Vibration device

1. A vibration device comprising:

diaphragms each having a flat-plate shape and including laminated layers that include a piezoelectric layer and being warped to oscillate due to expansion and contraction of the piezoelectric layer or due to an oscillatory force from outside, the diaphragms having mutually different resonance frequencies; and

a casing comprising an internal space for accommodating the diaphragms and a fixing part for fixing a portion of each of the diaphragms, the casing being able to transmit oscillations between the diaphragms and the outside via the fixing part.

2. The vibration device according to claim 1 , wherein

the diaphragms include a diaphragm having an entire width longer than an entire width of a fixed end of the diaphragm in a direction orthogonal to a direction extending from the fixing part toward a center of the diaphragm in a main surface of the diaphragm, the fixed end being fixed by the fixing part.

3. A vibration device comprising:

diaphragms, arranged in a same plane, each diaphragm including laminated layers that include a piezoelectric layer and being warped to oscillate due to expansion and contraction of the piezoelectric layer or due to an oscillatory force from outside, the diaphragms having mutually different resonance frequencies; and

a casing comprising an internal space for accommodating the diaphragms and a fixing part for fixing a portion of each of the diaphragms, the casing being able to transmit oscillations between the diaphragms and the outside via the fixing part.

4. The vibration device according to claim 3 , wherein

the diaphragms include a diaphragm having a main surface a part of which is cut out to define an opening, the opening surrounding another diaphragm.

5. The vibration device according to claim 4 , wherein

the diaphragms are concentrically arranged.

6. The vibration device according to claim 4 , wherein

the opening is deviated from a center of the main surface toward the fixing part.

7. The vibration device according to claim 3 , wherein

the diaphragms are arc plates having a same central angle, the diaphragms being arranged in a radial direction of a circle centered on a reference point, and

each of the diaphragms is fixed by the fixing part at both ends.

8. The vibration device according to claim 7 , wherein

the diaphragms have portions to be fixed by the fixing part, the portions extending oppositely or radially from the reference point.

9. The vibration device according to claim 3 , wherein

each of the diaphragms comprises:

two first straight sections extending parallel to each other, each of the first straight sections being fixed by the fixing part at one end; and

a second straight section coupling another end of one of the two first straight sections to another end of the other of the two first straight sections, and

the diaphragms are arranged such that a diaphragm is included inside a frame defined by the first straight sections and the second straight section of another diaphragm.

10. The vibration device according to claim 3 , wherein

the diaphragms are integrated with each other at portions to be fixed by the fixing part.

11. The vibration device according to claim 1 , wherein

the diaphragms are arranged in a thickness direction.

12. The vibration device according to claim 11 , wherein

the diaphragms have a same external dimension.

13. The vibration device according to claim 3 , wherein

the diaphragms are arranged in ascending or descending order of areas of main surfaces of the diaphragms.

14. The vibration device according to claim 3 , wherein

the diaphragms are arranged in ascending or descending order of thicknesses of the diaphragms.

15. The vibration device according to claim 3 , wherein

each of the diaphragms is provided with a weight.

16. The vibration device according to claim 15 , wherein

the diaphragms are arranged in ascending or descending order of weights of the weights provided to the respective diaphragms.

17. The vibration device according to claim 15 , wherein

the weight is disposed on a center line in each of the diaphragms, the center line extending from the fixing part through the center of the diaphragm.

18. The vibration device according to claim 15 , wherein

the weight is disposed at a position deviated from a center line in each of the diaphragms, the center line extending from the fixing part through the center of the diaphragm.

19. The vibration device according to claim 1 , further comprising:

an input-output unit that receives a voltage signal output by an external device and applies the voltage signal to the respective piezoelectric layers of the diaphragms or that extracts, as current, electric charges generated in the piezoelectric layers.

20. A vibration device comprising:

diaphragms each including laminated layers that include a piezoelectric layer and being warped to oscillate due to expansion and contraction of the piezoelectric layer or due to an oscillatory force from outside, the diaphragms having mutually different resonance frequencies;

a casing comprising an internal space for accommodating the diaphragms and a fixing part for fixing a portion of each of the diaphragms, the casing being able to transmit oscillations between the diaphragms and the outside via the fixing part; and,

an input-output unit that receives a voltage signal output by an external device and applies the voltage signal to the respective piezoelectric layers of the diaphragms or that extracts, as current, electric charges generated in the piezoelectric layers, wherein the fixing part is disposed at a position opposite to the input-output unit.

21. The vibration device according to claim 20 , wherein

at least one of the diaphragms has a cut-out portion that faces the input-output unit.

22. The vibration device according to claim 21 , wherein

at least one of the diaphragms has a main surface having a C-shape, a U-shape, or a recessed shape.

23. A vibration device according to claim 1 , further comprising:

another diaphragm having a same resonance frequency as one of the diaphragms.

24. A vibration device according to claim 1 , wherein intervals between the resonance frequencies of the diaphragms are determined such that a frequency response between adjacent resonance frequencies exceeds a frequency response of a single diaphragm.

25. A vibration device according to claim 1 , wherein a metal plate is laminated to a portion of a main surface of at least one of the diaphragms.

26. The vibration device according to claim 25 , wherein

the diaphragm to which the metal plate is laminated has an annular shape, and

the metal plate extends along an inner periphery of the diaphragm in a circumferential direction.

27. The vibration device according to claim 25 , wherein

the diaphragm to which the metal plate is laminated has an annular shape, and

the metal plate includes narrower sections and broader sections that adjoin each other in an alternate manner in a circumferential direction of the diaphragm.

28. The vibration device according to claim 25 , wherein

the diaphragm to which the metal plate is laminated has an annular shape,

the metal plate extends in a circumferential direction of the diaphragm, and

the metal plate has a width that decreases as a distance from the fixing part increases.

29. The vibration device according to claim 1 , wherein at least one of the diaphragms is an annular plate including narrower and thinner sections and broader and thicker sections that adjoin each other in an alternate manner in a circumferential direction of the diaphragm.

30. The vibration device according to claim 29 , wherein

the at least one of the diaphragms is coupled to a metal weight at a position most distant from the fixing part.

31. The vibration device according to claim 30 , wherein

the metal weight protrudes from the position coupled to the diaphragm in a direction along and parallel to the diaphragm.