GOLF CLUB HEAD

Abstract

This invention discloses a golf club head which has a hollow shell structure and includes a face portion, a sole portion, a crown portion, a back portion, a toe-side side portion, and a heel-side side portion. A ratio R/H×100% is 5% to 20%, where R is the radius of curvature of the upper corner edge on which the face portion and the crown portion intersect with each other, and H is the maximum head height.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hollow golf club head.

2. Description of the Related Art

Golf club heads which are made of a metal and have a hollow shell structure are widely used as wood type golf club heads such as a driver and a fairway wood type golf club head. In general, a hollow wood type golf club head includes a face portion for hitting a ball, a crown portion which forms the upper surface portion of the golf club head, a sole portion which forms the bottom surface portion of the golf club head, a side portion which forms the toe- and heel-side side surface portions of the golf club head, a back portion which forms the back surface portion, and a hosel portion in which a shaft is mounted. A shaft is inserted into the hosel portion and fixed by, for example, an adhesive. In recent years, a variety of golf clubs called utility clubs (hybrid clubs) have also become commercially available. As one type of utility golf club, various golf clubs having heads similar to the above-mentioned wood type golf club head (that is, heads each having a face portion, sole portion, side portion, back portion, crown portion, and hosel portion) are commercially available.

Although an aluminum alloy, stainless steel, or a titanium alloy is typically used as a metal which forms the hollow golf club head, a titanium alloy is especially widely used these days (for example, Japanese Patent Laid-Open No. 2003-88601).

In general, as the volume of a hollow golf club head increases, the air resistance of the head upon a swing also increases.

Japanese Patent Publication No. 7-93956 describes a groove formed in the crown portion to extend in the toe-to-heel direction so as to reduce the air resistance of the head.

As described in Japanese Patent Publication No. 7-93956, even if forming a groove in the crown portion produces an effect of reducing the air resistance of the head, this may hinder the flexure of the entire crown portion upon hitting a ball, thus producing a negative effect in terms of increasing the flight distance.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a golf club head which can reduce air resistance without forming a groove in the crown portion, and increase the flight distance.

According to the present invention, there is provided a golf club head which has a hollow shell structure and includes a face portion, a sole portion, a crown portion, a back portion, a toe-side side portion, and a heel-side side portion, wherein a ratio R/H×100% is 5% to 20%, where R is a radius of curvature of an upper corner edge on which the face portion and the crown portion intersect with each other, and H is a maximum head height. Note that the maximum head height H is the distance between a horizontal surface in contact with a lowest sole point and that in contact with a highest crown point while the golf club head is soled.

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

FIG. 1 is a perspective view of a golf club head according to an embodiment of the present invention;

FIG. 2 is a sectional view taken along a line II-II in FIG. 1;

FIG. 3 is a view for explaining the shape of the upper corner edge of the golf club head shown in FIG. 1;

FIG. 4 is an aerodynamic force diagram of the golf club head shown in FIG. 1; and

FIG. 5 is an aerodynamic force diagram of the conventional golf club head.

DESCRIPTION OF THE EMBODIMENTS

A golf club head 1 according to an embodiment will be described below with reference to FIGS. 1 to 4. Simply put, the golf club head 1 has a given loft angle, so air flows from the face portion to the crown portion in large amounts during a swing. For this reason, the upper corner edge of the head, on which the crown portion and the face portion intersect with each other, is rounded. Therefore, air that collides against the head upon a swing smoothly flows upwards, so the air resistance of the head upon a swing reduces. This makes it possible to easily raise the head speed to increase the flight distance. Also, in a driver head, a ball is placed on the tee and struck, so the head passes through a line higher in level than the ground surface by several centimeters. For this reason, the lower corner edge of the head, on which the face portion and the sole portion intersect with each other, is preferably rounded more than the upper corner edge of the head, on which the crown portion and the face portion intersect with each other. Little air flows through this lower portion due to factors associated with the loft angle. The sole portion is straighter (than the crown portion), and is therefore less likely to peel off.

The golf club head 1 uses a wood type golf club head (a driver in this embodiment) which has a hollow shell structure and includes a face portion 2, sole portion 3, back portion 4, crown portion 5, toe-side side portion 6, heel-side side portion 7, and hosel portion 8.

The face portion 2 forms a surface for hitting a ball, and is provided with grooves (scorelines) (not shown). The sole portion 3 forms the bottom surface portion of the golf club head 1, and the crown portion 5 forms the upper surface portion of the golf club head 1.

The back portion 4 forms the back surface portion of the golf club head 1. The toe-side side portion 6 and heel-side side portion 7 connect the back portion 4 and face portion 2 to each other. Also, the back portion 4, toe-side side portion 6, and heel-side side portion 7 connect the sole portion 3 and crown portion 5 to each other. A shaft (not shown) is inserted into the hosel portion 8, and fixed by an adhesive.

