Golf Club Head and Golf Club

Abstract

This invention provides a wood golf club head having a loft angle of not more than 15°. In this golf club head, a progression length FP from a leading edge of a face to an axis line of a shaft axis and a horizontal length VZG from the leading edge of the face to a center of gravity of the head in a depth direction satisfy the following expression; −2<VZG−2×FP<2.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wood golf club head and a golf club and, more particularly, to a wood golf club head having a loft angle of not more than 15° and a golf club.

2. Description of the Related Art

In a golf club, the shape of the head greatly influences playability, directionality of a hit ball, and the like. There have been provided and proposed heads with a variety of designs in order to improve ball catchability, playability, directionality of a hit ball, and the like by adjusting a face progression (FP) representing the length from the axis line of the shaft to the leading edge of the face, the center of gravity position, a gravity depth (VZG) representing the length from the leading edge of the face to the center of gravity in the depth direction, a gravity depth (ZG) representing the length from the face to the center of gravity, a loft angle, a gravity length (GL) representing the length from the axis line of the shaft to the center of gravity, the height of the sweet spot, and the like.

In general, as a factor of ball catchability, a small face progression (FP) is considered to provide high ball catchability and a large FP is considered to provide low ball catchability. In this specification, high ball catchability means that the head rotation is encouraged through impact so that it is easy to hook (difficult to slice) a ball, and low ball catchability means that the head rotation is not encouraged through impact so that it is easy to slice (difficult to hook) a ball. The center of gravity depth (VZG) represents a relative center of gravity depth in the head. Generally, a larger center of gravity depth tends to provide better ball catchability.

When ball catchability is excessively high or low, the playability becomes poor and the directionality of the hit ball becomes unstable. These phenomena are considered to occur because the behavior of the golf club head during a swing has a lack of stability and a stable head rotation cannot be controlled. A factor for controlling stable head rotation is assumed to be determined from the relationship between the hitting point, center of gravity position, and shaft axis, but no distinct relationship has been found.

As a golf club head that is focused on the FP value, one with an FP value falling within a range of 7 mm to 20 mm (both inclusive) has been proposed (for example, see Japanese Patent Laid-Open No. 11-178958). Another golf club head that is focused on the center of gravity depth (ZG) has also been proposed (for example, Japanese Patent Laid-Open No. 2002-210045).

With a design in which only the value of one factor such as the FP value or ZG value is defined, the behavior of the golf club head during a swing cannot be stabilized. Therefore, stable head rotation and ball catchability cannot be controlled, resulting in poor playability. Accordingly, a player cannot selectively hook or slice a ball. In addition, the directionality of the hit ball is unstable.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a wood golf club head and a golf club in which the behavior of the golf club head during a swing is stable, stable head rotation can be controlled, and playability and directionality of a hit ball are excellent.

According to an aspect of the present invention, there is provided a wood golf club head having a loft angle of not more than 15°, wherein a progression length FP from a leading edge of a face to an axis line of a shaft axis and a horizontal length VZG from the leading edge of the face to a center of gravity of the head in a depth direction satisfy the following expression; −2<VZG−2×FP<2. A golf club comprising such a wood golf club head is also provided.

The FP preferably satisfies 12 mm<FP<20 mm, and more preferably 12 mm<FP<17 mm.

Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawing).

BRIEF DESCRIPTION OF THE DRAWING

FIGURE is a side view of a golf club head 1 according to an embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawing.

FIGURE is a side view of a wood golf club head 1 including a hollow portion 10. A head main body 2 is provided with a hosel 3 and a face plate 5 is fixed to the head main body 2. A shaft (not shown) is mounted to the hosel 3, thereby forming a golf club. The loft angle of the golf club head 1 is formed to be 15° or less.

The progression length from a leading edge 41 of a face 4 to an axis line S of the shaft is defined as FP, that is, the face progression. The horizontal length from the leading edge 41 of the face 4 to a center of gravity G in the depth direction is defined as VZG, that is, the center of gravity depth.

The golf club head 1 is formed to satisfy −2<VZG−2×FP<2. The FP value preferably satisfies 12 mm<FP<20 mm, and more preferably 12 mm<FP<17 mm. When the FP value is 12 mm or less, a player feels a sense of discomfort for a head shape, and ball catchability becomes excessively high, resulting in the ball flying to the left. When the FP value is 20 mm or more, even though the behavior stability of the golf club head during a swing improves, ball catchability decreases.

The VZG value is set to satisfy −2<VZG−2×FP<2 described above in accordance with the FP value. The VZG value is preferably greater or equal to 24 mm and more preferably greater or equal to 25 mm. The VZG value is preferably 42 mm or less, more preferably 40 mm or less and still more preferably 38 mm or less.

