Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-06-03
2001-03-13
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S316010
Reexamination Certificate
active
06201341
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vibrator to be used for a vibrating gyroscope, and a vibrating gyroscope using the vibrator. More particularly, the present invention relates to a vibrator which is capable of detecting rotational angular velocities around two, non-parallel axes, and which is used for hand shake prevention of a video camera, the navigation system of an automobile, a pointing device or the like, and a vibrating gyroscope using the vibrator.
2. Description of the Related Art
A vibrating gyroscope which is generally known as a conventional vibrating gyroscope and has a tuning-fork type vibrator or a sound-piece type vibrator can detect only one rotational angular velocity around one axis. In recent years, however, the market has demanded a vibrating gyroscope capable of detecting two rotational angular velocities around two axes to provide increased sensitivity and accuracy.
To satisfy the demand, the applicant of the present invention has already proposed two types of vibrating gyroscopes as discussed below.
FIG. 8
shows a first example of a vibrating gyroscope disclosed in Japanese Unexamined Patent Publication No. 7-19878.
A vibrating gyroscope
100
includes a first riangular prismatic vibrator
101
and a second triangular prismatic vibrator
102
. The first vibrator
101
is provided with a first vibrating body
103
and two first piezoelectric elements
105
formed on two side surfaces of the first vibrating body
103
. Only one of the two first piezoelectric elements
105
is shown in the figure. The second vibrator
102
is provided with a second vibrating body
104
and two second piezoelectric elements
106
formed on two side surfaces of the second vibrating body
104
. only one of the two second piezoelectric elements
106
is shown in the figure.
The first vibrator
101
is joined with the second vibrator
102
so that the first vibrator
101
is approximately orthogonal to the second vibrator
102
in the vicinity of a center part of a surface on which no piezoelectric element is formed in the first vibrating body
103
and the second vibrating body
104
, respectively.
In the vibrating gyroscope
100
of such a construction, the two first piezoelectric elements
105
and the two second piezoelectric elements
106
are connected to an output end of a drive circuit (not shown). Further, the two first piezoelectric elements
105
are connected to an input end of a first detection circuit (not shown). Still further, the two second piezoelectric elements
106
are connected to an input end of a second detection circuit (not shown).
In this vibrating gyroscope
100
, a similar drive signal is inputted from the drive circuit to the two first piezoelectric elements
105
and the two second piezoelectric elements
106
, and the first vibrator
101
and the second vibrator
102
are respectively flexural-vibrated in a direction orthogonal to the joining surface of the first vibrating body
103
with the second vibrating body
104
.
When a rotational angular velocity around the axis of the first vibrator
101
is added in this condition, a Coriolis force is generated in a direction orthogonal to the vibrating direction. The vibrating direction of the first vibrator
101
is changed by the Coriolis force and results in a signal according to the rotational angular velocity being generated between the two first piezoelectric elements
105
. The signal is detected by a detection circuit to output a detected signal corresponding to the rotational angular velocity around the axis of the first vibrator.
Similarly, when the rotational angular velocity around the axis of the second vibrator
102
is added, the signal according to the rotational angular velocity is generated between the two second piezoelectric elements
106
. This signal is detected by the detection circuit to output a detected signal corresponding to the rotational angular velocity around the axis of the second vibrator.
This vibrating gyroscope
100
is thus capable of detecting two rotational angular velocities around two axes, i.e., the rotational angular velocity around the axis of the first vibrator
101
and the rotational angular velocity around the axis of the second vibrator
102
.
The vibrating gyroscope
100
has the following problems. First, an interference (a beat) is generated when the resonance frequencies of two vibrators are close to each other. A false angular velocity signal can, thus, be generated from each vibrator. This necessitates sufficiently separating the resonance frequencies in the driving direction and the detecting direction of the respective vibrators from each other by taking countermeasures such as by shaping each vibrator differently and completely attenuating the beat frequency whose component includes the difference in the resonance frequencies by using, e.g., a low-pass filter.
Respective drive circuits and detection circuits are required for the two kinds of vibrators, resulting in a number of circuits twice that of a single axis gyroscope, thereby doubling the cost.
A beat can be eliminated by exciting vibrators in two directions at the same frequency and the same phase. That is, a beat can be eliminated if the two resonance frequencies of the two vibrators in the driving direction are in complete agreement with each other.
However, it is practically impossible to make two resonance frequencies completely agree with each other, taking into consideration the temperature characteristic.
FIG. 9
shows a second example of a vibrating gyroscope disclosed in Japanese Unexamined Patent Publication No. 6-3153.
The vibrating gyroscope
110
includes a disk-like vibrating body
112
. Fan-shaped piezoelectric elements
114
a
,
114
b
,
114
c
,
114
d
,
114
e
,
114
f
,
114
g
,
114
h
whose central angle is approximately 45° are formed on one major plane of the vibrating body
112
, and these piezoelectric elements
114
a
-
114
h
are used for detection to obtain a signal corresponding to the rotational angular velocity.
A disk-shaped piezoelectric element
116
is formed on the other major plane of the vibrating body
112
, and used for driving in order to flexural-vibrate the vibrating body
112
.
The piezoelectric elements
114
a
,
114
d
and the piezoelectric elements
114
e
,
114
h
are connected to a first detection circuit (not shown), while the piezoelectric elements
114
b
,
114
g
and the piezoelectric elements
114
c
,
114
f
are connected to a second detection circuit (not shown).
Here, the x-axis direction is defined as the direction orthogonal to the major plane of the vibrating body
112
; the y-axis direction is defined as the direction which is orthogonal to the x-axis direction and passes between the piezoelectric elements
114
a
,
114
b
,
114
g
,
114
h
and the piezoelectric elements
114
c
,
114
d
,
114
e
,
114
h
,
114
f
; and the z-axis direction is defined as the direction which is orthogonal to the x-axis direction and passes between the piezoelectric elements
114
a
,
114
b
,
114
c
,
114
d
and the piezoelectric elements
114
e
,
114
f
,
114
g
,
114
h.
When a drive signal from a drive circuit (not shown) is applied to the piezoelectric element
116
, the vibrating body
112
is vibrated in the so-called concentric mode wherein a center part of the disk is vibrated reciprocally in the x-axis direction.
When a rotational angular velocity is applied around the z-axis in this condition, a Coriolis force is exerted in the y-axis direction. A difference is generated thereby between the voltage generated in the piezoelectric elements
114
a
,
114
d
and the voltage generated in the piezoelectric elements
114
e
,
114
h
, and the difference is detected by the first detection circuit to obtain the rotational angular velocity applied around the z-axis.
Similarly, when a rotational angular velocity is applied around the y-axis, a Coriolis force is exerted in the z-axis direction. A difference is generated thereby between the voltage generated in the piezoelectric elements
114
b
,
114
Dougherty Thomas M.
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
LandOfFree
Vibrator for detecting angular velocities about two axes and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vibrator for detecting angular velocities about two axes and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vibrator for detecting angular velocities about two axes and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2453873