Eddy current damper

Abstract

This invention provides an eddy current damper that does not require power and communication supply or constant monitoring, and allows for easy determination of whether or not thermal demagnetization is occurring through external visual inspection. [Solution] The eddy current damper comprises a screw shaft connected to a first part of the object to be damped, a nut screwed onto the screw shaft via a ball, a non-rotatable cylindrical conductive member connected to a second part of the object to be damped, a rotatable cylindrical magnet holder member coaxially arranged inside the conductive member and connected to the nut, a plurality of permanent magnets held by the magnet holder member, spaced apart from each other in the circumferential direction, facing the conductive member, and generating a Lorentz force on the magnet holder member due to eddy currents in the opposite direction to the rotation when the magnet holder member rotates in a magnetic field, a temperature-indicating material capable of detecting the temperature of the installation site on the conductive member, and an installation site determination means for determining an installation site for the temperature-indicating material that is suitable for approximating the temperature detected by the temperature-indicating material to the temperatures of the plurality of permanent magnets.

Description

[Technical Field]

[0001] The present invention relates to an eddy current damper that suppresses vibrations of structures, vehicles, and other objects to be damped by the damping effect of the magnetic field of a permanent magnet and eddy currents generated in a conductive member, and more particularly to an eddy current damper that allows for easy detection of abnormalities. [Background technology]

[0002] Conventionally, eddy current dampers are known that generate eddy currents in a conductive member that rotates relatively within the magnetic field of a permanent magnet in response to the vibration of a structure, and then use the Lorentz force generated by these eddy currents as a damping force to reduce vibration energy (see, for example, Patent Document 1). However, due to their configuration, if the magnetic flux density of the magnetic field through which the conductive member passes is not maintained as designed, the required damping performance cannot be secured, and the vibration suppression effect on the object to be damped, such as a structure or vehicle, cannot be sufficiently obtained.

[0003] The phenomenon of decreased magnetic flux density in permanent magnets is generally known as "demagnetization." Demagnetization can be classified into external demagnetization due to the influence of an externally applied magnetic field, internal demagnetization due to the influence of a magnetic field generated from the surface to the interior of the magnet, and thermal demagnetization due to temperature changes, depending on the cause. Of these factors, thermal demagnetization has the greatest impact on the damping performance of eddy current dampers. Specifically, when an eddy current damper is subjected to repeated deformation due to long-period ground motion, the temperature of the permanent magnet rises due to the absorbed energy, which can cause thermal demagnetization and adversely affect the damping performance of the damper. Therefore, in order to ensure the integrity of eddy current dampers, it is important to properly manage the temperature changes of the permanent magnet inside the damper.

[0004] Conventionally, an abnormality detection device for eddy current dampers is known, for example, the one disclosed in Patent Document 2. In one embodiment of this eddy current damper abnormality detection device, a magnetic sensor is disclosed to detect the magnetic flux density of the magnetic field passing through the conductive member, and an ECU (electronic control unit) determines an abnormality based on the detected magnetic flux density. In another embodiment, a temperature sensor is disclosed to detect the temperature of the permanent magnet, and an ECU determines an abnormality based on the detected temperature. In yet another embodiment, a current sensor is disclosed to detect the induced current (eddy current) generated in the conductive member, and a rotational speed sensor is disclosed to detect the relative rotational speed between the permanent magnet and the conductive member, and an ECU determines an abnormality based on the detected induced current and rotational speed. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 6905594 [Patent Document 2] Patent No. 7136727 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In the eddy current damper abnormality detection device described in Patent Document 2 above, power and communication are required for the operation of various sensors and ECUs. Therefore, in the case of a vibration-damping target object such as a structure on which an eddy current damper is installed, if a malfunction occurs in the electrical system or communication system due to an earthquake or the like, there was a possibility that the damper abnormality could not be properly detected.

[0007] Furthermore, in order to detect abnormalities, it would be necessary to maintain constant measurement by sensors and monitoring by the ECU, which could lead to a significant increase in costs.

[0008] The present invention was made to solve the above-mentioned problems, and aims to provide an eddy current damper that does not require the supply of power and communication or constant monitoring, and that allows for easy determination of whether or not thermal demagnetization has occurred by external visual inspection, thereby enabling easy confirmation of its integrity. [Means for solving the problem]

[0009] To achieve this objective, the eddy current damper according to claim 1 is an eddy current damper that is installed between a first part and a second part of an object to be damped that are relatively displaced, and which dampes vibration energy, comprising: a ball screw having a screw shaft at one end connected to the first part and a nut screwed onto the screw shaft via a ball; a conductive member provided as a non-rotatable cylindrical body with one end connected to the second part and arranged coaxially with the screw shaft; a magnet holding member provided as a rotatable cylindrical body arranged coaxially with the conductive member inside the conductive member and integrally connected to the nut; and the magnet holding member facing the conductive member. The present invention is characterized by comprising: a plurality of permanent magnets held on a surface, arranged with a distance between them in the circumferential direction, and facing a conductive member with a gap between them, wherein the plurality of permanent magnets are configured to generate a Lorentz force due to eddy currents in the direction opposite to the rotation of the magnet holding member when the magnet holding member rotates within the magnetic field of the plurality of permanent magnets; a temperature detection unit installed on the outer surface of the conductive member and capable of detecting and displaying the temperature of the installation site; and an installation site determination means for determining an installation site for the temperature detection unit that is suitable for approximating the temperature detected by the temperature detection unit to the temperature of the plurality of permanent magnets.

