This application claims the benefit of foreign priority to Japanese Patent Application No. JP2021-133638, filed Aug. 18, 2021, which is incorporated by reference in its entirety.
The present disclosure relates to a golf club head.
A golf club head in which an FRP member made of fiber reinforced plastic is used for the crown and/or the sole have been proposed. Using the FRP member, the weight of the crown and/or sole may be reduced. The weight reduced by the crown and/or sole can help to provide a discretionary weight margin that can be used to optimize the position of the center of gravity of the head, the moment of inertia, and the like.
The golf club head as described above is required to secure sufficient bonding strength between the metallic head body and the FRP member. In addition, golf club heads using an FRP member may have a problem that the striking sound do not reverberate for a long time.
The present disclosure has been made in view of the above circumstances and has a major object to provide a golf club head that can make the striking sound reverberate for a long time while realizing high joint strength between a metallic head body and an FRP member.
In one aspect of the present disclosure, a golf club head includes a metallic head body having an opening, and an FRP member fixed to the head body so as to close the opening. The FRP member is a fiber-reinforced plastic including fibers and thermoplastic resin. The head body includes a support portion around the opening. The support portion has a first surface for supporting the FRP member. The first surface is provided with at least one narrow groove having a groove width of 20 to 80 μm and a groove depth of 100 to 400 μm, and a part of the thermoplastic resin of the FRP member is solidified inside the at least one narrow groove.
Hereinafter, one or more embodiments of the present disclosure will be described with reference to the drawings. Note that the drawings contain representations that differ from the dimensional ratios of the actual structure to aid in the understanding of the present disclosure. Further, throughout the specification, the same or common elements are given the same reference numerals, and duplicate explanations are omitted. Furthermore, the specific configurations shown in the embodiments and drawings are for understanding the contents of the present disclosure, and the present disclosure is not limited to the specific configurations shown.
As used herein, the “reference state” of the head 1 means that the head 1 is placed on a horizontal plane HP with its lie angle and the loft angle of the head 1. The loft angle and lie angle are usually specified in product catalogs and the like. In the reference state, the virtual shaft axis centerline CL of the head 1 is arranged within a reference vertical plane VP perpendicular to the horizontal plane HP. The “virtual shaft axis centerline CL” is defined by the axis centerline of a shaft insertion hole 5a formed in a hosel 5 of the head 1. Unless otherwise noted herein, the head 1 is under the reference state.
As used herein, three directions are associated with the head 1 in the reference state. First, the direction x parallel to the horizontal plane HP and the vertical plane VP is defined as the toe-heel direction of the head 1. The direction y orthogonal to the vertical plane VP is the front-back direction of the head 1. In the front-back direction of the head, a club face 2 side is the front side, and the opposite side is the rear side (also called the back side). Further, the direction z orthogonal to both the above directions x and y is defined as the head vertical direction.
The head 1 according to the present embodiment, for example, is configured as a wood-type golf club head. Such a wood-type golf club head includes, for example, a driver (#1) as well as fairway woods. In another embodiment, the head 1 may be configured as a utility type or hybrid, for example.
The head 1, for example, includes the club face 2, a crown 3, a sole 4 and the like. In the present embodiment, the head 1 also includes a hollow portion i therein. A part of the hollow portion i may be filled with a foaming agent, a gel agent, or the like, for example.
The club face 2 is a part for striking a ball and is formed on the front side of the head 1. The outer surface (front surface) of the club face 2 constitutes a striking face 2a that comes into contact with a ball. Although not shown, the striking face 2a may be provided with a plurality of grooves extending in the toe-heel direction called face lines.
The crown 3 extends from an upper edge of the club face 2 to the rear of the head so as to form an upper surface of the head 1. The crown 3, for example, forms a portion excluding the club face 2 and the hosel 5 in a head plan view shown in
The sole 4 extends from a lower edge of the club face 2 to the rear of the head so as to form a bottom surface of the head 1. The sole 4, for example, forms a portion excluding the hosel 5 in a head bottom view.
In the present embodiment, the head 1 includes a metallic head body 1A having an opening 6, and an FRP member 1B fixed to the head body 1A so as to close the opening 6.
