대표
청구항
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1. A piezoelectric actuator comprising: a first plate having a planar first plate surface and an oppositely disposed planar second plate surface separated by a first plate thickness;a second plate having a planar third plate surface and an oppositely disposed planar fourth plate surface separated by a second plate thickness;a first electrode disposed on one of the planar first plate surface and the planar second plate surface and having a plurality of first fingers;a second electrode disposed on the same one of the planar first plate surface and the plan...
1. A piezoelectric actuator comprising: a first plate having a planar first plate surface and an oppositely disposed planar second plate surface separated by a first plate thickness;a second plate having a planar third plate surface and an oppositely disposed planar fourth plate surface separated by a second plate thickness;a first electrode disposed on one of the planar first plate surface and the planar second plate surface and having a plurality of first fingers;a second electrode disposed on the same one of the planar first plate surface and the planar second plate surface and having a plurality of second fingers alternated with the plurality of first fingers;a third electrode disposed on one of the planar third plate surface and the planar fourth plate surface and having a plurality of third fingers;a fourth electrode disposed on the same one of the planar third plate surface and the planar fourth plate surface and having a plurality of fourth fingers alternated with the plurality of third fingers; anda flexible diaphragm having a first diaphragm surface and an oppositely disposed second diaphragm surface, wherein one of the planar first plate surface and the planar second plate surface of the first plate faces and is rigidly secured to the first diaphragm surface, wherein one of the planar third plate surface and the planar fourth plate surface of the second plate faces and is rigidly secured to the second diaphragm surface,wherein a first electric field applied through the first electrode and the second electrode causes in-plane tensile stresses to elongate the first plate in a first direction, causes in-plane compressive stresses in a second direction, and causes transverse compressive stresses in a third direction, and wherein a second electric field applied through the first electrode and the second electrode causes compressive stresses to compress the first plate in the first direction, and causes tensile stresses in the second direction and the third direction, andwherein a third electric field applied through the third electrode and the fourth electrode causes in-plane tensile stresses to elongate the second plate in a fourth direction, causes in-plane compressive stresses in a fifth direction, and causes transverse compressive stresses in a sixth direction, and wherein a fourth electric field applied through the third electrode and the fourth electrode causes compressive stresses to compress the second plate in the fourth direction, and causes tensile stresses in the fifth direction and the sixth direction and wherein the first plate and the second plate are rigidly secured to the flexible diaphragm with the first direction of the first plate aligned parallel to the fourth direction of the second plate. 2. The piezoelectric actuator of claim 1, comprising a third electrode disposed on the other of the planar first plate surface and the planar second plate surface and having a plurality of third fingers; anda fourth electrode disposed on the other of the planar first plate surface and the planar second plate surface and having a plurality of fourth fingers alternated with the plurality of third fingers,wherein a third electric field applied through the third electrode and the fourth electrode causes in-plane tensile stresses to elongate the first plate in the first direction, causes in-plane compressive stresses in the second direction, and causes transverse compressive stresses in the third direction, wherein a fourth electric field applied through the third electrode and the fourth electrode causes compressive stresses to compress the first plate in the first direction, and causes tensile stresses in the second direction and the third direction. 3. The piezoelectric actuator of claim 2, wherein the first electric field and the third electric field are applied simultaneously by the electrodes, and the second electric field and the fourth electric field are applied simultaneously by the electrodes. 4. The piezoelectric actuator of claim 1, wherein the first electric field is applied to the first plate simultaneously with the fourth electric field being applied to the second plate, and the second electric field is applied to the first plate simultaneously with the third electric field being applied to the second plate. 5. A piezoelectric actuator comprising: a first plate having a planar first plate surface and an oppositely disposed planar second plate surface separated by a first plate thickness;a first electrode disposed on one of the planar first plate surface and the planar second plate surface and having a plurality of first fingers;a second electrode disposed on the same one of the planar first plate surface and the planar second plate surface and having a plurality of second fingers alternated with the plurality of first fingers; anda flexible diaphragm having a first diaphragm surface and an oppositely disposed second diaphragm surface, wherein one of the planar first plate surface and the planar second plate surface of the first plate faces and is rigidly secured to the first diaphragm surface,wherein a first electric field applied through the first electrode and the second electrode causes in-plane tensile stresses to elongate the first plate in a first direction, causes in-plane compressive stresses in a second direction, and causes transverse compressive stresses in a third direction, and wherein a second electric field applied through the first electrode and the second electrode causes compressive stresses to compress the first plate in the first direction, and causes tensile stresses in the second direction and the third direction,wherein a third electric field applied through the third electrode and the fourth electrode causes in-plane tensile stresses to elongate the second plate in a fourth direction, causes in-plane compressive stresses in a fifth direction, and causes transverse compressive stresses in a sixth direction, and wherein a fourth electric field applied through the third electrode and the fourth electrode causes compressive stresses to compress the second plate in the fourth direction, and causes tensile stresses in the fifth direction and the sixth direction, andwherein the plurality of first fingers and the plurality of second fingers are arranged on the one of the planar first plate surface and the planar second plate surface so that a higher concentration of the plurality of first fingers and the plurality of second fingers exists in a first area of the first plate along the first direction than in a second area of the first plate along the first direction. 