Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
2000-04-07
2001-06-12
Moller, Richard A. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
C073S504160
Reexamination Certificate
active
06244110
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vibration gyro sensor. In particular, the present invention relates to a vibration gyro sensor (scope) for detecting the angular velocity of rotation by utilizing the Coriolis force generated when a vibrator is rotated while making vibration, and a method for producing the vibration gyro sensor. The present invention also relates to a combined sensor including the vibration gyro sensor.
2. Background Art
The gyro sensor (scope), which is a sensor for detecting the angular velocity of rotation, has been hitherto used, for example, in inertial navigation systems of aircraft and shipping. Recently, the gyro sensor has been used for vehicle-carried navigation systems and for attitude control systems of automatically guided robot vehicles. Further, the gyro sensor has also been used, for example, for picture blurring-preventive systems of VTR cameras. In such circumstances, a compact type gyro sensor is required, which is appropriately used in various fields as described above. Accordingly, the vibration gyro sensor attracts attention.
As well-known, the vibration gyro sensor (scope) of this type has a basic structure comprising a driving piezoelectric element and a detecting piezoelectric element which adhere to a vibrator formed of a constant resilience metal represented by the elinvar alloy. In a rectangular coordinate system of x, y, z axes, when the vibrator is rotated about the z axis while giving bending vibration in the x axis direction to the vibrator by using the driving piezoelectric element, the Coriolis force acts in the y axis direction to the vibrator. Accordingly, the bending vibration in the y axis direction caused in the vibrator by the Coriolis force is detected as a voltage by the aid of the detecting piezoelectric element. The angular velocity is determined on the basis of the detected voltage.
However, in the case of the conventional vibration gyro sensor as described above, the amount of displacement of the vibrator, which is based on the vibration induced by the driving piezoelectric element, is small. Therefore, the voltage (electromotive force), which is detected by the detecting piezoelectric element, is small. As a result, the conventional vibration gyro sensor suffers from low sensitivity.
In addition, the driving piezoelectric element and the detecting piezoelectric element are glued and fixed to the vibrator by using an adhesive. Therefore, the adhesive intervenes between the vibrator and the piezoelectric elements. As a result, the stress is absorbed by the adhesive. This is problematic since the detection sensitivity is lowered.
When the vibrator comprises a member which is composed of a sound chip or a tuning fork formed of an elinvar alloy, a problem arises in that the characteristics of the vibrator tend to be affected by an ambient magnetic field, because the elinvar alloy is a ferromagnetic material. Further, due to the shape or the material of the vibrator as described above, there is an implicit problem that it is difficult to perform processing or machining when the resonant frequency of the vibrator is adjusted.
SUMMARY OF THE INVENTION
The present invention has been made to solve all of the problems as described above and provide a vibration gyro sensor having excellent sensitivity. Another object of the present invention is to provide a vibration gyro sensor made of ceramics, in which the characteristics of the vibrator are barely affected by an ambient magnetic field, processing or machining can be easily performed, and the electric characteristics can be advantageously adjusted.
The present invention provides a vibration gyro sensor which is constructed as a whole by an integrated fired product made of ceramics without using any magnetic material. Therefore, the vibration gyro sensor according to the present invention scarcely affected by any ambient magnetic field. Further, the vibration gyro sensor includes first plate-shaped sections and second plate-shaped sections which are thin-walled respectively and which are provided as easily bendable sections in driving and detecting directions for making displacement of vibrators respectively. Therefore, large displacement is obtained in any of the detecting and driving directions, thus giving a large electromotive force (voltage) generated depending on the displacement detected by piezoelectric/electrostrictive elements, and making it possible to effectively increase the detection sensitivity. Especially, the detecting section has a structure to which the stress is concentrated. Therefore, a large output is obtained.
Moreover, the vibration gyro sensor according to the present invention includes the detecting piezoelectric/electrostrictive elements which are formed in an integrated manner in accordance with a film formation method on the first plate-shaped sections for giving the detecting sections constructed by the integrated fired product made of ceramics. The piezoelectric/electrostrictive elements directly contact with the first plate-shaped sections without any intervening adhesive layer. Therefore, any absorption of stress, which would be otherwise caused due to the presence of such an adhesive layer, is effectively avoided. Accordingly, the displacement (bending vibration) of the vibrators, which is caused by the Coriolis force induced when the vibrators are rotated, can be effectively detected by the piezoelectric/electrostrictive elements, making it possible to advantageously contribute to the improvement in sensitivity.
In the vibration gyro sensor according to the present invention, for example, the electrode area of the piezoelectric/electrostrictive element provided on the detecting section can be easily changed by using an appropriate removing means such as a laser. Therefore, the vibration gyro sensor also has such a feature that its electric characteristics are easily adjusted.
In a preferred embodiment of the present invention, the vibrator is provided with a thin-walled excisable section extending from a forward end of the vibrator, and a resonance frequency of the vibrator is adjusted in accordance with an amount of excision of the excisable section. The thin-walled excisable section, which is provided at the end of the vibrator, is an easily processible or machinable portion. The resonance frequency of the vibrator can be easily adjusted to have a desired value by providing such an excisable section for trimming beforehand, and excising the excisable section by means of an appropriate excising means such as laser machining and ultrasonic machining.
In another preferred embodiment of the present invention constructed as described above, two of the vibrators are supported in parallel to one another by the support base, and the two vibrators are vibrated by the driving means in an excited manner in mutually opposite directions. In this embodiment, the vibration gyro sensor may be constructed such that the driving means comprises a third plate-shaped section which is more thin-walled than the vibrator and which is composed of the integrated fired product of ceramics together with the vibrator, and a driving piezoelectric/electrostrictive element formed in an integrated manner on the third plate-shaped section in accordance with the film formation method.
In still another preferred embodiment of the present invention constructed as described above, a support bar is arranged at a position which is located between the two vibrators and which is separated from the vibrators. The support bar is supported in an integrated manner by the support base together with the two vibrators.
In still another preferred embodiment of the present invention constructed as described above, the support base is constructed by an attachment frame which is disposed outside the vibrator and separated therefrom by a predetermined distance so that the vibrator is surrounded thereby. Provision of the attachment frame makes it possible to tightly fix the vibration gyro sensor, exhibiting a feature that a place for i
Namerikawa Masahiko
Ohnishi Takao
Shibata Kazuyoshi
Takeuchi Yukihisa
Burr & Brown
Moller Richard A.
NGK Insulators Ltd.
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