JPH01131354A - Precise vibration isolating device - Google Patents

Abstract

PURPOSE:To perform effective isolation of vibration, by a method wherein a passive damper and an active damper are formed with a pair of magnets positioned facing each other so that they are repelled to each other, and the one of the magnets is controlled as an electromagnet by means of a control signal. CONSTITUTION:A plurality of permanent magnets 21 and 22, with which a passive damper 2 is formed, are situated so that the same polarity sides are positioned facing each other. The permanent magnet 22 forms a conical surface or square conical surface, and the other permanent magnet 21 forms an uneven surface and receives a thrust load. Two sets of active dampers 5, the two of which making a set, are situated, and the vibration isolating bed 1 side is permanent magnet, and the other side is an electromagnet. In this constitution, a distance between the active dampers 5 is fluctuated by means of vibration to generate a brake force, and an output from a sensor 3, detecting vibration, is applied on the active damper 5 through a circuit part 4 to offset vibration.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a
Regarding a dense vibration isolator. .

[Prior Art] Conventionally, precision equipment such as electron microscopes and holography equipment, or reduction projection exposure equipment used in LSI manufacturing, do not interfere with the work even if extremely small vibrations or displacements occur during use. Otherwise, the product may become defective or the efficiency may deteriorate.

In order to eliminate the influence of such vibrations, these precision instruments are generally placed on a vibration isolator. Such precision vibration isolators include a system R (passive vibration isolator) that absorbs and attenuates vibrations applied to the vibration isolator using vibration absorbing means such as air springs and coil springs, and a vibration sensor installed on the vibration isolator. There is a device (active vibration isolator) that operates an actuator in response to a signal and actively isolates vibrations by applying vibrations that are in the opposite phase to the vibrations generated in the vibration isolator table. There is an active vibration control device disclosed in Japanese Patent No. 61-224015.

[Problems to be Solved by the Invention] By the way, in a vibration isolating device using an actuator, as shown in Fig. 7, the excitation force F applied to the vibration isolating table is detected by a vibration sensor, and its output is measured. When the phase is adjusted and amplified to drive the actuator to generate the damping force Fc, the damping force Fc must be applied in the opposite phase to the excitation force F and with a gain of 1 or less. In general, the phase and gain change depending on the frequency of vibration, and especially near the natural frequency of the system, the phase and gain are opposite to the vibration of the vibration isolation table and the gain is 1.
It was difficult to control the actuator to apply the following allocation force.

In addition, in conventional vibration isolators using actuators, a vertical force actuator such as a linear motor is usually used as the actuator (active brake).
- damping can only be done in one direction for each active damper, so one active damper is required for each degree of freedom of motion of the vibration isolator;
The present invention solves the above-mentioned conventional problems, and allows active braking to be performed with a small number of active brakes, and also makes it easy to control the allocated force. The purpose is to provide a precision vibration isolation table.

[Means for Solving the Problem] The precision vibration isolator of the present invention that achieves the above object includes a vibration isolator supported by a passive damper on a support base, and a sensor that detects vibrations of the vibration isolator. , a precision vibration isolator comprising a circuit unit that processes and amplifies the output of the sensor and outputs a control signal, and an active damper that is activated by the control signal and controls the vibration, the passive damper and The drive brake is characterized in that each pair of magnets is arranged opposite to each other so as to repel each other, and the active brake is characterized in that one of the magnets is an electromagnet controlled by the control signal; As a child.

By using a pair of magnets, one of which has a conical or pyramidal surface and the other of which has a concave surface corresponding to the conical or pyramidal surface, damping force is also applied in the direction of deviation of the magnets, thereby suppressing the vibration of the vibration isolating table. It is characterized by substantially canceling out each other.

[Function] Pair of permanent magnets a□ and a2, and permanent magnet bi and electromagnet b2
Considering minute vibrations in a system in which a load W is supported by a pair of , the natural frequency fn can be approximated by the following equation.

2π W ay y However, μ is the magnetic permeability, S is the supporting area, AT is the total excitation ampere turn, and y is the gap between the magnets. For simplicity, the gap between magnets a1 and a2, the magnet b work, and b2 The gaps are assumed to be equal.

In other words, if the ampere turn AT is changed, the spring constant k changes, and the natural frequency fn changes.

