WOOD-TYPE GOLF CLUB HEAD

Abstract

A wood-type hollow golf club head has a lateral moment of inertia Ma and a vertical moment of inertia Mb which has a ratio (Mb/Ma) of not less than 0.80. The head can be provided with a hollow structure divided in the front-back direction of the head into a front member, a rear member and a middle member therebetween, wherein the middle member has a specific gravity smaller than those of the front member and rear member.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a wood-type golf club head, more particularly to a segmented hollow structure capable of increasing the moment of inertia of the head.

In recent years, various wood-type golf club heads having large head volumes have been proposed. In general, such a large-sized club head has a large lateral moment of inertia around a vertical axis passing through the center of gravity of the head. Accordingly, even if the ball hitting position is off centered toward the toe or heel, the rotational motion of the head around the vertical axis becomes smaller, and thereby the directionality of the ball becomes stable.

On the other hand, if the ball hitting position is off centered toward the crown or sole, then due to the vertical gear effect, there is a possibility that the traveling distance of the ball is decreased.

As shown in FIG. 8, when the ball hits a position on the club face (f) above or below the sweet spot SS, a moment substantially equal to the product of an impulsive force F and the distance L1 or L2 to the center of gravity G of the head is caused on the club head (a). Due to this moment, the club head makes an angularly very small rotational motion around the horizontal axis passing through the center of gravity G parallel with the toe-heel direction. By the rotational motion of the head, the ball (b) contacting with the club face (f) is forced to make a rotational motion in the opposite direction due to the friction therebetween. Such phenomenon is called vertical gear effect.

Accordingly, in the case that the ball hitting position is above the sweet spot SS (upper hit), the backspin of the ball (b) is decreased and it becomes difficult to obtain a sufficient ballistic course height.

Contrary, in the case that the ball hitting position is under the sweet spot SS (lower hit), the backspin of the ball (b) is increased, therefore, there is a tendency that the ball rises high and receives a ballooning effect.

Thus, the carry distance is decreased in either case.

In order to stabilize the carry distance of the ball or lessen the variations of the carry distances even if the ball hitting position is off-centered upward or downward of the sweet spot, it is necessary to lessen the above-mentioned vertical gear effect. For this purpose, it is effective to decrease the above-mentioned rotational motion by increasing the vertical moment of inertia of the head around the horizontal axis passing through the center of gravity G parallel with the toe-heel direction.

In the meantime, according to the Rules of Golf, the upper limit for the volume of a club head is provided. Therefore, if the lateral moment of inertia and vertical moment of inertia are increased under such limitation, the mass of the club head is excessively increased, and problems arise such as a decrease in the head speed and deterioration of the swing balance.

SUMMARY OF THE INVENTION

It is therefore, an object of the present invention to provide a wood-type golf club head, in which variations of the carry distances between good shots and missed shots can be decreased without a substantial increase in the mass of the head.

According to the present invention, a wood-type hollow golf club head has a ratio (Mb/Ma) of the vertical moment of inertia Mb to the lateral moment of inertia Ma which is not less than 0.80.

Therefore, in the wood-type golf club head according to the present invention, the ratio (Mb/Ma) is large in comparison with conventional values. Thus, the vertical moment of inertia Mb becomes large for the lateral moment of inertia Ma, therefore, the rotational motion of the club head at the time of upper or lower hit can be lessened, and thereby the decrease in the carry distance is lessened. Further, since the lateral moment of inertia Ma becomes relatively small, it can be avoided to largely increase the mass of the club head.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a wood-type golf club head according to the present invention.

FIG. 2 is a front view thereof.

FIG. 3 is a top view thereof.

FIG. 4 is a cross sectional view taken along line X-X in FIG. 3.

FIG. 5 is an exploded perspective view showing a four-piece structure for the head.

FIG. 6 is a perspective view of Ref. 1 head used in the undermentioned comparison tests.

FIG. 7 is a perspective view showing Ref. 2 and Ref. 3 heads used in the undermentioned comparison tests.

FIG. 8 is a cross sectional view for explaining the vertical gear effect.

FIG. 9 is a plan view for explaining the lateral gear effect.

DEFINITIONS

In this specification, sizes, positions, directions and the like relating to the club head refer to those under a standard state of the club head unless otherwise noted.

