GOLF CLUB HEAD

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a golf club head.

2. Description of the Related Art

To improve the head speed of a golf club head at impact, a measure of reducing the air resistance to the golf club head has been proposed. For example, each of Japanese Patent Laid-Open No. 2013-538666, Japanese Patent Laid-Open No. 2009-000281, and Japanese Utility Model Laid-Open No. 60-135153 discloses a golf club head that reduces the air resistance by forming a plurality of dimples.

Forming dimples has a predetermined effect for reducing the air resistance. However, the air resistance does not decrease in proportion to the area of dimple formation. If air resistance reducing elements such as dimples are formed unnecessarily in a wide area, the manufacture of the golf club head may become complicated, or the appearance may be spoiled.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a golf club head comprising a crown portion, a face portion, and a hosel portion, wherein the crown portion includes a turbulence-promoting portion that extends from a heel side to a toe side and a back side.

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. 2A is a view of the golf club head in FIG. 1 viewed from the upper side;

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

FIG. 3A is a perspective view showing the section of a crown portion taken along a line II-II in FIG. 2A;

FIGS. 3B and 3C are views showing other examples of the structure of a turbulence-promoting portion;

FIGS. 4A and 4B are explanatory views of an air resistance; and

FIG. 5 is an explanatory view of another example.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a perspective view of a golf club head 10 according to an embodiment of the present invention. FIG. 2A is a view of the golf club head 10 viewed from an upper side. FIG. 2A is a view showing the golf club head 10 viewed from the upper side in a case where the golf club head 10 is grounded according to a predetermined lie angle and a predetermined loft angle.

The golf club head 10 forms a hollow member. The peripheral walls of the golf club head 10 constitute a face portion 11 that forms a face (striking face), a crown portion 12 that forms the upper portion of the golf club head 10, a sole portion 13 that forms the bottom portion of the golf club head 10, and a side portion 14 that forms the portion between the crown portion 12 and the sole portion 13. A turbulence-promoting portion 16 to be described later is formed on the crown portion 12 as an air resistance reducing element. The golf club head 10 also includes a hosel portion 15 in which a shaft is inserted and fixed.

In FIGS. 1 and 2A, an arrow dl indicates the face-back direction, and an arrow d2 indicates the toe-heel direction. Normally, the face-back direction is to a target line direction (target direction of a shot). The toe-heel direction can be defined as, for example, the direction to connect the toe-side end and the heel-side end of the sole portion 13 or the direction perpendicular to the face-back direction.

The golf club head 10 is a golf club head for a driver. However, the present invention is applicable to wood type golf club heads including a fairway wood other than drivers, utility (hybrid) golf club heads, and other golf club heads.

The golf club head 10 can be made of a metal material. Examples of the metal material are a titanium-based metal (for example, titanium alloy 6A1-4V-Ti), stainless steel, and a copper alloy such as beryllium copper.

The golf club head 10 can be assembled by joining a plurality of parts. For example, the golf club head 10 can be formed from a body member and a face member. The body member forms the peripheral portions including the crown portion 12, the sole portion 13, the side portion 14, the hosel portion 15, and the face portion 11. An opening is formed at part of the portion corresponding to the face portion 11. The face member is joined to the opening of the body member.

The hosel portion 15 will be described with reference to FIG. 2B in addition to FIGS. 1 and 2A. FIG. 2B is a sectional view taken along a line I-I in FIG. 1, that is, a sectional view taken along a plane perpendicular to the axis of the hosel portion 15.

In this embodiment, the hosel portion 15 has a cylindrical shape. However, the hosel portion 15 may have another tubular shape such as an elliptic cylindrical shape. A concave portion 15a is formed in the toe-side outer surface of the hosel portion 15. In this embodiment, the concave portion 15a has a circular shape (spherical shape). However, it may have a polygonal shape. Since the concave portion 15a is provided, the separation position of an airflow at impact can be changed to the back side as compared to a case without the concave portion 15a, and the air resistance caused by the presence of the hosel portion 15 can be reduced. The concave portion 15a has a depth of, for example, 0.1 mm to 1 mm and a diameter of, for example, 1 mm to 10 mm. The concave portion 15a can be provided, in the outer surface of the hosel portion 15, at a position within the hosel diameter in the face-back direction with respect to the toe-side end where the airflow readily separates as the center. The toe-side end position is preferable, as in this embodiment. In this embodiment, only one concave portion 15a is provided. However, a plurality of concave portions may be provided. When providing a plurality of concave portions, the plurality of concave portions can be provided in a direction parallel to the axial direction of the hosel portion 15, in the face-back direction, or in both directions.

