U.S. patent application number 13/494291 was filed with the patent office on 2012-12-20 for golf club head.
This patent application is currently assigned to BRIDGESTONE SPORTS CO., LTD. Invention is credited to Wataru BAN, Kozue WADA.
Application Number | 20120322580 13/494291 |
Document ID | / |
Family ID | 47354116 |
Filed Date | 2012-12-20 |
United States Patent
Application |
20120322580 |
Kind Code |
A1 |
WADA; Kozue ; et
al. |
December 20, 2012 |
GOLF CLUB HEAD
Abstract
A hollow golf club head according to this invention includes a
face portion, a crown portion, and a sole/side portion which
includes a sole portion and a side portion. This golf club head
includes a rib which extends from the toe side to the heel side in
the sole portion, and a weight portion which is provided in the
sole portion on the back side with respect to the rib, and
increases the amplitude of vibration of the sole portion. The
natural frequency of the first-order vibration mode of the sole
portion is 2,500 Hz or more. A mass m (g) of the weight portion
satisfies 1.ltoreq.m<6. The rib has a quadrangular
cross-sectional shape with a width b (mm) and a height h (mm), and
0.20.ltoreq.bh.sup.3/m.sup.4<8.00.
Inventors: |
WADA; Kozue; (Minato-ku,
JP) ; BAN; Wataru; (Chichibu-shi, JP) |
Assignee: |
BRIDGESTONE SPORTS CO., LTD
Tokyo
JP
|
Family ID: |
47354116 |
Appl. No.: |
13/494291 |
Filed: |
June 12, 2012 |
Current U.S.
Class: |
473/346 |
Current CPC
Class: |
A63B 53/0408 20200801;
A63B 53/04 20130101; A63B 53/045 20200801; A63B 53/0466 20130101;
A63B 53/0433 20200801; A63B 53/06 20130101; A63B 53/0412 20200801;
A63B 60/00 20151001 |
Class at
Publication: |
473/346 |
International
Class: |
A63B 53/04 20060101
A63B053/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 15, 2011 |
JP |
2011-133523 |
Claims
1. A hollow golf club head including a face portion, a crown
portion, and a sole/side portion which includes a sole portion and
a side portion, the head comprising: a rib which extends from a toe
side to a heel side in the sole portion; and a weight portion which
is provided in the sole portion on a back side with respect to said
rib, and increases an amplitude of vibration of the sole portion,
wherein a natural frequency of a first-order vibration mode of the
sole portion is not less than 2,500 Hz, a mass m (g) of said weight
portion satisfies 1.ltoreq.m<6, said rib has a quadrangular
cross-sectional shape with a width b (mm) and a height h (mm), and
0.20.ltoreq.bh.sup.3/m.sup.4<8.00.
2. The head according to claim 1, wherein the sole/side portion
includes a thick region on a side of the face portion, a thin
region, and a thick region on the back side in turn from the side
of the face portion to the back side, and said rib and said weight
portion are disposed in the thin region.
3. The head according to claim 1, wherein a head volume is not less
than 400 cc.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a golf club head and, more
particularly, to a technique for improving an impact sound.
[0003] 2. Description of the Related Art
[0004] In hollow golf club heads typified by a driver head,
techniques for improving an impact sound by appropriately designing
the hollow body construction have been proposed. For example,
Japanese Patent Laid-Open Nos. 11-155982 and 2003-275345 disclose
techniques for improving an impact sound by partially varying the
thickness of a sole portion. Also, Japanese Patent Laid-Open Nos.
2002-186691 and 2003-102877 disclose techniques for improving an
impact sound by providing a rib in a sole portion.
[0005] The volume of a hollow golf club head is increasing every
year, so its crown portion and sole portion are getting thinner,
and their areas are increasing along with this trend. Therefore, a
low-pitched impact sound is more likely to be generated at the time
of striking a golf ball. Under the circumstance, golfers who prefer
high-pitched impact sounds want golf club heads which generate
higher-pitched impact sounds. Partially varying the thickness of a
sole portion produces a certain effect of increasing the pitch of
an impact sound, as disclosed in Japanese Patent Laid-Open Nos.
11-155982 and 2003-275345. Providing a rib in a sole portion also
produces a certain effect of increasing the pitch of an impact
sound, as disclosed in Japanese Patent Laid-Open Nos. 2002-186691
and 2003-102877. These techniques increase the pitch of an impact
sound by increasing the degree of constraint of the sole portion.
However, as the degree of constraint of the sole portion increases,
an impact sound is more likely to have low loudness and poor
resonance.
