JPH05262600A - Sound wave floating device - Google Patents

Abstract

PURPOSE:To cope with deviation of resonance frequency of ultrasonic vibrator and to accurately detect generation of standing wave between a vibration plate and a reflection plate in a sound floating device to maintain a material in a non-contact state by utilizing a sound wave. CONSTITUTION:A sound wave floating device consists of an ultrasonic vibrator 1, a sine-wave oscillating means 2 to excite the ultrasonic vibrator 1, an electric current value detecting means 3 to discover a value of electric current flowing in the ultrasonic vibrator 1 and a resonance controlling means 4 which regulates oscillating frequency of the sine-wave oscillating means 2 according to variability of detected electric current value of the electric current value detecting means 3 and makes the oscillating frequency of the sine-wave oscillating means 2 coincident with the oscillating frequency of the ultrasonic vibrator 1. The sound wave floating device is further equipped with a distance changing means 5 for varying the distance between a vibration plate and a reflecting plate and a standing wave controlling means 6 for driving the distance changing means 5 based on the detected electric current value of the electric current value detecting means and forming a standing wave sound field between the vibration plate (a) and the reflection plate (b).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a sound wave to form a standing wave sound field by an ultrasonic wave between a vibrating plate and a reflecting plate to hold an object in a non-contact manner at a node position of the standing wave. It relates to a sonic levitation device.

In recent years, new materials have been developed in space such as microgravity. For example, under weightlessness, the difference in weight of a plurality of materials can be neglected. Therefore, it is attempted to develop a new material that cannot be obtained on the ground by homogeneously mixing the respective materials.

As one of the devices used for such development and the like, attention is paid to a sonic levitation device. The sonic levitation device uses a diaphragm and a reflector to form a standing wave sound field between the diaphragm and the reflector by the traveling wave from the diaphragm and the reflected wave from the reflector. Therefore, the sound pressure in the standing wave sound field can hold an object in a fixed position in a non-contact manner without touching the container.

By using this sonic levitation device, it becomes possible to grow crystals of useful materials such as proteins under the condition that influences from the container and the like are eliminated. That is, if an object can be held in a microgravity state without touching the container, the influence of surface tension from the container and contamination of impurities can be easily eliminated. In addition, by using the sonic levitation device, the material can be held at a fixed position, and even if the crystal growth takes a long time, it is possible to easily observe the change state, and the sonic levitation device has many advantages. It is known to have.

[0005]

2. Description of the Related Art There are two types of conventional sonic levitation devices, one that uses a speaker as a sound source and the other that uses an ultrasonic transducer. The speaker has an advantage that the vibration frequency can be easily changed, but has a drawback that a normal speaker has a usable frequency range limited to an audible frequency range and it is difficult to obtain a large sound pressure. On the other hand, the ultrasonic transducer has a resonance frequency peculiar to the ultrasonic wave region, and although the vibration frequency cannot be freely selected, it has an advantage that a large sound pressure can be obtained and requires a strong holding force. An ultrasonic transducer is used as a sound source of the sound wave floating device.

In a sound wave levitation device using an ultrasonic vibrator, a sinusoidal voltage having the same resonant frequency as the ultrasonic vibrator is applied to the ultrasonic vibrator to vibrate the ultrasonic vibrator. There is.

[0007]

However, in a sonic levitation device using an ultrasonic vibrator, the temperature of the ultrasonic vibrator rises due to the influence of the current flowing through the ultrasonic vibrator when used continuously for a long time. .. As the temperature rises, the resonance frequency of the ultrasonic transducer decreases. Therefore, in order to sufficiently resonate the ultrasonic vibrator, it is necessary to match the frequency of the applied voltage with a new resonance frequency of the ultrasonic vibrator.

Further, due to the shift of the resonance frequency of the ultrasonic transducer, the wavelength is changed and the standing wave is not generated between the vibrating plate and the reflecting plate. In order to recreate the standing wave sound field, it is necessary to adjust the distance between the diaphragm and the reflector, but at the time of adjustment, in order to confirm that the standing wave sound field was formed, the sound pressure Must be measured. However, in sound pressure measurement using a microphone, etc., the sound field was disturbed, so it was not possible to accurately confirm the formation of standing waves.

The present invention has been made in view of the above points, and an object thereof is to provide a sound wave levitation device capable of coping with a shift in the resonance frequency of an ultrasonic transducer. Another object of the present invention is to provide a sound wave levitation device capable of accurately detecting that a standing wave is generated between the vibration plate and the reflection plate.

