Piezoelectric generator

• US 8,847,468 B2
• Filed: 07/31/2012
• Issued: 09/30/2014
• Est. Priority Date: 02/09/2010
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Suzuki, Takashi
• Primary Examiner(s): Rosenau, Derek
• Assistant Examiner(s): GORDON, BRYAN P
• Application Number:
  US13/562,549
• Publication Number:
  US 20120293042A1
• Time in Patent Office: 791 Days
• Field of Search: 310/321, 310/339, 310/330, 310/331
• US Class Current: 310/339
• 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 provided on a tip end of the fixing part;

a weight part provided on a tip end of the cantilever;

a centroid adjustment part configured to adjust a position of a centroid of the weight part; and

a piezoelectric generating cell provided above the cantilever,

wherein the centroid adjustment part includes

a first electrode and a second electrode provided within the weight part, and

a charged or chargeable object provided between the first electrode and the second electrode.

2. The piezoelectric generator according to claim 1, further comprising:

a third electrode provided in a periphery of the charged or chargeable object,

wherein the third electrode is charged to a polarity opposite to that of at least one of the first electrode and the second electrode.

3. The piezoelectric generator according to claim 1, wherein the charged or chargeable object includes particles dipped in a liquid.

4. The piezoelectric generator according to claim 3, wherein the particles include microcapsules.

5. The piezoelectric generator according to claim 1, wherein the charged or chargeable object includes a rotational body having a surface area thereof divided into a positively charged area and a negatively charged area in a rotational direction of the rotational body.

6. The piezoelectric generator according to claim 1, wherein the charged or chargeable object includes charged particles encapsulated within a partitioned space.

7. The piezoelectric generator according to claim 1, wherein the charged or chargeable object includes an electrolytic solution supplied between the first electrode and the second electrode.

8. The piezoelectric generator according to claim 1, wherein the centroid adjustment part includes

a hollow space provided within the weight part,

a centroid moving body provided within the hollow space, and

a moving mechanism configured to move the centroid moving body.

9. The piezoelectric generator according to claim 8, wherein the moving mechanism includes an actuator including a piezoelectric body sandwiched between the first electrode and the second electrode.

10. The piezoelectric generator according to claim 8, wherein the moving mechanism includes a spring made of a shape-memory alloy.

11. The piezoelectric generator according to claim 1, further comprising:

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

12. The piezoelectric generator according to claim 11, wherein the centroid control circuit includes

an alternating circuit configured to alternately apply a forward direction voltage and a reverse 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.

13. The piezoelectric generator according to claim 11, 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.

14. The piezoelectric generator according to claim 11, 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.

15. The piezoelectric generator according to claim 14, wherein the vibration sensor includes a plurality of piezoelectric sensors having different resonance frequencies.

16. The piezoelectric generator according to claim 11, 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.

17. A piezoelectric generator, comprising:

a fixing part;

a cantilever provided on a tip end of the fixing part;

a weight part provided on a tip end of the cantilever;

a centroid adjustment part configured to adjust a position of a centroid of the weight part; and

a piezoelectric generating cell provided above the cantilever,

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.

18. A piezoelectric generator, comprising:

a fixing part;

a cantilever provided on a tip end of the fixing part;

a weight part provided on a tip end of the cantilever;

a centroid adjustment part configured to adjust a position of a centroid of the weight part; and

a piezoelectric generating cell provided above the cantilever,

wherein the centroid adjustment part includes

a plurality of centroid adjustment areas provided in the weight part, and

a centroid adjustment material selectively supplied to the plurality of centroid adjustment areas.

19. The piezoelectric generator according to claim 18, further comprising:

a recessed part provided in each of the plurality of centroid adjustment areas.