Micromechanical speed sensor

• US 6,898,972 B2
• Filed: 08/06/2001
• Issued: 05/31/2005
• Est. Priority Date: 08/18/2000
• Status: Expired due to Fees

• Current Assignee: EADS Deutschland GmbH (Airbus SE)
• Original Assignee: EADS Deutschland GmbH (Airbus SE)
• Inventors: Schalk, Josef, Voss, Ralf, Sassen, Stefan, Gleissner, Tanjo, Bauer, Karin, Lentner, Konrad
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US10/344,925
• Publication Number:
  US 20040011130A1
• Time in Patent Office: 1,394 Days
• Field of Search: 735/041.2, 735/041.4
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: Y10T 29/49007 Indicating transducer

Abstract

A micromechanical rotation speed sensor with a gimbals-mounted structure capable of vibration includes two vibration elements (4, 5) which are swivelled about two axes (A, B) oriented perpendicular toward each other. An excitation unit in the form of an electrode (7) sets the first vibration element (4) into a vibration about the first axis of rotation (A). A read out unit in the form of a read out electrode (8) records a tipping or vibration of the second vibration element (5) about the second axis of rotation (B) as a measure for the rotation speed of the sensor. Additional mass elements (6a, 6b) which are symmetrically aligned are situated on the upper side (2a) and the underside (2b) of the first vibration element (4) which form a rocker. The sensor is manufactured of at least three individually processed wafers which are finally joined together and form a top part (1), a midsection (2) and a bottom part (3).

Claims

1. A micromechanical rotation speed sensor comprising:

a first vibration element which is swivelled about a first axis,

a second vibration element which is swivelled about a second axis, said second axis oriented perpendicular toward the first axis;

an excitation unit for placing the first vibration element in vibration about the first axis;

a read out unit for recording vibrations of the second vibration element about the second axis; and

at least two additional mass elements fastened on the first vibration element which are oriented symmetrically in relation to a plane defined by the first and second axis, and a gap separation between said first vibration element and a fixed member for an excitation vibration of the first vibration element is greater than a gap separation between said second vibration member and said fixed member for a read out vibration of the second vibration element; and

a top portion hermetically sealed with said fixed member wherein each of said top portion and fixed member contain a recess for a respective one of said two additional mass elements.

2. The micromechanical rotation speed sensor according to claim 1, wherein the additional mass elements are manufactured separate from the first and second vibration element whereby form, size and/or material of the additional mass elements are selected in order to at least one of determine and influence sensor parameters.

3. The micromechanical rotation speed sensor according to claim 1, wherein the mass elements are axially symmetrical elements which are fastened on upper side and an underside of the first vibration element, whereby the mass elements are shaped as one of spheres, rectangular prisms, cylinders, cones, pyramids and prisms.

4. The micromechanical rotation speed sensor according to claim 1, wherein the first vibration element is a rocker and the second vibration element is a frame, whereby the rocker and the frame form a gimbals-mounted structure capable of vibration which is fastened in a retaining structure.

5. The micromechanical rotation speed sensor according to claim 1, wherein the additional mass elements are magnetic.

6. The micromechanical rotation speed sensor according to claim 1, wherein he additional mass elements are made of a material which has a higher density than the material of the first and second vibration element.

7. The micromechanical rotation speed sensor according to claim 1, wherein said sensor includes at least three combined wafers which form a bottom part, a midsection and a top part.

8. The micromechanical rotation speed sensor according to claim 7, wherein at least one of the bottom part and/or the top part is manufactured of alkali-containing glass wafers, whereby at least one of the wafers is provided with an electrode structure.

9. The micromechanical rotation speed sensor according to claim 7, wherein the first and second vibration element are constructed in the midsection whose upper side and underside are processed.

10. The micromechanical rotation speed sensor according to claim 1, wherein a gap separation between adjacent wafer parts or wafers, which makes possible a deflection of the first and/or second vibration element, is small in relation to the lateral extension of excitation and/or read out electrodes, whereby the ratio between gap separation and lateral electrode extension is smaller than 1:

10.

11. The micromechanical rotation speed sensor according to claim 10, wherein the ratio between gap separation is smaller than 1:

50.

12. The micromechanical rotation speed sensor according to claim 10, wherein the ratio between gap separation is smaller than 1:

100.

13. The micromechanical rotation speed sensor according to claim 1 characterized in that the additional mass elements are made of metal.

14. The micromechanical rotation sensor according to claim 1, wherein said sensor is a single crystal silicon, whereby the first and second vibration element are made of a single wafer.

15. The micromechanical rotation speed sensor according to claim 1, wherein at least one of the first and second vibration element is constructed in a non-rectangular manner.

16. The micromechanical rotation speed sensor according to claim 1, wherein the first and/or second vibration element has edges, which border on one another at an angle of more than 90 degrees.

17. The rotation speed sensor according to claim 1, wherein a frequency of operation of the actuating unit vibration and a frequency of operation of the sensor unit vibration are the lowest eigenmodes of the first and/or second vibration elements.

18. The micromechanical rotation speed sensor according to claim 1, wherein a surface ratio between the second vibration element and the first vibration element is greater than 5:

1.

19. The micromechanical rotation speed sensor according to claim 18, wherein the surface ratio is greater than 10:

1.

20. The micromechanical rotation speed sensor according to claim 1, further including a metallic coating for forming an electrode which is covered with a dielectric layer.

21. The micromechanical rotation speed sensor according to claim 1, which includes one or more electrodes surrounded by a closed printed conductor.

22. The micromechanical rotation speed sensor according to claim 1, further including an ohmic pressure contact for connection of a wafer which forms a midsection to a further wafer which forms one of a bottom and top part.

23. The micromechanical rotation speed sensor according to claim 1, further including a sensor interior which is hermetically sealed whereby buried printed conductors are provided for contacting electrodes in the sensor interior.

24. The micromechanical rotation speed sensor according to claim 1, wherein a common center of gravity of the additional mass elements lies in a point of intersection of the first axis and the second axis.