PIEZOELECTRIC GENERATOR

• US 20120293042A1
• Filed: 07/31/2012
• Published: 11/22/2012
• Est. Priority Date: 02/09/2010
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Suzuki, Takashi
• Granted Patent: US 8,847,468 B2
• Time in Patent Office: Days
• US Class Current: 310/321
• CPC Class Codes: H02N 2/181 Circuits; Control arrangements or methods
• CPC Class Codes: H02N 2/188 adapted for resonant operation
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

A piezoelectric generator includes a fixing part; a cantilever formed at a front edge of the fixing part; a weight part formed at a front end of the cantilever; a centroid adjustment part by which a position of a centroid of the weight part is adjusted; and a piezoelectric generating cell formed on top of the cantilever.

Claims

1. A piezoelectric generator comprising:

a fixing part;

a cantilever formed at a front edge of the fixing part;

a weight part formed at a front end of the cantilever;

a centroid adjustment part by which a position of a centroid of the weight part is adjusted; and

a piezoelectric generating cell formed on top of the cantilever.

2. The piezoelectric generator according to claim 1, wherein

the centroid adjustment part includes

a first electrode and a second electrode attached in the weight part, and

a charging object provided between the first electrode and the second electrode.

3. The piezoelectric generator according to claim 2, further comprising:

a third electrode formed around the charging object, the third electrode being charged to a polarity opposite to that of at least one of the first electrode and the second electrode.

4. The piezoelectric generator according to claim 2, wherein

the charging object is particles dipped in a liquid.

5. The piezoelectric generator according to claim 4, wherein

the particles are microcapsules.

6. The piezoelectric generator according to claim 2, wherein

the charging object is a rotational body having a surface area divided into a positively charged area and a negatively charged area in a rotational direction.

7. The piezoelectric generator according to claim 2, wherein

the charging object is charged particles encapsulated in a partitioned space.

8. The piezoelectric generator according to claim 2, wherein

the charging object is an electrolytic solution supplied between the first electrode and the second electrode.

9. The piezoelectric generator according to claim 2, wherein

the centroid adjustment part includes

a hollow space,

a centroid moving body placed in the hollow space, and

a moving mechanism configured to move the centroid moving body.

10. The piezoelectric generator according to claim 9, wherein

the moving mechanism is an actuator including a piezoelectric body sandwiched between the first electrode and the second electrode.

11. The piezoelectric generator according to claim 9, wherein

the moving mechanism includes a spring made of a shape-memory alloy.

12. The piezoelectric generator according to claim 2, further comprising:

a centroid control circuit configured to select a charging polarity that is positive or negative and to apply a voltage between the first electrode and the second electrode.

13. The piezoelectric generator according to claim 12, wherein

the centroid control circuit includes

an alternating circuit configured to alternately apply a forward direction voltage and an opposite direction voltage to the first electrode and the second electrode, and

a voltage adjustment circuit configured to gradually attenuate levels of the forward direction voltage and the opposite direction voltage.

14. The piezoelectric generator according to claim 12, further comprising:

an output determination device configured to transmit, to the centroid control circuit, a signal for selecting the charging polarity based on a measured time of a timer.

15. The piezoelectric generator according to claim 12, wherein

the centroid control circuit includes

an output determination device configured to select the charging polarity based on a detection result of at least one of an acceleration sensor and a vibration sensor.

16. The piezoelectric generator according to claim 15, wherein

the vibration sensor includes plural piezoelectric sensors having different resonance frequencies.

17. The piezoelectric generator according to claim 12, further comprising:

a signal transmitting device configured to

compare an output value of at least one of power and a voltage output from the piezoelectric generating cell with a reference value, and

transmit, to the centroid control circuit, an instruction signal for changing the charging polarity of the voltage to be applied to the first electrode and the second electrode, when the output value is less than the reference value.

18. The piezoelectric generator according to claim 1, wherein

the centroid adjustment part includes

a hollow space provided in the weight part, and

a filling material supplied into the hollow space in a disproportionate manner.

19. The piezoelectric generator according to claim 1, wherein

the centroid adjustment part includes

plural centroid adjustment areas provided in the weight part, and

a centroid adjustment material selectively supplied in the plural centroid adjustment areas.

20. The piezoelectric generator according to claim 19, further comprising:

recessed parts formed in the plural centroid adjustment areas.