GOLF CLUB SET AND GOLF CLUB

TECHNICAL FIELD

The present invention relates to a golf club set and a golf club.

BACKGROUND ART

A golf club set typically includes multiple clubs having different loft angles (JP 2012-61035A, for example). Clubs having low loft angles are used to achieve longer flight distances. On the other hand, clubs having high loft angles are used for shots when near the green, where the player often aims for a small area on the green. Clubs having high loft angles put an increased amount of backspin on the ball, which ensures the ball will stop on the green and is thus useful.

JP 2012-61035A is an example of the related art.

SUMMARY OF THE INVENTION

However, golf clubs included in past golf club sets have not sufficiently exploited such differences in loft angles for better performance, and there has been demand for further improvements. Having been achieved to address this issue, an object of the present invention is to provide a golf club set, and golf clubs included in the set, in which clubs having low loft angles can achieve longer flight distances and clubs having high loft angles can increase the amount of backspin.

A golf club set according to the present invention is constituted by a plurality of golf clubs having different loft angles. Each golf club includes a shaft and a golf club head. Each of the golf club heads includes a crown part, a face part, a sole part, and a hosel part attached to the shaft. In at least one combination of golf clubs, among the plurality of golf clubs, having different loft angles, the golf club head of the golf club having the higher loft angle is, when in a reference state, longer from a lowermost point to an uppermost point of the golf club head, excluding the hosel part, than the golf club head of the golf club having the lower loft angle.

In the above-described golf club set, the golf club head of the golf club having the higher loft angle can have a greater volume than the golf club head of the golf club having the lower loft angle.

In the above-described golf club set, the plurality of golf club heads can have the same length, in a face-back direction, between a point furthest on a face side and a point furthest on a back side, when in the reference state. Note that “the same length” is not limited to being exactly the same, and includes an allowance of no more than approximately 2 mm, for example.

In the above-described golf club set, the golf club heads can be hollow wood types.

In the above-described golf club set, the loft angles of the golf club heads can be from 16 to 35 degrees.

A golf club according to the present invention is a golf club included in a golf club set constituted by a plurality of golf clubs having different loft angles. Each golf club includes a shaft and a golf club head. Each of the golf club heads includes a crown part, a face part, a sole part, and a hosel part attached to the shaft. In at least one combination of golf clubs, among the plurality of golf clubs, having different loft angles, the golf club head of the golf club having the higher loft angle is, when in a reference state, longer from a lowermost point to an uppermost point of the golf club head, excluding the hosel part, than the golf club head of the golf club having the lower loft angle.

According to the present invention, a club having a lower loft angle can extend the flight distance, and a club having a higher loft angle can increase the amount of backspin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a golf club head according to an embodiment in a reference state.

FIG. 2 is a plan view corresponding to FIG. 1.

FIG. 3 is a cross-sectional view taken from a line A-A in FIG. 2.

FIG. 4A is a diagram illustrating the boundaries of a face part.

FIG. 4B is a diagram illustrating the boundaries of the face part.

FIG. 5 is a side view of golf clubs, in a golf club set, that have different loft angles.

FIG. 6 is a side view of a #3 utility and a #6 utility taken from FIG. 5.

EMBODIMENTS OF THE INVENTION

An embodiment of a golf club set according to the present invention will be described hereinafter with reference to the drawings. The golf clubs constituting the golf club set according to the present embodiment are utility type (also called “hybrid type”) golf clubs. The clubs are, for example, #2 to #6 utilities, having club lengths from 36 to 42 inches and loft angles from 15 to 35°. As will be described later, the clubs differ mainly in terms of the loft angle, the head height (head thickness), and so on. The following will first use a single golf club as an example to give a general overview of the structures common to the clubs. Then, the differences between the golf clubs in the golf club set will be described in detail.

1. Overview of Golf Club Head

First, a single golf club in the golf club set according to the present embodiment (a utility type golf club, for example) will be used as an example to describe the golf club head. FIG. 1 is a perspective view of a single golf club head in the golf club set according to the present embodiment, shown in a reference state. FIG. 2 is a plan view corresponding to FIG. 1. FIG. 3 is a cross-sectional view taken from a line A-A in FIG. 2. The reference state of the golf club head will be described later.

