JP6809046B2 - Shaft assembly and torsion measurement method for golf clubs - Google Patents

Description

The present invention relates to a shaft assembly for measuring the amount of twist of a shaft for a golf club, a twist measuring system including the same, and a twist measuring method.

Golf clubs are required to have characteristics that allow the ball to fly straight. It is considered that the characteristics of the golf club with respect to the left-right directionality depend in part on the torque of the shaft. Torque is an index showing the ease of twisting (torsional rigidity) of the shaft. In general, it is said that a shaft with a larger torque has a worse left-right directionality (is not stable), and a shaft with a smaller torque has a better left-right directionality.

As described above, the ease of twisting of the shaft can be a factor in determining the quality of the golf swing, so there is a demand for measuring the amount of twist of the shaft when an external force is applied to the golf club. In this regard, Patent Documents 1 and 2 disclose a method for measuring the amount of twist of the shaft during a golf swing.

Patent Document 1 prepares a golf club in which a marker is mounted on a jig protruding from a shaft, captures the swing motion of such a golf club from various directions with an optical motion capture system, and determines the position of the marker. The amount of twist is calculated by specifying by image processing. In Patent Document 2, two posture angle sensors are attached to the head side and the hand side of a golf club, and the amount of twist is calculated from the difference in posture angles by these sensors.

Japanese Unexamined Patent Publication No. 2013-102825 Japanese Unexamined Patent Publication No. 2012-143342

However, in the method of Patent Document 1, a large number of cameras must be installed, and the equipment becomes large. Furthermore, an error may occur due to the vibration of the jig to which the marker is attached. Further, in the method of Patent Document 2, an inertial sensor is used as the attitude angle sensor, but an error occurs in the inertial sensor due to drift. Such an error accumulates while the data of the angular velocity and the acceleration, which are the output values of the inertial sensor, are integrated in order to obtain the position and the attitude, and may eventually become a factor of lowering the accuracy.

An object of the present invention is to provide a shaft assembly, a twist measuring system, and a twist measuring method capable of measuring the twist amount of a shaft for a golf club with high accuracy with simple equipment.

The shaft assembly according to the first aspect includes a shaft for a golf club having a hollow structure extending in the shaft axial direction, a rod body, and a rotation angle meter. The rod body is arranged inside the shaft so as to extend between at least the first point and the second point along the shaft axial direction, and at the first point, the rod body freely rotates with respect to the shaft. Retained so that it can. The rotation angle meter measures the relative rotational displacement of the shaft with respect to the rod body at the first point.

The shaft assembly according to the second aspect is the shaft assembly according to the first aspect, and the rod body is fixed to the shaft so as to rotate following the shaft at the second point. ..

The shaft assembly according to the third aspect is the shaft assembly according to the second aspect, and the rod body is fixed to the shaft at the second point so as to follow the shaft and translate.

The shaft assembly according to the fourth viewpoint is a shaft assembly according to any one of the first to third viewpoints, and the first point is located within ± 200 mm in the direction from the butt end to the tip end of the shaft. To do.

The shaft assembly according to the fifth viewpoint is a shaft assembly according to any one of the first to fourth viewpoints, and the second point is located within 200 mm in the direction from the tip end to the butt end of the shaft. ..

The shaft assembly according to the sixth aspect is the shaft assembly according to any one of the first to fifth viewpoints, and the bending rigidity of the rod body is the bending rigidity of the shaft at the same position in the shaft axial direction. It is 1/10 or less.

The shaft assembly according to the seventh aspect is the shaft assembly according to any one of the first to sixth aspects, and the diameter of the rod body is 0.5 mm or more and 5.0 mm or less.

The shaft assembly according to the eighth aspect is the shaft assembly according to any one of the first to seventh aspects, and further includes a holder. The holder is arranged inside the shaft and holds the rod so as to prevent displacement of the rod with respect to the shaft in a direction orthogonal to the shaft axis.

