JP2008079969A - Wood type golf club head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the carry of a hit ball by reducing the back spin amount of the ball. <P>SOLUTION: This wood type golf club head 1 provided with a face 2 for hitting a ball and having a loft angle of 30° or less, has a plurality of face grooves 8 extending in the toe-heel direction on the face 2 and having the depth of 0.200-0.508 mm, and a plurality of auxiliary grooves 9 having the depth of 0.005-0.025 mm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wood type golf club head having a loft angle of 30 degrees or less, and more particularly to a wood type golf club head capable of increasing the flight distance of a hit ball by reducing the backspin amount of the ball.

  In golf clubs, flight distance performance is one of the important indicators. In particular, a driver, a fairway wood or a similar wood type golf club is required to have higher flight distance performance than an iron type golf club.

  By the way, a general wood type golf club head has a depth of center of gravity (distance from the center of gravity of the head to the sweet spot of the face) as large as approximately 18 mm or more. Easy to go up. For this reason, it is considered that reducing the backspin amount of the hit ball is advantageous for increasing the flight distance, and the effect has been confirmed in the actual hit test.

  Conventionally, a hollow wood-type golf club head has been proposed in the following Patent Document 1 for the purpose of improving the flight distance by increasing the launch angle of the ball while reducing the backspin amount. This club head has been proposed to increase the coefficient of friction of the face by increasing the width and depth of so-called face line grooves provided on the face and decreasing the arrangement pitch. This is because in a wood type golf club with a small loft angle, the larger the friction coefficient of the face, the lower the backspin amount of the ball, and as a result, a trajectory with a low rise that is advantageous for improving the flight distance can be obtained. Based on the knowledge.

JP 2006-61206 A

  However, the hollow wood-type golf club head of Patent Document 1 has a problem that durability of the face portion is lowered because face line grooves having a large depth and width are provided in the face portion having a small thickness. . Further, when hitting a ball, the surface layer of the golf ball (hereinafter sometimes simply referred to as “cover”) may be easily scraped, and the ball may be frequently damaged.

  On the other hand, a method of increasing the friction between the ball and the face by eliminating the face groove and subjecting the face to shot blasting to increase its ten-point average roughness is also conceivable. However, in such a mode, it is difficult to obtain sufficient friction between the face and the ball during play in rainy weather, and the flight distance is likely to vary greatly and miss shots are likely to occur.

  The present invention has been devised in view of the above circumstances. A face groove extending in the toe-heel direction and having a depth of 0.200 to 0.508 mm and a depth of 0.005 are provided on the face. For the purpose of providing a wood-type golf club head capable of reducing the backspin amount while suppressing the damage to the ball and consequently increasing the flight distance on the basis of providing an auxiliary groove of ~ 0.025 mm. Yes.

  The invention according to claim 1 of the present invention is a wood-type golf club head having a face for hitting a ball and having a loft angle of 30 degrees or less, extending to the face in the toe-heel direction. A plurality of face grooves having a depth of 0.200 to 0.508 mm and a plurality of auxiliary grooves having a depth of 0.005 to 0.025 mm are provided.

  The invention according to claim 2 is the wood type golf according to claim 1, wherein the ratio (d2 / d1) between the depth d1 of the face groove and the depth d2 of the auxiliary groove is 0.010 to 0.13. Club head.

  According to a third aspect of the present invention, in the wood type golf club head according to the first or second aspect, an interval between the auxiliary grooves is smaller than an interval between the face grooves.

  According to a fourth aspect of the present invention, the auxiliary groove includes a portion extending in a direction crossing the face groove, and an intersection angle between the face groove and the auxiliary groove is a horizontal plane at a specified lie angle and loft angle. 4. The wood type golf club head according to claim 1, wherein, in a grounded reference state, the toe side or the heel side is larger than the face center side including the sweet spot of the face.

  According to a fifth aspect of the present invention, in the wood type golf according to any one of the first to fourth aspects, the auxiliary groove has an arc shape having a center in a region within 5 mm in the toe-heel direction from the sweet spot of the face. Club head.

  The invention according to claim 6 is the wood type golf club head according to claim 5, wherein the center of the auxiliary groove is provided within a circle having a radius of 5 mm.

