JP3494696B2 - Electromagnetic 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 an electromagnetic acoustic transducer used as a sound source for an ultrasonic wave generator of a wet cleaner, a stratum exploration instrument, a seabed exploration instrument, a medical instrument for gallstone destruction, and the like.

[0002]

2. Description of the Related Art FIG. 5 is a schematic view of a main part of a conventional electromagnetic acoustic transducer used as an ultrasonic wave generation source or a sound source for various kinds of exploration equipment. Reference numeral 50 is a spiral winding of a conducting wire on the same plane. A spiral coil formed by turning, 51 is a pulse generation device for supplying pulse power of a predetermined cycle to the spiral coil 50, 52
Is a disk-shaped conductive vibration radiator. Pulse generator 5
Reference numeral 1 includes a DC power supply 511, a capacitor 512, and a changeover switch 513. The changeover switch 5
13, the control unit (not shown) controls the switching cycle.

In the electromagnetic acoustic transducer having such a structure, first, the changeover switch 513 is set on the DC power source 511 side, and the electric energy supplied from the DC power source 511 is stored in the capacitor 512. After a predetermined time,
When the changeover switch 513 is switched to the spiral coil 50 side and a large current is momentarily supplied to the spiral coil 50, an eddy current is induced in the vibration radiator 52. At this time, a strong electromagnetic repulsive force acts between the eddy current and the coil current, and the vibration radiator 52 is excited. By repeating this operation at a predetermined cycle, a large amount of pulsed sound waves are radiated from the main surface of the vibration radiator 52, that is, the surface directing the acoustic medium, in the direction of the arrow.

[0004]

By the way, in order to form a strong sound field, the oscillating radiator 52 is regularly pistoned in the direction shown by the arrow in FIG. It is preferable. However, in the conventional electromagnetic acoustic transducer that excites the disk-shaped vibration radiator 52 as described above, the extension vibration shown in FIG. 6A and the bending vibration shown in FIG. 6B are generated. Are excited at the same time, and the bending and extension vibrations, that is, the vibrations due to Poisson coupling, are generated. Therefore, there is a problem that the phase of the radiated sound wave becomes irregular, the sound field is disturbed, and the electromagnetic sound conversion efficiency decreases.

The acoustic medium that transmits the emitted sound waves is often a liquid. However, the vibration radiator 52
There is also a problem that the acoustic impedance of the liquid and the acoustic impedance of the liquid are remarkably different from each other, so that the impedances of the two are mismatched and the electromagnetic acoustic conversion efficiency cannot be improved. In view of such a problem, an object of the present invention is to provide an electromagnetic acoustic converter having a configuration capable of improving conversion efficiency.

[0006]

SUMMARY OF THE INVENTION An electromagnetic acoustic transducer provided by the present invention is a spiral coil having a structure in which a coil current flows by feeding pulsed power, an eddy current induced by the coil current, and the coil current. In an electromagnetic acoustic transducer having a vibrating radiator that causes sound waves to be emitted from its main surface due to the interaction of the vibrating radiator , the vibrating radiator is filled with a conductive solution.
It is characterized by comprising an insulated container . In addition,
It is preferable that the insulating container also has a uniform thickness and is formed in a hemispherical shell shape. Further, as another embodiment, a vibration radiator
Can also be composed of a conductive thin plate formed in a hemispherical shell shape.
Wear.

The coil surface of the spiral coil is formed in a hemispherical shell shape, and the distance between the coil surface and the back surface of the vibration radiator, that is, the back surface of the main surface is made substantially equal, or the vibration radiator has A configuration in which the peripheral portion is supported and fixed by a support member is also effective in solving the above problem.

[0008]

By using an insulating container filled with a conductive solution as a vibration radiator, transverse waves are not generated and vibration due to Poisson coupling is not excited. The acoustic impedance of the vibration emitters, so closer to the acoustic impedance of the liquid, the impedance matching is achieved when the acoustic medium is water, the electromagnetic acoustic conversion efficiency is enhanced remarkably. The vibration radiator has a thin plate structure.
In this mode, vibration in the thickness direction is generated during excitation.
Is suppressed.

Further , in the structure in which the coil surface of the spiral coil is also formed in a hemispherical shell shape and the distance between the coil surface and the back surface of the vibration radiator is substantially equal, the eddy current induced in the vibration radiator is reduced. Since the size is uniform and the electromagnetic repulsive force generated thereby is also uniform, the piston movement becomes smoother. Furthermore, when the peripheral portion of the vibration radiator is supported and fixed,
Although the motion form of the vibration radiator does not become a piston motion,
The extension vibration is excited and the volume displacement causes a motion form similar to the piston motion. Note that vibration radiation
When the body is formed into a hemispherical shell, its rigidity increases and
Occurrence of stinging vibration is also suppressed and the piston moves easily.

