 0.81 or less (z) 0.74 or more and 0.80 or less

[0149] The following are typical specifications for a driver head (including mini-drivers that are similar to drivers): (1a) to (1e). (1a) Curved striking face (1b) Hollow structure (1c) 300cm 3 Over 470cm 3 The following volume (1d) Real loft angle between 7 and 13 degrees (1e) The presence of a crown

[0150] Examples of fairway wood-type heads include the 3-wood (W#3), 4-wood (W#4), 5-wood (W#5), 7-wood (W#7), 9-wood (W#9), 11-wood (W#11), and 13-wood (W#13). The following (2a) to (2e) are typical specifications for fairway wood-type heads. (2a) Curved striking face (2b) Hollow structure (2c) 100cm 3 That's 300cm 3 smaller volume (2d) Real loft angle greater than 13 degrees and less than or equal to 33 degrees (2e) The presence of a crown

[0151] Examples of hybrid heads include the Hybrid 3 (H3), Hybrid 4 (H4), Hybrid 5 (H5), and Hybrid 6 (H6). The following (3a) to (3e) are typical configurations of hybrid heads. (3a) Curved striking face (3b) Hollow structure (3c) 90cm 3 over 140cm 3 The following volume (3D) Real loft angle between 15 and 33 degrees (3e) The presence of the crown

[0152] Hybrid heads are also called utility heads in Japan. Furthermore, hybrid heads are sometimes distinguished into wood-type and iron-type hybrid heads. Iron-type hybrid heads do not have a crown.

[0153] It has a crown, a loft angle (real loft angle) greater than 13 degrees, and a volume of 300 cm³. 3 Smaller heads may be classified as fairway wood-type heads or hybrid-type heads. Fairway wood-type heads and hybrid-type heads can be distinguished by W1 / W2. In Figure 13, the double-headed arrow W1 indicates the face-to-back width of the head. In Figure 13, the double-headed arrow W2 indicates the toe-to-heel width of the head. For hybrid-type heads, W1 / W2 is less than 0.65. For fairway wood-type heads, W1 / W2 is 0.65 or more. They have a crown and a volume of 300 cm³. 3 A head that meets the above criteria can be considered a driver head.

[0154] Figure 17(a) is a cross-sectional view along line aa in Figure 3, Figure 17(b) is a cross-sectional view along line bb in Figure 3, and Figure 17(c) is a cross-sectional view along line cc in Figure 3. Unlike Figures 5(a) to (c), these are complete cross-sectional views including the cross-section of the head thickness. Figure 17(a) is a cross-sectional view at the toe reference position. Figure 17(b) is a cross-sectional view at the center position. Figure 17(c) is a cross-sectional view at the heel reference position.

[0155] As explained in Figure 6, in each longitudinal section, the outer surface of the head 4 has points P1, P2, and P3 on the crown side, and points P1, P4, and P5 on the sole side.

[0156] On the crown side, the thickness at point P1 is X1 (mm), the thickness at point P2 is X2 (mm), and the thickness at point P3 is X3 (mm). On the sole side, the thickness at point P1 is Y1 (mm), the thickness at point P4 is Y2 (mm), and the thickness at point P5 is Y3 (mm). The thickness is the thickness between the outer and inner surfaces of the head 4. The thickness is measured in a longitudinal section, along the normal to the outer surface of the head 4.

[0157] As shown in Figure 17(a), X1 at the toe reference position is denoted as Xt1, X2 at the toe reference position is denoted as Xt2, and X3 at the toe reference position is denoted as Xt3. Similarly, Y1 at the toe reference position is denoted as Yt1, Y2 at the toe reference position is denoted as Yt2, and Y3 at the toe reference position is denoted as Yt3.

[0158] As shown in Figure 17(b), X1 at the center position is denoted as Xc1, X2 at the center position is denoted as Xc2, and X3 at the center position is denoted as Xc3. Similarly, Y1 at the center position is denoted as Yc1, Y2 at the center position is denoted as Yc2, and Y3 at the center position is denoted as Yc3.

[0159] As shown in Figure 17(c), X1 at the heel reference position is Xh1, X2 at the heel reference position is Xh2, and X3 at the heel reference position is X h It is set to 3. Also, Y1 at the heel reference position is set to Yh1, Y2 at the heel reference position is set to Yh2, and Y3 at the heel reference position is set to Y h It is considered to be 3.