Here, the standard state of the club head 1 is such that the club head is set on a horizontal plane HP so that the center line CL of the club shaft (not shown) is inclined at the lie angle (alpha) while keeping the club shaft center line CL on a vertical plane VP, and the club face 2 forms its loft angle (beta) with respect to the horizontal plane HP. Incidentally, in the case of the club head alone, the center line of the shaft inserting hole 7a can be used instead of the center line of the club shaft.

“Lateral moment of inertia Ma” is the moment of inertia around a vertical axis passing through the center of gravity G under the standard state.

“Vertical moment of inertia Mb” is the moment of inertia around a horizontal axis passing through the center of gravity G in the toe-heel direction of the head under the standard state.

“Sweet spot SS” is the point of intersection between the club face and a straight line N drawn normally to the club face 2 passing the center of gravity G of the head.

“Front-back direction” is a direction parallel with the above-mentioned straight line N projected on the horizontal plane HP.

“Toe-heel direction” is a direction parallel with the horizontal plane HP and perpendicular to the front-back direction.

“Club head height H” is the height measured from the horizontal plane HP to the highest point 4t of the crown portion 4 of the club head under the standard state, namely, the highest point of the head excluding the upwardly protruding hosel portion if any.

“Sweet spot height Hs” is the height measured from the horizontal plane HP to the sweet spot SS under the standard state.

“Gravity point height Hg” is the height measured from the horizontal plane HP to the center of gravity of the head G under the standard state.

“Wood-type golf club” is meant for at least number 1 to 5 woods, and clubs comprising heads having similar shapes thereto may be included.

Description of the Preferred Embodiments

An embodiment of the present invention will now be described in detail in conjunction with accompanying drawings.

In the drawings, golf club head 1 according to the present invention is a hollow head for a wood-type golf club such as driver (#1) or fairway wood, and the head 1 comprises: a face portion 3 whose front face defines a club face 2 for striking a ball; a crown portion 4 intersecting the club face 2 at the upper edge 2a thereof; a sole portion 5 intersecting the club face 2 at the lower edge 2b thereof; a side portion 6 between the crown portion 4 and sole portion 5 which extends from a toe-side edge 2c to a heel-side edge 2d of the club face 2 through the back face BF of the club head; and a hosel portion 7 at the heel side end of the crown to be attached to an end of a club shaft (not shown) inserted into the shaft inserting hole 7a. Thus, the club head 1 is provided with a hollow (i) and a shell structure with the thin wall. The hollow (i) in this example is a closed void space, but it may be filled with a foamed plastic, separating from the backside of the face 3.

The volume of the club head 1 is preferably set to be not less than 400 cc, more preferably not less than 425 cc, still more preferably not less than 450 cc in order to give a sense of ease when addressing the ball, and increase the moment of inertia and the depth of the center of gravity of the head which help to improve the carry distance and directionality of the ball trajectory. On the other hand, if the volume of the club head 1 is too large, then there is a possibility that the mass of the club is increased and the swing balance is deteriorated. Further, there is a possibility that the golf club head becomes not in conformity with the Rules of Golf. Therefore, the volume of the club head 1 is preferably not more than 470 cc, more preferably not more than 460 cc. Similarly, the mass of the club head 1 is preferably set to be not less than 175 g, more preferably not less than 180 g, still more preferably not less than 185 g, but preferably not more than 210 g, more preferably not more than 205 g.

According to the present invention, the ratio (Mb/Ma) of the vertical moment of inertia Mb to the lateral moment of inertia Ma is set to be not less than 0.80. Therefore, the carry distances can be stabilized, without excessive increase in the club head mass. In other words, since the vertical moment of inertia Mb becomes relatively large, even if the ball hitting position is off centered towards the upper side or lower side of the club face 2, the unfavorable rotational motion of the head can be reduced, and as a result, the decrease of the carry distance is lessened. Further, since the lateral moment of inertia Ma becomes relatively small, an excessive increase of the mass of the club head 1 becomes not needed. In this light, the ratio (Mb/Ma) of the moments of inertia is more preferably not less than 0.90, still more preferably not less than 1.00.

Since the ratio (Mb/Ma) of the moments of inertia is limited, the lateral moment of inertia Ma becomes small. But, as shown in FIG. 9, even if the ball hitting position is off the sweet spot SS of the club face 2 towards the toe or heel, by the lateral gear effect, the ball is provided with a sidespin which causes the ball towards the direction j of the target trajectory of the ball. If the ratio (Mb/Ma) becomes excessively increased, since the lateral moment of inertia Ma decreases largely, the directionality of the hit ball tends to deteriorate. Therefore, the ratio (Mb/Ma) of the moments of inertia is preferably not more than 1.20, more preferably not more than 1.15.

