TW202028632A - Eddy-current type damper - Google Patents

Abstract

An eddy-current type damper (1) includes: a cylindrical magnet holding member (5); a plurality of permanent magnets (6); a cylindrical conductive member (4); a screw shaft (2); a ball nut (3); and a connection mechanism (7). The permanent magnets (6) are fixed to the magnet holding member (5), and are disposed so as to be spaced apart from each other along the circumferential direction of the magnet holding member (5) and to be alternately reversed in magnetic pole arrangement along the circumferential direction. The conductive member (4) faces the permanent magnets (6) with a gap therebetween in the radial direction of the magnet holding member (5). The screw shaft (2) can reciprocate along the center axis direction of the magnet holding member (5). The ball nut (3) is engaged with the screw shaft (2), and movement of the screw shaft (2) causes relative rotation of the permanent magnets (6) and the conductive member (4). The connection mechanism (7) causes connection between the magnet holding member (5) and the conductive member (4) and causes the magnet holding member (5) and the conductive member (4) to rotate in opposite directions.

Description

Eddy current damper

The present invention relates to an eddy current type damper.

In order to protect the building from vibrations such as earthquakes, a vibration damping device is installed in the building. The vibration damping device converts the kinetic energy applied to the building into other energy such as heat energy, thereby suppressing the shaking of the building. As such a vibration damping device, an eddy current type damper is known.

The eddy current type damper is disclosed in, for example, 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 material connected to a screw shaft, a ball nut engaged with the screw shaft, and an auxiliary cylinder connected to the ball nut. The arrangement of the magnetic poles of a plurality of permanent magnets is mutually different. The hysteresis material is opposed to a plurality of permanent magnets and can rotate relatively. If kinetic energy is applied to the eddy current damper, the auxiliary cylinder and the ball nut will reciprocate in the axial direction, and the hysteresis material will be rotated by the action of the ball screw. In this way, hysteresis loss is generated and exercise energy is consumed. In addition, since the eddy current is generated in the hysteresis material, the kinetic energy is consumed due to the eddy current loss, and the damping force is obtained. These are described in Patent Document 1.

However, in the eddy current damper of Patent Document 1, the rotation direction of the hysteresis material is switched at the end of the reciprocating movement range of the ball nut. Therefore, as the ball nut approaches the end of the reciprocating movement range, the rotation speed of the hysteresis material will decrease, and the intensity of the generated eddy current will become weaker. In other words, the eddy current damper of Patent Document 1 cannot avoid the reduction of the damping force of the eddy current in the vicinity of the end of the reciprocating movement range of the ball nut due to its structure.

On the other hand, as a damper installed in a building, a fluid damper using a viscous fluid is known in addition to an eddy current damper. In the fluid damper, the piston reciprocates to obtain the damping force, so the damping force is reduced near the end of the reciprocating movement range of the piston.

A technique to improve the problem of the reduction of the damping force near the end of the reciprocating movement range of the fluid damper is disclosed in International Publication No. 2007/091399 (Patent Document 2).

In the fluid damper of Patent Document 2, a magnetic fluid is enclosed in a hydraulic cylinder, and the piston rod is composed of a magnetic part and a non-magnetic part. In the case where the piston rod is located near the center of the reciprocating movement range, the damping force is obtained by the viscous resistance of the magnetic fluid as in a normal fluid damper. On the other hand, if the piston rod approaches the end of the reciprocating range, the magnetic part of the piston rod approaches the magnetic field generating device (magnet, etc.), thereby forming a magnetic circuit. The magnetic field of the magnetic circuit increases the viscous resistance of the magnetic fluid, so that the damping force near the end of the reciprocating movement range can be increased. These are described in Patent Document 2. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Publication No. 5-86496 [Patent Document 2] International Publication No. 2007/091399

[The problem to be solved by the invention]

However, the technology of Patent Document 2 is related to a fluid type damper, and is fundamentally different in structure from an eddy current type damper. Therefore, it is difficult to adopt the technique of Patent Document 2 to an eddy current type damper.

