JP6182031B2 - Capacitance measurement device, capacitance-type surface sensor device, and capacitance-type liquid level detection device - Google Patents

Description

  The present invention relates to a capacitance measuring device, a capacitance type surface sensor device using the measuring device, and a capacitance type liquid level detecting device.

  An apparatus for determining whether or not a change in measured capacity is caused by an event to be detected is described in International Publication No. 2011/004727 (Patent Document 1). The apparatus has a reference capacitor Cs connected in series to the first potential source V1 side with respect to the measured capacitor Cx1, and one end is disposed between both ends of the reference capacitor connected to the first potential source V1. One switch, a second switch disposed between the other end of the capacitor to be measured, one end of which is connected to the second potential source or free space, and the other end of the reference capacitor, and both ends of the capacitor to be measured And a third switch disposed therebetween.

  When the first switch is closed and then the first switch is opened, and then the second switch is closed and the third switch is closed. The number of repetitions until the potential of the terminal of the reference capacitor Cs changes to the set potential Vref is counted. Then, based on the number of repetitions N1 and N2 when the time for operating the second switch is made different, it is determined whether or not the change in the measured capacity is caused by the event to be detected. To do.

  Further, Japanese Patent Laid-Open No. 2005-30901 (Patent Document 2) describes that each row of electrodes and a plurality of columns of electrodes face each other and each capacitance at a measurement target position in a matrix shape is measured. Yes. When the apparatus outputs a pulse signal to one of the capacitances at the measurement target position, the device measures the capacitance by measuring the current flowing through the other capacitance.

  Further, a capacitance measuring device is described in Japanese Patent No. 3379388 (Patent Document 3), Japanese Patent No. 2561040 (Patent Document 4), International Publication No. 2011/125725 (Patent Document 5), and the like. . In addition, apparatuses for detecting a liquid level using capacitance are described in JP-A-11-311562 (Patent Document 6) and JP-A-2006-337173 (Patent Document 7).

International Publication No. 2011/004727 JP 2005-30901 A Japanese Patent No. 3379388 Japanese Patent No. 2561040 International Publication No. 2011/125725 Japanese Patent Laid-Open No. 11-311562 JP 2006-337173 A

  By the way, conventionally, measurement of capacitance has been generally performed by measuring a current flowing through the other side of the capacitance when an AC voltage is applied to one side of the capacitance. However, when the capacitance is measured based on the current value, the current value becomes a small value, and therefore it is impossible to measure the capacitance with high accuracy due to the influence of noise.

In addition, by connecting another predetermined capacitance in series to the capacitance of the measurement target and applying a constant voltage, the capacitance of the measurement target is measured by measuring the potential between the capacitances. Can be calculated. That is, the measurement object in this case is not a current value but a voltage value. However, since the potential between the two capacitances is indefinite, the capacitance measured using the potential between the capacitances is not highly accurate. Further, the above-described conventional technique is a very complicated measuring device.
Further, in the apparatus described in Patent Document 5, it takes time until the capacitor C1 is charged, so it is not easy to measure the capacitance of the measurement target at high speed.

The present invention employs a method of measuring a potential between a capacitance to be measured and another predetermined capacitance connected in series, thereby improving measurement speed and noise resistance. An object of the present invention is to provide a capacitance measuring device capable of measuring a capacitance to be measured with high accuracy even when a potential between capacitances is measured.
It is another object of the present invention to provide a capacitance type planar sensor device and a capacitance type liquid level detection device using the measurement device. That is, a capacitive surface sensor device and a capacitive liquid level detection device capable of measuring a capacitance to be measured at high speed and with high accuracy are provided.

< First capacitance measuring device>
Therefore, the present inventors measure the capacitance of the measurement target by measuring the potential between the two capacitances by setting the state where the potential between the two capacitances is discharged to the ground potential as a reference state. I found it possible to do.
That is, the first capacitance measuring device includes an input voltage applying unit that applies an input voltage that is a constant voltage to one end side of the capacitance to be measured, and the other end of the capacitance to be measured. Connected in series with the other end of the capacitance to be measured and a ground potential, and connected in series with the other end of the capacitance to be measured A charge / discharge switching element that is connected in parallel to the bridge capacitor and discharges the charge on the other end of the capacitance to be measured to a ground potential in a closed state; and the input voltage is applied. The charge / discharge switching element is closed and the charge / discharge switching element is closed, and the charge / discharge switching element is discharged after the step of discharging the charge of the capacitance to be measured to the ground potential and the step of discharging. In the open state and in the state of applying the input voltage, the controller that performs the step of charging the capacitance of the measurement target, and the capacitance of the measurement target in the charging step by the controller And a measuring device that acquires a capacitance equivalent value of the measurement target based on a potential between the capacitor and the bridge capacitor.

  The bridge capacitor is connected in series to the capacitance to be measured, and the measuring instrument has a potential (intermediate potential) between the capacitance to be measured and the bridge capacitor, that is, the capacitance to be measured. The capacitance equivalent value is acquired based on the electric potential on the other end side. Here, since the intermediate potential of the two capacitors is indefinite, the capacitance measured using the intermediate potential is not highly accurate.

  However, by closing the charge / discharge switching element, the electrostatic charge of the measurement target is discharged. That is, the intermediate potential becomes the ground potential. This state is set as a reference state. That is, the intermediate potential in the reference state is equal to the ground potential. In other words, the intermediate potential can be calibrated by closing the charge / discharge switching element.

The measuring instrument measures the potential on the other end side of the capacitance to be measured when the charging / discharging switching element is opened and the input voltage is applied after being discharged. That is, the potential measured by the measuring instrument is a potential corresponding to the capacitance of the measurement target. Therefore, the first capacitance measurement device can measure the capacitance to be measured with high precision.

  Furthermore, since the above means is a method of measuring the capacitance using an intermediate potential, it is less susceptible to noise than in the case of current measurement, and the capacitance can be measured with high accuracy. . Furthermore, the measurement using the intermediate potential enables high-speed measurement. Further, the calibration for closing the charge / discharge switching element can be performed in a short time. This also makes it possible to measure the capacitance at high speed as a whole.

Further, in the first capacitance measuring device, the input voltage applying means connects the constant voltage power source to which the input voltage can be applied, one end side to one end side of the capacitance to be measured, and the other end Connecting the input voltage to one of the constant voltage power source and the ground potential, applying the input voltage to the capacitance of the measurement target by the constant voltage power source, and applying the input voltage to the capacitance of the measurement target. An input switching element that switches between a state in which no voltage is applied. Accordingly, the intermediate potential can be reliably set to the reference state potential, and a state in which the input voltage is applied to the capacitance to be measured can be reliably formed. As a result, a highly accurate capacitance equivalent value is acquired.

  Preferably, the capacitance measuring device is applied with a second input voltage as a constant voltage on one end side, and the other end side is connected to the other end side of the capacitance to be measured. Is further provided. Thereby, the capacitance equivalent value of the measurement object with high accuracy is acquired.

Preferably, the first state in which the input voltage and the second input voltage are not applied, the second state in which one of the input voltage and the second input voltage is applied and the other is not applied, the input voltage and the first The instrument is switched in the order of a third state in which two input voltages are applied, and a fourth state in which the one of the input voltage and the second input voltage is not applied and the other is applied. The capacitance equivalent value of the measurement target is acquired based on the potential on the other end side of the capacitance of the measurement target in the third state or the fourth state.
Thereby, the capacitance equivalent value of the measurement object with high accuracy can be obtained with certainty.

  Preferably, the capacitance of the bridge capacitor is larger than the capacitance between the other end side of the capacitance to be measured and the ground potential. This reliably reduces the degree of influence of the capacitance existing between the other end side of the capacitance to be measured and the ground potential. Therefore, a highly accurate capacitance equivalent value of the measurement target can be obtained.

  Preferably, the capacitance measuring device obtains each of a plurality of measurement target capacitance equivalent values in the sensor body, and the sensor body equivalent circuit includes a plurality of rows of first electrodes and the plurality of rows. A plurality of columns of second electrodes arranged so as to form a matrix with respect to the first electrodes of the rows, and the plurality of rows of first electrodes and the plurality of columns of second electrodes are provided at a plurality of positions where the three-dimensional intersections are respectively provided. A plurality of dielectric layers, and a capacitance equivalent value of a plurality of measurement objects in the sensor body is between the first electrode and the second electrode corresponding to each position of the plurality of dielectric layers. It is a capacitance equivalent value.