[0010] According to this eddy current damper, when vibration energy is input into a structure during an earthquake or the like, or when vibration energy due to high-load operation or the like is input into a vehicle, if a relative displacement occurs between the first and second parts of a vibration damping object such as a structure or a vehicle, the relative linear motion of the screw shaft connected to the first part is converted into the rotational motion of a nut, whereby a magnet holding member integrated with the nut rotates with respect to a conductive member coaxial therewith. As a result, when the magnet holding member rotates within the magnetic field of a permanent magnet, an eddy current (induced current) is generated on the surface of the conductive member facing the permanent magnet, and at the same time, a Lorentz force is generated by the interaction between this eddy current and the magnetic field of the permanent magnet. The Lorentz force due to this eddy current acts on the magnet holding member as a resistance force (braking force) in the direction opposite to its rotational direction, thereby exerting a damping effect and suppressing the vibration of the vibration damping object.

[0011] Further, according to this eddy current damper, a temperature detection unit capable of detecting and displaying the temperature of the installation site is installed on the outer peripheral surface of the conductive member. Also, the installation site of the temperature detection unit is determined by installation site determination means to be at a position such that the temperature detected by the temperature detection unit approximates the temperature of the permanent magnet. Therefore, by visually checking the temperature detection unit installed on the outer peripheral surface of the conductive member from the outside, the temperature of the permanent magnet can be estimated, and thereby the presence or absence of thermal demagnetization in the permanent magnet can be easily determined. As a result, the soundness of the eddy current damper can be easily confirmed without the need for supplying power and communication or constant monitoring.

[0012] The invention according to claim 2 is characterized in that, in the eddy current damper according to claim 1, the temperature detection unit includes a temperature indicating material capable of detecting the temperature of the installation site by irreversible discoloration.

[0013] According to this configuration, the temperature detection unit includes a temperature indicating material capable of detecting the temperature of the installation site by irreversible discoloration. Therefore, by visually checking the temperature indicating material installed on the outer peripheral surface of the conductive member from the outside, the maximum temperature reached by the permanent magnet can be estimated, and thereby the presence or absence of thermal demagnetization in the permanent magnet can be more accurately determined with higher accuracy.

[0014] The invention according to claim 3 is characterized in that, in the eddy current damper according to claim 2, it further comprises setting temperature determination means for determining the temperature at which the temperature indicating material changes color based on the thermal demagnetization temperature of a plurality of permanent magnets.

[0015] According to this configuration, since the setting temperature determination means determines the temperature at which the temperature indicating material changes color based on the thermal demagnetization temperature of the permanent magnet, by checking the presence or absence of color change of the temperature indicating material, the presence or absence of thermal demagnetization in the permanent magnet can be determined with higher accuracy.

[0016] The invention according to claim 4 is characterized in that, in the eddy current damper according to claim 1, the installation site determination means determines the installation site based on the relationship between the work amount of resistance due to eddy current and the surface temperature of the conductive member.

[0017] According to this configuration, the installation site determination means determines the installation site of the temperature detection part based on the relationship between the work amount of eddy current resistance and the surface temperature of the conductive member. That is, based on the change in the cumulative absorbed energy amount by the damper and the accompanying change in the surface temperature of the conductive member, the installation site is determined so that the temperature detected by the temperature detection part approximates the temperature of the permanent magnet. Therefore, by visually checking the temperature detection part from the outside, the presence or absence of thermal demagnetization in the permanent magnet can be determined with high accuracy.

[0018] The invention according to claim 5 is characterized in that, in the eddy current damper according to claim 3, the temperature determined by the setting temperature determination means is a temperature not lower than the thermal demagnetization temperature of a plurality of permanent magnets.

[0019] According to this configuration, since the setting temperature determination means determines the temperature at which the temperature indicating material changes color to a temperature not lower than the thermal demagnetization temperature of the permanent magnet, by checking the presence or absence of color change of the temperature indicating material, the presence or absence of thermal demagnetization in the permanent magnet can be determined with high accuracy.

[0020] The invention according to claim 6 is characterized in that, in the eddy current damper described in claim 1, the installation location determined by the installation location determination means is a position offset in the axial direction of the screw shaft with respect to the plurality of permanent magnets.

[0021] During the operation of the eddy current damper, the permanent magnet itself does not directly generate heat. On the other hand, the eddy currents generated on the inner surface of the conductive member are converted into heat. This heat conducts to the outer surface of the conductive member, raising its temperature, and simultaneously, through thermal radiation, raises the temperature of the permanent magnet held on the surface of the magnet holder facing the conductive member. At this time, the permanent magnet, which is heated by thermal radiation from the inner surface of the conductive member, will experience a temperature increase later than the outer surface of the conductive member, which is heated by thermal conduction. Therefore, by positioning the temperature detection unit on the outer surface of the conductive member at a location offset from the permanent magnet in the axial direction of the screw shaft, the temperature detected by the temperature detection unit can be approximated by the temperature of the permanent magnet. [Brief explanation of the drawing]

[0022] [Figure 1] This diagram schematically shows an example of applying an eddy current damper according to one embodiment of the present invention to a structure as a vibration damping device. [Figure 2] (a) A partially cutaway longitudinal section view and (b) A plan view showing an eddy current damper according to one embodiment. [Figure 3] Figure 2(a) is a schematic cross-sectional view along the line A-A' showing the magnetic circuit generated during the operation of an eddy current damper. [Figure 4] (a) A plan view showing an example of a temperature detection unit in an eddy current damper according to one embodiment, (b) A plan view showing an example of a state in which the temperature-indicating material has changed color, and (c) A schematic cross-sectional view of the temperature detection unit. [Figure 5] This diagram shows the configuration of the installation location determination means for determining the installation location of the temperature detection unit. [Figure 6] This flowchart shows the procedure for determining the installation location of the temperature detection unit. [Figure 7]This is a partially enlarged cross-sectional view of an eddy current damper showing an example of installation of an infrared sensor and thermocouple using an installation location determination means. [Figure 8] This is a schematic diagram showing an example of a test frame for dynamic vibration application to an eddy current damper. [Figure 9] This diagram illustrates the relationship between the work done by eddy current resistance, the surface temperature of a conductive material, and the temperature of a permanent magnet. [Figure 10] This diagram shows the configuration of the set temperature determination means for determining the discoloration temperature of a temperature-indicating material. [Figure 11] This is a flowchart showing the procedure for determining the set temperature of a temperature-indicating material. [Modes for carrying out the invention]

