PIEZOELECTRIC ACOUSTIC DEVICE AND ELECTRONIC APPARATUS

• US 20100246863A1
• Filed: 11/12/2008
• Published: 09/30/2010
• Est. Priority Date: 11/12/2007
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Kuroda, Jun, Takahashi, Masatake, Sasaki, Yasuhiro, Yokoyama, Yukio, Toki, Nozomi, Onishi, Yasuharu, Mori, Ukyo
• Granted Patent: US 8,385,578 B2
• Time in Patent Office: Days
• US Class Current: 381/190
• CPC Class Codes: H04R 1/2811 for loudspeaker transducers
• CPC Class Codes: H04R 17/00 Piezoelectric transducers; Electrostrictive transducers piezoelectric or electrostrictive elements in general H10N30/00; details of piezoelectric or electrostrictive motors, generators or positioners H10N30/00
• CPC Class Codes: H04R 2499/11 Transducers incorporated or for use in hand-held devices, e.g. mobile phones, PDA's, camera's

Abstract

A piezoelectric acoustic device comprises: at least two piezoelectric actuators; a support body that supports the at least two piezoelectric actuators; and a signal input unit that drives the at least two piezoelectric actuators at respective arbitrary times. At least one pair of piezoelectric actuators among the at least two piezoelectric actuators is arranged in such a manner that their sound radiation surfaces face each other with a predetermined gap.

Claims

1. A piezoelectric acoustic device comprising:

at least two piezoelectric actuators;

a support body that supports said at least two piezoelectric actuators; and

a signal input unit that drives said at least two piezoelectric actuators at respective arbitrary times;

wherein

at least one pair of piezoelectric actuators among said at least two piezoelectric actuators is arranged in such a manner that their sound radiation surfaces face each other with a predetermined gap.

2. The piezoelectric acoustic device as defined in claim 1, wherein said piezoelectric actuator includes:

at least one plate-like piezoelectric element that expands and contracts along the sound radiation surface;

a base joined to one side of said piezoelectric element; and

a diaphragm joined to said base and having a lower elasticity and a wider area than said base; and

said base transmits the expansion/contraction of said piezoelectric element to said diaphragm so as to generate sound waves.

3. The piezoelectric acoustic device as defined in claim 2, wherein said diaphragm and said support body are joined together.

4. The piezoelectric acoustic device as defined in claim 2, wherein

said piezoelectric actuator further includes a support member joined to an outer periphery of said diaphragm;

and

said support member and said support body are joined together.

5. The piezoelectric acoustic device as defined in claim 1, wherein

said support body includes a plate-like support board(s);

and

said at least two piezoelectric actuators and said plate-like support board surround a space defined by said at least one pair of piezoelectric actuators facing each other.

6. The piezoelectric acoustic device as defined in claim 5, wherein

said support board has a through hole that leads to the space defined by said at least one pair of piezoelectric actuators facing each other.

7. The piezoelectric acoustic device as defined in claim 1, having a rectangular parallelepiped formed by said piezoelectric actuators and said support body, wherein

said at least one pair of piezoelectric actuators is disposed on two facing faces of the rectangular parallelepiped;

and

said piezoelectric actuators or a part of said support body is disposed on the remaining four faces.

8. The piezoelectric acoustic device as defined in claim 1, wherein

said at least one pair of piezoelectric actuators has frequency characteristics different from each other.

9. The piezoelectric acoustic device as defined in claim 1, wherein

said piezoelectric actuator is of a bimorph type having at least two piezoelectric elements.

10. The piezoelectric acoustic device as defined in claim 1, wherein

said signal input unit synchronizes operations of said at least two piezoelectric actuators so that a space surrounded by said at least two piezoelectric actuators simultaneously expands or contracts.

11. An electronic apparatus comprising:

a piezoelectric acoustic device, wherein

said piezoelectric acoustic device includes;

at least two piezoelectric actuators;

a support body that supports said at least two piezoelectric actuators; and

a signal input unit that drives said at least two piezoelectric actuators at respective arbitrary times; and

wherein

at least one pair of piezoelectric actuators among said at least two piezoelectric actuators is arranged in such a manner that their sound radiation surfaces face each other with a predetermined gap.

12. The electronic apparatus as defined in claim 11 further comprising a case, wherein

said piezoelectric acoustic device is built therein so that at least one piezoelectric actuator faces said case.

13. The electronic apparatus as defined in claim 11 further comprising a case, wherein said piezoelectric acoustic device is built therein so that said piezoelectric actuator does not face said case.

14. The electronic apparatus as defined in claim 13, wherein

said case has at least one through hole that penetrates said case;

said support body has a plate-like support board(s);

said at least two piezoelectric actuators and said plate-like support board surround a space defined by said at least one pair of piezoelectric actuators facing each other;

said support board has a through hole that leads to the space defined by said at least one pair of piezoelectric actuators facing each other; and

said piezoelectric acoustic device is mounted so that said through hole of said case and said through hole of said support board face each other.