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JP2004221742

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DESCRIPTION JP2004221742
The present invention relates to a piezoelectric speaker, a speaker system using the same, and an
electronic device using the piezoelectric speaker, and it is an object of the present invention to
obtain a wide reproduction band. In order to achieve the above object, according to the present
invention, a diaphragm 7, a first piezoelectric thin film 14 provided in a first area 8 of the
diaphragm 7, and a first piezoelectric thin film 14 of the diaphragm 7 are provided. The second
piezoelectric thin film 14 provided in the second area 9 different from the area 8 of FIG. 8 is
provided, and the first and second areas 8 and 9 have different acoustic reproduction bands.
[Selected figure] Figure 2
Piezoelectric speaker, speaker system using the same, and electronic device using the
piezoelectric speaker
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
piezoelectric speaker using a piezoelectric body, a speaker system using the same, and an
electronic apparatus using the piezoelectric speaker. [0002] A piezoelectric speaker using a
piezoelectric body has a configuration in which one piezoelectric body is provided on one
diaphragm as described in, for example, Patent Document 1. [Patent Document 1] Japanese
Patent Application Laid-Open No. 11-164396 [Patent Document 1] [Prior Art to be Solved by the
Invention] The conventional piezoelectric speaker has a structure in which one piezoelectric body
is provided on one diaphragm as described above. There was a problem that it was difficult for
broadband reproduction to be difficult. That is, in the case where the piezoelectric body is
vibrated by distorting it, the acoustic reproduction band is inevitably narrowed due to the high Q
of the piezoelectric body. Accordingly, the present invention is directed to enabling broadband
reproduction. In order to achieve the above object, according to the invention of claim 1 of the
present invention, there is provided a diaphragm, and a first piezoelectric element provided in a
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first area of the diaphragm. A body, and a second piezoelectric body provided in a second area
different from the first area of the diaphragm, wherein the first and second areas have different
acoustic reproduction bands, respectively It is possible to obtain a piezoelectric speaker having a
wide reproduction band. That is, by providing at least first and second areas on the diaphragm
and making the acoustic reproduction bands of the areas different, it is possible to obtain a
piezoelectric speaker having a wide reproduction band. Next, the invention according to claim 2
is the piezoelectric speaker according to claim 1, wherein the first and second piezoelectric
members are each formed of a piezoelectric thin film, and the first and second piezoelectric
members are respectively piezoelectric If it is formed as a thin film, it can be formed at one time
on the vibrating plate using a piezoelectric thin film forming process. Next, according to the third
aspect of the present invention, the first piezoelectric body is provided in a first area on one
surface side of the diaphragm, and the second piezoelectric body is provided in a second area,
and the other surface side of the diaphragm is provided. The piezoelectric speaker according to
claim 1 or 2, further comprising a frame for forming a first area and a second area, wherein the
first area and the second area are formed on the other surface side of the diaphragm. By
providing a frame for the purpose, different acoustic reproduction bands can be easily formed in
the first and second areas. Next, the invention according to claim 4 is the piezoelectric speaker
according to any one of claims 1 to 3, in which the sizes of the first and second areas are made
different. By making the size of the area different, it is easy to create different acoustic
reproduction bands in the first and second areas.
Next, the invention according to claim 5 is the piezoelectric speaker according to any one of
claims 1 to 4, wherein the sizes of the first and second piezoelectric members are different, and
Different sound reproduction bands are likely to be produced in the two areas. Next, the
invention according to claim 6 is a speaker system including a speaker and the piezoelectric
speaker according to any one of claims 1 to 5, wherein the piezoelectric speaker has a sound
reproduction band higher than that of the speaker, Wide-band reproduction is possible by
widening the sound reproduction band in the high sound range by making the piezoelectric
speaker take charge of sound reproduction in the high sound range to be a piezoelectric speaker,
and by configuring the plurality of areas to be different sound reproduction bands. A speaker
system can be obtained. The invention according to claim 7 is an electronic device in which the
piezoelectric speaker according to any one of claims 1 to 5 is connected to a sound source, and
the piezoelectric speaker comprising a plurality of areas having different acoustic reproduction
bands is: Since broadband reproduction is possible, it becomes easy to appropriately reproduce
the signal from the sound source. BEST MODE FOR CARRYING OUT THE INVENTION An
embodiment of the present invention will be described below with reference to the attached
drawings. In FIG. 1, reference numeral 1 denotes a box of a speaker system, which has a
prismatic shape. A tweeter 2, a squawker 3, a woofer 4 and a bass reflex port 5 are arranged in
this order from the top to the bottom on the front of the box 1. Among these, the acoustic
reproduction band of the tweeter 2 is, for example, 5 KHz to 100 KHz. Further, the sound
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reproduction band of the scar 3 is set to 500 Hz to 5 KHz, and that of the woofer 4 is set to 20
Hz to 500 Hz. The bass reflex port 5 is intended to enhance a portion of 100 W or less in the
reproduction band of the woofer 4. FIG. 2 shows a state in which the tweeter 2 is taken out of the
box 1, 6 is a tweeter box, and the diaphragm 7 is exposed on the front surface thereof. As shown
in FIG. 2, the diaphragm 7 is provided with a plurality of three large, medium, and small areas 8,
9, and 10, respectively. Among these, the large area 8 is a 5 KHz to 80 KHz sound reproduction
band as shown in FIG. 3, and the middle area 9 is a 10 KHz to 100 KHz sound reproduction band
as shown in FIG. Area 10 has a sound reproduction band of 40 KHz to 100 KHz as small in FIG.