  That is, in the equivalent circuit, a plurality of capacitances to be measured are arranged in a matrix. Then, using the capacitance measuring apparatus described above, each of the matrix-like capacitance equivalent values to be measured can be obtained with high accuracy.

  Preferably, the measuring instrument applies the input voltage to one first electrode of the plurality of first electrodes, and the selected first electrode is connected to the ground potential. Solving simultaneous equations expressed by the respective voltages at the two electrodes and the capacitance at a plurality of positions where the selected second electrode and the plurality of rows of the first electrodes are three-dimensionally intersected as unknowns. Thus, each capacitance equivalent value as an unknown is acquired.

When measuring the potential on the other end side of a certain capacitance to be measured, there is a case where it is influenced by other capacitance. Therefore, as described above, the measurement device is represented by the capacitance of each measurement target and the capacitance that affects the capacitance of the measurement target, with the capacitances of the plurality of measurement targets as unknowns. Solve simultaneous equations. Therefore, each capacitance equivalent value as an unknown can be obtained with high accuracy.
<Second capacitance measuring device>
The second capacitance measuring device includes an input voltage applying unit that applies an input voltage that is a constant voltage to one end of the capacitance to be measured, and the other end of the capacitance to be measured. Connected in series with the other end of the capacitance to be measured and a ground potential, and connected in series with the other end of the capacitance to be measured A charge / discharge switching element that is connected in parallel to the bridge capacitor and discharges the charge on the other end of the capacitance to be measured to a ground potential in a closed state; and the input voltage is applied. The charge / discharge switching element is closed and the charge / discharge switching element is closed, and the charge / discharge switching element is discharged after the step of discharging the charge of the capacitance to be measured to the ground potential and the step of discharging. Open A controller for performing the step of charging the capacitance to be measured by setting the state and applying the input voltage, and in the step of charging by the controller, A capacitance measuring device comprising: a measuring device that acquires a capacitance equivalent value of the measurement target based on a potential between the bridge capacitor and a second input as a constant voltage on one end side The battery further includes a second capacitor to which a voltage is applied and the other end is connected to the other end of the capacitance to be measured.
<Third capacitance measuring device>
Further, the third capacitance measuring device includes an input voltage applying unit that applies an input voltage that is a constant voltage to one end side of the capacitance to be measured, and the other end of the capacitance to be measured. Connected in series with the other end of the capacitance to be measured and a ground potential, and connected in series with the other end of the capacitance to be measured A charge / discharge switching element that is connected in parallel to the bridge capacitor and discharges the charge on the other end of the capacitance to be measured to a ground potential in a closed state; and the input voltage is applied. The charge / discharge switching element is closed and the charge / discharge switching element is closed, and the charge / discharge switching element is discharged after the step of discharging the charge of the capacitance to be measured to the ground potential and the step of discharging. Open A controller for performing the step of charging the capacitance to be measured by setting the state and applying the input voltage, and in the step of charging by the controller, And a measuring instrument that acquires a capacitance-corresponding value to be measured based on a potential between the capacitor and the bridge capacitor.
The capacitance measuring device acquires each of a plurality of measurement target capacitance equivalent values in the sensor body, and the equivalent circuit of the sensor body includes a plurality of rows of first electrodes and a plurality of rows of first electrodes. A plurality of columns of second electrodes arranged so as to form a matrix with respect to one electrode, a plurality of rows of first electrodes, and a plurality of columns of second electrodes provided at a plurality of positions where the three-dimensional intersections are provided And a dielectric layer.
Furthermore, the capacitance equivalent values of the plurality of measurement targets in the sensor body are capacitance equivalent values between the first electrode and the second electrode corresponding to the respective positions of the plurality of dielectric layers. The measuring instrument applies the input voltage to one of the first electrodes of the plurality of rows, and connects the remaining first electrodes to the ground potential. By solving the simultaneous equations represented by the voltage and the capacitance at a plurality of positions where the selected second electrode and each of the plurality of rows of the first electrodes are three-dimensionally intersected as the unknown, Each capacitance equivalent value is acquired.

<Capacitive type surface sensor device>
Next, a capacitance type planar sensor device using the above-described capacitance measuring device will be described.
The capacitive surface sensor device according to this means includes a plurality of rows of first electrodes formed in a strip shape and arranged in parallel to each other, and a plurality of rows of second electrodes formed in a strip shape and arranged in parallel with each other. Each of the second electrodes in the plurality of columns and the first electrodes in the plurality of rows provided so as to face the first electrodes so that the positions facing the first electrodes in the plurality of rows are in a matrix. A dielectric layer provided between the first electrode and the second electrodes of the plurality of rows of second electrodes, and a matrix corresponding to the opposing positions of the first electrodes and the second electrodes The capacitance measuring device described above for acquiring a capacitance equivalent value at each of the respective positions, wherein one end side of the capacitance of the measurement target is the first electrode, and the measurement target static The other end side of the electric capacity is the second electrode.

  The planar sensor device has a plurality of measurement target capacitances arranged in a matrix. In this case, by using the capacitance measuring device described above, each of the matrix-like measurement target capacitance equivalent values can be obtained with high accuracy.

<Embodiment of Capacitance Type Surface Sensor Device>
Below, the suitable embodiment of the electrostatic capacitance type planar sensor apparatus which concerns on this means is demonstrated.
Preferably, the capacitance-type planar sensor device further includes a third electrode that is provided to face the second electrode opposite to the first electrode, and is connected to a ground potential. A capacitor formed by the second electrode and the third electrode is the bridge capacitor.
The third electrode is applied as one electrode of the bridge capacitor. Therefore, the structure becomes easy.

Preferably, the capacitance type planar sensor device further includes a third electrode provided so as to face the second electrode on the opposite side to the first electrode, and the capacitance measuring device includes: A second capacitor that is applied with a second input voltage as a constant voltage on one end side and is connected to the other end side of the capacitance to be measured on the other end side; A capacitor formed by the electrodes constitutes the second capacitor.
Since the capacitor formed by the second electrode and the third electrode constitutes the second capacitor, a dedicated second capacitor becomes unnecessary.

<Capacitance type liquid level detection device>
Next, a capacitance type liquid level detection device using the above-described capacitance measuring device will be described.
The capacitance-type liquid level detection device according to the present means includes a plurality of electrodes arranged in a height direction in a tank that stores liquid, and two electrodes selected from the plurality of electrodes. The above-described capacitance measuring device that acquires a capacitance equivalent value between the measurement target as a capacitance equivalent value of the measurement target, and determining the liquid level in the tank based on the capacitance equivalent value of the measurement target A determination unit.
By using the capacitance measuring device described above, each of the capacitance equivalent values to be measured can be obtained with high accuracy. Therefore, a highly accurate liquid level can be obtained.

<Embodiment of Capacitance Type Liquid Level Detection Device>
Below, the suitable embodiment of the electrostatic capacitance type liquid level detection apparatus which concerns on this means is demonstrated.
Preferably, the determination unit determines the liquid quality based on a capacitance equivalent value of the measurement target. The capacitance is a value corresponding to the liquid quality. Therefore, the liquid quality of the liquid in the tank can be obtained with high accuracy.

Preferably, the capacitance measuring device further includes a second capacitor to which a second input voltage as a constant voltage is applied to one end side and the other end side is connected to the other end side of the capacitance to be measured. A capacitor formed by the lower electrode and the lower electrode of the two electrodes to be measured constitutes the second capacitor, and the determination unit includes the measurement object. The boundary between different types of liquids is determined based on the capacitance equivalent value.
By comparing the capacitance between adjacent electrodes in the height direction, it can be seen that the same type of liquid exists if they match, and that different liquids exist if they are different. Therefore, when different types of liquid exist, the boundary can be obtained with high accuracy.

