MEMS accelerometer with proof masses moving in anti-phase direction normal to the plane of the substrate

• US 8,973,439 B1
• Filed: 02/24/2014
• Issued: 03/10/2015
• Est. Priority Date: 12/23/2013
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Baldasarre, Leonardo, Thompson, Matthew J.
• Primary Examiner(s): WILLIAMS, HEZRON
• Assistant Examiner(s): Redmann, Gregory J
• Application Number:
  US14/188,173
• Time in Patent Office: 379 Days
• Field of Search: 735/141.2
• US Class Current: 73/504.12
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0837 the mass being suspended so as to only allow movement perpendicular to the plane of the substrate, i.e. z-axis sensor
• CPC Class Codes: G01P 2015/086 using a torsional suspension spring

Abstract

A sensor is disclosed. The sensor includes a substrate and at least two proof masses. The sensor also includes a flexible coupling between the at least two proof masses and the substrate. The at least two coupling proof masses move in an anti-phase direction normal to a plane of the substrate in response to acceleration.

Claims

1. A sensor comprising:

a substrate; and

a mechanical structure, wherein the mechanical structure includes

at least two proof masses including a first proof mass and a second proof mass, and

a flexible coupling between the at least two proof masses and the substrate;

wherein the at least two proof masses move in an anti-phase direction normal to a plane of the substrate in response to acceleration of the sensor via an unbalancing torque.

2. The sensor of claim 1, wherein the flexible coupling further comprises:

at least one anchor; and

a torsional system;

the torsional system further including an anchoring spring connecting the at least one anchor and a first rotational lever;

a first torsional spring connects the first proof mass to the rotational lever with a first lever length; and

a second torsional spring connects the second proof mass to the first rotational lever with a second lever length.

3. The sensor of claim 2, wherein the first lever length and the second lever length of the first rotational lever are different.

4. The sensor of claim 3, wherein the flexible coupling further includes a second anchoring spring connecting the at least one anchor and a second rotational lever;

a third torsional spring connects the first proof mass to the second rotational lever with a third lever length; and

a fourth torsional spring connects the second proof mass to the second rotational lever with a fourth lever length;

wherein the second rotational lever rotates counter to the rotation of the first rotational lever in response to acceleration of the sensor.

5. The sensor of claim 4, wherein the third lever length and the fourth lever length of the second rotational lever are different.

6. The sensor of claim 4, further comprising magnetic material, wherein the magnetic material is on any of the at least two proof masses, on the first rotational lever, and the second rotational levers.

7. The sensor of claim 2, further comprising a translational system wherein the translational system includes a first translating spring connecting the at least one anchor to the first proof mass and a second translating spring connecting the at least one anchor to the second proof mass, wherein the first and second translating springs allow motion of the first and second proof masses in a direction normal to the plane of the substrate.

8. The sensor of claim 7, wherein each translating spring comprises a second rotational lever and at least two rotating spring;

wherein one of the rotating springs are coupled to the proof mass and other connected to the anchor.

9. The sensor of claim 2, wherein a displacement of the first rotational lever is measured by the transducer via capacitive sensing.

10. The sensor of claim 1, further comprising a transducer for measuring motion of the mechanical structure relative to the substrate.

11. The sensor of claim 10, wherein the motion of the at least two proof masses relative to the substrate is measured by the transducer via capacitive sensing.

12. The sensor of claim 11, wherein the one or more electrodes are located on the substrate.

13. The sensor of claim 11, further comprising a cap, wherein the mechanical structure is located between the cap and the substrate, wherein the one or more electrodes are located on the cap facing the mechanical structure.

14. The sensor of claim 10, wherein the displacement of the coupling springs is measured by the transducer via capacitive sensing.

15. The sensor of claim 1, wherein motion of the at least two proof masses relative to each other are measured by a transducer.

16. The sensor of claim 15, where in the transducer is a capacitive sensor.

17. The sensor of claim 1, wherein the unbalancing torque comprises a difference between a weight of the first proof mass and a weight of the second proof mass.

18. The sensor of claim 1, wherein the flexible coupling includes a lever, wherein the lever has a first length from an anchoring spring to the first proof mass and a second length from the anchoring spring to the second proof mass.

19. The sensor of claim 18, wherein the unbalancing torque comprises either a difference in the first length and the second length or by a difference in a first mass lever product comprising the weight of the first proof mass and the first lever length and a second mass lever product comprising the weight of the second proof mass and the second lever length.

20. A sensor comprising:

a substrate; and

a mechanical structure, wherein the mechanical structure includes

at least two proof masses,

a flexible coupling between the at least two proof masses and the substrate,

a magnetic material;

wherein the mechanical structure rotates around a first axis in response to a magnetic field;

wherein the at least two proof masses move in an anti-phase direction normal to a plane of the substrate in response to acceleration of the sensor via an unbalancing torque.

21. The sensor of claim 20, further comprising a transducer to measure out-of-plane motion of the mechanical structure;

and

wherein motion due acceleration and motion induced by magnetic field are measured by the transducer.

22. The sensor of claim 20, further comprises a signal processor to alter configuration of the transducer to switch between measuring motion due to acceleration and motion induced by magnetic field.