Patent Grant
10729944
This application claims a priority to Japanese Patent Application No. 2014-142866 filed on Jul. 11, 2014, which is hereby incorporated by reference in its entirety.
The present invention relates to a wood golf club head.
Various design targets are set when designing wood golf club heads. For example, JP 2010-99408A (hereinafter, called Patent Literature 1) discloses a wood golf club in which the vertical moment of inertia of the head can be increased while maintaining a low sweet spot height. More specifically, in Patent Literature 1, an oblong shape is circumscribed around a projected image of the head that is projected on a reference surface in the state in which the sole portion is placed on the reference surface with a given lie angle, and the oblong shape is divided into 3×3 equal oblong regions. Weight is distributed in the sole portion in units of the oblong regions. More specifically, the head is designed such that the weight in the oblong region in the center on the face side and the oblong region in the center on the back side is greater than the weight in the oblong region in the center on the toe side and the oblong region in the center on the heel side.
Normally, a design target value for the total weight of the golf club head is determined in advance, and in many cases, there is a limit on the surplus weight that can be distributed for increasing the moment of inertia of the head. For this reason, if weight is simply distributed in units of 3×3 oblong regions as in Patent Literature 1, it is quite conceivable to not be able to obtain a sufficient moment of inertia for the head with limited surplus weight.
An object of the present invention is to provide a wood golf club head having a large moment of inertia for the head.
A wood golf club head according to a first aspect of the present invention includes a hollow structure body having a face surface for hitting a ball. The hollow structure body has an inner surface and a thick portion in a predetermined region on the inner surface excluding a rear surface of the face surface. The thick portion is located outward of a virtual curved surface and has an outer surface extending along the virtual curved surface. The virtual curved surface is (a) a curved surface centered about a predetermined reference point located inside the hollow structure body or (b) a curved surface having a central axis that is a straight line passing through a reference point located inside the hollow structure body.
A wood golf club head according to a second aspect of the present invention is the golf club head according to the first aspect, wherein the virtual curved surface is a curved surface that extends along an outer surface of a virtual sphere or ellipsoid centered about the reference point, or a virtual cylinder, elliptical cylinder, cone, or elliptical cone having a central axis that is a straight line passing through the reference point.
A wood golf club head according to a third aspect of the present invention is the golf club head according to the first aspect or the second aspect, wherein the reference point is a point located in a range of 25.0 mm from a center of gravity of the golf club head.
A wood golf club head according to a fourth aspect of the present invention is the golf club head according to the third aspect, wherein the reference point is a point located in a range of 10.0 mm from the center of gravity.
A wood golf club head according to a fifth aspect of the present invention is the golf club head according to the fourth aspect, wherein the reference point is a point located in a range of 5.0 mm from the center of gravity.
A wood golf club head according to a sixth aspect of the present invention is the golf club head according to the fifth aspect, wherein the reference point is a point located in a range of 2.0 mm from the center of gravity.
A wood golf club head according to a seventh aspect of the present invention is the golf club head according to any of the first to sixth aspects, wherein the hollow structure body has a crown portion, a sole portion, and a side portion. The thick portion is provided on the sole portion.
A wood golf club head according to an eighth aspect of the present invention is the golf club head according to any of the first to seventh aspects, wherein the thick portion is located on a back side relative to a depth plane that is perpendicular to a horizontal plane, includes a center of gravity of the golf club head, and extends in a toe-heel direction.
A wood golf club head according to a ninth aspect of the present invention is the golf club head according to any of the first to eighth aspects, wherein the thick portion further has an outer surface that extends along the depth plane.
A wood golf club head according to a tenth aspect of the present invention is the golf club head according to any of the first to ninth aspects, wherein the thick portion is provided at at least a position on a toe side of the inner surface of the hollow structure body.
A wood golf club head according to an eleventh aspect of the present invention is the golf club head according to any of the first to tenth aspects, wherein the virtual curved surface is (a) a curved surface centered about a predetermined reference point located inside the hollow structure body.
A wood golf club head according to a twelfth aspect of the present invention is the golf club head according to any of the first to tenth aspects, wherein the virtual curved surface is (b) a curved surface having a central axis that is a straight line passing through a reference point located inside the hollow structure body.
According to the first aspect, the thick portion on the inner side (inner surface) of the hollow structure body of the golf club head is located outward of a virtual curved surface centered about a predetermined reference point in the hollow structure body or having a central axis that is a straight line passing through the reference point, and has an outer surface that extends along the virtual curved surface. As a result, a golf club head is provided in which weight is distributed in a balanced manner at positions distant from the predetermined reference point in the hollow structure body. Accordingly, weight can be distributed appropriately, and the moment of inertia of the head can be increased.