SUMMARY OF THE INVENTION
[0006] An objective of the present invention is to provide a golf
club head which generates a higher-pitched, louder impact sound
even when its head volume increases.
[0007] According to the present invention, there is provided a
hollow golf club head including a face portion, a crown portion,
and a sole/side portion which includes a sole portion and a side
portion, the head comprising: a rib which extends from a toe side
to a heel side in the sole portion; and a weight portion which is
provided in the sole portion on a back side with respect to the
rib, and increases an amplitude of vibration of the sole portion,
wherein a natural frequency of a first-order vibration mode of the
sole portion is not less than 2,500 Hz, a mass m (g) of the weight
portion satisfies 1.ltoreq.m<6, the rib has a quadrangular
cross-sectional shape with a width b (mm) and a height h (mm), and
0.20.ltoreq.bh.sup.3/m.sup.4<8.00.
[0008] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective view of a golf club head according
to an embodiment of the present invention;
[0010] FIG. 2A is a sectional view taken along a line X-X in FIG.
1;
[0011] FIG. 2B is a view of the golf club head when viewed from the
side of a sole portion;
[0012] FIG. 3 is a front view of the golf club head when viewed
from the side of a face portion;
[0013] FIG. 4 is a view for explaining the middle region; and
[0014] FIGS. 5A to 5C are views showing the vibration analysis
results.
DESCRIPTION OF THE EMBODIMENTS
[0015] FIG. 1 is a perspective view of a golf club head 10
according to an embodiment of the present invention when a rib 20
and a weight portion 21 provided inside it are seen through, FIG.
2A is a sectional view taken along a line X-X in FIG. 1, and FIG.
2B is a view of the golf club head 10 when viewed from the side of
a sole portion 131.
[0016] The golf club head 10 takes the form of a hollow body, and
its peripheral wall forms a face portion 11 which forms a face
surface (striking surface), a crown portion 12 which forms the
upper portion of the golf club head 10, and a sole/side portion 13.
The sole/side portion 13 forms the sole portion 131 which forms the
bottom portion of the golf club head 10, and a side portion 132
between the crown portion 12 and the sole portion 131. The side
portion 132 forms the side portion of the golf club head 10, and
includes a toe-side side portion 132a, heel-side side portion 132b,
and back-side side portion 132c. The golf club head 10 also
includes a hosel portion 15 in which a shaft is mounted.
[0017] The golf club head 10 is a driver golf club head. However,
the present invention is applicable to wood type golf club heads
including not only a driver golf club head but also, for example, a
fairway wood type golf club head, utility (hybrid) golf club heads,
and other hollow golf club heads. The golf club head 10 can be made
of a metal material such as a titanium-based metal (for example,
Ti-6Al-4V titanium alloy), stainless steel, or a copper alloy such
as beryllium copper.
[0018] The golf club head 10 can be assembled by bonding a
plurality of parts. The golf club head 10 can be formed from, for
example, a main body member and a face member. The main body member
forms the peripheral portions of the crown portion 12, sole portion
131, side portion 132, and face portion 11, and has an opening
partially formed in a portion corresponding to the face portion 11.
The face member is bonded in the opening in the main body
member.
[0019] Referring to FIGS. 1, 2A, and 2B, the elongated rib 20 and
the point-like weight portion 21 are formed on the inner upper
surface of the sole portion 131. The rib 20 adjusts the natural
frequency of the golf club head 10. The weight portion 21 increases
the amplitude of vibration of the sole portion 131 at the time of
impact.
[0020] In this embodiment, the rib 20 traverses the sole portion
131 in the toe-to-heel direction, and has its one end 20a connected
to the toe-side side portion 132a, and its other end 20b connected
to the heel-side side portion 132b. Although the rib 20 is formed
integrally with the sole portion 131 and side portions 132a and
132b in this embodiment, it may be provided as a separate member
and firmly fixed on the sole portion 131 and side portions 132a and
132b. The rib 20 has a quadrangular cross-sectional shape with a
width b (mm) and a height h (mm), as shown in FIG. 2A. The height h
of the rib 20 is that from the upper surface of the sole portion
131 (thin region S2).
[0021] The weight portion 21 increases the amplitude of vibration
of its vicinity to adjust the resonance and loudness of an impact
sound. The weight portion 21 is positioned on the back side with
respect to the rib 20. As the position of the rib 20 is closer to
the face portion 11 than the weight portion 21, it is easier to
increase the eigenvalue (natural frequency) of the first-order
vibration mode (primary vibration mode) of the sole portion 131. To
increase the amplitude of vibration of the sole portion 131, the
weight portion 21 is preferably disposed at the position of an
antinode of vibration of the sole portion 131 or in its vicinity.
