JP2000229135A - Golf club head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a golf club head ideal for drivers which achieves a smaller loss in flying range attributable to the curving of the ball by employing a hollow type head with a larger inertial moment to minimize the curving while maintaining a sufficient strength of the head of a golf club. SOLUTION: A hollow golf club head herein is 200 g or less in the weight of the head, 300-900 cc in volume and 4 mm or more in the minimum thickness of a face part and comprises a material with a specific strength of 30 kg/mm2 or more. In this case, at least one of a metal film and a metal fiber paper with or without open holes is laminated at a head surface layer part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a golf club head, and more particularly to a hollow wood type golf club head.

[0002]

2. Description of the Related Art In a golf club of a wood type such as a driver, a spoon, and a buffy, the flying distance and controllability (direction) of a ball are regarded as important. It is known that the flight distance and controllability of a ball are greatly affected by the moment of inertia about the center of gravity of the golf club head, and the moment of inertia increases in proportion to the volume of the golf club head. As for the club head of wood type golf clubs such as driver, spoon, buffy etc., in order to increase the moment of inertia, the mainstream type is a hollow type made of metal materials such as stainless steel, titanium alloy, aluminum high strength alloy etc. And
Also, the size of the head itself is increasing. In such a head, the flight distance is increased, the sweet spot is enlarged, and the bend of the hit ball is reduced as compared with a solid type head typified by a conventional Persimmon head.

[0003]

However, since the above-mentioned metal material has a large specific gravity, from the viewpoint of strength, it is limited to increase the volume of the hollow portion of the club head to increase the moment of inertia of the entire head. There is.

[0004] It is an object of the present invention to solve the above problems. That is, an object of the present invention is to provide a hollow type head having a larger moment of inertia while sufficiently maintaining the strength of a golf club head, so that the bend of a hit ball is extremely small, thereby resulting in a loss of flight distance. An object of the present invention is to provide a golf club head suitable for a driver or the like having a small size.

[0005]

SUMMARY OF THE INVENTION The present invention is a hollow golf club head having a head weight of 200 g or less, a volume of 300 to 900 cc, a minimum face thickness of 4 mm or more, and a specific strength of 30 kg. / Mm ² or more, and a golf club head in which at least one of a metal film having or not having openings and a metal fiber paper is laminated on a surface layer of the head.

The present invention also provides the golf club head, wherein the moment of inertia of the head is 4 × 10 ⁻⁴ kg · m ² or more.

Further, the present invention resides in the use of a carbon fiber woven fabric reinforced epoxy resin or the like as the material having a specific strength of 30 kg / mm ² or more in the above invention.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
First, the reason why by increasing the moment of inertia of a golf club head (hereinafter, simply referred to as "head"), the bending of a hit ball is reduced, and a reduction in flight distance due to this will be described.

When a golf club hits a golf ball (hereinafter, simply referred to as "ball"), the collision force between the head and the ball is expressed by the following equation (1).

## EQU1 ## Impact Force = Head Weight × Head Acceleration (1) On the other hand, this impact force corresponds to a change in the amount of momentum the ball receives during the impact time, and is expressed by the following equation (2).

## EQU2 ## Impact force = ball weight × (initial speed of ball × 2) ÷ collision time (2)

[0010] The collision time between the ball and the head when the golf club impacts the ball is actually measured to be 5 / 10,000 seconds by a method such as flash photography. on the other hand,
The weight of the ball is set at 46 g. Therefore,
If the initial velocity of the ball is 50 m / sec, a 940 kg load acts on the ball at the moment of impact.

Incidentally, it has been found by measurement that the deformation of the club shaft upon impact of the ball is zero. Therefore, at the time of impact, only kinetic energy is exchanged between the ball and the head, and it is assumed that a part of the kinetic energy of the head is transferred to the ball.

Therefore, the flight distance of the ball is determined by the kinetic energy of the head (ie, head weight × speed).
² ). That is, in order to extend the flight distance, one or both of the head weight and the head speed may be increased. However, there is a problem that it is practically difficult to catch the ball at the sweet spot on the striking surface of the head if these are increased unnecessarily.

