Angular velocity sensor

• US 5,908,986 A
• Filed: 03/03/1997
• Issued: 06/01/1999
• Est. Priority Date: 03/01/1996
• Status: Expired due to Fees

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Mitamura, Takeshi
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US08/811,464
• Time in Patent Office: 820 Days
• Field of Search: 73/504.12, 73/504.02, 73/504.03, 73/504.04, 73/514.32, 73/DIG. 1, 73/1.37, 73/511, 361/280
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

An angular velocity sensor comprises a silicon substrate, a vibration mass formed separate from the silicon substrate on a principal surface of the silicon substrate to vibrate in directions along first and second orthogonal axes, supporting portions for supporting the vibration mass and positioned symmetrically with respect to the first axis and the second axis and having equal spring constants in directions along the first and second axes, drive electrodes and driving means for driving the vibration mass in the direction along the first axis, and detection electrodes and detecting means for detecting displacement of the vibration mass in the direction along the second axis. The drive and/or detection electrodes of the angular velocity sensor are split into a plurality of capacitors which permit a plurality of voltage values to be applied to capacitors. Accordingly, when the vibration mass is rotated around a third axis perpendicular to the principal surface of the substrate while vibrating in the direction along the first axis, an angular velocity around the third axis can be measured by detecting a Coriolis force generated in the direction along the second axis.

Claims

1. An angular velocity sensor comprising:

(a) a substrate;

(b) a vibration mass positioned separate from said substrate in such a manner that said vibration mass is made possible to vibrate in at least a direction parallel to a principal surface of said substrate;

(c) at least two plate-like supporting portions positioned symmetrically with respect to a direction bisecting an angle between a first axis and a second axis both constituting an orthogonal coordinate system on a surface which is parallel to said principal surface of said substrate and includes said first axis and said second axis, said at least two plate-like supporting portions having equal spring constants in directions along said first axis and said second axis, and one end of each of said at least two plate-like supporting portions being fixed to said vibration mass and other end thereof being fixed to said substrate;

(d) drive electrodes consisting of vibration drive electrodes fixed to said vibration mass and stationary drive electrodes fixed to said substrate;

(e) detection electrodes consisting of vibration detection electrodes fixed to said vibration mass and stationary detection electrodes fixed to said substrate;

(f) driving means for driving said vibration mass to vibrate in said first axis direction by supplying voltage to said drive electrodes; and

(g) detecting means for detecting voltage derived by said detection electrodes and detecting a Coriolis force caused in a direction along said second axis by rotation around a third axis perpendicular to said principal surface of said substrate.

2. The angular velocity sensor of claim 1, wherein each of said at least two plate-like supporting portions comprises a plurality of elastic structural bodies which are aligned symmetrically with respect to said direction bisecting said angle between said first axis and said second axis.

3. The angular velocity sensor of claim 1, wherein said vibration drive electrodes and stationary drive electrodes are opposed to each other in said direction along said first axis to constitute parallel plate type capacitors.

4. The angular velocity sensor of claim 1, wherein said vibration detection electrodes and stationary detection electrodes are opposed to each other in said direction along said first axis to constitute parallel plate type capacitors.

5. The angular velocity sensor of claim 3, further comprising:

drive controlling means for detecting vibration amplitude in a drive state of said vibration mass, and controlling vibration amplitude in said direction along said first axis to be kept constant.

6. The angular velocity sensor of claim 4, further comprising:

reference electric capacitors connected to said stationary detection electrodes;

wherein reading signals are input to said stationary detection electrodes via said reference electric capacitors, and displacement of said vibration mass is detected according to signals generated by said stationary detection electrodes.

7. The angular velocity sensor of claim 5, further comprising:

reference electric capacitors connected to said stationary drive electrodes;

wherein drive voltage is input to said stationary drive electrodes via said reference electric capacitors, and vibration amplitude is detected according to voltage generated by said stationary drive electrodes and drive voltage is controlled by said drive controlling means to keep said amplitude constant.

8. The angular velocity sensor of claim 1, wherein said substrate is formed of a semiconductor substrate, and said vibration mass and said at least two plate-like supporting portions are formed of a polysilicon.

9. The angular velocity sensor of claim 8, wherein said driving means and said detecting means are integrated on a same semiconductor substrate.

10. The angular velocity sensor of claim 1, wherein said substrate, said vibration mass, and said at least two plate-like supporting portions are formed of a single crystal semiconductor.