[0023] Embodiments of the present invention will be described in detail below with reference to the drawings. In the embodiments, for the sake of clarity, structures and elements other than the main parts of the present invention will be simplified or omitted in the description. Also, the same elements will be denoted by the same reference numerals in the drawings. Note that the shapes and dimensions of each element shown in the drawings are schematic representations and do not represent the actual shapes and dimensions.

[0024] <Overview of Eddy Current Damper 1> The eddy current damper of the present invention is installed between a first and second part that are in relative displacement in an object to be damped, such as a structure or a vehicle, thereby attenuating the vibration energy input to the object. As will be described later, the eddy current damper of the present invention is installed in an inspectable location on the object to be damped so that its soundness can be determined by external visual inspection. Here, "inspectable" means that personnel performing an inspection can visually inspect the eddy current damper from the outside, whether directly or indirectly.

[0025] Figure 1 shows an example in which the eddy current damper 1 according to this embodiment is installed as a vibration damping device on an object S to be damped. In this example, the object S to be damped is a structure, and two eddy current dampers 1, 1 are horizontally installed on a portal frame composed of upper and lower beams BU, BL and left and right columns PL, PR, via ancillary structures 2 consisting of V-shaped braces and the like.

[0026] As shown in Figure 2, the eddy current damper 1 according to this embodiment comprises a ball screw 11, a magnet holding member 12, a conductive member 13, and a plurality of permanent magnets 14. The magnet holding member 12 and the conductive member 13 are each formed in a cylindrical shape and are arranged coaxially on the outside of the ball screw 11.

[0027] The ball screw 11 has a screw shaft 15 and a nut 16 that is screwed onto the screw shaft 15 via a number of balls (not shown). The screw shaft 15 extends on both sides of the nut 16 and fits into the first and second supported portions 12b and 12c of the magnet holding member 12, which will be described later. On one side (the right side in Figure 2(a)), it protrudes from the magnet holding member 12 and is rotatably connected to the first mounting fixture 17 via a universal joint 17a. The nut 16 has a main body portion 16a that is screwed onto the screw shaft 15 and a flange portion 16b integrally provided on the first mounting fixture 17 side of the main body portion 16a.

[0028] The magnet holding member 12 is made of a ferromagnetic material (for example, steel). The magnet holding member 12 is basically cylindrical and is arranged coaxially on the outside of the screw shaft 15. It has a large-diameter magnet mounting portion 12a located in the center, and small-diameter first and second supported portions 12b and 12c located to its right and left, respectively. The first and second supported portions 12b and 12c are rotatably fitted onto the screw shaft 15. The first supported portion 12b is fixed to the flange portion 16b of the nut 16, with the flange portion 16b of the nut 16 sandwiched between it and the magnet mounting portion 12a. On the other hand, the second supported portion 12c is provided integrally with the magnet mounting portion 12a. With the above configuration, the nut 16 and the magnet holding member 12 are integrally connected to each other.

[0029] The conductive member 13 is made of a conductive material (for example, steel). The conductive member 13 is basically cylindrical and is coaxially and non-rotatably positioned outside the magnet holding member 12. It has a large-diameter main body 13a located in the center, and small-diameter first support portion 13b and second support portion 13c located to its right and left, respectively. One end of the conductive member 13 is rotatably connected to the second mounting fixture 18 via the second support portion 13c and a universal joint 18a. Furthermore, the first and second support portions 13b and 13c are each provided with a radial bearing 19 and a thrust bearing 20, respectively, and the magnet holding member 12 is rotatably supported by the conductive member 13 at the first and second supported portions 12b and 12c via the radial bearing 19 and the thrust bearing 20, so as to be immovable in the axial direction.

[0030] The permanent magnets 14 are made of neodymium magnets, for example, and as shown in Figure 3, multiple permanent magnets 14 are arranged at equal intervals in the circumferential direction on the outer surface of the magnet mounting portion 12a of the magnet holding member 12, and face the inner surface of the conductive member 13 with a gap between them. The polarity of the multiple permanent magnets 14 is set to be different between adjacent pairs of permanent magnets 14, 14, and is arranged in the radial direction of the magnet holding member 12. It is also possible to set the polarity of the permanent magnets 14 to be different between adjacent pairs of permanent magnets 14, 14, and arranged in the circumferential direction of the magnet holding member 12.

[0031] The permanent magnet 14 can be configured to be fixed to the magnet holding member 12, for example, by an adhesive.

[0032] Furthermore, the eddy current damper 1 is equipped with a temperature detection unit 21 for determining whether or not thermal demagnetization occurs in the permanent magnet 14. The configuration and installation location of the temperature detection unit 21 will be described later.

[0033] <Basic operation of eddy current damper 1> Next, the basic operation of the eddy current damper 1 with the above configuration will be explained. When the eddy current damper 1 is used in the vibration damping device shown in Figure 1, it is horizontally mounted between the lower beam BL and the upper beam BU of the vibration-damping object S, which is a structure, via first and second mounting fixtures 17 and 18. In the eddy current damper 1, since the magnetic poles of the two circumferentially adjacent permanent magnets 14, 14 are different, as shown in Figure 3, their magnetic field lines M exit from the north pole of one permanent magnet 14, pass through the conductive member 13, enter the south pole of the other permanent magnet 14, exit from its north pole, pass through the magnet holding member 12, and return to the south pole of one permanent magnet 14, thereby forming a closed circuit (magnetic circuit) of magnetic field lines M.

