JPH0323758Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an amplitude type piezoelectric electromagnetic acoustic transducer that combines a piezoelectric type and an electromagnetic type.

Conventionally, amplitude-type electroacoustic transducers have been used as converters that convert current signals into sound, such as in headphones, earphones, speakers, buzzers, and telephones, or as converters that convert sound into current signals, such as microphones. ing. An earphone 1 shown in FIG. 1 is an example for explaining the configuration and principle of a conventional amplitude type electroacoustic transducer. In the same figure,
The diaphragm 2 is made of a thin film of iron material processed into a disk shape, and its peripheral edge is fixed or semi-fixed to the opening edge of the cup-shaped case 3. A pair of coils 5 and 6 are arranged in the case 3 so as to surround the permanent magnet 4, and the lines of magnetic force passing through the loop-shaped magnetic path 7 formed between the diaphragm 2 and the permanent magnet 4 are connected to the coil. The power is strengthened or weakened depending on how electricity is applied to 5 and 6. For this reason, the diaphragm 2
vibrates back and forth depending on the strength of the current applied to the coils 5 and 6, allowing the sound to be extracted.

Therefore, if a sinusoidal current with alternating positive and negative phases is applied to the coils 5 and 6 as an audio current, if the phase is such that the lines of magnetic force passing through the magnetic path 7 increase, the audio current will increase. The peak is emphasized and the amplitude of the diaphragm 2 becomes large, but if the phase is opposite,
The lines of magnetic force passing through the magnetic path 7 are reduced, and the diaphragm 2 cannot obtain the necessary amplitude. Therefore, the amplitude of the diaphragm 2 is asymmetrical in the front-rear direction and distortion is large, making it impossible to obtain good reproduced sound.

Furthermore, in the conventional earphone 1 described above, the peripheral edge of the diaphragm 2 is fixed or semi-fixed and is virtually impossible to displace, making it impossible to vibrate in the large stroke required for bass reproduction. In addition, since the structure uses the resonance point in the midrange of the diaphragm 2 to increase the playback band, it is difficult to reproduce faithfully from the midrange to the high range, and therefore the overall playback band is narrow. .

The present invention eliminates the above-mentioned drawbacks, and includes magnetically elastically supporting the peripheral edge of the piezoelectric diaphragm by the front and rear repulsive magnetic forces, and varying the repulsive magnetic force by the magnetic field generated in the coil by the signal current. By vibrating the piezoelectric diaphragm back and forth and also causing the piezoelectric diaphragm itself to vibrate due to the piezoelectric effect, a wide band audio output can be obtained, and vice versa, by using the current obtained by the vibration of the piezoelectric diaphragm, The purpose of the present invention is to provide an amplitude type piezoelectric electromagnetic acoustic transducer that enables broadband vibration detection.

Hereinafter, one embodiment of the present invention will be described with reference to FIG. 2 and subsequent figures. FIGS. 2 and 3 are a longitudinal sectional view showing an embodiment of an earphone to which the amplitude type piezoelectric electromagnetic acoustic transducer of the present invention is applied, and a circuit diagram for explaining the magnetization polarity of the coil.

In FIG. 2, the earphone 11 has a short-axis cylindrical case 12 made of a non-magnetic material such as aluminum, and its main parts are assembled in an iron holder 13 inside the case 12. The holder 13 is
It has a short-axis cylindrical shape with a U-shaped cross section, and its interior is divided into two by a plastic coil bobbin 14, which is also roughly cylindrical and has an E-shaped cross section. A pair of coils 15 and 16 are wound around the outer periphery of the coil bobbin 14, with different magnetization directions when energized. A pair of ring-shaped fixed permanent magnets 17 and 18 made of rubber ferrite are fixed to the openings at both ends of the coil bobbin 14, and a ring-shaped movable magnet made of rubber ferrite is located between the fixed permanent magnets 17 and 18. A piezoelectric diaphragm 20 having permanent magnets 19 as edges is provided.

The piezoelectric diaphragm 20 has electrodes 20b provided on both sides of a disk-shaped single plate 20a cut out from a well-known piezoelectric material such as barium titanate crystal, and the peripheral edge of the single plate 20a is provided with an edge. It is fixed to a movable permanent magnet 19 of. This piezoelectric diaphragm 2
0 itself exhibits a piezoelectric longitudinal effect by applying a voltage to the electrode 20b and vibrates back and forth, but its vibration band is higher than the vibration band of the movable permanent magnet 19.

In addition, in order to reduce the friction between the peripheral end surface of the movable permanent magnet 19 and the inner circumference of the coil bobbin 14, magnetic oil 21 is attached to the movable permanent magnet 19, which lubricates the sliding contact portion of the piezoelectric diaphragm 20 and seals it airtight. can be kept.

Here, the fixed permanent magnets 17 and 18 are magnetized with different polarities, and the lines of magnetic force emitted from one to the other form a closed loop that enters the other and returns to the other using the holder 13 as a magnetic path. The front and rear surfaces of the movable permanent magnet 19 are magnetized to have the same polarity as the opposing fixed permanent magnets 17 and 18, respectively.For this reason, the front and rear surfaces have different polarities, but both fixed permanent magnets 17 and 18 In the middle of
They receive repulsive magnetic force from each other. Therefore, the piezoelectric diaphragm 20 can be displaced in the front-rear direction with its peripheral edge being magnetically and elastically supported.

On the other hand, the coils 15 and 16 are connected to the coil bobbin 14.
The wires are wound in opposite directions with the center of the wire as the boundary. Therefore, as shown in FIG.
The center portions and the end portions of 4 have the same polarity and repel each other.

Note that both ends of the coils 15 and 16 are connected to corresponding electrodes 20b having the same polarity, but a divider circuit (not shown) or the like connects the coils 15 and 1
The band of the signal current supplied to the electrode 6 and the electrode 20b may be divided in advance into a middle/low range and a high range.

Now, when a positive phase signal current in the direction shown by the solid line in FIG. The magnetic field generated by the rear coil 16 weakens the magnetic force of the fixed permanent magnet 17, and the magnetic field generated by the rear coil 16 strengthens the magnetic force of the fixed permanent magnet 18. As a result, the repulsive magnetic force from the front against the movable permanent magnet 19 at the peripheral edge of the piezoelectric diaphragm 20 weakens, and the repulsive magnetic force from the rear increases, so the piezoelectric diaphragm 20 is deformed itself and displaced forward as a whole. .

Moreover, on the contrary, the electrode 20b and the coil 15,
16, when a signal current of opposite phase in the direction shown by the dotted line in FIG.
The magnetic field generated by the rear coil 16 strengthens the magnetic force of the fixed permanent magnet 17, and the magnetic field generated by the rear coil 16 weakens the magnetic force of the fixed permanent magnet 18. As a result, the repulsive magnetic force from the front against the movable permanent magnet 19 at the peripheral edge of the piezoelectric diaphragm 20 becomes stronger, and the repulsive magnetic force from the rear weakens, so that the piezoelectric diaphragm 20 is deformed itself and displaced rearward as a whole.

In this way, in the earphone 11, the piezoelectric diaphragm 20 itself vibrates due to the piezoelectric longitudinal effect, so the efficiency in the high frequency range is high, and the pair of coils 15 and 16 vary the repulsion magnetic force against the movable permanent magnet 19. Since the piezoelectric diaphragm 20 is displaced by push-pull operation, efficiency in the middle and low frequency ranges is high, and therefore the playback band is extremely wide. Furthermore, the waveform of the signal current changes both when the signal current is in positive phase and when it is in reverse phase. Since vibrations that are faithful to the original are obtained, almost no distortion occurs.

In addition, the piezoelectric diaphragm 20 has a peripheral portion with magnetic oil 21.
Since the free end is not mechanically restrained except for the slight viscous resistance caused by the vibration, it is possible to vibrate over a large stroke required for bass reproduction.

Furthermore, since the piezoelectric diaphragm 20 is of a full-plane drive type in which the entire piezoelectric diaphragm 20 vibrates back and forth, it is possible to reproduce faithfully over a wide range from the low frequency range to the ultra-high frequency range, unlike those that utilize the resonance of the piezoelectric diaphragm 20.

Furthermore, since the coils 15 and 16 are fixed and do not move, like a moving coil type,
The number of turns of the coils is not restricted due to the mass limit of the movable part, and as a result, the number of turns of the coils 15 and 16 can be increased to increase their resistance and enable large inputs and large outputs.

In addition, in the above embodiment, the case where an amplitude type piezoelectric electromagnetic acoustic transducer is applied to an earphone is taken as an example.
In addition to this, it can also be applied to, for example, a microphone that converts the displacement of the piezoelectric diaphragm 20 into an audio current, or a pulse meter.
It is also possible to measure pulses with very low cycles.

Furthermore, in the above embodiment, the rigidity of the piezoelectric diaphragm 20 can be reduced by bonding the uneven plate 22 made of Mylar film or the like into a wave shape, as shown in FIG. By lowering the resonance frequency, the vibration band of the piezoelectric diaphragm 20 itself can be lowered. In this case, piezoelectric diaphragm 2
Since the zero division vibration can be suppressed, the reproduction of mid-range sounds is improved, and at the same time, it is possible to listen to soft sounds without metallic sounds.

As explained above, according to the amplitude-type piezoelectric electromagnetic acoustic transducer of the present invention, a piezoelectric diaphragm whose peripheral edge is magnetized with different polarity in the front and rear is elastically supported by repulsive magnetic force from the front and back of the peripheral edge, and the signal current is is energized. Since the repulsive magnetic force is varied by the magnetic field of the coil and the piezoelectric diaphragm is vibrated back and forth, the vibration of the piezoelectric diaphragm itself due to the piezoelectric longitudinal effect enables high-efficiency reproduction in the high frequency range. The repulsive magnetic force that supports the periphery of the diaphragm from the front and back causes the diaphragm to vibrate through a push-pull action in response to the magnetic field of the coil, making it possible to reproduce high-efficiency mid- and low-frequency ranges. Since both can be reproduced faithfully, almost no distortion occurs, and the diaphragm has a structure in which the periphery is not subject to any mechanical restraint, so it can be used, for example, as a speaker or earphone to reproduce low frequencies. It is possible to vibrate over a large stroke required for this purpose, and because it is a fully driven type in which the entire diaphragm vibrates back and forth, unlike those that utilize the resonance of the diaphragm, it can generate vibrations over a wide range from low to ultra-high frequencies. This provides excellent effects such as faithful reproduction.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of an earphone illustrated to explain the configuration and principle of a conventional electromagnetic acoustic transducer, and Figs. 2 and 3 show an earphone to which the amplitude-type piezoelectric electromagnetic acoustic transducer of the present invention is applied. FIG. 4 is a vertical cross-sectional view showing one embodiment and a circuit diagram for explaining the magnetization polarity of the coil. FIG. 4 is a vertical cross-sectional view showing a modified example of the earphone. 11...Earphones, 12...Case, 13...
Holder, 14... Coil bobbin, 15, 16...
Coil, 17, 18...Fixed permanent magnet, 19...
Movable permanent magnet, 20...Piezoelectric diaphragm, 20a...
Single plate, 20b... Electrode, 21... Magnetic oil, 22...
...Uneven board.

Claims (1)

[Scope of utility model registration request] A coil bobbin with a coil wound around its outer periphery, a pair of fixed permanent magnets that are fixed to openings at both ends of the coil bobbin and magnetized with different polarities, and a surface facing the pair of fixed permanent magnets is magnetically A ring-shaped movable permanent magnet magnetized with repulsive polarity and displaceable in the axial direction on the inner periphery of the coil bobbin; and a piezoelectric material having electrodes on both sides of a plate-shaped piezoelectric material with the movable permanent magnet as an edge. An amplitude type piezoelectric electromagnetic acoustic transducer consisting of a diaphragm.