Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
1998-08-26
2001-04-03
Moller, Richard A. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
active
06209393
ABSTRACT:
This application is the national phase under 35 U.S.C. §371 of prior PCT International Application No. PCT/JP97/03862 which has an International filing date of Oct. 24, 1997 which designated the United States of America, the entire contents of which are hereby incorporated by reference.
1. Technical Field
The present invention relates to a vibratory gyroscope, and more particularly, to a vibratory gyroscope used for navigation and the like of an automobile and the like.
2. Background Art
FIG. 11
is a perspective view showing a structure of a conventional vibratory gyroscope. The above-mentioned vibratory gyroscope has a structure in which a exciting piezoelectric ceramic
3
and a detective piezoelectric ceramic
4
are stuck to a permanent elastic metal tuning fork type vibrator
1
having a square section. A principal axis direction of the permanent elastic metal tuning fork type vibrator
1
is taken as a Z axis, a normal direction of opposed one set of planes is taken as an X axis, and a normal direction of opposed another one set of planes is taken as a Y axis. The vibrator
1
is supported by supporting pins
2
a
,
2
b
,
2
c
and
2
d.
The operation of the vibratory gyroscope having such a structure will be explained next. By exciting the vibratory piezoelectric porcelain
3
by electric signal from a driving signal source (not shown), a flexural vibration is generated in the vibrator
1
within the X axis plane. If angular velocity is applied around the Z axis in this state, Coriolis force acts in a direction perpendicular to the X axis plane, and a vibration in the Y axis direction is generated. The vibration in the Y axis direction generated at this time is detected by the detective piezoelectric ceramic
4
, and the angular velocity can be measured.
Since the conventional vibratory gyroscope has the structure in which the permanent elastic metal and the piezoelectric ceramic are stuck, there is a problem that the manufacturing cost is increased.
Further, since the conventional vibratory gyroscope has a shape which is longer in the rotation axis (Z axis) direction, when it is mounted in an electronic equipment, it is difficult to meet requirement for reducing the equipment in size and thickness.
Therefore, it is a main object of the present invention to provide a vibratory gyroscope which does not require sticking, and which can reduce the manufacturing cost.
Another object of the present invention is to provide a vibratory gyroscope which can reduce its thickness and width.
DISCLOSURE OF THE INVENTION
As a result of a hard research, the present inventors have found that excellent characteristics are shown by a structure in which an angular velocity is obtained by providing a vibrator made of a piezoelectric substance with exciting electrodes to excite a vibration in a longitudinal direction by the exciting electrodes, and by detecting, by detective electrodes, a flexural vibration in a plane perpendicular to a rotation axis which is induced by Coriolis force generated by angular velocity around the rotation axis which is in a thickness wise direction of the vibrator.
On the contrary, by the same principle, it is also possible to excite the f lexural vibration so that a vibration in a longitudinal direction of the vibrator induced by Coriolis force generated by angular velocity around the rotation axis is detected by the detective electrodes provided on a portion of the vibrator, thereby obtaining the angular velocity.
When an electric signal of a resonance frequency in a longitudinal direction of the vibrator is input to the exciting electrodes, a longitudinal vibration is generated in the vibrator. In this state, if angular velocity around the rotation axis in the thicknesswise direction of the vibrator is applied, Coriolis force is generated in a direction perpendicular to both the rotation axis and the longitudinal vibration direction. By the generated Coriolis force and the longitudinal vibration, a flexural vibration is generated in a plane determined by the direction of the Coriolis force and the direction of the longitudinal vibration. The detective electrodes for detecting only this flexural vibration are provided on the portion of the vibrator, and the angular velocity is measured.
According to the vibratory gyroscope of the above-described structure, an angular velocity sensor can be realized only by forming the exciting electrodes and the detective electrodes on the piezoelectric substance and the like, and it is possible to simplify the structure and to largely reduce the manufacturing cost as compared with the conventional vibratory gyroscope.
Further, since the gyroscope is constructed such that the thicknesswise direction of the vibrator is taken as the rotation axis and the flexural vibration in the plane perpendicular to the rotation axis is detected by the detective electrodes provided on the portion of the vibrator, the shape of the gyroscope is narrow in width and thin in thickness, and it is possible to make the sensor smaller as compared with the conventional vibratory gyroscope of three-dimensional structure.
The present invention is based upon the above-mentioned findings, and according to a first aspect of the present invention, there is provided a vibratory gyroscope, characterized by comprising
a vibrator made of a piezoelectric substance;
exciting electrodes which are secured to the vibrator and are capable of exciting the vibrator to cause one of a longitudinal vibration and a flexural vibration; and
detective electrodes which are secured to the vibrator and are capable of detecting the other of the longitudinal vibration and the flexural vibration of the vibrator.
Preferably, the longitudinal vibration is a first longitudinal vibration mode, and the flexural vibration is a second flexural vibration mode.
According to a second aspect, there is provided a vibratory gyroscope, characterized by comprising:
a vibrator made of a piezoelectric substance and having a longitudinal direction, a widthwise direction and a thicknesswise direction which are perpendicular to one another;
exciting electrodes which are secured to the vibrator and are capable of exciting the vibrator to cause one of a vibration in the longitudinal direction and a flexural vibration; and
detective electrodes which are secured to the vibrator and are capable of detecting the other of the vibration in the longitudinal vibration and the flexural vibration of the vibrator.
Preferably, the vibration in the longitudinal direction is a longitudinal vibration, a rotation axis of the vibrator exists in the thicknesswise direction of the vibrator, and the flexural vibration is a vibration in a predetermined plane perpendicular to the thicknesswise direction.
Still preferably, the longitudinal vibration is a first longitudinal vibration mode, and the flexural vibration is a second flexural vibration mode.
Still preferably, the vibrator includes an exciting portion for exciting the vibrator, and a detective portion for detecting the other of the vibration in the longitudinal direction and the flexural vibration of the vibrator,
the exciting electrodes are secured to the exciting portion,
the detective electrodes are secured to the detective portion, and
the exciting portion and the detective portion are laminated in the thicknesswise direction.
Alternatively, the vibrator includes an exciting portion for exciting the vibrator, and a detective portion for detecting the other of the vibration in the longitudinal direction and the flexural vibration of the vibrator,
the exciting electrodes are secured to the exciting portion,
the detective electrodes are secured to the detective portion, and
the exciting portion and the detective portion are juxtaposed in a direction of a plane including the longitudinal direction and the widthwise direction of the rectangular parallelepiped.
Further, in the above-mentioned second aspect of the present invention, preferably, the exciting electrodes are provided in parallel to a plane which is substantially perpendicular to the thicknesswise directio
Kanayama Kouichi
Koiso Takeshi
Tomikawa Yoshiro
Birch & Stewart Kolasch & Birch, LLP
Mitsui Chemicals Inc.
Moller Richard A.
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