JP2893142B2 - Magnetic suspension type vibration isolation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic levitation type vibration isolation device utilizing magnetic attraction to insulate facilities, such as a semiconductor manufacturing apparatus and an electron microscope, which cause problems in accuracy due to vibration from an installation floor from floor vibration. Things.

[0002]

2. Description of the Related Art An air spring or a vibration isolator is provided below a floor plate to support a vibration isolating table that insulates a facility, such as a semiconductor manufacturing apparatus or an electron microscope, which causes problems in yield and accuracy due to vibration from an installation floor from floor vibration. Rubber and the like were used.

[0003] Further, in a vibration damping table of a type that actively controls the movement of a floor plate, a hydraulic or pneumatic cylinder or an electromagnetic solenoid has been used.

[0004]

In a passive type vibration isolation table which is vertically supported by using an air spring or an anti-vibration rubber,
A Vanemass resonance system is formed. Therefore, there is an anti-vibration effect at a frequency much higher than the resonance frequency of the resonance system, but there is no anti-vibration effect at a frequency lower than the resonance frequency. Further, since these supporting materials have a lateral rigidity greater than the supporting direction, a resonance system is formed both in the vertical direction and in the horizontal direction. Since the natural frequency in the horizontal direction is equal to or higher than that in the vertical direction, there is a drawback that the vibration isolation effect in the horizontal direction is inferior to that in the vertical direction.

[0005] By the way, since the natural frequency in the horizontal direction of a building always transmits a microtremor in the horizontal direction of the ground lower than the vertical direction, in a vibration isolator for installing a semiconductor manufacturing apparatus, an electron microscope, or the like, a horizontal direction is required. The anti-vibration effect is also required.

In some cases, active control is performed using an electromagnetic solenoid or a hydraulic / pneumatic cylinder as an actuator in order to improve the horizontal or vertical vibration isolation effect. Some restriction is given in two directions perpendicular to the control direction, and the vibration isolation effect in directions other than the control direction is reduced.

When the vibration isolation table is magnetically levitated using magnetic attraction only in the vertical direction, the bending natural frequency of the vibration isolation table is relatively close to the upper limit frequency of the control of the vibration isolation device. Therefore, the vibration isolation table oscillates at the natural frequency of the vibration isolation table itself, and the desired target may not be achieved.

The present invention has been made in view of the above points, and in addition to a vertical supporting method having no horizontal rigidity, a position of a sensor and a magnetic suspension actuator is set at a position where the natural frequency of the table is not excited. By placing
An object of the present invention is to provide a magnetic levitation type vibration isolation device having a table free from bending vibration of the table.

[0009]

According to the present invention, there is provided a magnetic levitation type anti-vibration apparatus having the following features. A yoke plate having a horizontal surface made of a magnetic material fixed to a rectangular floating table or an installation floor of a vibration isolator, and a suction device fixed to a vibration isolator frame installed on the floor or a rectangular floating table with a gap from the yoke plate. A magnetic suspension actuator comprising an electromagnet provided with an exciting coil for generating a magnetomotive force is disposed at the four corners or the center of four sides of a rectangular floating table, and the relative displacement between the floating table and the vibration isolator frame is measured. A vertical relative displacement sensor and a vertical acceleration sensor installed on a floating table are arranged at the center or four corners of four sides of the rectangular floating table, and the output of the vertical relative displacement sensor and the output of the vertical acceleration sensor are provided. A circuit for calculating the relative displacement and acceleration of the position of the magnetically suspended actuator, the target value and the acceleration of the position of the magnetically suspended actuator are set to zero. Characterized in that it comprises a compensation circuit and a power amplifier for controlling the magnetic attraction force acting between the electromagnets on the yoke plate and the vibration damping device frame fixed to the floating table so that.

[0010]

As described above, the magnetic suspension actuator is disposed at the center of the four corners or four sides of the rectangular levitation table, and the vertical relative displacement sensor for measuring the relative displacement between the levitation table and the vibration isolator frame; By arranging the vertical acceleration sensor installed on the table at the center or the four corners of the four sides of the rectangular floating table, the vibration modes of the bending natural frequencies fn1 and fn2 are excited or Since the detection cannot be performed, the transfer function from the magnetic suspension actuator to the sensor including the vertical non-contact relative displacement sensor and the acceleration sensor is as shown in FIG. 9, and the gain of the transfer function is obtained at the two bending natural frequencies fn1 and fn2. It does not grow.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are views showing a magnetic levitation type anti-vibration apparatus of the present invention. FIG. 1 is a sectional view of the magnetic levitation type anti-vibration apparatus. FIG. 2 is a block diagram of a control unit of the magnetic levitation type anti-vibration apparatus. FIG. 3 is a diagram showing an example of an arrangement diagram of actuators and sensors.

