Yaw rate sensor using surface acoustic wave

• US 20090133495A1
• Filed: 11/25/2008
• Published: 05/28/2009
• Est. Priority Date: 11/28/2007
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Arakawa, Kazuki, Teshigahara, Akihiko, Kano, Kazuhiko
• Granted Patent: US 8,181,521 B2
• Time in Patent Office: Days
• US Class Current: 73/504.10
• CPC Class Codes: G01C 19/5698 using acoustic waves, e.g. surface acoustic wave gyros

Abstract

A yaw rate sensor has two sets of exciting electrodes, perturbative weights and two sets of detecting electrodes on a surface of a piezoelectric substrate. The exciting electrodes excite first surface acoustic waves transmitted through the surface of the substrate in a propagation direction. The weights are oscillated by the waves and excite a second surface acoustic wave, transmitted through the surface of the substrate in a detection direction orthogonal to the propagation direction, in response to a yaw applied to the weights. The detecting electrodes measure an intensity of the second surface acoustic wave to detect the yaw rate. The sets of exciting electrodes are symmetrically placed with respect to a driving axis extending straight along the propagation direction. The group of weights is symmetric with respect to the driving axis.

Claims

1. A yaw rate sensor, comprising:

a substrate;

a group of exciting electrodes, disposed on a surface of the substrate, which excites a first surface acoustic wave and transmits the first surface acoustic wave through the surface of the substrate in a propagation direction;

a group of perturbative weights, disposed on the surface of the substrate, which is oscillated by the first surface acoustic wave in a thickness direction orthogonal to the propagation direction, generates a second surface acoustic wave excited by a Coriolis force, which is induced in response to the oscillation of the group of perturbative weights and a yaw applied to the perturbative weights, and transmits the second surface acoustic wave through the surface of the substrate in a detection direction orthogonal to both the propagation direction and the oscillation direction; and

a detecting unit, disposed on the surface of the substrate, which detects a yaw rate from an intensity of the second surface acoustic wave,

wherein the group of perturbative weights is symmetric with respect to a driving axis extending straight along the propagation direction, and the group of exciting electrodes is symmetric with respect to the driving axis.

2. The sensor according to claim 1, wherein the group of exciting electrodes has a first set of exciting electrodes placed on a first side of the driving axis in the detection direction and a second set of exciting electrodes placed on a second side of the driving axis opposite to the first side, and the sets of exciting electrodes are symmetrically placed with respect to the driving axis.

3. The sensor according to claim 2, wherein each of the exciting electrodes in the sets has a plurality of tooth portions each of which extends in the detection direction, and the tooth portions of one exciting electrode and the tooth portions of another exciting electrode in each of the sets are alternately arranged along the propagation direction.

4. The sensor according to claim 3, wherein each of the exciting electrodes in the sets has a bus bar extending in the propagation direction, the bus bar of one exciting electrode in each of the sets is connected with ends of the corresponding tooth portions facing a first side of the detection direction, and the bus bar of another exciting electrode in each of the sets is connected with ends of the corresponding tooth portions facing a second side of the detection direction opposite to the first side.

5. The sensor according to claim 4, wherein a weight area facing each set of exciting electrodes in the propagation direction and facing the detecting unit in the detection direction is partitioned into two first weight regions, through which straight lines prolonged in the propagation direction from the bus bars of the exciting electrodes in the set pass, and a second weight region placed between the first weight regions, and the perturbative weights are located in the second weight regions corresponding to the sets of exciting electrodes.

6. The sensor according to claim 5, wherein

the detecting unit has a first set of detecting electrodes and a second set of detecting electrodes,

the group of perturbative weights is symmetric with respect to an orthogonal axis extending straight along the detection direction,

the sets of detecting electrodes are symmetrically placed with respect to the orthogonal axis,

each of the detecting electrodes has a plurality of tooth portions each of which extends in the propagation direction,

the tooth portions of one detecting electrode and the tooth portions of another detecting electrode in each of the sets are alternately arranged along the detection direction,

each of the detecting electrodes in the sets has a bus bar extending in the detection direction,

