JP2019100396A - Eddy current damper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eddy current type damper capable of easily adjusting a damping force. An eddy current type damper 1 includes a screw shaft 7, a plurality of magnet holding rings 2, a plurality of first permanent magnets 3, a plurality of second permanent magnets 4, a plurality of conductive rings 5, and a screw. A ball nut 6 that meshes with the shaft 7 is provided. The plurality of magnet holding rings 2 are connected in the axial direction of the screw shaft 7. The plurality of first magnets 3 are held by each of the plurality of magnet holding rings 2. Each of the plurality of first magnets 3 is arranged along the circumferential direction of the magnet holding ring 2. The plurality of second magnets 4 are held by each of the plurality of magnet holding rings 2. Each of the plurality of second permanent 4s is arranged between the first magnets 3, and the arrangements of the first magnet 3 and the magnetic poles are reversed. Each of the plurality of conductive rings 5 has conductivity and faces the first magnet 3 and the second magnet 4 with a gap. The ball nut 6 is arranged inside the magnet holding ring 2 and the conductive ring 5 and fixed to the magnet holding ring 2. [Selection diagram] Fig. 2

Description

  The present invention relates to an eddy current damper.

  In order to protect the building from vibrations due to earthquakes, etc., a damping system is attached to the building. The vibration control device converts kinetic energy given to the building into other energy (eg, thermal energy). This suppresses large shaking of the building. The vibration control device is, for example, a damper. The types of dampers are, for example, oil type and shear resistance type. In general, oil type and shear resistance type dampers are often used in buildings. The oil type damper uses the incompressible fluid in the cylinder to damp the vibration. The shear resistance damper damps the vibration by using the shear resistance of the viscous fluid.

  However, the viscosity of the viscous fluid used in particular in shear resistant dampers depends on the temperature of the viscous fluid. That is, the damping force of the shear resistance damper depends on the temperature. Therefore, when using a shear resistant damper in a building, it is necessary to select an appropriate viscous fluid in consideration of the use environment. Further, in a damper using a fluid such as an oil type or a shear resistance type, the pressure of the fluid may rise due to temperature rise and the like, and mechanical elements such as the seal material of the cylinder may be damaged. As a damper whose damping force does not depend on temperature, there is an eddy current damper.

  A conventional eddy current type damper is disclosed, for example, in Japanese Patent Publication No. 5-86496 (Patent Document 1).

  The eddy current damper of Patent Document 1 includes a plurality of permanent magnets attached to a main cylinder, a hysteresis member connected to a screw shaft, a ball nut meshing with the screw shaft, and a sub cylinder connected to a ball nut. Equipped with The plurality of permanent magnets alternate in the arrangement of the magnetic poles. The hysteresis material faces the plurality of permanent magnets and is capable of relative rotation. When kinetic energy is given to the eddy current type damper, the sub cylinder and the ball nut move in the axial direction by the guidance of the main cylinder, and the hysteresis material is rotated by the action of the ball screw. Thereby, kinetic energy is consumed by the hysteresis loss. Further, it is described in Patent Document 1 that kinetic energy is consumed by an eddy current loss because an eddy current is generated in the hysteresis material.

Japanese Examined Patent Publication 5-86496

  In the eddy current damper of Patent Document 1, a plurality of permanent magnets are arranged along the circumferential direction. When kinetic energy is applied to the damper, the hysteresis material rotates in the magnetic field generated by each of the permanent magnets. At this time, eddy currents are generated in the regions of the surface of the hysteresis material facing the respective permanent magnets. Thereby, a damping torque is given to the rotating hysteresis material, and a damping force is generated.

  Here, the damping force of the eddy current damper is uniquely determined according to the size of the main cylinder provided with the permanent magnet and the size of the hysteresis material paired with the main cylinder. In the case of a conventional eddy current damper, appropriate dimensions of the main cylinder and the hysteresis material must be designed for each required damping force. In short, the conventional eddy current damper can not easily adjust the damping force.

  An object of the present invention is to provide an eddy current damper that can easily adjust the damping force.

  The eddy current damper according to the present embodiment is a screw shaft, a plurality of magnet holding rings connected in the axial direction of the screw shaft, and a plurality of first permanent magnets held by each of the plurality of magnet holding rings. A plurality of first permanent magnets each arranged along a circumferential direction of the magnet holding ring, and a plurality of second permanent magnets held by each of the plurality of magnet holding rings, each being a first permanent magnet It is a cylindrical conductive member which is disposed between magnets, and forms a pair with a plurality of second permanent magnets in which the arrangement of the first permanent magnet and the magnetic pole is reversed and a plurality of connected magnet holding rings, A conductive member which has flexibility and is opposed to the first permanent magnet and the second permanent magnet with a gap, and is disposed inside the magnet holding ring and the conductive member and fixed to the magnet holding ring or the conductive member, and has a screw shaft And a ball nut for meshing.

  According to the eddy current damper of the present embodiment, the number of magnet holding rings is selected for each required damping force. A selected number of magnet retaining rings are coupled. A conductive member of a length corresponding to the total length of the coupled magnet retaining ring is selected. The selected conductive member is assembled. This makes it easy to adjust the damping force.

FIG. 1 is a cross-sectional view of the eddy current damper in a plane along the axial direction. FIG. 2 is a partially enlarged view of FIG. FIG. 3 is a cross-sectional view in a plane perpendicular to the axial direction of the eddy current damper. FIG. 4 is a partially enlarged view of FIG. FIG. 5 is a perspective view showing a first permanent magnet and a second permanent magnet. FIG. 6 is a schematic view showing a magnetic circuit of the eddy current damper. FIG. 7 is a perspective view showing a first permanent magnet and a second permanent magnet in which the arrangement of magnetic poles is in the circumferential direction. FIG. 8 is a schematic view showing a magnetic circuit of the eddy current damper of FIG. FIG. 9 is a perspective view showing a modification of the arrangement of the first permanent magnet and the second permanent magnet. FIG. 10 is a cross-sectional view in a plane along the axial direction of the eddy current damper of the second embodiment. FIG. 11 is a cross-sectional view in a plane perpendicular to the axial direction of the eddy current damper of the second embodiment. FIG. 12 is a cross-sectional view of a surface of the eddy current damper of the third embodiment along the axial direction. FIG. 13 is a partially enlarged view of FIG. FIG. 14 is a cross-sectional view of a surface of the eddy current damper of the fourth embodiment along the axial direction. FIG. 15 is a cross-sectional view of a surface of the eddy current damper of the fifth embodiment along the axial direction. FIG. 16 is a diagram showing the results of the example. FIG. 17 is a diagram showing the results of the example. FIG. 18 is a diagram showing the results of the example. FIG. 19 is a diagram showing the results of the example.