In FIG. 1, the vibration isolator has a structure in which four corners of a rectangular levitation table 1 are arranged on a floor 2 of the vibration isolator of a building via a magnetic suspension actuator 10. The magnetic suspension actuator 10 is mounted on the rectangular floating table 1.
Yoke flat plate 11 having a horizontal surface made of a magnetic material fixed to the back surface of the device, a vibration isolator frame 15 installed on the floor 2 where the vibration isolator of the building is installed, and a yoke fixed to the vibration isolator frame 15 Excitation coil 1 for generating magnetomotive force to attract flat plate 11
3 and an electromagnet 14 having an electromagnet yoke 12.

A vertical non-contact relative displacement sensor 3 for measuring the relative displacement between the rectangular floating table 1 and the installation floor 2
1 is a relative displacement sensor holder 32 installed on the installation floor 2
It is fixed to. The target 33 of the vertical non-contact relative displacement sensor 31 is fixed to the rear surface of the rectangular floating table 1 via the target holder 34.
Further, an acceleration sensor 35 for measuring the acceleration of the rectangular levitation table 1 is installed near the vertical non-contact relative displacement sensor 31. The vertical non-contact relative displacement sensor 31 and the acceleration sensor 35 are arranged at the center of the four sides of the rectangular floating table 1, and based on the outputs of the vertical non-contact relative displacement sensor 31 and the acceleration sensor 35, the magnetic suspension is performed. A vertical magnetic attraction between the electromagnet 14 and the yoke flat plate 11 is controlled by a current flowing through the excitation coil 13 of the actuator 10 to control the relative displacement and acceleration of the floating table to predetermined values.

In the electromagnet 14 and the yoke flat plate 11, the surface area of the electromagnet yoke 12 of the electromagnet 14 facing the yoke flat plate 11 is made smaller than the surface area of the yoke flat plate 11 facing the electromagnet yoke 12, ie, Excitation coil 13 of yoke flat plate 11
Is larger than the facing area of the exciting coil 13.
However , even if the rectangular levitation table 1 and the installation floor 2 move relatively in the horizontal direction, a horizontal magnetic attraction force is generated.
So that there is no

In FIG. 2, the outputs of the vertical non-contact relative displacement sensor 31 and the acceleration sensor 35 are subjected to sensitivity adjustment using signal amplifiers 36 and 37, respectively, and then guided to compensation circuits 41 and 42. Each signal is amplified or attenuated (including off) by the gain adjustment circuits 43 and 44 while the table is floating, and then added by the adder 45 to obtain the signal 46. That is, a magnetic levitation type vibration isolator
With the configuration as shown in FIG.
When the bull 1 is levitated, the magnetic suspension actuator 1
At the position of 0, the relative displacement and the deviation value of the target are amplified, and the acceleration is
After the floating of the rectangular levitation table 1, the magnetic suspension
Reduce the relative displacement at the position of the tutor 10 and the deviation value of the target
Decay and acceleration will amplify.

The four signals 46, obtained from the four vertical non-contact relative displacement sensors 31 and the acceleration sensor 35 of the vibration isolator by the circuit having the configuration shown in FIG.
That is, from the signals 46-1, 46-2, 46-3, and 46-4, the vertical non-contact relative displacement sensor 31 and the magnetic suspension actuator 10 when the rectangular levitation table 1 makes a rigid vertical motion. Each of the magnetic suspension actuators 10 is provided by a conversion circuit 47 having a characteristic of the relationship of the directional displacement.
(The four magnetic suspension actuators 10-1 and 10-1 in FIG. 3
0-2, 10-3, 10-4) to calculate four signals 48 (signals 48-1, 48-2, 48-3, 48-4).
Output.

These signals 48 (signals 48-1 and 48-
2, 48-3, 48-4) supply a current proportional to the signal 48 to the exciting coil 13 of the electromagnet 14 via the power amplifier 49, and control the vibration of the rectangular levitation table 1. FIG. 3 is a diagram showing the arrangement of the magnetic suspension actuators and the sensors. The four magnetic suspension actuators 10, namely, the magnetic suspension actuators 10-1, 10-2, 10-3,
10-4 are arranged at four corners of the rectangular levitation table 1, respectively, and four sensor units 30 including the vertical non-contact relative displacement sensor 31 and the acceleration sensor 35, that is, the sensor units 30-1, 30-2, and 30 -3, 30-4
Are arranged at the center of four sides of the rectangular floating table 1, respectively. More specifically, the sensor unit 30-1 is located near the side A-D on the center line ac,
2 is near the side AB on the center line b-d, the sensor unit 30-3 is near the side BC on the center line ac, and the sensor unit 30-4 is on the side along the center line b-d. Place near CD.