As illustrated in FIGS. 1 to 3, the golf club head (also sometimes called simply a “head” hereinafter) 10 is a utility type golf club head. The head has a hollow construction with an internal space, and wall surfaces are formed by a face part 1, a crown part 2, a sole part 3, and a hosel part 4.

The face part 1 has a face surface, which is a surface that strikes a ball. The crown part 2 is adjacent to the face part 1 and forms an upper surface of the head 10. The sole part 3 mainly forms a bottom surface of the head 10, and constitutes the outer peripheral surface of the head 10 excluding the face part 1 and the crown part 2. In other words, in addition to the bottom surface of the head 10, a part extending from a toe side of the face part 1, across a back side of the head, and to a heel side of the face part 1 is part of the sole part 3. Furthermore, the hosel part 4 is a part provided adjacent to a heel side of the crown part 2, and has an insertion hole 41 into which a shaft (not shown) of a golf club is inserted. A center axis line Z of the insertion hole 41 coincides with an axis line of the shaft.

A reference state when the golf club head 10 is placed on a ground surface will be described next. First, as illustrated in FIG. 2, a state in which the center axis line Z is present in a plane P1 perpendicular to the ground surface and the head is placed on the ground surface at a prescribed lie angle and real loft angle, is defined as the “reference state”. The plane P1 is called a “reference vertical plane”. Also, as illustrated in FIG. 2, the direction of an intersecting line between the reference vertical plane P1 and the ground surface is called a “toe-heel direction”, and a direction perpendicular to the toe-heel direction and parallel to the ground surface is called a “face-back direction”.

In the present embodiment, a boundary between the face part 1 and the crown part 2, and a boundary between the face part 1 and the sole part 3, can be defined as follows. If a ridge line is formed between these elements, that ridge line serves as the boundary. However, if a clear ridge line is not formed, the boundaries are defined as follows. In each of cross-sections E1, E2, E3, and so on illustrated in FIG. 4A, each of which contains a straight line N connecting a head center of gravity G with a sweet spot SS, a position Pe where a curvature radius r of a face outer surface contour line Lf first reaches 200 mm while moving from the sweet spot side toward the face outer side, as illustrated in FIG. 4B, serves as a peripheral edge of the face part 1. This is defined as the boundary with the crown part 2 or the sole part 3. The “sweet spot SS” is a point of intersection between a normal line of the face surface passing through the head center of gravity G (the straight line N) and that face surface.

Additionally, in the present embodiment, a boundary between the crown part 2 and the sole part 3 can be defined as follows. If a ridge line is formed between the crown part 2 and the sole part 3, that ridge line serves as the boundary. However, if a clear ridge line is not formed between these elements, the head is placed in the reference state and a contour seen from directly above the center of gravity of the head 10 serves as the boundary.

The head 10 can be formed of, for example, a titanium alloy (Ti-6Al-4V, Ti-8Al-1Mo-1V, or the like) having a relative density of approximately 4.3 to 4.5. Aside from titanium alloys, the head can be formed using one or more of stainless steel, mariaging steel, an aluminum alloy, a magnesium alloy, an amorphous alloy, and so on, for example.

The volume of the golf club head 10 is preferably greater than or equal to 90 cm³and less than or equal to 460 cm³, for example.

2. Assembly Structure of Golf Club Head

As illustrated in FIG. 3, the golf club head 10 according to the present embodiment is formed by assembling a head main body 101, which includes the crown part 2 and the sole part 3, with a face member 102, which includes the face part 1 and a peripheral edge part 15 extending from the peripheral edges of the face part 1 to form a cup-like shape. The head main body 101 has an opening 18 surrounded by the crown part 2 and the sole part 3, and the face member 102 is attached so as to cover the opening 18. In other words, an end surface of the peripheral edge part 15 of the face member 102 butts against an end surface of the opening 18 in the head main body 101, and these are joined together by welding (for what is known as a “cup face construction”). The face member 102 is integrated with the head main body 101 by being attached to the edges of the opening 18 in the head main body 101. As a result, the peripheral edge part 15 of the face member 102 functions as a part of the crown part 2 and the sole part 3 of the head 10.

