ACCELERATION SENSOR

• US 20080016963A1
• Filed: 07/16/2007
• Published: 01/24/2008
• Est. Priority Date: 07/20/2006
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Epson Toyocom Corporation (Seiko Group)
• Inventors: WATANABE, Jun
• Granted Patent: US 7,536,910 B2
• Time in Patent Office: Days
• US Class Current: 73/514.29
• CPC Class Codes: G01P 1/023 for acceleration measuring devices
• CPC Class Codes: G01P 15/09 by piezoelectric pick-up
• CPC Class Codes: G01P 15/097 by vibratory elements

Abstract

An acceleration sensor, including: an oscillator unit for outputting an oscillator signal, the oscillator unit including a first piezoelectric vibrating reed having a vibrating arm that performs bending vibration, as well as an oscillator circuit for oscillating the first piezoelectric vibrating reed; a phase shifting unit for shifting and outputting a given phase angle of an output signal of the oscillator unit; a phase shift circuit unit provided with a second piezoelectric vibrating reed having a vibrating arm that performs bending vibration, arranged at an output side of the phase shifting unit; a multiplier for multiplying the output signal of the phase shift circuit unit by the output signal of the oscillator circuit; and a phase shift modification output unit which receives an output from the multiplier and outputs a value corresponding to a change in a phase shift angle of an input-output signal of the phase shift circuit unit; a resonant frequency of the second piezoelectric vibrating reed being equal to a frequency of the output signal of the oscillator unit, in a state where no acceleration is applied.

Claims

1. An acceleration sensor, comprising:

an oscillator unit for outputting an oscillator signal, the oscillator unit including;

a first piezoelectric vibrating reed having a vibrating arm that performs bending vibration; and

an oscillator circuit for oscillating the first piezoelectric vibrating reed;

a phase shifting unit for shifting and outputting a given phase angle of an output signal of the oscillator unit;

a phase shift circuit unit provided with a second piezoelectric vibrating reed having a vibrating arm that performs bending vibration, arranged at an output side of the phase shifting unit;

a multiplier for multiplying the output signal of the phase shift circuit unit by the output signal of the oscillator circuit; and

a phase shift modification output unit which receives an output from the multiplier and outputs a value corresponding to a change in a phase shift angle of an input-output signal of the phase shift circuit unit;

a resonant frequency of the second piezoelectric vibrating reed being equal to a frequency of the output signal of the oscillator unit, in a state where no acceleration is applied.

2. The acceleration sensor according to claim 1, wherein the first piezoelectric vibrating reed and the second piezoelectric vibrating reed are arranged so that an axis direction of the vibrating arm of the first piezoelectric vibrating reed and an axis direction of the vibrating arm of the second piezoelectric vibrating reed are opposite from each other.

3. The acceleration sensor according to claim 1, wherein a frequency-phase shift characteristic of the phase shift circuit unit is point symmetric with respect to the resonant frequency of the second piezoelectric vibrating reed without acceleration.

4. The acceleration sensor according to claim 1, wherein the first piezoelectric vibrating reed and the second piezoelectric vibrating reed are tuning fork vibrating reeds formed with a piezoelectric material.

5. The acceleration sensor according to claim 1, wherein the first piezoelectric vibrating reed and the second piezoelectric vibrating reed are double-ended tuning fork vibrating reeds formed with a piezoelectric material.

6. The acceleration sensor according to claim 1, further comprising:

a package accommodating the first tuning fork piezoelectric vibrating reed and an integrated circuit, both forming the oscillator circuit, and the second tuning fork piezoelectric vibrating reed included in a phase-shift circuit unit; and

a lid sealing the package in an air tight manner.

7. The acceleration sensor according to claim 6, wherein the package is formed having two cavities stacked one on top of the other, each cavity including an interconnection substrate, one cavity accommodating the first and the second tuning fork piezoelectric vibrating reeds, and the other cavity accommodating the integrated circuit.

8. The acceleration sensor according to claim 6, wherein the package is formed having two cavities stacked one on top of the other, having a shared interconnection substrate therebetween, one cavity accommodating the first and the second tuning fork piezoelectric vibrating reeds, and the other cavity accommodating the integrated circuit.