  The eddy current damper according to the present embodiment includes a screw shaft, a plurality of magnet holding rings, a plurality of first permanent magnets, a plurality of second permanent magnets, a cylindrical conductive member, and a ball nut engaged with the screw shaft. And. The plurality of magnet holding rings are coupled in the axial direction of the screw shaft. The plurality of first permanent magnets are held by each of the plurality of magnet holding rings. The plurality of first permanent magnets are each arranged along the circumferential direction of the magnet holding ring. The plurality of second permanent magnets are held by each of the plurality of magnet holding rings. Each of the plurality of second permanent magnets is disposed between the first permanent magnets, and the arrangement of the first permanent magnet and the magnetic pole is reversed. The conductive member is paired with a plurality of coupled magnet retaining rings. The conductive member is conductive and faces the first permanent magnet and the second permanent magnet with a gap. The ball nut is disposed inside the magnet holding ring and the conductive member and fixed to the magnet holding ring or the conductive member.

  According to the eddy current damper of the present embodiment, when kinetic energy is given to the damper, the screw shaft moves in the axial direction. The axial movement of the screw shaft causes the ball nut to rotate. Thereby, in the magnetic field generated by each of the first and second permanent magnets, the conductive member rotates relative to the first and second permanent magnets. At this time, eddy currents are generated in the regions of the surface of the conductive member facing the respective first and second permanent magnets. Thereby, a braking torque is given to the rotating conductive member, and a damping force is generated.

  In the eddy current damper of the present embodiment, the number of magnet holding rings is selected for each required damping force. Then, a selected number of magnet holding rings are connected. A conductive member of a length corresponding to the total length of the coupled magnet retaining ring is selected. The selected conductive member is assembled. This makes it easy to adjust the damping force. As the number of magnet retaining rings increases, the braking torque that indicates the damping force increases.

  The above-described eddy current damper of the present embodiment can adopt any of the following configurations (1) to (4).

  (1) The magnet holding ring is disposed inside the conductive member. The first permanent magnet and the second permanent magnet are attached to the outer circumferential surface of the magnet holding ring. A ball nut is fixed to the magnet holding ring.

  In this case, the inner circumferential surface of the conductive member faces the first and second permanent magnets with a gap. The axial movement of the screw shaft rotates the ball nut and the magnet holding ring. On the other hand, the conductive member does not rotate. As a result, the magnetic flux passing through the conductive member from the first and second permanent magnets changes, and an eddy current is generated on the inner peripheral surface of the conductive member. A demagnetizing field is generated by this eddy current, and a reaction force (braking torque) is applied to the rotating magnet holding ring. As a result, the screw shaft receives a damping force.

  Also, in this case, the conductive member is disposed on the outside of the magnet holding ring and contacts the outside air. Thereby, the conductive member is cooled by the outside air. As a result, the temperature rise of the conductive member can be suppressed.

  (2) The conductive member is disposed inside the magnet holding ring. The first permanent magnet and the second permanent magnet are attached to the inner circumferential surface of the magnet holding ring. The ball nut is fixed to the conductive member.

  In this case, the outer circumferential surface of the conductive member faces the first and second permanent magnets with a gap. The axial movement of the screw shaft rotates the ball nut and the conductive member. On the other hand, the magnet holding ring does not rotate. As a result, the magnetic flux passing through the conductive member from the first and second permanent magnets changes, and an eddy current is generated on the outer peripheral surface of the conductive member. A demagnetizing field is generated by this eddy current, and a reaction force is given to the rotating conductive member. As a result, the screw shaft receives a damping force.

  Also, in this case, the magnet holding ring is disposed on the outside of the conductive member to be in contact with the outside air. Thereby, the magnet holding ring is cooled by the outside air. As a result, the temperature rise of the first and second permanent magnets can be suppressed.

  (3) The magnet holding ring is disposed inside the conductive member. The first permanent magnet and the second permanent magnet are attached to the outer circumferential surface of the magnet holding ring. The ball nut is fixed to the conductive member.

  In this case, the inner circumferential surface of the conductive member faces the first and second permanent magnets with a gap. The axial movement of the screw shaft rotates the ball nut and the conductive member. On the other hand, the magnet holding ring does not rotate. As a result, the magnetic flux passing through the conductive member from the first and second permanent magnets changes, and an eddy current is generated on the inner peripheral surface of the conductive member. A demagnetizing field is generated by this eddy current, and a reaction force is given to the rotating conductive member. As a result, the screw shaft receives a damping force.

  Also, in this case, the conductive member is disposed on the outside of the magnet holding ring and contacts the outside air. Thus, the rotating conductive member is efficiently cooled by the outside air. As a result, the temperature rise of the conductive member can be suppressed.

  (4) The conductive member is disposed inside the magnet holding ring. The first permanent magnet and the second permanent magnet are attached to the inner circumferential surface of the magnet holding ring. A ball nut is fixed to the magnet holding ring.

  In this case, the outer circumferential surface of the conductive member faces the first and second permanent magnets with a gap. The axial movement of the screw shaft rotates the ball nut and the magnet holding ring. On the other hand, the conductive member does not rotate. As a result, the magnetic flux passing through the conductive member from the first and second permanent magnets changes, and an eddy current is generated on the outer peripheral surface of the conductive member. The eddy current generates a demagnetizing field, and a reaction force is given to the rotating magnet holding ring. As a result, the screw shaft receives a damping force.

  Also, in this case, the magnet holding ring is disposed on the outside of the conductive member to be in contact with the outside air. Thereby, the rotating magnet holding ring is efficiently cooled by the outside air. As a result, the temperature rise of the first and second permanent magnets can be suppressed.

  In a typical example, in the plurality of coupled magnet holding rings, the first permanent magnet is disposed along the axial direction of the screw shaft, and the second permanent magnet is disposed along the axial direction of the screw shaft . In this case, the first permanent magnet is adjacent to only the first permanent magnet in the axial direction of the screw shaft, and the second permanent magnet is adjacent to only the second permanent magnet. That is, permanent magnets of the same polarity are adjacent in the axial direction of the screw shaft. Hereinafter, such arrangement of permanent magnets is also referred to as NN-type arrangement.