The object of the present invention is to provide an eddy current type damper that improves the damping force near the end of the reciprocating movement range of a screw shaft. [Technical means to solve the problem]

The eddy current damper according to the embodiment of the present invention includes a cylindrical magnet holding member, a plurality of permanent magnets, a cylindrical conductive member, a screw shaft, a ball nut, and a coupling mechanism. A plurality of permanent magnets are fixed to the magnet holding member. The plurality of permanent magnets are arranged with a gap therebetween along the circumferential direction of the magnet holding member. A plurality of permanent magnets alternately reverse the arrangement of magnetic poles along the circumferential direction. The conductive member faces the plurality of permanent magnets with gaps in the radial direction of the magnet holding member. The screw shaft can reciprocate along the central axis of the magnet holding member. The ball nut is engaged with the threaded shaft, and the threaded shaft is moved to make the plurality of permanent magnets and the conductive member relatively rotate. The connecting mechanism connects the magnet holding member and the conductive member so that the magnet holding member and the conductive member rotate in opposite directions to each other. [Effects of Invention]

According to the eddy current damper of the present invention, the damping force near the end of the reciprocating movement range of the threaded shaft can be increased.

The eddy current damper of this embodiment includes a cylindrical magnet holding member, a plurality of permanent magnets, a cylindrical conductive member, a screw shaft, a ball nut, and a coupling mechanism. A plurality of permanent magnets are fixed to the magnet holding member. The plurality of permanent magnets are arranged with a gap therebetween along the circumferential direction of the magnet holding member. A plurality of permanent magnets alternately reverse the arrangement of magnetic poles along the circumferential direction. The conductive member faces the plurality of permanent magnets with gaps in the radial direction of the magnet holding member. The screw shaft can reciprocate along the central axis of the magnet holding member. The ball nut is engaged with the threaded shaft, and the threaded shaft is moved to make the plurality of permanent magnets and the conductive member relatively rotate. The connecting mechanism connects the magnet holding member and the conductive member so that the magnet holding member and the conductive member rotate in opposite directions to each other.

According to the eddy current type damper constructed in this way, if vibration is applied to the eddy current type damper and the screw shaft is displaced in the axial direction, the ball nut rotates. The rotation of the ball nut rotates the magnet holding member (or the conductive member), so that the permanent magnet and the conductive member are relatively rotated. In addition, due to the function of the connecting mechanism, the rotation direction of the conductive member (or magnet holding member) and the magnet holding member (or conductive member) is reversed. Thereby, the relative speed difference between the permanent magnet and the conductive member can be increased, and the damping force of the eddy current can be increased.

In addition, since the magnet holding member and the conductive member rotate with acceleration, the magnet holding member and the conductive member each generate inertial force. When the rotation direction of the magnet holding member and the conductive member is reversed, that is, when the threaded shaft is at the end of the reciprocating movement range, its inertial force becomes the maximum, which is transmitted to the threaded shaft through the connecting mechanism and the ball nut, and acts as a resistance thread The resistance of the movement of the axis to operate. In the eddy current damper of this embodiment, since both the magnet holding member and the conductive member rotate, the inertial force is larger than that of the eddy current damper in which either the magnet holding member and the conductive member rotate. Therefore, in the eddy current damper of the present embodiment, when the threaded shaft is located near the end of the reciprocating movement range, a resistive force due to inertial force greater than before can act. As a result, the resistance force to the movement of the screw shaft can be increased near the end of the reciprocating movement range of the screw shaft.

The above-mentioned eddy current type damper is preferably configured as follows. The coupling mechanism includes a first gear fixed to the magnet holding member, a second gear fixed to the conductive member, and a pinion gear that meshes with the first gear and the second gear.

Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. The same symbols are attached to the same or equivalent parts in the figures and the description is not repeated.

[First Embodiment] Fig. 1 is a cross-sectional view of the eddy current type damper of the first embodiment along the axial direction. The eddy current damper 1 includes a magnet holding member 5, a plurality of permanent magnets 6, a conductive member 4, a screw shaft 2, a ball nut 3, and a connecting mechanism 7. In addition, the "axial direction" in this specification represents the central axis direction of the threaded shaft 2, and the central axis of the threaded shaft 2 coincides with the central axis of the magnet holding member 5 and the conductive member 4. In addition, the “radial direction” in this specification means the radial direction of the magnet holding member 5 and the conductive member 4. The “circumferential direction” in this specification represents the circumferential direction of the magnet holding member 5 and the conductive member 4.