The metal material constituting the head body 1A is not particularly limited, but for example, one or more of stainless steel, maraging steel, titanium alloy, aluminum alloy, magnesium alloy and the like may be suitable. The head body 1A according to the present embodiment is entirely made of a titanium alloy, for example.
Referring to
As illustrated in
As illustrated in
The support portion 7 includes the above-mentioned first surface 7a facing the FRP member 1B side and a second surface 7b on the opposite side.
The narrow grooves 9 have groove widths w in a range from 20 to 80 μm, and groove depths d in a range from 100 to 400 μm. The first surface 7a may be provided with one or more narrow grooves that do not satisfy the above dimensions, but in this case, it is preferable that most of the narrow grooves meet the above dimensions.
In this embodiment, the FRP member 1B is made of a fiber reinforced plastic (CFRTP) containing fibers and thermoplastic resin. The FRP member 1B has a specific gravity smaller than that of the head body 1A. Thus, in the head 1 of the present embodiment, since a part of the crown 3 is formed by the FRP member 1B, the upper part of the head is lightened, and the center of gravity of the head 1 can be positioned lower, for example. In addition, the weight reduced by the crown 3 may be used as a discretionary weight margin to optimize the moment of inertia of the head 1, for example.
In the present embodiment, the FRP member 1B, for example, is formed in a plate shape as a whole, and its peripheral edge portion is joined to the first surface 7a of the support portion 7 of the head body 1A. As illustrated in
In this embodiment, no adhesive intervenes between the FRP member 1B and the first surface 7a. That is, the first surface 7a (including the narrow grooves 9) of the support portion 7 and the FRP member 1B are in direct contact with each other.
In the head 1 according to the present embodiment, a part of the thermoplastic resin of the FRP member 1B is solidified inside the narrow grooves 9 with a specific groove widths and depths formed on the first surface 7a of the support portion 7. Thus, the FRP member 1B can be firmly joined to the support portion 7 by the so-called “anchor effect”.
In order to quantitatively determine the bond strength between the head body 1A and the FRP member 1B, the inventors conducted bond strength tests in accordance with JIS-K6850 “Testing Method for Tensile Shear Bond Strength of Adhesively Bonded Materials”.
First, a test specimen 1 corresponding to an example was prepared. The test specimen 1 consists of a plate made of 6-4 titanium alloy with a plurality of narrow grooves formed, and an FRP member (100 mm×25 mm×1 mm, fiber direction is 0 degrees with respect to the longitudinal direction) consisting of carbon fibers and polyphenylene sulfide (PPS) as a thermoplastic resin were joined. Both members were joined by contacting the FRP member to the degreased plate without the intervention of adhesive and heating at 330 degrees C. for 30 minutes while pressing at a pressure of 3.5 MPa. The joined area was 12.5 mm×25 mm. The specifications of the narrow grooves and the groove depths on the surface of the plate were as follows.
Groove widths: 30 to 71 μm
Groove depths: 230 to 250 μm
Spacing of grooves: 0.083 mm (average value)
Number of grooves: 150
Longitudinal direction of the narrow groove: perpendicular to the direction of tensile shear
In addition, a test specimen 2 corresponding to a comparative example was also prepared. The test specimen 2 consists of the above 6-4 titanium alloy degreasing plate and the above the FRP member. No narrow grooves were formed on the surface of the plate. The surface of the plate was pre-blasted with 100 m blast materials. Test specimen 2 was bonded by an epoxy-based adhesive (DP420 manufactured by 3M) between the degreased plate and the FRP member in the same manner as above.
Next, a bond strength test was conducted in accordance with JIS-K6850. The tensile test speed was 10 mm/min. As a result of the test, the bond strength of the test specimen 2 was 4 MPa, while the bond strength of the test specimen 1 was 20 MPa, which was five times that. This confirmed the remarkable superiority of test material 1. Those skilled in the art would appreciate that the high bond strength verified with this test material 1 can be obtained for golf club heads as well.
The thermoplastic resin of the FRP member 1B of the present embodiment tends to have a smaller vibration damping coefficient (damping ratio) than that of thermosetting resin. Thus, when a ball is struck, the vibration damping effect of the FRP member 1B can be suppressed, and the striking sound can be reverberated for a long time.
In conventional heads of this type, epoxy-based or acrylic-based adhesives have been used to bond a metal body to an FRP member. However, these adhesives not only do not provide sufficient adhesive strength with the thermoplastic resin, but also tend to attenuate the vibration of the head when striking a ball. In the present embodiment, since no adhesive is interposed between the FRP member 1B and the support portion 7, the vibration characteristics of the head 1 can be improved and the striking sound can be reverberated longer.
The inventors conducted a vibration characteristic test using the above test specimens 1 and 2 in order to quantitatively understand the effect of sustaining the striking sound. In the vibration characteristic test, a triangular jig (contact tip) was fixed to the plate side of the titanium alloy of each test specimen with instant adhesive and attached to the exciter. Then, the anti-resonance peak was analyzed in the servo mode. Specifically, the damping (damping ratio) of the anti-resonance peak in the range of about 2000 to 4000 Hz, which is related to the sustainability of the striking sound of the golf club head, was obtained. The smaller the damping ratio, the longer the vibration will last.
As a result of the vibration characteristic test, it was confirmed that the damping of the test specimen 2, which corresponds to the configuration of the conventional head, was about 0.8% to 0.9%, while that of the test specimen 1, which corresponds to the example, was reduced to 0.2% to 0.4%, which is less than half of that. This confirms the significant superiority of the test specimen 1. Those skilled in the art will understand that the vibration characteristics (vibration persistence) verified by this test specimen 1 function in the golf club head to make the sound of striking the ball resonate for a long time.
As described above, the head 1 according to the present embodiment can make the striking sound reverberate for a long time while realizing a high joint strength between the head body 1A made of metal and the FRP member 1B.
In order to further enhance the anchor effect described above, the groove depths d of the narrow grooves 9 are more preferably equal to or more than 100 μm, still more preferably equal to or more than 200 μm. On the other hand, if the groove depths d of the narrow grooves 9 becomes too large, the permeability of the thermoplastic resin deteriorates and the strength of the support portion 7 may decrease. From this point of view, the groove depths d of the narrow grooves 9 are more preferably equal to or less than 400 μm, still more preferably equal to or less than 300 μm.
In order to further enhance the anchor effect described above, the groove widths w of the narrow grooves 9 are more preferably equal to or less than 80 μm, more preferably equal to or less than 60 μm, and the narrow grooves 9 be preferably made finer. On the other hand, if the groove widths w of the narrow grooves 9 become too small, the permeability of the thermoplastic resin into the narrow grooves 9 may deteriorate. From this point of view, the groove depths d of the narrow grooves 9 are more preferably equal to or more than 20 μm, still more preferably equal to or more than 40 μm.
As illustrated in
Distances p (distances between the directly adjacent centers of the grooves) of the narrow grooves 9 are not particularly limited, but if it becomes too small, the strength of the support portion 7 may decrease. From this point of view, the distances p of the narrow grooves 9 are preferably equal to or more than 0.04 mm, more preferably equal to or more than 0.06 mm, even more preferably equal to or more than 0.08 mm. On the other hand, if the distances p of the narrow grooves 9 become large, the anchor effect may decrease. From this point of view, the distances p of the narrow grooves 9 are preferably equal to or less than 0.5 mm, more preferably equal to or less than 0.2 mm, even more preferably equal to or less than 0.1 mm. Considering the workability of the narrow grooves 9, the distances p do not have to be constant and may be non-constant.
The extension orientation of the narrow grooves 9 is not particularly limited, but the plurality of narrow grooves 9 of the present embodiment extends along the contour edge 6e of the opening 6, as shown in
In general, when a ball is struck with the head 1, a shear force in the direction orthogonal to the contour edge 6e of the opening 6 tends to act between the first surface 7a of the support portion 7 and the FRP member 1B. Thus, by aligning the narrow groove 9 along the contour edge 6e of the opening 6, the deformation resistance to the above-mentioned shearing force can be enhanced at the joint. As a result, even when striking the ball repeatedly, the decrease in bond strength can be suppressed.
As illustrated in
As illustrated in
As illustrated in
As illustrated in
As the thermoplastic resin of the FRP member 1B, for example, nylon (PA), polypropylene (PP), polyphenylene sulfide (PPS), polyethersulfone (PES), polyetherimide (PEI), polycarbonate (PC), polyether terephthalate (PET), polyetherketone (PEK), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), phenoxy resin and the like may be employed. In particular, polyphenylene sulfide (PPS), polyetherimide (PEI), polyethersulfone (PES), polyetheretherketone (PEEK), phenoxy resin, etc., which have a small attenuation ratio, may be suitable.
The head 1 according to the present embodiment may be manufactured including a first step of preparing the head body 1A, a second step of preparing the FRP member 1B, and a third step of pressurizing and heating these overlapping portions.
In the first step, the narrow grooves 9 can be formed on the trajectory of a laser beam by irradiating the first surface 7a of the support portion 7 while moving the continuous wave laser beam in a predetermined pattern, for example. The groove widths w and groove depths d of the narrow grooves 9 can be adjusted as appropriate by adjusting the moving speed and/or the laser output during irradiation with the continuous wave laser. In addition, a part of the first surface 7a melted by the laser beam flows to the inlet side of the narrow groove 9 and solidifies, so that the first narrow grooves 9a with a narrow width of the inlet side can be formed. The head body 1A, such as
In the second step, one or more prepreg sheets cut into a predetermined shape are laminated, for example. This gives the FRP member 1B in the form of a plate like as shown in
In the third step, as shown exemplary in
In the third step described above, for example, a resistance spot welder, an ultrasonic welder head, etc. can be used for the welding device 12. In addition, pressurization may be performed with a die or the like, and heat energy may be separately applied by electromagnetic induction heating or the like.
In the embodiment shown in
While the particularly preferable embodiments in accordance with the present disclosure have been described in detail, the present disclosure is not limited to the illustrated embodiments, but can be modified and carried out in various aspects within the scope of the disclosure.
This disclosure includes the following aspects.
A golf club head comprising:
a metallic head body having an opening; and
an FRP member fixed to the head body so as to close the opening, the FRP member being a fiber-reinforced plastic including fibers and thermoplastic resin,
wherein
the head body comprises a support portion around the opening, the support portion having a first surface for supporting the FRP member,
the first surface is provided with at least one narrow groove having a groove width of 20 to 80 μm and a groove depth of 100 to 400 μm, and
a part of the thermoplastic resin of the FRP member is solidified inside the at least one narrow groove.
The golf club head according to note 1, wherein
no adhesive intervenes between the FRP member and the first surface.
The golf club head according to note 1 or 2, wherein
the at least one narrow groove comprises a plurality of narrow grooves formed at an interval.
The golf club head according to note 3, wherein
the interval is in a range from 0.04 to 0.5 mm.
The golf club head according to any one of notes 1 to 4, wherein
the at least one narrow groove extends along a contour edge of the opening.
The golf club head according to any one of notes 1 to 5, wherein
the support portion has a support width measured in a direction orthogonal to a contour edge of the opening, and
when the first surface is virtually divided into a first region on the contour edge side of the opening and a second region outside the first region by a width center line that divides the support width into two equal parts, an arrangement density of the at least one narrow groove in the second region is smaller than an arrangement density of the at least one narrow groove in the first region.
The golf club head according to any one of notes 1 to 6, wherein
the support portion has a thickness in a range from 0.5 to 1.2 mm.
The golf club head according to any one of notes 1 to 7, wherein
the first surface is recessed from an outer surface of the head body.
The golf club head according to any one of notes 1 to 8, wherein
the head body is made of a titanium alloy.
The golf club head according to any one of notes 1 to 9, wherein
the thermoplastic resin of the FRP member comprises polyphenylene sulfide, polyetherimide, polyethersulfone, polyetheretherketone or phenoxy.
The golf club head according to any one of notes 1 to 10, wherein
the head body comprises a crown and a sole, and
the opening is provided on the crown and/or the sole of the head body.
Number | Date | Country | Kind |
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2021-133638 | Aug 2021 | JP | national |