Golf club head

A head includes a face, a sole and a crown. The crown includes a first region and a second region. The first region includes a peak portion of the crown. The first region includes a first thick portion and a narrow groove. The second region includes a second thick portion. The narrow groove extends from a toe side to a heel side so as to divide the first region. The second region extends from the toe side of the first region, through a back side of the first region, to the heel side of the first region. The second thick portion has a wall thickness smaller than that of the first thick portion.

The present application claims priority on Patent Application No. 2018-021537 filed in JAPAN on Feb. 9, 2018. The entire contents of this Japanese Patent Application are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present disclosure relates to a golf club head.

Description of the Related Art

In a hollow head, a golf club head in which a wall thickness of a crown changes has been disclosed (for example, see JP8-280853).

SUMMARY OF THE INVENTION

The inventor of the present application has found a crown that can achieve an advantageous effect heterogeneous from the effect of the conventional technique. An object of the present disclosure is to provide a golf club head capable of consistently achieving a great flight distance by a new structure of a crown thereof.

In one aspect, a golf club head may include a face, a sole and a crown. The crown may include a first region and a second region. The first region may include a peak portion of the crown. The first region may include a first thick portion and a narrow groove. The second region may include a second thick portion. The narrow groove may extend from a toe side to a heel side so as to divide the first region. The second region may extend from the toe side of the first region, through a back side of the first region, to the heel side of the first region. The second thick portion may have a wall thickness smaller than that of the first thick portion.

In another aspect, the crown may include a peak vicinity region that is located on an up-down direction position falling within 12 mm of the peak portion. The first thick portion may be included in the peak vicinity region.

In another aspect, the narrow groove may be formed on an inner surface of the crown.

In another aspect, the narrow groove may be formed on an outer surface of the crown.

A wall thickness of the crown in the first thick portion is denoted by T1(mm), a wall thickness of the crown in the second thick portion is denoted by T2(mm), and a wall thickness of the crown in the narrow groove is denoted by TG (mm). T1may be greater than T2. T2may be greater than TG.

In another aspect, the number of the narrow grooves may be greater than or equal to 1 and less than or equal to 8.

In another aspect, the narrow groove may extend along an upper end edge of the face.

In another aspect, the crown may further include a transition region located between the first region and the second region. The narrow groove may extend so as to divide the transition region.

In another aspect, the head may have a volume of greater than or equal to 400 cc.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following will describe embodiments in detail with appropriate reference to the drawings.

A reference state, a reference vertical plane, a face-back direction, a toe-heel direction, and an up-down direction are defined in the present application. A state where a head2is placed on a horizontal plane HP at a predetermined lie angle and real loft angle is defined as the reference state. As shown inFIG. 10, in the reference state, a plane VP perpendicular to the horizontal plane HP includes a center line Z of a hosel hole. The plane VP is defined as the reference vertical plane. The predetermined lie angle and real loft angle are described, for example, in a product catalogue.

In the present application, the toe-heel direction is the direction of an intersection line NL of the reference vertical plane VP and the horizontal plane HP (seeFIG. 10).

In the present application, the face-back direction is a direction that is perpendicular to the toe-heel direction and parallel to the horizontal plane HP.

In the present application, the up-down direction is a direction that is perpendicular to the toe-heel direction and perpendicular to the face-back direction. In other words, in the present application, the up-down direction is a direction that is perpendicular to the horizontal plane HP.

In the present application, a face center Fc is defined. The face center Fc is determined as follows. First, an arbitrary point Pr roughly in the vicinity of the center of a face surface in the up-down direction and the toe-heel direction is selected. Next, a plane that passes through the point Pr, extends along the direction of a line normal to the face surface at the point Pr, and is parallel to the toe-heel direction is determined. The line of intersection of the plane and the face surface is drawn, and a midpoint Px thereof is determined. Next, a plane that passes through the midpoint Px, extends along the direction of a line normal to the face surface at the point Px, and is parallel to the up-down direction is determined. The line of intersection of the plane and the face surface is drawn, and a midpoint Py thereof is determined. Next, a plane that passes through the midpoint Py, extends along the direction of a line normal to the face surface at the point Py, and is parallel to the toe-heel direction is determined. The line of intersection of the plane and the face surface is drawn, and a midpoint Px thereof is newly determined. Next, a plane that passes through the new midpoint Px, extends along the direction of a line normal to the face surface at the point Px, and is parallel to the up-down direction is determined. The line of intersection of the plane and the face surface is drawn, and a midpoint Py thereof is newly determined. By repeating this process, Px and Py are sequentially determined. During the repeat of this process, when the distance between a new midpoint Py and the immediately previous midpoint Py becomes 0.5 mm or less for the first time, the new position Py (the final position Py) is set as the face center Fc.

