Micromechanical acceleration or coriolis rotation-rate sensor

• US 6,062,082 A
• Filed: 09/18/1997
• Issued: 05/16/2000
• Est. Priority Date: 06/30/1995
• Status: Expired due to Term

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Guenther, Gero, Funk, Karsten, Laermer, Franz, Schilp, Andrea
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): Kwok, Helen C.
• Application Number:
  US08/913,598
• Time in Patent Office: 971 Days
• Field of Search: 73/504.08, 73/504.03, 73/504.04, 73/504.12, 73/514.29, 73/514.37, 73/514.38, 73/514.32, 73/514.16, 310/308, 310/309, 310/338
• US Class Current: 73/514.16
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure

Abstract

An acceleration sensor, particularly a Coriolis rotation-rate sensor, having a swinging structure that is movably suspended on a substrate (base) and can be deflected due to an acceleration effect, the sensor further having an arrangement for generating a planar swinging movement of the swinging structure, particularly a rotational swinging movement, and an evaluating arrangement for detecting a deflection of the swinging structure that is stipulated by acceleration, particularly for detecting a Coriolis acceleration. The swinging structure (12) is rotatably suspended so as to perform a planar swinging movement, and should perform a planar, rotational swinging movement.

Claims

1. Acceleration sensor, particularly a Coriolis rotation-rate sensor, having

a substrate (22) (base) that has a bearing point (24),

a swinging structure (14, 16, 18, 20) rotatably suspended at the bearing point (24) for executing a planar swinging movement,

means for generating the planar swinging movement of the swinging structure, and

evaluating means for detecting an acceleration-stipulated deflection of the swinging structure, particularly for detecting a Coriolis acceleration;

and wherein the swinging structure (14, 16, 18,

     20) is connected to the bearing point (24) by springs (32,

     34) extending on a radius from the bearing point (24), and the springs (32,

     34) have a large height (h) in relation to their width (b), so interfering accelerations can already be mechanically suppressed directly at the acceleration sensor (10).

2. Acceleration sensor according to claim 1, wherein the swinging structure (12) is formed by two swinging masses (14, 16) disposed rotation-symmetrically with respect to the bearing point (24), with the masses being rigidly coupled to one another by webs (18, 20).

3. Acceleration sensor according to claim 2, wherein the swinging masses (14, 16) are respectively formed by a cylinder section (26) whose outer circumference (30) and inner circumference (28) have a radius (R_a, R_i) that extends around the bearing point (24).

4. Acceleration sensor according to claim 2, wherein the webs (18, 20) that connect the swinging masses (14, 16) are respectively connected to the bearing point (24) by a respective said spring (32, 34) extending on a radius of the swinging structure (12).

5. Acceleration sensor according to claim 2, wherein the swinging masses (14, 16) have an electrostatic comb drive (38).

6. Acceleration sensor according to claim 5, wherein the comb drive (38) has movable combs (40) that are disposed at end faces (36) of the swinging masses (14, 16) oriented in the circumferential direction of the swinging structure (12), with the combs meshing with combs (42) that are fixedly disposed on the substrate (22).

7. Acceleration sensor according to claim 2 wherein the swinging structure (12) has a total of four comb structures (38, 44), of which two are connected as an electrostatic comb drive (38) and two are connected as a capacitive read out (44).

8. Acceleration sensor according to claim 2, wherein an electronic position regulation (62) acting in the plane of the swinging movement, that is, laterally, is associated with the swinging structure (12).

9. Acceleration sensor according to claim 8, wherein the electronic position regulation (62) is formed by diametrically-opposite comb structures (68) disposed at outer circumferences (30) of the swinging masses (14, 16).

10. Acceleration sensor according to claim 2, wherein electrodes (54, 56) are disposed beneath the swinging masses (14, 16), with the electrodes forming a capacitive evaluation means with the swinging masses (14, 16) and serving in the detection of a see-saw movement (out-of-plane) of the swinging structure (12) that is stipulated by a rotation rate.

11. Acceleration sensor according to claim 10, wherein an electronic position regulation is used to detect the see-saw movement.

12. Acceleration sensor according to claim 1, wherein a natural frequency of out-of-plane torsional swinging (detection mode) already lies above a natural frequency of the torsion in the plane of the swinging movement due to suitable mechanical fastening of the springs (32, 34) to the swinging structure (12).

13. Acceleration sensor according to claim 10, wherein the electrode (54, 56) respectively disposed beneath a swinging mass (14, 16) has a smaller circle-segment surface than the swinging mass (14, 16).

14. Acceleration sensor according to claim 2, wherein the swinging masses (14, 16) are electrically contacted via the bearing point (24).

15. Acceleration sensor according to claim 2, wherein the swinging masses (14, 16) are electrically contacted by contact connections acting externally on the webs (18, 20).

16. Acceleration sensor according to claim 15, wherein the contact connections are formed by extremely-soft springs (78, 80) disposed in the planar swinging plane of the swinging structure (12).

17. Acceleration sensor according to claim 2, wherein electrical contacting of the swinging masses is effected via a polysilicon layer (buried contact paths or capacitor surfaces) buried in the substrate.

18. Acceleration sensor according to claim 2, wherein electrical contacting of the swinging masses is effected via buried, diffused zones in the substrate, diffused contact paths or diffused capacitor surfaces ("buried layer" contacting technique).

19. Acceleration sensor according to claim 2 wherein the length of the springs is short relative to the height of the springs.

20. Acceleration sensor according to claim 2 wherein there are two of said springs which extend radially and symetrically from the bearing point in opposite directions.