[0010]

EXAMPLES Test examples and examples of the present invention will now be described in detail with reference to the drawings. (Test Example 1) FIG. 1 is a cross-sectional configuration diagram of essential parts of an electromagnetic acoustic transducer according to Test Example 1 of the present invention. In FIG. 1, 11 is a spiral coil, and 10 is a vibration radiator composed of a hemispherical shell-shaped thin plate, and the material is titanium, duralumin, stainless steel, which has high rigidity and good electrical conductivity. A pulse generator 12 is composed of a DC power supply 121, a capacitor 122, and a changeover switch 123. The vibration radiator 1
It is assumed that 0 has its peripheral portion movably supported by a semi-fixed support body (not shown).

During operation, electric energy supplied from the DC power supply 121 is stored in the capacitor 122, and after a lapse of a predetermined time, the changeover switch 123 is changed over so that a large current is momentarily supplied to the spiral coil 11 . As a result, an eddy current is generated in the vibration radiator 10 , a strong electromagnetic repulsive force acts between the coil current and the eddy current, and a high-power pulse sound wave is emitted from the main surface of the vibration radiator 10 in the direction of the arrow. It

The operation up to this point is the same as that of the conventional electromagnetic acoustic transducer, but in this test example , since the shape of the vibration radiator 11 is different, the vibration mode to be excited is different. That is, since the vibration radiator 11 has a thin plate structure, vibration in the thickness direction is suppressed and harmful vibration due to Poisson coupling is suppressed. In addition, since it has a hemispherical shell shape, structural rigidity is increased, bending vibration is suppressed, and only piston movement is excited. As a result, the conventional problems can be solved and an electromagnetic acoustic converter having high electromagnetic acoustic conversion efficiency can be realized.

(Test Example 2) FIG. 2 is a cross-sectional configuration diagram of essential parts of an electromagnetic acoustic transducer according to Test Example 2 of the present invention. Since this test example is a modification of test example 1 , components having the same functions as those of the components shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. Only different parts will be described.

In this test example , a spiral coil 21 having a shape similar to that of the conductive vibration radiator 10 having a hemispherical shell shape is used, and the space between the spiral coil 21 and the vibration radiator 10 is made uniform. It was done. In the electromagnetic acoustic transducer having such a configuration, the spiral coil 2 is connected to the pulse generation device 12
When the pulsed electric power is supplied to 1, the distribution of the electromagnetic repulsive force acting on the vibration radiator 10 becomes uniform,
The movement of is more regular, and an electromagnetic acoustic transducer with an electromagnetic acoustic conversion efficiency higher than that of Test Example 1 can be realized.

Test Example 3 Next, an electromagnetic acoustic transducer according to Test Example 3 of the present invention will be described. In this test example , in the configuration of the test example 1 or the test example 2 , the peripheral edge portion of the hemispherical shell-shaped vibration radiator is supported and fixed by a support member. FIG. 3 is a partially enlarged view showing the vibration mode of the electromagnetic acoustic transducer of this configuration, where 30 is a conductive vibration radiator having a hemispherical shell shape, 31 is a spiral coil having a shape following the vibration radiator 30, and 34 is a spiral coil. Is a support member 34 for fixing the peripheral portion of the vibration radiator 30. Further, 33 indicates a displacement mode of the vibration radiator 30. Note that FIG.
Shows an example of the convex hemispherical shell-shaped vibration radiator 30 and the spiral coil 31, but the basic operation principle is a test example.
This is the same as the concave hemispherical shell shape described in 1 and Test Example 2 .

In the electromagnetic acoustic transducer having such a configuration,
When pulsed electric power is supplied to the spiral coil 31, the vibration radiator 30 tries to be displaced due to the electromagnetic repulsive force, but since the peripheral portion is fixed by the support member, the displacement mode 34 shown in the figure is used. Thus, while bending vibration is suppressed,
Stretching vibration occurs and the volume is displaced. Due to such a motion, the piston motion described in Test Example 1 or Test Example 2 does not occur, but the acoustic medium in contact with the vibration radiator 30 can be regularly driven. That is, as in the case of the piston movement, the sound wave can be efficiently emitted.

(Embodiment) FIG. 4 is a partially enlarged view of an electromagnetic acoustic transducer according to an embodiment of the present invention, showing an example of a case where the vibration radiator is made of a conductive solution. In the figure, 40 is an insulating container such as a resin formed in a hemispherical shell shape, 41 is a conductive solution, 42 is a thin film such as rubber, and 43 is water as an acoustic medium. As the conductive solution 41, saline solution, mercury, or other metal salt solution having good electric conductivity is used. In addition, 12 is a pulse generator, 31 is the insulating container 4.
It is a spiral coil having a shape following 0.