  In the present invention, a face of a wood type golf club head having a loft angle of 30 degrees or less, a face groove extending in the toe-heel direction and having a depth of 0.200 to 0.508 mm, and a depth of 0.005 to 0.005. Auxiliary grooves that are 0.025 mm are provided. The combination of the face groove and the auxiliary groove with such a limited depth reduces the backspin amount while preventing the ball from being damaged by optimizing the friction state between the face and the ball. The flight distance can be improved.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a front view of a reference state of a wood type golf club head (hereinafter, simply referred to as “club head” or “head”) 1 of the present embodiment, and FIG.

  Here, the reference state of the club head 1 means that the axial center line CL of the shaft is arranged in an arbitrary vertical plane VP and is inclined with respect to the horizontal plane HP at the lie angle β, and the face 2 is tilted to the vertical plane VP. Is inclined at a loft angle α (real loft angle, the same applies hereinafter) with respect to the plane VP1 parallel to the horizontal plane HP. Unless otherwise specified in the present specification, the head 1 is assumed to be in such a reference state. The vertical or height direction with respect to the club head 1 means the vertical or height direction with respect to the head 1 in the reference state.

  The club head 1 includes a face portion 3 having a face 2 as a surface for hitting a ball on the front surface, a crown portion 4 connected to the upper edge 2a of the face 2 and forming the upper surface of the face 2, and a lower edge 2b of the face 2 A sole portion 5 that forms a continuous bottom of the head, a side portion 6 that extends between the crown portion 4 and the sole portion 5 from the toe side edge 2c of the face 2 through the back face BF to the heel side edge 2d, and a crown portion 4 and a hosel portion 7 having a shaft insertion hole 7a on which a shaft (not shown) is mounted. Since the shaft center line of the shaft insertion hole 7a substantially coincides with the shaft center line CL of the shaft, it is used when the lie angle β is set.

  Further, as shown in FIG. 2, the club head 1 is provided with a hollow portion i therein. The hollow part i may be left hollow, or a weight adjusting material or the like may be provided. The wood type golf club head does not mean that the head material is made of a wood material, but has a head shape that has been mainly formed of a wood material, and specifically, a driver. (# 1), plusy (# 2), spoon (# 3), buffy (# 4) and creek (# 5) at least, and these heads have almost similar shapes, although they have different counts or names (For example, utility head).

  Further, as shown in FIG. 2, the club head 1 of the present embodiment includes a head body 1A having an opening Of on the face side, and a substantially cup-shaped face welded and fixed to the opening Of of the head body 1A. It has a metal and two-piece structure formed by the member 1B. In the present embodiment, the head body 1A is formed by a lost wax precision casting method, and the face member 1B is formed by, for example, pressing a rolled material. However, it goes without saying that the club head 1 of the present invention is not limited to the two-piece structure as described above, and can be implemented with various modifications.

  Although the metal material which comprises the club head 1 is not specifically limited, For example, 1 type, or 2 or more types, such as stainless steel, maraging steel, pure titanium, a titanium alloy, or an aluminum alloy, is preferable. However, a fiber reinforced resin or the like may be used for a part of the club head 1.

  In order to increase the flight distance of the hit ball, the present invention is directed to a count that places more importance on the flight distance performance, specifically, a wood type golf club head having a loft angle of 30 degrees or less. In particular, a club head having a loft angle α of 25 degrees or less, more preferably 20 degrees or less, and further preferably 15 degrees or less is desirable. The lower limit of the loft angle is not particularly defined, but is preferably 5 degrees or more in order to maintain a sufficient launch angle of the hit ball.

The volume of the club head 1 is not particularly limited, but is preferably 100 cm ³ or more, more preferably 200 cm ³ or more in order to increase resilience and increase the moment of inertia to stabilize the directionality of the hit ball. More preferably, 300 cm ³ or more is desirable. On the other hand, the increase in volume of the club head 1 is performed within a limited weight range, so that if the volume is increased too much, there is a problem such as a decrease in durability. From such a viewpoint, the volume of the club head 1 is preferably 500 cm ³ or less, more preferably 480 cm ³ or less, and still more preferably 460 cm ³ or less.

  The face 2 is provided with a face groove 8 and an auxiliary groove 9 in order to increase friction with the ball. As will be described later, such a combination of grooves can reduce the backspin amount of the hit ball while suppressing damage to the ball, and can provide a trajectory that is advantageous for a flight distance with a small rise.

