Piezoelectric transducer for an energy-harvesting system

Patent metadata

Field	Value
Publication number	US-9941821-B2
Application number	US-201414446237-A
Country	US
Kind code	B2
Filing date	Jul 29, 2014
Priority date	Jul 31, 2013
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

A piezoelectric transducer for energy-harvesting systems includes a substrate, a piezoelectric cantilever element, a first magnetic element, and a second magnetic element, mobile with respect to the first magnetic element. The first magnetic element is coupled to the piezoelectric cantilever element. The first magnetic element and the second magnetic element are set in such a way that, in response to relative movements between the first magnetic element and the second magnetic element through an interval of relative positions, the first magnetic element and the second magnetic element approach one another without coming into direct contact, and the interaction between the first magnetic element and the second magnetic element determines application of a force pulse on the piezoelectric cantilever element.

First claim

The invention claimed is:

1. A piezoelectric transducer for an energy harvesting system, comprising:
a semiconductor substrate including a first portion and sidewalls, the sidewalls extending from the first portion in a first direction;
a moveable mass coupled to the substrate, the moveable mass having a first surface and a second surface opposite to the first surface, the second surface of the moveable mass facing the first portion of the substrate;
a cantilever piezoelectric element coupled to the sidewalls of the substrate, the cantilever piezoelectric element extending from the sidewalls in a second direction that is transverse to the first direction, the cantilever piezoelectric element having a first surface a second surface opposite to the first surface, the second surface of the cantilever piezoelectric element facing the first portion of the substrate; and
a first magnetic element on the first surface of the cantilever piezoelectric element;
a second magnetic element on the first surface of the moveable mass, the first and second magnetic elements being movable with respect to each other, the first magnetic element and the second magnetic element being configured to generate a force pulse on the cantilever piezoelectric element by mutual magnetic interaction in response to relative movements between the first magnetic element and the second magnetic element through an interval of relative positions, the first magnetic element and the second magnetic element being configured to approach each other without mutual direct contact.

2. The transducer according to claim 1 wherein a distance between the first magnetic element and the second magnetic element is greater than a minimum distance in each relative position of the first magnetic element and the second magnetic element.

3. The transducer according to claim 1 wherein a direction of relative motion of the first magnetic element and the second magnetic element is transverse to the second direction.

4. The transducer according to claim 1 wherein the movable mass is elastically coupled to the substrate to oscillate in accordance with a transduction axis.

5. The transducer according to claim 4 wherein the cantilever piezoelectric element is anchored to the substrate.

6. The transducer according to claim 5 wherein the cantilever piezoelectric element extends toward the movable mass and the second magnetic element is at a perimeter of the movable mass.

7. The transducer according to claim 4 wherein the movable mass is elastically coupled to the substrate to translate along the transduction axis.

8. The transducer according to claim 7 wherein the transduction axis is parallel to a face of the substrate.

9. The transducer according to claim 7 wherein the transduction axis is perpendicular to a face of the substrate.

10. The transducer according to claim 4 wherein the movable mass is elastically coupled to the substrate to rotate about the transduction axis.

11. A transducer, comprising:
a semiconductor substrate including first and second sidewalls;
a moveable mass elastically coupled to the substrate;
a plurality of cantilever piezoelectric elements extending from the substrate towards the moveable mass, the plurality of cantilever piezoelectric elements including a first cantilever piezoelectric element extending from the first sidewall and a second cantilever piezoelectric element extending from the second sidewall, the first cantilever piezoelectric element being spaced from the second cantilever piezoelectric element by the moveable mass;
a plurality of first magnetic elements at free ends of the plurality of cantilever piezoelectric elements, respectively; and
a plurality of second magnetic elements on the moveable mass, each second magnetic element being substantially aligned with cantilever piezoelectric elements in a rest condition.

12. The transducer according to claim 11 wherein the second magnetic elements are configured to respectively interact with the first magnetic elements and respectively generate respective force pulses on the cantilever piezoelectric elements, respectively.

13. The transducer according to claim 11 wherein the movable mass has a quadrangular shape and the cantilever piezoelectric elements are in a comb-fingered arrangement, each cantilever piezoelectric element facing a side of the movable mass.

14. The transducer according to claim 11 wherein the movable mass has a quadrangular shape with four sides and for each of the four sides of the movable mass there is at least one of the cantilever piezoelectric elements that extends from the substrate towards the movable mass.

15. The transducer of claim 14 wherein the plurality of cantilever piezoelectric elements includes four groups of cantilever piezoelectric elements, the groups of cantilever piezoelectric elements extending perpendicularly to the sides of the movable mass, respectively, and extend substantially along the whole respective sides of the movable mass.

16. The transducer of claim 14 wherein the cantilever piezoelectric elements extends towards the movable mass without directly contacting the movable mass.

17. The transducer according to claim 11 wherein the movable mass has a circular shape and the first magnetic elements extend in a radial direction.

18. A method, comprising:
coupling a moveable mass to a substrate, the substrate including a first portion and sidewalk, the sidewalls extending from the first portion in a first direction, the moveable mass having a first surface and a second surface opposite to the first surface, the second surface of the moveable mass facing the first portion of the substrate;
coupling a cantilever piezoelectric element to the sidewalls of the substrate, the cantilever piezoelectric element extending from the sidewalls in a second direction that is transverse to the first direction, the cantilever piezoelectric element having a first surface a second surface opposite to the first surface, the second surface of the cantilever piezoelectric element facing the first portion of the substrate; and
coupling a first magnetic element to the first surface of the cantilever piezoelectric element;
coupling a second magnetic element to the first surface of the moveable mass, the first and second magnetic elements being movable with respect to each other, the first magnetic element and the second magnetic element being configured to generate a force pulse on the cantilever piezoelectric element by mutual magnetic interaction in response to relative movements between the first magnetic element and the second magnetic element through an interval of relative positions, the first magnetic element and the second magnetic element being configured to approach each other without mutual direct contact.

19. The method according to claim 18 wherein coupling the moveable mass includes elastically coupling the movable mass to the substrate to oscillate in accordance with a transduction axis.

20. The method according to claim 19 , further comprising:
anchoring the cantilever piezoelectric element to the substrate.

21. The method according to claim 20 wherein the cantilever piezoelectric element extends toward the movable mass, and the second magnetic element is at a perimeter of the movable mass.

22. The method according to claim 18 , further comprising:
oscillating the moveable mass at a first resonance frequency; and
oscillating the cantilever piezoelectric element at a second resonance frequency

Assignees

• St Microelectronics Srl

Inventors

• Procopio Francesco
• Valzasina Carlo
• Corigliano Alberto
• Ardito Raffaele
• Gafforelli Giacomo

Classifications

• H02N2/188 Primary

  adapted for resonant operation · CPC title

• H02N2/181

  Circuits; Control arrangements or methods · CPC title

• H02N2/186 Primary

  Vibration harvesters · CPC title