JPH0533071B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a ball hitting tool for sports. [Prior Art and its Problems] Generally speaking, using a golf club as an example of a ball hitting tool, the action of a golf club for hitting a golf ball can be summarized as follows. In other words, influence on trajectory...effect on spin, launch angle, and directionality; effect on ball initial velocity...effect on head speed; influence on coefficient of repulsion; of these, regarding spin, launch angle, and directionality, It is explained mechanically, focusing on the moment of inertia around the center of gravity. Also, head speed is explained with a focus on shaft in relation to swing. However, the issue of the coefficient of repulsion is an issue between the golf ball and the golf club, and the influence of the club (head) on the coefficient of repulsion during a collision (hit) has not been completely clarified. It had not been done. In general, conventional golf clubs have been made of materials such as persimmon (persimmon wood), ABS resin, carbon fiber reinforced resin (hereinafter sometimes abbreviated as CFRP), aluminum, and stainless steel. Conventionally, it has been thought that the harder a material is, the easier it is for a golf ball to rebound (larger the coefficient of repulsion) and the higher the initial velocity of the ball. Blue Damo compressed material is used instead of Persimmon,
Furthermore, carbon fiber reinforced resin (CFRP) is required to have a high fiber content, and has traditionally been thought to have a high repulsion coefficient because it is hard. The present invention breaks this conventional wisdom, and as a result of repeated numerous experiments over many years, we have found the optimal hardness to maximize the rebound and initial velocity of the ball. It was found that if the optimum hardness was exceeded, the repulsion deteriorated. They went further and discovered that the mechanical impedance of the ball and ball hitting tool was involved. [Object] An object of the present invention is to provide a ball hitting tool that increases the coefficient of repulsion when hitting a ball and brings the initial velocity of the ball close to the maximum. [Means for Solving the Problems] According to the first invention, the overall shape is a golf club, and in the vibration measurement method using a vibration exciter, the mechanical impedance of the club head that hits the golf ball is determined. , the mechanical impedance of the golf ball is configured to have a first-order minimum value in a frequency range near a frequency where the mechanical impedance shows a first-order minimum value, and the mechanical impedance of the club head is configured to have a first-order minimum value in a frequency range of 600Hz to 1600Hz. ,
It has a first order minimum value. According to the second invention, the overall shape is a tennis racket, a baseball bat, or a ping pong racket, and in the vibration measurement method using a vibration exciter, the mechanical impedance of the hitting portion that hits the corresponding ball is determined. , configured so that the mechanical impedance of the ball has a first-order minimum value in a frequency region near the frequency where the first-order minimum value is shown,
The mechanical impedance of the striking portion has a first-order minimum value in a frequency range of 110 Hz to 500 Hz. [Effect] The ball exhibits a unique mechanical impedance in response to the frequency of the applied mechanical vibration,
Furthermore, the hitting portion of the ball hitting tool also exhibits a unique mechanical impedance. The frequency at which each mechanical impedance exhibits a minimum value corresponds to the natural frequency. When the frequency of the applied mechanical vibration is gradually increased from zero, the minimum value that first appears, that is, the first-order minimum value, corresponds to the first-order natural frequency. The frequency at which the mechanical impedance of the hitting part of the ball hitting tool is at its minimum value - that is, the natural frequency of the ball hitting tool.
However, if the ball hitting tool is constructed so as to approximate the frequency at which the ball's mechanical impedance exhibits a minimum value, that is, the ball's natural frequency, the restitution coefficient increases. In particular, among the natural frequencies of first order, second order, third order...the first order has the greatest influence, and the first order natural frequency of the ball hitting tool is approximated to the first order natural frequency of the ball. By letting
Maximum repulsion is obtained. [Example] Hereinafter, the present invention will be explained in detail based on the illustrated example. First, to explain the mechanical impedance of a mechanical system, it is defined as "the ratio between the magnitude of a force acting on a certain point and the magnitude of the response speed at other points when this force is applied." That is, when the force applied from the outside is F and the response speed is V, the mechanical impedance Z is defined as Z=F/V. The ball hitting tool 1 according to the present invention is shown in FIGS. 5A to 5D.
