JP3240420B2 - Acoustic transducer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low frequency acoustic transducer for use in deep water.

[0002]

2. Description of the Related Art A typical type of a conventional underwater acoustic transducer is a Langevin type transducer,
Alternatively, bending shell type transducers such as a flex tensional type and a ring shell type have been devised to solve the problems of the Langevin type transducer.

[0003]

However, the conventional Langevin type transducer has a problem that the size and weight increase with respect to a low frequency.

The bent shell type transducer designed to solve the problem of the Langevin type transducer can be reduced in size and weight as compared with the Langevin type transducer. It was weak and had problems with use at depth.

It is an object of the present invention to provide a low-frequency acoustic transducer which can be used even at a large depth by reducing the size and weight of the transducer and making the drive portion of the magnetic fluid an internal / external pressure balance structure.

[0006]

According to the present invention, a cylindrical rigid outer shell having both ends open, a watertight and airtight bag accommodated inside the outer shell, From two sets of support metal fittings that expand from the inside of the bag to create an airtight chamber between the outer shell and the bag, a driving electromagnet fixed inside the bag, and a magnetic fluid filled inside the bag. Thus, an acoustic transducer characterized in that:

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIGS. 1 and 2, an acoustic transducer according to an embodiment of the present invention has an outer shell 1, a bag 2, a magnetic fluid 3, a core 4, a coil 5, a support fitting 6, a compressed gas 7, It comprises an airtight plug 8 and a pair of terminals 9.

Here, the outer shell 1 is formed of a cylindrical rigid body made of a non-magnetic material with both ends open. Bag 2
Has water tightness and air tightness, and is fixed to both inner ends of the outer shell 1. Both end surfaces of the bag 2 form an acoustic radiation surface 10. The magnetic fluid 3 is filled inside the bag 2.

The electromagnet constituted by the core 4 and the coil 5 is fixed inside the bag 2 by two sets of support fittings 6 made of a non-magnetic material. These two sets of support brackets 6
Also has a role of clamping the bag 2 at both inner ends of the outer shell 1 so as to sandwich it.

A compressed gas 7 such as air or helium is sealed between the outer shell 1 and the bag 2. The hermetic plug 8 has a role of closing the opening of the outer shell 1 provided for enclosing the compressed gas 7. A pair of terminals 9
Are connected to both ends of the coil 5 through the outer shell 1 and the bag 2.

By the way, a hydrostatic pressure Fw as shown in FIG. 3 acts on the acoustic radiation surface 10 of the bag 2 of the acoustic transducer in water.

Therefore, in order to balance the hydrostatic pressure Fw with the internal pressure of the acoustic transducer, the pressure FG1 of the compressed gas 7 sealed between the outer shell 1 and the bag 2 is changed to the hydraulic pressure at the working depth of the acoustic transducer. Adjust to a pressure suitable for.

The acoustic transducer of the present embodiment configured as described above operates as follows. In FIG. 4, a changeover switch S for changing the type of power supply used is shown.
When W is connected to the switching terminal A, the core 4
A constant voltage (DC signal) is applied to the electromagnet including the coil 5 and the coil 5, and a predetermined magnetic force is generated in the electromagnet.
As a result, the magnetic fluid 3 filled in the bag 2
It is drawn to both ends of the electromagnet with a predetermined force FM. Thereby, the sound radiating surface 10 of the bag 2 becomes +
Side to obtain the bias displacement.

The pressure FG2 in FIG. 4 is the pressure of the compressed gas 7 when this bias displacement is obtained. Next, FIG.
When the switch SW is switched to the switching terminal B side, an AC signal is superimposed on a DC signal, and the acoustic radiation surface 10 of the bag 2 vibrates in accordance with the AC signal.

FIG. 5 is a graph showing the displacement of the acoustic radiation surface 10 described above.

Here, at point a in FIG. 3, if an AC signal is applied to the electromagnet without bias displacement, even if the polarity of the electromagnet is reversed, the generated driving force will depend on the magnitude of the magnetic force regardless of the polarity. , The displacement of the sound emitting surface 10 is
Only in the + direction.

Therefore, at point b in FIG. 5, a bias displacement amount x is given, and at point c, an AC signal is superimposed thereon.
This can be converted as a displacement of the sound emitting surface 10.

In the above-described embodiment, the pressure of the compressed gas 7 is set to a constant value corresponding to the working depth. However, the pressure of the compressed gas 7 is not set to a fixed value.
A pressure compensating device that can adjust the atmospheric pressure according to the use depth may be attached so that the pressure can be freely changed from shallow to deep.

[0020]

According to the present invention, a magnetic fluid having a lower sound velocity than conventional materials such as metals and ceramics is used, so that the transducer can be reduced in size and weight, and its drive unit can be provided inside and outside. Because of the pressure balance structure, a low-frequency acoustic transducer that can be used even at a deep depth can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an acoustic transducer according to an embodiment of the present invention.

FIG. 2 is a radial sectional view of the acoustic transducer according to the embodiment of the present invention.

FIG. 3 is an operation principle diagram showing a force relationship when the acoustic transducer of the embodiment of the present invention has no driving force in water.

FIG. 4 is a schematic diagram showing an operation principle of the acoustic transducer according to the embodiment of the present invention in a state where a bias displacement is applied in water.

FIG. 5 is a diagram showing a relationship between a displacement amount of an acoustic radiation surface and a bias displacement in the acoustic transducer according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer shell 2 Bag 3 Magnetic fluid 4 Core 5 Coil 6 Support bracket 7 Compressed gas 8 Hermetic plug 9 Terminal 10 Sound emission surface

Claims (2)

(57) [Claims] A cylindrical rigid outer shell having both ends opened;
A water-tight and air-tight bag housed inside the outer shell, two sets of support fittings that are pushed out from the inside of the bag to form an airtight chamber between the outer shell and the bag, and the bag An acoustic transducer comprising: a driving electromagnet fixed inside; and a magnetic fluid filled in the bag. 2. The acoustic transducer according to claim 1, further comprising a pressure compensator capable of automatically adjusting a pressure of an air chamber formed between the outer shell and the bag according to a use depth.