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Description 11 Title of Invention
Bimorph electrostrictive oscillator
8. Detailed Description of the Invention The present invention relates to a bimorph
electrostrictive transducer that converts an electrical signal into mechanical displacement. 2.
Description of the Related Art A bimorph type electrostrictive vibrator in which two piezoelectric
element tips such as PZT are bonded to each other is well known in the related art for converting
electric energy into mechanical energy. FIG. 1 is a view showing a specific example of a bimorph
type electrostrictive vibrator. In the figure, an electrostrictive vibrator element is formed by
bonding the piezoelectric elements 1 and 2 together. The front and back surfaces of each of the
piezoelectric elements 1 and 2 are formed with electrodes (not shown) for applying a voltage V,
and both are bonded. 41 shows the electrostrictive vibrator shown in FIG. When the part 2 is
fogged in the length direction (direction of l), it bends when the maximum amount is not equal,
and the free end produces displacement. At this time, it is known that the displacement yoha,
here, the strain of the part of 51iI is the strain of the part of Szi. Piezoelectric element l. When a
voltage V is applied from the outside to the element 2, an electric field of E = V / (h / 2) is
generated in each element, and the piezoelectric elements 1 and 2 each have Sl '' dat Es' 52-d3, E
It produces only Φ. The above d31 is a piezoelectric constant. The tip is thus displaced by the
amount represented by. EndPage: 1 Conventionally, when attempting to increase the
displacement of the tip, the method of increasing the length 1) has been taken, but there is a
disadvantage that not only the shape becomes large but also the natural frequency decreases. In
addition, the piezoelectric element 1.2 is polarized in the direction indicated by the symbol of 士
in advance as shown in FIG. If the electric field E is forward as in the piezoelectric element 1
shown in FIG. 1 with respect to the polarization direction of the piezoelectric element, the
magnitude of the electric field E is restricted by the dielectric breakdown electric field. Also, in
the case where the electric field E is in the reverse direction like a piezoelectric element, the
polarization is disturbed when a certain electric field is exceeded. This polarization breakdown
electric field Ep is generally smaller than the dielectric breakdown electric field Emax. For
example, for certain PZTs, Emax is about 800 V / ff and Ep is about 200 v / 顛. Therefore, as
shown in FIG. 2, another power supply V 'is prepared, and a method of increasing displacement
by applying a large forward electric field to the piezoelectric element has been considered.
However, aside from the power supply V, there is a disadvantage that the power supply V 'having
a higher voltage than this is required and the cost becomes high. The present invention is
intended to significantly increase mechanical displacement and mechanical energy by making the
thickness of the piezoelectric element unequal on the forward and reverse sides of polarization.
The present invention will be described in detail in accordance with the drawings as follows: ":: *
*", @ fiAcc 'z., 6..
It is a figure which shows -44,3. The piezoelectric elements 11 and 12 are bonded together to
form an electrostrictive vibrator 13. Are configured. Electrodes are formed on the front and back
surfaces of the piezoelectric element 11j12, and a power supply V is applied to the electrode
portion as shown in the figure. Here, in the prior art, the thickness of the piezoelectric element
11.12 was generally the same. In the present invention, assuming that the thickness of the
piezoelectric element 11 is h1, the h2 of the other piezoelectric element 12 is J, = nJ '(' 0 <n <1).
When an electric field Ep by the power source V is applied to the electrostrictive vibrator 18 in
the reverse direction part of the piezoelectric element 12, the strength of the electric field
applied to the forward direction part of the piezoelectric element 11 is Ep / n. Therefore, the
electric field applied to the piezoelectric element f-11 is far greater than the electric field Ep
applied to the piezoelectric element. Therefore, in the above-mentioned PZT of Ep = 200 V 7
ypm, assuming that n-17, the strength of the electric field of the piezoelectric element 11 applied
to the forward direction becomes E = '800 V7 MIN and can be applied up to the limit of
insulation breakdown 1 . In the electrostrictive vibrator 13 as shown in FIG. , 12 is unequal, and
it is known that the deflection yn of the tip is: S1 = d31 El ′ ′ d3 t Ep / n. Here, the ratio to the
displacement yl when n = 1 is obtained. In the case of n-1 / 4 o, larger mechanical energy can be
taken out from the second-morph electrostrictive vibrator 13. That is, when a voltage V is applied
to each of the piezoelectric elements of the electrostrictive vibrator from the outside, the
potential energy stored in the electrostrictive vibrator [P] if the force to be applied is P to prevent
the displacement occurring at the tip. Jn is represented by Here, Pn is a force required to set the
displacement of the tip to 0 (yn-o). Therefore, it is understood from the theory of beams that y is
the end deflection of the beam Ey: Young's modulus, so 5 g ′ ′ EndPage: 2 ′ ′ where
v−b′he is a bimorph volume. Therefore, the ratio to the case of n-1 is: In the above-mentioned
material n = -1 /, Un = 2.560t, and energy 2.56 times that of the conventional one is obtained. As
described above, according to the electrostrictive vibrator of the present invention, it is not
necessary to change the external shape (length 11 thickness h 1 width b) of the vibrator at all,
and the natural frequency does not change, and the bimorph vibration It is possible to obtain a
larger amount of displacement and displacement energy than in the prior art without damaging
the characteristics as a child.
4. Brief description of the drawings FIGS. 1 and 2 show the structure of a conventional bimorph
type electrostrictive vibrator, FIG. 3 shows a 11.12i piezoelectric element according to the
present invention, 13; an electrostrictive vibrator, v1 □: power supply, h, h2: thickness of
piezoelectric element. Attorney Attorney Atsushi FukushiEndPage: 3
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