Golf club head

Abstract

To provide a golf club head having good catch of a ball and excellent carry performance.SOLUTION: A state in which a shaft axis Z is vertically arranged onto a horizontal surface hp, and a normal line Lf is in parallel to a first vertical surface V1 including the shaft axis Z is a 0 degree state. A direction which is in parallel to the first vertical surface V1 and in parallel to the horizontal surface hp is a projection direction PD1. A projection area of a head 4 in the projection direction PD1 in the case of rotation to a back side at θ° from the 0 degree state with the shaft axis Z as the rotational shaft is WAθ. In the projection area, an area of a first area for receiving force directing for opening a striking face by air resistance during downswing is Afθ, an area of a second area for receiving force directing for closing the striking face by the air resistance is Abθ, and a difference (Afθ-Abθ) is Sθ. S90 is -4,500 (mm2) or less, and S15 is 4,700 (mm2) or less.SELECTED DRAWING: Figure 15

Description

[Technical Field]

[0001] The present disclosure relates to golf club heads. [Background technology]

[0002] There is a demand for golf clubs with excellent distance performance. Distance performance can be improved by the performance of the head, shaft, or the entire club. To improve head-based distance performance, the center of gravity position and repulsion performance can be taken into consideration, as described in JP 2020-171434 A, for example. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-171434 Summary of the Invention [Problem to be solved by the invention]

[0004] It has been discovered that a golf club head with excellent distance performance can be achieved based on a technological concept different from that of conventional golf clubs.

[0005] One of the objects of the present disclosure is to provide a golf club head that has good ball gripping and excellent distance performance. [Means for solving the problem]

[0006] In one embodiment, the golf club head has a face portion that forms a hitting face, a crown portion that forms an outer crown surface, a sole portion that forms an outer sole surface, and a hosel portion that defines a shaft axis and to which the shaft is attached. The hitting face has a face center and a normal at the face center. The head width in the face-back direction is 100 mm or more. The head length in the toe-heel direction is 110 mm or more. The state in which the shaft axis is disposed perpendicular to a horizontal plane and the normal is parallel to a first vertical plane that includes the shaft axis is defined as a 0 degree state. A direction that is parallel to the first vertical plane and parallel to the horizontal plane is defined as a projection direction. When the head is rotated θ degrees toward the back from the 0 degree state with the shaft axis as the rotation axis, the projected area of the head in the projection direction is WAθ (mm 2 ), where θ is between 0 and 90. The projected area is divided into two regions by the shaft axis, and the region that receives a force in a direction to open the hitting face due to air resistance during the downswing is designated as the first region, and the region that receives a force in a direction to close the hitting face due to air resistance is designated as the second region, and the area of the first region is Afθ(mm 2 ) and the area of the second region is Abθ (mm 2 ) (Afθ-Abθ) is Sθ(mm 2 ) is said to be. S90 is -4500 (mm 2 ) or less. S15 is 4700 (mm 2 ) is as follows. [Effects of the Invention]

[0007] As one aspect, a golf club head that has good ball gripping ability and excellent distance performance can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows a golf club according to a first embodiment. [Figure 2]FIG. 2 is a front view of the head of the first embodiment as seen from the face side, showing the head in a standard state. [Figure 3] FIG. 3 is a plan view of the head of the first embodiment as viewed from the crown side. [Figure 4] FIG. 4 is a perspective view of the head of the first embodiment as viewed from the heel back side. [Figure 5] FIG. 5 shows a cross-sectional view of the outer surface of the head taken along line AA in FIG. [Figure 6] FIG. 6 shows a cross-sectional view of the outer surface of the head taken along line BB in FIG. [Figure 7] FIG. 7 shows a cross-sectional view of the outer surface of the head taken along line CC in FIG. [Figure 8] FIG. 8 shows a cross-sectional view of the outer surface of the head taken along line DD in FIG. [Figure 9] Fig. 9 is an enlarged view of the part surrounded by the square line Q1 in Fig. 5. In Fig. 9, an imaginary extension line of the crown base surface is added. [Figure 10] Fig. 10 is an enlarged view of the part surrounded by the square line Q2 in Fig. 7. In Fig. 10, an imaginary extension line of the crown base surface is added. [Figure 11] FIG. 11(a) is a view of the head in the 0 degree state as seen from the face side, and FIG. 11(b) is a view of the head in the 0 degree state as seen from the heel side. [Figure 12] FIG. 12 is a silhouette of the projection of the head in the 0 degree state. [Figure 13] Fig. 13(a) is a projection view of the head (first embodiment) in the 0 degree state, and Fig. 13(b) is a view in which the projection area in the 0 degree state is divided into a first region and a second region by the shaft axis. [Figure 14] Fig. 14(a) is a projection view of the head (first embodiment) in the 15-degree state, and Fig. 14(b) is a view in which the projection area in the 15-degree state is divided into a first region and a second region by the shaft axis. [Figure 15]Fig. 15(a) is a projection of the head (first embodiment) in a 90-degree state, and Fig. 15(b) is a diagram in which the projection area in the 90-degree state is divided into a first region and a second region by the shaft axis. [Figure 16] FIG. 16 is a diagram showing the movement of the club during the downswing. [Figure 17] Fig. 17(a) is a silhouette of the projection in the 0 degree state, and Fig. 17(b) is a diagram for explaining the additional area due to the silhouette convex portion. [Figure 18] FIG. 18 is a plan view of the head of the second embodiment as viewed from the crown side. [Figure 19] FIG. 19 is a perspective view of the head of the second embodiment with the sole facing upward, as viewed from the back-toe side. [Figure 20] Fig. 20(a) is a projection view of the head (second embodiment) in the 0 degree state, and Fig. 20(b) is a view in which the projection area in the 0 degree state is divided into a first region and a second region by the shaft axis. [Figure 21] Fig. 21(a) is a projection view of the head (second embodiment) in the 15-degree state, and Fig. 21(b) is a view in which the projection area in the 15-degree state is divided into a first region and a second region by the shaft axis. [Figure 22] Fig. 22(a) is a projection view of the head (second embodiment) in a 90-degree state, and Fig. 22(b) is a view in which the projection area in the 90-degree state is divided into a first region and a second region by the shaft axis. [Figure 23] FIG. 23 is a plan view of the head of the third embodiment as viewed from the crown side. [Figure 24] FIG. 24 is a perspective view of the head of the third embodiment with the sole facing upward, as viewed from the heel back side. [Figure 25] Fig. 25(a) is a projection view of the head (third embodiment) in the 0 degree state, and Fig. 25(b) is a view in which the projection area in the 0 degree state is divided into a first region and a second region by the shaft axis. [Figure 26]Fig. 26(a) is a projection view of the head (third embodiment) in the 15-degree state, and Fig. 26(b) is a view in which the projection area in the 15-degree state is divided into a first region and a second region by the shaft axis. [Figure 27] Fig. 27(a) is a projection of the head (third embodiment) in a 90-degree state, and Fig. 27(b) is a diagram in which the projection area in the 90-degree state is divided into a first region and a second region by the shaft axis. [Figure 28] FIG. 28 is a plan view of the head of the reference example as viewed from the crown side. [Figure 29] FIG. 29 is a perspective view of the head of the reference example with the sole facing upward, as viewed from the heel back side. [Figure 30] Fig. 30(a) is a projection of the head (reference example) in the 0 degree state, and Fig. 30(b) is a diagram in which the projection area in the 0 degree state is divided into a first region and a second region by the shaft axis. [Figure 31] Fig. 31(a) is a projection of the head (reference example) at a 15-degree angle, and Fig. 31(b) is a diagram in which the projection area at the 15-degree angle is divided into a first region and a second region by the shaft axis. [Figure 32] Fig. 32(a) is a projection of the head (reference example) at a 90-degree angle, and Fig. 32(b) is a diagram in which the projection area at the 90-degree angle is divided into a first region and a second region by the shaft axis. [Figure 33] FIG. 33 is a plan view of the head of Comparative Example 6 as viewed from the crown side. [Figure 34] Fig. 34(a) is a projection of the head (Comparative Example 6) in the 0 degree state, and Fig. 34(b) is a diagram in which the projection area in the 0 degree state is divided into a first region and a second region by the shaft axis. [Figure 35] Fig. 35(a) is a projection of the head (Comparative Example 6) at a 15-degree angle, and Fig. 35(b) is a diagram in which the projection area at the 15-degree angle is divided into a first region and a second region by the shaft axis. [Figure 36] Fig. 36(a) is a projection of the head (Comparative Example 6) in a 90-degree state, and Fig. 36(b) is a diagram in which the projection area in the 90-degree state is divided into a first region and a second region by the shaft axis. [Figure 37] FIG. 37 is a conceptual diagram for explaining the reference state. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, the present disclosure 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, an up-down direction, a face center, and a normal at the face center are defined.

[0011] The state in which the head is placed on the ground plane GP at a predetermined lie angle is considered to be the reference state. As shown in Figure 37, in this reference state, the shaft axis line Z is included in a plane VP perpendicular to the ground plane GP. The shaft axis line Z is the center line of the shaft when the shaft is attached to the head. Typically, the shaft axis line Z is the center line of the hosel hole. The plane VP is considered to be the reference vertical plane. The predetermined lie angle is listed, for example, in a product catalog.

[0012] In this reference state, the orientation of the face is determined so that the normal to the striking face at the face center is contained in a plane that is perpendicular to the reference vertical plane VP and perpendicular to the ground plane GP. In other words, in a planar view seen from above, the normal to the striking face at the face center is perpendicular to the reference vertical plane VP.

[0013] In the present application, the toe-heel direction is the direction of the intersection line NL between the reference vertical plane VP and the ground plane GP (see FIG. 37).

[0014] In the present application, the face-back direction is a direction perpendicular to the toe-heel direction and parallel to the ground plane GP.

[0015] In the present application, the vertical direction is a direction perpendicular to the toe-heel direction and perpendicular to the face-back direction. In other words, in the present application, the vertical direction is a direction perpendicular to the ground plane GP.