A golf club 8, a tennis racket 9, a baseball bat 10, and a ping pong racket 11 are illustrated in the figure.
etc., and is used in ball sports. In Figure 2, the horizontal axis represents the frequency N (unit: Hz) of the mechanical vibration applied to the ball hitting tool 1 or the ball, and the vertical axis represents the value obtained by multiplying the logarithm of the absolute value of the mechanical impedance Z by 20. Specifically, it will be shown how the mechanical impedance Z changes depending on the frequency N. As is clear from the same figure, ball hitting tool 1
Both a and the ball-striking tool 1b show a first-order minimum value at point P1 and a second-order minimum value at point P2. Indicates the minimum value of the fourth order. Also, as shown by the broken line in the same figure, the hit ball is similarly located at point P.
1 and P2 show primary and secondary minimum values, respectively.
(Additionally, the minimum values of the third order or higher are shown outside the figure.) Point P indicating the minimum values of the first order, second order, etc.
The frequencies of 1, P2... are so-called primary, secondary...
It is the natural frequency of ..., and is determined by the [mass-spring] system of the ball-hitting tool and ball as structures. 3A, 3B to 3E, and 4 show a method for measuring the mechanical impedance Z. That is, 12 is an excitation machine, which uses an electrodynamic type or a hydraulic type, and has a specimen mounting table 13,
Install ball 2. Alternatively, the ball hitting tools 1 include a golf club 8, a tennis racket 9, and a baseball bat 1.
0 or a ping pong racket 11 is attached to the specimen mounting base 13. Specifically, among the members constituting the ball hitting tool 1, the hitting section 3 for hitting the ball is attached to the specimen mount 13, and vibrations are transmitted to the hitting section 3. In FIG. 3B, the hitting portion 3 is a club head 8a, and in FIG. 3C, the hitting portion 3 is a gut surface 9a for hitting a tennis ball.
In FIG. 3D, this is the part (portion 10a shown with dots in the figure) where the baseball is directly hit, and in FIG. 3E, it is the blade part 11a of the ping pong racket 11. A first acceleration pick-up 14 is fixed to the specimen mounting base 13 of the vibrator 12, and a second acceleration pick-up 15 is fixed to the hitting portion 3 of the ball-hitting tool 1 or the ball 2. The first acceleration pickup 14 outputs the acceleration A1 of the mounting base 13 of the vibrator 12, that is, the acceleration applied to the ball hitting tool 1 or the ball 2 from the outside, and this output is sent to the power unit 16.
Via Dynamic Signal Analyzer 1
Enter 7. From the second acceleration pick-up 15, the ball 2 or ball hitting tool 1, which is the test object, is
The acceleration A2 is output, and this output is input to the dynamic signal analyzer 17 via another power unit 18. Using this dynamic signal analyzer 17 allows calculations in the frequency domain. That is, by integrating the acceleration A2 applied to the ball hitting tool 1 or the ball 2 once, the velocity V2 can be determined. On the other hand, the excitation force F1 is obtained from the acceleration A1 of the vibrator 12, and calculated in the frequency domain to determine the mechanical impedance Z, Z=
Determined by F1/V2. This mechanical impedance Z is displayed on the display 19 in the graph shown in FIG. In the actual measurement tests of the products of the present invention, the manufacturers and types of equipment shown in Table 1 below were used as the measuring devices shown in FIGS. 3 and 4. In addition, "PCB" in Table 1 is
PCBPIEZOTRONICS, INC. (USA,
New York).

