JP3853957B2 - Bimorph piezoelectric element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bimorph piezoelectric element, that is, a bimorph piezoelectric element that is formed by laminating two rectangular piezoelectric plates and has a uniform thickness throughout.
[0002]
[Prior art]
Conventionally, as a bimorph piezoelectric element, one disclosed in JP-A-1-190271 has been known. This bimorph piezoelectric element is configured to bend in a substantially U shape when one piezoelectric plate is extended and the other piezoelectric plate is contracted when a voltage is applied.
[0003]
[Problems to be solved by the invention]
However, since the conventional bimorph piezoelectric element has one direction of bending, it cannot be used as an actuator that operates in two directions.
[0004]
[Means for Solving the Problems]
An object of the present invention is to provide the bimorph piezoelectric element that can be used as an actuator that operates in two directions.
[0005]
In order to achieve the above object, according to the present invention, in a bimorph piezoelectric element that is formed by laminating two rectangular piezoelectric plates and has a uniform thickness throughout, it is provided at both end edges including two opposing sides. Two piezoelectric regions having the same thickness of both piezoelectric plates, and a second region in which the thickness of both piezoelectric plates changes between the first regions, and in the second region, The thickness of one of the piezoelectric plates gradually increases from both first region sides toward the center of the second region, and accordingly, the thickness of the other piezoelectric plate decreases from both first region sides to the first region. Bimorph piezoelectric elements are provided that gradually decrease toward the center.
[0006]
In the above-described configuration, when both first regions of the bimorph piezoelectric element are bent upward, for example, by application of voltage, the second region is bent downward accordingly. Thus, the bimorph piezoelectric element operates in two directions by utilizing the inverse piezoelectric effect.
[0007]
It is also possible to detect the bending angle in two directions by utilizing the piezoelectric effect (piezo effect) of the bimorph piezoelectric element.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
1 to 3, the bimorph piezoelectric element 1 is formed by laminating two rectangular first and second piezoelectric plates 2 and 3 and has a uniform thickness over the entire surface. Two first regions A ₁ located at both end edges including the sides and having the same thickness of both piezoelectric plates 2 and 3, and the thickness of both piezoelectric plates 2 and 3 located between both first regions A ₁ And a second region A ₂ in which is changed. In the second region A ₂ , the thickness of the upper first piezoelectric plate 2 gradually increases from both the first regions A ₁ side toward the central portion c of the second region A ₂ , and accordingly the lower side The thickness of the second piezoelectric plate 3 is gradually decreased from both the first regions A ₁ toward the central portion c (that is, t ₂ > t ₁ > t ₃ ).
[0009]
Foil-like copper electrodes 4 are provided on the planes of the first and second piezoelectric plates 2 and 3 and between the plates 2 and 3, respectively, and the lead wires 5 and 6 of the copper electrodes 4 on the plane side are power supply devices. For example, the lead wire 7 of the copper electrode 4 between both plates 2 and 3 is connected to the cathode (−) and the anode (+) of the power supply device. In this case, as the voltage is applied, the upper first piezoelectric plate 2 expands, and the lower second piezoelectric plate 3 contracts.
[0010]
The first and second piezoelectric plates 2 and 3 are PZT [Pb (Zr, Ti) O ₃ ], PLZT [(Pb, La) (Zr, Ti) O ₃ ], PMN [Pb (Mg, Nb) O ₃ ], A kind selected from PVDF (polyvinylidene fluoride) and the like.
[0011]
In the above configuration, when the upper first piezoelectric plate 2 is extended and the lower second piezoelectric plate 3 is contracted by applying a voltage, the thickness relationship between the two piezoelectric plates 2 and 3 is shown in FIG. Therefore, both the first regions A ₁ are curved upward so as to have the smallest radius of curvature Rmin, and the central portion c of the second region A ₂ faces upward so as to have the largest radius of curvature Rmax. Bend. And between the first region A ₁ and the central portion c is in the second region A _2, it curved upward as the radius of curvature from the first region A ₁ toward the central portion c gradually increases, as a result, As shown in FIG. 5, the second region A ₂ is curved downward with a radius of curvature R.
[0012]
Thus, the bimorph piezoelectric element 1 operates in two directions by utilizing the inverse piezoelectric effect.
[0013]
【The invention's effect】
According to the present invention, by configuring as described above, it is possible to provide a bimorph piezoelectric element that can be used as an actuator that operates in two directions using the inverse piezoelectric effect. It is also possible to detect a bending angle in two directions by utilizing the piezoelectric effect (piezo effect) of this bimorph piezoelectric element.
[Brief description of the drawings]
FIG. 1 is a perspective view of a bimorph piezoelectric element.
FIG. 2 is a sectional view taken along line 2-2 of FIG.
FIG. 3 is a cross-sectional view taken along line 3-3 of FIG.
4 is a view of the bimorph piezoelectric element in an operating state as viewed in the direction of arrows in FIGS.
FIG. 5 is a view taken in the direction of arrow 5 in FIG. 4;
[Explanation of symbols]
1 ............... bimorph piezo ......... first, second piezoelectric plate A _1, A ₂ ... first, second region c ............... central portion

Claims (1)

In a bimorph piezoelectric element constituted by bonding two rectangular piezoelectric plates (2, 3) and having a uniform thickness over the whole, both piezoelectric plates (2 , 3) and two first regions (A ₁ ) having the same thickness, and a second region in which the thicknesses of both piezoelectric plates (2, 3) vary between the first regions (A ₁ ). A region (A ₂ ), and in the second region (A ₂ ), the thickness of one of the piezoelectric plates (2) is the second region (A ₂ ) from both the first regions (A ₁ ) side. The thickness of the other piezoelectric plate (3) gradually decreases toward the central portion (c) from the first region (A ₁ ) side. A bimorph piezoelectric element characterized by comprising:

Images