Measuring and testing – Speed – velocity – or acceleration – Angular rate using gyroscopic or coriolis effect
Reexamination Certificate
2000-09-07
2002-12-24
Kwok, Helen (Department: 2856)
Measuring and testing
Speed, velocity, or acceleration
Angular rate using gyroscopic or coriolis effect
C310S370000
Reexamination Certificate
active
06497148
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a gyroscope and an input apparatus that uses the gyroscope, and more particularly relates to a gyroscope of the type that detects the displacement of a leg of a tuning fork particularly due to angular velocity input in the form of the capacitance change and an input apparatus that uses the gyroscope of this type.
2. Description of the Related Art
Heretofore, a gyroscope comprising a tuning fork consisting of conductive material such as silicon has been known. In the case of a gyroscope of this type, a leg of a tuning fork is vibrated in one direction, the vibration in the direction perpendicular to the above-mentioned vibration direction generated by Coriolis force is detected when the angular velocity round the center axis in the longitudinal direction of the leg is entered during vibration. Because the magnitude of the vibration generated by Coriolis force corresponds to the magnitude of the angular velocity, a gyrosensor is used as an angular velocity sensor, and for example, a gyrosensor is applied to a coordinate input apparatus or the like for a personal computer.
FIG. 33
is a diagram illustrating the structure of a tuning fork that is the main component of a conventional gyroscope. As shown in this diagram, the exemplary tuning fork
200
has three legs
201
and a support
202
that connects respective base sides of the legs
201
, and consists of silicon that is rendered conductive. The tuning fork
200
is fixed on the base plate
203
by the support
202
, and driving electrodes (not shown in the drawing) are provided respectively. under the legs
201
. Therefore, when a voltage is applied on the driving electrodes, the legs
201
are vibrated in the vertical direction by electrostatic attractive force.
In the case of a gyroscope of this type, horizontal vibration is caused when angular velocity round the rotation axis in the longitudinal direction of the legs
201
is entered during vertical vibration, and the horizontal vibration is detected by use of a pair of detection electrodes
204
disposed on both sides of each leg
201
. In detail, when a leg
201
is displaced in the horizontal direction, the gap between the detection electrode
204
disposed on one side of the leg
201
and the leg
201
is narrowed, the gap between the detection electrode
204
disposed on the other side of the leg
201
and the leg
201
is concomitantly widened, and as the result a pair of two electrostatic capacities formed by the detection electrodes
204
and the leg
201
changes. Based on the electrostatic capacity change, the magnitude of an input angular velocity can be detected.
In the case of a gyroscope having the structure described hereinabove, the narrow gap design between a leg
201
and adjacent legs
201
(referred to as inter-leg gap hereinafter) is limited because the detection electrodes
204
are disposed respectively on both sides of the legs
201
. In detail, assuming that the width of a detection electrode
204
is denoted by x
1
, the gap between a detection electrode
204
and an adjacent leg
201
and a gap between adjacent detection electrodes
204
are denoted by x
2
, then an inter-leg gap G=2×1+3×2. Because of the working limit of x
1
and x
2
in silicon working by means of general semiconductor device fabrication technique, the narrow inter-leg gap G design has been limited.
On the other hand, it has been found that “Q-value”, which is a performance index for representing the resonance magnitude of a device of this type becomes large if the inter-leg gap G of-a three-leg tuning fork is reduced. If Q-value could be made large, not only the detection sensitivity of angular velocity is expected to be improved but also the conversion efficiency from electric energy supplied to the device to vibration energy is expected to be improved, and thus the reduction of driving voltage will be reduced.
However as described hereinabove, though it is expected that the narrow inter-leg gap design is variously advantageous in miniaturization of a device, improvement of detection sensitivity, reduction of driving voltage, and the likes, the narrow inter-leg gap design has not been realized because the narrow inter-leg gap is limited in the case of the conventional gyroscope.
SUMMARY OF THE INVENTION
The present invention has been accomplished to solve the above-mentioned problem, and it is the object of the present invention to provide a high quality and low cost gyroscope that is variously advantageous as described hereinabove.
To achieve the above-mentioned object, the first gyroscope of the present invention is characterized by comprising a vibration member served as a tuning fork, a base material disposed so as to face to the above-mentioned vibration member, a driving means for driving the above-mentioned vibration member, a plurality of detection movable electrodes connected to each other in parallel and provided on the surface parallel to the displacement detection direction of the free end portion of the above-mentioned vibration member, each of which has a Width equal to or larger than the maximum amplitude in the displacement detection direction of the above-mentioned vibration member, and a plurality of detection fixed electrodes connected to each other in parallel and provided on the above-mentioned base material disposed so as to face to the above-mentioned plurality of detection movable electrodes and so as to form the capacitance between the above-mentioned plurality of detection fixed electrodes and the above-mentioned plurality of detection movable electrodes
The detection principle of the gyroscope of the present invention is based on the detection of the vibration of a vibration member of a tuning fork (equivalent to the “leg” described hereinbefore) by means of capacitance change like the conventional gyroscope. Usually, the capacitance C is represented by the following equation.
C
=&egr;·(
S/d
) (1)
(wherein &egr; denotes the dielectric constant, S denotes the area of an electrode, and d denotes a gap between electrodes)
In the case of the conventional gyroscope, the change of a gap between a leg and a detection electrode due to vibration, namely the capacitance change due to the change of a gap d between electrodes in the equation (1), is detected. On the other hand, in the case of the gyroscope of the present invention, the change of the facing area between detection electrodes due to vibration, namely the capacitance change due to the change of the electrode area S in the equation (1), is detected.
In detail, in the case of the first gyroscope of the present invention, on the vibration member side, a plurality of detection movable electrodes connected to each other in parallel are provided on the surface parallel to the displacement detection direction of the free end, each of which detection movable electrodes has a width equal to or larger than the maximum amplitude of the vibration member in the displacement detection direction. On the other hand, on the base material side, a plurality of detection fixed electrodes connected to each other in parallel are provided and disposed so as to face to the above-mentioned plurality of detection movable electrodes, each of which detection fixed electrodes has a width equal to or larger than the maximum amplitude of the vibration member in the displacement detection direction. The structure described hereinabove is the most important characteristic of the gyroscope of the first gyroscope of the present invention.
Because of the structure described hereinabove, when the angular velocity round the rotation axis in the longitudinal direction of, the vibration member is entered while the vibration member of the tuning fork is being vibrated by means of a driving means, the vibration in the direction orthogonal to the above-mentioned vibration direction is caused due to Coriolis force. At that time, the detection movable electrodes on the vibration member side is facing to the detection fix
Abe Munemitsu
Esashi Masayoshi
Shinohara Eiji
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Kwok Helen
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