The circuit structure of the electrostatic capacitance measuring apparatus 10 of 1st embodiment is shown. 5 is a timing chart of operations of switching elements SW10 and SW11, a potential Vin1 on one end side of a capacitance Cn to be measured, and an output voltage Vout in the first embodiment. The circuit structure of the electrostatic capacitance measuring apparatus 20 of 2nd embodiment is shown. The circuit structure of the electrostatic capacitance measuring apparatus 30 of 3rd embodiment is shown. 12 is a timing chart of operations of the switching elements SW10, SW11, SW12, the potential Vin1 on one end side of the capacitance Cn to be measured, the potential Vin2 on one end side of the second capacitor, and the output voltage Vout in the third embodiment. A measurement circuit when SW10 is in a closed state (ON) and SW11 and SW12 are connected to the ground potential is shown. A measurement circuit when SW10 is in an open state (OFF), SW11 is connected to a ground potential, and SW12 is connected to a power source is shown. A measurement circuit when SW10 is in an open state (OFF) and SW11 and SW12 are connected to a power source is shown. A measurement circuit when SW10 is in an open state (OFF), SW11 is connected to a power source, and SW12 is connected to a ground potential is shown. 14 is a timing chart of operations of the switching elements SW10, SW11, SW12, the potential Vin1 on one end side of the capacitance Cn to be measured, the potential Vin2 on one end side of the second capacitor, and the output voltage Vout in the fourth embodiment. The structure of the electrostatic capacitance type planar sensor apparatus 100 of 1st embodiment is shown, and the sensor main body 110 is shown as a top view. The structure of the capacitive surface sensor device 100 of FIG. 11 is shown, and the sensor body 110 is shown as a cross-sectional view. It is a circuit diagram at the time of taking out a part of sensor main body 110 of FIG. 11 and FIG. The entire measurement circuit when the capacitance at the measurement target position is C1 is shown. The circuit which substituted the measuring circuit of FIG. 14 is shown. The structure of the electrostatic capacitance type planar sensor apparatus 200 of 2nd embodiment is shown, and the sensor main body 110 is shown as sectional drawing. FIG. 16 shows a measurement circuit when the capacitance at the measurement target position is C1. In the capacitance-type planar sensor device 300 of the third embodiment, a measurement circuit when the capacitance at the measurement target position is C1 is shown. The electrostatic capacitance value of each electrostatic capacitance C1-C9 for demonstrating the electrostatic capacitance type planar sensor apparatus of 4th embodiment is shown. It is a graph which shows the difference in the electrostatic capacitance obtained by the method by simultaneous equations in the fourth embodiment, and the method by non-simultaneous equations. The structure of the electrostatic capacitance type liquid level detection apparatus 600 of 1st embodiment is shown. The detailed structure of the sensor main body 621 of FIG. 21 is shown. The equivalent circuit of the sensor main body 621 of the first embodiment is shown. The circuit structure of the electrostatic capacitance type liquid level detection apparatus 600 of 1st embodiment is shown. The detailed structure of the sensor main body 721 of the electrostatic capacitance type liquid level detection apparatus 700 of 2nd embodiment is shown. The circuit structure of the electrostatic capacitance type liquid level detection apparatus 700 of 2nd embodiment is shown. The detailed structure of the sensor main body 721 of the electrostatic capacitance type liquid level detection apparatus 800 of 3rd embodiment is shown. The circuit structure of the electrostatic capacitance type liquid level detection apparatus 800 of 3rd embodiment is shown.

<Capacitance measuring device of first embodiment>
As shown in FIG. 1, the capacitance measuring device 10 in the first embodiment is a device that measures an equivalent value of a capacitance Cn to be measured. The capacitance measuring device 10 includes a constant voltage power supply 11, a first input switching element SW11, a bridge capacitor 12, a charge / discharge switching element SW10, a controller 13, and a measuring instrument 14.

  The constant voltage power supply 11 (input voltage applying means) is a power supply that can apply an input voltage Vin that is a constant voltage. The first input switching element SW11 (input voltage applying means) has one end connected to one end of the capacitance Cn to be measured and the other end switched to one of the constant voltage power supply 11 and the ground potential. Connecting. That is, when the first input switching element SW11 is connected to the constant voltage power supply 11 side, the input voltage Vin is applied to one end side of the capacitance Cn to be measured. On the other hand, when the first input switching element SW11 is connected to the ground potential side, the input voltage Vin is not applied to one end side of the capacitance Cn to be measured.

  The bridge capacitor 12 is connected in series to the other end side of the capacitance Cn to be measured (a side different from the constant voltage power supply 11), and the other end side of the capacitance Cn to be measured and the ground potential. Connected between. That is, the capacitance Cn to be measured and the bridge capacitor 12 constitute a bridge circuit. Here, the capacitance of the bridge capacitor 12 is Cb.

  The charging / discharging switching element SW10 is connected in series to the other end side of the capacitance Cn to be measured, and is connected in parallel to the bridge capacitor 12. Furthermore, the charging / discharging switching element SW10 discharges the electric charge on the other end side of the capacitance Cn to be measured to the ground potential in the closed state.

  The controller 13 alternately performs the following discharging process and charging process. In other words, the controller 13 connects the first input switching element SW11 to the ground potential side and closes the charge / discharge switching element SW10 to thereby close the charge of the capacitance Cn to be measured to the ground. Discharge to potential (discharge process). Here, the state in which the first input switching element SW11 is connected to the ground potential side corresponds to a state in which the input voltage Vin is not applied to the capacitance Cn to be measured. Calibration can be performed by setting the electric charge of the capacitance Cn to be measured to the ground potential as a reference state by the discharging step.

  In addition, after the discharging step, the controller 13 connects the first input switching element SW11 to the constant voltage power supply 11 side and opens the charging / discharging switching element SW10, so that the measurement target The electrostatic capacity Cn is charged (charging process). Here, the state in which the first input switching element SW11 is connected to the constant voltage power supply 11 side corresponds to a state in which the input voltage Vin is applied to the capacitance Cn to be measured.

  When the controller 13 executes the charging process, the measuring instrument 14 is based on the potential Vout (hereinafter also referred to as “output voltage”) between the capacitance Cn to be measured and the bridge capacitor 12. The capacitance equivalent value of is acquired. The output voltage Vout corresponds to the potential on the other end side of the capacitance Cn to be measured.

  Here, the capacitance Cn to be measured, the capacitance Cb of the bridge capacitor 12, the input voltage Vin, and the output voltage Vout have the relationship of Expression (1).

  Further, the capacitance Cb and the input voltage Vin of the bridge capacitor 12 are known. Therefore, from the equation (1), the measuring instrument 14 can acquire the equivalent value of the capacitance Cn to be measured based on the output voltage Vout.

  Next, the relationship between the opening / closing timing of the charge / discharge switching element SW10 executed by the controller 13 and the potential Vin1 and the output voltage Vout on one end side of the capacitance Cn to be measured will be described with reference to FIG. From t1 to t2, the charging / discharging switching element SW10 is turned on (closed state). The first input switching element SW11 is connected to the ground potential side. Therefore, the potential Vin1 on one end side of the capacitance Cn to be measured becomes the ground potential.

  With the above operation, the electric charge of the capacitance Cn to be measured is discharged through the charging / discharging switching element SW10. As a result, the potential (output voltage) Vout between the capacitance Cn to be measured and the bridge capacitor 12 becomes the ground potential as the reference state. That is, the output voltage Vout is indefinite before the above operation, but the output voltage Vout is set to the ground potential by the above operation.

  Subsequently, at t2 to t4, the charging / discharging switching element SW10 is turned off (opened), and the first input switching element SW11 is connected to the constant voltage power supply 11 side. Accordingly, the potential Vin1 on one end side of the capacitance Cn to be measured becomes the input voltage Vin. By the operation described above, electric charge is charged in the capacitance Cn to be measured. After the time required for charging has elapsed, the measuring instrument 14 measures the output voltage Vout. In FIG. 2, the measuring instrument 14 measures the output voltage Vout from t3 to t4.

  Subsequently, from t4 to t5, the charging / discharging switching element SW10 is turned on (closed state), and the first input switching element SW11 is connected to the ground potential side. By this operation, the potential Vin1 on one end side of the capacitance Cn to be measured becomes a ground potential, and the charge of the capacitance Cn to be measured is discharged. That is, the output voltage Vout becomes the ground potential. Subsequently, from t5 to t9, the same operation as the above-described t1 to t5 is repeated.

  As described above, the bridge capacitor 12 is connected in series to the capacitance Cn to be measured, and the measuring instrument 14 has a potential on the other end side of the capacitance Cn to be measured, that is, the measurement target and the bridge. A capacitance equivalent value is acquired based on the potential (output voltage) Vout between the capacitor 12 and the capacitor 12. Here, since the intermediate potential between the two capacitors is indefinite, the capacitance measured using the intermediate potential is not highly accurate.

  However, as described above, by closing the charge / discharge switching element SW10, the electric charge of the capacitance Cn to be measured is discharged. That is, the output voltage (intermediate potential) Vout becomes the ground potential as the reference state. That is, the output voltage Vout can be calibrated by closing the charge / discharge switching element SW10.

