Process of making an acceleration detecting element

Details Process of making an acceleration detecting element Process of making an acceleration detecting element

2001-05-01

2004-09-07

Kwok, Helen (Department: 2856)

Measuring and testing

Speed, velocity, or acceleration

Angular rate using gyroscopic or coriolis effect

Reexamination Certificate

active

06786094

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vibrator used for an angular velocity sensor or the like.
2. Description of the Related Art
FIG. 4
illustrates a plan view of a conventional vibrator
2
constituting a conventional angular velocity sensor
1
. The vibrator
2
of the angular velocity sensor
1
shown in
FIG. 4
includes a substrate
3
in which a support fixed unit
4
, comb-shaped driving fixed electrode units
5
(
5
a
,
5
b
,
5
c
,
5
d
,
5
e
,
5
f
,
5
g
,
5
h
) and detecting fixed electrode units
6
(
6
a
,
6
b
,
6
c
,
6
d
,
6
e
,
6
f
) are each disposed in a fixed manner on the top face thereof. A vibrating body
8
is connected to the support fixed unit
4
via support units
7
(
7
a
,
7
b
).
The vibrating body
8
is spaced from the substrate
3
, is disposed so that it can vibrate, and is constructed by including driving beams
9
(
9
a
,
9
b
,
9
c
,
9
d
), an outer frame
10
, comb-shaped driving movable electrode units
11
(
11
a
,
11
b
,
11
c
,
11
d
,
11
e
,
11
f
,
11
g
,
11
h
), support units
12
(
12
a
,
12
b
), detecting beams
13
(
13
a
,
13
b
,
13
c
,
13
d
) that are coupling beams, an inner frame
14
, and comb-shaped detecting moveable electrode units
15
(
15
a
,
15
b
,
15
c
,
15
d
,
15
e
,
15
f
).
That is, one end side of each of the driving beams
9
a
and
9
b
is commonly connected to the support unit
7
a
, one end side of each of the driving beams
9
c
and
9
d
is commonly connected to the support beam
7
b
, and the other end side of each of the driving beams
9
a
,
9
b
,
9
c
, and
9
d
is commonly connected to the outer frame
10
.
This outer frame
10
, as described later, can vibrate in an X direction shown in FIG.
4
. The comb-shaped driving moveable electrode units
11
are each provided in the outer frame
10
so as to be interdigitated with and spaced from the corresponding comb-shaped driving fixed electrode units
11
. Pairs of the driving fixed electrode units
5
a
,
5
b
,
5
c
, and
5
d
and the driving moveable electrode units
11
a
,
11
b
,
11
c
, and
11
d
that correspondingly face each other constitute a first driving unit (driving unit), and pairs of the driving fixed electrode units
5
e
,
5
f
,
5
g
, and
5
h
and the driving moveable units
11
e
,
11
f
,
11
g
, and
11
h
constitute a second driving unit (driving unit).
The support units
12
a
and
12
b
are each formed in the outer frame
10
so as to extend towards the inside of the outer frame
10
. Furthermore, the detecting beams
13
a
and
13
b
are each formed so as to extend from the end side of the support unit
12
a
while the detecting beams
13
c
and
13
d
are each formed so as to extend from the support beam
12
b.
The inner frame
14
is commonly connected to the extended edge side of each of the detecting beams
13
a
,
13
b
,
13
c
, and
13
d
. This inner frame
14
can vibrate integrally with the outer frame
10
in the X direction, as described below, and can also vibrate in a Y direction with respect to the outer frame
10
. The comb-shaped detecting moveable electrode units
15
are each provided in the inner frame
14
so as to be interdigitated with and spaced from the corresponding comb-shaped detecting fixed electrode units
6
. Pairs of the detecting fixed electrode units
6
a
,
6
b
, and
6
c
and the detecting moveable electrode units
15
a
,
15
b
, and
15
c
that correspondingly face each other constitute a first detecting unit (vibration detecting unit in the Coriolis force direction). Pairs of the detecting fixed electrodes
6
d
,
6
e
, and
6
f
and the detecting moveable electrode units
15
d
,
15
e
, and
15
f
constitute a second detecting unit (vibration detecting unit in the Coriolis force direction). Among a plurality of pairs of the detecting fixed electrode units
6
and the detecting moveable electrode units
15
