Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Electrostrictive – magnetostrictive – or piezoelectric
Reexamination Certificate
2001-06-28
2004-12-14
Ni, Suhan (Department: 2643)
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Electrostrictive, magnetostrictive, or piezoelectric
C381S426000, C381S431000
Reexamination Certificate
active
06831985
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric speaker, and more particularly to a structure of a piezoelectric speaker in which a piezoelectric film is molded into a corrugate shape to form a vibrating diaphragm, and alternating signals are inputted into electrodes formed on the vibrating diaphragm to thereby generate sound wave.
A conventional speaker such as a Heil speaker or a ribbon speaker in which a thin film is molded into a corrugate shape and electrodes are formed to complete a vibrating diaphragm has been proposed. In the Heil speaker or ribbon speaker, both vertical ends in the vibrating diaphragm molded into a corrugate shape are fixed to a frame when the vibrating diaphragm is to be fixed to the frame. Both side ends that are wavy are not fixed and kept free. Since the electrodes formed on each crest and trough of the vibrating diaphragm are connected in series, the flowing current is also caused to flow through the electrodes connected in series.
FIG. 1
is a perspective view of a conventional piezoelectric speaker. In the corrugate shaped molded vibrating diaphragm
1
, after the vertical ends
3
-
1
have been bonded to the vertical frames
2
-
1
and
2
-
2
, the wavy side ends
4
are fixed to side frames
6
-
1
and
6
-
2
by adhesives
5
. Also, electrode lead terminals
8
-
1
and
8
-
2
deposited on piezoelectric films
7
-
1
and
7
-
2
and external lead lines
9
-
1
and
9
-
2
are screw-fastened together to the vertical frames
2
-
1
and
2
-
2
of plastics by means of bolts
10
-
1
and
10
-
2
. The acoustic signal current is inputted into the electrode lead terminals
8
-
1
and
8
-
2
from the external lead lines
9
-
1
and
9
-
2
.
Accordingly, the current for driving the vibrating diaphragm
1
is inputted concentratedly from first ends of the narrow thin lead electrode terminals
8
-
1
and
8
-
2
. However, since the electrodes
11
formed in the crests and troughs are connected in parallel, this system is different in electrode structure from the above-described Heil speaker or ribbon speaker.
However, if there would be no misunderstanding the representation of the numeral, only the main reference numeral will be used to collectively represent the components. This is the case also in other components that will be described hereunder. This rule will be applied to the components in the same manner.
However, since the above-described piezoelectric films
7
have a large static capacitance, if the frequency is increased, an impedance is lowered so that a large alternating current will flow. On the other hand, since the electrodes are manufactured by means of a thin coating method such as deposition, as shown in
FIG. 1
, all the signal applied to the electrodes is inputted from the electrode lead terminals
8
-
1
and
8
-
2
at first ends of the electrode leads
12
-
1
and
12
-
2
on the extension lines of the electrodes
11
. For this reason, a large amount of current is caused to flow into the thin narrow electrode lead terminals
8
-
1
and
8
-
2
. The electrode lead terminals
8
-
1
and
8
-
2
are evaporated to cause a breakdown of lines.
Also, as another problem, in order to generate a sufficient sound pressure in the piezoelectric speaker, the output voltage of an amplifier has to be further stepped up to apply a high voltage. Although it is not necessary to provide the voltage in the several kVs like a static speaker, since the peak voltage reaches about 100V even in the piezoelectric speaker, if the user's hand would touch the electrodes
11
, the side frames
6
-
1
and
6
-
2
, the vertical frames
2
-
1
and
2
-
2
and the like as shown in
FIG. 1
, there would be an electric accident.