[0034] From this state, when a relative horizontal displacement (inter-story displacement) occurs between the lower beam BL and the upper beam BU of the vibration-damping object S during an earthquake or other event, this relative displacement is transmitted, converting the linear motion of the screw shaft 15 relative to the conductive member 13 into rotational motion of the nut 16. As a result, the magnet holding member 12, which is integrated with the nut 16, rotates within the magnetic field of the permanent magnet 14 (arrow C in Figure 3). This generates eddy currents (induced currents) on the inner surface of the conductive member 13, and simultaneously generates a Lorentz force through the interaction between these eddy currents and the magnetic field of the permanent magnet 14. This Lorentz force then acts on the magnet holding member 12 as a resistive force (braking force) in the opposite direction to its rotation, thereby exerting a damping effect and suppressing the vibration of the vibration-damping object S.

[0035] <Configuration of temperature detection unit 21> Next, the configuration of the temperature detection unit 21 of the eddy current damper 1 will be described. The eddy current damper 1 is equipped with a temperature detection unit 21 on the outer surface of the conductive member 13 that is capable of detecting and displaying the temperature of the installation site Ps. The temperature detection unit 21 is provided for the purpose of determining whether thermal demagnetization has occurred in the permanent magnet 14, which is heated by the heat generated when the eddy currents produced by the operation of the eddy current damper 1 described above are converted into heat. Therefore, the temperature detected by the temperature detection unit 21 is required to be representative of the temperature of the permanent magnet 14. Furthermore, in order to estimate with high accuracy whether or not thermal demagnetization has occurred in the permanent magnet 14, it is preferable that the temperature detection unit 21 can detect the highest temperature reached at the installation site Ps and display its history. In this embodiment, as shown in Figure 2, a single temperature detection unit 21 is provided, but it is also possible to provide multiple temperature detection units 21 on the outer circumferential surface of the conductive member 13.

[0036] As shown in Figure 4, the temperature detection unit 21 in this embodiment is configured to include a temperature-indicating material 21a that can detect and display the highest temperature reached at the installation site Ps by irreversible discoloration. Figure 4(a) is a plan view showing an example of the external appearance of the temperature detection unit 21. As shown in the figure, the temperature detection unit 21 of this embodiment includes a temperature-indicating material 21a, a mounting plate 21b, a protective film 21c, and mounting bolts 21d.

[0037] Figure 4(c) is a schematic cross-sectional view of the temperature detection unit 21. As shown in the figure, the temperature-indicating material 21a has a multilayer structure comprising, from top to bottom, a polyester film 21e, a temperature-indicating element 21f, an adhesive 21g, a colorfast ink 21h, a polyester film 21e, and an adhesive 21g. The temperature-indicating material 21a is bonded to the mounting plate 21b by the adhesive 21g, and its surface is protected by a protective film 21c. The mounting plate 21b is provided with through holes for passing mounting bolts 21d, and the temperature detection unit 21 is fixed to the outer surface of the conductive member 13 by the mounting bolts 21d. It is also possible to omit the mounting plate 21b and directly bond the temperature-indicating material 21a to the outer surface of the conductive member 13. Furthermore, the protective film 21c can be omitted as appropriate.

[0038] The temperature-sensing material 21a in the temperature detection unit 21 of this embodiment has a plurality of temperature-sensing elements 21f, each set to a different temperature at which it changes color. Each temperature-sensing element 21f is a known temperature-sensing material that irreversibly changes color when it reaches a specific temperature, and can be used that has been set to any desired color change temperature according to the procedure for determining the set temperature described later. The installation location Ps for the temperature detection unit 21 on the outer surface of the conductive member 13 is determined by the installation location determination means 30, which will be described later, to be a position where its temperature approximates that of the permanent magnet 14, and the temperature detection unit 21 is installed at the determined installation location Ps. The detailed procedure for determining the installation location will be described later.

[0039] In this way, the temperature detected by the temperature detection unit 21 can be considered representative of the temperature of the permanent magnet 14. Therefore, by referring to the temperature indicated by the temperature detection unit 21, especially the highest temperature reached so far, it becomes possible to determine whether or not thermal demagnetization has occurred in the permanent magnet 14, and based on this, the soundness of the eddy current damper 1 can be easily determined.

[0040] It is preferable that the discoloration temperature of at least one of the temperature-indicating elements 21f of the temperature-indicating material 21a be set to a temperature equal to or higher than the thermal demagnetization temperature of the permanent magnet 14. This makes it possible to determine with high probability whether or not thermal demagnetization has occurred in the permanent magnet 14 by referring to at least one of the temperature-indicating elements 21f of the temperature-indicating material 21a. As shown in Figure 2, the temperature-indicating material 21a in this embodiment is configured with three temperature-indicating elements 21f arranged side by side, each set to a different discoloration temperature. The discoloration temperatures of each temperature-indicating element 21f are set to 120°C, 130°C, and 140°C, respectively, from left to right. The detailed procedure for determining the set temperatures of the temperature-indicating elements 21f of the temperature-indicating material 21a will be described later. Furthermore, the number of temperature-indicating elements 21f provided in the temperature-indicating material 21a is not limited to three; it may be configured with fewer or more temperature-indicating elements 21f. Also, the arrangement of the temperature-indicating elements 21f is not limited to the example of side-by-side arrangement, but can be any arrangement.