6. A piezoelectric actuator comprising: a first plate having a planar first plate surface and an oppositely disposed planar second plate surface separated by a first plate thickness;a first electrode disposed on one of the planar first plate surface and the planar second plate surface and having a plurality of first fingers;a second electrode disposed on the same one of the planar first plate surface and the planar second plate surface and having a plurality of second fingers alternated with the plurality of first fingers; anda flexible diaphragm having a first diaphragm surface and an oppositely disposed second diaphragm surface, wherein one of the planar first plate surface and the planar second plate surface of the first plate faces and is rigidly secured to the first diaphragm surface,wherein a first electric field applied through the first electrode and the second electrode causes in-plane tensile stresses to elongate the first plate in a first direction, causes in-plane compressive stresses in a second direction, and causes transverse compressive stresses in a third direction, and wherein a second electric field applied through the first electrode and the second electrode causes compressive stresses to compress the first plate in the first direction, and causes tensile stresses in the second direction and the third direction, andwherein the first plate has a first thickness in a first area of the first plate and a second thickness that is less than the first thickness in a second area of the first plate such that the first electric field causes greater in-plane tensile stresses in the first area along the first direction than in the second area of the first plate along the first direction. 7. A synthetic jet for generating an air jet, the synthetic jet comprising: a housing defining a hollow resonant chamber and having an orifice through a first wall of the housing placing the hollow resonant chamber in fluid communication with an ambient atmosphere surrounding the synthetic jet;a flexible diaphragm forming a second wall of the housing and having a first diaphragm surface and an oppositely disposed second diaphragm surface;a first plate having a planar first plate surface and an oppositely disposed planar second plate surface separated by a first plate thickness, wherein one of the planar first plate surface and the planar second plate surface of the first plate faces and is rigidly secured to the first diaphragm surface;a second plate having a planar third plate surface and an oppositely disposed planar fourth plate surface separated by a second plate thickness, wherein one of the planar third plate surface and the planar fourth plate surface of the second plate faces and is rigidly secured to the second diaphragm surface;a first electrode disposed on one of the planar first plate surface and the planar second plate surface and having a plurality of first fingers;a second electrode disposed on the same one of the planar first plate surface and the planar second plate surface and having a plurality of second fingers alternated with the plurality of first fingers;a third electrode disposed on one of the planar third plate surface and the planar fourth plate surface and having a plurality of third fingers; anda fourth electrode disposed on the same one of the planar third plate surface and the planar fourth plate surface and having a plurality of fourth fingers alternated with the plurality of third fingers,wherein a first electric field applied through the first electrode and the second electrode causes in-plane tensile stresses to elongate the first plate in a first direction, causes in-plane compressive stresses in a second direction, and causes transverse compressive stresses in a third direction, and wherein a second electric field applied through the first electrode and the second electrode causes compressive stresses to compress the first plate in the first direction, and causes tensile stresses in the second direction and the third direction, andwherein a third electric field applied through the third electrode and the fourth electrode causes in-plane tensile stresses to elongate the second plate in a fourth direction, causes in-plane compressive stresses in a fifth direction, and causes transverse compressive stresses in a sixth direction, and wherein a fourth electric field applied through the third electrode and the fourth electrode causes compressive stresses to compress the second plate in the fourth direction, and causes tensile stresses in the fifth direction and the sixth direction and wherein the first plate and the second plate are rigidly secured to the flexible diaphragm with the first direction of the first plate aligned parallel to the fourth direction of the second plate. 8. The synthetic jet of claim 7, comprising a third electrode disposed on the other of the planar first plate surface and the planar second plate surface and having a plurality of third fingers; anda fourth electrode disposed on the other of the planar first plate surface and the planar second plate surface and having a plurality of fourth fingers alternated with the plurality of third fingers,wherein a third electric field applied through the third electrode and the fourth electrode causes in-plane tensile stresses to elongate the first plate in the first direction, causes in-plane compressive stresses in the second direction, and causes transverse compressive stresses in the third direction, wherein a fourth electric field applied through the third electrode and the fourth electrode causes compressive stresses to compress the first plate in the first direction, and causes tensile stresses in the second direction and the third direction. 9. The synthetic jet of claim 8, wherein the first electric field and the third electric field are applied simultaneously by the electrodes, and the second electric field and the fourth electric field are applied simultaneously by the electrodes. 