JPH05168107A - Magnetic levitation mechanism - Google Patents

Abstract

PURPOSE:To provide a stabilized magnetic levitation mechanism at low cost by disposing a stopper closely to the underside of an upper balance point among two balance points where the gravity of levitating part balances with a levitating force which is the sum of attracting force and repelling force to be produced at an intermediate part by means of permanent magnets disposed at upper and lower securing parts. CONSTITUTION:Permanent magnets 4u, 4d are fixed, respectively, to upper and lover securing parts 2u, 2d. Permanent magnets 3u, 3d are further fixed to the opposite vertical ends of a levitating part 1 interposed between the securing parts 2u, 4u. The permanent magnets 4u, 3u oppose with unlike poles to be attracted each other whereas the permanent magnets 3d, 4d oppose with like poles to be repelled each other. Among two balance points where the gravity of the levitating part 1 balances with the levitating force, i.e., the sum of attracting force and repelling force, a stopper 5 is disposed closely to the underside of upper balance point. According to the constitution, a downsized stabilized levitation mechanism can be formed at low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic levitation mechanism capable of levitation of a floating portion against a fixed portion by magnetic force and maintaining the floating state.

[0002]

2. Description of the Related Art In the field where it is necessary to prevent the generation of dust, such as semiconductor manufacturing equipment, when carrying articles, etc.
Various magnetic levitation mechanisms have been proposed in order to prevent dust generation due to sliding, collision, and the like.

The magnetic levitation mechanism can be classified into, for example, a type using an electromagnet, a type using a permanent magnet, and a type using both of them together. Then, the magnetic levitation mechanism of the type using a permanent magnet is roughly classified into a type in which the levitation part is attracted and levitated by a magnetic attraction force, and a type in which the levitation part is levitated by a magnetic repulsion force.

Here, in the type that floats by the attraction force of the permanent magnet, for example, permanent magnets are respectively provided at a specific portion of the upper surface of the floating portion and a portion of the fixed portion facing the upper portion, and the polarities of the facing permanent magnets are different from each other. To place. On the other hand, in the type that uses the repulsive force of the permanent magnets, for example, permanent magnets are provided at one location on the lower surface of the floating portion and at the location of the fixed portion facing it, and the permanent magnets are arranged so that the polarities of the facing permanent magnets are the same. There is.

[0005]

However, when the repulsive force of the permanent magnet is used to levitate, the transverse direction (or the horizontal direction) is generated.
It is well known that there is a problem in that the force of displacement (lateral displacement force) acts and the state becomes unstable. It is also known that the rigidity of the lateral displacement force increases as the rigidity of the magnetic repulsion force increases.

On the other hand, when levitated by the attractive force of the permanent magnet, it is stabilized in the lateral direction, but it becomes unstable in terms of the balance between the magnetic attractive force and the gravity acting on the floating portion. In other words, there is a problem that it is unstable in the direction in which gravity or levitation force acts (vertical direction or vertical direction).

The present invention has been proposed in view of the above-mentioned problems of the prior art, and is a levitation mechanism using a permanent magnet, which has stability in the vertical direction and unstable rigidity in the lateral direction. The purpose is to provide a levitation mechanism that reduces the cost of the lateral stabilizing mechanism by reducing the cost.

[0008]

[Principle] The principle of the present invention will be described below.

First, considering the case of using magnetic repulsion to levitate, the magnetic repulsion decreases as the distance from the magnet increases. Here, the rate of decrease with distance is referred to as the rigidity of the repulsive force. The same applies to the lateral displacement, and the lateral displacement force decreases when laterally displaced. Here, the ratio of the lateral displacement force decrease to the displacement distance increase is referred to as lateral displacement rigidity.

If the fixed portion of the levitation mechanism is taken as the origin of FIGS. 1 and 2 and the vertical direction is y and the horizontal direction is x, the change characteristic of the magnetic repulsion force with respect to the vertical displacement (distance from the magnet) y is As shown in FIG. 1, the change characteristic of the lateral displacement force with respect to the lateral displacement x is as shown in FIG. 1 and 2, if a tangent line is drawn at one point on the characteristic curve, the tangent line (Fig. 1
The straight line t1 and the slope of the straight line t2 in FIG. 2 are the rigidity at that point. Here, the rigidity (straight line t1) shown in FIG. 1 is a stable rigidity because it descends to the right, and the rigidity (straight line t) shown in FIG.
In 2), the rigidity is unstable because it goes up to the right. It is known that the sum of stable rigidity at a certain point and unstable rigidity in two horizontal directions becomes zero. In other words, if the stable rigidity is large, the unstable rigidity also becomes large. As a result, in order to reduce the lateral displacement rigidity, it is only necessary to levitate the levitation unit at a position where the vertical rigidity is reduced, that is, to levitate at a position where the distance from the magnet is large. For that purpose, a strong permanent magnet may be used to increase the flying gap.

