Inertial sensor

• US 9,557,345 B2
• Filed: 06/19/2013
• Issued: 01/31/2017
• Est. Priority Date: 06/26/2012
• Status: Active Grant

• Current Assignee: Hitachi Automotive Systems Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi Automotive Systems Limited (Hitachi, Ltd.)
• Inventors: Maeda, Daisuke, Jeong, Heewon, Hayashi, Masahide
• Primary Examiner(s): Huber, Robert
• Assistant Examiner(s): Roberts, Herbert K
• Application Number:
  US13/921,505
• Publication Number:
  US 20130340524A1
• Time in Patent Office: 1,322 Days
• US Class Current: 1/1
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719
• CPC Class Codes: G01P 15/0888 for indicating angular acceleration
• 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

Abstract

In an inertial sensor, an acceleration sensor element section includes a first movable section configured to respond to acceleration applied thereto and a diagnosis electrode configured to displace the first movable section with an electrostatic force according to voltage application from a control circuit section. An angular velocity sensor element section includes a second movable section configured to respond to an angular velocity applied thereto and a driving electrode configured to displace the second movable section with an electrostatic force according to voltage application from the control circuit section. A voltage signal input to the driving electrode and a voltage signal input to the diagnosis electrode are the same voltage signal. The voltage signal input to the diagnosis electrode is a signal for detecting a mechanical failure. Carrier signal for detecting displacement of the first movable section has frequency higher than frequency of signal applied to the diagnosis electrode.

Claims

1. An inertial sensor comprising:

an acceleration sensor;

an angular velocity sensor; and

a control circuit configured to control the acceleration sensor and the angular velocity sensor, wherein

the acceleration sensor includes;

a first movable section held with first beams and configured to respond to acceleration applied thereto; and

a first electrode configured to displace the first movable section with an electrostatic force according to voltage application from the control circuit, the angular velocity sensor includes;

a second movable section, held with second beams independent from the first beams and mechanically isolated from the first movable section, configured to respond to an angular velocity applied thereto; and

a second electrode configured to displace the second movable section with an electrostatic force according to voltage application from the control circuit,

a voltage signal input to the first electrode of the acceleration sensor is generated from a clock synchronizing with a voltage signal input to the second electrode of the angular velocity sensor,

the voltage signal input to the first electrode of the acceleration sensor is a signal for detecting a mechanical failure,

a carrier signal for detecting displacement of the first movable section of the acceleration sensor has a frequency higher than a frequency of a signal applied to the first electrode, and

the acceleration sensor is configured to obtain, at a resonant frequency of the angular velocity sensor, a gain more than 0 dB due to a resonant frequency of the acceleration sensor that is configured to detect acceleration.

2. The inertial sensor according to claim 1, wherein the voltage signal input to the second electrode of the angular velocity sensor is a voltage signal synchronizing with a resonant frequency of the angular velocity sensor.

3. The inertial sensor according to claim 1, wherein the resonant frequency of the acceleration sensor is a frequency at which a gain is obtained more than 0 dB in a frequency component of the voltage signal input to the second electrode of the angular velocity sensor.

4. The inertial sensor according to claim 1, wherein

the control circuit includes an amplitude control circuit configured to adjust an amplitude of a voltage signal to control a vibration amplitude of the acceleration sensor to be fixed, and

the voltage signal input to the first electrode of the acceleration sensor is a voltage signal passed through the amplitude control circuit.

5. The inertial sensor according to claim 1, wherein the voltage signal input to the second electrode of the angular velocity sensor is a signal having a frequency obtained by multiplying a clock synchronizing with the voltage signal input to the first electrode of the acceleration sensor with an integer or dividing the clock by an integer.

6. The inertial sensor according to claim 5, wherein a resonant frequency of the acceleration sensor is a frequency at which a gain is obtained more than 0 dB in a frequency component of the voltage signal input to the second electrode of the angular velocity sensor.

7. The inertial sensor according to claim 1, wherein

the control circuit includes a time division processing circuit configured to process a diagnosis signal of the acceleration sensor and a detection signal of the angular velocity sensor in a time division manner, and

the time division processing circuit is shared in a time division manner as a detection circuit of the acceleration sensor and a detection circuit of the angular velocity sensor.

8. The inertial sensor according to claim 1, wherein

the first movable section of the acceleration sensor has mass asymmetrical with respect to a rotation axis for detecting acceleration,

the first electrode of the acceleration sensor is provided only on one side with respect to the rotation axis of the first movable section having the asymmetrical mass, and

a voltage signal from the control circuit is applied to the first electrode provided only on one side.

9. The inertial sensor according to claim 1, wherein

the acceleration sensor, the angular velocity sensor, and the control circuit are respectively formed on different chips, and

a first pad on a first chip connected to the first electrode of the acceleration sensor and a second pad on a second chip connected to the second electrode of the angular velocity sensor are respectively connected to a third pad for voltage application on a third chip of the control circuit by bonding wires.

10. The inertial sensor according to claim 9, wherein two pads are provided as each of the first pad, the second pad, and the third pad, and voltages of the respective pads have opposite phases each other.

11. The inertial sensor according to claim 1, wherein

the acceleration sensor and the angular velocity sensor are formed on a same first chip,

the control circuit is formed on a second chip different from the first chip,

the first electrode of the acceleration sensor and the second electrode of the angular velocity sensor are connected to a common first pad on the first chip by wires, and

the first pad on the first chip is connected to a second pad for voltage application on the second chip by a bonding wire.

12. The inertial sensor according to claim 11, wherein two pads are provided as each of the first pad and the second pad, and voltages of the respective pads have opposite phases each other.