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BACKGROUND OF THE INVENTION The horn-type piezoelectric ceramic speaker of the present
invention can be used as a speaker for producing sound by being incorporated into various
industrial devices and consumer devices.
2. Description of the Related Art An acoustic device that is polarized and has a thin electrode
attached to both sides is adhered to a diaphragm to make it a sounding body, and an alternating
voltage is applied to it to vibrate and generate sound is a buzzer, ringer, receiver for a telephone
As intercoms, etc., it is widely used in various industrial devices and consumer devices.
A conventional piezoelectric ceramic speaker having such a piezoelectric ceramic as a sound
generator is unsuitable for expanding and transmitting sound because the frequency band is
narrow or the sound pressure is low.
Therefore, in the past, in most cases, dynamic speakers were used. In addition, it is also
performed to increase the sound volume of the sound waves generated by the sound generator
with small volume through the horn whose cross-sectional area is gradually increased.
However, since the dynamic type speaker has a permanent magnet, it not only becomes heavy
but also leaks a magnetic force to the surroundings to disturb, for example, the screen of a
television or the speaker. When soldering a lead wire to a printed circuit board provided nearby,
the iron portion of the soldering iron is attracted to the magnet, which causes obstacles such as
difficulty in performing a fine soldering operation.
In addition, the dynamic type speaker is expensive also in terms of production cost, and various
measures are taken to reduce the cost, but at present the cost reduction is almost at the limit.
According to the present invention, a horn type piezoelectric ceramic speaker is constructed by
the following means.
(1) A thin plate of a polymer compound reinforced with inorganic fibers is used as a material of
the diaphragm, and a piezoelectric ceramic which is a polarized ceramic plate is bonded to the
diaphragm to drive the diaphragm.
Connect the horn to the above diaphragm.
The horn is adjacent to a standing wall and forms a spiral-shaped, zigzag-shaped curved guiding
path forming a long conducting path in a small area.
Since the diaphragm of the polymer compound reinforced with the inorganic fiber has a large
compliance and is light, the resonance frequency is lowered and the efficiency is improved, but
there is also the effect of further improving the wide-range frequency characteristics.
By connecting the vibration of the vibrating plate to which the above-described piezoelectric
ceramic is bonded to the horn having the curved sound guide path, it is possible to increase the
sound volume and sufficiently broaden the band.
The shape of the horn is a spiral shape, a zigzag shape or the like so as to lengthen the sound
guide path, so that the speaker can be miniaturized by forming it in a small casing.
Further, a voltage amplifier can be provided by utilizing a portion of the cover plate which is
removed from the diaphragm attachment portion as a printed circuit board.
This speaker does not require a power amplifier because of its high electrical impedance.
1 to 7 show a first embodiment of a horn type piezoelectric ceramic speaker according to the
present invention, FIG. 1 is a plan view, FIG. 2 is a side view, and FIG. 3 is an AA sectional view of
FIG. 4 is a plan view of the casing excluding the cover plate, FIG. 5 is a perspective view of the
same, FIG. 6 is a plan view of the cover plate, FIG. 7 is a cross-sectional view taken along line B-B
of FIG. FIG. 9 is a frequency characteristic diagram of only the diaphragm with the casing
In the horn-type piezoelectric ceramic speaker 1, the cover plate 3 is bonded to the casing 2, the
peripheral portion of the diaphragm 4 is bonded to the cover plate 3, and the piezoelectric
ceramic 5 is bonded to the diaphragm 4.
More specifically, as shown in FIGS. 4 and 5, the casing 2 has a spiral shape that gradually
expands around a position 6a of a sound hole 6 (described later) formed in the cover plate 3 and
gradually increases the cross-sectional area. A standing wall 7 is formed, and the standing wall 7
forms a spiral sound guiding groove 8.
The widest end 8a of the sound guide groove 8 opens out of the casing.
In this embodiment, an ABS resin is used as the material of the casing, but the invention is not
limited to this. For example, vinyl chloride or other heat-formable synthetic resin, or a pressformable metal such as aluminum alloy, brass or stainless steel is used. be able to.
As shown in FIGS. 6 and 7, the cover plate 3 has a recess 9 formed on the spiral center of the
vertical wall 7 of the casing, and a step 10 for bonding the peripheral portion of the diaphragm 4
to the lower portion thereof. Do.
A sound hole 6 is bored in the center of the recess 9 to communicate with the spiral center of the
casing. The material of the cover plate 3 is also the same as that of the casing 2.
The diaphragm 4 used the thin plate of the epoxy resin containing glass fiber as a high molecular
compound reinforced with inorganic fiber. In addition, thin plates of polymer compounds such as
ABS, epoxy, polyester, etc. containing glass fibers or carbon fibers can be used.
At the center of the diaphragm 4, a ceramic thin plate is polarized, and a piezoelectric ceramic 5
having thin electrodes (not shown) attached on both sides is adhered.