Accordingly, an integral surface formed by attaching the peripheral edge part 15 of the face member 102 to the head main body 101 forms the crown part 2 and the sole part 3 of the head 10. As such, the crown part 2 and the sole part 3 of the head main body 101 are, strictly speaking, parts of the crown part 2 and the sole part 3 of the head 10. However, this specification may not make this distinction, with the parts of the head main body 101 also being referred to simply as the crown part 2 and the sole part 3.

3. Structure of Crown Part

The crown part 2 will be described next. As illustrated in FIGS. 1 to 3, the crown part 2 includes a protruding part 21 located on the face part 1 side and a base part 22 located further on the back side than the protruding part 21. The protruding part 21 is mainly a band-shaped region extending along the face part 1 in the toe-heel direction. On the other hand, the base part 22 is a region occupying most of the crown part 2 at a position lower than the protruding part 21, and the peripheral edges of the base part 22 contact the sole part 3. A sloped surface 23, which forms a step, is formed at the boundary between the protruding part 21 and the base part 22. As such, the height of the face part 1 in an up-down direction is higher by the size of the step between the protruding part 21 and the base part 22.

The sloped surface 23 is formed so as to extend upward as the sloped surface 23 progresses toward the face part 1. Thus when the golf club head 10 is placed in the reference state, the sloped surface 23 can be seen from above. In other words, the sloped surface 23 can be seen by a golfer at address position. The sloped surface 23 is formed along the protruding part 21, and thus like the protruding part 21, is formed having what is a band shape when viewed in plan view.

As illustrated in FIG. 3, a width D of the protruding part 21 in the face-back direction is, for example, preferably from 5 to 25 mm and further preferably from 7 to 20 mm, when viewed in plan view.

Additionally, a width L of the sloped surface 23 in the face-back direction, when viewed in plan view, is, for example, preferably from 1 to 9 mm and further preferably from 2 to 7 mm. Furthermore, a height H of the sloped surface 23 is, for example, preferably from 0.5 to 8 mm, further preferably from 0.5 to 6 mm, and particularly preferably from 0.5 to 5 mm.

4. Method of Manufacturing Golf Club Head

An example of a method of manufacturing the aforementioned golf club head will be described next. First, the above-described head main body 101 and face member 102 are prepared. The head main body 101 and the face member 102 can be manufactured through a variety of methods. For example, the head main body 101 can be manufactured using a known casting method such as lost-wax precision casting. The face member 102 can be manufactured through a forging method, a process of pressing a flat plate, casting, or the like, for example. In this case, the pre-processing flat plate used for the face member 102 is processed such that the rolling direction substantially coincides with the direction from an upper part of the face part 1 on the toe side to a lower part on the heel side.

These are then joined through welding, for example (tungsten-inert gas (TIG) welding, plasma welding, laser welding, brazing, or the like). Then, once painting or the like has been carried out, the golf club head is complete.

Note that the head according to the present embodiment is formed by combining a head main body, which includes at least the sole part 3, with other parts. For example, the head can be formed by attaching, to the head main body, a separate member constituting only the face part 1; or a head main body in which an opening is provided in the crown part 2 can be formed, and the head can be completed by covering that opening with a separate member.

5. Differences Between Golf Clubs in Golf Club Set

Differences between clubs in the golf club set that have different loft angles will be described next with reference to FIG. 5 as well. FIG. 5 is a side view of multiple golf club heads in the reference state. FIG. 5 illustrates the heads of four golf clubs, having consecutive numbers, in the golf club set according to the present embodiment as an example. These are arranged in order from left to right, from the club having the lowest loft angle, i.e., a #3 utility (U#3), a #4 utility (U#4), a #5 utility (U#5), and a #6 utility (U#6). Note that in FIG. 5, the heads are illustrated in a slightly exaggerated manner to make the features of the invention with respect to the difference between the golf clubs clear. Thus the actual angles, shapes, and so on, which will be mentioned later with reference to Table 1, are different from those in FIG. 5, but this has no effect on the essence of the invention. Furthermore, dimensions of the heads described hereinafter refer to dimensions in the reference state unless otherwise specified.

