JPH08196665A - Golf club head - Google Patents

Abstract

PURPOSE: To increase moment of inertia, set the radius of a proper horizontal face bulge, and easily control the fall point of a ball by forming a through hole in the vertical direction including the center of gravity of a head, and setting the whole head into a circular shape. CONSTITUTION: A hosel section 5 is integrally molded on this metal head 1. A through hole 6 is formed in the direction of the vertical line Z including the center of gravity G of the head 1, and the whole head 1 is set into a circular shape. The moment of inertia around the vertical line Z of the head 1 is set to 3000gcm<2> or above, and the radius R of a horizontal face bulge is set to 400mm or above. The distance (d) (mm) from the center of gravity G to the center 2 of a face 3, the moment of inertia I (gcm<2> ), and the bulge radius R (mm) are set to the values satisfying the equation: R=(0.38.I+100)/(0.09.d+0.1).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a golf club head,
It is mainly related to metal wood.

[0002]

2. Description of the Related Art In recent years, many woods are made of metal and are hollow, and have a larger moment of inertia I around a vertical line including the center of gravity of the head than wood woods.
Therefore, it is easy to obtain a flight distance.

[0003]

However, the conventional hollow head has a limit in increasing the moment of inertia I. The reason will be described below.

In recent years, metal woods (heads) have been made of stainless steel and titanium alloys. A head made of these materials is generally manufactured by a precision casting method such as a lost wax method. However, it is difficult to form a thin portion by the precision casting method, and in particular, a titanium alloy is likely to have defects in the thin portion because the molten metal has a high viscosity. Therefore, in the case of a hollow integrally molded head with the hosel part integrally molded, the crown part (upper surface part) of the head
Is unnecessarily thick, the moment of inertia I cannot be made sufficiently large.

Therefore, a first object of the present invention is to provide a golf club head having a sufficiently large moment of inertia.

On the other hand, when the ball is hit at a position off the center of the face surface of the head, the ball is hit in a direction different from the intended direction and the ball is spun. These launching direction and spin differ depending on the value of the moment of inertia I. Therefore, when the moment of inertia I is simply increased, when the ball is hit at a position deviated from the center of the head, the launch direction of the ball in the horizontal direction and the spin of the ball change. Therefore, the drop point of the ball cannot be controlled simply by increasing the inertia moment I.

Therefore, a second object of the present invention is to set a proper horizontal face bulge radius for a head having a large moment of inertia to facilitate control of the ball drop point.

[0008]

In order to achieve the above-mentioned first object, the metal golf club head of the first invention is provided with a through hole extending vertically including the center of gravity of the head. , The whole is set in a ring. Also,
The golf club head of the second invention forms a ring-shaped head body by forming a through hole penetrating in the vertical direction including the center of gravity of the head, and has a specific gravity smaller than that of the head body, and
A closing plate made of a soft material is fixed or fixed to the head body, and at least one of the openings above and below the through hole of the head body is closed.

In these first and second inventions, the weight is distributed around the head, that is, at a position far from the center of gravity, so that the inertia moment I becomes large.

Next, the principle of increasing the velocity v of the hit ball when the moment of inertia I is increased will be described. When the face center 2 of the head 1 shown in FIG.
Since the head 1 rotates in the direction of the arrow ω, the inertia of the head 1 cannot be sufficiently transmitted to the ball 4. for that reason,
The hitting speed becomes smaller than that when hitting with the face center 2, and as a result, the flight distance becomes shorter.

There is generally a relationship of the following equation (1) between the reduction of the hitting speed and the moment of inertia I of the head 1. v = (1 + e) V / {(mL / I) +1+ (m / M)} (1) However, v: Velocity of the ball (ball) L: Distance from the normal line passing through the face center to the center point of the ball V : Velocity of the head in a horizontal plane before collision M: weight of the head m: weight of the ball e: coefficient of restitution of the ball Therefore, when the moment of inertia I is increased and the ball is hit with the face center 2 removed, It is possible to reduce the decrease in the speed.

By the way, when the ball is hit with the face center 2 removed, the rotation ω of the head 1 causes the direction of the face surface 3 to change, so that the ball hits the front as shown in FIG. 8B. 8a and 8c, a direction different from the intended direction (horizontal angle α
(Fig. 7)). At this time, the rotation ω of the head and the moment of inertia I have a relationship of the following equation (2). ω = (1 + e) V / {L + (I / m) + (I / M)} (2) According to the equation (2), when the inertia moment I is large,
Since the rotation ω of the head when the ball is hit with the center of the face removed is small, the direction of the hit ball is stable.

