Damping device

Abstract

Provided is a damper device that eliminates residual magnetic flux generated by a coil and continuously eliminates residual damping force generated by the damper device without performing special control. This damper device is provided with: a damper body in which a functional fluid, the apparent viscosity of which can be adjusted by means of a magnetic field, is sealed; and a shaft which is slidable in the axial direction with respect to the damper body and which has a helical thread groove extending in the axial direction on the outer periphery thereof, the damper being provided with a stationary body and a rotating body, the stationary body being provided with an electromagnetic part for generating a magnetic field, the electromagnetic part being provided with: a coil around which a wire is wound in the center of the shaft; a magnetic circuit forming member that accommodates the coil; the magnetic circuit forming member has a cylindrical space filled with a functional fluid, and the permanent magnet is disposed on a magnetic path based on a magnetic field inside the magnetic circuit forming member. And a rotating cylinder portion extending cylindrically in the axial direction, the rotating cylinder portion being inserted into the cylindrical space in a state where a gap is formed between the rotating cylinder portion and the magnetic circuit forming member.

Description

TECHNICAL FIELD

[0001] The present application relates to a damping device. BACKGROUND

[0002] In the past, a rotary damper is known, which is a damper using a functional fluid such as a magnetic viscous fluid, a functional fluid is interposed between a damper housing and a rotating body, and an attenuation force can be controlled by an electromagnetic coil. Such a damper generates a magnetic field in the damper housing by applying a direct current to the electromagnetic coil, and a strong magnetic body particle or the like in the functional fluid forms a chain-like bundle between the damper housing and the rotating body, and an attenuation force is generated by the shear resistance of the bundle.

[0003] In such a damper, adjustment and on-off of the attenuation force can be performed by control of the current to the electromagnetic coil. For example, as shown in Patent Literature 1, a damper control device is known, which encloses a functional fluid that generates an attenuation force in correspondence with a magnetic flux generated by a direct current voltage from a direct current power source to the electromagnetic coil, characterized in that the damper control device has an alternating current power source that applies an alternating current voltage to the electromagnetic coil, and a voltage control section that controls the alternating current power source to apply an attenuated wave alternating current voltage that gradually attenuates after a standing wave alternating current voltage that lasts for a prescribed period is applied to the electromagnetic coil.

[0004] According to such a damper control device, even if an attenuation force (hereinafter referred to as "residual attenuation force") is generated based on the influence of the residual magnetic flux at the time of off when the electromagnetic coil is not energized, the chain-like bundle formed by the functional fluid can be broken by the standing wave alternating current voltage and the attenuated wave alternating current voltage, and the residual attenuation force can be removed.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Publication No. 2018-128056 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] However, when the control device of the damper of the past is to be used for a shock absorber of a motor vehicle or the like, a residual attenuation force is generated every time a vibration is input to the damper, and in such a scenario where the concave-convex of the road surface changes drastically, there is a problem that the control of the alternating current voltage is complicated, and it is difficult to remove the residual attenuation force with respect to the input of continuous vibrations.

[0010] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a damping device that can cancel the residual magnetic flux by using a permanent magnet to generate a magnetic flux in the opposite direction to the residual magnetic flux generated by the coil, and continuously eliminate the residual attenuation force.

[0011] Methods for solving problems

[0012] The damping device of the present invention, which solves the above-mentioned problems, is characterized in that the damping device comprises: a damper body enclosed in a functional fluid capable of adjusting the apparent viscosity using a magnetic field; and a shaft slidably sliding axially relative to the damper body, having a helical threaded groove extending axially around the outer periphery of the shaft; the damper body comprising a stationary body and a rotating body; the stationary body comprising an electromagnetic part for generating the magnetic field; the electromagnetic part comprising: a coil with wire wound around its center; a magnetic circuit forming member housing the coil; and a permanent magnet having a cylindrical space filled with the functional fluid, the permanent magnet being disposed on a magnetic circuit based on the magnetic field inside the magnetic circuit forming member; the rotating body comprising: a rotating engaging portion engaging with the threaded groove; and a rotating cylindrical portion extending axially in a cylindrical shape, the rotating cylindrical portion being inserted into the cylindrical space with a gap formed between it and the magnetic circuit forming member.

