Gyro sensor

• US 20060123908A1
• Filed: 12/09/2005
• Published: 06/15/2006
• Est. Priority Date: 12/10/2004
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Ito, Hajime
• Granted Patent: US 7,434,466 B2
• Time in Patent Office: Days
• US Class Current: 73/514.320
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces

Abstract

The electrostatically-driven/capacitance-detection type gyro sensor has a sensing element including a movable part, the sensitivity of the sensing element and accordingly the sensitivity of a sensor output signal thereof being kept unchanged by controlling the amplitude of displacement or displacing velocity of the movable part and by using a reference voltage independent of variation of a power supply voltage, even there occurs a change in the vibrating state of the movable part due to temperature change or secular variation.

Claims

1. An electrostatically-driven/capacitance-detection type gyro sensor comprising:

a sensing element including

a movable part displaceable in a motion plane,

a first electrode provided in said movable part and applied with a bias voltage;

a second electrode applied with a drive signal to generate an electrostatic force acting on said movable part in order that said movable part vibrates along a first direction on said motion plane,

a third electrode forming a first variable capacitor with said movable part, a capacitance of said first variable capacitor varying in accordance with a displacement of said movable part along said first direction, and

a fourth electrode forming a second variable capacitor with said movable part, a capacitance of said second variable capacitor varying in accordance with a displacement of said movable part along a second direction on said motion plane, said second direction being orthogonal to said first direction;

a reference voltage generator generating, from a power supply voltage supplied from outside said gyro sensor, a reference voltage which is constant irrespective of variation of said power supply voltage;

a bias voltage generator generating said bias voltage by amplifying said reference voltage;

a capacitance-voltage converter converting said capacitance of said first variable capacitance into a first voltage signal whose voltage level varies following variation of said capacitance of said first variable capacitor, and converting said capacitance of said second variable capacitance into a second voltage signal whose voltage level varies following variation of said capacitance of said second variable capacitor;

a drive signal generator generating said drive signal by amplifying and phase-adjusting said first voltage signal, said drive signal having an offset voltage proportional to said reference voltage; and

a sensor output signal generator generating, from said second voltage signal, a sensor output signal having a magnitude corresponding to said voltage level of said second voltage signal, said sensor output signal having an offset voltage proportional to said power supply voltage.

2. The gyro sensor according to claim 1, wherein said drive signal generator includes a phase shifter for phase-shifting said first voltage signal in order that said drive signal has a phase allowing said movable part continues to vibrate along said first direction, and an amplifier for amplifying said first voltage signal in order that said drive signal has such an amplitude as to keep an amplitude of displacement of said movable part along said first direction is kept constant.

3. The gyro sensor according to claim 1, wherein said drive signal generator includes a phase shifter for phase-shifting said first voltage signal in order that said drive signal has a phase allowing said movable part continues to vibrate along said first direction, and an amplifier for amplifying said first voltage signal in order that said drive signal has such an amplitude as to keep an amplitude of displacing velocity of said movable part along said first direction is kept constant.

4. The gyro sensor according to claim 1, wherein said drive signal generator includes a phase shifter for phase-shifting said first voltage signal in order that said drive signal has a phase allowing said movable part continues to vibrate along said first direction, and said sensor output signal generator includes an amplifier amplifying said second voltage signal, said amplifier having a gain which is proportional to said power supply voltage and has a temperature characteristic compensating for a temperature characteristic of said second voltage signal.

5. The gyro sensor according to claim 1, wherein said drive signal generator includes a phase shifter for phase-shifting said first voltage signal in order that said drive signal has a phase allowing said movable part continues to vibrate along said first direction, and said sensor output signal generator includes an amplifier amplifying said second voltage signal, said amplifier having a gain which is inversely proportional to an amplitude of said first voltage signal and proportional to said power supply voltage.

6. The gyro sensor according to claim 1, wherein, said drive signal generator includes a phase shifter for phase-shifting said first voltage signal by differentiating said first voltage signal in order that said drive signal has a phase allowing said movable part continues to vibrate along said first direction, and said sensor output signal generator includes an amplifier amplifying said second voltage signal, said amplifier having a gain which is inversely proportional to an amplitude of a derivative of said first voltage signal and proportional to said power supply voltage.