the bus bar of one detecting electrode in each of the sets is connected with ends of the corresponding tooth portions facing a first side of the propagation direction,

the bus bar of another detecting electrode in each of the sets is connected with ends of the corresponding tooth portions facing a second side of the propagation direction opposite to the first side,

a second weight area facing the group of exciting electrodes in the propagation direction and facing each set of detecting electrodes in the detection direction is partitioned into two third weight regions, through which straight lines prolonged in the detection direction from the bus bars of the detecting electrodes in the set pass, and a fourth weight region placed between the third weight regions, and

the perturbative weights are located in a specific weight region in which the second weight regions overlap with the fourth weight regions corresponding to the sets of detecting electrodes.

7. The sensor according to claim 5, wherein each of the second weight regions has a first tooth alternation region ranging in the detection direction from open ends of the tooth portions of one exciting electrode to open ends of the tooth portions of another exciting electrode in the corresponding set, and the perturbative weights are located in the first tooth alternation regions.

8. The sensor according to claim 7, wherein

the detecting unit has a first set of detecting electrodes and a second set of detecting electrodes,

the group of perturbative weights is symmetric with respect to an orthogonal axis extending straight along the detection direction,

the sets of detecting electrodes are symmetrically placed with respect to the orthogonal axis,

each of the detecting electrodes has a plurality of tooth portions each of which extends in the propagation direction,

the tooth portions of one detecting electrode and the tooth portions of another detecting electrode in each of the sets are alternately arranged along the detection direction,

each of the detecting electrodes in the sets has a bus bar extending in the detection direction,

the bus bar of one detecting electrode in each of the sets is connected with ends of the corresponding tooth portions facing a first side of the propagation direction,

the bus bar of another detecting electrode in each of the sets is connected with ends of the corresponding tooth portions facing a second side of the propagation direction opposite to the first side,

a second weight area facing the group of exciting electrodes in the propagation direction and facing each set of detecting electrodes in the detection direction has a second tooth alternation region which ranges in the propagation direction from open ends of the tooth portions of one detecting electrode to open ends of the tooth portions of another detecting electrode in the corresponding set, and

the perturbative weights are located in a specific weight region in which the first tooth alternation regions overlap with the second tooth alternation regions corresponding to the sets of detecting electrodes.

9. The sensor according to claim 1, wherein the group of exciting electrodes has a first exciting electrode, a second exciting electrode symmetrically placed with the first exciting electrode with respect to the driving axis, and a third exciting electrode being symmetric with respect to the driving axis.

10. The sensor according to claim 9, wherein each of the exciting electrodes has a plurality of tooth portions each of which extends in the detection direction, the tooth portions of the first exciting electrode and a first part of the tooth portions of the third exciting electrode are alternately arranged along the propagation direction, and the tooth portions of the second exciting electrode and a second part of the tooth portions of the third exciting electrode are alternately arranged along the propagation direction.

11. The sensor according to claim 10, wherein each of the exciting electrodes has a bus bar, the bus bar of the first exciting electrode is connected with ends of the corresponding tooth portions facing a first side of the detection direction, the bus bar of the second exciting electrode is connected with ends of the corresponding tooth portions facing a second side of the detection direction opposite to the first side, the bus bar of the third exciting electrode is connected with ends of the first part of tooth portions facing the second side, and the bus bar of the third exciting electrode is connected with ends of the second part of tooth portions facing the first side.

12. The sensor according to claim 11, wherein a weight area facing the group of exciting electrodes in the propagation direction and facing the detecting unit in the detection direction is partitioned into three first weight regions, through which straight lines prolonged in the propagation direction from the bus bars of the exciting electrodes pass, and two second weight regions each of which is placed between two of the first weight regions, and the perturbative weights are located in the second weight regions.

