JP7007640B2 - Electrode expansion type capacitance type sensor - Google Patents

Description

The present invention relates to an electrode expansion type capacitance type sensor having an improved degree of freedom in setting a detection region as compared with the conventional case.

Capacitance sensors are used as proximity sensors to detect the presence or absence of conductive substances in space or movement information of conductive substances, inclusion sensors to detect the presence or absence of contents in packs, and temperature / humidity sensors to detect temperature or humidity. It's being used.

As such a capacitance type sensor, a capacitance type sensor in which two comb tooth type detection electrodes are arranged so that the comb teeth face each other on only one side of the base material is known. Further, when the detection electrode is arranged on only one side of the base material, manufacturing variation occurs. In order to prevent this, a capacitance type sensor in which the detection electrode is arranged on both sides of the thin film base material is also known. (See, for example, Patent Documents 1 and 2).

FIG. 1A shows a conventional capacitive sensor in which detection electrodes are arranged on both sides as shown in Patent Document 1, and FIG. 1B shows a cross-sectional view thereof. 1 (a) and 1 (b) show the base material 11, the first electrode 12 formed on the first surface of the base material 11, and the second electrode 12 on the side opposite to the first surface of the base material 11. A second electrode 13 formed on the surface of 2, a first lead-out wiring 14 drawn out on the first surface and applying a voltage to the first electrode 12, and a second lead-out wiring 14 drawn out on the second surface. A capacitance type sensor 10 comprising a second lead-out wire 15 for applying a voltage to the electrode 13 of the above is shown.

The first electrode 12, the second electrode 13, the first lead-out wiring 14, and the second lead-out wiring 15 are formed on the base material 11 by using a printing method such as a screen printing method. As the base material 11, for example, a thin film can be used. For example, when the first electrode 12 is a signal electrode and the second electrode 13 is a ground electrode, the area of the second electrode 13 that functions as a ground electrode is larger than that of the first electrode 12 that functions as a signal electrode. It is configured to be large.

In the conventional capacitive sensor 10 as shown in FIG. 1, the first and second electrodes 12 and 13 have a predetermined frequency and a predetermined frequency via the first and second lead-out wires 14 and 15, respectively. The AC voltage of the amplitude of is applied. As a result, the current and voltage between the first and second electrodes 12 and 13 are measured, and the capacitance value of the capacitance type sensor 10 is calculated based on the measured value.

In the capacitance type sensor 10, a detection region is defined by using electric lines of force from one of the first and second electrodes 12 and 13 toward the other. When an object enters the detection area of the capacitance type sensor 10, a part of the electric lines of force is absorbed by the object and the capacitance value of the capacitance type sensor 10 decreases. The amount of decrease in the capacitance value increases as the object approaches the capacitance type sensor 10. In this way, by detecting the change in the capacitance value of the capacitance type sensor 10, it is possible to acquire the presence / absence and motion information of the object.

Japanese Unexamined Patent Publication No. 2016-19588 Japanese Unexamined Patent Publication No. 2014-137240

K. Nomura, R. kaji, S. iwata, 8 outsiders, “A flexible proximity sensor formed by duplex screen / screen-offset printing and its application to non-contact detection of human breathing”, Scientific Reports 6, 1947 (2016).

As described above, in the capacitive sensor, the detection area is defined by using the electric lines of force from one of the two detection electrodes to the other, so that the detection area is defined by the shape and arrangement of the two detection electrodes. It changes according to the applied voltage. However, such an electrode shape, an electrode arrangement, and an applied voltage have a low degree of freedom in setting, and therefore the degree of freedom in setting the detection region is also limited.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a capacitance type sensor having an improved degree of freedom in setting a detection region as compared with the conventional case.

In order to achieve such an object, the capacitance type sensor according to the embodiment of the present invention is a capacitance type sensor whose capacitance value changes according to the approach of the object to be detected, and is static. The capacitance type sensor part that forms the capacitance and the expansion electrode that is not connected to the ground and has conductivity, and a part of the electric power line formed by the capacitance type sensor part is said. It comprises an expansion electrode that is absorbed by the expansion electrode and is arranged in a floating state so that an electric power line is also emitted from the expansion electrode , and the expansion electrode is within the initial detection region of the capacitance type sensor unit. It is characterized in that the initial detection area of the capacitance type sensor unit is expanded or contracted by being arranged so that at least a part thereof is present.

According to the present invention, it is possible to provide a capacitance type sensor having an improved degree of freedom in setting a detection region as compared with the conventional case.