The turbulence-promoting portion 16 will be described with reference to FIG. 3A in addition to FIGS. 1 and 2A. FIG. 3A is a perspective view showing the section of the crown portion 12 taken along a line II-II in FIG. 2A.

The turbulence-promoting portion 16 generates small turbulence on the surface, and suppresses separation of an airflow flowing on the surface of the crown portion 12 from the surface of the crown portion 12. When the turbulence-promoting portion 16 is formed at a position where airflow separation from the crown portion 12 readily occurs, the position where airflow separation occurs can be moved to the back side. As a result, the air resistance can be reduced.

In FIGS. 1 and 2A, the turbulence-promoting portion 16 is indicated by a thick line so that its presence can easily be visually recognized for descriptive convenience. However, visual recognition of the actual turbulence-promoting portion 16 is impossible or difficult depending on its structure. Conversely, the turbulence-promoting portion 16 may have a visually emphasized structure.

The turbulence-promoting portion 16 extends from the heel side to the toe side and the back side. The length and the position or area of the turbulence-promoting portion 16 can appropriately be set. If the turbulence-promoting portion 16 is formed over a wide area, the manufacture of the golf club head 10 may become complicated, or the appearance may be spoiled. That is, the turbulence-promoting portion 16 is preferably provided in a portion effective for reducing the air resistance.

In this embodiment, the turbulence-promoting portion 16 extends in a line or band shape from the base of the hosel portion 15 to the toe-side edge of the crown portion 12, and crosses the crown portion 12 obliquely in the toe-heel direction. When the turbulence-promoting portion 16 crosses the crown portion 12 as in this embodiment, an airflow flowing on the surface of the crown portion 12 hardly separates throughout in the toe-heel direction.

In this embodiment, the turbulence-promoting portion 16 has an outer shape that bends a plurality of times. This is because the turbulence-promoting portion 16 is formed following the positions where the airflow separates from the crown portion 12. However, the outer shape of the turbulence-promoting portion 16 may be simplified to a linear shape or arcuate shape.

In a wood type golf club head having a general shape, airflow separation from the crown portion at impact tends to occur relatively from a face-side position on the heel side and from a back-side position on the toe side. That is, a line that connects the positions where the airflow separates obliquely crosses the crown portion 12.

The turbulence-promoting portion 16 may be formed such that an angle e between the toe-heel direction and a virtual line L1 that connects the heel end and the sole end becomes 5 degrees (inclusive) to 50 degrees (inclusive), depending on the shape of the golf club head, though. The turbulence-promoting portion 16 is thus located in a region where the airflow separates in a case without the turbulence-promoting portion 16, and the airflow separation position can easily be moved to the back side.

In a wood type golf club head having a general shape, airflow separation from the crown portion at impact tends to occur at a position across over the top of the crown portion. In this embodiment, the turbulence-promoting portion 16 passes the back side of a top 12a of the crown portion 12. Hence, the turbulence-promoting portion 16 is located in the region where the airflow separates in a case without the turbulence-promoting portion 16, and the airflow separation position can easily be moved to the back side. Note that the top 12a can be defined as the highest position of the crown portion 12 in a case where the golf club head 10 is grounded according to a predetermined lie angle and a predetermined loft angle.

The turbulence-promoting portion 16 according to this embodiment is formed by roughening the surface of the crown portion 12. Out of the crown portion 12, a region S1 on the side of the face portion 11 with respect to the turbulence-promoting portion 16 is smoother than the turbulence-promoting portion 16. The turbulence-promoting portion 16 is thus prevented from being formed over a wide area. In addition, since the region S1 of the crown portion 12 on the side of the face portion 11 readily comes into golfer's sight upon addressing, it may be possible to reduce strange feeling or improve the appearance by forming a smoother surface.

In this embodiment, out of the crown portion 12, a region S2 on the back side with respect to the turbulence-promoting portion 16 is also smoother than the turbulence-promoting portion 16. The turbulence-promoting portion 16 is thus prevented from being formed unnecessarily in a wide area. The surface roughness of the region S1 and that of the region S2 may be equal in design.

As shown in FIG. 3A, the turbulence-promoting portion 16 according to this embodiment is formed by forming a number of concave portions 16a in the surface of the crown portion 12. Each concave portion 16a has a circular shape but may have a square shape. A width W of the turbulence-promoting portion 16 in the face-back direction can make the formation region of the narrow turbulence-promoting portion 16 small. However, if the formation region is too narrow, the turbulence promoting effect may decrease. Hence, the width W is preferably 2 mm to 30 mm. The surface roughness of the turbulence-promoting portion 16 is preferably, for example, 2 μm (inclusive) to 30 μm (inclusive) as an arithmetic mean roughness Ra.