The shaft assembly according to the ninth viewpoint is a shaft assembly according to any one of the first to eighth viewpoints, and the rotation angle meter is a main body portion that is relatively rotatable about the rotation axis and the rotation axis. And a detector that detects a signal representing the relative rotational displacement of the main body about the rotation axis. The main body is fixed to the shaft. The rod body is fixed to the rotating shaft so as not to rotate around the rotating shaft.

The twist measurement system according to the tenth viewpoint includes a shaft assembly according to any one of the first to ninth viewpoints and an arithmetic unit. The arithmetic unit acquires information on the rotational displacement from the rotary angle meter, and based on the rotational displacement, determines the amount of twist of the shaft around the shaft axis between the first point and the second point. calculate.

The twist measuring method according to the eleventh aspect includes the following steps (1) to (4).
(1) A step of preparing a shaft for a golf club having a hollow structure extending in the axial direction of the shaft.
(2) Inside the shaft, a rod body is arranged so as to extend between at least the first point and the second point along the shaft axial direction, and at this time, at the first point, with respect to the shaft. A step of holding the rod so that it can rotate freely.
(3) By applying an external force to the shaft on which the rod body is arranged, the shaft is twisted and deformed, and the relative rotational displacement of the shaft with respect to the rod body at the first point at this time is measured. Steps to do.
(4) A step of calculating the amount of twist of the shaft around the shaft axis between the first point and the second point based on the rotational displacement.

The twist measuring method according to the twelfth viewpoint is the twist measuring method according to the eleventh viewpoint, and the step of holding the rod body is such that the rod body rotates following the shaft at the second point. Includes a step of fixing the shaft to the shaft.

According to the first aspect, the rod body is arranged inside the shaft whose twist amount is to be measured. The rod body is arranged so as to extend between at least the first point and the second point along the shaft axial direction, and is held so that it can freely rotate with respect to the shaft at the first point. Therefore, at the first point, even if the shaft is rotationally displaced around the shaft axis, the rod body does not substantially follow the shaft and rotate. Therefore, such a rotational displacement of the shaft with respect to the rod body can be used to express the amount of twist of the shaft. Here, such a rotational displacement is measured by a rotational angle meter. Therefore, it is possible to measure the amount of twist of the shaft for a golf club with high accuracy with simple equipment.

The whole block diagram of the twist measurement system which concerns on one Embodiment of this invention. Longitudinal section of the shaft assembly. A block diagram showing the electrical configuration of a twist measurement system. The figure explaining the conversion data for converting the voltage data into the twist amount data. Side view of the equipment for deriving the converted data. The figure which looked at the equipment for deriving the conversion data from the B1 direction of FIG. 5A. A flowchart showing the flow of the twist measurement process.

Hereinafter, a shaft assembly for measuring the amount of twist of a shaft for a golf club according to an embodiment of the present invention, a twist measurement system including the same, and a twist measurement method will be described with reference to the drawings.

<1. Overall configuration of twist measurement system>
FIG. 1 shows an overall configuration diagram of the twist measurement system 100 according to the present embodiment. The twist measuring system 100 is a system for measuring the amount of bending of the shaft 12 of the golf club 10, and includes a shaft assembly 15 and a computer 8. The golf club 10 has a shaft 12 extending linearly, a head 13 fixed to one end side of the shaft 12, and a grip 11 fixed to the other end side of the shaft 12. The grip 11 is a portion that the golfer 7 grips by hand when swinging the golf club 10. Although not shown in FIG. 1, a rotation angle meter 2 is attached to the inside of the grip 11 (see FIG. 2). The rotation angle meter 2 is a sensor unit that measures a rotational displacement representing the amount of twist of the shaft 12, and is connected to the computer 8 via a cable 3. The rotation angle meter 2 constitutes the shaft assembly 15 together with the shaft 12 and the rod body 50 (see FIG. 2) which will be described later, which is arranged inside the shaft 12. Hereinafter, the configurations of the shaft assembly 15 and the computer 8 will be described, and then the twist measurement process for measuring the twist amount of the shaft 12 will be described.

