JPH02190640A - Precise vibration-proofing device - Google Patents

Abstract

PURPOSE:To prevent the function deterioration of a precision instrument due to the leakage magnetic flux and obtain adequate vibration-proofing by providing multiple legs on a surface plate, providing linear motors between a frame and lower sections of the legs, and covering the linear motors with magnetic shielding members. CONSTITUTION:A surface plate 20 mounted with a precision instrument 1 is supported by air springs 50 which are passive braking pieces on a frame 40 fixed on a floor 3 with leveling bolts 31. Linear motors 11-13 vibrate legs 21 of the surface plate 20 in the X-direction, Y-direction and Z-direction respectively to perform passive vibration-proofing of the surface plate 20. The linear motors 11-13 are covered with magnetic shielding members 22. Adequate vibration- proofing can be performed with no function deterioration of the precision instrument due to the leakage magnetic flux.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a precision vibration isolator, and particularly has an active vibration isolator that isolates vibrations from the floor and excitation of precision equipment mounted on a tower. Regarding precision vibration isolators.

[Issue M to be solved by the prior art and the invention] Conventionally, precision instruments such as electron microscopes and holography devices that use light and electron beams have been subject to vibrations that obstruct the optical path, and LSI manufacturing devices such as steppers have Because circuits are drawn one after another in the same location, alignment may be difficult due to vibrations, and processing time may be long, so they are placed on a vibration isolator. As such a vibration isolator, there has conventionally been a passive vibration isolator that damps vibrations using vibration absorbing means such as an air spring, a coil spring, or a vibration isolating rubber. but,
Although such a passive vibration isolator can isolate vibrations from the floor, it cannot effectively isolate vibrations such as the self-excitation of the precision equipment itself or the natural vibration of the vibration isolation table surface plate. Therefore, conventional methods have been used to detect each motion component of the vibration of the surface plate in the x, y, and z directions.
There is an active vibration isolator that operates active dampers in opposite phases in response to components of motion in each direction to actively isolate vibrations. In such an active vibration isolator, as shown in FIG. The vibration of the surface plate 2 is detected by a sensor 6 attached to the surface plate 2, and the signal from this sensor 6 is amplified by a preamplifier 7, processed by a control unit 8, and amplified by a power amplifier 9.
The active damper 10 is operated to excite vibrations that are in the opposite phase to the vibrations generated in the surface plate 2, thereby quickly eliminating vibrations. Although only the vibration isolation of one component of the motion component is illustrated here,
This provides vibration isolation in at least three directions.

A hydraulic actuator, an air actuator, an electromagnetic force actuator, etc. are used as the active brake 10 of such an active vibration isolator. Generally, an electromagnetic force actuator is used, and in particular, a linear motor such as a voice coil motor is used. is used.

However, linear motors such as voice coil motors have a large leakage magnetic flux, for example, in a voice coil motor that generates ION, the leakage magnetic flux density at the opening is about 3 Gauss, so there is a method of installing it covered with a thick iron plate etc. However, a leakage magnetic flux density of approximately 0.3 Gauss is observed. In addition, if the voice coil motor is structured with a low-leakage magnetic circuit, it is possible to suppress the leakage magnetic flux density to 1 Gauss or less, but this is because the leakage magnetic flux density in a state of fluctuation due to vibration is greater than the leakage magnetic flux density in a stationary state. , leakage magnetic flux in a stationary state is required to be shielded with high precision. Therefore, these leakage magnetic flux densities may be harmful depending on the equipment mounted on the surface plate 2, and in particular, in electron microscopes, X-ray steppers, etc., the leakage magnetic flux density must be reduced to several milliGauss, preferably 1 milliGauss or less, in order to maintain maximum performance. That is difficult.

[Object of the Invention] The present invention has been made in order to eliminate the above-mentioned drawbacks, and is capable of satisfying the space requirements, shielding the leakage magnetic flux of a linear motor with high precision, and eliminating the magnetic field that would be harmful to precision equipment mounted thereon. The purpose of the present invention is to provide a precision vibration isolator that does not cause vibrations.

[Means for Solving the Problems] In order to achieve the above object, the precision vibration isolator of the present invention includes a surface plate, a passive brake that supports the surface plate on a pedestal, and detects vibrations of the surface plate. A precision vibration isolator comprising a sensor that processes the output of the sensor, a control unit that processes the output of the sensor and outputs a control signal, and a linear motor that is an active brake operated by the control signal. The linear motor is provided between the pedestal and the lower part of the leg, and the linear motor is covered with a magnetic shielding member.

[Function] In order to reduce the strength of the magnetic field that the precision equipment receives from the linear motor, the precision vibration isolator of the present invention installs the linear motor between the lower part of the leg provided on the surface plate and the mount, and connects the precision equipment and the linear motor. This is achieved by increasing the distance between them. Since the strength of the magnetic field is roughly inversely proportional to the cube of the distance, it is possible to significantly reduce the magnetic flux density that precision equipment receives compared to conventional systems.