[0010]

FIG. 1 is a block diagram for explaining the principle of the present invention for achieving the above object. An acoustic wave levitation device that achieves the first object of the present invention is shown in FIG. Sine wave oscillating means 2, a current value detecting means 3 for detecting a current value of a current flowing through the ultrasonic transducer 1 by a voltage signal from the sine wave oscillating means 2, and a current value detecting means 3
The oscillating frequency of the sine wave oscillating means 2 is controlled according to the fluctuation of the current value detected by the step S1, so that the predetermined frequency of the voltage signal supplied to the ultrasonic transducer 1 matches the resonant frequency of the ultrasonic transducer 1. And the resonance control means 4 for doing so.

Further, a sound wave levitation device for achieving the second object of the present invention is an ultrasonic vibrator 1 for vibrating a diaphragm, and a sine wave oscillating means for supplying a voltage signal of a sine wave to the ultrasonic vibrator 1. 2, a current value detecting means 3 for detecting the current value of the current flowing through the ultrasonic transducer 1 by the voltage signal from the sine wave oscillating means 2, and a distance varying means for varying the distance between the diaphragm and the reflector. 5, and a standing wave control means for driving the distance varying means 5 based on the current value detected by the current value detecting means 3 to form a standing wave sound field between the diaphragm and the reflector. 6 and 6.

[0012]

Generally, the current value (actual AC value) detected by the current value detecting means 3 of the current flowing through the ultrasonic transducer 1 by the sine wave voltage signal from the sine wave oscillating means 2 is the sine wave voltage signal. When the frequency is changed, the resonance frequency fo of the ultrasonic transducer 1 becomes maximum at the resonance frequency fo, and there is a phenomenon that the resonance frequency fo gradually decreases as the resonance frequency fo increases.

FIG. 2 is a graph showing an example of the relationship between the frequency of the sine wave current for excitation supplied to the ultrasonic transducer and the amount of the current. That is, the change in the amount of current has a smooth mountain shape with the maximum at the resonance frequency fo = 21803 Hz (solid line L1).

The current value detected by the current value detecting means 3 forms a standing wave sound field between the diaphragm and the reflector when the position of the reflector is changed with respect to the diaphragm. For each position, there is a phenomenon that the current value significantly decreases compared to the current value at the position where the standing wave sound field is not formed. It should be noted that there are a plurality of positions of the reflection plate where the standing wave sound field is formed, and the distance between adjacent positions is ½ wavelength of the sound wave.

The present invention has been made paying attention to such a phenomenon, and by monitoring the current value detected by the current value detecting means 3, whether or not the ultrasonic transducer 1 is in a resonance state, Further, it is possible to easily know whether or not a standing wave sound field is formed between the diaphragm and the reflector.

To achieve the first object of the present invention, the resonance control means 4 controls the oscillation frequency of the sine wave oscillating means 2 in accordance with the fluctuation of the current value detected by the current value detecting means 3. The predetermined frequency of the voltage signal supplied to the ultrasonic vibrator 1 is made to match the resonance frequency of the ultrasonic vibrator 1. As a result, even if the resonance frequency of the ultrasonic transducer 1 shifts, an appropriate excitation current that follows the resonance frequency is supplied to the ultrasonic transducer 1, and the ultrasonic transducer 1 can maintain a sufficient resonance state.

In order to achieve the second object of the present invention, the standing wave control means 6 drives the distance varying means 5 based on the current value detected by the current value detecting means 3 to vibrate. A standing wave sound field is formed between the plate and the reflector. This makes it possible to accurately detect that a standing wave is generated between the diaphragm and the reflector.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a block diagram of the sonic levitation device according to the first embodiment. The sonic levitation device main body 31 includes an ultrasonic transducer 31b fixed to the frame 31a, a horn 31c connected to the ultrasonic transducer 31b, a diaphragm 31d connected to the horn 31c, and a diaphragm 31d facing the diaphragm 31d. And a reflection plate 31e that is provided in the same manner. A space 31f is defined between the diaphragm 31d and the reflector 31e. The space 31f is only defined by the diaphragm 31d and the reflector 31e that are arranged in parallel, and the others are open ends. The diaphragm 31d and the reflector 31e have, for example, a diameter of 120 mm and 3 to 7 m.
It is made of materials such as m-thick aluminum and duralumin. The space 31f is filled with a gas or a liquid that is a sound propagation medium, and an object to be suspended and held therein is inserted. If a standing wave is generated in the space 31f by vibrating the vibrating plate 31d and a traveling wave and a reflected wave formed by the traveling wave being reflected by the reflecting plate 31e, the node position of the standing wave (there may be a plurality of positions) Then, the inserted object is held.

