Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Patent
1997-05-07
1998-12-29
Chapman, John E.
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
310329, 310370, G01P 904
Patent
active
058544275
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a vibration type angular velocity sensor for use in the attitude control, navigation, etc. of mobile items such as aircrafts, automobiles, robots, ships, or vehicles, or an angular velocity sensor for use in the anti-blurring gear, remote controller etc. of still cameras, or video cameras.
BACKGROUND ART
An angular velocity sensor of the above category comprises a U-shape vibration member, on which piezoelectric elements are attached each forming a driving section and a detecting section. The tuning fork arm of piezoelectric elements is driven by a driving power source supplied to an electrode of a piezoelectric elements of said vibration member, and the Coriolis force generated at the detecting section is detected as an angular velocity signal to be taken out of the piezoelectric element of the detecting section.
In the above described structure, however, a signal taken out of the detection electrode contains, besides the angular velocity signal, unnecessary signals induced by the driving signal. Therefore, it needs a circuit to separate the unnecessary signal. A problem is that the signals other than angular velocity signal are not thoroughly separated by the circuit; part of which remains as noise, making it difficult to improve the detection characteristics.
BRIEF SUMMARY OF THE INVENTION
The present invention is intended to eliminate the influence due to noise from driving signal, thereby improving the detection characteristics of angular velocity signal.
In order to implement the objective, an angular velocity sensor according to the present invention comprises U-shape first and second piezoelectric elements bonded together sandwiching a detection electrode, said first piezoelectric element having in at least one of the tuning fork arms a first and a second driving electrodes on a surface opposite to the detection electrode and said second piezoelectric element having in a tuning fork arm corresponding to the tuning fork arm on which said first and second driving electrodes are disposed a third and a fourth driving electrodes on a surface opposite to the detection electrode; wherein, among said first through fourth driving electrodes, the first and the third driving electrodes disposed in diagonal arrangement across the detection electrode are coupled with a first driving power source while the second and the fourth driving electrodes disposed on another diagonal line across the detection electrode are coupled with a second driving power source which supplies a signal whose phase is inverse to that of said first driving power source, and at least one of the tuning fork arms of said U-shape first and second piezoelectric elements is polarized in a direction of thickness along which the first and the second piezoelectric elements are bonded together.
Under the above described constitution, the first and the third driving electrodes disposed in a diagonal arrangement in a tuning fork arm receive a driving signal from the first driving power source, while the second and the fourth driving electrodes disposed on another diagonal line in the tuning fork arm receive a driving signal from the second driving power source the phase of which signal being inverse to that of the first driving power source. The signals for driving the tuning fork arm are thus applied across a detection electrode, which means that the driving signals cancel to each other on the detection electrode, and are never mixed in a detection signal. As a result, the capability of detecting the angular velocity signal is improved.
Further, an angular velocity sensor according to the present invention comprises U-shape first and second piezoelectric elements bonded together sandwiching an intermediate electrode, said first piezoelectric element having in at least one of the tuning fork arms a first and a second driving electrodes and a first detection electrode on a surface opposite to the intermediate electrode and said second piezoelectric element having in a tuning fork arm correspond
REFERENCES:
patent: 5430342 (1995-07-01), Watson
patent: 5635786 (1997-06-01), Fujimoto et al.
Hatanaka Masakazu
Senda Hiroshi
Tamura Masami
Terada Jiro
Ushihara Masaharu
Chapman John E.
Matsushita Electric Industrical Co., Ltd.
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