[0013] Invention Effects

[0014] According to the damping device of the present invention, residual magnetic flux generated by the coil can be eliminated without special control, and residual damping force generated in the damping device can be continuously eliminated. Furthermore, for example, when the damping device of the present invention is used in a shock absorber for a motor vehicle, even when the road surface unevenness changes drastically and residual damping force is generated every time vibration is input to the damping device, complex AC voltage control is not required, and residual damping force can be easily removed relative to continuous vibration input. Attached Figure Description

[0015] Figure 1 This is a cross-sectional view illustrating a damping device according to an embodiment of the present invention.

[0016] Figure 2 yes Figure 1 AA section view in the image.

[0017] Figure 3 This is a graph showing the input current and attenuation force of the damping device according to an embodiment of the present invention.

[0018] Figure 4 This is a partial cross-sectional view illustrating an example of the configuration of the permanent magnets in a damping device according to an embodiment of the present invention. Detailed Implementation

[0019] The following description, with reference to the accompanying drawings, outlines embodiments of the damping device according to the present invention. It should be noted that the following embodiments do not limit the invention to any particular technical solution, and that not all combinations of features described in the embodiments are necessary for the solution of the invention.

[0020] Figure 1 This is a cross-sectional view illustrating a damping device according to an embodiment of the present invention. Figure 2 yes Figure 1 AA section view, Figure 3 This is a graph showing the input current and attenuation force of the damping device according to an embodiment of the present invention. Figure 4 This is a partial cross-sectional view illustrating an example of the configuration of the permanent magnets in a damping device according to an embodiment of the present invention.

[0021] like Figure 1 As shown, the damping device D according to this embodiment includes: a generally cylindrical damper body 1; and a shaft 2 that can slide freely in the axial direction relative to the damper body 1.

[0022] Shaft 2 is coaxially arranged with the damper body 1, with one end located inside the damper body 1 and the other end protruding outside the damper body 1.

[0023] A threaded groove 2a is formed on the outer periphery of the shaft 2, which engages with the rotary engagement portion 60 described later. Alternatively, a guide groove 2b is preferably formed on the outer periphery of the shaft 2, which engages with the linear engagement portion 20 described later.

[0024] The damper body 1 includes a stationary body 3 and a rotating body 4 arranged coaxially with the stationary body 3. The rotating body 4 is configured to be inside the stationary body 3 and to rotate freely relative to the stationary body 3 about an axis. As an example, the rotating body 4... Figure 1 As shown, it is held stationary by means of thrust bearing 5.

[0025] The stationary body 3 includes an electromagnetic part 10 capable of forming a magnetic circuit by applying a voltage based on a power supply device (not shown). Furthermore, it is preferable that the stationary body 3 includes a direct-acting engagement part 20 that guides the shaft 2 axially.

[0026] like Figure 1 As shown, the electromagnetic part 10 includes a coil 11 and a magnetic circuit forming member 12.

[0027] The coil 11 is formed by winding a conductive wire around the center of an axis. The coil 11 is electrically connected to the wire via a power supply device (not shown), thereby generating a magnetic field around the coil 11 according to the applied voltage. As an example, the coil 11 may also be configured to wind the wire in a cylindrical coil frame made of a resin material or the like. In addition, a through hole 11a is formed at the center of the axis of the coil 11, through which the cylindrical portion 13b of the magnetic yoke 13 (described later) can pass.

[0028] like Figure 1 As shown, the magnetic circuit forming member 12 includes a magnetic yoke 13 and a cover 14. The magnetic yoke 13 and the cover 14 are made of, for example, a magnetic material such as an ferrous material.

[0029] The magnetic circuit forming member 12 utilizes the magnetic field accompanying the energization of the coil 11 to form a magnetic flux loop using a magnetic yoke 13 and a cover 14. In this specification, the channel of the magnetic flux loop formed by the coil 11 is defined as the magnetic circuit M1. It should be noted that the magnetic force of the magnetic circuit M1 formed in the magnetic circuit forming member 12 is determined by the strength of the magnetic field based on the coil 11. Therefore, the number of turns of wire wound in the coil 11 is set according to the required magnetic force of the magnetic circuit M1.