FIG. 1is a plan view of the golf club head2according to a first embodiment.FIG. 2is the same plan view asFIG. 1. InFIG. 2, lines on an inner surface of a crown are shown by dashed lines.FIG. 3is a cross-sectional view taken along line A-A inFIG. 2.FIG. 4is an enlarged cross-sectional view in which a part ofFIG. 3is enlarged.FIG. 5is a cross-sectional view taken along line B-B inFIG. 2.FIG. 6is a cross-sectional view taken along line C-C inFIG. 2.FIG. 7is an enlarged plan view in which a part of the crown inFIG. 2is enlarged.

The head2includes a face4, a crown6, a sole8, and a hosel10. The face4includes a hitting surface14. The crown6extends from an upper edge4aof the face4toward the back of the head. The sole8extends from a lower edge4bof the face4toward the back of the head. The hosel10includes a hosel hole12. The head2is hollow. The head2is a wood type golf club head.

The head2has a two-piece structure. Members constituting the head2are a face member P1and a head body P2. The face member P1and the head body P2are welded to each other to produce the head2. InFIG. 1, a boundary line k1between the face member P1and the head body P2is shown by a two-dot chain line.

The crown6includes an inner surface16and an outer surface18. The inner surface16is a curved surface that projects toward an outside of the head. The inner surface16faces a hollow portion of the head2. The inner surface16is not visually recognized in the finished head2. The outer surface18is a curved surface that projects toward the outside of the head. The whole outer surface18is smoothly continuous.

The crown6includes a peak portion pk. Of the crown6, a portion located on the uppermost position in the up-down direction is the peak portion pk. The peak portion pk is determined based on the position of the outer surface18of the crown6. The up-down direction position of the peak portion pk is the uppermost in the outer surface18. In the present embodiment, the outer surface18of the crown6is a curved surface that projects upward. The peak portion pk is substantially a point.

The crown6includes a first region R1and a second region R2. The first region R1is a region including the peak portion pk of the crown6. The second region R2extends from the toe side of the first region R1, through the back side of the first region R1, to the heel side of the first region R1. In a planar view, the second region R2preferably occupies 50% or more of the area of the crown6, more preferably occupies 60% or more of the area of the crown6, and still more preferably occupies 70% or more of the area of the crown6.

The crown6further includes a third region R3. The third region R3is adjacent to the upper edge4aof the face4. The third region R3extends from the toe side toward the heel side. The third region R3extends along the upper edge4aof the face4. The third region R3is located on the face side relative to the first region R1. The third region R3is located on the face side relative to the second region R2.

The first region R1has a semicircular shape that projects backward.

A double-pointed arrow D inFIG. 2shows a head width. The head width D is a face-back direction width of the head2. A position Pa and a position Pb shown inFIG. 2are two positions by which the head width D is divided into three equal parts. The position Pa is a position separated by (⅓)D from the backmost point in the head2. The position Pb is a position separated by (⅔)D from the backmost point in the head2.

The first region R1is located on the face side relative to the position Pa. The whole first region R1is located on the face side relative to the position Pa.

The first region R1, the second region R2and the third region R3will be described in detail later.

The crown6includes a narrow groove mz. The narrow groove mz is provided on the inner surface16of the crown6. The narrow groove mz may be provided on the outer surface18of the crown6. The narrow groove mz may be provided on both the inner surface16and the outer surface18of the crown6.

In the present embodiment, a plurality of narrow grooves mz are provided. In the present embodiment, the number of the narrow grooves mz is greater than or equal to 2. In the present embodiment, the number of the narrow grooves mz is 3. The crown6includes a narrow groove mz1located on the most face side, and a narrow groove mz3located on the most back side. The crown6further includes a narrow groove mz2located between the narrow groove mz1and the narrow groove mz3.

The narrow groove mz1located on the most face side extends from the toe side to the heel side. A toe-side end of the narrow groove mz1is located on the toe side relative to the face center Fc. The toe-side end of the narrow groove mz1is located on the toe side relative to the peak portion pk. A heel-side end of the narrow groove mz1is located on the heel side relative to the face center Fc. The heel-side end of the narrow groove mz1is located on the heel side relative to the peak portion pk.

