Inertial sensor

• US 8,943,890 B2
• Filed: 07/31/2012
• Issued: 02/03/2015
• Est. Priority Date: 08/12/2008
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Jeong, Heewon, Fukuda, Hiroshi
• Primary Examiner(s): Williams, Hezron E
• Assistant Examiner(s): ZHONG, XIN Y
• Application Number:
  US13/563,557
• Publication Number:
  US 20120291546A1
• Time in Patent Office: 917 Days
• Field of Search: 735/040.4, 735/040.8, 735/041.2, 735/040.2
• US Class Current: 73/504.04
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

One inertial sensor detects an acceleration in a driving direction as well as an angular rate about one axis and an acceleration in a detecting direction at the same time. A driving-direction acceleration detecting unit is provided to members vibrating in mass members on the left and right via an elastic body. In this manner, when an acceleration is applied in the driving direction, the mass members on the left and right normally vibrated with a same amplitude and in opposite phases have displacement amounts in a same phase, and the driving-direction acceleration detecting unit detects the displacement amounts in the same phase as a capacitance change, thereby detecting the acceleration in the driving direction.

Claims

1. An inertial sensor comprising:

a basement layer having a main surface;

a first drive frame connected to the basement layer via a first elastic body having higher rigidity in a second direction than in a first direction, the first direction being parallel to the main surface and the second direction crossing the first direction;

a first Coriolis frame connected to the first drive frame via a second elastic body having lower rigidity in the second direction than in the first direction;

a first driving unit which vibrates the first drive frame in the first direction;

a second drive frame connected to the basement layer via a third elastic body having higher rigidity in the second direction than in the first direction;

a second Coriolis frame connected to the second drive frame via a fourth elastic body having lower rigidity in the second direction than in the first direction;

a second driving unit which vibrates the second drive frame in the first direction; and

a plurality of driving-direction acceleration detecting units, in which a first driving-direction acceleration detecting unit is connected to the first drive frame via a fifth elastic body, and a second driving-direction acceleration detecting unit is connected to the second drive frame via a sixth elastic body,

wherein the first driving unit and the second driving unit vibrate the first drive frame and the second drive frame in opposite phases in the first direction.

2. The inertial sensor according to claim 1, further comprising:

first and second fixed electrodes,

wherein the first driving-direction acceleration detecting unit includes a first movable electrode forming a first capacitance between the first fixed electrode,

wherein the second driving-direction acceleration detecting unit includes a second movable electrode forming a second capacitance between the second electrode, and

wherein an acceleration of the first direction is detected by taking a difference between a capacitance change of the first capacitance and a capacitance change of the second capacitance.

3. The inertial sensor according to claim 1,

wherein the first and the second driving units are each formed by a capacitive element arranged in a comb-teeth shape and are configured to vibrate the first and second drive frames in the first direction based on an electrostatic attractive force applied to the capacitive element.

4. The inertial sensor according to claim 1,

wherein an elastic body connecting the first drive frame and the second drive frame is fixed to the basement layer.

5. The inertial sensor according to claim 1,

wherein an elastic body connecting the first drive frame and the second drive frame is not fixed to the basement layer.

6. The inertial sensor according to claim 1,

wherein the basement layer is an SOI substrate.

7. The inertial sensor according to claim 1,

wherein the first drive frame, the first Coriolis frame, the first driving unit, the second driving unit, the second Coriolis frame, and the second driving unit are formed of conductive silicon, conductive poly-silicon, or a metal.

8. The inertial sensor according to claim 1, further comprising:

a first detecting unit that detects a displacement amount of the first Coriolis frame in the second direction based on the vibration of the Coriolis frame in the second direction; and

a second detecting unit that detects a displacement amount of the second Coriolis frame in the second direction based on the vibration of the Coriolis frame in the second direction.

9. The inertial sensor according to claim 8,

wherein the first and the second detecting units are each formed by a capacitive element arranged in a comb-teeth shape, and

wherein a displacement amount in the second direction is detected based on a capacitance change of the capacitive element.

10. The inertial sensor according to claim 8,

wherein an angular rate and acceleration in the second direction are detected based on the displacement amount in the second direction detected by the first detecting unit and the displacement amount in the second direction detected by the second detecting unit.

11. The inertial sensor according to claim 1, further comprising:

a first detection frame that is connected to the first Coriolis frame and configured to vibrate in the second direction in a same phase with the vibration in the second direction of the first Coriolis frame;

a first detecting unit that detects a displacement amount of the first detection frame in the second direction based on the vibration in the second direction;

a second detection frame that is connected to the second Coriolis frame and configured to vibrate in the second direction in a same phase with the vibration in the second direction of the second Coriolis frame; and

a second detecting unit that detects a displacement amount of the second detection frame in the second direction based on the vibration in the second direction.

12. The inertial sensor according to claim 11,

wherein the first and the second detecting units are each formed by a capacitive element arranged in a comb-teeth shape, and

wherein a displacement amount in the second direction is detected based on a capacitance change of the capacitive element.

13. The inertial sensor according to claim 11,

wherein an angular rate and acceleration in the second direction are detected based on the displacement amount in the second direction detected by the first detecting unit and the displacement amount in the second direction detected by the second detecting unit.