13. The sensor according to claim 12, wherein

the group of perturbative weights is symmetric with respect to an orthogonal axis extending straight along the detection direction,

the detecting unit has a first detecting electrode, a second detecting electrode symmetrically placed with the first detecting electrode with respect to the orthogonal axis, and a third detecting electrode being symmetric with respect to the orthogonal axis,

each of the detecting electrodes has a plurality of tooth portions each of which extends in the propagation direction,

the tooth portions of the first detecting-electrode and a first part of the tooth portions of the third detecting electrode are alternately arranged along the detection direction,

the tooth portions of the second detecting electrode and a second part of the tooth portions of the third detecting electrode are alternately arranged along the propagation direction,

each of the detecting electrodes has a bus bar,

the bus bar of the first detecting electrode is connected with ends of the corresponding tooth portions facing a first side of the propagation direction,

the bus bar of the second detecting electrode is connected with ends of the corresponding tooth portions facing a second side of the propagation direction opposite to the first side,

the bus bar of the third detecting electrode is connected with ends of the first part of the tooth portions facing the second side,

the bus bar of the third detecting electrode is connected with ends of the second part of the tooth portions facing the first side,

the weight area is partitioned into three third weight regions, through which straight lines prolonged in the detection direction from the bus bars of the detecting electrodes pass, and two fourth weight regions each of which is placed between two of the third weight regions, and

the perturbative weights are located in a specific weight region in which the second weight regions overlap with the fourth weight regions.

14. The sensor according to claim 12, wherein the second regions include a first tooth alternation region ranging in the detection direction from open ends of the tooth portions of the first exciting electrode to open ends of the first part of tooth portions of the third exciting electrode, another first tooth alternation region ranging in the detection direction from open ends of the tooth portions of the second exciting electrode to open ends of the second part of tooth portions of the third exciting electrode, and the perturbative weights are located in the first tooth alternation regions.

15. The sensor according to claim 14, wherein

the group of perturbative weights is symmetric with respect to an orthogonal axis extending straight along the detection direction,

the detecting unit has a first detecting electrode, a second detecting electrode symmetrically placed with the first detecting electrode with respect to the orthogonal axis, and a third detecting electrode being symmetric with respect to the orthogonal axis,

each of the detecting electrodes has a plurality of tooth portions each of which extends in the propagation direction,

the tooth portions of the first detecting electrode and a first part of the tooth portions of the third detecting electrode are alternately arranged along the detection direction,

the tooth portions of the second detecting electrode and a second part of the tooth portions of the third detecting electrode are alternately arranged along the propagation direction,

each of the detecting electrodes has a bus bar,

the bus bar of the first detecting electrode is connected with ends of the corresponding tooth portions facing a first side of the propagation direction,

the bus bar of the second detecting electrode is connected with ends of the corresponding tooth portions facing a second side of the propagation direction opposite to the first side,

the bus bar of the third detecting electrode is connected with ends of the first part of the tooth portions facing the second side,

the bus bar of the third detecting electrode is connected with ends of the second part of the tooth portions facing the first side,

the weight area has a second tooth alternation region ranging in the propagation direction from open ends of the tooth portions of the first detecting electrode to open ends of the first part of the tooth portions of the third detecting electrode, and another second tooth alternation region ranging in the propagation direction from open ends of the tooth portions of the second detecting electrode to open ends of the second part of the tooth portions of the third detecting electrode, and

the perturbative weights are located in a specific weight region in which the first tooth alternation regions overlaps with the second tooth alternation regions.

16. The sensor according to claim 1, wherein the group of perturbative weights is symmetric with respect to an orthogonal axis extending straight along the detection direction, and the detecting unit is symmetric with respect to the orthogonal axis which extends straight along the detection direction.

17. The sensor according to claim 16, wherein the detecting unit has a first detecting member and a second detecting member to place the perturbative weights between the detecting members, and the detecting members are symmetrically placed with respect to the driving axis.

18. The sensor according to claim 17, wherein each of the detecting members has a first set of detecting electrodes and a second set of detecting electrodes, and the sets of detecting electrodes in each of the detecting members are symmetrically placed with respect to the orthogonal axis.

19. The sensor according to claim 18, wherein each of the detecting electrodes has a plurality of tooth portions each of which extends in the propagation direction, and the tooth portions of one detecting electrode and the tooth portions of another detecting electrode in each of the sets are alternately arranged along the detection direction.

