JPH05231458A - Vibration isolator - Google Patents

Abstract

PURPOSE:To suppress the generation of micro vibration of a load while controlling the air quantity of an air spring precisely. CONSTITUTION:A conduit 3 is connected to an air spring 2 for supporting a load 1, and a valve means 4 is provided to switch the connection of this conduit 3 either to an intake duct 9 or an exhaust duct 10. The operation of this valve means 4 is controlled by the modulated wave from a controller 5 determined on the basis of the detection value from a vibration sensor 7 and a displacement sensor 8. The conduit 3 is provided interposingly with an expansion type muffler 12 and resonance type mufflers 13, 13 to damp micro vibration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration isolation device using an air spring.

[0002]

2. Description of the Related Art Conventionally, in precision equipment such as a semiconductor exposure apparatus and an electron microscope, in order to insulate vibration from the floor and keep it at a fixed position, the precision equipment is supported by a vibration isolation device using an air spring. Is being done. Generally, as this type of vibration isolation device, a load (the above-mentioned precision instrument) that is a support target by controlling the inflow and outflow of air into and out of the air spring.
It is known to keep a certain position. Then, aiming at higher precision control, there has been proposed one in which intake and exhaust to the air spring are performed by an on-off solenoid valve, and the on-off solenoid valve is controlled to be opened and closed by a pulse width modulated control signal. (See, for example, Japanese Patent Laid-Open No. 62-297552). This uses a pulse train of a constant frequency and changes each ratio (time ratio) per cycle of intake air and exhaust gas by the pulse width modulation so as to become a predetermined value according to the state of the load,
The amount of air flowing in and out of the air spring is controlled. That is, precise control is performed by alternately repeating intake and exhaust during a minute time so that the amount of air in the air spring becomes a predetermined control amount as a whole.

It is also known to use a servo valve such as an electropneumatic proportional valve for intake and exhaust to the air spring. In this case, a dither signal with a relatively high frequency is added to the control signal and added to the servo valve to reduce the influence of friction and the like on the spool of the servo valve to control a minute amount. Enabling is common practice. In other words, the dither signal causes minute vibrations in the spool to enable precise opening adjustment of the spool, thereby performing precise control.

[0004]

In the conventional vibration isolator described above, however, in the case of control by pulse width modulation, intake and exhaust are repeated for a very short time, so that a minute vibration is generated in the load at each repetition. There is an inconvenience to do. For example, when the load is supported in the vertical direction, the load rises when inhaling into the air spring and descends when exhausting, and this is repeated many times alternately, so that minute vibration occurs in the load.

Further, in the case of control by the dither signal, since the dither signal causes minute vibration in the spool, either or both of the intake amount and the exhaust amount become the original control signal due to the vibration. There is an inconvenience that the load fluctuates irrespectively, and the load fluctuates slightly as in the case of the pulse width modulation.

The present invention has been made in view of the above circumstances, and an object thereof is to suppress the generation of minute vibration of a load while precisely controlling the intake and exhaust amounts of the air spring. To do.

[0007]

In order to achieve the above object, the invention according to claim 1 is an air spring for supporting a load,
An air supply pipe for moving air into and out of the air spring, a valve means provided in the air supply pipe for adjusting the intake and exhaust amounts of the air spring, and a controller for controlling the operation of the valve means. It is assumed that you have it. Further, a silencer is provided at a position of the air supply line between the valve means and the air spring.

According to a second aspect of the present invention, in the first aspect of the present invention, the silencer is constituted by one or both of an expansion type silencer and a resonance type silencer.

[0009]

With the above construction, in the invention according to claim 1,
Since the vibrations that are minute pressure fluctuations other than the original control amount generated in the air supply pipeline due to the operation of the valve means are attenuated and removed by passing through the silencer, the above-mentioned minute fluctuations in the air in the air spring are eliminated. The generation of various vibrations is suppressed, and thus the generation of minute vibrations of the load is suppressed.

According to the invention of claim 2, in addition to the operation according to the invention of claim 1, vibrations in a relatively high frequency range are damped by the expansion type silencer, and comparison is made by the resonance type silencer. Vibration in the extremely low frequency region is damped. Therefore, by using both the silencers alone or in combination depending on the object to be removed which is the minute vibration, the minute vibration can be easily and surely removed.

[0011]

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

FIG. 1 shows a vibration isolator according to a first embodiment of the present invention, in which 1 is a load which is a support target of precision equipment, 2 is an air spring which supports the load 1, and 3 is this air. A conduit connected to the spring 2 for letting air in and out of it,
4 is a valve means for connecting the conduit 3 to the intake side or the exhaust side, and 5 is a controller for controlling the operation of the valve means 4,
Reference numeral 6 is a silencer interposed in the conduit 3.

