JP2009148615A - Golf club head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a golf club head by which joint strength between a cover member made of fiber reinforced resin and a head made of a metallic material is raised and good ball hitting feeling can be obtained. <P>SOLUTION: The golf club head 1 includes a head body formed of a metallic material and having at least one opening part O, a cover member FR1 formed of fiber reinforced resin to block the opening part O, and a hollow part set therein. The cover member FR1 has 25-60% of a resin content and the opening part O has an opening area projected to the head surface 15-70% of the total head surface area, and the ratio (L1/La) of head length La that is the longest length in the head front-rear direction from the leading edge Le to the last part of the head to the shortest distance L1 in the head front-rear direction from the leading edge Le to the opening part O1 is 0.40-0.85. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a golf club head configured using a metal material and a fiber reinforced resin.

  Conventionally, there has been proposed a so-called composite golf club head composed of a head body made of a metal material provided with an opening and a cover member made of a fiber reinforced resin that closes the opening (for example, the following patents) Reference 1 or 2). Since the fiber reinforced resin has a smaller specific gravity than a metal material, it helps to reduce the head weight. The reduced weight can be consumed, for example, to increase the size of the head, or can be distributed to the side portion or back face portion of the head such as a toe or heel. Therefore, such a composite head has an advantage that the degree of freedom in weight distribution design is high.

JP 2001-340499 A US Patent Publication 2001/0055995

  However, in the composite golf club head as described above, the joint portion between the head main body and the cover member is easily detached, and improvement in durability has been desired. It was also found that the impact of the composite head, which uses a fiber reinforced resin, transmitted to the player's hand when hitting the ball is not much different from that of a conventional metal head. Therefore, further improvement in feel at impact is desired.

  The present invention was devised in view of the above problems, and based on limiting the resin content of the fiber reinforced resin constituting the cover member to a certain range, the fiber reinforced resin and the metal material An object of the present invention is to provide a golf club head that increases the bonding strength and helps to obtain a good shot feeling.

  The invention according to claim 1 includes a head body made of a metal material provided with at least one opening, and a cover member made of a fiber reinforced resin that closes the opening, and a hollow portion is provided therein. The cover member includes an upper cover member that closes an upper opening provided in a crown portion of the head body, and the resin content of the upper cover member is 25-60. The opening area projected on the head surface is 15 to 70% of the total surface area of the head, and the maximum length in the head longitudinal direction from the leading edge Le of the head to the end of the head. A ratio (L1 / La) between a certain head length La and the shortest distance L1 in the head longitudinal direction from the leading edge Le to the upper opening is 0.40 to 0.85. Is a golf club head which is characterized the door.

  The invention according to claim 2 is the golf club head according to claim 1, wherein the ratio (L1 / La) is 0.5 or more.

  The invention according to claim 3 is the golf club head according to claim 1, wherein the ratio (L1 / La) is 0.6 or more.

  The invention described in claim 4 includes a head body made of a metal material provided with at least one opening, and a cover member made of fiber reinforced resin for closing the opening, and a hollow portion is provided inside. The cover member includes a lower cover member that closes a lower opening provided in a sole portion of the head body, and the resin content of the lower cover member is 25 to 25. The lower opening is 60%, and the opening area projected on the head surface is 15 to 70% of the total surface area of the head, and the maximum length in the head longitudinal direction from the leading edge Le of the head to the end of the head. The ratio (L2 / La) between the head length La and the horizontal shortest distance L2 from the leading edge Le to the lower opening is 0.30 to 0.70. It is a golf club head according to symptoms.

  The invention according to claim 5 is the golf club head according to claim 4, wherein the ratio (L2 / La) is 0.4 or more.

  The invention according to claim 6 is the golf club head according to claim 4, wherein the ratio (L2 / La) is 0.5 or more.

  The invention according to claim 7 includes a head body made of a metal material provided with at least one opening, and a cover member made of a fiber reinforced resin that closes the opening, and a hollow part is provided inside. The cover member includes an intermediate cover member that closes an intermediate opening provided in a side portion of the head main body, and the resin content of the intermediate cover member is 25 to 25. The intermediate opening is 60%, and the opening area projected on the head surface is 15 to 70% of the total surface area of the head, and the maximum length in the head longitudinal direction from the leading edge Le of the head to the end of the head The ratio (L3 / La) between the head length La and the shortest distance L3 in the head longitudinal direction from the leading edge Le to the intermediate opening is 0.50-0. It is a golf club head, which is a 80.

