Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-04-17
2001-08-28
Budd, Mark O. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S321000, C310S330000, C310S366000, C073S504130
Reexamination Certificate
active
06281618
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vibrating gyroscope, and more particularly to a vibrating gyroscope used, for example, to detect angular velocities for prevention of camera shake.
2. Description of the Related Art
FIG. 11
is a perspective view of an example of a conventional vibrating gyroscope. A vibrating gyroscope
1
includes a vibrating body
2
in, for example, the shape of a regular triangle. As seen in
FIGS. 11 and 12
, three peripheral surfaces of the vibrating body
2
have piezoelectric elements
3
a
,
3
b
, and
3
c
, respectively. To use the vibrating gyroscope
1
, as shown in
FIG. 12
, for example, a vibration circuit
4
is connected between the piezoelectric elements
3
a
and
3
b
and the piezoelectric element
3
c
. Also, the piezoelectric elements
3
a
and
3
b
are connected to a detection circuit
5
. The detection circuit
5
includes, for example, a differential circuit, a synchronous detection circuit, a smoothing circuit, and a DC amplifying circuit.
In the vibrating gyroscope
1
, a signal outputted from the piezoelectric element
3
c
is returned to the vibration circuit
4
. The vibration circuit
4
amplifies the returned signal and compensates the amplified signal in phase, thereby forming an exciting signal. The exciting signal thus obtained is fed to the piezoelectric elements
3
a
and
3
b
. This causes the vibrating body
2
to perform bending vibrations in the direction perpendicular to the surface where the piezoelectric element
3
c
is formed. In this state, bending states of the piezoelectric elements
3
a
and
3
b
are the same, and signals outputted therefrom are also the same. Therefore, no signal is outputted from the differential circuit in the detection circuit
5
. In a state where the vibrating body
2
is in bending vibration, rotation about an axis of the vibrating body
2
in the center generates a Coriolis force, thereby changing the vibration direction of the vibrating body
2
. This causes a difference between signals outputted from the piezoelectric elements
3
a
and
3
b
, and causes the differential circuit to output a signal. The output signal is then smoothed in the smoothing circuit, and the smoothed signal is amplified in the DC amplifying circuit. Therefore, measuring a signal outputted from the detection circuit
5
allows an angular rotation velocity to be detected.
For a vibrating gyroscope
1
shown in
FIG. 13
, a vibrating body
2
may be manufactured by coupling two piezoelectric substrates
6
a
and
6
b
. As indicated by arrows in
FIG. 13
, the piezoelectric substrates are polarized so as to oppose each other. In this case, electrodes
7
a
and
7
b
each extending in the length direction are formed on one of opposing surfaces of the vibrating body
2
, and an electrode
8
is formed on the entire surface of the other opposing surfaces thereof. Using the circuits shown in
FIG. 12
, the described vibrating gyroscope
1
also allows the angular velocity to be detected.
Nevertheless, with each of the vibrating gyroscopes described above, only the angular velocity about the axis of the vibrating body in the center can be detected, and only the angular velocity with respect to a single direction can be detected. Therefore, two units of the vibrating gyroscopes are required to detect angular velocities in two directions, and two vibration circuits are required to excite these vibrating gyroscopes. The vibration circuit is expensive, thereby increasing costs to detect angular velocities in multiple directions.
In view of the forgoing reasons, there has been a demand for a vibrating gyroscope capable of detecting angular velocities with respect to two directions by using a single element.
SUMMARY OF THE INVENTION
The present invention is directed to a vibrating gyroscope that satisfies this need. The vibrating gyroscope comprises two planar vibrating plates arranged to oppose each other. The two vibrating plates vibrate under buckling vibration mode and a second-order bending vibration mode which is degenerated with or close to the buckling vibration mode. The vibrating gyroscope detects Coriolis force by detecting displacements in amplitude balance of the second-order bending vibration modes generated when an angular rotation velocity around an axis parallel to surfaces of the vibrating plates is applied.
The described vibrating gyroscope may comprise an intermediate member formed between the two vibrating plates to form a spaced section between the two vibrating plates, and a plurality of exciting and detecting elements formed on the vibrating plates to vibrate the vibrating plates and to output signals generated by vibrations of the vibrating plates, wherein a first detecting section is formed according to a combination for the two adjacent exciting and detecting elements, a second detecting section is formed according to another combination for the two adjacent exciting and detecting elements, and the first detecting section and the second detecting section are arranged perpendicular to each other.
In this case, it is preferable that the exciting and detecting elements are not formed in positions opposing to the intermediate member, and are formed in positions opposing to the spaced section.
Also, the individual exciting and detecting elements are formed of piezoelectric substrates, and electrodes sectioned crosswise into four are formed on the piezoelectric substrates, whereby the electrodes and the piezoelectric substrates may be used to form the exciting and detecting elements.
Also, the vibrating plate may be formed of a metal plate, and piezoelectric elements sectioned crosswise into four and formed on the vibrating plate may be used to form the exciting and detecting element.
In addition, the intermediate member may be formed of a frame member in which a through opening is formed in its central portion.
Furthermore, the intermediate member may be formed of multiple members arranged on multiple end portions of the vibrating plates.
For example, by feeding exciting signals to all the exciting and detecting elements, buckling vibration is generated such that the amplitude of each of central portions of the vibrating reaches the maximum. When the angular velocity with each of the axes parallel to surfaces of the vibrating plates in the center is applied, the Coriolis force varies vibration of the vibrating plate in the quadratic bending vibration mode. When the buckling vibration and the vibration in the quadratic bending vibration mode are either degenerated or arranged similar, a point where the amplitude of the vibrating plate reaches the maximum vibrates deviating from the central portion of the vibrating plate. For this reason, the difference is caused between bending states of two exciting and detecting elements constituting one of the first and second detecting sections, and a signal corresponding to the Coriolis force is outputted from one of the first and second detecting sections. Since the first and second detecting sections are arranged perpendicular to each other, signals corresponding to angular velocities about respect to two directions that are perpendicular to each other can be obtained.
Since the vibrating plates and the intermediate member are immobilized, the exciting and detecting elements are preferably arranged at positions opposing the spaced section. This arrangement is made to cause the buckling vibration so that the amplitude at the central portion of the vibrating plate reaches the maximum.
In the described vibrating gyroscope, the piezoelectric substrate may be used for the vibrating plate, and the piezoelectric substrates and the electrodes sectioned crosswise into four thereon may be used to form the exciting and detecting element.
Also, the metal plate may be used for each of the vibrating plates. In this case, the exciting and detecting element is formed by the four piezoelectric elements sectioned crosswise and formed on the vibrating plate.
Furthermore, the intermediate member is provided to form the spaced
Fujimoto Katsumi
Ishitoko Nobuyuki
Budd Mark O.
Murata Manufactuirng Co., Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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