1. Field of the Invention
The present invention relates to a metallic hollow golf club head and, more particularly, to a large golf club head such as a driver.
2. Description of Related Art
As a wood-type golf club head such as a driver and a fairway wood, metallic hollow golf club heads have been widely used. Generally, hollow wood-type golf club heads have a face part for hitting a ball, a crown part constituting the top surface portion of the golf club head, a sole part constituting the bottom surface portion of the golf club head, a side part constituting the side surface portions on the toe side, back side, and heel side of the golf club head, and a hosel part. In this hosel part, a shaft is inserted and fixed by an adhesive or the like.
As a metal forming the hollow golf club head, an aluminum alloy, stainless steel, or titanium alloy has been used, and especially titanium alloy has been used widely in recent years.
Japanese Patent Provisional Publication No. 11-216203 discloses a golf club head in which the thickness on the front edge side along the face part of the sole part is increased. In FIG. 2 of this publication, this thick part is provided throughout the whole of the front edge of the sole part, and in FIG. 4 of this publication, the thick part is provided on the toe side and the heel side.
Conventionally, to increase the shot carry of a metallic hollow golf club head, development for increasing the rebound of the ball by utilizing the deflection (trampolining effect) of the face surface has been carried out. However, since the golf rules governing the upper limit of the rebound coefficient have been revised, carry now has to be increased by other measures. In the case of what is called a high-rebound type golf club head utilizing the trampolining effect, although a long carry can be attained when a ball is hit by the face center, such a long carry cannot be obtained when the hit point deviates from the face center (off-center hit).
According to the golf club head described in the aforementioned Japanese Patent Provisional Publication No. 11-216203, the center of gravity of the head can be lowered while the balance of inertia moment is maintained. However, in FIG. 2 of the publication, since the thick part exists throughout the whole from the toe to the heel of the front edge of the sole part, the deflection of the face part at the ball hit time is restrained as a whole, so that the carry decreases.
Also, in FIG. 4 of the publication, since the thick part is provided separately on the sole side and the heel side, the deflection of the face part at the time of off-center hit is restrained, so that the carry decreases. In addition, since the deflection of the face part at the time when a ball is hit by the face center is great, the rebound coefficient easily exceeds the limit placed by the golf rules.