  The invention according to claim 8 is the golf club head according to claim 7, wherein the ratio (L3 / La) is 0.6 or more.

  In the golf club heads according to the first, fourth, and seventh aspects of the present invention, the resin content of the cover member is 25 to 60%. The value of the resin content is larger than that of a conventional general fiber reinforced resin. According to experiments by the inventors, it has been found that the bonding strength between the fiber reinforced resin and the metal material is improved as the resin content of the fiber reinforced resin is increased. The reason is presumed that the crack resistance at the bonding interface of the fiber reinforced resin is improved by reducing the fiber amount of the fiber reinforced resin. Therefore, in the golf club head of the present invention, the bonding strength between the cover member and the metal material is improved as compared with the conventional composite type head. Further, since the resin has a vibration absorbing action that quickly attenuates the vibration, the cover member quickly absorbs the vibration of the head by increasing the resin content of the fiber reinforced resin. This is useful for impressing the player with a good shot feeling.

  Further, in the golf club heads of the inventions described in claims 1, 4 and 7, the ratios (L1 / La), (L2 / La) or (L3 / La) are limited to a certain range. Thus, the cover member is disposed behind the head. For this reason, not only the face portion but also the portion located behind and where a large impact force acts upon hitting the ball is formed of the metal material, and the deterioration of durability is surely prevented.

It is a perspective view of the standard state of the head which shows the embodiment of the present invention. FIG. It is a front view of FIG. It is a bottom view of FIG. It is AA sectional drawing of FIG. It is a disassembled perspective view of a head. It is an expanded view which expands and shows the prepreg of a cover member. It is a top view which shows other embodiment of a head. It is the bottom view.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view of a golf club head (hereinafter, simply referred to as “head”) 1 of the present embodiment in a reference state, FIG. 2 is a plan view thereof, FIG. 3 is a front view thereof, and FIG. 5 is a bottom view thereof, FIG. 5 is an enlarged cross-sectional view taken along line AA of FIG. 2, and FIG. 6 is an exploded perspective view of the head. The reference state of the head 1 is a state in which the sole surface is in contact with the horizontal plane HP as a specified lie angle and loft angle (real loft angle).

  The head 1 of the present embodiment includes a face portion 3 having a face surface 2 that is a surface for hitting a ball, a crown portion 4 that is continuous with the face portion 3 and forms the top surface of the head, and a bottom surface of the head that is continuous with the face portion 3 and forms the head bottom surface. A sole portion 5, a side portion 6 that extends between the crown portion 4 and the sole portion 5 and extends from the toe 3 a of the face portion 3 through the back face to the heel 3 b, and a shaft (not shown) provided on the heel side. A hollow type driver (# 1) or a fairway wood having a neck portion 7 into which one end is inserted and having a hollow portion i provided therein is exemplified.

Although not particularly limited, the head 1 of the present embodiment desirably has a head volume of, for example, 300 cm ³ or more, more preferably 400 cm ³ or more, and still more preferably 420 cm ³ or more. Such a head 1 increases the sense of security when it is held, and helps to increase the sweet area and the moment of inertia. The upper limit of the head volume is not particularly defined, but is practically preferably 500 cm ³ or less, for example, and is preferably 470 cm ³ or less when complying with R & A and USGA rules.

  As shown in FIG. 6, the head 1 includes a head body M made of a metal material and a cover member FR made of a fiber reinforced resin.

  The head main body M is provided with at least one, in this example, a plurality, more specifically three openings O1, O2 and O3 in this example. The opening O does not include the shaft insertion hole 7 a provided in the neck portion 7. The opening O is useful for reducing the weight of the head body M by reducing the amount of metal material having a large specific gravity. This helps to increase the degree of freedom in weight distribution design. Further, by dividing the opening portion O into a plurality of portions, for example, it is possible to secure a total sufficient opening area while reducing the individual opening area and preventing an excessive decrease in strength of the head body M, for example. From such a viewpoint, the number of the opening portions O is preferably 2 or more, more preferably 3 or more, and from the viewpoint of productivity, preferably 5 or less, more preferably 4 or less.