<2. Composition of each part>
<2-1. Shaft assembly>
FIG. 2 is a vertical sectional view of the shaft assembly 15. As shown in the figure, the shaft 12 has a hollow structure and is a cylindrical member extending in the shaft axis A1 direction. The shaft shaft A1 is a central shaft in the longitudinal direction of the shaft 12. The diameter of the shaft 12 is gradually increased from the tip end 12A side toward the butt end 12B side. The shaft 12 is made of a material that easily bends or twists when an inertial force such as a centrifugal force during a golf swing is applied, and is typically made of carbon.

Inside the shaft 12, the rod body 50 is arranged parallel to the shaft axis A1 direction. The rod body 50 and the shaft 12 are aligned so as to be coaxial with each other. The rod body 50 extends linearly from the vicinity of the tip end 12A of the shaft 12 to the vicinity of the butt end 12B. The rod body 50 is an elastic body, and in the present embodiment, it is composed of a wire, more specifically, a piano wire. The diameter of the rod body 50 is preferably 0.5 mm or more and 5.0 mm or less from the viewpoint of maintaining the strength of the rod body 50 and reducing the weight. It is preferable that the rod body 50 has a flexural rigidity smaller than that of the shaft 12 over the entire length of the rod body 50 when compared with each other at the same positions in the shaft axis A1 direction. This is because if the bending rigidity of the rod body 50 is large, the bending rigidity of the shaft 12 may be affected in some cases, and the characteristics of the shaft 12 may be changed. More specifically, the flexural rigidity of the rod body 50 is preferably 1/10 or less of the flexural rigidity of the shaft 12 at the same position in the shaft axis A1 direction.

The rod body 50 is fixed to the shaft 12 at the tip end 12A. At this time, the end portion 50A on the tip end 12A side of the rod body 50 is fixed so as to follow the portion near the tip end 12A of the shaft 12 and rotate and translate. In the present embodiment, the end portion 50A of the rod body 50 is attached to the shaft 12 via the jig 61. The jig 61 is composed of a columnar insertion portion 61A inserted into the shaft 12 so as to be crimped to the inner peripheral surface of the shaft 12, and a flange portion 61B arranged at one end of the insertion portion 61A. The flange portion 61B serves to prevent the insertion portion 61A from entering the shaft 12. The end portion 50A of the rod body 50 is aligned so that the rod body 50 and the insertion portion 61A are coaxial with each other, and is firmly fixed to the insertion portion 61A by a method such as welding.

On the other hand, a jig 62 is attached to the butt end 12B of the shaft 12, and a rotation angle meter 2 is attached to the jig 62. The jig 62 is firmly fixed so as not to substantially rotate and translate with respect to a portion of the shaft 12 near the butt end 12B. In the present embodiment, the jig 62 has a cylindrical side wall portion 62B and a dividing plate 62A that divides the space inside the side wall portion 62B into two along the shaft axis A1 direction. The dividing plate 62A is a disk-shaped member having an opening in the center, and is arranged so as to be orthogonal to the central axis of the side wall portion 62B. The side wall portion 62B is partially inserted into the shaft 12 so as to be crimped to the inner peripheral surface of the portion near the butt end 12B of the shaft 12. The mode of fixing the shaft 12 and the jig 62 is not particularly limited, but for example, it can be fixed by using a tightening mechanism such as a screw or a pipe band, or an adhesive.

Further, on the butt end 12B side, the grip 11 is fitted to the shaft 12 and the jig 62 so as to cover the outer peripheral surface of the side wall portion 62B of the shaft 12 and the jig 62. The grip 11 is crimped to the outer peripheral surfaces of the shaft 12 and the side wall portion 62B, and is firmly fixed so as not to substantially rotate and translate with respect to a portion of the shaft 12 near the butt end 12B. Further, an opening is formed in the end portion (hereinafter, referred to as a grip end) 11A of the grip 11 opposite to the head 13 for the cable 3 (see FIG. 1) to pass through.