[0160] The wall thickness Xt3 is smaller than the wall thickness Xc3. The wall thickness Xc3 is smaller than the wall thickness Xh3. On the crown side, the following relationship (g) holds: (g)Xt3 <Xc3<Xh3

[0161] In the main striking area, the wall thickness X3 changes continuously in the toe-heel direction. In this main striking area, the wall thickness X3 becomes thinner towards the toe.

[0162] As shown in Figure 17(a), wall thickness Xt1 is greater than wall thickness Xt2. Wall thickness Xt1 is greater than wall thickness Xt3. Wall thickness Xt2 is greater than wall thickness Xt3. Wall thickness Yt1 is greater than wall thickness Yt2. Wall thickness Yt1 is greater than wall thickness Yt3. Wall thickness Yt2 is greater than wall thickness Yt3.

[0163] As shown in Figure 17(b), wall thickness Xc1 is greater than wall thickness Xc2. Wall thickness Xc1 is greater than wall thickness Xc3. Wall thickness Xc2 is greater than wall thickness Xc3. Wall thickness Yc1 is greater than wall thickness Yc2. Wall thickness Yc1 is greater than wall thickness Yc3. Wall thickness Yc2 is greater than wall thickness Yc3.

[0164] As shown in Figure 17(c), wall thickness Xh1 is greater than wall thickness Xh2. Wall thickness Xh1 is greater than wall thickness Xh3. Wall thickness Xh2 is greater than wall thickness Xh3. Wall thickness Yh1 is greater than wall thickness Yh2. Wall thickness Yh1 is greater than wall thickness Yh3. Wall thickness Yh2 is greater than wall thickness Yh3.

[0165] Thus, at the toe reference position, center position, and heel reference position, the following relationships (i1) and (i2) hold true on the crown side. (i1)X1>X3 (i2)X1>X2>X3

[0166] Furthermore, at the toe reference position, center position, and heel reference position, the following relationships (j1) and (j2) hold true on the sole side. (j1)Y1>Y3 (j2)Y1≧Y2>Y3

[0167] From the viewpoint of improving toe durability and maintaining toe rebound, it is preferable that, as in the first to fourth embodiments above, when relationship (a) or (a1) is satisfied, the following relationship (g) described above is also satisfied. (g)Xt3 <Xc3<Xh3

[0168] From the viewpoint of improving toe durability and maintaining toe rebound, as in the fifth embodiment described above, when the above relationship (b) or (b1) is satisfied, it is preferable that the wall thickness Yt3 is smaller than the wall thickness Yc3, and that the wall thickness Yc3 is smaller than the wall thickness Yh3, and it is even more preferable that the following relationship (h) holds. In this case, it is also preferable that the wall thickness Y3 changes continuously in the toe-heel direction in the main impact area. (h)Yt3 <Yc3<Yh3

[0169] From the viewpoint of improving toe durability and maintaining toe rebound, the wall thickness Xt3 is preferably 1.2 mm or less, more preferably 1.1 mm or less, and even more preferably 1.0 mm or less. From the viewpoint of head durability, the wall thickness Xt3 is preferably 0.4 mm or more, more preferably 0.5 mm or more, and even more preferably 0.6 mm or more.

[0170] From the viewpoint of rebound performance, the wall thickness Xc3 is preferably 1.2 mm or less, more preferably 1.1 mm or less, and even more preferably 1.0 mm or less. From the viewpoint of head durability, the wall thickness Xc3 is preferably 0.4 mm or more, more preferably 0.5 mm or more, and even more preferably 0.6 mm or more.

[0171] From the viewpoint of rebound performance, the wall thickness Xh3 is preferably 1.2 mm or less, more preferably 1.1 mm or less, and even more preferably 1.0 mm or less. From the viewpoint of head durability, the wall thickness Xh3 is preferably 0.4 mm or more, more preferably 0.5 mm or more, and even more preferably 0.6 mm or more.

