JPH0474053B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetically levitated vibration isolation table, and in particular, it is used in semiconductor manufacturing equipment, electron microscopes, etc., where vibrations from the installation floor cause problems in yield and accuracy. This relates to a high-precision vibration isolation table that insulates equipment from floor vibrations.

[Prior Art] Conventionally, in order to insulate equipment such as semiconductor manufacturing equipment and electron microscopes, where vibration from the installation floor causes problems in yield and accuracy, from floor vibration, vibration isolation tables have been supported. Air springs and anti-vibration rubber were used on the underside of the shaking table floorboard. In addition, in a type of vibration isolation table that actively controls the movement of the floor plate, a hydraulic or pneumatic cylinder or an electromagnetic solenoid is used to eliminate the vibration of the vibration isolation table floor plate.

[Problems to be Solved by the Invention] Here, in a passive vibration isolation table supported in the vertical direction using an air spring or vibration isolating rubber, a spring mass resonance system is formed. Therefore, although there is a vibration isolation effect at frequencies considerably higher than the resonance frequency, there is a problem in that the vibration isolation effect is not very effective at frequencies below the resonance frequency.

In addition, the horizontal natural frequency of the building in which the vibration isolator frame is installed is lower than the vertical natural frequency, and it constantly transmits the horizontal microtremors of the ground.
In vibration isolation tables for installing semiconductor manufacturing equipment, electron microscopes, etc., a vibration isolation effect is particularly required in the horizontal direction. However, since the support materials used for air springs and vibration isolators have greater lateral rigidity (horizontal rigidity) than in the support direction, a resonant system is formed in the horizontal direction even when vertical support is provided. Since the natural frequency of the resonance system in the horizontal direction is equal to or higher than that in the vertical direction, the vibration isolation effect in the horizontal direction is inferior to that in the vertical direction, and the above requirements cannot be met.

On the other hand, in order to improve the vibration isolation effect in the horizontal or vertical direction, there are examples of active control using electromagnetic solenoids or hydraulic/pneumatic cylinders as actuators. However, due to the characteristics of the actuator, some kind of restraint is applied in two directions perpendicular to the control direction, and as a result, there is a problem that the vibration isolation effect in directions other than the control direction is reduced.

The present invention was proposed in view of the problems of the prior art described above, and aims to provide a magnetically levitated vibration isolation table that can be supported in the vertical direction without having rigidity in the horizontal direction.

[Means for Solving the Problems] A magnetically levitated vibration isolator of the present invention includes a floor plate and a frame, and the magnetically levitated vibration isolator table magnetically levitates the floor plate using a magnetic suspension device. A magnetic suspension system consists of a yoke plate made of magnetic material fixed to the floorboard, an electromagnet fixed to the frame with a small gap from the yoke plate, and a relative displacement system that measures the relative displacement between the floorboard surface and the electromagnet. a sensor, a displacement vibrometer fixed to the frame, an adder that adds the output signal from the relative displacement sensor and the output signal from the displacement vibrometer, and a sensor that adds the output signal from the relative displacement sensor to the output signal from the displacement vibrometer; It includes a compensation circuit and a power amplifier for controlling the magnetic attraction force acting between the two.

In implementing the present invention, it is preferable that three or more of the magnetic suspension devices are provided for one floor plate.

Further, it is preferable that a film of a conductive material be formed on the surface of the yoke flat plate on the floorboard.

[Principle of the Invention] The operating principle of the magnetically levitated vibration isolation table of the present invention having the above configuration will be explained with reference to FIGS. 4 and 5.

First, the principle of operation of the magnetically levitated vibration isolation table when the installed floor vibrates in the vertical direction will be explained with reference to FIG. In FIG. 4, the vertical absolute height of the upper surface (floor surface) of the vibration isolation table floor plate 10 is indicated by the symbol H1,
The vertical absolute height of the lowest end of the electromagnet 21 fixed to the vibration isolator frame 24 is indicated by the symbol H2, and the dimension of the minute gap between the surface of the vibration isolator floor plate 10 and the lowest end of the electromagnet 21 is indicated by the symbol Z. is shown. Therefore, H1=H2−Z. Then, the amount of vibration in the vertical direction of the vibration isolator floor plate 10 is Z1, and the vibration isolator frame 24 (the floor on which the vibration isolator is installed) is
Assuming that the amount of displacement (vibration) is Z2, and the amount of displacement of the relative gap between the vibration isolation table floor plate 10 and the lowest end of the electromagnet 21 is Z3, Z1=Z2+Z3...(A). However, when Z becomes small, Z3 is negative, and when Z becomes large, Z3 is positive. Further, the positive and negative values of Z1 and Z2 are determined with the directions of arrows Z1 and Z2 in FIG. 4 being positive.

