JP2001190715A - Wood club head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wood club head the bulge radius of which is set optimum to dial with a large head with a volume of 250 ml (cc) and over. SOLUTION: In a metal wood club head with a hollow core, which has a head volume of 250 ml (cc) and over, its bulge radius (mm) is set within the range of ±10% with the value obtained from the following formula as a center value. bulge radius = (-0.0237×ZG3+2.6721×ZG2-101.15ZG+1530)×(IY/0.157) In the above formula, ZG represents the depth of the center of gravity and IY the moment of inertia around Y-axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The head volume is 250 ml (c
c) The face shape of the wood club head having the metal hollow shell structure described above.

[0002]

2. Description of the Related Art The hitting surface of a wood club, that is, the surface of a face, has a uniform radius of curvature in the left-right direction from the toe to the heel and in the vertical direction from the leading edge at the lower end of the face to the top edge at the upper end of the face. Are formed. The former radius of curvature is called a bulge radius, and the latter radius of curvature is called a roll radius. The reason why the surface of the face is formed into a constant curved surface is
This is for controlling a gear effect when an off-center hit as described later is performed.

[0003] In particular, even when the ball is hit slightly off the center of the face to the toe or heel side, so-called off-center hit, the ball can fly straight in the target direction due to the bulge radius. For example, when the toe is hit off-center,
The effect of hook spin on the ball caused by the gear effect and the hitting ball bending to the left can be corrected by pushing the hitting ball to the right by tilting the face surface by the bulge radius and it can fly almost to the target direction. . In addition, when an off-center hit is made to the heel side, a slice spin occurs on the ball due to the gear effect and the hit ball curves to the right.The tilt of the face surface due to the bulge radius pushes the hit ball to the left. It can be corrected and fly almost in the direction of aim.

[0004] The effect of the roll radius is that when an off-center hit is made to the underside of the face, a back spin occurs on the ball due to the gear effect, and the ball is blown up too high. By hitting the ball slightly downward with the slope of the ball, the flight distance can be extended moderately by suppressing the ball, and if the ball is hit off center on the upper side of the face, the ball is slightly upward with the upward slope of the face surface By launching, the ball can be prevented from stalling and falling during flight due to overspin generated on the ball by the gear effect.

[0005]

The bulge radius is 10 inches (254 mm), which was empirically set in an era when the head material was persimmon (persimmon tree) and the head volume was as small as 200 ml (cc) or less. Values have long been followed within the golf industry. In addition, this 1
The setting of the value of 0 inches is based on the fact that the head material is made of wood and the volume is as small as 200 ml or less in the aforementioned era, so that the value of the moment of inertia, which is a head function closely related to the gear effect, and the center of gravity of the head It is presumed to be largely related to the depth value. Incidentally, the value of the moment of inertia in this era is 15 to 20 g · mm · sec ²
(0.147 to 0.196 μN · m · sec ² ), and the depth of the center of gravity is 25 to 32 mm.

[0006] However, recently, a new lightweight and high-strength material typified by a titanium alloy has been adopted as the head material, and the head volume has been increased to 250 to 350.
ml, the moment of inertia of the head is 30 g · mm · sec ² (0.
Since it has become larger than 3 μN · M · sec ² ), the bulge radius of 10 inches, which has been conventionally used for a long time, is not appropriate. Therefore, in view of the above situation, the object of the present invention is to achieve a volume of 250 m.
It is an object of the present invention to provide a wood club head having an optimum bulge radius corresponding to a large head of 1 (cc) or more.

[0007]

In order to achieve the above object, a wood club head according to the present invention has a head volume of 250 ml (c).
c) A wood club head having a hollow metal shell structure described above, wherein a bulge radius (mm), which is a radius of curvature that forms a curved surface extending from the toe of the face to the heel direction,
It is set in the range of ± 10% with the value obtained by the following equation as the center value. Bulge radius = (− 0.0237 × ZG ³ +2.6271)
× ZG ² −101.15ZG + 1530) × (IY /
0.157) Here, ZG represents the depth of the center of gravity and the unit is mm, and IY represents the moment of inertia around the Y axis defined below, and the unit is μN.
・ M · sec ²

In general, the gear effect means that when a ball hits the face surface of a golf club head out of the center and collides with the face of the golf club, slipping does not occur at a contact point between the two. It is explained by considering that the gear causes rotation so that the gear rotates. In other words, when hit off-center on the toe side, the head is rotated clockwise by the force of the collision (right-handed, the same applies hereinafter), and the frictional force of the contact point between the face and the ball causes the ball to rotate. , A counterclockwise spin is generated. As a result, the flight direction of the hit ball can be bent in a certain direction under the influence of the spin of the ball.