  Then, the measuring instrument 14 is opened when the charge / discharge switching element SW10 is opened and the input voltage Vin is applied to one end of the capacitance Cn to be measured. The potential on the other end side of the capacitance Cn is measured. That is, the potential measured by the measuring instrument 14 is a potential corresponding to the capacitance Cn to be measured. Therefore, the capacitance measuring device 10 can measure the capacitance Cn to be measured with high accuracy.

<Capacitance measuring device of second embodiment>
As shown in FIG. 3, the capacitance measuring device 20 of the second embodiment includes a power source 11, a bridge capacitor 12, a charging / discharging switching element SW <b> 10, a controller 13, and a measuring instrument 14.

  The capacitance measuring device 20 of the second embodiment adds a capacitance Cy to the capacitance measuring device 10 of the first embodiment. The electrostatic capacity Cy is an electrostatic capacity that exists between the other end side of the electrostatic capacity Cn to be measured and the ground potential. For example, the capacitance Cy is formed between the electrode on the other end side of the capacitance Cn to be measured and an electrode existing nearby.

  That is, the bridge capacitor 12 is connected in parallel to the capacitance Cy. Here, the capacitance Cb of the bridge capacitor 12 is set to be larger than the capacitance Cy. The capacitance Cy can be estimated in advance to some extent. Therefore, the capacitance Cb of the bridge capacitor 12 is set. In particular, the capacitance Cb of the bridge capacitor 12 may be set to 100 times or more of the capacitance Cy.

  Here, the capacitance Cn to be measured, the capacitance Cb of the bridge capacitor 12, the input voltage Vin, the output voltage Vout, and the capacitance Cy have a relationship of Expression (2).

  As is clear from Equation (2), when the capacitance Cb of the bridge capacitor 12 is sufficiently larger than the capacitance Cy, (Cb + Cy) is a value approximated to Cb. Therefore, the capacitance Cn to be measured is derived from the same relationship as in the equation (1). Thus, the influence degree of the electrostatic capacity Cy between the other end side of the electrostatic capacity Cn to be measured and the ground potential is surely reduced. Therefore, an equivalent value of the capacitance Cn to be measured with high accuracy can be obtained.

<Capacitance measuring apparatus of third embodiment>
As shown in FIG. 4, the capacitance measuring device 30 of the third embodiment includes a constant voltage power supply 11, a bridge capacitor 12, a charging / discharging switching element SW <b> 10, a controller 13, a measuring instrument 14, and a first input switching element. SW11, second capacitor 31, and second input switching element SW12 are provided.

  The capacitance measuring device 30 of the third embodiment has a second capacitor 31 and a second input switching element SW12 added to the capacitance measuring device 20 of the second embodiment. The second capacitor 31 is applied with a second input voltage Vin (the same as the input voltage Vin in the present embodiment) as a constant voltage at one end, and the other end is connected to the other end of the capacitance Cn to be measured. Connected.

  The second input switching element SW12 has one end connected to one end of the second capacitor 31, and the other end connected to one of the constant voltage power supply 11 and the ground potential in a switchable manner. That is, when the second input switching element SW12 is connected to the constant voltage power supply 11 side, the second input voltage Vin is applied to one end side of the second capacitor 31. On the other hand, when the second input switching element SW12 is connected to the ground potential side, the second input voltage Vin is not applied to one end side of the second capacitor 31.

  Here, the switching timing of each switching element SW10, SW11, SW12 executed by the controller 13, the potential Vin1 on one end side of the capacitance Cn to be measured, the potential Vin2 on one end side of the second capacitor 31, and the output voltage Vout The relationship is as shown in FIG.

  As shown in FIG. 5, in the charging / discharging switching element SW10, t1 to t2 and t5 to t6 are turned on (closed state), and t2 to t5 and t6 to t9 are turned off (open state). In the first input switching element SW11, t1 to t3 and t5 to t7 are connected to the ground potential, and t3 to t5 and t7 to t9 are connected to the constant voltage power supply 11. In the second input switching element SW12, t1 to t2, t4 to t6, and t8 to t9 are connected to the ground potential, and t2 to t4 and t6 to t8 are connected to the constant voltage power supply 11.

  Here, a state in which the input voltage Vin is not applied to one end side of the capacitance Cn to be measured and the second input voltage Vin is not applied to one end side of the second capacitor 31 is defined as a first state. A state in which the input voltage Vin is not applied to one end side of the capacitance Cn to be measured and the second input voltage Vin is applied to one end side of the second capacitor 31 is a second state. A state in which the input voltage Vin is applied to one end side of the capacitance Cn to be measured and the second input voltage Vin is applied to one end side of the second capacitor 31 is referred to as a third state. A state in which the input voltage Vin is applied to one end side of the capacitance Cn to be measured and the second input voltage Vin is not applied to one end side of the second capacitor 31 is defined as a fourth state.

  And as shown in FIG. 5, it switches in order of a 1st state, a 2nd state, a 3rd state, and a 4th state. At this time, the output voltage Vout is as shown in the bottom column of FIG. Then, the measuring instrument 14 has a potential Vo2 on the other end side of the capacitance Cn to be measured in the second state (t2 to t3) and a potential Vo3 on the other end side of the capacitance Cn to be measured in the third state. The equivalent value of the capacitance Cn to be measured is acquired based on the difference (Vo2−Vo3). Alternatively, the measuring instrument 14 acquires an equivalent value of the capacitance Cn to be measured based on the potential Vo4 on the other end side of the capacitance Cn to be measured in the fourth state (t4 to t5).

Here, the configuration of the equivalent circuit and the output voltage Vout in each of the first state to the fourth state will be described with reference to FIGS.
In the first state (t1 to t2 in FIG. 5), the charging / discharging switching element SW10 is in a closed state, and the first and second input switching elements SW11 and SW12 are connected to the ground potential. Therefore, the circuit in this state is as shown in FIG. As shown in FIG. 6, all of the capacitances Ca, Cn, Cy, Cb are all connected to the ground potential, and the other of these capacitances Ca, Cn, Cy, Cb is connected to the measuring instrument 14. Furthermore, since the charging / discharging switching element SW10 is in the closed state, the other potential of the capacitances Ca, Cn, Cy, Cb is a ground potential (here, 0 (zero)). The potential Vo1 (output voltage Vout) measured by the measuring instrument 14 at this time is expressed by Expression (3). That is, the potential Vo1 is 0 as the reference state potential.

  In the second state (t2 to t3 in FIG. 5), the charging / discharging switching element SW10 is open, the first input switching element SW11 is connected to the ground potential, and the second input switching element SW12 is the constant voltage power source. 11 is connected. At this time, as shown in FIG. 7, one of the capacitances Ca is connected to the constant voltage power supply 11, and one of the other capacitances Cn, Cy, Cb is connected to the ground potential. That is, the potential Vo2 measured by the measuring instrument 14 is an intermediate potential between the capacitance Ca and the total value of the capacitances Cn, Cy, Cb. The potential Vo2 measured by the measuring instrument 14 at this time is expressed by Expression (4). That is, the potential Vo2 is a potential corresponding to the electrostatic capacitance Ca of the second capacitor 31.

In the third state (t3 to t4 in FIG. 5), the charging / discharging switching element SW10 is in an open state, and the first and second input switching elements SW11 and SW12 are both connected to the constant voltage power supply 11. At this time, as shown in FIG. 8, one of the capacitances Ca and Cn is connected to the constant voltage power supply 11, and one of the other capacitances Cy and Cb is connected to the ground potential. The other of Cn, Cy, and Cb is connected to the measuring instrument 14. That is, the potential Vo3 measured by the measuring instrument 14 is an intermediate potential between the total value of the capacitances Ca and Cn and the total value of the capacitances Cy and Cb. The potential Vo3 measured by the measuring instrument 14 at this time is expressed by Expression (5). That is, the potential Vo3 is a potential corresponding to the total value of the capacitances Ca and Cn.

  In the fourth state (t4 to t5 in FIG. 5), the charging / discharging switching element SW10 is open, the first input switching element SW11 is connected to the constant voltage power supply 11, and the second input switching element SW12 is grounded. Connected to potential. At this time, as shown in FIG. 9, one of the capacitances Cn is connected to the constant voltage power supply 11, and one of the other capacitances Ca, Cy, Cb is connected to the ground potential. The other of Cn, Cy, and Cb is connected to the measuring instrument 14. That is, the potential Vo4 measured by the measuring instrument 14 is an intermediate potential between the capacitance Cn and the total value of the capacitances Ca, Cy, and Cb. The potential Vo4 measured by the measuring instrument 14 at this time is expressed by Expression (6). That is, the potential Vo4 is a potential corresponding to the capacitance Cn to be measured.