[0016] In the present application, the face center Fc is determined as follows: First, an arbitrary point Pr is selected that is approximately near the center of the hitting face in the up-down direction and the toe-heel direction. Next, a plane is determined that passes through this point Pr, extends along the normal to the hitting face at point Pr, and is parallel to the toe-heel direction. A line of intersection between this plane and the hitting face is drawn, and its midpoint Px is determined. Next, a plane is determined that passes through this midpoint Px, extends along the normal to the hitting face at point Px, and is parallel to the up-down direction. A line of intersection between this plane and the hitting face is drawn, and its midpoint Py is determined. Next, a plane is determined that passes through this midpoint Py, extends along the normal to the hitting face at point Py, and is parallel to the toe-heel direction. A line of intersection between this plane and the hitting face is drawn, and its midpoint Px is newly determined. Next, a plane is determined that passes through this new midpoint Px, extends along the normal to the hitting face at point Px, and is parallel to the up-down direction. A line of intersection between this plane and the striking face is drawn, and its midpoint Py is newly determined. This process is repeated to sequentially determine Px and Py. During this process, the new position Py (final position Py) when the distance between the new midpoint Py and the previous midpoint Py is first 0.5 mm or less is the face center Fc.

[0017] Fig. 1 is an overall view of a golf club 2 including a head 4 according to a first embodiment of the present disclosure. Fig. 2 is a front view of the head 4. Fig. 2 is a view of the head 4 in the standard state as seen from the face side. Fig. 3 is a plan view of the head 4 as seen from the crown side. Fig. 4 is a perspective view of the head 4 as seen from the heel back side.

[0018] 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.

[0019] The golf club 2 is a driver (number 1 wood). Typically, the club length of a driver is 43 inches or more. Preferably, the golf club 2 is a wood-type golf club.

[0020] The shaft 6 is a tubular body. The shaft 6 has a hollow structure. The material of the shaft 6 is fiber-reinforced resin. The shaft 6 is a so-called carbon shaft. Preferably, the shaft 6 is formed by curing a prepreg sheet. In this prepreg sheet, the fibers are oriented substantially in one direction. A prepreg in which the fibers are oriented substantially in one direction is also called a UD prepreg. "UD" stands for unidirectional. A prepreg other than a UD prepreg may also be used. For example, the fibers contained in the prepreg sheet may be woven. The shaft 6 may include metal wire. The material of the shaft 6 is not limited and may be, for example, metal.

[0021] The grip 8 is the part that is held by the golfer during a swing. Rubber compositions and resin compositions are examples of materials for the grip 8. The rubber composition of the grip 8 may contain air bubbles.

[0022] Although not shown, the head 4 has a hollow structure. In this embodiment, the head 4 is a wood type. The head 4 is a driver head. Preferred materials for the head 4 include metal and fiber-reinforced plastic. Examples of the metal include titanium alloy, pure titanium, stainless steel, maraging steel, and mild steel. Examples of the fiber-reinforced plastic include carbon fiber-reinforced plastic. The head 4 may be a composite head having a metal portion and a non-metal portion. Examples of the material for the non-metal portion include fiber-reinforced plastic. From the viewpoint of strength, the fiber-reinforced plastic is preferably carbon fiber-reinforced plastic.

[0023] As shown in Figures 2 to 4, 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 hitting face 10a. The hitting face 10a is the outer surface of the face portion 10. The hitting face 10a is also simply referred to as the face. The crown portion 12 forms a crown outer surface 12a. The sole portion 14 forms a sole outer surface 14a. The hosel portion 16 has a shaft hole 16a.

[0024] The striking face 10a has a face center Fc defined as above. The striking face 10a has a normal Lf. The normal Lf is a normal at the face center Fc.

[0025] The head 4 has a protrusion 20 on its outer surface. In this embodiment, the protrusion 20 is provided on the crown portion 12. The crown portion 12 has the protrusion 20 on the crown outer surface 12a. Although not shown, the protrusion 20 is hollow. The protrusion 20 forms a convex portion on the crown outer surface 12a and a concave portion on the crown inner surface. The protrusion 20 may be solid.

[0026] The entire protrusion 20 is located on the heel side of the face center Fc. In a plan view, the entire protrusion 20 is located on the heel side of the centroid CR.

[0027] In the front view of the head seen from the face side (FIG. 2), the protrusion 20 is not visible. In the front view of the head seen from the face side (FIG. 2), the protrusion 20 does not form the outer contour line CL1 of the head 4. In other words, the outer contour line is the contour line of the silhouette.

[0028] In this embodiment, the entire protrusion 20 is provided on the crown outer surface 12a. As shown in FIG. 3, the head 4 has an outer contour line CL2 in a plan view of the head 4. As shown in FIG. 3, the protrusion 20 does not reach the outer contour line CL2. The protrusion 20 does not extend to any part other than the crown outer surface 12a. In the plan view of the head 4 (FIG. 3), the entire protrusion 20 is visible.

[0029] The plan view of the head 4 is a projection of the head in the reference state onto a plane parallel to the ground plane GP. This plan view (FIG. 3) is also called a plan view.

[0030] In a plan view of the head 4, the protrusion 20 may reach the outer contour line CL2. In other words, the protrusion 20 may form the outer contour line CL2. The protrusion 20 may extend to a portion other than the crown outer surface 12a. For example, the protrusion 20 may extend from the crown outer surface 12a to the sole outer surface 14a. For example, the protrusion 20 may extend from the crown outer surface 12a to the outer surface of the side portion (skirt portion). As will be described later, the position of the protrusion 20 is not limited in the present disclosure.

[0031] The portion of the crown outer surface 12a that does not have the protrusion 20 is formed by a base surface b1. The base surface b1 is a smoothly continuous convex curved surface. This convex curved surface is a curved surface that is convex toward the outside of the head 4. As shown in FIG. 3, the base surface b1 belonging to the crown outer surface 12a includes the centroid CR of the head 4 in a plan view. The centroid CR is the centroid of the figure formed by the outer contour line CL2.

[0032] FIG. 5 shows the section line of the outer surface of the head 4 in a cross-sectional view taken along line AA in FIG. 3. FIG. 6 shows the section line of the outer surface of the head 4 in a cross-sectional view taken along line BB in FIG. 3. FIG. 7 shows the section line of the outer surface of the head 4 in a cross-sectional view taken along line CC in FIG. 3. FIG. 8 shows the section line of the outer surface of the head 4 in a cross-sectional view taken along line DD in FIG. 3. FIGS. 5 to 8 include the section line of the crown outer surface 12a. In this application, the section line of the outer surface of the head 4 is also simply referred to as the section line.

[0033] The protrusion 20 has a contour line CL20, an upper surface 22, and a side wall surface 24. The contour line CL20 is a boundary line between the base surface b1 and the protrusion 20. In the plan view of the head 4 (FIG. 3), the contour line CL20 of the protrusion 20 is substantially quadrangular (substantially trapezoidal). In the present application, the term "substantially" includes a configuration in which the sides are curved (not straight) and a configuration in which the corners are rounded. In the contour line CL20 in the plan view of the head (FIG. 3), the radius of curvature of the sides is preferably 25 mm or more, more preferably 40 mm or more, and more preferably 50 mm or more. In the contour line CL in the plan view of the head (FIG. 3), the radius of curvature of the rounded corners is preferably 10 mm or less, more preferably 7 mm or less, and more preferably 5 mm or less. The contour line CL20 forms a substantially quadrangular shape.

[0034] The top surface 22 and the side wall surface 24 may be defined by a ridgeline. In a cross-sectional line of the outer surface of the protrusion 20, this ridgeline may be identified as a point or a bend apex having a radius of curvature of 5 mm or less. The radius of curvature of this cross-sectional line may vary depending on the direction of the cross-section, but in determining the radius of curvature to define the ridgeline, a cross-section that minimizes the radius of curvature is selected.

[0035] In a plan view (plan view) of the head 4, the protrusion 20 may be a substantially polygonal shape. When this substantially polygonal shape is a substantially N-sided shape, N may be an integer equal to or greater than 3. N may also be an integer equal to or greater than 3 and equal to or less than 20.

[0036] The contour line CL20 has a first side CL21, a second side CL22, a third side CL23, and a fourth side CL24. The first side CL21 constitutes the side on the toe side and face side of the protrusion 20. The first side CL21 extends toward the back side as it approaches the toe side. The first side CL21 connects the second side CL22 and the fourth side CL24.

[0037] The second side CL22 constitutes the heel-side and face-side side of the protrusion 20. The second side CL22 extends toward the back side as it approaches the heel side. The second side CL22 connects the first side CL21 and the third side CL23.

[0038] The third side CL23 constitutes the heel-side and back-side side of the protrusion 20. The third side CL23 extends toward the toe side and then toward the back side. The third side CL23 connects the second side CL22 and the fourth side CL24. The third side CL23 is a curved line that convexly extends toward the outside of the head 4.

[0039] The fourth side CL24 constitutes the toe-side and back-side side of the protrusion 20. The fourth side CL24 extends toward the back side as it approaches the heel side. The fourth side CL24 connects the third side CL23 and the first side CL21.

[0040] The second side CL22, the third side CL23, and the fourth side CL24 each serve as a base point of the side wall surface 24. That is, the second side CL22, the third side CL23, and the fourth side CL24 each form a boundary line between the side wall surface 24 and the base surface b1. On the other hand, the first side CL21 does not serve as a base point of the side wall surface 24. The first side CL21 forms a boundary line between the base surface b1 and the top surface 22.

[0041] In the present application, a cross-sectional line in a cross section along the toe-heel direction is also simply referred to as a transverse cross-sectional line. FIG. 5 is an example of a transverse cross-sectional line. A transverse cross-sectional line on the outer surface of the head 4 is also simply referred to as a transverse cross-sectional line. In the present application, a cross-sectional line in a cross section along the face-back direction is also simply referred to as a longitudinal cross-sectional line. FIG. 7 is an example of a longitudinal cross-sectional line. A longitudinal cross-sectional line on the outer surface of the head 4 is also simply referred to as a longitudinal cross-sectional line.

