KR100279187B1 - Vibration generator - Google Patents

Abstract

By assembling a plurality of permanent magnets, it is possible to provide a vibration generating mechanism that can realize a compact and low noise exciter.

At least two permanent magnets (12, 14, 46, 48) facing each other with a repulsive stimulus are disposed apart from each other, and the link mechanism (16, 50) is connected to one of the permanent magnets (12, 46). . In addition, since the driving force of the drive sources 18 and 52 is applied to the permanent magnets 12 and 46 through the link mechanisms 16 and 50, the permanent magnets 12 and 46 are applied to the other permanent magnets. It is possible to periodically reciprocate with respect to (14, 48), and by virtue of this reciprocating motion, the opposing areas of the permanent magnets (12, 14, 46, 48) are changed to vibrate the other permanent magnets (14, 48). You can.

Description

Vibration generator

The present invention relates to a vibration generating mechanism in a horizontal or vertical direction, and more particularly, to a vibration generating mechanism for generating vibration energy in either the horizontal or vertical direction by using the repulsive force of a plurality of permanent magnets.

Conventionally, an oscillator which artificially generates vibration is used to investigate vibration characteristics of a structure. Moreover, as an excitation group, a coin type thing, an unbalanced mass, and a cam type thing are generally known.

However, in a vibrator using a crank mechanism such as a crank, since a direct load is applied to the driving motor, a relatively large driving motor is required, and in the case of a coin type, there is a problem in that low frequencies cannot be coped with.

In addition, due to the large scale of the device itself, not only the securing of the installation site and construction work are required, but also the forced heat cooling is required due to the large amount of heat generated, so that the joint evaluation cannot be performed by the exhaust sound of a fan or the like. There was this.

In addition, since all the said excitation groups are complicated, heavy, and expensive, a light weight and a cheap thing are desired.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and an object thereof is to provide a vibration generating mechanism that can realize a compact and low noise exciter by assembling a plurality of permanent magnets.

1 is a schematic diagram showing an equilibrium position of an input side and an output side of two permanent magnets in the magnetic spring of the present invention.

FIG. 2 is a graph of basic characteristics showing the relationship between the applied load and the displacement amount from the equilibrium position of the permanent magnet in the magnetic spring of FIG. 1; FIG.

3 is a graph showing the relationship between the measured load and the displacement amount.

Fig. 4 is a schematic diagram showing the input / output thinking method in the charge model assuming that the magnetic force is uniformly distributed on the cross section of the permanent magnet, where (a) is suction and (b) is repulsion. (c) shows the repulsion of the site different from (b), respectively.

Fig. 5 is a schematic diagram of a mirror moved in a permanent magnet facing the same magnetic pole with respect to one of the other (the opposite area is changed).

FIG. 6 is a graph showing loads in the X-axis and Z-axis directions with respect to the X-axis movement amount when calculated based on FIG. 5; FIG.

FIG. 7 shows the displacement amount when the separation distance of the permanent magnet of FIG. 5 is kept constant, when one side is moved from the fully deviated state to the other fully lap state and then moved from this state to the completely deviated state. Graph showing the relationship with the load.

Fig. 8 is a schematic diagram of a case in which a permanent magnet has opposing dynamic magnetic poles and one side is rotated relative to the other (the opposing area is changed).

FIG. 9 is a graph showing a maximum load with respect to an opposing area when the permanent magnet is rotated based on FIG. 8. FIG.

Fig. 10 is a graph showing the relationship between the distance between magnets and a load when a neodymometer magnet is adopted as a permanent magnet.

Fig. 11 is a perspective view of a slide type principle model for changing geometric dimensions by changing opposing areas of permanent magnets.

12 is a graph showing the relationship between input and output obtained by the slide-type principle model of FIG.

FIG. 13 is a schematic perspective view of a first vibration generating mechanism showing an application example of the slide-type principle model of FIG.

14 is a schematic perspective view of a second vibration generating mechanism showing an application example of the slide-type principle model of FIG.

15 is a schematic view showing a mechanical model of the vibration generating mechanism of the present invention.

Fig. 16 is a block diagram of closed loop control in the case of using VCM as a driving source of the vibration generating mechanism and driving VCM with sin waves.

Fig. 17 is a graph showing sin waves used as driving waves.

18 is a graph showing a random wave used as a driving wave.

