GOLF CLUB HEAD

Abstract

A golf club head having a hollow portion therein, the head includes a main body including a crown portion and a sole portion, and a face member forming at least a part of a striking face for striking a ball. The main body is made of a first material having a first specific gravity. The face member is formed of a second material having a second specific gravity smaller than the first specific gravity. The main body is provided with at least one slit that penetrates the main body, and the at least one slit extends in a head-front-back direction.

Description

RELATED APPLICATIONS

This application claims the benefit of foreign priority to Japanese Patent Application No. JP2022-079499, filed May 13, 2022, which is incorporated by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to a golf club head having a hollow portion therein.

BACKGROUND OF THE DISCLOSURE

The following patent document 1 discloses a golf club head having a head outer shell and a face member fixed to a concave portion of the head outer shell. The face member is composed of a fiber-reinforced plastic using carbon fibers and the like.

Patent Document 1

• Japanese Unexamined Patent Application Publication No. H06-47111

SUMMARY OF THE DISCLOSURE

In the golf club head as described above, the face portion is lightened by using low specific gravity material for the face member. By reducing the weight of the face portion, a weight margin is obtained. Distributing this weight margin away from the head center of gravity can provide a golf club head with a high moment of inertia.

On the other hand, low specific gravity materials, such as fiber reinforced plastic generally have low durability. Therefore, the face members made of low specific gravity materials need to be thick-walled. A thick-walled face member has high bending rigidity, which may reduce the repulsion performance of the club head when striking a ball.

One object of the present disclosure is to provide a golf club head capable of reducing the weight of the face portion without deteriorating repulsion performance.

In one aspect of the present disclosure, a golf club head having a hollow portion therein, the head includes a main body including a crown portion and a sole portion, and a face member forming at least a part of a striking face for striking a ball. The main body is made of a first material having a first specific gravity. The face member is formed of a second material having a second specific gravity smaller than the first specific gravity. The main body is provided with at least one slit that penetrates the main body, and the at least one slit extends in a head-front-back direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a golf club head according to an embodiment;

FIG. 2 is a front view of the golf club head according to an embodiment;

FIG. 3 is a plan view of the golf club head according to an embodiment;

FIG. 4 is a bottom view of the golf club head according to an embodiment;

FIG. 5 is a cross-sectional view taken along the lines V-V of FIG. 3;

FIG. 6 is a cross-sectional view taken along the line VI-VI of FIG. 3;

FIG. 7 is a plan view of a slit;

FIG. 8 is a plan view of the slit according to another example;

FIG. 9 is a plan view of the slit according to yet another example;

FIG. 10 is a cross-sectional view taken along the lines X-X of FIG. 9;

FIG. 11 is a bottom view of the golf club head according to another embodiment;

FIG. 12A is a front view of a golf club head, and

FIG. 12B is a cross-sectional view taken along the line s1 of FIG. 12A.

DETAILED DESCRIPTION OF THE DISCLOSURE

Hereinafter, one or more embodiments of the present disclosure will be described below based on the drawings.

Throughout the embodiments, the same elements and portions are denoted by the same reference characters, and duplicate explanations are omitted.

FIGS. 1 to 4 respectively show a perspective view, a front view, a plan view, and a bottom view of a golf club head (hereinafter, simply referred to as “head”) 1 according to the present embodiment.

[Reference State, Etc.]

In FIGS. 1 to 4, the head 1 is in a reference state. The reference state is the state that the head 1 is placed on a horizontal plane HP with the lie angle α (FIG. 2) and the loft angle (not illustrated) defined for the head 1. In the reference state, the shaft centerline CL of the head 1 is located in the reference vertical plane VP (FIG. 3). The shaft centerline CL is defined by the axis centerline of a shaft insertion hole 7a formed in the hosel portion 7 of the head 1. Unless otherwise mentioned herein, the head 1 shall be placed in the reference state.