[Magnet holding member] Figure 2 is an enlarged view of a part of Figure 1. The magnet holding member 5 has a cylindrical shape including an inner peripheral surface and an outer peripheral surface. A part of the screw shaft 2 and a part of the ball nut 3 are housed inside the inner peripheral surface. A plurality of permanent magnets 6 are fixed to the outer peripheral surface. In other words, the magnet holding member 5 holds a plurality of permanent magnets 6. In order to prevent the magnetic flux from the permanent magnet 6 from leaking to the outside, the material of the magnet holding member 5 is preferably a magnetic body such as carbon steel or cast iron. In this case, the magnet holding member 5 functions as a yoke.

One end part of the magnet holding member 5 is fixed to the flange part of the ball nut 3 through the 1st gear 7A mentioned later. Then, if the ball nut 3 rotates, the magnet holding member 5 also rotates accompanying this. The other end of the magnet holding member 5 becomes a free end and is supported by the housing 8 through the thrust bearing 24.

[permanent magnet] Fig. 3 is a sectional view taken along the line III-III in Fig. 1. In FIG. 3, only the magnet holding member 5, the plurality of permanent magnets 6, and the conductive member 4 are shown, and the illustration of other structures is omitted. The plural permanent magnets 6 are fixed to the outer peripheral surface of the magnet holding member 5. The plurality of permanent magnets 6 are arranged in the circumferential direction of the magnet holding member 5, and a gap is provided between two permanent magnets 6 adjacent to each other.

Fig. 4 is an enlarged view of a part of Fig. 3. The plurality of permanent magnets 6 face the inner circumferential surface of the conductive member 4 with a gap in the radial direction. The size of the gap is as small as possible in order for the magnetic flux from the permanent magnet 6 to reach the conductive member 4 efficiently. In addition, the distance between each permanent magnet 6 and the inner peripheral surface of the conductive member 4 is preferably fixed.

The plural permanent magnets 6 are arranged by alternately inverting the arrangement of magnetic poles along the circumferential direction of the magnet holding member 5. In other words, the permanent magnets 6 adjacent to each other in the circumferential direction of the magnet holding member 5 alternately reverse the arrangement of the magnetic poles. In addition, in FIG. 4, although the arrangement of the magnetic poles of the permanent magnet 6 is in the radial direction of the conductive member 4, the arrangement of the magnetic poles is not limited to this. For example, the magnetic poles of the permanent magnet 6 may be arranged in the axial direction of the magnet holding member 5 (that is, the axial direction of the screw shaft).

[Conductive member] 1, the conductive member 4 has a cylindrical shape. Inside the conductive member 4 (the inner space of the cylinder), a part of the screw shaft 2, a part of the ball nut 3, the magnet holding member 5 and the permanent magnet 6 are housed. That is, the conductive member 4 is arranged outside the magnet holding member 5. From another point of view, the conductive member 4 is arranged concentrically with the magnet holding member 5. The conductive member 4 surrounds the magnet holding member 5. Since the eddy current is generated by the magnetic field formed by the permanent magnet 6, the material of the conductive member 4 is a conductive material such as steel.

2, one end of the conductive member 4 becomes a free end, and is supported by the housing 8 through the second gear 7B, the thrust bearing 24, and the gear fixing member 7D described later. The other end of the conductive member 4 becomes a free end and is supported by the housing 8 through the thrust bearing 24.

[Threaded shaft] 1, the threaded shaft 2 is a member extending linearly, and a threaded portion is formed on the outer peripheral surface. The screw shaft 2 is fixed to a mounting member 22 installed in a building. If the building shakes, its vibration will be transmitted to the threaded shaft 2 through the mounting part 22. As a result, the threaded shaft 2 is displaced in the axial direction and reciprocates in synchronization with the vibration.

Fig. 1 shows a state where the screw shaft 2 is positioned at the center of the reciprocating movement. The so-called reciprocating movement center position represents the center of the reciprocating movement range along the axial direction of the screw shaft 2. The eddy current type damper 1 is installed in a building with the threaded shaft 2 at the center of the reciprocating movement.

[Ball nut] The ball nut 3 and the threaded shaft 2 constitute a ball screw. When the threaded shaft 2 is displaced in the axial direction, the ball nut 3 will rotate. That is, the ball nut 3 transforms the parallel movement of the threaded shaft 2 into a rotational movement.

The ball nut 3 includes a through hole and a flange. A threaded shaft 2 is inserted into the through hole. On the inner peripheral surface of the through hole, a threaded portion that meshes with the threaded portion of the threaded shaft 2 is formed. The flange portion has a hollow disc shape (ring shape) when viewed from the axial direction.