* Explanation of symbols for main parts of the drawings

2, 4, 12, 14, 36, 40, 42, 46, 48, 62, 66, 68, 70: permanent magnet

6: Expectation 8: Linear Slider

10: L type angle 16, 50: Link mechanism

18, 52: VCM 34: Load adjustment spring

76: sin table 78: digital-to-analog converter

80: VCM amplifier 82: Potentiometer

84: comparator

In order to achieve the above object, the invention described in claim 1 includes at least two permanent magnets opposed to each other and opposed to each other, a link mechanism connected to either one of the permanent magnets, and the link mechanism through the link mechanism. And a drive source for driving the permanent magnets of the permanent magnets, wherein the one or more permanent magnets are reciprocated periodically with respect to the other permanent magnets to change the opposing area of the permanent magnets to vibrate the other permanent magnets. It is a vibration generating mechanism characterized in that.

In addition, the invention described in claim 2 spaces the at least two permanent magnets in the vertical direction, while each pair of the permanent magnets is spaced in the vertical direction in a state in which the opposing stimulus is opposed to each of the permanent magnets. It is characterized by using a repulsive force of a pair of permanent magnets to support the load applied in the vertical direction.

In the invention according to claim 3, in the invention according to claim 2, a load adjusting means is attached to a part of the linking mechanism, and the load adjusting means eliminates the horizontal load applied to the one permanent magnet. It is characterized by.

In the invention according to claim 4, in the invention according to claim 1, the at least two permanent magnets are spaced apart in the first horizontal direction, and a pair of permanent magnets are placed on one side of the permanent magnets in the first horizontal direction. Wherein the repulsive stimulus is spaced apart from each other so that one of the at least two permanent magnets and one of the pair of permanent magnets are vibrated in the first horizontal direction with respect to the other permanent magnet corresponding thereto. It is done.

In the invention according to claim 5, in the invention according to claim 4, the pair of permanent magnets are separated from each other in a state in which the repulsive stimulus is opposed to each other in a second horizontal direction perpendicular to the first horizontal direction. By connecting one of the pair of permanent magnets to the link mechanism, the repulsive force in the second horizontal direction between the permanent magnets facing each other is balanced.

(Example)

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described, referring drawings.

In the case of a magnetic spring structure having at least two permanent magnets spaced apart from each other and opposing the same magnetic poles, the separated permanent magnets are non-contacting, so when ignoring friction loss or the like of the structure itself, By changing the static magnetic field (magnification arrangement) with a small input by using nonlinear output (return) on the same line as () and using the independence of the non-contact treatment and the instability of the floating control system. Negative attenuation tends to occur.

The present invention has been made in view of this fact, by changing the geometric dimensions between two permanent magnets on the input side (rolling line) and output side (returning) by a mechanism or external force in the movement stroke, and converting them into repulsive force in the movement system. The repulsive force on the output side is greater than the repulsive force on the input side from the equilibrium position of the two permanent magnets.

The basic principle is described below.

Fig. 1 is a schematic diagram showing the equilibrium positions of two permanent magnets 2 and 4 on the input side and the output side, and the load applied to either permanent magnet in Fig. 2 and the displacement amount from the equilibrium position of the two permanent magnets. The basic characteristics of the magnetic spring structure showing the relationship with

As shown in FIG. 1, the equilibrium position and the spring constant of the input side of the permanent magnet 4 with respect to the permanent magnet 2 are x ₀ and k ₁ , respectively, and the equilibrium position and the spring constant of the output side x respectively. _{When 1} and k ₂ are used, area conversion is performed between x ₀ and x ₁ , and the following relationship is established at each equilibrium position.

-k ₁ / x ₀ + mg = 0

-k ₂ / x ₁ + mg = 0

k ₂ ＞ k ₁

Therefore, the static characteristics show negative attenuation characteristics as shown in Fig. 2, and it can be considered that the potential value at the position x ₁ and the position x ₀ is the potential energy of oscillation.

Moreover, when the model of FIG. 1 was produced and the relationship between load and displacement amount was measured by changing the time to apply a load, the graph as shown in FIG. 3 was obtained. This is because when the two permanent magnets 2 and 4 are close to the closest position, a large repulsive force is applied, and when the displacement amount from the equilibrium position changes slightly, friction loss occurs due to the damper effect of the magnetic spring. It is interpreted that the attenuation term appears.