[0041] As shown in Figure 4(a), the temperature detection unit 21 is installed on the outer surface of the conductive member 13 and is configured to allow visual confirmation from the outside of a temperature-indicating element zone that shows whether or not each temperature-indicating element 21f has changed color, a temperature guideline zone that shows a guideline for the temperature at which each temperature-indicating element 21f changes color, and a determination zone that shows the state of the permanent magnet 14 estimated from the color change of each temperature-indicating element 21f. Figure 2(b) shows an example of the state in which each temperature-indicating element 21f has changed color. Each temperature-indicating element 21f may change to a different color, or they may change to the same color. Furthermore, the length of time or frequency of reaching a set temperature may be represented by a gradient of color density, the size of the discolored area, etc. Furthermore, the three display zones in the temperature detection unit 21 described above do not necessarily need to be all three; they can be omitted or other display zones added as appropriate.

[0042] <Configuration of the installation location determination means 30> Next, the configuration of the installation location determination means 30, which determines the installation location Ps of the temperature detection unit 21 on the outer circumferential surface of the conductive member 13, will be described. As mentioned above, in order to determine whether or not thermal demagnetization occurs in the permanent magnet 14, the temperature detected by the temperature detection unit 21 must be close to the temperature of the permanent magnet 14, and for this purpose, it is necessary to appropriately determine the installation location Ps of the temperature detection unit 21. In this embodiment, before installing the temperature detection unit 21 on the outer circumferential surface of the conductive member 13, the installation location determination means 30 determines an appropriate installation location Ps of the temperature detection unit 21.

[0043] Figure 5 is a schematic diagram showing the configuration of the installation location determination means 30 in this embodiment. As shown in the figure, the installation location determination means 30 comprises an arbitrary number of thermocouples 31, an infrared sensor 32, a converter 33, a data acquisition device 34, and an analysis device 35.

[0044] The thermocouple 31 is connected to an arbitrary point P on the outer surface of the conductive member 13. x It is installed at any point P x Temperature T(P x It generates a voltage corresponding to the specified value. The infrared sensor 32 is a non-contact temperature sensor and is installed in a through-hole provided in the conductive member 13 at a location facing any one of the multiple permanent magnets 14. It generates an electrical signal corresponding to the temperature T(M) of the permanent magnet 14. However, if a through-hole is provided in the conductive member 13, moisture and other elements may enter the inside of the conductive member 13 through the through-hole, potentially causing the permanent magnet 14 to rust. Therefore, in this embodiment, temperature measurement is performed using a test specimen rather than an actual eddy current damper 1. The converter 33 is electrically connected to the thermocouple 31 and the infrared sensor 32 via cables, etc., and amplifies the voltage and electrical signals received from them, converts them into predetermined physical quantities, and transmits them to the acquisition device 34. The data acquisition device 34 transmits the physical quantities received from the converter 33 to the analysis device 35 by wireless or wired means.

[0045] The analysis device 35 is, for example, an information processing device such as a personal computer. The analysis device 35 may consist of a single device, or it may consist of multiple devices that combine an information processing device and a server device, etc. The analysis device 35 is equipped with a CPU, RAM, ROM, and I / O interface, etc. (not shown), and performs the control process for determining the installation location, which will be described later, by reading and executing a program stored in the RAM or ROM.

[0046] <Procedure for determining the installation location> Next, the procedure for determining the installation location Ps of the temperature detection unit 21 by the installation location determination means 30 will be explained. Figure 6 is a flowchart showing the procedure for determining the installation location.

[0047] First, in step 401 (illustrated as S401; the same applies hereafter), an infrared sensor 32 is attached to a through hole in the conductive member 13, making it possible to measure the temperature of the permanent magnet 14. Then, in step 402, an infrared sensor 32 is attached to an arbitrary point P in the conductive member 13. x At an arbitrary point P, x Thermocouples 31 are installed according to the number of points P x It is in a state where it can generate a voltage corresponding to the temperature.

[0048] Figure 7 shows an example of the installation of the infrared sensor 32 and thermocouple 31 using the installation location determination means 30. In this example, a through hole is provided in the conductive member 13 opposite one of the multiple permanent magnets 14 held by the magnet holding member 12, and the infrared sensor 32 is installed using this through hole. Thermocouples 31 are also installed at six arbitrary points P1 to P6 arranged along the axial direction on the main body 13a of the conductive member 13. The infrared sensor 32 and each thermocouple 31 are electrically connected to the converter 33 by a cable, and the detected electrical signals are made available to be transmitted to the converter 33.

[0049] Next, in step 403, the eddy current damper 1 is installed on the test frame 100, and dynamic excitation is performed by displacement control using the test frame 100. As a result, the eddy current damper 1 is activated, generating eddy currents on the inner surface of the conductive member 13, and the conductive member 13 and the permanent magnet 14 are heated up as the eddy currents are converted into heat.

[0050] Figure 8 shows an example of a test frame 100 to which an eddy current damper 1 is attached for dynamic excitation. This test frame 100 is a portal frame composed of an upper beam 101, a lower beam 102, and left and right reaction force blocks 103, 103. One of the left and right reaction force blocks 103, 103 is equipped with a dynamic actuator 104 that generates vibration under the control of a controller (not shown). As shown in FIG. 8, the eddy current damper 1 is horizontally mounted between the dynamic actuator 104 and the other reaction force block 103 via the first and second fixtures 17 and 18. A load cell 107 for measuring the damper reaction force and a T-shaped jig for guiding the movement of the eddy current damper 1 by the linear motion rail 105 are mounted between the dynamic actuator 104 and the eddy current damper 1. Further, a displacement gauge 106 for measuring the displacement amount of the screw shaft 15 of the eddy current damper 1 is attached to the eddy current damper 1.