The load 1 is installed on the floor (not shown) via the air spring 2, and the air spring 2 elastically supports the load 1 by the air filled therein. Then, the load 1 is sucked into the air spring 2 through the conduit 3 and the load 1 is raised, and conversely, the load is discharged and the load 1 is lowered. The load 1 is provided with a vibration sensor 7 for detecting an acceleration accompanying the vibration of the load 1, and a displacement sensor 8 for detecting a displacement amount of the load 1 from a predetermined reference position is close to the load 1. Are arranged in a non-contact state.

The valve means 4 is constituted by an electromagnetic valve for switching on / off the 3 port 2 position, and the conduit 3 is adapted to communicate with only one of the intake pipe line 9 and the exhaust pipe line 10. .. That is, in the valve means 4, the intake pipe 9 is fully opened and the exhaust pipe 10 is fully closed by the intake operation, and conversely, the exhaust pipe 10 is fully opened by the exhaust operation. The intake pipe line 9 is fully closed. When the valve means 4 is operated by the control signal from the controller 5 and connected to the intake pipe line 9, air is introduced into the air spring 2 through the conduit 3, and
When connected to the exhaust line 10, air is forced out of the air spring 2 through the conduit 3. The conduit 3, the intake conduit 9 and the exhaust conduit 10 constitute an air supply conduit 11 for taking air in and out of the air spring 2.

The controller 5 is a pulse width modulator 5a.
Is provided, and the operation of the valve means 4 is controlled based on the detection values from the vibration sensor 7 and the displacement sensor 8 connected to the controller 5. In this control, air is taken in and out of the air spring 2 in a direction to suppress the vibration of the load 1 according to the acceleration detection value and the displacement amount by the both sensors 7 and 8, and the load 1 is restored to a fixed position. The air is moved in and out of the air spring 2 in the direction of movement. In other words, the above control both suppresses the vibration of the load 1 and holds it at a fixed position.

Air is taken in and out of the air spring 2 by comparing an intake portion (for example, a low level portion) and an exhaust portion (for example, a high level portion) whose pulse width is modulated by the pulse width modulator 5a alternately arranged. This is done by operating the valve means 4 with a pulse train of a predetermined high frequency (for example, 100 Hz). The pulse train is modulated so that the ratio (time ratio) of the intake portion and the exhaust portion per one cycle becomes a predetermined value. By changing this time ratio, the pulse train is supplied to the air spring 2. The amount of air taken in and out is set to a predetermined control amount as a whole. That is, for example, if the intake portion is set to 50% and the exhaust portion is set to 50%, conditions such as the intake pressure of the intake pipe line 9 are set so that the amount of air in the air spring 2 is kept constant as a whole. If it is set, for example, 51% of the intake part and 49% of the exhaust part are set.
When it is set to%, as a result of the repetition of the intake operation and the exhaust operation, the air spring 2 is inhaled by a large time ratio.

The silencer 6 includes one expansion silencer 12 and a plurality (three in this example) of resonance silencers 13, 13, 1.
3 and these are interposed in series with the conduit 3.

As shown in detail in FIG. 2, the expansion type silencer 12 has a cavity portion 12a, an inlet pipe portion 12b communicating with one end side of the cavity portion 12a, and the other end side of the cavity portion 12a. It is basically composed of an outlet pipe portion 12c communicating with each other, and the inlet pipe portion 12b and the outlet pipe portion 12c constitute a part of the conduit 3.

The length L and the cross-sectional area S of the hollow portion 12a.
And the length L of the inlet pipe portion 12b and the outlet pipe portion 12c
1, 1 and L2 and the cross-sectional areas S1 and S2 are set to predetermined values so as to exhibit predetermined attenuation characteristics in accordance with conditions such as the frequency of the modulated wave. The expansion silencer 12 expands and diffuses a sound wave, which is a minute pressure fluctuation in the conduit 3, at one end side of the cavity 12a to dilute the acoustic energy density and then squeeze it at the other end side. The attenuation effect is obtained in a wide range with respect to sound waves of a relatively high frequency of a certain frequency or higher.