Also, magnetic shielding is to prevent the magnetic field from spreading.

Since it is effective to block the source at the source, magnetic shielding members are provided on the legs and pedestal provided on the surface plate to cover the linear motor.

[Example] Hereinafter, an example of the precision vibration isolator of the present invention will be described with reference to FIGS. 1 and 2.

FIG. 1 is a schematic configuration diagram of one embodiment, and FIG. 2 is a partial sectional view of one embodiment.

In FIG. 1, the surface plate 20 on which the precision instrument 1 is mounted is a stone surface plate, and is supported by an air spring 50, which is a passive brake, on a pedestal 40 fixed to the floor 3 with leveling bolts 31. The components of the vibration of the surface plate 20 in the X direction, Y direction, and Z direction are detected by sensors 61, 62, and 63, respectively.
Each is amplified by a preamplifier 71, 72, 73, and a phase correction circuit 81, 82, 83, which is a control unit, adjusts the phase so as to excite vibrations that are in the opposite phase to the vibration generated in the surface plate 20, and then the power amplifier 91, 92, 93 After amplification by surface plate 20
The output is output to the linear motors 11, 12, and 13 provided between the lower part of the leg 21 provided in
Nos. 1, 12, and 13 perform active vibration isolation of the surface plate 20 by vibrating the legs 21 of the surface plate 20 in the X direction, Y direction, and Z direction, respectively. As mentioned above, each leg is provided with sensors in the X direction, Y direction, and two directions, a preamplifier, a phase correction circuit, a power amplifier, and a linear motor to perform vibration isolation.

The linear motors 11, 12 and 13 are further covered with a magnetic shielding member 22 made of iron plate or the like, as shown in FIG. The linear motors 11, 12, 13 have a magnet 14 and a moving coil 15, as shown in the cross-sectional view of FIG. The coil head 16 moves up and down.
The legs 21 of the surface plate 20 are moved by this movement.

If the magnetic shielding member 22 is not provided, the magnetic lines of force generated from the magnet 24 will be diffused as shown by H, but the magnetic shielding member 2
If 2 is provided, it can be shielded without being diffused like M. The magnetic shielding member 22 includes an inner frame 23 fixed to a pedestal 40 and an outer frame 24 fixed to legs 21. If the inner frame 23 is fixed to the frame 40 here, the linear motor 11
．． 12 and 13 completely without increasing the weight of the surface plate 20.

As explained above, by using a voice coil motor with a low leakage magnetic circuit, the leakage magnetic flux can be reduced to 1710 mm compared to using a normal linear motor, and the distance between precision equipment and the voice coil motor can be increased. By using magnetic shielding members, it can be reduced to 1/3, and further to 1/100 by using magnetic shielding members. The magnetic flux that precision equipment receives is 1 compared to when no countermeasures are taken.
/3000, and the actually measured magnetic flux density of about 3 Gauss can be reduced to 1 milli Gauss. This reduction in static leakage magnetic flux is sufficient even when the precision equipment is subject to vibration, and the performance of the precision equipment is not degraded by the magnetic field, making it possible to perform vibration isolation [ [Effects of the Invention] As is clear from the above embodiments, according to the precision vibration isolator of the present invention, the legs are provided on the surface plate and the linear motor is provided between the lower part of the leg and the frame, so that the precision vibration isolator on the surface plate is The distance between the equipment and the linear motor is increased, and since the linear motor is covered with a magnetic shielding member, it is possible to shield the leakage magnetic flux of the linear motor, and it is possible to achieve proper vibration isolation without causing functional deterioration of precision equipment due to leakage magnetic flux. It can be carried out.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of the precision vibration isolator of the present invention, FIG. 2 is a partial sectional view of the embodiment, FIG. 3 is a partial sectional diagram for explaining the embodiment, and FIG. The figure is a schematic configuration diagram of a conventional precision vibration isolator. Fig. 1 1...... Precision equipment 20... Surface plate 40... Frame 50... Air spring (passive Brake) 61.6
2.63... Sensor 81. 82, 83... Phase correction circuit (control unit) 11.
12.13...Linear motor 21...Leg 22...Magnetic shielding member representative Patent attorney Moritani -O

Claims (1)

[Claims] a surface plate, a passive brake that supports the surface plate on a pedestal, a sensor that detects vibration of the surface plate, a control unit that processes the output of the sensor and outputs a control signal, and a control unit that processes the output of the sensor and outputs a control signal; A precision vibration isolator comprising a linear motor that is an active brake that operates, wherein a plurality of legs are provided on the surface plate, the linear motor is provided between the pedestal and the lower part of the legs, and the linear motor is A precision vibration isolator characterized by being covered with a magnetic shielding member.