  Here, as described above, the measuring instrument 14 has an equivalent value of the capacitance Cn to be measured based on the potential Vo4 on the other end side of the capacitance Cn to be measured in the fourth state (t4 to t5). Can be obtained. In the case of measurement using the potential Vo4, switching between the first state and the fourth state is sufficient. However, since the potential Vo4 is a value close to the ground potential, it may be affected by noise.

  Therefore, the measuring instrument 14 has a potential Vo2 on the other end side of the capacitance Cn to be measured in the second state (t2 to t3) and a potential Vo3 on the other end side of the capacitance Cn to be measured in the third state. By acquiring the equivalent value of the capacitance Cn to be measured based on the difference (Vo2−Vo3), a more accurate capacitance equivalent value can be obtained. That is, by switching the timing of the first input switching element SW11 and the second input switching element SW12 in the order of the first state → second state → third state → fourth state as shown in FIG. The difference between the two-state output voltage Vo2 and the third-state output voltage Vo3 can be used.

<Capacitance Measuring Device of Fourth Embodiment>
Next, the capacitance measuring device of the fourth embodiment differs from the capacitance measuring device 30 of the third embodiment only in the switching operation of the charging / discharging switching element SW10. As shown in FIG. 10, the charging / discharging switching element SW10 has t1 to t2, t3 to t6, and t7 to t9 turned off (open state), and t2 to t3 and t6 to t7 turned on (closed state). It is said. The first and second input switching elements SW11 and SW12, the potential Vin1 on one end side of the capacitance Cn to be measured, and the potential Vin2 on one end side of the second capacitor 31 are the same as in the third embodiment.

  Calibration is performed using the charging / discharging switching element SW10 in the second state where the switching element SW10 is in the closed state as a reference state. That is, the output voltage Vout indicates a value in which the output voltage Vo2 in the second state (t2 to t3, t6 to t7) is zero. Therefore, the measuring instrument 14 can acquire the equivalent value of the capacitance Cn to be measured only by measuring the output voltage Vo3 in the third state.

<Capacitance type planar sensor device of first embodiment>
Next, a capacitance type planar sensor device using the above-described capacitance measuring device will be described.
(Overall structure of capacitive sensor device)
As shown in FIGS. 11 and 12, the electrostatic capacitance type planar sensor device 100 includes a sensor main body 110 formed in a sheet shape (planar shape), and electrostatic capacitance between electrodes in the sensor main body 110. (Capacitance to be measured) is measured.

  Here, the sensor main body 110 can be applied as a pressure-sensitive sensor that detects a position and size to which an external force is applied, and is applied as a touch panel that detects a position where a conductor such as a human finger contacts or approaches. You can also. As shown in FIGS. 11 and 12, the capacitance type planar sensor device 100 includes a sensor main body 110 and a capacitance measuring device 160.

(Detailed configuration of sensor body 110)
In the present embodiment, the sensor main body 110 is formed in a sheet shape and has a flexible and stretchable property. The sensor body 110 can have a curved shape as well as a planar shape. However, in the following, referring to FIGS. 11 and 12, a planar sensor body 110 is taken as an example. As described above, when the sensor body 110 is applied as a touch panel, flexibility and stretchability are not necessarily required.

  The sensor body 110 includes a plurality of rows of first electrodes 120 (121 to 128), a plurality of columns of second electrodes 130 (131 to 138), a dielectric layer 141, and insulating layers 142 and 143 (shown in FIG. 12). Is provided. Each of the first electrodes 121 to 128 of the plurality of rows of first electrodes 120 is formed in a band shape, and is arranged so as to extend in the vertical direction of FIG.

  Each of the second electrodes 131 to 138 of the plurality of rows of the second electrodes 130 is formed in a strip shape, and is disposed so as to extend in the left-right direction in FIG. In FIG. 11, the plurality of rows of the first electrodes 120 and the plurality of columns of the second electrodes 130 are illustrated with 8 rows and 8 columns, but the present invention is not limited thereto.

  The plurality of rows of the first electrodes 120 and the plurality of columns of the second electrodes 130 are provided to face each other with a distance in the surface normal direction (the front-rear direction in FIG. 11 and the up-down direction in FIG. 12). And both are arrange | positioned so that the opposing position of the 1st electrode 120 of multiple rows and the 2nd electrode 130 of multiple columns may become a matrix form. That is, the respective first electrodes 121 to 128 are opposed to the respective second electrodes 131 to 138, and the opposing positions thereof are in a matrix shape of 8 rows × 8 columns. Each of the matrix-like positions of 8 rows × 8 columns can be a capacitance measurement target position.

  Moreover, each 1st electrode 121-128 and each 2nd electrode 131-138 are shape | molded by mix | blending a conductive filler in an elastomer or resin. The first and second electrodes 120 and 130 are flexible and extendable and contractible.

  Examples of the elastomer constituting the first and second electrodes 120 and 130 include silicone rubber, ethylene-propylene copolymer rubber, natural rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, acrylic rubber, and epichloro. Hydrin rubber, chlorosulfonated polyethylene, chlorinated polyethylene, urethane rubber, etc. can be applied. In addition, the conductive filler blended in the first and second electrodes 120 and 130 may be particles having conductivity, and for example, fine particles such as carbon materials and metals can be applied. Examples of the resin constituting the first and second electrodes 120 and 130 include polyester resin, modified polyester resin, polyether urethane resin, polycarbonate urethane resin, vinyl chloride-vinyl acetate copolymer, phenol resin, and acrylic resin. Polyamideimide resin, polyamide resin, nitrocellulose, modified cellulose and the like can be applied.

  The dielectric layer 141 is provided between the first electrodes 121 to 128 and the second electrodes 131 to 138. When the sensor body 110 is applied as a pressure-sensitive sensor, the dielectric layer 141 can be compressed and deformed so that the thickness varies depending on an external force.

  The dielectric layer 141 is formed of an elastomer or a resin, and has the property of being flexible and stretchable, like the first and second electrodes 120 and 130. Examples of the elastomer constituting the dielectric layer 141 include silicone rubber, acrylonitrile-butadiene copolymer rubber, acrylic rubber, epichlorohydrin rubber, chlorosulfonated polyethylene, chlorinated polyethylene, and urethane rubber. Examples of the resin constituting the dielectric layer 141 include polyethylene resin, polypropylene resin, polyurethane resin, polystyrene resin (including crosslinked foamed polystyrene resin), polyvinyl chloride-polyvinylidene chloride copolymer, and ethylene-acetic acid copolymer. Coalescence etc. can be applied.

  The insulating layers 142 and 143 are provided so as to cover the surface on the first electrode 120 side and the back surface on the second electrode 130 side, respectively. The insulating layers 142 and 143 have the property of being flexible and stretchable, like the first and second electrodes 120 and 130. As the elastomer or resin constituting the insulating layers 142 and 143, for example, the materials described as the elastomer or resin constituting the dielectric layer 141 are applied.

  As shown in FIG. 12, when the sensor main body 110 configured as described above receives an external force F that compresses in the surface normal direction of the sensor main body 110 (vertical direction in FIG. 12), the dielectric layer 141 faces. Compresses and deforms in the normal direction. As a result, the separation distance between the first and second electrodes 120 and 130 located at the site to which the external force F is applied is reduced. In this case, it changes so that the electrostatic capacitance between the 1st, 2nd electrodes 120 and 130 in the said part may become large. Therefore, the position where the external force F is received can be measured by measuring the change in capacitance for each of the matrix positions where the first electrodes 121 to 128 and the second electrodes 131 to 138 face each other. Furthermore, the magnitude of the external force F can be measured by measuring the absolute value of each capacitance at the matrix position.

(Sensor circuit)
Here, as shown in FIG. 11, the sensor main body 110 includes, for example, eight rows of first electrodes 120 and eight columns of second electrodes 130. However, in order to facilitate the description of the capacitance measuring device, the first electrode 120 (121 to 123) in three rows and the second electrode 130 (131 to 133) in three columns will be described below.