The narrow groove mz3located on the most back side extends from the toe side to the heel side. A toe-side end of the narrow groove mz3is located on the toe side relative to the face center Fc. The toe-side end of the narrow groove mz3is located on the toe side relative to the peak portion pk. A heel-side end of the narrow groove mz3is located on the heel side relative to the face center Fc. The heel-side end of the narrow groove mz3is located on the heel side relative to the peak portion pk.

The narrow groove mz2located between the narrow groove mz1and the narrow groove mz3extends from the toe side to the heel side. A toe-side end of the narrow groove mz2is located on the toe side relative to the face center Fc. The toe-side end of the narrow groove mz2is located of the toe side relative to the peak portion pk. A heel-side end of the narrow groove mz2is located of the heel side relative to the face center Fc. The heel-side end of the narrow groove mz2is located on the heel side relative to the peak portion pk.

All the narrow grooves mz extend from the toe side to the heel side. The toe-side ends of all the narrow grooves mz are located on the toe side relative to the face center Fc. The toe-side ends of all the narrow grooves mz are located on the toe side relative to the peak portion pk. The heel-side ends of all the narrow grooves mz are located on the heel side relative to the face center Fc. The heel-side ends of all the narrow grooves mz are located on the heel side relative to the peak portion pk.

The narrow groove mz1extends substantially along the toe-heel direction. The absolute value of an angle between the narrow groove mz1and the toe-heel direction is preferably less than or equal to 20 degrees, more preferably less than or equal to 15 degrees, and still more preferably less than or equal to 10 degrees.

The narrow groove mz2extends substantially along the toe-heel direction. The absolute value of an angle between the narrow groove mz2and the toe-heel direction is preferably less than or equal to 20 degrees, more preferably less than or equal to 15 degrees, and still more preferably less than or equal to 10 degrees.

The narrow groove mz3extends substantially along the toe-heel direction. The absolute value of an angle between the narrow groove mz3and the toe-heel direction is preferably less than or equal to 20 degrees, more preferably less than or equal to 15 degrees, and still more preferably less than or equal to 10 degrees.

The angle between each narrow groove mz and the toe-heel direction means an angle formed by a width-direction center line L of the narrow groove mz and the toe-heel direction. As the width-direction center line L,FIG. 2shows a width-direction center line L1of the narrow groove mz1, a width-direction center line L2of the narrow groove mz2, and a width-direction center line L3of the narrow groove mz3. For determining the width-direction center line L, a face-back direction center point of an opening width of the narrow groove mz is considered. A set of the face-back direction center points is the width-direction center line L. The width-direction center line L is determined on the plan view (FIG. 2) of the head2. The angle formed by the width-direction center line L and the toe-heel direction is an angle on the plan view (FIG. 2) of the head2. The plan view is also referred to as a planar view.

The narrow groove mz1located on the most face side is the longest in the narrow grooves mz. The narrow groove mz3located on the most back side is the shortest in the narrow grooves mz. The narrow groove mz2is shorter than the narrow groove mz1. The narrow groove mz3is shorter than the narrow groove mz2. The narrow grooves mz are shortened toward the back side. The length of the narrow groove mz is measured along the toe-heel direction.

The narrow groove mz1is located on the back side relative to the hosel hole12. All the narrow grooves mz are located on the back side relative to the hosel hole12. The narrow groove mz1is located on the back side relative to a hosel end face12a. All the narrow grooves mz are located on the back side relative to the hosel end face12a.

The narrow groove mz1is located on the back side relative to the third region R3. All the narrow grooves mz are located on the back side relative to the third region R3.

A position Pc shown inFIG. 2is a position that divides the head width D into two equal parts. The position Pc is a position in the face-back direction.

The narrow groove mz3is located on the face side relative to the position Pc. All the narrow grooves mz are located on the face side relative to the position Pc.

The peak portion pk is located on the face side relative to the position Pc.

The peak portion pk is located on the toe side relative to the face center Fc. However, a toe-heel direction distance between the peak portion pk and the face center Fc is small. The toe-heel direction distance between the peak portion pk and the face center Fc is preferably less than or equal to 20 mm, and more preferably less than or equal to 15 mm.

As to the above-described position Pb, the narrow groove mz1is located on the face side relative to the position Pb. The narrow groove mz3is located on the back side relative to the position Pb. The location of the first region R1includes the position Pb.

The peak portion pk is located on the back side relative to the narrow groove mz1. The peak portion pk is located between the narrow groove mz1and the narrow groove mz2. The peak portion pk may be located on the face side relative to the narrow groove mz1. The peak portion pk may be located between the narrow groove mz2and the narrow groove mz3. The peak portion pk may be located on the back side relative to the narrow groove mz3.

