Measuring and testing – Specimen stress or strain – or testing by stress or strain... – Specified electrical sensor or system
Reexamination Certificate
2003-07-10
2004-11-23
Lefkowitz, Edward (Department: 2855)
Measuring and testing
Specimen stress or strain, or testing by stress or strain...
Specified electrical sensor or system
Reexamination Certificate
active
06820494
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a capacitance type sensor suitably used for detecting a force applied from outside.
2. Description of the Related Art
A capacitance type sensor is in general use as a device for converting magnitude and direction of a force applied by an operator into electric signal. For example, a device having the capacitance type sensor for inputting operation of multidimensional direction incorporated as a so-called joystick is used as an input device of a mobile phone.
A capacitance type sensor can be used to input an operation having a specified dynamic range as a magnitude of a force applied by an operator. Among others, a capacitance type force sensor having a capacitance element formed by two electrodes to detect an applied force on the bags of changes of capacitance values caused by variations of distance between the electrodes is now in practical use in a variety of fields in terms of the advantage that the structure can be simplified to reduce costs.
For example, Japanese Laid-open (Unexamined) Patent Publication No. Hei 7(1995)-200164 discloses a capacitance type sensor
510
as shown in FIG.
21
. The capacitance type sensor
510
has a substrate
520
, an elastic rubber plate
530
disposed over the substrate
520
, an electrode part
540
disposed on a lower surface of the elastic rubber plate
530
, an electrode part
500
-
504
arranged on an upper surface of the substrate
520
(See FIG.
22
), a presser plate
560
for fixedly supporting the elastic rubber plate
530
to the substrate
520
, and an electronic device
580
arranged on a lower surface of the substrate
520
. The electrode part
500
-
604
comprises electrodes part
501
,
502
arranged to be symmetric with respect to the Y-axis, electrodes part
503
,
504
arranged to be symmetric with respect to the X-axis, and an annular electrode part
500
arranged around the outside of those electrodes part. The periphery of the electrode part
540
is in contact with the electrode part
500
connected to ground and thus is connected to ground through the electrode part
500
.
When an operator presses down the elastic rubber plate
530
, the electrode part
540
is displaced downwardly increasingly with the displacement force, so that the distances between the electrode part
540
and the four electrodes part
501
-
504
are changed. Then, the capacitance values of the capacitance elements formed between the four electrodes part
501
-
504
and the electrode part
540
are changed. By detecting the changes of the capacitance values, magnitude and direction of a force applied by the operator can be recognized.
This capacitance type sensor
510
is suitably used for a device that can detect magnitude of a force applied by the operator when pressing down the elastic rubber plate
530
, but is not suitable for a device having the switch function of selectively switching between two different modes (e.g. on-state and off-state). Accordingly, when this capacitance type sensor is built in equipment as a device having a multidirectional switch function, the capacitance type sensor can hardly be used as it is and is required to add switch functions corresponding to the respective directions.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a capacitance type sensor applicable to either of a device for sensing magnitude of a force for each direction and a device having switch function.
In accordance with the first aspect of the present invention, there is provided a capacitance type sensor comprising a detective member, a first electrode being opposite to the detective member, a second electrode arranged between the detective member and the first electrode and constituting capacitance elements with the first electrode, the second electrode being displaceable in a same direction as the detective member when the detective member is displaced, one or more first switching electrodes being opposite to the detective member, and one or more second switching electrodes arranged between the detective member and the first switching electrode(s) in such a relation as to be opposite to the first switching electrode(s) and also spaced apart from the first switching electrodes), the second switching electrodes being contactable with the first switching electrodes increasingly with displacement of the detective member, wherein the first and second switching electrodes are arranged to overlap with the first and second electrodes with respect to a displacement direction of the detecting member, and wherein the capacitance type sensor is capable of recognizing the displacement of the detective member on the basis of a detection, using a signal input to the first electrode, of a change in capacitance value of the capacitance element caused by a change in distance between the first electrode and the second electrode.
According to this construction, since displacement of the detective member is recognized by detecting variations of the capacitance values of the capacitance elements caused by changes in distance between the first electrode and the second electrode, magnitude of a force applied to the detective member from outside can be recognized. Also, since contact of the first switching electrodes with the second switching electrodes) can be recognized, this can be used as the switching function. Accordingly, the capacitance type sensor of the invention can be used as a device having the function of outputting the displacement of the detective member (the magnitude of a force applied to the detective member from outside) in the form of signal (analog signal) and/or a device having the switch function. Thus, this capacitance type sensor has the function as a composite device useable as either of the former device and the latter device, so that the need to re-create the sensor for either of the purposes mentioned above is eliminated.
The first and second switching electrodes and the first and second electrodes are arranged to overlap with each other with respect to the displacement direction of the detective member (arranged in two layers with respect to a vertical direction, for example). This can practically solve the problem, involved in the arrangement wherein the first and second switching electrodes are disposed in a plane substantially common with the first and second electrodes, that due to the first and second switching electrodes being disposed inside of the first electrode or the second electrode, an effective area for the first electrode or the second electrode is reduced, causing significant reduction in sensitivity of the capacitance type sensor. This can also solve the problem that due to the first and second switching electrodes being disposed outside of the first electrode or the second electrode, a relatively large area is required for placement of the electrodes included in the sensor, causing increase in size of the sensor.
The expression that “displacement of the detective member can be recognized” has substantially the same meaning as the expression that “a force applied to the detective member from outside”.
The capacitance type sensor of the present invention may further comprise a first substrate disposed on the side opposite to the second electrode with respect to the first electrode and having the first electrode on its surface, a second substrate disposed on the side opposite to the first electrode with respect to the second electrode and having the second electrode on its surface, a first switching substrate disposed on the side opposite to the second switching electrode(s) with respect to the first switching electrodes and having the first switching electrodes on its surface, and a second switching substrate disposed on the side opposite to the first switching electrode(s) with respect to the second switching electrodes and having the second switching electrodes on its surface. According to this construction, since the first and second electrodes and the first and second switching electrodes are arranged
Davis Octavia
Lefkowitz Edward
NITTA Corporation
Osha & May L.L.P.
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