  In another typical example, in the plurality of coupled magnet holding rings, the first permanent magnet and the second permanent magnet are alternately arranged along the axial direction of the screw shaft. In this case, the first permanent magnet is adjacent to only the second permanent magnet in the axial direction of the screw shaft, and the second permanent magnet is adjacent to only the first permanent magnet. That is, permanent magnets of different polarity are adjacent in the axial direction of the screw shaft. Hereinafter, such an arrangement of permanent magnets is also referred to as an NS type arrangement.

  However, in the plurality of coupled magnet holding rings, the arrangement form of the first permanent magnet and the second permanent magnet is not limited to the above-described typical example. For example, the first permanent magnet is adjacent to a portion of the first permanent magnet and a portion of the second permanent magnet in the axial direction of the screw shaft, and the second permanent magnet is a portion of the first permanent magnet and the second permanent magnet It may be adjacent to part of

  In the eddy current damper of the present embodiment, the conductive member may include a plurality of conductive rings connected in the axial direction of the screw shaft, and the plurality of conductive rings may be paired with each of the plurality of magnet holding rings. . That is, one magnet holding ring and one conductive ring may be paired. According to such an eddy current damper, the number of magnet holding ring and conductive ring pairs is selected for each required damping force. A selected number of magnet retaining rings are coupled and a selected number of conductive rings are coupled. This makes it easy to adjust the damping force. In this case, it is not necessary to select a conductive member of a length corresponding to the total length of the coupled magnet retaining rings. That is, it is not necessary to prepare a plurality of conductive members having different lengths.

  In the eddy current damper of the present embodiment, the connection method of the plurality of magnet holding rings is not particularly limited. The connection methods include welding, keys, shrink fitting, screws, pins, bolts, press-fits, splines, and the like. When a conductive member consists of a plurality of conductive rings, the connection method of a plurality of conductive rings is not particularly limited. The connection methods include welding, keys, shrink fitting, screws, pins, bolts, press-fits, splines, and the like.

  In the case of the NN-type arrangement, magnetic repulsion acts between the axially adjacent permanent magnets. Therefore, it is preferable to be careful not to shift the magnet holding rings due to magnetic repulsion. In such a situation, the first permanent magnet is adjacent to a portion of the first permanent magnet and a portion of the second permanent magnet in the axial direction of the screw shaft, and the second permanent magnet is a portion of the first permanent magnet The same is true when adjacent to a part of the second permanent magnet. On the other hand, in the case of the NS type arrangement, a magnetic attraction force acts between the axially adjacent permanent magnets. Therefore, the displacement between the magnet holding rings is naturally prevented by the magnetic attraction force.

  Here, in the case of the NN type arrangement, it is preferable that the gap between the permanent magnets axially adjacent to each other (hereinafter, also referred to as “magnet gap”) be small. In this case, as shown in the embodiment described later, if the magnet gap is in the range of 0 to 20 mm, the braking torque increases as the magnet gap decreases, and if the magnet gap exceeds 20 mm, the braking torque becomes almost constant. It is because Therefore, the lower limit of the magnet gap in this case is preferably 0 mm (no gap). The lower limit of the magnet gap may be 5 mm or 10 mm. The upper limit of the magnet gap in this case is not particularly limited. However, if the magnet gap is too large, the entire damper increases in size. Therefore, the upper limit of the magnet gap in this case is preferably 50 mm, more preferably 40 mm, and still more preferably 30 mm.

  On the other hand, in the case of the NS type arrangement, the magnet gap is preferably large. In this case, as shown in the embodiment described later, if the magnet gap is in the range of 0 to 20 mm, the braking torque increases as the magnet gap is larger, and if the magnet gap exceeds 20 mm, the braking torque is almost constant. It is because However, the magnet gap in this case may be 0 mm (no gap). This is because braking torque is generated even if the magnet gap is 0 mm. The lower limit of the magnet gap in this case may be 5 mm or 10 mm. The upper limit of the magnet gap is not particularly limited. However, if the magnet gap is too large, the entire damper increases in size. Therefore, in this case, the upper limit of the magnet gap is preferably 50 mm, more preferably 40 mm, and still more preferably 30 mm.

  Hereinafter, the eddy current damper of the present embodiment will be described with reference to the drawings.

First Embodiment
FIG. 1 is a cross-sectional view of the eddy current damper in a plane along the axial direction. FIG. 2 is a partially enlarged view of FIG. Referring to FIGS. 1 and 2, the eddy current damper 1 includes a plurality of magnet holding rings 2, a plurality of first permanent magnets 3, a plurality of second permanent magnets 4, and a plurality of conductive rings 5. A ball nut 6 and a screw shaft 7 are provided. The plurality of conductive rings 5 are connected. The plurality of conductive rings 5 connected form a cylindrical conductive member. The conductive member is paired with the plurality of magnet holding rings 2. Specifically, each of the plurality of conductive rings 5 is paired with each of the plurality of magnet holding rings 2. Therefore, the number of conductive rings 5 is the same as the number of magnet holding rings 2. In the first embodiment, an example in which the number of pairs of the magnet holding ring 2 and the conductive ring 5 is four is shown.

Magnet holding ring
The plurality of magnet holding rings 2 have a cylindrical shape with the screw shaft 7 as a central axis. The plurality of magnet holding rings 2 are connected in the axial direction of the screw shaft 7. Specifically, substantially cylindrical holders 12 are provided at both axial ends of the plurality of magnet holding rings 2. The plurality of magnet holding rings 2 are sandwiched between the two holders 12 by the plurality of long bolts 13 penetrating the two holders 12. Thereby, the plurality of magnet holding rings 2 are firmly connected. The coupled magnet holding ring 2 is integral with the holder 12.

  The connected magnet holding ring 2 can accommodate the ball nut 6 and the screw shaft 7. The material of the magnet holding ring 2 is not particularly limited. However, the material of the magnet holding ring 2 is preferably steel or the like having high permeability. The material of the magnet holding ring 2 is, for example, a ferromagnetic material such as carbon steel or cast iron. In this case, the magnet holding ring 2 serves as a yoke. That is, the magnetic flux from the first permanent magnet 3 and the second permanent magnet 4 hardly leaks to the outside, and the damping force of the eddy current damper 1 is increased. As described below, the magnet holding ring 2 is rotatable relative to the corresponding conductive ring 5. The plurality of magnet holding rings 2 are the same size and the same material. However, the plurality of magnet holding rings 2 may not be the same size, or may not be the same material.