In FIG. 3, (a) is a graph in the case of applying a constant load, and the time to which load was applied in order of (a), (b), (c) is shortening. In other words, the static characteristics vary depending on the method of applying the load, and the longer the time for applying the load, the greater the reverse.

In addition, the rare earth magnet does not depend on the magnetic field for the strength of magnetization. That is, since the internal magnetic moment is hardly affected by the magnetic field, the intensity of magnetization hardly changes on the potato curve, and almost maintains the value of the strength of the saturation magnetization. Therefore, in the rare earth magnet, input and output can be considered using a difference model that assumes that the magnetic domains are uniformly distributed on the cross section.

Figure 4 illustrates such a way of thinking, the magnet is defined as a set of magnets of the smallest unit, calculated by classifying the relationship of the force between each unit magnet to three.

(a) Aspiration (both r and m are the same, so define two types as one)

f ⁽¹⁾ = (m ² / r ² ) dx ₁ dy ₁ dx ₂ dy ₂

f _x ⁽¹⁾ = f ⁽¹⁾ cosθ

f _z ⁽¹⁾ = f ⁽¹⁾ sinθ

(b) repulsion

f _x ⁽²⁾ = f ⁽²⁾ cosθ

f _z ⁽²⁾ = f ⁽²⁾ sinθ

(c) repulsion

f _x ⁽³⁾ = f ⁽³⁾ cosθ

f _z ⁽³⁾ = f ⁽³⁾ sinθ

therefore,

-f _x = 2f _x ⁽¹⁾ -f _x ⁽²⁾ -f _x ⁽³⁾

-f _z = 2f _z ⁽¹⁾ -f _z ⁽²⁾ -f _z ⁽³⁾

Here, Coulomb's law is expressed as

F = K (q ₁ q ₂ / r ² ) r: distance

q = MS q ₁ , q ₂ : Magnetic

(m) M (m): strength of magnetization

S: Area

The force can be obtained by integrating the above -f _x and -f _z in the range of the dimensions of the magnet.

As shown in FIG. 5, the graph of FIG. 6 calculates by moving the opposing magnet from the state which fully wrapped each magnetic gap (x-axis movement amount = 0 mm) to the completely shifted state (x-axis movement amount = 50 mm). However, the term "internal magnetic moment is constant" is defined. However, when the magnetic gap is small, it is disturbed around the magnet.

The calculation result is also substantially in agreement with the measured value, the force moving from point a to b in Fig. 2 is the x direction load, the output is expressed as the z direction load, and the relationship of input <output due to instability It is statically clarified.

FIG. 7 is a graph showing the relationship when the separation distance of the magnet shown in FIG. 5 is maintained at 3 mm and moved from the completely displaced state to the fully wrapped state and then moved from this state to the completely displaced state. This graph shows that the absolute value of the x-direction load is the same and the output direction is reversed. When it approaches the complete lap state, it becomes a resistance, that is, attenuation, and accelerates when the transition from the complete lap state is completely shifted. It is shown.

Also, as shown in FIG. 8, when the rotation angles of the opposing magnets were changed, a graph as shown in FIG. 9 was obtained. As a matter of course, the maximum load decreases when the opposing area decreases, and it is shown that the output can be changed through area conversion by applying a predetermined input.

Fig. 10 is a graph showing the relationship between the distance between the magnets and the load in the case of employing a neodymometer magnet as a permanent magnet, and the repulsive force increases with mass increase. Where the repulsive force F

F∝Br ² × (geometric dimension) Br: strength of magnetization

The geometric dimension refers to a dimension determined by the separation distance of the opposing magnet, the opposing area, the magnetic flux density, the strength of the magnetic field, and the like. When the magnetic materials are the same, the strength (Br) of the magnetization is constant, so that the repulsive force of the magnet can be changed by changing the geometric dimensions.

Fig. 11 shows a slide-type principle model in which one of the permanent magnets 2 and 4 is slid relative to the other to change the geometric dimensions by changing the opposing area.

As shown in FIG. 11, the permanent magnet 2 is freely attached to the base 6 by sliding, and the linear slider 8 is fixed to the base 6 and is vertically installed on the upper side thereof. . The linear slider 8 is freely attached to the L-shaped angle 10, and the lower surface of the L-shaped angle 10 has a permanent magnet 4 facing the same (repulsive) magnetic pole against the permanent magnet 2. It is fixed in a state.