A distance varying device 32 for adjusting the distance from the diaphragm 31d so as to generate a standing wave in the space 31f is connected to the reflector 31e. The distance varying device 32 is
A ball screw 32a fixed to the reflection plate 31e, a gear 32c attached to the ball screw 32a, a gear 32d that meshes with outer teeth of the gear 32c, and a pulse that rotates the gear 32d when the shaft is fixed to the gear 32d. It is composed of a motor 32e. In the distance variable device 32, the pulse motor 32
When e is driven, the ball screw 32a is moved in the vertical direction via the gear 32d and the gear 32c, the position of the reflection plate 31e is changed, and the distance between the vibration plate 31d and the reflection plate 31e can be adjusted.

The function synthesizer 33 is a sine wave oscillator capable of generating a sine wave voltage signal having an arbitrary frequency and an arbitrary voltage level, and varies the frequency of the generated signal according to a control signal from the outside. The sine wave voltage signal output from the function synthesizer 33 is amplified by the amplifier 34 and output as an applied voltage to the ultrasonic transducer 31b. The ultrasonic vibrator 31b is excited by the input voltage and vibrates. However, the current sensor 35 is inserted between the amplifier 34 and the ultrasonic transducer 31b. The current sensor 35 includes the amplifier 34 to the ultrasonic transducer 3
The effective current value of the alternating excitation current supplied to 1b is detected and output to the control device 36.

In the control device 36, the function synthesizer 33 is operated based on the detected current value from the current sensor 35.
And the pulse signal to the pulse motor 32e of the distance varying device 32. Control device 3
Reference numeral 6 is a personal computer or the like, and sends a control signal to the function synthesizer 33 or the like by using a communication means such as GPIB.

Next, the contents of control performed by the control device 36 will be described. First, it is assumed that the function synthesizer 33 outputs a sine wave voltage signal of 21803 Hz, which is the initial resonance frequency fo of the ultrasonic vibrator 31b, and the ultrasonic vibrator 31b is in a resonance state.

FIG. 4 is a graph showing an example of the change over time of the ultrasonic transducer 31b. That is, as the sine wave voltage signal of 21803 Hz continues to be output from the function synthesizer 33, as time passes,
The current value detected by the current sensor 35 on the vertical axis decreases, and after 30 minutes, it decreases by 40%. This is a phenomenon that occurs because the resonance frequency of the ultrasonic transducer 31b deviates from 21803 Hz, and the resonance frequency of the ultrasonic transducer 31b at this time deviates to 21773 Hz according to the measurement result. That is, it is as shown by the broken line L2 in FIG.

Therefore, the frequency of the sinusoidal voltage signal from the function synthesizer 33 is set to the ultrasonic transducer 3
It is necessary to follow the new resonance frequency of 1b. Therefore, the control device 36 sends a control signal to the function synthesizer 33 to slightly increase or decrease the frequency of the sinusoidal voltage signal from the function synthesizer 33. Then, how the current value detected by the current sensor 35 changes is observed. When the detected current value of the current sensor 35 simply increases and then begins to decrease, changing the frequency of the sinusoidal voltage signal is stopped. As a result, the ultrasonic transducer 31b is brought into a resonance state at the new resonance frequency.

With this new resonance frequency, the diaphragm 31d
Since the standing wave sound field previously formed in the space 31f between the reflector 31e and the reflector 31e disappears, the reflector 31e
Needs to be moved again to find again the distance between the diaphragm 31d and the reflector 31e where the standing wave sound field is formed.

By the way, the reflection plate 31 is different from the vibration plate 31d.
When the position of e is changed, the detected current value of the current sensor 35 at each position where the standing wave sound field is formed in the space 31f is larger than the current value at the position where the standing wave sound field is not formed. There is a phenomenon that it drops sharply. Focusing on this phenomenon, the control device 36 controls the distance varying device 32 based on the current value detected by the current sensor 35 to form a standing wave sound field.

That is, the position of the reflection plate 31e where the standing wave sound field is formed is calculated in advance to obtain an approximate position, and a pulse signal is output to the pulse motor 32e to move the reflection plate 31e to that position. To do. Then, the reflector 31
The position of e is moved up or down and the detected current value of the current sensor 35 is observed. When the detected current value of the current sensor 35 simply decreases and then increases, changing the position of the reflection plate 31e is stopped. As a result, a standing wave sound field is formed in the space 31f.

Next, a second embodiment of a simplified type in which the distance between the diaphragm 31d and the reflector 31e is manually changed will be described. FIG. 5 is a block diagram of the sound wave levitation device according to the second embodiment. Of the constituent parts of this device, the same constituent parts as those of the sound wave levitation device of the first embodiment shown in FIG. 3 are designated by the same reference numerals as those in FIG.

In the sonic levitation device of the second embodiment, the ball screw 51 to which the reflecting plate 31e is fixed is provided, and the ball screw 51 and the reflecting plate 31e are moved in the vertical direction by rotating them manually. In addition, the control device 5
3 controls the function synthesizer 33 according to the current value detected by the current sensor 35, and the control method is the same as that of the first embodiment.

