Balanced angular accelerometer

• US 6,718,826 B2
• Filed: 02/28/2002
• Issued: 04/13/2004
• Est. Priority Date: 02/28/2002
• Status: Expired due to Fees

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Zarabadi, Seyed R., Johnson, Jack D., Jay, Ian D., Noll, Tracy A., Christenson, John C.
• Primary Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US10/085,536
• Publication Number:
  US 20030159512A1
• Time in Patent Office: 775 Days
• Field of Search: 735/140.1, 735/140.2, 735/143.2, 735/143.8
• US Class Current: 73/514.38
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01P 15/0888 for indicating angular acceleration
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

A balanced angular accelerometer is provided having a substrate, a fixed electrode with a plurality of fixed capacitive plates, and a rotational inertia mass with a central opening and substantially suspended over a cavity and including a plurality of movable capacitive plates arranged to provide a capacitive coupling with the first plurality of fixed capacitive plates. The accelerometer has a central member and an outer member fixed to the substrate. According to one embodiment, a plurality of inner support arms extend between the central member and the inertia mass and a plurality of outer support arms extend between the inertia mass and the outer member to support the mass over the cavity. According to another embodiment, one or more cut out apertures are formed in the inertia mass to compensate for a channel and signal line so as to balance the inertia mass about the center of the inertia mass.

Claims

1. An angular accelerometer comprising:

a substrate;

a fixed electrode supported on the substrate and including a first plurality of fixed capacitive plates;

a rotational inertia mass substantially suspended over a cavity and including a central opening and a plurality of movable capacitive plates arranged to provide a capacitive coupling with said first plurality of fixed capacitive plates;

a central member fixed to said substrate and located substantially in the central opening of said rotational inertia mass;

an outer member supported on the substrate and located radially outward from the rotational inertia mass;

a first plurality of support arms extending between said central member and said rotational inertia mass; and

a second plurality of support arms extending between the rotational inertia mass and the outer member, wherein the first and second plurality of support arms allow rotational movement of the rotational inertia mass upon experiencing an angular acceleration about a sensing axis.

2. The angular accelerometer as defined in claim 1 further comprising:

an input electrically coupled to one of the fixed electrode and the rotational inertia mass for receiving an input signal; and

an output electrically coupled to the other of the fixed electrode and the rotational inertia mass for providing an output signal which varies as a function of change in the capacitive coupling and is indicative of sensed angular acceleration.

3. The angular accelerometer as defined in claim 2, wherein one of said input and output is electrically coupled to said rotational inertia mass via one of said second plurality of support arms.

4. The angular accelerometer as defined in claim 1, wherein said first and second plurality of support arms each comprises a radial extending arm.

5. The angular accelerometer as defined in claim 1, wherein each of said second plurality of support arms comprises a folded semi-circular portion.

6. The angular accelerometer as defined in claim 1, wherein said first and second plurality of support arms are substantially equiangularly located.

7. The angular accelerometer as defined in claim 1, wherein said rotational inertia mass is substantially centrally located, and said first fixed electrode is radially outward from said rotational inertia mass.

8. The angular accelerometer as defined in claim 1, wherein said substrate comprises a silicon substrate.

9. The angular accelerometer as defined in claim 1, wherein said angular accelerometer is fabricated by a trench etching process.

10. The angular accelerometer as defined in claim 1, wherein said first and second plurality of support arms each comprises at least four equiangularly located support arms.

11. The angular accelerometer as defined in claim 1, wherein each of said first and second plurality of support arms are flexible so as to bend during angular acceleration about the sensing axis, and yet rigid to resist bending due to acceleration about non-sensing axes.

12. An angular accelerometer comprising:

a substrate;

a first bank of variable capacitors formed of a first plurality of fixed capacitive plates and a first plurality of movable capacitive plates;

a second bank of variable capacitors formed of a second plurality of fixed capacitive plates and a second plurality of movable capacitive plates;

a rotational inertia mass configured as a ring having a central opening and rotatable in response to angular acceleration and electrically coupled to said first and second plurality of movable capacitive plates and arranged so that said first and second plurality of movable capacitive plates form capacitive couplings with said first and second plurality of fixed capacitive plates;

a central member fixed to said substrate and centrally located within said central opening of the rotational inertia mass and separated from the rotational inertia mass;

an outer member supported on the substrate and located radially outward from the rotational inertia mass;

a first plurality of support arms extending between said central member and said rotational inertia mass; and

a second plurality of support arms extending between said rotational inertia mass and said outer member, wherein the first and second plurality of support arms support said rotational inertia mass and movable capacitive plates relative to said first and second fixed capacitive plates and further allow rotational movement of the rotational inertia mass upon experiencing an angular acceleration about a sensing axis.

13. The angular accelerometer as defined in claim 12 further comprising:

a first input electrically coupled to said first plurality of fixed capacitive plates;

a second input electrically coupled to said second plurality of fixed capacitive plates; and

an output electrically coupled to said rotational inertia mass for sensing an output signal indicative of angular acceleration in response to rotation of said rotational inertia mass.

14. The angular accelerometer as defined in claim 13, wherein said output is electrically coupled to said rotational inertia mass via one of said second plurality of support arms.

15. The angular accelerometer as defined in claim 12, wherein said first and second plurality of support arms each comprises a radial extending arm.

16. The angular accelerometer as defined in claim 12, wherein each of said second plurality of support arms comprises a folded semi-circular portion.

17. The angular accelerometer as defined in claim 12, wherein said first and second plurality of support arms are substantially equiangularly located.

18. The angular accelerometer as defined in claim 12, wherein said substrate comprises a silicon substrate.

19. The angular accelerometer as defined in claim 12, wherein said angular accelerometer is fabricated by a trench etching process.

20. The angular accelerometer as defined in claim 12, wherein said first and second plurality of support arms each comprises at least four equiangularly located support arms.

21. A micromachined angular accelerometer comprising:

a substrate;

a fixed electrode supported on the substrate and including a first plurality of fixed capacitive plates;

a rotational ring having a central opening and including a plurality of movable capacitive plates at the outer perimeter and arranged to provide a capacitive coupling with the first plurality of fixed capacitive plates, said rotational ring being suspended over a cavity and rotationally movable relative to said fixed electrode;

a central member fixed to said substrate and located within the central opening of the rotational ring;

an outer member fixed to said substrate and located radially outward from said rotational ring;

a first plurality of support arms extending between said central member and the rotational ring;

a second plurality of support arms extending between said rotational ring and said outer member, wherein the first and second plurality of support arms support said rotational ring relative to said fixed electrode and allow rotational movement of the rotational ring upon experiencing an angular acceleration about a sensing axis;

an input electrically coupled to one of the fixed electrode and the rotational ring for receiving an input signal; and

an output electrically coupled to the other of the fixed electrode and the rotational ring for providing an output signal which varies as a function of change in the capacitive coupling and is indicative of angular acceleration.

22. The angular accelerometer as defined in claim 21, wherein one of the input and output is electrically coupled to the rotational ring via one of the second plurality of support arms.

23. The angular accelerometer as defined in claim 21, wherein each of said first and second plurality of support arms comprises an integrally formed support arm formed by removing material on opposite sides of said support arm.

24. The angular accelerometer as defined in claim 21, wherein each of said second plurality of support arms comprises a folded semi-circular portion.

25. The angular accelerometer as defined in claim 21, wherein said first and second plurality of support arms each comprises a radial extending support arm.

26. The angular accelerometer as defined in claim 21, wherein each of said first and second plurality of support arms comprises two pairs of oppositely opposed support arms, wherein said two pairs are arranged approximately ninety degrees relative to one another.