As illustrated in FIG. 5, in the golf club set according to the present embodiment, a length L, in the face-back direction, between a point furthest on the face side and a point furthest on the back side (called a “head width” hereinafter), is the same in each golf club head. Specifically, a head width W can be set to a range of from 50 to 80 mm, for example. However, the heights of the heads, with the exception of the hosel parts 4, are different. To describe in more detail, a height B from the lowermost point of the head 10 when the head 10 is arranged on a horizontal plane H, or in other words, from the horizontal plane H, to the uppermost point of the head 10 (called a “head thickness B” hereinafter), is greater in clubs having higher loft angles. Following the changes in the head thickness B, a length A of face surface in the planar direction is also greater in clubs having higher loft angles. The volume of the head 10 is furthermore generally greater in clubs having higher loft angles. Table 1 shows examples of the aforementioned dimensions and so on of these four clubs. However, Table 1 is merely an example, and the dimension can be changed as appropriate. Note that a center of gravity height is a height from the center of gravity of the head in the horizontal plane H, and the SS height is a height from the SS point (sweet spot) of the head in the horizontal plane H.

TABLE 1

U#3
U#4
U#5
U#6

LOFT ANGLE (deg)
18.0
20.0
23.0
26.0

LIE ANGLE (deg)
59.5
60.0
60.5
61.0

HEAD VOLUME (cc)
114
118
121
119

A (mm)
33.0
34.5
36.0
36.5

B (mm)
34.0
35.0
36.0
36.0

L (mm)
65.5
65.5
65.5
65.5

CENTER OF GRAVITY
11.7
12.0
12.3
12.3

HEIGHT (mm)

SS HEIGHT (mm)
18.8
19.6
20.5
21.5

6. Effects

According to the embodiment described thus far, the following effects can be achieved.

(1) FIG. 6 illustrates the heads of the #3 utility (U#3) and the #6 utility (U#6) taken from FIG. 5, for comparative purposes. In FIG. 6, U#6, which is the club having the higher loft angle, has a higher SS point than U#3, which is the club having the lower loft angle. In other words, U#6 has a higher loft angle than U#3, and thus the SS point is geometrically higher from the outset. However, as described above, the head thickness B is greater as well, which raises the center of gravity G and makes the SS point even higher.

Thus when a ball 80 is struck, U#6, in which the contact point K is further from the SS point, rotates more easily in the Z direction (the up-down direction) about the center of gravity. The so-called gear effect increases as a result, and thus the amount of backspin, which is rotation in an SP direction, can be increased. Accordingly, clubs having higher loft angles, used for shots where the green is near, can increase the amount of backspin even more. Note that utility type clubs having loft angles of from 16 to 35 degrees as mentioned above often strike balls located directly on the ground surface, and thus the contact point K is often geometrically lower than the SS point.

On the other hand, the U#3 has both a low loft angle and a low head thickness, which lowers the center of gravity G and further lowers the SS point. As such, the distance between the SS point and the contact point K of the ball 80 is shortened, which reduces rotation in the Z direction about the center of gravity G of the head at the time of impact. This not only makes it possible to suppress a drop in the hitting angle of the ball, but the SS point being closer to the contact point reduces the gear effect and reduces the amount of backspin, which is rotation in the SP direction.

Accordingly, a club having a low loft angle improves the flight distance of the ball by suppressing a drop in the hitting angle of the ball and reducing the amount of backspin. Clubs having low loft angles are used more often for longer shots, and thus this effect is particularly useful, and makes it possible to extend the flight distance of the ball even further.

Thus with the golf club set according to the present embodiment, clubs having lower loft angles can extend the flight distances more, whereas clubs having greater loft angles can increase the amount of backspin more.