11. The angular velocity sensor of claim 1, wherein said substrate is formed of a semiconductor substrate, and said vibration mass and said at least two plate-like supporting portions are formed of a metal stacked by electroplating.

12. The angular velocity sensor of claim 10, wherein said driving means and said detecting means are integrated on a same semiconductor substrate.

13. The angular velocity sensor of claim 11, wherein said driving means and said detecting means are integrated on a same semiconductor substrate.

14. The angular velocity sensor of claim 1, wherein a pair of angular velocity sensors set forth in claim 1 are provided such that respective vibration masses are driven in opposite phase, and an angular velocity of rotation around a third axis is measured based on a difference between outputs detected in a direction along said second axis and an acceleration in a direction along said second axis is measured based on a sum of said outputs detected in said direction along said second axis.

15. The angular velocity sensor of claim 1, wherein said drive electrodes consisting of at least four electrode pairs, each electrode pair consisting of said vibration drive electrodes and said stationary drive electrodes, and at least two electrode pairs among said four electrode pairs are caused to vibrate in a direction along said first axis by electrostatic attractive force generated by applying simultaneously drive voltages V1, V2 to said at least two electrode pairs, and then, under an assumption that electrostatic capacitances between said at least two electrode pairs are set to C1 and C2 respectively, information concerning vibration amplitude of said vibration mass in said direction along said first axis is detected based on a sum of said electrostatic capacitances C1 and C2 and information concerning displacement of said vibration mass caused by said Coriolis force in said direction along said second axis is detected based on a difference between said electrostatic capacitances C1 and C2.

16. The angular velocity sensor of claim 15, further comprising:

compensating means for detecting information concerning said displacement of said vibration mass caused by said Coriolis force in said direction along said second axis based on said difference between said electrostatic capacitance C1 and C2, adjusting respectively amplitudes of drive voltages V1 and V2 according to said information derived, and canceling said Coriolis force affecting to said vibration mass.

17. The angular velocity sensor of claim 15, further comprising:

drive controlling means for detecting information concerning said vibration amplitude of said vibration mass in said direction along said first axis based on said sum of said electrostatic capacitance C1 and C2, adjusting respectively said amplitudes of said drive voltages V1 and V2 according to said information derived, and holding said vibration amplitude of said vibration mass to be constant.

18. The angular velocity sensor of claim 15, wherein said drive voltages applied to said vibration mass are addition signals consisting of voltage varying at a first frequency with time and voltage varying at a second frequency higher than said first frequency with time, and reference electric capacitors C_ref are connected to said stationary drive electrodes constituting said at least two electrode pairs, respectively, and wherein said drive voltages are applied to respective stationary drive electrodes via said reference electric capacitors C_ref respectively, then said electrostatic capacitance C1 and C2 are measured by detecting potentials on respective connection points between said reference electric capacitors C_ref and said stationary drive electrodes in synchronism with said first frequency and said second frequency.

19. The angular velocity sensor of claim 16, wherein said drive voltages applied to said vibration mass are addition signals consisting of voltage varying at a first frequency with time and voltage varying at a second frequency higher than said first frequency with time, and reference electric capacitors C_ref are connected to said stationary drive electrodes constituting said at least two electrode pairs, respectively, and wherein said drive voltages are applied to respective stationary drive electrodes via said reference electric capacitors C_ref respectively, then said electrostatic capacitance C1 and C2 are measured by detecting potentials on respective connection points between said reference electric capacitors C_ref and said stationary drive electrodes in synchronism with said first frequency and said second frequency.

20. The angular velocity sensor of claim 17, wherein said drive voltages applied to said vibration mass are addition signals consisting of voltage varying at a first frequency with time and voltage varying at a second frequency higher than said first frequency with time, and reference electric capacitors C_ref are connected to said stationary drive electrodes constituting said at least two electrode pairs, respectively, and wherein said drive voltages are applied to respective stationary drive electrodes via said reference electric capacitors C_ref respectively, then said electrostatic capacitance C1 and C2 are measured by detecting potentials on respective connection points between said reference electric capacitors C_ref and said stationary drive electrodes in synchronism with said first frequency and said second frequency.