Wood golf club heads according to several embodiments of the present invention will be described below with reference to the drawings.
Before describing several embodiments of the present invention, the following describes the process that led the inventor of the present invention to arrive at the following embodiments.
Through careful examination carried out by the inventor of the present invention, it was found that in the design of a thick portion arranged inside a golf club head having a hollow structure (note: arranged in a region excluding the rear surface of the face surface), in order to increase the moment of inertia of the head, it is sufficient to omit the formation of a thick portion inward of a virtual curved surface centered about the center of gravity, and form a thick portion outward of this virtual curved surface. Distributing the weight in this way makes it possible to skew the weight obtained by the thick portion to a position separated as far as possible from the center of gravity. In other words, an increase in the moment of inertia of the head is achieved by concentrating the weight at a position distant from the center of gravity.
Note that simply from the viewpoint of increasing the moment of inertia of the head, it is desirable that a point serving as a reference for defining the center or the central axis of the virtual curved surface (hereinafter, called a reference point M) exactly matches the center of gravity. Of course, in reality, there are various design-related constraints in the design of the head (including the shape, weight, center of gravity position, appearance, and the like). Accordingly, although somewhat of a deviation of the reference point M from the center of gravity is envisioned, similar effects can be expected as long as the reference point M is located in the vicinity of the center of gravity.
The face portion 1 has a face surface for hitting a ball, and constitutes the front portion of the head 100. The face surface is approximately flat. The crown portion 2 is adjacent to the face portion 1, and constitutes the upper surface of the head 100. The sole portion 3 constitutes the bottom surface of the head 100, and is adjacent to the face portion 1 and the side portion 4. Also, the side portion 4 is the portion between the crown portion 2 and the sole portion 3, and is the portion that extends from the toe side of the face portion 1, across the back side of the head 100, and to the heel side of the face portion 1. Furthermore, the hosel portion 5 is the portion provided adjacent to the heel side of the crown portion 2, and has an insertion hole 51 for the insertion of the shaft (not shown) of the golf club.
The following describes the aforementioned reference state. As shown in
In the present embodiment, the boundary between the crown portion 2 and the side portion 4 can be defined as follows. Specifically, if a ridge line is formed between the crown portion 2 and the side portion 4, that ridge line serves as the boundary. On the other hand, if a clear ridge line is not formed, the boundary is the outline that is seen when the head 100 is placed in the reference state and viewed from directly above a center of gravity G of the head 100. The same follows in the case of the boundary between the sole portion 3 and the side portion 4 as well, and if a ridge line is formed, that ridge line serves as the boundary. On the other hand, if a clear ridge line is not formed, the boundary is the outline that is seen when the head 100 is placed in the reference state and viewed from directly below the center of gravity G of the head 100.
The volume of the head 100 is, for example, preferably 300 cm3 or more, more preferably 400 cm3 or more, and particularly preferably 420 cm3 or more. The head 100 having such a volume is useful in increasing comfort when the club is held and also increasing the sweet spot area and the moment of inertia of the head. Note that although an upper limit is not particularly defined for the volume of the head 100, practically it is, for example, desirably 500 cm3 or less, or desirably 470 cm3 or less when complying with R&A or USGA rules and regulations.
The head 100 can be formed from a titanium alloy having a specific gravity of approximately 4.0 to 5.0, for example. Besides a titanium alloy, the head can be formed from one or two or more materials selected from among stainless steel, maraging steel, an aluminum alloy, a magnesium alloy, an amorphous alloy, and the like. Also, there is no limit to being a metal material, and the head can also be formed using a fiber-reinforced plastic or the like.
The head 100 of the present embodiment is constituted by assembling the face portion 1 to a head body 6 having the crown portion 2, the sole portion 3, the side portion 4, and the hosel portion 5. The head body 6 and the face portion 1 are joined to each other by welding or the like. The head body 6 is a hollow structure that has the crown portion 2, the sole portion 3, and the side portion 4 as outer walls and has an opening on the face portion 1 side, and the face portion 1 is attached so as to block this opening. The head body 6 and the face portion 1 that are described above can be manufactured using various methods. For example, the head body 6 can be manufactured by casting using a known lost-wax precision casting method or the like. Also, the face portion 1 can be manufactured using a forging method, for example. The structure of the face portion 1 will be described in detail below.
