Actuator

• US 20060125346A1
• Filed: 12/14/2005
• Published: 06/15/2006
• Est. Priority Date: 12/15/2004
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Yoda, Mitsuhiro
• Granted Patent: US 7,420,315 B2
• Time in Patent Office: Days
• US Class Current: 310/309
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: H02N 1/002 Electrostatic motors

Abstract

An actuator having a rotation central axis includes: an insulative frame; movable comb electrodes having first electrode teeth; a movable portion between the movable comb electrodes; supporting portions on the frame supporting the movable comb electrodes and the movable portion; fixed comb electrodes on the frame corresponding to the movable comb electrodes and provided with second electrode teeth; first elastic connecting portions connecting the movable comb electrodes to the supporting portions so each movable comb electrode can rotate around the rotation central axis; and second elastic connecting portions connecting the movable portion to the movable comb electrodes so that the movable portion can rotate around the rotation central axis. Each movable comb electrode is driven by an alternating voltage between each fixed comb electrode and movable comb electrode. Part of the first electrode teeth overlaps part of the second electrode teeth when no alternating voltage is applied.

Claims

1. An actuator having a rotation central axis, the actuator comprising:

a frame having an insulative property;

a pair of movable comb electrodes spaced apart from each other, each of the pair of movable comb electrodes having a side surface and being provided with at least one set of first electrode teeth which are arranged side by side with a predetermined interval on the side surface thereof;

a movable portion provided between the pair of movable comb electrodes;

a pair of supporting portions provided on the frame for supporting the pair of movable comb electrodes and the movable portion;

at least one pair of fixed comb electrodes provided on the frame at the positions which respectively correspond to the pair of movable comb electrodes, each of the at least one pair of fixed comb electrodes being provided with one set of second electrode teeth which are arranged side by side with a predetermined interval so as to be cooperatively associated with the first electrode teeth of the corresponding movable comb electrode;

at least one pair of first elastic connecting portions which respectively connect the pair of movable comb electrodes to the pair of supporting portions so that each of the movable comb electrodes can rotate around the rotation central axis of the actuator with respect to the corresponding supporting portion; and

at least one pair of second elastic connecting portions which respectively connect the movable portion to the pair of movable comb electrodes so that the movable portion can rotate around the rotation central axis of the actuator in accordance with the rotation of the movable comb electrodes,

wherein each of the pair of movable comb electrodes is driven by means of Coulomb force generated by applying an alternating voltage between each of the fixed comb electrodes and the corresponding movable comb electrode, whereby the movable portion rotate, and

wherein the first electrode teeth of each of the pair of movable comb electrodes and the second electrode teeth of each of the corresponding at least one pair of fixed comb electrodes are configured so that at least a part of the first electrode teeth of each of the movable comb electrodes overlaps with a part of the second electrode teeth of the corresponding fixed comb electrode in a state where no alternating voltage is applied therebetween.

2. The actuator as claimed in claim 1, wherein at least a part of the first electrode teeth of each of the movable comb electrodes overlaps with a part of the second electrode teeth of the corresponding fixed comb electrode in a state where no alternating voltage is applied therebetween when viewed from the rotation central axis of the actuator.

3. The actuator as claimed in claim 2, wherein one of the tip of each of the first electrode teeth and the tip of each of the second electrode teeth completely overlaps with the other.

4. The actuator as claimed in claim 1, wherein each of the first electrode teeth has a first width in a direction perpendicular to the frame and each of the second electrode teeth has a second width in a direction perpendicular to the frame, in which the first width of each of the first electrode teeth is larger than the second width of each of the second electrode teeth when viewed from the rotation central axis of the actuator.

5. The actuator as claimed in claim 4, wherein, in the case where the first width of each of the first electrode teeth is defined as A (μ

m) and the second width of each of the second electrode teeth is defined as B (μ

m), then A and B satisfy the relation;

1.0≦

A/B≦

3.0.

6. The actuator as claimed in claim 4, wherein each of the first electrode teeth has upper and lower edges in the width direction thereof and each of the second electrode teeth has upper and lower edges in the width direction thereof, in which either the upper edge or the lower edge of each of the first electrode teeth is substantially aligned with the corresponding edge of each of the second electrode teeth in a state where no alternating voltage is applied therebetween when viewed from the rotation central axis of the actuator.