The position of an antinode of vibration of the sole portion 131
generally falls within the middle region in both the toe-to-heel
direction and the face-to-back direction of the golf club head when
viewed from the bottom side. Hence, the weight portion 21 is
preferably disposed in the middle region.
[0022] The middle region can be specified in the following way.
First, as shown in FIG. 3, when the golf club head 10 is grounded
so that an angle .theta.1 (lie angle) formed between a shaft axis
line L0 and the grounding surface is a specific lie angle defined
for the golf club head 10, and the loft angle is a specific loft
angle (this grounding state will be referred to as specific
grounding hereinafter), a grounding point C of the sole portion 131
is determined as a point on the center line of the dimension of the
golf club head 10 in the toe-to-heel direction. Note that when the
sole portion 131 is grounded in a plane defined on the grounding
surface, its grounding point C is determined as the center in the
widthwise direction.
[0023] Next, as shown in FIG. 4, an intersection point PF between
the face portion 11 and a face parallel to the center line defined
by the grounding point C, and an intersection point PB between the
back end and this face, both when the golf club head 10 is viewed
from the bottom side while being kept in a specific grounding
state, are defined. A position CP one half of a distance L1 between
the intersection points PF and PB is defined as the center point.
Also, the dimension of the golf club head 10 in the toe-to-heel
direction is defined as L2.
[0024] The middle region R can be defined by a dimension W1 in the
face-to-back direction (flight trajectory direction) and a
dimension W2 in the toe-to-heel direction upon defining the
position CP as its center. The dimension W1 can be, for example,
0.4.times.L1 to 0.6L.times.1, and the dimension W2 can be, for
example, 0.4.times.L2 to 0.6.times.L2.
[0025] Although the weight portion 21 has a circular cylindrical
shape in this embodiment, it may have other shapes. Although the
weight portion 21 is formed integrally with the sole portion 131 by
locally increasing the thickness of the sole portion 131 in this
embodiment, it may be attached to the sole portion 131 as a
separate member. If the weight portion 21 is provided as a separate
member, it preferably uses a member (for example, a screw) having a
specific gravity higher than a material which forms the sole
portion 131. Again, if the weight portion 21 is provided as a
separate member, it may be detachable from the sole portion 131 so
as to be replaced with another weight portion 21 having a different
weight. With this arrangement, the user can perform impact sound
adjustment.
[0026] Referring to FIG. 2B, in this embodiment, the sole/side
portion 13 includes a thick region S1 on the side of the face
portion 11, a thin region S2, and a thick region S3 on the back
side in turn from the side of the face portion 11 to the back side.
In this embodiment, the rib 20 and weight portion 21 are disposed
in the thin region S2. A plurality of lines BL indicate the
boundary lines between the regions S1 to S3.
[0027] The thicknesses of the peripheral wall in the regions S1 to
S3 satisfy S1>S2 and S3>S2. The thin region S2 has a
thickness of, for example, 0.8 mm, the thick region S1 has a
thickness of, for example, 1.4 mm, and the thick region S3 has a
thickness of, for example, 1.3 mm. Also, the face portion 11 has a
thickness of, for example, 3 mm, and the crown portion 12 has a
thickness of, for example, 0.6 mm (inclusive) to 0.7 mm
(inclusive).
[0028] The thin region S2 is formed to traverse at least the sole
portion 131 from the toe side to the heel side. Although the thin
region S2 extends even to the side portions 132a and 132b in this
embodiment, it may be formed only in the sole portion 131.
[0029] The thick region S1 is formed on the side of the face
portion 11 with respect to the thin region S2 to be adjacent to the
thin region S2. In this embodiment, the thick region S1 starts from
a boundary portion BD between the sole portion 131 and the face
portion 11, and extends up to the thin region S2. Although the
thick region S1 extends even to the side portions 132a and 132b in
this embodiment, it may be formed only in the sole portion 131. In
this case, the thick region S1 may be formed only in part of the
sole portion 131.
[0030] The thick region S3 is formed on the back side (on the side
of the back-side side portion 132c) with respect to the thin region
S2 to be adjacent to the thin region S2. Although the thick region
S3 extends even to the side portions 132a and 132b and back-side
side portion 132c in this embodiment, it may be formed only in the
sole portion 131, only in the sole portion 131 and back-side side
portion 132c, or only in the sole portion 131 and side portions
132a and 132b.