[0051] In parallel with the dynamic excitation of the eddy current damper 1, the installation site determination means 30 measures the temperature T(M) of the permanent magnet 14 as step 404, and measures the temperature T(P x at an arbitrary point P x ) as step 405. Then, in step 406, the installation site determination means 30 determines whether or not the obtained temperature T(P x at the arbitrary point P x ) is approximated to the temperature T(M) of the permanent magnet 14.

[0052] If the determination result in step 406 is NO and it is determined that the obtained temperature T(P x at the arbitrary point P x ) is not approximated to the temperature T(M) of the permanent magnet 14, in step 407, the installation point of the thermocouple 31 is changed, and the process returns to step 402 to install the thermocouple at a new arbitrary point P x , and steps 403 to 406 are repeated again.

[0053] On the other hand, if the determination result in step 406 is YES and it is determined that the obtained temperature T(P x at the arbitrary point P x ) is approximated to the temperature T(M) of the permanent magnet 14, the arbitrary point P x is determined as the installation site Ps of the temperature detection unit 21, and this flow is terminated.

[0054] In the example shown in Figure 7, thermocouples 31 are installed at each of the six arbitrary points P1 to P6. Therefore, step 406 is performed for each of the temperatures T(P1) to T(P6) at the six arbitrary points P1 to P6. If it is determined that any of the temperatures approximate the temperature T(M) of the permanent magnet 14, then step 408 is performed for the arbitrary point where that temperature was measured. If it is determined that multiple temperatures approximate the temperature T(M) of the permanent magnet 14, then step 408 is performed for the arbitrary point that more closely approximates the temperature T(M) of the permanent magnet 14.

[0055] In this embodiment, as the determination in step 406, an arbitrary point P is determined based on the relationship between the amount of work done by the eddy current resistance of the eddy current damper 1 and the surface temperature of the conductive member 13. x Temperature T(P x It is determined whether ) approximates the temperature T(M) of the permanent magnet 14. Here, the work done by the eddy current resistance E is the sum of the values ​​obtained by multiplying the load Qe (see Equation 1 below), which is calculated by subtracting the friction Qf and screw efficiency λ of the eddy current damper 1 from the total damper force F measured using the load cell 107, and the displacement δ of the eddy current damper 1 measured using the displacement meter 106, from the first data point to the mth data point, as shown in Equation 2 below. For example, the screw efficiency λ is 1.4 and the friction Qf is 14.3.

[0056] [Mathematics 1] Qe(i) = F(i) / λ-Qf

[0057]

number

[0058] Figure 9 shows the work done by the eddy current resistance calculated as described above, and the arbitrary point P. x Temperature T(P xThis is an example of a relationship diagram showing the relationship between the permanent magnet 14 and the temperature T(M) of the eddy current damper 1. In this example, the relationship between the temperatures T(P1) to T(P6) of six arbitrary points P1 to P6, the temperature T(M) of one permanent magnet 14, and the work done by the eddy current resistance of the eddy current damper 1 is shown. From this diagram, it can be seen that in this example, the temperature T(M) of the permanent magnet 14 and the temperature T(P1) of the arbitrary point P1 are approximate. That is, the temperature rise of the permanent magnet 14 and the arbitrary point P1 due to the work done by the eddy current damper 1 are roughly the same, and it can be determined that the temperature T(P1) of the arbitrary point P1 represents the temperature T(M) of the permanent magnet 14, so the arbitrary point P1 can be determined to be the installation site Ps. For example, the criteria for determining whether something is an approximation or not is an arbitrary point P. x Temperature T(P x The system can be configured to determine if an approximation is true when the gradient of the change in ) is within ±10% of the gradient of the change in the temperature T(M) of the permanent magnet 14.

[0059] Furthermore, if it is difficult to directly measure the surface temperature of the permanent magnet, such as when it is not possible to provide a through hole in the conductive member 13 of the eddy current damper 1, or when it is not possible to prepare a test specimen of the eddy current damper 1, the temperature change rate of the permanent magnet 14 may be calculated using the following formula 3, and this can be set to an arbitrary point P. x Temperature T(P x The installation location Ps may be determined by comparing it with the gradient of ).

[0060] [Math 3] ΔT(M)(℃)=0.010~0.015·E(kJ)

[0061] During the operation of the eddy current damper 1, the permanent magnet 14 heats up due to thermal radiation from eddy currents generated on the inner surface of the conductive member 13. Therefore, because the heat transfer is slower compared to the outer surface of the conductive member 13 which heats up due to heat conduction from the inner surface, the permanent magnet 14 heats up more slowly than the outer surface of the conductive member 13 near the inner surface where the eddy currents are generated. Consequently, the portion of the outer surface of the conductive member 13 that is approximately the same temperature as the permanent magnet 14 is usually located at a position offset (away) from the permanent magnet 14 in the axial direction of the screw shaft.

[0062] <Configuration of the set temperature determination means> Next, the configuration of the setting temperature determination means 40, which determines the discoloration temperature of the temperature-indicating element 21f of the temperature-indicating material 21a, will be described. As described above, in order to determine whether or not thermal demagnetization occurs in the permanent magnet 14, the temperature detected and displayed by the temperature detection unit 21 must be such that the occurrence of thermal demagnetization in the permanent magnet 14 can be estimated with high accuracy. In the case of a temperature detection unit 21 that estimates the highest temperature reached by the permanent magnet 14 using the temperature-indicating material 21a, as in this embodiment, it is preferable that at least one of the multiple temperature-indicating elements 21f of the temperature-indicating material 21a has a discoloration temperature set to a temperature equal to or greater than the thermal demagnetization temperature of the permanent magnet 14. In this embodiment, before the temperature detection unit 21 is installed on the outer surface of the conductive member 13, the setting temperature determination means 40 determines the setting temperature Ts at which the temperature-indicating element 21f of the temperature-indicating material 21a discolors.