  The face groove 8 is formed of a plurality of grooves that extend in the toe-heel direction and are spaced apart from each other. Here, the face groove 8 extending in the toe-heel direction is sufficient to be understood as extending substantially horizontally when the face groove 8 is observed with the naked eye in the reference state. This is natural because the club head 1 does not return to the reference state strictly at the time of impact of the ball. From such a viewpoint, the face groove 8 includes an aspect in which it is inclined at least about ± 4 degrees with respect to the horizontal direction.

  In the present embodiment, the face groove 8 is provided apart from the edges 2 a to 2 d without reaching the edges 2 a to 2 d of the face 2. In addition, as long as the area where the face groove 8 is provided includes the main hitting area of the face 2, the position of the face groove 8 is not particularly limited.

  FIG. 3 shows an enlarged view in which the surface of the face 2 in FIG. 2 is enlarged. The face groove 8 of the present embodiment has a substantially square groove in cross section, and extends in the toe-heel direction (length direction) with substantially the same cross-sectional shape. The depth d1 of the face groove 8 is 0.200 to 0.508 mm. If the depth d1 is less than 0.200 mm, the friction between the face 2 and the ball cannot be sufficiently increased, and as a result, it is difficult to reduce the backspin amount of the hit ball. From such a viewpoint, the depth d1 of the face groove 8 is more preferably 0.250 mm or more, and further preferably 0.300 mm or more. In addition, when the depth d1 of the face groove 8 exceeds 0.508 mm, the ball violates R & A golf rules and the ball is easily damaged when hit. From this point of view, the depth d1 of the face groove 8 is preferably 0.500 mm or less.

  If the face groove 8 is not provided on the face 2, slipping is likely to occur between the ball and the face in the rain, and the backspin amount of the hit ball cannot be expected, and the directionality of the hit ball is likely to vary. There is.

  The cross-sectional shape of the face groove 8, the groove width GW1, the arrangement interval SW of the face grooves 8, 8 and the like are preferably determined within a range not violating the golf rules.

  In other words, the cross-sectional shape of the face groove 8 is not limited to the above-described square groove shape, and as shown in FIGS. 4A, 4B, and 4C, for example, the groove toward the groove bottom. Any substantially symmetrical shape such as a substantially trapezoidal shape, a V shape or an arc shape with a small width may be used. As shown in FIG. 4, the edge of the face groove 8 is finished in a circular shape with a radius of 0.020 inch (0.508 mm) or less based on the golf rules, but preferably 0.14-0. Chamfered with a radius r of 18 mm is desirable.

  Further, the groove width GW1 of the face groove 8 is set to 0.90 mm or less based on the golf rules, but is preferably 0.50 mm or more, and more preferably 0, in order to reliably exert the frictional force by the face groove 8. .55 mm or more, more preferably 0.60 mm or more is desirable. As shown in FIG. 4A, the groove width GW1 of the face groove 8 is measured by the internal rule “30 degree measurement method” of R & A.

  Further, the face grooves 8 are provided at a constant arrangement interval SW. The arrangement interval SW is determined to be not less than 3 times the groove width GW1 and not less than 0.075 inch (1.905 mm) based on the golf rules. In order to more reliably exert the frictional force by the face groove 8. Preferably, it is formed to be 7 times or less, more preferably 5 times or less of the groove width GW1. Here, the arrangement interval SW of the face grooves 8 is a distance between the outer ends 8e and 8e of the adjacent face grooves 8 as shown in FIG.

  The auxiliary grooves 9 of the present embodiment are provided in substantially the entire area of the face 2 except for the position where the face grooves 8 are formed. Each of these auxiliary grooves 9 is provided at a fixed arrangement interval and without crossing each other.

  The inventors conducted extensive research to increase the friction coefficient of the face 2 and reduce the damage of the ball at the time of hitting the ball. As a result, the face 2 has a deep face groove 8 (which can satisfy the golf regulations) Based on the fact that the auxiliary groove 9 having a smaller depth than this is provided, it has been found that damage to the ball can be suppressed while increasing friction with the ball.

  Conventionally, when a ball is hit with a club head in which only the face groove 8 is provided on the face 2, the cover of the ball greatly digs into the inside of the face groove 8, and the face groove 8 shears to cause a large friction on the ball. Power is given. However, when a part of the cover of the ball is completely cut by the face groove 8 due to the shearing, the frictional force in the groove portion is interrupted.