The sweet spot here is a point at which a straight line passing through the center of gravity of the head intersects the head's striking surface (face) at right angles. If the ball does not hit the sweet spot of the head, the ball fluctuates in the ball flying direction. Assuming that the loft angle of the face is 0 degrees, the deflection of the ball in the flight direction in the horizontal plane is calculated as follows.

When the ball hits outside the sweet spot of the head, a rotational torque is generated around the vertical axis passing through the center of gravity of the head, and the head rotates. This rotation torque is calculated by the following equation. Here, it is assumed that the player hits the ball 3 cm left or right in the horizontal plane from the sweet spot.

[0015]

Rotational torque = collision force × distance from center of gravity to hitting point (3) = 940 × 0.03 = 28.2 kg · m (3 ′) Also, the rotational energy of the head is:

## EQU4 ## Rotational energy = moment of inertia × angular acceleration (4)

Since the rotational energy and the rotational torque are balanced, the angular acceleration during the rotation of the head can be obtained from the equations (3 ') and (4). Here, the moment of inertia of the head is set to 2 × 10 ⁻⁴ kg · m ² of a general head.

[Equation 5] Angular acceleration = 28.2 kg · m × 9.8 m / sec² ÷ 2 × 10^-4kg ・ m ² = 1.38 × 10 6 rad / sec²  When the rotational speed is obtained by multiplying the angular acceleration by the collision time,
1.38 × 10 6 × 0.0005 = 690 rad / se
c, and the rotation angle is represented by the following equation (5).
It is calculated as 9 degrees.

[Equation 6] Rotation angle = angular acceleration × (collision time) ² ÷ 2 (5)

From the above calculation, when the ball is hit 3 cm away from the sweet spot of the head, the head becomes 5 hits.
It turns out that it rotates 9.9 degrees in / 10000 seconds.
Therefore, the launch angle of the ball shifts to the left or right due to the rotation of the head, and according to a simple calculation, 200 m
In the case of the flight distance, the vehicle is shifted leftward or rightward by about 30 m from the target point.

Further, the rotational movement of the head is applied to the ball.
Consumes part of the kinetic energy of the head to be transmitted
The ball's flight distance.
You. When calculating the decrease in flight distance, the kinetic energy of the head
ー is weight x (head speed) ² Is represented by $ 2
With a head weight of 200g and a head speed of 50m /
If it is sec, it will be 250J. On the other hand, the head rotation
Energy is moment of inertia x (rotational speed)² $ 2
Therefore, the moment of inertia is 2 × 10^-4kg ・
m² And the rotation speed is 690 rad / sec.
It becomes 48J. In other words, the head rotated when hitting
Sometimes about 20% of the kinetic energy of the head is lost
As a result, the flight distance is shortened by about 20%.

When the above-mentioned theoretical calculation is performed by changing the moment of inertia of the head and the deviation of the ball from the target point and the decrease in the flight distance are obtained, the results shown in the graphs of FIGS. 1 and 2 are obtained. . The vertical axis in FIG. 1 represents the deviation of the ball (bending of the hit ball) from the target point in the case of a flight distance of 200 m, and the vertical axis in FIG. 2 represents the decrease in the flight distance corresponding to the rate of loss of kinetic energy. The horizontal axes of the graphs in FIGS. 1 and 2 represent the moment of inertia of the head. 1 and 2
In the graph, the theoretical calculation was performed in the same manner as described above, except that the head weight was 200 g, the head speed at impact was 40 m / sec, and the deviation of the ball hit point from the sweet spot was 2 cm.

From these graphs, it can be seen that by increasing the moment of inertia of the head, the bending of the ball is reduced even if the hit point of the ball slightly deviates from the sweet spot of the head, and the decrease in the flight distance due to this is also reduced. Understand.

FIG. 3 shows the moment of inertia in the present invention.
As shown in FIG. 5, when the sole 2 of the head 1 is placed so as to land on a horizontal plane, that is, when the head 1 is in a normal use position, the moment around the vertical axis H passing through the center of gravity G is referred to. In FIG. 3, reference numeral 3 denotes a face, 4 denotes a crown, and 5 denotes a neck.