In the electromagnetic acoustic transducer having such a structure, an eddy current is induced in the conductive solution 41 when pulse power is supplied from the pulse generator 12 to the spiral coil 31.
At the same time, the electromagnetic repulsive force acts on the conductive solution 41 to excite the container 40. At this time, since there is no transverse vibration, only longitudinal wave components pass through the thin film 42 without loss of electrical energy. Transmitted to the water 43. That is, vibration due to Poisson coupling, which is harmful in forming a strong sound field, is suppressed, so that efficient sound wave radiation is performed. Also,
Since the acoustic impedance of the conductive solution 41 and the acoustic impedance of the water 43 are close to each other, impedance matching is achieved and a highly efficient electromagnetic acoustic transducer can be realized.

In this embodiment, the insulating container 40
An example in which the shapes of the (conductive solution 41) and the spiral coil 31 are made into a hemispherical shell has been described, but this is a suitable example, and it is sufficient if the spiral coil 31 can induce an eddy current in the conductive solution 41. However, it does not necessarily have to have the shape shown in FIG.

Although the present invention has been described with reference to a plurality of test examples and examples, the present invention devises the shapes of the vibration radiator and the spiral coil to prevent vibration due to Poisson coupling during sound wave radiation. Since the main point is to prevent,
The invention is not limited to the configuration example of FIG. 4, and design changes can be made without departing from the spirit of the invention.

The electromagnetic acoustic transducer of the test example of the present invention
Like a hemispherical shell with a vibration radiator that emits sound waves.
The rigidity of the formed conductor thin plate is high.
Maru, vibration and bending in the thickness direction during excitation
Generation of vibration is suppressed and the effect of Poisson coupling is mitigated
Is effective. Also, it makes it easier for the piston to move.
Thus, efficient electromagnetic sound conversion becomes possible.

[0022]

[Effect of the Invention] electroacoustic transducer of the present invention, the vibrating radiator
In an insulative container of uniform thickness filled with a conductive solution.
Since it is configured, shear waves do not occur and vibration due to Poisson coupling
Motion also has the effect of not being excited, and in addition, the sound of the vibration radiator
Acoustic impedance of an acoustic medium whose impedance is a liquid
As it approaches dance, impedance matching is achieved and
It also has the effect of increasing the magnetoacoustic conversion efficiency.

Further, since the coil surface of the spiral coil is formed in a hemispherical shell shape and the gap between the coil surface and the back surface of the vibration radiator is made substantially equal, the magnitude of the eddy current induced in the vibration radiator is increased. Is uniform and the electromagnetic repulsive force generated thereby is also uniform, so that there is an effect that the piston motion of the vibration radiator becomes smoother.

Further, since the peripheral portion of the vibration radiator is supported and fixed, extensional vibration is excited and the volume of the vibration radiator is displaced, so that a motion form similar to a piston motion can be easily formed. You can

As described above, according to the present invention, electromagnetic sound with good conversion efficiency, which is suitable for an ultrasonic wave generation source in a cleaning device, a sound source for a stratum probe or a seabed probe, or a sound source for gallstone destruction in a medical device. A converter can be provided.

[Brief description of drawings]

FIG. 1 is a main part configuration diagram of an electromagnetic acoustic transducer according to a first test example of the present invention.

FIG. 2 is a main part configuration diagram of an electromagnetic acoustic transducer according to Test Example 2 of the present invention.

FIG. 3 is a configuration diagram of essential parts of an electromagnetic acoustic transducer according to Test Example 3 of the present invention.

FIG. 4 is a main part configuration diagram of an electromagnetic sound transducer according to an embodiment of the present invention.

FIG. 5 is a main part configuration diagram of a conventional electromagnetic acoustic transducer.

FIG. 6 is a diagram for explaining a displacement mode of a vibration radiator in a conventional electromagnetic acoustic transducer, in which (a) shows extensional vibration and (b) shows bending vibration.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Tsuchiya 2-10-4 Fukui Tsushima, Okayama City, Okayama Prefecture (72) Inventor Eiichi Ando 2-1, 3 Shibasaki, Chofu City, Tokyo Within Shimada Rika Kogyo Co., Ltd. ( 56) References JP 61-172551 (JP, A) JP 5-245151 (JP, A) JP 5-220156 (JP, A) JP 1-97995 (JP, A) (58) ) Fields surveyed (Int.Cl. ⁷ , DB name) B06B 1/04

Claims (4)

(57) [Claims] 1. A spiral coil having a structure in which a coil current flows by feeding of pulsed electric power, and a vibration radiator that radiates a sound wave from its main surface by the interaction between the eddy current induced by the coil current and the coil current. In the electro-acoustic transducer according to the present invention, the vibrating radiator is composed of an insulating container filled with a conductive solution. 2. The electromagnetic acoustic transducer according to claim 1, wherein the insulating container is formed in a hemispherical shell shape with a uniform thickness. 3. The electromagnetic acoustic conversion system according to claim 2 , wherein the coil surface of the spiral coil is formed in a hemispherical shell shape, and the distance between the coil surface and the vibration radiator is substantially equal. vessel. 4. The method of claim 1 periphery of the vibrating radiator is characterized by comprising fixedly supported by the support member also
Is the electromagnetic acoustic transducer described in 2 .