  On the other hand, in the club head 1 using both the face groove 8 and the auxiliary groove 9 as in the present invention, the ball cover is deformed so as to bite into not only the face groove 8 but also the auxiliary groove 9 at the time of hitting. To do. Thereby, the distortion of the cover is widely dispersed in both the face groove 8 and the auxiliary groove 9 on the contact surface between the ball and the face 2, and the amount of the cover biting into the face groove 8 is reduced as a relative thing. This prevents the cover from being cut even during shearing by the face groove 8, thereby suppressing the loss of frictional force at this portion. Moreover, since the ball can obtain a frictional force from the auxiliary groove 9 as well, it is presumed that the frictional force greater than the conventional one can be obtained while preventing the ball from being damaged by these synergistic actions.

  In the wood type golf club head having a small loft angle (that is, a wood type golf club head having a loft angle of 30 degrees or less), when the coefficient of friction with respect to the ball of the face increases, the action of reducing the backspin amount of the hit ball is as follows. Although it has already been described in several documents, it is explained here just in case.

  7A to 7D do not show the impact state of the ball in time series. As shown in FIG. 7A, the impacted ball B is deformed and comes into close contact with the face 2 in a relatively wide range. At this time, the ball B receives a frictional force M in a direction along the face 2 and a vertical force from the face 2 from the face 2. Conventionally, focusing only on this frictional force M, it has been considered that the backspin amount of the ball B increases as the frictional force M increases.

  However, when the process during the impact of the ball B is examined in detail, the cover B2 of the ball B is caused by the shearing force that pulls the cover B2 in the direction of the frictional force M, as shown in FIG. It was found that the position P1 of the core portion B1 and the position P2 of the cover B2 are relatively displaced in the circumferential direction. Such misalignment between the core portion B1 and the cover B2 tends to be restored as the deformation of the impacted ball B starts to be restored to the original state. Due to this restoring force, a shearing force in the opposite direction acts between the core part B1 and the cover B2, and the positions P1 and P2 are neutral positions where there is no displacement (FIG. 7 (c)). It is launched from the face 2 at a position further beyond (FIG. 7D).

  At this time, it has been found that the internal spin in the forward direction, which is opposite to the back spin, remains in the core portion B1, and the back spin amount of the ball decreases as the internal spin increases. Such an influence of the internal spin is particularly noticeable in a club head having a small loft angle, and its strength increases in proportion to the friction coefficient of the face 2. Accordingly, in the wood type club head having a loft angle of 30 degrees or less, when the friction coefficient of the face 2 is increased, the internal spin is increased and the back spin amount is reduced.

  In order to exhibit the above effects more effectively, the depth d2 of the auxiliary groove 9 needs to be 0.005 to 0.025 mm. When the depth d2 is less than 0.005 mm, the distortion generated in the cover of the ball at the time of hitting cannot be dispersed in the auxiliary groove 9, and as a result, damage to the ball cannot be sufficiently suppressed. From such a viewpoint, the depth d2 of the auxiliary groove 9 is more preferably 0.010 mm or more, and further preferably 0.015 mm or more. If the depth d2 exceeds 0.025 mm, in addition to violating the golf rules, the difference from the depth d1 of the face groove 8 is reduced, and the effect of dispersing the distortion of the ball cover is reduced. Can no longer function.

  Further, in order to enhance the above-described effect with a better balance, it is desirable to define a ratio (d2 / d1) between the depth d1 of the face groove 8 and the depth d2 of the auxiliary groove 9. That is, when the ratio (d2 / d1) is increased, the depth d1 of the face groove 8 is relatively decreased, and the frictional force on the ball may be decreased. Conversely, the ratio (d2 / d1) is decreased. In this case, the depth d2 of the auxiliary groove 9 is relatively small with respect to the face groove 8, and there is a possibility that the effect of dispersing the distortion of the above-described ball cover cannot be sufficiently exhibited. From such a viewpoint, the ratio (d2 / d1) is preferably 0.010 or more, more preferably 0.030 or more, still more preferably 0.050 or more, and the upper limit is preferably 0.13. Below, more preferably 0.10 or less, still more preferably 0.80 or less.