It is a figure which illustrates the conventional capacitance type sensor. It is a figure which illustrates the capacitance type sensor which concerns on Example 1 of this invention. It is a figure for demonstrating the principle of the capacitance type sensor which concerns on this invention. It is a figure for demonstrating the principle of the capacitance type sensor which concerns on this invention. It is a figure for demonstrating the principle of the capacitance type sensor which concerns on this invention. It is a figure for demonstrating the principle of the capacitance type sensor which concerns on this invention. It is a figure which illustrates the capacitance type sensor which concerns on Example 2 of this invention. It is a figure which illustrates the conductor approach test result of the capacitance type sensor. It is a figure which shows the test condition of the conductor approach test shown in FIG.

(Example 1)
FIG. 2 shows an electrode expansion type capacitance type sensor according to the first embodiment of the present invention. FIG. 2A is a schematic side view of the capacitance type sensor according to the first embodiment of the present invention, and FIG. 2B is a schematic top view of the capacitance type sensor according to the first embodiment of the present invention. be. FIG. 2A shows an electrode expansion type capacitance type sensor 100 including a capacitance type sensor unit 110 forming a capacitance and an expansion electrode 120. In the electrode expansion type capacitance type sensor 100, the capacitance value changes according to the approach of the object to be detected.

The capacitance type sensor unit 110 is, for example, two comb-tooth type electrodes formed so that the comb teeth face each other on one side of the base material, or formed so as to face each other on both sides of the base material. It can be composed of two asymmetrical flat plates with different areas. As the base material, for example, a thin film composed of polyethylene terephthalate, polyethylene naphthalate, polyimide, or the like can be used. Further, the detection electrode used in the capacitance type sensor unit 110 is made of a conductive material such as copper, silver, gold, aluminum, nickel, tin, and carbon, and is printed by a printing method such as a screen printing method or vapor deposition. It can be formed by using various methods such as a method and a sputtering method.

Further, as shown in FIG. 2B, the electrode expansion type capacitance type sensor 100 includes a capacitance type sensor unit 110 and a high frequency power supply 101 that applies an AC voltage having a predetermined amplitude at a predetermined frequency. , A measuring unit 102 such as an LCR meter for measuring the capacitance value of the electrode expansion type capacitance type sensor 100, and a control unit 103 for executing various processes in the electrode expansion type capacitance type sensor 100, which will be described later. A storage unit 104 for storing an initial detection threshold range and a set detection threshold range is provided.

The expansion electrode 120 is installed as a floating electrode in the initial detection region of the capacitance type sensor unit 110 described later. The expansion electrode 120 is not connected to the capacitive sensor unit 110 and is not grounded. The expansion electrode 120 is made of a conductive material such as a conductive solution containing an electrolyte or a metal material. The expansion electrode 120 can take various forms including its size and shape, such as a flat plate type, a rod type, a star type, a disk type, and a curved surface type. When a conductive solution containing an electrolyte is used as the expansion electrode 120, the electrolyte to be used may be, for example, sodium chloride, potassium hydroxide, hydrochloric acid, or the like, and the preferred concentration range is the electrolyte. Although it depends on the type of the above, it can be, for example, 10 μM or more.

The expansion electrode 120 is arranged so that at least a part of the expansion electrode 120 exists in the initial detection region of the capacitive sensor unit 110. As a result, a part of the electric lines of force formed by the capacitance type sensor unit 110 is absorbed by the expansion electrode 120, and the electric lines of force are also emitted from the expansion electrode 120 itself. Depending on the form and arrangement position of the expansion electrode 120, the detection area of the electrode expansion type capacitance type sensor 100 can be expanded or contracted.

The "initial detection area" of the capacitance type sensor unit 110 means that the detection target is directed toward the capacitance type sensor unit 110 in a state where the expansion electrode 120 is not provided in the vicinity of the capacitance type sensor unit 110. The region where the measured capacitance value exceeds the initial detection threshold range when approached from a distance. Here, the "initial detection threshold range" is, for example, a state in which the object to be detected is not detected (undetected state) and the expansion electrode 120 is not provided in the initial detection region. The capacitance value of the capacitance type sensor unit 110 is measured using this, and set based on (μ ± 3σ) obtained from the average value (μ) and sample standard deviation (σ) of the obtained capacitance value. (See, for example, Non-Patent Document 1).