[First Permanent Magnet and Second Permanent Magnet]
FIG. 3 is a cross-sectional view in a plane perpendicular to the axial direction of the eddy current damper. FIG. 4 is a partially enlarged view of FIG. FIG. 5 is a perspective view showing a first permanent magnet and a second permanent magnet. Referring to FIGS. 3 to 5, the plurality of first permanent magnets 3 and the plurality of second permanent magnets 4 are attached to the outer peripheral surface of each of the plurality of magnet holding rings 2. The first permanent magnet 3 is arranged along the circumferential direction of the magnet holding ring 2 around a screw axis. Similarly, the second permanent magnets 4 are arranged along the circumferential direction of the magnet holding ring 2 around the screw axis. The second permanent magnet 4 is disposed between the first permanent magnets 3. That is, the first permanent magnets 3 and the second permanent magnets 4 are alternately arranged along the circumferential direction of the magnet holding ring 2.

  The magnetic poles of the first permanent magnet 3 and the second permanent magnet 4 are arranged in the radial direction of the magnet holding ring 2. The arrangement of the magnetic poles of the second permanent magnet 4 is opposite to the arrangement of the magnetic poles of the first permanent magnet 3. For example, referring to FIGS. 4 and 5, in the radial direction of magnet holding ring 2, the N pole of first permanent magnet 3 is disposed outside, and the S pole thereof is disposed inside. Therefore, the south pole of the first permanent magnet 3 is in contact with the magnet holding ring 2. On the other hand, in the radial direction of the magnet holding ring 2, the N pole of the second permanent magnet 4 is disposed inside, and the S pole thereof is disposed outside. Therefore, the N pole of the second permanent magnet 4 contacts the magnet holding ring 2.

  Referring to FIG. 5, the arrangement of permanent magnets 3 and 4 of connected magnet holding rings 2 is an NN-type arrangement. Specifically, in the connected magnet holding ring 2, the first permanent magnet 3 is disposed along the axial direction of the screw shaft 7. Similarly, the second permanent magnet 4 is disposed along the axial direction of the screw shaft 7. In this case, the first permanent magnet 3 is adjacent to only the first permanent magnet 3 in the axial direction of the screw shaft 7, and the second permanent magnet 4 is adjacent to only the second permanent magnet 4. That is, permanent magnets 3 and 4 of the same polarity are adjacent in the axial direction of the screw shaft 7.

  The size and the nature of the second permanent magnet 4 are the same as the size and the nature of the first permanent magnet 3. The first permanent magnet 3 and the second permanent magnet 4 are fixed to the magnet holding ring 2 by an adhesive, for example. Of course, not only the adhesive but also the first permanent magnet 3 and the second permanent magnet 4 may be fixed by screws or the like.

[Conductive ring (conductive member)]
Referring to FIGS. 1 and 2, a plurality of conductive rings 5 as conductive members have a cylindrical shape with screw shaft 7 as a central axis. The plurality of conductive rings 5 are connected in the axial direction of the screw shaft 7. Specifically, a substantially cylindrical housing 14 is provided at each of both axial ends of the plurality of conductive rings 5. The plurality of conductive rings 5 are sandwiched between the two housings 14 by the plurality of elongated bolts 15 penetrating the flanges 14 a of the two housings 14. Thereby, the plurality of conductive rings 5 are firmly connected. The connected conductive ring 5 is integral with the housing 14.

  The connected conductive ring 5 can accommodate the connected magnet holding ring 2, the first permanent magnet 3, the second permanent magnet 4, the ball nut 6, and the screw shaft 7. That is, the magnet holding ring 2 is concentrically disposed inside the corresponding conductive ring 5. The inner circumferential surface of the conductive ring 5 faces the first permanent magnet 3 and the second permanent magnet 4 held by the corresponding magnet holding ring 2 with a gap. As described later, in order to generate an eddy current on the surface (inner peripheral surface) of the conductive ring 5, the conductive ring 5 rotates relative to the corresponding magnet holding ring 2. Therefore, a gap is provided between the conductive ring 5 and the first permanent magnet 3 and the second permanent magnet 4. The fixture 8 a is connected to one housing 14 integral with the connected conductive ring 5. The fixture 8a integral with the conductive ring 5 (housing 14) is fixed in the building support surface or in the building. Therefore, the conductive ring 5 does not rotate around the screw shaft 7.

  The conductive ring 5 as a conductive member has conductivity. The material of the conductive ring 5 is, for example, a ferromagnetic material such as carbon steel or cast iron. In addition, the material of the conductive ring 5 may be a weak magnetic material such as a ferritic stainless steel, or a nonmagnetic material such as an aluminum alloy, an austenitic stainless steel, or a copper alloy. A metal layer with high conductivity such as copper, copper alloy or the like may be provided on the surface of the conductive ring 5 opposed to the first and second permanent magnets 3 and 4. Methods of forming a metal layer on the conductive ring 5 include plating, build-up welding, brazing, thermal spraying, thermal diffusion bonding, and the like. The plurality of conductive rings 5 are the same size and the same material. However, the plurality of conductive rings 5 may not be the same size, or may not be the same material.

  A housing 14 integral with the connected conductive ring 5 rotatably supports a holder 12 integral with the connected magnet holding ring 2. For example, referring to FIG. 1, a radial bearing 9 is provided between holder 12 and housing 14 in the radial direction of magnet holding ring 2. Further, a thrust bearing 10 is provided between the holder 12 and the housing 14 in the axial direction of the magnet holding ring 2. The types of the radial bearing 9 and the thrust bearing 10 are not particularly limited, and it is a matter of course that a ball type, a roller type, a sliding type or the like may be used.

[Ball nut]
The ball nut 6 is disposed inside the coupled magnet holding ring 2 and the coupled conductive ring 5. The ball nut 6 is fixed to a holder 12 integral with the coupled magnet holding ring 2. Therefore, when the ball nut 6 rotates, the coupled magnet holding ring 2 also rotates. The type of ball nut 6 is not particularly limited. The ball nut 6 may use a well-known ball nut. A threaded portion is formed on the inner circumferential surface of the ball nut 6.

