Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-08-23
2001-07-17
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S330000, C310S331000, C310S321000
Reexamination Certificate
active
06262516
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a parallel plate structure provided with a PZT lead (Pb) Zirconate Titanate) thin-film bimorph and method of fabrication thereof, and more particularly, to structures used as piezoelectric actuators.
A bimorph, which is known in the prior art, includes a plate-like substrate, two PZT devices (lead zirconate titanate: ceramics containing a solid solution of lead titanate and lead zirconate), which are formed on the front and rear surfaces of the substrate and which function as piezoelectric devices, and electrodes formed on each PZT device. Voltage is applied to both of the PZT devices so that one of the PZT devices expands while the other contracts. Since this deforms the bimorph entirely in a certain direction, the bimorph is used as an actuator.
However, when employing preformed PZT devices, it is difficult to make the devices thinner in subsequent processes. Accordingly, the production of a more compact bimorph is difficult. Furthermore, alot of time is requiring to adhere the PZT devices to the front and rear surfaces the substrate. This lengthens the fabrication time of the bimorph.
Additionally, since the bimorph is formed as a monolithic single plate, the bimorph is apt to deform in an undesirable direction. This results in a shortcoming in which the bimorph twists and does not deform accurately.
SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide a parallel plate structure having a PZT thin-film bimorph that deforms by a large degree.
Another objective of the present invention is to provide a parallel plate structure having a PZT thin-film bimorph that is optimal for mass-production, can be made more compact, and resists twisting.
A further objective of the present invention is to provide a parallel plate structure having a PZT thin-film bimorph that has superior productivity.
A parallel plate structure, which is provided with a bimorph, according to the present invention, has a thin PZT thin-film formed on a first and second surface of a titanium substrate. Thus, the bimorph is more compact. This, in turn, makes the entire structure more compact. Furthermore, the parallel plate structure is a duplex structure in which a pair of bimorphs are superimposed by way of a spacer. Hence, the structure has improved rigidity and resists twisting.
When deforming the structure, voltage having opposite polarities is applied to adjacent electrodes on a first surface of each bimorph. As a result, the portion of the PZT thin-film to which an electric field in the polarity direction is applied contracts, while the portion of the PZT thin-film to which an electric field in the direction opposite the polarity direction is applied expands.
Due to the application of the same voltage, each bimorph deforms in the same direction. Due to the application of voltage having different polarities to the adjacent electrodes on each surface of each bimorph, the portions of the PZT thin-film to which the voltage of different polarities are applied deform in opposite directions. As a result, since the portions of the PZT thin-film corresponding to the adjacent electrodes deform in opposite directions, the structure is bent in an S-shaped or reversed S-shaped manner and deformed.
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Arai Fumihito
Fukuda Toshio
Itoigawa Koichi
Iwata Hitoshi
Addison Karen
Buyan Robert D.
Kabushiki Kaisha Tokai Rika Denki Seisakusho
Ramirez Nestor
Stout, Uxa Buyan & Mullins, LLP
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