20. The sensor according to claim 19, wherein each of the detecting electrodes in the detecting unit has a bus bar extending in the detection direction, the bus bar of one detecting electrode in each set is connected with ends of the corresponding tooth portions facing a first side of the propagation direction, and the bus bar of another detecting electrode in each set is connected with ends of the corresponding tooth portions facing a second side of the propagation direction opposite to the first side.

21. The sensor according to claim 20, wherein a weight area facing the group of exciting electrodes in the propagation direction and facing each set of detecting electrodes in the first detecting member in the detection direction is partitioned into two first weight regions, through which straight lines prolonged in the detection direction from the bus bars of the detecting electrodes in the set pass, and a second weight region placed between the first weight regions, and the perturbative weights are located in the second weight regions corresponding to the sets of detecting electrodes in the first detecting member.

22. The sensor according to claim 21, wherein each of the second weight regions has a first tooth alternation region ranging in the propagation direction from open ends of the tooth portions of one detecting electrode to open ends of the tooth portions of another detecting electrode in the corresponding set, and the perturbative weights are located in the first tooth alternation regions.

23. The sensor according to claim 16, wherein the detecting unit has a first detecting electrode, a second detecting electrode symmetrically placed with the first detecting electrode with respect to the orthogonal axis, and a third detecting electrode being symmetric with respect to the orthogonal axis.

24. The sensor according to claim 23, wherein each of the detecting electrodes has a plurality of tooth portions each of which extends in the propagation direction, the tooth portions of the first detecting electrode and a first part of the tooth portions of the third detecting electrode are alternately arranged along the detection direction, and the tooth portions of the second detecting electrode and a second part of the tooth portions of the third detecting electrode are alternately arranged along the propagation direction.

25. The sensor according to claim 24, wherein each of the detecting electrodes has a bus bar, the bus bar of the first detecting electrode is connected with ends of the corresponding tooth portions facing a first side of the propagation direction, the bus bar of the second detecting electrode is connected with ends of the corresponding tooth portions facing a second side of the propagation direction opposite to the first side, the bus bar of the third detecting electrode is connected with ends of the first part of tooth portions facing the second side, and the bus bar of the third detecting electrode is connected with ends of the second part of tooth portions facing the first side.

26. The sensor according to claim 25, wherein a weight area facing the group of exciting electrodes in the propagation direction and facing the detecting unit in the detection direction is partitioned into three first weight regions, through which straight lines prolonged in the detection direction from the bus bars of the detecting electrodes pass, and two second weight regions each of which is placed between two of the first weight regions, and the perturbative weights are located in the second weight regions.

27. The sensor according to claim 26, wherein the second weight regions include a first tooth alternation region ranging in the propagation direction from open ends of the tooth portions of the first detecting electrode to open ends of the first part of the tooth portions of the third detecting electrode, and another first tooth alternation region ranges in the propagation direction from open ends of the tooth portions of the second detecting electrode to open ends of the second part of the tooth portions of the third detecting electrode, and the perturbative weights are located in the first tooth alternation regions.

28. The sensor according to claim 2, wherein a first part of the perturbative weights are located to face the first set of exciting electrodes in the propagation direction, a second part of the perturbative weights are located to face the second set of exciting electrodes in the propagation direction, and the detecting unit is located between the first part of the perturbative weights and the second part of the perturbative weights.

29. The sensor according to claim 28, wherein the first part of the perturbative weights and the second part of the perturbative weights are symmetrically placed with respect to the driving axis.

30. The sensor according to claim 28, wherein the first surface acoustic wave is excited in response to oscillations of the sets of exciting electrodes at a common frequency, and phases of the oscillations of the sets of exciting electrodes are opposite to each other.

31. The sensor according to claim 28, wherein the detecting unit is symmetric with respect to the driving axis.

32. The sensor according to claim 28, wherein the first part of the perturbative weights is symmetric with respect to an orthogonal axis extending straight along the detection direction, the second part of the perturbative weights is symmetric with respect to the orthogonal axis, and the detecting unit is symmetric with respect to the orthogonal axis.

33. The sensor according to claim 1, further comprising a pair of reflectors, disposed to place the group of exciting electrodes and the perturbative weights between the reflectors, which reflect the first surface acoustic wave and form a standing wave between the reflectors.