The operation of the magnetic levitation type anti-vibration apparatus having the above configuration will be described in detail below. The natural modes of bending of a rectangular floor panel close to a square are as shown in FIGS. In these figures, nodes of the natural vibration mode that do not vibrate are indicated by broken lines. Normally, the natural frequency fn1 in FIG. 4 is smaller than the natural frequency fn2 in FIG. The magnetic suspension actuator is a
When it is arranged on the -c, b-d line, the natural frequency fn1 is not excited. When the magnetic suspension actuator is arranged on the lines AC and BD, the natural frequency fn2 is not excited.

When the sensors are arranged on lines ac and bd, the natural frequency fn1 is not detected. When the sensors are arranged on the lines AC and BD, the natural frequency fn2 is not detected. Therefore, the following can be said.

(1) When the magnetic suspension actuator 10 and the sensor unit 30 are arranged on the lines ac, bd, AC, and BD, <represents AC, BD. 6, the transfer function from the magnetic suspension actuator 10 to the sensor unit 30 is as shown in FIG. 6, and the two bending natural frequencies fn1 and fn2
Increases the gain of the transfer function.

(2) In the case where the magnetic suspension actuator 10 or the sensor unit 30 is arranged on the line ac, bd, the vibration mode of the natural frequency fn1 cannot be excited or detected. Therefore, the transfer function from the magnetic suspension actuator 10 to the sensor unit 30 is as shown in FIG. 7, and the gain of the transfer function at the natural frequency fn1 is as shown in FIG.
It does not grow as shown.

(3) When the magnetic suspension actuator 10 or the sensor unit 30 is arranged on the lines AC and BD, the vibration mode of the natural frequency fn2 cannot be excited or detected. Therefore, the transfer function from the magnetic suspension actuator 10 to the sensor unit 30 is as shown in FIG. 8, and the gain of the transfer function at the natural frequency fn2 does not increase as in FIG.

(4) The magnetic suspension actuator 10 is a-
The sensor unit 30 is disposed on the line c, b-d,
If they are arranged on the lines C and BD or vice versa, vibration modes of the natural frequencies fn1 and fn2 cannot be excited or detected. Therefore, the transfer function from the magnetic suspension actuator 10 to the sensor unit 30 is as shown in FIG. 9, and the two natural frequencies fn
At 1 and fn2, the gain of the transfer function no longer increases.

In this embodiment, the sensor unit 30 and the magnetic suspension actuator 10 are arranged as described in (4) above, and the acceleration of the vibration isolation table is controlled to 0 without exciting the bending natural frequency of the installation floor 2. What you want to do.

In the above embodiment, the yoke flat plate 11 constituting the magnetic suspension actuator 10 is fixed to the rectangular levitation table 1, and the anti-vibration device frame 15 to which the electromagnet 14 having the excitation coil 13 is fixed is installed on the floor 2. However, the magnetic levitation type anti-vibration device of the present invention is not limited to this, and the yoke flat plate 11 is installed on the installation floor 2 on the contrary, and the magnetic suspension actuator is installed. A configuration in which an anti-vibration device frame to which an electromagnet provided with an excitation coil is fixed is fixed to a rectangular levitation table, and an anti-vibration device frame 15 to which an electromagnet 14 including an excitation coil 13 is fixed is fixed to the rectangular levitation table 1. The good is natural.

[0026]

As described above, according to the present invention, the rectangular floating table supports only the vertical direction having no rigidity in the horizontal direction by the magnetic attraction force. There is no influence of vibration in the direction or the natural frequency of bending of the rectangular floating table. Therefore,
An excellent effect of being able to provide a high-precision magnetic levitation type vibration isolation device having a vibration isolation table that does not vibrate due to the vibration of the installation floor 2 is obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a magnetic levitation type vibration isolation device of the present invention.

FIG. 2 is a block diagram of a control unit of the magnetic levitation type vibration isolation device of the present invention.

FIG. 3 is a diagram showing an example of an arrangement of a magnetic suspension actuator and a sensor according to the present invention.

