IRON TYPE GOLF CLUB HEAD

Abstract

An iron type golf club head includes a hitting face that has a plurality of score lines and a face center, a back surface, a sole surface, a top blade and a face thickness. On the back surface, a thick wall portion is formed over a region including a score line center position, the thick wall portion having a face thickness of greater than that of a part on the toe side thereof and greater than that of a part on the heel side thereof. The thick wall portion is formed such that it extends toward the toe side as it goes toward the blade side from the sole side. The iron type golf club head has a loft angle of greater than or equal to 46?. The face thickness is defined as a distance between the hitting face and the back surface.

Claims

1. An iron type golf club head comprising: a hitting face that includes a plurality of score lines and a face center; a back surface; a sole surface; a top blade; and a face thickness that is defined as a distance between the hitting face and the back surface, wherein on the back surface, a thick wall portion is formed over a region including a score line center position, the thick wall portion having a face thickness of greater than the face thickness of a part on a toe side of the thick wall portion and greater than the face thickness of a part on a heel side of the thick wall portion, the thick wall portion is formed such that it extends toward the toe side as it goes toward a blade side from a sole side, and the golf club head has a loft angle of greater than or equal to 46?.

2. The golf club head according to claim 1, wherein the face thickness of the thick wall portion decreases toward the blade side.

3. The golf club head according to claim 1, wherein the thick wall portion is disposed over a region that includes the face center.

4. The golf club head according to claim 1, further includes an upper thick wall portion that is thicker than an upper end of the thick wall portion and is located on the blade side of the thick wall portion.

5. The golf club head according to claim 1, wherein when a thick wall portion region obtained by projecting the thick wall portion onto the hitting face is divided into the following four parts: a heel upper part that is located on the heel side and blade side with respect to the face center; a toe upper part that is located on the toe side and blade side with respect to the face center; a toe lower part that is located on the toe side and sole side with respect to the face center; and a heel lower part that is located on the heel side and sole side with respect to the face center, an area of the toe upper part is greater than an area of the heel upper part, is greater than an area of the toe lower part, and is greater than an area of the heel lower part.

6. The golf club head according to claim 1, wherein when a thick wall portion region obtained by projecting the thick wall portion onto the hitting face includes a heel upper part that is located on the heel side and blade side with respect to the face center, and a toe upper part that is located on the toe side and blade side with respect to the face center, an area of the toe upper part is greater than or equal to two times an area of the heel upper part.

7. The golf club head according to claim 1, wherein when a thick wall portion region obtained by projecting the thick wall portion onto the hitting face is divided into the following two parts: an upper part that is located on the blade side with respect to the face center; and a lower part that is located on the sole side with respect to the face center, an area of the upper part is greater than an area of the lower part.

8. The golf club head according to claim 1, wherein when a thick wall portion region obtained by projecting the thick wall portion onto the hitting face is divided into the following two parts: a toe part that is located on the toe side with respect to the face center; and a heel part that is located on the heel side with respect to the face center, an area of the toe part is greater than an area of the heel part.

9. The golf club head according to claim 1, wherein the golf club head is produced by forging.

10. A golf club comprising the golf club head according to claim 1, a shaft and a grip.

11. A golf club set comprising two or more golf clubs according to claim 10, wherein the greater the loft angle is, the larger an area of the thick wall portion is.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 shows a golf club set according to a first embodiment;

[0009] FIG. 2 is a perspective view of a first head according to the first embodiment;

[0010] FIG. 3A and FIG. 3B are back views of the head in FIG. 2, and FIG. 3A is a shaded view;

[0011] FIG. 4A and FIG. 4B are front views of the head in FIG. 2 as viewed from the front of its hitting face, and FIG. 4A is a shaded view;

[0012] FIG. 5A is a cross-sectional view taken along line a-a in FIG. 3A, FIG. 5B is a cross-sectional view taken along line b-b in FIG. 3A, FIG. 5C is a cross-sectional view taken along line c-c in FIG. 3A, FIG. 5D is a cross-sectional view taken along line d-d in FIG. 3A, and FIG. 5E is a cross-sectional view taken along line e-e in FIG. 3A;

[0013] FIG. 6A and FIG. 6B are back views of a second head according to the first embodiment, and FIG. 6A is a shaded view;

[0014] FIG. 7A and FIG. 7B are front views of the head in FIG. 6 as viewed from the front of its hitting face, and FIG. 7A is a shaded view;

[0015] FIG. 8A is a cross-sectional view taken along line a-a in FIG. 6A, FIG. 8B is a cross-sectional view taken along line b-b in FIG. 6A, FIG. 8C is a cross-sectional view taken along line c-c in FIG. 6A, FIG. 8D is a cross-sectional view taken along line d-d in FIG. 6A, and FIG. 8E is a cross-sectional view taken along line e-e in FIG. 6A;

[0016] FIG. 9A and FIG. 9B are back views of a third head according to the first embodiment, and FIG. 9A is a shaded view;

[0017] FIG. 10A and FIG. 10B are front views of the head in FIG. 9 as viewed from the front of its hitting face, and FIG. 10A is a shaded view;

[0018] FIG. 11A is a cross-sectional view taken along line a-a in FIG. 9A, FIG. 11B is a cross-sectional view taken along line b-b in FIG. 9A, FIG. 11C is a cross-sectional view taken along line c-c in FIG. 9A, FIG. 11D is a cross-sectional view taken along line d-d in FIG. 9A, and FIG. 11E is a cross-sectional view taken along line e-e in FIG. 9A;

[0019] FIG. 12A and FIG. 12B are back views of a head according to a second embodiment, and FIG. 12A is a shaded view;

[0020] FIG. 13A and FIG. 13B are back views of a head according to a third embodiment, and FIG. 13A is a shaded view;

[0021] FIG. 14A and FIG. 14B are back views of a head according to a fourth embodiment, and FIG. 14A is a shaded view;

[0022] FIG. 15 is the same back view as FIG. 3B;

[0023] FIG. 16 is a figure obtained by superposing a projected figure of the back view of FIG. 15 on the front view of FIG. 4B, and the projected figure is prepared by projecting the back view of FIG. 15 onto the hitting face;

[0024] FIG. 17 is the same figure as FIG. 16; and

[0025] FIG. 18 is a conceptual diagram for illustrating a reference state.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Hereinafter, embodiments will be described in detail with appropriate references to the accompanying drawings.

[Reference State]

[0027] The reference state is a state where a head is placed on a horizontal plane HP in a state where the horizontal plane HP and score lines gv are parallel to each other. When a head is in the reference state, a center axis line Z (a shaft axis line Z) of a shaft hole of the head lies on a reference perpendicular plane VP (see FIG. 18). The reference perpendicular plane VP is a plane perpendicular to the horizontal plane HP. In the reference state, the score lines gv are parallel to the horizontal plane HP and parallel to the reference perpendicular plane VP.

[Toe-Heel Direction]

[0028] In a head which is in the reference state, the direction of an intersection line between the reference perpendicular plane VP and the horizontal plane HP is the toe-heel direction. The toe-heel direction is parallel to the score lines.

[Face-Back Direction]

[0029] The face-back direction is a direction that is perpendicular to the toe-heel direction and parallel to the horizontal plane HP. The face-back direction is also referred to as a front-rear direction. The face side is also referred to as front side. The back side is also referred to as rear side.

[Up-Down Direction]

[0030] The up-down direction is a direction that is perpendicular to the toe-heel direction and perpendicular to the face-back direction.

[Projected Figure]

[0031] The projected figure is a figure obtained by projecting an object onto a plane parallel to a hitting face (plane including the hitting face). The direction of the projection is perpendicular to the hitting face.

[Blade-Sole Direction]

[0032] The blade-sole direction is a direction of a straight line that extends in the up-down direction in the projected figure.

[Toe Reference Position]

[0033] When toe-side ends of a plurality of score lines are arranged in a straight line, the position of the toe-side ends is the toe reference position. When toe-side ends of a plurality of score lines are not arranged in a straight line as in a head having full score lines (full face lines), however, a position that is spaced 18.5 mm apart from a toe-most point of the hitting face toward the heel side is defined as the toe reference position. The toe reference position is a position in the toe-heel direction.

[Heel Reference Position]

[0034] The score lines have respective heel-side ends. A heel-most position of the heel-side ends is the heel reference position. Usually, the position of the heel-side end of a longest score line coincides with the heel reference position. The heel reference position is a position in the toe-heel direction.