[0030] The magnetic yoke 13 has a cylindrical portion 13b extending axially, and a flange portion 13c extending radially outward from one end of the cylindrical portion 13b. The magnetic yoke 13 holds the coil 11 by allowing the cylindrical portion 13b to pass through a through-hole 11a of the coil 11 and by having the flange portion 13c abut against one end face of the coil 11. Furthermore, the cylindrical portion 13b has a through-hole 13a passing through the center of the shaft. The through-hole 13a is formed with a diameter larger than the outer diameter of the shaft 2, allowing the shaft 2 to pass through.

[0031] like Figure 1 As shown, the magnetic yoke 13 has a plurality of permanent magnets 15 located on the channel of the magnetic circuit M1 and inside the rotating cylindrical portion 50 of the rotating body 4 described later.

[0032] like Figure 1 as well as Figure 2 As shown, the permanent magnet 15 is a flat plate extending axially and arranged in a ring along the outer peripheral surface 13d of the yoke 13. The permanent magnet 15 is configured such that the direction of its magnetic flux is opposite to the orientation of the magnetic circuit M1 based on the coil 11, and a magnetic flux loop is generated by means of the yoke 13 and the cover 1. That is, the permanent magnet 15 generates a magnetic flux loop in the direction that cancels out the magnetic circuit M1 based on the coil 11. In this specification, the channel of the magnetic flux loop based on the permanent magnet 15 is defined as magnetic circuit M2.

[0033] Additionally, preferably, between adjacent permanent magnets 15, such as Figure 2As shown, a predetermined gap G is formed. The magnetic circuit M1 passing through the gap G is not blocked by the magnetic circuit M2 based on the permanent magnet 15.

[0034] like Figure 1 As shown, the cover 14 is a cylindrical member extending axially, and houses the cylindrical portion 13b of the coil 11 and the yoke 13 inside. Furthermore, one end face of the cover 14 abuts against the flange portion 13c of the yoke 13. Therefore, the magnetic circuit M1 based on the coil 11 and the magnetic circuit M2 based on the permanent magnet 15 can be maintained without interruption, ensuring a ring-shaped magnetic flux.

[0035] A cylindrical space 16 is formed between the inner peripheral surface 14a of the cover 14 and the outer peripheral surface 13d of the cylindrical portion 13b of the magnetic yoke 13, and the cylindrical space 16 is filled with a functional fluid F.

[0036] As an example, functional fluid F can be a magnetic fluid, also known as a magneto-rheological fluid (MR fluid), which disperses strongly magnetic particles such as iron powder in a liquid like oil. When not subjected to a magnetic field, functional fluid F exhibits the same behavior as ordinary working oil. However, when a magnetic field is applied externally, the strongly magnetic particles uniformly dispersed in the liquid link together along the direction of the magnetic field, forming chain-like bundles. These bundles resist flow, thus increasing the apparent viscosity of functional fluid F. This change in viscosity due to the magnetic field is reversible, and the original state can be restored by removing the magnetic field. Furthermore, the degree of viscosity change can be adjusted by varying the strength of the magnetic field.

[0037] The direct-acting engagement portion 20 supports the shaft 2 so that it can move axially. As an example, the direct-acting engagement portion 20 is formed with a load rolling groove 22 corresponding to the guide groove 2b of the shaft 2.

[0038] The direct-acting engagement portion 20 is mounted on the shaft 2 via a plurality of balls 21 that roll between a guide groove 2b formed on the shaft 2 and a load rolling groove 22. The shaft 2 is assembled to be able to circulate axially along the load rolling groove 22 with a limited capacity relative to the direct-acting engagement portion 20.

[0039] Alternatively, the direct-acting engagement portion 20 may have an axially extending, unloaded rolling path (not shown), with both ends of the unloaded rolling path connected to the load rolling groove 22, thereby allowing the balls 21 to circulate infinitely within the direct-acting engagement portion 20. It should be noted that while the method of infinite circulation with an unloaded rolling path has been described, the method of infinite circulation is not limited to this; various circulation methods can be employed. For example, the end plate mounted at the end of the direct-acting engagement portion 20 may have a circulation structure.

[0040] The rotating body 4 has: a rotating engagement portion 60 that guides the rotating body 4 to rotate about the axis relative to the axis 2; and a rotating cylindrical portion 50 that is inserted into the cylindrical space 16 of the stationary body 3.

[0041] The rotating engagement part 60 has, for example, a load rolling groove 62 corresponding to the threaded groove 2a of the shaft 2.