The housing 25 of the rotation angle meter 2 is fixed on the dividing plate 62A of the jig 62. The housing 25 is housed in the space far from the butt end 12B of the two spaces divided by the dividing plate 62A inside the side wall portion 62B. The housing 25 is firmly fixed to the dividing plate 62A so as not to substantially rotate and translate. The mode of fixing at this time is not particularly limited, but for example, it can be fixed by using a fixture such as a nut or by using an adhesive. As is clear from the above, the jig 62 makes the housing 25 of the rotation angle meter 2 firmly so as not to substantially rotate and translate with respect to the portion near the butt end 12B of the shaft 12. It is fixed.

An opening is formed in the center of the dividing plate 62A, and a rotation shaft 21 protruding from the housing 25 of the rotation angle meter 2 is inserted into the opening. The rotating shaft 21 penetrates the dividing plate 62A and reaches the closed space C1 defined by the shaft 12 and the jig 62. The rotating shaft 21 extends along the shaft axis A1 direction and is aligned so as to be coaxial with the shaft 12.

In the closed space C1, the end portion 50B of the rod body 50 on the butt end 12B side is firmly fixed so as not to substantially rotate and translate with respect to the rotation axis 21 of the rotation angle meter 2. The rod body 50 is aligned so as to be coaxial with the rotation shaft 21. Further, the rotating shaft 21 can freely rotate around the shaft shaft A1 with respect to the housing 25. Therefore, the end portion 50B of the rod body 50 can also freely rotate around the shaft axis A1 with respect to the housing 25 and thus to the butt end 12B. The mode of fixing the end portion 50B of the rod body 50 and the rotating shaft 21 is not particularly limited, but in the present embodiment, the end portion 50B is attached to the rotating shaft 21 via the coupling 63. The coupling 63 has a member composed of a bottom portion 63A and a side wall portion 63B rising from the bottom portion 63A, and a screw 63C entering the opening provided in the side wall portion 63B. The end portion 50B of the rod body is fixed to the bottom portion 63A by welding or the like, and the rotating shaft 21 is inserted into the side wall portion 63B. Then, by inserting the screw 63C deeper into the side wall portion 63B, the rotating shaft 21 is pressed by the tip of the screw 63C, and the rotating shaft 21 is fixed so as not to be substantially rotated and translated in the side wall portion 63B. can do. The coupling 63 is preferably made of metal in order to secure high rigidity against deformation in the bending direction.

Further, as shown in FIG. 2, a holder 70 for holding the rod body 50 is arranged inside the shaft 12. The holder 70 is a member for preventing the rod body 50 from being displaced with respect to the shaft 12 in the direction orthogonal to the shaft axis A1. In the present embodiment, the holders 70 are installed at a plurality of locations along the shaft axis A1 direction at predetermined intervals. The rod body 50 penetrates the holder 70 along the shaft axis A1 direction. The holder 70 is preferably made of a lightweight material such as a sponge. Further, it is preferable that the rod body 50 is soft enough not to affect the twisting of the rod body 50. With such a holder 70, for example, when the shaft 12 bends during a golf swing, the rod body 50 also bends in accordance with the shaft 12. That is, the holder 70 plays a role of always arranging the rod body 50 substantially along the central axis of the shaft 12 even when the shaft 12 is bent and deformed. As a result, the difference in deflection between the tip end 12A and the butt end 12B can be canceled, and only the difference in rotational displacement due to twist can be evaluated more accurately.