  In order to further enhance the above-described effect, as shown in FIG. 3, the groove width GW2 of the auxiliary groove 9 is preferably 0.10 mm or more, more preferably 0.15 mm or more, and further preferably 0.20 mm or more. However, it is preferably 0.50 mm or less, more preferably 0.45 mm or less, and still more preferably 0.40 mm or less. If the groove width GW2 of the auxiliary groove 9 is less than 0.10 mm, the effect of dispersing the distortion of the cover of the ball may be reduced. Conversely, if the groove width GW2 exceeds 0.50 mm, the ball is damaged. It becomes easy.

  In the present embodiment, the auxiliary groove 9 has a substantially arc-shaped cross section. However, like the cross-sectional shape of the face groove 8, the auxiliary groove 9 has a square groove shape or a substantially pedestal whose groove width decreases toward the groove bottom. Various shapes such as a shape, a V shape, an arc shape, or a combination thereof can be adopted.

  The auxiliary grooves 9 are preferably formed at a constant arrangement interval HW, and in particular, the arrangement interval HW is preferably smaller than the arrangement interval SW of the face groove 8. Thereby, since more auxiliary grooves 9 can be brought into contact with the ball at the time of hitting, the above-described effect can be further enhanced. From such a viewpoint, the arrangement interval HW of the auxiliary grooves 9 is preferably 20% or less, more preferably 10% or less of the arrangement interval SW of the face grooves 8. On the other hand, if the spacing HW between the auxiliary grooves 9 is too small, the productivity may deteriorate. From such a viewpoint, the arrangement interval HW of the auxiliary grooves 9 is 3% or more of the arrangement interval HW of the face grooves 8, more preferably 5% or more. In addition, the arrangement | positioning space | interval HW of the auxiliary groove 9 is taken as the length of the part pinched | interposed by the adjacent auxiliary grooves 9 and 9, as FIG. 3 shows.

  The auxiliary groove 9 of the present embodiment has a circular arc shape (non-linear shape) extending from the sweet spot SS of the face to the center Y in a region Y within 5 mm in the toe-heel direction, and is provided substantially concentrically. It is done. As a more preferred embodiment, as shown in FIG. 1, it is desirable that the auxiliary groove 9 is formed in an arc having a center O substantially on the sweet spot SS. Here, as shown in FIG. 2, the sweet spot SS is an intersection of the perpendicular line N and the face 2 that is lowered from the head gravity center G to the face 2.

  Such an auxiliary groove 9 is, for example, in the vicinity of the sweet spot SS, even when the ball is impacted in a toe down where the toe of the face 2 is lowered during a swing or a heel down where the heel is lowered. By including a portion extending substantially horizontally (portion where the tangent is horizontal), an effective frictional force capable of suppressing backspin can be applied to the ball.

  Further, the arc-shaped auxiliary groove 9 having the center O on the sweet spot SS includes a portion extending in a direction intersecting with the face groove 8, and the face groove in the face central region including the sweet spot SS (for example, the region Y). 8, the intersection angle with the face groove 8 is increased on the toe side or the heel side. For this reason, when the ball is hit on the heel side with respect to the sweet spot SS in the toe-down state, or when the ball is hit on the toe side with respect to the sweet spot SS in the heel-down state, the auxiliary groove 9 is horizontal at each hit ball position. The direction can be approached and an effective frictional force capable of suppressing backspin can be applied to the ball in the same manner as described above. The intersecting angle between the face groove 8 and the auxiliary groove 9 is an angle formed between the tangent drawn to the auxiliary groove 9 at this position and the face groove 8.

  Further, when the centers of the arc-shaped auxiliary grooves 9 are different from each other, a change in the arrangement interval of the auxiliary grooves 9 or interference between the auxiliary grooves 9 may occur, and the frictional force may not be efficiently transmitted to the ball. . From such a viewpoint, it is particularly desirable that substantially all the auxiliary grooves 9 have one common center O. However, in consideration of accuracy during manufacture, it is desirable that each center of the arcuate auxiliary groove 9 is provided within a circle having a radius of 5 mm. Further, the arcuate auxiliary grooves 9 are not concentric circles but include spiral forms extending in a spiral shape without intersecting each other.

