US20090291775A1 - Wood-type golf club head - Google Patents

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 inFIG. 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 inFIG. 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 theclub head1 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 theclub face2 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 theshaft inserting hole7acan 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 theclub face2 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 thehighest point4tof thecrown portion4 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 leastnumber 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 head1 according to the present invention is a hollow head for a wood-type golf club such as driver (#1) or fairway wood, and thehead1 comprises: aface portion3 whose front face defines aclub face2 for striking a ball; acrown portion4 intersecting theclub face2 at theupper edge2athereof; asole portion5 intersecting theclub face2 at thelower edge2bthereof; aside portion6 between thecrown portion4 andsole portion5 which extends from a toe-side edge2cto a heel-side edge2dof theclub face2 through the back face BF of the club head; and ahosel portion7 at the heel side end of the crown to be attached to an end of a club shaft (not shown) inserted into theshaft inserting hole7a.Thus, theclub head1 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 theface3.
• The volume of theclub head1 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 theclub head1 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 theclub head1 is preferably not more than 470 cc, more preferably not more than 460 cc. Similarly, the mass of theclub head1 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 theclub face2, 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 theclub head1 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 inFIG. 9, even if the ball hitting position is off the sweet spot SS of theclub face2 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 theclub head1 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, theclub head1 in this embodiment is divided into at least three members; afront member1A, arear member1B and amiddle member1C therebetween as shown inFIG. 4 andFIG. 5.
• Thefront member1A forms theface portion3, thehosel portion4 and afront body9 of the head Thefront body9 is such a part extending backward from the edge of theclub face2 so as to form the front parts of the crown, sole andside portions4,5 and6.
• In this embodiment, thefront member1A is composed of two pieces which are a face plate1A1 forming a major part of theface portion3, and an annular frame1A2 provided with an opening O1 into which the face plate1A1 is fitted. The annular frame1A2 includes thehosel portion7 and the above-mentionedfront body9, and an opening O2 is formed in the rear thereof. Thus, the annular frame1A2 in this example is tubular. Thefront member1A can be formed as one body of a single material, for example, formed by forging, press molding or the like. However, thefront member1A in this embodiment is made up of two pieces, therefore, the face plate1A1 and annular frame1A2 can be made of different materials.
• For example, in order to increase the durability, theface plate1A can be formed as a high-strength forging of a metal material. The annular frame1A2 can be formed as a casting of a metal material in order to increase the production efficiency.
• Therear member1B 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 therear member1B.
• In this embodiment, thefront member1A andrear member1B 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-mentionedmiddle member1C is a tubular body having an annularfront edge11 and an annularrear edge12 and forms a middle body of the head including middle parts of the crown, sole andside portion4,5 and6 as shown inFIG. 5.
• Themiddle member1C is made of a material having a specific gravity smaller than those of thefront member1A andrear member1B, for example aluminum alloy, magnesium alloy and the like. Further, aside from such metal materials, a fiber reinforced resin can be used suitably.
• Themiddle member1C andfront member1A are fixed each other by overlapping their edges and using an adhesive agent. Themiddle member1C andrear member1B are fixed each other by overlapping their edges and using an adhesive agent.
• In this embodiment, the rear edge of thefront member1A is provided with a steppedpart9ato which the front edge of themiddle member1C is fit. Therear edge12 of themiddle member1C is provided with a steppedpart12ato which the front edge of the rear member is fit. Owing to the steppedparts9aand12a,an overlap joint is possible while making the outer surfaces of themembers1A,1B and1C flush with each other in the joint parts, and the joint strength is improved.
• As explained above, theclub head1 is divided into at least three in the front-back direction, and themiddle member1C 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 themiddle member1C in the front-back direction.
• Preferably, the size Wm ofmiddle member1C 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 theclub head1 in the front-back direction.
• Each of thefront edge11 andrear edge12 of themiddle member1C 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 themiddle member1C includes the center of gravity G therein. For example, as shown inFIG. 3, in the plane view of the head under the standard state, the center of gravity G is located between thefront edge11 andrear edge12 of themiddle member1C. Accordingly, thefront member1A andrear member1B 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 inFIGS. 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 inFIG. 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 and3) were as shown inFIG. 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 (15)

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 toclaim 1, wherein

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

3. The golf club head according toclaim 1, wherein

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

4. The golf club head according toclaim 1, wherein

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

5. The golf club head according toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 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 toclaim 13, wherein

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

15. The golf club head according toclaim 13, wherein

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

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