JPH0714936Y2 - Ultrasonic transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an ultrasonic wave transmitter / receiver for transmitting and receiving ultrasonic waves in the air, and particularly to improvement of reception characteristics.

[Prior Art] Ultrasonic waves are emitted into the air to perform various measurements such as the distance to the target, the moving speed of the target, and the liquid level, and an ultrasonic transducer is used to transmit and receive ultrasonic waves. There is.

FIG. 4 is a sectional view of a conventional ultrasonic wave transmitter / receiver, wherein 1 is a cylindrical transducer for transmitting ultrasonic waves, 2 is a cylindrical transducer for receiving ultrasonic waves, 3 Is an acoustic blocking agent provided between the transmitting oscillator 1 and the receiving oscillator 2,
Reference numeral 6 is a shaft, 7 is a cone-shaped reflector that changes the direction of radiation of ultrasonic waves, and 8 is a mounting screw.

The conventional ultrasonic transmitter / receiver is configured as described above, and the transmission oscillator 1 and the reception oscillator 2 use a rubber material or the like having a predetermined sound absorption characteristic in order to suppress acoustic coupling between the oscillators. It is laminated concentrically via the acoustic blocking member 3 and is fixed along the central axis of the reflector 7 by a shaft 6 and a mounting screw 8 made of a non-metallic material having a large acoustic attenuation.

When a voltage is applied to the electrodes provided on the inner and outer surfaces of the transmitting oscillator 1 having a cylindrical shape, a lateral effect causes extension along the circumference to generate radial stress, and the fundamental frequency at which the circumference has just one wavelength. The breathing vibration of the is performed and the ultrasonic wave is radiated in the radial direction. The ultrasonic waves reflected by the inner surface of the conical reflector 7 are radiated in the central axis direction. Further, the ultrasonic waves reflected from the target object are received by the receiving transducer 2 via the reflector 7 and converted into an electric signal.

FIG. 5 shows operation waveforms of a conventional ultrasonic transmitter / receiver, where is a leak signal from the transmitting oscillator 1 to the receiving oscillator 2, is a received signal obtained from a reflected signal from a target, and is a received signal. The interference signal directly received by the vibrator 2 is a threshold value for detecting the received signal.

The reflected signal from the target object received by the ultrasonic wave transmitter / receiver is supplied to a receiving circuit, a measuring circuit, etc., and a signal having a level exceeding a threshold value is detected and used for measurement or the like.
At this time, the level of the interference signal is low in order to ensure the predetermined measurement accuracy by stabilizing the operation and improving the reproducibility.
The rising edge of the received signal near the threshold value is required to be steep and stable.

Ultrasonic transducers that transmit and receive in the air are installed outdoors for a long period of time and exposed to the atmosphere, so the ambient temperature for each season,
It must withstand the humidity and environment such as plant sufficiently and operate stably.

[Problems to be Solved by the Invention] In the conventional ultrasonic transducer as described above, the transmitting oscillator 1 and the receiving oscillator 2 are concentrically stacked on the shaft 6 made of a non-metallic material to form a reflector. 7 is fixed in the direction of the central axis. At this time, the receiving transducer 2 is provided on the opening surface side of the reflector 7, and the transmission and reception of ultrasonic waves are performed via the reflection of the inner surface of the reflector 7 by the radial vibration of the transducer. Further, the reflected signal from the target object is received by the receiving transducer 2 via the reflector 7.

However, since the cylindrical oscillator has a Poisson's ratio in the vertical direction, a part of the reflected signal is sensitive to the longitudinal vibration of the receiving oscillator 2 and is directly received to be an interference signal. Since the interference signal is received prior to the received signal, the rising waveform of the received signal as a combined signal due to the interference of the two signals becomes warm and the waveform constantly fluctuates.

Therefore, there is a problem that the crossing position between the threshold value and the received signal in the signal detection varies, and an error occurs in the detection of the received signal due to the phase and level variation of the interference signal.

The present invention was made to solve such a problem, and suppresses a reception signal reflected from a target object and directly applied to the reception transducer 2, and a reception signal via the reflector 7 can be stably supplied. An object of the present invention is to obtain an ultrasonic wave transmitter / receiver capable of highly accurately detecting a signal by a threshold value.

[Means for Solving the Problem] An ultrasonic wave transmitter / receiver according to the present invention comprises a cylindrical transmitting oscillator and a receiving oscillator which are concentrically stacked and arranged, and the transmitting oscillator and the receiving oscillator are arranged. It is equipped with a conical reflector that is concentric with the child and has a height equal to or higher than the height at which the transmitting oscillator and the receiving oscillator are stacked, and transmits ultrasonic waves emitted from the transmitting oscillator in the radial direction of the cylinder. In the ultrasonic transducer, the ultrasonic wave reflected by the inner surface of the conical reflector is directed toward the target object, and the ultrasonic wave reflected from the target object is reflected by the inner surface of the conical reflector and is received by the receiving transducer. Of the transducers for transmission and the transducers for reception that are stacked and arranged, a convex reflector made of a metal material is provided on the front end face of the oscillator on the front side of the target so as to cover the front end face of the oscillator. It is a thing.

[Operation] In this invention, since the reflector made of the metal material having the convex shape is provided at the end of the receiving oscillator, the signal directly applied to the receiving oscillator of the reflected signal from the target object in the space is provided. Is scattered and reflected at a wide angle by the above-mentioned reflector having a large acoustic impedance and the reception level is significantly suppressed. Therefore, since the level of the interference signal is reduced, the influence of the interference signal on the ultrasonic signal received by the receiving transducer is reduced, and the ultrasonic signal is almost the signal received via the reflector.