There is no vertical vibration in the vibration isolation table frame 24,
When Z2 is zero, the current in the excitation coil 30 of the electromagnet is controlled so that the relative gap Z between the electromagnet 21 and the floorboard 10 is constant. If the relative gap Z is constant, the displacement Z3 is zero, and therefore,
From the above formula (A), Z1 becomes zero, and the vibration isolation table floor plate 10
no longer vibrates in the vertical direction.

On the other hand, when the vibration isolation table frame 24 is vibrating in the vertical direction, the displacement vibration amount Z2 of the vibration isolation table frame 24 (the floor on which the vibration isolation table is installed), the electromagnet 21 and the floor plate 1
The current of the excitation coil 30 of the electromagnet is controlled so that the sum of the displacement amount Z3 and the relative gap Z between the two and zero becomes zero. As is clear from the above equation (a),
The sum of Z2 and Z3 is the vertical vibration amount Z1 of the vibration isolation table floor plate 10, and when this becomes zero,
The floorboard 10 does not vibrate.

By controlling the current of the electromagnet 21 in this way, it is possible to support the vibration isolation table floor plate 10 without contact and without being affected by the vibration Z2 of the frame 24, so that the installation floor or frame is Even if it vibrates, the vibration isolation table floor plate 10 does not vibrate.

Next, a case where horizontal vibration acts on the vibration isolation table installation floor or frame 24 will be described with reference to FIGS. 4 and 5. As is clear from FIG. 5, the electromagnet 21 fixed to the vibration isolation table frame 24
The projected area of the portion facing the vibration isolator floor plate 10 (see reference numeral 21 in FIG. 5) is much smaller than the surface area of the yoke 11 fixed to the vibration isolator floor plate 10. Therefore, even if the electromagnet 21 moves in the horizontal direction, as long as it does not move out of the yoke 11, the magnetic flux lines 4 of the electromagnet 21
The distribution of (Figure 4) does not change. Therefore, even if the installation floor or the frame 24 vibrates in the horizontal direction, it will not be vibrated in the horizontal direction by the vertical attraction force of the electromagnet 21, and no disturbance will be applied to the vibration isolation table floor plate 10. Not done. In addition, since the magnetic attraction force in the vertical direction does not change, even if the installation floor or frame 24 vibrates in the horizontal direction, the vibration isolation table floor plate 10
does not vibrate vertically.

In addition, when the conductive material film 12 is formed on the surface of the yoke 11 on the vibration isolating table floor plate 10, the frame 24
When the vibration isolation table floor plate 10 vibrates relative to the horizontal direction,
The magnetic flux lines 40 of the electromagnet 21 move, and eddy currents are generated in the conductive material film 12, as shown in FIG. As a result, a magnetic force RF in the opposite direction is generated that cancels the displacement caused by the horizontal relative vibration between the frame 24 and the vibration isolator floor plate 10, and suppresses the vibration.

[Function] According to the magnetically levitated vibration isolation table of the present invention, the output signal from the relative displacement sensor and the output signal from the displacement vibrometer are input to the adder, and both signals are added to determine the vibration isolation table floor plate. Find the displacement due to vibration. Then, in response to the output from the adder, the magnetic attraction force acting between the yoke fixed to the vibration isolator floor plate and the stator electromagnet on the fixed frame is compensated so that the displacement becomes zero. controlled by a circuit and a power amplifier. As a result, the vibration isolating table floor plate is magnetically levitated and supports the vibration isolating table floor plate in the vertical direction without generating a force in the horizontal direction.

Here, the magnetic attraction force of the stator electromagnet is controlled so that the amount of vibration in the vertical direction of the vibration isolating table floor plate is always zero, so that the vibration isolating table floor plate does not vibrate in the vertical direction. Further, even if the floor or frame on which the vibration isolation table is installed vibrates in the horizontal direction, the distribution of the magnetic flux lines of the electromagnet does not change, and the vibration isolation table floor plate is not vibrated in the horizontal direction.

Furthermore, it is advantageous to form a film of a conductive material on the surface of the yoke flat plate of the vibration isolating table floor plate, since this generates a force that suppresses horizontal vibrations.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.

1 and 2 show a first embodiment of the present invention, and as clearly shown in FIG. are magnetic yoke 11a, 11
b, 11c, and 11d (4 locations) are attached. A small gap Z (FIG. 1) is provided between the vibration isolating table floor plate 10 and the yoke 11, and the stator electromagnets 21a, 21
b, 21c, and 21d are arranged, and the stator electromagnet is equipped with a coil that generates an upward magnetomotive force, and its surface area is smaller than the opposing surface area of the yoke flat plate on the vibration isolating table floor plate. It is fixed to the installed frame 24.

