Piezoelectric rotary electrical energy generator

• US 6,194,815 B1
• Filed: 02/19/1999
• Issued: 02/27/2001
• Est. Priority Date: 10/25/1996
• Status: Expired due to Fees

• Current Assignee: Ocean Power Technologies, Inc.
• Original Assignee: Ocean Power Technologies, Inc.
• Inventors: Carroll, Charles B.
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): MEDLEY, PETER M
• Application Number:
  US09/253,269
• Time in Patent Office: 739 Days
• Field of Search: 310/339, 310/332, 310/311
• US Class Current: 310/339
• CPC Class Codes: H02N 2/18 producing electrical output from mechanical input, e.g. generators for measurement devices G01

Abstract

A piezoelectric generator comprises one or more inner hubs, an outer, stationary support, and a plurality of strap-like piezoelectric power generating elements mounted between the hubs and the outer support. The hubs are mounted for relative rotation on a first shaft mounted eccentrically on a second shaft having an axis of rotation coincident with central axis of the outer support. Rotation of the eccentric first shaft causes the hubs to follow a circular path around the outer support axis but without rotation of the hub around its own axis. The movements of the hubs cause alternate straining and destraining of the piezoelectric elements for generating electrical energy. For obtaining high energy conversion efficiency, the elements are arranged in groups of three or more substantially identical elements which are identically strained but symmetrically out-of-phase with one another.

Claims

1. A piezoelectric, electrical energy generator comprising first and second supports, a first piezoelectric power generating element mounted between said two supports for being variably, elastically strained along an axis intersecting said two supports, means for causing one of said supports to circle relative to the other of said supports for causing substantially continuous variable straining of said element in response to continuous relative circling, said first element being one of a plurality of substantially identical elements all of which are secured between respective first and second supports all mounted for causing identical circling movements of each of said first supports relative to respective said second supports for continuously variably straining all of the elements, each of said power generating elements comprising an elongated strip of electroded piezoelectric material secured between said supports, and said elongated strip being folded to form a loop having two free ends and a bight intermediate said two ends, said bight being engaged with said first support, and said two free ends being secured to said second support.

2. A generator according to claim 1, wherein said second support comprises a post, and said two free ends are wrapped, in sandwiched together relationship, around said post.

3. A piezoelectric, electrical energy generator comprising an outer support structure having an axis of elongation, a first elongated hub having an axis of elongation disposed within said outer structure, a plurality of piezoelectric elements secured between first points on said hub and respective second points on said structure, means for causing relative movements between said hub and said support structure for causing circular orbiting of said first points relative to said second points for alternately straining and destraining said piezoelectric elements for generating electrical energy, said hub being mounted for eccentric orbiting of the hub axis around the axis of said support structure for causing said relative movements, said first points on said hub being spaced equally around a circle having said hub axis as a center, said second points on said support structure being spaced equally around a circle having said structure axis as a center, said relative movements causing means causing said hub axis to orbit along a circle around said structure axis without rotation of said hub around its own central axis, said hub being mounted co-axially on a first shaft for rotation relative thereto, said first shaft being mounted for eccentric rotation around a second shaft having an axis of rotation co-axial with said support structure axis components including said hub, said first shaft and said plurality of piezoelectric elements secured between first and second points on said hub and on said structure, respectively, comprising a first generator section disposed along a first length of said second shaft, and including a second generator section substantially identical to said first generator section disposed along a second length of said second shaft spaced from said first length along the axis of elongation of said second shaft and including components identical to said components of said first generator section operably interconnected to one another and to said structure as are said components of said first generator section, the direction of eccentricity of said first shaft with respect to said second shaft of said first generator section being off-set 90 degrees from the eccentricity of said first shaft with respect to said second shaft of said second generator section, said first points on said hub in each generation section being equally divided and spaced along a pair of first parallel straight lines disposed on respective sides of, and equally spaced from a first plane parallel to said straight lines and intersecting said hub axis, and said second points on said support structure being arranged in correspondence with their respective hub first points and along a pair of second parallel lines disposed on respective sides of, and equally spaced from a second plane parallel to said second straight lines and intersecting said structure axis.

4. A piezoelectric electrical energy generator comprising a fixed support structure mounting thereon a rotatable shaft having an elongated axis of rotation, first and second substantially identical power generating sections spaced along said shaft, each said section comprising:

(a) a hub having a central axis mounted on said shaft for eccentric rotation of said hub axis around said shaft axis without rotation of said hub around its own central axis;

(b) first and second linear arrays of first supports disposed along first and second oppositely disposed edges, respectively, of said hub, said arrays being parallel to one another and equally spaced from a plane parallel to said arrays and intersecting said hub axis;

(c) first and second parallel linear arrays of second supports disposed on said support structure and parallel to one another and equally spaced from a plane parallel to said arrays of second supports and intersecting said shaft axis, each of said first supports being associated with a respective second support;

(d) a first plurality of piezoelectric elements mounted between respective first supports of said first array of first supports and associated respective second supports of said first array of second supports, and a second plurality of piezoelectric elements mounted between respective supports of said second array of first supports and associated respective second supports of said second array of said second supports;

whereby all of said first plurality of elements are simultaneously and identically variably strained in response to said hub rotation and said second plurality of elements are similarly variably strained but 180 degrees out of phase of the straining of said first plurality of elements, and

the central axis of the hub of the first section rotating around the shaft axis synchronously with the rotation of the central axis of the hub of the second section but 90 degrees out-of-phase therewith, whereby said first and second plurality of elements of said first section are variably strained 90 degrees out-of-phase with said first and second pluralities of elements of said second section for causing the sum of torques on said shaft to be zero.