The peak portion pk may be located on one of the narrow grooves mz. For example, the peak portion pk may be located on the narrow groove mz1. The peak portion pk may be located on the narrow groove mz2. The peak portion pk may be located on the narrow groove mz3.

As well shown inFIG. 3andFIG. 4, the first region R1includes a first thick portion M1. The first thick portion M1has a wall thickness of T1(mm). The first thick portion M1is a region having a wall thickness of T1. T1is the largest wall thickness in the crown6. The first thick portion M1is a largest wall-thickness portion that has the largest wall thickness in the crown6. The first thick portion M1is provided in the first region R1only.

The first region R1includes the first thick portion M1and the narrow grooves mz. More specifically, the first region R1includes the whole first thick portion M1and parts of the narrow grooves mz. The first region R1is constituted by only the first thick portion M1and the narrow grooves mz. The first region R1does not include the second thick portion M2.

Each narrow groove mz is formed by the first thick portion M1located on both sides of the narrow groove mz. The narrow groove mz is formed by the first thick portion M1adjacent to the face side of the narrow groove mz, and the first thick portion M1adjacent to the back side of the narrow groove mz. As shown in an enlarged portion ofFIG. 4, a face side surface ms1of the narrow groove mz is formed by a first thick portion M11adjacent to the face side of the narrow groove mz. Aback side surface ms2of the narrow groove mz is formed by a first thick portion M12adjacent to the back side of the narrow groove mz. The first thick portion M1is divided by the narrow grooves mz.

The second region R2includes the second thick portion M2. The second region R2further includes the narrow grooves mz. The second region R2includes the whole second thick portion M2and parts of the narrow grooves mz. The second region R2is constituted by only the second thick portion M2and the narrow grooves mz. The second thick portion M2is provided in the second region R2only. The second region R2does not include the first thick portion M1.

The second thick portion M2occupies almost the whole second region R2. Of the second region R2, a portion excluding the narrow grooves mz is the second thick portion M2. The ratio of the area of the second thick portion M2to the area of the second region R2is preferably greater than or equal to 90%, and more preferably greater than or equal to 95%. This ratio may be 100%.

The second thick portion M2has a wall thickness of T2(mm) (seeFIG. 4). The second thick portion M2is a region having a wall thickness of T2. T2is smaller than T1.

The crown6has a wall thickness in the narrow grooves mz of TG (mm) (seeFIG. 4). TG is smaller than T2. TG is smaller than T1. The narrow grooves mz are smallest wall-thickness portions having the smallest wall thickness in the crown6.

The third region R3has a wall thickness of T3(mm) (seeFIG. 4). T3is smaller than or equal to T1. T3may be equal to T1. T3may be smaller than T1. T3is greater than T2. T3may be smaller than T2. T3may be equal to T2.

In the present application, wall thicknesses of the crown, such as T1, T2, T3, T4, Tt and TG, are measured along the direction of a line normal to the outer surface18of the crown6. The direction of the normal line is determined at each measurement point.

As shown inFIG. 2, each narrow groove mz has a toe-side end Et and a heel-side end Eh. The narrow groove mz1includes a toe-side end Et1and a heel-side end Eh1. The narrow groove mz2includes a toe-side end Et2and a heel-side end Eh2. The narrow groove mz3includes a toe-side end Et3and a heel-side end Eh3.FIG. 5shows the toe-side end Et2of the narrow groove mz2and the heel-side end Eh2of the narrow groove mz2.

The crown6includes a transition region Rt. As shown inFIG. 2, the transition region Rt is located between the first region R1and the second region R2. As shown inFIG. 2, the transition region Rt has a half-annular shape. An inner boundary line k1of the transition region Rt is the boundary line between the first region R1and the transition region Rt. An outer boundary line k2of the transition region Rt is the boundary line between the transition region Rt and the second region R2.

The transition region Rt may not be present. The second region R2may be adjacent to the first region R1.

The transition region Rt includes a thickness transition portion Mt. As shown inFIG. 6, the thickness transition portion Mt has a wall thickness Tt of changing from T1to T2. Tt gradually changes from T1to T2. Tt is increased toward the first region R1. Tt is decreased toward the second region R2.

The transition region Rt includes the thickness transition portion Mt and the narrow grooves mz. More specifically, the transition region Rt includes the whole thickness transition portion Mt and parts of the narrow grooves mz. The transition region Rt is constituted by only the thickness transition portion Mt and the narrow grooves mz.

