JP2001074569A - Planar capacitance type twist strain sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify bonding onto a detected structure and handling, and to convert the level of twist strain from a change in the capacitance into a change in the frequency to facilitate signal processing. SOLUTION: In this sensor, a dielectric film layer 2 of which a dielectric constant changes by a strain is formed on one main face of a flexible rectangular plate type insulative sheet 1 using an insulative plastic to make its thickness substantially uniform, and a pair of electrode patterns are formed to have plural oblique line-like electrodes 3a, 4a extended in parallel to get alternately into each other while inclined by about 45' with respect to one direction where a detected structure is extended respectively from a pair of linear common electrodes 3, 4 opposed to a surface of the dielectric film layer 2, so as to provide capacitance. Capacitor terminals are connected to the common electrodes 3, 4, and the paired electrode patterns acts as a capacitor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torsional strain sensor mainly for detecting torsional strain applied to a structure to be detected, and more particularly, to a torsional strain sensor formed on a surface of a dielectric film layer whose dielectric constant changes due to strain. The present invention relates to a flat-plate capacitive torsional strain sensor for detecting the magnitude of torsional distortion accompanying elastic deformation of a structure to be detected based on a change in capacitance of a capacitor due to an electrode pattern.

[0002]

2. Description of the Related Art Conventionally, this type of torsional strain sensor is capable of detecting a torsional strain applied to a plate-like or column-shaped structure to be detected extending in a uniaxial direction having a flat or curved outer surface. A so-called strain gauge whose resistance changes due to strain is well known.

FIG. 5 illustrates a conventional torsional strain sensor and its application example. FIG. 5A is a perspective view showing a state in which a strain gauge 23 is bonded to a structure to be detected as a torsional strain sensor. (A) shows strain gauge 2
3 relates to an enlarged perspective view of FIG.

[0004] Here, as shown in FIG.
As shown in FIG. 5A, an outer peripheral surface 2 of a cylinder 21 having one end fixed to a pedestal 24 as a structure to be detected using a strain gauge 23 formed by a thin film pattern of an e-Ni-based alloy.
FIG. 2 shows that the torsion strain of the cylinder 21 can be detected by bonding such that the strain detection axis is aligned with a direction inclined by 45 degrees with respect to the direction of one axis (center axis) in which the cylinder 21 extends. .

When the torsion of the cylinder 21 is detected by the strain gauge 23 in such a state, when a torsional moment is applied to the cylinder 21 to generate a torsional strain in the cylinder 21, the center of the cylinder 21 is attached to the portion where the strain gauge 23 is bonded. An elongational strain in a direction inclined by 45 degrees with respect to the axial direction and a compressive strain in a direction perpendicular thereto are generated. By detecting a change in resistance value according to the elongational strain and the compressive strain, the torsion of the cylinder 21 is detected. Distortion can be detected.

[0006]

In the case of the above-described strain gauge as a torsional strain sensor, when the strain gauge is bonded to the structure to be detected, the strain detection axis is set at 45 with respect to one axial direction in which the structure to be detected extends. In addition to the problem that high precision is required for adhesion and handling is complicated because it is necessary to match the direction of inclination, the resistance value changes in principle according to the change in elongation strain and compression strain. Therefore, there is also a disadvantage that the signal processing circuit becomes complicated, for example, an analog-digital conversion circuit is required when performing signal processing using a microcomputer or the like.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and its technical problem is that it is easy to adhere to and handle a structure to be detected and to reduce the magnitude of torsional distortion. An object of the present invention is to provide a flat-plate capacitive torsional strain sensor capable of converting a change in capacitance into a change in frequency and easily performing signal processing.

[0008]

According to the present invention, there is provided a torsional strain sensor for detecting a torsional strain applied to a structure to be detected extending in a uniaxial direction. The surface of the dielectric film layer whose dielectric constant changes due to strain formed to have a substantially uniform thickness on the main surface is applied to the surface of the dielectric film layer by a pair of linear common electrodes facing each other by about 45 in the uniaxial direction. By forming a pair of electrode patterns so as to have a plurality of oblique lines extending in parallel so as to be staggered and staggered, a flat-plate type capacitance type torsional strain sensor having capacitance is obtained.

Further, according to the present invention, there is provided the above-mentioned flat capacitive torsion strain sensor, wherein the flat insulating sheet is made of an insulating plastic or ceramics. can get.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The flat-type capacitive torsional strain sensor of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows the basic structure of a flat-plate type capacitive torsional strain sensor according to one embodiment of the present invention. FIG. 1 (a) relates to a plan view, and FIG. It relates to a side view.