In the case of levitation due to magnetic repulsive force, there is only one balance point between the weight W of the floating portion and the repulsive force,
The balance point is a stable equilibrium point in the vertical direction.

Next, the case of using magnetic attraction to levitate will be considered with reference to FIGS.

In the case of levitation by magnetic attraction, the characteristics are as shown in FIG. The sum of the stable rigidity and the unstable rigidity is zero even if the surface is levitated by the magnetic attraction force. However, contrary to the case of levitation due to magnetic repulsion, the rigidity in the vertical direction, that is, the rigidity of the attraction force rises to the right, resulting in unstable rigidity, and lateral displacement rigidity (line t4 in FIG. 4) becomes stable rigidity. Further, the equilibrium point between the magnetic attractive force and the gravity acting on the floating portion becomes an unstable equilibrium point. Therefore, in the case of levitation by magnetic attraction, active control is necessary to maintain the levitation state near the equilibrium point. And to maintain stability in the vertical direction without active control,
It is also necessary to use magnetic repulsion together.

When the magnetic attraction force and the repulsion force are used together, the sum of the forces is a vertical displacement y as shown in FIGS.
To U-shaped. Then, there are two points that balance the weight W of the floating portion, that is, two intersections (equilibrium points) with the straight line W in the y direction, and the equilibrium point above (right in FIG. 5) is unstable and below (see FIG. The left equilibrium point of 5 becomes stable.

In FIG. 5, a U-shaped characteristic curve and a straight line W
The area surrounded by and indicates the energy required to move the levitation section from the lower equilibrium point to the upper equilibrium point. Then, the gradient of the tangent line (reference numeral t5) of the lower equilibrium point (the left equilibrium point in FIG. 5) is the vertical direction (y direction).
Shows the stable rigidity, and the lateral displacement rigidity has the opposite sign. From this fact, it is understood that the straight line W may be brought close to the bottom of the U-shaped curve as shown in FIG. 6 in order to reduce the lateral displacement rigidity. That is, by adjusting the magnetic strength of the permanent magnet, the weight of the floating portion, and the distance between the upper and lower fixed parts, the straight line W is
By approaching the bottom of the letter-shaped curve, it is possible to reduce the lateral displacement rigidity while the magnetic levitation force (the sum of repulsive force and absorbing force) and the weight of the levitation part are balanced. ..

Here, if the straight line W is brought into contact with the bottom of the U-shaped curve, both the vertical rigidity and the lateral displacement rigidity become zero. However, since this is not practical, the distance between the two equilibrium points (see FIGS. 5 and 6) should be slightly separated to provide appropriate vertical rigidity. This suitable rigidity means that the upper equilibrium point (unstable equilibrium point) cannot be approached by an external force resulting from the usage condition of the magnetic levitation mechanism.
In practice, for safety, it is convenient to provide a stopper such as an emergency bearing just below the upper equilibrium point. Although lateral displacement rigidity cannot be avoided, the cost can be reduced by, for example, the active control mechanism for stabilizing the lateral displacement, which can be reduced.

[0017]

The magnetic levitation mechanism of the present invention is constructed on the basis of the above-described principle, and includes a levitation part and a fixed part having permanent magnets on the upper and lower parts, and the upper permanent magnet is levitation. The polarity is set so that the attractive force acts between the fixed part and the fixed part, and the polarity of the lower permanent magnet is set so that the repulsive force acts between the floating part and the fixed part. There are two equilibrium points at which the levitation force, which is the sum of the force and repulsion force, and the gravity acting on the levitation portion are equal, and a stopper is provided in the lower vicinity of the upper equilibrium point.

In carrying out the present invention, the floating portion is provided with one or more permanent magnets in a ring shape or vertically or horizontally separated from each other, and the magnetic repulsion acting between the permanent magnets of the fixed portion. It is preferable that the force and the suction force (both act as a levitation force in the vertical direction) act at different points on the levitation portion. One of the fixed portion and the floating portion on which the attractive force acts may be a magnetic material that exerts the attractive force.

Further, it is preferable that a member made of an electrically good conductor such as copper is fixed to each of the floating portion and the fixed portion in the space or side surface between the permanent magnets of the floating portion and the fixed portion.

Further, in at least one space existing between the floating portion and the fixed portion, two good conductors are provided in total in the vicinity of the surface of the permanent magnet facing the space, and the fixed portion and the floating portion are provided. The parts are preferably mechanically fixed to the good conductors on the side far from each.