[Screw shaft]
The screw shaft 7 penetrates the ball nut 6 and engages with the ball nut 6 through the ball. On the outer peripheral surface of the screw shaft 7, a screw portion corresponding to the screw portion of the ball nut 6 is formed. The screw shaft 7 and the ball nut 6 constitute a ball screw. The ball screw converts the axial movement of the screw shaft 7 into the rotational movement of the ball nut 6. The fixture 8 b is connected to the screw shaft 7. The fixture 8b integral with the screw shaft 7 is fixed in the building support surface or in the building. In the case where the eddy current damper 1 is installed, for example, in the seismic isolation layer between the inside of the building and the building support surface, the fixture 8b integral with the screw shaft 7 is fixed in the building, and the conductive ring 5 The fixture 8a integral with 14) is fixed to the building support surface. In the case where the eddy current damper 1 is installed, for example, in any layer in a building, the fixture 8b integral with the screw shaft 7 is fixed to the upper beam side of any layer and integrated with the conductive ring 5 The fixture 8a is fixed to the lower beam side between arbitrary layers. Therefore, the screw shaft 7 does not rotate around the axis.

  Fixation of the fixture 8b integral with the screw shaft 7 and the fixture 8a integral with the conductive ring 5 may be reversed to the above description. That is, the fixture 8b integral with the screw shaft 7 may be fixed to the building support surface, and the fixture 8a integral with the conductive ring 5 may be fixed inside the building.

  The screw shaft 7 can be advanced and retracted along the axial direction inside the coupled magnet holding ring 2 and the coupled conductive ring 5. Therefore, when kinetic energy is given to the eddy current damper 1 by vibration or the like, the screw shaft 7 moves in the axial direction. When the screw shaft 7 moves in the axial direction, the ball nut 6 rotates about the screw shaft by the action of the ball screw. As the ball nut 6 rotates, the plurality of coupled magnet holding rings 2 rotate. As a result, since the first permanent magnet 3 and the second permanent magnet 4 integral with the magnet holding ring 2 rotate relative to the corresponding conductive ring 5, an eddy current is generated in each of the conductive rings 5. As a result, a damping force is generated in the eddy current damper 1 to damp the vibration.

  In the eddy current damper 1 of the present embodiment, the number of pairs of the magnet holding ring 2 and the conductive ring 5 is selected for each required damping force. Then, the selected number of magnet holding rings 2 are connected, and the selected number of conductive rings 5 are connected. This makes it easy to adjust the damping force.

  Subsequently, the generation principle of the eddy current and the generation principle of the damping force by the eddy current will be described.

[Attenuation force due to eddy current]
FIG. 6 is a schematic view showing a magnetic circuit of the eddy current damper. Referring to FIG. 6, in each of the magnet holding rings 2, the arrangement of the magnetic poles of the first permanent magnet 3 is opposite to the arrangement of the magnetic poles of the adjacent second permanent magnets 4 in the circumferential direction. Therefore, in each of the magnet holding rings 2, the magnetic flux emitted from the N pole of the first permanent magnet 3 reaches the S pole of the adjacent second permanent magnet 4. The magnetic flux emitted from the N pole of the second permanent magnet 4 reaches the S pole of the adjacent first permanent magnet 3. Thus, a magnetic circuit is formed among the first permanent magnet 3, the second permanent magnet 4, the conductive ring 5 and the magnet holding ring 2. Since the gap between the first and second permanent magnets 3 and 4 and the conductive ring 5 is sufficiently small, the corresponding conductive ring 5 is in the magnetic field.

  When the magnet holding ring 2 rotates (see the arrow in FIG. 6), the first permanent magnet 3 and the second permanent magnet 4 move relative to the conductive ring 5. Therefore, the magnetic flux passing through the surface of the conductive ring 5 (in FIG. 6, the inner peripheral surface of the conductive ring 5 opposed to the first permanent magnet 3 and the second permanent magnet 4) changes. As a result, an eddy current is generated on the surface of the conductive ring 5 (the inner peripheral surface of the conductive ring 5 in FIG. 6). When an eddy current is generated, a new magnetic flux (demagnetizing field) is generated. The new magnetic flux prevents relative rotation between the magnet holding ring 2 (the first permanent magnet 3 and the second permanent magnet 4) and the conductive ring 5. In the case of this embodiment, the rotation of the magnet holding ring 2 is hindered. If rotation of the magnet holding ring 2 is prevented, rotation of the ball nut 6 integral with the magnet holding ring 2 is also prevented. If the rotation of the ball nut 6 is blocked, the axial movement of the screw shaft 7 is also blocked. This is the damping force (damping torque) of the eddy current damper 1. Eddy current generated by kinetic energy due to vibration or the like raises the temperature of the conductive member. That is, kinetic energy given to the eddy current damper is converted to thermal energy to obtain a damping force.

  According to the eddy current damper of the present embodiment, the arrangement of the magnetic poles of the first permanent magnet is reversed to the arrangement of the magnetic poles of the second permanent magnet adjacent to the first permanent magnet in the circumferential direction of the magnet holding ring . Therefore, a magnetic field due to the first permanent magnet and the second permanent magnet is generated in the circumferential direction of the magnet holding ring. Further, by arranging a plurality of first permanent magnets and second permanent magnets in the circumferential direction of the magnet holding ring, the amount of magnetic flux reaching the conductive ring is increased. As a result, the eddy current generated in the conductive ring increases and the damping force of the eddy current damper increases.

[Modification of arrangement of magnetic poles of permanent magnets for each of magnet holding rings]
In the above description, in each of the magnet holding rings, the magnetic poles of the first permanent magnet and the second permanent magnet are arranged in the radial direction of the magnet holding ring. However, the arrangement of the magnetic poles of the first permanent magnet and the second permanent magnet is not limited to this.

  FIG. 7 is a perspective view showing a first permanent magnet and a second permanent magnet in which the arrangement of magnetic poles is in the circumferential direction. Referring to FIG. 7, in each of the magnet holding rings 2, the arrangement of the magnetic poles of the first permanent magnet 3 and the second permanent magnet 4 is along the circumferential direction of the magnet holding ring 2. Even in this case, the arrangement of the magnetic poles of the first permanent magnet 3 is opposite to the arrangement of the magnetic poles of the second permanent magnet 4. A ferromagnetic pole piece 11 is provided between the first permanent magnet 3 and the second permanent magnet 4.

  FIG. 8 is a schematic view showing a magnetic circuit of the eddy current damper of FIG. Referring to FIG. 8, in each of magnet holding rings 2, the magnetic flux emitted from the N pole of first permanent magnet 3 passes through pole piece 11 to reach the S pole of first permanent magnet 3. The same applies to the second permanent magnet 4. Thereby, a magnetic circuit is formed among the first permanent magnet 3, the second permanent magnet 4, the pole piece 11 and the conductive ring 5. Thus, the damping force is obtained in the eddy current damper 1 as described above.

[Modification of arrangement of permanent magnets between coupled magnet holding rings]
In the above description, in the arrangement of the first permanent magnet and the second permanent magnet of the coupled magnet holding rings, the first permanent magnet is disposed along the axial direction of the screw shaft, and the second permanent magnet is the screw shaft. The case where it arrange | positions along an axial direction was demonstrated. However, the arrangement of the first permanent magnet and the second permanent magnet is not limited to such an NN-type arrangement.

  FIG. 9 is a perspective view showing a modification of the arrangement of the first permanent magnet and the second permanent magnet. Referring to FIG. 9, the arrangement of permanent magnets 3 and 4 of connected magnet holding rings 2 is an NS type arrangement. Specifically, in the coupled magnet holding ring 2, the first permanent magnets 3 and the second permanent magnets 4 are alternately arranged along the axial direction of the screw shaft 7. In this case, the first permanent magnet 3 is adjacent to only the second permanent magnet 4 in the axial direction of the screw shaft 7, and the second permanent magnet 4 is adjacent to only the first permanent magnet 3. That is, the permanent magnets 3 and 4 of different poles are adjacent in the axial direction of the screw shaft 7.

  As shown in the embodiment described later, in the case of the NN type arrangement, the braking torque is significantly increased as the magnet clearance is smaller if the magnet clearance is in the range of 0 to 10 mm. When the rotational speed of the first and second permanent magnets 3 and 4 (the magnet holding ring 2) relative to the conductive ring 5, that is, the rotational speed of the ball nut is high (eg 750 rpm), the axially adjacent permanent magnets 3 The braking torque in the NN-type arrangement is larger than the braking torque in the NS-type arrangement if the gap between the four members (magnet gap) is in the range of 0 to 7.5 mm. In this case, if the magnet gap is in the range of 10 to 40 mm, the braking torque in the NS type arrangement is larger than the braking torque in the NN type arrangement. Here, when the magnet gap is 0 mm, the braking torque in the NN type arrangement is maximum. When the magnet gap is 30 mm, the braking torque in the NS type arrangement is maximum.

  When the rotational speed of the ball nut is low (e.g. 250 rpm), the braking torque in the NN type arrangement is larger than the braking torque in the NS type arrangement if the magnet gap is in the range of 0 to 40 mm.

  Therefore, the arrangement of permanent magnets in the axial direction (example: NN-type arrangement, NS-type arrangement) and magnets according to the assumed rotational speed of the ball nut and the damping force (braking torque) required by the rotational speed The gap may be selected as appropriate. For example, in the case of adopting the NN type arrangement, the magnet gap is preferably 0 to 10 mm. It is because the improvement of damping force can be realized. The upper limit of the magnet gap in that case is preferably 7.5 mm, more preferably 5 mm.

[One Example of Coupling Method of Magnet Holding Ring]
As described above, in the case of the NS type arrangement, connection of the magnet holding ring can be easily performed by utilizing the magnetic attraction force acting on the permanent magnet of the different polarity.

  In the case of the NN type arrangement, the connection of the magnet holding ring can be performed by utilizing the magnetic attraction force acting on the permanent magnet of the different polarity and the magnetic repulsion force acting on the permanent magnet of the same polarity. For example, a plurality of keys are provided at equal intervals around the axis of the magnet holding ring at the end of one of the two magnet holding rings to be connected. The key protrudes in the axial direction of the magnet holding ring, and the tip of the key is bent outward in the radial direction of the magnet holding ring. At the end of the other magnet holding ring, a plurality of key grooves respectively corresponding to the plurality of keys are provided. The key groove is formed in a bowl shape on the inner circumferential surface of the magnet holding ring. The key groove has a start area extending along the axial direction of the magnet holding ring, an intermediate area extending along the circumferential direction, and a terminal area extending along the axial direction.

  In the connection operation, first, the end of one magnet holding ring is made to face the end of the other magnet holding ring. That is, the tip of the key is aligned with the beginning of the key groove, and the tip of the key is inserted into the beginning of the key groove. At the time of this insertion, the permanent magnets provided in the two magnet holding rings to be connected are arranged in mutually different poles in the axial direction. Therefore, the tip of the key is naturally inserted along the start end area of the key groove by the magnetic attraction force. Next, one of the magnet holding rings is rotated about the axis with respect to the other magnet holding ring. That is, the tip of the key is moved along the middle region of the key groove. When the permanent magnets are arranged axially in the same pole in the same axial direction as the rotation is performed, the rotational force is released. Thereby, the magnetic repulsion causes the tip of the key to move along the end region of the key groove and to stop at the end of the key groove. Then, a pin is driven into the boundary between the middle area and the end area of the key groove. This prevents the tip of the key from coming off the keyway. In this way, it is possible to connect the magnet retaining rings of the NN arrangement.

  In the first embodiment described above, the case where the magnet holding ring is disposed inside the conductive ring, the first permanent magnet and the second permanent magnet are attached to the outer circumferential surface of the magnet holding ring, and the magnet holding ring rotates further did. However, the eddy current damper of the present embodiment is not limited to this.

Second Embodiment
In the eddy current damper of the second embodiment, the magnet holding ring is disposed outside the conductive ring and does not rotate. Eddy current is generated by rotation of the inner conductive ring.

  FIG. 10 is a cross-sectional view in a plane along the axial direction of the eddy current damper of the second embodiment. FIG. 11 is a cross-sectional view in a plane perpendicular to the axial direction of the eddy current damper of the second embodiment. Referring to FIGS. 10 and 11, the plurality of coupled magnet holding rings 2 can accommodate the plurality of coupled conductive rings 5, the ball nut 6, and the screw shaft 7. The first permanent magnet 3 and the second permanent magnet 4 are attached to the inner circumferential surface of each of the plurality of magnet holding rings 2. Therefore, the outer circumferential surface of the conductive ring 5 faces the first permanent magnet 3 and the second permanent magnet 4 held by the corresponding magnet holding ring 2 with a gap.