[Score Line Center Position]

[0035] A position that divides a distance between the toe reference position and the heel reference position into two equal parts in the toe-heel direction is defined as the score line center position. Normally, the center position of the longest score line coincides with the score line center position. The score line center position is a position in the toe-heel direction. As described above, even when a head having full score lines is used, the toe reference position can be set at a position corresponding to the toe reference position in a head having normal score lines. Accordingly, when a head having full score lines are used, the score line center position can also be set at a position corresponding to the score line center position in a head having normal score lines.

[Face Center]

[0036] On the score line center position, a center point of the width of the hitting face in the up-down direction is defined as the face center. A face center is also present on the back surface. The face center on the back surface is a point obtained by projecting the face center of the hitting face onto the back surface. The direction of the projection is perpendicular to the hitting face.

[Leading Edge]

[0037] In a cross section of a head taken in the face-back direction, a point located at the front-most position is determined. This point is determined in each of cross sections taken at different positions in the toe-heel direction. A set of the points is defined as the leading edge. The leading edge is the front edge of a sole surface.

[Trailing Edge]

[0038] When a radius of curvature of a sole surface is sequentially measured rearward in a cross section of a head taken in the face-back direction, a point at which the radius of curvature becomes first less than or equal to 5 mm is determined. A set of the points is defined as the trailing edge. The trailing edge is the rear edge of the sole surface.

[0039] The present disclosure includes a disclosure of a golf club head and a disclosure of a golf club set. FIG. 1 shows a golf club set 2 according to a first embodiment of the present disclosure. The golf club set 2 is an iron type golf club set. The golf club set 2 includes golf clubs each having a loft angle of greater than or equal to 46?. The upper limit of the loft angle is preferably less than or equal to 70?, more preferably less than or equal to 65?, and still more preferably less than or equal to 62?. The golf club set 2 is a wedge golf club set. The loft angle in the present disclosure means a real loft angle. The real loft angle means a loft angle with respect to the shaft axis line Z.

[0040] The golf club set 2 includes two or more golf clubs 4 having loft angles different from each other. In the golf club set 2, the golf clubs 4 may have the same club length, or may have club lengths different from each other. From the viewpoints of the combination of clubs and restriction on the total number of clubs (14 clubs) in a golf club set, the number of clubs of the golf club set 2 can be greater than or equal to 2 and less than or equal to 5, further greater than or equal to 2 and less than or equal to 4, still further greater than or equal to 2 and less than or equal to 3.

[0041] In the present embodiment, the golf club set 2 includes three golf clubs 4. A first golf club 41, a second golf club 42 and a third golf club 43 constitute the three golf clubs. The loft angle of the second golf club 42 is greater than the loft angle of the first golf club 41. The loft angle of the third golf club 43 is greater than the loft angle of the second golf club 42. All clubs in the golf club set 2 have the same club length.

[0042] The loft angle of the first golf club 41 can be greater than or equal to 46? and less than 52?. In the present embodiment, the loft angle of the first golf club 41 is 50?. The loft angle of the second golf club 42 can be greater than or equal to 52? and less than 56?. In the present embodiment, the loft angle of the second golf club 42 is 54?. The loft angle of the third golf club 43 can be greater than or equal to 56? and less than or equal to 62?. In the present embodiment, the loft angle of the third golf club 43 is 58?.

[0043] The golf club set 2 includes: at least one golf club A that has a loft angle of greater than or equal to 46? and less than 54?; and at least one golf club B that has a loft angle of greater than or equal to 54? and less than or equal to 62?. In the present embodiment, the first golf club 41 is the golf club A, and the second golf club 42 and the third golf club 43 are the golf club B.

[0044] Each golf club 4 includes a shaft sf and a grip gp. The first golf club 41 includes a head 100 that is a first head. The second golf club 42 includes a head 200 that is a second head. The third golf club 43 includes a head 300 that is a third head. The loft angle of the first head (head 100) can be greater than or equal to 46? and less than 52?. In the present embodiment, the loft angle of the head 100 is 50?. The loft angle of the second head (head 200) is greater than the loft angle of the first head (head 100). The loft angle of the second head (head 200) can be greater than or equal to 52? and less than 56?. In the present embodiment, the loft angle of the head 200 is 54?. The loft angle of the third head (head 300) is greater than the loft angle of the second head (head 200). The loft angle of the third head (head 300) can be greater than or equal to 56? and less than or equal to 62?. In the present embodiment, the loft angle of the head 300 is 58?.

[0045] FIG. 2 is a perspective view of the head 100 of the first embodiment as viewed from the back side. FIG. 2 is a shaded view. FIG. 3A and FIG. 3B are back views of the head 100. FIG. 3A is a shaded view. FIG. 4A and FIG. 4B are external views of the head 100 as viewed from the front of its hitting face. FIG. 4A is a shaded view. FIG. 5A is a cross-sectional view taken along line a-a in FIG. 3A. FIG. 5B is a cross-sectional view taken along line b-b in FIG. 3A. FIG. 5C is a cross-sectional view taken along line c-c in FIG. 3A. FIG. 5D is a cross-sectional view taken along line d-d in FIG. 3A. FIG. 5E is a cross-sectional view taken along line e-e in FIG. 3A. FIG. 5A to FIG. 5D show cross sections taken in the up-down direction, which are also referred to as vertical cross sections. FIG. 5E shows a cross section taken in the toe-heel direction, which is also referred to as a horizontal cross section.

[0046] The head 100 is an iron type golf club head. The head 100 is a muscle-back iron type golf club head. The head 100 may be a cavity-back iron type golf club head. There is no limitation on the club number of the head 100. In the present embodiment, the loft angle of the head 100 is 50?.

[0047] The head 100 includes a hitting face 102 that has a face center Fc, a back surface 104, a sole surface 106, and a top blade 108. The head 100 also includes a hosel portion 110. The hosel portion 110 has a shaft hole 110a.

[0048] The hitting face 102 is also simply referred to as a face. The hitting face 102 has a plurality of score lines gv. If the score lines gv are disregarded, the hitting face 102 is a flat surface. When a golfer hits a golf ball with a golf club, the hitting face 102 comes into contact with the ball. The score lines gv are arranged at regular intervals. All of the score lines gv are parallel to each other. The score lines gv include a longest score line gv1. A plurality of longest score lines gv1 are formed. The score lines gv contribute to increase and stability in backspin rate.

[0049] Each score line gv has a toe-side end 112. The positions in the toe-heel direction of the toe-side ends 112 of all the score lines gv coincide with each other. The position in the toe-heel direction of the toe-side ends 112 is the toe reference position Pt.

[0050] Note that the score lines gv may be formed on almost the entirety of the hitting face 102. Such arrangement of the score lines gv is also referred to as full score lines or full face lines. In a head having full score lines, each score line gv extends to reach the vicinity of the outer edge of the hitting face 102. For this reason, the toe-side ends 112 are disposed in the vicinity of the toe-side edge of the hitting face 102. In this arrangement, the positions in the toe-heel direction of the toe-side ends 112 are not in a straight line. Except a head having such full score lines, the position of the toe-side ends 112 of the score lines can be the toe reference position Pt.

[0051] At least one score line gv has a heel-most end 114. In the present embodiment, the heel-most end 114 is the heel-side end of each longest score line gv1. The heel-most end 114 is positioned in the vicinity of a heel-side edge 116 of the hitting face 102. The edge 116 is a boundary between the hitting face 102 which is a flat surface and a non-flat portion 118 that is connected to the hosel portion 110. The position in the toe-heel direction of the heel-most end 114 is the heel reference position Ph. A plurality of ends 114 are located at the same position in the toe-heel direction.

[0052] As described above, a position that divides a distance between the toe reference position Pt and the heel reference position Ph into two equal parts is the score line center position Pc. The score line center position Pc is a position in the toe-heel direction. The hitting face 102 has an up-down directional width W1 in the score line center position Pc. The center point of the up-down directional width W1 is the face center Fc.

[0053] A double-pointed arrow D1 in FIG. 4B shows a distance between the toe reference position Pt and the heel reference position Ph. The distance D1 is measured in the toe-heel direction. In the present embodiment, the distance D1 is equal to the length of the longest score lines gv1. The score line center position Pc is a position that divides the distance D1 into two equal parts.

[0054] The head 100 includes a leading edge Le and a trailing edge Te. The leading edge Le is the front edge of the sole surface 106. The trailing edge Te is the rear edge of the sole surface 106.