Further, as shown in detail in FIG. 3, each resonance type silencer 13 has a neck portion 13a branched from the conduit 3,
The inlet pipe portion 13c is composed of the hollow portion 13b communicating with the neck portion, and the conduit 3 on one side from the joining portion with the neck portion 13a.
The other side constitutes the outlet pipe portion 13d. The length L3 and the cross-sectional area S3 of the neck portion 13a, the volume V of the cavity 13b, the lengths L4 and L5 and the cross-sectional areas S4 and S5 of the inlet pipe portion 13c and the outlet pipe portion 13d correspond to the modulated wave. It is set to a predetermined value so as to exhibit a predetermined attenuation characteristic according to conditions such as frequency. In each resonance type silencer 13, the inside of the neck portion 13a acts as a mass and the inside of the cavity portion 13b acts as a spring, and the sound energy is consumed and attenuated by a kind of resonance action. Attenuating effect can be obtained for sound waves of a certain frequency and its vicinity, which is relatively low.

Next, the operation and effect of the first embodiment will be described.

The vertical movement of the load 1 is detected by the vibration sensor 7 and the displacement sensor 8 as an acceleration and a displacement amount, and the detected values are input to the controller 5. The controller 5 suppresses the vibration of the load 1 based on the detected value, and
A pulse width modulator 5 is obtained as a control signal to the valve means 4 based on the amount of air taken in and out of the air spring 2 required to move the load 1 up and down in the direction to restore it to a fixed position.
The modulated wave is output from a. The valve means 4 repeats the intake operation and the exhaust operation based on this modulated wave, while filling or exhausting the air as a whole through the conduit 3 in the air spring 2 or balancing the intake and the exhaust.

At this time, since the valve means 4 repeats the intake operation and the exhaust operation in a minute time (for example, 10 msec), a minute pressure fluctuation alternating with the frequency of the modulated wave, that is, a minute pressure fluctuation. Vibrations are generated in the air in the conduit 3, and harmonics having the above-mentioned frequency as a fundamental frequency are generated in the conduit 3 to generate minute vibrations.
These vibrations are attenuated by passing through the muffler 6 such as the resonance muffler 13 and the expansion muffler 12, so that the air in the air spring 2 is in a state where the minute vibrations are removed. .. That is, each resonance silencer 1 described above
It is possible to damp vibrations in a relatively low frequency region by a kind of resonance action in 3 and to damp vibrations in a relatively high frequency region by expansion and diffusion action in the cavity 12a of the expansion silencer 12. can do. Therefore, according to the present vibration isolator, minute vibrations of the load 1 can be generated as compared with the conventional device in which air is directly taken in and out of the air spring 2 from the valve means 4 without passing through the silencer 6. It can be suppressed as much as possible.

Further, since three resonance silencers 13 are combined so as to obtain a predetermined damping effect, each resonance can be compared with a case where one damping effect is obtained. The shape silencer 13 can be made relatively small, and an increase in the volume of the entire vibration isolation device can be suppressed.

FIG. 4 shows a case in which the valve means 4 of each device is operated by the same modulated wave using the vibration isolator of the first embodiment and the vibration isolator excluding the silencer 6 from the same device. The results of a comparative test in which the vibration (acceleration) generated in each load 1 is measured are shown, where the horizontal axis is the frequency, the vertical axis is the acceleration acting on the load 1, and the polygonal line shown by the solid line is the vibration isolation device of the first embodiment. The acceleration spectrum of the load 1 and the polygonal line indicated by the alternate long and short dash line are the acceleration spectrum of the load in the case of the device excluding the silencer 6 from the same device. The reference value of acceleration on the vertical axis is 1
It is Gal. As a result, in the case of the vibration isolator excluding the silencer 6, the modulated wave of the frequency f which is the drive signal of the valve means 4 and the harmonic of n times (n = 2, 3, ...) The frequency f. The peak value of acceleration occurred in load 1. On the other hand, in the case of the vibration isolator of the first embodiment having the silencer 6,
The peak value of the acceleration is removed and the acceleration acting on the load 1 is suppressed to a relatively small fluctuation.

FIG. 5 shows a vibration isolator according to a second embodiment of the present invention, in which 14 is a valve means and 15 is a controller which controls the operation of the valve means 14.

The valve means 14 is composed of a servo valve such as an electropneumatic proportional valve, and a spool is operated by a control signal input from the controller 15 to control the intake pipe 9 and the exhaust pipe 10 by the control signal. The conduit 3 is communicated with the opening according to the above.

The controller 15 is provided with a dither signal generator 15a, and based on the acceleration detection value acting on the load 1 from the vibration sensor 7 and the displacement amount of the load 1 from the displacement sensor 8, the load 1 of the load 1 is detected. Vibration is suppressed and load 1
The amount of air taken in and out of the air spring 2 for restoring the air pressure to a constant position is obtained, and a control signal corresponding to the opening degree of the intake pipe 9 and the exhaust pipe 10 that achieves the amount taken out is outputted. ing. The dither signal generator 15a superimposes a predetermined dither signal on the control signal from the controller 15, and the drive signal on which the dither signal is superposed is the valve means 14a.
Entered in.