  Further, in the face 2, the total length Lf of the face grooves, which is the sum of the lengths of all the face grooves 8, is not particularly limited, but if it is too small, a sufficient frictional force cannot be transmitted to the ball. There is a possibility that the backspin amount may increase, and miss shots are likely to occur during play in rainy weather. On the contrary, if the total length Lf of the face grooves is increased, the golf rules may be violated, the layout design of the face grooves 8 and the like may be difficult, and productivity may be deteriorated. From this point of view, the total length Lf of the face grooves is preferably 200 mm or more, more preferably 250 mm or more, further preferably 300 mm or more, and the upper limit is preferably 850 mm or less, more preferably 800 mm or less. More preferably, 750 mm or less is desirable.

  Similarly, the total length Lh of the auxiliary grooves, which is the sum of the lengths of all the auxiliary grooves 9 in the face 2, is not particularly limited, but if it is too small, the effect of dispersing the distortion of the ball cover is sufficiently obtained. There is a risk of not being able to. On the other hand, when the total length Lh of the auxiliary grooves is increased, the layout design or the like becomes difficult and the productivity may be deteriorated. From this point of view, the total length Lh of the auxiliary grooves is preferably 2000 mm or more, more preferably 2500 mm or more, further preferably 3000 mm or more, and the upper limit is preferably 15000 mm or less, more preferably 14500 mm or less. More preferably, it is 14000 mm or less.

  Each of the face groove 8 and the auxiliary groove 9 can be formed by pressing a face 2 on a die having a projection having a shape obtained by inverting the three-dimensional shape of each groove, or by cutting using a lathe. However, press working is desirable from the viewpoint of productivity. In addition, when the grooves 8 and 9 are formed by pressing, there are a method of processing both the grooves 8 and 9 by a single press, and a method of pressing the grooves 8 and 9 in separate processes. Can be adopted. The former method is preferable in that the productivity can be further improved.

  On the other hand, in the latter case, a method of forming the face groove 8 after forming the auxiliary groove 9 first, and a method of forming the auxiliary groove 9 after forming the face groove 8 first are possible. In the case where the face groove 8 is formed first and then the auxiliary groove 9 is formed, a part of the auxiliary groove 9 that has been plastically deformed by press working may protrude into the groove of the face groove 8. As a manufacturing method of the club head 1, it is desirable to include a step of first forming the auxiliary groove 9 having a small depth and then forming the face groove 8 having a large depth.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the specific embodiments shown in the drawings. For example, in the embodiment of FIG. 1, the center O of the auxiliary groove 9 made of an arc is provided on the sweet spot SS, but is not limited to this, and can be shifted vertically from there. For example, as shown in FIG. 5, the auxiliary groove 9 can be formed in a straight line. In the embodiment of FIG. 5, an auxiliary groove 9 that is substantially parallel to the face groove 8, that is, extends in a straight line substantially horizontally along the toe-heel direction is illustrated. Further, as shown in FIG. 6, for example, the auxiliary groove 9 includes a central auxiliary groove 9C extending substantially horizontally and linearly in the center region of the face 2 in the toe-heel direction, and a vertical direction on the toe side and the heel side. Further, it may include a toe side auxiliary groove 9T and a heel side auxiliary groove 9H which extend in a straight line. As described above, the present invention can be implemented with various modifications.

  Wood-type golf club heads were prototyped based on the specifications shown in Table 1, and the flight distance, variation thereof, and variation in directionality were tested. Each test was conducted in both sunny and rainy conditions.

  For comparison, a similar test was performed on a club head (Comparative Examples 1 to 3) having no auxiliary groove on the face.

  In each example, the face groove and the auxiliary groove were simultaneously formed by forging using a mold having both the protrusion for forming the face groove and the protrusion for forming the auxiliary groove. Further, in Examples 1A, 2A and 3A, as shown in FIG. 5, auxiliary grooves made of straight lines extending horizontally were provided. On the other hand, in Examples 1B, 2B, and 3B, as shown in FIG. 1, an auxiliary groove made of an arc having a center at the sweet spot was provided. The common specifications for each club head are as follows.

