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JPS5985916

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DESCRIPTION JPS5985916
[0001]
The present invention relates to a resonant vibration sensor suitable for detecting elastic
vibration in a vibrating object, and more particularly to a resonant vibration sensor having
excellent detection sensitivity for a predetermined frequency. Configuration of Conventional
Example and Problems Thereof Conventionally, as a sensor for detecting elastic vibration in a
vibrating object, a rectangular bimorph piezoelectric vibrator having a cantilever structure of
bending vibration mode in which the resonance frequency is matched to the natural frequency of
the vibrating object is used. It is well known. However, stress generated mechanically or due to a
temperature change causes a deviation in the support portion, and a stable resonance frequency
can not be obtained. Then, the bonded piezoelectric vibrator piece is melted and cut by a laser
processing machine or the like to obtain a bending vibrator that resonates at a predetermined
frequency, and by supporting and fixing the periphery of the bending vibrator, resonance having
a stable resonance frequency I was getting a mold vibration sensor. However, when performing
laser processing, it is known that there is a hole larger than the beam diameter of the laser due to
the non-penetration at the processing start point due to non-penetration of the auxiliary gas, and
cuts off the laser beam when processing is completed. It is also known that this also has a large
hole due to the time delay of the shutter. FIG. 1 shows such a conventional bending vibrator in
which a bending vibration mode vibrator is localized by laser processing in a piezoelectric
vibrator in which two disk-shaped piezoelectric elements having polarization axes in the
thickness direction are bonded to each other. And show the processing result when the start and
end of processing are positioned in the vibration part. Figure (()) is a top view, (b) is a vertical
cross-sectional view, (c) is a bottom view, and electrical continuity is established at the electrodes
1a / and 2a 'of the disk-shaped piezoelectric elements 1, 2 As shown in the figure, the diskshaped piezoelectric elements 1 and 2 are adhered and bonded to form a bonded piezoelectric
vibrator, and the bonded piezoelectric vibrator is cut through by means of a laser processing
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machine (the part 3 cut thereafter is slit And the top electrode 1a is a portion surrounded by the
slit 3 and an output voltage output portion, and the bottom electrode 2a is a partial electrode
from the portion surrounded by the slit 3 to the periphery thereof belongs to. When the portion
from the periphery to the periphery of the slit 3 of the bonded piezoelectric transducer is a
supported portion, the portion surrounded by the slit 3 functions as a flexible cantilever mode
cantilever vibration type. However, since the vibrating portion of the bending vibrator has the
start and end points of the laser processing, a hole larger than the width of the slit is formed, and
the length dimension of the vibrating portion changes, so that the resonance frequency changes.
In addition, since the processing is started from the unpenetrated state at the processing start
point, the melt blowout is insufficient due to the disturbance of the auxiliary gas flow of the laser
processing machine, so the conductive melt adheres considerably to the cut surface, causing
vibration. It will lower the insulation resistance between the urban electrodes. Furthermore, since
the thermal strain at the start and end of processing is larger than that at other portions, if it is
located in the vibrating portion, there is a drawback that the long life and reliability are lacking.
The object of the present invention is to solve such a drawback, and design and manufacture of a
vibration sensor having resonance at a predetermined frequency by separating the processing
start and end portions by laser processing from the vibrating portion of the bending vibrator. It is
an object of the present invention to provide a vibration sensor which can be easily operated and
can achieve long life and high reliability. Configuration of the Invention In the present invention,
a slit is formed on a piezoelectric vibrator in which two plate-like piezoelectric elements having
polarization axes in the thickness direction are bonded to each other by melt cutting by laser
processing or the like to form a slit. The enclosed portion is a bending vibration mode vibrator, in
which the starting end and the end to be subjected to the through portion cutting are separated
from the bending vibration mode vibrator portion. Description of the embodiment FIG. 2 shows a
case where a bending vibration mode vibrator is machined into the bonded piezoelectric vibrator
according to the present invention, the case where the machining start and end parts are
separated from the vibration part, FIG. Is a top view, FIG. (B) is a longitudinal sectional view, and
FIG. (C) is a bottom view. Processing is started from just beside the vibrating portion of the
flexural vibration mode vibrator, and the slit 3 is cut as shown by an arrow, and then machining
is finished immediately beside the vibrating portion. Since the portion surrounded by the slit 3 is
the vibration portion of the flexural vibration mode vibrator, the resonance frequency Fr is
determined by the vibration portion length t and the thickness of the vibration portion and is
expressed as p roc T, / z2. The length of the vibrating portion can be made constant regardless of
the size of the hole at the start and end of processing, and the resonance frequency can be easily
adjusted to a predetermined frequency. Further, by using only the vibration part and the output
extraction part as the electrodes 1a and 2a, it is possible to prevent the insulation resistance drop
between the electrodes caused by the melt adhering to the cut surface of the processing start and
end parts. Furthermore, although the thermal strain is large at the processing start and end
portions, it has high reliability because it is not located in the vibrating portion. Further, since a
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plurality of bending vibration mode vibrators can be processed into the same bonded
piezoelectric vibrator, the detection sensitivity at a predetermined frequency is increased or
correlation is made by making the bending vibration mode vibrators identical or different. It will
be excellent. As apparent from the above description, according to the present invention, since
the length of the vibrating portion of the flexural vibration mode vibrator can be made constant,
the resonance frequency can be easily adjusted to a predetermined frequency, and the insulation
resistance between the electrodes is lowered. It has the feature of being able to prevent
Still further, since a plurality of flexural vibration mode vibrators can be localized to the samebonded piezoelectric vibrator, there is also a feature that a plurality of elements having the same
resonance frequency or different resonance frequencies can be selected.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a view showing a conventional example in which a bending vibration mode vibrator is
localized by laser processing in a pasted 9 bonded piezoelectric vibrator, (a) is a top view, (b) is a
longitudinal sectional view, c) is a bottom view, FIG. 2 shows an embodiment according to the
present invention, in which the processing start and end portions of the bending vibration mode
vibrator are separated from the vibrating portion, (,) is a top view, (b ) Is a longitudinal sectional
view, and (c) is a bottom view.
1.2 · · · Disk-like piezoelectric element, 3 · · · through slit slit, 1 a + 2 a · · · · electrode. 1 (0) (b) (C)
FIG. 2 (0) (b) (C)
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