[0042] The rotating engagement part 60 is mounted axially relative to the shaft 2 by means of a plurality of balls 61 rolling between the threaded groove 2a and the load rolling groove 62. Additionally, the rotating engagement part 60 has a return element (not shown).

[0043] The return piece is fixed to the rotary engagement part 60 by turning several times over the threaded groove 2a of the shaft 2. A ball 61, scooped up from the threaded groove 2a of the shaft 2 by the end of the return piece, rolls within the return piece and is fed back into the threaded groove 2a several turns earlier. Thus, the ball 61 is configured to circulate infinitely within the rotary engagement part 60. It should be noted that while the method of using the return piece has been described as an infinite circulation method, the infinite circulation method is not limited to the return piece. Various circulation methods can be used. For example, the end plate mounted on the axial end of the rotary engagement part 60 can have a circulation structure, or a reverser can be used to restore the ball 61 to a predetermined number of turns.

[0044] The rotating cylindrical portion 50 is made of a magnetic material, such as an ferrous material, and is formed as a thin-walled cylinder extending axially. The rotating cylindrical portion 50 is inserted into a cylindrical space 16 filled with a functional fluid F. The inner circumferential surface 50a of the rotating cylindrical portion 50 and the outer circumferential surface 13d of the magnetic yoke 13, and the outer circumferential surface 50b of the rotating cylindrical portion 50 and the inner circumferential surface 14a of the cover 14, respectively, have gaps and are opposed to each other. In this specification, the gap between the inner circumferential surface 50a and the outer circumferential surface 13d is defined as gap S1, and the gap between the outer circumferential surface 50b and the inner circumferential surface 14a is defined as gap S2. The functional fluid F is sandwiched between gaps S1 and gap S2.

[0045] Preferably, at the other end of the magnetic yoke 13 and the other end of the cover 14, such as Figure 1 As shown, an oil seal 31 is installed with sealing gaps S1 and S2. Using such an oil seal 31, the functional fluid F filling the cylindrical space 16 can be prevented from leaking into the external space.

[0046] Next, an example of the operation of such a damping device D will be explained.

[0047] As an example, the damping device D according to this embodiment can be used in shock absorbers for motor vehicles, etc. In this case, the damping device D is installed with the damper body 1 on the vehicle body side and the axle 2 on the wheel side, and is arranged with the axial direction of the damping device D in the vertical direction.

[0048] When a vehicle equipped with the damping device D travels over uneven road surfaces, the axle 2 mounted on the wheel side slides axially relative to the damper body 1 mounted on the vehicle body side. At this time, the axle 2 can slide relative to the damper body 1 without rotation because the guide groove 2b engages with the direct-acting engagement part 20. Furthermore, since the axle 2 is configured to pass through the through hole 13a of the magnetic yoke 13, it can slide in a manner that does not interfere with the interior of the damper body 1.

[0049] Since the threaded groove 2a engages with the rotating engagement part 60, the rotating body 4 rotates around the shaft as it slides axially. The rotating body 4 is mounted on the stationary body 3 by means of the thrust bearing 5, so it rotates coaxially with respect to the stationary body 3 without moving axially.

[0050] As described above, the rotating body 4 includes a rotating cylindrical portion 50 that is inserted into a cylindrical space 16 filled with a functional fluid F. Therefore, the rotating cylindrical portion 50 rotates in the functional fluid F along with the rotation of the rotating body 4.

[0051] At this time, when current is input to coil 11, a magnetic circuit M1 is formed by the generated magnetic field. In addition, the magnetic circuit M1 passes through gap S1 and gap S2. Functional fluid F is filled in gap S1 and gap S2, so the strongly magnetic particles dispersed in the functional fluid F according to the magnetic circuit M1 are linked together along the direction of the magnetic flux and form a chain-like bundle.

[0052] With such a bundle formed, when the rotating cylinder 50 rotates in the functional fluid F, shear resistance is generated by the bundle formed in the gaps S1 and S2. That is, according to the damping device D of this embodiment, the apparent viscosity of the functional fluid F can be adjusted by controlling the input current to the coil 11, and the damping characteristics corresponding to the requirements can be obtained.

[0053] Next, the case where the damping force of the damping device D according to this embodiment is zero will be explained.

[0054] Generally, it is known that when a magnetic field is generated by inputting current into a coil, even if control is performed by disconnecting the current, a ring-shaped magnetic flux remains around the coil. This is due to the magnetization of the components forming the magnetic circuit. Therefore, according to conventional damping devices, even if the current input to the coil is disconnected, a bundle based on the residual magnetic flux remains in the functional fluid, preventing the damping force of the damping device from reaching zero.

[0055] The damping device D according to this embodiment has a permanent magnet 15 disposed in the channel of the magnetic circuit M1 generated by the coil 11. Furthermore, the permanent magnet 15 is configured such that the direction of the magnetic flux in the magnetic circuit M2 is opposite to that in the magnetic circuit M1. Therefore, according to the damping device D according to this embodiment, the magnetic circuit M2 based on the permanent magnet 15 cancels the residual magnetic flux in the magnetic circuit M1 based on the coil 11, and by disconnecting the current input to the coil 11, the attenuation force of the damping device D can be made zero.

[0056] In addition, such as Figure 2 As shown, the permanent magnets 15 are arranged in a ring shape with gaps G between adjacent permanent magnets 15. The magnetic circuit M1 passing through the gaps G is not blocked by the magnetic circuit M2 based on the permanent magnets 15. Therefore, although the damping device D has permanent magnets 15 that generate a magnetic circuit M2 in the opposite direction to the magnetic circuit M1 based on the coil 11, any damping force can be obtained by controlling the current input to the coil 11.

[0057] Thus, according to the damping device D of this embodiment, without special control, the residual magnetic flux based on the coil 11 can be eliminated, and the residual attenuation force generated in the damping device D can be continuously eliminated.

[0058] It should be noted that since the strength of the magnetic field based on the residual flux is essentially constant, when the current input to coil 11 is disconnected, the permanent magnet 15 generated by the flux ring with a specified magnetic force can make the damping force of the damping device D zero, as described above. On the other hand, if the strength of the magnetic field based on the residual flux is smaller than expected, when the current input to coil 11 is disconnected, a damping force may sometimes be generated by the magnetic field generated by the permanent magnet 15.

[0059] Specifically, when the strength of the magnetic field based on residual flux is smaller than expected, such as Figure 3 As shown, when the current input to coil 11 is lower than a certain value indicated at point A, the strength of the magnetic field based on permanent magnet 15 is greater than the strength of the magnetic field generated by the current input to coil 11, or the strength of the magnetic field based on residual flux. At this time, even if the current input to coil 11 is disconnected, the attenuating force shown at point B is generated through the magnetic field based on permanent magnet 15.

[0060] Thus, when the strength of the magnetic field based on the residual flux is smaller than the strength of the magnetic field based on the permanent magnet 15, it is preferable to control the current input to the coil 11 based on the current value generated by the difference between the strength of the magnetic field based on the permanent magnet 15 and the strength of the magnetic field based on the residual flux. That is, when determining the attenuation characteristics of the damping device D, it is preferable to control the input current based on the current value at point A, where the sum of the attenuation force based on the coil 11 and the attenuation force based on the permanent magnet 15 is the lowest.

[0061] Next, the effects of the damping device D according to this embodiment other than those described above will be explained.

[0062] Generally, it is known that strongly magnetic particles dispersed in functional fluids will precipitate over a certain period of time due to the influence of gravity. Therefore, in conventional damping devices, when the damping device is not operated for a long time without inputting current to the coil, it is assumed that strongly magnetic particles will precipitate in the lower vertical direction of the space filled with functional fluid.

[0063] Furthermore, it was confirmed that when a conventional damping device, which has the same structure as the damping device D according to this embodiment except for lacking a permanent magnet 15, is put into operation after being left for a long time, the damping force is higher than the set value immediately after starting, and the damping force becomes the set value after a certain period of time after starting.

[0064] This is believed to be because, in conventional damping devices, due to prolonged placement, the density of strongly magnetic particles within the functional fluid F increases in the high residual magnetic field environment inside the cylindrical space 16, resulting in an increase in the apparent viscosity of the functional fluid F immediately after startup. Furthermore, it is believed that after a certain period of time following startup, when the functional fluid F is thoroughly stirred within the cylindrical space 16, the strongly magnetic particles are uniformly dispersed within the functional fluid F, thus forming a uniform bundle within the cylindrical space 16, and the apparent viscosity of the functional fluid F reaches a predetermined value.