The measurement of the moment of inertia is performed by a two-pending pendulum method using the apparatus shown in FIG. FIG.
In the figure, reference numeral 1 denotes a cross section of the head.
Is mounted on a support 6 having a flat disk-shaped moment of inertia. The support 6 is suspended from the base 8 by two wires 7, 7. First, in this state, the support base 6 is opened after being twisted and freely rotated,
The period T at that time is measured. Next, from the period T measured here, the moment of inertia Ig of the head is calculated by the following equation (6).

[0023]

(Equation 7) Ig: Moment of inertia of the head Ib: Moment of inertia of the support platform mg: Weight of the head mb: Weight of the support platform T: Period g: Gravitational acceleration a: ab in FIG. 4: bh in FIG. 4: h in FIG. In FIG. 4, a represents wires 7, 7 on the support base 6.
And b of the fixed distance of the wires 7 and 7 in the base 8
And h indicate the distance between the base 8 and the support 6.

As described in detail above, by increasing the moment of inertia of the head, the bending of the hit ball can be reduced and the flight distance can be reduced. To increase the moment of inertia of the head, the size of the head may be increased. However, if the weight of the head is unnecessarily increased when the size of the head is increased, a swing or the like becomes difficult. Therefore,
In practice, the upper limit of the head weight is 200 g. Therefore, in order to increase the size while keeping the weight of the head constant, it is necessary to make the structure of the head hollow and make the volume as large as possible.

However, for example, when the head weight is 200 g and the volume which is an index indicating the size of the head is 300 c.
c, When a large hollow head having a moment of inertia of 3 × 10 ⁻⁴ kg · m ² , which is another index indicating the size of the head, is made of a metal material such as stainless steel, a titanium alloy, or an aluminum high-strength alloy, The thickness of the head must be reduced, and as a result, the head may be broken by the impact at the time of hitting the ball. And the moment of inertia is 4 × 10 ⁻⁴ kg · m ²
It was confirmed by experiments that when a larger head was made of such a metal material as described above, a portion such as a face portion having a thickness of 1 mm or less was formed, which actually caused breakage when hitting a ball.

The reason for this is that these metal materials have a large specific gravity, so that the specific strength (tensile strength (kg / mm
² ) / specific gravity). Actually, the specific strength of these metal materials is 14 to 16 kg / mm ² , and the upper limit of the moment of inertia of the head is 3 × 10 ⁻⁴ kg · m ² for the material having such a specific strength. Therefore, it is difficult to increase the size (volume) of the head and increase the moment of inertia in the head made of the metal material.

However, as can be seen from the graphs of FIGS. 1 and 2, at least the moment of inertia of the head must be at least 4 × 10 ⁻⁴ kg so that the amount of bending of the hit ball and the decrease in the flight distance fall within an allowable range. · desirably m is ² or more, it is necessary to set the volume of the head to obtain the moment of inertia of this range above 300 cc.

On the other hand, if the volume of the head is increased, the thickness of the face portion must be reduced, and such a head may be damaged when hitting a ball. Specifically, to prevent the hollow head from being damaged when hitting a ball,
However, it has been found from studies that a material having a specific strength of 30 kg / mm ² or more and a head volume of 900 cc or less must be used for this purpose.

As a material having a specific strength of 30 kg / mm ² or more, reinforcing fibers such as carbon fibers, glass fibers, aramid fibers, and polyester fibers are impregnated with a matrix resin such as an epoxy resin, an unsaturated polyester resin, and a vinyl ester resin. Although there is a fiber reinforced plastic, carbon fiber is preferred as a reinforcing fiber in terms of strength, and in particular, when carbon fiber is oriented in two orthogonal directions, impact resistance can be secured on all surfaces. preferable. In addition,
High elasticity such as tungsten powder in the matrix resin,
By dispersing the high-density component, the vibration characteristics of the head can be improved, and the sound when hitting the ball can be improved.