[Head Coordinate System]

As used herein, an x-y-z coordinate system is associated with the head 1. The x-axis is defined as the axis orthogonal to the reference vertical plane VP and parallel to the horizontal plane HP. The y-axis is parallel to both the reference vertical plane VP and the horizontal plane HP. The z-axis is defined as the axis orthogonal to both the x-axis and y-axis. For the head 1, the direction along the x-axis is defined as the head-front-back direction, the direction along the y-axis as the toe-heel direction, and the direction along the z-axis as the head-up-down direction. The side of the face portion 2 is the front side and the opposite side is the back side with respect to the head-front-back direction.

[Head Basic Structure]

As shown in FIG. 3 in a partially broken section, the head 1 according to the present embodiment includes a hollow portion (i) therein. For example, this hollow portion (i) may be used as a space as it is, or a gel agent for weight adjustment may be placed in a part of it.

The head 1 according to the present embodiment, for example, is configured as a wood type. The head 1 of the wood type includes, for example, at least a driver, a fairway wood, a hybrid, and the like. The head 1 in this embodiment is configured as a driver.

For example, the head 1 includes a face portion 2, a crown portion 3, a sole portion 4, a toe 5 and a heel 6 which are arranged so as to surround the hollow portion (i).

The face portion 2 is the portion that strikes a ball and is formed on the front side of the head 1. The face portion 2 includes a striking face 2a that is in direct contact with the ball. Although not shown in the figure, the striking face 2a may be provided with face lines. The face lines are grooves extending in the toe-heel direction.

The face portion 2 includes a periphery E defining the boundary of the striking face 2a. As used herein, the periphery E of the face portion 2 is the ridge line if it is visible to the naked eye as a clear ridge line. On the other hand, if such a ridge line is not clearly formed, the periphery E of the face portion 2 is obtained as follows. First, as illustrated in FIG. 12A, cross sections s1, s2, s3 . . . , including the normal N passing the center of gravity G of the head and the sweet spot SS are specified. Next, as illustrated in FIG. 12B, in each of the cross sections s1, s2, s3 . . . , the positions E where the radius of curvature r of the contour line Lf of the striking face 2a becomes 200 mm for the first time from the sweet spot SS side toward outwardly of the face portion are specified, and a series of these positions E in the cross sections is defined as the periphery E of the face portion 2. Of this peripheries E, the boundary portion with the crown portion 3 is defined as the upper edge 2b of the face portion 2, and the boundary portion with the sole portion 4 is defined as the lower edge 2c of the face portion 2.

The crown portion 3 extends from the upper edge 2b of the face portion 2 backwardly of the head so as to form an upper surface of the head. The hosel portion 7 is provided on the heel side of the crown portion 3. The hosel portion 7 has the shaft insertion hole 7a for fixing a shaft (not illustrated). The crown portion 3 is the portion excluding the face portion 2 and the hosel portion 7 in a plan view of the head shown in FIG. 3.

As illustrated in FIG. 4, the sole portion 4 extends from the lower edge 2c of the face portion 2 backwardly of the head so as to form a bottom surface of the head. The sole portion 4 is the portion excluding the hosel portion 7 in a bottom view of the head.

FIG. 5 is a cross-sectional view taken along the lines V-V of FIG. 3. As shown in FIG. 5, the head 1 includes a main body 100 and a face member 200.

The main body 100 includes the crown portion 3 and the sole portion 4. In the present embodiment, the main body 100 further includes the hosel portion 7 and a face peripheral portion 101. The face peripheral portion 101 is the peripheral portion of the opening O formed in the face portion 2. The face peripheral portion 101 forms the peripheral portion of the opening O formed in the face portion 2. In the present embodiment, the main body 100, for example, includes the crown portion 3, the sole portion 4, the hosel portion 7, and the face peripheral portion 101 integrally formed. In another embodiment, the main body 100 may be formed by joining multiple members.

The main body 100 is made of a first material having a first specific gravity. Although the first material is not particularly limited, one or more metallic materials may be suitable, for example. Examples of such metallic materials include titanium, titanium alloys, stainless steel, maraging steel, and the like. In some preferred embodiments, the first material is a metal material having a specific gravity equal to or more than 4.0, preferably equal to or more than 4.4, and titanium alloy (specific gravity of about 4.5) is particularly suitable. In addition, when the main body 100 is composed of multiple materials, the first specific gravity may be specified by an average specific gravity obtained by weighting the specific gravity of each material by their volume.