[0055] The head 100 has a face thickness T. The face thickness T is measured in a direction that is perpendicular to the hitting face 102. The face thickness T is a distance between the hitting face 102 and the back surface 104. As shown in the cross-sectional views of FIG. 5A to FIG. 5D, the face thickness T in a lower part of the hitting face 102 is a distance between by the hitting face 102 and the sole surface 106. In the present disclosure, the face thickness T is also simply referred to as a thickness. The terms thick and thin in the present disclosure are used for the face thickness T.

[0056] The head 100 includes a thick wall portion 120. The thick wall portion 120 is a part whose face thickness T is greater than the face thickness T of a part on the toe side of the thick wall portion 120 and greater than the face thickness T of a part on the heel side of the thick wall portion 120. At any position of the thick wall portion 120 in the up-down direction, the thick wall portion 120 is thicker than the adjoining part on its toe side and/or is thicker than the adjoining part on its heel side. The thick wall portion 120 is disposed over a region that includes the face center Fc. The thick wall portion 120 continuously extends from the position of the face center Fc. The thick wall portion 120 is formed such that it extends toward the toe side as it goes toward the blade side from the sole side. Only one thick wall portion 120 is provided.

[0057] As shown in FIG. 5B, in the vertical cross sections, the thickness T of the thick wall portion 120 decreases toward the blade side (upward). In the vertical cross sections, the thickness T of the thick wall portion 120 continuously decreases toward the blade side (upward). The variation in thickness T of the thick wall portion 120 is not limited. For example, the thick wall portion 120 may include a part in which the thickness T is unchanging.

[0058] As shown in FIG. 5E, in the horizontal cross section, the thickness T of the thick wall portion 120 is unchanging. In the horizontal cross section, the thickness T of the thick wall portion 120 may vary and may continuously vary.

[0059] A toe thin-wall portion 122 is provided on the toe side of the thick wall portion 120. In horizontal cross sections, the toe thin-wall portion 122 is thinner than the thick wall portion 120. The toe thin-wall portion 122 adjoins the toe-side end of the thick wall portion 120. The toe thin-wall portion 122 extends to reach an outer edge 104a of the back surface 104. The toe thin-wall portion 122 does not have to reach the outer edge 104a of the back surface 104. A heel thin-wall portion 124 is provided on the heel side of the thick wall portion 120. In horizontal cross sections, the heel thin-wall portion 124 is thinner than the thick wall portion 120. The heel thin-wall portion 124 adjoins the heel-side end of the thick wall portion 120. The heel thin-wall portion 124 extends to reach the outer edge 104a of the back surface 104. The heel thin-wall portion 124 does not have to reach the outer edge 104a of the back surface 104. The outer edge 104a includes the top blade 108.

[0060] The minimum value of the thickness T of the thick wall portion 120 may be greater than the maximum value of the thickness T of the toe thin-wall portion 122. The minimum value of the thickness T of the thick wall portion 120 may be greater than the maximum value of the thickness T of the heel thin-wall portion 124.

[0061] The presence of the thick wall portion 120 can be confirmed in cross sections taken along the toe-heel direction (horizontal cross sections). FIG. 5E is an example of the horizontal cross sections. In the horizontal cross sections, a portion (hereinafter referred to as a first portion F1) thicker than a part on the toe side of the first portion F1 and thicker than a part on the heel side of the first portion F1 is the thick wall portion 120. The first portion F1 includes the face center Fc. The first portion F1 constitutes a large part of the thick wall portion 120. The thick wall portion 120 further includes a portion (hereinafter referred to as a second portion F2) that extends continuously from the first portion F1 and is thicker than either a part on the toe side of the second portion F2 or a part on the heel side of the second portion F2. In the present embodiment, the second portion F2 is located on the toe side of the upper end part of the thick wall portion 120. The horizontal cross section can be obtained at each position in the up-down direction. The presence of the thick wall portion 120 can be confirmed in each horizontal cross section. The presence of the toe thin-wall portion 122 and the presence of the heel thin-wall portion 124 can also be confirmed in each horizontal cross section.

[0062] As shown in FIG. 5A to FIG. 5D, the back surface 104 includes a blade side region Rt and a sole side region Rs. The sole side region Rs is a part located near the sole surface 106 and has a great face thickness T. The blade side region Rt is a part located on the upper side of the sole side region Rs. The sole side region Rs has a great thickness T because of the presence of the sole. As shown in FIG. 5A to FIG. 5D, in the vertical cross sections, the face thickness T becomes maximum at or in the vicinity of the trailing edge Te. When the radii of curvature of the back surface 104 are sequentially measured upward from the bottom in a vertical cross section, a point B1 at which the radius of curvature first becomes a local minimum value can be found. The point B1 having the first minimum value can be defined as a boundary point between the blade side region Rt and the sole side region Rs.

[0063] The thick wall portion 120 includes a first thick wall part 120a that is located in the blade side region Rt, and a second thick wall part 120b that is located in the sole side region Rs. The thick wall portion 120 may be constituted by the first thick wall part 120a only. The second thick wall part 120b does not have to be present.

[0064] The back surface 104 includes an upper thick wall portion 130. The upper thick wall portion 130 is provided on the blade side of the thick wall portion 120. The face thickness T of the upper thick wall portion 130 is greater than the face thickness T of the upper end of the thick wall portion 120. The face thickness T of the upper thick wall portion 130 is greater than the maximum value of the face thickness T of the upper end of the thick wall portion 120. The presence of the upper thick wall portion 130 can be confirmed in the vertical cross sections. In each vertical cross section, the face thickness T of the upper thick wall portion 130 is greater than the face thickness T of the upper end of the thick wall portion 120. Only one upper thick wall portion 130 is provided. Two or more upper thick wall portions 130 may be provided. The upper thick wall portion 130 is located on the toe side with respect to the face center Fc.

[0065] FIG. 6A and FIG. 6B are back views of the head 200. FIG. 6A is a shaded view. FIG. 7A and FIG. 7B are external views of the head 200 as viewed from the front of its hitting face. FIG. 7A is a shaded view. FIG. 8A is a cross-sectional view taken along line a-a in FIG. 6A. FIG. 8B is a cross-sectional view taken along line b-b in FIG. 6A. FIG. 8C is a cross-sectional view taken along line c-c in FIG. 6A. FIG. 8D is a cross-sectional view taken along line d-d in FIG. 6A. FIG. 8E is a cross-sectional view taken along line e-e in FIG. 6A.

[0066] The head 200 is an iron type golf club head. The head 200 is a muscle-back iron type golf club head. The head 200 may be a cavity-back iron type golf club head. The loft angle of the head 200 is greater than the loft angle of the head 100. The loft angle of the head 200 is greater than 50?. In the present embodiment, the loft angle of the head 200 is 54?.

[0067] The head 200 includes a hitting face 202 that has a face center Fc, a back surface 204, a sole surface 206, and a top blade 208. The head 200 also includes a hosel portion 210. The hosel portion 210 has a shaft hole 210a.

[0068] The hitting face 202 has a plurality of score lines gv. The score lines gv include a longest score line gv1.

[0069] The head 200 includes a leading edge Le and a trailing edge Te. The head 200 has a face thickness T.

[0070] The head 200 includes a thick wall portion 220. The thick wall portion 220 is a part whose face thickness T is greater than the face thickness T of a part on the toe side of the thick wall portion 220 and greater than the face thickness T of a part on the heel side of the thick wall portion 220. At any position of the thick wall portion 220 in the up-down direction, the thick wall portion 220 is thicker than the adjoining part on its toe side and is thicker than the adjoining part on its heel side. The thick wall portion 220 is disposed over a region that includes the face center Fc. The thick wall portion 220 continuously extends from the position of the face center Fc. The thick wall portion 220 is formed such that it extends toward the toe side as it goes toward the blade side from the sole side.

[0071] As shown in FIG. 8B, the thickness T of the thick wall portion 220 decreases toward the blade side (upward). The thickness T of the thick wall portion 220 continuously decreases toward the blade side (upward). As shown in FIG. 8E, the thickness T of the thick wall portion 220 is unchanging in the horizontal cross section.

