Multiaxial acceleration sensor and angular velocity sensor

• US 8,117,912 B2
• Filed: 03/26/2009
• Issued: 02/21/2012
• Est. Priority Date: 09/18/2008
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kawakubo, Takashi, Nagano, Toshihiko, Nishigaki, Michihiko
• Primary Examiner(s): WILLIAMS, HEZRON
• Assistant Examiner(s): Shabman, Mark A
• Application Number:
  US12/411,861
• Publication Number:
  US 20100064804A1
• Time in Patent Office: 1,062 Days
• Field of Search: None
• US Class Current: 73/504.03
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01P 15/0922 of the bending or flexing mode type
• CPC Class Codes: G01P 15/14 by making use of gyroscopes gyroscopes per se G01C19/00
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass

Abstract

In a angular rate sensor, a weight and a base are connected directly through piezoelectric bimorph detectors and piezoelectric bimorph exciters each having a bent portion. When acceleration is applied to the weight, the weight is displaced so as to deform the piezoelectric bimorph detectors. Due to this deformation, charges generated in the piezoelectric bimorph detectors are detected so as to detect acceleration. If an angular rate is applied to the weight when the weight is vibrated by the piezoelectric bimorph exciters, Coriolis force is generated in the weight so as to deform the piezoelectric bimorph detectors. Due to this deformation, charges generated in the piezoelectric bimorph detectors are detected so as to detect the angular rate.

Claims

1. A triaxial accelerometer comprising:

a weight to which an acceleration is applied;

a base having a hollow space which allows the weight to move;

a plurality pairs of piezoelectric bimorph detectors having one ends connected to the base and other ends connected to the weight so as to support the weight movably with respect to the acceleration, which are arranged in a plane having first and second axes perpendicularly crossed on the weight, the plurality pairs of piezoelectric bimorph detectors including

first pair of piezoelectric bimorph detectors arranged symmetrically with respect to the first axis,

second pair of piezoelectric bimorph detectors arranged symmetrically with respect to the second axis, and

third and fourth pairs of the piezoelectric bimorph detectors arranged symmetrically with respect to the first and second axes,

wherein each of the piezoelectric bimorph detectors is so shaped as to have first and second straight portions linearly extended from the one end and the other end, respectively, and bent portions coupling the first and second straight portions and extended in a bent shape from the straight portions, and

each of the piezoelectric bimorph detectors has a deformable laminated structure having first, second and third electrodes and first and second piezoelectric films which are disposed between the first and second electrodes, and the second and third electrodes, respectively, the first, second and third electrodes generating voltages depending on a deformation of the laminated structure which is produced due to the acceleration applied to the weight; and

a detection circuit which detects each of three dimensional components of the acceleration from the voltages.

2. The accelerometer according to claim 1, wherein the bent portion of the piezoelectric bimorph detector is formed as to have a frame shape.

3. The accelerometer according to claim 1, wherein the piezoelectric bimorph detector includes first and second parts, and each of the first, second and third electrodes includes a pair of electrode plates extended into each of the first and second parts, the first electrode in the first portion, the second electrode in the second part and the third electrode in the first part are connected electrically through a via hole formed in the piezoelectric film, and the first electrode in the second part, the second electrode in the first part and the third electrode in the second part are connected electrically through the via hole formed in the piezoelectric film.

4. The accelerometer according to claim 1, wherein the first piezoelectric film and the second piezoelectric film are polarized in a thickness direction and formed of aluminum nitride (AlN) or zinc oxide (ZnO).

5. A biaxial angular rate sensor comprising:

a weight to which one or both of an acceleration and a Coriolis force are applied;

a base having a hollow space which allows the weight to move;

first and second pairs of piezoelectric bimorph detectors having one ends connected to the base and other ends connected to the weight so as to support the weight movably with respect to the acceleration and/or the Coriolis force, which are arranged in a plane having first and second axes perpendicularly crossed on the weight, wherein the first pair of piezoelectric bimorph detectors are arranged symmetrically with respect to the first axis, the second pair of piezoelectric bimorph detectors are arranged symmetrically with respect to the second axis, and each of the piezoelectric bimorph detectors is so shaped as to have first and second straight portions linearly extended from the one end and the other end, respectively, and first bent portions coupling the first and second straight portions and extended in a bent shape from the first and second straight portions;

third and fourth pairs of piezoelectric bimorph exciters having one ends connected to the base and other ends connected to the weight so as to support the weight, wherein the piezoelectric bimorph exciters are arranged in the plane having the first and second axes, the third pair of piezoelectric bimorph exciters are arranged symmetrically with respect to the first axis, the fourth pair of piezoelectric bimorph exciters are arranged symmetrically with respect to the second axis, and each of the piezoelectric bimorph exciters is so shaped as to have third and fourth straight portions linearly extended from the one end and the other end, respectively, and second bent portions coupling the third and fourth straight portions and extended in a bent shape from the third and fourth straight portions;

wherein each of the piezoelectric bimorph detectors and the piezoelectric bimorph exciters has a deformable laminated structure having first, second and third electrodes and first and second piezoelectric films which are disposed between the first and second electrodes, and the second and third electrodes, respectively, the first, second and third electrodes of the piezoelectric bimorph detectors generating voltages depending on a deformation of the laminated structure which is produced due to the acceleration applied to the weight, and each of the piezoelectric bimorph exciters is deformed due to an application of AC voltage so that each of the piezoelectric bimorph exciter vibrates the weight so as to generates the Coriolis force with the angular rate around the first and second axes of the weight; and

a detection circuit which detects the acceleration and/or the angular rate acting around the first and second axes from the voltage.

6. The angular rate sensor according to claim 5, further comprising two pairs of fifth and sixth piezoelectric bimorph detectors to detect an acceleration in a third axis direction, the third axis intersecting the intersection and being perpendicular to the virtual plane, wherein the angular rate sensor detects each component of the angular rate around the first and second axes and/or each component of the first, second and third axes of the acceleration.

7. The angular rate sensor according to claim 5, wherein the first and second bent portions are formed in a frame shape.

8. The angular rate sensor according to claim 5, wherein each of the piezoelectric bimorph detector and the piezoelectric bimorph exciter includes first and second parts and the first electrode, the second electrode and the third electrode include a pair of electrode plates extended into each of the first and second portions, the first electrode in the first part, the second electrode in the second part and the third electrode in the first part are connected electrically through a via hole formed in the piezoelectric film, and the first electrode in the second part, the second electrode in the first part and the third electrode in the second part are connected electrically through the via hole formed in the piezoelectric film.

9. The angular rate sensor according to claim 5, wherein the first piezoelectric film and the second piezoelectric film are polarized in a thickness direction and formed of aluminum nitride (AlN) or zinc oxide (ZnO).

10. The angular rate sensor according to claim 5, wherein the detection circuit comprises a frequency filter to separate a component originating from the acceleration and a component originating from the angular rate from the detection signal.