[0042] The inflection point on the cross-sectional line can be a point that constitutes the contour line CL20. In other words, this inflection point can be the starting point of the protrusion 20. The cross-sectional line of the base surface b1 is a curve that is convex toward the outside of the head 4. The inflection point is a point where the curve that is convex toward the outside of the head 4 changes into a curve that is convex toward the inside of the head 4.

[0043] The vertex of the bend in the cross-sectional line can be a point that constitutes the contour line CL20. In other words, this vertex can be the starting point of the protrusion 20. The cross-sectional line of the base surface b1 is a convex curve that extends outward from the head 4. The line that connects to this curve and bends upward forms a vertex. This vertex faces inward from the head 4. This vertex can be the starting point of the protrusion 20.

[0044] The inflection point on the longitudinal cross section line can be a point that constitutes the contour line CL20. In other words, this inflection point can be the starting point of the protrusion 20. The longitudinal cross section line of the base surface b1 is a curve that is convex toward the outside of the head 4. The inflection point is a point where the curve that is convex toward the outside of the head 4 changes into a curve that is convex toward the inside of the head 4.

[0045] The vertex of the bend in the longitudinal section line can be a point that constitutes the contour line CL20. In other words, this vertex can be the starting point of the protrusion 20. The longitudinal section line of the base surface b1 is a curve that convexly extends outward from the head 4. The line that connects to this curve and bends upward forms a vertex. This vertex faces inward from the head 4. This vertex can be the starting point of the protrusion 20.

[0046] Typically, the contour line CL20 can be determined by the inflection points or the vertices. In selecting the cross-section line for this determination, the transverse cross-section line may be prioritized over the longitudinal cross-section line. In this case, the transverse cross-section line is used to identify the inflection points or the vertices. If it is difficult to identify them using the transverse cross-section line, the longitudinal cross-section line can be used. The contour line of the protrusion 20 that is clearly visible can be considered to be the contour line CL20.

[0047] The protrusion 20 is a portion that protrudes from the base surface b1. An imaginary extension surface b2 can be identified below the protrusion 20, which is an extension of the base surface b1. The protrusion 20 is a portion that protrudes from the imaginary extension surface b2. The imaginary extension surface b2 can be considered to be the base surface b1 that would be formed in the installation area of the protrusion 20 if the protrusion 20 were not present. The imaginary extension surface b2 is formed continuously with the base surface b1. The imaginary extension surface b2 is a curved surface that is convex toward the outside of the head 4. The imaginary extension surface b2 is smoothly connected to the base surface b1.

[0048] Fig. 9 is an enlarged view of a portion surrounded by a square line Q1 in Fig. 5. Fig. 10 is an enlarged view of a portion surrounded by a square line Q2 in Fig. 7.

[0049] The cross-sectional line in FIG. 9 has an imaginary extension line b3 drawn thereon, which can constitute the imaginary extension surface b2. The imaginary extension line b3 is a curved line that convexly extends outward from the head 4. The imaginary extension line b3 smoothly connects to the cross-sectional line of the base surface b1. The imaginary extension surface b2 can be formed by a collection of imaginary extension lines b3.

[0050] The imaginary extension line b3 smoothly connects the cross-sectional line on one side of the protrusion 20 with the cross-sectional line on the other side of the protrusion 20. The imaginary extension line b3 can be drawn as a Bezier curve. Known Bezier curves include quadratic Bezier curves and cubic Bezier curves. A quadratic Bezier curve has one control point. A cubic Bezier curve has two control points. Preferably, a cubic Bezier curve is used. The Bezier curves in FIGS. 9 and 10 are cubic Bezier curves.

[0051] 9, the cross-sectional line has a first starting point P1 and a second starting point P2. The first starting point P1 and the second starting point P2 are points on the contour line CL20.

[0052] To define the effective tangent at the first starting point P1, points P11 and P12 are defined on the opposite side of the first starting point P1 from the protrusion 20. Point P11 is 0.5 mm away from the first starting point P1. Point P12 is 0.5 mm away from point P11. These 0.5 mm distances are the distance along the cross-sectional line. Points P11 and P12 are points on the cross-sectional line. A tangent line L1 at point P1 to a circle that passes through the three points P1, P11, and P12 is determined. If points P1, P11, and P12 are collinear, this line can be defined as the tangent line L1.

[0053] Similarly, to define the effective tangent at the second starting point P2, points P21 and P22 are set on the opposite side of the second starting point P2 from the protrusion 20. Point P21 is 0.5 mm away from the second starting point P2. Point P22 is 0.5 mm away from point P21. These 0.5 mm distances are the distance along the cross-sectional line. Points P21 and P22 are points on the cross-sectional line. A tangent line L2 at point P2 to a circle passing through the three points P2, P21, and P22 is determined. If points P2, P21, and P22 are on the same line, this line can be taken as the tangent line L2.

[0054] Once the tangent line L1 and the tangent line L2 are determined, the intersection point Px of the tangent line L1 and the tangent line L2 is determined. Furthermore, the midpoint M1 between the point P1 and the point Px is determined, and the midpoint M2 between the point P2 and the point Px is determined.

[0055] A Bezier curve can be drawn with point P1 as the start point, midpoint M1 as the first control point, midpoint M2 as the second control point, and point P2 as the end point. In Figure 9, this Bezier curve is the virtual extension line b3. Since there are two control points, this Bezier curve is a cubic Bezier curve.

[0056] An imaginary extension line b3 can be defined at any position in the face-back direction. A set of these imaginary extension lines b3 can define an imaginary extension plane b2.

[0057] A similar Bezier curve can be defined for a vertical section line. As shown in Fig. 10, the vertical section line has a first starting point P1 and a second starting point P2. The first starting point P1 and the second starting point P2 are points on the contour line CL20.

[0058] To define the effective tangent at the first starting point P1, points P11 and P12 are set on the opposite side of the first starting point P1 from the protrusion 20. Point P11 is 0.5 mm away from the first starting point P1. Point P12 is 0.5 mm away from point P11. These 0.5 mm distances are the distance along the longitudinal section line. Points P11 and P12 are points on the longitudinal section line. A tangent line L1 at point P1 to a circle that passes through the three points P1, P11, and P12 is determined. If points P1, P11, and P12 are on the same line, this line can be taken as the tangent line L1.

[0059] Similarly, to define the effective tangent at the second starting point P2, points P21 and P22 are set on the opposite side of the second starting point P2 from the protrusion 20. Point P21 is 0.5 mm away from the second starting point P2. Point P22 is 0.5 mm away from point P21. These 0.5 mm distances are the distance along the longitudinal section line. Points P21 and P22 are points on the longitudinal section line. A tangent line L2 at point P2 to a circle that passes through the three points P2, P21, and P22 is determined. If points P2, P21, and P22 are on the same line, this line can be taken as the tangent line L2.

[0060] Once the tangent line L1 and the tangent line L2 are determined, the intersection point Px of the tangent line L1 and the tangent line L2 is determined. Furthermore, the midpoint M1 between the point P1 and the point Px is determined, and the midpoint M2 between the point P2 and the point Px is determined.

[0061] A Bezier curve can be drawn with point P1 as the start point, midpoint M1 as the first control point, midpoint M2 as the second control point, and point P2 as the end point. In Figure 10, this Bezier curve is the virtual extension line b4.

[0062] An imaginary extension line b4 can be defined at any position in the toe-heel direction. A set of these imaginary extension lines b4 can define an imaginary extension plane b2.

[0063] In some cases, the protrusion reaches the outer peripheral edge (outer contour line CL4) of the crown portion. In this case, the protrusion may have only one starting point on the transverse cross section and / or longitudinal cross section, which is formed at the boundary between the protrusion and the base surface b1. When there is only one starting point, the imaginary extension line b3 may be an arc along the radius of curvature of the starting point. That is, in this case, the imaginary extension line b3 may be a circle passing through three points: the first point, which is the starting point; a second point 0.5 mm away from the first point; and a third point 0.5 mm away from the second point.

[0064] In determining the imaginary extension plane b2, the transverse section lines may be used in preference to the longitudinal section lines. The imaginary extension plane b2 may be determined by a set of imaginary extension lines b3 based on the transverse section lines. If the set of imaginary extension lines b3 is unclear, the imaginary extension plane b2 may be determined by a set of imaginary extension lines b4 based on the longitudinal section lines.

[0065] The height Ht of the protrusion 20 may be defined as the height from the imaginary extension plane b2. As shown in FIG. 9, a normal LN to the imaginary extension plane b2 at a certain point f1 has an intersection f2 with the outer surface of the protrusion 20. The distance from point f1 to the intersection f2 may be defined as the height Ht of the protrusion 20 at the intersection f2. Note that if the protrusion has a point where it does not intersect with the normal LN to the imaginary extension plane b2 but does intersect with the normal to the base plane b1, the height Ht of that point is defined as the height from the base plane b1. In this case, the length of the normal line is also the height Ht.

[0066] [0 degree state, θ degree state, projection direction] In the present application, a 0 degree state and a θ degree state including this 0 degree state are defined. Furthermore, a projection direction is defined.

[0067] 11(a) and 11(b) show the head 4 in a 0-degree state. The viewpoint direction differs by 90° between FIG. 11(a) and FIG. 11(b). To facilitate comparison between FIG. 11(a) and FIG. 11(b), the three axes (x-axis, y-axis, and z-axis) of a three-dimensional Cartesian coordinate system are indicated in these figures.

[0068] The state in which the shaft axis Z is arranged perpendicular to the horizontal plane hp and the normal line Lf of the striking face 10a is parallel to a first vertical plane V1 that includes the shaft axis Z is defined as the 0 degree state.

[0069] The first vertical plane V1 is perpendicular to the horizontal plane hp. In Fig. 11(a), the first vertical plane V1 is shown as a straight line overlapping the shaft axis line Z. In Fig. 11(b), the first vertical plane V1 is a plane parallel to the paper surface.

