Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-05-25
2001-07-03
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S316010, C310S319000
Reexamination Certificate
active
06255760
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a driving apparatus of a piezoelectric vibrator used for a gyroscope, etc., more particularly, to a driving apparatus of a piezoelectric vibrator capable of being driven by a stable phase.
2. Description of the Related Art
FIG. 17
is a circuit constructional diagram showing driving means and detecting means of a piezoelectric vibrator for a conventional gyroscope;
FIG. 18
is a perspective view showing a piezoelectric vibrator of a three-leg tuning fork type used for a gyroscope;
FIG. 19
shows one constructional example of an end surface of a piezoelectric vibrator and is a front view thereof in the view of a direction of an arrow
19
in
FIG. 18
;
FIG. 20
is a front view showing another constructional example of the end surface of the piezoelectric vibrator; and FIGS.
21
(A) and
21
(B) show diagrams using a conventional method of obtaining the median of a phase differential between two voltage outputs, FIG.
21
(A) shows a case wherein a differential of amplitudes is equal to zero, and FIG.
21
(B) shows a case wherein amplitudes have a differential.
As shown in
FIG. 17
, the conventional gyroscope comprises: a piezoelectric vibrator
1
; driving means (AC drive signal source)
10
for supplying a drive signal to the piezoelectric vibrator
1
; and detecting means
20
for detecting an output signal from the piezoelectric vibrator
1
.
To start with, the piezoelectric vibrator
1
will be described. As shown in
FIG. 18
, the piezoelectric vibrator
1
is formed by adhering a piezoelectric material to both the front and back surfaces of a plane plate, which is made up of a constant-modulus material such as elinvar, alternatively by a plate material which is formed by a piezoelectric material such as PZT or crystal wholly. The piezoelectric vibrator
1
has three vibrating legs
1
u
,
1
v
and
1
w
which are formed in a forked manner at one end of the piezoelectric vibrator
1
. As shown in
FIG. 18
,
FIG. 19
, and
FIG. 20
, pairs of drive electrodes
1
a
and
1
b
, a and b, and
2
a
and
2
b
are formed onto the front surfaces of the vibrating legs
1
u
,
1
v
, and
1
w
, so as to extend in parallel from one end portion to a base end portion. Pairs of output electrodes
1
c
and
1
d
, c and d, and
2
c
and
2
d
are also formed onto the back surfaces of the vibrating legs
1
u
,
1
v
, and
1
w
, respectively. An earth electrode G is formed in the middle of the output electrodes c and d on the back surface of the vibrating leg
1
v
as a center, so as to extend from one end portion to the base end portion.
Arrows in
FIG. 19
indicate dielectric polarizing directions of the piezoelectric material at the three vibrating legs
1
u
,
1
v
, and
1
w
of the piezoelectric vibrator
1
. The dielectric polarizing directions are the same at the vibrating legs
1
u
and
1
w
of the piezoelectric vibrator
1
on both right and left sides. The dielectric polarizing directions of the center vibrating leg
1
v
contrast with the vibrating legs
1
u
and
1
w
on the right and left sides horizontally and vertically, respectively (a differential polarizing type).
In the piezoelectric vibrator
1
of the differential polarizing type, if supplying the same drive signal S to the drive electrodes
1
a
and
1
b
, a and b, and
2
a
and
2
b
from the driving means (AC drive signal source)
10
, a piezoelectric effect causes the vibrating legs
1
u
,
1
v
, and
1
w
to be vibrated to an X-direction serving as an array direction of the vibrating legs, as shown in FIG.
19
.
A primary or multiple mode causes deformation vibration bending to the X-direction in the vibrating legs
1
u
,
1
v
, and
1
w
. The vibrating leg
1
u
and
1
w
on both sides are driven by the same phase. The vibrating leg
1
v
at the center is driven so that this phase is different from the vibrating legs
1
u
and
1
w
by &pgr; (180°), respectively. That is, when the vibrating legs
1
u
and
1
w
on both sides have an amplitude direction as a (+X)-direction at a certain point, the center vibrating leg
1
v
has an amplitude direction of a (−X)-direction.
As mentioned above, if setting the vibrating legs to a rotational system having a Z-direction with a vibrated state, Coriolis force works in a direction perpendicular to the vibrating direction (X-direction) to the vibrating legs, and the vibrating legs are vibrated to a Y-direction. With respect to a vibrating component due to the Coriolis force, the phases of the vibrating legs
1
u
and
1
w
on both sides are also opposite to the phase of the center vibrating leg
1
v
. When Coriolis force causes the vibrating legs
1
u
and
1
w
on both sides to have an amplitude component of a (+Y)direction at a certain point, the center vibrating leg
1
v
has an amplitude of a (−Y)-direction.
As shown in
FIG. 20
, in case of a piezoelectric vibrator (the same polarizing type)
1
b
such that all of the dielectric polarizing directions of the vibrating legs
1
u
,
1
v
, and
1
w
are formed to have the same direction, drive signal S
1
and S
2
having a differential phase of 180° each other are supplied between adjacent drive electrodes on one vibrating leg, respectively. In other words, the drive signal S
1
is supplied to the drive electrodes
1
b
and
2
b
in the (+X)-direction in the vibrating legs
1
u
and
1
w
on both sides, and the drive signal S
2
is supplied to the drive electrodes
1
a
and
2
a
in the (−X)-direction therein. Contrarily, the d rive signal S
2
is supplied to the drive electrode b in the (+X)-direction in the vibrating leg
1
v
, and the drive signal S
1
is supplied to the drive electrode a in the (−X)-direction therein. As stated above, the drive signals S
1
and S
2
are supplied to the drive electrodes of the vibrating legs
1
u
,
1
v
, and
1
w
, respectively, thereby enabling the piezoelectric vibrator
1
B to be vibrated similarly to the piezoelectric vibrator
1
.
If setting the piezoelectric vibrator (the differential polarizing type)
1
or
1
b
(the same polarizing type) to any desired rotational system, current outputs I
1
and I
2
like sine waves with different phases are outputted between the earth electrode G and the output electrode c and between the earth electrode G and the output electrode d, respectively. A signal is outputted so that the median of the phase differential between the current outputs I
1
and I
2
is synchronized with a timing of a leading edge of the drive signal S. Properly speaking, the driving means
10
is feedback-controlled so that the drive signal S is synthesized with the median of the phase differential between the current outputs I
1
and I
2
.
The next description turns to the operation of the driving means
10
and the detecting means
20
. It is noted that it is assumed that when setting the phase differential between the current outputs I
1
and I
2
to &lgr;, &lgr;/2 as the median of the phase differential &lgr; is set to a reference point (0 deg) of the phase.
As shown in
FIG. 17
, the driving means
10
comprises: I/V (current/voltage) converting means
11
; adding means
12
; first phase shifting means
13
; a coupling capacitor C
1
; binarizing means
14
; second phase shifting means
15
; gain varying means
16
; and buffer means
17
. The detecting means
20
comprises binarizing means
21
and phase differential detecting means
22
.
In the piezoelectric vibrator
1
, the output electrodes c and d of the center vibrating leg
1
v
are connected to the I/V (current/voltage) converting means
11
which is provided for the first stage of the driving means
10
. The I/V (current/voltage) converting means
11
is constructed by an operational amplifier, etc. mainly, and comprises I/V converting circuits
11
A and
11
B, to which a resistor, a capacitor, and the like are attached externally around the operational amplifier, etc. The output electrode c of the piezoelectric vibrator
1
is connected to an input terminal
11
a
1
of the I/V c
Hasegawa Kazuo
Takai Daisuke
Addison Karen
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Ramirez Nestor
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