Next, the configuration of the rotation angle meter 2 will be described. As described above, in the present embodiment, the housing 25 of the rotation angle meter 2 is fixed to the butt end 12B so as not to rotate, and the rod body 50 rotates around the rotation shaft 21 protruding from the housing 25. It is fixed to the impossible. Therefore, the rotation angle meter 2 can measure the relative rotational displacement of the shaft 12 with respect to the rod body 50 at the butt end 12B. Further, the rod body 50 has a fixed end formed on the tip end 12A side, but has a free end formed on the butt end 12B side, so that the golf club 10 is substantially twisted and deformed during the swing operation. Absent. Therefore, the rotational displacement measured by the rotational angle meter 2 represents the amount of twist of the shaft 12 between the tip end 12A and the butt end 12B. The torsional rigidity of the rod body 50 is such that the torsion of the rod body 50 caused by the torque required to rotate the rotating shaft 21 with respect to the housing 25 of the rotation angle meter 2 is measured by the rotation angle meter 2. It is preferably small enough to be negligible for twisting of the shaft 12.

FIG. 3 is a block showing the electrical configuration of the torsion measurement system 100. As shown in FIG. 3, the rotation angle meter 2 according to the present embodiment is a potentiometer, and the detector 20 is housed in the housing 25. The detector 20 can detect a voltage signal representing the relative rotational displacement of the housing 25 around the rotating shaft 21. More specifically, the detector 20 has three terminals T1 to T3. Then, when the rotation shaft 21 rotates with respect to the housing 25, the terminal T2 moves between the terminals T1 and T3, and the voltage between the terminals T2 and T3 changes. Therefore, the voltage between the terminals T2 and T3 is a signal representing the relative rotational displacement of the rotating shaft 21 with respect to the housing 25, and thus the rotational displacement of the shaft 12 with respect to the rod body 50 at the butt end 12B. These terminals T1 to T3 are connected to each of the three voltage lines L1 to L3 constituting the cable 3. The voltage lines L1 and L3 are connected to the constant voltage power supply 9, and a constant voltage is applied between the terminals T1 and T3 by the constant voltage power supply 9. On the other hand, the voltage lines L2 and L3 are connected to the A / D converter 31 of the computer 8. That is, the voltage data measured by the rotation angle meter 2 is transmitted to the computer 8.

<2-2. Computer>
Next, the configuration of the computer 8 will be described. The computer 8 is a device that calculates the amount of twist of the shaft 12 based on the voltage data output from the rotation angle meter 2. The computer 8 is a general-purpose computer as hardware, and is realized as a laptop computer, a desktop computer, a smartphone, a tablet, or the like. The program 5 is installed in the computer 8 from a computer-readable recording medium 90 such as a CD-ROM, or from another device via a network such as the Internet. The program 5 is an operation described later in the computer 8. To execute.

The computer 8 includes an A / D converter 31 in addition to a display unit 81, an input unit 82, a storage unit 83, a control unit 84, and a communication unit 85. Then, these parts 81 to 85, 31 are connected via a bus line 86. The A / D converter 31 may be a built-in type or an external type. In the present embodiment, the display unit 81 is composed of a liquid crystal display or the like, and displays information described later to the user. Further, the input unit 82 is composed of a mouse, a keyboard, a touch panel, and the like, and receives an operation from the user on the computer 8. The communication unit 85 is a communication interface that enables communication between the computer 8 and an external device. The control unit 84 is composed of a CPU, a ROM, a RAM, and the like, and reads and executes the program 5 in the storage unit 83. The storage unit 83 is composed of a non-volatile storage device such as a hard disk. In addition to storing the program 5, various data are stored in the storage unit 83.

The A / D converter 31 is connected to the voltage lines L2 and L3 included in the cable 3 and digitally converts an analog signal representing the voltage between the terminals T2 and T3 output from the rotation angle meter 2. The converted voltage data is stored in the storage unit 83. Further, the storage unit 83 also stores the conversion data 83A for converting the voltage data into the data of the twist amount of the shaft 12.