  In the second embodiment, the plurality of magnet holding rings 2 are sandwiched between the two housings 14. Thereby, the plurality of magnet holding rings 2 are connected. The coupled magnet holding ring 2 is integral with the housing 14. The plurality of conductive rings 5 are sandwiched between the two holders 12. Thereby, the plurality of conductive rings 5 are connected. The connected conductive ring 5 is integral with the holder 12.

  The fixture 8 a shown in FIG. 1 is connected to one housing 14 integral with the coupled magnet holding ring 2. Therefore, the magnet holding ring 2 does not rotate around the screw shaft 7. On the other hand, the ball nut 6 is connected to the holder 12 integral with the connected conductive ring 5. Therefore, when the ball nut 6 rotates, the connected conductive ring 5 rotates. Even in such a configuration, as described above, since the first permanent magnet 3 and the second permanent magnet 4 integral with the magnet holding ring 2 rotate relative to the corresponding conductive ring 5, An eddy current is generated in each. As a result, a damping force is generated in the eddy current damper 1 to damp the vibration.

Third Embodiment
In the eddy current damper of the third embodiment, the magnet holding ring is disposed inside the conductive ring and does not rotate. Eddy current is generated as the outer conductive ring rotates.

  FIG. 12 is a cross-sectional view of a surface of the eddy current damper of the third embodiment along the axial direction. FIG. 13 is a partially enlarged view of FIG. Referring to FIGS. 12 and 13, the plurality of connected conductive rings 5 can receive the plurality of connected magnet holding rings 2, the ball nut 6, and the screw shaft 7. The first permanent magnet 3 and the second permanent magnet 4 are attached to the outer peripheral surface of each of the plurality of magnet holding rings 2. Accordingly, the inner circumferential surface of the conductive ring 5 faces the corresponding magnet holding ring 2 with a gap between the first permanent magnet 3 and the second permanent magnet 4.

  In the third embodiment, the plurality of magnet holding rings 2 are sandwiched between two holders 12. Thereby, the plurality of magnet holding rings 2 are connected. The coupled magnet holding ring 2 is integral with the holder 12. The plurality of conductive rings 5 are sandwiched between the two housings 14. Thereby, the plurality of conductive rings 5 are connected. The connected conductive ring 5 is integral with the housing 14.

  The fixture 8 a is connected to one holder 12 integral with the coupled magnet holding ring 2. Therefore, the magnet holding ring 2 does not rotate around the screw shaft 7. On the other hand, the ball nut 6 is connected to the housing 14 integral with the connected conductive ring 5. Therefore, when the ball nut 6 rotates, the connected conductive ring 5 rotates. Even in such a configuration, as described above, since the first permanent magnet 3 and the second permanent magnet 4 integral with the magnet holding ring 2 rotate relative to the corresponding conductive ring 5, An eddy current is generated in each. As a result, a damping force is generated in the eddy current damper 1 to damp the vibration.

Fourth Embodiment
In the eddy current damper of the fourth embodiment, the conductive ring is disposed inside the magnet holding ring and does not rotate. Eddy current is generated as the outer magnet holding ring rotates.

  FIG. 14 is a cross-sectional view of a surface of the eddy current damper of the fourth embodiment along the axial direction. Referring to FIG. 14, the plurality of coupled magnet holding rings 2 can accommodate the plurality of coupled conductive rings 5, the ball nut 6, and the screw shaft 7. The first permanent magnet 3 and the second permanent magnet 4 are attached to the inner circumferential surface of each of the plurality of magnet holding rings 2. Therefore, the outer circumferential surface of the conductive ring 5 faces the first permanent magnet 3 and the second permanent magnet 4 held by the corresponding magnet holding ring 2 with a gap.

  In the fourth embodiment, the plurality of magnet holding rings 2 are sandwiched between two housings 14. Thereby, the plurality of magnet holding rings 2 are connected. The coupled magnet holding ring 2 is integral with the housing 14. The plurality of conductive rings 5 are sandwiched between the two holders 12. Thereby, the plurality of conductive rings 5 are connected. The connected conductive ring 5 is integral with the holder 12.

  The fixture 8 a shown in FIG. 1 is connected to one holder 12 integral with the connected conductive ring 5. Therefore, the conductive ring 5 does not rotate around the screw shaft 7. On the other hand, the ball nut 6 is fixed to the housing 14 integral with the coupled magnet holding ring 2. Therefore, when the ball nut 6 rotates, the coupled magnet holding ring 2 rotates. Even in such a configuration, as described above, since the first permanent magnet 3 and the second permanent magnet 4 integral with the magnet holding ring 2 rotate relative to the corresponding conductive ring 5, An eddy current is generated in each. As a result, a damping force is generated in the eddy current damper 1 to damp the vibration.

  As described above, when the eddy current damper generates a damping force, the temperature of the conductive ring rises. The first permanent magnet and the second permanent magnet face the conductive ring. Therefore, the temperature may rise due to the radiant heat from the conductive ring for the first permanent magnet and the second permanent magnet. If the temperature of the permanent magnet is increased, the magnetic force may be reduced.

  In the eddy current damper of the first embodiment, the conductive ring 5 is disposed outside the magnet holding ring 2. That is, the conductive ring 5 is disposed at the outermost side to be in contact with the outside air. Thus, the conductive ring 5 is cooled by the outside air. Therefore, the temperature rise of the conductive ring 5 can be suppressed. As a result, the temperature rise of the first permanent magnet 3 and the second permanent magnet 4 can be suppressed.

  In the eddy current damper of the second embodiment, the magnet holding ring 2 is disposed outside the conductive ring 5. That is, the magnet holding ring 2 is disposed at the outermost side to be in contact with the outside air. Thereby, the magnet holding ring 2 is cooled by the outside air. Therefore, the first permanent magnet 3 and the second permanent magnet 4 can be cooled through the magnet holding ring 2. As a result, the temperature rise of the first permanent magnet 3 and the second permanent magnet 4 can be suppressed.

  In the eddy current damper of the third embodiment, the conductive ring 5 is disposed outside the magnet holding ring 2. That is, the conductive ring 5 is disposed at the outermost side to be in contact with the outside air. In addition, the conductive ring 5 rotates around the screw shaft 7. Thus, the rotating conductive ring 5 is efficiently cooled by the outside air. Therefore, the temperature rise of the conductive ring 5 can be suppressed. As a result, the temperature rise of the first permanent magnet 3 and the second permanent magnet 4 can be suppressed.