Also, the conventional structure in which the vibrating diaphragm
1
formed by the piezoelectric film into the corrugate shape is fixed to the frame shown in
FIG. 1
suffers from a problem that, if the sound pressure is somewhat increased, the vibrating diaphragm
1
is vibrated in universal directions to generate a busy sound at a predetermined frequency to generate noise.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a piezoelectric speaker in which a breakdown of an electric lead terminal is prevented when a large amount current is caused flow into a thin narrow electrode lead terminal, any electric accident may be prevented in an electrode and a frame that would be likely to be touched by hands, the precision of position and shape of the electrode formed by using a mask is enhanced, and the generation of busy sound that becomes noise may be prevented even at a predetermined frequency of the vibrating diaphragm.
In order to attain the above objects, according to the present invention, there is provided a piezoelectric speaker comprising a vibrating diaphragm
1
formed by two piezoelectric films
7
-
1
,
7
-
2
being put together and made in a bimorph type, and formed into a corrugate shape as the whole to have crests
16
-
1
and troughs
16
-
2
alternately and to have walls
17
which connect the crests
16
-
1
and the troughs
16
-
2
and structured such that side ends
4
-
1
,
4
-
2
corresponding to the right and left ends of the vibrating diaphragm
1
are attached to side frames
6
-
1
,
6
-
2
placed at the right and the left of the vibrating diaphragm
1
and one longitudinal end
3
-
1
and the other longitudinal end
3
-
2
of the vibrating diaphragm
1
are attached to vertical frames
2
-
1
,
2
-
2
disposed between the right and left side frames
6
-
1
,
6
-
2
and that electrodes
11
-
1
,
11
-
2
are formed on the vibrating diaphragm
1
to generate sound waves by alternate signals being input to the electrodes
11
-
1
,
11
-
2
, wherein each of the right and left side frames
6
-
1
,
6
-
2
fixing the right and left side ends
4
-
1
,
4
-
2
of the vibrating diaphragm
1
is sectioned into an upper plate
19
-
1
and a lower plate
19
-
2
by the right side end
4
-
1
or the left side end
4
-
2
of the vibrating diaphragm
1
formed in the corrugate shape as the whole, and a vibrating diaphragm supporting portion
31
of the upper plate
19
-
1
and a vibrating diaphragm supporting portion
32
of the lower plate
19
-
2
are formed in the same corrugate shape as the corrugate shape of the side ends
4
-
1
,
4
-
2
of the vibrating diaphragm
1
so that the side ends
4
-
1
,
4
-
2
of the vibrating diaphragm supporting portion
31
of the upper plate
19
-
1
and the vibrating diaphragm supporting portion
32
of the lower plate
19
-
2
in the state of the corrugate shape of the vibrating diaphragm
1
being maintained.
According to this structure, the side ends
4
-
1
,
4
-
2
of the vibrating diaphragm
1
formed into a corrugate shape are clamped by the pair of upper and lower plates
19
-
1
,
19
-
2
the vibrating diaphragm supporting portions of which are formed in the corrugate shape, to form the side frames
6
,
6
-
1
,
6
-
2
, and the electrodes
11
-
1
,
11
-
2
formed on the surface of the vibrating diaphragm
1
are connected at a plurality of positions by conductive leads
20
mounted on the side frames
6
-
1
,
6
-
2
to output.
Accordingly, it is possible to firmly fix the vibrating diaphragm
1
to the side frames
6
-
1
,
6
-
2
and to prevent the current from concentrating on a local part of the thin electrode lead terminals
8
-
1
,
8
-
2
.
Furthermore, in the piezoelectric speaker according to the present invention, the vibrating diaphragm
1
is clamped by the upper plate
19
-
1
and the lower plate
19
-
2
in such a way that the side ends
4
-
1
,
4
-
2
of the vibrating diaphragm
1
project from the side frames
6
-
1
,
6
-
2
, electrode leads
12
-
1
,
12
-
2
are formed on projections
23
so projected, and the electrode leads
12
-
1
,
12
-
2
are connected by the leads
20
.
With such an arrangement, the side ends
4
-
1
,
4
-
2
of the vibrating diaphragm
1
are fixed to the frame so as to project from the side frames
6
-
1
,
6
-
2
composed of the pair of the upper and lower clamp
Ni Suhan
Sheets Kendal M.
Zito Joseph J.
Zito tlp
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