[0070] A direction parallel to the first vertical plane V1 and parallel to the horizontal plane hp is defined as a projection direction PD1. The projection direction PD1 is perpendicular to the shaft axis line Z.

[0071] As will be described later, the head 4 is rotated by θ° around the shaft axis Z, but the first vertical plane V1 does not rotate even when the head 4 is rotated, and the projection direction PD1 does not change.

[0072] 12 is a projection of the head 4 in the 0-degree state, projected in the projection direction PD1. This projection is shown as a silhouette. As will be described later, the area of this silhouette is WA0.

[0073] Unless otherwise specified, the projection view in this application refers to a projection view projected in a projection direction PD1. This projection view is a parallel projection view projected with light rays parallel to the projection direction PD1.

[0074] In the present application, the state in which the head 4 in the 0-degree state is rotated θ degrees to the back side around the shaft axis line Z as the rotation center is defined as the θ-degree state. For example, the state in which the head 4 in the 0-degree state is rotated 15 degrees to the back side around the shaft axis line Z as the rotation center is the 15-degree state. For example, the state in which the head 4 in the 0-degree state is rotated 30 degrees to the back side around the shaft axis line Z as the rotation center is the 30-degree state. For example, the state in which the head 4 in the 0-degree state is rotated 90 degrees to the back side around the shaft axis line Z as the rotation center is the 90-degree state.

[0075] The angle θ is set to be equal to or greater than 0° and equal to or less than 90°. This range of angle θ corresponds to the movement of the head 4 from the start of face rotation to impact during the downswing.

[0076] FIG. 13(a) shows the head 4 in a 0-degree state. FIG. 14(a) shows the head 4 in a 15-degree state. FIG. 15(a) shows the head 4 in a 90-degree state. In FIGS. 13(a), 14(a), and 15(a), the projection direction PD1 is perpendicular to the paper. As these figures show, when the head 4 is in a θ-degree state, the attitude of the head 4 with respect to the projection direction PD1 changes based on the angle θ.

[0077] The θ-degree state reflects the relationship between the posture of the head 4 during the downswing and the direction of movement of the head 4. The projection direction PD1 corresponds to the direction of movement of the head 4 during the downswing. In other words, the projection direction PD1 corresponds to the direction of the airflow hitting the head 4 during the downswing. In the projection direction PD1, the direction of movement of the head and the direction of the airflow are opposite to each other. In the drawings of the present application, the projection direction PD1 is shown as the direction of the airflow. Note that the terms "projection direction," "head movement direction," "head movement direction," "airflow direction," and "airflow direction" use the terms "direction" and "orientation" differently. These terms use the terms "direction" and "orientation" in a mathematical sense. In other words, "direction" is an expression combining two "orientations," and two "orientations" exist in one "direction" along a straight line.

[0078] FIG. 16 shows the movement of the golf club 2 during the downswing. The swing starts with a backswing, passes through the top of the swing, and transitions to the downswing, leading to impact. As the downswing progresses, the head speed accelerates. Also, as the downswing progresses, the posture of the head changes.

[0079] At a certain point during the downswing, the shaft 6 of the golf club 2 becomes parallel to the ground. The position of the golf club 2 at this time is also referred to as position 9. The position of the club at impact is also referred to as position 6. In these terms, the golf club 2 during the swing is likened to the hands of a clock. That is, for example, position 9 corresponds to the 9 o'clock position on a clock (analog clock).

[0080] During the downswing, a wrist turn occurs and face rotation progresses. Face rotation typically begins at or near position 9. Face rotation allows the striking face 10a to face the target direction at impact.

[0081] If the moving direction of the head 4 is considered to correspond to the projection direction PD1, then the posture of the head 4 is at 90 degrees at the start of face rotation. If the moving direction of the head 4 is considered to correspond to the projection direction PD1, then the posture of the head 4 is at 0 degrees at impact. The posture of the head 4 from the start of face rotation to impact corresponds to the θ-degree state when θ is continuously changed from 90 degrees to 0 degrees. As impact approaches, θ decreases.

[0082] During the downswing, the head 4 moves with its heel leading and is subjected to air resistance during this movement. The inventors have found that the direction of movement of the head 4 during face rotation substantially corresponds to the above-mentioned projection direction PD1. The θ-degree state, where θ is between 0 and 90 degrees, reflects changes in head posture as face rotation progresses. By considering the θ-degree state and projection direction PD1, the state of the head 4 during the downswing can be appropriately evaluated.

[0083] [WAθ, Afθ, Abθ, Sθ] When the shaft axis Z is rotated from 0 degrees to the back side by θ degrees, the projected area of the head 4 in the projection direction PD1 is WAθ (mm 2 For example, the projection area of the head 4 in the projection direction PD1 in the 0 degree state is WA0 (mm 2 ) where WA0 is the projected area in the 0 degree state. For example, when the club head 4 is rotated 15 degrees to the back side from the 0 degree state with the shaft axis Z as the rotation axis, the projected area of the club head 4 in the projection direction PD1 is WA15 (mm 2 ) where WA15 is the projected area in the 15 degree state. For example, when the club head 4 is rotated 30 degrees from the 0 degree state to the back side with the shaft axis Z as the rotation axis, the projected area of the club head 4 in the projection direction PD1 is WA30 (mm 2 ) where WA30 is the projected area in the 30 degree state. For example, when the club head 4 is rotated 90 degrees from the 0 degree state to the back side with the shaft axis Z as the rotation axis, the projected area of the club head 4 in the projection direction PD1 is WA90 (mm 2 ) WA90 is the projected area at a 90 degree angle. WAθ is the overall projected area of the head 4.

[0084] Therefore, for example, the projected area of the silhouette of the projection drawing in the 0 degree state shown in FIG. 12 is WA0.

[0085] Each projection can be divided into a first region and a second region by the shaft axis Z. The first region is the region that receives a force that opens the hitting face due to air resistance during the downswing. The second region is the region that receives a force that closes the hitting face due to air resistance. The first region is the region closer to the face or toe side of the shaft axis Z. The second region is the region closer to the back or heel side of the shaft axis Z.

[0086] Of the projected area WAθ, the area of the first region is Afθ (mm 2 ) is set. For example, of the projected area WA0, the area of the first region is set to Af0. For example, of the projected area WA15, the area of the first region is set to Af15. For example, of the projected area WA30, the area of the first region is set to Af30. For example, of the projected area WA90, the area of the first region is set to Af90.

[0087] On the other hand, the area of the second region in the projected area WAθ is Abθ (mm 2 ) is used. For example, of the projected area WA0, the area of the second region is set to Ab0. For example, of the projected area WA15, the area of the second region is set to Ab15. For example, of the projected area WA30, the area of the second region is set to Ab30. For example, of the projected area WA90, the area of the second region is set to Ab90.

[0088] FIG. 13(b) is a diagram in which a projection of the head 4 at a 0-degree angle is divided into two regions by the shaft axis line Z. FIG. 14(b) is a diagram in which a projection of the head 4 at a 15-degree angle is divided into two regions by the shaft axis line Z. FIG. 15(b) is a diagram in which a projection of the head 4 at a 90-degree angle is divided into two regions by the shaft axis line Z. Since the head 4 is for a right-handed person, in these projections, the left side of the shaft axis line Z is the first region, and the right side of the shaft axis line Z is the second region.

[0089] 13(b), the area of the portion hatched with dashed lines is Af0, and the area of the portion hatched with solid lines is Ab0. The sum of Af0 and Ab0 is WA0.

[0090] 14(b), the area of the portion hatched with dashed lines is Af15, and the area of the portion hatched with solid lines is Ab15. The sum of Af15 and Ab15 is WA15.

[0091] For example, in the 90-degree state in Figure 15(b), the area of the portion shown with dashed hatching is Af90, and the area of the portion shown with solid hatching is Ab90. The sum of Af90 and Ab90 is WA90.

[0092] In this way, for any θ between 0 and 90 degrees, the projected area WAθ in the θ degree state is divided into the area Afθ of the first region and the area Abθ of the second region.

[0093] The value obtained by subtracting Abθ from Afθ, that is, the difference (Afθ-Abθ), is Sθ (mm 2 ) For example, the difference (Af0-Ab0) is defined as S0. For example, the difference (Af15-Ab15) is defined as S15. For example, the difference (Af30-Ab30) is defined as S30. For example, the difference (Af90-Ab90) is defined as S90.

[0094] During a swing, air resistance acts on the head 4. This air resistance can act as a force that rotates the head 4 about the shaft axis line Z. This air resistance depends on the projected area of the head 4 in the projection direction corresponding to the direction of the air flow.

[0095] The air resistance experienced by the first region causes the head 4 to rotate in a direction that opens the face 10a. Therefore, the larger Afθ, the more likely the face 10a will open. On the other hand, the air resistance experienced by the second region causes the head 4 to rotate in a direction that closes the face 10a. Therefore, the larger Abθ, the more likely the face 10a will close. Furthermore, the larger Abθ is relative to Afθ, the more likely the face 10a will close.

[0096] The head 4 is designed so that the area of the second region is large at the start of face rotation. That is, the head 4 is designed so that Ab90 is large. This increases air resistance in the second region, making it easier for a force to act in the direction of closing the face 10a. In the 90-degree position, the area Ab90 of the second region is large (see FIG. 15(b)), and by utilizing this large Ab90, face rotation is promoted. Furthermore, the head 4 is designed so that the area of the first region is small immediately before impact. That is, the head 4 is designed so that Af15 is small. This reduces air resistance in the first region, making it easier for face rotation to occur. Furthermore, by reducing Af15 of the first region, which accounts for a large proportion of the projected area WA15 immediately before impact, air resistance acting on the entire head is suppressed, and head speed can be improved. Because the head speed is high immediately before impact, air resistance is likely to increase. Therefore, by reducing Af15, the air resistance acting on the head 4 can be effectively suppressed.