  In the eddy current damper of the fourth embodiment, the magnet holding ring 2 is disposed outside the conductive ring 5. That is, the magnet holding ring 2 is disposed at the outermost side to be in contact with the outside air. In addition, the magnet holding ring 2 rotates around the screw shaft 7. Thereby, the rotating magnet holding ring 2 is efficiently cooled by the outside air. Therefore, the first permanent magnet 3 and the second permanent magnet 4 can be cooled through the magnet holding ring 2. As a result, the temperature rise of the first permanent magnet 3 and the second permanent magnet 4 can be suppressed.

Fifth Embodiment
The eddy current damper of the fifth embodiment is a modification of the eddy current damper of the first embodiment described above.

  FIG. 15 is a cross-sectional view of a surface of the eddy current damper of the fifth embodiment along the axial direction. Referring to FIG. 15, the eddy current damper 1 of the present embodiment includes one cylindrical conductive member 5A instead of the plurality of conductive rings connected in the first embodiment. The characteristics of the conductive member 5A are the same as the characteristics of the conductive ring described above.

  According to the eddy current damper 1 of the present embodiment, the number of the magnet holding rings 2 is selected for each required damping force. Then, the selected number of magnet holding rings 2 are connected. A conductive member 5A of a length corresponding to the total length of the coupled magnet holding ring 2 is selected. The selected conductive member 5A is assembled. This makes it easy to adjust the damping force.

  The conductive member 5A of the fifth embodiment can also be applied instead of the plurality of conductive rings connected in the second to fourth embodiments.

  In order to confirm the performance of the eddy current damper of the present embodiment, the braking torque was investigated by numerical analysis for the eddy current damper of the first embodiment described above. As an analysis model, a model of NN type arrangement and a model of NS type arrangement were adopted.

  In each model, the number of magnet holding ring and conductive ring pairs was two. The number of permanent magnets included in each of the magnet holding rings was 30. The material of the magnet holding ring was SS400 (rolled steel material for general structure specified in JIS G 3101), and a copper layer was formed on the inner circumferential surface of the conductive ring facing the permanent magnet. The electrical resistivity of the magnet holding ring was 15.9 μΩ · cm, and the electrical resistivity of the copper layer was 1.55 μΩ · cm. In the analysis using each model, the gap between adjacent permanent magnets in the axial direction (magnet gap) was changed. Furthermore, in the analysis using each model, the relative rotation number of the magnet holding ring (permanent magnet) to the conductive ring, that is, the rotation number of the ball nut was changed. The braking torque generated was investigated for each magnet gap and rotation speed.

  16-19 is a figure which shows the result of an Example. Of these figures, FIG. 16 shows the results when the rotational speed is 100 rpm. FIG. 17 shows the results when the rotational speed is 250 rpm. FIG. 18 shows the results when the rotational speed is 500 rpm. FIG. 19 shows the results when the rotational speed is 750 rpm.

  From the results shown in FIGS. 16 to 19, the following is shown. In the case of the NN type arrangement, when the magnet gap is in the range of 0 to 10 mm, the braking torque is significantly increased as the magnet gap is smaller. Referring to FIG. 19, when the rotational speed is as high as 750 rpm, the braking torque in the NN-type arrangement is larger than the braking torque in the NS-type arrangement if the magnet gap is in the range of 0 to 7.5 mm. In this case, if the magnet gap is in the range of 10 to 40 mm, the braking torque in the NS type arrangement is larger than the braking torque in the NN type arrangement. When the magnet gap was 0 mm, the braking torque in the NN type arrangement became maximum. When the magnet gap was 30 mm, the braking torque in the NS type arrangement became maximum.

  Referring to FIGS. 16 and 17, when the rotational speed is as low as 100 rpm and 250 rpm, the braking torque in the NN-type arrangement is the braking torque in the NS-type arrangement if the magnet gap is in the range of 0 to 40 mm. It was bigger than.

  The eddy current damper of the present embodiment has been described above. Since the eddy current is generated by a change in magnetic flux passing through the conductive ring 5 (conductive member 5A), the first permanent magnet 3 and the second permanent magnet 4 may rotate relative to the conductive ring 5. Further, as long as the conductive ring 5 is present in the magnetic field generated by the first permanent magnet 3 and the second permanent magnet 4, the positional relationship between the conductive ring 5 and the magnet holding ring 2 is not particularly limited.

  In addition, it goes without saying that the present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention.

  INDUSTRIAL APPLICABILITY The eddy current damper of the present invention is useful as a seismic control device and seismic isolation device for a building.

1: Eddy current type damper 2: Magnet holding ring 3: First permanent magnet 4: Second permanent magnet 5: Conductive ring 5A: Conductive member 6: Ball nut 7: Screw shaft 8a, 8b: Fitting 9: Radial bearing 10 : Thrust bearing 11: pole piece 12: holder 13: bolt 14: housing 14 a: flange 15: bolt

Claims (4)

Screw shaft,
A plurality of magnet holding rings axially connected to the screw shaft;
A plurality of first permanent magnets held by each of the plurality of magnet holding rings, each of the plurality of first permanent magnets being arranged along a circumferential direction of the magnet holding ring;
A plurality of second permanent magnets held by each of the plurality of magnet holding rings, each being disposed between the first permanent magnets, and in which the arrangement of the first permanent magnet and the magnetic pole is reversed Of the second permanent magnet,
A cylindrical conductive member paired with the plurality of coupled magnet holding rings, the conductive member having conductivity and facing the first permanent magnet and the second permanent magnet with a gap therebetween;
An eddy current damper, comprising: a ball nut disposed inside the magnet holding ring and the conductive member, fixed to the magnet holding ring or the conductive member, and meshed with the screw shaft. An eddy current damper according to claim 1, wherein
In the plurality of coupled magnet holding rings, the first permanent magnet is disposed along the axial direction of the screw shaft, and the second permanent magnet is disposed along the axial direction of the screw shaft. Eddy current damper. An eddy current damper according to claim 1, wherein
The eddy current damper according to any one of the plurality of coupled magnet holding rings, wherein the first permanent magnet and the second permanent magnet are alternately arranged along the axial direction of the screw shaft. An eddy current damper according to any one of claims 1 to 3, wherein
The eddy current damper, wherein the conductive member comprises a plurality of conductive rings connected in the axial direction of the screw shaft, and the plurality of conductive rings are paired with the plurality of magnet holding rings.

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