Inertial Sensor

• US 20130133422A1
• Filed: 08/08/2011
• Published: 05/30/2013
• Est. Priority Date: 08/11/2010
• Status: Active Grant

• Current Assignee: Hitachi Automotive Systems Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi Automotive Systems Limited (Hitachi, Ltd.)
• Inventors: Yamanaka, Kiyoko, Jeong, Heewon, Nakamura, Toshiaki, Hayashi, Masahide
• Granted Patent: US 9,229,025 B2
• Time in Patent Office: Days
• US Class Current: 73/504.03
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups

Abstract

In order to provide an inertial sensor capable of suppressing a wrong diagnosis even in an adverse environment such that sudden noise occurs, an inertial sensor is provided with a movable part (105), a first detection unit (C1, C2) for detecting the amount of displacement of the movable part (105), a forced vibration means (503, C3, C4) for forcedly vibrating the movable part (105) by applying a diagnosis signal, a physical quantity calculation unit (502) for calculating the physical quantity from a detection signal from the first detection unit (C1, C2), and an abnormality determination unit (504) for determining the presence or absence of the abnormality for the physical quantity using the diagnosis signal obtained via the first detection unit (C1, C2), and is used within a vehicle, the inertial sensor further comprising a second sensor (510) mounted in the same vehicle and connected to the abnormality determination unit (504).

Claims

1. An inertial sensor, comprising:

a first substrate;

a first cavity formed on the first substrate;

a first fixed part formed in the first cavity;

a first elastically deformed part formed in the cavity and connected to the fixed part;

a first movable part formed in the first cavity and connected to the elastically deformed part;

a first capacity sensing element which includes a first capacitative element that mutually opposes a first fixed electrode formed in the first cavity and a first movable electrode formed in the movable part and which outputs the variation of the capacity of the first capacitative element caused when the movable part is displaced by external force;

a first physical quantity calculation terminal connected to a first physical quantity calculating device that calculates the physical quantity of the external force based upon the variation of the capacity output from the first capacity sensing element;

a forced oscillation generating device which includes a second capacitative element that mutually opposes a second fixed electrode formed in the first cavity and a second movable electrode formed in the movable part, which includes a terminal for applying a diagnostic signal for applying a diagnostic signal between the second fixed electrode and the second movable electrode and which generates electrostatic force between the second fixed electrode and the second movable electrode by applying a diagnostic signal to the terminal for applying the diagnostic signal and forcedly oscillates them;

an abnormality determination device which is indirectly connected to the first physical quantity calculation terminal and which judges whether the first capacity sensing element is abnormal or not based upon forced oscillation generated in the forced oscillation generating device;

a second substrate installed in the same vehicle as the first substrate;

a second cavity formed on the second substrate;

a second fixed part formed in the second cavity;

a second elastically deformed part formed in the second cavity and connected to the second fixed part;

a second movable part formed in the second cavity and connected to the second elastically deformed part;

a second capacity sensing element which includes a third capacitative element that mutually opposes a third fixed electrode formed in the second cavity and a third movable electrode formed in the second movable part and which outputs the variation of the capacity of the third capacitative element caused when the second movable part is displaced by external force; and

a second physical quantity calculation terminal connected to a second physical quantity calculating device that calculates the physical quantity of the external force based upon the variation of the capacity output from the second capacity sensing element, wherein;

in the abnormality determination device, a result of determining abnormality is varied depending upon a value acquired from the second physical quantity calculation terminal.

2. The inertial sensor according to claim 1, wherein:

a range of physical quantity output from the second physical quantity calculation terminal is larger than a range of physical quantity output from the first physical quantity calculation terminal.

3. The inertial sensor according to claim 1, wherein:

a frequency response band of physical quantity output from the second physical quantity calculation terminal is larger than a frequency response band of physical quantity output from the first physical quantity calculation terminal.

4. The inertial sensor according to claim 1, wherein:

a first physical quantity calculating mechanism including the first capacity sensing element is an acceleration sensor; and

a second physical quantity calculating mechanism including the second capacity sensing element is an acceleration sensor.

5. The inertial sensor according to claim 1, wherein:

a first physical quantity calculating mechanism including the first capacity sensing element is an acceleration sensor; and

a second physical quantity calculating mechanism including the second capacity sensing element is an angular velocity sensor.

6. The inertial sensor according to claim 1, wherein:

a first physical quantity calculating mechanism including the first capacity sensing element and a second physical quantity calculating mechanism including the second capacity sensing element are formed on the same substrate.

7. The inertial sensor according to claim 1, wherein:

the abnormality determination device compares a value acquired from the second physical quantity calculation terminal and predetermined voltage.

8. The inertial sensor according to claim 7, wherein:

the abnormality determination device further compares an amplitude of the diagnostic signal and a predetermined amplitude reference value.

9. The inertial sensor according to claim 8, wherein:

the abnormality determination device compares an amplitude of the diagnostic signal and the predetermined amplitude reference value when a value acquired from the second physical quantity calculation terminal is equal to or below the predetermined voltage.

10. The inertial sensor according to claim 1, wherein:

pressure of the first cavity is different from that of the second cavity.

11. An inertial sensor which is provided with a first movable part, a first sensing element that has a fixed electrode and that detects the displacement of the first movable part using capacity between the movable part and the fixed electrode, a forced oscillation generating device that forcedly oscillates the first movable part by applying a diagnostic signal, a first physical quantity calculating device that calculates physical quantity based upon a detection signal from the first sensing element and an abnormality determination device that determines whether the physical quantity is abnormal or not using the diagnostic signal acquired via the first sensing element and which is used in a vehicle, further comprising:

a second sensor mounted in the same vehicle as the vehicle and connected to the abnormality determination device.

12. The inertial sensor according to claim 11, wherein:

an output signal from the second sensor is input to the abnormality determination device.

13. The inertial sensor according to claim 12, wherein:

the physical quantity is acceleration; and

the output signal from the second sensor is also an acceleration signal.

14. The inertial sensor according to claim 11, wherein:

the forced oscillation generating device is provided with a switch that turns on/off the diagnostic signal to the movable part.