[Link organization] 2, the connecting mechanism 7 includes a first gear 7A, a second gear 7B, and a planetary gear 7C. Both the first gear 7A and the second gear 7B have a ring shape and are arranged concentrically with each other. In this embodiment, the conductive member 4 to which the second gear 7B is fixed is arranged outside the magnet holding member 5 to which the first gear 7A is fixed. Therefore, the second gear 7B surrounds the first gear 7A.

Fig. 5 is a sectional view taken along the line V-V in Fig. 1. In FIG. 5, only the connection mechanism 7 is illustrated, and the illustration of other structures is omitted. The first gear 7A has a ring shape, and teeth are formed on the outer peripheral surface. That is, the first gear 7A is an external gear. The type of teeth of the first gear 7A is not particularly limited. The first gear 7A is, for example, flat teeth, helical teeth, or the like. The second gear 7B has a ring shape and has teeth formed on the inner peripheral surface. That is, the second gear 7B is an internal gear. The type of teeth of the second gear 7B is not particularly limited, but is the same type as the teeth of the first gear 7A. The diameter of the inner peripheral surface of the second gear 7B is larger than the diameter of the outer peripheral surface of the first gear 7A. The planetary gear 7C meshes with the first gear 7A and the second gear 7B. That is, the planetary gear 7C is arranged between the first gear 7A and the second gear 7B in the radial direction. The connecting mechanism 7 may also include more than two planetary gears 7C. In this case, the plural planetary gears 7C are preferably arranged at equal intervals along the circumferential direction.

2, the first gear 7A is arranged between one end of the magnet holding member 5 and the flange of the ball nut 3. The first gear 7A is fixed to both the magnet holding member 5 and the ball nut 3. The fixing method is not particularly limited, but for example, the connection of a bolt, the bonding of an adhesive, and the like. The first gear 7A rotates synchronously with the ball nut 3, and with this, the magnet holding member 5 also rotates synchronously with the ball nut 3.

The second gear 7B is arranged between one end of the conductive member 4 and the thrust bearing 24. The second gear 7B is fixed to both the conductive member 4 and the thrust bearing 24. The thrust bearing 24 is supported by the housing 8 through the gear fixing member 7D. The second gear 7B can rotate with respect to the housing 8. Along with the rotation of the second gear 7B, the conductive member 4 may also rotate in synchronization with the second gear 7B.

The planetary gear 7C, the first gear 7A, and the second gear 7B are arranged at positions capable of meshing with each other in the axial direction, and preferably arranged at the same positions in the axial direction.

The connection mechanism 7 may further include a gear fixing member 7D. The gear fixing member 7D is fixed to the housing 8. The gear fixing member 7D supports the planetary gear 7C to be rotatable and restricts the movement of the planetary gear 7C in the axial, radial and circumferential directions. By providing such a gear fixing member 7D, the pinion gear 7C can be stably engaged with the first gear 7A and the second gear 7B.

The connection mechanism 7 may include plural gear fixing members 7D. That is, in the case where plural planetary gears 7C are provided, one planetary gear 7C may be supported by one gear fixing member 7D. However, the number of gear fixing members 7D may be one, and one gear fixing member 7D may support a plurality of planetary gears 7C.

The operation when vibration is applied to the eddy current damper of the first embodiment of this structure will be described.

If vibration is applied to the building, the vibration will be transmitted to the attachment 22, and the threaded shaft 2 will be displaced in the axial direction. When the screw shaft 2 is displaced, the ball nut 3, the first gear 7A, the magnet holding member 5, and the plurality of permanent magnets 6 rotate in the same direction due to the action of the ball screw. By rotating the first gear 7A, the pinion gear 7C engaged with the first gear 7A is rotated, and the second gear 7B engaged with the pinion gear 7C is rotated.

Here, due to the function of the planetary gear 7C, the rotation direction of the second gear 7B is opposite to the rotation direction of the first gear 7A. Since the conductive member 4 is fixed to the second gear 7B, the conductive member 4 also rotates in the opposite direction to the first gear 7A. That is, in the eddy current damper of the first embodiment, when vibration is applied, the conductive member 4 and the plurality of permanent magnets 6 (magnet holding members 5) rotate in opposite directions to each other.