This flat-plate capacitive torsional strain sensor is:
Insulating plastic (or ceramics)
Is formed on one main surface of a flexible rectangular flat-type insulating sheet 1 using a dielectric film layer 2 whose dielectric constant changes due to strain so that the thickness becomes substantially uniform. Alternatively, it is formed in a thin film shape and is inclined by about 45 degrees from the pair of linear common electrodes 3 and 4 facing the surface of the dielectric film layer 2 with respect to the uniaxial direction in which the structure to be detected extends. A pair of electrode patterns are formed so as to have a plurality of diagonal electrodes 3a and 4a extending in parallel so as to alternately enter each other and have a capacitance.

Here, a capacitor terminal is connected to the linear common electrodes 3 and 4, and the linear common electrode 3 and the oblique line electrode 3a are connected.
And a pair of electrode patterns formed by the linear common electrode 4 and the oblique line electrode 4a function as a capacitor having a capacitance.
Further, in the case of the electrode pattern here, the linear common electrode 3,
4 are provided along one opposite side of the insulating sheet 1, and the oblique electrodes 3a, 4a
The electrode is formed as an interdigital electrode inclined at an angle of about 45 degrees with respect to the extension direction of the reference numeral 4.

In such a flat plate type capacitance type torsional strain sensor, the insulating sheet 1 is bonded to the structure to be detected.
Since the torsional distortion can be detected using the direction of one of the opposite sides as the axis of rotation, it is easy to adhere to and handle the structure to be detected, and torsional distortion due to the elastic deformation of the structure to be detected. Can be converted from a change in capacitance to a change in frequency, so that signal processing can be easily performed.

FIG. 2 is a plan view of an electrode pattern shown for explaining the principle of strain detection by a flat-plate capacitive torsional strain sensor including such interdigital electrodes.

The electrode pattern here is disposed on one of the long sides of the rectangular flat insulating sheet 1 'opposite to each other, and extends from the linear common electrode 3' to which the capacitor terminal 5 is connected to one end. A plurality of linear electrodes 3a 'extend in a direction perpendicular to the existing direction. Similarly, the linear electrodes 3a' are arranged on the other long side of the insulating sheet 1 'opposite to each other, and a capacitor terminal 6 is connected to one end. A plurality of linear electrodes 4a 'extend in a direction perpendicular to the extending direction from the linear common electrode 4', and the linear electrodes 3a ', 4a' are arranged in parallel so as to alternately enter. It is formed as an interdigital electrode.

Here, a rectangular flat insulating sheet 1 'made of zirconia porcelain having relatively excellent flexibility is used, and a lead-based high dielectric constant dielectric material used for a ceramic capacitor is provided on the surface thereof. A body film layer 2 is formed, and a pair of electrode patterns including a linear common electrode 3 and a linear electrode 3a 'and a linear common electrode 4 and a linear electrode 4a' are further formed on the linear electrodes 3a 'and 4a'. Is formed so that the extending direction is parallel to the short side of the rectangular flat type insulating sheet 1 ′ to constitute a flat type capacitive torsion strain sensor having one capacitor having a capacitance.

In such a flat plate type capacitive torsional strain sensor, the rectangular flat plate type insulating sheet 1 'is
When bent in a direction perpendicular to the extending direction of a 'and 4a',
When the electrode surface is deformed in a convex shape as the distance between the linear electrodes 3a 'and 4a' adjacent to each other changes, the dielectric film layer 2 undergoes elongation strain, and the electrode surface becomes concave. When deformed, compressive strain occurs in the dielectric film layer 2.

Then, this flat plate type capacitive torsional strain sensor is cut into an appropriate length using a pressurizing device as shown in FIG. In the state where the portion is supported, the central portion is pressed in parallel with the short side direction by a knife-edge-shaped pressing plate 7 to measure the force (g) -capacitance change rate (%) characteristics. The results were as shown. In FIG. 4, the characteristics indicated by □ are measured values when the back side of the electrode surface is pressed, and the characteristics indicated by Δ are measured values when the electrode surface is pressed.

From FIG. 4, it can be seen that in the case of the characteristics indicated by □ where the back side of the electrode surface is pressurized, the capacitance increases as the pressing force increases, despite the deformation that the electrode spacing increases. On the contrary, in the case of the characteristics indicated by the symbol △ where the electrode surface is pressed, the static It can be seen that the capacitance value is small and the dielectric film layer 2 has a so-called "positive strain-dielectric constant characteristic" in which the dielectric constant in that direction increases when a strain is applied.