Specifically, the conversion data 83A is the data as shown in FIG. As shown in FIG. 4, the voltage between the terminals T2 and T3 and the angle of the rotating shaft 21 with respect to the housing 25 are in a proportional relationship. The converted data 83A is information for specifying this proportional relationship. The voltage between the terminals T2 and T3 takes a value corresponding to the rotational displacement of the rotating shaft 21 with respect to the housing 25, in other words, the relative rotational displacement of the shaft 12 with respect to the rod body 50 at the butt end 12B. In other words, the voltage between the terminals T2 and T3 takes a value corresponding to the amount of twist of the shaft 12 around the shaft shaft A1 between the tip end 12A and the butt end 12B. The conversion data 83A is data for converting the voltage data from the rotation angle meter 2 into data on the amount of twist of the shaft 12 between the chip end 12A and the butt end 12B.

The converted data 83A can be derived as follows, for example, by using the equipment 4 as shown in FIGS. 5A and 5B. 5A is a side view of the equipment 4, and FIG. 5B is a view of the equipment 4 as viewed from the B1 direction of FIG. 5A. However, in FIG. 5A, the vicinity of the grip 11 is drawn as a cross-sectional view. As shown in these figures, the equipment 4 includes a shaft assembly 15, and the grip 11 is fixed via a fixture such as a three-claw chuck so that the shaft 12 extends horizontally. At this time, the shaft 12 is firmly fixed so that the butt end 12B does not substantially rotate and translate with respect to the ground. At this time, the grip 11 can be omitted and the jig 62 can be fixed.

Further, the jig 40 is attached in the vicinity of the tip end 12A of the shaft 12. The jig 40 has a ring-shaped portion 41 that winds around the shaft 12 so as to tighten the shaft 12 from the outside, and an arm 42 that projects horizontally from the ring-shaped portion 41 in the radial direction. A weight 43 is suspended from the arm 42. As a result, the load by the weight 43 is applied to the position eccentric from the axial center of the shaft 12. Further, a needle 44 extending in a direction orthogonal to the shaft axis A1 is fixed to the tip end 12A.

In the above equipment 4, the amount of twist of the shaft 12 around the shaft shaft A1 can be varied by changing the hanging position of the weight 43 on the arm 42 or by changing the weight of the weight 43. Change. Then, while changing the amount of twist in this way, voltage data is collected by the rotation angle meter 2. The voltage data is input to the computer 8 and converted into digital data. At the same time as collecting voltage data, the rotational displacement of the needle 44 around the shaft axis A1 is measured. Since the butt end 12B of the shaft 12 does not displace with respect to the ground, the rotational displacement of the needle 44 at this time is the amount of twist of the shaft 12 around the shaft shaft A1 between the tip end 12A and the butt end 12B. Will be represented. Then, the data of the rotational displacement of the needle 44 is input to the computer 8, and the computer 8 calculates the rotational displacement of the needle 44, that is, the relationship between the twist amount of the shaft 12 and the voltage between the terminals T2 and T3. The data representing this relationship is the conversion data 83A.

<3. Twist measurement process>
Hereinafter, the twist measurement process for measuring the twist amount of the shaft 12 will be described with reference to FIG. Here, the amount of twist of the shaft 12 during the golf swing is measured.

First, in step S1, the shaft 12 and the grip 11 are prepared, and the rod body 50, the rotation angle meter 2, the jigs 61 and 62, and the coupling 63 are prepared, and these are assembled to prepare the shaft assembly 15 described above. .. More specifically, inside the shaft 12, the rod body 50 is fixed so as to extend from the vicinity of the tip end 12A to the vicinity of the butt end 12B along the shaft axis A1 direction. At this time, the rod body 50 is attached so that the end portion 50B on the butt end 12B side of the rod body 50 can freely rotate with respect to the shaft 12. Further, the end portion 50A on the tip end 12A side of the rod body 50 is fixed to the shaft 12 so as not to rotate. Then, the shaft assembly 15 is fixed to the head 13 to manufacture the golf club 10 described above.

