JP2000051405A - Golf club head - Google Patents

Abstract

(57) [Summary] [Problem] To provide a golf club head having a hollow head having a large moment of inertia while maintaining a sufficient 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. To provide a golf club head having a small size and suitable for a driver or the like. SOLUTION: The hollow golf club head 1 is made of a material having a specific strength of 30 kg / mm ² or more.
The golf club head 1 having a weight of 200 g or less, a volume of 300 to 900 cc, and a minimum thickness of the face portion of 4 mm or more. The moment of inertia of the golf club head 1 is 4 ×
It is preferably at least 10 ⁻⁴ kg · m ² . Further, it is preferable to use a carbon fiber bidirectional reinforced epoxy resin or the like for the material having the specific strength of 30 kg / mm ² or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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 wood type golf clubs such as a driver, a spoon, and a buffy, flight distance and controllability 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 since the moment of inertia increases in conjunction with the volume of the golf club head, As for the club head of wood type golf clubs such as driver, spoon, buffy, etc., the hollow type made of metal material such as stainless steel, titanium alloy, aluminum high-strength alloy, etc. in order to increase the moment of inertia has become mainstream. And the head itself is becoming larger.

[0003] Certainly, such a head has a longer flight distance, a larger sweet spot, and a smaller bend of the hit ball than a solid head typified by the previous Persimmon head.

[0004]

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

[0005] 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 bending of the hit ball is extremely small, thereby resulting in a loss of flight distance. It is an object of the present invention to provide a golf club head which is small and suitable for a driver or the like.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a hollow golf club head made of a material having a specific strength of 30 kg / mm ² or more, wherein the weight of the head is 200 g or less, the volume is 300 to 900 cc, and Minimum thickness is 4mm
The above is solved by the golf club head.

The golf club head preferably has a moment of inertia of 4 × 10 ⁻⁴ kg · m ² or more. Further, it is preferable to use a carbon fiber bidirectional reinforced epoxy resin or the like for the material having the specific strength of 30 kg / mm ² or more.

[0008]

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

When the golf club hits a ball, the collision force between the head and the ball is represented by the following formula: collision force = head weight × head acceleration. On the other hand, the impact force corresponds to a change in momentum received by the ball during the impact time, and is represented by the following equation. Collision force = weight of ball x (initial velocity of ball x 2) / collision time ... (2)

The collision time between the ball and the head is actually measured to be 5 / 10,000 seconds by a method such as flash photography, and the weight of the ball is determined to be 46 g. Therefore, if the initial velocity of the ball is 50 m / sec, a load of 940 kg acts on the ball at the moment of impact.

By the way, since it has been clarified by measurement that the deformation of the club shaft at the time of impact of the ball is zero, at the time of impact, only the exchange of kinetic energy occurs between the ball and the head. It is estimated that a part of the kinetic energy of the head is moving to the ball.

Therefore, the flight distance of the ball is proportional to the kinetic energy of the head (ie, weight × speed ² ). That is, to increase 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 hitting surface of the head if these are increased unnecessarily.

The sweet spot here refers to a point at which a straight line passing through the center of gravity of the head intersects at right angles with the striking surface (face) of the head. 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 in the head about a vertical axis passing through its center of gravity, and the head rotates. This rotation torque is calculated by the following equation. Here, it is assumed that the user hits the sweet spot 3 cm left or right in the horizontal plane. Rotational torque = collision force × distance from the center of gravity to the strike point... (3) = 940 × 0.03 = 28.2 kg · m (3 ′) The rotational energy of the head is: rotational energy = inertia Moment x angular acceleration ... (4) Since the rotational energy and the rotational torque are balanced, the angular acceleration at the time of 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.
And Angular acceleration = 28.2 kg · m × 9.8 m ² / sec ² ÷ 2
× 10 −4 kg · m ² = 1.38 × 10 ⁶ rad / sec ^{2 When} this angular acceleration is multiplied by the collision time to obtain the rotation speed,
1.38 × 10 ⁶ × 0.0005 = 690 rad / se
c, and the rotation angle is represented by the following equation: rotation angle = angular acceleration × (collision time) ² ÷ 2 (5), and is calculated to be 9.9 degrees.

From the above calculations, if the ball is hit 3 cm away from the sweet spot of the head, the head will lose 5 cm.
It turns out that it rotates 9.9 degrees in / 10000 seconds.
For this reason, the launch angle of the ball is shifted leftward or rightward by the rotation of the head, and according to a simple calculation, 200
In the case of a flight distance of m, the vehicle is shifted leftward or rightward by about 30 m from the target point.

Further, since the rotational movement of the head consumes a part of the kinetic energy of the head to be transmitted to the ball, the flying distance of the ball is adversely affected. When calculating the decrease in the flight distance, the kinetic energy of the head is represented by weight × (head speed) ² ÷ 2, so that the head weight is 200 g and the head speed is 50 m /
If it is sec, it will be 250J. On the other hand, since the rotational energy of the head is represented by the moment of inertia × (rotational speed) ² ÷ 2, the moment of inertia is 2 × 10 ⁻⁴ kg · m.
^{2. If} the rotation speed is 690 rad / sec,
48J. That is, when the head rotates at the time of hitting the ball, about 20% of the kinetic energy of the head is lost, and 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 of 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 of FIG. 2 represents the decrease amount of the flight distance corresponding to the rate of kinetic energy loss. . The horizontal axes of the graphs in FIGS. 1 and 2 represent the moment of inertia of the head. In the graphs of FIGS. 1 and 2, the theoretical calculation is performed in the same manner as described above, with the head weight being 200 g, the head speed at the time of impact being 40 m / sec, and the deviation of the hit point of the ball from the sweet spot being 2 cm.

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

Here, the moment of inertia in the present invention means the center of gravity G when the sole 2 of the head 1 is placed on a horizontal plane as shown in FIG. , The moment about the vertical axis H passing through. In the drawing, reference numeral 3 is a face,
4 is a crown and 5 is 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 a hollow head, and this head 1 has a flat disk-shaped support base 6 having a known moment of inertia.
It is placed on. The support 6 is suspended from the base 8 by two wires 7, 7.

First, in this state, the support base 6 is twisted and then opened and freely rotated, and the period T at that time is measured. Then, from the period T measured here, the following equation (A)
To calculate the moment of inertia of the head.

(Equation 1)

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 decrease in 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, May become thin and may be destroyed by the impact of the impact. When a larger head having a moment of inertia of 4 × 10 ⁻⁴ kg · m ² is made of these metal materials, a portion such as a face portion having a thickness of 1 mm or less is formed, which may cause breakage when hit. Was confirmed experimentally.

The reason for this is that the specific strength (tensile strength (kg / mm ² ) / specific gravity) is reduced due to the large specific gravity of these metal materials. 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 about 3 × 10 ⁻⁴ kg · m ² for materials having such specific strength. Therefore, it is impossible to increase the size (volume) of the head of the metal material described above to increase the moment of inertia.

However, as can be seen from the graphs of FIGS. 1 and 2, in order for the amount of bending of the hit ball and the decrease in the flight distance to be within an allowable range, at least the moment of inertia of the head is 4 × 10 ⁻⁴ kg. M ² or more is desirable, and the volume of the head needs to be 300 cc or more to obtain the moment of inertia in this range. On the other hand, if the volume of the head is too large, the thickness of the face portion becomes thin, and the head may be damaged when hit. Specifically, in order to prevent the hollow head from being damaged at the time of hitting, the minimum thickness of the face portion is set to 4
mm or more, but this requires a specific strength of 3
Using a material of 0 kg / mm ² or more, the volume of the head is 90
As a result of earnest research, it has been found that it is necessary to reduce the pressure to 0 cc or less.

As a material having a specific strength of 30 kg / mm ² or more, reinforcing fibers such as carbon fiber, glass fiber, aramid fiber and polyester fiber 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 preferable as a reinforcing fiber in terms of strength and the like, and in particular, the use of a carbon fiber oriented in two orthogonal directions ensures impact resistance to all surfaces. It is preferable in that it can be performed. On the other hand, as the matrix resin, an epoxy resin is preferable in terms of strength and moldability. When a high elasticity and high density component such as tungsten powder is dispersed in the matrix resin, the vibration characteristics of the head can be improved and the sound when hit can be improved. In the case of a carbon fiber bidirectional reinforced epoxy resin using an orthogonal bidirectionally oriented carbon fiber as a reinforcing fiber and an epoxy resin as a matrix resin, the carbon fiber content is preferably in a range of 40 to 70% by volume. Is 35 to 60 kg / mm ² .

As the carbon fiber bidirectional reinforced epoxy resin, specifically, a prepreg in which an uncured epoxy resin is impregnated into a roving cloth, a plain weave cloth, or the like made of high elastic carbon fiber, for example, “Pyrofil TR31100-3”
40 "(manufactured by Mitsubishi Rayon Co., Ltd.) or the like.