(2) A club having a higher loft angle, such as U#6, has a greater head thickness B, which increases the moment of inertia in the up-down direction of the head. This reduces deviation in the rotation direction, in the up-down direction of the head, at the time of impact, which stabilizes the hitting angle of the ball. The flight distance of the ball can be stabilized as a result. Clubs having high loft angles in particular have a shorter club length and a lower head rotation radius during the swing, and thus compared to clubs having low loft angles, impact the ball while the head travels at a more acute angle with respect to the grass surface. This makes it more likely for the contact point on the face surface to vary in the up-down direction, and more likely for the head to deviate in the up-down rotation direction at the time of impact. However, according to the present embodiment, deviation can be reduced and the flight distance of the ball can be stabilized, even for clubs having high loft angles.

(3) Clubs having higher loft angles generally also have higher head volumes, which increases the moment of inertia in the up-down direction. The same effect as that described above in (2) can thus be achieved.

(4) With the golf club set according to the present embodiment, the head width W is the same for all of the golf clubs. In other words, all of the clubs have the same head width W regardless of the loft angle. The following effects can be achieved as a result. First, a method in which the center of gravity G is located further on the back side, i.e., the center of gravity depth is increased, can be used to geometrically raise the SS point. However, utilities are often used on the rough as well, and thus if the head width W is increased, the sole part 3 will become longer in the face-back direction, which increases the resistance between the sole part 3 and the ground surface. As such, according to the present embodiment, as described above, resistance during the swing is reduced by keeping the head width W constant even as the loft angle is increased, while the SS point is kept high by increasing the head thickness as the loft angle is increased.

(5) In the crown part 2, the protruding part 21 is formed to be higher than the base part 22 by using the sloped surface 23, and thus the height of the face part 1 can be increased by the amount by which the protruding part 21 has been made higher. This makes it possible to improve the rebound performance at the face part 1. Additionally, only the protruding part 21 is formed to be higher in the crown part 2, whereas the base part 22, which occupies most of the crown part 2, is formed in a position that is lower than the protruding part 21. This makes it possible to lower the center of gravity of the head.

7. Variations

An embodiment of the present invention has been described thus far. However, the present invention is not intended to be limited to the above-described embodiment. Many variations can be made thereon without departing from the essential spirit of the present invention. The following variations can also be combined as appropriate. The following variations are possible, for example.

7.1

Although the foregoing embodiment describes increasing the head thickness in clubs having higher loft angles, this relationship does not absolutely have to hold true for all of the consecutive-numbered golf clubs in the golf club set. In other words, it is sufficient for this relationship to hold true between any of the clubs having a high loft angle and any of the clubs having a low loft angle in the golf club set. Thus, for example, in the clubs from U#3 to U#6, the relationship of the head thicknesses B can be set to U#3<U#4=U#5<U#6, or can be set to U#3<U#4<U#5=U#6.

7.2

Although the foregoing embodiment describes the volume of the head 10 generally being greater in clubs having higher loft angles, the volume of the head 10 does not absolutely need to increase with the loft angle. For example, although the volume of the head 10 increases in order from U#3 to U#5 in the foregoing embodiment, U#6 may have a lower volume than U#5 and a greater volume than U#4.

7.3

Although the head widths are the same for all of the clubs in the foregoing embodiment, the head widths do not absolutely need to be the same, and can instead be set to vary.

7.4

Although the crown part 2 of the head includes the protruding part 21 in the foregoing embodiment, the shape of the protruding part 21 is not particularly limited. A crown part 2 not having the protruding part 21 is possible as well.

7.5

The “golf club set” according to the present invention refers to a golf club set including the same type of golf clubs, and a single golf club set includes only utility type golf clubs as described above. However, in addition to utility type golf clubs, the golf club set according to the present invention can be constituted by wood type golf clubs having hollow heads, such as drivers or fairway woods, for example.

LIST OF REFERENCE NUMERALS

- 1 Face part
- 2 Crown part
- 3 Sole part

GOLF CLUB SET AND GOLF CLUB

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