On the other hand, so-called side spin ω _B is generated on the ball 4 with the rotation of the head 1. for that reason,
The ball 4 flies along a curved line as shown in FIGS. 8 (a) and 8 (c). The face surface 3 of the head 1 has a convex shape with a constant radius of curvature so that the amount of the side spin ω _{B in} FIG. It is set on a curved surface, and its radius of curvature is called the radius of the horizontal face bulge (bulge radius R). Here, when the inertia moment I is set to a large value of 3,000 gcm ² or more, the rotation of the head 1 becomes smaller than that when the inertia moment I is small, so the ball launching direction α does not swing inward or outward by a large amount. Also, the side spin ω _B becomes smaller. Therefore, if the bulge radius R is set to a small value as in the conventional case, the possibility of miss shots increases.

Therefore, in the third invention, the moment of inertia I
Is set to 3,000 gcm ² or more, and the bulge radius R is set to
It is set to 400 mm or more. The moment of inertia I is preferably 3,200 gcm ² or more, and more preferably 3,400 gcm ^2.
Set to gcm ² or more.

In this way, by increasing the bulge radius R, the direction in which the ball 4 projects and the side spin ω
_Since it is balanced with the amount of _B , the possibility of miss shots can be reduced.

Next, a method for obtaining an appropriate bulge radius R will be described. The amount of the side spin ω _B differs depending on the depth of the center of gravity (distance from the face surface 3 to the center of gravity G of the head) d of the head 1 in FIG. 7 and the moment of inertia I. Therefore, an appropriate bulge radius R is set according to these values. There is a need to.

Maltby refers to "Golf Club Design, F
itting Alteration & Repair 2ndby Maltby: 1982
Chapter 36 (published in May, 2013) shows the relationship between the depth of center of gravity d and the appropriate bulge radius R as shown in equation (3) below. d = 0.074 + (1 / 1.63R) (3) However, the units of d and R are decimeter. However, this relational expression is a value considered for a solid wooden head, and the moment of inertia I is taken into consideration. Not not.
Therefore, it cannot be directly applied to a metal head having a larger moment of inertia I than a wooden head.
Therefore, an appropriate bulge radius R is obtained by taking the inertia moment I into consideration in the following procedure.

(I) The mechanism of the side spin ω _B is formulated in consideration of the moment of inertia I. (ii) Correct the above equation by experiment. (iii) The relationship between the launch angle α of the ball and the side spin ω _B is calculated from a theoretical formula by designing according to the formula showing the appropriate bulge radius R of Maltby. (iv) After substituting the necessary parameters into the theoretical equation,
A bulge radius R that obtains the relationship between the ball launch angle α and the spin ω _B obtained in ii) is obtained. The details of these steps (i) to (iv) will be described below.

(I) Formulation of Side Spin Mechanism A hit ball can be considered as a collision phenomenon between a head and a ball. According to the second and third laws of dynamics, the movements of the head 1 and the ball 4 before and after the hit ball of FIG. 2A have the following relationships. _{mv X = P n ... (11} ) mv Y = P t ... (12) I B ω B = P t r ... (13) M (V X -V XO) = - P n ... (14) M (V Y −V _YO ) = − P _t (15) I (ω−ω _O ) = − P _t b + P _n a (16) where subscripts X and Y: normal and tangential components P _t : ball the tangential direction of the impulse P _n applied to: impulse I of the normal direction applied to the ball _B: the moment of inertia of the ball ω _B: ball of the angular velocity (side spin) ω: head of the angular velocity r: the radius of the ball subscript O: Before collision (b, a): The collision point (contact point between the head and the ball) is the origin, the normal to the collision surface is the X axis, and the tangential direction to the collision surface is Y.
Coordinates of center of gravity G when axis is taken

Here, the relative velocity of the ball 4 to the head 1 at the collision point immediately after the collision is S = v _Y + rω, where S is the component in the tangential direction to the collision surface and C is the component in the normal direction to the collision surface. _B− (V _Y + bω) (17) C = v _X − (V _X −aω) (18)

On the other hand, assuming that there is no slip in the tangential direction Y on the collision surface and the normal direction X follows the coefficient of restitution e, S = 0 (19) C = e · V _XO (20) Equation (11) above By solving the relationship of equations (20) to (20), the relationship between the moment of inertia I of the head 1, the depth of the center of gravity d, the head speed V, etc. and the spin ω _B of the ball can be evaluated. Side spin ω
_B is represented by the following theoretical formula (21).

[0022]

[Equation 1]

Here, from the geometrical relationship such as the bulge radius R and the distance L in FIG. 2B, V _{XO and the} like in the equation (21) are as follows.
It is expressed as in equations (22) to (26). sinβ = L / (R + r) (22) -b = R- (R-d) cosβ (23) -a = (R-d) sinβ (24) V _XO = V cosβ (25) V _YO = −Vsin β (26) Further, the horizontal launch angle α and the angle β have the relationship of the following equation (27). v _Y / v _X = tan (α-β) (27)

Therefore, the depth of center of gravity d, the head weight M,
By setting the moment of inertia I of the head, the bulge radius R, the distance L, the coefficient of restitution e, and the speed V of the head, the speed v of the ball after hitting, the horizontal launch angle α, the side spin ω
_B etc. can be calculated.

