JPS6120199B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sealed ultrasonic transmitter/receiver used in fish finders, depth sounders, etc. to transmit ultrasonic waves underwater and receive the echoes. Two different types of high-frequency electrical signals are applied alternately to the strain transducer, and the resonance impedance of the two frequencies based on the sound pressure applied by the transducer is made the same by adjusting the thickness of the wave transmitting and receiving side plates of the sealed case. This system generates transmission and reception of ultrasonic waves of different frequencies.

Modern fish finders, depth sounders, etc. do not use single-frequency ultrasonic waves as in the past, but instead alternately transmit ultrasonic waves with two different frequencies, such as 50 kHz and 200 kHz, and record the echoes of each. However, since the resonance impedance of the two frequencies is different, electrostrictive vibrations with different vibration characteristics are generated. Two sealed ultrasonic receivers, each with a separate encapsulated waveguide, are cut and driven, and each echo reception signal is adjusted by a matching transformer to record a record that is proportional to the strength of the echoes of two different frequencies. Otherwise, the ability to detect underwater information cannot be accurately increased, and the circuit configuration becomes complicated.

The present invention is configured to transmit and receive two types of high frequency waves by adjusting the resonance impedance of each of the different frequencies to the same level using the sealed case itself that encloses one electrostrictive vibrator. This invention has an inventive step in that the matching transformer and related circuits can be omitted.

An embodiment of the present invention will be described with reference to the accompanying drawings. In the figure, 1 is a circular electrostrictive vibrator, and silver electrodes 2 and 3 are provided on both sides of the vibrator in a known manner. 4 is a cork that surrounds the back and circumferential surface of the electrostrictive vibrator 1.
A porous bedclothing material such as foamed rubber, which is covered with an insulating case 7 made of synthetic rubber, synthetic resin, etc.
Covered lead wires 5 and 6 connected to silver electrodes 2 and 3, respectively
is passed through an insulating tube 9 provided as an extension on the back of the case 7.

Two different types of vibration voltages are applied to the electrostrictive vibrator 1 through coated lead wires 5 and 6, and by alternately applying the two types of vibration voltages, the vibration in the thickness direction is
Use a material that produces 200kHz high-frequency vibration and 50kHz low-frequency vibration in the radial direction. Although the wave transmitting/receiving side plate 8 of the insulating case 7 resonates when sound pressure is applied to it based on the two types of vibrations of the electrostrictive vibrator 1,
The resonance impedance varies depending on the thickness (t). The present invention makes the resonance impedance of the wave transmitting/receiving side plate 8, which is sensitive to the above-mentioned high frequency vibration and low frequency vibration of the electrostrictive vibrator 1, the same by selecting the thickness (t). The attached graph is a curve diagram showing the results of measuring changes in high frequency resonance impedance and low frequency impedance by using epoxy resin for the insulating case 7 and varying the thickness (t) of the wave transmitting/receiving side plate 8. Therefore, it was confirmed that the curves of the two types of resonance impedances intersect when the thickness (t) of the wave transmitting/receiving side plate 8 becomes 5.2 mm. That is, by selecting the thickness (t) of the wave transmitting/receiving side plate 8, the resonance impedance of the two frequencies can be made the same.

In an ultrasonic transducer that transmits ultrasonic waves underwater and receives the echoes, the wave transmitting/receiving side plate of the case is
Ultrasonic waves, which are effective for fish finders, depth sounding, etc., must be met to have a resonant impedance that harmonizes with the frequency of the electrostrictive vibrator built into the case, and at the same time to be approximately equal to the acoustic impedance of water. The above conditions are the same even when transmitting and receiving two types of ultrasonic waves of different frequencies are transmitted and received in a single case without having the ability to transmit and receive waves. The present invention satisfies these two conditions, that is, the conditions that are compatible with the transmission and reception of ultrasonic waves of two different frequencies, by selecting the thickness (t) of the wave transmission and reception side plates of the insulating case, and the resonance of the two frequencies. The impedance of each transducer is the same, so there is no need to use two ultrasonic transducers with different characteristics or a matching transformer to adjust the echo level of each transducer. This has the advantage that the circuit configuration dependent on the circuit can also be simplified.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional side view of one embodiment of the present invention;
The figure is a graph showing the relationship between changes in the thickness of the wave transmitting/receiving side plate 8 and changes in two types of resonance impedance. 1 → Electrostrictive vibrator, 7 → Insulation case, 8 → Transmission/reception side plate.

Claims (1)

[Claims] 1 A single voltage oscillator that generates vibrations at two different frequencies by alternately applying two different types of high-frequency electric signals is sealed in an insulating case, and the two A sealed ultrasonic transducer characterized by having the same frequency resonance impedance.