7. The actuator as claimed in claim 1, wherein the at least one pair of fixed comb electrodes and the pair of movable comb electrodes are formed by subjecting a first base material to predetermined processes.

8. The actuator as claimed in claim 7, wherein the pair of supporting portions, the movable portion, the at least one pair of first elastic connecting portions and the at least one pair of second elastic connecting portions are formed by subjecting a base material common to the first base material to predetermined processes.

9. The actuator as claimed in claim 7, wherein the at least one pair of fixed comb electrodes and the pair of movable comb electrodes are separately formed by subjecting the first base material to patterning so that each of the at least one set of first electrode teeth does not come into contact with the corresponding second tooth.

10. The actuator as claimed in claim 7, wherein the first base material is formed of silicon.

11. The actuator as claimed in claim 1, wherein the frame is constructed from a laminated structure which comprises an intermediate layer formed of silicon oxide and a second base material formed of silicon and laminated on the intermediate layer.

12. The actuator as claimed in claim 1, wherein the frame is provided with an opening at a portion corresponding to the movable portion and/or the pair of movable comb electrodes.

13. The actuator as claimed in claim 1, wherein each of the pair of movable comb electrodes has an electrode base and the at least one set of first electrode teeth, and the at least one set of first electrode teeth are provided at one end of the electrode base of each of the pair of movable comb electrodes in a direction substantially perpendicular to the rotation central axis.

14. The actuator as claimed in claim 13, wherein the at least one set of first electrode teeth include two sets of first electrode teeth, in which each set of the two sets of first electrode teeth is respectively provided at both ends of the electrode base of each of the pair of movable comb electrodes in a direction substantially perpendicular to the rotation central axis.

15. The actuator as claimed in claim 1, wherein one or more through-hole is formed in each of the pair of movable comb electrodes.

16. The actuator as claimed in claim 1, further comprising a light reflecting portion provided on the movable portion.

17. The actuator as claimed in claim 1, wherein, in the case where the spring constant of the first elastic connecting portion is defied as k₁ and the spring constant of the second elastic connecting portion is defined as k₂, k₁ and k₂ satisfy the relation:

k₁>

k₂.

18. The actuator as claimed in claim 1, wherein the actuator is of the type which employs a two-degree-of-freedom vibration system, and the frequency of the alternating voltage is set so as to be substantially the same as a lower resonance frequency of resonance frequencies of the two-degree-of-freedom vibration system at which the pair of movable comb electrodes and the movable portion resonate.

19. The actuator as claimed in claim 1, wherein at least one of the pair of first elastic connecting portions and the pair of second elastic connecting portions includes a piezoresistive element.

20. An actuator having a rotation central axis, the actuator comprising:

a frame having an insulative property;

a movable comb electrode provided with one set of first electrode teeth which are placed side by side with a predetermined interval, the movable comb electrode having an opening;

a movable portion provided in the opening of the movable comb electrode;

a pair of supporting portions provided on the frame for supporting the movable comb electrode and the movable portion;

two fixed comb electrodes provided on the frame at the positions which corresponds to the movable comb electrode in a direction substantially perpendicular to the rotation central axis, each of the two fixed comb electrodes being provided with one set of second electrode teeth which are arranged side by side with a predetermined interval so as to be cooperatively associated with the at least one set of first electrode teeth of the movable comb electrode;

at least one pair of first elastic connecting portions which respectively connect the movable comb electrode to the pair of supporting portions so that the movable comb electrode can rotate around the rotation central axis of the actuator with respect to the pair of supporting portions; and

at least one pair of second elastic connecting portions which respectively connect the movable portion to the movable comb electrode so that the movable portion can rotate around the rotation central axis of the actuator in accordance with the rotation of the movable comb electrode,

wherein the movable comb electrode is driven by means of Coulomb force generated by applying an alternating voltage between each of the fixed comb electrodes and the movable comb electrode, whereby the movable portion rotate, and

wherein the first electrode teeth of the movable comb electrode and the second electrode teeth of each of the fixed comb electrodes are configured so that at least a part of the first electrode teeth of the movable comb electrode overlaps with a part of the second electrode teeth of each of the fixed comb electrodes in a state where no alternating voltage is applied therebetween.