The rising waveform of the signal from the ultrasonic transmitter / receiver is steep and stabilized, the detection signal by the threshold value is stable, and a signal used for highly accurate measurement can be obtained.

[Embodiment] An embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a sectional view showing an embodiment of the present invention, in which 1, 2, 3, 6, 7, 8, and 10 are the same as the above-mentioned conventional transducers, and 4 is reflected from a target object. A reflector that scatters and reflects ultrasonic waves, and 5 represents a holding member in which the reflector 4 is provided at one end of the shaft 6.

In the ultrasonic transmitter / receiver configured as described above, the transmitting oscillator 1 and the receiving oscillator 2 each have a cylindrical shape,
On the central axis of the opening surface of the conical reflector 7 by the holding member 5 having the shaft 6 and the mounting screw 8 which have the same resonance frequency and the circumference is equal to one wavelength and are concentrically arranged via the acoustic blocking material 3. It is fixed to.

The ultrasonic wave emitted from the transmitting oscillator 1 is reflected by the inner surface of the reflector 7 to be formed into a predetermined beam and emitted into the air. The reflected wave from the target pointed by the ultrasonic wave transmitter / receiver reaches the ultrasonic wave transmitter / receiver, is reflected by the inner surface of the reflector 7, and is received by the receiving transducer 2.

However, since both the transmitting oscillator 1 and the receiving oscillator 2 generate longitudinal vibration in addition to the vibration mode in the radial direction and have sound pressure sensitivity of longitudinal vibration, a part of the reflected wave reaching the ultrasonic transducer Is directly added to the receiving oscillator 2, but at the tip of the holding member 5 for fixing the receiving oscillator 2 to the reflector 7,
A reflector 4 is attached which is made of a metal material whose acoustic impedance is significantly higher than that of air and which has a convex spherical surface shape having a circumference equal to or larger than that of the cylindrical vibrator. The shaft 6 attached to the holding member 5 is made of a non-metallic material having a large sound attenuation.

FIG. 2 is a cross-sectional view showing another example of the reflector, and the reflector 4 provided at the end of the holding member 5 has a conical shape, and thus the cylindrical shape of the receiving transducer 2 on the opening side of the reflector 7. Since the end portion of the receiver is covered with the reflector 4, the receiving vibrator 2
The reflected wave directly applied to the surface is scattered and reflected at almost a wide angle by the reflector 4 having a curved surface such as a spherical surface or a conical shape.

As a result, the level of the interference signal is significantly reduced, and the influence on the received signal is reduced.

FIG. 3 shows an example of operation waveforms according to the present invention,
Is the same as the above-mentioned operation waveform, but since the interference due to the interference signal is significantly reduced at the rising portion of the received signal, the rising waveform of the received signal is steep and stable because the fluctuation due to the interference signal is suppressed. The detection of the received signal by the threshold value is stabilized, and it can contribute to the improvement of reproducibility and measurement accuracy in various measurements such as level measurement using aerial ultrasonic waves.

This device can be widely used for measurement using aerial ultrasonic waves in fields and chemical plants.

Even if the surface of the reflector 4 is made of a non-metallic material and is covered with a metallic material, the same operation can be performed.

[Effects of the Invention] As described above, the present invention has two transducers arranged concentrically in the central axis direction of the reflector as a target among the transducers for transmission and the transducers for reception stacked. On the other hand, a simple structure in which the front end face of the oscillator on the front side is fixed by a holding member provided with a convex reflector made of a metal material so as to cover the front end face of the oscillator Although a part of the reflected ultrasonic waves is directly applied to the receiving transducer, the ultrasonic waves are scattered and reflected at a wide angle by the reflector provided at the end of the holding member and are hardly received.

Therefore, most of the received signals are received by the transducer for reception via the reflector, so the influence of the interference signal is significantly reduced, and the rising waveform of the received signal can be made steep and stable. The detection signal can be stabilized, and it can contribute to the improvement of reproducibility and measurement accuracy in measurement using aerial ultrasonic waves.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is a sectional view showing another example of a reflector, FIG. 3 is an example of an operation waveform according to the present invention, and FIG. FIG. 5 is a sectional view of the ultrasonic wave transmitter / receiver, and FIG. 5 is an operation waveform of the conventional ultrasonic wave transmitter / receiver. In the figure, 1 is a transmitting oscillator, 2 is a receiving oscillator, 3
Is an acoustic barrier, 4 is a reflector, 5 is a holding member, 6 is a shaft, 7 is a reflector, 8 is a mounting screw, 10 is a connector, is a leakage signal, is a received signal, and is a threshold value. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] 1. A transmission oscillator and a reception oscillator, which are cylindrical in shape, are concentrically stacked and arranged concentrically with the transmission oscillator and the reception oscillator, and the transmission oscillator and the reception oscillator. Is provided with a conical reflector having a height equal to or higher than the laminated height, and ultrasonic waves emitted from the transmitting oscillator in the radial direction of the cylinder are reflected by the inner surface of the conical reflector and directed toward a target object. An ultrasonic wave transmitter / receiver in which ultrasonic waves reflected from a target object are reflected by the inner surface of the conical reflector and received by a receiving vibrator, wherein the target among the transmitting vibrators and the receiving vibrators in the stacked arrangement is used. An ultrasonic transmitter / receiver characterized in that a convex reflector made of a metal material is provided on a front end surface of a vibrator on the front side of an object so as to cover the front end surface of the vibrator.