  The head main body M of the present embodiment includes the face portion 3, the crown main wall portion 10 provided with the upper opening O1 and forming the main portion of the crown portion 4, the lower opening portion O2, and the sole portion. 5 that includes the sole main wall portion 11 that forms the main portion of 5, the side main wall portion 12 that is provided with an intermediate opening portion O3 and forms the main portion of the side portion 6, and the neck portion 7. Illustrated. The head main body M of this embodiment is one in which the above-mentioned parts are integrally formed by casting, but the manufacturing method is not particularly limited. That is, the head main body M includes one formed by forging, casting, pressing, rolling, or the like to form two or more parts and then integrally joining them by welding or the like.

  The head main body M of this embodiment is exemplified by a titanium alloy (Ti-6Al-4V) having a specific gravity of approximately 4.4 to 4.5. As the metal material of the head main body M, one or more of, for example, stainless steel, maraging steel, titanium, aluminum alloy, magnesium alloy or amorphous alloy are used in addition to the titanium alloy.

  As in the head main body M of the present embodiment, the face portion 3, the crown main wall portion 10, the sole main wall portion 11, the side main wall portion 12 and the neck portion 7 are integrally formed in advance. It is preferable in terms of good finishing accuracy of corners and loft angles. In addition, since the head main body M includes the side main wall portion 12, more weight can be distributed around the head, which is useful for increasing the moment of inertia.

  The crown main wall portion 10 includes a crown surface portion 10a that forms a substantially outer surface portion of the crown portion 4, and a crown receiving portion 10b whose surface is recessed with a step from the crown surface portion 10a toward the hollow portion i. Are illustrated. The upper opening O1 is provided on the back face side of the crown portion 4, and a crown receiving portion 10b is formed around the opening O1. A relatively large impact force is generated in the crown portion 4 at the time of hitting. Accordingly, the upper opening O1 is provided as far as possible from the face surface 2, and the face surface 2 side of the crown main wall portion 11 is a crown surface portion 10a having high rigidity, thereby improving durability.

As shown in FIG. 5, the head length La which is the maximum length in the head longitudinal direction from the leading edge Le of the head 1 (the position closest to the face surface 2 in the reference state) to the rearmost part of the head, and the leading edge The ratio (L1 / La) with the shortest distance L1 in the head longitudinal direction from Le to the upper opening O1 is 0.40 or more, more preferably 0.50 or more, and further preferably 0.60 or more. Even if the shortest distance L1 is too large, a sufficient opening area cannot be ensured in the crown portion 4, and the lowering of the center of gravity of the head is likely to be hindered. From such a viewpoint, the upper limit of the ratio is preferably 0.85 or less, more preferably 0.80 or less. As shown in FIG. 2, the head front-rear direction is a direction parallel to a normal line N that is lowered from the head gravity center G to the face surface 2 in plan view in the reference state.

Similarly, the sole main wall portion 11 includes a sole surface portion 11a forming a substantially outer surface portion of the sole portion 5, and a sole receiving portion 11b whose surface is recessed with a step from the sole surface portion 11a to the hollow portion i side. including. The lower opening portion O2 is provided close to the back face side of the sole portion 5 in the same manner as the upper opening portion O1. The sole receiving portion 11b is formed in an annular shape around the lower opening O2. As a result, the sole main wall portion 11 also helps to secure a sufficient opening area while ensuring strength. As described above, the ratio (L2 / La) between the head length La and the horizontal shortest distance L2 from the leading edge Le to the lower opening O2 is 0.30 or more, more preferably 0. .40 or more, more preferably 0.50 or more, and the upper limit is 0.70 or less , more preferably 0.60 or less.

Further, the side main wall portion 12 is provided around a side surface portion 12a that forms a substantially outer surface portion of the side portion 6 and an intermediate opening portion O3, and the surface has a step from the side surface portion 12a to the hollow portion i side. And a recessed side receiving portion 12b. Further, for the same reason as the crown main wall portion 11 or the sole main wall portion 11, the head length La and the shortest distance L3 in the head longitudinal direction from the leading edge Le to the intermediate opening O3 (shown in FIG. 4). Ratio (L3 / La) is 0.30 or more, more preferably 0.40 or more, still more preferably 0.50 or more, and the upper limit is 0.80 or less, more preferably It is 0.70 or less, more preferably 0.60 or less.

