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JPH0955999

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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 JPH0955999
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
vibration pickup for sensing vibrations such as sound waves, and is particularly useful for
obtaining stable performance and reliability against changes in operating temperature
conditions.
[0002]
2. Description of the Related Art An example of the structure of a conventional vibration pickup
will be described below with reference to the drawings. The vibration pickup is of the
piezoelectric type. FIG. 5 is a cross-sectional view of a conventional vibration pickup. In the
figure, 1 is a sealed housing, 2 is a diaphragm fitted in fitting holes on both sides of the sealed
housing 1, 3 is piezoelectrics mounted on the outer surface of the diaphragm 2, 4 is an inner
surface of the diaphragm 2. A weight supported via the connecting rod 5, 6 is a through hole
bored in the lower part of the sealed case 1, 7 is a viscous liquid filled in the gap of the sealed
case 1, 8 is a seal of the through hole 6, 9 Reference numeral denotes a seal portion of the
diaphragm 2 and the sealed case 1, and reference numeral 10 denotes an output terminal
connected to the piezoelectric element 3. The sealed casing 1 is attached to a microphone casing
or the like via a vibration blocking member (not shown) for blocking transmission of vibration to
other devices.
[0003]
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1
And each component was connected as follows and the vibration pick-up was comprised. That is,
the piezoelectric element 3 is attached to the diaphragm 2 which is fitted and sealed in a fitting
hole which is bored at both ends of the sealed casing 1, and a weight is formed in a space
surrounded by the sealed casing 1 and the diaphragm 2. 4 is enclosed and connected by the
diaphragm 2 and the connecting rod 5, and the space formed by the sealed housing 1, the
diaphragm 2, the weight 4 and the connecting rod 5 is filled with the viscous liquid 7, A vibration
pickup is formed by connecting so as to extract the vibration of the vibrator 2 as a voltage from
the output terminal 10 connected to the piezoelectric electrons 3.
[0004]
In the vibration pickup of the above configuration, the sealed casing 1 and the diaphragm 2
resonate by vibration such as a sound wave and vibrate with the weight 4 as a reference. Then,
the pressure applied to the piezoelectric electrons 3 changes due to the vibration of the
diaphragm 2, and the stress generated in the piezoelectric electrons 3 changes according to the
change in the pressure to distort the piezoelectric electrons 3. The piezoelectric electrons 3
generate a voltage according to the change due to the stress, and take out the change of the
vibration such as the sound wave as the change of the voltage through the output terminal 10.
[0005]
FIG. 6 is an explanatory view of a vibration system model of the vibration pickup at a constant
temperature. The vibration system model represents the relationship between the diaphragm 2,
the piezoelectric element 3 and the weight 4, and the sealed case 1. In the figure, m is the mass
of the weight 4, k is a spring constant consisting of the diaphragm 2 and the piezoelectric
electrons 3, C is the viscous resistance of the viscous liquid 7 filled in the sealed housing 1, and x
is the balance point of the weight 4 Let f (x) be the displacement frequency of the forced
vibration. In addition, the mass of the connecting rod 5 shall be disregarded.
[0006]
When the entire sealed casing 1 resonates due to vibration such as a sound wave, the weight 4 is
equivalent to forced oscillation with respect to the casing main body 1. When the weight 4
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vibrates to displace x amount with respect to the casing main body 1, the force due to the
displacement is transmitted to the diaphragm 2 and the piezoelectric electrons 3, and both are
distorted. Then, the distortion of the pressure electrons 3 is the output voltage. Here, the
distortion amount and the output voltage have the property of being proportional to the
characteristic limit of the piezoelectric 3. At this time, the viscous liquid 7 acts as a viscous
resistance in the sealed housing and functions as stabilization of the vibration characteristic.
[0007]
However, in general, the volume expansion coefficient, which represents the rate of volume
change due to temperature change, largely differs depending on the substance, and therefore the
configuration other than the volume expansion coefficient of the viscous liquid and the viscous
liquid constituting the vibration pickup The volume expansion coefficient of the body has a
difference of one digit or more in order. That is, among substances used as viscous liquids, even
substances having as small as possible a coefficient of volumetric expansion result in a
coefficient of volumetric expansion which is an order of magnitude greater than that of
components other than viscous liquid.