  A circuit diagram of the sensor main body 110 in this case is expressed as shown in FIG. That is, capacitances C1 to C9 are formed between the first electrodes 121 to 123 and the second electrodes 131 to 133, respectively. For example, the capacitance between the first electrode 121 and the second electrode 131 is C1, and the capacitance between the first electrode 122 and the second electrode 132 is C5. Here, the terminals of the first electrodes 121 to 123 are Pi1 to Pi3, and the terminals of the second electrodes 131 to 133 are Po1 to Po3.

(Configuration of capacitance measuring device)
Next, the configuration of the capacitance measuring device 160 will be described with reference to FIGS. 14 and 15. Here, the capacitance measuring device 160 of the present embodiment employs the circuit configuration of the capacitance measuring device 30 of the third embodiment described with reference to FIG.

  In FIG. 13, the terminals Pi1 to Pi3 of the first electrodes 121 to 123 in the sensor body 110 are switched in order, and the terminals Po1 to Po3 of the second electrodes 131 to 133 are switched in order. It is done. However, for ease of explanation, first, a case where the capacitance C1 is measured with the opposed position of the first electrode 121 and the second electrode 131 as a measurement target position will be described with reference to FIG.

  As shown in FIG. 14, the capacitance measuring device 160 includes a constant voltage power supply 11, a bridge capacitor 12, a charging / discharging switching element SW10, a controller 13, a measuring instrument 14, a first input switching element SW11, and a second capacitor. 31, a second input switching element SW 12, measurement target change switches SW 121 to SW 123, SW 131 to SW 133. Here, in the capacitance measuring device 160 of the present embodiment, the same components as those of the capacitance measuring device 30 of the third embodiment are denoted by the same reference numerals.

  The measurement target change switches SW121 to SW123 connect one of the terminals Pi1 to Pi3 of the first electrodes 121 to 123 to the constant voltage power supply 11 and connect the remaining two to the ground potential. And measurement object change switch SW121-SW123 can switch the terminal connected to the constant voltage power supply 11. FIG. The measurement target change switches SW131 to SW133 connect one of the terminals Po1 to Po3 of the second electrodes 131 to 133 to the measuring instrument 14 and connect the remaining two to the ground potential. And measurement object change switch SW131-SW133 can switch the terminal connected to the measuring device 14. FIG. Here, the measurement object change switch SW121 is connected to the constant voltage power supply 11, the switch SW131 is connected to the measuring instrument 14, and the other switches SW122, SW123, SW132, SW133 are connected to the ground potential.

  The bridge capacitor 12 has a set constant capacitance Cb. One of the bridge capacitors 12 is connected to each of the second electrodes 131 to 133 via the measurement target change switches SW131 to SW133. The other of the bridge capacitor 12 is connected to the ground potential. The capacitance Cb of the bridging capacitor 12 is a constant that is larger than the capacitance at other positions in the matrix-like position located between the second electrode 131 at the measurement target position and the ground potential. Set to a value. The capacitance Cb of the bridge capacitor 12 is set to a constant value that is, for example, 100 times or more of the capacitance at the other position. When the capacitance at the measurement target position is C1, the capacitance at other positions in the matrix-like position is the total value of C2 and C3. That is, the capacitance Cb of the bridge capacitor 12 is set to be 100 times or more the total value of C2 and C3.

  Here, when measuring the capacitance C1, the capacitances C4 and C7 between the first electrode 121 and the ground potential have little influence on the potential Vout measured by the measuring instrument 14. Further, the capacitances C5, C6, C8, C9 between the other first electrodes 122, 123 connected to the ground potential and the other second electrodes 132, 133 connected to the ground potential are also potentials. It has little effect on Vout. Accordingly, the electric circuit of the sensor main body 110 in FIG. 14 can be represented by being replaced as shown in FIG. In FIG. 15, for generalization, the capacitance C1 is represented as Cn representing the capacitance to be measured, and the total of the capacitances C2 and C3 is represented as Cy. Each symbol is the same as the symbol in the capacitance measuring device 30 of the third embodiment.

  Therefore, the circuit shown in FIG. 15 corresponds to the circuit shown in FIG. Therefore, as described with reference to FIG. 4, by operating each of the switching elements SW10, SW11, and SW12, the measuring instrument 14 can acquire the capacitance C1 at the measurement target position with high accuracy.

<Capacitance type planar sensor device of the second embodiment>
A capacitance type planar sensor device 200 according to a second embodiment will be described with reference to FIGS. 16 and 17. As shown in FIG. 16, the sensor main body 210 of the capacitive surface sensor device 200 has a third electrode 220 added to the sensor main body 110 shown in FIG. 12. The third electrode 220 is provided so as to face the second electrode 130 on the opposite side to the first electrode 120, and is connected to the ground potential. That is, the third electrode 220 is provided on the back surface side (the lower side in FIG. 16) of the second electrode 130 via the insulating layer 230. The third electrode 220 is approximately the same size as the insulating layer 143. The back side of the third electrode 220 is covered with an insulating layer 143.

  A circuit diagram in this case is shown in FIG. A capacitor formed by the second electrode 130 and the third electrode 220 functions as the bridge capacitor 12 in FIG. That is, the electrostatic capacitance between the second electrode 130 and the third electrode 220 is Cb. Thus, since the bridge capacitor 12 is configured using the third electrode 220, it is not necessary to provide a dedicated capacitor. Therefore, the structure becomes easy. Further, since the capacitances Cn and Cb are formed as an integral member, both follow the temperature change, for example. Therefore, even if the temperature changes, the capacitance Cn to be measured can be measured with high accuracy.

<Capacitance type planar sensor device of the third embodiment>
A capacitance type planar sensor device 300 according to a third embodiment will be described with reference to FIG. As shown in FIG. 18, the sensor main body of the capacitive surface sensor device 300 is configured in the same manner as the sensor main body 210 shown in FIG. However, the third electrode 220 is not connected to the ground potential, but is connected to the second input switching element SW12.

  That is, as shown in FIG. 18, the capacitor formed by the second electrode 130 and the third electrode 220 constitutes the second capacitor 31. That is, the capacitance between the second electrode 130 and the third electrode 220 is Ca. Therefore, a dedicated second capacitor is not necessary. Furthermore, since the capacitances Cn and Ca are formed as an integral member, both follow the temperature change, for example. Therefore, even if the temperature changes, the capacitance Cn to be measured can be measured with high accuracy.

<Capacitance type planar sensor device of the fourth embodiment>
A capacitance type planar sensor device according to a fourth embodiment will be described with reference to FIGS. 19 and 20. In the above-described embodiment, the measuring instrument 14 includes the potential Vo2 on the other end side of the capacitance Cn to be measured in the second state (t2 to t3) and the other end side of the capacitance Cn to be measured in the third state. Based on the difference (Vo2−Vo3) from the potential Vo3, the equivalent value of the capacitance Cn to be measured is obtained. Alternatively, the measuring instrument 14 acquires an equivalent value of the capacitance Cn to be measured based on the potential Vo4 on the other end side of the capacitance Cn to be measured in the fourth state (t4 to t5). .

  In this embodiment, unlike the calculation method, the measuring instrument 14 acquires the capacitance Cn to be measured by solving simultaneous equations. The simultaneous equations when the unknowns are the capacitances Cn1, Cn2, and Cn3 are expressed by Expression (7). In other words, the simultaneous equations of Equation (7) are obtained as follows: the input voltage Vin, the respective voltages Vout1, Vout2, and Vout3 at the selected second electrode 131, and the selected second electrode 131 and the first of a plurality of rows as unknowns. It is represented by electrostatic capacitances Cn1, Cn2, Cn3 at a plurality of positions that three-dimensionally intersect with each of the electrodes 121, 122, 123.

  Capacitances Cn1, Cn2, and Cn3 are obtained by solving the simultaneous equations of Expression (7). Similarly, the other capacitances Cn4 to Cn9 can be obtained by solving simultaneous equations.

  Here, when the capacitances of C1 to C9 are set to 1 pF to 9 pF, the method of solving the simultaneous equations of this embodiment is compared with the method of the above embodiment. The results are as shown in FIG. In FIG. 20, a white circle is a set capacity, a white square is a result of the method for solving the simultaneous equations of the present embodiment, and a black circle is a result of the method of the non-simultaneous equations in the above embodiment.

  As shown in FIG. 20, the method for solving simultaneous equations has a higher accuracy in capacitance than the method using non-simultaneous equations. Here, in the method based on the non-simultaneous equations, it is considered that this is because when the potential on the other end side of the capacitance of a certain measurement target is measured, it is influenced by other capacitance. Therefore, since the method for solving simultaneous equations is an operation that takes into account other capacitances, a highly accurate capacitance can be obtained.