In order to produce a head made of a carbon fiber bidirectional reinforced epoxy resin, for example, the prepreg is cut into a required shape, and a required number of pieces are laminated 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 pressurized air is injected into the bag at the same time, and the laminated prepreg is cured while being pressed against the mold.

The specific strength is 35 kg at a carbon fiber content of 40% by volume.
Creating a / mm hollow head volume 400cc with ² carbon fiber bidirectional 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 a sufficient breaking strength. Therefore, there is no danger of the head being broken by an impact at the time of impact.

It should be noted that, besides the carbon fiber bidirectional reinforced epoxy resin, the material having a specific strength of 30 kg / mm ² or more and usable for the head of the present invention is an expensive material, such as C / C composite. There is.

As described above, 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 one, and preferably has a value of the moment of inertia of 4 × 10 ^-4 kg · m ² or more. And Therefore, even when the ball is slightly deviated from the sweet spot on the face of the head and the ball is hit, the bend of the ball is extremely small, and a decrease in the flight distance due to the bend of the ball can be reduced. In addition, the specific strength is 30 kg / m
because of the use of m ² or more materials, increasing the moment of inertia can increase the thickness of the head, it is possible to prevent damage of the head due to the striking and the like. Particularly, in the face part which receives an impact, the minimum thickness of the face is set to 4 mm or more so that stress is not concentrated on a part of the face. be able to.

In the head of the present invention, a metal plate is disposed 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, and a balance weight or foam is provided inside the hollow. A body can also be provided.

[0033]

EXAMPLES "Pyrofil TR311" manufactured by Mitsubishi Rayon Co., Ltd. as a carbon fiber bidirectional reinforced epoxy resin prepreg.
0-340 "(carbon fiber content 40% by volume)
The prepreg was cut into a predetermined shape, and a required number of the prepregs were laminated on the inner surface of a two-piece female mold for molding. When assembling the molds together, a nylon tubular bag was disposed inside.

This female mold was placed in a heating furnace and the temperature was set to 130.
At the same time, the mixture was heated at a temperature of 1 ° C. for 1 hour, and simultaneously pressurized air with a pressure of 4 kg / cm ² G was injected into the nylon bag. After curing, the mold was cracked to obtain the target head. This head weighs 180 g, moment of inertia 6.0 × 10 ⁻⁴ kg · m ² ,
The volume was 700 cc, the minimum thickness of the face portion was 5 mm, and the loft angle was 13 degrees.

A golf club was obtained by attaching a carbon fiber two-way reinforced epoxy resin shaft to the head. This golf club was attached to a swing robot, and was not damaged even when it was repeatedly hit 1000 times at a head speed of 50 m / sec. Further, when this golf club was subjected to a field test by a swing robot at a head speed of 40 m / sec, it was confirmed that the ball was concentrated in a range of several meters at a landing point 200 m away from the tee shot point. Was.

[0036]

As described above, in the golf club head according to the present invention, since the bending of the hit ball is extremely small as compared with the conventional golf club, and the flight distance does not decrease, the golf club head does not fly well and does not bend. You can get a club. In addition, since the thickness of the face portion is sufficiently ensured, the club head is not damaged when hit.

[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 the relationship between the moment of inertia and the amount of decrease in flight distance.

FIG. 3 is an explanatory diagram for explaining the definition of the moment of inertia of the head according to the present invention.

FIG. 4 is a schematic configuration diagram showing an apparatus for measuring a moment of inertia in the present invention.

[Explanation of symbols]

 1 Head 2 Sole 3 Face 4 Crown 5 Neck 6 Support 7 Wire 8 Base

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takumi Ishimori 4-1-1 Ushikawa-dori, Toyohashi-shi, Aichi F-term in the Toyohashi Plant of Mitsubishi Rayon Co., Ltd. (reference) 2C002 AA02 CH01 CH06 MM02

Claims (3)

[Claims] 1. A hollow golf club head made of a material having a specific strength of 30 kg / mm ² or more, wherein the weight of the head is 200 g or less, the volume is 300 to 900 cc, and the minimum thickness of the face portion is 4 mm or more. Golf club head. 2. The head has a moment of inertia of 4 × 10 ^-4 k
^2. The golf club head according to claim 1, which has a g · m ² or more. 3. The golf club head according to claim 1, wherein the material is a carbon fiber bidirectional reinforced epoxy resin.