Next, the damping force of the eddy current type damper of the first embodiment operated in this way will be described. As the damping force of the eddy current damper of the first embodiment, there are damping force due to eddy current and resistive force due to inertial force.

[Damping force caused by eddy current] Fig. 6 is a schematic diagram showing the magnetic path of the eddy current type damper of the first embodiment. In the plural permanent magnets 6, the magnetic poles of the adjacent permanent magnets 6 are reversed. Therefore, the magnetic flux from the N pole of a certain permanent magnet 6 passes through the magnet holding member 5 and reaches the S pole of the adjacent permanent magnet 6. The magnetic flux from the N pole of the permanent magnet 6 passes through the conductive member 4 and reaches the S pole of the permanent magnet 6. That is, the two adjacent permanent magnets 6, the magnet holding member 5, and the conductive member 4 form a magnetic circuit.

If vibration is applied to the eddy current damper and the plurality of permanent magnets 6 and the conductive member 4 are relatively rotated, the magnetic flux passing through the inner peripheral surface of the conductive member 4 changes, and an eddy current is generated in the conductive member 4. If eddy current is generated, new magnetic flux (diamagnetic field) will be generated. The diamagnetic field will operate in a direction that hinders the rotation of the conductive member 4. Since the conductive member 4 rotates in conjunction with the magnet holding member 5 through the coupling mechanism 7, if the rotation of the conductive member 4 is hindered, the rotation of the magnet holding member 5 (that is, the rotation of the ball nut 3) is hindered. If the rotation of the ball nut 3 is hindered, the movement of the threaded shaft 2 in the axial direction is also hindered, and the vibration is attenuated. This becomes the damping force caused by the eddy current.

The strength of the damping force caused by the eddy current depends on the relative rotational speed difference between the permanent magnets 6 and the conductive member 4. At this point, in the eddy current damper of the first embodiment, since the plurality of permanent magnets 6 (magnet holding member 5) and the conductive member 4 rotate in opposite directions to each other, it differs from only the plurality of permanent magnets 6 and the conductive member 4. Compared with the case where either one rotates, the relative speed difference between the plurality of permanent magnets 6 and the conductive member 4 can be made larger.

That is, according to the eddy current damper of the first embodiment, even if the rotation speed of the ball nut 3 is the same as in the past, a larger damping force due to the eddy current can be obtained. Next, the resistive force caused by the inertial force will be described.

[Resistance force caused by inertial force] 1, in the eddy current damper of the first embodiment as described above, if vibration is applied to the eddy current damper, the threaded shaft 2 is reciprocated in the axial direction in synchronization with the vibration, and the above action The damping force caused by the eddy current.

However, the damping force caused by the eddy current is not always fixed, but fluctuates in response to the displacement of the threaded shaft 2 from the center of the reciprocating movement (the speed of the threaded shaft 2 in the axial direction).

Fig. 7 is a diagram showing the displacement, velocity, and acceleration of the threaded shaft when a sine wave vibration is applied to the eddy current type damper. In Fig. 7, the reciprocating movement center position of the screw shaft is set to phase 0. Observe the graph of the displacement and speed of the threaded shaft. As the displacement of the threaded shaft approaches the end of the reciprocating range (π/2) from the center of the reciprocating movement, the speed of the threaded shaft will decrease at the end of the reciprocating movement range. , The speed becomes 0. After that, the threaded shaft changes the direction of movement. With the displacement of the threaded shaft from the end of the reciprocating movement to the reciprocating center position (π), the speed of the threaded shaft will increase and become the maximum at the reciprocating center position. The speed of the screw shaft is proportional to the intensity of the eddy current generated in the conductive member. Therefore, the damping force caused by the eddy current becomes the largest at the center of the reciprocating movement of the threaded shaft, becomes weaker as it approaches the end of the reciprocating movement range, and becomes zero at the end of the reciprocating movement range.

On the other hand, observe the graph of the displacement and acceleration of the threaded shaft. As the displacement of the threaded shaft moves from the center of the reciprocating movement to the end of the reciprocating range (π/2), the acceleration of the threaded shaft will increase and it will reciprocate. The end of the moving range becomes the largest. This point is the same for the acceleration in the rotation direction of the magnet holding member and the conductive member that are linked to the screw shaft through the coupling mechanism and the ball nut. That is, when the screw shaft is positioned at the end of the reciprocating movement range, the acceleration in the rotation direction of the magnet holding member and the conductive member becomes the maximum.