[0063] Figure 10 is a schematic diagram showing the configuration of the set temperature determination means 40 in this embodiment. As shown in the figure, the set temperature determination means 40 comprises an infrared sensor 42, a converter 43, a data collector 44, and an analysis device 45. Note that the infrared sensor 32, converter 33, data collector 34, and analysis device 35 in the installation location determination means 30 described above may be used as the infrared sensor 42, converter 43, data collector 44, and analysis device 45 in the set temperature determination means 40.

[0064] The infrared sensor 42 is a non-contact temperature sensor and, like the infrared sensor 32 described above, is attached to a through-hole in the conductive member 13 that faces any one of the multiple permanent magnets 14, and generates an electrical signal corresponding to the temperature T(M) of the permanent magnet 14. As described above, in this embodiment, in order to prevent oxidation of the permanent magnet 14 due to the ingress of moisture, etc., temperature measurement is performed using a test specimen rather than an actual eddy current damper 1. The converter 43, like the converter 33 described above, is electrically connected to the infrared sensor 42 via a cable or the like, amplifies the electrical signal received from the infrared sensor 42, converts it into a predetermined physical quantity, and transmits it to the acquisition device 44. The data acquisition device 44, like the data acquisition device 34 described above, transmits the physical quantities received from the converter 43 to the analysis device 45 by wireless or wired means. The analysis device 45, like the analysis device 35 described above, is an information processing device such as a personal computer. The analysis device 45 may consist of a single device or multiple devices combining an information processing device and a server device. The analysis device 45 is equipped with a CPU, RAM, ROM, and I / O interface (not shown), and performs the control process for determining the set temperature, which will be described later, by reading and executing a program stored in the RAM or ROM.

[0065] <Procedure for determining the set temperature> Next, the procedure for determining the set temperature Ts of the temperature-indicating material 21a temperature-indicating element 21f of the temperature detection unit 21 by the set temperature determination means 40 will be explained. Figure 11 is a flowchart showing the procedure for determining the set temperature.

[0066] First, in step 501, the damping performance (performance before continuous excitation) Fb(t0) of the eddy current damper 1 at an initial temperature T(M) of the permanent magnet 14, t0°C, is confirmed. This performance confirmation is performed, for example, by performing performance confirmation excitation on the eddy current damper 1 using the test frame 100 described above, and is based on the damping performance obtained therefrom. The excitation conditions for this performance confirmation excitation should preferably be representative of the performance of the eddy current damper, for example, a sinusoidal wave of 5 cycles, a frequency of 0.5 Hz, and a maximum speed of 25 cm / s. Furthermore, the performance of the eddy current damper 1 is evaluated, for example, by the load at the maximum speed during the second cycle.

[0067] Next, in step 502, continuous excitation is performed on the eddy current damper 1 using the test frame 100 with the aim of increasing the temperature T(M) of the permanent magnet 14. The excitation conditions for this continuous excitation can be set as appropriate, but for example, a sinusoidal wave with a frequency of 0.5 Hz and a maximum velocity of 4 cm / s may be continuously input. Alternatively, for example, a sinusoidal wave with 5 cycles, a frequency of 0.5 Hz and a maximum velocity of 10 cm / s may be intermittently input.

[0068] This continuous excitation occurs when the temperature T(M) of the permanent magnet 14 is set to a predetermined arbitrary temperature t max This is carried out until it reaches a certain temperature. That is, as step 503, during the continuous excitation of step 502, the temperature T(M) of the permanent magnet 14 reaches an arbitrary temperature t max A determination is made as to whether or not the temperature T(M) of the permanent magnet 14 reaches an arbitrary temperature t. max If the temperature has not been reached (the result of the judgment is NO), continuous excitation is continued until the temperature T(M) of the permanent magnet 14 reaches an arbitrary temperature t max If the condition is met (the result is YES), proceed to the next step 504. Note that any temperature t max This can be, for example, the thermal demagnetization temperature expected for the permanent magnet 14 used. The initial arbitrary temperature t max For example, it could be set to 120°C.

[0069] In step 504, continuous vibration is terminated, and the permanent magnet 14 is cooled until its temperature T(M) drops to the initial temperature t0°C. After cooling is complete, the process proceeds to step 505.

[0070] In step 505, the eddy current damper 1 is subjected to vibration under the same conditions as the vibration used to confirm performance before continuous vibration in step 501, and the performance Fa(t0) of the eddy current damper 1 after continuous vibration is evaluated under the same conditions.

[0071] In the following step 506, the performance Fb(t0) before continuous excitation and the performance Fa(t0) after continuous excitation are compared, and it is determined whether Fb(t0) > Fa(t0). If the result of this determination is NO, that is, if the performance of the eddy current damper 1 has not deteriorated after continuous excitation, then at an arbitrary temperature t max Depending on the circumstances, it may be determined that thermal demagnetization of the permanent magnet 14 has not occurred. In this case, step 507 is set to an arbitrary temperature t max Change the temperature to a higher setting than the current one, and repeat steps 502 through 506.

[0072] On the other hand, if the result of step 506 is YES, that is, if it is confirmed that the performance of the eddy current damper 1 has deteriorated after continuous excitation, then the arbitrary temperature t max Upon reaching a certain temperature, it is determined that thermal demagnetization of the permanent magnet 14 has occurred, and in the next step 508, the arbitrary temperature t max The set temperature Ts of at least one temperature-indicating element 21f is determined.

[0073] Furthermore, in the determination in step 506, in order to avoid misjudgments due to measurement errors, etc., it may be set so that it is determined that the performance after continuous vibration has deteriorated only when a difference of a predetermined amount or more is observed between the performance Fb(t0) before continuous vibration and the performance Fa(t0) after continuous vibration. For example, it may be set so that it is determined that the performance after continuous vibration has deteriorated if the performance Fa(t0) after continuous vibration is 10% or more lower than the performance Fb(t0) before continuous vibration.