  When the respective ratios (L1 / La), (L2 / La), and (L3 / La) are limited, not only the face portion 3 but also a portion that is located behind the portion and a large impact force acts upon hitting a ball. Since it is also formed of a metal material, it is possible to reliably prevent a decrease in durability.

  An upper cover member FR1, a lower cover member FR2, and an intermediate cover member FR3 are joined to the receiving portions 10b, 11b, and 12b, respectively. The cover members FR1, FR2 and FR3 are separated without contacting each other, but may be integrated. In the present embodiment, the cover members FR1 to FR3 are fixed to the receiving portions 10b, 11b and 12b with an adhesive. Each of the receiving portions 10b, 11b and 12b absorbs the thickness of the cover member FR disposed on each of the steps, and serves to finish the head main body M and the cover member FR flush with each other.

  As shown in FIG. 5, the length Wa of each of the receiving portions 10b to 12b measured in a direction perpendicular to the edge of each opening O is not particularly limited, but if it is too small, the head main body M and the cover member FR Since the bonding area becomes small, the bonding strength tends to decrease. On the other hand, if it is too large, the area of the opening O tends to be small and a sufficient weight reduction effect tends not to be obtained. From such a viewpoint, the width Wa is, for example, 5.0 mm or more, preferably 10.0 mm or more, and the upper limit is 30.0 mm or less, more preferably 20.0 mm or less, and particularly preferably 15.0 mm or less. . Needless to say, the width Wa may be changed in each part.

  As shown in FIG. 6, the cover member FR of the present embodiment is an upper cover that is spaced apart from each other and closes each opening (the upper opening O1, the lower opening O2, and the intermediate opening O3). A plurality (specifically, three) of the member FR1, the lower cover member FR2, and the intermediate cover member FR are included. Each cover member FR is a plate-like body that is curved with a small thickness and a smooth curved surface. The cover member FR of the present embodiment is formed separately from the head main body M, and is fixed to each opening O of the head main body M using an adhesive.

  The fiber reinforced resin constituting the cover member FR is a composite material in which fibers as a reinforcing material and a matrix resin are combined, and has a specific gravity smaller than that of a metal material. For this reason, the head 1 of the present invention can achieve a great weight reduction effect in combination with the opening O provided in the head main body M. The reduced weight can be used, for example, to lower the position of the center of gravity by being distributed to an appropriate position of the head body M, or to be distributed to the side portion 6 to increase the moment of inertia. Therefore, the head 1 of the present invention has a high degree of freedom in weight distribution design.

  The matrix resin is preferably, for example, an epoxy resin, an unsaturated polyester resin, a vinyl ester resin, a phenol resin, a nylon resin, or a polycarbonate resin. The fibers are preferably organic fibers such as carbon fibers, glass fibers, aramid fibers or polyphenylene benzoxazole resin fibers (PBO fibers), and metal fibers such as amorphous fibers or titanium fibers. In particular, carbon fibers having a low specific gravity and a high tensile strength are particularly preferable. In addition, a fiber contains either a long fiber or a short fiber, or both.

  Further, the tensile modulus of the fiber is not particularly limited, but if it is too small, the rigidity of the cover member FR cannot be secured and the durability tends to decrease. Conversely, if it is too large, the cost increases and the tensile strength decreases. Tend to invite. From such a viewpoint, the elastic modulus of the fiber is 50 GPa or more, more preferably 100 GPa or more, further preferably 150 GPa or more, particularly preferably 200 GPa or more, and the upper limit is preferably 450 GPa or less, more preferably 350 GPa or less, and further Preferably it is 300 GPa or less. The tensile elastic modulus is a value measured according to “Carbon Fiber Test Method” of JIS R7601. The cover member FR of the present embodiment is made of a fiber reinforced resin in which an epoxy resin and a carbon fiber are combined, and has a specific gravity of approximately 1.3 to 1.4.