FIG. 7is a plan view in which a part ofFIG. 2is enlarged. InFIG. 7, the regions are shown using respective hatchings. The first region R1is shown by a solid-line hatching. The second region R2is shown by a dashed-line hatching. The third region R3is shown by a two-dot-chain-line hatching.

The crown6includes a fourth region R4. InFIG. 7, the fourth region R4is a plain portion without hatching. The fourth region R4is adjacent to the back side of the third region R3. The fourth region R4extends from the toe side to the heel side.

The fourth region R4can be a second thickness transition portion. The fourth region R4includes a portion located on a boundary between the third region R3and the second region R2. In this portion, the fourth region R4may have a wall thickness T4of gradually changing from T3to T2. The fourth region R4includes a portion located on a boundary between the third region R3and the first region R1. In this portion, the fourth region R4may have a wall thickness T4of gradually changing from T3to T1. T4is preferably smaller than T1.

As described above, the first region R1is shown by the solid-line hatching. As described above, the first region R1is a semicircular region. Of the first region R1, portions excluding the narrow grooves mz are the first thick portion M1. The narrow grooves mz are long and narrow regions surrounded by dashed lines.

As described above, the second region R2is shown by the dashed-line hatching. The second region R2is disposed so as to surround the transition region Rt on the toe side, the back side and the heel side. The transition region Rt is disposed so as to be adjacent to the outside of the first region R1, and the second region R2is disposed so as to be adjacent to the outside of the transition region Rt. Of the second region R2, a portion excluding the narrow grooves mz is the second thick portion M2. Toe-side end portions and heel-side end portions of the narrow grooves mz are located in the second region R2, and are not the second thick portion M2.

The transition region Rt is shown by a one-dot-chain-line hatching. The transition region Rt is a half-annular region. Of the transition region Rt, portions excluding the narrow grooves mz are the thickness transition portion Mt.

As shown inFIG. 7, the narrow groove mz1intersects the first region R1. The toe-side end portion of the narrow groove mz1reaches the second region R2by the narrow groove mz1being continuous from the first region R1and intersecting the transition region Rt. The heel-side end portion of the narrow groove mz1reaches the second region R2by the narrow groove mz1being continuing from the first region R1and intersecting the transition region Rt.

The narrow groove mz2intersects the first region R1. The toe-side end portion of the narrow groove mz2reaches the second region R2by the narrow groove mz2being continuous from the first region R1and intersecting the transition region Rt. The heel-side end portion of the narrow groove mz2reaches the second region R2by the narrow groove mz2being continuous from the first region R1and intersecting the transition region Rt.

The narrow groove mz3intersects the first region R1. The toe-side end portion of the narrow groove mz3reaches the second region R2by the narrow groove mz3being continuous from the first region R1and intersecting the transition region Rt. The heel-side end portion of the narrow groove mz3reaches the second region R2by the narrow groove mz3being continuous from the first region R1and intersecting the transition region Rt.

Thus, all the narrow grooves mz intersect the first region R1. The toe-side end portions of all the narrow grooves mz reach the second region R2by the narrow grooves mz being continuous from the first region R1and intersecting the transition region Rt. The heel-side end portions of all the narrow grooves mz reach the second region R2by the narrow grooves mz being continuous from the first region R1and intersecting the transition region Rt.

As shown inFIG. 7, the narrow groove mz1divides the first region R1. That is, the narrow groove mz1extends from a toe-side edge t10of the first region R1to a heel-side edge h10of the first region R1. The toe-side edge t10is located on the toe side relative to the peak portion pk. The heel-side edge h10is located on the heel side relative to the peak portion pk.

The narrow groove mz2divides the first region R1. That is, the narrow groove mz2extends from a toe-side edge t20of the first region R1to a heel-side edge h20of the first region R1. The toe-side edge t20is located on the toe side relative to the peak portion pk. The heel-side edge h20is located on the heel side relative to the peak portion pk.

The narrow groove mz3divides the first region R1. That is, the narrow groove mz3extends from a toe-side edge t30of the first region R1to a heel-side edge h30of the first region R1. The toe-side edge t30is located on the toe side relative to the peak portion pk. The heel-side edge h30is located on the heel side relative to the peak portion pk.

Thus, all the narrow grooves mz divide the first region R1.