Further, in the electrode expansion type capacitance type sensor 100 according to the first embodiment, the setting detection threshold range is set with the expansion electrode 120 installed in the initial detection region. Here, the "set detection threshold range" is, for example, a state in which the object to be detected is not detected (undetected state) and at least a part of the expansion electrode 120 is provided in the initial detection region. , The capacitance value of the capacitance type sensor unit 110 is measured using an LCR meter, and can be obtained from the average value (μ) and sample standard deviation (σ) of the obtained capacitance value (μ ± 3σ). Can be set as a reference (see, for example, Non-Patent Document 1).

In the electrode expansion type capacitance type sensor 100 according to the first embodiment, the control unit 103 can detect the object to be detected when the measured capacitance value exceeds the set detection threshold range.

The principle of the electrode expansion type capacitance type sensor according to the present invention will be described with reference to FIGS. 3 to 6. As shown in FIG. 3 (b), even if the conductor is placed at a position away from the capacitance type sensor unit 110 after being grounded to the ground and then the ground connection is released, the conductor is placed in a floating state. As shown in (a), the signal indicating the capacitance value does not respond. At this time, it can be said that the conductor is outside the initial detection region. In this state, the control unit 103 acquires the measured value of the capacitance value of the capacitance type sensor unit 110 from the LCR meter, and the average value (μ) and the sample standard deviation (σ) of the obtained capacitance value. ), The initial detection threshold range is set with reference to (μ ± 3σ) and stored in the storage unit 104.

As shown in FIG. 4B, even if the conductor to be detected is brought closer to the upper end of the floating conductor from a distance while the conductor is placed outside the initial detection region and the ground is released. As shown in FIG. 4A, the signal does not respond and does not exceed the initial detection threshold range.

On the other hand, as shown in FIG. 5B, when the conductor is placed in the vicinity of the capacitance type sensor unit 110 after being grounded and connected to the ground, and then the ground connection is released to bring the conductor into a floating state, FIG. As shown in (a), the signal responds and its capacitance value increases beyond the initial detection threshold range. At this time, the conductor is in a state within the initial detection region. In this state, the control unit 103 acquires the measured value of the capacitance value of the capacitance type sensor unit 110 from the LCR meter, and the average value (μ) and the sample standard deviation (σ) of the obtained capacitance value. ), The set detection threshold range is set with reference to (μ ± 3σ) and stored in the storage unit 104.

As shown in FIG. 6B, with the conductor placed in the initial detection region and ungrounded, the operation and withdrawal of the object to be detected approaching from a distance toward the upper end of the floating conductor. As shown in FIG. 6A, when the operation is repeated, the capacitance value exceeds the set detection threshold range at the time of approaching, and the capacitance value is within the set detection threshold range at the time of leaving. It can be seen that the detection target can be detected, and that the arranged conductor in the floating state acts as an expansion electrode for expanding / contracting the initial detection region.

The electrode expansion type capacitance type sensor according to the present invention is used, for example, for detecting the presence / absence of a detected object, for measuring a close distance to a detected object, or for a constant distance to the detected object. For example, it can be used for measuring physical characteristics such as the size of the object to be detected and the relative permittivity. For example, when strict detection is required such as for measuring the close distance to the detected target, the set detection threshold range is set by performing threshold correction (initial calibration) for each detected target when the device is started. Is preferably adjusted for each detection target. In addition, when strict detection is not required as in the case of detecting the presence / absence of the object to be detected, for example, the set detection threshold range is set based on (μ ± 3σ) so as to include some individual differences in the human body. It is preferable to adjust.

According to the electrode expansion type capacitance type sensor 100 according to the first embodiment, the detection region can be freely controlled by changing the size, shape, etc. of the conductive substance acting as the expansion electrode. In addition, since the detection area can be expanded or contracted simply by arranging the expansion electrode within the initial detection area of the capacitance type sensor unit, a cable-free and highly flexible installation and design capacitance type sensor can be realized. It becomes possible.

(Example 2)
FIG. 7 shows a capacitance type sensor according to the second embodiment of the present invention. FIG. 7A is a schematic side view of the capacitance type sensor according to the second embodiment of the present invention, and FIG. 7B is a schematic top view of the capacitance type sensor according to the first embodiment of the present invention. be. FIG. 7A shows an electrode expansion type capacitance type sensor 200 including a capacitance type sensor unit 210 and an expansion electrode 220.

As shown in FIG. 7A, the capacitance type sensor unit 210 includes the base material 211, the first printing electrode 212 ₁ formed on the first surface of the base material 211, and the base material 211. A first drawer that is drawn out on the first surface and applies a voltage to the first print electrode 212 ₁ formed on the _second surface opposite to the first surface. It includes a print wire 213 ₁ and a second drawer print wire 213 ₂ that is drawn out on the second surface and applies a voltage to the second print electrode 212 ₂ .