In the case of a carbon fiber woven fabric reinforced epoxy resin using orthogonal bidirectionally oriented carbon fibers as the reinforcing fibers and an epoxy resin as the matrix resin, the carbon fiber content is preferably in the range of 40 to 70% by volume. Has a specific strength of 35 to 60 kg / mm ² . Specific examples of the carbon fiber reinforced epoxy resin include a prepreg obtained by impregnating an uncured epoxy resin into a roving cloth, a plain weave cloth, or the like made of a high elastic carbon fiber, for example, "Pyrofil (registered trademark)" manufactured by Mitsubishi Rayon Co., Ltd. TR3110-3
40 "or the like.

In order to produce a head made of carbon fiber reinforced epoxy resin, for example, the above-mentioned prepreg is cut into a required shape, and a required number of pieces are laminated in the orthogonal direction on the inner surface of a halving female mold for molding. . Next, a tube-shaped bag made of nylon or the like is arranged inside when the two-piece female mold is combined. Next, the mold is placed in a heating furnace, heated and simultaneously pressurized air is injected into the bag, and the laminated pre-leg is cured while being pressed against the mold.

The specific strength is 35 kg with the carbon fiber content of 40% by volume.
Creating a / mm hollow head volume 400cc with ² carbon fiber woven fabric-reinforced epoxy resin, the moment of inertia is imparted ^{4 × 10 -4 kg · m 2} , next, the moment of inertia of sufficient magnitude to head be able to. In this case, the thickness of the head is 3 m at the thinnest part.
m, the minimum thickness of the face portion is 6 mm, and the face portion can have sufficient breaking strength, and there is no fear of the head being broken by an impact at the time of hitting a ball.

It should be noted that, besides carbon fiber reinforced epoxy resin, the material having a specific strength of 30 kg / mm ² or more, and which can be used for the head of the present invention, is expensive, but may be a C / C composite or the like. There is.

The golf club head of the present invention has a head volume of 300 cc or more and has a higher moment of inertia than the conventional head, and preferably has a value of the moment of inertia of 4 × 10 ⁻⁴ kg · m ² or more. Therefore, even when the ball hits the ball slightly out of the sweet spot on the face of the head, the bending of the ball is small, and the decrease in the flight distance due to the bending of the ball can be reduced.

Further, since a material having a specific strength of 30 kg / mm ² or more is used, the thickness of the head can be increased even if the moment of inertia is increased, and the destruction of the head due to a hit ball or the like can be prevented. it can. In particular, in the face portion which receives an impact, by setting the minimum thickness of the face to 4 mm or more so that stress is not concentrated on a part of the face, the head is prevented from being broken by hitting the ball up to a volume of 900 cc. be able to.

In the head of the present invention, at least one of a metal film and a metal fiber paper is laminated on the head surface layer. This makes it possible to further improve the wear resistance and impact strength of the carbon fiber woven fabric reinforced epoxy resin constituting the head. At the same time, the head can also be provided with a design property. Materials for metal film and metal fiber paper include titanium, stainless steel, nickel, aluminum, brass,
Copper, iron, or the like can be used, and the thickness is 0.01 to 0.5.
A range of 5 mm is suitable.

The metal film and the metal fiber paper can be used in a state where glass fiber scrim cloth is laminated and integrated. As the metal film, there are a metal film having an opening and a metal film having no opening, and both can be used. The metal film having an opening includes a film opened by punching or the like, and a film opened by opening a slit and extending in a direction perpendicular to the slit, and both can be used. FIG. 5 (a)
Metallic fiber paper on the face of the head including the score line, metal film punched on the crown, FIG.
(B) shows a golf head in which a metal film having slit-stretched apertures is laminated on the sole portion. Since a metal film or a metal fiber paper having an aperture is rich in flexibility, it is easy to follow a curved surface or an uneven surface, and the degree of freedom in shape is increased.

In the head of the present invention, a metal plate is arranged on the sole to lower the position of the center of gravity, a back metal is attached to move the position of the center of gravity backward, a balance weight or foam is provided inside the hollow. A body can also be provided.