The face member 200, for example, has a plate-like shape. As shown in FIG. 1, in the present embodiment, the face member 200 has a contour shape 200e that is located inside of the periphery E of the striking face 2a. The face member 200 is attached to an opening O formed in the main body 100. Thus, the face member 200 constitutes at least a portion (in this embodiment, a major portion) of the striking face 2a. The face member 200 is not limited to the plate-like shape of this embodiment, and may be, for example, a cup-like shape having a short length turnback portion extending behind of the head.

In some preferred aspects, as shown in FIG. 5, the face peripheral portion 101 of the main body 100 is formed with a receiving portion 102 that supports the periphery of the back surface of the face member 200. As a result, the face member 200 is more firmly attached to the face peripheral portion 101. The fixing between the main body 100 and the face member 200 is not particularly limited, but may be performed using, for example, an adhesive or the like.

The face member 200 is formed of a second material having a second specific gravity smaller than the first specific gravity. The second material is not particularly limited as long as it has a second specific gravity smaller than the first specific gravity. As the second material, metal materials such as magnesium, magnesium alloys, aluminum, aluminum alloys, beryllium alloys, and the like may be employed. In addition, plastic materials such as fiber reinforced plastic can be adopted. As a preferred aspect, in this embodiment, a carbon fiber-reinforced plastic material (with a specific gravity of about 1.4) is used. Alternatively, the reinforcing fibers may be fibers other than carbon fibers.

The face member 200 is made of a material with relatively low specific gravity and thus tends to have low durability. Therefore, it is preferable that the face member 200 has a thickness enough not to impair durability. When the second material is a fiber-reinforced plastic as in the present embodiment, the thickness T of the face member 200 is, for example, equal to or more than 3.0 mm, preferably equal to or more than 4.0 mm, and more preferably equal to or more than 5.0 mm. The face member 200, which has been thickened in this way, can exhibit high bending rigidity and exhibit sufficient durability even after repeated ball hits. On the other hand, in order to achieve desirable weight reduction in the face portion 2, the thickness T of the face member 200 is, for example, equal to or less than 9.0 mm, preferably equal to or less than 8.5 mm, and more preferably equal to or less than 8.0 mm.

[Slit(s)]

As shown in FIGS. 1 to 3, in the head 1 according to the present embodiment, the main body 100 is provided with at least one slit 10 that penetrates the main body 100. In the present embodiment, a plurality of slits 10 is provided on the crown portion 3. In another embodiment, as shown in FIG. 11, one or more slits 10 may be provided on the sole portion 4, in addition to the crown portion 3, or except the crown portion 3.

FIG. 6 is a cross-sectional view taken along the line VI-VI of FIG. 3, and FIG. 7 is an enlarged view of one of the slits 10. As shown in FIG. 6 and FIG. 7, each slit 10 has a Length L in the head-front-back direction, and a width W in the toe-heel direction. In the present embodiment, the length L of each slit 10 is larger than the width W of the slit 10. Thus, each slit 10 is elongated in the head-front-back direction.

Effect of the Embodiment

The face portion 2 includes the face member 200 having the second specific gravity smaller than the first specific gravity of the main body 100. Thus, the face portion 2 can be reduced in weight. The reduced weight of the face portion 2 provides a new weight margin. The weight margin means a discretionary and arbitrarily usable amount of weight not exceeding the weight limit set for the head 1, usually used to adjust the center of gravity of the head 1 to a preferred location. By placing the weight margin farther from the center of gravity of the head, for example, it is possible to increase the moment of inertia around the axis passing through the center of gravity of the head. Such a golf club head can provide flexibility and stabilizes the direction of hit balls.