[0031] The principle of improving an impact sound in this
embodiment will be described next. In general, with an increase in
head volume, the head peripheral wall needs to be thinner and the
area of each portion increases, so the eigenvalue of the entire
head decreases, and the eigenvalue (natural frequency) of the
first-order vibration mode of the sole portion 131, in turn,
decreases. Therefore, a low-pitched impact sound is more likely to
be generated at the time of striking a golf ball in that case. In
this embodiment, the sole portion 131 is constrained by providing
the rib 20, so the eigenvalue of its first-order vibration mode
increases. This makes it possible to increase the pitch of an
impact sound.
[0032] Also, in this embodiment, because the thick region S1, the
thin region S2, and the thick region S3 are formed in the sole/side
portion 13 in turn from the face side to the back side, the thin
region S2 is more likely to vibrate at the time of striking a golf
ball. By providing the rib 20 in the thin region S2, the thin
region S2 is constrained by the rib 20, thus making it possible to
further increase the pitch of an impact sound. Further, providing
the weight portion 21 in the thin region S2 that is more likely to
vibrate makes it possible to further increase the amplitude of
vibration of the sole portion 131, thus improving the loudness and
resonance of an impact sound.
[0033] As the degree of constraint of the sole portion 131 is
increased using the rib 20, an impact sound can have a higher pitch
but still has low loudness and poor resonance. However, in this
embodiment, because the weight portion 21 is provided, the
amplitude of vibration of the sole portion 131 at the time of
impact increases. Therefore, a higher-pitched, louder impact sound
can be generated even when the head volume increases. The head
volume is, for example, 400 cc (inclusive) to 460 cc
(inclusive).
[0034] The eigenvalue (natural frequency) of the first-order
vibration mode of the sole portion 131 may decrease upon providing
the weight portion 21. However, the natural frequency of the
first-order vibration mode of the sole portion 131 is kept as high
as 2,500 Hz or more using the rib 20 or using the rib 20 and the
thick/thin regions together, as in this embodiment.
[0035] The rib 20 advantageously increases the pitch of an impact
sound but disadvantageously decreases its loudness, while the
weight portion 21 advantageously increases the amplitude of
vibration of the sole portion 131 so as to increase the loudness of
an impact sound but disadvantageously decreases its pitch, as
described above. Accordingly, it is important not only to
individually adjust the rib 20 and weight portion 21 but also to
optimize their balance.
[0036] The weight portion 21 has a mass m (g) that satisfies
1.ltoreq.m<6. The amplitude increasing effect is poor if the
mass m is smaller than 1 g, while it is difficult to increase the
pitch of an impact sound if the mass m is 6 g or more.
[0037] The second moment of area (bh.sup.3/12) of the rib 20 is one
factor which influences the degree of constraint of the sole
portion 131 by the rib 20. Hence, bh.sup.3 can be used as an index
for the degree of constraint. To keep the eigenvalue (natural
frequency) of the first-order vibration mode of the sole portion
131 as high as 2,500 Hz or more, bh.sup.3 is preferably 50 or more.
bh.sup.3 is more preferably 100 or more. If the degree of
constraint is too high, the loudness of an impact sound may not
increase even when the weight portion 21 is provided. Accordingly,
bh.sup.3 is preferably 700 or less and more preferably 650 or less.
When the width b and height h are individually defined, they
preferably satisfy 0.5<b<3 and 2<h<7, respectively.
[0038] To evaluate the balance between the rib 20 and the weight
portion 21, bh.sup.3/m.sup.4 is used as an index for this balance.
The denominator m.sup.4 is a parameter associated with the mass of
the weight portion 21, and is the fourth power of this mass in
correspondence with the order of bh.sup.3. The numerator bh.sup.3
is a parameter associated with the second moment of area of the rib
20.
[0039] If the bh.sup.3/m.sup.4 value is relatively large, the
second moment of area of the rib 20 is large relative to the mass
of the weight portion 21, that is, an impact sound with a
relatively high pitch but low loudness is generated. However, if
the bh.sup.3/m.sup.4 value is relatively small, an impact sound
with a relatively low pitch is generated. When
0.20.ltoreq.bh.sup.3/m.sup.4<8.00, it is possible to generate an
impact sound having both a high pitch and loudness.
EXAMPLE
[0040] Models of a plurality of golf club heads were designed on a
computer, and vibration analysis was performed for each model on
the computer. All these models are driver heads with the same shape
and the same volume of 460 cc, and are different only in the
specifications of a rib 20 and a weight portion 21. Note that these
golf club heads are made of a titanium alloy (Ti-6Al-4V).