[0065] The following effect was confirmed: the damping device D of this embodiment, which has a permanent magnet 15, is different from the conventional damping device described above. Even when it is left for a long time, it can still obtain the set value of attenuation force after it has just been started.

[0066] This is believed to be because the damping device D according to this embodiment has a permanent magnet 15, so even when no current is input to the coil, the strongly magnetic particles in the functional fluid F are appropriately dispersed under the magnetic flux density that is appropriately averaged by the residual magnetic flux of the magnetic circuit M1 based on the coil 11 and the magnetic circuit M2 based on the permanent magnet 15. That is, it is believed that the damping device D according to this embodiment can prevent the precipitation of strongly magnetic particles in the functional fluid F by using the permanent magnet 15.

[0067] It should be noted that in the above embodiment, only one rotating cylindrical portion 50 is formed in the rotating body 4, which is inserted into the cylindrical space 16 filled with functional fluid F. However, multiple rotating cylindrical portions 50 may also be formed in the rotating body 4 depending on the magnitude of the attenuation force of the required damping device D.

[0068] Furthermore, in the above embodiment, the case where the permanent magnet 15 is only disposed inside the rotating cylindrical portion 50 of the rotating body 4 has been described. The permanent magnet 15 can be disposed on the channel of the magnetic circuit M1 based on the coil 11, for example, it could be as follows: Figure 4 As shown in (a), the configuration on both the inner and outer diameter sides of the rotating cylindrical portion 50 can also be as follows: Figure 4 As shown in (b), it is configured on both the inner and outer diameter sides of coil 11, or it can also be as shown in (b). Figure 4 As shown in (c), it is positioned in a position that does not overlap radially with the coil 11 and the rotating cylinder 50.

[0069] It should be noted that, in the above embodiments, the damping device D was described as being used in shock absorbers for motor vehicles, etc., but the damping device D involved in this embodiment is not limited to this, and can also be used in suspension devices mounted on small mobile bodies, delivery robots, etc. As can be seen from the description of the technical solution, such modifications or improvements are also included within the technical scope of the present invention.

[0070] Explanation of reference numerals in the attached figures

[0071] 1 Damper body; 2 Shaft; 2a Threaded groove; 3 Stationary body; 4 Rotating body; 10 Electromagnetic part; 11 Coil; 12 Magnetic circuit forming component; 15 Permanent magnet; 16 Cylindrical space; 50 Rotating cylindrical part; 60 Rotating engaging part; D Damping device; F Functional fluid; M1, M2 Magnetic circuit.

Claims

1. A damping device, characterized in that, The damping device includes: The damper body, which is sealed with a functional fluid whose apparent viscosity can be adjusted using a magnetic field; and The shaft, which can slide freely along the axial direction relative to the damper body, The outer circumference of the shaft has a helical threaded groove extending axially. The damper body comprises a stationary body and a rotating body. The stationary body has an electromagnetic component that generates the magnetic field. The electromagnetic component includes: a coil with wire wound around its center; a magnetic circuit forming member housing the coil; and a permanent magnet. The magnetic circuit forming component has a cylindrical space filled with the functional fluid. The permanent magnet is disposed within the magnetic circuit forming member on a magnetic circuit based on the magnetic field. The rotating body includes: a rotating engaging portion that engages with the threaded groove; and a rotating cylindrical portion that extends in a cylindrical shape along the axial direction. The rotating cylindrical portion is inserted into the cylindrical space with a gap formed between it and the magnetic circuit forming member.

2. The damping device according to claim 1, characterized in that, The permanent magnet is configured such that the magnetic flux of the permanent magnet cancels out the orientation of the magnetic flux of the magnetic circuit.

3. The damping device according to claim 1, characterized in that, The permanent magnet is configured as a ring coaxial with the coil.

4. The damping device according to claim 3, characterized in that, The permanent magnets are arranged in multiples with gaps between them.

5. The damping device according to claim 3, characterized in that, The permanent magnet is disposed on the inner diameter side of the rotating cylindrical section.

6. The damping device according to claim 1, characterized in that, The damping device is installed on the wheels of the moving body as a suspension device.

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