Electromechanical actuator, method for electrical excitation of an electromechanical actuator and ultrasonic motor

Patent metadata

Field	Value
Publication number	US-11545609-B2
Application number	US-201816772853-A
Country	US
Kind code	B2
Filing date	Dec 14, 2018
Priority date	Dec 15, 2017
Publication date	Jan 3, 2023
Grant date	Jan 3, 2023

Abstract

Disclosed is electromechanical actuator for ultrasonic motor in the shape of an n-sided regular polygon plate with n being equal to or greater than five. The polygon plate has two larger main surfaces and at least five smaller side surfaces connecting the main surfaces with each other. Two electrodes are arranged on one of the main surfaces and are electrically isolated from each other by a linear isolation area. One electrode is arranged on the other of the main surfaces. The polygon plate comprises an electromechanical material that undergoes a deformation when electric voltage is applied to the electrodes. The material of the electromechanical actuator comprises a single or polycrystalline piezoelectric ceramic with piezoelectric charge constant d31 differing from piezoelectric charge constant d32 both in sign and in value. The piezoelectric charge constants d31 and d32 define a first and second main deformation direction of the actuator perpendicular to each other. The orientation of the linear isolation area is parallel to either deformation direction.

First claim

The invention claimed is:

1. An electromechanical actuator for an ultrasonic motor, the electromechanical actuator comprising:
a plate which is formed of two main surfaces extending along each other and being oriented contrary to each other, the plate having side surfaces extending transversely to the two main surfaces and connecting the two main surfaces with each other;
two electrodes which are isolated from each other by an isolation area and which are arranged symmetrically to each other on a first of the two main surfaces thereby defining a symmetry axis; and
at least one electrode arranged on a second of the two main surfaces, the plate comprising an electromechanical material that undergoes a deformation under the influence of an electric voltage;
wherein the material of the electromechanical actuator comprises a single crystalline piezoelectric ceramic with its piezoelectric charge constant d31 differing from its piezoelectric charge constant d32 both in sign and in value, with the piezoelectric charge constant d31 defining a first main deformation direction of the electromechanical actuator and with the piezoelectric charge constant d32 defining a second main deformation direction of the electromechanical actuator, and with the first main deformation and the second main deformation direction being arranged transversely to each other, wherein an orientation of the symmetry axis is parallel to the first main deformation direction or to the second main deformation direction.

2. The electromechanical actuator according to claim 1 , wherein the electromechanical material of the plate that undergoes a deformation:
receives a first excitation voltage at a first of the two electrodes which are arranged on the first main surface so as to use the first of the two electrodes as an excitation electrode, wherein a second of the two electrodes arranged on the first main surface is kept floating; and
receives a second excitation voltage having a phase difference of 180° with respect to the first excitation voltage at the electrode arranged on the second main surface, so as to use the electrode arranged on the second main surface as a common electrode.

3. The electromechanical actuator according to claim 1 , wherein the isolation area extends entirely between the two electrodes.

4. The electromechanical actuator according to claim 3 , wherein the two main surfaces have a shape of an n-sided polygon plate with n being equal to or greater than three.

5. The electromechanical actuator according to claim 3 , wherein the two main surfaces have a shape of an n-sided regular polygon plate with n being equal to or greater than five.

6. The electromechanical actuator according to claim 3 , wherein the two main surfaces extend parallel to each other.

7. The electromechanical actuator according to claim 3 , wherein the electromechanical actuator comprises at least one friction device which is arranged on at least one of the side surfaces wherein the friction device comprises a friction surface for contacting an element to be driven.

8. The electromechanical actuator according to claim 7 , wherein the friction device comprises a friction element which is made of a homogenous material.

9. An ultrasonic motor, comprising the electromechanical actuator according to claim 3 and an element to be driven, wherein the electromechanical actuator comprises a contact surface section which interacts with the element to be driven for moving the same relative to the electromechanical actuator.

10. The electromechanical actuator according to claim 1 , wherein the two main surfaces have a shape of an n-sided polygon plate with n being equal to or greater than three.

11. The electromechanical actuator according to claim 1 , wherein the two main surfaces have a shape of an n-sided regular polygon plate with n being equal to or greater than five.

12. The electromechanical actuator according to claim 1 , wherein the two main surfaces extend parallel to each other.

13. The electromechanical actuator according to claim 1 , wherein the electromechanical actuator comprises at least one friction device which is arranged on at least one of the side surfaces wherein the friction device comprises a friction surface for contacting an element to be driven.

14. The electromechanical actuator according to claim 13 , wherein the friction device comprises a friction element which is made of a homogenous material.

15. An ultrasonic motor, comprising the electromechanical actuator according to claim 1 and an element to be driven, wherein the electromechanical actuator comprises a contact surface section which interacts with the element to be driven for moving the same relative to the electromechanical actuator.

16. A method for electrical excitation of an electromechanical actuator, comprising:
providing the electromechanical actuator comprising a plate which is formed of two main surfaces extending along each other and being oriented contrary to each other and which is formed of side surfaces extending transversely to the two main surfaces and connecting the two main surfaces with each other, two electrodes which are isolated from each other by an isolation area and which are arranged symmetrically to each other on a first of the two main surfaces thereby defining a symmetry axis, and at least one electrode arranged on a second of the two main surfaces, wherein the plate comprises an electromechanical material that undergoes a deformation under the influence of an electric voltage, wherein the material of the electromechanical actuator comprises a single crystalline piezoelectric ceramic with its piezoelectric charge constant d 31 differing from its piezoelectric charge constant d 32 both in sign and in value, with the piezoelectric charge constant d 31 defining a first main deformation direction of the electromechanical actuator and with the piezoelectric charge constant d 32 defining a second main deformation direction of the electromechanical actuator, and with the first main deformation and the second main deformation direction being arranged transversely to each other, wherein an orientation of the symmetry axis is parallel to the first main deformation direction or to the second main deformation direction;
applying a first excitation voltage to a first of the two electrodes which are arranged on the first main surface so as to use the first of the two electrodes as an excitation electrode, wherein a second of the two electrodes arranged on the first main surface is kept floating; and
applying a second excitation voltage having a phase difference of 180° with respect to the first excitation voltage to the electrode arranged on the second main surface, so as to use the electrode arranged on the second main surface as a common electrode.

Assignees

• Phys Instrumente Pi Gmbh & Co Kg

Inventors

• Koc Burhanettin
• Delibas Bülent

Classifications

• H02N2/002 Primary

  using only longitudinal or radial modes · CPC title

• H02N2/0075 Primary

  Electrical details, e.g. drive or control circuits or methods · CPC title

• H01L41/187

  Electricity · mapped topic

• H01L41/0986 Primary

  Electricity · mapped topic

• H10N30/206 Primary

  using only longitudinal or thickness displacement, e.g. d33 or d31 type devices · CPC title