The turbulence-promoting portion 16 can also be formed by a method other than the concave portions 16a. For example, the turbulence-promoting portion 16 can be formed by a plurality of grooves. FIG. 3B shows an example. In the example of FIG. 3B, a plurality of grooves 16b extending in the extending direction of the turbulence-promoting portion 16 are formed. The turbulence-promoting portion 16 can also be formed by, for example, a plurality of linear convex portions or a number of point-like convex portions. FIG. 3C shows an example. In the example of FIG. 3C, a plurality of linear convex portions 16c extending in the extending direction of the turbulence-promoting portion 16 are formed.

Examples of the method of forming the turbulence-promoting portion 16 are casting, forging, laser machining, blasting, and milling.

The effect of reducing the air resistance of the hosel portion 15 by the turbulence-promoting portion 16 and the concave portion 15a will be described next with reference to FIGS. 4A and 4B. FIGS. 4A and 4B are views schematically showing an airflow acting on the golf club head 10 immediately before impact. FIG. 4A shows a case where the turbulence-promoting portion 16 and the concave portion 15a are absent as a comparative example. FIG. 4B shows this embodiment.

As shown in FIG. 4A, immediately before impact, the airflow to the golf club head 10 flows in the face-back direction. An airflow flowing on the surface of the crown portion 12 changes to a laminar flow on the side of the face portion 11 and separates halfway. In addition, an airflow flowing on the toe side of the hosel portion 15 separates near the toe-side end of the outer surface of the hosel portion 15. The earlier the airflow separates, the larger the air resistance to the golf club head 10 is.

In this embodiment shown in FIG. 4B, small turbulence is generated by the turbulence-promoting portion 16, airflow separation on the crown portion 12 delays, and the separation position shifts to the back side. Additionally, because of the presence of the concave portion 15a, separation of the airflow flowing on the toe side of the hosel portion 15 also delays, and the separation position shifts to the back side. As a result, the air resistance to the golf club head 10 can be reduced.

As a detailed example, a case where the turbulence-promoting portion 16 is formed by the plurality of grooves 16b, as shown in FIG. 3B, was simulated on a computer. Note that FIG. 3B shows the grooves 16b as easy to recognize, and their scale does not necessarily match the actual scale. Each groove 16b was a groove having a U-shaped section. The groove width was 0.2 mm, the groove depth was 0.02 mm, and the pitch between the grooves was 0.4 mm. The width W of the turbulence-promoting portion 16 was 12 mm, and the surface roughness of the turbulence-promoting portion 16 was 5 μm as the arithmetic mean roughness Ra. As a result, a model with the turbulence-promoting portion 16 exhibited improvement of the air resistance as compared to a model without the turbulence-promoting portion 16.

To minimize the area of the turbulence-promoting portion 16, the turbulence-promoting portion 16 is provided at the airflow separation position described with reference to FIG. 4A.

The position of the turbulence-promoting portion 16 can be determined by a simulation on a computer. That is, the airflow at impact is simulated for a prototype of a golf club head without the turbulence-promoting portion 16, and portions of the crown portion 12 where the airflow separates are specified. The turbulence-promoting portion 16 is then designed so as to follow and include the specified portions. A golf club head including the turbulence-promoting portion 16 is thus manufactured. This makes it possible to more easily reduce the air resistance to the golf club head without forming the turbulence-promoting portion 16 over a wide area.

Other Embodiments

In the above-described embodiment, only one turbulence-promoting portion 16 is provided. However, a plurality of turbulence-promoting portions 16 may be formed. FIG. 5 shows an example. In the example of FIG. 5, a turbulence-promoting portion 16A and a turbulence-promoting portion 16B that are spaced apart in the face-back direction are formed. Although two turbulence-promoting portions are formed here, three or more turbulence-promoting portions may be provided. However, the number is preferably two from the viewpoint of preventing the turbulence-promoting portions from unnecessarily increasing.

The turbulence-promoting portion 16A is the same as the above-described turbulence-promoting portion 16. The turbulence-promoting portion 16B can have the same structure as the above-described turbulence-promoting portion 16. However, the position is different, and the turbulence-promoting portion 16B is formed on the back side with respect to the turbulence-promoting portion 16A. If improvement of the separation position by the turbulence-promoting portion 16A is insufficient, the turbulence-promoting portion 16B can be provided at a portion where the airflow separates relatively early. When the turbulence-promoting portion 16B is provided, the airflow separation position on the crown portion 12 can further be shifted to the back side, and the air resistance can be reduced.

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. 2014-250300, filed Dec. 10, 2014 which is hereby incorporated by reference herein in its entirety.

GOLF CLUB HEAD

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