  In the head 1 of the present invention, the resin content of the fiber reinforced resin is set to 25 to 60% in the cover member FR. The “resin content” is the weight ratio of the resin to the total weight of the fiber reinforced resin. The weight of the resin can be obtained by chemically decomposing and removing only the resin from the fiber reinforced resin to be measured, taking out only the fiber, and subtracting the total weight of the fiber from the previously measured weight of the fiber reinforced resin. it can. In order to chemically remove the resin from the fiber reinforced resin, for example, a heated nitric acid solution is used. For example, methyl ethyl ketone is used to chemically remove the resin from the prepreg. When the cover member FR is composed of a plurality spaced apart from each other, it is sufficient that the average value of the resin content of each cover member FR satisfies the numerical range, but preferably the resin content of each cover member FR is It is desirable to satisfy both numerical ranges.

  The inventors paid attention to a matrix resin of a fiber reinforced resin. In general, the role of the matrix resin in the fiber reinforced resin is to solidify the fiber and maintain the shape, and it is considered that the matrix resin is not substantially involved in the rigidity itself. However, the inventors have found that the matrix resin in the composite head 1 has a great influence on the adhesion to the metal material and the shot feeling.

  One of the occurrences of peeling at the bonding interface between a metal material and a fiber reinforced resin is that the surface of the fiber reinforced resin has a fine crack due to the stress in the vertical or shear direction acting on the bonding interface. Thus, it is considered to include those that grow to an adhesive interface and lead to peeling. On the other hand, when the resin content of the fiber reinforced resin is increased, the amount of fibers is relatively decreased, and as a result, the crack resistance at the adhesion interface of the fiber reinforced resin is improved. Therefore, increasing the proportion of the matrix resin in the fiber reinforced resin leads to an improvement in the adhesive strength with the metal material.

  Next, the feeling of hitting will be described. In the conventional technique, since the focus was only on increasing the rigidity of the cover member FR, the amount of fibers was increased. For this reason, the resin content is about 20%, and it is considered that there was no superior shot feel compared to the metal head 1. However, the matrix resin exhibits a vibration absorbing action that quickly attenuates vibration compared to a metal material. Therefore, as in this embodiment, by setting the resin content of the fiber reinforced resin to a certain value or more, it is useful to quickly attenuate the vibration of the head with the cover member FR and impress the player with a good shot feeling.

  From the above viewpoints, the resin content is preferably 30% or more, more preferably 35% or more, and still more preferably 40% or more. On the other hand, when the resin content in the fiber reinforced resin is increased, the rigidity of the fiber reinforced resin itself is reduced with a decrease in the amount of fibers. For this reason, a difference in rigidity from the head main body becomes large at the bonding interface, and stress concentration tends to occur at the bonding interface, which also causes a decrease in durability. From such a viewpoint, the upper limit of the resin content is set to 60%, more preferably 55% or less, and still more preferably 50% or less. When there are a plurality of cover members FR, the resin content may be the same or different. Particularly preferably, for cover members that are less affected by impact force at the time of hitting the ball, the resin content is generally increased to further improve the feel at impact, while for cover members that are relatively affected by impact force, the resin content is increased. Can be made relatively small. Specifically, it is desirable that the resin content of the upper and lower cover members FR1 and FR2 is smaller than the resin content of the intermediate cover member FR3.

  The shock absorbing action is obtained by the cover member FR that closes the opening O. Therefore, if the area of the opening O is not sufficient, the area occupied by the cover member FR is also reduced, and as a result, it is difficult to obtain the above-described shock absorbing action. Therefore, although not particularly limited, the opening area So obtained by projecting the opening O onto the head surface (when there are a plurality of openings O, the total opening area is the total opening area) is 15 of the head total surface area Sh. % Or more, preferably 20% or more, and more preferably 30% or more. On the other hand, even if the opening area So is too large, the strength of the head main body M is easily lost. From such a viewpoint, the opening area So of the opening O is preferably 70% or less, more preferably 60% or less, and still more preferably 50% or less of the total head surface area Sh. The head total surface area Sh is specified by filling a hole for inserting a shaft provided in the neck portion 7.