By adjusting the sidespin and the launch angle θ of the ball (b) by adjusting the radius of curvature R of the face bulge, the carry distance and directionality of the hit ball can be prevented from deteriorating.

In order to effectively derive the above function, the vertical moment of inertia Mb is preferably set to be not less than 3500 g sq.cm, more preferably not less than 3700 g sq.cm, still more preferably not less than 4000 g sq.cm. If the moment of inertia Mb becomes less than 3500 g sq.cm, there is a tendency that the decrease in the carry distance becomes increased when the ball hitting position is upward or downward of the sweet spot. If the vertical moment of inertia Mb becomes too large, on the other hand, there is a possibility that the head becomes not in conformity with the Rules of Golf. Therefore, the vertical moment of inertia Mb is preferably not more than 6000 g sq.cm.

It is effectual for increasing the ratio (Mb/Ma) of the moments of inertia to increase the vertical moment of inertia Mb and/or to decrease (not to excessively increase) the lateral moment of inertia Ma.

Further, it is effectual for increasing the vertical moment of inertia Mb to distribute the mass at the positions far from the horizontal axis as much as possible. Such mass distribution can be achieved by, for example, changing the thickness of the crown portion and sole portion and/or disposing a separate weight member made of a material having a large specific gravity.

Furthermore, to increase the height H of the club head 1 is effectual for increasing the vertical moment of inertia Mb. In concrete terms, the club head height H is preferably set to be not less than 40 mm, more preferably not less than 42 mm, still more preferably not less than 45 mm. However, the head volume has its upper limit, therefore, if the club head height H is excessively increased, the shape of the club head becomes odd. Further, when the head is addressed to the ball, the size of the club head viewed by the golfer becomes small, and as a result, there is a possibility that the golfer can not feel a sense of ease. In this light, the club head height H is preferably set to be not more than 58 mm, more preferably not more than 56 mm, still more preferably not more than 55 mm.

It is effectual for decreasing the lateral moment of inertia Ma to decrease the projected area of the club head on the horizontal plane and/or to distribute the head mass at positions near the vertical axis passing through the center of gravity of the head G.

The gravity point height Hg is preferably set to be not less than 20.0 mm, more preferably not less than 21.0 mm, still more preferably not less than 22.0 mm.

The sweet spot height Hs is preferably set to be not less than 25.0 mm, more preferably not less than 26.0 mm, still more preferably not less than 27.0 mm.

If the gravity point height Hg is less than 20.0 mm, or the sweet spot height Hs is less than 25.0 mm, then miss hits such that the ball hits the upper region of the club face than the sweet spot SS are liable to occur. In this case, there is a tendency that the rotational motion of the club head becomes larger and the carry distance is decreased. On the other hand, if the height Hg or height Hs becomes larger, then miss hits such that the ball hits the lower region of the club face than the sweet spot SS are liable to occur. In this case too, there is a tendency that the rotational motion of the club head becomes larger and the carry distance is decreased. Therefore, the gravity point height Hg is preferably not more than 30.0 mm, more preferably not more than 29.0 mm, still more preferably not more than 28.0 mm. The sweet spot height Hs is preferably not more than 35.0 mm, more preferably not more than 34.0 mm, still more preferably not more than 33.0 mm.

The ratio (Mb/Hg) of the vertical moment of inertia Mb and the gravity point height Hg is preferably set to be not less than 1250 g cm, more preferably not less than 1400 g cm, still more preferably not less than 1500 g cm. If the ratio (Mb/Hg) is small, then the vertical moment of inertia Mb is decreased and the vertical gear effect is unfavorably increased, or the gravity point height Hg is increased and miss hits such as lower hits become liable to occur, the launch angle of the ball is decreased, the ball is soon fallen, the backspin is increased and the ball rises very high and have a ballooning effect. Thus the traveling distance is liable to decrease. If the ratio (Mb/Hg) becomes increased, miss hits such as upper hits are liable to occur, therefore, the backspin is decreased and the traveling distance is decreased. Thus, the ratio (Mb/Hg) of the vertical moment of inertia Mb and the gravity point height Hg is preferably set to be not more than 2800 g cm, more preferably not more than 2000 g cm, still more preferably not more than 1600 g cm.