As a result of the inventors' analysis, it was found that when the ball is struck with the striking face 2a of the face portion 2, the crown portion 3 is subjected to tensile deformation in the toe-heel direction in addition to bending deformation in the head-front-back direction. The sole portion 4 also shows almost the same deformation as the crown portion 3. Therefore, if the tensile stiffness in the toe-heel direction of the main body 100 is reduced, the repulsion performance of the head 1 can be improved. Based on these findings, the head 1 according to the present embodiment is composed of the face member 200 with high rigidity and the main body 100 with slits 10 extending in the head-front-back direction. As a result, in the head 1 according to the present embodiment, even if the face member 200 is made rigid, the main body 100 bends sufficiently in the toe-heel directions when the ball is struck, and the decrease in the repulsion performance of the head 1 can be suppressed. As described above, the head 1 according to the present embodiment can reduce the weight of the face portion 2 without decreasing the repulsion performance.

A more preferred form of the present disclosure will be described below.

[Slit Length/Width]

As shown in FIG. 7, each slit 10 includes a frontmost end 10a and a backmost end 10b in the head-front-back direction. These frontmost end 10a and backmost end 10b are respectively located on the frontmost side of the slit 10 and on the backmost side of the head. In order to effectively promote the deflection in the toe-heel direction of the main body 100, the length L of the slits 10 is, for example, equal to or more than 10 mm, preferably equal to or more than 12 mm, more preferably equal to or more than 15 mm. On the other hand, if the length L of the slits 10 is excessively large, the durability of the main body 100 may decrease. From this point of view, the length L of the slits 10 is, for example, equal to or less than 40 mm, preferably equal to or less than 30 mm, more preferably equal to or less than 25 mm.

In order to effectively promote the deflection in the toe-heel direction of the main body 100, the width W of the slits 10 is, for example, equal to or more than 0.5 mm, preferably equal to or more than 1 mm, more preferably equal to or more than 2 mm. On the other hand, a larger width W of the slits 10 may decrease the durability of the main body 100. From this point of view, the width W of slits 10 is, for example, equal to or less than 10 mm, preferably equal to or less than 8 mm, more preferably equal to or less than 6 mm. The width W of the slits 10 can be constant or variable. Note that the width W of the slits 10 may be constant except at both ends, or it may vary as described below.

[Slit Angle]

In a head plan view, each slit 10 defines a reference straight line 10c passing through the frontmost end 10a and the backmost end 10b. In some preferred aspects, the reference straight line 10c of each slit 10 has an angle equal to or less than 15 degrees with respect to the head-front-back direction (i.e., the x-axis). Such a slit 10 can effectively promote the deflection of the main body 100 in the toe-heel direction when hitting a ball on the toe or heel side of the face portion.

In order to more effectively promote the deflection of the main body 100 in the toe-heel direction, the angle of the reference straight line 10c of each slit 10 is preferably equal to or less than 10 degrees, more preferably equal to or less than 5 degrees. When the reference straight line 10c is inclined with respect to the head-front-back direction, the inclination direction of the reference straight line 10c is not particularly limited. Each slit 10 of the present embodiment extends linearly parallel to the head-front-back direction, but one or more slits 10 may be formed in an arc, zigzag, wave, or other non-linear shape.

[Contour Shape of Slit(s)]

As shown in FIG. 7, in a plan view of each slit 10, each of contours on a frontmost end 10a side and a backmost end 10b side of the slit 10 preferably has an arc shape. In this way, each slit 10 does not have sharp corners near the frontmost end 10a and/or the backmost end 10b, which can relieve the stress concentration thereto. In the present embodiment, the frontmost end 10a and the backmost end 10b are both arc-shaped.

FIG. 8 illustrates a plan view of another example of a slit 10. As shown in FIG. 8, a width Wb on the backmost end 10b side of the slit 10 is preferably greater than a width Wa on the frontmost end 10a side of the slit 10. According to the inventors' experiments, the tensile deformation of the crown portion 3 and the sole portion 4 in the toe-heel direction tends to be larger when the ball is struck as it moves away from the periphery E of the face portion 2 toward the back of the head. Therefore, if the width Wb of the backmost end 10b side of the slit 10 is larger than the width Wa of the frontmost end 10a side of the slit 10, the main body 100 can be elastically deformed more effectively when the ball is struck, and the decrease in the repulsion performance can be further suppressed. In addition, the increase in stress near the backmost end 10b side of the slit 10 can be effectively suppressed and the durability of the main body 100 can be improved.