<Comparative Example 1, Example 1A, Example 1B>
Loft angle: 10.5 (counter: driver)
Head volume: 460cm ³
Head body: Cast product of Ti-6Al-4V Face member: Press-formed product of Ti-6Al-4V Joining method of head body and face member: Plasma welding Face thickness: 3.3 mm (sweet spot), 2 .5mm (peripheral area)
Crown and side thickness: 0.7mm
Sole thickness: 1.2mm

<Comparative Example 2, Example 2A, Example 2B>
Loft angle: 20.5 (count: 7th wood)
Head volume: 136cm ³
Head body: Cast product of stainless steel (CUSTOM450 manufactured by Carpenter, USA) Face member: Press-molded product of stainless steel (same as above) Joining method of head body and face member: TIG welding Face thickness: 3.3 mm (sweet spot) ), 2.5mm (peripheral area)
Crown thickness: 0.7mm
Side thickness: 1.0mm
Sole thickness: 1.1-4.1mm

<Comparative Example 3, Example 3A, Example 3B>
Loft angle: 28.0 (count: utility 6)
Head volume: 120cm ³
Head body: Cast product of stainless steel (CUSTOM450) Face member: Press-molded product of stainless steel (same as above) Joining method of head body and face member: TIG welding Face thickness: 2.6 mm (sweet spot), 2.1 mm (Peripheral area)
Crown thickness: 0.7mm
Side thickness: 1.0mm
Sole thickness: 1.2-4.0mm
The test method is as follows.

<Hit distance of hit ball>
FRP shafts (SV-3003J Flex SR manufactured by SRI Sports) are attached to each club head, and the total length is 45 inches (Comparative Example 1, Examples 1A and 1B) and 41.5 inches (Comparative Example 2, implementation). Example 2A and 2B) and 39 inch (Comparative Example 3, Examples 3A and 3B) wood-type golf clubs were prototyped. Next, each test club was attached to a swing robot, and 10 golf balls (“SRIXON” (registered trademark) Z-UR manufactured by SRI Sports) were hit at a head speed of 40 m / s. And the average value of the flight distance (carry + run) of the hit ball was obtained. The larger the value, the better.

<Flight distance variation>
From the results of the above test, the difference between the maximum flight distance and the minimum flight distance of the hit ball was calculated for each club, and the total average value was shown. The smaller the value, the better the variation in flight distance.

<Directional variation>
From the results of the above test, for each club, the amount of deviation of each hit ball with respect to the target flying ball direction (calculated as a positive value regardless of whether it shifted to the left or right) was measured, and the total average value thereof was shown. The smaller the numerical value, the better the variation in directionality.
Table 1 shows the test results.

  As a result of the test, it was confirmed that the flying distance of the head of the example increased in any group of loft angles as compared with the comparative example without the auxiliary groove. In particular, Examples 1B, 2B, and 3B, in which the auxiliary grooves are arcuate, were confirmed to have good results in all performances as compared to Examples 1A, 2A, and 3A having auxiliary grooves parallel to the face grooves.

1 is a front view of a golf club head showing an embodiment of the present invention. It is the AA sectional view. It is an expanded sectional view of a face part. (A)-(c) is an expanded sectional view of a face groove | channel. It is a front view of the golf club head which shows other embodiment of this invention. It is a front view of the golf club head which shows other embodiment of this invention. (A)-(d) is sectional drawing which shows the state of the impact of a ball | bowl and a face in time series. 2 is a front view of a golf club head of Comparative Example 1. FIG.

Explanation of symbols

1 Golf club head 2 Face 8 Face groove 9 Auxiliary groove α Loft angle SS Sweet spot

Claims (6)

A wood-type golf club head having a face for hitting a ball and having a loft angle of 30 degrees or less,
A plurality of face grooves extending in the toe-heel direction and having a depth of 0.200 to 0.508 mm on the face;
A wood-type golf club head, comprising a plurality of auxiliary grooves having a depth of 0.005 to 0.025 mm.   The wood-type golf club head according to claim 1, wherein a ratio (d2 / d1) between the depth d1 of the face groove and the depth d2 of the auxiliary groove is 0.010 to 0.13.   The wood-type golf club head according to claim 1 or 2, wherein an interval between the auxiliary grooves is smaller than an interval between the face grooves. The auxiliary groove includes a portion extending in a direction intersecting with the face groove,
The intersection angle between the face groove and the auxiliary groove is larger on the toe side or the heel side than the center side of the face including the sweet spot of the face in a reference state in which the face groove and the loft angle are in contact with a horizontal plane at a specified lie angle and loft angle. The wood type golf club head according to any one of 1 to 3.   5. The wood type golf club head according to claim 1, wherein the auxiliary groove has an arc shape having a center in a region within 5 mm in a toe-heel direction from a sweet spot of a face.   6. The wood type golf club head according to claim 5, wherein the center of the auxiliary groove is provided within a circle having a radius of 5 mm.

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