[0072] A toe thin-wall portion 222 is provided on the toe side of the thick wall portion 220. In horizontal cross sections, the toe thin-wall portion 222 is thinner than the thick wall portion 220. The toe thin-wall portion 222 adjoins the toe-side end of the thick wall portion 220. The toe thin-wall portion 222 extends to reach an outer edge 204a of the back surface 204. A heel thin-wall portion 224 is provided on the heel side of the thick wall portion 220. In horizontal cross sections, the heel thin-wall portion 224 is thinner than the thick wall portion 220. The heel thin-wall portion 224 adjoins the heel-side end of the thick wall portion 220. The heel thin-wall portion 224 extends to reach the outer edge 204a of the back surface 204.

[0073] As shown in FIG. 8A to FIG. 8D, the back surface 204 includes a blade side region Rt and a sole side region Rs. The sole side region Rs is a part located near the sole surface 206 and has a great face thickness T. The blade side region Rt is a part located on the upper side of the sole side region Rs. As shown in FIG. 8A to FIG. 8D, in the vertical cross sections, the face thickness T becomes maximum at or in the vicinity of the trailing edge Te. The point B1 is a boundary point between the blade side region Rt and the sole side region Rs.

[0074] The thick wall portion 220 includes a first thick wall part 220a that is located in the blade side region Rt, and a second thick wall part 220b that is located in the sole side region Rs. The back surface 204 includes an upper thick wall portion 230. The upper thick wall portion 230 is provided on the blade side of the thick wall portion 220. The face thickness T of the upper thick wall portion 230 is greater than the face thickness T of the upper end of the thick wall portion 220. The face thickness T of the upper thick wall portion 230 is greater than the maximum value of the face thickness T of the upper end of the thick wall portion 220.

[0075] FIG. 9A and FIG. 9B are back views of the head 300. FIG. 9A is a shaded view. FIG. 10A and FIG. 10B are external views of the head 300 as viewed from the front of its hitting face. FIG. 10A is a shaded view. FIG. 11A is a cross-sectional view taken along line a-a in FIG. 9A. FIG. 11B is a cross-sectional view taken along line b-b in FIG. 9A. FIG. 11C is a cross-sectional view taken along line c-c in FIG. 9A. FIG. 11D is a cross-sectional view taken along line d-d in FIG. 9A. FIG. 11E is a cross-sectional view taken along line e-e in FIG. 9A.

[0076] The head 300 is an iron type golf club head. The head 300 is a muscle-back iron type golf club head. The head 300 may be a cavity-back iron type golf club head. The loft angle of the head 300 is greater than the loft angle of the head 200. The loft angle of the head 300 is greater than 54?. In the present embodiment, the loft angle of the head 300 is 58?.

[0077] The head 300 includes a hitting face 302 that has a face center Fc, a back surface 304, a sole surface 306, and a top blade 308. The head 300 also includes a hosel portion 310. The hosel portion 310 has a shaft hole 310a.

[0078] The hitting face 302 has a plurality of score lines gv. The score lines gv include a longest score line gv1.

[0079] The head 300 includes a leading edge Le and a trailing edge Te. The head 300 has a face thickness T.

[0080] The head 300 includes a thick wall portion 320. The thick wall portion 320 is a part whose face thickness T is greater than the face thickness T of a part on the toe side of the thick wall portion 320 and greater than the face thickness T of a part on the heel side of the thick wall portion 320. At any position of the thick wall portion 320 in the up-down direction, the thick wall portion 320 is thicker than the adjoining part on its toe side and is thicker than the adjoining part on its heel side. The thick wall portion 320 is disposed over a region that includes the face center Fc. The thick wall portion 320 continuously extends from the position of the face center Fc. The thick wall portion 320 is formed such that it extends toward the toe side as it goes toward the blade side from the sole side.

[0081] As shown in FIG. 11B, the thickness T of the thick wall portion 320 decreases toward the blade side (upward). The thickness T of the thick wall portion 320 continuously decreases toward the blade side (upward). As shown in FIG. 11E, the thickness T of the thick wall portion 320 is unchanging in the horizontal cross section.

[0082] A toe thin-wall portion 322 is provided on the toe side of the thick wall portion 320. In horizontal cross sections, the toe thin-wall portion 322 is thinner than the thick wall portion 320. The toe thin-wall portion 322 adjoins the toe-side end of the thick wall portion 320. The toe thin-wall portion 322 extends to reach an outer edge 304a of the back surface 304. A heel thin-wall portion 324 is provided on the heel side of the thick wall portion 320. In horizontal cross sections, the heel thin-wall portion 324 is thinner than the thick wall portion 320. The heel thin-wall portion 324 adjoins the heel-side end of the thick wall portion 320. The heel thin-wall portion 324 extends to reach the outer edge 304a of the back surface 304.

[0083] As shown in FIG. 11A to FIG. 11D, the back surface 304 includes a blade side region Rt and a sole side region Rs. The sole side region Rs is a part located near the sole surface 306 and has a great face thickness T. The blade side region Rt is a part located on the upper side of the sole side region Rs. As shown in FIG. 11A to FIG. 11D, in the vertical cross sections, the face thickness T becomes maximum at or in the vicinity of the trailing edge Te. The point B1 is a boundary point between the blade side region Rt and the sole side region Rs.

[0084] The thick wall portion 320 includes a first thick wall part 320a that is located in the blade side region Rt, and a second thick wall part 320b that is located in the sole side region Rs. The back surface 304 includes an upper thick wall portion 330. The upper thick wall portion 330 is provided on the upper side of the thick wall portion 320. The face thickness T of the upper thick wall portion 330 is greater than the face thickness T of the upper end of the thick wall portion 320. The face thickness T of the upper thick wall portion 330 is greater than the maximum value of the face thickness T of the upper end of the thick wall portion 320.

[0085] The head 100, the head 200 and the head 300 included in the golf club set 2 of the first embodiment have the same structure except for the difference in loft angle. The head 100, the head 200 and the head 300 are heads according to the first embodiment.

[0086] FIG. 12A and FIG. 12B are back views of a head 400 according to a second embodiment. FIG. 12A is a shaded view. The head 400 is an iron type golf club head. The head 400 is a muscle-back iron type golf club head. The head 400 includes a hitting face (not shown in the drawings) that has a face center Fc, a back surface 404, a sole surface 406, and a top blade 408. The head 400 also includes a hosel portion 410. The structure of the hitting face is the same as those of the head 100, 200, and 300. The loft angle of the head 400 is greater than or equal to 46?.

[0087] The head 400 includes a thick wall portion 420. The thick wall portion 420 is disposed over a region that includes the face center Fc. The thick wall portion 420 continuously extends from the position of the face center Fc. The thick wall portion 420 is formed such that it extends toward the toe side as it goes toward the blade side from the sole side. The thickness T of the thick wall portion 420 decreases toward the blade side (upward). The thickness T of the thick wall portion 420 continuously decreases toward the blade side (upward).

[0088] A toe thin-wall portion 422 is provided on the toe side of the thick wall portion 420. In horizontal cross sections, the toe thin-wall portion 422 is thinner than the thick wall portion 420. The toe thin-wall portion 422 adjoins the toe-side end of the thick wall portion 420. The toe thin-wall portion 422 extends to reach an outer edge 404a of the back surface 404.

[0089] A heel thin-wall portion 424 is provided on the heel side of the thick wall portion 420. In horizontal cross sections, the heel thin-wall portion 424 is thinner than the thick wall portion 420. The heel thin-wall portion 424 adjoins the heel-side end of the thick wall portion 420. The heel thin-wall portion 424 extends to reach the outer edge 404a of the back surface 404. The heel thin-wall portion 424 includes a first thin-wall part 424a and a second thin-wall part 424b that is thinner than the first thin-wall part 424a. The first thin-wall part 424a adjoins the heel-side end of the thick wall portion 420. The second thin-wall part 424b is located on the heel side of the first thin-wall part 424a. The second thin-wall part 424b extends to reach the outer edge 404a of the back surface 404.

[0090] As described above, the head 100, the head 200 and the head 300 include the upper thick wall portion 130, the upper thick wall portion 230 and the upper thick wall portion 330, respectively. On the other hand, the head 400 does not include an upper thick wall portion. That is, the head 400 does not include a part thicker than the upper end of the thick wall portion 420 on the blade side of the thick wall portion 420.

[0091] The back surface 404 includes a blade side region Rt and a sole side region Rs. In the head 400, the thick wall portion 420 does not include a part that is located in the sole side region Rs. The entirety of the thick wall portion 420 is located in the blade side region Rt.