As shown inFIG. 7, the narrow groove mz1divides the transition region Rt. The narrow groove mz1divides the transition region Rt at two locations. The narrow groove mz1divides the transition region Rt on the toe side and the heel side. On the toe side, the narrow groove mz1extends from an inner edge t10of the transition region Rt to an outer edge t12of the transition region Rt. On the heel side, the narrow groove mz1extends from an inner edge h10of the transition region Rt to an outer edge h12of the transition region Rt. The inner edge t10and the outer edge t12are located on the toe side relative to the peak portion pk. The inner edge h10and the outer edge h12are located on the heel side relative to the peak portion pk.

The narrow groove mz2divides the transition region Rt. The narrow groove mz2divides the transition region Rt at two locations. The narrow groove mz2divides the transition region Rt on the toe side and the heel side. On the toe side, the narrow groove mz2extends from an inner edge t20of the transition region Rt to an outer edge t22of the transition region Rt. On the heel side, the narrow groove mz2extends from an inner edge h20of the transition region Rt to an outer edge h22of the transition region Rt. The inner edge t20and the outer edge t22are located on the toe side relative to the peak portion pk. The inner edge h20and the outer edge h22are located on the heel side relative to the peak portion pk.

The narrow groove mz3divides the transition region Rt. The narrow groove mz3divides the transition region Rt at two locations. The narrow groove mz3divides the transition region Rt on the toe side and the heel side. On the toe side, the narrow groove mz3extends from an inner edge t30of the transition region Rt to an outer edge t32of the transition region Rt. On the heel side, the narrow groove mz3extends from an inner edge h30of the transition region Rt to an outer edge h32of the transition region Rt. The inner edge t30and the outer edge t32are located on the toe side relative to the peak portion pk. The inner edge h30and the outer edge h32are located on the heel side relative to the peak portion pk.

Thus, all the narrow grooves mz divide the transition region Rt. All the narrow grooves mz divide the transition region Rt at two locations. All the narrow grooves mz divide the transition region Rt on the toe side and the heel side.

In the present application, a peak vicinity region is defined. The peak vicinity region is a region that is located on an up-down direction position falling within X mm of the peak portion pk. The peak vicinity region is determined based on the outer surface18of the crown6. As shown inFIG. 8, of the peak portion pk, an outer peak point pk1located on the outer surface18of the crown6is determined. When the peak portion pk is a region, not a point, the outer peak point pk1is a center of figure of the region in the planar view.

A first virtual plane PL1that includes the outer peak point pk1is defined. The first virtual plane PL1is parallel to the horizontal plane HP. Moreover, a second virtual plane PL2that is located at a position separated downward by X mm from the outer peak point pk1is defined. The second virtual plane PL2is also parallel to the horizontal plane HP. Intersection lines L2of the second virtual plane PL2and the inner surface16of the crown6are determined. A portion surrounded by the intersection lines L2is the peak vicinity region Rp (seeFIG. 8).

The first thick portion M1is included in the peak vicinity region Rp located on the up-down direction position falling within X mm of the peak portion pk. The peak vicinity region Rp includes the whole first thick portion M1. The peak vicinity region Rp includes the whole first region R1.

If X (mm) for defining the peak vicinity region Rp is excessively large, the peak vicinity region Rp is too enlarged. In this respect, X (mm) is preferably 12 (mm). In light of further narrowing the peak vicinity region Rp thereby to concentrate a region in which the first thick portion M1is present in the vicinity of the outer peak point pk1, X (mm) may be 10 (mm), or may be 8.5 (mm).

As described above, in the head2, the narrow grooves mz are formed on the inner surface16of the crown6. In the head2, the narrow grooves mz are not formed on the outer surface18of the crown6.

The narrow grooves mz may be formed on the outer surface of the crown.FIG. 9shows a cross-sectional view of a head20according to a modification example. InFIG. 9, the head20includes a face24and a crown26. In the head20, the narrow grooves mz are formed on an outer surface28of the crown26. In the head20, the narrow grooves mz are not formed on an inner surface30of the crown26.

The narrow grooves mz may be formed on both the outer surface and the inner surface of the crown.

As described above, the first region R1is located on a position that includes the peak portion pk. The first region R1includes the first thick portion M1having a large wall thickness. The first region R1is constituted by only the first thick portion M1and the narrow grooves mz. A certain amount of weight is distributed to the upper portion of the crown by the presence of the first region R1, whereby an up-down MI is increased. The up-down MI means a moment of inertia of the head. When an axial line passing through the center of gravity of the head and extending in the toe-heel direction is denoted by ZL1, the up-down MI is the moment of inertia about the axial line ZL1. Thus, the first region R1achieves an effect of increasing the up-down MI.