Thus, in a wood club, the face surface is formed to have a specific radius of curvature in response to a bend in the flight direction based on the gear effect when the face is decentered and hit. The flight direction (ballistic) of the hit ball
Corrections have been made.

Here, the magnitude of the gear effect is related to the ease of rotation of the head when hitting a ball. The ease of rotation of the head can be represented by the moment of inertia (I) of the head, as is well known. When the ball is hit with a force F at a distance r from the center of gravity of the head (see FIG. 3), an F × r moment acts on the head at the point of contact with the ball on the face surface. This moment causes the head to rotate clockwise at an angular velocity ω. When the magnitude of the moment of inertia of the head is represented by I and this is expressed by an equation, Iω = F × r, ie, ω = F × r / I,
(F and r are vectors).

Therefore, in the case of a small head, such as a persimmon head, which is entirely made of wood, the moment of inertia is small and the angular velocity ω of the head becomes large at the time of hitting, and the spin amount of the ball increases to produce a large gear effect. In the case of the large metal head described above, the moment of inertia is extremely large and the head is difficult to rotate. Therefore, the angular velocity ω is a small value, the spin amount of the ball is small, and the gear effect is small. For this reason, in a head having a large moment of inertia, if the bulge radius is as small as a Persimmon head, a hit ball struck largely off the target direction due to a steep inclination of the face surface when an off-center hit is performed The trajectory is not corrected sufficiently by the gear effect, resulting in a jump far from the target.

Based on such considerations, the present invention provides:
It is proposed that the bulge radius be set by the following equation which is obtained by multiplying the bulge radius of the proven persimmon head by a ratio of the moment of inertia around the Y axis based on the bulge radius of 10 inches. Bulge radius = (Bulge radius of persimmon head) × (Y
In other words, the magnitude of the bulge radius is corrected based on the magnitude of the moment of inertia of the head based on the above equation. In the present invention, as the value of the moment of inertia around the Y axis of the persimmon head, 0.157 μN · m · sec ² , which is the value of the standard persimmon head selected by the inventor, is used.

Further, in the present invention, the influence of the depth of the center of gravity of the head on the bulge radius was also studied. As shown in the table of FIG. 4, a persimmon head arbitrarily selected (tourney W55, manufactured by McGregor Co.)
With respect to the five types of wood clubs A to E in which only the depth of the center of gravity was changed at intervals of 5 mm from 20 mm to 40 mm, the ball was hit when the core was removed from the toe side of the face surface. The trajectory was examined by computer simulation, and the bulge radius for landing at the target point by trajectory correction was determined by trial and error. These values are listed in the table of FIG.

Next, the relationship between the value of the bulge radius and the depth of the center of gravity for each of the clubs A to E obtained in this manner is graphed as shown in FIG. It was found like a formula. Bulge radius = (− 0.0237 × ZG ³ +2.6271)
× ZG ² −101.15ZG + 1530)

After all, in the wood club head according to the present invention, the bulge radius of the wood club head according to the present invention is determined in consideration of both the moment of inertia around the Y axis of the head and the depth of the center of gravity. It is set by the equation described in item 1. However, the bulge radius calculated by the formula described in claim 1 is a center value of a preferable value proposed by the present invention, as described below.

In the golf industry since the days of the Persimmon head, the head shape was freely selected while the bulge radius was set to the same 10 inches (254 mm), and the inertia moment was ± 10%. Variations have been accepted for practical use. Therefore, also in the present invention, in setting the bulge radius, if a value within a range of ± 10% is used with the value obtained from the expression of claim 1 as a center value, the effect of the present invention is sufficiently practical. It can be regarded as a range that can be obtained.

In other words, the bulge radius is equal to the central value + 1.
When the value exceeds 0%, the bulge radius becomes too large, and it becomes difficult to correct the bending of the hit ball due to the gear effect on the face curved surface (that is, by the inclination of the face surface).
On the other hand, if the center value is less than -10%, the bulge radius becomes too small, the inclination of the face surface becomes large, and the launch direction of the off-center hit ball is set in the target direction (target flight direction). ) Significantly deviates from the reverse bend due to the gear effect, resulting in unintended trajectory and landing.

According to the results of analysis of many existing club heads by the inventor, the head volume has recently been increased to 250.
ml (cc) or more is the mainstream, and when the head volume increases, the depth of the center of gravity tends to increase proportionally.
c) Above, as long as the head shape is reasonable,
The depth of the center of gravity is generally 26 mm or more. Therefore, the formula for setting the bulge radius proposed by the present invention is applied to a metal head having a volume of 250 ml (cc) or more and a center of gravity depth of 26 mm or more. Is preferred.