Further, as shown in FIG. 7B, the electrode expansion type capacitance type sensor 200 includes a capacitance type sensor unit 210 and a high frequency power supply 201 that applies an AC voltage having a predetermined amplitude at a predetermined frequency. , For example, a measuring unit 202 such as an LCR meter for measuring the capacitance value of the electrode expansion type capacitance type sensor 200, a control unit 203 for executing various processes in the electrode expansion type capacitance type sensor 200, and initial detection. A storage unit 204 for storing a threshold range and a setting detection threshold range is provided. The first and second print electrodes 212 ₁ and 212 ₂ are connected to the high frequency power supply 201 and the measuring unit 202 via the first and second drawer print wirings 213 ₁ and 213 ₂ .

The first print electrode 212 ₁ , the second print electrode 212 ₂ , the first drawer print wiring 213 ₁ and the second drawer print wiring 213 ₂ are, for example, copper, silver, gold, aluminum, nickel, tin, and the like. It can be made of a conductive material such as carbon, and can be formed by using a printing method such as a screen printing method.

For example, when the first print electrode 212 ₁ is used as a signal electrode, the second print electrode 212 ₂ is used as a ground electrode, and the object to be detected is on the side of the first print electrode 212 ₁ which is a signal electrode, it functions as a ground electrode. The area of the second print electrode 212 ₂ is larger than that of the first print electrode 212 ₁ .

As described above in the first embodiment, the expansion electrode 220 is transparent provided around the capacitance type sensor unit 210 so that at least a part of the expansion electrode 220 is present in the initial detection region of the capacitance type sensor unit 210. It is placed on an arbitrary support (not shown) such as a styrene case.

Also in the electrode expansion type capacitance type sensor 200 according to the second embodiment, the capacitance measured in a state where the expansion electrode 220 is arranged in the initial detection region of the capacitance type sensor unit 210 in the same manner as in the first embodiment. The set detection threshold range was set with reference to (μ ± 3σ) by obtaining (μ ± 3σ) from the mean value (μ) and the sample standard deviation (σ).

In the electrode expansion type capacitance type sensor 200 according to the second embodiment, the control unit 203 can detect the object to be detected when the measured capacitance value exceeds the set detection threshold range.

FIG. 8 illustrates the conductor proximity test results for a capacitive sensor. Further, FIG. 9 shows the test conditions of the conductor proximity test. As shown in FIG. 9, in this test, the capacitance type sensor was installed on a table with a height of 17 mm, and a transparent styrene case with a square size of 159 mm and a height of 35 mm was used as a support for installing the expansion electrode. Covering the periphery, the position 301 (distance between fingertip and sensor center is about 18 mm) directly above the sensor of the transparent styrene case and the position 302 of the corner of the transparent styrene case (distance between fingertip and sensor center is about 114 mm) shown in FIG. Then, the experimenter's finger as the object to be detected was brought close to it. A polyethylene naphthalate film having a thickness of 0.1 mm is used as the base material 211, the diameter of the first printing electrode 212 ₁ is 1 mm, the diameter of the second printing electrode 212 ₂ is 18 mm, and an AC voltage of 200 kHz and an amplitude of 1 V is used. Was applied, and the capacitance value was measured using an LCR meter.

In FIG. 8, when nothing is placed, a stainless steel plate is placed, a glass material is placed, a container containing tap water is placed, and an electrolyte is placed in the transparent styrene case as a support, respectively. When a container containing the contained aqueous solution is placed, by bringing the fingertip close to the position 301 or 302 from above so as not to touch the placed object, the absolute value of the amount of change in the capacitance value from the predetermined reference value | ΔC | was calculated.

As shown in FIG. 8, when nothing is placed on the transparent styrol case, the absolute value | ΔC | of the amount of change at position 301 is larger than the absolute value | ΔC | of the amount of change at position 302, and at position 302. It can be seen that the detection sensitivity is lower than that of the position 301.

Further, when the glass is arranged on the transparent styrene case, the absolute value | ΔC | of the change amount of the capacitance value at the position 302 is the absolute value of the change amount of the capacitance value at the position 302 when the expansion electrode is not arranged. The value is equivalent to the value | ΔC |, and it can be seen that the detection sensitivity is lower at the position 302 than at the position 301. This is because the glass does not have conductivity and does not contribute to the expansion of the detection area.