[0021]

According to the present invention as described above, the magnetic strength of the permanent magnet, the weight of the floating portion, and the distance between the upper and lower fixed portions are adjusted,
By bringing the straight line W shown in FIGS. 5 and 6 close to the bottom of the U-shaped curve, the magnetic levitation force and the weight of the levitation part are balanced according to the principle described above with reference to FIGS. It is possible to realize a state in which the lateral displacement rigidity is sufficiently small. Further, since the lateral displacement rigidity, that is, the lateral unstable rigidity is small, only a small addition mechanism is required and the cost can be reduced.

Here, vibration can be damped by fixing a member made of a good electric conductor to each of the floating portion and the fixed portion. This is because if an electrically good conductor such as copper is provided not only on the air gap having a strong magnetic field but also on the side surface of the magnet, an eddy current is generated and a damping effect, that is, vibration damping is generated by the eddy current.

[0023]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 7 shows a first embodiment of the present invention, which includes a floating portion 1 and fixing portions 2u, 2d arranged on the upper side and the lower side thereof. The floating portion 1 is provided with upper and lower permanent magnets 3u and 3d, and the polarity of the upper magnet 3u is set so as to attract the permanent magnet 4u of the upper fixed portion 2u, while the lower magnet 3d is lowered. The polarity is set so as to repel the permanent magnet 4d of the fixed portion 2d.
Either one of the permanent magnets 3u and 4u may be a magnetic material such as iron.

A stopper 5 is arranged near the permanent magnet 4u of the upper fixed portion 2u. Where the permanent magnet 4u
The vicinity matches the vicinity of the upper equilibrium point in the equilibrium point where the sum of the magnetic attraction force between the permanent magnets 3u and 4u and the magnetic repulsion force between the permanent magnets 3d and 4d balances the gravity acting on the floating portion 1. .. In other words, the stopper 5 is provided near the lower side of the upper equilibrium point.

In this embodiment, the permanent magnets 3u, 3
d, 4u, 4d magnetic strength, weight and size of the floating portion 1, distance between the upper and lower fixed portions 2u, 2d, permanent magnets 3u, 4
By appropriately adjusting the distance between u and the distance between the permanent magnets 3d and 4d, the straight line W shown in FIGS. 5 and 6 can be brought close to the bottom of the U-shaped curve, and the lateral displacement rigidity can be sufficiently reduced. You can do it. The stopper 5 will be described later.

FIG. 8 shows a second embodiment of the present invention.
In this embodiment, the plate-shaped floating portion 11 is provided with permanent magnets 12L and 12R at both left and right ends. The fixed portion formed by facing a pair of U-shaped members 13L and 13R has permanent magnets 14L, 14R, 15L and 15R arranged above and below the inside (side facing the floating portion 11). ing. Here, the polarities are set so that the upper permanent magnets 14L and 14R attract the permanent magnets 12L and 12R of the floating portion 11 and the lower permanent magnets 15L and 15R repel the permanent magnets 12L and 12R. There is. Then, at the closest position above the inner side surfaces of the U-shaped members 13L, 13R,
A stopper 16 is installed. That is, in the embodiment of FIG. 8, the magnetic attraction force between the permanent magnets 12L and 14L, the magnetic attraction force between the permanent magnets 12R and 14R, the magnetic repulsion force between the permanent magnets 15L and 12L, and the permanent magnet 15 are used.
The upper equilibrium point of the equilibrium points where the sum of the magnetic repulsive forces between R and 12R balances with the gravity acting on the floating portion 11 is set near the stopper 16.

Note that FIG. 8 can also be regarded as a rotary type levitation mechanism having the xy axes as the rotation center axes. In that case, the magnet in the drawing may be interpreted as a ring-shaped cross-sectional view.
Further, it goes without saying that the magnets 14L and 14R may be magnetic materials such as iron.

Next, referring to FIGS.
(FIG. 7) and the action of the stopper 16 (FIG. 8) will be described. 9 to 11 respectively show the floating portion 1 in the embodiment of FIG.
Is located below the equilibrium point (FIG. 9: FIG. 12).
Y1), the state where the levitation part 1 is located at the equilibrium point of the upper part (FIG. 10: y2 in FIG. 12), and the levitation part 1 is located at the bottom of the magnetic levitation force characteristic curve (FIG. 11). : Y3) is shown in FIG. Then, when the distance between the floating portion 1 and the upper fixed portion 2u becomes less than y3, both are adsorbed. Therefore, stoppers 5 and 16 (for example, touchdown bearings) are provided slightly below y3 to prevent contact between the two.