In the present invention, the bulge radius (R)
When the head 1 is overlooked, the face surface 2
Is an arc (see FIG. 3) convex outwardly, and
As shown in FIG. 6, which is a cross-section of a head in a normal address posture taken along a plane parallel to one target direction, at each position of the face surface 2, the face surface at that position is determined. The radius has a center on a line perpendicular to 2. The inertia moment about the Y axis (IY) is, as shown in the sectional view of the head in FIG.
The moment of inertia is about an axis (Y-axis) parallel to the tangent to the face surface in (c) and passing through the center of gravity of the head. The depth of the center of gravity (ZG) of the head 1 is defined as a perpendicular (S) to the face surface 2 from the center of gravity (CG) of the head, and a center of gravity from the point where the perpendicular (S) intersects the face surface 2. (C
G) is the distance on the vertical line.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described with reference to FIGS. The table shown in FIG. 1 shows the dimensions of the wood club head of this embodiment. The wood club head of this embodiment has a volume of 270 ml.
This is a driver-club head having a hollow shell structure made of a titanium alloy (cc). As shown in FIG. 6, the depth of the center of gravity (ZG) of the head is defined by a cross section of the head cut along a plane which passes through the center of gravity (CG) of the head 1 in a normal address posture and is parallel to the target direction. A perpendicular (S) is made to the face surface 2 from the center of gravity (CG) of the head 1 and a distance on the perpendicular from the point where the perpendicular (S) intersects the face surface 2 to the center of gravity (CG) is 27. 6mm
Is set to

When the value of ZG (27.6 mm) is applied to the above “relational expression between bulge radius and depth of center of gravity”,
At this time, a bulge radius of 240 mm is required. next,
With the value of the bulge radius obtained in this way of 240 mm,
The above-described correction of the moment of inertia about the Y axis of the head is added. That is, in the head specification table shown in FIG. 1, the moment of inertia around the Y axis of the head of this embodiment is 0.274.
Therefore, this value is substituted into the term of the inertia moment about the Y axis (IY) in the equation of claim 1 to finally set the bulge radius of 460 mm in this embodiment.

The trajectory of the thus designed head of this embodiment was tested by a computer simulation. As a comparative example, the bulge radius is 2
A wood club head having an extremely small setting of 40 mm and all other head dimensions identical to those of the present embodiment was designed and tested at the same time. The test was performed at a head speed of 45 m / sec. The test was performed for a case where the ball was hit at a position 15 mm away from the face center on the face surface toward the toe side, and the trajectory trajectories of the head of the example and the head of the comparative example were compared.

FIG. 2 shows the trajectories of the two in the target direction (TT). As is apparent from the drawing, in the head of the present embodiment, the hit ball hit at the beginning rightward by the curved surface of 460 mm is returned to the left by hook spin based on the gear effect of the head, and is indicated by TT in the figure. -It is possible to land near the line in the get direction. On the other hand, in the case of the comparative example, the ball hit from a curved surface having a small radius of curvature of 240 mm jumps largely rightward and is not well controlled by the hook spin due to the gear effect of the head. Has landed on From these results, it was confirmed that the effect of the present invention was extremely remarkable.

[0024]

According to the present invention, the relationship between the bulge radius, the depth of the center of gravity of the head, and the moment of inertia is experimentally determined, and the bulge radius is set based on an equation that takes those influences into consideration. Therefore, an optimal bulge radius can be set for a large wood club head whose head volume is increased to 250 ml (cc) or more by adopting a high-strength and lightweight metal material. Therefore, the directionality of the hit ball of the large wood club head as described above can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a table showing dimensions of a head according to an embodiment.

FIG. 2 is a diagram illustrating test results (trajectory trajectories).

FIG. 3 is a diagram illustrating a relationship between a moment of inertia around a Y axis of a head and an angular velocity.

FIG. 4 is a table showing dimensions of a head in which the influence of the depth of the center of gravity is examined.

FIG. 5 is a diagram showing the relationship between the depth of the center of gravity and the bulge radius.

FIG. 6 is a diagram showing a cross section of a head.

[Explanation of symbols]

 1 head 2 face surface

Claims (2)

[Claims] 1. A wood club head having a metal hollow shell structure having a head volume of 250 ml (cc) or more, wherein a bulge radius is a radius of curvature forming a curved surface extending from a toe of a face to a heel direction. mm) is set in a range of ± 10% around a value obtained by the following equation as a center value. Bulge radius = (− 0.0237 × ZG ³ +2.6271)
× ZG ² −101.15ZG + 1530) × (IY /
0.157) Note that ZG represents the depth of the center of gravity and the unit is mm, and IY represents the moment of inertia about the Y axis passing through the center of gravity of the head and parallel to the face tangent at the face center, and the unit is μN · m ·.
and sec ^2. 2. The wood club head according to claim 1, wherein the depth of the center of gravity is 26 mm or more.