[0172] From the viewpoint of improving toe durability and maintaining toe rebound, the wall thickness Yt3 is preferably 1.3 mm or less, more preferably 1.2 mm or less, and even more preferably 1.1 mm or less. From the viewpoint of head durability, the wall thickness Yt3 is preferably 0.5 mm or more, more preferably 0.6 mm or more, and even more preferably 0.7 mm or more.

[0173] From the viewpoint of rebound performance, the wall thickness Yc3 is preferably 1.3 mm or less, more preferably 1.2 mm or less, and even more preferably 1.1 mm or less. From the viewpoint of head durability, the wall thickness Yc3 is preferably 0.5 mm or more, more preferably 0.6 mm or more, and even more preferably 0.7 mm or more.

[0174] From the viewpoint of rebound performance, the wall thickness Yh3 is preferably 1.3 mm or less, more preferably 1.2 mm or less, and even more preferably 1.1 mm or less. From the viewpoint of head durability, the wall thickness Yh3 is preferably 0.5 mm or more, more preferably 0.6 mm or more, and even more preferably 0.7 mm or more.

[0175] The thickness of the boundary between the striking face and the crown surface decreases towards the back, which allows the area closer to the face to be stronger while dispersing stress concentration and allowing the boundary to flex. From the viewpoint of head durability and rebound performance, the first to fifth embodiments (heads 4, 24, 44, 64, 84) above preferably satisfy the following relationship (i1) and more preferably satisfy relationship (i2) in at least one cross section in the main striking area. (i1)X1>X3 (i2)X1>X2>X3

[0176] The thickness of the boundary between the striking face and the sole surface decreases towards the back, which allows the area closer to the face to be stronger while dispersing stress concentration and allowing the boundary to flex. From the viewpoint of head durability and rebound performance, the first to fifth embodiments (heads 4, 24, 44, 64, 84) described above preferably satisfy the following relationship (j1) and more preferably satisfy relationship (j2) in at least one cross-section in the main striking area. (j1)Y1>Y3 (j2)Y1≧Y2>Y3

[0177] With regard to the embodiments described above, the following additional notes are disclosed. The following additional notes are the claim set at the time of filing the Japanese application. [Note 1] It has a striking face including the face center, a crown surface, and a sole surface. The boundary between the striking face and the crown surface has a radius of curvature R. The boundary between the striking face and the sole surface has a radius of curvature S. The aforementioned striking face has a face height F, The head has a head thickness T, At a position 15 mm toe-side from the face center, the radius of curvature R is Rt, the radius of curvature S is St, the face height F is Ft, and the head thickness T is Tt. At the face center position, the radius of curvature R is Rc, the radius of curvature S is Sc, the face height F is Fc, and the head thickness T is Tc. At a position 15 mm heel-side from the face center, when the radius of curvature R is Rh, the radius of curvature S is Sh, the face height F is Fh, and the head thickness T is Th, Ft / Tt is smaller than Fh / Th. A golf club head that satisfies either relationship (a) or (b) below. (a) Rt > Rc ≥ Rh (b) St > Sc ≥ Sh [Note 2] A golf club head as described in Appendix 1 that satisfies the following relationship (a). (a) Rt > Rc ≥ Rh [Note 3] A golf club head as described in Appendix 2, with an Rt / Rh ratio of 1.2 or higher. [Note 4] A driver head, wherein said curvature radius Rt is 9.5 mm or more and 13.5 mm or less, said curvature radius Rc is 7.5 mm or more and 11.5 mm or less, The golf club head according to any one of Supplementary Notes 1 to 3, wherein said curvature radius Rh is 6.0 mm or more and 10.0 mm or less. [Supplementary Note 5] A loft angle greater than 13°, A head volume less than 300 cm 3 , said curvature radius St is smaller than said curvature radius Rt, said curvature radius Sc is smaller than said curvature radius Rc, The golf club head according to any one of Supplementary Notes 1 to 3, wherein said curvature radius Sh is smaller than said curvature radius Rh. [Supplementary Note 6] A fairway wood type head, wherein said curvature radius Rt is 10.0 mm or more and 14.0 mm or less, said curvature radius Rc is 8.0 mm or more and 12.0 mm or less, The golf club head according to Supplementary Note 5, wherein said curvature radius Rh is 6.0 mm or more and 10.0 mm or less. [Supplementary Note 7] A hybrid type head, wherein said curvature radius Rt is 7.5 mm or more and 11.5 mm or less, said curvature radius Rc is 6.0 mm or more and 10.0 mm or less, The golf club head according to Supplementary Note 5, wherein said curvature radius Rh is 4.5 mm or more and 8.5 mm or less. [Description of Reference Numerals]