Therefore, when a material having a large "strain-permittivity characteristic" is used as the material of the dielectric film layer 2, a change in the capacitance between the capacitor terminals 5 and 6 is caused simply by a change in the electrode interval. It is larger than the change in capacitance.

Incidentally, the torsional strain can be decomposed into an elongation strain in the direction of +45 degrees and a compressive strain in the direction of -45 degrees with respect to the torsional axis direction. In the case of the capacitance type torsional strain sensor, the oblique lines 3a, 4 are determined depending on whether the torsional strain is positive or negative (the direction of the torsion).
The dielectric constant in the opposite direction of a changes, the value of the capacitance between the capacitor terminals changes, and the magnitude of the torsional distortion generated from this change can be detected.

In the meantime, in the embodiment of the flat type capacitive torsion strain sensor shown in FIG. 1, a case has been described in which one is used as a structure to be detected to detect torsional strain.
One more sensor is used and the two sensors are
If the sensors are arranged so as to form an angle of degrees and the difference between the detection outputs of these sensors is detected, the detection sensitivity can be almost doubled, and unnecessary signals (for example, surrounding signals) commonly generated in each sensor can be obtained. (A component such as a characteristic variation depending on a temperature change) can be canceled. In addition, in the flat-plate type capacitive torsional strain sensor according to the embodiment, the case where the insulating sheet 1 is used to form the dielectric film layer 2 having the strain-dielectric constant change characteristic has been described. Even if a conductive metal is used, the same effect can be obtained by forming the dielectric film layer 2 via an insulator having a low dielectric constant.

[0024]

As described above, according to the flat-plate-type capacitive torsional strain sensor of the present invention, a flexible insulating sheet is used, and the dielectric constant changes due to distortion on the surface of the insulating sheet. Since a dielectric film layer is formed, and a pair of electrode patterns are formed on the surface of the dielectric film layer to provide a capacitance, one of the insulating sheets is bonded to the structure to be detected. Since the torsional strain can be detected flexibly using the direction of the side to be rotated as the axis of rotation, it is easy to adhere to and handle the structure to be detected, and the magnitude of the torsional strain due to the elastic deformation of the structure to be detected. Can be converted from a change in capacitance to a change in frequency, and signal processing can be easily performed. As a result, the shape of the structure to be detected is not limited to a flat plate or a bar, but even if it is a curved surface, adhesion and torsional distortion can be easily detected, and the LC oscillation circuit has a simple structure and a simple signal processing circuit. Can be configured.

[Brief description of the drawings]

FIGS. 1A and 1B show a basic configuration of a flat-plate capacitive torsional strain sensor according to an embodiment of the present invention, wherein FIG. 1A is related to a plan view and FIG. 1B is related to a side view.

FIG. 2 is a plan view of an electrode pattern shown for explaining the principle of strain detection by a flat-plate capacitive torsional strain sensor including interdigital electrodes.

FIG. 3 is a side view schematically showing a pressing device that presses the flat-plate-type capacitive torsional strain sensor shown in FIG. 2;

FIG. 4 is a graph showing a result of measurement of a pressing force-capacitance change rate characteristic in a flat-plate capacitive torsional strain sensor in a state where the pressure is applied by the pressing device shown in FIG. 3;

5A and 5B illustrate a conventional torsional strain sensor and an application example thereof, wherein FIG. 5A is a perspective view showing a state in which a strain gauge is bonded to a structure to be detected as a torsional strain sensor, and FIG. Is related to an enlarged perspective view of a strain gauge.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 1 'Insulating sheet 2 Dielectric film layer 3, 4, 3', 4 'Linear common electrode 3a, 4a Diagonal electrode 3a', 4a 'Linear electrode 5, 6 Capacitor terminal 7 Pressure plate 21 Column 22 Outer periphery Surface 23 strain gauge 24 pedestal

Claims (2)

[Claims] 1. A torsional strain sensor for detecting torsional strain applied to a structure to be detected extending in a uniaxial direction, wherein a thickness of the flexible flat insulating sheet is substantially uniform on one main surface thereof. With respect to the surface of the dielectric film layer in which the dielectric constant changes due to the strain formed so as to be inclined from the pair of linear common electrodes facing each other at about 45 degrees with respect to the uniaxial direction so as to enter alternately. A pair of electrode patterns are formed so as to have a plurality of obliquely extending electrodes extending in a direction, and a capacitance is provided. 2. The flat capacitive torsional strain sensor according to claim 1, wherein an insulating plastic or ceramic is used as a material of the flat insulating sheet. Torsional strain sensor.