Inertia sensor

• US 9,182,421 B2
• Filed: 05/25/2011
• Issued: 11/10/2015
• Est. Priority Date: 07/06/2010
• Status: Active Grant

• Current Assignee: Hitachi Astemo Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi Automotive Systems Limited (Hitachi, Ltd.)
• Inventors: Jeong, Heewon, Degawa, Munenori, Hayashi, Masahide
• Primary Examiner(s): Kwok, Helen
• Application Number:
  US13/807,284
• Publication Number:
  US 20130098152A1
• Time in Patent Office: 1,630 Days
• Field of Search: 735/041.2, 735/041.4, 735/040.2, 735/040.4
• US Class Current: 1/1
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 19/574 the devices having two sensing masses in anti-phase motion
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames

Abstract

This invention is directed to provision of high-performance inertial sensor that can sustain SNR even in an environment where vibration disturbance exists. A vibration type inertial sensor comprises: two deadweights (2, 3); means (C1, C2, C3, C4, +vd, −vd) for displacing the two dead weights in the anti-phase; two sets of electrodes (C5, C6, C7, C8) for detecting, as capacitance changes, the displacements of the two dead weights; and a C/V converting unit (53) for converting the capacitance changes of the electrodes to electric signals. In the vibration type inertial sensor, a set of electrodes (e.g., C5 and C8), which exhibit an increased electrostatic capacitance therebetween in the case where the two dead weights (2, 3) are displaced in the anti-phase, are electrically connected to each other, and a set of electrodes (e.g., C6 and C7), which exhibit a reduced electrostatic capacitance therebetween in the foregoing case, are electrically connected to each other, and further these sets of electrodes are connected to the C/V converting unit (53).

Claims

1. A vibration type inertial sensor comprising:

two dead weights;

two sets of driving electrodes applying driving signals to the two dead weights, the signals for displacing the two dead weights in anti-phase with each other along a first direction;

two sets of first electrodes detecting displacements of the respective two dead weights as electrostatic capacitance changes; and

a first C/V converting unit converting the capacitance changes of the first electrodes into electrical signals, wherein

the first electrodes in a set whose electrostatic capacitance changes in a third direction when the two dead weights are displaced in anti-phase in the first direction are electrically connected with each other, the first electrodes of the other set whose electrostatic capacitance changes in a fourth direction opposite to the third direction when the two dead weights are displaced in anti-phase in the first direction are electrically connected with each other, and the respective sets of the first electrodes are connected with the first C/V converting unit.

2. The inertial sensor according to claim 1, wherein the two sets of the first electrodes detect the displacements of the respective two dead weights in the first direction as electrostatic capacitance changes.

3. The inertial sensor according to claim 2 further comprising:

two sets of second electrodes detecting displacements of the respective two dead weights along a second direction different from the first direction as electrostatic capacitance changes; and

a second C/V converting unit converting the capacitance changes of the second electrodes into electrical signals, wherein

the second electrodes in a set whose electrostatic capacitance changes in a fifth direction when the two dead weights are displaced in anti-phase in the second direction are electrically connected with each other, the second electrodes in the other set whose electrostatic capacitance changes in a sixth direction opposite to the fifth direction when the two dead weights are displaced in anti-phase in the second direction are electrically connected with each other, and the respective sets of the second electrodes are connected with the second C/V converting unit.

4. The inertial sensor according to claim 3 further comprising two sets of servo electrodes controlling oscillations in the second direction by electrostatic force, wherein,

the servo electrodes in a set whose electrostatic capacitance changes in a seventh direction when the two dead weights are displaced in anti-phase in the second direction are electrically connected with each other, and the servo electrodes in the other set whose electrostatic capacitance changes in a eighth direction opposite to the seventh direction when the two dead weights are displaced in anti-phase in the second direction are electrically connected with each other.

5. The inertial sensor according to claim 1, wherein the two dead weights are mechanically coupled with each other to form a tuning fork structure having a path for oscillation energy.

6. The inertial sensor according to claim 5, wherein the lowest vibration mode frequency of the two dead weights in the first direction, in the second direction different from the first direction, or in both the directions is an in-phase vibration mode, and the second lowest vibration mode is an anti-phase vibration mode.

7. The inertial sensor according to claim 5, wherein each of the two dead weights includes:

a driven element supported by supporting beams that are easy to be displaced in the first direction and hard to be displaced in the second direction different from the first direction; and

a Coriolis element suspended from the driven element with detection beams that are hard to be displaced in the first direction and easy to be displaced in the second direction, the Coriolis element being displaced in the second direction in proportion to applied angular velocity while following the motion of the driven element.

8. The inertial sensor according to claim 7, wherein the lowest vibration mode frequency of the two driven elements of the two dead weights is an in-phase vibration mode in the first direction, and the second lowest vibration mode is an anti-phase vibration mode.

9. The inertial sensor according to claim 7, wherein the lowest vibration mode frequency of the two Coriolis elements of the two dead weights is a mode of translational vibration in the second direction.

10. The inertial sensor according to claim 7, wherein the driven element is in the shape of a letter Y and has three ends at which the supporting beams are placed.

11. The inertial sensor according to claim 7, wherein the first electrodes form a comb finger structure.

12. The inertial sensor according to claim 3, wherein the two sets of the first electrodes detect displacements of the respective two dead weights in the second direction different from the first direction as electrostatic capacitance changes.

13. The inertial sensor according to claim 1 further comprising a high frequency vibration damping device for damping high frequency vibration disturbance components.