Non-linear piezoelectric mechanical-to-electrical generator system and method

• US 7,436,104 B2
• Filed: 10/20/2006
• Issued: 10/14/2008
• Est. Priority Date: 10/20/2006
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Clingman, Dan J., Arbogast, Darin J.
• Primary Examiner(s): Dougherty; Thomas M
• Application Number:
  US11/551,515
• Publication Number:
  US 20080100181A1
• Time in Patent Office: 725 Days
• Field of Search: 310/26, 310/339
• 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 30/304 Beam type

Abstract

A non-linear, piezoelectric mechanical-to-electrical generator especially well adapted for use with a Stirling engine, to thus form an electrical power generation system. In one form the generator includes a flexible beam that is configured in a bowed orientation to exert a compressive stress on a piezoceramic stack. A mechanical, linearly reciprocating member is positioned against the flexible beam at a midpoint of the beam. The mechanical member applies a force to the flexible beam that initially tends to flatten the flexible beam, which increases the compressive stress applied to the piezoceramic stack, thus compressing the stack and causing it to generate an electrical output signal. When the mechanical member removes the force, the flexible beam reverts to its initial, bowed configuration. This allows the piezoceramic stack to decompress, and it generates another electrical signal. This alternating compressing and decompressing of the piezoceramic stack causes a series of electrical signals to be generated from the stack. The apparatus forms a lightweight, compact means for converting a linear, reciprocating mechanical output signal into electrical power.

Claims

1. A non-linear power generator system comprising:

a flexible beam for receiving a mechanical input, the flexible beam being supported in a bowed configuration;

an electrically responsive member supported against one end of the flexible beam so as to be under a compressive force exerted by said flexible beam; and

said flexible beam being adapted to move towards a flattened shape from said bowed shape in response to said mechanical input, to transmit said mechanical input to said electrically responsive member, to cause a compression of said electrically responsive member that results in an electrical output signal being generated by said electrically responsive member.

2. The system of claim 1, wherein said mechanical input comprises an oscillating mechanical input signal.

3. The system of claim 2, wherein said mechanical input is provided by a piston of a Stirling engine.

4. The system of claim 1, further comprising a coupling assembly including a plurality of wheels for interfacing an end of said flexible beam to an end of said electrically responsive member.

5. The system of claim 1, wherein a change in length of said electrically responsive member is approximated by the formula:

$\mathrm{\Delta <br><br>}<br><br><br><br>\mathrm{length}<br><br><br><br>\mathrm{of}<br><br><br><br>\mathrm{electrically}<br><br><br><br>\mathrm{responsive}<br><br><br><br>\mathrm{member}=\frac{{\mathrm{\pi <br><br>}}^2<br><br>D^2}{4<br><br>L}$

where “

D”

represents the distance separating a line bisecting the free ends of the flexible beam, and a line tangent to the midpoint of the beam; and

where “

L”

represents the length of the unbowed flexible beam.

6. The system of claim 1, wherein said flexible beam provides a varying force amplification factor approximated by the following equation:

$\mathrm{Fm}=\frac{{\mathrm{\pi <br><br>}}^2<br><br>D}{2<br><br>L}$

where Fm is the force magnification factor of said mechanical input signal.

7. The system of claim 1, wherein said electrically responsive member comprises a piezoceramic stack.

8. The system of claim 1, wherein said electrically responsive member comprises a magnetostrictive material.

9. A method for generating electrical power from a mechaniical signal, comprising:

using a flexible beam secured under compression to assume a bowed orientation, to receive said mechanical signal;

using said flexible beam to transmit said mechanical signal to an electrically responsive member;

supporting said electrically responsive member such that said member experiences a compressive stress from said flexible beam; and

using said flexible beam to alternatively compress and decompress said electrically responsponsive member, in response to said mechanical signal, to generate electrical output signals from said electrically responsive member.

10. The method of claim 9, wherein using said flexible beam to transmit said mechanical signal comprises using said flexible beam to also amplify said mechanical signal as said mechanical signal is applied by said flexible beam to said electrically responsive member.

11. The method of claim 9, further comprising using a Stirling engine to generate said mechancial signal.

12. The method of claim 9, wherein using said flexible beam to transmit said mechanical signal to an electrically reponsive member comprises using said flexible beam to transmit said mechanical signal to one of a piezoceramic stack and a magnetostrictive member.