(Ii) Correction of theoretical formula Since the above theory contains some assumptions, experiments are performed to make corrections. In the experiment, the ball was made to collide with the wall instead of the head, and the spin and the like at that time were measured. As a result, it was found that the experimental and theoretical calculations were in good agreement when the diameter of the ball was made slightly smaller. It is presumed that this is because the ball is flattened by the force at the time of collision, and the radius r of the ball in the formula is substantially reduced. Therefore, the radius r in the theoretical formula (2) is set to a value smaller than the actual radius of the ball.

(Iii) Ball launch angle α and spin ω
Calculation of the relationship with _{B Using the} depth of center of gravity d indicated by Maltby and the value of the head having an appropriate bulge radius R corresponding to it, the side spin ω _B and the launch angle α generated when the ball is hit with the head are calculated. It was calculated by a theoretical formula. When obtaining this relationship, Maltby does not show the moment of inertia I of the head, but since most golf club heads at that time were wooden (persimmon) heads, the value of the moment of inertia was calculated.
It was set to 1,800 gcm ² . FIG. 3 shows the calculation results of four types of heads having different depths of gravity d.

The horizontal launch angle α increases uniformly as the hitting point moves away from the center of the face (L increases), and at the same time, the side spin ω _B also uniformly increases, but the spin amount ω _B and the horizontal launch angle α are also increased. It can be seen that α has almost the same relationship among the four types of heads. That is, in the optimum bulge setting, the horizontal launch angle α and the spin number ω _B have a constant relationship, and the horizontal launch angle is 0 ° and the spin number is 0 rpm.
It has a linear relationship with a horizontal launch angle of 5 degrees and a spin rate of about 1,200 rpm.

(Iv) Ball launch angle α and spin ω _B
Calculation of bulge radius R satisfying the relation of ## EQU1 ## Next, the moment of inertia I and the like are substituted into the theoretical formula, and the bulge radius R satisfying the relation between the optimum horizontal launch angle α and spin ω _B of FIG. 3 is obtained. This bulge radius R is the optimum bulge for the head having the moment of inertia I etc. substituted into the theoretical formula. By repeating the same operation, the relationship diagram of the bulge radius R, the moment of inertia I, and the depth d of the center of gravity as shown in FIG. 4 can be obtained. By formulating this relational diagram, the following formula (30) is obtained. R = (0.38 · I + 100) / (0.09 · d + 0.1) (30) However, the unit is R: mm I: gcm ² d: mm. By setting the bulge radius R that satisfies the above expression (30), it becomes easy to control the falling point of the ball, and therefore, miss shots are reduced.

[0029]

An embodiment of the present invention will be described below with reference to the drawings. As shown in the perspective view of FIG. 1A, a metal head 1 made of aluminum or titanium alloy is integrally formed with a hosel portion 5. Center of gravity G of the head 1 in FIG.
1C, a through hole 6 is formed in the direction of the vertical line Z in FIG. 1C, and the entire head 1 is set in an annular shape. In this head 1, the moment of inertia I around the vertical line Z is set to 3,000 gcm ² or more, and the radius (bulge radius) R of the horizontal face bulge is set to 400 mm or more. Furthermore, the center of gravity G
It is preferable to set the distance d (mm) from the center 2 of the face 3 to the center 2 of the face surface 3, the moment of inertia I (gcm ² ) and the bulge radius R (mm) to values that generally satisfy the following expression (30). R = (0.38 ・ I + 100) / (0.09 ・ d + 0.1) (30)

Next, test examples and comparative examples will be shown. Test Example 1: When an annular head as shown in FIG. 1 was manufactured using aluminum, a head having an inertia moment I = 3,600 gcm ² was obtained. Test Example 2: A titanium alloy (6A14V titanium alloy) was used to fabricate an annular head having the same shape as in FIG.
A head having an inertia moment I = 4,000 gcm ² was obtained. Comparative Example 1: A hollow head (Fig. 7) was made of stainless steel, and the moment of inertia I was 2,400 gcm.
^Two heads were obtained. Comparative Example 2: A hollow head (FIG. 7) was manufactured using a titanium alloy (6A14V titanium alloy), and a head having an inertia moment I = 2,800 gcm ² was obtained.

It is understood that the weights of these heads are set to be equal to each other, so that the inertia moment I is larger in the annular head than in the hollow head.