[0092] FIG. 13A and FIG. 13B are back views of a head 500 according to a third embodiment. FIG. 13A is a shaded view. The head 500 is an iron type golf club head. The head 500 is a muscle-back iron type golf club head. The head 500 includes a hitting face (not shown in the drawings) that has a face center Fc, a back surface 504, a sole surface 506, and a top blade 508. The head 500 also includes a hosel portion 510. The structure of the hitting face is the same as those of the head 100, 200, and 300. The loft angle of the head 500 is greater than or equal to 46?.

[0093] The head 500 includes a thick wall portion 520. The thick wall portion 520 is disposed over a region that includes the face center Fc. The thick wall portion 520 continuously extends from the position of the face center Fc. The thick wall portion 520 is formed such that it extends toward the toe side as it goes toward the blade side from the sole side. The thickness T of the thick wall portion 520 decreases toward the blade side (upward). The thickness T of the thick wall portion 520 continuously decreases toward the blade side (upward).

[0094] A toe thin-wall portion 522 is provided on the toe side of the thick wall portion 520. In horizontal cross sections, the toe thin-wall portion 522 is thinner than the thick wall portion 520. The toe thin-wall portion 522 adjoins the toe-side end of the thick wall portion 520. The toe thin-wall portion 522 extends to reach an outer edge 504a of the back surface 504.

[0095] A heel thin-wall portion 524 is provided on the heel side of the thick wall portion 520. In horizontal cross sections, the heel thin-wall portion 524 is thinner than the thick wall portion 520. The heel thin-wall portion 524 adjoins the heel-side end of the thick wall portion 520. The heel thin-wall portion 524 extends to reach the outer edge 504a of the back surface 504.

[0096] As with the head 400, the head 500 does not include an upper thick wall portion. That is, the head 500 does not include a part thicker than the upper end of the thick wall portion 520 on the blade side of the thick wall portion 520.

[0097] The back surface 504 includes a blade side region Rt and a sole side region Rs. As with the head 400, in the head 500, the thick wall portion 520 does not include a part that is located in the sole side region Rs. The entirety of the thick wall portion 520 is located in the blade side region Rt.

[0098] FIG. 14A and FIG. 14B are back views of a head 600 according to a fourth embodiment. FIG. 14A is a shaded view. The head 600 is an iron type golf club head. The head 600 is a muscle-back iron type golf club head. The head 600 includes a hitting face (not shown in the drawings) that has a face center Fc, a back surface 604, a sole surface 606, and a top blade 608. The head 600 also includes a hosel portion 610. The structure of the hitting face is the same as those of the head 100, 200, and 300. The loft angle of the head 600 is greater than or equal to 46?.

[0099] The head 600 includes a thick wall portion 620. The thick wall portion 620 is disposed over a region that includes the face center Fc. The thick wall portion 620 continuously extends from the position of the face center Fc. The thick wall portion 620 is formed such that it extends toward the toe side as it goes toward the blade side from the sole side. The thickness T of the thick wall portion 620 decreases toward the blade side (upward). The thickness T of the thick wall portion 620 continuously decreases toward the blade side (upward).

[0100] A toe thin-wall portion 622 is provided on the toe side of the thick wall portion 620. In horizontal cross sections, the toe thin-wall portion 622 is thinner than the thick wall portion 620. The toe thin-wall portion 622 adjoins the toe-side end of the thick wall portion 620. The toe thin-wall portion 622 extends to reach an outer edge 604a of the back surface 604.

[0101] A heel thin-wall portion 624 is provided on the heel side of the thick wall portion 620. In horizontal cross sections, the heel thin-wall portion 624 is thinner than the thick wall portion 620. The heel thin-wall portion 624 adjoins the heel-side end of the thick wall portion 620. The heel thin-wall portion 624 extends to reach the outer edge 604a of the back surface 604.

[0102] As with the heads 100, 200 and 300, the head 600 includes an upper thick wall portion 630. That is, the head 600 includes the portion 630 thicker than the upper end of the thick wall portion 620 on the blade side of the thick wall portion 620.

[0103] The back surface 604 includes a blade side region Rt and a sole side region Rs. As with the heads 100, 200 and 300, in the head 600, the thick wall portion 620 includes a part 620b that is located in the sole side region Rs. That is, the thick wall portion 620 includes a first thick wall part 620a that is located in the blade side region Rt and the second thick wall part 620b that is located in the sole side region Rs.

[0104] In the heads 100, 200, 300, 400 and 500, the thick wall portion does not reach the trailing edge Te. On the other hand, in the head 600, the thick wall portion 620 extends to reach the trailing edge Te.

[0105] The above-described heads 100, 200, 300, 400, 500, and 600 exhibit the following advantageous effects.

[0106] The thick wall portion is formed such that it extends toward the toe side as it goes toward the blade side from the sole side. Because of this structure, the extending direction of the thick wall portion on the back surface becomes similar to the swing path of the head in a shot made with the head face open. Accordingly, even when the head hits balls at varied hitting points in the up-down direction, the head can hit balls at positions within the thick wall portion. This improves feel at impact in shots made with the head face open.

[0107] Delicate sense of feel is required for shots made with the head face open, for example, bunker shots and approach shots. In addition, in such a shot made with the head face open, a high accuracy is required for contact between the head and a ball. Feel at impact with a golf ball can affect the results of swings and shots. Improvement in feel at impact can enable the golfer to achieve precise distance control.

[0108] Because of the presence of the toe thin-wall portion and the heel thin-wall portion, the thickness T of the thick wall portion can be increased, which can improve feel at impact. Because of the configuration in which the thick wall portion is sandwiched between the toe thin-wall portion and the heel thin-wall portion, the thick wall portion can be located in a region that has a high probability of hitting balls.

[0109] The thickness T of the thick wall portion decreases toward the blade side (upward). The sole side part having a higher probability of hitting balls has a larger thickness, which can improve feel at impact. This structure can also lower the position of the center of gravity of the head. This can make the position of the sweet spot closer to a position having a highest probability of hitting balls, and thus can further improve feel at impact.

[0110] The thick wall portion includes the first thick wall part located in the blade side region Rt. The face thickness T tends to be thinner in the blade side region. The blade side region Rt, however, has a high probability of hitting balls when the head hits balls with the head face open. The presence of the thick wall portion in the blade side region Rt improves feel at impact in shots made with the head face open.

[0111] The upper thick wall portion is provided in the heads 100, 200, 300 and 600. By providing the upper thick wall portion in addition to the thick wall portion, an up-down MI can be increased. The increased up-down MI can suppress variation in launch angles of hit balls when the head hits balls at varied hitting points in the up-down direction. Since hitting points tend to vary in the up-down direction in shots made with the head face open, this advantageous effect is particularly effective for heads used with the head face open. Note that the up-down MI means the moment of inertia of a head about a rotation axis that passes through the center of gravity of the head and is parallel to the toe-heel direction.

[0112] FIG. 15 is the back view of the head 100 as with FIG. 3B. In FIG. 15, the thick wall portion 120 is indicated by cross hatching. Structures of the head 100 are explained below while referring to FIG. 15, FIG. 16 and FIG. 17, and these structures are included also in the head 200 and the head 300.

[0113] The thick wall portion 120 has an area S. The area S is an area of a thick wall portion region S1 indicated by the cross hatching. The area S is measured in the projected figure.

[0114] The thick wall portion 120 has a toe contour line kt that is a contour line on the toe side, a heel contour line kh that is a contour line on the heel side. The toe contour line kt is formed such that it extends toward the toe side as it goes toward the blade side from the sole side. The heel contour line kh is formed such that it extends toward the toe side as it goes toward the blade side from the sole side.

[0115] A directional line Lt is defined by the toe contour line kt. When the toe contour line kt includes a curved portion, the directional line Lt can be determined at the midpoint of the toe contour line kt. The midpoint is a point that divides the width of the toe contour line kt in the blade-sole direction into two equal parts. When the toe contour line kt is curved at the midpoint, the directional line Lt can be a tangent line to the toe contour line kt at the midpoint. A directional line Lh is defined by the heel contour line kh. When the heel contour line kh includes a curved portion, the directional line Lh can be determined at the midpoint of the heel contour line kh. The midpoint is a point that divides the width of the heel contour line kh in the blade-sole direction into two equal parts. The directional line Lt and the directional line Lh are measured in the projected figure. When the heel contour line kh is curved at the midpoint, the directional line Lh can be a tangent line to the heel contour line kh at the midpoint. The directional line Lt extends toward the toe side as it goes toward the blade side from the sole side. The directional line Lh extends toward the toe side as it goes toward the blade side from the sole side.

[0116] A double-pointed arrow ?t in FIG. 15 shows an angle of the directional line Lt with respect to the toe-heel direction. A double-pointed arrow ?h in FIG. 15 shows an angle of the directional line Lh with respect to the toe-heel direction. The angles ?t and ?h are measured in the projected figure. The angle ?t is greater than the angle ?h. This configuration of ?t>?h contributes to selectively locating the thick wall portion at a region that is likely to come into contact with a ball in shots made with the head face open.

[0117] The thick wall portion 120 has a width directional center line LC1. The thick wall portion 120 has a center point C1 in a horizontal cross section (see FIG. 5E). The center point C1 in a horizontal cross section can be determined in each horizontal cross section. The width directional center line LC1 is a set of the center points C1. The width directional center line LC1 extends toward the toe side as it goes toward the blade side from the sole side.

[0118] A double-pointed arrow ?c in FIG. 15 shows an angle of the width directional center line LC1 with respect to the toe-heel direction. The angle ?c is measured in the projected figure. The angle ?c is greater than the angle ?h. The angle ?c is smaller than the angle ?t. Note that the width directional center line LC1 may be a straight line or may be a curved line. When the width directional center line LC1 is a curved line, the angle ?c can be determined based on tangent lines to the curved line at points on the curved line.

[0119] From the viewpoint of conformity of the shape of the thick wall portion to the swing path of the head in a shot made with the head face open, the angle ?t is preferably less than or equal to 90?, more preferably less than or equal to 80?, and still more preferably less than or equal to 70?. By providing the toe thin-wall portion instead of the thick wall portion in a region that has a low probability of hitting balls, an increased weight can be allocated to the thick wall portion, and the thickness T of the thick wall portion can also be increased. From this viewpoint, the angle ?t is preferably greater than or equal to 45?, more preferably greater than or equal to 50?, and still more preferably greater than or equal to 55?.

[0120] From the viewpoint of conformity of the shape of the thick wall portion to the swing path of the head in a shot made with the head face open, the angle ?c is preferably less than or equal to 85?, more preferably less than or equal to 75?, and still more preferably less than or equal to 65?. From the viewpoint of conformity of the shape of the thick wall portion to the swing path of the head in a shot made with the head face open, the angle ?c is preferably greater than or equal to 40?, more preferably greater than or equal to 45?, and still more preferably greater than or equal to 50?.

[0121] From the viewpoint of conformity of the shape of the thick wall portion to the swing path of the head in a shot made with the head face open and from the viewpoint of providing the heel thin-wall portion instead of the thick wall position in a region that has a low probability of hitting balls, the angle ?h is preferably less than or equal to 80?, more preferably less than or equal to 70?, and still more preferably less than or equal to 60?. From the viewpoint of locating the thick wall portion on the upper side region of the hitting face which tends to come into contact with a ball in shots made with the head face open, the angle ?t is preferably greater than or equal to 35?, more preferably greater than or equal to 40?, and still more preferably greater than or equal to 45?.

[0122] FIG. 16 is a figure obtained by superposing the projected figure of FIG. 15 onto FIG. 4B. FIG. 16 shows the projected figure of the thick wall portion 120 projected onto the hitting face 102. The projected figure of the thick wall portion 120 is indicated by dashed line cross hatching. The region of this projected figure is also referred to as the thick wall portion region.

[0123] The thick wall portion region S1 (thick wall portion 120) includes a part located on the score line center position Pc. The thick wall portion region S1 (thick wall portion 120) includes a part located on the toe reference position Pt. The thick wall portion region S1 further includes a toe outside part S10 that is located on the toe side with respect to the toe reference position Pt. The toe outside part S10 is located on the blade side with respect to the face center Fc.

[0124] The thick wall portion region S1 (thick wall portion 120) does not include a part located on the heel reference position Ph. Alternatively, the thick wall portion region S1 (thick wall portion 120) may include a part located on the heel reference position Ph.

[0125] The thick wall portion region S1 is divided into two parts by a straight line L1 that passes through the face center Fc and extends in the toe-heel direction. These two parts are constituted by an upper part S12 located on the blade side of the straight line L1 and a lower part S14 located on the sole side of the straight line L1. That is, the upper part S12 is a part located on the blade side with respect to the face center Fc. The lower part S14 is a part located on the sole side with respect to the face center Fc. Of the thick wall portion, the entirety of a part located in the upper part S12 is the first thick wall part. The area of the upper part S12 is greater than the area of the lower part S14. The thick wall portion is selectively located on a region that is likely to come into contact with a ball in a shot made with the head face open, whereby the thick wall portion is less likely to be disposed on a region that is less likely to hit a ball. This can increase the thickness of the thick wall portion located on a region that is likely to come into contact with a ball, which can improve feel at impact in shots made with the head face open.

[0126] The thick wall portion region S1 is divided into two parts by a straight line L2 that passes through the face center Fc and extends in the blade-sole direction. These two parts are constituted by a toe part S16 located on the toe side of the straight line L2 and a heel part S18 located on the heel side of the straight line L2. The toe part S16 is a part located on the toe side with respect to the face center Fc. The heel part S18 is a part located on the heel side with respect to the face center Fc. The area of the toe part S16 is greater than the area of the heel part S18. The thick wall portion is selectively located on a region that is likely to come into contact with a ball in a shot made with the head face open, whereby the thick wall portion is less likely to be disposed on a region that is less likely to hit a ball. This can increase the thickness of the thick wall portion located on a region that is likely to come into contact with a ball, which can improve feel at impact in shots made with the head face open.

[0127] An intersection point P1 between the straight line L2 and the width directional center line LC1 is positioned on the sole side with respect to the face center Fc. The thick wall portion region S1 extends toward the toe-blade side with respect to the face center Fc.

[0128] A point P2 in FIG. 16 is an upper-most point of the hitting face 102 on the heel reference position Ph. The thick wall portion 120 extends further toward the blade side than the upper-most point P2. The thick wall portion extends in a region that is likely to come into contact with a ball in a shot made with the head face open, which improves feel at impact.

[0129] FIG. 17 is the same figure as FIG. 16. From the viewpoints of avoiding congestion of reference symbols and making the figures easier to understand, FIG. 17 is shown in addition to FIG. 16.

[0130] As shown in FIG. 17, the thick wall portion region S1 can be divided into four parts by the straight line L1 and the straight line L2. Of the thick wall portion region S1, a part on the blade side with respect to the straight line L1 and on the heel side with respect to the straight line L2 is defined as a heel upper part S21. The heel upper part S21 is a part located on the blade side and heel side with respect to the face center Fc. Of the thick wall portion region S1, a part on the blade side with respect to the straight line L1 and on the toe side with respect to the straight line L2 is defined as a toe upper part S22. The toe upper part S22 is a part located on the blade side and toe side with respect to the face center Fc. Of the thick wall portion region S1, a part on the sole side with respect to the straight line L1 and on the toe side with respect to the straight line L2 is defined as a toe lower part S23. The toe lower part S23 is a part located on the toe side and sole side with respect to the face center Fc. Of the thick wall portion region S1, a part on the sole side with respect to the straight line L1 and on the heel side with respect to the straight line L2 is defined as a heel lower part S24. The heel lower part S24 is a part located on the heel side and sole side with respect to the face center Fc. The entirety of a part of the thick wall portion located in the toe upper part S22 is the first thick wall part.

[0131] The thick wall portion region S1 includes the heel upper part S21, the toe upper part S22, the toe lower part S23, and the heel lower part S24. The area of the toe upper part S22 is larger than the area of the heel upper part S21. The area of the toe upper part S22 is larger than the area of the toe lower part S23. The area of the toe upper part S22 is larger than the area of the heel lower part S24. The toe upper part S22 has the largest area among the four parts. The area of the toe upper part S22 can be greater than or equal to two times the area of the heel upper part s21, further can be greater than or equal to three times the area of the heel upper part s21, and still further can be greater than or equal to four times the area of the heel upper part s21. The area of the toe upper part S22 can be less than or equal to ten times the area of the heel upper part s21, further can be less than or equal to nine times the area of the heel upper part s21, and still further can be less than or equal to eight times the area of the heel upper part s21. The area of the heel upper part S21 is smaller than the area of the toe lower part S23. The area of the heel upper part S21 is smaller than the area of the heel lower part S24. The thick wall portion is more largely provided in a region having a higher probability to hit a ball in shots made with the head face open, whereby the thick wall portion can be located in a region that is more likely to hit a ball. In addition, the thick wall portion located in a region less likely to hit a ball is reduced, whereby the thickness T of the thick wall portion can be increased. For these reasons, feel at impact is improved in shots made with the head face open.

[0132] As shown in FIG. 7B, a score line region Sg is defined in the present disclosure. In FIG. 7B, the score line region Sg is indicated by one-dot chain line hatching. The score line region Sg means a region in which score lines gv are provided. More specifically, the score line region Sg is a region surrounded by an upper-most score line gv2, a lower-most score line gv3, a straight line that extends on the toe reference position Pt, a straight line that extends on the heel reference position Ph, and a connecting line Lg. Line segments that connect heel ends of adjacent score lines can be drawn for score lines whose heel ends are located on the toe side with respect to the heel reference position Ph. A line constituted by one or more of the line segments is the connecting line Lg. In FIG. 7B, the connecting line Lg is indicated by a dashed line.

[0133] The score line region Sg includes a toe upper region Sg1. Of the score line region Sg, a part located on the upper side and toe side with respect to the face center is the toe upper region Sg1. FIG. 7B shows the toe upper region Sg1 with two-dot chain line hatching.

[0134] Referring back to FIG. 17, the toe upper part S22 overlaps the toe upper region Sg1. A ratio of a part of the toe upper region Sg1 which is overlapped by the toe upper part S22 to the entirety of the toe upper region Sg1 can be greater than or equal to 50%, further can be greater than or equal to 60%, further can be greater than or equal to 70%, and still further can be greater than or equal to 80%. This ratio may be 100%. By providing the thick wall portion at a region that is likely to come into contact with a ball in shots made with the head face open, feel at impact can be improved.

[0135] The thick wall portion region S1 is hardly formed in a region other than the score line region Sg. A large part of the blade side region Rt except the score line region Sg is occupied by the toe thin-wall portion and the heel thin-wall portion. A ratio of a part of the thick wall portion region S1 which is located in the score line region Sg to the entirety of the thick wall portion region S1 is preferably greater than or equal to 80%, more preferably greater than or equal to 85%, and still more preferably greater than or equal to 90%. This ratio may be 100%. By increasing this ratio, the thick wall portion can be selectively located in a region that is likely to come into contact with a ball in shots made with the head face open, and can be prevented from being located in a region that is less likely to come into contact with a ball in shots made with the head face open.

[0136] The upper thick wall portion 130 includes a part that is located on the upper side of the score line region Sg. The upper thick wall portion 130 includes a part that is located on the upper side of the upper-most score line gv2. The upper thick wall portion 130 includes a part located on the toe side of the toe reference position Pt. The presence of the upper thick wall portion 130 can effectively increase the up-down MI of the head.

[0137] A double-pointed arrow W2 in FIG. 17 shows a width of the hitting face 102 on the toe reference position Pt. The width W2 is measured in the blade-sole direction. A double-pointed arrow W3 in FIG. 17 shows a width of the toe contour line kt of the thick wall portion 120. The width W3 is measured in the blade-sole direction. A double-pointed arrow W4 in FIG. 17 shows an entire width of the thick wall portion 120. The entire width W4 is measured in the toe-heel direction. A double-pointed arrow W5 in FIG. 17 is a width of the upper end of the thick wall portion 120. The width W5 is measured in the toe-heel direction. A double-pointed arrow W6 in FIG. 17 is a width of the lower end of the thick wall portion 120. The width W6 is measured in the toe-heel direction. A double-pointed arrow W7 in FIG. 17 is an entire height of the thick wall portion 120. The entire height W7 is measured in the blade-sole direction.

[0138] From the viewpoint of locating the thick wall portion in a region that is likely to come into contact with a ball in shots made with the head face open, a ratio of the width W3 to the width W2 is preferably greater than or equal to 40%, more preferably greater than or equal to 45%, and still more preferably greater than or equal to 50%. An excessively large thick wall portion imposes restrictions on the thickness T of the thick wall portion. From this viewpoint, the ratio of the width W3 to the width W2 is preferably less than or equal to 70%, more preferably less than or equal to 65%, and still more preferably less than or equal to 60%.

[0139] From the viewpoint of locating the thick wall portion in a region that is likely to come into contact with a ball in shots made with the head face open, a ratio of the width W5 to the width W6 is preferably greater than or equal to 40%, more preferably greater than or equal to 42%, and still more preferably greater than or equal to 45%. An excessively large thick wall portion imposes restrictions on the thickness T of the thick wall portion. From this viewpoint, the ratio of the width W5 to the width W6 is preferably less than or equal to 70%, more preferably less than or equal to 65%, and still more preferably less than or equal to 60%.

[0140] As described above, the distance D1 is a distance between the toe reference position Pt and the heel reference position Ph (FIG. 4B). From the viewpoint of locating the thick wall portion in a region that is likely to come into contact with a ball in shots made with the head face open, a ratio of the width W6 to the distance D1 is preferably greater than or equal to 70%, more preferably greater than or equal to 80%, and still more preferably greater than or equal to 90%. An excessively large thick wall portion imposes restrictions on the thickness T of the thick wall portion. From this viewpoint, the ratio of the width W6 to the distance D1 is preferably less than or equal to 110%, more preferably less than or equal to 105%, and still more preferably less than or equal to 100%.

[0141] The width W6 is greater than the width W5. The entire width W4 is greater than the width W6. The height W7 is greater than the width W5. These configurations contribute to selectively locating the thick wall portion in a region that is likely to come into contact with a ball in shots made with the head face open.

[0142] From the viewpoint of enhancing feel at impact, the face thickness T at the face center Fc located in the thick wall portion is preferably greater than or equal to 6.0 mm, more preferably greater than or equal to 6.1 mm, and still more preferably greater than or equal to 6.2 mm. From the viewpoint of restriction on the weight of the head, the face thickness T at the face center Fc is preferably less than or equal to 10 mm, more preferably less than or equal to 9 mm, and still more preferably less than or equal to 8 mm.

[0143] From the viewpoint of saving weight for increasing the thickness of the thick wall portion, the thickness T of the toe thin-wall portion is preferably less than or equal to 5.7 mm, more preferably less than or equal to 5.5 mm, and still more preferably less than or equal to 5.3 mm. From the viewpoint of strength, the thickness T of the toe thin-wall portion is preferably greater than or equal to 3.0 mm, more preferably greater than or equal to 3.5 mm, and still more preferably greater than or equal to 4.0 mm.

[0144] From the viewpoint of saving weight for increasing the thickness of the thick wall portion, the thickness T of the heel thin-wall portion is preferably less than or equal to 5.7 mm, more preferably less than or equal to 5.5 mm, and still more preferably less than or equal to 5.3 mm. From the viewpoint of strength, the thickness T of the heel thin-wall portion is preferably greater than or equal to 3.0 mm, more preferably greater than or equal to 3.5 mm, and still more preferably greater than or equal to 4.0 mm.

[0145] From the viewpoint of increasing the up-down MI, the maximum value of the thickness T of the upper thick wall portion is preferably greater than or equal to 6.0 mm, more preferably greater than or equal to 6.1 mm, and still more preferably greater than or equal to 6.2 mm. From the viewpoint of allocating increased weight to the thick wall portion, the maximum value of the thickness T of the upper thick wall portion is preferably less than or equal to 10 mm, more preferably less than or equal to 9 mm, and still more preferably less than or equal to 8 mm.

[0146] The method for producing the head is not particularly limited. Examples of the producing method include forging and casting. Examples of the casting may include lost-wax precision casting. From the viewpoint of feel at impact, forging is preferable. By hitting metal in the process of forging the head, voids in the metal are eliminated, grain refinement occurs in the metal, and the metallographic structure is densified. The forging process forms a unique metallographic structure. A head produced by forging is excellent in feel at impact. Accordingly, feel at impact is further improved by the synergistic effect of the thick wall portion and the forging.

[0147] The material of the head is not particularly limited. The head may be made of a metal, may be made of a nonmetal, or may be made of a combination of a metal and a nonmetal. From the viewpoint of feel at impact, the head is preferably made of a metal. Examples of the metal include iron, stainless steel, maraging steel, pure titanium, and a titanium alloy. Examples of the iron include soft iron (a low carbon steel having a carbon content of less than 0.3 wt %). From the viewpoint of feel at impact, the head is preferably made of soft iron. From the viewpoint of feel at impact, the head is preferably made of soft iron and produced by forging. When the head is made of stainless steel, the head is preferably produced by casting.