FIG. 13 shows a third embodiment of the present invention. The outline is the same as that of the first embodiment (FIG. 7), but a flat plate member 20 made of a good electric conductor such as copper is provided on the upper surface of the floating portion 1 and the upper surface of the lower fixing portion 2d. this is,
A strong magnetic field gap between the permanent magnets (in FIG. 13, the permanent magnet 3
The damping effect by the eddy current (not shown) generated in the good conductor in the space between u and 4u and the space between 3d and 4d,
It is intended to reduce vibration.

Further, in the embodiment of FIG. 14, two good conductors 22, 22 are interposed between the fixed part 2 and the permanent magnets (not shown in FIG. 14) of the floating part 1 to fix the fixed part 2 and the floating part. 1 by means of mechanical means 24, 24 to a good conductor 22 on the side far from each
Is fixed. Further, FIG. 15 shows an embodiment in which good conductors 26, 26 having different shapes from the good conductors 22, 22 of FIG. 14 are used. The reason for providing the good conductor on the far side is that the relative movement between the fixed portion and the floating portion is performed at the highest magnetic flux density to improve the damping effect.
If a good conductor is also provided on the side surface of the permanent magnet, the damping effect is further improved. In any of the examples, the damping effect is improved according to the same principle as the example of FIG.

[0032]

According to the magnetic levitation mechanism of the present invention described above, the lateral displacement rigidity at a stable equilibrium point where the magnetic levitation force and the weight of the levitation part are balanced can be made sufficiently small, so that, for example, active control is possible. When the stable rigidity is added by a motion such as rotation or rotation, the stable rigidity to be added can be small. Further, since the floating gap is increased, a large amount of members made of good electrical conductors can be used, so that vibration damping is improved.

As described above, according to the present invention, the magnetic levitation using the permanent magnet can be made at low cost, and the vibration can be damped well.
The purpose of this is to expand the application range of the magnetic levitation mechanism.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing a relationship between a magnetic repulsive force and a vertical displacement, for explaining the principle of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between lateral displacement force and vertical displacement in a levitation mechanism that uses magnetic repulsion.

FIG. 3 is a characteristic diagram similar to FIG. 1 showing the relationship between magnetic attraction and vertical displacement.

FIG. 4 is a characteristic diagram showing a relationship between a lateral displacement force and a vertical displacement in a levitation mechanism using a magnetic attraction force.

FIG. 5 is a characteristic diagram showing a relationship between a magnetic levitation force and a vertical displacement when a magnetic attraction force and a magnetic repulsion force are used together.

FIG. 6 is a characteristic diagram showing the relationship between the magnetic levitation force and the vertical displacement as in FIG. 5, but showing a condition under a condition different from that in FIG.

FIG. 7 is a front view showing the first embodiment of the present invention.

FIG. 8 is a front view showing a second embodiment of the present invention.

FIG. 9 is a front view showing a state in which the floating portion 1 is located below the equilibrium point in the first embodiment.

FIG. 10 is a front view showing a state where the floating portion 1 is located at an equilibrium point in the first embodiment.

FIG. 11 is a front view showing a state in which the levitation portion 1 is located at the bottom of the levitation force characteristic curve in the first embodiment.

FIG. 12 is a characteristic diagram similar to FIG. 5, showing the states of FIGS. 9 to 11 at positions on the levitation force characteristic curve.

FIG. 13 is a front view of the third embodiment of the present invention.

FIG. 14 is a front view of another embodiment of the present invention.

FIG. 15 is a front view of still another embodiment of the present invention.

[Explanation of symbols]

t1, t2, t3, t4, t5 ... tangent line at equilibrium point W ... floating weight y, y1, y2, y3 ... vertical displacement x ... lateral displacement 1, 11 ... floating Part 2, 2u, 2d, 13L, 13R ... Fixed part 3u, 3d, 4u, 4d, 12L, 12R, 14L, 1
4R, 15L, 15R ... Permanent magnet

Claims (2)

[Claims] 1. An upper part and a lower part include a floating part having a permanent magnet and a fixed part, wherein the upper permanent magnet is set to have a polarity such that an attractive force acts between the floating part and the fixed part, and the lower part has a lower polarity. The polarity of the permanent magnet is set so that the repulsive force acts between the floating portion and the fixed portion, and the levitation force, which is the sum of the attraction force and the repulsive force, is equal to the gravity acting on the floating portion. A magnetic levitation mechanism characterized in that there are two points and a stopper is provided in the vicinity of the lower side of the upper equilibrium point. 2. A magnetic material is used instead of the permanent magnet for either one of the floating portion and the fixed portion on which the attractive force acts.
The magnetic levitation mechanism described.