Next, using the golf clubs equipped with the heads of the above-mentioned Test Examples 1 and 2 and Comparative Examples 1 and 2, the hitting speed when the ball was hit with the center 2 of the face 3 removed was investigated. The result is shown in FIG. In FIG. 5, the horizontal axis represents the distance L from the center of the face, and the vertical axis represents the hitting speed (initial velocity of the ball). As is clear from this figure, by increasing the moment of inertia I, the initial velocity of the ball is increased, so that the flight distance is extended.

Further, when the launch angle α when the hitting point deviates from the center of the face by 2 cm, the test examples 1 and 2 are shown.
In contrast, 1.2 degrees and 1.1 degrees, while Comparative Example 1,
At 2, it was 1.7 and 1.5 degrees. Therefore, it can be seen that by increasing the moment of inertia I, the launch angle α is reduced, so that the directionality of the hit ball is improved.

FIG. 6 shows a cross section of another embodiment. In FIG. 6, the golf club head 1 has a head body 10
And upper and lower closing plates 7 and 8. The head main body 10 is a molded product made of a titanium alloy or aluminum in which a through hole 6 penetrating in the vertical direction including the center of gravity of the head 1 is formed and has an annular shape. On the other hand, the upper and lower closing plates 7 and 8
Is a head body 10 such as rubber or resin.
It is made of a soft material having a smaller specific gravity than that of the head body 10 and is adhered to the head body 10 to close the openings 6a and 6b above and below the through hole 6 of the head body 10. In addition,
The closing plates 7 and 8 may be provided on only one of the upper side and the lower side, and it is preferable that the surface thereof is smoothly connected to the surface of the head body 10. Further, the closing plates 7 and 8 may be formed of a light and soft metal, and may be further fixed to the head body 10 with screws.

[0035]

As described above, according to the first or second aspect of the present invention, since the through hole is formed in the head and the entire head is annular, the moment of inertia of the head can be remarkably increased. Therefore, even when the sweet spot is removed, it is possible to obtain a golf club in which the flight distance is less reduced and the hitting ball has less swing in the launch direction. Further, since this head can be manufactured by the precision casting method using the lost wax method, there is no welded portion in the head, so that the head is easy to manufacture and there is no risk of cracks in the head.

According to the third aspect of the invention, the moment of inertia I is set to a large value of 3,000 gcm ² or more and the bulge radius R is set to 400 mm or more. Therefore, even when the sweet spot is removed, the hit ball is hit. Since the swing of the ball in the launch direction is small and the amount of side spin is small, it becomes easy to control the falling point of the ball.

[Brief description of drawings]

FIG. 1 is a perspective view, a plan view and a side view of a golf club head showing an embodiment of the present invention.

FIG. 2 is a plan view showing a mechanical relationship and a geometrical relationship between a head and a ball when hitting a ball.

FIG. 3 is a characteristic diagram showing the relationship between the horizontal launch angle and the spin number when the head has an appropriate bulge radius.

FIG. 4 is a characteristic diagram showing a relationship among appropriate bulge radius, moment of inertia and depth of center of gravity.

FIG. 5 is a characteristic diagram showing a relationship between a hitting position and a hitting speed.

FIG. 6 is a sectional view of a golf club head showing another embodiment.

FIG. 7 is a plan view showing a general head.

FIG. 8 is a schematic plan view showing a relationship between a hitting position and a trajectory of a ball.

[Explanation of symbols]

 1: Head 2: Center of face surface 3: Face 4: Ball 5: Hosel part 6: Through hole 7, 8: Closing plate 10: Head body d: Distance from center of gravity to center of face surface R: Bulge radius G: Center of gravity Z: Vertical line

Claims (5)

[Claims] 1. A head of a golf club in which a hosel portion is integrally formed, and a through hole penetrating in a vertical direction including a center of gravity of the head is formed in the head of the golf club. 2. A golf club head having a hosel part integrally formed, wherein a through hole penetrating in the vertical direction including the center of gravity of the head is formed to form an annular head body, and the specific gravity is smaller than that of the head body. A head of a golf club, in which a closing plate made of a soft material is fixed or fixed to the head body so that at least one of openings above or below the through hole of the head body is closed. 3. In a head of a metal golf club having a hosel portion integrally formed, a moment of inertia I about a vertical line including the center of gravity of the head.
Is set to 3,000 gcm ² or more and the radius R of the horizontal face bulge is set to 400 mm or more. 4. The moment of inertia I about a vertical line including the center of gravity of the head according to claim 1 or 2.
Is set to 3,000 gcm ² or more and the radius R of the horizontal face bulge is set to 400 mm or more. 5. The distance d (mm) from the center of gravity to the center of the face surface, the moment of inertia I (gcm ² ) and the radius R (mm) according to claim 3 or 4,
A golf club head set to a value according to the following equation (30). R = (0.38 ・ I + 100) / (0.09 ・ d + 0.1) (30)