Here, if an object accelerates, it is well known that inertial force will act in the direction opposite to the direction of acceleration. Looking at this point for the magnet holding member and the conductive member, when the screw shaft is at the end of the reciprocating movement range, the acceleration of the magnet holding member and the conductive member will be the largest, so the inertial force of the magnet holding member and the conductive member will also be the largest . Then, the inertial force of the magnet holding member and the conductive member is transmitted to the threaded shaft through the coupling mechanism and the ball nut, and its orientation is a direction that prevents the threaded shaft from moving toward the center position of the reciprocation. In other words, due to the inertial force of the magnet holding member and the conductive member, the movement of the screw shaft in the axial direction is hindered, so that the movement amount of the screw shaft is reduced.

1, in the eddy current damper 1 of the first embodiment, the magnet holding member 5 and the conductive member 4 rotate in opposite directions to each other. Therefore, the resistive force of the movement of the screw shaft 2 caused by the inertial force generated by the eddy current damper 1 of the first embodiment is higher than that of the eddy current when only one of the magnet holding member 5 and the conductive member 4 rotates. The resistive force caused by the inertial force generated by the type damper 1 is still large. In addition, the magnitude of the inertial force of the magnet holding member 5 and the conductive member 4 depends on the magnitude of the magnet holding member 5 and the conductive member 4 in the radial direction. In this regard, in the eddy current damper 1 of the first embodiment, the conductive member 4 is arranged on the outer side of the magnet holding member 5 in the radial direction, so the radial direction is larger. Therefore, the magnitude of the inertial force of the conductive member 4 can become larger, and the resistance force to the movement of the threaded shaft 2 caused by the inertial force can be further increased.

That is, in the eddy current damper 1 of the first embodiment, the conductive member 4 and the magnet holding member 5 (permanent magnet 6) rotate in opposite directions to each other, so the gap between the conductive member 4 and the permanent magnet 6 The larger the relative speed difference can increase the damping force caused by the eddy current. Moreover, although the damping force caused by the eddy current becomes weaker as the screw shaft 2 approaches the end of the reciprocating movement range, this can be caused by the inertial force of both the conductive member 4 and the magnet holding member 5. The resistance force of the movement of axis 2 compensates.

In particular, in the long-period vibration that may cause serious damage to the building, the amplitude (displacement amount of the screw shaft 2) tends to increase. Therefore, the attenuation of such large-amplitude vibration is the eddy current of the first embodiment Type dampers are effective.

In addition, in the eddy current damper 1 of the first embodiment, the ball nut 3 is arranged inside the conductive member 4 and the magnet holding member 5 and does not move in the axial direction. With this structure, it is not necessary to provide the movable range of the ball nut 3 in the axial direction of the eddy current damper, and the eddy current damper can be reduced in size.

Above, the eddy current type damper of the first embodiment has been described. However, the eddy current damper of the present invention is not limited to the above-mentioned first embodiment, and may be the following embodiment.

[Second Embodiment] The eddy current type damper of the second embodiment will be described.

Fig. 8 is a partially enlarged view of a cross-sectional view of a plane along the axial direction of the eddy current damper of the second embodiment. The eddy current damper of the second embodiment is different from the eddy current damper of the first embodiment in that the arrangement relationship between the magnet holding member 5 and the conductive member 4 is reversed. In addition, the arrangement relationship between the first gear 7A and the second gear 7B is reversed, which is also different from the eddy current damper of the first embodiment. That is, in the second embodiment, the magnet holding member 5 to which the first gear 7A is fixed is arranged outside the conductive member 4 to which the second gear 7B is fixed. In this case, the first gear 7A is an internal gear, and the second gear 7B is an external gear. The other structure of the eddy current type damper of the second embodiment is the same as that of the eddy current type damper of the first embodiment, so detailed description is omitted.

The eddy current damper of this second embodiment is the same. Since the magnet holding member 5 (permanent magnet 6) and the conductive member 4 rotate in opposite directions to each other, the same thing as the eddy current damper of the first embodiment is obtained. effect.

