Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
2000-05-01
2002-09-17
Moller, Richard A. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
active
06450030
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a sensor device and particularly to a sensor device which can detect a rotational angular velocity, inclination and linear acceleration and is utilized for automobile body control, correction of video camera shake, and so on.
2. Description of the Related Art
FIG. 8
is a block diagram showing the circuit of a sensor device employed for automobile body control, and so on. The sensor device
10
contains a vibrator
12
. The vibrator
12
contains a vibrating body
14
of a rectangular solid as shown in FIG.
9
. The vibrating body
14
is formed by joining, for example, two piezoelectric substrates
16
and
18
. These piezoelectric substrates
16
and
18
are polarized so that their polarization is opposite to each other as shown by the arrows in FIG.
9
. On one piezoelectric substrate
16
, a groove
20
is formed so as to extend in the length direction of the vibrating body
12
in the middle of the width direction. Further, two grooves
22
and two grooves
24
extending in the width direction of the piezoelectric substrate
16
are formed so as to sandwich the portions corresponding with the two nodal points at bending vibration of the vibrating body
14
.
On the surface of the piezoelectric substrate
16
divided by these grooves
20
,
22
, and
24
, electrodes are formed. Among these electrodes, the electrodes
26
and
28
formed between the inside grooves
22
and
24
are used as detection portions for outputting signals in response to a vibration of the vibrating body
14
. Further, on the other piezoelectric substrate
18
, a common electrode is formed.
The vibrator
12
is supported by supporting members
32
,
34
,
36
, and
38
formed by metal wires, etc. The supporting member
32
is connected to the electrodes
40
sandwiched by the two grooves
22
by welding, soldering, etc. This supporting member
32
is electrically connected to the electrode
26
. Similarly, the supporting member
34
is connected to the electrode
42
sandwiched by the two grooves
24
. This supporting member
34
is electrically connected to the electrode
28
. Further, the supporting members
36
and
38
are connected to the common electrode
30
at the portions corresponding to the nodal points of the vibrating body
14
. These supporting members
32
,
34
,
36
, and
38
are formed in a bent shape and contained in a case
44
.
The electrodes
26
and
28
of the vibrator
12
are connected to buffers
50
and
52
, respectively. These buffers
50
and
52
are connected to a synthetic circuit
54
, and the sum of the output signals from the buffers
50
and
52
is obtained in the synthetic circuit
54
. The output signal of the synthetic circuit
54
is returned to an oscillation circuit
56
, and amplified and phase shifted in the oscillation circuit
56
. In this way, an excitation signal is produced, and the excitation signal obtained is input into the common electrode
30
. Further, the buffers
50
and
52
are connected to a differential circuit
58
, and the difference between the output signals from the buffers
50
and
52
is obtained. The output signal of the differential circuit
58
is input into a synchronous detection circuit
60
, and detected in synchronization with the signal of the synthetic circuit
54
. The signal detected in the synchronous detection circuit
60
is integrated in a integration circuit
62
and amplified in a DC amplifier.
In this sensor device
10
, the vibrating body
14
vibrates under bending mode in the direction normal to the surface on which the common electrode
30
is formed, by an excitation signal obtained in the oscillation circuit
56
. At this time, because the supporting members
32
,
34
,
36
, and
38
support the portions corresponding to the nodal points of the vibrating body
14
, there is little vibration leak of the supporting members
32
through
38
. However, it cannot be said that there is no vibration leak from the supporting members
32
through
38
, and the supporting members
32
through
38
are slightly vibrated. At this time, because the supporting members
32
through
38
are formed in a bent shape, the vibration of the supporting members
32
through
38
is absorbed, which prevents the vibration from leaking to the case
44
.
Further, from the differential circuit
58
, the difference between the signals output from the electrodes
26
and
28
is output. The output signal of the differential circuit
58
is detected in synchronization with the signal of the synthetic circuit
54
at the synchronous detection circuit
54
. In the absence of any rotation, because the bending condition of the electrode portions
26
and
28
of the vibrating body
14
is the same, the same signal is output from the electrodes
26
and
28
as shown in FIG.
10
. Therefore, any signal is not output from the differential circuit
58
.
In such a condition, when rotation takes place about the axis of the vibrating body
14
, a Coriolis force acts and the vibration direction of the vibrating body
14
is changed. Because of that, the bending condition of the electrode portions
26
and
28
is made different, and a difference is caused between the signals output from the electrodes
26
and
28
. For example, as shown in
FIG. 11
, when the output signal of the electrode
26
increases, the output signal of the electrode
28
decreases. Therefore, from the differential circuit
58
, the difference between these signals is output. Furthermore, because the change of the vibration direction of the vibrating body
14
is in accordance with the strength of the Coriolis force, the output signals of the electrodes
26
and
28
are also changed to be proportional to the Coriolis force. Further, because the output signal of the synthetic circuit
54
is the sum of the signals of the electrodes
26
and
28
, the output signal of the differential circuit
58
and the signal of the synthetic circuit
54
are in phase. Therefore, by detecting the output signal of the differential circuit
58
in synchronization with the signal of the synthetic circuit
54
, only the positive portion of the output signal of the differential circuit
58
can be detected. And by integrating the output signal of the synchronous detection circuit
60
through the integration circuit
62
and by amplifying it using the DC amplifier
64
, a positive DC signal proportional to the Coriolis force can be obtained.
When the vibrator
12
is rotated inversely, as shown in
FIG. 12
, the output signal of the electrode
26
decreases and the output signal of the electrode
28
increases. Therefore, the output signal of the differential circuit
58
becomes in opposite phase to that in FIG.
11
. On the contrary, because the output signal of the synthetic circuit
54
is in phase with
FIG. 11
, only the negative portion of the output signal of the differential circuit
58
is detected at the synchronous detection circuit
60
. Therefore, a negative DC signal proportional to the Coriolis force can be obtained at the DC amplifier
64
. Thus, the magnitude of a rotational angular velocity can be detected from the output signal of the DC amplifier
64
, and the direction of a rotational angular velocity can be detected from the polarity of the output signal of the DC amplifier
64
.
The use of such a sensor device
10
as, for example, a rollover sensor of automobiles, etc. has been considered. When an automobile is turned sideways, the roll-over sensor is to detect the rotational angular velocity and inflate a side air bag, and as a result, protect people from a traffic accident, which might result in injury or death. Further, the detection of rotational angular velocity using a sensor device is used for preventing video camera shake.
However, when an automobile is turned sideways while it is parked in a sloping place, the time from the start to finish of the turning is shorter than the case where the automobile is parked in a horizontal place, and accordingly it is required to inflate a si
Moller Richard A.
Murata Manufacturing Co. Ltd.
Ostrolenk Faber Gerb & Soffen, LLP
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