[0178] 2···Golf club 4, 24, 44, 64, 84···Head 6···Shaft 8···Grip 10, 30, 50, 70, 90···Face portion 10a, 30a, 50a, 70a, 90a... Impact face 12, 32, 52, 72, 92... Crown section 12a, 32a, 52a, 72a, 92a... Crown surface 14, 34, 54, 74, 94... sole 14a, 34a, 54a, 74a, 94a... sole surface 16, 36, 56, 76, 96... Hosel section k1... Outer edge of the striking face F···Face height Ft...Face height at the toe reference position Fc...Face height at the center position Fh...Face height at heel reference position T...head thickness Tt... Head thickness at the toe reference position Tc...Head thickness at the center position Th...Head thickness at heel reference position R... Radius of curvature of the boundary between the striking face and the crown surface Rt... The radius of curvature of the boundary between the striking face and the crown surface at the toe reference position. Rc... The radius of curvature of the boundary between the striking face and the crown surface at the center position. Rh... The radius of curvature at the boundary between the striking face and the crown surface at the heel reference position. S... Radius of curvature of the boundary between the striking face and the sole surface St... The radius of curvature of the boundary between the striking face and the sole surface at the toe reference position. Sc... The radius of curvature of the boundary between the striking face and the sole surface at the center position. Sh... The radius of curvature of the boundary between the striking face and the sole surface at the heel reference position. Z... Shaft axis< / fc> < / fc> < / tc> < / sc> < / fc> < / tc> < / sc> < / fc> < / sc> < / fc> < / sc>

Claims

1. A golf club head having a striking face including the face center, a crown surface, and a sole surface, The boundary between the striking face and the crown surface has a radius of curvature R. The boundary between the striking face and the sole surface has a radius of curvature S. The striking face has a face height F, The aforementioned golf club head has a head thickness T, At a position 15 mm toe-side from the face center, the radius of curvature R is Rt, the radius of curvature S is St, the face height F is Ft, and the head thickness T is Tt. At the face center position, the radius of curvature R is Rc, the radius of curvature S is Sc, the face height F is Fc, and the head thickness T is Tc. When, at a position 15 mm heel-side from the face center, the radius of curvature R is Rh, the radius of curvature S is Sh, the face height F is Fh, and the head thickness T is Th, If Ft / Tt is smaller than Fh / Th, A golf club head that satisfies at least one of the following relationships (a) and (b). (a) Rt>Rc≧Rh (b) St>Sc≧Sh

2. A golf club head according to claim 1 that satisfies the following relationship (a). (a) Rt>Rc≧Rh

3. The golf club head according to claim 2, wherein Rt / Rh is 1.2 or greater.

4. It is a driver head, The radius of curvature Rt is 9.5 mm or more and 13.5 mm or less. The radius of curvature Rc is 7.5 mm or more and 11.5 mm or less. The golf club head according to any one of claims 1 to 3, wherein the radius of curvature Rh is 6.0 mm or more and 10.0 mm or less.

5. If the loft angle is greater than 13°, Head volume is 300 cm³ ３ Smaller than, The radius of curvature St is smaller than the radius of curvature Rt, The radius of curvature Sc is smaller than the radius of curvature Rc, The golf club head according to any one of claims 1 to 3, wherein the radius of curvature Sh is smaller than the radius of curvature Rh.

6. It has a fairway wood-type head, The radius of curvature Rt is 10.0 mm or more and 14.0 mm or less. The radius of curvature Rc is 8.0 mm or more and 12.0 mm or less. The golf club head according to claim 5, wherein the radius of curvature Rh is 6.0 mm or more and 10.0 mm or less.

7. It is a hybrid head, The radius of curvature Rt is 7.5 mm or more and 11.5 mm or less. The radius of curvature Rc is 6.0 mm or more and 10.0 mm or less. The golf club head according to claim 5, wherein the radius of curvature Rh is 4.5 mm or more and 8.5 mm or less.

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