However, as described above, if vibration is applied to the eddy current damper and the permanent magnet 6 and the conductive member 4 are relatively rotated, an eddy current is generated in the conductive member 4. At this time, the temperature of the conductive member 4 rises and thermally expands due to Joule heat. In the first embodiment, the conductive member 4 to which the second gear 7B is fixed is arranged outside the magnet holding member 5 to which the first gear 7A is fixed. That is, the second gear 7B is arranged outside the planetary gear 7C. In this case, if the conductive member 4 thermally expands, the backlash between the second gear 7B and the star gear 7C will increase. In contrast, in the second embodiment, the conductive member 4 to which the second gear 7B is fixed is arranged inside the magnet holding member 5 to which the first gear 7A is fixed. That is, the second gear 7B is arranged inside the planetary gear 7C. In this case, if the conductive member 4 thermally expands, the backlash between the second gear 7B and the planetary gear 7C becomes smaller. If the backlash between the second gear 7B and the planetary gear 7C becomes smaller, the smooth rotation of the planetary gear 7C may be hindered. Therefore, in terms of ensuring smooth rotation of the planetary gear 7C, the first embodiment is better than the second embodiment.

The tooth profile of the second gear 7B and the planetary gear 7C that mesh with each other is preferably an involute tooth profile. As long as the involute tooth profile is engaged with each other, even if the backlash is fluctuating, it can be engaged with a fixed rotation speed. That is, even when the conductive member 4 thermally expands, the relative rotation speed of the permanent magnet 6 and the conductive member 4 can be maintained. If the tooth profile of the planetary gear 7C is an involute tooth profile, the first gear 7A meshed with the planetary gear 7C also has an involute tooth profile.

In the above, the eddy current type damper of this embodiment has been described. In addition, the present invention is not limited to the above-mentioned embodiment, and various changes can be made naturally within the scope not deviating from the gist of the present invention.

For example, in the eddy current dampers of the first embodiment and the second embodiment, the ball nut 3 may not be fixed to the magnet holding member 5 but may be fixed to the conductive member 4. [Industrial availability]

The eddy current damper of the present invention is useful for vibration damping devices and shock absorbers of buildings.

1: Eddy current damper 2: threaded shaft 3: Ball nut 4: conductive member 5: Magnet holding member 6: Permanent magnet 7: Linking institutions 7A: First gear 7B: 2nd gear 7C: Planetary Gear 7D: Gear fixing member 8: shell 22: Installation parts 24: Thrust bearing

[Fig. 1] is a cross-sectional view of the surface along the axial direction of the eddy current damper of the first embodiment. [Figure 2] is an enlarged view of a part of Figure 1. [Fig. 3] is a sectional view taken along the line III-III in Fig. 1. [Fig. [Fig. 4] is an enlarged view of a part of Fig. 3. [Fig. 5] is a sectional view taken along the line V-V in Fig. 1. [Fig. 6] is a schematic diagram showing the magnetic path of the eddy current type damper of the first embodiment. [Fig. 7] is a diagram showing the displacement, velocity, and acceleration of the screw shaft when the sine wave vibration is applied to the eddy current type damper. [Fig. 8] is a partially enlarged view of a cross-sectional view of a plane along the axial direction of the eddy current damper of the second embodiment.

2: threaded shaft

3: Ball nut

4: conductive member

5: Magnet holding member

6: Permanent magnet

7: Linking institutions

7A: First gear

7B: 2nd gear

7C: Planetary Gear

7D: Gear fixing member

8: shell

22: Installation parts

24: Thrust bearing

Claims (2)

An eddy current type damper with: Cylindrical magnet holding member; A plurality of permanent magnets, which are fixed to the magnet holding member, are arranged with gaps between each other along the circumferential direction of the magnet holding member, and the arrangement of the magnetic poles is alternately reversed along the circumferential direction; A cylindrical conductive member facing the plurality of permanent magnets with a gap in the radial direction of the magnet holding member; A threaded shaft, which can reciprocate along the central axis of the aforementioned magnet holding member; A ball nut that engages with the threaded shaft to move the threaded shaft to thereby make the plurality of permanent magnets and the conductive member relatively rotate; and The connecting mechanism connects the magnet holding member and the conductive member to rotate the magnet holding member and the conductive member in opposite directions to each other. The eddy current type damper according to claim 1, wherein: The aforementioned linking mechanism includes: The first gear fixed to the magnet holding member, The second gear fixed to the aforementioned conductive member, A star gear that meshes with the first gear and the second gear.

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