Since such a vibration system has a relatively high natural frequency fn, appropriate fn? can be obtained by adjusting the excitation energy (ampere turn AT). You can take it to the iF area.

In other words, the ratio between the external vibration frequency and the natural frequency can be adjusted so that a stable gain and phase of the allocated force can be obtained. In such a vibration system, when the vibration applied from the outside is detected by a speed sensor, the damping force has a phase vR adjustment between +90° and -1800, and a gain of 1.
A control signal (current) may be applied to the electromagnet b8 so that the current is less than the current.

Next, the principle of damping in the direction of deviation will be explained.

As shown in FIG. 1 (Ca), the repulsive force F between the bipolar magnetic members A and B, which are disposed facing each other with an interval of 0, is given by the following equation.

t0 That is, the force F is the magnetic energy Em of the volume of the gap
is proportional to the differential of the interval t0.

If the axes of magnetic member A and magnetic member B are not misaligned, the force F cos θ in the direction perpendicular to the axis is canceled out, and the force F in the axial direction
only sin θ, and an axial force acts on the magnetic member A (or magnetic member B).

However, θ is the angle between the outer periphery of member A and the concave inner wall.

On the other hand, as shown in the same figure (b), magnetic member A and magnetic member B
When the center of deviates, each repulsive force becomes Fz > F due to the difference in magnetic energy between the interval t, t2 and the volume of the gap.
z, and (F, -F2) cos θ acts as a centering force, that is, a damping force in the direction of deviation. Therefore, by adjusting θ, the interval t
By appropriately selecting 0, the characteristics of the system can be stabilized.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

The precision vibration isolator shown in Fig. 2 mainly consists of a vibration isolator 1 on which the equipment to be isolated is mounted, a passive damper 2 that supports the vibration isolator 1 with the repulsive force of a permanent magnet, and a vibration isolator 2 that supports the vibration isolator 1 with the repulsive force of a permanent magnet. A sensor 3 that detects vibrations including disturbances and self-excitation, a circuit section 4 that processes the output of the sensor 3 and sends out control signals, and an anti-vibration table 1 that provide an output with an opposite phase to the vibrations. It consists of an active damper 5 that isolates vibrations.

The passive brake 2 consists of, for example, four pairs of permanent magnets 21 and 22, one permanent magnet 21 is fixed to the vibration isolation table 1 side, the other permanent magnet 22 is fixed to the support body 6 side, and the permanent magnet 2
1 and 22 are arranged so that the same polarity sides face each other, and their repulsive force (total of 4 pairs) can absorb approximately 80% of the load of the vibration isolation table.
% support. Furthermore, the permanent magnet 22 has a conical or pyramidal shape, while the permanent magnet 21 has a concave surface corresponding to the conical or pyramidal surface of the permanent magnet 22, so that it can receive a thrust load. There is.

The sensor 3 is of any suitable type, such as a piezoelectric type or an electromagnetic type, and is attached to the vibration isolation table 1 to detect the acceleration in the Z-axis direction in which the vibration isolation table 1 is to be controlled. do.

For example, when a disturbance acts on the vibration isolation table 1 and the vibration isolation table 4 vibrates, the sensor 3 detects this vibration in the state of acceleration or displacement.

As shown in the block diagram in FIG. 3, the circuit section 4 includes a filter 41, a phase/gain adjustment circuit 42, and a power amplifier 43.
The output from the sensor 3 is subjected to signal processing, and a control current is applied to the active brake 5 so that it is in the opposite phase to the acceleration or excitation force of the vibration isolation table and has a gain of 1 or less.

For example, when a speed sensor is used as the sensor 3, displacement is obtained with a 90' phase shift in the integrating circuit (FIG. 4).

Since the damping force can be applied in a phase opposite to the velocity, the phase/gain adjustment circuit 42 is configured to output a signal Ic having a phase shift of 90' with respect to the obtained displacement. In areas where the vibration frequency is high, that is, where the passive damper has good damping characteristics, it is preferable that the active damper 5 not work, so the gain is limited by the filter 41.