[Table] According to the measurement method using the above-mentioned measuring device, there is an advantage that the first-order minimum value of the mechanical impedance Z can be clearly confirmed. Therefore, in Figure 2 and Figures 3A to 3E,
If the frequency at which the mechanical impedance Z of the ball 2 exhibits the first minimum value P1 is Nb, then the ball hitting tool 1 according to the present invention has a mechanical impedance Z
However, the physics of the mass distribution of the ball hitting tool 1, the spring constant of each component, etc., shows the first-order minimum value P1 in the frequency region D (shaded area in FIG. 2) shown by the following equation. Select specific characteristics. (1-n)・Nb≦N≦(1+n)・Nb... However, 0≦n≦0.3 Specifically, one ball hitting tool 1a has a first-order minimum value near the lower limit of frequency N that satisfies the above formula. The other ball hitting tool 1b shows a first-order minimum value near the upper limit of the frequency N that satisfies the above equation. In this formula, n=0.3, n=0.2, n=0.1, n=
By substituting 0.05 into each, the frequency domain D becomes the following equations: 0.7Nb≦N≦1.3Nb … 0.8Nb≦N≦1.2Nb … 0.9Nb≦N≦1.1Nb … 0.95Nb≦N≦1.05Nb … It is indicated by. Frequency region D that satisfies any of the above expressions
The ball-striking tool 1 according to the present invention is configured such that the mechanical impedance Z thereof has a primary minimum value P1. In other words, the mechanical impedance Z of ball 2 is 70% to 130%, 80% to 120% of the frequency Nb at which the first minimum value P1 is
%, 90% to 110%, or 95% to 105%, the ball hitting tool 1 is configured such that the mechanical impedance Z of the ball hitting tool 1 exhibits the first minimum value P1. Here, 70% to 130%
However, a sufficiently large repulsion coefficient can be obtained, but from 95% to
105% provides the best rebound of the ball. FIG. 1 shows the results of actual measurements using the same measuring device and the same measuring method as in FIG. 2, using a golf club as an example of a ball hitting tool and a golf ball as a ball. In the figure, the characteristics of the golf ball are indicated by a broken line B. First-order minimum value P at frequency Nb = 1150Hz
1, and further shows second-order and third-order minimum values P2 and P3 at N=3600 and 5450Hz, respectively. Golf balls currently on the market have different frequencies Nb at which they exhibit the first-order minimum value P1 depending on their structure (one-piece ball, two-piece ball, three-piece ball, thread-wound ball, etc.), but the measured temperature 25
In the case of ℃, this frequency Nb exists in the range shown as 600≦Nb≦1600... In addition, in the present invention, the frequency Nb indicating the first-order minimum value P1 is (as shown in FIGS. 3A to 3G)
In order to determine the value by excitation with the vibrator 12 - by the excitation measurement method using the vibrator, the present invention (one of the inventors) has already proposed and described it in the ball hitting tool of Application No. 143929/1983. The numerical value is different from the frequency Nb (indicating the first-order minimum value) determined by the impact vibration method, which is a measurement method in which a hitting force (impact) is actually applied by hanging the ball hitting tool in a free state. The reason why the frequency Nb indicating the first-order minimum value differs between the two measurement methods is presumed to be due to the difference in the boundary conditions of how the golf ball is held. The boundary condition is that the exciter 12 is fixed to the mount 13 (in FIGS. 3A to 3G), whereas the latter is suspended in a freely supported state. Also,
The former has high measurement accuracy, while the latter has relatively low measurement accuracy.As a result, the latter cannot detect the original first-order minimum value of the object to be measured (ball), but detects the second-order extreme value (impact It is also possible to estimate that it is detected as a first-order minimal object in the vibration method. However, there is no doubt that both measurement methods can achieve a large repulsion effect by measuring the ball and its hitting tool using the same measurement method, and by matching only the first-order minimum values of the measurement methods. The results of actually measuring the mechanical impedance of a conventional golf club are shown by a thin solid line. The golf club indicated by the solid line is a wood-type club that has been commonly used in the past and has a head made of Persimmon, and the frequency N of the first-order minimum value P1 is
It is 2050Hz. Another golf club indicated by a solid line is a wood-type club that has a carbon head and has been commonly used in the past, and has a first-order minimum value of P1.