In addition, when a container containing tap water is placed on the transparent styrene case, since tap water has low conductivity, there is a slight increase in | ΔC |, but the capacitance at position 302 when the expansion electrode is not placed. The value is almost the same as the absolute value | ΔC | of the amount of change in the value, and it can be seen that the detection sensitivity is lower at the position 302 than at the position 301.

On the other hand, when a stainless steel plate or a container containing an aqueous solution containing an electrolyte is placed on the transparent styrene case, the absolute value | ΔC | of the amount of change in the capacitance value equivalent to that of the position 301 can be obtained even at the position 302. Therefore, it is understood that the detection region is expanded by arranging a sufficiently conductive expansion electrode such as a stainless steel plate or a container containing an aqueous solution containing an electrolyte on the transparent styrene case.

According to the electrode expansion type capacitance type sensor 200 according to the second embodiment, by applying the printing technology to the manufacturing process, it is possible to freely control the detection area while realizing a lower manufacturing cost. Become.

In the above embodiment, an example of detecting an object by measuring the capacitance value of the capacitance type sensor unit with an LCR meter has been shown, but the present invention is not limited to this, and for example, the static capacity type sensor unit is static. Whether or not the measured value of the parameter exceeds the set detection threshold range with at least one of a group of parameters including the capacitance value, impedance Z, resistance R, reactors X, admittance Y, conductance G and susceptance B as the measured value. It may be configured to detect the target by determining whether or not. Further, in the above embodiment, the capacitance type sensor may further include a coil connected in series or in parallel to the capacitance type sensor unit, and in this case, the group of the above parameters includes the capacitance type sensor unit and the coil. The resonance frequency in the LC resonance circuit composed of and may be further included.

Further, in Example 2 above, an example in which the expansion electrode is arranged on a transparent styrene case as a support is shown, but the present invention is not limited to this, and the electrolyte as the expansion electrode is placed in a container such as a fishbowl, for example. It may be configured to be filled with a solution containing the above, and various combinations may be configured so as not to deviate from the principle / concept of the present invention.

Claims (7)

It is a capacitance type sensor whose capacitance value changes according to the approach of the object to be detected.
Capacitance type sensor unit that forms capacitance and
It is an expansion electrode that is not connected to the ground and has conductivity, and a part of the electric power line formed by the capacitance type sensor unit is absorbed by the expansion electrode, and the electric force is also obtained from the expansion electrode. An expansion electrode, which is arranged in a floating state so that a line can be emitted ,
Equipped with
The expansion electrode is arranged so that at least a part thereof exists in the initial detection region of the capacitance type sensor unit, and is characterized in that the initial detection region of the capacitance type sensor unit is expanded or contracted. Capacitive sensor. The capacitance type sensor unit is
With the base material
A first printed electrode formed on the first surface of the substrate, and a first printed electrode.
Claim 1 is characterized by comprising a second printed electrode formed on a second surface of the base material opposite to the first surface and having an area different from that of the first printed electrode. Capacitive sensor described in. It is further provided with a measuring unit for measuring at least one parameter in a group of parameters including the capacitance value, impedance, resistance, reactance, admittance, conductance and susceptance of the capacitance type sensor unit. The capacitive sensor according to claim 1 or 2. The capacitance type sensor further includes a coil connected in series or in parallel to the capacitance type sensor unit.
The capacitance type sensor according to claim 3, wherein the parameter group further includes a resonance frequency in an LC resonance circuit composed of the capacitance type sensor unit and the coil. The capacitance type sensor is configured to detect the object to be detected when the measured value of the parameter exceeds the set detection threshold range.
The set detection threshold range is the capacitance type sensor unit measured in a state where the object to be detected is not detected and at least a part of the expansion electrode is provided in the initial detection region. The capacitance type sensor according to claim 3 or 4, wherein the range is set with reference to (μ ± 3σ) obtained from the average value (μ) of the measured values and the sample standard deviation (σ). In the initial detection region, when the object to be detected is brought close to the capacitance type sensor unit in a state where the expansion electrode is not provided, the measured value of the parameter is within a predetermined initial detection threshold range. The capacitance type sensor according to any one of claims 3 to 5, wherein the area exceeds. The predetermined initial detection threshold range is an average value (μ) of the measured values of the parameters measured in a state where the object to be detected is not detected and the expansion electrode is not provided in the initial detection region. ) And the capacitance type sensor according to claim 6, wherein the range is set with reference to (μ ± 3σ) obtained from the sample standard deviation (σ).

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