The ratio (Mb/H) of the vertical moment of inertia Mb and club head height H is preferably set to be not less than 60 g cm, more preferably not less than 635 g cm, still more preferably not less than 700 g cm, but preferably not more than 1200 g cm, more preferably not more than 900 g cm, still more preferably not more than 800 g cm. If the ratio (Mb/H) becomes small, then the vertical moment of inertia Mb becomes small and the vertical gear effect is unfavorably increased, or the club head height H is increased and the sweet spot height Hs is also increased and as a result miss hits such as lower hits are liable to increase. If the ratio (Mb/H) becomes large, then in the case that the club head height H is small, miss hits such as top hits are liable to occur.

In order to satisfy the requirement for the ratio (Mb/Ma) of the moments of inertia, the club head 1 in this embodiment is divided into at least three members; a front member 1A, a rear member 1B and a middle member 1C therebetween as shown in FIG. 4 and FIG. 5.

The front member 1A forms the face portion 3, the hosel portion 4 and a front body 9 of the head The front body 9 is such a part extending backward from the edge of the club face 2 so as to form the front parts of the crown, sole and side portions 4, 5 and 6.

In this embodiment, the front member 1A is composed of two pieces which are a face plate 1A1 forming a major part of the face portion 3, and an annular frame 1A2 provided with an opening O1 into which the face plate 1A1 is fitted. The annular frame 1A2 includes the hosel portion 7 and the above-mentioned front body 9, and an opening O2 is formed in the rear thereof. Thus, the annular frame 1A2 in this example is tubular. The front member 1A can be formed as one body of a single material, for example, formed by forging, press molding or the like. However, the front member 1A in this embodiment is made up of two pieces, therefore, the face plate 1A1 and annular frame 1A2 can be made of different materials.

For example, in order to increase the durability, the face plate 1A can be formed as a high-strength forging of a metal material. The annular frame 1A2 can be formed as a casting of a metal material in order to increase the production efficiency.

The rear member 1B forms a rear body of the head including the extreme rear end HB of the club head, and an opening O3 is formed in the front thereof. Thus, it has a shape like a cup. Incidentally, in order to adjust the position of the center of gravity of the head G and/or the values of the moment of inertia, a separate weight member (not shown) made of a material having a large specific gravity can be attached to the rear member 1B.

In this embodiment, the front member 1A and rear member 1B are made of one or more kinds of metal materials. Preferably, stainless steel, maraging steel, pure titanium, titanium alloy and the like are used. In the case of the titanium alloy, for example Ti-6Al-4v, Ti-5.5Al-1Fe, Ti-15V-3Cr-3Al-3Sn, Ti-15Mo-5Zr-3Al, Ti-13V-11Cr-3Al and the like having a large strength are preferred.

The above-mentioned middle member 1C is a tubular body having an annular front edge 11 and an annular rear edge 12 and forms a middle body of the head including middle parts of the crown, sole and side portion 4, 5 and 6 as shown in FIG. 5.

The middle member 1C is made of a material having a specific gravity smaller than those of the front member 1A and rear member 1B, for example aluminum alloy, magnesium alloy and the like. Further, aside from such metal materials, a fiber reinforced resin can be used suitably.

The middle member 1C and front member 1A are fixed each other by overlapping their edges and using an adhesive agent. The middle member 1C and rear member 1B are fixed each other by overlapping their edges and using an adhesive agent.

In this embodiment, the rear edge of the front member 1A is provided with a stepped part 9a to which the front edge of the middle member 1C is fit. The rear edge 12 of the middle member 1C is provided with a stepped part 12a to which the front edge of the rear member is fit. Owing to the stepped parts 9a and 12a, an overlap joint is possible while making the outer surfaces of the members 1A, 1B and 1C flush with each other in the joint parts, and the joint strength is improved.

As explained above, the club head 1 is divided into at least three in the front-back direction, and the middle member 1C is made of the material having the smallest specific gravity, therefore, without the need of largely decreasing the lateral moment of inertia Ma, the vertical moment of inertia Mb can be effectively increased. Further, it is possible to adjust the moments of inertia Ma and Mb easily by changing the size Wm of the middle member 1C in the front-back direction.

Preferably, the size Wm of middle member 1C at every position measured on the outer surface of head in the front-back direction of the head is set to be not less than 45%, more preferably not less than 50%, but not more than 75%, more preferably not more than 70% of the maximum size W of the club head 1 in the front-back direction.