In the following step S2, the golfer 7 swings the golf club 10. At this time, since an inertial force such as a centrifugal force is applied to the golf club 10, the shaft 12 is deformed by bending, twisting, or the like. Of these deformations, the torsional deformation is measured as time-series voltage data by the rotation angle meter 2 mounted on the golf club 10. This time-series voltage data is sequentially input to the A / D converter 31 of the computer 8 via the cable 3. The A / D converter 31 converts time-series voltage data, which is analog data, into digital data, and then stores this in the storage unit 83.

In the following step S3, the control unit 84 calculates the amount of twist of the shaft 12 between the tip end 12A and the butt end 12B based on the voltage data acquired in step S2. More specifically, with reference to the conversion data 83A, the time-series voltage data is converted into the time-series shaft 12 twist amount data.

In the following step S4, the control unit 84 outputs the data of the time-series twist amount calculated in the step S3. Specifically, a screen showing the time-series twist amount data is displayed on the display unit 81. At this time, the time-series twist amount data is appropriately processed into a display format so that the user can easily understand the result, such as by graphing.

<4. Modification example>
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the following changes can be made. In addition, the gist of the following modified examples can be combined as appropriate.

<4-1>
In the above embodiment, the amount of twist of the shaft 12 between the tip end 12A and the butt end 12B was measured. However, the present invention can be used to measure the amount of twist between any two points along the shaft axis A1 direction on the shaft 12. From the viewpoint of analyzing the twisting characteristics of the shaft 12, one point is preferably installed within ± 200 mm from the butt end 12B toward the tip end 12A, and more preferably within ± 100 mm. The other point is preferably set within 200 mm from the tip end 12A toward the butt end 12B.

<4-2>
In the above embodiment, the rotation angle meter 2 is realized as a potentiometer, but the configuration of the rotation angle meter 2 is not limited to this as long as the rotational displacement of the shaft 12 with respect to the rod body 50 can be measured. For example, a rotary encoder can be used instead of the potentiometer. A rotary encoder also generally has a rotation axis and a housing that can rotate relatively around the rotation axis, and magnetically or optically detects a signal corresponding to these relative rotational displacements.

<4-3>
In the above embodiment, the end portion 50A on the tip end 12A side of the rod body 50 is a fixed end, and the end portion 50B on the butt end 12B side is a free end. However, the present invention is not limited to this embodiment, and for example, not only the end portion 50B on the butt end 12B side but also the end portion 50A on the tip end 12A side can be configured to be freely rotatable with respect to the shaft 12. Then, a rotation angle meter 2 is also prepared on the tip end 12A side, and the relative rotational displacement of the shaft 12 with respect to the rod body 50 at the tip end 12A is measured. Then, in the computer 8, the difference in the rotational displacement measured by the two rotational angle meters 2 can be calculated as the amount of twist of the shaft 12.

<4-4>
In the above embodiment, the voltage data is transmitted from the rotation angle meter 2 to the computer 8 as analog data, and is converted into digital data in the computer 8. However, an A / D converter is mounted on the shaft assembly 15, and after the output value of the rotation angle meter 2 is A / D converted by this A / D converter, voltage data is transmitted to the computer 8 and the communication unit 85 You may want to receive this. Further, in the above embodiment, the voltage data is transmitted from the shaft assembly 15 side to the computer 8 by wire, but it can also be transmitted wirelessly. In this case, for example, a communication module such as an I / O interface may be mounted on the shaft assembly 15.

Further, on the shaft assembly 15 side, the voltage data can be converted into the amount of twist of the shaft 12. This embodiment can be realized, for example, by mounting a CPU and a memory in addition to the A / D converter and the communication module on the shaft assembly 15 and storing the conversion data 83A in the memory. The data of the twist amount after conversion can be transmitted to an external device such as a computer 8 and displayed on the display unit 81.