[0041] Each model has the same arrangement as the golf club head 10
shown in FIGS. 1, 2A, and 2B, and includes a rib 20, a weight
portion 21, and a sole/side portion 13 which includes a thick
region S1 on the side of a face portion 11, a thin region S2, and a
thick region S3 on the back side in turn from the side of the face
portion 11 to the back side. The thin region S2 has a dimension of
65 mm in the face-to-back direction, and a thickness of 0.6 mm. A
distance LW of the weight portion 21 from an intersection point PF
is 50 mm, and a distance LR of the rib 20 from the intersection
point PF is 35 mm.
[0042] A width b (mm) and a height h (mm) of the rib 20 were set so
that the bh.sup.3 value changes for each model within the range of
50 to 650. Also, a mass m (g) of the weight portion 21 was set so
as to change for each model within the range of 0 (without a weight
portion) to 8(g).
[0043] In vibration analysis, the pitch (frequency), resonance
(vibration time), and loudness (amplitude) of an impact sound were
calculated.
[0044] FIG. 5A is a view showing the mass m of the weight portion
21, the bh.sup.3 value of the rib 20, and the calculation result of
the eigenvalue (natural frequency) of the first-order vibration
mode of each model. The tolerance of the eigenvalue of the
first-order vibration mode is 2,500 Hz or more, and calculation
results that fall within this tolerance are indicated by shaded
portions. If the mass m of the weight portion 21 is 6 g or more, a
natural frequency of 2,500 Hz or more cannot be achieved.
Accordingly, the mass m of the weight portion 21 must be smaller
than 6 g. If the bh.sup.3 value is 50 or more, a natural frequency
of 2,500 Hz or more can be achieved. Accordingly, the width b and
height h must be set so that the bh.sup.3 value is 50 or more.
[0045] FIG. 5B is a view showing the mass m of the weight portion
21, the bh.sup.3 value of the rib 20, and the evaluation result of
the resonance and loudness of an impact sound generated by each
model. The resonance and loudness were evaluated using four grades
(A to D). Grade A is the best, and grades A and B fall within the
tolerance (shaded portions). The larger the mass m, and the smaller
the bh.sup.3 value of the rib 20, the better the resonance and
loudness of an impact sound become. Conversely, the smaller the
mass m, and the larger the bh.sup.3 value of the rib 20, the poorer
the resonance and loudness of an impact sound become. When the
weight portion 21 is provided (mass m.noteq.0), there is a model
that has a bh.sup.3 value of 650 and is evaluated as grade D, and
this means that the evaluation result degrades as the bh.sup.3
value increases. Hence, bh.sup.3 is preferably 700 or less and more
preferably 650 or less.
[0046] FIG. 5C is a view showing the mass m of the weight portion
21, the bh.sup.3 value of the rib 20, and the bh.sup.3/m.sup.4
value of each model. Each shaded portion shown in FIG. 5C is a
portion in which the shaded portions shown in FIGS. 5A and 5B
overlap each other, that is, indicates a model in which the
eigenvalue (natural frequency) of the first-order vibration mode is
2,500 Hz or more and the evaluation result of the resonance and
loudness of an impact sound is A or B, so it generates a
satisfactory impact sound. As can be seen from FIG. 5C, no model
having a bh.sup.3/m.sup.4 value less than 0.20 generates a
satisfactory impact sound. Hence, the bh.sup.3/m.sup.4 value must
be 0.20 or more.
[0047] The upper limit of bh.sup.3/m.sup.4 has a maximum value of
3.13 in a model in which the weight portion 21 has a mass of 2 g
and the rib 20 has a bh.sup.3 value of 50 among models which
generate satisfactory impact sounds. However, the upper limit is
expected to have a larger value in consideration of the
relationships between changes in bh.sup.3/m.sup.4 of the five
models in which the weight portion 21 has a mass of 2 g, and
changes in the natural frequency shown in FIG. 5A and the
evaluation result of the resonance and loudness of an impact sound
shown in FIG. 5B. In a model in which the weight portion 21 has a
mass of 2 g and the rib 20 has a bh.sup.3 value of 200, the
bh.sup.3/m.sup.4 value is 12.50 and the natural frequency falls
within the tolerance but the evaluation result of the resonance and
loudness of an impact sound is grade C. Hence, a satisfactory
impact sound is expected to be produced when the bh.sup.3/m.sup.4
value is the average between 3.13 and 12.50, that is, less than
8.00.
[0048] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0049] This application claims the benefit of Japanese Patent
Application No. 2011-133523, filed Jun. 15, 2011, which is hereby
incorporated by reference herein in its entirety.
* * * * *