<Others of capacitive surface sensor device>
In the sensor devices of the second and third embodiments, the capacitances Cn and Cb or the capacitances Cn and Ca are formed as an integral member. In addition, the capacitances Cn, Ca, Cb may be formed as an integral member. Thereby, even if the temperature changes, the capacitance Cn to be measured can be measured with higher accuracy. Note that it is not necessary to superimpose all the electrodes, and the above effect can be obtained even if each electrode is formed on the same substrate.

<Capacitance type liquid level detection device of first embodiment>
Next, a capacitance type liquid level detection device using the above-described capacitance measuring device will be described.
(Overall structure of capacitance type liquid level detection device)
With reference to FIG. 21, the structure of a capacitive liquid level detection device (hereinafter referred to as a liquid level detection device) will be described. The liquid level detection device detects the liquid level and liquid quality in the fuel tank 610 of the vehicle. As shown in FIG. 21, the fuel tank 610 is mounted on a vehicle and stores gasoline as fuel.

  Here, the liquid to be supplied may contain water or methanol in addition to gasoline. The liquid level detection device determines the liquid quality in the fuel tank 610, that is, whether the liquid is gasoline, water, methanol, or the like. Further, the liquid level detection device determines the liquid level, that is, the gasoline level, the water level, and the methanol level. Note that, for example, the present invention can also be applied to the determination of other liquids or when floating substances are present.

  The fuel tank 610 has a recess 611 at the bottom in the center in the left-right direction of the vehicle, and has a recess 612 on the top surface corresponding to the recess 611. That is, the bottom recess 611 and the top recess 612 face each other in the vertical direction. An opening hole 613 is formed on the upper surface of the fuel tank 610. A detachable connector is connected to the opening hole 613.

  The fuel tank 610 is provided with an electrode unit 620 constituting the capacitive liquid level detection device 600. The electrode unit 620 is located at the center of the fuel tank 610 in the left-right direction of the vehicle, and is fixed between the upper and lower recesses 611 and 612 in the fuel tank 610.

  The electrode unit 620 includes a sensor main body 621 formed in a rod shape, and an urging member 622 provided at the upper end of the sensor main body 621 so as to be extendable from the upper end surface of the sensor main body 621. The sensor body 621 is disposed at the lower end in a recess 611 at the bottom of the fuel tank 610. The biasing member 622 biases the recess 612 on the top surface of the fuel tank 610 (relative to the extension direction) in the extended state. In this way, the electrode unit 620 is fixed between the bottom recess 611 and the top recess 612 of the fuel tank 610.

  Furthermore, the sensor main body 621 includes a plurality of electrode pairs 626a to 626i that are arranged in the fuel tank 610 while being shifted in the vertical direction (height direction). The electrostatic capacitance between each electrode pair of the plurality of electrode pairs 626a to 626i varies depending on the type of fluid present.

  The liquid level detection device 600 includes a capacitance measuring device 630 and a determination unit 640 that are electrically connected to the plurality of electrode pairs 626a to 626i of the electrode unit 620.

  The capacitance measuring device 630 is disposed outside the fuel tank 610, and the capacitance measuring device described above is substantially applied. The determination unit 640 determines the liquid level and the liquid quality of the liquid in the fuel tank 610 based on the capacitances C1 to C9 obtained by the capacitance measuring device 630.

(Sensor body of electrode unit)
Next, the sensor main body 621 of the electrode unit 620 will be described in detail with reference to FIG. A plurality of electrode pairs 626a to 626i are disposed on the surface of the base material of the sensor main body 621 while being shifted in the height direction. The capacitances of the electrode pairs 626a to 626i are C1 to C9 in order from the bottom.

  Wirings 627a to 627c (hereinafter referred to as application-side wirings) that are electrically connected are formed on one electrode of each of the plurality of electrode pairs 626a to 626i. In addition, wirings 628 a to 628 c (hereinafter referred to as output-side wirings) that are electrically connected are formed on the other electrode of each electrode pair.

  The first application side wiring 627a is connected to the electrode pairs 626a, 626d and 626g, the second application side wiring 627b is connected to the electrode pairs 626b, 626e and 626h, and the third application side wiring 627c is an electrode. Connected to pairs 626c, 626f, 626i. The first output side wiring 628a is connected to the electrode pair 626a, 626b, 626c, the second output side wiring 628b is connected to the electrode pair 626d, 626e, 626f, and the third output side wiring 628c is connected to the electrode Connected to pairs 626g, 626h, 626i.

  Here, the terminals connected to the application-side wirings 627a, 627b, and 627c are Pi1, Pi2, and Pi3, respectively, and the terminals connected to the output-side wirings 628a, 628b, and 628c are Po1, Po2, and Po3, respectively. To do.

An equivalent circuit of the sensor body 621 described above is expressed as shown in FIG. Therefore, the circuit of the liquid level detection device 600 is expressed as shown in FIG. That is, the liquid level detection device 600 is equivalent to a matrix-like circuit, like the capacitive surface sensor device 100 . If it does so, the electrostatic capacitance type planar sensor apparatus 100 mentioned above can be applied to the liquid level detection apparatus 600 similarly.

  And the determination part 640 determines the liquid level in each height based on the electrostatic capacitance C1-C9 in each height which the measuring device 14 acquired. At the same time, the determination unit 640 can determine the liquid quality at each height based on the capacitances C1 to C9 at each height.

<Capacitance type liquid level detection device of the second embodiment>
In the liquid level detection apparatus 600 of the first embodiment, the electrodes constituting each electrode pair are positioned at the same height. As shown in FIG. 25, the liquid level detection device 700 of this embodiment disposes the electrodes 726a to 726t in the height direction. The electrodes connected to the application side wirings 727a to 727c and the electrodes connected to the output side wirings 728a to 728c are alternately arranged in the height direction.

  An equivalent circuit in this case is as shown in FIG. In FIG. 26, the capacitance of the measurement target is Cn1, and the capacitance of the second capacitor 31 (corresponding to reference numeral 31 in FIG. 24) is Ca1. Thus, the capacitor formed by the lower electrode 726b and the lower electrode 726a of the two electrodes 726b and 726c to be measured constitutes the second capacitor 31 described above.

  The determination unit 740 determines a boundary between different types of liquids based on the equivalent values of the capacitances Cn1 to Cn8 to be measured. For example, if the same kind of liquid exists at positions 726b to 726c and 726a to 726b between the electrodes adjacent in the height direction, Cn1 and Ca1 are the same. Then, the difference between the potential corresponding to Cn1 and the potential corresponding to Ca1 becomes zero.

  On the other hand, if different types of liquid exist at positions 726b to 726c and 726a to 726b between the electrodes adjacent in the height direction, Cn1 and Ca1 have different values. Then, the difference between the potential corresponding to Cn1 and the potential corresponding to Ca1 is not zero. The determination unit 740 determines the boundary of the liquid based on this difference.

<Capacitance type liquid level detection device of the third embodiment>
Next, the liquid level detection apparatus 800 of 3rd embodiment is demonstrated with reference to FIG. 27 and FIG. The liquid level detection device 800 of the present embodiment is different from the liquid level detection device 700 of the second embodiment in that the output side wirings 828a to 828c are used as the bridge capacitor 12.

  That is, the output-side wirings 828a, 828b, and 828c are formed sufficiently long in the height direction of the electrode unit 620. By doing so, as shown in FIG. 28, the output-side wirings 828 a, 828 b, and 828 c constitute the electrode of the bridge capacitor 12. Therefore, the liquid level detection device 800 of the present embodiment does not need to be provided with a dedicated bridge capacitor 12.