In FIG. 1, the vibration isolation table floor plate 10 and stator electromagnets 21a, 21b, 21c, 21d (in FIG. 1, only the members with subscripts a and b are shown,
The illustration of members with subscripts c and d is omitted.
The same applies to other members) Relative displacement sensor 22 that measures the relative displacement (Z3 in Figure 4)
a, 22b, 22c, and 22d are installed near the electromagnet, and a vibration isolator frame 24 installed in a building (not shown) measures the displacement vibration (Z2 in FIG. 4) of the installation floor or the frame itself. A displacement vibration meter 23 is attached. Output signals from the relative displacement sensors 22a to 22d are amplified by relative displacement sensor amplifiers 31a to 31d and sent to adders 33a to 33d, and output signals from the displacement vibrometer 23 are amplified by relative displacement sensor amplifiers 31a to 31d and sent to adders 33a to 33d.
3b, 33c, and 33d, and the adder adds both signals to obtain the amount of displacement of the vibration isolation table floor plate 10 (Z1 in FIG. 4). Then, the adders 33a and 3
Compensation circuits 34a, 34b, 34c, 34d and power amplifiers 35a, 35b, 35c, 35d operate in response to outputs from 3b, 33c, 33d.
The compensation circuit and the power amplifier are connected to gaps Z, that is, yokes 11a, 11b, 11c, and 11d fixed to the vibration isolator floor plate 10 so that the displacement Z1 of the vibration isolator floor plate 10 becomes zero. and stator electromagnets 21a, 21 on the fixed frame 24.
b, 21c, and 21d. As a result, the floor plate 10 is magnetically levitated by the magnetic suspension device, and the vibration isolating table floor plate is supported in the vertical direction without generating any force in the horizontal direction.

FIG. 3 shows a second embodiment of the invention. In this embodiment, the vibration isolating table floor plate 10 is connected to the electromagnet supporting portion 4.
0a and a workpiece placement portion 42 are separated to increase the effective surface area of the placement portion 42. The other configurations and functions are substantially the same as those in the first embodiment, so their explanations will be omitted.

[Effects of the Invention] According to the present invention, there is provided a method for supporting a vibration isolation table floor plate without having rigidity in the horizontal direction and so that vibration does not occur in the vertical direction. It is not affected by vibrations. Therefore, it is possible to realize a high-precision vibration isolation table having a floor plate that does not vibrate due to vibrations of the installation floor. In addition, it has all the advantages of a non-contact vibration isolation table.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a vibration isolation table and its control device in a first embodiment of the magnetically levitated vibration isolation table of the present invention;
Fig. 2 is a plan view of the vibration isolating table in the first embodiment, Fig. 3 is a block diagram of the vibration isolating table and its control device in the second embodiment of the present invention, and Fig. 4 shows the operating principle of the present invention. FIG. 5, a partial front view, is a diagram showing the relative positional relationship between the horizontal installed floor vibration and the electromagnet, also showing the principle of operation. 10... Vibration isolation table floor plate, 11, 11a, 11b, 1
1c, 11d... Yoke on the floorboard, 12... Conductive material film,
21, 21a, 21b, 21c, 21d... Electromagnet, 22, 22a, 22b, 22c, 22d... Displacement sensor, 23... Absolute displacement vibration meter, 24... Vibration isolator frame, 30... Electromagnetic coil, 31... Relative displacement sensor amplifier , 32...absolute displacement vibration amplifier, 33,
33a, 33b...Adder, 34, 34a, 34b
...Phase compensation circuit, 35, 35a, 35b...Power amplifier.

Claims (1)

[Claims] 1. A magnetically levitated vibration isolation table comprising a floor plate and a frame, in which the floor plate is magnetically levitated by a magnetic suspension system, wherein the magnetic suspension system includes a yoke flat plate made of a magnetic material fixed to the floor plate, and a yoke plate made of a magnetic material fixed to the floor plate. An electromagnet fixed to the frame with a small gap from the steel plate, a relative displacement sensor that measures the relative displacement between the floor plate surface and the electromagnet, a displacement vibrometer fixed to the frame, and the output signal and displacement from the relative displacement sensor. It includes an adder that adds the output signal from the vibration meter, a compensation circuit that controls the magnetic attraction force that acts between the yoke flat plate and the electromagnet in response to the output of the adder, and a power amplifier. A magnetically levitated vibration isolation table characterized by: