Inertial sensor

Patent metadata

Field	Value
Publication number	US-2017191830-A1
Application number	US-201515313242-A
Country	US
Kind code	A1
Filing date	Apr 8, 2015
Priority date	May 23, 2014
Publication date	Jul 6, 2017
Grant date	—

Abstract

An inertial sensor having a simple configuration by vacuum sealing a resonator which detects acceleration and exploits a resonance vibration using a high Q value MEMS device. The sensor includes: a detecting proof mass and beam which detects acceleration; a driving electrode which excites the detecting proof mass and beam; a resonant frequency tuning electrode which changes the resonant frequency of the detecting proof mass and beam; and a detecting circuit which applies voltage to the resonant frequency tuning electrode for changing the resonant frequency to cancel a change of the resonant frequency of the detecting proof mass and beam when the acceleration is applied to the detecting proof mass and beam during the vibration of the detecting proof mass and beam by the voltage applied to the detecting proof mass and beam, and outputs the acceleration based on a value of the voltage applied to resonant frequency tuning electrode.

First claim

1 . An inertial sensor comprising:
a first resonator which detects acceleration; a capacitive first electrode which excites the first resonator; a capacitive second electrode which changes a resonant frequency of the first resonator; and a detecting circuit which applies voltage to the second electrode to change the resonant frequency such that a change of the resonant frequency of the first resonator is canceled when the acceleration is applied to the first resonator during a vibration of the first resonator due to application of voltage to the first resonator, and outputs the acceleration based on a value of the voltage applied to the second electrode.

2 . The inertial sensor according to claim 1 , wherein bias voltage which changes the resonant frequency is applied in advance to the second electrode in a steady state in which the acceleration is not applied to the first resonator, and
the resonant frequency of the first resonator in the steady state is to be a resonant frequency lower than that in a state in which the bias voltage is not applied.

3 . The inertial sensor according to claim 1 , further comprising a second resonator which detects angular velocity,
wherein the second resonator which detects the angular velocity and the first resonator which detects the acceleration are vacuum sealed in one chamber.

4 . The inertial sensor according to claim 3 , wherein the detecting circuit controls voltage applied to the second electrode such that the resonant frequency of the first resonator which detects the acceleration is matched with the resonant frequency of the second resonator which detects the angular velocity.

5 . The inertial sensor according to claim 2 , wherein a plurality of the first resonators which detects the acceleration is arranged,
a plurality of the first electrodes, a plurality of the second electrodes, and a plurality of the detecting circuits are arranged to correspond to a plurality of the first resonators, and each of the detecting circuits controls the voltage applied to the second electrode such that the resonant frequency of the first resonator which detects the acceleration is to be the same frequency.

6 . The inertial sensor according to claim 5 , further comprising a second resonator which detects angular velocity,
wherein each of the detecting circuit controls the voltage applied to the second electrode such that the resonant frequency of the first resonator which detects the acceleration is matched with the resonant frequency of the second resonator which detects the angular velocity.

7 . The inertial sensor according to claim 5 , further comprising a plurality of the second resonators which detects the angular velocity,
wherein each of the detecting circuits controls the voltage applied to the second electrode such that the resonant frequency of the first resonator which detects the acceleration is matched with the resonant frequency of one of the second resonators which detect the angular velocity.

8 . The inertial sensor according to claim 5 , wherein each of the detecting circuits compares the resonant frequency of the first resonator which detects the acceleration with a resonant frequency of an outside resonator having a high Q value higher than the Q value of the first resonator, and controls such that the resonant frequency of the first resonator is to be close to the resonant frequency of the outside resonator having the high Q value.

9 . The inertial sensor according to claim 3 , comprising more than one first resonator which detects the acceleration,
more than one second resonator which detects the angular velocity, and one oscillation circuit which generates a clock signal which excites the more than one first resonator and the more than one second resonator.

10 . The inertial sensor according to claim 3 , comprising more than one first resonator which detects the acceleration,
more than one second resonator which detects the angular velocity, and a diagnostic circuit which diagnoses failure based on comparison of the resonant frequencies between the more than one first resonator and the more than one second resonator.

11 . The inertial sensor according to claim 10 , wherein the diagnostic circuit diagnoses the failure based on comparison of voltage which excites the more than one first resonator and the more than one second resonator at a predetermined amplitude, or amplitude obtained during the vibration by a predetermined voltage.

12 . The inertial sensor according to claim 11 , wherein the diagnostic circuit diagnoses the failure based on the comparison of the resonant frequency and the amplitude based on a change of temperature obtained by a temperature sensor arranged on an integrated circuit of the inertial sensor.

Assignees

• Hitachi Automotive Systems Ltd

Inventors

• Maeda Daisuke
• Jeong Heewon
• Hayashi Masahide

Classifications

• G01C19/5726 Primary

  Signal processing · CPC title

• G01P15/125

  by capacitive pick-up · CPC title

• G01C19/5776

  Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719 · CPC title

• G01C19/5769

  Manufacturing; Mounting; Housings · CPC title

• G01C19/5755

  the devices having a single sensing mass · CPC title