[0008]
Therefore, in the above-described vibration pickup, since the viscous liquid is sealed by the
sealed housing and the diaphragm, when there is a temperature change, the volume change of
the components other than the viscous liquid with respect to the volume change of the viscous
liquid Can not follow, and the volume expansion of the viscous liquid will apply pressure to the
sealed housing and the diaphragm. For this reason, as shown in FIG. 7, when the temperature
change increases and it is in the pressurized state, the diaphragm is pushed out from the
reference position even in the initial state where there is no vibration such as a sound wave. The
piezoelectric electrons are also deformed along with that. In this initial state, when vibration such
as a sound wave occurs, the diaphragm and the piezoelectric electrons undergo excessive
deformation as compared with normal, so that the output voltage becomes unstable and there is
a problem that the performance becomes defective. . In addition, since the expansion volume
integral due to the temperature change of the viscous liquid acts as a pressure on the
components other than the viscous liquid, the problem of the viscous liquid flowing out occurs
when the pressure becomes higher than the seal portion strength. There is. Due to this problem,
there is a problem that the vibration characteristic of the vibration pickup changes. Furthermore,
there is a problem that peeling or the like occurs at the connection portion between the other
components of the vibration pickup due to the steady deformation caused by the temperature
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change.
[0009]
Furthermore, as shown in FIG. 8, in the case of a negative pressure state where the temperature
change is reduced, the diaphragm is pushed in from the reference position even in the initial
state where there is no vibration such as sound waves. Along with this, piezoelectric electrons are
also deformed. In this initial state, when vibration such as a sound wave occurs, the diaphragm
and the piezoelectric electrons are excessively deformed as compared with the normal case, so
the output voltage becomes unstable and the problem of performance failure is is there. In
addition, there is a problem that vacuum bubbles are generated in the viscous liquid due to
excessive shrinkage of the viscous state. In addition, it is impossible to specify the generation
position of the vacuum bubble, for example, as shown in FIG. 4, when generated between the
diaphragm and the weight, the viscosity resistance Cn changes and the viscosity of the vibration
system of the vibration pickup itself A change occurs in the term f (t), the vibration characteristic
fluctuates, and there is a problem of poor performance. Further, in the negative pressure state, as
in the pressurized state, there is a problem that peeling occurs.
[0010]
According to the present invention, therefore, a piezoelectric element is mounted on a diaphragm
which is fitted and hermetically connected to a fitting hole bored at both ends of a sealed casing,
and the sealed casing and the diaphragm are provided. And enclosing the weight in the space
enclosed by the connecting member and connecting the vibrating plate and the connecting rod,
filling the space formed by the sealed housing, the vibrating plate, the weight, and the connecting
rod with a viscous liquid; In a vibration pickup which takes out vibration of a vibrator as a
voltage from an output terminal connected to piezoelectric electrons, a through hole is bored in a
sealed housing, and the through hole is sealed by a deformable closing body.
[0011]
According to such a configuration, it is possible to absorb the volume change of the viscous
liquid due to the temperature change by the closing body.
[0012]
An embodiment of the present invention will be described below with reference to the drawings.
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The vibration pickup is of the piezoelectric type.
FIG. 1 is a cross-sectional view of the vibration pickup of the embodiment. In the figure, 1 is a
sealed housing, 2 is a diaphragm fitted in fitting holes on both sides of the sealed housing 1, 3 is
piezoelectrics mounted on the outer surface of the diaphragm 2, 4 is an inner surface of the
diaphragm 2. A weight supported via the connecting rod 5, 6 is a through hole bored in the lower
part of the sealed case 1, 7 is a viscous liquid filled in the gap of the sealed case 1, 8 is a seal of
the through hole 6, 9 Reference numeral denotes a seal portion of the diaphragm 2 and the
sealed case 1, and reference numeral 10 denotes an output terminal connected to the
piezoelectric element 3. Further, 11 is a through hole bored in the upper part of the sealed case 1
in the figure, and 12 is mainly intended for pressure absorption due to volume change caused by
temperature change of viscous liquid, and is sealed in the fitting hole 11 of the sealed case 1 It is
a closed body connected. The closure body 12 is preferably formed in a bellows shape and
formed of an elastic body, but is not limited to this, and may be formed, for example, of an elastic
body formed in a hollow shape or an elastic body formed in a film shape. Further, it may be
formed of a rigid body having a collapsible bellows. The sealed casing 1 is attached to a
microphone casing or the like via a vibration blocking member (not shown) for blocking
transmission of vibration to other devices.
[0013]
And each component was connected as follows and the vibration pick-up was comprised. That is,
the piezoelectric element 3 is attached to the diaphragm 2 which is fitted and sealed in a fitting
hole which is bored at both ends of the sealed casing 1, and a weight is formed in a space
surrounded by the sealed casing 1 and the diaphragm 2. 4 is enclosed and connected by the
diaphragm 2 and the connecting rod 5, and the space formed by the sealed housing 1, the
diaphragm 2, the weight 4 and the connecting rod 5 is filled with the viscous liquid 7, The
vibration of the vibrator 2 is taken out as a voltage from the output terminal 10 connected to the
piezoelectric electrons 3, and the through hole 11 is bored in the sealed casing, and the through
hole 11 is deformed by the deformable closure 12. Sealed to form a vibration pickup.