In this embodiment, two sets (four active brakes) of active brakes 5 are installed, one set of two being installed, and one of them is mounted on the vibration isolating table 1 through a permanent magnet 51 as shown in FIG. It consists of a head 52 that is connected to the pole 54 and a pole 54 that is fixed to an electromagnet 53. The electromagnet 53 has a magnetic core 55 and a driving line 5
6, and the core 55 is fixed to the support 6 side. The pole 54 has a conical or pyramidal shape, and -
The head 52 has a concave surface corresponding to the pole 54, a conical surface or a pyramidal surface. It is assumed that a steady current (direct current) flows through the drive winding 56 so that the opposite sides of the head 52 and the pole 54 have the same polarity. Approximately 20% of the load of the vibration isolation table 1 (the remainder of the force supported by the passive controller 2) is supported by the repulsive force between the head 52 and the pole 54 determined by this steady current. Furthermore, the active brake 5 is equipped with a magnetic shielding plate 57 on the outer periphery to prevent the magnetic path from leaking to the outside, and also has an air flow 5 for cooling the core 55 and the drive winding 56.
8 is formed. Since the precision vibration isolator is generally used in a clean room, it is preferable that the air flow 58 for air cooling is formed by suction.

In the active brake 5 configured as described above, a steady current Io (Fig. 6) for supporting the vibration isolation table is normally applied to the drive winding 56, and the head 52 and the pole 54 are maintained at a predetermined interval. However, when the distance between the head 62 and the pole 64 changes due to vibration, a current is generated in the drive winding 56 due to the change in the magnetic energy 7 during that time, and its internal resistance generates a braking force and the sensor 3 detects vibration, and the circuit unit 4 processes the output of the sensor 3 to apply a control current Ic (Ic(Io)). They are controlled to have opposite phases and a gain of 1 or less.

When a braking force having a phase opposite to the excitation force is applied to the head 62 in this manner, a damping force is generated in the direction in which the head 52 and the poles 54 are arranged, that is, in the vertical direction, and a damping force is generated in the head 52 and the pole 54.
The vibration of the vibration isolation table 1 fixed to the head 52 can be canceled out in a practical manner by the damping force in the direction of deviation caused by the shape of the pole 54.

Note that the gap between the head 52 and the pole 54 also acts as a vibration limiter. For this purpose, it is also effective to attach an M tube material such as rubber to the head 52 and/or the pole 54 to absorb shock. Further, the sensor 3 and the circuit section 4 are preferably attached to each active brake, and vibrations are detected only in the vertical direction.

[Effects of the Invention] As is clear from the above explanation, in the precision vibration isolator of the present invention, the vibration isolator is supported by the repulsive force of the magnet, so the natural frequency can be appropriately adjusted and active control is possible. It can also facilitate force actuators (active brakes)
By using a specific shape for damping in the horizontal direction at the same time as in the vertical direction, vibrations generated in the vibration isolation table can be effectively isolated with a small number of installations, and the equipment can be simplified. It is possible to aim for

[Brief explanation of the drawing]

Figures 1 (a) and (b) are diagrams explaining the present invention in detail, Figure 2 is a schematic diagram showing an embodiment of the precision vibration isolator of the present invention, and Figure 3 is an embodiment of the present invention. 4 is a diagram showing the waveforms of each signal, FIG. 5 is a diagram showing an active brake according to an embodiment of the present invention, FIG. 6 is a diagram showing the control current, and FIG. 7 is a diagram showing the control current. 6 which is a schematic diagram of an active vibration isolator 1...Vibration isolation table 2...Passive damper 21.22...Permanent magnet 3... ...Sensor 4...Circuit part 5...Active brake 51...Permanent magnet 53...Electromagnet 6...Support stand substitute Person Patent Attorney Moritani - Drifting Figure 1 (a) (b) Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A vibration isolation table supported by a passive damper on a support body;
Consisting of a sensor that detects the vibration of the vibration isolation table, a circuit section that processes and amplifies the output of the sensor and outputs a control signal, and an active brake that is activated by the control signal and controls the vibration. In the precision vibration isolator, the passive damper and the drive damper each include a pair of magnets that are arranged opposite to each other so as to repel each other, and the active damper includes an electromagnet in which one of the magnets is controlled by the control signal. A precision vibration isolator characterized by: 2. In the active brake, one of the pair of magnets arranged opposite to each other has a conical surface or a pyramidal surface, and the other has a concave surface corresponding to the conical surface or pyramidal surface, and the active brake is configured to respond to the vibration. 2. The precision vibration isolator according to claim 1, wherein the vibration is substantially canceled by applying forces to the vibration isolator in the direction in which the magnets are arranged and in the direction of displacement of the magnets.