[0097] By promoting face rotation, the ball can be better gripped. By improving grip, impacts with the face 10a open are suppressed, which can increase the flight distance. Furthermore, by improving head speed, the flight distance can be increased.

[0098] "Good grip" means that the face 10a is less likely to open upon impact. In a head with good grip, the face 10a is likely to be square or slightly closed upon impact. In a head with good grip, the energy of the head is efficiently transmitted to the ball, resulting in a strong trajectory and increased flight distance.

[0099] From the viewpoint of promoting face rotation and improving head speed, the difference (Af90-Ab90) is S90 (mm 2 ) is preferably small. From this point of view, S90 is -4500 (mm 2 ) or less is preferable, and -4550 (mm 2) or less is more preferable, and -4600 (mm 2 ) or less is more preferable, and -4700 (mm 2 ) or less is more preferable. Considering the constraints on the head volume, the S90 is -5100 (mm 2 ) or more is preferable, and -5000 (mm 2 ) or more is more preferable, and -4900 (mm 2 ) or higher is more preferable.

[0100] From the viewpoint of promoting face rotation and improving head speed, the difference (Af15-Ab15) is S15 (mm 2 ) is preferably small. From this point of view, S15 is 4700 (mm 2 ) or less is preferable, and 4650 (mm 2 ) or less is more preferable, and 4600 (mm 2 ) or less is more preferable, and 4550 (mm 2 ) or less is more preferable, and 4500 (mm 2 ) or less is more preferable. From the viewpoint of increasing the moment of inertia of the head 4 and widening the sweet spot, it is preferable that the head volume is large. From this viewpoint, S15 is 4200 (mm 2 ) or more is preferable, and 4300 (mm 2 ) or more is more preferable, and 4400 (mm 2 ) or higher is more preferable.

[0101] The head can be designed so that, at the start of face rotation, the projected area of the second region is increased while suppressing the projected area of the entire head. Increasing the air resistance of the second region makes it easier for the face 10a to close. From these viewpoints, the ratio (WA90 / Ab90) is preferably equal to or less than 1.205, more preferably equal to or less than 1.200, and still more preferably equal to or less than 1.195. A head in which Ab90 is excessively large relative to Af90 may cause discomfort with the head shape. From this viewpoint, the ratio (WA90 / Ab90) is preferably equal to or greater than 1.100, more preferably equal to or greater than 1.130, and still more preferably equal to or greater than 1.160.

[0102] The head can be designed so that the projected area of the second region is increased while the projected area of the entire head is reduced immediately before impact. This reduces the air resistance of the entire head, potentially increasing head speed. Furthermore, the increased air resistance of the second region facilitates closing of the face 10a, potentially promoting face rotation. From these perspectives, the ratio (WA15 / Ab15) is preferably equal to or less than 7.00, more preferably equal to or less than 6.80, and even more preferably equal to or less than 6.50. A head in which Af15 is too small relative to Ab15 may cause discomfort with the head shape. From this perspective, the ratio (WA15 / Ab15) is preferably equal to or greater than 5.50, more preferably equal to or greater than 5.80, and even more preferably equal to or greater than 6.00.

[0103] Increasing the absolute value of S90 at the start of face rotation can increase the force that causes the face 10a to close. Furthermore, decreasing the absolute value of S15 immediately before impact can decrease the force that causes the face 10a to open, and can also reduce air resistance. From the viewpoint of promoting face rotation and increasing head speed, the ratio (|S90| / |S15|) is preferably equal to or greater than 1.00, more preferably equal to or greater than 1.06, more preferably equal to or greater than 1.10, and even more preferably equal to or greater than 1.12. From the viewpoint of discomfort with the head shape, the ratio (|S90| / |S15|) is preferably equal to or less than 1.20, more preferably equal to or less than 1.18, and even more preferably equal to or less than 1.16.

[0104] Note that "|S90|" means the absolute value of S90, and "|S15|" means the absolute value of S15. In this embodiment, S90 is a negative value, so |S90| is -S90. On the other hand, S15 is a positive value, so |S15| is equal to S15.

[0105] As shown in FIG. 15(a), in the head 4, the protrusion 20 is visible in the projection at a 90-degree angle. The protrusion 20 forms an outer contour in the projection at a 90-degree angle. The protrusion 20 affects Ab90. The protrusion 20 increases Ab90. On the other hand, as shown in FIG. 13(a), in the head 4, the protrusion 20 is not visible in the projection at a 0-degree angle. The protrusion 20 does not form an outer contour in the projection at a 0-degree angle. The protrusion 20 does not affect Af0. The protrusion 20 does not increase Af0. The protrusion 20 does not increase Ab0. As shown in FIG. 14(a), in the head 4, the protrusion 20 is not visible in the projection at a 15-degree angle. The protrusion 20 does not form an outer contour in the projection at a 15-degree angle. The protrusion 20 does not affect Af15. The protrusion 20 does not increase Af15. The protrusion 20 does not increase Ab15. The protrusion 20 contributes to reducing S90 while not increasing S15. The protrusion 20 contributes to reducing the ratio (WA90 / Ab90) while not increasing the ratio (WA15 / Ab15). The protrusion 20 contributes to increasing the ratio (|S90| / |S15|).

[0106] FIG. 17(a) shows a silhouette of a projection of the head 4 in a 90-degree state. In this projection, the outline of the head 4 has a convex portion 30. This convex portion 30 is also referred to as a silhouette convex portion. As described above, the protrusion 20 is visible in the projection at a 90-degree state. The silhouette convex portion 30 is formed by the protrusion 20. The silhouette convex portion 30 expands Ab90.

[0107] An inflection point on the outline of the projection of the head 4 can be the starting point of the silhouette convex portion 30. An apex of a bend on the outline of the projection of the head 4 can be the starting point of the silhouette convex portion 30. In this embodiment, apexes, rather than an inflection point, are the starting points of the silhouette convex portion 30 on both sides of the silhouette convex portion 30. As shown in FIG. 17(b), in the silhouette convex portion 30 of this embodiment, apexes P31 and P32 of the bend are the starting points of the silhouette convex portion 30.

[0108] A cubic Bezier curve can also be drawn for this silhouette protrusion 30 using the method described above. The Bezier curve is shown by the two-dot chain line in FIG. 17(b). This Bezier curve is a curve that smoothly connects the curves adjacent to both sides of the silhouette protrusion 30. This Bezier curve can be the contour line 30a of a projection drawing when the protrusion 20 does not exist. The area enclosed by the line of the silhouette protrusion 30 and the imaginary contour line 30a is shown by hatching. This area is the area added by the protrusion 20. This area is also referred to as the added area. The protrusion 20 increases WA90 by the amount of this added area. The protrusion 20 increases Ab90 by the amount of this added area.

[0109] From the viewpoint of increasing the additional area at Ab90 in the 90-degree position and increasing the air resistance of the second region, the maximum value of the height Ht of the protrusion 20 is preferably 2 mm or more, more preferably 2.5 mm or more, and even more preferably 3 mm or more. If the height Ht is too large, an additional area is generated at Af15 in the 15-degree position, increasing the air resistance of the first region. From this viewpoint, the maximum value of the height Ht of the protrusion 20 is preferably 12 mm or less, more preferably 10 mm or less, and even more preferably 8 mm or less.

[0110] Even if the protrusion forms the outline of the projection, there are cases where a silhouette convex portion is not formed in the projection. For example, if the protrusion reaches the outer peripheral edge of the crown portion and extends along this outer peripheral edge, a silhouette convex portion may not be formed. However, even in such cases, the protrusion increases the projected area WAθ in the projection.

[0111] Fig. 18 is a plan view of the head 104 of the second embodiment. Fig. 19 is a perspective view of the head 104 with the sole 114 facing upward, viewed from the back-toe side. Fig. 20(a) shows the head 104 in a 0-degree state. Fig. 21(a) shows the head 104 in a 15-degree state. Fig. 22(a) shows the head 104 in a 90-degree state. In Figs. 20(a), 21(a), and 22(a), the projection direction PD1 is perpendicular to the paper surface.

[0112] Fig. 20(b) is a diagram in which a projection of the head 104 at a 0-degree angle is divided into two regions by the shaft axis line Z. Fig. 21(b) is a diagram in which a projection of the head 104 at a 15-degree angle is divided into two regions by the shaft axis line Z. Fig. 22(b) is a diagram in which a projection of the head 104 at a 90-degree angle is divided into two regions by the shaft axis line Z.

[0113] The head 104 has a face portion 110, a crown portion 112, a sole portion 114, and a hosel portion 116. The face portion 110 has a hitting face 110a. The hitting face 110a is the outer surface of the face portion 110. The crown portion 112 forms a crown outer surface 112a. The sole portion 114 forms a sole outer surface 114a. The hosel portion 116 has a shaft hole 116a.

[0114] The striking face 110a has a face center Fc defined as above. The striking face 110a has a normal Lf. The normal Lf is the normal at the face center Fc.

[0115] The head 104 has a protrusion 120 on its outer surface. In this embodiment, the protrusion 120 is provided on the sole portion 114. The sole portion 114 has the protrusion 120 on the crown outer surface 114a. Although not shown, the protrusion 120 is hollow. The protrusion 120 forms a convex on the sole outer surface 114a and a concave on the sole inner surface. The protrusion 120 may be solid. The protrusion 120 is located on the back side of the sole portion 114. The protrusion 120 is located on the back side of the center of gravity of the head 104.

[0116] In this embodiment, the entire protrusion 120 is provided on the sole outer surface 114a, and does not extend to any part other than the sole outer surface 114a.

[0117] 20(b), the area of the portion hatched with dashed lines is Af0, and the area of the portion hatched with solid lines is Ab0. The sum of Af0 and Ab0 is WA0.

[0118] 21(b), the area of the portion hatched with dashed lines is Af15, and the area of the portion hatched with solid lines is Ab15. The sum of Af15 and Ab15 is WA15.

[0119] 22(b), the area of the portion hatched with dashed lines is Af90, and the area of the portion hatched with solid lines is Ab90. The sum of Af90 and Ab90 is WA90.

[0120] As shown in FIG. 22(a), the protrusion 120 of the head 104 is visible in a projection at a 90-degree angle. As shown in FIG. 22(b), the protrusion 120 forms an outer contour in a projection at a 90-degree angle. The protrusion 120 affects Ab90. The protrusion 120 increases Ab90. The protrusion 120 does not increase Af90. As shown in FIG. 20(a), the protrusion 120 of the head 104 is visible in a projection at a 0-degree angle. As shown in FIG. 20(b), the protrusion 120 forms an outer contour in a projection at a 0-degree angle. However, the effect of the protrusion 120 on Af0 is small. The protrusion 120 barely increases Af0. The protrusion 120 does not increase Ab0. As shown in FIG. 21(a), in the head 104, the protrusion 120 is not visible in the projection view at a 15-degree angle. As shown in FIG. 21(b), the protrusion 120 does not form an outer contour line in the projection view at a 15-degree angle. The protrusion 120 does not affect Af15. The protrusion 120 does not increase Af15. The protrusion 120 does not increase Ab15. The protrusion 120 contributes to reducing S90 while not increasing S15. The protrusion 120 contributes to reducing the ratio (WA90 / Ab90) while not increasing the ratio (WA15 / Ab15). The protrusion 120 contributes to increasing the ratio (|S90| / |S15|).

[0121] As shown in Figure 22(b), the projection at a 90-degree angle has a silhouette convex portion 130. As described above, the protrusion 120 is visible in the projection at a 90-degree angle. The silhouette convex portion 130 is formed by the protrusion 120. The silhouette convex portion 130 expands Ab90.

[0122] As shown in Figure 20(b), the projection in the 0 degree state has a silhouette convex portion 132. The silhouette convex portion 132 is formed by the protrusion 120. Af0 is expanded by the silhouette convex portion 132. However, the additional area by the silhouette convex portion 132 is small.

[0123] In the 90-degree state, the protrusion 120 forms an additional area in the second region and no additional area in the first region (FIGS. 22(a) and 22(b)). In the 15-degree state, the protrusion 120 forms no additional area in the first region and no additional area in the second region (FIGS. 21(a) and 21(b)). In the 0-degree state, the protrusion 120 forms almost no additional area in the first region and no additional area in the second region (FIGS. 20(a) and 20(b)). The additional area in the second region in the 90-degree state is defined as D90. The additional area in the first region in the 15-degree state is defined as M15. The additional area in the first region in the 0-degree state is defined as M0. As described above, M0 is small in the head 104. From the viewpoint of face rotation, M0 / D90 is preferably equal to or less than 0.3, more preferably equal to or less than 0.2, more preferably equal to or less than 0.1, and more preferably equal to or less than 0. M15 / D90 is preferably equal to or less than 0.3, more preferably equal to or less than 0.2, more preferably equal to or less than 0.1, and most preferably 0. In the head 104, the additional area M15 is zero.

[0124] Fig. 23 is a plan view of the head 204 of the third embodiment. Fig. 24 is a perspective view of the head 204 with the sole 214 facing upward, viewed from the heel back side. Fig. 25(a) shows the head 204 in a 0 degree state. Fig. 26(a) shows the head 204 in a 15 degree state. Fig. 27(a) shows the head 204 in a 90 degree state. In Fig. 25(a), Fig. 26(a), and Fig. 27(a), the projection direction PD1 is perpendicular to the paper surface.

[0125] Fig. 25(b) is a diagram in which a projection of the head 204 at a 0-degree angle is divided into two regions by the shaft axis line Z. Fig. 26(b) is a diagram in which a projection of the head 204 at a 15-degree angle is divided into two regions by the shaft axis line Z. Fig. 27(b) is a diagram in which a projection of the head 204 at a 90-degree angle is divided into two regions by the shaft axis line Z.

[0126] The head 204 has a face portion 210, a crown portion 212, a sole portion 214, and a hosel portion 216. The face portion 210 has a hitting face 210a. The hitting face 210a is the outer surface of the face portion 210. The crown portion 212 forms a crown outer surface 212a. The sole portion 214 forms a sole outer surface 214a. The hosel portion 216 has a shaft hole 216a.

[0127] The striking face 210a has a face center Fc defined as above. The striking face 210a has a normal Lf. The normal Lf is the normal at the face center Fc.

[0128] The head 204 has a protrusion 220 on its outer surface. In this embodiment, the protrusion 220 is provided on the sole portion 214. The sole portion 214 has the protrusion 220 on the sole outer surface 214a. Although not shown, the protrusion 220 is hollow. The protrusion 220 forms a convex portion on the sole outer surface 214a and a concave portion on the sole inner surface. The protrusion 220 may be solid.

[0129] The protrusion 220 is located on the heel side of the sole portion 214. The protrusion 220 is located on the heel side of the center of gravity of the head 204. The protrusion 220 is located on the heel side of the shaft axis line Z. The head 204 does not have a skirt portion (side portion). The sole outer surface 214a of the head 204 extends to the outer edge of the crown surface 212a. If the head has a skirt portion between the crown portion 212 and the sole portion 214, the protrusion 220 may be provided on this skirt portion.

[0130] 25(b), the area of the portion hatched with dashed lines is Af0, and the area of the portion hatched with solid lines is Ab0. The sum of Af0 and Ab0 is WA0.

[0131] 26(b), the area of the portion hatched with dashed lines is Af15, and the area of the portion hatched with solid lines is Ab15. The sum of Af15 and Ab15 is WA15.

[0132] 27(b), the area of the portion hatched with dashed lines is Af90, and the area of the portion hatched with solid lines is Ab90. The sum of Af90 and Ab90 is WA90.

[0133] As shown in FIG. 27(a), in the head 204, the protrusion 220 is visible in the projection at a 90-degree angle. However, as shown in FIG. 27(b), in the projection at a 90-degree angle, the protrusion 220 does not form an outer contour. The protrusion 220 does not affect Ab90. The protrusion 220 does not increase Ab90. The protrusion 220 does not affect Af90. The protrusion 220 does not increase Af90. As shown in FIG. 25(a), in the head 204, the protrusion 220 is visible in the projection at a 0-degree angle. As shown in FIG. 25(b), the protrusion 220 forms an outer contour in the projection at a 0-degree angle. The protrusion 220 increases Ab0. On the other hand, the protrusion 220 does not increase Af0. As shown in FIG. 26(a), the protrusion 220 of the head 204 is visible in a projection at a 15-degree angle. As shown in FIG. 26(b), the protrusion 220 forms an outer contour in a projection at a 15-degree angle. The protrusion 220 increases Ab15. On the other hand, the protrusion 220 does not affect Af15. The protrusion 220 does not increase Af15. The protrusion 220 also contributes to reducing S15 without increasing S90. The protrusion 220 also contributes to reducing the ratio (WA15 / Ab15) without increasing the ratio (WA90 / Ab90). The protrusion 220 contributes to increasing the ratio (|S90| / |S15|).

[0134] As shown in FIG. 26(b), in the projection at 15 degrees, the outline of the head 204 has a silhouette convex portion 230. The silhouette convex portion 230 is formed by the protrusion 220. The silhouette convex portion 230 expands Ab15. In the projection at 15 degrees, Ab15 has an additional area added by the protrusion 220.

[0135] As shown in FIG. 25(b), in the projection at the 0-degree angle, the outline of the head 204 has a silhouette convex portion 232. The silhouette convex portion 232 is formed by the protrusion 220. The silhouette convex portion 232 expands Ab0. In the projection at the 0-degree angle, Ab0 has an additional area added by the protrusion 220. The additional area at the 0-degree angle is larger than the additional area at the 15-degree angle.

[0136] In the 90 degree state, the protrusion 220 does not form an additional area in the second region and does not form an additional area in the first region (FIGS. 27(a) and 27(b)). In the 15 degree state, the protrusion 220 does not form an additional area in the first region and forms an additional area in the second region (FIGS. 26(a) and 26(b)). In the 0 degree state, the protrusion 220 does not form an additional area in the first region and forms an additional area in the second region (FIGS. 25(a) and 25(b)).

[0137] At the start of face rotation (90 degrees), Abθ is greater than Afθ. Therefore, S90 is negative. As face rotation progresses, θ decreases continuously from 90° to 0°. As θ decreases, Afθ increases and Abθ decreases. Just before impact, Afθ is greater than Abθ. In other words, S15 is positive.

[0138] As θ changes continuously from 90° to 0°, the difference (Afθ - Abθ) changes from negative to positive. Therefore, there exists a θ when Afθ and Abθ are the same and the difference (Afθ - Abθ) is zero. In other words, there exists a θ when Sθ is zero.

[0139] When Sθ is negative, the projected area Abθ of the second region is larger than the projected area Afθ of the first region. Because Abθ is relatively large, face rotation can be promoted. Increasing the time during which Sθ is negative during the downswing can lengthen the time during which face rotation is assisted. From this perspective, θ when Sθ is zero is preferably 55° or less, more preferably 53° or less, more preferably 52° or less, and still more preferably 51° or less. From the perspective of achieving a natural head shape, θ when Sθ is zero is preferably 43° or more, more preferably 45° or more, and still more preferably 47° or more.

[0140] As mentioned above, at the start of face rotation, Abθ is large and the ratio (WAθ / Abθ) is less than 2.0. That is, WA90 / Ab90 is less than 2.0. As face rotation progresses and θ decreases, Abθ decreases and Afθ increases. As θ continuously changes from 90° to 0°, Afθ and Abθ become the same, and WAθ / Abθ becomes 2.0. Just before impact, WA15 / Ab15 is greater than 2.0. At impact, WA0 / Ab0 is greater than 2.0.