In the second embodiment, the manual adjustment of the reflection plate 31e in the vertical direction is performed by observing the holding state of a floating object, and the position of the reflection plate 31e is adjusted to the position calculated by the resonance frequency. Is measured and moved.

Further, a second embodiment will be described in which it is possible to easily detect that a standing wave sound field is formed when the resonance frequency shift of the ultrasonic transducer does not matter for a short time. To do.

FIG. 6 is a block diagram of a sound wave levitation device according to the third embodiment. Of the constituent parts of this device, the same constituent parts as those of the sound wave levitation device of the first embodiment shown in FIG.
The same reference numerals are given and the description is omitted.

In the sound wave levitation device according to the third embodiment, the function synthesizer 61 is a sine wave oscillator which generates a sine wave voltage signal having a frequency preset to a predetermined value. That is, the function synthesizer 61 generates a sine wave voltage signal having the same frequency as the initial resonance frequency of the ultrasonic transducer 31b. Further, the control device 62 controls the distance varying device 32 according to the detected current value of the current sensor 35, and the control method is the same as that of the first embodiment.

As a result, when the ultrasonic transducer is used for only a short time and the resonance frequency of the ultrasonic transducer does not shift, a standing wave sound field is formed by the acoustic wave levitation device of the third embodiment having a simple structure. Can be accurately detected.

Although the sound wave levitation device of the present invention is supposed to be used in the space of microgravity, depending on the size of the object to be suspended and the propagation medium of the sound wave,
It is a device that can be used on the ground.

[0036]

As described above, according to the present invention, the resonance control means controls the oscillation frequency of the sine wave oscillating means in accordance with the detected current value of the current value detecting means. Even if there is a deviation, an appropriate applied voltage that follows the resonance frequency is supplied to the ultrasonic vibrator, and the ultrasonic vibrator can maintain a sufficient resonance state.

Further, the standing wave control means drives the distance varying means based on the current value detected by the current value detecting means to form a standing wave sound field between the diaphragm and the reflector. To This makes it possible to accurately detect that a standing wave is generated between the diaphragm and the reflector.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a graph showing an example of the relationship between the frequency of the voltage applied to the ultrasonic vibrator and the amount of current flowing in the ultrasonic vibrator.

FIG. 3 is a block diagram of a sound wave levitation device according to a first embodiment.

FIG. 4 is a graph showing an example of changes with time of an ultrasonic transducer.

FIG. 5 is a block diagram of a sound wave levitation device according to a second embodiment.

FIG. 6 is a block diagram of a sound wave levitation device according to a third embodiment.

[Explanation of symbols]

 1 ultrasonic transducer 2 sine wave oscillating means 3 current value detecting means 4 resonance control means 5 distance varying means 6 standing wave control means

Claims (3)

[Claims] 1. A sonic levitation device for forming an acoustic field of a standing wave between a diaphragm and a reflector to hold an object at a node position of a standing wave, the ultrasonic wave vibrating the diaphragm at a natural resonance frequency. A sonic wave oscillator (1), a sine wave oscillating means (2) for supplying a sine wave voltage signal of a predetermined frequency to the ultrasonic wave oscillator (1), and a voltage signal from the sine wave oscillating means (2) Current value detecting means (3) for detecting the current value of the current flowing through the ultrasonic transducer (1), and the sine wave oscillating means according to the fluctuation of the current value detected by the current value detecting means (3). Resonance control means for controlling the oscillation frequency of (2) so that the predetermined frequency of the voltage signal supplied to the ultrasonic transducer (1) matches the resonance frequency of the ultrasonic transducer (1) ( 4) and a sonic levitation device comprising: 2. The distance varying means (5) for varying the distance between the vibrating plate and the reflecting plate, and the distance varying means based on the current value detected by the current value detecting means (3). A standing wave control means (6) for driving the means (5) to form a standing wave sound field between the diaphragm and the reflector. Sonic levitation device. 3. A sound wave levitation device for forming a standing wave sound field between a diaphragm and a reflector to hold an object at a node position of a standing wave, the ultrasonic vibrator (1) vibrating the diaphragm. ), A sine wave oscillating means (2) for supplying a sine wave voltage signal to the ultrasonic transducer (1), and the ultrasonic transducer (1) according to the voltage signal from the sine wave oscillating means (2). Current value detecting means (3) for detecting the current value of the current flowing through the device, distance varying means (5) for varying the distance between the diaphragm and the reflector, and the current value detecting means (3). A standing wave control means (6) for driving the distance varying means (5) based on the detected current value to form a standing wave sound field between the diaphragm and the reflector. And a sound wave levitation device.