21. The angular velocity sensor of claim 15, wherein said drive voltages V1, V2 vary at a first frequency with time and has a first time period during when no drive voltage is applied but a read voltage V_c is applied, and reference electric capacitors C_ref are connected to said stationary drive electrodes constituting said at least two electrode pairs, respectively, and wherein said drive voltages V1, V2 are applied via said reference electric capacitors C_ref respectively so that the read voltage V_c is applied to said stationary drive electrodes, then said electrostatic capacitance C1 and C2 are measured by detecting potentials on respective connection points between said reference electric capacitors C_ref and said stationary drive electrodes in synchronism with said read voltage.

22. The angular velocity sensor of claim 16, wherein said drive voltages applied to said vibration mass vary at a first frequency with time and has a first time period during when no drive voltage is applied but a read voltage is applied, and reference electric capacitors C_ref are connected to said stationary drive electrodes constituting said at least two electrode pairs, respectively, and wherein said drive voltages are applied to respective stationary drive electrodes via said reference electric capacitors C_ref respectively so that the read voltage V_c is applied to said stationary drive electrodes, then said electrostatic capacitance C1 and C2 are measured by detecting potentials on respective connection points between said reference electric capacitors C_ref and said stationary drive electrodes in synchronism with said read voltage.

23. The angular velocity sensor of claim 17, wherein said drive voltages applied to said vibration mass vary at a first frequency with time and has a first time period during when no drive voltage is applied but a read voltage is applied, and reference electric capacitors C_ref are connected to said stationary drive electrodes constituting said at least two electrode pairs, respectively, and wherein said drive voltages are applied to respective stationary drive electrodes via said reference electric capacitors C_ref respectively so that the read voltage V_c is applied to said stationary drive electrodes, then said electrostatic capacitance C1 and C2 are measured by detecting potentials on respective connection points between said reference electric capacitors C_ref and said stationary drive electrodes in synchronism with said read voltage.

24. The angular velocity sensor of claim 15, wherein said drive voltages applied to said vibration mass vary at a first frequency with time and has a first time period during when no drive voltage is applied, and reference electric capacitors C_ref are connected to said stationary drive electrodes constituting said at least two electrode pairs, respectively, and wherein said drive voltages are applied to respective stationary drive electrodes via said reference electric capacitors C_ref respectively and a read voltage is applied to said vibration mass during said first time period, then said electrostatic capacitance C1 and C2 are measured by detecting potentials on respective connection points between said reference electric capacitors C_ref and said stationary drive electrodes in synchronism with said read voltage.

25. The angular velocity sensor of claim 16, wherein said drive voltages applied to said vibration mass vary at a first frequency with time and has a first time period during when no drive voltage is applied, and reference electric capacitors C_ref are connected to said stationary drive electrodes constituting said at least two electrode pairs, respectively, and wherein said drive voltages are applied to respective stationary drive electrodes via said reference electric capacitors C_ref respectively and a read voltage is applied to said vibration mass during said first time period, then said electrostatic capacitance C1 and C2 are measured by detecting potentials on respective connection points between said reference electric capacitors C_ref and said stationary drive electrodes in synchronism with said read voltage.

26. The angular velocity sensor of claim 17, wherein said drive voltages applied to said vibration mass vary at a first frequency with time and has a first time period during when no drive voltage is applied, and reference electric capacitors C_ref are connected to said stationary drive electrodes constituting said at least two electrode pairs, respectively, and wherein said drive voltages are applied to respective stationary drive electrodes via said reference electric capacitors C_ref respectively and a read voltage is applied to said vibration mass during said first time period, then said electrostatic capacitance C1 and C2 are measured by detecting potentials on respective connection points between said reference electric capacitors C_ref and said stationary drive electrodes in synchronism with said read voltage.

27. The angular velocity sensor of claim 1, wherein at least one of said stationary drive electrodes and said stationary detection electrodes have a structure which is fixed to said substrate at two locations or is fixed to said substrate, and

further comprising a stopper for limiting a displacement of said vibration mass in a direction along said third axis.

28. The angular velocity sensor of claim 27, wherein said vibration mass includes a plurality of cavities in which at least one of said stationary drive electrodes and said stationary detection electrodes are provided, capacitors are formed by inner walls of said plurality of cavities and said stationary drive electrodes or said stationary detection electrodes opposing to said inner walls.

29. The angular velocity sensor of claim 27, wherein said stopper is a canopy-like structure fixed with the same structural body as said vibration mass.

30. The angular velocity sensor of claim 27, wherein said stopper is a canopy-like structure made of silicon nitride.

31. The angular velocity sensor of claim 29, wherein said stopper is a canopy-like structure made of polysilicon.