Double bimorph electromechanical element

• US 6,437,485 B1
• Filed: 12/20/2000
• Issued: 08/20/2002
• Est. Priority Date: 12/20/2000
• Status: Expired due to Term

• Current Assignee: Piezomotor Uppsala AB
• Original Assignee: Piezomotor Uppsala AB
• Inventors: Johansson, Stefan
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US09/739,906
• Publication Number:
  US 20020074901A1
• Time in Patent Office: 608 Days
• Field of Search: 310/330, 310/331, 310/332, 310/328, 310/366
• US Class Current: 310/332
• CPC Class Codes: H02N 2/0015 using only bending modes
• CPC Class Codes: H02N 2/021 using intermittent driving, e.g. step motors, piezoleg motors
• CPC Class Codes: H10N 30/2041 Beam type
• CPC Class Codes: H10N 30/2043 connected at their free ends, e.g. parallelogram type

Abstract

The present invention discloses motors using electromechanical, preferably piezoelectric, elements (30). The element (30) comprises at least two movable parts or displacement portions (32A, 32B) interconnected by a passive part (31). Each displacement section (32A, 32B) comprises at least one bimorph (33A, 33B), where the active volumes extend in parallel out from the passive part (31), and so are the electrodes (12) arranged between the electromechanical layers. The displacement portions (32A, 32B) are positioned in substantially the same plane and parallel to the body (20) to be moved. Contact portions are arranged at the central passive part (31) and at the displacement portions (32A, 32B). In one embodiment, the central contact portion is an actuating surface (34C) and the other are attaching portions (36A, 36B) for attachment to a stator (24). In another embodiment, the central contact portion is an attaching portion and the other are actuating surfaces. The actuating surfaces (34C) are in both cases movable relative to the attaching portions (36A, 36B) in two dimensions.

Claims

1. An electromechanical motor, comprising:

a stator part (24), a body (20) to be moved, and at least one monolithic electromechanical element (30);

said monolithic electromechanical element (30) having a general elongated shape, extending substantially parallel to a main displacement direction (X) of said body (20);

said monolithic electromechanical element (30) comprising a first displacement portion (32A) and a second displacement portion (32B) interconnected by a passive section (31);

said first displacement portion (32A) and said second displacement portion (32B) in turn comprising a first bimorph section (33A) and a second bimorph section (33B), respectively;

said first and second bimorph sections extending in an elongation direction of said monolithic electromechanical element (30) and having at least two active volumes each (14A, 14B, 16A, 16B) and electrodes (12) for activation of said active volumes (14A, 14B, 16A, 16B);

said active volumes (14A, 14B, 16A, 16B) having at least one electromechanical layer each;

a perpendicular to a main surface of said electromechanical layers and said electrodes, respectively, being arranged substantially perpendicular to a surface of said body, on which said monolithic electromechanical element acts;

said passive section (31) having an actuating surface (34C);

said first displacement portion (33A) and said second displacement portion (33B) having an attaching portion (36A, 36B) each arranged at a distance from said passive section (31); and

said active volumes (14A, 14B, 16A, 16B) being activatable in at least two different combinations, whereby said actuating surface (34C) is movable with respect to said attaching portions (36A, 36B) in a two-dimensional space (X, Z).

2. The electromechanical motor according to claim 1, wherein each of said first and second displacement portions being separately and restorably contractable in the main displacement direction to move said actuating surface in the main displacement direction.

3. The electromechanical motor according to claim 1, wherein said attaching portions (36A, 36B) being substantially fixed to the stator (24) with respect to motion in said main displacement direction (X) of said body (20).

4. The electromechanical motor according to claim 1, wherein said electromechanical element has a general beam shape, having said attachment portions (36A, 36B) in the vicinity of both ends (35B, 35D) thereof, said actuating surface (34C) being arranged substantially in the center part of said beam.

5. The electromechanical motor according to claim 1, wherein said passive section (31) comprises a lever (44), said actuating surface (34C) being arranged at a tip of said lever (44), providing a translation of said actuating surface (34C) by a rotation of said passive section (31).

6. The electromechanical motor according to claim 1, wherein said electromechanical element has a general circular arc shape.

7. The electromechanical motor according to claim 6, wherein said electromechanical layers and said electrodes are arranged substantially parallel to a tangential plane of said circular arc shape.

8. The electromechanical motor according to claim 6, wherein said electromechanical layers and said electrodes being arranged substantially perpendicular to a tangential plane of said circular arc shape.

9. The electromechanical motor according to claim 1, wherein each of said first and second displacement portions (32A, 32B) comprises at least two bimorph sections (33A, 33C;

33B, 33D), abutted edge to edge, whereby each of said first and second displacement portions has at least four active volumes (60A-D;

60E-H).

10. The electromechanical motor according to claim 1, wherein said actuating surface comprises friction increasing geometrical structures (49).

11. The electromechanical motor according to claim 1, wherein an electrode (40D) between two said electromechanical layers in said first displacement portion (32A) is connected to ground and an electrode (40A) between two said electromechanical layers in said second displacement portion (32B) is connected to a voltage corresponding to a maximum value of an exciting voltage of said electromechanical elements (U).

12. The electromechanical motor according to claim 1, wherein said electromechanical layers comprise a hard piezoelectric material and said electromechanical layers are pre-polarized in the same direction in all said active volumes.

13. The electromechanical motor according to claim 1, wherein said electromechanical element (30) operates by repetitive small steps relative said body (20).

14. The electromechanical motor according to claim 1, wherein said stator comprises a resilient member (52) pressing said electromechanical elements towards said body (20), said resilient member (52) being a metallized flexible printed circuit board.

15. The electromechanical motor according to claim 1, wherein portions (47A, 47B) of said stator part (24) to which said electromechanical elements (30) are attached are easily tiltable.

16. The electromechanical motor according to claim 15, wherein said portions of said stator part to which said electromechanical elements are attached are tabs of a flexible material (47A, 47B).

17. The electromechanical motor according to claim 1, wherein said electromechanical elements (30) are easily tiltable relative attaching portions (49A, 49B) of said stator part (24).

18. The electromechanical motor according to claim 17, wherein said attaching portions of said electromechanical elements are attached to solder bumps (49A, 49B) on said stator part (24).

19. The electromechanical motor according to claim 18, further comprising metal vias (51) in said stator part connected to said solder bumps (49A, 49B).

20. An electromechanical motor, comprising:

a stator with a metallized flexible circuit board;

an electromechanical element comprising first and second bimorph sections and a passive section that is between said first and second bimorph sections, said passive element comprising an actuating surface; and

said first bimorph section at a distal end thereof in turn comprising a first attachment portion that attaches said distal end of said first bimorph section to said stator, and said second bimorph section at a distal end thereof in turn comprising a second attachment portion that attaches said distal end of said second bimorph section to said stator,

said metallized flexible circuit board pressing said electromechanical element toward a body to be moved by said motor.

21. An electromechanical motor, comprising:

a stator having a circuit board with two flexible tabs on a surface thereof;

an electromechanical element comprising first and second bimorph sections, and a passive section that is between said first and second bimorph sections, said passive element in turn comprising an actuating surface; and

said first bimorph section at a distal end thereof in turn comprising a first attachment portion that attaches said distal end of said first bimorph section to one of said two tabs and said second bimorph section at a distal end thereof in turn comprising a second attachment portion that attaches said distal end of said second bimorph section to the other of said two tabs.

22. The motor of claim 21, further comprising a metal film on said tabs that is stiffer than said tabs.