The slit 8 shown in FIG. 8 includes a first portion 10d extending backwardly of the head from the frontmost end 10a side and a second portion 10e having a circular contour that is connected to the first portion 10d. In this embodiment, the first portion 10d extends with a constant width Wa. The width Wb of the second portion 10e is larger than the width Wa of the first potion 10d. Such a slit 10 can effectively suppress the stress increase near the backmost end 10b of the slit 10, where the deformation of the main body 100 is likely to increase. In some preferred aspects, the width Wb of the second portion 10e is equal to or more than 1.5 times the width Wa of the first portion 10d, more preferably equal to or more than 2.0 times.

[Preferred Position of Slit(s) (Head-Front-Back Direction)]

In some preferred aspects, the minimum distance D between the frontmost end 10a of each slit 10 and the periphery E of the face portion 2 is, for example, equal to or less than 10 mm, preferably equal to or less than 3 mm, more preferably equal to or less than 1 mm. In FIG. 3, the minimum distance D between the upper edge 2b which is as the periphery E of the striking face 2a and the frontmost end 10a of one of the slits 10 is shown. The periphery E of the face portion 2 is a corner where the face portion 2 and the main body 3 are connected, and the rigidity around the periphery E tends to be high, resulting in relatively small deformation when the ball is struck. Thus, there is an advantage that the increase of stress near the frontmost end 10a of each slit 10 is effectively suppressed by making the frontmost end 10a of each slit 10 closer to the periphery E.

[Preferred Position of Slit(s) in Toe-Heel Direction]

When one or more slits 10 are provided in the crown portion 3, in a plan view of the head shown in FIG. 3, it is preferable that at least one slit 10 is provided within the projection area A1 of the face member 200 to the back of the head. Similarly, when one or more slits 10 are provided in the sole portion 4, in a bottom view of the head shown in FIG. 11, it is preferable that at least one slit 10 is provided within the projection area A1 of the face member 200 to the back of the head. By providing the slits at such positions, the deflection in the toe-heel direction of the main body 100 can be further promoted when striking a ball. In addition, the main body 100 is deflected more effectively at the hitting point in the area near the position of at least one of the slits 10 when the ball is hit, further suppressing the deterioration of the repulsion performance. Thus, it is preferable to provide the slit(s) 10 in the region of low repulsion performance in order to further promote the toe-heel deflection of the main body 100 when a ball is struck. Alternatively, if the slit 10 is provided at two locations centered on the region of low repulsion performance, it is preferable to further promote the toe-heel deflection of the main body 100 when striking a ball over a wider range of striking points.

[Thick-Walled Portion Around Slit(s)]

FIG. 9 is a plan view of yet another example of a slit 10, and FIG. 10 is a cross-sectional view taken along the lines X-X of FIG. 10. When hitting a ball, the main body 100 is subjected to bending stress due to bending in the head-front-back direction and tensile stress due to tensile deformation in the toe-heel direction, and high stress is likely to occur around the slits 10 of the main body 100. In view of maintaining higher strength of the main body 100, a thick-walled portion 11 may be provided at least partially around at least one slit 10. The thick-walled portion 11 can disperse stresses in the periphery of the slit 10 and suppress significant localized stress increases.

In the present embodiment, the thick-walled portion 11 is formed into a continuous shape to surround the slit 10. Such a thick-walled portion 11 is more effective in relieving stresses around the slit 10 of the main body 100.

In the present embodiment, the thick-walled portion 11 includes, for example, an inner thick-walled portion 11a raised on the hollow portion (i) side. The inner thick-walled portion 11a is raised toward the hollow portion (i) from the inner surface of the reference thick-walled portion 3a formed by the reference thickness tc of the crown portion 3. The thickness boundary between the inner thick-walled portion 11a and the reference thick-walled portion 3a is a virtual boundary defined by a smooth extension of the inner surface of the reference thick-walled portion 3a to the slit 10.