[0014]
In the vibration pickup of the above configuration, the sealed casing 1 and the diaphragm 2
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resonate by vibration such as a sound wave and vibrate with the weight 4 as a reference. Then,
the pressure applied to the piezoelectric electrons 3 changes due to the vibration of the
diaphragm 2, and the stress generated in the piezoelectric electrons 3 changes according to the
change in the pressure to distort the piezoelectric electrons 3. The piezoelectric electrons 3
generate a voltage according to the change due to the stress, and the change of the vibration of
the sound wave or the like is taken out as the change of the voltage through the output terminal
10. The above normal operation is the same as the above conventional case, and the closure 12
does not act specially. The closure 12 acts when the ambient temperature changes and a viscous
liquid volume change occurs.
[0015]
Next, the action of the closure 12 according to the operating temperature conditions will be
described. 2 is an explanatory view of the state at the time of filling and sealing, FIG. 3 is an
explanatory view of the state at the time of expansion, and FIG. 4 is an explanatory view of the
state at the time of contraction. In addition, although the temperature at the time of filling sealing
is demonstrated as normal temperature, it is good also as any temperature not only this but a
temperature at the time of filling sealing. As shown in FIG. 2, at the time of filling and sealing (at
normal temperature), the viscous liquid 7 does not apply pressure to the diaphragm 2. The
height of the closed body 12 at this time is taken as a reference height x. The reference height x
is set at a position where contraction can be performed in both the direction in which the bellows
of the occlusion body 12 extends and the direction in which the bellows collapses.
[0016]
As shown in FIG. 3, at the time of expansion (at a temperature higher than normal temperature),
the viscous liquid 7 expands. The volume change associated with this expansion is absorbed by
the occlusion body 12 extending by the volume increase height x1-x. Therefore, the viscous
liquid 7 does not apply pressure to the diaphragm 2, and the characteristics at normal
temperature do not change, so the diaphragm 2 is not deformed.
[0017]
As shown in FIG. 4, at the time of contraction (at a temperature lower than normal temperature),
the viscous liquid 7 contracts. The volume change associated with this contraction is absorbed by
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the closure 12 contracting by the volume reduction height x2-x. Therefore, since the viscous
liquid 7 does not apply pressure to the diaphragm 2 and the characteristics at the normal
temperature do not change, neither the diaphragm 2 is deformed nor vacuum bubbles are
generated.
[0018]
According to the vibration pickup of the above embodiment, since the volume change due to the
volume change of the viscous liquid 7 is absorbed by the closing body 12, even if the
temperature change occurs, the viscous liquid 7 can be sealed. The effect of being able to
maintain the characteristics of the initial state is obtained without applying pressure to the body
or the vibrating body.
[0019]
As described above, according to the vibration pickup of the present invention, since the volume
change caused by the volume change of the viscous liquid is absorbed by the closed body, even if
the temperature change occurs, The viscous liquid has an effect that the characteristics of the
initial state can be maintained without applying pressure to the sealed casing or the vibrator.
For this reason, even if the use conditions such as the amount of the viscous liquid present in the
sealed housing or the ambient temperature are changed, an effect that stable characteristics can
be obtained without affecting the vibration characteristics can be expected.
[0020]
Brief description of the drawings
[0021]
1 cross-sectional view of the vibration pickup of the embodiment
[0022]
Fig. 2 State explanatory drawing at the time of filling and sealing
[0023]
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Fig. 3 State explanatory drawing at the time of expansion
[0024]
Fig. 4 State explanatory drawing at the time of contraction
[0025]
Fig. 5 Cross section of the conventional vibration pickup
[0026]
Fig. 6 An illustration of a vibration system model at a constant temperature
[0027]
Fig. 7 State explanatory drawing at the time of expansion
[0028]
Fig. 8 State explanatory drawing at the time of contraction
[0029]
Fig. 9 An illustration of the vibration system model at the time of temperature change
[0030]
Explanation of sign
[0031]
DESCRIPTION OF SYMBOLS 1 Sealed case 2 Diaphragm 3 Piezoelectric 4 Weight 6 Through hole
7 Viscous liquid 8 Seal part 9 Seal part 10 Output terminal 11 Through hole 12 Blocking body
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