Each of the front edge 11 and rear edge 12 of the middle member 1C is formed substantially along a plane which is substantially parallel with the above-mentioned vertical plane VP or slightly leaned back so as to become substantially parallel with the club face, in other words, inclined at an angle of from zero to the loft angle (beta).

It is preferable that the middle member 1C includes the center of gravity G therein. For example, as shown in FIG. 3, in the plane view of the head under the standard state, the center of gravity G is located between the front edge 11 and rear edge 12 of the middle member 1C. Accordingly, the front member 1A and rear member 1B which are relatively heavy members are located at positions far from the center of gravity G of the head. Thus, the moments of inertia Ma and Mb can be improved in a well balanced manner.

Comparison Tests

Wood-type golf club heads (lie 56.0 degs., loft 11.5 degs.) having specifications shown in Table 1 were made and tested.

Example heads (Exs.1-6) had the basic structure shown in FIGS. 1-5. The moments of inertia was adjusted by changing the size Wm of the middle member and the mass of the weight member. The front member, middle member and rear member were fixed to each other by the use of an epoxide resin adhesive. In Ex.1, the middle member was made of a magnesium alloy (AZ80, specific gravity=1.6, thickness=1.0 mm). In Exs.2-6, the middle members were made of a carbon fiber reinforced resin (specific gravity 1.6, thickness=about 0.8 mm), wherein the middle member had a five-layered structure formed by laminating and hot forming prepreg sheets of carbon fiber (“HR40” Mitsubishi Rayon Co., Ltd., tensile elastic modulus=392 GPa).

Comparative head (Ref. 1) was as shown in FIG. 6, made up of a main body (B) provided with a front opening and a top opening, a face plate (A) covering the front opening, and a crown plate (C) covering the top opening and made of a magnesium alloy (AZ80). The face plate (A), crown plate (c) and main body (B) were fixed to each other by the use of an epoxide resin adhesive.

Comparative heads (Ref. 2 and 3) were as shown in FIG. 7, made up of a main body (B) provided with a front opening and a top opening, a face plate (A) provided with a turnback and covering the front opening, and a crown plate (c) covering the top opening and made of Ti-15V-3Cr-3Al-3Sn. The face plate (A), crown plate (C) and main body (B) were fixed to each other by means of welding.

The details of the tests are as follows.

Ball Traveling Distance Test

The above-mentioned club heads were attached to identical FRP shafts (SRI sports Limited “MP400”, flex R) to make 45-inch wood clubs. Each club was mounted on a swing robot, and hit three-piece balls five times at a head speed of 40 m/s with respect to each of the following hitting positions, and the traveling distances (carry+run) were measured to obtain their mean value.

Position 10 mm above the sweet spot (upper hit)

Position at the sweet spot (center hit)

Position 10 mm under the sweet spot (lower hit)

Traveling Distance Variation Test by Swing Robot with respect to each of the above-mentioned golf clubs, the maximum traveling distance and the minimum traveling distance were determined from all of the three hitting positions, and the different therebetween was calculated. Thus, the smaller value is better.

Traveling Distance Variation Test by Golfers

With respect to each of the above-mentioned golf clubs, each of ten average golfers having handicaps ranging from 10 to 20 hit golf balls ten times to obtain the difference between the maximum traveling distance and minimum traveling distance. Then, the mean value of the differences obtained from the ten golfers was calculated.

The test results are shown in Table 1.