For example, the inner thick-walled portion 11a is continuous around the slit 10 without interruption. This can suppress the increase in stress during ball striking over the entire circumference of the slit 10 and can improve the durability of the main body 100.

Although a thickness ta of the inner thick-walled portion 11a is not particularly limited, it is preferably, for example, equal to or more than 0.5 mm, preferably equal to or more than 1.0 mm, more preferably equal to or more than 1.5 mm, in order to fully demonstrate the stress reduction effect in the region around the slit 10. In order to suppress the weight increase of the head 1, the thickness ta of the inner thick-walled portion 11a is, for example, equal to or less than 5.0 mm, preferably equal to or less than 4.0 mm, more preferably equal to or less than 3.0 mm.

In addition, the thick-walled portion 11 may include, for example, an outer thick-walled portion 11b raised on the outer surface of the head. The outer thick-walled portion 11b may form the thick-walled portion 11 together with the inner thick-walled portion 11a or in place of the inner thick-walled portion 11a.

The outer thick-walled portion 11b is raised outwardly from the outer surface 4o of the reference thick-walled portion 3a formed by the reference thickness tc of the crown portion 3. The thickness boundary between the outer thick-walled portion 11b and the reference thick-walled portion 3a is a virtual boundary defined by a smooth extension of the outer surface of the reference thick-walled portion 3a to the slit 10.

Although a thickness tb of the outer thick-walled portion 11b is not particularly limited, in order to fully demonstrate the effect of reducing tensile stress in the toe-heel direction around the slit 10, for example, it may be equal to or more than 0.5 mm, preferably equal to or more than 1.0 mm, more preferably equal to or more than 1.5 mm. If the thickness tb is too thick, the bending rigidity in the head-front-back direction increases, which in turn increases the bending stress in the head-front-back direction of the head. In order to fully demonstrate the effect of reducing the bending stress in the head-front-back direction around the slit and to suppress the weight increase of the head 1, the thickness tb of the outer thick-walled portion 11b is, for example, equal to or less than 5.0 mm, preferably equal to or less than 4.0 mm, more preferably equal to or less than 3.0 mm.

As shown in FIG. 9, a width TW of the inner thick-walled portion 11a and the outer thick-walled portion 11b is not particularly limited, but it is, for example, equal to or more than 1.0 mm, preferably equal to or more than 2.0 mm, more preferably equal to or more than 3.0 mm, in order to fully demonstrate the stress reduction effect in the periphery of the slit 10. In addition, in order to suppress the increase in weight of the head 1, the width TW of the inner thick-walled portion 11a and the outer thick-walled portion 11b is, for example, equal to or less than 15.0 mm, preferably equal to or less than 12.0 mm, mor preferably equal to or less than 10.0 mm. The width TW is measured orthogonally to the edge of the slit 10, as illustrated in FIG. 9.

[Slit Cover]

A cover (not illustrated) made of an elastic material such as rubber, plastic, elastomer, etc. may be provided. Such a cover can prevent foreign objects from entering the slits 10 without interfering with the deformation of the main body 100 in any way.

While the particularly preferable embodiments in accordance with the present disclosure have been described in detail, the present disclosure is not limited to the illustrated embodiments, but can be modified and carried out in various aspects within the scope of the disclosure.

Example

Next, more detailed example of the present disclosure will be described. A finite element model of a golf club head (example) with three slits on the crown portion having the basic shape shown in FIGS. 1 to 5 and based on the specifications in Table 1 was created. The head is configured to include the main body, the face member, the weight member and a sleeve (a shaft-mounting part incorporated in the hosel). The head has a volume of 460 cc. The positions of the three slits are 15 mm from the geometric center of the striking face to the toe, 5 mm from the center of the striking face to the heel, and 20 mm from the center of the striking face to the heel, in the plan view of FIG. 3. Then, the coefficient of restitution at the face center of the example was calculated by computer simulation. For comparison, the coefficient of restitution of the golf club head whose face member is made of titanium alloy (Comparative Example 1) and the golf club head whose slits are removed from the Example (Comparative Example 2) are also calculated by the computer simulation in the same way. For each head, the weight member and sleeve are identical.

[Calculation of Coefficient of Restitution]

Regarding the coefficient of restitution, according to the “Interim Procedure for Measuring the Coefficient of Restitution of an Iron Clubhead Relative to a Baseline Plate Revision 1.3 Jan. 1, 2006” stipulated by the USGA (United States Golf Association), the COR was calculated. The simulation results are shown in Table 1.

	TABLE 1
	Comparative	Comparative
	example 1	example 2	Example
Main body	Titanium	Titanium	Titanium
	alloy	alloy	alloy
Specific gravity of main body	4.5	4.5	4.5
(first specific gravity)
Face member	Titanium	CFRP	CFRP
	alloy
Specific gravity of face member	4.5	1.4	1.4
(second specific gravity)
Number of slit(s) of main body	0	0	3
Face weight (g)	30	17.7	17.7
Main body weight (g)	138.8	144	144
Weight member weight (g)	10.3	10.3	10.3
Sleeve weight (g)	9.1	9.1	9.1
Total head weigh (g)	188.2	181.1	181.1
COR	0.894	0.890	0.893

As can be seen from Table 1, in comparison with Comparative Example 1, the Example achieved a weight reduction of 12.3 g for the face portion and 6.6 g for the entire head. In addition, it was confirmed that the Example obtained a COR almost equal to that of Comparative Example 1, and that the decrease in repulsion performance was suppressed.

[Additional Note]

The present disclosure includes the following aspects.

[Disclosure 1]

A golf club head having a hollow portion therein, the head comprising:

• • a main body comprising a crown portion and a sole portion; and
  • a face member forming at least a part of a striking face for striking a ball, wherein
  • the main body is made of a first material having a first specific gravity,
  • the face member is formed of a second material having a second specific gravity smaller than the first specific gravity,
  • the main body is provided with at least one slit that penetrates the main body, and
  • the at least one slit extends in a head-front-back direction.

[Disclosure 2]

The golf club head according to disclosure 1, wherein

• • the at least one slit comprises a plurality of slits, and
  • the plurality of slits is provided on the crown portion of the main body.

[Disclosure 3]

The golf club head according to disclosure 1 or 2, wherein

• • the second material comprises a fiber reinforced plastic.

[Disclosure 4]

The golf club head according to any one of disclosures 1 to 3, wherein

• • the at least one slit has a length in the head-front-back direction ranging from 10 to 40 mm and has a width in a toe-heel direction ranging from 0.5 to 10 mm.

[Disclosure 5]

The golf club head according to any one of disclosures 1 to 4, wherein

• • the striking face has a periphery,
  • the at least one slit has a frontmost end in the head-front-back direction, and
  • a shortest distance between the frontmost end and the periphery is equal to or less than 10 mm.

[Disclosure 6]

The golf club head according to disclosure 5, wherein

• • the shortest distance is equal to or less than 3 mm.

[Disclosure 7]

The golf club head according to any one of disclosures 1 to 6, wherein

• • the at least one slit has a frontmost end and a backmost end in the head-front-back direction, and
  • in a plan view of the at least one slit, each of contours on a frontmost end side and a backmost end side has an arc shape.

[Disclosure 8]

The golf club head according to any one of disclosures 1 to 7, wherein

• • the at least one slit has a frontmost end and a backmost end in the head-front-back direction, and
  • a width on a backmost end side of the at least one slit is greater than a width on a frontmost end side of the at least one slit.

[Disclosure 9]

The golf club head according to disclosure 8, wherein

• • the at least one slit comprises a first portion extending backwardly of the head from the frontmost end side and a second portion having a circular contour that is connected to the first portion.

[Disclosure 10]

The golf club head according to any one of disclosures 1 to 9, wherein

• • a thick-walled portion is formed at least partially around the at least one slit.

[Disclosure 11]

The golf club head according to disclosure 10, wherein

• • the thick-walled portion comprises an inner thick-walled portion raised on a hollow portion side of the head.

[Disclosure 12]

The golf club head according to disclosure 10 or 11, wherein

• • the thick-walled portion comprises an outer thick-walled portion raised on an outer surface side of the head.