The frequency N is 2225Hz. Therefore, the frequency N at which the mechanical impedance Z of the conventional golf club takes the first minimum value P1 is significantly outside the frequency range D near the frequency at which the mechanical impedance Z of the golf ball takes the first minimum value P1. . Based on the above-mentioned technical concept of the present invention, a wood-type golf club in which the mass distribution of the club head, shaft, etc., as well as the spring constant and damping coefficient are set, draws a curve as shown by the thick solid line, and the mechanical impedance Z is of the first order. Frequency N showing minimum value P1
was 1250Hz. That is, in the formula, n=
Equivalent to 0.087. The minimum value P1 of this golf club exists within the frequency domain D drawn to satisfy the equation in FIG. This golf club (referred to as) according to the present invention shown in FIG. 1, the conventional golf club (referred to as A comparison of the performance of (referred to as) golf clubs with heads is shown in Table 2. A two-piece ball (with an ionomer resin cover) having the characteristics shown by the broken line B in the figure was used as the ball, and an actual shooting test was conducted.

〔Effect of the invention〕

The present invention has the following significant effects due to the above-described configuration. A ball 2 to be hit and a ball hitting tool 1 for hitting the ball
The best combination of these results in a large repulsion coefficient, which gives the ball 2 a large initial velocity and allows it to fly a long distance. In the past, batting tools were designed based on intuition and experience, and through repeated trial and error.
According to the present invention, it has become possible to easily and reliably obtain a ball hitting tool having excellent ball repelling performance. Among the natural frequencies of primary, secondary, tertiary, etc., the primary has a particularly large effect on repulsion performance, and by bringing these primary frequencies closer to each other, repulsion performance can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 shows a golf club of the present invention and a conventional golf club.
Fig. 2 is a characteristic curve diagram showing actual measurement results for different types of golf clubs and hit balls, and shows changes in mechanical impedance with respect to the frequency of vibration applied by a vibration exciter. FIGS. 3A to 3G are characteristic curve diagrams showing changes in mechanical impedance with respect to the frequency of vibration applied by a vibration exciter.
The figures are simplified explanatory diagrams showing methods of vibrating a ball or the entirety of various ball-hitting tools or their striking parts using a vibration exciter, and Figure 4 is a block diagram showing an example of a device for measuring mechanical impedance. , FIGS. 5A to 5D are front views showing various ball-hitting tools, FIG. 6 is a diagram showing the case of a golf club as the ball-hitting tool, and is a diagram for explaining the mass distribution of the club head.
The figure is a perspective view for explaining the configuration of a golf club head. 1... Batting tool, 2... Ball, 3... Hitting section,
8...Golf club, 8a...Club head, 9
...Tennis racket, 10 ...Baseball bat, 11
...Ping pong racket, 12...Vibrator, Z...
...Mechanical impedance, D...Frequency domain, N...Frequency, P1...First-order minimum value (point).

Claims (1)

[Claims] 1. The overall shape is a golf club, and in the vibration measurement method using a vibration exciter, the mechanical impedance of the club head that hits the golf ball is
The mechanical impedance of the golf ball is configured to have a first-order minimum value in a frequency range near the frequency where the first-order minimum value is shown, and the mechanical impedance of the club head is configured to have a first-order minimum value in a frequency range of 600Hz to 1600Hz. A ball hitting tool characterized by having a first order minimum value. 2. If the overall shape is a tennis racket, baseball bat, or ping pong racket, and in the vibration measurement method using a vibration exciter, the mechanical impedance of the hitting part that hits the corresponding ball is the mechanical impedance of the ball. It is configured to have a first-order minimum value in a frequency region near the frequency showing the first-order minimum value, and the mechanical impedance of the striking portion has a first-order minimum value in a frequency region of 110Hz to 500Hz. A ball hitting tool characterized by: