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JP2005033232

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JP2005033232
[PROBLEMS] To provide a low magnetic field, light weight, low distortion, speaker capable of
large output. A thin plate-shaped current / mechanical vibration conversion element, a pair of
conductive wires for supplying a drive current to the conversion element, a resonator fixed to a
peripheral portion of the conversion element, and the conversion element A speaker comprising
one end fixed near the central portion and a fixed shaft extending substantially perpendicularly
from the conversion element, and the other end of the fixed shaft is fixed to another structure.
[Selected figure] Figure 5
Speaker using piezoelectric element
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
loudspeaker, and more particularly to a loudspeaker for generating sound by driving a resonator
by means of a current / deformation or mechanical vibration transducer. [0002] FIG. 1 shows the
structure of a typical loudspeaker belonging to the prior art. The illustrated speaker 10 has a
conical frame 13 whose diameter decreases from the flange portion 11 to the base 12, a field
portion 14 fixed to the base 12 of the conical frame 13, and a flange of a conical frame whose
outer edge 15 is substantially conical. The central portion 16 is fixed in the vicinity of the portion
11, and the central portion 16 is composed of a diaphragm 17 supported so as to be freely
movable in the axial direction near the base 12 of the frame 13 and a voice coil 18 fixed to the
diaphragm 17. When an electrical signal is applied through a gold wire (not shown), the drive
force in the axial direction of the voice coil is received by the action of the current flowing
through the voice coil and the magnetic field generated by the magnetic field unit, and vibrates
together with the diaphragm 17 in the axial direction. Generate voice by FIG. 2 shows the
structure of a speaker using a piezoelectric element, which also belongs to the prior art. The
illustrated speaker 20 has a shape similar to that of the speaker 10 shown in FIG. 1, but there is
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no voice coil and no field section, and instead a drive section 21 consisting of a piezoelectric
element is attached to the center section of the diaphragm 27 It is done. The driving portion 21
of the piezoelectric element is a disk-like thin film whose peripheral portion is fixed by an
annular member 22, and is deformed out of plane in response to a driving current applied by a
gold wire not shown. Sound is generated by vibrating the diaphragm 27 by this out-of-plane
deformation. SUMMARY OF THE INVENTION A great number of designs have already been
proposed for the structure of the loudspeaker shown in FIG. However, due to the structure in
which the voice coil is driven by the magnetic field, the magnetic field is essentially generated,
and when the speaker is incorporated in a weak electrical device, there is a problem that the
magnetic field affects the surrounding devices. Further, although magnetic shielding can be
achieved by covering the periphery of the field portion with a metal plate or the like, there is a
problem that the weight of the speaker, which is increased due to the field portion and the voice
coil, is further increased. Although the piezoelectric element drive type speaker shown in FIG. 2
does not generate a magnetic field and is lightweight, it has the possibility of solving many of the
problems with the speaker, but the center of the thin film piezoelectric element Since the
diaphragm is driven only by the part, when a large mechanical load is added, the piezoelectric
element tends to generate high-order deformation modes and distort the sound.
That is, compared to a system driven by a voice coil, a large output with low distortion can not be
generated. SUMMARY OF THE INVENTION The present invention aims to solve the abovementioned problems of the prior art, and more specifically, it does not generate a magnetic field,
and is lightweight. The purpose is to provide a speaker capable of generating a large volume with
low distortion. In order to achieve this goal, according to the present invention, a thin plate
current / mechanical vibration conversion element, a pair of conductive wires for supplying a
drive current to the conversion element, and a peripheral portion of the conversion element are
fixed. And a fixed shaft having one end fixed near the central portion of the conversion element
and extending substantially perpendicularly from the conversion element, and fixing the other
end of the fixed shaft to another structure Propose a speaker (first configuration) to be used. In a
typical case, the vibration conversion element is a disk-like piezoelectric element, and the
resonator is a foamed plastic which is light in weight and high in rigidity according to its own
weight. The piezoelectric element fixed at its central portion with a fixed shaft is deformed by the
drive current to vibrate the foamed plastic resonator to generate sound. In contrast to the
conventional diaphragm in which sound is generated by deformation, in the configuration of the
present invention, since the resonator ideally performs rigid body movement, energy conversion
efficiency to sound waves is high and distortion is low simultaneously. In order to achieve the
above object, the present invention also provides a thin plate current / mechanical vibration
conversion element, a pair of conductive lines for supplying a drive current to the conversion
element, and a periphery of the conversion element. And a base member having a mass greater
than the sum of the mass of the conversion element and the resonance element, and one end
thereof is fixed near the central portion of the conversion element and extends substantially
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perpendicularly from the conversion element A speaker (second configuration) having a fixed
shaft whose other end is fixed to the base member. The speaker having the second configuration
is a configuration similar to the speaker having the first configuration described above, but the
base member having a large mass instead of fixing the other end of the fixed shaft to another
structure Differs in that it is fixed to Since the weight of the base member is large while the
piezoelectric element and the resonator are extremely light, when sound is generated, the sound
acts almost like the fixed end. Therefore, the actions and effects described for the first
configuration apply as they are for the second configuration. In the case of the second
configuration, the base member can also serve as an enclosure that accommodates the
piezoelectric element and the resonator, thereby further increasing the portability.
The present invention further provides a thin plate current / mechanical vibration converter, a
pair of conductive wires for supplying a drive current to the converter, and a periphery of the
converter. A speaker (third configuration) including a resonator fixed to a part and an additional
mass fixed near the central part of the conversion element. In the third configuration, the second
configuration corresponding to the base member is typically an additional mass attached to the
piezoelectric element, so that the size can be further reduced. If the mass of the additional mass
is large compared to the mass of the piezoelectric element or the resonator, the resonator can be
sufficiently vibrated, so the operation and effect described in the first and second configurations
are the third. The same applies to the configuration. Furthermore, in the third configuration,
since the piezoelectric element and the additional mass are small, they can be accommodated
inside the resonator, which is typically made of foamed plastic. That is, the speaker is in the form
of a box made of expanded polystyrene, and can be used extremely easily. DETAILED
DESCRIPTION OF THE PREFERRED EMBODIMENTS The features of the present invention will be
described in more detail below with reference to preferred embodiments of the invention. FIG. 3
shows a first embodiment of the present invention. The disc-shaped diaphragm 30 having a
structure in which a piezoelectric element is attached to a thin metal plate, that is, the current /
mechanical vibration conversion element has its central portion fixed to one end of the fixed
shaft 31 and the other end of the fixed shaft 31 Is fixed to a structure not shown. The periphery
of the diaphragm 30 is fixed at the center of the disk-shaped resonator 32, and the thickness of
the resonator 32 is thinner toward the outer periphery. When a drive current (not shown) is
applied to the diaphragm 30 having a piezoelectric element through the same electric wire from
a drive amplifier, the diaphragm is deformed out of plane according to the current waveform.
Since the diaphragm 30 is fixed at its central portion by the fixed shaft 31, the deformation
vibrates the resonator 32, which generates a sound. This mechanism for converting an electrical
signal into mechanical vibration is that the resonator 32 is vibrated by the periphery of the
diaphragm, and the resonator 32 made of a lightweight and highly compatible material is
supported only by the diaphragm 30. Because of this, they move in a rigid manner as a whole.
For this reason, the speaker of the above configuration based on the present invention has a high
conversion efficiency and at the same time a small distortion. As a piezoelectric element, for
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example, a single crystal piezoelectric element which is any one of ADP, LiNbO3, LiTaO3,
Ba2NaNb3O15, ZnO, CdS, Bi12GeO20, BaTiO3-based, PZG-5, PZG-Pb (Mg1 / 3Nb2 / 3) Ceramics
that are any of O3, PZG-In (Li3 / 5W2 / 5) O3, PZG-Pb (Sn1 / 2Sb1 / 2) O3, (Pb, Nd) (Ti, Mn, Tn)
O3, PVF2, PbTiO3 series Piezoelectric elements, polymeric piezoelectric elements that are PVF2
or rubber / PZT, and Zn / O, AlN / Al2O3 thin films can be used.
Further, as a material constituting the resonator 32, a material which is light in weight, high in
rigidity, and in which vibration damping is not too large is preferable. Since the resonator does
not transmit force to other structures, it is sufficient that rigidity is high with respect to
obedience, and it is not always necessary that the absolute value of synthesis be high. If the
internal attenuation is large, the conversion efficiency is reduced, and if the internal attenuation
is small, the natural vibration tends to be emphasized and the sound tends to be distorted, so
there is an optimal value of the internal attenuation to reproduce a faithful voice. As a material of
the resonance body, specifically, foamed plastic, particularly, foamed plastic material, foamed
polyurethane, foamed polyolefin, foamed polystyrene, foamed polyethylene / polystyrene
copolymer, foamed polyethylene terephthalate, foamed polyvinyl chloride, foamed acrylic And
effervescent phenol can be suitably used. FIG. 4 is a conceptual view showing a second
embodiment of the present invention. In this embodiment, the speaker has a housing 40 whose
mass is much larger than that of the diaphragm 30 and the resonator 32, and the fixed shaft 31
connects the housing 40 and the central portion of the diaphragm 30. ing. The housing 40 has
the front surface of the resonator 32 released but covers all other surfaces, and functions as an
enclosure. The front surface of the housing 40 is closed by the front plate 41 except for the front
surface of the resonator 32, and the periphery of the resonator 32 and the edge of the opening
of the front plate 41 may be a void, or the composite is extremely low. In particular, it may be
connected by a material that does not constrain the axial movement. In the case of the abovementioned configuration, the diaphragm 30 receives a constraining force from the casing 40
having a large mass, which is substantially the same as that by the rigid body. Therefore, as in
the embodiment shown in FIG. 3, the resonator vibrates rigidly. The action of the housing 40 is
basically to fix the central portion of the diaphragm 30, so it does not have to be an enclosure,
and there is no problem even if it is a simple weight. FIG. 5 is a conceptual view showing a third
embodiment of the present invention. The vibrating plate 30 having the piezoelectric element is
fixed to the resonator 50 made of foamed plastic at its periphery, and the whole is
accommodated in the resonator 50. The resonator 50 is a box as a whole and can stand on its
own. In this embodiment, an additional mass 51 is attached to the center of the diaphragm 30.
The mass of the additional mass 51 is greater than at least the sum of the mass of the diaphragm
30 and the mass of the resonator 50. An opening is provided on the front surface of the
resonator 50 at a position corresponding to the diaphragm.
In the present invention, the diaphragm 30 itself does not vibrate air, but the diaphragm is used
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to drive the resonator 50 to generate sound, so the opening is not essential to the present
invention. When a drive current is applied to the diaphragm 30 and the diaphragm is deformed
and vibrated, the resonator 50 is vibrated by receiving the reaction force of the additional mass
51. Since the entire speaker is mounted on a desk, for example, the vibration of the resonator 50
which also serves as the enclosure receives some resistance due to the friction with the surface,
but in fact the influence of the resistance on the sound quality is minor It is. With the above
configuration, it is possible to reduce the weight of the speaker as a whole. Therefore, for
example, a pair of speakers used as speakers for headphones can be removed from the headband
and placed on a desk and used as desk speakers. When mounted on a desk, compared to when
used as headphones, it sounds like the bass has become weak due to the relationship of distance,
so in order to offset this effect, the additional mass is made removable, so headphones It can be
removed when using it as an additional weight, and it can be attached when using it on a desk.
This can be easily realized, for example, by bonding magnets from both sides of the diaphragm.
Here, various shapes such as a circle, a rectangle, and a rectangle having an aspect ratio of a
golden ratio can be considered as the shape of the diaphragm, but a wave propagating through
the diaphragm at the time of vibration is reflected at a boundary and standing It is desirable that
the shape is not a wave forming shape. From that point of view, a shape having a star-like cut is
also preferable. Although the above description has been made with personal use of the
piezoelectric element as a diaphragm for driving a resonator, the basic principle can be applied to
a speaker using a voice coil. it can. In this case, although it is inevitable that the generation of the
magnetic field and the weight increase, it is inevitable that the vibration conversion element
receives a reaction force from the fixed end, the base member or the additional mass member
and makes the lightweight and relatively compatible resonator The point of exercise is similar to
the above embodiment. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual view
showing the structure of a speaker belonging to the prior art. FIG. 2 is a conceptual view showing
a structure of a speaker using a piezoelectric element belonging to the prior art. FIG. 3 is a
conceptual view showing a first embodiment of the present invention. FIG. 4 is a conceptual view
showing a second embodiment of the present invention. FIG. 5 is a conceptual view showing a
third embodiment of the present invention.
[Description of the code] 10: Speaker 11: flange 12: base 13: conical frame 13 14: field 15: outer
edge 17: diaphragm 17 18 · · Voice coil 18 30 · · · diaphragm 31 · · · fixed shaft 32 · · · resonance
body 40 · · · housing 50 · · · resonance body 51 · · · additional mass
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