Metal working – Piezoelectric device making
Reexamination Certificate
2003-09-26
2004-10-26
Tugbang, A. Dexter (Department: 3729)
Metal working
Piezoelectric device making
C029S594000, C029S852000, C029S846000, C073S504140
Reexamination Certificate
active
06807716
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to composite vibrators, vibration gyros using the vibrators, and electronic apparatuses incorporating the gyroscopes. In addition, the invention relates to methods of manufacturing the composite vibrators. More particularly, the invention relates to composite vibrators incorporated in video cameras with a shake preventing function, car navigation systems, pointing devices, or the like, vibration gyroscopes using the vibrators, electronic apparatuses incorporating the vibration gyroscopes, and methods of manufacturing the composite vibrators.
2. Description of the Related Art
FIG. 22
shows a perspective view of a conventional vibration gyroscope. In this figure, a vibration gyroscope
60
includes a tuning bar vibrator
600
and a frame
610
. The turning bar vibrator
600
includes a first piezoelectric member
101
polarized in its thickness direction, with a first electrode
104
a
and a second electrode
104
b
having the same dimensions being formed on a main surface thereof, a second piezoelectric member
102
polarized in its thickness direction, with a third electrode
105
formed on a main surface thereof, and conductive support members
106
a
,
106
b
,
106
c
, and
106
d
. The first electrode
104
a
and the second electrode
104
b
are arranged in the longitudinal direction of the tuning bar vibrator
600
at a predetermined distance in the width direction. The other main surface of the first piezoelectric member
101
is bonded to the other main surface of the second piezoelectric member
102
via an intermediate electrode
103
. In each of the first and second piezoelectric members
101
and
102
, a ratio between the length L
1
of the thickness direction and the length L
2
of the width direction, that is, the value of L
1
/L
2
is set to be approximately 1. In the tuning bar vibrator
600
, in positions (near nodes N
1
and N
2
) in which the nodes N
1
and N
2
(axes) of bending vibrations at both free ends in the thickness direction are projected perpendicularly to a main surface of the tuning bar vibrator
600
, the support member
106
a
is connected to the first electrode
104
a
, the support member
106
b
is connected to the second electrode
104
b
, and the support members
106
c
and
106
d
are connected to the third electrode
105
. The frame
610
is made of resin and has a sufficiently large mass. The end portions of the support members
106
a
,
106
b
,
106
c
, and
106
d
are fixed to the frame
610
.
The vibration gyroscope
60
having the above structure performs bending vibrations at both free ends when an excitation signal is applied to the third electrode
105
via the support members
106
c
and
106
d
. The nodes obtained in the vibrations are N
1
and N
2
as axes orienting in the width direction of the vibration gyroscope
60
. When there is applied an angular velocity whose rotational axis is the longitudinal direction of the tuning bar vibrator
600
, the vibration gyroscope
60
performs bending vibrations at both free ends in the width direction orthogonal to the direction of excitation. The vibration nodes obtained in this case are N
3
and N
4
as axes orienting in the thickness direction substantially at the center in the width direction of the vibration gyroscope
60
. Signals of bending in the width direction are output from the first electrode
104
a
and the second electrode
104
b.
In the vibration gyroscope
60
, when the tuning bar vibrator
600
vibrates in the thickness direction and the width direction, the center of gravity shifts. Then, the vibrations of the tuning bar vibrator
600
partially leak to the outside frame
610
via the support members
106
a
,
106
b
,
106
c
, and
106
d
. The frame
610
absorbs the vibrations leaking from the tuning bar vibrator
600
.
Conventional vibration gyroscopes are described in Japanese Unexamined Patent Application Publication No. 7-332988, and the like.
In general, a vibrator gyroscope requires miniaturization. Particularly, the length of the longitudinal direction of a tuning bar vibrator needs to be reduced, since the length is longer than the lengths of the widthwise and thickness directions thereof. However, the sensitivity of a vibration gyroscope is proportional to a given angular velocity, a vibration velocity of a vibrator, and the mass of the vibrator. Thus, when the length of the longitudinal direction of the tuning bar vibrator is reduced, the mass of the composite vibrator decreases and thereby the sensitivity of the vibration gyroscope is deteriorated.
In addition, when the vibrations of the tuning bar vibrator leaks outside, the amplitude of the vibrator is attenuated. As a result, the sensitivity of the vibration gyroscope is deteriorated.
In addition, due to the deteriorated sensitivity of the vibration gyroscope, the ratio of noise with respect to signal increases. Furthermore, since the temperature characteristics of support members and an acceleration detecting circuit become more influential, a value detected for an angular velocity tends to change.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a composite vibrator which can maintain high sensitivity even when miniaturized.
In addition, it is another object of the invention to provide a method of easily manufacturing the composite vibrator.
In addition, it is another object of the invention to provide a vibration gyroscope using the composite vibrator, which can maintain high sensitivity even when miniaturized.
In addition, it is another object of the invention to provide an electronic apparatus using the vibration gyroscope capable of accurately detecting an angular velocity to precisely control the angular velocity.
To this end, according to the present invention, there is provided a composite vibrator including a plurality of tuning bar vibrators having the same length and support members for supporting the tuning bar vibrators. In this composite vibrator, the tuning bar vibrators with both ends free are arranged in a direction orthogonal to a longitudinal direction of the tuning bar vibrators and are coupled with each other in the vicinity of nodes of bending vibrations.
In addition, the plurality of tuning bar vibrators may include at least two tuning bar vibrators having the same configuration.
In addition, each tuning bar vibrator may include an electrode to which a signal for exciting the tuning bar vibrator is applied and an electrode from which a signal corresponding to bending vibration of the tuning bar vibrator in a direction orthogonal to the direction of excitation is output.
In addition, adjacent tuning bar vibrators may be excited in mutually opposite directions.
In addition, a resonant frequency in the exciting direction of at least one of the tuning bar vibrators may coincide with a resonant frequency in the direction orthogonal to the exciting direction.
In addition, at least two electrodes formed in the longitudinal direction of a main surface of each tuning bar vibrator may be arranged at a predetermined distance in the width direction thereof.
According to the present invention, there is provided a vibration gyroscope including a driving unit for driving the composite vibrator and a detecting unit for detecting an angular velocity via the composite vibrator.
Further there is provided an electronic apparatus including the above vibration gyroscope.
There is provided a method of manufacturing a composite vibrator. The method includes a first step of bonding an auxiliary substrate to a second main surface of a base substrate, a second step of completely cutting the base substrate from the direction of a first main-surface side of the base substrate while leaving a part of the auxiliary substrate to form a plurality of tuning bar vibrators arranged in a width direction, the relative positions of the tuning bar vibrators being retained by the auxiliary substrate, a third step of bonding support members to the first main surfaces of the tuning bar vibrators,
Keating & Bennett LLP
Murata Manufacturing Co. Ltd.
Nguyen Tai
Tugbang A. Dexter
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