The increase in the up-down MI suppresses deviations of the head resulting from variations of hitting points in the up-down direction. As a result, variations in flight distance can be decreased.

The inventor conducted an analysis of hitting points of high-level golf players such as professional golf players, and has found that high-level golf players often hit balls at an upper side relative to a sweet spot. By hitting a ball at an upper side relative to the sweet spot, the hitting surface is leaned toward a direction in which the loft angle is increased, and thus a dynamic loft is increased. As a result, a launch angle of the hit ball is increased. High-level golf players tend to prefer this increased launch angle.

However, as a result of hitting at an upper side relative to the sweet spot, the hitting point is likely to be located apart from the sweet spot. When the hitting point is located apart from the sweet spot, rebound performance deteriorates. The deterioration in rebound performance decreases flight distance.

In addition, when the hitting point is located apart from the sweet spot, a backspin rate is decreased due to a gear effect.

When the backspin rate is excessively low, a lifting force that acts on the hit ball is decreased. High-level golf players can intentionally add sidespin to hit a fade or a draw. When the backspin rate is excessively low, the lifting force becomes insufficient, whereby the flight distance deteriorates when the sidespin is added. As a result, controllability of the hit ball is worsened.

In the present embodiment, a certain amount of weight is distributed to the upper side by the presence of the first thick portion M1. For this reason, the sweet spot is shifted to the upper side to be closer to the hitting points. As a result, the rebound performance is enhanced. In addition, the gear effect is suppressed by making the sweet spot closer to the hitting points. For this reason, the backspin rate is increased, thereby suppressing reduction in flight distance when the sidespin is added. As a result, controllability of the hit ball is enhanced.

In addition, the whole first thick portion M1is located in the peak vicinity region Rp. For this reason, the sweet spot is shifted to the upper side to further enhance the rebound performance and the controllability of the hit ball.

The first thick portion M1increases the rigidity of the crown. The increased rigidity suppresses elastic deformation of the crown at hitting, and thus can reduce the rebound performance of the head. In the present embodiment, the narrow grooves mz extending from the toe side to the heel side are formed, whereby the rigidity of the crown against the hitting force can be reduced. As a result, reduction in rebound performance of the head is suppressed.

As described above, the narrow grooves mz extend so as to divide the first region R1. For this reason, the effect of reducing the rigidity of the crown is further enhanced.

As described above, the narrow grooves mz extend so as to divide the transition region Rt. For this reason, the effect of reducing the rigidity of the crown is further enhanced.

In the head2, the narrow grooves mz are formed on the inner surface16of the crown6. The crown6is bent so as to contract in the face-back direction by hitting. The narrow grooves mz formed on the inner surface16facilitates the bending of the crown6. Therefore, the rebound performance is enhanced. Note that like the head20shown inFIG. 9, the narrow grooves mz may be disposed on the outer surface of the crown. Also in this case, the rigidity of the crown is suppressed as compared with a crown having no narrow grooves mz.

As described above, the wall thickness T1of the first thick portion M1is greater than the wall thickness T2of the second thick portion M2. In light of increasing the weight of the first region R1, a ratio (T1/T2) is preferably greater than or equal to 1.1, more preferably greater than or equal to 1.2, and still more preferably greater than or equal to 1.3. In view of the strength of the crown6, an excessively small wall thickness T2is not preferable. In this respect, the ratio (T1/T2) is preferably less than or equal to 2, more preferably less than or equal to 1.9, and still more preferably less than or equal to 1.8. In the head2, the wall thickness T1was set to 1.0 mm, and the wall thickness T2was set to 0.75 mm.

The wall thickness TG of the crown in the narrow grooves mz is smaller than the wall thickness T1, and also smaller than the wall thickness T2. The increased rigidity of the crown due to the presence of the first thick portion M1can be effectively reduced by decreasing the wall thickness TG. The narrow grooves mz can effectively reduce the rigidity of the first region R1while maintaining the weight distribution to the first region R1. In the head2, the wall thickness TG was set to 0.6 mm.

The wall thickness TG in the narrow grooves mz is, for example, preferably greater than or equal to 0.3 mm and preferably less than or equal to 0.7 mm. Particularly in light of the effect of rigidity reduction, the wall thickness TG is, for example, preferably less than or equal to 0.6 mm. The wall thickness T1is preferably greater than or equal to 0.6 mm and preferably less than or equal to 1.2 mm. The wall thickness T2is preferably greater than or equal to 0.4 mm and preferably less than or equal to 0.9 mm.