  Further, when the opening area of each of the opening portions O1, O2, and O3 is reduced, there is a tendency that the opening portion (and the cover member FR that covers the opening portion) does not provide light weight and a sufficient impact absorbing function. If it is too much, the durability of the head 1 is likely to be deteriorated. From such a viewpoint, although not particularly limited, the opening area of each of the openings O1, O2, and O3 is preferably 3% or more, more preferably 5% or more of the total head surface area Sh, and the upper limit is desirable. It is preferably 40% or less, more preferably 35% or less, and still more preferably 30% or less. Note that the opening areas of the openings 01, 02, and 03 can be set within a preferable range in any combination of the above upper limit and lower limit.

  As a more preferred embodiment, the opening O is, as shown in FIG. 3, the lower region A1, which is a region having a height equal to or less than 1/6 of the head maximum height H from the horizontal plane HP in the reference state, At least two regions of the upper region A3 which is a region having a height of 2/3 or more of the head maximum height H from the horizontal plane HP, and an intermediate region A2 between the lower region A1 and the upper region A3, more preferably 3 It is desirable to be provided at a position including two regions. As a result, the openings O are provided in a distributed manner in the head main body M, and it is possible to effectively reduce the weight and improve the feel at impact.

  The head 1 of this embodiment is exemplified by a cover member FR that is formed separately from the head body M and then fixed to the head body M with an adhesive. However, for example, a so-called internal pressure molding method is adopted in which a sheet-like uncured prepreg is attached to the opening O of the head main body M, and the cover member FR is integrated with the head main body M at the same time as molding by putting it into a mold. It may be adopted. In the internal pressure molding method, a bladder is disposed in advance in the hollow portion i of the head main body M, and by expanding the bladder, the prepreg is molded into a preferable shape by receiving heat and pressure from the inside and the outside.

  Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be applied to, for example, an iron type or utility type golf club head having a hollow structure. Further, the shape of the opening O is not limited to the specific shape shown in the figure, and it is needless to say that various changes can be made.

  Based on the specifications in Table 1, wood-type golf club heads (Examples and Comparative Examples) were prototyped and subjected to various tests and measurements. The head main body was a cast product using a titanium alloy (Ti-6Al-4V). The cover member is a unidirectional prepreg formed by aligning carbon fiber “HR40” (tensile modulus: 392 GPa) manufactured by Mitsubishi Rayon Co., Ltd. in one direction and impregnating it with a matrix resin (bisphenol A type epoxy resin). Was formed using 5 sheets. As shown in Table 1, prepregs having a resin content of 20%, 30%, 35%, 40%, 50%, 60% and 70% were prepared. In addition, in the case of using a plurality of cover members, the resin content is the same.

  Further, as shown in FIG. 7, the cover member is a first prepreg in which the longitudinal direction of the carbon fiber f of the prepreg P is inclined by 90 ° (toe-heel direction) with respect to the front-rear direction of the head. It was formed by heating and curing a laminated body in which five layers of P1 and second prepreg P2 oriented at 0 ° were alternately arranged. Further, the cover member was integrally bonded to the head body using an adhesive (EW2214 manufactured by Sumitomo 3M).

Each head was targeted for a head volume of 400 cm ³ , a real loft angle of 11 ° and a lie angle of 57 °. The thickness of the cover member was substantially 0.8 mm. In the following, only the features of the comparative example and the example will be briefly described.
<Comparative Examples 1 and 2>
The resin content of the fiber reinforced resin of the cover member is 70% and 15%, respectively.
<Comparative Example 3>
All of the head is made of a titanium alloy and has no opening and no cover member.
<Example 11>
As shown in FIG. 8 and FIG. 9, one opening and one cover member are provided.
<Example 12>
By adjusting the position of the opening of the head body, a head body having no opening in the lower region was obtained.
<Example 13>
The position of the opening of the head main body was adjusted to obtain a head main body having no opening in the intermediate region.
<Comparative example 4>
The position of the opening of the head main body was adjusted to obtain a head main body having no openings in the intermediate region and the lower region.
<Examples other than the above>
By adjusting the position of the opening of the head body, a head body having openings in the lower region, the middle region and the upper region was obtained. The evaluation method is as follows.