[0148] The heads according to the above-described first to fourth embodiments are solid heads with no hollow interior. Each head may have a hollow interior. When the head has a hollow interior, the hollow interior is preferably provided in the sole side region Rs. It is preferable that a hollow interior is not provided in the thick wall portion located in the blade side region Rt. For example, the hollow interior can be provided within the sole side region Rs and on the toe side with respect to the face center Fc. Weight that is saved by providing the hollow interior can be allocated to the thick wall portion, which can increase the thickness of the thick wall portion. Weight that is saved by providing the hollow interior can be allocated to the sole, which can enlarge the sole width.

[0149] In the golf club set 2, the areas S of the thick wall portions of the heads are different from each other. The greater the loft angle of the head is, the larger the area S of the thick wall portion is. That is, the area S in the head 200 is greater than the area S in the head 100. The area S in the head 300 is greater than the area S in the head 200. A head having a greater loft angle is likely to have greater opportunity to hit balls with the head face open, and its swing path tends to be descending blow. For this reason, a head having a greater loft angle is likely to have greater opportunity to hit balls at an upper and toe side position of the hitting face, and tends to cause increased variation in hitting points in the up-down direction. By increasing the area S as the loft angle becomes greater, the thick wall portion can cover the varied hitting points, which can improve feel at impact. On the other hand, a head having a smaller loft angle has less opportunity to hit balls with the head face open, and its swing path tends to be level blow. For this reason, a head having a smaller loft angle has less opportunity to hit balls at an upper and toe side position of the hitting face, and variation of the hitting points in the up-down direction tends to be reduced. Accordingly, the area S can be reduced as the loft angle of the head becomes smaller, and weight that is saved by the reduced area S can be used to increase the thickness of the thick wall portion. Alternatively, the save weight can be used to locate the center of gravity of the head at more preferable position. Thus, the change of the area S enables the head to have optimized feel at impact according to its loft angle.

[0150] In the golf club set 2, the entire heights W7 of the thick wall portions of the heads are different from each other. The greater the loft angle of the head is, the greater the entire height W7 of the thick wall portion is. That is, the height W7 in the head 200 is greater than the height W7 in the head 100. The height W7 in the head 300 is greater than the height W7 in the head 200. A head having a greater loft angle is likely to have greater opportunity to hit balls with the head face open, and its swing path tends to be descending blow. For this reason, a head having a greater loft angle is likely to have greater opportunity to hit balls at an upper and toe side position of the hitting face, and tends to cause increased variation in hitting points in the up-down direction. By increasing the height W7 as the loft angle becomes greater, the thick wall portion can cover the varied hitting points, which can improve feel at impact. On the other hand, a head having a smaller loft angle has less opportunity to hit balls with the head face open, and its swing path tends to be level blow. For this reason, a head having a smaller loft angle has less opportunity to hit balls at an upper and toe side position of the hitting face, and variation of the hitting points in the up-down direction tends to be reduced. Accordingly, the height W7 can be reduced as the loft angle of the head becomes smaller, and weight that is saved by the reduced height W7 can be used to increase the thickness of the thick wall portion. Alternatively, the save weight can be used to locate the center of gravity of the head at more preferable position. Thus, the change of the height W7 of the thick wall portion enables the head to have optimized feel at impact according to its loft angle.

[0151] In the golf club set of the present disclosure, golf clubs constituting the golf club set do not necessarily have to be sold simultaneously. A plurality of golf clubs belonging in the same series and having loft angles different from each other are encompassed by the golf club set in the present disclosure even when these clubs are sold separately. Whether a plurality of golf clubs belong to the same series or not can be determined by brand names, product names, and product catalogs, for example.

[0152] The following Clauses are a part of the disclosure included in the present disclosure.

[Clause 1]

[0153] An iron type golf club head including: [0154] a hitting face that includes a plurality of score lines and a face center; [0155] a back surface; [0156] a sole surface; [0157] a top blade; and [0158] a face thickness that is defined as a distance between the hitting face and the back surface, wherein [0159] on the back surface, a thick wall portion is formed over a region including a score line center position, the thick wall portion having a face thickness of greater than the face thickness of a part on a toe side of the thick wall portion and greater than the face thickness of a part on a heel side of the thick wall portion, [0160] the thick wall portion is formed such that it extends toward the toe side as it goes toward a blade side from a sole side, and [0161] the golf club head has a loft angle of greater than or equal to 46?.

[Clause 2]

[0162] The golf club head according to clause 1, wherein [0163] the face thickness of the thick wall portion decreases toward the blade side.

[Clause 3]

[0164] The golf club head according to clause 1 or 2, wherein [0165] the thick wall portion is disposed over a region that includes the face center.

[Clause 4]

[0166] The golf club head according to any one of clauses 1 to 3, further includes an upper thick wall portion that is thicker than an upper end of the thick wall portion and is located on the blade side of the thick wall portion.

[Clause 5]

[0167] The golf club head according to any one of clauses 1 to 4, wherein [0168] when a thick wall portion region obtained by projecting the thick wall portion onto the hitting face is divided into the following four parts: a heel upper part that is located on the heel side and blade side with respect to the face center; a toe upper part that is located on the toe side and blade side with respect to the face center; a toe lower part that is located on the toe side and sole side with respect to the face center; and a heel lower part that is located on the heel side and sole side with respect to the face center, [0169] an area of the toe upper part is greater than an area of the heel upper part, is greater than an area of the toe lower part, and is greater than an area of the heel lower part.

[Clause 6]

[0170] The golf club head according to any one of clauses 1 to 5, wherein [0171] when a thick wall portion region obtained by projecting the thick wall portion onto the hitting face includes a heel upper part that is located on the heel side and blade side with respect to the face center, and a toe upper part that is located on the toe side and blade side with respect to the face center, [0172] an area of the toe upper part is greater than or equal to two times an area of the heel upper part.

[Clause 7]

[0173] The golf club head according to any one of clauses 1 to 6, wherein [0174] when a thick wall portion region obtained by projecting the thick wall portion onto the hitting face is divided into the following two parts: an upper part that is located on the blade side with respect to the face center; and a lower part that is located on the sole side with respect to the face center, [0175] an area of the upper part is greater than an area of the lower part.

[Clause 8]

[0176] The golf club head according to any one of clauses 1 to 7, wherein [0177] when a thick wall portion region obtained by projecting the thick wall portion onto the hitting face is divided into the following two parts: a toe part that is located on the toe side with respect to the face center; and a heel part that is located on the heel side with respect to the face center, [0178] an area of the toe part is greater than an area of the heel part.

[Clause 9]

[0179] The golf club head according to any one of clauses 1 to 8, wherein [0180] the golf club head is produced by forging.

[Clause 10]

[0181] A golf club including the golf club head according to any one of clauses 1 to 9, a shaft and a grip.

[Clause 11]

[0182] A golf club set including two or more golf clubs according to clause 10, wherein [0183] the greater the loft angle is, the larger an area of the thick wall portion is.

LIST OF REFERENCE SYMBOLS

[0184] 2 Golf club set [0185] 4 Golf club [0186] 41 First golf club [0187] 42 Second golf club [0188] 43 Third golf club [0189] 100 Golf club head (First golf club head) [0190] 200 Golf club head (Second golf club head) [0191] 300 Golf club head (Third golf club head) [0192] 400, 500, 600 Golf club head [0193] 102, 202, 302 Hitting face [0194] 104, 204, 304, 404, 504, 604 Back surface [0195] 108, 208, 308, 408, 508, 608 Top blade [0196] 122, 222, 322, 422, 522, 622 Toe thin-wall portion [0197] 124, 224, 324, 424, 524, 624 Heel thin-wall portion [0198] 120, 220, 320, 420, 520, 620 Thick wall portion [0199] 130, 230, 330, 630 Upper thick wall portion [0200] gv Score line [0201] Le Leading edge [0202] Te Trailing edge [0203] Fc Face center [0204] Rt Blade side region [0205] Rs Sole side region

[0206] The above descriptions are merely illustrative and various modifications can be made without departing from the principles of the present disclosure.

[0207] The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. The use of the terms a, an, the, and similar referents in the context of throughout this disclosure (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. As used throughout this disclosure, the word may is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, as used throughout this disclosure, the terms comprising, having, including, and containing are to be construed as open-ended terms (i.e., meaning including, but not limited to,) unless otherwise noted.