Piezoelectrostatic generator

• US 4,952,836 A
• Filed: 04/27/1989
• Issued: 08/28/1990
• Est. Priority Date: 04/27/1989
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Robertson, Glen A.
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US07/343,656
• Time in Patent Office: 488 Days
• Field of Search: 310/330-332, 310/339, 310/340
• US Class Current: 310/339
• CPC Class Codes: H02N 2/18 producing electrical output from mechanical input, e.g. generators for measurement devices G01
• CPC Class Codes: H10N 30/306 Cantilevers

Abstract

A piezoelectrostatic generator includes a plurality of elongated piezoelectrostatic elements having first and second ends, with the first ends fixedly mounted in a cylindrical housing and the second extending radially inwardly toward an axis. A shaft movable along the axis is connected to the inner ends of the elements to produce bending forces in piezoelectric strips within the elements. Each element includes a pair of strips mounted in surface contact and in electrical series to produce a potential upon bending, Electrodes spaced from the strips by a solid dielectric material act as capacitor plates to collect the potential charges.

Claims

1. A piezoelectrostatic element, comprising:

first and second flat, elongated strips of piezoelectric material, each of said strips having first and second ends and first and second parallel planar surfaces, each said strip producing an electrical potential across its first and second surfaces in response to mechanical bending thereof, said strips being mounted in intimate surface-to-surface contact in a common plane and in electrical series to produce, upon bending, an electrical potential across the noncontacting surfaces of the mounted strips;

first and second elongated layers of dielectric material mounted on and being coextensive with, the noncontacting surfaces of said piezoelectric strips, respectively;

first and second elongated electrode strips mounted on, and being at least coextensive with, said first and second dielectric layers, respectively, said electrode strips being parallel to said piezoelectric strip surfaces and spaced from said piezoelectric strips by said dielectric layers; and

an insulating layer surrounding said piezoelectric strips, dielectric layers and electrode strips to form a piezoelectrostatic element;

means fixedly mounting said element at one end, the other end thereof being movable with respect thereto to bend said piezoelectric strips to produce said electrical potential, said potential appearing across said electrode strips; and

means connected to said relatively movable end for driving said movable end to produce a component of motion along an axis perpendicular to said common plane.

2. The element of claim 1, wherein said electrode strips include electrical contact portions extending out of said insulating layer

3. The element of claim 2, wherein said piezoelectric strips are wedge-shaped to taper inwardly from said fixed end to said relatively movable end.

4. The element of claim 1, wherein said means mounting said element comprises a cylindrical housing coaxial with said axis, said element extending radially from said housing toward said axis.

5. The element of claim 4, wherein said means for driving said movable end comprises shaft means connected to said relatively movable end.

6. The element of claim 5, wherein said means for driving further includes motor means.

7. A piezoelectrostatic generator, comprising:

a housing;

a plurality of elongated piezoelectrostatic elements each having first and second ends, each said element having its first end fixedly mounted to said housing and its second end relatively movable to produce a bending motion in said element to thereby form a stator, each of said piezoelectrostatic elements comprising a pair of first and second elongated strips of piezoelectrostatic material, each said strip having first and second parallel planar surfaces, each said strip producing an electrical potential across its first and second surfaces in response to mechanical bending thereof, said first and second strips being mounted to place corresponding surfaces in intimate surface-to-surface contact in a common plate and in electrical series to produce, upon bending, an electrical potential across the noncontacting surfaces of the mounted strips;

first and second elongated layers of dielectric material mounted on and being coextensive with, the noncontacting surfaces of said piezoelectric strips, respectively;

first and second elongated electrode strips mounted on, and being at least coextensive with, said first and second dielectric layers, respectively, said electrode strips being parallel to said piezoelectric strip surfaces and spaced from said piezoelectric strips by said dielectric layers;

drive means connected to said relatively movable ends of said elements to produce a component of motion in each element along an axis perpendicular to said common plane of said element; and

electrical contact means connected to said first and second electrodes of each said element for collecting the electric potential produced by bending said piezoelectrostatic

8. The generator of claim 7, wherein said housing is cylindrical and has a central axis, and wherein said elements are fixedly mounted at the periphery thereof and extend inwardly toward said axis.

9. The generator of claim 7, wherein said plurality of elements extend around said housing to form an annular stator, and wherein said drive means is coaxial with said housing and is connected to the relatively movable ends of said elements to produce a component of motion in each element along said housing axis.

10. The generator of claim 9, further including a second plurality of elongated piezoelectrostatic elements substantially identical to said first-mentioned plurality of piezoelectrostatic elements to form a second stator, said first and second stators being mounted side-by-side in said housing.

11. The generator of claim 10, wherein said drive means is connected to said first and second stators.

12. The generator of claim 11, wherein said drive means includes motor means for reciprocally driving said elements along said housing axis.

13. The generator of claim 12, further including connector means for electrically interconnecting selected electrode strips of said piezoelectrostatic elements.