<Durability>
Each test head is fitted with the same shaft made by FRP (MP200, Flex R, manufactured by SRI Sports Co., Ltd.) to produce a 45-inch wood golf club, and each test club is attached to a swing robot with a head speed of 50 m. Each two-club golf ball was hit with 4000 balls at a sweet spot SS (FIG. 2) on the face surface for each club. The evaluation was made based on the number of hit balls in which the head was damaged.

<Hit feel>
The hit feeling was compared between each of the test clubs and a comparative club having a head (Comparative Example 3) that was entirely made of a titanium alloy. The testers were 10 right-handed golfers (handicap 5 to 15), and recorded the number of people who felt that the impact at the time of hitting was less than that of Comparative Example 3 and the shot feeling was good. The larger the value, the better.

<Inertia moment>
In the standard state of the head, the moment of inertia around the vertical axis passing through the center of gravity of the head (left and right moment of inertia), the toe passing through the center of gravity of the head and perpendicular to the head longitudinal direction, and the moment of inertia around the horizontal axis in the heel direction (upper and lower inertia) Moment) was measured using MOMENT OF INERTIA MEASURING INSTRUMENT MODEL NO.005-002 manufactured by INERTIA DYNAMICS Inc. The larger the value, the smaller the head blur at the time of a miss shot and the better. Table 1 shows the test results.

  As a result of the test, the examples had improved durability and hitting sound, and the significant effects of the present invention could be confirmed. It was also confirmed that the moment of inertia was large and the degree of freedom in weight distribution design was high.

DESCRIPTION OF SYMBOLS 1 Golf club head 2 Face surface 3 Face part 4 Crown part 5 Sole part 6 Side part 7 Neck part 10 Crown main wall part 11 Sole main wall part 12 Side main wall part FR Cover member FR1 Cover member FR2 Lower cover member FR3 Middle cover member O Opening O1 Upper opening O2 Lower opening O3 Middle opening A1 Lower area A2 Middle area A3 Upper area

Claims (8)

  A golf club head including a head body made of a metal material provided with at least one opening, and a cover member made of a fiber reinforced resin for closing the opening, and having a hollow inside.
  The cover member includes an upper cover member that closes an upper opening provided in a crown portion of the head body,
  The resin content of the upper cover member is 25 to 60%, and the upper opening has an opening area projected on the head surface of 15 to 70% of the total head surface area.
  The ratio (L1) of the head length La, which is the maximum length in the head longitudinal direction from the leading edge Le of the head to the head end, and the shortest distance L1 in the head longitudinal direction from the leading edge Le to the upper opening. / La) is 0.40 to 0.85, a golf club head.   The golf club head according to claim 1, wherein the ratio (L1 / La) is 0.5 or more.   The golf club head according to claim 1, wherein the ratio (L1 / La) is 0.6 or more.   A golf club head including a head body made of a metal material provided with at least one opening, and a cover member made of a fiber reinforced resin for closing the opening, and having a hollow inside.
  The cover member includes a lower cover member that closes a lower opening provided in a sole portion of the head body,
  The resin content of the lower cover member is 25 to 60%, and the lower opening has an opening area projected on the head surface of 15 to 70% of the total head surface area.
  The ratio (L2 / La) of the head length La, which is the maximum length in the head longitudinal direction from the leading edge Le of the head to the head end, and the horizontal shortest distance L2 from the leading edge Le to the lower opening. ) Is 0.30 to 0.70.   The golf club head according to claim 4, wherein the ratio (L2 / La) is 0.4 or more.   The golf club head according to claim 4, wherein the ratio (L2 / La) is 0.5 or more.   A golf club head including a head body made of a metal material provided with at least one opening, and a cover member made of a fiber reinforced resin for closing the opening, and having a hollow inside.
  The cover member includes an intermediate cover member that closes an intermediate opening provided in a side portion of the head body,
  The resin content of the intermediate cover member is 25 to 60%, and the intermediate opening has an opening area projected on the head surface of 15 to 70% of the total head surface area.
  The ratio (L3) of the head length La, which is the maximum length in the head longitudinal direction from the leading edge Le of the head to the head end, and the shortest distance L3 in the head longitudinal direction from the leading edge Le to the intermediate opening. / La) is 0.50 to 0.80, a golf club head.   The golf club head according to claim 7, wherein the ratio (L3 / La) is 0.6 or more.