In the slide-type principle model of the above structure, the permanent magnets (2, 4) of 50 mmL x 25 mmW x 10 mmH (brand name: NEOMAX-39SH) are used and the permanent magnets (2) are loaded using a load of 3.135 kg in total. ), A result as shown in FIG. 12 was obtained.

Fig. 12 shows the experimental values of the input and output as one J. An output day of about 4 J is obtained for an input day of about 0.5 J. A magnetic spring composed of two opposing permanent magnets 2 and 4 is obtained. By using the negative attenuation characteristic of the excitation or by changing the sperm energy, it is possible to take out a large output day with a small input day.

Fig. 13 shows a first magnitude generating mechanism showing an application example of the slide-type principle model.

The vibration generating mechanism shown in FIG. 13 includes a first permanent magnet 12 free of sliding movement, a second permanent magnet 14 freely moving up and down by a predetermined distance from the first permanent magnet 12, and a first permanent magnet. And a driving source 18 such as a VCM (voice coil motor) for sliding the first permanent magnet 12 through the lining mechanism 16, and The first permanent magnet 12 and the second permanent magnet 14 are placed in a state in which the same (repulsive) magnetic poles face each other. The link mechanism includes a rod 20 connected to the first permanent magnet 12, a first lever 22 having one end rotatably connected to an approximately middle portion of the rod 20, and the other of the first lever 22. And a second lever 24 having a freely rotatable end, and a third lever 26 having one end freely rotatable with an approximately middle portion of the first lever 22. The end is freely attached to the base 28 such as a base plate, for example, and the other end of the third lever 26 is connected to the reciprocating shaft 18a of the drive source 18. In addition, the end opposite to the connecting end of the rod 20 with the first permanent magnet 12 is loosely inserted into the rod support portion 30 and at the same time, the stopper 32 and the rod support portion 30 fixed to the rod 20. A spring 34 as a load adjusting means is wound around the rod 20 between the rod and the rod 20.

In the above configuration, when the first permanent magnet 12 is reciprocated in the horizontal direction from the driving source 18 via the link mechanism 16 in the state where the load W is applied to the second permanent magnet 14, The second permanent magnet 14, in which the same magnetic pole is opposed to the first permanent magnet 12, moves in the vertical direction. That is, the vibration generating mechanism of FIG. 13 generates vibration by periodically changing the opposing areas of the pair of permanent magnets 12 and 14 facing each other, thereby generating periodic vibration in the vertical direction.

Then, according to the load W applied to the second permanent magnet 14, the pair of permanent magnets 36 and 38 on one side of the first and second permanent magnets 12 and 14, and on the other side In addition, the pair of permanent magnets 40 and 42 may be disposed to face the same magnetic poles. In this configuration, the second permanent magnet 14 and the permanent magnets 38 and 42 disposed on both sides thereof are fixed to, for example, the base plate 44, while the base plate 44 is supported (28). It is possible to generate periodic vibrations in the load W by freely attaching the sliding movement in the vertical direction through a plurality of vertical axes or the like.

When the above configuration is described in more detail, while supporting the load with the stationary magnets 36, 38, 40, 42, the amplitude is temporarily set to the volume of the magnet having the equilibrium point (first permanent magnet 12), The vibration of the magnet 12 generates the vertical vibration. The stroke amount of the excitation magnet 12 is set by the load curve, the amplitude, and the load mass. The center of gravity is the reference position and the neutral position of the drive source 18 is set. The assist mechanism (load adjusting spring 34, etc.) is used to set the bone magnetic force of the load to set the neutral position. Here, the bone magnetic of the load refers to a position where the horizontal load applied to the excitation magnet 12 through the second permanent magnet 14 is resolved by the assist mechanism of the driving source and is in a balanced state.

In addition, the top dead center and the bottom dead center in the vertical direction are determined by the horizontal stroke amount of the excitation magnet 12, and the wrap amount and the gap amount with respect to the second permanent magnet 14 of the excitation magnet 12 at the top and bottom dead centers. The horizontal and vertical loads of each point are determined. The spring constant of the assist mechanism of the drive source 18 is determined by the horizontal load at the top and bottom dead centers.