Since it comprises as mentioned above, if a signal voltage is applied to the electrode affixed on
both surfaces of the piezoelectric ceramic 5, the piezoelectric ceramic 5 will deform | transform
according to a signal, and the diaphragm 4 will vibrate in connection with this.
The compression wave (sound wave) of the air generated by this passes through the sound hole
6 and enters the sound guiding groove 8 and travels through the spiral sound guiding groove to
exit from the end 8a into the atmosphere. Thus, the volume of the sound wave generated by the
diaphragm 4 can be enlarged and heard.
In this way, raising the sound pressure through the passage to which the sound wave generated
by the diaphragm is gradually expanded has been conventionally performed by coupling the
horn to the sounding body, but this embodiment is a piezoelectric ceramic sounding body And
the casing 2 with the spiral sound-conduction groove adjacent to the standing wall, and the cover
plate 3 together with the cover plate 3 form a horn with a long sound-conduction path to
increase the sound pressure and improve the frequency characteristics It was possible. The size
of this speaker is 94 mm in the vertical direction in FIG. 1, 72 mm in width, 20 mm in thickness,
and has the frequency characteristics of FIG. 8 and shows high sound pressure in the range of
500 to 2000 Hz. This characteristic diagram is measured with an input voltage 24VP-P and a
distance to the measuring microphone of 10 cm. This horn-type piezoelectric ceramic speaker is
obtained by combining a diaphragm to which piezoelectric ceramic is attached and a spiral horn
to obtain a small-sized speaker having characteristics extended to a wide band, particularly to a
low frequency range. The frequency characteristics of only the piezoelectric ceramic 5 and the
diaphragm 4 when the cover plate 3 is removed from the casing have a peak at about 1200 Hz
as shown in FIG. It can be seen that the coupling increases the gain of the low-pitched range so
that the voice can be heard in a near natural state.
The piezoelectric ceramic speaker has capacitive impedance characteristics, and is 10 kΩ to
several hundreds Ω at 300 to 3000 Hz. This is a value close to 100 times that of the dynamic
type speaker, and therefore the current consumption is nearly 1/100, and it can be driven
without using a power amplification circuit necessary for driving the dynamic type speaker.
FIG. 10 shows a second embodiment of the present invention and is a longitudinal sectional view
of a lid plate cut in the same manner as FIG. In this embodiment, a thin portion 4a is formed on a
part of a lid plate to form a diaphragm. The cover plate 3a is formed of a glass fiber-containing
epoxy resin, and the diaphragm attachment portion is thinly formed to 0.2 mm. As the material
of the cover plate, similarly to the diaphragm of Example 1, a polymer compound such as glass
fiber, polyester containing carbon fiber, ABS, epoxy and the like can be used. It is possible to
form a thin-walled portion up to a thickness of 0.1 mm on a part of these resins when molding a
lid plate or the like. The piezoelectric ceramic 5 is bonded to the thin portion 4a and coupled to
the same casing 2 as in the first embodiment. Also in this case, the cover plate 3 and the standing
wall 7 may be formed in the same body, and the bottom plate of the casing 2 may be separately
formed and then joined to the former.
11 to 14 show a third embodiment of the present invention, FIG. 11 is a plan view of a casing,
FIG. 12 is a perspective view thereof, FIG. 13 is a plan view of a lid plate, and FIG. FIG.
In the third embodiment, vertical walls 7b and 7c are protruded between vertical walls 7a formed
around the rectangular bottom plate of the casing 2a, and sound guiding grooves are formed in a
zigzag shape adjacent to each other across vertical walls 7b and 7c. It is opened to the
atmosphere at the open end 8a.
The sound hole 6 provided in the cover plate 3a overlapping the casing 2a is formed at an
eccentric position of the circular recess 9 so as to be located at the beginning of the bent sound
guide groove 8.
Although the cover plate 3b of the third embodiment has a quadrangular structure in which the
separate diaphragm 4 is bonded, the diaphragm is formed in the same body as the casing as in
the second embodiment. You can also.
[Advantage of the Invention] (1) Since the piezoelectric ceramic speaker and the spiral horn such
as spiral or zigzag are combined, it is excellent in weather resistance and environmental
resistance, and hardly causes failure due to temperature and rain water. It is effective to install it
as an intercom outdoors.
Also, there is no failure due to magnetic leakage.
(2) Because the electrical impedance is high, the volume can be increased without the need for a
power amplifier.
(3) It has a high degree of freedom in design in the shape of a bent sound groove and can be
made compact, so it can be easily incorporated into the housing of various devices.
(4) The use of a polymer compound such as epoxy resin reinforced with inorganic fibers such as
glass fiber and carbon fiber, ABS resin, etc., and forming the cover plate and the diaphragm in the
same body can make the manufacture remarkably easy.
(5) The cover plate can be used as a circuit board of a voltage amplifier or the like.
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description, jph07222284
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