FIG. 4 is an explanatory diagram of a primary bending natural vibration mode of a floating table having a frequency of fn1.

FIG. 5 is an explanatory diagram of a secondary bending natural vibration mode of a floating table having a frequency of fn2.

FIG. 6 is a diagram showing a transfer function from an actuator to a sensor when an actuator and a sensor are arbitrarily arranged.

FIG. 7 is a diagram showing a transfer function from the actuator to the sensor when the actuator and the sensor are arranged at nodes of the primary bending natural vibration mode.

FIG. 8 is a diagram showing a transfer function from the actuator to the sensor when the actuator and the sensor are arranged at the nodes of the secondary bending natural vibration mode.

FIG. 9 is a diagram showing a transfer function from the actuator to the sensor when the actuator is arranged at the node of the primary bending natural vibration mode and the sensor is arranged at the node of the secondary bending natural vibration mode, or in the reverse arrangement. .

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 rectangular floating table 2 installation floor 10 magnetic suspension actuator 11 yoke flat plate 12 electromagnet yoke 13 excitation coil 14 electromagnet 15 anti-vibration device frame 31 vertical non-contact relative displacement sensor 32 relative displacement sensor holder 33 relative displacement sensor target 34 target Holder 35 Acceleration sensor 36, 37 Signal amplifier 41, 42 Compensation circuit 43, 44 Gain adjustment circuit 45 Adder 47 Conversion circuit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B01L 9/00 F16F 15/03 G12B 9/08

Claims (5)

(57) [Claims] 1. A yoke plate having a horizontal surface made of a magnetic material fixed to a rectangular floating table of a vibration isolator, and a gap provided from the yoke plate to be fixed to a vibration isolator frame installed on a floor and to start suction. A vertical relative displacement sensor for arranging magnetic suspension actuators comprising an electromagnet having an exciting coil for generating a magnetic force at four corners of the rectangular floating table and measuring a relative displacement between the floating table and the vibration isolator frame And a vertical acceleration sensor installed on a levitation table are arranged at the center of four sides of the rectangular levitation table, and the position of a magnetic suspension actuator is determined based on the output of the vertical relative displacement sensor and the output of the vertical acceleration sensor. A circuit for calculating the relative displacement and acceleration of the magnetic suspension actuator. Magnetic levitation type vibration damping device characterized by comprising a compensation circuit and a power amplifier for controlling the magnetic attraction force acting between the electromagnets on the vibration isolator frame fixed to Bull. 2. A yoke plate having a horizontal surface made of a magnetic material fixed to a rectangular levitation table of a vibration isolator, and a gap provided from the yoke plate so as to be fixed to a vibration isolator frame installed on a floor and to start suction. A magnetic suspension actuator comprising an electromagnet provided with an exciting coil for generating a magnetic force is disposed at the center of four sides of the rectangular floating table, and a vertical relative measuring the relative displacement between the floating table and the vibration isolator frame. Displacement sensors and vertical acceleration sensors installed on the levitation table are arranged at four corners of the rectangular levitation table, and the position of the magnetic suspension actuator is determined based on the output of the vertical relative displacement sensor and the output of the vertical acceleration sensor. A circuit for calculating the relative displacement and acceleration of the vibration isolating device. Magnetic levitation type vibration damping device characterized by comprising a compensation circuit and a power amplifier for controlling the magnetic attraction force acting between the electromagnets on the yoke plate which is fixed to the upper table the vibration isolator frame. 3. The vertical magnetic levitation type vibration damping device according to claim 1, wherein when the rectangular levitation table is levitated, the relative displacement at the position of the magnetic suspension actuator and the deviation value of the target are amplified. The magnetic levitation vibration isolator is characterized in that the acceleration is attenuated, and after the ascent, the relative displacement at the position of the magnetic suspension actuator and the target deviation are attenuated, and the acceleration is amplified. 4. A vertical magnetically levitated vibration isolator according to claim 1, 2 or 3, wherein a vibration isolator frame to which an electromagnet provided with an exciting coil constituting the magnetic suspension actuator is fixed is rectangularly levitated. A magnetic levitation type anti-vibration apparatus, wherein a yoke plate having a horizontal surface made of a magnetic material is fixed to a table and installed on a floor. 5. The vertical magnetic levitation type vibration damping device according to claim 1, wherein the area of the yoke plate of the magnetic suspension actuator facing the exciting coil is the area of the exciting coil facing the exciting coil. A magnetic levitation type vibration isolator characterized by being larger.