Fig. 14 shows a second vibration generating mechanism showing an application example of the slide type principle model.

The vibration generating mechanism shown in FIG. 14 moves in the X-axis direction with the first permanent magnet 46 at a predetermined distance from the first permanent magnet 46 and the first permanent magnet 46 free of sliding movement in the Y-axis direction. VCM for sliding the first permanent magnet 46 through the second permanent magnet 48, the linking mechanism 50 connected to the first permanent magnet 46, and the linking mechanism 50 free of relative movement ( A drive source 52 such as a voice coil motor) is provided, and the first permanent magnet 46 and the second permanent magnet 48 are arranged in a state in which the same (repulsive) magnetic poles face each other. The link mechanism includes a first rod 54 having one end connected to the first permanent magnet 46, a first lever 56 having one end freely connected to the other end of the first rod 54, and a first lever. The other end of the 56 is provided with a second lever 58 having one end freely connected to the rotation, and a second rod 60 having one end freely connected to the rotation about the middle of the first lever 56. In addition, the other end of the second rod 60 is connected to the third permanent magnet 62, which is free to slide in the Y-axis direction, while the other end of the second lever 58 is a reciprocating shaft ( 52a). The first lever 56 is rotatably attached to the base 64 between the connecting portion of the second lever 58 and the connecting portion of the second rod 60.

In addition, the fourth permanent magnet is spaced apart from the third permanent magnet 62 in the Y-axis direction, and the same permanent magnetic pole as the third permanent magnet 62 faces the first permanent magnet. On the opposite side of 46), the fifth and sixth permanent magnets 68 and 70 are freely moved relative to each other in the X-axis direction.

In the above configuration, the second permanent magnet 48 and the sixth permanent magnet 70 extend in parallel with the base 64 and are fixed to the base plate (not shown) spaced apart from the base 64 by a predetermined distance. When the first permanent magnet 46 is reciprocated in the Y-axis direction by the drive source 52 through the link mechanism 50, either the base 64 and the base plate reciprocate in the X-axis direction with respect to the other side. do. That is, the vibration generating mechanism of Fig. 14 generates excitation by periodically changing the opposing areas of the pair of opposing permanent magnets 46 and 48 to generate periodic vibrations in the horizontal direction.

In Fig. 14, 72 and 74 indicate the movable magnets, that is, the sliders to which the first permanent magnets 46 and the third permanent magnets 62 are freely attached.

In more detail, the volume of the movable magnet (first permanent magnet 46) to be excited in the horizontal direction (X-axis direction in Fig. 14) is determined by the vibration amplitude, and the stroke amount and the movable magnet 46 The load characteristics satisfying the load mass condition and the vibration acceleration are determined from the relationship between the wrap amount and the gap amount with the second permanent magnet 48 opposite to). The load value of the balance magnet (third permanent magnet 62) is determined so as to resolve the reaction force from the load requirement at the neutral position and bring it into a balanced state. Further, the load-bending curve is determined by a load value that balances the reaction force in the slide direction of the movable magnet at the maximum amplitude point in both the X-axis and the Y-axis, and the input from the driving source 52 and the input of the balance magnet. Based on this, the moving range and the volume which consider the lever ratio of the balance magnet are determined.

Next, control of the vibration generating mechanism having the above configuration will be described.

A sin wave or a random wave is used as the drive wave of the drive sources 18 and 52 such as VCM, and in order to control (feedback) the VCM or the like to a predetermined position or acceleration, as shown by the mechanical model of FIG. Sensors such as potentiometers that detect movement are needed.

That is, when the sin wave is used as the driving wave, the rotary encoder is sensed by detecting the movement of the excitation band (the plate 44 in FIG. 13 or the plate or base 64 in FIG. A position sensor such as a potentiometer or the like is required, and in order to control the acceleration by sensing the acceleration of the excitation stand, an acceleration sensor is required. In addition, when a random wave is used as the driving wave, a position sensor such as a rotary encoder for detecting the movement of the excitation band is required.

FIG. 16 shows a block diagram of the closed loop control in the case where VCM is used as the drive sources 18 and 52 and the VCM is driven with the sin wave shown in FIG.