The following describes the thick-wall structure in the head body 6 with reference to
Specifically, in the present embodiment, a thick portion 10 is formed on the sole portion 3 in the head body 6, as shown in
Note that a sweet spot SS is shown in
In the present embodiment, the thick portion 10 has a constant height h1, and an upper surface 10b of the thick portion 10 that defines the height h1 is flat. In other words, the thick portion 10 has the upper surface 10b (outer surface) that is located on the sole side of a base plane P1 (see
Here, for the sake of convenience in the description, a depth plane P2 is defined as the plane that includes the center of gravity G, extends in the toe-heel direction, and is perpendicular to the plane H (see
The reference point M that determines the position of the aforementioned virtual cylinder V1 is preferably located in a range of 25.0 mm from the center of gravity G, and more preferably is located in a range of 10.0 mm from the center of gravity G. Also, the reference point M is more preferably located in a range of 7.0 mm from the center of gravity G, further preferably located in a range of 5.0 mm from the center of gravity G, further preferably located in a range of 2.0 mm from the center of gravity G, further preferably located in a range of 1.0 mm from the center of gravity G, and further preferably located in a range of 0.5 mm from the center of gravity G. In particular, the deviation between the reference point M and the center of gravity G in the face-back direction is preferably 2.0 mm or less, and more preferably 1.0 mm or less. The smaller the distance between the reference point M and the center of gravity G is, the more uniformly the thick portion 10, which is arranged centered about the reference point M, is arranged around the center of gravity G, and the greater the expected increase in the horizontal moment of inertia is.
As described above, in the present embodiment, the thick portion 10 on the inner side of the head body 6 is configured to be located outward of the virtual cylinder V1 and have an outer surface that extends along the virtual cylinder V1. As a result, the weight is distributed in a balanced manner at positions distant from the central axis L1 that passes through the reference point M in the vicinity of the center of gravity G and extends in the vertical direction, and it is possible to increase the horizontal moment of inertia of the head 100.
A golf club head 200 according to a second embodiment will be described below with reference to
Specifically, in the second embodiment as well, a thick portion 20 is formed on the sole portion 3 in the head body 6, as shown in
In the second embodiment as well, an upper surface 20b of the thick portion 20 is flat. Note that a height h2 thereof is not constant, and the thick portion 20 of the present embodiment has the upper surface 20b (outer surface) that is located on the sole side of a base plane P3 (see
The reference point M that serves as the center of the aforementioned virtual sphere V2 is preferably located in a range of 25.0 mm from the center of gravity G, and more preferably is located in a range of 10.0 mm from the center of gravity G. Also, the reference point M is more preferably located in a range of 7.0 mm from the center of gravity G, further preferably located in a range of 5.0 mm from the center of gravity G, further preferably located in a range of 2.0 mm from the center of gravity G, further preferably located in a range of 1.0 mm from the center of gravity G, and further preferably located in a range of 0.5 mm from the center of gravity G. In particular, the deviation between the reference point M and the center of gravity G in the top-sole direction is preferably 2.0 mm or less, and more preferably 1.0 mm or less. Also, the deviation between the reference point M and the center of gravity G in the face-back direction is preferably 2.0 mm or less, and more preferably 1.0 mm or less. The smaller the distance between the reference point M and the center of gravity G is, the more uniformly the thick portion 20, which is arranged centered about the reference point M, is arranged around the center of gravity G, and the greater the expected increase in the moment of inertia in various directions around the center of gravity G is.
As described above, in the present embodiment, the thick portion 20 on the inner side of the head body 6 is configured to be located outward of the virtual sphere V2 and have an outer surface that extends along the virtual sphere V2. As a result, the weight is distributed in a balanced manner at positions distant from the reference point M in the vicinity of the center of gravity G, and it is possible to increase the moment of inertia in various directions around the center of gravity G.
A golf club head 300 according to a third embodiment will be described below with reference to
Specifically, in the third embodiment as well, a thick portion 30 is formed on the sole portion 3 in the head body 6, as shown in
Since it is desirable to design the reference point M that determines the position of the aforementioned virtual cylinder V3 so as to match the center of gravity G, the reference point M is preferably located in a range of 2.0 mm from the center of gravity G, preferably located in a range of 1.0 mm from the center of gravity G, and more preferably located in a range of 0.5 mm from the center of gravity G. In particular, the deviation between the reference point M and the center of gravity G in the top-sole direction is preferably 1.0 mm or less. The smaller the distance between the reference point M and the center of gravity G is, the more uniformly the thick portion 30, which is arranged centered about the reference point M, is arranged around the center of gravity G, and the greater the expected increase in the vertical moment of inertia is.
As described above, in the present embodiment, the thick portion 30 on the inner side of the head body 6 is configured to be located outward of the virtual cylinder V3 and have an outer surface that extends along the virtual cylinder V3. As a result, the weight is distributed in a balanced manner at positions distant from the central axis L3 that passes through the reference point M in the vicinity of the center of gravity G and extends in the horizontal direction, and it is possible to increase the vertical moment of inertia of the head 300.
A golf club head 400 according to a fourth embodiment will be described below with reference to
Specifically, in the fourth embodiment as well, a thick portion 40 is formed on the sole portion 3 in the head body 6, as shown in
The reference point M that determines the position of the aforementioned virtual cone V4 is preferably located in a range of 25.0 mm from the center of gravity G, and more preferably is located in a range of 10.0 mm from the center of gravity G. Also, the reference point M is more preferably located in a range of 7.0 mm from the center of gravity G, further preferably located in a range of 5.0 mm from the center of gravity G, further preferably located in a range of 2.0 mm from the center of gravity G, further preferably located in a range of 1.0 mm from the center of gravity G, and further preferably located in a range of 0.5 mm from the center of gravity G. In particular, the deviation between the reference point M and the center of gravity G in the face-back direction is preferably 2.0 mm or less, and more preferably 1.0 mm or less. The smaller the distance between the reference point M and the center of gravity G is, the more uniformly the thick portion 40, which is arranged centered about the reference point M, is arranged around the center of gravity G, and the greater the expected increase in the horizontal moment of inertia is.
As described above, in the present embodiment, the thick portion 40 on the inner side of the head body 6 is configured to be located outward of the virtual cone V4 and have an outer surface that extends along the virtual cone V4. As a result, the weight is distributed in a balanced manner at positions distant from the central axis L4 that passes through the reference point M in the vicinity of the center of gravity G and extends in the vertical direction, and it is possible to increase the horizontal moment of inertia of the head 400.
Although embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications can be made without departing from the gist of the invention. The following are examples of modifications that can be made. Any combination of the features of the following variations can be used as appropriate.
6-1
In the above embodiments, the virtual curved surface for determining the arrangement of the thick portions 10 to 40 is a curved surface that extends along the outer surface of a cylinder, a sphere, or a cone, but it may be a curved surface that extends along the outer surface of an ellipsoid, an elliptical cylinder, or an elliptical cone. In this case, the ellipticity of the ellipsoid, and the bottom surfaces of the elliptical cylinder and the elliptical cone can be set appropriately so as to obtain a desired moment of inertia for the head, but the ratio of the long side to the short side is preferably 2 or less, more preferably 1.5 or less, further preferably 1.3 or less, further preferably 1.2 or less, and further preferably 1.1 or less. Also, the virtual curved surface can be another curved surface that defines a recessed curved surface that is recessed toward the reference point M. In this case, the above-described preferable value ranges in the case of the ellipsoid and the like can be applied to the extent of the ellipticity of the recessed curved surface as well. Note that the distance between the reference point M and the point on the recessed curved surface farthest from the reference point M is considered to be the long side, and the distance between the reference point M and the point on the recessed curved surface closest to the reference point M is considered to be the short side.
6-2
The thick portions 10 to 40 are not limited to be formed on the sole portion 3, and can be formed at any position on an inner wall surface of the hollow structure body of the head 100, excluding the rear surface of the face surface. Accordingly, instead of or in addition to the inner wall surface of the sole portion 3, a thick portion having an outer surface that extends along a virtual curved surface can also be formed on an inner wall surface of the crown portion 2, the side portion 4, or the like.
6-3
The axis of the virtual cylinder or the virtual cone for defining the virtual curved surface is not limited to extending along the vertical direction or the horizontal direction, and can be set to any direction in which the moment of inertia of the head is to be increased.
The following describes a working example of the present invention. Note that the present invention is not limited to the following working example.
Here, the golf club head shown in
The following table shows the horizontal moment of inertia around the center of gravity G in the above-described working example and comparative example, and it was confirmed that the horizontal moment of inertia is increased in the working example. Also, it was confirmed that in the working example, the smaller the distance between the center of gravity G and the reference point M is, the greater the increase in the horizontal moment of inertia is.
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