[0039]

Next, the present invention will be further described with reference to examples. "Pyrofil (registered trademark) TR3" manufactured by Mitsubishi Rayon Co., Ltd. as a carbon fiber woven fabric reinforced epoxy resin prepreg.
110-340 "(carbon fiber content: 40% by volume), this prepreg is cut into a predetermined shape, and the required number of pieces are laminated on the inner surface of a halving female mold at right angles in two directions. When the film was arranged on the outermost layer and this mold was assembled and assembled, a nylon tubular bag was arranged inside.

The titanium film, as shown in FIG.
Slit 11- at regular intervals on titanium film 11
6 and perpendicular to the slit 11-1 (FIG. 6).
An arrow is shown in FIG. Metallic hybrid prepreg (Nippon Steel Corporation) in which a prepreg obtained by impregnating a glass fiber scrim cloth with a 130 ° C.-curable epoxy resin on both sides of a titanium expanded metal having openings 11-2 formed by stretching in the direction MX0100 / 00 manufactured by Chemical Co., Ltd.
1 / 1120-K03 / R10 / K03 (trade name)) was used.

The female mold was placed in a heating furnace and the temperature was set to 130.
While heating at a temperature of 1 ° C. for 1 hour, pressurized air at a pressure of 4 kg / cm ² G was injected into the nylon bag at the same time. After curing,
The target head was obtained by breaking the mold. This head uses a carbon fiber woven fabric reinforced epoxy resin having a specific strength of 60 kg / m.
m ² × weight 180 g, moment of inertia 6.0 × 10 ^-4
kg · m ² , volume 700 cc, minimum face thickness 5 mm, and loft angle 13 °.

A golf club was formed by attaching a carbon fiber woven fabric reinforced epoxy resin shaft to the head. The golf club was attached to a swing robot, and the head speed was set at 50 m / sec, and the ball was not hit even when hit repeatedly 1,000 times. When the golf club was set to a head speed of 40 m / sec and subjected to a field test by a swing robot, the ball was concentrated in a range of several meters at a landing point 200 m away from the tee shot point. Was confirmed.
Since the entire surface of the golf club head was covered with the titanium film, the abrasion of the face portion and the sole portion could be prevented from expanding. Also, the titanium sole was excellent in design because of the slit aperture film.

[0043]

As described above, the golf club head of the present invention has a very small bending of the ball when hit with a ball as compared with a conventional golf club head, and therefore does not have a decrease in flight distance. A golf club which does not fly and bend can be obtained. In addition, since the thickness of the face portion is sufficiently ensured, the club head is not damaged at the time of hitting, and the metal film or / and the metal fiber paper are arranged on the surface, so that the abrasion resistance is improved. or,
Also excellent in design.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the moment of inertia and the bending of a hit ball.

FIG. 2 is a graph showing a relationship between a moment of inertia and a decrease in a flight distance.

FIG. 3 is an explanatory diagram for explaining a definition of a moment of inertia.

FIG. 4 is a schematic configuration diagram illustrating a measuring device of a moment of inertia.

FIG. 5 is an external perspective view showing a golf head in which a metal film and a metal fiber paper are laminated.

FIG. 6 is an explanatory view showing a method of manufacturing a metal film having slits and apertures.

[Description of Signs] 1 Head 2 Sole 3 Face 4 Crown 5 Neck 6 Support base 7 Wire 8 Base 9 Metal fiber paper 10 Metal film with punched hole 11 Metal film with slit stretched hole G Head center of gravity H Vertical axis

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takumi Ishimori 4-1-1 Ushikawa-dori, Toyohashi-shi, Aichi F-term (reference) at Mitsubishi Rayon Co., Ltd. Toyohashi Office 2C002 AA02 CH06 LL01 MM02 MM04 MM07

Claims (3)

[Claims] 1. A hollow golf club head having a weight of 200 g or less and a volume of 300 to 900 c.
c, the minimum thickness of the face part is 4 mm or more, and the specific strength is 3
A golf club head made of a material of 0 kg / mm ² or more and having at least one of a metal film having or not having openings and a metal fiber paper laminated on a surface layer of the head. 2. The head has a moment of inertia of 4 × 10 ^−4.
The golf club head according to claim 1, wherein the weight is not less than kg · m ² . 3. The golf club head according to claim 1, wherein the material is a carbon fiber woven fabric reinforced epoxy resin.