TABLE 1
Head	Ex. 1	Ex. 2	Ex. 3	Ex. 4	Ex. 5	Ex. 6
club head mass (g)	195.7	196.1	195.0	195.2	195.6	195.5
front member
face plate 1A1
material	Ti—6Al—4V
manufacturing method	press molding of rolled material
annular frame 1A2
material	Ti—6Al—4V
manufacturing method	lost-wax precision casting
middle member
material	AZ80	carbon fiber reinforced resin
manufacturing method	die casting	hot forming
rear member
material	Ti—6Al—4V
manufacturing method	casting
weight member	none	W—Ni alloy
head volume (cc)	461	461	459	460	460	462
gravity point height Hg (mm)	26.3	27.1	24.8	25.1	26.5	25.4
club head height H (mm)	58.2	55.8	50.2	51.0	51.3	50.6
sweet spot height Hs (mm)	32.1	33.5	30.8	31.0	32.5	31.5
lateral moment of inertia Ma (g sq.cm)	4360	5210	4480	4000	3920	3740
vertical moment of inertia Mb (g sq.cm)	3700	4250	3960	3670	3810	3880
Mb/Ma	0.849	0.816	0.884	0.918	0.972	1.037
Mb/Hg	1407	1568	1597	1462	1438	1528
Mb/H	636	761	789	720	743	767
traveling distance
upper hit (yard)	209.5	215.7	212.5	210.2	210.8	208.5
center hit (yard)	214.5	217.0	215.2	214.0	215.5	212.9
lower hit (yard)	207.4	212.3	209.5	206.0	208.1	206.3
variation of traveling distance
by robot (yard)	7.1	4.7	5.7	8.0	7.4	6.6
by golfers (yard)	15.7	12.1	13.9	16.7	14.2	14.6
	Head	Ref. 1	Ref. 2	Ref. 3
	club head mass (g)	194.9	195.3	195.5
	head volume (cc)	458	461	460
	crown plate (C)
	material	AZ80	15-3-3-3Ti	15-3-3-3Ti
	manufacturing method	press molding	press molding	press molding
	face plate (A)
	material	Ti—6Al—4V	Ti—5.5Al—1Fe
	manufacturing method	press molding	forging
	head main body (B)
	material	Ti—6Al—4V
	manufacturing method	lost-wax precision casting
	weight member	W—Ni alloy
	gravity point height Hg (mm)	28.5	30.5	31.0
	club head height H (mm)	63.5	62.5	60.0
	sweet spot height Hs (mm)	34.8	37.5	37.0
	lateral moment of inertia Ma (g sq.cm)	4200	4200	5150
	vertical moment of inertia Mb (g sq.cm)	2600	3000	3520
	Mb/Ma	0.619	0.714	0.683
	Mb/Hg	912	984	1135
	Mb/H	409	480	587
	traveling distance
	upper hit (yard)	207.6	209.0	211.3
	center hit (yard)	213.5	214.0	216.5
	lower hit (yard)	200.9	201.5	205.3
	variation of traveling distance
	by robot (yard)	12.6	12.5	11.2
	by golfers (yard)	21.0	19.5	17.5

From the test results, it was confirmed that, according to the present invention, it is possible to increase the traveling distances while decreasing the variation thereof.

The present invention is suitably applied to driving heads whose loft angles are from 8 to 15 degrees.

Claims

1. A wood-type hollow golf club head having a lateral moment of inertia Ma and a vertical moment of inertia Mb which has a ratio (Mb/Ma) of not less than 0.80.

2. The golf club head according to claim 1, wherein

the ratio (Mb/Ma) is not less than 0.90.

3. The golf club head according to claim 1, wherein

the ratio (Mb/Ma) is not less than 1.00.

4. The golf club head according to claim 1, wherein

the vertical moment of inertia Mb is 3500 to 6000 g sq.cm.

5. The golf club head according to claim 1, which has a hollow structure divided in the front-back direction of the head into a front member, a rear member and a middle member therebetween, wherein

the middle member is tubular and has a specific gravity smaller than those of the front member and rear member.

6. The golf club head according to claim 1, wherein

the volume of the head is not less than 400 cc and not more than 470 cc.

7. The golf club head according to claim 1, wherein

the mass of the head is not less than 175 g and not more than 210 g.

8. The golf club head according to claim 1, wherein

the vertical moment of inertia Mb is not less than 3500 g sq.cm and not more than 6000 g sq.cm.

9. The golf club head according to claim 1, wherein

the height H of the head is not less than 40 mm and not more than 58 mm.

10. The golf club head according to claim 1, wherein

the gravity point height Hg of the head is not less than 20.0 mm and not more than 30.0 mm.

11. The golf club head according to claim 1, wherein

the height Hs of the sweet spot is not less than 25.0 mm and not more than 35.0 mm.

12. The golf club head according to claim 1, wherein

the ratio (Mb/Hg) of the vertical moment of inertia Mb to the gravity point height Hg is not less than 1250 g cm and not more than 2800 g cm.

13. The golf club head according to claim 1, wherein

the ratio (Mb/H) of the vertical moment of inertia Mb to the club head height H is not less than 635 g cm and not more than 1200 g cm.

14. The golf club head according to claim 13, wherein

the ratio (Mb/H) is not more than 900 g cm.

15. The golf club head according to claim 13, wherein

the ratio (Mb/H) is not more than 800 g cm.