Measuring and testing – Speed – velocity – or acceleration – Acceleration determination utilizing inertial element
Reexamination Certificate
2001-03-12
2003-01-21
Moller, Richard A. (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Acceleration determination utilizing inertial element
Reexamination Certificate
active
06508125
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to an electrostatic capacitance type acceleration sensor, an electrostatic capacitance type angular acceleration sensor and an electrostatic actuator manufactured by the semiconductor micromachining technique.
2. Description of the Background Art
FIGS. 12
to
15
show a structure of an electrostatic capacitance type acceleration sensor
300
in the background art. More particularly,
FIG. 12
is a top view of the electrostatic capacitance type acceleration sensor
300
,
FIG. 13
is a perspective view of the electrostatic capacitance type acceleration sensor
300
,
FIG. 14
is a cross-sectional view at a cutting plane line C—C in FIG.
12
and
FIG. 15
is a cross-sectional view at a cutting plane line D—D in FIG.
12
.
The electrostatic capacitance type acceleration sensor
300
detects acceleration on the basis of the change in capacitance between a movable electrode
307
and a fixed electrode
304
. The fixed electrode
304
consists of a supporting part
304
b
formed on a substrate
301
such as a silicon substrate and a plurality of comblike electrodes
304
a
protruding from the supporting part
304
b.
The movable electrode
307
consists of a ridge
307
b
and a plurality of comblike electrodes
307
a
protruding from the ridge
307
b
and alternately arranged between each of the comblike electrodes
304
a
of the fixed electrode
304
. The movable electrode
307
is held apart from the substrate
301
by a beam
303
that is coupled with a supporting part
302
formed on the substrate
301
.
When acceleration in a direction such as Y direction in
FIG. 12
is applied to the electrostatic capacitance type acceleration sensor
300
, the beam
303
is deformed elastically to move the movable electrode
307
. A distance between the comblike electrode
307
a
and the comblike electrode
304
a
is thereby changed, to change capacitance between the fixed electrode
304
and the movable electrode
307
. Therefore, acceleration can be detected quantitatively by monitoring this change in capacitance from outside.
The width of the beam
303
(the length in a X direction in
FIG. 12
) is arranged to be larger than the widths of the supporting part
302
and the ridge
307
b
of the movable electrode
307
for the reason that the rigidity of the beam
303
should be lowered. Here, the rigidity of the beam
303
is determined depending on the configuration of the beam
303
. The flexibility of the beam
303
is increased as its rigidity is lowered, to thereby increase sensitivity of the movable electrode
307
to acceleration.
Further, a diagnostic electrode
308
for diagnosing breakdown and malfunction, for example, is formed on the substrate
301
. When a voltage is applied to the diagnostic electrode
308
, an electrostatic force is generated against the comblike electrode
307
a
of the movable electrode
307
. Then, the movable electrode
307
is displaced on receipt of the electrostatic force to diagnose whether the movable electrode
307
functions normally or not.
Each of these electrodes is formed by processing a conductive material such as polysilicon or single-crystalline silicon stacked on the substrate
301
using the semiconductor micromachining technique.
In the above-described electrostatic capacitance type acceleration sensor
300
, the problem may be caused that when acceleration is applied excessively, the comblike electrode
307
a
of the movable electrode
307
and the comblike electrode
304
a
of the fixed electrode
304
collide with each other to damage both electrodes.
Such problem may also occur in an electrostatic capacitance type angular acceleration sensor and an electrostatic actuator.
SUMMARY OF THE INVENTION
A first aspect of the present invention is directed to an electrostatic capacitance type acceleration sensor comprising: a substrate; a first supporting part formed on the substrate; a first movable electrode supported by the first supporting part apart from the substrate; a second supporting part formed on the substrate; and a second movable electrode supported by the second supporting part apart from the substrate, wherein amounts of movement of the first and second movable electrodes are different from each other during application of acceleration.
According to a second aspect of the present invention, the electrostatic capacitance type acceleration sensor according to the first aspect further comprises a diagnostic electrode, wherein a distance between the diagnostic electrode and at least one of the first and second movable electrodes is larger than a distance between the first movable electrode and the second movable electrode.
According to a third aspect of the present invention, in the electrostatic capacitance type acceleration sensor according to the first aspect, the second movable electrode and the second supporting part include a plurality of them.
According to a fourth aspect of the present invention, in the electrostatic capacitance type acceleration sensor according to the third aspect, the first movable electrode and the first supporting part also include a plurality of them.
A fifth aspect of the present invention is directed to an electrostatic capacitance type acceleration sensor comprising: a substrate; a supporting part formed on the substrate; a movable electrode supported by the supporting part apart from the substrate; and a fixed electrode formed on the substrate, wherein one of the fixed electrode and a pair of the movable electrode and the supporting part includes a plurality of them.
According to a sixth aspect of the present invention, in the electrostatic capacitance type acceleration sensor according to the fifth aspect, another of the fixed electrode and the pair of the movable electrode and the supporting part also includes a plurality of them.
A seventh aspect of the present invention is directed to an electrostatic capacitance type angular acceleration sensor comprising: a substrate; a first supporting part formed on the substrate; a first movable electrode supported by the first supporting part apart from the substrate; a second supporting part formed on the substrate; and a second movable electrode supported by the second supporting part apart from the substrate, wherein amounts of movement of the first and second movable electrodes are different from each other during application of angular acceleration, and wherein at least one of the first and second movable electrodes is driven by applying a potential difference between the first movable electrode and the second movable electrode.
An eighth aspect of the present invention is directed to an electrostatic actuator comprising: a substrate; a first supporting part formed on the substrate; a first movable electrode supported by the first supporting part apart from the substrate; a second supporting part formed on the substrate; and a second movable electrode supported by the second supporting part apart from the substrate, wherein at least one of the first and second movable electrodes is driven by applying a potential difference between the first movable electrode and the second movable electrode.
According to the first aspect of the present invention, the first and second movable electrodes are movable provided and the amounts of movement of both movable electrodes are different from each other during application of acceleration. Therefore, similar to an electrostatic capacitance type acceleration sensor having a fixed electrode and a movable electrode in the background art, acceleration can be detected by the change in capacitance between the first movable electrode and the second movable electrode. Further, since both of the first and second electrodes are designed to be movable, the first and second movable electrodes are unlikely to collide with each other even when acceleration is applied excessively. Therefore, a probability of damage to the first and second movable electrodes is low.
According to the second aspect of the present invention, since a distance b
Mitsubishi Denki & Kabushiki Kaisha
Moller Richard A.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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