10, 20, 30, 160, 630: capacitance measuring device, 11: constant voltage power supply, 12: capacitor for bridge, 13: controller, 14: measuring instrument, 31: second capacitor, 100, 200, 300: static Capacitance type planar sensor device 110, 210: sensor main body, 120: first electrode, 130: second electrode, 141: dielectric layer, 142, 143, 230: insulating layer, 220: third electrode, 600, 700 , 800: Capacitance type liquid level detection device, 621, 721: Sensor body, 626a to 626i, 726a to 726t: Electrode, 640, 740: Determination unit, SW10: Switching element for charge / discharge, SW11: For first input Switching element, SW12: Second input switching element, Cn, Cn1: Capacitance to be measured, Cb: Blipping Capacitance of use capacitor 12, Ca, Ca1: capacitance of the second capacitor 31

Claims (13)

An input voltage applying means for applying an input voltage that is a constant voltage to one end side of the capacitance to be measured;
A bridge capacitor connected in series to the other end side of the capacitance to be measured, and connected between the other end side of the capacitance to be measured and a ground potential;
It is connected in series to the other end side of the capacitance to be measured, and is connected in parallel to the bridge capacitor, and the electric charge on the other end side of the capacitance to be measured is ground potential in the closed state. A charge / discharge switching element that discharges into
After the step of discharging the charge of the capacitance to be measured to the ground potential by making the input voltage not applied and closing the charge / discharge switching element, and after the step of discharging, A controller that performs the step of charging the capacitance to be measured by opening the charge / discharge switching element and applying the input voltage;
In the step of charging by the controller, a measuring device that acquires a capacitance equivalent value of the measurement target based on a potential between the capacitance of the measurement target and the bridge capacitor;
Equipped with a,
The input voltage applying means includes
A constant voltage power supply capable of applying the input voltage;
One end side is connected to one end side of the capacitance to be measured, the other end side is connected to one of the constant voltage power source and a ground potential, and the input voltage is electrostatically measured by the constant voltage power source. A first input switching element for switching between a state applied to a capacitor and a state where the input voltage is not applied to the capacitance to be measured;
Ru with a capacitance measuring device. The capacitance measuring device is
A second input voltage as a constant voltage is applied to one end side, and the other end side is further provided with a second capacitor connected to the other end side of the capacitance to be measured.
The capacitance measuring device according to claim 1 . A first state in which the input voltage and the second input voltage are not applied, a second state in which one of the input voltage and the second input voltage is applied and the other is not applied, the input voltage and the second input voltage Switch to the third state to apply, the fourth state to apply the other without applying the one of the input voltage and the second input voltage,
The measuring device acquires a capacitance equivalent value of the measurement target based on a potential on the other end side of the capacitance of the measurement target in the second state, the third state, or the fourth state.
The capacitance measuring device according to claim 2 . Capacitance of the bridge capacitor, to the capacitance between the other end and the ground potential of the capacitance of the measurement object, and a large capacitance, one of claims 1 to 3 A capacitance measuring device according to one item. The capacitance measuring device acquires each of a plurality of measurement target capacitance equivalent values in the sensor body,
The equivalent circuit of the sensor body includes a plurality of rows of first electrodes, a plurality of columns of second electrodes arranged in a matrix with respect to the plurality of rows of first electrodes, and the plurality of rows of first electrodes. And a plurality of dielectric layers provided at a plurality of positions where the plurality of rows of second electrodes are three-dimensionally crossed,
The capacitance equivalent values of the plurality of measurement objects in the sensor body are capacitance equivalent values between the first electrode and the second electrode corresponding to the respective positions of the plurality of dielectric layers.
The capacitance measuring device according to any one of claims 1 to 4 . The measuring instrument is
When the input voltage is applied to one first electrode of the plurality of first electrodes and the remaining first electrodes are connected to the ground potential, the respective voltages at the selected second electrodes;
Capacitances at a plurality of positions that are three-dimensionally intersected with each of the selected second electrode and the plurality of rows of first electrodes, as unknowns,
By solving the simultaneous equations represented by
The capacitance measuring device according to claim 5 , wherein each capacitance equivalent value as an unknown is acquired. An input voltage applying means for applying an input voltage that is a constant voltage to one end side of the capacitance to be measured;
A bridge capacitor connected in series to the other end side of the capacitance to be measured, and connected between the other end side of the capacitance to be measured and a ground potential;
It is connected in series to the other end side of the capacitance to be measured, and is connected in parallel to the bridge capacitor, and the electric charge on the other end side of the capacitance to be measured is ground potential in the closed state. A charge / discharge switching element that discharges into
After the step of discharging the charge of the capacitance to be measured to the ground potential by making the input voltage not applied and closing the charge / discharge switching element, and after the step of discharging, A controller that performs the step of charging the capacitance to be measured by opening the charge / discharge switching element and applying the input voltage;
In the step of charging by the controller, a measuring device that acquires a capacitance equivalent value of the measurement target based on a potential between the capacitance of the measurement target and the bridge capacitor;
A capacitance measuring device Ru provided with,
Is applied to the second input voltage as a constant voltage to the one end, the other end Ru further comprising a second capacitor connected to the other end of the capacitance of the measurement object, the capacitance measuring device. An input voltage applying means for applying an input voltage that is a constant voltage to one end side of the capacitance to be measured;
A bridge capacitor connected in series to the other end side of the capacitance to be measured, and connected between the other end side of the capacitance to be measured and a ground potential;
It is connected in series to the other end side of the capacitance to be measured, and is connected in parallel to the bridge capacitor, and the electric charge on the other end side of the capacitance to be measured is ground potential in the closed state. A charge / discharge switching element that discharges into
After the step of discharging the charge of the capacitance to be measured to the ground potential by making the input voltage not applied and closing the charge / discharge switching element, and after the step of discharging, A controller that performs the step of charging the capacitance to be measured by opening the charge / discharge switching element and applying the input voltage;
In the step of charging by the controller, a measuring device that acquires a capacitance equivalent value of the measurement target based on a potential between the capacitance of the measurement target and the bridge capacitor;
A capacitance measuring device Ru provided with,
The capacitance measuring device acquires each of a plurality of measurement target capacitance equivalent values in the sensor body,
The equivalent circuit of the sensor body includes a plurality of rows of first electrodes, a plurality of columns of second electrodes arranged in a matrix with respect to the plurality of rows of first electrodes, and the plurality of rows of first electrodes. And a plurality of dielectric layers provided at a plurality of positions where the plurality of rows of second electrodes are three-dimensionally crossed,
The capacitance equivalent values of the plurality of measurement objects in the sensor body are capacitance equivalent values between the first electrode and the second electrode corresponding to the respective positions of the plurality of dielectric layers,
The measuring instrument is
When the input voltage is applied to one first electrode of the plurality of first electrodes and the remaining first electrodes are connected to the ground potential, the respective voltages at the selected second electrodes;
Capacitances at a plurality of positions that are three-dimensionally intersected with each of the selected second electrode and the plurality of rows of first electrodes, as unknowns,
By solving the simultaneous equations represented by
You get the respective capacitance equivalent value as unknowns, the capacitance measuring device. A plurality of rows of first electrodes formed in a strip shape and arranged in parallel to each other;
A plurality of rows of second electrodes formed in a strip shape and arranged in parallel to each other, provided opposite to the first electrodes so that the positions facing the first electrodes of the plurality of rows are in a matrix shape A plurality of rows of second electrodes;
A dielectric layer provided between each first electrode of the plurality of rows of first electrodes and each second electrode of the plurality of columns of second electrodes;
The capacitance measuring device according to any one of claims 1 to 8, wherein a capacitance equivalent value at each of the matrix-like positions corresponding to the opposing positions of the respective first electrodes and the respective second electrodes is acquired. When,
With
One end side of the capacitance to be measured is the first electrode,
The capacitance type planar sensor device, wherein the other end side of the capacitance to be measured is the second electrode. The capacitive surface sensor device further includes a third electrode provided to face the second electrode opposite to the first electrode, and connected to a ground potential.
The capacitance type planar sensor device according to claim 9 , wherein a capacitor formed by the second electrode and the third electrode is the bridge capacitor. The capacitance type planar sensor device further includes a third electrode provided to face the second electrode on the opposite side to the first electrode,
The capacitance measuring device further includes a second capacitor to which a second input voltage as a constant voltage is applied to one end side and the other end side is connected to the other end side of the capacitance to be measured,
The capacitance type planar sensor device according to claim 9 , wherein a capacitor formed by the second electrode and the third electrode constitutes the second capacitor. In the tank for storing the liquid, a plurality of electrodes arranged shifted in the height direction,
The capacitance measuring device according to claim 1 , wherein a capacitance equivalent value between two electrodes selected from the plurality of electrodes is acquired as a capacitance equivalent value of the measurement target. When,
A determination unit for determining a liquid level in the tank based on a capacitance equivalent value of the measurement target;
A capacitance type liquid level detection device comprising: The capacitance type liquid level detection device according to claim 12 , wherein the determination unit determines a liquid quality based on a capacitance equivalent value of the measurement target.

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