The material and volume of the golf club head 1 are not particularly limited as far as they fall within the range of an ordinal wood head. For example, a material such as a titanium alloy, stainless steel, or the like can be employed, and the volume can be about 350 cc to 500 cc.

Note that when the volume is 400 cc or more, the center of gravity length representing the length the perpendicular from the axis line S to the center of gravity G is preferably 50 mm or less, more preferably 40 mm or less. When the volume is 400 cc or more, the center of gravity length generally becomes long, resulting in poor playability. The playability can be improved by decreasing the center of gravity length. The center of gravity length is preferably greater or equal to 25 mm.

When the volume of the golf club head 1 is large and is about 400 cc or more, it increases a hitting sound and worsens feeling of playability and hitting feel. For this reason, it is preferable to mount a member made of a material having a relatively low specific gravity as a metal and a vibration damping effect, such as magnesium or a magnesium alloy, to the back face on the toe and heel sides so as to reduce the hitting sound and improve the feeling of playability. This alloy member is shaped into a screw 7 which can be screwed toward the hollow portion 10 from a recessed portion 8 provided in the back face.

A large-size head having a large volume readily provides low ball catchability. Accordingly, the wall thickness of the crown portion from the face 4 side to the back face side is preferably increased as compared to other head portions. For example, it is possible to form a wall thickness L of the hosel 3 on the back face side to be 0.6 mm; a wall thickness M on the further back face side, 0.7 mm; and a wall thickness N on the still further back face side, 1.0 mm. With this arrangement, the ball catchability can improve.

EXAMPLE

Samples of Examples 1 to 3 and Comparative Examples 1 to 9 were fabricated as the golf club heads 1 each having the head main body 2 made of a titanium alloy and the face plate 5 made of titanium. All the golf club heads of Examples 1 to 3 and Comparative Examples 1 to 9 had a volume of 410 cc but different FP values (mm) and VZG values (mm). A golfer actually hit a ball using each golf club head of Examples 1 to 3 and Comparative Examples 1 to 9 and checked the feeling of ball catchability, that of the behavior stability during a swing, the side spin, the launch direction, and the trajectory. Table 1 shows the results. Note that in Table 1, the units of FP and VZG −2×FP are in mm. A plus sign (+) of a value of the side spin represents a slice spin and a minus sign (−) represents a hook spin. When viewed from above with respect to the target line, the clockwise spin is represented by +and the counterclockwise spin is represented by −. The unit of the side spin is rpm. Trajectory indicates a shift amount in the left and right with respect to the target direction. A plus value indicates a case in which the trajectory shifted to the right with respect to the target direction, and a minus value indicates a case in which the trajectory shifted to the left. The unit of the trajectory is in m.

	TABLE 1
				Behavior
				Stabillity
		VZG	Catchabl-	During		Launch
		−2 ×	ility	Swing	Side	Direc-	Trajec-
	FP	FP	(Feeling)	(Feeling)	Spin	tion	tory
Compar-	13	−4	Good	Large	200	Right	10
ative				flight
Example				curveture
1
Example	13	0	Good	◯Stable	−200	Center	−5
1
Compar-	13	4	Good	Unstable	−600	Left	−15
ative
Example
2
Compar-	16	−4	Excellent	Large	400	Right	15
ative				flight
Example				curveture
3
Example	16	0	Excellent	◯Stable	0	Center	0
2
Compar-	16	4	Excellent	Unstable	−400	Left	−15
ative
Example
4
Compar-	18	−4	Poor	Large	600	Right	20
ative				flight
Example				curveture
5
Example	18	0	Poor	◯Stable	200	Center	5
3
Compar-	18	4	Poor	Unstable	−200	Left	−10
ative
Example
6
Compar-	21	−4	Worst	Large	800	Right	25
ative				flight
Example				curveture
7
Compar-	21	0	Worst	◯Stable	400	Center	15
ative
Example
8
Compar-	21	4	Worst	Unstable	0	Left	5
ative
Example
9

As shown in the results in Table 1, in Examples 1 to 3, the golf club head during a swing has a stable behavior, excellent playability, and excellent directionality of the hit ball.

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.

This application claims the benefit of Japanese Patent Application No. 2007-64896, filed Mar. 14, 2007, which is hereby incorporated by reference herein in its entirety.

Claims

1. A wood golf club head having a loft angle of not more than 15°, wherein

a progression length FP from a leading edge of a face to an axis line of a shaft axis and a horizontal length VZG from the leading edge of the face to a center of gravity of the head in a depth direction satisfy the following expression: −2<VZG−2×FP<2.

2. The head according to claim 1, wherein the FP satisfies 12 mm<FP<20 mm.

3. The head according to claim 2, wherein the FP satisfies 12 mm<FP<17 mm.

4. A golf club comprising a wood golf club head according to claim 1.