Although the golf club head 1 is made of a metal in this embodiment (titanium or a titanium alloy in this embodiment), at least part of the crown portion 5 may be made of CFRP (Carbon Fiber Reinforced Plastics). Note that a cone which has a specific gravity of 8 or more and especially about 10 to 16, and is made of, for example, copper, a copper-lead alloy, a tungsten alloy, or a copper-lead-tungsten alloy may be provided in an appropriate portion on the golf club head 1.

In this embodiment, the upper corner edge of the golf club head 1, on which the face portion 2 and the crown portion 5 intersect with each other, is rounded more than that of the conventional golf club head. More specifically, in longitudinal sectional views (FIGS. 2 and 3) taken along a line which runs in the front-to-back direction and passes through the face center while the golf club head 1 is soled, when the contact point between the upper corner edge and a tangent to the outer surface of the upper corner edge, which is inclined by 45° backwards from the vertical direction, is defined as A, a point on the upper edge of the face portion 2 is defined as B, and a point C which forms a line segment AC having the same length as a line segment AB is set on the side of the crown portion 5, the upper corner edge is rounded so that a ratio R/H×100% is 5% to 20% and especially 10% to 15%, where R is the radius of curvature of an arc which passes through the points B, A, and C, and H is the maximum head height. In contrast to this, the conventional titanium driver head has a ratio R/H×100%=about 2% to 4%.

Note that the upper edge of the face portion 2 is defined as a point at which the radius of curvature of a face surface formed by a surface that is approximately flat but is slightly convexly curved starts to increase in the longitudinal sectional view shown in FIG. 3. That is, referring to FIG. 3, the radius of curvature of the face surface is constant on the side below the point B, but is larger on the side above the point B than on the side below the point B.

In a golf club head having an upper corner edge rounded more than the conventional golf club head in this manner, air that collides against the head upon a swing smoothly flows upwards, so the air resistance of the head upon a swing is low. FIG. 4 is an aerodynamic force diagram showing the flow of air from the upper corner edge to the vicinity of the crown portion when a wind tunnel test is conducted for a golf club head 1 having a ratio R/H (maximum head height)×100%=12%. FIG. 5 is an aerodynamic force diagram of the conventional golf club head which has a ratio R/H (maximum head height)×100%=3% and an angled upper corner edge. In the conventional golf club head, the laminar flow of air separates from the crown portion on the upper corner edge, so the air resistance of the head is high, as shown in FIG. 5. In contrast to this, in the golf club head shown in FIG. 4, which has a rounded upper corner edge, the laminar flow of air along the crown portion reaches the rear portion of the crown portion, so the air resistance of the head is low.

Note that the lower corner edge on which the face portion and the sole portion intersect with each other, and the heel- and toe-side corner edges on which the face portion and the heel- and toe-side side portions intersect with each other may be rounded as well. The present invention is preferably applicable to a driver head having a volume of 400 cc or more and, for example, 430 to 460 cc.

Example

A golf club (driver) was manufactured by mounting a carbon shaft in a titanium driver head (Example) having a volume of 460 cc and a ratio R/H×100%=12% so that the club length was 45 inches. The average of the head speeds at which this driver was swung five times was 39.7 m/sec.

The head speed of a driver on which a driver head (Comparative Example) having the same specifications as the driver head according to the Example except for having a ratio R/H×100%=3% was mounted was measured in the same way as above and found to be 39.4 m/sec.

The above-mentioned result verifies that the head speed increases when the upper corner edge is rounded more.

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. 2011-132523, filed Jun. 14, 2011, which is hereby incorporated by reference herein in its entirety.

Claims

1. A golf club head which has a hollow shell structure and includes a face portion, a sole portion, a crown portion, a back portion, a toe-side side portion, and a heel-side side portion, wherein

a ratio R/H×100% is 5% to 20%, where R is a radius of curvature of an upper corner edge on which the face portion and the crown portion intersect with each other, and H is a maximum head height.

2. The head according to claim 1, wherein the ratio is 10% to 15%.

3. The head according to claim 1, wherein

in a longitudinal sectional view taken along a line which runs in a front-to-back direction and passes the face center,

when a contact point between the upper corner edge and a tangent to an outer surface of the upper corner edge, which is inclined by 45° backwards from a vertical direction, is defined as A,

a point on an upper edge of the face portion is defined as B, and

a point C which forms a line segment AC having a length equal to a length of a line segment AB is set on a side of the crown portion,

the radius of curvature is equal to a radius of curvature R of an arc which passes through the points B, A, and C.