3, and tweeter 2 of the sound reproduction band of 5 KHz to 100 KHz is formed as described
above as a total of areas 8 to 10 of these three. There is.
FIG. 4 shows an enlarged cross-sectional view of the IV-IV line portion of the diaphragm 7 in FIG.
That is, three large to small areas 8 to 10 shown in FIGS. 2 and 4 are formed on one diaphragm
7. First, a 500 μm Si base 11 is provided on the back surface side of the 30000 Å diaphragm 7
made of SiO 2 shown in FIG. The base 11 is provided with openings 8 a to 10 a (8 a part is not
shown) in accordance with the large, middle, and small areas 8 to 10. That is, the openings 8a to
10a are also large 8a, 9a middle, and 10a small according to the areas 8 to 10 corresponding
thereto. Next, the lower electrode 12 made of Pt is provided on the surface side of the diaphragm
7. A piezoelectric thin film 14 made of PZT is provided on the lower electrode 12 corresponding
to the openings 8 a to 10 a via the buffer layer 13. Further, an insulating film 15 made of resin is
provided on the lower electrode 12 in the outer peripheral portion of the piezoelectric thin film
14, and an upper electrode 16 is provided on the insulating film 15. The sound source signals
are supplied in parallel to the piezoelectric thin films 14 corresponding to the three large to
small areas 8 to 9 via the upper electrodes 16 as shown in FIG. In FIG. 5, reference numeral 17
denotes a sound source, to which an amplification means 18 is connected, and to this
amplification means 18 piezoelectric thin films 14 of large to small areas 8 to 10 in parallel as
understood from the above. Is connected. Further, protective circuits 19a to 19c for overcurrent,
phase control circuits 20a to 20c, and gain adjustment circuits 21a to 21c are interposed
between the piezoelectric thin film 14 and the amplification means 18 in each of the areas 8 to
10, respectively. It is done. As a result, the tweeter 2 can obtain flat sound pressure frequency
characteristics in a wide high frequency band from 5 KHz to 100 KHz as shown in the
composition of FIG. Thus, the ability to obtain flat sound pressure frequency characteristics at a
wide and high frequency from 5 KHz to 100 KHz in this way leads to an increase in the value of
the speaker system in FIG. That is, in general, the human audio frequency is said to be 20 Hz to
20 KHz, but there is also a question as to whether there is a need for the tweeter 2 of the present
embodiment described above.
However, as a matter of course, sounds of 20 KHz or more that are said to be incapable of being
heard by humans are naturally present in the natural world, and 20 Hz to 20 KHz of sounds
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resulting from interference of such high frequency sounds. It can be said that you are listening to
For example, even a musical instrument emits a sound of 20 KHz or more as a matter of course.
The cymbal is said to be a typical thing. Therefore, if it is possible to reproduce even from 5 KHz
to 100 KHz as in the tweeter 2 of the present embodiment, a state in which it can be heard
directly in nature will be reproduced. This is also consistent with the fact that it is currently
required to output up to 100 KHz as an audio source 17 even if it is an audio device, for example.
FIG. 6 shows another embodiment of the present invention. In this embodiment, the tweeter 2 is
a single unit different from FIG. That is, in the electronic device that has already been purchased,
it is a so-called retrofit type in order to enhance high-range reproduction. Although this is not
shown, the protection circuits 19a to 19c, phase control circuits 20a to 20c, and gain adjustment
circuits 21a to 21c shown in FIG. 5 are built in, and although not shown, connection terminals
are provided. doing. As described above, according to the present invention, the diaphragm, the
first piezoelectric member provided in the first area of the diaphragm, and the first area of the
diaphragm are different. A piezoelectric speaker comprising a second piezoelectric body provided
in a second area, wherein the first and second areas are configured to have different acoustic
reproduction bands, and has a wide reproduction band. You can get it. That is, by providing at
least first and second areas on the diaphragm and making the acoustic reproduction bands of the
areas different, it is possible to obtain a piezoelectric speaker having a wide reproduction band.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a speaker box according
to an embodiment of the present invention. FIG. 2 is a perspective view of a tweeter box
according to an embodiment of the present invention. Sound pressure frequency characteristic
diagram [Figure 4] A sectional view of a loudspeaker according to an embodiment of the present
invention (a sectional view taken along line IV-IV in Figure 2) [Fig. 5] A block diagram according
to an embodiment of the present invention [Fig. A perspective view of a tweeter box according to
another embodiment of the present invention Description of symbols 1 box 2 tweeter 3 skooka 4
woofer 5 bass reflex port 6 tweeter box 7 diaphragm 8 area (large) 9 area (medium) 10 area
(small) 11) Si base 12 lower electrode 13 buffer layer 14 piezoelectric thin film 15 insulation
film 16 upper electrode 17 sound source 18 amplification means 19a protection circuit 19b
protection circuit 9c protection circuit 20a the phase control circuit 20b the phase control circuit
20c phase control circuit 21a gain adjustment circuit 21b gain adjustment circuit 21c gain
adjustment circuit
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