In Fig. 16, data is output from the sin wave table 76 to the D / A (digital-to-analog converter 78) at a predetermined timing (for example, every 1 msec), and the voltage value is PWM (pulse width modulation). The VCMs 18 and 52 are driven by inputting them to a VCM amplifier 80 such as a control amplifier, etc. A potentiometer 82 is connected to the VCMs 18 and 52, and the value and output of the potentiometer 82 are comparators. The second difference is output to the D / A 78 to drive the VCMs 18 and 52 to the target position, and the sin wave table 76 is connected to a personal computer, for example. By transmitting the start command from the personal computer, a predetermined sin wave can be output from the sin wave table 76, and the output can be continued until a stop command or a clear command is transmitted.

It is also possible to use a random wave as shown in Fig. 18 as the drive wave, and output the amplitude value from the amplifier 80 at a predetermined timing based on the start command transmitted from the personal computer, and the VCMs 18, 52. ) Can be closed loop control so as to be set at the target position, and its output can be maintained until the next data is transmitted from the amplifier 80.

Since this invention is comprised as mentioned above, it has the following effects.

According to the invention described in claim 1 of the present invention, one of at least two permanent magnets facing each other by the driving force from the driving source is reciprocated periodically to change the opposing permanent magnets by vibrating the other permanent magnets. Since the load applied to the other permanent magnet can be vibrated using the repulsive force of the permanent magnet, it is easy to manufacture a compact, low-cost vibration generating mechanism with low noise.

Further, according to the invention of claim 2, the at least two permanent magnets are spaced apart in the vertical direction, while a pair of permanent magnets are spaced apart in the vertical direction in a state in which opposing magnetic poles are opposed to each of the pair of permanent magnets. Since the repulsive force of the pair of permanent magnets is used to support the load applied in the vertical direction, it is possible to cope with a large load and to generate a desired vibration.

In addition, according to the invention as set forth in claim 3, a load adjusting means is attached to a part of the link mechanism, and the load adjusting means is used to cancel the horizontal load applied to the one permanent magnet. There is no need to do this, and the vibration generating mechanism can be made compact.

According to the invention of claim 4, the at least two permanent magnets are spaced apart in the first horizontal direction, while one pair of permanent magnets are spaced apart in a state in which the repulsive stimulus is opposed to the first horizontal direction. Since one of the opposing permanent magnets is caused to vibrate in the first horizontal direction with respect to the corresponding other permanent magnets, the vibrations in the horizontal direction can be generated by a low noise, compact and inexpensive vibration generating mechanism.

Further, according to the invention of claim 5, the pair of permanent magnets are separated from each other in a state in which the repulsive stimulus is opposed in the second horizontal direction perpendicular to the first horizontal direction, and one of them is connected to the link mechanism. This makes it possible to balance the repulsive force in the second horizontal direction between the permanent magnets facing each other, so that it is not necessary to increase the driving force of the driving source, and the vibration generating mechanism can be made compact.

Claims (5)

At least two permanent magnets opposed to each other and opposed to each other by a repulsive stimulus, a linking mechanism connected to one of the permanent magnets, and a driving source for driving the one permanent magnet through the linking mechanism. And vibrating the one permanent magnet periodically with respect to the other permanent magnet to change the opposing area of the permanent magnet so as to vibrate the other permanent magnet. The method of claim 1, wherein the at least two permanent magnets are spaced apart in the vertical direction, and a pair of permanent magnets are spaced in the vertical direction on both sides of the permanent magnet in the vertical direction with the opposing stimulus facing each other. Vibration generating mechanism characterized in that to support the load applied in the vertical direction by using the repulsive force of the permanent magnet. The vibration generating mechanism according to claim 2, wherein a load adjusting means is attached to a part of the linking mechanism so that the horizontal load applied to the one permanent magnet is released by the mounting adjusting means. The method of claim 1, wherein the at least two permanent magnets are spaced apart in the first horizontal direction, while a pair of permanent magnets are spaced apart from each other in a state in which the repulsive stimulus is opposed to the first horizontal direction. And vibrate one of the at least two permanent magnets and one of the pair of permanent magnets in the first horizontal direction with respect to the other permanent magnet corresponding thereto. The method of claim 4, wherein the pair of permanent magnets are separated from each other in a state in which the repulsive stimulus is opposed to each other in a second horizontal direction perpendicular to the first horizontal direction, and at least one of the pair of permanent magnets is And a linking mechanism to balance the repulsive force in the second horizontal direction between the permanent magnets facing each other.