Measuring and testing – Dynamometers – Responsive to multiple loads or load components
Reexamination Certificate
2000-02-11
2002-04-30
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Dynamometers
Responsive to multiple loads or load components
C073S514070, C073S03200R, C073S780000
Reexamination Certificate
active
06378381
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a sensor for detecting force or acceleration, and relates particularly to a capacitance sensor for detecting force or acceleration in a particular axial direction in an XYZ three-dimensional coordinate system using a capacitance element.
Force sensors and acceleration sensors are used in numerous industrial devices as a means of detecting a particular physical quantity, and as an input device for use with digital devices. Sensors using capacitance elements (capacitance sensors) in particular are used as a low cost data capturing and input device for use with computer devices because of their simple construction and ability to reduce cost.
Capacitance sensors for detecting force or acceleration use a capacitance element of which the electrode gap is changed by the force or acceleration being detected, and detect the desired force or acceleration based on the change in the capacitance of this element. More recent sensors of this type use a plurality of capacitance elements arrayed at specific locations to separately detect a desired two-dimensional or three-dimensional force or acceleration component. U.S. Pat. No. 5,406,848 and U.S. Pat. No. 5,421,213, for example, teach the basic principle of a multi-dimensional capacitance sensor for detecting force, acceleration, or magnetism.
A problem with the various capacitance sensors of the related art is, however, that interference between different detection axes occurs when detecting force or acceleration along a specific detection axis. A multi-dimensional capacitance sensor typically has a dedicated capacitance element along each detection axis with each said element independently outputting a detection value. During actual sensor operation, however, the detected value is affected slightly by the action of the force or acceleration component on an axis other than the intended detection axis of the sensor. This makes it necessary to implement some corrective measure, such as providing a compensation circuit for cancelling the effect of interference between force or acceleration components on different axes. Such measures ultimately complicate the overall structure of the device, and increase production cost.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to provide a sensor using capacitance element for obtaining by means of a simple construction an accurate detection value with no interference from another detection axis.
(1) The first feature of the present invention resides in a capacitance sensor using a capacitance element for detecting force or acceleration in a specific axis direction in an XYZ three-dimensional coordinate system having an X-axis, a Y-axis and a Z-axis, comprising:
a bottom fixed layer and a top fixed layer fixed with a specific gap therebetween and with surfaces thereof parallel to an XY plane and intersected by the Z-axis;
a displacement layer disposed between the bottom fixed layer and the top fixed layer so as to maintain a reference state substantially parallel to the XY plane under conditions in which a force or an acceleration is not at work, and to displace from the reference state when a force or an acceleration is at work;
a working body connected to a part of the displacement layer for causing displacement of the displacement layer based on an action of force or acceleration;
a positive X-axis bottom electrode formed on a top surface of the bottom fixed layer at a position corresponding to a positive region of the X-axis;
a negative X-axis bottom electrode formed on a top surface of the bottom fixed layer at a position corresponding to a negative region of the X-axis;
a positive X-axis top electrode formed on a bottom surface of the top fixed layer at a position corresponding to the positive region of the X-axis;
a negative X-axis top electrode formed on a bottom surface of the top fixed layer at a position corresponding to the negative region of the X-axis;
a displacement electrode formed on a bottom surface of the displacement layer at a position corresponding to the positive X-axis bottom electrode;
a displacement electrode formed on a bottom surface of the displacement layer at a position corresponding to the negative X-axis bottom electrode;
a displacement electrode formed on a top surface of the displacement layer at a position corresponding to the positive X-axis top electrode; and
a displacement electrode formed on a top surface of the displacement layer at a position corresponding to the negative X-axis top electrode;
where a positive X-axis bottom capacitance element is formed by the positive X-axis bottom electrode and an opposing displacement electrode;
a negative X-axis bottom capacitance element is formed by the negative X-axis bottom electrode and an opposing displacement electrode;
a positive X-axis top capacitance element is formed by the positive X-axis top electrode and an opposing displacement electrode;
a negative X-axis top capacitance element is formed by the negative X-axis top electrode and an opposing displacement electrode; and
a detection means having a function for detecting a force or an acceleration acting in an X-axis direction based on a difference between
a sum of a capacitance of the positive X-axis bottom capacitance element and a capacitance of the negative X-axis top capacitance element, and
a sum of a capacitance of the negative X-axis bottom capacitance element and a capacitance of the positive X-axis top capacitance element.
(2) The second feature of the present invention resides in a capacitance sensor described in the first feature, further comprising:
a positive Y-axis bottom electrode formed on a top surface of the bottom fixed layer at a position corresponding to a positive region of the Y-axis;
a negative Y-axis bottom electrode formed on a top surface of the bottom fixed layer at a position corresponding to a negative region of the Y-axis;
a positive Y-axis top electrode formed on a bottom surface of the top fixed layer at a position corresponding to the positive region of the Y-axis;
a negative Y-axis top electrode formed on a bottom surface of the top fixed layer at a position corresponding to the negative region of the Y-axis;
a displacement electrode formed on a bottom surface of the displacement layer at a position corresponding to the positive Y-axis bottom electrode;
a displacement electrode formed on a bottom surface of the displacement layer at a position corresponding to the negative Y-axis bottom electrode;
a displacement electrode formed on a top surface of the displacement layer at a position corresponding to the positive Y-axis top electrode; and
a displacement electrode formed on a top surface of the displacement layer at a position corresponding to the negative Y-axis top electrode;
where a positive Y-axis bottom capacitance element is formed by the positive Y-axis bottom electrode and an opposing displacement electrode;
a negative Y-axis bottom capacitance element is formed by the negative Y-axis bottom electrode and an opposing displacement electrode;
a positive Y-axis top capacitance element is formed by the positive Y-axis top electrode and an opposing displacement electrode; and
a negative Y-axis top capacitance element is formed by the negative Y-axis top electrode and an opposing displacement electrode; and
the detection means has a further function for detecting a force or an acceleration acting in a Y-axis direction based on a difference between
a sum of a capacitance of the positive Y-axis bottom capacitance element and a capacitance of the negative Y-axis top capacitance element, and
a sum of a capacitance of the negative Y-axis bottom capacitance element and a capacitance of the positive Y-axis top capacitance element.
(3) The third feature of the present invention resides in a capacitance sensor described in the first or second feature, wherein the bottom electrodes and the top electrodes are symmetrical to the XZ plane or YZ plane.
(4) The fourth feature of the present invention resides in a capacitance sensor described in the third
Itano Hiromichi
Okada Kazuhiro
Taniguchi Nobumitsu
Davis Octavia
Fuller Benjamin R.
Ladas & Parry
Wacoh Corporation
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