JPS6128475Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to an ultrasonic transducer used underwater, such as in depth sounders and fish finders. A diaphragm is produced by bonding a disk-shaped electrostrictive element with metalized electrode surfaces on both main surfaces, an insulated wire consisting of a pair of lead wires connected to both electrode surfaces, and the electrostrictive element on the bottom surface. and an insulating head consisting of a large-diameter base that encloses the electrostrictive element and a vibration absorbing material that covers the outside and upper surface thereof, and a small-diameter head that extends upward from the base and protects the insulated wire. Underwater ultrasonic transmitter/receiver devices consisting of a housing are widely used in depth sounders and fish finders, but they are especially used in situations where many fishing boats are crowded together in a relatively small fishing area, such as in fish finders. In some cases, it has the disadvantage of causing interference. In other words, this type of underwater ultrasonic transducer uses ultrasonic vibrations in two directions, the radial direction and the thickness direction, of a disc-shaped electrostrictive element, and usually a high frequency vibration of 200 KHz in the thickness direction for nearby or shallow water depths. On the contrary, low radial vibration of 50KHz is used for vibrations far away or at deep water depths, but in this case, when the frequency used is high thickness vibration of 200KHz, the directivity angle is narrow and the sound is There is no problem as the pressure decreases and the sound waves are also easily attenuated, making it difficult to cause interference with detection waves from other fishing boats. However, when using low radial vibrations such as 50KHz, the direction is opposite to this. The angle is wide, the sound pressure is high, and the sound waves are also difficult to attenuate. Therefore, when the fishing boats mentioned above are crowded together, there is a risk of interference with the detection waves of other nearby fishing boats. This interference has a radial resonance frequency of 50KHz.
This can be prevented by increasing or decreasing the resonant frequency within a small range of several KHz from This had a drawback of causing angle fluctuations, which made it difficult to put it into practical use. The present invention is an underwater ultrasonic transducer that utilizes ultrasonic vibrations in two directions: the radial direction and the thickness direction. We succeeded in reducing the size, and the embodiments shown in the drawings will be described below. In the figure, 1 is a disk-shaped electrostrictive element with metalized electrode surfaces 1a and 1a' formed by baking silver on both main surfaces, 2
is an insulated wire consisting of a pair of lead wires 2a, 2a' that connects to the metallized electrode surfaces 1a, 1a' of the electrostrictive element;
3 is a vibration absorbing material made of a porous material such as cork or foam rubber that covers the outside and top surface of the electrostrictive element 1; 4 encapsulates the electrostrictive element 1 and the vibration absorbing material 3 and covers the insulated wire 2; The insulating casing 4 has a bottom surface 4a' that comes into contact with the electrostrictive element 1 and serves as a diaphragm, and a diameter that is formed upwardly from the bottom surface 4a' to enclose the electrostrictive element 1 and the vibration absorbing material 3. A small-diameter base 4a extends upward from the large base 4a, covers and protects the insulated wire 2, and is screwed into a support rod 5 protruding from the hull (not shown) by a screw 4b' provided at the upper end. These components are the same as conventional ones, but in the present invention, the electrostrictive element 1 has a small hole 1b for lowering the radial vibration of the element below the basic resonance frequency. is characterized by being bored in the axial direction perpendicular to the main surface. Therefore, the resonant frequency in the radial direction of the electrostrictive element decreases in accordance with the center hole diameter. When a center hole is drilled in a 46 mm × 10 mm ^t electrostrictive element with a resonant frequency in the direction set to 200KHz, the resonant frequency in the radial direction is almost the same as the resonant frequency in the thickness direction and the directivity angle, as shown in the table below. Responds sensitively without fluctuation Up to a center hole diameter of 6 mm, the rate is approximately 0.5 KHz for a hole diameter of 1 mm, and at the above 6 mm, it is 47 KHz.
This enables accurate depth sounding and fish finding work by preventing interference with detection waves from other ships nearby.

[Table] Note that the small hole 1b in the axial direction for reducing the radial vibration of the electrostrictive element 1 may be provided in a part off the center line, but it is not necessary to drill it on the center line in order to prevent waveform distortion. The hole diameter is preferably set so as to lower the radial resonance frequency by several KHz or less, particularly by 2 to 3 KHz, than the fundamental frequency, although it varies depending on the frequency constant and dimensions of the electrostrictive element. Therefore, the effects shown in the previous table can be obtained.

[Brief explanation of the drawing]

The drawing is a longitudinal section showing the main parts of the present invention. 1... Electrostrictive element, 1b... Through hole, 3... Vibration absorbing material, 4... Insulating casing.

Claims (1)

[Scope of utility model registration request] In devices that utilize ultrasonic vibrations in two specified frequency ranges in two directions, the radial direction and the thickness direction, an electrostrictive element is enclosed in an insulating casing together with a vibration absorbing material.
An underwater ultrasonic transducer characterized by having an axial through hole that reduces the radial resonance frequency without affecting the thickness direction resonance frequency.