[Disclosure 13]

The golf club head according to any one of disclosures 1 to 12, wherein

• • the at least one slit comprises a plurality of slits, and
  • the plurality of slits is provided on the sole portion of the main body.

Claims

1. A golf club head having a hollow portion therein, the head comprising: a main body comprising a crown portion and a sole portion; anda face member forming at least a part of a striking face for striking a ball, whereinthe main body is made of a first material having a first specific gravity,the face member is formed of a second material having a second specific gravity smaller than the first specific gravity,the main body is provided with at least one slit that penetrates the main body, andthe at least one slit extends in a head-front-back direction.

2. The golf club head according to claim 1, wherein the at least one slit comprises a plurality of slits, andthe plurality of slits is provided on the crown portion of the main body.

3. The golf club head according to claim 1, wherein the second material comprises a fiber reinforced plastic.

4. The golf club head according to claim 1, wherein the at least one slit has a length in the head-front-back direction ranging from 10 to 40 mm and has a width in a toe-heel direction ranging from 0.5 to 10 mm.

5. The golf club head according to claim 1, wherein the striking face has a periphery,the at least one slit has a frontmost end in the head-front-back direction, anda shortest distance between the frontmost end and the periphery is equal to or less than 10 mm.

6. The golf club head according to claim 5, wherein the shortest distance is equal to or less than 3 mm.

7. The golf club head according to claim 1, wherein the at least one slit has a frontmost end and a backmost end in the head-front-back direction, andin a plan view of the at least one slit, each of contours on a frontmost end side and a backmost end side has an arc shape.

8. The golf club head according to claim 1, wherein the at least one slit has a frontmost end and a backmost end in the head-front-back direction, anda width on a backmost end side of the at least one slit is greater than a width on a frontmost end side of the at least one slit.

9. The golf club head according to claim 8, wherein the at least one slit comprises a first portion extending backwardly of the head from the frontmost end side and a second portion having a circular contour that is connected to the first portion.

10. The golf club head according to claim 9, wherein the first portion has a portion extending with a constant width Wa, andthe second portion has a width Wb equal to or more than 1.5 times the width Wa of the first portion.

11. The golf club head according to claim 1, wherein a thick-walled portion is formed at least partially around the at least one slit.

12. The golf club head according to claim 11, wherein the thick-walled portion comprises an inner thick-walled portion raised on a hollow portion side of the head.

13. The golf club head according to claim 11, wherein the thick-walled portion comprises an outer thick-walled portion raised on an outer surface side of the head.

14. The golf club head according to claim 11, wherein the thick-walled portion is formed into a continuous shape to surround the at least one slit.

15. The golf club head according to claim 14, wherein a width TW of the thick-walled portion measured orthogonally to an edge of the at least one slit ranges from 1.0 mm to 15.0 mm.

16. The golf club head according to claim 1, wherein the at least one slit comprises a plurality of slits, andthe plurality of slits is provided on the sole portion of the main body.

17. A golf club head having a hollow portion therein, the head comprising: a main body comprising a crown portion and a sole portion; anda face member forming at least a part of a striking face for striking a ball, whereinthe main body is made of a first material having a first specific gravity,the face member is formed of a second material having a second specific gravity smaller than the first specific gravity,the main body is provided with at least one slit that penetrates the main body,the at least one slit extends in a head-front-back direction,the at least one slit has a frontmost end and a backmost end in the head-front-back direction,the striking face has a periphery,a shortest distance between the frontmost end and the periphery is equal to or less than 10 mm,in a head plan view, the at least one slit defines a reference straight line passing through the frontmost end and the backmost end, andthe reference straight line has an angle equal to or less than 15 degrees with respect to the head-front-back direction.

18. A golf club head having a hollow portion therein, the head comprising: a main body comprising a crown portion and a sole portion; anda face member forming at least a part of a striking face for striking a ball, whereinthe main body is made of a first material having a first specific gravity,the face member is formed of a second material having a second specific gravity smaller than the first specific gravity,the main body is provided with at least one slit that penetrates the main body, andthe at least one slit comprises a portion extending in a head-front-back direction.