10. The synthetic jet of claim 7, wherein the first electric field is applied to the first plate simultaneously with the fourth electric field being applied to the second plate, and the second electric field is applied to the first plate simultaneously with the third electric field being applied to the second plate. 11. A synthetic jet for generating an air jet, the synthetic jet comprising: a housing defining a hollow resonant chamber and having an orifice through a first wall of the housing placing the hollow resonant chamber in fluid communication with an ambient atmosphere surrounding the synthetic jet;a flexible diaphragm forming a second wall of the housing and having a first diaphragm surface and an oppositely disposed second diaphragm surface;a first plate having a planar first plate surface and an oppositely disposed planar second plate surface separated by a first plate thickness, wherein one of the planar first plate surface and the planar second plate surface of the first plate faces and is rigidly secured to the first diaphragm surface;a first electrode disposed on one of the planar first plate surface and the planar second plate surface and having a plurality of first fingers; anda second electrode disposed on the same one of the planar first plate surface and the planar second plate surface and having a plurality of second fingers alternated with the plurality of first fingers,wherein a first electric field applied through the first electrode and the second electrode causes in-plane tensile stresses to elongate the first plate in a first direction, causes in-plane compressive stresses in a second direction, and causes transverse compressive stresses in a third direction, and wherein a second electric field applied through the first electrode and the second electrode causes compressive stresses to compress the first plate in the first direction, and causes tensile stresses in the second direction and the third direction, andwherein the plurality of first fingers and plurality of second fingers are arranged on the one of the planar first plate surface and the planar second plate surface so that the first electric field cause greater in-plane tensile stresses in a first area of the first plate along the first direction than in a second area of the first plate along the first direction. 12. A synthetic jet for generating an air jet, the synthetic jet comprising: a housing defining a hollow resonant chamber and having an orifice through a first wall of the housing placing the hollow resonant chamber in fluid communication with an ambient atmosphere surrounding the synthetic jet;a flexible diaphragm forming a second wall of the housing and having a first diaphragm surface and an oppositely disposed second diaphragm surface;a first orthotropic plate having a planar first plate surface and an oppositely disposed planar second plate surface separated by a first plate thickness, wherein one of the planar first plate surface and the planar second plate surface of the first plate faces and is rigidly secured to the first diaphragm surface, wherein the first orthotropic plate has a first direction in the plane of the first orthotropic plate, a second direction in the plane of the first orthotropic plate, and a third direction transverse to the plane of the first orthotropic plate, and wherein the first orthotropic plate has a first d coupling coefficient in the first direction that is greater than a second d coupling coefficient in the second direction;a first electrode disposed on one of the planar first plate surface and the planar second plate surface; anda second electrode disposed on one of the planar first plate surface and the planar second plate surface, wherein a first electric field applied through the first electrode and the second electrode causes in-plane tensile stresses to elongate the first orthotropic plate in the first direction, and wherein a second electric field applied through the first electrode and the second electrode causes compressive stresses to compress the first orthotropic plate in the first direction. 13. The synthetic jet of claim 12, wherein the first electrode is disposed on the planar first plate surface and the second electrode is disposed on the planar second plate surface. 14. The synthetic jet of claim 12, wherein the first electrode is disposed on the planar first plate surface and has a plurality of first fingers, and wherein the second electrode is disposed on the planar first plate surface and has a plurality of second fingers alternated with the plurality of first fingers. 15. The synthetic jet of claim 12, comprising a second orthotropic plate having a planar third plate surface and an oppositely disposed planar fourth plate surface separated by a second plate thickness, wherein one of the planar third plate surface and the planar fourth plate surface of the second orthotropic plate faces and is rigidly secured to the second diaphragm surface, wherein the second orthotropic plate has a fourth direction in the plane of the second orthotropic plate, a fifth direction in the plane of the second orthotropic plate, and a sixth direction transverse to the plane of the second orthotropic plate, and wherein the second orthotropic plate has a third d coupling coefficient in the fourth direction that is greater than a fourth d coupling coefficient in the fifth direction;a third electrode disposed on one of the planar third plate surface and the planar fourth plate surface; anda fourth electrode disposed on one of the planar third plate surface and the planar fourth plate surface, wherein a third electric field applied through the third electrode and the fourth electrode causes in-plane tensile stresses to elongate the second orthotropic plate in the fourth direction, and wherein a fourth electric field applied through the third electrode and the fourth electrode causes compressive stresses to compress the second orthotropic plate in the fourth direction. 16. The synthetic jet of claim 12, wherein the first d coupling coefficient in the first direction has a variable value so that the first electric field causes greater in-plane tensile stresses in a first area of the first orthotropic plate along the first direction than in a second area of the first orthotropic plate along the first direction. 17. The synthetic jet of claim 12, wherein the first orthotropic plate comprises: a bundle formed by a plurality of piezoceramic fibers aligned side-by-side across a plate width of the first orthotropic plate in the second direction; andan interstitial material encasing the bundle formed by the plurality of piezoceramic fibers.