10 Golf club 100 Twist measurement system 12 Shaft 12A Tip end (second point)
12B butt end (1st point)
15 Shaft assembly 2 Rotation angle meter 20 Detection unit 21 Rotation shaft 25 Housing (main body)
50 Bar 70 Holder 8 Computer (arithmetic unit)
A1 shaft shaft

Claims (12)

A shaft for golf clubs with a hollow structure that extends in the axial direction of the shaft,
A rod body that is arranged inside the shaft so as to extend between at least the first point and the second point along the shaft axial direction, and is freely arranged with respect to the shaft at the first point. A rod that is held so that it can rotate and is fixed to the shaft at the second point so that it rotates following the shaft .
A shaft assembly comprising a first rotation angle meter that measures the relative rotational displacement of the shaft with respect to the rod at the first point. A shaft for golf clubs with a hollow structure that extends in the axial direction of the shaft,
A rod body that is arranged inside the shaft so as to extend between at least the first point and the second point along the shaft axial direction, and at the first point and the second point, the shaft. A rod that is held so that it can rotate freely with respect to
A first rotation angle meter that measures the relative rotational displacement of the shaft with respect to the rod body at the first point, and
A second rotation angle meter that measures the relative rotational displacement of the shaft with respect to the rod body at the second point.
A shaft assembly. At the second point, the rod is fixed to the shaft so as to follow and translate the shaft.
The shaft assembly according to claim 1 . The first point is located within ± 200 mm in the direction from the butt end of the shaft toward the tip end.
The shaft assembly according to any one of claims 1 to 3. The second point is located within 200 mm in the direction from the tip end of the shaft toward the butt end.
The shaft assembly according to any one of claims 1 to 4. The flexural rigidity of the rod is 1/10 or less of the flexural rigidity of the shaft at the same position in the axial direction of the shaft.
The shaft assembly according to any one of claims 1 to 5. The diameter of the rod is 0.5 mm or more and 5.0 mm or less.
The shaft assembly according to any one of claims 1 to 6. Further comprising a holder which is arranged inside the shaft and holds the rod in a direction orthogonal to the shaft axis so as to prevent the rod from being displaced with respect to the shaft.
The shaft assembly according to any one of claims 1 to 7. The first rotation angle meter includes a rotation axis, a main body portion that can rotate relatively around the rotation axis, and a detector that detects a signal representing a relative rotational displacement of the main body portion around the rotation axis. Have,
The main body is fixed to the shaft and
The rod is fixed to the axis of rotation so that it cannot rotate around the axis of rotation.
The shaft assembly according to any one of claims 1 to 8. With the shaft assembly according to any one of claims 1 to 9.
A calculation for acquiring information on the rotational displacement from the first rotational angle meter and calculating the amount of twist of the shaft around the shaft axis between the first point and the second point based on the rotational displacement. A twist measurement system equipped with a device. Steps to prepare a shaft for a golf club with a hollow structure extending in the axial direction of the shaft,
Inside the shaft, a rod body is arranged so as to extend between at least the first point and the second point along the shaft axial direction, and at this time, the rod body is freely arranged with respect to the shaft at the first point. A step of holding the rod body so that it can rotate and fixing the rod body to the shaft so as to rotate following the shaft at the second point .
A step of twisting and deforming the shaft by applying an external force to the shaft on which the rod body is arranged, and measuring the relative rotational displacement of the shaft with respect to the rod body at the first point at this time. ,
A step of calculating the amount of twist of the shaft around the shaft axis between the first point and the second point based on the rotational displacement.
Twist measurement method. Steps to prepare a shaft for a golf club with a hollow structure extending in the axial direction of the shaft,
Inside the shaft, a rod body is arranged so as to extend between at least the first point and the second point along the shaft axial direction, and at this time, at the first point and the second point, the shaft And the step of holding the rod so that it can rotate freely with respect to
By applying an external force to the shaft on which the rod body is arranged, the shaft is twisted and deformed, and the relative rotational displacement of the shaft with respect to the rod body at the first point and the second point at this time. Steps to measure and
A step of calculating the amount of twist of the shaft around the shaft axis between the first point and the second point based on the rotational displacement at the first point and the second point.
including,
Twist measurement method.

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