[0141] When WAθ / Abθ is smaller than 2.0, Abθ is larger than Afθ. Increasing the time during which WAθ / Abθ is smaller than 2.0 can increase the time during which face rotation is assisted. From this perspective, θ when WAθ / Abθ is 2.0 is preferably 55° or less, more preferably 53° or less, more preferably 52° or less, and still more preferably 51° or less. From the perspective of achieving a natural head shape, θ when WAθ / Abθ is 2.0 is preferably 43° or more, more preferably 45° or more, and still more preferably 47° or more.

[0142] (S15-S0) / 15 is the rate of change of Sθ with respect to θ immediately before impact (θ is 0 to 15°). As the angle shifts from the 15-degree state (immediately before impact) to the 0-degree state (impact), Afθ increases, and Sθ also increases. Therefore, (S15-S0) / 15 is a negative value. Immediately before impact, the head speed accelerates, increasing the influence of air resistance. By reducing the absolute value of this rate of change, Afθ is suppressed when θ is between 0 and 15 degrees, making it easier for the face to return. From this perspective, (S15-S0) / 15 is preferably greater than -45, more preferably greater than -35, and even more preferably greater than -30. If the face returns too much, the ball will suddenly hook (known as a "cheep-in" in Japanese or a "duck hook" in English). In respect of preventing such hits, (S15-S0) / 15 is preferably equal to or less than -10, more preferably equal to or less than -15, and still more preferably equal to or less than -20.

[0143] (S30-S15) / 15 is the rate of change of Sθ with respect to θ before impact (θ is 15 to 30°). As the angle changes from the 30-degree state (before impact) to the 15-degree state (just before impact), Afθ increases, and Sθ also increases. Therefore, like (S15-S0) / 15, (S30-S15) / 15 is a negative value. By making the absolute value of the rate of change when θ is in the range of 0 to 15° smaller than the absolute value of the rate of change when θ is in the range of 15 to 30°, Afθ is suppressed when θ is in the range of 0 to 15°, making it easier for the face to return. From this perspective, it is preferable that (S30-S15) / 15 is smaller than (S15-S0) / 15. In other words, it is preferable that the following relationship holds: SL 0-15 >SL 15-30 However, SL 0-15 is [(S15-S0) / 15], and SL 15-30 is [(S30-S15) / 15]. As mentioned above, SL 0-15 and SL 15-30 are both negative values, the magnitude relationship is reversed when comparing absolute values.

[0144] In Figure 2, the double-headed arrow H1 indicates the head length in the toe-heel direction. With the head in the reference state, a plane XP is determined that is parallel to the ground plane GP and 0.875 inches above the ground plane GP. The point on the heel side of the intersection between this plane XP and the outer surface of the head is determined to be the heel reference point Ph. This heel reference point Ph is determined to be the starting point on the heel side of the head length H1. In Figure 18, the double-headed arrow W1 indicates the head width in the face-back direction.

[0145] A large head has a large moment of inertia and a wide sweet spot, but it also has high air resistance. In the present disclosure, this air resistance can be utilized to increase the force in the direction of closing the face, thereby improving the ability to hit the ball. From this perspective, a large head is preferable.

[0146] From the viewpoint of utilizing air resistance to improve grip and the moment of inertia, the head width W1 in the face-back direction is preferably 100 mm or more, more preferably 101 mm or more, and still more preferably 102 mm or more. From the viewpoint of the golf rules that regulate head volume, the head width W1 is preferably 127 mm or less, more preferably 126 mm or less, and still more preferably 125 mm or less.

[0147] From the viewpoint of utilizing air resistance to improve grip and the viewpoint of the moment of inertia, the head length H1 in the toe-heel direction is preferably 110 mm or more, more preferably 111 mm or more, and still more preferably 112 mm or more. From the viewpoint of the golf rules that regulate head volume, the head length H1 is preferably 129 mm or less, more preferably 128 mm or less, and still more preferably 127 mm or less.

[0148] From the perspective of utilizing air resistance to improve grip and the moment of inertia, the head volume is 400cm 3 More than 410cm is preferable. 3 More than 420cm is preferable. 3 More than 430cm is preferable.3 More than 440cm is preferable. 3 More than 450cm is preferable. 3 From the viewpoint of golf rules, the head volume is 470 cm 3 Less than 465cm is preferable. 3 Less than 460cm is preferable. 3 The following is more preferred:

[0149] The double-headed arrow FP in Figure 18 indicates face progression. The face progression FP is the length from the shaft axis Z to the frontmost point of the head. The face progression FP is measured along the face-back direction.

[0150] If the face progression FP is excessively small, the head shape will feel unnatural. From this viewpoint, the face progression FP is preferably equal to or greater than 13 mm, more preferably equal to or greater than 14 mm, and still more preferably equal to or greater than 15 mm. If the face progression FP is excessively large, the head shape will feel unnatural. From this viewpoint, the face progression FP is preferably equal to or less than 23 mm, more preferably equal to or less than 22 mm, and still more preferably equal to or less than 21 mm.

[0151] Fig. 28 is a plan view of the head 304 of a reference example. Fig. 29 is a perspective view of the head 304 with the sole 314 facing upward, viewed from the heel back side. Fig. 30(a) shows the head 304 in a 0-degree state. Fig. 31(a) shows the head 304 in a 15-degree state. Fig. 32(a) shows the head 304 in a 90-degree state. In Figs. 30(a), 31(a), and 32(a), the projection direction PD1 is perpendicular to the paper surface.

[0152] Fig. 30(b) is a diagram in which a projection of the head 304 at a 0-degree angle is divided into two regions by the shaft axis line Z. Fig. 31(b) is a diagram in which a projection of the head 304 at a 15-degree angle is divided into two regions by the shaft axis line Z. Fig. 32(b) is a diagram in which a projection of the head 304 at a 90-degree angle is divided into two regions by the shaft axis line Z.

[0153] The head 304 has a face portion 310, a crown portion 312, a sole portion 314, and a hosel portion 316. The face portion 310 has a hitting face 310a. The hitting face 310a is the outer surface of the face portion 310. The crown portion 312 forms an outer crown surface 312a. The sole portion 314 forms an outer sole surface 314a. The hosel portion 316 has a shaft hole 316a.

[0154] No protrusions are provided on the outer surface of head 304. In all projections of head 304, there is no additional area due to the protrusions. Ab90 (FIG. 32(b)) has no additional area due to the protrusions. Ab15 (FIG. 31(b)) has no additional area due to the protrusions. Ab0 (FIG. 30(b)) has no additional area due to the protrusions.

[0155] If the head 304 is made shallower, Af15 and Af0 decrease, but Ab90 also decreases. Therefore, the force that causes the face 10a to close can decrease in the initial stage of face rotation. A shallow head is a head with a small vertical dimension.

[0156] If the head 304 is made deeper, Ab90 increases, but Af15 and Af0 also increase. This can increase the force that opens the face 10a near impact. Also, air resistance experienced by the entire head 304 near impact increases, which can decrease head speed. A deep head is a head with a large vertical dimension. [Example]

[0157] The effects of the present disclosure will be clarified below by examples, but the present disclosure should not be interpreted as being limited based on the description of these examples.

[0158] [Examples 1 to 3] As Example 1, a head having the same shape as head 4 of the first embodiment was created. As Example 2, a head having the same shape as head 104 of the second embodiment was created. As Example 3, a head having the same shape as head 204 of the third embodiment was created.

[0159] [Comparative Examples 1 to 5] Comparative Example 1 was a driver head manufactured by Sumitomo Rubber Industries, Ltd. under the trade name "XXIO 10 PRIME." Comparative Example 2 was a driver head manufactured by Sumitomo Rubber Industries, Ltd. under the trade name "SRIXON Z725" (loft angle 10.5 degrees). Comparative Example 3 was a driver head manufactured by Sumitomo Rubber Industries, Ltd. under the trade name "SRIXON ZR-30" (loft angle 10.5 degrees). Comparative Example 4 was a driver head manufactured by Sumitomo Rubber Industries, Ltd. under the trade name "SRIXON ZR-700" (loft angle 10.5 degrees). Comparative Example 5 was a driver head manufactured by Sumitomo Rubber Industries, Ltd. under the trade name "XXIO 11" (loft angle 10.5 degrees). As with the above-mentioned reference examples, Comparative Examples 1 to 5 did not have protrusions on the crown or sole.

[0160] Comparative Example 6 FIG. 33 is a plan view of the head 404 of Comparative Example 6, viewed from the crown side. FIG. 34(a) is a projection of the head 404 at a 0-degree angle. FIG. 34(b) is a diagram in which the projection area at the 0-degree angle is divided into a first region and a second region by the shaft axis. FIG. 35(a) is a projection of the head 404 at a 15-degree angle. FIG. 35(b) is a diagram in which the projection area at the 15-degree angle is divided into a first region and a second region by the shaft axis. FIG. 36(a) is a projection of the head 404 at a 90-degree angle. FIG. 36(b) is a diagram in which the projection area at the 90-degree angle is divided into a first region and a second region by the shaft axis. The head 404 has a face portion 410, a crown portion 412, a sole portion 414, and a hosel portion 416. The face portion 410 has a hitting face 410a. The crown portion 412 forms a crown outer surface 412a. The sole portion 414 forms a sole outer surface 414a. The hosel portion 416 has a shaft hole 416a. The head 404 has a protrusion in the approximate center of the sole outer surface 414a. Clubs equipped with the head of Comparative Example 6 are currently widely available on the market.

[0161] The specifications and evaluation results of the example are shown in Table 1 below. The specifications and evaluation results of the comparative example are shown in Table 2 below.

[0162] [Table 1]

[0163] [Table 2]

[0164] As these evaluation results show, the superiority of the present disclosure is clear.

[0165] The following notes are provided regarding the above-described embodiments. [Appendix 1] a face portion that forms a hitting face; a crown portion forming an outer surface of the crown; a sole portion forming an outer surface of the sole; a hosel portion to which a shaft is attached and to which a shaft axis is determined; A golf club head having: the striking face having a face center and a normal at the face center; The head width in the face-back direction is 100 mm or more, The head length in the toe-heel direction is 110 mm or more, The shaft axis is disposed perpendicular to a horizontal plane, and a state in which the normal line is parallel to a first vertical plane including the shaft axis is defined as a 0 degree state. a direction parallel to the first vertical plane and parallel to the horizontal plane is set as a projection direction; When the head is rotated θ degrees from the 0 degree state toward the back side with the shaft axis as the rotation axis, the projected area of the head in the projected direction (where θ is 0 to 90) is WAθ (mm 2 ) and The projected area is divided into two regions by the shaft axis, and of these, a region that receives a force in a direction to open the hitting face due to air resistance during the downswing is defined as a first region, and a region that receives a force in a direction to close the hitting face due to air resistance is defined as a second region, The area of the first region is Afθ (mm 2 ) and The area of the second region is Abθ (mm 2 ) and The difference (Afθ-Abθ) is Sθ (mm 2 ) when S90 is -4500 (mm 2 ) or less, S15 is 4700 (mm 2 ) Golf club head. [Appendix 2] a face portion forming a hitting face; a crown portion forming an outer surface of the crown; a sole portion forming an outer surface of the sole; a hosel portion to which a shaft is attached and to which a shaft axis is determined; A golf club head having: the striking face having a face center and a normal at the face center; The head width in the face-back direction is 100 mm or more, The head length in the toe-heel direction is 110 mm or more, The shaft axis is disposed perpendicular to a horizontal plane, and a state in which the normal line is parallel to a first vertical plane including the shaft axis is defined as a 0 degree state. a direction parallel to the first vertical plane and parallel to the horizontal plane is set as a projection direction; When the head is rotated θ degrees from the 0 degree state toward the back side with the shaft axis as the rotation axis, the projected area of the head in the projected direction (where θ is 0 to 90) is WAθ (mm 2 ) and The projected area is divided into two regions by the shaft axis, and of these, a region that receives a force in a direction to open the hitting face due to air resistance during the downswing is defined as a first region, and a region that receives a force in a direction to close the hitting face due to air resistance is defined as a second region, The area of the first region is Afθ (mm 2 ) and The area of the second region is Abθ (mm 2 ) and The difference (Afθ-Abθ) is Sθ (mm 2 ) when The ratio (WA90 / Ab90) is 1.205 or less, A golf club head having a ratio (WA15 / Ab15) of 7.00 or less. [Appendix 3] a face portion that forms a hitting face; a crown portion forming an outer surface of the crown; a sole portion forming an outer surface of the sole; a hosel portion to which a shaft is attached and to which a shaft axis is determined; A golf club head having: the striking face having a face center and a normal at the face center; The head width in the face-back direction is 100 mm or more, The head length in the toe-heel direction is 110 mm or more, The shaft axis is disposed perpendicular to a horizontal plane, and a state in which the normal line is parallel to a first vertical plane including the shaft axis is defined as a 0 degree state. a direction parallel to the first vertical plane and parallel to the horizontal plane is set as a projection direction; When the head is rotated θ degrees from the 0 degree state toward the back side with the shaft axis as the rotation axis, the projected area of the head in the projected direction (where θ is 0 to 90) is WAθ (mm 2 ) and The projected area is divided into two regions by the shaft axis, and of these, a region that receives a force in a direction to open the hitting face due to air resistance during the downswing is defined as a first region, and a region that receives a force in a direction to close the hitting face due to air resistance is defined as a second region, The area of the first region is Afθ (mm 2 ) and The area of the second region is Abθ (mm 2 ) and The difference (Afθ-Abθ) is Sθ (mm 2 ) when A golf club head having a ratio (|S90| / |S15|) of 1.00 or more. Here, |S90| means the absolute value of S90, and |S15| means the absolute value of S15. [Appendix 4] 4. The golf club head according to any one of claims 1 to 3, wherein θ is 55° or less when Sθ is zero. [Appendix 5] 5. The golf club head according to any one of claims 1 to 4, wherein θ is 55° or less when the ratio (WAθ / Abθ) is 2.0. [Appendix 6] (S15-S0) / 15 is -35(mm 2 / deg). [Appendix 7] Head volume is 400cm 3 The golf club head according to any one of Supplementary Notes 1 to 6 above. [Appendix 8] 8. The golf club head according to any one of claims 1 to 7, wherein the face progression is 13 mm or more and 23 mm or less. [Appendix 9] A protrusion is provided on the outer surface of the head, 9. The golf club head according to any one of claims 1 to 8, wherein the protrusion increases Ab90 and does not increase Af15. [Appendix 10] 10. The golf club head according to claim 9, wherein the protrusion is provided on the outer surface of the crown. [Explanation of symbols]

[0166] 2. Golf clubs 4, 104, 204, 304... head 6. Shaft 10, 110, 210, 310...Face part 10a, 110a, 210a, 310a... Hitting face (face) 12, 112, 212, 312... Crown part 12a, 112a, 212a, 312a... Crown outer surface 14, 114, 214, 314... Sole part 14a, 114a, 214a, 314a... Sole outer surface 16, 116, 216, 316... Hosel part 20, 120, 220...protrusion Z: Shaft axis PD1...Projection direction

Claims

1. a face portion that forms a hitting face; a crown portion forming an outer surface of the crown; a sole portion forming an outer surface of the sole; a hosel portion to which a shaft is attached and to which a shaft axis is determined; A golf club head having: the striking face having a face center and a normal at the face center; The head width in the face-back direction is 100 mm or more, The head length in the toe-heel direction is 110 mm or more, The shaft axis is disposed perpendicular to a horizontal plane, and a state in which the normal line is parallel to a first vertical plane including the shaft axis is defined as a 0 degree state, a direction parallel to the first vertical plane and parallel to the horizontal plane is set as a projection direction; When the golf club head is rotated θ degrees from the 0 degree state to the back side with the shaft axis as the rotation axis, the projected area of the golf club head in the projected direction (where θ is 0 to 90) is WAθ (mm ２ ) and the projected area is divided into two regions by the shaft axis, and of these, a region that receives a force in a direction to open the hitting face due to air resistance during a downswing is defined as a first region, and a region that receives a force in a direction to close the hitting face due to air resistance is defined as a second region; The area of the first region is Afθ (mm ２ ) and The area of the second region is Abθ (mm ２ ) and The difference (Afθ-Abθ) is Sθ (mm ２ ) when S90 is -4500 (mm ２ ) or less, S15 is 4700 (mm ２ ) a golf club head that is less than or equal to:

2. a face portion that forms a hitting face; a crown portion forming an outer surface of the crown; a sole portion forming an outer surface of the sole; a hosel portion to which a shaft is attached and to which a shaft axis is determined; A golf club head having: the striking face having a face center and a normal at the face center; The head width in the face-back direction is 100 mm or more, The head length in the toe-heel direction is 110 mm or more, The shaft axis is disposed perpendicular to a horizontal plane, and a state in which the normal line is parallel to a first vertical plane including the shaft axis is defined as a 0 degree state, a direction parallel to the first vertical plane and parallel to the horizontal plane is set as a projection direction; When the golf club head is rotated θ degrees from the 0 degree state to the back side with the shaft axis as the rotation axis, the projected area of the golf club head in the projected direction (where θ is 0 to 90) is WAθ (mm ２ ) and the projected area is divided into two regions by the shaft axis, and of these, a region that receives a force in a direction to open the hitting face due to air resistance during a downswing is defined as a first region, and a region that receives a force in a direction to close the hitting face due to air resistance is defined as a second region; The area of the first region is Afθ (mm ２ ) and The area of the second region is Abθ (mm ２ ) and The difference (Afθ-Abθ) is Sθ (mm ２ ) when The ratio (WA90 / Ab90) is 1.205 or less, A golf club head having a ratio (WA15 / Ab15) of 7.00 or less.

3. a face portion that forms a hitting face; a crown portion forming an outer surface of the crown; a sole portion forming an outer surface of the sole; a hosel portion to which a shaft is attached and to which a shaft axis is determined; A golf club head having: the striking face having a face center and a normal at the face center; The head width in the face-back direction is 100 mm or more, The head length in the toe-heel direction is 110 mm or more, The shaft axis is disposed perpendicular to a horizontal plane, and a state in which the normal line is parallel to a first vertical plane including the shaft axis is defined as a 0 degree state, a direction parallel to the first vertical plane and parallel to the horizontal plane is set as a projection direction; When the golf club head is rotated θ degrees from the 0 degree state to the back side with the shaft axis as the rotation axis, the projected area of the golf club head in the projected direction (where θ is 0 to 90) is WAθ (mm ２ ) and The projected area is divided into two regions by the shaft axis, and of these, a region that receives a force in a direction to open the hitting face due to air resistance during a downswing is defined as a first region, and a region that receives a force in a direction to close the hitting face due to air resistance is defined as a second region, The area of the first region is Afθ (mm ２ ) and The area of the second region is Abθ (mm ２ ) and The difference (Afθ-Abθ) is Sθ (mm ２ ) when A golf club head having a ratio (|S90| / |S15|) of 1.00 or more. Here, |S90| means the absolute value of S90, and |S15| means the absolute value of S15.

4. 4. The golf club head according to claim 1, wherein θ is 55° or less when Sθ is zero.

5. 5. The golf club head according to claim 1, wherein θ is 55° or less when the ratio (WAθ / Abθ) is 2.

0.

6. (S15-S0) / 15 is -35 (mm ２ 6. The golf club head according to claim 1, wherein the angle of curvature is greater than 1 / deg.

7. Head volume is 400 cm ３ 7. The golf club head according to claim 1, wherein the first and second shafts are arranged parallel to each other.

8. 8. The golf club head according to claim 1, wherein a face progression is equal to or greater than 13 mm and equal to or less than 23 mm.

9. a protrusion is provided on the outer surface of the golf club head; 9. The golf club head according to claim 1, wherein the protrusion increases Ab90 and does not increase Af15.

10. The golf club head according to claim 9 , wherein the protrusion is provided on the outer surface of the crown.

Images