[0074] As described in detail above, in this embodiment, the installation location determination means 30 searches for a location on the outer surface of the conductive member 13 where the operating temperature of the eddy current damper 1 approximates the temperature T(M) of the permanent magnet 14, and this location is determined to be the installation position Ps of the temperature detection unit 21. Therefore, by visually observing the temperature displayed by the temperature detection unit 21 on the outer surface of the conductive member 13 from the outside, the temperature of the permanent magnet 14 can be estimated, and the presence or absence of thermal demagnetization in the permanent magnet 14 can be easily determined. This makes it possible to easily and inexpensively confirm the integrity of the eddy current damper 1 without requiring power and communication supply or constant monitoring.

[0075] In particular, the temperature detection unit 21 of this embodiment is equipped with a temperature-indicating material 21a that displays the temperature reached at the installation site Ps by irreversible discoloration. Therefore, by visually observing the temperature-indicating material 21a installed on the outer surface of the conductive member 13 from the outside (whether directly or indirectly), the highest temperature reached by the permanent magnet 14 can be estimated, thereby enabling a simple and low-cost determination of whether or not thermal demagnetization has occurred in the permanent magnet 14 with greater accuracy.

[0076] Furthermore, the installation location determination means 30 of this embodiment determines the installation location Ps of the temperature detection unit 21 based on the relationship between the amount of work done by the eddy current resistance and the surface temperature of the conductive member 13. That is, the installation location Ps is determined based on the change in the cumulative amount of absorbed energy by the eddy current damper 1 and the resulting change in the surface temperature of the conductive member 13, so that the temperature detected by the temperature detection unit 21 approximates the temperature of the permanent magnet 14. Therefore, by visually observing the temperature detection unit 21 from the outside, it is possible to determine with high accuracy whether or not thermal demagnetization has occurred in the permanent magnet 14.

[0077] Furthermore, in this embodiment, the temperature setting means 40 determines that the temperature at which the temperature indicator material 21a changes color is equal to or higher than the temperature at which the permanent magnet 14 changes color, based on the temperature demagnetization temperature of the permanent magnet 14. Therefore, by checking whether or not the temperature indicator material 21a changes color, it is possible to determine with higher accuracy whether or not thermal demagnetization has occurred in the permanent magnet 14.

[0078] It should be noted that the present invention is not limited to the embodiments described and can be implemented in various ways. For example, in the embodiment, when determining the installation location Ps of the temperature detection unit 21 and the set temperature Ts of the temperature-indicating element 21f of the temperature-indicating material 21a, a through-hole was made in the conductive member 13 using a test specimen of the eddy current damper 1, and infrared sensors 32 and 42 were attached to this through-hole. However, it is also possible to provide a through-hole in the conductive member 13 in the actual eddy current damper 1. In this case, for example, the through-hole provided in the conductive member 13 can be closed with an openable and closable hatch and reused as an inspection window for the permanent magnet 14.

[0079] Furthermore, the detailed configuration of the damper shown in the embodiments is merely illustrative and can be modified as appropriate within the scope of the present invention. [Explanation of Symbols]

[0080] 1. Eddy current damper 11 Ball screw 12 Magnet holding member 13 Conductive material 14 Permanent Magnets 15 Screw shaft 16 nuts 21 Temperature detection unit 21a Temperature indicating material 30 Installation site determination means 40 Setting temperature determination means S Vibration-damping target object BU upper beam (1st part) BL Lower beam (2nd part)

Claims

1. An eddy current damper is installed between a first part and a second part of an object to be damped, which are relatively displaced, and which dampens vibration energy. A ball screw having a screw shaft at one end connected to the first part, and a nut that is screwed onto the screw shaft via a ball, A conductive member is provided as a non-rotatable cylindrical body, with one end connected to the second portion and arranged coaxially with the screw shaft, A magnet holding member is provided inside the conductive member as a rotatable cylindrical body, arranged coaxially with the conductive member and integrally connected to the nut, A plurality of permanent magnets are held on the surface of the magnet holding member facing the conductive member, arranged with spacing between them in the circumferential direction, and facing the conductive member with a gap between them, wherein when the magnet holding member rotates within the magnetic field of the plurality of permanent magnets, the plurality of permanent magnets are configured to generate a Lorentz force in the magnet holding member due to eddy currents in the direction opposite to the rotation, A temperature detection unit is installed on the outer surface of the conductive member and is capable of detecting and displaying the temperature of the installation site. The installation location of the temperature detection unit includes an installation location determination means for determining a location suitable for approximating the temperature detected by the temperature detection unit to the temperature of the plurality of permanent magnets, An eddy current damper characterized by having the following features.

2. The eddy current damper according to claim 1, characterized in that the temperature detection unit comprises a temperature-indicating material capable of detecting the temperature of the installation site by irreversible discoloration.

3. The eddy current damper according to claim 2, further comprising a setting temperature determination means for determining the temperature at which the temperature-indicating material changes color based on the thermal demagnetization temperatures of the plurality of permanent magnets.

4. The eddy current damper according to claim 1, characterized in that the means for determining the installation location determines the installation location based on the relationship between the amount of work done by the eddy current and the surface temperature of the conductive member.

5. The eddy current damper according to claim 3, characterized in that the temperature determined by the setting temperature determination means is a temperature equal to or greater than the thermal demagnetization temperature of the plurality of permanent magnets.

6. The eddy current damper according to claim 1, characterized in that the installation location determined by the installation location determination means is a position offset in the axial direction of the screw shaft with respect to the plurality of permanent magnets.

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