In the head2and the head20, the number of the narrow grooves mz is 3. The number of the narrow grooves mz is not limited. In light of increasing weight distribution to the first region R1, the number of the narrow grooves mz is preferably less than or equal to 8, more preferably less than or equal to 7, and still more preferably less than or equal to 6. In light of suppressing the rigidity of the first region R1and facilitating the bending of the crown, the number of the narrow grooves mz is preferably greater than or equal to 1, more preferably greater than or equal to 2, and still more preferably greater than or equal to 3.

As shown inFIG. 2, the narrow grooves mz extend along the upper edge4aof the face4. All the narrow grooves mz extend along the upper edge4aof the face4. The narrow grooves mz arc substantially perpendicular to a direction in which a force caused by the impact of a ball is applied. The narrow grooves mz extending in such a direction facilitate the deformation of the crown6by the force. The narrow grooves mz can effectively reduce the rigidity of the first region R1against the force while maintaining the weight distribution to the first region R1.

The aboved-described “the narrow grooves mz extend along the upper edge4aof the face4” means that the rate of change in the face-back direction distance between the width-direction center line L and the upper edge4ais less than or equal to 5%. The face-back direction distance is measured in the planar view (FIG. 2).

In light of increasing weight distribution to the first region R1, the proportion of the first thick portion M1in the first region R1is preferably large. When the area of the first region R1is denoted by AR1, and the area of the first thick portion M1is denoted by AM1, then a ratio (AM1/AR1) is preferably greater than or equal to 0.6, more preferably greater than or equal to 0.65, and still more preferably greater than or equal to 0.7. In view of the presence of the narrow grooves mz, the ratio (AM1/AR1) is preferably less than or equal to 0.98, more preferably less than or equal to 0.95, and still more preferably less than or equal to 0.9. The area AR1and the area AM1are measured in the planar view.

In light of concentrating weight to the first region R1, the area of the second thick portion M2is preferably greater than the area AM1. When the area of the second thick portion M2is denoted by AM2, a ratio (AM2/AM1) is preferably greater than or equal to 3, more preferably greater than or equal to 3.5, and still more preferably greater than or equal to 4. In view of the presence of the first thick portion M1, the ratio (AM2/AM1) is preferably less than or equal to 5, more preferably less than or equal to 4.8, and still more preferably less than or equal to 4.5. The area AM2is measured in the planar view.

A head having a large head volume includes a hitting surface having a large area. In the head including the hitting surface having a large area, variations in hitting points in the up-down direction also tend to be increased. The variations can reduce the controllability of the hit ball. For this reason, the present disclosure is more effective in a head having a large head volume. In this respect, the head volume is preferably greater than or equal to 400 cc, more preferably greater than or equal to 420 cc, and still more preferably greater than or equal to 430 cc. In view of the Golf Rules, the head volume is preferably less than or equal to 470 cc.

The method for forming the narrow grooves mz is not limited. Examples of the formation method of the narrow grooves mz include casting, forging, NC processing, and chemical milling. In light of accuracy, the NC processing may be adopted.

The material of the head is not limited. Examples of the material of the head include metal and CFRP (carbon fiber reinforced plastic). Examples of the metal include one or more metals selected from pure titanium, a titanium alloy, stainless steel, maraging steel, an aluminum alloy, a magnesium alloy, and a tungsten-nickel alloy. Examples of stainless steel include SUS630 and SUS304. A specific example of stainless steel is CUSTOM 450 (manufactured by Carpenter Technology Corporation). Examples of the titanium alloy include 6-4 titanium (Ti-6Al-4V) and Ti-15V-3Cr-3Sn-3Al. As described above, the present disclosure is effective in a head having a large head volume. In this respect, the material of the head is preferably the titanium alloy. In the same respect, the material of the crown is preferably the titanium alloy.

The method for producing the head is not limited. Normally, a hollow head is produced by joining two or more members to each other. The method for producing each member that constitutes the head is not limited, and examples of the method include casting, forging, and press forming.

Examples of the structure of the head include a two-piece structure in which two members each of which is integrally formed are joined together, a three-piece structure in which three members each of which is integrally formed are joined together, and a four-piece structure in which four members each of which is integrally formed are joined together.

The present disclosure can be applied to all types of golf club heads such as a wood type head, a utility type head, and a hybrid type head.

The above description is merely illustrative example, and various modifications can be made without departing from the principles of the present disclosure.