that constitute the first and second detecting units, the pair of the detecting fixed electrode unit
6
c
and the detecting moveable electrode unit
15
c
and the pair of the detecting fixed electrode unit
6
f
and the detecting moveable electrode unit
15
f
constitute a driving monitoring unit.
A conductor pattern for supplying electric power from the outside to each of the driving fixed electrode units
5
and a conductive pattern for conductively connecting to each of the detecting fixed electrode units
6
are formed though they are not shown.
The vibrator
2
shown in
FIG. 4
is constructed in the above-described manner. In this vibrator
2
, when an alternating driving voltage (driving signal) is applied between the driving fixed electrode units
5
and the driving moveable electrode units
11
that face each other, making use of elasticity of each of the driving beams
9
, the vibrator
8
vibrates (i.e., drive-vibrates) in the X-direction shown in
FIG. 4
, in which the support units
7
a
and
7
b
are caused to serve as fulcrums, in accordance with changes in the magnitude of electrostatic force based on the driving voltage.
In a state in which the overall vibrating body
8
is vibrated in the X direction in this manner, when the vibrating body
8
rotates about an axis in the Z direction (in the direction perpendicular to the drawing), the Coriolis force is generated in a direction, which is perpendicular to both the vibrating direction (X direction) of the vibrating body
8
and the center axis direction (Z direction) of rotation of the vibrating body
8
, that is, the Coriolis force is generated in the Y direction. This Y-direction Coriolis force causes the inner frame
14
of the vibrating body
8
to vibrate (i.e., detect-vibrate) in the Y direction relatively to the outer frame
10
, making use of the support units
12
a
and
12
b
as fulcrums and the elasticity of each of the detecting beams
13
.
By detecting the change in the capacitance between the detecting fixed electrode units
6
and detecting moveable electrode units
15
based on this Y-direction detecting-vibration, the magnitude of the angular velocity around the Z axis can be detected.
Normally, in order to avoid adverse effects such as air damping, the vibrator
2
is contained in a housing space defined by, for example, a glass member and is sealed in a depressurized state. In this case, the driving fixed electrode units
5
and the detecting fixed electrode units
6
of the vibrator
2
are constructed so as to be conductively connectable to the outside via a through-hole disposed in, for example, the glass member.
In
FIG. 5
, one example of a signal processing circuit connected to the vibrator
2
is shown along with main parts of the vibrator
2
. This signal processing circuit
20
is constructed by including a first detecting C-V converting unit
21
, a second C-V converting unit
22
, a summing amplifying unit
23
, a differential amplifying unit
24
, an AGC (Auto Gain Control) unit
25
, a phase inverting unit
26
, and a synchronous detecting unit
27
. In
FIG. 5
, the driving fixed electrode units
5
, the detecting fixed electrode units
6
, the detecting movable electrode units
15
and the vibrating body
8
of the vibrator
2
are illustrated in a simplified manner so that the construction of the signal processing circuit can be easily described.
The first detecting C-V converting unit
21
has a construction for converting the total capacitance between the detecting fixed electrode units
6
(
6
a
,
6
b
,
6
c
) and the detecting moveable electrode units
15
(
15
a
,
15
b
,
15
c
), which constitute the first detecting unit of the vibrator
2
, into a voltage and for outputting the converted signal. The second detecting C-V converting unit
22
has a construction for converting the total capacitance between the detecting fixed electrode units
6
(
6
d
,
6
e
,
6
f
) and the detecting moveable electrode units
15
(
15
d
,
15
e
,
15
f
), which constitute the second detecting unit, into a voltage and for outputting the converted signal.
When the vibrating body
8
vibrates only in the X-direction, the signal

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