Since the other structure of the vibration isolator according to the second embodiment is the same as that of the first embodiment, the same members are designated by the same reference numerals and the description thereof is omitted.

In the case of the second embodiment, the spool of the valve means 14 is set to a predetermined opening based on the control signal of the controller 15, and an amount of air corresponding to this opening is passed through the conduit 3. It is put in and taken out from the air spring 2.
At this time, since the spool vibrates at a position of the predetermined opening degree at a relatively high frequency due to the dither signal, the intake amount or the exhaust amount repeats minute fluctuations due to the vibration. That is, in addition to the pressure fluctuation based on the original control signal, a minute pressure fluctuation is generated in the air in the conduit 3, and a harmonic having the fundamental frequency of the vibration frequency of the spool is generated in the conduit 3. Then, this minute vibration is attenuated by passing through the muffler 6 such as the resonance muffler 13 and the expansion muffler 12, so that other than the original control amount, as in the first embodiment. It is possible to remove a minute vibration due to the dither signal, which is a minute fluctuation component. Therefore, the air amount of the air spring 2 can be reliably adjusted to the control amount based on the original control signal, and the pressure fluctuation in the air spring 2 due to the minute vibration can be prevented from occurring. This makes it possible to suppress the vibration of the load 1 and hold it at a fixed position in a stable state.

The present invention is not limited to the first and second embodiments described above, but includes various other modifications. That is, in the first and second embodiments, the expansion silencer 12 and the resonance silencer 13 are combined as the silencer 6, but the silencer 6 is not limited to this, and the pressure variation to be removed is not affected. The number, combination, etc. may be changed accordingly. For example, a muffler can be configured with only one of an expansion muffler or a resonance muffler, or another type of muffler, for example, a so-called side branch muffler, or a sound absorbing or reactance muffler. The mufflers may be configured independently or in combination.

In the first and second embodiments described above, the expansion silencer 12 is composed of a simple hollow portion 12a.
However, the present invention is not limited to this, and for example, it may be configured by a cavity portion provided with an insertion tube or a coupling cavity inside.

In the first and second embodiments, the air spring 2 is used to support the load 1 in the vertical direction to form the vibration isolator, but the present invention is not limited to this. In addition to the vertical direction, for example, the vibration isolator may be configured to support the load 1 in the horizontal direction or the diagonal direction.

Further, in the first and second embodiments,
The silencer is configured to eliminate unnecessary pressure fluctuations caused by modulated waves or dither signals.
The present invention is not limited to this, and when unnecessary pressure fluctuations are added to a frequency range different from the original control amount, the unnecessary pressure fluctuations may be removed.

[0035]

As described above, according to the vibration isolator of the first aspect of the present invention, the valve means for sucking and discharging the air spring can be precisely controlled by using the modulated wave or the dither signal. It is possible to reduce the small vibrations of air in the conduit and in the air spring, which have occurred conventionally due to these modulated waves, by attenuating it and reduce the amount of air in the air spring precisely according to the original control amount. The generation of minute vibrations of the load can be suppressed as much as possible while controlling.

According to the second aspect of the present invention, the expansion silencer can damp vibrations in a relatively high frequency range, and the resonance muffler can damp vibrations in a relatively low frequency range. Therefore, by using these in combination or alone depending on the vibration to be removed, the effect according to the invention described in claim 1 can be easily and surely achieved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is an enlarged sectional view of the expansion silencer of FIG.

FIG. 3 is an enlarged sectional view of the resonance silencer of FIG.

FIG. 4 is a relationship diagram of frequency and acceleration showing a comparison test result.

FIG. 5 is a view corresponding to FIG. 1 showing a second embodiment.

[Explanation of symbols]

 1 Load 2 Air Spring 3 Conduit 4, 14 Valve Means 5, 15 Controller (Controller) 6 Silencer 9 Intake Pipeline 10 Exhaust Pipeline 11 Air Supply Pipeline 12 Expansion Silencer 13 Resonance Silencer

Claims (2)

[Claims] 1. An air spring for supporting a load, an air supply line for introducing air into and out of the air spring, and a valve means provided in the air supply line for adjusting intake and exhaust amounts of the air spring. A vibration control device for controlling the operation of the valve means, wherein a silencer is provided at a position of the air supply pipe between the valve means and the air spring. Vibration isolation device. 2. The vibration isolator according to claim 1, wherein the silencer comprises one or both of an expansion type silencer and a resonance type silencer.